Patent GB-478757-A (GB)
Title: Improvements in grinding machine
IPC: B24B19/02
Filed: 1936-10-20
Abstract: 478,757. Grinding screw - threads, taps, hobs, &c. JONES & LAMSON MACHINE CO. Oct. 20, 1936, No. 28554. Convention date, Oct. 25, 1935. [Class 60] A machine for grinding screw-threads, taps, hobs, or helical or circular grooves and the like comprises a rotary work holder, a grinding- wheel, means for producing traverse between the work on the holder and the wheel, feed means for effecting relative movement between the wheel and the work transverse to the direction of traverse, a lever operatively connected intermediate it ends with the feed means and a plurality of independent means acting on the lever for'modifying the relative transverse movement, at least one of the independent means acting at each side of point of connection with the feed means. Headstock construction. The headstock 4 comprises a spindle bearing block with inclined and vertical faces bearing on the corresponding faces of a traversing carriage 3 to which it may be clamped. The headstock spindle 20, Fig. 15, is mounted in ball-bearings 22 and at its nose portion 21 is provided with a guard 23 preventing the entry of foreign material. In order to prevent overrunning of the spindle when its drive is reversed or reduced to a lower speed, a brake shoe 31 keyed to the spindle is maintained under the constant action of a spring applied brake ring 25. The spindle is driven from a splined shaft 56 through gears 55 and 40 which latter is journalled in a sleeve 35 keyed to the spindle and has secured in an annular groove 52 a driving block which engages, according to its direction of rotation, either a segment flange 39 or an abutment block 47 secured to a flange 36 on the sleeve 35. The spacing between the block and the flange 39 and block 47 is so adjusted that on reversal of the drive all the backlash in the gear train is taken up when the block is in driving engagement. Tailstock construction. The tailstock 5 comprises a block which may be clamped to the carriage 3 in a similar manner to the headstock and provided with a slide 75, Fig. 23, in which is mounted the centre 76. The slide is adjustable transversely by means of oppositely tapered jibs 81, 82 and for longitudinal adjustment is provided with a rack co-operating with a gear wheel on a rock-shaft operated by a lever 95. Grinding - wheel mounting. The grinding wheel 100, Fig. 10, is carried by a shaft 101 driven from a motor 109, Fig. 2, all these members being mounted on a cradle having an arcuate bearing portion 112, with its centre of curvature substantially concentric with the centre of the grinding wheel, by which it is carried on a saddle 113 adjustable to and from the traversing carriage 3 on rollers 126. The angular position of the saddle is determined, according to the helix angle of threaded work being ground, by means of nuts 115 and thread rods 116 pivoted to the saddle and this position is indicated by means of a scale and pointer. Work rotating and speed control mechanism. The work is supported between the headstock and tailstock and is rotated from a motor 200, through a coupling 202, Fig. 25, shafts 203, 206 and 208, gear-box 209, shaft 210, coupling 212, shaft 213, a relatively long gear 217, a gear 21 driving a shaft 220, gear casing 221 and the splined shaft 56. For two-way grinding, that is when the work is rotated in opposite directions during traverse in different directions, the parts within the gear-box are as shown in Fig. 26. The shaft 208 drives a shaft 230 through change-gear mechanism including a gear 231 and a sliding gear sleeve 233. Shaft 230 in turn drives a shaft 245 through sliding gear change sleeves having gears such as 232, 250 so that there are nine possible speeds for the shaft 245 for one speed of the shaft 208. In the two-way grinding position sliding and fixed clutch collars 255 and 256 respectively are brought into operative engagement so that a gear 257 on the collar 255 drives a gear 258 which is journalled on a shaft 210 but may be clutched to the shaft by a clutch 259 for one direction of rotation. To rotate the shaft 210 in the other direction clutch 259 is released and a similar clutch 260 is engaged. The clutches 259 and 260 are actuated by a rock lever 261 from a bar 262 and a shift collar 264, Fig. 25. With the clutch 260 in engagement the drive from the shaft 245 is through a shaft 265, a pinion portion 266 of the clutch collar 256 meshing with a gear 267 journalled on the shaft 265 and clutched thereto by a clutch collar 268 so that a gear 270 keyed to the shaft 265 drives the shaft 210. The shaft 210 may be driven at other speeds from the gear 267 by employing change-gear mechanism associated with a shaft 278 and another clutch collar 284. The clutch collar 255 is moved axially by a shift lever 290 engaged at its lower end by a push rod operable through a hand wheel and rack. The lever 290 also moves a sliding gear sleeve 300 mounted on a splined part of the shaft 208. For one-way grinding the clutch 255 is disengaged and one of the gears 301, 310 on the sleeve 300 meshes with the corresponding gear 302, 311 on a sleeve 303 journalled on the shaft 230. The shaft 210 is then driven in one direction through a gear 304, the gear 257 on the released clutch collar 255, gear 258 and clutch 259. The drive in the other direction with the clutch 260 in operative engagement is as previously described and has the same speed range but for the drive through the clutch 259 during the idle traverse of the work carriage only two relatively high speeds determined by the position of the sleeve 300 are available. When cutting fluted articles such as taps, the clutch collars 268, 284 may be operated to give a higher speed when the flutes are presented to the grinding wheel than when the lands between the flutes are presented. Overrunning of the shaft 210 is prevented by a brake 315 operated through a push rod from the lever 336 controlling the shift collar 264 of the clutches 259 and 260 so that the brake is applied by a spring during the time the clutches are being reversed. Traversing carriage and spindle reversing mechanism. The carriage 3 carries a lead screw 400 which passes through a nut 406 held against axial movement. The nut may be rotated by a hand wheel 403 for a manual adjustment of the carriage. The screw may be rotated from the gear casing 221 from which the work shaft 56 is also rotated through a manually operable clutch 420. The reversal of the drive is effected by power. As the work carriage 3 approaches either end of its stroke, one or other of a pair of adjustable dogs 500 engages the arm 502 of a rock-shaft 505 and so depresses a rod 508, Fig. 35, and through a rocking lever 509 raises an arm 513 forming part of a yoke 514, Fig. 33a so rotates a hub 516 mounted on a rock-shaft 518. The hub also carries an arm 520 having a roller 521 engaging a cam 530 mounted on a shaft 532 and having two diametrical recesses 580, Fig. 37. The other end of the rock-shaft carries an arm 540 having pins 541 and 542 engaging a cam 544 secured to a shaft 545. The shaft 545 is slidable axially and may be clutched to a shaft 547 by clutch elements 552, 553 which engage under the action of a spring when the arm 540 is rocked away from the cam 544. Shaft 547 is driven from the motor 200 through shaft 206 and gears 551 and 550, Fig. 25. When the clutch elements engage the lay shaft 532 is rotated through gears 570, 571, the cam roller 572 at the end of the shaft actuates the lever 336 to reverse the clutches 259 and 260. During the rotation of the lay shaft the cam 530 acting on the roller 521 keeps the arm 540 out of engagement with the cam 544 until the shaft has made half a revolution when the roller 521 enters one of the recesses 580 permitting the pin 542 to engage a notch to stop the shaft 545 in a definite angular position. As will be later explained, the half revolution of the lay shaft may be interrupted to allow truing of the grinding wheel while the clutches 259 and 260 are in neutral position. The rod 508 may be depressed manually by means of a hand lever 506 but this is made ineffective except during the stationary periods of the lay shaft by mean of a flange 533, Fig. 33a which holds the end of the arm 513 out of the path of the rocking lever 509 at all other times. Grinding-wheel slide-actuating mechanism. The lay shaft 532 also controls the feed of the grinding-wheel carriage 113 to and from the work and for this purpose is provided with a cam 600 in a groove 601 of which rides a follower 602 journalled in an arm 603 of a rock-shaft 604, Fig. 51. This rock-shaft extends to the front of the machine where it carries a bar 605 having a longitudinal groove to receive adjustable dogs 610 which at the rotation of the lay shaft are rocked to engage pivoted arms 613, 614 and thus move upwardly a bar 619 which operates through a push rod 620 and pawl 635, Figs. 7 and 50, to rotate a ratchet wheel 632. If one of the dogs is removed rotation of the ratchet occurs at one end of the traverse only. The ratchet is keyed to a pinion 636 meshing with a gear ring 637 keyed to a sleeve 641 threaded on to a screw 642 at the end of a non-rotatable but axially moving bar 645 attached to the carriage 113 through a sleeve 657. Spring-tensioned chains 660 are provided to take up backlash. The axial movement of the bar 645 due to the ratchet may be modified by a two-armed lever 649 which is pivoted on pins 648 so as to be operatively connected with the sleeve 641. The upper end of this lever may be operated upon by a cam 671, Fig. 11, carried by the work carriage 3 or by another cam 675 when for example grinding tapers or holes as will be explained later. A cam 680 operates on the lower end of the lever to move the carriage to and from the work at the end of each traverse for one-way grinding and for this purpose the cam is reciprocated by a rooking lever 691 mounted at its lower end on an eccentric of a shaft 697, Fig. 35, rotated by a pini