Improvements in or relating to electrical control mechanism for controlling the speed of a rotatable element

877,211. Control of several A.C. motors. ELECTRIC & MUSICAL INDUSTRIES Ltd. March 3, 1958 [March 15, 1957], No. 8548/57. Class 38 (3). A suction roller 8a is coupled to a split-phase induction motor 27 for winding-on or unwinding magnetic tape from a spool 8 driven by motor 26. When the spool 8 is being rotated in the winding direction, the motor 27 is driven by the roller 8a and its starting winding is energized from source 28 so that a voltage is induced in the running winding which, upon the speed of the split-phase motor reaching a predetermined value, operates relay 30 to de-energize motor 26. This prevents the linear speed of the tape from becoming excessive as the diameter of the tape on the spool 8 increases. The winding-operation of the motor 26 is initiated by closure of switch 19 due to lateral pressure of the tape in compartment 10 of bin 6, a switch 22 being closed when the lower part of compartment 11 is filled with tape so as to enable motor 26 to remove tape from the compartment 11. When the roller 8a is required to unwind tape from spool 8 into the compartment 11, switch 18 is closed and motor 27 is fully energized. At the same time, relay 30 is energized to disconnect the motor 26. When the switch 18 opens, the motor 26 is energized through resistor 35, and a portion of tape is kept taut between roller 8a and spool 8, a switch 34 opening to de-energize the motor 26 if the roller 8a is caused to rotate in a direction opposite to that obtained when the motor 27 is fully energized. A switch 40 operates to reverse the direction of the tape, the filling and emptying of bin 7 being similar to that of bin 6. Specifications 877,209 and 877,210 are referred to.