Patent GB-455454-A (GB)
Title: Metal cutting machines
IPC: B23B7/12
Filed: 1935-08-02
Abstract: 455,454. Lathes. FRITZSCH, F. A., 3055, Colerain Avenue, Cincinnati, Ohio, U.S.A. Aug. 2, 1935, No. 22024. [Class 83 (iii)] [See also Group XXIV] A metal-cutting machine tool such as a lathe has a tool support fed by screw and nut mechanism wherein the nut is rotated to move the screw axially therethrough, further means being provided to move the nut axially in the opposite direction to the screw to retard the feed movement at the end of the cut and then to reduce the feed to zero to give a pause before reversal. The work 1 is mounted between centres 2, 3, the latter being carried in a sleeve operated by a handle 10 and clamped to the bearing 8 by a handle 11. The front tool carriage comprises a cross slide 15 mounted on a longitudinally movable saddle 17 while the rear tool carriage comprises a cross slide 21 and longitudinally movable rear saddle 23. The headstock spindle is driven from a main motor 28 provided in the base, and driving a pulley 34, Fig. 2, connected by gears 40, cross-shaft 39, change gears 44, cross-shaft 42, and worm gearing 47 to the spindle. The spindle is connected through a shaft 55 and change gears, Fig. 5, to a pair of parallel shafts 60, 61 connected to the front and rear feed shafts 51, 52 respectively. Shear pins are included in the feed-shaft drives as a safety device. Independent means operated by separate independent electric motors 101, 102 are provided for operating the feed shafts for quick traverse movements in either direction. The shaft 60 is connected through worm gearing 72, Fig. 11, clutch 116, sleeve 76, and worm gearing 77, to a sleeve 79 driving a nut 140 running on a non-rotary screw shaft 80 coupled to the feed-shaft 51, Fig. 15 which is thus moved axially. The shaft 61 is connected by a similar gear train to the rear rotary feed-shaft 52. The shaft 105 of the motor 101 is connected by spiral gears 107, 108, Fig. 11 to the shaft 73. The hub of the gear 108 has cam-like projections 122 so that when the quick traverse motor is running the sleeve 76 is moved endwise thus disengaging the clutch 116 while the sleeve 76 is driven at high speed, the cam parts 127, Fig. 19 resting on the step 123 of the sleeve 76. When the quick traverse motor is stopped the sleeve 76 resumes the position shown in Fig. 19, the clutch 116 of the slow feed being engaged and the motor armature being rotated idly from the sleeve 76. This gives the slow feed movement at the end of which the quick traverse motor is started in the reverse direction to give a quick return movement after which the motor is stopped while the step 128 prevents re-engagement of the low speed clutch, the cycle being then completed. Similar gearing is arranged in the drive from the motor 102. The screw 80, thus moved axially in either direction, is coupled to the feed - shaft by a coupling 148 and the feedshaft has an auxiliary screw 152 rotating in a nut 153, Fig. 28, secured to a cam plate 155. By releasing the coupling 148 the feed-shaft may be rotated independently by hand to position the saddle on the bed to ' which it may be clamped. The cam plate, which has limited movement longitudinally of the saddle has a slot 161 engaged by a roller 166 on a block 169 adjustably secured to the cross slide, a graduated knob 173 being provided for setting of the tool position. A clamp 175 operated by an axially movable cam bar 181, Fig. 30, secures the cross slide to adjusted position. When the feed-shaft moves axially the cam plate 155 moves with it to impart a transverse movement to the cross slide, the cam plate being readily interchangeable for different cross slide movements. Further axial movement of the feed screw then causes movement of the saddle in either direction along the bed. The nut 140 on the shaft 80 has end thrust bearings 216, 217 in a sleeve 201 which is normally held against axial movement by a roller 203 engaging a cam groove 215 in the sleeve and having endwise adjustment to take up wear. A longitudinal movement is imparted to the nut 140 in the opposite direction to the feed movement of screw 80. For this purpose an intermediate sleeve 222, Fig. 15, splined on the nut has clutch teeth 224 which may be engaged to rotate the sleeve 201 with the feed nut. When this occurs the cam groove 215 causes the sleeve 201 to be moved axially thus modifying and reducing the feed speed of the tool. At the end of the feed the nut movement thus produced is practically equal and opposite to the feed speed of the screw so that the feed stops to give a tool pause before reversal. The intermediate sleeve is operated to engage the clutch 224 by means of a finger 247 on the coupling 144 which acts through a segment 242 and rack bar 234 to operate a finger 227 to engage the clutch. The reverse movement of the sleeve 201 at the end of the feed is cushioned by a spring plunger 258, Fig. 12, coacting with a shoe 261. The rear feed-shaft 52 carries a worm 276, Fig. 27, driving a cam drum 285 for operating the rear cross slide for facing, grooving, cutting off or like operations the rear saddle being adjustably secured to its longitudinal ways. The cam coacts with a roller carried by a block which is adjustably connected by a micrometer screw 291 with the rear cross slide. After adjustment the block and slide are clamped together at 297. If desired the rear carriage may be operated by similar mechanism to that described for the front carriage or the latter may be similar to the rear carriage. The cam drum is driven at feed speeds from the spindle and at quick traverse speeds from the motor 102 through mechanism similar to that described above. The terminal portions of the cam drum groove have no lead so as to enable the tool to clean up the cut before reversal. Braking means for the rear tool movement comprises a fluid pump supplied from a control valve 32, Fig. 26. At the end of the reverse quick traverse of the motor 102, a tappet operates on arm 341 to move a piston 335 of the valve so as to choke the pump output and apply the brake. Means may also be provided for selectively latching the cam plate to the carriage and carriage to the bed to ensure the correct sequence of movement of the front tools. If it is desired to feed the front tools in a direction away from the lathe axis the cam plate 155 is reversed on its longitudinal axis. Electrical control is provided for timing the various operations of the machine. The double pole switch 401, Fig. 35, comprises contacts 403 controlling the main motor 28 and contacts 402 controlling the reversing of the motor 101. Thus while the traversing motor is reversed to return the tools the spindle is stopped by the sleeve 201 which carries a shoe 404, Fig. 16, which operates an arm 409 to make a contact 413 for operating the switch 401. This action occurs when the cam sleeve 201 is moved axially at the final part of the feed movement. An arm 421, Fig. 15, controls a switch 428 to open the forward circuit of the motor 101 at the end of the tool approach movement. A tappet 432 adjustably positioned in a bore of the screw 80 coacts with the switch arm 421 so that at a predetermined point in the outward movement of the screw 80 the tappet engages the switch arm and engages the feed movement. The switch 428 is reset on the return movement. A collar 441 on the spindle 80 operates a switch 449 to stop the reverse traverse of the tool. In the form shown the rear tool slide has automatic cross movement only, the quick forward movement being initiated by closing the switch 452, Fig. 35, in the forward circuit of the main motor and a switch 453 in the quick traverse motor circuits. At a predetermined point a switch 454 in the circuit of motor 102 is broken by the tappet wheel mechanism whereupon the slow cam feed is effective at the end of which the main motor circuit is opened and switch 461 closed by the tappet 466 to initiate the reverse movement of motor 102. The switch is held closed by relay mechanism. At the end of the return movement the motor circuit 102 is broken to complete the cycle by a tappet 353. When, at the end of the tool feed movements the main motor is de-energized switches are closed in the reversing circuit of this motor to apply a brake thereto. As soon as reverse movement begins the switches are automatically opened and the motor stops. Either or both the motors 101, 102 may be included in the automatic circuits of the machine this being effected from selectors 494, 501, Fig. 35. A stop button 541 may be actuated to break all the electric circuits of the machine. The performance of both turning and facing cycles is described in the Specification.