Patent GB-912775-A (GB)
Title: Grinding machine feed mechanism
IPC: B24B47/06
Filed: 1961-05-17
Abstract: 912,775. Grinding. CINCINNATI MILLING MACHINE CO. May 17, 1961 [Sept. 7, 1960], No. 17953/61. Class 60. [Also in Group XXVI] A grinding machine has a base and a wheel-head slidably received thereon, and a feed motor and a driving train to effect transmission of motive power from the feed motor to the wheelhead for feed movement thereof, the driving train including a lost-motion mechanism comprising a selectively operable, fixed displacement, rapid traverse motor selectively operable to provide a fixed rapid movement of the wheelhead, the rapid traverse motor having a member movable a fixed distance therein on operation of the rapid traverse motor, a feed shaft being connected with both the feed and rapid traverse motors, the rapid traverse motor and the movable member being movable in response to feed movement of the shaft, and means connecting the movable member of the rapid traverse motor to the wheel-head for movement thereof. A universal grinding machine has a wheelhead 10 carrying a grinding wheel 24 and guard 26 and mounted for movement, toward and away from the table 16 on which the work is supported, on ways of an intermediate member 12 pivotally adjustable on the base 18. A rack 30 fixed to the wheel-head is engaged by a split pinion having a lower part 32a fixed to a drive shaft 34 and an upper part 32b fixed to a torsion bar 36 received through the drive shaft 34 and having secured thereto a clamp 38 held against rotation relative to drive shaft 34 by pins, whereby backlash is prevented. The drive shaft 34 is supported in the base portion 20 in tapered bearings 40, 42. A paddle motor body 44, 46, 48 is received on the shaft 34, with interposed bearings 54, 56, and held in place by nuts 50, 52. The body part 48 is formed as a worm-wheel meshing with a worm 58 fixed on a feed shaft 22. A radial wall member 64 secured to the body part 46 has positive stops 68, 68, co-operating with stop pads 70, 70, on a paddle segment 66 secured to the shaft 34. Pressure fluid is selectively supplied to one side or the other of the paddle 66 through ports 72, 74 in the shaft connected to lines 76, 78 and through ports 64a, 64a in the wall member 64, these ports each including an adjustable ball restriction. Gear 104 is connected through gears 108, 110 to the feed shaft 22. Gears 102, 164 are connected through worm-gearing 114, 116 and gears 120, 122 to an hydraulic feed motor 118. To initiate a grinding cycle a lever 80 of cycle start valve 82 is pulled forward so that pressure from pump P is connected to a pressure switch 5PS; pushing lever 80 in the opposite direction connects the pressure to a pressure switch 4PS to terminate automatic cycling. Upon operation of the pressure switch 5PS a solenoid 1SOL is energized to actuate wheelhead control valve 94. Pressure fluid passes through selector valve 96 and effects movement of a shifter 100 to the right, meshing gear 102 with gear 104 in hand wheel mechanism 106. Exhaust fluid from the shifter flows through selector valve 96 and by-pass valve 168. Actuation of the wheel-head control valve 94 also connects lines 76, 78 to pressure and exhaust respectively, so that the paddle 66 executes its full travel, rotating the shaft 34 to cause a fixed amount of rapid advance of the wheelhead 10. On completion of this movement, pressure switch 3PS is operated whereby solenoid 2SOL is energized, actuating pilot valve 126 to open motor cut-off valve 130; operation of pressure switch 3PS also energizes solenoid 4SOL actuating pilot valve 136 to open fast rate cut-off valve 140. Thus, pressure fluid flows through pressure-reducing valve 142, check valve 146, motor cut-off valve 130 and motor-reversing valve 148 to the feed motor 118 which rotates, so causing rotation of the paddle motor body and thereby rotation of the shaft 34 to produce a feed movement of the wheel-head 10. Fluid exhausts from the feed motor 118 through motor-reversing valve 148, fast rate cut-off valve 140 and fast grind rate valve 158. After a predetermined amount of feed movement, solenoid 4SOL is de-energized so that fast rate cut-off valve 140 closes so that return fluid from the feed motor 118 cannot pass through fast grind rate valve 158; instead it passes through filter 160 and slow grind rate valve 162. After a small amount of feed at the slower rate, feed is stopped completely by a position stop engaged by the hand-wheel mechanism 106. After a predetermined time, solenoid 1SOL is de-energized actuating wheel-head control valve 94 to reverse the fluid pressure differential in the paddle motor so that the paddle 66 returns rapidly to its initial position whereby the shaft 34 rapidly retracts the wheel-head 10 a distance equal to the rapid advance movement. Actuation of the wheel-head control valve 94 also causes pressure fluid to pass through selector valve 96 to attempt to move shifter 100 to the left, tending to engage gears 164, 110 to reverse the rotation of the feed shaft 22. At the same time, pressure fluid causes the plunger in the motor-reversing valve 148 to move upward at a rate controlled by a restriction 166; during the shift the feed motor 118 is momentarily reversed allowing the backlash between the gears to mesh; thereafter the feed motor 118 again rotates in the original direction. Simultaneously with the rapid retraction solenoid 3SOL is energized actuating valve 171 actuating by pass valve 168 so that exhaust fluid from the feed motor 118 passes direct to the drain line, whereby the feed motor 118 rotates rapidly to restore the wheel-head to its starting position. At the start of the retraction stroke the feed motor and rapid retraction motor may be operating simultaneously for a brief period, so the wormwheel 114 has an over-running clutch to prevent rotation of the feed motor by the rapid retraction movement of the paddle motor. The feed motor runs until the wheel-head has reached its initial position; solenoid 2SOL is de-energized so that motor cut-off valve 130 closes; solenoid 3SOL is de-energized, actuating by-pass valve 168 to restore the hydraulic system to its original condition ready for another cycle.