Coating processes – Direct application of electrical – magnetic – wave – or... – Polymerization of coating utilizing direct application of...
Reexamination Certificate
2000-10-10
2001-10-30
Pianalto, Bernard (Department: 1762)
Coating processes
Direct application of electrical, magnetic, wave, or...
Polymerization of coating utilizing direct application of...
C427S163200, C427S385500, C427S389800, C427S444000, C427S558000, C427S559000, C427S595000
Reexamination Certificate
active
06309712
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates in general to a curing apparatus used in the drawing process of an optical fiber, and more particularly to an apparatus that cures the photocurable coating as the coated fiber passes through the apparatus.
BACKGROUND
The manufacture of fiber optic cable involves drawing a preform to form a fiber. The drawn fiber is coated with a photocurable coating, and then exposed to ultraviolet (UV) radiation to cure the coating. The UV light activates photoinitiators in the coating that trigger the coating reaction as a whole. Typically, an irradiator tube, which is transparent to UV radiation, defines a space through which the fiber travels. The irradiator tube maintains an atmosphere which is inert with respect to the coating on the fiber, and also shields the fiber from vigorously circulated lamp coolant (blown air for example).
The polymerization (or curing) reaction is affected by several factors. First, oxygen in the irradiator tube inhibits the polymerization reaction. Oxygen may exist in the coating starting materials and in the irradiator tube during the cure process. The oxygen very rapidly combines with the activated photoinitiators in the coating to form a chemical with low reactivity. This essentially halts the curing reaction. Conventionally, therefore, an inert gas flow is provided through the irradiator tube to displace the oxygen in the fiber curing environment.
Second, the polymerization reaction rate is proportional to the UV light intensity to which the coating is exposed. Conventionally, therefore, by-products (or fumes) of the polymerization reaction are exhausted from the irradiator tube. Otherwise, these by-products would deposit on the irradiator tube and reduce the UV radiation impinging on the coating.
Third, it is important to strike a balance between the low oxygen concentration within the irradiator tube and the exhaustion of the coating cure by-products (or fumes) from the irradiator tube. For a particular application, the flow rate of the inert gas remains constant, and the flow rate of the exhaust is adjusted to achieve the desired balance. For example, if the exhaust flow is increased, the coating cure fumes are more effectively exhausted out of the irradiator tube. However, if the exhaust flow is too high, too much oxygen enters into the irradiator tube, thereby defeating the optimization of the curing reaction.
The conventional techniques for curing the coating on a fiber involve providing an inert gas flow through the irradiator tube and exhausting the curing fumes from the irradiator tube. Although these conventional techniques are generally thought to be acceptable, they are not without shortcomings. In particular, excessive amounts of oxygen and curing fumes still remain in the irradiator tube, thereby reducing the curing reaction efficiency. The curing fumes are particularly problematic because they darken the irradiator tube based on curing throughput. Thus, the irradiator tube must be periodically replaced. The replacement process reduces manufacture yields and limits the size of the draw run.
Further, the inert gas flows within the irradiator tube cause the fiber to vibrate when drawn. These vibrations may be inadvertently detected by a device that monitors the quality of the coating. As a result, the quality inspecting device may incorrectly determine that the fiber coating has defects.
SUMMARY OF THE INVENTION
The invention resides in an apparatus for curing a photocurable coating provided on a fiber. The apparatus includes an irradiator tube, an injection assembly, and an exhaust assembly.
The injection assembly is provided on an upstream end of the irradiator tube. The injection assembly receives an inert gas flow. The injection assembly includes a diffuser that separates the inert gas flow into a counter flow and a tube flow. The counter flow flows in a counter (or opposite) direction with respect to the fiber travel direction, and the tube flow flows in a laminar fashion, through the irradiator tube, in the fiber travel direction.
The exhaust assembly is provided on a downstream end of the irradiator tube. The exhaust assembly has an exhaust vent that draws the tube flow from the irradiator tube. An air opening is provided between the downstream end of the irradiator tube and the exhaust vent.
The present invention also resides in a method for curing the photocurable coating provided on the fiber. First, the coated fiber is transported through the irradiator tube in a fiber travel direction. An inert gas flow is directed toward the upstream end of the irradiator tube. The inert gas flow is then separated into a counter flow and a tube flow. The counter flow is directed along the coated fiber in a direction that is counter to the fiber travel direction. The tube flow is directed through the irradiator tube in a laminar fashion, and in the fiber travel direction. The tube flow is drawn from a downstream end of the irradiator tube and passed through a vent. Finally, an air flow is passed into the drawn tube flow, before the drawn tube flow passes through the vent.
The above and other features of the invention including various and novel details of construction and process steps will now be more particularly described with reference to the accompanying drawings and pointed out in the claims. It will be understood that the particular apparatus and method for curing a photocurable coating provided on a fiber embodying the invention is shown by way of illustration only and not as a limitation of the invention. The principles and features of this invention may be employed in varied and numerous embodiments without departing from the scope of the invention.
REFERENCES:
patent: 4591724 (1986-05-01), Fuse et al.
patent: 5000541 (1991-03-01), DiMarcello et al.
patent: 5062687 (1991-11-01), Sapsford
patent: 5114738 (1992-05-01), Savage
patent: 5157755 (1992-10-01), Ooe et al.
patent: 5171609 (1992-12-01), Ury
patent: 5235666 (1993-08-01), Ooe et al.
patent: 5320658 (1994-06-01), Ohga et al.
patent: 5320659 (1994-06-01), Ishiguro et al.
patent: 5346520 (1994-09-01), Meabon et al.
patent: 5593736 (1997-01-01), Cowen et al.
patent: 5636307 (1997-06-01), Cowen et al.
patent: 5828071 (1998-10-01), Bourghelle et al.
patent: 5851450 (1998-12-01), Rennie et al.
patent: 5942020 (1999-08-01), Marcelissen
Pedrido Carlos
Schuepbach Olivier
Alcatel
Pianalto Bernard
Sughrue Mion Zinn Macpeak & Seas, PLLC
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