GB1251165A - - Google Patents

Abstract

1,251,165. Energizing electromagnetic actuators. INTERNATIONAL BUSINESS MACHINES CORP. 30 June, 1970, No. 31525/70. Heading H3T. [Also in Divisions G5 and H1] Rebound of an electro-magnetic actuator is reduced by detecting the rebound and applying to the operating coil a pulse in a direction to oppose the rebound. Fig. 3 shows a centretapped operating coil 13 energized by transistors T5 and T7 in one direction or the other according to the polarity of a signal applied at 29, 30. Concurrently with a change of this signal a pulse is applied at 31 which operates a monostable circuit SS1 to pulse transistor T1 or the corresponding transistor T6 to provide additional current during the early part of the changeover period to speed of the movement. A detector circuit 38, T7 (one for each end of the coil) detects the pulse (T3, Fig. 2 not shown) in the unenergized side of the coil due to the rebound. This, via an AND gate 35 and a monostable circuit SS2, momentarily applies an additional pulse to the transistor T1 or T6 connected to the energized end of the winding to oppose the rebound. A delay 37 and a latch 36 prevents incorrect operation. The invention is applied to the mechanism for arresting the traversing drive for a magnetic disc store. The drive is effected by a lead screw and is arrested by pawls 2 mounted on spring arms 4. They are moved out of engagement with the ratchet by a member 9, 18 carrying a coil 12 located in an annular gap in a fixed magnet 10, 11. Resilient stops 22, 23 absorb some of the energy of movement to reduce the rebound. It is stated that the coil could be stationary and a magnetic former could operate the device. In addition a single coil could be used.