EP0867914A1 - Mercury vapour discharge lamp including an amalgam - Google Patents
Mercury vapour discharge lamp including an amalgam Download PDFInfo
- Publication number
- EP0867914A1 EP0867914A1 EP98302183A EP98302183A EP0867914A1 EP 0867914 A1 EP0867914 A1 EP 0867914A1 EP 98302183 A EP98302183 A EP 98302183A EP 98302183 A EP98302183 A EP 98302183A EP 0867914 A1 EP0867914 A1 EP 0867914A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- lamp
- mercury
- vapour pressure
- amalgam
- temperature
- 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
Images
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J61/00—Gas-discharge or vapour-discharge lamps
- H01J61/02—Details
- H01J61/12—Selection of substances for gas fillings; Specified operating pressure or temperature
- H01J61/18—Selection of substances for gas fillings; Specified operating pressure or temperature having a metallic vapour as the principal constituent
- H01J61/20—Selection of substances for gas fillings; Specified operating pressure or temperature having a metallic vapour as the principal constituent mercury vapour
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C7/00—Alloys based on mercury
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J61/00—Gas-discharge or vapour-discharge lamps
- H01J61/02—Details
- H01J61/24—Means for obtaining or maintaining the desired pressure within the vessel
- H01J61/28—Means for producing, introducing, or replenishing gas or vapour during operation of the lamp
Definitions
- This invention relates to gas discharge lamps, and in particular to fluorescent lamps employing a mercury low pressure discharge.
- the invention is useful with both electroded and electrodeless discharge lamps but is particularly applicable to compact electrodeless fluorescent discharge lamps.
- the resonance radiation of mercury has a wavelength of 253.7 nm which, in a fluorescent lamp, is converted to visible light on striking phosphors coating the inside of the envelope of the lamp.
- the efficacy of the lamp that is the ratio of the visible light power output to the electrical power input, is dependent to a large degree on the vapour pressure of the mercury within the lamp, the optimum pressure being approximately 0.8 Pa.
- the vapour pressure is determined by the lowest temperature within the lamp, the lamp's cold spot, the optimum vapour pressure being obtained when the cold spot is approximately 40°C.
- Such lamps and their fixtures are therefore designed so that during operation at normal ambient temperatures the cold spot is at the design temperature of about 40°C.
- an amalgam can provide a stable region in which the vapour pressure of the mercury is relatively insensitive to changes in temperature.
- a discussion of this effect can be read in an article by J Bloem et al., Journal of the Illuminating Engineering Society, April 1977, pages 141-146 entitled "Some New Mercury Alloys For Use in Fluorescent Lamps".
- the amalgam is formulated such that the stable region corresponds to a mercury vapour pressure of about 0.8 Pa, the amalgam being positioned such that the amalgam is heated within a range of temperatures during operation which corresponds to the region of stable mercury vapour pressure.
- Such amalgams have proved to be particularly useful with compact mercury discharge fluorescent lamps which have a relatively high power density associated with correspondingly higher operating temperatures.
- Discharge lamps generally operate in the arc discharge region which has a steeply negative voltage/current characteristic and such lamps have to employ a ballast component to prevent current runaway.
- the supply voltage must be kept above a maintenance voltage below which the operation of the lamp will become unstable and the discharge may be extinguished.
- Usual designs allow a maximum of about a 15% drop in the supply voltage before such extinction occurs.
- the stabilisation of the vapour pressure with temperature by the amalgam further reduces the degree of dimming that can be obtained by reducing the power input to the lamp.
- the present invention seeks to provide a mercury discharge fluorescent lamp having enhanced dimming characteristics. Accordingly, the present invention provides a mercury discharge lamp which includes an amalgam for controlling the mercury vapour pressure within the lamp, the amalgam being selected and positioned within the lamp to provide a substantially optimum vapour pressure of mercury at the temperature of the amalgam corresponding to the maximum rated operating power of the lamp, the optimum vapour pressure being close to a minimum at said temperature, and adjacent a region of steeply rising mercury vapour pressure with falling temperature, such that a reduction in the operating power of the lamp causes a fall in temperature and hence an increase in the vapour pressure of the mercury to effect dimming of the lamp.
- a rate of increase of mercury vapour pressure in the range 0.1 to 0.5 Pa per degree Centigrade fall in temperature is sustained over a temperature range appropriate to the level of dimming required and tailored to the thermal characteristics of the lamp to effect dimming of the lamp.
- Figure 1 shows the variation of mercury vapour pressure above a typical amalgam as a function of temperature.
- the amalgam is selected such that the maximum A is at or near the optimum operating pressure for a mercury discharge lamp of 0.8 Pa.
- the lamp is then designed such that the amalgam is positioned within the lamp so that when it is operating at its rated input power the amalgam is heated to the temperature T A corresponding to the desired operating mercury vapour pressure.
- this provides relatively stable operation of the lamp as the vapour pressure is relatively insensitive to changes in temperature of the amalgam.
- the amalgam is selected such that the minimum B corresponds to the optimum operating pressure of 0.8 Pa and the amalgam is suitably positioned within the lamp so that it is near the corresponding operating temperature T B , corresponding to this optimum pressure, during operation of the lamp.
- the mercury vapour pressure is more sensitive to temperature changes of the amalgam and in particular to reduction in its temperature. Reducing the operating temperature of the amalgam by a small amount results in a relatively large increase in the mercury vapour pressure as compared to that obtainable with comparable temperature drops in the prior art lamps and hence provides enhanced dimming over previously known lamps.
- the present invention is applicable to both electroded and electrodeless fluorescent lamps and in particular to compact fluorescent lamps.
- the amalgam can be located near the cathode at the point which reaches the desired operating temperature TB because of the heated cathode. Reducing power to the lamp reduces the temperature of the amalgam and so results in the required dimming of the lamp. For an electrodeless fluorescent lamp this is of particular significance as a large power reduction will lead to extinction of the lamp.
- the local minimum, B, of the mercury vapour pressure to which the amalgam is heated during full rated operation of the lamp has a region of mercury vapour pressure stability bordered by a steeply rising vapour pressure with falling temperature.
- This rising vapour pressure with falling temperature is preferably in the range 0.1 to 0.5 Pa per degree Centigrade, and optimally is approximately 0.28 Pa per degree Centigrade. This characteristic can be achieved, in general by reducing the proportion of mercury in the lamp relative to the quantity of the base alloy.
- the proportion of the mercury to the base alloy is less than about 1 atomic percent. This allows an amalgam to be selected which has a minimum in the mercury vapour pressure curve near the desired optimum pressure with fine tuning of the minimum obtained by adjusting the atomic percent of mercury relative to the base alloy.
- a further advantage of the present invention is that the preferred low percentage of mercury reduces the potential adverse environmental impact of such lamps once their useful life is finished.
- Figure 2 in the upper curve, marked “New Invention”, shows the pressure/temperature diagram of an example using the amalgam Pb 0.47 Sn 0.47 Ag 0.06 with 0.2 atomic percent Hg. That amalgam has a region of stability C around the optimum vapour pressure of mercury of 0.8 Pa over the temperature range 170 to 240°C. This amalgam is useful, for example, in electrodeless fluorescent lamps where the operating temperature is in that range.
- the temperature of the amalgam enters the region of steeply changing mercury vapour pressure, zone D.
- the vapour pressure of mercury in zone D increases steeply with reducing temperature resulting in dimming of the lamp.
- the amalgam is suitable for providing dimming by virtue of its pressure/temperature characteristic. This amalgam produces in zone D a 40% to 50% dimming for a reduction of 5 to 6 watts in a 23 watt fluorescent lamp.
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Discharge Lamp (AREA)
Abstract
Description
Although not essential to the operation of the present invention, it is preferable that the proportion of the mercury to the base alloy is less than about 1 atomic percent. This allows an amalgam to be selected which has a minimum in the mercury vapour pressure curve near the desired optimum pressure with fine tuning of the minimum obtained by adjusting the atomic percent of mercury relative to the base alloy.
Claims (6)
- A mercury discharge lamp including an amalgam for controlling the mercury vapour pressure within the lamp, the amalgam being selected and positioned within the lamp to provide a substantially optimum vapour pressure of mercury at the temperature of the amalgam corresponding to the maximum rated operating power of the lamp, the optimum vapour pressure being close to a minimum at said temperature, and adjacent a region of steeply rising mercury vapour pressure with falling temperature, such that a reduction in the operating power of the lamp causes a fall in temperature and hence an increase in the vapour pressure of the mercury to effect dimming of the lamp.
- A mercury discharge lamp including an amalgam for controlling the mercury vapour pressure within the lamp, the amalgam being selected and positioned within the lamp to provide a substantially optimum vapour pressure of mercury at the temperature of the amalgam corresponding to the maximum rated operating power of the lamp, the optimum vapour pressure being close to a minimum at said temperature, and adjacent a region of steeply rising mercury vapour pressure with falling temperature, such that a reduction in the operating power of the lamp causes a fall in temperature and hence a rate of increase of mercury vapour pressure in the range 0.1 to 0.5 Pa per degree Centigrade fall in temperature sustained over a temperature range appropriate to the level of dimming required and tailored to the thermal characteristics of the lamp to effect dimming of the lamp.
- A mercury discharge lamp as claimed in Claim 2 wherein said rate of increase of mercury vapour pressure is approximately 0.28 Pa per degree Centigrade.
- A mercury discharge lamp as claimed in any one of Claims 1 to 3 in which the concentration of mercury in the lamp relative to the parent alloy of the amalgam is less than 1 atomic percent.
- A mercury discharge lamp as claimed in any one of Claims 1 to 4, the lamp being an electroded lamp.
- A mercury discharge lamp as claimed in any one of Claims 1 to 4, the lamp being an electrodeless lamp.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB9706399A GB2323701A (en) | 1997-03-27 | 1997-03-27 | Gas discharge lamp |
GB9706399 | 1997-03-27 |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0867914A1 true EP0867914A1 (en) | 1998-09-30 |
EP0867914B1 EP0867914B1 (en) | 2000-09-20 |
Family
ID=10809978
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP19980302183 Expired - Lifetime EP0867914B1 (en) | 1997-03-27 | 1998-03-24 | Mercury vapour discharge lamp including an amalgam |
Country Status (4)
Country | Link |
---|---|
EP (1) | EP0867914B1 (en) |
JP (1) | JPH113681A (en) |
DE (1) | DE69800314T2 (en) |
GB (1) | GB2323701A (en) |
Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5598069A (en) * | 1993-09-30 | 1997-01-28 | Diablo Research Corporation | Amalgam system for electrodeless discharge lamp |
WO1997013000A1 (en) * | 1995-10-05 | 1997-04-10 | General Electric Company | Amalgam for use in fluorescent lamps comprising lead, tin, mercury together with another of the group silver, magnesium, copper, nickel, gold and platinum |
Family Cites Families (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
NL8400756A (en) * | 1984-03-09 | 1985-10-01 | Philips Nv | LOW-PRESSURE MERCURY DISCHARGE LAMP. |
NL8702123A (en) * | 1987-09-08 | 1989-04-03 | Philips Nv | LOW-PRESSURE MERCURY DISCHARGE LAMP. |
US5204584A (en) * | 1990-09-28 | 1993-04-20 | Toshiba Lighting & Technology Corporation | Low pressure mercury vapor discharge lamp |
-
1997
- 1997-03-27 GB GB9706399A patent/GB2323701A/en not_active Withdrawn
-
1998
- 1998-03-19 JP JP6917598A patent/JPH113681A/en not_active Withdrawn
- 1998-03-24 EP EP19980302183 patent/EP0867914B1/en not_active Expired - Lifetime
- 1998-03-24 DE DE1998600314 patent/DE69800314T2/en not_active Expired - Fee Related
Patent Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5598069A (en) * | 1993-09-30 | 1997-01-28 | Diablo Research Corporation | Amalgam system for electrodeless discharge lamp |
WO1997013000A1 (en) * | 1995-10-05 | 1997-04-10 | General Electric Company | Amalgam for use in fluorescent lamps comprising lead, tin, mercury together with another of the group silver, magnesium, copper, nickel, gold and platinum |
Non-Patent Citations (1)
Title |
---|
BLOEM J ET AL: "SOME NEW MERCURY ALLOYS FOR USE IN FLUORESCENT LAMPS", JOURNAL OF THE ILLUMINATING ENGINEERING SOCIETY, vol. 6, no. 3, April 1977 (1977-04-01), pages 141 - 147, XP000615021 * |
Also Published As
Publication number | Publication date |
---|---|
GB9706399D0 (en) | 1997-05-14 |
DE69800314D1 (en) | 2000-10-26 |
DE69800314T2 (en) | 2001-04-26 |
EP0867914B1 (en) | 2000-09-20 |
GB2323701A (en) | 1998-09-30 |
JPH113681A (en) | 1999-01-06 |
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