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1. A pump for dispensing liquids from a reservoir, comprising:
a piston-chamber forming body having a cylindrical chamber, said chamber having a chamber wall, an outer open end and an inner end in fluid communication with the reservoir, a piston forming element slidably received in the chamber having an inner end in the chamber and an outer end which extends outwardly from the open end of the chamber, a one-way inlet valve in the chamber inwardly of the piston forming element permitting fluid flow outwardly in the chamber past the inlet valve and preventing fluid flow inwardly in the chamber past the inlet valve, a one-way outlet valve carried on the piston forming element proximate the inner end of the piston forming element permitting fluid flow outwardly in the chamber past the outlet valve and preventing fluid flow inwardly in the chamber past the outlet valve, the inlet valve coaxially slidable inwardly in the chamber from an outer position displaced from the inner end of the chamber toward at least one inner position closer to the inner end of the chamber than the outer position, the inlet valve and the piston-chamber forming body coupled to each other in frictional engagement sufficient to prevent relative coaxial sliding of the inlet valve in the chamber under forces experienced due to pressures developed across the inlet valve in normal operation of the pump to dispense fluid, wherein on engagement of the inner end of the piston-forming element with the inlet valve, with the inlet valve in a position on the piston-chamber forming body axially outward of the inner position, while the inner end of the piston-forming element applies axially inwardly directed force to the inlet valve sufficient to coaxially slide the inlet valve inwardly overcoming the frictional engagement of the inlet valve and the piston chamber-forming body, the inlet valve slides coaxially inwardly with the inner end of the piston forming element relative the piston-chamber forming body toward the inner position, the inlet valve comprising a circular inlet flexing disc extending radially outwardly from a central support member, the circular inlet flexing disc having an elastically deformable edge portion proximate the chamber wall circumferentially thereabout, the circular inlet flexing disc substantially preventing fluid flow past the circular inlet flexing disc in an inward direction, and the circular inlet flexing disc elastically deforms away from the chamber wall to permit fluid flow past the circular inlet flexing disc in an outward direction. |
