GB691123A - Improvements in or relating to apparatus for measuring yarn tension - Google Patents

Abstract

691,123. Electric indicating systems. NATIONAL RESEARCH DEVELOPMENT CORPORATION. July 5, 1951 [July 15, 1950], No. 17762/50. Class 40 (i). The tension of a yarn, e.g. in a knitting machine, is measured by passing the yarn around fixed pulleys 5, 6 and over a pulley 1 mounted on a pair of cantilever springs 2A, 2B which with fixed plates 3, 4, 7, 8 form a differential condenser whose capacity varies in accordance with yarn tension and is measured in a bridge circuit, Fig. 1. The condenser forms two adjacent arms of the bridge, the other two arms consisting of like opposed coils CC1, CC2 of a transformer T3. The bridge is fed from an oscillator 11, and zeroized by a trimmer differential condenser 9, having an adjustably rotated blade 9a. The bridge output taken from the secondary W of transformer T3 is amplified at 10 and passed through a cathode follower 12, rectifier 20, and a further cathode follower 22 to a recorder 21. The output from 12 is also fed through a diode 13 arranged to lengthen the peaks of the bridge output signal, and through a further. cathode follower 14 to a diode 15 which having no leak resistance across its condenser 16 lengthens the output peaks still further, the peak value being measured by a valve voltmeter 18, 19, which may be reset for a new period peak measurement by a discharge switch 17. The transformer T3 is preferably mounted on the measuring head.