U.S. patent number 3,578,888 [Application Number 04/817,475] was granted by the patent office on 1971-05-18 for fluid pump having internal rate of pressure gain limiting device.
This patent grant is currently assigned to Abex Corporation. Invention is credited to Cecil E. Adams.
United States Patent |
3,578,888 |
Adams |
May 18, 1971 |
**Please see images for:
( Certificate of Correction ) ** |
FLUID PUMP HAVING INTERNAL RATE OF PRESSURE GAIN LIMITING
DEVICE
Abstract
A fluid pressure energy-translating device such as a fluid pump
or motor, having a pressure-loaded element, such as a bushing, port
plate or cheek plate, held in position in the device by fluid under
pressure, which pressure is relieved by a rate of pressure gain
control mechanism whenever pressure surges or peaks occur in the
pressure loading.
Inventors: |
Adams; Cecil E. (Columbus,
OH) |
Assignee: |
Abex Corporation (New York,
NY)
|
Family
ID: |
25223175 |
Appl.
No.: |
04/817,475 |
Filed: |
April 18, 1969 |
Current U.S.
Class: |
418/133;
418/269 |
Current CPC
Class: |
F04C
14/265 (20130101); F01C 21/0863 (20130101) |
Current International
Class: |
F01C
21/08 (20060101); F01C 21/00 (20060101); F04c
015/00 () |
Field of
Search: |
;103/126,126 (BY,PA)/
;103/136 (R--1)/ ;103/136,41,42 ;230/152 ;418/133,269 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Croyle; Carlton R.
Assistant Examiner: Goodlin; Wilbur J.
Claims
I claim:
1. A fluid energy translating device having a zone of high pressure
and a zone of low pressure, an inlet and an outlet for said zone of
high pressure and zone of low pressure, said device including a
housing, rotary translating means, a stator encompassing said
translating means in said housing, a cheek plate which is movable
in said housing with respect to said stator and said translating
means in a direction parallel to the axis of said translating
means, wall means defining a pressure chamber on the side of said
cheek plate which is opposite to said translating means, said cheek
plate forming one wall of said chamber, fluid under pressure in
said chamber urging said cheek plate toward said stator and
translating means, a fluid passage means interconnecting said
chamber with a low-pressure zone, and a normally closed valve means
including a movable valve closure element located in said passage
means, said valve means being operable to open and dump fluid from
said chamber to said low-pressure zone in response to the rate of
pressure gain in said chamber exceeding a preset value.
2. The energy-translating device of claim 1 wherein said rate of
pressure gain responsive valve comprises a valve chamber bore
communicating at an inlet point with said fluid passage means and
at an outlet point with said low-pressure zone, said inlet point
and said outlet point of said bore being spaced apart, a valve seat
in said bore between the points of communication thereof with said
inlet and said outlet, said movable valve closure element being
resiliently urged by a spring toward said valve seat, said valve
closure element including a piston movably mounted within said
valve chamber bore, restricted passageway means interconnecting the
portions of said bore on opposite sides of said piston to the inlet
point of said bore, the end of said valve chamber bore located on
the side of said piston which is spaced away from said valve seat
being closed except for said restricted passageway means, said
valve closure element presenting a larger area to action of the
pressure of said pressure chamber on the side away from the valve
seat than is presented to the action of the same pressure on the
side of the valve closure element located adjacent the valve seat
so that the net differential force acting against said valve
closure element cooperates with said spring to bias said valve
closure element to a normally closed position,
said restricted passageway means being of such a size that it
restricts the passage of fluid therethrough so that fast rates of
pressure increases in said inlet cause said valve to open and spill
fluid to said low-pressure zone through said valve seat.
3. The energy-translating device of claim 2 wherein said restricted
passageway is located within said piston.
4. A fluid energy translating device having a zone of high pressure
and a zone of low pressure, an inlet and an outlet for said zone of
high pressure and zone of low pressure, said device including a
housing, a rotary translating means movable within said housing,
and a pressure-loaded holddown element movably mounted within said
housing, a fluid chamber defined on one side of said element, said
chamber being connected to a source of high pressure so that fluid
under pressure in said chamber urges said element to a
pressure-loaded position, fluid passage means connecting said
pressure chamber to a zone of low pressure, and valve means
including a movable valve closure element mounted within said
passage means, said valve means being responsive to excessive rates
of pressure gain in said pressure chamber to open and dump fluid
from said chamber to said low-pressure zone.
5. The device of claim 4 wherein said fluid energy translating
device comprises a rotary vane pump and wherein said
pressure-loaded holddown element comprises a cheek plate of said
pump.
6. The energy-translating device of claim 4 wherein said rate of
pressure gain responsive valve comprises a valve chamber bore
communicating at an inlet point with said fluid passage means and
at an outlet point with said low-pressure zone, said inlet point
and said outlet point of said bore being spaced apart, a valve seat
in said bore between the points of communication thereof with said
inlet and said outlet, said movable valve closure element being
resiliently urged by a spring toward said valve seat, said valve
closure element including a piston movably mounted within said
valve chamber bore, restricted passageway means interconnecting the
portions of said bore on opposite sides of said piston to the inlet
point of said bore, the end of said valve chamber bore located on
the side of said piston which is spaced away from said valve seat
being closed except for said restricted passageway means, said
valve closure element presenting a larger area to action of the
pressure of said pressure chamber on the side away from the valve
seat than is presented to the action of the same pressure on the
side of the valve closure element located adjacent the valve seat
so that the net differential force acting against said valve
closure element cooperates with said spring to bias said valve
closure element to a normally closed position,
said restricted passageway means being of such a size that it
restricts the passage of fluid therethrough so that fast rates of
pressure increases in said inlet cause said valve to open and spill
fluid to said low-pressure zone through said valve seat.
7. The energy-translating device of claim 6 wherein said restricted
passageway is located within said piston.
8. A hydraulic pump including a stator, a rotor within said stator,
a zone of high pressure and a zone of low pressure defined between
said stator and said rotor, an inlet and an outlet for said zone of
low pressure and zone of high pressure, an element which is movable
with respect to said stator and said rotor, one side of said
element partially defining a pressure chamber for urging said
element toward at least one of said rotor and stator, fluid passage
means communicating between said pressure chamber and a zone of low
pressure, valve means including a movable valve closure located
within said passage means, said valve means being responsive to
excessive rates of pressure increase in said chamber to open and
dump fluid from said chamber to said low-pressure zone.
9. The hydraulic pump of claim 8 wherein said element comprises a
cheek plate which is movable with respect to said stator and rotor
in a direction parallel to the axis of said rotor.
10. The pump of claim 8 wherein said rate of pressure change
responsive valve means comprises a valve chamber communicating at
an inlet point with said pressure chamber and at an outlet point
with said low-pressure zone, said inlet point and said outlet point
of said chamber being spaced apart, a valve seat in said valve
chamber between the points of communication thereof with said inlet
and said outlet, said valve closure being resiliently urged by a
spring toward said valve seat, said valve closure including a
piston movably mounted within said valve chamber, restricted
passageway means connecting both sides of said piston to the
pressure of said pressure chamber, the end of said valve chamber
located on the side of said piston which is spaced away from said
valve seat being closed except for said restricted passageway
means, said valve closure presenting a larger area to action of the
pressure of said pressure chamber on the side away from the valve
seat than is presented to the action of the same pressure on the
side of the valve closure located adjacent the valve seat so that
the net differential force acting against said valve closure
cooperates with said spring to bias said valve closure to a
normally closed position,
said restricted passageway means being of such a size that it
restricts the passage of fluid therethrough so that fast rates of
pressure increases in said inlet cause said valve to open and spill
fluid to said low pressure zone through said valve seat.
11. The valve of claim 10 wherein the rate of pressure change
responsive valve closure is generally cone shaped and said valve
seat is circular in cross section.
12. The valve of claim 10 wherein said restricted passageway
extends through said piston.
13. A hydraulic pump including a stator, a rotor within said
stator, a zone of high pressure and a zone of low pressure defined
between said stator and said rotor, an inlet and an outlet for said
zone of low pressure and zone of high pressure, a cheek plate which
is movable with respect to said stator and said rotor in a
direction parallel to the axis of said rotor, one side of said
cheek plate normally abutting said stator, pressure in said zone of
high pressure tending to urge the cheek plate away from said rotor,
said cheek plate separating said zone of high pressure from said
zone of low pressure, wall means defining a pressure chamber on the
side of said cheek plate which is opposite to said rotor, said
cheek plate forming one wall of said chamber, fluid pressure in
said chamber tending to urge said cheek plate toward said rotor,
first fluid passage means connecting said chamber at all times to
said zone of high pressure, second passage means connecting said
chamber to said zone of low pressure, and a normally closed valve
means located in said second passage means, said valve means being
responsive to excessive rate of pressure gain in said chamber to
open and spill fluid from said chamber to said low pressure
zone.
14. The pump of claim 13 wherein said valve means is operable to
respond to pressure rates of change irrespective of the initial
pressure at which such change is initiated if such change exceeds a
predetermined value.
15. The pump of claim 13 wherein said rate of pressure gain
responsive valve means comprises a valve chamber communicating at
an inlet point with said second fluid passage means and at an
outlet point with said low-pressure zone, said inlet point and said
outlet point of said valve chamber being spaced apart, a valve seat
in said valve chamber between the points of communication thereof
with said inlet and said outlet, a movable valve closure means
resiliently urged by a spring toward said valve seat, said valve
closure means including a piston movably mounted within said valve
chamber, restricted passageway means interconnecting the portions
of said valve chamber on opposite sides of said piston to the inlet
point of said valve chamber, the end of said valve chamber located
on the side of said piston which is spaced away from said valve
seat being closed except for said restricted passageway means, said
valve closure means presenting a larger area to action of the
pressure of said pressure chamber on the side away from the valve
seat than is presented to the action of the same pressure on the
side of the valve closure means located adjacent the valve seat so
that the net differential force acting against said valve closure
means cooperates with said spring to bias said valve closure means
to a normally closed position,
said restricted passageway means being of such a size that it
restricts the passage of fluid therethrough so that fast rates of
pressure increases in said inlet cause said valve closure means to
open and spill fluid to said low-pressure zone through said valve
seat.
16. The energy-translating device of claim 15 wherein said
restricted passageway is located within said piston.
17. A fluid energy translating device having a zone of high
pressure and a zone of low pressure, an inlet and an outlet for
said zone of high pressure and zone of low pressure, said device
including a housing, a rotary translating means movable within said
housing, said translating means including fluid displacement
cavities and a pressure-loaded fluid sealing element movably
mounted within said housing, a fluid chamber defined on one side of
said element, the opposite side of said element being exposed to
said displacement cavities, each of said displacement cavities
alternately being exposed to said zones of high pressure and zones
of low pressure, said chamber being connected through an orifice to
a source of high pressure so that fluid under pressure in said
chamber urges said element to a position that effects a seal
between said zone of high pressure and said zone of low pressure,
fluid passage means connecting said pressure chamber to a zone of
low pressure, and a valve including a movable valve closure element
mounted within said passage means, said valve closure element being
responsive to excessive rates of pressure gain in said pressure
chamber to momentarily open and bypass fluid from said chamber to
said low pressure zone, thereby permitting said fluid sealing
element to move to a position whereby fluid from those displacement
cavities which are located in the high pressure zone is bypassed
from said zone of high pressure to said zone of low pressure.
18. The energy-translating device of claim 17 wherein said valve
comprises a valve chamber bore communicating at an inlet point with
said fluid passage means and at an outlet point with said
low-pressure zone, said inlet point and said outlet point of said
bore being spaced apart, a valve seat in said bore between the
points of communication thereof with said inlet and said outlet,
said valve closure element including a piston movably mounted
within said valve chamber bore, restricted passageway means
interconnecting the portions of said bore on opposite sides of said
piston to the inlet point of said bore, the end of said valve
chamber bore located on the side of said piston is spaced away from
said valve seat being closed except for said restricted passageway
means, said valve closure element presenting a larger area to
action of the pressure of said pressure chamber on the side away
from the valve seat then is presented to the action of the same
pressure on the side of the valve closure element located adjacent
the valve seat so that the net differential force acting against
said valve closure element biases said valve closure element to a
normally closed position,
said restricted passageway means being of such a size that it
restricts the passage of fluid therethrough so that only fast rates
of pressure increases in said inlet cause said valve to open and
spill fluid to said low-pressure zone through said valve seat.
19. The energy-translating device of claim 18 which further
includes a resilient spring for biasing said valve closure element
into a closed position.
20. The energy-translating device of claim 18 wherein said
restricted passageway means is located within said piston.
21. A fluid energy translating device having a zone of high
pressure and a zone of low pressure, an inlet and an outlet for
said zone of high pressure and zone of low pressure, said device
including a housing, rotary translating means having fluid
displacement cavities therein, said cavities being alternately
exposed to said zones of high pressure and low pressure, a stator
encompassing said translating means in said housing, a cheek plate
which is movable in said housing with respect to said stator and
said translating means in a direction parallel to the axis of said
translating means, wall means defining a pressure chamber on the
side of said cheek plate which is opposite to said translating
means, said cheek plate forming one wall of said chamber, the
opposite of said cheek plate being exposed to said displacement
cavities, fluid under pressure in said chamber urging said cheek
plate toward said stator and translating means to effect a seal
between said zones of high pressure and low pressure, a fluid
passage means interconnecting said chamber with a low-pressure
zone, and a normally closed valve including a movable valve closure
element located in said passage means, said valve being operable to
open and dump fluid from said chamber to said low-pressure zone
when pressure gain in said chamber exceeds a safe operating
condition of said fluid energy translating device, the dumping of
fluid from said chamber being operable to cause said cheek plate to
move away from and out of sealing engagement with said translating
means whereby fluid from those cavities which are located in the
high-pressure zone is bypassed from said high-pressure zone to said
zone of low pressure.
22. The energy-translating device of claim 21 wherein said valve
comprises a valve chamber bore communicating at an inlet point with
said fluid passage means and at an outlet point with said
low-pressure zone, said inlet point and said outlet point of said
bore being spaced apart, a valve seat in said bore between the
points of communication thereof with said inlet and said outlet,
said valve closure element including a piston movably mounted
within said valve chamber bore, restricted passageway means
interconnecting the portions of said bore on opposite sides of said
piston to the inlet point of said bore, the end of said valve
chamber bore located on the side of said piston which is spaced
away from said valve seat being closed except for said restricted
passageway means, said valve closure element presenting a larger
area to action of the pressure of said pressure chamber on the side
away from the valve seat than is presented to the action of the
same pressure on the side of the valve closure element located
adjacent the valve seat so that the net differential force acting
against said valve closure element biases said valve closure
element to a normally closed position,
said restricted passageway means being of such a size that it
restricts the passage of fluid therethrough so that only fast rates
of pressure increases in said inlet cause said valve to open and
spill fluid to said low-pressure zone through said valve seat.
23. The energy-translating device of claim 22 which further
includes sa resilient spring for biasing said valve closure element
into a closed position.
24. The energy-translating device of claim 23 wherein said
restricted passageway means is located within said piston.
25. A hydraulic pump including a stator, a rotor within said
stator, a zone of high pressure and a zone of low pressure defined
between said stator and said rotor, an inlet and an outlet for said
zone of low pressure and zone of high pressure, a fluid-sealing
element which is movable with respect to said stator and said rotor
to effect a seal between said zone of high pressure and zone of low
pressure, one side of said element partially defining a pressure
chamber for urging said sealing element into engagement with at
least one of said rotor and stator, fluid passage means
communicating between said pressure chamber and a zone of low
pressure, a valve including a movable valve closure located within
said said passage means, said valve being responsive to excessive
rates of pressure increase in said chamber to open and dump fluid
from said chamber to said low-pressure zone, the dumping of fluid
from said chamber being operable to cause said sealing element to
move away from and out of sealing engagement with said one of said
rotor and stator whereby fluid is bypassed between said element and
said one of said rotor and stator from said zone of high pressure
to said zone of low pressure.
26. The hydraulic pump of claim 25 wherein said element comprises a
cheek plate which is movable with respect to said stator and rotor
in a direction parallel to the axis of said rotor.
27. The pump of claim 25 wherein said valve comprises a valve
chamber bore communicating at an inlet point with said fluid
passage means and at an outlet point with said low-pressure zone,
said inlet point and said outlet point of said bore being spaced
apart, a valve seat in said bore between the points of
communication thereof with said inlet and said outlet, said valve
closure element including a piston movably mounted within said
valve chamber bore, restricted passageway means interconnecting the
portions of said bore on opposite sides of said piston to the inlet
point of said bore, the end of said valve chamber bore located on
the side of said piston which is spaced away from said valve seat
being closed except for said restricted passageway means, said
valve closure element presenting a larger area to action of the
pressure of said pressure chamber on the side away from the valve
seat than is presented to the action of the same pressure on the
side of the valve closure element located adjacent the valve seat
so that the net differential force acting against said valve
closure element biases said valve closure element to a normally
closed position,
said restricted passageway means being of such a size that it
restricts the passage of fluid therethrough so that only fast rates
of pressure increases in said inlet cause said valve to open and
spill fluid to said low-pressure zone through said valve seat.
28. The energy-translating device of claim 27 which further
includes a resilient spring for biasing said valve closure element
into a closed position.
29. The energy-translating device of claim 28 wherein said
restricted passageway means is located within said piston.
30. A hydraulic pump including a stator, a rotor within said
stator, a zone of high pressure and a zone of low pressure defined
between said stator and said rotor, an inlet and an outlet for said
zone of low pressure and zone of high pressure, a cheek plate which
is movable with respect to said stator and said rotor in a
direction parallel to the axis of said rotor, one side cheek plate
normally abutting said stator, said cheek plate sealingly
separating said zone of high pressure from said zone of low
pressure, wall means defining a pressure chamber on the side of
said cheek plate which is opposite to said rotor, said cheek plate
forming one wall of said chamber, fluid pressure in said chamber
tending to urge said cheek plate toward said rotor to seal said
zone of high pressure from said zone of low pressure, first fluid
passage means connecting said chamber at all times to said zone of
high pressure, second passage means connecting said chamber to said
zone of low pressure, and a normally closed valve located in said
second passage means, said valve being responsive to excessive rate
of pressure gain in said chamber to open and spill fluid from said
chamber to said low-pressure zone, the spilling of fluid from said
chamber being operable to permit said cheek plate to move away from
said rotor and thereby bypass fluid directly from said zone of high
pressure to said zone of low pressure.
31. The pump of claim 30 wherein said valve is operable to respond
to pressure rates of change irrespective of the initial pressure at
which such change is initiated if such change exceeds a
predetermined value.
32. The energy-translating device of claim 30 wherein said valve
comprises a valve chamber bore communicating at an inlet point with
said second fluid passage means and at an outlet point with said
low-pressure zone, said inlet point and said outlet point of said
bore being spaced apart, a valve seat in said bore between the
points of communication thereof with said inlet and said outlet,
said valve closure element including a piston movably mounted
within said valve chamber bore, restricted passageway means
interconnecting the portions of said bore on opposite sides of said
piston to the inlet point of said bore, the end of said valve
chamber bore located on the side of said piston which is spaced
away from said valve seat being closed except for said restricted
passageway means, said valve closure element presenting a larger
area to action of the pressure of said pressure chamber on the side
away from the valve seat than is presented to the action of the
same pressure on the side of the valve closure element located
adjacent the valve seat so that the net differential force acting
against said valve closure element biases said valve closure
element to a normally closed position,
said restricted passageway means being of such a size that it
restricts the passage of fluid therethrough so that only fast rates
of pressure increases in said inlet cause said valve to open and
spill fluid to said low-pressure zone through said valve seat.
33. The pump of claim 32 which further includes a resilient spring
for biasing said valve closure element into a closed position.
34. The energy-translating device of claim 33 wherein said
restricted passageway means is located within said piston.
Description
The primary objective of this invention has been to provide an
improved structure in fluid pressure energy-translating devices and
particularly in fluid pumps operable when the device is subjected
to operating conditions that would normally cause sudden increases
in pressure or shock loads to instantaneously prevent such shock or
peak pressure loading of a port or cheek plate so that the plate
may momentarily move away from sealing engagement with the pumping
chambers, and momentarily reduce the pump delivery into the system,
and thereby prevent damage to the pump and system components.
The invention described and claimed herein is applicable to all
fluid pumps or motors which include a bushing, port plate or cheek
plate, the position of which is determined by fluid pressures. For
purposes of describing one preferred embodiment of the invention,
it is illustrated and described herein as applied to a vane-type
hydraulic pump but it is to be understood that its application is
not limited to such devices.
Fluid pumps and energy-translating devices have long been known of
the type that include a stator which encompasses or surrounds a
rotor and in which there is a movable element, such as an end
bushing, port plate or cheek plate which forms a wall at one side
of the stator and rotor and is urged toward them by a spring and
fluid pressure means. When these known devices are pumping fluid,
the movable element, such as a cheek plate, is urged toward the
rotor and stator by fluid pressure so that the cheek plate is
clamped very tightly to the stator and forms a seal therewith to
positively prevent any flow of fluid between the cheek plate and
stator. In this type of pump, the occurrence of a sudden pressure
peak or surge tends to cause the cheek plate to move away from the
rotor and the vanes until a partial short circuit develops between
the cheek plate and the rotor, thereby tending to relieve the
pressure overload condition. Upon the development of this partial
short circuit, some fluid leaks from the pressure port or exhaust
of the pump to the low-pressure intake, the high shock pressure
condition being somewhat relieved, since reduced pump volume is
delivered into the circuit.
However, the ability for this action to occur in former pump
designs is limited and does not, in all cases, prevent undesirable
pressure peaks from occurring that can not only damage the pump,
but other system components as well. Former designs are limited
because of the limited compressibility of the small volume of fluid
in the chamber that provides clamping pressure to the cheek
plate.
It has therefore been an objective of this invention to augment the
ability of the pressure loaded movable element or cheek plate to
move to increase the temporary short circuit during shock
conditions to eliminate undesirable peak pressures in the
system.
These objectives are accomplished and this invention is predicated
upon the concept of placing a rate of pressure gain valve that
employs a hydraulic spring and poppet principle in a pump in a
position to relieve pressure peaks from the clamping side of a
pressure-loaded cheek plate, bushing, port plate, and/or pressure
plate. This valve is operative in the event of a pressure peak or
tendency for a sudden increase in pressure that exceeds a
predetermined rate to allow the cheek plate to move away from the
rotor and the vane and thereby create a substantial, temporary
short circuit on the pressure side of the plate. This short circuit
allows the fluid to pass from the pressure zone of the port plate
to the suction or exhaust zone, thereby limiting the pressure
causing the peak. By simultaneously and temporarily limiting the
pressure on the clamping side of the cheek plate by venting it
through a rate of pressure gain control valve, the ability of the
pump to develop high pressure is also temporarily limited. Thus,
the ability of the pump as a pressure generator is limited until
the reason for the occurrence of pressure peaks is eliminated. In
other words, this rate of pressure gain valve allows an acceptable
rate of pressure buildup on the clamping side of the cheek plate
during normal operation, but prevents excessively high rates of
pressure buildup which often cause peak system pressures
substantially higher than relief valve settings, when slow response
relief valves are used.
Another object of this invention is to provide means within a pump
to momentarily bypass some of the pump displacement volume from its
outlet pressure zones to its inlet port when, for any reason, the
outlet port senses a sudden increase in pressure of a magnitude
that would result in pressure peaks over and above a desired safe
maximum system pressure, wherein the rate of pressure gain to which
the mechanism responds can be changed.
A further object is to provide means for controlling the duration
of the time period during which the bypassing of pump displacement
volume is sustained.
The construction of the valve which relieves these conditions is
such that it requires no minimum pressure to actuate it and it is
therefore equally responsive to a dangerous pressure rising
condition at 10 pounds per square inch as it is to a pressure gain
which is initiated at 1,000 pounds per square inch. Consequently, a
single valve is applicable to all types and sizes of fluid pumps
and motors.
These and other objects and advantages of this invention will be
more readily apparent from the following description of the
drawings in which:
FIG. 1 is an axial section of a vane-type pump incorporating a
preferred embodiment of the invention, and
FIG. 2 is a partial transverse or radial section taken along line
2-2 of FIG. 1.
The invention of this application is illustrated in the drawings as
applied to a vane pump. It should be appreciated, however, that the
invention is equally applicable to any type of pump or motor, such
as a gear or piston type of pump or motor to control or limit the
rate of pressure rise of fluid in the system which also acts upon
various pressure-loaded elements such as port plates, cheek plates,
bushings and/or pressure-responsive holddown mechanisms.
The pump to which the invention is applied by way of illustration
includes a housing or casing formed by a body casting 1 having a
generally cylindrical interior chamber, and an end cap 2 having a
cylindrical boss 3 which telescopes into the end of the body and is
sealed thereto by an O-ring 4. The end wall 5 of the body opposite
the end cap 2 includes a bore through which the pump-operating
shaft 6 extends. Shaft 6 is supported for rotation in this bore by
a bearing (not shown) which is secured against axial movement in
the bore. Shaft 6 extends from the body 1 into end cap 2 and is
carried for rotation therein by a needle-type roller bearing 7
mounted within a central bore in the end cap.
Cylindrical boss 3 of the end cap is finished to form a flat inner
surface which is clamped against a side or radial face 8 of a cam
ring 9. It may be mentioned here that the cam ring itself as well
as the housing and cam ring together are sometimes referred to in
the art as a stator.
A fluid intake passageway 10 extends radially into body 1 and
communicates with a pair of internal annular channels 11, 12 which
encircle the internal cavity within the body. These annular
channels 11, 12 distribute fluid from the intake passageway 10 to
suction ports to be described.
The cam ring 9 is supported radially by an annular rib 13 formed in
the body 1 between the annular channels 11, 12. The cam ring 9
encircles a rotor 14 which is connected to shaft 6 through a
motion-permitting spline joint 15 that permits proper running
alignment between the rotor, the flat surface of the cylindrical
boss 3, and a movable cheek plate 16. As can best be seen in FIG.
2, the rotor 14 is provided with a plurality of radial vane slots
17 in each of which a vane 18 is mounted.
The cam ring 9 has a cam surface 19 that is contoured to provide a
balanced or symmetrical pump construction in which there are
diametrically opposite low pressure or suction zones 20, fluid
transfer zones 21, high pressure or exhaust zones 22, and sealing
zones 23 formed between the cam surface 19 and the rotor 14 (see
FIG. 2). In order to provide the opposed zones, the cam surface 19
is formed in part from a first pair of arcs of equal radii which
extends across the fluid transfer zones 21 and, in part by a second
pair of arcs of shorter radii than the first pair of arcs which
extends across the sealing zones 23. These pairs of arcs are
interconnected by cam surfaces which extend across the low- and
high-pressure zones 20 and 22 respectively.
Cheek plate 16 is finished to provide a smooth flat surface on the
inner side thereof which abuts the cam ring 9, and has a central
bore 24 surrounded by a cylindrical boss 25 which extends into the
bore in the wall 5 of the body 1 and is sealed thereto by an O-ring
26. The outer cylindrical surface of cheek plate 16 is sealed to
body 1 by an O-ring 27 and is urged into sealing engagement by a
spring (not shown herein) described and shown in U.S. Pat. No.
3,076,414, issued Feb. 5, 1963 and assigned to the assignee of this
application.
The cheek plate 16 is movable axially in the body 1 and is urged
toward rotor 14 by fluid pressure supplied from the high-pressure
zone 22 through passageway 28 and orifice 29 to a pressure chamber
30 formed between the body and the outer face 31 of the cheek
plate. The cheek plate functions in the nature of an axially
movable, nonrotatable piston under the pressure supplied by the
fluid in chamber 30 to maintain it in engagement with the adjacent
side face of the cam ring 9. A light spring (not shown) biases the
cheek plate axially toward engagement with the adjacent side face
of the cam ring.
Intake passageway 10 communicates through annular channels 11, 12
around the cam ring 9 to suction ports spaced 180.degree. apart.
Two suction ports, one of which is shown at 50 in FIG. 2, are
formed in cheek plate 16 and are fed by channel 12, and two
additional suction ports (not shown) are formed in end cap 2 and
are fed by channel 11. These suction ports in the end cap and cheek
plate are identical in shape and are axially aligned with the
suction zones 20 between rotor 14 and cam surface 19. Each suction
port has a branch passage, the opening of one of which is
designated at 51, whereby the suction port communicates with the
inner ends 32 of vane slots 17 in the rotor 14 as well as with the
inlet zones 20.
As shown in FIG. 1, the end cap 2 includes two diametrically
opposed crescent-shaped exhaust or pressure ports 52, 52 which are
spaced substantially 90.degree. from the suction ports. Similarly,
pressure ports 56, 56 are formed in cheek plate 16 which are
axially aligned with the pressure zones 22 and with ports 52, 52 in
the end cap. Each pressure port 52 and 56 communicates with the
inner ends 32 of the vane slots 17 in the rotor as the vane slots
pass the ports through branch ports 54. Pressure ports 52, 52 are
connected with a fluid outlet or delivery chamber 34 by a
passageway 35 in the end cap 2.
In the direction of rotor movement (clockwise as shown by the arrow
in FIG. 2), the cam surface 19 progressively recedes from the
periphery of the rotor 14 across the suction zones 20. In the
transfer zones 21 cam surface 19 has a nearly constant radial
spacing from the rotor, and across the exhaust zones 22 the cam
surface progressively approaches the rotor 14 as it comes into
close proximity with the periphery of the rotor 14 in the sealing
zones 23. Fluid from the suction ports 50 is drawn into the fluid
transport pockets defined between the successive vanes as those
pockets become larger when the vanes 18 move through the suction
zones 20. The fluid is positively displaced from the pockets as the
volume thereof diminishes when the vanes move through the pressure
zones 22, to thereby effect a pumping action.
Each vane 18 is provided with grooves 36 which are formed in its
outer edge and opposite side edges. One or more channels or bores
37 are also provided in each vane which communicate between the
outer groove 36 of the vane and the inner end 32 of the vane slot.
The grooves 36 and channels 37 insure that the fluid pressure
acting on the first area or outer end surface or tip of any given
vane will be substantially balanced at all times by the pressure
acting on the second area or inner end surface of that vane.
For the pump to operate at high efficiency it is necessary to
maintain a continuous sealing engagement between the vane tips or
outer end surface with the cam surface 19, regardless of changes in
the arcuateness of the cam surface. To provide the hydraulic
pressure for this purpose, one or more radial bores or piston
cylinders 38 is formed in the rotor 14, extending inwardly from the
inner end 32 of each vane slot 17. The bores 38 are interconnected
at their inner ends with an annular pressure chamber 57 having
fluid under pressure therein. Thus, fluid can flow into and out of
pressure chamber 57 only through radial bores 38.
As best seen in FIG. 2, the pressure chamber 57 communicates with
the bores 38 through orifices or flow restrictors 46 having
cross-sectional dimensions which are small relative to the diameter
of the bores 38. Within the pressure chamber 57, and intermediate
the flow restrictors 46, are fluid velocity reducing chambers 58.
The pressure chamber 57 is constructed, in part, by defining in
rotor 14 an annular groove 46. The chambers 58 are formed in a
sleeve 40. Thereafter the sleeve is fitted and sealed in an axial
recess in rotor 14 with the chambers 58 intermediate the annular
groove 46, thus forming the pressure chamber 57. Hence, the
pressure chamber 57 includes the annular groove 46 and the chambers
58.
A generally cylindrical pin or piston valve element 41 is received
in each radial bore 38. Each piston 41 includes an axial bore 42
and is slidable in its cylinder 38 with which it is closely fitted
so that leakage of fluid along the external walls of the piston is
negligible. The outer end of each piston 41 is conically tapered as
at 43 and forms a valve with the flat inner edge surface 44 of each
vane 18. The lower end surface of each piston is preferably
chambered, as at 47, and presents a surface with which the fluid
pressure force within the chamber 39 may cooperate to force the
piston outwardly against the inner edge surface 44 of each vane.
The admission of fluid to the radial bores 38 is regulated by the
balance of forces between the fluid pressure force acting inwardly
upon the conical taper 43, tending to open the valve, and the
opposing force arising from the fluid pressure in chamber 39 and
the centrifugal force, tending to close the valve. The length of
the piston 41 is such as to permit it to move into and out of
engagement with the flat inner edge surface 44 of the vane 18,
regardless of the position of the vane in its slot.
In operation, valve 41, 44 at the outer end of the piston functions
in the manner of a check valve. When fluid pressure at the inner
end 32 of a vane slot acting upon the conical taper 43 of the
piston 41 sufficiently exceeds the pressure in chamber 39, the
piston is moved inwardly in its bore 38 and valve 41, 44 opens.
Pressure fluid in the inner end 32 of vane slot 17 flows inwardly
through bore 42 toward chamber 57 and restores, maintains, or
increases the fluid pressure in the pressure chamber as necessary
to balance the fluid pressure acting to open the valve 41, 44. This
action occurs when the vane slot 17 traverses a pressure zone 22,
for fluid pressure in the zone 22 is usually the highest in the
pump and the pressure in chamber 57 is somewhat lower. When a vane
18 is traversing a suction zone 20, the fluid pressure in chamber
57 exceeds the opposing fluid pressure on end 43 of piston 41, and
the piston is held against the inner end 44 of the vane, to close
valve 41, 44 and to urge the vane 44 radially outwardly in its slot
17.
The pump per se heretofore described is well known and is
completely described in U.S. Pat. No. 3,401,641, issued Sept. 17,
1968, and U.S. Pat. No. 3,076,414, issued Feb. 5, 1963, and
assigned to the assignee of this application. It forms no part of
the invention of this application except in combination with the
novel valve 60 hereinafter completely described.
The invention of this application consists of the provision of a
control valve in combination with the pump. This valve is connected
to the pressure chamber 30 and is operative to relieve sudden
pressure surges in the chamber 30 before those pressure changes can
result in damage to the pump. Pressure surges of the type to be
relieved by valve 60 often far exceed the pressure setting of any
relief valve in the hydraulic system which is being supplied with
fluid by the pump. Because of their suddenness these short duration
pressure peaks cannot be relieved by conventional pressure relief
valves, because these valves cannot react quickly enough to relieve
the condition. The valve 60 functions in cooperation with cheek
plate 16 to temporarily short circuit some of the pump delivery
back to the suction or inlet port, to relieve the pressure peaks in
the pump outlet 34, and thereby minimize or eliminate damage to the
pump and other system components which would otherwise result from
these pressure peaks.
Valve 60 is located within the casing 1 and comprises a bore 61
connnected at its inner end by a passage 62 to the pressure chamber
30. A shoulder 63 is defined by a stepped section of the bore 61
between a small diameter inner end section 64 and a larger diameter
intermediate section 65. The outer end of the section 65 of the
bore is threaded as at 66 and accommodates a threaded closure or
sealing plug 67.
A piston 68 is slidably mounted within the intermediate section 65
of the bore. It has a conically shaped valve or valve closure 69
formed on its inner end. This conically shaped end section or valve
69 is engageable with the shoulder 63 to form a seal between the
end section 64 and the intermediate section 65 of the bore. In
other words, the shoulder 64 acts as a valve seat and the conical
end section 69 of the piston 68 acts as a valve closure between the
end section 64 and the intermediate section 65 of the bore section
61.
The end section or chamber 64 is connected by the conduit 62 to the
high-pressure chamber 30 and the intermediate section or chamber 65
is connected by a conduit 70 to the inlet port or suction port 10
of the pump.
A closed fluid compression chamber 71 is defined by or between the
inner end 72 of the plug 67 and the outer end of the piston 68.
This chamber 71 is enlarged by a central bore 75 which extends from
the outer end of the piston to a point adjacent the inner end. An
orifice 29 in cheek plate 16 connects chamber 30 to the source of
pressure in outlet port 56, and a small restricted orifice 76
connects the chamber 71 to the pressure chamber 64, so that under
static conditions or when pressures in the system change slowly,
the pressure behind the piston 68 urging it inwardly to close the
valve seat 63 rises and falls in unison with the control pressure
in the chamber 30 which urges the cheek plate into engagement with
the cam ring. This is the same pressure as that on the exhaust port
or pressure port of the pump and is the highest pressure in the
pump, except when pressure in the exhaust port changes rapidly.
The area of the piston on the outside or valve closure side 73 of
the piston 68 is slightly greater than the area on the inside of
the piston exposed to the same high or control pressure of the
pressure chamber 30. Consequently, the net force differential
lightly urges the valve 69 to a closed condition. To further assist
this small differential force in maintaining the valve closed and
to hold the valve closed when there is no fluid in the valve 60, a
low force spring 78 is located between the inner end 72 of the plug
and the outer end of the piston. The spring 78 also functions in
cooperation with orifice 76 to control the rate of closing of the
valve 69 after it has been opened. It should be noted that neither
the small fluid force differential nor the spring offer much
resistance to opening the valve 69.
In operation, the rate of pressure gain control valve 60 remains
closed at all times except upon the occurrence of a very high rate
of pressure increase or gain. In the event of a sudden pressure
gain in the pressure port 52 and then in the chamber 30, pressure
in the chamber 64 increases at a faster rate than it can be
equalized by flow of fluid through the restricted orifice 76. In
other words, in the event that a sudden stoppage of flow in the
system tends to cause a very sudden pressure increase, flow through
the restricted orifice 76 is insufficient to provide immediate
pressure equalization on opposite sides of the piston 68. Since the
hydraulic fluid is slightly compressible, the higher pressure in
the chamber 64 causes the fluid in the chamber 71 to be compressed
by stroking of piston 68, and thereby opens the valve 69. This
allows fluid from the chamber 30 to spill through passage 62,
chamber 64, and the valve seat 63 to the intake or suction port 10.
Since chamber 30 is supplied by fluid flowing from pressure port 56
through restricted orifice 29, a loss of fluid from chamber 30
creates a pressure differential on the opposite sides of cheek
plate 16. Therefore, the cheek plate 16 will move away from cam
ring 9 which causes a momentary short circuit of fluid from the
outlet zones to the inlet zones of the pump. The volume of fluid
being pumped to the system is momentarily reduced and therefore
results in a reduction of the rate of pressure increase in the
system.
After the high rate of pressure rise has subsided, the spring 78 is
able to reclose the valve 69 as sufficient flow is able to pass
through the orifice 76 into the chamber 71. The rate of closing can
be controlled by the strength of the spring 78, the size of the
orifice 76 and the volume of chamber 71. The cheek plate is now
free to move back relatively slowly by flow-entering chamber 30
through orifice 29, and the cheek plate will again be clamped in
sealing engagement with the cam ring 9, which stops the temporary
short circuit.
If desired, the rate of pressure gain to which the valve is
responsive may be made adjustable or variable by substituting a
threaded screw for the tapered plug 67. By varying the size of the
compression chamber 71 with this screw, the volume of fluid
contained in the chamber 71 may be varied and the rate of pressure
gain required to compress the fluid to the degree required to open
the valve 69 may be altered.
It should be understood that the cheek plate 66 described and
illustrated in U.S. Pat. No. 3,076,414 could readily be substituted
for the cheek plate 16 illustrated herein, and thereby obtain the
advantages of this invention, as well as the advantages of the
invention claimed in U.S. Pat. No. 3,076,414.
While I have described only a single preferred embodiment of my
invention, those persons skilled in the arts to which this
invention pertains will readily appreciate numerous changes and
modifications which may be made without departing from the spirit
of my invention. Therefore, I intend to be limited only by the
scope of the appended claims.
* * * * *