Hydraulic work support

An improved hydraulic work support (10) having a plunger (18) that is shifted between retracted and extended positions by hydraulic fluid is disclosed. The work support includes a base (12); a tubular housing (14) partially received in the base and having a central bore (40); a tubular sleeve (16) received within the central bore; a general cylindrical plunger (18) positioned at least partially within the sleeve, the plunger being movable within the bore along the longitudinal axis; and a piston cylinder assembly (20) positioned within the central bore for selectively shifting the plunger along the longitudinal axis of the bore between a lowered, retracted position and a raised, extended position under the influence of hydraulic fluid. The piston cylinder assembly includes a cylinder (94) positioned within the sleeve and having a piston chamber (96) formed therein; a piston (98) movably received within the piston chamber; and an elongated piston rod (100) having a lower end coupled with the piston and an opposite upper end extending from the cylinder and coupled with the plunger. The piston and piston rod are shifted upward in the piston chamber when fluid is delivered to a first fluid passageway (34) formed in the base to shift the plunger to its raised, extended position. The piston and piston rod are shifted downward in the piston chamber when fluid is delivered to a second fluid passageway (36) formed in the base to return the plunger to its lower, retracted position.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to hydraulic work supports for supporting 
workpieces during machining or other operations. More particularly, the 
present invention relates to a hydraulic work support having a plunger 
axially shiftable within a bore of a housing and an improved piston 
cylinder assembly for shifting the plunger between extended and retracted 
positions under the influence of hydraulic fluid. 
2. Description of the Prior Art 
Hydraulic work supports are commonly used to support workpieces during 
operations thereon. Conventional work supports include a plunger axially 
shiftable within a bore of a housing. The plunger is shifted upward to an 
extended position under the influence of fluid pressure to engage the 
workpiece and is then returned to a lowered, retracted positions under the 
influence of a compression spring when the workpiece is to be released. 
A problem with these types of prior art hydraulic work supports is that the 
return springs do not provide a controlled rate of return and tend to lose 
their elasticity and compressive forces after repeated uses. Prior art 
attempts to provide a hydraulic work support with a plunger that is 
shifted in both directions under the influence of fluid pressure have been 
largely unsuccessful due to fluid sealing problems and other problems 
peculiar to hydraulic work supports. 
OBJECTS AND SUMMARY OF THE INVENTION 
The present invention solves the above-described problems and provides a 
distinct advance the art of hydraulic work supports. More particularly, 
the present invention provides a hydraulic work support having a plunger 
that is shifted in both directions by hydraulic fluid. 
The hydraulic work support of the present invention broadly includes a base 
having a recess therein; a tubular housing partially received in the 
recess of the base and having a central bore; a tubular sleeve received 
within the central bore of the housing; a general cylindrical plunger 
positioned at least partially within the sleeve, the plunger being movable 
within the bore along the longitudinal axis of the bore; and a piston 
cylinder assembly positioned within the sleeve and coupled with the 
plunger for selectively shifting the plunger along the longitudinal axis 
of the bore between a lowered, retracted position and a raised, extended 
position under the influence of hydraulic fluid. 
The piston cylinder assembly includes a cylinder positioned in the sleeve 
and having a piston chamber formed therein; a piston movably received 
within the piston chamber; and an elongated piston rod having a lower end 
coupled with the piston and an opposite upper end extending from the 
cylinder and coupled with the plunger. The piston and piston rod are 
shifted upward in the piston chamber when fluid is delivered to a first 
fluid passageway formed in the base to shift the plunger to its raised, 
extended position. The piston and piston rod are shifted downward in the 
piston chamber when fluid is delivered to a second fluid passageway formed 
in the base to return the plunger to its lower, retracted position. 
In preferred forms, the sleeve includes a deformable section that is 
shifted radially inward against the plunger under the influence of 
hydraulic fluid when the plunger reaches its fully extended position to 
lock the plunger in place.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Turning now to the drawing figures, and particularly FIG. 3, a hydraulic 
work support 10 constructed in accordance with a preferred embodiment of 
the invention is illustrated. The work support 10 broadly includes a base 
12, a tubular housing 14 supported on the base, a tubular sleeve 16 
mounted within the housing, a generally cylindrical plunger 18 positioned 
at least partially within the sleeve, and a piston cylinder assembly 
broadly referred to by the numeral 20 coupled with the plunger for 
selectively shifting the plunger between a lowered, retracted position and 
a raised, extended position under the influence of hydraulic fluid. 
In more detail, the base 12 is generally rectangular in shape and includes 
an internally threaded sidewall 22 defining a generally circular recess 24 
having a bottom wall 26. As best illustrated in FIG. 2, the base includes 
three vertically extending mounting holes 28 for receiving bolts or other 
fasteners for fastening the base to a fixture, table, or other platform. 
Although the base is depicted and described herein as a separate 
component, it may also comprise an integral portion of a fixture, table, 
or platform. 
The base 12 also includes first and second fluid inlet ports 30,32 formed 
in its front face as depicted in FIG. 1. The first fluid port communicates 
with an elongated fluid passageway 34 that, in turn, leads to an opening 
near the center of the bottom wall 26 of the recess 24 (FIG. 3). The 
second fluid inlet port communicates with a fluid passageway 36 that leads 
to a second opening in the bottom wall nearer the base sidewall 22. The 
inner walls of the first and second fluid inlet ports may be threaded for 
coupling with complimentary threaded hydraulic fluid lines. 
The tubular housing 14 is generally cylindrical in shape and includes a 
sidewall 38 defining a cylindrical central bore 40 having a vertically 
extending longitudinal axis. The housing has a lower portion 42 that is 
received within the base recess 24 and an upper portion 44 that extends 
upwardly from the top of the base. The exterior of the sidewall 38 is 
threaded to engage the threading formed in the base sidewall 22 to hold 
the housing on the base 12. 
The housing lower portion 42 includes an inner annular groove 46 that 
defines an annular shoulder 48 between the lower and upper portions of the 
housing. The lowermost end of the housing lower portion also includes an 
inner annular notch or cutout section 50 at its lowermost end that 
receives a sealing element 52 such as an O-ring. 
The housing upper portion 44 includes a slightly increased thickness 
inwardly extending annular flange 54 near its uppermost end having an 
annular radial groove 56 formed therein that receives a sealing element 58 
such as an O-ring. The uppermost end of the housing also includes an inner 
annular cutout section 60 that receives a wiping element 62 to prevent any 
foreign material from entering the top of the work support. 
The sleeve 16 is also generally cylindrical in shape and is received within 
the central bore 40 of the housing 14. The sleeve includes a lower flange 
64 that is received within the annular groove 46 in the housing to hold 
the sleeve in the housing. The lower end of the flange also includes an 
exterior annular cutout section 66 that cooperates with the housing cutout 
section 50 to support the O-ring 52. The inner wall of the lower end of 
the flange includes internal threading. 
The sleeve 16 also includes an upper, thin-walled deformable section 68 
spaced slightly inward of the inner wall of the housing 14 to define an 
annular fluid chamber 70 therebetween. The upper end of the deformable 
section includes an outwardly extending flange 72 that engages the flange 
54 in the housing and the O-ring 58 to seal the top of the annular fluid 
chamber. As described in more detail below, when fluid is delivered to the 
annular fluid chamber, it exerts an inwardly directed radial force on the 
deformable section of the sleeve that shifts it radially inward against 
the plunger 18 for locking the plunger in a desired position. 
The sleeve flange 64 also includes an annular fluid-receiving channel 74 
(FIGS. 3 and 4) and a vertically extending groove 76 (FIGS. 3 and 6) that 
connects the annular channel to the annular fluid chamber 70 between the 
sleeve and the housing. 
The plunger 18 is generally cylindrical in shape and is positioned in the 
sleeve 16 for movement between a lowered, retracted position (FIG. 3) and 
a raised, extended position (FIG. 5). The upper portion of the plunger 
includes a cylindrical, central bore 78 therein having an open, internally 
threaded upper end. The lower portion of the plunger includes a downwardly 
extending annular rim 80 defining a relatively larger diameter, generally 
cylindrical bore 82 therein having an open lower end. The midsection of 
the plunger includes a radially inwardly extending flange 84 that defines 
an opening 86 extending between the bores 78,82. 
A compression spring 88 is positioned within the bore 78 of the plunger 18 
and is held therein by a contact bolt 90 that is threaded into the upper 
end of the bore. The bottom of the spring rests on a washer 92 placed in 
the lower end of the bore. 
The piston cylinder assembly 20 is positioned within the sleeve 16 and is 
coupled with the plunger 18 for selectively shifting the plunger along the 
longitudinal axis of the bore between its lowered and raised positions. As 
best illustrated in FIG. 5, the cylinder assembly includes a cylinder 94 
including a sidewall defining an enclosed piston chamber 96, a piston 98 
moveably received within the piston chamber, and an elongated piston rod 
100 extending upwardly out of the top of the cylinder. 
In more detail, the cylinder 94 is positioned within the sleeve flange 64 
and includes a lower, base portion 102 and an upwardly extending, reduced 
diameter neck portion 104. The base portion is held in the sleeve 16 by 
external threading on its lowermost end that engages the internal 
threading on the lower end of the sleeve flange. The outer wall of the 
base portion includes a pair of annular grooves 106 that receive a pair of 
corresponding sealing elements 108 such as O-rings. The bottom wall of the 
base portion includes an annular groove 110 that receives a similar 
sealing element 112. 
The piston chamber 96 has a lower end that opens to the bottom of the base 
recess 24 and an opposite, upper end that includes a radially enlarged 
area 114. The lower, open end of the piston chamber is in fluid 
communication with the fluid passageway 34 leading to the first fluid 
inlet port 30. The upper end of the piston chamber is in fluid 
communication with a fluid passageway 116 formed diagonally through the 
cylinder that is in turn in fluid communication with the passageway 36 
leading to the second fluid inlet port 32. 
The base portion 102 of the cylinder further includes a fluid passageway 
118 and a connecting annular channel 120 that connect the lower end of the 
piston chamber 96 to the annular channel 74 formed in the sleeve. As 
described above, the annular channel 74 is in fluid communication with the 
vertical groove 76 in the sleeve, which connects to the annular fluid 
chamber 70 between the deformable section of the sleeve 68 and the inner 
wall of the housing 14. Thus, fluid that enters the lower end of the 
piston chamber 96 through the first fluid inlet port 30 travels up the 
passageway 118, through the annular channel 120, the annular channel 74, 
and the vertical groove 76, and to the annular fluid chamber 70 as 
described in more detail below. 
The cylinder neck 104 includes an open top, internally threaded bore 122. A 
threaded plug 124 having a central bore 126 formed therethrough is 
threaded into the open top of the bore 122 to hold a seal 128 therein. The 
cylinder neck, which is reduced in diameter relative to the cylinder base 
102, defines an annular opening 130 between the cylinder and the inner 
wall of the sleeve for receiving the lower annular rim 80 of the plunger 
18 when the plunger is shifted to its lowered position. 
The piston 98 is movably received within the piston chamber 96 and includes 
a central annular channel 132 that receives an O-ring or other sealing 
element 134. 
The piston rod 100 includes a lower end 136 attached to the upper end of 
the piston 98 and an opposite upper end 138 that extends through the plug 
bore 126 and the opening 86 in the plunger 18. A cap screw 140 is threaded 
into the upper end of the piston rod so that it is in contact with the 
washer 92 supporting the lower end of the compression spring 88. 
In operation, the work support 10 is mounted on a fixture, table, or other 
platform and hydraulic fluid lines are connected to the first and second 
fluid ports 30,32 to deliver fluid to and discharge fluid from the 
passageways 34,36 in communication with the piston chamber 96. The work 
support is typically initially in the state illustrated in FIG. 3., 
wherein the plunger 18 is in its lowered, retracted position. 
To raise the plunger 18 to support a workpiece 142 as illustrated in FIG. 
5, fluid is delivered to the first fluid port 30 to pressurize the lower 
end of the piston chamber 96 with fluid and fluid is allowed to be 
discharged from the second fluid port 32 to drain the upper end of the 
piston chamber. The fluid entering the lower end of the piston chamber 
exerts an upward force on the lower face of the piston 98, thereby 
shifting the piston upwardly in the piston chamber. This raises the piston 
rod 100, which in turn pushes upwardly against the lower end of the 
compression spring 88. As long as the contact bolt 90 on the top of the 
plunger has not contacted the workpiece or other object, the spring 
remains essentially fully expanded and transfers the upward force from the 
piston rod to the plunger to raise the plunger. Once the contact bolt 
contacts the workpiece and stops, however, the piston rod continues to 
rise to slightly compress the spring. This provides a cushioning effect so 
that the contact bolt firmly holds the workpiece without marring or 
otherwise damaging the surface of the workpiece. 
While the piston rod 100 is shifting the plunger 18 towards its fully 
extended position, fluid also travels from the lower end of the piston 
chamber 96, up the passageway 118, through the annular channel 100 in the 
cylinder, through the annular channel 74 and vertical groove 76 in the 
sleeve flange 64, and to the annular fluid chamber 70 between the 
deformable section 68 of the sleeve and the inner wall of the housing. As 
the pressure of the fluid in the annular fluid chamber increases, it 
exerts a radial pressure on the deformable section of the sleeve, thereby 
causing it to shift radially inward against the plunger 18 for locking the 
plunger in its fully extended position. The passageway, channels, and 
groove that deliver fluid to the annular fluid chamber are sized to 
deliver sufficient fluid to cause the deformable section to shift inward 
only after the piston assembly has fully extended the plunger to its 
raised position to prevent the plunger from locking in an intermediate 
position. 
When it is desired to release the workpiece 142, hydraulic fluid is 
delivered to the upper end of the piston chamber 96 through the second 
fluid inlet port 32 and fluid is allowed to discharge from the lower end 
of the piston chamber through the first fluid inlet port 30. This reduces 
the fluid pressure in the lower end of the piston chamber and the annular 
fluid chamber 70, thus allowing the deformable section 68 of the sleeve 16 
to flex outward back to its original position to release its grip on the 
plunger 18. Additionally, the compression spring 88 expands to its 
original position and pushes the piston rod 100 down slightly so that the 
cap screw 140 attached to the upper end of the piston rod seats itself 
against the flange 84 in the plunger as illustrated in FIG. 3. At the same 
time, the fluid entering the upper end of the piston chamber exerts a 
downward force on the upper end of the piston 98 to shift the piston, 
piston rod 100, and plunger 18 to their lowermost position as illustrated 
in FIG. 3, thus releasing the workpiece. 
Although the invention has been described with reference to the preferred 
embodiment illustrated in the attached drawing figures, it is noted that 
equivalents may be employed and substitutions made herein without 
departing from the scope of the invention as recited in the claims.