Cutlery – Combined cutlery or combined with ancillary feature – With material-holder or disposal
Patent
1988-07-08
1991-07-16
Eley, Timothy V.
Cutlery
Combined cutlery or combined with ancillary feature
With material-holder or disposal
30901, B25F 300
Patent
active
050313215
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to cleaving apparatus particularly but not exclusively for use in the field of optical communications for cleaving optical fibres.
BACKGROUND AND SUMMARY 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 microns to 250 microns.
When optical power is to be transmitted into or out of the end of an optical fibre, the geometric characteristics of the fibre end affect the manner in which the power is transmitted. It is usually 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 to be fusion joined, it is known that if either end face is not perpendicular, optical power loss can be significantly increased at the joint. 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 the core diameter is about 8 microns and the overall diameter including core and cladding is in the region of 125 microns.
An acceptable fibre end face can be obtained by clamping the fibre under a controlled axial tension and striking it on its outermost glass surface with a cleaver blade. The blade scores the fibre by entering the fibre to a very small depth relative to the diameter of the fibre, and the cleaving is effected by the longitudinal tension in the fibre. The tension may be applied during, or after, the scoring. In some known cleaving tools the cleaver blade may be mounted on a lever which drops under the influence of gravity and/or a spring to bring the blade into contact with the fibre.
In our prior European patent application, publication No: EP-A-0 152 289 (British Telecommunications) a cleaver blade is mounted as part of a rotatable cleaver assembly which is balanced about its axis of rotation. The cleaver blade is attached to an arm which extends radially from the wheel and strikes the fibre upon rotation of the wheel. A stop attached to the wheel abuts against a reference surface being adjustable. Although this apparatus has found wide acceptance, and gives improved and acceptable cleaving, the accuracy of cleaving can be reduced after operation in adverse environments. For example the blade may intrude too far into the fibre due to inaccuracy in calibration arising from temperature effects. Poor cleaving can also arise from physical jogging of the apparatus during the scoring operation. It is an object of the present invention to provide an apparatus which is more robust and less subject to poor cleaving in adverse conditions when used in the field.
Another known apparatus for cleaving optical fibres is a device in which the fibre is held manually at one end on a leaf spring support, and is clamped at the other end by a pivotable jaw carrying the cleaver blade. In operation the jaw carrying the cleaver blade is moved towards the fibre on the leaf spring by operation of one hand, the other hand holding the main end of the fibre in place, and scoring is effected by the blade being lightly pressed against the fibre. The blade is yieldable by retracting into a bore against spring pressure after the score has been made, and the moving jaw is stopped eventually by resting against the leaf spring on either side of the fibre. After scoring, an axial tension is applied by bending the leaf s
REFERENCES:
patent: 2459864 (1949-01-01), Bissett et al.
British Telecommunications public limited company
Eley Timothy V.
Fridie Jr. Willmon
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