Cable closure

Abstract: To reduce the number of parts, assembly work time and cost of a cable closure including a two-splittable cylindrical sleeve for covering the cable junction point, and a pair of two-dividable annular end plates fitted to both inner ends of the sleeve to close spaces between the cables and the sleeve, the end plates are formed by a rigid plastic material and gaps between the cable and the end plates are sealed by rubber airtight tape wound around the cable by adjusting the number of turns according to cable diameter. Further, two cable gripping means are fixed to the end plates, respectively to protect the junction point from external force applied between the two cables by the strength of the sleeve coupled to the end plates.

Description: The present invention relates to a cable closure for a junction of two cables as described in the preamble of present claim 1. Usually, two communication cables are connected to each other by removing cable sheath from a cable to expose a cable core and by connecting the two exposed cable cores. In this case, since it is necessary to protect the cable junction point from water and external force, a cable closure of airtight structure is attached to the cable junction point. In addition, the cable and cable closure thereof are often filled with pressurized gas (e.g., air, nitrogren gas, etc., of about 1 at.) in order to improve the waterproof reliability thereof, which is called "gas maintenance." In this case, the cable closure is further required to prevent the pressurized gas from leaking from the inside to the outside thereof. Further, since various cables of different diameters exist, another requirement exists that the cable closure must be applicable to any junction point of cables of various diameters. Further, as the cables are usually laid down in open air, other requirements exist for sufficient durability, easy assembly/disassembly work, high strength, etc., in addition to the above-mentioned airtightness. Document DE-A-25 21 803 describes a cable closure for a junction of two cables which comprises a cylindrical sleeve with integrated end plates and a sealing means. The disadvantage is that for various cables of different diameters, there is a separate sleeve with adapted end plates necessary. Furthermore, no gripping means are provided to protect the cable junction from external force. In another prior art cable closure as shown in Figures 1(A), 1(B), and 1(C), however, since the cable junction point is protected from an external force by cable gripping members fixed to the cable core through a slit formed in the cable sheath, and is protected from water by non-elastic adhesive sealing tape material placed in spaces between the cable, elastic end plates, and sleeve, various problems exist in that (a) firstly, various end plates must be prepared according to cables of different diameters and, further, the sleeve must be fastened against the elastic end plates by a great force for providing airtightness, thus resulting in hard assembly work; (b) secondly, various-sized cable gripping members must be prepared according to cables of different diameters and plural slits must be formed in the cable sheath; (c) thirdly, since non-elastic adhesive sealing tape material is used, it takes a lot of time to disassemble the assembled cable closure; and (d) finally, since sealing washers for preventing the flow of the non-elastic sealing material are required, a great number of the components are needed to assemble the final cable closures, resulting in time consumption. The arrangement of this prior art cable closure and its drawbacks will be disclosed in more detail hereinafter with reference to Figures 1(a), 1(B), and 1(C) under DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT. Document US-A-4,538,021 describes a cable closure for a junction of two cables which also comprises a two-part cylindrical sleeve which has end plates fitted to both inner ends of the sleeve and an elastic sealing tape wound around the cable for sealing gaps between the cable and the end plates. The sealing tape is disposed between two retaining washers. This means, that for other diameters of the cable, the washers have to be adapted. Furthermore, there are no gripping means provided to protect the cable junction from external force. With these problems in mind, therefore, it is the object of the invention to provide a cable closure which avoids lower applicability to cables of different diameters, insufficient airtightness for long periods of time, and lower assembling and disassembling work efficiency. In accordance with invention, this object is solved by the characterizing part of present claim 1. Since the airtightness between the cable and the end plates can be obtained by winding elastic airtight tape, even if a gap between the cable and the inner circumferential surface of the end plate changes according to change in the cable diameter, it is possible to adjust or fill the gap with airtight tape, thus eliminating the need for preparing various-sized end plates according to the cable diameter. Further, it's possible to eliminate the prior art sealing washers, thus reducing the costs thereof. Since the cable gripping member can grip the cable sheath by adjustably moving the cable fastening screws in the vertical direction thereof, it's possible to markedly reduce a number of elements, eliminating the need for preparing various-sized cable gripping members according to the cable diameters. Further, it is not necessary to form slits on the cable sheaths, thus reducing the cost and the assembly time thereof. Further developments of the invention are claimed in the subclaims. BRIEF DESCRIPTION OF THE DRAWINGS The features and advantages of the cable closure according to the present invention over the prior-art cable closure will be more clearly appreciated from the following description of the preferred embodiment of the invention taken in conjunction with the accompanying drawings and in which: Fig. 1(A) is a perspective and partly exploded view showing an example of prior-art cable closure; Fig. 1(B) is an enlarged exploded view showing cable gripping members incorporated in the prior-art cable closure shown in Fig. 1(A); Fig. 1(C) is an enlarged exploded view showing an end plate incorporated in the prior-art cable closure shown in Fig. 1(A); Fig. 2 is a perspective, partly broken view showing a cable closure according to the present invention; Fig. 3 is a perspective and exploded view showing an end plate incorporated in the cable closure of the present invention shown in Fig. 2; Fig. 4 is an enlarged side view showing an end plate and a cable gripping member incorporated in the cable closure of the present invention shown in Fig. 2; Fig. 5 is an enlarged cross-sectional view taken along the line A-A in Fig. 4; and Fig. 6(A) is an enlarged cross-sectional view of elastic sealing airtight tape used for the cable closure according to the present invention; Fig. 6(B) is a side view of the same elastic sealing airtight tape shown in Fig. 6(A); and, Fig. 7 is a view showing the elastic sealing airtight tape wound around a reel. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS To facilitate understanding of the present invention, a reference will be made to a prior-art cable closure, with reference to the attached drawings. In Figs. 1(A), (B) and (C) two cables 100 are connected and protected by winding an insulating tape around the cable junction point 120. A cable closure is roughly composed of a two-slittable cylindrical sleeve 200, a set of cable gripping members 300 and a pair of two-dividable annular end plates 400. The sleeve 200 can be split into two semicylindrical sleeve members 220 and fixed to each other with plural bolts 240 by putting two flange portions 220A of one sleeve member 220 upon those 220A of the other sleeve member 220 with elastic adhesive sealing tape material 230 intervening between the two flange portions 220A. Each of the cable gripping members 300 comprises a pair of inner semicircular members 310 inserted into a space between a cable core (not shown) and a cable sheath 101 through slits 101a formed in the cable sheath 101 as shown in Fig. 1(B) (in which only the flat portions of the members 310 are shown); a pair of outer semicircular members 320 (each including an inner member 320A and an outer member 320B) fitted to an outer circumferential surface of the cable sheath 101, and a pair of connecting bars 330. These three, inner semicircular members 310, outer semicircular members 320 and connecting bars 330 are fixed to each other simultaneously with plural bolts 340 so as to protect the cable junction point 120 from external force applied between the two cables 100 by the strength of the connecting bars 330. The end plate 400 also can be divided into two semiannular end plate members 420. As depicted in Fig. 1(C) each semiannular end plate member 420 made of elastic (rubber) material is formed with a pair of semicircular flange portions 420A, an outer semicircular recessed portion 420B formed between the two flange portions 420A, an inner semicircular recessed portion 420C, two inner washer holding portions 420D, and two flat surface recessed portions 420E. These two semiannular end plate members 420 are fixed to each other with four bolts 450 with non-elastic adhesive sealing tape material 480 intervening between the two flat surface recessed portions 420E of the two end plate members 420. In assembly of the cable closure as described above, non-elastic adhesive sealing tape material 500 is attached to the outer circumferential surface of the cable sheath at two positions where the two end plates 400 are fixed. In this case, two sealing material support washers 500A made of elastic (rubber) material are fitted to the cable 100, as depicted in Fig. 1(C), for prevention of the sealing material 500 from being slipped away from the predetermined positions. The semiannular end plate members 420 are fixed to each other with the four bolts 450 by putting the adhesive sealing tape material 480 upon the two flat surface recessed portions 420E thereof and by engaging the outer circumferential surfaces of the sealing material support washers 500A with the inner circumferential surface of the cable washer holding portions 420D thereof, with the adhesive sealing tape material 500 sandwiched between the two semiannular end plate members 420. Thereafter, a similar non-elastic adhesive sealing tape material 600 is attached to the outer semicircular recessed portions 420B of the two fixed end plate members 420. Further, the two semicylindrical sleeve members 220 are fixed with the bolts 240 by engaging the sealing material 600 (or the two flange portions 420A of the end plate 420) with the recessed portion 220B formed on the inner end circumferential surface of the sleeve member 220. In this case, the two sealing members 230 are put between the two flange portions 220A of the two sleeve members 220, respectively, as already described. In the above-mentioned prior-art cable closure, the cable junction point 120 is covered by two end plates 400 and the sleeve 200. The airtightness between the cable 100 and the end plates 400 can be attained by the non-elastic adhesive sealing tape material 500 attached around the cable 100 and between the two sealing material rubber support washers 500A. Here, it should be noted that these two rubber support washers 500A serve only to support sealing material 500 and not to serve as airtighting members. The airtightness between the end plates 400 and the sleeve 200 can be attained by the similar non-elastic adhesive sealing tape material 600 attached around the end plates 400. The airtightness between the two semiannular end plate members 420 can be attained by the two non-elastic adhesive sealing tape material 480 attached applied onto the two flat surface recessed portions 420E of the end plate members 420. Further, the airtightness between the two semicylindrical sleeve members 220 can be attained by the elastic adhesive sealing tape materials 230. In summary, in the prior-art cable closure, non-elastic adhesive sealing tape material is used to obtain airtightness of the cable closure. Further, the cable junction point 120 is reinforced against external force applied between the two cables 100 by the connecting bars 330 of the cable gripping members 300. In the prior-art cable closure, however, there exist various problems as follows: (1) Higher cost (a) Since the cable gripping members 300 including the inner semicircular members 310, and the outer semicircular member 320 must be fitted to the cable 100, it has been necessary to previously prepare many kinds of the cable gripping members 300 of different sizes according to various cables of different diameters. (b) Since the space between the cable 100 and the end plates 400 is sealed by the non-elastic adhesive sealing material 500, there inevitably exists a limit of the amount of the sealing material to be provided around the cable 100. Therefore, it has been necessary to previously prepare many kinds of end plates 400 and the sealing washers 500A according to various cables of different diameters. Or else, an inner semicircular hollow portion of the end plate 400 must be adjusted according to the size of the cable, at each site of construction, with a special tool, and also a thickness of the end plate 400 in the longitudinal direction thereof must be made thick enough to attain the airtightness. (2) Longer assembling time (a) Since four or six slits 101a must be formed on the cable sheath 101 before inserting the inner semicircular members 310 into between the cable core and the cable sheath, it takes a relatively long assembly time. (b) Since the airtightness between the cable 100 and the end plates 400 and that between the end plates 400 and the sleeve 200 are maintained by the non-elastic adhesive sealing tape material 500 and 600, the end plates 400 must be made of an elastic (rubber) material. In this case, ever if the end plate 400 is fastened tightly with the end plate bolts 450, since the end plate 400 is deformed partially or locally, it has been necessary to tightly fasten the two sleeve members 220 with the sleeve bolts 240 to compress the end plates 400 in the radially inward direction thereof uniformly over the circumferential direction thereof. Therefore, many sleeve bolts 240 has been tighten by applying a torque as large as 180 kg-cm to each bolt 240, thus resulting in hard assembly work within a relatively small working space such as within a manhole. The above-mentioned problem results from the fact that in the prior-art closure device, the airtightness is mainly dependent upon the adhersive force of the adhersive tape. (3) Others (a) Since the cable junction point is reinforced by the connecting bars 330, and furthermore the slits 101a are formed in the cable sheath 101, the inner space, defined within the cable closure, capable of storing the cable 100 is reduced. (b) Since adhesive sealing material is used for providing airtightness of the cable closure, it takes much time in disassembling the cable closure when the cables are required to be reconnected. In view of the above description, reference is now made to an embodiment of the cable closure according to the present invention. The feature of the cable closure of the present invention is to attain the airtightness between the cable and the end plates and between the end plates and the sleeve, in dependence upon rigid (e.g. plastic) end plates and elastic (rubber) airtight members, so as to be applicable to any cables of different diameters. Further, another feature of the present invention is to provide simple cable gripping members engaged with each end plate, without use of any connecting bars, so as to reinforce the strength of the cable junction point by the aid of the sleeve. The cable closure of the present invention is roughly composed of a two-splittable cylindrical sleeve 20, a pair of annular cable gripping members 30 including three cable fastening screws, and a pair of two-dividable annular end plates 40. It should be noted that the annular end plate 40 may be divided into, e.g., three or more plates. With reference to Fig. 2, the sleeve 20 can be divided into two semicylindrical sleeve members 22, and fixed to each other with plural sleeve fastening members 24 each composed of a metal band 24A and a buckle 24B. These sleeve fastening members 24 are arranged at regular intervals along the longitudinal direction of the sleeve 20. Further, two elastic (rubber) sealing members 23 are disposed between two end surfaces 22A of each sleeve member 22, when the two sleeve members 22 are fixed to each other, to provide airtightness between the two. Further, each sleeve member 22 is formed with two inner end recessed portions 22B engageable with the end plates 40. The feature of the sleeve 20 of the present invention is formed with no flange portions as in the prior-art sleeve shown in Fig. 1(A). This is because it is unnecessary to strongly tighten the end plates 40 by the sleeve 20. Therefore, the shape of the sleeve 20 can be minimized and simplified. With reference to Figs. 4 and 5, the cable gripping members 30 comprise a two-separable annular, screw support member 31, plural (e.g. three) cable fastening screws 32, and plural arcuate cable push members 34 each formed with a plurality of conical projections 34a on the radially inward surface thereof. The two-separable annular screw support member 31 is formed with a large-diameter portion 31a, along the circumferential surface of which the cable fastening screws 32 are arranged at regular angular intervals, and a small-diameter portion 31b formed with a recessed portion engageable with the end plate 40. The arcuate cable push member 34 is rotatably attached to an innermost end of the cable fastening screw 32. This cable fastening screw 32 provided with the movable cable push member 34 is screwed into a threaded hole 31c formed on the circumferential surface of the annular screw support member 31 from the inside thereof. In assembly, the two semiannular screw support members 31 are fixed to each other with bolts 33 with the cable 10 intervening between the two 31. Thereafter, the three cable fastening screws 32 are screwed radially inward toward the cable 10 uniformly so that the three arcuate cable push members 34 can be brought into contact with the outer circumferential of the cable sheath 11 uniformly for cable gripping. Since the conical projections 34a formed on the inner surface of the arcuate cable push member 34 go into the cable sheath, the cable 10 is firmly gripped by the cable gripping member 30. With reference to Fig. 3 and 5, each end plate 40 also can be divided into two semiannular end plate members 42. In this embodiment, the end plate 40 is made of a rigid material such as plastic (being different from the prior-art rubber end plate 400 shown in Fig. 1). Each end plate member 42 is formed with a pair of semicircular flange portions 42A, an outer semicircular recessed portion 42B formed between the two flange portions 42A, an inner semicircular portion 42C formed with inner semicircular projections 42C-1 (Fig. 5) for gripping the seal member 50, and an end inner semicircular recessed portion 42D engageable with the cable gripping member 30, and two flat surface recessed portion 42E. The sealing method of the above-mentioned major elements will be described hereinbelow. To seal the cable 10 and the end plate 40, an elastic (rubber) airtight tape 50 is wound two or three turns around the cable 10 as shown in Fig. 3. However, the number of turns of this airtight tape is adjustable according to the diameter of the cable. In the same way, to seal the end plate 40 and the sleeve 20, an elastic airtight tape 60 similar to the above-described airtight tape 50 is wound around the outer semicircular recessed portion 42B of the end plate member 42 as shown in Fig. 5. To seal the two end plate members 42, a non-elastic adhesive sealing tape material 48 is sandwiched between the two flat surface recessed portions 42E of the two end plate members 42. To seal the two semicylindrical sleeve members 22, a longitudinal gasket strip 23 is sandwiched between the two end surfaces 22A of the two sleeve members 22. As the above-mentioned airtight rubber tape, it is preferable to use ethylene propylene rubber called EPDM ( E thylene P ropylene D iene M ethylene) whose hardness is approximately 55 degrees when measured by a A-type spring hardness tester standardized in JIS. In this test method, a certain number (6 or more) of rubber tapes are stacked to obtain a test sample whose thickness is 12 mm or more; a test surface of the hardness tester is brought into contact with the surface of the test sample to measure a distance (degree) that a test needle (urged by a spring load (1000 gf or 9.81 N) and projecting through a hole formed in the test surface) is pushed back by an elastic force of the test rubber sample. Fig. 6(A) and 6(B) show an example of the dimensions of the airtight tape. In Fig. 6(A), the thickness thereof is about 2 mm and the width thereof is about 28 mm. Further, it is particularly preferable to apply an adhesive (width: 4 mm; thickness: 0.05 mm) onto both side ends of one surface of the airtight tape in order to facilitate tape winding work (because, it is unnecessary to hold the tape by the hand for prevention of tape from being loosened). Further, the total length of the airtight tape is about 2600 mm as shown in Fig. 6(B) and wound around a reel with a separator paper intervening between the two as depicted in Fig. 7. The airtight tape is wound around the cable 10 by removing the separator paper from the tape. The assembling procedure of the cable closure of the present invention will be described hereinbelow. The two cable gripping members 30 are first fixed to the cable 10 at two positions a predetermined distance away from each other on both the sides of the junction point 12. Each cable gripping member 30 is separated into two semiannular screw support members 31 and fixed with bolts 33 by passing the cable 10 through the central hollow portion formed by the two screw support members 31. Thereafter, the three cable fastening screws 32 are tightened with a screw driver whose torque can be determined at any desired value to bring each arcuate cable push member 34 into tight contact with the cable sheath. Under these conditions, since the conical projections 34a of the cable push member 34 go into the cable sheath, it is possible for the cable push member 34 to grip the cable firmly. The elastic (rubber) airtight tape 50 is wound around the cable 10 near the two fixed cable gripping members 30, as shown in Fig. 3. In this case, the turns of the airtight tape 50 is determined under consideration of the cable diameter. Thereafter, each end plate 40 is separated into two semiannular end plate members 42 and fixed with bolts 45 by sandwiching the wound airtight tape 50 between the two end plate members 42, and the sealing member (non-elastic sealing material) 48 between the two flat surface recessed portions 42E of the end plate members 42. Further, when the two end plate members 42 are fixed to each other, the inner semicircular recessed portion 42D of the end plate members 42 are engaged with the small-diameter portion 31b of the cable gripping member 30. The elastic (rubber) airtight tape 60 is wound around the outer recessed portions 42B of the end plate 40 by a predetermined turn. The sleeve 20 is separated into two semicylindrical sleeve members 22 and fixed with plural sleeve fastening members 24 with the outer circumferential portions (i.e. the airtight tape 60) of the two end plates 40 engaged with the two inner end recessed portions 22B formed in the sleeve members 22. When the two sleeve members 22 are fixed to each other, the gasket strip 23 is attached to the two end surfaces 22A of each of the two sleeve members 22. Under these assembled conditions, since the two cable gripping members 30 are connected to the sleeve 20 via the two rigid end plates 40, it is possible to protect the cable junction point 12 from external force applied between the two cables by the strength of the sleeve 20. Furthermore, since the airtightness between the cable 10 and end plates 40 is achieved by the airtight tape, the airtightness between the end plates 40 is attained by the adhesive sealing material, the airtightness between the sleeve 20 and end plates 40 is established by another airtight tape having the same material but different shape from that of the first-mentioned airtight tape, and also the airtightness between the sleeves 20 is provided by the longitudinal gasket strip 23, it is possible to protect the cable junction point 12 from water or to prevent the inner pressurized gas from leaking outside. In the above embodiment, it is preferable to form the end plates 40 and the sleeve 20 by the same material from the airtightness standpoint, because there exists no difference in expansion and contraction rates between the end plates 40 and the sleeve 20. Further, although the cable gripping member 30 is provided separately from the end plate 40, it is also preferable to form the screw support member 31 integral with the end plate member 42. Further, when a large mechanical strength is required for the end plate to protect the cable junction point from external force according to the circumference, it is preferable to form the end plates by a plastic material reinforced by glass fiber or to provide ribs for the end plate. The cable closure according to the present invention as described above has various advantages as follows: (a) Since the airtightness between the cable 10 and the end plates 40 can be obtained by winding elastic airtight tape 50, even if a gap between the cable 10 and the inner circumferential surface of the end plate 40 changes according to change in cable diameter, it is possible to adjustably fill the gap with the airtight tape 50, thus eliminating the need of preparing various sized end plates 40 according to the cable diameters. Further, it is possible to eliminate the prior-art sealing washers 500A, thus reducing the cost thereof. (b) Since the cable gripping member 30 can grip the cable sheath by adjustably moving the cable fastening screws 32 in the radial direction thereof, it is possible to markedly reduce the number of elements, eliminate the need of preparing various sized cable gripping members according to the cable diameters. Further, it is unnecessary to form slits on the cable sheath, thus reducing the cost and the assembly time thereof. (c) Since the airtightness between the cable 10 and the end plates 40 and between the end plates 40 and the sleeve 20 can be attained by elastic sealing material respectively, it is possible to markedly reduce the sleeve tightening force from 180 kg-cm (in prior art) to 70 kg-cm (in the invention). (d) Therefore, it is possible to fasten the sleeve 20 with plural bands 24, in place of bolts, without providing the flange portions (as in the prior art), thus minimizing the sleeve size and facilitating the assembly work. (e) Since the cable gripping members 30, the end plates 40 and the sleeve 20 are fixed integral with each other, it is possible to eliminate the connecting bars (as in the prior art), thus increasing the inner space within the cable closure. (f) Since no adhesive sealing material is used for attaining airtightness, it is possible to facilitate the disassembly work. As described above, in the cable closure according to the present invention, since the airtightness between various elements can be attained by adjustably providing a rubber airtight tape, a single predetermined-sized end plate is applicable to various cables of different diameters. Further, since the cable can be simply gripped by turning the cable fastening screws and reinforced by sleeve linked to the cable gripping means via the end plates, it is possible to reduce the number of cable gripping elements and facilitate the assembly work. In practice, it is possible to reduce the assembly time by about 40 to 50% and the device cost by about 25 to 35% as compared with the prior-art cable closure shown in Fig. 1.

Claims: A cable closure for closing a junction point (12) of two cables (10) having a sleeve (20) for covering the cable junction point (12); a plurality of end plates (40) of rigid material fitted to both inner ends of said sleeve (20) for closing spaces between the cables (10) and said sleeve (20); a first elastic sealing means (50) arranged in gaps between the cables (10) and said end plate (40) for sealing the gaps; and a cable gripping means (30) coupled to each of said end plates (40) for gripping the cables (10) to protect the cable junction point (12) from external force applied between the two cables (10), independent of the strength of said sleeve (20) coupled to said end plate (40), characterized in that said first elastic sealing means (50) is an elastic airtight tape (50) wound around the cable (10) by adjusting the number of tape turns according to cable diameter; and said cable gripping means (30) comprises: a pair of annular screw support members (31) and a plurality of cable fastening screws (32) screwed into a plurality of threaded holes formed at regular angular intervals along an outer circumference of each of said annular screw support member (31) so as to be movable in the radial direction of said screw support member (31). The cable closure of claim 1, wherein said elastic airtight tape (50) is made of an ethylene propylene rubber. The cable closure of claim 1, wherein said elastic airtight tape (50) is coated with adhesive agent applied on both outer side ends of one surface of the tape (50) for providing an easy tape winding around the cable. The cable closure of claim 1, wherein said sleeve (20) is a two-splittable cylindrical sleeve member (22) fastened by plural sleeve fastening bands (24A) each provided with a buckle (24B). The cable closure of claim 4, wherein said two-splittable cylindrical sleeve members (22) are formed by the same material as that of said end plates (40).

Inventors: HINOHARA TSUNETO, HIRATA MASATO, KATSUSE MITSUYOSHI, KOSUGI KENJI, KOTANI YUJI, NIMIYA TAKAYUKI, TAKAHASHI HIROSHI, YUHARA KAZUKI, HINOHARA, TSUNETO, HIRATA, MASATO, KATSUSE, MITSUYOSHI, KOSUGI, KENJI, KOTANI, YUJI, NIMIYA, TAKAYUKI, TAKAHASHI, HIROSHI, YUHARA, KAZUKI
Applicants: NIPPON TELEGRAPH & TELEPHONE, NIPPON TELEGRAPH AND TELEPHONE CORPORATION
Application year: 1988
Main classification: H02G15
IPC codes: G02B6, H02G15