Patent GB-277322-A (GB)
Title: Improvements in metal turning lathes
IPC: B23B3/00
Filed: 1927-09-02
Abstract: 277,322. Potter & Johnston Machine Co., (Assignees of Curtis, M. S.). Sept. 10, 192G, [Convention date]. Lathes; headstocks; speed-controlling mechanism.-A metal-turning lathe comprises a worksupport, a tool support, means for giving them relative movement, independent means for feeding the tool support and means for securing one or more tool-holders in various positions on the tool-support, comprising a replaceable table on which the holders are removably mounted. The chuck-spindle 14 is driven from a constant speed pulley 16 through gears 33, change gears 30, clutch 23, and either of the gear trains 20, 21. The gear 20 is loose on the clutch shaft 22, while the gear 21 is connected therewith by a ratchet which is over-run when the clutch is engaged with the gear 20. The clutch is operated through linkage 25 from tappets on a cam drum 27. A second cam drum 87 acts on a roller under the tool-saddle 13 to give it movements to and from the work, the roller being carried on an adjustable slide to vary the stroke in relation to the work. The two cam drums are driven by bevel and worm gearing 84, 89 respectively from a shaft 15, this shaft also driving the independent forward and reverse feed movement of the toolholders carried by the saddle 13 and being itself driven through a clutch controlled at 83 from the cam drum 27, connecting with a shaft 70. The latter may be driven at a constant high speed for idle movements by a chain connection 37 with the belt pulley 16, or at a variable cutting speed synchronized with the chuck-spindle speed through gearing 40, chain 43 and further change speed and two-speed reduction gearing 50, the two drives being controlled by a clutch 79 operated from the cam drum 27 and embodying over-running ratchet gearing. Feed motions; reversing-mechanism. - The independent drives for the tool-holders 99, Figs. 1 and 3, are derived from two interconnected shafts 103, 104, Fig. 3, the former of which is rotated through gearing 127, Fig. 1 from a shaft 124 connected by a clutch 128 with an elongated pinion 123. The latter is driven in opposite directions by a clutch-pinion 135, Figs. 1 and 5 rotatably but axially fixed on a shaft 136 which is non-rotatable but mcved axially by a yoke 137 and a cam 138. The two gears 132, 133 with which the gear 135 may he made to engage are rotated continuously in opposite directions through gear trains 131, 129 from the shaft 15, the cam 138 being driven intermittently from the gear 133 by a pin 140 thereon engaging at each revolution with a four-slot Geneva wheel 141, carrying two opposed pins 143 meshing with the teeth of a gear 144 to which the cam is attached. A fixed pin 148 engages a radial slot in a flange 146 of the clutch gear 135 when the latter is in the neutral position, the action being such that the clutch-gear always disengages from either of the gears 132, 133 in such a position that the slot is opposite the pin 148 and also moves out of neutral position with the clutch parts ready to engage either of the gears. The cam 138 has straight portions for maintaining the clutch-gear 135 in the forward, reverse or neutral positions, the changes through neutral always taking place while the cam is receiving its intermittent rotation, and the length of the forward part of the cam being always equal to the length of the reverse part so as to withdraw the tools to their initial positions. Saddles; slide - rests; copying - mechanism; cutting-off mechanism.-The saddle 13, Figs. 1 and 3, carries a removable base-plate 97 located by dowel pins, to which the tool-holder slides 99 are adjustably attached. The attachment may be by means of T-slots 149 or holes drilled in the plate 97 at the required positions. A separate plate may be provided for each set-up of the slides, the setting-up being in each case performed while the plate is removed from the machine. The plate may be laterally adjustable within guide strips 151 on the saddle by means of a screw 152, or it may be pivotally adjustable on a base attached to the saddle. The base 98, Fig. 9, of each tool-slide carries a worm-cam 100 engaging a roller 102 in the slide 99 and each cam is driven separately from the shafts 103, 104, by a shaft 110 connected by worm and bevel gearing slidable thereon and enclosed in casings 118 slidably connected to the side of the saddle 13. Some of the slides 99 may be inclined to the lathe axis in which case the drive is taken from a casing 119 having a rotatably adjustable cover 120 and a bevel drive directly on the shaft 110. Contour work may be operated upon without the aid of formers by moving the saddle and toolslides simultaneously in intersecting directions. In operation, while the machine is at rest the work is inserted in the chuck. On starting the machine the feed shaft 15 is driven directly from the pulley 16 and the cam drum 87 is revolved rapidly to advance the saddle 13 to the work until the clutch 79 is operated by the cam drum 27 to drive the shaft 15 at the slow cutting speed. This may take place before the forward limit of the saddle is reached so that cutting can take place before and during the independent feed movements of the slides 99. The cutting operations may take place during a single revolution of the cam drums, and the rotation of the latter is thereupon stopped while the work-piece is changed. The clutch levers controlled by the cam drum 27 are also adapted for hand control.