US Patent 9810359 Pipe coupling

Each gripper washer 22 is disposed between a gasket retaining ring 18 and an end connector 14. The gripper washers 22 can be any size and dimension, and made from any material, including but not limited to plastic, polyvinyl chloride, or metal. The gripper washers 22 are a washer-like structure, typically a metallic structure that comprises an interior diameter, a concentric inner periphery and an exterior periphery 24. Each gripper washer 22 is disposed between a gasket retaining ring 18 and an end connector 14, such that the exterior periphery 24 of the gripper washer 22 is in contact with, or in close proximity to, the shoulder 20 of the gasket retaining ring 18.