Patent ID: 6199827
Filing Date: 2001-03-13
Classification: B66F,F16K

Abstract:
An extendable or inflatable lifting device having a pressure release valve assembly (10); wherein the device comprises an enclosure having a first part (30) movable relative to second part (31) by applied fluid pressure; wherein the valve assembly (10) is mounted on one of the parts (30,31) and comprises a valve (13) exposed to pressure inside the enclosure and is attached to and actuable by an actuating tether (33) which is located in the enclosure and is attached to the other of said parts (30,31) to cause the valve (13) to open and release fluid from within the enclosure when the distance between the parts (30,31) reaches a limit determined by the length of the tether (33); and characterised in that the valve (13) which is actuated by the tether is a second valve (13) of the assembly (10) which second valve (13) releases fluid into the valve assembly (10) to actuate a first valve (12), which first valve (12) is arranged to open automatically only when the pressure within the valve assembly (10) is greater than the pressure outside the enclosure.