Patent GB-779348-A (GB)
Title: Improvements in and relating to automatic controlling devices
IPC: G05B19/42
Filed: 1953-09-14
Abstract: 779,348. Electric control systems. SCHMID, W. K. Sept. 14, 1953 [Sept. 13, 1952], No. 25343/53. Class 40 (1). [Also in Groups XXII and XXIII] The invention relates to feeler apparatus for scanning a template or workpiece, and means for selecting and maintaining predetermined measuring values obtained during the scanning to effect subsequent operations. A workpiece may be compared with the template by comparing measuring values obtained using the feeler apparatus, with the predetermined measuring values obtained with the template, or with predetermined measuring values which represent a template of specified shape. Wood-trimming (Fig. 1).-Spring-loaded, follow-up type feeler gauges 2, 3 located one on each side of a wooden plank 6 fixed to a table 1, are mounted on supports 4, 5 carrying stops 7, 9 which engage with movable stops 8, 10 when moving inwards. The plank and table are moved longitudinally so that the feelers scan the individual edges, and when the complete length has been scanned the stops 8, 10 are clamped in their maximum inner positions, and circular saws 15, 19 are moved up to the stops. The table 1 is then moved longitudinally backwards to allow the edges of the plank to be trimmed by the saws 15, 19 to the maximum width. The stops 8, 10 may be on a notched shaft to give only predetermined widths of the plank. Template copying device.-A template ABCDE (Fig. 3) is traced by a feeler 64 (Fig. 7) which passes on one of five different direction orders I-V (Fig. 4) depending on the degree of pressure between the feeler and the template. The rectangular components of the motion are obtained from motors 66, 68, and the angle of travel in the oblique directions II, IV is varied by stepping the arms of controllers 72, 73 controlling the speed of motors 66, 68. Each time the feeler passes into position I, III or V a pulse is sent to a magnet 58 (Fig. 5) or 75 of an electromagnetic ratchet device 59 to step the arms of the controllers 72, 73 until the correct direction of travel is obtained, corresponding to the contour of the template. The controllers 72, 73 are short-circuited when the feeler is moving in direction I, III or V. The sequence of directions is also recorded on a series of potentiometers 92, 93, 94, one of each change in contour. The potentiometers are initially all coupled to the shaft 76 carrying controllers 72, 73. After the first group of stepping operations, when the feeler is scanning contour BC, a time switch disconnects the first potentiometer 92 with its arm set in the direction corresponding to contour BC. Similarly, potentiometer 93 is next released with its arm set in accordance with the direction of contour CD, and potentiometer 94 set in accordance with contour DE. When the template is again followed by the feeler, the pulses emitted at each change to position I, III or V cause an electromagnetic stepping device 95 to connect potentiometers 92, 93, 94 in turn to set the position of the controllers 72, 73 so that the tool may attain the new direction of motion immediately. In another arrangement (Fig. 8) the sequence of movements of the controllers is also followed by a rotary switch 112 connected to a generator 114 whose variable frequency output signal is recorded on a tape 117. By operating a switch 118 the tape recording is fed through a series of tuned relays FR1- FR9 which selectively set the controller arms to conform with the contour of the template. Shape-testing device.-A feeler 126 (Fig. 9) in following the contours of a workpiece 127 causes successive operation of four relays R1-R4, whereby the supports 124, 125 move in the two component directions. To check that the shape of the workpiece is e.g. square, the supports 124, 125 operate the sliders 130, 128 of potentiometers 131, 129 which are incorporated in a bridge circuit 132 (Fig. 10). The bridge is initially balanced. If movements in the four directions are all equal and occur in the correct sequence, an electromagnetic stepping device 134 is rotated two steps by operation of solenoid 147 with pulses received from a galvanometer 133 in the bridge diagonal each time the bridge is rebalanced, to close the energizing circuit of a control relay 139 which then completes a circuit for further operations. The apparatus may be extended to measure three dimensions or ratios, and close the circuit for the next operation only when the three dimensions are correct when determined in the correct sequence. Position testing device.-In order to ascertain when a workpiece 172 (Fig. 14) is correctly located on a work-bench 166, a plurality of feelers, as shown, 171, 176, are employed for controlling movement in the two component directions, associated with variable resistors 174, 179 which are incorporated in bridge circuits. When each resistance is balanced in its own bridge circuit against a predetermined value, the workpiece is correctly located for subsequent operations which are initiated by closure of a control relay by pulses received from each of two bridge circuits at balance. Specifications 762,966 and 766,013, [Group XXII], are referred to.