GB977716A - Improvements in or relating to electric template copying servo systems - Google Patents

Abstract

977, 716. Template-followers. PEGASUS LABORATORIES Inc. May 6, 1961, No. 16532/61. Heading G3N. In a copy-milling machine in which a probe follows a template, a template feed signal at 90 degrees to the error signal is derived from the error signal. The lower end of a vertical probe, Fig. 2 (not shown), conversally pivoted at the upper end, contacts the edge of a template. The cores of two differential transformers 22, 23 mounted at right angles to each other, are connected to the probe to detect x and y axis deflections respectively. Transformers 22, 23 are excited by sine waves 90 degrees out of phase from source 21 and the resulting modulated signals are demodulated at 26, 27 to provide D.C. signals across resistors 76, 80 and 77, 81 proportional to X and Y deflections. The modulated signals are also applied to a circuit 28, Fig. 5 (not shown) where they are added, and the resultant after amplification and squaring is separately demodulated with both signals from source 21 to provide two reference X and Y D.C. signals across resistors 31, 32. These resistors are centre-tapped to earth, and the negative going reference signals are applied through resistors 78, 79 to oppose the basic deflection signals so as to maintain the probe at a constant reference deflection. A portion of the resulting X and Y error signals is tapped off potential dividers 80, 81 and applied to X and Y axis control amplifiers 82, 83. A portion of the positive going Y reference signal from resistor 31 is also added to the X axis amplifier 82, and a portion of the negative going X reference signal from resistor 32 is added to the Y axis amplifier 83 to provide forward feed components. The amplifiers 82, 83 control hydraulic servomotors 86, 87 with velocity feed-back from tachometers 88, 89.