Abstract: A pressure responsive seal ring assembly includes a first and second arcuate-shaped ring segment configured for non-interlocking assembly onto a plunger body. A tab extends beyond a first end of each ring segment and is received by a recessed portion in the first end of the opposing ring segment. The tabs and recessed portions provide a gap in the outer peripheral surface of the assembled ring. A second tab extends beyond a second end of the second ring segment and is received by a recessed portion in the second end of the first ring segment. Pads provide an inter-space effective for allowing fluid flow between the interior peripheral surface and the plunger body. The ring segments expand radially outward with an increase in pressure to provide a seal and retract radially inward with a decrease in pressure. The ring segments, however, remain connected and resist fluid flow therebetween.

Abstract: A lap used for the grinding, fining and polishing of glass and plastic lenses is constructed of a one-piece injection-molded reinforced polymer body. The front surface of the lap is curved and adapted to receive an abrasive pad. The rear of the lap has a skeletal rib structure of projecting interconnected ribs. Polymers suitable for forming the lap include various crystalline polymers and copolymers having adequate chemical resistance, strength, rigidity and thermal resistance.