JPH0313696B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a thermal protector that detects a rise in temperature of a device and disconnects a circuit.

(Background Art) Conventionally, this type of thermal protector has been formed by combining a temperature-sensitive contact portion and a current fuse portion that are formed separately, but this has the disadvantage that the structure is complicated and the cost is high.

(Objective of the Invention) The present invention has been made in view of the above points, and an object of the present invention is to provide a thermal protector that is simple in structure, low in cost, and in which arcing is difficult to continue when the current fuse section is blown. That is.

(Disclosure of the Invention) (Embodiment 1) Fig. 1 shows an embodiment of the present invention, in which 1 is a temperature-sensitive contact consisting of a U-shaped movable contact spring 2, a bimetal 3, and terminal plates 4a and 4b. When the temperature exceeds a predetermined value, the bimetal 3 deforms and pushes up the leg 2a of the movable contact spring 2, thereby separating the movable contact 5 from the fixed contact 6.
Reference numeral 7 denotes a notch that forms a current fuse part 8. This notch 7 is provided on the outside of the leg piece 2b of the movable contact 2, and the narrow part formed inside the notch 7 is the current fuse part 8, and is a temperature-sensitive contact. When the section 1 is housed in the case 9, the current fuse section 8 is arranged approximately at the center of the case 9.

Now, if the coil of a device (for example, a fluorescent lamp ballast) is overheated by a rare shot, etc., the bimetal 3 will detect the heat and reverse, pushing up the leg piece 2a of the movable contact spring 2 and causing the movable contact 5 to It is pulled away from the fixed contact 6, the circuit is briefly broken, and the current flowing to the device is momentarily cut off. On the other hand, when a large current flows through the device, such as when an overvoltage is mistakenly applied (applying 200V to a 100V device) or when a short circuit occurs, the temperature of the device will rise rapidly. Does not follow the rise.
Therefore, a large current flows through the movable contact 5 while it is in contact with the fixed contact 6, but at this time, the current fuse portion 8 blows and breaks the circuit, thereby preventing the equipment from burning out. By the way, when the current fuse part 8 melts, the metal vapor may adhere to the inner wall of the case 9 and an arc may continue to occur. By arranging the current fuse section 8 approximately at the center of the case 9, the distance from the inner wall is made as large as possible, making it difficult for arcs to continue to occur, thereby reliably preventing equipment burnout. This also means that the protector itself can be prevented from being burnt out.

(Example 2) Figures 2 and 3 show another example, in which notches 7, 7a are provided in the leg piece 2b of the movable contact spring 2, and a plurality of current fuse parts 8, 8a are provided. If one of the current fuse parts 8 is blown and an arc is generated and the circuit is not reliably broken, the current fuse part 8a is subsequently blown.

Now, even though both current fuse parts 8 and 8a have blown, if arcs A ₁ to A ₄ occur through the inner wall of case 9 to which metal vapor has adhered, as shown in FIG. Since the overall arc voltage (sum of each arc voltage) is larger than that in the case of only 8 arc voltages, it becomes difficult for the arc to continue, and the circuit can be broken more reliably.

(Effects of the Invention) The present invention is constructed as described above, and the current fuse section is formed by providing cutouts at important points in the movable contact spring of the temperature-sensitive contact section, so the construction is simplified and the cost is reduced. In addition, by providing a notch on the outside of one leg of the U-shaped movable contact spring and using the narrow part formed on the inside as the current fuse part, the current fuse part can be separated from the inner surface of the case. Since the protector is placed at a position where the protector is fused, it is difficult for the arc to continue at the time of melting, and it is possible to prevent burnout of the equipment and the protector itself. In other words,
In the present invention, since the current fuse section is provided in the center of the case away from the inner surface of the case, when the current fuse section is blown, metal vapor adheres to the inner surface of the case and is transmitted through the metal attached section. This has the effect that arcs do not occur continuously, and it is possible to prevent equipment burnout or thermal protector itself from burning out due to continued arcing.

[Brief explanation of drawings]

Fig. 1 is a perspective view of essential parts of an embodiment of the present invention;
The figure is a top view of the main parts of the same as the above, and FIG. 3 is a top view of the main parts showing the operation of the same. 1 is a temperature-sensitive contact portion, 2 is a movable contact spring, 7 is a notch, 8 is a current fuse portion, and 9 is a case.

Claims (1)

[Claims] 1. In a thermal protector in which a temperature-sensing contact and a current fuse are integrally housed in a case, a notch is provided on the outside of one leg of the U-shaped contact spring that constitutes the temperature-sensing contact, and a cutout is provided on the inside of the A thermal protector characterized in that the formed narrow width portion is used as a current fuse portion, and the current fuse portion is disposed at a position away from the inner surface of the case.