GB2549254A

GB2549254A - A lamp

Info

Publication number: GB2549254A
Application number: GB1604533.8A
Authority: GB
Inventors: Edwin Sims-Hilditch John
Original assignee: Neptune Europe Ltd
Current assignee: Neptune Europe Ltd
Priority date: 2016-03-17
Filing date: 2016-03-17
Publication date: 2017-10-18
Also published as: GB201604533D0

Abstract

A lamp with a concave surface 123 with an apex 109. The apex has a light absorbing area surrounded by a reflecting area. The lamp is configured to receive a light source 117 such that the light source is directed towards the light absorbing area, which is preferably a substantially flat matt surface. The reflecting area may form an annular area around the light absorbing area. The light source may be located at the focal point of the concave surface, which may be hemispherical, paraboloid or conical. The lamp may have an arm 115 bridging the concave surface, which houses the light source, preferably at the focal point of the concave surface. The arm may have a further light absorbing portion, preferably a matt surface, facing the apex of the concave surface. The light source is preferably a light emitting diode.

Description

A lamp

Field of the Invention

The present invention concerns a lamp. More particularly, but not exclusively, this invention concerns a light-emitting diode reflector lamp.

Background of the Invention A light-emitting diode (LED) is a solid-state semiconductor device which emits light when a voltage is applied to it. LED lamps are energy efficient, compact and lightweight (fitting easily onto an electronic circuit board). They are long-lasting and provide sharp-edged and bright lighting compared to traditional incandescent bulbs and halogen and "energy-saving" bulbs. An LED lamp has the additional advantage of providing an instant light compared to "energy-saving" bulbs, which can take some-time to "warm up". LED lamps typically have one or more LEDs on a single-chip or a plurality of chips. They utilise a high current (high-power), alternating-current (AC) or other power source. LED lamps often have a candle, golf-ball or traditional light-bulb shape. An LED lamp may be in the form of a reflector lamp including a reflecting cup. The beam emitted from such a LED reflector lamp is typically reflected light rather than directly emitted light. This enables control of the light beam, in particular to provide both directional and concentrated lighting. In a LED reflector lamp, the LED is usually supported by an arm which bridges the reflecting cup. An approximately annular lighting pattern in the main beam is typically produced by the emitted light. Previous developments in the field have focussed on improving uniformity of the reflected beam. EP2330340(A2) discloses recesses or protrusions in a reflecting cup body and particularly a plurality of grid veins arranged in a matrix in which each grid vein has a protruded or recessed curved surface, to smooth out the beam pattern. US5272408 (A) discloses in the context of a filament bulb, techniques for controlling the beam pattern from a reflector lamp including roughening the reflecting surface microscopically or macroscopically, and/or introducing small local deformations on the reflector surface to limit the beam spread.

An additional problem with LED reflector lamp design not addressed in the prior-art, despite the above developments, is the existence of a dim but unwanted annulus, in or around the main beam, produced by light reflected and emitted from the lamp in a direction not parallel to the main beam. The unwanted reflected light can be a halo creating a more diffuse light around the edge of the main beam and reducing its sharp edge.

Another problem is heating of the semiconductor chip. Whilst LEDs have a high luminous efficacy (generating little heat), in a typical LED reflector lamp arrangement some light is scattered from the reflecting cup back towards the LED chip, heating the LED chip. The performance and lifespan of the chip can be limited by the heating.

Another problem in a typical LED reflector lamp arrangement having an arm to support the LED is the shadow cast by that arm.

The present invention seeks to mitigate at least one of the above-mentioned problems. Alternatively or additionally, the present invention seeks to provide an improved lamp.

Summary of the Invention

According to a first aspect of the invention, there is provided a lamp comprising a concave surface having an apex, the lamp being structured to receive a light source such that the light source is positioned and oriented to emit light towards the apex, wherein the concave surface comprises a light-absorbing portion at the apex and a reflecting portion surrounding the light-absorbing portion.

Providing such a lamp can reduce and/or substantially eliminate secondary reflections within the concave surface. Providing such a lamp can reduce and/or substantially eliminate any halo surrounding the main beam. Providing such a lamp can provide a light beam having a sharp edge. Such an arrangement may be particularly desirable if directional and/or concentrated lighting is required.

The lamp may be structured such that the light source is positioned near the focal point of the concave surface. The lamp may be structured such that the light source is positioned at the focal point of the concave surface. The lamp may have a longitudinal axis, passing through the apex and the light source, and rotational symmetry, for example of order two, about that longitudinal axis.

The concave surface may be hemi-spherical, paraboloidal or conical. The concave surface is preferably a reflecting cup.

The reflecting portion may comprise a metallic surface. The reflecting portion may be an annulus which entirely surrounds the light-absorbing portion.

There may be a flat region at the apex of the concave surface. The light-absorbing portion may be flat.

The light-absorbing portion may be or comprise a matt surface layer adjacent the concave surface. The matt surface layer may be a coating, for example paint. The matt surface layer may be black, or a colour sufficiently dark as to substantially eliminate reflections.

The surface area of the light-absorbing portion may be between 2% and 10% of the surface area of the reflecting portion. The surface area of the lightabsorbing portion may preferably be between 4% and 5% of the surface area of the reflecting portion. The lightabsorbing portion may be substantially the same width, or slightly narrower, than the central width of the arm. A light-absorbing portion of that size may reduce secondary reflections and unwanted heating without casting a further shadow within the emitted beam.

The lamp may comprise an arm which bridges the concave surface. The concave surface may contain one or more recesses for accommodating the arm. The arm may have a further light-absorbing portion, which may face the light-absorbing portion of the concave surface. The further light-absorbing portion may comprise a further matt surface layer. The further matt surface layer may be a coating, for example paint. The further matt surface layer may be black, or a colour sufficiently dark as to substantially eliminate reflections. A lamp according to at least some example embodiments of the invention can reduce and/or substantially eliminate any shadow cast on the main beam by the arm.

The light beam emitted from the lamp may have a beam angle of less than 15 degrees with respect to the longitudinal axis of the lamp. The light beam emitted from the lamp may have a beam angle of less than 13 degrees with respect to the longitudinal axis of the lamp.

The light source preferably is or comprises a LED.

Light incident upon the light source may be reduced and/or substantially eliminated. Such an arrangement may reduce unwanted heating of the light source and/or extend its lifespan. This may be especially beneficial in an LED reflector lamp in which emitted light is typically reflected onto the light source.

Example embodiments of present invention may be especially beneficial when a spot-light is required.

The lamp may have additional optional features including: a housing, a heat sink and/or a source of power .

According to a second aspect of the invention, there is provided a lamp assembly comprising a light source and a lamp, wherein the lamp is a lamp according to the first aspect of the invention.

Embodiments of the invention as described above, unlike other developments in the industry which focus on reflecting cup surface and housing design, use one or more light-absorbing portions to modify the pattern of reflected light within (and emitted from) the reflecting cup. Embodiments of the present invention utilise absorption of light, in particular within the reflecting cup and/or on the underside of the arm, to reduce light incident upon the light source and/or to prevent unwanted secondary reflections of light within the reflecting cup and/or to reduce light incident upon the arm.

Description of the Drawings

An embodiment of the present invention will now be described by way of example only with reference to the accompanying drawings of which:

Figure 1 is a top view of a lamp according to an embodiment of the invention;

Figure 2 is a side view of the lamp of Figure 1; and

Figure 3 is an alternative side view of the lamp of Figure 1; and

Figure 4 is an exploded plan view of the lamp of Figure 1; and

Figure 5 is a schematic diagram of the same embodiment of the invention; and

Figure 6 is a schematic diagram of an example prior-art lamp .

Detailed Description

The exterior of the example lamp (Figs. 2 to 4) comprises a bi-pin base 101 fixed to a housing 103 with a rim 105. The housing 103 is made from aluminium and the base 101 is made from plastic. The full length of the lamp in this example, from pin to rim, is 68mm.

Within the housing 103 sits a reflector cup 107 (Figs. 1 and 4). The reflector cup 107 has a concave surface 123 having a flat portion at its apex 109. Above the concave surface 123 is an arm 115. The concave surface 123 contains two recesses 111 through which the arm 115 extends. The concave surface 123 is typically made from aluminium and the arm 115 from aluminium. A semiconductor chip 117 is affixed to the arm 115 such that it faces the apex 109 of the concave surface 123 and is at its focal point.

The apex 109 of the reflector cup 107 is coated in a matt light-absorbing material (indicated through the arm 115 as a dashed circle in Figure 1) creating a black spot 119. The black spot 119 has diameter 7.5mm in this example, which constitutes 4% to 5% of the surface area of the concave surface 123. The underside 121 of the arm 115 is also coated in a matt light-absorbing material.

Figure 5 shows, in the same example embodiment of the invention, the path of light rays emitted by the semiconductor chip 117 radially toward the concave surface 123 and then their reflection out of the reflector cup 107. Light rays incident upon the black spot 119 are absorbed and not reflected, reducing light reflected onto the underside of the arm 115 and hence reducing the shadow cast and also reducing light reflected back onto the light source 117. Light rays which are reflected onto the underside 121 of the arm 115 are absorbed, preventing further reflection. Thus light rays reflected from the concave surface 123 either side of the black spot 119 form a parallel beam which is emitted from the reflector cup 107 either side of the arm 115. The halo effect is thus reduced.

Figure 6 shows a comparable ray diagram of an example prior-art lamp. There is no black spot, nor light-absorbing coating on the underside of the arm 115. Light rays are reflected from the apex 109 of the concave surface 123 back onto the semiconductor chip 117 (those rays not shown) or onto the arm 115 from which they are secondarily reflected and pass obliquely out of the reflector cup 107, creating inhomogeneities in the lighting pattern produced by the lamp, typically including a halo around the main beam.

Whilst the present invention has been described and illustrated with reference to a particular embodiment, it will be appreciated by those of ordinary skill in the art that the invention lends itself to many different variations not specifically illustrated herein. Where in the foregoing description, integers or elements are mentioned which have known, obvious or foreseeable equivalents, then such equivalents are herein incorporated as if individually set forth. Reference should be made to the claims for determining the true scope of the present invention, which should be construed so as to encompass any such equivalents. It will also be appreciated by the reader that integers or features of the invention that are described as preferable, advantageous, convenient or the like are optional and do not limit the scope of the independent claims.

Claims

1. A lamp comprising a concave surface (123) having an apex (109), the lamp being structured to receive a light source (117) such that the light source (117) is positioned and oriented to emit light towards the apex (109), wherein the concave surface (123) comprises a light-absorbing portion (119) at the apex (109) and a reflecting portion surrounding the light-absorbing portion (119).

2. A lamp according to claim 1 structured such that the light source (117) is positioned at the focal point of the concave surface (123) .

3. A lamp according to claim 1 or 2 having a longitudinal axis and rotational symmetry about that longitudinal axis .

4. A lamp according to any preceding claim wherein the concave surface (123) is substantially hemi-spherical, paraboloidal or conical.

5. A lamp according to any preceding claim wherein the reflecting portion is an annulus which entirely surrounds the light-absorbing portion (119).

6. A lamp according to any preceding claim wherein the light-absorbing portion (119) comprises a matt surface layer adjacent the concave surface (123) .

7. A lamp according to any preceding claim wherein the surface area of the light absorbing portion (119) is between 2% and 10% of the surface area of the reflecting portion.

8. A lamp according to any preceding claim wherein the light absorbing portion (119) is substantially flat.

9. A lamp according to any preceding claim comprising an arm (115) which bridges the concave surface.

10. A lamp according to claim 9 wherein the concave surface (123) contains recesses (111) for accommodating the arm (115).

11. A lamp according to claim 9 or 10 wherein the arm (115) includes a further light-absorbing portion and said further light-absorbing portion faces the light-absorbing portion (119) of the concave surface (123) .

12. A lamp according to any of claims 9 to 11 wherein the further light-absorbing portion comprises a further matt surface layer adjacent the arm (115).

13. A lamp according to any preceding claim wherein the light source (117) comprises a LED.

14. A lamp assembly comprising a light source (117) and a lamp, wherein the lamp is a lamp according to any one of claims 1 to 13.

15. A lamp substantially as herein described with reference to any of Figs. 1, 2, 3, 4, and 5 of the accompanying drawings .