A liquid dispenser comprising a dispenser body and a valve housing. The dispenser body has a pump mechanism, an intake port adapted for fluid communication with a source of liquid, and an intake liquid flow path providing fluid communication between the intake port and the pump mechanism. The dispenser body further comprises a discharge conduit and a discharge liquid flow path providing fluid communication between the pump mechanism and discharge conduit. The discharge conduit has a downstream end through which dispensed liquid exits the discharge conduit. The valve housing has first and second portions, a fluid passageway within the first and second portions, and a discharge port in the second portion and in fluid communication with the fluid passageway. The first portion of the valve housing is attached to the dispenser body adjacent the downstream end of the discharge conduit so that the passageway of the valve housing is in fluid communication with the discharge conduit. The liquid dispenser further includes a check valve positioned in the passageway of the valve housing. The check valve is moveable between a closed position for blocking fluid flow between the pump mechanism and discharge port and an open position for permitting fluid flow.

A pre-compression pump sprayer has a spring biased discharge poppet valve element with a seal in engagement with the wall of the piston stem, a seal interruption to establish a discharge valve open position, and an upstream directed throttle valve presenting a two-stage pressure build-up discharge valve establishing a predetermined pressure threshold which when exceeded by fluid pressure generated in the pump chamber during pumping immediately opens the throttle valve and abruptly releases the fluid pressure at the valve open position. The valve has an elongated probe extending into the pump chamber of an extent as to shift the poppet valve open upon engaging the inlet check valve upon a full downstroke of the piston for evacuating air from the pump chamber out through the discharge orifice to effect pump priming. During pumping operation, product is sucked back from around the discharge orifice into the discharge passage at the commencement of the piston suction stroke as the discharge valve remains momentarily open. An inlet check valve has a center of gravity located upstream of its valve seat to assure accurate seating of the inlet valve during pump operation at angles tilted from upright. And, a dry piston return spring is optionally provided, as is a diametral container vent seal.

This invention provides a power delivery device (10) for delivering a fixed volume of flowable material to a specific site, the power delivery device (10) comprising pumping means (14) for forcing a predetermined volume of the flowable material through at least one flow path (38,40) of the power delivery device (10) by means of line pressure exerted on the flowable material; and valve means (12), operatively connected to the pumping means (14), for selectively opening and closing the at least one flow path (38, 40) through which the flowable material moves such that the predetermined volume of flowable material can be sprayed out of the power sprayer (10) when the at least one flow path (40) is open and can be redirected to fill the power sprayer (10) when the at least one flow path (40) is closed.