Precompression dosing pump with improved priming action.

摘要

An especially useful precompression metering pump belonging to the prior art is difficult to prime because of the high compressibility of the air initially contained in its chamber. In order to overcome this difficulty in its operation, the present invention provides, next to the pump's usual output valve, elastic means 20 and at least one cylindrical part 10, which supplementary components form a second output valve.
<??>In one particular embodiment, these two latter components are housed one on top of the other inside the outlet channel 33 of the pump-activating rod 31. To this end they press when at rest against, respectively, a constriction 32 in the form of a spur and a shoulder 34, both of which are formed in this channel. In the course of normal operation, it is the pump's differential piston 4 which draws back, so that the metering pump operates just as in the prior art. In the priming phase, however, the actuating rod 31 can be driven fully in, with the result that the part 10 lifts off the constriction 32. This modification thus makes it possible to expel the air initially contained inside the pump chamber 23 to the outside.
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