Drainage valve structure

Claim 1

A drainage valve structure in connection with a water line of an underground sprinkling system having in combination a cylindrical pipe coupling member having a cylindrical bore, a nipple connected with said coupling member having a reduced passage relative to its bore in communication with said bore of said coupling member, said passage having an upper valve seat within said bore of said coupling member and having a transverse curvature corresponding to the transverse curvature of said bore and being flush therewith, said passage having a lower valve seat within the bore of said nipple, a flexible valve head convexo-concave in form being disposed in said housing to overlie said upper valve seat, a valve head within the bore of said nipple to seat on said lower valve seat, a valve stem somewhat greater in length than the length of said passage extending through said passage and connecting said valve heads, and said upper valve head being deformed by normal water pressure of the water present in said coupling member to seat against and seal said upper valve seat and to retain its convexo-concave form under less than normal water pressure to permit the passage of water througe said passage and said lower valve head seating against said lower valve seat in the absence of normal water pressure in said valve housing responsive to the pressure of ground waters.