METHOD AND APPARATUS FOR OPERATING SELECTOR

摘要

A method and apparatus for operating a switching device such as a clutch or brake for a moveable element such as a shaft which is driveable by a prime mover such as a rack and pinion device. The clutch selectively connects the shaft to the prime mover and the brake alternately and selectively connects the shaft to the housing. A motor sinusoidally reciprocates the rack by way of an eccentric drive and the rack drives a pinion on the input side of a pneumatic clutch and brake unit. The clutch is always operated in only one direction of movement and the moveable shaft can thereby be intermittently driven in one direction. A continuously rotating motor shaft carries a signal generator disc having a signal generating track in the form of recesses which are scanned photoelectrically. An operating signal which holds the clutch engaged during one half period is received by the signal generator and delivered by a control device. Switching devices such as clutches and brakes possess a certain reaction time between the occurrence of the operating signal and the instant when the clutch or brake becomes effective. The reaction time creates a problem relative to the desired requirement that the switching device become effective as close as possible to zero passage of the speed of the driving element so that the strain on the components and their wear is low. This problem is addressed by providing an actuating signal at an angular position which precedes the zero angle and initiates a delay period which does not change with a change in the rotary speed of the motor and is disposed in front of the speed zero passage by about the reaction time of the switching device.