Patent GB-633825-A (GB)
Title: Thread grinding machine
IPC: B24B19/02
Filed: 1946-02-18
Abstract: 633,825. Screw-thread grinding machines. DALZEN, W. R., DALZEN, F. R., and DALZEN, L. M. Feb. 18, 1946, No. 5029. Convention date, July 23, 1945. [Class 60] A thread grinding machine includes a cradle pivotally mounted on the top of the base of the machine and carrying a longitudinal reciprocal work slide movable parallel to said cradle and spaced from a longitudinally adjustable grinding wheel housing slide mounted also on said top, said grinding wheel housing slide having an inclined guide means extending substantially at right angles to the direction of movement of said longitudinal reciprocal work slide on said cradle, and a grinding wheel head supporting slide mounted for reciprocal movement on said guide means. A cradle 13, Fig. 14, pivotally mounted on the base top 12, has a work slide 14 mounted thereon by ball bearings; the grinding wheel 422, Fig. 1, is mounted in wheel head slide 16 adjustable upon inclined slideway 200, Fig. 14, on grinding wheel housing slide 15 adjustable longitudinally of the machine on slideway on the base top 12. Driving shaft 17, Fig. 13, drives through bevel gears 22, 23 a shaft 27 which drives by gear 30 and idler 33 a gear 35 ; a shaft 37 secured to the work slide 14 so as to reciprocate therewith is feathered through the gear 35 so as to be rotated thereby and carries mitre gear 48, Fig. 18, meshing with mitre gear 67, Fig. 4, on inclined shaft 68 mounted in the work slide 14 ; the shaft 68 carries worm 77 driving worm-wheel 80 on a hollow shaft 82 carrying work spindle centre 86, Fig. 3, and spindle drive plate 88. An adjustable tailstock 380, Fig. 5, is provided. The sleeve 82, Fig. 3, carries gears 90, 91 engageable respectively with gears 93 or 94, Fig. 5, shiftable, by an actuating lever, on countershaft 95 which drives, through change gear 103 and intermediate change gears, a change gear 116, Fig. 3, on a hollow shaft 118 to which is secured by draw-bar 132 a lead screw 129 engaging a nut assembly carried by a bracket 134 on the cradle. The nut assembly comprises two nuts 187, 191, Fig. 12. The nut 187 is rotatably adjustable by means of a hand wheel 162 acting through gearing for longitudinal indexing of the work, e.g. for grinding multiple threads or for picking up the lead of an existing thread, or for grinding separate non-connecting annular threads on a work piece; a spring-pressed pin 155 engages locking slot 156 in index disc 157, a manuallyactuated handle 144 being provided for withdrawing the pin from the slot. Locking in the adjusted position is effected by screw 180. The nut 191 is adjustable relative to the nut 187 for obtaining the desired degree of fit between the lead screw and nuts, The shaft 27, Fig. 13, drives through change gears 57, 58 a shaft 59 carrying a relieving cam 64, Fig. 18, which engages a block 325, Fig. 19, on a lever 326, the other end of which has a block 336 engaging the underside of the cradle 13 ; the cradle has trunnions 52, 53, Figs. 13 and 18, embracing swivel cones 42, 50 supported by the base top and surrounding the shaft 37. The fulcrum 327, Fig. 19, of the lever 326 is adjustable and an indicator is provided to show the position of the fulcrum and hence the amount of relief imparted. A handle 350, Fig. 13, is provided which through crank and link 339, Fig. 19, draws lever 326 down so as to remove block 325 from range of action of the cam. The grinding wheel slide 15 is longitudinally adjustable on dovetail slideway 226, Figs. 13 and 14, on the base top by means of a screwed shaft 226<SP>1</SP>, Fig. 13, mounted on the base top and engaging a nut 227<SP>1</SP> on the slide 15. The grinding wheel housing slide 16, Fig. 7, is movable in inclined slideway 200 on the slide 15; a nut 205 rotatably mounted in a part 203 of the slide 16 engages a screw 210 which at its lower end is slidably splined to shaft 213 having mitre gear 222 meshing with mitre gear 223 slidably splined on a shaft 224, Fig. 13, mounted on the base top; the shaft 224 has a mitre gear 235 (which can be restrained against rotation by a brake band) meshing with mitre gear 237 on a shaft 238 having hand wheel 243; thus adjustment of slide 16 on slide 15 may be effected manually. The nut 205 has secured thereto a sleeve 206, Fig. 7, slidably splined in  a ratchet-wheel 255 engaged by pawls carried  by a slider 251, Fig. 6, which is reciprocated by means of a bell-crank lever 259, biassed by spring 262 and operated by a solenoid 271; the free end of the lever 259 contacts a cam 265 which can be indexed around so as to vary the stroke of the slider 251, which is pressed against the actuating end of the lever 259 by a spring 251<SP>1</SP>. The screw 205 can be moved axially by means of a lever pivoted at 285, Fig. 7, and actuated by a crank 276 rotated by an electric motor 274 under push-button control; cams 289 on the crank disc co-operate with a limit switch operating member 290, so that on pressing the push-button, the crank makes a half-rotation to elevate the grinding wheel head for inspection of the work or changing the same and for dressing the grinding wheel, and on again pressing the button the crank makes a further half-rotation to lower the grinding wheel head to its original position. The grinding wheel 422 is carried by a drum 418, Fig. 7, rotatably mounted in part 417 of the slide 16: rotary adjustment is effected by a hand wheel actuating a worm meshing with an arcuate rack on the drum 418; for locking the drum 418 in adjusted position, an arcuate part 426 of the drum carries a bolt 427 engaging a T-slot in an arcuate part of the support. The motor 442 driving the grinding wheel by means of a belt is mounted on a plate 435 pivoted at 436 to the drum, and adjusted by one or more adjustable plugs 436<SP>1</SP> supported in rubber blocks, thus affording a resilient mounting for the motor and means for tensioning the driving belt. Dogs 142, Fig. 4, carried by the work slide 14 are arranged to engage the upper end of lever 365, Fig. 16, pivoted to cradle 13, the lower end 367 of the lever being linked to a second lever 368 pivoted to base top, the upper end of lever 368 having a handle 373 for manual operation, and the lower end carrying a block through which extends a stud 370, the ends of which engage limit switches for arresting the traverse. The motor for. rotating the work and traversing the work slide and the motor for rotating the grinding wheel are direct current motors delivering constant torque regardless of load, speed adjustment being by rheostats; if alternating current supply is used, a rectifier is used to supply direct current to these motors. Wheel trueing.-A grinding wheel trueing housing 446, Fig. 28, is vertically adjustable, by screw 448, on slide, 447 which is in turn vertically adjustable, by manually-adjusted screw 452, on a bracket 451 attached to the grinding wheel supporting head. Manual adjustment of housing 446 is effected by hand wheel 456 on a shaft 454 which through bevel gears 457, 458 rotates the screw 448. In addition, a pawl, actuated by a solenoid 459, co-operates with a ratchet-wheel 464 on the shaft 454. When the grinding wheel is retracted from the work, the solenoid 459 is energized to feed the truer into the grinding wheel; solenoid 271 is also energized to feed the grinding wheel towards the work by an amount sufficient to compensate for the reduction in grinding wheel diameter caused by the trueing. The trueing device itself is constructed as in U.S.A. Specification 2,439,263.