received by the International Bureau on 14 September 2020 (14.09.2020).

Claims:

1.

An industrial gas spring comprising:

a casing including an axially extending side wall, an open end, a transversely extending end wall axially spaced from the open end, and a gas pressure chamber defined in part by the side and end walls;

a piston rod received at least in part in the casing for reciprocation between extended and retracted positions and having an inner end communicating with the pressure chamber and an outer end extending generally axially outwardly of the open end of the casing when the piston rod is in the extended position; and

a pressure relief assembly carried by the end wall with:

a membrane configured with a first face communicating with the pressure chamber and a second face communicating with the exterior of the casing; and

a plunger having a cylindrical peripheral surface and a first end having a projection adjacent part of the cylindrical peripheral surface with a sharp edge adjacent the membrane and configured to breach the membrane and a second end axially spaced from the first end, disposed in the pressure chamber and configured to be engaged by the piston rod to move the plunger to breach the membrane by the sharp edge of the projection when the piston rod overtravels its design intended maximum retracted position.

2.

The gas spring of claim 1, which also comprises a first blind bore in the end wall forming the first face of the membrane and communicating with the pressure chamber and a second blind bore in the end wall forming the second face of the membrane and communicating with the exterior of the casing.

3.

The gas spring of claim 2, wherein the plunger comprises a body with a the cylindrical portion of the plunger at least partially between the first and second ends of the plunger and the cylindrical portion of the plunger is received in part in the first blind bore.

19 The gas spring of claim 3, wherein the projection of the plunger comprises at least two circumferentially spaced apart and axially extending fingers adjacent the first end of the plunger and each having a relatively sharp edge for breaching the membrane when the edges are advanced at least partially through the membrane by overtravel of the piston rod moving the plunger toward the membrane.

5.

The gas spring of claim 4, wherein the sharp edges are configured to be adjacent the periphery of the first bore.

6.

The gas spring of claim 4, wherein each edge is spaced radially inwardly of the cylindrical portion of the body of the plunger and radially inwardly of the periphery of the first bore.

7.

The gas spring of claim 3, wherein the body also has only a single projection adjacent the first end of the plunger with the sharp edge configured to breach the membrane when moved at least partially through the membrane by the overtravel of the piston rod.

8.

The gas spring of claim 3, which also comprises a vent passage through the plunger body.

9.

The gas spring of claim 3, which also comprises a recess in the cylindrical surface and extending generally axially along the body to provide at least part of a vent passage between the pressure chamber and the membrane.

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10.

The gas spring of claim 1, wherein the membrane is a homogeneously integral part of the end wall. 11.

The gas spring of claim 2, wherein the membrane is a homogeneously integral part of the end wall.

12.

The gas spring of claim 3, wherein the membrane is a homogeneously integral part of the end wall.

13.

The gas spring of claim 1, wherein the membrane is a separate piece from the end wall and removable from the end wall, a bore in the end wall communicating with the pressure chamber and a counterbore in the end wall communicating with the exterior of the end wall, the plunger being received in the bore, the separate membrane being received in the counterbore and communicating with the pressure chamber, and a collar removably received in the counterbore and bearing on and retaining the separate membrane in the counterbore and having a through passage communicating the membrane with the exterior of the gas spring.

14.

The gas spring of claim 13, wherein the collar includes external threads engageable with complimentary threads in the counterbore.

15.

The gas spring of claim 1, comprising a passage through the end wall and communicating with the pressure chamber and the exterior of the gas spring, a body received in the passage, a blind bore in the body, the membrane being carried by the body and at least in part in the blind bore in the body, the blind bore communicating with the pressure chamber and with the first face of the membrane, and the plunger is received in the blind bore with its first end adjacent the membrane.

21 The gas spring of claim 15, wherein the membrane extends generally transversely across at least part of the blind bore and is at least part of a closed end of the blind bore.

17.

The gas spring of claim 15, wherein the membrane is a homogeneously integral part of the body and projects generally radially into the blind bore adjacent a closed end of the blind passage.

18.

The gas spring of claim 17, wherein the plunger in part is frictionally received and retained in the blind passage of the body.

19.

The gas spring of claim 18 which also comprises a sleeve of a yieldable material and encircling at least part of the plunger and received in the bore through the end wall and extending generally axially to at least the second end of the plunger.

20.

The gas spring of claim 15, wherein the body includes external threads threadably engageable with complimentary threads in the passage through the end wall.

21.

The gas spring of claim 15, wherein the body is frictionally received with an interference fit in the passage through the end wall.

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