GB2217105A - Excitation coils for electrodeless lamps - Google Patents
Excitation coils for electrodeless lamps Download PDFInfo
- Publication number
- GB2217105A GB2217105A GB8907565A GB8907565A GB2217105A GB 2217105 A GB2217105 A GB 2217105A GB 8907565 A GB8907565 A GB 8907565A GB 8907565 A GB8907565 A GB 8907565A GB 2217105 A GB2217105 A GB 2217105A
- Authority
- GB
- United Kingdom
- Prior art keywords
- coil
- layer
- conductor
- exterior surface
- fabricated
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- 230000005284 excitation Effects 0.000 title claims description 20
- 239000004020 conductor Substances 0.000 claims description 27
- 239000000463 material Substances 0.000 claims description 17
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 11
- 229910052802 copper Inorganic materials 0.000 claims description 11
- 239000010949 copper Substances 0.000 claims description 11
- TZCXTZWJZNENPQ-UHFFFAOYSA-L barium sulfate Chemical compound [Ba+2].[O-]S([O-])(=O)=O TZCXTZWJZNENPQ-UHFFFAOYSA-L 0.000 claims description 8
- 229910052581 Si3N4 Inorganic materials 0.000 claims description 7
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 claims description 7
- CPLXHLVBOLITMK-UHFFFAOYSA-N Magnesium oxide Chemical compound [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 claims description 6
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 6
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 claims description 6
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 claims description 6
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims description 6
- 229910052709 silver Inorganic materials 0.000 claims description 6
- 239000004332 silver Substances 0.000 claims description 6
- 229910052782 aluminium Inorganic materials 0.000 claims description 5
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 5
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 claims description 3
- 229910052804 chromium Inorganic materials 0.000 claims description 3
- 239000011651 chromium Substances 0.000 claims description 3
- 239000003989 dielectric material Substances 0.000 claims description 3
- 239000000395 magnesium oxide Substances 0.000 claims description 3
- 239000000843 powder Substances 0.000 claims description 3
- 239000000377 silicon dioxide Substances 0.000 claims description 3
- 239000002320 enamel (paints) Substances 0.000 claims description 2
- 230000004936 stimulating effect Effects 0.000 claims description 2
- 239000010410 layer Substances 0.000 description 18
- 239000007787 solid Substances 0.000 description 4
- 230000031700 light absorption Effects 0.000 description 3
- 239000003973 paint Substances 0.000 description 3
- 239000011248 coating agent Substances 0.000 description 2
- 238000000576 coating method Methods 0.000 description 2
- 239000007789 gas Substances 0.000 description 2
- 239000002826 coolant Substances 0.000 description 1
- -1 copper Chemical compound 0.000 description 1
- 230000008878 coupling Effects 0.000 description 1
- 238000010168 coupling process Methods 0.000 description 1
- 238000005859 coupling reaction Methods 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 230000000593 degrading effect Effects 0.000 description 1
- 235000012489 doughnuts Nutrition 0.000 description 1
- 238000010891 electric arc Methods 0.000 description 1
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 1
- 229910052737 gold Inorganic materials 0.000 description 1
- 239000010931 gold Substances 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 238000007747 plating Methods 0.000 description 1
- 230000001681 protective effect Effects 0.000 description 1
- 230000005855 radiation Effects 0.000 description 1
- 230000003595 spectral effect Effects 0.000 description 1
- 239000002344 surface layer Substances 0.000 description 1
- 238000001429 visible spectrum Methods 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J65/00—Lamps without any electrode inside the vessel; Lamps with at least one main electrode outside the vessel
- H01J65/04—Lamps in which a gas filling is excited to luminesce by an external electromagnetic field or by external corpuscular radiation, e.g. for indicating plasma display panels
- H01J65/042—Lamps in which a gas filling is excited to luminesce by an external electromagnetic field or by external corpuscular radiation, e.g. for indicating plasma display panels by an external electromagnetic field
- H01J65/048—Lamps in which a gas filling is excited to luminesce by an external electromagnetic field or by external corpuscular radiation, e.g. for indicating plasma display panels by an external electromagnetic field the field being produced by using an excitation coil
Landscapes
- Physics & Mathematics (AREA)
- Electromagnetism (AREA)
- Engineering & Computer Science (AREA)
- Plasma & Fusion (AREA)
- Discharge Lamps And Accessories Thereof (AREA)
- Circuit Arrangements For Discharge Lamps (AREA)
- Vessels And Coating Films For Discharge Lamps (AREA)
Description
1.
i n n,41 7 105 RD-17,373 EXCITATION COILS FOR HID ELECTRODELESS LAMPS The present invention relates to a coil for exciting a plasma discharge, and, more specifically, to a coil for exciting a visible light-producing plasma in a high-intensity- discharge (HID) electrodeless lamp.
It is now well known that visible light can be produced from a plasma discharge excited by RF current. The RF current is provided by an excitation coil which is generally exterior to the lamp in which the discharge is excited and is coupled to the discharge plasma. It is of prime importance that the excitation coil not only has low RF resistive loss, but also has physical characteristics which allow the majority of the light, released from the plasma discharge, to be utilized and not bp! blocked by the coil itself. Thus, light intercepted by the excitation coil decreases the overall efficacy of the source, so that it is desirable to reduce interception and absorption of light by the excitation coil to as low an amount as possible.
An aspect of the present invention provides a radio frequency (RF) coil for an HID electrodeless lamp, the coil having a stable specular or diffuse reflective surface. The surface permits nearly all of the light generated by the lamp to escape without significant blockage by the coil without degrading under the conditions of operation of the lamp.
In accordance with one embodiment of another aspect, an excitation coil for stimulating a high-intensity-discharge plasma in an electrodeless discharge lamp, comprises: at least one turn of a conductor to be arranged generally external to a cylindrical volume in which the plasma is to be excited; and at least one layer, upon the exterior surface of the coil conductor, of a material having a visible light 1 1 1 1 RD-17.373 reflection factor greater than about 0.85, and preferably as close to 100%, as possible. For excitation coils wound with conductors of copper, aluminum and the like, a thin layer of silicon nitride over an underlying layer of polished silver as a specular reflective layer can be used. A diffuse reflector can be provided by a layer of a barium sulfate, titania, alumina or magnesia powder, alone or with an underlying adhesionincreasing intermediate layer.
In another embodiment, the surface of the conductor, e.g. of copper or aluminum, is polished and a passivating, light transmissive, layer is put on the polished surface. The layer may be of silicon nitride, alumina or silica.
The present invention will be better understood upon reading of the following illustrative description, when considered in conjunction with the drawings in which:
Figure 1 is a somewhat schematic-side view of a HID plasma discharge lamp, a companion RF excitation coil, and an excitation source and useful in appreciation of the environment in which the present invention operates; Figure 2 is a sectional view of a first presently preferred embodiment of reflectively-coated excitation coil in accordance with the principles of the present invention; and Figure 2b is a sectional view of another presently preferred embodiment of reflectively-coated excitation coil in accordance with the principles of the present invention.
Detailed Description of the Invention
Referring initially to Figure 1, a high-intensity discharge (HID) lamp 10 comprises a transparent envelope 11 J i i 1 1 i 1 i J i i RD-17,373 1 enclosing a volume Ila containing a quantity of at least one gas in which a discharge arc plasma 12 is produced responsive to the flow of a radiofrequency (RF) current in an excitation coil 14 positioned beyond the exterior of enve- lope 11. The RF current I rf flow is responsive to an excitation source 16 providing a RF volta.ge V rf between excitation coil ends 14a and 14b. Typically, arc discharge plasma 12 is in the shape of a toroidal ring, or doughnut, in a plane substantially perpendicular to the direction of the magnetic field B induced by excitation coil 14. For proper magnetic coupling between coil 14 and arc 12, arc 12 should intercept as many magnetic lines as possible from the coil, so that the arc 12 will usually be relatively close to coil 14. Therefore, instead of all of the light produced by arc 12 reaching distant locations, some will be intercepted by coil 14 and reduce the overall efficacy of light source 10. It is thus highly desirable to have relatively little light absorption by coil 14. The conductor of coil 14 may be solid or hollow, as the RF current only flows upon the conductor surface, to a depth known as the RF skin depth. For a copper conductor, and at a frequency of about 13.56 MHz. (which is a relatively standard "industrial" frequency at which HID lamps are often operated), the skin depth is about 0.2 millimeter. Because skin depth is so small, the conductor must have as high an electrical conductivity as possible, so that copper is usually utilized, often with a surface layer of silver or gold to reduce RF losses. The optical reflection factor of most such materials is poor, with the possible exception of a polished silver surface.
However, silver and other materials, such as copper, will generally not maintain a well polished surface under exposure to heat, radiation or atmospheric gases. Thus, if coil materials such as copper or silver are utilized, the coil RD-17,373 surface will soon have undesirably large light absorption, or, said in other words, will not initially have, and/or will not maintain, a very high reflectance to at least visible light.
Referring now to Figures 2a and 2b, in accordance.with an embodiment, a specular-or diffused reflective surface is provided upon the exterior surface of an RF excitation coil 14 for a HID electrodeless lamp, by forming thereon at least one layer of a highly reflective material upon the coil surface. A thin layer 18 (Figure 2a) of a passivating, light-transmissive dielectric material, such as alumina, silica, silicon nitride and the like, can, in one presently preferred embodiment, be fabricated directly upon the exterior surface 14s of the conductor of coil 14.
Illustratively, in Figure 2a, a tubular conductor is utilized, with a thin conductive wall 14c and a hollow interior 14d, as might be utilized for carrying a liquid coolant through the coil, to remove heat therein. It should be understood that the coil may be a solid wire, such as the solid conductor 14'c shown in Figure 2b, as long as the surface 14's of the conductor is treated similarly, whatever the cross-sectional shape and characteristics of the RFcurrent-carrying portion of the coil conductor may be. As an example, a coil was formed of a polished aluminum conductor with a thin layer 18 of silicon nitride deposited thereon, and was measured to have a net light reflection -factor of 0.89 (i.e. 89 percent of the total impingent light was reflected from the coated coil conductor).
In another presently preferred embodiment, exem- plified in Figure 2b, the conductor 14'c (which may be a hollow tube or a solid wire, of round, square or other cross-sectional shape) has a first layer 20 formed thereon, for the purpose of protecting the underlying conductor (such i i i 1 i - i j 1 1 1 1 i l> V 1 1 RD-17,373 as a protective plating of chromium, having a thickness of say 1000 angstroms so that the main portion of the RF current is carried in the copper conductor surface) and/or for improving adhesion of an outermost layer 22 to the underlying coil conductor exterior surface 14's. In addition to an outer layer 22 providing a highly reflective specular coating, outer layer 22 can be-of a material forming a diffuse, light- reflective surface. For example, a layer 22 of powdered barium sulfate was applied to a coil 14'c of copper conductor. The barium sulfate was in the form of a paint usually utilized for coating the surface of an integrating sphere, which paint is available as material No. 6080 from Eastman Kodak Co. To increase adhesion of the sphere paint to the copper, a thin layer 20 of matte-finish white enamel paint was utilized. A light reflectance factor of 0.982 was measured. Other diffuse reflecting powders, such as those of titania, alumina, magnesia, and the like, will be stable under atmospheric conditions found in the surroundings of an electrodeless lamp, and can provide the required high reflection of incident light throughout the visible spectrum and into the near ultraviolet and infrared spectral domains.
While several presently preferred variations of a novel reflectivelycoated RF excitation coil for a HID lamp, having a specular or diffused reflective layer upon the exterior surface thereof, have been described by way of example herein, many modifications.and variations willnow become apparent to those skilled in the art. The invention is not intended to be limited by the specific details and instrumentalities presented by way of explanation of the preferred embodiments described herein.
C 1 RD-17,373
Claims (19)
1. An excitation coil, for stimulating a high intensity discharge plasma in an electrodeless discharge lamp, comprising:
at least one turn of a conductor arranged about an imaginary surface defining a volume in which said plasma can be located, said conductor having an exterior surface: and a layer, upon said exterior surface, of a material imparting to the coil a reflection factor greater than about 0.85.
2. The coil of claim 1, wherein the layer has a specular reflective exterior surface.
3. The coil of claim 2, wherein the conductor is fabricated of a material selected from the group consisting of copper and aluminum.
4. The coil of claim 3, wherein the layer material is a passivating and light-transmissive dielectric material.
5. The coil of claim 4, wherein the dielectric material is selected from the group consisting of alumina, silica and silicon nitride.
6. The coil of claim 4, further comprising an intermediate layer of another material, between the conductor exterior surface and the reflective layer.
7. The coil of claim 6, wherein the intermediate layer is fabricated of chromium.
8. The coil of claim 7, wherein the chromium intermediate layer has a thinness of about 1000 Angstroms.
9. The coil of claim 6, wherein the dielectric layer is fabricated of silicon nitride and the intermediate layer is a layer of polished silver fabricated upon the coil exterior surface, under the silicon nitride layer.
fl i i i i 1 I i I J i 1 1 C, 1:
RD- 17, 3 73
10. The coil of claim 1, wherein the layer has a diffuse reflective exterior surface.
11. The coil of claim 10, wherein the conductor is fabricated of a material selected from the group consisting of copper and aluminum.
12. The coil of claim 11, wherein the layer material is selected from the group consisting of barium sulfate, titania, alumina and magnesia.
13. The coil of claim 12, wherein the layer material is a powder.
14. The coil of claim 10, further comprising an intermediate layer of another material, between the conductor exterior surface of the reflective layer.
15. The coil of claim 14, wherein the another material is selected to increase the adhesion of the reflec-. tive layer to the conductor exterior surface.
16. The coil of claim 15, wherein the another material is an enamel paint.
17. A high intensity discharge electrodeless lamp comprising an excitation coil according to any preceding claim.
18. A coil substantially as hereinbefore described with reference to Figure 2 a or 2b.
19. A lamp substantially as hereinbefore described with reference to Figure 1 together with figure 2a or 2b.
Published 1989 at The Patent Office. State House, 6671 HighHolborn, London WCIR 4TP.PurLher copies maybe obtained from The PatentOfftce. Sales Branch, St Mary Cray, Orpington, Kent BR5 3RD. Printed by Multiplex techniques ltd. St Mary Cray, Kent, Con. 1/87
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US17804488A | 1988-04-05 | 1988-04-05 |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB8907565D0 GB8907565D0 (en) | 1989-05-17 |
| GB2217105A true GB2217105A (en) | 1989-10-18 |
| GB2217105B GB2217105B (en) | 1992-11-18 |
Family
ID=22650950
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB8907565A Expired - Lifetime GB2217105B (en) | 1988-04-05 | 1989-04-04 | Hid electrodeless lamps |
Country Status (5)
| Country | Link |
|---|---|
| JP (1) | JPH0212753A (en) |
| DE (1) | DE3910431A1 (en) |
| FR (1) | FR2631740B1 (en) |
| GB (1) | GB2217105B (en) |
| NL (1) | NL191867C (en) |
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0541344A1 (en) * | 1991-11-04 | 1993-05-12 | General Electric Company | Luminaire including an electrodeless discharge lamp as a light source |
| EP0595520A1 (en) * | 1992-10-26 | 1994-05-04 | General Electric Company | Electrodeless fluorescent lamp |
| US5498937A (en) * | 1993-02-16 | 1996-03-12 | U.S. Philips Corporation | Electrodeless high-pressure discharge lamp having coil supports of aluminum nitride supporting individual coil turns |
| US5587226A (en) * | 1993-01-28 | 1996-12-24 | Regents, University Of California | Porcelain-coated antenna for radio-frequency driven plasma source |
| WO2001003476A1 (en) * | 1999-07-02 | 2001-01-11 | Fusion Lighting, Inc. | Inductive electrodeless lamp providing rotating electric field |
| US20130181600A1 (en) * | 2010-09-09 | 2013-07-18 | Wenjun Chen | Inner coupling electrodeless lamp |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5545953A (en) * | 1995-06-16 | 1996-08-13 | Osram Sylvania Inc. | Electrodeless high intensity discharge lamp having field symmetrizing aid |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1265264A (en) * | 1970-02-10 | 1972-03-01 | ||
| EP0207333A1 (en) * | 1985-06-26 | 1987-01-07 | General Electric Company | Electrodeless high pressure sodium iodide arc lamp |
| US4705987A (en) * | 1985-10-03 | 1987-11-10 | The United States Of America As Represented By The United States Department Of Energy | Very high efficacy electrodeless high intensity discharge lamps |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3319119A (en) * | 1965-10-22 | 1967-05-09 | Hewlett Packard Co | Metal vapor spectral lamp with mercury and a metal halide at subatmospheric pressure |
-
1989
- 1989-03-31 FR FR8904240A patent/FR2631740B1/en not_active Expired - Fee Related
- 1989-03-31 DE DE19893910431 patent/DE3910431A1/en active Granted
- 1989-04-04 JP JP8416589A patent/JPH0212753A/en active Pending
- 1989-04-04 NL NL8900824A patent/NL191867C/en not_active IP Right Cessation
- 1989-04-04 GB GB8907565A patent/GB2217105B/en not_active Expired - Lifetime
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1265264A (en) * | 1970-02-10 | 1972-03-01 | ||
| EP0207333A1 (en) * | 1985-06-26 | 1987-01-07 | General Electric Company | Electrodeless high pressure sodium iodide arc lamp |
| US4705987A (en) * | 1985-10-03 | 1987-11-10 | The United States Of America As Represented By The United States Department Of Energy | Very high efficacy electrodeless high intensity discharge lamps |
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0541344A1 (en) * | 1991-11-04 | 1993-05-12 | General Electric Company | Luminaire including an electrodeless discharge lamp as a light source |
| EP0595520A1 (en) * | 1992-10-26 | 1994-05-04 | General Electric Company | Electrodeless fluorescent lamp |
| US5587226A (en) * | 1993-01-28 | 1996-12-24 | Regents, University Of California | Porcelain-coated antenna for radio-frequency driven plasma source |
| US5498937A (en) * | 1993-02-16 | 1996-03-12 | U.S. Philips Corporation | Electrodeless high-pressure discharge lamp having coil supports of aluminum nitride supporting individual coil turns |
| WO2001003476A1 (en) * | 1999-07-02 | 2001-01-11 | Fusion Lighting, Inc. | Inductive electrodeless lamp providing rotating electric field |
| US20130181600A1 (en) * | 2010-09-09 | 2013-07-18 | Wenjun Chen | Inner coupling electrodeless lamp |
Also Published As
| Publication number | Publication date |
|---|---|
| GB8907565D0 (en) | 1989-05-17 |
| FR2631740A1 (en) | 1989-11-24 |
| GB2217105B (en) | 1992-11-18 |
| NL191867B (en) | 1996-05-01 |
| NL8900824A (en) | 1989-11-01 |
| DE3910431C2 (en) | 1991-07-11 |
| DE3910431A1 (en) | 1989-10-19 |
| FR2631740B1 (en) | 1996-01-05 |
| NL191867C (en) | 1996-09-03 |
| JPH0212753A (en) | 1990-01-17 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 19970404 |