Severing by tearing or breaking – Methods – With preliminary weakening
Patent
1985-11-25
1987-05-26
Yost, Frank T.
Severing by tearing or breaking
Methods
With preliminary weakening
83586, 83607, 225 96, 225101, C03B 3716
Patent
active
046678620
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to cleaving apparatus for use in the field of optical communications and particularly but not exclusively for use in the cleaving of optical fibres.
BACKGROUND OF THE INVENTION
Optical fibres generally comprise filaments of optically transparent, non-ductile, "glassy" materials, for example vitreous silica, boro-silicate, or metal fluoride glasses. To enable guided transmission to take place, the fibres require a core and a cladding. Occasionally the function of the cladding may be performed by, for example, the surrounding air. In practice, however, optical fibres employed to transmit information usually have cores and claddings.
Different types of optical fibre will have different dimensions associated with them but, generally, the outer diameter varies (with fibre type) over a range of from 60 .mu.m to 250 .mu.m.
When optical power is to be transmitted into or out of the end of an optical fibre, the giometric characteristics of the fibre end affect the manner in which the power is transmitted. It is often desirable that the fibre should be provided with a flat end face which lies perpendicular to the longitudinal axis of the fibre. For instance if two fibres for use in optical communications are fusion jointed, it is known that if either end face is not perpendicular, optical power loss can be significantly increased at the joint. For example, the two fibre ends may tend to ride past one another during making of the joint, leading to misalignment of the fibres. Where a major part of the optical power is carried by a fibre core this power loss can be substantial and monomode fibres are known to be particularly susceptible as a result of their small core diameters. Typically these are about 8 .mu.m in a fibre whose overall diameter including core and cladding is in the region of 125 .mu.m.
An acceptable fibre end face can be obtained by clamping the fibre under a controlled axial tension, free from any torsional strain, and striking it on its outermost glass surface with a cleaver blade. In known cleaving tools the cleaver blade may be mounted in a sliding cleaver which is propelled along a horizontal bearing surface to bring the blade into contact with the fibre. Alternatively the blade may be mounted on a lever which drops under the influence of gravity to bring the blade into contact with the fibre.
Problems of reliability have been encountered with such arrangements. For instance, the action of both types of arrangement can be extremely sensitive to changes in orientation, or to movement, of the cleaving tool.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a cleaving tool wherein the characterisitics of the striking action of the cleaver blade against a fibre to be cleaved are less sensitive to external influences.
According to a first aspect, the present invention provides cleaving apparatus, comprising a rotatably mounted cleaver, wherein the cleaver is balanced about its axis of rotation.
Cleaving apparatus according to the present invention lends itself in particular to cleaving optical fibres.
Conveniently, the cleaver may comprise a disc rigidly mounted on a coaxial shaft, the shaft being rotatably mounted at or near its ends.
Preferably the cleaving apparatus further comprises tensioning means for applying axial tension to an optical fibre wherein the tensioning means comprises a pair of hingedly separable optical fibre clamps.
Cleaving tools of this latter type have the advantage that both the striking action of the cleaver blade and the axial tension applied to the optical fibre tend not to be susceptible to dirty bearing surfaces.
BRIEF DESCRIPTION OF THE INVENTION
A cleaving tool according to an embodiment of the invention will now be described with reference to the drawings in which:
FIG. 1 shows a perspective view of the cleaving tool.
FIG. 2 shows a cross section taken along the line A--A in FIG. 1, viewed in the direction indicated by the arrows.
FIG. 3 shows a cross section taken along the line
REFERENCES:
patent: 745965 (1903-12-01), Lyon
patent: 2048360 (1936-07-01), Spanel et al.
patent: 4557049 (1985-12-01), Cribbs et al.
Millar Colin A.
Potter David J.
Talbott David
Wood Thomas D. S.
British Telecommunications PLC
Yost Frank T.
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