Lightning-protection device in a modular blade
A lightning-protection device in a modular blade that connects the outboard module, where the lightning strikes, to the inboard module through which the lightning is conducted to the hub, and includes the lightning down conductor cable. The device is an elastic element with greater electrical conductivity than the adhesive used to affix the inserts in holes previously drilled inside the carbon fiber and that make up the metal joint of the modular blade. The device is an elastomer with a preferably toroidal shape thar surrounds each and every one of the metal elements that make up the joint of the blade and covers the gap formed between the carbon fiber of the cap and the aforementioned metal elements. The use of other shapes and other conductive materials that allow its geometry to be elastic is an option.
1 . A device for lightning protection in a modular blade ( 100 ), wherein metal connection elements are arranged in an upper cap ( 5 ) and in a lower cap, both on the side of an outboard module ( 2 ) and on the side of an inboard module ( 3 ), each of the metal connection elements ( 4 ) comprising one or several prestressed bolts ( 10 ), which are threaded into inserts ( 11 ) that are glued into previously drilled holes in the interior of a carbon fibre composite material ( 6 ) by means of an adhesive ( 12 ), characterized in that it comprises:
a spark gap, ( 7 ) which is an elastic element with greater electrical conductivity than that of the adhesive ( 12 ) used to glue the drilled inserts ( 11 ) inside the carbon fibre ( 6 ),
the spark gap ( 7 ) is arranged between the cap ( 5 ) and the elements of the metal joint
the spark gap ( 7 ) is elastic, which ensures contact with the cap ( 5 ) and the metal joining elements during the assembly and operation of the blade.
2 . Device for lightning protection in a modular blade according to claim 1 , wherein each spark gap ( 7 ) has a toroidal shape and surrounds each and every one of the elements that form the metal joint.
3 . Device for lightning protection in a modular blade according to claim 1 , wherein the spark gap ( 7 ) is a conductive elastomer and has a section with protuberances to improve contact with the composite material and with the metallic part of the joint.
4 . Device for lightning protection in a modular blade according to claim 1 , where the spark gap ( 7 ) is formed by a metallic material with a geometry that allows its elasticity.
5 . Device for lightning protection in a modular blade according to claim 1 , wherein a single bolt ( 10 ′) is screwed into the inserts ( 11 ) of the outboard ( 2 ) and the inboard ( 3 ) with a metallic wedge element composed of washers ( 13 ) and a central wedge ( 14 ) crossed by their corresponding transverse screws whose tightening achieves prestressing and the spark gap ( 7 ) is arranged between the smooth face of the bushing ( 13 ) and carbon fibre ( 6 ).
6 . Device for lightning protection in a modular blade according to claim 1 , where an elastomer is presented with a double ring and an inclined step between both ( 7 ′), where the ring with the largest diameter is the thinnest and is arranged in contact with the carbon fibre ( 6 ) and the inner ring, with a smaller diameter, is arranged in contact with the washer ( 13 ).
7 . Device for lightning protection in a modular blade according to claim 1 , wherein it presents a metallic material formed by two C-shaped rings facing and overlapping, with an internal spring ( 7 ″) that provides the required elasticity and is arranged between the carbon fibre ( 6 ) and the washer ( 13 ).