Dispensing pump with priming feature

摘要

The present invention relates to a precompression pump with a feature to evacuate air trapped in the pump chamber to thereby assist in priming the pump. In particular, the present invention relates to a precompression pump which uses mechanisms to create gaps of very small size to bridge two seals on a pump piston, in a way that the small size of the gaps allows the passage of trapped air, but because of the viscosity of any liquid in the pump chamber does not allow the passage of liquid past the seals on the pump piston. Flats which define a chord of the inner circumference of the cylinder wall can be used to create the appropriate gaps. In addition, the core creating the inner circumference can be photochemically etched to provide a roughened surface with asperities which create the appropriate gaps. The priming mechanisms preferably create air gaps around both seals of the pump piston.