Patent GB-571825-A (GB)
Title: Improvements in or relating to devices for automatic lathes
IPC: B23Q5/34
Filed: 1943-07-15
Abstract: 571,825. Lathes. TAREX SOC. ANON. July 15, 1943, No. 11518. Convention date, June 20, 1942. [Class 83 (iii)] A turning or screw-cutting attachment for lathes, which may alternatively be built into the lathe, has a control for giving a cutting traverse to the tool and variable means for determining the speed at which the tool is fed by said control. The attachment comprises a base 1 secured by screws 2 to the lathe frame and having a guide 3 for a transverse slide 29 carrying a longitudinal slide 28 on which the cutter 28<1> is mounted. The cutter may perform screw-cutting or plain turning on the work W. The slide 28 is actuated by a link 44 having a bowl 43 engaging an inclined slot 42 on a slide 40 which is movable transversely on guides 41 of the base 1 by a lead screw 26 rotated by gearing from the headstock spindle 17a. The slot 42 is formed in a circular plate angularly adjustable on the slide 40 so that the inclination of the slot enables a fine adjustment of the tool traverse to be obtained independently of the pitch of the screw 26 and the gear train which drives the screw, or the direction of feed may be reversed without reversing the rotation of the screw. The spindle 17a drives a shaft 21 through gearing 16 and a main clutch 14, the shaft 21 driving a clutch 23 through gearing 18 and also driving a clutch 24 in the reverse direction through shaft 21 and gearing 19d, and either clutch may be engaged to drive a shaft 22 connected, by bevel gears 25 to the lead screw 26. The clutch 23 rotates at a low speed for cutting and the clutch 24 at a higher speed for the return traverse of the tool. At the end of a cutting traverse on the work W a dog 49 on the slide 40 trips a lever 50 and allows a lever 52 to be spring-actuated to disengage clutch 23 and engage clutch 24, and on completion of the return traverse a dog 51 on the slide 40 rocks the lever 52 to reverse the drive for the next cutting traverse. Alternatively, the lever 50 may be replaced by a load and fire arrangement consisting of a lever pivoted at 60, Fig. 3, having arms 52 engageable by the dogs 49, 51 and arms 52a carrying spring plungers 73a co-operating with a lever 61 also pivoted at 60. When the lever 52 is rocked on completion of a tool traverse the spring 73a is compressed until a stop 74a on the lever trips a spring catch 63a to release the lever 61 and allow the spring to shoot the lever 61 from one clutchengaged position to the other, this lever acting on the clutches through pivoted arms 66 and spring links 70 to compensate for wear in the friction clutch 24 and maintain this clutch in engagement. In a simplified construction, the slide 40, Fig. 7, carrying the cam groove 42 for feeding the slide 28 longitudinally, is actuated through a rack and pinion 82 and linkage 82<1> from a spiral cam 80 and transverse feed is imparted to the slide 29 by a rack and pinion 32 and linkage 32<1> actuated by a cam 84. The slide 3 is arranged radially to the lathe axis and at an inclination which will not interfere with the front and rear tool slides, and the base 1 may be formed integral with the lathe. Depth of cut feeds.-When cutting screwthreads by means of a number of traverses of the slide 28, the slide 29 is withdrawn for each return traverse by means of a link 34, Fig. 5, having a two-position slot 36 engaging a roller 35 on the rack 33 engaged by the pinion 32. The link is movable in the slide 29 by a lever 48 rocked at opposite ends of the movements of the slide 40 by means of tappets 46, 47 thereon, thus setting the slide 29 in the cutting or relieved position, the increased cut for each operative traverse being effected by the cam 30 acting on the pinion 32 through linkage 301 and shaft 30<11>. Stop-motions.-During the last rearward traverse of the slide 28 in a screw-cutting operation, a cam 5 rocks a lever 8 to compress a spring 8<1> against a lever 12 operating the main clutch 14 and on completion of the traverse a tappet 51a on the slide 40 rocks a lever 55 connected by a link 55<1> to a lever 56, thus releasing this lever from a catch 56a on the lever 12 and allowing the latter to be moved by the spring 8<1> to stop the drive to the attachment. During intermediate rearward traverses of the slide 40, the lever 56 is rocked, but the lever 8 has not been moved to clutch-disengaging position by the cam 5.