Patent GB-1049254-A (GB)
Title: Improvements relating to the control of machine tools
Inventor: AMSBURY CLIFFORD ROY
IPC: B24B49/00
Filed: 1965-04-08
Abstract: 1,049,254. Grinding. ROLLS-ROYCE Ltd. April 8, 1965, No. 15033/65. Heading B3D. [Also in Division G1] Gauging apparatus comprises a support member, a part of which is provided with at least one pair of electrical terminals and with means for readily connecting and disconnecting an electrical conductor between the terminals of the or each pair, means for mounting the support member on a machine tool in a position such that the or each conductor will be ruptured by the tool of the machine tool when the tool has reached a respective predetermined position, and means, operable when the support member is so mounted, for adjusting the position of the part with respect to the body of the machine tool, the or each pair of terminals being connected in an electrical circuit which contains a warning device which, in operation, assumes a warning condition when the respective conductor is ruptured. Workpieces 13 are mounted on a rotary table 12 which carries them beneath a grinding wheel 11. The table has electromagnets for holding the base 20 of a support member 14. A post 22 secured to the base 20 supports a non-conductive block 25 vertically adjustable by a nut 24 on a threaded part of the post. The block 25 has a recess 32 in which is mounted a replaceable non- conductive insert 33 having a protuberance 34 engaging beneath conductors 15, 16 so as to bow them. Each conductor may be constituted by a strip of thin copper foil backed by a wider strip of insulating material and may be formed by a printed circuit technique. The upper surface of the conductor 15 stands about 0À020 inch proud of the upper surface of the conductor 16. The opposite ends of each conductor are clamped against curved seats 35, 36 of the block 25 by members 40, 41 connected by a bolt 42 passing through a hole 43 in the block 25; the bolt 42 is insulated from the member 40 by a washer 44. Each clamp member 40 has a stud 45 slidable in a block 46, a spring 51 being interposed between the block 46 and the head of the bolt. A hole 52 in the block 46 receives an eccentric 53 on a spindle 54 rotatable by a head 55. Each pair of clamp members 40, 41 carries terminals 56, 57. At the beginning of grinding lamps 61, 84, 85 are alight. The operator feeds the grinding wheel. When the workpieces are 0À020 inch oversize, the grinding wheel grinds through the conductor 15 and the lamp 61 is extinguished. When the workpieces are to size the grinding wheel grinds through the conductor 16 deenergizing relay 75; contacts 80, 81 open and the lamp 84 is extinguished, whereupon the operator discontinues the grinding wheel feed; contacts 80, 82 close and current is supplied to a heating coil 93 so that after a time delay a bimetallic strip 87 is sufficiently heated to open contacts 91, 92 and the lamp 85 is extinguished, whereupon the operator stops the machine. During the time delay period any inaccuracy due to the pressure with which the grinding wheel has previously been forced against the workpieces is corrected; the duration of the time delay is adjusted by a variable resistance 94 controlling the current supplied to the heating coil 93.