Abstract:
An insulation arrangement for thermally and acoustically insulating an aircraft fuselage, which comprises at least one insulation packet arranged on an exterior skin of the aircraft. The insulation packet includes dimensionally rigid foam, and comprises a shape corresponding at least with a structural component on the exterior skin, as the result of which the insulation packet is retained on the structural component even without any additional attachment elements. As a result, ventilation openings need not be provided, thereby reducing condensation water accumulating in aircraft insulation.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This is a continuation of International Patent Application PCT/EP2011/068272, filed Oct. 19, 2011, which claims priority to German Patent Application No. 10 2010 048 998.0, filed Oct. 20, 2010, and to U.S. Provisional Patent Application No. 61/405,020, filed Oct. 20, 2010, which are incorporated herein by reference in their entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    The technical field relates to an insulation arrangement for thermally and acoustically insulating an aircraft fuselage, an aircraft with an aircraft fuselage, and an insulation arrangement installed therein, as well as to an insulation packet. 
       BACKGROUND 
       [0003]    Conventional insulation packets for thermally and acoustically insulating an aircraft fuselage consist for the most part of voluminous nonwoven materials, which are used in matte form, comprise attachment openings through which retainers are passed, and can be easily compressed during attachment to the fuselage structure by means of attachment clips to be secured to the retainers. To prevent moisture from penetrating into the insulation material, use is made of sheathing films that incorporate ventilation holes to enable pressure compensation and prevent damage to the film when installing the insulation packet. At the same time, the ventilation holes prevent the insulation packets from expanding in flight given a drop or rise in cabin pressure. 
         [0004]    During a prolonged flight, condensation water accumulates inside of such insulation packets, which primarily has two essential causes. On the one hand, the insulation packets can directly abut the inside of the structure of the aircraft fuselage, which is coated with a thin film of condensation water after practically every flight. On the other hand, moist air makes its way into the insulation packets as the result of convective effects and diffusion by way of the ventilation holes and also diffusion through the closed sheathing film, where they lead to water condensation when the incoming air drops below the dew point during flight owing to the low temperatures of the aircraft fuselage. To remove the condensation water, drainage holes are often incorporated on the bottom of the insulation packets, but are only effective under certain conditions, since part of the condensation water gets retained in the form of drops on the pores or fibers of the insulation material. Furthermore, additional moist air gets into the insulation packets through the drainage holes, which can accelerate water condensation in the insulation even more. In the end, this leads to extra weight in the aircraft and accelerated ageing of the insulation. 
         [0005]    EP 1 124 720 B1 and US 20040175516 A1 show an insulation arrangement for insulating the interior of an aircraft with insulation packets, which are completely enveloped by film that allows the diffusion of gases. 
         [0006]    In addition, other objects, desirable features and characteristics will become apparent from the subsequent summary and detailed description, and the appended claims, taken in conjunction with the accompanying drawings and this background. 
       SUMMARY 
       [0007]    Consequently, the present disclosure provides an insulation arrangement for an aircraft in which an accumulation of condensation water can be diminished or avoided entirely, while maintaining at least the same quality of insulation and at most the same weight in relation to known insulation arrangements for aircraft. 
         [0008]    One aspect of the present disclosure shows the insulation arrangement for thermally and acoustically insulating an aircraft fuselage, comprising at least one insulation packet that is applicable on an exterior skin of the aircraft fuselage. What makes the insulation arrangement according to the present disclosure special is that the insulation packet includes dimensionally stiff foam and comprises a shape corresponding at least with a structural component on the exterior skin, as the result of which the insulation packet is retained on the structural component even without any additional attachment elements. 
         [0009]    As a consequence, the insulation arrangement comprises one or more insulation packets, which do not consist of a voluminous, soft and compressible material that enables compression during clip assembly. Rather, the term “dimensionally stiff” means that the used foam is dimensionally stable enough to make it as incompressible as possible, requiring that the shape be tailored to the structures to be insulated. According to the present disclosure, the insulation packet is shaped to correspond with at least one structural component in such a way as to be automatically retained on this structural component without additional attachment elements. This could be realized by various measures, which can yield a positive or non-positive connection. 
         [0010]    The statement that the insulation packet is applicable on the exterior skin is not to be construed as a limitation in the form of a direct positioning of insulation packets on the exterior skin. Rather, insulation arrangements usually extend in a gap that is enveloped by the interior cladding of a passenger cabin and an exterior skin of the aircraft, without requiring any direct contact with the exterior skin in the process. Therefore, insulation packets can be positioned directly in the exterior skin, or also form a gap. 
         [0011]    The special advantage to using dimensionally stiff foam is that the nearly achieved incompressibility makes it possible to omit the ventilation holes required for purposes of pressure compensation. As a result, ventilation can also not allow moist air to get into the insulation packet, thereby eliminating a possible source of condensation water. In addition, the absence of ventilation holes also tangibly reduces the danger of bursting during assembly by comparison to glass wool or other voluminous materials. Pressure must be compensated throughout a flight even in the case of foam, but the foam itself already realizes this without any further precautionary measures, so that even pressure changes during individual flight missions are not expected to destroy the foam. 
         [0012]    Let it be noted at this juncture that dimensionally stiff foams of this kind can be realized both as closed-cell and open-cell foams, for example comprised of melamine or polyamide. Open-cell foams are susceptible to the entry of moist air and its condensation within the foam material. This can be prevented by correspondingly encapsulating the insulation packet, wherein the capsule can be designed as a sheathing film or lamination, while the use of closed-cell foams would at the same time eliminate the need for this capsule. In the latter case, however, the weight of the insulation packet would distinctly rise by comparison to an insulation packet made of open-cell foam, which is why open-cell foams with a sheathing film or lamination may be preferred. 
         [0013]    In one exemplary embodiment, the unstressed insulation packet, in order to establish a clamping attachment between two spaced apart structural components arranged on the exterior skin, comprises a first extension length that exceeds the distance between these two structural components. This enables a clamping attachment for the insulation packet, since the dimensionally rigid foam material could allow itself to be compressed when exposed to a compressive force by slightly exceeding a length defined by the distance between two structural components, wherein the foam material attempts to return to its original shape from this compressed state owing to its dimensional rigidity. If the foam material is incorporated between two structural components, a repelling force hence always acts on the ends of the insulation packet that touch the structural components, leading to a non-positive connection by clamping in the insulation packet. In addition to the corresponding length, the insulation packet should also comprise other geometric properties that are able to accommodate specific shapes of the structural components, for example bulges, bends, undercuts, shoulders and the like. 
         [0014]    Alternatively or additionally, an insulation packet of the insulation arrangement according to the present disclosure comprises at least one recess or shoulder, through which the insulation packet can establish a positive connection with a structural component or other insulation packet. A recess can here also be a depression. For example, a flat, even insulation packet could be positively mounted between two fuselage frames in such a way that the head profile of two fuselage frames engage into the recesses of an insulation packet arranged in between them, and are thereby held in place. An insulation packet could further comprise a recess on the side facing the fuselage skin for accommodating a longitudinal stiffening component, thereby additionally securing an end position of the insulation packet. 
         [0015]    In addition, if required or desired for improving the insulation, shaping the recesses makes it possible to easily establish a defined distance from the exterior skin to create a gap. Given a pressure reduction inside the cabin, an insulation packet sheathed in film would expand and at least partially seal the gap, which could be used to at least partially block a flow path between field insulation and the fuselage skin and/or an interior cladding, thereby reducing the introduction of harmful, moist air from the cabin into the area of the insulation packet, and again releasing the gap on the floor for drying purposes. 
         [0016]    In one example, such an insulation packet can comprise an even, flat shape. This makes the insulation packet especially well suited for manufacturing a so-called “field insulation”, for example which covers a skin field region lying between two fuselage frames with a plurality of such insulation packets. The radial extension of an even, flat insulation packet should be distinctly less during integration than the radial extension of the profile of the fuselage frames between which the insulation packet is located. 
         [0017]    In another embodiment of the present disclosure, the insulation packet comprises a recess that outwardly extends in a profile cross section of the insulation packet in order to envelop a structural component in a flush manner. Given the dimensional rigidity of the foam, the recess should correspond with the shape of the structural component. In one example, such an insulation packet can be used for a fuselage frame whose cross section could comprise an L, T, double-T or C shape. Therefore, the recess in the insulation packet corresponding thereto makes it possible to secure, plug or hook the insulation packet directly onto the fuselage frame, for example, so that it envelops this profile in a flush manner. 
         [0018]    In an embodiment of the present disclosure, the insulation packet comprises a flat, flexible drainage element, which comprises a capillary active material, and extends outwardly from an interior of the insulation packet to an end of the insulation packet. The drainage element is capable of removing condensation water from the insulation packet that accumulated inside the insulation packet during the flight. A portion of the capillary active material, which could encompass aramide or glass fabric, projects out, reliably extracting liquid condensation water from inside of the insulation packet based on the principle of a wick. 
         [0019]    In an embodiment, the drainage element is arranged at a lower end of the insulation packet, and extends out of the insulation packet, pointing in the direction away from the exterior skin. This is particularly sensible, since the side of the insulation packet facing the aircraft cabin is the drier side, because it is exposed to the heat from the air in the aircraft cabin, which is rather warm by comparison to the exterior skin, and can thereby dry off the element. 
         [0020]    In an embodiment, the insulation packet comprises a drainage opening at its lower end, which ensures that condensation water arising as the result of leaks in the insulation packet, its sheathing film, lamination or the like can be easily removed. When using just a single drainage opening, there is a very slight danger that moist air will get into the insulation path in this way and condense there. 
         [0021]    In one embodiment of the present disclosure, two sequential insulation packets overlap each other like scales. This must be understood as meaning that two insulation packets arranged one over the other form an overlapping region, wherein the lower end of the upper insulation packet lies on the upper end of the lower insulation packet. As a result, a drainage element could very easily be guided out of a lower end of an upper insulation packet in the overlapping region, come to lie on a side of an underlying insulation packet facing the passenger cabin, so as to be dried there. Similarly, a liquid-tight drainage film or the like can be guided on the side of an upper insulation packet in an overlapping region that faces the aircraft skin along the exterior skin in front of the underlying insulation packet. In this way, the condensation water can run downwardly along the exterior skin under the force of gravity, without there being any danger that condensation water will get between two insulation packets in the direction of the passenger cabin. 
         [0022]    In an embodiment, the insulation arrangement further comprises a liquid-tight drainage film, which, on a side of an upper insulation packet in an overlapping region that faces the exterior skin, is guided along the exterior skin in front of the underlying insulation packet. In this way, arising condensation water can flow along the exterior skin on the insulation packets without getting into adjacent insulation packets or into an aircraft cabin. 
         [0023]    In one embodiment of the present disclosure, a gap is formed between the insulation packet and exterior skin of the aircraft fuselage for discharging condensation water and providing added insulation by way of an air cushion. Because of the larger distance between the insulation packet and exterior skin, this gap also diminishes the danger of condensation water entering into the respective insulation packet, so that the dimensionally rigid foam combined with the gap to the exterior skin already brings about a clear reduction in the danger that condensation water will accumulate. 
         [0024]    In an embodiment, the insulation packet comprises a sheathing film, which incorporates at least one vent valve, so as to ensure pressure compensation inside the insulation packet given pressure changes in the cabin, but also while compressing the foam in the insulation packet during the installation process. 
         [0025]    In one embodiment, the insulation arrangement according to the present disclosure also comprises an insulation packet comprised of a flexible, voluminous material having a sheathing film that accommodates at least one vent valve. As opposed to a ventilation hole, the vent valve is set up to open a flow cross section for ventilation purposes only starting at a prescribed differential pressure. The latter is completely closed when the differential pressure drops below a level determined by the design of the vent valve. During assembly of the respective insulation packet, the vent valve permits the compression of the insulation packet, but simultaneously also allows ventilation during takeoff and landing phases once a specific differential pressure is present on the vent valve. However, a permanently present opening is prevented. As a result, damage to the sheathing film can be precluded, and continuous exposure of the insulation packet to moist air can be clearly reduced. 
         [0026]    The present disclosure also provides an aircraft with an aircraft fuselage and a passenger cabin located therein, which is equipped with an insulation arrangement described above. 
         [0027]    Further, an insulation packet with the features described above is also provided. Dimensionally rigid, foam-based insulation packets can also be used to upgrade already existing aircraft (“retrofit”), so that the latter can benefit from the special advantages of lacking condensation water accumulation. 
         [0028]    A person skilled in the art can gather other characteristics and advantages of the disclosure from the following description of exemplary embodiments that refers to the attached drawings, wherein the described exemplary embodiments should not be interpreted in a restrictive sense. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0029]    The various embodiments will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and wherein: 
           [0030]      FIG. 1  shows a conventional aircraft insulation from prior art. 
           [0031]      FIG. 2  shows a sectional view of an insulation arrangement according to the present disclosure. 
           [0032]      FIG. 3  shows an insulation arrangement according to the present disclosure, limited to a field insulation packet. 
           [0033]      FIG. 4  shows a side view of an insulation arrangement according to the present disclosure. 
           [0034]      FIG. 5  shows an insulation packet with a drainage fleece. 
           [0035]      FIG. 6  shows an insulation packet with a ventilation valve. 
           [0036]      FIG. 7  shows an aircraft having at least one passenger cabin insulated with the insulation arrangement according to the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0037]    The following detailed description is merely exemplary in nature and is not intended to limit the present disclosure or the application and uses of the present disclosure. Furthermore, there is no intention to be bound by any theory presented in the preceding background or the following detailed description. 
         [0038]      FIG. 1  shows a single, mat-like insulation packet  2  according to prior art. The insulation packet  2  essentially consists of a voluminous core material  4  for insulation, which is enveloped by a sheathing film  6  having a series of ventilation holes  8 . The latter are provided both to be able to compensate for pressure and compress the insulation packet  2  during assembly, so that the sheathing film  6  can be prevented from bursting. However, moist air gets through the ventilation holes  8  and into the core material  4 , where it is always accumulated, but adheres for the most part to fibers due to the voluminous material, and only drips partially out of the insulation packet  2  again by way of drainage holes  10 . 
         [0039]      FIG. 2  shows an insulation arrangement  12  according to the present disclosure, which reveals insulation packets  14 ,  16 ,  18 ,  20  and  22  including dimensionally stiff foam, which are spaced apart from an exterior skin  24  and automatically retained on fuselage frames  26  and  28 . The fuselage frames  26  and  28  are joined with the exterior skin  24  of the aircraft via connection elements  30  and  32 , and comprise a distance d from each other. Situated between the fuselage frames  26  and  28  is the insulation packet  14 , which comprises an essentially flat, mat-like shape, and when not exposed to a stress has a length  1  somewhat larger than the distance d of the two fuselage frames  26  and  28 . Lightly compressing the insulation packet  14  forces it back into its original shape, thereby exposing the fuselage frames  26  and  28  to a repelling compressive force, causing it to become clamped between the fuselage frames  26  and  28 . Due to the flat shape and the provided installation position, the insulation packet  14  in conjunction with the insulation packets  20  and  22  forms the field insulation. 
         [0040]    In order to accommodate a beveled area of the fuselage frame  26 , the insulation packet  14  comprises a recess  34  that simultaneously yields a positive, hooking connection between the insulation packet  14  and the frame  26 . This facilitates assembly of the insulation packet  14 , since one end of it can be hooked into the beveled area of the fuselage frame  26 , after which its opposite end is constantly compressed, sliding along the fuselage frame  28  toward the exterior skin  24 , finally coming to rest in the end position as depicted on  FIG. 2 . 
         [0041]    The insulation packets  16  and  18  each comprise a recess  36  and  38 , which corresponds with the shape of the respective fuselage frame  26  and  28 . As a consequence, they can be stacked on the fuselage frame  26  and  28 , and upon reaching the end position shown on  FIG. 2  enter into a positive connection with the respective fuselage frame  26  or  28 , thereby ensuring a secure hold. The insulation packets  16  and  18  comprise the frame insulation by way of their shape and installation position. 
         [0042]    In addition to the above, the insulation packet  14  comprises two shoulders  40  and  42 , which are arranged in an insulation packet  14  in such a way that the insulation packets  16  and  18  come to rest in their installed position. This increases the attachment quality of the insulation packet  14  due to the radially acting safeguarding device, along with the attachment quality of the insulation packets  16  and  18  by pressing the insulation packets  16  and  18  against the fuselage frames  26  and  28 . 
         [0043]    The depiction on  FIG. 3  presents a view rotated by an angle of 90° of a plane formed by the exterior skin  24 . It shows an insulation packet  114  that comprises recesses  44 , in which longitudinal stiffening components  46  (so-called “stringers”) can be positioned. This additionally secures the end position of the insulation packet  14 . In addition, the recesses  44  can be easily shaped to establish a defined distance from the exterior skin  24  to create a gap  48 . 
         [0044]      FIG. 4  shows two insulation packets  14  arranged one atop the other, in which the lower end  50  of an upper insulation packet  14  sits on the upper end  52  of a lower insulation packet. At the lower end  50  of the upper insulation packet  14 , a drainage element  54  outwardly projects like a wick from the core of the insulation packet  14 , which carries condensation water drops  56  to the outside. The drainage element  54  lies on a side of the insulation arrangement according to the present disclosure facing an aircraft cabin  58 , while a drainage film  60  is arranged by means of adhesive tape  62  on the side of the insulation arrangement facing the exterior skin  24 , projecting from the upper insulation packet  14  under the lower insulation packet  14 , so that condensation water drops  56  can flow by the insulation packets  14  without getting into the insulation packets  14  or to the aircraft cabin  58 . 
         [0045]    The drainage element  54  is fabricated out of a capillary active material, for example aramide or a glass fabric, and routes out of the insulation packets any condensation water that managed to get into the insulation packets  14  despite the sheathing or encapsulation and absence of ventilation holes, and can dry due to exposure to heat from the aircraft cabin  56 . 
         [0046]    For purposes of further illustration,  FIG. 5  presents a three-dimensional, isometric view of an insulation packet  14  with such a drainage felt  54 . The extension of the drainage element  54  into the insulation packet  14  determines the quality of condensation water capturing. 
         [0047]      FIG. 6  shows another insulation packet  64 , which comprises a voluminous, compressible core material similar to the prior art on  FIG. 1 . Despite the advantages to the insulation arrangement according to the present disclosure, it may be necessary to use such a compressible insulation packet  64  at some hard to reach locations on the aircraft fuselage or locations where the stiffening components comprise a complex geometry. In order to minimize the consequences of having to ventilate in terms of the forming condensation water in the insulation packet  64 , conventional ventilation holes are replaced by vent valves  66  that only provide an opening cross section once a certain differential pressure has been reached, so that ventilation can take place. These vent valves  66  can comprise a membrane-like, dimensionally stable disk with one or multiple slits, which only yields starting at a certain load, thereby opening the slit that is closed when not exposed to a load. As a result, the insulation packet  64  can be ventilated during assembly, while a continuous exposure to moist air is prevented during cruising flight. 
         [0048]    Finally,  FIG. 7  shows an aircraft  68  comprising a passenger cabin  58 , in which the insulation arrangement according to the present disclosure could be used. 
         [0049]    While at least one exemplary embodiment has been presented in the foregoing detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the present disclosure in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment, it being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope of the present disclosure as set forth in the appended claims and their legal equivalents.