Low-pressure sodium discharge lamp having a collar-like heat shield

• US 4,808,877 A
• Filed: 09/29/1987
• Issued: 02/28/1989
• Est. Priority Date: 02/15/1985
• Status: Expired due to Fees

• Current Assignee: US Philips Corporation (Koninklijke Philips N.V.)
• Original Assignee: US Philips Corporation (Koninklijke Philips N.V.)
• Inventors: Vervecken, Karel R., Netten, Adriaan
• Primary Examiner(s): Moore, David K.
• Assistant Examiner(s): WIEDER, KENNETH A
• Application Number:
  US07/104,541
• Time in Patent Office: 518 Days
• Field of Search: 313/25, 313/493, 313/492, 313/43, 313/634, 313/623, 313/609, 313/611, 313/612
• US Class Current: 313/25
• CPC Class Codes: H01J 61/34 Double-wall vessels or containers
• CPC Class Codes: H01J 61/523 Heating or cooling particular parts of the lamp
• CPC Class Codes: H01J 61/74 having a main light-emitting filling of difficult vaporisable metal vapour, e.g. sodium

Abstract

The low-pressure sodium discharge lamp according to the invention has a U-shaped discharge tube (1) with seals (4, 5), through which current-supply conductors (6, 7) extend to electrodes (8, 9). A supporting member (14) fixes the discharge tube (1) in an outer bulb (10). Upright collars (18, 19) at the supporting member (14), which surround the seals (4, 5) throughout their lengths, prevent the discharge tube from becoming leaky at high-frequency operation and the lamp from reaching the end of its life prematurely.

Claims

1. A low-pressure sodium discharge lamp comprising:

a U-shaped gas-tight discharge tube having seals at its free ends and a sodium-containing filling,

electrodes arranged in the discharge tube near the free ends between which a discharge is maintained during lamp operation;

a gas-tight outer bulb which is arranged to surround the discharge tube and having a lamp cap;

current-supply conductors extending through the seals and electrically connecting each electrode to the lamp cap; and

a support for the discharge tube comprising a disc-shaped portion having openings through which the seals of the discharge tube extend, and means for fixing the support within the outer bulb, said support comprising at least one collar-like heat shield at least partially surrounding one of said seals for reducing heat loss from said one seal, said heat shield being spaced from said one seal and extending for substantially the length of said one seal.

2. A low-pressure discharge lamp as claimed in claim 1, wherein said support comprises two of said collar-like heat shields, each of which partially surrounds and is spaced from a respective seal.

3. A low-pressure discharge lamp as claimed in claim 1, wherein each of the collar-like heat shields has a U-shaped cross-section with an open end, and said shields are arranged so that the open ends face each other.

4. A low-pressure sodium discharge lamp comprising:

a U-shaped gas-tight discharge tube having seals at its free ends and a sodium-containing filling, electrodes arranged in the discharge tube near the free ends between which a discharge is maintained during lamp operation;

a gas-tight outer bulb which is arranged to surround the discharge tube and having a lamp cap;

current-supply conductors extending through the seals and electrically connecting each electrode to the lamp cap; and

a support for the discharge tube comprising a disk-shaped portion having openings through which the seals of the discharge tube extend, and means for fixing the support within the outer bulb, said support comprising a rim having an outer surface formed at the edge of one of said openings and a collar-like heat shield at least partially surrounding that one of said seals passed through said one opening, said heat shield extending for substantially the length of said one seal and being fixed on the outer surfaces of said rim such that said heat shield is spaced a distance radially from said one seal at least equal to the thickness of said rim for reducing heat loss from said one seal.

5. A low-pressure discharge lamp as claimed in claim 4, wherein

said support member comprises two said rims and two said collar-like heat shields, each of said heat shields being fixed on the outer surfaces of a respective rim.

6. A low-pressure discharge lamp as claimed in claim 5, wherein each of the collar-like heat shields has a U-shaped cross-section with an open end, and said shields are arranged so that the open ends face each other.

9. A lamp as claimed in claim 6, wherein said support and said collar-like heat shields are metallic, and said heat shields are welded to a respective rim.

10. A lamp as claimed in claim 9, wherein said means for fixing said support to said outer bulb comprises a plurality of resilient tongues bearing against said outer bulb.

7. A low-pressure sodium discharge lamp, comprising:

(a) an outer envelope;

(b) a low-pressure discharge device within said outer envelope having a sodium-containing gas filling and seals at its free ends, and a pair of electrodes each being arranged proximate a respective seal;

(c) current-supply conductors which extend through said seals and are connected to a respective electrode; and

(d) means for supporting said discharge device within said outer envelope, a portion of said support means at least partially surrounding each said seal and extending substantially along the length of each said seal, said portion being free of contact with said seals and being effective as a heat shield to reduce the heat loss from said seals so that the normal operating temperature of said seals is increased and the condensation of sodium proximate said seals is suppressed.

8. A lamp as claimed in claim 7 wherein said portion of said support means comprises a collar-like heat shield attached to said support means.

11. A low-pressure sodium discharge lamp, comprising:

a discharge device sealed in a gas tight manner, having a sodium containing filling, and comprising a pair of parallel straight sections having adjacent sealed ends, electrodes arranged in said straight sections proximate said sealed ends, and current-supply conductors each connected to a respective electrode;

an outer envelope having a lamp cap within which said discharge device is arranged, each of said current-supply conductors being connected to a respective portion of said lamp cap;

a metallic support for supporting the discharge tube comprising a planar portion having an opening through which said sealed ends extend, said planar portion being transverse to said straight sections and axially positioned between said sealed ends and said electrodes such that said sealed ends and the major part of said straight sections lie on opposite sides of said planar portion, and a plurality of resilient tongues bearing against said outer envelope for fixing said support with respect to said outer envelope; and

a pair of metallic collar-like shields attached to said support for reducing the heat loss from a respective seal so that the normal operating temperature of said seals is increased and the condensation of sodium proximate said seals is suppressed, each heat shield extending from said support in the direction of said seals away from straight sections and having a U-shaped cross-section with an open end, each heat shield at least partially surrounding its respective seal and extending for substantially the length of its respective seal, and said heat-shields being arranged with said open ends facing each other.

12. A lamp as claimed in claim 11, wherein said heat shields are welded to said support.