AN ADAPTOR FOR EFFECTING A TIGHT BEND IN A COAXIAL CABLE

Abstract: An adaptor for effecting a small radius-of-curvature bend in a relatively large diameter coaxial cable comprises a central, preferably plastics, bellows-type protective element 10, at opposite ends of which are attached respective connectors 2,3 for attachment externally to a relatively large diameter coaxial cable, each connector attached internally to a flexible, relatively small diameter coaxial cable 6 which extends from one connector to the other connector through the protective bellows-type element 10. Thus a tight bend can be achieved without significant transmission losses.

Description: The invention relates to a coaxial cable adaptor for effecting a small radius-of-curvature bend in a coaxial cable having a relatively large outside diameter, especially in a low-loss, high-frequency type coaxial cable. Generally, a flexible coaxial cable cannot be bent to a radius of curvature below a certain allowable radius. This condition is dictated by the high frequency transmission characteristics of the cable and its geometry. However, as is described in Japanese Patent Publication (Kokai) No. 56-94,802, in order to eliminate transmission noise, even with the radius of curvature above the allowable minimum value, the bent portion of the cable conventionally should be maintained rigid. Because, in the case of a low-loss, high-frequency type coaxial cable, the central conductor has a relatively large outside diameter, the cable itself has a relatively large outside diameter. Accordingly, its minimum radius of curvature is large as well. If, under these conditions, the bendable portion of the cable is made rigid, it would be difficult to provide highly efficient space utilization in the electronic device or machine in which the cable is used. A requirement exists for an adaptor which makes it possible to obtain small radius of curvature, even with coaxial cables of large diameters. The FR-A-2503942 discloses a method for the manufacture of curved coaxial connectors which are adapted for high-frequency equipments. In accordance with this known method, a section of a semi-rigid coaxial cable is used which comprises a central conductor enclosed by an insulator which itself is covered with an external conductor consisting of copper. The coaxial cable section is to be bended by means of a tool of the type of a tube bender. Furthermore, the bended cable section is provided with a conducting metallic layer on its outer surface, and, subsequently several further mechanical treatment stages are required in order to obtain the completed coaxial connector. This known manufacturing method needs a considerable expenditure of material and mechanical work. The DE-A-2743424 discloses a connecting element for current connecting or carrying bars. The connecting element comprises coupling pieces on its respective ends serving for connecting the respective ends of two adjacent current connecting bars to each other. Each of the coupling pieces has electrical contact elements which are connected to an electrical current conductor passing through a cable sheating of the connecting element. A plurality of parallel ribs is provided on the outer surface of the cable sheating with the contour shape of the ribs corresponds to the contour shape of the coupling pieces and of the current connecting bars, respectively. The known connecting element can be brought in a position bent off by 90°, e.g. as the cable-like current conductor passing through the connecting element is flexible, however, the connecting element according to the prior art is not useful for connecting coaxial cables. The present invention is based on the problem to eliminate disadvantages inherent in the conventional coaxial cables and to provide an adaptor which makes it possible to obtain small radius of curvature, even with coaxial cables of relatively large diameters. According to the present invention, this problem is solved by the combination of the features of the characterising clause of claim 1. Further advantageous developments of the invention can be taken from the subclaims. According to the present invention, an adaptor is provided for effecting a small radius-of curvature bend in a relatively large diameter coaxial cable. The adaptor comprises a central, preferably plastics, bellow-type protective element, at either end of which is attached a respective connector for attachment externally to a relatively large diameter coaxial cable, each connector being internally connected to a flexible, relatively small diameter coaxial cable which extends from one connector to the other connector through the protective bellow-type element. Because of the bellow-type element and the relatively small diameter of the flexible coaxial cable in the adaptor, a small radius-of curvature effective bend in the relatively large diameter coaxial cable assembly can be achieved without significant transmission losses. More specifically according to the invention, the above purpose is achieved by providing an adaptor for a coaxial cable comprising coaxial connectors on both sides of the protective element, the connectors having large diameters at their external ends for connection to large diameter coaxial cables, and small diameters at their internal ends for connection to a flexible, small diameter coaxial cable which is installed between the connectors and is electrically connected to their internal ends, the protective element surrounding the flexible, small diameter coaxial cable, and spaced therefrom, and attached at both ends to the internal portions of the connectors. Because the space between the coaxial connector on one side of the adaptor and the coaxial connector on the other side of the adaptor is spanned by a flexible, small diameter coaxial cable which is maintained in electrical contact with both connectors, the cables being connected may have, instead of their direct interconnection, a diameter which is substantially larger than the allowable minimum radius of curvature. In addition, the bent portion need not be rigid and can be freely bent in any required direction. The large diameter coaxial cable and the flexible, small diameter coaxial cable may have characteristic impedances matched to each other. In general, the flexible, small diameter coaxial cable of the adaptor may cause a certain transmission loss, but, because the length of this small diameter cable is very short, the share of this loss in the total system will be insignificant. The invention will now be particularly described, by way of example, with reference to the accompanying drawings in which the single figure is a side elevational view, partly in cross section, of a coaxial adaptor made in accordance with one embodiment of the invention. In the illustrated embodiment of the invention, a coaxial cable adaptor 1 has at its one end a coaxial connector 2 of a female type, and, on the other end, a coaxial connector 3 of a male type. The one end of the adaptor is provided with a female type pin 4 which is surrounded by an outer conductor connection sleeve 5 so that a space is formed between the sleeve and pin 4. The sleeve 5 has a large diameter at its front portion and a smaller diameter at the rear portion. In addition, it is maintained in electrical contact with an outer conductor 7 of a flexible, small diameter coaxial cable 6, the characteristic impedance of which is matched with that of the sleeve. In a similar manner, coaxial connector 3 has a male type pin 8 at the centre of its external end. Male pin 8 is surrounded by an outer conductor connection sleeve 9 which has a large diameter at its external end and a reduced diameter at its internal end. Connection sleeve 9 is maintained in electrical contact with the outer conductor 7 of the above mentioned flexible, small diameter coaxial cable 6. The core conductor of cable 6 electrically connects female pin 4 and male pin 8 located on both external ends of coaxial connectors 2 and 3, repsectively. On the outside, the flexible, small diameter coaxial cable 6 is protected by a protective element 10 which encloses and is spaced from cable 6, the element 10 being formed as a caterpillar-type bellow. Protective element 10, preferably made of plastics, has at its annular opposite ends portions 11 which are engaged with supporting flanges 12 and 13 on connectors 2 and 3, respectively as shown. Protective element 10 could alternatively be made of rubber or even kraft paper in some cases. When adaptor 1 is attached, for example, to a large diameter coaxial connector 16 located at the end of a large diameter coaxial cable 15, as shown in phantom line, the cable can be bent at the place of its connection through 90 o , as shown in the attached drawing, or can be bent in the direction perpendicular to the plane of the drawing. Because, in the bent state, the radius of curvature of the cable does not exceed the allowable minimum, it does not lose its transmission characteristics. Because coaxial cable 6 of adaptor 1 has a very small diameter, it may have certain transmission losses, which, however, are insignificant compared to the total transmission loss in view of a very short length of the small diameter cable. The effect of such a construction is that it occupies a very small space in an assembly of coaxial cables of large diameter. This, in turn, improves the compactness of a corresponding electronic device or machine.

Claims: A coaxial cable adaptor (1) for effecting a small radius-of-curvature bend in a coaxial cable (15) having a relatively large outside diameter, especially in a low-loss, high-frequency type coaxial cable, comprising a central, bellow-like protective element (10) having two ends (11), said bellow-like protective element (10) being attached at each of its ends (11) to a coaxial connector (2, 3) for external attachment to a relatively large diameter coaxial cable (15), each connector (2, 3), being internally connected to a flexible, relatively small diameter coaxial cable (6) which extends from one said connector (2) to the other said connector (3) through said bellow-like protective element (10), such that, when said adaptor (1) is connected to said large diameter coaxial cable (15) the outer conductor of said large diameter coaxial cable is in electrical contact with the outer conductor (7) of said small diameter coaxial cable (6) and the inner conductor of said large diameter coaxial cable (15) is in electrical contact with the inner conductor of said small diameter coaxial cable (6) through said bellow-like protective element (10), said large diameter coaxial cable (15) and said small diameter coaxial cable (6) having matched characteristic impedances, whereby, because of the below-like protective element (10) and the relatively small diameter of the flexible coaxial cable (6) within the adaptor (1), a small radius-of-curvature effective bend in the relatively large diameter coaxial cable (15) is achieved. The adaptor of claim 1 wherein said bellow-like protective element (10) is made of plastic. The adaptor of claim 1 wherein said bellow-like protective element (10) is made of rubber. The adaptor of claim 1 wherein said bellow-like protective element (10) is made of kraft paper.

Inventors: YASUMOTO, HIROMI
Applicants: JUNKOSHA CO. LTD.
Application year: 1987
Main classification: H01R17
IPC codes: H01R31, H01R13