JPH01152917A - Closure for communication cable - Google Patents

Abstract

PURPOSE:To enable mass production to be attained decreasing components in their kind and quantity by using half-split end face plates of foamed plastic and facilitating hole drilling work while tightening the drilled end face plates to a cable through a seal material from a diametric direction to fix the plates. CONSTITUTION:A foam plastic made half-split end face plate 3-1 is provided with a hole suitable for the outside diameter of a cable 1 to be connected. The cable 1 is mounted to this hole through a seal material 5, and a metal band is fitted to a groove 16 for seal material. The end face plate 3-1 is firmly mounted to the cable 1 by threads. Here, a wire is set in wire storage grooves 15, 15' on the peripheral surface of the end face plate 3-1. The end of the wire is bent and twisted, and a twisted end 12'-1 is fitted in a notch 14. Next, removing the metal band, the seal material 5 is wound in place of the metal band, and the seal material is fitted in a groove on the vertically split part of a connecting case 2-1. On the top of this seal material, the connecting case is mounted, and the connection is completed by tightening the case with the metal band 13.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a closure applied to the connection of a communication cable's jacket.

(Prior art) Publications related to a container (hereinafter referred to as a closure) containing a communication cable connection part of this type of technology include Japanese Patent Publication No. 62-22125 filed by the present applicant and There is one disclosed in 1986-51730, and publications related to the airtight structure of the closure include IEICE Transactions B, '87/
11, VoL, J70-B, All.

Yoshinori Kubota and 3 others, Estimation of treatment life of closures using rubber parts, P1374-1383. Publications regarding the fracture life of mechanical materials include Latest Reliability Testing Technology Comprehensive Manual, Applied Technology Publishing Co., Ltd., P47.

FIG. 2 is a front view, partially in section, of a conventional closure. In FIG. 2, the left side cross-section (7) cuts the vicinity of the introduction part of the communication cable 1 in the longitudinal direction of the closure, and the right side cross-section (A) cuts the connection case 2.
A part of it is shown cut away.

In FIG. 2, 1.1' is a communication cable, 2 is a connection case, 3, 3' are rubber end plates, 4.4/ is a rubber cheek, 5 and 5' (not shown) are sealing materials, 6 is a support pipe; 7 and 7' (not shown) are internal fittings; 8;
8' is an external metal fitting, 9 and 9' are connecting rods, 10.10' is a tightening means having a bolt, and 11.11' is a core wire connection part, and the closure 30 is constituted by each of these members. There is. Note that a rubber rod-shaped gasket (not shown) is used between the connection case 2 of the closure 30 and another connection case 2' (not shown) to maintain airtightness. That is, the closure 30 has a rubber tube 4 at the center of a pair of rubber end plates 3, 3' provided on both sides.
．． 4'f via communication cable 1. l'f is inserted and connected, and the end sheaths of the communication cables 1, 1/ are formed so as to be pressed by internal fittings 7, 7' and external fittings 8, 8', thereby providing mechanical strength maintaining means and airtight means. It is fully configured.

(Problems to be Solved by the Invention) Communication cable closures are often installed in underground manholes, and therefore have many chances of being submerged in water. The communication cable is filled with 650 gf/cm of dry air (hereinafter referred to as gas) to prevent water from penetrating into the communication cable even if the cable is submerged in water, so the closure is required to be airtight. Further, a mechanical strength maintaining section is required so that external mechanical force applied to the communication cable does not adversely affect the core wire connection section. Conventional closure 3 shown in Figure 2
0 has an air-tight structure that uses a sealing material as its main component, ensuring highly reliable airtightness, but the gas-tight member tends to swell due to the gas sealed in the cable. Unfortunately, to prevent this, it is necessary to make it thick. Furthermore, vulcanization is required to manufacture rubber members, and the thicker the rubber, the longer the vulcanization time. For example, the vulcanization time for a 40 mm ridge end face plate is 40 minutes. Therefore, it has the disadvantage of being expensive.

It is necessary to prepare rubber tubes according to the outer diameter of the communication cable, which makes it difficult to mass-produce a wide variety of products in small quantities, and also poses problems in terms of product management.

Furthermore, even if you try to maintain mechanical strength between the rubber end plate and the communication cable by tightening it from the outside, because rubber is an elastic material, it will not be possible to obtain sufficient strength, and for example, it will not be possible to maintain mechanical strength between the rubber end plate and the communication cable. There were also structural drawbacks such as the need to provide a holding section.

Next, regarding the mechanical strength retaining part, if the communication cable is tightly tightened with a half metal fitting, lateral pressure will be applied to the communication cable's black wire, for example, to the optical fiber black wire, which will increase loss. The internal metal fittings were prepared in pairs with the external metal fittings according to the outer diameter of the cable, and these were also produced in small quantities with a wide variety of products, which hindered mass production and caused problems in terms of material management.

As mentioned above, if rubber end plates are used, mechanical strength retaining parts are required in other parts, resulting in larger or longer closures, or the need for wire connections. There was a problem of limiting the amount of space available.

The purpose of the present invention is to solve the above-mentioned problems and to significantly reduce the types and numbers of closure components for communication cables, thereby enabling mass production, and significantly reducing costs by shortening the manufacturing time of end plates. Another object of the present invention is to provide a communication cable closure that allows various combinations of connections within the effective surface of the end plate.

(Means for Solving the Problems) In order to solve the above-mentioned problems, the communication cable closure of the present invention is a communication cable closure having a connection case, an end plate, and a sealing member. A cylindrical connection case, means for externally connecting the connection case at multiple locations in the longitudinal direction, and an insertion hole provided at both ends of the connection case through which a communication cable is inserted through the center of each side surface; Left and right I made of disc-shaped closed-cell foamed plastic divided into upper and lower parts.
Mechanical strength maintaining means and airtight maintaining means are respectively provided between the end plate of M and the communication cable inserted through the insertion hole of the end plate. Furthermore, wide and narrow grooves are formed on the outer peripheral surface of the plastic end plate, and the foaming degree of the plastic decreases from the center toward the outer circumference and thickness direction. In addition, both sides of the plastic foam were sandwiched between solid plastic bodies (hereinafter referred to as plastic solid bodies).

(Function) The present invention uses a half-split end plate made of foamed plastic, and at the connection site, drills a cable passing hole 'fr-, which is an insertion hole corresponding to the outer diameter of the cable, and attaches the cable to this hole. By tightening and fixing the face plate from the radial direction and connecting it to the connection case, the joint between the end plate and the cable simultaneously maintains airtightness and mechanical strength, significantly reducing the number of component parts. The outer diameter of the communication cable is allowed to vary by ±10% with respect to the standard outer diameter.

When constructing an airtight retaining section using rubber end plates and rubber tubes for cables with different outer diameters, as in the conventional closure shown in Fig. 82 above, a plurality of end plates and rubber tubes are used in correspondence with the outer diameters of the cables. is necessary. Furthermore, regardless of the cable outer diameter, a space is required out of the effective area of the end plate that extends to the outer diameter of the tube protrusion. As a result,
When two or more cables are drawn into an end plate, the outer diameter of the end plate and hence the closure cannot be made smaller even if the core wire connection portion is made smaller, and miniaturization is not possible. Similarly, when tightening a cable with an external metal fitting of a specified inner diameter, the mechanical strength retaining part cannot maintain strength if the outer diameter of the cable changes to one side, and lateral pressure is applied to the core wire on the center side, and in the case of optical cables, Internal fittings are essential as losses increase.

The problems with conventional closures, such as the need to prepare the inner and outer fittings according to the cable outer diameter and the increased number of parts, can be solved by using the end plate of the present invention. Since the cable is opened, an appropriate tightening force can be applied to the cable as designed, and mechanical strength can be maintained without applying lateral pressure to the core wire, and a sealing material can also be used between the cable jacket and the end plate. By doing so, airtightness can be ensured at the same time, resulting in a significant reduction in the number of component parts.
This end plate can be processed in a short time and is inexpensive.

In addition, since the holes are drilled in the end plate according to the outer diameter of the cable, the effective area of the end plate can be used effectively. By eliminating this, the closure can be made smaller.

Furthermore, multi-branch connection becomes possible under the condition that the sum of the outer diameters of the cables to be connected is less than or equal to the effective end face diameter.

(Example) An example of the present invention will be explained with reference to the drawings. [Example 1
] FIG. 1 is a front view of one embodiment of the present invention, partially shown in cross section. In FIG. 1, the left-hand partial cross-sectional view (1) is a cut of the vicinity of the introduction part of the communication cable 1 in the longitudinal direction of the closure of the above-mentioned embodiment, and the right-hand partial cross-sectional view (1) is the connection case 2. -1 is partially cut away and shown.

In FIG. 1, 1 and 1' are communication cables, 2-1 is a connection case, and 3-1 and 3-1' are upper and lower halves of end plates made of foamed plastic, each consisting of a pair of left and right halves.

5.5' is a sealing material, 12.12' is a wire, and the wire 12 is for tightening the half-split end plates 3-1 and 3-1'f. 13, tightening is a means,
The tightening means 13 is configured to attach the divided connection case 2-1 from the outside and tighten the connection case 2-1f using a metal band and screw means provided at the end thereof.

FIG. 3 shows split end plates 3-1 and 3-1'f before forming cable insertion holes according to an embodiment of the present invention.FIG. 3(a)
is a side view, and FIG. 3(b) is a front view. Split end plate 3
-1 and 3-1' are formed by dividing a disk-shaped foamed plastic member along the center line 17 as shown in the figure, but at the intersection of the center line 17 and the circumferential surface, end plates 3-1, 3-1, 3-1' are divided from the circumference. 3-1
A cutout groove 14 is provided inside the holder.

75.15' is a narrow wire storage groove, 16 is a wide groove for attaching a seal, and 17 is a dividing portion. The wire storage grooves 15 and 15' are provided near both sides of the side peripheral surfaces of the split end plates 3-1 and 3-1', and the seal mounting grooves 15 and 15' are provided inside the wire storage grooves 15 and 15'.
6 is provided.

Next, a description will be given with reference to FIGS. 1 and 3.

To assemble this closure, first, although not shown, a hole is made using a tool to match the outer diameter of the cable 1 to be connected. Attach the cable l to the hole drilled in the half-split end plate 3-1 through the sealing material 5, and insert the sealing material attachment groove 1.
Attach a metal band to 6 and tighten the screws to attach the end plate 3.
-1 Securely attach all cables. The metal band has protrusions that enable tightening, and the connection case 2-1 cannot be tightened as it is. For this reason, the end plate 3-1
A wire is attached to the wire storage groove 15.15' on the outer peripheral surface of the wire and twisted up, and the twisted end 12'-1 is bent into the notch 14. Next, the metal band is removed, and then the sealing material 5 is wrapped around it, and the sealing material is attached to the groove of the vertically divided part of the connection case 2-1. 1 and intersect with the sealing material 5 wrapped around it.

The connection case 2-1 is placed on top of this, and the metal band 13 is tightened to complete the connection. Rubber parts or a combination of rubber parts and a sealing material may be used for the sealing material portion 5 and the vertically divided portion of the connection case 2-1.

Since the most important part of this closure is the halved end plate 3-1 made of foamed plastic, the end plate 3-1 will be explained in detail below using the drawings.

FIGS. 4(a) and 4(b) show changes in the density and degree of foaming in the radial direction of the end plate 3-1 which was injection molded with a dart in the center. The thickness direction also changes similarly. Also, in Figure 5,
The foaming state in the radial cross section is shown. The bubbles shown here must be closed cells in consideration of the airtightness, moisture permeability, water permeability, etc. of the end plate 3-1.

A hole corresponding to the outer diameter of the cable is usually formed in the end plate 3-1 from the center (gate portion) of the end plate 3-1.

In the foamed state shown in FIG. 5, the closer the bubbles are to the center, the larger the diameter of the bubbles, making it easier to make holes.

On the other hand, the degree of foaming (apparent density) is measured by mechanical strength (bending strength,
The relationship between compressive strength and tensile strength is as shown in Figure 6.
The strength decreases as the degree of foaming increases. However, as shown in FIG. 7, the cable jacket strength, which defines the mechanical strength of the closure, decreases as the outer diameter decreases, indicating that the degree of foaming may be large near the center of the end plate 3-1.

That is, it is possible to obtain the mechanical strength of the end plate 3-1 that matches the strength of the cable jacket.

Next, maintaining airtightness between the end plate 3-1 and the cable 1 will be described. FIG. 8 shows a cross-sectional view of a sample device for estimating the life of an airtight part using a sealing material. 1 is a communication cable, 5 is a sealing material, 18 is a lead pipe, 19 is a spacer that facilitates separation between the cable and the sealing material, 20 is a terminal sealing part, 21 is a space for sealing gas, 22 is a gas seal Inlet 23 indicates a lead pipe caulking part.

In the sample device shown in FIG.
The sealing material 5 was wrapped around the tube until the gap within the tube was approximately 1 mm, and the lead pipe was caulked to a position of 40 times the thickness of the sealing material.The effective length of the sealing material was 6 cm as shown in the figure.

In order to estimate the airtight life of this sample device, the gas pressure sealed in the lead pipe 18 was varied, and the time until gas leakage occurred was defined as the life. The main underground cables are installed inside manholes, and the temperature inside the manholes is the highest in Japan at 30 degrees Celsius and the lowest at -5 degrees Celsius, exhibiting a heat cycle 2 that occurs once a year. For this reason, the maximum temperature for the closure is +30°C and the minimum temperature is -10°C.
, one heat cycle per day was applied. It is known that the fracture life distribution of mechanical materials follows a lognormal distribution (see "Latest Reliability Testing Technology Comprehensive Manual" edited by Kenji Kitayo, p. 47, Applied Technology Publishing Co., Ltd.). For this purpose, the gas sheath 21 in the lead pipe 18 is filled with gas '6, and the gas pressure f
3 kgf/C1rL2.2 kgf/cIrL2r
1 kgf/cr/L2 and the bubble bursting time when the heat cycle was changed was defined as the life span, and the test results are plotted on lognormal probability paper and are shown in FIG. 1kgf/cr
The rL2 sample did not show hermetic failure even after 150 cycles. The average lifespan is calculated from Figure 9 and is 3kgr/
38 cycles are obtained with crrL2 and 95 cycles with 2 kgf/crn2.

There is a linear relationship between repeated stress and life as a fatigue failure of mechanical materials on a log-log plot (Reference P21 on the previous page).
reference). For this reason, the relationship between the average life determined from FIG. 9 and the filled gas pressure is determined and shown in FIG. 10. The lifespan of the cable is estimated to be 700 cycles before the cable breaks due to the gas pressure of 650gf/crrL2 sealed in the cable, which is equivalent to 700 years if we focus only on the number of heat cycles.

Even considering the variation in life as shown in Figure 10, the length of the effective Schiffle material is approximately 2 to 3 crIL, and therefore the width of the end plate 3-1 is approximately 2 to 4α. It is.

On the other hand, a hole is made at a position r from the center of the end plate 3-1 in FIG.
The pressed state (cross-sectional view) is shown in FIG. 11.

The sealing material is divided by the walls of the bubbles, as shown in Figure 8, where the caulked portion is increased, which lengthens the gas leakage path, and confines the sealing material with the bubble walls (membrane).
The stress applied to the sealing material is maintained for a long period of time, ensuring highly reliable airtightness. Therefore, the length of the effective sealing material set based on the sample shown in FIG. 9 can be made even shorter.

[Example 2] Compression molded foam exhibits a relatively uniform expansion degree distribution. If the degree of foaming is increased, the end plate becomes soft, making it impossible to maintain mechanical strength or ensure long-term airtightness.

On the other hand, if the degree of foaming is reduced, drilling becomes difficult and it cannot be put to practical use. For this reason, as shown in FIG. 12, an end plate can be used in which the mechanical strength maintaining section and the airtight maintaining section are separated and a solid body and a foam body are bonded together with an adhesive.

13-2 is a solid plastic part, 13-3 is a plastic foam part, and 13-4 is an adhesive part. In Fig. 12, the adhesive part 13-4 is located in the area excluding the effective surface where the hole is made.
f is provided. This removes the cut pieces when drilling holes, making the process easier.

Mechanical strength is maintained by the plastic solid body part 13-2,
Airtightness is maintained primarily by the plastic foam portion 13-3f and secondary by the plastic solid portion 13-2f.

The plastic solid body part 13-2 may be a low foaming body.

(Effect of the invention) As explained above, by using the half-split end plate made of foamed plastic, drilling becomes easier and
By tightening and firmly fixing the end plate with holes to the cable from the radial direction via the sealing material, mechanical strength and airtightness are maintained at the same time in this part. Therefore, the mechanical strength maintaining part of the conventional connection part is no longer necessary, and the cost can be significantly reduced by significantly reducing the number of component parts, and the effective space within the closure can be expanded (the closure can be made smaller). Also,
The number of parts constituting the airtight part can be reduced, and by replacing rubber parts with plastic, the manufacturing speed can be significantly improved, and both have the advantage of being able to realize a significant reduction in price.

This closure can be applied to sheath connections for various cables.

[Brief explanation of the drawing]

FIG. 1 is a front view of an embodiment of the present invention, partially shown in cross section;
Figure 2 is a front view of a conventional closure, partially shown in section;
FIG. 3 is an explanatory diagram of a split end plate according to an embodiment of the present invention;
The figure is an explanatory diagram of the density and foaming degree in the radial direction of the injection molded end plate, Figure 5 is an explanatory diagram of the foaming state of the radial cross section of the end plate 3-1, and Figure 6 is an explanatory diagram of the foaming degree and the degree of foaming of the foamed plastic end plate. Figure 7 is an explanatory diagram of the relationship between cable outer diameter and cable sheath strength. Figure 8 is a cross-sectional view of a device for estimating the airtight life of a joint using a sealing material. Figure 10 is an explanatory diagram showing the relationship between the number of heat cycles and cumulative failure rate, Figure 10 is an explanatory diagram of the relationship between average life (number of heat cycles) and sealed gas pressure, and Figure 11 is an illustration of the relationship between the end plate 3-1 in Figure 5. An enlarged partial cross-sectional explanatory view showing a state in which a hole is made at the position r from the center and the sealing material 5 is interposed between the cable 1 and the end plate 3-1, and FIG. 12 shows the plastic '15E body and It is a sectional view of Example 2 of the end plate to which the foam part was joined. 1.1'... Communication cable, 2, 2-1... Connection case, 3.3'°°° rubber end plate, 3-1.3-1
'... Foamed plastic end plate, 4, 4'... Mu tube, 5, 5/... Seal material, 6... Support pipe, 7, 7'... Internal metal fittings, 8.8 '... External metal fittings, 9,9'... Connecting rod, 10.10'... Tightening means with Deltora, 11.11'... Core wire connection part,
12.12'...wire, 12'-1...threaded end of wire, 13...means for tightening, 14...notch,
15... Groove for storing wire, 16... Groove for attaching sealing material, 17... Divided portion of half-split end plate, 18... Lead pipe, 19... Part in space, 20... Terminal sealing part, 21・
...Space for gas filling, 22...Gas filling port, 23
... Lead pipe caulking part. 1.1-----Communication cable 13-1-Tightening means 2-1----Connection case 20-
--- Closure 3-1, 3-1' --- Single foam plastic half-split end plate 5.5' --- Sealing material 12.12' --- Wire 12'-1 ---- Front view of an embodiment of the present invention showing a part of the twisted end of the wire Fig. 1 Front view of a conventional claw wire partially shown in cross section Fig. 2 Side view Front view a (Q) ( b) An explanatory diagram of a split end plate according to an embodiment of the present invention. Figure 3 (1)) Plan view. An explanatory diagram of the density and degree of foaming in the radial direction of the injection molded end plate. Figure 4. Radial direction of the end plate 3-1. Explanatory diagram of foaming state in cross section Figure 5. Relationship between foaming degree and mechanical strength of foamed glass end plate Step diagram Figure 6. Explanatory diagram of relationship between cable outer diameter and cable jacket strength Figure 7. Number of heat cycles and An explanatory diagram showing the relationship between cumulative failure rate. An explanatory diagram showing the relationship between average life (number of heat cycles) and sealing pressure. A hole is made at the position r from the center of the end plate 3-1 in Figure 5, and the cable 1 Fig. 11 is an enlarged partially cutaway explanatory diagram of the state in which the sealing material 5 is interposed between the end face plate 3-1 and the end face plate 3-1 is pressed. Figure 12 March 1, 1986

Claims (4)

[Claims] (1) In a communication cable closure having a connection case, an end plate, and a sealing member, a hollow horizontal half-cylindrical connection case divided into upper and lower parts, and means for externally tightening the connection case at multiple points in the longitudinal direction and a pair of left and right end face plates made of disc-shaped closed-cell foamed plastic, which are provided at both ends of the connection case and have insertion holes through which communication cables are inserted in the centers of both sides, and are divided into upper and lower parts at the center. and a communication cable inserted through the insertion hole of the end plate, and a mechanical strength maintaining means and an airtight maintaining means are respectively provided between the communication cable and the communication cable inserted through the insertion hole of the end plate. (2) The disc-shaped end plate divided into upper and lower parts has a wide groove in the center along the entire circumference of its outer circumferential surface, and has narrow grooves adjacent to both sides of the groove. The communication cable according to claim 1, characterized in that the end plate is provided with a notch in the circumferential surface portion into which the narrow width groove is divided, and a cable insertion hole is provided after the connection case is attached. closure (3) The communication cable closure according to claim 1, wherein the degree of foaming of the end plate decreases from the center toward the outer circumference and thickness. (4) The end plate is characterized in that both sides of the plastic foam are sandwiched between thin plastic solid bodies, and a portion of both contact surfaces near the outer periphery is glued.
Closures for communication cables as described in section