Patent ID: 6910405

Claim:
A system to inject a secondary fluid into a primary fluid, comprising: a fluid powered motor driven by a primary fluid stream; a liquid additive injection pump driven by the fluid powered motor; and an on/off switch mechanism coupled to the fluid powered motor to selectively suspend operation of the fluid powered motor; wherein the fluid powered motor comprises: (a) a piston movable within a housing between upstroke and down stroke positions; (b) a valve mechanism establishing a differential pressure within the housing to produce movement of the piston; (c) an over-center mechanism coupled to the valve mechanism to toggle the valve mechanism between open and closed positions; and (d) an actuating shaft coupled to the over-center mechanism, the actuating shaft including a piston upstroke stop that causes toggling of the valve mechanism at an upstroke position of the piston during normal reciprocating movement of the piston; further wherein the on/off switch mechanism axially displaces the actuating shaft relative to the housing wherein the piston upstroke stop assumes an offset position when the on/off switch mechanism is in the “off” position such that the piston upstroke stop can not be engaged to cause toggling of the valve mechanism when the piston reaches its upstroke position.