Proportional Rotational Damper

grabcad

A rotational damper which offers little damping during low speed operation but high damping during high speed operation. Rotational motion of the door is translated via gears to rotation of a hub with radially mounted paddles which spin in a (Newtonian) viscous fluid. The paddles are hinged at one end. The paddles have a small degree of rotational freedom and can rotate so that they provide either a high or low drag. They are held in place with torsional springs. During low speed operation, the torsion on the springs is greater than the moment of drag, so the paddles remain in the low drag position. As the speed of operation increases, the moment of drag increases until it overcomes that of the spring, and rotates to the high drag position. This results in low damping at low speed and high damping at high speed. In the presented configuration, little damping is offered in reverse mode, however, this could easily be modified to having the same response in either direction by placing the axis of rotation of the paddle in the middle of the blade instead of on the end. The device also has the advantage of being rotational, so it offers some inertial (acceleration) damping as well. The effectiveness of the device could be improved by using a non-Newtonian shear thickening fluid. The device can be mounted in the ceiling or conventionally.