Patent GB-584065-A (GB)
Title: Improvements in or relating to grinding or abrading machines
IPC: B24B47/20
Filed: 1943-08-17
Abstract: 584,065. Grinding &c. machines. CINCINNATI MILLING MACHINE CO. Aug. 17, 1943, No. 13364. Convention date, Aug. 13, 1942. [Class 60] Automatic infeeding mechanism for grinding-machines comprises means for moving the wheel rapidly to the work, feeding the wheel slowly to grind the work to size with a slight dwell to allow the grinding-wheel to clean up, and for automatically returning the wheel to the starting position, the movements being effected by mechanically - controlled fluid - pressure means ; fluid-operated traversing mechanism for the machine table is also provided which is interlocked with the infeed mechanism so that inadvertent power or manual movement of the table is prevented during the cycle of operations. The machine comprises a bed on which is slidable longitudinally a work-table and a transversely movable slide carrying the grinding-wheel. The table is moved by a cylinder 15<1>, Fig. 6, and a piston 16 connected to the table by a rod 17, and admission and exhaust of pressure fluid is controlled by a rotatable valve 23 having sections 18 ... 21 operated by a lever 24 and gearing 24<1>. The lever has a central or stop position, a running position 25 and a third position 26 in which automatic retraction of the grinding-wheel is effected. The wheel-head is provided with a cylinder 27, Fig. 2, for receiving a rack piston, the rack portion 31 of which gears with a pinion 29 on the upper end of a shaft 30 journalled in tho bed 10, the lower end of the shaft carrying a worm-wheel engaging a worm 33. The worm is supported for axial movement in the bed by a piston 34 and a journal 35, the piston sliding in a cylinder 36 and the journal being supported in a bearing 37 in the bed. The rack piston and cylinder 27 are used to give rapid movement to the wheel-head, and axial movement of the orm is used to effect the feeding movements rotation of the worm adjusts the wheel-head to change the final position of the grinding-wheel. Fig. 5 shows the hydraulic control circuit with the parts in a position just prior to automatic reversal, the wheel-head being in retracted position. The cylinder 27 is in two parts 38, 39 and the corresponding piston portions 40, 41 slide therein. Fluid pressure has been connected to the cylinder 39 and, since the pinion 29 is locked by its connection to the worm 33 and the rack is also locked, the pressure in the cylinder 39 moves the slide 15 to the rear; when, however, the forward end of the piston 40 engages.the end of the cylinder 38 to stop the movement, the pinion 29 may be rotated to move the head 15. The axial movement of the worm 33 is limited to that required for feeding movement ; the cylinder 36 is connected at all times to a source of fluid pressure and the piston 34 and worm 33 are constantly urged to the right, Fig. 2, movement being controlled by an infeed cam 45 adjustable across the axis of the worm whereby the worm may advance for feeding until it engages a thrust plate 44 on the machine bed. For additional movement of the worm it is rotated by a hand wheel 46 connected through gearing 47 to a shaft 48 connected by a slidable joint 50 to the rod 49 of the piston 34. When fluid is admitted to the cylinder 38, and the cylinder 39 is connected to exhaust, the wheel-head advances until it strikes and is stopped by the end of the piston 41, the cam 45 then moving in the direction of the arrow 51 to allow the worm to move axially for feeding ; the length of the rapid traverse may be adjusted by the screw 52 in the cylinder 39. The cycle is controlled by a rotary valve 57, fluid being supplied by a pump 60 from a reservoir 62. The system includes an infeed control valve 73, a reversing valve 79 to a tailstock valve 88, a switch 95, a feed control cylinder 142 with a valve 112, a grinding-head control valve 118, a rate control valve 152, a tarry valve 168, a pilot valve 161 and a control for returning to manual control 180, 187, On operating the starting lever, fluid pressure is supplied to the tailstock valve 88 whereby the tailstock pushes a workpiece into engagement with the headstock and opens a port 92 to operate the switch 95 to start the rotation of the work. The infeed control valve 73 connects pressure to the rapid traverse motor to move the wheel-head in, and to connect pressure to the reversing valve for the feed rate motor. The feed rate control piston 113 moves the cam 45 at a rate selected by the setting of the valve 151, and by the time. the feed is completed the cam 45 has moved out of engagement with its follower, the worm-shaft has engaged the positive stop 44, and the crankarm tripped the pilot valve 161. Fluid pressure is now admitted by the channel 167 and tarry valve 168 to the reversing valve 79 which shifts to return the control lever 64 to its stop position. The port 69 is thus connected to exhaust and, the port 67 being connected to pressure, the rapid traverse motor starts the return movement of the wheel-head. Due to the connection of the port 69 to exhaust, pressure is relieved in the tailstock valve, the infeed control valve and the pressure switch 95, which stops rotation of the work. The hydraulic system for controlling the power traversing of the table comprises the stop and start control valve 24, a reversing valve 195, Fig. 6, and a pilot valve 196, the plunger of which is moved by a crank operated by a lever and table dogs. The valve is connected by a port 197 and line 59 to pressure fluid and has ports 198, 199 connected through the sections 18, 20 of the control valve to lines 200, 201 leading to the cylinder 15<1>. The reversing valve has a plunger 210 with annular grooves 211, 212 and ports 213, 214 which may be connected through a line 215 and rate control valve 216 to the pilot valve which has a plunger 217 with grooves 222, 223 to control pressure and exhaust to and from the reversing valve , delay valves 240, 241 and check valves 202, 203 are provided between the valves. The pilot valve also serves to operate a pick feed mechanism 246, Fig. 5, actuated by a piston 247 slidable in a cylinder 248 connected by lines 249, 250 to a reversing valve 251, the plunger 252 of which moves under control by the table pilot valve 1946 to which it is connected by lines 255, 256, each of which includes a pair of oppositely directed check valves 257, 258. The valve 251 is connected by a line 267 to a start and stop valve 269 for the feed mechanism, which has a plunger 270. When the pilot valve is moved, the piston 247 is actuated, a single shifting movement of the pilot valve causing the piston to effect a complete reciprocation. The piston 247 has thereon rack teeth 277 engaging a gear 278 integral with an arm 280 carrying a pawl 281, normally held by a heel 282 and abutment 283 from contact with a ratchet-wheel 284, but upon clockwise rotation dropping into engagement therewith; the ratchet-wheel operates the gearing 47 and worm 33 through gearing 285, 286. The feed may be stopped by a button 288 on the gear 286 positioned so as to engage the pointed end of the plunger 270 to move this to the left; this causes the valve to stop the pressure in the line 267 from being communicated to the piston 247 ; since the plunger 270 cannot be re-ret manually, a valve 292 is provided for this purpose. After cessation of the feed, the table makes one or more reciprocations and is then stopped by operation of the lever 24; both ends of the cylinder 15 also are connected to pressure, so that manual operation of the table is possible. Mechanism for this manual operation is shown in Fig. 3, and comprises a hand wheel 302 on a shaft 303, which may actuate a gear 314 driving an idler 315 in mesh with a rack 316 on the table 13, either at slow or fast speed, gearing 304, 307, 308, 309, 311, 312, 313 being provided for this purpose, the shaft 303 being movable axially to engage one or other set of gears and held in position by a spring detent 310, a hub 321 on the gear 313 with a reduced portion 323 acting as a piston in a chamber 325 connected to a port 327 of the table start-and-stop mechanism serves to move the gear 314 out of engagement with the gear 315 so as to provide an interlock to prevent manual operation during power operation. An interlock to prevent starting of the table until the wheel-head has contacted the stop 44 is also provided comprising a locking notch 330 on the valve plunger 23 and a spring-pressed plunger 331 withdrawn by pressure fluid through a channel 337 when the infeed piston 113 is actuated. In addition to changing the feed rate by the valve 152, larger changes may be made by changing the angularity of the cam 45. For this purpose the cam is mounted in a holder bearing on rollers and connected to the rack 144, the cam being backed by two stops, one of which is of hexagon shape with sides of different lengths ; by rotation of this stop the angularity of the cam is adjusted accordingly. The strike of the piston 247 is adjustable by a stop in the cylinder 248 to vary the length of infeed increments.