Fluid-operated cylinder

Claim 1

A fluid operated cylinder including a cylindrical housing, a piston slidable therein and a sealing member between said piston and said cylindrical housing, said sealing member being in the form of a deformable liner of substantially elastomeric material, said liner defining a cylinder cavity and extending over a length at least equal to the piston stroke length and allowing slidable movement of the piston therein, the normal diameter of said deformable liner being normally less than the inner diameter of said cylindrical housing thereby forming a tubular interspace therebetween, an interspace fluid within said interspace and wherein, according to the improvement, said liner has at least one opening at least near the end of stroke position of the piston, said opening providing communication between said tubular interspace and sAid cylinder cavity, said interspace fluid being the same as the cylinder operating fluid contained within said cylinder cavity and said piston having a diameter greater than the normal diameter of said liner and such as to press the liner portion nearest to said piston against the cylinder walls so as to separate thereby said interspace in two portions.