GB850023A - Improvements in or relating to sizing controls on grinding machines - Google Patents

Abstract

850,023. Grinding. NEWALL ENGINEERING CO. Ltd., and TEMPLE, W. K. Nov. 25, 1958 [Nov. 25, 1957], No. 36726/57. Class 60. A grinding machine comprises in combination, means for feeding grinding wheel and work together, sensing apparatus comprising a wear-resistant feeler to engage the grinding wheel as a result of feed movement sufficient to grind the work to a predetermined size, an electrical piek-up connected to the feeler, an electrical circuit connected to the pick-up which includes means for electronic amplification of vibratory pick-up current resultant from engagement and a signal or relay operated by the amplified current. If the machine is handcontrolled, amplified current could operate an audible signal such as a buzzer to cause the operator to stop the feed, take note of the point reached and separate the grinding wheel and work. Alternatively the amplified current will operate a relay controlling drive mechanism to retract the grinding wheel. The amplified current may serve to memorise and establish the feed for subsequent operations, and in cases where the wear of the grinding wheel is slow, this permits of so mounting the sensing apparatus that it can be swung out of the way during operations on a series of workpieces and then brought into action prior to another series. The grinding wheel 13 is carried by a slide 12 mounted on the bed 11. The workpiece 18 is carried by a table 15 mounted on guideway 14 on the bed. A cross-slide 17 on table 15 carries an upstanding hinged bracket 19 with a forwardly projecting portion 20 to which is secured a slightly flexible cantilever bar 22 provided at its lower end with a smooth-faced diamond 23. Connected to the cantilever arm is the contact member 34 of a pick-up unit 24 which may be a piezo-electric crystal or of moving iron or moving coil type. The pick-up is electrically connected to an amplifier 27 connected to a relay 28 controlling the automatic feed device 31 of the grinding wheel slide 12. The relay may, for example, control an electro-hydraulic feed valve at 31 if the feed is hydraulically operated or it may control an electric motor at 31 if the feed is motor operated. The circuit may be tuned so that it is receptive only to a certain band of frequencies including the resonant frequency of the cantilever arm, and may include filter circuits to reject unwanted frequencies due to general machine vibrations. The diamond 23 is set at the position which corresponds to the desired termination of the grinding wheel feed.