JPH0374453B2 - - 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.

[Conventional technology]

Figures 1 and 2 are, for example, published in Japanese Patent Application Laid-Open No. 57-57447.
FIG. 2 is a sectional view showing the conventional fuse operation display device and the entire fuse shown in FIG.
1 is an insulating tube made of porcelain or resin; 2 is a terminal metal made of copper that is attached to both ends of the insulating tube 1 in a sealed manner for connection to an electric circuit (not shown); and 3 is a terminal metal attached to the insulating tube 1. A main fuse element 4 made of a low-resistance material such as silver is housed and connected at its end to the terminal metal 2, and is installed on one terminal metal 2, and when the main fuse element 3 is fused, the fuse element 10 is displayed. The display member 12
An operation display device 5 is closed with terminal metals 2, 2 except for the inside of the operation display device 4, and is filled in an insulating cylinder 1,
This is an arc extinguishing agent made of silica sand that extinguishes the arc generated after the fuse elements 3 and 10 are fused. FIG. 1 is an enlarged view of the operation display device 4, in which 6 is attached to the terminal metal 2 so as to surround the opening 2a made in the center of one terminal metal 2, and prevents the arc extinguishing agent 5 from flowing in. Display chamber made of insulator, 6b
7 is an opening provided in the lower part 6a of the display chamber 6, and 7 is housed in the display chamber 6 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 has a small opening 7b at the other end than the opening 2a. A display cap 8 having a large flange 7c is housed in the display cap 7, with one end abutting the inner surface of the tip 7a of the display cap 7 and the other end abutting the bottom 6a of the display chamber 6.
9 is a head 9a larger than the tip opening 7b of the display cap 7;
and a body portion 9b that is thinner than the opening 7b and a body portion 9b that is narrower than the opening 7b.
is drawn into the interior through the tip opening 7b of the display cap 7, passes through the inside of the biasing device 8, and is applied to the bottom 6 of the display chamber 6.
When it extends to near point a and holds back the trunk 9b, the head 9
12 is a display member composed of the display cap 7 and the display rod 9; 10 is connected at both ends to terminal metals 2, 2; On the way, it enters the display chamber 6 through the opening 6b, passes through the cross hole 9c at the end opposite to the head of the body 9b of the display rod 9, and holds the display member 12 using a high-resistance material such as a nicram wire. The display fuse element 11 is pressed against the wall of the opening 6b of the display chamber and stored in a state where the display fuse element 10 holds the display member 12 against the biasing force of the biasing device 8. It is a wedge-shaped insulating plug that is fixed in place.

Next, the operation will be explained.

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 niklam. Therefore, most of the current at all times flows through the main fuse element 3. When an excessive current such as a short circuit current flows through the fuse, the fuse element 3 mainly melts and becomes high resistance, and when the current is commutated to the display fuse element 10 and the display fuse element 10 melts, the main fuse element 3 and An arc is generated in both 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 13 as shown in FIG. 3 is formed where the display member 12 was held back and the display fuse element portion 10c leading out from the display chamber 6 into the arc extinguishing agent 5 was located.

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 that holds the display member 12 in the display chamber 6 and has poor heat conduction than that in the display chamber 6, 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 part 10b that holds the display member 12 in place first, the part 10 in the arc extinguisher is used.
The portion 10b that holds the display member in place may be made thinner than the portion a, or may be made of a material with higher resistance.

[Problem that the invention aims 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 after operation, the display member 12 must be pulled. The part 10 of the display fuse element that is stopped and led out from the display chamber 6 into the arc extinguisher 5
The internal gas blows out from the hole 13 formed by fusing the fuse, and further blows out from the opening 2a of the terminal metal 2 to the outside of the fuse. After that, the heat from the fuse is gradually transferred to the surrounding air and cooled down.
Eventually, the temperature of the fuse becomes equal to the temperature of the atmosphere. During the cooling period after the internal gas is released, the air pressure inside the fuse becomes negative, and the atmosphere is then sucked in through the hole 13 formed by blowing out the portion 10c of the display fuse element. 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 inhaled, the falgelite and the arc quenching agent absorb water, reducing the insulation resistance and causing a risk of re-flash shorting in conventional fuses.

This invention was made to solve the above-mentioned problems, and the purpose is to obtain a fuse that does not inhale air or rainwater and does not cause re-flash even when the fuse is cooled down after operation. shall be.

[Means for solving problems]

The fuse according to the present invention is a plug made of a heat-softening material that fixes the display fuse element by pressing it against the wall of the opening of the display chamber through which the display fuse element extends from the arc-extinguishing agent into the display chamber. It has been established.

[Function] Even when the fuse of this invention operates and the internal pressure becomes high, the plug made of a heat-softening material softens and closes the hole formed when the display fuse element melts, allowing the internal gas to escape. Avoid blowing out. Therefore, after cooling, high humidity air or rainwater is not inhaled, and flash flashing is prevented.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, reference numeral 11 denotes a plug made of a heat-softening material, which is an opening in the display chamber 6 through which the display fuse element 10, whose both ends are connected to terminal metals 2, 2, extends into the display chamber 6. 6b, and presses and fixes the display fuse element 10 against the wall of the opening 6b of the display chamber 6. The rest of the configuration is the same as the conventional one, so the explanation will be omitted.

Here, the material of the plug 11 must be a material that is softened by the melting of the fuse elements 3 and 10 and the subsequent heat of the arc, and has no air permeability. Examples of such materials include Tetron,
Thermoplastic polymer compounds such as nylon are effective, and if greater strength is required to permanently restrain the fuse element displayed as a wedge, the above thermoplastic polymer compounds may be reinforced with glass fibers. things are valid.

Next, the operation will be explained.

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 fuse element 10 has a fuse at the location where the part 10c extending from the arc extinguishing agent 5 into the display chamber 6 was located. A small hole 13 as shown in Figure 3 is formed, but the temperature inside the fuse is
Due to the melting of the fuse elements 3 and 10 and the generation of arc, the pressure becomes very high and becomes a high pressure. softens and deforms to close the small hole 13,
This prevents the gas inside the fuse 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 inhaled.Therefore, there is no drop in insulation resistance due to water absorption by falgelite and arc quenching agent. It is possible to eliminate the risk of re-flashing.

In addition, in the above embodiment, the main fuse element 3
The display fuse element 10 is installed in parallel with the display fuse element 10, but in the case of a fuse with an extremely small rated current, the display fuse element 10 also serves as the main fuse element 3, and the main fuse element 3 is omitted. This invention is also effective.

〔Effect of the invention〕

As described above, according to the present invention, a plug made of a heat-softening material is provided in the display chamber as an opening for the display fuse element to extend into the display chamber from inside the arc-extinguishing agent, so that the fuse operates. Even if the inside becomes high pressure, the internal gas will not blow out to the outside, and high humidity air and rainwater will not be inhaled after cooling, which has the effect of preventing a decrease in insulation resistance and re-flash shorting.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing a fuse according to an embodiment of the present invention, particularly its operation display device and its vicinity, FIG. 2 is a cross-sectional view showing the entire fuse, and FIG. 3 is a main view of a conventional fuse after operation. FIG. In the figure, 1 is an insulating tube, 2 is a terminal metal, 4 is an operation indicator, 5 is an arc extinguisher, 6 is an indicator chamber, 8 is a biasing device, 10 is a fuse element, 11 is a plug, and 12 is an indicator member. be. In addition, in the figures, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] 1 An insulating tube, a display chamber provided on one side of the terminal metal provided at both ends of the insulating tube, and a display member housed in this display chamber that constantly receives an operating force in the direction of display operation outside the display chamber. operation display device,
Inside the insulating cylinder, each end is connected to each of the terminal metals, and extends into 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. the fuse element, the arc extinguishing agent filled in the insulating cylinder except for the display chamber, and the heat that presses the fuse element against the wall of the opening of the display chamber and fixes the fuse element against the operating force. A fuse with a plug made of softenable material.