GB2499782A

GB2499782A - LED lamp having shell structure

Info

Publication number: GB2499782A
Application number: GB1202941.9A
Authority: GB
Inventors: Nigel Alastair Dent
Original assignee: Zeta Controls Ltd
Current assignee: Zeta Controls Ltd
Priority date: 2012-02-21
Filing date: 2012-02-21
Publication date: 2013-09-04
Anticipated expiration: 2032-02-21
Also published as: GB2499782B; GB201202941D0

Abstract

An electric lamp 10 comprises a plurality of electrically-powered light sources 34 (such as LEDs); at least one electrical connector 54 electrically connected to the light sources; and a structure to which the light sources are mounted with different orientations and to which the connector(s) is/are mounted. The structure has the form of a shell 100 with apertures 108 therethrough so that ambient air can pass through the apertures and circulate into and out of the shell. The shell is assembled from a plurality of separately formed shell portions 88,90. The light sources are mounted in thermal contact with mounting portions of the shell, and the mounting portions are thermally conductive so that they can dissipate heat away from the light sources. By mounting the light sources on and in thermal contact with apertured shell, heat can readily be dissipated from the light sources, and the light sources can conveniently be oriented in different directions.

Description

-1 -TITLE

Electric lamps DESCRIPTION

This invention relates to electric lamps. The invention was conceived while developing a 'low-energy' replacement for a conventional 60 Watt general lighting service ('GLS') tungsten-filament light bulb. However, the invention is also applicable to many other general types of electric lamp.

5 It is well known that the light-producing efficiency of tungsten-filament bulbs is low and that light-emitting diodes ('LEDs') can nowadays be produced having a far higher light-producing efficiency. However, despite producing significantly less heat than tungsten filament bulbs having the same light output, it is very important that the junction temperature of an LED is maintained below a limit value, otherwise the LED will immediately blow. Furthermore, 10 even if an LED is operated with its junction below its limit temperature, its life expectancy decreases with increasing operating temperature. Moreover, the light-producing efficiency of LEDs decreases with increasing operating temperature.

It is also well known that a GLS bulb has a fairly uniform light radiation pattern over a very large angle, for example from 0 to 150 degrees or more relative to the axis of the bulb. By 15 contrast, LEDs generally have a far smaller radiation angle unless special optics are provided. Furthermore, the light output from a single commonly-available high-power LED is substantially less than from a 60 Watt tungsten-filament bulb.

One way of emulating a GLS tungsten-filament using LED technology would therefore be to mount a number of LEDs in a cluster with the LEDs pointing in different directions. 20 However, mounting the LEDs in a cluster increases the difficulty in dissipating heat from the LEDs so as to keep their junction temperatures low. Also, mounting a large number of LEDs in a cluster so that they face in different directions creates manufacturing difficulties.

An aim of the present invention, or at least of specific embodiments of it, is to produce an electric lamp which has a plurality of light sources oriented in different directions, which 25 facilitates cooling of the light sources, and which can be manufactured relatively simply and inexpensively.

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In accordance with the present invention, there is provided an electric lamp comprising a plurality of electrically-powered light sources (such as LEDs); at least one electrical connector electrically connected to the light sources; and a structure to which the light sources are mounted with different orientations and to which the connector(s) is/are mounted. The structure 5 has the form of a shell with apertures therethrough so that ambient air can pass through the apertures and circulate into and out of the shell. The shell is assembled from a plurality of separately formed shell portions. The light sources are mounted in thermal contact with mounting portions of the shell, and the mounting portions are thermally conductive so that they can dissipate heat away from the light sources.

10 By mounting the light sources on and in thermal contact with the apertured shell, heat can readily be dissipated from the light sources, and the light sources can conveniently be oriented in different directions.

In a preferred embodiment, the shell is assembled from: a first such shell portion having a substantially hemispherical outline; and a second such shell portion which is connected to the 15 first shell portion and to which the connector is mounted.

The shell portions may be formed by die-casting or moulding. Alternatively, they may be formed by pressing and forming sheet material.

The structure is preferably substantially rigid. At least some of the mounting portions are preferably formed of metal. At least some of the mounting portions are preferably integrally 20 formed. These features result in a robust structure.

Each of the light sources preferably has a rear face which is substantially flat and is mounted on a respective substantially flat part of such a mounting portion. This can simplify manufacture of the light sources and assembly of the lamp. The light sources are preferably substantially rigidly mounted on the mounting portions.

25 The lamp may have an axis, and the light sources may be substantially regularly arranged around the axis.

Each light source may have an optical axis, and the optical axes of all or at least a first group of the light sources may lie substantially on a first common cone. The axis of the first common cone may be substantially coaxial with the axis of the lamp, and the optical axes of a 30 second group of the light sources may lie substantially on a second common cone substantially

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coaxial with the first common cone. With these features, the lamp can be arranged to emulate a GLS bulb or a spotlight.

The lamp is preferably devoid of an enclosure enveloping the light sources, so as not to hinder the circulation of air. The invention also extends to such an electric lamp in combination 5 with a lamp fitting having at least one electrical connector engaging the electrical connector(s) of lamp. In this case the lamp fitting is preferably devoid of an enclosure enveloping the light sources of the lamp.

A specific embodiment of the present invention will now be described, purely by way of example, with reference to the accompanying drawings, in which:

10 Figure 1 is an exploded isometric view of an electric lamp;

Figure 2 is an isometric view of the lamp of Figure 1 partly assembled; and

Figure 3 is an isometric view of the lamp of Figure 2 fully assembled.

Referring to the drawings, an electric lamp 10 is shown, emulating a conventional GLS bulb. As shown in Figure 1, the main components of the bulb 10 are a base shell half 88, a top 15 shell half 90, a bayonet or Edison screw (BC or ES) connector cap 54, a printed circuit board 92 populated with various electrical components 37, a pair of wire guides 94,96, ten LEDs 34 and a plug 98. Interconnecting wires between the circuit board 92 and the LEDs 34 are not shown in the drawings.

The shell halves 88,90 are thin-wall die-castings of aluminium. As shown in Figure 3, 20 the shell halves 88,90 together form a pear-shaped shell 100, with the top shell half 90 being approximately hemi-spherical and forming the rounded end of the pear shape, and with the base shell half 88 forming the remainder of the pear shape. The base shell half 88 has an open ended neck 102 which is fitted to the connector cap 54. Each shell half 88,90 is formed with five equiangularly-spaced flat-bottomed depressions 104 in its outer surface, with the depressions 25 104 in the base shell half 88 being inclined at an angle of about 45 degrees to the cap 54 end of the shell 100, and with the depressions 104 in the top shell half 90 being inclined at an angle of about 45 degrees to the rounded end of the shell 100. The flat bottom of each depression 104 is formed with a through-hole 106 covering only a small proportion of the area of the flat bottom. Between each adjacent pair of depressions 104 in each shell half 88,90, a respective generally-30 triangular through-hole 108 is formed for ventilation purposes. At the rounded end of the top shell half 90A, a central through-hole 110 is also formed, for receiving the plug 98. The plug

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98 is formed with an array of ventilation holes. Adjacent their mating edges, the shell halves 88,90 have cooperating ribs 112 which can be clinched, crimped or punched so that they interlock to hold the shell halves 88,90 together. Between the ribs 112, the mating edges are formed with notches 114 (Figure 1) which align in pairs when the shell halves 88,90 are 5 connected together so as to form further through holes 116 (Figure 3) in the shell 100.

Opposite their light-emitting faces, the LEDs 34 have flat rear faces corresponding in outline to the shape of the flat bottoms of the depressions 104 in the shells 98,100. The rear faces of the LEDs 34 also have protruding electrical connectors 118 which align with the holes 106 in the depressions 104 when the LEDs are fitted to the shell 100.

10 The printed circuit board 92 has a pair of input terminals 120 adjacent its lower end for connection to mains supply contacts of the connector cap 54. Nearer its upper end the printed circuit board 92 has a pair of output terminals 122 for connection to a series circuit of the ten LEDs. The printed circuit board 92 and its components 37 may be contrived to perform any required functions for driving the LEDs 34 including voltage step-down, current regulation, 15 temperature compensation, flashing and dimming.

Each wire guide 94,96 is a press- or click-fit into the respective shell half 88,90 adjacent its mating edge. Each wire guide 94,96 is an annular moulded plastic part with grooves into which lengths of wire (not shown) are press-fitted. The wires of each guide 94,96 may be arranged, for example, to connect the five LEDs 34 of the respective shell half in series 20 between a respective output terminal 122 of the printed circuit board 92 and a wire of the other guide 96,94.

In one example of a method of assembly of the lamp 10, the neck of the base shell half 88 is fitted into the connector cap 54 and is secured thereto, for example by bonding, clinching, crimping or riveting. The circuit board 92 is then inserted into the base shell half 88 and its 25 input terminals 120 are connected to the supply contacts of the connector cap 54 by soldering. Resin or silicone is then deposited into the connector cap 54 to hold the circuit board 92 steady. Each wire guide 94,96 is then press- or click-fitted to its respective shell half 88,90; the LEDs 34 are bonded by their flat rear faces to the flat bottoms of the depressions 104 with their connectors 118 protruding into the holes 106, and the wires of the wire guides 94,96 are 30 electrically connected to the LED connectors 188 by soldering. The shell halves 88,90 are then offered up to each other, and the wires of the wire guides 94,96 are connected to each other and to the output terminals 122 of the circuit board 92 by soldering. The shell halves 88,90 are then mated and mechanically fixed to each other by inserting tools into each adjacent pair of the

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holes 116 and clinching the mating ribs 112 situated between those holes 116. The plug 98 is then fitted to the hole 110.

It will be appreciated that the shell halves 88,90 and connector cap 54 can form a very rigid structure. The flat rear faces of the LEDs 34 and the flat bottoms of the depressions 104 of 5 the shell 100 provide a good thermal path from the LEDs 34 to the thermally conducting shell 100. The shell 100 has a substantial external exposed area from which heat can be dissipated. Furthermore, the shell 100 has an even greater exposed area internally, and the holes 108, 116 permit ambient air to circulate in and out of the shell 100 to cool the internal surface.

It will be appreciated that many modifications and developments may be made to the 10 lamp 10 and its method of manufacture. For example, the final soldering stage may be carried out using a soldering tool inserted through the aperture 110 in the top shell half 90 after the shell halves 88,90 have been mechanically connected together. The circuit board 92 and its components 37, and any other exposed electrical parts may be potted in resin or otherwise insulated. Barbed push-fit connections may be provided between the circuit board 92 and the 15 connector cap 54 and/or between the wire guides 94,96 and the circuit board 92 and/or between the wire guides 94,96 and the LEDs 34 so as to reduce the amount of soldering or obviate the need for any soldering. The wire guides and their wires may be replaced by conductors stamped and pressed out of sheet metal and then over-moulded with plastics material. The body of the connector cap 54 (particularly if it is an ES cap) may be insulated from the base shell half 88, 20 for example using an insert-moulded plastic part in the cap body. Alternatively, the body of the connector cap 54 (particularly if it is a BC cap) may be integrally formed with the base shell half 88.

It should be noted that the embodiment of the invention has been described above purely by way of example and that many modifications and developments may be made thereto within 25 the scope of the present invention.

Claims

-6-CLAIMS

1. An electric lamp comprising:

a plurality of electrically-powered light sources;

at least one electrical connector electrically connected to the light sources; and a structure to which the light sources are mounted with different orientations and to which the connector(s) is/are mounted;

wherein:

the structure has the form of a shell with apertures therethrough so that ambient air can pass through the apertures and circulate into and out of the shell;

the shell is assembled from a plurality of separately formed shell portions;

the light sources are mounted in thermal contact with mounting portions of the shell;

and the mounting portions are thermally conductive so that they can dissipate heat away from the light sources.

2. A lamp as claimed in claim 1, wherein:

the shell is assembled from:

a first such shell portion having a substantially hemispherical outline; and a second such shell portion which is connected to the first shell portion and to which the connector is mounted.

3. A lamp as claimed in claim 1 or 2 , wherein:

the shell portions are formed by die-casting or moulding.

4. A lamp as claimed in claim 1 or 2, wherein:

the shell portions are formed by pressing and forming sheet material.

5. A lamp as claimed in any preceding claim, wherein:

the structure is substantially rigid.

6. A lamp as claimed in any preceding claim, wherein:

at least some of the mounting portions are formed of metal.

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7. A lamp as claimed in any preceding claim, wherein:

at least some of the mounting portions are integrally formed.

8. A lamp as claimed in any preceding claim, wherein:

each of the light sources has a rear face which is substantially flat and is mounted on a respective substantially flat part of such a mounting portion.

9. A lamp as claimed in any preceding claim, wherein:

the light sources are substantially rigidly mounted on the mounting portions.

10. A lamp as claimed in any preceding claim, wherein:

the lamp has an axis; and the light sources are substantially regularly arranged around the axis.

11. A lamp as claimed in any preceding claim, wherein:

each light source has an optical axis.

12. A lamp as claimed in claim 11, wherein:

the optical axes of all or at least a first group of the light sources lie substantially on a first common cone.

13. A lamp as claimed in claim 12 when indirectly dependent on claim 10, wherein:

the axis of the first common cone is substantially coaxial with the axis of the lamp.

14. A lamp as claimed in claim 12 or 13, wherein:

the optical axes of a second group of the light sources lie substantially on a second common cone substantially coaxial with the first common cone.

15. A lamp as claimed in any preceding claim, wherein:

the light sources are LEDs.

16. A lamp as claimed in any preceding claim, wherein:

the lamp is devoid of an enclosure enveloping the light sources.

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17. An electric lamp substantially as described with reference to the drawings.

18. An electric lamp as claimed in any preceding claim in combination with a lamp fitting, wherein:

the lamp fitting has at least one electrical connector engaging the electrical connector(s) of lamp; and the lamp fitting is devoid of an enclosure enveloping the light sources of the lamp.