Optical fibre cutting tool

A hand tool for providing an optical fibre with an end face which is flat and lies in a plane radial to the fibre axis comprises four elongate members extending side by side. The first member is of tubular form and surrounds the other three members and has, mounted near one of its ends, jaws of two pairs of jaws transversely spaced on opposite sides of the longitudinal axis of the member and, between the jaws, a table having a curved surface. The second member is pivotally connected to the first member at its end remote from the table about an axis extending transversely of the members, is urged away from an internal surface of the first member by a leaf spring and carries, near its other end, the other jaws of the transversely spaced pairs of jaws. The jaws of one pair of jaws are mounted to exert a tensile force on the fibre. The third member is pivotally connected to the first member at its end remote from the table about an axis extending transversely of the members, is urged away from the first member by the leaf spring and carries near its other end an elongate cutter. The fourth member is pivotally connected at one of its ends to the first member and has an intermediate part that causes the third and second members to pivot against the action of the leaf spring.

This invention relates to a hand tool for providing an optical fibre with 
an end face that is substantially flat and lies in a plane radial to the 
axis of the fibre so that when the optical fibre is jointed or spliced to 
another optical fibre with a similar end face light losses at the joint or 
splice are as low as possible. 
In the Complete Specification of our British Pat. No. 1519232, there is 
described and claimed a hand tool for this purpose comprising at least two 
members inter-connected 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; a table having a curved surface carried on one of the members, 
the centres of curvature of the curved surface lying on an axis 
substantially normal to said direction of movement of the member or 
members; an elongate cutter associated with the table and mounted on the 
other or another of the members, the cutting edge of the cutter being 
substantially normal to tangents of the curved surface of the table; and 
two pairs of jaws transversely spaced on opposite sides of the table and 
cutter, one jaw of each pair being mounted on one member and one jaw of 
each pair being mounted on the other or another member. The arrangement is 
such that when an optical fibre is positioned between the jaws of the 
pairs of jaws so that it lies across the curved surface of the table 
substantially normal to the cutting edge of the cutter, and the member or 
members is or are caused to move towards the other member or members to 
cause the pairs of jaws to grip the optical fibre, at least one pair of 
the pairs of jaws applies a tensile force to the optical fibre to stretch 
it across the curved surface of the table and the cutting edge contacts 
and is caused to move transversely across the optical fibre to score the 
fibre to such an extent that the tensioned fibre breaks to form end faces 
of the fibre that are substantially flat and lie in planes radial to the 
axis of the fibre. 
The jaws of one of the pairs of jaws are preferably both so resiliently 
mounted on the members that, when the jaws move towards one another to 
grip an optical fibre between them, the parts of the jaws in contact with 
the fibre tend to move away from the table and from the other pair of jaws 
thereby exerting a tensile force on the fibre in a direction substantially 
normal to the cutting edge. 
A hand tool as described and claimed in our aforesaid patent in which the 
jaws of one of the pairs of jaws are both so resiliently mounted on the 
members that, when the jaws move towards one another to grip an optical 
fibre between them, the parts of the jaws in contact with the fibre tend 
to move away from the table in a direction substantially normal to the 
cutting edge to effect said tensile force on the fibre will, for 
convenience, hereinafter be referred to as "a hand tool of the kind 
described". 
It is an object of the present invention to provide an improved hand tool 
of the kind described which is especially suitable for use in cutting a 
single mode optical fibre and which can be readily used in the field by 
semi-skilled or unskilled personnel. 
According to the invention, the improved hand tool comprises four elongate 
members extending side by side; the first of which elongate members is of 
substantially tubular form and surrounds the other three elongate members 
and has, mounted on the member at or near one of its ends, one jaw of each 
of two pairs of jaws tranversely spaced on opposite sides of the 
longitudinal axis of the member and, between said jaws, a table having a 
curved surface whose axes of curvature lie on a rectilinear axis extending 
lengthwise of the member; the second of which elongate members is 
pivotally connected to the tubular first member at its end remote from the 
table about an axis extending transversely of the members, is urged away 
from an internal surface of the tubular first member by spring means and 
carries, at or near its other end, the other jaw of each of said 
transversely spaced pairs of jaws, the jaws of one pair of the pairs of 
jaws being so shaped and/or resiliently mounted on the first and second 
members that, when the jaws move towards one another to grip an optical 
fibre between them, the parts of the jaws in contact with the fibre will 
tend to move away from the table and from the other pair of jaws to effect 
a tensile force on the fibre; the third of which elongate members is 
pivotally connected to the tubular first member at its end remote from the 
table about an axis extending transversely of the members, is urged away 
from the second member by said spring means and carries at or near its 
other end an elongate cutter having a cutting edge which is substantially 
normal to tangents of the curved surface of the table; and the fourth of 
which elongate members is pivotally connected at one of its ends to the 
tubular first member about an axis extending transversely of the members 
and is so shaped intermediate of its ends that, when it is caused to pivot 
towards the third and second members, an intermediate part of said fourth 
member bears against the third member to cause the second and third 
members to pivot against the action of said spring means and so cause the 
jaws of the pairs of jaws to grip an optical fibre positioned therebetween 
and to cause the cutting edge to contact and move transversely across the 
tensioned optical fibre to score the fibre to such an extent that the 
fibre breaks to form end faces of the fibre that are substantially flat 
and lie in planes radial to the axis of the fibre. 
Preferably, the fourth member carries at or near one of its ends a button 
which protrudes through a hole in the wall of the tubular first member and 
which can be pressed by an operator to cause the fourth member to pivot 
towards the third member so that the intermediate part of the fourth 
member bears against the third member. 
We have found that, since pivotal movement of the third member carrying the 
cutter is effected by inter-engagement between the intermediate part of 
the fourth member and the third member, the manner and/or force with which 
an operator effects pivotal movement of the fourth member does not have 
any deleterious effect on pivotal movement of the third member. As a 
result, substantially no forces are transmitted to the third member in a 
direction transverse to the third member or in such a direction as to tend 
to twist the third member. Furthermore, the significant mechanical 
advantage of the arrangement gives better control of the force necessary, 
and reduces the muscular effort required, to operate the hand tool. Thus, 
for substantially all operators of the improved hand tool of the present 
invention, the hand tool will score an optical fibre to such an extent 
that the tensioned fibre breaks to form end faces of the fibre that are 
substantially flat and lie in planes radial to the axis of the fibre. 
Preferably, the elongate cutter is carried by a supplementary member which 
is detachably secured to the third member in such a way that the cutting 
edge of the cutter can be adjusted with respect to the associated table in 
a direction substantially parallel to the cutting edge. This arrangement 
has two important advantages; firstly, during the life of the hand tool, 
the elongate cutter can be adjusted with respect to the table in a 
direction substantially parallel to its cutting edge to ensure that, 
during the life of the cutter, substantially the whole length of the 
cutting edge is used and, secondly, when desired an elongate cutter can 
readily be replaced by another elongate cutter. 
The elongate cutter is preferably carried by a strip of resilient metal 
which extends in a direction substantially parallel to the cutting edge of 
the cutter and which is secured at each of its ends to the supplementary 
member. The strip of resilient metal is preferably so shaped that, as the 
third member is caused to pivot and the cutting edge of the elongate 
cutter is caused to contact an optical fibre stretched across the curved 
surface of the table, the cutting edge is caused to move across the 
optical fibre to score the optical fibre. 
Preferably, the jaws of one of the pairs of jaws are resiliently mounted on 
the first and second members by leaf springs so orientated that the pair 
of jaws cannot move with respect to the table in a direction substantially 
normal to the cutting edge and the jaws of the other of the pairs of jaws 
are resiliently mounted on the first and second members by leaf springs 
inclined at such an angle to the leaf springs of the jaws of the first 
pair of jaws that, when the jaws move towards one another to grip an 
optical fibre between them, the parts of the jaws in contact with the 
fibre tend to move away from the table and from the first pair of jaws. 
In a preferred embodiment, each of the pairs of jaws has associated optical 
fibre guide means which is positioned adjacent the pair of jaws and remote 
from the table. Each of the optical fibre guide means preferably includes 
a substantially flat support surface having, extending substantially 
normal to the cutting edge of the elongate cutter, a step or shoulder 
against which an optical fibre, to be positioned between the jaws of the 
pairs of jaws, can be laid. If desired, the support surface of each of the 
optical fibre guide means may have two or more steps or shoulders 
extending substantially normal to the cutting edge of the elongate cutter 
to provide for simultaneous scoring of two or more optical fibres. 
Preferably, the support surface of the optical fibre guide means 
associated with the pair of jaws which cannot move with respect to the 
table in a direction substantially normal to the cutting edge of the 
elongate cutter carries spring loaded clamp means for clamping an optical 
fibre against the step or shoulder on the surface. 
The optical fibre guide means are preferably carried by a separately formed 
elongate member which extends transversely of and is permanently or 
detachably secured to the first elongate member. 
The table is preferably so detachably secured to the tubular first member 
that its position with respect to the pairs of jaws can be adjusted in a 
direction substantially parallel to the cutting edge of the elongate 
cutter.

Referring to FIGS. 1 to 4, the preferred hand tool comprises four major 
components, namely a first elongate member 1 of tubular cross-section 
consisting of an elongate base member 1a and, detachably secured to the 
base member, a separately formed elongate cover member 1b; a second 
elongate member 2 which at one of its ends is pivotally connected to the 
elongate base member 1a about an axis 12 extending transversely of the 
members; a third elongate member 3 which at one of its ends is pivotally 
connected to the base member 1a about an axis 13 extending transversely of 
the members; and a fourth elongate member 4 which is pivotally connected 
to the undersurface of the cover member 1b at a position intermediate of 
the ends of the cover member about an axis 14 extending transversely of 
the members. 
Mounted at or near the end of the elongate base member 1a remote from the 
pivotal axes 12 and 13 is a table 6 having curved surface 7, the centres 
of curvature of which lie on an axis substantially normal to the pivotal 
axes 12 and 13. The table 6 is detachably secured to the elongate base 
member 1a by screws 8 so that its position with respect to the elongate 
base member can be adjusted in a direction substantially normal to the 
pivotal axes 12 and 13. Also mounted on the elongate base member 1a at the 
end remote from the pivotal axes 12 and 13 on opposite sides of the table 
6 are one jaw 16', 17' of each of two pairs 16, 17 of jaws for gripping an 
optical fibre positioned across the table. The other jaws 16", 17" of the 
pairs 16, 17 of jaws are carried at or near the neighbouring end of the 
second elongate member 2. The jaws 16', 16" of the pair 16 of jaws are 
resiliently mounted, respectively, on the base member 1a and second 
elongate member 2 by leaf springs 26 so orientated that the pair of jaws 
cannot move with respect to the table 6 in a direction substantially 
parallel to the pivotal axes 12 and 13. The jaws 17', 17" of the pair 17 
of jaws are each so shaped and resiliently mounted, respectively, on the 
base member 1a and second elongate member 2 by leaf springs 27 inclined at 
an angle to leaf springs 26, that, when the jaws move towards one another 
to grip an optical fibre between them, the parts of the jaws in contact 
with the fibre tend to move away from the table 6 and from the other pair 
16 of jaws thereby exerting a tensile force on the fibre in a direction 
transverse to the longitudinal axis of the hand tool. 
The third elongate member 3 has detachably secured to its end remote from 
the pivotal axis 13 a supplementary member 23 to the undersurface of which 
is attached a strip 24 of resilient metal which extends in a direction 
lengthwise of the hand tool and to the undersurface of which is secured an 
elongate cutter 25 whose cutting edge is normal to tangents of the curved 
surface 7 of the table 6. The supplementary member 23 is so detachably 
secured to the third member 3 by screws 28 that the cutting edge of the 
cutter 25 can be adjusted with respect to the table 6 in a direction 
parallel to the cutting edge. 
The fourth elongate member 4 carries at its end remote from the pivotal 
axis 14 a button 30 which protrudes through a hole 31 in the cover member 
1b and which can be pressed by an operator to cause the fourth member to 
pivot towards the third member so that an intermediate part 32 of the 
fourth elongate member bears against the third elongate member 3 to cause 
the third elongate member and the second elongate member 2 to pivot 
against the action of leaf spring 18. The third elongate member 3 carries 
a screw 44 which depends downwardly between the bodies 19 and through a 
hole in the second elongate member 2 and which, when the third and second 
elongate members are caused to pivot against the action of leaf spring 18, 
will abut a fine adjustment screw 45 upstanding from the base member 1a 
and by means of which the depth of score effected in an optical fibre by 
the cutter 25 can be finely adjusted. 
Each of the pairs 16, 17 of jaws has an associated optical fibre guide 36, 
37 which is positioned adjacent the pairs of jaws and remote from the 
table 6 and which is carried by a separately formed elongate member 34 
which extends transversely of and is detachably secured to the base member 
1a. Each optical fibre guide 36, 37 includes a flat support surface 
having, extending substantially normal to the cutting edge of the elongate 
cutter 25, a shoulder 36', 37' against which an optical fibre, to be 
positioned between the jaws of the pairs 16, 17 of jaws, can be laid. 
Preferably, as is illustrated in FIG. 5, the optical fibre guide means 36 
carries a spring loaded clamp 38 by means of which an optical fibre is 
clamped to, and against the shoulder 36' of, the guide.