Patent GB-841487-A (GB)
Title: A machine tool power transmitting mechanism
IPC: B23Q5/48
Filed: 1957-05-23
Abstract: 841,487. Variable-speed gearing; screw and nut mechanisms. KEARNEY & TRECKER. CORPORATION. May 23, 1957 [July 5, 1956], No. 16375/57. Classes 80 (2) and 80 (3). Twin nuts 63, 64, Fig. 2, co-operating with a non-rotatable screw 57, particularly for driving the reciprocable table 23 of a milling machine, are adapted to be driven in either direction at a slow or fast speed from a driving shaft 39. For fast speed a gear 176 on shaft 39 drives a gear 172 which is clutched by a multiple plate friction clutch 202 to a shaft 167. Gears 226 and 234 free on a shaft 222 are driven in opposite directions from the shaft 167 through a gear 225 and a gear 231 and idler 232 respectively. Clutches 240 and 241 are adapted to be selectively operated to clutch gears 226 or 234 to their shaft 222 to drive a twin gear 80 in mesh with gears 73, 74 on the nuts 63, 64 in one direction or the other. For a slowspeed drive clutch 202 is disengaged and a clutch 194 engaged to clutch a gear 163 to the shaft 167. The gear 163 is driven through a train 161, 55, 49, 48 from the output shaft 47 of a change-speed box 45 of the pick-off or shiftable gear type, the input shaft 44 of which is driven through gears 42, 43 from the driving shaft 39. The clutches 202 and 194 are actuated by fluid-pressure supplied to pistons 182, 183 respectively from pipes 207, 208 while the clutches 240, 241 are actuated by fluid-pressure supplied to pistons 258, 248 respectively from pipes 269, 270<SP>1</SP>. The clutches 202, 194 are controlled by an electrically actuated rate change valve 351, Fig. 3, whilst the clutches 240, 241 are controlled by an electricallyactuated direction valve 321. An interlock valve 296 is arranged between the valves 351 and 321. As shown in Fig. 3, the spools 323 and 298 of valves 321 and 296 respectively are maintained in a neutral position by springs, whilst the spool 352 of valve 351 is urged by a spring to its right-hand position. In this condition both the directional clutches 240, 241 are engaged by fluid pressure from supply line 290 through pipes 326, 327 to lock the shaft 222 and its driven turn-gear 80 against rotation. The pressure fluid is also supplied to both ends of the interlock valve spool 298 to maintain it balanced in which condition pressure is cut off from the rate change valve 351 and neither of the clutches 202 or 194 is actuated. To effect a drive in one direction or the other of the driven gear 80 solenoid 342 or 343 of valve 321 is energized, resulting in the movement of valve spool 323 one way or the other to release the pressure in and disengage one of the clutches 240, 241. Simultaneously, pressure is relieved at one end of the spool 298 of valve 296 for it to move to the left or right to supply pressure through valve 351 and pipe 308 to engage the slow speed clutch 194. For a fast speed the solenoid 358 of valve 351 is energized to move spool 352 to the left to relieve the pressure in clutch 194 and direct pressure to engage the fast clutch 202. An electrical control circuit is provided with suitable relays and interlocks for the spindle and feed motors of a milling machine with stop and start buttons, left, right and stop table buttons, and a rate change button for controlling the solenoids 342, 343 and 358. The twin nuts 63, 64, Fig. 2, co-operating with the screw 57 provide for backlash eliminating means comprising a thrust bearing 83 engaging one nut 64 and acted upon by a sleeve 71 having a helical ball-and-groove connection in a fixed guide sleeve 85. This sleeve 71 is adapted to be rotated to apply axial loading on the nut 64 by gearing 94, 95, 98, 103. The gear 103 is in the form of a circular rack which can be rotated as well as moved axially to rotate gear 98 and has a splined sliding connection 104, Fig. 5, with an adjusting shaft 137. The shaft 137 is normally locked by a serrated ring 147 in a collar 145 but can be moved axially against a spring 149 and then rotated by a wrench in a socket 150 to effect the desired backlash loading on the nut 64. This backlash loading is arranged to act only when the slow speed drive is in operation and to be automatically released when the fast speed is brought in. Fluid pressure is arranged to act on a piston 120 to move the rack 103 axially to release the backlash loading when pressure is supplied to the fast clutch 202 (see also Fig. 3). Specification 841,488 is referred to.