Pump for concrete and the like

Claim 1

In a pump for pumping concrete and the like, fluent media having a supply container for supplying the fluent media to the pump, two cylinders in communication with said supply container each cylinder having a discharge opening and a piston movably disposed therein, means for operating said pistons in mutually opposed motion so that as the piston in one of said cylinders performs a delivery stroke the piston in the other of said cylinders performs an intake stroke, a delivery conduit for delivering the fluent media from the pump, said delivery conduit having an entrance end, and a valve arrangement for alternately directing the fluent media from respective ones of said discharge openings of said cylinders the pistons of which are performing a delivery stroke, to the entrance end of said delivery conduit the improvement wherein said valve arrangement comprises: housing means fixedly disposed between said cylinder and said delivery conduit and communicating with said supply container; a pivot tube movably mounted within said housing means, said pivot tube having one end in permanent communication with the entrance end of said delivery conduit and downwardly depending skirt portions, the outside surface of which are of inclined wedge shape; means for pivoting said tube about an axis of rotation so that the other end thereof is alternately brought into a registering position with the discharge ends of respective ones of said cylinders the pistons of which are performing a delivery stroke whereby fluent media is conveyed from said respective ones of said cylinders through said tube to said delivery conduit, and delivered to the other respective ones of said cylinders the pistons of which are performing an intake stroke, from said supply container through connecting ducts which include a planar surface substantially perpendicular to said axis of rotation of said pivot tube and defined between a respective one of said skirt portions of said tube when said tube is in said registering positions, and an adjacent inner wall of said housing means, said skirt portions acting to slide beneath and scrape fluent media in said connecting ducts along said planar surface and prevent clogging therein as said tube is alternately pivoted between said registering positions.