Lamp including burner and electronics with improved heat management

FIELD OF THE INVENTION

The present invention relates to a lamp. More specifically, the invention relates to a lamp including a burner and an electronic circuit for operating the burner.

BACKGROUND OF THE INVENTION

Most filament lamps sold today have a standard electrical and mechanical connector part, e.g. an E14, E26 or E27 screw connector or, B22 bayonet connector or other types. While generally the heat generated by the filament and the resulting operating temperatures are not critical, they may prove problematic if an electronic circuit is to be integrated into the lamp.

US 5,458,505 shows a lamp with a cooling system. In one embodiment, there is provided a housing with a standard threaded plug for engagement in a standard socket. A printed wiring board comprises circuitry to operate a halogen lamp. The halogen lamp is provided on a heat sink, and a lamp cover is provided around it. The heat sink has holes, and further holes are provided in the lower part of the housing. A fan is arranged to drive air over the electronics. The air enters through openings along the circumference of the base and is exhausted though further openings in a lower part of the base.

It is the object of the invention to provide a lamp if an electronic circuit integrated into the lamp where effective heat management measures protect the electronic circuit from a critically high temperature.

BRIEF DESCRIPTION OF THE INVENTION

This object is achieved by a lamp according to claim 1. Dependent claims refer to preferred embodiments of the invention. According to the invention, a lamp comprises a base with an electrical and mechanical connector part and a transparent or translucent cover, which may correspond in shape, e.g. to the known glass bulb in previously known standard lamps. Within the cover, a burner is arranged. In the present context, the term burner will be used for any type of light

generating element. Preferably, the burner comprises a burner vessel and electrical contacts. Preferably, the burner is of a filament type, e.g. a halogen lamp.

The base, which is preferably of substantially cylindrical shape, comprises a mounting cavity. Within the mounting cavity, an electronic circuit is arranged. This may be any type of electronic circuit. It may be separate, but is preferably electrically connected to the connector part and/or to the burner.

For the purpose of heat management, a partition member is provided which seals the mounting cavity from the burner. It should be noted that the cavity need not be "sealed" in a vacuum-tight sense, but that the partition member prevents the circulation of hot air from the burner into the mounting cavity. However, there are ventilation openings arranged to ventilate air to and from the burner.

The inventors have recognized that a strict separation between a cool section (mounting cavity for electronics) and a hot section (where the burner is arranged) is preferable in terms of heat management of the lamp. Ventilation of the hot section serves to dissipate heat effectively. However, by sealing the mounting cavity, transport of heat into the mounting cavity is effectively limited.

According to a preferred embodiment of the invention, the partition member comprises a first shell member and a second shell member. The first shell member is arranged to seal the mounting cavity, whereas the second shell member is arranged to mechanically hold the burner. The shell members are arranged on top of each other with a separation space between the members. At least one of the shell members may be provided cup-shaped to leave this separation space. The separation space may be sealed, so that it acts as a blind air chamber. Alternatively, the separation space may also be part of the ventilation path. Thus, heat conduction is effectively limited. In a further preferred embodiment, at least one of the shell members comprises an outer ring arranged along the circumference of the base. This serves to achieve an overall simple construction.

As explained above, the electronic circuit may be of any type, including electronic circuits that are not associated with burner operation. Preferably, it is suited for operating the burner i.e. supply electrical energy to the burner in a controlled manner. This may comprise switching the burner on or off as well as dimming the burner. Preferably, the receiver may be suited to receive power line commands over the electrical connection. The electronic circuit further comprises a control circuit for operating the burner according to the control commands, e.g. switching on/off or dimming the burner accordingly.

The convection of air through the ventilation openings may exclusively rely on natural convection, e.g. caused by a chimney effect due to temperature differences. Alternatively, it is also possible that a fan is provided within the base for ventilating air through the openings. This may especially be advantageous if- e.g. due to the orientation of the lamp - natural convection is not regarded as sufficient.

In a preferred embodiment, the fan comprises an inlet and an outlet region. The fan transports air from inlet to outlet. There are channel means provided to guide the air. These channel means may comprise any type of guiding construction, i.e. walls. A first channel means guides cool air from an opening to the inlet region. A second channel means guides hot air from the outlet region to a different one of the openings. It should be noted that in the present context the words "cool" and "hot" are used to distinguish the air drawn in from the outside (cool) and the air transported away from around the area of the burner (hot). The different channels are not connected so that hot air and cool air do not mix inside the lamp.

According to a preferred embodiment, the fan is arranged such that inlet and outlet regions are separated in axial direction of the base. An axial fan type may easily be integrated into the base in this orientation.

According to a further preferred embodiment, the ventilation openings are exclusively arranged in a circle along the circumference of the base. Most preferably, the circle is arranged in the region where the cover is mounted to the base. This arrangement has proven to be an exceptionally good choice. The ventilation openings further serve to limit the effective cross-section of the base in this transition area between the hot section (cover, burner) and the cool section (mounting cavity). During operation of the lamp, this region is arranged at a greater distance from the socket, so that cool air may be effectively drawn in.

According to a further preferred embodiment, the base and/or the cover are arranged so that there is no straight path from the ventilation openings to the inside of the cover. Within the cover, the burner is arranged with its electrical contacts. By providing a labyrinth structure (no straight path), possible hazards are avoided which may occur if a conducting element, e.g. a wire is inserted into the openings. Most preferably, the path from the ventilation openings to the inside of a cover includes at least one turn of at least 90°. This helps to effectively prevent the hazard described above.

A further improvement relates to electrical and mechanical arrangement of the burner. The burner, e.g. a halogen burner, comprises a burner vessel with protruding contact rods. The burner is mounted by mechanically fixing the contact rods at the partition member, e.g. by molding in the contact rods. Further, electrical leads are provided, which are

connected between the contact rods and the electronic circuit. The electrical leads have a smaller cross section than the contacts rods. This is based on finding that in heat distribution from the burner to the electronics, the contact rods may play an important part. Usually, these contact rods are provided much thicker than necessary for the pure electrical connection, due to the fact that they also serve as a mechanical connection-. If the contact rods are extended up to the electronic circuit, a large amount of heat may be conducted by them. However, if mechanical fixing is already achieved at the partition member, the thinner electrical leads may provide electrical contact between the electronic circuit and the rods, thus limiting the heat transfer. In the following, embodiments of the invention will be described with reference to the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 a side view of a lamp according to a first embodiment of the invention; Fig. 2 a side, sectional view of the lamp of Fig. 1;

Fig. 3 a side, exploded view of the lamp of Fig. 1, Fig. 2; Fig. 4a a sectional view of a shell element of the lamp of Fig. 1 with a section along line A.. A;

Fig. 4b a sectional view of the shell element from Fig. 4a with the section taken along line B.. B;

Fig. 5 a perspective, enlarged sectional view of a central portion of the lamp of Fig. 1;

Fig. 6 a side view of a lamp according to a second embodiment of the invention; Fig. 7 a side, sectional view of the lamp of Fig. 6;

Fig. 8 a side, exploded view of the lamp of Fig. 6;

Fig. 9 an enlarged, sectional side view of a top portion of a lamp according to a third embodiment of the invention;

Fig. 10 a side, exploded view of elements of the lamp of Fig. 9; Fig. 11 an enlarged, sectional side view of a top portion of a lamp according to a fourth embodiment of the invention;

Fig. 12 a side, exploded view of elements of the lamp of Fig. 11;

Fig. 13 a side view of a lamp according to a fifth embodiment of the invention;

Fig. 14 a side, sectional view of the lamp of Fig. 13;

Fig. 15 a side, exploded view of the lamp of Fig. 13;

Fig. 16 a perspective, partly sectional view of the lower part of the lamp of Fig. 13;

Fig. 17 a sectional view of the lamp of Fig. 13 with the section taken along line CC;

Fig. 18 a partly sectional side view of the lamp of Fig. 13 with the section taken along line D..D of Fig. 17.

DETAILED DESCRIPTION OF THE EMBODIMENTS Fig. 1 shows a first, nowadays preferred embodiment of a lamp 10. The lamp

10 has a base 12 with a screw connection 14. The screw connection for all embodiments will be shown as an E27 screw connection, although the skilled person will appreciate that different connections, e.g. an E14 screw connection, a bayonet connection, or other connection, could also be used. The lamp 10 further includes a glass bulb 16. As shown in Fig. 1, a halogen burner 18 is arranged in glass bulb 16. While the bulb type shown has a narrow shape, it will be appreciated that other shapes are possible.

Base 12 is a hollow plastic part with an interior space 20. Within the interior space 20, an electronic circuit is arranged. As is visible in Fig. 3, the electronic circuit comprises two circuit boards 22 arranged vertically in the space 20. The circuit boards 22 are electrically connected to the connector 14 and to the burner 18. The circuits are powered from connector 14. One of the circuit boards 22 is a control circuit which supplies electrical power from the connector 14 to the burner 18 in a switched manner. Thus, the control circuit may turn the burner 18 on or off. By PWM operation, the burner 18 may also be dimmed. The other circuit board 22 comprises a radio receiver to receive control commands. The received commands are passed to the control circuit, so that the burner 18 is operated according to theses commands.

In operation of the lamp 10, the heat generated by the burner 18 needs to be properly dissipated, so that the temperature of the circuits 22 in space 20 of the base 12 does not exceed critical limits. As will be explained further on, a number of measures have been taken for improved heat management of the lamp 10. For the purpose of heat management, the lamp 10 is divided into a hot burner zone inside bulb 16 and a cool electronics zone inside base 12.

Measures for keeping these zones separated include Reduced Conduction.

As will become apparent, measures have been taken to reduce heat conduction between the burner zone and the electronics zone. The burner 18 is arranged high inside bulb 16 to increase the distance. In a central section of the lamp 10, a partition member 24, 24a, 24b is arranged to isolate the zones from one another. Blind air chambers 36 may be provided. Further, the conductors leading from the electronics 22 to the burner 18 have a reduced diameter. Cooling by Convection

The lamp 10 comprises ventilation openings 26 which are connected to the inside of the bulb 16, so that heat generated by the burner 18 may be dissipated by convection. However, the space 20 inside base 12, where the circuits 22 are mounted, is closed off, so that convection from the hot burner zone cannot introduce heat into the electronics zone.

As visible from Fig. 3, a partition member 24 is arranged between the base 12 and the bulb 16, and may therefore also be referred to as the interface between these two parts. The partition member 24 comprises a shell ring 28 made of a plastic material and a glass shell 30 mounted above shell ring 28. The glass shell is cup shaped. Because of its shape it will be referred to as a glass flare 30.

As visible from Fig. 3, Fig. 5, the burner 18 comprises a glass burner vessel and protruding legs (contact rods) 32. The contact rods 32, which in the present embodiment are fixed at the burner by clips 34 (see Fig. 5) serve both for mechanical mounting of the burner 18 and electrical connection thereof.

The legs 32 are molded into the glass shell 30. Glass shell 30 has the shape of a glass flare with a hollow inside space 36. The legs 32 are securely held in glass flare 30.

Electrical leads 38 in glass flare 30 are directly fastened to the legs 32 for electrical connection. Only these electrical leads 38 enter the space 20 of the base 12. As visible from Fig. 5, the electrical leads 38 have significantly reduced diameter by comparison to the legs 32. Preferably, the diameter of the electrical leads 38 is less than 50%, most preferably less than 30% of that of the legs 32. In a preferred example, the legs have a diameter of 1.1 mm, and the electrical leads 38 have a diameter of 0.2 mm. The electrical leads 38 extend through the space 36 of the glass flare 30 and also through the shell 28 into the space 20 in base 12. Here, they are connected to the electronics 22.

The shell ring 28 is shown in Fig. 4a, 4b. It has an outer ring, which in the assembled lamp 10 is positioned at the outer periphery of the lamp, in between base 12 and bulb 16. Shell ring 24 is mounted on top of hollow base 12 to seal the base.

On the outer ring, four slots 26 are provided as ventilation openings. The ventilation openings 26 form a circle along the circumference of the lamp 10. As visible from the arrows shown in Fig. 4a, cool air from the outside may enter through the ventilation openings 26 into the interior of bulb 16. Also, hot air from inside bulb 16 may exit through the ventilation openings 26. If the lamp 10 is mounted in horizontal direction, this type of convection will occur automatically caused by a sort of chimney effect.

The path of air (shown by dashed arrow lines) going through the ventilation openings 26 is provided such that there is no straight path through the ventilation openings 26 into the inside of bulb 16. Preferably, the path has in each case a turn of about 90°, which serves to prevent electrical hazards resulting from objects being inserted into the ventilation openings 26.

The partition member 24 is assembled, as shown in Fig. 2, by mounting glass flare 30 on top of shell ring 28. Glass flare 30 may be mounted by different types of connection, including snap-in connections, or with a separate holder element as shown in Fig. 5. Glass flare 30 and shell ring 28 are mounted on top of each other, so that a separation space 36 remains between them.

As will become apparent below, it is possible that the separation space 36 is closed off, so that no convection occurs, and that the chamber, which centrally extends over a significant portion of the cross-section of the interface, serves to isolate the hot burner zone from the cool electronics zone.

However, in the preferred embodiment, the glass flare 30 has a hole 31 in its top portion, which connects the separation space 36 to the inside of the cover 16. By heating from the burner 18, a chimney effect may be caused in glass flare 30 to promote the exchange of air through the ventilation openings 26. In the following, a second embodiment of the invention will be described with reference to drawings Fig. 6-Fig. 8. As the second embodiment corresponds in large parts to the first embodiment, only differences between the embodiments will be explained in detail. Parts common to both embodiments will be referred to by identical reference numerals.

The second embodiment differs from the first embodiment by different mounting of the burner 18 and different construction of a partition member 24a.

In the second embodiment, the partition member 24a also comprises a shell ring 28, which is slightly differently shaped from that of the first embodiment. However, it also comprises an outer ring with ventilation openings 26 provided in a circle along the circumference.

The second part of the partition member 24a is an upper shell 30a made of a plastic material. As shown in Fig. 7, upper shell 30a is arranged on shell ring 28, so that a central blind air chamber 36 remains between the two. As in the first embodiment, here also the partition member 24 is in essence a double-walled partition with excellent insulation properties.

The upper shell 30a is cup-shaped. A plurality of inner ventilation holes 27 are provided in the upper shell 30a. As visible from Fig. 7, the path of air (dashed arrows) through the outer ventilation openings 26 includes a first section provided between the shell ring 28 and the upper shell 30a and then leads trough the inner ventilation holes 27. The path is not straight, so that any electrical hazards are avoided.

The legs 32 of burner 18 are mechanically fixed to upper shell 30a. The legs 32 are fixed to a holding block 42, which is part of the upper shell 30a. The legs 32 are bent through 90°, with their ends further secured in holding blocks 44. Thus, burner 18 is mechanically fixed to the upper shell 30a. As the upper shell 30a is received in shell ring 28, the burner is fixed to the partition member.

Again, electrical leads 38 of significantly reduced diameter lead from the legs 32 to the electronics 22.

In the following, a third embodiment will be explained with reference to Fig. 9, Fig. 10 and a fourth embodiment will be explained with reference to Fig. 11, Fig. 12. The third and fourth embodiment differ from the second embodiment in the way the burner 18 is mounted on the partition member.

In the third embodiment, the shell ring 28 is the same as in the second embodiment. The second part of the partition member 24b is provided as a holder 30b, which includes a cup-shaped shell 46 of about the same shape as the corresponding part in the second embodiment. The shell 46 is provided with holes 27 and received in the shell ring 28, so that a double-walled partition member 24 with a blind air chamber 36 and labyrinth air paths is provided.

Holder 30b further comprises a holding part 48 which receives the lower part of burner 18. A metallic spring member 50 is inserted into the holder part 48, so that the burner 18 is clamped and therefore mechanically fixed.

The fourth embodiment largely corresponds to the third embodiment. A ceramic holder part 30c holds the burner 18. The burner 18 is glued to the holder part 30c. Alternatively, it may also be fixed by ceramic cement. In this embodiment, the legs of the holder part 30c have holes 52 to weaken the diameter. This serves to reduce heat conduction.

In the following, a fifth embodiment will be explained with reference to Figs. 13-18. Again, like numerals refer to like parts in all embodiments.

As in the first embodiment described above, the lamp 10 has four slotted ventilation openings arranged in a circle along the circumference of the base 12. However, according to the fifth embodiment, convection cooling of the hot burner zone does not rely on natural convection. Instead, a fan 54 is provided to draw in air from the outside and feed the air to the inside of the bulb 16.

Consequently, the ventilation openings comprise designated inlet openings 26a and outlet openings 26b. The fan 54 is of axial type. As shown in Fig. 16, it is mounted in a specially adapted shell ring 28a. The fan 54 is mounted coaxially in the lamp 10, so that it transports air in axial direction towards the burner 18.

As shown in Fig. 18, shell ring 28a comprises a plate 56 sealing the cavity 20. Protrusions 58 from the plate 56 serve to hold the circuit board 22. The shell ring 28 is divided into four quadrants, corresponding to the four ventilation openings 26a, 26b. Inlet openings 26a and outlet openings 26b are arranged alternately. The split section of Fig. 18 shows to the right an inlet opening 26a. Here, the path from inlet opening 26a to the interior of bulb 16 is blocked by a blocking wall 60, so that air from the outside is only drawn in through fan 54. To the left, an outlet opening 26b is shown. Here, blocking wall 60 is not present. Instead, a partition wall 62 is provided isolating the fan 54 from the outlet opening 56. Thus, hot air from inside the bulb 16 exits through outlet opening 26b.

As visible from Fig. 18, the air transported from the fan 54 is directed into the interior of glass flare 30. Glass flare 30 at the top has a ventilation channel 31, which allows the air from the inside to enter the bulb 16. Consequently, this leads to air exiting from inside the bulb 16 as explained above.

It will be appreciated by the skilled person that the fan arrangement as shown with regard to the fifth embodiment may alternatively also be included with any other of the embodiments mentioned above.