Overheat protector for heating element with manual reset

A manually reset overheat protector for electric heating elements comprises a control contact mechanism in the lower cavity of the housing and a diaphragm in the upper cavity. The diaphragm, along with its handle and a capillary extending from it, forms a temperature-sensing device. When the capillary, wound around the heating element, is heated under abnormal conditions, it triggers the diaphragm to activate, rapidly cutting off the power supply to the heating element and preventing dry burning. The advantages of this invention are its simple structure, small size, and low cost; rapid and reliable operation; and the fact that the main body of the overheat protector does not need to be directly immersed in the heating medium. It is particularly suitable for overheat protection of heating elements in various electrical appliances and equipment.

Instruction Manual for Manually Reset Overheat Protector for Electric Heating Elements

This invention relates to the field of overheat protection technology for heating elements, specifically a manually reset overheat protector for electric heating elements.

Most existing household appliances and daily electrical appliances use electric heating elements as their heating conversion components. Due to the continuous increase in the surface load of electric heating elements, especially those used for heating liquid media, their surface load can reach 20 W/cm² or even higher. If the heated liquid is insufficient or excessively evaporates, the heating element will be exposed above the liquid surface, causing it to burn out. This can result in damage to household appliances or, in severe cases, electrical short circuits and fires, with potentially disastrous consequences.

The purpose of this invention is to provide a manually reset overheat protector for heating elements that does not require direct immersion in the heating medium. When the heating element is in an abnormal state, it can quickly cut off the power supply to prevent dry burning.

This invention is achieved as follows: An overheat protector for heating elements with manual reset includes upper and lower cavities of the housing. A control contact mechanism, consisting of terminals and stationary contacts, a moving contact plate and moving contacts, and a spring, is located in the lower cavity. The temperature sensing device consists of a diaphragm box, a diaphragm box handle, and a capillary tube extending from the diaphragm box, all located in the upper cavity. The diaphragm box is triggered by heat when heated under abnormal conditions via the capillary tube tightly wound around the heating element. A push rod is provided between the diaphragm box and the control contact mechanism to reset the control contacts.

The advantages of this utility model are its simple structure, small size, low cost, rapid and reliable operation, large capacity, and the fact that the overheat protector body does not need to be directly immersed in the heating medium. It is particularly suitable for overheat protection of electric heating elements used in various household appliances, home appliances, and production equipment.

Figure 1 is a schematic diagram of the structure of this utility model under normal operating conditions;

Figure 2 is a schematic diagram of the structure of this utility model under abnormal operating conditions;

Figure 3 is a schematic diagram of the circuit principle of this utility model applied to temperature control and overheat protection of electric heating elements in electric water heaters.

The following embodiments further illustrate this utility model in detail.

Referring to Figure 1, the housing 13 has an upper cavity 5 and a lower cavity 14. The diaphragm box 4 and the diaphragm box handle 2 are integrated. One end of the capillary tube 1 passes through the cap 7, and the diaphragm box handle 2 is moved to the center of the cap 7. At this time, the H-type retaining spring 3 is inserted and pushed to the normal position, so that one end of the diaphragm box handle 2 is in close contact with the cap 7, and the other end is in close contact with the H-type retaining spring 3. Next, the cap 7, containing the temperature sensing device consisting of capillary tube 1, diaphragm box 4, and diaphragm box handle 2, is fitted into the upper cavity 5 of housing 13 and tightened. Terminals 9 with riveted moving contacts 8 are installed on the left and right sides of the lower cavity 14 of housing 13. Then, push rod 6 is installed, and moving contact piece 11 with riveted moving contact 10 and spring 12 are sequentially fitted from its lower end. Finally, end cap 15 is installed, thus forming a heating element overheat protector with manual reset.

As shown in Figure 2, when the heating element is operating abnormally, the heating element temperature rises rapidly, and the capillary tube 1 wound around the tube is simultaneously heated. The working fluid pressure inside the temperature sensing device also rises sharply, causing a corresponding displacement of the diaphragm box 4 at the other end of capillary tube 1. When the temperature reaches overheating, the internal pressure of the temperature sensing device also reaches the set action value. The elastic element of diaphragm box 4 jumps abruptly, pushing push rod 6 downward, opening the moving contact 10 and stationary contact 8, thereby cutting off the power supply to the heating element.

Figure 3 shows the circuit diagram of this utility model applied to temperature control and overheat protection of electric water heaters. The capillary tube 1 is wound around the electric heating element 16. T1 is a thermostat that controls the temperature of the hot water output by the electric water heater. Under certain circumstances, when the electric heating element 16 is operating abnormally, its temperature rises rapidly. When it reaches overheating, the working fluid pressure in the temperature sensing device reaches the set activation value, causing the elastic element of the diaphragm box 4 to jump, pushing the push rod 6 downwards. This opens the previously closed moving contact 10 and stationary contact 8, thereby cutting off the power supply to the electric heating element 16, achieving overheat protection and preventing dry burning. Because the diaphragm box 4 has a double-locking function, when the overheat protector T2 cuts off the power to the electric heating element 16, the temperature of the heater will inevitably drop slowly, but the diaphragm box 4 will not reset and reconnect the power supply, achieving true safety protection. If it is necessary to reconnect the power supply to the heating element 16, a manual reset can be performed by pressing the push rod 6 to restore the diaphragm box 4 to the shape shown in Figure 1. The moving contact 10 will re-engage with the stationary contact 8, reconnecting the power supply to the heating element 16, and normal operation will be restored.