Abstract:
A method for installing an electric system into an aircraft fuselage. The object to provide a method for simply and quickly installing an electric system into an aircraft fuselage, wherein the electric system is as little heavy and space consuming as possible, and wherein a wide range of customized alternatives of the electric system is possible, is achieved by the steps of providing a fuselage element extending along an aircraft longitudinal axis and including an outer skin and an interior surface, providing a foil sheet of an electrically insulating substrate material, attaching said foil sheet on the inner side of said fuselage element, applying particles of electrically conductive material onto the inner surface of said attached foil sheet opposite the outer skin in a predetermined pattern, such that the accumulated particles of electrically conductive material form electric conductor elements along said inner surface of said foil sheet.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to and the benefit of European Patent Application No. EP 12182914.7 and to U.S. Provisional Application No. 61/696,601, both of which were filed on Sep. 4, 2012, the entire disclosures of which are both incorporated by reference herein. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention relates to a method for installing an electric system into an aircraft fuselage. A further aspect of the present invention relates to an aircraft fuselage element being provided with an electric system. 
       BACKGROUND 
       [0003]    An electric system within the meaning of the present invention may basically be any kind of electric system including electric conductor elements for conducting electric current through said fuselage, in particular electric conductor elements and electric circuit elements usually arranged in an aircraft between the fuselage structure, i.e. the outer skin and the supporting elements, and the interior fitting, i.e. the cabin wall parts. 
         [0004]    Such electric systems installed in aircraft fuselages known in the art usually comprise a plurality of large cable looms which extend between the fuselage structure and the interior fitting in parallel to said fuselage longitudinal axis and the properties and dimensions of which are adapted to the requirements of the specifically customized interior fitting and intended use of the respective aircraft. Thus, one disadvantage of the electric systems of fuselages known in the art is that the high extent of cable looms which is necessary for power supply, control signals and data transfer in the latest aircrafts involves considerable weight and space requirement, which both negatively affect efficiency of an aircraft design. 
         [0005]    Another disadvantage of the prior art fuselage electric systems is that a quick and simple exchange of parts of said electric system, which may be desirable e.g. for service or customizing purposes, is considerably difficult, as the entire cable looms or other electric system parts have to be removed or dismounted to merely change or add e.g. single cables. Such disassembly of the electric system for service or customizing purposes is time-consuming and cost-intensive. Moreover, the range of customization is limited by the predetermined dimensions and properties of available cables, cable looms, and further electric system parts. 
         [0006]    A further disadvantage of the prior art fuselage electric system is that the installation of said systems into a fuselage during aircraft construction is considerably complex and time-consuming, as a large amount of cables and other electric parts, such as plug connectors or electric circuit elements, has to be provided, assembled, and mounted into said fuselage. 
       SUMMARY 
       [0007]    Therefore, it is the object of the present invention to provide a method for simply and quickly installing an electric system into an aircraft fuselage, wherein the electric system is as little heavy and space consuming as possible, and wherein a wide range of customized alternatives of the electric system is possible. 
         [0008]    This object is achieved by a method for installing an electric system into an aircraft fuselage, said method comprising the steps of:
   a. providing a fuselage element extending along an aircraft longitudinal axis and comprising an outer skin and an interior surface,   b. providing a foil sheet of an electrically insulating substrate material,   c. attaching said foil sheet on the inner side of said fuselage element,   d. applying particles of electrically conductive material onto the inner surface of said attached foil sheet opposite the outer skin in a predetermined pattern, such that the accumulated particles of electrically conductive material form electric conductor elements along said inner surface of said foil sheet.   
 
         [0013]    In such a manner by using a flexible foil sheet attached to the inner side of the fuselage element as a substrate element and by subsequently coating electric conductor elements onto said foil sheet a simple and quick method for installing an electric system into a fuselage is provided. Said foil sheet coated with electric conductor elements can easily be removed and replaced by a new plain uncoated foil sheet which, subsequently, can be coated with e.g. an updated or differently customized assembly of electric conductor elements. The process of installing the electric system inside a fuselage during aircraft construction may be highly accelerated and simplified, as the predetermined pattern in which particles of electrically conductive material are applied onto the inner surface of said foil sheet may be executed by a computer controlled particle applying device. No manually connecting of cables or cable looms is necessary any more. Also connection errors can easily be reduced. 
         [0014]    Moreover, a fuselage electric system comprising merely a coated foil sheet consumes only a minimum of space and weights much less than the cable looms which are to be replaced by said foil sheet. In summary, by the method according to the present invention efficiency of the process of aircraft construction and servicing as well as efficiency of said aircraft in use may be considerably increased. 
         [0015]    A fuselage element within the meaning of the present invention may be either an entire aircraft fuselage or only a fuselage section. A fuselage section may be a section in the direction of the fuselage longitudinal axis and/or an angular section, i.e. a complete circumferential cylinder shell or only an angular section of said cylinder shell. 
         [0016]    The substrate material may be of any flexible electrically insulating material. The foil sheet may be bent such that it is adjusted to said inner side of the fuselage element, before it is attached thereto. In particular, the foil sheet may be attached onto the inner side of the outer skin, the supporting elements, e.g. frames and stringers, or onto separate clamping elements connected to the outer skin or the supporting elements. The foil sheet is preferably attached to said fuselage inner side in such a way that it can not move or shake inside said fuselage. The thickness of the foil sheet may be adapted to the required stiffness of the foil. The application of particles of electrically conductive material is carried out by a respective computer controlled particle applying device, such as a digital printing device. Such device may be adapted to be positioned and operate inside an enclosed fuselage element. 
         [0017]    Particles of electrically conductive material within the meaning of the present invention may be of any kind of material suitable for conducting electric current, in particular a metallic material such as copper, aluminium, wolfram, brass, iron, chrome, or associated alloys, a semiconductor material such as silicon, or a non-metallic material such as graphite. 
         [0018]    The predetermined patterns, i.e. the topography, the lateral size and the width, according to which the particles of electrically conductive material are applied onto the aircraft structure component are controlled by the temporal variation of the position at which said particles of electrically conductive material are applied onto said inner surface of the foil sheet, as well as on the mass flow rate of said particles of electrically conductive material which are applied onto said inner surface of the foil sheet. In this manner, such patterns control the extent, in particular the thickness, width, and length, as well as the direction and shape of the extension of the electric conductor elements, i.e. the predetermined patterns define the paths and the shape as well as the properties of the electric conductor elements. 
         [0019]    According to a preferred embodiment subsequent to applying particles of electrically conductive material onto said inner surface of said foil sheet, the following step is performed:
   e. applying particles of electrically insulating material onto the inner surface of said foil sheet and onto the electric conductor elements in a predetermined pattern, such that the accumulated particles of electrically insulating material form an insulating layer for the electric conductor elements.   
 
         [0021]    Particles of electrically insulating material within the meaning of the present invention may for example be a plastic or ceramic material. However, other materials such as insulating lacquers may be employed as well. The particles for application may be of the same electrically insulating material as the substrate material of the foil sheet. 
         [0022]    The particles of electrically insulating material may be applied onto the inner surface of the foil sheet and onto the particles of electrically conductive material forming electric conductor elements, so that the insulating layer insulates the electric conductor elements to the environment. However, the insulating layer may be formed discontinuously, so that at certain locations the electric conductor element is not insulated and may be connected to another electric conductor element by e.g. a plug or a switch. 
         [0023]    In particular, it is preferred that step d. and step e. are carried out repeatedly in such an order and by means of such predetermined patterns that an electric circuit element having a layered structure is formed on the inner surface of said foil sheet. An electric circuit element within the meaning of the present invention may be any kind of electric circuit element, for example a resistor, a diode, a transistor, a capacitor, an inductor, an operational amplifier, or other circuit elements. In particular, switches, sensors and actuators may be formed in such a manner. 
         [0024]    Layers of particles of electrically insulating material and layers of particles of electrically conductive material may be applied to the inner surface of the foil sheet alternately, wherein each layer is formed in such a way that a certain structure of electric conductor elements is embedded in a matrix of electric insulating material, thereby together forming an electric circuit element or elements. Also, carbon nano tubes being part of electric circuit elements may be employed by being admixed to the particles of electrically conductive material. Thus, this embodiment facilitates the formation of actuators like switches or lighting elements on the inner surface of the foil sheet. 
         [0025]    In another preferred embodiment the particles of electrically conductive material and/or the particles of electrically insulating material are applied onto the inner surface of the foil sheet and onto the electric conductor elements by means of an ink jet printing device. Such ink jet printing device may be any kind of ink jet printing device, in particular a drop on demand ink jet printing device having a bubble jet print head, a piezo print head, or a pressure valve print head. Further, the operation of the ink jet printing device, in particular the operation of the print head, is preferably controlled by a digital controlling device which is adapted to be programmed for controlling the print head to apply particles of electrically conductive material and particles of electrically insulating material onto the inner surface of the foil sheet in a predetermined pattern. 
         [0026]    The ink jet printing device may also comprise a distance sensor adapted to measure the distance between the print head and the respective position on the surface to be coated, so that for different distances a different amount of particles of electrically conductive or electrically insulating material may be applied to said surface in order to form a preferably planar outer surface of the insulating layer and/or electric conductor element. Multiple print heads applying particles of electric conductive material and particles of electric insulating material in parallel are also conceivable. Further, a laser device may be provided directly on or separate from the ink jet printing device in order to apply laser radiation onto the particles of electrically conductive and/or electrically insulating material, thereby laser sintering the electric conductor element and the insulating layer, respectively. The ink jet printing device may be constructed, such that it may also operate in the inside of an enclosed fuselage 
         [0027]    In yet another preferred embodiment subsequent to applying particles of electrically conductive material onto the inner surface of said foil sheet, the following step is performed:
   d.1 subjecting the particles of electrically conductive material to laser radiation by means of a laser device, such that the particles melt due to the heat transferred to the particles through the laser radiation, thereby forming integrally formed electric conductor elements.   
 
         [0029]    That means the particles are laser sintered. The laser device may be any kind of laser device adapted for laser sintering said particles of electrically conductive material. Also the insulating layer of particles of electrically insulating material may be laser sintered by the laser device. After the electric conductor elements and the insulating layer have been laser sintered, i.e. after the application of laser radiation onto their particles of electrically conductive and electrically insulating material, they are solidified and thus their shape has become fixed in a predetermined pattern. In addition, melting of the particles and subsequent solidifying results in an integrally formed conductor element without grain boundaries at which oxidation may occur, leading to an increased resistance of the conductor element. The laser device is arranged “behind” any devices provided for application of particles of electrically conductive and/or electrically insulating material when seen in the moving direction of the devices so that irradiation subsequent to application of the particles is easily possible. 
         [0030]    In a further preferred embodiment prior to the step of attaching said foil sheet on the inner side of said fuselage element, at least one power supply cable is attached to the inner side of said fuselage element at such a position, that the power supply cable is sandwiched between said foil sheet and the inner side of the fuselage element. Such power supply cable may operate as an electric backbone for the electric system applied on the foil sheet and may supply electric power to the electric conductor elements on said foil sheet. As said backbone power supply cables usually do not need to be customized and in order to reduce dimensions of the foil sheet, said power supply cable is not included within the foil sheet. 
         [0031]    In yet a further embodiment prior to the step of attaching said foil sheet on the inner side of said fuselage element, at least one data transmission cable is attached to the inner side of said fuselage element at such a position, that the data transmission cable is sandwiched between said foil sheet and the inner side of the fuselage element. Such data transmission cable may operate as a data backbone for the electric system applied on the foil sheet and may supply data to the electric conductor elements on said foil sheet. 
         [0032]    In particular, it is preferred that the power supply cable and/or the data transmission cable are/is inductively coupled to an electric conductor element on said foil sheet. Coils may be provided on said foil sheet or on the respective power supply or data transmission cable. In such a manner the foil sheet may be provided with electric power and/or data, without the foil sheet being directly connected to said power supply cable/data transmission cable. An uncomplicated removal of the foil sheet without detaching from the power supply or data transmission cable is therefore possible. 
         [0033]    In another aspect of the present invention an aircraft fuselage element being provided with an electric system, the fuselage element having an outer skin and a plurality of supporting elements extending along the interior surface of the outer skin, said fuselage element further comprising a foil sheet of an electrically insulating substrate material, attached on the inner side of said fuselage element, wherein particles of electrically conductive material are deposited onto the inner surface of said foil sheet opposite the outer skin in a predetermined pattern, such that the accumulated particles of electrically conductive material form electric conductor elements along the inner surface of said foil sheet. 
         [0034]    In such a manner by employing a foil sheet attached to the inner side of the fuselage element as a substrate element and coated electric conductor elements onto said foil sheet a simple and flexible electric system is provided which can be quickly installed into a fuselage. Said foil sheet coated with electric conductor elements can easily be removed and replaced by a new plain uncoated foil sheet which, subsequently, can be coated with e.g. an updated or again customized version of an assembly of electric conductor elements. Thus, the advantages mentioned in relation to the method discussed before are achieved as well by the fuselages or fuselage sections according to the present invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0035]    In the following preferred embodiments of the method and the aircraft fuselage element according to the present invention are described by means of a drawing. The drawing shows in 
           [0036]      FIG. 1  a flow diagram illustrating an embodiment of the method for installing an electric system into an aircraft fuselage, 
           [0037]      FIG. 2  a perspective view of a fuselage element and a foil sheet according to the present invention, 
           [0038]      FIG. 3  a perspective view of the fuselage element and foil sheet shown in  FIG. 2 , the foil sheet being attached on the inner side of said fuselage element and coated by means of an ink jet printing device, 
           [0039]      FIG. 4  a cross sectional view of the foil sheet attached to the fuselage element shown in  FIG. 3 , said foil sheet being coated by means of an ink jet printing device and laser sintered by means of a laser device, and 
           [0040]      FIG. 5  a cross sectional view of the foil sheet attached to the fuselage element shown in  FIG. 4 , provided with complete electric conductor elements and an insulating layer. 
       
    
    
     DETAILED DESCRIPTION 
       [0041]    In  FIG. 1  a flow diagram is shown illustrating the method steps of an embodiment of the method for installing an electric system  1  into an aircraft fuselage according to the present invention. 
         [0042]    As a first step a fuselage element  3  extending along an aircraft longitudinal axis  5  and comprising an outer skin  7  and a plurality of support elements  9  extending along the interior surface of the outer skin  7  is provided (step a.), as illustrated in  FIG. 2 . The fuselage element  3  may be an entire fuselage or only a fuselage section, said fuselage section forming either a section with respect to either the aircraft longitudinal axis  5  or an angular section of the essentially cylindrically shaped fuselage. The support elements  9  may be e.g. frames and stringers. 
         [0043]    The next step involves providing a foil sheet  11  of an electrically insulating substrate material (step b.), see e.g.  FIG. 2 . In the present embodiment the substrate material is a light-weight and flexible material which has considerable high electric resistance and the surface of which has at least average adhesion properties, so that it may be coated via common coating technologies such as ink jet printing. 
         [0044]    Further, a power supply cable  13  and a data transmission cable  15  are provided and attached to the inner side  17  of the fuselage element  3  (step b.1), as shown in  FIG. 2 . The power supply cable  13  and the data transmission cable  15  serve as power backbone and data backbone, respectively, for the fuselage element  3  and are formed separate from the foil sheet  11 , i.e. are not directly connected to the foil sheet  11 . The power supply cable  13  and the data transmission cable  15  extend in this preferred embodiment essentially parallel to the aircraft longitudinal axis  5 . 
         [0045]    In the following step the foil sheet  11  is attached on the inner side  17  of said fuselage element  3 , wherein said power supply cable  13  and said data transmission cable  15  are sandwiched between said foil sheet  11  and the inner side  17  of the fuselage element  3  (step c.), as it is illustrated in  FIG. 3 . The foil sheet  11  is attached to the inner side  17  of the fuselage element  3 , in particular to the inner side of the support elements  9 , in such a way that it may not move or shake during operation of the respective aircraft. Further, the foil sheet  11  is adapted to the shape of the inner side  17  of the fuselage element  3 , i.e. bent into a curved form. 
         [0046]    According to the next step particles of electrically conductive material  19  are applied onto the inner surface  21  of said attached foil sheet  11  opposite the outer skin  7  in a predetermined pattern, such that the accumulated particles of electrically conductive material  19  form electric conductor elements  23  along the inner surface  21  of said foil sheet  11  (step d.), as it is illustrated in  FIGS. 3 and 4 . 
         [0047]    Basically, any electrically conductive material may be applied, such as aluminium, wolfram, brass, iron, chrome, or associated alloys, a semiconductor material such as silicon, or a non-metallic material such as graphite, but in the present embodiment particles of copper material are applied. In the preferred embodiment described herein said particles of electrically conductive material  19  are applied by an ink jet printing device  25  which is controlled by a computer controlled device. The predetermined pattern in which the particles of electrically conductive material  19  are applied corresponds to the desired shape of the electric conductor elements  23  extending on the inner surface  21  of the foil sheet  11 . Further, means are provided on said foil sheet  11  and on said power supply cable  13  and data transmission cable  15  to inductively couple the power supply cable  13  and the data transmission cable  15  to an electric conductor  23  element on said foil sheet  11 . Said means may be coils. In particular said coils may be arranged on the foil sheet  11  by depositing a correspondingly shaped conductor element via the ink jet printing device  25 . In such a way power and data may be transported through the respective power supply cable  13  and data transmission cable  15  to the electric conductor elements  23  on the foil sheet  11  without being directly connected to the foil sheet  11 . 
         [0048]    Subsequently, said particles of electrically conductive material  19  after being applied onto the inner surface  21  of the foil sheet  11  are subjected to laser radiation  27  by means of a laser device  29 , such that the particles  19  melt due to the heat transferred to the particles  19  through the laser radiation  27 , so that after solidification forming integrally formed electric conductor elements  23  are achieved (step d.1; see  FIG. 4 ). In such a manner the particles of electrically conductive material  19  are laser sintered and grain boundaries at which oxidation may occur, are removed. The laser device  29  may be connected to the ink jet printing device  25  and may be moved together with said ink jet printing device  25  along the inner surface  21  of said foil sheet  11  in a moving direction D, wherein the laser device  29  is arranged directly behind, i.e. downstream to, the ink jet printing device  25 . 
         [0049]    As a final step particles of electrically insulating material  31  are applied onto the inner surface  21  of said foil sheet  11  and onto the electric conductor elements  23  in a predetermined pattern, such that the accumulated particles of electrically insulating material  31  form an insulating layer  33  for the electric conductor elements  23  (step e.), as illustrated in  FIG. 5 . The insulating material may be a plastic, ceramic, or lacquer material. The predetermined pattern is of such a form that the electric conductor elements  23  are insulated to the environment, but no insulating material is wasted. The particles of electrically insulating material  31  may be applied onto the inner surface  21  of said foil  11  sheet and onto the electric conductor elements  23  by means of an ink jet printing device  25 , and may be subjected to laser radiation  27  by a laser device  29  in order to be laser sintered, as it was the case with respect to the particles of electrically conductive material  19 . The same or another ink jet printing device  25  and laser device  29  may be employed for applying both the particles of electrically conductive and electrically insulating material  19 ,  31 . 
         [0050]    As indicated by dashed arrow C, steps d. and e. may be carried out repeatedly in such an order and by means of such predetermined patterns that an electric circuit element  35  having a layered structure is formed on the inner surface  21  of said foil sheet  11 , i.e. electric conductor elements  23  are formed in a certain shape having multiple layers with insulating layers  33  being interposed between the layers of electric conductor elements  23  where necessary, so that as a result an electric circuit element  35  is formed. Such an electric circuit element  35  may be a resistor, a diode, a transistor, a capacitor, an inductor, an operational amplifier, or other circuit elements. 
         [0051]    Moreover, it should be noted that it is within the scope of the present invention that a layer of particles of electrically insulating material  31  may directly be deposited onto the foil sheet  11  before the electrically conductive material  19  is deposited, i.e. step e. may be carried out before step d. In addition, it is also within the scope of the invention if the steps of attaching power supply and/or data transmission cables  13 ,  15  (step b.1) or of curing the deposited material  19 ,  31  by means of laser irradiation (step d.1) are omitted as indicated by arrows A and B. 
         [0052]    As a result, with the method according to the present invention an aircraft fuselage element  3  is provided with an electric system  1  in a cost effective manner. The fuselage element  3  has an outer skin  7  and a plurality of support elements  9  extending along the interior surface of the outer skin  7 . Said fuselage element  3  further comprises a foil sheet  11  of an electrically insulating substrate material which is attached on the inner side  17  of said fuselage element  3 . Onto the inner surface  21  of said foil sheet  11  opposite the outer skin  7  particles of electrically conductive material  19  are deposited in a predetermined pattern, wherein the accumulated particles of electrically conductive material  19  form electric conductor elements  23  along the inner surface  21  of said foil sheet  11 . Electric circuit elements  35  may be formed by said electric conductor elements  23 . Further, particles of electrically insulating material  31  are deposited onto the inner surface  21  of said foil sheet  11  and onto the electric conductor elements  23  in a predetermined pattern, wherein the particles of electrically insulating material  31  form an insulating layer  33  for the electric conductor elements  23 . A power supply cable  13  and a data transmission cable  15  are attached on the inner side  17  of said fuselage element  3  at a position, where they are sandwiched between the foil sheet  11  and the inner side  17  of the fuselage element  3 . Said power supply cable  13  and said data transmission cable  15  are inductively coupled to electric conductor elements  23  on the foil sheet  11 . 
         [0053]    By means of the before described method an electric system  1  can easily and quickly be installed and exchanged in an aircraft fuselage. Moreover, an aircraft fuselage element  3  provided with an electric system  1  installed and formed in such a way is highly efficient in view of weight and interior space.