A construction and use thereof FIELD OF THE INVENTION AND PRIOR ART This invention relates to a construction comprising one or sev- eral ribs and a plate attached thereto by means of a connecting arrangement. Furthermore, the invention relates to the use of such a construction for the formation of a ceiling. Even though the invention will be described below for the purpose of exem- plification in respect of such ceilings, it is emphasised that the inventional construction also is usable in other connections. It is particularly emphasised that, even though the example describes an embodiment where the rib and the plate are curved, the inventional construction can also be utilised in such cases where the plate is in a plane state and the ribs are straight in the sense that they have their longitudinal extension in the plane of the plate.

It is for instance known to utilise constructions of the kind men- tioned by way of introduction as ceilings in structures such as railway-carriages. In such cases it is desirable that the plate is convexly curved in the direction towards the space where goods or people are to be. The ribs are located on the side of the plate facing away from said space. In order to achieve the curvature of the plate curved ribs are used, against which the plate is bent and fixed. A problem with known constructions has appeared to be that the used connecting arrangement for fastening the ribs and the plate has not been able to resist the strains caused as a consequence of relative movements between the ribs and the plate. Consequently, these strains have resulted in that the connecting arrangements have collapsed. According to known technique, glue joints have been used between the ribs and the

plate. Within the concept of"glue joints"are here embraced all sorts of glue-like joints, for instance enclosings in plastic or laminations of the ribs against one of the sides of the plates.

Broken glue joints can result in that the plates bend in an undesired way, i. e. that the plates will not completely follow the curvature of the ribs. The method used so far in attempting to prevent such failures is to make the connection between the ribs and the plate more and more high-strength, possibly by using means such as screws, bolt joints etc. However, this has not resulted in any satisfactory solution to the problem.

The problems mentioned above are caused due to the fact that the plate and the ribs are produced of different materials with different characteristics. As an example may be mentioned that the ribs can consist entirely or partly of aluminium, whereas the plates can be of a laminate of plastic. These different materials expand/contract differently at varying temperatures. A problem that is at least as serious, if not more serious, is that the laminate material of the plates tends to expand/contract more than the rib material at increasing/decreasing moisture content in the atmosphere.

PURPOSE OF THE INVENTION The object of the present invention is to provide ways to improve the connecting arrangement between rib and plate for the purpose of creating a connection able to maintain a satisfactory connection without for that sake there being a risk of varying parameters, such as temperature and humidity, degrading the connection or otherwise conferring unacceptable consequences on the construction, such as deformations.

SUMMARY OF THE INVENTION According to the invention, the posed object is solved in that the connecting arrangement comprises at least two connecting

means having a different function in relation to each other, namely a first connecting means for attaching, in a first con- necting zone limited in the longitudinal direction of the rib to an extension smaller than the length of the rib, the separate rib and the plate to each other undisplacably in the longitudinal direc- tion of the separate rib, and second connecting means for at- taching, in one or several second connecting zones separated from the first zone, the rib and the plate to each other with rela- tive freedom of movement between them in the longitudinal di- rection of the rib.

The recited solution implies that the connecting arrangement no longer has to overcome differences concerning the expan- sion/contraction of the ribs and the plate caused by varying pa- rameters, such as temperature and humidity. Instead, there is an undisplacable fastening between the rib and the plate in one single first connecting zone limited in the longitudinal direction of the rib, whereas in the other existing second connecting zone or zones there is relative freedom of movement between the plate and the rib. Expansions/contractions due to variations in temperature and/or humidity are consequently allowed to take place by relative movability in the second connecting zones so that such expansions/contractions no longer cause a build-up of strains being hazardous to the construction. In that way, it is guaranteed that the plate and the ribs will always be maintained in the desired state defined by the shape of the ribs, without subjecting the connecting arrangement to hazardous strains and without the plate being deformed, which occurred according to previous technique.

According to a preferred embodiment of the invention, the sec- ond connecting means in a separate second connecting zone is formed of at least one yoke fastened to the plate, in which yoke the rib is movably received. Other designs of the second connecting means are however also possible as long as relative movability is provided. For instance, the rib could be provided

with sections, which would be movably received in guides fastened to the plate.

According to a preferred embodiment of the invention, the first connecting means is formed of a glue joint between the rib and the plate. Consequently, this glue joint gives rise to the connec- tion between the plate and the rib, which is undisplacable in the longitudinal direction of the rib. However, a glue joint is not nec- essary for the application of the invention. Consequently, such a glue joint could be replaced by a screw joint or a bolt joint, which consequently forms the undisplacable connection. How- ever, in this case it is essential that the undisplacable connec- tion is limited to an extension in the longitudinal direction of the rib which is so small that expansions/contractions in the con- struction caused by varying parameters such as temperature and humidity will not result in an unacceptable build-up of strains. In this connection, it is pointed out that the first con- necting zone ideally should be almost point-like, i. e. have a minimal extension in the longitudinal direction of the rib. As a comment concerning the utilisation with screw joints or bolt joints, it is pointed out that such joints also would be possible to use in the second connecting zones where relative freedom of movement is required between rib and plate, but then particular measures have to been taken in order to provide said freedom of movement, as an example it may be pointed out that occur- ring screws or bolts would have to be displacable in relation to the rib, the plate or both, as seen in the longitudinal direction of the rib. This could be provided by means of oblong slits in rib and/or plate, in which case the longer dimension of the slits would have to be directed along the longitudinal direction of the rib. The preferred embodiment with glue joint and yokes, men- tioned by way of introduction, will however create prerequisites of achieving the advantage, which will later be described in more detail, that the side of the plate facing away from the rib does not have to show any signs of connecting means, which are disturbing in appearance.

Further features of the inventional construction are defined in the dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings: Fig 1 is a schematic view illustrating the inventional con- struction in a supporting structure, Fig 2 is an enlarged detailed view of the construction with its rib and plate, the rib being seen transversally to its longitudinal direction, Fig 3 is a view of the construction according to fig 2 seen from above, Fig 4 is a cut along the line IV-IV in fig 3 and Fig 5 is a cut along the line V-V in fig 3.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT As appear most closely from fig 2 and 3, the construction ac- cording to the invention has at least one rib 1 and a plate 3 fastened thereto by means of a connecting arrangement gener- ally denoted as 2. Depending on the size of the plate, two or more such ribs 1 can be arranged at a mutual distance and in an essentially parallel relation.

Primarily, the ribs are supposed to be prefabricated to the curved shape illustrated in fig 2, whereas the plate 3 from a plane initial state is supposed to be brought into the curved shape according to fig 2 and kept in this shape by means of the connecting arrangement 2. During the application of the con-

necting arrangement 2, the plate 3 is supposed to be hold in a suitable way against the rib, for instance by means of some suitable fixture. However, this is not anything crucial to the in- ventional idea; the plate 3 can very well be prefabricated to a curved shape corresponding to the shape of the rib, and besides the ribs 1 can be completely straight and the plate 3 completely plane in case any curvature is not at all required.

The connecting arrangement 2 comprises at least two connect- ing means having a different function in relation to each other, namely first connecting means, indicated with 4, for attaching the separate rib 1 and the plate 3 to each other, undisplacably in the longitudinal direction of the rib, in a first connecting zone, indicated by means of the circle 5, limited in the longitudinal direction of the rib to an extension smaller than the length of the rib, and second connecting means, indicated with 6, for attaching the rib and the plate to each other, with relative freedom of movement between them in the longitudinal direction of the rib, in second connecting zones indicated with 7 and separated from the first zone 5.

The first connecting zone 5 is suitably located in the central area of the rib, as appears from fig 2 and 3. However, this is not necessary. There is nothing to prevent that the first connecting zone 5 is displaced away from the central area of the rib; it would be possible to locate the first connecting zone 5 in the area at one of the ends of the rib so that an undisplacable con- nection between rib and plate occurs there, and instead locate one or several connecting zones 7, allowing relative movability, between this connecting zone, located at a first end of the rib, and the other end of the rib. The location of the two connecting zones 5,7 having different connecting characteristics depends on whether the relative movement between the rib and plate is to occur at both ends of the rib or only at one of the ends. Con- sequently, the conclusion is that there is a complete freedom to locate the connecting zone 5 anywhere along the longitudinal

extension of the rib 1, as long as the zone 5 is not having a longer extension in the longitudinal direction of the rib than al- lowing the avoidance of the problems, mentioned by way of in- troduction, with strains due to different expansion/contraction between rib and plate.

In the example it is illustrated how four second connecting zones 7 are present. The number of such connecting zones 7 can however vary from one and up depending on the conditions.

In case the first connecting zone 7 is located in the central area of the rib 1, at least one connecting zone 7 is arranged between each of the ends of the rib and the first connecting zone 5. In the example, the first connecting means 4 in the first connecting zone 5 is supposed to be formed of a glue joint between the rib and the plate.

The second connecting means 6 in each of the zones 7 is in the example intended to comprise at least one yoke fastened to the plate, in which yoke the rib 1 is movably received. This is more closely illustrated in fig 4. The yoke is here denoted 8. It has a part which is U-shaped in cross-section, in which part the rib 1 is received. Furthermore, the yoke is in the example provided with two flanges 9 extending outwards from the U-shaped part of the yoke, which flanges are fixed to the plate 3 by glue. Be- sides, the plate 3 is in fig 4 illustrated as consisting of two lay- ers, a first layer 10 of which can be a base layer, whereas the second layer 11 constitutes a surface layer located on the side of the plate facing away from the rib 1. An elastic insert 12 can be placed between the yoke 8 and the rib 1.

In the example it is illustrated how the yokes 8 have a relatively limited extension along the rib 1. However, there is nothing to prevent such a yoke being implemented as a relative long pro- file along the longitudinal direction of the rib 1, in which profile the rib is movably received. According to a variant, there could in the embodiment according to fig 3 be one single long yoke on

each side of the first connecting zone 5, which yoke extends from the first connecting zone 5 up to the respective end of the rib. In such a case, the yoke would have to be curved in corre- spondence to the curved shape of the rib and the plate. Moreo- ver, according to a further variant, one single long yoke of that kind could have essentially the same length as the rib and re- ceive the rib essentially in its entirety, in which case the first connecting zone 5 could be realised by the first connecting means 4 forming a fixed connection between this elongated yoke, in itself fastened to the plate 3, and the rib 1, for instance in that the first connecting means 4 would be implemented by means of fastening members in the form of a screw or a bolt extending through the rib 1 and the lateral shanks of the yoke 8.

This would bring about an embodiment where the second con- necting zone 7 could be said to overlap the first connecting zone 5. The definition occurring in claim 1 that one or several occur- ring second connecting zones 7 is to be separated from the first connecting zone 5 is consequently to be interpreted in a wide sense. For the purpose of the invention, it is sufficient if the term"separated"in this respect implies that the second con- necting means in the form of for instance one or several yokes 8 is to be capable of establishing a relative freedom of movement between rib and plate allowing connection in a zone which is to be possible to define as separated from the first connecting zone 5, but an overlapping of the zones 5 and 7 does not con- flict with the inventional idea.

In fig 1 it is illustrated how the inventional construction appear- ing from fig 2 is integrated in a supporting structure generally denoted as 13. According to a preferred embodiment, the con- struction is here hold in the supporting structure 13 in that out of two edges 14 of the plate 3 extending transversally to the longitudinal direction of the rib 1, at least one is movably re- ceived in a mounting 15 of the supporting structure 13. In prac- tice, it is preferred that both of these edges 14 are received in associated mountings 15. These mountings suitably have a fe-

male-like character and receive the edges 14 of the plate 3 with such a clearance that maximally possible expansion of the plate 3 will not result in that the edges 14 of the plate will be pressed against the bottoms of the thus female-like mountings and cause strains in the construction or the supporting structure 13. The in- ventional construction forms, according to fig 1, a limiting sur- face, denoted as 16, for a space in the supporting structure, which space is denoted as 17. It is the side of the plate 3 facing away from the rib 1 that forms this limiting surface 16.

In the example of fig 1, the intention is that the limiting surface 16 is to form a ceiling. This will be convexly curved in direction towards the space 17. In the example, the supporting structure 13 is intended to constitute the ceiling section of a vehicle, in particular a railway-carriage. Consequently, the space 17 is in- tended to constitute a space for receiving goods or persons. The curved shape of the inventional construction provides a spare space 18 behind the same, in which electric fittings etc can be placed.

The invention is of course not only limited to the illustrated em- bodiment. Above it has been described how the invention can be modified without departing from the field of protection defined by subsequent claims. Further modifications are possible to per- form for men skilled in the art, once the inventional idea has been presented. Within the scope of such modifications are choices of other connecting means than those exemplified above. Consequently, the present invention does not relate to choices of certain connecting means known per se, but uses these on one hand for the establishment of a satisfactory con- nection but on the other hand this connection allows expan- sions/contractions caused by relative movements between rib and plate.