Patent EP0074188A2 successfully refreshed from Google Patents.
EP0074188A2
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EP
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High pressure discharge lamps
Assignee: EMI Group Ltd
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Filing: 1982-08-13
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Granted: —
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Expires: 2002-08-13
Abstract
Abstract In a high pressure sodium discharge lamp it has been found that rectification can be prevented by ensuring the amalgam does not make electrical contact with the electrode (17). To achieve this according to the invention a small shoulder member (11) is provided on the inside face of the end wall. Although the small height (1) effectively reduces the temperature differential between the bottom of the shoulder and the top (11a) the necessary differential to prevent the amalgam condensing out the top of the shoulder member is maintained by ensuring the width (W) of the shoulder member is a predetermined minimum thickness.
Inventors
- 👤 Paul Linley Denbigh
- 👤 Richard John Seddon
- 👤 Bryan Frederick Jones
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-09 07:42
CPC Classifications
H; H01; H01J; H01J61/00; H01J61/02; H01J61/04; H01J61/10; H01J61/82; H01J61/825
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
154 words
A high pressure discharge lamp, said lamp including an arc tube of light transmitting ceramic material, the arc tube including an end wall extending radially inwardly from the arc tube wall to define a central aperture, an electrical lead in member sealed within the aperture along the length of said aperture, said lead in member being joined to an electrode shank member carrying an electrode element, said end wall including an inner surface exposed to radiation from the electrode element when the lamp is running, said inner surface including a shoulder member adjacent the central aperture, the height of the shoulder member above the inner surface not being sufficient to substantially shield the inner surface from the electrode element and the width of the shoulder member being such that the temperature differential between the top surface of the shoulder and the inner surface is sufficient to prevent amalgam contacting the electrical lead in member.
Claim 2
Dependent Claim
154 words
A high pressure discharge lamp, said lamp including an arc tube of light transmitting ceramic material, the arc tube including an end wall extending radially inwardly from the arc tube wall to define a central aperture, an electrical lead in member sealed within the aperture along the length of said aperture, said lead in member being joined to an electrode shank member carrying an electrode element, said end wall including an inner surface exposed to radiation from the electrode element when the lamp is running, said inner surface including a shoulder member adjacent the central aperture, the height of the shoulder member above the inner surface not being sufficient to substantially shield the inner surface from the electrode element and the width of the shoulder member being such that the temperature differential between the top surface of the shoulder and the inner surface is sufficient to prevent amalgam contacting the electrical lead in member.
Claim 3
Dependent Claim
21 words
A high pressure discharge lamp according to claim 1 wherein the shoulder member is an integral part of the end wall.
Claim 4
Dependent Claim
32 words
A high pressure discharge lamp according to claim 1 wherein the shoulder member is formed by a part of a top hat shaped member sealed within an aperture in the end wall.
Claim 5
Dependent Claim
23 words
A high pressure discharge lamp according to any preceding claim wherein the width of the shoulder member is between 0.2 and 0.5 mm.
Claim 6
Dependent Claim
23 words
A high pressure discharge lamp according to any preceding claim wherein the length of the shoulder member lies between 1.5 and 4 mm.
Claim 7
Dependent Claim
102 words
A high pressure discharge lamp according to any preceding claim wherein the width of the shoulder member is determined according to the equation: where r = inner radius of shoulder member (m). r 2 = outer radius of shoulder member (m). T 1 = temperature of lower end of shoulder member (°K). T 2 = temperature of upper end of shoulder member (°K). K = thermal conductivity of alumina (assumed 8.8 7 Wm -1 K -1 ). = Stefan's constant (5.67 x 10 -8 Wm -2 K -4 ). = 0.4116 (emissivity of alumina, dimensionless). 1 = length of stepped portion (m).
Claim 8
Dependent Claim
26 words
A high pressure discharge lamp according to claim 1 wherein the height of the shoulder member is 2 mm and the width 'w' is 0.5 mm.
Claim 9
Dependent Claim
22 words
A high pressure discharge lamp according to claim 1 wherein the shoulder member does not screen any part of the electrode element.
Claim 10
Dependent Claim
59 words
A high pressure discharge lamp according to claim 1 wherein the electrical lead in member protrudes past the shoulder member on the side of the end wall exposed to radiation from the electrode element when the lamp is running and the joint between the electrical lead in member and the electrode shank member is made in this discharge space.
Claim 11
Dependent Claim
19 words
A high pressure discharge lamp according to claim 9 wherein the electrical lead in member comprises a niobium tube.
Claim 12
Dependent Claim
18 words
A high pressure discharge lamp according to claim 9 wherein the electrical lead in member comprises niobium wire.
Claim 13
Dependent Claim
20 words
A high pressure discharge lamp according to claim 9 where the electrical lead in member comprises an electrically conducting cermet.
Claim 14
Dependent Claim
16 words
A high pressure discharge lamp according to claim 1 wherein the arc tube comprises polycrystalline alumina.
References Cited (Backward Citations)
No citation records indexed.
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