Information
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Patent Grant
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6669521
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Patent Number
6,669,521
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Date Filed
Wednesday, September 26, 200122 years ago
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Date Issued
Tuesday, December 30, 200320 years ago
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Inventors
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Original Assignees
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Examiners
- Reichard; Dean A.
- Nino; Adolfo
Agents
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CPC
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US Classifications
Field of Search
US
- 445 26
- 445 38
- 445 42
- 445 43
- 445 53
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International Classifications
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Abstract
A method of removing contaminants from a double-ended arc discharge tube includes the steps of providing at least one capillary channel at each end of the tube, where the ends of the tube are sealed closed except at the capillary channels, and introducing a flushing gas into the tube through one capillary channel at one end of the tube and removing the flushing gas and contaminants through another capillary channel at another end of the tube. During manufacture, the double-ended arc discharge tube has a sealed electrode and an open capillary channel at each end of the tube.
Description
BACKGROUND OF THE INVENTION
The present invention is directed to a method of removing contaminants from a double-ended arc discharge tube and to a configuration of the arc discharge tube during manufacture.
With reference to
FIG. 1
, a conventional arc lamp
10
includes a double-ended arc discharge tube
12
with electrodes
14
and
16
sealed in opposite ends of tube
12
. Foils
18
and
20
in press seal regions
22
and
24
electrically connect electrodes
14
and
16
to external leads
26
and
28
. Tubulation
30
is attached to an opening in a side of tube
12
that leads to discharge region
32
. The interior surface of discharge region
32
and electrodes
14
and
16
contain contaminants that should be removed to improve lamp performance. The contaminants are removed with a flushing gas that is fed into discharge region
32
and then removed, carrying away the contaminants. Tubulation
30
includes an inner needle
34
through which a flushing gas is introduced into region
32
and an annular portion around needle
34
through which the flushing gas and contaminants are removed. This lamp is disclosed in U.S. Pat. No. 5,176,558 that is incorporated by reference.
As is apparent from
FIG. 1
, the inlets and outlets for the flushing gas are very close to each other at one side of tube
12
. This is necessary because tubulation
30
is desirably small to avoid a large hole in the side of tube
12
that must be closed later. The closure of such a hole is accomplished with a tip-off that can undesirably distort the side of tube
12
and is a cold spot during lamp operation that degrades lamp color and uniformity of emitted light.
However, the small tubulation hole forces the inlet and outlet for the flushing gas close to each on one side of tube
12
, and the cleaning action of the flushing gas is reduced. Some areas of the interior of tube
12
receive less flow and contaminants may remain in such areas. Further, flushing gas may be wasted because the close proximity of the inlet and outlet may allow clean flushing gas to be immediately drawn through the outlet before it has been flushed through the interior of tube
12
. A more robust and economical cleaning action, preferably without the tip-off, is desirable.
One technique for introducing a flushing gas without a tip-off is disclosed in U.S. Pat. No. 5,037,342 that is also incorporated by reference. This patent relates to a single-ended arc discharge tube that includes a removable pipe in the sealed end through which gases and materials are introduced into the arc discharge region. Flushing gas can be provided through the removable pipe and thus the tube does not require a tip-off.
However, the flushing gas is introduced and removed from the same orifice and thus the removable tube affords the same, less rigorous, cleaning action noted above because the flushing gas does not flow generally uniformly throughout the interior of the tube. Further, the insertion and removal of the pipe adds steps and complexity to the process.
In a further embodiment of this patent in which the arc discharge tube is placed in an outer envelope that includes only a gas fill, two capillaries are provided in the sealed end of the outer envelope. However, the two capillaries are close to each other in one end of the outer envelope and cannot be used for thorough cleaning. Indeed, the patent recognizes this shortcoming and states that the two capillaries are useful where only a fill gas is to be introduced and the need for high purity is less important.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a novel method for flushing contaminants from a double-ended arc discharge tube that offers rigorous and economical cleaning action without forming a tip-off on the arc discharge tube.
A further object of the present invention is to provide a novel method of removing contaminants from a double-ended arc discharge tube that includes the steps of providing at least one capillary channel at each end of the tube, where the ends of the tube are sealed closed except at the capillary channels, and introducing a flushing gas into the tube through at least one capillary channel at one end of the tube and removing the flushing gas and contaminants through one or more capillary channels at another end of the tube.
A yet further object of the present invention is to provide a double-ended arc discharge tube that, during manufacture, has a sealed electrode and one or more capillary channels at each end of the arc discharge tube.
Another object of the present invention is to provide a novel method of making a double-ended arc discharge tube, that includes the steps of providing a cylinder of light transmissive material, inserting electrodes into each end of the cylinder, pressing the light transmissive material to seal the electrodes and form an unfilled double-ended arc discharge tube while at each of the pressed ends leaving open at least one capillary channel, removing contaminants from the tube by flushing a gas lengthwise through the tube using the capillary channels at both ends of the tube, introducing a fill gas and lamp chemicals into the tube using at least one of the capillary channels, and closing the capillary channels.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1
is a pictorial representation of a double-ended arc discharge tube of the prior art illustrating a known method of flushing the tube with a tubulation.
FIG. 2
is a plan view of a double-ended arc discharge tube incorporating the novel method disclosed herein.
FIG. 3
is a side view of the embodiment of FIG.
2
.
FIG. 4
is a cross sectional view of the embodiment of
FIG. 2
, taken through line IV—IV, showing open capillary channels.
FIG. 5
is a cross sectional view of the embodiment of
FIG. 2
showing closed capillary channels.
DESCRIPTION OF PREFERRED EMBODIMENTS
With reference now to
FIGS. 2-5
, the method of the present invention improves the flow of flushing gas through a double-ended arc discharge tube by providing capillary channels at both ends of the tube. Flushing gas is introduced through the capillary channel at one end of the tube and the flushing gas and contaminants are removed through the capillary channel at the other end of the tube. The straight flow of gas through the entire tube improves the cleaning action of the flushing gas without wasting the gas, and without the undesirable tip-off.
As shown in
FIGS. 2-4
, during manufacture of an arc discharge tube, tube
40
includes an arc discharge region
42
between press seal regions
44
and
46
. Electrodes
48
and
50
extend into discharge region
42
from respective press seal regions
44
and
46
and are electrically connected to respective external leads
52
and
54
with foils
56
and
58
. Each press seal region
44
and
46
is sealed closed with the foil as is conventional in such tubes, except that at least one capillary channel
60
extends from outside tube
40
through the respective press seal region
44
and
46
into discharge region
42
. Capillary channels
60
are a passageway for a gas or solid material that is to be placed inside discharge region
42
. While one capillary channel
60
at each end will provide satisfactory results, better results are achieved with at least two capillary channels
60
spaced apart on either side of the foil, such as shown in FIG.
2
. More channels
60
can be provided to further improve the uniformity of the flushing gas flow through discharge region
42
, but congestion in the seal region suggests that two channels should be sufficient.
A flushing gas is introduced into discharge region
42
through capillary channels
60
at one end of tube
40
and removed from discharge region
42
through capillary channels
60
at the other end of tube
40
. The flow can be continuous in one direction or may alternate directions. In either event, the flow is more uniform than provided by one or more openings in one side or at one end of the discharge region. The flushing gas removes contaminants from the interior of discharge region
42
and from electrodes
48
and
50
.
The method of making a double-ended arc discharge tube includes the steps of providing a tube of light transmissive material cut from a longer cylinder of such material, such as quartz. Electrode structures, which may be conventional, are inserted into each end of the cylinder. This may be accomplished one end at a time by sliding the tube over an electrode structure held upright on a holder. The electrode structures may include the electrode that is in the discharge region, the foil portion that is typically molybdenum, and the exterior lead. The tube may be heated at the end into which the electrode structure is inserted and the heated tube pressed onto the foil portions of the electrodes at respective ends of the cylinder to seal the electrodes into the pressed material and form an unfilled double-ended arc discharge tube.
The pressing may be accomplished with press feet that have a recess that forms the capillary channel. As indicated by the pattern for the press seal region shown in
FIG. 4
, the press feet may have round mold recesses at the ends that are the inverse of the press seal region pattern shown. The capillary channels need not be round, although round channels are more easily formed.
For example, a press seal machine may be employed to hermetically seal the electrical leads to a quartz tube. The electrical lead may be positioned on a mount holder on the press seal apparatus with the electrode upright. The quartz tube may be lowered onto the lead and mechanically held in place. Gas burners may be placed in close proximity to the quartz tube and the burners may be rotated around the tube. When the quartz temperature reaches approximately 2100° C., burner rotation may be stopped. The mechanical press feet are then deployed for use. The opposing press mechanisms travel towards one another to pinch the hot plastic quartz and capture the lead. The foils provide the hermetic seal and the electrodes that are typically tungsten protrude into the discharge region. The process is repeated at the other end of the tube. With proper press feet design, the capillary channels will remain adjacent to the leads.
Thereafter, contaminants are removed from the tube by flushing a gas lengthwise through the tube using the capillary channels at both ends of the tube. The flushing gas may be a conventional flushing gas, such as an inert gas.
A fill gas and any solid lamp chemicals that are to be introduced into the discharge region (mercury, conventional metal halide salts, etc.) may be introduced into the tube using at least one of the capillary channels. The fill gas may be the same as the flushing gas, if appropriate. The flushing gas and the fill gas may be pumped into the capillary channels from a source of gas or may be drawn into the capillary channels at one end of the tube by applying a vacuum at the capillary channels at the other end of the tube. To this end, a vacuum pump may be provided.
As shown in
FIG. 5
, the capillary channels are then closed by heating the glass to form closed channels
60
′ that seal the fill gas and the other material inside the discharge region.
While embodiments of the present invention have been described in the foregoing specification and drawings, it is to be understood that the present invention is defined by the following claims when read in light of the specification and drawings.
Claims
- 1. A method of removing contaminants from a double-ended arc discharge tube, the method comprising the steps of:providing an electrode and at least one capillary channel through each end of a double-ended arc discharge tube, the ends of the arc discharge tube being sealed closed except at the capillary channels; and introducing a flushing gas into the arc discharge tube through one capillary channel at one end of the arc discharge tube and removing the flushing gas and contaminants from the arc discharge tube through another capillary channel at another end of the arc discharge tube.
- 2. The method of claim 1, wherein the capillary channels are round and are formed with a press that has a corresponding round mold pattern.
- 3. A method of making a double-ended arc discharge tube, comprising the steps of:providing a cylinder of light transmissive material; inserting electrodes into each end of the cylinder, each electrode having a foil portion; pressing the light transmissive material onto the foil portions of the electrodes at respective ends of the cylinder to seal the electrodes and form an unfilled double-ended arc discharge tube, while at each of the pressed ends leaving open at least one capillary channel; removing contaminants from the tube by flushing a flushing gas lengthwise through the tube and through the capillary channels at both ends of the tube; introducing a fill gas and lamp chemicals into the tube using at least one of the capillary channels; and closing the capillary channels.
- 4. The method of claim 3, wherein the step of removing contaminants comprises the step of pumping the flushing gas into the capillary channels at one end of the tube.
- 5. The method of claim 3, wherein the step of removing contaminants comprises the step of drawing the flushing gas into the capillary channels at one end of the tube by applying a vacuum at the capillary channels at the other end of the tube.
- 6. The method of claim 3, wherein each end of the tube has two of the capillary channels.
- 7. A method of making a double-ended arc discharge tube, comprising the steps of:cutting a quartz tube from a quartz cylinder; positioning a first electrical in-lead in a first end of the cut quartz tube; heating the first end of the cut quartz tube; pinching the first end of the quartz tube to capture the first in-lead using press feet that have a recess that forms a first capillary channel in the pinched first end of the quartz tube; positioning a second electrical in-lead in a second end of the cut quartz tube; heating the second end of the cut quartz tube; pinching the second end of the quartz tube to capture the second in-lead using press feet that have a recess that forms a second capillary channel in the pinched second end of the quartz tube; introducing a flushing gas into the arc discharge tube through one of the first and second capillary channels and removing the flushing gas and contaminants from the arc discharge tube through the other of the first and second capillary channels; introducing a fill gas and lamp chemicals into the arc discharge tube through at least one of the first and second capillary channels; and closing the first and second capillary channels.
US Referenced Citations (21)