Abstract:
A method for opening a dome for the protection of a device to be protected, fitted in a part described as fixed, in which, in the initial position before opening, a generally plane interface separates the dome from the fixed part, is provided. The method includes connecting the dome to the fixed part by at least two independent double-link connections that are movable in rotation between the dome and the fixed part. The links in a single connection being fitted in common to the dome and to the fixed part to form overall a pantograph in the shape of an isosceles trapezium which, during opening, opens out by pivoting until maximum opening is achieved, so that the dome moves away from the fixed part via a combination of movements in translation and in rotation.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a U.S. National-Stage entry under 35 U.S.C. §371 based on International Application No. PCT/FR2012/051455, filed Jun. 26, 2012 which was published under PCT Article 21(2) and which claims priority to French Application No. 1155687, filed Jun. 27, 2011, which are all incorporated herein by reference in their entirety. 
     TECHNICAL FIELD 
     The technical field relates to a method for opening a dome for the protection of a device to be protected, in particular of a structure for receiving and/or emitting waves such as a radar device or a telecommunications antenna, in particular for opening an aircraft radome, and also a radome equipped with a pantograph capable of implementing this method. 
     Systems for opening domes for the protection of structures, such as aircraft radomes, are in general designed to be able to fulfil different requirements related to use, maintenance, manufacture and assembly, taking into consideration, in particular, the problems of weight and corrosion. 
     In one example, opening systems have a fixed part and a movable part consisting of movable mechanical elements that define rectilinear, lateral circular, or pivoting opening kinematics. 
     BACKGROUND 
     It is known, for example in the field of aeronautics, that opening systems can have extension members chosen from among rectilinear or gooseneck arms, hinges, removable fixing devices and/or lateral arms and rods. 
     Thus, the rectilinear arms on the circumference of the dome enable the rotary shaft to be reached when the dome is opened. Adjustments can then be made during assembly. In addition, rectilinear arms of this kind constitute a solution that does not produce significant excess mass. 
     The use of gooseneck arms with the same aim, inside the circumference of the dome, requires more weight because this solution needs additional means on the rotary shaft, which shaft must be situated behind the movable part. The presence of this additional part means that the interface between the structure to be protected and the mechanism for opening is complex and expensive. The seal at this interface is also complex and the unit is made heavier. 
     In a configuration that opens laterally, the arms are fitted to a common hinge and the movement of each arm is guided by a link rod. This configuration produces the same disadvantages as the solution above. In addition, lateral opening is not optimum for maintenance, as it then requires a double access for two operators, which can involve interactions with the maintenance platform. 
     Opening via external hinges is a lighter solution than the preceding one but, like the solution with rectilinear arms, it requires more adjustments and increases the aerodynamic drag. 
     The above systems for opening can be implemented only with rigid movable parts. Thus, composite radomes for aircraft must be stiffened, for example via a metal frame. This involves additional costs, and weight and complexity of the movable assembly. In addition, a stiffening frame requires a rigid interface with a chassis for mounting the fixed structure. The result is an increase in the amounts of play and the presence of aerodynamic steps between the radome and the fixed part. 
     A system for opening via removable fasteners enables the structure to be made lighter because no additional opening mechanism is used. In addition, the movable part does not need to be dimensioned to receive the housings of the structural mechanisms when the movable part is open. 
     The advantages of this solution lie in the fact that the movable part is more easily positioned during assembly and meets the aerodynamic requirements. Thus, when the movable part is open during maintenance operations, it is held by a specific tool. 
     The disadvantages arise from the time devoted to withdrawing the fasteners in general beyond the maintenance objectives, and the need for basic service equipment which is not always available. 
     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 
     The aim of the various embodiments of the present disclosure is to effect the opening a protective dome without the disadvantages described above, in particular simple and rapid opening that allows access to a device (for example, a radar communication device and/or other communication systems) without risk of corrosion or damage (resistant to extreme loads and to wind), rapidly assembled and adjusted using simple tools, weighs little, economical in its costs and with a reduced aerodynamic drag. 
     To do this, the present disclosure provides unique kinematics combining two movements in such a way as to move the dome away while rapidly opening a working space. 
     More specifically, the present disclosure relates to a method for opening a protective dome for a device to be protected, in one example, a structure for telecommunication by emission/reception of waves that is fitted in a part described as fixed. In the initial position before opening, an interface (generally a plane for reasons of sealing) separates the dome from the fixed part. In this method, the dome is connected to the fixed part by at least two independent double-link connections that are movable in rotation between the dome and the fixed part. The links in a single connection are fitted in common to form overall a pantograph in the shape of an isosceles trapezium which, during opening, opens out by pivoting until opening is complete. This opening out is effected in such a way that the dome moves away from the fixed part via a combination of movements in translation and in rotation. 
     Inclining the links to form a trapezium enables the system to be stiffened by proper maintenance of lateral stability during and at the end of opening. 
     Advantageously, the links of each connection are mounted in articulation on the periphery of the dome, in one example, on the internal rim of the dome. This arrangement enables stability to be increased. 
     Furthermore, the movable links of a connection are dimensioned so that the opening kinematics starts with a phase of movement of the dome substantially in translation perpendicular to the plane of the interface, followed by a phase of movement of the dome substantially in translation and rotation around a fixed axis parallel to the axis of pivot of the pantograph. Advantageously, the opening kinematics is an opening out upwards in use mode, the final position of the dome defining, relative to its initial position, an angle of opening of between about 30° and about 80°, in one example, between about 40° and about 50°. There is provision for automatic locking, advantageously at the end of a telescopic extension, when the dome has reached its final open position. 
     In addition, the links on the dome advantageously have a resilience that enables adjustment to be avoided. 
     The present disclosure also relates to a radome capable of being connected to a fixed part, in particular according to the above method. A radome of this kind has a dome-shaped protective cover and articulated linking mechanisms of which the first extremities can be connected in rotation to the protective cover. Second extremities can be connected in rotation to the fixed part onto which a communication system to be protected by the radome is mounted. The linking mechanisms consist of at least two pairs. The extremities of each connecting pair are mounted on a common fitting via means for connecting in rotation. Each connecting pair forms one of the sides of a pantograph shaped as an isosceles trapezium. This double-link architecture, of linkage and arm, the extremities of which are attached to a common fitting, advantageously enables the masses to be reduced, as the kinematics parts and fittings are light in structure. 
     According to various embodiments: each pair consists of two linking elements made up of a rectilinear guide linkage and an arm of greater mechanical strength, each element of each pair being capable of pivoting overall around a fixed axis; and each pair consists of two linking elements made up of a rectilinear guide linkage and an arm of greater mechanical strength, each element of each pair being capable of pivoting overall around a fixed axis. In addition, according to various embodiments, at least two telescopic rods are capable of being attached in rotation to the radome and to the fixed part in order to produce automatic locking when the radome has reached its final open position; and the means for connection in rotation of the extremities of the connecting pairs to the radome are swivel bearings on a support made of resilient material (known as “shock mount” or “silent block” bearings). 
     Further, according to various embodiments, the sides of the isosceles trapezium form an angle of about 50° to about 70°, in one example, about 60°, with the bases; and the linkage and the arm of a connecting pair have, in lateral projection when in use, a constant angle of separation, in one example, from about 5° to about 30°, for example, from about 10° to about 25°. In various embodiments, the arms of greater mechanical strength are curved, form two edges machined as ribs and are connected to the support by double shear; and advantageously, the stiffness of the arms of each connecting pair is calculated under bending load around a vertical axis passing through the extremity on the fixed part in such a way as to limit deflection of the dome under extreme loads. 
     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 
       The various embodiments will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and wherein: 
         FIG. 1  is a perspective view of the nose of an aircraft with a radome; 
         FIGS. 2 and 3  are two views, upper and lateral respectively, of an example of a radome according to the present disclosure in the intermediate and fully open positions respectively; 
         FIG. 4 , diagrams  4   a  to  4   k  illustrate lateral views of the progressive opening of the radome according to the previous drawings, between an initial position attached to the fixed part and a fully open position; 
         FIGS. 5 and 6  illustrate a connecting pair with linkage and curved arm in a frontal view of the rim of the radome and in a perspective view between the radome and the fixed part; and 
         FIGS. 7 and 8  are views in cross section of the means for connection in rotation of an extremity of an arm and an extremity of a linkage on the fixing support of the radome. 
     
    
    
     DETAILED DESCRIPTION 
     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. 
     Throughout this text, the part on which the radome rests, an extremity of an aircraft fuselage in the case of the examples that follow, is described as fixed because it serves as a reference for the movement to open the radome. The central axis X′X in the drawings is horizontal, in other words, parallel to the ground on which the aircraft stands, a vertical plane being perpendicular to the ground. The qualifiers “upper” and “lower”, or equivalent terms, relate to the relative positions of the parts of a single object, for example the radome, relative to the ground. 
     In  FIG. 1 , the nose of an aircraft A consists of a radome  1  formed from a dome of composite material capable of protecting a radar antenna. The radome  1  is connected to the fuselage  10  of the aircraft A, this fuselage constituting the part described as fixed. The radome and the fuselage are connected by fasteners  11  and centring elements  12  to facilitate fitting. 
     With reference to the upper view shown in  FIG. 2 , the example of a radome  1  is in an intermediately open position. This radome is made of a composite material. This drawing is simplified so that the only linking elements shown are two connecting pairs  21  and  22 , which are symmetrical relative to the central vertical plane V 1  passing through the central axis X′X. The links  21  and  22  consist of a linkage  2   a  and of a curved arm  20   a  with two machined edges forming ribs framing a plane wall. These links are made of a metal alloy, for example an aluminium alloy. The mechanical strength of the arms is greater than that of the linkages. 
     In the plane of  FIG. 2 , parallel to the ground S, these links—in particular the arms  20   a  and  20   b  as shown in the drawing—form the sides C 1  and C 2  of an isosceles trapezium-shaped pantograph TI of which the bases B 1  and B 2  are shown in dot-and-dash lines. In the plane of the drawing, the linkages  2   a  and the arms  20   a  of a single pair  21  or  22  appear generally parallel and form an angle of approximately 60° relative to a vertical plane V 2  parallel to the entry face F 1  of the fixed part (see  FIG. 3 ) and to the bases B 1 , B 2 . The connecting pairs  21  and  22  are mounted in common on a single support at their extremities (symmetrically relative to the plane V 1 ): on, respectively, the fittings  31 , at the inner rim Bi of the cover forming the radome  1  (see  FIG. 3 ), and the fittings  33  for the entry face of the fixed part. These mountings in common on a single fitting advantageously allow a common absorption of the forces transmitted. 
     In the lateral view shown in  FIG. 3 , the entry face F 1  of the fixed part  10  is shown vertically. Approximately at the centre of this face F 1 , a radar antenna  13  is mounted. In this drawing, a connecting pair  21  and a telescopic rod  41  fixed, at its extremities, to the inner rim Bi of the radome  1  and to the face F 1  via appropriate hinges  4  and  4 ′ for connection in rotation. The telescopic rod  41  conceals an identical telescopic rod  42 , situated symmetrically relative to the vertical plane V 1  passing through the central axis X′X. Each telescopic rod  41 ,  42  is positioned vertically to the common fitting of the corresponding connecting pair  21 ,  22  at a distance greater than the length of the pair. In addition, by virtue of the positioning on a common fitting and at the periphery of the radome, each connecting pair  21 ,  22  is shorter than the corresponding telescopic rod  41 ,  42 . The result of this is a saving in length and thus in mass. Furthermore, the telescopic rods  41  and  42  have an automatic locking position corresponding to the maximum final openness Omax of the radome  1  relative to the face F 1  of the fuselage. In the example, the maximum opening is approximately 44°. The operator applies a force (arrow E) until maximum opening is achieved. 
     The angle of separation a between the arm  20   a  and the linkage  2   a  of each connecting pair  21  is approximately 16° in the example shown in lateral projection. A separation of this kind makes it possible to prevent the radome from simply rotating around the axis formed by the front extremity of the linkages  2   a  (see the description with reference to  FIG. 6 ). In addition, the axes of rotation of the arm  20   a  and of the linkage  2   a  are not parallel in order to impose a kinematics on the linking elements, linkages and arms (likewise, see the description with reference to  FIG. 6 ). 
     Diagrams  4   a  to  4   k  in  FIG. 4  show the progressive change in the opening of the radome  1  in lateral views, between the initial position (diagram  4   a ) where the circular lip  1   a  of the radome  1  is disposed as an interface against the face F 1  of the fixed part  10  and the final position (diagram  4   k ) corresponding to the maximum opening Omax. The operator lifts the radome  1 , applying increasing thrust from the lower part of the radome  1  (arrow E) until the telescopic rods  41  and  42  lock. The opening kinematics is an opening upwards in use mode (arrow E). The linkages  2   a  and, respectively, the arms  20   a  of the connecting pairs  21  and  22  pivot around axes that are symmetrical relative to the vertical plane V 1  (see  FIG. 2 ), respectively AA′, BB′ and CC′, DD′. The telescopic rods  41  and  42  pivot around an axis FF′ at the hinge  4 . 
     In diagrams  4   a  to  4   k , the same reference symbols used in the previous drawings refer to the same elements. 
     The dimensions and positions of the connecting pairs  21  and  22  are adjusted so that: in a first phase of translation of the radome (arrows T), illustrated in diagrams  4   a  to  4   c , the lip  1   a  of the radome  1  remains substantially parallel to the face F 1  of the fixed part  10 , and—in a second phase of rotation of the radome (arrows R), illustrated in diagrams  4   d  to  4   k , the radome pivots around an axis parallel to the axis FF′ in addition to a translation forwards and upwards (parallel to the arrow E). 
     This breakdown into two phases makes it possible, in particular, to prevent the gasket between the radome and the fixed part from shearing. This is because the separation of the radome is solely axial via the pure translation at the beginning of the kinematics of the movement. Thus, the gasket retains its strength and its sealing function for an appreciably longer period of time. 
     The partial frontal view of the inner rim Bi of the radome  1  according to  FIG. 5  shows a connecting pair  21  with its fittings for attachment to the radome and to the fixed part (which is not shown for reasons of visibility), referenced  31  and  33  respectively. 
     The fitting  31  is rigidly connected to the inner rim Bi of the radome  1 . This fitting  31  has two swivel bearings,  3   a  and  30   a , to receive in rotation the respective adapted extremities of the linkage  2   a  of the connecting pair  21 . The other extremities of the rod  2   a  and the linkage  20   a  are received in rotation on the fitting  33  capable of being rigidly connected to the fixed part  10  (see  FIG. 6 ). 
     The arm  20   a  is curved and has two machined edges  21   a  and  22   a  connected by a plane wall  23   a , these two arms merging into a single arm at the extremity mounted on the fitting  31 , and coming at the other extremity into articulation on the axis of rotation of the other fitting  33 . 
     A centring sphere  12  is also shown in  FIG. 5 . This element is also fixed at the rim Bi of the radome  1  and comes into articulation on a complementary centring element rigidly connected to the fixed part in order to provide positioning via centring. 
     The fitting  33  on the face F 1  of the fixed part of the fuselage  10  appears more clearly in the perspective view shown in  FIG. 6  which uses the same reference symbols for identical elements. In this drawing, the connections of the linkage  2   a  and the arm  20   a  to the attachment fitting  33  of the fixed part  10  are shown in a frontal view, and in a perspective view between the radome  1  and the fixed part  10  and also to the fitting  31  of the radome  1 . In particular, the extremities  20   e  and  2   e  ( 20 ′ e  and  2 ′ e  respectively) of the arm  20   a  and the linkage  2   a  respectively are received in rotation by swivel bearings  30   a  and  3   a  ( 30 ′ a  and  3 ′ a  respectively) formed on the attachment fitting  31  of the radome  1  (the attachment fitting  33  of the fixed part  10  respectively). In this drawing it is apparent that the linkage  2   a  and the arm  20   a  are oriented in two different directions. Thus, the axes of rotation of the linkage  2   a  and the arm  20   a , combined with those of the bearings  30   a  and  30 ′ a  for the arm  20   a ,  3   a  and  3 ′ a  respectively for the linkage  2   a , are not parallel to one another at the dome  1  and at the fixed part  10 . In other variants, this non-parallelism of the axes is effected on the dome and/or on the fixed part. The axes of rotation of the linkage  20   a  and the arm  2   a  of each connection thus have a non-zero angle in two different planes. The angle of separation a between the arm  20   a  and the linkage  2   a  is shown here in a lateral view, substantially as actual size. This separation is generally between about 15° and about 20°, approximately 16° in the example. 
     The connections in rotation on these swivel bearings advantageously bring into play bearing supports made of resilient material, for example of rubber or synthetic elastomer. The views in cross-section given in  FIGS. 7 and 8  show in greater detail the configuration of such connections in rotation, in this case the connections of the arm  20   a  and of the linkage  2   a  to the bearings  30   a  and  3   a  of the fitting  31  shown in  FIGS. 5 and 6 . 
     With reference to  FIG. 7 , the extremity  20   e  of the arm  20   a  is swivelably mounted on the bearing  30   a  via a quick release pin  30   b . Elements  30   r  of resilient material serving as bellows provide resilience in all the axes. 
     In  FIG. 8 , the extremity  2   e  of the linkage  2   a  is swivelably mounted on a quick release pin  20   x  of the bearing  3   a  mounted on the fitting  31  via rings 3 lb. The knuckle  2   e  is provided with an elastomer material  20   r.    
     The knuckles  2   e  and  20   e  provided with elastomer material  20   r  and  30   r  have a radial stiffness that is determined so that its maximum displacement (corresponding to the maximum tolerance range of the assembly) is reached for the load corresponding to the locking of the locks at the periphery of the radome. 
     The present disclosure is not restricted to the examples described or shown above. It is, for example, possible to provide more than two telescopic rods or varied forms of the linkages or coupling rods, and also other types of connection of the movable elements to the radome and to the fixed part, or other geometries at the junctions of these elements. 
     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.