Electric lamp and discharge devices – With luminescent solid or liquid material – With gaseous discharge medium
Reexamination Certificate
1994-09-06
2001-07-24
Wu, Xiao (Department: 2674)
Electric lamp and discharge devices
With luminescent solid or liquid material
With gaseous discharge medium
C427S064000
Reexamination Certificate
active
06265821
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention generally relates to fluorescent tubes and more particularly to serpentine fluorescent tubes for use in avionics equipment.
In today's aviation industry, avionics engineers are involved in a continuing quest to improve the optical performance of avionics displays. One particular area of concern is fluorescent lamps for back-lighting liquid crystal displays.
Typically, fluorescent lamps utilized in the avionics industry are serpentine and are constructed by creating a linear transparent glass tube and coating the interior of the tube with a fluorescent phosphor substance. The linear coated tubes are then fashioned into a serpentine shape by heating the glass tube to its working temperature and then bending the tube.
Another method has been to bend uncoated tubes into a “U” shape and then apply the phosphors via the typical phosphor slurry flush coat method used for linear tubes. Success has been claimed for uniform application of phosphors to “U” shapes using the flush coat method, but “S” shaped or “M” shaped tubes have not been uniformly phosphor coated with the typical slurry deposition method. In order to make “S” or “M” shaped tubes, it has been attempted to weld together 2 or 3 “U” shaped phosphor slurry coated tubes to create “S” and “M” shaped lamps respectively.
While these methods have been used widely in the past all existing methods of fabricating serpentine tubular lamps have several serious draw backs. First of all, when the tubes are bent after coating, the efficiency of the phosphors is diminished as a result of exposure to the high temperature required to allow bending of the tube. Secondly, the bending of the tube results in lacerations or cracks in the phosphor coating. This results in a diminution in luminance uniformity and chromaticity uniformity, as well as the absolute luminance per unit area.
In the method involving welding several slurry coated “U” shaped tubes together, the areas where the “welding” occurs are exposed to high temperatures and the phosphors therein are degraded as a result.
Consequently, there exists a need for improved manufacture of fluorescent tubes for use in the avionics industry, in which phosphor efficiency and uniformity of luminance and chromaticity are not degraded as a result of the fabrication process.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a fluorescent tube with enhanced phosphor efficiency.
It is a feature of the present invention to include a phosphor coating on the tube that is not reheated to a uniform temperature sufficient to bend the tube.
It is an advantage of the present invention to eliminate the adverse effects on the phosphors which occurs when they are heated to a temperature sufficient to bend the tube.
It is another object of the present invention to improve optical performance of fluorescent tubes.
It is another feature of the present invention to have a serpentine tube which is not bent after coating of the phosphor.
It is additional advantage of the present invention to eliminate the cracks and lacerations due to the bending of the tube and thereby reduce some of the adverse effects upon the uniformity of luminance and chromaticity.
The present invention provides an improved fluorescent tube having a non-reheated and non-bent phosphor coating disposed therein, which is to designed to satisfy the aforementioned needs, provide the previously propounded objects, include the above described features, and achieve the already articulated advantages. The invention is carried out in a “laceration-less” phosphor coating within the fluorescent tube in the sense that the lacerations typically associated with bending a phosphor coated tube into a serpentine shape have been eliminated. Additionally, the invention is carried out in an “excessive heat exposure-less” method in the sense that the excessive and phosphor damaging heat exposure associated with bending or welding a pre-phosphor coated tube is eliminated. Instead, the fluorescent tube contains a non-reheated and non-bent phosphor coating disposed therein after the fluorescent tube has been bent to a serpentine shape.
Accordingly, the present invention provides for a fluorescent tube having a uniform phosphor coating disposed therein which has not been heated to a temperature sufficient to permit bending of the fluorescent tube and which has not been cracked or lacerated to bending of the tube after coating of the phosphors.
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Eppele Kyle
Jensen Nathan O.
O'Shaughnessy James P.
Rockwell Collins, Inc.
Wu Xiao
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