Patent GB-959428-A (GB)
Title: Control mechanism for grinding machine
IPC: B21B28/02
Filed: 1962-09-20
Abstract: 959,428. Grinding. CINCINNATI MILLING MACHINE CO. Sept. 20, 1962 [Oct. 5, 1961], No. 35827/62. Heading B3D. A machine for grinding the peripheral face of a rotatable workpiece comprises support means for the workpiece mounted for rotation about its longitudinal axis, traversing means for effecting longitudinal movement of a grinding wheel relative to the workpiece, a drive motor for the grinding wheel, disabling means for disabling said traversing means in response to a reduction in the torque on said drive motor below a predetermined value, and delay means for inhibiting the operation of said disabling means for a preselected time interval after the torque has fallen below said value and for preventing said disabling means from becoming effective if the torque is restored to said value within said time interval. A grinding machine includes a headstock 10 and a tailstock 11 between which a workpiece, e.g. a roll, is supported for rotation about its longitudinal axis by a motor 12 on the headstock. A bed 15 has ways 16, 17 supporting a carriage 18 for longitudinal movement in a direction parallel to the axis of the workpiece, this movement being effected by an electric motor 2M on the carriage driving, through a speed reducer comprising gears and a worm and wormwheel, a pinion meshing with a rack 19 on the bed 15. The carriage carries limit switches 1LS, 2LS co-operating with dogs 27, 28 adjustably attached to the bed 15. The carriage 18 has ways 31, 32 supporting a cross-feed slide 29 for movement transversely of the axis of the workpiece. This movement is effected by rotating a shaft 36 journalled in the slide and having thereon a worm 37 meshing with a worm-wheel 38 attached to a nut 39 meshing with a screw 40 non-rotatably secured to the carriage 18. The shaft 36 is connected to an electric motor 3M and also, through a magnetic clutch 1MC and bevel gears, to a shaft 48; the latter can be rotated, through bevel gears, by a hand wheel 49 or, through bevel gears, worm and worm-wheel and magnetic clutch 3MC, by an hydraulic pick-feed motor MF. The motor MF is controlled by a valve 62; with solenoid 1 SOL de-energized both sides of the motor are connected to exhaust, and when solenoid 1 SOL is energized valve 62 is actuated to supply pressure fluid to the motor MF which runs at a speed determined by the setting of a flow control valve 64, so that pick feed of the slide 29 takes place, its amount being determined by the length of time that the solenoid remains energized. The slide 29 carries a motor 1M driving, through belts in a guard 33, a grinding wheel 34. To restore the proper geometry to the face of a worm roll 70, whether it be straight, convex or concave, a scrub grinding programme is first carried out. A cut is established starting at one end 71 of the roll face and traversing the grinding wheel toward the centre of the roll. When the cut deteriorates as, e.g. at 72, the carriage is stopped, the wheel is pick-fed into the roll a predetermined amount to re-establish the cut and the carriage is returned to 71. Here the carriage is again reversed and the wheel once more fed into the roll to re-establish the cut. The carriage is again traversed toward the centre of the roll until the cut again deteriorates, e.g. at 73. The carriage movement is again reversed after pick-feeding the grinding wheel. This operation is repeated at 74 and 75. The machine is now stopped and the scrubbing operation repeated from the opposite end of the roll face until the desired geometry of the roll has finally been established. To improve the quality of the finish by removing the least possible amount of material from the roll face while maintaining the previously established geometry, a rough grinding programme is next carried out, comprising establishing a determined value of stock removal starting at one end of the roll face and traversing the wheel along the full length of the roll with the automatic control mechanism compensating for wheel wear by further infeeding of the wheel as necessary during the traversing movement. A finish grinding programme is finally carried out which is similar to the rough grinding programme but without automatic infeeding of the wheel during traverse to compensate for wheel wear. The electrical control circuits are energized through a transformer 84. The operator can select either a manual cycle or a programme cycle by a selector switch 2 SEL. In the " MANUAL " position, depression of one of power cross-feed push-buttons 15PB, 16PB energizes timer relay 3TR whereby after a delay, a relay 3MF or 3MR is energized to move the cross-feed slide in or out, the delay preventing operation of the slide by inadvertent momentary depression of a push-button. When relays 3MF, 3MR are both de-energized, a rectifier 1 RECT is energized, energizing magnetic clutch winding 1MC so enabling manual adjustment of the cross-feed slide by hand wheel 49; when a pick-feed timer O-TR is energized the magnetic clutch coil 3MC is also energized enabling movement of the crossfeed slide by the pick-feed motor MF. The carriage motor 2M is a D.C. motor, its speed being adjustable by a rheostat 85 and its direction of rotation being controlled by relays GR, GL in turn controlled by relays CRR, CRL respectively. The grinding wheel motor 1M is a D.C. motor, is started and stopped by ganged switches 9MKS and its speed is adjustable by a rheostat 86. Shunts 87, 88, 89, 90 are connected in series with the armature circuit. Manual cycle.-With selector switch 2 SEL tuned to " MANUAL," the carriage " Feed Right " push-button 20PB and the carriage " Feed Left " push-button 22PB are enabled, permitting feeding movement of the carriage to the right or left to be controlled manually by the push-buttons. Depression of one of these push-buttons energizes relay CRR or CRL, thus energizing relay CRA, the relays being held after release of the push-button. The carriage will continue its travel to the opposite end of the roll where contacts of limit switch 1LS or 2LS open to de-energize relay CRR or CRL and stop the carriage. Other contacts of limit switch 1LS or 2LS close energizing relay 105CR or 106CR energizing the other of relays CRR, CRL to cause the carriage to start toward the opposite end of the roll, the relay being held so that the carriage continues its movement along the roll until it reaches the opposite end when the limit switch is operated and causes another automatic reversal of the carriage. Automatic traversing of the carriage continues until the selector switch 2 SEL is turned to " OFF." The direction of carriage travel can be reversed at any time by depressing the appropriate pushbutton 20PB or 22PB. Each reversal of the carriage during " MANUAL " may, if desired, be accompanied by an automatic pick-feed of the grinding wheel toward the roll, by setting a selector switch 4 SEL to " AUTO," energizing a relay CRX so that at the end of a traverse the clutch and timing motor of timer O-TR are energized to initiate a pick-feed. Energizing timer O-TR energizes timer relay 105TR energizing relay 113R energizing solenoid 1 SOL activating valve 62 to start the pick-feed motor MF. When timer O-TR times out relay 116CR is energized, conditioning relays 6R, 6L for energization when contacts of a tarry timer TRT close at the end of the tarry period. At this time, relay GR or GL will be energized along with timer relay TRA. Contacts of the latter time open after a short delay to allow time for relay GR or GL and latching relay G1CR to pick up before the contacts of tarry timer TRT open. When relay GR or GL is energized, a circuit is provided to latching relay G1CR which provides a circuit to relays GR, GL after the contacts of the tarry timer TRT have opened. When the selector switch 4 SEL is turned to " OFF," relay CRX is de-energized so that relay 116CR is held energized so as to enable carriage traverse to begin as soon as the tarry timer TRT times out. Thus, in a manual cycle the carriage 18 travels back and forth between the limit stops 27, 28 with either automatic pick-feed of the slide 29 on each reversal of the carriage, with manual feed by hand wheel 49 or with power feed by motor 3M under the control of push-buttons 15PB, 16PB. Carriage reversal can be effected at any point in the traverse by depression of push-button 20PB, or 22PB and the carriage may be stopped by moving switch 2 SEL to " OFF." Meter relays.-Meter relays 1CMR (LOW SCRUB), 2CMR (HIGH SCRUB) and 3CMR (HIGH ROUGH) are connected across the shunts 87, 88, 89 to control traverse and pickfeed. Each relay consists of a meter movement with contacts on the indicating pointer and on a normally adjustable arm; a locking coil wound on the same bobbin as the measuring coil maintains firm pressure on the contacts once they have been closed. High and low limit contacts are provided. The meter relays have associated therewith sampling relays 4RY, 5RY, 6RY for periodically breaking the circuit through the locking coil and operating relays 1RY, 2RY, 3RY controlled by the contacts of the meter relays. When scrub control relay 102CR is energized, a D.C. charging circuit for a capacitor C4 is established. As the capacitor charges, the relay 4RY is energized breaking the charging circuit. The capacitor C4 then discharges through the relay coil maintaining the relay energized for a predetermined time interval after which the relay drops out and the charging cycle is repeated. With relay 4RY energized, if the high limit contacts 96 of meter relay 1CMR are closed by the action of the measuring coil 97, as they normally will be during a scrubbing operation, a charging circuit for a capacitor C1 is established through the locking coil 98. The time required for the capacitor Cl to charge is less than the " on " time of relay 4RY. When relay 4RY is de-energized, the circuit through the locking coil is broken. The time required for relay 1RY to drop out is longer t