557,443. Milling-machines. KEARNEY & TRECKER CORPORATION. Aug. 1, 1941, No. 9856. Convention date, May 3, 1940. [Class 83 (iii)] [Also in Group XXIV] A machine tool such as a milling machine has the spindle driven by change speed gearing driven through a hydraulically operated main clutch which is under the control of a manually operated control valve, means being provided to turn the change speed gearing slowly and to disengage the main clutch while gear changes are being made. In the application to a vertical-spindle milling-machine the vertically-movable knee 23 carries a transverse saddle 24 supporting the usual longitudinal work table 25 and the spindle is carried in a sliding head 27. The main motor 30 drives through multiple belts 32 and friction clutch 35, a main shaft 36 connected through speed-changing mechanism which is as described in U.S.A. Specification 2,240,973, shaft 38, gears 39 and range changing gears 50 to the spindle 28. The range changer gives two sets of spindle speeds, by means of a sliding spindle gear 49 on shaft 41, this gear being connectable either to gear 45 on the spindle or to internal teeth 50 on a gear 47 in constant mesh with a gear 46 on the spindle. The gear 49 is operated by a fork by partial rotary movement of a shaft 51 operated from a hand knob 52, lugs being provided to locate the knob in either position of the gear 49 as shown by a pointer 58. Axial movement of the shaft 51 actuates hydraulic gearing to disengage the main driving clutch 35 and engage a slow-speed driving connection to facilitate the change. For this purpose the said axial movement acts to rotate a shaft 62 connected to the piston 64 of a hydraulic control valve 63 associated with a valve 66 operated by a speed-changing lever 67 in the manner described in U.S.A. Specification 2,240,973. The unlatching movement of either of the handles 52, 67 preparatory to changing gear causes main clutch 35 to be disconnected and a slow speed drive to be rendered operative as described in U.S.A. Reissue 21434. Fluid from a pump 70 is delivered through a port 74 to valve 63 and in the position shown this fluid passes through lines 76, 79 to the clutch control valve 81 which may also be actuated by hand levers 83, 88 which are interconnected with a pin 86 actuating the valve plunger as shown in Fig. 18. When the lever 83 is in the full line position, Fig. 20, pressure fluid flows through line 105 to the lower end of cylinder 106 thus raising piston 107 and acting through bell crank 109 and central rod 141 to engage the main clutch 35 through toggle mechanism 142. When the piston 107 is fully raised it uncovers a port 134 leading through line 125 and valve 81 to a port 128 connected to the lubricating system of the machine. In the position B of the clutch lever 88 the piston 82 is moved to cause disengagement of the clutch 35 and engagement of a brake 130. In this position pressure fluid flows through line 112 to the top of piston 107 and when the lowest position of this piston is reached a port 134 leading to the lubrication system is uncovered. A third position of the clutch levers may be used for an emergency stop, the full hydraulic pressure being in this case exerted on the piston 107 and the lubricating system being cut off If a range changing movement is required the knob 52 is moved axially thereby shifting piston 64 to the right, Fig. 20, so that fluid may pass to line 152 and thence to line 157 and cylinder 158 moving plunger 82 to the right. Fluid also flows to port 163 of relay valve 118 which is lifted against a spring and permits flow through line 164 and passage 167 to a plunger 170 in the piston 107. This allows a flow to the upper side of piston 107 and moves the piston until plunger 170 registers with passage 168. Flow to the upper end of cylinder 106 is then stopped with the clutch in a neutral position. In this position the relay valve allows flow to a line 183 thus shifting a piston 185 and operating a pivoted arm 186 to engage the clutch 192 of the low speed driving mechanism 188. This gearing includes a continuously driven gear 190 and speed reducing mechanism 189. After the range changing operation has been completed the knob 52 is returned to latched position thus returning valve 64 and causing the clutch of the slow speed drive to be disengaged by cutting off flow from the cylinder 184. To restart the machine on the new range one of the levers 83, 88 is moved first to position B and then to the start position A. For speed changing by the lever 67 the latching handle 201 is first withdrawn. This shifts valve plunger 155 to allow flow to line 157, thus moving valve 82 to the right to disengage the main clutch and engage the slow speed clutch by operations similar to those relating to the movements of control knob 52. A modification of the hydraulic control system is also described. In the application to a horizontal milling machine, Fig. 10, the range-changing mechanism includes gears 245, 246, fixed on the spindle 247 and co-operating with a sliding couplet 249, 250, which is actuated by a lever 256 mounted adjacent the speed dial and associated with a valve-operating latching- handle 258. The range changing lever moves through 180 degrees and carries indicators 261, 262 coacting with markings on the speed dial which shows high range speeds alternating with low range speeds. The feed motions of the work supports are derived from a rapid traverse shaft 272 and a feed shaft 271 the latter being driven only when the main clutch is engaged. For this purpose main shaft 36, Fig. 3, carries a gear 193 connected by sleeve 280 and spur gearing 282 to the shaft 271. The drive for the continuously running shaft 272 is derived from gear 190 through gears including bevel gearing 287 and gears 290 ... 292. The feed mechanism operates table gearing including a pair of oppositely driven gears 295, 296, coacting with a sliding clutch Sleeve 297 splined on the table screw 298, the clutch being operated by a member 302 actuated by a bell crank 303 and control rod actuated from a lever 312 in front of the table. The nut for the feed screw comprises a fixed part 315 secured to the saddle and a movable part 318 connected by serrations 319 to a yoke 321 which has lugs 322, 323 coacting with screws 324, 325 by which the nut may be adjusted so that its two parts engage opposite flanks of the thread on the screw. The yoke may be readjusted when necessary to compensate for wear. The power adjustment of the head 27 is effected from a shaft 326 in the knee; this shaft driving a vertical shaft 328 connected by bevel gearing 329, and reversing bevel gearing 332 to a vertical shaft 334 geared to a nut on an elevating screw. The reversing clutch is operated by a hand lever 343. A pair of trip dogs 348 may be adjustably mounted on the head 27 for engaging posts connected with linkage located between the hand lever and the reversing clutch to stop the head at either of two locating pistons in its path of travel. A multiple position stop 351, Fig. 2, is also arranged to co-operate with a trip rod so as to stop the head at a selected position on its downward movement. To slide the head manually a hand wheel 353 is rotated to drive the shaft 334. Specification 557,476, [Group XXIV], also is referred to.