Piston type pump

Claim 1

A piston type pump comprising: a. a pump casing defining a fluid supply chamber and at least one axially elongate casing bore having an inner end communicating with the supply chamber and an outer end opening at the outer side of the casing remote from the supply chamber; b. a pump cartridge assembly having means removably mounting the same in said casing bore for assembly and removal as a unit therefrom, said cartridge assembly including: 1 a cartridge body having a cartridge bore extending axially thereinto from its inner end and defining a cylinder portion at the inner end of the cartridge body and a head portion at the outer end of the cartridge body, said head portion having outlet passage means therein communicating with the cylinder portion and an outlet check valve in said outlet passage means arranged to open for flow from the cylinder portion and to close to prevent return flow, and 2 a cylinder sleeve formed of a material different from the material of the cartridge body and disposed entirely within the inner end of said cylinder portion of the cartridge body for radial support thereby and having a radially tight fit in the cartridge bore to seal the interface therebetween, said cylinder sleeve having the outer end thereof spaced from the adjacent end of the cartridge bore to form an annular recess at the outer end of the cylinder sleeve, c. a pump piston slidable in said cylinder sleeve defining a motive chamber between the piston and the head portion of the cartridge body, said piston having inlet passage means communicating the supply chamber with the motive chamber and inlet check valve means in the inlet passage means arranged to open for flow of fluid into the motive chamber; and d. piston actuator means in said supply chamber operatively engaging said pump piston to cyclically reciprocate the same.