JPH04274120A - Thermal protector - Google Patents

Abstract

PURPOSE:To double the security/protection function of a contact switching type thermal protector against the excessive temperature-rise in which a heat- responsive working plate used for preventing an excessive rise in the temperature of an electrical load is employed. CONSTITUTION:In a vessel 11, is received a fabricated body wherein a fixed electrode 3 having a fixed contact 2 at one end of an elastic metal-body 1 is arranged to face a moving electrode 6 having a moving contact 5 at one end of a heat responsive working plate 4. A thermally sensitive fusible-body 12 is arranged between the vicinity of the back face of the elastic metal-body whereto the fixed contact 2 of the fixed electrode 3 is attached and the vessel 11 or a supporting body substitutable therefor, and also a locking means 13 is provided near an end portion on the side of the moving contact of the heat- responsive working plate 4, and when the circumambient temperature of a thermal protector rises abnormally above the fusing temperature of the thermally sensitive fusible-body 12, the thermally sensitive fusible-body 12 is fused so as to normally open the fixed contact 2 and the moving contact 5.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a thermal protector using a thermally responsive element, especially when the surrounding temperature rises abnormally.
This relates to a thermal protector that keeps the contacts open at all times and has a dual safety protection function against overtemperature.

0002

2. Description of the Related Art A thermal protector using a thermally responsive plate has a fixed electrode and a movable electrode as main parts. The fixed electrode is made of a metal plate, and the movable electrode is made of a thermally responsive element. When the movable electrode curves and deforms due to a temperature change, the electrodes are arranged so that they face each other so that when the movable electrode is bent and deformed due to a temperature change, one end of both electrodes comes into contact and separates, and the electric circuit connected to both electrodes is interrupted. and is fixedly supported at the other end. A fixed contact and a movable contact are attached to the contact points between both electrodes so that they can withstand multiple interruptions. The other end of the metal plate of the fixed electrode is implanted in a support means such as a resin bead, but the movable electrode is connected and fixed to a metal movable electrode terminal, and the other end of this movable electrode terminal is supported. The means are planted and fixed. Both electrodes are housed in a container, and the fixed electrode and movable electrode terminals pass through the support means to which lead wires are connected.

Thermal protectors are attached to motors, fluorescent lamp ballasts, etc., electrically connected in series with these loads, and used to protect these loads from overheating. In other words, when the load fails and the temperature rises,
The thermal protector contacts open, opening the electrical circuit. When the load temperature decreases and reaches the thermal protector's return temperature, the contacts close and the current is turned on again. The thermal protector repeats opening and closing until the cause of the load failure is removed or the power is turned off, keeping the load below a certain temperature and protecting the load from abnormal overheating or fire. This is the thermal protector's primary safety protection against overtemperature.

0004

[Problem to be Solved by the Invention] However, if there is a delay in removing this fault or turning off the power, and the thermal protector continues to open and close the load for a long period of time, the thermal protector's durability limit for opening and closing times will eventually be exceeded, and the contacts will remain closed all the time. state,
The load may overheat and create a fire hazard.

SUMMARY OF THE INVENTION An object of the present invention is to provide a thermal protector that has a second safety protection function against overheating by allowing the contacts to be kept open when the load abnormally overheats.

[0006]

[Means for Solving the Problems] In order to achieve the above object, the thermal protector of the present invention has a fixed electrode made of an elastic metal plate, a movable electrode made of a thermally responsive plate, and these electrodes face each other at low temperatures. comprising a support means for supporting both electrodes at the other end so that they are in contact and separated by deformation of the thermally responsive material at a high temperature above a certain temperature, and a container containing the fixed electrode, the movable electrode, and the support means, A temperature-sensitive meltable body is provided behind the fixed electrode, a locking means is provided in a deformation range of the movable electrode, and the temperature-sensitive meltable body is melted at a desired second constant temperature equal to or higher than the constant temperature. The fixed electrode can be moved back, and when the fixed electrode is moved back, the locking means prevents the movable electrode from coming into contact with the fixed electrode.

[0007]

[Operation] Since the thermal protector of the present invention is constructed as described above, when the temperature rises due to a load failure,
It repeats opening and closing in the same way as before, keeps the load temperature below the intended value, fulfills the first safety protection function against overtemperature of the load, and furthermore, in the event that the cause of this load failure is not removed , or the thermal protector continues to open and close the load for a long time without the power being cut off, and eventually the thermal protector exceeds its opening/closing endurance limit and both electrodes become permanently closed, even if the load starts to overheat abnormally. , when the ambient temperature of the thermal protector reaches the melting temperature of the temperature-sensitive fusible body, the temperature-sensitive fusible body melts, so that both electrodes are permanently open, protecting the load from smoke or fire hazards. . That is, it fulfills the second safety protection function against overtemperature of the load.

[0008]

[Embodiment] As shown in FIG. 1, a thermal protector according to an embodiment of the present invention consists of an elastic metal plate 1, a fixed electrode 3 having a fixed contact 2 attached to one end, and a movable contact 5 having a thermally responsive plate 4 attached. A movable electrode 6 consisting of a fixed contact 2 and a movable contact 5
They are arranged facing each other so that they are in contact with each other. Movable electrode 6
A movable electrode terminal 7 is fixed to the other end, and the other end 8 of the fixed electrode and the movable electrode terminal 7 are fixed by support means 9 made of a resin bead, and the other end 8 of the fixed electrode and the movable electrode terminal A lead wire 10 is attached to the support means 9 on the outer side of the support means 9, and then the assembly is housed in a container 11. The thermally responsive plate 4 is a so-called bimetal made by gluing together two metal sheets having different coefficients of expansion. A trimetal that has a similar function may also be used. A concave portion is provided in the center so that the change in state between discontinuation and continuation becomes clear due to the elastic jump phenomenon or snap action. Here, the fixed electrode 3
A temperature-sensitive fusible material 12 is placed between the back surface of the fixed contact 2 and the container 11.
Place. The thermosensitive fusible body 12 melts at a second constant temperature at which the thermal protector must break the electrical circuit in any way. As the temperature-sensitive fusible body 12, temperature-sensitive pellets of organic compounds whose melting temperatures can be selected from various types, low-melting point fusible alloys, etc. are used. The fixed electrode 3 is
At normal times, the temperature-sensitive fusible body 12 is somewhat compressed due to its elasticity, and after the temperature-sensitive fusible body 12 is melted, it must be supported so as to curve backward. The same effect can be obtained by separately providing a support instead of the container 11 and arranging the temperature-sensitive fusible body 12 between the fixed electrode 1 and the support. The temperature-sensitive fusible body 12 is arranged at a position near the back surface of the fixed contact 2 where the influence of heat generated from the fixed contact 2 is as small as possible. Further, if necessary, a heat shield may be inserted between the fixed electrode 1 and the temperature-sensitive fusible body 12. A locking means 13 consisting of a step is provided near the end of the movable electrode 6 on the movable contact 5 side. That is, the locking means 13 is provided in the middle of the bottom surface of the container 11. This locking means 13
2 is not melted, both contacts 2 and 5 are reliably electrically connected, but after the temperature-sensitive meltable body 12 is melted and the fixed electrode 3 is opened due to its elasticity, both contacts 2 and 5 are reliably electrically connected. Set the position so that it is in the open state. Then, it is sealed and fixed with a resin filler 14. The melting temperature of the temperature-sensitive fusible body 13 is the second temperature that the thermal protector must be disconnected from in any case.
temperature.

[0009]

[Effects of the Invention] The thermal protector of the present invention is attached to a load such as a motor or a fluorescent lamp ballast in the same way as conventional ones, and when the temperature rises due to a failure of the load, the contacts are repeatedly opened and closed to reduce the temperature of the load. Of course, it is necessary to protect the load by limiting it to a certain value or less. Furthermore, in the unlikely event that the thermal proctor continues to open and close the load for an extended period of time without eliminating the cause of this load failure or disconnecting the power supply,
Even if the movable electrode's durability limit for opening and closing is exceeded and both electrodes become permanently closed and the load begins to overheat abnormally, the ambient temperature of the thermal protector will reach the melting temperature of the thermosensitive fusible material. At this time, the temperature-sensitive meltable body melts, and the fixed electrode 3 is warped by its own elasticity so that it does not separate from the movable electrode 6. The movable electrode 6 is stopped by the locking means 13 and cannot approach the fixed electrode 3. As a result, both electrodes are permanently open, protecting the load from smoke or fire hazards. Further, depending on the selection of the melting temperature of the temperature-sensitive fusible material, it is possible to protect the load without seriously impairing its function. Furthermore, small and inexpensive temperature-sensitive fusible materials are available, and double safety protection against overheating of the load can be achieved at low cost without significantly changing the shape or size of conventional thermal protectors. A functional thermal protector can be realized.

[Brief explanation of the drawing]

[Fig. 1] A vertical cross-sectional view of a thermal protector according to an embodiment of the present invention.

[Fig. 2] A vertical cross-sectional view showing the state after the temperature-sensitive fusible material is melted in the same thermal protector.

[Explanation of symbols]

1 Elastic metal plate 2 Fixed contact 3 Fixed electrode 4 Thermal response plate 5. Movable contact 6. Movable electrode 9 Support means 11 Container 12 Temperature-sensitive meltable material 13 Locking means

Claims (1)

[Claims] Claim 1: A fixed electrode made of an elastic metal plate and a movable electrode made of a thermally responsive plate; these electrodes face each other at low temperatures, and at high temperatures above a certain temperature, they separate due to deformation of the thermally responsive material. A thermal protector comprising a support means supporting an electrode at the other end, and a container housing the fixed electrode, the movable electrode, and the support means, the thermal protector having a temperature-sensitive fusible body behind the fixed electrode, A locking means is provided in a deformation range of the movable electrode, and the temperature-sensitive meltable body melts at a desired second constant temperature equal to or higher than the constant temperature to enable the fixed electrode to retreat; A thermal protector characterized in that, when the thermal protector is moved backward, the locking means prevents the movable electrode from coming into contact with the fixed electrode.