Expansible chamber

Claim 1

AN EXPANSIBLE CHAMBER COMPRISING A LINER AND A PISTON MOVABLE THEREIN, SAID PISTON INCLUDING A METAL BODY HAVING AN OUTER SURFACE OF FUSIFORM SHAPE AND AN ELASTOMER DOUBLE LIP SEAL SLEEVE AROUND SAID BODY EXTENDING FROM ADJACENT ONE END OF SAID BODY TO ADJACENT THE OTHER END THEREOF AND HAVING AN INNER SURFACE CORRELATIVE TO THAT OF SAID OUTER SURFACE OF THE METAL BODY AND UNITIZED THEREWITH, SAID SEAL SLEEVE INCLUDING A BAN AROUND THE WAIST OF THE METAL BODY WHICH BAND HAS A THICKNESS IN THE RANGE OF 1/32 TO 3/8 INCH, SAID BAND BEING THE PORTION OF THE SLEEVE OF MINIMUM THICKNESS, SAID SLEEVE HAVING A SHORE DUROMETER (TYPE A) HARDNESS IN THE RANGE 60 TO 95, SAID SLEEVE BEING CEMENTED TO SAID BODY AND MOLDED AND VULCANIZED IN PLACE, THE SAID OUTER SURFACE OF THE FUSIFORM SHAPED METAL BODY INCLUDING PORTIONS OF DIFFERING TAPER, THE CROSS SECTION OF THE OUTE SURFACE OF THE METAL BODY BEING AT LEAST APPROXIMATELY CONVEX FROM ADJACENT SAID ONE END THEREOF TO ADJACENT SAID OTHER END THEREOF, THE CROSS-SECTIONAL INTERNAL ANGLE BETWEEN ADJACENT PORTIONS OF SAID OUTER SURFACE OF THE BODY OF DIFFERING TAPERS BEING OBTUSE, SAID PORTION OF THE BODY WHOSE SURFACE IS AT LEAST APPROXIMATELY CONVEX IN CROSS-SECTION INCLUDING PORTIONS ADJACENT EACH SIDE OF SAID BAND HAVING A TAPER ANGLE LYING IN THE RANGE OF FIVE TO FIFTEEN DEGREES AND PORTIONS ADJACENT THE ENDS OF THE PISTON BODY HAVING A TAPER ANGLE GREATER THAN THAT OF THE PORTIONS ADJACENT SAID BAND, THERE BEING CYLINDRICAL NECKS AT EACH END OF SAID BODY.