Patent GB-858381-A (GB)
Title: Improvements in or relating to apparatus for maintaining constant cutting speed in lathes and like machine tools
Inventor: COX ALAN JOHN
IPC: B23Q5/16
Filed: 1955-12-02
Abstract: 858,381. Lathe-details. BIRMINGHAM SMALL ARMS CO. Ltd. Feb. 22, 1957 [Dec. 2, 1955], No. 34488/55. Class 83 (3). A lathe or like machine-tool is adapted to maintain a constant cutting-speed and incorporates a regulating device, controlling the rotational speed of the spindle, which is actuated by the cross-feed of the tool-slide through the medium of a cam co-operating with combined gear and cross-link mechanism, the proportional rotary movement of said gear being magnified by servo-mechanism into rotary movement of increased power sufficient to operate the regulating device. Constant cutting speed for a tool 5, Fig. 1, operating on a workpiece 7, is obtained by transmitting the linear movements of the tool-slide 6 by rack-andpinion 9, 10, to rotary movement of a shaft 11. The latter drives a speed-control device 8 having a cam 13, Figs. 2 and 3, within a casing 14 which transmits movements to a follower 16 on a bell-crank 15. The lever rotates about a fixed-pivot 15<1>, and its other end carries a pin 161 engaging a radial slot 17 in a toothed wheel 18. This wheel is freely-mounted on a shaft 19 coaxial with and entering the end of the hollow-shaft 12, to which the cam 13 is secured. The wheel 18 engages a rack 20 slidable on an upright guide 21 and having a pin 22 accommodated in a slot 23 in a cross-link 24. The latter is mounted on a pivot 25 slidingly engaged in slots 26 in the limbs 27<1> of a forked-arm 27 keyed to the shaft 19, the pivot also being. guided at its ends in lateral-slots 28<1> in a pair of guide-plates 28 which restrain the movement of the arm 27 to a fixed-plane, and retain the pivot 25 in a fixed path. The other end of the cross-link 24 is similarly provided with a slot 29 engaged by a pin 30 on a rack 31 slidable on an upright-guide 32, and engaging a toothedwheel 33. This wheel is journalled in a bearing 34 mounted in another part 14<1> of the casing, and has connected to it, a cup-shaped member 35 rotatable on the shaft 19 and in the bearing 34. A similar, oppositely-arranged, cup-shaped member 37 is keyed to the right-hand end, Fig. 2, of the shaft 19. The cup-shaped members have clutch-teeth which may be engaged selectively by a slidable member 39, 43, which moves under control of a push-pull valve member 54. The clutch part 41 is rotatable, and has a splined connection to a rotating part 57 in the casing 14<111>. This part has a fluid servo-connection to a rotatable toothed wheel 98 which magnifies the rotation of part 41 and increases the power-level thereof. The wheel 98 rotates, through gearing 102- 104, the control-wheel 4, Fig. 1, of a known speed regulator 3 driving the lathe-spindle 1, a prime-mover 2 giving a fixed-speed input drive to the regulator. A graduated dial 36, Fig. 2, is secured to the end of shaft 19 and, with the control valve 53 withdrawn, the clutch part 39 engages the corresponding part 37 so that the speed may be initially adjusted, for the range required. The valve 53 is then pushed to the left, and the clutch part 39 also moves to the left by fluid-pressure into the position shown in Fig. 2, where adjustment of the speed-regulator becomes automatic, dependent on the linear transverse movement of the tool-slide 6.