GB2317046A

GB2317046A - A discharge lamp

Info

Publication number: GB2317046A
Application number: GB9618469A
Authority: GB
Inventors: Dieter Strueber
Original assignee: Individual
Current assignee: Individual
Priority date: 1996-09-04
Filing date: 1996-09-04
Publication date: 1998-03-11
Also published as: GB9618469D0

Abstract

A low-pressure mercury vapour discharge lamp, e.g. a compact fluorescent lamp, comprises a discharge vessel 11 coated with a fluorescent material and filled with an inert gas, a lamp base 12 on which the discharge vessel is mounted and inside which electronic circuits for starting and sustaining discharge are contained and a fitting 14 for electrical connection to a power source. A coupling 13, e.g. a screwthread, is formed on the lamp base for making detachable connection with an enclosure 20 which comfortably accommodates the discharge vessel while allowing light dissemination from the discharge vessel. The enclosure allows use of the lamp in cold environments. It may have an opening with an adjustable aperture to avoid overheating when the environment warms up.

Description

AN IMPROVED COMPACT FLUORESCENT LAMP The present invention relates to a low-pressure mercury vapour discharge lamp, in particular it relates to a low-pressure mercury vapour discharge lamp of the type more commonly known as a compact fluorescent lamp or energy saving lamp.

Compact fluorescent lamps are very popular among consumers because they can provide a high illuminating intensity from a relatively compact source with a low power input. Such lamps also have a very long operating life which would not otherwise be available from other conventional lamps such as incandescent lamps or other types. This type of lamp usually has a lamp base inside which the discharge control circuits are located and on which base there is mounted an envelope of a discharge vessel usually comprising a tubular glass component segment coated with a suitable fluorescent powder, or a plurality of such segments interconnected of. Usually, these lamps are provided with a singleended connection head, such as the screw- or bayonet-type heads usually found in conventional incandescent lamps, at the bottom of the lamp base for making connection to a power socket and to allow such a lamp to replace conventional incandescent bulbs.

The discharge vessel is usually filled with an inert gas, such as Argon, and liquid mercury.

Initially a discharge arc will be created in the argon gas along the length of the tubular segments of the discharge vessel when a sufficient potential difference is established across the electrodes. After the temperature within the discharge vessel has been raised due to the discharge arc to a level sufficient to cause adequate vaporisation of the liquid mercury already present within the vessel, a mercury vapour discharge arc results which interacts with the fluorescent material coated on the inner surface of the discharge vessel, thus radiating fluorescent light.

It is well known that the ambient temperature for optimum operation of a compact fluorescent lamp is in the region of 20-30 degree Celsius and that these lamps do not operate efficiently if the ambient temperature drops far below the optimum range. If the ambient temperature drops further to well below the freezing point, for example minus 17 degree Celsius or bellow, most compact fluorescent lamps stop giving out luminance. Although an Argon discharge is maintained, there is inadequate mercury vapour inside the vessel to produce a mercury vapour discharge. While the inert gas discharge arc in itself generates heat, the intrinsic tubular configuration of the discharge vessel represents a good heat radiator and the heat generated by the discharge is not sufficient to cause or sustain adequate mercury vaporisation since the heat will be dissipated as soon as it is generated. Thus, if the ambient operating temperature drops below this luminous temperature", such an "energy saving lamp" would merely become a non-luminous energy dissipator.

This limitation means that energy saving lamps are not suitable for outdoor use in cold climates or even for indoor use where domestic heating is not provided. In areas with moderate summers and severe winters when outdoor temperature could sometimes fall below the luminous temperature, users would have to use incandescent bulbs during winters and change to energy saving lamps during non-winter periods.

It is therefore desirable to improve the design of energy saving compact fluorescent lamps so that their inherent limitation would not too adversely limit their otherwise wide public utility.

According to the present invention, there is provided a low-pressure mercury vapour discharge lamp comprising a discharge vessel filled with an inert gas, a lamp base on which the discharge vessel is mounted and inside which electronic discharge circuits are contained, means for connecting the lamp to a power source and a detachable enclosure means which substantially surrounds said discharge vessel.

Preferably, cooperating coupling means are provided on said lamp base and said enclosure means. Preferably said coupling means are of a screw-thread, snap-fit or bayonet type.

Preferably said enclosure means is formed with an aperture.

Preferably, the opening of said aperture is adjustable. Preferably said enclosure means is made of a transparent or translucent material. Preferably said enclosure means comprises a base made of a non-brittle material.

A preferred embodiment of the present invention will now be described by way of example only and with reference to the accompanying drawings in which: Figure 1 shows a perspective view of the present invention; and Figure 2 shows a perspective view of an example of an enclosure of the present invention.

Referring to the drawings, there is shown a compact fluorescent lamp 1 comprising a discharge vessel 11, a lamp base 12 on which a coupling means 13 is provided and a connection head 14 at the bottom of the lamp base 12 for connecting to a power socket. The discharge vessel 11 usually comprises an envelope of tubular segments 15 which is filled with an inert gas such as Argon, internally coated with a suitable fluorescent material and mounted with electrical filaments 16. To facilitate mercury vapour discharge, an adequate amount of liquid mercury is maintained inside the discharge vessel 16.

Electronic circuits for starting and sustaining discharge by building up an adequate potential difference between the electrodes are usually contained within the base housing 12 which is usually made of an insulating material for safety reasons. A connection head 14, which makes electrical connection between a power socket and the electronic circuits within the base housing 12, is provided at the bottom of the base housing 12. This connection head is commonly a screw-head type, but bayonet or other types are also widely used. On the surface of the base housing 12 there is provided a coupling means 13 which, in the present embodiment, comprises screw threads formed integrally thereon for making detachable connection with a corresponding enclosing means to be described below.

Referring to figure 2, there is shown an enclosing means 20 which comprises a main housing 21 and base 22. The main housing 20 is made preferably of an insulating material which is also transparent or translucent, for example, glass or acrylic, so that light produced by the discharge vessel can be disseminated to the surroundings. The base 22 can be made of the same material as the main housing 21 but is preferably made of a non-brittle material for easy handling. The base 22 is a collar formed at the bottom of the main housing for strengthening the neck part of the main housing 21 and is formed with coupling means 23 thereon. The coupling means 23 formed on the base 22 is provided for making detachable connections with the corresponding coupling means 13 formed on the lamp base 12 so that a user may interchange lamps and enclosing means as he so wishes. Accordingly, the coupling means used could be screw-thread, bayonet, snap-fit or other suitable types corresponding to the coupling means located on the lamp base 12.

The enclosing housing is preferably shaped and dimensioned to provide an adequate internal space to comfortably accommodate the discharge vessel 11. To facilitate an even distribution of light in most directions, the front part of the main housing 21 is preferably substantially spherical unless a special illuminating effect in certain directions is required. The shape of an conventional light bulb housing which has a spherical front part that narrow down to approximately the dimension of the lamp base provides a good example which can comfortably accommodate the discharge envelope while giving out light sufficiently in most directions.

After the enclosing means 20 has been connected to the lamp base 12 and the electronic circuits are put into operation, the heat generated by the initial inert gas discharge will be substantially maintained in the space within the enclosing means 20 because of the insulating properties of the main housing 21 and the air trapped inside. When the temperature inside the main housing has been built up above the luminous temperature, adequate mercury vaporisation can take place and luminous discharge can then take place. With the provision of such an enclosing means 20, an energy saving lamp could operate even if the temperature outside the main housing 21 is well below the luminous temperature. When the outside temperature becomes warm, the enclosing means is no longer required and the user can simply remove the enclosing means.

In an alternative embodiment, an opening with an adjustable aperture may be provided on the main housing, for example an adjustable or slidable grille or window, so that the size of the opening may be varied by the user. With such an adjustable aperture, a user does not have to remove the enclosing means to avoid overheating when the ambient temperature is warm and may simply open the aperture to allow air circulation in order to reduce air temperature within the main housing 21.

The availability of the present invention of an enclosing means further provides an aesthetic effect which would not otherwise be available to an energy saving lamp due to the inherent tubular shape of the discharge vessels. Various attempts to improve the aesthetic appearance of an energy saving lamp have resulted in lamps having spiral, helical or twisted tubular segments but their monotonous but intrinsic tubular out-look can nevertheless not be eradicated. With the present invention, a user can easily change the appearance of an energy saving lamp by using removable enclosures of various shapes and configurations. Such an aesthetic effect could further be enhanced through the use of a fogged or translucent main housing so that the tubular segments would be obscured.

Finally, while only the screw-thread type connection means has been described hereinbefore, it shall be appreciated that other removable connection mechanisms, such as a snap-fitting design, or a bayonet-type fitting comprising an assembly of lugs and recesses could equally well be used.

Claims

CLAIMS:

1) A low-pressure mercury vapour discharge lamp comprising a discharge vessel filled with an inert gas, a lamp base on which the discharge vessel is mounted and inside which electronic discharge circuits are contained, means for connecting the lamp to a power source and a detachable enclosure means which substantially surrounds said discharge vessel.

2) A lamp as claimed in claim 1 wherein co-operating coupling means are provided on said lamp base and said enclosure means.

3) A lamp according to claim 1 or 2 wherein said coupling means are of a screw-thread, snap-fit or bayonet type.

4) A lamp according to any preceding claim wherein said enclosure means is formed with an aperture.

5) A lamp according to claim 4 wherein the opening of said aperture is adjustable.

6) A lamp according to any preceding claim wherein said enclosure means is made of a transparent or translucent material.

7) A lamp according to any preceding claim wherein said enclosure means comprises a base made of a non-brittle material.

8) A low-pressure mercury vapour discharge lamp substantially as hereinbefore described with reference to the accompanying drawings.

9) A low-pressure mercury vapour discharge lamp comprising a discharge vessel filled with an inert gas, a lamp base on which the discharge vessel is mounted and inside which electronic discharge circuits are contained, means for connecting the lamp to a power source, and coupling means formed a said lamp base for coupling to an enclosure means for surrounding said discharge vessel.

10) A low-pressure mercury vapour discharge lamp substantially as hereinbefore described with reference to figure 1 of the accompanying drawings.

11) An enclosure for a low-pressure mercury vapour discharge lamp comprising a body portion for surrounding the discharge vessel, said body portion being formed substantially of transparent a translucent material, and a neck portion formed with coupling means for detachable coupling to the base of said low-pressure mercury vapour discharge lamp.

12) An enclosure for a low-pressure mercury vapour discharge lamp substantially as hereinbefore described with reference to figure 2 of the accompanying drawings.