GB475295A - Improvements in or relating to means for keeping the cutting speed constant in turning lathes and like machine tools when the working diameter changes - Google Patents

Abstract

475,295. Turning. TRIGGS, W. W. (P. I. V. Ketten und Getriebe Ges.) Aug. 11, 1936, No. 22085. [Class 83 (iii)] In an arrangement for maintaining the cutting speed constant when the work diameter changes in lathes and like machines, a controlled member coupled to the cross-feed spindle or slide makes equal displacements for changes of the work radius in geometric progression and this controlled member is directly coupled to the control member of a speed regulating device which for equal variations of the control member produces speed variations in geometric progression. A lathe, Figs. 3 and 4, in which the spindle 6 is driven by a fluid pump and motor set 1, 2, regulated by cam grooves in a member 16, and an electric motor 3, the feed shaft 29 for the surfacing motion of the slide 11 is connected by worm gearing 28 to a camdisc 26 which for displacements of the crossslide in G.P. gives equal displacements to the rack bar 25 ; the latter transmits equal movements to the cam member 16 which is adapted to give corresponding spindle speed changes in G.P. The transmission between the rack bar 25 and cam member 16 may be disengaged to alter the relation between the cutting radius and corresponding spindle speed to obtain a new range of values at constant cutting speed by a clutch 20 and hand wheel 21. In place of the worm drive 28 a fluid motor may be used in the manner of a servo device and the hand wheel 21 may be arranged so that adjustment can be effected while the machine is running. A modified arrangement comprises a friction disc drive 42, 43, Fig. 6, and chain and toothed gearing for driving the spindle 6, the friction pulley 42 being moved along its shaft by a. cam-disc 62 which is rotated by ratchet mechanism 53, 54 from the feed shaft 29, the latter also rotates through worm gearing a cam-disc 26 which controls the position of a mask 58 for the ratchet mechanism. For changes in the cutting radius in G.P. the cam-disc 62 makes equal displacements, and the pulley 42 is thereby adjusted to give speed changes in G.P. This arrangement may be adjusted for different cutting speed ranges by lifting the pawl 54 and moving the ratchet wheel. A similar control arrangement is described with a regulating resistance and electric motor drive in place of the friction pulley and disc drive. A simpler modified arrangement comprises a crank and connecting rod, Fig. 9 (dotted), connection between the cross slide 82 and a control shaft 84, the latter roughly executing equal movements to movements of the cross slide in G.P. The control shaft operates the expanding cones of a stepless drive for the spindle to give speed changes in G.P. for equal movements of the control shaft. A hand-lever 93 permits adjustment of the relative positions of the control member and speed control through a friction drive for effecting different ranges of cutting speeds, and an indicator 94 with two logarithmic scales shows the cutting speeds in use. In place of the crank and connecting rod, a cam plate 95, Fig. 11, may be used to move the control shaft 84 through the lever 97 provided with a roller 95 for contacting the cam plate. A similar cam plate control is described for operating an electric servomotor which controls the movements of the control shaft. A further servomotor device has stepped contacts arranged on the slide or on a drum connected thereto and spaced apart in G.P. Specification 391,005 is referred to.