Ring manufacture, productive of face contact seal

Apparatus for lapping against lapping surface means the side of a split torsion piston ring which, when torsionally distorted by pressure bringing the torsion piston ring into collapsed state conforming to a bore size for which it is normally designed, becomes closed or substantially so, and which, when worked while so torsionally distorted, has at one stage the inner periphery only of said side of the ring projecting into local contact with the confronting lapping surface means, said apparatus comprising:

• a ring fixture having open mouth means for receiving the ring to establish the lapping contact aforesaid;
• a lap surface confronting said mouth means in spaced apart relation to the ring fixture;
• said mouth means having approximately bore size to insure retention of the ring substantially precisely in collapsed state at all times;
• a power cylinder having a compressive-force-transmitting connection to said fixture, effectively with the mouth means of the latter holding the ring relative to the lap surface so that at one stage said side of twisted and under light lap pressure forms a slight angle to said surface whereby the side is provided with a lapped narrow sealing band which is at the locally contacting inner periphery and which forms an angle of intersection with the major portion of the side, and so that at another stage said side if distorted under heavy lap pressure has the major portion thereof compressed untwisted into flattened state against said surface while so collapsed;
• means for causing relative movement between the fixture and lap surface in at least one direction of lap;
• and
• separate means of two-stage, fluid pressure connection to the power cylinder from respectively a source of light fluid pressure and a source of heavy fluid pressure, whereby at said one stage light fluid pressure in the cylinder causes the lapping force exerted by the ring fixture on the inner periphery of the ring to be limited to a light pressure force, and at said other stage heavy fluid pressure causes the ring fixture to exert a heavy pressure lapping force on said flattened major portion of the ring side.