U.S. patent number 3,720,221 [Application Number 05/103,869] was granted by the patent office on 1973-03-13 for high pressure implement hydraulic circuit.
Invention is credited to John L. Hufeld, Donald J. Larson, Howard A. Marsden, James P. Mueller, William B. Norick.
United States Patent |
3,720,221 |
Hufeld , et al. |
March 13, 1973 |
HIGH PRESSURE IMPLEMENT HYDRAULIC CIRCUIT
Abstract
A relatively low pressure hydraulic control system for a high
pressure work output system in which a control valve is selectively
actuated to position a variable displacement axial piston pump to
control the flow in the work output system and to position a
directional valve which controls the direction of work output. In
such a system wherein two work outputs are provided, thereby
requiring two control valves, a priority valve may be utilized in
the low pressure system so that a signal from one of the control
valves will always override a signal from the other control valve
in controlling the axial piston pump.
Inventors: |
Hufeld; John L. (Peoria,
IL), Larson; Donald J. (Joliet, IL), Marsden; Howard
A. (Pekin, IL), Mueller; James P. (East Peoria, IL),
Norick; William B. (Joliet, IL) |
Family
ID: |
26800951 |
Appl.
No.: |
05/103,869 |
Filed: |
January 4, 1971 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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868964 |
Oct 21, 1969 |
3575000 |
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Current U.S.
Class: |
137/112;
137/107 |
Current CPC
Class: |
F15B
11/17 (20130101); F15B 2211/20576 (20130101); F15B
2211/25 (20130101); F15B 2211/20553 (20130101); Y10T
137/2557 (20150401); F15B 2211/6355 (20130101); F15B
2211/255 (20130101); Y10T 137/2567 (20150401); F15B
2211/7142 (20130101) |
Current International
Class: |
F15B
11/00 (20060101); F15B 11/17 (20060101); F16k
031/12 () |
Field of
Search: |
;137/107,112,113 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Nilson; Robert G.
Parent Case Text
This application is a divisional of U.S. patent application Ser.
No. 868,964 filed Oct. 21, 1969, now U.S. Pat. No. 3,575,000 issued
to Hufeld et al.
Claims
What is claimed is:
1. A priority valve in combination with a high pressure output of a
variable displacement pump supplying at least two separate fluid
implement circuits comprising:
a valve body having at least two circuit inlets one connected to
each fluid implement circuit and an outlet connected to a pressure
responsive pump control unit;
an axially movable valve spool disposed in said valve body to
control fluid communication between said two circuit inlets and
said outlet by opening and closing axially spaced ports in said
valve body,
biasing means urging said valve spool in a direction to close all
of said ports controlling fluid communication between said two
circuit inlets and said outlet said biasing means including a
primary biasing and a secondary biasing means, said secondary
biasing operable to abruptly increase the force of the biasing
means against further axial movement of said valve spool subsequent
to communication of one of said circuit inlets with said outlet;
and
two separate fluid reaction members having unequal fluid reaction
areas with one fluid reaction area having fluid communication with
one of said circuit inlets and the other fluid reaction area having
fluid communication with said other circuit inlet, said fluid
reaction members arranged to oppose said biasing means when their
fluid reaction areas are pressurized to open fluid communication
between one of said circuit inlets and said outlet whereby said
circuit inlet connected to the larger fluid reaction area will
connect its associated implement circuit to said outlet to the
exclusion of the other implement circuit.
2. The combination defined in claim 1 wherein the fluid reaction
members are coaxially aligned with said member with the larger
fluid reaction area abutting on the valve spool and the fluid
reaction member with the smaller fluid reaction area arranged to
act through said former fluid reaction member.
3. The combination defined in claim 1 wherein the biasing means
includes a fluid chamber in fluid communication with a pump relief
valve operable to close any communication between the two circuit
inlets and the outlet when a preselected relief pressure is
exceeded.
4. A priority valve in combination with a high pressure variable
volume fluid delivery circuit having a variable displacement pump
connected to said delivery circuit to supply pressurized fluid, a
pressure responsive pump control unit, at least two fluid implement
circuits communicating with said fluid delivery circuit and a pump
relief valve connected in said fluid delivery circuit,
comprising:
a valve body having at least two circuit inlets, each of said
inlets connected to a separate one of the fluid implement circuits
and an outlet connected to the pressure responsive pump control
unit;
an axially movable valve spool disposed in said valve body operable
to independently connect either one of said circuit inlets with
said outlet and to disconnect both of said circuit inlets with said
outlet in different axially positions within said valve body;
biasing means urging said valve spool in a direction to disconnect
said circuit inlets with said outlet;
two separate fluid reaction members having unequal fluid reaction
areas with one fluid reaction area having fluid communication with
one of said circuit inlets and the other fluid reaction area having
fluid communication with said other circuit inlet, said fluid
reaction members arranged to oppose said biasing means when their
respective fluid reaction surfaces are pressurized to open fluid
communication between one of said circuit inlets and said outlet;
and
a fluid chamber in said valve body associated with said biasing
means and in fluid communication with the pump relief valve
operable to axially move said valve spool to disconnect all of said
circuit inlets with said outlet when a preselected pump relief
pressure is exceeded by pressurized fluid from said pump relief
valve acting on said valve spool.
Description
BACKGROUND AND SUMMARY OF THE INVENTION
As hydraulically controlled machinery becomes larger and more
complex, the component parts used in controlling such machinery,
such as cylinders, connecting lines, and valves, must be increased
in size so as to withstand the high pressure forces which are
developed both by the control system itself and by reaction forces
from the work. With increased flow and higher pressures, leakage
within directional valves which utilize cylindrical spools has
become a problem and the costs of manufacture of such valves has
greatly increased due to the close tolarances which must be
maintained.
If the control systems are simply increased in size and the supply
of fluid comparably increased, the excess flow must be throttled
back to the tank or reservoir during times when all the flow is not
desired to perform a particular function. The excess flow is
converted to heat and wasted in the throttling process. Similarly,
when the machinery is stalled, much energy is again wasted.
In machinery having articulated movement, it is quite desirable to
reduce the number of large high pressure lines that are required to
pass over the swivel joints. For this reason, directly operated
control valves are not suitable for use on the large articulated
machines since the valves would have to be mounted close to the
operator's station, requiring a considerable number of high
pressure hoses to pass over swivel joints.
The high pressure implement hydraulic control system of the present
invention utilizes a variable displacement, axial piston-type pump
that is capable of producing the increased flows and pressures that
are necessary to operate large modern machinery. Although any
desired machinery may be so operated, the system is especially
adaptable to articulated machinery since it obviates the problem of
high pressure lines passing over swivel joints.
Essentially, the invention involves the use of a high pressure
machinery actuating circuit which is operated and controlled by a
low pressure control circuit.
With this system, the operator can limit the flow necessary to
perform a particular function reducing heat and energy losses -
thereby making the system more efficient. Additionally, the control
of pump displacement allows the utilization of directional valves
having poppet-type spools, since the throttling is not done by the
spools. Use of the poppet-type spools provides positive leakage
control and decreases overall manufacturing costs of the
directional valve packages. Precise control of the directional
valve is achieved by the use of pilot-operated, vented check valve
arrangements to control the actions of the poppet-type spools, and
is synchronized with the rest of the pilot system so that the
directional valves will function at the proper times.
Should the machinery become stalled, the pump is automatically
adjusted to a low delivery rate while maintaining the same pressure
or cylinder force, causing a reduction in heat and energy loss. In
such a case, the engine power demand is also substantially
reduced.
To reduce the number of high pressure lines crossing the swivel
joints, the main control valves will be mounted close to the
components they control and will be actuated by the low pressure,
pilot system. The displacement of the variable displacement pump is
also controlled by the pilot system and the control of the
displacement and directional valve is synchronized so that the
proper amount of supply fluid and pressure is available at all
times.
It is therefore an object of this invention to provide a hydraulic
system wherein the pressure and direction of flow in a high
pressure circuit are controlled by a low pressure circuit.
It is also an object of this invention to provide a hydraulic
circuit which may be used to control an articulated machine while
not requiring a large number of high pressure lines to pass over
the machine's swivel joints.
It is also an object of this invention to provide a high pressure
machinery actuating circuit which is operated and controlled by a
low pressure control circuit.
It is a further object of this invention to provide a hydraulic
system capable of producing the high pressures required by today's
machinery while maintaining a high degree of efficiency by
constantly controlling the fluid flow in the system.
It is also an object of this invention to control the high pressure
fluid flow in such a system by means of a low pressure actuated,
variable displacement, axial piston-type pump.
It is also an object of this invention to provide a hydraulic
circuit having high efficiency due to the reduction of heat and
energy losses through the control of hydraulic flow necessary to
perform a particular function.
It is a further object of this invention to provide a hydraulic
circuit utilizing directional valves having poppet-type spools.
It is a further object of this invention to provide in such a
circuit a system which produces positive leakage control while
decreasing overall manufacturing costs of the directional
valves.
It is a still further object of this invention to provide, in such
a circuit, precise directional valve control through the use of
pilot-operated, vented check valve arrangement to control the
actions of poppet-type spools.
It is also an object of this invention to provide such a circuit
wherein, when the machine is stalled, automatic adjustment to the
circuit occurs to allow a low fluid delivery rate while maintaining
a constant pressure.
Other objects of the invention will become apparent to those
skilled in the art upon perusal of the following description in
light of the accompanying drawings which illustrate preferred
embodiments of the invention. Embodiments using similar or
equivalent structure, which are included in the scope of the
appended claims, will become obvious to those skilled in the art
without departing from the present invention as defined in the
appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1 and 2, when combined by placing FIG. 2 to the right of FIG.
1, illustrate a complete schematic of the high pressure implement
hydraulic circuit of the instant invention;
FIGS. 3-6 illustrate schematic sectional views of an
operator-actuated control valve utilized in the subject hydraulic
circuit, with the valve spool in various positions of
actuation;
FIGS. 7-9 illustrate schematic sectional views of a priority valve
which may be utilized in the subject circuit with the valve spool
subjected to varying degrees of actuation;
FIGS. 10 and 11 illustrate schematic sectional views of a pilot
valve in the subject hydraulic circuit, with the valve spool in
unactuated and fully actuated positions respectively;
FIG. 12 illustrates a schematic sectional view of a servo valve in
the subject circuit;
FIG. 13 illustrates a schematic sectional view of a sequence valve
used in the control circuit; and
FIG. 14 is a sectional schematic illustration of a directional
valve in the subject circuit;
FIG. 15 is a schematic view of a modified embodiment of that
portion of the invention shown in FIG. 2;
FIG. 16 is a sectional schematic illustration of a modified
embodiment of the directional valve shown in FIG. 14, utilized in
the circuit of FIG. 15;
FIGS. 17 and 18 are modified embodiments of the valves illustrated
in FIGS. 10 and 11, which may be utilized in the circuit shown in
FIG. 15; and
FIG. 19 is a sectional schematic illustration of a modified
embodiment of the directional valve shown in FIG. 16 which may be
utilized in the circuit of FIG. 15 with slight modification
thereof.
DETAILED DESCRIPTION
The following description relates to the use of a high pressure
implement hydraulic circuit in any desired application. For ease in
illustration, however, the description will refer to the use of the
circuit on large loaders wherein lift and tilt circuits will be
designed to utilize maximum pressures up to about 6,000 psi. Many
modifications of the circuit, including deletion and duplication of
elements, will be obvious to those skilled in the art when using
the circuit for other applications.
It should be noted that the lift and tilt circuits in the system
are, in many respects, duplicate circuits. Therefore, the following
description will be essentially directed toward the lift circuit
upon the understanding that similar actions cause similar results
in the tilt circuit. Of course, where distinctions do exist between
the circuits, they will be fully discussed.
Now referring to the schematic illustration of the circuit shown in
FIGS. 1 and 2 together, a charging pump 21 drawing fluid from a
reservoir or tank 23 passes the fluid through a line 25, a steering
valve 27, a cooler 29, a filter 31, and lines 33 and 35 to a
variable displacement, axial piston-type pump 37.
When steering control valve 27 is actuated by the operator, fluid
is directed from pump 21 to the steering cylinders (not shown) and
back again through lines 39 and 41 so that the flow to pump 37 is
not interrupted when the vehicle is being steered.
When pump 37 is in a neutral position, it requires very little flow
or pressure through line 35. In such a condition of operation, the
fluid in line 33 passes into line 43 and through a bypass check
valve 45 which allows the flow to bypass the pump and pass into the
main supply manifold 47. With the lift and tilt circuits, which
will be more fully described below, in "hold" positions, fluid in
line 47 will pass through a sequency valve 49, lines 51 and 53,
sequence valve 55, line 57, and back to the tank 23.
Although the pressure of the fluid delivered by pump 21 to line 33
is normally governed by a relief valve 59, when pump 37 is in the
neutral condition previously described, the pressure in line 33 is
dictated only by line losses, thus reducing horsepower loss while
maintaining full supply lines.
When either the lift or the tilt circuit is actuated, causing pump
37 to be stroked, pressure in line 47 will close check valve 45,
and that portion of the charging flow not needed to supply pump 37
will be returned to tank 23 through relief valve 59.
A control pump 61 also draws hydraulic fluid from tank 23 for
actuation of the various control valves in the implement hydraulic
circuit. Fluid from the control pump is delivered through a line 63
and a filter 65 to an accumulator charging valve 67. The fluid is
then directed through the charging valve into a line 69 which
delivers the fluid to a pair of closed-center control valves 71 and
73. The fluid in line 69 is also delivered to a linear servo valve
75 through a line 77 and is then directed to an actuating cylinder
79, when the servo valve is shifted in either one of two operating
directions. A relief valve 81 maintains a maximum pressure of about
625 psi in the lines 69 and 77.
Pump 61 also supplies fluid to the accumulator and brake circuit,
when needed, through a line 83.
As previously stated, it will be assumed that the invention is
being applied to a loader having a lift circuit which is controlled
by valve 71 and a tilt circuit which is controlled by valve 73.
In FIGS. 3-6, there are illustrated schematic sectional views of a
control valve which may be either lift control valve 71 or tilt
control valve 73, with the discussion directed to it as the
former.
FIG. 3 illustrates the valve in its closed-center, unactuated, or
hold condition wherein fluid entering the valve through line 69 is
blocked from passage through the valve by suitable lands on the
valve spool 85.
RAISE
When the operator wishes to raise the loader bucket, he actuates
the spool 85 to the position shown in FIG. 4 and labeled R in FIGS.
1 and 3 by means of any suitable linkage (not shown). Control
fluid, maintained at 625 psi, is available to valve 71 through line
69, wherein it is directed to annuli 87 and 89 by a passage 91.
Movement of the spool 85 to the R raise position overcomes the
force exerted by a centering spring 93. This causes pressurized
fluid in annulus 89 to be communicated to an annulus 95, via an
annular groove 97, and then into a line 99 via passage 121. The
pressure in line 99 can be controlled by the operator between the
limits of O and 625 psi by means of variable area throttling slots
123 between land 125 and annular groove 97 on the spool 85. The
pressure in line 99 increases as the spool is moved to the right,
and when spool 85 is in the position shown in FIG. 4, i.e., its
fully shifted position, control pressure in line 99 is 625 psi.
As will be explained later, the pressure in line 99 will be used to
properly sequence the other control valves when it is in a range
from 0 to 300 psi. When it is between 300 and 625 psi, it is used
to stroke the linear servo valve 75, thereby creating an implement
pump flow proportional to the control pressure, i.e., 300-625
psi.
Thus the operator has the ability to actuate the lift cylinder at
any velocity he desires. Since valves 71 and 73 are essentially
identical, it can be seen that the operator also has the ability to
actuate the tilt cylinder at any desired velocity.
When the spool 85 is in the extreme raise position, as shown in
FIG. 4, a plunger 127 is forced into a detent groove 129 by a
spring 131. This action will cause the spool to be maintained in
that position either until a signal is received by valve 71 in a
manner to be explained later, or until the operator manually
actuates the spool 85, causing the plunger to ride up the sides and
out of the groove. Thus the operator is relieved of the necessity
of holding the control lever in the raise position during that
portion of the work cycle.
Referring again to FIGS. 1 and 2, line 99 directs the pressurized
fluid from valve 71 to a shuttle valve 133 which is shifted by the
fluid so that the fluid is directed through a line 139 to a
priority valve 141 which will be described later.
The fluid in line 99 is also directed to a line 135 leading to a
kick-out valve (not shown), mounted on the lift cylinder, and to a
pilot valve 137.
Referring to FIGS. 10 and 11, fluid from line 99 enters a chamber
143 in valve 137 and the force of the pressurized fluid works
against the end of a spool 145 to move the spool to the right,
against a force developed by a spring 147, to a maximum position as
shown in FIG. 11. The pre-load on spring 147 is such that the spool
145 will attain the position shown in FIG. 11 when the pressure in
chamber 143 reaches 150 psi.
As spool 145 moves to the right, pressure in a line 149, which is
the same as the pressure in line 53, (see FIG. 2) will be directed
from an annulus 151 to an annulus 153, via an annular groove 155,
into a passage 157, and then to line 159 for a purpose to be
described later.
With respect to priority valve 141, FIGS. 7-9, the line 139 directs
the pressurized fluid to an annulus 161 via a passage 163 to which
a passage 165 is interconnected. As the manipulation of spool 85 in
valve 71 provides an increase in pressure in line 139, that
pressure is also sensed in a chamber 167 in the valve 141, via
passage 165. The force in chamber 167 acts upon a piston 169 which,
in turn, acts on a piston 171 and a spool 173, to move the pistons
and the spool against a force exerted by a spring 175, to the
position shown in FIG. 8. When control pressure in line 139 reaches
approximately 200 psi, the position of the pistons and spool as
shown in FIG. 8 will be attained, and even though the signal
pressure increases to 625 psi, the spool 173 will not move further
to the left because of the small reaction area of piston 169 as
opposed to the additional force of a spring 177 against which the
slidable assembly now abuts. At that time, pressurized fluid in
annulus 161 will be in communication with an annulus 179 via
annular groove 181. This fluid is then directed to a line 183 via a
passage 185.
The line 183 directs the fluid to the linear servo valve 75 as
shown in FIGS. 1 and 12. The fluid is directed into a chamber 187
wherein it works against a piston area 189 on a reciprocable spool
191 located in the valve 75, to move the spool against a force
developed by a spring 193.
As this occurs the previously mentioned pressurized fluid in line
77 enters an annular groove 195 and is communicated to a line 197
by the annular groove. As shown in FIG. 1, the line 197
communicates with the actuating cylinder 79, and introduction of
pressurized fluid into the head end of the cylinder will cause the
cylinder housing 221 to move upwardly since the rod 223 is
pivotably secured to the vehicle frame. Since the housing 221 is
pinned to the body of pump 37, an upward movement of he housing
imparts an upward movement to the pump. As the fluid enters the
head end of cylinder 79 through line 197, fluid is expelled from
the rod end of the cylinder through line 431. When the fluid enters
valve 75 through line 431, it enters an annular groove 212 around
the sleeve 191 which connects with a drain line 214 so as to return
the fluid to tank 23.
Since the body of valve 75 is fastened to pump 37 and a rod 225 of
the valve is fastened to the vehicle frame, the resultant upward
movement of the body of valve 75, relative to the spool 191
therein, will close off the supply of pressurized fluid from line
77 to line 197, thereby cutting off flow of fluid to cylinder 79
and stopping the rotation of the pump 37 at its desired
displacement position. Thus, the pump delivers oil flow to the line
47 in proportion to the pressure of the fluid in line 183.
When priority valve 141 is returned to a neutral position so that
pressure is released from line 183, the force of spring 193 will
move sleeve 191 downwardly so that line 197 is connected to
passages 214 which are in communication with an enlarged inner
diameter 216 in sleeve 191. The enlarged inner diameter is in
communication with the annular groove 212 by means of a passage
218. This allows fluid in the head end of the actuating cylinder 79
to be expelled to tank 23 since pressure in line 77 will be
directed to the rod end of the actuating cylinder via annular
groove 195, passage 429, and line 431. This will effectively swivel
the pump 37 back to its minimum displacement position.
Referring once again to the pilot actuated valve 137 (FIGS. 10 and
11), when the valve is actuated to the position shown in FIG. 11,
the pressure in line 159 will set a shuttle valve 227 (FIG. 2) to
communicate the fluid from line 149 to a line 229 which, in turn,
communicates with a main directional control valve 231, the
operation of which will be described later. The fluid in line 229
also connects with a shuttle valve 233 which is shifted so that the
fluid from line 229 is communicated to a line 235 which is
connected to the sequence valve 55.
Referring now to FIG. 13, it can be seen that fluid entering the
sequence valve through line 235 acts against a poppet 237 and the
combined pressure of the fluid and the force of a biasing spring
239 serve to set the poppet so as to block the flow of fluid from
line 53 to return line 57. This allows pressure to build up in line
53, as required, up to a maximum of approximately 6,000 psi as
determined by the setting of a relief valve 241 (FIG. 1).
As shown in FIGS. 2 and 11, movement of the spool 145 of valve 137
to the position shown in FIG. 11 will also open a line 243 to tank
23 via a line 245. The opening of line 243 to tank will aid in the
conditioning of valve 231 for operation as described below.
A sectional schematic view of the main control valve 231 is shown
in FIG. 14. Since the valve is a directional-type valve, all of the
components that are in the lower half of a figure are identical to
and function in a manner similar to the components shown in the
upper half.
As described above, the line 243 will be fully open to tank when
the spool 145 in pilot valve 137 is fully shifted. When this
occurs, a combination of force from a spring 247 and hydraulic
force from fluid in chamber 249 will move a piston 251 away from a
poppet valve 253 and the poppet will function as a load check
valve. The hydraulic fluid in chamber 249 enters the chamber via
orifices 255 in the poppet and is communicated to the orifices via
a chamber 257 and line 259 connecting the chamber to the head end
of a lift cylinder 261. The hydraulic pressure exerted by this
fluid is created by the normal load reaction forces exerted by the
bucket on the lift cylinder 261. Thus, the pressure in chamber 249
forces piston 251 away from the poppet 253, but also serves to hold
the poppet against its seat.
As the operator strokes the control valve 71 so that a control
pressure of at least 300 psi is reached, the pump 37 provides a
flow through lines 47 and 53. As a result, a build-up of fluid
pressure in line 53 and passage 263 occures. When this pressure
raises to a level slightly higher than the load reaction pressure
in passage 257, poppet 253 will move upwardly and allow a flow of
fluid from passage 263 to passage 257, which fluid is then directed
to the head end of the lift cylinder 261 via line 259.
During this operation, no fluid in passage 263 can move past poppet
265 for a reason which will become obvious later.
Also during this time, a check valve spool 267 will be maintained
against its seat by the combined force of a spring 269 and fluid
under pressure in chamber 271. The fluid pressure in chamber 271 is
gained by fluid entering the chamber from passage 257 via an
orifice 273 in the head of the spool. Since the fluid in chamber
271 will act upon an area of the spool equal to the area against
which the fluid in chamber 257 will act, the spring 269 will
normally cause the check valve spool to be retained against its
seat. The pressure in chambers 257 and 271 will be blocked from
tank by a poppet-type relief valve 275, which will be maintained
against its seat by the force exerted by a spring 277, unless the
pressure in chamber 271 exceeds the pressure setting predetermined
by the spring 277.
The flow of high pressure fluid through line 259 and into the head
end of lift cylinder 261 will cause fluid to be expelled from the
rod end of the cylinder into a line 279. The line 279 communicates
with a chamber 281 in the bottom half of valve 231.
As previously stated, line 229 is connected to line 53 through the
pilot valve 137 connection of lines 159 and 149. Therefore,
pressure developed by the pump 37 will be exerted in a chamber 283
in valve 231 and will work against a piston 285, moving it to the
right against force developed by a spring 287. This relieves the
pre-load on a spring 289 and thereby relieves a poppet valve 291,
allowing the fluid flowing into chamber 281 from line 279 to pass
into tank 23 via a line 293. This occurs since the relief of the
poppet-type relief valve allows the unseating of a check valve 295,
similar to valve 267, in the lower half of the directional valve
231.
Should cylinder 261 attempt to run faster than that velocity
dictated by the pressure flow of pump 37, the pressure in line 53
decreases since the pump is not actuated to an amount required for
that movement. When this pressure decreases to about 200 psi, the
force of spring 287 overcomes the hydraulic force in chamber 283,
and piston 285 moves to the left, setting the poppet-type valve
291, so that the lower check valve 295 reseats and restricts the
flow of fluid exiting through line 293. Pump pressure will then
build up to a level required to position piston 285 so that the
check valve 295 meters a flow rate out of cylinder 261 equal to the
pump input of the cylinder.
Throughout the above sequence of events, pressure in line 149 is
provided through a spool in a pilot valve 297 to a line 299. Valve
297 is similar to valve 137 and, during this time, the spool in
valve 297 is in the position shown in FIG. 10. This causes piston
321 to set poppet-type valve 265 (FIG. 14) so as to prohibit flow
of fluid from passage 263 into passage 281 since the area of piston
321 is large enough that the pressure in passage 263 cannot
overcome it due to the smaller area of valve 265. Thus, fluid in
passage 263 cannot move into chamber 281.
As mentioned previously, fluid under pressure in line 99 is
communicated to a line 135 which delivers the fluid to a kick-out
valve of conventional design mounted on the lift cylinder. When the
lift cylinder reaches its maximum stroke, a cam will open a spool
in the kick-out valve so that flow is provided to an annular
chamber 323 (FIG. 4) around spool 85 of valve 71 from a line 325.
Pressure will build in chamber 323 due to the orifice 323a in the
drain passage of the valve 71, to counteract the force from spring
131 and retract plunger 127, allowing the force of spring 93 to
return the spool 85 to the neutral position, thereby stopping the
raise cycle.
ALTERNATE EMBODIMENT
The total hydraulic circuitry for the alternate embodiment can be
seen by separating FIGS. 1 and 2 and placing FIGS. 1 and 15 in a
similar end-for-end position. The valves illustrated in FIGS. 16-18
are those utilized in the alternate embodiment.
When it is desired to put the machine of the alternate embodiment
in the raised mode, valve 71 is actuated in the manner previously
described, with identical results relative to line pressurization,
priority valve actuation, etc. Pilot flow from line 69 is directed
to line 99 which connects with shuttle valve 133 to direct pilot
fluid to the valve 141 and to a second stage pilot valve 138 which
replaces the previously described valve 137. Valve 138 is shown in
cross-section in FIGS. 17 and 18 in the unactuated and fully
actuated positions respectively. Pilot pressure in line 99 will
shift the valve 138 so that pump pressure in line 149 will be
directed to a line 158 via an annulus 154, an annular groove 156
around spool 146, and annulus 160, since spool 146 is shifted to
the right against force from spring 148, as shown in FIG. 18.
With line 158 at pump pressure from line 149, the shuttle valve 228
will be shifted so that line 158 is communicated with a line 230.
The line 230 communicates with the modified directional control
valve 232 and a shuttle valve 234. When line 230 is pressurized,
shuttle valve 234 is shifted so that line 230 will be connected to
a line 236 to set the sequence valve 55 for proper operation of the
directional valve 232.
The modified directional control valve 232 is shown in detail in
FIG. 16, and pressurization of line 230 will condition the valve
for actuation of lift cylinder 261 as follows:
A check valve spool 254 is moved to the right against a force from
a spring 248 so that pump fluid under pressure from line 53 and
passage 264 can get into passage 258, via an annular groove 256
around spool 254 and a chamber 250 containing the spring 248. Fluid
under pressure in chamber 258 will be directed to a chamber 272,
through an orifice 274, so that pressure can aid the force of a
spring 270 in blocking a check valve 268 in the closed position.
Thus, fluid in passage 258 will be directed to lift cylinder 261
via a line 260.
The poppet-type relief valve, shown generally at 276, will protect
the circuit from any over-pressure conditions in that when a
predetermined pressure is reached, it will open and vent the spring
chamber 272 to tank through passage 252 and line 252a.
Since spool 350 will not be under the influence of a pilot
pressure, the spring 352 will keep it in the position shown in FIG.
16 to prevent communication between passage 252 and a line
252b.
Pressurization in line 230 is also directed to a chamber 284 and
will move a spool 286 upwardly against force from a spring 288.
Upward movement of the spool 286 will connect a passage 322 to tank
line 252b via an annular groove 286a around spool 286. This will
cause the chamber behind the load check valve 296 to be at tank
pressure so that the load check valve can be opened, thereby
connecting line 280 to the tank line 294 via a passage 282 and an
annulus 282a. Thus, fluid can be expelled from the rod-end of the
lift cylinder 261 during the raise mode when pump fluid is directed
to the head end of the cylinder as described above.
LOWER
When the operator wishes to lower the loader bucket, he actuates
the spool 85 to the position shown in FIG. 5 and labeled L in FIGS.
1 and 3, overcoming the centering force of spring 93.
The 625 psi control fluid available to valve 71 through line 69 is
again directed to annuli 87 and 89 via passage 91. The pressurized
fluid in annulus 89 is blocked by land 125 on the spool 85; on the
other hand, the fluid in annulus 87 is delivered to an annulus 327
via an annular groove 329. The fluid is then passed into a line 331
through passage 333. The pressure in line 331 can be controlled by
the operator between the limits of 0 and 625 psi by means of
variable area throttling slots 335 between land 337 and annular
groove 329 on the spool. The pressure in line 331 increases as the
spool is moved to the left, and when spool 85 is in the position
shown in FIG. 5, control pressure in line 331 is 625 psi.
When the control pressure in line 331 is in a range from 0 to 300
psi, it is used to properly sequence the other control valves and
when it is between 300 and 625 psi, it is used to stroke the linear
servo valve 75, thereby creating an implement pump flow
proportional to the controlled pressure, i.e., 300-625 psi.
Thus the operator has the ability to lower the loader bucket at any
velocity he desires.
Referring again to FIGS. 1 and 2, line 331 directs the pressurized
fluid from valve 71 to shuttle valve 133 which is shifted by the
fluid so that the fluid is directed to line 139 and priority valve
141. The priority valve is actuated by the control fluid in the
same manner as previously described for the raise mode, relative to
FIG. 8.
The fluid in line 331 is also directed to a pilot valve 297 which
is identical in construction to the pilot valve 137 which was
previously described. As shown in FIGS. 10 and 11, the line
reference numerals in parentheses refer to those lines leading to
and from valve 297 which are distinct from the lines leading to and
from valve 137. Since the interior structure of the valves are
identical, however, the same reference numerals are used in the
following discussion wherever possible. Similar use of parentheses
will be used relative to FIGS. 17 and 18 when describing the
alternate embodiment.
Fluid from line 331 enters chamber 143, in valve 297, and the force
of the pressurized fluid works against the end of spool 145, moving
the spool to the right against the force developed by spring 147,
to the position shown in FIG. 11. The preload on spring 147 is such
that the spool 145 will attain the position shown in FIG. 11 when
the pressure in chamber 143 reaches 150 psi.
A spool 145 of valve 297 moves to the right, pressure in line 149
(which is the same as pressure in line 53) will be directed from an
annulus 151 to an annulus 153 via an annular groove 155, into a
passage 157, and then to a line 339.
The fluid in line 339 sets a shuttle valve 341 which then directs
the fluid to a line 343. Fluid passing through line 343 then sets
shuttle valve 233 and, passing through line 235, sets sequence
valve 55 in the manner previously described relative to FIG. 13.
Additionally, the fluid in line 343 passes through line 345 to a
chamber 347 in control valve 231 (FIG. 14) where it serves to
actuate a piston 349 against the biasing force of a spring 351,
thereby relieving poppet valve 275. This allows fluid flowing into
chamber 257 from line 259 and the head end of lift cylinder 261 to
pass into tank 23 via a line 353. This occurs since the relief of
the poppet-type relief valve 275 allows the unseating of check
valve 267.
As shown in FIGS. 2 and 11, movement of the spool 145 of valve 297
to the position shown in FIG. 11 will open line 299 to tank 23 via
a line 355. Since valve 137 is in the unactuated position shown in
FIG. 10, line 149 provides pressure to a line 243 through the valve
so that load check valve 253 in the main directional control valve
231, is maintained in the closed position. On the other hand, since
line 299 is vented to the tank through valve 297, which is in the
position shown in FIG. 11, load check valve 265 of the directional
valve allows fluid in chamber 263 to pass into chamber 281 and the
rod end of lift cylinder 261 via line 279.
In other words, when the operator places spool 85 of control valve
71 in the lower position, fluid passes through the main directional
control valve 231 in the opposite direction to that which occurs
when spool 85 is placed in the raise position.
ALTERNATE EMBODIMENT
With reference to FIGS. 1 and 15-18, when the valve 71 is shifted
to the L or lower position, the second stage pilot valve 298 will
be activated, causing pressure in line 149 to be transmitted to a
line 340 to shift a shuttle valve 342. This connects line 340 with
a line 344 which, in turn, connects with a line 300, a line 346,
and shuttle valve 234.
As shown in FIG. 16, the line 300 will direct pressure so as to
shift a check valve spool 266 which is identical to the spool 254.
Pressure in line 346 will be directed to a chamber 348 to move
spool 350 downwardly to vent the chamber behind the load check
valve 268. Due to these events, pump flow from line 53 will be
directed to passage 282 and since that passage will be blocked from
the line 294 by load check valve 296 in a manner similar to the way
that load check valve 268 blocked line 354 in the raise mode, pump
fluid will be directed to the lift cylinder 261 via line 280.
Movement of spool 350 downwardly, due to the flow in line 346,
causes passage 252 to be vented to line 252b, and thereby to tank
23, to unload the check valve 268 and permit fluid being expelled
from lift cylinder 261 to be returned to tank via line 260, passage
258, and a line 354.
FLOAT
When the operator moves the control spool 85 of valve 71 to the
float position shown in FIG. 6 and labeled F in FIGS. 1 and 3, the
bucket is allowed to move up or down as external forces dictate and
flow from lift cylinder 261 can pass to and from tank 23 as
needed.
With the control spool in the position shown in FIG. 6, line 69 is
connected to a line 357 via annuli 89 and 361 and annular groove
363. Thus, a control signal of 625 psi is sent to shuttle valves
341 and 227, setting the shuttle valves and passing the fluid to
lines 229 and 343, thereby causing relief of poppet-type relief
valves 275 and 291 and setting of sequence valve 55, all in the
previously described manner.
Line 69 is also connected, via passage 91, annulus 87, groove 329,
annulus 327, and passage 333 to line 331. As previously described,
the fluid in line 331 actuates priority valve 141 to create a flow
in line 53 and also actuates pilot valve 297 to connect line 299 to
tank, thereby releasing piston 321 so as to allow valve 265 (in
valve 231) to act as a check valve.
Since load check valve 253 is held closed because pilot valve 137
is not actuated and since sequence valve 55 is closed and poppet
valve 291 is relieved as described, the flow in line 53 will pass
load check valve 265 and valve 295 and return to tank via line 293.
Since the flow in line 53 is returning to tank, the fluid passing
from line 149 to 339 through valve 297 will not have great enough
pressure to effect the setting of shuttle valve 341.
With the hydraulic system set in this manner, it can readily be
seen that the system will allow a true "float" of the bucket but is
in a condition to allow immediate force application to lift
cylinder 261 when the operator actuates spool 85 of the control
valve to the lower position. Thus, for example, the operator can
allow the bucket to fall by means of gravity and immediately move
the bucket to a digging position at the bottom of the fall with no
time delay.
During any mode of operation, make-up valves 365 and 367 are used
in a conventional manner to replenish the fluid supply, if
necessary, when the pressure of fluid in either chamber 257 or
chamber 281 falls below the pressure in tank 23.
ALTERNATE EMBODIMENT
Once again with respect to the alternate embodiment, in FIG. 17,
with the valve 138 in its neutral position, the annulus 160 is
connected to a tank line 246 via an annulus 152 and the annular
groove 156. Therefore, line 158 will be at tank pressure so that
the shuttle valve 228 (FIG. 15) can be shifted to condition the
circuitry for the float mode. When valve 71 is shifted to the float
position, pilot pressure from line 69 is directed to line 357 and
will shift shuttle valves 228 and 342 so that lines 230 and 346
will be pressurized. This has the effect of unloading both the
valves 268 and 296 to permit free flow of fluid within the
directional control valve and allow the lift cylinder 261 to let
the bucket drop to the ground by gravitational force alone.
TILT CIRCUIT
With respect to the tilt circuit, it should be noted that the dump
and rack back modes, labeled D and RB (FIG. 1), as controlled by
valve 73, are identical to and operate in the same manner as the
raise and lower modes as controlled by valve 71, with the exception
that flow through the sequence valve 49 does not return to tank but
instead communicates to line 53 as shown in FIG. 2. Also, fluid
flow from the lower half of directional valve 369, in the tilt
circuit, is directed to line 53 via a line 371 and a check valve
373. The check valve 373 prevents high pressure fluid from flowing
back into the low pressure side of the directional valve 369. This
allows activation of the lift system when the vehicle bucket is
being dumped. When the bucket is being racked back, the upper half
of valve 369 will be the load pressure side of the valve and fluid
returning from the tilt cylinder 375 will go directly to tank via
line 377 and will not be available to the lift system. Consequently
activation of the lift system is interrupted during the rack back
portion of the work cycle.
In priority valve 141, during a tilt operation, pressure from the
tilt control valve 73 is directed through a line 379, a shuttle
valve 381 and a line 383 to an annulus 385 via a passage 387 in
valve 141. Control pressure in passage 387 is also directed through
a passage 389 to a chamber 391 wherein it acts against piston 171
to drive spool 173 to the extreme left position shown in FIG. 9
against the forces of springs 175 and 177. The piston 171 is sized
such that, at a control pressure of 300 psi in line 383, the spool
173 is shifted to the FIG. 9 position. The control signal is then
supplied through annulus 385, annular groove 393, annulus 395,
passage 185, and line 183 to the linear servo valve 75 for control
of the displacement of pump 37.
Thus it can be seen that the tilt signal will override the lift
signal. For example, if the lift control valve is calling for
maximum pressure in line 139, 625 psi will be urging piston 169 to
the left. However, the force available against the smaller piston
is inadequate to move the spool 173 past the position shown in FIG.
8. If the tilt control valve is also actuated, the tilt signal
causes the spool to be moved to the position shown in FIG. 9 by the
time it reaches 300 psi, causing an interruption of the lift signal
from line 139. The tilt control signal is now supplied to the
linear servo valve 75 and the displacement of the pump can be
further increased to supply both the lift and tilt circuits
adequately.
If the maximum pressure output of pump 37 should ever exceed 6,000
psi, a pilot-operated relief valve 241 will automatically activate
to relieve that pressure. In so doing, some of the relieved flow
will pass through the pilot portion of the valve and through a line
397 back to tank 23. However, a small orifice 399 restricts the
flow through line 397 enough to produce a pressure in a line 421
which communicates with the priority valve 141. Fluid under
pressure in line 421 is communicated to chamber 423 in the priority
valve and the combined force resulting from this pressure in
chamber 423 and the biasing force of springs 175 and 177 is large
enough to overcome the force being developed in either chamber 167
or 391, so that the spool 173 will be moved back toward the neutral
position.
In that event, pressure in line 183 is communicated to tank via
passage 185, annulus 179, annular groove 181, annulus 425, and a
line 427. This will cause the pressure in chamber 187 of servo
valve 75 to reduce to tank pressure and allow force from the spring
193 to move spool 191 downwardly, communicating annuli 195 and 429
so as to transfer fluid from line 77 to line 431 and force pump 37
to return to the zero displacement position. This assures that
parts and components will not be damaged during the overpressure
condition and that over-heating will not occur.
ALTERNATE EMBODIMENT
It is felt that the description of the original embodiment,
together with the description of the alternate embodiment for the
three operational modes, will cause the operation of the machine
utilizing the alternate embodiment to be obvious.
MODIFIED ALTERNATE EMBODIMENT
The modified alternate embodiment of FIG. 19 is essentially
identical with that illustrated in FIG. 16; therefore, wherever
possible, identical identification labels have been utilized.
Except as explained below, the operation of the two valves is the
same. The distinctions between the two directional valves occur
primarily with respect to the structure and operation of the load
check valves 268 and 296.
Under certain conditions of operation, it may prove to be desirable
to provide greater stability in the operation of the check valves
268 and 296. This can effectively be accomplished by eliminating
the apertures 274 (FIG. 16) from the valves, and installing inserts
411 and 413 (FIG. 19) in the compartments 252 and 322,
respectively. Insert 411 may be provided with an aperture 415 which
communicates with passage 258 via a line 417 which is connected to
line 260 in the manner illustrated. Similarly, an aperture 419 and
insert 413 communicates with passage 282 via a line 421 which is
connected to line 280.
Referring to the upper half of the valve for example, the pressure
in passage 258 is communicated to chamber 272 via line 260, line
417, aperture 415, and passage 252. When the pressure in passage
258, and therefore passage 252, reaches a predetermined level, the
poppet relief valve 276 will be opened so that the passage 252 and
the chamber 272 will be connected to tank. This will allow pressure
in passage 258 to work against the face of the check valve 268 and
move it from its seat so that the passage 258 can be opened to tank
23 via line 354.
When the head end of the cylinder 261 is thus relieved, and it is
desired to maintain a controlled flow of fluid from the passage 258
to the line 354, the valve spool 350 will be moved downwardly
against the force of spring 352 by pressure exerted through line
346 in response to manipulation of the main control valve. When the
spool 350 is shifted, fluid flows from line 417 around an annular
groove on the spool, past a land 350a, and into the line 252b. A
pressure drop in passage 272 will occur as a result of this
connection, allowing the valve 268 to unseat. This pressure drop is
modulatable by adjustment of the position of land 350a. Further
movement of the spool 350 will cause the effect of the pressure
drop on check valve 268 to change from the control of land 350a to
land 350b, which influences flow from line 417 to the annular
groove.
Flow check valve 268 will open only so when there is pump pressure
available to maintain spool 350 in the shifted position. The flow
from line 417 to line 252b can thus be modulated in relation to the
pressure on the head end of cylinder 261 and the position of spool
350. This flow will be considerably greater than that which can
flow through a small orifice, such as 274 of the FIG. 16
embodiment, while maintaining the regulation and response of the
load check valve 268 at a very satisfactory level. The placement of
the insert 411 within the passage 252 allows the system to function
satisfactorily as a relief valve by means of poppet 276.
Thus, the Applicants have provided a vastly-improved control system
wherein a rather low pressure hydraulic system is utilized to
operate and control a high-pressure work output system. The
invention has been illustrated and described relative to two
possible embodiments and it is realized that many other
embodiments, modifications, etc., will be obvious to those skilled
in the art which do not exceed the purview of the following
claims.
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