Piston, especially for a pneumatic cylinder

Claim 1

A piston, especially for a pneumatic cylinder, comprising a disc-shaped piston head having a peripheral sliding surface thereon and opposed annular outer end walls, said head comprising two head section halves respectively containing said outer end walls and having a central bore therein lying along a central axis of the piston head, a piston rod extending through said bore, said head having mounted thereon a sealing element with at least one annular sealing lip extending outwardly of said sliding surface, said sealing lip being of elastic and resilient material and being of conical form relative to the central axis, an outer free edge of said lip thereby being capable of sealingly engaging the wall of the cylinder, said section halves having inner end walls respectively opposite said outer end walls, said inner end walls having open annular recesses therein defining a cavity containing a quantity of lubricant, means on said piston rod bearing against said section halves for permitting limited axial movement of said halves relative to said rod, spring means disposed in said recesses for biasing said inner end walls away from one another, and said sealing element having radial passages therein communicating with said cavity, whereby said lubricant is caused to exit said cavity and flow through said passage to the wall of the cylinder as one of said sections axially shifts relative to said rod as pressure is applied against said one section during operation of the piston.