Note: Descriptions are shown in the official language in which they were submitted.
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Title: Multi-Function Hydraulic Valve Assembly
FIELD OF THE INVENTION
[0001] The invention is related to hydraulic systems, and in particular,
to a multi-function hydraulic valve assembly.
BACKGROUND OF THE INVENTION
[0002] The use of hydraulic systems for moving or lifting loads is well
known. Typically, such systems utilize hydraulic fluid under pressure to drive
hydraulic operators, such as piston/cylinder arrangements. A piece of
machinery, such as a hoist or a truck, may require several hydraulic operators
to move the load in different ways. Typically, the various hydraulic operators
are each controlled by a lever located in the cab of the machine or vehicle.
One example where hydraulic systems are used in this way are lift trucks.
[0003] Lift trucks are vehicles which are used to pick up and move
loads from place to place. A conventional lift truck includes a carriage which
supports a pair of forks. The forks are maneuvered into place by the lift
truck
operator and are used to pick up the load. The carriage rides vertically in a
mast, which also supports the carriage. In addition the mast may be tilted
backward to facilitate stabilizing the load on the forks. Two separate
hydraulic
operators are used to move the carriage vertically and to tilt the mast.
[0004] Several attachments to enhance the capabilities of the lift truck
are known in the art. One such attachment is a side shift assembly which
facilitates aligning the spaced pair of forks with the load. The term "side
shifting" is used to describe the concept of shifting the forks as a spaced
pair
either left or right of the vehicle center line. This function provides the
operator
with a greater margin for error when aligning the vehicle with the load. A
hydraulic operator, such as a piston/cylinder arrangement is typically used by
the side shifting assembly to move a frame to which the forks are secured.
[0005] Another attachment to enhance the capability of a lift truck is a
fork positioning assembly. The term fork positioning is used to describe the
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concept of changing the relative spacing between the forks to accommodate
loads of different widths. Again, a hydraulic operator, such as a
piston/cylinder
arrangement is used in the fork positioning assembly to move the forks.
[0006] A cab of a conventional lift truck provides three levers to operate
three hydraulic operators. Accordingly, if a user requires four hydraulic
operators, such as, for example, by installing a fork positioning attachment,
an
additional lever must be installed to operate the fork positioning attachment.
(0007] Alternatively, prior art systems permit operation of two separate
hydraulic operators with a single lever on a lift truck. These systems utilize
an
electrical circuit to toggle between the two hydraulic operators. Prior to
moving the lever which actuates the hydraulic system, the user would activate
the electrical switch to select the appropriate hydraulic operator. This
system
adds expense and complexity to the design of the lift truck. In addition,
electrical cables must be provided and extended over the lift truck mast.
[0008] Accordingly, there is a need for a hydraulic valve assembly
which permits selectable hydraulic operation of more than one hydraulic
operator with a single lever.
SUMMARY OF THE INVENTION
(0009] According to a first aspect of the invention, a hydraulic valve
assembly for delivering hydraulic fluid from a supply of hydraulic fluid to
one of
a first hydraulic operator and a second hydraulic operator is provided. The
assembly comprises:
[0010] a) a valve block defining:
i) a first supply port adapted for fluid communication with said supply;
ii) a second supply port adapted for fluid communication with said
supply;
iii) a first operator port adapted for fluid communication with said first
hydraulic operator;
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iv) a second operator port adapted for fluid communication with said
second hydraulic operator;
v) a third operator port adapted for fluid communication with said first
hydraulic operator;
vi) a fourth operator port adapted for fluid communication with said
second hydraulic operator;
vii) a first chamber, said first chamber being in fluid communication
with said first supply port, said first operator port, and said second
operator port;
viii) a second chamber, said second chamber being in fluid
communication with said second supply port, said third operator port
and said fourth operator port;
[0011] b) a first selection valve located in said first chamber and a
second selection valve located in said second chamber, said first and second
selection valves being adapted to move in unison, said first and second
selection valves operable between a first position when said hydraulic fluid
is
at a first pressure and a second position when said hydraulic fluid is at a
second pressure, where in said first position, said first selection valve
permits
fluid communication between said first supply port and said first operator
port,
and said second selection valve permits fluid communication between said
second supply port and said third operator port, where, in said second
position, said first selection valve permits fluid communication between said
first supply port and said second operator port, and said second selection
valve permits fluid communication between said second supply port and said
fourth operator port; wherein said first pressure is lower than said second
pressure.
[0012] According to a second aspect of the invention, a hydraulic valve
assembly for delivering hydraulic fluid from a supply of hydraulic fluid to
one of
a first hydraulic operator and a second hydraulic operator is provided. The
assembly comprises:
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[0013] a) a valve block defining:
i) a supply port adapted for fluid communication with said supply;
ii) a first operator port adapted for fluid communication with said first
hydraulic operator;
iii) a second operator port adapted for fluid communication with said
second hydraulic operator;
iv) a chamber, said chamber being in fluid communication with said
supply port, said first operator port, and said second operator port;
[0014] b) a selection valve located in said chamber, said selection
valve operable between a first position when said hydraulic fluid is at a
first
pressure and a second position when said hydraulic fluid is at said second
pressure, where in said first position, said selection valve permits fluid
communication between said supply port and said first operator port, where in
said second position, said first selection valve permits fluid communication
between said supply port and said second operator port; wherein said first
pressure is lower than said second pressure.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] The invention will now be described, by way of example only,
with reference to the accompanying figures, where:
[0016] Figure 1 is a schematic of a hydraulic system for a lift truck;
[0017] Figure 2 is a perspective view of a valve assembly according to
a preferred embodiment of the present invention;
[0018] Figure 3 is a cross-sectional view of a valve block for the
preferred embodiment of Figure 2;
[0019] Figure 4 is a perspective view of a selection valve for the
preferred embodiment of Figure 2;
[0020] Figure 5A is a cross-sectional view of the preferred embodiment
of Figure tin a first position showing fluid flow in one direction;
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[0021] Figure 5B is a cross-sectional view of the preferred embodiment
in the first position as shown in Figure 5A, but showing fluid flow in an
opposite direction;
[0022] Figure 5C is a cross-sectional view of the preferred embodiment
of Figure 2 in a second position showing fluid flow in one direction;
[0023] Figure 5D is a cross-sectional view of the preferred embodiment
in the second position, as shown in Figure 5C, but showing fluid flow in the
opposite direction; and
[0024] Figure 6 is a schematic view showing the preferred embodiment
of Figure 2 connected to a side shifter and fork positioner.
DETAILED DESCRIPTION OF THE INVENTION
[0025] Figure 1 shows a hydraulic system for a lift truck connected to a
valve assembly 10 according to a preferred embodiment of the present
invention. The valve assembly 10 is connected to a control panel 11 by a first
hydraulic supply tine 12 and a second hydraulic supply line 14. The control
panel 11 is connected to a hydraulic fluid tank 16 by a tank supply line 18
and
a tank return line 20: A pump (not shown) is connected to the tank supply line
18 to provide the hydraulic fluid under pressure.
[0026] Referring again to Figure 1, the control panel 11 includes a
hydraulic circuit 26 to interchangeably connect the tank supply and return
lines 18, 20 to the first and second hydraulic supply lines 12 and 14. The
circuit 26 is operated in a conventional manner and will not be further
described.
[0027] The circuit 26 is hydraulically connected to three corresponding
levers in the lift truck cab. Other similar circuits may be used to control
other
vehicle functions such as mast tilting, carriage raising, and the like. For
convenience, only the lever 28 for operating the particular circuit 26 is
shown.
It will be understood by those skilled in the art that other types of
actuators
may be provided.
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[0028] Referring now to Figure 2, the valve assembly includes a valve
block 30, which preferably has a box-like shape. A first supply port 32 and a
second supply port 34 are provided in the valve block 30. The first and
second supply ports 32, 34 communicate with first and second hydraulic
supply lines 12, 14 (shown in Figure 1 ), respectively.. Preferably the supply
ports 32, 34 are located on the same face of the block 30. An orifice valve
35(shown in Figures 5A-5D) is preferably provided between the supply ports
32 and 34. The function of this orifice valve is discussed below. Preferably,
the diameter of the orifice valve may be about 0.043 inches.
[0029] Referring now to Figure 3, a first chamber 36 and a second
chamber 38 are provided in the valve block 30. The first and second
chambers 36, 38 communicate with first and second supply ports 32, 34 via
first and second block channels 40 and 42.
[0030] Referring again to Figure 3, four operator ports are provided in
the valve block 30. Preferably, a first operator port 44 and a second operator
port 46 are provided on one face of the block 30, and a third operator port 48
and a fourth operator port 50 are provided on the opposite face of the block
30. The first and second operator ports 44, 46 communicate with the first
chamber 36. The third and fourth operator ports 48, 50 communicate with the
second chamber 38.
[0031] Referring now to Figure 6, The first and third operator ports 44,
48 are connected to corresponding ports (not shown) of a first conventional
hydraulic operator 80. The first hydraulic operator may be, for example, a
fork
positioning cylinder. The second and fourth operator ports 46, 50 are
connected to corresponding ports (not shown) of a second hydraulic operator
82. The second hydraulic operator may be, for example, a side shifting
cylinder.
[0032] Referring again to Figure 3, a pilot channel 52 is provided in the
valve block 30. The pilot channel 52 communicates with first and second
chambers 36, 38. The pilot channel 52 also communicates with first and
second block channels 40, 42, all three meeting at an intersection 54. As
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shown schematically in Figures 5A-5D, a bi-directional valve 56 is located in
the intersection 54. Preferably, the bi-directional valve is a conventional
ball
and shuttle valve. The bi-directional valve alternatively connects pilot
channel
52 with block channel 40 or block channel 42.
[0033] Referring now to Figures 4 and 5A-D, a first conventional
selection valve 60 is located in the first chamber 36 and a second
conventional selection valve 61 is located in the second chamber 38.
Preferably, the selection valves 60, 61 are identical. Preferably, such valves
are commercially available from various valve manufacturers. One useful
example is a valve sold by Hydraforce Inc. (Model No. PD 10-40). The first
selection valve 60 includes a generally cylindrical valve housing 62 mounted
in the first chamber 36. The cylindrical valve housing 62 has an open end
proximate to the pilot channel 52, and defines an internal valve chamber 64.
The cylindrical valve housing 62 also includes a plurality of radially
directed
circumferentially arranged openings 65 for communicating with the first
chamber 36. A moving valve body 66 is located within the valve chamber 64
of valve housing 62. The valve body 66 has a pressure surface 68 adjacent
the open end of the valve housing 62. The valve body 66 has a narrower
portion which defines an annular space 69. The radially directed openings 65
communicate with the annular space 69 between the valve body 66 and the
valve housing 62. The valve body 66 is connected to a spring 74 located in a
closed end of the cylindrical valve housing 62. Valve body 66 may be moved
relative to valve housing 62 by collapsing the spring 74. The spring 74 biases
the valve body 66 to the position shown in Figures 5A and 5B. Preferably, the
spring resistance is configured such that a pressure of 315 PSI or greater
applied to pressure surface 68 is required to collapse the spring 74 so that
the
valve body 66 may move to the position shown in Figures 5C and 5D.
[0034] A number of external O-rings 70, 72 are provided to seal
portions of the first selection valve 60 against portions of the wall of the
first
chamber 36. Internal O-rings (not shown) are also provided to seal the upper
and lower ends of the annular space 69 from the remainder of the valve
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chamber 64 to prevent bleeding of fluid between the valve body 66 and valve
housing 62.
(0035] As the second selection valve 61 is the same as the first
selection valve 60, it will not be described in detail.
[0036] Referring now to Figure 6, the operation of the valve assembly
according to the present invention will now be described. For
convenience, the operation of the present invention will be described in
conjunction with a conventional hydraulically-operated fork positioner 80 and
side shifter 82 for a lift truck. For the purposes of the description, the
first
10 hydraulic operator will be the fork positioner, and the second hydraulic
operator will be the side shifter. It will be understood by those skilled in
the art
that the present invention may be operated with any two hydraulic operators
requiring different pressure, and is not confined to fork positioners and side
shifters, or to hydraulic operators for lift trucks. The operators could be
used
for any desired function, such as rotating, tilting, clamping, or the like.
[0037] Referring to Figure 1, when the lift truck operator wishes to
actuate the fork positioner in a first direction, such as to narrow the forks,
the
operator moves the lever 28 part-way in one direction. The circuit 26 is
partially activated to supply hydraulic fluid from the hydraulic fluid tank 16
along tank supply line 18, through section 22, and then to the first hydraulic
supply line 12. Because, the circuit 26 is only partly activated, the flow
rate of
hydraulic fluid in the first hydraulic supply line 12 is low, resulting in low
pressure as explained below. Preferably, low pressure means pressure
below 315 PSI.
[0038] Referring now to Figure 5A, the hydraulic fluid enters the first
supply port 32 and flows into first channel 40. The pressure of the fluid in
first
block channel 40 moves the bi-directional valve 56 into a position permitting
fluid communication between first block channel 40 and pilot channel 52,
while sealing off communication between second block channel 42 and the
pilot channel 52. The pressure of the fluid in the pilot channel 52 acts on
the
pressure surface 68 of each of the selection valves 60, 61. Because the
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pressure is below 315 PSI, neither of the valve bodies 66 of the selection
valves 60, 61 move. Accordingly, the annular channels of selection valves 60
and 61 remain aligned with first operator port 44 and third operator port 48,
respectively. The supply fluid in first block channel 40 also enters the
annular
space 69 through the radially directed openings 65 in the cylindrical housing
62 of the first selection valve 60. The fluid exits from the annular space 69
of
first selection valve 60 through additional radially directed openings 65 and
enters first operator port 44. The fluid is prevented from entering second
operator port 46 by O-ring 70 and the internal O-rings of the selection valve
60.
[0039] Referring to Figure 6, the hydraulic fluid travels to the fork
positioner 80 by line 84 connected to first operator port 44. As the fork
positioner is actuated to narrow the forks, hydraulic fluid also leaves the
fork
positioner 80 and enters third operator port 48 via line 86. The fluid is
routed
to second block channel 42 through the second selection valve 61, in a similar
but reverse manner as described for first selection valve 60. The fluid exits
the valve assembly 10 at second supply port 34 along second supply line 14.
[0040] Referring now to Figure 1, the fluid travels along second
hydraulic supply line 14 to circuit 26 and is directed into tank return line
20 to
complete the loop.
[0041] If the operator wishes to widen the forks, the operator moves
the lever 28 part-way in the opposite direction causing the circuit 26 to
partially activate so that section 24 is employed to direct a low pressure
flow
of fluid from the hydraulic fluid supply.tank 16 into the second hydraulic
supply
line 14.
[0042] Referring now to Figure 5B, the hydraulic fluid enters the valve
block 30 via the second supply port 34 and into the second block channel 42.
The bi-directional valve 56 is moved in the other direction such that it is
now
the second block channel 42 which communicates with the pilot channel 52.
Because it is low pressure fluid, neither of the valve bodies 66 of selection
valves 60 and 61 move from the position shown in Figure 2B. However, the
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hydraulic fluid flows through second selection valve 61 in the same manner as
described for the first selection valve 60. The hydraulic fluid flows out of
third
operator port 48 and into line 86 to the fork positioner 80. This causes the
fork positioner to operate in the opposite direction.
[0043] Hydraulic fluid flowing out of fork positioner 80 into line 84,
enters the valve assembly 10 at first operator port 44. The returning fluid is
directed into first channel 40 by the first selection valve 60, as described
above. The fluid exits at first supply port 32 and is returned to the tank
return
line 20 via first supply line 12. Thus, moving the lever 28 either way causes
the fork positioner 80 to move in either direction (i.e. narrowing or widening
the fork spacing).
[0044] Referring to Figure 1, if the lift truck operator wishes to actuate
the side shifter in one direction, the operator moves the lever 28 all the way
in
the first direction. The circuit 26 is fully activated, routing the fluid from
tank
supply line 18 through section 22 to first supply line 12. Full activation of
circuit 26 results in high pressure in first supply line 12. Preferably, high
pressure means pressure of 315 PSI or higher.
[0045] Referring to Figure 5C, the hydraulic fluid enters the first
chamber 36 along the same path as described for the narrowing function of
the fork positioner. In addition, the now high pressure fluid passes to the
pilot
channel 52 and acts against surface 68 of each of the valve bodies 66 of the
selection valves 60 and 61. Because the pressure in the pilot channel 52
acting against pressure surface 68 of each valve body 66 is greater than the
resistance of the respective springs 74, the valve body 66 of each selection
valve moves against the spring 74. This moves the valve bodies 66 to the
positions shown in Figures 5C and 5D, and thereby permits fluid in first block
channel 40 to flow through annular space 69 and into second operator port
46. O-ring 72 prevents fluid communication with first operator port 44.
Accordingly, hydraulic fluid flows to the side shifter 82 along line 88.
Hydraulic fluid returns to fourth operator port 50 along line 90, then through
selection valve 61. The fluid flows through the valve block 30 and out through
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the second supply port 34 in a manner analogous to the manner described
above. The fluid is returned to the tank in the same manner as described for
the narrowing function of the fork positioner.
[0046] If the lift truck operator wishes to actuate the side shifter in the
opposite direction, the operator moves the lever 28 all the way in the
opposite
direction, thus employing component 24, and thereby initiating high pressure
flow as described above. As shown in Figure 5D, the path of the high
pressure hydraulic fluid flow through the system is reversed, as described for
the widening function of the fork positioner. The valve assembly operation is
as described above.
[0047] Preferably, the hydraulic operators are able to achieve their
required functions while operating at different pressures. One pressure is
referred to herein as the lower pressure, while the other pressure is referred
to as the higher pressure. Absolute values are, of course, widely variable.
However, it is preferred that the two pressures differ by about 50 PSI. For
example, in one lift truck, fork positioning can be successfully preformed
using
pressures of less than 250 PSI, while side shifting can be accomplished using
pressures above 325 PSI. Other pressures and other pressure differentials
can be used depending on the vehicle and the implements being controlled.
The high pressure in the supply lines 12 and 14 is achieved by moving lever
28 quickly to the full open position in the desired direction. When the lever
is
moved, maximum flow rate through the control panel 11 occurs and pressure
quickly builds in the supply line 12 or 14. If the forks are loaded, there
will be
resistance to movement of the fork positioning cylinder. Therefore, pressure
will quickly build. As this occurs, pressure quickly builds within the valve
block
30, which shifts selection valves 60 and 61, as explained above. This, in
turn,
brings full fluid pressure on the side shift cylinder to achieve the desired
side
shift. If the forks are not loaded, there may be an initial tendency of the
fluid
to flow toward the fork positioner. However, this will be minimal as full
fluid
flow is occurring through the control panel 11 and fluid pressure will very
quickly build up to cause movement of the selection valves 60 and 61.
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[0048] When fork positioning is desired, the lever is moved in the
desired direction only part way. The initial fluid pressure available at
control
panel 11 is usually relatively low and, in any event, only a restricted flow
occurs. The restricted flow occurs at a lower pressure, and thus, fluid
reaching the valve assembly 10 is at the lower pressure. Because fork
positioning occurs when the forks are not loaded, the forks can be moved
using the lower pressure. Thus, the restricted fluid continues to flow as the
forks move and pressure does not build up in supply lines 12 or 14 or in valve
block 30. This, in turn, means the selection valves 60 and 61, remain in the
starting position shown in Figures 2A and 2B under the pressure exerted by
spring 74 and fork positioning continues to occur for as long as desired and
in
the direction desired
[0049] The orifice valve 35 may be provided to reduce any hammer
effect which may be caused by sudden changes in direction of the fluid flow.
[0050] The preferred embodiment of the invention described above is
configured to provide selectable, two-way, hydraulically actuated movement.
However, certain hydraulic operators may require only one way movement.
The return movement of the hydraulic operator may be provided by some
other source, such as a spring or gravity. For such hydraulic operators, the
second supply port 34, second block channel 42, second selection valve 61,
bi-directional valve 56, and third and fourth operator ports 48, 50 may be
omitted.
[0051] The present invention may be embodied in other specific forms
without departing from the spirit or essential characteristics thereof. The
presently disclosed embodiments are therefore to be considered in all
respects as illustrative and not restrictive, the scope of the invention being
indicated by the appended claims rather than the foregoing description, and
all changes which come within the meaning and range of equivalency of the
claims are therefore intended to be embraced therein.
