EP1493169A1

EP1493169A1 - High intensity discharge lamps, arc tubes and methods of manufacture

Info

Publication number: EP1493169A1
Application number: EP02725573A
Authority: EP
Inventors: Abbas Lamouri; Juris Sulcs; Yongwei Gu
Original assignee: Advanced Lighting Technologies Inc
Current assignee: Advanced Lighting Technologies Inc
Priority date: 2002-04-09
Filing date: 2002-04-09
Publication date: 2005-01-05
Also published as: KR20040103742A; AU2002256129A1; JP2005522842A; CN1513194A; KR100760712B1; WO2003088295A1; CN101552169A; EP1493169A4; CN100550258C

Abstract

A tipless arc tube (12) for a high intensity discharge lamp and method of manufacture wherein, through reliance on the different density of gases to isolate the sealed atmosphere, the arc tube end (38) may remain open to an uncontrolled atmosphere during both the step of gas full and the subsequent step of hermetically sealing the tube by a pinch seal at the lead assembly (32). Further, the final pressure of the fill gas sealed within the arc tube (12) may be controlled by controlling the temperature of the fill gas during sealing thus obviating the need to employ a pump to control the fill gas pressure.

Description

HIGH .INTENS ITY DI SCHARGE LAMPS , ARC TUBES

AND METHODS OF MANUFACTURE

BACKGROUND OF THE INVENTION

The present invention generally relates to high intensity discharge ("HID") lamps,

arc tubes, and methods of manufacture.

HID lamps such as metal halide and mercury lamps have found widespread use in

lighting large outdoor and indoor areas such as athletic stadiums, gymnasiums,

warehouses, parking facilities, and the like, because of the relatively high efficiency,

compact size, and low maintenance of HID lamps when compared to other lamp types.

Metal halide lamps are often preferred because of the efficiency of such lamps in

producing white light.

HID lamps include an arc tube supported within an outer lamp envelope. The arc

tube comprises a generally tubular body of light transmissive material such as quartz or

ceramic material which forms a hermetically sealed light emitting chamber containing the

lamp fill material and an inert fill gas. Generally, there are several types of arc tube

bodies for HID lamps. One type of arc tube body is a "cylindrical" body formed from

quartz tubing having the diameter of the generally cylindrical arc tube chamber in which

the chamber is formed by pinch-sealing the end portions of the tubing. Another type of

arc tube body is a "formed" body which is formed from quartz tubing of a much smaller

diameter in which a bulbous light emitting chamber is formed by expansion under

internal pressure between two end portions having the much smaller diameter of the

tubing. The aforementioned types of arc tube bodies are used in forming "double-ended"

arc tubes, i.e. arc tubes having spaced apart electrodes with one sealed at each end. The arc tubes for HID lamps may also be "single-ended" arc tubes having a bulbous chamber

sealed at its only end.

An arc tube includes a pair of spaced apart electrodes between which the arc is

established during operation of the lamp. In a double-ended arc tube, an electrode lead

assembly is sealed in each end portion of the arc tube. The electrode lead assembly

typically comprises a tungsten electrode, a molybdenum foil, and an outer molybdenum

lead.

In the manufacture of double-ended arc tubes for HLD lamps, either cylindrical

body or formed body arc tubes, the light emitting chamber is sealed by positioning the

electrode lead assemblies in each end portion of the arc tube body, heating a portion of

each end portion, and then shrinking or pinching the heated portion around the electrode

lead assembly positioned therein to thereby fix the position of the assembly relative to the

arc tube body and to form a hermetic seal. The temperature of the heated portions

typically reaches about 2000°C or more. At these high temperatures, the metallic

components of the electrode lead assembly positioned within the end portion are highly

susceptible to corrosion when exposed to an uncontrolled atmosphere such as the air

surrounding a factory production line, and any corrosion may significantly degrade the

performance of the lamp and possibly lead to the mechanical failure of the lead assembly.

Thus it is important to avoid exposure of the electrode lead assemblies to an uncontrolled

atmosphere when the temperature of the assemblies is elevated during the manufacturing process.

In the context of the present invention, an "uncontrolled atmosphere" is any

atmosphere other than one in which the composition of the atmosphere is strictly

controlled such as the atmosphere in a glove box. The atmosphere surrounding a factory

production line is considered to be an uncontrolled atmosphere even though there may be

some control of the temperature, humidity, particulate content etc. of the atmosphere.

In the manufacture of HID lamps, the light emitting chamber of the arc tube body

is dosed with solid lamp fill material such as one or more metal halides. This material is

susceptible to moisture contamination when exposed to an uncontrolled atmosphere

which significantly degrades the performance of the lamp. Thus in the manufacturing

process, it is also important to avoid exposure of the solid lamp fill material to

contaminating atmospheres.

In a known method of making arc tubes for HLD lamps, an arc tube body is

formed from vitreous material such as quartz. A fill/exhaust tube is then fused near the

longitudinal center of the body where the light emitting chamber will be formed. The

exhaust tube provides a means for communication between the interior of the chamber

and the exterior of the arc tube body. The electrode lead assemblies are positioned and

then pinch-sealed in the end portions of the arc tube body. During the pinch-sealing

process, a non-reactive gas is introduced into the chamber through the fill/exhaust tube to

prevent the exposure of the metallic components of the electrode lead assemblies to air when the components are heated during the sealing process, to thereby prevent corrosion

of the metallic components. In the context of this invention, a "non-reactive" gas is a gas

which is non-reactive with respect to the lamp components including, for example, the

electrode lead assemblies and lamp fill material.

Once the ends of the arc tube body are sealed, the solid fill material and mercury

are introduced into the chamber through the fill/exhaust tube. An inert fill gas is then

introduced into the chamber at the desired fill pressure and the fill/exhaust tube is fused

closed to thereby hermetically seal the chamber.

This prior art method suffers from several disadvantages including the substantial

disadvantage that the chamber wall includes an irregularity at the point where the

fill/exhaust tube was attached and then fused closed and tipped off. This irregularity may

cause a cold spot on the wall of the chamber where halides will condense during

operation of the lamp, and the condensation of halides may have a significant effect on

the color uniformity of the light emitted from the lamp. The irregularity in the chamber

may also disturb the light emitted from the chamber and the condensed halides may

create shadows, making it difficult to control and direct the light. This is especially

undesirable in optical systems such as fiber optics, projection display, and automotive

headlamps. These disadvantages have a greater detrimental effect on lower wattage

lamps which are smaller and where the irregularity includes a greater portion of the

chamber wall. A further disadvantage of the arc tube having a fused closed fill exhaust tube

applies to arc tubes mounted within a protective shroud or within tubular outer

envelopes. The portion of the fill/exhaust tube which has been fused closed protrudes

radially from the chamber wall of the arc tube. Thus a cylindrical shroud or tubular

envelope must be of a larger diameter to envelope an arc tube with a radially protruding

tip.

The prior art has developed methods of making "tip-less" arc tubes to obviate the

deficiencies of the arc tube having a fused closed fill/exhaust tube. However, the prior

art methods of making tipless arc tubes require the use of a controlled environment

during at least some of the process steps.

Generally, the known methods of making tipless arc tubes include the steps of

providing an arc tube body; positioning and then sealing an electrode lead assembly in

one end portion of the arc tube body; introducing the solid lamp fill material and an inert

fill gas into the interior of the body through the remaining open end portion of the body;

and positioning and then sealing another electrode lead assembly in the remaining open

end portion of the body to thereby form a hermetically sealed light emitting chamber.

To prevent oxidation of the metallic components of the first electrode lead

assembly during the sealing process of the first end portion, it is known to introduce a

non-reactive gas into the interior of the body through the other end portion to thus create

a flow of non-reactive gas past the lead assembly during the sealing process. This prevents exposure of the metallic components to a reactive atmosphere such as moisture

laden air during the sealing process. The non-reactive gas is commonly introduced into

the interior of the body by conventional means such as fitting a hose over the end of the

open end portion or inserting a probe into the interior of the body through the open end

portion.

The interior of the body is then filled with a non-reactive gas through the open

end portion prior to the introduction of the solid lamp fill material. The lamp fill material

is typically stored in a dry non-reactive atmosphere and thus may be introduced into the

interior of the body without contamination.

To prevent oxidation of the metallic components of the second electrode lead

assembly during the sealing process of the second end portion, the prior art teaches that

the interior of the arc tube body must be isolated from an uncontrolled atmosphere once

the solid fill material and mercury are introduced into the interior of the arc tube body

and the second electrode lead assembly is positioned in the remaining open end portion.

The prior art teaches that the interior of the arc tube may be isolated from an

uncontrolled atmosphere by either (i) placing the arc tube body in a controlled

atmosphere such as a glove box as taught in U.S. Patent No. 5,108,333 to Heider et al.

dated April 28, 1992 or (ii) connecting the open end to a vacuum system which provides

the necessary seal as taught in U.S. Patent No. 5,505,648 to Nagasawa et al. dated April

9, 1996. As illustrated by the prior art, one end portion of the arc tube body must be long enough to enclose the entire electrode lead assembly when the assembly is positioned

within the end portion. Once the arc tube is isolated, the arc tube body is filled with the

inert fill gas at the desired pressure and then the end portion is fused closed to the outside

of the electrode lead assembly to enclose the entire assembly within the body. The arc

tube may then be removed from the glove box or vacuum system and the second end

portion is sealed by shrinking or pinching, after which the excess portion of the end

portion may be removed to expose the outer lead of the electrode lead assembly.

The prior art methods suffer from the significant disadvantage of the requirement

for isolating the arc tube body from the uncontrolled atmosphere. This has generally

required the use of a glove box or vacuum system. Such methods are complex and

difficult to automate.

Accordingly, it is an object of the present invention to obviate many of the

deficiencies of the prior art and provide a novel HLD lamp, arc tube and method of

making arc tubes.

It is another object of the present invention to provide a novel arc tube and

method of making arc tubes for HLD lamps which obviates the need to perform any

process steps within a controlled atmosphere.

It is a further object of the present invention to provide a novel arc tube and

method of making tipless arc tubes for HLD lamps in which the arc tube remains open to

an uncontrolled atmosphere during the step of finally sealing the arc tube. It is yet another object of the present invention to provide a novel arc tube and

method of making tipless arc tubes for HLD lamps in which communication of an inert

fill gas with an uncontrolled atmosphere such as air is maintained until the arc tube is

hermetically sealed.

It is yet a further object of the present invention to provide a novel arc tube and

method of making arc tubes for HLD lamps which obviates the need to remove a portion

of the end portion to expose the outer portion of the electrode lead assembly.

It is still another object of the present invention to provide a novel arc tube and

method of making arc tubes for HLD lamps in which each end portion of the arc tube

body has substantially the same length as the end portions of the finished arc tube.

It is still a further object of the present invention to provide a novel apparatus for

extending the tubular opening formed by the end portion of an arc tube body and method

of making arc tubes for HLD lamps.

It is often desirable to obtain a final fill gas pressure which is significantly below

atmospheric pressure at substantially room temperature, i.e., pressures below 500 torr.

Final fill gas pressures below about one-half atmosphere are common and may be as low

as about 30 torr. A fill pressure of about 100 torr is common in metal halide lamps. In

order to obtain such final subatmospheric fill pressures, the prior art uses mechanical

means to evacuate the interior of the arc tube to the desired pressure prior to hermetically

sealing the interior of the arc tube, i.e., by fusing closed the fill/exhaust tube or shrinking or pinching the remaining open end portion in a tipless arc tube. Such methods require

the use of expensive pumps and/or vacuum systems, are complex, and difficult to

automate.

The patent to Heider et al. discloses that a "slight" under-pressure of the fill gas

may be obtained by heating the fill gas and fusing closed the open end portion within a

glove box and then removing the arc tube from the glove box to shrink or pinch seal the

remaining unpinched end portion. Heider et al. disclose raising the temperature of the

fill gas by only 100°C prior to fusing closed the arc tube to obtain a slight under-pressure

when the fill gas cools. If the fill gas is heated at atmospheric pressure, a temperature

differential of 100°C will provide a final fill gas pressure of greater than 500 torr when

the arc tube is sealed and cooled. There is no disclosure in Heider et al. that a

significantly subatmospheric fill pressure, i.e., a pressure less than 500 torr, may be

obtained by this process, or that the fill gas temperature may be controlled outside of a

glove box while open to an uncontrolled atmosphere.

Accordingly, it is yet another object of the present invention to provide a novel arc

tube and method of making arc tubes for HLD lamps which obviates the need to

mechanically evacuate the arc tube to obtain a significantly subatmospheric fill pressure.

method of making arc tubes for HLD lamps in which the temperature of the fill gas is

controlled prior to sealing the arc tube in an uncontrolled atmosphere. It is yet another object of the present invention to provide a novel arc tube and

method of making arc tubes for HLD lamps having significantly subatmospheric fill

pressure in which there is no pressure differential at the time of sealing.

These and many other objects and advantages of the present invention will be

readily apparent to one skilled in the art to which the invention pertains from a perusal of

the claims, the appended drawings, and the following detailed description of the

preferred embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a cross-sectional view of an arc tube body having a bulbous light

emitting chamber.

Figures 2a - e illustrate the prior art process steps for forming the arc tube body

illustrated in Figure 1.

Figure 3 a illustrates the step of heating the end portion of an arc tube body while

flushing the interior of the body with an inert gas during the pinch sealing process.

Figure 3b is a cross-sectional view of an arc tube body having an electrode lead

assembly pinch sealed in one end.

Figure 4 is a schematic illustrating an electrode lead assembly.

Figure 5 illustrates the step of introducing the solid lamp fill material and mercury

into the interior of the chamber.

Figure 6 is a cross-sectional view of a prior art arc tube body having its elongated end portion tipped off beyond the electrode lead assembly.

Figure 7 illustrates the step of heating the upper end portion of an arc tube body

while maintaining the interior of the body open to the surrounding atmosphere.

Figure 8 is a cross-sectional view of an arc tube made by one method of the

present invention.

Figure 9 is a cross-sectional view of one embodiment of an arc tube body

according to the present invention.

Figure 10 is a cross-sectional view of an arc tube made from the arc tube body

illustrated in Figure 9.

Figure 11a illustrates the step of flushing and filling the arc tube body with the

final fill gas according to the present invention.

Figure 1 lb illustrates the step of positioning the electrode lead assembly and pinch

sealing the second end portion of the arc tube according to the present invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention finds utility in arc tubes for all types and sizes of HLD lamps

and methods of manufacture of such lamps generally. By way of example only, certain

aspects of the present invention will be described in connection with tipless quartz

formed body arc tubes for double-ended metal halide lamps.

Figure 1 illustrates a prior art arc tube body which has been formed from a quartz

tube. The arc tube body 10 comprises a bulbous light emitting chamber 12 intermediate open tubular end portions 14,16. The arc tube body 10 may be formed using any suitable

conventional method.

Formed body arc tubes may be manufactured in the manner described in the

Lamouri et al. copending patent application Serial No. 09/597,547 filed June 19, 2000,

and entitled "Horizontal Burning HLD Lamps And Arc Tubes" assigned to the assignee

of the present invention. Figures 2a - e illustrate such a method of forming arc tubes

from quartz tubing (Fig. 2a) by loading the tubing on a lathe and heating the tubing (Fig

2b), gathering the heated tube by axial movement of the tube (Fig. 2c), and expanding

with internal pressure the gathered tube against a mold (Fig. 2d) to obtain the desired

shape of the arc tube body (Fig. 2e). The thickness of the arc tube body may be adjusted

by the amount of quartz accumulated in the gathering process and the shape of the arc

tube body is determined by the shape of the mold.

As shown in Figure 3a and 3b, a first electrode lead assembly 18 is positioned

within the open tubular end portion 14 and the end portion 14 is sealed using a

conventional pinch sealing process. During the pinch sealing process, a portion of the

end portion 14 is heated to soften the quartz, and then the softened portion is pressed

together and around the portion of the electrode lead assembly 18 positioned therein

using conventional pinch jaws (not shown) forming pinch seal 20. The pinch seal 20

fixes the position of the assembly 18 relative to the arc tube body 10 and provides a hermetic seal between the interior of the chamber 12 and the exterior of the body 10

through the end portion 14.

The electrode lead assembly 18 may be a conventional lead assembly comprising

several metallic components including a tungsten electrode 22, a molybdenum foil 24,

and a molybdenum outer lead 26 as shown in Figure 4. During the pinch sealing process,

the metallic components may reach temperatures as high as 2000°C or more when the

quartz is softened. At such high temperatures, the metallic components are highly

susceptible to corrosion if exposed to moisture in a reactive atmosphere such as air. To

prevent such corrosion, an inert gas is introduced into the chamber 12 through the

remaining open tubular end portion 16 and flows past the lead assembly 18 during the

pinch sealing process. The gas may be introduced by any conventional means such as

insertion of a probe 28 as shown in Figure 3a or the connection of a hose (not shown) to

the open end portion 16. The gas may be any inert gas such as nitrogen or argon or

mixtures thereof.

The next step is to dose the arc tube body with the desired fill material by

introducing the material into the chamber 12 through the remaining open end portion 16.

The solid lamp fill material 30 may be introduced into the chamber 12 through the

remaining open end portion 16 by any conventional means such as a pin type dispenser

of lamp fill pellets manufactured by APL Engineered Materials, Inc. Mercury 31, if

desired, may also be introduced into the chamber 12 through the end portion 16 by any conventional means. Figure 5 illustrates an arc tube body 10 having lamp fill pellets 30

and mercury 31 within the chamber 12.

The remaining steps in the process include the flushing and filling of the chamber

with the final fill gas, the positioning of the second electrode lead assembly in the

remaining open end portion, and the sealing of the remaining open end portion. As

discussed with respect to the pinch sealing of the first end portion, it is important to

prevent the exposure of the metallic components of the electrode lead assembly to a

corrosive atmosphere at high temperature.

The prior art methods teach the necessity to isolate the components from an

uncontrolled atmosphere by either (i) placing the arc tube body in a glove box, or (ii)

connecting the open end of the arc tube body to a vacuum system prior to filling the

interior of the arc tube body with the final fill gas and positioning the second electrode

lead assembly. As shown in Figure 6, the open end portion 16 may be fused closed

outside the lead assembly 32 once the final fill pressure is obtained to isolate the interior

of the chamber 12 containing an inert atmosphere. Thus the prior art prevents corrosion

of the metallic components of the lead assembly during the pinch sealing of the end

portion 16 by isolating the components in an inert atmosphere within the interior of the

arc tube body.

It has been discovered that the isolation of the interior of the arc tube from an

uncontrolled atmosphere by use of a glove box or vacuum system may be obviated by orienting the arc tube body 10 so that the open end portion 16 extends upwardly as

shown in Figures 5 and 7, and relying on the relative weight of the fill gas to air to

maintain a fill of inert gas within the arc tube body. The final inert fill gas may be

introduced into the interior of the chamber 12 by insertion of a suitable conventional

probe 34. The fill gas may be any inert gas such as argon, neon, xenon, krypton, or a

combination thereof. In the preferred embodiment of the invention, the fill gas

comprises a mixture of argon and krypton. The mixture of argon and krypton is heavier

than air and will tend to remain within the interior of the arc tube body 10 so long as the

body remains in a substantially vertical orientation, thus retarding the influx of the

lighter contaminated air of the uncontrolled atmosphere surrounding the arc tube.

The interior of the arc tube body 10 is flushed and filled with the fill gas to the tip

38 of the end portion 16 so that all other gases are displaced. Once the arc tube body is

flushed and filled, the probe 34 may be removed and the second electrode lead assembly

32 is positioned within the end portion 16 as shown in Figure 7. The end portion 16

must extend sufficiently above the lead assembly 32 so that the lead assembly 32 will

remain immersed in the column of fill gas within the end portion 16 despite some mixing

of the fill gas with the uncontrolled atmosphere surrounding the arc tube body near the

tip 38 of the end portion 16.

As shown in Figures 7 and 8, the second end portion 16 may then be sealed by a

conventional pinch sealing process. A portion of the end portion 16 is heated to soften the quartz, and then the softened portion is pressed together and around the portion of the

electrode lead assembly 32 positioned therein using conventional pinch jaws (not shown)

forming pinch seal 36. The pinch seal 36 fixes the position of the assembly 32 relative to

the arc tube body 10 and provides a hermetic seal between the interior of the chamber 12

and the exterior of the body 10 through the end portion 16. In another embodiment, the

end portion may be sealed by a shrink sealing process.

As further illustrated in Figure 8, the chamber 12 is now hermetically sealed from

the exterior of the arc tube body 10. The excess portion of the end portion 16 may then

be removed to expose the outer lead 42 of the electrode lead assembly 32.

Figures 9 and 10 illustrate another emdodiment of the present invention. The arc

tube body 50 may be formed having a chamber 52 intermediate the open end portions

54,56. The end portions 54,56 may have substantially the same length. In the preferred

embodiment, the length of the end portions 54,56 of the arc tube body 50 may be

substantially the length of the end portions of the finished arc tube so that the step of

trimming the excess portion of the second end portion once the chamber is sealed may be

eliminated. However, it remains necessary to provide a column of fill gas which is

sufficiently long so that the second electrode lead assembly 58 positioned within the

second end portion 56 is completely immersed in fill gas during the pinch sealing process

of the second end portion.

In one embodiment of the present invention, the column of fill gas may be extended beyond the length of the end portion by communication of the open end portion

with a mechanical means forming an elongated shaft having substantially the same

diameter as the outside diameter of the end portion. In the embodiment shown in Figures

11a and 1 lb, a flush and fill block 60 forms a main shaft 62 which communicates with

the open end portion 56 of the arc tube body 50 during the steps of positioning the

electrode lead assembly 58, flushing/filling the body 50 with the final fill gas, and pinch

sealing the end portion 56.

The block 60 forms the main shaft 62 and one or more auxiliary shafts 64 which

provide communication between the main shaft 62 and the surrounding atmosphere. The

open end of the end portion 56 may be positioned relative to the block 60 to effect

communication of the main shaft 62 with the tubular opening formed by the end portion

56. The interior of the arc tube chamber 52 and open end portion 56 may be flushed and

filled with the final fill gas by insertion of a conventional probe 66 into the chamber 52

as shown in Figure 11a.

Once the arc tube body 50 is flushed and filled with the final fill gas, the probe 66

may be removed. The fill gas now fills the end portion 56 and the main shaft 62 and

tends to remain within the shaft 62 as a result of the relative weight of the fill gas to the

surrounding atmosphere. The electrode lead assembly 58 may then be positioned within

the end portion 56 and main shaft 62 using a conventional assembly holder 68 as shown

in Figure l ib. With the fill gas filling the shaft 62 to the top, the electrode lead assembly 58 may be completely immersed in the fill gas to prevent corrosion during the pinch

sealing process. Once the electrode lead assembly 58 is positioned, the end portion 56

may be pinch sealed using a conventional pinch seal process. In another embodiment,

the end portion 56 may be sealed by a shrink seal process.

In many applications, it is desirable to provide an arc tube having a fill gas

pressure which is significantly below atmospheric pressure at substantially room

temperature, e.g., pressures lower than 500 torr. Arc tubes having fill gas pressure below

one-half atmosphere and even as low as 30 torr are common. In order to obtain such

subatmospheric fill gas pressures, the prior art methods use mechanical systems such as

vacuum pumps to control the fill gas pressure prior to fusing closed the end portion and

then pinch or shrink sealing the end portion to finally seal the chamber. Such mechanical

systems are expensive and the process steps using such systems are difficult to automate.

In one aspect of the present invention, the use of such mechanical systems is

obviated in providing significantly subatmospheric fill gas pressures in arc tubes. During

the final pinch sealing process to hermetically seal the upper end portion 16,56,

communication between the interior of the chamber 12,52 and the uncontrolled

atmosphere surrounding the arc tube body 10,50 is maintained. Thus the pressures of the

fill gas and surrounding atmosphere are the same and the fill gas may expand or contract

responsive to the temperature of the fill gas relative to the temperature of the surrounding

atmosphere. In order to obtain a significantly subatmospheric fill gas pressure at substantially room temperature, the arc chamber may be heated to thereby elevate the

temperature of the fill gas during the pinch sealing process to thereby reduce the density

of the fill gas within the chamber at the time the chamber is hermetically sealed. The

pressure of the fill gas at the time the chamber is sealed will be equal to the pressure of

the surrounding atmosphere because communication between the atmospheres is

maintained during the sealing process. In the uncontrolled atmosphere of a factory

production area, the pressure will be substantially atmospheric pressure and elevating the

temperature of the fill gas will result in flow of fill gas from the arc tube through the

open end portion to prevent contamination from the mixing of the gases at the end of the

tube. When the arc tube and fill gas cools to room temperature, the pressure of the fill

gas in the fixed volume of the chamber will be reduced and the final pressure of the fill

gas at substantially room temperature may be controlled by controlling the temperature of

the fill gas at the time the chamber is sealed.

In a preferred embodiment, a burner 70 applies direct heat to the bulbous chamber

52 of the arc tube body 50 during the pinch sealing process to control the temperature of

the fill gas within the chamber 52. The intensity of the burner 70, and thus the amount of

heat applied to the fill gas, may be controlled according to the desired fill gas pressure of

the completed arc tube.

Alternatively, in another aspect of the invention, the fill gas may be cooled at the

time the chamber is hermetically sealed to obtain a superatmospheric fill gas pressure at substantially room temperature. Care must be given to prevent contamination, e.g., by

continuing to introduce fill gas into the arc tube during the cooling process.

While preferred embodiments of the present invention have been described, it is to

be understood that the embodiments described are illustrative only and the scope of the

invention is to be defined solely by the appended claims when accorded a full range of

equivalence, many variations and modifications naturally occurring to those of skill in

the art from a perusal hereof.

Claims

WHAT IS CLAIMED IS:

1. A method of making an arc tube for a lamp comprising the steps of:

(a) providing an arc tube body comprising open tubular end portions;

(b) positioning the arc tube body so that the tubular end portions are

substantially vertical;

(c) positioning a first electrode lead assembly in the lower open tubular end

portion while flushing the interior of the body with an inert gas introduced

through the upper open tubular end portion;

(d) hermetically seahng the lower tubular end portion and fixing the position

of the first electrode lead assembly relative to the arc tube body by:

(i) heating a portion of the lower tubular end portion, and

(ii) pinch-sealing the heated portion of the lower tubular end portion

around the portion of the assembly positioned therein;

(e) introducing the lamp fill material into the interior of the arc tube body

through the upper tubular end portion;

(f) flushing and filling the interior of the arc tube body with an inert fill gas

through the upper tubular end portion;

(g) positioning a second electrode lead assembly in the upper tubular end

portion; and

(h) hermetically sealing the upper tubular end portion and fixing the position of the second electrode lead assembly relative to the arc tube body by:

(i) heating a portion of the upper tubular end portion while maintaining

communication between the interior of the arc tube body and the

atmosphere surrounding the arc tube body through the upper tubular

end portion, and

(ii) pinch-sealing the heated portion of the upper tubular end portion

around the portion of the assembly positioned therein,

the sealing of the upper end portion being the final seal to hermetically seal the

interior of the arc tube body.

2. The method of Claim 1 including the step of maintaining the pressure of

the fill gas at substantially atmospheric pressure while modifying the temperature of the

fill gas relative to the temperature of the atmosphere surrounding the arc tube body at the

time the interior of the body is hermetically sealed so that the pressure of the fill gas will

differ from the pressure of the surrounding atmosphere when the fill gas returns to the

temperature of the surrounding atmosphere.

3. The method of Claim 2 wherein the temperature of the fill gas is

sufficiently elevated at the time the interior of the arc tube body is hermetically sealed so

that the pressure of the fill gas will be substantially subatmospheric at the temperature of

the surrounding atmosphere.

4. The method of Claim 3 further comprising the step of heating the portion of the arc tube body between the tubular end portions while heating the upper tubular end

portion during the step of hermetically sealing the upper tubular end portion to thereby

elevate the temperature of the inert fill gas relative to the temperature of the surrounding

atmosphere prior to pinch sealing the upper tubular end portion.

5. The method of Claim 1 wherein the inert fill gas is heavier than the

atmosphere surrounding the arc tube body to thereby reduce the mixing of the fill gas

with the surrounding atmosphere during the sealing of the upper end portion.

6. The method of Claim 5 further comprising the step of heating the portion

of the arc tube body between the tubular end portions while heating the upper tubular end

atmosphere to thereby effect flow of the fill gas out of the interior of the arc tube body

during the step of pinch sealing the upper tubular end portion.

7. The method of Claim 6 wherein the lamp fill material comprises one or

more metal halides and the fill gas comprises one or more inert gases.

8. The method of Claim 1 wherein the arc tube body comprises a bulbous

light emitting chamber intermediate the tubular end portions.

9. The method of Claim 1 wherein the tubular end portions have substantially

the same length.

10. The method of Claim 9 further comprising the step of extending the length of the upper tubular end portion beyond the electrode lead assembly positioned therein so

that the electrode lead assembly is completely immersed in fill gas at the time the upper

end portion is pinch sealed.

11. The method of Claim 9 wherein the length of the end portions of the arc

tube body is substantially the same as the length of the end portions of the sealed arc

tube.

12. The method of Claim 1 wherein the arc tube body is cylindrical.

13. The method of Claim 1 wherein the lamp fill material comprises mercury

and one or more metal halides and the fill gas comprises argon, xenon, or krypton or a

mixture thereof.

14. The method of Claim 13 wherein the lamp fill gas comprises argon and

krypton.

15. A method of making an arc tube for a high intensity discharge lamp

wherein the arc tube includes fill gas at subatmospheric pressure at substantially room

temperature, said method comprising the steps of:

elevating the temperature of the fill gas in the interior of the arc tube body relative

to the temperature of an uncontrolled atmosphere surrounding the body at substantially

atmospheric pressure while maintaining communication between the fill gas and the

surrounding atmosphere; and

hermetically sealing the arc tube body while the temperature of the fill gas is elevated so that the pressure of the fill gas sealed within the interior of the arc tube will

be subatmospheric when the temperature of the fill gas is no longer elevated.

16. The method of Claim 15 further comprising the step of controlling the

elevated temperature of the fill gas to obtain a desired fill gas pressure when the arc tube

is sealed and the fill gas temperature is no longer elevated.

17. The method of Claim 15 wherein the step of elevating the temperature of

the fill gas comprises the step of heating the longitudinally central portion of the arc tube

body.

18. The method of Claim 15 comprising the steps of:

sealing one tubular end portion of the body;

sealing the other tubular end portion of the body to thereby form a hermetically

sealed light emitting chamber between the sealed end portions; and

heating the chamber to thereby elevate the temperature of the fill gas within the

chamber during the step of sealing the other tubular end portion.

19. The method of Claim 18 wherein the end portions are pinch-sealed.

20 The method of Claim 18 wherein the end portions are shrink-sealed.

21. The method of Claim 15 wherein the fill gas is inert and the surrounding

atmosphere is air.

22. The method of Claim 21 wherein the inert fill gas comprises argon.

23. The method of Claim 15 wherein the pressure of the fill gas sealed within the chamber is below one-half atmosphere at substantially room temperature.

24. The method of Claim 23 wherein the fill gas pressure is between about 30

torr and about 350 torr.

25. The method of Claim 15 wherein the step of hermetically sealing the arc

tube body comprises the step of sealing a tubulation extending from a light emitting

chamber of the arc tube.

26. The method of Claim 15 wherein the arc tube body comprises a light

emitting chamber having a single open end.

27. The method of Claim 15 wherein the arc tube body comprises ceramic

material.

28. The method of Claim 15 wherein the arc tube body comprises quartz.

29. The method of Claim 15 wherein the step of hermetically sealing the arc

tube body comprises the steps of positioning one or more electrode lead assemblies in an

open end portion of the body, and sealing the end portion around the one or more

electrode lead assemblies positioned therein to thereby fix the position of the one or more

electrode lead assemblies and hermetically seal the arc tube body.

30. In a method of making an arc tube having a hermetically sealed light

emitting chamber containing fill gas having a subatmospheric pressure at substantially

room temperature, the improvement wherein no step is performed in a controlled

atmosphere and wherein the subatmospheric fill gas pressure at substantially room temperature is obtained without mechanically evacuating the chamber.

31. A method of making an arc tube for a high intensity discharge lamp having

fill gas hermetically sealed within the light emitting chamber of the arc tube wherein the

pressure of the fill gas is less than one-half atmosphere at substantially room temperature,

said method comprising the steps of:

elevating the temperature of the fill gas within the chamber to effect flow of fill

gas from the chamber as a result of the elevated temperature thereof; and

hermetically sealing the chamber after sufficient fill gas has flowed from the

chamber so that the pressure of the fill gas sealed within the chamber will be less than

one-half atmosphere when the temperature of the fill gas is no longer elevated.

32. The method of Claim 31 wherein the fill gas flows from the chamber

through an open tubular end portion of the arc tube.

33. The method of Claim 31 wherein the arc tube comprises a pair of tubular

end portions.

34. The method of Claim 31 wherein the arc tube comprises a single end

portion.

35. The method of Claim 31 wherein the chamber is intermediate sealed end

portions and the fill gas flows from the chamber through an open tubulation.

36. The method of Claim 31 wherein the fill gas is inert and flows from the

chamber into an uncontrolled atmosphere.

37. The method of Claim 31 wherein the fill gas pressure at substantially room

temperature is between about 30 torr and about 350 torr.

38. The method of Claim 31 wherein the step of hermetically sealing the arc

electrode lead assemblies and hermetically seal the arc tube body.

39. In a method of making an arc tube having sealed light emitting chamber

containing fill gas having a pressure of less than one-half atmosphere at substantially

room temperature, the improvement wherein the subatmospheric fill gas pressure is

obtained without the step of mechanically evacuating the chamber.

40. A method of making a tipless arc tube for a high intensity discharge lamp

having a hermetically sealed light emitting chamber intermediate a pair of pinch-sealed

end portions and a fill gas sealed within the chamber, said method comprising the steps

of:

flushing and filling the interior of the chamber with fill gas through an open end"

portion; and

hermetically sealing the chamber by pinch-sealing the open end portion while

maintaining communication between the fill gas and the atmosphere surrounding the arc

tube through the end portion until the chamber is sealed.

41. The method of Claim 40 further comprising the step of positioning the arc

tube so that the open tubular end portion extends upward during the steps of flushing and

filling and sealing the chamber.

42. The method of Claim 41 wherein the fill gas is heavier than the

surrounding atmosphere.

43. The method of Claim 42 wherein the fill gas is inert and the atmosphere

surrounding the arc tube is air.

44. The method of Claim 42 wherein the fill gas comprises argon or xenon.

45. The method of Claim 40 wherein the fill gas is inert and the atmosphere

surrounding the arc tube is air.

46. The method of Claim 40 wherein the arc tube comprises quartz.

47. In a method of making an arc tube for an arc discharge lamp including the

steps of filhng the arc tube with inert fill gas through an open tubular end portion thereof

and then forming a pinch seal in the end portion to thereby hermetically seal the arc tube,

the improvement comprising the step of maintaining the interior of the arc tube open to

the atmosphere surrounding the arc tube through the tubular end portion until the pinch

seal is formed, thereby eliminating the need to control the atmosphere surrounding the

arc tube at the time the pinch seal is formed.

48. In a method of making an arc tube comprising the steps of filling a light

emitting chamber with fill gas and then sealing the chamber, the improvement wherein communication between the fill gas within the chamber and an uncontrolled atmosphere

surrounding the chamber is maintained until the chamber is sealed.

49. The method of Claim 48 further including the step of elevating the

temperature of the fill gas within the chamber relative to the surrounding atmosphere to

thereby effect a flow of fill gas out of the chamber during the sealing thereof.

50. The method of Claim 49 wherein the pressure of the fill gas within the

sealed arc tube is subatmospheric at substantially room temperature.

51. The method of Claim 48 wherein the fill gas is inert and the atmosphere

surrounding the arc tube is air.

52. The method of Claim 48 wherein the fill gas is introduced into the light

emitting chamber through an open end portion of the arc tube.

53. The method of Claim 48 wherein the fill gas is introduced into the light

emitting chamber through an open fill tube.

54. A method of making a tipless arc tube having a hermetically sealed light

emitting chamber containing a fill gas, said method comprising the steps of:

placing the tipless chamber in a gaseous atmosphere;

flushing and filling the chamber with the fill gas through an open end portion of

the arc tube; and

hermetically sealing the chamber by sealing the end portion while maintaining

communication of the fill gas through the end portion with the gaseous atmosphere surrounding the arc tube,

the composition of the fill gas being different from the composition of the gaseous

atmosphere surrounding the arc tube.

55. The method of Claim 54 wherein the gaseous atmosphere is air and the fill

gas is inert.

56. The method of Claim 54 wherein the gaseous atmosphere is non-reactive

and the fill gas is inert.

57. The method of Claim 54 wherein the step of hermetically sealing the

chamber comprises the step of pinch-sealing the end portion.

58. The method of Claim 54 wherein the step of hermetically seahng the

chamber comprises the step of shrink-sealing the end portion.

59. The method of Claim 54 wherein the open end portion of the arc tube

extends substantially upward and the fill gas is heavier than the gaseous atmosphere.

60. A method of making an arc tube in a first atmosphere including the steps of

introducing the lamp fill gas into the interior of the arc tube chamber through an open

end portion of the arc tube and then forming a seal in the end portion to thereby

hermetically seal the arc tube chamber from the first atmosphere while maintaining

communication between the fill gas and the first atmosphere until the seal is formed, the

composition of the first atmosphere surrounding the arc tube being different than the

composition of the fill gas.

61. The method of Claim 60 wherein the fill gas is non-reactive and the first

atmosphere is reactive.

62. The method of Claim 61 wherein the fill gas is inert and the first

atmosphere is air.

63. The method of Claim 60 wherein the fill gas is non-reactive and the first

atmosphere is non-reactive.

64. The method of Claim 63 wherein the fill gas is inert.

65. The method of Claim 64 wherein the first atmosphere is inert.

66. The method of Claim 60 wherein the arc tube is double ended.

67. The method of Claim 60 wherein the arc tube is single ended.

68. A method of making an arc tube for a high intensity discharge lamp

comprising the steps of:

providing a quartz arc tube body comprising a bulbous hght emitting chamber

intermediate tubular end portions of substantially the same length;

sealing an electrode lead assembly in one end portion;

introducing the lamp fill material, mercury, and an inert fill gas into the chamber

through the other end portion; and

sealing an electrode lead assembly in the other end to thereby hermetically seal the

chamber.

69. In a method of making an arc tube for a high intensity discharge lamp including the steps of providing an arc tube body having a bulbous light emitting

chamber intermediate tubular end portions and pinch sealing an electrode lead assembly

in each end portion to thereby hermetically seal the light emitting chamber, the

improvement wherein substantially equal length end portions of the sealed arc tube are

obtained without the step of removing the end of either end portion after the arc tube is

sealed

70. The method of Claim 69 wherein the lengths of the end portions are

substantially the same at the time of sealing each end portion.

71. A quartz arc tube body from which an arc tube may be formed comprising

a bulbous chamber intermediate open tubular end portions of substantially the same

length.

72. The arc tube body of Claim 71 wherein the length of the tubular end

portions of the arc tube body is substantially the same as the length of the end portions of

the formed arc tube.

73. The arc tube body of Claim 70 wherein the interior of the chamber is open

to the atmosphere surrounding the body only through the open tubular end portions.

74. A quartz arc tube body from which an arc tube may be formed comprising

a bulbous light emitting chamber intermediate open tubular end portions, each end

portion being of a length which is sufficiently short to expose at least a portion of an

electrode lead assembly sealed therein.

75. The arc tube body of Claim 74 wherein the lengths of the end portions are

substantially the same.

76. A method of making an arc tube comprising the steps of:

(a) providing an arc tube body comprising an arc tube chamber intermediate

open tubular end portions, the interior of the chamber being open to the

atmosphere only through the end portions;

(b) positioning a first electrode lead assembly in one of the end portions;

(c) pinch sealing the end portion around a portion of the first electrode lead

assembly positioned therein to thereby fix the position of the assembly

relative to the arc tube body and to provide a hermetic seal between the end

portion and the first electrode lead assembly;

(d) introducing solid lamp fill material, mercury, and an inert fill gas into the

arc tube chamber through the other end portion;

(e) positioning a second electrode lead assembly in the other end portion;

(f) pinch sealing the other end portion around a portion of the second electrode

lead assembly positioned therein to thereby fix the position of the assembly

relative to the arc tube body and to hermetically seal the arc tube chamber

while maintaining communication between the chamber atmosphere

through the other end portion until the chamber is hermetically sealed.

77. A method of making a tipless arc tube comprising the steps of: (a) providing an arc tube body comprising a bulbous light emitting chamber

intermediate open tubular end portions, the chamber being open to the exterior of the arc

tube body only through the end portions;

(b) positioning an electrode lead assembly into one of the open tubular end

portions;

(c) flowing an inert gas past the electrode lead assembly;

(d) pinch sealing the tubular end portion around the electrode lead assembly

positioned therein while the inert gas is flowing thereby;

(e) dosing solid lamp fill material into the interior of the chamber through the

remaining open tubular end portion of the arc tube body;

(f) dosing mercury into the interior of the chamber through the remaining open

tubular end portion of the arc tube body;

(g) discharging fill gas into the chamber through the remaining open tubular

end portion to thereby displace all other gasses from the chamber;

(h) positioning a second electrode lead assembly into the remaining open

tubular end portion;

(i) controlling the temperature of the fill gas within the chamber to thereby

control the density of the fill gas to be hermetically sealed within the chamber; and

(j) pinch sealing the remaining open tubular end portion around the electrode

lead assembly positioned therein to thereby hermetically seal the chamber.

78. The method of Claim 77 wherein the pressure of the fill gas sealed within

the chamber is subatmospheric at substantially room temperature.

79. The method of Claim 77 wherein the pressure of the fill gas sealed within

the chamber is superatmospheric at substantially room temperature.

80. The method of Claim 77 wherein the arc tube body is positioned so that the

remaining open tubular end portion extends upward and the fill gas is heavier than the

atmosphere surrounding the arc tube.

81. The method of Claim 77 wherein the arc tube body is positioned so that the

remaining open tubular end portion extends downward and the fill gas is lighter than the

atmosphere surrounding the arc tube.

82. In a method of making an arc tube including the steps of introducing lamp

fill gas into the interior of the arc tube chamber through an open tubular end portion of

the arc tube and then forming a seal in the end portion to thereby hermetically seal the arc

tube chamber from the surrounding atmosphere wherein the pressure of the fill gas sealed

within the chamber is less than one-half atmosphere at substantially room temperature,

the improvement wherein there is no pressure differential between the pressure of the fill

gas and the pressure of the atmosphere surrounding the arc tube at the time the chamber

is sealed.

83. The method of Claim 82 wherein the pressure of the atmosphere

surrounding the arc tube body at the time the chamber is sealed is substantially atmospheric pressure.

84. An apparatus for facilitating the filling and sealing of an arc tube body

open at one end to an uncontrolled atmosphere comprising:

a body having a substantially vertical main shaft and one or more auxiliary shafts,

said main shaft being open to an uncontrolled atmosphere at the upper end and

adapted at the lower end to mate with the open tubular end of a bulbous arc tube body

for sealably establishing communication between the lower end of said main shaft and

the tubular end of an arc tube body when mated therewith;

said one or more auxiliary shafts being adapted at one end for sealing

communication with a controlled atmosphere and providing communication with said

main shaft intermediate the length thereof so that the atmosphere within an arc tube when

mated with said main shaft may be selectively controlled, and

an electrode lead assembly holder for selectively positioning an arc tube electrode

lead assembly in said main shaft so that when an arc tube is mated with said main shaft

the electrode lead assembly extends into the bulbous chamber of the arc tube.

85. The apparatus of Claim 84 including a sealer for selectively pinch sealing

the open tubular end of an arc tube about an electrode lead assembly when the arc tube is

mated with said main shaft with an electrode lead assembly positioned by said electrode

lead holder.

86. The apparatus of Claim 84 wherein the length of said main shaft is sufficient, when combined with the length of the tubular end of the arc tube mated with

said main shaft, to prevent substantial mixing of the controlled atmosphere in the arc

tube with the uncontrolled atmosphere at the upper end of said main shaft to thereby

prevent exposure of the arc tube lead assembly positioned therein to a mixed atmosphere.

87. An apparatus for filling and sealing of an arc tube body open at one end to

an uncontrolled atmosphere comprising:

a passageway open to an uncontrolled atmosphere at the upper end and adapted at

the lower end to mate with the open tubular end of a bulbous arc tube body for sealably

establishing communication between the lower end of said passageway and the tubular

end of an arc tube body when mated therewith;

a source of a controlled atmosphere for introducing a controlled atmosphere into

an arc tube when mated with said passageway;

an electrode lead assembly holder for positioning an arc tube electrode lead

assembly within said passageway so that the electrode lead assembly extends into the

bulbous chamber of an arc tube when mated with said passageway; and

a pinch sealer for selectively sealing the arc tube to the electrode lead assembly

when the arc tube is mated with said passageway and when the electrode lead assembly is

positioned therein,

whereby the atmosphere of an arc tube when mated with said passageway may be

controlled by said source despite the communication of the arc tube through said passageway to an uncontrolled atmosphere at the time the electrode lead assembly is

positioned into the arc tube by said holder, and at the time the arc tube is sealed by said

pinch sealer.

88. A method of pinch sealing an arc tube having a bulbous chamber and

tubular end portions substantially equal in length to the desired length of the completed

pinch seal comprising the steps of:

(a) pinch sealing a first electrode lead assembly in a first end portion while

passing a controlled atmosphere through the end portion;

(b) inserting fill material into the bulbous chamber though the other tubular

end portion;

(c) positioning a second electrode lead assembly partially within the lower end

of a removable passageway;

(d) sealably mating the lower end of the removable passageway to the other

tubular end portion to thereby extend the effective length of the end portion while

maintaining communication between the upper end of the passageway and an

uncontrolled atmosphere, the second electrode lead assembly extending into the bulbous

chamber;

(e) passing a sufficient volume of a controlled atmosphere through the

passageway and the other tubular end portion into the arc tube to substantially eliminate

the uncontrolled atmosphere therefrom; (f) pinch sealing the second electrode lead assembly in the other tubular end

portion while maintaining the upper end of the passageway in communication with an

uncontrolled atmosphere; and

(g) removing the passageway,

the existence of the removable passageway during the pinch sealing of the other

end portion materially reducing the entry of the uncontrolled atmosphere into the arc tube

during the pinch sealing process.

89. The method of Claim 88 including the further step of heating the bulbous

portion of the arc tube to thereby expand the controlled atmosphere to insure an outflow

of the controlled atmosphere from the arc tube during the sealing process and an internal

arc tube pressure less than the pressure of the uncontrolled atmosphere.

90. A method of pinch sealing an arc tube having a bulbous chamber and

pinch seal comprising the steps of:

(a) pinch sealing a first electrode lead assembly in a first end portion;

(b) inserting the fill material into the arc tube through the other tubular end

portion;

(c) positioning a second electrode lead assembly partially within the lower end

of a removable passageway;

(d) sealably mating the lower end of the removable passageway to the other tubular end portion to thereby extend the effective length of the end portion beyond the

desired length of the completed pinch seal and to position the electrode lead assembly

within the other end portion;

(e) pinch sealing the second electrode lead assembly in the other tubular end

portion; and

(f) removing the passageway.