Patent Application
20130298365
The present invention concerns an actuating system of sectors of a device for producing an airplane fuselage.
The patent application PCT WO 2007/148301 describes a device for producing an airplane fuselage in which a lamination mandrel is delimited, by an external surface which defines a rotation solid (in particular a cylinder) with respect to a symmetry axis. The lamination mandrel is adapted to receive and support a band of impregnated synthetic material which is wound and deposited on the external surface of the mandrel in a lamination phase forming a plurality of overlapped layers. Said overlapped layers are subjected to a subsequent high temperature polymerisation process under vacuum in an autoclave for forming a structural section of the airplane (typically a tubular portion of fuselage).
The lamination mandrel comprises a plurality of sectors angularly spaced about the axis and borne by guides which extend radially from a supporting grid structure. The sectors are mobile between: an expanded lamination position in which the sectors have greater rectilinear edges parallel to the axis arranged side by side and the external surfaces of the sectors opposite the axis, define the external surface; and contracted disassembling position in which the sectors approach the axis moving away from the trace of the surface to allow extraction of the lamination mandrel from the structural section of the airplane at the end of the polymerisation process under vacuum.
In the expanded lamination position it is essential for the sectors to maintain an angularly and axially stable position with respect to one another since any alight movements between the parts can irreparably alter the geometry of the structural section. For example the patent applicant has pointed out that a lamination mandrel used for producing structural sections of large passenger airplanes must have low dimensional tolerances, below—for example—0.5 mm.
The movement of each sector from the expanded lamination position to the contracted disassembling position is normally performed by means of a screw—nut screw actuating system driven by an electric motor positioned on the supporting grid structure.
Said screws are normally made of steel which, as is known, is a metal that expands considerably at high temperatures; the patent applicant has in fact observed that at the temperatures normally reached in an autoclave (around 200-300°C.) the screws normally used elongate by a few mm (for example approximately ten mm), moving the sectors from the expanded lamination position reached when cold to an expanded position in which the external surface has a greater diameter than that of the external surface, again when cold.
Said phenomenon results in the structural section of the airplane having dimensions not corresponding to the design dimensions, therefore it cannot be used (for example since it is not able to couple with other sections).
The need is therefore felt to produce a sector actuation system that solves the above-mentioned technical problem and is not sensitive to the thermal cycles performed in the autoclave.
The documents DE195 25 023, JP2002 361541, U.S. Pat. No. 4,802,558 and US 2010/155984 represent known prior art.
The preceding object is achieved by the present invention which relates to an actuating system of sectors of a device for producing an airplane fuselage in which a lamination mandrel is delimited by an external surface which defines a rotation solid with respect to a symmetry axis; said lamination mandrel is adapted to receive and support a band of impregnated synthetic material which is deposited and wound on the external surface forming a plurality of overlapping layers which are subjected to a high temperature polymerisation process under vacuum for forming a structural section of the airplane; the lamination mandrel comprises a plurality of sectors angularly spaced about the axis and mobile along guides between:—an expanded lamination position in which the sectors have greater rectilinear edges parallel to the axis arranged side by side and the external surfaces of the sectors opposite the axis define together said external surface; and—a contracted disassembling position in which at least part of said sectors approaches the axis moving away from the trace of the surface to reduce the radial dimensions of the mandrel and allow extraction of said mandrel from the structural section of the airplane; each sector being provided with a screw—nut screw type actuating system comprising a threaded rectilinear element extending along a radial rotation axis, a nut screw and motor means, characterised in that said threaded rectilinear element comprises an internal shaft made of a first material and extending along said rotation axis and an external tubular portion made of a second material, axially mounted on a portion of said internal shaft and provided externally with said threading; said first material having a dilatation coefficient smaller than the dilatation coefficient of the second material; constraint means are provided between said internal shaft and said external tubular portion adapted to prevent angular displacement of the external tubular portion with respect to the internal shaft allowing a linear sliding of the external tubular portion with respect to the internal shaft; a first end portion of the external tubular portion being connected to a respective end portion of said internal shaft; a thermal stress applied to said threaded element producing a sliding of a second free end portion of the external tubular portion with respect to the internal shaft so that said stress does not produce an overall elongation of the threaded rectilinear element and each sector remains in the previously defined expanded lamination position also following said thermal stress.
The invention will now be illustrated with reference to the accompanying figures which show a preferred embodiment example in which:
In
In particular the device 2 (
For example, the band can be deposited by causing the mandrel 4 to rotate about the axis 7 and causing the lamination head (not illustrated) to translate in a coordinated manner along said axis 7 For example, the patent application US2005/0039843 illustrates a lamination head. At the end of lamination of the band, the band of impregnated composite material is subjected to a polymerisation process under vacuum to produce a tubular structural section of the airplane. Said process is carried out by placing the lamination mandrel 4 in an autoclave (not illustrated) and performing a. thermal heating cycle of known type.
In the example shown, the external surface 5 is cylindrical and the lamination mandrel 4 is used to produce a cylindrical tubular portion of the airplane fuselage.
The lamination mandrel 4 comprises a plurality of sectors 12 (
The sectors 12 are mobile between:
The supporting structure 10 extends between a first and a second annular end portion 16a, 16b (
The frustoconical end portions 17a, 17b are made of a metallic material and each delimit a central opening 18 coaxial with the axis 7.
The patent application WO 2007/148301 provides an example of embodiment and use of a structure of the above-mentioned type and of the end portions 17a, 17b.
Each sector 12 comprises a curved metallic wall 20 (
The adjacent edges 13 of two contiguous sectors 12 are adapted to position themselves one above the other in a perimeter overlap region 13s (
Between the stiffening structure 21 of each sector 12 and the supporting structure, a pair of rectilinear guides 17 (of known type and therefore not further illustrated) is provided, adapted to support the sector 12 and allow a linear translation movement, in a radial direction with respect to the axis 7 and in opposite directions, of each curved wall 20 between the expanded and contracted lamination positions.
The movement of each sector is achieved by an actuating system (illustrated on an enlarged scale in
Again according to the present invention the actuating system 27 is of the screw—nut screw type and comprises a nut screw 29 borne by the supporting structure 10 and rotated by the motor 28 (for the sake of simplicity, the transmission is not illustrated in
Alternatively the nut screw 29 could be arranged on the stiffening surface 21 of a sector 12 and the threaded element 31 borne by the supporting structure 10 and rotated by the motor 28.
The threaded element 31 comprises an internal shaft 33 (
The first metallic material (for example INVAR 36) has a dilatation coefficient smaller than the dilatation coefficient of the second metallic material (for example steel).
For example the steel can have the following thermal dilatation coefficient (expressed in mm/° C.)
As is known, Inver is a metal alloy consisting mainly of iron (64%) and nickel (36%), with traces of carbon and chromium, discovered by the Swiss Nobel prize-winner physicist Charles Edouard Guillaume. Its thermal dilatation coefficient (approximately 10-6 K-1 in length) is approximately one tenth compared to that of steel.
The second metallic material has a dilatation coefficient greater than the dilatation coefficient of the first material but has better mechanical strength characteristics than those of the first material.
The shaft 33 has a first end portion 33a from which a rectangular plate 36 extends which in turn is hinged to a bracket 37 which extends radially from the stiffening structure 21 towards the axis 7.
The first end portion 33a is not covered by the cylindrical tubular portion 34 and has a smaller diameter than the portion of the shaft 33 covered by the cylindrical portion 34.
A second end portion 33b of the shaft 33 is provided with an axial hole housing a terminal portion of a screw 46 used to fix in a stable manner a first end portion 34a of the tubular portion 34 to the shaft 33.
Between the internal shaft 33 and the tubular portion, angular constraint means 38 are provided, adapted to prevent angular displacement of the tubular portion 34 with respect to the internal shaft 33 (arid therefore allow transfer of the torque generated by the electric motor 28 to the shaft 33) but allowing linear sliding of the tubular portion 34 with respect to the internal shaft 33 following thermal stress applied to the threaded element 31 as a whole.
For example, the constraint means 38 can be made of a plurality of longitudinal ribs 50 (for example with triangular section—
In this way a temperature increase applied to the threaded element 1 (the temperature increase is caused by a thermal cycle performed in an autoclave) produces a deformation of the tubular portion 34 which elongates, moving the second end portion 34b of the tubular portion towards the plate 35 (the constraint means 38 allow relative sliding between the parts and the second end portion 34b is free to move) with respect to the internal shaft 33 which is not subject to significant dimensional variations due to the material used. The overall length of the threaded element 31 in any case increases very little since it is defined by the distance between the end portions 33b and 33a of the internal shaft 33 which has an extremely limited dilatation coefficient. In this way, the thermal stress produces a limited overall elongation of the threaded rectilinear element 31 which depends only on the reduced elongation of the first material.
Therefore, the autoclave heating of the device 2 does not entail a shifting of the sectors 12 with respect to the position defined prior to the heating. The required dimensional tolerances of the tubular fuselage element of the airplane are thus guaranteed.
Furthermore the nut screw couples with threads made of wear-resistant metallic material, thus providing a robust actuating system able to withstand a plurality of sector opening/closing cycles.
| Number | Date | Country | Kind |
|---|---|---|---|
| T02012A 000284 | Mar 2012 | IT | national |
