JPH0311169B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a gas dam terminal of a cable such as a communication cable or an optical cable.

(Prior Art) In order to connect a cable such as a communication cable or an optical cable to a connection box, communication equipment, etc., a gas dam terminal portion with a flange is formed at the end of the cable. A conventional gas dam terminal is a gas dam formed by filling a dam-forming resin across the cable sheath and the flange through which multiple core wires are exposed by peeling off the sheath at the end of the cable. It is completed.

However, in such a gas dam end part, the flange is only bonded to the dam-forming resin on its inner surface, so when tension is applied to the cable, the bond between the flange and the dam-forming resin is easily broken. It was hot. In addition, in such a structure, even if the flange and the dam-forming resin are bonded with adhesive, atmospheric moisture will continue to infiltrate for many years through the bonding surface between the flange and the dam-forming resin at the outer periphery of the gas dam end. However, there was a drawback that the adhesive strength decreased. For example, when an ethyl acetate-based resin is used as an adhesive, the adhesion to a steel flange is 4 to 5 kg/10 mm (90° peeling,
tensile speed 100mm/min), 5~6Kg/10mm at 60℃
60
℃, 0.4-2Kg/10 when the humidity is over 95%
mm, causing significant humidification deterioration. In addition, in the example of a dam-forming resin made of urethane and an adhesive made of ethylene-vinyl acetate-glycidyl methacrylate, the weight was 7 to 9 kg/10 mm at 70°C.
℃ and humidity of 95% or higher, it decreases to 2-5 kg/10 mm after 1000 hours. Although these test results are all accelerated deterioration tests under worst-case conditions, they suggest the possibility of a decrease in adhesive strength due to the presence of water or humidity.

(Object of the Invention) An object of the present invention is to provide a gas dam end portion of a cable that can prevent the bonding strength and airtightness between the flange and the dam-forming resin from decreasing due to tension or humidity.

(Structure of the Invention) According to the present invention, the outer sheath is peeled off at the end of the cable to expose a plurality of core wires, each of the core wires is passed through a flange, and the core wires are inserted between the flange and the end of the cable. In the gas dam end portion of the cable in which a gas dam is formed by filling a dam-forming resin around each core wire, the flange is a cylinder embedded in the dam-forming resin on a surface that contacts the dam-forming resin. The cylindrical protrusion has a tip-side outer circumferential portion bonded to the dam-forming resin via an adhesive layer, and a flange-side outer circumferential portion of the cylindrical protrusion and the dam-forming resin are bonded to each other via an adhesive layer. A pressurized flowable sealing layer is provided in between, and the dam-forming resin is cured while the pressurized flowable sealing layer is pressurized.

(Example) Examples of the present invention will be described in detail below with reference to the drawings. 1 and 2 show a first embodiment of a gas dam end portion 1 of a cable according to the present invention. A cable 2, such as an optical cable, has an outer sheath 3 made of plastic or the like peeled off at its end to expose a plurality of core wires 4 and a central tension member 5. The central tension member 5 is
The tension member body 5A is made of a steel wire, and the outer periphery of the tension member body 5A is covered with a soft polymer layer 5B made of plastic or the like. Each exposed core wire 4 and tension member main body 5A pass through a hole drilled in a flange 6 made of metal such as stainless steel and are led out to the opposite side of the flange 6. The flange 6 is preferably made of stainless steel, which has high mechanical strength and is lightweight.
It may be made of brass, copper, iron, etc. In the case of the stainless steel flange 6, the surface is coated with copper, to improve adhesion with the dam forming resin described later
Nickel chrome, zinc, gold, silver or a composite plating thereof can be applied. The tension member main body 5A is held on the flange 6 by a stopper 7. A dam-forming resin 8 is filled over the flange 6 and the cable jacket 3 around each core wire 4 and the central tension member 5 to form a gas dam 9. As the dam forming resin 8, a thermosetting resin such as epoxy resin, urethane, or foamed polyurethane is used.

The flange 6 has a cylindrical protrusion 6A embedded in the dam-forming resin 8 on its surface that contacts the dam-forming resin 8. This cylindrical protrusion 6A has a radius that can surround each core wire 4 and the central tension member 5 at a distance on its outer periphery. The outer peripheral portion of the tip side of the cylindrical protrusion 6A is adhered to the dam forming resin 8 via the adhesive layer 10. Examples of the adhesive forming the adhesive layer 10 include ethylene-ethyl acrylate copolymer, ethylene vinyl acetate copolymer, ionomer resin,
Ethylene-vinyl acetate-vinyl alcohol terpolymer, ethylene-vinyl acetate-glycidyl methacrylate, ethylene-acrylic acid, etc. are used, and depending on the combination of materials for the dam-forming resin 8 and the flange 6, one of them can be used. Selected appropriately. Since this adhesive is thermoplastic, it can be wrapped in a tape shape around the outer periphery of the tip side of the cylindrical protrusion 6A, tightened from the outside with a crosslinked rubber band having rubber elasticity, and heated and fused in a heating chamber. Alternatively, after tightening with a cross-linked rubber band, it can be fused by wrapping an electric heating wire thereon and heating it. The crosslinked rubber band is then removed, and the adhesive layer 10 is fused to the dam-forming resin 8 by the heat generated during filling with the dam-forming resin 8. Further, a pressurized fluid sealing layer 11 is provided between the flange side outer peripheral portion of the cylindrical protrusion 6A and the dam forming resin 8 by wrapping a sealing tape around the cylindrical protrusion 6A. This pressurized flowable sealing layer 11 is formed of a mixture mainly consisting of butyl rubber, polyisobutylene, and carbon black, for example. In this case, the pressurized flowable sealing layer 11 is compressed by the foaming pressure of, for example, urethane foam used as the dam-forming resin 8, or by the contraction force when the dam-forming resin 8 solidifies, and the repulsive force causes the flange 6 to The cylindrical protrusion 6A and the dam forming resin 8 are press-fitted to maintain airtightness. An adhesive layer 12 is provided on the outer periphery of the cable sheath 3 within the dam-forming resin 8 to achieve adhesion between the cable sheath 3 and the dam-forming resin 8. Further, a pressurized flowable sealing layer as described above may be provided on the outer periphery of the cable jacket 3 within the dam-forming resin 8 at a position closer to the outside.

In the gas dam end portion 1 of such a cable, for example, a flange of a junction box is connected to the outer surface of the flange 6 via an O-ring or the like. Then, when gas pressure is applied from the junction box side, gas enters in the direction of A → B through the hole drilled in the flange 6, and in the direction of A → B → C → D → E → F → G → H → I. trying to convey. However, in this embodiment, since the adhesive layer 10 is present on the outer circumferential surface of the distal end side of the cylindrical protrusion 6A, the flow of gas along the path E→F→G is blocked. Furthermore, even if moisture intrudes from the outside through the path I→H→G→F and attempts to reduce the adhesive strength of the adhesive layer 10, it approaches the flange 6 and pressurizes the outer periphery of the cylindrical protrusion 6A. Sealing layer 1
1 exists to block the path GFE, it is possible to prevent the adhesive strength of the adhesive layer 10 from decreasing due to the presence of moisture. In particular, dam-forming resin 8
When the adhesive layer 10 is cured, the area FGHJ around the pressurized fluid sealing layer 11 becomes a closed room, and the pressurized fluid sealing layer 11 in this closed room is covered with the dam forming resin 8. The cylindrical protrusion 6A is pressurized inward at the foaming pressure or contraction pressure of
The surface FGH on the flange 6 is pressurized by this pressurized fluid sealing layer 11 with a force equivalent to the applied pressure, and the pressurized fluid sealing layer 11 and the cylindrical protrusion 6A are The interface FGH with the flange 6 is hermetically sealed, and moisture can be sufficiently prevented from entering. In addition, the interfaces G-H, H-J, and J between the pressurized flowable sealing layer 11, the dam-forming resin 8, and the adhesive layer 10
-F also, the pressurized flowable sealing layer 11 is pressed against the dam-forming resin 8 and the adhesive layer 10 by internal pressure, and the generation of gas paths is also prevented at these interfaces. On the other hand, the interface between the surfaces of the core wire 4 is also pressed together by the foaming pressure or contraction pressure of the dam-forming resin 8, and the generation of gas paths at the interface is prevented. Furthermore, when the flange 6 has the cylindrical protrusion 6A on the inner surface side, the adhesive surface with the dam-forming resin 8 extends in the axial direction of the gas dam 9. Since the bonded portion between the cylindrical protrusion 6A and the cylindrical protruding portion 6A opposes each other by shearing force, the bonding strength is sufficiently increased compared to the bonded portion between only the inner surface of the flange 6 and the dam-forming resin 8.

Experimental example Flange: Stainless steel SUS304 Cylindrical protrusion: Protrusion length 30mm Pressurized flowable sealing layer: Width 15mm, thickness 0.4mm
Sealing tape: A mixture tape mainly composed of butyl rubber, polyisobutylene, and carbon black Adhesive layer: Formed by wrapping hot melt tape around 15 mm wide and 0.4 mm thick Hot melt tape: Ethylene-acrylic Ethyl acid copolymer tape Dam forming resin: Urethane foam, foaming rate approximately 10%
(Weight ratio) For such a gas dam terminal, -30℃ to +
After 100 cycles at 70°C heat cycle (0.7 kg/cm ² gas pressurized at -30°C), there was no gas leak and good gas sealing properties were observed.

FIG. 3 shows a second embodiment of the invention. In the gas dam end portion 1 of this embodiment, the thickness of the pressurized fluid sealing layer 11 is thicker than that of the first embodiment.

In this way, the sealing effect can be further improved.

(Effects of the Invention) As explained above, in the gas dam end portion of the cable according to the present invention, the cylindrical protrusion is provided on the inner surface of the flange and embedded in the dam forming resin, so that the tensile force applied to the cable is acts as a shearing force, which improves the bonding strength between the flange and the dam-forming resin, and also improves the gas tightness at the interface between the two. Furthermore, in the present invention, since an adhesive layer is provided on the outer peripheral portion of the tip side of the cylindrical protrusion described above to bond the cylindrical protrusion and the dam forming resin, even if gas pressure is applied from the flange side, This adhesive layer can prevent gas leaks.
Furthermore, in the present invention, a pressurized fluid sealing layer is provided on the outer peripheral portion of the cylindrical protrusion on the flange side for sealing, thereby preventing moisture from entering from the interface between the outer peripheral portion of the flange and the dam-forming resin. Therefore, a decrease in adhesive strength due to moisture in the adhesive layer can be prevented.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view of a first embodiment of a gas dam terminal of a cable according to the present invention, FIG. 2 is an enlarged view of the main part of FIG. 1, and FIG. 3 is a main part of a second embodiment of the present invention. FIG. DESCRIPTION OF SYMBOLS 1... Terminal part of gas dam, 2... Cable, 3... Outer covering, 4... Core wire, 6... Flange, 6A... Cylindrical protrusion, 8... Dam forming resin, 9... Gas dam, 10... Adhesive layer, 11... Pressurized flowable sealing layer, 12...
adhesive layer.

Claims (1)

[Claims] 1. The outer sheath is peeled off at the end of the cable to expose a plurality of core wires, each core wire is passed through a flange, and a wire is passed around each core wire across the flange and the end of the cable. In a gas dam end portion of a cable filled with a dam-forming resin to form a gas dam, the flange has a cylindrical protrusion embedded in the dam-forming resin on a surface that contacts the dam-forming resin; The outer circumferential portion on the tip side of the cylindrical protrusion is adhered to the dam-forming resin via an adhesive layer, and a pressurized fluid seal is provided between the outer circumferential portion on the flange side of the cylindrical protruding portion and the dam-forming resin. A gas dam end portion of a cable, characterized in that the dam-forming resin is cured under pressure with the pressurized flowable sealing layer.