Claims:

1.

A pressure relief device for mounting to an outer surface of a closed housing and about a vent opening in the surface, said device comprising: a) a collar attachable to said surface and upstanding from about said vent opening; b) a valve disk fitting over said collar, said valve disk having a depending skirt surrounding said collar; c) a spring urging said valve disk towards said collar for closing said vent opening ; d) a single gasket having a first surface for effecting a first seal between said valve disk and said collar and a peripheral surface for effecting a second seal between said collar and skirt, said peripheral surface being arranged to maintain a sealing contact with said skirt after the breaking of said first seal.

2.	A pressure relief device as in Claim 1 wherein said collar has an end face and a rib upstanding from said end face, said end face and rib together defining a seat for said gasket.

3.	A pressure relief device as in Claim 2 wherein said gasket comprises: a) a flat section resting on said end face; b) an upstanding portion surrounding said rib; and c) a lip extending radially inward over the top of said lip.

4.	A pressure relief device as in Claim 3 wherein said retaining ring is disposed on said flat section and surrounds said upstanding portion.

5.	A pressure relief device as in Claim 3 wherein the thickness of said upstanding portion is greater than the thickness of either said flat section or said lip.

6.	A pressure relief device as in Claim 3 wherein said upstanding portion and said lip merge in a rounded inner edge.

7.	A pressure relief device as in Claim 6 wherein said rib has a rounded outer edge matching the profile of said rounded inner edge.

8.	A pressure relief device as in Claim 3 wherein said peripheral surface is on an outer portion of said gasket flat section, said peripheral surface being in a wiping relationship with the inner surface of said skirt to effect said second seal.

9.	A pressure relief device as in Claim 8 wherein said peripheral surface effects said second seal at a level below the plane of said first seal.

10.

A pressure relief device as in Claim 8 wherein: a) said valve disk has an undersurface seated against said lip by the force of said bias means to effect said first seal; b) said lip having an inner diameter that establishes a first circular area smaller than the total area of said undersurface; and c) said first circular area being in communication with said vent opening whereby said valve disk separates from said lip when the pressure within the housing that is exerted on said first circular area provides a force that overcomes said bias means.

11.

A pressure relief device as in Claim 10 wherein the separation of said valve disk from said lip exposes the total area of said valve disk under surface to the pressure within said housing and said pressure being contained by said second seal and causing the sudden movement of said valve disk away from said gasket until said skirt clears said flat section of said gasket thereby opening said pressure relief device.

12.	A pressure relief device as in Claim 8 wherein said collar has a beveled outer edge underlying said gasket outer portion and said outer portion overhangs said beveled outer edge.

13.	A pressure relief device as in Claim 12 wherein said outer portion is flexible and able to flex towards said beveled edge for maintaining a wiping relationship with the inner surface of said skirt as said valve disk moves towards a closed position against said lip.

14.

A pressure relief device for mounting to an outer surface of a closed housing and about a vent opening in said surface, said pressure relief device comprising: a) a tubular collar attachable to said surface and about said opening, said collar having an end face; b) a rib upstanding from said end face; c) a gasket seated on said end face and surrounding said rib; d) said gasket having a flat section including an outer peripheral portion extending radially from said collar end face, an upstanding portion surrounding said rib and a lip extending radially inward over the top of said rib; e) a retaining ring disposed against said gasket flat section and surrounding said upstanding portion for attaching said gasket to said end face; f) a valve disk having an under surface in facing relationship with said lip and a depending skirt surrounding said collar, said valve disk being arranged for movement axially towards and away from said collar end face with the inner peripheral surface of said skirt being in wiping engagement with said gasket outer peripheral portion; g) bias means urging said valve disk axially towards said gasket to seat said valve disk undersurface against said lip thereby establishing a first seal in a plane generally parallel to the plane of said vent opening while said gasket outer portion bears against the inner surface of said skirt to establish a second seal in a plane generally normal to the plane of said vent opening; and h) said first seal defining a circular area of said under surface in communication with said vent opening that is smaller than the total area of said under surface.

15.	A pressure relief device as in Claim 14 wherein said collar has a beveled outer edge underlying said gasket outer peripheral portion and said outer peripheral portion over hangs said beveled edge.

16.

A pressure relief device as in Claim 15 wherein said gasket outer peripheral portion maintains a seal after the undersurface of said valve disk separates from said gasket lip responsive to a housing pressure which, when communicated to said circular area produces a force that overcomes said bias to move said valve disk away from said gasket.

17.	A gasket for a pressure relief device comprising: a first planar surface for effecting a first seal, and a peripheral surface for effecting a second seal, the peripheral surface circumscribing the first planar surface.

18.	The gasket of claim 17 further comprising; a flat section; an upstanding portion connected to the flat section; and a lip, connected to the upstanding portion, extending in a direction opposite from the flat section.

19.	The gasket of claim 18 in which the upstanding portion is thicker than the flat section.

20.	The gasket of claim 17 comprising a reinforcing ring embedded in the gasket.

21.	The gasket of claim 17 in which the peripheral surface is perpendicular to the first planar surface.

22.	The pressure relief device of claim 1 in which the spring is arranged axially with respect to the valve disk and the collar.

23.	The pressure relief device of claim 1 in which the first seal lies in a plane generally parallel to the plane of the vent opening.

24.	The pressure relief device of claim 1 in which the second seal lies in a plane generally normal to the vent opening.

25.

The pressure relief device of claim 1 comprising a retaining ring attaching the gasket to the collar. AMENDED CLAIMS [received by the International Bureau on 24 June 2002 (24.06.02); original claim 17 amended; remaining claims unchanged (1 page)] 15. A pressure relief device as in Claim 14 wherein said collar has a beveled outer edge underlying said gasket out peripheral portion and said outer peripheral portion over hangs said beveled edge.

26.

16 A pressure relief device as in Claim 15 wherein said gasket outer peripheral portion maintains a seal after the undersurface of said valve disk separates from said gasket lip responsive to a housing pressure which, when communicated to said circular area produces a force that overcomes said bias to move said valve disk away from said gasket.

27.

17 A gasket for a pressure relief device comprising : a seal member having a first planar surface for effecting a first seal in a first plane, and a peripheral surface for effecting a second seal in a second plane, the second seal being a wiping seal and, the peripheral surface circumscribing the first planar surface.

28.	18 The gasket of claim 17 further comprising ; a flat section ; an upstanding portion connected to the flat section ; and a lip, connected to the upstanding portion, extending in a direction opposite from the flat section.

29.	19 The gasket of claim 18 in which the upstanding portion is thicker than the flat section.

30.	20 The gasket of claim 17 comprising a reinforcing ring embedded in the gasket.

31.	21 The gasket of claim 17 in which the peripheral surface is perpendicular to the first planar surface.

32.	22 The pressure relief device of claim 1 in which the spring is arranged axially with respect to the valve disk and the collar.

33.	23 The pressure relief device of claim 1 in which the first seal lies in a plane generally parallel to the plane of the vent opening.

34.	24 The pressure relief device of claim 1 in which the second seal lies in a plane generally normal to the vent opening.

35.	25 The pressure relief device of claim 1 comprising a retaining ring attaching the gasket to the collar.