Packing chambers for o-rings

Claim 1

IN AN ARRANGEMENT FOR EFFECTING A SEAL BETWEEN TWO RELATIVELY MOVABLE MEMBERS INCLUDING AN ANNULAR PACKING CHAMBER BETWEEN THE MEMBERS, GENERALLY FOUR-SIDES IN RADIAL SECTION AND DEFINED BY A PAIR OF OPPOSED GENERALLY RADIALLY-FACING SURFACES, ONE ON EACH OF THE MEMBERS, AND A PAIR OF OPPOSED GENERALLY AXIALLY-FACING SURFACES, AND A RESILIENT PRESSSURE-DEFORMABLE PACKING O-RING IN THE CHAMBER, THE O-RING BEING GENERALLY CIRCULAR IN RADIAL SECTION WHEN UNCONFINED, SLIGHTLY COMPRESSED BETWEEN THE RADIALLY-FACING SURFACES, AND SUBJECT TO BEING FORCED AGAINST ONE OF THE AXIALLY-FACING SURFACES BY MECHANICAL OR FLUID PRESSURE FORCE, THE IMPROVEMENT THAT THE ONE AXIALLY-FACING SURFACE IS AT LEAST PARTLY CONVEX IN RADIAL SECTION AND INITIALLY IS ENGAGED WITH THE O-RING ALONG SUBSTANTIALLY A LINE OF CONTACT LOCATED GENERALLY AT THE MAJOR AXIAL DIMENSION OF THE O-RING AND GENERALLY MIDWAY BETWEEN THE RADIALLY-FACING SURFACES, WHEREBY THE O-RING CAN BE DEFORMED TO A GREATER EXTENT AGAINST THE ONE AXIALLY-FACING SURFACE THAN IF THE LATTER WERE FLAT IN THE PLANE OF THE APEX OF THE CONVEX PORTION OF SAID ONE AXIALLY-FACING SURFACE AND WHEREBY AN INCREASE IS OBTAINED IN THE RATIO BETWEEN THE AXIAL THICKNESS OF THE O-RING WHEN UNCONFINED AND THE AXIAL THICKNESS OF THE O-RING SUBSTANTIALLY MIDWAY BETWEEN THE RADIALLY-FACING SURFACES, WHEN THE O-RING IS DEFORMED AGAINST THE ONE AXIALLY-FACING SURFACE TO AN EXTENT TO SUBSTANTIALLY CONFORM THERETO.