Hydraulic reservoir

Claim 1

IN A HYDRAULIC SYSTEM, A PRESSURIZED HYDRAULIC RESERVOIR ADAPTED TO OPERATE AT ALL ATTITUDES COMPRISING: A CYLINDRICAL HOUSING WALL, AN END CAP AT ONE END OF SAID HOUSING WALL, A PISTON HAVING A PISTON HEAD AND PISTON ROD, SAID PISTON HEAD BEING MOUNTED FOR RECIPROCAL AXIAL MOVEMENT WITHIN SAID HOUSING WALL, A FLEXIBLE BLADDER HAVING AN OPEN END, A CLOSED END AND A CYLINDRICAL SIDE WALL, SAID OPEN END OF SAID BLADDER BEING SEALED TO SAID END CAP, SAID CYLINDRICAL SIDE WALL OF SAID BLADDER BEING DISPOSED FLUSH ALONG SAID INNER SURFACE OF SAID CYLINDRICAL HOUSING WALL, SAID CLOSED END BEING ATTACHED TO ONE SURFACE OF SAID PISTON HEAD WHEREBY SAID CLOSED END WILL RECIPROCATE WITH SAID PISTON HEAD, THE DIAMETER OF SAID PISTON HEAD BEING SUFFICIENTLY SMALLER THAN THE INSIDE DIAMETER OF SAID HOUSING WALL SO AS TO PERMIT AXIAL MOVEMENT OF SAID PISTON HEAD AND SAID CLOSED END OF SAID BLADDER WITHOUT DEVELOPING APPRECIABLE FRICTION WITH SAID HOUSING WALL, A FLANGE ON SAID PISTON ROD, SAID FLANGE HAVING A DIAMETER SUBSTANTIALLY LESS THAN THE DIAMETER OF SAID PISTON HEAD, A CYLINDRICAL SIDE WALL IN SEALING RELATION WITH SAID FLANGE, SAID FLANGE BEING MOVABLE AXIALLY WITHIN SAID SIDE WALL, AND MEANS FOR APPLYING SYSTEM PRESSURE TO ONE SIDE OF SAID FLANGE, WHEREBY THE ONLY SIGNIFICANT FRICTION IMPEDING MOVEMENT OF SAID PISTON HEAD WITHIN SAID HOUSING WALL IS THE FRICTION BETWEEN SAID FLANGE AND SAID SIDE WALL.