Glass manufacturing – Fiber making apparatus
Reexamination Certificate
1995-11-08
2001-03-06
Hoffmann, John (Department: 1731)
Glass manufacturing
Fiber making apparatus
C065S531000, C065S484000, C065S529000
Reexamination Certificate
active
06196028
ABSTRACT:
The invention relates to apparatus for supporting a preform, an installation for manufacturing or building up an optical fiber preform and provided with such apparatus, methods implemented in such an installation, and preforms manufactured or built up using such methods.
BACKGROUND OF THE INVENTION
The invention relates more particularly to apparatus for supporting a preform manufactured or built up in an installation for manufacturing or building up preforms having central cores. This type of installation conventionally includes at least translation means and rotation means having a horizontal axis of rotation and on which the supporting core of the preform to be manufactured or built up is mounted, and plasma-torch and material-supply means disposed radially relative to said supporting core so as to make or build up said preform by coating.
The rotation means rotate the supporting core, and the plasma-torch and material-supply means are moved in axial translation parallel to the supporting core so as to deposit the layers making up the preform being manufactured on the supporting core using known principles and/or methods. In a variant, the preform is moved in translation while the torch remains stationary.
Such means are also implemented for “building up” an existing preform so as to thicken it.
After manufacturing or building up the preform, a cooling stage is currently necessary prior to the preform cutting stage during which the preform is cut manually. During the cutting stage, an operator inserts a support under the preform and cuts the preform by means of a blow-torch or the like. The cooling stage is a safety requirement made necessary by the presence of the operator.
Such a method gives rise to a significant loss of time due to preform cooling. Any shortening of the cooling stage considerably increases operator accident risks. However, locally re-heating a cooled preform, during the cutting stage, can have considerable adverse effects on the uniformity and the optical qualities of the preform in the re-heated zone. In particular, cracks may occur. It is therefore necessary to strike a compromise between quality and safety as a result of the human presence during the cutting stage.
Furthermore, the size of a preform is currently limited in particular by its weight. The preform sags under its own weight. Such sagging runs the risk of breaking an end-piece. Moreover, such sagging can have adverse effects on the uniformity of the preform.
OBJECTS AND SUMMARY OF THE INVENTION
An object of the present invention is to provide apparatus for supporting the preform, whereby it is possible to reduce both the risks of breaking an end-piece and also the mechanical stresses due to the mass of the preform, and therefore to increase the diameter and/or the length of the preform.
Another object of the present invention is to provide apparatus for and a method of automatically or semi-automatically supporting the preform, whereby the presence of an operator is no longer necessary so as to reduce significantly the duration of the separation stage, and so as to avoid quality defects caused by re-heating the preform.
To these ends, the invention provides apparatus for supporting a preform manufactured in an installation for manufacturing or building up preforms having central cores. The installation includes at least rotation means having a horizontal axis of rotation and two mounting points between which the supporting core of the preform to be manufactured or built up is mounted, plasma-torch and material-supply means disposed radially relative to said supporting core and being mounted to move in axial translation relative to and parallel to the supporting core so as to make the preform around the supporting core. The apparatus of the invention includes controlled support means constituting additional localized abutment points between said mounting points for said preform being manufactured or built up.
Advantageously, the controlled support means comprise: means for detecting the sag of the preform; at least one support element mounted on controlled positioning means mounted to move between an active end position in which said support element is in contact with said preform being manufactured, and an inactive end position in which the support element is not in contact with said preform being manufactured; and servo-control means for servo-controlling the controlled positioning means in the active end position to a predetermined reference value for the sag of the preform.
The support element includes at least one free wheel whose axis is parallel to the supporting core, which wheel is mounted to rotate freely on the controlled positioning means, and has a tread strip which comes into tangential contact with the preform being manufactured, in the active end position.
The controlled support means are prevented from moving in axial translation relative to the preform.
According to another characteristic of the invention, the positioning means include synchronization means for synchronizing them with the relative movement in axial translation between the preform and the plasma-torch and material-supply means, so as to go to the inactive end position when the plasma-torch and material-supply means cross paths with the positioning means.
Advantageously, the apparatus includes a plurality of support elements, each of which has associated positioning means, the elements being disposed at regular axial intervals and radially to the horizontal axis of rotation of the rotation means.
In their active end positions, the free wheels are preferably in contact with the bottom of the periphery of the preform.
The invention also provides an installation for manufacturing or building up preforms having central cores, said installation including at least rotation means which have a horizontal axis of rotation and on which the supporting core of the preform to be manufactured or built up is mounted, plasma-torch and material-supply means disposed radially relative to said supporting core and being mounted to move in axial translation relative to and parallel to the supporting core so as to manufacture or build up said preform around said supporting core. According to the invention, the installation includes support apparatus as described above.
The invention also provides a method of supporting a preform being manufactured or built up in an installation as described above, in which method:
the value of the sag stress of the preform is compared with the reference value;
the positioning means are controlled so as to reach said reference value; and
the positioning means are controlled such that they are synchronized with the relative movement in axial translation between the preform and the plasma-torch and material-supply means, so that the positioning means go to the inactive end position when the plasma-torch and material-supply means cross paths with said positioning means.
The invention further provides a method of cutting a preform manufactured or built up in an installation as described above, in which method, immediately after manufacture or building-up, and with the preform still rotating:
the value of the sag stress of the core is compared with the reference value;
the positioning means are controlled so as to reach said reference value;
the plasma torch is positioned facing the chosen cutting section; and
the plasma torch is actuated so as to cut the preform.
A first advantage of the present invention is that the mass of the preform is no longer a limiting factor. In particular, this makes it possible to increase the diameter or the length of preforms without any risk of an end-piece breaking or of the preform being deformed significantly under its own weight.
Another advantage of the present invention is that it is possible to make the preform-cutting stage automatic, thereby considerably reducing the time necessary for removing and storing a manufactured or built-up preform, eliminating the human risk factor, and improving the quality of the resulting preforms.
REFERENCES:
patent: 1948560 (19
Goudeau Jacques
Humbert Patrick
Landi Joël
Ripoche Pierre
Alcatel Fibres Optiques
Hoffmann John
Sughrue Mion Zinn Macpeak & Seas, PLLC
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