GB890368A - A machine tool index mechanism - Google Patents

Abstract

890,368. Electric selective signalling systems. KEARNEY & TRECKER CORPORATION. March 5, 1959 [March 10, 1958], No. 7663/59. Class 40 (1). [Also in Group XXII] A machine tool in which a shaft is selectively positioned by means of an electric follow-up system comprises a control switching means for establishing an electric signal representing the desired position of the shaft, means coupled to the shaft for continuously producing an electric signal representing the actual position of the shaft, and means responsive to the difference between the desired position signal and the actual position signal for controlling a motor whereby the shaft is driven to the desired position by the shortest route. As described, a multiple tool holder 38, Fig. 1, only one tool 60 being shown, is positioned in a desired one of twenty possible positions under the control of a manually set switch; Fig. 9, having a code plate, Fig. 10, so arranged in conjunction with five sensing elements to differently mark a group of five lines for each of the switches twenty possible positions (as tabulated in Fig. 12, not shown). Control is effected by a conventional follow-up loop, the desired position, as set on the switch, being represented first as a combination of markings on five leads 346 to 350, Fig. 7, and then via a transformer network and relays 261-263, 246 and 247 as a phase significant A.C. potential on a line 208, by which it is applied to a comparator 210 and the actual position of the multiple tool holder being represented by a continuously variable phase significant A.C. potential derived from a synchro 175 and being applied to the comparator by a line 212. The comparator, Fig. 8, compares the two-phase significant signals and causes a contact 302 to energize either a forwards or a backwards line depending upon whether the actual position phase is less than 180 degrees behind the desired position phase or whether the actual position phase is less than 180 degrees ahead of the desired position phase, and this causes the motor, which is hydraulic, to drive the multiple tool carrier to the desired position by the shortest route. The comparator also includes a voltage-sensitive device 289 which marks a " creep by-pass signal " line except when the two signals are nearly in phase and this signal functions to allow a notched cam to control the fine positioning of the multiple tool holder and after this is effected a final position is achieved by a tapered cylinder which is advanced, hydraulically, into a tapered hole to lock the multiple tool holder. The sequence of operations is controlled by a relay sequencing unit (lower half, Fig. 7, not shown) and includes various safety interlocks to ensure, for example, that the multiple tool holder is unlocked before being driven. Once the multiple tool holder has been positioned gears can be engaged, under control of the sequencing unit, to drive the tool. Specification 866,627 is referred to.