Manual spray pump

Abstract

A manual spray pump comprises a cylinder consisting of different diameter portions integral with one another and extending from one another and large and small pistons having respective collars of different diameters and fitted in respective cylinder portions in elastic contact with the inner wall thereof for reciprocal movement in the axial direction. The small piston is coupled to the large piston such as to receive liquid pressure therefrom, and a valve body provided at the top of the small piston co-operates with a valve seat of the large piston to constitute an opening valve. Further, in order to control or suppress too sensitive action of the small piston under low liquid pressure when actuating the opening valve with the liquid pressure exerted from the large piston to the small piston, the small piston is provided with an integral additional piston member of a still smaller diameter or is adapted to produce a frictional force in part of its portion coupled to the large piston. Still further, part of the cylinder wall is provided, at a position near the position of the end of downward stroke of either large or small piston, with an escapement hole for releasing the residual liquid pressure so as to be able to bring a sudden end to the spraying and eliminate spraying under low liquid pressure.