Hydraulic cylinder

A hydraulic cylinder usable as a shock-absorbing trim and tilt cylinder for adjusting the position of an outboard motor or outdrive unit of a boat, is provided with a piston including pilot-operated valve means which stepwise responds at a precisely setable pressure, to pressures resulting from impact of an outboard motor or outdrive unit upon an obstacle, the valve means then departing as a poppet-type relief valve to allow the outboard motor or outdrive unit to return to operative position following the impact. The hydraulic cylinder is provided with an integral conduit formed by milling a groove or slot from a point adjacent its mounting end to the point adjacent its rod end, and fastening a cover over the groove. The cylinder's mounting eye end is provided with passages that cooperate with passages in its mounting pin to supply hydraulic fluid to first and second chambers defined by the piston within the cylinder, one of the passages in the mounting eye end intersecting the integral conduit to supply fluid to the rod-end chamber defined by the piston.

The instant application is related to the field of hydraulics. In 
particular, this application relates to the structure of pistons and 
housings of hydraulic cylinders. 
BACKGROUND OF THE INVENTION 
Hydraulic cylinders, such as are useful in numerous applications, have been 
provided with valved pistons, for use as shock absorbers, and with pistons 
including valves suiting them for shock absorber use on boats, for 
tilting, or for trimming and tilting a drive unit for a boat such as an 
outboard motor or an outdrive unit, for allowing it to pivot upwardly when 
the propulsion unit strikes an obstacle, to avoid damage to the propulsion 
unit, and to let the propulsion unit return to operative position in a 
controlled manner following contact with the obstacle, if warranted. Such 
shock absorbers have been provided with stop pistons, providing an 
adjustable retracted-position cylinder end, which could be moved under 
hydraulic control to set a trim position for the outdrive or outboard 
unit, and cause the piston, and the drive unit, to return to a preset trim 
position following collision with an obstacle. 
In order to obtain the flow rates necessary through the shock absorber 
piston to allow rapid movement when an associated outboard motor or 
outdrive unit strikes an obstacle, numerous small valves are 
conventionally used. In one such system, a piston is provided with seven 
small valves, acting as paralleled jounce valves, for allowing the piston 
to move upon contact of the drive unit with an obstacle, and an eighth 
rebound valve to allow the drive unit to return to operative position. The 
use of this multitude of valves, while functional, has certain 
deficiences. For instance, the use of eight separate valves provides eight 
separate hydraulic leak paths, any of which may interfere with the proper 
operation of the hydraulic cylinder. Eight separate valve seats must be 
machined in bores through the piston, seven substantially identical 
precision springs must be selected or obtained, since it is not 
practicable to make all eight valves individually adjustable, or to adjust 
the valves to begin to open at a definite pressure in a simple manner. 
Also, the individual poppet-type relief valves are not precisely 
controllable, to provide an operating pressure which may be set to 
correspond to the mechanical strength of the outboard motor or outdrive 
unit members to act only when it is necessary to protect them from damage. 
If the pressure of these multiple relief valves is set too high, the 
structure of the drive unit will be damaged. If set too low, the drive 
unit may spend excessive time with its propeller out of the water, 
increasing the opportunity for engine damage, or, accelerating with the 
propeller rotation reversed may pull the outboard motor or outdrive unit 
out of the water, also causing overspeed. This adjustment is difficult and 
troublesome, since poppet-type valves are proportionally responsive, 
allowing some flow at a low pressure and greater flow at greater pressure. 
Valves which allow adequate flow at impact-caused pressure may allow the 
drive unit to gradually be pulled out of the water by reversed operation 
of the drive unit. 
As a partial solution to this problem, a single large valve which operates 
in a stepwise manner at a predetermined and easily adjustable pressure has 
been provided, and placed adjacent to the hydraulic cylinder, to provide a 
precisely controllable operating pressure. Such a device is disclosed in 
co-pending application Ser. No. 146,891, filed May 5, 1980. This device, 
while providing improved performance, is placed remote from the piston of 
the hydraulic cylinder, so that its actuation in the presence of the 
impulse pressure caused by an outboard motor or outdrive unit striking an 
obstacle is delayed by the mechanical expansion of the components subject 
to the impulse pressure, so that the structure of the outboard motor or 
outdrive unit may be subjected to considerable mechanical stress before 
the pressure at the relief valve rises to its preset operating pressure, 
necessitating that the relief valve be set at a lower than optimum 
pressure to ensure protection of other mechanical components. 
Also, in order to supply hydraulic fluid to both ends of a hydraulic 
cylinder, so that a piston, or a stop piston, may be moved in both 
directions within the cylinder, complicated and potentially fragile 
structure has been provided. Separate lines have been provided between a 
source of hydraulic fluid, such as a reversible hydraulic pump, and the 
opposite ends of the hydraulic cylinder. These separate lines provide two 
separate potential failure items, which may be degraded by age and 
weathering, or be caught and torn upon an obstacle. As is known, one end 
of a cylinder may be supplied with hydraulic fluid through a mounting pin, 
which includes conduits or passages which align with conduits or passages 
in the housing of the hydraulic cylinder. The opposite end of the 
hydraulic cylinder is conventionally supplied with fluid by placing a 
separate conduit or hose along the side of the housing of the hydraulic 
cylinder, and which may be fastened to the side of the hydraulic cylinder, 
such as by welding. It is also known to use a hollowed rib, such as a 
hollowed rib used to protect tie bolts used in a cylinder assembly with a 
separate cylinder tube and end caps, to convey working fluid to the end of 
the cylinder remote from the mounting pin or pivot. 
Such external conduit means are often complex and difficult to assemble, 
contain numerous fittings which may be apt to leak, or present undesirable 
protrusions from the hydraulic cylinder. 
The instant invention provides a hydraulic cylinder which overcomes these 
and other deficiencies of previous similar cylinders. 
SUMMARY OF THE INVENTION 
The instant invention provides a hydraulic cylinder, usable as a shock 
absorber in numerous applications, or as a trim and tilt cylinder for use 
with an outboard motor or outdrive unit of a boat, which includes a valve 
structure in its piston which acts as a single, large area, pilot-operated 
jounce valve, capable of operating at a precise and predeterminable high 
pressure, in immediate and stepwise response to pressures generated within 
the hydraulic cylinder such as by a collision of the outboard motor or 
outdrive unit with an obstacle, such as an underwater obstacle, and which, 
using the same valve components, acts as a low-pressure poppet-type 
proportional-flow jounce valve, to allow the outboard motor or outdrive 
unit to return to its operating position in a controlled manner, with the 
different forces applied to the hydraulic cylinder due to the varying 
geometry of the outboard motor or outdrive system as it returns to initial 
position producing differing flows through the jounce valve. Also, to 
avoid expensive and troublesome external lines, a hydraulic cylinder 
according to the invention includes mounting means which are adapted to 
cooperate with a mounting pin or pivot provided with conduits connected to 
a source of hydraulic fluid, to supply hydraulic fluid to both ends of the 
hydraulic cylinder. A first passage or conduit directly connects a first 
of the two chambers defined by the piston within the hydraulic cylinder to 
the source of fluid, and a second passage or conduit interconnects the 
conduit of the mounting pin or pivot with a conduit formed by milling a 
slot along the side of the hydraulic cylinder, between a point adjacent 
the mounting end, to a point adjacent the far or rod end, and fastening a 
cover over the slot, such as by welding, to form an integral conduit to 
provide hydraulic fluid to a second chamber at the rod end of the 
hydraulic cylinder. 
Thus, it is a primary object of the invention to provide a hydraulic 
cylinder with a piston including valve means including a first large valve 
assembly, and a second smaller valve assembly, the second smaller valve 
assembly acting as a pilot valve to provide the first valve with a 
stepwise response at a predetermined pressure when the piston is moved in 
a first direction within the cylinder, the first valve assembly also 
acting as a low-pressure poppet-type relief valve, operable in a 
proportional manner at a substantially lower pressure when the piston is 
caused to be moved in a second direction. It is an advantage of the 
invention that a single large valve may be used in place of a multiple of 
smaller valves. It is a feature of the invention that this single large 
valve, with stepwise operation, may be preset to operate in a stepwise 
manner at a repeatable, definite, and easily setable predetermined 
pressure. 
It is a further advantage of the invention that such a valve may be made 
operable in a linear manner, in an opposite direction, at a lower 
pressure, providing a proportional response at a lower pressure applied in 
an opposite direction to the first high pressure. It is an advantage of 
the invention that no separate valve structure need be provided for a 
rebound or return valve in the piston of a hydraulic cylinder according to 
the invention. It is a feature of the invention that the spring means 
which serves to retain a valve element of the large valve in a desired 
position when the valve is unpressurized also serves as the spring of a 
proportionally-responsive poppet valve in response to reversed pressure 
across the piston. 
It is a further object of the invention to provide a housing for a 
hydraulic cylinder with an integral conduit, so that hydraulic connections 
to both ends of the cylinder may be physically made at only a single end. 
It is an advantage of the invention that structure external to the housing 
may be avoided. It is a feature of the invention that an integral conduit 
is formed by milling a slot along the side of the housing between points 
adjacent to the first and second ends of the cylinder, and welding a cover 
member over the slot, to form an integral conduit, which is connected to 
the source of hydraulic fluid by a bore or conduit in the mounting portion 
of the hydraulic cylinder, and connected to the interior of the cylinder 
at the far end by providing an aperture through the wall of the housing.

DETAILED DESCRIPTION OF THE INVENTION 
Referring to the drawings, there is shown a hydraulic cylinder 10 having a 
housing 12 with an integral conduit 14, and including a piston 17 
incorporating valve means according to the invention. 
As can be best seen in FIG. 2, housing 12 defines an exterior or outer 
surface 15 and an inner surface 16 which defines a working chamber having 
a first end 18 and a second end 20. As shown, piston 17 divides this 
working chamber into a first chamber 22 and a second chamber 24. 
As best shown in FIG. 2, the preferred embodiment includes a conventional 
cup-shaped stop piston 26 in chamber 22, between piston 17 and end 18, to 
provide in conventional manner an effective variable-length cylinder or 
variable retracted position cylinder. Such stop pistons are conventionally 
used in various applications, including use in marine trim and tilt 
systems for outboard motors and outdrive units, so that the trim position 
may be adjusted under hydraulic control, instead of being set by a cam 
controlled by a pull wire, or by stop pins which may be repositioned, so 
that optimum drive unit and hull trim may be established and maintained 
even if the distribution of loads within the boat is changed during its 
operation. 
As can be seen most clearly in FIGS. 2 and 3, piston 17 has a first surface 
disposed adjacent first end 18, and a second surface 30 disposed adjacent 
second end 20. As can also be seen, the piston assembly, and the valve 
means incorporated in piston 17, includes a portion of piston rod 32, 
which protrudes from the second surface 30 of piston 17, extends through 
second chamber 24 and protrudes from first or rod end 34 of cylinder 10. 
As will become apparent, piston rod 32 provides a convenient method of 
adjusting rebound pressure, should such be desired. As shown, piston rod 
32 includes a conventional eye portion 36, to provide a pivotable 
connection to any desired mechanical element. In the preferred use of the 
preferred embodiment of the invention, eye portion 36 is connected to a 
conventional outboard motor or outdrive unit. 
As can be seen most clearly in FIG. 3, piston 17 includes an axially and 
linearly extending aperture 38. Although described and shown as lying on 
the central axis of piston rod 32, it will be apparent that it need not 
lie on the axis of piston rod 32, and that, if desired, piston 17 may 
easily be modified to allow the valve structure according to the invention 
to be used with a double-ended cylinder. As shown, axially and linearly 
extending aperture 38 includes a first entry portion 40, a valve seat 
portion 42 including a valve seat 44 in communication with entry portion 
40, a valve pocket portion 46 in communication with entry portion 40, and 
a first spring pocket portion 48 in communication with valve pocket 46. 
Piston 17 also includes a second axially and linearly extending aperture 
50, which also may be repositioned as necessary without departing from the 
scope and spirit of the invention, which includes a second entry portion 
formed in first surface 28, shown as provided with screw threads 54, a 
second spring pocket portion 56 in communication with entry portion 52 and 
a second valve seat portion 58 including a valve seat 60. 
As can be seen, various passages are defined by piston 17 interconnecting 
apertures 38 and 50. As shown, a first passage 62 interconnects spring 
pocket 48 and valve seat 60 of valve seat portion 58. As can be seen, 
passage 62 includes several parts, including a first part 64 shown as an 
axial extension of spring pocket 48, a cross bore 66, an angled bore 68 
and a passage 70. 
As can be seen, spring pocket 48, first part 64, and cross bore 66 are 
formed in a portion of piston rod 32, which engages the body 72 of valve 
16 threadably, by means of mating threads 74, and includes seal means 
shown as an O-ring 76 in seal groove 78. As can be seen in FIG. 3, angled 
bore 68 may be conveniently formed before assembly of piston rod 32 and 
piston body 72. Also, a second passage or bore 80 interconnects second 
surface 30 and valve seat portion 42. 
Body 72 sealingly engages inner surface 16 by means of seal means shown as 
O-ring 82 disposed in seal groove 84. 
As shown in FIGS. 2 and 3, a first valve element 90 shown as a valve ball 
is disposed in valve pocket portion 46, and urged against valve seat 44 by 
a resilient means shown as a spring 92 disposed in first spring pocket 48. 
A small aperture, here shown as a gap, interconnects valve seat portion 44 
and first spring pocket portion 48. As shown, valve ball 90 is selected so 
as to define a small gap 94 between its surface 96 and a peripheral wall 
98 of valve pocket portion 46. As will become apparent, the flow area of 
gap 94 must be smaller than the flow area of passage 70 for proper 
operation of the disclosed valve means. 
A second valve element shown as valve ball 100 is disposed in second valve 
seat portion 58, and urged against valve seat 60 by a resilient means 
shown as a spring 102 disposed in second spring pocket portion 56. Spring 
102 is retained by an apertured plug 104 having an axial aperture 106, 
which may be a hexagonal aperture, if desired, and screw threads 108, 
which cooperate with screw threads 54 to retain aperture plug 104 in 
second entry portion 52. 
As can be seen, assembling a piston 17 according to the invention is a 
simple and convenient operation. Valve ball 100 is placed in second 
aperture 50, and followed by spring 102 and apertured plug 104, which is 
subsequently rotated to adjust the force provided to valve ball 100 by 
spring 102. A valve ball 90 is placed against seat 44, a spring 92 is 
placed in first spring pocket 48, which is preferably formed in an end 
portion 114 of piston rod 32, an O-ring 76 is placed in seal groove 78, 
and rod 32 is screwed into body 72 by means of mating threads 74. To avoid 
the necessity of precising positioning cross bore 66 in alignment with 
angle bore 68, cross bore 66 is connected to an annular groove 116, which 
may, if desired, be made wider than the diameter of angle bore 68, so that 
mating threads 74 may be used to adjust the pressure applied to valve ball 
90 by spring 92. 
As will be apparent, when a force is supplied to piston rod 32 to urge it 
to move in a first or jounce direction shown by arrow 122, the fluid 
pressure against second surface 32 will increase. This increased pressure 
will cause fluid to attempt to flow through second passage or bore 80 to 
valve seat portion 42, where its passage through entry portion 40 is 
blocked by valve ball 90. However, due to the small aperture shown as gap 
94, this pressure also appears in first spring pocket portion 48, first 
part 64, cross bore 66 and annular groove 16 of first passage 62, angle 
bore 68 and passage 70. When the pressure in passage 70 exceeds the 
pressure which will cause movement of valve ball 100 away from valve seat 
60, hydraulic fluid will flow past valve ball 100, through second spring 
pocket portion 58 and entry portion 52. A slight movement of valve ball 
100 will thus cause a sudden drop in the pressure appearing in passage 70, 
angle bore 68, cross bore 66 and first spring pocket portion 48. Then, the 
pressure appearing at second surface 30 and in valve seat portion 42 being 
higher than the pressure appearing in first spring pocket portion 48, 
valve ball 90 will be stepwise pushed off valve seat 44, and fluid will 
flow from valve seat portion 42, through entry portion 40, to relieve the 
pressure appearing at second surface 30. By making the flow area of the 
aperture shown as gap 94 substantially smaller than the flow area of 
passage 70, a very small movement of valve ball 102 will be sufficient to 
cause full opening of the valve defined by valve ball 90 and valve seat 
44. This also avoids the necessity of conventional complicated machining 
operations for providing fluid passages around springs which may assume 
their solid height during a jounce cycle, since, in the instant invention, 
there is very little change in length of spring 102, and spring 92, which 
serves largely only to hold valve ball 90 against seat 44 against the 
force of gravity and other nonspecific accelerations, is not part of the 
main flow path through valve seat portion 42. 
When a force is applied to piston rod 32 in a second or rebound direction 
as shown by arrow 126, fluid in first chamber 22 will apply pressure to 
first surface 28. When this pressure rises to a low value, such as 
approximately 30 to 50 pounds per square inch, valve ball 90 will begin to 
be displaced from valve seat 44, allowing the flow of fluid through entry 
portion 40, valve seat portion 42 and passage or bore 80, to second 
chamber 24. As will be apparent, a higher pressure present at first 
surface 28 will cause a greater deflection of valve ball 90, and a greater 
opening between valve ball 90 and valve seat 44 proportional to applied 
pressure. There is no flow through valve spring pocket 48 or past valve 
ball 100, since, preferably, a pressure of 2,000 to 3,000 pounds per 
square inch is necessary to deflect valve ball 100. 
Of course, this desired pressure varies with the diameter of housing 12 of 
hydraulic cylinder 10, as well as with the designed load of associated 
mechanical components. This desired operating pressure may be easily 
adjusted by placing piston 16 in a tubular fixture to apply fluid pressure 
against second surface 30 of a desired magnitude. Then, apertured plug 104 
is rotated in screw threads 54 to vary the force applied to valve ball 100 
by a spring 102 until fluid begins to flow from first entry portion 40. 
Thus, a single easy adjustment, as opposed to selection of a matched set 
of precision springs, is sufficient to set an actuating pressure, and, the 
valve action is stepwise upon actuation, rather than having an opening 
proportional to applied pressure, which is believed to cause greater 
mechanical fatigue of associated mechanical components. 
This flow allows piston 17 to move in the direction shown by arrow 126 
until it is mechanically stopped. In the preferred embodiment, piston 17 
is mechanically stopped by a conventional cup-shaped stop piston 26, which 
sealingly engages inner surface 16 by means of O-rings 130 in seal grooves 
132. Body 72 of piston 17 is provided with a stepped portion 134 which 
cooperates with cup-shaped stop piston 26 so that piston 17 retains stop 
piston 26 in proper alignment within housing 12, and stop piston 26 helps 
to support piston 17 against transverse loads. Body 72 is also provided 
with a second stepped portion 136 adjacent second surface 30, for a 
similar purpose when piston rod 32 is fully extended. 
FIGS. 5, 6 and 7 relate to alternate embodiments of the invention, which 
may be suitable for certain applications, and which utilize valve means 
including poppet members rather than ball members. 
In FIG. 5, a piston 17a is shown, which is physically identical to piston 
17a, except for the absence of valve balls 90 and 100, and which operates 
in exactly the same manner, and may be modified in the same manner. In 
FIG. 5, the valve ball 90 of FIG. 3 is replaced with a valve member shown 
as a poppet member 220, having a first portion 222 which cooperates with 
valve seat 44, and intermediate portion 224 which defines an aperture 
shown as aperture 226 therethrough, and a body portion 228 which acts as a 
guide for poppet member 220 in cooperation with peripheral wall 98 of 
valve pocket portion 46. As will be apparent, the relationship between the 
flow area of aperture 226 to that of passage 70 must be the same as that 
between small gap 94 and passage 70 in the description regarding the 
structure shown in FIG. 3. 
Referring briefly to FIGS. 6 and 7, there is shown a poppet member 220a 
which is interchangeable as a valve member with poppet member 220. Like 
poppet member 220, poppet member 220a includes a first portion 222a, an 
intermediate portion 224a and a body portion 228a. However, an aperture 
shown as bypass groove 226a replaces aperture 226 of poppet member 220, 
and serves the same function as aperture 226, or as gap 94, and bears the 
same relationship with the flow area of passage 70 for proper operation. 
As shown, bypass groove 226 is formed in peripheral surface 230 of body 
portion 228a. As illustrated, valve members shown as poppet members 220 
and 220a are generally cup-shaped, and define a spring pocket portion 232 
which cooperates with resilient means shown as spring 92. As will become 
apparent, poppet members 220 or 220a may be provided with means such as a 
projection in spring pocket portion 232 cooperating with resilient means 
such as spring 92 to maintain such a spring in a centered position, or the 
size of the spring relative to first portion 222, 222a may be adjusted to 
utilize the contour of first portion 222, 222a as a spring positioning 
surface. 
Also in FIG. 5, the second valve element shown as valve ball 100 in FIG. 3 
is here shown as a valve poppet member 234 having a generally conical 
shaped seating portion 236 which cooperates with valve seat 60, and a stem 
portion 238 adapted to be received within the coils of resilient means 
shown as spring 102. As will be apparent, valve poppet member 234 operates 
in exactly the same way as second valve element or valve ball 100. It is 
believed that the existence of stem portion 238 may be advantageous in 
reducing valve chatter in some applications. 
As will be apparent, piston 17a is assembled in the same fashion as piston 
17, except that a poppet member 220, 220a is substituted for valve ball 
90, and a valve poppet member 234 is substituted for a valve ball 100. 
Hydraulic cylinder 10 is provided with mounting means 138 at a second or 
mounting end 140 including a transverse bore 142 adapted to receive a 
mounting pin 144, which includes first and second conduits for supplying 
fluid to first and second chambers 22 and 24. A first conduit portion 146 
is connected through a radial passage 148 to an annular groove 150, which 
is positioned in alignment with a first passage in mounting means 138 
which is connected to first chamber 22. A second conduit portion 154 is 
connected to a radial passage 156, which is in turn joined to an annular 
groove 158, which is positioned in alignment with a second passage 160 
formed in mounting means 138. FIG. 1 is broken away at portion 162 to show 
that passage 160, in the preferred embodiment is formed by a bore which 
intersects transverse bore 142, and is plugged at an exterior surface 164 
of mounting means 138 by a ball 166 which is driven into passage 160. 
Mounting pin 144, and corresponding portions of mounting means 138, are 
adapted to prevent undesired flow of fluid, in conventional manner. A seal 
means, shown as O-ring 168, is disposed in a seal pocket 170, formed by 
annular grooves in both bore 142 and in mounting pin 44, to prevent the 
flow of fluid from annular groove 150 to annular groove 158. A seal means, 
shown as an O-ring 172, is disposed in a seal pocket 174 defined by 
annular grooves in both bore 142 and mounting pin 144, to prevent the 
leakage of fluid from annular groove 158 to the exterior of hydraulic 
cylinder 10. Seal means, shown as O-rings 173 and 174, are disposed in 
seal pockets 176 and 178, respectively, also defined by annular grooves in 
both bore 142 and pin 144, to prevent the leakage of fluid from annular 
groove 150 to the exterior of cylinder 10. Seal means 173 is provided 
primarily as a dirt seal, although functioning as a secondary fluid 
pressure seal. 
Referring particularly to FIGS. 1, 2 and 4, passage 160 intersects integral 
conduit 14, which is defined by a slot or groove, shown as a shallow, 
flat-bottom slot or groove 182 in exterior surface 15 extending from a 
point adjacent mounting end 140 to a point 186 adjacent rod end 34, and 
covered by a cover member, here shown as a cover member 188 shown as a 
generally C-shaped cover, which is fastened over groove 182, such as by 
welding, preferably electron beam welding, at seams 190, 192, thus forming 
integral conduit 14. Slot or groove 182 is preferably formed by milling, 
although it may also be part of an extrusion, if it is desired to form 
cylinder 10 in several parts. As shown, an aperture 194 is provided 
through housing 12 to interconnect integral conduit 14 and second chamber 
24. 
Rod end 34 of cylinder 10 may be sealed in any convenient conventional 
manner. However, in the preferred embodiment, a rod seal means 200, which 
engages housing 12 by means of mating threaded portions 202, includes 
means shown as O-ring 204 for sealing between rod seal means 200 and inner 
surface 16, and a rod seal 206 and rod wiper 208 for sealing between 
piston rod 32 and chamber 24. As shown, rod seal means 200 is cup shaped, 
including a portion 210. Portion 210 may be made as long as desired, to 
provide threaded portions 202 as long as desired, to withstand a desired 
pressure. Since portion 210 is shown as extended inwardly, towards end 
140, beyond aperture 194, rod seal means 200 is provided with an annular 
groove 212 which is aligned with aperture 194, and further includes at 
least one aperture 214 interconnecting annular groove 212 and second 
chamber 24. 
Thus, the preferred embodiment of the invention provides a hydraulic 
cylinder which includes a piston having valve means which operate in a 
stepwise manner at a pressure that can be easily and precisely set, and 
which includes a rugged integral conduit for fluid on its exterior 
surface, to allow the use of an inexpensive and rugged solid piston rod 
with such a hydraulic cylinder, and which requires no external fluid 
lines, since its mounting pin includes its fluid supply conduits. 
As will be apparent, numerous modifications and variations of the 
illustrated embodiment of the invention may be easily made by one skilled 
in the art, and various features of the preferred embodiment may obviously 
be used in isolation from others, without departing from the spirit and 
scope of the invention.