GB2174085A - An improved optical fibre cutting tool - Google Patents

Abstract

A hand tool for providing simultaneously several optical fibres with end faces that are flat and lie in a common plane radial to the fibre axes includes guide means on one side of a cutting table for maintaining the optical fibres parallel to one another and normal to the cutting edge of an elongate cutter and gripping means on the other side of the table for applying a tensile force to the optical fibres to stretch them across the table. The gripping means is operatively independent of the guide means and of the members operating the cutting action. The hand tool can be used by semi-skilled or unskilled personnel.

Description

SPECIFICATION An improved optical fibre cutting tool This invention relates to a hand tool for providing simultaneously a plurality of optical fibres with end faces that are substantially flat and lie in a common plane radial to the axes of the fibres so that when the optical fibres are jointed or spliced to other optical fibres with similar end faces light losses at the joints or splices are as low as possible. The hand tool is especially, but not exclusively, suitable for use with optical fibre ribbon, for example optical fibre ribbon of the kind comprising a plurality of optical fibres arranged side by side with their axes lying in a substantially common plane and embedded in an elongate body of plastics material.

it is an object of the invention to provide an improved hand tool for this purpose which can be effectively used by semi-skilled and unskilled personnel.

According to the invention, the improved hand tool comprises at least two members interconnected in such a way that at least one of the members is constrained to move in a direction towards or away from the other member or members and is urged away from the other member or members by associated spring means; means for causing said moveable member or members to move towards the other member or members against the action of said associated spring means; a table having a smooth surface carried by a first of said members; an elongate cutter which is associated with the table and which is mounted on the other member or another of the members and which has a rectilinear cutting edge; guide means carried by the first member on one side of the table for maintaining a plurality of optical fibres extending across the table substantially parallel to one another and substantially normal to the rectilinear cutting edge of the elongate cutter with their axes lying in a substantially common plane; and gripping means carried by the first member on the other side of the table for gripping and applying a tensile force to the optical fibres to stretch them across the surface of the table, which gripping means is operatively independent of the guide means and of the means for causing said moveable member or members to move towards the other member or members, the arrangement being such that when a plurality of optical fibres are clamped by the guide means and are stretched across the table by the gripping means and the moveable member or members is or are caused to move towards the other member or members, the rectilinear cutting edge will contact and effect a score in each of the optical fibres to such an extent that the tensioned fibres will break to form end faces on the fibres that are substantially flat and lie in a common plane radial to the axes of the fibres.

Preferably, the optical fibre guide means comprises a fixed elongate body which extends transversely with respect to the elongate cutter and which has in its upper surface a plurality of grooves having transverse cross-sections of substantially identical shape and size and extending substantially parallel to one another and substantially normal to the rectilinear cutting edge of the elongate cutter and, pivotally mounted on the elongate body for clamping optical fibres in the grooves, a lever which is urged towards the closed or clamping position by associated spring means. Each groove preferably has a transverse cross-section of approximately V-shape and, in a preferred embodiment, one side face of each V-shaped groove is substantially normal to the upper surface of the elongate body and the other side face of each groove is inclined at an acute angle thereto.

The gripping means for applying tension to optical fibres extending across the table preferably comprises a pair of jaws carried by the first member, at least one of which jaws is constrained to move towards the other jaw against the action of associated spring means urging the jaws apart and, independently operable with respect to the guide means and to the means for causing said moveable member or members to move towards the other member or members, means for causing the or each jaw to move towards the other jaw against the action of said associated spring means to grip optical fibres therebetween, the jaws being so mounted and/or their interengaging surfaces being of such a shape that as the jaws grip the optical fibres a tensile force is applied to the optical fibres.The jaws may be so resiliently mounted on the first member that, when the or each jaw moves towards the other jaw to grip optical fibres between them, the parts of the jaws in contact with the fibres tend to move away from the table and from the guide means thereby exerting a tensile force on the fibres in a direction substantially normal to the rectilinear cutting edge. The means for causing the or each jaw to move towards the other jaw preferably comprises a cam rotatably mounted on the first member and operated by a knurled knob.

Preferably, the spring means which urges the moveable member or members away from the other member or members is of such a form that, when the moveable member or members is or are caused to move towards the other member or members against the action of said spring means, the rectilinear cutting edge of the elongate cutter is caused to move in the direction of its length across optical fibres stretched across the table to score the fibres to such an extent that the tensioned fibres will break to form end faces on the fibres that are substantially flat and lie in a common plane radial to the axes of the fibres.

The rectilinear cutting edge of the elongate cutter is preferably of a length equal to or greater than the width of said plurality of grooves constituting said guide means.

The substantially smooth surface of the table is preferably of convexly curved form, the centres of curvature of the curved surface lying on an axis substantially parallel to the rectilinear cutting edge.

Preferably, adjustable means is provided on at least one of the members for adjusting, within a limited range, the depth of the score which the rectilinear cutting edge will effect in optical fibres stretched across the table. This adjustable means may take the form of a pair of adjustable screws which are longitudinally spaced in the first member in a direction parallel to the rectilinear cutting edge and which when the moveable member or members is or are caused to move towards the other member or members are adapted to engage the member carrying the elongate cutter to limit the depth of score.

In a preferred embodiment, the improved hand tool comprises three elongate members extending side-by-side and interconnected together, the first of which elongate members is of substantially tubular form and surrounds the other two elongate members, the second of which elongate members is resiliently mounted in and with respect to the tubular elongate member by at least two longitudinally spaced inclined leaf springs and the third of which elongate members is pivotally connected to the tubular elongate member about an axis transverse to the members, the table, guide means and gripping means being mounted on the tubular elongate member, the elongate cutter being carried on the resiliently mounted second elongate member and the pivotable third elongate member being so shaped intermediate of its ends that, when it is caused to move towards the resilientiy mounted second elongate member, an intermediate part or intermediate parts of the pivotable third elongate member bears or bear directly or indirectly against the resiliently mounted second elongate member to cause the second elongate member to move lengthwise against the action of the inclined leaf springs and the rectilinear cutting edge to effect the required scores in the optical fibres stretched across the table.

Preferably, the pivotable third elongate member carries a button positioned close to the end remote from the transverse pivotal axis of the member, which button protrudes through an aperture in the tubular elongate member and can be pressed by an operator to cause the pivotablethird elongate memberto pivot towards the resiliently mounted second elongate member so that the intermediate part or parts of the pivotable third elongate member bears or bear against the resiliently mounted second elongate member.

Since lengthwise movement of the resiliently mounted second elongate member carrying the elongate cutter is effected by inter-engagement between the intermediate part or parts of the pivotable third elongate member and the second elongate member, the manner and/or force with which an operator effects pivotable movement of the pivotable third elongate member does not have any deleterious effect on lengthwise movement of the resiliently mounted second elongate member. As a result, substantially no forces are transmitted to the second elongate member in a direction transverse to the member or in such a direction as to tend to twist the member.Thus, for substantially all operators of the improved hand tool of the present invention, the hand tool will score a plurality of optical fibres to substantially the same depth so that all optical fibres will break to form on the fibres end faces which are substantially flat and lie in a substantially common plane radial to the axes of the fibres.

It will be appreciated that where the plurality of optical fibres are components of an optical fibre ribbon it will be necessary to separate a sufficient length of the optical fibres from the ribbon to enable the optical fibres to be positioned in the grooves of the guide means.

The invention is further illustrated, by way of example, by the accompanying drawings, in which: Figure lisa plan view of the preferred form of the improved hand tool; Figure2 is an end view of the hand tool shown in Figure 1 drawn on an enlarged scale; Figure 3 is a cross-sectional view of the hand tool taken on the line Ill-Ill in Figure 2, and Figure 4 is a transverse cross-sectional view of the guide means of the hand tool drawn on a greatly enlarged scale.

Claims (15)

1. A hand tool for providing simultaneously a plurality of optical fibres with end faces that are substantially flat and lie in a common plane radial to the axes of the fibres, which hand tool comprises at least two members interconnected in such a way that at least one of the members is constrained to move in a direction towards or away from the other member or members and is urged away from the other member or members by associated spring means; means for causing said movable member or members to move towards the other member or members against the action of said associated spring means; a table having a smooth surface carried by a first said members; an elongate cutter which is associated with the table and which is mounted on the other member or another of the members and which has a rectilinear cutting edge; guide means carried by the first member on one side of the table for maintaining a plurality of optical fibres extending across the table substantially parallel to one another and substantially normal to the rectilinear cutting edge of the elongate cutter with their axes lying in a substantially common plane; and gripping means carried by the first member on the other side of the table for gripping and applying a tensile force to the optical fibres to stretch them across the surface of the table, which gripping means is operatively independent of the guide means and of the means for causing said movable member or members to move towards the other member or members, the arrangement being such that when a plurality of optical fibres are clamped by the guide means and are stretched across the table by the gripping means and the movable member or members is or are caused to move towards the other member or members, the rectilinear cutting edge will contact and effect a score in each of the optical fibres to such an extent that the tensioned fibres will break to form end faces on the fibres that are substantially flat and lie in a common plane radial to the axes of the fibres.

2. A hand tool as claimed in Claim 1, wherein the optical fibre guide means comprises a fixed elongate body which extends transversely with respect to the elongate cutter and which has in its upper surface a plurality of grooves having transverse cross-sections of substantially identical shape and size and extending substantially parallel to one another and substantially normal to the rectilinear cutting edge of the elongate cutter and, pivotally mounted on the elongate body for clamping optical fibres in the grooves, a lever which is urged towards the closed or clamping position by associated spring means.

3. A hand tool as claimed in Claim 2, wherein each groove of the optical fibre guide means has a transverse cross-section of approximately V-shape.

4. A hand tool as claimed in Claim 3, wherein one side face of each V-shaped groove of the optical fibre guide means is substantially normal to the upper surface of the elongate body and the other side face of each groove is inclined at an acute angle thereto.

5. A hand tool as claimed in any one of the preceding Claims, wherein the gripping means for applying tension to optical fibres extending across the table comprises a pair of jaws carried by the first member, at least one of which jaws is constrained tomove towards the other jaw against the action of associated spring means urging the jaws apart and, independently operable with respect to the guide means and to the means for causing said movable member or members to move towards the other member or members, means for causing the or each jaw to move towards the other jaw against the action of said associated spring means to grip optical fibres therebetween, the jaws being so mounted and/or their interengaging surfaces being of such a shape that as the jaws grip the optical fibres a tensile force is applied to the optical fibres.

6. A hand tool as claimed in Claim 5, wherein the jaws are so resiliently mounted on the first member that, when the or each jaw moves towards the other jaw to grip optical fibres between them, the parts of the jaws in contact with the fibres tend to move away from the table and from the guide means thereby exerting a tensile force on the fibres in a direction substantially normal to the rectilinear cutting edge.

7. A hand tool as claimed in Claim 5 or 6, wherein the means for causing the or each jaw to move towards the other jaw comprises a cam rotatably mounted on the first member and operated by a knurled knob.

8. A hand tool as claimed in any one of the preceding Claims, wherein the spring means which urges the movable member or members away from the other member or members is of such a form that, when the movable member or members is or are caused to move towards the other member or members against the action of said spring means, the rectilinear cutting edge of the elongate cutter is caused to move in the direction of its length across optical fibres stretched across the table to score the fibres to such an extent that the tensioned fibres will break to form end faces on the fibres that are substantially flat and lie in a common plane radial to the axes of the fibres.

9. A hand tool as claimed in any one of the preceding Claims, wherein the rectilinear cutting edge of the elongate cutter is of a length equal to or greater than the width of said plurality of grooves constituting said guide means.

10. A hand tool as claimed in any one of the preceding Claims, wherein the substantially smooth surface of the table is of convexly curved form, the centres of curvature of the curved surface lying on an axis substantially parallel to the rectilinear cutting edge.

11. A hand tool as claimed in any one of the preceding Claims, wherein adjustable means is provided on at least one of the members for adjusting, within a limited range, the depth of the score which the rectilinear cutting edge will effect in optical fibres stretched across the table.

12. A hand tool as claimed in Claim 11, wherein said adjustable means is in the form of a pair of adjustable screws which are longitudinally spaced in the first member in a direction parallel to the rectilinear cutting edge and which when the movable member or members is or are caused to move towards the other member or members are adapted to engage the member carrying the elongate cutter to limit the depth of score.

13. A hand tool as claimed in any one of the preceding Claims, wherein three elongate members extend side by side and are interconnected together, the first of which elongate members is of substan tially tubular form and surrounds the other two elongate members, the second of which elongate members is resiliently mounted in and with respect to the tubular elongate member by at least two longitudinally spaced inclined leaf springs and the third of which elongate members is pivotally connected to the tubular elongate member about an axis transverse to the members, the table, guide means and gripping means being mounted on the tubular elongate member, the elongate cutter being carried on the resiliently mounted second elongate member and the pivotable third elongate member being so shaped intermediate of its ends that when it is caused to move towards the resiliently mounted second elongate member, an intermediate part or intermediate parts of the pivotable third elongate member bears or bear directly or indirectly against the resiliently mounted second elongate member to cause the second elongate member to move lengthwise against the action of the inclined leaf springs and the rectilinear cutting edge to effect the required scores in optical fibres stretched across the table.

14. A hand tool as claimed in Claim 13, wherein the pivotable third elongate member carries a button positioned close to the end remote from the transverse pivotal axis of the member, which button protrudes through an aperture in the tubular elongate member and can be pressed by an operator to cause the pivotable third elongate member to pivot towards the resiliently mounted second elongate member so that the intermediate part or parts of the pivotable third elongate member bears or bear against the resiliently mounted second elongate member.

15. A hand tool for providing simultaneously a plurality of optical fibres with end faces that are substantially flat and lie in a common plane radial to the axes of the fibres substantially as illustrated in the accompanying drawings. ~~~~~~~~~~