Speed-regulated positioning drive

Claim 1

A positioning system comprising, in combination, a drive motor having a drive member; an output shaft and means mounting the output shaft for rotation; an electromagnetically activatable clutch operative when activated for coupling the output shaft to the drive member, the clutch including a movable coupling structure movable between a first position coupling the output shaft to the drive member and a second position in which the output shaft and output shaft are not coupled; an electromagnetically activatable brake operative when activated for braking the output shaft, the brake including a movable braking structure movable between a first position applying braking force to the output shaft and a second position not applying braking force to the output shaft; negative-feedback speed control means including command transducer means generating a desired-speed signal, feedback transducer means generating a actual-speed signal and activating means operative in dependence upon the speed error indicated by the desired- and actual-speed signals for activating the clutch and the brake by applying thereto pulse-width-modulated actuating signals; and positioning means including means generating a position signal indicating when the output shaft has reached a predetermined angular position and means operative when activated for responding to the position signal and stopping the output shaft by activating the brake, further including roller-bearing means mounting the movable coupling structure of the clutch and the movable braking structure of the brake independently of each other on the output shaft non-rotatable relative to the output shaft but axially shiftable relative to the output shaft with a low-friction roller-bearing action, furthermore including a guide body mounted on the output shaft non-rotatable relative thereto, the guide body having a ring-like succession of angularly spaced axially extending openings encircling the output shaft, the roller-bearing means comprising a plurality of roller-bearing connectors each located in one of said openings, circumferentially successive ones of the roller-bearing connectors being alternately connected to the movable coupling structure of the clutch and to the movable braking structure of the brake, respectively, each roller-bearing connector comprising a guide sleeve coupled to a respective one of the movable braking structure of the brake and the movable coupling structure of the clutch, and a ball-bearing sleeve surrounding the guide sleeve and positioning for free rotation a plurality of spherical bearings, the negative-feedback speed control means including a monostable circuit connected to the output of the feedback transducer means and a timing capacitor connected to the monostable circuit, the monostable circuit controlling the charging of the timing capacitor, and furthermore including means for changing the discharge time of the timing capacitor in dependence upon the commanded speed, the feedback transducer means comprising means for generating pulses at a rate proportional to the rotary speed of the output shaft and frequency-multiplying means receiving the pulses and producing pulses of a higher frequency likewise proportional to the rotary speed of the output shaft, the frequency-multiplying means comprising a monostable circuit which produces an output pulse in response to the leading flank of an input pulse and also an output pulse in response to the trailing flank of an input pulse, the positioning signal being a positioning pulse, the positioning means comprising means for commanding that the output shaft be arrested at the predetermined angular position, means operative in response thereto for detecting the leading flank of the positioning pulse and automatically changing the commanded rotary speed for the output shaft to a lower shut-off value, and means responsive to the trailing flank of the positioning pulse for triggering the arresting of the output shaft.