Electricity: conductors and insulators – Feedthrough or bushing – Compression
Patent
1989-04-25
1990-03-27
Lee, John D.
Electricity: conductors and insulators
Feedthrough or bushing
Compression
49167, 174 86, 350 9623, 439 31, G02B 644
Patent
active
049115103
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a corner guide which can be used in guiding a flexible longitudinal element, which has a minimum permissible bend radius, around a corner. The invention finds particular application in optical fibre installations.
It is sometimes necessary to guide an element of the above type around a corner in circumstances where space is limited. For instance, at least part of an optical communications system may have to be installed in a domestic or office environment. Conveniently optical fibres forming part of such a system may be laid around the edge of a room at floor level, for instance just above the skirting board. Almost inevitably in many cases, they will then have to follow round a corner of the room. This can give rise to a problem because an optical fibre typically has a minimum permissible bend radius of the order of 25 to 30 mm to avoid fibre damage and/or significant optical losses. Optical fibre bundles may have even greater minimum bend radii, for instance 50 mm or more. Even single optical fibres cannot therefore be bent directly through a right angle to follow the corner of a room.
In another example, optical fibres might be used to make connections between a hinged panel and a piece of associated equipment, for instance in an optical racking system. The fibre or fibres may then have to accommodate a changing angle between the panel and the equipment.
In the past a former unit having the minimum permissible radius of curvature has been used so that an optical fibre or an optical fibre containing cable is simply bent round a corner at that minimum radius. The use of such a former unit however means that the fibre or cable does not fit right into an angular corner and such corners have to be "rounded off". This leads to corner installations protruding into the room.
In Japanese patent application 57-81203 there is disclosed a corner protector for indoor optical leads, the protector comprising a conduit having a pair of arms linked by an almost 180.degree. bend, the bend lying in a single plane. The arms of the protector are themselves bent about their mid points, so their straight distal ends remote from the near 180.degree. bend are in a common plane one with the other, but are disposed orthogonally. When the protector is installed the distal end of one arm is secured to a surface on one side of the corner, the distal end of the second arm is secured to a surface on the other side of the corner with the near 180.degree. bend positioned at the corner with the tangent to its apex orthogonal to the line of the corner. The near 180.degree. bend and the bends in the two arms are each of a radius no less than the fibre's minimum bend radius, satisfying the minimum bend radius requirement. By making the bore of the conduit sufficiently large, it is possible to make a corner protector which fits tight to the corner, although of course the conduit itself stands proud of the wall/corner surface. Indeed it is the degree to which the outer surface of the conduit must protrude from the surface to which the conduit is mounted that constitutes one of the more significant disadvantages of the Japanese arrangement. It should also be noted, however, that unlike the present invention, the Japanese arrangement is not suitable for use where there is movement such that the angle of the corner varies, as it does at a hinge.
The present invention has for its general object to alleviate or to overcome disadvantages related to prior art devices. A particular object of the invention is to guide a longitudinal element, for instance an optical fibre or an optical fibre containing cable, around a corner in a convenient manner, without bending the element at less than a permissible minimum radius of curvature or subjecting it to a significant degree of torsion.
The present invention provides a corner guide for guiding a longitudinal element to follow a corner, which guide comprises a support member for supporting the element, and guide means for guiding an element supported by the support member to
REFERENCES:
patent: 4412711 (1983-11-01), Suska
Patent Abstracts of Japan, vol. 6, No. 162 (P-137)[1040] Aug. 25, 1982; & JP-A-57 81 203 (Nippon Denshin Denwa Kosha) 05-21-1982, (and English translation of same).
Review of the Electrical Communication Laboratories, vol. 22, No. 4, 1984, "Design and Performance of Optical Drop and Indoor Cables" by Kukita et al.-pp. 636-645.
Thomas, "Cabling to Hinged Electrical Assemblies", Electronic Production, May-Jun. 1964, p. 25.
British Telecommunications PLC
Lee John D.
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