GB2420172A

GB2420172A - Lamp with air cooling and heat sink

Info

Publication number: GB2420172A
Application number: GB0522961A
Authority: GB
Inventors: James Andrew Fowler
Original assignee: Individual
Current assignee: Individual
Priority date: 2004-11-11
Filing date: 2005-11-10
Publication date: 2006-05-17
Also published as: GB0424892D0; GB0522961D0

Abstract

A lighting device comprises a housing 15 having an array of LEDs (7, fig 3) and an air flow path. The air flow path is defined between an inlet 27 and outlet 21. Located in the air flow path is a heat sink 19 for receiving heat generated by the LEDs. Air moving means is mounted within the housing for forcing air along the air flow path. The air moving means may be an electric fan 23. The device may include filters and an illuminated magnifier. The light may be suitable for dentistry to provide illumination for colour matching.

Description

LIGHTING DEVICE

Field of Invention

This invention relates to lighting devices, in particular to lighting devices incorporating light emitting diodes (LEDs).

Background to the Invention

Although lighting devices incorporating LEDs have been known for some time, they are in general low power devices. More recently high power LED lights have become available, generating, for instance, from 1 to 5 watts. They generate considerable amounts of heat and have been used mainly in floor lighting and similar applications where heat dissipation is not a problem.

There is a need for a lighting device which is both a powerful source of light and which can provide lighting which matches as closely as possible desired conditions such as daylight. An example is lighting used by dentists where very good illumination is required and where colour matching, for instance for teeth crowns, can be carried out under conditions which reproduce normal daylight. The light elements themselves should have characteristics which are stable over a long time and LED light sources can provide these characteristics.

Statements of the Invention

According to the present invention there is provided a lighting device comprising a housing having mounted therein an array of LED elements, said housing having an air inlet and an air outlet and defining an air flow path therebetween, and, mounted within the housing and located in said air flow path, heat transfer means for receiving heat generated by said LED elements and air moving means for causing air to be drawn into the housing via said inlet, moved along said air flow path and expelled from said housing via said outlet.

Accordingly, a lighting device in accordance with the present invention provides an integral device comprising, located within a housing, the light source itself, a heat sink for taking up the heat generated by the light source and means for transferring the heat from the heat sink to the exterior of the housing.

Preferably the heat transfer means comprises a fanned sheet metal arrangement mounted adjacent the LED array and the air outlet.

Preferably the air moving means is a fan mounted between the heat transfer means and the air inlet.

Preferably the housing is formed from a first part within which the LED array and heat transfer means are mounted and in a second part within which the air moving means is mounted.

The two part housing may be of substantially cylindrical form with the two parts having a common longitudinal axis and being connected together in a longitudinal side by side arrangement about said axis.

The air moving means may typically be an electric fan. Alternatively it may be in the form of liquid cooling means which may give particularly effective cooling.

The lighting device of the invention may have many applications. Use in dentistry has already been mentioned. Another application is in hospitals, particularly for use by surgeons during operations. LED light elements do not produce infrared radiation and accordingly such a lighting device, incorporating LED elements, is of particular use where the avoidance of drying during the operation is a consideration.

Further uses may be as inspection lamps or hand held torches, in architectural applications and as indicationldirection lamps.

A lighting device in accordance with the present invention may incorporate an illuminated magnifier.

When viewing highly glossy material through an illuminated magnifier, there can be a considerable amount of glare. This problem can be largely eliminated by making use of a pair of crossed polarising filters. A first polarising filter is placed between the light source and the subject and a second filter between the subject and the magnifying lens. With the second filter positioned at 900 to the first filter, this arrangement will block substantially all of the specula reflections which allowing diffuse light to pass.

The lighting device of the invention may include both daylight and so called warm white light sources. Such a device may be used by, for instance, a dental technician working with light curing composites while building restorations. The composites are designed to cure under exposure to light having wavelengths from 400 to 480 nanometers. The lighting device will allow the technician to work with composites under a warm white lamp without curing whilst still enabling the use of a daylight lamp for other lamp.

The lighting device of the invention is provided with an array of discrete elements, each element having its own lens. By providing different lens patterns and controlling the tensity of individual elements, the beam of light from the device can be controlled.

Brief Description of the Drawings

The accompanying drawings are as follows:- Figure 1 illustrates a first embodiment of a lighting device in accordance with the present invention; Figure 2 is a longitudinal section of the lighting head of a lighting device similar to that shown in Figure 1; Figure 3 shows the front of the lighting head of Figure 2; Figure 4 shows the rear of the lighting head of Figure 2; Figure 5 shows the air flow into and out of the lighting head of Figure 2; Figure 6 illustrates a second embodiment of a lighting device in accordance with the present invention.

Figure 7 is another view of part of the lighting device of Figure 6; Figure 8 shows the use of polarising filters with an illuminated magnifier; Figure 9 shows diagrammatically the use of polarising filters Figure 10 illustrates that the spectral power distribution for daylight; Figure 11 illustrates the spectral power distribution of a warm white light source; and Figure 12 illustrates the use of groups of LEDs with differing lens patterns in a lighting device of the invention.

Detailed Description of the Invention

Embodiments of the invention will now be described, by way of examples only.

Referring to Figures 1 to 5 of the accompanying drawings, the first embodiment of a lighting device in accordance with the present invention is in the form of a gooseneck lamp having a base 1 with a flexible stalk 3 and a lighting head 5. Head 5 is of broadly cylindrical form with an array of LED elements 7 being mounted behind a lens assembly 9 at that end of head 5 remote from stalk 3.

Referring more particularly to Figures 2 to 4, the head 5 of the lighting device is in the form of two part housing, a first part 11 being a cylindrical tube and a second part 13 being of a generally arrowhead shape in cross-section and for plugging into part 11 to form the overall housing 15 as best illustrated in Figure 5.

Within the housing 15 there is mounted, from front to rear, an acrylic window 17, a lens assembly 9 and, rearwardly therefrom, an LED array 7.

Behind LED 7 there is arranged a heat sink 19 in the form of a fanned metal sheet arrangement. Adjacent heat sink 19 housing 15 is provided with an air outlet in the form of a plurality of openings or vents 21.

Mounted rearwardly of heat sink 19 (within the second part 13 of the housing 15) is an electric fan 23 which is located adjacent cable entry port 25. Arranged around entry port 25 are a plurality of air inlet openings 27.

During operation of the above described lighting device, heat is generated by the LED array and this heat transfers to the heat sink 19 and the fan 23 draws air into the housing 15 through inlets 27. The air is propelled through the heat sink 19 where it extracts heat therefrom and thence out of the housing via outlets 21. In this way a very effective cooling of the lighting device is achieved.

Referring to Figures 6 and 7 of the accompanying drawings, a second embodiment of a lighting device in accordance with the present invention is illustrated. This second embodiment is in the form of a ring light in which a housing ring 31 is mounted for rotation within bracket 33 which in turn is connected to arm 35 and further arm 37 in such a way that the ring housing 23 can be moved into virtually any position relative to the object to be viewed, for instance, by a dentist or dental technician.

Figure 7 shows the 12 LED elements carried by the ring housing 31.

Referring to Figures 8 and 9 of the accompanying drawings the present invention may incorporate an illuminated magnifier. However such a device may result in a considerable amount of glare when used with highly glossy subject matter, as illustrated in the left hand view of Figure 8.

The glare problem can be virtually eliminated by the use of a pair of crossed polarising filters as illustrated in the right hand view of Figure 8. As illustrated in Figure 9 a first polarising filter is placed between the light source and the subject, and a second filter between the subject and the magnifying lens. When the second filter is positioned at 90 to the first filter almost all of the specula reflections are blocked whereas the diffuse light is allowed to pass.

Figure 10 illustrates the spectral power distribution for a daylight light source. This shows a considerable content of light with a wavelength between 400 and 480 nanometers. Such light will cure the composites used by dental laboratories in building restorations and, accordingly, premature curing can result. Figure 11 illustrates the spectral power distribution of the warm light source which contains far less radiation in the range 400 to 480 nm. Use of such a light source avoids the premature curing of the composite.

A lighting device in accordance with the present invention may include a switchable lamp incorporating both daylight and warm white light sources allowing the technician to work with composites under a warm white lamp without premature curing but still allowing him to use daylight light for other work.

A lighting device in accordance with the present invention may have groups of LEDs with differing lens patterns as a result of which the beam of light from the lamp can be controlled. Figure 12 illustrates an arrangement in which half of the LEDs have a wide unfocused beam while the other half have a narrow focused beam. Dimming the first half while brightening the second half will cause the lamp beam to focus from a wide angle to a narrow focused beam.

Claims

1. A lighting device comprising a housing having mounted therein an array of LED elements, said housing having an air inlet and an air outlet and defining an air flow path therebetween, and, mounted within the housing and located in said air flow path, heat transfer means for receiving heat generated by said LED elements and air moving means for causing air to be drawn into the housing via said inlet, moved along said air flow path and expelled from said housing via said outlet.

2. A lighting device according to claim 1, wherein the heat transfer means comprises a fanned sheet metal arrangement mounted adjacent the LED array and the air outlet.

3. A lighting device according to claim 1 or 2, wherein the air moving means is a fan mounted between the heat transfer means and the air inlet.

4. A lighting device according to any preceding claim wherein the housing is formed from a first part within which the LED array and heat transfer means are mounted and in a second part within which the air moving means is mounted.

5. A lighting device according to claim 5, wherein the two part housing is of substantially cylindrical form with the two parts having a common longitudinal axis and being connected together in a longitudinal side by side arrangement about said axis.

6. A lighting device according to any preceding claim, wherein the air moving means is an electric fan.

7. A lighting device according to any preceding claim, wherein the air moving means is a liquid cooling means.

8. A lighting device according to any preceding claim, wherein said device further comprises an illuminated magnifier.

9. A lighting device according to any preceding claim, wherein a first polarising filter is placed between the light source and a subject and a second filter is placed between the subject and the magnifying lens thereby reducing glare.

10. A lighting device according to claim 9, wherein the second filter is positioned at 900 to the first filter.

11. A lighting device according to any preceding claim, wherein the array of LEDs elements have differing lens patterns.

12. A light device as substantially herein described with reference to the accompanying description and Figures 1-5 and 8-9 or Figures 6-7 and 8- 9.