Safety valve

Claim 2

A valve comprising a housing having a bore, the bore having an inlet and an outlet for fluid, a piston slidably engaged within the bore, at least one ball element seated in the wall of the bore and projecting from said wall normally to provide an abutment for one end of the piston, a collapsible member extending across the bore of the housing and adjacent an end of the piston to hold said at least one ball element seated in said wall thereby to retain the piston in a valve-closed position axially of the bore against the effect of pressurized fluid, and pressure-responsive means responsive to a precalculated change of external pressure to apply a load of precalculated magnitude to said collapsible member to cause collapse of said member and allow movement of the piston along the bore to a valve-open position thereby to release the fluid through the valve.

Claim 3

A valve according to claim 1 wherein the pressure responsive means comprises a plunger located adjacent the collapsible member so that an increase of pressure at or above a precalculated magnitude applied to the plunger causes the plunger to apply a load to said member sufficient to collapse said member and thereby allow the piston to move along the bore in the housing.

Claim 4

A valve comprising a housing having a bore, the bore having an inlet and an outlet for fluid, a piston slidably engaged within the bore and movable from a first position to a second position, the piston being releasably retained in said first position against the effect of pressurized fluid by releasably retaining means which comprises at least one ball element seated in the wall of the bore and projecting from said wall normally to provide an abutment for one end of the piston, and a collapsible member extending across the bore of the housing and adjacent an end of the piston to hold said at least one ball element seated in said wall thereby to retain the piston in its first position, pressure responsive means responsive to a precalculated change of external pressure to release the retaining means, and wherein the outlet is an outlet port extending from the bore to the exterior of the housing, the piston preventing escape of pressurized fluid through said port from the bore when the piston is in its first position, and the piston uncovering at least part of said port when the piston is in its second position.

Claim 5

A valve comprising a housing having a bore, the bore having an inlet and an outlet for fluid, a piston slidably engaged within the bore and movable from a first position to a second position, the piston being releasably retained in said first position against the effect of pressurized fluid by releasably retaining means which comprises at least one ball element seated in the wall of the bore and projecting from said wall normally to provide an abutment for one end of the piston, and a collapsible member extending across the bore of the housing and adjacent an end of the piston to hold said at least one ball element seated in said wall thereby to retain the piston in its first position, pressure responsive means responsive to a precalculated change of external pressure to release the retaining means, and wherein the outlet is an outlet port extending from the bore to the exterior of the housing, the piston preventing escape of pressurized fluid through said port from the bore when the piston is in its first position, and the piston uncovering at least part of said port when the piston is in its second position.

Claim 6

A valve according to claim 3 wherein the pressure-responsive means comprises a plunger located adjacent the collapsible member so that an increase of pressure at or above a precalculated magnitude applied to the plunger causes the plunger to apply a load to said member sufficient to collapse said member and thereby allow the piston to move along the bore in the housing.