Patent GB-316205-A (GB)
Title: Electric tracer control for lathes
IPC: B23Q35/12
Filed: 1929-01-02
Abstract: 316,205. Keller Mechanical Engineering Corporation, (Assignees of Shaw, J. C., and Shaw, R. D.). July 25, 1928, [Convention date]. Lathes. - A copying-lathe of the kind having a fixed template or pattern cooperating with a tracer on the tool-slide has the longitudinal and transverse toolslides operated by feed screws, each of which may be rotated in either direction by one of a pair of oppositely rotating electro- .magnetic clutches. The circuits to the clutches are at a high voltage (110-120 volts) and are .operated by relay circuits of low voltage (10-14 volts) which are under the control of contact switches actuated by the tracer. For operating on work A between centres, as shown in Figs. 1 and 2, the circuits are set for traversing the saddle 108 to the right or left and the tracer controls the in and out movements of the slide 125 in conformity with the pattern whilst for operating on work A, Fig. 4, on a face-plate the circuits are set for cross traverse of the slide 125 and the saddle 108 is controlled bv the tracer. The machine comprises a bed 101, Fig. 1, carrying the saddle 108 and head- and tail-stocks 102, 103 respectively. The spindle 105 is rotated from an electric motor through cone-pulleys 106 and the lead screw 107 for the saddle is driven from an extension 123 of the spindle through bevel gearing 121 and a bevel wheel 120 which drives bevels 118 in opposite directions. A two-faced electromagnetic clutch 117 is capable of being clutched to either of the wheels 118 and is connected to the lead-screw through spur gearing 113, 110. Alternatively the bevel wheels 118 may be driven by a separate motor. The feed screw 126 for the cross slide 125 is driven through a shaft 129, a reversing magnetic clutch 134 and gearing 132 from a motor 130, the motor and gearing being mounted on the saddle. A bracket 135, Figs. 2 and 4, carried by the cross slide which also carries the tool 124, has mounted thereon the tracer 137 adapted to co-operate with a pattern 139 on a bracket 141 adjustably attached at 142 to a slot in the bed 101. For face-plate work the pattern is arranged as shown in Fig. 4 while for centre work the pattern is rotated in a horizontal plane through 90‹. The tracer comprises a cylindrical body 137, Fig. 5, secured to the bracket 135, in which is mounted a spindLe 151 by means of a ball joint 152 so that the lower end 138 can move universally in a substantially horizontal plane in contact with the pattern. The rear end 153 of the spindle is rounded and co-operates with a conical socket 154 in a lever 155 pivoted at 156- to a fixed cover 157 on the sleeve. Adjustabletension and compression springs 162, 164 respectively tend to maintain the lever in the position shown in Fig. 5 with a contact 158 thereon engaging a fixed adjustable contact 159 in a plate 160 attached to the cover 157. A rear contact 167 on the lever 155 co-operates, on oscillation of the lever, with a contact 168 on a second lever 170 pivoted to the cover at 171, an adjustable spring 172 serving to maintain a contact 174 on the lever 170 in engagement with a fixed adjustable contact 175 on the plate 160. The contacts. 158, 167 on the lever 155 control the relay circuits 34, 52 respectively and serve to earth these circuits through the sleeve 137 at 166, while the contacts 159, 168, 174 and 175 are mounted in insulating bushings. The low tension current for the relays is supplied by a generator G driven by a motor M and the high tension current for the clutches and the motors is derived from supply mains L-, L+. Motors T, L, controlled by the starting switches of usual construction shown at the left hand bottom corner of Fig. 5 drive the magnetic clutches 134, 118 respectively, and condensers 144, 145 are connected across the terminals of the clutches. A hand-controlled switchboard is provided in which the switch 185 closes the circuit for the main spindle drive and the switch 186 for the motors M, T and L, the switch 187 closes the high tension circuit 12 and the relay circuit 51 from the generator G, the switch 188 determines the direction of the transverse or longitudinal feed in centre or face-plate turning respectively, the switch 189 closes the circuit 32 and the switch 190 closes the circuit 34. A rotary two-positdon drum switch is also provided in which a double row of fixed contacts 184 may be brought against either of the movable contacts T, L, the former setting the circuits for transverse feed of the slide 125 with in and out movements of the saddle 108 and the latter for longitudinal feed of the saddle and in and out movements of the cross slide. The various circuits are connected through two terminal boards 147, 148. In operation, for operating on the work shown in Fig. 4 with transverse inward feed of the slide 125, the contacts T are engaged with the contacts 184, the switch 188 is moved to the right and all the other switches are closed. If the tracer is out of contact with the pattern the contacts 158, 159 will be closed thus energising relay magnets 178, 180. The former will open the switch arm 182 and break the circuit to the " in " clutch 134, preventing movement of the slide 125, and the latter will pull the switch arm 183 to close circuit 7, through the drum switch and circuit 1, to the " in " clutch 118 causing the tool to be fed axially towards the work. As soon as the tracer meets the pattern the spindle 151 will rock the lever 155 just sufficient to open the contacts 158, 159, thereby releasing the arm 182 and allowing the arm 183 to assume the neutral position shown. The transverse " in " feed (clutch 134) will then become operative alone and will continue so long as the transverse face of the pattern remains perpendicular to the lathe axis. Should a hollow portion of the pattern be encountered the transverse and longitudinal feeds alternate until thedeepest portion has been passed. When the tracer engages a rising portion of the pattern the transverse feed will increase the lateral pressure on the tracer point sufficiently to engage the back contacts 167, 168, thereby energising the relay magnets 179, 181, causing the transverse feed to be stopped by the arm 182 aud the longitudinal " out " feed to be started by the arm 183 and circuits 8, 2. Longitudinal " out " and transverse " in " feeds will then alternate until the projection or rising portion on the pattern has been surmounted. Should the engagement of the contacts 167, 168 fail to stop the transverse feed the pressure on the tracer will increase and cause the second lever 170 to be rocked, thereby disengaging the contacts 174, 175 and breaking the circuit 31, 32 to the clutch 134 and allowing the " out " longitudinal feed to operate until the pressure has been relieved. For operating on centre work, as shown in Fig. 1, the pattern is turned through 90‹ so that its contour is parallel to the lathe axis and the drum switch is rotated so as to bring the contacts L in engagement with the contacts 184. The circuits are then set so that one of the clutches 118, (determined by the position of switch 188), will be controlled by the switch arm 182 and the two clutches 134 are controlled by the switch arm 183, actuated by the tracer relays. Specification 233,747 is referred to.