HAND-ACTUATABLE PUMP ASSEMBLY

摘要

An improved, hand actuatable pump assembly. A stem and piston assembly extend into a valve body. The piston sealingly engages the wall of the valve body and together they define a pressure chamber therebelow. The piston seals a discharge passageway in the stem. As the pump assembly is primed, air in the pressure chamber escapes through the discharge passageway. When the pump is ready for use, the force of hydraulic pressure below the piston opens communication between the pressure chamber and passageway. When the piston nears the end of the stroke, it is mechanically held open to complete dispensing. At all times, a positive seal between the piston and the valve body wall is maintained to prevent passage of the contents of the pressure chamber therebetween, thereby to minimize sticking and clogging of the pump assembly.