Importance

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Abstract

A switching assembly for a hydraulic pump jack has a non-magnetic cylinder and a piston that is reciprocally movable within the interior bore of the cylinder. The piston has circumferential sealing means to engage the interior surface of the cylinder, and carries a magnetic element. A fluid source supplies a working fluid to the cylinder to move the piston within the cylinder. At least one magnetic sensor having a unique sensor value is externally mounted adjacent to the non-magnetic cylinder and senses at least a top of a piston stroke and the bottom of the piston stroke. A controller receives signals from the magnetically-actuated sensors as the magnetic element carried by the piston comes in proximity with and influences the at least one magnetic sensor. The controller controls piston positioning by selectively controlling the flow of working fluid to the cylinder.

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First Claim