Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates ~o flow and pressure
compensated valves and pump circuits incorporating the same and
particularly to a flow and pressure compensated valve which can
be used to control the output of a variable stroke piston pump
alone or in conjunction with a gear pump in parallel therewith.
The use of 10w and pressure compensated valves in
conjunction with gear pumps is common in the hydraulic field.
Such systems require some sort of by-pass or compensated inlet
section in order to be operative because of the fixed displace-
ment of the gear pump. This system is, of course, energywasteful because of the horsepower lost in pumping oil which is
not used for working but simply by-passed.
Variable displacement piston pumps, such as swash
plate pumps, have long been available. However, no simple
system for using standard valve configurations to use such
pumps to provide flow and pressure compensation are available.
`; We have developed a valve structure based upon a
- conventional open center type valve using a special spool which
provides a signal to control the displacement of a variable
displacement piston pump to provide a flow and pressure compen-
sated system without the loss of horsepower associated with
ixed displacement gear pumps. Our invention can be used in
connection with a single variable displacement piston pump or
in a system using a variable displacement piston pump and a
gear pump in parallel.
; We provide a valve housing having a central outlet
- chamber, a pair of parallel inlet pressure chambers, one on the
` opposite side of said outlet chamber, a pair of work chambers,
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one on the opposite sides o said parallel chambers and a pair
of exhaust chambers, one at each end of the housing on opposite
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sides of the work chambers, a pair of work ports connected to said work
chambers, an inlet port connected to said parallel chambers, an outlet port
connected to said outlet chamber, a bore extending through the housing inter-
secting all of said chambers, and an elongate spool extending through said
bore and movable therein, said spool having an axial bore at each end, a
pair of spaced radial passages in each end of said spool communicating be-
tween the outside of said spool and the axial bore at each end and adapted
to connect a work chamber and the outlet pressure chamber when the spool is
moved to deliver pressure fluid from a parallel chamber to said work chamber,
whereby said outlet pressure chamber provides a pressure signal for control-
ling the displacement of a variable displacement piston pump.
Thus, in accordance with one broad aspect of the invention, there
is provided a flow and pressure compensated valve and pump system capable
of controlling the input to said valve from a variable displacement piston
pump comprising a variable displacement pump, an elongate valve housing, a
central outlet chamber in said valve housing, a pair of parallel inlet
pressure chambers on opposite sides of said outlet chamber, a pair of work
chambers on opposite sides of said parallel chamber, a pair of exhaust cham-
bers on opposite sides of said work chambers, a pair of work ports connected
to said work chambers, an inlet port adapted to receive pressure fluid from
said variable displacement pump connected to said parallel chambers, an out-
let port connected to said outlet chamber, a bore extending longitudinally
through said valve housing intersecting all of said chambers, and an elongate
spool extending through said bore and movable therein, said spool having an
axial bore at each end, a pair of spaced radial passages in each end of said
:' spool communicating between the outside of said spool and the axial bore at
two space points in each bore, and adapted to connect one work chamber and
` the outlet chamber when the spool is moved to a work position connecting a
;~ parallel chamber and said one work chamber whereby said outlet pressure
; 30 chamber provides a pressure signal from said one work chamber through an
outlet port, and a pump compensator on said variable displacement pump for
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controlling the displacement of said variable displacement piston pump in
accordance with said pressure signal.
In accordance with another broad aspect of the invention there is
provided a valve and hydraulic pump circuit providing compensated flow and
pressure comprisin~ at least one variable displacement piston pump, a control
compensator on said pump adapted to vary the displacement of said pump in re-
sponse to a pressure differential between the pump output and a second pres-
sure applied thereto, a valve housing, means delivering pressure fluid from
said pump to said valve housing a connection from said means delivering pres-
sure fluid to said valve housing delivering a pressure fluid signal to said
control compensa~or on said pump, a central outlet chamber in said housing, a
pair of parallel inlet pressure chambers on opposite sides of said outlet
chamber, a pair of work chambers on opposite sides of said parallel chambers,
a pair of exhaust chambers on opposite sides of said work chambers, a pair of
work ports connected to said work chambers, an inlet port adapted to receive
pressure fluid connected to said parallel chambers, an outlet port connected
to said outlet chamber, a bore extending longitudinally through said housing
intersecting all of said chambers, and an elongate spool extending through
said bore and movable therein, said spool having an axial bore at each end, a
pair of spaced radial passages in each e~.d of said spool communicating between
the outside of said spool and the axial bore at two spaced points in each bore,
and adapted to connect one work chamber and the outlet chamber when the spool
is moved to a work position connecting a parallel chamber and said one work
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!~`` chamber, means connecting said outlet chamber to said control compensator on
said pump whereby said compensator is provided with a pressure signal from said
work chamber to form a pressure differential with the outlet pump pressure
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~ fluid signal to vary the pump displacement.
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In the foregoing general description we have set out certain ob-
jects, purposes and advantages of our invention. Other objects, purposes and
`~ 30 advantages will be apparent from a consideration of the following description
` and the accompanying drawings in which:
~; Figure 1 is a section through a valve according to this invention;
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Figure 2 is a schematic drawing of a multiple valve arrangement
receiving pressure fluid from a variable displacement piston pump whose
displacement is controlled by a signal from said valves;
Figure 3 is a schematic drawing of a multiple valve arrangement
receiving pressure fluid from a gear pump and a variable displacement piston
pump in parallel where the displacement of the piston pump is controlled by
said valves; and
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Figure 4 is a section through a second embodiment of
valve according to this invention.
Referring to the drawings we have illustrated a valve
housing 10 of conventional open center, parallel passage design
having a center chamber 11, connected to an outlet port 12, a
` pair of chambers 13 and 14 on opposite sides of center chamber11 which normally are inlet chambers connected to an inlet port
15, a pair of parallel chambers 16 and 17 on opposite sides of
chambers 13 and 14 connected to inlet port 18 and outlet port
19, a pair of work chambers 20 and 21 on opposite sides of the
parallel chambers having corresponding work ports 22 and 23 and
a pair of exhaust chambers 24 and 25 on opposite sides of the
work chambers 2~ and 23 and connected to ports 26 and 27.
A central elongate bore 30 extends from end to end of
the housing 10, intersecting all of chambers 11, 13, 14, 16,
~; 17, 20, 21, 24 and 25. ~n elongate spool 31 is movable in bore30. Spool 31 has a central groove 32 which in the neutral
position connects chambers 11, 13 and 14, and a pair of grooves
33 and 34 on opposite sides of central groove 32 and within
work chambers 22 and 23 in the neutral position. Spool 31 has
axial bores 35 and 36 at its opposite ends, spaced radial
passages 37 and 38 from bores 35 and 36 adjacent the inner ends
35a and 36a of bores 35 and 36 and spaced radial passages 39
and 40 respectively Erom bores 35 and 36 to grooves 33 and
34. Each of bores 35 and 36 is divided between passages 37 and
` 38 and 39 and 40 by plugs 41 and 42 with central axial passages
` 43 and 44 which are normally closed by spring loaded balls 45
and 46.
The valve of this invention may be used alone or in
multiples as illustrated in Figu~es 2 and 3 to cont~ol the
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displacement of a variable displacement piston pump. In Figure
2, I have illustrated a variable displacement piston pump 50
delivering pressure fluid to the parallel chambers 16 and 17 of
successive valves through an inlet section 51 and block plate
52 which permits inlet pressure fluid from pump 50 to go to
parallel passages only and blocks normal inlet chambers 13 and
14 and inlet port 15. Center chambers 11 and outlet port 12
are connected by line 59 to a control compensator 60 on pump 50
which controls the displacement of the pump. Control compen-
sator 60 is connected through line 61 to the output of pump 50
and the pressure differential between line 59 and line 61
causes the compensator 60 to adjust the displacement of pump
50.
In Figure 3 I have illustrated a system with a gear
pump 70 in parallel with a variable displacement piston pump 71
both delivering fluid to a special compensated inlet valve 72
which connects the input line 73 with the parallel chambers 16
and 17 and connects the open center passages 13 and 14 with
pump compensator 75 on pump 71 through line 76. The
compensator inlet valve also is provided with a relief valve
portion which by-passes fluid to the exhaust chambers of the
valve because of the gear pump 70 and the constant volume which
it provides.
~' In Figure 4, we have illustrated a second embodiment
of this invention in which a cylindrical cartridge 80 contain-
ing a ball, spring and seat is substituted for the ball, spring
and seat of Figure 1. All other parts are the same and bear
like numbers with a prime sign.
In the foregoing specification, we have set ou-t
certain preferred practices and embodiments of our invention,
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however, it will be ~lnderstood that ~he invention may be
otherwise embodied within the scope of the following claims.
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