Controlled force actuator system

An automotive clutch comprising:

• a friction pad to releasably couple a rotatable power input to a power output;
• a pressure plate arranged to transmit a range of normal force to the friction pad, the range of normal force varying between minimum and maximum values;
• a back plate rotatable with the power input and spaced from the pressure plate;
• and
• a controlled force actuating system including a positive spring and a negative Belleville spring arranged in series between the pressure plate and the back plate, the positive spring having a positive force/deflection ratio and being initially in a relaxed condition and the negative Belleville spring having a negative force/deflection ratio and being initially in a loaded energy storing condition, and a movable control device engaging at least the negative Belleville spring so that movement of the control device releases stored energy from the negative Belleville spring to the positive spring, thereby to apply the combined energy stored in both the positive and negative Belleville springs between the back plate and the pressure plate, the negative and positive force deflection ratios being related so that the positive and negative springs are in equilibrium at the maximum value of normal force and so that the absolute values of the force deflection ratios differ by a control force in the control device that remains substantially the same for changes in deflection of the positive and negative springs throughout the remainder of the range of normal force.

A friction brake comprising:

• a fixed support;
• a rotatable member;
• a friction pad mounted on the fixed support for frictional engagement with the rotatable member under a range of normal force varying between minimum and maximum values;
• a controlled force actuating system including a positive spring and a negative Belleville spring arranged in series between the friction pad and the fixed support, the positive spring having a positive force/deflection ratio and being initially in a relaxed condition and the negative Belleville spring having a negative force/deflection ratio and being initially in a loaded energy storing condition, and a movable control device engaging at least the negative Belleville spring so that movement of the control device releases stored energy from the negative Belleville spring to the positive spring, thereby to apply the combined energy stored in both the positive and negative Belleville springs between the fixed support and the friction pad, the negative and positive force deflection ratios being related so that the positive and negative springs are in equilibrium at the minimum value of normal force and so that thee absolute values of the force deflection ratios differ by a control force in the control device that remains substantially the same for changes in deflection of the positive and negative springs throughout the remainder of the range of normal force.