GB934191A - Improved temperature controlling apparatus - Google Patents

Abstract

934,191. Automatic temperature control. MINNESOTA MINING & MANUFACTURING CO. June 3, 1960, No. 19783/60. Class 38 (4). [Also in Group XIII] In an automatic temperature control system for a crystal oven, a switch responsive to the temperature within the oven controls the electrical supply to thermoelectric junctions inside and outside the oven so that the oven is heated and/or cooled as necessary to maintain the temperature constant. In Fig. 1 a piezo - electric crystal 22 is mounted between electrodes 24, 26 loaded by a spring 28 within an insulating chamber 12 having a cap 14. A bimetallic strip 68 responsive to the temperature within the chamber adjusts the position of a contact 70 so that if the temperature within the chamber rises above a value determined by the setting of a contact 72 a circuit is completed to pass current from a D.C. source 80, 82 through dissimilar semi-metallic elements P, N in such a direction that heat is absorbed by the thermo-electric junctions within the chamber and exhausted by the junctions outside the chamber. The temperature within the chamber is thus maintained constant at a value below the ambient temperature so that the frequency of a valve oscillator 86 associated with the crystal is constant. Suitable materials for the thermoelectric junction elements are described. In a modification, Fig. 3 (not shown), bimetallic strip 68 controls a two-way switch so that current is passed in one or other direction through the thermo-electric junctions to heat or cool the chamber as necessary to maintain its temperature at a value below, at, or above ambient temperature.