| 摘要 |
<p>A precompression pump has a feature (40,41) to evacuate air trapped in a pump chamber thereby to assist in priming the pump. Gaps of very small size are created to bridge two seals (30,31) on a pump piston (2), in a way such 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 (30,31) on the pump piston (2). Flats which define a chord of the inner circumference of the cylinder wall (33) can be used to create the appropriate gaps and/or a core used to create the inner wall (33) can be photochemically etched to provide a roughened surface (70,71) with asperities which create the appropriate gaps. The priming mechanisms preferably create air gaps around both seals (30,31) of the pump piston (2). <IMAGE></p> |
