Patent GB-451157-A (GB)
Title: Improvements in and relating to electrically operated turning lathes
IPC: B23B7/14
Filed: 1935-08-16
Abstract: 451,157. Lathes. TRIGGS, W. W., 57, Lincoln's Inn Fields, London.-(Pratt & Whitney Co.; 430, Capitol Avenue, Hartford, Connecticut, U.S.A.) Aug. 16, 1935, No. 23049. [Class 83 (iii)] [See also Group XXXVII] In a lathe for producing repetition work having a stepped formation, the feed motions of the tool are effected by electrically operated means controlled by circuits which are energized by switches moving in unison with the tool and coacting with adjustable stops to cause sequential operations of the tool so as to perform a cycle of movements and then come to rest. Feed-motions, toothed.-The headstock spindle 22, Figs. 1 and 2 is driven by a motor 27 through gearing 25 and carries a gear 28 driving a shaft 33 from which all the feed motions are derived. Longitudinal feed of the saddle 4 is effected by a lead screw 7 driven by gearing 54 from a shaft 52 which carries at its ends electromagnetic clutches 59, 67 rotated in opposite directions from the shaft 33 by gear trains 35, 55, and 45, 48 respectively, the ratios of the two trains being arranged so that the idle traverse to the right is at a higher speed than the cutting feed to the left. The slide rest 8 is fed transversely by a screw 12 rotating on the saddle and driven by gearing 13, 16 Fig. 2, from a splined shaft 18, Fig. 1, carrying electromagnetic clutches 60, 68 rotated in opposite directions and at different speeds from the gear trains 55, 48 which rotate the lead screw 7. Automatic-stop feed motions; depth of feed, determining.-The circuits of the electromagnetic clutches 60, 68 for controlling the transverse feeds of the slide rest 8 are energized by switches A, B, Fig. 5, carried by an arm 88, Figs. 1 and 2, mounted on the saddle 4 and co-operating with pairs of stops 75 adjustably mounted in T-slots 72 on the slide rest. The switch A is mounted on a vertical pivot 79 and is normally closed by a spring 81 but is opened by the stop 75 when the tool has been fed in to the correct depth The switch B is mounted on a horizontal pivot and has a lateral bevelled extension 85 adapted to slide under a stop 75<1> to open the switch against a spring to limit the " out " feed of the tool. The electromagnetic clutches 59, 67 for controlling the longitudinal feeds of the saddle 4 are energized by a switch C, Fig. 4A, mounted on an arm 104 carried by the saddle and co-operating with stops 98 adjustably mounted in T-slots 96 in a bracket 95 secured to the lathe bed. The switch is normally closed by a spring but is opened by contact with a stop 98 to limit the feed of the saddle towards the headstock. The arms 88, 104 are moved on the saddle during an idle " out " feed of the tool so as to set the switches carried thereby into position for engaging the next stop or stops for determining the succeeding feed step, and for this purpose are provided with racks 110, 111, Fig. 9, engaging pinions driven by gearing 120 from oppositely rotating electromagnetic clutches 131 driven by a separate motor 134, Fig. 2. Cams M, N, are also driven by the gearing 120 and actuate switches 148, 149, the switch 149 controlling a circuit for energizing the appropriate clutch 131 for giving the step by step movements to the slides 88, 104 during a cycle of operations and the switch 148 controlling a circuit for energizing the reverse clutch 131 for restoring the slides to their initial positions on completion of a cycle. The cam N thus rotates at the same speed as the clutch 131, and the cam M at one eighth of this speed, through gearing 123, when eight steps are used for completing a cycle. For accurate work the stops 75, 98 consist of the plungers of micrometers 76, 99 mounted in brackets 73 attached to the T-slots 72, 96, but where precision is not necessary the stops may consist of plain rods 751, Fig. 5, adjustably clamped in the brackets 73. The clutches are actuated by current supplied from mains whilst these main circuits are controlled by relays supplied from a separate generator driven by a motor on the mains, the relay circuits being on the " earthed return " system whilst the main circuits are on a two wire system, the negative leads being broken by the relay switches. Operation.-To produce a stepped workpiece as shown in Fig. 9, a cycle of operations is started by manually closing a switch, which actuates a relay to energize the " in " transverse clutch to feed the tool towards the work. When the required depth of cut has been reached, the first stop 75 encounters the switch arm A, thereby cutting out the " in " feed, and actuating a relay to energize the longitudinal feed towards the headstock. This continues until the switch arm C encounters the first stop 98, thereby stopping the longitudinal feed and actuating a relay to energize the " out " transverse feed. This continues until the switch arm B runs off the stop 751, allowing the spring to close a switch and actuate relays which stop the " out feed and simultaneously energize the clutch 131 for moving the arms 88, 104 carrying the switches to their second position. During this movement the cam N makes a complete revolution and then opens the switch 149, thereby de-energizing the clutch 131 and bringing the arms 88, 104 to rest in their new positions, and the cam M rotates one eighth of a revolution to allow the switch 148 to be closed by a spring. The switch 148 is in a circuit controlling a relay which energizes the reverse clutch 131, but energization of this clutch is prevented by a switch 263 on a longitudinal limit switch 152 being open, since the switch lever 152 is now clear of a dog 154 on the lathe bed. The movement of the arms 88, 104 relatively to the stops 75, 98 opens the switch B by causing its lateral projection 85 to slide under the next stop 75<1> and closes the switch C by relieving it from the first stop 98, thus placing the circuits in condition for another cycle of feed transversely " in," longitudinally towards the headstock, and transversely " out," the arms 88, 104 then being set for the third group of stops 75, 98. On completion of the final longitudinal traverse towards the headstock a metal stud 108 mounted on the stationary bracket 95 and insulated therefrom makes contact with switch fingers 109 on the saddle 4 which completes a circuit to throw over a reversing switch and energize the clutch for longitudinal traverse away from the headstock. This circuit includes a switch 227 on the lever 152 so that when the saddle reaches its extreme right hand position the lever rides on the dog 154 as shown in Fig. 9 to open the switch 227 and stop this traverse, and simultaneously close the switch 263, thereby completing the circuit previously prepared by the cam M to energize the reverse clutch 131 and return the slides 88, 104 to their original positions. The cams M, N, rotate in the reverse direction during this movement until the switch 148 is opened by the cam M to break the circuit to the relay controlling the reverse clutch 131 and thus bring the parts to rest in position for starting a cycle on a new work-piece. Opening of the switch 149 each time the cam N rotates in the reverse direction is ineffective, since this switch controls the forward clutch 131 only. A limit switch 151, actuated by an insulated lug 150 on the slide rest 8 is provided to break the circuit to the " out " transverse clutch when the saddle reaches its outward limit of travel.