Switching assembly for a hydraulic pump jack

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.

What is claimed is: 
     
         1 . A switching assembly for a hydraulic pump jack, said switching assembly comprising:
 (a) a non-magnetic cylinder having an exterior surface and an interior surface, said interior surface defining an interior bore;   (b) a piston reciprocally movable within the interior bore of the cylinder and having circumferential sealing means engageable with the interior surface of the cylinder;   (c) a magnetic element carried by the piston;   (d) an array of magnetically-triggered sensors mounted to the exterior surface of the cylinder at selected axially-spaced intervals; and   (e) a controller adapted to receive signals from the magnetically-triggered sensors;   
       wherein:
 (f) the cylinder is adapted to receive a working fluid such that the piston is axially movable within the cylinder in response to injection of working fluid into the cylinder; 
 (g) the controller will receive signals from the magnetically-triggered sensors as the magnetic element carried by the piston comes in proximity with and influences the magnetically-triggered sensors as the piston moves axially within the cylinder; and 
 (h) the controller is adapted to control the axial position of the piston within the cylinder by selectively controlling the flow of working to the cylinder. 
 
     
     
         2 . The switching assembly of  claim 1 , wherein:
 (a) the cylinder has a lower end and an upper end;   (b) the cylinder is adapted to receive a working fluid proximal to said lower end of the cylinder, such that injection of a working fluid into the cylinder will cause upward movement of the piston within the cylinder; and   (c) gravity will effect downward movement of the piston within the cylinder.   
     
     
         3 . The switching assembly of  claim 1 , wherein:
 (a) each of the magnetically-triggered sensors has a unique sensor value; and   (b) the controller is adapted to determine the axial position of the piston within the cylinder based upon the unique sensor values of the signals received from the magnetically-triggered sensors.   
     
     
         4 . The switching assembly of  claim 3 , wherein the unique sensor value of each of the magnetically-triggered sensors in the array varies incrementally. 
     
     
         5 . The switching assembly of  claim 3 , wherein the unique sensor value associated with at least one of the magnetically-triggered sensors is a resistance value. 
     
     
         6 . A switching assembly for a hydraulic pump jack, said switching assembly comprising:
 (a) a non-magnetic cylinder having:
 a.1 an exterior surface and an interior surface, said interior surface defining an interior bore; 
 a.2 a lower end; and 
 a.3 an upper end that is higher than the lower end; 
   (b) 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;   (c) a magnetic element carried by the piston;   (d) a fluid source supplying a hydraulic working fluid to the cylinder, such that injection of working fluid into the cylinder will cause the piston to move toward the upper end of the cylinder;   (e) an array of magnetically-triggered sensors mounted to the exterior surface of the cylinder at selected axially-spaced intervals, each said magnetically-triggered sensor having a unique sensor value, wherein the unique sensor value of each magnetically-triggered varies incrementally from the lower end of the cylinder to the upper end of the cylinder; and   (f) a controller adapted to receive signals from the magnetically-triggered sensors;   
       wherein:
 (g) the controller will receive signals from the magnetically-triggered sensors as the magnetic element carried by the piston comes in proximity with and influences the magnetically-triggered sensors as the piston moves axially within the cylinder; and 
 (h) the controller is adapted to determine precise piston positioning within the cylinder based upon the unique sensor values of the signals received and controlling piston movement by selectively controlling the flow of working fluid from the fluid source to the cylinder. 
 
     
     
         7 . The switching assembly of  claim 6 , wherein the unique sensor value associated with at least one of the magnetically-triggered sensors is a resistance value. 
     
     
         8 . The switching assembly of  claim 6 , wherein downward movement of the piston within the cylinder is effected by gravity.