Importance

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Abstract

The disclosure relates to an improved chuck force control and compensating means for rotary machine tools, such as lathe. The control is used with power-operated chucks and provides reliable and effective compensation for the effect of centrifugal force, which otherwise tends to reduce gripping force on the workpiece. The control includes a static adjust signal generator, for establishing the desired level of gripping force upon the workpiece, and a rotation speed responsive signal generator, for generating a signal which is a function of the square of the rotational speed. These two signals are combined and serve to actuate a servo valve to control hydraulic pressure delivered to the power operated chuck. Hydraulic pressure increases with increased rotational speed, in order to maintain chucking force at a constant level. A feedback circuit detects the level of hydraulic pressure and compares to the combined signals, developing a fault signal where the output hydraulic pressure does not agree with the signal delivered to the controlling servo valve. The circuit includes a redundant, parallel system for generating static and dynamic signals, combining them and comparing them to the primary combined signals. The redundant system prevents an unintended loss of chucking force in the event of failure of any of the primary signal generating components.

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First Claim