GB2028573A - Improvements in or relating to discharge lamps - Google Patents
Improvements in or relating to discharge lamps Download PDFInfo
- Publication number
- GB2028573A GB2028573A GB7833208A GB7833208A GB2028573A GB 2028573 A GB2028573 A GB 2028573A GB 7833208 A GB7833208 A GB 7833208A GB 7833208 A GB7833208 A GB 7833208A GB 2028573 A GB2028573 A GB 2028573A
- Authority
- GB
- United Kingdom
- Prior art keywords
- discharge
- discharge tube
- bimetallic
- strip
- discharge lamp
- 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.)
- Withdrawn
Links
- 229910001507 metal halide Inorganic materials 0.000 claims abstract description 5
- 150000005309 metal halides Chemical class 0.000 claims abstract description 5
- 238000010891 electric arc Methods 0.000 claims description 2
- 101100313377 Caenorhabditis elegans stip-1 gene Proteins 0.000 claims 1
- 101100313382 Dictyostelium discoideum stip-2 gene Proteins 0.000 claims 1
- 101100516335 Rattus norvegicus Necab1 gene Proteins 0.000 claims 1
- 101150059016 TFIP11 gene Proteins 0.000 claims 1
- 239000000463 material Substances 0.000 abstract description 2
- 239000011521 glass Substances 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 2
- 239000011248 coating agent Substances 0.000 description 2
- 238000000576 coating method Methods 0.000 description 2
- 239000000470 constituent Substances 0.000 description 2
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 229910052792 caesium Inorganic materials 0.000 description 1
- TVFDJXOCXUVLDH-UHFFFAOYSA-N caesium atom Chemical compound [Cs] TVFDJXOCXUVLDH-UHFFFAOYSA-N 0.000 description 1
- 210000000078 claw Anatomy 0.000 description 1
- 230000001447 compensatory effect Effects 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000006073 displacement reaction Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 238000007689 inspection Methods 0.000 description 1
- QSHDDOUJBYECFT-UHFFFAOYSA-N mercury Chemical compound [Hg] QSHDDOUJBYECFT-UHFFFAOYSA-N 0.000 description 1
- 229910052753 mercury Inorganic materials 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 239000010453 quartz Substances 0.000 description 1
- 229910052706 scandium Inorganic materials 0.000 description 1
- SIXSYDAISGFNSX-UHFFFAOYSA-N scandium atom Chemical compound [Sc] SIXSYDAISGFNSX-UHFFFAOYSA-N 0.000 description 1
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 1
- 229910052708 sodium Inorganic materials 0.000 description 1
- 239000011734 sodium Substances 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J61/00—Gas-discharge or vapour-discharge lamps
- H01J61/02—Details
- H01J61/54—Igniting arrangements, e.g. promoting ionisation for starting
- H01J61/541—Igniting arrangements, e.g. promoting ionisation for starting using a bimetal switch
Landscapes
- Vessels And Coating Films For Discharge Lamps (AREA)
Abstract
In a metal halide discharge lamp having two main discharge electrodes and one auxiliary starting electrode mounted in a discharge tube 10 and a bimetallic switch to keep the auxiliary electrode disconnected from both of the main electrodes while the discharge lamp is operating at its normal operating temperature, the bimetallic switch comprises a strip of bimetallic material 23 which is fixed at one end, close to the discharge tube 10, to a metallic frame 16 which supports the discharge tube 10 inside the outer envelope 14 and which extends to engage one of the terminals 18 adjacent the seal 17. As shown the strip 23 has a portion 24 near its end remote from the discharge tube 10 which is folded to extend transversely of the remainder of the strip. When closed, the switch connects current-limiting resistor 22 via frame 16 to the terminal 18. <IMAGE>
Description
SPECIFICATION
Improvements in or relating to discharge lamps
Lamps
The invention relates to metal halide discharge lamps and in particular to bimetallic switcher for use in such lamps.
Our patent specification number 1 343 780 discloses the use of a bimetallic switch in a metal halide discharge lamp having two main discharge electrodes and one auxiliary starting electrode adjacent one of the main electrodes. The bimetallic switch is arranged to keep the auxiliary electrode disconnected from both the main electrodes while the discharge tube is operating at its normal operating temperature. When the discharge tube is initially switched on, the bimetallic switch is closed and connects the auxiliary electrode through a current-limiting resistor to the main electrode which is remote from the auxiliary electrode.
According to the invention there is provided a metal halide discharge lamp comprising an arc discharge tube with main discharge electrodes and an auxiliary starting electrode and an outer envelope within which the discharge tube is supported, the outer envelope having a seal region through which pass two terminal leads which are connected to respective main electrodes of the lamp and one of which is connected by way of a current-limiting resistor and a bimetallic switch to the auxiliary electrode, wherein the bimetallic switch comprises a bimetallic strip fixed at one end close to the discharge tube and extending to engage the said one terminal lead close to its point of entry into the envelope through the seal region.
The invention will be further described by way
of example and with reference to the
accompanying drawings in which:
Fig. 1 is a view of a discharge lamp embodying the invention.
Fig. 2 is a side view of the switch of the lamp shown in Fig. 1.
Referring to the drawings, a discharge lamp comprises a quartz discharge tube 10 having two
main discharge electrodes and one auxiliary
starting electrode (not shown in the drawings), the
main electrodes being at opposite ends of the
discharge tube 10 and the auxiliary electrode
being adjacent one of the main electrodes. The filling in the discharge tube 10 has the following constituents in the ranges given: Mercury 20 to 1 50 milligrams
Sodium lodide 10 to 60 milligrams
Scandium lodide 2 to 25 milligrams
Caesium lodide 1.0 to 10 milligrams
Argon gas filling at pressure 10 to 100 torr.
In operation the estimated pressure within the discharge tube 10 is approximately within the range 3 to -6 atmospheres. It will be appreciated that the details of the filling of the discharge tube 1 0 refer to one of many examples of discharge lamps embodying the invention. Further optional constituents of the discharge tube filling are given in our co-pending application number 34471/76.
The discharge tube 10 is supported inside an outer envelope of porosilicate glass 14 by two metallic frames 1 5 and 16, the space between the outer envelope and the discharge tube being filled with nitrogen. Connecting leads 11 and 12 for the main electrodes, and a connecting lead 1 3 for the auxiliary electrode, extend from the discharge tube 10. A glass flared stem tube 1 7 seals the outer envelope 14 and supports two power input terminal leads 18 and 19 which are connected by wires 20 and 21 to the leads 11 and 12 of the main electrodes. The metallic frame 16 is mounted on a metallic collar 25 arranged around the barrel of the glass flared stem tube 1 7, and supports the discharge tube 10 by gripping the pinched region at one end of the tube.The outer frame 1 5 grips the pinched region at the outer end of the discharge tube 10 and has a claw arrangement which grips a dimple 27 in the outer envelope 14. A connector cap 26 covers the join between the flared portion of the stem tube 1 7 and the outer envelope 14, and enables connections to be made to the terminal leads 18 and 19.
A current-limiting resistor 22 is connected at one end to the auxiliary electrode lead 13 and at the other end to one of the metallic frames 16. A thermal switch comprises a strip of bimetallic material 23 mounted at one end on the metallic frame 16, the frame 16 completing the electrical circuit between the strip 23 and the resistor 22.
The strip 23 extends from its mounting on the metallic frame 16 in a direction away from the discharge tube 1 0. The strip 23 is folded near the end remote from the mounting such that a portion 24 of the strip extends transversely of the remainder. The portion 24 of the strip can engage the power input terminal lead 18 which is connected to the main electrode remote from the auxiliary electrode.
When starting the lamp the thermal switch is in the closed position ie. with the portion 24 of the bimetallic strip 23 in contact with the terminal lead 1 8, and the auxiliary electrode is thus connected to the power supply and functions normally. At some later time when the temperature of the lamp has increased the bimetallic strip 23 bends and contact between the portion 24 of the strip and the terminal lead 1 8 is broken. The auxiliary electrode ceases to function and discharge continues between the main electrodes. The thermal switch can be such as to open and close at substantially the same temperature.
In Fig. 2 the open position of the strip 23 is shown by a broken line.
The arrangement of thermal switch described above has several advantages over other proposed switch arrangements. The bimetallic strip 23 extends away from the discharge tube 10 and so experiences a temperature gradient along its length. The end of the strip 23 which is nearest the discharge tube 10 gets substantially hotter than the end remote from the tube, and so the strip 23 does not bend uniformly as its temperature increases. The portion of the strip near the tube undergoes most distortion and this results in a large displacement of the end of the strip remote from the discharge tube. This in turn results in a rapid making or breaking of contact with the terminal lead 1 8 at a specific temperature.
When the switch is in the closed position changes in ambient temperature have little effect on the contact pressure developed between the strip 23 and the terminal lead 1 8 because, for a given change in temperature, the portion 24 of the strip and the remainder of the strip bend in opposite directions. This compensatory effect does not significantly influence the making or breaking of contact when the lamp is in use because this depends on the high temperature developed at one end of the strip as described above.
Discharge lamps constructed according to the invention are cheaper to produce than known designs of lamps which have an insulated bridge mounted on the lower metallic frame to supDort a terminal lead in a position where it can make contact with a bimetallic strip mounted on the auxiliary electrode lead. The operation of the switch can be observed through the portion of the outer envelope 14 near the connector cap 26, where the envelope is not covered by a phosphor coating. Inspection of the switch in the earlier types of lamp was prevented by the phosphor
coating because the bimetallic strip did not extend to near the connector cap.
The advantageous features described above
result in improved reliability of the discharge
lamps embodying the invention compared with
the earlier designs.
In some circumstances, typically where the
lamp is operated in or around the vertical cap-up
position inside an enclosure, the bimetal switch
may attain a sufficient temperature to cause it to
engage the outer bulb. This is beneficial, since in
alternative constructions which do not embody
this feature the switch pressure in the 'cold' condition may be reduced after repeated cycles under such conditions. In the present case the bimetal movement is restrained, thus ensuring that good 'cold' contact pressure is maintained between the strip and terminal lead 18 throughout the life of the lamp.
Claims (7)
1. A metal halide discharge lamp comprising an arc discharge tube with main discharge electrodes and an auxiliary starting electrode and an outer envelope within which the discharge tube is supported, the outer envelope having a seal region through which pass two terminal leads which are connected to respective main electrodes of the lamp and one of which is connected by way of a current-limiting resistor and a bimetallic switch to the auxiliary electrode, wherein the bimetallic switch comprises a bimetallic strip fixed at one end close to the discharge tube and extending to engage the said one terminal lead close to its point of entry into the envelope through the seal region.
2. A discharge lamp according to claim 1, wherein the bimetallic strip is fixed at the said one end to a metallic frame which supports the discharge tube inside the outer envelope of the discharge lamp.
3. A discharge lamp according to claim 1 or 2, wherein the bimetallic strip is folded near the-end remote from the discharge tube such that a portion of the stip extends transverely of the remainder and engages the said one terminal lead.
4. A discharge lamp according to claim 2, wherein the said current-limiting resistor is connected between the auxiliary electrode and the metallic frame, the metallic frame providing an electrically-conductive connection between the resistor and the bimetallic strip.
5. A discharge lamp according to any preceding claim, wherein the bimetallic strip can engage the said outer envelope when the lamp is in use and the bimetallic switch is open.
6. A discharge lamp according to any preceding claim wherein the bimetallic switch is such as to open and close at substantially the same temperture.
7. A discharge lamp substantially as hereinbefore described with reference to the accompanying drawings.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB7833208A GB2028573A (en) | 1978-08-14 | 1978-08-14 | Improvements in or relating to discharge lamps |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB7833208A GB2028573A (en) | 1978-08-14 | 1978-08-14 | Improvements in or relating to discharge lamps |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| GB2028573A true GB2028573A (en) | 1980-03-05 |
Family
ID=10499030
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB7833208A Withdrawn GB2028573A (en) | 1978-08-14 | 1978-08-14 | Improvements in or relating to discharge lamps |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2028573A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4963790A (en) * | 1985-12-27 | 1990-10-16 | Gte Products Corporation | Low wattage metal halide discharge lamp |
| EP0547589A1 (en) * | 1991-12-17 | 1993-06-23 | Gte Products Corporation | Compact arc discharge lamp with thermal switch |
-
1978
- 1978-08-14 GB GB7833208A patent/GB2028573A/en not_active Withdrawn
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4963790A (en) * | 1985-12-27 | 1990-10-16 | Gte Products Corporation | Low wattage metal halide discharge lamp |
| EP0547589A1 (en) * | 1991-12-17 | 1993-06-23 | Gte Products Corporation | Compact arc discharge lamp with thermal switch |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |