Switching assembly for a hydraulic pump jack

Abstract

A switching assembly for a hydraulic pump jack has a non-magnetic cylinder. A piston is reciprocally movable within the interior bore of the cylinder. The piston has circumferential sealing means to engage the interior surface of the cylinder. A magnetic element is carried by the piston. A fluid source supplies a working fluid to the cylinder, wherein the piston is moved by injecting working fluid into the cylinder. At least one magnetic sensor is externally mounted adjacent to the non-magnetic cylinder that senses at least a top of a piston stroke and the bottom of the piston stroke. A controller receives signals from the magnetically actuated sensor as the magnet 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 working fluid supplied by the fluid source to the cylinder.

1 . A switching assembly for a hydraulic pump jack, comprising in combination:
 a non-magnetic cylinder with an exterior surface and an interior surface that defines an interior bore;   a piston reciprocally movable within the interior bore of the cylinder, the piston having circumferential sealing means to engage the interior surface of the cylinder;   a magnetic element carried by the piston;   a fluid source supplying a working fluid to the cylinder, wherein the piston is moved by injecting working fluid into the cylinder;   at least one magnetic sensor externally mounted adjacent to the non-magnetic cylinder that senses at least a top of a piston stroke and the bottom of the piston stroke;   a controller that receives signals from the magnetically actuated sensor as the magnet element carried by the piston comes in proximity with and influences the at least one magnetic sensor, the controller controlling piston positioning by selectively controlling the working fluid supplied by the fluid source to the cylinder.   
     
     
         2 . The switching assembly of  claim 1 , wherein the cylinder has a lower end and an upper end, the upper end being higher than the lower end, the working fluid serving to raise the piston from the lower end toward the upper end, and gravity serving to return the piston from the upper end to the lower end. 
     
     
         3 . The switching assembly of  claim 1 , wherein the magnetic sensor is a linear displacement transducer sensor bar that extends along the height of the non-magnetic cylinder. 
     
     
         4 . The switching assembly of  claim 1 , further comprising a seal for sealing the well when the piston is in a lower position, the non-magnetic cylinder being removable to expose the piston in the lower position. 
     
     
         5 . A switching assembly for a hydraulic pump jack, comprising in combination:
 a non-magnetic cylinder with an exterior surface, an interior surface that defines an interior bore, a lower end and an upper end that is higher than the lower end;   a piston reciprocally movable within the interior bore of the cylinder, the piston having circumferential sealing means to engage the interior surface of the cylinder;   a magnetic element carried by the piston;   a fluid source supplying a hydraulic working fluid to the cylinder, wherein the piston is raised from the lower end toward the upper end by an injection of working fluid into the cylinder;   a linear displacement transducer (LDT) sensor bar mounted to the exterior surface of the cylinder, the LDT sensor bar continuously measuring the position of the piston; and   a controller that receives signals from the LDT sensor bar as the magnet element carried by the piston travels along the non-magnetic cylinder, the controller controlling piston movement by selectively controlling the working fluid supplied by the fluid source to the cylinder in response to the received signals.   
     
     
         6 . The switching assembly of  claim 5 , wherein the piston returns from the upper end to the lower end by force of gravity. 
     
     
         7 . The switching assembly of  claim 5 , further comprising a seal for sealing the well when the piston is in a lower position, the non-magnetic cylinder being removable to expose the piston in the lower position.