GB2483469A

GB2483469A - Resin Curing Device and Method

Info

Publication number: GB2483469A
Application number: GB1014941.7A
Authority: GB
Inventors: Daniel Thomas Jones; Jeffrey Noel
Original assignee: Gurit UK Ltd
Current assignee: Gurit UK Ltd
Priority date: 2010-09-08
Filing date: 2010-09-08
Publication date: 2012-03-14
Anticipated expiration: 2030-09-08
Also published as: DE102011053375A1; GB201014941D0; GB2483469B

Abstract

A kit for curing resin in a fibre-reinforced resin composite comprises an illumination device 2 producing curing radiation and at least one device 4a,4b for mounting to the composite. A series of indexed interconnections 24 provide for selective fitting of the illumination device at a series of locations along the mounting device with the radiation emitting face spaced from the composite. The illumination device may comprise an annular array of ultraviolet emitting diodes in a face of a jig manually removably fitted to a mounting device which may be in the form of a flexible elongate strap. A lamp unit (70, figure 7) may be mounted to slide along guide bars off the jig. The strap may be wrapped around a substrate with ends engaged to secure it, or alternatively secured with a suction device. The indexed interconnections may comprise uniformly spaced male elements engaging holes of the illumination device. The male elements may comprise a base 44 and a toggle 24 rotatable to lock the illumination device in place. Once a portion of the composite has been cured the illumination device can be moved along the mounting device by a pitch of the male elements to cure the adjacent portion. The kit may be used to repair turbine wind blades.

Description

Resin Curing Kit and Method The present invention relates to a kit for curing a matrix resin in a fibre-reinforced resin composite material a resin curing device, the kit including an illumination device for producing radiation, in particular ultraviolet (UV) radiation, for curing matrix resin in fibre-reinforced resin composite materials. The present invention also relates to a resin curing method.

Many articles are composed of fibre-reinforeed resin composite materials. Some articles may become damaged and require repair of the fibre-reinforced resin composite material, which requires removal of the damaged material and filling of the cavity or void so made with new fibre-reinforced resin composite material which is bonded securely and robustly to the previous material. The resin generally requires careful curing in situ to ensure a sound repair.

For example, it is sometimes necessary to repair large articles such as boat hulls or wind turbine blades which are composed of fibre-reinforced resin composite materials. The repair of such articles is problematic because access to the repair site may be difficult or precarious, particularly for a wind blade which may have a length of up to 60 metres and be located up to 100 metres of the ground. There is a need for a repair technology which is easy and reliable to use under such inaccessible conditions.

It is known to provide thermosetting resin materials for fibre-reinforced resin composite materials which are curable by ultraviolet (UV) radiation. However, to use such known UV curable repair materials outdoors requires a robust high intensity UV light source, because ambient UV radiation is inadequate to cure the resin to the required degree of cure and sufficient depth for an effective repair. The UV curable thermosetting resin material would not cure properly unless given a high intensity UV radiation dose. Such a known high intensity UV light source needs to be sealed against dirt and moisture ingress in order to be reliable usable in ambient conditions in situ on a wind blade or boat hull or other large object.

I

Mercury vapour lamps are known for use as a UV radiation source. However, such lamps are sensitive to shock and cannot be switched on and off repeatedly without damage to the lamp. In addition, a warm-up time is also needed for the lamp to reach its nominal intensity after switch on. Accordingly, mercury vapour lamps are not practical to use for in situ repairs.

Light emitting diode (LED) lamps offer a viable option to curing UV curable repair materials outdoors in situ. LED emitters can be switched on and off without damage, have long service lives, typically greater than 10,000 hours, and reach nominal intensity very quickly, typically less than 1 second. Furthermore, LED emitters can be selected to emit UV radiation in a desired U"! radiation band to achieve effective resin curing, the band being selected to avoid short wavelength light, typically UV A, with the 405mm, 395nm, 375nm or 365mm wavelength being the most preferred. The lower wavelengths are less desirable as they tend to be more damaging to the human body from a health and safety perspective. Also, the power intensity of UV radiation emitted from an LED tends to drop very rapidly with distance from the UV source compared to a mercury vapour lamp, thereby reducing the potential for accidental exposure damage and any need for consequential light shielding devices to mitigate the problem of accidental exposure to UV radiation. Therefore LED emitters are more intrinsically safe than mercury vapour lamps.

However, currently LED emitters are more expensive than mercury vapour lamps to provide a give UV intensity over a given illumination zone. Also, U"! wavelength selection to match UV initiators in the UV curable resin, and accommodate UV absorbance by any pigments within the resin, is more critical. Still further, the LED UV source needs to be close to the U"! curable resin material in order reliably to achieve an effective cure.

Different types of UV emitting LEDs are commercially available. Single LED emitters are common in torches and strip lighting, but do not provide the UV radiation power density required. Higher density LED chips are capable of achieving the minimum threshold of UV radiation power density. The UV radiation power intensity varies greatly with distance from the lamp head.

Current high intensity LED light bars or lamp heads are formed from many LEDs arranged as a continuous array to give the required total power density over a given illumination area. Light emitted from each LED is not focused into a narrow beam but projects over an increasing large circular area as the distance from the unit increases.

It is known to use lens array technology to bring the power of multiple LEDs to a focused area, or to increase a practical working distance from the light source to the target, such LEDs with lenses being available from Cicarstone Technologies, Inc., Minneapolis, USA However, such LEDs incorporating lenses arc more expensive than conventional LED emitters.

For a given height distance from the LED, the UV radiation power intensity also reduces as the radius of the planar circular area increases.

When applying UV radiation to a UV curable resin, if the intensity of the UV irradiation on the resin material is too high, there is a risk of an exotherm in thick repairs, typically having greater than 4mm thickness, leading to potential material damage. Conversely, if the intensity of the UV irradiation on the material is too low, the repair material does not cure fully and so cannot reach its desired thermal and mechanical properties. Low intensity UV light is also not able to penetrate significantly into the laminate stack and the maximum curable thickness is limited.

Variations in the UV intensity can also cause different rates and levels of cure that can also cause surface wrinkles and other blemishes in coating materials due to the different cure and rates of shrinkage. If the LED head is too far away for the repair zone, typically 60mm, then the UV radiation intensity may be too low for achieving a good cure.

To attempt to achieve consistent UV radiation over an illumination area, thereby avoiding non-illuminated gaps, the UV radiation from adjacent, and even non-adjacent, LEDs overlaps. Accordingly, significant edge effects occur in a typical LED light bat' formed from many individual LEDs arranged in an array format. The UV radiation power intensity tends to peak in the centre of the array due to the accumulation of UV radiation energy from neighbouring LEDs, and is significantly less at the edges of the illumination, and some UV energy irradiates past the lamp edges. The greater the distance of the illuminated area from the UV radiation source, the more the variation as the UV radiation from each LED diverges over a larger area.

It is possible to fit a lens to each LED to reduce the divergence but this adds complexity and cost to the design.

In conveyor based applications where the thermosetting resin passes under a UV lamp head at a given line speed, the variations in intensity are less critical as the effects are averaged out and the resin receives an average dose of UV radiation.

For in situ repairs to UV curable thermosetting resin materials of fibre-reinforced resin composite materials, in which the repair zone may be variable in size and the substrate may be variable in dimensions and geometry, it would be difficult to ensure that the repair zone receives the same dose of UV radiation to ensure full resin cure without under or over exposure. For example, the UV lamp may be translated across the repair zone, but is would be difficult consistently and repeatedly to progress the lamp at a fixed rate relative to the repair without setting up a complex lamp holder and drive system accurately to control the relative speed of the lamp to the repair and maintain the same fixed height of the lamp head above the repair zone. Also, such a system may be completely impractical in demanding applications, for example when the operator needs to abseil down a wind blade 100 meters off the ground and exposed to the weather.

The present invention aims to provide a kit for curing a matrix resin in a fibre-reinforced resin composite material, by irradiating the resin with radiation such as ultraviolet radiation, and an associated resin curing method, which at least partly solve the problems of known devices and methods summarised above.

The present invention provides a kit for curing a matrix resin in a fibre-reinforced resin composite material, the kit comprising an illumination device for producing radiation for curing a matrix resin in a fibre-reinforced resin composite material, and at least one mounting device for mounting to a substrate of the fibre-reinforced resin composite material, wherein the mounting device comprises a series of indexed interconnections therealong for selective releasable fitting of the illumination device at a selected one of a series of locations along the mounting device with the radiation emitting face spaced from the substrate.

Preferably, the illumination device comprises an array of a plurality of radiation emitting elements mounted in a radiation emitting face of the illumination device, and wherein the radiation emitting elements are ultraviolet radiation emitting diodes.

Optionally, the radiation emitting elements are mounted in a housing unit to form a manually locatable jig which is removably mountable to the at least one mounting device, and the jig has at least one locating device for removably fitting the jig to a respective mounting device. Further optionally, the housing unit is mounted on a slider assembly of the jig extending between the opposed ends of the jig, and the housing unit is slidable between at least two positions spaced along the slider assembly.

The present invention further provides a method of curing a matrix resin in a fibre-reinforced resin composite material, the method comprising the steps of: (a) fitting at least one mounting device to a substrate of a fibre-reinforced resin composite material, wherein the mounting device comprises a series of indexed interconnections therealong; (b) fitting an illumination device at a selected indexed location along the mounting device, the illumination device having a radiation emitting face facing the substrate and engaging at least one interconnection; and (c) irradiating the substrate with radiation from the illumination device for a period of time sufficient to cure a matrix resin in the composite material.

Preferably, the radiation is ultraviolet radiation provided from an array of a plurality of ultraviolet radiation emitting diodes. Optionally, the radiation emitting face is spaced a selected distance from the substrate by fitting at least one front face of the illumination device to the at least one mounting device.

Typically, the radiation emitting face is located between a pair of longitudinally separated front faces of the illumination device, each front face being fitted to a respective interconnection.

Optionally, the illumination device forms a manually locatable jig, and in step (b) the jig is removably mounted to the mounting device which is fitted to the substrate.

Typically, the mounting device comprises a series of indexed interconnections therealong for selective fitting of the illumination device to a selected indexed location, and steps (b) and (c) are carried out a plurality of times to irradiate an enlarged area comprising a plurality of individual irradiated areas.

Optionally, each individual irradiated area corresponds to one of the series of indexed interconnections to irradiate a composite area of the substrate composed of a plurality of individual illumination areas. Alternatively, at least two individual irradiated areas correspond to a respective one of the series of indexed interconnections, the radiation emitting face being movable between at least two positions when the illumination device is fitted to the mounting device.

Typically, the matrix resin to be cured is in a repair of a fibre-reinforced composite material, such as a wind blade.

In a preferred embodiment, the illumination device comprises an annular array of a plurality of ultraviolet radiation emitting elements mounted in a radiation emitting

S

face of the illumination device, the array surrounding a central non-irradiating area.

Optionally, the ultraviolet radiation emitting elements are ultraviolet radiation emitting diodes. Preferably, the array is arranged so that a preset number of ultraviolet radiation emitting elements is located in each of at least two axial directions extending away from a geometric centre of the annular array. The array is typically shaped as a parallelepiped, optionally a rectangular alTay. The annular array may have a substantially rectangular outer edge and a substantially rectangular inner edge. Optionally, the outer and inner edges each have a major length and a minor length, the minor length of the inner edge having a staggered configuration of ultraviolet radiation emitting elements at two opposed longitudinal ends of a central inactive non-irradiating area surrounded by the array. Typically, the staggered configuration of the array converges towards a central location of reduced length of the annular array.

Typically, each ultraviolet radiation emitting element has a predetermined beam angle, and the beam angles of adjacent ultraviolet radiation emitting elcments intersect at a predetermined distance from the ultraviolet radiation emitting elements.

Optionally, the beam angles of adjacent ultraviolet radiation emitting elements intersect and overlap across an entire illumination field of the annular array of ultraviolet radiation emitting elements at a predetermined distance from the ultraviolet radiation emitting elements.

Typically, a pitch between adjacent ultraviolet radiation emitting elements in the array is from 2 to 8 mm, optionally from 4 to 6 mm. Preferably, the annular array is substantially rectangular and has an external length of from 200 to 800 mm, optionally from 200 to 400 mm and/or has an external width of from 20 to 100 mm, optionally from 40 to 50 mm. The array may define a substantially rectangular central non-irradiating area and the non-irradiating area may have a length of from to 750 mm, optionally from 40 to 350 mm, and a width of from S to 50 mm, optionally from 10 to 20 mm. Typically, the central non-irradiating area is from 30 to 50% of the total area of the array and the central non-irradiating area.

The illumination device may further comprise at least one spacer extending forwardly of the radiation emitting face to define at least one front mounting surface of the illumination device. Optionally, the at least one spacer comprises a pair of mutually separated spacers located at opposite edges of the illumination device. Typically, the at least one spacer is adapted to space the array from the substrate a predetermined distance of from 10 to 100mm.

The illumination device is optionally a portable battery powered device.

The present invention is at least partly predicated on the finding by the present inventor that a mechanically simple but reliable and robust system for use in the field to repair composite materials can have a fixed sized UV lamp which can be combined with a device to maintain the lamp at a fixed height above the material to cure a patch of UV curable material and then index the lamp a fixed pitch distance to cure another adjacent patch of material until the complete repair area is cured.

The present invention is also at least partly predicated on the finding by the present inventor that an annular array of radiation emitting elements can be more economical and more power efficient by using fewer LEDs to provide a more uniform radiation intensity over a repair area on a substrate of a composite material, which can avoid problems of under curing of the resin matrix or over curing, which can lead to overheating in particular of thick laminates.

Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:-FIG. 1 shows a schematic perspective view of a kit comprising an illumination device for producing ultraviolet radiation and a mounting device therefore in accordance with a first embodiment of the invention; FIG. 2 shows in greater detail a schematic perspective view of part of a mounting device of FIG. 1; FIG. 3 shows a schematic perspective view of a first variation of the kit of FIGs. 1 and 2 when used to repair a wind turbine blade;

B

FIG. 4 shows a schematic perspective view of a second variation of the kit of FIGs. 1 and 2 when used to repair a wind turbine blade; FIG. 5 shows a plan view of the use of the kit of FIG. 1 to cure a repair area on a substrate according to one embodiment of the present invention; FIG. 6 shows a plan view of an illumination device in accordance with a further embodiment of the present invention; FIG, 7 shows a part-sectional side view of the illumination device of FIG. 6; FIG. 8 shows an area on a substrate showing plural irradiation zones for irradiation according to an embodiment of a method according to the present invention; FIG. 9 shows a perspective bottom view of the illumination device showing an LED array of the illumination device according to one embodiment of the present invention; FIG, 10 shows the intersecting beam angles of adjacent LEDs in an array comprised in an embodiment of an illumination device of the present invention; FIG. 11 shows a graph of the relationship between illumination intensity and distance both modelled according to the present invention and using an illumination device according to an embodiment of the present invention; FIG. 12 shows a graph of the relationship between illumination intensity and distance using another illumination device having a continuous LED array; and FIG, 13 shows a side view of an illumination device in accordance with a further embodiment of the present invention.

Referring to FIG. 1, there is shown a kit comprising an illumination device 2 for producing ultraviolet radiation and a mounting device 4 therefore in accordance with a first embodiment of the invention. The illumination device 2 includes a UV radiation emitting front face 6 for producing ultraviolet radiation for curing a matrix resin in a fibre-reinforced resin composite material. As described hereinafter, the illumination device 2 comprises a support plate and an array of a plurality of ultraviolet radiation emitting elements, in particular light emitting diodes (LEDs) mounted on the radiation emitting front face 6 of the support plate. The front face 6 is part of a housing 8 which comprises control electronics (not shown) for powering the LEDs, switchgear 10 for operating the device, one or more cooling fans 12 for cooling the housing 8, and an integral power supply (such as a battery, not shown) or a power supply cable 14.

The illumination device 2 is portable. The housing 8 is fixedly mounted between opposed grip handles 16a, 16b, at opposed ends of the radiation emitting front face 6.

The grip handles 16 provide a pair of mutually separated opposed spacer elements 1 8a, 1 Sb at opposite ends of and extending away from the front face 6. The spacer elements l8a, l8b provide a height offset h between the lower surface 19 of the spacer elements 1 8a, 1 Sb and the LEDs in the front face 6. The spacer elements 1 8a, 1 8b are adapted to space the LEDs a predetermined distance away from the surface of the fibre-reinforced resin composite material. Typically, the predetermined distance is from 10 to 100mm, preferably from 25 to 50mm, most typically 30 to 40mm.

The illumination device 2 forms a manually locatable jig 20 which is removably mountable to the at least one mounting device 4. Each spacer element 1 8a, 1 Sb has a locating device 22 for removably fitting the jig 20 to a respective mounting device 4.

In the illustrated embodiment, a pair of the mounting devices 4 is provided, each adapted to fit to a respective spacer element 1 8a, 1 Sb.

As shown in greater detail in FIG. 2, each mounting device 4 comprises a series of indexed interconnections 24 therealong for selective fitting of a selected interconnection 24 to the locating device 22 of a respective spacer element 18. The interconnections 24 extend from an upper surface 26 of an elongate body 28 of the mounting device 4. A rear surface 30 of the elongate body 28 is provided with a friction pad 32 for non-slip engagement between the mounting device 4 and an underlying substrate. The elongate body 28 may be longitudinally reinforced against inadvertent stretching, for example by being made or reinforced with inextensible material, or by one or more longitudinally extending reinforcing wires 34 fixed to the opposed ends 36 of the elongate body 28. The elongate body 28 is mounted on an elongate flexible strap 40.

In one embodiment, as shown in FIG. 3, the elongate flexible strap 40 has spaced ends which can be removably engaged together, for example connecting at a grip pad 39 on the strap 40, to allow the strap 40 to be wrapped as a closed loop around a substrate, as illustrated a wind turbine blade 41, with the spaced ends in a selected longitudinal relationship to provide a desired internal wrap dimension for the strap 40, in another embodiment, as shown in FIG. 4, the elongate flexible strap may be omitted and the mounting device 4 has at least one vacuum suction device 42 for removably attaching the mounting device 4 to a substrate. Optionally, two such vacuum suction devices 42 are provided, each at a respective opposed end of the mounting device 4.

The jig 20 and mounting device 4 have co-operating connections for releasably fitting the jig 20 at a selected indexed position along the length of the mounting device 4.

The jig 20 can subsequently be removed from the mounting device 4 and fitted at another selected indexed position along the length of the mounting device 4.

The indexed interconnections 24 comprise a series of male elements 44 linearly extending along the mounting device 4 and the locating device 22 comprises a hole 50 for receiving a respective male element 44. At least one male element 44 comprises a fixed base part 46 and a rotatable toggle 48 on the base part 46. Rotation of the toggle 48 (to a closed orientation, at right angles to the base part 46, shown for the toggle 48 on the right hand side of FIG. 2) when the base part 46 is received in the hole 50 temporarily locks the spacer element 18 to the mounting device 4. Typically all of the male elements 44 comprise such a toggle 48, although a toggle 48 may be provided on the male elements 44 of only one of the two mounting devices 4.

In the illustrated embodiment of FIG. 1, two mounting devices 4, each for fitting to a respective spacer element 18, are provided and the male elements 44 of each mounting device 4 comprise the fixed base part 46 and the rotatable toggle 48, The indexed interconnections 24 are mutually spaced by a predetermined pitch spacing p to provide a pitch guide for permitting the jig 20 to be successively mounted at a series of linearly extending mutually adjacent locations with the indexed pitch p therebetween corresponding to the desired pitch, to provide a substantially uniform illumination intensity in a linear direction along the locations.

As shown in FIG. 3, which shows the repair of a wind blade 41, the straps 40 are wrapped around the wind blade 54 and their ends joined together, optionally using an enlarged and frictional grip pad 39. This securely fits the mounting devices 4 to the blade surface 56 at the desired locations, with the repair area 58 therebetween. An operator 0 may access the repair location using an abseil rope 55, and may carry the repair materials, such as a supply of repair patches of fibre-reinforced UV curable resin composite material, in prepreg form, which may be stored away from ambient light in a quiver 60. The operator may also carry a mastic gun 62 containing a coating resin, A power pack 64 for providing electrical power to the jig 20 may be carried by the operator.

As shown in FIG. 4, which also shows the repair of a wind blade 54, the mounting devices 4 are fitted to the wind blade 54 using the vacuum suction devices 42, typically spaced at opposed ends of the mounting device 4. This securely fits the mounting devices 4 to the blade surface 56 at the desired locations, with the repair area 58 therebetween. An operator 0 may access the repair location 58 using an access platform 66, and again the operator may carry the repair materials and a power pack.

The spaced mounting devices 4 may be fitted in any convenient orientation on opposed sides of the repair location 58.

Referring additionally to FIG. 5, in the method of curing a matrix resin in a fibre-reinforced resin composite material, the plurality of ultraviolet radiation emitting elements in the front face is spaced a predetermined distance away from the surface of a fibre-reinforced resin composite material comprising a matrix resin curable by ultraviolet radiation, This is achieved by attaching the mounting devices 4 to the substrate so that they are laterally spaced a distance corresponding to the distance between the spacer elements. Then the jig 20 is fitted to a first opposed pair of indexed interconnections 24 at one end of the mounting devices 4 and locked in position by rotating the toggle 48 after the base part 46 is received in the respective hole 50. This defines a first illumination zone on the substrate. The front face 6 is spaced a predetennined distance away from the substrate surface, the distance being the combination of the thickness of the elongate body 28 and the height offset between the lower surface of the spacer elements 18 and the LEDs in the front face 6.

With the jig above the first illumination zone, the substrate surface is irradiated with ultraviolet radiation from the LED array for a period of time sufficient to cure the matrix resin at the first illumination zone of the repair area 58.

Then the jig 20 is manually removed from the first opposed pair of indexed interconnections 24, and fitted to the adjacent second opposed pair of indexed interconnections 24. The jig 20 is again locked in position by rotating the toggle 48 after the base part 46 is received in the respective hole 50. This defines a second illumination zone on the substrate, adjacent to, and optionally partially overlapping the first illumination zone. With the jig above the first illumination zone, the substrate surface is irradiated with ultraviolet radiation from the LED array for a period of time sufficient to cure the matrix resin at the second illumination zone of the repair area 58.

This sequence of steps is repeated until sufficient sequential adjacent illumination zones have been irradiated to cure the resin in the entire repair area. FIG. S shows a series of adjacent illumination zones Zl, Z2, Z3, Z4, Z5 encompassing the repair area 58. When one illumination zone Zi, Z2, Z3, Z4, Z5 is being illuminated with the UV radiation, one or more of the other illumination zones Zl, Z2, Z3, Z4, ZS, such as the adjacent zone or zones, may be masked against UV radiation The indexed pitch spacing p of the male elements 44 defines the indexed pitch spacing of the illumination zones Zi, Z2, Z3, Z4, Z5 to eliminate manual positioning error. This avoids the risk of under cure where the lamp is indexed a greater value leaving an under exposed zone between each exposed area or conversely excessive time to complete the cure where the lamp is indexed a conservative amount to build in manual positional tolerance allowance. The ability to improve the positional tolerance also allows some of the lower intensity irradiation incident outside the lamp footprint to be used as part of the effective curing zone. With this improved positional tolerance these areas are reliably exposed again in the successive adjacent patch cure such that by receiving a double, but lower intensity dose, these overlap areas are also fully cured.

The spacer elements 18, together with the elongate body 28 of predetermined thickness, ensure that the array of LEDs is accurately spaced from the substrate across the entire repair area. This also ensures accurately controlled irradiation intensity and resin curing.

In an alternative embodiment, the spacer elements 18 may be adapted to engage the substrate surface directly so as solely to define the height spacing between the LEDs and the irradiated substrate surface. In either embodiment, the height spacing between the LEDs and the irradiated substrate surface may be a predetermined distance which is from 10 to 100mm, preferably from 25 to 50mm, most typically 30 to 40mm.

A further embodiment of the illumination device 68 is illustrated in FIGs. 6 and 7. In this embodiment, an elongate LED lamp unit 70 having a front irradiating face 72 is mounted for longitudinal sliding motion on at least one slider bar 74 which is supported at opposed ends 76, 78 by respective mounting elements 80, 82. Each mounting element 80, 82 has a lower part 84, 86 adapted for selective temporary locking engagement with an indexed connection 24 of a mounting device 4, for example of any type as described earlier. For example, each lower part 84, 86 may include a hole 88 for receiving a rotatable toggle 48 mounted on a base part 46, as described earlier.

The at least one slider bar 74 and mounting elements 80, 82 form a support frame 88 that allows the lamp unit 70 to slide up and down on a linear bearing system 90. The linear bearing system 90 comprises a slider block 92 mounted on a helically threaded rotatable shaft 94 which is rotatable by a rotary drive unit 96, which optionally can be connected to a source of electrical power. The rotatable shaft 94 is disposed between a pair of slider bars 74. The drive unit 96 can be operated accurately to position the lamp unit 70 at a selected location along the slider bars 74. A fine positioning control, either powered or manual in the form of a control knob 97, and/or a clamp 99 for locking the slider block 92 carrying lamp unit 70 in a selected location, may be provided.

The opposed longitudinal sides of the support frame 88 may have respective walls 98 which act as UV shields to prevent UV radiation from the lamp unit 70 form irradiating the surface of the substrate other than that which is covered by the cavity enclosed by the illumination device 68. For enabling the operator to see the position of the lamp unit 70, one or more windows 100 may be provided in the walls 98.

Alternatively or in addition, a scale (not shown), for example showing distance in mm, may be provided along the length of the illumination device 68 to enable the operator accurately to position the lamp unit 70 relative to a selected area of the wind blade, the substrate of which is shown as S in FIG. 7.

This embodiment permits illumination zones which are longitudinally adjacent, and spaced in the direction of the slider bar 74, to be successively illuminated with only a single positioning of the illumination device 68 on the mounting devices 4 affixed to the substrate. The lamp unit 70 can be slid along the slider bar 74 between plural, i.e. two or more, positions using the drive unit 96.

The mounting elements 80, 82 accordingly constitute a quick release fitting, by cooperation of the hole 88 and the rotatable toggle 48, to enable rough positioning of the illumination device 68 on the substrate, and then the drive unit 96 can be operated to achieve a precision setting for the lamp unit 70 for irradiating a respective illumination zone.

This embodiment overcomes the difficulty of achieving accurate vertical alignment when placing the straps 40 on a wind blade, as shown for example in FIGs. 3 and 4.

The advantage of the illumination device 68 of this embodiment is that the two positioning straps 40 can be roughly placed on the blade in the vertical direction and the illumination device 68 fitted thereto in an approximate vertical orientation relative to the desired illumination zones.

The lamp unit 70 can then be slid vertically into position on the slider bars 74 with the entire illumination device 68 fixed in position on the wind blade. The vertical position of the lamp unit 70, in other words the longitudinal position of the lamp unit 70 relative to the support frame 88 of the illumination device 68, can be seen through the window tOO and set accurately using the scale.

After the first zone has been irradiated, such as zone 1 in FIG. 8, the lamp unit 70 can be slid to an adjacent zone, such as zone 2 in FIG. 8. For a wind blade, as shown in FIGs, 3 and 4, typically the two zones 1 and 2 would be vertically oriented, but for other substrates they may be oriented in another direction. After zone 2 has been irradiated, the illumination device 68 is removed from the substrate and re-attached at an adjacent position determined by the pitch p, and then the successive illumination of zones 3 and 4 adjacent to zones 2 and 1 is carried out. This cycle is then repeated to illuminate zones 5 and 6.

In this way, all of the zones are illuminated in sequence, so that the entire repair area is accurately illuminated, but plural illuminations may be carried out between repositioning of the entire illumination device on the substrate. This increases irradiation accuracy and also decreases the time required to carry out the entire repair process. As described earlier, even though the irradiation device defines a housing closed against UV radiation emission from impacting the substrate other than within the area defined by the illumination device 68, one or more of the zones may be masked against UV radiation when another zone, such as an adjacent zone, is being irradiated to minimise the risk of excessive UV radiation of any part of the repair area.

The LED array of the illumination device may have a regular or irregular array of LEDs in the front face 6, with the entire front face 6 having LEDs disposed therein.

However, in accordance with a particularly preferred embodiment of the present invention, as shown in FIG. 9, an array of a plurality of ultraviolet radiation emitting elements of the illumination device may have an annular configuration.

An annular array 110 of a plurality of ultraviolet radiation emitting elements 112, such as LEDs, are mounted on a radiation emitting face 114 of a support plate 116 which is fitted to the housing 118 to define the front face 120. An annulus 122 of the plurality of ultraviolet radiation emitting elements 112 surrounds a central inactive non-irradiating area or cavity 124 not having any such ultraviolet radiation emitting elements 112. The array 110 includes plural ultraviolet radiation emitting elements 112 such as LEDs in each length or width direction A, B of the annular array 110.

The array 110 is arranged so that a preset number of LEDs 112 is located in each of at least two orthogonal axial directions extending away from a geometric centre of the annular array 110. The array 110 is typically shaped as a parallelepiped, optionally a rectangular array, and has a substantially rectangular outer edge 126 and a substantially rectangular inner edge 128. The inner edge 128 has a staggered configuration 130 of ultraviolet radiation emitting elements 112 at the two opposed longitudinal ends of the central inactive non-irradiating area 124, the array 110 converging towards a central, in the width direction B, location of reduced length of the annular array 110.

In FIG. 9 the number of elements 112 shown is purely illustrative and a smaller number than is typically used is shown, for clarity of illustration. The dimensions and aspect ratio of the array 110, the radiation emitting face 114 and the central inactive non-irradiating area cavity 124 may readily be varied.

LEDs are commercially available as a chip including an array of LEDs. In one particular embodiment, a series of three substantially rectangular LED chips 132, 134, 136 is serially arranged. Each chip 132, 134, 136 has 198 LEDs in a rectangular array, providing a total of 594 LEDs for the three chips 132, 134, 136. A central cavity 124 was formed as shown in FIG. 9 by inactivating the centrally located LEDS, leaving an annulus of 364 LEDs, representing about 61% functioning LEDs, Each ultraviolet radiation emitting element 112 has a predetermined beam angle, even though a lens for the LED emitter may be omitted. The beam angles B of adjacent ultraviolet radiation emitting elements 112 intersect at a distance from the ultraviolet radiation emitting elements 112 corresponding to the predetermined distance D as shown in FIG. 10. Typically, the beam angles B of adjacent ultraviolet radiation emitting elements 112 intersect and overlap across an entire illumination field of the annular array 110 of ultraviolet radiation emitting elements 112 at a distance from the ultraviolet radiation emitting elements corresponding to the predetermined distance D. Typically, a pitch, or separation distance d, between adjacent ultraviolet radiation emitting elements 112 in the array 110 is from 2 to 8 mm, optionally from 4 to 6 mm.

The annular array 110 is typically substantially rectangular and has an external length of from 200 to 800 mm, optionally from 200 to 400 mm and/or an external width of from 20 to 100 mm, optionally from 40 to 50 mm. In a preferred embodiment, the array 110 defines a substantially rectangular central cavity 124 and the cavity 124 has a length L of from 100 to 750 mm, optionally from 40 to 350 mm, and a width W of from S to 50 mm, optionally from 10 to 20 mm. Typically, the central cavity 124 defined in the annular array 110 has an area which is from 30 to 50% of the total area of the array 110 and the cavity 124.

Although a rectangular array is illustrated, in which the LEDs are rectangularly spaced, other spacing configurations and orientations may be employed. For example, the ultraviolet radiation emitting elements, such as LEDs could be hexagonally spaced in a hexagonal or substantially rectangular array. Typically too, the ultraviolet radiation emitting elements, such as LEDs may be spaced along directions forming a parallelepiped, which is a known manner of mounting an array of plural LEDs on a support comprising a chip.

By providing a central cavity 124 within the array 110, this minimises excessive UV irradiation at the centre of an illumination zone as compared to a continuous array without a central cavity. The cavity is shaped and dimensioned with respect to the beam angles and the UV radiation intensity so that when the array 110 is located at the predetermined distance from the substrate to be irradiated, there is minimal beam overlap in the centre of the illumination zone so that the danger of over-irradiating the resin, causing an undesired exotherm, is minimised. The provision of a cavity also renders the illumination intensity across the illumination zone more uniform.

Therefore, to obtain a more even intensity the centre section of the array of LEDs is omitted, which avoids a higher intensity centre. The selection of the cure time is driven by the lowest intensity irradiation provided by the array.

It should be clear to those skilled in the art that the shape and dimensions of both the array and the cavity can readily be determined by those skilled in the art dependent upon what LEDs have been selected and the desired radiation intensity at the required irradiation distance.

Referring to FIG. 13, according to a further modification of the illumination device of any of the embodiments of the present invention, the illumination device 200 may be provided with a front (or lower) radiation emitting face 202 which has a curvature 204, for example to match the curvature of an intended substrate. The curvature may be about one or plural axes, and simple or complex. In FIG. 13 the curvature 204 is exaggerated (as compared to the curvature typically employed) for the purpose of clarity of illustration.

In one embodiment, when the radiation emitting face 202 is rectangular, the curvature is about an axis parallel to a longitudinal direction of the radiation emitting face 202, and so in the minor, i.e. transverse or width, direction. Such a curvature is particularly suitable for an illumination device intended for use in cui'ing repair areas on the surface of a wind turbine blade. The curvature makes it easier to conform the radiation emitting face 202 to the transverse, or width, curvature typically found on a wind turbine blade, the illumination device being oriented to match the curvature of the blade surface, for example longitudinally oriented with respect to the blade length as shown in FIGs. 3 and 4.

This curvature assists maintaining the required substantially uniform height of the radiation emitting face 202 from the surface across its area and particularly at the opposite longitudinal ends of the illumination device 200, especially at the tip of the blade which has higher curvature, and thereby maintains uniformity of radiation intensity during the curing cycle.

The radiation emitting face 202 may be planar or curved in the major, i.e. longitudinal or length, direction. Generally, the curvature in the longitudinal direction of the blade is sufficiently small that the height of a radiation emitting face 202 which is planar in the longitudinal direction is sufficiently uniform over the length of the array to achieve uniform curing.

In a particularly preferred embodiment, the radiation emitting face 202, and optionally an adjacent part of the body of the illumination device 200, is flexible and resilient.

This permits the radiation emitting face 202 to be flexed to a desired curvature so as to match the curvature of a substrate, with the resilience holding the radiation emitting face 202 at the desired curvature throughout an illumination cycle. Thereafter, the radiation emitting face 202 may be flexed to a different curvature. Such a flexible structure may be provided by providing a flexible plate or housing for mounting the LEDs, the flexibility being achieved by either an intrinsically flexible material, for example of plastics material or rubber, and/or by providing one or more hinges, for example living hinges, in the material, the hinges extending in one or more orientations.

The present invention is further illustrated by the following non-limiting Example.

Example 1

It has been found that at a given height from an illuminated surface the radiation intensity at the surface of a single LED follows the following relationship; 1(r) = a Equationl Where r is the radial distance from the LED centre and the constants a, b, and c are fitted to experimental data.

At a given coordinate (x,y) the radial distance Rn from LED number n can be written as; r(x, y, n) = -x)2+ (f,1 -y)2 Equation 2 Where; n = LED Number i = X coordinate of LED n j =i coordinate of LED n Therefore the intensity contribution at any position from LED n can be written as I(x,y,n)=a'b The intensity of an array design can be calculated by summing the contribution from each LED using the relationship; I(x, y) = a. b A software model has been written using this relationship to study the effect of different array designs.

A part populated LED array having the annular structure shown in FIG. 9 was modelled using software previously experimentally validated by finding the constants a, b, c of Equation 1. The rectangular array had a 286mm x 44mm dimension, with 364 LEDs spaced by 5.5mm in the length direction and 4.4ntm in the width direction.

The centre three LEDS rows (rows 5, 6 and 7 of 11 in total) were inactive, except for LEDs 1 to 7 for rows 5 and 7 and LEDs 1 to 6 for row 6. The radiation intensity across the surface was predicted using this software with the height of the array being 40mm from the irradiated surface.

Figure 11 shows the relationship between the predicted intensity vs. length of the LED array determined at two positions across the width of the array; line C corresponding to the longitudinal edge of the array, as shown in the inset diagram of FIG. 11, and line D extending along a central longitudinal line of the array and across the central cavity 124 which is not populated with emitting LEDs.

It may be seen that the predicted intensity is constant along each line after an initial lower intensity region at each longitudinal end of the array. The constant region for line D has 120% nominal power, resulting from the additive effect of the LED illumination, whereas the constant region for line C has 100% nominal power.

Such an LED lamp unit was also constructed and the nominal power of the UV emissions along lines C and D were measured. The actual measure values are also shown on FIG. 11. It may be seen that for the edge longitudinal line, line C, the actual measured values are very close to the predicted values, providing a substantially constant power central region along the length of about 100% nominal power. For line D, the actual measured values were also close to the predicted values, but were even lower that the predicted values. The result was that across the width of the lamp unit the UV intensity differed by less than 20%. For example, at 143 mm from the longitudinal ends, corresponding to a longitudinal mid-position, the UV intensity at the width-wise or lateral mid position was only 12% higher than the UV intensity at the longitudinal edge.

The closeness of the predicted and measured values shows the robustness of the modelling, particularly in a region where the array is populated with UV emitters.

This structure providing an annular array of UV emitting elements therefore provides a substantially uniform UV intensity.

Comparative Example 1 The LED lamp array of Example 1 was modelled using the same model applied to a fully-populated LED array, i.e. without an annular array having a central cavity as for Example 1. The results are shown in FIG. 12. Figure 12 shows the relationship between the predicted intensity vs. length of the LED array determined at two positions across the width of the array; line A corresponding to the longitudinal edge of the array, as shown in the inset diagram of FIG. 12, and line B extending along a central longitudinal line of the array, the array being fully populated with emitting LEDs and there being no central cavity as in Example 1.

It may be seen, again, that the predicted intensity is constant along each line after an initial lower intensity region at each longitudinal end of the array. The constant region for line B has nearly 130% nominal power, resulting from the additive effect of the LED illumination, whereas the constant region for line A has 100% nominal power.

Comparative Example 1 shows that in the centre of the fully populated array, the predicted LW intensity is significantly higher, nearly 30% higher, than the LW intensity at the edges.

Accordingly, a comparison of Example 1 and Comparative Example 1 shows that the part populated emitter array, in the form of an annular array, in accordance with this aspect of the present invention has more uniform intensity across the minor and major axis of the array (Line C and D) as compared to a fully populated array (Lines A and B). The usable length of the array is also increased with the part populated array reaching 90% of the nominal design power (Line C vs. Line A) more quickly than the fully populated array design, indicated a reduced edge effect problem.

The part populated array had 39% fewer LEDs than the ftilly populated array and offered a significant cost saving as the cure step is determined by the intensity at the array edge and not the array centre. In addition the maximum power at the centre is reduced and therefore the risk of uneven cure of surface coatings, or exotberm in thicker laminates, is reduced.

The Example therefore shows the technical effect of achieving more uniform radiation across the width of the array when using an annular array of light emitters such as LEDs.

Claims

Claims 1. A kit for curing a matrix resin in a fibre-reinforced resin composite material, the kit comprising an illumination device for producing radiation for curing a matrix resin in a fibre-reinforced resin composite material, and at least one mounting device for mounting to a substrate of the fibre-reinforced resin composite material, wherein the mounting device comprises a series of indexed interconnections therealong for selective releasable fitting of the illumination device at a selected one of a series of locations along the mounting device with the radiation emitting face spaced from the substrate.
2. A kit according to claim 1 wherein the illumination device comprises an array of a plurality of radiation emitting elements mounted in a radiation emitting face of the illumination device, and wherein the radiation emitting elements are ultraviolet radiation emitting diodes.
3. A kit according to claim 1 or claim 2 wherein the radiation emitting elements are mounted in a housing unit to form a manually locatable jig which is removably mountable to the at least one mounting device, and the jig has at least one locating device for removably fitting the jig to a respective mounting device.
4. A kit according to claim 3 the housing unit is mounted on a slider assembly of the jig extending between the opposed ends of the jig, and the housing unit is slidable between at least two positions spaced along the slider assembly.
5. A kit according to any one of claims 1 to 4 wherein the mounting device comprises at least one elongate flexible strap.
6. A kit according to claim 5 wherein the elongate flexible strap has spaced ends which can be removably engaged together to allow the strap to be wrapped around a substrate, with the spaced ends in a selected longitudinal relationship to provide a desired internal wrap dimension for the strap.
7. A kit according to claim 5 wherein the mounting device has at least one vacuum suction device for removably attaching the mounting device to a substrate.
8. A kit according to any one of claims 1 to 7 wherein the indexed interconnections comprise a series of male elements linearly extending along the mounting device and the illumination device comprises a hole for receiving a respective male element.
9. A kit according to claim 8 wherein at least one male element comprises a fixed base part and a rotatable toggle on the base part, wherein rotation of the toggle when the base part is received in the hole temporarily locks the illumination device to the mounting device.
10. A kit according to any one of claims 1 to 9 wherein the mounting device comprises two mounting devices, each for fitting to a respective one of two mutually spaced parts of the illumination device.
11. A kit according to any one of claims 1 to 10 wherein the indexed interconnections are mutually spaced by a predetermined pitch for permitting the illumination device to be successively mounted at a series of linearly extending mutually adjacent locations with the index therebetween corresponding to the desired pitch.
12. A method of curing a matrix resin in a fibre-reinforced resin composite material, the method comprising the steps of: (d) fitting at least one mounting device to a substrate of a fibre-reinforced resin composite material, wherein the mounting device comprises a series of indexed interconnections therealong; (e) fitting an illumination device at a selected indexed location along the mounting device, the illumination device having a radiation emitting face facing the substrate and engaging at least one interconnection; and (f) irradiating the substrate with radiation from the illumination device for a period of time sufficient to cure a matrix resin in the composite material.
13. A method according to claim 12 wherein the radiation is ultraviolet radiation provided from an. array of a plurality of ultraviolet radiation emitting diodes.
14. A method according to claim 12 or claim 13 wherein the radiation emitting face is spaced a selected distance from the substrate by fitting at least one front face of the illumination device to the at least one mounting device.
15. A method according to any one of claims 12 to 14 wherein the radiation emitting face is located between a pair of longitudinally separated front faces of the illumination device, each front face being fitted to a respective interconnection.
16. A method according to any one of claims 12 to 15 wherein the illumination device forms a manually locatable jig, and in step (b) the jig is removably mounted to the mounting device which is fitted to the substrate.
17. A method according to any one of claims 12 to 16 wherein the mounting device comprises a series of indexed interconnections therealong for selective fitting of the illumination device to a selected indexed location, and steps (b) and (c) are carried out a plurality of times to irradiate an enlarged area comprising a plurality of individual irradiated areas.
18. A method according to claim 17 wherein each individual irradiated area corresponds to one of the series of indexed interconnections to irradiate a composite area of the substrate composed of a plurality of individual illumination areas.
19. A method according to claim 17 wherein at least two individual irradiated areas correspond to a respective one of the series of indexed interconnections, the radiation emitting face being movable between at least two positions when the illumination device is fitted to the mounting device.
20. A method according to any one of claims 12 to 19 wherein the matrix resin to be cured is in a repair of a fibre-reinforced composite material.
21. A method according to claim 20 wherein the fibre-reinforced composite material is in a wind blade.
22. A wind blade repaired by the method of claim 21.