US Patent 7140388 Dual ball valve air vent valve

A unitary valve housing has an upper and lower portion. The upper portion has an inner chamber for accommodating two spaced apart balls and a cylindrical side skirt with oppositely positioned openings. The lower portion is cylindrical in shape and has a top shelf with adjacent circular openings for seating the two balls and openings communicating with a bottom of the lower portion. The two openings on the upper portion side skirt are aligned with oppositely positioned openings in a side of the lower housing. A secondary shelf is located in the lower housing below each of the two circular openings contiguous with the side openings. A lower end of the lower housing portion is attached to a conduit.