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Power driven equipment safety device

  • US 4,319,146 A
  • Filed: 05/23/1980
  • Issued: 03/09/1982
  • Est. Priority Date: 05/23/1980
  • Status: Expired due to Term
First Claim
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1. A safety device adapted for use with equipment to prevent opening of a door on said equipment to gain access to a compartment containing a power driven mechanism until an AC induction motor which drives said mechanism approaches zero rotational speed, said device including:

  • (a) a protective housing adapted to be mounted on the equipment closely adjacent the access door;

    (b) sensor means operative in response to a predetermined back EMF produced by the rotational speed of the induction motor;

    (c) bolt means mounted on the housing means and engageable with the access door of the power driven equipment and movable between door locked and unlocked positions for preventing opening of the access door until the rotational speed of the induction motor approaches zero;

    (d) a solenoid mounted within the housing and operated by the sensor means upon the rotational speed of the motor and back EMF thereof approaching zero; and

    (e) lever means mounted within the housing means and movable into and out of locking engagement with the bolt means by the solenoid means, said lever means being in locking engagement with the bolt means preventing movement of the bolt means from locked to unlocked position until the rotational speed of the motor approaches zero, whereupon the solenoid means is operated by the sensor means and moves the lever means out of locking engagement with the bolt means permitting the bolt means to be moved from locked to unlocked position.

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