Optical fiber built-in composite insulator and method of producing the same

Abstract: An optical fiber built-in type composite insulator has at least two insulator bodies (1-1,1-2) each having a penetration bore (2-1,2-2). At least one optical fiber (3) is inserted in the bores. Silicone rubber elements (5-1,5-2) seal the outer ends of the bores. Concentric O-rings (9-1,9-2) seal at the opposing end surfaces of adjacent insulator bodies. A silicone rubber element (10) lies between the O-rings. The bores are filled with silicone grease (4). The inner O-ring (9-1) is resistant to the grease. This construction can effectively prevent leakage of the silicone grease, bending and breakage of the optical fiber, leakage of electric current along the penetration bores, short circuits and can provide other advantages.

Description: The present invention relates to an optical fiber built-in type composite insulator which is used mainly in detection systems for finding out fault points at electric power transmission lines, electric power distribution lines, and transformer substations, etc., and a method of producing the same. Heretofore, in order to automatically find out fault points in electric power supply systems, optical fiber built-in type composite insulators have been used which have a function to transmit signals from optical sensors provided at power supply source side to detectors provided at grounded side. US-A-3 485 940 describes an electrical insulator in which insulator modules are stacked on top of each other around a central tube. The modules are glued together at their joints, and an insulating adhesive fills the gap between the modules and the tube. An optical device e.g. an optical fibre runs through an insulating material e.g. polyurethane foam, which is packed inside the tube. Also, in the optical fiber built-in type composite insulators having stacked and joined insulator bodies, there are known those having a flexible connector metallic fitting between the end surfaces of the opposing insulator bodies, those directly joining the end surfaces of the opposing insulator bodies tightly, and those directly joining the end surfaces of the opposing insulator bodies tightly and having connector metallic fittings arranged on the outer circumferential surfaces of the insulator bodies for clamping and fixing the joined end surfaces of the insulator bodies. In such optical fiber built-in type composite insulators having stacked and joined insulator bodies, a sealing material filled between the connector metallic fittings and the outer circumferential surface of the insulator bodies, between the opposing end surfaces of the insulator bodies, or in the interior of the penetration bores, is deteriorated due to impregnation with moisture penetrated through the cement from the exterior, or the sealing material is impregnated with moisture and thermally expanded in the narrow gaps to destroy the insulator body when the temperature of the insulator is elevated. Usually, in joining two insulator bodies, the insulator bodies each having a connector metallic fitting around the end of the outer circumferential surface thereof are joined at their opposing end surfaces, and sealed at their outer circumferential surfaces of the joined portion by a sealing member, and the joined portion is fixed and clamped by the connector metallic fittings with a cementing material therebetween. If the sealing is broken to permit rain drops, etc., to penetrate into the penetration bores through the opposing end surfaces of the insulator bodies, a leakage current is liable to flow along the penetration bores and short circuited trouble is likely to occur. In addition, the joined state of the insulator bodies at the end surfaces can not be maintained for a long time by a mere fixing and clamping by means of the conventional connector metallic fittings, etc., so that joining strength of the joined portion is decreased with the elapse of time. Moreover, in case when the connector metallic fittings are directly abutted to the opposing end surfaces of the insulator bodies, or in case when the opposing end surfaces of the insulator bodies are directly abutted to each other, the opposing end surfaces of the insulator bodies can not absorb large mechanical shocks which might occur therebetween sufficiently, so that the opposing end surfaces are liable to conflict with each other and hence destructed at the time of earthquake, etc. Furthermore, when producing an optical fiber built-in type composite insulator having stacked and joined multi insulator bodies by stacking a multiple number of insulator bodies by means of connector metallic fittings, inserting an optical fiber in the penetration bores of the insulator bodies, and filling a silicone rubber in the penetration bores, all the assembling works have to be performed in a production plant, because the penetration bores are so small that the filling work has to be performed by an aspiration system. In addition, the insulator bodies have to be stacked before the work of inserting the optical fiber in the penetration bores, so that the production plant becomes to a large size, and the height of the stacked bodies can not be changed or varied, even if such change is required. An object of the present invention is to obviate the above drawbacks. Another object of the present invention is to provide an optical fiber built-in type composite insulator of a high reliability having stacked and joined insulator bodies, which can prevent leakage of silicone grease or a sealing material from joined portion or packing portion of the stacked and joined insulator bodies. A further object of the present invention is to provide an optical fiber built-in type composite insulator having stacked and joined insulator bodies, which can prevent leakage of the sealing material and destruction of the insulator bodies due to thermal expansion and prevent penetration of rain drops, etc., in the joined portion from the exterior so as to prevent the short circuited troubles along the penetration bores, and which can maintain joining strength of the joined portion for a long period of time. A still further object of the present invention is to provide an optical fiber built-in type composite insulator having stacked and joined insulator bodies, which can prevent destruction of the insulator bodies even when the sealing material is leaked and thermally expanded in the joining portion, which can prevent the penetration of rain drops, etc., in the joined portion from the exterior to prevent the short circuited troubles along the penetration bores, and which can absorb mechanical shocks which might be produced at the opposing end surfaces of the stacked insulator bodies at the time of earthquake, etc., to prevent destruction of the joined opposing end surfaces of the insulator bodies. Another object of the present invention is to provide an optical fiber built-in type composite insulator having stacked and joined insulator bodies, which can afford easy assembling works thereof also at outside of the production plant, which can minimize the production plant, and which can vary the height of the stacked insulator bodies, if desired. The invention is set out in claim 1. The present invention may include an insulator body having a penetration bore in its central axis portion, at least one optical fiber inserted in the penetration bore, and a silicone grease sealingly filled in the middle portion of the penetration bore, comprising, silicone rubbers sealingly filled in the upper and lower end portions of the penetration bore, and a corrosion resistant partition wall arranged between the silicone grease and the silicone rubbers. The present invention may comprise silicone rubbers sealingly filling the upper and lower end portions of the communicated penetration bores of the stacked and connected insulator bodies and a corrosion resistant partition wall arranged between the silicone grease and the silicone rubbers. The present invention may include insulator bodies in which the upper and lower end portions of the penetration bores penetrating the central portion of the insulator body are sealed substantially by silicone rubbers, and a partition wall made of a corrosion resistant material not reactive with a silicone grease, such as, nitrile rubber, butyric rubber, urethane rubber, polychloroprene rubber, styrene butadiene rubber, isoprene rubber, natural rubber, epoxy resin, acrylic resin, phenolic resin, polyvinylformal resin, polyvinylbutyral resin, or copolymeric nylon, etc., is arranged at the portion of the penetration bore that contacts with the silicone grease, and preferably a porous rubber made of, for example, nitrile rubber, butyric rubber, or urethane rubber, etc., is arranged in the inside of the partition wall, so that the silicone rubbers and the silicone grease are separated from each other and prevented from reacting with each other and the sealing is kept safe without being broken, and a leakage of the silicone grease from the upper and lower ends of the penetration bores can be eliminated. In the arrangement of the present invention, the insulator bodies may be stacked in multiple numbers, the dual O-rings are provided on the joining portion of the stacked insulator bodies, and at least the inner O-ring that contacts with the silicone grease is made of a stable material that does not react with the silicone grease, for example, nitrile rubber, butyric rubber, or urethane rubber, etc., so that breakage of the sealing at the joining portion can be prevented and hence leakage of the silicone grease from the joining portion of the insulator bodies can be prevented. In addition, the provision of the silicone rubber between the dual O-rings can provide a more satisfactory sealing of the joining portion of the insulator bodies. In the arrangement of the present invention, if at least one spacer made of epoxy resin, or urethane rubber, etc., for fixing the optical fiber in the penetration bores of the stacked insulator bodies is provided at the joining portion of the stacked insulator bodies, the optical fiber in the penetration bores of the stacked insulator bodies can be advantageously prevented from bending and breakage. In the arrangement of the present invention, tapered portions may be provided on the upper and lower end portions of the penetration bores of the insulator bodies, so that the sealing by the silicone rubber at the sealing portion is prevented from breakage. Silicone rubber having superior adhesive property to the insulator bodies is introduced and sealed in the whole of the penetration bores instead of silicone grease, so that leakage of silicone grease from the sealing portion and the stacked packing portion can be eliminated. A spacer may be used for adjusting the positioning of the optical fiber in the stacked insulator bodies, so that the optical fiber can be fixed firmly without a displacement thereof in the stacked insulator bodies. For a better understanding of the present invention, reference is made to the accompanying drawings, in which: Fig. 1 is a schematic crosssectional view of an example of an optical fiber built-in type composite insulator body suitable for use in the present invention; Fig. 2 is a schematic crosssectional view of an example of a composite insulator embodying the invention; Fig. 3 is a schematic crosssectional view of an example of another composite insulator embodying the invention; and Figs. 4a and 4b are respectively a schematic crosssectional view of yet another example of a composite insulator embodying the invention, showing an arrangement of the spacer. Numberings in the drawings. 1, 1-1, 1-2 ... insulator body 2, 2-1, 2-2 ... penetration bore 3 ... optical fiber 4 ... silicone grease 5, 5-1, 5-2 ... silicone rubber 6-1, 6-2 ... partition wall 7 ... O-ring 8-1 through 8-4 ... flange type connector metallic fitting 9-1, 9-2 ... O-ring 10 ... silicone rubber 11 ... spacer 15 ... perforation hole 16-1, 16-2 ... spacer Throughout the different views of the drawings, the same reference number represents the same part, element or portion, unless otherwise specified. Referring to Fig. 1, an embodiment of a composite insulator body suitable for use in the present invention is shown. In this embodiment, an optical fiber 3 is inserted in a penetration bore 2 penetrating the central axis portion of an insulator body 1, and silicone rubbers 5-1, 5-2 are provided on the upper and lower ends of the insulator body 1 in order to prevent a silicone grease 4 in the penetration bore 2 from flowing out therefrom. Between the silicone rubbers 5-1, 5-2 and the silicone grease 4, are provided partition walls 6-1, 6-2 made of a corrosion resistant material, such as, nitrile rubber, butyric rubber, urethane rubber, epoxy resin, acrylic resin, or the like material which does not react with the silicone grease 4, and also cushioning members 7-1, 7-2 made of a porous rubber for absorbing expansion and shrinkage of the silicone grease 4. Referring to Fig. 2, an embodiment of the composite insulator of the present invention is shown, wherein a multiple number of insulator bodies are stacked and joined to construct the optical fiber built-in type composite insulator. In this embodiment, an optical fiber 3 is inserted in penetration bores 2-1, 2-2 penetrating the central axis portions of stacked and joined two insulator bodies 1-1, 1-2, and the upper end of the penetration bore 1-1 and the lower end of the penetration bore 2-2 are sealed by silicone rubbers 5-1, 5-2, in order to prevent a silicone grease 4 in the penetration bores 2-1, 2-2, from flowing out therefrom. On the both ends of the insulator bodies 1-1, 1-2, are provided flange type connector metallic fittings 8-1 through 8-4, and the metallic fittings 8-2, 8-3 serve to connect the insulator bodies 1-1, 1-2. In addition, dual O-rings 9-1, 9-2 made of a resilient material are provided in the joining portion of the insulator bodies 1-1, 1-2 which is the boundary layer of the lower end of the insulator body 1-1 and the upper end of the insulator body 1-2, and the inner O-ring 9-1 is made of nitrile rubber, butyric rubber, or urethane rubber, etc., which is stable and hardly reacts with the silicone grease 4. Between the dual O-rings 9-1, 9-2 is provided a silicone rubber 10 for improving the sealing property of the joining portion. In the inside of the O-ring 9-1 is provided a spacer 11 having a perforation hole in the center for allowing insertion of the optical fiber 3, in order to adjust the position of the optical fiber 3. Referring to Fig. 3, an embodiment of the composite insulator of the present invention is shown, wherein a multiple number of insulator bodies are stacked and joined to construct a composite insulator. The sealing structures at the upper end portion of the penetration bore 2-1 of the insulator body 1-1 and the lower end portion of the penetration bore 2-2 of the insulator body 1-2 are the same as those shown in Fig. 1, and the structure of the joining portion of the lower end of the insulator body 1-1 and the upper end of the insulator body 1-2 is the same as that shown in Fig. 2. This embodiment can achieve improvements in both sealing properties at the upper and lower end portions of the first aspect and at the joining portion of the insulator bodies of the second aspect. Referring to Figs. 4a and 4b, a state of the spacer 11 in a composite insulator is shown. In the embodiment shown in Fig. 4a, a single spacer 11 is used similarly as in the embodiments of Figs. 2 and 3. That is, a spacer 11 having in its central axis portion perforation holes 15 of numbers corresponding to numbers of the optical fibers 3 to be inserted in the penetration bores is arranged at the boundary layer between the lower end of the insulator body 1-1 and the upper end of the insulator body 1-2. For that purpose, preferably, the thickness of the spacer 11 is equal to or slightly thinner than a thickness of the resilient O-rings 9-1, 9-2 of mounted state, or recessed portions for mounting the spacer 11 are provided on the lower end surface of the insulator body 1-1 and the upper end surface of the insulator body 1-2. In the embodiment shown in Fig. 4b, two spacers are used. That is, spacers 16-1, 16-2 each having the central portion recessed to the direction of the insulator body 1-1 or to the direction of the insulator body 1-2 and having perforation holes 15 of numbers corresponding to numbers of the optical fiber 3 to be inserted in the penetration bores 2-1, 2-2, are sandwiched in the joining layer between the lower end of the insulator body 1-1 and the upper end of the insulator body 1-2 in such a fashion as to make an angle of 90° to each other. By this arrangement, even if the positions of the penetration bores 2-1, 2-2 are displaced widely to each other, the spacers 16-1, 16-2 can more satisfactorily adjust a bending of the optical fibers 3 and prevent breakage of the optical fiber 3 than in the case of single spacer 11, because the central portions of the spacers 16-1, 16-2 are also displaced relative to the displacement of the penetration bores 2-1, 2-2. In such case, preferably ring-shaped auxiliary members made of a porous rubber are provided around the central portions of the spacers 16-1, 16-2. As is apparent from the foregoing explanations, the leakage of inner silicone grease to the exterior of the composite insulator through the sealings can effectively be prevented by improving the structure of the joining portion of the stacked insulator bodies according to the present invention. The leakage of the inner silicone rubber to the exterior of the composite insulator through the seal, the bending of the optical fiber, and the breakage of the optical fiber can be prevented effectively by providing tapered portions at the upper and lower end portions of the penetration bore, sealing the penetration bore by a silicone rubber after insertion of the optical fiber, and providing the spacer at the boundary of the stacked insulator bodies for fixing the optical fiber.

Claims: An optical fiber built-in type composite insulator comprising at least two insulator bodies (1) each having a penetration bore (2) in their central portion, at least one optical fiber (3) inserted in the penetration bores (2), the insulator bodies (1) being stacked and joined by a bonding material (10) provided in a space between opposing end surfaces of the stacked and joined insulator bodies (1) thereby to provide an airtight seal between the insulator bodies (1), characterized in that the composite insulator further comprises flange type metallic connector fittings (8) joined to the insulator bodies (1) to join the stacked insulator bodies (1) so as to align the penetration bores (2), silicone grease (4) sealingly filled in a middle portion of the penetration bores (2), and an inner O-ring (9-1) and an outer O-ring (9-2) arranged at the joined portion of the insulator bodies (1), at least the inner O-ring (9-1) being constituted from a material stable to the silicone grease (4), and said bonding material (10) being a silicone rubber sealingly filled between the two O-rings (9-1, 9-2). An optical fiber built-in type composite insulator according to claim 1, wherein the optical fiber (3) is located by at least one spacer (11) provided at the joining portion of the insulator bodies. An optical fiber built-in type composite insulator according to claim 1 or claim 2, wherein the penetration bores (2) comprise tapered sections at the upper and lower end portions of the joined bores, and silicone rubber (5) sealingly fills and bonds around the optical fiber (3) in the penetration bores (2) at the upper and lower end portions. An optical fiber built-in type composite insulator according to any one of claims 1 to 3, wherein at least one of the O-rings (9) is made of a resilient material and is provided between the opposing end surfaces of the insulator bodies (1). An optical fiber built-in type composite insulator according to any one of the preceding claims having silicone rubber (5) sealingly filled in the upper and lower end portions of the joined penetration bores (2), and corrosion resistant partition walls (6,7) arranged between the silicone grease (4) and the silicone rubber (5). An optical fiber built-in type composite insulator according to claim 5, wherein each corrosion resistant partition wall (6) comprises a porous rubber portion (7).

Inventors: DOI KENJI, IKEDA MITSUJI, KATSUKAWA HIROYUKI, MORI KOICHI, NAKANISHI KAZUMI, NOZAKI MASAYUKI, OKAJIMA HISAKAZU, SEIKE SHOJI, DOI, KENJI, IKEDA, MITSUJI, KATSUKAWA, HIROYUKI, MORI, KOICHI, NAKANISHI, KAZUMI, NOZAKI, MASAYUKI, OKAJIMA, HISAKAZU, SEIKE, SHOJI
Applicants: NGK INSULATORS LTD, NGK INSULATORS, LTD.
Application year: 1989
Main classification: H01B17
IPC codes: H01B17, G02B6