Electronic control for an elevator braking system

Details Electronic control for an elevator braking system Electronic control for an elevator braking system

1998-12-23

2001-01-16

Salata, Jonathan (Department: 2838)

Elevator, industrial lift truck, or stationary lift for vehicle

Having specific load support drive-means or its control

Includes control for power source of drive-means

C187S288000

Reexamination Certificate

active

06173813

ABSTRACT:

FIELD OF THE INVENTION
The invention relates generally to an elevator safety system and in particular to an elevator safety system including an accelerometer for sensing elevator over-acceleration and over-speed conditions.
PRIOR ART
Elevators are presently provided with a plurality of braking devices which are designed for use in normal operation of the elevator, such as holding the elevator car in place where it stops at a landing and which are designed for use in emergency situations such as arresting the motion of a free-falling elevator car.
One such braking device is provided to slow an over-speeding elevator car which is travelling over a predetermined rate. Such braking devices typically employ a governor device which triggers the operation of safeties. In such elevator systems a governor rope is provided which is looped over a governor sheave at the top of the hoistway and a tension sheave at the bottom of the hoistway and is also attached to the elevator car. When the governor rope exceeds the predetermined rate of the elevator car, the governor grabs the governor rope, pulling two rods connected to the car. The rods pull two wedge shaped safeties which pinch a guide rail on which the elevator car rides thereby braking and slowing the elevator car.
Triggering safeties using a conventional, centrifugal governor has drawbacks. The governor rope often moves and occasionally such movements can have an amplitude strong enough to disengage the governor rope from its pulley and trigger the safety. In addition, the response time of a governor triggered safety is dependent upon the constant time of the rotating masses of the governor, the sheaves and the governor rope length. This leads to a delay in actuating the safeties and an increase in the kinetic energy of the elevator car that must be absorbed by the safeties. Lastly, the conventional governor triggered safeties require numerous mechanical components which requires significant maintenance to ensure proper operation.
BRIEF SUMMARY OF THE INVENTION
An exemplary embodiment of the invention is directed to a controller for use in an elevator braking system. The controller includes an accelerometer for detecting acceleration of an elevator car and generating an acceleration signal. An over-acceleration detection module compares the acceleration signal to an acceleration threshold. If the over-acceleration detection module detects an over-acceleration condition, a first switching device disrupts power to a solenoid in order to activate a braking assembly.
The braking assembly includes a brake linkage positionable in a first position and a second position. A spring biases the brake linkage towards the second position. A solenoid exerts magnetic force on a portion of said brake linkage counteracting said spring and maintaining said brake linkage in said first position. If power to the solenoid is interrupted by the controller or a power outage, the solenoid releases the brake linkage to brake the elevator.
The elevator braking system of the present invention provides benefits over conventional systems. The use of an electronic controller to detect over-acceleration and over-speed conditions results in more rapid deployment of the braking assembly thus reducing the amount of kinetic energy to be absorbed by the braking assembly. The braking assembly incorporates a fail safe design so that if power in the system is interrupted for any reason, the braking assembly is actuated to stop descent of the elevator car.


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