Abstract: A pump consists of a valve box in which a valve chamber inlet and outlet are each provided with a valve, and reciprocating member in a cylinder that communicates with the valve chamber of the valve box to open the valves. A pressure action chamber is provided between the valve box and the cylinder and a pressure force member divides the pressure action chamber into a valve chamber side and a cylinder side. On the cylinder side of the pressure action chamber thus divided is an action medium that transmits to the pressure force member changes in the volume of the pressure action chamber produced by the action of the reciprocating member. A valve device consists of a concave valve seat and a number of fluid passages formed therein which open into the said concavity. Either the valve seat or the valve-piece is formed of, or covered with, a hard resilient material, or one is formed of the hard resilient material and the other is covered with a hard resilient material.

Abstract: A pump consists of a valve box in which a valve chamber inlet and outlet are each provided with a valve, and a reciprocating member in a cylinder that communicates with the valve chamber of the valve box to open the valves. A pressure action chamber is provided between the valve box and the cylinder and a pressure force member divides the pressure action chamber into a valve chamber side and a cylinder side. On the cylinder side of the pressure action chamber thus divided is an action medium that transmits to the pressure force member changes in the volume of the pressure action chamber produced by the action of the reciprocating member. A valve device consists of a concave valve seat and a number of fluid passages formed therein. Which open into the recess formed by the concave valve seat. Either the valve seat or the valve-piece is formed of, or covered with, a hard resilient material, or one is formed of the hard resilient material and the other is covered with a hard resilient material.