Patent Application
20220410206
The present invention relates to devices and methods for applying coatings to highly curved component surfaces. The present invention in particular relates to devices and methods for applying a coating material to or on the edges of a component, in particular to devices and methods for applying an erosion protection coating material. The present invention further relates to the use of these coatings as erosion protection of components which move in gaseous or liquid media, in particular the use as an edge protection for rotor blades, wings or hydrofoils.
Surfaces of objects which are exposed to mechanical stress by erosion are generally provided with erosion protection. The term erosion is hereafter defined as the damage of a material caused by liquid or solid substances moving in the shape of drops or particles within a gaseous or liquid medium. A well-known example is erosion by rain, hail, dust or sand on rotor blades of wind turbines and helicopters, on aircraft wings, and on marine screw propellers.
The resistance of surfaces to erosion is achieved by the application of coatings which are sufficiently elastic to absorb the impact forces and which at the same time show sufficient hardness and abrasion resistance. The entire surface of a component, for example, a rotor blade, can be coated with these erosion protection coatings. It is, however, also possible to coat only particularly exposed surface areas of the component, such as, for example, the front edge of the rotor blade.
The terms edge protection and edge protection coating are hereafter defined as a coating applied to the edge of a component, in particular an erosion protection coating. The edge is referred to as the section of a component where two surfaces abut one another.
The front edges of rotor blades, wings or hydrofoils are usually highly curved surfaces to which the application of liquid or pasty coating materials is difficult. WO 2008/157013 describes methods for applying pasty repair lacquers to a rotor blade via an applicator. These applicators are used for repairing erosion damage to the rotor blade coatings. In order to maintain the aerodynamic properties of the rotor blades, the depressions, abrasions or holes caused by erosion must be levelled out in the coating without impairing the shape of the blade through the application of excess material. During a repair process, only the damaged sections of a coating are generally repaired, the latter being rather small in comparison to the total surface. Commonly known applicators are not suitable for applying an edge protection coating, which must have a uniform layer thicknesses over the entire length of a rotor blade.
An aspect of the present invention is to provide improved devices and methods for producing erosion protection coatings, in particular edge protection coatings.
In an embodiment, the present invention provides a device for applying at least one coating material to a substrate surface. The device includes a flexible base plate comprising a toothing which is mounted on at least one side of the flexible base plate as a toothed side, a channel which is arranged parallel to the toothed side, and at least one sealing lip which is arranged on a side of the channel which faces away from the toothed side.
The present invention is described in greater detail below on the basis of embodiments and of the drawings in which:
The device according to the present invention is designed in the manner of a doctor blade so that liquid or pasty materials, such as, for example, coating materials, can be applied uniformly and continuously to a curved substrate surface. With the aid of the device according to the present invention, materials can easily be applied to or on the edges of a component. The device has a base plate made of a flexible material, with a toothing being attached to at least one of its sides. On the base plate, a channel with at least one filler neck and several outlets parallels the toothed side. The coating material, such as a liquid or a pasty coating material, is conducted via the filler necks and is then applied to the surface of the component via the outlets. A sealing lip is arranged on the side of the channel which faces away from the toothed side, the sealing lip preventing an undesired escape of the material or coating material.
Suitable materials for the base plate are sufficiently flexible and chemical-resistant plastics. The term resistance to chemicals is hereafter defined as the property of substances to withstand stress caused by chemicals without reducing the functional value. In an embodiment, the employed plastic material can, for example, be resistant to the action of constituents of the coating material compositions, in particular resistant to the action of coating materials from which erosion protection coatings are produced. The term coating material is hereafter defined as a liquid or pasty composition which, after having been applied to a substrate, forms a coating through curing. The curing process comprises both drying by evaporating the solvents and the chemical reaction of constituents of the composition.
Due to its special design, the device according to the present invention can be adapted very precisely to the contours of the component to be coated. In an embodiment of the present invention, the flexible base plate has a bending radius of up to 10 mm. In particular plastics with elasticity modules in the range of 1000 to 1600 MPa, for example, 1050 to 1550 MPa, for example, 1100 to 1500 MPa, are therefore employed.
The toothing according to the present invention consists of a structure which is arranged on one or more sides of the base plate. It can be attached to only one of the sides or, additionally, to the adjoining sides. The toothing comprises a number of teeth which are mounted with a tooth width (h) and a distance (i) parallel to one another on the base plate. The tooth width (h) is in the range from 0.2 to 0.7 mm, for example, from 0.3 to 0.6 mm, for example, from 0.4 to 0.5 mm. The distance (i) between two teeth is 1.6 to 2.6 mm, for example, 1.8 to 2.4 mm, for example, 2.0 to 2.2 mm.
The teeth are designed so that they are perpendicular to the plate and have a height (e). The teeth furthermore have a length (g), with a length section projecting beyond the side edge of the plate. According to the present invention, the length of this section, which corresponds to the tooth length (f), can, for example, correspond to the tooth height (e). The tooth height (e) and the tooth length (f) are in the range from 0.2 to 5.0 mm. Depending upon the viscosity of the employed coating material, the layer thickness of the applied liquid or pasty coating material can be determined through the selected ratio of tooth height (e) to distance (i). This is referred to below as wet film layer thickness.
Protective coatings are generally thick-layered and have dry film layer thicknesses of between 100 and 1000 μm. The term dry film layer thickness is hereafter defined as the thickness of the cured or dried coating. In order to produce such protective coatings, the employed coating materials must therefore be applied in corresponding wet film layer thicknesses.
Edge protection coatings for wings or rotor blades must in particular not impair the aerodynamics of these components, i.e., coating materials must be applied so that the coating on the heavily stressed front edge has the required layer thickness. The layer thickness should also be as low as possible on the wing or rotor blade surfaces in order to avoid impairments due to changes in the aerodynamic profile of the wings or rotor blades. The dry film layer thicknesses at the front edges can, for example, be in the range of between 100 and 2000 μm, while the dry film layer thicknesses on the surfaces can, for example, be below 50 μm. In an embodiment, the device according to the present invention has tooth-free sections at the outer edges of the toothed side of the base plate in order to obtain these layer thickness profiles. The length ratio of the edge-side, toothless sections to the central, toothed section is selected according to the desired layer thickness profile and the shape of the component to be coated.
In an embodiment of the present invention, the teeth can, for example, be designed to be round and/or oval on one side or on both sides. It has surprisingly been found that teeth with a lower bearing surface on the substrate are particularly advantageous. This circumstance reduces the risk of slipping of the device during the application, while only thin striae are produced which may easily vanish. The term striae is hereafter defined as the lines where no or only very little material can be applied, since the teeth which rest on the substrate prevent these areas from being covered during the application process.
In an embodiment, the device according to the present invention can, for example, have a channel which is arranged parallel to the toothed side and through which the coating material to be applied is conducted. The channel on the side facing the toothed side also has several openings through which the conducted coating material can flow off. These outlets can, for example, be arranged at regular intervals so that the coating material is uniformly applied to the substrate. The channel can have at least one filler neck in order to allow a continuous supply. The channel can, for example, be provided with two filler necks, each of which is attached to its opposite end. The device may be connected to a dosing system via the filler necks which allows a uniform, predetermined supply of the coating material.
The channel according to the present invention further shows suitable cross sections in order to keep the flow resistance of the coating material as low as possible. The size of the cross section of the channel as well as the size of the outlets are thus dependent upon the properties of the coating material, such as, for example, the viscosity.
In an embodiment, the channel can, for example, be designed to be flexible in order not to impede the movement of the flexible base plate. Suitable embodiments are tubular or undulating elements having a sufficient stability in order to provide a uniform material flow during the application process. The channel can, for example, be designed as a corrugated hose or a corrugated pipe.
In an embodiment, the channel can, for example, be mounted at a certain distance to the toothed side. During the application process, a reservoir for the coating material is thereby formed between the substrate surface and the device according to the present invention. The mentioned distance and consequently also the size of the reservoir are chosen so that the employed coating material may flow off continuously and uniformly through the outlets.
The device can, for example, furthermore have at least one sealing lip which is arranged on the side of the channel which faces away from the toothed side. The sealing lip delimits the reservoir and avoids an undesired flowing off or a leakage of the coating material.
The drawings schematically illustrate an exemplary embodiment of the device according to the present invention.
The device according to the present invention can in particular be used for applying coating materials to or on edges of a component. Due to its properties, the device can easily adapt to the contours of highly curved surfaces, for example, on edges of components. A continuous and uniform application of coating material is thus achieved, as is required for producing protective coatings, in particular for producing coatings for erosion protection at the front edges of rotor blades, wings or hydrofoils. With the aid of the device according to the present invention, coating materials can be applied without interruption and in a constant layer thickness profile as was described above.
In an embodiment of the present invention, the device can, for example, be employed in methods for producing a protective coating. The methods comprise the following steps:
(a) providing a coating material;
(b) applying the coating material to a component via the device according to the present invention; and
(c) curing the applied coating material until a coating is obtained.
The method according to the present invention allows the production of thick-layered protective coatings which show dry film layer thicknesses in the range from 100 to 2000 μm, for example, 300 to 1500 μm, for example, 450 to 1000 μm, for example, 600 to 750 μm. These layer thicknesses are hereby generated, for example, at the edges of a component, for example, at the front edges of hydrofoils, wings and rotor blades.
Coating materials which are suitable for the use in the method show sufficient flowability and can be free of solvents. In the case of solvent-free compositions, the dry film layer thickness corresponds to the wet film layer thickness. Coating materials for producing erosion protection coatings can, for example, be employed according to the present invention.
Particular preference is given to the use of coating material compositions as are described in German patent application DE 102017003034 A1. In each case, these compositions have a parent component containing trifunctional polycaprolactone polyols, polycarbonate diols or polycaprolactone polyols as well as polycarbonate diols as binders, and a hardener component containing crystallization-resistant, isocyanate-functional prepolymers as a curing agent. The compositions for producing an erosion protection coating which are described in DE 102017003034 A1 are hereby expressly incorporated by reference.
According to the present invention, the coating material can, for example, be applied to only one part of the surface of the component in step (b). The coating material can, for example, be applied to or on the edges of the component.
The curing of the applied coating material until a coating is obtained can, for example, be carried out in step (c) at a temperature in the range from 10 to 70° C., for example, in the range from 15 to 26° C., for example, in the range from 40 to 70° C., in particular from 50 to 65° C.
The use of the method according to the present invention can, for example, be used for coating the edges of rotor blades, wings or hydrofoils, in particular for coating edges which are exposed to erosion to a great extent.
The present invention is not limited to embodiments described herein; reference should be had to the appended claims.
1 Doctor blade
2 Flexible base plate
3 Toothing
3
a Tooth
4 Channel
5 Filler neck
6 Outlet
7 Sealing lip
e Tooth height
f Tooth length
g Total length
h Tooth width
i Distance
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2019 134 132.9 | Dec 2019 | DE | national |
This application is a U.S. National Phase application under 35 U.S.C. § 371 of International Application No. PCT/DE2020/101050, filed on Dec. 10, 2020 and which claims benefit to German Patent Application No. 10 2019 134 132.9, filed on Dec. 12, 2019. The International Application was published in German on Jun. 17, 2021 as WO 2021/115539 A1 under PCT Article 21(2).
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/DE2020/101050 | 12/10/2020 | WO |
