| 摘要 |
The invention concerns a pump comprising a substantially cylindrical body (1) defining internally a metering chamber (11) whereof the lower end (1a) is provided with an intake orifice (10) equipped with a valve (12) and the upper end is provided with an outlet (20a) and closed by a piston (2) capable of moving in said chamber (11) by cooperating with elastic return means (4) outside the chamber (11), between a support up stop and a limit down stop. Said piston (2) comprises a central core (21) integral with the bottom end (23a) of a hollow axial rod (23) whereof the top end (23b) projects outside the metering chamber (11) and a coaxial sleeve (22), connected to said rod (23) by an elastic articulation (24) ensuring a sealed contact with the chamber (11) internal wall and defining with said core (21) a ring-shaped evacuating conduit (20) capable of being opened by displacement of said sleeve (22) with respect to the core (21), and the pump body (1) upper part being closed by a flange (3) whereof the internal surface forms the piston (2) up stop and the external surface serves as bottom support for the elastic return means (4). Said flange (3) is provided with an axial bore (30) wherein moves the hollow rod (23) integral with the piston. The invention is characterized in that said sleeve comprises a top ring (22b) designed to be urged into sealed engagement in a peripheral groove (31) arranged in said flange (3) internal surface.
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