Patent GB-1316315-A (GB)
Title: Control system for dc motors
IPC: B66B9/10
Filed: 1970-12-04
Abstract: 1316315 Unloading SPERRY RAND CORP 4 Dec 1970 [22 Dec 1969] 57807/70 Heading B8E [Also in Division H2] In a D.C. motor driven article storage unit, Figs. 1, 2 (not shown), the motor being supplied from an A.C. source, the carriers (18) are moved until that one corresponding to a pressed button, for example 46 or 47, is at the bottom of an access opening, there being as many buttons as carriers. The precise stopping position is determined by means of a motor driven commutator, Figs. 3, 4 (not shown), having a set of rings 26<SP>1</SP>- 28<SP>1</SP>, 30<SP>1</SP> upon each of which a brush 40<SP>1</SP>-43<SP>1</SP>, rides and a ring of segments 31<SP>1</SP>-34<SP>1</SP> upon which ride a number of brushes, for example 45<SP>1</SP>, 45a<SP>1</SP> the number of brushes being equal to the number of carriers (18), and equi-angularly spaced. One revolution of the commutator corresponds to one circulation of the set of carriers (18). Normal operation.-Pressing of button 46, Fig. 5, renders transistor T7 conductive, via segment 34<SP>1</SP> and ring 27<SP>1</SP>, energizing relay coil AUX a short interval before coil UP thus closing contacts AUX, Fig. 6, closing UP3 and opening UP4, so that rectifier D1, D2, SCR1, SCR2 is rendered conductive under the control of firing angle controller 61, the firing signal being communicated via unidirectional switch SUS. Armature current flows via SCR6, SCR3 and the series field, and when, due to increasing armature speed, the armature voltage has increased to a given limit, relay coil STR is energized closing contacts STR1 to increase the power supplied to the motor, for full speed running, and, by closing contacts STR2, energizing coil DB consequently opening contacts DB, placing R4 in a circuit to be used for emergency braking. Transistor T7 is locked on via UP1 and SLO4. When segment 31<SP>1</SP> moves under brush 45<SP>1</SP>, transistor T6 is also rendered conductive, energizing coil SLO, contacts SLO4, as well as SLO1, SLO3, Fig. 6, opening, whilst SLO2 closes, causing the firing angle to be set for slow operation, and initially putting the motor armature in a braking circuit including R1, R2, thyristor SCR-7 being fired via SLO2. Slow operation continues until the gap 63 is under brush 45<SP>1</SP>, whence coils AUX before UP before SLO are de-energized, the required carrier (18) stopping at the bottom of the opening, dynamic braking being provided via SCR5, the series field, contacts DB and diode D4. The disposition of rings 33<SP>1</SP>, 34<SP>1</SP> ensures that movement is in the direction for the shortest travel distance of the required carrier, either one of transistors T7, T5, Fig. 5, being rendered conductive. Overspeed control.-Consequent upon motor overspeed due to unbalanced carrier loads, the excess armature voltage appearing across potentiometer R5, Fig. 6, causes neon light N-1 to ignite, the radiation reducing the resistance of nearby mounted photoresistor RX-1, igniting SCR-7 to put armature A in a braking circuit via R1, R2. Emergency braking.-In the event of power failure, relay coil DB, Fig. 6, is held energized for an adjustable time by capacitor C7, so that R4 is initially held in a braking circuit, and subsequently cut out, to avoid jerking of the carriers (18). The general arrangement is displayed in Fig. 7 (not shown).