Low-friction reciprocating pump

Abstract

A reciprocating pump for pumping a fluid, especially for pumping a fluid such as UV ink which is subject to solidification when exposed to frictional forces. The pump has an internal displacement chamber with an inlet, and outlet, and a plunger which is reciprocally movable in the chamber. The plunger reciprocates through an axial passage in the housing at one end of the chamber, the passage being sized to receive the plunger with a clearance fit. First and second seals are positioned in the axial passage. Each seal is annular in shape and extends between the plunger and housing in sealing contact therewith. The pump housing is free from a bearing which contacts the plunger or guides its motion, such that the sealing contacts between the plunger and seals are the only contacts of the plunger in the housing.

Description

BACKGROUND OF THE INVENTION [0001] This invention relates to reciprocating pumps for pumping fluids, and more particularly to a pump which lengthens the operational life of the pump by reducing the frictional forces expended on the fluid being pumped. The pump is described primarily herein for application in pumping a fluid which is subject to solidification when exposed to frictional forces. However, it is understood that the pump and seal assembly may be applied to efficiently pump any type of fluid. [0002] Ink that is cured with ultraviolet (UV) energy has widespread use in the printing and graphic display industries. That type of ink is highly viscous and has a unique chemistry which requires special handling and pumping needs. Its material composition includes a monomer, instead of a solvent as in conventional inks, such that it solidifies when irradiated. Unfortunately, UV ink is also sensitive to mechanical shear stress (i.e., friction) which produces heat and initiates solid...

AI Technical Summary

Benefits of technology

[0003] Among the several objects and features of the present invention may be noted the provision of a fluid pump which exerts less frictional force on the fluid being pumped; the provision of such a pump which effectively pumps a highly viscous fluid including UV ink; the provision of such a pump which is sealed to prevent leakage of fluid; and the provision of such a pump which is efficient and durable in use and cost-efficient to construct.

Problems solved by technology

Unfortunately, UV ink is also sensitive to mechanical shear stress (i.e., friction) which produces heat and initiates solidification of the ink.

Consequently, solidified polymers form and accumulate in the pump which cause the pump to bind and ultimately fail.

Of particular concern are gaps between close-fitting parts which have relative movement.

UV ink which reaches these gaps is prone to solidify.

Aggravating this problem is that the plunger assembly must be sealed to prevent leaks.

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