Patent ID: 6296080
Filing Date: 2001-10-02
Classification: B66B

Abstract:
A variable traction mechanism, comprising:a rotary actuator;first and second wheels pivotably connected to an elevator car via first and second linking members, respectively;said first and second wheels riding on opposing sides of a guide rail for said elevator car;said rotary actuator including means for sensing when said first wheel exceeds a predetermined speed of rotation and locking said first wheel to said rotary actuator;a first spring acting between said second wheel and a first pivot point on said rotary actuator;a second spring acting between a center of said second wheel and a second pivot point on said rotary actuator; andwherein said first and second pivot points are located such that a friction force between said first wheel and said guide rail times a length of a normal to a direction of said friction force passing through a center of said first wheel plus a second spring force of said second spring times a length of a normal to a direction of said second spring force passing through said center of said first wheel is greater than a first spring force times a length of a normal to a direction of said first spring force of said first spring passing through said center of said first wheel.