SINGLE-ACTION THERMAL SWITCH (ALTERNATIVES) AND ELECTRIC HEATING ELEMENT INCORPORATING SINGLE- ACTION THERMAL SWITCH (ALTERNATIVES) Russian patent published in 2003 - IPC

FIELD: electrical engineering; tubular electric heating elements protected against overheating in abnormal operation ( poor heat dissipation conditions). SUBSTANCE: thermal switch is proposed of three alternatives with respect to its mechanical design. Thermal switch of first alternative has temperature sensor in the form of open easy- melting metal or alloy tube filled with promoting agent whose fusing temperature and electric conductivity are lower than those of temperature sensor; two contacts made of metal tube and partially fitted onto opposing ends of temperature sensor and soldered to its outer surface. Contacts are spaced minimum 0.6 mm apart. Thermal switch of second alternative has its temperature sensor non-filled with promoting agent. Thermal switch has definite optimal dimensions. Thermal switch of third alternative is characterized in that its outer and/or inner surface, or all its surfaces are coated with thin layer of promoting agent. Electric heating element incorporating proposed single-action thermal switch is proposed of two alternatives. Heating element of first alternative has two contact leads and high-resistance spiral wire one of whose ends is rigidly fixed to one of contact leads and other end, to thermal switch. The latter has temperature sensor in the form of easy-melting conducting material tube and two contacts. Spiral wire end fixed to thermal switch is inserted in one of its contacts and clamped therein. Hole at end of spiral wire part inserted in thermal switch contact is closed with plug. Distance from spiral wire and plug to temperature sensor is minimum 0.1 mm. Second contact lead is partially inserted in second contact of thermal switch and clamped therein. Electric heating element of second alternative incorporating proposed thermal switch is provided with second spiral wire one of whose ends is fixed to contact lead and other one is inserted in contact of thermal switch and clamped therein. EFFECT: enhanced quality, simplified design. 14 cl, 17 dwg