Chemical injection pumps are used to introduce small, measured quantities of a chemical additive into a primary fluid flow line for admixture with the primary fluid, such chemicals including demulsifiers, methanol, corrosion inhibitors, etc. In general, these pumps are both controlled and operated by a single fluid flow to pressurize and depressurize a piston and cylinder assembly so as to move the operating piston through its power stroke upon cylinder pressurization and allow the piston return stroke upon cylinder depressurization. BALANCING VALVESIn one prior pump design, the cylinder pressure is fed back to a diaphragm-controlled valve arrangement to provide a fluid oscillator that controls the flow of fluid to and from the cylinder.

Although the oscillator-type pump is effective, the range and precision of adjustment of the cyclic rate of the piston are limited. Also, pumps of this type appear to be properly functioning even though the operating piston, due to malfunction, is not moving through its cycle.

Accordingly, recognizing this latter trait but more importantly to provide a pump which more effectively controls the cyclic rate and stroke of the operating piston, I have invented a chemical pump that does not utilize fluid pressure feedback to control the operating piston. Bellow Seal ValveMy device utilizes a variable pilot mechanism having a pair of pressure responsive diaphragms forming a control fluid chamber therebetween. The diaphragms are movably responsive to chamber pressurization/depressurization as provided by a control fluid flow independent of a power fluid flow routed to and from the cylinder of the operating piston. This chamber pressure modification is provided by control fluid inlet and outlet valve assemblies which are actuated upon the completion of the power and return strokes of the operating piston. Upon diaphragm response, corresponding to the pressure modification of the pilot chamber, the cylinder inlet/outlet valves are alternately opened and closed to control the power fluid flow into and out of the cylinder. Accordingly, I have provided a pump actuator utilizing a variable pilot mechanism operably independent of the cylinder pressurization, which allows for an effective, finely tuned control of the cyclic rate of the operating piston.Forged Steel Valves I have also provided means for adjusting the length of the power stroke therein independent of this cyclic rate control. Furthermore, if a malfunction occurs that causes the piston to stall, my pump will not falsely indicate that it is functioning normally.

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2011-12-13

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