U.S. patent application number 11/786825 was filed with the patent office on 2007-11-01 for method of operating a hydraulic system for a loader machine.
This patent application is currently assigned to J.C. BAMFORD EXCAVATORS LIMITED. Invention is credited to David A. Cook, Ben Covell.
Application Number | 20070251129 11/786825 |
Document ID | / |
Family ID | 34066583 |
Filed Date | 2007-11-01 |
United States Patent
Application |
20070251129 |
Kind Code |
A1 |
Cook; David A. ; et
al. |
November 1, 2007 |
Method of operating a hydraulic system for a loader machine
Abstract
A method of operating a hydraulic system of a loader arm
carrying a working implement, the system having a ride improvement
system and a selection valve connected to first and second chambers
of a ram which operates the loader arm. A check valve assembly is
provided, with the check valve assembly being responsive to
pressure changes in the second chamber. The check valve assembly,
when closed, prevents fluid from passing between the first chamber
to the selection valve. Means are provided communicating the fluid
pressure in the second chamber to the check valve, with the means
responsive to pressure changes in the second chamber to open the
check valve. The selection valve is operable to raise the loader
arm with the system arranged to permit passage of fluid between the
first chamber and the accumulator while permitting fluid to pass
from the second chamber to a low pressure region.
Inventors: |
Cook; David A.; (Cheadle,
GB) ; Covell; Ben; (Staffordshire, GB) |
Correspondence
Address: |
MARSHALL, GERSTEIN & BORUN LLP
233 S. WACKER DRIVE, SUITE 6300
SEARS TOWER
CHICAGO
IL
60606
US
|
Assignee: |
J.C. BAMFORD EXCAVATORS
LIMITED
Staffordshire
GB
|
Family ID: |
34066583 |
Appl. No.: |
11/786825 |
Filed: |
April 13, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10885325 |
Jul 6, 2004 |
7204086 |
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11786825 |
Apr 13, 2007 |
|
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|
09866311 |
May 25, 2001 |
7089734 |
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11786825 |
Apr 13, 2007 |
|
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Current U.S.
Class: |
37/195 |
Current CPC
Class: |
E02F 9/2207 20130101;
E02F 9/2217 20130101; E02F 9/2203 20130101; B66F 9/22 20130101;
B66F 9/0655 20130101; E02F 9/2221 20130101 |
Class at
Publication: |
037/195 |
International
Class: |
E02F 1/00 20060101
E02F001/00 |
Foreign Application Data
Date |
Code |
Application Number |
May 25, 2000 |
GB |
0012602.9 |
Claims
1-6. (canceled)
7. A hydraulic system for a wheeled loader having a loader arm
assembly which is movable between raised and lowered positions by
means of a hydraulic actuator device, the system comprising: a
selection valve having first and second ports for directing
hydraulic fluid to a cylinder, the cylinder having first and second
chambers, the first chamber connected to the first port and the
second chamber connected to the second port; a hydraulic
accumulator connected to the hydraulic actuator device between the
first port and the first chamber; a first control valve connected
to the hydraulic actuator device between the hydraulic accumulator
and the first chamber; a second control valve connected to the
hydraulic actuator device between the second port and the second
chamber, the second control valve further connected to a hydraulic
reservoir; and a hose burst check valve connected to the hydraulic
actuator device between the first port and the hydraulic
accumulator; wherein the first control valve is movable between a
first position in which passage of hydraulic fluid is permitted
only from the hydraulic accumulator toward the first chamber and a
second position in which passage of hydraulic fluid is permitted in
bi-directionally between the hydraulic accumulator and the first
chamber, the second control valve is movable between a first
position in which passage of hydraulic fluid through the second
control valve is prevented and a second position in which passage
of hydraulic fluid through the second control valve is permitted,
and the hose burst check valve normally allows one-way hydraulic
fluid flow from the first port to the first chamber, but the hose
burst check valve is arranged to permit two-way hydraulic fluid
flow between the first chamber and the first port when hydraulic
fluid is directed from the second port to the hose burst check
valve.
8. The system according to claim 7 wherein the hose burst check
valve is a pilot valve.
9. The system according to claim 7 wherein the selection valve is
manually operable.
10. The system according to claim 7 wherein the first and second
control valves are electrically operated solenoid valves to which
current is supplied by a manually operable switch means.
11. The system according to claim 7 wherein the first and second
control valves are biased towards the first position.
12. The system according to claim 11 wherein the first and second
control valves are spring biased towards the first position.
13. The system according to claim 7 wherein at least one of said
accumulator, control valves, check valve assembly and connecting
pipes are made of metal.
Description
BACKGROUND OF THE INVENTION
[0001] This invention relates to a method of operating a hydraulic
system for a loading machine, such as a wheeled loader having a
loader arm assembly which carries a working implement and in which
the loader arm assembly is connected to the body and which is
movable between raised and lowered positions by means of a
hydraulic ram.
[0002] It is known to improve the ride of a wheeled loader by
connecting an hydraulic accumulator into the hydraulic hose which
feeds hydraulic fluid into said ram means to raise the loader arm
assembly. As a result when the wheeled loader is travelling across
a site, or when travelling along a road, the loader arm assembly is
suspended in spring manner by the accumulator and so the wheeled
loader is able to travel with less pitch and bounce than would
otherwise have been the case.
[0003] However, such a ride improvement system has not been
provided hitherto in a loader vehicle including a loader arm
assembly connected at, or adjacent to, the rear end of the assembly
to the body at, or adjacent to, the rear end of the body so that
the loader arm assembly extends forwardly whereby, in a lowered
position of the arm assembly, the working implement is disposed in
front of the body, where such a vehicle is provided with a hose
burst check valve.
SUMMARY
[0004] According to at least one disclosed example of the present
invention, we provide a method of operating a hydraulic system of a
loader machine, the loader machine having a loader arm assembly
connected to a body so that in a lowered position of the loader arm
assembly, a working implement carried at an outer end of the loader
arm assembly is disposed in front of the body, and which loader arm
assembly is movable between raised and lowered positions by means
of a hydraulic ram of the hydraulic system, the hydraulic system
further including a ride improvement system including a hydraulic
accumulator which is connected to the hydraulic ram, and a
selection valve connected to each of a first and second chamber of
the hydraulic ram, and a check valve assembly connected between the
first chamber and the selection valve such that the check valve,
when in a closed condition, prevents fluid under pressure passing
from the first chamber to the selection valve, and the check valve
assembly having hydraulic fluid responsive means responsive to
hydraulic fluid pressure in the second chamber to move the check
valve assembly to an open condition, and there being means to
connect the hydraulic fluid pressure in the second chamber to the
check valve assembly, the method including operating the selection
valve to raise the loader arm assembly by feeding fluid under
pressure to one chamber of the ram and to receive fluid at a lower
pressure from the second chamber of the ram, or to lower the loader
arm assembly by feeding fluid under pressure to the second chamber
of the ram and to receive fluid at a lower pressure from the first
chamber of the ram, and wherein the method includes operating the
selection valve to raise or lower the loader arm assembly, and when
the selection valve means is operated to raise the loader arm
assembly, permitting the passage of hydraulic fluid between the
first chamber of the hydraulic ram and the accumulator, and whilst
permitting the passage of hydraulic fluid from the second chamber
to a low pressure region.
[0005] Desirably, when the selection valve is operated to lower the
loader arm assembly, the passage of hydraulic fluid from the second
chamber to the low pressure region is prevented, and thus
sufficient hydraulic pressure will be provided to the hydraulic
pressure sensing means to open the check valve assembly and to
permit fluid to pass from the first chamber of the ram, back to the
selection valve.
[0006] If desired, the method may include moving a first control
valve which is connected between the first chamber of the hydraulic
ram and the hydraulic accumulator, between a first position in
which the passage of hydraulic fluid between the first chamber of
the hydraulic ram and the accumulator is permitted and a second
position in which passage of hydraulic fluid to the accumulator is
prevented. However in another arrangement, such a first control
valve need not be provided, so that the ride improvement system is
potentially permanently in an active condition.
[0007] The method includes moving a control valve which is
connected between the second chamber and the low pressure region
between a first position in which passage of hydraulic fluid
therethrough to the low pressure region is permitted, in which
condition the loader arm assembly may be raised, and a second
position in which the flow of hydraulic fluid to the low pressure
region is prevented, so that the loader arm assembly may be
lowered.
[0008] Although the step of moving the control valve which is
connected between the second chamber and the low pressure region
between its first and second positions may be carried out purely
manually, in a preferred arrangement the selection valve is
provided with a switch to sense when the selection valve is
operated to lower the loader arm assembly, and wherein the method
includes sensing operation of the selection valve to lower the
loader arm assembly, and moving at least the second control valve
to the second position in response. Thus, in accordance with the
disclosed example, the method step of moving the control valve to
permit lowering of the loader arm assembly may be achieved
automatically.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] Embodiments of the invention will now be described with
reference to the accompanying drawings wherein:
[0010] FIG. 1 is a side view of a vehicle according to the
invention,
[0011] FIG. 2 is a diagrammatic circuit diagram showing the flow of
hydraulic: fluid and valve positions in normal operation of the
vehicle during lifting of the arm,
[0012] FIG. 3 is a view similar to that of FIG. 2 but showing
normal operation during lowering of the arm,
[0013] FIG. 4 is a view similar to that of FIG. 2 but showing a
travel position of the vehicle with the ride improvement means
engaged,
[0014] FIG. 5 is a view similar to that of FIG. 4 but showing a
boom lift position and ride improvement means engaged.
[0015] FIG. 6 is a view similar to that of FIG. 4 but showing flow
of fluid in a boom lower position with the ride improvement means
engaged;
[0016] FIG. 7 is a diagrammatic circuit diagram of a second
embodiment of the invention.
DETAILED DESCRIPTION
[0017] Referring to the drawings, a wheeled loader vehicle includes
a body 10 supported, in conventional manner, on two pairs of front
and rear wheels 11, 12 each of which is steerable and each of which
is driven by a suitable transmission and differential means from an
engine which may be disposed as desired on the vehicle. The body 10
has a rear end 13 and a front end 14. A loader arm assembly 16, at
a position adjacent its rear end, is pivotally mounted to the body
10 adjacent the rear end 13 of the body, about an axis 15. The
loader arm assembly 16 in the present example, is a two part boom
having an outer part 16a, within which is telescoped an inner part
16b and which parts are slidable relative to each other by
hydraulic ram means so as to provide an extendible loader arm
assembly. If desired the vehicle may have a two or more part boom
or an un-extendible single part boom.
[0018] At the front end of the boom assembly 16 is a downwardly
extending nose part 17 by which a working implement 18 is
releasably carried in conventional manner. If desired, the working
implement 18 may be a pair of lifting tines as shown or may be a
bucket or any other suitable working implement.
[0019] The loader arm assembly may be connected to the body at or
adjacent the rear thereof, by any suitable pivot means disposed at
or adjacent the rear of the loader arm assembly.
[0020] The loader arm assembly 16 is pivotable about the axis 15
between raised and lowered positions. In the lowered position
working implement 18 is disposed in front of the vehicle front end
14. The loader arm assembly 16 is movable between said raised and
lowered positions by a ram assembly 20, which in the present
example includes a single ram. The ram assembly 20, in conventional
manner, includes a cylinder part 21 and a piston rod 22. The piston
rod 22 is connected at one end to a bracket 23 depending downwardly
from the underside of the part 16a of the lowered arm assembly by
means of a pivot pin 24a whilst the cylinder 21 is connected, at
its lower end, by a pivot pin 24b to a part of the body 10.
Obviously extension and retraction of the piston rod 22 from the
cylinder 21 causes pivotal raising and lowering of the arm assembly
16.
[0021] Within the cylinder 21 is a first chamber 25, on one side of
the piston 27, which is of cylindrical configuration and a second
chamber 26 on the opposite side of the piston 27, see FIGS. 2 to 5,
to the first chamber 25 and which is of annular configuration in
cross section. Mounted on the cylinder 21 is a conventional
accumulator means 30 made of, in the present example, steel and
connected by a pipe 31 to a first control valve 32. A second
control valve 33 is connected by a line 34 including flexible hoses
and/or rigid pipes to an hydraulic reservoir or other low pressure
area 35.
[0022] Each control valve 32, 33 is an electrically operated
solenoid valve and which is movable between a first or "at rest"
position in which passage of fluid is prevented in one direction of
the valve 32 and in both directions in the valve 33 and a second
position in which passage of fluid is permitted. Both control
valves 32, 33 are normally spring biased by a spring means 36 to
the position in which flow of fluid is prevented as illustrated in
FIG. 2 and FIG. 3.
[0023] A line 38, including a rigid pipe 38a and a flexible line
38b, connects the first chamber 25 of the ram 20 to a first port
40a of a selection valve 40 via a hose burst check valve 39. The
first control valve 32 is connected by a line 37, including a rigid
pipe, to the line 38 between ram chamber 25 and the hose burst
check valve 39. The hose burst check valve 39 is a pilot valve that
is normally maintained closed in the direction to prevent flow of
fluid under pressure from the chamber 25 to the valve 40 but it may
be opened by supply of pilot pressure on line 41, including a rigid
pipe, from a line 42, including a rigid pipe 42a and flexible hoses
42b which extends between a second port 40b of the selection valve
40 and the chamber 26 of the ram 20. The line 42 is connected by a
line 43 to the second control valve 33.
[0024] In use, as best shown in FIG. 2, during normal operation,
when it is desired to lift the arm, fluid under pressure is fed
from the first port 40a of the selection valve 40 along the line 38
through the one-way check valve within the hose burst check valve
39. As boom suspension has not been selected there is no electrical
supply to valves 32 and 33 and they remain in the normally closed
position. As the telescopic boom 16 is raised, by the supply of
fluid to the chamber 25, fluid under lower pressure is fed from the
chamber 26 along line 42 into a port 40b of the selection valve 40.
The valve 33, of course, being, like the valve 32, maintained in
the position shown in FIG. 2 to prevent flow of fluid therethrough
by virtue of no electrical supply being supplied to the solenoid
thereof.
[0025] Referring now to FIG. 3, when it is desired to lower the
loader arm assembly the valve 40 is actuated to feed fluid under
pressure through port 40b along line 42 into the chamber 26 and
thus fluid under lower pressure is fed from chamber 25 along line
38 through hose burst check valve 39 which is maintained in an open
position by virtue of supply of pilot pressure on line 41 which
extends from line 42.
[0026] Referring now to FIG. 4, when it is desired to operate the
ride improvement means i.e. boom suspension means the system is
activated by operation of a suitable electric control so that
electrical supply is provided to the valves 32, 33 to move them
from the positions shown FIGS. 2 and 3 to the positions shown in
FIGS. 4 to 6 in which passage of hydraulic fluid is permitted.
[0027] In this position fluid can flow both to the accumulator 30
and also to the reservoir 35 in accordance with the external forces
imposed on the piston 27 to displace fluid to or from chambers 25,
26. Such a condition is shown in FIG. 4. As a result the loader arm
is supported by the action of the accumulator on the hydraulic
fluid and it is, in effect, sprung.
[0028] Referring now to FIG. 5, when it is desired to raise the
loader arm assembly whilst the ride improvement means is engaged,
the valve 40 is actuated to feed fluid from port 40a under pressure
along line 38 into the chamber 25 whilst fluid from the chamber 26
passes along the line 42 back to the valve 40. At the same time the
suspension of the arm assembly is suspended by the accumulator 30
as described hereinbefore in connection with the FIG. 4.
[0029] Referring now to FIG. 6, when it is desired to lower the
boom whilst the ride improvement means is engaged, the actuation of
the valve 40 to raise pressure at port 40b, by virtue of switch 44,
has the effect of collapsing the electrical signal to valve 33
which becomes closed and so allows pressure to be raised in line 42
which feeds fluid under pressure to chamber 26, whilst fluid in
chamber 25 is fed via line 38 through the hose burst check valve 39
to the port 40a of the valve 40. The hose burst check valve 39 is
maintained open by pilot pressure fluid on line 41 which extends
from line 42.
[0030] Whilst in this example the accumulator 30, valves 32, 33 and
check valve 39 are all disposed on the cylinder 21, if desired one
or more of these components may be positioned as desired and made
of material as desired where permitted by local regulations.
[0031] Referring now to FIG. 7 an alternative embodiment is
illustrated. Similar parts to those shown in FIGS. 1 to 6 are
indicated by the same reference numerals.
[0032] In this example, the first control valve indicated at 32 in
the hydraulic system of the previous figures, is removed, and the
accumulator 30 is connected by the rigid pipe 37 to the line 38 at
a point between the hose burst check valve assembly 39 (or check
valve assembly 39) and the ram assembly 20.
[0033] The loader vehicle operates similarly to the loader vehicle
described with reference to the previous figures, to provide both
ride improvement and hose burst protection, by the provision of the
host burst protection or check valve assembly 39.
[0034] However, it will be appreciated that without the presence of
the first control valve 32 which is moveable as described above to
a second position to prevent the flow of hydraulic fluid to the
accumulator 30, the ride improvement system would be permanently
"on" or active.
[0035] In a first active state, when the second control valve 33 is
in the "at rest" or first position shown in FIG. 7, it will be
appreciated that it is possible to raise the loader arm assembly 16
by operating the selection valve 40, to develop pressure in the
lines 38b and 38 connected to the first chamber 25 of the ram
assembly 20 with fluid expelled from second chamber 26 passing
along line 42 back to the selection valve 40, the hose burst
protection valve assembly 39 maintaining the condition shown in
FIG. 7 to provide protection in the event of a hose burst in the
line between the hose burst protection valve 39 and the selection
valve 40.
[0036] Moreover in the first active state, the loader arm assembly
16 may be lowered by operating the selection valve 40, to develop
pressure in the line 42 to and in the second chamber 26 of the ram
assembly 20. Pressure may be thus developed in the line 42 and
second chamber 26 because the second control valve 33 is in its
first position i.e. closed to prevent fluid passing from the line
42 to the low pressure region 35. Thus a pilot pressure is
transmitted, along line 41, to the hose burst protection or check
valve assembly 39 which thus moves to the condition indicated in
FIG. 3, so that fluid expelled from the first chamber 25 may pass
through the hose burst protection or check valve assembly 39 back
to and through the selection valve 40.
[0037] In a second active state, whilst the line 38 between the
hose burst protection or check valve assembly 39 and the ram
assembly 20 is connected to the accumulator 30 by virtue of the
absence of the first control valve 32, the second control valve 33
is moved to second position shown in FIG. 4 when fluid flow from
the line 42 between the second chamber 25 of the ram assembly 40
and the selection valve 40, through the second control valve 33 to
the low pressure region 35, is permitted. In this state, although
ride improvement is provided as the accumulator 30 is still
connected to the line 38 between the host burst protection or check
valve assembly 39, and the first chamber 25 of the ram assembly 20,
and the loader arm may be lifted by applying pressure to lines
38b/38. However, fluid expelled from the second chamber 26 of the
ram assembly 20 may pass to the low pressure region 35 through the
second control valve 33.
[0038] It will be appreciated that the primary role of the second
control valve 33 when in its first "at rest" position is to prevent
the flow of pressurised fluid from the line 42 connected to the
second chamber 26 of the ram assembly 20, to the low pressure
region 35, although the particular second control valve 33 shown in
the drawings prevents fluid flow in both directions through the
valve 33.
[0039] In the embodiment of FIG. 7 preferably the second control
valve 33 is moved between its first and second positions, e.g. by
the operation of a solenoid or other electrically operated
actuator, under the control of a manually actuated switch, although
preferably under the automatic control of the switch 44 provided on
the selector valve 40, to switch the control valve 33 to its first
position so that fluid is prevented from passing to the low
pressure region 35, whenever it is desired to lower the loader arm.
Desirably in this embodiment, the second control valve 33 is "at
rest" in its second position when fluid flow through the control
valve 33 is permitted and an electrical signal is supplied to the
control valve 33 to move the control valve to its first position to
prevent fluid flow at least to the low pressure region 35, when the
selector valve 40 is operated such as to lower the loader arm.
[0040] In each of the embodiments described, by virtue of either
the one way check valve within the first control valve 32 (in the
embodiments shown in FIGS. 1 to 6) or the direct connection between
the accumulator 30 and the line 38 between the hose burst
protection or check valve assembly 39 and the first chamber 25 of
the ram assembly 20, the pressure in the accumulator 30 can never
exceed the pressure in first chamber 25. When the first control
valve 32 where provided, is in its second position as seen in FIGS.
4 and 5, or permanently in the FIG. 7 embodiment, the accumulator
30 will provide at least some ride improvement as the loader
vehicle travels over the ground irrespective of the position of the
second control valve 33, as movements of the loader arm at least
downwardly will be damped by the action of the accumulator 30. In
each embodiment, when the second chamber 26 of the ram 20 is
connected to the low pressure region 35, when the second control
valve 33 is in its second position, the ride improvement system
will be fully active.
[0041] In each mode of operation described above, in the event of a
host burst in the line 38b between the host burst protection of
check valve assembly 39 and the selection valve 40 when highly
pressurised, e.g. during lifting, or in the hose between where the
second control valve 33 and the line 42 to the selection valve 40
are connected when highly pressurised, e.g. during lowering, the
hose burst protection or check valve assembly 39 will be closed or
close, to prevent the escape of pressurised fluid from the line 38a
between the first chamber 25 and the hose burst protection or check
valve assembly 39, so that the loader arm is prevented from
collapsing and thus possible creating an unstable and possibly
dangerous situation.
[0042] Although the invention has been described in relation to a
wheeled loader vehicle, it will be appreciated that the invention
may be applied to any other mobile machine requiring a ride
improvement system for a loader arm. For example the invention may
be applied to a tracked or partly tacked machine or vehicle, or to
a mobile crane.
[0043] The features disclosed in the foregoing description, or the
following claims, or the accompanying drawings, expressed in their
specific forms or in terms of a means for performing the disclosed
function, or a method or process for attaining the disclosed
result, as appropriate, may, separately, or in any combination of
such features, be utilised for realising the invention in diverse
forms thereof.
* * * * *