GB190427970A - Improvements in Selfacting Sliding and Screw-cutting Lathes - Google Patents

Abstract

27,970. Greenwood, T. Dec. 21. L a t h, es; toolholders.-The overhead motion of a lathe is formed as part of the lathe itself, which has a gap of adjustable width. The shaft of the tailstock is traversed, for boring, by gearing from the feedshaft, and indicator mechanism is used for putting in the feed-screw for screw-cutting. The overhead motion is contained in a bracket 2 on the fixed headstock 1<1>, which may be made separately or in one casting with the foundationplate 1 of the lathe. A countershaft 3 carries two pairs of loose and fast pulleys 5, 6 to which open and crossed belts are fitted, the latter being shifted by forks operated by a handle 9. A second countershaft driven from the other shaft by gears 15 or 16 carries the top cone pulley 17, the small step on which is of the same size as the largest step on the lower cone 37. The lathe bed 18 is secured on the foundation-bed 1 by means of hook bolts engaging undercut slots, and means are provided for bringing the bed in line with the fixed headstock and for adjusting the width of the gap. A bracket 35 carries pinions 34 and can move longitudinally, for reversing the direction of feed, to be driven either by a pinion 21 or by the wheel 36 on the cone pulley. The pinions 34 drive a pinion on the shaft 23 which engages with wheels on the rocking arm 25 and drives the feathered shaft 26, and a bracket is moved along the shaft to make the pinion drive any wheel in the gear box 22, from which by suitable gearing the feed-shaft is driven. The screwed shaft 40 of the loose headstock is fed forward by bevel gearing, driven from the feed-shaft and engaging a bevel-wheel 47, a nut box 53, Figs. 1 and 3, serving to transmit the motion of the latter to the screw as desired. This nut box has blocks 49 which run in grooves and are moved forward to engage the screw by pins 49<1> engaging spiral grooves 53<1> in the casing 53. A spring-controlled stop-piece engages recesses in screws 57, 58 and so limits the relative movement of the sleeve. The indicator mechanism for. putting in the feed-nut in screw-cutting, Fig. 5, consists of a bracket 59 carrying a stud 60 on which an index-wheel 61, the teeth of which engage a single tooth on the leading-screw and which is thus partially rotated for each turn of the latter, is mounted. Integral with the index-wheel is a boss 63 carrying teeth 63<1> of varying length, and a pin 68, adjustably mounted on a spindle 65, is turned aside by a tooth, and, on being returned by the spring 70, it is made to cause a bell 73 to be struck. For odd pitches, the wheel 61 may be chalked and a pointer 80 set to it and the bell put out of gear. An extra tool-holder, Fig. 10, with independent adjustment may be mounted in the upper part of the slide rest. The tool 77 is held by a set-screw 78 and collar 79 in a channel holder 76. A slot in a pivoted lever 80 engages a pin in the holder and so gives motion to the latter. An adjustable screw 83 may be used for adjusting the depth of the cut, the screw being carried in a pivoted arm 83<1> which can be swung out of the way of the holder.