Tilt control mechanism, particularly for knee-tilt chair

Abstract

The seat and pedestal of a chair are joined by a knee-tilt control mechanism which includes a first support fixed to the underside of the seat adjacent the front edge thereof, and a second support fixed to the upper end of the pedestal and having a sidewardly extending tube. The first support has bearing hubs which are rotatably engaged with the tube to define a horizontal tilt axis. A restoring mechanism is disposed within the tube for exerting a restoring torque urging the seat upwardly into a horizontal position. The restoring mechanism employs compression springs within the tube on axially opposite sides of a pre-torque member which can be rotated to adjust the initial spring compression. The springs bear against actuators which rotate with the bearing hubs. The actuators have radially projecting followers for engagment with ramp-like cams formed circumferentially of the tube. When the seat is tilted rearwardly, the followers ride against the cam ramps and cause the actuators to be displaced axially to increase the spring compression in accordance with the cam profile. The cams have a nonlinear profile so that the spring compression and restoring torque increases at a first rate throughout the initial tilt angle, such as from 0.degree. to 5.degree., which rate decreases throughout the remaining tilt.