Patent GB-803522-A (GB)
Title: Improvements in or relating to a tracer-controlled lathe or the like
IPC: B23B3/28
Filed: 1955-05-06
Abstract: 803,522. Copying-lathes. SUNDSTRAND MACHINE TOOL CO. May 6, 1955 [Aug. 11, 1954], No. 13173/55. Class 83 (3). A tracer-controlled lathe has a carriage movable in one direction relative to a worksupporting spindle, a tool slide mounted on the carriage for movement in another direction relative to the carriage, a tracer mechanism including a tracer-control unit on the tool slide having a template follower engageable with a template for controlling movement of the tool slide in said other direction, means pivotally mounting the tracer-control unit for adjustment about an axis to adjust the follower in said other direction, and means for pivotally adjusting the tracer-control unit to take a number of cuts on a single workpiece under control of a single template. The work-supporting spindle 16, Fig. 2, is driven from a motor 20 through a multiple-belt drive 22, a clutch and brake, having a clutch-coil 23 and a brake coil 25, and pick-off gears 24. The carriage 12 is driven by a feed screw 28 which is driven from two sources to provide a forward feed and a rapid return. A chain 29 drives, from the workspindle 16, a manually-controllable feed clutch 30, pick-off gears 32, differential or planetary gearing 36, shaft 38 and gearing 42. The feed screw may also be driven from a high-speed rapid-return motor 44, multiple-belt drive 46, brake 48, shaft 50 and again the planetary gear 36 &c. The brake 48 is electrically controlled to be released on energization of motor 44. and applied when this motor is de-energized. The spindle motor 20 and the high-speed motor 44 are automatically controlled to move the carriage 12 through a cycle of operations, to include up to four cuts on a workpiece. The motors are controlled by limit switches 1LS, 3LS, 4LS, 5LS, Fig. 2b, which are actuated by adjustable dogs 82-85 on a disc 78 driven from the gearing 42, Fig. 2, in the carriage drive. The dogs may be adjusted on the disc to actuate the switches to provide succeeding cuts of progressively greater length. The lathe may also be provided with a rear tool slide 61 arranged for transverse movement on the bed in timed relation to the front carriage and moved by a cam drum 72 driven also from the shaft 38. A lost-motion device 104-107 may be incorporated in the drive to the carriage so that the rear tool slide is actuated to effect a facing operation after the movement of the carriage has taken place. Copying attachment.-A hand-operated transversely adjustable slide 12<SP>1</SP>, Fig. 2, on the carriage supports a base plate 112, Fig. 3, carrying a tool slide 113 movable by hydraulic piston- and-cylinder means 123, 125. The slide 113 may carry a turret tool rest 114 with two tools 115, 116, the turret being indexed by rack and pinion and fluid-pressure cylinder 120, the latter either manually or automatically controlled by a valve 250. Pressure for moving the tool slide 113 is provided by a pump and a motor 149, and is controlled by a valve unit 146 which carries a stylus 151. The stylus engages a template 153 secured to the bed, and normally movement of the stylus over the template gives a corresponding tool movement through known valve means. At the end of a feed stroke, however, a solenoid-operated device in the valve unit is deenergized to allow a rapid withdrawal of the tool slide to clear the work. The tool is automatically restored to its working position at the start of a new feed stroke. The valve unit and stylus are pivoted at 135 to a bracket 133, the latter being mounted for transverse adjustment on a bracket 131 which is in turn longitudinally adjustable on an arm 130 extending from the tool slide. The valve unit is biased towards the bracket 133 by a spring 140. The pivotal axis 135 of the valve unit is slightly inclined to the centre line of the lathe so that when the stylus is stepped slightly away from the template, for adjusting the cut, the tool is given a transverse increase in cut, and also a slight longitudinal increase so that it takes a cut on the face of the workpiece in addition to the longitudinal cut. The increased cut on successive strokes is obtained through a cam piece 142 on the tilting valve unit bearing successively on stops 172 of varying radii on an indexible drum 171. The latter is indexed at the end of each return stroke of the carriage by a pawl 194 engaging studs 174 projecting from a disc on the same spindle 170 as the drum 171. The pawl, which is pivoted at 198 on a slide 185 and is biased towards the projections, is moved by an arm 204 connected to the slide which is universally coupled to a further arm 205 adapted to strike a stop 207 on the bed when the carriage returns to its starting position. A workpiece W<SP>1</SP>, Fig. 4a, is turned in a three-cut cycle comprising rough, semi-finish and finish cuts R<SP>1</SP>, S<SP>1</SP> and F<SP>1</SP> respectively. The final diameter may be controlled by a gauge pin secured to the bracket 133, in lieu of one of the indexible pins 172. This gives greater uniformity where a number of similar workpieces are being produced. A further set of radial pins 175 is provided on the disc 173, and these serve to actuate an arm 180 and limit switch 7LS, which conditions the control circuit for starting by a manual switch, and stops the cycle at the end of the prearranged number of cuts.