WO2010007571A2

WO2010007571A2 - Burner

Info

Publication number: WO2010007571A2
Application number: PCT/IB2009/053024
Authority: WO
Inventors: Jozef Merx; Norbert Vondenhoff; Andre Michel
Original assignee: Philips Intellectual Property & Standards Gmbh; Koninklijke Philips Electronics N.V.
Priority date: 2008-07-18
Filing date: 2009-07-13
Publication date: 2010-01-21
Also published as: WO2010007571A3

Abstract

A burner (12) for a lamp (10), particularly a high discharge lamp, comprising a glass body (16) comprising an intended connecting area (26) for connecting a bulb (14) to the glass body (16), wherein the glass body (16) comprises at least one lead (24) protruding outwards from the glass body (16) for applying a voltage and a connecting foil (22) connected to the lead (16), wherein the connecting foil (22) protrudes into at least a part of the connecting area (26). Surprisingly it was found that it is not necessary to adapt the bulb (14) such that the risk for cracks of the bulb (14) is reduced, but to adapt the burner (12) of the lamp (10). Since the connection foil (22) is arranged at least in a part of the connecting area (26) a reduction of the risk for cracks of the bulb (14) is reduced due to the airtight seal by the connection foil (22) leading to a reduced risk of a reduced lifetime of the lamp (10) without significantly increasing the manufacturing costs.

Description

BURNER

FIELD OF THE INVENTION

The invention relates to the field of burners used for lamps, particularly high-pressure discharge lamps, which may be used for automotive headlamps.

BACKGROUND OF THE INVENTION

A typical high-pressure discharge lamp comprises two electrodes protruding into a discharge vessel, where a discharge arc between the electrodes may be provided by means of an applied high voltage. The discharge vessel is part of a burner which is connected to a bulb, by which the burner is received. The connection between the burner and the bulb is provided by heating and/or partially melting the bulb in a connect- ing area, particularly by a rolling process, for providing an airtight connection. During the rolling process rolls rub with pressure onto the bulb at the connecting area until the bulb is such heated that a secure connection between the bulb and the burner in the connecting area is provided. Leads are led within the burner from the outside along the connecting area to the electrodes for applying voltage. Inside the burner connecting foils made from mainly Mo are provided, wherein each connecting foil is arranged between one lead and one electrode for connecting the lead and the electrode via the connecting foil. Due to the ductility of the connecting foil an air tight seal between quartz and the foil can be obtained, resulting in a current conducting feedthrough construction.

It has been observed at quality checks that a part of the manufactured lamps may comprise a reduced lifetime due to small cracks of the bulb in the connecting area. These lamps have to be sorted out leading to more production waste and increased manufacturing costs. In addition, these failures can occur during lifetime, resulting in early failures at customer. SUMMARY OF THE INVENTION

It is an object of the present invention to provide a solution leading to a lamp, particularly a high-pressure discharge lamp, by which the risk of a reduced lifetime and/or inferior lamp properties is reduced without significantly increasing the manufacturing costs.

This object is achieved by a burner for a lamp, particularly a high-pressure discharge lamp, comprising a glass body comprising an intended connecting area for connecting a bulb to the glass body, wherein the glass body comprises at least one lead protruding outwards from the glass body for applying a voltage and a connecting foil connected to the lead, wherein the connecting foil protrudes into at least a part of the connecting area.

Surprisingly it was found that it is not necessary to adapt the bulb such that the risk for cracks and/or air inclusions of the bulb is reduced, but to adapt the burn- er of the lamp. Since the connection foil is arranged at least in a part of the connecting area a reduction of the risk for cracks of the bulb is achieved leading to a reduced risk of a reduced lifetime of the lamp. A significantly increasing of the manufacturing costs is prevented since the manufacturing process has not to be change and it is only necessary to adapt the length of the electrodes and/or the foil. Particularly it possible to shift only the position of the connecting foil slightly so that the same connecting foil as before may be used. It is believed that the connecting foil in contrast to the lead provides an airtight seal, so that the burner in the connecting area in itself is airtightly sealed, so that a crack in the connecting area does not lead to a leak in the inner tube - outer tube connection. At the same time the risk is reduced that a mechanical shock could affect the airtight connection. This leads to an increased lifetime of the lamp. It is understood that the connection area is not only a surface of the burner but a three dimensional axial part of the burner with a radial extent.

Particularly the connecting foil protrudes along the whole axial extension of the connecting area. This leads to an airtight seal at the whole axial length of the con- necting area.

Preferably the connecting foil protrudes partially outwards with respect to the connecting area. The connecting foil may protrude in axial direction at both sides of the connecting area. Further it can be safeguarded to connect the lead and/or the electrode outside the connecting area.

Most preferred the length of the connecting foil in axial direction is longer than the length of the connecting area in axial direction. The arrangement of the connecting foil may be facilitated. Further even after the connecting process the connecting foil may be correctly arranged without the danger of a misalignment caused by thermal extensions.

Particularly the connecting foil comprises a higher ductility than the glass body. Form changes during the connecting process may be mainly compensated by the connecting foil. Stresses within the glass body and the bulb may be reduced or even prevented.

Preferably the connecting foil comprises mainly Mo. Molybdenum proved a good electrical conductivity as well as a good ductility at the temperatures occurring during use of a high discharge lamp.

In a preferred embodiment the lead is arranged only within a part of the connecting area, wherein the ratio r of the length of the lead arranged within the connecting area and the length in axial direction of the connecting area is 0.001 < r < 0.5, particularly 0.002 < r < 0.25, preferably 0.003 < r < 0.1 and most pre- ferred 0.004 < r < 0.005. Since the lead may only protrude much less than 50% of the axial length of the connecting area into the connecting area a low ductility of the lead does not affect the lifetime of the lamp. Particularly more and cheaper materials may be selected for the lead. In a more preferred embodiment the lead is arranged completely outside of the connecting area. Particularly a second connecting area is provided at an opposite side of the burner with respect to the connecting area, wherein a second connecting foil protrudes into at least a part of the second connecting area. The opposite side of the burner may be designed as previously described. Particularly both sides are correspondingly designed. The invention further relates to a lamp, particularly high-pressure discharge lamp, comprising a bulb and a burner, which may be designed as previously de- scribed, received by the bulb, wherein the bulb and the burner are airtight connected to each other in at least one connecting area. Due to the connecting foil arranged at the connecting area an airtight seal is provided in this area, leading to a reduced risk of a reduced lifetime without significantly increasing the manufacturing costs. The invention further relates to an automotive headlamp comprising a lamp, which may be designed as previously described. Due to the connecting foil arranged at the connecting area an airtight seal is provided. Even when mechanical shocks during operation of an automobile occur, a reduced risk of a reduced lifetime without significantly increasing the manufacturing costs is provided.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.

In the drawings:

FIG. 1 is a schematical sectional view of a high-pressure discharge lamp according to the state of the art and FIG. 2 is a schematical sectional view of a high-pressure dis- charge lamp according to the invention.

DETAILED DESCRIPTION OF EMBODIMENTS

As illustrated in FIG. 1 the high-pressure discharge lamp 10 for use in an automobile headlamp comprises a burner 12 received by a bulb 14. The burner 12 comprises a glass body 16 forming a discharge vessel 18 into which an electrode 20 protrudes. The electrode 20 is connected to a connecting foil 22 comprising mainly molybdenum. The connecting foil 22 is further connected to a lead 24 protruding outwards from the glass body 16 of the burner 12. The burner 12 comprises a connecting area 26 defined by an axial part of the glass body 16, which is in airtight connection to the bulb 14. Within the connecting area 26 the bulb 14 is connected to the glass body 16 of the burner 12 by a rolling process.

According to the state of the art as illustrated in FIG. 1 the lead 24 is arranged along the whole axial length of the connecting area. The connecting foil 22 is completely arranged outside and spaced to the connecting area 26 within the bulb 14. As illustrated in FIG. 2 according to the invention the connecting foil 22 is arranged along the whole length of the connecting area 26 and even protrudes outwards. The lead 24 as well as the electrode 20 are connected to the connecting foil 22 outside the connecting area 26. In comparison to the lamp 10 illustrated in FIG. 1 only the length of the electrode 20 and/or of the connecting foil 22 are changed for providing the connecting foil 22 inside the connecting area.

While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive; the invention is not limited to the disclosed embodiments. For example, it is possible to operate the invention in an embodi- ment wherein the connecting foil 22 and/or the lead 24 and/or the electrode 20 protrude partially into the connecting area 26. Although only one side of the lamp 10 is illustrated it is clear that the opposite side of the lamp 10 may comprise some or all features as described with respect to the illustrated side. Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measured cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.

Claims

CLAIMS:

1. Burner (12) for a lamp (10), particularly a high-pressure discharge lamp, comprising

- a glass body (16) comprising an intended connecting area (26) for connecting a bulb ( 14) to the glass body (16), wherein the glass body (16) comprises

- at least one lead (24) protruding outwards from the glass body (16) for applying a voltage and

- a connecting foil (22) connected to the lead (24), wherein the connecting foil (22) protrudes into at least a part of the connecting area (26).

2. Burner (12) according to claim 1 wherein the connecting foil (22) protrudes along the whole axial extension of the connecting area (26).

3. Burner (12) according to claim 1 wherein the connecting foil (22) protrudes partially outwards with respect to the connecting area (26).

4. Burner (12) according to claim 1 wherein the length of the connecting foil (22) in axial direction is longer than the length of the connecting area (26) in axial direction.

5. Burner (12) according to claim 1 wherein the connecting foil (22) comprises a higher ductility than the glass body (16).

6. Burner (12) according to claim 1 wherein the connecting foil (22) comprises mainly Mo.

7. Burner (12) according to claim 1 wherein the lead (24) is arranged only within a part of the connecting area (26), wherein the ratio r of the length of the lead (24) arranged within the connecting area (26) and the length in axial direction of the connecting area (26) is 0.001 < r < 0.5, particularly 0.002 < r < 0.25, preferably 0.003 < r < 0.1 and most preferred 0.004 < r < 0.005.

8. Burner (12) according to claim 1 wherein the lead (24) is arranged completely outside of the connecting area (26).

9. Burner (12) according to claim 1 wherein a second connecting area is provided at an opposite side of the burner (12) with respect to the connecting area (26), wherein a second connecting foil protrudes into at least a part of the second connecting area.

10. Lamp, particularly high-pressure discharge lamp, comprising a bulb (14) and a burner (12) according to claim 1 received by the bulb (14), wherein the bulb (14) and the burner (12) are airtightly connected to each other in at least one connecting area (26).

11. Automotive headlamp comprising a lamp (10) according to claim 10.