Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to a hydraulic jack with a
pump and valve unit releasably received between a piston and
cylinder combination and a hydraulic fluid reservoir.
Ease of maintenance and simplicity of construction
are of primary concern for hydraulic jacks in general and
hydraulic camper jacks in particular. Hydraulic camper
jacks are used for raising truck campers so that they can be
removed from the backs of trucks or placed thereon.
Components such as O rings wear out as eventually
do check valves and components of the pump. Earlier camper
jacks have attempted to provide a construction allowing for
easy serviceability of such items. However, previous jacks
have not permitted access to all serviceable components,
excluding the main piston and cylinder combination, with a
single operation. Additionally, some prior jacks have
relied upon threaded connections for hydraulic sealing which
are prone to leaking and damage when the jacks are dis-
assembled and assembled. Earlier jacks with even the
simpler maintenance provisions require wrenches to gain
access to the serviceable hydraulic parts.
In earlier patents, United States Patent 3,782,689
to Barosko discloses a combination valve and seal used in a
hydraulic jack. United States Patent-3,350,063 to Thurlow
and 4,015,822 to Rasmussen both disclose camper jacks.
United States Patent 3,985,389 to Bonfield discloses a
hydraulic jack for use with wheel chairs.
Ring-type check valves for use in hydraulic
systems are disclosed in United States Patent 2,790,597 to
Turpin, 3,297,106 to Hanson, 3,298,394 to Chorkey, 3,303,910
to Gavillet, 3,511,271 to Pollinger and 3,618,690 to Johnson.
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The invention is in a hydraulic device comprising
a piston movable within a cylinder; a reservoir to contain
hydraulic fluid; a pump to force fluid from the reservoir
to the cylinder to move the piston within the cylinder;
S pump conduit means extending through the pump to allow
hydraulic communication between the reservoir and the cy-
linder; a reservoir conduit communicating the reservoir
with an inlet for the pump conduit; a cylinder conduit
communicating the cylinder with an outlet for the pump
conduit; a first check valve to prevent reverse flow from
the pump to the reservoir; a second check valve to prevent
reverse flow from the cylinder to the pump and is the im-
provement whereby the device has a chamber positioned be-
tween the reservoir and the cylinder and the pump and the
first and second check valves are formed in a single unit
adapted to be a liquid-tight seal within the chamber; and
releasable means to locate the single unit within the cham-
ber, whereby the device may be serviced by removal of the
releasable means, withdrawal of the single unit and re-
20 placement with a complete single unit. `
Preferably, the chamber and the unit are cylin-
drical and have generally equal diameters, the unit ex-
tending through the chamber.
When compared with prior art hydraulic jacks,
embodiments of the present invention offer distinct ad-
vantages and surprising results. For example, by using the
pump and valve unit, all serviceable components outside the
main piston and cylinder combination can be removed from the
jack with a single operation. The pump and valve unit can
be retained within the jack by easily removable means such
as C clips so that no wrenches are required for disassem-
bly. The misuse of wrenches during disassembly and
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assembly is a well known cause of damage to jacks. More-
over, the use of the pump and valve unit means that all of
the hydraulic sealing can be accomplished by reliable and
serviceable means such as O rings. There is no need to rely
upon threaded connections with their inherent tendency to
leak. If desired, all hydraulic components of the camper
jack, outside the main piston and cylinder combination, can
be replaced in a single operation by the removal and re-
placement of the pump and valve unit. However, when leaking
occurs due to failure of the seals, all of the O rings can
be replaced easily once the pump and valve unit is removed.
Figure 1 is a side elevational view of a camper
jack according to an embodiment of the invention; and
Figure 2 is a sectional view showing a portion of
the jack of Figure 1, including the pump and valve unit, in
elevation.
The drawings illustrate one embodiment of the
invention which comprises a hydraulic camper jack 1 which is
similar in overall configuration to earlier jacks used for
the same purpose. The body of the jack includes the com-
bination of the elongate hydraulic cylinder 2 and the piston
4. The piston 4 is an elongate rod which extends slidably
through the aperture 6 in the bottom of the cylinder 2.
Hydraulic seals 8 are provided for hydraulic sealing about
the piston 4 near the bottom of the cylinder 2. A stop-ring
9 prevents the piston 4 passing through aperture 6. The
piston 4 is downwardly connected to the base plate 10 of the
jack 1. An inner tube 13 is connected to base 10 and
extends upwardly about cylinder 2. An outer tube 12 extends
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downwardly from the hydraulic fluid reservoir 14, on the top
of the jack 1, and slidably about inner tube 13. Reservoir
14 is mounted on cylinder 2.
The ~ack 1 is raised by the action of pump 16,
operated by the handle 18, which transfers hydraulic fluid
downwardly from reservoir 14 to the cylinder 2. When it is
desired to lower the jack, there is a release valve 20 which
allows fluid to return from cylinder 2 to the reservoir 14
when opened. The jack 1 can be used to raise a Truck camper
when one of the jacks is mounted on each corner of the
camper by means of the bracket 22.
The jack 1 includes a cylindrical pump and valve
unit 24 which is shown in better detail in Figure 2. The
unit 24 is releasably received within the chamber 28 which
comprises a cylindrical bore passing diametrically through
the body 26 of the jack between the reservoir 14 and the
cylinder 2. Unit 24 is secured in this position by the
shoulder 30 which contacts the body 26 of the pump at one
end of the chamber 28 and by the C clip 32 at the opposite
end of the chamber.
The pump 16 comprises a pump cylinder 34 which
extends axially into the member 24 from one end thereof. A
pump piston 36 is slidably received within cylinder 34 and
the O ring 38, received within the annular groove 40 of the
unit 24, provides sealing between the piston 36 and the
cylinder 34. As seen in Figure 1, the handle 18 of the pump
16 is pivotally connected to the piston 36 by means of link
42 and a link pin 44. A link 46 and a pair of link pins 48
and 50 pivotally connect link 42 to the reservoir 14. As
may be easily be appreciated, an upward movement of handle
18 moves piston 36 outwardly from cylinder 34, while a
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downward movement moves the piston into the cylinder.
Referring again to Figure 2, a conduit 52 in the
body 26 of the pump 16 communicates upwardly with the hy-
draulic fluid reservoir 14 and extends downwardly to the
chamber 28. Similarly, a cylinder conduit 54 communicates
downwardly with the interior of cylinder 2 and upwardly with
the chamber 28. There is a pump conduit 56 through the
member 24 which connects the reservoir 14 to the cylinder 2
by means of conduit 52 and conduit 54. Conduit 56 has a
first end 57 which communicates with reservoir conduit 52
and a second end 59 which communicates with cylinder conduit
54.
Pump conduit 56 includes the bore 58, which passes
diametrically through unit 24 and the axial bore 60 com-
municating therewith. A larger axial bore 62 extends frombore 60 to the pump cylinder 34. A plurality of passageways
64 extend outwardly through unit 24 to the annular groove
66. Groove 66 communicating with the cylinder conduit 54.
Jack 1 has check valves for permitting the fluid
to be pumped from reservoir 14 to the cylinder 2, but
preventing the reverse flow of fluid. A first ball-type
check valve 68 is operable between the pump 16 and the
reservoir 14 to permit a flow of fluid from the reservoir to
the pump. The ball of the check valve is biased against the
25 seat 70, formed between bore 60 and bore 62, by a coil
spring 72 which is received within the groove 74 in bore 62.
A second, O ring-type check valve 76 comprises a resilient O
ring tightly received within the annular groove 66 of unit
24.
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In operation, spring 72 normally keeps check valve
68 engaged with seat 70, but the suction within cylinder 34
when handle 18 is raised, and piston 36 moved outwardly,
moves the check valve 68 inwardly against the pressure of
the spring 72 and permits hydraulic fluid to pass from
reservoir 14 downwardly through conduit 52 and in-to the
cylinder 34 through pump conduit 56. An upward flow of
fluid from cylinder 2 and conduit 54 is prevented by check
valve 76 which is sucked inwardly to seal the passageways 64
when the handle is raised. When the handle 18 is subse-
quently pushed downwardly, moving piston 36 towards check
valve 68, the ball is forced against seat 70 and prevents
the fluid from returning to reservoir 14. However, the pre-
ssure of fluid as piston 36 moves inwardly expands check
valve 76 so it is raised away from passageways 64 and
allows the hydraulic fluid to flow from pump 16 to cylinder
2 through the annular groove 66 and cylinder conduit 54.
Jack 1 includes seals between the unit 24 and the
cylindrical chamber 28 to prevent a leakage of hydraulic
fluid during the pumping operation. The seals consist of
three resilient O rings 78, 80 and 82 received within the
annular grooves 84, 86 and 88 of unit 24 respectively. Seals
78 and 80 are to each side of the first end 57 of pump
conduit 56. Similarly, seals 80 and 82 are to each side of
the second end 59 of conduit 56.
In order to lower jack 1, it is provided with the
release valve 20 which has a threaded portion 94 threadedly
received within the correspondingly tapped portion 96 of the
axial bore 98 extending inwardly from the end of unit 24
opposite the pump 16. When the valve 20 is tightened in the
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bore 98, its portion 99 sealingly engages the seat 100
formed in the bore while its portion 101 engages seat 103 of
the bore. Bore 98 forms part of a release conduit 102, also
formed by diametrical bores 104 and 106 in unit 24. Bore
104 communicates upwardly with reservoir 14 by means of
reservoir conduit 108, while bore 106 communicates down-
wardly with cylinder 2 by means of cylinder conduit 110.
Normally, valve 20 is tightened against seats 100 and 103 to
prevent fluid from flowing upwardly from cylinder 2 to
reservoir 14 through the release conduit 102. However, when
it is desired to lower the jack, valve 20 is unscrewed
slightly, permitting a flow of fluid to pass upwardly
through conduit 110 and bore 106 past valve 20 and upwardly
to the reservoir 14.
O rings 112 and 114 received within annular
grooves 116 and 118 of unit 24 provide seals between the
unit 24 and chamber 28 to either side of the first end 120
of release conduit 102 which communicates with reservoir
conduit 108. Similarly, O ring 114 and O ring 78 provide
seals on opposite sides of the second end 122 of reIease
conduit 122 which communicates with cylinder conduit 110.
To prevent unwanted movement downwardly of plate
10 a safety catch may be provided. The catch comprises a
stud 121 to receive an angle member 122. Foot 124 of angle
member 122 fits beneath plate 10. Angle member 122 is
retained in position by, for example, a wing nut 126 en-
gaging stud 121. When nut 126 is removed angle member 122
may be removed from stud 121 and the jack can then be
operated.
The jack is simple to operate. When the truck
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camper is stopped first the release valves 20 are slackened
slightly on the jacks attached to the truck camper. As each
valve 20 is opened base 10 is moved downwardly, for example
with the foot, to contact a solid base, for example the
ground. Each jack should be left about 30 seconds after
base 10 has been moved to allow liquid in the reservoir to
move into the cylinder 2 to establish equilibrium. When
equilibrium is established valves 20 are closed and the
jacks operated by moving handles 18. As indicated above
this transfers hydraulic fluid from reservoir 14 to cylinder
2. Pressure within cylinder 2 is increased causing lifting
of the cylinder 2 about the piston 4 to raise the jack, and
then the camper attached to each bracket 22. The jacks are
lowered by opening valves 20.
~ When it is desired to remove unit 24 for inspec-
tion or servicing, it is simply necessary to remove C clip
32 and valve 20. Once this is accomplished, unit 24 can be
removed from the body 26 of jack 1 by a sliding movement
outwardly in the direction of pump 16. It should be em-
phasized that the jack need not be removed from the truckcamper. Access to such components as the O rings, check
valves 76 and 68 and the pump 16 is accomplished simulta-
neously. The entire unit 24 can be easily replaced if
desired or separate components such as the O rings can be
replaced readily. No tools are required for this disassem-
bly or the reassembly.
When compared with prior art jacks, the preferred
embodiment of the present invention offers a considerably
simplified hydraulic arrangement with improved service-
ability. Moreover, the use of such features has the ring-
type check valve 76 improves the economy and reliability of
the jack when compared with earlier devices.
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