Electric lamp and discharge devices – Having heating means to control gas/vapor – gas or vapor... – Vapor generating
Reexamination Certificate
1996-01-31
2001-09-04
Patel, Nimeshkumar D. (Department: 2879)
Electric lamp and discharge devices
Having heating means to control gas/vapor, gas or vapor...
Vapor generating
C313S546000, C313S566000
Reexamination Certificate
active
06285126
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to electric discharge lamps, and is directed more particularly to a fluorescent lamp containing mercury, and to a method for dispensing mercury into a fluorescent lamp.
BACKGROUND OF THE INVENTION
Fluorescent lamps are well-known in the art and are used for a variety of types of lighting installations. Such lamps are characterized as low pressure discharge lamps and include an elongated envelope, whose interior surface is coated with a layer of phosphor, and an electrode at each end of the envelope. The envelope also contains a quantity of an ionizable medium, such as mercury, and a starting gas at a low pressure, generally in the range of 1 to 5 mm Hg. The starting gas may consist of argon, neon, helium, krypton, xenon or a combination thereof.
One of the most commonly used methods for introducing mercury into such lamps is by use of a mechanical dispensing unit which forms part of an “exhaust machine”. In such a machine, mercury is dispensed by the action of a slotted plunger passing through a reservoir of mercury and into a closed exhaust chamber housing an exhaust tube. The mercury falls through the exhaust tube into the lamp. This method of dispensing mercury has many drawbacks. The mercury dispensing unit complicates the exhaust machine, and the amount of mercury introduced into the lamp envelope by this method cannot be precisely controlled. Further, the lamp during processing is at a high temperature and is in open communication with the exhaust machine. As a result, it is inevitable that a portion of the introduced mercury evaporates and disappears from the lamp, or a portion of the filling gas is driven out of the lamp. Still further, the introduction of mercury through the exhaust tube involves the risk of mercury getting stuck in the exhaust tube so that after lamp sealing, the lamp contains too little or no mercury at all. For these reasons, an overdose of mercury is required to ensure the lamp retains a minimum amount of mercury. Finally, working with mercury on the exhaust machine requires additional safety precautions on medical grounds.
An alternative method for dispensing mercury is to place inside the lamp a mercury compound that is inert under lamp processing conditions but can later be activated to release mercury. Disadvantageously, this method releases impurities, which then require special gettering. Moreover, this method requires a relatively long period of time to activate the mercury compound, typically 5 to 30 seconds. As a result, this method of dispensing mercury does not readily lend itself to high speed production machinery.
Another method of introducing mercury into an arc discharge lamp is set forth in U.S. Pat. No. 4,553,067, issued on Nov. 12, 1985 to Roche, et al. Therein, a mercury dispensing target is located within an exhausted lamp having a coil at each end of the lamp. The dispensing target is affixed to a lead-in wire adjacent to one of the coils. During processing, the mercury target is heated by bombarding the target with a directed stream of electrons produced by one of the coils, which causes the contained mercury to be released. Although this method reduces mercury release time to about 3 seconds, it is desirable to obtain further reductions.
U.S. Pat. No. 4,870,323, which issued on Sept. 26, 1989, to Parks, Jr., et al, describes a method for dispensing mercury into a fluorescent lamp wherein portions of the mount structure are coated with an insulating coating (e.g., zirconium dioxide). A directed stream of electrons is focused to a portion of the mercury dispensing capsule devoid of the insulating coating. Although this method is effective in reducing the mercury release time, the application of an insulating coating to the various portions of the mount structure may be impractical in commercial production.
There is thus a need for a fluorescent lamp having mercury therein and for a method for dispensing mercury into the lamp, such that the amount of mercury can be precisely controlled, there is no need for introducing excess mercury into the lamp, the mercury can be quickly released into the lamp envelope, there are generated no medical hazards, and the process is readily adaptable for high-speed commercial production of lamps.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide a fluorescent lamp having therein a precise amount of mercury, wherein all the mercury introduced into the lamp remains in the lamp and there is no need for providing excess mercury to the lamp to ensure completing the lamp with a required amount of mercury therein.
A further object of the invention is to provide such a lamp as is amenable to high-speed production.
A still further object of the invention is to provide a method for dispensing mercury into a fluorescent lamp envelope, such that a precise amount of contained mercury can be introduced into the envelope and quickly released therein.
A still further object of the invention is to provide such a method as is substantially free from medical hazards.
With the above and other objects in view, as will hereinafter appear, a feature of the present invention is the provision of a fluorescent lamp comprising a sealed transparent elongated envelope containing a gas fill, a coil at each of two ends of the elongated envelope, the coils extending widthwise of the envelope, and lead-in conductors connected to each of the coils and connectable to an external source of electric current. The lamp further comprises a capsule containing mercury and mounted within the envelope at one of the ends of the envelope, the capsule being connected to one of the lead-in conductors of one of the coils, the capsule having a base end disposed in a widthwise plane of the envelope in which is disposed the one coil and disposed adjacent to a center portion of the one coil, the capsule having a body portion extending axially in the envelope toward the other of the coils. The other coil is adapted, upon energization by the electric current, to emit electrons toward the capsule to heat and burst the capsule, to release the mercury into the envelope.
In accordance with a further feature of the invention, there is provided a method for releasing mercury into a fluorescent lamp having a sealed, transparent, elongated envelope with two ends, a coil at each of the two ends, the coils extending widthwise of the envelope, and lead-in conductors connected to each of the coils and connectable to an external source of electric current. The method comprises the steps of providing a capsule containing mercury, mounting the capsule at one of the ends of the envelope by connecting the capsule to one of the lead-in conductors of one of the coils, disposing a base end of the capsule in a widthwise plane of the envelope in which is disposed the one coil, with the capsule extending axially in the envelope toward the other of the coils, and energizing the other coil by the connecting of the lead-in conductors to the source of electric current, to cause emission of electrons from the other coil towards the capsule to heat and burst the capsule, to release the mercury into the envelope.
The above and other features of the invention, including various novel details of construction and combinations of parts, 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 device and method steps embodying the invention are shown by way of illustration only and not as limitations of the invention. The principles and features of this invention may be employed in various and numerous embodiments without departing from the scope of the invention.
REFERENCES:
patent: 2283189 (1942-05-01), Cox
patent: 4056750 (1977-11-01), Latassa
patent: 4282455 (1981-08-01), Latassa et al.
patent: 4427919 (1984-01-01), Grenfell
patent: 4553067 (1985-11-01), Roche et al.
patent: 4754193 (1988-06-01), Holmes et al.
patent: 4823047 (1989-04-01), Holmes et al.
patent: 5278473 (1994-01-01), Parks Jr., et
Evans Tyra Newman
Hallock Joseph L.
Bessone Carlo S.
Osram Sylvania Inc.
Patel Nimeshkumar D.
Williams Joseph
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