Apparatus for detecting changes in inclination or acceleration

In an apparatus for monitoring the operation of a well pumping unit which includes a walking beam having a sucker-rod string attached thereto and a power unit for oscillating said beam about a horizontal axis to reciprocate said rod string for producing fluid from an underground location, the improvement which comprises apparatus for detecting the position of the rod string during reciprocation of said rod string, said position detecting means comprising:

• support means operatively connected to said walking beam for oscillatory movement;
• means defining a magnetic-field sensor rigidly secured to said support means;
• cantilever spring means having one end portion rigidly secured to said support means at a point removed from said sensor means;
• magnet means secured to said cantilever spring means at a position removed from said one end and disposed closely adjacent to said sensor means, said magnetic means moving arcuately relative to said sensor means in response to oscillation of said walking beam between a centered position wherein said walking beam is at about the mid-point of its oscillatory movement and said cantilever spring means is disposed in a vertical plane over the center of said sensor means, and wherein pivotal movement of said walking beam in both directions from said centered position deflects said cantilever spring means due to gravitational forces acting on said magnet means from one side to the other side of said plane for providing a linear voltage output signal that is proportional to said relative movement and is useable for determining the position of said rod string;
• weight means secured to said spring means at a location adjacent said magnetic means;
• stop means rigidly secured to said support means on both sides of the path of movement of said weight means for preventing excessive deflection of and damage to said spring means;
• and
• a printed circuit board rigidly secured to said support means and structurally supporting said magnetic-field sensor means, said cantilever spring means performing its functions with a high degree of repeatablility and with substantially infinite life at an extremely low price.