Patent GB-586843-A (GB)
Title: Improvements in or relating to grinding or abrading machines
IPC: B24B47/20
Filed: 1943-11-11
Abstract: 586,843. Grinding &c. machines. CINCINNATI MILLING MACHINE CO. Nov. 11, 1943, No. 18762. Convention date, Dec. 26, 1942. [Class 60] A grinding &c. machine comprises means for effecting movement of the grinding wheel support relative to the work support including a feed screw connected to the former, a piston on one end of the screw for advancing the grinding wheel support rapidly and stop means including a cam for limiting such rapid movement, the cam being operated to feed the support by power means responsive to the movement of the screw. The machine, a cylindrical grinder, comprising a bed supporting a reciprocable work table and a grinding wheel support mounted for movement at right angles to the direction of movement of the work, is provided with a manual control and also with an automatic infeed control to move the wheel rapidly up to the work, to feed the wheel slowly to grind the work followed by a dwell and to effect a rapid return movement. During the operation the work table is locked until grinding is finished, the table being released automatically for reciprocation during the dwell for cleaning up the work ; all of the operations are effected by fluid pressure means. The movements of the grinding wheel support are effected through either one of two connections, one comprising a nut 14, Fig. 14, on the support engaging a screw 15 journalled in the bed, and the other comprising a piston 16 integral with the screw and movable in a cylinder 17 to impart axial movement to the screw ; rapid return of the screw is effected by a separate piston 22 and cylinder 23 ; the cylinder 17 has a head 18 adjustable by a screw 19 to limit the return movement of the wheel head. Manual adjustment of the wheel head is effected by rotation of the screw 15 through gearing 25, 27 and rapid adjustment may also be effected by rotation of the screw by a hydraulic motor 28 connected by gearing 29 to the shaft 26 carrying the gear 25. The grinding cycle is started by a valve 30 which is moved to one of two positions by a pilot valve 31, the plunger 32 of which is operable manually by a lever 33, the valves being connected by channels 38, 40 ; movement of the valve plunger 32 downwards from stop or return position causes the plunger 41 of the valve 30 to move to the right. This connects the cylinder 17 to a pressure line 45 and, through a valve 49 arranged in the cylinder head, allows the fluid to move the piston at a slow rate ; as the piston moves, the valve 49 is caused to follow up by a spring 52, thereby accelerating the movement, fluid in the cylinder 23 being exhausted through the piston-rod 24 and a deceleration valve block 55 in which is a piston 56 connected to a valve piston 57 which is movable in a housing 58 and the valve allowing free escape of fluid from the cylinder 23 when the piston 16 is moving. As the screw 15 moves to the left it rotates a lever 71, pivoted at 72, which moves the plunger 56 so that the spool 75 of the valve 55 causes deceleration of the movement of the wheel slide until the plunger 57 is fired by pressure on a central spool 76, whereafter the slide moves under control of a cam ; the firing of the valve connects pressure fluid to a port 80 of a feed cylinder 81 connected at its other end to a check valve 84 and feed rate control valve 85. The cylinder 81 has therein a piston 89 having thereon rack teeth 90 which engage a pinion 91 meshing with a rack on a slide 93 carrying the feed rate control cam 94, this being engaged by a roller 97 on a second lever 95 pivoted at 72 and engaging the end of the screw ; as the piston 89 moves down, the cam allows the screw and slide to move to the left at a feed rate controlled by the setting of the valve 85. The shaft 98 of the pinion 91 has thereon a lever 99 which, as the feed reaches its completion, shifts a valve plunger 100 acting as a pilot valve to reverse and return the slide, the pilot valve being connected to a reversing valve 106 by a channel 104 which also has connections to a check valve 109, a throttle valve 108 and an interlock valve 111. The interlock valve prevents actuation of the table traverse during infeed, but thereafter releases the traverse so that a small reciprocation of the table may be effected to finish the work; the traverse is under the control of a valve 112 connected to a table start-stop valve 120 controlling the movement of the table. The valve 112 is connected by a channel 123 to the interlock valve and cannot be moved until, on completion of feed, the plunger 125 of the interlock valve 111 is moved to the left ; the table traverse can then be initiated, but can continue only for so long as the dwell continues, this being determined by the valve 108, which allows pressure to build up at a predetermined rate to move the plunger 107 of the reversing valve 106. Fluid also passes then to a valve 132, by which it is passed to a port 143 in the valve 31, thus moving the plunger 32 upward. This causes reversal of the plunger 41 of the valve 30 to admit fluid to the cylinder 23 ; the connections to the cylinder 81 are also reversed so that the piston 89 moves upward at a rapid rate, and the lever 99 releases the plunger 100, whereby the plunger 107 and the plunger 125 of the interlock valve are returned to start position. As the piston completes its movement, it engages the end of the plunger 49 so as to cause restriction of flow of exhaust and thereby to decelerate the movement of the slide. The manual means for operating the pinion 25 comprises a hand wheel 153 and sun and planet gearing carried by a stud shaft driving the gear 25 through gears 169, 180, 181, the gear 181 being carried by a tubular shaft 182 journalled in the machine bed; the shaft also carries a gear 185 which meshes with a gear 186 on one member of a hydraulically-operated clutch. The other member 187 carries a fluidoperable plunger 188 for connecting the two members. The amount of rotation of the screw is indicated, both when manually and power operated, by a fixed mark and graduations on a ring which also carries one or more adjustable markers and micrometric adjustment is effected by the sun and planet drive which is thrown into or out of operation by a sliding knob 174, and withdrawal of a locking pin 165, a dog adjustably carried by the wheel co-operating with a removable stop carried by the machine bed. Means is provided for easing the load on the hand wheel comprising the motor 28 and a control valve 223, which is actuated by a lever 224 frictionally connected to the shaft 182 so as to move the plunger in the appropriate direction and then to slip ; the valve 223 is connected by channels 229, 230 to a rapid traverse control valve 233 from which channels 244, 245 lead to a safety valve 248 from which channels 254, 255 lead to the motor 28 ; pressure of fluid to the motor is adjusted to a valve to cause the motor to exert torque, but not actually to turn by two relief valves 258, 260 whilst a third relief valve 257 is set for much higher pressure. The rapid traverse valve 233 is used when quick movements of the wheel head are required to change the zone of movement during a grinding cycle, and the valve is operable under control of a pilot valve 267 to supply the high-pressure fluid to the motor 28 ; the valve 267 is operable by a lever 269 normally held in neutral position by springs. When the rapid movement is initiated, the hydraulic clutch is disconnected so that the hand wheel is also inoperative. The safety valve 246 is provided to prevent the nut 14 from over-travelling the end of the screw 15 and is actuated by a trip rod 297 carrying dogs 298 engaged by an abutment 299 on the slide.