GB868034A - Improvements in screwcutting lathes - Google Patents

Abstract

868,034. Screw-cutting lathes. FARROW, B. J. Jan. 21, 1960 [Jan. 28, 1959], No. 3078/59. Class 83 (3). A device for facilitating the correct engagement of the nut and lead-screw in screw-cutting lathes comprises a timing disc and a series of gear-wheels of different sizes arranged on a spindle mounted in the lathe apron or a plate attached thereto, a second spindle carrying a pinion to engage any of the gear-wheels and thus drive the timing disc, this pinion being connected to a worm-wheel engaging the lead-screw, means being provided on a slide carried by the apron or plate to co-operate with a shaped part of the timing disc so that the nut and lead-screw only engage at a predetermined position of the timing disc. The plate 20, Figs. 2 and 3, carrying the device is secured to the right-hand side of the lathe apron in the example described. The first spindle 23, Fig. 5, carries an integral masking disc 25, Fig. 7, adapted to mask two, three, or all of the slots in a timing disc 27, Fig. 6, carried by a sleeve 26, Fig. 5, rotatable on the spindle 23. A spring-pressed bush 50 on the squared end of spindle 23 has a stud 44 to retain the discs in the predetermined relative angular setting. A set of " cone " gear-wheels 30-34 are secured to the sleeve 26 to rotate the timing disc and a selected one of these is engaged by an idle pinion 57, Figs. 2 and 3, mounted on a slidable fork 56 to connect a long gear 53 to the selected " cone " gear. The gear 53 is secured to the second spindle 24, the other end of which carries a worm-wheel 64 in constant mesh with the lead-screw 15. A slide 66, Fig. 5, on the back of the plate 20 carries a half-nut 65 which may be engaged with the lead-screw 15 by a lever 76 with an eccentric peg engaging a slot in the slide. A latch 67 secured to the slide prevents engagement of the half-nut until the unmasked opening on the timing disc comes into line and allows the latch to move upwards into it, thus giving the correct position of engagement for the particular thread being cut. Automatic stop. Movement of the handle 76 to effect engagement rotates a further latch member 73, Fig. 2, which engages under the latch 67 to hold it in position against the downward pull of a spring. A lever 90 arranged underneath the plate 20 is adapted to contact an adjustable stop 17 on the lathe frame to stop the screw-cutting motion by rotating the handle 76 through an arm 84 and thus allowing the latch 73 to move to the left by spring 72.