Patent GB-981876-A (GB)
Title: Improvements in and relating to measuring or control apparatus
Inventor: SARGROVE JOHN ADOLPH
IPC: B07C5/08
Filed: 1961-04-25
Abstract: 981,876. Measuring electrically. SHEFFIELD TWIST DRILL & STEEL CO. Ltd. April 19, 1962 [April 25, 1961], No.14898/61. Heading G1N. The diameter and tapes of an elongated tool bit, or the like, whose cross-sectional shape is approximately, but not precisely, circular is determined by rotating the tool bit between gauging surfaces which contact the tool bit at a first point to generate an electrical signal which is a function of the separation of the surfaces, generating a similar signal indicative of the separation of gauging surfaces contacting the tool bit at a second point, and comparing the signals. Drill bits in hopper 23 are fed one at a time into a groove 25 (Fig. 7) in a test bed 26, 27 by means of a compressed-air actuated push rod (not shown). The bottom of the groove is raised by cam 83 to eject the bit and cause it to be engaged by a drive plate 34 so that it rolls along the test bed. The tip of the drill meanwhile rotates under test shoe 37 which actuates transducer 38. When the bit reaches groove 40 it is realigned and then ejected by cam 87. The end of the fluted part of the bit then rotates under test shoe 41 which actuates transducer 42. After realignment in groove 43 the bit is rolled by drive plate 35 beneath test shoe 44 associated with transducer 45. Finally it rolls down incline 53 over control flaps 54, 55 which are open or closed depending on whether the bit is over or under size, or correct. Bits of different diameter and length are accommodated by adjusting knob 111 to raise bar 51 carrying drive plates 34, 35 and by rotating threaded shaft 110, using a knob (not shown), to move test bed 27 towards or away from 26. Control circuitry (Figs.19A to C). The differential transformer type transducers 38, 42, 45 produce short pulses corresponding to the raised cutting edges on the drill bit. The outputs from the first two transducers are fed through indicating instruments 200, 201, 202 to separate channels each containing a low pass filter, a D.C. amplifier, a pulse lengthener and an oscillator, and then to a recording head. The shank measuring channel is similar except that the output is not recorded. The signals recorded on memory drum 130 are picked up at 223, 224, the tip signal after a 240 degrees delay and the flute signal after a 120 degrees delay. The signals are then amplified and passed to tolerance checking circuits. The amplitude of the tip signal, after demodulation at 226, is first checked at 241. The tip signal is also compared at 248 with the demodulated flute signal, and at 249 with the demodulated shank signal. If all dimensions are satisfactory a connection is established between leads 268, 269, and flap 54 is opened. If any dimension is too small neither flap opens, and if any dimension is too large flap 55 opens. Cams mounted on a shaft 147A, 147B driven synchronously with recording drum 130, through servosystem 144, 253, 145, 146, cancel the relay hold circuits, reset the pulse lengtheners and prepare the discriminators, which include blocking oscillator type trigger units, after each measurement. Further cams actuage air valves to operate traversing cylinder 50 for bar 51, actuator 28 for cams 83, 87, 88, a cylinder 72 which operates a hopper agitating device, and cylinder 66 operating the pusher arm which ejects the tool bits from the hopper into groove 25. A detector shoe and microswitch 203 are provided at the hopper outlet to detect bits which are excessively large.