Patent GB-860255-A (GB)
Title: Improvements in automatically controlled machine tools
Inventor: JUDSON CHARLES ALAN
IPC: B23Q15/00
Filed: 1955-03-01
Abstract: 860,255. Electric measuring and control systems. BIRMINGHAM SMALL ARMS CO. Ltd. May 30, 1956 [March 1, 1955], No. 5989/55. Class 40 (1). [Also in Groups XXII, XXXIX and XL (b)] A machine-tool controlled by a coded record, includes means for automatic perception of the wear of the cutting-edge of the cutting-tool by inspection of the surfacefinish of a workpiece and means for effecting a warning, or bringing the operation of the cutting-tool to an end, on departure of the surface finish from a predetermined standard. The machine-tool may be stopped and the worn tool replaced or resharpened. The inspecting means may be a stylus traversing, or traversed by, the surface of the workpiece and operating electrically, mechanically, hydraulically or pneumatically. Electro-dynamic inspecting means (see Figs. 1, 2).-A stylus 2 is mounted in a tool-slide (not shown) moved parallel to the workpiece axis and inspects the workpiece after the cutting operation ceases. The stylus forms part of a pick-up 3 which includes cylindrical magnet 12 sliding on rod 8, and fixed coil 11 connected via terminal block 16 connected to an integrator circuit to give a current proportional to magnet displacement. The integrator circuit is connected to an amplifier with available A.C. and D.C. outputs (see Fig. 3, not shown) fed to an A.C. or D.C. relay (see Fig. 4, not shown) via a variable resistor as sensitivity control; the relay contacts close the circuit to an audible or visual alarm and, via a switch, actuate a relay which operates the main switch of the machine-tool and stops it. In another arrangement (see Fig. 5, not shown) the first relay can operate also a positioning-device for replacement of the worn tool; a delay device is provided so that unnecessary tool replacement does not occur on premature operation of the first relay. A thyratron may be used in place of the first relay. Photo-electric inspecting means (see Fig. 10).- The surface finish may be compared optically with that of a standard surface. Light from a stroboflash is reflected from the surface of workpiece and from a standard surface into two photo-cells 40, 41 connected to a differential circuit whose amplified output can be connected to either of the relay/thyratron circuits used with the above electro-dynamic pick-up. Alternatively, a dual photo-cell can be used, the above optical system being modified to cause one light beam to fall on one sensitive pole of the cell and the other beam on the other sensitive pole. General.-The inspecting means may scan continuously a part of the workpiece surface that is clear of the cutting-tool or it may be brought into operation intermittently by the code element. If a tool makes several cuts the inspecting means may be brought into operation only in connection with the final cut. In a machine with several cutting-tools inspecting- means may be used in connection with each tool, cessation of cutting being effected when the surface finish produced by any one tool falls below the corresponding standard. The inspecting means may be instructed directly from the machine, e.g. after a specified number of components have been produced. Specifications 841,682, 860,256 and 860,257 are referred to.