CA2097628A1 - Vented hid vehicle capsule - Google Patents

Abstract

Abstract of the Disclosure An arc discharge headlamp capsule that provides a low stress coupling, ultraviolet light shielding, and seal cooling for an arc discharge headlamp capsule is disclosed. A wedge and retainer structure mate with an end of the arc tube, so as to firmly, but not stressfully support the arc tube. A cover shields against ultraviolet light, that is vented to allow cooling of the capsule seals. The vented cover also acts as an electric insulator positioned between the input and output leads of the lamp. - 23 -

Description

VENTED HID VEHICLE CAPSULE
1. Technical Field The invention relates to electric lamps and particularly to small Yolume arc dlscharge lamps. More particularly the invention is concerned with a shield structure for a small Yolume arc discharge automobile lamp.

2. Background Art Small volume arc discharge lamps are belng developed for use as vehicle headlamps. These lamps offer lon~
service lives, with high electrical efficiency. Moreover, these lamps have small optical sources that should improve headlamp optics. The enclosed lamp volume is roughly the slze of a pea, so lamp manufacture can start with a small diameter tube. Because of the small light source, the reflector optics may also be made small. The difficulty is that the arc must then be precisely located in the reflector. The lamp becomes quite hot, and needs support by hiqh temperature materials, which are normally metals and ceramics. Unfortunately, metals and ceramics are hard, and precise coupling of the arc tube with metal or ceramic can rexult in strain between the arc tube and the support.
Since the practical manufacture of arc tubes, and metal or ceramic support structures normally results in some dimensional variation of the parts, some of the manufactured lamp tubes and support combinations may have high contact, and stress, while others have low contact and stress. The coupling stress is made worse by the thermal expanslon and contract~on of the components as the lamp is turned on and off. Arc tube fracture, or inaccurate optical positioning 2~97628 are then possible results in a portion of arc tubes pinched in metal support structures. There is then a need for an arc discharge headlamp capsule that can withstand the temperatures of operation, and still precisely locate the arc tube without excessive stress.
In most arc lamps, where there is high voltage drop, an electric field can exist between the input and output leads.
This is particularly true where one of the leads passes parallel and adjacent the lamp capsule. Arc tubes are commonly doped with metals that ionize in the arc. Sodium is a particularly important example. The resulting electric field can cause the ionized dopants to migrate to, and even through the capsule wall. The migrating materlal is then lost from the arc process, upsetting the lamp chemistry, and arc color spectrum. The migrating material also helps devitrify the capsule wall, leading to envelope failure.
One known solution is to enclose the parallel lead in an insulating sleeve. This is only as effective as the amount of insulation used around the parallel lead. Unfortunately, the parallel lead and the insulating sleeve block a portion of the emitted light. Increasing the amount of lnsulation then reduces the amount of useful light, and increases the amount of stray light that becomes headlamp glare. There is then a need for a headlamp design wherein the insulation of the exterior parallel lead i~ adequate to a~sure long envelope life, with minimal loss or dispersion of generated light.
Arc lamps operate at high temperatures. The preferred material to contain the arc process is quartz, as it is substantially chemically inert, optically clear, and has good high temperature mechanical stability. Quartz does not block the ultraviolet light produced by arc lamps. The ultraviolet light may injure the adjacent plastic components, or if allowed to escape, can injure a viewer's 2~628 eyes. The ultraviolet light problem should also be accounted for even when a lamp is partially broken, as when a stone breaks a protective cover lens. There is then a continuing problem of how to reflect or absorb the ultraviolet light safely. There is then a need for a headlamp design that adequately absorbs or reflects ultraviolet light safely.
One method of controlling ultraviolet light is to enclose the lamp in a glass cover. Glass absorbs ultraviolet light, while quartz does not. Lamps have also been made with the inner capsule sealed to an outer glass envelope. The outer glass envelope necessarily holds in some of the generated lamp heat. The higher heat increases seal stress, and enhances the likelihood that the lamp will leak and fail. There is then a need for a lamp design that does not unduly increase capsule seal temperatures.
A related problem concerns the energy management of the arc tube. The physics of the arc process is carefully designed for a particular operation temperature. Where thermal conduction from the arc tube differs, for example where the support structure has a low or high amount of contact with the arc tube, heat builds up, or i8 lost too quickly from the arc tube. The physics of the arc changes, thereby affecting the lamp optics, life and color. There is then a need for a support structure that from one arc tube to the next forms a consistent thermal contact.
Related prior patents include the following:
U.S. patent 4,734,612 issued to Hiroki Sasaki et al on March 29, 1988 for a High Pressure Metal Vapor Discharge Lamp shows a double ended lamp capsule with lead~ welded to support wires. One support wire extends through a lnsulating sleeve and then, in parallel with the second wire, extend through a seal area of an enclosing capsule.
Sasaki is ~enerally concerned with an insulated preheater.

3 r~ 6 2 8 U.S. patent 4,754,373 issued to Lee W. Otto et al on June 28, 1988 for a Automotive Headlamp shows a double ended filamented lamp capsule positioned in an automobile headlamp reflector. Otto shows generally how a double ended lamp capsule may be welded and aligned axially as part of a headlamp.
U.S. patent 4,799,135 issued to Shinji Inukai on January 17, 1989 for Headlight for Vehicle shows an are discharge tube sealed in an outer jacket.
U.S. patent 4,894,585 issued to Toru Segoshi on January 16, 1990 for Combination Lamp shows an are discharge tube and filament lamp sealed in an outer jacket.
U.S. 4,920,459 issued to Harold L. Rothwell et al on April 24, 1990 for Arc Discharge Headlamp System shows an arc discharge vehicle headlamp. The arc discharge tube is show in an enclosed capsule that is not vented.
U.S. patent 4,978,8~4 issued to Johannes Van Vliet et al on December 18, 1990 for Metal Halide Discharge Lamp shows a arc discharge capsule enclosed in a surrounding envelope.
U.S. patent 5,032,758 issued to John M. Davenport et al on July 16, 1-991 for a Precision Tubulation for Self Mounting Lamp shows an arc discharqe axially aligned on a headlamp cap~ule.
U.S. patent 5,036,439 issued to Friedich Hoffmann et al on July 30, 1991 for a Car Headli~ht Lamp and Method of Manufacturing Same shows a double ended arc discharge lamp capsule held in a metal reflector or shield. The reflector includes spring tabs that press against the lamp tube to properly position the shleld.
U.S. patent 5,039,904 issued to Walter J. Kosmatka on Au~ust 13, 1991 for a Moun~ for Miniature Arc Lamp shows a double ended arc discharge tube, axially mounted in a headlamp. One end of the tube is captured in a threaded 2~97~28 structure including O-rings. The forward lead is ducted away from the capsule base to pass through the reflector body for exterior electrical connection.
U.S. patent 5,051,658 issued to Dirk Van Pi~keren on September 24, 1991 for a an Electric High-Pressure Dischar~e Lamp for Use as a Motor Vehicle Headlamp shows a double ended arc discharge tube. The length of one end is pinched between two metal arms. The arms are supported on a bush that is in turn connected to a tube and holder body.
U.S. patent 5,059,855 issued to Shinichi Irisawa et al on October 22, 1991 for a Discharge Lamp Base Construction shows a double ended arc discharge tube welded by its leads at each end. The forward lead extends back through an insulating sleeve to a base. The leads are otherwise ducted through the body of the base.
EPO patent disclosures 0 321 866, and 0 321 867 for Manfred G~ugle's Hochdruckenladungslampe show an arc discharge headlamp capsule sealed in an outer container.
Japanese publication 4-4555, by Koito Manufacturing Company Limited for a Discharge Lamp Apparatus, dated January 9, 1992 shows a vehicle headlamp capsule. The capsule is enclosed in an outer envelope that is sealed to a base. Four holes are formed in the base, and ducted to the edge of the base. A forward connection rod is also enclosed in the outer envelope, and is ~acketed in a ceramic sleeve.

2~762~
Disclosure of the Invention An arc discharge headlamp capsule that provides a low stress coupling, ultraviolet light shielding, and seal cooling for the arc discharge capsule may be formed from an arc discharge tube having a forward end with a forward lead, and a rear end with a rear lead, a holder supporting the arc discharge tube, having a vent passa~e formed therein leading from an exterior opening to an interior opening, a vented cover made of a light transmissive material coupled to the holder, extending around and substantially enclosing the arc discharge envelope and the interior opening of the holder vent passage, and having a vent passage to allow air flow from the volume enclosed by the vent cover to the exterior, means for electrically connecting the forward lead, and means for electrically connecting the rear lead.

Brief DescriPtion of the Drawinqs FIG. 1 shows a cross sectional view of a preferred embodiment of an arc discharge headlamp capsule.
FIG. 2 shows a cross sectional view of an alternative preferred embodiment of an arc discharge headlamp capsule.
~5 FIG. 3 shows a cross sectional view of an alternative preferred embodiment of an arc discharge headlamp capsule.
FIG. 4 shows a front to side perspective view of an alternative preferred embodiment of an arc discharge headlamp capsule.
FIG. 5 shows a side to rear perspective view of a wedge.
FIG. 6 shows an axial cross sectional view of a wedge.
FIG. 7 shows a forward end view of a wedge.
FIG. 8 shows a perspective view of a retainer.
FIG. 9 shows an axial cross sectional view of a retainer.

2Q97~2~
FIG. 10 shows a transaxial~cross section of a retainer.

Be~t Mode for Carrying Out the Invention S FIG. 1 shows a preferred embodiment of an arc discharge headlamp capsule 10. The preferred arc discharge headlamp capsule may be assembled from a doubled ended arc tube 12, wedge 24, retainer 38, vented cover 62, forward connector rod 76, insulating sleeve 82, RF ring 86, base 88, electronics package 92, and rear cover 94.
The doubled ended arc tube 12 may be formed from a quartz tube to include an arc discharge envelope 16 electrically supplied at a forward end through a forward lead 18, and a rear lead 20, at a rear end 22. The preferred arc tube 12 i8 a cylindrical quartz tube, with a closed arc discharge envelope 16 formed along a middle region of the tube. The arc discharge envelope 16 may vary in size and shape, but examples are known to include a volume of about 0.20 to 0.50 milliliter. Extending forward along the axis of the arc tube 12 is a forward lead 18 that i8 typically press or vacuum sealed to the quartz tubing.
Extending rearward along the axis of the arc tube 12 is a ~imilar sealed rear lead 20. ~y way of example arc tu~e 12 i8 shown as a cylindrical, double ended, press sealed arc 2S tube wlth an approximately elliptical arc discharge envelope. Most other double ended capsule conflgurations may ~e used.
The arc tube 12 i9 held alon~ the rear end 22 by a holder. Numerous alternative holder designs are possible.
The preferred holder consists of a wedge 24C retainer 38, RF
ring 86, and base 88. The holder may include additional features such as an electronics package 92, and a rear cover g4. FIG. g shows a side to rear perspective view of a wedge. FIG. 6 shows an axial cross sectional view of a ' ' ' 2~7628 wedge. FIG. 7 shows a forward end view of a wedge. The rear end 22 of the arc tube 12 slips axially into the wedge 24. The wedge 24 is formed from a slightly flexible, high temperature resistant material, such as a qlass filled S polyamide-nylon plastic. The wedge 24 has a wedge axis 26, an interior cylindrical wall 28, and a conical exterior wall 30. Formed in the wedge 24 is an interior wall designed to be conformal with the surface of the rear end 22 of the arc tube 12. Since the preferred arc tube 12 is cylindrical, the preferred wedge 24 interior wall is cylindrical. The preferred wedge 24 is also axially split on one side by an axial split wall 36 to form a narrow gap. The preferred axial split wall 36 joins the interior cylindrical wall 28 to the conical exterior wall 30 thereby forming an expansion gap allowing expansion and contraction of the interior passage. Since the wedge 24 is slightly flexible, the axial gap allows the diameter of the interior cylindrical wall 28 to be slightly expanded or contracted. The expansion and contraction allows the wedge 24 to be accurately fitted to the arc tube 12.
The exterior wedge surface is sloped, and the preferred embodiment has a generally conical form, coaxially aligned with the wedge axls 26. In the preferred embodiment, the conical exterior wall 30 also includes coaxial ribs 32 and on each side of each rib 32 are ad~acent troughs 34. The preferred axial ribs 32 extend above the surrounding surface of the conical exterlor wall 30 and thereby act ag the first contact points when the wedge 24 is positioned in and again~t a similarly shaped conical cavity. The troughs 34 are indentations in the conical surface, extending adjacent each rib 32, and having a combined cavity volume approximately equal to the volume of the respectively adjacent extended rib 32. When the ribs 32 are melt fused, the troughs 34 act as reservoirs to receive and retain the 2~3762~
melting wedge material. By way of example ribs 32 are shown as having blade shapes, while the troughs 34 are shown as havlng semicircular cross sections. Other cross sectional configurations where volume of the ribs 32 approximates the volume of the troughs 34 are thought to be acceptable. The troughs 34 may be eliminated from the design, but sealing alignment between the wedge 24 and the retainer 38 is thought to then be less accurately controlled. The ribs 32 also act as energy focusers that determine the first melting points during sonic welding.
FIG. 8 shows a p~rspective view of a retainer 38. FIG.
9 shows an axial cross sectional view of a retainer 38.
FIG. 10 shows a transaxial cross sectional view of a retalner 38. The wedge 24 is designed to fit axially and conformally into the retainer 38. The retainer 38 has a retainer axis 40, a conical interior wall 42 defining a ! conical cavity, and a forward lead passage 46. The cavity defined by the interior wall 42 i8 intended to substantially mate with the exterior wall of the wedge 24. The two surfaces should then be similarly sloped, and have compatible diameters. In the preferred embodiment, the two surfaces are generally conical, with similar slopes. The preferred conical interior wall 42 is coax~al with the retalner axis 40, and is similar to the conical exterior wall 3Q of the wedge 24. In the preferred embodiment, a retainer lip 44 i8 formed at the forward end of the conical interior wall 42. The retainer lip 44 extends slightly into the conical cavity, and extends slightly along the retainer axis 40. The retainer l~p 44 should be relatively small in height, perhaps less than or equal to the height of the axial rib 32 formed on the wedge 24, or less than or equal to one percent of the diameter of the conical cavity where the retainer lip 44 is located. The wedge 24 may then be snugly fitted to the retainer 38 with ribs 32 butted against .

2~7~28 the conical interior wall 42. The ribs 22 also contact the retainer lip 44, but since the retainer is made of a slightly flexible material that is subsequently melted along the interior surface, the retainer lip 44 is not functionally so large as to prevent rib 22 to interior wall 42 contact, and ultimately for exterior wall 30 from contacting interior wall 42. The retainer 38 also includes a forward lead passage 46 that extends from a forward side, through to a rear side of the retainer 38. The forward lead passage 46 may be positioned to be offset from the conical interior wall 42. The exterior surface of the retainer 38 is formed to include an exterior RF ring channel 48. The exterior RF ring channel 48 encircles the retainer 38 in a plane perpendicular to the retainer axis 40, and is located ad~acent where the retainer 38 couples to the base 88. The preferred RF ring channel 48 additionally includes four spreaders 5~ positioned at about equal angles around the retainer axis 40. The exterior limits of the spreaders 50 have greater radial distance from the retainer axis 40 than do the intermediate RF ring channel 48 portions, thereby forming hills and valleys along the RF ring channel 48.
The forward face of the retainer 38 i8 formed to include a ring groove 54. The ring groove 54 may be coaxial with the retainer axis 40, and may have a diameter greater than the smallest diameter of the interior conical wall, and less than the distance from the retainer axis 40 to the forward connector passage. The ring groove 54 is sufficiently deep to mate with and support a vented cover 62 for the arc tu~e 12. The retainer 38 is additionally formed to include a vent passage 56 from an exterior side of the ring groove 54 to an interior side of the ring groove 54.
I~ the preferred embodiment, an first internal step 58 is formed along an outside port~on of the ring groove 54. The rearward depth of the adjacent ring groove 54 is also greater than the remaining portions of the ring groove 54.
A similar second internal step 60 is formed on the adjacent portion of the retainer 38 inside the region enclosed by the ring groove 54, thereby forming a vent passage 56 undercutting the ring groove 54. In the preferred embodiment, the headlamp capsule 10 is operated with the arc tube 12 horizontal. The retainer vent passage 56 is then located at the lowest, rearmost point of the vo~ume enclosed by the vented cover 62. When a vented cover 62 is positloned in the ring groove 54, air can then flow from the exterior, through the vent passage 56 formed under the cover rim 66 of the vented cover 62 positioned in the ring groove 54, and into the region enclosed by the vented cover 62.
A cover rim 66 of a vented cover 62 may be coupled to the forward face of the retainer 38 by being press fitted into the ring groove 54. The vented cover 62 may be made of glass, and may have the same cover rim 66 inside diameter and outside diameter dimensionx as does the rinq groove 54.
The vented cover 62 may be a cylindrical section. The preferred embodiment of the vented cover 62 additionally has a rounded over forward end. The forward end is sufficiently open to allow the forward lead 18 to project through a cover vent 68 to be electrically connected, and sufficiently open to allow a gas flow 69 out from the region enclosed by the vented cover 62, around the forward lead 18. Nonetheless, the vented cover 62 along with the forward seal and the forward lead 18, intercept substantially all sight lines through the cover vent 68 to the arc discharge e~velope 16.
Little or no ultraviolet light may then pass through the cover vent 68 to a viewer. If necessary a metal or glass baffle 96, FIG. 3, may be attached to the forward lead to interrupt sight lines through the cover vent 68.
In an alternative embodiment, the vented cover 64 extends from the forward s~de of the retainer 38 to the 2~9762~
forward seal reqion of the arc tube 12. FIG. 2 shows a cross sectional view of an alternative preferred embodiment of an arc discharge headlamp capsule wherein the seal region protrudes through the vented cover 64. The forward seal region of the arc tube 12, and the forward lead 18 extend forward of the forward most portion of the vented cover 64.
The forward end is sufficiently open to allow the forward seal region and forward lead 18 to project through the cover vent 70, and sufficiently open to allow a gas flow 69 out from the region enclosed by the cover tube, around the forward seal region and the forward lead 18. Again a baffle, like baffle 96, may be attached to interrupt sight lines. The preferred vented cover 64 then has the general form of a test tube with a hole in the bottom with either the forward lead 18 or the forward seal region poking through the hole.
In a further, less preferred, alternative, the base passage 56, as an undercut channel around the rim 60 of the vented cover 62 is removed, and a cover hole 74 is formed in vented cover 72 near the holder. FIG. 3 shows a cross sectional view of an alternative preferred embodiment of an arc dlscharge headlamp capsule, wherein a side hole is form~d in the vented cover. Forming a cover hole 74 in the side of a glass tube is not as economic as forming the undercut passage through the holder, but the design would function as an adequate substitute. Similarly, an air passage through the holder to the enclosed volume of the vented cover 62 may be formed. In each deslgn example described, the preferred inlet vent is on the rear or low side of the arc discharge envelope 16, and the preferred outlet vent is on the high or forward side of the arc discharge envelope 16. ~ flow 69 of air can then move through the length of the vented cover, passing by the rear seal region, the arc discharge envelope 16, and the forward 2~97~28 seal re~ion. Air, heated by the discharge tube, is then discharged into the relatively more open, central region of the lamp, as opposed to being discharged against the face of the holder, or in the more tightly contained regions in the rear of a lamp reflector.
The forward connector rod 76 may be any sufficiently stiff and conductive rod for electrically connecting the forward end of the lamp capsule.- The retainer 38, along the forward lead passage 46, fits axially and conformally over the forward connector rod 76. The forward lead 18 is welded to the forward connector rod 76 at a forward weld 78. The forward connector rod 76 is then connected to the electronics package 92.
The forward connector rod 76 passes through an insulating sleeve 82. The insulatin~ sleeve 82 may be made of an insulating ceramic, or glass in the form of long tube.
The retainer 38 may support the insulating sleeve 82 along the rear end 84 portion. In the preferred embodiment, a rear portion of the insulating sleeve 82 is inserted in the forward lead passage 46 of the retainer 38. In the preferred embodiment, the ceramic insulating sleeve 82 has a loose fitting clearance f$t to retainer 38. The loose fit prevents the sleeve from being stressed and fractured if bumped slightly. The retainer 38 clasps the insulating sleeve 82 at a rear end 84, while the forward connector rod 76 is substantially enclo~ed in the insulating sleeve 82.
By way of example, insulatlng sleeve 82 i~ shown a~ a long cylindrical tube made of steatite ceramic.
The retainer 38 is encircled in the exterior qroove by an RF ring 86. The RF ring 86 may be formed from a metal, and therefore sub~ect to radio frequency ~RF) radiation heating. When positioned to contact the retainer 38 in the exterior RF rin~ channel 48, the RF ring 86 can be fused to a plastic that melts when in contact with a heated metal.

The preferred RF ring 86 is a coil of springy metal wire. A
coil of two or three turns has been found to be sufficient.
By way of example, RF ring 86 is shown as a two turn coil of stainless steel. Other suitable RF ring configurations are thought to be applicable.
The retainer 38 is held in the base 88. The base 88 may be formed with a cylindrical interior wall 90 having nearly the same diameter as the exterior spherical section wall 52 of the retainer 38. Welded to the rear end of the forward connector rod 76 is a electronics package 92. The electronics package 92 may include controls for some or all of the circuitry for startlng and sustaining the arc discharge. The rear lead 20 is also connected to the electronics control package 92.
Coupled to the base 88, enclosing the electronics package 92 may be a cover 94. The preferred base 88 is additionally formed with exterior surface features for aligning, sealing, and locking the lamp capsule in place in a lamp receptacle. Surface features, such as a bayonet mount ring, O-ring seal, lock ring and so forth, are felt to be features of common sklll subject to a particular designer's preference.
An arc discharge lamp capsule may be assembled by first forming a double ended arc tube 12 with a forward lead 18 extending from one end, and a rear lead 20 protrudinq from an opposite second end. A retainer 38 is positioned around the rear end 22 of the tube. The rear end 22 of the capsule ~s threaded through a wedge 24. Since the wedge 24 is slightly flexible, the wedge 24 may be opened by expanding the gap adjacent the split wall 24. The diameter of the interior cylindrical passage may then be expanded slightly, if needed. Similarly, the split gap may be closed slightly, and the interior cylindrical passage may be narrowed. The arc tube 12, and wedge 24 fit may then be adjusted to accommodate any manufacturing variances. The wedge 24 is advanced along the tube until the wedge 24 exterior ribs 32 butt against the conical interior wall 42 and retainer lip 44. The vented cover 62 is placed over the forward end of the arc tube 12 and advanced to mate with the ring groove 54 formed on the face of the retainer 38. The retainer 38 and vented cover 62 may be held together by a tight compression fit, or by epoxy. The forward lead 18 extends forward of the forwardmost portion of the vented cover 62. An insulating sleeve 82 is inserted into the retainer 38's forward lead passaqe 46, and a forward connector rod 76 is slipped through the insulating sleeve 82 to leave a forward end ad~acent the forward lead 18, while a rear end 84 of the connector rod 76 extends out the rear side of the retainer 38. The forward lead 18 and forward connector rod 76 are then welded together to mechanically hold the forward end of the arc tube 12, and electrically connect the forward lead 18. Substantially all of the forward connector rod 76 is then positioned outside of the vented cover 62, and is further enclosed in the insulating sleeve 82. In the present design, the forward connector rod is separated from the inner capsule by the vented cover 62, which acts as a first electric insulator, and the insulating sleeve, a second insulator. Slnce the forward lead is positioned outside of the vented cover 62, the insulating air gap between the input and output leads can be made larger, further increasing the lead insulation. A metal or glass baffle 94 may be attached to the end of the forward lead.
The arc tube 12, and wedge 24 coupling is adjusted as the wedge 24 mates with the retainer 38. The wedge 24 then places a small, and broadly distributed clamping stres~ on the arc tube 12. The mechanical stress on the arc tube 12 ~s then small, and unlikely to cause fracture of the arc tube 12. Additionally, the thermal contact between the arc 2~97~28 tube 12, and wedge 24 is similar, if not effectively equal, from one lamp assembly to the next. The wed~e 24 and retainer 38 are then sonically welded together to hold the accuracy of the fitted clamping permanently. The enerqy directing ribs 32 melt, and fuse with the adjacent conical interior wall 42, and retainer lip 44. Excess material from the melting ribs 32 runs off into the adjacent troughs 34 allowing the conical exterior wall 30 to fit precisely against the conical interior wall 42. The wedge 24 and retainer 38 are then firmly, and precisely fixed to each other. The RF ring 86 is then mounted in the exterior RF
ring channel 48. The rear end extension of the forward connector rod 76 and the rear lead 20 are connected to the electronics package 92. The assembly of the arc tube 12, lS wedge 24, retainer 38, forward connector rod 76, insulating sleeve 82, RF ring 86, and electronics package 92 is then inserted in the tubular end of the base 88. The lamp is then lit. The arc tube 12 is then positioned in a preferred location by rotating and pivoting the retainer 38 along the spherlcal section exterior surface 52 with respect to the cylindrical interior wall 90. The rotation and pivotlng motions have relatively small dimensions, perhaps a millimeter at most. With the arc of the arc tube 12 in the preferred position, the RF ring 86 may be heated by a radio frequency power source to fuse the retainer 38 along the spreaders 50 with the heated RF ring 86, and the heated RF
ring 86 similarly fuses to the base 88 alon~ the cylindrical interior wall 90. The arc tube 12 is then fixed properly, and permanently in place. Connecting wires for the electronics package 92 are threaded out through the rear cover 94, and the rear cover 94 is couple to the base 88, around the elec~ronics packsge 92.
In a workln~ example some of the dimensions were approximately as follows: The arc tube was made of quartz 2~97~28 and had a length of about 6.2 centimeters, and a diameter of 6.0 millimeters. The conical wedge was made of a glass filled polyamide-nylon (Amodel A-1133), and had an interior cylindrical wall diameter of 6.0 millimeters. The exterior diameter was 13.08 millimeters, and the overall height was 12.07 millimeters. The wedge had a conical exterior wall with a slope of 15 degrees, and six axial ribs with heights of 0.38 millimeters and 60 degree blade like edges.
Adjacent on each side of each rib was a trough (six ribs, twelve trou~hs) with a semicircular cross section. A six degree qap was formed in the wedge forming an axial split.
The retainer was made of a glass filled polyamide-nylon (Amodel A-1133), and had a conical interior wall with a fifteen degree slope, and a 9.52 millimeter depth. A
retainer lip was formed at the forward end of the conical interior wall that extended into the conical interior 0.00254 millimeters (0.0001 inch), and along the axis 0.000254 millimeters (0.00001 inch~. The retainer also had a forward lead passage, an exterior RF ring channel, four ~preaders positioned equally around the retainer axis. The exterior surface of the retainer had a portion in the form of a spherical section having a diameter of 22.22 millimeters. The forward face of the retainer was formed to include a circular ring groove axially centered with a diameter of 15.0 millimeter3, a ring width of l.S
millimeters, and a depth of S.0 millimeters. An undercut passage was formed along the ring groove diametrically opposite the forward connector passage, so as to receive an inflow of air from beneath the vented cover. The vented cover was made of glass, and had a diameter of lS.0 millimeters, a wall thickness of l.S millimeters, and a length of 20.0 millimeters. The forward end of the vented cover was rounded over, and had a vent passage of 6.0 millimeters axially centered. The forward connector rod was 2Q~28 made of nickel plated steel, and had a forward weld to the forward lead, a rear weld to the first connector. The lnsulating slee~e was made of a ceramic (steatite), and was about 4.8 centimeters lonq, and had about a 2.0 millimeter outer diameter, and a 1.0 millimeter inside diameter. The RF ring was made of 1.27 millimeter (0.05 inch) stainless steel wire formed in a 19.43 millimeter (0.765 inch) diameter coil of two and a quarter turns. The base was made of a glass filled polysulfone (Mindel) plastic. A
positioning and mounting ring was formed on the exterior of the base. The disclosed dimensions, configurations and embodiments are as examples only, and other suitable configurations and relations may be used to implement the invention.
While there have been shown and described what are at present considered to be the preferred embodiments of the invention, it will be apparent to those skilled in the art that various changes and modifications can be made herein without departing from the scope of the invention defined by the appended claims. A multiplicity of undercu~ passagesor holes through the vented cover may be formed. Other means for coupling the retainer to the base may be positioned in the ring channel, including epoxy, and spring clips.

Claims (10)

Claims What is claimed is:

1. A vented arc discharge headlamp capsule comprising:
a) an arc discharge tube having a forward end with a forward lead, and a rear end with a rear lead, b) a holder supporting the arc discharge tube, having a vent passage formed therein leading from an exterior opening to an interior opening, c) a vented cover made of a light transmissive material coupled to the base, extending around and substantially enclosing the arc discharge envelope and the interior opening of the base vent passage, coupled to the holder, and having a vent passage to allow air flow from the volume enclosed by the vent cover to the exterior, d) means for electrically connecting the forward lead, and e) means for electrically connecting the rear lead.

2. The arc discharge headlamp capsule in claim 1, wherein the holder includes:
a) a wedge having an axis, an interior wall defining an interior passage formed to be conformal with the rear end of the arc tube, and a sloped exterior wall, positioned around the rear end of the arc discharge tube, with the exterior wall sloped away from the forward end of the arc tube, and b) a retainer, having an axis, a sloped interior wall defining a central passage and an interior cavity substantially conformal with the exterior wall of the wedge, positioned around and mated to the wedge to substantially butt the exterior wall of the wedge to the interior wall of the retainer.

3. The arc discharge headlamp capsule in claim 1, wherein the vented cover extends to enclose the entire arc discharge capsule.

4. The arc discharge headlamp capsule in claim 1, wherein the vented cover extends to enclose the rear seal, the arc discharge envelope, and a portion of the forward seal.

5. The arc discharge capsule in claim 1, wherein the forward lead is coupled to a support rod that extends on an exterior side of the vented cover and rearward through the retainer.

6. The arc discharge capsule in claim 1, wherein the exterior wall of the wedge has a generally conical form.

7. The arc discharge capsule in claim 1, further including a baffle positioned adjacent the forward vent opening formed in the vented cover, and exending to substaintially interrupt forward sight lines through the vent opening.

8. An arc discharge headlamp capsule comprising:
a) an arc discharge tube having a forward end with a forward lead, and a rear end with a rear lead, b) a wedge having an axis, a interior wall defining an interior passage formed to be conformal with the rear end of the arc tube, and a substantially conical exterior wall, positioned around the rear end of the arc discharge tube, with the exterior wall sloped away from the forward end of the arc tube, having a plurality of axial ribs formed on the exterior wall, and adjacent each of the axial ribs is a trough, an axial split wall joining the interior wall to the exterior wall thereby forming a expansion gap allowing expansion and contraction of the interior passage c) a retainer, having an axis, a sloped interior wall defining a central passage and an interior cavity substantially conformal with the exterior wall of the wedge, positioned around and mated to the wedge to substantially butt the exterior wall of the wedge to the interior wall of the retainer, a portion of the exterior surface of the retainer adjacent the base has the form of a section of a sphere, and adjacent the spherical surface portion, the exterior surface of the retainer is also form to a define a ring channel extending around the retainer axis, d) a metal ring positioned in the ring channel of the retainer, fused in at least one first place to the retainer, and fused in at least one second place to a base, e) a base supporting the retainer, exterior opening to an interior opening, f) a vented cover made of a light transmissive material coupled to the base, extending around and substantially enclosing the arc discharge envelope and the interior opening of the base vent passage, and having a vent passage to allow air flow from the volume enclosed by the vent cover to the exterior, g) means for electrically connecting the forward lead, and h) means for electrically connecting the rear lead.

9. A vented arc discharge headlamp capsule comprising:
a) an arc discharge tube having a forward end with a forward lead, and a rear end with a rear lead, b) a holder supporting the arc discharge tube, c) a vented cover made of a light transmissive material coupled to the base, extending around and substantially enclosing the arc discharge envelope having a first vent passage adjacent the holder leading from an exterior side of the vent cover to an interior side of the vent cover, the vent cover being coupled to the holder, and having a second vent passage to allow air flow from the volume enclosed by the vent cover to the exterior, with the forward lead extending through the second vent passage, d) means for electrically connecting the forward lead, and e) means for electrically connecting the rear lead.

10. Each and every novel feature or novel combination of features herein disclosed.