Patent GB-649084-A (GB)
Title: Automatic lathe
IPC: G05B19/06
Filed: 1946-01-11
Abstract: 649,084. Control of motors. BICKEL, C. A., BRANDENBURG, S. A. and FOSTER, T. D. Jan. 11, 1946, No. 1053. Convention date, May 7, 1945. [Class 38(iii)] [Also in Group XXII]  A lathe provided with a crossslide for movement towards and away from the work-axis has a motor for the drive of the cross- 'slide and a differential, a driving connection extending between a first side of the differential and the cross-slide, a high speed drive between the motor and a second side of the differential, and a slowspeed drive between the motor and a third side of the differential with switch means operated in accordance with the movement of the slide to render the drives alternately effective and ineffective. In practice the lathe which is fully automatic and electrically controlled, (see Group XXII), is provided with a front cross-slide 85 on which a top tool slide 159 is arranged, a rear slide 169 and a slidable tailstock centre 59. Each of these members is moved by a separate electric motor controlled by a rotating drum 152, 165, 172, 81 respectively on which buttons are secured to operate micro-switches secured to arms such as 85c which move with the members. Control-The five individual motors for driving the spindle, feeding the slides, and moving the tailstock, respectively, are reversible variable-speed D.C. motors each supplied by a D.C. generator and controlled by mechanically coupled rheostats in the conventional variable field, variable armature voltage control method. In practice all the generators such as 171G, Fig. 14, are driven from the same A.C. motor (not shown). Motors 31, 75 and 160, have dynamic brake resistors connected across their armatures to bring the latter to a quick stop when the circuits are opened. Considering the circuit for motor 171, this has its armature connected with the armature of generator 171G through relay coil 280 and normally closed blades 261b and 261d. Reversing connections at 261a and 261c are provided and the purpose of coil 280 is to cut out resistance in field coils of motor 171 when the motor has been brought up to speed. Fig. 21 (not shown) gives the layout of the field circuits and controls for the motors and generators. Fig. 20, shows the main supply lines at L 1 , L 2  with a relay coil 173 connected by a line 174 to a starting switch 175. Normally closed relay blades and a holding circuit around switch 175 are included. With the machine at rest the four switches 80, 85d 156b, and 170c are closed by engagement of their operating plungers with the rear stops or buttons on the respective control drums 85, 152, 165, and 172. Switch 175 initiates operation of the machine which then continues automatically according to the settings of the buttons on the control drums and the control circuits utilized. The headstock motor 31 is started and subsequently feed of tailstock to engage work, fast and slow speed movements of cross slides, feed movement of top tool slide and finally return of all members to the start position, takes place. Four ratchet relays, 1-4, Fig. 20, are used to switch in the consecutive control circuits required. Each relay consists of a spring-pressed pawl 205 pivoted on a slidable member 200 operated in one direction by a solenoid 180 and returned by a spring 210. The pawl is adapted to effect the step-by-step rotation of a ratchet wheel 212 secured to the spindle 213 of switch-arm 215. Movement of the latter in an anti-clockwise direction winds up a spiral spring 214 which returns the arm 215 to the initial position when a locking pawl 217 is withdrawn by a further solenoid 229.