Torque compensated cam assembly and method

A torque compensated cam assembly, comprising:

• a. a cam having an axis of rotation and a plurality of surfaces, each defining a path at a variable distance from the axis of rotation;
• b. a plurality of cam followers, each disposed in contact with a different one of said surfaces, so that each cam follower is acted upon by a radially directed force due to its contact with said one surface as the cam rotates, the contact between said one surface and said cam follower also producing a varying tangential force that acts on the cam as said cam follower moves along said surface, a total of the tangential forces thus developed by all of the cam followers producing a varying total torque acting on the cam;
• c. a torque compensation track disposed on the cam and having a non-planar surface with a varying predefined shape;
• d. a torque compensation follower that is in contact with the non-planar surface of the torque compensation track as the cam rotates;
• and
• e. a spring connected to bias the torque compensation follower against the non-planar surface of the torque compensation track, producing a compensating torque that is substantially equal and opposite in the direction of rotation to the varying total torque produced by the plurality of cam followers, as the cam rotates about its axis of rotation.

A torque compensated cam assembly for use in a reciprocating pump to maintain a substantially constant load on a prime mover that drives the pump, comprising:

• a. a cam rotatably driven by a prime mover to rotate about an axis;
• b. cam follower means that contact the cam at a varying radial distance from the axis as the prime mover rotates the cam about said axis, producing a torque that varies with a rotational position of the cam, said torque at times being directed so as to aid rotation and at other times being directed so as to impede rotation of the cam by the prime mover;
• and
• c. torque compensation means for producing a compensating torque that is generally equal and opposite in rotational direction to the torque produced by the cam follower means so that a substantially constant load is presented to the prime mover as it rotatably drives the cam.