JPH0336201Y2 - - Google Patents

Description

[Detailed description of the invention] (1) Industrial application field The present invention relates to a dam fitting provided at the part where a stub cable is introduced and connected to a repeater housing, and in particular improves the sealing reliability of the cord inside the stub cable. This invention relates to an improved structure for fixing stub cables to dam fittings.

When transmitting telegraph, telephone, and various data signals over land, cables with internal signal lines are used.
Mainly installed underground. For long-distance transmission, amplifiers are installed at appropriate locations to compensate for signal attenuation, and the attenuated signals are amplified to an appropriate level. This cable,
All amplifiers are airtight and watertight, and the part introduced into the repeater is connected to the main cable for transmission via a cable called a stub cable, which is more flexible and easier to handle. Further, a dam fitting is provided in the repeater through which the cable is introduced, and the cable is introduced in an airtight structure by means of the dam fitting.

Stub cables that require hermetic sealing are lead coated to maintain reliable transmission characteristics.
Moreover, pressurized gas at an appropriate pressure is sealed inside. Connect a stub cable to a repeater installed in an underground manhole.
The dam metal fitting is once airtightly connected to the repeater, and the dam metal fitting is airtightly connected to the repeater, and the cord led out from the stub cable is connected to the amplifier inside the repeater.

(2) Prior Art The dam fitting and the stub cable are generally connected and fixed by soldering for airtight sealing. FIG. 1 shows a cross-sectional view of the main parts of an improved structure for fixing the stub cable to the dam metal fitting, which was devised by the present inventors. In FIG. 1, 1 is a dam fitting made of metal (for example, brass). The dam fitting 1 has a cable attachment part 11 at its outer end to which the stub cable 2 is introduced, and a sealing part 12 that is continuously opened from the cable attachment part 11 toward the inside of the dam fitting. and a flange 13 for attachment to a repeater casing (not shown) formed protruding from the outer periphery of the main body.

The stub cable 2 has a coaxial cord 23 for transmitting signals, an intervening line 24 for a meeting line, etc. covered with a lead sheath 22, and the outside of the lead sheath 22 is further protected with a resin outer sheath 21.

In the above configuration, the dam fitting 1 and the stub cable 2 are assembled by cutting off a predetermined length of the outer sheath 21 and the lead sheath 22 at the end of the stub cable 2, respectively, and leading out and dispersing the plurality of coaxial cords 23 and intervening wires 24. , exposing 22 portions of the lead coating. Then, the surfaces of the coaxial cord 23 and the intervening wire 24 are subjected to known adhesion pretreatment so that the fixing material 3 and sealing material 4, which will be described later, will be firmly adhered to them.

Next, the end of the stub cable 2 is inserted into the cable attachment part 11 of the dam fitting 1, the exposed lead coating 22 is positioned as shown, and the lead is carefully attached using a special process using mainly lead. 5 to obtain fixation and airtightness.

With the opening on the right side of the dam fitting 1 facing upward in the vertical direction, a highly viscous adhesive material (e.g., epoxy resin) 3 is injected into the sealing part 12 and hardened to connect the coaxial cord 23 and the intervening wire 24 to the sealing part. It is fixed for the purpose of being immovably fixed to the inner surface of 12. Next, a low-viscosity sealing material (e.g., epoxy resin) 4 is injected into the inside of the dam fitting 1 body and cured, thereby airtightly sealing the inner surface of the dam fitting 1, the coaxial cord 23, and the intervening wire 24 without any gaps. do.

The flange 13 is attached to the dam fitting mounting portion of the repeater housing (not shown) and is airtightly mounted. Therefore, the area to the right of the flange 13 is inside the repeater. The coaxial cord 23 and intervening wire 24 that have been led out are connected to the circuit main part of the relay device.

(3) Problems to be solved by the invention In order to attach the dam fitting 1 to the repeater, it must be brought into the underground manhole where the repeater is installed, but at this time, the stub cable 2 is near the lead fitting. It may be bent. The present inventors confirmed this by conducting a bending experiment as shown in FIG. 2 on the stub cable with the dam fitting.

As a result, for example, when the stub cable 2 is bent to a radius of approximately 500 mmR, as shown by the dotted line in Figure 2,
The coaxial cord 23 inside from the center is indicated by arrow A from the end.
In addition, the outer coaxial cord 23 from the center was pulled in from the end in the direction of arrow B, and it was found that for a cable with an outer diameter of about 600 mmφ, this force reached a maximum of about 100 kg. .

For this purpose, the structure shown in FIG.
The coaxial cord 23 and the intervening wire 24 are attached by the fixing material 3.
was fixed, and the role of airtight sealing was shared by the sealing material 4, which has a weak fixing force. However, the adhesive material 3, which is hard and has a strong fixing force, has a large volumetric shrinkage when hardened, and for this reason. It was found that a gap was created between the sealing part 12 and the inner surface of the sealing part 12, and sealing was not achieved at this part.

This means that the coaxial cord 23 and the intervening wire 24 are integrated by the fixing material 3 and do not move relative to each other, but they can move using the fixing material 3 as a block unit. Due to the bending of the stub cable 2, the inside of the center of the cable moves as if being pushed out toward the other end of the stub cable 2, but the pulling action of the outside causes the block of the fixing material 3 to move. Furthermore, due to the difference in temperature, the outer covering 21
Expansion and contraction occurs between the inner and outer conductor metals of the coaxial cord 23 due to the difference in their linear expansion coefficients, and this causes the block of the fixing material 3 to advance and retreat with respect to the sealing portion 12.

The above-described movement works to peel off the coaxial wire 23 and the intervening wire 24, which are buried and passed through the sealing material 4, from the soft sealing material 4. This poses a problem in that the airtight condition sealed by the sealant 4 may be impaired.

(4) Means for Solving the Problems In order to solve the above-mentioned problems of the stub cable fixing structure to the dam fitting, according to the present invention, the dam fitting has an opening at its outer end and a stub cable is attached to the dam fitting. A cable attachment part for introducing the stub cable, a sealing part that is continuously opened from the cable attachment part toward the inside of the dam fitting, and an inner periphery of the sealing part that corresponds to the cord led out from inside the stub cable. The lead-sheathed part of the stub cable introduced into the cable attachment part is hermetically fixed by lead fitting, and the cord introduced into the sealing part is A resin fixing material was injected and fixed to prevent the cord from moving in the longitudinal direction, and a resin sealing material was injected from the opening at the inner end of the dam fitting to airtightly seal the cord and the inner surface of the dam fitting. It can be achieved by leaning.

(5) Effect According to the above configuration means, the cord is fixed by the fixing material injected and hardened into the sealing part, and the fixing material is fixed by the plurality of protrusions formed on the inner periphery of the sealing part. Each cord is reliably fixed to the sealing portion via the fixing material, and movement in the longitudinal direction is prevented. This eliminates the movement of the cord with respect to the sealing material portion, improving the reliability of airtightness, and fulfilling the intended purpose of the two-stage fixing and sealing structure.

(6) Embodiments Hereinafter, embodiments of the structure for fixing a stub cable to a dam fitting according to the present invention will be described with reference to the drawings.

FIG. 3 is a sectional view of essential parts for explaining one embodiment of the present invention. In FIG. 3, the stub cable fixing structure to the dam fitting of this invention is the same as in FIG.
It is configured by hermetically sealing with a sealing material 4. Here, a particularly important point is that a plurality of protrusions 121 are provided along the circumference on the inner surface of the sealing part 12 in the dam fitting 1. Since the structure is as described above, the parts other than the protrusion 121 are given the same reference numerals as those in FIG. 1, and the explanation of these same parts will be omitted.

The protrusions 121 integrally formed on the inner surface of the sealing part 12 added to the present invention extend along the circumferential direction, and a plurality of protrusions 121 are continuously formed in an uneven convex shape. The protrusion 121 can be formed by continuously cutting an annular part on the inner surface of the sealing part 12 and cutting the annular part intermittently at required points in the length direction. Each of these plurality of protrusions 121 has a plurality of coaxial cords 23
There is a corresponding relationship. The intervening line 24 is located in the central portion.

The reason why there are a plurality of protrusions 121 is to ensure that the fixing material 3 in the longitudinal direction on both sides is secured in the concave and convex portions of the unevenness to have sufficient tensile force, and to prevent the block of the fixing material 3 from rotating. It is necessary to do so. Therefore, by providing the protrusion 121, the movement of the block of the fixing material 3 is prevented and the position is fixed, and as a result, the coaxial cord 2
3. The intervening wire 24 is stably fixed.

Even if the stub cable with a dam fitting is bent when connecting it to the repeater housing installed in the manhole, the moving force applied to the coaxial cable 23 is suppressed by the sealing part 12. Therefore, movement of the coaxial cord 23 toward the sealant 4 can be eliminated. Similar movements due to temperature changes can also be suppressed. Therefore, sufficient airtightness can be guaranteed for a long period of time.

As is clear from the above explanation, according to the structure for fixing the stub cable to the dam fitting according to the present invention,
When connecting to a repeater installed in an underground manhole, there is no risk of bending the cable or poor airtightness due to temperature changes after connection, improving the quality and reliability of the gas dam. This allows for longer life.

[Brief explanation of the drawing]

Figure 1 is a side sectional view of the main part of the structure devised during the development process for fixing the stub cable to the dam fitting of the present invention, Figure 2 is an explanatory diagram showing the problems caused by bending found through experiments, and Figure 3 The figure is a side cross-sectional view of a main part of an embodiment of the present invention that solves the problems shown in Figure 1. Identical parts are designated by the same reference numerals throughout the figures. In the figure, 1 is a dam fitting, 2 is a stub cable, 3 is a fixing material, 4 is a sealing material, 5 is a lead fitting, 1
1 is a cable attachment part, 12 is a sealing part, 13 is a flange, 21 is an outer coating, 22 is a lead coating, 23 is a coaxial cord, 24 is an intervening wire, and 121 is a protrusion.

Claims (1)

[Scope of utility model registration request] The dam fitting has a cable attachment part that opens at its outer end to introduce the stub cable, a sealing part that is continuously opened from the cable attachment part toward the inside of the dam fitting, and a sealing part of the sealing part. The inner periphery has a plurality of protrusions formed corresponding to the cords led out from inside the stub cable, and the lead sheathing part of the stub cable introduced into the cable attachment part is sealed and fixed by lead fitting. A resin fixing material is injected and fixed to the cord introduced into the sealing part to prevent the cord from moving in the longitudinal direction, and the cord and the inner surface of the dam fitting are inserted through the opening at the inner end of the dam fitting. A stub cable fixing structure to a stub fitting that is characterized by being injected and sealed with an airtight resin sealant.