GB390436A - An improved system for detecting faults in the cutting edges of sharp edged tools - Google Patents

Abstract

390,436. Testing physical qualities of materials. PETERS, P. N., Wallkil, New York, U.S.A. Oct. 8, 1932, No. 28069. [Class 106 (ii).] The condition of the cutting edges of razor blades, milling cutters, blanking dies, and other sharp-edged bodies is investigated by means for creating a difference in potential, between the body and the surrounding medium, sufficiently high to cause a flux along the cutting- edge, and a detector to measure the intensity of the flux either at various points or over the entire edge. The flux may be electric, magnetic, thermal, or electromagnetic. Electric means, Fig. 2, comprise a bar 4, galvanometer G, and blade 1 in an A.C. or D.C. circuit. To investigate the efficiency point-by-point, the bar 4, perpendicular to the cutting edge 2, and at a fixed distance therefrom, is moved parallel to itself along the edge. Overall efficiency is determined by placing the bar 4 parallel to the edge. The blade may be covered by insulating material 3. In another form, the blade, charged sufficiently to ionize the air, is placed between the plates of a condenser in series with a battery and a telephone detector. A neon tube may replace the condenser. A visible method comprises charging the blade with a brush and observing the luminous discharge through an oil, air, or solid dielectric to an electrode. The discharge may be observed by eye or photo-electric cell, or it may be recorded on a photographic plate. Spark or ultra-violet discharge may be used. A magnetic method comprises supporting the blade on one pole of an electromagnet and moving a bar such as 4, Fig. 2, between the cutting-edge and the other magnet pole. A galvanometer connected across the bar inindicates variations in current induced in it due to irregularities of the cutting-edge. Alternatively, the blade itself may be magnetized and its edge moved past an iron particle suspended from a pivot carrying a mirror which deflects a beam of light along a scale. Fig. 10 shows a thermal method. A blade 1, heated by a coil 23 expands, by radiation, a single- or bi-metallic strip 24 to pivot a mirror 18 and obtain deflections on a scale 22. An electromagnetic method comprises using the blade-edge as a sending antenna and measuring the variations in intensity of signals received on a receiving antenna moved parallel to the edge. The detectors may have amplifying circuits. The system is capable of automatic detection and grading of cutting tools according to the efficiency of their edges.