Patent GB-1045276-A (GB)
Title: Improvements in or relating to automatic or semi-automatic screw-thread chasing machines
Inventor: DAVIS LOUIS ALLAN
IPC: B23G1/02
Filed: 1962-08-24
Abstract: 1,045,276. Lathes. PLESSEY-UK Ltd. Aug. 9, 1963 [Aug. 24, 1962], No. 32552/62. Headings B3B and B3T. In a screw-cutting lathe comprising longitudinal and cross-slides 16, 37 mounted on a saddle 15, a further slide 39 is interposed between the cross-slide and the chasing tool for rapidly withdrawing the tool beyond the normal range of the cross-slide, to provide access to the work and for returning it to the normal position. The spindle is driven, through a multispeed gear-box, further gears, chains 5, 6 and a clutch-and-brake mechanism 7, 8, 9, by a reversing electromotor 2. The mechanism 7, 8, 9 is operated by a lever 10 and held in the drive position by a linkage 12, 13 acting against a spring 14 and releasable by a triggermechanism at the end of a chasing operation. A face-cam 26 controls movement of the slide 16, the cam-shaft 24 being geared at 22, 23 to a shaft 17 clutched at 20 to a drive shaft 18. The cross-slide 37 is controlled by a cam 28 one face of which increases the cut after each traverse of the longitudinal slide 16, while the other face withdraws the cross-slide during return movements of slide 16. A feed pawl 27 operated by the cam 28 advances a ratchetwheel 29 connected to a pinion 30 which rotates a gear segment 31 against the influence of a return spring 46. An eccentric 32 turned by the segment 31 carries a normally non- rotatable cam 33 which raises a follower rack 34 during feed movements of the eccentric. The rack engages a pinion 35 meshing with a feed rack 36 which advances the cross-slide against the influence of a return spring. At the end of each traverse of the longitudinal slide, the opposite side of the cam 28, through a lever 56 and link 57, rotates the cam 33, causing the follower 34 to fall and withdrawal of the cross-slide 37. At a predetermined depth of cut, a pin 53 on the ratchet 29 strikes a lever 52, releasing a cam 48 which rotates, disengaging a retention pawl 47 and the feed pawl 27 from the ratchet 29. The cam 48 is geared to the shaft 12, which is rotated by the spring 14 when the cam is released, this rotation causing the rod 13 to stop the spindle. The chuck may open automatically at the end of the screw-cutting operation. The operation may be stopped manually by a lever 54 connected to the lever 52. A tool-feed attachment 58 carrying longitudinal, cross and vertical tool-slides, and also controlling the auxiliary slide unit 39 for the chasing tool, a chuck or mandrel-operating unit 42, a unit 11 for operating the clutch-andbrake mechanism 2-9, a unit 21 for operating the dog-clutch 20 and a unit 45 for feeding articles from a magazine 44, is mounted on the saddle, opposite the slide 37. The feeder unit 45 operates a spring-pressed ejector 43 in the spindle 1, and the units may consist of solenoids or, as shown, pneumatic cylinders. An adjustable stop 59 is provided on the chuck-cylinder 42. The attachment 58, Figs. 3 and 5, comprises an electromotor reduction-gear unit 61 driving a cam-shaft 62. A cam 64 on the cam-shaft, through a bell-crank lever 65, operates a vertical slide 63 carrying a longitudinally movable slide 66 supporting a turning, facing or boring tool. Slide 66 is operated by a cam 68 and a bellcrank lever 69, micrometer setting devices 70, 71 being interposed between the levers and the slides. A cross-slide 72 with a tool-holder 76, carrying a facing or grooving tool, is operated by a third cam-and-lever system 73, 74 and may be operative to machine the work while the screw-thread is being cut. A further camshaft driven synchronously with cam-shaft 62, carries cams operating valves 77-81 for controlling the supply of compressed-air to the pneumatic cylinders 11, 21, 40, 42 and 45.