GB1456756A - Feed rate changing device in grinding apparatus - Google Patents

Abstract

1456756 Grinding TOYODA-KOKI KK [24 May 1973] 22446/74 Heading B3D [Also in Division G3] In a grinding machine, the feedrate of wheel G towards workpiece W is changed upon alteration of the input potential to amplifier 27 which occurs when contact is made between workpiece W and a conductive coolant fluid, supplied via nozzle 20 coupled to the amplifier, and wetting the wheel. The source of potential may be D.C. 25 or A.C., (251), Figs. 3, 6, 7 (not shown), in which case the circuit includes capacitative coupling between the wetted wheel and an electrode (250, Fig. 3), (450, Fig. 7) encompassing the periphery of the wheel, or on one or both sides of it, or a pair of electrodes (250, 360, Fig. 6) sandwiching, or both on one side of, the grinding location. The output of amplifier 27 rectified if necessary by rectifier (252) passes to comparators 29, 28 receiving preset values from units 31, 30, the comparator outputs controlling a relay circuit 40 to, respectively, enable the instigation of rapid feed towards the workpiece, only provided that no short circuit via excess fluid between the insulating wheel mounting and the machine body exists, detected by an excess of the amplifier output voltage over the setting of unit 31, and to control the change from rapid to grinding feed rate when, at a predetermined separation of the wheel periphery and the workpiece, the amplifier output is reduced to a level corresponding to the setting of unit 30, the grinding feed being retained until desired workpiece size is reached. During the use of grinding feedrate, valve 10 is operated to provide extra coolant via nozzle 8. The fluid supply to nozzle 20, which may encompass the sides and periphery of the wheel, see Fig. 5 (not shown) may be atomized with air, by unit (253, Fig. 6). The nozzle 20 may be below the grinding location, (Fig. 7). The relay circuit controls magnetic changover valves 14, 15 controlling direction and rate of a fluid supply to an hydraulic feed 11, 13. The wheel may be insulating {vitrified}, or, if conducting, is insulated from shaft 5 by insulating member 24. A baffle (400, Fig. 7) prevents the fluid from nozzle (20) from scattering over the wheel front. Safety device.-Should the wheel motor drive current as detected by transformer 35 exceed a value set in unit 38, relay circuit 40 operates to rapidly retract the wheel.