Importance

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Abstract

A new and improved automatic venting back pressure valve is provided in a valve body including a back pressure chamber having a fluid inlet and a fluid outlet. A spring loaded back pressure member covers the fluid outlet which is movable between a normally closed position wherein the back pressure member seals off the fluid outlet and an open position wherein the back pressure member is displaced from the fluid outlet to permit fluid to flow through the back pressure chamber from fluid inlet to fluid outlet in response to increased fluid pressure in the back pressure chamber. A gas by-pass orifice is disposed in an upper portion of the back pressure chamber which connects the back pressure chamber to a downstream portion of the fluid outlet. The gas by-pass orifice has a diametrical dimension selected to permit flow of gases through the orifice but to substantially not permit flow of liquids through the orifice. Air or gas entering the back pressure valve is automatically vented from the back pressure chamber as the valve fills with each pump stroke to maintain hydraulic firmness and provide improved more accurate fluid flow.

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First Claim