GB934174A - Improvements in or relating to electrically controlled driving apparatus - Google Patents

Abstract

934,174. Change-speed control. ELECTRIC & MUSICAL INDUSTRIES Ltd. Dec. 7, 1960 [Dec. 30, 1959], No. 44170/59. Class 80 (2). An electrically controlled driving apparatus comprises means for driving a rotatable member in the forward or reverse direction, a brake for decelerating the member, means for generating an electrical signal when the speed of the member falls to or below a predetermined value, control means for removing the forward drive and applying the brake to initiate reversal, and means responsive to the signal to remove the brake and reverse the drive. The invention may be applied to the drive for one of a pair of computer spools regulating the passage of magnetic tape to and from an associated storage bin, the system shown comprising electric motor-driven magnetic powder clutches 4, 6 for rotating the spool in the forward and reverse directions, a magnetic powder brake 5 and associated memory control unit 1, memory unit 2 and spool control unit 3. Unit 1 comprises an " AND " gate 7 with inputs from a spool-driven tachometer and the brake 5; unit comprises two AND gates 10, 11 and two " OR " gates 12, 13, one input of gate 12 receiving the command signals; unit 3 comprises two AND gates 16, 17 and an OR gate 18 controlling the clutches 4, 6 and brake 5 respectively, the output from the bin sensing apparatus being fed to the trigger circuit 15 of gate 17. The tachometer supplies positive (1) signals when the spool is stationary and negative (0) signals when it is rotating, and the arrangement is such that command signals fed to gate 12 are only effective to energize clutch 4 or 6 when the bin sensing signal indicates that the bin has completed a previously initiated filling or emptying operation. Thus, 0 command signals fed to gate 12 to condition clutch 6 only make the drive effective when a 0 bin sensing signal fed to circuit 15 indicates that the bin is empty and requires filling, since under these conditions if the brake 5 is applied and the spool is stopped they each feed a 1 signal to gate 7, and a 0 bin signal feeds a 0 signal to gate 17 and a 1 signal to gate 16, the latter passing a 1 signal to clutch 6. Simultaneously, gate 18 receives a 1 signal from gate 16 and a 0 signal from gate 17 and passes a 1 signal to circuit 9 so that a 0 signal is fed to brake 5 to release the latter and allow the spool to be driven. Similarly, a 1 command signal fed to gate 12 conditions clutch 4 to drive the spool in the reverse direction when a 1 bin signal fed to circuit 15 indicates that the bin is full and requires emptying. Specifications 930,554 and 934,173 are referred to.