Hydraulic cylinder retainer

This is a retaining device for locking pistons that have retractable sliding arms. The retaining device has a first ring portion having interior, exterior, and two end surfaces with screw receiving areas. A receiving area for a holding screw extends from the interior surface to the exterior surface of the first ring portion. A second ring portion also has interior, exterior, and two end surfaces with screw receiving areas. The ring portions are assembled through use of screws to form a collar. A holding screw with a handle, sized to be threaded into the receiving area of the first ring portion, locks the retaining device onto the piston arm.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The instant invention relates to an easy-to-use locking device for use with 
hydraulic pistons. 
2. Brief Description of the Prior Art 
Conventional automotive vehicle bodies have closures, such as hoods, deck 
lids, or tail gates, which are swingably supported on the vehicle body for 
movement between open and closed positions. It is also conventional to 
provide an extendible and collapsible support strut or hold-open device to 
hold the closure in its open position. These devices can be either 
mechanical, pneumatic, or a combination thereof. 
One type of mechanical device utilizes a pair of telescoping members that 
are respectively connected to the closure and vehicle body, and which are 
urged toward an extended position by a spring to hold the closure in its 
open position. In such devices the spring force has to be overcome to 
collapse the telescoping members when the closure is moved to its closed 
position. Examples of such devices are shown in U.S. Pat. Nos. 4,512,600; 
3,319,993; 3,891,111; 3,611,892; and 3,851,908. Pneumatic hold-open 
devices, such as gas spring struts, etc. operate in much the same manner. 
Examples of such devices are shown in U.S. Pat. Nos. 3,883,126; 3,977,712; 
and 4,307,875. 
The gas springs, or hydraulic pistons, are commonly used in pivoting a 
trunk lid, hatch-back of an automobile, or rear door of a mini-van, 
between open and closed positions. The gas springs are subject to wear, 
leakage, and temperature. A gas spring which, when new, will reliably have 
a lift in excess of 30 lbs., will, over time, lose its lift capability in 
colder temperatures. Additionally, over time, the gas will leak out 
completely, causing failure in all temperatures. In the event of a gas 
leak, or general wear, the reliability of the gas spring is eliminated and 
other means must be used to maintain the door in the open position. The 
rear door of a mini-van can weigh upwards of 100 pounds, and the doors on 
full sized vans and trucks can be substantially heavier. A door's 
unexpectedly coming down can cause a substantial amount of physical damage 
to anyone who is hit. Replacement of the gas springs is expensive, and, in 
some instances, may not be warranted. 
Several patents have issued which have addressed the problem of the failure 
of the gas spring props, among them U.S. Pat. No. 4,596,383 to Howard. 
These patents, however, have solved the problem through the addition at 
the time of manufacture of an ternal locking device. Although a good 
safety feature, the external locking device does not address the problem 
of the millions of cars which currently do not have the external locks. 
Additionally, this is a feature which is either initially placed on cars 
at the time of manufacture or added separately at a later date. 
The instant invention overcomes the problems of the prior art by providing 
a easy-to-use, inexpensive add-on device to lock the gas springs in the 
desired position.

SUMMARY OF THE INVENTION 
The present invention features a retaining device for locking a pistons 
that has a retractable sliding arm. The retaining device has a first ring 
portion having interior, exterior, and two end surfaces. Each of the end 
surfaces has a connecting means. A receiving area for a holding means 
extends from proximate the midpoint of the interior surface to the 
exterior surface of the first ring portion. The holding means, is sized to 
permit it to be threaded into the receiving area of the first ring 
portion. In operation, a screw or bolt having a Rockwell hardness of at 
least RC-45-53 with a concave end is preferred. A handle attaches to one 
end of the holding means. Preferably, the handle is L shaped with a 
hexagonal cross section. 
The second ring portion also has interior, exterior, and two end surfaces. 
Each end surface of the second ring portion also has a connecting means. 
As assembled, the connecting means of the end surfaces of the first ring 
portion attach to the connecting means of the end surfaces of the second 
ring portion, forming a collar. The connecting means of the first ring 
portion are a pair of threaded holes, extending from the interior surface 
through to the exterior surface, sized to accept screws, bolts, or other 
fastening means. The second ring portion is configured to allow the screw 
or bolt heads to fit flush with or below the exterior surface. The 
connecting means are preferably configured to receive hexagonal tightening 
means. The handle configured for tightening the connecting means. 
Alternatively, the connecting means of the retaining device are a pair of 
protruding members and a pair of receiving members, which interlock to 
form a pair of dovetail joints when assembled. This type of connecting 
means may further include other fastening means, as mentioned above. 
The retaining device may be configured so that the second ring portion has 
an interior surface less than that of the first ring portion. 
The retaining device may also include a bushing which fits within the 
interior area of the collar. The bushing also includes a pair of legs 
configured to overlap the collar. 
DETAILED DESCRIPTION OF THE INVENTION 
The need for easily applied locks arises from the failure rate on the 
hydraulic and gas props which is further increased with the decrease in 
temperature. The failure rate is compounded with the age of the unit in 
combination with lower temperatures. The charts illustrate the performance 
rate vs. temperature of new, FIG. 20, 5 year old FIG. 21, and 10 year old, 
FIG. 22, gas props. 
FIG. 1 illustrates the preferred embodiment of the assembled collar lock 
10. The collar lock 10 can be used on the shaft of gas support props or 
hydraulic pistons to support auto hoods, trunks, truck cap, and rear and 
side doors, and can also be used as an improved lock for screen doors. The 
standard split-ring collar can be purchased as an off-the-shelf item. The 
split-ring collar requires the center area to be re-drilled, taking the 
interior area from the elliptical shape of the original production to the 
required circular interior. Alternatively, bushings or shims can be used 
to create the circular interior, thereby replacing the bore operation and 
reducing the production costs. The bushings and shims are discussed in 
detail further herein. The original split collar also requires tapping a 
set screw hole, as described further herein. The collar lock 10 is a 
two-piece, donut-shaped unit which is retained in the circular shape by 
screws 24 and 26. When separated, the collar lock 10 is formed of two 
horse-shoe units, the screw-receiving portion 12, and the screw-insert 
portion 18. The exterior diameter of the collar lock 10 is approximately 
19 mm. The thickness of the collar lock 10 is variable and not as critical 
as the diameter, although the collar lock 10 cannot be so thick as to 
interfere with the functioning of the gas spring prop. In the assemble 
state, the collar lock 10 has a center area 34 for receiving the piston 
arm. The dimension of the center area 34 is slightly greater, 
approximately 0.3 to 0.5 mm, than the piston arm to allow the collar lock 
10 to slide along the arm. The screw-receiving portion 12 is tapped along 
its flat portion to form screw-receiving areas 14 and 16. The screw-insert 
portion 18 is initially drilled to form insert areas 28 and 30 and then 
tapped to form screw-receiving areas 20 and 22. The insert areas 28 and 30 
are optimally drilled to allow the screws 24 and 26 to be recessed within 
the screw-insert portion 18. Dependent upon the manufacturer's desired 
profit margin, this step can be eliminated. The depth and width of the 
insert areas 28 and 30 must be slightly greater than the screw heads 24a 
and 26a to prevent friction. The length of the screw-receiving areas 14 
and 16 in the screw-receiving portion 12 must be of a length equal to that 
of the shaft of the screws 24 and 26, thereby allowing the screws 24 and 
26 to recess completely within the screw-insert portion 18. The screws 24 
and 26 are preferably configured to receive an Allen wrench, however any 
type of screw head can be used. The center of the semi-circular periphery 
of the screw-receiving portion 12 is tapped through to the center area 34 
at approximately the center point, to receive the set screw 32. The set 
screw-receiving area 38 must be tapped to exactly receive the set screw 
32. The set screw 32 must be as centered as possible to provide the 
maximum hold. If the set screw-receiving area 38 is off-center, the set 
screw 32 does not come in direct contact with the piston arm, thereby 
compromising the hold. The set screw 32 must have a shaft length which 
allows the set screw 32 to extend into the center area 34 when tightened. 
The set screw 32 has affixed to one end an Allen wrench 36, which is 
preferably dimensioned to correspond to the screw heads 24a and 26a. The 
handle portion 40 of the Allen wrench 36 requires a length of 
approximately 11/4 inches or less in order to allow for closure of the 
piston and door as well as storage in the vehicle when closed. The leg 42 
of the Allen wrench 36 can vary depending upon use. The recommended length 
for the leg 42 is approximately 3/8 inch for use with pistons and can have 
a greater leg length when being used with other installations. The Allen 
wrench 36 can be welded, soldered, or glued to the set screw 32 to provide 
a one piece unit. The Allen wrench 36 and the set screw 32 can be left as 
individual units; however, the one-piece unit is preferable for 
convenience. It is preferred to use an Allen wrench 36 as a handle as it 
provides dual usage in tightening the screws; however, any configuration 
can be used. The L-shape provided by the Allen wrench 36 provides the 
leverage required for tightening the set screw 32; however, as discussed 
further herein, other handle configurations can be used. 
The set screw 32 must be manufactured with a Rockwell hardness of at least 
RC-45-53 to provide the reliability required. The machine screws D, E and 
F below all equaled the RC-45-53 hardness requirement. The set screw 32 
actually cuts into the piston arm to provide a greater grip and prevent 
sliding. The ability to cut into the piston arm prevents the need to 
over-tighten the set screw 32. Failure of the set screw 32 will cause 
failure of the entire unit, thereby allowing the units being held to fall, 
with possible injury resulting. The 10/32 inch diameter machine screw 
provides a sharper cut into the arm of the piston, providing greater hold 
at higher pressures. The 1/4 inch diameter does not hold as well, nor does 
it cut into the piston arm as well. The following chart indicates the 
holding power of six varied set screws on a 5/16"/8 mm shock shaft. The 
standard torque use was 25 in/lb. The following bolts/screws were used in 
the testing indicated in FIG. 23: 
A=Brass 1/4--20 thread screw 
B=Grade 5 Bolt 1/4--20 pointed 
C=Grade 5 bolt 1/4--20 cupped 
D=1/4.times.20 cupped machine screw (RC-45-53) 
E=#10.times.24 cupped machine screw (RC-45-53) 
F=#10.times.32 cupped machine screw (RC-45-53) 
The torque vs. holding power is illustrated in the graph of FIG. 24. The 
set screw is shown tightened at various levels of torque, demonstrating 
the increased holding power in pounds as the set screw is tightened. Five 
inch pounds of tightening holds 40 pounds; 10 inch pounds of tightening 
holds 115 pounds; 15 inch pounds of tightening 155 pounds, etc. 
The unassembled collar lock 10 is shown in FIG. 2 wherein the 
screw-receiving portion 12 and the screw-insert portion 18 are separated. 
It is in this unassembled state that the collar lock 10 is placed on the 
piston arm 82 (FIG. 8) and then screwed together, as described further 
herein. The end views of the screw-receiving portion 12 and the 
screw-insert portion 18 are illustrated in FIGS. 3, 4, 5 and 6. The insert 
areas 28 and 30 are shown in FIG. 3, with the screw-receiving areas 20 and 
22 extending therefrom. The opposite side, FIG. 4, shows the exiting side 
of the screw-receiving areas 22 and 20. The set screw-receiving area 38 in 
the screw-receiving portion 12, FIGS. 5 and 6, is shown extending through 
the screw-receiving portion 12. As shown, the screw-receiving areas 14 and 
16 extend only part-way through the screw-receiving portion 12. 
In FIG. 7 the screw-receiving portion 12 and screw-insert portion 18 have 
been placed together, ready to receive the screws 24 and 26. The screws 24 
and 26 are inserted into the insert areas 28 and 30 until contact is made 
with the screw-receiving areas 20 and 22. The screws 24 and 26 are 
tightened, engaging with the tapped screw-receiving areas 20 and 22 and 
the screw-receiving areas 14 and 16. The screws 24 and 26 are tightened, 
securing the screw-receiving portion 12 and the screw-insert portion 18 
and creating a circular configuration. The set screw 32 is tightened to 
extend into the center area 34 an amount to lock the collar lock 10 onto 
the piston arm 82, preventing the piston arm 82 from sliding into the 
piston body 86. 
In FIG. 8 the collar lock 10 has been placed on the piston arm 82. The 
collar lock 10 is placed on the piston arm 82 while the piston 84 is in 
the closed position. The screw-receiving portion 12 and the screw-insert 
portion 18 are placed around the piston arm 82 and the screws 24 and 26 
tightened to prevent the screw-receiving portion 12 and the screw-insert 
portion 18 from separating. The door, or other unit, is placed in the 
desired position and the collar lock 10 slid to a position adjacent the 
piston body 86. The Allen wrench 36 is tightened until the set screw 32 
grabs the piston arm 82, preventing the collar lock 10 from moving and, 
subsequently, the piston arm 82 from sliding into the closed position. 
In FIG. 9, the preferred end of the set screw 32 is clearly shown in a 
cross view. The center of the set screw 32 has been drilled out to form a 
cup area 90. The cup area 90 has a diameter only slightly less that the 
diameter of the set screw 32, thereby forming a cutting edge which can dig 
into the steel, of the piston arm 82. The cup area 90 within a screw shaft 
is known in the prior art. As an alternative, the screw can have a 
standard point, such as a sheet metal screw. The pointed screws, however, 
do not retain their point and rapidly wear, thereby requiring continual 
replacement. 
FIGS. 10 and 11 illustrate alternate embodiments to the set screw 32. The 
set screw 100 of FIG. 10 is provided with a round, knob-type head 102 with 
which to tighten the set screw 100. This can be a bolt-type screw with any 
one of a number of screw heads, as well known in the prior art. The set 
screw 110 in FIG. 11 is a T-shape with a cross-bar handle 112. The 
cross-bar handle 112 provides additional leverage over the set screw 
configuration of FIG. 10. This configuration, however, is more complex to 
manufacture than the L-shaped handle heretofore described. A shim 114 has 
been added to the end of the shaft 116. The shim 114 provides an 
additional cutting edge to increase the ability of the set screw 110 to 
hold the collar lock in place without slippage. 
The standard pistons, or gas lift props, are manufactured in three primary 
sizes. In order to adapt to the size variations, bushings 122 can be added 
to the interior of the collar lock 10 to reduce the size, as shown in FIG. 
12. The bushings 122 are manufactured in two sizes, 8 mm and 6 mm. The 
center area 34 of the collar lock 10 is bored at just over 10 mm. Through 
the addition of the bushing 122, the center area 34 of the collar lock 10 
can be reduced to either the 8 mm or 6 mm sizing. The bushing 122 is a 
C-shaped unit which fits within the center area 34 of the collar lock 10. 
The bushing 122 is held in place during assembly of the collar lock 10 
through the friction created by sliding leg 124 and leg 126 over the 
screw-receiving portion 12 and the screw-insert portion 18. The distance A 
of the bushing 122 is slightly greater than the distance B of the collar 
lock 10, thereby providing a mild friction fit. Although the friction fit 
is not critical to the functioning of the collar lock, the assembly is 
substantially more convenient. One half of the bushing 122 must be drilled 
to allow the set screw 32 through from the collar lock 10. 
An alternate embodiment to the collar lock 10 is shown in FIG. 13, wherein 
rather than using screws 24 and 26 to lock the dovetail first portion 132 
and the dovetail second portion 134, dove tails are provided. The dovetail 
first portion 132 and the dovetail second portion 134 are mirror images, 
each having a dovetail-receiving area 138 and a dovetail 136. The dovetail 
136 is slid into the dovetail-receiving area 140 and dovetail 142 is slid 
into dovetail-receiving area 138. The sizing between the dovetails 142 and 
136 and the dovetail-receiving areas 138 and 140 preferably provide a 
friction fit, thereby keeping the dovetail first portion 132 and the 
dovetail second portion 134 locked together. As an alternative, the 
dovetail first portion 132 can be drilled with a retaining screw-receiving 
area 142 to further secure the two units together. The first portion 132 
is tapped with a set screw-receiving area 144 to allow the dovetail collar 
130 to be locked in the appropriate position, as heretofore noted. 
FIG. 14 illustrates the L-spacers 146 which are placed between the the 
screw-receiving portion 12 and the screw-inset portion 18. The L-spacers 
146, as illustrated herein, are provided with a lip which prevents 
slippage of the L-spacer 145 toward the center area 34 of the collar lock 
10. Alternatively, the spacers can be a rectangular piece which does not 
extend beyond the collar lock 10. The L-spacers 146, at a 0.060 thickness, 
will re-center the football shaped bore without the necessity of re-boring 
the center. The 0.060 thickness of the L-spacer 145 re-centers the collar 
lock 280 as described herein for gas spring props; however, for other 
applications, such as hydraulic jacks, as the size of the collar lock 
increases, the flanges must also increase accordingly. The L-spacers 146 
are tapped or bored in order to receive screws 224 and 226 which hold the 
L-spacers 146 in position by securing the L-spacers 146 between the the 
screw-receiving portion 12 and the screw-insert portion 18 with screws 224 
and 226. The screws 224 and 226 have a greater length than screws 24 and 
26 in order to fully engage the screw-receiving portion 12. 
An alternate to the bushing 122 is illustrated in FIG. 15. The flange 148 
has a semi-circular body 156 which has an outer-periphery 154 slightly 
less than the interior of the screw-insert portion 18. The flange 148 is 
provided with a pair of spacers 150 and 152 which extend from the 
semi-circular body 156 of the flange 158. The spacers 150 and 152 are 
either tapped or bored to allow for the screws 224 and 226 to pass 
through. The interior surface 158 of the flange 148 has diameter less than 
that of the screw-insert portion 18, thereby allowing for adjustability in 
the interior area of the collar lock 280. The piston arm fits into the 
closely dimensioned interior surface 158 and is secured there by set screw 
32. This prevents any lateral movement within the larger area of the 
screw's receiving portion 12. This adjustability allows the 
screw-receiving portion 12 and the screw-insert portion 18 of the collar 
lock 10 to be used with piston arms which have a diameter less than the 
interior diameter of the basic collar lock 10. The interior surface 158 of 
the flange 148 can be manufactured in several diameters to accommodate 
various piston arms. 
An alternative embodiment to the collar lock 10 is illustrates in FIGS. 16 
and 17 as collar look 300. The collar lock 300 uses the screw-receiving 
portion 12 of the collar lock 10 with a screw-insert portion 302. The 
screw-insert portion 302 has an exterior diameter 306 which is equal to 
the exterior diameter 310 of the screw-receiving portion 12. The interior 
diameter 304 of the screw-insert portion 302 has a diameter less than that 
of the interior diameter 308 of the screw-receiving portion 12. The piston 
arm sits within the interior diameter 304 of the screw-insert portion 302 
and is locked in place as previously described herein. 
The addition of a screw-insert portion, which allows for small diameter 
piston arms, can be incorporated in the embodiment disclosed in FIG. 13. 
The dimensions provided herein are suggested for use with gas props, etc. 
provided on trucks, automobiles, etc., or with screen door openers. The 
tolerances on the foregoing dimensions are approximately 1/2 mm. The 
collar lock disclosed herein can be made larger to accommodate other 
applications and the dimensions provided herein are suggest for particular 
uses and should not limit the scope of the invention. The collar lock can 
be used on any hydraulic piston or gas prop, or any other mechanism which 
operates on a slide basis. Hydraulic jacks are an example of an ideal 
application and would only require dimension changes. The collar lock of 
the instant invention can sustain weights up to 250 pounds of pressure and 
can therefore be used for a wide variety of applications. 
Although all of the collar lock configurations described above are 
generally cylindrical in shape, any other geometric configuration can be 
used providing it meets the constraints imposed by the application. 
Since other modifications and changes varied to suit particular operating 
requirements and environments will be apparent to those skilled in the 
art, the invention is not considered limited to the examples chosen for 
the purposes of disclosure, and covers all changes and modifications which 
do not constitute departures from the true spirit and scope of this 
invention. 
GLOSSARY 
Collar lock 10 
Screw-receiving portion 12 
Screw-receiving area 14 
Screw-receiving area 16 
Screw-insert portion 18 
Screw-receiving area 20 
Screw-receiving area 22 
Screw 24 
Screw 26 
Screw head 24a 
Screw head 26b 
Insert area 28 
Insert area 30 
Set screw 32 
Center area 34 
Allen wrench 36 
Set screw-receiving area 38 
Handle portion 40 
Leg 42 
Piston arm 82 
Piston 84 
Piston body 86 
Cup area 90 
Set screw 100 
Round, knob-type head 102 
Set screw 110 
Cross-bar handle 112 
Shim 114 
Shaft 116 
Bushings 122 
Leg 124 
Leg 126 
Dovetail collar 130 
Dovetail first portion 132 
Dovetail second portion 134 
Dovetail 136 
Dovetail-receiving area 138 
Dovetail-receiving area 140 
Dovetail 142 
Set screw-receiving area 144 
L-spacers 146 
Flange 148 
Spacer 150 
Spacer 152 
Outer periphery 154 
Semi-circular body 156 
Interior surface 158 
Screw 224 
Screw 226 
Collar lock 280 
Collar lock 300 
Screw-insert portion 302 
Interior diameter 304 
Exterior diameter 306 
Interior diameter 308 
Exterior diameter 310