U.S. patent number 3,768,263 [Application Number 05/212,357] was granted by the patent office on 1973-10-30 for hydraulic control system for two-speed winch.
This patent grant is currently assigned to Hyster Company. Invention is credited to John E. Olson, Glenn A. Waller.
United States Patent |
3,768,263 |
Olson , et al. |
October 30, 1973 |
HYDRAULIC CONTROL SYSTEM FOR TWO-SPEED WINCH
Abstract
The hoisting winch of a mobile crane is driven by two hydraulic
motors connected to a common drive shaft. A control system for the
motors includes manually controlled directional and speed control
valves. The speed control valve optionally connects the motor
hydraulically either in parallel for low-speed, high-torque
operation or in series for high-speed, low-torque operation. A
speed-limiting feature automatically shifts the speed valve to or
maintains it in its low-speed position whenever the load is too
heavy to be handled by the system in its high-speed mode. The
hydraulic circuit of the control system also provides
anticavitation protection for the motors when in its high-speed
mode.
Inventors: |
Olson; John E. (Portland,
OR), Waller; Glenn A. (Portland, OR) |
Assignee: |
Hyster Company (Portland,
OR)
|
Family
ID: |
22790666 |
Appl.
No.: |
05/212,357 |
Filed: |
December 27, 1971 |
Current U.S.
Class: |
60/425; 60/483;
91/519; 60/427; 60/905 |
Current CPC
Class: |
F16H
61/4043 (20130101); F16H 61/444 (20130101); B66D
1/44 (20130101); F16H 2063/3033 (20130101); Y10S
60/905 (20130101); F16H 61/4183 (20130101) |
Current International
Class: |
B62D
11/18 (20060101); B62D 11/06 (20060101); F16H
61/40 (20060101); F16h 039/50 () |
Field of
Search: |
;60/53WW,53R,420,424,425,427,435,483,484,905 ;91/412 |
References Cited
[Referenced By]
U.S. Patent Documents
|
|
|
2953903 |
September 1960 |
Skoog et al. |
3073123 |
January 1963 |
Hodgson et al. |
3473442 |
October 1969 |
Farmer et al. |
|
Primary Examiner: Geoghegan; Edgar W.
Claims
I claim:
1. A hydraulic control system for a two-speed winch including a
winch drum driven by a pair of hydraulic motors drivingly connected
to a common power transmission, said control system comprising:
a source of hydraulic pressure fluid,
a hydraulic fluid circuit interconnecting said source and said
hydraulic motors,
directional control valve means in said circuit (a) operable in a
first neutral position to interrupt flow of pressure fluid from
said source to said motors, (b) operable in a second hoist position
to direct fluid under operating pressure to said motors in a
direction for winding cable on said drum and (c) operable in a
third lowering position to direct fluid under operating pressure to
said motors in a direction for unwinding cable from said drum,
speed control valve means in said circuit between said directional
control valve means and said motors operable in a first low-speed
position to connect siad motors hydraulically in parallel with said
source and operable in a second high-speed position to connect said
motors hydraulically in series with said source when said
directional control valve is in either its hoist or lowering said
positions,
said speed control valve means being normally biased to said
low-speed position and being selectively positionable in said
high-speed position, with said directional control valve means in
said hoist position, only when the maximum inlet pressure at said
motors is below a predetermined pressure level.
2. A control system according to claim 1 wherein said speed control
valve means is selectively operable by a fluid pressure tending to
move said valve means to said high-speed position and is sensitive
to said motor inlet pressure in a manner opposing movement of said
valve means to said high-speed position when said directional
control valve is in said hoist position.
3. A control system according to claim 1 wherein said speed control
valve means comprises a spool valve having a valve spool and means
biasing said spool to the low-speed position of said valve, fluid
pressure valve-operating means selectively operable to act against
said spool in a direction tending to shift said spool to said
high-speed position, and speed-limiting means including pilot
passage means in said circuit extending, with said circuit in a
hoist mode, between an inlet side of one of said motors and said
valve means in a manner such that motor inlet pressure acts on said
spool in a direction opposing said fluid pressure valve-operating
means.
4. A control system according to claim 3 wherein motor inlet
pressure above a predetermined pressure level indicative of a winch
load beyond the high-speed mode capacity of said motors is operable
acting through said pilot passage means to shift said spool to said
low-speed position.
5. A control system according to claim 1 wherein said speed control
valve means when in said high-speed position completes a
recirculation subcircuit operable in the hoist and lowering modes
of said circuit to recirculate pressure fluid from the outlet side
of at least one of said motors to the inlet side of at least one of
said motors to inhibit cavitation at said motors.
6. A hydraulic control system for a two-speed winch including a
winch drum driven by a pair of hydraulic motors drivingly connected
to a common power transmission, said control system comprising:
a source of hydraulic pressure fluid,
a hydraulic fluid circuit interconnecting said source and said
hydraulic motors,
directional control valve means in said circuit (a) operable in a
first neutral position to interrupt flow of pressure fluid from
said source to said motors, (b) operable in a second hoist position
to direct fluid under operating pressure to said motors in a
direction for winding cable on said drum and (c) operable in a
third lowering position to direct fluid under operating pressure to
said motors in a direction for unwinding cable from said drum,
speed control valve means in said circuit between said directional
control valve means and said motors operable in a first low-speed
position to connect said motors hydraulically in parallel with said
source and operable in a second high-speed position to connect said
motors hydraulically in series with said source when said
directional control valve is in either its hoist or lowering said
positions,
said speed control valve means when in said high-speed position
being operable to complete a recirculation subcircuit operable in
the hoist and lowering modes of said circuit to recirculate
pressure fluid from the outlet side of at least one said motor to
the inlet side of at least one said motor and thereby inhibit
cavitation at said motors.
7. A hydraulic control system for a two-speed winch driven by a
pair of hydraulic motors drivingly connected to a common drive
transmission, said system comprising:
a hydraulic fluid circuit interconnecting a pump means and said
motors and including selectively operable directional control valve
means and speed control valve means, said speed control valve means
being biased to a low-speed position, but selectively movable to a
high-speed position,
and speed-limiting means operable to maintain said speed control
valve means in said low-speed position when the maxi-mum inlet
pressure at said motors exceeds a predetermined limit pressure
level.
8. A hydraulic control system for a two-speed winch driven by a
pair of hydraulic motors drivingly connected to a common drive
transmission, said system comprising:
a hydraulic fluid circuit interconnecting a pump means and said
motors and including selectively operable directional control valve
means and speed control valve means,
speed-limiting means operable to maintain said speed control valve
means in a low-speed position when the maximum inlet pressure at
said motors exceeds a predetermined limit pressure level,
and selectively operable speed control valve-actuating means for
shifting said speed valve means between high-speed and low-speed
positions,
said speed-limiting means being operable to override said
valve-actuating means and maintain said speed valve means in, or
shift said speed valve means to, said low-speed position when said
limit pressure is exceeded.
9. A hydraulic control system for a two-speed winch driven by a
pair of hydraulic motors drivingly connected to a common drive
transmission, said system comprising:
a hydraulic fluid circuit interconnecting a pump means and said
motors and including selectively operable directional control valve
means and speed control valve means,
speed-limiting means operable to maintain said speed control valve
means in a low-speed position when the maximum inlet pressure at
said motors exceeds a predetermined limit pres-sure level,
and anticavitation means operable at a high speed position of said
speed valve means to protect said motors from cavitation.
10. A hydraulic control system for a two-speed winch driven by a
pair of hydraulic motors drivingly connected to a common drive
transmission, said system comprising:
a hydraulic fluid circuit interconnecting a pump means and said
motors and including selectively operable directional control valve
means and speed control valve means,
and anticavitation means operable in a high-speed position of said
speed valve means to provide a regenerative motor subcircuit of
said hydraulic circuit and thereby ensure adequate flow to both
said motors.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a hydraulic control system for a
two-speed, two-motor, hydraulic motor-driven hoisting winch.
2. Description of the Prior Art
It is known that a crane winch can be selectively driven at two
different speeds through two hydraulic motors driving through a
common drive shaft by selectively connecting the motors
hydraulically either in series or in parallel using a suitable
speed control valve. Such a winch driving system is shown, for
example, in U.S. Pat. No. 3,390,785, issued July 2, 1968.
However, such prior two-speed hydraulic winch systems have no
speed-limiting feature. That is, there is nothing to prevent the
operator from shifting from the low-speed to the high-speed mode,
even if the load to be hoisted is too heavy to be handled by the
winch or its hydraulic system in the high-speed mode. Under such
circumstances the system simply relieves excess pressure buildup
through an appropriate relief valve while a check valve in the
circuit prevents the load from back-driving the motors. However,
the load remains at a standstill so long as the speed valve remains
in its high-speed position, and valuable production time is
lost.
Such prior winch-operating systems may also have an anticavitation
protection feature which prevents cavitation at the motors while
reeling in cable at high speed under light load or while paying out
cable at high speed under heavy load. However, prior systems
usually require a pressure-sensitive valve to provide this feature,
which necessitates another movable control element capable of
malfunction affecting the entire control circuit. Also, such an
anticavitation valve usually operates by restricting return flow
through the circuit, thereby limiting winch speed. Such a valve is
also usually only operative when lowering a load so that there is
no cavitation protection in the hoist mode.
SUMMARY OF THE INVENTION
The present invention is a control system providing two
speed-torque modes for a winch while also having a built-in
automatically operating speed-limiting feature which prevents
shifting the speed control to its high-speed mode. thereby
maintaining it in its low-speed mode, unless the system in its
high-speed mode is capable of hoisting the winch load.
The present invention also provides a hydraulic control circuit
with built-in anticavitation protection operable in its high-speed
mode regardless of the directional mode of the system. A
recirculation subcircuit is automatically completed when the speed
control is positioned in its high-speed mode so as to recirculate
fluid from the inlet to the outlet sides of the motors and thereby
ensure that the motor inlets have an adequate supply of fluid.
A primary object of the present invention is to provide a control
system for a two-speed, two-motor hydraulic motor-driven winch
having a speed control that can normally be shifted at the will of
the operator between its high-and low-speed positions but which
cannot be shifted from its low-speed position when the load being
handled is too heavy to be lifted in the high-speed mode. Thus load
hoisting is not interrupted by an overly heavy load. Hoisting
simply continues at a lower speed.
A second important object is to provide a control system as
described which provides anticavitation protection for the two
hydraulic winch motors when operating in the high-speed mode,
regardless of the directional mode, without requiring additional
valving for this purpose and without restricting the winch
speed.
BRIEF DESCRIPTION OF THE DRAWINGS
The foregoing and other objects, features and advantages of the
present invention will become more apparent from the following
detailed description and accompanying drawings, wherein:
FIGS. 1 through 5 are hydraulic circuit diagrams illustrating a
control system of the invention in various modes of operation.
DETAILED DESCRIPTION
General
Referring to the drawings, FIG. 1 shows a control system of the
invention for controlling the operation of a winch 10 used for
hoisting loads on a mobile crane. The winch includes a winch drum
12 for storing cable. The drum is rotated in either direction
through a drive shaft 14 driven by two hydraulic motors 16, 17. The
winch also includes a brake 18 including a brake drum 18a forming
an extension of the winch drum, brake shoe 18b and brake cylinder
18c. The brake cylinder houses a piston 18d connected by its piston
rod to the brake shoe. The brake shoe is normally maintained in
engaged position against the brake drum when the control system is
de-energized by a spring 18e within the brake cylinder behind the
piston.
The control system includes a hydraulic control circuit
interconnecting the motors 16, 17 and a fixed displacement
hydraulic pump 20. The pump is driven by a suitable motor 22. A
suction line 24 extends from the pump into a hydraulic fluid
reservoir 26. The pump outlet is connected to a pressure line 28
leading to a directional control valve 30. A second, return line 32
leads from valve 30 back to reservoir 26. In the center, neutral
position 30a of valve 30 shown in FIG. 1, a valve passage 31
completes a fluid circuit from the pump back to reservoir through
the valve without any fluid flow through the remainder of the
circuit including the motors 16, 17.
The directional control valve 30 is a three-position control valve
having in addition to its center, neutral position 30a, a "down"
position 30b for paying out cable from the winch drum and thereby
lowering a load, and an "up" position 30c for reeling in cable and
thus hoisting a load.
In addition to the directional control valve, the circuit includes
as one of its primary components the speed control valve means 34.
Such means includes a manually controlled two-position valve spool
36 shiftable within a valve body 38 having enlarged valve cavities
39, 40, 41 and intermediate cavity restrictions 42, 43. The spool
is normally biased to its left-hand, low-speed position as shown in
FIG. 1 by the urging of a spring 44 at the right-hand end 57 of the
main valve cavity.
An air pressure-powered valve-actuating means 46 includes a
manually operated air valve 47 which when opened connects an air
line 48 leading from an air pump 50 and accumulator 52 to an air
line 54. Air line 54 communicates with the end 56 of the speed
valve cavity in opposition to spring 44 and when pressurized, at
for example 100 psi, shifts spool 36 against spring pressure to its
high-speed position as shown in FIGS. 3 and 5.
Two main hydraulic fluid passages extend between the directional
control valve 30 and speed control valve 34, one passage 58
extending through a check valve 60 to valve cavity 39 and the other
62 extending directly to valve cavity 41. Three passages then
extend between the speed control valve and the motors, including a
first passage 64 between valve cavity 39 and one side of motor 16,
a second passage 66 between valve cavity 40 and the corresponding
side of motor 17 and a third passage 68 with branches 69, 70
extending from valve cavity 41 to the opposite sides of the two
motors 16, 17. An extension 71 of line 68 leads to the lower end of
brake cylinder 18c to release the brake when the line is
pressurized.
The circuit also includes a bypass valve 78 off of line 58 which
bypasses fluid around check valve 60 in the "down" directional mode
of operation of the circuit. A quick dump valve 86 off of line 62
is capable of bypassing fluid to reservoir around directional valve
30 when the latter valve is shifted from its up mode back to
neutral. The usual system high-pressure relief valve 90 is also
provided upstream of directional valve 30 to relieve the system of
excessively high pressures. Typically, quick-dump valve 86 might be
set to dump at 50 psi. Bypass valve 78 might be set to close at 300
psi in line 62.
Speed Control Feature
The control system described includes a speed control feature
provided by a pilot line 74 leading from a connection with line 64
to the spring end 57 of the speed valve cavity. When the circuit is
in its "hoist" mode, as represented by FIGS. 4 and 5, pilot line 74
senses the inlet pressure at motor 16 and transmits such pressure
to the spring end of the speed valve cavity. If such pilot pressure
exceeds a predetermined pressure level, for example 1,000 psi,
indicative of the system's inability to raise a load acting on
winch drum 12 in the high-speed position of valve 36, then such
pressure, transmitted through the pilot line, overcomes any air
pressure acting at the opposite end 56 to prevent spool 36 from
shifting to its high-speed position. If spool 36 is already in its
high-speed position, it will shift back to its low-speed position
automatically when the pressure at the motor inlet becomes
excessive. That is, any hydraulic pressure exceeding the
preselected limit pressure acting through pilot line 74 acts
through pilot line 74 at end 57 of the valve cavity together with
the pressure of spring 44 to prevent any counteracting
valve-actuating air pressure acting through line 54 at the opposite
end 56 of the cavity from shifting or maintaining the valve spool
in its high-speed position.
The speed-limiting feature described acts in the same way when the
circuit is in its down mode to prevent the pay-out of cable under a
heavy load at an excessive speed. In this case, as shown, for
example, in FIGS. 2 and 3, the pilot line 74 senses the outlet
pressure of motor 16 and such pressure when beyond the speed limit
pressure will cause valve spool 36 to shift to its low-speed
position to slow down the lowering speed and thus limit the extent
to which the load on the winch cable can back-drive motors 16 and
17 as pumps.
Anticavitation Feature
FIG. 3, illustrating the circuit in its high-speed down mode, shows
the circuit's built-in anticavitation feature in operation. In this
mode directional spool 30 is shifted to its down position 30b and
air valve 47 is actuated to admit air to the left-hand end 56 of
the speed spool cavity to shift the speed spool 36 to its
high-speed position shown. In these posi-tions of the directional
and control spools, fluid flow is from pump 20 to valve cavity 41
via line 62. Fluid flows from this cavity into line 68. At the
intersection of lines 68 and 70, the flow divides, one part going
into line 70 to the inlet side of motor 17 and another part going
on to line 69 and to the inlet of motor 16, the division of flow
being dictated by the respective fluid pressures at the inlets of
motors 16, 17. Exhaust fluid from motor 16 flows through line 64 to
valve cavity 39, and back to reservoir through line 58.
However, the exhaust flow from motor 17 cannot take the same direct
path as just described. In this regard, exhaust flow from motor 17
is through line 66 into speed valve cavity 40. The flow is blocked
at this point from entering valve cavity 39 and return line 58 by
the speed valve land 36b. Instead, exhaust flow in cavity 40 flows
across cavity restriction 43 and spool groove 36a back to valve
cavity 41 and line 68 to be recirculated through the motors. Thus
exhaust flow from motor 17 cannot return to reservoir until it has
also passed through motors 16. Therefore the motors are
hydraulically series-connected in this mode of the circuit and
exhaust fluid from motor 17 is recirculated through the motor
circuit from its outlet side to the inlet sides of the motor,
thereby ensuring an adequate pressure at the motor inlets to
prevent cavitation, which might otherwise easily result in this
high-speed down mode, particularly under heavy cable loads.
A similar recirculation occurs when the circuit is in its
high-speed up mode as shown in FIG. 5. In this case, the flow of
fluid under operating pressure at the motor end of the circuit is
first through line 64 to motor 16. Exhaust flow from the outlet
side of motor 16 is through line 69 and from there to line 68 and
into speed valve cavity 41. From there flow proceeds across valve
cavity restriction 43 as permitted by spool land 36a into valve
cavity 40 and motor inlet line 66 to the inlet side of motor 17.
Exhaust flow from motor 17 is then through line 70 back into line
68 and valve cavity 41, across valve groove 36a and into return
line 62 back to reservoir. Thus in this high-speed, up mode there
is also a recirculation of fluid from the outlets of both motors to
the inlet of motor 17. This recirculation has the dual purposes of
connecting motor 17 in series with motor 16 and preventing
cavitation at the inlet of motor 17.
OPERATION
Neutral Mode
In the neutral mode of the circuit, shown in FIG. 1, there is no
fluid flow through the motor portion of the circuit. Directional
control valve is in its centered neutral position 30a, and all flow
from pump 20 is through line 28, valve passage 31 and line 32 back
to reservoir. There being no flow to the motors or to line 68,
there is no flow through line 71 to the brake cylinder 18c.
Therefore, brake shoe 18b is applied to brake drum 18a to prevent
free-spooling of the winch drum 12 under load.
Down, Low-Speed Mode
To operate the system in its down, low-speed mode as shown in FIG.
2 so as to pay out cable slowly from winch drum 12, air valve 47
remains closed, directional valve 30 is shifted to its down
position 30b, and, because of the condition of air valve 47, speed
valve spool 36 remains in its low-speed position shown.
Fluid flow under operating pressure is from pump 20 through line
28, directional valve passage 76, line 62, speed valve cavity 41,
and line 68 to branch lines 69, 70, and from there to the inlets of
both motors 16, 17. Simultaneously line 71 and the lower end of
brake cylinder 18c are pressurized, thereby releasing brake shoe
18b from brake drum 18a so that the winch drum can rotate.
Exhaust flow from motors 16, 17 is through lines 64 and 66 into
valve cavities 39, 40 respectively. Flow from both cavities then
proceeds through line 58 and through bypass valve 78, bypassing
check valve 60, to directional valve passage 80 and from there
through line 32 back to reservoir 26.
Thus in this condition of the circuit, the motors 16 and 17 are
connected hydraulically in parallel so that each receives only
approximately one-half of the available flow, thereby operating
them at half their top speeds, assuming the motors are of identical
capacity. At the same time the torque developed by the motors is
double that which would be produced when the motors are
series-connected.
Down, High-Speed Mode
To shift from the low-speed to the high-speed down mode as shown in
FIG. 3, air valve 47 is opened to admit air pressure to end 56 of
the speed valve cavity. Assuming that the load is not so great that
it would back-drive the motors to an extent producing an excessive
outlet pressure in line 64 and thus pilot line 74, valve 36 shifts
to its high-speed position shown in FIG. 3 under the influence of
air pressure at 56. Directional valve 30 remains in its down
position 30b. Flow is as it is in the low-speed down mode from pump
20 through line 28, valve passage 76, and line 62 to valve cavity
41 and then through line 68 to branch lines 69 and 70 to the inlets
of motors 16 and 17.
However, in the high-speed mode the exhaust flow from the motors is
different, as discussed previously with respect to the
anticavitation feature, in that exhaust flow from motor 17 is
blocked from entering return line 58 by speed valve land 36b.
Instead, such flow recirculates through valve cavity restriction
43, cavity 41 and line 68 to the inlet sides of the motors 16, 17.
Eventually such flow returns to reservoir through motor 16, line
64, cavity 39 and line 58. Since all flow is forced through motor
16, the motors 16, 17 are in effect hydraulically series connected,
thereby driving them and the connected winch drum 12 at high speed
and low torque, that is, at approximately double their speeds when
connected in parallel.
As previously mentioned in discussing the speed-limiting feature,
speed valve spool 36 automatically shifts back to its low-speed
position when the outlet pressure of motor 16 exceeds a
predetermined pressure of, say 1,000 psi. This would indicate that
the load on the winch is so great that it is back-driving the
motors at an excessive speed and therefore perhaps lowering the
load at a dangerously high speed.
Up, Low-Speed Mode
Operation of the system in an up mode at low speed is illustrated
in FIG. 4. In this mode, air valve 47 is closed, placing speed
valve spool 36 in its low-speed position. Directional spoool 30 is
shifted to its up position 30c. In these positions of the
directional and speed valves, flow is from pump 20 through line 28,
a directional valve passage 82, line 58, and check valve 60 into
speed valve cavity 39. Flow is then from both cavities 39 and 40,
as permitted by spool land 36a, into both motor inlet lines 64, 66
to the inlet sides of motors 16, 17. Exhaust flow from the motors
and lines 60, 70 pressurizes line 71 to disengage the brake. Return
flow proceeds through line 68, speed valve cavity 41, line 62,
directional valve passage 84 and line 32 back to reservoir. In this
mode, the speed valve 36 connects motors 16 and 17 hydraulically in
parallel, thereby driving the motors at low speed but at a high
torque suitable for lifting heavy loads.
If the load being hoisted is too heavy to be lifted in the
high-speed mode, an excessive inlet pressure develops at motor 16
and in line 64. This pressure, transmitted by pilot line 74 to the
right-hand end 57 of the speed valve cavity, prevents shifting of
the speed valve spool 36 to its high-speed position, even if
commanded to shift by the operator through the opening of air valve
47.
Up, High-Speed Mode
To change from low speed to high speed when hoisting, the operator
simply opens air valve 47 to admit air under pressure to the
left-hand end 56 of the speed valve cavity. Assuming that the load
being hoisted is not so great that it causes an excessively high
inlet pressure in line 64 and thus pilot line 74, speed valve spool
36 shifts to its high-speed position shown in FIG. 5 against the
pressure of spring 44. In this position, flow is from pump 20
through line 28, through passage 82 of the directional valve, line
58 and check valve 60 into speed valve cavity 39. From this cavity
flow is to line 64 only and to the inlet of motor 16. From the
outlet of motor 16, exhaust flow is through lines 69 and 68 to
valve cavity 41. From cavity 41 at least part of the flow, induced
by low pressure at the inlet of motor 17, is across cavity
restriction 43, as permitted by spool groove 36a, into line 66 and
to the inlet of motor 17. Exhaust flow from motor 17 is to line 70
and then is recirculated to line 68 and from there through valve
cavity 41 to either return line 62 and to reservoir 26 or back to
line 66, depending on the inlet pressure at motor 17.
Thus all flow goes initially through motor 16 before returning to
reservoir. In addition, there will be at least sufficient flow
through motor 17 to prevent cavitation because of the position of
speed valve spool groove 36a permitting recirculating flow from
both motor outlets to the inlet of motor 17.
Having illustrated and described what is presently a preferred form
of my invention, it should be apparent to those skilled in the art
that the same permits of modification in arrangement and detail. I
claim as my invention all such modifications as come within the
true spirit and scope of the following claims.
* * * * *