Patent Description:
In common aircraft design, circumferential stiffening frames as well as longitudinally arranged axial stiffening elements are provided to stiffen the outer skin of the aircraft fuselage. After connecting the skin, the stiffening frames, and the longitudinal stiffening elements to form a structure, fittings are attached to the stiffening frames and the stiffening elements to hold overhead stowage bins or the like. For this, often a laser beam aligned in the fuselage of the aircraft is used to manually align and drill drill holes for the fittings in a plurality of consecutive stiffening frames in order to provide an exact spatial alignment of the drill holes. The laser beam indicates an interface axis to the overhead stowage bins. While the drill holes are drilled, no other work is conducted inside the structure. Furthermore, this process is time-consuming.

<CIT> describes a monument support system for an aircraft. The system includes multiple aircraft frame elements. An adapter bridge is coupled to the aircraft frame elements and has multiple attachment points. A coupling member is coupled to the adapter bridge. A monument is coupled to the frame elements via the adapter bridge and the coupling member.

<CIT> describes a quickly releasable stowage bin mountable on one or more support panels affixed to the interior of an aircraft. In the installation of a single stowage bin, quickly releasable mounting mechanisms affix the upper and lower portion of the stowage bin to the upper and lower portion of a support panel or panels. Each support panel are initially aligned in the factory whereby a conversion of the aircraft from freighter mode to full or partial passenger mode, results in a rapid, easy, secure, and quality installation of each stowage bin. The quickly releasable mounting mechanisms also facilitate the rapid and easy removal of each stowage bin from within a compartment of the aircraft during conversion of that compartment from passenger mode to freighter mode.

<CIT> describes a system with a frame with first and second spaced apart edges, a first holder couplable to the fuselage structure and embodied for articulated connection to a first region of the frame that is close to the first edge, a second holder couplable to the fuselage structure, and a strut. A first end of the strut is connectable in an articulated manner to the second holder. A second end of the strut is connectable in an articulated manner to a second region of the frame near the second edge and remote from the first edge. The frame and the strut form a triangular structure with the first and second holders. The strut and the frame form two sides of the triangular structure. A length of the first and/or second side is variable to adjust the position of the frame.

<CIT> describes a connecting device that comprises an eccentric pin as well as an eccentric sleeve intended to be mounted on the eccentric pin so as to allow, by suitable rotational positioning of the eccentric sleeve on the eccentric shaft, compensating for any clearance between circular holes superimposed on the mechanical parts to be linked together by means of said linking device. The connecting device also comprising locking elements capable of locking the eccentric pin and the eccentric sleeve in rotation, said connecting device thus making it possible to generate a fast, clean link capable of compensating for play locally.

It is thus an object of the invention to propose a structural system for an aircraft that allows a faster attachment of pieces of equipment inside the aircraft structure, wherein the equipment is spatially alignable as exact as possible in the structure. This object is met by the structural system for an aircraft according to the features of claim <NUM>. Advantageous improvements and further embodiments may be gathered from the subclaims and the following description.

According to the invention, a structural system for an aircraft is provided, comprising circumferential stiffening frames for stiffening a fuselage of the aircraft, the stiffening frames comprising a cross-sectional profile having a web enclosed by a radial inner flange and a radial outer flange, at least one first bracket, and at least one attachment device connectable to the at least one first bracket for fastening a piece of equipment to the at least one first bracket, wherein the stiffening frames each comprise a first pattern of drill holes adapted for receiving the at least one first bracket, wherein the at least one first bracket is adapted to protrude from the stiffening frames in a radial direction when attached, and wherein the attachment device is adapted for fastening the piece of equipment in a variable, arrestable radial distance to the respective first bracket. The structural system further comprises at least one support frame attachable to the piece of equipment, the at least one support frame having a first attachment region for connecting to the at least one first bracket and having a second attachment region for connecting to a further connecting element. The support frame has a substantially triangular shape.

The circumferential stiffening frames are based on common circumferential stiffening frames. It is conceivable that the structural system comprises a plurality of stiffening frames in a staggered manner along the longitudinal axis of an aircraft, while they extend perpendicularly to the longitudinal axis. The circumferential stiffening frames may preferably comprise a circumferentially closed contour.

The at least one circumferential stiffening frame comprises a cross-sectional profile having a web that substantially extends in a radial direction, i.e. perpendicular to the longitudinal axis of the aircraft. At the inner delimitation of the web, the inner flange is arranged. Together with the web it may create a T-shape or an L-shape. In the latter case, the inner flange may be arranged to extend only to a single side of the web. At an outer delimitation of the web, the outer flange may be provided, which may be designed in analogy to the inner flange. The cross-sectional profile may thus comprise a T-shape, an S-shape, a C-shape, or an intermediate shape.

According to the invention, the circumferential stiffening frames each comprise the first pattern of drill holes. These are drilled into the stiffening frames before the installation of the frames. Thus, when the aircraft structure is created, the installation of pieces of equipment may be conducted by selecting stiffening at suitable positions to install one or a plurality of first brackets. Consequently, drill holes do not need to be drilled after directly before installation. Thus, the plurality of stiffening frames allow a flexible and fast installation. Unavoidable, manufacturing-induced measure tolerances can be compensated by the attachment device. This is adapted for adjusting and arresting a radial distance from the bracket that is fixed to the first pattern of drill holes. For example, it may comprise an eccentrical component, which is connectable to the piece of equipment and may be rotatable and arrestable. However, solutions with a thread or other length-variable devices may also be conceivable.

The interior space of the aircraft structure, which comprises the structural system according to the above, is blocked for a clearly shorter time than with common installation procedures and structural setups. The structural system according to the invention thus allows a faster and more flexible installation of pieces of equipment. The structural system may further comprise at least one second bracket, wherein the stiffening frames each comprise a second pattern of drill holes adapted for receiving the at least one second bracket, and wherein the second pattern is arranged at a distance to the first pattern.

According to the invention, the structural system further comprises at least one support frame attachable to the piece of equipment, the at least one support frame having a first attachment region for connecting to the at least one first bracket and a having a second attachment region for connecting to a further connecting element. The support frame may be realized as a rigid component, which is attachable to a piece of equipment. It is conceivable that the support frame is directly attachable to the first bracket and the second attachment region, i.e. the further connecting element. Thus, the support frame may be aligned in the same plane as a single stiffening frame. For example, if the piece of equipment is an overhead stowage compartment, it may comprise a case or housing that encloses a stowage volume and has two end faces that will be aligned to either face forward or backward. The support frame may be directly attached to one of these end faces. The support frame may additionally be designed in such a way that at least one protruding lug or web is provided that is capable of connecting the support frame to the at least one first bracket and/or the further connecting element.

The further connecting element may comprise the at least one second bracket in combination with the at least one attachment device. Thus, the support frame is directly connected to two brackets, wherein each of them comprises an attachment device that has a radial tolerance compensation feature.

According to the invention, the support frame has a substantially triangular shape. Therefore, one of the edges, i.e. a bottom edge, of the support frame may be aligned to run parallel to a floor in the cabin of the respective aircraft, the two other edges run from the bottom edge to a top peak that is connectable to the first bracket. The support frame may have a grid, stripe, or skeleton shape, in which as much material may be left out as possible to minimize the weight of the support frame.

The structural system may further comprise axial stiffening elements, wherein the stiffening frames comprise radial outer cutouts for letting the axial stiffening elements pass through in a transverse direction to the respective stiffening frame, and wherein at least one of the axial stiffening elements comprises a third pattern of drill holes for receiving at least one third bracket. The axial stiffening elements, which may also be referred to as longitudinal stiffening elements or stringers, extend along the longitudinal axis of an aircraft structure on the inner surface of the aircraft skin. They also provide the possibility to attach a piece of equipment to the aircraft structure. As the axial stiffening elements extend along the longitudinal axis, they may be predestined for a providing a supporting force along a longitudinal axis.

The structural system may further comprise a tie rod having a variable length and may be connectable to the at least one third bracket for supporting the piece of equipment in a longitudinal direction. A tie rod may simply be bolted to the third bracket and hold the piece of equipment in a variable distance. Hence, manufacturing induced tolerances can be compensated to align the respective piece of equipment in a spatially desired manner independent of measurement deviations of the aircraft structure.

The attachment device may comprise a rotatable and arrestable sleeve having an eccentric borehole for tolerance compensation in a radial direction. By rotating the eccentric sleeve about the eccentric axis, a simple tolerance compensation preferably in a plane perpendicular to the longitudinal axis may be provided.

It may be advantageous if the first pattern is arranged in a top region of the circumferential stiffening frames. Thus, the first pattern serves for attaching the respective piece of equipment in an upper region of the cabin at a clear distance from e.g. a cabin window or a central region of a lining segment. The first pattern may thus provide for a vertical support.

Exemplarily, the second pattern may be arranged in a lateral region of the circumferential stiffening frames. The second pattern may thus serve for a support of the piece of equipment in a lateral direction.

The invention further relates to an aircraft, having a structural system according to the above description and at least one piece of equipment attachable to at least one of the circumferential stiffening frames of the structural system through the at least one first bracket.

In the aircraft, the at least one piece of equipment comprises an overhead stowage bin.

Still further, the at least one piece of equipment may be attachable to the structural system through the at least one second bracket and/or the third bracket.

Other characteristics, advantages and potential applications of the present invention result from the following description of the exemplary embodiments illustrated in the figures.

Furthermore, identical or similar objects are identified by the same reference symbols in the figures.

<FIG> shows a structural system <NUM> for an aircraft in a spatial view. Here, a plurality of circumferential stiffening frames <NUM> are shown. These provide a circumferentially closed contour and are arranged at a distance to each other along a longitudinal axis of the respective aircraft. The stiffening frames <NUM> comprise a web <NUM>, an inner flange <NUM> and an outer flange <NUM>. A skin <NUM> is arranged on the outer flanges <NUM> of all circumferential stiffening frames <NUM>. Thus, a hollow cylindrical fuselage structure is created. In addition, longitudinal, axial stiffening elements <NUM> are provided, which cross the stiffening frames <NUM> and run through radial outer cutouts <NUM>.

The stiffening frames <NUM> comprise a first pattern <NUM> of drill holes <NUM> in the web <NUM>. These drill holes allow to attach a first bracket <NUM> to the first pattern <NUM>, exemplarily by bolts or screws. The first bracket <NUM> has a roughly triangular shape with a straight base attached to the web <NUM> and a circularly rounded tip that protrudes away from the frame <NUM>. A piece of equipment <NUM>, which is shown as an overhead stowage compartment, is directly attached to the first bracket <NUM> in its protruding part.

For compensating manufacturing-induced measurement tolerances, the first bracket <NUM> comprises an attachment device <NUM> having a rotatably supported sleeve <NUM> with an eccentric borehole <NUM>. A connection element <NUM> can be inserted into the borehole <NUM> and will then assume a position given by the rotational position of the sleeve <NUM> adjustable and arrestable through an adjustment element <NUM>. The connection element <NUM> is introduced into the piece of equipment <NUM> and connects it to the first bracket <NUM>. By rotating the sleeve <NUM>, the radial distance of the connection element <NUM> to the inner flange <NUM> is adjustable. The sleeve <NUM> is arrestable to maintain the adjusted rotational position. It may be useful to use a device exemplarily shown in <CIT>.

A second pattern <NUM> of drill holes <NUM> is arranged in a vertically distanced region of the stiffening frames <NUM>. Here, a second bracket <NUM> is attached. A first tie rod <NUM> having a variable length is connected to the second bracket <NUM> and the piece of equipment <NUM>. Due to the position of the second pattern <NUM>, the first tie rod <NUM> is oriented substantially horizontally. Thus, the piece of equipment <NUM> is supported in a lateral direction. For compensating manufacturing induced measure tolerances, the length of the first tie rod <NUM> is adjusted after installation.

The axial stiffening elements <NUM> comprise a third pattern <NUM> of drill holes <NUM>. It is adapted for receiving a third bracket <NUM>, to which a second tie rod <NUM> is attached. The third brackets <NUM> are placed in one of the radial outer cutouts <NUM>. The second tie rod <NUM> connects the third bracket <NUM> with the piece of equipment <NUM>. The second tie rod <NUM> clearly extends clearly in an axial, longitudinal direction. Due to the use of a tie rod, a variable distance to the third bracket <NUM> can be assumed to provide for a tolerance compensation.

In an alternative structural system <NUM> shown in <FIG>, an attachment device <NUM> is attached to the second bracket <NUM>, such that the second bracket <NUM> is directly connectable to a piece of equipment <NUM>. In the shown example, the piece of equipment <NUM> is modified and comprises a support frame <NUM>. It is a rigid component, which comprises a first attachment region <NUM> having a first lug <NUM> protruding at an upper end in a vertical direction, as well as a second attachment region <NUM> having a second lug <NUM> extending at a lateral end in a lateral direction toward the skin <NUM>. The first lug <NUM> is connected to the first bracket <NUM>, while the second lug <NUM> is connected to the second bracket <NUM> through the attachment device <NUM>. The support frame <NUM> comprises a central cutout <NUM>, which is provided for reducing the weight of the support frame <NUM>. Furthermore, the support frame <NUM> exemplarily comprises a bottom edge <NUM>, which is oriented substantially horizontal, e.g. parallel to a cabin floor. The second tie rod <NUM> is attached to the third bracket <NUM> and a connecting element <NUM>, which is attached to and exemplarily protrudes from the attachment device <NUM>. Thus, a support in the longitudinal direction is provided.

By providing the stiffening frames <NUM> exemplarily having two patterns <NUM> and <NUM> of drill holes <NUM> as well as axial stiffening elements <NUM> having a third pattern <NUM> of drill holes <NUM>, pieces of equipment may flexibly be installed without requiring the drilling of drill holes directly from inside the structure prior to installation of the pieces of equipment. Tolerance compensation may be conducted through the use of tie rods or the above mentioned attachment devices.

In <FIG>, the process of attaching pieces of equipment is shown. <FIG> shows the stiffening frames <NUM> and the axial stiffening elements <NUM>, which together with the skin <NUM> create an aircraft structure. In <FIG>, first brackets <NUM>, second brackets <NUM> and third brackets <NUM> are attached as previously shown in selected stiffening frames <NUM> and axial stiffening elements <NUM>. In <FIG>, the piece of equipment <NUM> is advanced to the first and second brackets <NUM> and <NUM>. In <FIG>, the attachment devices <NUM> are adjusted for tolerance compensation. Also, the second tie rod <NUM> is installed and adjusted in its length. In <FIG>, the process of <FIG> is slightly modified for fixing the piece of equipment <NUM>. Here, the eccentric boreholes <NUM> of the attachment devices <NUM> are adjusted through the use of a laser beam <NUM> provided from an external source. The laser beam <NUM> comprises a defined spatial alignment to the structure and is used for aligning all the boreholes <NUM> this defined spatial alignment, such that the laser beam <NUM> extends through all first brackets <NUM> after the alignment. <FIG> shows the attachment of the piece of equipment <NUM> afterwards.

<FIG> shows an aircraft <NUM> having a fuselage <NUM> created by the structural system <NUM> or <NUM> together with the skin <NUM>. Inside, a plurality of pieces of equipment <NUM> or <NUM> is installed.

Claim 1:
A structural system (<NUM>, <NUM>) for an aircraft (<NUM>), comprising:
circumferential stiffening frames (<NUM>) for stiffening a fuselage (<NUM>) of the aircraft, the stiffening frames (<NUM>) comprising a cross-sectional profile having a web (<NUM>) enclosed by a radial inner flange (<NUM>) and a radial outer flange (<NUM>);
at least one first bracket (<NUM>); and
at least one attachment device (<NUM>) connectable to the at least one first bracket (<NUM>) for fastening a piece of equipment (<NUM>, <NUM>) to the at least one first bracket (<NUM>),
wherein the stiffening frames (<NUM>) each comprise a first pattern (<NUM>) of drill holes (<NUM>) adapted for receiving the at least one first bracket (<NUM>);
wherein the at least one first bracket (<NUM>) is adapted to protrude from the stiffening frames (<NUM>) in a radial direction when attached; and
wherein the attachment device (<NUM>) is adapted for fastening the piece of equipment (<NUM>, <NUM>) in a variable, arrestable radial distance to the respective first bracket (<NUM>);
wherein the structural system (<NUM>, <NUM>) further comprises at least one support frame (<NUM>) attachable to the piece of equipment (<NUM>, <NUM>),
the at least one support frame (<NUM>) having a first attachment region (<NUM>) for connecting to the at least one first bracket (<NUM>) and having a second attachment region (<NUM>) for connecting to a further connecting element; and
wherein the support frame (<NUM>) has a substantially triangular shape.