Method of fabricating rotary equipment for a rotary wing, provided with a deicer, said rotary equipment, and a drone provided with said rotary equipment

A piece of rotary equipment for a drone, the rotary equipment having a rotary assembly including at least one blade. The rotary assembly includes at least one furrow that extends in a skin from a first end to a second end, the at least one furrow being at least arranged over the blade, the at least one furrow presenting at least one change of direction on the blade, the rotary assembly including at least one deicer having an electrically conductive track that extends in the at least one furrow, the electrically conductive track extending from a first terminal to a second terminal, the first terminal being present at the first end and the second terminal being present at the second end, the deicer including a protective layer covering the electrically conductive track.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to French patent application No. FR 1770681 filed on Jun. 27, 2017, the disclosure of which is incorporated in its entirety by reference herein.

BACKGROUND OF THE INVENTION

(1) Field of the Invention

The present invention relates to a method of fabricating rotary equipment for a rotary wing provided with a deicer, to said rotary equipment, and to a drone provided with said rotary equipment.

The invention thus lies in the narrow technical field of drones, and of deicer systems for drones.

2) Description of Related Art

A helicopter is sometimes provided with a deicer system. The deicer system may comprise heater mats arranged in the blades of the main rotor of the helicopter. Each heater mat is arranged between a leading edge cover of a blade and a body of the blade. The heater mats are powered electrically by a source of electrical energy arranged in the helicopter. Under such circumstances, electricity transfer means is arranged in a rotor mast that drives the main rotor in rotation, the electricity transfer means comprising a stationary portion that is electrically connected to the source of electrical energy and a movable portion that is electrically connected to the heater mats.

That technology is proven, but does not appear to be transposable to a drone having rotors, in particular a drone of small size.

Specifically, a drone is of small size. Under such circumstances, the rotors of the drone comprise blades that are also of small size. Consequently, arranging a heater mat in a blade of a drone rotor would appear to be difficult. In addition, the electrical connectors suitable for connecting two electric wires usually present dimensions that are too large, given the dimensions of the blades of a rotor of a drone.

It is therefore difficult to envisage arranging a deicer on a drone blade.

Furthermore, a drone rotor is rotated by a solid rotor mast, which appears to be incompatible with arranging helicopter electricity transfer means.

In another aspect, there exists a method of fabrication known as laser direct structuring (LDS). That method is used to generate an electrically conductive track on a support. The support presents a composite or thermoplastic material including an additive, with the additive being in the form of an organic metal. The additive is “activated” by passing a laser. The laser creates microscopic craters and scores in which copper can be firmly anchored by dipping the part in a catalyst bath.

That method is not associated with deicing a blade, but serves to obtain parts that are not electrically resistive in order to avoid loss of signal. Those parts therefore appear to be ill-suited for being subjected to heating by the Joule effect.

Documents CN 101 859 613, US 2015/175805, and US 2015/280312 deal with the LDS method.

Document US 2016/363367 is very far removed from the field of the invention, since it deals with a refrigerator.

BRIEF SUMMARY OF THE INVENTION

An object of the present invention is thus to propose a method making it possible to obtain rotary equipment for a drone, which equipment is provided with a deicer.

The invention provides in particular a method of fabricating a piece of rotary equipment for a drone. The rotary equipment contributes at least in part to providing the drone with propulsion and/or lift. The rotary equipment comprises a rotary assembly provided with a deicer, the rotary assembly having at least one blade. The method comprises fabricating said piece of rotary equipment by a laser direct structuring method by performing the following steps:

fabricating the rotary assembly, the rotary assembly having a skin, the skin comprising a composite material provided with an organic metal;

using a laser to make at least one furrow in an outside face of the skin, the furrow extending from a first end to a second end, the furrow being formed at least over said at least one blade, the furrow presenting at least one change of direction on said at least one blade;

making an electrically conductive track of the deicer in said at least one furrow by dipping the rotary assembly in a bath containing a metal, e.g. copper, said electrically conductive track extending from a first terminal to a second terminal, the first terminal being present at the first end and the second terminal being present at the second end; and

covering the electrically conductive track with a protective layer.

The term “change of direction” means that the electrically conductive track is not a straight line. The electrically conductive track may thus present a segment entering a blade and a segment leaving the blade in an electricity flow direction along the electrically conductive track.

Under such circumstances, the method enables a rotary assembly to be fabricated by conventional methods, e.g. by 3D printing, by molding, by injection molding.

The rotary assembly also presents a skin including an organic metal so as to be capable of being structured by a laser direct structuring method. Known materials compatible with that method can be envisaged. For example, the structure may comprise a copper-filled composite material.

During such laser direct structuring, a laser digs a groove in the rotary assembly to follow a predefined pattern. This groove is referred to for convenience as a “furrow”. Since the laser can be arranged on a robotic arm, it can draw furrows of complex shape, e.g. spiral-shapes, zigzag. Each furrow also receives an electrically conductive track, e.g. made of copper, that is made during a metal-plating step.

Optionally, each blade has at least one electrically conductive track extending sinuously over at least the leading edge of the blade.

A portion of the electrically conductive track constitutes an electrically resistive deicer member of a deicer, while other segments represent electrical connection lines.

Unlike conventional laser direct structuring methods that seek to make electrical tracks of low resistance, the invention proposes making an electrical track that presents considerable resistance in order to provide Joule-effect heating at the voltage applied to the terminal.

Specifically, the Applicant has observed that it is possible to obtain an electrically conductive track of small dimensions that conveys electricity, the electricity presenting a particular voltage at the terminals of the electrically conductive track in order to heat the blade for deicing purposes.

Under such circumstances, the method makes it possible to obtain a blade of small dimensions that is provided with a deicer.

Furthermore, the electrically conductive track can operate with relatively little electrical energy, thereby optimizing the electrical energy sources of the drone.

In addition, the electrically conductive track can serve to increase the mechanical strength of the blade.

Furthermore, one or more or each of the electrically conductive tracks is covered by a protective layer, e.g. of the pyranol resin type. This protective layer tends to slow down the erosion of an electrically conductive track.

The method of the invention may also include one or more of the following characteristics.

Thus, the rotary assembly may be made solely out of the material constituting the skin.

In another option, the fabrication of the rotary assembly may include a step of making a central core and a step of covering said central core with said skin.

For example, a blade body made of wood may be covered in the skin of the invention.

In an aspect, said electrically conductive track extends over a length from the first terminal to the second terminal, said electrically conductive track extending in a thickness direction from a bottom face in contact with a bottom of said at least one furrow to a top face, said electrically conductive track extending in a width direction between two sides respectively in contact with two flanks of said at least one furrow, and each of said thickness and said width may lie in the range 30 micrometers (μm) included to 60 μm included.

This size makes it possible to obtain a resistive electrically conductive track that provides Joule-effect heating when the electrical track conveys electricity, and in particular an electric current corresponding to a voltage of the order of 10 volts (V) to 14 V across the terminals of the electrically conductive track.

In an aspect, the rotary assembly may comprise at least two blades and a hub, said at least two blades being carried by said hub, and said at least two blades and said hub may form a single piece.

The blades and the hub form a single piece that may be made in one operation.

In an aspect, the electrically conductive track may extend over said hub and over at least one blade, said first end and said second end together with the first terminal and the second terminal being present on said hub.

For example, a single electrically conductive track may extend sinuously over all of the blades and the hub.

In addition to a method, the invention also provides a piece of rotary equipment for a drone, the rotary equipment having a rotary assembly that includes at least one blade.

The rotary assembly includes a skin with at least one furrow extending over an outside face of said skin from a first end to a second end, said at least one furrow being formed at least in said blade, said at least one furrow presenting at least one change of direction in said blade, said rotary assembly including at least one deicer, said deicer comprising an electrically conductive track extending in said at least one furrow, said electrically conductive track extending from a first terminal to a second terminal, the first terminal being present at the first end and the second terminal being present at the second end, said deicer having a protective layer covering said electrically conductive track.

The rotary equipment may further comprise one or more of the following characteristics.

Thus, the rotary assembly may include a central core arranged inside said skin.

In an aspect, said electrically conductive track extends over a length from the first terminal to the second terminal, said electrically conductive track extending in a thickness direction from a bottom face in contact with a bottom of said at least one furrow to a top face, said electrically conductive track extending in a width direction between two sides respectively in contact with two flanks of said at least one furrow, said thickness and said width each lying in the range 30 μm to 60 μm.

In an aspect, said rotary assembly may comprise at least two blades and a hub, said at least two blades being carried by said hub, and said at least two blades and said hub may form a single piece.

Unlike a helicopter, all of the blades and the hub may form a single piece, and thus a single block.

In an aspect, an electrically conductive track may extend over said hub and over at least one blade, said first end and said second end together with said first terminal and said second terminal being present on said hub.

In an aspect, said protective layer may comprise a polyurethane varnish.

Such a protective layer can easily be applied with a varnish spray can.

In addition to a piece of rotary equipment for a drone, the invention also provides a drone having a body, the body carrying at least one rotor. Under such circumstances, said at least one rotor includes a piece of rotary equipment of the invention.

For example, all of the rotors comprise a piece of rotary equipment of the invention.

In aspect, said drone includes an electric motor having a frame and a rotor mast, said rotor mast being mechanically connected to said rotary assembly, and said drone may include electricity transfer means, said electricity transfer means having a stationary portion electrically connected to a movable portion, said stationary portion being electrically connected to an electrical energy source, said movable portion being electrically connected to said first terminal and to said second terminal, said movable portion being secured to said rotor mast and being arranged around the rotor mast.

The drone thus possesses one or more energy sources. Furthermore, each energy source may comprise one or more optionally rechargeable batteries.

Under such circumstances, a rotor provided with a piece of rotary equipment of the invention co-operates with electricity transfer means arranged around a rotor mast. Each electricity transfer means serves to allow electricity to flow from an electrical energy source placed in a stationary reference frame to each blade of a rotor present in a rotary reference frame.

Where applicable, a single energy source may be connected to all of the electricity transfer means of the drone.

The term “electricity transfer means” is used herein to designate equipment that enables electricity to be transferred between a stationary reference frame and a rotary reference frame while it is rotating, possibly while also transforming the electricity.

By way of example, it is possible to use “slip ring” type transfer means. Such transfer means comprise at least one slip ring and at least one brush in contact with the slip ring. In one variant, the slip ring is carried by the movable portion and each brush is carried by the stationary portion. In another variant, the slip ring is carried by the stationary portion and each brush is carried by the movable portion.

In another example, the electricity transfer means may comprise a rotary transformer. By way of example, it is possible to use a transformer of the type described in Document U.S. Pat. No. 5,572,178.

Furthermore, the drone may include a switch or the equivalent so that each electrically conductive track of the drone is either electrically powered or not. The switch may be remotely controlled by a deicer control via a wireless link. Optionally, the deicer control may cause either all of the blades to be deiced or may prevent deicing on all of the blades. The deicer control is then of the on/off type.

In an aspect, the movable portion may be secured to a resilient member, said resilient member being secured to the rotor mast.

The resilient member may comprise a band adhesively bonded on the rotor mast. For example, the band may comprise an elastomer.

The resilient member may tend to allow the electricity transfer means to operate in the presence of a small axial offset of the rotor mast.

In an aspect, said stationary portion may be secured to said frame.

For example, the electric motor may comprise a frame and a rotor mast projecting from the frame. The rotor mast then passes through the electricity transfer means in order to be secured to the rotary assembly.

The stationary portion of the electricity transfer means is then locked on the frame of the motor. The stationary portion thus does not move in rotation in the reference frame of the drone, unlike the movable portion which rotates together with the rotor mast relative to the frame.

In an aspect, at least two wires may extend from said movable portion respectively to said first terminal and to said second terminal, one of said at least two wires being placed against said first terminal and one of said at least two wires being located against said second terminal, a heat-shrink sleeve surrounding said at least two wires and said first terminal and said second terminal.

Each wire may be soldered and/or adhesively bonded to a terminal under the heat-shrink sleeve. The sleeve provides the electrical connection with mechanical and environmental protection.

In an aspect, the energy source may deliver electricity at a voltage lying in the range 12 V to 14 V.

Several voltage levels are possible. In preferred manner, the energy source delivers electricity at a voltage level lying in the range 12 V to 14 V in order to optimize deicing.

DETAILED DESCRIPTION OF THE INVENTION

Elements present in more than one of the figures are given the same reference in each of them.

FIG. 1shows a piece of rotary equipment for a drone of the invention.

This piece of rotary equipment comprises an aerodynamic rotary assembly10that is provided with at least one blade11. By way of example, the rotary assembly10has a plurality of blades11that are optionally rigidly secured to a hub12. The hub12may then be fastened to a rotor mast of a drone.

Where appropriate, the hub12and the blades11may form a single piece, unlike rotors provided with blades that are pinned to a hub, for example.

Furthermore, the rotary assembly10presents a skin13. Depending on the variant, the rotary assembly10may comprise one or more central cores covered by the skin13, or it may comprise a single optionally-solid structure13that defines the skin13.

Independently of the presence or the absence of a central core within the skin13, the rotary assembly10includes at least one deicer30.

Thus, the rotary assembly10has at least one furrow20formed in the skin13, and in particular in an outside face14of the skin13facing an outside medium EXT situated outside the rotary assembly10. The furrow20is substantially defined by a bottom and by flanks forming a U-shape so that the furrow is open towards the outside medium EXT.

The furrow20extends from a first end21to a second end22. The furrow20follows a sinuous path over the outside face14of the skin13going from its first end to its second end, and running along at least one blade11. Furthermore, the furrow20presents at least one change of direction23on the blade11in order to enter and leave an aerodynamic segment of the blade. For example, at least one furrow20runs along and/or in the immediate proximity of the leading edge16of the blade11.

By way of example, a single furrow runs along a plurality of blades11, or indeed over all of the blades11and also over the hub.

Furthermore, each piece of rotary equipment includes at least one deicer30.

Under such circumstances, each deicer30of a piece of rotary equipment10has an electrically conductive track31arranged in a furrow20. The deicer is thus integrated in the rotary assembly, with the deicer and the rotary assembly forming an inseparable whole. The electrically conductive track31thus extends lengthwise from a first electrical terminal32to a second electrical terminal33. The first terminal32is arranged at the first end21of a furrow20, with the second terminal33being arranged at the second end22of the furrow.

Where appropriate, a single electrically conductive track31extends over the hub12and over at least one blade11, or indeed at least two blades11. The first end21and the second end22of a furrow, together with said first terminal32and said second terminal33of the electrically conductive track arranged in the furrow are present on the hub12.

An electrically conductive track31may present thickness and width that are small relative to the voltage present between the first terminal32and the second terminal33of the electrically conductive track31. For example, the thickness and the width may lie in the range 30 μm to 60 μm, with said voltage lying in the range 12 V to 14 V.

Furthermore, the deicer30may include at least one protective layer35that covers at least one electrically conductive track31.

FIGS. 2 to 4show a method of the invention for fabricating such a rotary assembly10provided with an integrated deicer30.

With reference toFIG. 2, the method includes a step of fabricating the rotary assembly10.

FIG. 2shows a rotary assembly10comprising for convenience only one blade11in order to illustrate the invention. Nevertheless, the rotary assembly10may further comprise a hub, and possibly a plurality of blades together forming a single piece.

During this fabrication step, a rotary assembly10that has a skin13is fabricated. In particular, the skin13is made out of at least one material that is provided with an organic metal, e.g. a copper-filled composite material.

Optionally, the rotary assembly10may be made by performing a molding method, an injection molding method, a 3D printing method, . . . .

Optionally, the fabrication step may include a substep of fabricating one or more central cores15, followed by a substep of covering each central core15with said skin13.

At the end of the fabrication step, the rotary assembly10is thus obtained. This rotary assembly10comprises at least a skin13having an outside face14.

Under such circumstances, and with reference toFIG. 3, the method includes a step of using a laser to make at least one furrow20in the outside face14by the laser direct structuring method. At least one furrow extending from a first end21to a second end22is dug by a laser in the skin13, the furrow20presenting at least one change of direction on a blade11.

Subsequently, and with reference toFIG. 4, the method includes a step of making an electrically conductive track31of a deicer30.

The electrically conductive track31is formed in each furrow20by dipping the rotary assembly10in a bath containing a metal, e.g. using a method of metal-plating by electrolysis. Each electrically conductive track31thus extends from a first terminal32to a second terminal33.

Optionally, at least one electrically conductive track31extends over the hub12and over at least one blade11, the first end21and the second end22together with the first terminal32and the second terminal33being present on said hub12.

Thereafter, the method includes a step of covering one or each electrically conductive track31with a protective layer35. For example, a polyurethane varnish is sprayed onto each electrically conductive track31.

The laser may be designed so as to obtain electrically conductive tracks31that present particular dimensions.

By construction, each electrically conductive track31extends over a length between the first terminal32and the second terminal33of the electrically conductive track31. Furthermore, the electrically conductive track extends in its thickness direction36from a bottom face44in contact with a bottom41of said at least one furrow20to a top face38covered in the protective layer35. In addition, the electrically conductive track31extends in its width direction37between two sides39and40that are respectively in contact with two flanks42and43of the furrow receiving the track. The laser may then be designed so that the thickness36and the width37each lie in the range 30 μm to 60 μm.

With reference toFIG. 5, a piece of rotary equipment of the invention may be arranged on a drone1. The drone1may have a body2carrying at least one rotor5, e.g. via an arm3. The rotor thus includes a piece of rotary equipment of the invention. Optionally, each rotor5includes a respective piece of rotary equipment of the invention.

FIG. 6shows such a rotor5having a piece of rotary equipment of the invention. This configuration is optionally reproduced by all of the rotors5.

In order to rotate the rotary assembly10of a piece of rotary equipment of a rotor5, the drone1has an electric motor50. The electric motor50is connected to an electrical energy storage member75, possibly via a switch76or the equivalent. The electric motor50, or the switch76, if any, may be remotely controlled by piloting control means91forming part of a remote control90.

The electric motor50has a frame51carried by an arm3. The electric motor50thus possesses an outlet shaft that projects from the frame51. The outlet shaft constitutes a rotor mast52that is constrained to rotate with the rotary assembly10. The rotor mast52is optionally solid. By way of example, the rotary assembly then comprises a hub12fastened to a free end zone of the rotor mast by conventional means, such as for example screw fastening, adhesive, riveting, welding, stapling, . . . means.

Furthermore, the drone1has a source of electrical energy70for causing electricity to flow in each electrically conductive track31of the rotary assembly10. This electrical energy source70may comprise one or more optionally rechargeable batteries . . . . The electrical energy source70may for example be located in the body2. The electrical energy source70may deliver electricity at a voltage lying in the range 12 V to 14 V, for example. Furthermore, the electrical energy source70and the above-mentioned electrical energy storage member75may constitute single electrical energy storage means or two different electrical energy storage means.

The drone is then provided for each rotor with respective electricity transfer means that are electrically interposed between the electrical energy source and the rotary assembly of the rotor in order to transfer electricity from the stationary reference frame of the body2to a rotary reference frame of the rotor5and the rotary assembly10, while they are rotating.

Under such circumstances, the electricity transfer means60comprise a stationary portion61that is electrically connected to a movable portion63of the electricity transfer means60.

The stationary portion61is optionally secured to the frame51of the electric motor, via a protective casing67of the electricity transfer means, if any.

The movable portion63is secured to the rotor mast52, having the rotor mast52passing therethrough. By way of example, the movable portion63comprises a tube surrounding the rotor mast52.

Optionally, the movable portion63is fastened to a resilient member64by conventional means such as screw fastening, adhesive, riveting, welding, staple means. The resilient member64is also secured to the rotor mast52. For example, the resilient member comprises a band with a bead of adhesive fastening the band to the rotor mast52.

Furthermore, the stationary portion61is electrically in communication with the movable portion63. For example, the electricity transfer means has brushes62in contact with slip rings. In one variant, the stationary portion carries the brushes, with the movable portion carrying the slip rings in contact with the brushes. In another variant, the movable portion carries the brushes and the stationary portion carries the slip rings in contact with the brushes. The stationary portion may surround the movable portion. The movable portion may surround the rotor mast locally.

Nevertheless, any type of electricity transfer means could be envisaged.

Furthermore, the stationary portion61is electrically connected to the electrical energy source70by an electrical connection. This electrical connection may comprise one or more electric wires together with a switch71for the equivalent.

Where appropriate, the switch71of the electricity transfer means may be remotely controlled using a deicer control92carried by a remote control90. In the presence of a plurality of rotary assemblies that are electrically powered via respective electricity transfer means connected to switches, the deicer control may serve to control all of the switches. Alternatively, an electrical energy source may be connected to a single switch71, the switch71being connected to all of the electricity transfer means of the drone.

Furthermore, the movable portion63is electrically connected to the first terminal32and to the second terminal33of each electrically conductive track of a rotary assembly.

Under such circumstances, at least two wires65,66extend from the movable portion63respectively to the first terminal32and to the second terminal33of an electrically conductive track.

A first wire65is thus placed against the first terminal32and a second wire66is located against the second terminal33. A heat-shrink sleeve80may be arranged around the connection by surrounding the first wire65and the second wire66together with the first terminal32and the second terminal33.

Such a fastener system may optionally serve to enable the rotary assembly to be disassembled easily.