Patent Publication Number: US-7210275-B2

Title: Method to joggle a structural element and structural element joggled according to this method

Description:
RELATED APPLICATION 
     The present application claims priority to French Application No. 03 51117 filed Dec. 18, 2003. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a method to joggle a structural element and a structural element joggled according to this method. Joggling a structural element comprises joggling such a structural element so as to create an offset between two of its parts. In the context of the invention, the structural element to be joggled is a beam with any section whatsoever comprising, in its profile, a strut and wings at the two ends of this strut. The invention is aimed at reducing a length in the offset given by a joggling operation. The present invention can be applied to special advantage, but not exclusively, in the field of aeronautics. 
     A joggled structural element is generally used to strengthen a link between two parts, such as two parts of an aircraft that are not aligned with each other. 
     2. Description of the Prior Art 
       FIG. 1  shows a view of such a prior art joggled structural element  100 . This structural element herein has an I-shaped section that could have any section whatsoever, such as a C-shaped or U-shaped section. This structural element  100  has a first wing  101 , a second wing  102 , and a strut  103 . The first wing  101  has a thickness E 1  and the second wing  102  has a thickness E 2 . This joggled structural element  100  is used to set up or reinforce a link between a part  121  and a part  122 . 
     The first wing  101  and the second wing  102  are each deployed in a plane that forms a non-zero angle with a plane of the strut  103 , itself located in the plane of the  FIG. 1 . In a particular embodiment, these wings  101  and  102  are each deployed in a plane that is perpendicular to a plane of the strut  103 . There is a linking joggle  104  between a first part  105  and a second part  106  of the structural element. This joggle  104  corresponds to the part of the structural element  100  that is bent. This joggle  104  gives an offset between the first part  105  and the second part.  106 . The offset extends in the plane of the strut  103  of the structural element with an offset height H measured along a direction perpendicular to the plane of the wings  101  and  102 , and with an offset length L measured in a direction parallel to the planes of the strut  103  and of the wings  101  and  102 . 
     This length L is computed as a function of a thickness of a wing. In one exemplary embodiment, for structural elements comprising wings  101  and  102  with equal thicknesses E 1  and E 2 , the length L is on the whole equal to six times the thickness of a wing. This ratio between the thickness of a wing and the length L varies as a function of the material out of which the structural element is made. The length L is as short as possible but cannot be reduced as much as is desired. Indeed, the proportion of six times the thickness of the wing is a constraint that cannot be flouted without a risk of deterioration of the structural element. 
     In the prior art, when the thicknesses E 1  and E 2  of the wings  101  and  102  are different, the length L is computed from the thickness of the bigger of the two wings. In  FIG. 1 , the length L is therefore equal to six times the thickness E 1  of the thick wing  101 . In its joggle  104 , the structural element  100  therefore has identical slopes on both sides of the wings  103  and  104 . 
     The fact that the slopes are identical raises a problem. Indeed, the joggled structural element  100  is used to strengthen a link between two parts  121  and  122  having a difference in level. A space  130  depending on the length L can be seen between the parts  121  and  122  and the structural element  100 . Since the length L of the offset given by the joggle is very great, the space  130  between the parts and the structural element is great. At the position of such a space  130 , the joggled structural elements of the prior art therefore do not optimally participate in strengthening the link between the parts  121  and  122 . 
     It is an object of the invention to resolve this problem of excessive space  130  between the structural element  100  and the parts  121  and  122 . 
     SUMMARY OF THE INVENTION 
     To this end, the invention implements especially a joggled structural element comprising offset lengths computed as a function of each of the thicknesses of the structural element. 
     More specifically, the length of the offset given by the joggling of the side with the wing of great thickness is greater than the length of the offset given by the joggle on the side with the wing of small thickness. In the invention, these lengths are no longer identical. 
     The joggle in the joggled structural element according to the invention has a particular geometry in which the ends of the joggle form a quadrilateral resembling a trapezoid except for the slopes. In this quadrilateral, no side is parallel to another. Projections of the joggle ends on the side with the wing of small thickness are preferably located inside projections of the joggle ends on the side with the wing of great thickness. 
     In practice, the wing of small thickness is placed flat against two unaligned parts for which the link between them has to be reinforced. In one example of an embodiment, the length of the offset obtained by the joggling on the side with the wing of small thickness is equal to N times the length of the small thickness, while this length would have been equal to N times the length of the big thickness with a prior art joggling technique. With the invention, the space between the two linking parts and the joggled structural element is therefore limited. In one example, N is equal to six but varies as a function of the nature of the material out of which the structural element is made. 
     To make a joggled structural element, the invention implements a method in which a punch is used to press on a structural element wedged between this punch and an anvil. 
     More specifically, a punch is made with a part having low declivity that extends over a length proportional to the thickness of the wing of great thickness. An anvil is also made. This anvil has a part with high declivity that extends over a length proportional to a thickness of the wing of small thickness. The anvil is fixed. The punch is mobile. 
     After the punch and the anvil have been made, the side of the structural element with the wing of small thickness is placed against the anvil. Then, the punch is placed against the side of the structural element having the wing of great thickness. The punch is placed so that projections of ends of the part of the anvil having a slope in the sense opposite to a push or a pressure are placed between projections of the end of the part of the punch having a slope in the sense of the pressure. In particular embodiments, certain projections may be indistinguishable from each other. 
     Pressure is then applied to the punch in such a way that the structural element is compressed between the punch and the anvil. Since the slope segments of the punch and of the anvil are different, the shapes imprinted by this punch and this anvil on either side of the joggle of the structural element are different. 
     As a variant, the punch has a steep-sloped segment and the anvil has a shallow-sloped segment. 
     The invention therefore relates to a structural element with two wings and a strut, a first wing, whose plane forms a non-zero angle with a plane of the strut, being a wing of great thickness and a second wing, whose plane forms a non-zero angle with a plane of the strut, being a wing of small thickness, the structural element being formed with a linking joggle placed between a first part and a second part of the structural element, the joggle giving an offset between the first part and the second part, the offset extending in the plane of the strut of the structural section with a height measured along a direction perpendicular to the plane of the wings and with a length measured in a direction parallel to the planes of the strut and the wings, wherein the structural element comprises a shallow slope in the joggle of the side having the wing of great thickness, and a steep slope in the joggle of the side having the wing of small thickness. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be understood more clearly from the following description and the accompanying figures. These figures are given by way of an illustration that in no way restricts the scope of the invention. Of the figures: 
         FIG. 1  shows a prior art joggled structural element playing a role of a strengthening piece between two joined parts. 
         FIG. 2  shows a joggled structural element according to the invention playing a role of strengthening piece between two joined parts. 
         FIG. 3  shows a joggling method according to the invention. 
       The elements common to the several figures keep the same references from one figure to another. 
     
    
    
     MORE DETAILED DESCRIPTION 
       FIG. 2  shows the structural element  200  joggled according to the invention, comprising, as in  FIG. 1 , the strut  103 , the first wing  101  of great thickness E 1  and the second wing  102  of small thickness E 2 . This joggled structural element  200  plays a linking role between the parts  111  and  110 , such as parts of an aircraft. 
     The linking joggle  201  gives an offset between the first part  105  and the second part  106  of the structural element  200 . This offset is relative to a plane P of alignment between these two parts. This offset extends in the plane of the strut of the structural element with a height H measured along the direction perpendicular to the planes of the wings and with a length L 1  or L 2  measured in a direction parallel to the planes of the strut and of the wings. 
     The height H of the offset on the side with the wing of great thickness and that of the side with the wing of small thickness are identical. By contrast, the length L 1  of the offset on the side with the wing  101  of great thickness is greater than the length L 2  on the side with the wing  102  of small thickness. Thus, the structural section  200  has a shallow slope in the joggle  201 , on the side with the wing  101  of great thickness, and a steep slope in the joggle  201 , on the side with the wing  102  of shallow thickness. 
     In general, the length L 1  is proportional to the thickness E 1  of the wing  101  and the length L 2  is proportional to a thickness E 2  of the wing  102 . In one example of an embodiment, the lengths L 1  and L 2  are respectively equal to six times the great thickness E 1  and six times the small thickness E 2 . However, this ratio varies as a function of the nature of the material out of which the structural element  200  is made. However, the joggle  201  with a steep slope on the side with the wing  102  of small thickness, stretches between the two parts  105  and  106 , on a length L 2  equal to six times the thickness of this wing of small thickness. The joggle  201  with small thickness on the side with the wing of large thickness, extends between the two parts  105  and  106 , on a length equal to six times the thickness of this wing of large thickness. The ratio between the lengths L 1  and L 2  and the thicknesses E 1  and E 2  may vary in an interval of real values ranging between four and ten. 
     Furthermore, in the joggled structural element according to the invention, projections of ends of the linking joggle  201 , on the steep slope side, are located between projections of ends of the linking joggle  201  on the shallow slope side. More specifically, the ends of the joggle  201  on the side with the wing  102  of small thickness are projected along a direction perpendicular to the wings  101  and  102 , and in a sense that goes from the small wing  102  to the large wing  101 . The projections of these ends are located between projections of ends of the joggle  201  on the side with the wing  101  of great thickness, along a direction perpendicular to the wings  101  and  102 , and in a reverse sense going from the large wing  101  to the small wing  102 . 
     In one particular embodiment, a projection of an end of the joggle  201 , on the steep slope side, along the above-mentioned direction and sense, is indistinguishable from a projection of an end of the joggle, on the shallow slope side, along the above-mentioned reverse direction and sense. 
     These projections may reveal a distance P 1  and a distance P 2 . The distance P 1 , which stretches in a direction parallel to the planes of the strut  103  and of the wings  101  and  102 , separates opposite ends of the joggle  201 . A distance P 2 , that extends in the direction parallel to the plane of the strut  103  and of the wings  101  and  102 , separates the other opposite ends of the joggle  201 . In general, these distances P 1  and P 2  are different. 
     In the embodiment where the projections of ends are indistinguishable, the distance D 1  or the distance D 2  is zero. This embodiment is shown in dashes in the figure. 
     The joggle  201  thus has a completely different geometry from that of the joggle  104  of the structural element of  FIG. 1 . Indeed, the ends of the joggle  210  form a quadrilateral  210  wherein, contrary to a quadrilateral associated with the joggle  104 , no side is parallel to another. 
     The geometry of the joggle  201  is determined as a function of a space factor, a geometry of an external system, or stops surrounding the structural element  300 . The geometry can also be determined relative to a mechanical reinforcement indicated in a specifications sheet. 
     As compared with  FIG. 1 , the space  130  between the structural element  200  and the parts  121  and  122  are reduced so as to meet the requirements of an engineering and design department. In one example, this reduction of space meets the constraints related to a joining rigidity or a resistance between the parts  110  and  111 . 
       FIG. 3  shows steps of the joggling method used to make the joggled structural element of  FIG. 2 . This method is implemented on a straight structural element  300  comprising wings  101  and  102  of great thickness and small thickness. 
     To obtain the joggled structural element  300 , a fixed anvil  301  is made. This fixed anvil has a steep-sloped segment  302  stretching between two parts  303  and  304  parallel along the length L 2 . This length L 2  is proportional to a thickness E 2  of the wing  102  of small thickness. 
     Thus a punch  311  is made comprising a shallow-sloped segment  312  that stretches between two parts  313  and  314  parallel along a length L 1 . This length L 1  is proportional to a thickness of the wing  101  of great thickness. In one implementation of the method, the lengths L 1  and L 2  of the steep-sloped and shallow-sloped segments  302  and  312  are respectively equal to N times the thickness of the wing  101  of great thickness and N times the thickness of the wing  102  of small thickness. N is a real number which, in one example, is equal to 6. However, N varies as a function of the nature of the material out of which the structural element  300  is made. 
       FIG. 3   a  shows a step in which the wing  102  of small thickness of the structural element  300  is placed against the anvil  301 . Then the punch  311  is placed against the wing  101  of great thickness of the structural element  300 . 
     More precisely, ends of the steep-sloped end  302  are placed so that projections of the ends of the steep-sloped end  302  in the inverse sense of a push or pressure, are located between projections of the ends of the shallow-sloped segment  312  in the sense of the pressure. The punch  311  is then in an initial position. 
     In a particular implementation of the method, one end of the shallow-sloped segment  312  is placed so that the projection of this end is the same as the projection of an end of the steep-sloped segments  302 . 
     A distance P 1  is observed between an end of the steep-sloped segment  302  and an end of the shallow-sloped segment  312 . A distance P 2  is also observed between another end of the steep-sloped segment  302  and another end of the low-sloped segment  312 . These distances are observed along a direction parallel to the plane of the strut  103  and of the wings  101  and  102 . The length of these distances P 1  and P 2  can be adjusted by the positioning of shims  321  and  322 . 
     These two shims  321  and  322  furthermore maintain the punch  311  when it is placed against the wing  101  of great thickness. The shims  321  and  322  and the anvil  301  are fixed and connected to each other by means of parts  330  that can be fixedly joined to a frame. 
       FIG. 3   b  shows a step in which a pressure is applied to the punch  311 , so that this punch  311  and the anvil  301  imprint their shape on the structural element  300 . To exert this pressure, the shim  321  is withdrawn laterally and pressure forces are exerted on the punch  311 . These pressure forces F 1  are applied along a direction perpendicular to the planes of the wings  101  and  102  and in a sense going from the wing  101  of great thickness to the wing  102  of small thickness. As a variant, the shim  321  is not withdrawn and the anvil slips between the two shims  321  and  322 . More specifically, in this variant, the shim  322  does not shift laterally to release the punch. The punch  311  then has a degree of liberty enabling it to slide between the shims  321  and  322 . The shims  321  and  322  hold the punch  311  solely when it is being placed and then allow it to shift during the application of the pressure. 
     These forces F 1  are applied locally in a zone of the slope segments  302  and  312 . As a variant, these forces F 1  are not only applied in the zone of the slope segments  302  and  312 , but also in a zone surrounding these slope segments  302  and  312 . In applying the forces F 1  in a zone that surrounds the segments  302  and  312 , it is possible to obtain a more precise joggling, the slopes achieved in the joggling being very sharp. These forces F 1  may be generated by means of a press or a jack. A screw or any other mechanical machine exerting mechanical forces may also generate these forces F 1 . 
       FIG. 3   c  shows a step in which the joggled structural element is released from the grip of the anvil  301  and the punch  311  used in the method. In this step, first of all pressure forces F 2  opposite to the pressure forces F 1  are exerted so that the punch  311  is no longer in contact with the structural element  300 . Then, following the arrow B, the shim  322  is shifted so that the punch  312  is again blocked. As a variant, the shim  322  is not shifted laterally and the punch slides vertically between the shims  321  and  322  to return to an initial position. The shims  321  and  322  then have a configuration providing for a locking of the punch  311 . 
     The initial structural section  300  is joggled according to the dimensions of the anvil  301  and the punch. Indeed, in the joggle  201 , the slopes are formed on the side having the thick wing  103  and the side having the wing  104  of small thickness. Ends of the joggle  210  form the vertices of the particular quadrilateral  210 . In the variant in which end projections are indistinguishable, namely where the distance P 1  or the distance P 2  is zero, the quadrilateral  210  has a side perpendicular to a horizontal plane. 
     Then, along the arrow C, the structural section  100  is released from the anvil  301 . 
     Naturally, the slope segments  302  and  312  can be reversed. Thus, the punch  311  may comprise the steep-sloped segment  302  which extends over a length proportional to a thickness of the wing  102  of small thickness. The anvil  304  then has a shallow-sloped segment  312  which stretches over a length proportional to a thickness of the wing  101  of great thickness. The structural element  300  is then turned over so that each of its wings faces the slope segment that corresponds to it. 
     The structural element of the invention to be joggled herein has two wings but it could have more than two wings. The structural element to be joggled may, for example, have three wings or four wings that are parallel to one another, the joggled structural element obtained comprising the same number of wings. The punch then has a shape matching the number of wings of the structural element to be joggled. In a particular embodiment, the punch has several levels that get placed flat against the different wings of the structural element. 
     The joggling of the structural element can be done cold or hot. The determining of the temperature at which the structural element must be joggled depends on the shape of the section of this structural element and on the nature of the material out of which this structural element is made.