Patent 1275092 Summary

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A hydraulic fluid flow control cartridge for use
with a hydraulic fluid pump and for controlling flow of
hydraulic fluid between a reservoir and the hydraulic fluid
pump and from the hydraulic fluid pump to a fluid pressure
chamber, the hydraulic fluid flow control cartridge comprising:
a first cartridge passage having a first check valve
means for selectively providing for fluid flow from the
hydraulic fluid reservoir to the hydraulic fluid pump, said
first check valve means including means for preventing fluid
flow from said hydraulic fluid pump to the reservoir,
a second cartridge passage having second check valve
means for selectively providing for hydraulic fluid flow from
said hydraulic fluid pump to said fluid pressure chamber but
preventing fluid flow from said fluid pressure chamber to said
hydraulic fluid pump, and
means responsive to the hydraulic fluid pressure in
the pump for automatically causing hydraulic fluid in the
hydraulic fluid pump to be vented to the reservoir whenever the
hydraulic fluid pressure in the pump exceeds a selected maximum
hydraulic fluid pressure, the means for selectively venting
including a third cartridge passage.

2. A hydraulic fluid flow control cartridge as set
forth in claim 1 wherein said means for automatically causing
hydraulic fluid in the hydraulic fluid pump to be vented
includes a valve seat in said third passage, a valve member
engageable with said valve seat and movable away from said
valve seat to permit fluid flow from said pump to said
reservoir, and spring means engageable with the valve means and
resiliently biasing the valve means against the valve seat.



3. A hydraulic fluid flow control cartridge as set
forth in claim 1 wherein said means for automatically causing
hydraulic fluid in the hydraulic fluid pump to be vented
provides for venting of fluid pressure from the pump while
maintaining fluid pressure in the fluid pressure chamber.



4. A hydraulic fluid flow control cartridge as set
forth in claim 1 wherein said cartridge comprises a
cylindrical body having a generally cylindrical periphery and
having a longitudinal axis, and wherein each of said cartridge
passages has a longitudinal axis, and wherein the respective
longitudinal axes of said cartridge passages are spaced apart
with respect to one another and are generally parallel to said
longitudinal axis of the cylindrical body.



5. A hydraulic fluid flow control cartridge as set
forth in claim 4 and further including a transverse passage
extending from said third cartridge passage to said generally
cylindrical periphery, said transverse passage providing fluid
communication between said third cartridge passage and the
reservoir.



6. A hydraulic fluid flow control cartridge as set
forth in claim 5 wherein said transverse passage intersects
said first cartridge passage between said first check valve and
the reservoir.

11


7. A hydraulic fluid pump assembly comprising:
a pump base including at least one bore,
a pump cylinder adapted to be connected in fluid
communication by a first fluid passage to a hydraulic fluid
reservoir, and adapted to be connected by a second fluid
passage to a fluid pressure chamber, the pump cylinder being in
communication with the bore of the pump base,
a pump piston housed in the pump cylinder and
reciprocably movable to cause fluid to be pumped from the
reservoir to the fluid pressure chamber, and
hydraulic fluid control cartridge means housed in the
bore, the hydraulic fluid control cartridge means including
means for controlling the flow of hydraulic fluid from the
hydraulic fluid reservoir to the pump cylinder, means for
controlling hydraulic fluid flow from the pump cylinder to the
fluid pressure chamber, and high pressure relief means for
providing for flow of hydraulic fluid from the pump cylinder to
the reservoir when the hydraulic fluid pressure in the pump
cylinder exceeds a predetermined hydraulic fluid pressure, the
high pressure relief means including means responsive to the
hydraulic fluid pressure in the pump cylinder for automatically
causing hydraulic fluid in the pump cylinder to be vented to
the reservoir whenever the hydraulic fluid pressure in the pump
cylinder exceeds a selected maximum hydraulic fluid pressure.

8. A hydraulic fluid pump assembly as set forth in
claim 7 wherein said means responsive to the hydraulic fluid
pressure in the pump cylinder for automatically causing
hydraulic fluid in the hydraulic fluid pump to be vented
provides for venting of fluid pressure from the pump cylinder
while maintaining fluid pressure in the fluid pressure chamber.

12

9. A hydraulic fluid pump assembly as set forth in
claim 7 wherein said hydraulic fluid control cartridge means
includes a cartridge having a first cartridge passage having a
first check valve means for selectively providing for fluid
flow from the hydraulic fluid reservoir to the pump cylinder,
said first check valve means including means for preventing
fluid flow from the pump cylinder to the reservoir, a second
cartridge passage having second check valve means for
selectively providing for hydraulic fluid flow from the pump
cylinder to said fluid pressure chamber but preventing fluid
flow from said fluid pressure chamber to said pump cylinder,
and a third cartridge passage including means for selectively
venting hydraulic fluid in the pump cylinder to the reservoir
when the hydraulic fluid pressure in the pump cylinder exceeds
a maximum value.

10. A hydraulic fluid flow pump assembly as set forth
in claim 9 wherein said means responsive to the hydraulic
fluid pressure in the pump cylinder for automatically causing
hydraulic fluid in the pump cylinder to be vented includes a
valve seat in said third cartridge passage, a valve member
engageable with said valve seat and movable away from said
valve seat to permit fluid flow from said pump cylinder to said
reservoir and spring means engageable with the valve means and
resiliently biasing the valve means against the valve seat.

13

11. A hydraulic fluid pump assembly as set forth in
Claim 9 wherein said cartridge comprises a cylindrical body
having a generally cylindrical periphery and having a
longitudinal axis, and wherein each of said cartridge passages
has a longitudinal axis, and wherein the respective
longitudinal axes of said cartridge passages are spaced apart
with respect to one another and are generally parallel to said
longitudinal axis of the cylindrical body.

12. A hydraulic fluid pump assembly as set forth in
claim 11 and further including a transverse passage extending
from said third cartridge passage to said generally cylindrical
periphery, said transverse passage providing fluid
communication between said third cartridge passage and the
reservoir.

13. A hydraulic fluid pump assembly as set forth in
claim 12 wherein said transverse passage intersects said first
cartridge passage between said first check valve and the
reservoir.
14


14. A hydraulic unit assembly comprising:
a ram cylinder,
a ram housed in said ram cylinder,
a hydraulic fluid reservoir,
a hydraulic fluid pump including a pump
body, a first fluid passage providing fluid communication
between the hydraulic fluid reservoir and the pump body, a
second fluid passage providing fluid communication between the
pump body and the hydraulic cylinder,
a hydraulic fluid pump cylinder operably connected to
the pump body,
a pump piston housed in the pump cylinder and
reciprocably movable to cause fluid to be pumped, and
hydraulic fluid control cartridge means housed in the
pump body, the hydraulic fluid control cartridge means
including means for controlling the flow of hydraulic fluid
from the hydraulic fluid reservoir to the pump cylinder, means
for controlling hydraulic fluid flow form the pump cylinder to
the ram cylinder, and high pressure relief means for providing
for flow of hydraulic fluid from the pump cylinder to the
reservoir when the hydraulic fluid pressure in the pump
cylinder exceeds a predetermined hydraulic fluid pressure, the
high pressure relief means including means responsive to the
hydraulic fluid pressure in the pump cylinder for automatically
causing hydraulic fluid in the pump cylinder to be vented to
the reservoir whenever the hydraulic fluid pressure in the pump
cylinder exceeds a selected maximum hydraulic fluid pressure.


15. A hydraulic unit assembly as set forth in claim
14 wherein said means responsive to the hydraulic fluid
pressure in the pump cylinder for automatically causing
hydraulic fluid in the hydraulic fluid pump to be vented
provides for venting of fluid pressure from the pump cylinder
while maintaining fluid pressure in the ram cylinder.

16. A hydraulic unit assembly as set forth in claim
14 wherein said hydraulic fluid control cartridge means
includes a cartridge including a first cartridge passage having
a first check valve means for selectively providing for fluid
flow from the hydraulic fluid reservoir to the pump cylinder,
said first check valve means including means for preventing
fluid flow from the pump cylinder to the reservoir, a second
cartridge passage having second check valve means for
selectively providing for hydraulic fluid flow from the pump
cylinder to said ram cylinder but preventing fluid flow from
said ram cylinder to the pump cylinder, and a third cartridge
passage including means for selectively venting hydraulic fluid
in the pump cylinder to the reservoir when the hydraulic fluid
pressure is the pump cylinder exceeds a maximum value.

17. A hydraulic unit assembly as set forth in claim
16 wherein said means responsive to the hydraulic fluid
pressure in the pump cylinder for automatically causing
hydraulic fluid in the pump cylinder to be vented to the
reservoir includes a valve seat in said third passage, a valve
member engageable with said valve seat and movable away from
said valve seat to permit fluid flow from said pump to said
reservoir and spring means engageable with the valve means and
resiliently biasing the valve means against the valve seat.

16

18. A hydraulic unit assembly as set forth in claim
16 wherein said cartridge comprises a cylindrical body having a
generally cylindrical periphery and having a longitudinal axis,
and wherein each of said cartridge passages has a longitudinal
axis, and wherein the respective longitudinal axes of said
cartridge passages are spaced apart with respect to one another
and are generally parallel to said longitudinal axis of the
cylindrical body.

19. A hydraulic unit assembly as set forth in claim
18 and further including a transverse passage extending from
said third cartridge passage to said generally cylindrical
periphery, said transverse passage providing fluid
communication between said third cartridge passage and the
reservoir.

20. A hydraulic unit assembly as set forth in claim
19 wherein said transverse passage intersects said first
cartridge passage between said first check valve and the
hydraulic fluid reservoir.

17

21. A portable hydraulic crane comprising
a support structure,
a boom supported by said support structure, the boom
including a lifting end and an opposite end supported by the
support structure such that the lifting end of the boom is
vertically movable,
a hydraulic lift cylinder assembly having opposite
ends, said hydraulic lift cylinder assembly including a
telescoping piston and a lift cylinder, one of said piston and
lift cylinder being connected to said boom and the other of
said piston and lift cylinder being supported by said support
structure,
means for selectively supplying hydraulic fluid to
said lift cylinder to cause extension of said piston and
cylinder and upward movement of said lifting end of said boom,
said means for selectively supplying hydraulic fluid to said
lift cylinder including
a reservoir containing hydraulic fluid,
a hydraulic fluid pump operably
connected by a first fluid passage to said reservoir and
operably connected by a second fluid passage to said lift
cylinder, said hydraulic fluid pump including a pump cylinder
and a pump piston housed in said pump cylinder for reciprocal
movement,
means for selectively causing reciprocating movement
of said pump piston in said pump cylinder, said pump piston
being extensible with respect to said pump cylinder to draw
hydraulic fluid into said pump cylinder and said pump piston
being retractable in said pump cylinder to discharge hydraulic
fluid from said pump cylinder, and

18



(Claim 21 con't.)

a hydraulic fluid control cartridge, said hydraulic
fluid control cartridge including means for controlling the
flow of hydraulic fluid from said hydraulic fluid reservoir to
said pump cylinder, means for controlling hydraulic fluid flow
from said pump cylinder to said lift cylinder, and high
pressure relief means for providing for flow of hydraulic fluid
from said pump cylinder to said reservoir when the hydraulic
fluid pressure in said pump cylinder exceeds a predetermined
hydraulic fluid pressure, the high pressure relief means
including means responsive to the hydraulic fluid pressure in
the pump cylinder for automatically causing hydraulic fluid in
the pump cylinder to be vented to the reservoir whenever the
hydraulic fluid pressure in the pump cylinder exceeds a
selected maximum hydraulic fluid pressure,



22. A portable hydraulic crane as set forth in claim
21 wherein said means for selectively supplying hydraulic fluid
to said lift cylinder includes a base, said base including said
hydraulic fluid passage connecting said reservoir to said
hydraulic fluid pump, and including said hydraulic fluid
passage from said pump to said hydraulic cylinder, and wherein
said base includes a bore housing said hydraulic fluid control
cartridge.
19





23. A portable hydraulic crane as set forth in claim
22 wherein said bore has opposite ends, one of said ends
housing said pump cylinder, and an opposite end terminating in
said passage between said pump and said lift cylinder, said
hydraulic fluid control cartridge being housed in said bore
between said opposite ends of said bore, and said passage from
said hydraulic fluid reservoir to said pump intersecting said
bore intermediate said opposite ends of said bore and adjacent
said hydraulic cartridge.



24. A portable hydraulic crane as set forth in claim
21 wherein said hydraulic lift cylinder assembly includes a
base having a bore and wherein said hydraulic fluid control
cartridge includes a body housed in said bore, said means for
controlling hydraulic fluid flow from said hydraulic fluid
reservoir to said pump cylinder including a first cartridge
passage in said cartridge body, a first check valve in said
first cartridge passage, said first cartridge passage
communicating with said first fluid passage, and said first
check valve preventing fluid flow from said pump cylinder to
said hydraulic fluid reservoir, said means for controlling
hydraulic fluid flow from said fluid pump to said lift cylinder
including a second cartridge passage in said cartridge body and
a second check valve in said second cartridge passage for
preventing fluid flow from said lift cylinder to said fluid
pump, and said high pressure relief means including a third
cartridge passage in said cartridge body, said third cartridge
passage communicating with said first cartridge passage, and
said third cartridge passage including a valve seat, a ball
selectively engageable with said valve seat, and spring means
for forcing said ball into engagement with said valve seat,
said spring means permitting said ball to move away from said
valve seat when said hydraulic fluid pressure in said pump
cylinder exceeds a selected maximum fluid pressure.

21


25. A portable hydraulic crane as set forth in claim
24 wherein said cartridge body includes a longitudinal axis,
wherein said cartridge passages are generally parallel to said
longitudinal axis and wherein said cartridge body further
includes a radially extending passage from said third passage
to said first fluid passage, said radially extending passage
intersecting said first passage in said cartridge between said
first check valve and said first fluid passage.



26. A portable hydraulic crane as set forth in claim
21 wherein said cartridge is cylindrical and includes opposite
ends, one of said opposite ends including a periphery, and seal
means between said periphery of said one of said opposite ends
and said bore, and the other of said opposite ends including a
periphery and seal means surrounding said other of said
opposite ends.

22

~L27~

HYD~AULIC AppAKArrus INCLUDI~G
_HYDRAUL_C FLUI~ ~LOW CONTROL CARTRIDGE

FIEL~ OF THE I~V~NTION
The present invention is directed to
manually operable hydraulic cylinders used in a
number of applica~ions such as in portable hydraulic
cranes, and more particularly to hydraulic fluid flow
control assemblies used with such hydraulic
cylinders.

BACKGROUND OF THE INVENTION
In many applications of hydraulic pump
assemblies it is important that means be provided to
limit the Eluid pressure generated by the pump to
prevent damage to the hydraulic ram cylinders
connected to the hydraulic pump or dalnage to other
structural components supported by the hydraulic
rams. For example, in the case of a conventional
bottle jack, it is important that the hydraulic fluid
pressure supplied by the hydraulic fluid pump to the
jack ram cylinder not exceed the capacity of tne ram
cylinder. In the case of a portable hydraulic crane
of the type including a boom supported by a hydraulic
ram it is important that the boom should not be used
to lift objects which will overload the crane and
that the hydraulic ram not be pemitted to apply an
upward force on the boom which will structually
overload the crane. In some prior art portable
cranes the base of the hydraulic assembly is provided
with a high pressure fluid relief passage extending
from the hydraulic pump to the fluid reservoir to
relieve fluid from the pump to the reservoir in the
event tne fluid pressure generated in the pump
exceeds a selected maximum pressure. The fluid
relief passage in the base includes a valve seat, and

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--2--

a ball held in engagement with the valv~ seat by a
compression springO The compression spring applies
sufficient force on t~e ball that the ball engages
the valve seat and precLudes fluid flow unless the
fluid pressure generated by the pump reaches a
maximum selected value.

SUi`lMA~Y 0~ TH~3 INVE~TIO~
The present invention includes an
improved means for controlling hydraulic fluid flow
between a hydraulic fluid reservoir and a hydraulic
fluid pump and between the hydraulic fluid pump and
the hydraulic ram cylinder.
More specifically, the invention
includes a fluid flow control cartridge for use in
connection with a hydraulic fluid pumping assembly
and for providing for control of hydraulic fluid flow
from a reservoir to a hydraulic fluid pump, control
of hydraulic fluid flow from the hydraulic fluid pump
to a hydraulic ram, and relief of hydraulic fluid
from the hydraulic fluid pump to the hydraulic fluid
reservoir in the event the hydraulic fluid pressure
generated by the nydraulic fluid pu-mp is greater than
a predetermined or selected maximum pressure.
In one embodiment of the invention a
hydraulic pump is operably connected by a first fluid
passage to a reservoir and operably connected by a
second fluid passage to a ram cylinder, the hydraulic
fluid pump including a pump cylinder and a piston
housed in the pump cylinder for reciprocal movement.
Means are also provided for selectively causing
reciprocating movement of the pump piston. A
hydraulic fluid control cartridge is also provided,
the hydraulic fluid control cartridge including means

~z~s~
--3--

for controlling the flow of hydraulic fluid from tne
hydraulic fluid reservoir to the pump, means for
controlling hydraul1c fluid flow from the hydraulic
fluid pump to the ram cylinder, and hign pressure
relief means for providing for flow of hydraulic
fluid from the hydraulic fluid pump to the reservoir
when the hydraulic fluid pressure in the pump exceeds
a predetermined hydraulic fluid pressure.
In one embodiment of the invention the
hydraulic pump includes a base having a bore with one
end housing the pump cylinder, and an opposite end
terminating in a fluid passage extending between the
pump cylinder and the ram cylinder. The hydraulic
cartridge is noused in the bore, and the fluid
passage from the hydraulic fluid reservoir to the
pump intersects the ~ore adjacent the hydraulic
cartridge.
In a preferred form of the invention
the cartridge includes a body having a first
cartridge passage including a first check valve, the
first chec~ valve preventing fluid flow from the pump
cylinder to the hydraulic fluid reservoir. The body
also includes a second cartridge passage having a
second check valve preventing fluid flow from the
cylinder to the fluid pump, and a thir~ hydraulic
fluid passage communicating with the passage from the
reservoir to the pump cylinder, the third passage
including a valve seat, a ball selectively engageable
with the valve seat, and spring means for forciny the
ball into engagement with the valve seat. The spring
permits the ball to move away from the valve seat
when the hydraulic fluid pressure in the pump
cylinder exceeds a selected value.

9~


One of the principal features of the
invention is that the hydraulic fluid flow control
cartridge contains all of the valves used to control
flow of hydraulic fluid from the reservoir to the
pump and from the pump to the hydraulic cylinder, and
including the pressure relief valve operably
connected to the reservoir to vent hycZraulic fluid
pressure to the reservoir in the event: hydraulic
fluid pressure generated ~y the pump becomes
excessive.
The control cartridge is also
conveniently mounted in a Dore provided in tne base
of the hydraulic unit, and the use of the control
cartridge eliminates the need for the provision of
valve seats and check valves to be provided in the
body of the hydraulic unit base. The control
cartridge eliminates the need for separate pressure
relief valves to be provided in the hydraulic base.
Accordingly, manufacture of the base requires less
machining of passages and valve seats in the base.
The provision of the control cartridge including the
hign pressure relief valve also permits more
economical assembly of the product.
One of the advantages of the use of the
hydraulic fluid flow control cartridge is that the
bores provided in the cartridge and housing the check
valves and the fluid pressure relief valve are
relatively small and are conveniently machined in the
cartridge, and only a single workpiece is machined.
If the bores and valve seats are individually
machined into the hydraulic unit base, substantially
more machining and tooliny is required.
Additionally, since the control
cartridge is relatively small and because the bores

~7~

--5--

in the cartridge can comprise three generally
parallel axially extending bores and a single
radially extending bore, the control cartridge can be
machined on automatic machine centers. A further
advantage realized from machining a small work piece
is that less scrap is generated. Additionally, the
machining of the larger workpiece, such as the unit
base, can be done with less sophisticated machines
since the oase will not include machined valve seats.
Various other features and advantages
of the invention will be apparent by reference to the
following description of a preferred embodiment, from
the drawings and from the claims.

BRI~F DESCRIPTION OF THE DRAWINGS
Fig. 1 is a perspective view of a
portable hydraulic crane embodying the present
invention~
FigO 2 is an enlarged illustration of a
manual hydraulic fluid pump included in the portable
hydraulic crane illustrated in Fig. 1.
Fig. 3 is an enlarged cross section
view of apparatus shown in Fig. 2.
Fig. 4 is a perspective view of the
hydraulic cartridge illustrated in Fig. 3.
Fig. 5 is an enlarged cro~s section
view of the hydraulic cartridge illustrated in
Figs. 3 and 4.
~ efore describing a preferred
embodiment of the invention, it is to be understood
~hat the invention is not limited in its application
to the details of construction and to the arrangement
of the components set forth in the following
description or illustrated in the drawings~ The





invention is capable of other em~odiments and of
~eing practiced and carried out in various ways.
A:Lso, i~ is to be unders~oo~ that tne phraseology and
terminology employed herein are for the purpose of
description and should not ~e regarde~ as limiting.

DESCRIPTION OF A PREFERRED EMBODIMENT
Illustrated in Fig. 1 is a portable
crane 10 including a hydraulic fluid pUMp aSSelllbly
embodying the invention. The portable crane 10
includes a base 1~ supported for movement by a
plurality of wheels 14, and an upwardly extending
support structure 16 supported by the base 12~ A
boom 18 has one end pivotally joined to the upper end
20 o~ the suppor~ structure 16 and includes a free
end 22 for use in lifting a product to be supported
by the crane.
A hydraulic unit assembly 24 has one
end supported by a frame 26, tne frame 26 in turn
being supported by the base 1~. An opposite end of
the hydraulic unit assembly 24 is pivotally connected
to the boom 18 intermediate the opposite ends of the
boom. In the illustrated assembly the hydraulic unit
assembly 24 includes a hydraulic ram cylinder 30
supported at its lower end by the frame 26, and
includes a ram 32 having an upper end pivotally
connected to the boom 18.
The hydraulic unit assembly 24 also
includes a hydraulic fluid reservoir 34 (Fig. 3) and
a hydraulic fluid pump 36 carried by a base structure
38 of tne hydraulic unit assembly 24. More
specifically, as shown in Figs. 2 and 3, the base 38
supports a pump cylinder 40, and the base includes a
high pressure hydraulic fluid port or passage 42

751~


intended to provide fluid communication between the
pump cylinder 40 and the ram cylinder 30. The base
38 also includes a low pressure hydraulic fluid
passage 44 between the hydraulic fluid reservoir 34
and the pump cylinder 40.
A piston 46 is housed in the pump
cylinder 40, and a pump handle or lever 48 is
provided for causing manual reciprocal movement of
the pump piston 46 in the pump cylinder 40. Tne pump
handle is pivotally supported by a support bracket S0
and is pivotably connected to t~e pump piston 46 by a
pin 52 such that manual movement of the pump handle
48 will cause reciprocal movement of tne pump piston
46 in the pump cylinder 40.
In the illustrated arrangement, the
lower end 56 of the pump cylinder 40 is threaded into
~ore 58 provided in the base 38 sucn that the lower
end 56 of the pump cylinder is fixed in the bore.
I~leans are also provided for controlling
the flow of hydraulic fluid from the hydraulic fluid
reservoir 34 to the pump cylinder 40, flow of
hydraulic fluid from the pump cylinder 40 to the ram
cylinder 30 and flow of hydraulic fluid from the pump
cylinder 40 to the reservoir 34 in the event the
hydraulic fluid pressure generated in the pump
cylinder 40 exceeds a selected pressure. The means
for controlliny hydraulic fluid flow comprises a
hydraulic fluid flow control cartridge 60 housed in a
portion of the bore 58 below the pump cylinder 56.
The hydraulic cartridge 60 is shown more specifically
in Figs. 4 and 5 and includes a generally cylindrical
body 62 housed in the bore 58, and including a
circumferential groove 64 surrounding the periphery
of the body 62 and intermediate the opposite ends of

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the body. The lower end of the cartridge 60 includes
a shoulder 61 forced into fluid tight engagement with
a complementary shoulder 63 of the bore 58, and the
lower end of the pump cylinder 40 engages the flat
upper surface 65 of the cartridge 60 to force the
shoulder 61 into engagement with shoulder 63 and to
provide a fluid tight seal between the pump cylinder
40 and the cartridge 60.
As best illustrated in Fig. 3, the
circumferential groove 64 of the hydraulic cartridge
body 62 communicates with the passage or port 44 from
the hydraullc fluid reservoir 34. Fluid flow from
the passage 44 to the chamber of the pump cylinder 40
is provided by a radially extending passage 70 and an
axially extending passage 72. A filter screen 73 is
also provlded to prevent contaminants from entering
passage 70. The passage 72 also includes a check
valve 74 precluding fluid flow from tne pump cylinder
40 to the reservoir 34 but permitting free flow of
fluid from tAe reservoir 34 to the pump cylinder 40.
The check valve 74 includes a valve seat 76 and a
ball 78 selectively engageable with the valve seat 76.
The hydraulic cartridge 60 also
includes a passage 80 extending axially through the
cartridge body 62 and providing for fluid flow from
the pump cylinder 40 to the nigh pressure port 42.
The passage 80 includes a check valve comprised of a
valve seat 82 and a ball 84 engageable witn the valve
seat 82 to prevent reverse flow from the high
pressure port 42 to the pump cylinder. A llght
compression spring 86 is provided to maintain the
ball 84 in position against the valve seat 82.
The hydraulic cartridge 60 also
includes a high pressure overload valve 88 for

~7S~2


discharging hydraulic fluid to the reservoir 34 when
tne pressure in the pump cylinder 40 exceeds a
selected value. In the illustrated arrangement a
bore 90 extends axially through the cartridge body
62, the bore 90 including a valve seat 92. A ball 94
seats against the valve seat 92. The ball 94 is
normally maintained in engagement with the valve seat
92 by a compression spring 96. The compression
spring 9G provides sufficient force on the ball 94
that the oall will move away from the valve seat 92
only af~er the hydraulic fluid pressure in the pump
cylinder 40 reaches a selected maximum pressure. In
the illustrated arrangement the compression spring 96
is held in place agalnst the ball ~4 by an adjustable
plug 98. The adjustable plug 98 is threaded into a
threaded portion of the ~ore 90 and includes a lower
end 97 including a seal 99 adapted to form a fluid
tight seal witn the smooth surface portion 93 of the
bore 90. An upper end 95 of the plug 98 is threaded
into a threaded portion 91 of the bore 90. A
transverse or radially extending bore 100 intersects
the axially extending bore 90 and provides
communication with the passage 70 whereby hydraulic
fluid can be vented past tne relief valve 88 through
passage 44 to the reservoir 34.
While in the illustrated arrangement
the cartridge includes a one piece body, in other
arrangements the ~low control cartridge could be
comprised of a plurality of cartridge bodies housed
in the bore 58 or housed in a plurality of bores each
communicating with the pump cylinder.
Various features of the invention are
set forth in the following claims.