U.S. patent number 3,774,401 [Application Number 05/266,505] was granted by the patent office on 1973-11-27 for automatic control system for use with a hydraulic drive system.
This patent grant is currently assigned to CMI Corporation. Invention is credited to Thomas E. Allen.
United States Patent |
3,774,401 |
Allen |
November 27, 1973 |
**Please see images for:
( Certificate of Correction ) ** |
AUTOMATIC CONTROL SYSTEM FOR USE WITH A HYDRAULIC DRIVE SYSTEM
Abstract
An automatic control system for use with a hydraulic drive
system which includes a source of pressurized hydraulic fluid and
first and second hydraulic drive motors deriving their power from
said source of pressurized hydraulic fluid, comprising a
differential valve in fluid communication with the source of
pressurized hydraulic fluid and a flow divider in fluid
communication with the differential valve and with a flow
compensator. The flow compensator is in fluid communication with
the first and second hydraulic drive means. A compensator valve
member is carried by the flow compensator for controlling the
relative rates of flow of hydraulic fluid to the first and second
hydraulic drive motors in response to load variations encountered
by the hydraulic drive means. A control unit is in fluid
communication with the source of pressurized hydraulic fluid and
with the flow divider and includes a control valve member for
controlling hydraulic fluid signals being sent therefrom to the
flow divider. An actuator is operatively connected to the control
valve member for actuating the control valve member in response to
stimulus from a source external to the automatic control system. A
flow divider valve member is carried by the flow divider for
controlling the relative rates of flow of hydraulic fluid through
the flow divider in response to the hydraulic fluid signals from
the control unit.
Inventors: |
Allen; Thomas E. (Mustang,
OK) |
Assignee: |
CMI Corporation (Oklahoma City,
OK)
|
Family
ID: |
23014844 |
Appl.
No.: |
05/266,505 |
Filed: |
June 26, 1972 |
Current U.S.
Class: |
60/420; 91/517;
180/6.48; 60/476; 104/244.1; 404/84.05 |
Current CPC
Class: |
F16H
61/47 (20130101); F16H 61/46 (20130101); F16H
61/456 (20130101); B62D 11/183 (20130101) |
Current International
Class: |
B62D
11/18 (20060101); B62D 11/06 (20060101); F16H
61/46 (20060101); F16H 61/40 (20060101); F15b
011/22 () |
Field of
Search: |
;60/395,420,476,97E
;180/6.48 ;104/244.1 ;404/84 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Geoghegan; Edgar W.
Claims
What is claimed is:
1. An automatic control system for use with a hydraulic drive
system of the type which includes a source of pressurized hydraulic
fluid and first and second hydraulic drive means deriving their
power from said source of pressurized hydraulic fluid,
comprising:
differential valve means, having an inlet in fluid communication
with said source of pressurized hydraulic fluid and having an
outlet, for providing a hydraulic pressure differential between the
inlet and outlet thereof;
a flow divider having first and second signal inlets, a power
inlet, and first and second power outlets, the power inlet thereof
being in fluid communication with the outlet of said differential
valve means and the first and second power outlets thereof being in
fluid communication with said first and second hydraulic drive
means, respectively;
a first control unit having an inlet in fluid communication with
said source of pressurized hydraulic fluid and having first and
second signal outlets in fluid communication with the first and
second signal inlets of said flow divider, respectively;
first control valve means carried by said first control unit
between the inlet thereof and the first and second signal outlets
thereof for controlling the relative rates of flow of hydraulic
fluid through the first and second signal outlets of said first
control unit to the first and second signal inlets of said flow
divider, respectively;
first actuation means operatively connected to said first control
valve means for actuating said first control valve means in
response to stimulus from a source external to said automatic
control system;
flow divider valve means carried by said flow divider between the
power inlet thereof and the first and second power outlets thereof,
and in fluid communication with the first and second signal inlets
thereof for controlling the relative rates of flow of hydraulic
fluid from the power inlet to the first power outlet and from the
power inlet to the second power outlet in response to the relative
flow rates of hydraulic fluid from said first control unit.
2. An automatic control system as defined in claim 1 wherein said
first actuation means is characterized further to include:
sensor means operatively connected to said first control valve
means for actuating said first control valve means;
tracer means operatively connected to said sensor means and
engageable with a suitable reference datum for actuating said
sensor means in response to stimulus imparted thereto by said
reference datum; and
wherein said sensor means actuates said first control valve means
in response to the actuation of said sensor means by said tracer
means.
3. An automatic control system as defined in claim 1 wherein said
first actuation means is characterized further to include:
lever means operatively connected to said first control valve means
for actuating said first control valve means in response to the
application of manual force to said lever means.
4. An automatic control system as defined in claim 1 characterized
further to include:
a second control unit having an inlet in fluid communication with
said source of pressurized hydraulic fluid and having first and
second signal outlets in fluid communication with the first and
second signal inlets of said flow divider, respectively;
second control valve means carried by said second control unit
between the inlet thereof and the first and second signal outlets
thereof for controlling the relative rates of flow of hydraulic
fluid through the first and second signal outlets of said control
unit to the first and second signal inlets of said flow divider,
respectively; and
lever means operatively connected to said second control valve
means for actuating said second control valve means in response to
the application of manual force to said lever means.
5. An automatic control system as defined in claim 4 wherein said
first actuation means is characterized further to include:
sensor means operatively connected to said first control valve
means for actuating said first control valve means; and
tracer means operatively connected to said sensor means and
engageable with a suitable reference datum for actuating said
sensor means in response to stimulus imparted thereto by said
reference datum; and
wherein said sensor means actuates said first control valve means
in response to the actuation of said sensor means by said tracer
means.
6. An automatic control system as defined in claim 1 characterized
further to include:
valve means interposed between the first and second power outlets
of said flow divider and said first and second hydraulic drive
means for reversing the direction of operation of said first and
second hydraulic drive means.
7. An automatic control system for use with a reversible hydraulic
drive system of the type which includes a reversible pump having a
first port and a second port for providing a source of pressurized
hydraulic fluid, and first and second reversible hydraulic drive
motors deriving their power from said pressurized hydraulic fluid,
each of said reversible hydraulic drive motors having a first port
and a second port with the second ports thereof in fluid
communication with the second port of said reversible pump,
comprising:
differential valve means, having a first port in fluid
communication with the first port of said reversible pump, a second
port, a high-pressure outlet port, and a low-pressure return port,
for providing a hydraulic pressure differential between the
high-pressure outlet and the low-pressure return thereof regardless
of the direction in which said reversible pump is pumping hydraulic
fluid;
a flow divider having first and second signal inlets, and first,
second and third power ports formed therein, the first power port
thereof being in fluid communication with the second port of said
differential valve means;
a flow compensator having first, second, third and fourth power
ports formed therein, the first and second power ports thereof
being in fluid communication with the second and third power ports
of said flow divider, respectively, the third power port thereof
being in fluid communication with the first port of said first
reversible hydraulic drive motor, and the fourth power port thereof
being in fluid communication with the first port of said second
reversible hydraulic drive motor, and having first and second
selector ports formed therein;
selector valve means having first and second inlet ports formed
therein in fluid communication with the first and second power
ports of said flow compensator, respectively, having first and
second outlet ports formed therein in fluid communication with the
first and second selector ports to said flow compensator,
respectively, and having first and second actuation ports formed
therein in fluid communication with the first and second ports of
said reversible pump, respectively, for placing the first power
port and the first selector port of said flow compensator in fluid
communication and placing the second power port and the second
selector port of said flow compensator in fluid communication when
said reversible pump is pumping hydraulic fluid out through the
first port thereof and, alternately, for placing the first power
port and the second selector port of said flow compensator in fluid
communication and placing the second power port and the first
selector port of said flow compensator in fluid communication when
said reversible pump is pumping hydraulic fluid out through the
second port thereof;
compensator valve means carried by said flow compensator between
the first and third power ports thereof, and between the second and
fourth power ports thereof for controlling the relative rates of
flow of hydraulic fluid through said first and second reversible
hydraulic drive motors from said flow compensator in response to
load variations encountered by said first and second reversible
hydraulic drive motors when said reversible pump is pumping
hydraulic fluid out through the first port thereof;
a first control unit having an inlet in fluid communication with
the high-pressure outlet of said differential valve means and
having first and second signal outlets in fluid communication with
the first and second signal inlets of said flow divider,
respectively;
first control valve means carried by said first control unit
between the inlet thereof and the first and second signal outlets
thereof for controlling the relative rates of flow of hydraulic
fluid through the first and second signal outlets of said first
control unit to the first and second signal inlets of said flow
divider, respectively;
first actuation means operatively connected to said first control
valve means for actuating said first control valve means in
response to stimulus from a source external to said automatic
control system; and
flow divider valve means carried by said flow divider between the
first power port and the second and third power ports thereof, and
in fluid communication with the first and second signal inlets
thereof for controlling the relative rates of flow of hydraulic
fluid between the first power port and the second power port and
between the first power port and the third power port in response
to the relative pressure of hydraulic fluid acting on said flow
divider valve means through the first and second signal inlets of
said flow divider.
8. An automatic control system as defined in claim 7 wherein said
first actuation means is characterized further to include:
sensor means operatively connected to said first control valve
means for actuating said first control valve means; and
tracer means operatively connected to said sensor means and
engageable with a suitable reference datum for actuating said
sensor means in response to stimulus imparted thereto by said
reference datum; and
wherein said sensor means actuates said first control valve means
in response to the actuation of said sensor means by said tracer
means.
9. An automatic control system as defined in claim 7 wherein said
first actuation means is characterized further to include:
lever means operatively connected to said first control valve means
for actuating said first control valve means in response to the
application of manual force to said lever means.
10. An automatic control system as defined in claim 7 characterized
further to include:
a second control unit having an inlet in fluid communication with
the high-pressure outlet of said differential valve means and
having first and second signal outlets in fluid communication with
the first and second signal inlets of said flow divider,
respectively;
second control valve means carried by said second control unit
between the inlet thereof and the first and second signal outlets
thereof for controlling the relative rates of flow of hydraulic
fluid through the first and second signal outlets of said control
unit to the first and second signal inlets of said flow divider,
respectively; and
lever means operatively connected to said second control valve
means for actuating said second control valve means in response to
the application of manual force to said lever means.
11. An automatic control system as defined in claim 10 wherein said
first actuation means is characterized further to include:
sensor means operatively connected to said first control valve
means for actuating said first control valve means; and
tracer means operatively connected to said sensor means and
engageable with a suitable reference datum for actuating said
sensor means in response to stimulus imparted thereto by said
reference datum; and
wherein said sensor means actuates said first control valve means
in response to the actuation of said sensor means by said tracer
means.
12. An automatic control system for use with a hydraulic drive
system of the type which includes a source of pressurized hydraulic
fluid and first and second hydraulic drive means deriving their
power from said source of pressurized hydraulic fluid,
comprising:
differential valve means, having an inlet in fluid communication
with said source of pressurized hydraulic fluid and having an
outlet, for providing a hydraulic pressure differential between the
inlet and outlet thereof;
a flow divider having first and second signal inlets, a power
inlet, and first and second power outlets, the power inlet thereof
being in fluid communication with the outlet of said differential
valve means;
a flow compensator, having first and second power inlets and first
and second power outlets, the first and second power inlets thereof
being in fluid communication with the first and second power
outlets of said flow divider, respectively, and the first and
second power outlets thereof being in fluid communication with said
first and second hydraulic drive means, respectively;
compensator valve means carried by said flow compensator between
the first power inlet and the first power outlet, and between the
second power inlet and the second power outlet thereof for
controlling the relative rates of flow of hydraulic fluid to said
first and second hydraulic drive means from said flow compensator
in response to load variations encountered by said first and second
hydraulic drive means;
a first control unit having an inlet in fluid communication with
said source of pressurized hydraulic fluid and having first and
second signal outlets in fluid communication with the first and
second signal inlets of said flow divider, respectively;
first control valve means carried by said first control unit
between the inlet thereof and the first and second signal outlets
thereof for controlling the relative rates of flow of hydraulic
fluid through the first and second signal outlets of said first
control unit to the first and second signal inlets of said flow
divider, respectively;
first actuation means operatively connected to said first control
valve means for actuating said first control valve means in
response to stimulus from a source external to said automatic
control system;
flow divider valve means carried by said flow divider between the
power inlet thereof and the first and second power outlets thereof,
and in fluid communication with the first and second signal inlets
thereof for controlling the relative rates of flow of hydraulic
fluid from the power inlet to the first power outlet and from the
power inlet to the second power outlet in response to the relative
flow rates of hydraulic fluid from said first control unit
communicated to the first and second signal inlets of said flow
divider.
13. An automatic control system as defined in claim 12 wherein said
first actuation means is characterized further to include:
sensor means operatively connected to said first control valve
means for actuating said first control valve means; and
tracer means operatively connected to said sensor means and
engageable with a suitable reference datum for actuating said
sensor means in response to stimulus imparted thereto by said
reference datum; and
wherein said sensor means actuates said first control valve means
in response to the actuation of said sensor means by said tracer
means.
14. An automatic control system as defined in claim 12 wherein said
first actuation means is characterized further to include:
lever means operatively connected to said first control valve means
for actuating said first control valve means in response to the
application of manual force to said lever means.
15. An automatic control system as defined in claim 12
characterized further to include:
a second control unit having an inlet in fluid communication with
said source of pressurized hydraulic fluid and having first and
second signal outlets in fluid communication with the first and
second signal inlets of said flow divider, respectively;
second control valve means carried by said second control unit
between the inlet thereof and the first and second signal outlets
thereof for controlling the relative rates of flow of hydraulic
fluid through the first and second signal outlets of said control
unit to the first and second signal inlets of said flow divider,
respectively; and
lever means operatively connected to said second control valve
means for actuating said second control valve means in response to
the application of manual force to said lever means.
16. An automatic control system as defined in claim 15 wherein said
first actuation means is characterized further to include:
sensor means operatively connected to said first control valve
means for actuating said first control valve means; and
tracer means operatively connected to said sensor means and
engageable with a suitable reference datum for actuating said
sensor means in response to stimulus imparted thereto by said
reference datum; and
wherein said sensor means actuates said first control valve means
in response to the actuation of said sensor means by said tracer
means.
17. An automatic control system as defined in claim 12
characterized further to include:
valve means interposed between the first and second power outlets
of said flow compensator and said first and second hydraulic drive
means for reversing the direction of operation of said first and
second hydraulic drive means.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates generally to automatic control systems for
use with hydraulic drive systems, and more specifically, but not by
way of limitation, to automatic control systems for use with heavy
construction machinery such as paving machines or the like.
2. Brief Description of the Prior Art
Known examples of the prior art teach various systems for
automatically controlling hydraulic drive systems. Certain of these
systems employ complex and expensive mechanically and electrically
actuated valving to provide a desired degree of control. Many prior
art systems have not been entirely satisfactory due to the expense
involved in both the manufacture and maintenance of various
component parts thereof. Others of the prior art systems have not
been entirely satisfactory due to delay in response of the drive
system to the control signals sent thereto by the automatic control
system, and due to wander or oscillation inherent in the automatic
control system.
SUMMARY OF THE INVENTION
The present invention contemplates an improved automatic control
system for use with a hydraulic drive system of the type which
includes a source of pressurized hydraulic fluid and first and
second hydraulic drive means deriving their power from said source
of pressurized hydraulic fluid. The automatic control system
comprises differential valve means, having an inlet in fluid
communication with the source of pressurized hydraulic fluid and
having an outlet, for providing a hydraulic pressure differential
between the inlet and outlet thereof. A flow divider having first
and second signal inlets, a power inlet, and first and second power
outlets communicates with the outlet of the differential valve
means via the power inlet thereof. A flow compensator having first
and second power inlets and first and second power outlets, is
connected to the flow divider via the first and second power inlets
thereof in fluid communication with the first and second power
outlets of the flow divider, respectively. The flow compensator is
further in fluid communication with the first and second hydraulic
drive means by means of the first and second power outlets,
respectively, thereof. Compensator valve means is carried by said
flow compensator between the first power inlet and the first power
outlet, and between the second power inlet and the second power
outlet thereof for controlling the relative rates of flow of
hydraulic fluid to said first and second hydraulic drive means from
said flow compensator in response to load variations encountered by
said first and second hydraulic drive means. A first control unit
having an inlet in fluid communication with the source of
pressurized hydraulic fluid and having first and second signal
outlets is in fluid communication with the first and second signal
inlets of the flow divider by means of the first and second signal
outlets thereof, respectively. First control valve means is carried
by the first control unit between the inlet thereof and the first
and second signal outlets thereof for controlling the relative
rates of flow of hydraulic fluid through the first and second
signal outlets of the first control unit to the first and second
signal inlets of the flow divider, respectively. First actuation
means is operatively connected to the first control valve means for
actuating the first control valve means in response to stimulus
from a source external to the automatic control system. Flow
divider valve means is carried by the flow divider between the
power inlet thereof and the first and second power outlets thereof,
and in fluid communication with the first and second signal inlets
thereof for controlling the relative rates of flow of hydraulic
fluid from the power inlet to the first power outlet and from the
power inlet to the second power outlet in response to the relative
flow rates of hydraulic fluid from the first control unit into the
first and second signal inlets of the flow divider.
An object of the present invention is to provide an improved
automatic control system for use with a hydraulic drive system
which will automatically compensate for deviation of the hydraulic
drive system from a desired path.
Another object of the present invention is to provide an improved
automatic control system for use with a hydraulic drive system
which will automatically compensate for variations in the loads
encountered by the individual hydraulic drive motors of the
hydraulic drive system.
Yet another object of the present invention is to provide an
improved automatic control system for use with a hydraulic drive
system which is all-hydraulic in operation.
A still further object of the present invention is to provide an
automatic control system for use with a hydraulic drive system
employing components which are inexpensive to manufacture and
maintain.
Other objects and advantages of the present invention will be
evident from the following detailed description when read in
conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a substantially diagrammatical perspective view
illustrating the apparatus of the present invention installed on a
hydraulically driven self-propelled vehicle.
FIG. 2 is a schematic diagram illustrating one form of the
automatic control system of the present invention.
FIG. 3 is a cross-sectional view of one form of flow divider for
use with the present invention illustrating the details of
construction thereof.
FIG. 4 is a cross-sectional view of one form of flow compensator
for use with the present invention illustrating the details of
construction thereof.
FIG. 5 is a schematic diagram illustrating another form of the
automatic control system of the present invention.
FIG. 6 is a cross-sectional view of another form of flow divider
for use with the present invention illustrating the details of
construction thereof.
FIG. 7 is a cross-sectional view of another form of flow
compensator for use with the present invention illustrating the
details of construction thereof.
FIG. 8 is a cross-sectional view of one form of bi-directional
differential valve for use with the present invention illustrating
the details of construction thereof.
FIG. 9 is a cross-sectional view of the valve of FIG. 8 showing the
disposition of the valve member when the pump is driven in the
forward direction.
FIG. 10 is a cross-sectional view of the valve of FIG 8 showing the
disposition of the valve member when the pump is driven in the
reverse direction.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to the drawings, and to FIG. 1 in particular, the
apparatus of the present invention is generally designated by the
reference character 10. The apparatus 10 includes a self-propelled
vehicle 12 comprising a frame 14 and four hydraulic motor-driven
track units 16 positioned at each of the four corners of the frame
14 and supporting the frame 14 on the ground.
While the vehicle 12 is described herein to include four hydraulic
motor-driven track units 16, i6 will be readily understood that the
present invention is equally well suited for use with vehicles
having two drive units disposed respectively on opposite sides of
the vehicle.
Mounted on and supported by the frame 14 is an automatic control
assembly 18. Details of the construction of the automatic control
assembly 18 will be described in greater detail hereinafter.
A track drive pump 20 is mounted on the frame 14 and is connected
to the automatic control assembly 18 by means of a pair of
hydraulic conduits 22 and 24. The track drive pump 20 is driven by
a power take-off which is driven by a suitable engine such as an
internal combustion engine of the piston or turbine type (not
shown). A hydraulic fluid reservoir 26 is mounted on the frame 14
and is in fluid communication with the track drive pump 20 by means
of a hydraulic conduit 28. A hydraulic fluid filter 30 is
interposed in the conduit 28 between the track drive pump 20 and
the hydraulic fluid reservoir 26. In certain applications,
alternate or additional filters may be desirable.
Hydraulic track drive motors 32, 34, 36 and 38 are mounted
respectively on and drivingly connected to the hydraulic
motor-driven track units 16. The first port 32a of the track drive
motor 32 is in fluid communication with the automatic control
assembly 18 via hydraulic conduits 40 and 42. The second port 32b
of the track drive motor 32 is in fluid communication with the
automatic control assembly via hydraulic conduits 44 and 46. The
first port 34a of track drive motor 34 is in fluid communication
with the automatic control assembly 18 via hydraulic conduits 40
and 48. The second port 34b of track drive motor 34 is in fluid
communication with the automatic control assembly 18 via hydraulic
conduits 50 and 44.
It should be noted that it may be desirable in certain
circumstances to include a conventional flow divider at the
junction of conduits 42 and 48 to divide the flow of hydraulic
fluid therethrough from conduit 40. Similarly, it may also be
desirable to include a second conventional flow divider at the
junction of conduits 60 and 54 to divide the flow of hydraulic
fluid therethrough from conduit 52. In addition, a conventional
flow divider may also be included at the junctions of conduits 46
and 50 to divide the flow of hydraulic fluid therethrough from
conduit 44. Similarly, it may also be desirable to include a
conventional flow divider at the junction of conduits 62 and 58 to
divide the flow of hydraulic fluid therethrough from conduit 56.
Such flow dividers may suitably be of the 50--50 type which is well
known to those skilled in the art.
The first port 36a of track drive motor 36 is in fluid
communication with the automatic control assembly 18 via hydraulic
conduits 52 and 54. The second port 36b of track drive motor 36 is
in fluid communication with the automatic control assembly 18 via
hydraulic conduits 56 and 58. The first port 38a of track drive
motor 38 is in fluid communication with the automatic control
assembly 18 via hydraulic conduits 52 and 60. The second port 38b
of track drive motor 38 is in fluid communication with the
automatic control assembly 18 via hydraulic conduits 56 and 62.
A hydraulic manual steering control assembly 64 is mounted on the
frame 14 and is in fluid communication with the automatic control
assembly 18 via hydraulic supply conduit 66 and hydraulic signal
conduits 68 and 70.
A sensor control assembly 72 is mounted on and to one side of the
frame 14. The sensor control assembly 72 is in fluid communication
with the automatic control assembly 18 via hydraulic supply conduit
74 and hydraulic signal conduits 76 and 78. The sensor control
assembly 72 includes a sensor unit 80 operatively connected thereto
by means which will be described in greater detail hereinafter.
Each sensor unit 80 is provided with a tracer 82 which engages a
string line or grade line 84 which is supported above the surface
of the ground to provide a suitable reference datum to facilitate
the automatic steering of the apparatus 10. A shut-off valve 86 is
installed in the hydraulic supply conduit 74 intermediate the
sensor control assembly 72 and the automatic control assembly 18 to
provide means for manually deactivating the sensor control assembly
72 when desired.
The sensor control assembly 72 is preferably mounted on the vehicle
12 proximate the forward end thereof when the vehicle 12 is moving
in the forward direction. Conversely, the sensor control assembly
72 is preferably mounted on the vehicle 12 proximate the rear end
thereof when the vehicle 12 is moving in the reverse direction.
A heat exchanger 88 is mounted on the frame 14 and is in fluid
communication with the hydraulic fluid reservoir 26 via conduit 90.
The bypass outlet 92 of the track drive motor 32 is in fluid
communication with the heat exchanger 88 via hydraulic conduits 94,
96 and 98. The bypass outlet 100 of the track drive motor 34 is in
fluid communication with the heat exchanger 88 via hydraulic
conduits 102, 96 and 98. The bypass outlet 104 of the track drive
motor 36 is in fluid communication with the heat exchanger 88 via
hydraulic conduits 106, 108 and 98. The bypass outlet 110 of the
track drive motor 38 is in fluid communication with the heat
exchanger 88 via hydraulic conduits 112, 108 and 98. The track
drive motors 32, 34, 36 and 38 are adapted, by means of their
internal valving, to direct excess fluid volume through the
respective bypass outlets 92, 100, 104 and 110 through the
associated hydraulic conduits to the heat exchanger 88. At the heat
exchanger 88 the excess hydraulic fluid is cooled and directed from
the heat exchanger 88 through hydraulic conduit 90 to the hydraulic
fluid reservoir 26 for re-use in the hydraulic drive system of the
apparatus 10.
It will be readily apparent to those skilled in the art that the
apparatus 10 may be propelled over the ground by means of the four
hydraulic motor-driven track units 16 which are driven respectively
by the track drive motors 32, 34, 36 and 38, which track drive
motors derive their power from the flow of hydraulic fluid
emanating from the track drive pump 20 and conveyed thereto through
the previously described hydraulic conduits and the automatic
control assembly 18. Control of the relative speed and power
outputs of the track drive motors 32, 34, 36 and 38 is achieved by
the automatic control assembly 18 interposed between the track
drive pump 20 and the track drive motors. Preferred embodiments of
the automatic control assembly 18 will be described in detail
hereinafter.
DESCRIPTION OF THE EMBODIMENT OF FIGS. 2, 3 AND 4
FIG. 2 generally illustrates, in schematic form, the automatic
control assembly 18 in fluid communication with the hydraulic
manual steering control assembly 64, the sensor control assembly
72, the shut-off valve 86, and the track drive motors 32 and 38 as
described in detail above. The track drive motors 34 and 36 are not
illustrated in FIG. 2, it being believed that it will be readily
apparent to one skilled in the art that the operation of the motors
34 and 36 is substantially identical to the operation of motors 32
and 38 which will be described in detail herein. FIG. 2 also
illustrates the track drive pump 20 in fluid communication with the
automatic control assembly 18 as described above.
The automatic control assembly 18 includes a differential valve
114. The inlet 116 of the differential valve 114 is in fluid
communication with the first port 20a of the track drive pump 20
via hydraulic conduits 118 and 22.
The automatic control assembly 18 also includes a flow divider 120
having first and second signal inlets 122 and 124, a power inlet
126 and first and second power outlets 128 and 130. The power inlet
126 of the flow divider 120 is in fluid communication with the
outlet 132 of the differential valve 114 via conduit 134.
A shuttle valve 136 having an outlet 138 is in fluid communication
with the first signal inlet 122 of the flow divider 120 via conduit
40. A second shuttle valve 142 having an outlet 144 is in fluid
communication with the second signal inlet 124 of the flow divider
120 via conduitl 146.
The shuttle valve 136 also includes a first inlet 148 and a second
inlet 150. The first inlet 148 is in fluid communication with the
sensor control assembly 72 via conduits 152 and 76. The second
inlet 150 is in fluid communication with the hydraulic manual
steering control assembly 64 via conduits 154, 156 and 68.
The second shuttle valve 142 includes a first inlet 158 and a
second inlet 160. The first inlet 158 is in fluid communication
with the sensor control assembly 72 via conduits 162 and 78. The
second inlet 160 is in fluid communication with the hydraulic
manual steering control assembly 62 via conduits 164, 166 and
70.
The second inlet 150 of the shuttle valve 136 is also in fluid
communication with the power inlet 126 of the flow divider 120 via
conduits 154, 168 and 134. An orifice 170 is interposed in conduit
168 intermediate conduits 154 and 134. The second inlet 160 of the
shuttle valve 142 is also in fluid communication with the power
inlet 126 of the flow divider 120 via conduits 164, 172 and 134. An
orifice 174 is interposed in the conduit 172 intermediate the
conduits 164 and 134.
The automatic control assembly 18 further includes a flow
compensator 176. The flow compensator 176 includes first and second
power inlets 178 and 180, and first and second power outlets 182
and 184. The first and second power inlets 178 and 180 are in fluid
communication with the first and second power outlets 128 and 130
of the flow divider 120, respectively.
Included in the automatic control assembly 18 is a forward-reverse
control valve 186. The valve 186 includes an inlet port 188, a
foward outlet port 190 and a reverse outlet port 192. The inlet
port 188 is in fluid communication with the first port 20a of the
track drive pump 20 via conduits 194, 196, 118 and 22. The valve
186 is illustrated in the forward mode with the inlet port 188 and
the forward outlet port 190 in fluid communication with one
another. It will be readily apparent that the valve 186 may be
placed in the reverse mode by placing the inlet port 188 in fluid
communication with the reverse outlet port 192 by moving the
control lever 198 in the direction indicated by the arrow 200 to
the reverse position.
The automatic control assembly 18 further includes a pair of
forward-reverse spool valves 202 and 204. The spool valve 202
includes power ports 206, 208, 210 and 212. The spool valve 202
also includes a pair of control ports 214 and 216.
The spool valve 204 includes power ports 218, 220, 222 and 224. The
spool valve 204 also includes a pair of control ports 226 and
228.
The forward outlet port 190 of the forward-reverse control valve
186 is in fluid communication with the control port 214 of spool
valve 202 via conduits 230 and 232. The forward outlet port 190 is
also in fluid communication with the control port 226 of spool
valve 204 via conduits 230 and 234. The reverse outlet port 192 of
the forward-reverse control valve 186 is in fluid communication
with the control port 216 of spool valve 202 via conduits 236 and
238. The reverse outlet pport 192 is also in fluid communication
with the control port 228 of spool valve 204 via conduits 236 and
240.
The first power outlet 182 of the flow compensator 176 is in fluid
communication with the power port 206 of spool valve 202 via
conduit 242. The second power outlet 184 of the flow compensator
176 is in fluid communication with power port 218 of the spool
valve 204 via conduit 244.
The power port 208 of spool valve 202 is in fluid communication
with the second port 20b of the track drive pump 20 via conduits
246, 248 and 24. The power port 220 of spool valve 204 is in fluid
communication with the second port 20b of the track drive pump 20
via conduits 250, 248 and 24. The power port 210 of spool valve 202
is in fluid communication with the track drive motor 32 via
conduits 252, 40 and 42. The power port 212 of spool valve 202 is
in fluid communication with the track drive motor 32 via onduits
254, 44 and 46. The power port 222 of spool valve 204 is in fluid
communication with the track drive motor 28 via conduits 256, 52
and 60. The power port 224 of spool valve 204 is in fluid
communication with the track drive motor 38 via conduits 258, 56
and 62.
The hydraulic manual steering control assembly 64 preferably
includes a conventional hydraulic differential flow control valve
260 having an inlet port 262 and a pair of signal outlet ports 264
and 266. The valve 260 may be suitably actuated by a manually
operated control lever or the like as shown at 268. The inlet port
262 of the contorl valve 260 is in fluid communication with the
automatic control assembly 18 and the first port 20a of the track
drive pump 20 via conduits 66, 196, 118 and 22. The signal outlet
264 is in fluid communication with conduit 68 and the signal outlet
266 is in fluid communication with the conduit 70.
The sensor control assembly 72 includes a conventional hydraulic
differential flow control valve 270 having an inlet port 272 and a
pair of signal outlet ports 274 and 276. The signal outlet port 274
is in fluid communication with conduit 76 and the signal outlet
port 276 is in fluid communication with conduit 78. The inlet port
272 is in fluid communication with the automatic control assembly
18 and the track drive pump 20 via conduits 74, 278, 118 and 22. As
described above, a shut-off valve 86 is installed in the conduit 74
intermediate the inlet port 272 of the sensor control assembly 72
and the automatic control assembly 18. The hydraulic differential
flow control valve 270 is of conventional construction and its
operation will be readily apparent to those skilled in the art.
The sensor unit 80 is operatively connected to the hydraulic
differential flow control valve 270 of the sensor control assembly
72 in order to actuate the valve 270 in response to variation in
the position of the sensor unit 80 relative to the string line or
grade line 84. The sensor unit 80 may be directly connected to the
valve 270 by mechanical means or may be connected electrically to
the valve 270 to provide actuation thereof. Such sensor units are
well known in the art and need not be described in detail
herein.
The valves 260 and 270 are commonly referred to as selector or
directional control valves. The valve 260 is preferably of the low
gain type while the valve 270 is preferably of the high gain type.
In each of the valves 260 and 270 the cross-sectional flow area to
one or the other signal outlet ports is directly proportional to
the input signal from the control lever 268 or the sensor unit 80,
respectively.
As shown in FIG. 3, the flow divider 120 comprises a valve body 280
and a valve member 282 slidably disposed therein. The valve body
280 includes a bore 284 extending therethrough and intersecting the
opposite end portions 286 and 288 thereof. A counterbore 290 is
formed in the bore 284 intersecting the end portion 286 and forming
an annular wall 292 in the valve body 280. A counterbore 294 is
formed in he bore 284 intersecting the opposite end portion 288 of
the valve body 280 and forming an annular wall 296 therein.
A central annular chamber 298 is formed in the medial portion of
the valve body 280 and includes opposite annular walls 3oo and 302
interconnected by a cylindrically shaped annular surface 304. The
annular chamber 298 is coaxial with the bore 284.
A second annular chamber 306 is formed in the valve body 280
coaxial with the bore 284 and intermediate the counterbore 280 and
the central annular chamber 298. The annular chamber 306 includes
opposite annular walls 308 and 310 interconnected by a
cylindrically shaped annular surface 312.
A third annular chamber 314 is formed in the valve body 280 coaxial
with the bore 284 therethrough and intermediate the central annular
chamber 298 and the counterbore 294. The annular chamber 314
includes opposite annular walls 216 and 218 interconnected by a
cylindrically shaped annular surface 320.
The first signal inlet 122 of the flow divider 120 communicates
with an annular chamber 322 formed by the counterbore 290. The
second signal inlet 124 of the flow divider 120 communicates with
an annular chamber 324 formed by the counterbore 294. The power
inlet 126 of the flow divider 120 communicates with the central
annular chamber 298. The first and second power outltes 128 and 130
of the flow divider 120 communicate with the annular chambers 306
and 314, respectively.
The valve member 282 is slidably dispose in the bore 284 of the
valve body 280. The substantially cylindrically shaped outer
periphery 326 of the valve member 282 has a diameter sized to
provide a substantially fluid-tight seal between the outer
periphery 326 and the walls of the bore 284. A cylindrically shaped
extension 328 is formed on one end portion 329 of the valve member
282 and extends into the annular chamber 324. The extension 328 is
coaxial with the outer periphery 326 of the valve member 282. An
annular shoulder 330 interconnects the cylindrical surface 332 of
the extension 328 and the cylindrically shaped outer periphery
326.
A bore is formed in the cylindrically shaped extension 328 coaxial
with the cylindrical surface 332. A counterbore 336 is formed in
the valve member 282 intersecting the end portion 338 thereof and
communicating with the bore 334 in the extension 328. A removable
orifice 340 is threadedly secured in the end portion 342 of the
extension 328. A plug 344 having an aperture 346 formed therein is
threadedly secured in the counterbore 336 at the end portion 338 of
the valve member 282. A removable orifice 348 is threadedly secured
in the aperture 346.
Two ports 350 are formed in the valve member 282 providing
communication between the chamber 352 formed therein by the
counterbore 336 and the central annular chamber 298 in the valve
body 280.
A plurality of ports 354 are formed in the valve member 282
proximate to the end protion 338 thereof. The ports 354 provide
fluid communication between the chamber 352 and the cylindrically
shaped outer periphery 326 of the valve member 282. Similarly, a
plurality of ports 356 are formed in the valve member 282 proximate
to the end portion 329 thereof. The ports 356 provide fluid
communication between the chamber 352 and the cylindrically shaped
outer periphery 326 of the valve member 282. Preferably, the valve
member 282 includes ten ports 354 and ten ports 356. The diameters
of the ports 354 and 356 are preferably identical. As shown in FIG.
3, the ports 354 are divided with five ports on one side of the
valve member 282 and five ports on the opposite side diiametrically
opposed thereto. Similarly, the ports 356 are divided with five
ports on one side of the valve member 282 and with five ports on
the other side diametrically opposed thereto. The ports 354 and 356
are drilled or otherwise formed in the valve member 282 on centers
substantially equal to the diameter of the ports. It should also be
noted that the centers of the five ports 354 and 356 on one side of
the valve member 282 are preferably staggered approximately
one-half the diameter of a port from the centers of the ports 354
and 356, respectively, formed in the opposite side of the valve
member 282. The staggered relation of the ports 354 and 356
provides smooth transition as the valve member 282 moves left or
right within the valve body 280. It should be noted that the
arrangement and/or diameter of the ports 354 and 356 may be varied
to achieve other than linear flow response to movement of the valve
member 282 within the valve body 280. It should further be noted
that other forms of ports such as long slots may be substituted for
the previously described plurality of ports 354 and 356.
As shown in FIG. 3, the valve member 282 is positioned in its
center of medial position within the valve body 280. In this
position, it will be observed that five ports 354 communicate
between the chamber 352 of the valve member 282 and the annular
chamber 306 of the valve body 280. Similarly, five ports 356
provide communication between the chamber 352 of the valve member
282 and the annular chamber 314 of the valve body 380. The
remaining ports 354 and 356 are blocked by the cylindrical walls of
the bore 284 and therefore provide no communication between the
chamber 352 and the chambers 306 and 314.
As will be readily apparent to those skilled in the art, as the
valve member 282 moves either left or right of the central or
medial position the cross-sectional area of the ports 354 and 356
providing fluid communication between the chamber 352 and the
cylindrically shaped outer periphery 326 of the valve member 282
always remains equal to the total cross-sectional area of 10
ports.
The valve member 282 is urged into its central or medial position
relative to the valve body 280 as shown in FIG. 3, by means of a
spring assembly 358 disposed within the chamber 324 formed by the
counterbore 294 in the valve body 280. The spring assembly
comprises two identical annular spring seats 360 and 362. Each
spring seat 360 and 362 has a cylindrically shaped aperture 364
formed therein and is L-shaped in cross-section with an outwardly
extending flange portion 366 and a cylindrically shaped portion
368. An annular end wall 370 is formed on each flange portion
366.
The spring seat 360 is slidably disposed on the cylindrically
shaped extension 328 with the extension 328 extending through the
aperture 364 formed therein. The end wall 370 thereof abuts the
annular shoulder 300 of the valve member 282 and also abuts the
annular wall 296 of the valve body 280 when the valve member 282 is
positioned in its central or medial position. The annular spring
seat 362 is slidably disposed on the cylindrically shaped extension
328 with the extension 328 extending through the aperture 364
therein and with the end wall 370 thereof facing away from the
annular spring seat 360. The annular spring seats 360 and 362 are
retained on the cylindrically shaped extension 328 by means of a
snap ring 372 disposed in an annular groove 374 formed in the
cylindrical surface 332 of the extension 328.
The spring assembly 358 further includes a coil spring 376 disposed
about the cylindrically shaped extension 328. The coil spring 376
is supported at each end thereof by the respective cylindrically
shaped portion 368 of the respective annular spring seat 360 and
362. An annular sleeve 378 having an L-shaped cross-section and
having a first end face 380 and a second end face 382 is disposed
within the counterbore 294 with the first end face 380 thereof
abutting the end wall 370 of the annular spring seat 362.
End plates 384 and 386 are secured respectively to the opposite end
portions 286 and 288 of the valve body 280 by suitable means such
as a plurality of threaded cap screws 388. A suitable fluid-tight
seal is provided between the end plates 384 and 386 and the valve
body 280 by means of O-rings 390 disposed in annular grooves 392
formed in the end plates 384 and 386.
The second end face 382 of the annular sleeve 378 abuts the end
plate 386. Movement of the valve member 282 within the valve body
280 is yieldably resisted by the urging of the coil spring 376.
Movement of the valve member 282 to the right, as viewed in FIG. 3,
is resisted by the urging of the coil spring 376 acting through the
end plate 386, the annular sleeve 378, the spring seat 362, the
coil spring 376, the spring seat 360, and the annular shoulder 330
of the valve member 282. Movement of the valve member 282 to the
left, as viewed in FIG. 3, is resisted by the urging of the coil
spring 376 acting through the annular wall 296 of the valve body
280, the spring seat 360, the coil spring 376, the spring seat 362,
the snap ring 372, and the cylindrically shaped extension 328 of
the valve member 282.
As shown in FIG. 4, the flow compensator 176 comprises a valve body
394 and a valve member 396 slidably disposed therein. The valve
body 394 includes a bore 398 extending therethrough and
intersecting the opposite end portions 400 and 402 thereof. A
counterbore 404 is formed in the bore 398 intersecting the end
portion 402 and forming an annular wall 406 in the valve body
394.
A first annular chamber 408 is formed in the valve body 394 and
includes opposite annular walls 410 and 412 interconnected by a
cylindrically shaped annular surface 414. The annular chamber 408
is coaxial with the bore 398.
A second annular chamber 416 is formed in the valve body 394
coaxial with the bore 398. The annular chamber 416 includes
opposite and annular walls 418 and 420 interconnected by a
cylindrically shaped annular surface 422.
The first power inlet 178 of the flow compensator 176 communicates
with the first annular chamber 408. The second power inlet 180 of
the flow compensator 176 communicates with the second annular
chamber 416.
A third annular chamber 424 is formed in the valve body 394 coaxial
with the bore 398 therethrough and intermediate the first annular
chamber 408 and the end portion 400 of the valve body 394. The
annular chamber 424 includes opposite annular walls 426 and 428
interconnected by a cylindrically shaped annular surface 430.
A fourth annular chamber 432 is formed in the valve body 394
coaxial with the bore 398 therethrough and intermediate the second
annular chamber 416 and the end portion 402 of the valve body 394.
The annular chamber 432 includes opposite annular walls 434 and 436
interconnected by a cylindrically shaped annular surface 438.
The first power outlet 182 of the flow compensator 176 communicates
with the third annular chamber 424; and the second power outlet 184
of the flow compensator 176 communicates with the fourth annular
chamber 432.
The valve member 396 is slidably disposed in the bore 398 of the
valve body 394. The cylindrically shaped outer periphery 440 of the
valve member 396 has a diameter sized to provide a substantially
fluid-tight seal between the outer periphery 440 and the walls of
the bore 398. The valve member 396 includes opposite end faces 442
and 444, each lying in a plane normal to the longitudinal axis of
the valve member 396. A cylindrically shaped chamber 446 is formed
in one end of the valve member 396 with one end thereof
intersecting the end face 442. A second cylindrically shaped
chamber 448 is formed in the opposite end of the valve member 396
with one end thereof intersecting the end face 444. It should be
noted that the chambers 446 and 448 do not communicate with each
other within the valve member 396.
Two ports 450 are formed in the valve member 396 providing
communication between the chamber 446 formed therein and the first
annular chamber 408 formed in the valve body 394. Two ports 452 are
formed in the valve member 396 providing communication between the
chamber 448 formed therein and the second annular chamber 416
formed in the valve body 394. Two ports 454 are formed in the valve
member 936 providing communication between the chmaber 446 formed
therein and the third annular chamber 424 formed in he valve body
394. Two ports 456 are formed in the valve member 396 providing
communication between the chamber 448 formed therein and the fourth
annular chamber 432 formed in the valve body 394.
As shown in FIG. 4, the member 396 is positioned in its center or
medial position within the valve body 394. It will be observed that
the centerline of the ports 454 and the centerline of the ports 456
are positioned substantially in the planes of the annular walls 426
and 436 of the third and fourth annular chambers 424 and 432,
respectively.
End plates 458 and 460 are secured respectively to the opposite end
portions 400 and 402 of the valve body 394 by suitable means such
as a plurality of threaded cap screws 462. A suitable fluid-tight
seal is provided between the end plates 458 and 460 and the valve
body 394 by means of O-rings 464 disposed in annular grooves 466
formed in the end plates 458 and 460.
The valve member 396 is of such length that when it is displaced to
the extreme left, as viewed in FIG. 4, with the end face 442
thereof abutting the end plate 458, the cross-sectional area of
fluid communication between the chamber 446 of the valve member 396
and the third annular chamber 424 of the valve body 394 via the
ports 454 is closed off entirely. At the same time, the
communication between the chamber 448 and the valve member 396 with
the fourth annular chamber 442 of the valve body 394 via the ports
456 is at a maximum. Alternately, when the valve member 396 is
displaced to the extreme right, as viewed in FIG. 4, with the end
face 44 thereof abutting the end plate 460, the cross-sectional
area of fluid communication between the chamber 448 of the valve
member 396 with the fourth annular chamber 432 of the valve body
394 is closed off entirely. At the same time, communication between
the chamber 446 of the valve member 396 with the third annular
chamber 424 of the valve body 394 via the ports 454 is at a
maximum. It should be noted that regardless of the relative
position of the valve member 396 within the valve body 394 the
communication between the chamber 446 of the valve member 396 and
the first annular chamber 408 of the valve body 394 remains
unchanged. Similarly, the communication between the chamber 448 of
the valve member 396 and the second annular chamber 416 of the
valve body 394 via the ports 452 remains unchanged regardless of
the position of the valve member 396 relative to the valve body
394.
It should be noted that the previously described flow divider 120
and flow compensator 176 may be advantageously housed in a single
unitary valve body. Such a valve body would include all of the
features described for the valve bodies 280 and 394 of the flow
divider 120 and flow compensator 176, respectively, and would place
the first and second power outlets 128 and 130 of the flow divider
120 in fluid communication with the first and second power inlets
178 and 180, respectively, of the flow compensator 176 within the
combined valve body. Furthermore, the end plates 458 and 384 may be
advantageously combined into one end plate as may end plates 460
and 386. In either configuration the functions of the flow divider
120 and the flow compensator 176 would be identical.
OPERATION OF THE EMBODIMENT OF FIGS. 2, 3 AND 4
In operation, the track drive pump 20 is driven by the engine and
power take-off (not shown) to provide a source of pressurized
hydraulic fluid. The pressurized hydraulic fluid provided by the
pump 20 may be in either a low pressure range of from 600 to 1,500
psi or in a high pressure range of from 1,500 to 3,500 psi. While
these pressure ranges are disclosed as oreferable for the operation
of the present invention, it is not intended that the present
invention be limited thereby.
The pressurized hydraulic fluid is directed from the first port 20a
of the pump 20 through conduits 22 and 118 to the inlet 116 of the
differential valve 114. The hydraulic fluid passes through the
differential valve 114 and exits from the outlet 132 thereof. The
differential valve 114 provides a pressure differential of
approximately 75 psi between the high pressure inlet 116 in the
lower pressure outlet 132. The hydraulic fluid is then directed
from the outlet 132 through conduit 134 to the power inlet 126 of
the flow divider 120.
Pressurized hydraulic fluid is also directed from the pump 20 via
conduits 22, 118, 278 and 74 to the inlet port 272 of the sensor
control assembly 72. In order for the pressurized hydraulic fluid
to reach the inlet port 272 of the sensor control assembly 72 it is
necessary for the shut-off valve 86, installed in conduit 74, to be
in its open position. If the shut-off valve 86 is in the closed
position the sensor control assembly 72 is deactivated and performs
no function in the operation of the present invention. The
pressurized hydraulic fluid flows from the inlet port 272 through
the differential flow control valve 270 of the sensor control
assembly 72 and exits therefrom through the signal outlet port 274
and 276. The hydraulic fluid emanating from the signal outlet port
274 flows to the first inlet 148 of shuttle valve 136 via conduits
76 and 152. The hydraulic fluid emanating from the signal outlet
port 276 flows to the first inlet 158 of shuttle valve 142 via
conduits 78 and 162.
Pressurized hydraulic fluid also flows from the pump 20 to the
inlet port 262 of the hydraulic differential flow control valve 260
of the hydraulic manual steering control assembly 64 via conduits
22, 118, 196 and 66. The hydraulic fluid entering the inlet port
262 passes through the hydraulic differential flow control valve
260 and exits therefrom through signal outlets 264 and 266. A
portion of the hydraulic fluid emanating from the signal outlet 264
flows to the second inlet 150 of the shuttle valve 136 via conduits
68, 156 and 154. The remaining portion of the hydraulic fluid
emanating from the signal outlet 264 flows to the power inlet 126
of the flow divider 120 via conduits 68, 156, 168 and 134. It
should be noted that the last-mentioned hydraulic fluid must also
pass through orifice 170 in conduit 168. The passage of the
hydraulic fluid through the orifice 170 provides the pressure drop
required in order for the hydraulic fluid to reach the lowered
pressure of the hydraulic fluid emanating from the outlet 132 of
the differential valve 114.
A portion of the hydraulic fluid emanating from the signal outlet
266 flows to the second inlet 160 of the shuttle valve 142 via
conduits 70, 166 and 164. The remaining portion of the hydraulic
fluid emanating from the signal outlet 266 flows to the power inlet
126 of the flow divider 120 via conduits 70, 166, 172 and 134. It
should be noted that this hydraulic fluid must also pass through
orifice 174 in the conduit 172 which provides the necessary
pressure drop for the hydraulic fluid to reach the lower pressure
of the hydraulic fluid emanating from the outlet 132 of the
differential valve 114.
Pressurized hydraulic fluid entering either of the inlets 148 or
150 of the shuttle valve 136 exits therefrom through outlet 138 and
flows to the first signal inlet 122 of the flow divider 120 via
conduit 140. Pressurized hydraulic fluid entering either of the
inlets 158 or 160 of the shuttle valve 142 exits therefrom through
outlet 144 and flows to the second signal inlet 124 of the flow
divider 120 via conduit 146.
The hydraulic fluid entering the power inlet 126 of the flow
divider 120 passes through the power inlet 126 into the chamber 352
in the valve member 282 via the central annular chamber 298 of the
valve body 280 and the ports 350 formed in the valve member 282.
The hydraulic fluid entering the first signal inlet 122 of the flow
divider 120 flows into the annular chamber 322 of the valve body
280 through the first signal inlet 122, and then flows from the
annular chamber 322 into the chamber 352 of the valve member 282
through the orifice 348. The hydraulic fluid entering the second
signal inlet 124 of the flow divider 120 flows into the annular
chamber 324 of the valve body 280 through the second signal inlet
124, and then flows from the annular chamber 324 into the chamber
352 of the valve member 282 through the orifice 340 and the bore
334 of the extension 328.
It should be noted that the hydraulic fluid in the annular chambers
322 and 324 is at a pressure approximately 75 psi greater than the
hydraulic fluid contained within the chamber 352 of the valve
member 282. As the hydraulic fluid enters the annular chambers 322
and 324 flows into the chamber 352 through the respective orifices
348 and 340 the pressure drops to that of the hydraulic fluid
within the chamber 352 of the valve member 282.
The hydraulic fluid in the chamber 352 of the valve member 282
flows therefrom through the ports 354 and 356 into the second and
third annular chambers 306 and 314 of the valve body 280,
respectively. The hydraulic fluid entering the second annular
chamber 306 through the ports 354 exits therefrom through the first
power outlet 128; and the hydraulic fluid entering the third
annular chamber 314 through the ports 356 exits therefrom through
the second power outlet 130. The hydraulic fluid exiting from the
first power outlet 128 of the flow divider 120 flows therefrom into
the first power inlet 178 of the flow compensator 176. The
hydraulic fluid exiting from the second power outlet 150 of the
flow divider 120 flows therefrom into the second power inlet 180 of
the flow compensator 176.
Orifices 170, 174, 340 and 348 can be sized to provide various
steering rates in response to manual and sensor signal inputs.
The hydraulic fluid entering the first power inlet 178 of the flow
compensator 176 flows therefrom into the chamber 446 of the valve
member 396 through the first annular chamber 408 of the valve body
394 and the ports 450 of the valve member 396. The hydraulic fluid
entering the second power inlet 180 of the flow compensator 176
flows therefrom into the chamber 448 formed in the valve member 396
through the second annular chamber 416 of the valve body 394 and
the ports 452 formed in the valve member 396. The hydraulic fluid
in the chamber 446 of the valve member 396 flows therefrom through
the ports 454 formed in the valve member 396 and the third annular
chamber 424 of the valve body 394 and exits from the flow
compensator 176 through the first power outlet 182. The hydraulic
fluid in the chamber 448 of the valve member 396 flows therefrom
through the ports 456 in the valve member 396 and the fourth
annular chamber 432 of the valve body 394 and exits from the flow
compensator 176 through the second power outlet 184.
The hydraulic fluid exiting from the first power outlet 182 of the
flow compensator 176 flows therefrom to the power port 206 of the
forward-reverse spool valve 202 via conduit 242. The hydraulic
fluid exiting from the second power outlet 182 of the flow
compensator 176 flows therefrom to the power port 218 of
forward-reverse spool valve 204 via conduit 244. When the
forward-reverse spool valves 202 and 204 are in their forward
positions, the hydraulic fluid entering power port 206 of spool
valve 202 exits therefrom through power port 210, and the hydraulic
fluid entering the power port 218 of spool valve 204 exits
therefrom through power port 222.
The hydraulic fluid exiting from power port 210 of spool valve 202
flows therefrom through conduits 252, 40 and 42 to track drive
motor 32 thereby driving the motor 32 in a forward direction. Most
of the hydraulic fluid passing through the track drive motor 32 is
routed therefrom back to the power port 212 of the spool valve 202
via conduits 44, 46 and 254. Excess hydraulic fluid volume bypassed
by the internal valving of the track drive motor 32 is directed
from bypass outlet 92 through conduits 94, 96 and 98 to heat
exchanger 88 and from heat exchanger 88 through conduit 90 to
reservoir 26.
Hydraulic fluid exiting from power port 222 of spool valve 204
flows therefrom through conduits 256, 52 and 60 to track drive
motor 38 thereby driving the motor 38 in a forward direction. Most
of the hydraulic fluid passing through track drive motor 38 is
routed therefrom back to power port 224 of spool valve 204 via
conduits 56, 62 and 258. Excess hydraulic fluid volume bypassed by
the internal valving of track drive motor 38 is directed from
bypass outlet 110 through conduits 108, 112 and 98 to heat
exchanger 88 and from heat exchanger 88 through conduit 90 to
reservoir 26.
Hydraulic fluid entering power port 212 of spool valve 202, when
spool valve 202 is in the forward position, exits therefrom through
power port 208 and flows back to track drive pump 20 via conduits
246, 248 and 24. Similarly, when spool valve 204 is in the forward
position hydraulic fluid entering power port 224 exits therefrom
through power port 220 and flows back to the track drive pump 20
via conduits 250, 248 and 24.
To place the forward-reverse spool valves 202 and 204 in the proper
forward or reverse positions, hydraulic fluid is directed from the
first port 20a of the pump 20 through the forward-reverse control
valve 186 to the appropriate control ports on the spool valves 202
and 204. Pressurized hydraulic fluid flows to the inlet port 188 of
the forward-reverse control valve 186 from the pump 20 via conduits
22, 118, 196 and 194. When the forward-reverse control valve 186 is
in the forward position, as shown in FIG. 2, the hydraulic fluid
entering the inlet port 188 flows through the valve 186 and exits
from the forward outlet port 190. The hydraulic fluid exiting from
the forward outlet port 190 communicates with the control ports 214
and 226 of the spool valves 202 and 204, respectively. Fluid
communication between the forward outlet port 190 and control port
214 of spool valve 202 is accomplished via conduits 230 and 232;
and fluid communication between the forward outlet port 190 and the
control port 226 of spool valve 204 is accomplished via conduits
230 and 234.
When the forward-reverse control valve 186 is placed in the reverse
position by moving the control lever 198 in the direction of the
arrow 200, the pressurized hydraulic fluid entering inlet port 188
of the valve 186 exits therefrom through reverse outlet port 192.
The reverse outlet port 192 is in fluid communication with control
ports 216 and 228 of spool valves 202 and 204, respectively. The
pressurized hydraulic fluid emanating from reverse outlet port 192
communicates with control port 216 via conduits 236 and 238 thereby
placing spool valve 202 in the reverse position. The hydraulic
fluid emanating from reverse outlet port 192 also communicates with
control port 228 of spool valve 204 via conduits 236 and 240
thereby placing spool valve 204 in the reverse position.
At this point it should be noted that, while a single
forward-reverse control valve 186 is disclosed for simultaneously
controlling the forward-reverse spool valves 202 and 204, it will
be understood that it may be preferable to control the spool valves
202 and 204 individually by separate forward-reverse control valves
similar to the previously described valve 186. In addition, the
spool valves 202 and 204 may be individually controlled by separate
mechanical means such as manually operated levers directly
connected to the valves 202 and 204, respectively. Such individual
control of the spool valves 202 and 204 will permit one spool valve
to be placed in the reverse mode while the other spool valve is
simultaneously placed in the forward mode thereby permitting the
vehicle 12 to make spot turns to the left or the right about a
vertical axis.
When forward-reverse spool valve 202 is in the reverse position,
hydraulic fluid entering the valve 202 through power port 206 exits
the valve 202 through power port 212 and flows to the track drive
motor 32 via conduits 254, 44 and 46 thereby driving the track
drive motor 32 in the reverse direction. Most of the hydraulic
fluid passing through track drive motor 32 flows therefrom through
conduits 40, 42 and 252 to power port 210 of spool valve 202. The
hydraulic fluid entering power port 210 passes through spool valve
202 and exits from power port 208 to return to the second port 20b
of the pump 20 via conduits 246, 248 and 24.
When forward-reverse spool valve 204 is in the reverse position,
hydraulic fluid entering port 218 of the spool valve 204 exits
therefrom through power port 224 and flows through conduits 258, 56
and 62 to track drive motor 38 thereby driving track drive motor 38
in the reverse direction. Most of the hydraulic fluid passing track
drive motor 38 flows therefrom through conduits 52, 60 and 256 to
power port 222 of spool valve 204. Hydraulic fluid entering power
port 222 passes through spool valve 204 and exits from power port
220 to return to the second port 20b of the pump 20 via conduits
250, 248 and 24.
When track drive motors 32 and 38 are driven in the reverse
direction, excess hydraulic fluid volume bypassed by the internal
valving of the track drive motors 32 and 38 is directed from bypass
outlets 92 and 110, respectively, back to the reservoir 26 as
previously described in detail for the forward operation of the
track drive motors 32 and 38.
It will be readily apparent to those skilled in the art that the
valving described for providing the reversing of the flow of
hydraulic fluid to the track drive motors 32 and 38 may be actuated
in any number of well-known ways. One such way would be by the
application of direct mechanical force to the valves 202 and 204
either in substitution for the hydraulic actuation means previously
described, or as a back-up actuation system in addition to the
hydraulic actuation system. Another suitable actuation means would
be the utilization of electric solenoids for actuation of the
valves 202 and 204.
Automatic control of the output of track drive motors 32 and 38 is
accomplished by properly setting the sensor control assembly 72
such that the tracer 82 will properly engage the string-line or
grade-line 84 to provide actuation of the hydraulic differential
flow control valve 270. When the sensor control assembly 72 is
properly adjusted on the apparatus 10, as illustrated in FIG. 1,
the shut-off valve 86 is placed in the open position to permit the
flow of pressurized hydraulic fluid from the pump 20 through
conduits 22, 118, 278 and 74 to the inlet port 272 of the hydraulic
differential flow control valve 270.
The forward-reverse control valve 186 is placed in the forward
position thereby causing the spool valves 202 and 204 to be placed
in the forward position when the pump 20 is driven by the engine
through the power take-off, as shown in FIG. 2. When the apparatus
10 is in proper alignment with the string line 84, as sensed by the
sensor control assembly 72, pressurized hydraulic fluid from the
pump 20 passes through the appropriate conduits through the
differential valve 114 and into the flow divider 120 where the
hydraulic fluid entering power inlet 126 thereof is equally divided
and emanates from the flow divider 120 through the first and second
power outlets 128 and 130 in streams having substantially equal
flow rates. The hydraulic fluid emanating from the power outlets
128 and 130 enters the flow compensator 176 through the first and
second power inlets 178 and 180 thereof, respectively. Assuming
that the loads encountered by track drive motors 32 and 38 are
equal, the separate streams of hydraulic fluid entering the first
and second power inlets 178 and 180 exit the first and second power
outlets 182 and 184, respectively, of the flow compensator 176 at
equal flow rates. The hydraulic fluid emanating from the first
power outlet 182 flows through appropriate conduits and the spool
valve 202 to the track drive motor 32 thereby driving the motor 32
in a forward direction. Similarly, the hydraulic fluid emanating
from the second power outlet 184 flows through appropriate conduits
and the spool valve 204 to the track drive motor 38 thereby driving
the motor 38 in the forward direction.
Since the rates of flow of hydraulic fluid exiting from the first
and second power outlets 182 and 184 of the flow compensator 176
are equal, the respective track drive motors 32 and 38 are
therefore driven at the same speed. It will, therefore, be readily
apparent that the apparatus 10 will then be driven alongside the
string line 84 on a path parallel thereto.
If for some reason the apparatus 10 should deviate from the desired
path parallel to the string line 84, the sensor control assembly 72
will sense the movement of the apparatus 10 away from or into the
string line 84 and, through the sensor unit 80 and the tracer 82,
the hydraulic differential flow control valve 270 will be actuated
to cause automatic correction of the path of the apparatus 10 to
bring it back to the desired path parallel to the string line
84.
If the apparatus 10 deviates from the desired path toward the
string line 84 the deviation is sensed by the sensor control
assembly 72 which causes the hydraulic differential flow control
valve 270 to be actuated by the sensor unit 80 causing hydraulic
fluid to emanate from the signal outlet port 276 while there is no
flow of hydraulic fluid emanating from the signal outlet port 274.
The hydraulic fluid exiting from the signal outlet port 276 flows
through conduits 78 and 162 into the first inlet 158 and out the
outlet 144 of shuttle valve 142. The hydraulic fluid exiting from
the outlet 144 flows through conduit 146 into the second signal
inlet 124 of the flow divider 120.
As best shown in FIG. 3, the hydraulic fluid entering the second
signal inlet 124 of the flow divider 120 flows into the annular
chamber 324 formed therein and exerts hydraulic pressure on the
valve member 282 thereby urging the valve member 282 to the left
within the valve body 280, as viewed in FIG. 3. The hydraulic fluid
within the annular chamber 324 flows therefrom through orifice 340
into chamber 352 in the valve member 282. As the hydraulic fluid
flows through the orifice 340, the pressure thereof drops to that
of the hydraulic fluid within the chamber 352.
Since hydraulic fluid is entering the second signal inlet 124 while
there is no flow of hydraulic fluid entering the first signal inlet
122, the hydraulic pressure urging the valve member 282 to the left
is greater than the hydraulic pressure urging the valve member 282
to the right. Due to this pressure differential being exerted on
the valve member 282, the valve member 282 is displaced to the left
an amount proportional to the differential in these two hydraulic
pressures thereby overcoming, to some extent, the urging of spring
assembly 358.
When the valve member 282 moves from the center position within the
valve body 280 to the left, it will be readily apparent that the
cross-sectional area of fluid communication between the chamber 352
and the third annular chamber 314 afforded by the ports 356 is
increased an amount proportional to the displacement of the valve
member 282 to the left. Similarly, it will also be readily apparent
that the cross-sectional area of fluid communication between the
chamber 352 and the second annular chamber 306 afforded by the
ports 354 is decreased in an amount proportional to the
displacement of the valve member 282 to the left within the valve
body 280.
As a result of the previously described displacement of the valve
member 282 to the left within the valve body 280, in response to
the differential hydraulic signal received from the sensor control
assembly 72, the rate of flow of hydraulic fluid emanating from the
third annular chamber 314 through the second power outlet 130 is
proportionally greater than the rate of flow of the hydraulic fluid
emanating from the second annular chamber 306 through the first
power outlet 128. The stream of hydraulic fluid emanating from the
second power outlet 130 flows through the flow compensator 176 and
the spool valve 204 in the previously described conduits to the
track drive motor 38 while the stream of hydraulic fluid emanating
from the first power outlet 128 flows through the flow compensator
176 and the spool valve 202 and the previously described conduits
to the track drive motor 32. Since the rate of flow of the stream
of hydraulic fluid entering track drive motor 38 is proportionally
greater than the rate of flow of the stream of hydraulic fluid
entering track drive motor 32, the speed of the track drive motor
38 is increased proportionally over the speed of the track drive
motor 32 thereby causing the apparatus 10 to swing away from the
string line 84 back toward its proper line of direction parallel to
the string line 84.
As the apparatus 10 approaches proper alignment with the string
line 84, the sensor control assembly 72 senses the approach of the
apparatus 10 toward proper alignment and causes the hydraulic
differential flow control valve 270 to be gradually actuated back
into its neutral position so that hydraulic fluid ceases to emanate
from the signal outlet port 276 thereof when the apparatus 10 is
again in proper alignment with the string line 84. When hydraulic
fluid flow from the control valve 270 ceases, the hydraulic
pressures acting on the opposite ends of the valve member 282 of
the flow divider 120 are equal thus permitting the valve member 282
to be properly centered within the valve body 280 by the spring
assembly 358. When the valve member 282 is in the center position
the rates of flow of hydraulic fluid emanating from the first and
second power outlets 128 and 130 of the flow divider 120 are
substantially equal and the resulting speeds of the track drive
motors 32 and 38 are also substantially equal.
If the apparatus 10 deviates from the desired path away from the
string line 84, the deviation is sensed by the sensor control
assembly 72 which causes the hydraulic differential control valve
270 to be actuated by the sensor unit 80 causing hydraulic fluid to
emanate from the signal outlet port 274 while there is no flow of
hydraulic fluid emanating from the signal outlet port 276. The
hydraulic fluid exiting from the signal outlet port 274 flows into
the first signal inlet 122 of the flow divider 120 via the
previously described conduits and shuttle valve 136.
As described above, the hydraulic fluid entering the second signal
inlet 124 of the flow divider 120 flows into the annular chamber
324 and exerts hydraulic pressure on the valve member 282 thereby
urging the valve member 282 to the left within the valve body 280,
as viewed in FIG. 3. The hydraulic fluid within the annular chamber
324 flows therefrom through orifice 340 into chamber 352 in the
valve member 282. As the hydraulic fluid flows through the orifice
340 the pressure thereof drops to that of the hydraulic fluid
within the chamber 352.
Since hydraulic fluid is entering the first signal inlet 122 while
there is no flow fo the hydraulic fluid entering the second signal
inlet 124, the hydraulic pressure urging the valve member 282 to
the right is greater than the hydraulic pressure urging the valve
member 282 to the left. Due to this pressure differential being
exerted on the valve member 282, the valve member 282 is displaced
to the right in an amount proportional to the differential in these
two hydraulic pressures thereby overcoming, to some extent, the
urging of spring assembly 358.
When the valve member 282 moves from the center position within the
valve body 280 to the right, it will be readily apparent that the
cross-sectional area of fluid communication between the chamber 352
and the third annular chamber 314 afforded by the ports 356 is
decreased an amount proportional to the displacement of the valve
member 282 to the right. Similarly, it will be also readily
apparent that the cross-sectional area of fluid communication
between the chamber 352 and the second annular chamber 306 afforded
by the ports 352 is increased an amount proportional to the
displacement of the valve member 282 to the right within the valve
body 280.
As a result of the previously described displacement of the valve
member 282 to the right within the valve body 280, in response to
the differential hydraulic signals received from the sensor control
assembly 72, the rate of flow of hydraulic fluid emanating from the
second annular chamber 306 through the first power outlet 128 is
proportionally greater than the rate of flow of the hydraulic fluid
emanating from the third annular chamber 314 through the second
power outlet 130. As described above, the stream of hydraulic fluid
emanating from the second power outlet 130 flows through the flow
compensator 176 and the spool valve 204 to the track drive motor 38
while the stream of hydraulic fluid emanating from the first power
outlet 128 flows through the flow compensator 176 and the spool
valve 202 to the track drive motor 32. Since the rate of flow of
the stream of hydraulic fluid entering track drive motor 32 is
proportionally greater than the rate of flow of the stream of
hydraulic fluid entering track drive motor 38, the speed of the
track drive motor 32 is increased proportionally over the speed of
track drive motor 38 thereby causing the apparatus 10 to swing back
toward the string line 84 and its proper line of direction parallel
to the string line 84.
As the apparatus 10 approaches proper alignment with the string
line 84, the sensor control assembly 72 senses the approach of the
apparatus 10 toward proper alignment and causes the hydraulic
differential flow control valve 270 to be gradually actuated back
into its neutral position so that hydraulic fluid ceases to emanate
from the signal outlet port 274 thereof when the apparatus 10 is
again in proper alignment with the string line 84. When hydraulic
fluid flow from the control valve 270 ceases, the hydraulic
pressures acting on the opposite ends of the valve member 282 in
the flow divider 120 are equal thus permitting the valve member 282
to be properly centered within the valve body 280 by the spring
assembly 358. When the valve member 282 is in the center position
the rates of flow of hydraulic fluid emanating from the first and
second power outlets 128 and 130 of the flow divider 120 are
substantially equal and the resulting speeds of the track drive
motors 32 and 38 are also substantially equal.
It will be readily apparent to those skilled in the art that the
operation of the sensor control assembly 72 and the flow divider
120 during the forward movement of the apparatus 10 applies equally
when the apparatus 10 is operated in the reverse direction. The
apparatus 10 is placed in condition to operate in the reverse
direction by placing the forward-reverse control valve 186 in the
reverse position thereby causing the spool valves 202 and 204 to be
placed in the reverse position when the pump 20 is driven by the
engine through the power take-off. Automatic correction of the path
of the apparatus 10 when deviating from the proper path parallel to
string line 84 is accomplished just as described above for forward
operation of the apparatus 10.
When the apparatus 10 is moving in the forward direction and is
following the proper path parallel to the string line 84, it is not
uncommon for the track drive motors 32 and 38 driving the apparatus
10 through the respective hydraulically driven track units 16 to
encounter different loads thereby requiring greater power from one
track drive motor than from the other in order for the apparatus 10
to continue along the proper path. The apparatus of the present
invention provides for the automatic adjustment of the power
outlets of the track drive motors through the action of the flow
compensator 176.
As previously described above, when the apparatus 10 is properly
following a path parallel to the string line 84 the flow rates of
the streams of hydraulic fluid emanating from the first and second
power outlets 128 and 130 of the flow divider 120 are equal. When
the track drive motors 32 and 38 are each encountering the same
amount of load, the streams of hydraulic fluid entering the first
and second power inlets 178 and 180 of the flow compensator 176
from the first and second power outlets 128 and 130 of the flow
divider 120, are also equal. The stream of hydraulic fluid entering
the first power inlet 178 flows into the chamber 446 formed in the
valve member 396 through the ports 450.
Similarly, the stream of hydraulic fluid entering the second power
inlet 180 flows into the chamber 448 formed in the valve member 396
through ports 452. The hydraulic fluid in the chamber 446 flows
through ports 454 into the third annular chamber 424 and out
therefrom through the first power outlet 182 of the flow
compensator 176. The hydraulic fluid in the chamber 448 flows
therefrom through the ports 456 into the fourth annular chamber 432
and out therefrom through the second power outlet 184 of the flow
compensator 176.
The stream of hydraulic fluid emanating from the first power outlet
182 flows through the spool valve 202 to the track drive motor 32
through the previously described conduits. The hydraulic stream
emanating from the second power outlet 184 flows therefrom through
the spool valve 204 to the track drive motor 38 through the
previously described interconnecting conduits.
If the track drive motor 32, for example, encounters a greater load
than the track drive motor 38 the rate of flow of hydraulic fluid
into the track drive motor 32 is reduced thus increasing the
pressure of the hydraulic fluid in the conduits interconnecting the
first power outlet 182 and the track drive motor 32 over the
hydraulic pressure of the hydraulic fluid in the conduits
interconnecting the track drive motor 38 and the second power
outlet 184. The increase in hydraulic pressure at the first power
outlet 182 over the hydraulic pressure at the second power outlet
184 is communicated through the ports 454 and 456 into the
respective chambers 446 and 448. Since the hydraulic pressure in
the chamber 446 is greater than the hydraulic pressure in the
chamber 448, the valve member 396 is displaced to the right within
the valve body 394 in an amount proportional to the pressure
differential between the hydraulic fluid in the chamber 446 and the
hydraulic fluid in the chamber 448.
As the valve member 396 is displaced to the right within the valve
body 394, as viewed in FIG. 4, the cross-sectional area of fluid
communication between the chamber 446 and the third annular chamber
424 afforded by the ports 454 is increased while the
cross-sectional area of fluid communication between the chamber 448
and the fourth annular chamber 432 afforded by the ports 456 is
decreased. The maximum displacement of the valve member 396 to the
right within the valve body 394 is mechanically limited by the
abutment of the end face 444 of the valve member 396 with the end
plate 460. It should be noted that when the end face 444 abuts the
end plate 460, fluid communication between the chamber 448 and the
fourth annular chamber 432 through the ports 456 is preferably
completely eliminated.
It will be readily apparent that displacement of the valve member
396 to the right within the valve body 394 will decrease the
cross-sectional area of fluid communication between the second
power inlet 180 and the second power outlet 184 and simultaneously
increase the cross-sectional area of fluid communication between
the first power inlet 178 and the first power outlet 182. In
effect, a dummy load is introduced between the second power inlet
180 and the second power outlet 184 which results in substantially
equal hydraulic pressure drops between the first power inlet 178
and the first power outlet 182, and between the second power inlet
180 and the second power outlet 184. Thus, the hydraulic fluid
streams emanating from the first and second power outlets 128 and
130 of the flow divider 120 will encounter substantially equal
loads regardless of the loads encountered by the track drive motors
32 and 38.
On the other hand, if the track drive motor 38 encounters a greater
load than that encountered by the track drive motor 32, the
pressure of the hydraulic fluid communicating between the chamber
448 and the track drive motor 38 will be increased proportionally
over the pressure of the hydraulic fluid communicating between the
chamber 446 and the track drive motor 32. This differential in
hydraulic pressure causes the displacement of the valve member 396
to the left within the valve body 394 in an amount proportional to
the pressure differential between the hydraulic fluid in the
chamber 448 and the hydraulic fluid in the chamber 446.
As the valve member 396 is displaced to the left in the valve body
394, as viewed in FIG. 4, the cross-sectional area of fluid
communication between the chamber 448 and the fourth annular
chamber 432 afforded by the ports 456 is increased while the
cross-sectional area of fluid communication between the chamber 446
and the third annular chamber 424 is decreased. The maximum
displacement of the valve member 396 to the left within the valve
body 394 is mechanically limited by abutment of the end face 442 of
the valve member 396 with the end plate 458. It should be noted
that when the end face 442 abuts the end plate 458, fluid
communication between the chamber 446 and the third annular chamber
424 through the ports 454 is preferably completely eliminated.
It will be readily apparent that the displacement of the valve
member 396 to the left within the valve body 394 will increase the
cross-sectional area of fluid communication between the second
power inlet 180 and the second power outlet 184 and simultaneously
decrease the cross-sectional area of fluid communication between
the first power inlet 178 and the first power outlet 182. In
effect, as noted above, a dummy load is introduced between the
first power inlet 178 and the first power outlet 182 which results
again in substantially equal hydraulic pressure drops between the
first power inlet 178 and the first power outlet 182, and between
the second power inlet 180 and the second power outlet 184. Thus,
again, the hydraulic fluid streams emanating from the first and
second power outlets 128 and 130 of the flow divider 120 will
continue to encounter substantially equal loads regardless of the
loads encountered by the track drive motors 32 and 38.
It should also be noted that the operation of the flow compensator
176 when the apparatus 10 is in proper condition to move in the
reverse direction is identical to that previously described. The
displacement of the valve member 396 in either direction within the
valve body 394 in response to load variations encountered by the
track drive motors 32 and 38 is proportional to the differential
between the respective loads encountered thereby. It will be
readily apparent that as the differential between the loads
encountered by the track drive motors continually increases or
decreases, the resulting displacement of the valve member 396
within the valve body 394 continuously controls the hydraulic
pressure drops between the first power inlet 178 and first power
outlet 182, and between the second power inlet 180 and second power
outlet 184, thus maintaining these hydraulic pressure drops
substantially equal regardless of the loads encountered by the
track drive motors 32 and 38.
It should also be noted that provision has been made for manually
overriding the automatic control of the apparatus 10 by the
automatic control assembly 18 by means of the hydraulic manual
steering control assembly 64. The hydraulic manual steering control
assembly 64 also provides the primary means of steering the
apparatus 10 when the shut-off valve 86 is placed in the closed
position thereby deactivating the previously described sensor
control assembly 74.
If the shut-off valve 86 is in the closed position with the sensor
control assembly 72 deactivated, and the operator desires to steer
the forwardly moving apparatus 10 to the right, the operator moves
the control lever 268 in the direction R as shown in FIG. 2. The
movement of the control lever 268 in the direction R causes the
hydraulic fluid entering the hydraulic differential flow control
valve 260 through the inlet port 262 to emanate from the signal
outlet 266 in a stream having a greater flow rate than the stream
of hydraulic fluid emanating from the signal outlet 264. The
differential in the flow rates of the hydraulic fluid streams
emanating from the signal outlets 266 and 264 is proportional to
the magnitude of the movement of the control lever 268 by the
operator. The stream of hydraulic fluid emanating from the signal
outlet 266 flows through the previously described conduits to the
shuttle valve 142 and from the shuttle valve 142 through the
conduit 146 to the annular chamber 324 of the flow divider 120. The
stream of hydraulic fluid emanating from the signal outlet 264
flows through the previously described conduits to shuttle valve
136 and from shuttle valve 136 through conduit 140 to the annular
chamber 322 of the flow divider 120.
As described in detail above for the automatic operation of the
automatic control assembly 18, the difference in the hydraulic
pressures acting on the opposite ends of the valve member 282
causes the displacement thereof to the left, as viewed in FIG. 3,
within the valve body 280 and results in a proportionally greater
flow of hydraulic fluid to the track drive motor 38 than the flow
rate of hydraulic fluid to the track drive motor 32 thereby
increasing the speed of the track drive motor 38 over the speed of
the track drive motor 32 and causing the apparatus 10 to swing to
the right.
It will be readily apparent to those skilled in the art that the
movement by the operator of the control lever 268 in the direction
L, as shown in FIG. 2, will cause displacement of the valve member
282 to the right within the valve body 280 of the flow divider 120,
thereby causing the track drive motor 32 to operate at a speed
greater than that of the track drive motor 38 thereby causing the
apparatus 10 to swing to the left.
The operation of the hydraulic manual steering control assembly 64
when used to override the control signals of the sensor control
assembly 72 is identical to that described in detail above.
Assuming the shut-off valve 86 is in the open position and the
sensor control assembly 72 is activated, it will be readily
apparent to those skilled in the art that if the flow rate of
hydraulic fluid emanating from the signal outlet 264 of the
hydraulic steering control assembly 74 is greater than the flow
rate of the hydraulic fluid emanating from the signal outlet 274 of
the sensor control assembly 72, the shuttle valve 136 will check
the flow of hydraulic fluid entering the first inlet 148 thereof
thereby allowing the hydraulic fluid entering the second inlet 150
to pass into the check valve and out through the outlet 138 to flow
to the flow divider 120 through conduit 140. Similarly, if the flow
rate of hydraulic fluid emanating from the signal outlet 266 of the
hydraulic manual steering control assembly 64 is greater than the
flow rate of hydraulic fluid emanating from the signal outlet port
276 of the sensor control assembly 72, the shuttle valve 142 will
act to close the first inlet 158 thereof and open the second inlet
160 thereof, thereby passing hydraulic fluid into the check valve
142 to exit from the outlet 144 thereof and flow to the flow
divider 120 through conduit 146.
It should be noted that when the sensor control assembly 72 is
deactivated by placing the shut-off valve 86 in the closed
position, the shuttle valves 136 and 142 will operate to close the
respective inlets 148 and 158 thereof. It should also be noted that
when the sensor control assembly 72 is activated by placing the
shut-off valve 86 in the open position and when the hydraulic
manual steering control assembly 64 is in the neutral position, the
shuttle valves 136 and 142 will operate to close the respective
inlets 150 and 160 thereof.
DESCRIPTION OF THE EMBODIMENT OF FIGS. 5, 6, 7 AND 8
FIG. 5 generally illustrates, in schematic form, a slightly
modified automatic control assembly 18a in fluid communication with
the hydraulic manual steering control assembly 64, the sensor
control assembly 72, the track drive pump 20, the shut-off valve
86, and the track drive motors 32 and 38 as previously described in
detail. The track drive motors 34 and 36 are not illustrated in
FIG. 5 for the same reason as explained in the discussion of the
automatic control assembly 18 above.
The automatic control assembly 18a comprises a bidirectional
differential valve 500. The bi-directional differential valve 500
includes a first inlet-outlet port 502, a second inlet-outlet port
504, a high pressure outlet port 506 and a low pressure return port
508. The first inlet-outlet port 502 is in fluid communication with
the first port 20a of the track drive pump 20 via conduits 118 and
22.
The automatic control assembly 18a also includes a slightly
modified flow divider 120a having first and second signal inlets
122 and 124, a power inlet 126 and first and second power outlets
128 and 130. The power inlet 126 of the flow divider 120a is in
fluid communication with the second inlet-outlet port 504 of the
differential valve 500 via conduit 134.
A shuttle valve 136 having an outlet 138 is in fluid communication
with the first signal inlet 122 of the flow divider 120a via
conduit 140. A second shuttle valve 142 having an outlet 144 is in
fluid communication with the second signal inlet 124 of the flow
divider 120a via conduit 146.
The shuttle valve 136 further includes a first inlet 148 and a
second inlet 150. The first inlet 148 is in fluid communication
with the sensor control assembly 72 via conduits 152 and 76. The
second inlet 150 is in fluid communication with the hydraulic
manual steering control assembly 64 via conduits 154, 156 and
68.
The second shuttle valve 142 further includes a first inlet 158 and
a second inlet 160. The first inlet 158 is in fluid communication
with the sensor control assembly 72 via conduits 162 and 78. The
second inlet 160 is in fluid communication with the hydraulic
manual steering control assembly 64 via conduits 164, 166 and
70.
The second inlet 150 of the shuttle valve 136 is also in fluid
communication with the low pressure return port 508 of the
bi-directional differential valve 500 via conduits 154, 510 and 512
with an orifice 514 interposed in conduit 510 intermediate conduits
154 and 512. The second inlet 160 of the shuttle valve 142 is also
in fluid communication with the low pressure return port 508 of the
bi-directional differential valve 500 via conduits 164, 516 and 512
with an orifice 518 interposed in conduit 516 intermediate conduits
164 and 512.
The outlet 138 of shuttle valve 136 is in fluid communication with
the low pressure return port 508 of the bi-directional differential
valve 500 via conduits 140, 520 and 512 with an orifice 522
interposed in conduit 520 intermediate conduits 140 and 512. The
outlet 144 of shuttle valve 142 is also in fluid communication with
the low pressure return port 508 of the bi-directional differential
valve 500 via conduits 146, 524 and 512 with an orifice 526
interposed in conduit 524 intermediate conduits 146 and 512.
The automatic control assembly 18a further includes a slightly
modified flow compensator 176a. The flow compensator 176a includes
first and second power inlets 178 and 180, and first and second
power outlets 182 and 184. The flow compensator 176a further
includes first and second reverse-compensation inlets 528 and
530.
The hydraulic manual steering control assembly 64 preferably
includes a conventional hydraulic differential flow control valve
260, described above, having an inlet port 262 and a pair of signal
outlet ports 264 and 266. The valve 260 may be suitably actuated by
a manually operated control lever or the like as shown at 268. The
inlet port 262 of the control valve 260 is in fluid communication
with the high pressure outlet port 506 of the bi-directional
differential valve 500 via conduits 66, 532 and 534. The signal
outlet 264 is in fluid communication with the conduit 68 and the
signal outlet 266 is in fluid communication with the conduit
70.
The sensor control assembly 72 includes a conventional hydraulic
differential flow control valve 270, described above, having an
inlet port 272 and a pair of signal outlet ports 274 and 276. The
signal outlet port 274 is in fluid communication with conduit 76
and the signal outlet port 276 is in fluid communication with
conduit 78. The inlet port 272 is in fluid communication with the
high pressure outlet port 506 of the bi-directional differential
valve 500 via conduits 74, 536 and 534. As described above, a
shut-off valve 86 is installed in the conduit 74 intermediate the
inlet port 272 of the sensor control assembly 72 and the automatic
control assembly 18a. The hydraulic differential flow control valve
270 is of conventional construction and its operation will be
readily apparent to those skilled in the art.
The sensor unit 80 is operatively connected to the hydraulic
differential flow control valve 270 of the sensor control assembly
72 for actuation of the valve 272 in response to variation in the
position of the sensor unit 80 relative to the string line 84. The
sensor unit 80 may be directly connected to the valve 272 by
mechanical means or may be connected electrically to the valve 272
to provide actuation thereof. Such sensor units are well-known in
the art and need not be described in detail herein.
The automatic control assembly 18a further includes a hydraulically
actuated selector spool valve 538 having first and second control
ports 540 and 542, first and second inlets 544 and 546, and first
and second outlets 548 and 550. The first control port 540 is in
fluid communication with the first inlet-outlet port 502 of the
bi-directional differential valve 500 via conduits 552 and 118. The
second control port 542 is in fluid communication with the second
port 20b of the track drive pump 20 via conduits 554, 556 and 24.
The second control port 542 is also in fluid communication with the
track drive motor 32 via conduits 554, 558, 44 and 46. The second
control port 542 is further in fluid communication with the track
drive motor 38 via conduits 554, 560, 56 and 62.
The first port 32a of the track drive motor 32 is in fluid
communication with the first power outlet 182 of the flow
compensator 176a via conduits 40, 42 and 562. The first port 38a of
the track drive motor 38 is in fluid communication with the second
power outlet 184 of the flow compensator 176a via conduits 52, 60
and 564.
The first power outlet 128 of the flow divider 120a is in fluid
communication with the first power inlet 178 of the flow
compensator 176a via conduit 566. The first inlet 544 of the
selector valve 538 is in fluid communication with the first power
outlet 128 of the flow divider 120a via conduits 568 and 566. The
second power outlet 130 of the flow divider 120a is in fluid
communication with the second power inlet 180 of the flow
compensator 176a via conduit 570. The second inlet 546 of the
selector valve 538 is in fluid communication with the second power
outlet 130 of the flow divider 120a via conduits 572 and 570.
As shown in FIG. 6, the flow divider 120a comprises a valve body
280 and a slightly modified valve member 282a slidingly disposed
therein. The valve body 280 is identical to the valve body 280
described above for the flow divider 120 and therefore will not be
described in detail again. The valve member 282a is substantially
identical to the previously described valve member 282 of the flow
divider 120 and the same reference characters will be used to
designate those portions of the valve member 282 which are
unchanged therefrom.
The cylindrically shaped outer periphery 326 of the valve member
282a has a diameter sized to provide a substantially fluid-tight
seal between the outer periphery 326 and the walls of the bore 284
through the valve body 280. A cylindrically shaped extension 328 is
formed on one end portion 329 of the valve member 282a and extends
into the annular chamber 324 of the valve body 280. The extension
328 is coaxial with the outer periphery 326 of the valve member
282a. An annular shoulder 330 interconnects the cylindrical surface
332 of the extension 328 and the cylindrically shaped outer
periphery 326.
A bore 336a is formed in the valve member 282a intersecting the end
portion 338 thereof. The bore 336a extends only partially through
the valve member 282a thereby forming a chamber 252a therein. A
slightly modified plug 344a having no aperture formed therein is
threadedly secured in the bore 336a at the end portion 338 of the
valve member 282a.
Two ports 350 are formed in the valve member 282a providing
communication between the chamber 352a formed therein and the
central annular chamber 298 of the valve body 280.
A plurality of ports 354 are formed in the valve member 282a
proximate to the end portion 338 thereof. The ports 354 provide
fluid communication between the chamber 352a and the outer
periphery 326 of the valve member 282a. Similarly, a plurality of
ports 356 are formed in the valve member 282a proximate to the end
portion 329 thereof. The ports 356 provide fluid communication
between the chamber 352a and the outer periphery 326 of the valve
member 282a. Preferably, the valve member 282a includes 10 ports
354 and 10 ports 356. The arrangement of the ports 354 and 356 in
the valve member 282a is identical to the arrangement previously
described for the valve member 282 and will not be described in
detial again. It should be noted that the valve member 282a is
positioned in its center or medial position within the valve body
280 as shown in FIG. 6.
As will be readily apparent to those skilled in the art, as the
valve member 282a moves either left or right of the central or
medial position, the cross-sectional area of ports 354 and 356
providing fluid communication between the chamber 352a and the
outer periphery 326 of the valve member 282a always remains equal
to the total cross-sectional area of 10 ports.
The valve member 282a is urged into its central or medial position
relative to the valve body 280, as shown in FIG. 6, by means of the
spring assembly 358 described in detail above. The spring assembly
358 is retained on the cylindrically shaped extension 328 by means
of a snap ring 372 disposed in an annular groove 374 formed in the
cylindrical surface 332 of the extension 328. The previously
described annular sleeve 378 is disposed within the annular chamber
324 of the valve body 280 with the first end face 380 thereof
abutting the spring assembly 358 and with the second end face 382
thereof abutting the end plate 386.
FIG. 7 illustrates a slightly modified flow compensator 176a
comprising a slightly modified valve body 394a and a slightly
modified valve member 396a slidably disposed therein. Since the
slightly modified flow compensator 176a is identical in many
respects to the previously described flow compensator 176, like
elements will be identified by the same reference characters used
previously.
The slightly modified valve body 394a differs from the previously
described valve body 394 only in the addition of the first and
second reverse compensation inlets 528 and 530 which provide fluid
communication between the exterior of the valve body 394a and the
bore 398 extending through the valve body 394a.
The valve member 396a is slidably disposed in the bore 398 of the
valve body 394a. The cylindrically shaped outer periphery 440a of
the valve member 396a has a diameter sized to provide a
substantially fluid-tight seal between the outer periphery 440a and
the walls of the bore 398. The valve member 396a includes opposite
end faces 442a and 444a, each lying in a plane normal to the
longitudinal axis of the valve member 396a. A cylindrically shaped
chamber 446a is formed in one end of the valve member 396a with one
end thereof intersecting end face 442a. A counterbore 574 is formed
in the chamber 446a intersecting the end face 442a. A second
cylindrically shaped chamber 448a is formed in the opposite end of
the valve member 396a with one end thereof intersecting the end
face 444a. A counterbore 576 is formed in the chamber 448a
intersecting the end face 444a. It should be noted that the
chambers 446a and 448a do not communicate with each other within
the valve member 396a.
First and second circumferential grooves 578 and 580 are formed in
the medial portion of the valve member 396a. The circumferential
grooves 578 and 580 communicate respectively with the first and
second reverse compensation inlets 528 and 530 of the valve body
394a. Each groove 578 and 580 is of sufficient width to provide
full fluid communication with the respective inlets 528 and 530
throughout the full range of displacements of the valve member 396a
within the valve body 394a.
A first transverse bore 582 extends transversely through the valve
member 396a communicating at each end thereof with the first
circumferential groove 578. The bore 582 intersects the previously
described bore 446a providing fluid communication between the first
reverse compensation inlet 528 of the valve body 294a and the end
face 442a of the valve member 396a. A second transverse bore 584
extends transversely through the valve member 396a with its
opposite ends intersecting the second circumferential groove 580.
The bore 582 intersects the cylindrical chamber 448a thereby
providing fluid communication between the second reverse
compensation inlet 530 of the valve body 394a and the end face 444a
of the valve member 396a.
First and second longitudinal grooves 586 and 588 are formed in the
cylindrically shaped outer periphery 440a of the valve member 396a.
The grooves 586 and 588 provide fluid communication between the
first annular chamber 408 and the third annular chamber 424 of the
valve body 394a. The longitudinal groove 586 includes a first end
wall 590 and a second end wall 592. The second longitudinal groove
588 includes a first end wall 594 and a second end wall 596. While
the grooves 586 and 588 are preferred other forms of passages, such
as an annular groove or the like, may be substituted therefor.
Third and fourth longitudinal grooves 598 and 600 are formed in the
cylindrically shaped outer periphery 440a of the valve member 396a.
The longitudinal grooves 598 and 600 provide fluid communication
between the second annular chamber 416 and the fourth annular
chamber 432 of the valve body 394a. The longitudinal groove 598
includes a first end wall 602 and a second end wall 604. The
longitudinal groove 600 includes a first end wall 606 and a second
end wall 608. While the grooves 598 and 600 are preferred, other
forms of passages, such as an annular groove or the like, may be
substituted therefor.
The valve member 396a is of such length that when it is displaced
to the left, as viewed in FIG. 7, with the end face 442a thereof
abutting the end plate 458, the cross-sectional area of fluid
communication between the annular chambers 408 and 424 of the valve
body 394a is closed off entirely by the respective end walls 590
and 594 of the grooves 586 and 588. Alternately, when the valve
member 396a is displaced to the extreme right, as viewed in FIG. 7,
with the end face 444a thereof abutting the end plate 460, the
cross-sectional area of fluid communication between the annular
chambers 416 and 432 of the valve body 394a is closed off entirely
by the respective end walls 606 and 604 of the grooves 598 and 600.
It should be noted that regardless of the relative position of the
valve member 396a within the valve body 394a the cross-sectional
area of fluid communication between the grooves 586 and 588 and the
annular chamber 424 will preferably be equal to or greater than the
cross-sectional area of fluid communication between the grooves 586
and 588 and the annular chamber 408. Similarly, the cross-sectional
area of fluid communication between the grooves 598 and 600 and the
annular chamber 432 will preferably be equal to or greater than the
cross-sectional area of fluid communication between the grooves 598
and 600 and the annular chamber 416.
It should be noted that the previously described flow divider 120a
and the flow compensator 176a may be advantageously housed in a
single unitary valve body. Such a valve body would include all of
the features described for the valve bodies 280 and 394a of the
flow divider 120a and flow compensator 176a, respectively, and
would place the first and second power outlets 128 and 130 of the
flow divider 120a in fluid communication with the first and second
power inlets 178 and 180, respectively, of the flow compensator
176a within the combined valve body. Furthermore, the end plates
458 and 384 may be advantageously combined into one end plate as
may the end plates 460 and 386. In either of the described
configurations the functions of the flow divider 120a and the flow
compensator 176a would be identical.
As shown in FIG. 8, the bi-directional differential valve 500
comprises a valve body 610 and a valve member 612 slidably disposed
therein. The valve body 610 includes a bore 614 extending
therethrough and intersecting the opposite end of portions 616 and
618 thereof.
A counterbore 620 is formed in the bore 614 intersecting the end
portion 616 and forming an annular wall 622 therein. A second
counterbore 624 is formed in the bore 614 intersecting the opposite
end portion 618 of the valve body 610 and forming an annular wall
626 therein.
The counterbore 620 forms a first annular chamber 628 within the
valve body 610 adjacent the end portion 616 thereof. The
counterbore 624 forms a second annular chamber 630 within the valve
body 610 adjacent the end portion 618 thereof.
A third annular chamber 632 is formed in the valve body 610 coaxial
with the bore 614 and includes opposite annular walls 634 and 636
interconnected by a cylindrically shaped annular surface 638. A
fourth annular chamber 640 is formed in the valve body 610 coaxial
with the bore 614 therethrough and includes opposite annular walls
642 and 644 interconnected by a cylindrically shaped annular
surface 646.
The previously mentioned high pressure outlet port 506 communicates
with the bore 614 intermediate the third and fourth annular
chambers 632 and 640 thereby providing fluid communication between
the bore 614 and the exterior of the valve body 610. A threaded
plug 648 is threadedly secured in the counterbore 620. The threaded
plug 648 includes an aperture 650 formed therein coaxial with the
bore 614 and providing the previously described first inlet-outlet
port 502 of the valve 500. The plug 648 further includes an
inwardly facing annular end face 652 formed thereon. A second
threaded plug 654, identical to the threaded plug 648, is
threadedly secured in the counterbore 624 of the valve body 610.
The aperture 650 formed in the plug 654 provides the previously
mentioned second inlet-outlet port 504 of the valve 500. The plug
654 also includes an inwardly facing annular end face 652 formed
thereon.
The valve member 612 includes a cylindrically shaped outer
periphery 656 and opposite end portions 658 and 660. A first
circumferential groove 662 is formed in the outer periphery 656 of
the valve member 612 and includes opposite annular walls 664 and
666 interconnected by a cylindrically shaped circumferential
surface 668. A second circumferential groove 670 is formed in the
outer periphery 656 of the valve member 612 and includes opposite
annular walls 672 and 674 interconnected by a cylindrically shaped
circumferential surface 676.
The valve member 612 further includes opposite blind bores 678 and
680 formed therein coaxial with the axis of the valve member 612. A
first counterbore 682 is formed in the blind bore 678 and a second
counterbore 684 is formed in the blind bore 680. The bore 678 and
the counterbore 682 formed therein form a chamber 686 in the valve
member 612. Similarly, the bore 680 and the counterbore 684 formed
therein form a chamber 688 in the valve member 612.
A pair of ports 690 provide fluid communication between the bore
678 and the cylindrically shaped circumferential surface 668 of the
valve member 612. A pair of ports 692 provide fluid communication
between the bore 680 and the cylindrically shaped circumferential
surface 676 of the valve member 612.
The valve member 612 is yieldably urged into its normal, centered
position, as shown in FIG. 8, by means of a pair of coil
compression springs 694 and 695 disposed respectively in the
counterbores 682 and 684 of the valve member 612. Each coil spring
694 and 695 is secured at the end thereof opposite the valve member
612 in an annular spring seat 696 having an L-shaped cross-section.
The spring seats 696 bear respectively against the end faces 652 of
the threaded plugs 648 and 654.
The previously described low pressure return port 508 is in fluid
communication with the bore 614 through the valve body 610 via
passageways 698 and 700 formed in the valve body 610. The
passageway 698 communicates with the bore 614 intermediate the
first annular chamber 628 and the third annular chamber 632 formed
in the valve body 610. The passageway 700 communicates with the
bore 614 intermediate the second annular chamber 630 and the fourth
annular chamber 640 formed in the valve body 610.
Operation of the Embodiment of FIGS. 5, 6, 7 and 8
In operation, the track drive pump 20 is driven by the engine and
power take-off (not shown) to provide a source of pressurized
hydraulic fluid. The pressurized hydraulic fluid provided by the
pump 20 may be in either a low pressure range of from 600 to 1,500
psi or in a high pressure range of from 1,500 to 3,500 psi. While
these pressure ranges are disclosed as preferable for the operation
of this embodiment of the present invention, it is not intended
that the present invention be limited thereby.
Forward and reverse operation of the apparatus 10 is provided by
alternately driving the track drive pump 20 in what will be called
the forward direction or, alternately, driving the pump 20 in the
reverse direction. This particular mode of operation is contrasted
with the previously described mode of operation wherein the track
drive motors 32 and 38 were reversed by means of actuation of
forward-reverse spool valves which served to switch the point of
introduction of the stream of pressurized hydraulic fluid in the
respective track drive motors 32 and 38.
Referring now to FIG. 5, it will first be assumed that the
apparatus 10 is to be driven in the forward direction which is
accomplished by driving the pump 20 in a forward direction. The
pressurized hydraulic fluid is directed from the first port 20a of
the pump 20 through conduits 22 and 118 to the first inlet-outlet
port 502 of the bi-directional differential valve 500. The
pressurized hydraulic fluid entering the port 502 forces the valve
member 612 downwardly against the resistance of the lower coil
spring 695 as best shown in FIG. 9. When the valve member 612 is
displaced downwardly to a point where the annular wall 666 thereof
is slightly below the annular wall 642 of the valve body 610,
hydraulic fluid will flow from the port 502 through the first
annular chamber 628 of the valve body 610, the chamber 686 in the
valve member 612, through the ports 690 into the third annular
chamber 632 of the valve body 610, from the chamber 632 into the
chamber 640 through the interconnecting portion of the bore 614,
from the chamber 640 through the ports 692 in the valve member 612
into the chamber 688, from the chamber 688 of the valve member 612
into the second annular chamber 630 of the valve body 610, and from
the chamber 630 out through the second inlet-outlet port 504 of the
valve 500. As the hydraulic fluid passes from the third annular
chamber 632 into the fourth annular chamber 640 of the valve body
610, the hydraulic pressure thereof is reduced due to the
constriction in the path of flow caused by the proximity of the
annular wall 666 to the annular wall 642. The amount of this
hydraulic pressure drop is controlled by the spring rate of the
lower coil spring 695 which spring resists the downward
displacement of the valve member 612 within the valve body 610. The
spring rate of the lower spring 695 is such that the pressure drop
is preferably approximately 75 psi.
It will also be readily apparent that a portion of the hydraulic
fluid in the fourth annular chamber 640 will flow outwardly from
the bore 614 through the low pressure return port 508. It will also
be readily apparent that a portion of the hydraulic fluid flowing
from the third annular chamber 632 will pass outwardly from the
bore 614 in the valve body 610 through the high pressure outlet
port 506.
It should be noted, therefore, that when the pump 20 is operating
in the forward direction, the pressure of the hydraulic fluid
exiting from the high pressure outlet port 506 is substantially
equal to the pressure of the hydraulic fluid entering the first
inlet-outlet port 502, and the hydraulic pressure of the streams of
hydraulic fluid exiting from the second inlet-outlet port 504 and
returning to the low pressure return port 508 are each preferably
approximately 75 psi less than the hydraulic pressure of the stream
of hydraulic fluid exiting from the high pressure outlet port
506.
The stream of hydraulic fluid emanating from the high pressure
outlet port 506 of the bi-directional differential valve 500 flows
in part to the inlet port 272 of the sensor assembly 72 via
conduits 534, 536 and 74. In order for the pressurized hydraulic
fluid to reach the inlet port 272 of the sensor control assembly 72
it is necessary for the shut-off valve 86, in the conduit 74, to be
in its open position. If the shut-off valve 86 is in the closed
position the sensor control assembly 72 is deactivated and performs
no function in the operation of the present invention. The
remainder of the hydraulic fluid emanating from the high pressure
outlet port 506 flows to the inlet port 262 of the hydraulic manual
steering control assembly 64 via conduits 534, 532 and 66.
The operation of the sensor control assembly 72 in the hydraulic
manual steering control assembly 64 and the operation of the
slightly modified flow divider 120a is substantially identical to
the operation previously described for the system illustrated in
FIG. 2 and, therefore, will not be described again. It should be
noted, however, that hydraulic fluid flowing from the outlet 138 of
shuttle valve 136 flows through conduits 140, 520 and 512 and
orifice 522 to return to the low pressure outlet port 508 of the
bi-directional differential valve 500. The hydraulic fluid
emanating from the outlet 138 of the shuttle valve 136 communicates
the hydraulic pressure thereof through the first signal inlet 122
of the flow divider 120a to act upon the end portion 338 of the
valve member 282a thereby urging the valve member 282a to the right
as viewed in FIG. 6.
Similarly, the hydraulic fluid flowing from the outlet 144 of the
shuttle valve 142 flows through conduits 146, 524 and 512 and the
orifice 526 to the low pressure outlet port 508 of the
bi-directional differential valve 500. The hydraulic pressure of
the fluid emanating from the outlet 144 is communicated through
conduit 146 and the second signal inlet 124 of the flow divider
120a to act upon the end portion 329 of the valve member 282a
thereby urging the valve member 282a to the left as viewed in FIG.
6.
Pressurized hydraulic fluid flowing from the first port 20a of the
track drive pump 20 is communicated with the first control port 540
of the hydraulically actuated selector spool valve 538 via conduits
22, 118 and 552. The introduction of pressurized hydraulic fluid
into the first control port 540 places the first inlet 544 and the
first outlet 548 in fluid communication while placing the second
inlet 546 and the second outlet 550 in fluid communication.
The stream of hydraulic fluid emanating from the first power outlet
128 of the flow divider 120a flows through conduit 566 into the
first power inlet 178 of the flow compensator 176a. The stream of
hydraulic fluid emanating from the second power utlet 130 of the
flow divider 120a flows through conduit 570 into the second power
inlet 180 of the flow compensator 176a. The hydraulic pressure of
the stream of hydraulic fluid emanating from the first power outlet
128 of the flow divider 120a is communicated to the first reverse
compensation inlet 528 of the flow compensator 176a through
conduits 566 and 568 and selector valve 538. The hydraulic pressure
of the stream of hydraulic fluid emanating from the second power
outlet 130 of the flow divider 120a is communicated to the second
reverse compensation inlet 530 of the flow compensator 176a through
conduits 570 and 572 and selector valve 538.
The stream of hydraulic fluid entering the first power inlet 178 of
the flow compensator 176a flows therethrough to emanate from the
first power outlet 182 via the first annular chamber 408 of the
valve body 394a, the first and second longitudinal grooves 586 and
588 of the valve member 396a, and the third annular chamber 424 of
the valve body 394a. The hydraulic fluid entering the second power
inlet 180 of the flow divider 176a flows therethrough to emanate
from the second power outlet 184 via the second annular chamber 416
of the valve body 394a, the third and fourth longitudinal grooves
598 and 600 of the valve member 396a, and the fourth annular
chamber 432 of the valve body 394a.
The hydraulic fluid emanating from the first power outlet 182 of
the flow compensator 176a flows to the first port 32a of track
drive motor 32 via conduits 562, 40 and 42. The hydraulic fluid
emanating from the second power outlet 184 of the flow compensator
176a flows to the first port 38a of the track drive motor 38 via
conduits 564, 52 and 60. The track drive motors 32 and 38 are
thereby driven in the forward direction. Most of the hydraulic
fluid passing through the track drive motor 32 and out the second
port 32b is routed therefrom back to the second port 20b of the
track drive pump 20 via conduits 44, 46, 558, 556 and 24. Excess
hydraulic fluid bypassed by the internal valving of the track drive
motor 32 is directed from bypass outlet 92 through conduits 94, 96
and 98 to heat exchanger 88 and from heat exchanger 88 through
conduit 90 to reservoir 26. Most of the hydraulic fluid passing
through track drive motor 38 and out the second port 38b is routed
therefrom back to the track drive pump 20 via conduits 56, 62, 560,
556 and 24. Excess hydraulic fluid volume bypassed by the internal
valving of track drive motor 38 is directed from bypass outlet 110
through conduits 108, 112 and 98 to heat exchanger 88 and from heat
exchanger 88 to conduit 90 to reservoir 26.
The operation of the flow compensator 176a, when the apparatus 10
is operated in the forward direction, is substantially identical to
the operation previously described for the flow compensator 176. If
the track drive motor 32 encounters a greater load than that
encountered by the track drive motor 38, the hydraulic pressure in
the conduits leading to the track drive motor 32 will increase
proportionally over the hydraulic pressure of the hydraulic fluid
in the conduits leading to the track drive motor 38. This increased
hydraulic pressure is communicated through the previously described
conduits to the first reverse compensation inlet 528 of the flow
compensator 176a. This hydraulic pressure is communicated therefrom
to the end face 442a of the valve member 396a via the first
circumferential groove 578 of the valve member 396a, the first
transverse bore 582, and through the cylindrically shaped chamber
446a of the valve member 396a. The proportionally lower hydraulic
pressure of the hydraulic fluid supplying the track drive motor 38
is communicated through the previously described conduits to the
second reverse compensation inlet 530 of the flow compensator 176a.
This lower hydraulic pressure is communicated to the end face 444a
of the valve member 396a via the second circumferential groove 580,
the second transverse bore 584, and the cylindrically shaped
chamber 448a of the valve member 396a.
The differential in the hydraulic pressures acting on the opposite
end faces 442a and 444a of the valve member 396a causes a resulting
displacement of the valve member 396a to the right, as viewed in
FIG. 7, within the valve body 394a thereby resulting in a
proportional increase in cross-sectional area of fluid
communication between the grooves 586 and 588 of the valve member
396a and the first annular chamber 408 of the valve body 394a
while, simultaneously, reducing the cross-sectional area of fluid
communication between the grooves 598 and 600 of the valve member
396a and the second annular chamber 416 of the valve body 394a. The
maximum displacement of the valve member 396a to the right within
the valve body 394a is mechanically limited by the abutment of the
end face 444a of the valve member 396a with the end plate 460.
It should be noted that when the end face 444a abuts the end plate
460, fluid communication between the second annular chamber 416 and
the fourth annular chamber 432 through the grooves 598 and 600 is
greatly reduced but is not entirely eliminated.
It will be readily apparent that displacement of the valve member
396a to the right within the valve body 394a will decrease the
cross-sectional area of fluid communication between the second
power inlet 180 and the second power outlet 184 and simultaneously
increase the cross-sectional area of fluid communication between
the first power inlet 178 and the first power outlet 182. In
effect, a dummy load is introduced between the second power inlet
180 and the second power outlet 183 which results in substantially
equal hydraulic pressure drops between the first power inlet 178
and first power outlet 182, and between the second power inlet 180
and the second power outlet 184. Thus, the hydraulic fluid streams
emanating from the first and second power outlets 128 and 130 of
the flow divider 120a will encounter substantially equal loads
regardless of the loads encountered by the track drive motors 32
and 38.
On the other hand, if the track drive motor 38 encounters a greater
load than that encountered by track drive motor 32, the hydraulic
pressure of the hydraulic fluid supplying the track drive motor 38
will proportionally increase over the hydraulic pressure of the
hydraulic fluid supplying the track drive motor 32. This
differential in hydraulic pressure will be communicated through the
first and second reverse compensation inlets 528 and 530 of the
flow compensator 176a thereby causing a proportional displacement
of the valve member 396a to the left within the valve body 394a, as
viewed in FIG. 7. Maximum displacement of the valve member 396a to
the left within the valve body 394a is mechanically limited by the
abutment of the end face 442a of the valve member 396a with the end
plate 458.
As the valve member 396a moves to the left within the valve body
394a, the cross-sectional area of fluid communication between the
second annular chamber 416 and the fourth annular chamber 432 of
the valve body 394a afforded by the grooves 598 and 600 of the
valve body 396a increases while the cross-sectional area of fluid
communication between the first annular chamber 408 the third
annular chamber 424 of the valve body 394a afforded by the grooves
586 and 5588 of the valve member 396a decreases. In effect, a dummy
load is introduced between the first power inlet 178 and the first
power outlet 182 which results in substantially equal pressure
drops across the flow compensator 176a between the first power
inlet 178 and the first power outlet 182, and between the second
power inlet 180 and the second power outlet 184. Thus, the
hydraulic fluid streams emanating from the first and second power
outlets 128 and 130 of the flow divider 120a will encounter
substantially equal loads as noted above.
It should be noted that when the valve member 396a is displaced the
maximum amount to the left with the end face 442a thereof abutting
the end plate 458 the cross-sectional area of fluid communication
between the first annular chamber 408 and the third annular chamber
424 is entirely closed off.
To operate the present invention in the reverse direction thereby
driving the apparatus 10 in a reverse direction, the track drive
pump 20 is driven in the reverse direction by the engine through
the power take-off (not shown). When the pump 20 is operated in the
reverse direction, high pressure pressurized hydraulic fluid is
directed from the port 20b to the track drive motors 32 and 38 via
conduits 24, 556, 558, 44 and 46, and conduits 24, 556, 560, 56 and
62, respectively. The pump 20 also provides pressurized hydraulic
fluid to the second control port 542 of the hydraulically actuated
selector spool valve 538 via conduits 24, 556, 554. The track drive
motors 32 and 38 are driven in the reverse direction, and the
selector valve 538 is actuated to place the first inlet 544 in
fluid communication with the second outlet 550, and to place the
second inlet 546 in fluid communication with the first outlet
548.
The above noted actuation of the selector valve 538 prevents the
valve member 396a of the flow compensator 176a from being
improperly displaced within the valve body 394a in the event one of
the track drive motors encounters a greater load than the other
track drive motor.
If, for example, track drive motor 32 would encounter a greater
load than track drive motor 38 the hydraulic pressure drop across
the track drive motor 32 from the pump 20 to the first power outlet
182 of the flow compensator valve 176a would be greater than the
hydraulic pressure drop across the track drive motor 38 from the
pump 20 to the second power outlet 184 of the flow compensator
176a. Assuming the valve member 396a to be in its medial position
within the valve body 394a, it will be readily apparent that the
pressure of the hydraulic fluid emanating from the first power
inlet 178 of the flow compensator 176a will be less than the
hydraulic pressure of the hydraulic fluid emanating from the second
power inlet 180 of the flow compensator 176a.
The higher hydraulic pressure of the hydraulic fluid emanating from
the second power inlet 180 is communicated to the end face 442a of
the valve member 396a via conduits 570 and 572, selector valve 538,
the first reverse compensation inlet 528, the first circumferential
groove 578, the first transverse bore 582, and the cylindrically
shaped chamber 446a. Similarly, the lower hydraulic pressure of the
stream of hydraulic fluid emanating from the first power inlet 178
of the flow compensator 176a is communicated to the end face 444a
of the valve member 396a via conduits 566 and 568, the selector
valve 538, the second reverse compensation inlet 530, the second
circumferential groove 580, the second transverse bore 584, and the
cylindrically shaped chamber 448a.
This pressure differential acting upon the opposite end faces 442a
and 444a of the valve member 396a causes the valve member 396a to
move to the right within the valve body 394a thereby tending to
cause some restriction to the flow of hydraulic fluid from the
track drive motor 38 through the flow compensator 176a and
emanating from the second power inlet 180 thereof.
Since the hydraulic pressures of the streams of hydraulic fluid
emanating from the track drive motors 32 and 38 and flowing to the
flow compensator 176a are relatively low in comparison to the
hydraulic pressure of the hydraulic fluid supplied to the track
drive motors 32 and 38, the pressure differential between the two
streams of hydraulic fluid entering the flow compensator 176a is of
very low magnitude. It will be readily apparent, however, that if
the selector valve 538 were to remain in the forward position with
the first inlet 544 communicating with the first outlet 548 and the
second inlet 546 communicating with the second outlet 550 the valve
member 396a would move to the left instead of to the right thereby
shutting off the lower pressure hydraulic fluid stream thus
incapacitating the system.
Similarly, if the track drive motor 38 encounters greater load than
the track drive motor 32 the valve member 396a will be displaced to
the left within the valve body 394a. This actuation of the valve
member 396a will be readily apparent to those skilled in the art in
view of the detailed discussion above and, therefore, will not be
described in detail again.
The stream of hydraulic fluid emanating from the first power inlet
178 of the flow compensator 176a flows through conduit 566 and
enters the first power outlet 128 of the flow divider 120a. The
stream of hydraulic fluid emanating from the second power inlet 180
of the flow compensator 176 flows through conduit 570 and enters
the second power outlet 130 of the flow divider 120a. The stream of
hydraulic fluid flowing into the first power outlet 128a flows into
the chamber 352a of the valve member 280a via the second annular
chamber 306 and the ports 354. The stream of hydraulic fluid
entering the second power outlet 130 flows into the chamber 352a
via the third annular chamber 314 and the ports 356.
The cross-sectional area of fluid communication between the second
annular chamber 306 and the chamber 352a is controlled by the
displacement of the valve member 282a within the valve body 280 as
is the cross-sectional area of fluid communication between the
third annular chamber 314 and the chamber 352a. The displacement of
the valve member 282a within the valve body 280 is controlled by
the sensor control assembly 72, the hydraulic manual steering
control assembly 64, or a combination of the two as described in
detail above.
It will be readily apparent that an increase in the hydraulic
pressure communicated to the end portion 329 of the valve member
282a over the hydraulic pressure communicated to the end portion
338 of the valve member 282a will cause the valve member 282a to be
displaced to the left in the valve body 280 thereby causing an
increase in cross-sectional area available for the return flow of
hydraulic fluid emanating from the track drive motor 38 while
proportionally decreasing the cross-sectional area available for
the return flow of hydraulic fluid emanating from the track drive
motor 32. The increase in flow rate of hydraulic fluid flowing
through the track drive motor 38 relative to the flow rate of
hydraulic fluid through the track drive motor 32 will cause the
apparatus 10 to swing away from the string line 84 either in
response to a signal from the sensor control assembly 72 or from
the hydraulic manual steering control assembly 64.
It will be readily apparent that movement of the valve member 282a
to the right will provide a proportional increase in speed of the
track drive motor 32 over the track drive motor 38 thereby causing
the apparatus 10 to swing toward the string line 84 in response to
either a signal from the sensor control assemby 72 or the hydraulic
manual steering control assembly 64.
The hydraulic fluid within the chamber 352a exits therefrom through
ports 350 and the central annular chamber 298 to exit from the flow
divider 120a through the power inlet 126. The hydraulic fluid flows
from the power inlet 126 through the conduit 134 and enters the
bi-directional differential valve 500 through the second
inlet-outlet port 504 and causes the valve member 612 thereof to
displace upwardly against the urging of spring 694 within the bore
614 therethrough as illustrated in FIG. 10. Hydraulic fluid having
approximately the same hydraulic pressure as the fluid entering the
second inlet-outlet port 504 flows through the chamber 688 of the
valve member 612 and flows therefrom through ports 692 to exit from
the valve body 610 through the high pressure outlet port 506.
A portion of the hydraulic fluid entering the second inlet-outlet
port 504 passes around the annular wall 674 of the valve member 612
into the third annular chamber 632 of the valve body 610 and flows
therefrom through passageway 698 to exit from the valve body 610
through the low pressure outlet port 508. The pressure of the
hydraulic fluid exiting from the low pressure outlet port 508 is
approximately 75 psi less than the pressure of hydraulic fluid
entering the second inlet-outlet port 504.
A portion of the hydraulic fluid entering the third annular chamber
632 passes therefrom through the ports 690 into the chamber 686 of
the valve member 612, and flows therefrom through the first annular
chamber 628 and out the first inlet-outlet port 502 of the valve
body 610. The hydraulic pressure of the hydraulic fluid exiting
through the first inlet-outlet port 502 is approximately 75 psi
less than the pressure of the hydraulic fluid entering the second
inlet-outlet port 504.
It will readily be seen that the novel design of the bi-directional
differential valve 500 provides a pressure differential between the
high pressure outlet port 506 and the low pressure outlet port 508
thereof of approximately 75 psi regardless of the direction in
which the track drive pump 20 is pumping the hydraulic fluid in the
system. This novel bi-directional differential valve 500 provides
the necessary pressure differential essential for the proper
operation of the sensor control assembly 72 and the hydraulic
manual steering control assembly 64 regardless of the direction in
which the track drive pump 20 is being driven.
It should be noted that the automatic control system of the present
invention is well suited for controlling the flow of hydraulic
fluid to various other hydraulic drive elements such as hydraulic
power cylinders or the like. Such an automatic control system will
find application as an automatic grade control system for use with
highway construction equipment where it is necessary to accurately
control the position of a grader blade or pavement slip-forming
apparatus or the like relative to a predetermined reference datum
such as a grade line or string line.
From the foregoing detailed description of the various embodiments
of the automatic control system for use with a hydraulic drive
system, it can be readily seen that the present invention provides
an improved system which will automatically compensate for
deviation of the driven vehicle from the desired path and
variations in load encountered by the hydraulic drive motors
propelling the vehicle. It may be further readily seen that the
system constructed in accordance with the present invention
provides an all-hydraulically controlled system capable of
operating on pressurized hydraulic fluid received from a single
drive pump. It should, however, be noted that either or both of the
control assemblies 72 and 64 may be driven by one or more separate
pumps driven independently of the track drive pump 20.
Changes may be made in the construction and arrangement of parts or
elements of the various embodiments as disclosed herein without
departing from the spirit and scope of the present invention.
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