Abstract:
A vehicle construction includes a body with a base, a roof, two longitudinal walls joining the base and the roof and at least four wheels connected to the base, which base, roof and longitudinal walls comprise sandwich panels which are jointed to one another at their longitudinal edges. The thickness of the sandwich panel forming the base is of the same order of magnitude as the thickness of the roof or sandwich panel forming a longitudinal wall and the sandwich panels of base, roof and longitudinal walls form a bending- and torsion-resistant tube.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a vehicle construction comprising a body with a base, a roof, two longitudinal walls joining the base and the roof and at least four wheels connected to the base, which base, roof and longitudinal walls comprise sandwich panels which are jointed to one another at their longitudinal edges. 
     A vehicle construction of this type, constructed as a rail vehicle, is disclosed in FR-A 2 704 507. The body of this known vehicle is positioned on a fairly high base construction, which base construction consists of a sheet of sandwich material which has longitudinal reinforcements on its underside, in the region between the two bogies. 
     The known vehicle construction has the disadvantage that the floor thereof is at a high level, which depends on the height of the longitudinal reinforcements beneath the baseplate. A construction of this type is not suitable for vehicles which are intended for short distance transport, for example local transport. For transport of this type it is important to facilitate entry and alighting as far as possible, tow which end as low as possible a floor is preferably used. 
     A relatively low, flat loading deck is already used in vehicles of conventional construction, that is to say vehicles with a normal chassis of steel girders with a super-structure of lattice construction mounted thereon. However, said vehicles lack the advantage which the construction using sandwich panels provides, such as a low mass and modular construction, which makes possible variations in the design and size of the vehicles. Moreover, the fuel consumption is high as a consequence of the relatively heavy construction. 
     SUMMARY OF THE INVENTION 
     The aim of the invention is, therefore, to provide a vehicle construction of the abovementioned type which, on the one hand, has the advantages of a sandwich construction, such as lower mass, and which, on the other hand, nevertheless offers a low, float loading deck. Said aim is achieved in that the thickness of the sandwich panel forming the base is of the same order of magnitude as the thickness of the roof or sandwich panel forming a longitudinal wall and in that the sandwich panels of base, roof and longitudinal walls form a bending- and torsion-resistant tube. Such a tube is self-supporting and does not require a separate supporting frame. 
     With the self-supporting vehicle construction according to the invention the required rigidities are supplied by the panels which act together as a tube. That is to say, flexural stresses in the longitudinal direction are taken up by both the roof and the base. The advantage of this is that the base does not have to take up the entire bending moment, as a consequence of which the thickness of the baseplate can remain restricted to the same order of magnitude as the thickness of the sandwich panel concerned. 
     Furthermore, a sandwich floor construction makes it possible to achieve a flat floor over a substantial length of the vehicle, With conventional designs this flatness is restricted to a few meters. As a result it is possible, for example, to give a 10 meter bus the same transport capacity as a conventional 12 meter bus. 
     The floor of the vehicle, which deck is completely free from reinforcing ribs and the like projecting downward from the underside, can consequently be located at a low height above the road. The vehicle construction according to the invention is thus outstandingly suitable for local transport, such as a tram or bus, since with this construction the advantage of a relatively low weight (advantageous in connection with frequent braking and pulling away from stops) is combined with a low entry height. 
     In particular, the thickness of the sandwich panel forming the base can be between 1.5 and 2.5 times as great as the thickness of the sandwich section forming the roof. 
     Preferably, the thickness is approximately twice as great as the thickness of the sandwich section forming the roof. 
     As is known, a sandwich construction is particularly suitable for absorbing distributed stresses which are not generated as concentrated point or line stresses. A construction of this type can also certainly be stressed in its plane; on absorption of stresses perpendicular to its plane, separate measures must be taken which make it possible for gradual introduction of such stresses. 
     In this context the sandwich panels forming the longitudinal walls can, according to a further improvement, be integrally extended at their underside by an essentially horizontal base strip, the base strips being fixed to the longitudinal edges of the sandwich panel which forms the remainder of the base. 
     In contrast to the vehicle construction disclosed in FR-A 2 704 507, there is no stress concentration in the corner join between longitudinal walls and base. Especially in the case of a fully laden deck, the bending moments in the transverse direction at the location of such a corner join can give rise to high stresses, which must be absorbed by supplementary frame components. 
     Preferably, the transverse dimension of each strip and of the sandwich panel joined thereto are chosen such that under nominal stress the bending moments, viewed in the transverse direction, are minimal at the location of the join between strips and base panel. 
     The join between said parts is consequently subjected to hardly any flexural stress, with the advantage that lightweight edge sections which are integrated in the sandwich panels can suffice at this join. 
     As has been stated, the base of the vehicle construction according to the invention can be located at a low height above the road. The entry and alighting height can be kept as low as possible if recesses to accommodate wheels are provided in the sandwich panels forming the base and the longitudinal walls, one wheel housing being fixed to the edge of each of said recesses. Moreover, the vehicle can be equipped with conventional wheelchair access installations. 
     Said wheel housings are preferably likewise made of a sandwich material. The tube construction of the body remains closed as a result, such that the wheel recesses produce virtually no weakening. 
     The support points for the wheel suspension are integrated in the sandwich panel forming the base. 
     The suspension points for wheels and power source consist of mounting plates with a rubber bearing, which mounting plates are each surrounded by and are fixed to reinforcing sections which are incorporated in the sandwich panel of the base. The supporting forces provided by the wheels can thus be transmitted uniformly into the baseplate, such that the sandwich construction is able to transmit these stresses in an optimum manner. 
     The sandwich panels forming the base, the roof and/or a longitudinal wall can carry fixing sections on their longitudinal edges facing one another, by means of which fixing sections said sandwich panels are fixed two by two. 
     The longitudinal walls may consist of mutually connected wall modules. The length of the longitudinal walls may be adapted easily thereby, dependent from the vehicle length. Moreover, damaged parts may be replaced in a convenient way. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be explained in more detail below with reference to a few illustrative embodiments shown in the figures. 
     FIG. 1 shows a (partial) exploded view of a bus construction according to the invention. 
     FIG. 2 shows a corresponding view of a tram construction. 
     FIG. 3 shows a perspective view of the finished bus construction. 
     FIG. 4 shows a corresponding view of the finished tram construction 
     FIG. 5 shows a top view of that sandwich panel of the bus construction which forms the base. 
     FIG. 6 shows a partial perspective and cross-sectional view of the bus construction, 
     FIG. 7 shows a detail of the body. 
     FIG. 8 shows detail VIII—VIII according to FIG.  5 . 
     FIG. 9 shows detail IX according to FIG.  6 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The bus construction shown in FIGS. 1 and 6 comprises a base  1 , roof  2  and two longitudinal walls  3 , which consist of modules  4 ,  5 ,  6 , each constructed as a sandwich panel. Each of the base  1 , roof  2 , and walls  3  is made up of two skins  7 ,  8 , between which a core material  9  is incorporated. For the base  1  and the roof  2 , the skins can, for example, be made of aluminium, the panels for the longitudinal walls  3  can, for example, comprise skins of glass fibre-reinforced material. 
     Windows  10  are glued into the longitudinal walls  3  in a known manner, such that the longitudinal walls  3  have a sufficiently high shear resistance, despite the large openings. 
     As can be seen in FIGS. 6-9, the longitudinal walls  3  are fixed to the base  1  and, respectively, the roof  2  at their longitudinal edges by means of integral fixing sections  11 ,  12 . 
     The sandwich panels forming the longitudinal walls ( 3 ,  43 ) may be integrally extended at their underside by an essentially horizontal base strip ( 33 ), the base strips ( 33 ) being fixed to the longitudinal edges of the sandwich panel which forms the remainder of the base ( 1 ,  41 ). Further, the sandwich panels forming the longitudinal walls ( 3 ,  43 ) may be integrally extended at their top by an essentially horizontal roof strip ( 35 ), the roof strips ( 35 ) being fixed to the longitudinal edges of the sandwich panel which forms the remainder of the roof ( 2 ). 
     As can be seen in FIG. 1, the body of the bus construction is completed by a front wall  13  and rear wall  14 , which contain, inter alia, a windscreen  15  and, respectively, a rear window  16 . Said front wall  13  and rear wall  14  can also be fixed at their edges to the longitudinal walls  3  and, respectively, the base  1  and the roof  2 , such that the finished body construction has an appreciable rigidity with respect to torsion and bending. 
     As is shown in FIGS. 1 and 5, the baseplate has integral fixing sections  17 ,  18  which run in the longitudinal direction. Furthermore, a number of integral fixing sections  19  which run in the transverse direction are provided. 
     Fixing sections of this type can also have been fitted in the sandwich panels forming the roof  2  and the sandwich panels forming the side walls  3 . 
     A number of suspension points  20  for the front wheel assembly  22  and a number of suspension points  21  for the rear wheel assembly  23  are arranged between said integral fixing sections  17 - 18 . Said wheel assemblies are fixed to the suspension points  20  and  21 , respectively, by means of mounting plates  24 , each of which has a rubber bearing  25 , by which mean vibration-free support of the body construction is ensured. 
     Suspension points  26  and support  27  which carry the power source  28  and the transmission are also accommodated in the sandwich panel forming the base  1 . 
     At its rearmost end, the sandwich panel  1  forming the base is constructed such that it rises stepwise, in such a way that space is created for the power source  28 . This construction is entirely dependent on the type of drive to be installed. This construction is generic to such an extent that various drive lines are simple to attach. 
     The sandwich panel  1  forming the base is flat on its underside, such that the floor surface, as defined by said panel  1 , can be located at a low level. In this context, recesses  29 ,  30  are made in said panel in order to create space for the wheels. Corresponding recesses are also made in the longitudinal walls  3 . Said recesses are closed off by means of wheel housings  31 ,  32 , which preferably are also made of sandwich material, in such a way that a complete body construction having the requisite flexural and torsional rigidity is obtained. 
     The tram construction shown in FIGS. 2 and 4 in principle corresponds o the bus construction shown in the other figures. Said tram construction consists of a sandwich panel  41 , forming the base, and sandwich panel  42 , forming the roof, as well as longitudinal wall modules  44 ,  45  and  46 , which form the longitudinal walls  43 . 
     The base  41  is provided with suspension points  47  to which the live ring of bogies  48  is fixed. 
     Here again the baseplate  41  is provided with recesses  49  to accommodate the wheels (not shown) of the live rings  48 , as a result of which the floor of the base  1  can remain at a low level. 
     The wheel housings  50  cover the recesses  49  in the base  41  and corresponding recesses in the longitudinal walls  43 . 
     The base  41  is also provided with a turntable  51  for coupling up to a further rail vehicle. 
     The front of the rail vehicle is closed by means of a front wall  52  consisting of rigid panels and a windscreen  53 . 
     FIG. 6 also shows two seat rails  60 ,  61 , one of which is also shown in cross-section in FIG.  7 . Each seat rail  60 ,  61  has an outside  62  shaped correspondingly to the contour of longitudinal wall  3 , in particular the contour of the base strip  33  the wall strip  34  adjoining the latter, and a sloping inside  63 . The interior space enclosed between the sides  62 ,  63  is divided into two hollow spaces  65 ,  66  by means of partition  64 . 
     The seat rail  60 ,  61  is fixed to walls  3  and forms a rigid element from which the seats can be suspended. To this end the seat rail has two longitudinal slots  67 ,  68 . The upper longitudinal slot  67  is undercut, such that rod  75  of a seat frame can be hooked therein and can be retained against tensile forces. 
     The lower longitudinal slot absorbs the compressive forces from rod  69  of the seat frame. 
     The seat rails  60 ,  61  thus absorb the concentrated forces generated by the local points of engagement of the rods  75 ,  69  of the seat frames and transmit these, uniformly distributed, to the longitudinal wall  3 . 
     The cross-section shown in FIG. 8 shows the linking section  70  in that part of the sandwich panel  1  which rises stepwise, which linking section joins the horizontal panel section  72  to the vertical panel section  71 . 
     To transmit the stresses between said sections  71 ,  72 , the section has tubing  73  which is divided by partition  74  into two areas of triangular cross-section. Said triangular shapes provide high rigidity, without the wall thicknesses of linking section  70  having to be too high. 
     The section  70  also has flanges  75 , between which the panel sections  71 ,  72  can be accommodated and fixed by means of bolts or pins  76 .