Patent GB-605323-A (GB)
Title: Improvements in or relating to machine-tools, especially screw-cutting lathes
IPC: B23G1/04
Filed: 1945-04-06
Abstract: 605,323. Lathes. ETABLISSEMENTS AERA, SOC. A R.L. April 6, 1945, No. 8541. Convention date, Dec. 23, 1943. [Class 83 (iii)] A thread-cutting lathe or other machine tool in which the cutting tool has both a longitudinal and a transverse movement includes a combination of means for effecting the required transverse movement comprising a return cam for controlling the engagement and disengagement of the tool at the beginning and end of each traverse, an advance cam which is adapted to effect an advancing of the tool at each traverse, and means for controlling the advance cam, these latter means being such as to enable the number of traverses for a uniform total depth of cut to be selected at will. The headstock spindle 3, Fig. 4, is driven by V-belts from an electric motor 55 provided with a speed controlling device 62 and driving the pulley 83 through a clutch and brake arrangement 66, 69 respectively, Fig. 5 (back view). The clutch is disengaged and the brake engaged automatically at the end of a complete thread-cutting operation by a cam 15, Fig. 4, operating the release latch of the brake device through linkage 48-51. The headstock spindle may be driven directly from the pulley 84 or through a back-gear train, operated by sliding gears, and drives, through sliding and pick-off gears, the main feed shaft 2. The cam 1 for the longitudinal screwing feed is mounted on the end of shaft 2 and operates a slidable rod 8 provided with a roller 7 which is held against the cam by a spring 9. The rod 8 has its rearward movement limited by an adjustable screw stop 112. The tool saddle 117, Figs. 13 and 16, carries a subsidiary longitudinal slide 10 to which is secured a bracket with a clamping handle 151 so arranged that rotation in one direction clamps the slide 10 to the rod 8 while rotation in the opposite direction lifts a bridge-piece 149 to clamp the slide 10 to the saddle 117. The saddle is adjusted along the bed by rack and pinion means and may be clamped in adjusted position to the bed. The slide 10, Fig. 12, carries a transverse slide 130, also rotatably adjustable, and is pressed away from the work by an adjustable, compression spring 114, a roller 159 secured to a pin carried by this slide engaging a cam bar 161 for imparting a copying or tapering motion to the tool. The cam bar 161 is mounted on a plate 162 which is capable of limited rotative adjustment to vary the taper. A further plate 163 secured under the plate 62 is adapted to move transversely in guides on the saddle and carries at one end a movable finger 19 for contacting a control cam 17. The finger is provided with a quick release cam 177 operated against spring-pressure by a handlever 181 so that the spring 114 may quickly withdraw the tool from its cutting position if required, the cut is restored by operating the lever in the reverse direction to force the finger 19 into its original position against the cam 17. The tool 11 is carried in a square rest 139 rotatably adjustable on a subsidiary transverse slide 133 which may be adjusted relatively to the slide 130 by screw and nut mechanism. Gearing and cam means are provided, driven from the shaft 2, for' in-feed of the tool and withdrawal at the beginning and end of each cut, respectively, and for increasing the amount of cut at each new traverse, the operations being stopped automatically at the end of a predetermined number of traverses. This is accomplished by the shaft 2 driving, through gears 6, 14, Figs. 2 and 3, a cam 12 at the same speed as the main screw-threading cam 1. The cam 12 has a depression A, B, which withdraws the tool for the non-cutting quick return movement of the tool slide and rod 8. This cam also carries a pin 20 which oscillates a slotted lever 21 forming part of a sleeve 22 rotating about the shaft 2. The opposite end of the sleeve carries a rack segment 23 which oscillates a gear-wheel 24 to which is connected a ratchet feed gear 28, 29 for a further cam 15. A number of ratchet feed wheels may be employed operable selectively and the stroke of which may be controlled by rotatable masking plates 30. The cam 15, which has a gradual rise, may thus be given a small or big stepped motion according to the increase in depth of cut required at each new traverse. The cam 15, as previously explained, carries a stop which operates the linkage to throw out the clutch in the motor drive and apply the brake when a thread is finished to the required depth. The motions of the cams 12 and 15 are superimposed through the arms 39, 40 and rod 41 on a pivoted lever 35 which transmits the motion to a longitudinal shaft 18 to which is slidably keyed the cam 17. The latter is adjustable between collars 44, 45, Fig. 3, to bring steeper operating portions into use as required and may be a composite structure, the elements of which are relatively adjustable to vary the profile. An adjustable stop 155, Fig. 4, is provided on a block 154 for limiting the tool carriage movement. The tailstock, Fig. 18, has the centre arranged in an adjustable spring-pressed sleeve 190 with axial fine adjustment from a hand wheel 199 and quick adjustment through a rack 191 and hand wheel-operated pinion 195. The latter adjustment is adapted for quick release by a ratchet 198 controlled from a lever 200, the centre returning under control of a coil spring arranged about the axis of the hand wheel 197, return motion being limited by an adjustable stop 203.