Abstract
A cooling module, which is securable to one or more thermal transfer members for an LED curing apparatus, wherein the cooling module comprises a first finned heat sink and a second finned heat sink; wherein the first finned heat sink is removably securable to the second finned heat sink to provide at least one aperture therebetween, wherein each of a plurality of fins protrude from the first finned heat sink and from the second finned heat sink and each fin is substantially perpendicular to the length of the or each aperture, wherein the first finned heat sink is removably secured proximal to the second finned heat sink by at least one locking member, and wherein the or each locking member is inserted such that its length is parallel to the length of the or each aperture.
Claims
1. A cooling module, which is securable to one or more thermal transfer members for an LED curing apparatus, wherein the cooling module comprises: a first finned heat sink and a second finned heat sink; wherein the first finned heat sink is removably securable to the second finned heat sink to provide at least one aperture therebetween, wherein each of a plurality of fins protrude from the first finned heat sink and from the second finned heat sink and each fin is substantially perpendicular to the length of the or each aperture wherein the first finned heat sink is removably secured proximal to the second finned heat sink by at least one locking member, and wherein the or each locking member is inserted such that its length is parallel to the length of the or each aperture.
2. The cooling module according to claim 1, wherein the cooling module is securable to one or more thermal transfer members.
3. The cooling module according to claim 1, wherein the cooling module comprises a row of substantially cylindrical apertures.
4. The cooling module according to claim 1, comprising a row of apertures along its midline, wherein an inner surface of the first finned heat sink is proximal to an inner surface of the second finned heat sink substantially along the midline of the cooling module.
5. The cooling module according to claim 1, comprising one or more thermal transfer members wherein the first finned heat sink and the second finned heat sink are secured to the or each thermal transfer member.
6. The cooling module according to claim 1, wherein the cooling module is substantially symmetrical about a rotational axis of symmetry positioned along its midline.
7. The cooling module according to claim 1, wherein the first and second finned heat sink each comprise an array of fins wherein each fin is equidistant from an adjacent fin.
8. The cooling module according to claim 1, wherein the or each locking member brings the first finned heat sink into locking engagement with the second finned heat sink and wherein the first finned heat sink is removably secured proximal to the second finned heat sink by at least two locking members.
9. The cooling module according to claim 1, wherein the or each locking member is spaced apart from the or each fin of the first finned heat sink and the or each fin of the second finned heat sink.
10. The cooling module according to claim 1, wherein the first finned heat sink comprises at least one locking tab for interlocking with at least one locking tab on the second finned heat sink.
11. The cooling module according to claim 1, wherein the first finned heat sink comprises at least one locking tab for interlocking with at least one locking tab on the second finned heat sink and the or each locking tab is L-shaped or U shaped.
12. The cooling module according to claim 1, wherein the first finned heat sink comprises at least one locking tab for interlocking with at least one locking tab on the second finned heat sink and movement of the first finned heat sink away from the second finned heat sink moves the or each locking tab of the second finned heat sink into an interlocking configuration.
13. The cooling module according to claim 1, wherein the first finned heat sink comprises at least one locking tab for interlocking with at least one locking tab on the second finned heat sink such that when the or each locking tab of the first finned heat sink and the or each locking tab of the second finned heat sink are interlocked, further movement of the first finned heat sink away from the second finned heat sink is restricted.
14. The cooling module according to claim 1, wherein the first finned heat sink comprises at least one locking tab for interlocking with at least one locking tab on the second finned heat sink and wherein the or each locking member comprises a tension pin or a resilient pin or a spring pin or a screw insertable between the at least one locking tab of the first finned heat sink and the at least one locking tab of the second finned heat sink to prevent movement of the first finned heat sink away from the second finned heat sink.
15. The cooling module according to claim 1, wherein the first finned heat sink comprises at least one locking tab for interlocking with at least one locking tab on the second finned heat sink and wherein the or each locking member is insertable between the at least one locking tab of the first finned heat sink and the at least one locking tab of the second finned heat sink to lock the locking tabs together in a locked configuration.
16. The cooling module according to claim 1, wherein the first finned heat sink and the second finned heat sink are aluminium.
17. An LED curing apparatus comprising: an LED array comprising a plurality of LEDs mounted on an LED heat sink; at least one cooling module according to claim 1 secured around one or more thermal transfer members, wherein a first end of the or each thermal transfer member is proximal to the LED array and a second end of the or each thermal transfer member is held substantially within the at least one cooling module.
18. A method of installation of at least one cooling module according to claim 1 into an LED curing apparatus, wherein the LED curing apparatus comprises a plurality of thermal transfer members, comprising: removably securing a first finned heat sink to a second finned heat sink to provide at least one aperture therebetween, wherein a thermal transfer member is held within each of the at least one apertures; adjusting the position of the or each thermal transfer member; locking the first finned heat sink to the second finned heat sink by insertion of at least one locking member to form a cooling module; attaching the cooling module to an LED heat sink supporting an LED array.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0200] The invention will now be described by way of example with reference to the accompanying drawings, in which:
[0201] FIG. 1a shows a perspective view of a cooling module for an LED print curing apparatus in accordance with the present invention.
[0202] FIG. 1b shows a perspective view of an alternative embodiment of the cooling module for an LED print curing apparatus shown in FIG. 1a.
[0203] FIG. 2 shows a side view of a cooling module for an LED print curing apparatus in accordance with the present invention.
[0204] FIG. 3 shows a view from above of a first finned sink in accordance with the present invention.
[0205] FIG. 4a shows a view from above of a first finned heat sink interlocking with a second finned heat sink (heat pipes not shown) in a maintenance or assembly configuration in accordance with the present invention.
[0206] FIG. 4b shows a view from above of a first finned heat sink locked to a second finned heat sink (heat pipes not shown) in a use configuration in accordance with the present invention.
[0207] FIG. 5 shows a view from above of a first finned heat sink locked to a second finned heat sink (heat pipes not shown) in a use configuration in an alternative to the present invention.
[0208] FIG. 6 is a cross-sectional view through a cooling system for an LED print curing apparatus.
[0209] FIG. 7a is a perspective view of a heat pipe and collar as shown in FIG. 6.
[0210] FIG. 7b is a perspective view of an alternative embodiment of the thermal transfer member of FIG. 7a, wherein the thermal transfer member is a metal rod with a collar.
[0211] FIG. 8 is a cross-sectional view of the heat pipe and collar shown in FIG. 7a.
[0212] FIG. 9 shows a cross section through an LED curing apparatus and the air flow path therethrough for a preferred embodiment wherein air is pulled through the LED curing apparatus.
[0213] FIG. 10 shows a perspective external view of the LED curing apparatus of the FIG. 9 showing the direction of air flow through the apparatus.
[0214] FIG. 11 shows a cross section through an LED curing apparatus and the air flow path therethrough for an embodiment wherein air is blown through the LED curing apparatus.
[0215] FIG. 12 shows a perspective external view of the LED curing apparatus of FIG. 11 showing the direction of air flow through the apparatus.
DETAILED DESCRIPTION
[0216] Referring to FIG. 1a, FIG. 1b, FIG. 2 and FIG. 3, a cooling module 1, 1′ is shown and comprises a first finned heat sink 3 and a second finned heat sink 5. The first finned heat sink 3 is substantially symmetrical to the second finned heat sink 5 about a central axis 7 or midline where the internal surface 3a of the first heat finned sink 3 is proximal to and spaced apart from the internal surface of the second heat finned sink 5. Each finned heat sink 3, 5 is an aluminium extrusion and is shaped to maximise heat transfer away from the heat sink 3, 5 through a plurality of fins 9, which are substantially cuboidal, and each fin protrudes perpendicular to the central axis 7. The plurality of fins 9 are equally spaced from each other so that each fin 9 is spaced from the adjacent fin 9 by a uniform distance. For example, each fin 9 has a width of about between about 1.5 mm and 5 mm and is spaced from the adjacent fin 9. In a preferred embodiment, the fin 9 has a width of about 1.5 mm at its tip with a width increasing towards the midline of the fin with a pitch of 3.5 mm.
[0217] Referring to FIG. 1a, FIG. 1b and FIG. 3, the internal surface 3a of the first finned heat sink 3 comprises a series of semi-cylindrical recesses 3b. The internal surface (not shown) of the second finned heat sink 5 also comprises a series of semi-cylindrical recesses 5b and is symmetrical about the central axis 7 where the internal surface 3a of the first finned heat sink 3 is proximal to the internal surface 5a of the second finned heat sink 5. That is, each of the recesses 3b, 5b have the shape of a longitudinal half of a cylinder. As shown in FIGS. 1a and 1b, when the first finned heat sink 3 is removably secured to the second finned heat sink 5 the internal face of the first heat sink 3a is spaced apart from the internal face of the second heat sink 5a so that a plurality of substantially cylindrical recesses 11 are formed therebetween.
[0218] Referring to FIGS. 1a, and 2, in a use configuration, the cooling module 1 is secured to a plurality of thermal transfer members, shown as heat pipes 20.
[0219] In alternative embodiments, as shown in FIG. 1b, the cooling module is secured to a plurality of thermal transfer members; for example, a metal rod 20′ or a metal pipes, such as a copper rod or a copper pipe. The semi-cylindrical recesses 3b are substantially the same radius as the outer radius of the metal rod 20′. For example, each metal rod 20′ has a radius of about 4 mm and the cylindrical aperture formed by the semi-cylindrical recesses 3b, 5b have a radius of about 4 mm. This ensures that each metal rod 20′ is firmly held in place and that the heat transfer is as efficient as possible from each metal rod 20′ to the surrounding finned heat sink 3, 5. This maximises the heat transfer away from each metal rod 20′ to the fins 9 of each heat sink 3, 5.
[0220] As shown in FIG. 1a, a heat pipe 20 is received in each of the cylindrical recesses 11. Each heat pipe 20 is held securely within the cooling module 1 to ensure optimum thermal contact between the condenser section 21 of the heat pipe 20 and the cylindrical recess 11 into which the heat pipe is received. The heat pipes 20 secure the first and second finned heat sinks 3, 5 of the cooling module 1 in a tight clamping arrangement. The semi-cylindrical recesses 3b, 5b are substantially the same radius as the outer radius of the heat pipe 20. For example, each heat pipe has a radius of about 4 mm and the cylindrical aperture formed by the semi-cylindrical recesses 3b, 5b have a radius of about 4 mm. This ensures that each heat pipe 20 is firmly held in place and that the heat transfer is as efficient as possible from each heat pipe 20 to the surrounding finned heat sink 3, 5. This maximises the heat transfer away from each heat pipe 20 to the fins 9 of each heat sink 3, 5.
[0221] Referring to FIGS. 3, 4a and 4b. Each finned heat sink 3, 5 comprises an interlocking tab 15. In the embodiment shown in FIG. 3, the interlocking tab 15 is substantially L-shaped.
[0222] Referring to FIG. 4a, in a maintenance configuration, each of the plurality of thermal transfer members, such as heat pipes or metal rods (not shown) are located and held within a cylindrical recesses 11 between the first finned heat sink 3 and the second finned heat sink 5. The tab 15 of the first finned heat sink 3 interlocks with the tab 15 of the second heat sink 5 so that the cooling module 1 is held around the thermal transfer members (metal rods or heat pipes) but can be adjusted to allow for ease of insertion of multiple heat pipes into the cooling module. The interlocking tabs 15 stay linked whilst allowing partial movement of the first finned heat sink 3 and the second finned heat sink 5 around the thermal transfer members/heat pipes. In this maintenance configuration there is a small gap between the tab 15 of the first finned heat sink 3 that is interlocked to abut with the tab 15 of the second heat sink 5.
[0223] For installation of the cooling module, the thermal transfer members, such as heat pipes 20 or metal rods 20′ are first fitted to an LED heat sink on which LEDs are mounted. A carefully measured dose of heat transfer paste is applied to the semi-cylindrical recesses 3b, 5b of both the first finned heat sink 3 and the second finned heat sink 5. The first finned heat sink 3 and the second finned heat sink 5 are then interlocked as far as the interlocking tabs 15 allow. The interlocked finned heat sinks 3, 5 are then precisely lowered over and around the heat pipes 20. The first finned heat sink 3 is spaced apart from the second finned heat sink 5 when they are brought together to form the cylindrical apertures. The first finned heat sink 3 and the second finned heat sink 5 are mechanically clamped together by the interlocking tabs 15 for ease of installation.
[0224] Referring to FIGS. 4b, when all of the required thermal transfer members/heat pipes (not shown) are held in the desired position a locking pin 17 is inserted into the or each small gap between the tab 15 of the first finned heat sink 3 that is interlocked with the tab 15 of the second heat sink 5. In this final stage of installation, insertion of the locking pin 17 releases the mechanical clamp between the interlocking tabs 15 to transfer the locking force to the or each locking pin 17. The locking pin 17 is a tension pin or a spring pin. Referring to FIG. 1b, in an alternative embodiment a screw 17′, for example, a threaded screw, is inserted into the or each small gap between the tab (not shown) of the first finned heat sink 3 that is interlocked with the tab (not shown) of the second finned heat sink 5.
[0225] Referring to FIG. 4b and FIG. 3, insertion of a locking pin 17 or a screw 17′ in a direction parallel to the axis of the cylindrical recess 11 forces the tab 15 of the first finned heat sink 3 into locking engagement with the tab 15 of the second finned heat sink 5. Thus, each heat pipe 20 is held securely with the cylindrical recess 11 in the cooling module 1 so that the condenser section 21 is held against the finned heat sinks 3, 5 for optimum thermal transfer of heat from the heat pipe 20 to the fins 9.
[0226] Referring to FIG. 2, the evaporator section of each of the heat pipes 20 protrudes from the base of the cooling module 1 to be secured proximal to the LED heat sink in the lamphead.
[0227] Referring to FIGS. 4a and 4b, in a maintenance position without the locking pin or screw inserted, the first and second finned heat sinks 3, 5 can move in a direction shown by arrow 25 towards and away from a thermal transfer member/heat pipe/s contained between them in the cylindrical recesses. Referring to FIG. 4b, when the locking pin 17, or in alternative embodiments a screw, is inserted, in a use position, the first and second finned heat sinks 3, 5 are forced towards each other in a direction shown by arrow 27 so that their internal surfaces are proximal to each other and are locked in position.
[0228] In use with an LED curing apparatus, a plurality of cooling modules are arranged along the length of the LED curing apparatus around a plurality of thermal transfer members, for example heat pipes or metal rods. The cooling modules have a length of about 25 mm and are arranged substantially along the full length of the lamphead and are locked in place by the locking pins or screws. For known devices, the thermal transfer members, for example heat pipes or metal rods are spaced at increments of about 2.5 cm for a range of lengths from 2.5 cm to 250 cm. The cooling modules of the present invention are configured so that the cooling modules can be conveniently installed on site; for example, during an on-site repair. The cooling modules can be fixed to the thermal transfer members, for example heat pipes or metal rods, after the LEDs are attached to the LED heat sink.
[0229] The lamphead comprises an array of LED modules (not shown), wherein each LED module is a unit containing one or more LEDs. In use, each LED is a radiation source for curing print or a coating on a substrate (not shown). It is understood that the LED modules form a linear radiation source to direct radiation continually onto a substrate during curing. The LED modules comprise boards that rest on a heat sink (not shown). This LED heat sink is adjacent to the evaporator section of each of the plurality of heat pipes or to one end of each of a plurality of metal rods.
[0230] In use, the LEDs are arranged to emit radiation from an outer, substrate-facing side through a “curing window” onto a substrate (not shown) to be cured. In alternative embodiments of the present invention, the “curing window” comprises a lens or reflector. The lamphead is an elongate shape and can be fitted directly onto a machine, or is a slideable cuboidal cassette which, in use, is slideable into a housing. When inserted into the housing, the LED modules form a solid radiation emitting face.
[0231] Referring to FIGS. 1a and 2 in use, heat is transferred away from the inner face of the LED modules to the evaporator section 23 of the heat pipes 20. Heat is carried from the evaporator section 23 of each heat pipe 20 to the condenser section 21 that is held substantially within the cooling module 1. In alternative embodiments, as shown in FIG. 1b, heat is carried from a first end of a thermal transfer member, such as a metal rod to a second end of a thermal transfer member/metal rod within the cooling module 1′. Heat is then efficiently transferred though the first and second finned heat sink 3, 5 so that the LEDs are rapidly and efficiently cooled. Furthermore, the configuration of the present invention ensures that the cooling modules 1 hold the thermal transfer members/heat pipes 20′, 20 in place, achieving good thermal contact between the finned heat sinks 3, 5 and the thermal transfer members/heat pipes 20′, 20, wherein the clamping force between the heat sinks 3, 5 and the thermal transfer members/heat pipes 20′, 20 is uniform along the length of the cooling module 1.
[0232] The heat pipes 20 of first embodiment of the present invention use known heat pipe technology to take up heat generated by the LED modules (not shown). In use, when the lamphead is switched on and the LEDs are radiating to cure a substrate, heat generated by the LEDs is transferred away from the rear, inner face of each LED module to an aluminium heat sink (not shown). Heat is carried away from the LEDs and the copper heat sink by the heat pipe/s 20 and is then carried away from the heat pipes 20 by the first and second finned heat sinks 3, 5. On heating, the liquid held within the core of the heat pipe 20 is vaporised and the heat is carried away before the liquid re-condenses and a wick transports the liquid back to the base of the heat pipe 20. Heat is rapidly transferred from the LED modules to the heat pipes 20 and to the cooling modules.
[0233] Referring to FIG. 1a and FIG. 1b, to access the thermal transfer members 20, 20′ for maintenance or repair, the pins 17 or screws 17′ securing the cooling module 1 around the heat pipes 20 or metal rods 20′ are removed. With the pins 17 or screws 17′ removed, the first finned heat sink 3 is able to move away from the second finned heat sink 5 increasing the size of the cylindrical recesses and allowing the cooling module 1 to be removed from the heat pipes 20 or metal rods 20′. Movement of the first finned heat sink 3 and second finned heat sink 5 away from each other causes the locking tabs 13, 15 to move into an interlocking position. This maintains the first finned heat sink 3 interlocked with the second finned heat sink 5 so that the components of the cooling module 1, 1′ remain assembled when the cooling module is in a maintenance configuration. The cooling module 1 can then be removed from the thermal transfer members; i.e. the heat pipes 20, shown in FIG. 1a and the metal rods shown in FIG. 1b, if required.
[0234] Referring to FIGS. 6 and 8, a cooling system 31 for an LED print curing apparatus is shown. The cooling system 31 comprises an LED mount 33. In use a plurality of LEDs 35 are mounted on the LED mount 33. In use, the LEDs are arranged to emit radiation from an outer, substrate-facing side. The cooling system 31 supports a plurality of thermal transfer members, such as copper rods or copper heat pipes 39, wherein the heat pipes 39 sit within the body of the LED mount 33 and transfer heat away from the LEDs 35 to a cooling module 43. It is understood that in further embodiments, an alternative thermal transfer member rather than the heat pipe shown in FIGS. 6 and 8 is used; for example, a metal rod.
[0235] The cooling system 31 comprises an aluminium LED mount 33, which carries heat generated by the LEDs 35 away from the LEDs 35 to the thermal transfer members/copper heat pipes 39. The dimensions of the aluminium heat sink 33 are carefully configured to be fitted within the lamphead of a curing apparatus (not shown). The cooling system 31 comprising the LED mount 33, LEDs 35 and thermal transfer members/heat pipes 39 form a modular system. In use, multiple cooling systems 31 are arranged along the length of a curing apparatus. The plurality of thermal transfer members/heat pipes 39 are a passive heat transfer system to efficiently carry heat away from the LEDs 35. In one embodiment of the present invention, the modular system comprises two heat pipes 39 per length of LED mount 33.
[0236] With reference to FIG. 6 and FIGS. 7a and 7b, each of the thermal transfer members/copper heat pipes 39′, 39 are provided with a copper collar 37, 37′ which is soldered to the heat pipe 39, 39′. The collar 37, 37′ includes a screw thread 37b, 37b′ on a substantial portion of an outer surface thereof and a smooth, non-threaded portion 37a, 37a′. The LED mount 33 comprises a series of substantially cylindrical bores 41, which have a threaded inner surface for engagement with the corresponding screw thread 37b, 37b′ on the outer surface of a copper collar 37, 37′. This allows the thermal transfer members/heat pipes 39′, 39 to be screwed into the bores 41 in the LED mount 33 for secure attachment thereto with the collar 37, 37′. The collar shown in FIG. 11a is surrounding the evaporator section of the heat pipe 39 so that when attached each heat pipe 39 is fully contained within the LED mount 33 when fitted to the cooling system 31. The collar shown in FIG. 11b is surrounding a first end of the metal rod/thermal transfer member 39′ so that when attached each metal rod/thermal transfer member 39′ is fully contained within the LED mount 33 when fitted to the cooling system 31. In use, this allows the LEDs 35 to be mounted to the LED mount 33 before the thermal transfer members/metal rods/heat pipes 39′, 39 are each fitted into a respective bore 41.
[0237] Referring to FIG. 7b, the collar 57′ and metal rod 59′ are formed as a single piece. This improves thermal transfer and reduces the time and complexity of installation.
[0238] The configuration shown in FIGS. 6, 7a, 7b and 8 significantly improves the ease of installation of the thermal transfer members/heat pipes 39′, 39 within a curing apparatus. In use, the LEDs 35 are attached to the LED mount 33 and the thermal transfer members/heat pipes 39′, 39 are attached at a later stage. This minimises the installation time in a clean room because only the LEDs need to be installed in this controlled environment, whilst other components of the cooling system can be installed at the location of use of the apparatus. Multiple LED mounts 33 having LEDs 35 attached thereto are installed in the chassis of a curing apparatus before the thermal transfer members/heat pipes 39′, 39 are screwed into the LED mount 33 and attached thereto by the mating engagement of the screw thread 37b, 37b′ on the outer surface of the collar 37, 37′ with the threaded inner surface of the bore 41 into which the heat pipe 39 or metal rod 39′ is received. The present invention allows for ease of assembly of the LED mounts 33 into the curing apparatus before the thermal transfer members/heat pipes 39′, 39 and further cooling components are installed. Furthermore, the thermal transfer members/heat pipes 39′, 39 and other cooling components can be removed and replaced; for example, if these components fail or require cleaning, without the sealed chassis of the apparatus containing the LEDS being removed. Removal of the LEDS is more likely to damage the delicate LEDs and the configuration described with regard to FIGS. 6, 7a, 7b and 8 significantly reduces the risk of damage or contamination of the LEDs.
[0239] A ceramic paste (not shown) is provided between the outer surface of each of the heat pipe collars 37, 37′ and the respective inner surface of the bore 41 in which the thermal transfer members/heat pipe 39′, 39 is held. The ceramic paste prevents voids forming between the collar 37′, 37 and the bore 41, which ensures optimum thermal contact between the LED mount 33 and the thermal transfer members/heat pipes 39′, 39 because there are no thermal barriers to the heat transfer away from the LED mount 33 and so away from the LEDs 35, in use.
[0240] In the example shown in which corresponding screw threads 37b, 37b′ are provided on the external surface of the collar 37, 37′ and the internal surface of the bore 41, it will be appreciated that the ceramic paste can be applied to one or both threaded surfaces before the thermal transfer members/metal rods/heat pipes 39′, 39 are screwed into the LED mount 33. During installation, the rotation of the external threaded surface of the collar 37′, 37 against the internal threaded surface of the bore 41 spreads the ceramic paste so that any voids are eliminated.
[0241] Referring to FIGS. 6 and 7a, in use, the central core of each heat pipe 39 contains a liquid, such as water or ammonia, which prior to heating is held by a wick structure (not shown). The heat pipe 39 contains a vacuum so that the liquid will boil and take up heat generated by the LEDs 35 at a temperature below the boiling point of the liquid at atmospheric pressure. The water will boil and effectively transfer latent heat from the LEDs 35 modules at this lower temperature. In use, when the LED print curing apparatus is switched on and the LEDs 35 are radiating to cure a substrate, heat generated by the LEDs 35 is transferred away from the rear, inner face of the LEDs 35 to the LED mount 33. Heat is carried away from the LED mount 33 by the heat pipe/s 39 to a cooling module 43. On heating, the liquid held within the core of the heat pipe 39 is vaporised and the heat is carried away before the liquid re-condenses and the wick transports the liquid back to the base of the heat pipe 39. The heat pipe/s 39 ensures that heat is carried away quickly and efficiently from the LEDs 35 and condensation of the liquid contained within the core of the heat pipe 39 is enhanced by capillary action.
[0242] As shown in FIG. 6, the evaporator section of each heat pipe 39 is adjacent to the LED mount 33 and the LEDs 35 that are mounted thereon. The opposing end—i.e., the condenser end of each heat pipe 39 is held within a cooling module 43. In a preferred embodiment, the cooling module 33 is an air-cooled finned heat sink.
[0243] As shown with particular reference to FIG. 7a, 7b and FIG. 8, in order to increase the contact surface area of the collars 37, 37′ and the bores 41, the outer walls of the collars 37, 37′ are shaped to fit against correspondingly shaped walls of the bores 41. Each collar 37, 37′ has a smooth, rounded base section 37a, 37a′, which is received into a bore 41. The mechanical fit of the threaded portion 37b, 37b′ with the threaded portion of the bore 41 in addition to the heat transfer material (not shown) between the external surface of the collar 37, 37′ and the thermal transfer members/metal rod/heat pipe 39′, 39 and the internal surface of the bore 39 ensures that there are no voids such that thermal transfer is optimised.
[0244] Referring to FIGS. 9 and 10, an LED curing apparatus 51 is shown comprising a housing 53. The housing 53 comprises an outer casing wherein LEDs (not shown) are mounted at the base 58 of the housing 53 and an air inlet 77 is positioned in an upper face 59 of the housing 53. The air inlet 77 is an elongate opening along substantially the entire length of the upper face of the apparatus 51. The base 58 of the LED curing apparatus 51 is the substrate-facing surface with the or each LED radiation source arranged thereon. In a preferred embodiment, the LED radiation source is a UV radiation source. In alternative embodiments, the LED radiation source is an infra-red radiation source. The upper face of the apparatus 51 is substantially parallel to and spaced apart from the base of the apparatus 51. An air outlet 52 is positioned at a first end 56 of the apparatus 51, wherein the first end 56 is perpendicular to and between the base 58 and the upper face 59 of the apparatus 51. The air outlet 52 is attached to ducting connected to a source of ambient or cooled air.
[0245] The LED curing apparatus 51 comprises a plurality of LEDs (not shown) mounted to an LED mount. The inner walls of the housing 53 and the cavities formed therein are shaped to control air pressure and air flow through the LED curing apparatus 51. The housing 53 is substantially cuboidal comprising outer walls 53 and inner walls 70 to which further components are mounted. The shape of the inner walls of the housing 53 controls air pressure and so air flow through the device.
[0246] Referring to FIG. 9, an inner wall of the housing 70 defines an upper air channel 72 through which air from the air inlet 77 passes into the curing apparatus 51. The upper air channel 72 is parallel to the outer walls 53 of the housing. Preferably, the width of the upper air channel 72 is about 4 mm. The upper air channel 72 increases in width to about 10 mm and passes from the air inlet 77 to an inlet cavity or void 71.
[0247] A plurality of thermal transfer members, shown in FIGS. 9 and 10 to be heat pipes 14, are mounted along the length of the LED curing apparatus 1. In alternative embodiments, an alternative thermal transfer member is used; for example, as shown in FIG. 1b, the thermal transfer member is a metal rod. In the embodiment shown in FIG. 9, each heat pipe 64 is held securely within a cooling module 57, ensuring optimum thermal contact between the heat pipe 64 and a substantially cylindrical recess into which each heat pipe is received. The or each thermal transfer member/heat pipe 64 passes through the inlet cavity or void 71 of the housing 53. The cooling module 57 comprises a first finned heat sink 61 and a second finned heat sink 63. The first finned heat sink 61 is substantially symmetrical to the second finned heat sink 63 about a central axis or midline. Each finned heat sink 61, 63 is shaped to maximise heat transfer away from the heat sink 61, 63 through a plurality of fins (not shown), which are substantially cuboidal. In alternative embodiments, it is understood that equivalent heat sinks could be used. For example, an arrangement of pins or blades could be used, including a skived heat sink. It is also envisaged that alternative configurations of the present invention include finned heat sinks in alternative positions to carry heat away from the thermal transfer members, which are either heat pipes or metal rods.
[0248] The inner walls of the housing 53 define a main cavity or void 71 below the or each finned heat sink 61, 63 and a second cavity or outlet void 74 above the or each finned heat sink 61, 63 through which heated air 75 exits the LED curing apparatus 51. For example, the cross-sectional area of the air path through the outlet void 74 is about 1.2 times greater than the cross-sectional area of the air path through the inlet void 71.
[0249] The first finned heat sink 61 and the second finned heat sink 63 are removably held within the housing 53 by a shaped extrusion 65 comprising a base 67a, 67b and two upstanding walls 68. The base 67a, 67b and upstanding walls 68 are formed of a shaped extrusion, wherein each upstanding wall 68 is substantially perpendicular to the base 67a, 67b and held within the outer walls of the housing 53. The base 67 comprises a first base member 67a and a second base member 67b, which are substantially parallel to the LED mount. The first and second base members 67a, 67b partially cover the base of the respective finned heat sink 61, 63. The first finned heat sink 61 is housed above the first base member 67a and the second finned heat sink 63 is housed above the second base member 67b. The base members 67a, 67b are spaced apart from each other to form a restriction in the air flow through a gap therebetween to provide an air inlet 69 into the finned heat sinks 61, 63 through which air is pulled.
[0250] Referring to FIGS. 9 and 10, air 77 is pulled into the apparatus by a source of air connected by ducting to the outlet 52. Typically, the air pressure at the outlet ducting is about −2050 Pa relative to ambient pressure and the pressure of air drawn into the air inlet 77 is between about −350 Pa to −500 Pa relative to ambient pressure. The air pressure is higher at the inlet 77 to the apparatus to create suction so that air is pulled through the apparatus 1 from the inlet 77 to the outlet 52. The air 76 flows from the inlet 77 around an air passage 72 along the inner walls of the housing 53 and enters the open, inlet cavity/void 71 below the or each finned heat sink 61, 63 to expand such that air pressure decreases to about −500 Pa to −450 Pa relative to ambient pressure. The air from the open cavity/void 71 adjacent to the LED mount then flows, i.e., is pulled into the finned heat sinks 61, 63 to carry heat away from the heat sinks 61, 63.
[0251] The air inlet 69 into the finned heat sinks 61, 63 controls i.e., throttles the air flow entering the finned heat sinks 61, 63 from the inlet cavity 71 of the housing 53 to create a turbulent flow of air through the finned heat sinks 61, 63. When the heated air 75 is carried out of the finned heat sinks 61, 63 it expands into the second cavity or outlet void 74 so that pressure decreases again.
[0252] The restriction 67a, 67b proximal to the or each finned heat sink 61, 63 reduces the cross sectional area of the air flow path from the open inlet cavity 71 below the finned heat sink 61, 63. The reduction in the cross sectional area of the air flow path from the inlet cavity 71 to the finned heat sinks 61, 63 is by a ratio of about 1:2.3 (inlet cavity:finned heat sink). The reduction in the cross-sectional area of the air flow path from the cavity 71 below the heat sinks 61, 63 to the or each finned heat sink 61, 63 reduces by more than 50%. In an example apparatus 51, the air inlet 69 between the outer wall of the thermal transfer member/heat pipe 64 and the restriction 67a, 67b is about 8.5 mm (A) so that the open area per heat sink is about 410 mm.sup.2. Air enters the finned heat sinks 61, 63 through the air inlet 69 and passes across the fins of the heat sinks 61, 63, wherein the distance (B) along, i.e., the length of each fin from the outer wall of the thermal transfer member/heat pipe 64, is about 19.5 mm. When air flows into the heat sinks 61, 63, the restriction of the air flow by the first and second base members 67a, 67b causes significant turbulence of the air passing into the finned heatsinks 61, 63, which increases heat transfer from the fins to the surrounding air. This increases the cooling achieved by the finned heat sinks 61, 63.
[0253] The size and shape of the housing 53, the air inlet 77, the air passage 72, the cavity 71, the base supports 67a, 67b and the second cavity/outlet void 74 are carefully configured to decrease relative air pressure moving through the apparatus 1 and maximise cooling of the finned heat sinks 61, 63. The configuration of the present invention ensures that air flows through the apparatus 51 to carry heat away from the thermal transfer members 64, for example heat pipes 64 or metal rods (not shown) and ensures that cooling is substantially uniform along the length of the device 51. The air in the inlet cavity 71 below the finned heat sinks 61, 63 is at a higher pressure than the air in the outlet cavity 74 above the finned heat sinks 61, 63. The air pressure decreases when the air moves out of the finned heat sinks 61, 63 to the outlet cavity 74.
[0254] The air pressure outside the apparatus 51 at the air inlet 77 through which air is pulled into the apparatus 51 is about +101 kPa. The air pressure decreases when the air reaches the open sections/cavities 71, 74 into which it expands. The air pressure in the inlet cavity 71 is about −600 Pa relative to ambient pressure and the air pressure of the heated air 75 exiting the finned heat sinks 61, 63 that is pulled towards the air outlet 52 is about −1150 Pa relative to ambient pressure.
[0255] The present invention can be configured for any length of apparatus—i.e., according to the required application. The ratios of the air path sections as air flows from the air inlet 77 to the air outlet 52 is controlled to achieve the required air flow and so uniform cooling along the length of the apparatus 51.
[0256] Examples of the cross-sectional areas of the air flow passage though each section of the apparatus 51 are set out in Table 1 below for an apparatus having a 30 cm length:
TABLE-US-00001 TABLE 1 30 cm length apparatus cross sectional Position area of the air flow passage (mm.sup.2) Air inlet (27) 1964 Air inlet into the 3280 finned heat sinks (19) Outlet cavity (24) 3910 Outlet ducting 6718
[0257] Referring to FIG. 10, in a preferred embodiment of the present invention, air 73 is pulled into the air inlet 77, which is along the length of the housing 53, from a single fan (not shown) at the air outlet 552 at a first end 6 at the rear of the housing 553. The fan can be connected to the housing 53 by ducting and the fan is positioned remotely from the apparatus 51. Referring to FIG. 9, air 76 is pulled through the housing 53 and enters the cooling module 57 through the air inlet 69 between the first base member 67a and the second base member 67b. The air inlet 69 effectively controls the air flow entering the cooling module 57. The air inlet/gap 69 through which air enters the finned heat sinks 61, 63 chokes—i.e., restricts and controls the air flow into the finned heat sinks 61, 63. The air then passes along the plurality of fins and through the first and second finned heat sinks 61, 63 adjacent to the thermal transfer members 64, for example, heat pipes 64 or metal rods. The heated air 75 is pulled out of the housing 53 to the outlet cavity 74 and to the outlet 52 to exit and so cool the LED curing apparatus 51.
[0258] With reference to FIG. 9, the uniformity of pressure, air flow and so cooling along the length of the apparatus 51 was measured by positioning sensors at fixed points (Position 1—air inlet channel 72; Position 2—air channel into open cavity 71; Position 3—outlet cavity 74). It can be seen from the results shown in Table 2 below that the pressure measurements are substantially uniform along the length of the apparatus:
TABLE-US-00002 TABLE 2 Gauge Pressure (Pa) - relative to ambient pressure Measurement Position along the length of the apparatus (mm) Point 116.25 192.75 269.25 345.75 1 −357 −377 −473 −440 2 −650 −783 −757 −823 3 −483 −470 −473 −447
[0259] Referring to FIGS. 11 and 12, an LED curing apparatus 51′ of an alternative embodiment is shown, cool air 73′ is blown into and along the length of the housing 53′ from a single fan (not shown) into the air inlet 52″ at a first end (rear) of the housing 53′. The fan can be connected to the housing by ducting and the fan is positioned remotely from the apparatus 51′. The cool air 73′ enters the cooling module 57′ through the air inlet 69′ between the first support 67a′ and the second support 67b′. The air inlet 69′ effectively controls the air flow entering the cooling module 57′. The air inlet/gap 69′ through which air enters the finned heat sinks 61′, 63′ chokes—i.e., restricts and controls the air flow into the finned heat sinks 61′, 63′. The air then passes along the plurality of fins and through the first and second finned heat sinks 61′, 63′ adjacent to the condenser section of the heat pipe. The heated air 75′ rises upwards through the cooling module 57′ to the outlet 77′ to leave the housing 53′.
[0260] The above described embodiments have been given by way of example only, and the skilled reader will naturally appreciate that many variations could be made thereto without departing from the scope of the claims.
[0261] Within this specification embodiments have been described in a way which enables a clear and concise specification to be written, but it is intended and will be appreciated that embodiments may be variously combined or separated without parting from the invention. For example, it will be appreciated that all preferred features described herein are applicable to all aspects of the invention described herein and vice versa.
[0262] Within this specification, the term “about” means plus or minus 20%, more preferably, plus or minus 10%, even more preferably, plus or minus 5%, most preferably, plus or minus 2%.
[0263] Within this specification, the term “substantially” means a deviation of plus or minus 20%; more preferably, plus or minus 10%; even more preferably, plus or minus 5%, most preferably, plus or minus 2%. Within this specification, reference to “substantially” includes reference to “completely” and/or “exactly.” That is, where the word substantially is included, it will be appreciated that this also includes reference to the particular sentence without the word substantially.
