PRECOMPRESSION METERING PUMP

摘要

A prior art precompression metering pump which incorporates a differential piston forming part of the pump chamber inlet valve and its outlet valve is difficult to prime, especially in the case of metering paste products. In the improved pump there is disposed between the differential piston and the main piston of the pump a collar consisting of a ring from which project substantially axial tongues which are slightly inwardly inclined and each provided with a head. The collar moves inside the pump body so that normal operation proceeds as if it were not present. To prime the pump, however, the user depresses the collar until it contacts a step on the pump body. The tongues then bend so that their heeds, interposed between the two pistons, move the latter apart (by a wedging effect or by a lever arm effect, or by a combination of the two). This is followed by mechanical opening of the pump chamber outlet valve whereby the air initially contained in the pump chamber escapes to the exterior.