Poppet trip device for hydraulic cylinders

The poppet trip device of the present invention is adapted for hydraulic cylinder units having a poppet axially movable within a poppet sleeve extended through the piston of the hydraulic cylinder unit. A head end of the poppet extends outwardly from the piston for engaging the head end of the cylinder in response to movement of the piston to the cylinder head end whereby the poppet is unseated and fluid communication is established through the poppet sleeve. Since the piston is spaced from the free end of the piston rod, however, engagement of the piston rod with the base end of the cylinder leaves the base end of the poppet spaced from the cylinder base end. The trip device or contact member of the present invention therefore is supported between the cylinder base end and piston for engaging the base end of the poppet in response to movement of the piston rod to the cylinder base end whereby the poppet is unseated and fluid communication is established through the poppet sleeve.

BACKGROUND OF THE INVENTION 
The present invention relates generally to hydraulic cylinder units and 
more particularly to a device for tripping the poppet of a hydraulic 
cylinder unit piston to enable synchronization. 
It has become desirable in various industries to have hydraulic cylinders 
that move in synchronization with each other, whether it be a retracting 
motion or an extending motion or both. Such a set of cylinders are 
referred to as series cylinders. 
To insure that the set of cylinders do not get out of synchronization due 
to volume differentials inherent within the cylinders, a means to bypass 
fluid around the piston at the end of either the retracting and/or 
extending motion must be incorporated into the hydraulic cylinders. 
A known type of series cylinder in the prior art includes a poppet in the 
piston rod, the poppet being tripped when it strikes the end of the 
cylinder butt plate. But this means for bypassing fluid across the piston 
is expensive to manufacture and difficult to assemble and maintain. 
Another problem associated with series cylinders of the prior art is that 
they have generally been highly susceptible to contamination. This is 
because the poppet seat mechanisms have been formed of a relatively soft 
material so that the high velocity fluid passing through the poppet tends 
to embed foreign matter into the valve seats. 
These and other problems of the prior art are believed to be resolved by 
the poppet trip device of the present invention. 
Accordingly, a primary object of the present invention is to provide an 
improved series cylinder. 
Another object is to provide a series cylinder including a movable poppet 
installed within the piston thereof. 
A further object is to provide such a series cylinder including means for 
tripping or unseating the poppet at both ends of the hydraulic cylinder 
unit. 
A further object is to provide such a series cylinder including means for 
enabling a piston mounted poppet to indirectly contact the base end of the 
cylinder for tripping the poppet. 
Another object is to provide an hydraulic cylinder poppet trip device which 
is easy and economical to manufacture and easy to assemble and maintain. 
A further object is to provide a series cylinder poppet trip device which 
has little or no susceptibility to contamination. 
SUMMARY OF THE INVENTION 
The poppet trip device of the present invention is adapted for hydraulic 
cylinder units wherein a movable poppet is installed within the piston 
thereof. At the head end of the cylinder, through which the piston rod 
extends, the poppet is tripped by direct engagement with the cylinder head 
end thereby to unseat the poppet and provide fluid communication through 
the poppet sleeve. At the base end of the hydraulic cylinder unit, 
however, the poppet is spaced from the cylinder base end because of the 
retaining nut on the end of the piston rod. Accordingly, the present 
invention provides a poppet trip device or contact member which is 
supported within the cylinder between the base end and piston for 
engagement with the poppet in response to movement of the piston rod to 
the cylinder base end thereby to unseat the poppet and establish fluid 
communication through the poppet sleeve. 
The contact member is preferably carried on the piston rod and secured 
between the piston and retaining nut. The contact member may be a spring 
clip having an outwardly extended arm biased toward the cylinder base end 
but deflectable toward the piston for tripping the poppet when the arm 
engages the base end of the cylinder.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
A hydraulic cylinder unit 10, shown in FIGS. 1 and 2, includes an elongated 
cylinder 12 having a head end 14 and base end 16 secured to the opposite 
ends thereof by a set of elongated bolts 18. The head end 14 includes an 
opening 20 through which the piston rod 22 is axially slidably received as 
shown best in FIG. 2. A clevis 24 having a removable pin 26 is secured 
onto the exterior end of the piston rod 22. A piston 28 is secured onto a 
reduced diameter interior end portion 30 of piston rod 22 by a retaining 
nut 32. Seal rings 34 and 36 provide a fluid tight seal between the piston 
28 and the piston rod 22 and cylinder 12 respectively. 
The head end 14 of hydraulic cylinder unit 10 includes a hydraulic fluid 
port 38 which communicates through a passageway 40 with the interior of 
cylinder 12. A suitable fitting 42 is secured within port 38 for selective 
connection through a suitable valve to either a hydraulic fluid reservoir 
or source of hydraulic fluid under pressure. Head end 14 carries a pair of 
seal rings 44 and 46 which engage the piston rod 22 and inner surface of 
cylinder 12 respectively. 
The base end 16 of hydraulic cylinder unit 10 includes what shall be 
referred to as a butt plate portion 48 extending transversely across the 
end of the cylinder 12 and an annular base end cap flange 50 which extends 
axially into one end of cylinder 12 interiorly of butt plate portion 48. A 
seal ring 52 carried on flange 50 provides a fluid type seal between the 
flange and cylinder 12. Base end 16 is also provided with a hydraulic 
fluid port 54 equipped with a fitting 56 for providing fluid communication 
through a passageway 58 to the interior of cylinder 12. A pair of ears 60 
and 62 extend outwardly from base end 16 for supporting a removable clevis 
pin 64 in the usual manner. 
Referring to FIGS. 2, 6 and 7, it is seen that a poppet sleeve or bore 66 
is generally axially extended through the piston 28 for slidably 
supporting a poppet 68 therein. Poppet sleeve 66 has a reduced diameter 
head end forming a tapered valve seat at 70. The base end of poppet sleeve 
66 is adapted to receive an annular plug 72 which forms another valve seat 
74. 
Poppet 68, in the preferred embodiment of FIG. 4, includes a central body 
portion 76 which is formed of square section stock having the edges 
rounded so as to be both rotatably and axially slidably supported within 
the poppet sleeve 66 while permitting fluid passage axially of the poppet 
between the flats thereof and the cylindrical sleeve 66. Body portion 76 
is somewhat shorter than the distance between valve seats 70 and 74 and 
tapers inwardly at its ends to define valve heads 78 and 80 respectively. 
Reduced diameter head and base ends 82 and 84 of poppet 68 extend axially 
from the valve head to give the poppet an overall length somewhat greater 
than the thickness of piston 28. 
The poppet trip device of the present invention comprises a spring clip 86 
shown in perspective in FIG. 5. Spring clip 86 includes a flat annular 
portion 88 having an opening 90 for receiving the piston rod 22. 
Spring clip 86 further includes an arm 92 extended outwardly from flat 
portion 88 at an inclined angle to the plane of the flat portion. Finally, 
spring clip 86 includes a peripheral shoulder 94 which cooperates with a 
stop pin 96 (FIG. 3) on the base end of piston 28 to positively position 
the spring clip relative to the piston and prevent rotation of the spring 
clip. It is seen in FIGS. 6 and 7 that the spring clip 86 is fitted onto 
piston rod 22 and sandwiched between the piston 28 and retaining nut 32 so 
that arm 92 extends radially outwardly from piston rod 22 and toward the 
cylinder base end 16. It is seen in FIG. 3 that when shoulder 94 engages 
stop pin 96, the spring clip arm 92 is positioned for registration with 
the poppet 68 as described hereinbelow. 
In operation, it is desirable to bypass hydraulic fluid through the poppet 
sleeve 66 of piston 28 at the end of the extension, retraction or both 
motions of the piston in order to synchronize hydraulic cylinder unit 10 
with another hydraulic cylinder unit which coacts in series. Referring 
first to the extension motion of the hydraulic cylinder unit 10, hydraulic 
fluid under pressure is introduced into the base end port 54 which causes 
the poppet 68 to be seated against valve seat 70 and the piston to move to 
its extended position in engagement with head end 14. It is seen in FIG. 7 
that when the piston 28 engages head end 14, the head end 82 of poppet 68 
also engages the head end so as to unseat the poppet and establish 
hydraulic fluid communication through the poppet sleeve 66. Note that the 
cylinder head end 14 includes an annular recess at 98 to permit fluid 
communication from the poppet sleeve 66 to passageway 40 and port 38. 
Upon retraction of the hydraulic cylinder unit 10, hydraulic fluid under 
pressure is introduced through port 38 and passageway 40 to seat the 
poppet against the opposite valve seat 74 and move the piston to the left 
as seen in FIGS. 2 and 6 into engagement with the base end cap flange 50. 
Since the butt plate portion 48 of the cylinder base end 16 is recessed 
inwardly of the base end cap flange 50 to accommodate the retaining nut 
32, the base end 84 of poppet 68 remains in spaced relation from the 
cylinder base end. But as the piston 28 approaches its retracted position, 
the spring clip arm 92 engages the base end cap flange 50 so as to be 
deflected toward the piston into engagement with the base end 84 of poppet 
68 thereby tripping the same and establishing fluid communication through 
the poppet sleeve 66. 
Accordingly, the poppet trip device or spring clip 86 of the present 
invention enables the poppet to be tripped at the retracted position for 
the piston in much the same manner as at the extended position for the 
piston even though the cylinder base end 16 is recessed so as to prevent 
direct engagement with the poppet 68. The spring clip arm 92 enables the 
poppet to indirectly engage the base end cap flange 50 for tripping of the 
poppet in response to movement of the piston to its fully retracted 
position. 
The positioning of the poppet sleeve 66 and poppet 68 at a position 
radially intermediate the piston rod 22 and cylinder 12 enables the piston 
assembly to be easily and economically manufactured and installed. 
Furthermore, the operation of the poppet of the present invention is easy 
to understand thereby rendering less technical any field repair which may 
be necessary. Finally, both the poppet 68 and both valves seats 70 and 74 
are formed of steel or a material of at least equivalent hardness so as to 
have little or no susceptibility to contamination due to the embedding of 
foreign matter carried in the high velocity fluid passing through the 
poppet sleeve 66 at the end of each stroke of the piston. 
Whereas the poppet trip device is shown in the preferred embodiment as 
carried on the piston rod, it is contemplated that in alternate 
embodiments, it may be fixed to the cylinder base end for engagement with 
the base end of the poppet when the piston is moved to its retracted 
position. 
Accordingly, there has been shown and described a hydraulic cylinder unit 
including a poppet trip device which accomplishes at least all of the 
stated objects.