JPH087693A - Manufacture of fuse spring built-in thermostat - Google Patents

Abstract

PURPOSE:To provide a highly reliabble thermostat of a simple structure and small occupation volume by inspecting the thermostat in its manufacture process despite of having a built-in fuse spring impossible to make repetitive action. CONSTITUTION:In the manufacture of a fuse spring built-in thermostat with a built-in fuse spring 8 consisting of a spring 8a fixed by an easy-melt alloy or synthetic resin 8b in its deformed state, the fuse spring 8 part and other basic thermostat part are independently manufactured. Impossibility of repetitive action of the spring 8 results in a sampling inspection at every manufacture lot in a sampling inspection process. In a built-in process, the spring 8 having passed the inspection is built in the basic thermostat part having passed the inspection. After that, the sampling and outward appearance inspection of the completed article is performed before its shipment.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the function of a thermostat that reversibly opens and closes a circuit at a first predetermined temperature, and permanently when the temperature exceeds a second predetermined temperature higher than the first predetermined temperature. The present invention relates to a method of manufacturing a thermostat with a built-in fuse spring, which has the function of a temperature fuse that opens a fuse.

[0002]

2. Description of the Related Art A conventional temperature switch incorporated in an electric heater or the like has a thermostat which reversibly opens and closes a circuit when the temperature exceeds a first predetermined temperature, and in case of failure of the thermostat, a first A thermal fuse is combined which permanently shuts off the circuit when a second predetermined temperature, which is higher than the predetermined temperature, is exceeded.

[0003]

In relatively low cost electrical appliances, it is desirable to combine these thermostats and thermal fuses into one in order to reduce manufacturing costs. However, since different parts are incorporated, the structure becomes complicated, and it is difficult to reduce the manufacturing cost as compared with the conventional technology. In addition, product inspection is difficult.
Therefore, such a thing has not been realized.

The present invention is a thermostat having a thermal fuse function of forcibly and permanently separating the fixed contact and the movable contact of the thermostat when they are fused and cannot be separated from each other. It is an object of the present invention to provide a manufacturing method that has a small occupied volume.

[0005]

A first fixed conductor having a first terminal connected to an external circuit at one end, and a second fixed conductor having a second terminal connected to an external circuit at one end. A base that supports the first fixed conductor and the second fixed conductor while electrically insulating them from each other, a fixed contact provided on the first fixed conductor, and one end of the second fixed conductor. An elastic conductor fixed to the movable conductor, a movable contact arranged at the other end of the elastic conductor so as to be in contact with the fixed contact, and reversibly reverses the sign of the curvature of its shape when the temperature exceeds a first predetermined temperature. A bimetal plate, which is arranged so as to deform the elastic conductor when the sign of curvature is changed, and the elastic conductor deforms so that the fixed contact and the movable contact come into contact with or separate from each other, and the spring is deformed. Fuse fixed A method of manufacturing a thermostat with a built-in fuse spring, comprising a ring, wherein when the temperature exceeds a second predetermined temperature, the fixing of the spring is released, the spring presses the elastic conductor, and the movable contact is permanently separated from the fixed contact. The fuse spring characterized in that the fuse spring part and the other basic thermostat part are manufactured independently, and the fuse spring part is extracted and inspected for each manufacturing lot, and the fuse spring of the passing manufacturing lot is incorporated into the basic thermostat. Manufacturing method of built-in thermostat.

[0006]

A description will be given of a case where the spring is a coil spring and a fuse spring is used which is fixed by an easily melted alloy in a compressed state of the coil spring. In the coil spring, when the melting point of the easily meltable alloy or the synthetic resin, which is the second predetermined temperature, is exceeded, the easily meltable alloy or the synthetic resin is melted, and the spring must expand.

In the present invention, the function inspection is performed on the coil springs randomly extracted from each manufacturing lot. That is, the easily melted alloy or synthetic resin melts,
Check the temperature at which the spring extends. As a result, only fuse springs belonging to the lot determined to meet the standard are incorporated into the basic thermostat part.

The basic thermostat portion has a function equivalent to that of a normal thermostat in which contacts are turned on and off by a bimetal. Therefore, this portion can be non-destructively inspected and, if necessary, can be inspected for all products or for each lot.

The thermostat manufactured by the method of the present invention has a high reliability in spite of including the part of the fuse spring which operates only once.

The fuse spring can also be realized using a shape memory alloy. At this time, for example, a coil spring elongated at a high temperature is formed, and this is deformed into a coil spring compressed at a low temperature. When the temperature exceeds the transformation of the shape memory alloy, the spring momentarily expands and the movable contact 6 separates from the fixed contact 2.

[0011]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of an example of a thermostat manufactured by the method according to the present invention.

The first fixed conductor 1 has a first terminal 1a connected to an external circuit at one end. A tongue-shaped portion 1b is provided at the center of the first fixed conductor 1, the tongue-shaped portion 1b is bent in a step shape, and the fixed contact 2 is attached to the end of the tongue-shaped portion. A perspective view of the first fixed conductor 1 is shown in FIG.

Similarly, the second fixed conductor 3 has a second terminal 3a connected to an external circuit at one end, and a tongue-shaped portion 3b is provided in the central portion, and the tongue-shaped portion 3b has a step shape. It is bent.

The first fixed conductor 1 and the second fixed conductor 3 are
It is embedded in a base body 4 made of an electrically insulating synthetic resin, and is electrically insulated and fixed to each other.

One end of the elastic conductor plate 5 is fixed to the tongue portion 3b of the second fixed conductor, and the movable contact 6 is provided at the other end of the elastic conductor plate 5. The movable contact 6 is arranged at a position where it can contact the fixed contact 2.

The elastic conductor plate 5 is provided with a claw 5a formed in a C shape and bent in a step shape, and the bimetal plate 7 is held by the elastic conductor plate 5 by the claw 5a.

The bimetal plate 7 is made of a bimetal material that changes the sign of the curvature of the shape when the temperature exceeds a predetermined temperature. In this embodiment, a hole is formed in the central portion of the elastic conductor plate 5,
The tops of the projections 4a provided on the base body 4 penetrate through this hole. As a result, when the sign of the curvature of the shape of the bimetal plate 7 is changed, the movable contact 6 is momentarily separated from the fixed contact 2,
Alternatively, a so-called snap action of contact is obtained.

A fuse spring 8 is arranged below the elastic conductor plate 5 and is fixed to the substrate 4.

The fuse spring 8 used in the embodiment of FIG. 1 has the following structure as shown in the perspective view of FIG.
The coil spring 8a is embedded in the easily meltable alloy 8b in a state of being contracted and deformed.

The fuse spring 8 is, for example, as shown in FIGS.
As shown in FIG. 3, the coil spring 8b is placed in the female die 9a, the columnar easy-melting alloy is placed in the center of the coil spring 8b, and the male die 9b is used to press and crimp it. The fuse spring 8 is preferably coated with at least one kind of flux to prevent oxidation.

Alternatively, the fuse spring 8 can be obtained by immersing the spring in a melted easily melted alloy in a deformed state and solidifying the spring in the deformed state.

When the temperature becomes higher than the melting point of the easily melted alloy which is the second set temperature, the easily melted alloy melts and the coil spring 8b extends as shown in FIG. 3 to push up the elastic conductor plate 5. As a result, the movable contact 6 separates from the fixed contact 2. This is an irreversible process, and this state is maintained even when the temperature drops and the easily melted alloy solidifies. That is, the fuse spring 8 functions as a thermal fuse.

In another embodiment, the coil spring may push up the bimetal plate 7 and, as a result, push up the elastic conductor plate 5.

It is preferable that the length of the coil spring becomes 1.5 times or more when it is moved from the compressed state to the extended state.

The fuse spring 10 is housed in the concave portion 4b, and when the coil spring is extended, it is brought into contact with the elastic conductor plate 5 to prevent metal droplets from scattering.

FIG. 7 is a cross-sectional view of another preferred embodiment of fuse spring 8. In this embodiment, at least the side surface and the upper surface of the fuse spring 8 are covered with the cap 8c.

The easily melted alloy is melted, and the coil spring 8a
When is extended, the metal droplet 8d may be scattered as shown by the dotted line in FIG. In the embodiment of FIGS. 7 and 8, the cap 8c prevents the metal droplet 8d from scattering.

FIG. 9, FIG. 10 and FIG. 11 show another example of a fuse spring built-in thermostat manufactured by the manufacturing method of the present invention. This embodiment differs from the embodiment of FIG. 1 only in the structure of the fuse spring. Therefore, the same reference numerals are given to the corresponding members in both embodiments, and the description of those members will be omitted.

The fuse spring 10 of this embodiment is
The elastic plate 10a is formed by bending the elastic plate 10a by about 180 °, inserting a protrusion 10b provided near one end of the elastic plate 10a into a hole 10c provided near the other end, and fixing the elastic plate 10a with an easily meltable alloy or a synthetic resin 10d.

The fuse spring 10 has a through hole 10
d and 10e are provided, and are arranged so that the projection 4a of the base 4 penetrates. At this time, a portion in which the protrusion 10b is fixed with the easily-melting alloy or the synthetic resin is housed in the recess 4b provided in the base 4.

When the temperature becomes higher than the melting point of the easily melted alloy or the synthetic resin, the fixing of the elastic plate of the fuse spring 10 is released, and one end 10f of the elastic plate pushes up the elastic conductor plate 5 from below. As a result, the movable contact 6 separates from the fixed contact 2. At this time, even if a molten droplet is formed, it does not scatter outside the concave portion 4b. This is an irreversible process, and this state is maintained even if the temperature is lowered, as in the case of FIG.

12 and 13 show the fuse spring 1
2 is another embodiment of the present invention. In this embodiment, the torsion coil spring 11a is immersed in a melted easily melted alloy or synthetic resin in a deformed state, and the easily melted alloy or synthetic resin 11b is fixed in a deformed state of the torsion coil spring 11a. The fuse spring 11 is formed by. Such a fuse spring 11 is arranged in place of the fuse spring 8 of FIG.

When the melting point of the easily melted alloy or the synthetic resin is exceeded, the fuse spring 11 is released from the fixing and one end moves in the direction of the arrow in FIG. When the elastic conductor plate 4 is pushed up when it moves in the direction of the arrow, the movable contact 6 is separated from the fixed contact 2, and this is an irreversible process, as in the embodiment of FIG.

FIG. 14 shows a flow chart of the method according to the invention.

In the basic thermostat part manufacturing process, for example, the part except the part of the fuse spring 8 of FIG. 1 is manufactured.

On the other hand, in the fuse spring manufacturing process, for example, the fuse springs shown in FIGS. 1, 4, 7, 10, and 12 are manufactured.

Since the fuse spring cannot be repeatedly operated, the sampling inspection is performed for each manufacturing lot in the sampling inspection process.

The inspection is carried out, for example, when the temperature of the fuse spring is raised, the temperature at which the spring expands due to melting of the easily melted alloy or synthetic resin, or exceeding the transformation temperature of the shape memory alloy. Inspect whether or not the standard is met by measuring.

In the assembling step, the fuse spring that has passed the inspection is incorporated into the basic thermostat portion that has passed the inspection. Since the part of the basic thermostat performs repetitive motion, 100% inspection or sampling inspection is performed by a known method. After that, the finished product is subjected to a sampling inspection, a visual inspection, and the like before shipment.

[0041]

EFFECTS OF THE INVENTION A thermostat with a built-in fuse spring that cannot be repeatedly operated,
By performing an inspection during the manufacturing process, it is possible to provide a highly reliable thermostat with a built-in fuse spring.

[Brief description of drawings]

FIG. 1 is a conceptual cross-sectional view of a fuse spring built-in thermostat manufactured by the method of the present invention.

FIG. 2 is a perspective view of the first fixed conductor 1 of FIG.

3 is a conceptual abbreviated view of the state of the thermostat with a fuse spring shown in FIG. 1 above a second predetermined temperature.

FIG. 4 is a perspective view of a preferred example of a fuse spring.

5 is a cross-sectional view in a step of manufacturing the fuse spring of FIG.

6 is a cross-sectional view in a step of manufacturing the fuse spring of FIG.

FIG. 7 is a sectional view of another preferable example of the fuse spring.

8 is a conceptual drawing showing a state of the fuse spring of FIG. 7 at a second predetermined temperature or higher.

FIG. 9 is a cross-sectional view of another preferred embodiment of a fuse spring.

FIG. 10 is a perspective view for explaining the function of the fuse spring of FIG.

FIG. 11 is a perspective view for explaining the function of the fuse spring of FIG.

FIG. 12 is a cross-sectional view of yet another preferred embodiment of a fuse spring.

13 is a cross-sectional view of the fuse spring of FIG.

FIG. 14 is a flow chart of a method according to the present invention.

[Explanation of symbols]

 1 First Fixed Conductor 2 Fixed Contact 3 Second Fixed Conductor 4 Base 5 Elastic Conductor Plate 6 Moving Contact 7 Bimetal Plate 8 Fuse Spring 10 Fuse Spring 11 Fuse Spring

Claims (5)

[Claims] 1. A first fixed conductor having at one end a first terminal connected to an external circuit, and a second fixed conductor connected to the external circuit.
A second fixed conductor having one terminal at one end, a base body that supports the first fixed conductor and the second fixed conductor while electrically insulating them from each other, and a base provided on the first fixed conductor. A fixed contact, an elastic conductor having one end fixed to the second fixed conductor, a movable contact arranged at the other end of the elastic conductor so as to be in contact with the fixed contact, and when the temperature exceeds a first predetermined temperature, It is a bimetal plate that reversibly reverses the sign of the curvature of the shape, and is arranged so as to deform the elastic conductor when the sign of the curvature is changed. Alternatively, a bimetal that separates and a fuse spring that is fixed in a deformed state of the spring are provided, and when the second predetermined temperature is exceeded, the fixing of the spring is released, the spring presses the elastic conductor, and the movable contact The above In the method of manufacturing a thermostat with a built-in fuse spring that is permanently separated from the constant contact, the fuse spring part and the other basic thermostat parts are manufactured independently, and the fuse spring part is inspected for each manufacturing lot A method of manufacturing a thermostat with a built-in fuse spring, characterized in that the fuse spring of is incorporated into a basic thermostat. 2. The fuse spring is obtained by fixing a coil spring in a compressed and deformed state with an easily meltable alloy or a synthetic resin, and inspecting the fuse spring portion, the fuse spring is in an extended state at a predetermined temperature. The method of manufacturing a thermostat with a built-in fuse spring according to claim 1, wherein the above is confirmed. 3. The fuse spring is formed by deforming a leaf spring and fixing both ends of the leaf spring close to each other with an easily fusible alloy or a synthetic resin. The fuse spring portion is inspected at a predetermined temperature. The method for manufacturing a thermostat with a built-in fuse spring according to claim 1, characterized in that it is confirmed to open the fuse. 4. The fuse spring is a torsion coil spring fixed in a torsionally deformed state using an easily-melting alloy or a synthetic resin. When the fuse spring is inspected, the torsional deformation is released at a predetermined temperature. The method for manufacturing a thermostat with a built-in fuse spring according to claim 1, characterized in that the above is confirmed. 5. Regarding the basic thermostat part,
The method for manufacturing a fuse spring built-in thermostat according to claim 1, wherein an inspection is performed to confirm that the bimetal is deformed at a predetermined temperature and the fixed contact and the movable contact are opened or closed.