WO2004066686A1

WO2004066686A1 - Discharge lamp unit with a stable connection between lamp base and starter housing

Info

Publication number: WO2004066686A1
Application number: PCT/IB2004/000098
Authority: WO
Inventors: Tilo STÖCKERT
Original assignee: Philips Intellectual Property & Standards Gmbh; Koninklijke Philips Electronics N. V.
Priority date: 2003-01-22
Filing date: 2004-01-12
Publication date: 2004-08-05

Abstract

A discharge lamp unit (10) is described. The discharge lamp unit (10) comprises a burner (12) with a discharge vessel (14) which is retained in an annular lamp base part (18). The annular lamp base part (18) comprises a retaining ring (22) and a connecting flange (26). The lamp base part (18) is fastened to a box-type housing (28) for the accommodation of an ignition device for the discharge lamp. For this purpose, the front face (42) of the connecting flange (26) is glued or fused to a receiving surface at the upper side (30) of the housing (28). In a further embodiment of the invention, a depression (52) for accommodating the flange (26) is provided at the upper side (30) of the housing (28).

Description

Discharge lamp unit with a stable connection between lamp base and starter housing

The invention relates to a discharge lamp unit.

Discharge lamps have been used also in the automotive field for a number of years. They comprise a discharge vessel for light generation, in which a gas discharge is generated between two electrodes. The discharge vessel is part of a usually elongate glass or ceramic body which is denoted a burner.

The discharge lamp is ignited through the application of a high ignition voltage of, for example, 10 to more than 20 kN to the electrodes. The circuits necessary for igniting the discharge lamp, comprising in particular an ignition transformer and possibly further electrical components, is accommodated in a housing in lamps of the types used nowadays, which housing is connected to the burner and to a lamp base so as to form a discharge lamp unit. To achieve an exact positioning of such a discharge lamp unit in a headlight, the latter comprises a larnpholder of standardized shape and dimensions.

DE 197 12 584 discloses a headlight lamp construction with a discharge lamp. A burner is adjustably held in a two-part lamp base. The two-part lamp base comprises a flange at its lower side, which flange comprises a groove in which the edge of a box-type housing is held.

Because of the comparatively high weight of the ignition device provided in the housing, stringent requirements are imposed on the mechanical strength when a discharge lamp unit is used in an automobile. This strength is insufficient under certain circumstances in known connections of the interlocking type.

DE 199 13 942 shows a discharge lamp unit in which the lamp base and the housing for the ignition device are partly formed from mutually shared components. The burner is positioned in an upper part of the lamp base. The upper part of the lamp base comprises the retaining ring at one side. At the other side, it forms a portion of a box-type housing for the ignition device at the lower side.

Lamp base parts are preferably manufactured in an injection molding process. Usually, a synthetic material that is highly temperature-resistant and electrically well insulating is used because high operating temperatures are reached during operation of discharge lamps, and high voltages are also applied during ignition. Manufacturing difficulties may arise in the case of a lamp base part such as the upper part in DE 199 13 942, in which parts of the housing of small wall thickness and parts of the lamp base of great wall thickness for accommodating the burner are combined into one component.

It is accordingly an object of the invention to provide a discharge lamp unit in which a good mechanical connection is safeguarded in combination with a simple construction.

This object is achieved by means of a discharge lamp unit as claimed in claim 1. Dependent claims relate to advantageous embodiments of the invention.

According to the invention, an annular lamp base part is provided, preferably a part manufactured in an inj ection molding process from a synthetic material resistant to high temperatures and with good electrical insulation. The burner is retained in the annular lamp base part, preferably by means of metal tags which are formed integrally with the part at one side and which are connected to a sleeve of the burner at the other side.

The annular lamp base part comprises the standardized retaining (prefocus) ring for accommodation in a headlight. According to the invention, the lamp base part in addition comprises a connecting flange by means of which it is fastened to a box-type housing for the accommodation of an ignition device.

The lamp base part is fastened to the box-type housing, according to the invention, at the front face of the connecting flange. This flange is glued or fused with a contact surface thereof to the upper side of the housing.

The annular lamp base part is a component of a particularly simple construction, which can accordingly be manufactured inexpensively. Its manufacture by an injection molding technique can be readily controlled, also if a synthetic material resistant to high temperatures is used, for example PPS or LCP. The connecting flange, which is preferably formed at a cylindrical transition region, results in a comparatively large, preferably circular contact surface between the lamp base part and the upper side of the housing. Gluing or fusing on such an enlarged surface leads to a particularly high mechanical strength.

The front face of the connecting flange is preferably chosen to be as large as possible. A circular contact surface with a width of 2 mm to 10 mm, in particular 5 mm to 8 mm, is preferred. The external diameter of the connecting flange is preferably greater than the external diameter of a cylindrical transition region. An upper limit for the external diameter of the connecting flange follows from considerations regarding handling and material saving. The connecting flange should not be so large that it projects laterally from the housing. hi a further embodiment of the invention, a circular depression may be provided at the upper side of the housing, in which depression the connecting flange can be accommodated. Preferably, said depression, which may be constructed, for example, in the form of a reduction in wall thickness of the housing in the relevant region, has a depth such that the upper side of the flange accommodated therein forms a continuous surface with the free surface of the upper side of the housing.

An embodiment of the invention will now be explained in more detail with reference to drawings, in which:

Fig. 1 is a side elevation of a first embodiment of a discharge lamp unit;

Fig. 2 is a longitudinal sectional view of part of the discharge lamp unit of Fig. 1;

Fig. 3 is a perspective view of the lamp base part of Fig. 1;

Fig. 4 is a rear elevation of the lamp base part of Fig. 2;

Fig. 5 is a side elevation of a second embodiment of a discharge lamp unit; and Fig. 6 is a longitudinal sectional view of part of the discharge lamp unit of Fig.

5.

Fig. 1 shows a discharge lamp unit 10 in side elevation. A burner 12 is constructed as a glass bulb with a discharge vessel 14, in which a gas discharge can be excited between two electrodes.

A metal sleeve 16 is fastened to the burner 12. The burner 12 is retained in a lamp base part 18 by means of this metal sleeve 16. Metal tags 20 are foraied from the lamp base part 18, integral therewith at one end. At their respective free ends, said tags are fastened to the sleeve 16 by means of laser welding.

The lamp base part 18 is substantially cylindrical and has an annular cross- section. It comprises a retaining (prefocus) ring 22, a cylindrical transition region 24 merging into the latter and having a diameter smaller than the retaining ring 22, and a connecting flange 26 merging into the transition region 24, The discharge lamp unit 10 further comprises a housing 28 for accommodating an ignition device (not shown). The housing 28 is of a box-type shape. The housing 28 is connected to the lamp base part 18 at the upper side 30.

The electrodes of the discharge vessel 14 are electrically connected to a central contact 34 and a rear contact 36, the latter being connected through a ceramic tube 38. An ignition device accommodated in the housing 28 is connected to said contacts. The power supply for the ignition device is provided through a lateral plug connector, for which the housing 28 provides a socket 40.

Fig. 2 shows the lamp base part 18 and the housing 28 has a, usually circular, opening 32 at its upper side 30. The lower end of the burner 12 (not shown) projects through said opening 32.

The lamp base part 18 is manufactured as an integral part by injection molding from a synthetic material that is resistant to high temperatures and has a good electrical insulation, for example PPS or LCP. The housing consists of an integral basic body 28 and a cover 44 which are both manufactured by injection molding from a synthetic material, for example PPS or LCP. The cover 44 is fastened to the housing 28 after mounting of the ignition device. The wall thickness of the housing 28 is approximately 1 mm, i.e. smaller than the wall thicknesses in radial direction of the lamp base part 26.

The lamp base part 18 is connected to the housing 28 at the annular contact surface between a front face of the connecting flange 26 and the upper side 30 of the housing 28. An annular circular contact region is created thereby. In this contact region, the two synthetic resin parts are joined together by fusion with a heating element, ultrasonic fusion, high-frequency fusion, friction fusion, or other fusion processes. A sturdy mechanical connection is obtained because of the comparatively large contact surface area. In a further embodiment, the stable connection to the contact surface is obtained by gluing. One-component or two-component adhesives may be used, for example epoxy resin adhesives. Preferred are adhesives which do not evolve gases₃ at least not after a suitable treatment.

The wide, annular connecting flange 26 is the decisive factor in obtaining the stability of the connection. This flange has an external diameter in the example shown which corresponds approximately to the external diameter of the retaining ring 22. The external diameter of the flange 26 is greater than that of the cylindrical transition region 24. hi an alternative embodiment (not shown), the external diameter of the connecting flange 26 is smaller than that of the retaining ring 22. The lamp base part 18 of Fig. 1 is shown once more in Figs. 3 and 4 (without metal tags 20). The retaining ring 22 has a shape in accordance with the standard for accommodation in a headlight. It has projections 46 (cf. Fig. 1) at the upper side and cavities 48 in the circumferential region (cf. Fig. 3) for positioning. Fig. 4 shows the annular surface 42 of the connecting flange 26 in rear elevation. In this example, the internal diameter of the connecting flange is 18 mm and its external diameter 32 mm. The width B is thus 7 mm. The positions of the projections 46 and the cavities 48 of the retaining ring 22 are also shown in this elevation.

Figs. 5 and 6 show a second embodiment of a discharge lamp unit 50, with its lamp base part and housing in cross-sectional view. The discharge lamp unit 50 corresponds largely to the discharge lamp unit 10 of Fig. 1. Identical elements had been given the same reference numerals.

In the second embodiment of a discharge lamp unit 50, a recess 52 is provided at the upper side 30 of the housing 28. The wall thickness of the upper side 30 of the housing 28 is reduced in the region 52 such that the connecting flange 26 is accommodated to its full height in the depression 52. This results in a flush transition, i.e. without a step, between the upper side 30 of the housing 28 and the upper side of the connecting flange 26. The flange 26 is accordingly no longer visible in the side elevation of Fig. 5. The depression 52 has a circular annular cross-section. The connection of the front face 42 of the flange 26 to the contacting upper side of the depression 52 is realized by means of the fusion or adliesion methods mentioned above.

Claims

CLAIMS:

1. A discharge lamp unit with

- a burner (12) with a discharge vessel (14) which is retained in an annular lamp base part (18),

- wherein the lamp base part (18) comprises a retaining ring (22) and a connecting flange (26),

- and wherein the lamp base part (18) is fastened to a housing (28) for accommodating an ignition device in that a front face (42) of the connecting flange (26) is glued or fused by a contact surface to the upper side (30) of the housing (28).

2. A unit as claimed in claim 1, wherein

- an annular circular contact surface is formed between the lamp base part (18) and the upper side (30) of the housing (28).

3. A unit as claimed in claim 2, wherein - the annular circular contact surface has a width of 2 mm to 10 mm.

4. A unit as claimed in any one of the preceding claims, wherein

- the lamp base part (18) consists of the retaining ring (22), a cylindrical transition region (24), and the connecting flange (26), - such that the external diameter of the connecting flange (26) is greater than that of the transition region (24).

5. A unit as claimed in any one of the preceding claims, wherein the lamp base part (18) is a component manufactured in an injection molding process from a synthetic material resistant to high temperatures and having a good electrical insulation.

6. A unit as claimed in any one of the preceding claims, wherein an annular circular depression (52) is provided at the upper side (30) of the housing (28) for accommodating the connecting flange (26).

7. A unit as claimed in claim 6, wherein - the connecting flange (26) is accommodated in the depression (52) such that the upper side of the flange lies flush with the free surface of the upper side (30) of the housing (28).

8. A unit as claimed in any one of the preceding claims, wherein - metal tags (20) project from the lamp base part (18), one end of each tag being integral with the lamp base part (18), and - wherein said tags (20) are connected to a sleeve (16) of the burner (12).