This invention relates to an LED device, and to an arrangement in which a plurality of individual LED devices are used in an array to form a lamp.
LEDs are in increasingly common usage in applications in which a light source is required. One such application is in the curing of inks and the like. In this application, a number of LEDs are arranged in an array, the LEDs being controllable, individually, to permit irradiation of an entire irradiable area (by operation of all of the LEDs) or irradiation of just selected regions of the entire area (by operation of just some of the LEDs). The LEDs used in the light source are of the type designed to emit light in the UV wavelengths. UV LEDs typically produce significant heat levels, and require cooling, in use.
One known LED arrangement for use in this type of application comprises an array of individually controllable UV LEDs, each of which is bonded to a common heat sink, for example of water cooled or air cooled form. The LEDs used in this type of application are expensive, and are often fairly unreliable, sometimes having a life span of as low of 500 hours. The applications in which the LEDs are used require all of the LEDs of the array to be in working order. If just one of the LEDs has failed, then the entire array is rendered unusable and must be replaced. Obviously, replacement of an entire array is inefficient if only one or very few of the LEDs thereof have failed. Replacement of individual LEDs of an array is a complex, time consuming operation as the LEDs need to be removed from the heat sink and, in-addition, need removal from the associated control circuit.
It is an object of the invention to provide an LED arrangement in which the disadvantages set out hereinbefore are overcome or of reduced effect.
According to the present invention there is provided an LED device comprising an LED mounted upon a circuit board, an electrical connector carried by the circuit board, and a heat sink carried by the circuit board and arranged to conduct heat away from the LED.
The LED may comprise a miniature array of LEDs.
Preferably, the LED is arranged to emit light in the UV wavelengths.
The heat sink is preferably of tapering form, for example of generally conical form. The heat sink may be of, for example, aluminium construction but it will be appreciated that a range of other materials of good thermal conductivity, for example copper, could be used.
The heat sink may be of hollow form.
The heat sink is preferably provided with a retaining recess within which a seal device is located to permit sealing of the heat sink to a manifold. The sealing device may comprise an O-ring. The manifold may be arranged to be supplied with water or another liquid coolant which can flow over and around the heat sink to assist in cooling.
Alternatively, the manifold may be of sealed form including a recess into which heat sink is receivable, heat transferring from the heat sink to the manifold and from there to the coolant, in use. The manifold is preferably designed to accommodate the heat sinks of a plurality of such LED devices.
It will be appreciated that, with such an arrangement, if one of the LED devices fails, that LED device can be removed from the manifold and replaced. Replacement of the LED device is a relatively simple process. The remaining LED devices can be left in position. Consequently, there is no need to replace all of the LED devices, including those which are still operational, thus efficiency savings can be made.
A light collector device may be associated with the LED device.
The invention further relates to an LED arrangement comprising a manifold having a plurality of openings formed therein, and a plurality of LED devices of the type defined hereinbefore, the heat sink of each LED device extending through or into a respective one of the openings, and the electrical connectors of the LED devices being releasably connected to a control circuit mounted upon or associated with the manifold.
The openings formed in the manifold are conveniently shaped to seal with seal devices, for example in the form of O-rings, associated with the LED devices.
The invention will further be described, by way of example, with reference to the accompanying drawings, in which:
Referring to
Bonded to the rear of the miniature array 16, and carried by the circuit board 10, is a heat sink 20. The heat sink 20 is of generally frustoconical form and defines, at a point close to its connection to the circuit board 10, a recess 22 of annular form. The heat sink 20 is of a material of good thermal conductivity, for example aluminium or copper. As shown in
The manifold 26 is arranged to carry an array of LED devices of the type illustrated in
In use, whilst all of the LED devices are operating correctly, the operation of each LED device is controlled by the control circuit, control signals being transmitted to the LED devices via the connectors 32 and connecting pins 14. It will be appreciated that, depending upon the desired mode of operation, all of the LED devices may be illuminated or, alternatively, only some of the LED devices may be illuminated at any given time. Heat from the junctions of the LED devices is conducted via the heat sinks 20 to the liquid coolant within the manifold 26. The generally frustoconical form of the heat sinks 20 results in a relatively large surface area thereof being available for heat transfer to the liquid coolant, thus assisting in heat transfer.
If it is determined that one of the LED devices has developed a fault, for example the miniature array 16 thereof is no longer operational or is no longer able to emit light at a required intensity, that one of the LED devices is removed from the manifold 26 and replaced with a new LED device. During the removal operation, the connecting pins 14 are disconnected from the associated connector 32 and the heat sink 20 is removed from the manifold 26. The replacement operation requires the heat sink 20 of the replacement LED device to be introduced into the appropriate opening in the manifold 26, the connecting pins 14 to be located in cooperation with the corresponding connector 32, and in the LED device being pushed home so that the O-ring associated with the replacement LED device forms a seal with the manifold 26. The LED arrangement is then, once again, ready for use.
It will be appreciated that, during the removal and replacement operation the opening in the manifold 26 is not sealed and so care needs to be taken to ensure that the manifold 26 is orientated to avoid the escape of liquid coolant.
The arrangement of the invention is advantageous in that, in the event of a failure, only the failed one or ones of the LED devices needs to be replaced, those that are still operational being kept in use. As a result, cost and efficiency saving can be made. Further, replacement can be achieved swiftly as there is no need to de-bond the LED device from a heat sink or to separate and remake a complex electrical connection with the control circuit board.
Although the arrangement described hereinbefore is of a liquid cooled form, it will be appreciated that the invention is also applicable to air or gas cooled arrangements, and appropriate modifications can be made to the arrangement described herein to permit such use without departing from the scope of the invention.
Rather than have the coolant flow over and around the heat sink 20, the heat sink 20 may simply be received within a recess formed in the manifold 26, the manifold 26 having coolant flowing therein. Such an arrangement may require the manifold to be of a material of better thermal conductivity, but does have the benefit that coolant will not be able to escape during replacement of the LED devices.
Referring to
The heat sink 20 is shown, in this embodiment, as being of generally cylindrical form but it will be appreciated that other forms, for example conical forms, are also possible. Further, the recess 20a is shown as being of cylindrical form but could be, for example, conical, and may be provided with ribs or grooves or the like if desired.
In the arrangement of
As with the other embodiments, the internal and external shape of the heat sink 20 may be modified, and ribs, grooves or other formations may be provided if desired. Further, the coolant flow direction may be reversed if desired.
It will be appreciated that in the arrangements of
In the arrangement of
A number of other modifications and alterations may be made to the arrangements described herein without departing from the scope of the invention. For example, many other types of seal arrangement could be used. One possibility is the use of bonded seals, but it will be appreciated that the invention is not restricted in this regard. Further, the direction and manner in which coolant flows through the manifold and/or over the heat sinks may vary from the arrangements outlined hereinbefore, and the heat sinks may be of a wide range of shapes and sizes without departing from the scope of the invention.
Number | Date | Country | Kind |
---|---|---|---|
0809650.5 | May 2008 | GB | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
---|---|---|---|---|
PCT/GB2009/001317 | 5/26/2009 | WO | 00 | 4/14/2011 |