GB2075764A

GB2075764A - Tool for stripping plastics coating from optical fibres

Info

Publication number: GB2075764A
Application number: GB8007731A
Authority: GB
Original assignee: Standard Telephone and Cables PLC
Current assignee: STC PLC
Priority date: 1980-03-06
Filing date: 1980-03-06
Publication date: 1981-11-18
Also published as: AU6795581A; JPS5939721B2; JPS56137309A

Abstract

A pair of interlocking single filament or multifilament loops (6, 7) are mounted on the opposed operating ends (4, 5) of a pliers action type hand tool. An aperture is formed between the two loops through which an optical fibre (31) complete with soft plastics primary coating (32) is inserted. The loops are tensioned by operation of the tool, and while this tension is maintained the fibre is removed causing the coating to be stripped off by the tightened loops. The loops may not permanently interlock (Figure 4, not shown). <IMAGE>

Description

SPECIFICATION Tool for stripping plastics coatings from optical fibres This invention relates to a tool for stripping a soft plastics primary coating from a glass optical fibre of the type that is provided first with a relatively thin soft primary coating and then later with a thicker harder secondary plastics coating to provide mecha nical protection.

A typical optical fibre of this type has a diameter of 125 microns. The primary coating thickness is about 40 microns, and the secondary about 400 microns.

The primary coating is typically a silicone resin such as that marketed by Dow Corning under the designa tion Sylgard 182, while the secondary coating is typically a polyamide resin.

With fibre of this type the secondary coating can conveniently be stripped with wire strippers of a conventional design. The use of such strippers can not normally be relied upon entirely to remove the primary coating, and in many instances leaves the primary coating intact. However in the manufacture of many types of connectors and splices it is necessary to have this primary coating removed.

Previously it has been suggested that the primary coating can be removed by dipping the fibre end into an acid or other suitable solvent. Mechanical methods have also been attempted using metallic scraper elements. An alternative approach has been to form a loose overhand knot in a suitable fine filament, pass the optical fibre through the loop in the knot, draw the knot tight and then drag it off the end of the fibre drawing the primary coating with it.

The present invention concerns a hand tool de veloped from this last-mentioned approach.

According to the present invention there is pro vided a hand tool for stripping a primary plastics coating from a glass optical fibre which tool consists of a pair of pliers which has a pair of moveable jaws each supporting a loop of filamentary material, which jaws are moveable such that the loop of each jaw may be tensioned by the loop of the other.

There follows a description of hand tools embody ing the present invention in preferred forms. The description refers to the accompanying drawings in which: Figures 1 and 2 depict alternative forms of pliers action tool, and Figures 3 and 4 depict alternative configurations of loops for the tools of Figures 1 and 2.

A convenient format for the hand tool is that of a pair of pliers. Such pliers may have the conventional cross-over form depicted in Figure 1, in which a squeezing together of the two handles 10, 11 causes the jaws 12, 13 to move together. Such a construc tion has the mechanical action of internal circlip pliers. Alternatively the tool may be as depicted in Figure 2, and have the mechanical action of external circlip pliers in which a squeezing together of the two handles 20, 21 causes the jaws, 22, 23 to move apart.

In each case the jaws have bifurcated ends 4, 5, each carrying a loop 6,7 of filamentary material.

Two basic loop configurations are possible. One is as depicted in Figure 3 in which the two loops are permanently interlocked, and the other is as depicted in Figure 4 in which the two loops are completely separable. In the case of the Figure 3 configuration, the two loops can conveniently be made from a single length of the filamentary material knotted together at 8. This filamentary material may be a single filament or a multifilament strand. In the case of a single filament strand, a suitable source of material is polyamide fishing line. Polyamide fishing line having a breaking strain of about 2 kg and a nominal diameter of 0..18 mm was found satisfactory for stripping 125 micron diameter optical fibre.Similar line having a breaking strain of about 2.5 kg and a nominal diameter of 0.25 mm was found to be a little too large to give reliable results on this diameter of fibre, while the finer line having a breaking strain of only about 1 kg stripped the fibre well, but was a little too susceptible to breakage to be entirely satisfactory when subjected to rough handling. These results were obtained using the loop configuration as depicted in Figure 3, and in which the length of the line was such that the angle between the two limbs of each loop was about 30".

Referring again to Figure 3 a portion of the secondary plastics coating 30 is removed from the end of a length of optical fibre to expose a portion of fibre 31 covered with a primary plastics coating 32.

The secondary coating may conveniently be removed using wire strippers of conventional design.

The ends 4, 5 of the jaws of the tool are removed inwardly so that loop 6 is released from engagement with loop 7. The stripped end of the fibre is next inserted through the aperture thus formed between the two loops, and then the jaws are moved outwardly to tighten the loops around the fibre immediately beneath the end of the secondary coating. Then, with the tension maintained, the exposed portion of the primary coating is stripped off the fibre by pulling the tool down off the fibre.

If the loop configuration of Figure 3 is used in conjunction with pliers having an action of the type depicted in Figure 1,the loops may be tensioned during the stripping operation by the action of a spring 14. This may be augmented by the operator gripping the handles in such a way that he is able to urge them apart. With pliers having the alternative type of action as depicted in Figure 2 a spring 24 is optionally provided to bias the jaws together, and the loops are tensioned together by clenching the handles together against the action of the spring.

The loop configuration of Figure 3 is easy to operate provided the filamentary material has sufficient stiffness so that when the jaws are moved together a well-defined aperture is formed between the two loops. The polyamide single filament fishing line referred to previously has been found to have quite adequate stiffness for the purpose.

If however a much more flexible material is used, such as for instance one of the multifilament aramid yarns sold by Dupont under the designation Kevlar, any problem of trying to thread the optical fibre end into an aperture formed between two interlocked loops may be avoided by adopting the loop cónfigur- ation of Figure 4. In this configuration the two loops are entirely separable, but are arranged to come together with one end of the loop engaged above the corresponding end of the other loop, and the other end of the first loop engaged beneath the corresponding other end ofthe other loop. With this configuration no threading of the optical fibre is required. The jaws are moved apart to disengage the two loops, the fibre is placed between the jaws, and then, when the jaws are moved together again, the fibre automatically becomes trapped between the two loops. This configuration of loops may also be used either with the internal circlip type of pliers action tool depicted-in Figure 1 or with the external circlip type of pliers action tool depicted in Figure 2.

Claims

1. A hand tool for stripping a primary plastics coating from a glass optical fibre which tool consists of a pair of pliers which has a pair of moveable jaws each supporting a loop of filamentary material which jaws are moveable such that the loop of each jaw may be tensioned by the loop of the other.

2. A hand tool as claimed in claim 1 wherein each loop is made of a single filament.

3. A hand tool as claimed in claim 1 wherein each loop is made of multifilamentary material.

4. A hand tool as claimed in claim 1,2, or 3 wherein the jaws are the jaws of a pair of pliers.

5. A hand tool ds claimed in claim 4wherein the pliers have the mechanical action of internal circlip pliers.

6. A hand tool as claimed in claim 4 wherein the pliers have the mechanical action of external circlip pliers.

7. A hand tool as claimed in any preceeding claim wherein the arrangement of the loops is such thattheytension each other by the retraction ofthe jaws from each other.

8. A hand tool as claimed in any of claims 1 to 6 wherein the arrangement of the loops is such that they tension each other by the advancement of the jaws towards each other.

9. A hand tool for stripping a primary plastics coating from a glass optical fibre which tool is substantially as hereinbefore described with reference to the accompanying drawings.