595,383. Boring engine cylinders. JOHNSON, W. G., and FORWARD, H. June 4, 1945, No. 14066. [Class 83 (iii)] Boring-heads.-In a cylinder boring or like machine driven from an electric motor through a change-speed gear, automatic means are provided for operating the change-speed selector mechanism so as to stop the rotary drive of a boring head and reverse its forward feed after a predetermined length of cut, and for disengaging the reverse feed after a predetermined return movement of the boring head, hand-controlled means being provided for reconnecting the boring-head drive and forward feed. The main components comprise a base 10, Fig. 1, adapted to be clamped by a cylinder block, an electric motor 34 driving an input shaft 36, Fig. 6, of a gearbox 12, a feed shaft 31, a drive shaft 26, a transmission casing 14 carrying a feed nut 30, and a boring spindle 13 sliding in a guide 11 on the base. The cutter 15 is adjustably mounted in a head which has also locating pins 18, Fig. 7, adjusted radially to locate the head in the bore by the tapered end of a rod 20 in screwed engagement with a cap 23. The boring head is rotated by a hollow spindle 16 having a pulley 17 driven by a belt 24, Fig. 2, connected over a spring-urged jockey pulley 29 to a pulley 25 splined on the drive shaft 26. Rotation of the feed shaft 31 in the feed nut 30 can thus move the transmission casing and boring spindle up or down in relation to the base. In the gearbox 12, two compound pinions 38, 40 and 43, 45, Fig. 5, fixed to a lay shaft 39 rotatably mounted on a spindle 91 are driven by the engagement of the ,gear 38 with a pinion 37, Fig. 6, on the input shaft 36 and themselves drive two pinions 41 and 44 rotatably mounted on the feed shaft 26 and also a pinion 46 rotatably mounted on a reverse feed shaft 47, Fig. 4. To start the cut- and-feed, a hand lever 72, Figs. 1 and 4, is operated so that a rockshaft 71, by means of a lever 73, moves a dog clutch selector mechanism 52 from a neutral position into engagement with either the pinion 41 or 44 according to the speed of cut required. The drive shaft 26 is then rotated to drive the cutter and through a worm 27, Fig. 6, to rotate a worm-wheel 49 mounted on a hollow shaft 50, Fig. 4. At this stage, the worm-wheel is engaged with the shaft 50 by pressing in a knob 86 so that a cam face on a rod 81 within the shaft forces balls 83 out through slots in the shaft into engagement with recesses in a member 85 fixed to the worm-wheel and so the shaft and a bevel pinion 80 fixed thereto are rotated to drive the feed shaft 31 through a bevel pinion 33 At the end of the cutting stroke, an adjustable part 87, Fig. 2, on the transmission casing contacts a plunger 92, Fig. 4, and depresses a spring-urged pivoted catch 70, Figs. 4 and 8, allowing a compression spring 58 to move an operating member 53 downwardly within the hollow reverse layshaft 47. A V-shaped head 57 at the lower end of the operating member engages one of two prongs 79 on an arm 78 on the rockshaft 71 and rocks the shaft back to the neutral position of the selector mechanism, interrupting the rotation of the drive shaft 26 and locking the rockshaft against engagement of the rotary drive during the subsequent reverse traverse. Also an abutment 66 mounted on a number of balls 67 located in slots in the layshaft and a race in the operating member moves the rod 81 within the hollow shaft 50 outwardly so as to disengage the ball clutch 83, 85 and disconnect the drive shaft 26 from the feed shaft 31. Finally, the downward movement of the operating member 53, after taking up the lost motion provided between it and an encircling cam-faced sleeve 62, Fig. 9, moves the sleeve to force balls 64 outwards to engage recesses in the pinion 46, so clutching the pinion to the reverse layshaft, which, through the pinion 48 fixed thereto and the part 32 of the compound pinion on the feed shaft, rotates the feed shaft so that the cutter is withdrawn from the bore. When the cutter is fully withdrawn, a boss on the casing 14 contacts an adjustable head 56, Fig. 2, on a rod 54 extending upwards from the operating member and raises the member against the spring 58 so that the pinion 46 is de-clutched, the rockshaft 71 is free, the abutment 66 is clear of the rod 81 and the catch 70 is re-engaged. The feed-shaft can be manually rotated by means of the wheel 51, after engaging the clutch 90.