Heating member for an ice protection system; parts equipped therewith and method for operating

Abstract

In order to improve the effectiveness and efficiency of ice protection systems, the invention proposes a layered thermo-electric heating member for an ice protection system, preferably for aerial vehicles, the heating member comprising a plurality of active layers and a separation layer between adjacent active layers, wherein each active layer comprises a conductive track that is configured to, when supplied with electrical power, generate a heat power density distribution, wherein each conductive track is configured such that the heat power density distribution is varying depending on a position along at least one active layer dimension of each active layer.

Description

[0001] HEATING MEMBER FOR AN ICE PROTECTION SYSTEM; PARTS EQUIPPED THEREWITH AND METHOD FOR OPERATING

[0002] The invention relates to a heating member for an ice protection system. The invention further relates to an aerodynamic part, a propeller, and an aircraft equipped with said heating member.

[0003] In the field of aviation, from small unmanned aerial vehicles up to large passenger or freight aircraft, the buildup of ice on critical surfaces, such as (high-)lift surfaces or control surfaces, or propeller blades of all kinds is an important issue. Typically ice protection measures are distinguished into two broad groups: anti- icing measures and de-icing measures. Anti-icing measures are designed to avoid the build-up of ice on the protected surface, whereas de-icing measure are designed to remove ice build-up from the protected surface.

[0004] US 11 034457 B2 discloses a method for determining if icing has occurred on a surface of an aircraft, the method comprising heating a surface of an aircraft; after the heating has stopped, measuring the temperature of the surface as it cools; and determining if icing has occurred on the surface in dependence on the measured temperature. Advantageously, embodiments provide improved techniques for the detection of icing and the prevention, or mitigation, of icing when it has formed.

[0005] WO 2022 / 175 208 A1 and WO 20221258 849 A1 disclose a propulsion system for an aircraft propeller comprising a rotatable shaft, electrical connections at an aircraft end of the shaft for connection terminals of an electrical power source, wherein the propeller end has electrical connections for supplying electrical power to heating elements on the propeller.

[0006] EP 3 091 816 B1 and EP 3657 905 B1 disclose measures for a uniform heat distribution in resistive heaters for anti-icing and de-icing.

[0007] EP 2 658 777 B1 , EP 3 575218 B1 and EP 3 704 022 A1 disclose different ice protection systems and controllers / methods for anti-icing and de-icing.

[0008] EP 2 828 164 B1 discloses an apparatus for detecting critical states of a surface, wherein a hermetically sealed sensor is used. WO 20221032 321 A1 discloses a measuring arrangement for detecting deformations, such as bending of the outer surface, of a structural element of a wind turbine.

[0009] EP 3 726 926 A1 discloses a heating mat with an electrically insulating carrier on which resistor elements are arranged as heating elements and electrical conductor tracks, wherein the conductor tracks connect the PTC resistor elements to connection points for the connection of a power supply.

[0010] US 10 737 793 B2 discloses systems and methods for an ice detector with a movable airfoil.

[0011] EP 2 956661 B1 discloses a method for monitoring the operation of a wind turbine. During operation of the wind turbine, rotor blade vibrations are recorded by means of a measurement device and an instantaneous natural frequency of the rotor blade is determined from the recorded rotor blade vibrations.

[0012] US 9 555 894 B2 discloses an aircraft ice protection system comprising an ice protection device, an onboard power source, a controller, and an optimizer which conveys operation-optimizing instructions to the controller.

[0013] EP 1 716 044 B1 discloses an aircraft system for control of the application of power to a plurality of devices in the aircraft comprising a plurality of local control modules. Each local control module controls the application of the power to the group of at least one device.

[0014] EP 3450 320 A1 , EP 3473 595 A1 and EP 4 074603 A1 also disclose measures for anti-icing and / or de-icing.

[0015] Some of the known ice protection systems use heated air that was generated by the engines for the anti- / de-icing process, but may also include electrical supplements such as piezo elements or heating elements. In the course of increasing electrification of the aviation industry, mainly prompted by the desire to allow for carbon neutral flights, and the increase in small remote-controlled platforms, which typically are fully electric, there is a need for improved full-electric ice protection.

[0016] It is the object of the invention to provide improved full-electric ice protection measures.

[0017] The object is achieved by the subject-matter of the independent claims. Preferred embodiments are subject-matter of the dependent claims.

[0018] The invention provides a layered thermo-electric heating member for an ice protection system, preferably for aerial vehicles, the heating member comprising a plurality of active layers and a separation layer between adjacent active layers, wherein each active layer comprises at least one conductive track for generating heat from electric current, wherein each conductive track is configured for generating a layer heat power density distribution, wherein the layer heat power density distributions of different active layers or of different conductive tracks are differing from each other, and / or wherein at least one layer heat power density distribution varies dependent on a position along at least one active layer dimension of the respective active layer.

[0019] Preferably, each conductive track is configured such that the layer heat power density distribution varies continuously, linearly, in a step-wise manner, in repeating patterns, and / or randomly along the at least one active layer dimension or a direction that is perpendicular relative to the active layers.

[0020] Preferably, at least one conductive track is configured such that its layer heat power density distribution increases along the at least one active layer dimension from a first heating power that is greater than or almost zero to a second heating power.

[0021] Preferably, a first conductive track is configured for generating a first layer heat power density distribution and a second conductive track is configured for generating a second layer heat power density distribution. Preferably, the first and second conductive tracks are configured such that the first and second layer heat power density distributions are able to collectively generate a total heat power density distribution that differs from each layer heat power density distribution from which the total heat power density distribution is composed.

[0022] Preferably, the first and second conductive tracks are configured such that the total heat power density distribution is constant, increases, or decreases along the at least one active layer dimension or each active layer dimension.

[0023] Preferably, at least one conductive track includes at least one meandering portion for defining the respective layer heat power density distribution, wherein the meandering portion has a first leg portion and a second leg portion that are spaced apart from each other.

[0024] Preferably, the first leg portion and the second leg portion are connected via a connecting portion.

[0025] Preferably, the first and second leg portions extend at an angle relative to each other and / or at an angle relative to the connecting portion.

[0026] Preferably, the relative angle is selected from a group consisting of an acute angle, a right angle, and an obtuse angle.

[0027] Preferably, the first and second leg portions extend parallel to each other.

[0028] Preferably, at least one conductive track includes a thickness varying portion for defining the respective layer heat power density distribution. Preferably, the thickness varying portion has a conductive track thickness that varies along a dimension of the thickness varying portion, preferably along the longest dimension of the thickness varying portion.

[0029] Preferably, at least one conductive track includes a width varying portion for defining the respective layer heat power density distribution. Preferably, the width varying portion has a conductive track width that varies along a dimension of the width varying portion, preferably along the longest dimension of the width varying portion.

[0030] Preferably, the heating member includes at least one contiguous portion that includes at least one active layer, and the contiguous portion is bendable. Preferably, the contiguous portion includes at least one rim portion that is tailored to cover an aerodynamic part.

[0031] Preferably, the heating member includes a first rim portion and a second rim portion that are disposed on different rims, preferably opposite rims, of the contiguous portion, wherein the first rim portion is tailored to cover one side of the aerodynamic part and the second rim portion is tailored to cover another side, preferably opposite the one side, of the aerodynamic part.

[0032] Preferably, the heating member includes a first rim portion and a second rim portion that are disposed on different rims, preferably opposite rims, of the contiguous portion, wherein the first rim portion is tailored to cover a portion on one side of the aerodynamic part and the second rim portion is tailored to cover an adjacent portion on the same side of the aerodynamic part.

[0033] The invention provides a method for operating a heating member of any of the preceding claims, the method involving supplying at least one active layer or at least one conductive track with an electric current to generate a layer heat power density distribution.

[0034] Preferably, a plurality of active layers is sequentially supplied with an electric current to generate a total heat power density distribution that has seemingly moving power minima and / or maxima due to the sequential supply of electric current.

[0035] Preferably, the electric current has a temporal variation that follows a step-wise, a linear, a non-linear, a triangular, a sawtooth, or a sinusoidal pattern. Preferably, at least one active layer is intermittently de-energized.

[0036] The invention provides a method for manufacturing a heating member, the method comprising: a) providing a substrate with at least one side having conductive material that is coated with a photoresistive layer; b) selectively exposing the photoresistive layer by means of a light source, wherein light emitted from the light source is selectively allowed to illuminate the photoresistive layer to selectively cure the photoresistive layer; c) developing the result of step b); and d) etching the result of step c) to obtain a conductive track.

[0037] Preferably, step a) involves providing a substrate having conductive material on two opposite sides, wherein each conductive material is coated with a photoresistive layer.

[0038] Preferably, step b) involves subsequently or simultaneously exposing the photoresistive layer on each side.

[0039] Preferably, step b) involves an LCD-panel selectively blocking or allowing illumination of the photoresistive layer.

[0040] Preferably, in step c) developing involves removal of uncured material of the photoresistive layer by a developer to expose conductive material previously covered by the uncured material.

[0041] Preferably, in step d) etching involves removal of conductive material by an etchant to etch away the exposed conductive material from the substrate to form conductive tracks.

[0042] The invention provides an aerodynamic part for an aircraft, the aerodynamic part supporting or having embedded therein a preferred heating member.

[0043] Preferably, the aerodynamic part is chosen from a group consisting of a wing, a high-lift device, a propeller and a rotor blade.

[0044] The invention provides a propeller for an aircraft, such as an unmanned aerial vehicle, the propeller comprising a propeller hub and a plurality of rotor blades protruding therefrom, wherein at least one rotor blade and / or the propeller hub comprise a preferred heating member. Preferably, each heating member is disposed on one rotor blade.

[0045] The invention provides an aircraft comprising a preferred heating member, a preferred aerodynamic part, and / or a preferred propeller.

[0046] Preferably, each conductive track is configured such that the layer heat power density distribution varies along at least one active layer dimension. The layer heat power density distribution can vary continuously, in a step-wise manner, linearly, non-linearly, in repeating patterns, randomly, and / or any other desired configuration. Overall, the superposition of all layer heat power density distributions of the active layers preferably results in a total heat power density distribution variable by the ratio of supplied power to the individual active layers.

[0047] Preferably, a first active layer comprises a first conductive track configured to generate a first layer heat power density distribution and a second active layer, that is preferably adjacent to the first active layer, comprises a second conductive track configured to generate a second layer heat power density distribution, wherein the first and second conductive tracks are configured such that their respective layer heat power density distributions run opposite relative to each other.

[0048] Preferably, a first active layer comprises a first conductive track configured to generate a first layer heat power density distribution and a second active layer, that is preferably adjacent to the first active layer, comprises a second conductive track configured to generate a second layer heat power density distribution, wherein the first and second conductive tracks are configured such that their respective layer heat power density distributions vary along different active layer directions.

[0049] Preferably, the respective layer heat power density distributions vary along active layer directions that include a predetermined but arbitrary angle. Preferably, the respective layer heat power density distributions vary along active layer directions that include an angle that is selected from the group consisting of 15°, 30°, 45°, 60°, 90° and 180°.

[0050] Preferably, at least one or each conductive track comprises an increasing track thickness along at least one active layer dimension.

[0051] Preferably, the heating member includes at least one contiguous portion that includes each active layer, and the contiguous portion is bendable, wherein the contiguous portion includes at least one rim portion that is bendable so as to coincide with an edge portion of an aerodynamic part, when installed in a bent state on the aerodynamic part.

[0052] Preferably, the heating member includes a first rim portion and a second rim portion that are disposed on opposite rims of the contiguous portion, wherein the first and second rim portions are bendable so as to coincide with the same edge portion of an aerodynamic part, when installed in a bent state on the aerodynamic part.

[0053] An idea in this disclosure are thermo-electric heating elements used as part of a fully electric ice protection system (IPS) for aeronautical applications. A typical heating member includes one or multiple heater layers, also called active layers. In some embodiments, the heater layers manufactured out of resistive conductive material are superimposed in a multilayer configuration to deliver multiple / tunable power densities and / or redundancy.

[0054] This approach is particularly interesting for components / applications where power density changes in the spanwise and / or chordwise direction are desired. This is particularly useful if the conditions are not temporally steady due to changes of the airflow and icing conditions, i.e., all components exposed to icing conditions. Specifically, rotor blades, propellers, generally all components with a relative movement to the main structure / airframe are advantageously supplied with variable power densities in spanwise and / or chordwise direction in order to operate at maximum efficiency and effectiveness. Individual active layers can be designed such that each individual heating power density has the same, but phase shifted repeating pattern. The total superimposed heating power density forms a homogeneous power distribution over all dimensions.

[0055] It is also possible to secure the functionality of the heating element, even if single heater layers fail.

[0056] In some embodiments the multi-layer thermo-electric heating element of the ice protection system comprises a base layer. The substrate can also act as the base layer in case the material properties are according to the necessities of the used manufacturing process.

[0057] In some embodiments at least one heater layer manufactured out of conductive materials, such as, but not limited to, copper, carbon, aluminum, heatable inks, carbon nanotubes, graphene. The conductive tracks act as heating elements due to Joule effect, i.e. current is conducted through the tracks thereby causing resistive heating.

[0058] Each heater layer may contain a heat power density distribution which may vary at least in one direction. Some embodiments have multiple layers that have a repeating heat power density distribution pattern but are rotated in plane relative to each other, e.g., to form heat spots at predefined locations. Some embodiments have multiple layers with heat power density distributions that alternate along the stacking direction. In some embodiments a heating element is composed of multiple heater layers, where the superimposition of the multiple layer heat power density distributions can create a total heat power density distribution. The total heat power density distribution can be varied in multiple directions according to the layer heat power density distributions of each heater layer and the power supplied to each heater layer.

[0059] In some embodiments, in order to achieve a variable layer heat power density in a single heater layer, the conductive material and / or the layout of potential tracks is altered. Such alterations may be changing the material properties, e.g., density, composition, thickness, etc., or the layout design, e.g., track width, track height, track to track distance, etc.

[0060] In some embodiments separation layers / conductive insulation layers between the heater layers can be formed. It is preferred that the separation layers are as thin as possible to allow a sufficient heat flux to the external surface. In some embodiments the separation layers include a heat conduction or heat radiation optimization, e.g., by means of suitable fillers. In some embodiments an external protective coating is applied to the heating member. The protective coating can be chosen from a group comprising, polymer, metal, ceramic, diamond-like carbon (DLC). In case of a metal coating, a further electrically insulating layer may be applied.

[0061] The heater layers can be manufactured with various manufacturing processes, which include photoimaging of a photoresistive mask and subsequent etching of conductive material; selective laser activation and growth of palladium / conductive materials on the activated areas directly on the substrate surface or a pre-deployed base layer; direct inkjet printing on the substrate surface; or in general any other suitable method to produce electric resistive heaters on a 2D or 3D surface.

[0062] In some embodiments an electrically conductive material is positioned on a base material, which is electrically non-conductive material. The base material might be flexible or stiff.

[0063] In some embodiments the substrate may also act as the base layer. In some embodiments the conductive material is based on the base layer or substrate.

[0064] In some embodiments a photoresistive paint, dry-film or other material is used to cover the surface of the conductive material.

[0065] In some embodiments the substrate might be two-dimensional (flat), e.g., having no functional extension in the third dimension, 2.5 dimensional, e.g., composed of two- dimensional substrates that are stacked along the third dimension, or three-dimensional, e.g., having cambering or curvature. The 2.5 dimensional substrates may approximate true 3D features, such as cambering or curvature.

[0066] In some embodiments an imaging tool selectively cures the photoresist material to create a negative or positive shape of the desired conductive trace layout.

[0067] In some embodiments the uncured material is stripped and the etching mask is complete. In some embodiments the element is placed in an etching bath, which removes the conductive material wherever it is uncovered by the mask.

[0068] In some embodiments, after etching, the remaining mask is cleaned off and the final heater layout remains.

[0069] In some embodiments, the steps can be repeated multiple times to produce multiple heater layers on top of each other, or done simultaneously and merged afterwards.

[0070] In some embodiments the foil shape resembles the geometry of the substrate (rotors, propellers, wings, other substrates relevant to icing).

[0071] In some embodiments the foils are wrapped around the substrate geometry and adhered directly to the external surface of the substrate. In some embodiments the flexible heating foils are co-cured with the composite rotors / propellers and integrated in the structure.

[0072] In some embodiments a top coating may be applied.

[0073] Another approach for manufacturing a heating member involves the material of a base layer or the substrate being selectively activated with a laser spot.

[0074] In some embodiments the exact position of activation is set with a multi-axis positioning device which can focus the laser spot on the substrate according to the track design.

[0075] In some embodiments a suitable substrate or base layer is given, upon which a laser activation for the subsequent plating with palladium and a conductive material is possible. After the selective laser activation is completed, the substrate is placed in chemical baths to plate the selectively activated areas with palladium.

[0076] In some embodiments the same or another bath may grow a conductive material on the palladium manufactured by this process and can be a part of the external surface of the three-dimensional substrate.

[0077] The selective laser activation can be done anywhere on a three-dimensional geometry, as long as access with a laser is geometrically possible.

[0078] In some embodiments the selective laser activation and track growth is made on a two-dimensional base material (carrier foil), which is adhered to the substrate geometry afterward.

[0079] Another approach for manufacturing involves printing of the conductive traces. In some embodiments inkjet printing tracks are created on a base layer or the substrate directly.

[0080] In some embodiments positions which are covered with the inkjet are according to the track design. A multi-axis positioning tool can be used to deposit the ink on the desired locations.

[0081] In some embodiments the multi-layer heating element with heater layers manufactured by this process are part of the external surface of the substrate. The inkjet printing can be done anywhere on the geometry, as long as access with a deposition tool (nozzle) is geometrically possible.

[0082] In some embodiments the inkjet printing is made on a two-dimensional base material (carrier foil), which is adhered to the substrate geometry afterward.

[0083] Other manufacturing processes are possible, as long as the heater layers are manufactured out of conductive materials and per heater layer the heat power density distribution varies at least in one direction. Multiple heater layers therefore create a total heat power density distribution that varies in multiple directions by changing the power input on the various heater layers.

[0084] In some embodiments multilayered heating elements can be applied on metallic surfaces (e.g., aluminum, titanium, steel alloys, ...) or on polymers (such as thermoplastics, carbon fiber reinforced polymers, ...).

[0085] In some embodiments the heating elements may be integrated in an IPS for use in aeronautical applications, especially on light vehicles with limited power, including fixed wing aircraft and rotorcraft, as well as on hovering aircraft (balloons, blimps, zeppelins...)

[0086] In some embodiments the active IPS can activate the heating elements in different modes depending on the situation.

[0087] In an anti-icing mode ice growth is prevented. Typically, the surface temperature is chosen high enough to ensure an evaporation of the impacting supercooled water droplets or to enable an early shedding of the liquid water droplets instead of gliding back on the surface (runback). If this is given it can be assumed that no ice forms on the unprotected area of the airfoil behind the heating system.

[0088] A de-icing mode allows that a specific layer of ice grows on the surface, which is then shed by the IPS. In the de-icing mode, the power is turned on after a critical ice layer thickness has formed on the surface. In the de-icing mode, the surface temperature is chosen to be high enough to shed off the ice layer in a short time.

[0089] In some embodiments the heating elements of the IPS can be applied to all aerodynamic part surfaces, including lift and control surfaces (wing, propeller, rotor blades, ...) and other surfaces prone to icing (radome, nacelle, ...).

[0090] In some embodiments the heating elements can either be automatically activated based on the reading from the icing / aircraft sensors or manually by the pilot.

[0091] Embodiments of the invention are described with reference to the accompanying schematic drawings. Therein:

[0092] Fig. 1 depicts a perspective cross-section of a heating member installed on an aerodynamic part;

[0093] Fig. 2 depicts a variant of the heating member of Fig. 1;

[0094] Fig. 3 illustrates a heat power density distribution of the heating member;

[0095] Fig. 4 illustrates a variant of the heat power density distribution of the heating member;

[0096] Fig. 5 illustrates another variant of the heat power density distribution of the heating member;

[0097] Fig. 6 illustrates an embodiment of operating a heating member;

[0098] Fig. 7 depicts another embodiment of a heating member for a rotor blade; Fig. 8 illustrates installation of the heating member on the rotor blade; and

[0099] Fig. 9 depicts an embodiment of a method for manufacturing a heating member.

[0100] Referring to Fig. 1 a portion of an aerodynamic part 10 is illustrated in a perspective view and cross-section. The aerodynamic part 10 can be an airfoil of some sort, in particular a rotor blade 12.

[0101] The aerodynamic part 10 includes a surface that forms a substrate layer 14. The substrate layer 14 is typically formed by the outermost surface of the aerodynamic part 10, in particular without an installed heating member 16.

[0102] As shown in Fig. 1, the aerodynamic part 10 includes a heating member 16 that is formed by a plurality of layers. The heating member 16 is fixed, preferably bonded, to the substrate layer 14 via an adhesive layer 18. The adhesive layer 18 includes a suitable adhesive.

[0103] The heating member 16 can be covered by a top coat 20. The top coat 20 is aerodynamically even. In other words, the top coat 20 is formed with such a surface quality that the airflow is not unnecessarily disturbed.

[0104] The heating member 16 includes a carrier layer 22. The carrier layer 22 is electrically insulating. The carrier layer 22 is preferably a thin foil layer, preferably a polyimide foil layer. The carrier layer 22 may also be made of PCB material that is formed as a foil.

[0105] The heating member 16 includes a first active layer 24 that is disposed on the carrier layer 22. The first active layer 24 includes a first conductive track 26 (Fig. 3). The first conductive track 26 includes a resistive material that is able to conduct electrical power. The first conductive track 26 can include copper plating, graphite, carbon nanotubes, or other suitable material. Upon applying electrical power, the resistive material generates heat.

[0106] The heating member 16 includes a separation layer 28. The separation layer 28 is electrically insulating. The separation layer 28 can be formed by a thin foil layer, preferably a polyimide foil layer. The separation layer 28 is disposed on the first active layer 24. The separation layer 28 covers the conductive track 26. The separation layer 28 may also be formed to fill spaces between portions of the conductive track 26.

[0107] The heating member 16 includes a second active layer 30. The second active layer 30 is generally identical to the first active layer 24, with the difference that a second conductive track 32 has a different configuration compared to the first conductive track 26.

[0108] Referring to Fig. 2, a heating member 16’ is shown. The heating member 16’ includes the first active layer 24 and the second active layer 30 that are separated by the separation layer 28. The heating member 16’ does not need the carrier layer 22. Instead, the heating member 16’ is adhesively bonded to the substrate layer 14 using a polymer base layer 18’. The polymer base layer 18’ is electrically insulating. The polymer base layer 18’ preferably includes a cured resin that bonds the heating member 16’ and the substrate layer 14 together.

[0109] Fig. 3 depicts a vertically exploded view of the heating member 16 (carrier layer 22 omitted for sake of clarity). As shown, the first active layer 24 includes the first conductive track 26 and the second active layer 30 includes the second conductive track 32.

[0110] The first conductive track 26 is structured to meander. As indicated in Fig. 3, the first conductive track 26 has decreasing width from left to right. In other words, the resistance of the first conductive track 26 increases from left to right. It should be noted that instead of varying the width, it is also possible to vary the thickness of the first conductive track 26, and / or the spacing between each meander.

[0111] As further indicated in Fig. 3, the first conductive track 26 generates a first layer heat power density distribution 34. The first layer heat power density distribution 34 illustrates the dependence of the heat power density (typically measured in W / m2) from the location on the first active layer 24. The shape of the first conductive track 26 influences the first layer heat power density distribution 34.

[0112] As illustrated in this example, the first layer heat power density distribution 34 exhibits a greater heat power density value, where the first conductive track 26 has a smaller width (right), and a smaller heat power density value, where the first conductive track 26 has a greater width (left). The first conductive track 26 is structured such that the first layer heat power density distribution 34 is linear. It should be noted that other (nonlinear) heat power density distributions are possible.

[0113] The second conductive track 32 is formed similar to the first conductive track 26, but with an opposite second layer heat power density distribution 36. In other words, the second conductive track 32 is shaped such that the second layer heat power density distribution 36 exhibits a smaller heat power density value on the right that increases linearly towards a greater heat power density value on the left.

[0114] Fig. 4 illustrates a variant of the layer heat power density distributions of a heating member 16”. The heating member 16” is included in the aerodynamic part 10, which is a rotor blade 38 that is attached to a propeller hub 40. The rotor blade 38 defines a spanwise direction (left-right in Fig. 4) and a chordwise direction (up-down in Fig. 4). The heating member 16” is configured differently in that it includes three active layers 24”, 30”, 42” that are separated by two separation layers 28”, 44”.

[0115] The heating member 16”, specifically the first active layer 24”, is configured such that a first layer heat power density distribution 34” has a linear decrease in heating power density from the propeller hub 40 along the spanwise direction. The first active layer 24” is further configured such that the first layer heat power density distribution 34” has a constant heat power density along the chordwise direction.

[0116] The first separation layer 28” is arranged on the first active layer 24” to electrically insulate it from the second active layer 30”.

[0117] The heating member 16”, specifically the second active layer 30”, is configured such that a second layer heat power density distribution 36” has a linear increase in heating power density from the propeller hub 40 along the spanwise direction. The second active layer 30” is further configured such that the second layer heat power density distribution 36” has a linear increase from a trailing edge 46” along the chordwise direction towards a leading edge 48”.

[0118] The second separation layer 44” is arranged on the second active layer 30” to electrically insulate it from the third active layer 42”.

[0119] The heating member 16”, specifically the third active layer 42”, is configured such that a third layer heat power density distribution 50” has a linear increase in heating power density from the propeller hub 40 along the spanwise direction. The third active layer 42” is further configured such that a third layer heat power density distribution 52” has a linear decrease from the trailing edge 46” along the chordwise direction towards the leading edge 48”.

[0120] Preferably, the second and third active layers 30”, 42” are configured such that their respective second and third layer heat power density distributions 36”, 52” are such that in sum the total heat power density distribution along the chordwise direction corresponds to the layer heat power density of the first active layer 24” along the chordwise direction.

[0121] Referring to Fig. 5 and Fig. 6 a method for operating a variant of the heating member 16” is described in more detail. Fig. 5 and Fig. 6 show diagrams, where one spatial dimension of the heating member 16" is plotted on the x-axis and respective layer heat power densities are plotted on the y-axis.

[0122] In Fig. 5, the first three diagrams from the top show the spatial layer heat power density distributions 34”, 36”, 50” of the first to third active layers 24”, 30”, 42”, respectively. Each layer heat power density distribution 34”, 36”, 50” follows a triangular wave pattern. In other words, the conductive tracks 26, 32 are structured such that a triangular wave patter emerges for each active layer 24”, 30”, 42”.

[0123] In Fig. 5 the fourth diagram from the top shows a superposition of the three layer heat power density distributions 34”, 36”, 50”. The first to third heat power density distributions 34”, 36”, 50” are positioned such that the first and second layer heat power density distributions 34”, 36” have a 1 / 3 phase shift and the first and third layer heat power density distributions 34”, 50” have a 2 / 3 phase shift.

[0124] In Fig. 6 the diagrams each show a combination of the layer heat power density distributions 34”, 36”, 50” of two active layers that get supplied with electric current while the remaining active layer is unpowered. Furthermore the total heat power density distributions 54”, 56”, 58” are illustrated.

[0125] In Fig. 6 the top diagram shows a first total heat power density distribution 54” that is given by the superposition of the first and second heat power density distributions 34”, 36” of the first and second active layers 24”, 30”, respectively.

[0126] In Fig. 6 the middle diagram shows a second total heat power density distribution 56” that is given by the superposition of the second and third heat power density distributions 36”, 50” of the second and third active layers 30”, 42”, respectively.

[0127] In Fig. 6 the bottom diagram shows a third total heat power density distribution 58” that is given by the superposition of the first and third heat power density distributions 34”, 50” of the first and third active layers 24”, 42”, respectively.

[0128] In the embodiment shown in Fig. 6, the first to third diagram could be moments within a timeline, where the active heater layers 24”, 30”, 42” are sequentially supplied with electric current as illustrated such that the resulting total heat power density distribution propagates along at least one dimension of the heating member 16” over time.

[0129] In Fig. 6 the first diagram shows the total heat power density distribution 54” in the first moment in time. In Fig. 6 the second diagram shows the total heat power density distribution 56” in a further moment in time, which has a phase shift of 1 / 3 relative to the first total heat power density distribution 54”. In Fig. 6 the third diagram shows the total heat power density distribution 58” in a still further moment in time, which has a phase shift of 2 / 3 relative to the first total heat power density distribution 54”. This may generate more complicated patterns depending on the structure of the conductive tracks and the design of their respective heat power density distributions.

[0130] In a variant, other heat power density distributions can be used, e.g., sinusoidal, sawtooth or any other periodic pattern. In other variants that are compatible with both previously described variants, the supplied electric current to the active layers 24”, 30”, 42” is varied over time, such that other total heat power density distributions, spatial and / or temporal propagations are established.

[0131] With this embodiment it is possible to generate a moving heat power density distribution that has heat maximums and minimums that move in a direction determined by the heat power density distributions of the active heaters and the temporal current supply to the active layers. Referring to Fig. 7 and Fig. 8, the heating member 16 is described in more detail, where the heating member 16 is adapted to be attached to the rotor blade 38.

[0132] Referring to Fig. 7, the heating member 16 has one contiguous portion 104, a first terminal portion 106 and a second terminal portion 108. The contiguous portion 104 includes a plurality of partitions 110. A first partition 112 is shaped such that it covers the rotor blade back side 82, and a second partition 114 is shaped such that it covers the rotor blade front side 96. The heating member 16 is installed on the same rotor blade 38 with its contiguous portion 104. The first and second terminal portions 106, 108 may be installed on the propeller hub 40.

[0133] The first and second terminal portions 106, 108 include leads for attaching the heating member 16 to a power supply. The first and second terminal portions 106, 108 are integrally formed with the contiguous portion 104.

[0134] The first partition 112 comprises a contour that is derived from a rotor blade back side 82. The first partition 112 may be formed such that it can cover the whole rotor blade back side 82. The first partition 112 comprises a first trailing edge rim 86 and a first blade tip rim 88.

[0135] The first trailing edge rim 86 is shaped such that in the installed position, the first trailing edge rim 86 is substantially parallel to a rotor blade trailing edge 92. The first trailing edge rim 86 is preferably shaped such that the first trailing edge rim 86 coincides with the rotor blade trailing edge 92 along the spanwise direction.

[0136] The first blade tip rim 88 is shaped such that in the installed position, the first blade tip rim 88 is substantially parallel to a rotor blade tip portion 94. The first blade tip rim 88 is preferably shaped such that the first blade tip rim 88 coincides with the rotor blade tip portion 94 along the chordwise direction.

[0137] The second partition 114 comprises a contour that is derived from a rotor blade front side 96. The second partition 114 is formed such that it can cover the whole rotor blade front side 96. The second partition 114 comprises a second trailing edge rim 100 and a second blade tip rim 102.

[0138] The second trailing edge rim 100 is shaped such that in the installed position, the second trailing edge rim 100 is substantially parallel to the rotor blade trailing edge 92. The second trailing edge rim 100 is preferably shaped such that the second trailing edge rim 100 coincides with the rotor blade trailing edge 92 along the spanwise direction.

[0139] The second blade tip rim 102 is shaped such that in the installed position, the second blade tip rim 102 is substantially parallel to the rotor blade tip portion 94. The second blade tip rim 102 is preferably shaped such that the second blade tip rim 102 coincides with the rotor blade tip portion 94 along the chordwise direction. The first and second partitions 112, 114 are preferably disposed on the respective rotor blade back side 82 and rotor blade front side 96 of the same rotor blade 38.

[0140] Fig. 8 illustrates installation of the heating member 16 on the rotor blade 38. As illustrated more closely in the figure, the heating member 16 is provided. The heating member 16 can be attached by adhesively bonding it to the aerodynamic part 10. The heating member 16 is wrapped around the rotor blade 38 to cover the rotor blade back side 82 and the rotor blade front side 96.

[0141] The first partition 112 is attached to the rotor blade back side 82. The second partition 114 is attached to the rotor blade front side 96. The first and second terminal portions 106, 108 are preferably attached to the propeller hub 40.

[0142] Referring to Fig. 9, a manufacturing method for the heating member 16 is described in more detail. In a first step S51 , a carrier foil 120 having conductive material 122 on both sides is provided. The conductive material 122 is coated with a photoresistive layer 124.

[0143] In a second step S52, the carrier foil 120 is inserted into an exposure apparatus 126. The exposure apparatus 126 is known per se. A preferred configuration involves a UV-light source 128 that can be selectively masked off with an LCD-panel 130. Other light sources, i.e. wavelengths, are possible depending on the properties of the material chosen for the photoresistive layer 124.

[0144] As indicated in Fig. 9, there are some deactivated LCD pixels 132, i.e. these pixels block the UV-light from the UV-light source 128. Where the UV-light is blocked, the material in the photoresistive layer 124 is uncured material 134. Where UV-light was allowed to impinge on the material of the photoresistive layer 124, the material is now cured material 136.

[0145] In a third step S53, the exposed carrier foil 120 is moved into a developer bath 138. The developer bath 138 removes the uncured material 134, e.g. by dissolution, and exposes the conductive material 122 at those locations. The developer bath 138 leaves the cured material 136 in place. The developed carrier foil 120 may be rinsed with water to stop the developer from further reactions.

[0146] In a fourth step S54, the developed carrier foil 120 is moved into an etching bath 140. The composition of the etching bath 140 depends on the conductive material 122. For example, if copper is chosen as the conductive material 122, the etching bath 140 may involve ferric chloride (FeCh), cupric chloride (CuCh) or alkaline etch (Cu2+(NH3)4Ch). The developed carrier foil 120 is etched as long as is necessary for partial removal of the conductive material 122 at the respective desired locations. After etching, the etched carrier foil 120 can again be rinsed with water to stop the etching process. In a fifth step S55, the cured material 136 is removed with an appropriate solvent.

[0147] Now, the carrier foil 120 forms the separation layer 28 between the first and second active layers 24, 30, containing the first and second conductive track 26, 32, respectively. The heating member 16 is finished.

[0148] List of reference signs:

[0149] 10 aerodynamic part

[0150] 12 rotor blade

[0151] 14 substrate layer

[0152] 16 heating member

[0153] 16’ heating member

[0154] 16” heating member

[0155] 18 adhesive layer

[0156] 18’ base layer

[0157] 20 top coat

[0158] 22 carrier layer

[0159] 24 first active layer

[0160] 24” first active layer

[0161] 26 first conductive track

[0162] 28 separation layer

[0163] 28” first separation layer

[0164] 30 second active layer

[0165] 30” second active layer

[0166] 32 second conductive track

[0167] 34 first layer heat power density distribution

[0168] 34” first layer heat power density distribution

[0169] 36 second layer heat power density distribution

[0170] 36” second layer heat power density distribution

[0171] 38 rotor blade

[0172] 40 propeller hub

[0173] 42” third active layer

[0174] 44” second separation layer

[0175] 46” trailing edge

[0176] 48” leading edge

[0177] 50” third layer heat power density distribution

[0178] 52” third layer heat power density distribution

[0179] 54” total heat power density distribution

[0180] 56” total heat power density distribution

[0181] 58” total heat power density distribution

[0182] 82 rotor blade back side

[0183] 86 first trailing edge rim 88 first blade tip rim

[0184] 90 rotor blade leading edge

[0185] 92 rotor blade trailing edge

[0186] 94 rotor blade tip portion

[0187] 96 rotor blade front side

[0188] 100 second trailing edge rim

[0189] 102 second blade tip rim

[0190] 104 contiguous portion

[0191] 106 first terminal portion

[0192] 108 second terminal portion

[0193] 110 partition

[0194] 112 first partition

[0195] 114 second partition

[0196] 120 carrier foil

[0197] 122 conductive material

[0198] 124 photoresistive layer

[0199] 126 exposure apparatus

[0200] 128 UV-light source

[0201] 130 LCD-panel

[0202] 132 deactivated LCD pixel

[0203] 134 uncured material

[0204] 136 cured material

[0205] 138 developer bath

[0206] 140 etching bath

[0207] 551 first step

[0208] 552 second step

[0209] 553 third step

[0210] 554 fourth step

[0211] 555 fifth step

Claims

Claims1. A layered thermo-electric heating member for an ice protection system, preferably for aerial vehicles, the heating member comprising a plurality of active layers and a separation layer between adjacent active layers, wherein each active layer comprises at least one conductive track for generating heat from electric current, wherein each conductive track is configured for generating a layer heat power density distribution, wherein the layer heat power distributions of different active layers or of different conductive tracks are differing from each other, and / or wherein at least one layer heat power density distribution varies dependent on a position along at least one active layer dimension of the respective active layer.

2. The heating member according to claim 1, wherein each conductive track is configured such that the layer heat power density distribution varies continuously, linearly, in a step-wise manner, in repeating patterns, and / or randomly along the at least one active layer dimension or a direction that is perpendicular relative to the active layers.

3. The heating member according to claim 2, wherein at least one conductive track is configured such that its layer heat power density distribution increases along the at least one active layer dimension from a first heating power that is greater than or almost zero to a second heating power.

4. The heating member according to any of the preceding claims, wherein a first conductive track is configured for generating a first layer heat power density distribution and a second conductive track is configured for generating a second layer heat power density distribution, wherein the first and second conductive tracks are configured such that the first and second layer heat power density distributions are able to collectively generate a total heat power distribution that differs from each layer heat power density distribution from which the total heat power distribution is composed.

5. The heating member according to claim 4, wherein the first and second conductive tracks are configured such that the total heat power density distribution is constant,increases, or decreases along the at least one active layer dimension or each active layer dimension.

6. The heating member according to any of the preceding claims, wherein at least one conductive track includes at least one meandering portion for defining the respective layer heat power density distribution, wherein the meandering portion has a first leg portion and a second leg portion that are spaced apart from each other.

7. The heating member according to claim 6, wherein the first leg portion and the second leg portion are connected via a connecting portion.

8. The heating member according to claim 6 or 7, wherein the first and second leg portions extend at an angle relative to each other and / or at an angle relative to the connecting portion.

9. The heating member according to claim 8, wherein the relative angle is selected from a group consisting of an acute angle, a right angle, and an obtuse angle.

10. The heating member according to claim 9, wherein the first and second leg portions extend parallel to each other.

11. The heating member according to any of the preceding claims, wherein at least one conductive track includes a thickness varying portion for defining the respective layer heat power density distribution, wherein the thickness varying portion has a conductive track thickness that varies along a dimension of the thickness varying portion, preferably along the longest dimension of the thickness varying portion.

12. The heating member according to any of the preceding claims, wherein at least one conductive track includes a width varying portion for defining the respective layer heat power density distribution, wherein the width varying portion has a conductive track width that varies along a dimension of the width varying portion, preferably along the longest dimension of the width varying portion.

13. The heating member according to any of the preceding claims, wherein the heating member includes at least one contiguous portion that includes at least one active layer,and the contiguous portion is bendable, wherein the contiguous portion includes at least one rim portion that is tailored to cover an aerodynamic part.

14. The heating member according to claim 13, wherein the heating member includes a first rim portion and a second rim portion that are disposed on different rims, preferably opposite rims, of the contiguous portion, wherein the first rim portion is tailored to cover one side of the aerodynamic part and the second rim portion is tailored to cover another side, preferably opposite the one side, of the aerodynamic part.

15. The heating member according to claim 13, wherein the heating member includes a first rim portion and a second rim portion that are disposed on different rims, preferably opposite rims, of the contiguous portion, wherein the first rim portion is tailored to cover a portion on one side of the aerodynamic part and the second rim portion is tailored to cover an adjacent portion on the same side of the aerodynamic part.

16. A method for operating a heating member of any of the preceding claims, the method involving supplying at least one active layer or at least one conductive track with an electric current to generate a layer heat power density distribution.

17. The method of claim 16, wherein a plurality of active layers is sequentially supplied with an electric current to generate a total heat power density distribution that has seemingly moving power minima and / or maxima due to the sequential supply of electric current.

18. The method of claim 16 or 17, wherein the electric current has a temporal variation that follows a step-wise, a linear, a non-linear, a triangular, a sawtooth, or a sinusoidal pattern.

19. The method of any of the claims 16 to 18, wherein at least one active layer is intermittently de-energized.

20. A method for manufacturing a heating member, the method comprising: a) providing a substrate with at least one side having conductive material that is coated with a photoresistive layer;b) selectively exposing the photoresistive layer by means of a light source, wherein light emitted from the light source is selectively allowed to illuminate the photoresistive layer to selectively cure the photoresistive layer; c) developing the result of step b); and d) etching the result of step c) to obtain a conductive track.

21. The method of claim 20, wherein step a) involves providing a substrate having conductive material on two opposite sides, wherein each conductive material is coated with a photoresistive layer.

22. The method of claim 21 , wherein step b) involves subsequently or simultaneously exposing the photoresistive layer on each side.

23. The method of any of the claims 20 to 22, wherein step b) involves an LCD-panel selectively blocking or allowing illumination of the photoresistive layer.

24. The method of any of the claims 20 to 23, wherein in step c) developing involves removal of uncured material of the photoresistive layer by a developer to expose conductive material previously covered by the uncured material.

25. The method of any of the claims 20 to 24, wherein in step d) etching involves removal of conductive material by an etchant to etch away the exposed conductive material from the substrate to form conductive tracks.

26. An aerodynamic part for an aircraft, the aerodynamic part supporting or having embedded therein a heating member of any of the claims 1 to 15.

27. The aerodynamic part of claim 26, that is chosen from a group consisting of a wing, a high-lift device, a propeller and a rotor blade.

28. A propeller for an aircraft, such as an unmanned aerial vehicle, the propeller comprising a propeller hub and a plurality of rotor blades protruding therefrom, wherein at least one rotor blade and / or the propeller hub comprise a heating member of any of the claims 1 to 15.

29. The propeller according to claim 28, wherein each heating member is disposed on one rotor blade.

30. An aircraft comprising a heating member of any of the claims 1 to 15, an aerodynamic part of any of the claims 26 or 27, and / or a propeller of any of the claims 28 or 29.

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