GB2373103A

GB2373103A - Bend limiting apparatus for a cable

Info

Publication number: GB2373103A
Application number: GB0104092A
Authority: GB
Inventors: Steven John Blanks
Original assignee: Spirent PLC
Current assignee: Spirent PLC
Priority date: 2001-02-20
Filing date: 2001-02-20
Publication date: 2002-09-11
Also published as: GB0104092D0

Abstract

A restraining device 10 limits the amount by which a cable bends. The device has a spine 11 and two 'C' clips 12 at each end of the spine 11 so that the device 10 can be attached to a cable. The spine 11 has a central flexible flat strip 13 with a number of segments 14 running along the strip 13. The spine can bend up to a certain radius determined by a small gap 15 which is left between each segment 14. This arrangement allows for bending in one plane. An alternative arrangement having the segments 14 replaced by disc (23, fig 3) allows bending in any direction. Fastenings may be provided to secure the device 10 to a support structure.

Description

A RESTRAINING DEVICE FOR ELONGATE FLEXIBLE MEMBERS

This invention relates to a restraining device for elongate flexible members and more particularly but not solely to a restraining device for optical fibre.

Optical fibres are generally fed through elongate flexible tubes which serve to protect and contain the fibres. It is well known that optical fibres must not be bent through more than an allowable curvature (e. g. a minimum radius of curvature of 100mm), so as to prevent damage to the fibres and to maintain the transmission efficiency thereof.

It is often difficult to judge whether a bend in a tube containing optical fibres is too great and thus the minimum bend radius of fibres is often exceeded.

We have now devised a restraining device for fitting to an elongate flexible member which alleviates the abovementioned problems.

In accordance with this invention, there is provided a restraining device for fitting to an elongate flexible member, the device comprising an elongate spine and means at opposite ends of the spine for embracing the member, the spine being bendable longitudinally of itself up to a predetermined minimum radius of curvature.

In use, the spine can be fitted to an optical fibre cable or to a tube carrying one or more optical fibres. When the tube or cable is bent, the device prevents it from being bent through more than a predetermined amount corresponding to the minimum bend radius of the optical fibre (s).

In this manner, no damage will be cause to the fibre (s) by excessive bending. Furthermore, there will be no loss of transmission efficiency.

In one embodiment the spine is bendable within one plane only. However, in order that complex bends can be formed, the spine may be bendable within two orthogonal planes.

Preferably the spine comprises a plurality of interconnected segments having a gap between adjacent segments,

the width of the gap governing the bending radius.

Preferably the spine is a one-piece formation of plastics material. The spine may be moulded from plastics material. Alternatively, it may be extruded.

Preferably the embracing means comprises separate members which are attachable to the spine.

The embracing means may comprise resiliently flexible c-shaped clips which can easily be snap engaged onto the member.

Preferably fastening means are provided on the device to enable the device to be fastened to a support structure and thereby serve as a means for mounting the cable or tube to the structure.

Embodiments of this invention will now be described by way of examples only and with reference to the accompanying drawings, in which: FIGURE 1 is a perspective view of an embodiment of restraining device in accordance with this invention; FIGURE 2 is a side view of the device when fitted to tubing containing optical fibres; and FIGURE 3 is a perspective view of a spine portion of an alternative embodiment of restraining device.

Referring to Figure 1 of the drawings, there is shown a restraining device 10 for fitting to a length of tubing containing optical fibres. The device 10 comprises an elongate spine 11 formed as a one-piece moulding or extrusion from plastics material and two c-shaped plastics clips 12 for respectively attaching to opposite ends of the tubing.

The spine 11 may be provided as a length which can be cut to the desired size. Alternatively, the spine 11 may be formed to the correct length.

The spine 11 comprises a longitudinally extending central flat strip 13 having a series of segments 14 disposed symmetrically along its opposite sides. A small gap 15 is provided between each adjacent segment 14.

The c-shaped clips 12 extend outwardly from the spine 11, perpendicular to the plane of the strip 13.

Referring to Figure 2 of the drawings, in use the device is applied to a length of tubing 10 containing optical fibres at a point where it is desired to bend the tubing.

The device is applied by snap engaging the c-shaped clips 12 at opposite ends of the device over the tubing. The spine 11 enables the tubing to be bent along its length within a plane which extends normal to the plane of the strip 13. The gap 15 between the segments 14 on one side of the strip closes as the spine 11 is bent, up to a point where the adjacent segments 14 abut each other and prevent continued bending of the spine 11.

It will be appreciated that the width of the gap 15 between adjacent segments thus determines the degree through which the spine 11 and hence the tubing 10 can be bent.

The device of Figures 1 and 2 only permits bending in either direction within one plane. However, referring to Figure 2 of the drawings, there is shown a spine 21 of an alternative embodiment of restraining device which permits bending within any plane.

The device comprises a longitudinally-extending circular-section core 22 provided with a series of discs 23 mounted normal and concentrically thereof. Adjacent pairs of discs 23 are rigidly interconnected by bracing members 24 to define segments 25, which are separated by a gap 26.

In use, the device operates exactly as the previous embodiment, except that the spine can be bent in any direction or combination of directions until the disc faces of adjacent segments 25 abut each other.

In an alternative embodiment, fastenings may be provided on the clips 12 enabling the device to be fastened to a support structure. In this manner the device can also serve as a means for mounting the tubing 10 to a support structure.

A device in accordance with this invention is extremely simple in construction but yet provides a reliable way of ensuring that the minimum bend radius of optical fibres is not exceeded.

Claims

1. A restraining device for fitting to an elongate flexible member, the device comprising an elongate spine and means at opposite ends of the spine for embracing the member, the spine being bendable longitudinally of itself up to a predetermined minimum radius of curvature.

2. A restraining device as claimed in claim 1, in which the spine is bendable within one plane only.

3. A restraining device as claimed in claim 1, in which the spine is bendable within two orthogonal planes.

4. A restraining device as claimed in any preceding claim, in which the spine comprises a plurality of interconnected segments having a gap between adjacent segments, the width of the gap governing the bending radius.

5. A restraining device as claimed in any preceding claim, in which the spine is a one-piece formation of plastics material.

6. A restraining device as claimed in claim 5, in which the spine is moulded from plastics material.

7. A restraining device as claimed in claim 5, in which the spine is extruded.

8. A restraining device as claimed in any preceding claim, in which the embracing means comprises separate members which are attachable to the spine.

9. A restraining device as claimed in any preceding claim, in which the embracing means may comprise resiliently flexible c-shaped clips which can be snap engaged onto the member.

10. A restraining device as claimed in any preceding claim, in which fastening means are provided on the device to enable the device to be fastened to a support structure.

11. A restraining device substantially as herein described with reference to Figures 1 and 2 or Figure 3 of the accompanying drawings.