US Patent 8038176 Seal with rigid stop ring

A seal for pipe couplings and a method of connecting pipe elements. The seal has an elastic ring surrounding a rigid ring. The elastic ring has side portions connected by a recessed center portion. The recessed center portion has a diameter no greater than the final diameter of the elastic ring in its deformed shape which effects a fluid tight joint. The seal is positioned between segments of a pipe coupling. Pipe elements are inserted into the elastic ring against the rigid ring from opposite sides of the coupling. The segments are drawn toward one another by fasteners, compressing the side portions and effecting the fluid tight joint.