Patent GB-647915-A (GB)
Title: Improvements in or relating to indexing devices or mechanisms such as a dividing head, circular table and the like
IPC: B23Q16/06
Filed: 1947-10-21
Abstract: 647,915. Gearing, variable speed. HINDS, S., and JAUCH, R. J. Oct. 21, 1947, No, 28111. Convention date, Feb. 27. [Class 80(ii)] (Also in Groups XX and XXII] A variable-speed mechanism which is embodied in indexing mechanism for dividing a circle into any desired number of equal sectors (see Group XXII) comprises ten vertical rotatable shafts 1, 2......, which are shown in developed form in Fig 21 and are arranged in a circle around the axis of a shaft 116, being provided with gears 212, 214...... for selective engagement by three gears 284, 297, 242, Fig. 4, mounted, respectively, on a toothed carrier 286, toothed carrier 292, and ring gear 242. The gears 212, 214....... are driven from the shaft 4 of the gear 218 at speeds which increase in equal steps, the final gear 230 being driven at ten times the speed of the gear 212. The shaft 4 is itself driven from the hand-driven shaft 116 through gears 114, 112, 110, and the outlet shaft 62 of the device is also driven from the gear 110 in either direction as determined by which of two gears 80 on a rotatable plate 78 is swung into the gear train. The gear 284 can be moved into engagement with the gears on any of the first nine shafts or a mutilated can mesh with the gears on any of the ten shafts, and the gears 297, 242 gear 240, Fig. 21, serving as a fixed stop. The mechanism is such that the speed of rotation ofa sleeve 280 on the shaft 116 is modified in accordance with whichever of the gears 284, 297, 242, or combination of these gears, is in mesh with the gears 212 214...... Assuming, for example that the fourth gear 218 is in mesh with the gear 242 as shown in Fig 4, rotation of the shaft 116 causes the gear 218 to act, through gears 248,258 and a double gear 260, 264, on a rotatable carrier 262, to rotate a sleeve 268 which is rotatable on the sleeve 280; a gear 270 on the lower end of the sleeve 268 then acts through a double gear 272, 276 on a rotatable carrier 274 to rotate the sleeve 280. If the gear 284 also engaged one of gears 212, 214......., it would rotate the carrier 274 through the gear 282 so as to cause a modified movement, first of the gear 272, and then, through the gears 276, 278, of the sleeve 280. The additional engagement of one of the gears 212, 214... by the gear 297 would cause the carrier 262 to be rotated through the gears 262, 264 to modify the rotation of the sleeve 268 and, through the gears 272, 276, 278, the sleeve 280. The resultant modified movement of the sleeve 280 is, therefore, in accordance with whichever of the gears 212, 214...... is effective. To provide the desired setting, the toothed carriers 286, 292 and ring gear 246 are operated from gears 338, 368, 394,  Fig. 4, mounted respectively, on shafts 300, 302, 304 controlled by knobs 306, 344, 376. The shafts are connected through gearing with dial plates 318, 356, 390,Fig. 2, visible through windows 320, 358, 392, arid each shaft is so mounted that it can only be operated after depression against a spring so as to release it from engagement with a detent.  To stop rotation of the sleeve 280 and shaft 116 after the desired movement, spring-pressed pawls 540, 542, ,582, 606,Figs. 3 and 5, co-operate with ratchets 410, 414 fixed on the sleeve 280 and unitary ratchets 446, 448 mounted on a gear 442 rotatable on the sleeve 280. Both the gear 442 and a gear 448 fixed on the sleeve 280 mesh with a gear 420, the gear 418 thereby serving to drive a resettable counter forregistering each sub-division of a circle.The ratchet 410 has a singlenotch registering with one of five notches in the ratchet 414, and the ratchets 446, 448 have one and ten notches, respectively. A cam 450, Figs. 2 and 3, which is:journalled for rotation as permitted by a spring 468, is provided withfour notches for co-operationwith the pawls; the setting of the cam determines which pawls engage the notchesand are therefore effective to co-operate withthe ratchets for stopping thesleeve280 after the desired interval. The pawl 540 engages only the ratchet 414 and stops the sleeve 280 after one-fifth of a revolution. The pawl 582 co-operates with the three ratchet 410, 444, 448, and, because of the ratio of the teeth of gears 418, 442, notches in these ratchets are only aligned to receive the pawl after two revolutions ; similarly, the pawl 606, which co-operates with the ratchets 410, 414, 446 stops the sleeve after twenty revolutions: the pawl 542 is  similar to, and may be effective at the same time as, the pawl 540 so as to stop the sleeve 280 after one-tenth of a revolution. To set the cam 450, the lever 486 of a gear segment 492, which is rotatable about the axis of the shaft 116, has a spring-pressed button 488 engageable with a series of notches 474, 476... in an index plate 484. These notches relate, as indicated, to different ranges of subdivisions into which a circle can be divided, and, depending upon the setting of the button, the'cam 450 is rotated by the engagement of a stop 498 on the gear segment 492 with the operating lever 462 of the cam. The gear segment 492 is in mesh through a gear segment 502 with gears 510, 508, Fig. 2, on the shafts of the dial plates 390,356. The gears 510, 508 carry shutters 514, 512 for masking the windows, and, when in masked position, each shutter locks the corresponding dial plate and prevents actuation of its operating knob. With the button 488 in notch 474 (i.e. for a range of subdivisions from 1 to 10), both shutters 514, 512 mask the windows 358, 392 and only the knob 306 can be operated With the button in notch 476, (i.e. subdivisions from 11 to 99), only the window 358 is unmasked and only the knobs 306, 344 are operable. When the notches 478, 480 are engaged, both windows are unmasked and all the knobs can be operated. In operation, the button 488 is first set to the range within which the desired number of subdivisions lies, so as to position the cam 450 to make the correct pawl effective, the appropriate knobs 306, 344, 376 are then actuated to cause the gears 284,297, 242 to engage the selected gears 212, 214..., and the handle 116 is rotated by its hand crank 408 until the effective pawl engages the ratchet 414 and stops rotation of the sleeve 280.