Patent Grant
11920774
The present application claims priority to GB Patent Application Serial No. 2201293.4, filed Feb. 1, 2022, GB Patent Application Serial No. 2201298.3, filed Feb. 1, 2022, and GB Patent Application Serial No. 2215540.2, filed Oct. 20, 2022, the contents of each of which are incorporated herein by reference in their entirety.
The present invention relates to an improved cooling system for an LED curing apparatus for printing and coating applications and a method of installation of an improved cooling system.
The use of LED (light-emitting diode) arrays for curing in printing and coating applications is becoming increasingly popular as an alternative to traditional mercury arc lamps. However, a limitation to the use of LEDs in existing curing apparatus, which have a standard heat sink and known cooling systems to carry heat away from the LEDs, is that the apparatus must be run at a reduced power to prevent overheating of the LEDs.
There is a need to ensure that heat generated is efficiently transferred away from the high density LEDs. The use of LEDs in print curing applications requires high density packing of LEDs on a circuit board, such that a very large amount of heat is generated across a small area. It is important that the LEDs do not overheat and become damaged or fail. Effective cooling is also needed to ensure that the curing effect is not sub-optimal; that the substrate that is cured is not damaged by the excess heat created; and that the efficiency of the LEDs is not reduced by ineffective cooling.
To increase the radiation output of the LED curing apparatus, it is necessary to increase the number of LEDs. However, for curing applications requiring a linear array having a fixed area, an increase in the number of LEDs requires an increase in LED density and a reduction in LED spacing. These factors increase the amount of heat generated, such that there is a need for efficient, reliable and uniform cooling to ensure the long-term viability of the LEDs.
A currently proposed solution is described in the applicant's prior published European patent publication EP3406446, which discloses a plurality of heat pipes held within a water-cooled holder. However, cooling of this prior art system requires a water inlet and a water outlet channel. Further known devices are air-cooled and have fans integrated into the LED lamphead. However, there are limitations to the cooling effect that can be achieved using such known devices and air-cooled devices can only currently be operated at lower power. Further, existing air-cooled devices are complex, bulky and incompatible with being integrated into known housings for UV LED print curing apparatus. Thus, there remains a significant need to provide an improved cooling system for LED curing apparatus for printing and coating applications. There are also significant environmental benefits in improving the efficiency of the cooling system because this reduces the power that needs to be supplied to cool the lamphead and so the environmental impact of the curing process.
The present invention sets out to provide an improved LED curing apparatus, an improved cooling module for an LED curing apparatus and a method of installation of a cooling module into an LED curing apparatus, which alleviates the problems described above.
In one aspect, the invention provides a cooling module, which is securable to one or more thermal transfer members for an LED curing apparatus, wherein the cooling module comprises:
It is understood that “length” refers to the longest dimension of the aperture.
Preferably, the cooling module is an LED curing apparatus cooling module.
Preferably, the or each thermal transfer member is a metal rod.
Preferably, the or each thermal transfer member is a heat pipe.
Optionally, the or each thermal transfer member is a metal rod or a metal pipe. Further optionally, the or each thermal transfer member is a copper rod or a copper pipe.
Preferably, the first finned heat sink and the second heat sink are extruded.
Optionally, the first finned heat sink and the second heat sink comprise a plurality of blades. Further optionally, the first finned heat sink and the second heat sink comprise a plurality of skived fins or blades.
The present invention is a significant improvement because the first and second finned heat sinks maximise heat transfer away from the cooling module.
Preferably, the at least one aperture is substantially cylindrical.
Preferably, the cooling module comprises a row of apertures. More preferably, a row of substantially cylindrical apertures.
Preferably, the cooling module comprises 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.
It is understood that in the context of this invention “proximal to” means that the first finned heat sink is close to the second finned heat sink.
It is understood that in the context of this invention the “midline” of the cooling module is the line or plane of the body of the cooling module equidistant from the outer finned surfaces of the first and second finned heat sinks. The outer surfaces are furthest from the length of the thermal transfer members/heat pipes in use.
Preferably, the cooling module comprises one or more heat pipes; more preferably, the or each heat pipe is substantially cylindrical.
Preferably, the cooling module comprises one or more thermal transfer members; more preferably, the or each thermal transfer member is substantially cylindrical.
Preferably, the cooling module comprises one or more metal rods; more preferably, the or each metal rod is substantially cylindrical.
Preferably, the or each thermal transfer member is substantially in contact with the wall of the aperture into which it is received.
Preferably, the or each metal rod is substantially in contact with the wall of the aperture into which it is received.
Preferably, the or each heat pipe is substantially in contact with the wall of the aperture into which it is received.
Preferably, the first finned heat sink and the second finned heat sink are secured to the or each thermal transfer member.
Preferably, the first finned heat sink and the second finned heat sink are secured to the or each metal rod.
Preferably, the first finned heat sink and the second finned heat sink are secured to the or each heat pipe.
Preferably, the first finned heat sink is spaced apart from the second finned heat sink by the or each thermal transfer member.
Preferably, the first finned heat sink is spaced apart from the second finned heat sink by the or each metal rod.
Preferably, the first finned heat sink is spaced apart from the second finned heat sink by the or each heat pipe.
Preferably, the first finned heat sink is spaced apart from the second finned heat sink by the or each thermal transfer member along the mid-line of the cooling module.
Preferably, the first finned heat sink is spaced apart from the second finned heat sink by the or each metal rod along the mid-line of the cooling module.
Preferably, the first finned heat sink is spaced apart from the second finned heat sink by the or each heat pipe along the mid-line of the cooling module.
The configuration of the cooling module of the present invention maximises the efficiency of cooling by increasing the heat transfer away from an LED curing system using a thermal transfer member/s, such as a metal rod/s or heat pipes. The finned heat sinks can be closely fitted to the thermal transfer member; for example, so that the cylindrical apertures are each adjacent to the condenser section of a heat pipe/s received in a respective cylindrical aperture. The present invention maximises the efficiency of heat transfer away from the LEDs and then from the thermal transfer member, such as metal rods or heat pipes, by allowing multiple thermal transfer members (metal rods or heat pipes) to be fitted close together and maximising the transfer of heat away from the cooling module by maximising the number of fins and the surface area through which heat can be transferred away.
Preferably, the axis of each cylindrical aperture is positioned equidistant from the outer edge of the first finned heat sink and from the outer edge of the second finned heat sink.
The axis of the or each cylindrical aperture is the segment containing the centre of the two bases of the cylinder.
Preferably, the cooling module is substantially symmetrical about a rotational axis of symmetry positioned along its midline.
It is understood that in the context of this invention, “symmetrical” refers to the shape and configuration of the first finned heat sink being the same as the shape and configuration of the second finned heat sink. That is, in use the first finned heat sink could take the place of the second finned heat sink if it were rotated by 180-degrees.
Preferably, the fins of the first finned heat sink are aligned to be symmetrical with the fins of the second heat sink about the midline of the cooling module.
Preferably, the first and second finned heat sink each comprise an array of fins wherein each fin is equidistant from an adjacent fin.
The symmetry and the uniform arrangement of the fins of both the first and second finned heat sink ensures that there is equal cooling along the length of each finned heat sink and across the width of the cooling module/s. For example, in an air cooled device the velocity of air along the fins and so along the length of the lamphead in which the cooling modules are installed is uniform, such that the cooling effect along the length of the lamphead is uniform. Similarly, the symmetry of the cooling module/s ensures that the velocity of air and the rate of cooling across the width of the lamphead is also uniform. This improves the quality of the cured substrate and minimises the risk of damage to any of the LEDs.
Preferably, the first finned heat sink is removably secured proximal to the second finned heat sink by at least one locking member, wherein the or each locking member brings the first finned heat sink into locking engagement with the second finned heat sink. More preferably, the first finned heat sink is removably secured proximal to the second finned heat sink by at least two locking members, wherein the or each locking member brings the first finned heat sink into locking engagement with the second finned heat sink.
Preferably, 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.
The arrangement of the present invention allows for the first and second finned heat sink to be coupled together without the or each locking member interfering with the fins that protrude from the first and second finned heat sink. Thus, the locking member does not reduce the capacity for heat transfer away from the thermal transfer members (heat pipes or metal rods) via the finned heat sinks. If the cooling module requires fixings that are not spaced apart from the fin/s of the heat sink then the surface area available for heat transfer away from the cooling module is reduced. The configuration of the locking member does not take up space that is better utilised by a fin/s to maximise cooling. Furthermore, the locking member does not interfere with the uniform arrangement of the fins along the length of the cooling module so that, for an air-cooled device, air flow through the fins is uniform along the length of the cooling module and the lamphead to which it is fitted.
Preferably, 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.
More preferably, the first finned heat sink comprises at least two locking tabs for interlocking with at least two locking tabs on the second finned heat sink.
The present invention ensures that the force exerted on the thermal transfer members (heat pipe/s or metal rods) by the first finned heat sink is equal to the force exerted on the thermal transfer members (heat pipe/s or metal rod/s) by the second finned heat sink.
It is understood that “interlocking” refers to component parts that, in use, mechanically connect and fit together so that movement of the connected parts is constrained.
Preferably, the or each locking tab is L-shaped or U shaped.
The arrangement of the present invention allows for the two component parts; i.e., the first and second finned heat sinks, to be conveniently held in place around the thermal transfer member; for example, the heat pipes, before the finned heat sink is locked into position. The two-stage securing process allows for location and adjustment of the components before they are fixed into position and avoids any risk of damage or misalignment of the heat pipes within the cooling module. The carefully configured interlocking arrangement of the locking tabs is an efficient way to position and secure the finned heat sink without the use of additional tools or fixings.
Preferably, 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.
Preferably, 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.
Preferably, 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, the first finned heat sink is spaced apart from the second finned heat sink.
More preferably, 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, the first finned heat sink is spaced apart from the second finned heat sink by about 2 mm.
Preferably, the first finned heat sink and the second finned heat sink are secured to the or each thermal transfer member (metal rod or heat pipe) with a gap between each thermal transfer member (metal rod or heat pipe) and the substantially cylindrical aperture into which it is received of less than or equal to about 1 mm.
Preferably, the or each locking member comprises a tension pin or a resilient pin or a spring pin 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.
Optionally, the or each locking member comprises a screw; preferably, a threaded 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.
The mechanical action of the locking member of the present invention is to be biased towards opening so that the first finned heat sink and the second finned heat sink are forced together. The locking member ensures that the cooling module is securely held in position around the thermal transfer members (metal rods or heat pipes) irrespective of heat fluctuations, variations in the size of the metal rods/heat pipes, or misalignments.
Preferably, insertion of the or each locking member 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 prevents movement of the first finned heat sink away from the second finned heat sink.
Preferably, insertion of the or each locking member 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 locks the first finned heat sink in position spaced apart from the second finned heat sink.
The locking member of the present invention allows the cooling module to be locked in position without the use of additional tooling or fixings.
Preferably, the or each locking member is inserted such that its length is parallel to the length of the or each aperture.
By using a locking member, such as an elongate locking pin or a screw, locking of the first finned heat sink to the second finned heat sink is achieved without losing any surface area of the fins, which maximises heat transfer away from the cooling modules. Furthermore, the locking member/s do not increase the overall size of the cooling module and so do not increase the size of the lamphead with which the cooling module is used.
Preferably, 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.
Preferably, the locking member further comprises at least one stop at a first end.
Preferably, the locking member is tapered at a second end.
Preferably, the locking tabs are immovable in a locked configuration.
Preferably, the first finned heat sink and the second finned heat sink are aluminium. Optionally, the first finned heat sink and the second finned heat sink are copper.
The arrangement of the present invention allows for the cooling modules to be built off-site and conveniently installed on site. The configuration of the first and second finned heat sinks and the locking members allows for easy repair and replacement of the thermal transfer members (metal rods or heat pipes), if required.
In a further aspect the invention provides an LED curing apparatus comprising:
In a further aspect the invention provides an LED curing apparatus comprising:
Preferably, the or each thermal transfer member is a heat pipe.
Preferably, the or each thermal transfer member is a metal rod.
Preferably, the LED curing apparatus is for printing and coating applications.
Preferably, the at least one cooling module is locked to the or each metal rod by insertion of at least one locking member; more preferably, the at least one cooling module is locked to the or each metal rod by insertion of at least two locking members.
Preferably, the at least one cooling module is locked to the or each heat pipe by insertion of at least one locking member; more preferably, the at least one cooling module is locked to the or each heat pipe by insertion of at least two locking members.
The use of at least two locking members has been found to be advantageous in preventing any twisting of the first and second finned heat sinks within the cooling module.
Preferably, wherein the or each locking member is inserted into the surface of the or each cooling module that is furthest from the LED array.
Preferably, the LED curing apparatus is air cooled and comprises at least one inlet through which cool air enters the LED curing apparatus and at least one outlet through which heated air leaves the LED curing apparatus.
The thermal transfer member (metal rod or heat pipe) arrangement within the improved cooling module of the present invention is highly effective at removing heat from the densely packed LED array to each finned heat sink.
The cooling modules of the present invention offer a significant improvement in heat transfer away from the LEDs. This significantly reduces the maintenance requirements and environmental damage of unnecessary replacement of the LEDs, whilst also ensuring that the “down time” of the apparatus in the event of failure of the LEDs is significantly reduced.
Preferably, the LED curing apparatus comprises a plurality of cooling modules along the length of the LED curing apparatus.
The “length” is understood to refer to the greatest of the three dimensions of the LED curing apparatus.
The orientation of the apertures of the present invention ensures that the thermal transfer members (metal rods or heat pipes) are positioned to maximise heat transfer away from the heat sink and the LED array. If heat pipes are used, the evaporator section of the heat pipe is closest to the hottest part of the apparatus (LED array). The condenser section of the heat pipe is furthest from the LED array. This heat pipe arrangement ensures that heat is rapidly transferred away from the LEDs and from one end of the heat pipe to the other.
The present invention ensures that a large amount of heat is conducted quickly and efficiently away from each of the one or more LED modules in the LED array. The solution provided by the present invention allows the LED curing apparatus to operate at full power, if required, because the conduction of heat away from the LEDs is much improved. The use of thermal transfer members—i.e. metal rods or heat pipe technology in addition to the improved cooling modules ensures that the heat transfer away from the LEDs is maximised with only a low fluid/air flow requirement. The present invention quickly and efficiently removes the significant amount of heat generated by the LED modules. It is also possible to achieve uniformity of cooling along the length and across the width of the lamphead/apparatus.
The use of highly efficient thermal transfer members, i.e. using metal rods or heat pipe technology together with the finned, shaped heat sinks of the cooling modules allows for an optimal curing effect to be achieved, whilst the LEDs forming the LED array can be operated at a full range of power levels. By ensuring that the risk of overheating is minimised, if not eliminated, the LEDs last longer before it is necessary to replace them; whilst maintenance requirements are reduced. Thus, the present invention offers significant cost and environmental benefits.
The cooling system of the present invention is well-suited to cooling of LED modules, which are a linear source of radiation used for print curing. The arrangement of the metal rods/heat pipes and the cooling modules are carefully configured to be compatible with the small volume available in the housing of the LED curing apparatus and the inclusion of the cooling modules does not interfere with the substrate-facing (outer face) of the LED modules.
In a further aspect, the present invention provides a method of installation of at least one cooling module into an LED curing apparatus, comprising a plurality of thermal transfer members:
Preferably, the or each thermal transfer member is a heat pipe.
Preferably, the or each thermal transfer member is a metal rod.
Preferably, the at least one cooling module is a cooling module as described herein.
Preferably, the or each locking member is an elongate locking member; more preferably, the or each locking member is an elongate pin that is inserted such that its length is parallel to the length of the or each aperture.
Optionally, the or each locking member is a screw, preferably a threaded screw, that is inserted such that its length is parallel to the length of the or each aperture
Preferably, the method of installation further comprises applying a thermal transfer material to the at least one aperture.
More preferably, the thermal transfer material is a thermal transfer paste.
In a further aspect, the present invention provides a cooling system for an LED curing apparatus comprising at least one LED mount for mounting a plurality of LEDs; at least one bore in the LED mount;
at least one thermal transfer member wherein the or each thermal transfer member is removably connected to a bore; and
wherein each thermal transfer member comprises a collar having an outer surface to mate with an inner surface of a bore.
Preferably, the or each thermal transfer member is a metal rod.
Preferably, the collar is attached to a first end of the metal rod.
Preferably, the collar and the metal rod and formed as a single piece.
Optionally, the present invention provides a cooling system for an LED curing apparatus comprising at least one LED mount for mounting a plurality of LEDs; at least one bore in the LED mount;
at least one heat pipe comprising an evaporator section and a condenser section, wherein the or each heat pipe is removably connected to a bore; and
wherein each heat pipe comprises a collar having an outer surface to mate with an inner surface of a bore.
Preferably, the collar is attached to the evaporator section of the heat pipe.
Preferably, the outer surface of the or each collar is shaped to mate with a shaped inner surface of a respective bore.
Preferably, the outer surface of the or each collar comprises a threaded portion to mate with a threaded inner surface of a respective bore.
Preferably, the threaded portion is a substantial part of the or each collar.
Preferably, the or each collar is a connecting band; more preferably, an annular band.
Optionally, the or each collar is cylindrical having a base at a first end and an opening at an opposing second end.
Preferably, the or each thermal transfer member is soldered to a collar.
Preferably, the or each heat pipe is soldered to a collar.
Preferably, the or each metal rod is soldered to a collar.
Preferably, the LED mount comprises a thermal transfer material between the or each thermal transfer member and the bore.
Preferably, the LED mount comprises a thermal transfer material between the or each metal rod and the bore.
Preferably, the LED mount comprises a thermal transfer material between the or each heat pipe and the bore.
Preferably, the thermal transfer material is a high performance thermal interface material. More preferably, the thermal transfer material has a thermal conductivity greater than about 5 W/mK.
Preferably, the thermal transfer material is a ceramic paste.
Preferably, the thermal transfer material is provided between the collar and the bore to which the collar is removably connected.
Preferably, the cooling system comprises one or more LEDs mounted on the LED mount.
Preferably, the or each thermal transfer member is positioned adjacent to the LEDs.
Preferably, the or each metal rod is positioned adjacent to the LEDs.
Preferably, the or each heat pipe is positioned adjacent to the LEDs.
Preferably, the LED mount comprises aluminium.
Preferably, the LED mount comprises an aluminium block.
Preferably, the or each collar comprises copper.
Preferably, the or each collar comprises a threaded portion and a non-threaded portion. Preferably, the or each collar comprises a threaded portion and a smooth portion.
Preferably, the or each bore is substantially cylindrical.
In a further aspect, the present invention provides a cooling module comprising the cooling system for an LED print curing apparatus as previously described, wherein the or each thermal transfer member is also connected to at least one air-cooled heat sink.
Preferably, the thermal transfer member is a metal rod.
Preferably, the thermal transfer member is a heat pipe.
Preferably, the cooling module comprises at least one finned heat sink.
According to another aspect of the present invention, there is provided a print curing apparatus comprising a cooling system as described herein.
Preferably, the print curing apparatus is a UV curing apparatus.
In a further aspect, the invention provides an LED curing apparatus comprising:
Preferably, wherein the housing comprises an inlet cavity below the or each finned heat sink and an outlet cavity above the or each finned heat sink to maintain a higher air pressure below the or each finned heat sink and a lower air pressure above the or each finned heat sink.
More preferably, the LED curing apparatus further comprises a source of air and the air pressure in the inlet cavity below the or each finned heat sink is higher than the air pressure in the outlet cavity above the or each finned heat sink to cause the flow of air along the or each air passage through the housing from the or each inlet to the or each air outlet through the or each finned heat sink.
Preferably, the housing is cuboidal.
Preferably, the at least one air inlet is at a first end of the apparatus.
Preferably, the first end of the apparatus is substantially perpendicular to the base of the apparatus.
Preferably, the at least one air inlet comprises an elongate opening.
Preferably, the at least one air inlet comprises an elongate opening in the upper face of the apparatus.
Preferably, air is pulled out of the housing through the or each air outlet and pulled into the housing through the or each air inlet.
Preferably, the LED curing apparatus comprises a source of air and the air pressure decreases from the at least one air inlet to the inlet cavity and decreases further from the inlet cavity to the outlet cavity and decreases further again from the outlet cavity to the or each air outlet.
Preferably, the housing comprises an upper air channel between the air inlet and the inlet cavity. More preferably, at least part of the upper air channel is substantially parallel to the outer walls of the housing. Preferably, the width of the upper air channel is between about 3 to about 5 mm; more preferably, the width of the upper air channel is about 4 mm.
Preferably, the LED curing apparatus comprises a plurality of LEDs in a linear array.
Preferably, wherein the air passage comprises at least one restriction proximal to the or each finned heat sink.
Preferably, wherein the air passage comprises at least one restriction below the or each finned heat sink.
More preferably, the restriction below the or each finned heat sink reduces the cross sectional area of the air flow path from the inlet cavity below the or each heat sink to the or finned heat sink.
Preferably, the reduction in the cross sectional area of the air flow path from the inlet cavity below the or each finned heat sink to the or each finned heat sink is by a ratio of between 1:2 to 1:3 (inlet cavity:finned heat sink); more preferably, the reduction in the cross sectional area of the air flow path from the cavity below the or each finned heat sink to the or each finned heat sink is by a ratio of 2:5 (inlet cavity:finned heat sink); most preferably, the reduction in the cross sectional area of the air flow path from the cavity below the or each finned heat sink to the or each finned heat sink is by a ratio of 1:2.3 (inlet cavity:finned heat sink).
Preferably, the cross sectional area of the air flow path from the cavity below the or each finned heat sink to the or each finned heat sink reduces by more than 50%.
Preferably, wherein the air passage comprises at least one restriction proximal to the or each finned heat sink and at least one further restriction proximal to the at least one air outlet.
Preferably, the LED curing apparatus further comprises at least one source of cool air and at least one fan to move air into the or each air passage.
Preferably, the LED curing apparatus further comprises at least one source of cool air and at least one fan to blow air into the or each air passage.
Optionally, the LED curing apparatus comprises at least one source of cool air and a plurality of fans.
Preferably, the LED curing apparatus comprises at least one source of a cool air and at least one fan positioned at a distance from the LED curing apparatus; more preferably, the LED curing apparatus further comprises ducting wherein the or each fan is connected to the LED curing apparatus by the ducting.
Preferably, the at least one air inlet is at a first end of the apparatus and the opposing second end of the apparatus is sealed.
Preferably, the or each LED radiation source is arranged at the base of the apparatus.
Preferably, the first end of the apparatus is substantially perpendicular to the base of the apparatus.
Preferably, the or each air outlet is at a first end of the apparatus.
Preferably, the or each air outlet is at a first end of the apparatus and the opposing second end of the apparatus is sealed.
Preferably, the at least one air outlet comprises an elongate opening.
Preferably, the at least one air outlet comprises an outlet in the upper face of the apparatus.
It is understood that in the context of this invention, the “base of the apparatus” is the substrate-facing surface with the or each LED radiation source arranged thereon. The upper face of the apparatus is substantially parallel to and spaced apart from the base of the apparatus.
Preferably, wherein the air pressure at or near the LED mount is greater than air pressure at or near to the finned heat sink.
Preferably, the pressure difference between the inlet cavity and the outlet cavity exceeds between about 150 Pa and 400 Pa along the length of the LED curing apparatus; more preferably, the pressure difference between the inlet cavity and the outlet cavity exceeds between about 150 Pa and 300 Pa along the length of the LED curing apparatus; most preferably, the pressure difference between the inlet cavity and the outlet cavity exceeds about 150 Pa along the length of the LED curing apparatus.
Preferably, the air pressure in the inlet cavity proximal to the or each finned heat sink is between about −310 Pa and −610 Pa relative to atmospheric pressure.
Preferably, the air pressure in the or each outlet cavity is between about
−1150 Pa and −650 Pa relative to atmospheric pressure.
Preferably, the or each finned heat sink comprises at least one air inlet through which air enters from the housing into the finned heat sink.
Preferably, the ambient absolute temperature of air along the length of the LED curing apparatus is substantially uniform.
It is understood that “length” refers to the longest dimension of the LED curing apparatus.
Preferably, the dimensions of the air inlet of the or each finned heat sink restricts the air flow through the inlet.
Preferably, the LED curing apparatus comprises at least one thermal transfer member.
Preferably, the LED curing apparatus comprises at least one heat pipe.
Optionally, the LED curing apparatus comprises at least one metal rod or at least one metal pipe.
Preferably, the LED curing apparatus comprises a plurality of heat pipes.
Preferably, the LED curing apparatus comprises a plurality of metal rods or a plurality of metal pipes.
Within this specification, the term “substantially” is understood to refer to a variation of less than about 20%; preferably, less than about 10%; preferably, less than about 5%; preferably, less than about 2%.
For the purposes of clarity and a concise description, features are described herein as part of the same or separate embodiments; however, it will be appreciated that the scope of the invention may include embodiments having combinations of all or some of the features described.
The invention will now be described by way of example with reference to the accompanying drawings, in which:
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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.
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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.
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.
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.
Referring to
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.
Referring to
Referring to
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.
With reference to
Referring to
The configuration shown in
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.
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.
Referring to
As shown in
As shown with particular reference to
Referring to
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.
Referring to
A plurality of thermal transfer members, shown in
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.
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.
Referring to
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.
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 mm2. 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.
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.
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.
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.
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:
Referring to
With reference to
Referring to
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.
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.
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%.
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.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2201293 | Feb 2022 | GB | national |
| 2201298 | Feb 2022 | GB | national |
| 2215540 | Oct 2022 | GB | national |
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