Diaphragm pump

Claim 1

A diaphragm pump comprising: a housing of hollow cylindrical shape which defines a cylindrical cavity having first and second ends, and which includes an end wall at said first end of said cavity, said second end being open, and said end wall of the housing being formed with an inlet opening and an outlet opening, both communicating with said cavity; a flexible diaphragm extending across said second end of the cavity and defining a pump chamber at one side of the diaphragm, the diaphragm having a peripheral portion which is arranged in fluid-tight relationship with respect to the housing, the remainder of the diaphragm being deflectable between a position in which the diaphragm is generally flat and a position in which the diaphragm is of outwardly bowed convex configuration; drive means for repeatedly moving the diaphragm between said generally flat position and said outwardly bowed position; first valve means associated with said inlet opening in the end wall of the housing for controlling entry of fluid to said pump chamber; second valve means associated with said outlet opening in the end wall of the housing for controlling delivery of fluid from said chamber; and, a generally cylindrical insert disposed in said pump chamber and dimensioned to fit closely in the said chamber between said end wall and said diaphragm, said insert defining, adjacent said diaphragm, a concave end face of a shape which is generally complementary to the shape of the diaphragm in said outwardly bowed configuration, and which defines with the diaphragm an effective portion of the pump chamber which closely corresponds in volume to the volume swept by the diaphragm in moving between its said positions, the insert being formed with two passageways which communicate respectively with said inlet and outlet openings in the end wall of the pump housing, and both of which open into said end face of the insert, so that a fluid to be pumped is conducted to and from said effective portion of the pump chamber along said passageways in use.