Rod saver speed control method and apparatus

Abstract

A motor speed controller ( 100 ) identifies the position of a pump rod ( 14 ). At one or more critical positions of the rod, the motor speed controller ( 100 ) adjusts the speed of the motor to change the movement of the pump rod ( 14 ). The critical positions and the rate of change of speed at each critical position can be user-specified.

1 . A Rod Saver apparatus for automatically controlling the speed of a pump rod throughout its normal operating cycle comprising: 
 means for determining an actual position of said pump rod;    means for comparing the sensed actual position with a plurality of predetermined critical positions; and    means for adjusting said pump rod speed at the plurality of predetermined critical positions during each cycle of said pump rod.    
   
   
       2 . The Rod Saver apparatus of  claim 1  wherein a pump motor moves said pump rod and said means for adjusting said pump rod speed adjusts the speed of said pump motor.  
   
   
       3 . The Rod Saver apparatus of  claim 2  wherein said pump motor is a variable frequency motor.  
   
   
       4 . The Rod Saver apparatus of  claim 3  wherein said variable frequency motor is selected from an electrical, a mechanical, or a hydraulic motor.  
   
   
       5 . The Rod Saver apparatus of  claim 1  wherein plurality of predetermined critical positions are selected by a user of said Rod Saver apparatus.  
   
   
       6 . The Rod Saver apparatus of  claim 1  wherein said means for determining said pump rod actual position is a means for sensing said pump rod actual position.  
   
   
       7 . The Rod Saver apparatus of  claim 6  wherein said means for sensing said pump rod actual position is a sensor situated on a pump attached to said pump rod.  
   
   
       8 . The Rod Saver apparatus of  claim 2  wherein said means for determining said pump rod actual position is determined from the minimum and maximum movement of said pump rod and the speed of said pump motor.  
   
   
       9 . A Rod Saver method for automatically controlling the speed of a pump rod throughout its normal operating cycle comprising: 
 determining an actual position of said pump rod in a stroke cycle;    comparing the actual position with a user-selectable position;    associating a change of speed with the user-selectable position; and    adjusting said pump rod speed by the rate of change at the user-selectable position when the user-selectable position is equal to the actual position.    
   
   
       10 . The Rod Saver method of  claim 9  wherein a pump motor moves said pump rod and said pump rod speed is adjusted by adjusting the speed of said pump motor.  
   
   
       11 . The Rod Saver method of  claim 10  wherein said pump motor is a variable frequency motor.  
   
   
       12 . The Rod Saver method of  claim 12  wherein said variable frequency motor is selected from an electrical, a mechanical, or a hydraulic motor.  
   
   
       13 . The Rod Saver method of  claim 9  wherein said pump rod actual position is determined by detecting said actual position.  
   
   
       14 . The Rod Saver method of  claim 13  wherein said pump rod actual position is detected by a sensor situated on a pump attached to said pump rod.  
   
   
       15 . The Rod Saver method of  claim 10  wherein said pump rod actual position is determined from the minimum and maximum movement of said pump rod and the speed of said pump motor.