Importance

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Abstract

A piston pump for a backpack sprayer, which operates reliably without damage due to scoring of the wall of the piston cylinder by powders such as wetable solids, which tend to be abrasive and score or scratch the piston cylinder wall which is of plastic material. The pump has a plastic piston cylinder. A liner provided by a sleeve of metal which is not subject to scratching and is of sufficient thickness to maintain a cylindrical shape of the piston wall. The seal of the piston rides on the piston wall liner as the piston reciprocates in pumping the spraying liquid and particles suspended therein from a tank into a pressure chamber in the tank, from which pressure chamber the spraying liquid is extracted for spraying via a hose and a spraying nozzle. The sleeve is molded upon injection of the plastic providing the piston cylinder pump by being mounted on a core having a step which partially overlaps an edge of the sleeve. Upon injection of the plastic and cooling thereof in the mold, the sleeve is captured and held against axial movement in the cylinder by a step in the plastic which partially overlaps the end of the sleeve. Preferably the sleeve is metal which is harder than the particles of the spraying liquid, and may suitably be of stainless steel.

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First Claim