JPH0421293B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention relates to a fuse that protects equipment and circuits by blowing out and cutting off the current when an excessive current flows due to a short circuit accident or the like occurring in an electric circuit. be.

[Prior art] Figures 6 and 7 are, for example, disclosed in Japanese Patent Application Laid-Open No. 57-57447.
FIG. 3 is a sectional view showing a conventional fuse and its operation display device shown in FIG. In the figure, 1 is an insulating tube made of porcelain or a microwave oven, 2 is a terminal metal made of copper that is attached to both ends of the insulating tube 1 in a sealed manner and is connected to an electric circuit (not shown), and 3 is an insulating tube. A main fuse element made of a low-resistance material such as silver is housed in a tube 1 and its end is connected to a terminal metal 2. A main fuse element 4 is installed in one terminal metal 2 and is displayed as the main fuse element 3 melts. An operation display device which displays that the fuse has operated by blowing out the fuse element 10 and protruding the display member 12; 5 is the terminal metal 2 excluding the inside of the operation display device 4;
This is an arc extinguishing agent made of silica sand that is filled in an insulating cylinder 1 closed by a fuse element 2 and extinguishes the arc generated after the fuse elements 3 and 10 are fused. FIG. 7 is an enlarged view of the operation display device 4.
is a case made of an insulating material that surrounds an opening 2a formed in the center of one terminal metal 2 and prevents the arc extinguishing agent 5 from flowing in, and has an opening 6b in the bottom 6a. Note that the case 6 forms a display chamber 6c. 7 is a display cap which is housed in the display chamber 6c and has a cylindrical shape that is thinner than the opening 2a of the terminal metal 2, has a small opening 7b at the tip 7a, and a flange 7c larger than the opening 2a at the other end; 8 is the display cap; 7, one end is in contact with the inner surface of the tip 7a of the display cap 7, and the other end is in contact with the inner surface of the tip 7a of the display cap 7.
The terminal metal 2 is placed in contact with the bottom 6a of the display cap 7.
A biasing device consisting of a pushing spring that applies biasing force so as to protrude outward from the opening 2a of the display cap 7; reference numeral 9 denotes a head 9a larger than the tip opening 7b of the display cap 7 and the opening 7b.
The body 9b becomes thinner and the body 9b is drawn into the display cap 7 from the tip opening 7b, passes through the inside of the biasing device 8, and extends close to the bottom 6a of the case 6, thereby extending the body 9b. A display rod 12 is a display member composed of the display cap 7 and the display rod 9, and 10 is connected to terminal metal 2 at both ends. , 2, and an opening 6 is connected to the opening 6 on the way.
Enter the display chamber 6c from b and press the body 9 of the display rod 9.
A display fuse element made of a high resistance material such as nichrome wire holds the display member 12 through the cross hole 9c at the end opposite to the head of b, and 11 connects the display fuse element 10 to the wall of the opening 6b of case 6. This is a plug made of a wedge-shaped insulating material that is pressed against the display fuse element 10 to hold the display member 12 in a retained state against the biasing force of the biasing device 8.

FIG. 8 shows another example of the structure of the conventional fuse operation display device disclosed in U.S. Pat. In this example, the display member 12 and the biasing device 8 are housed in a recess 1a provided in the insulating tube 1.
A functions as the display chamber 6c in the case of the configuration shown in FIG. 7 above. In addition, the display fuse element 10 holding the display member 12 enters the insulating cylinder through the small hole 1b formed at the bottom of the recess 1a, and is fixed at both ends to the terminal metal in a tensioned state. The display member 12 is retained without being fixed by the plug 11 in the case of the configuration shown in FIG.

FIG. 9 shows still another example of a different configuration of the conventional fuse operation display device disclosed in Utility Model Application Publication No. 58-344, and is an enlarged sectional view of the main part.
In this example, the display device 4 is attached to one terminal metal 2 in the same manner as in the configuration shown in FIG. 7 above. In the figure, 13 is a cylindrical member made of copper or iron that surrounds the opening 2a made in the center of the terminal metal 2 and is attached to the terminal metal 2. 14 is a cylindrical member that seals the end of the cylindrical member 13 and has a small hole in the center. The lid 14 is made of an insulator and has a cylindrical member 13.
It is held by the reduced diameter portion 13a. The display fuse element 10 passes through the transverse hole 9c of the display rod 9 and holds the display member 12 in place.One end of the display fuse element 10 is wrapped around the protrusion 13b of the cylindrical member 13 and fixed by caulking, and the other end is attached to the lid 14. It is pulled out through the small hole 14a of the lid 14 and connected to the other terminal metal 2, and is fixed by the crimp sleeve 15 at the point where it exits from the small hole 14a of the lid 14. In this example,
The cylindrical member 13 and the lid 14 form a display chamber 16, which differs greatly from the case shown in FIG. It is a point.

Next, the operation will be explained. Although the explanation will mainly be made using the configurations shown in FIGS. 6 and 7 as an example, the configurations shown in FIGS. 8 and 9 are basically the same.

The main fuse element 3 and the display fuse element 10 are electrically connected in parallel, but the main fuse element 3 is made of low-resistance silver, and the display fuse element 10 is made of high-resistance nichrome. Therefore, most of the current normally flows through the main fuse element 3. and,
When an excessive current such as a short circuit current flows through the fuse, the main fuse element 3 melts and becomes high resistance, and when the current is commutated to the display fuse element 10 and the display fuse element 10 melts,
An arc is generated in both the main fuse element 3 and the display fuse element 10, and this arc is extinguished by the action of the surrounding arc extinguisher 5, thereby interrupting the excessive current. Then, the display member 12, which is released from the hold by the display fuse element 10 melting, is moved outside from the opening 2a of the terminal metal 2 by the biasing force of the biasing device 8, and the display member 12 is moved to the outside from the opening 2a of the terminal metal 2. The portion 7c protrudes until it comes into contact with the inner surface of the terminal metal 2 and stops, indicating that the fuse has operated. After operation, a hole 17 is formed at the location where the display member 12 was held back and the display fuse element portion 10c led out from the display chamber 6c into the arc extinguishing agent 5, as shown in FIG. .

Here, the display fuse element 10 is fused at a portion 10 buried in the arc-extinguishing agent 5 with good thermal conductivity.
It first occurs in the part 10b in the air where the display member 12 is held back in the display chamber 6c than that in the air, and then progresses to the part 10a in the arc-extinguishing agent, so generally the display fuse Both elements 10a and 10b are made to have the same thickness, but in order to more reliably fuse the portion 10b that holds the display member 12 in place first, the elements 10a and 10b are made to hold the display member more in place than the portion 10a in the arc extinguisher. part 10b
In some cases, it is made thinner or made of a material with higher resistance.

[Problem that the invention seeks to solve]

In conventional fuses, the temperature inside the fuse becomes extremely high due to the generation of arc following the melting of the fuse element due to excessive current, resulting in high pressure, so the display member 12 must be held back after operation. The internal gas blows out from the hole 17 formed by blowing out the portion 10c of the display fuse element led out from the display chambers 6c, 1a, 16 into the arc extinguishing agent 5, and furthermore, this gas blows out from the opening 2a of the terminal metal 2. and erupts out of the fuse. After that, the heat of the fuse is gradually transferred to the surrounding air and cooled down, and eventually the temperature of the fuse becomes equal to the temperature of the atmosphere. During the cooling period after releasing this internal gas, the air pressure inside the fuse becomes negative pressure,
This time, reverse the above display fuse element 10c.
Atmospheric air is sucked in through the hole 17 formed by fusing the portion. At this time, if the atmospheric humidity is high, moisture will be sucked into the fuse, and especially if the fuse is for outdoor use and operates during rain, rainwater will be sucked in. After the arc generated in the fuse elements 3 and 10 is extinguished by the action of the surrounding arc extinguishing agent 5, the constituent metals of the fuse element are diffused into the molten arc extinguishing agent 5 and are called FULGURITE. However, when the moisture is absorbed, the falgelite and the arc quenching agent absorb water, reducing the insulation resistance and causing a risk of flash shorting in conventional fuses.

This invention was made to solve the above-mentioned problems, and aims to provide a fuse that does not inhale air or rainwater and does not cause flashbacks even if it is cooled down after the fuse operates. purpose.

[Means for solving problems]

The fuse according to the present invention is provided with a heat-softening member attached to the case at a portion where the display fuse element leads out from the display chamber into the arc-extinguishing agent, and the display fuse element is passed through or opened in the heat-softenable member. It is derived from the boundary between the nearby case and the thermosoftening member.

[Effect]

Even when the fuse in this invention operates and the internal pressure becomes high, the heat-softening member softens and closes the hole formed when the display fuse element melts, so that the internal gas does not blow out to the outside. do. Therefore, after cooling, high humidity air or rainwater is not inhaled, and flash flashing is prevented.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to FIGS. 1 to 3. 1, 2, and 3 show examples in which the present invention is applied to fuses with conventional structures shown in FIGS. 7, 8, and 9, respectively. The opening 6b of the case 6 is located at the portion where the display fuse element 10 is led out from the respective display chambers 6c, 1a, 16 into the arc extinguisher 5.
The display fuse element 10 is a heat-softening member installed in the vicinity of the heat-softening member 18, and the display fuse element 10 is led out by passing through the heat-softenable member 18. The rest of the configuration is the same as the conventional one, so the explanation will be omitted.

Here, the heat-softening member 18 is made of a material that softens due to the melting of the fuse elements 3 and 10 and the subsequent heat of the arc, and has no air permeability. A suitable material is one that adheres to 10 and acts as a seal. An example of such a material is a thermoplastic polymer compound that is commercially available as a hot melt adhesive that is heated to form a liquid or grease, applied to the assembled operation display device, and then cooled and hardened. confirmed.

Next, the operation will be explained. The configuration shown in FIG. 1 will be described as an example, but the other configurations shown in FIG. 2 or 3 are basically the same.

When an excessive current flows through the fuse and the display fuse element 10 is blown, the display member 12 released from the retainer is moved to the terminal metal 2 by the biasing force of the biasing device 8.
It projects from the opening 2a of the fuse to indicate that the fuse has operated, but at this time, after the operation, the part 10c of the display fuse element 10 leading out from the display chamber 6c into the arc extinguishing agent 5 is located at the location shown in FIG. A small hole 19 as shown in FIG. Even if an attempt is made to blow out through the fuse 19, the heat softening member 18 softens and is deformed by being pressurized from the surrounding area by the above-mentioned high pressure, as shown by the arrow in FIG. Gas is prevented from blowing out to the outside. Therefore, even if the fuse cools down afterwards, unlike conventional fuses, the internal pressure becomes negative and air and rainwater will not be sucked in. Therefore, there is no drop in insulation resistance due to water absorption by falgelite and arc extinguisher. , the risk of re-flashing can be eliminated.

In the above embodiment, the display fuse element 10 is connected to the arc extinguisher 5 from the display chamber 6c, 1a or 16.
A heat-softening member 18 is placed in the display chamber in the portion led out into the inside of the display chamber.
4, the display fuse element 10 is inserted along the outer surface of the display chamber 6, and as shown in FIG. It may be fixed with a thermosoftening member 18.

In addition to the above configuration example, the operation display device also includes:
For example, there are cases where the device is installed protruding outside the terminal metal as shown in Fig. 1 of JP-A-57-101318, and there are various other configurations, but this method can also be used for operation display devices with different configurations. The invention is valid.

Further, in the above embodiment, the main fuse element 3 and the display fuse element 10 are provided in parallel, but in the case of a fuse with an extremely low rated current, the display fuse element 10 also serves as the main fuse element 3, and the main fuse element 3 is eliminated. This invention is also effective for such things.

〔Effect of the invention〕

As described above, according to the present invention, since the heat softening member attached to the case is provided at the part where the fuse element leads out from the display chamber into the arc extinguishing agent, the inside becomes high pressure when the fuse operates. However, internal gas does not blow out to the outside, and high humidity air and rainwater are not inhaled after cooling, which has the effect of preventing a drop in insulation resistance and re-flash shorting.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a fuse according to an embodiment of the present invention, particularly showing its operation display device and its vicinity, and FIGS. 2 and 3 are cross-sectional views showing examples in which the present invention is implemented in fuses of other different structures. 4 is a cross-sectional view showing a fuse operation display device and its vicinity according to another embodiment of the present invention, FIG. 5 is a cross-sectional view showing the main part of the fuse of the present invention after operation, and FIG. is a sectional view showing a conventional fuse, No. 7
9 to 9 are sectional views showing different conventional fuse operation display devices and their vicinity, and FIG. 10 is a sectional view showing the main parts of the conventional fuse after operation. In the figure, 4 is an operation display device, 5 is an arc extinguisher,
6 is a case, 6c, 1a, and 16 are display chambers, 8 is a biasing device, 10 is a fuse element, 12 is a display member, and 18 is a thermoplastic member. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Scope of Claims] 1. An insulating tube, a terminal metal provided at both ends of the insulating tube, a case provided on one side of the terminal metal to form a display chamber and having an opening in the insulating tube, and an opening in the display chamber. An operation display device comprising a display member housed in the insulating cylinder and constantly receiving an operating force in the direction of the display operation to the outside of the insulating cylinder; A fuse element that enters the display chamber and is locked to the display member so as to hold the display member in the display chamber against the operating force, and an arc-extinguishing material filled in the insulating cylinder except for the display chamber. , and a fuse comprising a thermosoftening member that closes an opening of the case and is attached to the case near the opening to fix the fuse element near the opening to the case. 2. Claim 1, characterized in that the heat-softening member is heated to make it into a liquid or grease state, and after being applied to the case, it is cooled and hardened.
Fuses listed in section.