GB895273A - Improvements in or relating to bar feeds for automatic lathes and other machine tools - Google Patents

Abstract

895,273. Automatic lathes. BIRFIELD ENGINEERING Ltd. July 5, 1960, No. 3723/61. Class 83 (3). An automatic bar feed, particularly adapted for use with sliding-headstock automatic lathes, incorporates a metering device which, as a fresh bar is fed forwardly by a pusher along a feed tube, comes into operation when the forward end of the bar passes a predetermined point and acts to position said forward end a preset distance beyond said predetermined point. A main support tube 1, Figs. 1 and 2, is mounted on pillars 2 of adjustable height and the components of the bar feed are clamped to the tube 1. A feed tube 3 which is in alignment with the lathe spindle is disposed at the bottom of an inclined storage rack formed by a spaced series of fixed inclined rack members 4. The feed tube has afixedtroughlike lower portion 5 closed by a series of separately hinged lid sections 6. A supply of stockbars is placed side by side on the rack members 4 with the lowest bar resting against a series of step members. Automatic mechanism lifts the lowest bar over the steps when the feed tube 3 is empty and the lid portions raised to replenish the tube. A pusher 7 is arranged for movement along the feed tube 3 to feed the bar and has a self-locking collet 8 at its forward end to grip the rear end of the bar. This collet comprises gripping balls 73, Fig. 8, moving in a taper 72 and carried by the spring-pressed collet 8. An ejector 67 within the collet operates, on retraction of the pusher, to push out the slug end to fall through an opened ejection slot. The upper run of an endless pusher chain 9, Figs. 1 and 2, is arranged alongside the feed tube 3 and a member 10 connects the chain 9 to the pusher 7. The sections 6 are raised in turn automatically as the member 10 enters a section. The chain 9 is driven from the rear end of the support tube 1 by a motor 20, Fig. 9, through a spring-loaded friction clutch 22, dog clutch 23 and chain drive 24 to a sprocket 25. The latter is mounted on a shaft 26 coupled to one member 27 of a dog clutch the other member 28 of which is fixed. Air cylinders 30 and 32 respectively, control operation of the dog clutches 23, and 27, 28, the latter when locked holding the new stock in its preset position until the lathe collet takes over. The metering device includes a hanging weight and pulley assembly 34, Fig. 1, which weight loads a sprocket 35, Fig. 10, engaged with the pusher chain 9 and tends to move the pusher in the bar-feed direction. An air-operated dog-clutch 37 is arranged to couple the sprocket 35 to the chain drive 39 and weight assembly 34. During a retracting movement of the pusher powered by the motor 20 (see above) the weights of the assembly 34 are wound up. A metering air cylinder 40 is connected to a rack 42 engaged with a pinion 43 and a friction clutch 44 controlled by an air cylinder 45 couples the pinion 43 to the sprocket 45 at the commencement of the metering stroke of the pusher. Operation. All the movements of the bar feed parts are controlled automatically by pneumatic cylinders and valves. An auxiliary cam-shaft arranged in the housing 57, Fig. 1, and driven from the main cam-shaft of the machine controls some of the valves. These controls include the retraction of the pusher at the end of a machine cycle and the closing of a gate in the front end of the feed tube (predetermined point). The main cam-shaft of the machine is also stopped and a timing device operated to allow a fresh bar to be rolled into the trough of the feed tube. The fresh bar is fed rapidly up to the gate by the weight means and contact with the gate engages the rear end with the collet of the pusher. The gate is next opened but the bar feed now comes under control of the metering device which moves it forward a set distance such that the next operation of the cutting-off tool in the machine trims the end of the fresh bar. The bar is locked in this position until the lathe collet takes over. Further feed of the pusher is by the weight system and the cutting-off tool is used as a stock-stop. When the remaining stock is not sufficient for two complete components the weight loading is removed and headstock collet comes back into contact with pusher collet. A slug of constant length is thus produced and on final rearward movement the pusher collet is opened to release the slug which falls through a gap in the forward part of the feed tube which has been opened up by sliding part of the tube transversely under control of a pneumatic cylinder.