Temperature sensitive devices for use in conjunction with temperature control systems

摘要

838,295. Electric measuring systems. RHEOSTATIC CO. Ltd. March 27, 1957 [April 27, 1956], No. 13018/56. Class 40 (1). [Also in Groups XIII and XXXV] A device sensitive to rate of change of temperature comprises two thermally-sensitive elements having similar coefficients of expansion, coupled together to operate a variable resistance in a temperature control system. The tube 2 acts as a heat shield for the rod 1 during the application of heat, so that the rod expands less than the tube and the resulting movement of arm 5 operates the slider 7 on resistance 8. At a steady temperature both elements expand or contract the same amount and the resistance has a value fixed by adjusting knob 9. The change in value of resistance 8 therefore corresponds only with a rate of change of temperature. In the circuit of Fig. 3, resistance 36 is rate-dependent and is arranged in circuit with temperature-varied resistance 32 and feed-back controlled resistance 34 to vary the current through the coils 26, 27 of a balanced relay 28 operating in either direction a servomotor 35. In an alternative embodiment of the device (Fig. 2, not shown) two similar liquidfilled tubes 10, 11 operate through expandable capsules 12, 13 on arms 14, 15 to vary the position of slider 20 on resistance 18. Tube 11 is heat-lagged, 21, and responds more slowly to change of temperature than does tube 10. In Figs. 4 and 5 (not shown), are alternative control circuits for use with the device.