Coach bodies for e. g. railway coaches have conventionally been produced as self-supporting hollow boxes built up around a construction of iron or aluminium sections clad with iron or aluminium plates. However, such a construction is relatively heavy and furthermore has the serious disadvantage of not having in itself a nice, even'surface with an acceptable finish neither on the inside or the outside. Therefore, the construction must be painted and internally be fitted with a thermal and acoustic insulation of e. g. foamed plastic, and an outer cladding of wood or plastic. Thereby, the coach bodies will be expensive to produce and difficult to maintain. Such a coach body is known from e. g. US Patent No. 5,287, 813.

With a view to overcome these problems solutions have been devised that aim at constructing the walls of the coach bodies as sandwich constructions with a core of e. g. foamed plastic cast together on either side with an outer layer of fibre- reinforced plastic. Thereby, both the inside and the outside of the walls are immediately given an acceptable finish simultaneously with especially the foamed plastic core providing the desired thermal and acoustic insulation.

Such coach bodies are known from US Patent No. 5,042, 395, US Patent No 3,100, 458, and FR Patent No. 2,613, 995, which however are not designed as self-supporting, integral hollow boxes.

US Patents Nos. 6,122, 125 and 5,857, 414 describe coach bodies with longitudinal reinforcements that in the afore-mentioned case consist of banding of metal or fibre reinforced plastic

extending along the roof and floor of the coach body and in the last-mentioned case consist of bars of fibre-reinforced plastic located near the roof of the coach body and anchored in the ends of the coach body.

In one aspect of the invention a coach body of the kind mentioned in the opening paragraph is provided that is light and self-supporting.

In a second aspect of the invention a coach body of the kind mentioned in the opening paragraph is provided that is reinforced by reinforcements located inside the walls of the coach body.

In a third aspect of the invention a coach body of the kind mentioned in the opening paragraph is provided that is constructed as an integral unit.

In a fourth aspect of the invention a coach body of the kind mentioned in the opening paragraph is provided that has walls that in themselves are thermally and acoustically insulating.

In a fifth aspect of the invention a coach body of the kind mentioned in the opening paragraph is provided that has walls that in themselves are vibration reducing.

In a sixth aspect of the invention a coach body of the kind mentioned in the opening paragraph is provided that in use has a small deflection and low natural frequency.

In a seventh aspect of the invention a coach body of the kind mentioned in the opening paragraph is provided that has a simple construction and is inexpensive to produce.

In an eight aspect of the invention a method is provided for producing a coach body of the kind mentioned in the opening

paragraph having a desired complete finish on both the inside and outside of the walls of the coach body.

The novel and unique feature according to the invention, whereby this is achieved, is the fact that at least one of the walls of the coach body is at least partially constructed as a sandwich construction comprising a mainly plate-shaped core of foamed plastic having two sides and two edges, at least one carbon fibre bar located along at least one of the edges of the core, at least two two-way reinforcements extending along each their side of the core and the at least one carbon fibre bar and made of steel with a breaking strength of minimum 70 kPa, two outer layers preferably made of fibre-reinforced plastic and extending along the outer side of each their two- way reinforcement, and a matrix of plastic for joining the outer layers, the two-way reinforcements, the core, and the carbon fibre bars.

A coach body can obtain the required strength in a conventional way by using e. g. the longitudinal reinforcements described in the above US Patents Nos. 6,122, 125 and 5,857, 414. The strength cannot be greater because use is instead made of carbon fibre bars with a far greater specific strength. This is due to the fact that the strength of the coach body is not defined by the carbon fibre bars but by the weakest link of the construction, which is the plastic and the adhesion between this and the surface of the carbon fibre bars. The very great strength of the carbon fibre bars are therefore only utilized to a very small extent.

The two-way reinforcement can be composed of at least two layers of mainly parallel steel wires located with a relatively small spacing and forming an angle with the wires in at least one second layer. This two-way reinforcement is suited for. absorbing especially shear forces affecting the coach body and it furthermore advantageously contributes to

the great rigidity, the small deflection and low natural frequency of the coach body.

To avoid disturbing and disfiguring exterior reinforcements, the carbon fibre rods and the two-way reinforcements can furthermore be embedded in the walls of the coach body.

In one embodiment at least the side walls of the coach body can be constructed as a whole sandwich construction.

The walls of such a coach body are normally broken by openings for doors and windows. These openings weaken the structure which therefore can be reinforced in these places by at least one additional carbon fibre bar embedded in an area above the opening and/or by a frame of carbon fibres embedded in an area around the opening.

In a second embodiment the sandwich construction can be in the nature of bars extending along an upper area of the side walls of each coach body. In this case the forces affecting the body coach to flection are essentially absorbed by these bars. In the floor of the coach body one or more carbon fibre bars can furthermore be embedded for strengthening the structure additionally.

Each carbon fibre bar can conveniently be composed of a number of smaller parallel carbon fibre bars joined by a plastic.

If the components of the sandwich construction are cast together in a two-sided form by means of infusion casting, the very great advantage is obtained in that both the outside and inside of the walls of each coach body are immediately given a surface of an acceptable ready-made finish that either can be left as it is or also can be painted if desired.

In an advantageous embodiment of the method according to the invention the vertical walls can be cast in a first process step, after which the two vertical walls are infusion cast in a subsequent process step in two-sided forms together with sandwich constructions forming the horizontal walls of the coach body. Thereby the coach body will form an integral unit.

The invention will be explained in greater details below, describing only exemplary embodiments with reference to the drawing, in which Fig. 1 is a fractional cross-sectional exploded view of a sandwich construction for a wall for a coach body according to the invention, Fig. 2 is the sandwich construction in fig. 1 in a state cast together, Fig. 3 is a longitudinal view of the sandwich construction in fig. 1, Fig. 4 is a perspective exploded view of a coach body according to the invention, Fig. 5 is a view of the coach body in fig. 4 in a state cast together, Fig. 6 is on a larger scale a cross-sectional exploded view of a bar for the coach body in figs. 4 and 5, Fig. 7 is the view in fig. 6 in a state cast together, Fig. 8 is a side elevational fractional view of a vertical wall for a second embodiment of the coach body according to the invention partly in section,

Fig. 9 is a cross-sectional view of the casting of a bottom, which during this is integrated, with two of the side walls in fig. 9, Fig. 10 is a cross-sectional view of the casting of a roof which during this is integrated with two of the side walls in fig. 9, and Fig. 11 is a cross-sectional view of the finished coach body.

In the following it is assumed that the coach body according to the invention is used for a rail vehicle such as e. g. a carriage or tramcar. It is noted that the coach body however also can be used for other purposes, for example a bus.

The coach body is constructed of composite materials and preferably by means of infusion casting which is a casting method known to a person skilled in the art.

Fig. 1 is a fractional exploded view of a sandwich construction for a wall for the coach body according to the invention. The components forming part of the construction are, given in succession from within, a mainly plate-shaped core 1 made of a solid plastic foam, a carbon fibre bar 2, two sets of wire layers 3 with steel wires 4, and two sets of fibre glasses 5.

Within the scope of the invention the wall can however be constructed with a different number of carbon fibre bars, wire layers, and fibre glass layers than the ones mentioned above.

Fig. 2 shows the components cast together by means of a suitable plastic 6, which for example can be Epoxy, Vinylester, Polyester, Acrylat, or Fenol, and which together with the fibre glasses 5 form an outer layer 7 and a matrix for the steel wires 4.

Casting takes place in a form provided with surfaces forming, as impressions on the surfaces of the respective wall, a desired beautiful, smooth finish. This finish can readily stand alone but can also be painted if desired.

The reinforcements are placed inside the sandwich construction. A wall completely or partly constructed in this way is therefore not disfigured by outer reinforcements.

Thereby the advantage is obtained in that there is no need to fit the coach with expensive, inside claddings.

Furthermore the thermal and acoustic insulation of e. g. foamed plastic is furthermore saved, which conventionally is mounted on the inside of the wall as especially the core of the wall fulfils the last-mentioned function.

In fig. 3 showing a longitudinal section through the sandwich construction in fig. 2, it is seen that the carbon fibre bar 2 is extending in the longitudinal direction whereas the steel wires 4 in one of the wire layers 3 intersect the steel wires 4 in the second wire layer 3 at an angle of 90°.

The carbon fibre bar 2 is essentially intended for absorbing the forces affecting the sandwich construction to flection whereas the intersecting wire layers 3 are essentially intended for absorbing the shear stresses.

Use of carbon fibre bars means that the sandwich construction and thereby the coach body according to the invention obtain a very great rigidity and a very low weight. This combination furthermore ensures that the allowable deflection and natural frequency are respected with a coach body which is simple and inexpensive to produce.

The two-way reinforcement is suited for absorbing especially the shear forces that affect the coach body, and it

furthermore advantageously contributes to the great rigidity, small deflection and low natural frequency of the coach body.

For the purpose steel with a breaking strength of minimum 70 kPa is used.

The properties of the composite structure furthermore mean that a coach body with walls according to the invention in itself acts reducing on the vibrations which the coach body is subjected to during operation.

Figs. 4 and 5 show an exploded view and a cast state respectively of a coach body according to the invention for a tramcar.

The coach body has a roof 8, a floor 9, and two side walls 10.

In each side wall are made, in this case, two door openings 11 and two window openings 12.

The coach body is reinforced by two bars 13 in form of sandwich constructions 13 embedded in an upper area of each side wall 10, and two longitudinal-and transverse respectively carbon fibre bars 14 and 15 embedded in the floor. The side walls 10 are cast together with the roof 8 and the floor 9 in a way that will be described in detail later on.

The load on the floor is transmitted via the side walls 10 to the bar 13 which thus serves for chiefly absorbing the loads affecting the coach body to flection.

Figs. 6 and 7 show in detail that the bar 13 is constructed in the same way as shown in figs. 4 and 5. Like parts are therefore similarly referenced. In this case the carbon fibre bars are however composed of several smaller carbon fibre bars adhered to each other by means of an adhesive.

Fig. 8 is a side elevational fractional view partly in longitudinal section of a side wall for a second embodiment of a coach body. This wall is in its entirety constructed as a sandwich construction according to the invention.

A carbon fibre bar 16 is embedded in an upper area of the side wall and a second carbon fibre bar 17 is embedded in a lower area. These carbon fibres serve for absorbing bending stresses from loads on the coach body. Shear stresses are absorbed by the intersecting wire layers 18 embedded in the side wall.

The side wall is constructed with door openings 19 and window openings 20. However, these openings weaken the function of the side walls as load-carrying structure.

A carbon fibre frame 21 is therefore embedded in the area around each window opening 19 and an additional carbon fibre bar 22 is embedded above each door opening 19, and a carbon fibre frame (not shown) can possibly also be embedded in an area around the door openings. The carbon fibre frame 21 and the additional carbon fibre bar 22 compensate for the part of the side wall that is missing in the door opening 19 and the window opening 20 respectively.

Figs. 9,10, and 11 show how an integrated coach body with two of the side walls 23 shown in fig. 8 is made.

In this case the side walls 23 are constructed with lower and upper, respectively, legs 24 and 25 forming an angle with the actual side wall.

In fig. 9 the two side walls 23 are with their lower legs 24 first placed on top of and possibly sucked onto a first lower form part 26.

Then the components 1-7 described above and shown in figs.

1,2, and 3 are placed in dry state on top of the first lower form part and at least partly on top of the lower legs 24, after which a first upper form part 27 is placed on top of these components and at least partly also on top of and possibly sucked onto the lower legs 24.

Now the two form parts 26 and 27 together with the side walls 23 and the lower legs 24 of these walls form a closed form which, by means of infusion casting, is filled with a suitable plastic which as matrix casts the components together.

When. the plastic has tempered, the form parts 26 and 27 are removed via an opening in the end of the coach body. The floor 28 of the coach body has now been formed and simultaneously been cast together with the side walls 23 and/or the legs 24 of these walls.

This situation is shown in fig. 10, in which a second lower form part 29 is placed and possibly sucked up under the upper legs 25 of the two side walls.

Then the components 1-7 described above and shown in figs.

1,2, and 3 are placed in dry state on top of the second lower form part 29 and at least partly also on top of the upper legs 25, after which a second upper form part 30 is placed on top of these components and at least partly also on top of and possibly sucked onto the upper legs 25.

The two form parts 29 and 30 together with the side walls 23 and the upper legs 25 of these walls now form a closed form which, by means of infusion casting, are filled with a suitable plastic which as matrix casts the components together.

When the plastic has tempered, the form parts 29 and 30 are removed via an opening in the end of the coach body.

The roof 31 of the coach body has now been formed and simultaneously been cast together with the side walls 23 and/or the upper legs 25 of these walls.

This situation is shown in fig. 11 in which the finished coach body 32 now appears as an integrated unit.