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Motorized anti-backlash linear actuator

  • US 4,974,464 A
  • Filed: 07/11/1989
  • Issued: 12/04/1990
  • Est. Priority Date: 03/17/1988
  • Status: Expired due to Term
First Claim
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1. Motorized anti-backlash linear actuator comprising, in combination:

  • a source of rotary motion comprising a motor;

    a hollow armature in the motor mounted for rotation about a central axis;

    the armature surrounding a hollow shaft and secured directly thereto to rotate the shaft about the axis;

    the hollow shaft being one piece, inwardly threaded along its entire length and extending the entire length of the armature;

    frame means mounting the motor for internal rotational movement only at a fixed location in space and preventing its movement lengthwise of the axis;

    an externally threaded non-rotating rod extendable from and movable linearly along the axis relative to the fixed location of the motor;

    a continuously operating, rotatable anti-backlash nut assembly to produce substantially backlash-free linear motion of the rod lengthwise of the axis, the nut assembly comprising the hollow shaft within the armature and a cooperating spring means outside the motor;

    the threads of the hollow shaft and the rod being in direct physical contact;

    a field coil surrounding the armature to impart rotary motion to the unit;

    the anti-backlash nut assembly being secured to the hollow shaft such that the armature, the shaft and the anti-backlash nut assembly rotate as a unit at the fixed location in space while prevented by the frame from moving linearly;

    thereby to impart to the rod non-rotating linear motion lengthwise of the axis relative to the fixed location in space and which motion is substantially backlash-free.

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