Device and methods for producing edge protection coatings

Description

[0001] The present invention relates to devices and methods for applying coatings to highly curved component surfaces. It relates in particular to devices and methods for applying a coating material to or on the edges of a component, especially devices and methods for applying an erosion-resistant coating material. It further relates to the use of these coatings as erosion protection for components moving in gaseous or liquid media, in particular their use as edge protection for rotor blades, wings, or airfoils.

[0002] Surfaces of objects exposed to mechanical stresses from erosion are generally treated with an erosion protection coating. In the following, erosion is defined as the damage to a material caused by liquid or solid substances moving in the form of droplets or particles in a gaseous or liquid medium. Well-known examples include erosion by rain, hail, dust, or sand on the rotor blades of wind turbines and helicopters, on aircraft wings, and on ship propellers.

[0003] Surface resistance to erosion is achieved by applying coatings that are sufficiently elastic to absorb impact forces while simultaneously possessing adequate hardness and abrasion resistance. These erosion protection coatings can be applied to the entire surface of a component, such as a rotor blade. Alternatively, only particularly exposed surface areas of the component, such as the leading edge of the rotor blade, can be coated.

[0004] In the following, the terms edge protection and edge protection coating refer to a coating applied to the edge of a component, in particular an erosion protection coating. An edge is defined as the section of a component where two surfaces meet.

[0005] The leading edges of rotor blades, wings, or airfoils are typically highly curved surfaces, making the application of liquid or paste-like coatings difficult. Applicators and dispensing tips used to repair erosion damage to rotor blade coatings are known from WO 2008 / 157013 and US 2017 / 0239682. To maintain the aerodynamic properties of the rotor blades, depressions, abrasions, or holes in the coating caused by erosion must be filled without compromising the blade's shape through excess material application. Typically, repairs only address the damaged areas of the coating, which are small compared to the total surface area.

[0006] From DE 202018001242, notched trowels with lateral wheels are known, which enable the uniform application of adhesives for attaching tiles or slabs. From DE 202008011551, squeegee tools with a handle and a smoothing lip are known, which enable the application and smoothing of floor coatings in a single step. With these tools, coating materials can be applied to flat surfaces with uniform layer thicknesses.

[0007] The object of the present invention is therefore to provide improved devices and methods for the production of erosion protection coatings, in particular edge protection coatings. This object is achieved according to the present claims. Further embodiments are disclosed in the description.

[0008] The device according to the invention is designed in the manner of a squeegee so that liquid or pasty materials, such as coatings, can be applied evenly and continuously to a curved substrate surface. With the aid of the device according to the invention, materials can be easily applied to or onto the edges of a component. The device has a base plate made of a flexible material, with teeth provided on at least one of its sides. Parallel to the toothed side, a channel runs along the base plate with at least one inlet and several outlet openings. The coating material, such as liquid or pasty coatings, is fed in through the inlets and dispensed onto the surface of the component through the outlet openings.On the side of the channel facing away from the toothed side, a sealing lip is arranged which prevents unwanted leakage of the material or coating material.

[0009] Suitable materials for the base plate are sufficiently flexible and chemically resistant plastics. In the following, chemical resistance is understood to mean the property of materials to withstand exposure to chemicals without diminishing their usability. In a preferred embodiment, the plastic used is resistant to the effects of components of the coating material compositions, especially those used to produce erosion control coatings. The term coating material is understood to mean a liquid or pasty composition which, after application to a substrate, forms a coating by curing. The curing process includes both drying through the evaporation of solvents and the chemical reaction of components of the composition.

[0010] Due to its special design, the device according to the invention can be adapted very precisely to the contours of the component to be coated. In a preferred embodiment according to the invention, the flexible base plate achieves a bending radius of up to 10. mm. Therefore, plastics with elastic moduli in the range of 1000 to 1600 MPa, preferably 1050 to 1550 MPa, and especially preferably 1100 to 1500 MPa, are used.

[0011] The toothing according to the invention consists of a structure arranged on one or more sides of the base plate. It can be attached to only one side or additionally to the adjacent sides. The toothing comprises a number of teeth which are arranged parallel to one another on the base plate with a tooth width (h) and a distance (i). The tooth width (h) is in the range of 0.2 to 0.7 mm, preferably 0.3 to 0.6 mm, and particularly preferably 0.4 to 0.5 mm. The distance (i) between two teeth is 1.6 to 2.6 mm, preferably 1.8 to 2.4 mm, and particularly preferably 2.0 to 2.2 mm.

[0012] The teeth are designed to be perpendicular to the plate and have a height (e). Furthermore, the teeth have a length (g), a segment of which projects beyond the side edge of the plate. Preferably, according to the invention, the length of this segment, which corresponds to the tooth length (f), corresponds to the tooth height (e). The tooth height (e) and the tooth length (f) are in the range of 0.2 to 5.0 mm. Depending on the viscosity of the coating material used, the layer thickness of the applied liquid or paste-like coating material can be determined by the selected ratio of tooth height (e) to spacing (i). This is hereinafter referred to as the wet film thickness.

[0013] Protective coatings are generally thick-film coatings with dry film thicknesses between 100 and 1000 µm. In the following, dry film thickness refers to the thickness of the cured or dried coating. Therefore, to produce such protective coatings, the coating materials used must be applied in corresponding wet film thicknesses.

[0014] In particular, edge protection coatings for wings or rotor blades must not impair the aerodynamics of these components; that is, coating materials must be applied in such a way that the coating has the required layer thickness at the highly stressed leading edge. On the wing or rotor blade surfaces, however, the layer thickness should be as small as possible to avoid impairments caused by changes in the aerodynamic profile of the wings or rotor blades. Preferably, the dry film layer thicknesses at the leading edges are in the range of 100 to 2000 µm, while the dry film layer thicknesses on the surfaces are below 50 µm. To achieve these layer thickness profiles, the device according to the invention, in a preferred embodiment, has toothless sections at the outer edges of the toothed side of the base plate.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.

[0015] In a further embodiment of the present invention, the teeth are shaped to be round or oval on both sides. Surprisingly, it has been found that teeth with a smaller contact area on the substrate are particularly advantageous. Firstly, this reduces the risk of the device slipping during application. Secondly, this method produces only narrow grooves that can easily disappear. Grooves are defined as the strips in which little or no material can be applied because the teeth in contact with the substrate prevent application.

[0016] The device according to the invention has a channel arranged parallel to the toothed side, through which the coating material to be applied is fed. Furthermore, the channel has several openings on the side facing the toothed side, through which the supplied coating material can flow out. These outlet openings are arranged at regular intervals so that the coating material is applied evenly to the substrate. To enable a continuous feed, the channel can have at least one filling nozzle. Preferably, the channel is provided with two filling nozzles, each located at opposite ends. The device can be connected to a metering system via the filling nozzles, which allows for a uniform, predetermined feed of the coating material.

[0017] The channel according to the invention further comprises suitable cross-sections to minimize the flow resistance of the coating material. The size of the channel cross-section and the outlet openings depend on the properties of the coating material, such as its viscosity.

[0018] In another advantageous embodiment, the channel is flexible so as not to impede the movement of the flexible base plate. Suitable designs include tubular or corrugated elements that possess sufficient stability to ensure a uniform material flow during the application process. Preferably, the channel is designed as a corrugated hose or tube.

[0019] In another preferred embodiment, the channel is positioned at a distance from the toothed side. In this way, a reservoir for the coating material is formed between the substrate surface and the device according to the invention during application. The size of the distance, and thus also the size of the reservoir, is selected such that the coating material can flow continuously and evenly from the outlet openings.

[0020] Preferably, the device further comprises at least one sealing lip, which is arranged on the side of the channel facing away from the toothed side. The sealing lip limits the reservoir and prevents unwanted flow or leakage of the coating material.

[0021] The drawings Fig. 1 , Fig.2 und Fig. 3 The figures schematically represent an exemplary embodiment of the device according to the invention. Fig. 1 shows a squeegee according to the invention (1).

[0022] The flexible base plate (2) has serrations (3) on one side. Furthermore, a channel (4) is provided on the base plate (2), which has a filling nozzle (5) at each of its two ends. Several outlet openings (6) are provided on the side of the channel (4) facing the serrations (3). A sealing lip (7) is provided on its opposite side.

[0023] Fig. 2 Figure 1 shows an enlarged section of the serrated side of the doctor blade (3) in plan view. The serration comprises a number of teeth (3a) which are mounted parallel to each other on the base plate with a tooth width (h) and a distance (i). The teeth (3a) are designed such that they project beyond the base plate by a length, which is referred to below as the tooth length (f).

[0024] Fig. 3Figure 1 shows a cross-section of one of the teeth (3a) of the doctor blade. The tooth (3a) is designed to be perpendicular to the plate (2) and has a height (e). It has a total length (g), with a segment of this length, referred to as the tooth length (f), extending beyond the side edge of the plate (2). In the illustrated embodiment, the tooth length (f) and the tooth height (e) are equal.

[0025] The device according to the invention can be used, in particular, for applying coating materials to or onto component edges. Due to its properties, the device can readily adapt to the contours of highly curved surfaces, such as those found on the edges of components. This results in a continuous, uniform application of coating material, as required for the production of protective coatings, especially for erosion protection coatings on the leading edges of rotor blades, wings, or airfoils. With the aid of the device according to the invention, coating materials can be applied in a single, uninterrupted pass with a consistent layer thickness profile, as described above.

[0026] In a further embodiment of the present invention, the device is used in methods for producing a protective coating. These methods comprise the following steps: (a) Providing a coating material (b) Applying the coating material to a component using the device according to the invention (c) Curing the applied coating material to form a coating

[0027] Using the method according to the invention, thick protective coatings can be produced which have dry film thicknesses in the range of 100 to 2000 µm, preferably 300 to 1500 µm, particularly preferably 450 to 1000 µm, and most preferably 600 to 750 µm. These layer thicknesses are preferably produced at component edges, particularly preferably at the leading edges of wings, wings, and rotor blades.

[0028] Coating materials suitable for use in the process exhibit sufficient flowability and can be solvent-free. In solvent-free compositions, the dry film thickness corresponds to the wet film thickness. According to the invention, coating materials are preferably used for the production of erosion control coatings.

[0029] Coating material compositions such as those known from German patent application DE 102017003034 A1 are particularly preferred. These compositions each comprise a base component containing trifunctional polycaprolactone polyols, polycarbonate diols, or polycaprolactone polyols and polycarbonate diols as binders, and a hardener component containing crystallization-resistant, isocyanate-functional prepolymers as hardeners. The compositions disclosed in DE 102017003034 A1 for the production of an erosion protection coating are hereby expressly included.

[0030] According to the invention, preferably the coating material is applied in step (b) only to a portion of the component's surface. Preferably, the coating material is applied to the edges or at the edges of the component.

[0031] The curing of the applied coating material to form a coating in step (c) preferably takes place at a temperature in the range of 10 to 70 °C, preferably in the range of 15 to 26 °C, more preferably in the range of 40 to 70 °C, and in particular 50 to 65 °C.

[0032] The method according to the invention is particularly preferably used for coating the edges of rotor blades, wings or airfoils, especially for coating edges that are particularly exposed to erosion.

Claims

1. Device for applying coating materials to a substrate surface, with the device having a base plate (2), with a toothing (3) mounted in at least one of its sides, a channel (4) which is arranged parallel to the toothed side, as well as at least one sealing lip (7) arranged on the side of the channel (4) which faces away from the toothed side, characterised by the base plate (2) being a base plate made from a flexible material and by the channel (4) comprising several regularly arranged outlets (6).

2. Device according to claim 1, characterised in that the flexible base plate (2) reaches a bending radius of up to 10 mm.

3. Device according to claim 1 or 2, characterised in that the toothing (3) comprises a number of teeth (3a) which are perpendicular to the base plate (2).

4. Device according to one of the preceding claims, characterised in that the device has toothless sections at the outer edges of the toothed side.

5. Device according to one of the preceding claims, characterised in that the teeth (3a) have a length section (f) which projects beyond the base plate.

6. Device according to one of the preceding claims, characterised in that the channel (4) has at least one filler neck (5).

7. Use of the device according to any one of the claims 1 to 6 for the application of a coating material.

8. Method for producing a protective coating, with the method comprising the following steps (a) providing a coating material, (b) applying the coating material to a component by means of the device according to one of the claims 1 to 7, (c) curing the applied coating material until a coating is obtained, characterised in that the device is a device according to one of the claims 1 to 6.

9. Method according to claim 8, characterised in that coating materials for producing an erosion protection coating are employed in step (a).

10. Method according to claim 8 or 9, characterised in that in step (b) the coating material is applied to only one part of the surface of the component.

11. Method according to one of the claims 8 to 10, characterised in that in step (b) only the edge of a rotor blade, a wing or a hydrofoil is coated.