Importance

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Abstract

The invention is concerned with the rapid release of frictional force which is acting to reduce relative movement between contacting surfaces, the normal actuating means being unaffected. One application is in an anti-lock braking system in vehicles, particularly motor-cycles. A sensor monitors wheel angular velocity, calculates deceleration and when this exceeds a predetermined value the sensor causes ultrasonic vibrations to be applied to brake pads effectively reducing friction without release of brake operating pressure to enable resumption of normal rotation. A short duration dc pulse of appreciable magnitude may be applied to the transducer at the onset of the normal input signal to produce a short duration surge to rapidly break the frictional force between the friction member and the moveable member to enhance speed of release. The transducer may also be applied directly to the end wall of a friction member hydraulic operating cylinder when ultrasonic vibrations will be transmitted through the operating fluid to the piston connected to the friction member. The end wall of the cylinder is of a suitable matching material to facilitate transmission of the ultrasonic energy, and the piston is formed so as to minimize attenuation. The invention can also be applied to friction clutches operating in either rotary or linear senses to cause release when overloading or overspeeding occurs or to give gradual engagement in accordance with a predetermined program.

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First Claim