JPS6013159Y2 - current limiting fuse - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to the structure of a current-limiting fuse that is compact and has a (breakage) indicating function.

A current-limiting fuse is one of three types (current-limiting, discharge, and retraction) classified based on the arc-extinguishing method.The fuse element is placed inside a heat-resistant cylinder made of a heat-resistant porcelain pipe or reinforced plastic. Figure 1 shows a typical example of the structure of a conventional current limiting fuse.

In Fig. 1, 1 is a cross-sectional view showing the structure, 1.2 is a fuse terminal (hardware), 3 and 3' are alarm circuit terminals, 4 is the fuse body, 5 is a lid (fitted from above), and 6 is a cross-sectional view showing the structure. The through hole in the lid is used for screwing the main body and lid together.

7 is an alarm contact, and 8 is a display window. Note that when the fuse element is disconnected, the alarm contact 7 will be pressed by the spring a to close the alarm circuit terminals 3 and 3' and operate the alarm circuit. Since it can be added as long as there is a blank space, alarm contacts will not be considered in the following.

1 and 2 are external views of the fuse tube, and 3 is a sectional view of the fuse tube, which will be easier to understand if compared with figure 1.

4 is a fuse pipe assembly process diagram.

In these figures, 9 is the fuse tube body (phenol)
, 10 is a disk (fiber), 11 is a fuse'tM
(phenol), 12 is arc quenching agent (silica sand) filling part, 13
14 is an adhesive, and 14 is a hollow portion.

To assemble the fuse tube, as shown in FIG. 1, the disk 10 is press-fitted into the fuse tube body 9, and then the fuse tube body is filled with silica sand.

Next, the adhesive 13 is applied to the inside of the fuse tube cover, the fuse tube cover 11 is inserted, and the fuse tube cover is bonded by heating and curing.

FIG. 15 is a schematic diagram of the method of assembling the main body of the fuse tube, in which adhesive is applied to the surface of the fuse pipe attachment part 16 of the main body 4,
The fuse pipe that has passed through the fuse wire 15 is placed on it and fixed using a jig so that it does not move.

Next, the adhesive is heated and cured by placing it in a constant temperature bath.

After curing, the jig is removed and the fuse wires 15 are wrapped around the terminals 1 and 2 and soldered.

The above is an explanation of the structure and assembly method of a conventional current limiting fuse.
The σ operation is such that when some overcurrent flows through the fuse, the fuse element inside the cavity blows out, cutting off the circuit.

In addition, when an excessive current flows, the fuse element inside the cavity and the arc extinguisher instantly melts and vaporizes, generating an arc, but the metal gas in the vaporized arc extinguisher rapidly diffuses and permeates into the arc extinguisher. The arc energy is also absorbed by the arc extinguisher.

Furthermore, since the traces of the fuse element have a high resistance, the voltage between the terminals of the fuse rises rapidly, suppressing the rise of the overcurrent to a much lower value than the original value, and increasing the arc resistance to complete the circuit interruption.

At this time, the metal gas inside the cavity is not released to the outside because both ends of the cavity are narrow parts with dimensions almost the same as the diameter of the fuse wire, and this does not adversely affect the breaking performance of the fuse.

However, this fuse has the following drawbacks.

A. The number of parts in the fuse tube is large, making it difficult to assemble.

(b) Adhesive is used to join the fuse tube body 9 and the fuse tube cover 11 and the fuse tube body 9 and the fuse body 4. It is difficult and requires a jig.

b) After adhesion, heat curing treatment at 100°C for about 1 hour is required, which slows down the process.

(c) The connection of the fuse wire (the winding is done by soldering afterward and the screw connection 6 between the fuse body 4 and the lid 5 is done by hand, which requires a large number of man-hours.

2. Since the fusing display window 8 does not have a cover, the operation of the alarm contact may become uncertain due to dust entering through the window.

E: If a large shock or vibration is applied to the fuse, the soldered part of the fuse wire on fuse terminal 1 will move slightly, causing the fuse wire to be strongly pressed against the narrow part of the fuse body and mechanically break. It is impossible to manufacture a fuse that requires a fine fuse wire.

The present invention eliminates the above-mentioned drawbacks and improves workability by allowing assembly by an automatic assembly machine.The present invention will be described in detail below.

FIG. 2 shows an example of the structure of the current limiting fuse according to the present invention, and part 1 is a cross-sectional view showing the structure.

Although not shown, an alarm contact similar to that shown in FIG. 1, housed in a suitable holder, is inserted into the blank space 30 on the left side of FIG. However, in this invention, an alarm contact is not provided.

2 to 5, 2 is an external view of the fuse tube, 3 is a sectional view of the fuse tube, 4 is an explanatory diagram of the fuse tube assembly process, and 5 is an explanatory diagram of the method of assembling the fuse body.

25 in these figures is the fuse tube body (made of phenol),
26 is a hollow part with an open end, 27 is an arc extinguishing agent (silica sand, etc.)
A filling part, 28 is an arc extinguishing agent, and 29 is a fuse tube cover.

First, a fuse tube main body 25 as shown in FIG. 4 is filled with silica sand, and then a fuse tube lid 29 is press-fitted to obtain a fuse tube as shown in FIGS. 2 and 3.

Next, the fuse wire 15 is inserted, but since the fuse wire is thin, the tip portion 15 is spot-welded to the terminals 21 and 22.
A is plated with silver to facilitate spotting.

Next, the method of assembling the fuse body will be explained with reference to FIG.

The fuse body consists of two parts: the main body 20, a front panel that fits into the main body 20, and a lid part 33 that serves as a cover for the top and both sides.

20 is a molded main body made of TBT, for example, and a lid portion 33 is also molded of the same material.

In assembling, first, terminal metal fittings such as 21 and 22 are inserted into the parts 20a and 20b of the main body 20, that is, the terminal metal press-fitting portions.

Next, connect the fuse tube to 20c of the main body 20 as shown in Fig. 2.
.

20d, that is, after press-fitting the fuse pipe, both ends 15a of the fuse wire are spotted on the terminals 21 and 22, respectively.

Next, attach a transparent plastic window to the groove 34 of the lid part 33 (note that the diagram of the lid part 33 is a rear view from the opposite direction to the diagram of the fuse body 20) so that the fuse contact can be seen from the outside. Insert the display window cover 24 into the fuse body 20.

This insertion is performed using a heat pressure caulking boss 32 provided on the lid portion 33.
(Two cylindrical bodies that can protrude from the panel 33a of the lid part 33,
Note that 33 in the figure indicates the position of the upper panel and 23 indicates the position of the side panel) into the two boss through holes 31 provided in the fuse body 20, and the bosses connect the fuse body and the lid. A sealed current-limiting fuse is obtained by heat-pressure caulking.

The effect of the current limiting fuse of the present invention assembled as described above is that the i-fuse tube disk 10 is integrated with the fuse tube main body 25, and the lid 29 is press-fitted, so that assembly work efficiency is improved.

ii Since the fuse pipe and the fuse body 20 are joined by a press-fit method, not only the number of man-hours is reduced, but there is no process stagnation, and assembly automation can be realized.

ji The fuse wires are connected by spot welding, which reduces man-hours and enables automation.

iv The fuse body 20 and the lid part 33 are joined together using a heat pressure caulking method, which reduces the number of man-hours and enables assembly using an automatic machine.

■ The tip of the hollow part of the fuse tube body is open, so
Shocks and vibrations no longer apply excessive force to the fuse wire, making it possible to provide fuses with minute capacities.

A cover has been added to the fusion indicator window, which not only improves the reliability of the alarm operation, but also prevents a small amount of metal gas that is generated in the cavity of the fuse tube body from escaping the fuse when excessive current flows. °C helps prevent spills.

[Brief explanation of the drawing]

Figure 1 shows an example of the structure of a conventional current-limiting fuse, in which 1 is a cross-sectional view, 2 is an external view of the fuse tube, 3 is a sectional view of the fuse tube, and 4 is a cross-sectional view of the fuse tube.
5 is a fuse tube assembly process diagram, and 5 is an assembly diagram of the fuse tube to the main body. Figure 2 shows an example of the structure of the current limiting fuse according to the present invention, in which 1 is a cross-sectional view, 2 is an external view of the fuse tube, 3 is a sectional view of the fuse tube, 4 is an explanatory diagram of the assembly of the fuse tube, and 5 is the fuse body FIG. 3 is an explanatory diagram of an assembly method. 1.2... Fuse terminal (hardware), 3,3'.
...Alarm circuit terminal, 4...Fuse body, 5...Lid, 6...Screw hole, 7...
...Alarm contact, 8...Display window, 9...
... Fuse pipe, 10 ... Disk, 11 is fuse pipe cover, 12 ... Arc extinguishing agent filling part, 13 ...
...Adhesive, 14...Cavity, 15...
...Fuse wire, 15a...Tip of 15, 1
6...Fuse tube mounting part, 20...Fuse body, 21, 22...Fuse terminal (hardware), 23...Lid, 24... ...Display window cover, 25...Fuse tube body, 26...
...Cavity, 27... Arc-extinguishing agent filling part, 28...
... Arc extinguishing agent, 29 ... Fuse tube cover, 30
...Blank section, 31 ...Boss through hole, 3
2...Boss for hot pressure caulking, 33...Lid portion, 34...Groove.

Claims (1)

[Scope of utility model registration request] The fuse body consists of a fuse body made of heat-resistant thermoplastic synthetic resin that has a fusing display window with a transparent cover, a boss that is joined to the fuse body by heat-pressure caulking, and a fuse lid that has an upper part, left and right sides, and a front panel. A fuse tube is formed by press-fitting a lid into a fuse tube main body, which has an external view of the fuse tube and a press-fitting part for fuse terminal hardware, and integrally forms a cavity with an open end, a disk, and an arc-extinguishing agent filling part in this order. A current-limiting fuse characterized by the fact that the fuse terminal and the fuse terminal hardware are press-fitted.