Hydraulically operated mine prop

Claim 1

A HYDRAULIC MINE PROP COMPRISING, IN COMBINATION, AN EXTERNAL TUBULAR PROP MEMBER CLOSED AT ONE END; AN INTERNAL PROP MEMBER PROJECTING WITH CLEARANCE INTO SAID EXTERNAL PROP MEMBER AND HAVING AN INNER END MOVABLE TOWARD AND AWAY FROM SAID CLOSED END; A PROP PISTON SECURED TO SAID INNER END OF SAID INTERNAL PROP MEMBER, SAID PROP PISTON INCLUDING A SEALING PORTION SLIDABLY GUIDED IN SAID EXTERNAL PROP MEMBER AND SEALINGLY ENGAGING THE INNER SURFACE THEREOF TO FORM THEREWITH BETWEEN SAID CLOSED END AND SAID SEALING PORTION A PRESSURE CHAMBER, AND A CONNECTING PORTION CONNECTING SAID SEALING PORTION TO SAID INNER END OF SAID INTERNAL PROP MEMBER FOR MOVEMENT THEREWITH AND IN A MANNER RESISTANT TO TENSION AND COMPRESSION, SAID CONNECTING PORTION BEING AT LEAST IN PART FORMED FROM ELASTICALLY DEFORMABLE MATERIAL AND SAID PART HAVING SUCH AN ELASTIC DEFORMABILITY SO AS TO PERMIT LIMITED UNIVERSAL TILTING MOVEMENT OF SAID SEALING PORTION OF SAID PISTON RELATIVE TO SAID INTERNAL PROP MEMBER AS WELL AS LIMITED MOVEMENT OF SAID SEALING PORTION IN DIRECTION TRANSVERSE TO THE AXIS OF SAID INTERNAL PROP MEMBER, WHEREBY SLIGHT MISALIGNMENT OF THE PROP MEMBER WILL RESULT IN ELASTIC DEFORMATION OF SAID PART OF THE CONNECTING PORTION OF SAID PISTON WITHOUT AFFECTING UNIFORM SEALING ENGAGEMENT OF SAID SEALING PORTION WITH THE INNER SURFACE OF THE EXTERNAL PROP MEMBER, SAID PROP PISTON BEING FORMED WITH A CENTRAL BORE EXTENDING COAXIALLY WITH SAID PISTON THROUGH THE WHOLE LENGTH THEREOF; AND MEANS FOR FEEDING PRESSURE FLUID INTO AND OUT OF SAID PRESSURE CHAMBER.