GB929424A - Improvements in tension control apparatus - Google Patents

Abstract

929,424. Automatic tension control. HEENAN & FROUDE Ltd. Feb. 19, 1962 [March 14, 1961], No. 6255/62. Class 38 (4). An induction motor M1 drives a reel R through an eddy-current coupling whose field winding 8 is excited to regulate the tension in web 12 driven by rolls 14. The angular velocity of the reel decreases in relation to web speed as the diameter of the coil increases, the torque transmitted to the reel being increased at the same time. A desired torque is established by reference voltage circuit RV associated with thyratron 22 in circuit with the winding 8, a potentiometer 32 being adjusted automatically in accordance with the coil diameter by means of two-phase motor M. The circuit RV also comprises a bias potentiometer 46, tension potentiometer 52, and potentiometer 60 which is adjusted in accordance with the build-up ratio of the coil. A circuit TC for detecting the actual torque comprises current transformer 72 associated with step-up transformer 80. The portion of the in-phase voltage component which represents electro-mechanical losses in the motor and coupling is vectorally cancelled by adjusting potentiometer 88. The out-ofphase voltage component of the signal obtained by the current transformer 72 is vectorally cancelled by adjusting potentiometer 104. A potentiometer 70 is adjusted to increase the maximum available torque when the coil diameter reaches its maximum value. A diametersensing circuit DS is associated with the motor M and comprises tachometer generators G1, G2, coupled to shaft 10 and rolls 14 respectively, and having their outputs in opposition. At the start of a winding operation, the output voltages of generators G1, G2 are equal, the initial magnitudes being set by potentiometer 152. Thyratron 184 is out off by adjusting potentiometer 214 in bias voltage circuit BC, the motor M being de-energized. As winding proceeds, the output of generator G1 decreases, thyratron 184 conducts, and motor windings 174, 176 are energized. Movement of motor M re-positions potentiometer 168 to select a larger portion of the signal from generator G1 which is sufficient to equal that from generator G2. The motor M then stops, this operation being repeated to reposition potentiometer 168 in direct proportion to the coil diameter. By pre-setting potentiometer 60 in the reference voltage circuit RV, the torque may be made to increase linearly with coil diameter at different rates to maintain constant web tension or to allow the tension to decrease as the diameter increases. Information relating to the coil diameter in a temporarily stopped position is retained by the potentiometers 32, 168. The circuit may be modified to control the tension during an unwinding operation. An indicating circuit IC is supplied with the torque-responsive signal and comprises a current-sensitive meter T as well as potentiometer 242 which is adjusted in accordance with coil diameter. The resultant current through the meter is proportional to the web tension.