Power driven equipment safety device
First Claim
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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Accused Products
Abstract
A safety device for power driven equipment which mechanically locks an access door on the equipment in closed position until the power drive motor has coasted to a stop. A manually operated locking bolt for the access door is pivotally mounted on a housing in which the control components for the safety device are contained. A locking plate is rigidly mounted on the pivot shaft of the locking bolt within the housing for movement with the shaft and bolt. A solenoid operated locking lever is pivotally mounted in the housing and is engageable with the locking plate when the solenoid is energized to prevent movement of the locking bolt from its door locking position. A bolt mounted on the locking plate actuates a switch which is electrically connected in the drive motor control circuit to open the circuit when the lock bolt moves to an unlocked position. A voltage sensitive relay (ZVM) maintains the control solenoid energized even after the drive motor is deenergized by the voltage produced by the back EMF of the coasting motor rotor. Therefore, only when the motor rotor becomes or approaches a stationary condition will the ZVM deenergize the solenoid which disengages the locking lever from the locking plate to permit the locking bolt to be manually moved to unlocked position for opening of the access door of the equipment.
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Citations
18 Claims
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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:
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(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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. In an improved power driven piece of equipment of the type having an electric drive motor, a work performing mechanism located within a compartment of the equipment and driven by the electric motor, a door providing access into the compartment, and electric circuit means operatively connecting the drive motor to a supply of electric power, wherein the improvement includes safety latch means mounted on the equipment and engageable with the access door to prevent access into the mechanism compartment until the drive motor is stationary, said safety latch means including:
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(a) bolt means mounted on the equipment and engageable with the access door, said bolt means being movable between locked and unlocked positions with respect to said access door; (b) sensor control means including a voltage sensitive relay operatively connected with the electric circuit means and responsive to the back EMF voltage produced by the drive motor; (c) solenoid means connected with said electric circuit means and controlled by the sensor control means, with said solenoid means being energized in relationship to the back EMF voltage produced by the rotation of the drive motor; and (d) lever means movable into locking engagement with the bolt means upon energization of the solenoid means when the bolt means is in locked position to maintain the bolt means in locked position with the access door until rotation of the drive motor approaches zero, whereupon the sensor control means deenergizes the solenoid means to move the lever means out of locking engagement with the bolt means. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17)
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18. In an improved power driven piece of equipment of the type having an AC electric induction drive motor, a work performing mechanism located within a compartment of the equipment and driven by the induction motor, a door providing access into the compartment, and electric circuit means operatively connecting the drive motor to a supply of electric power, wherein the improvement includes safety latch means mounted on the equipment and engageable with the access door to maintain the door in a locked condition and prevent access into the mechanism compartment until the drive motor is almost stationary, said safety latch means including:
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(a) bolt means mounted on the equipment and engageable with the access door for preventing opening of said door until the drive motor is almost stationary; (b) sensor control means operatively connected with the electric circuit means and bolt means for maintaining the bolt means in locking engagement with the access door until the back EMF voltage produced by the rotation of the rotor of the induction drive motor approaches zero; (c) solenoid means operatively connected with said electric circuit means and bolt means and controlled by the sensor control means for maintaining the bolt means in locking engagement with the access door, said solenoid means being maintained energized until the back EMF voltage produced by the rotation of the drive motor approaches zero; and (d) lever means maintained in locking engagement with the bolt means by the solenoid means when the bolt means is in locked position and the solenoid means is energized to maintain the bolt means in locked position with the access door until rotation of the drive motor approaches zero, whereupon the back EMF of said motor approaches zero and the sensor control means in response to the EMF approaching zero deenergizes the solenoid means moving the lever means out of locking engagement with the bolt means permitting the bolt means to be moved to unlocked position with respect to the access door.
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Specification