TRAILER TO BE COUPLED TO A VEHICLE, AND METHOD AND MOULD FOR THE MANUFACTURE OF COMPONENTS FOR SAME

Abstract: A trailer (2) or caravan for coupling to a towing vehicle is normally composed of a series of different materials which react differently to temperature variations and moisture. Also, their corrosive characterisitics are very different and herewith also their lifetime and thus the lifetime of the trailer. The production of the known trailers with said diverse materials requires considerable working operations, and involves up to several different trade groups in connection with the assembly. With the object of achieving longer lifetime, less weight and herewith greater loading capacity, and also lower production costs, a trailer (2) of the kind disclosed is characterised in that the superstructure (6), the chassis (4) and towing-bar/triangle (8) consist of one and the same self-supporting construction of composite materials comprising external shells between which a core of suitable core material is placed. A method and a mould are also disclosed for the forming of items (16) of PVC-based cellular plastic.

Description: Trailer to be coupled to a vehicle, and method and mould for the manufacture of components for same. The present invention concerns trailers or camping caravans which are to be coupled to a towing vehicle, and a method and a mould for the manufacture of components for same . Such trailers/caravans are well-known and are mass produced, and are built following quite traditional construc- tion methods and design. Normally, the construction of such a trailer consists of a chassis built up of metal profiles on which some form or another of superstructure is placed, e.g. an open/closed bed for use in the transport of articles, goods or livestock, or in certain cases a shed or a cabin consisting of an insulated bottom-, wall- and ceiling-plates, so that the cabin can be used for habitation, as a sales- vehicle or for similar purposes. Under the chassis there are mounted axles, wheels, brakes and equipment with which the trailer can be towed etc. The construction is configured in such a manner that it is the chassis which is the supporting part of the trailer. In addition to being self-supporting, the chassis must thus also support the superstructure which is chosen to be placed on the trailer, and that load which is placed on/in the super- structure. This means that with the known methods of construction, the result is generally a construction with relatively great weight in relation to the load-carrying capacity, in that as rule there are certain limitations on the total weight . Moreover, the known trailers are composed of a number of different materials, such as iron, steel, aluminium, wood, sheets of wood-fibre and plastic, possibly insulated with foam of various kinds, rubber and diverse screws, bolts, rivets etc. These materials react differently to variations in temperature, moisture and wear, and their corrosive characteristics are very different, and herewith also their lifetime and the lifetime of the trailer. Moreover, the construction of the known trailers with said materials involves many working operations, and also up to several different trade groups in connection with the assembly. Furthermore, the existence of the many different materials in the construction calls for a great deal of maintenance of various kinds, and moreover it will be difficult to undertake renewal of the appearance and construction of such trailers while using traditional materials and concepts. Attempts to achieve a certain degree of freedom with regard to the construction of trailers have resulted in the superstructures for trailers being configured as units moulded in one piece, for example as sandwich-built units consisting of an external and an internal plate construction, between which an insulating foam material is placed for the insulation of the superstructure. An example of this is disclosed in EP 0 061 919 A2 , which shows a trailer floor moul- ded in one piece, consisting of glass-fibre reinforced plastic with a core of polyurethane foam, and comprising an under-frame in the form of longitudinal beams for the strengthening of the floor. However, it is not disclosed how the floor of the trailer is supported on wheels for mobility, which means that it must be assumed that this construction is configured to be placed on a chassis of traditional construction. EP 0 102 777 Al discloses an example of an integrally-moulded construction of a supporting truck bed which is built up of glass-fibre reinforced plastic filled with foamed plastic material, but also this is intended for mounting on a traditional chassis with wheels, brakes etc. The above-mentioned publications are all examples of constructions of self-supporting superstructures which for transport are suitable for mounting on a traditional chassis supported by wheels, and provided with brakes, towing equipment etc., and where the object is to provide a quick changeover capability in connection with the use of a standard chassis with different types of superstructures, and hence with the subsequent disadvantages in the form of relatively great weight, corrosion etc. From DK 0603/91 L there is known a sales vehicle which has a car-bed moulded substantially in one piece in a self-supporting sandwich construction of at least two layers of glass-fibre reinforced plastic with at least one intermediate layer of plastic. However, in the cases where the sales vehicle is mobile, its construction comprises an integrated axle shaft of metal, and a tow bar, similarly of metal, and consequently with the above-mentioned disadvantages. With the invention, however, it has been realised that the above-mentioned disadvantages with trailers of the disclosed type can be overcome with a construction where the superstructure, chassis and tow-bar/triangle consist of one and the same self-supporting construction of composite materials, comprising external shells between which a core of suitable core material is disposed. Considerable advantages are achieved hereby, including a reduction in the weight of up to 50%, which provides greater loading capacity and herewith fewer transports and reduced driving (lower fuel consumption) . Moreover, considerable advantages are achieved with regard to the shape of the trailer, so that the wind resistance can be reduced. Furthermore, the said materials do not corrode, which means that the lifetime of the trailer is increased to a considerable degree, and herewith also the resale value of the trailer. With the construction of the trailer according to the invention without an independently built-up chassis, the possibility is also provided for a completely free configura- tion of the trailer, in that both supporting and non- supporting parts of the trailer are built up of materials which belong to the same family, which means that the characteristics of the materials can be utilised in an optimum man- ner in connection with construction strength and shape. It is thus possible to produce trailers with an external design which matches the cars from different manufacturers, and which further satisfy various customer requirements regarding design. With the view to achieving a lower centre of gravity for the trailer according to the invention, the wheel suspensions can consist of a through-going axle which is an integrated part of the construction of the self-supporting bed. There is hereby achieved greater stability when driving with the trailer, and lower costs in the form of energy consumption during transport as a consequence of the lower wind resistance. A further advantage achieved with this configuration is that the wheel suspensions constitute a reinforcement of the loading capacity of the bed of the trai- ler. The through-going axle can with advantage also consist of a rubber torsion-bar suspension axle, whereby there is achieved a further lowering of the centre of gravity of the trailers/caravans which require a suspension system. Out of regard for a reduction of the weight of the trailer, the through-going axle or the rubber torsion-bar suspension axle can with advantage consist of a tube made of an extruded composite material . This provides the further advantage that use is made of an axle material which has the same material characteristics as the remaining part of the trailer, which reduces stresses in the construction under conditions of varying temperature. Out of regard for the prevention of corrosion in cables etc. in connection with brakes, the trailer can fur- ther comprise rod connections configured in suitable composite materials and led through channels, similarly configured in suitable composite material, between the coupling link and brake mechanism. The construction of trailers according to the invention will necessitate assemblies in corners, transitions between roof and walls, and walls and floor/bed etc. Normally, the assemblies here are effected by the cutting of the core material together with the cutting of bevels on the a- butting assembly surfaces, or by obtuse butt assembly followed by a gluing together of said surfaces, after which the core material is covered with flexible composite sheet material, the abutting side edges of which are often bevel ground, after which said sheet material is glued to the sur- faces of the core material, whereby a sandwich construction with particularly good strength characteristics, insulation characteristics etc. is achieved. The above-mentioned traditional methods of assembly are relatively labour-demanding, and are used mainly at edge and corner assemblies, but materials are known for establishing of rounded transitions, e.g. between roof and sides, comprising rod-shaped, rectangular elements of the core material which are glued at intervals to a fibre matting, so that in the laying of a number of the above-mentioned elements over e.g. a curved template, and subsequent fixing by the application of an adhesive, for example epoxy, a more-or-less rounded transition with e.g. a 90 -degree angle can be achieved. In order to obtain a completely rounded transition, as a consequence of the rectangular shape of the rods it will be ne- cessary to carry out a subsequent grinding of the corner part. Hereafter, the finished corner part is inserted as transition element between the surfaces to be assembled, and is glued to the opposing end surfaces. However, with the invention it has been realised that the forming of rounded parts of certain types of PVC- based, plate-formed core materials can be effected without the need for subsequent grinding-away of edges, this being carried out by heating the plate- formed core material to a given temperature, and subsequent insertion of the heated material in a mould heated to a preferred temperature, in which over a suitable period of time the material is cooled down to a temperature at which the material becomes stable in shape, after which the formed material is removed from the mould and used in the assembly of two adjoining side surfaces. There is hereby achieved a saving in working operations, including the fixing with epoxy adhesive and grinding. Moreover, in addition to considerably improved strength characteristics, a more aesthetic appearance is achieved in the transition between the two surfaces which are assembled at the formed corners, and the formation of cracks is avoided, which is not the case when the known technique is used. It is preferred to carry out the heating of the plate-formed core material to a temperature lying within the interval of 100-115°C, typically between 102-110°C and preferably to 108°C. It is preferred that the mould is heated to a temperature lying within the interval of 70-90°C, typically bet- ween 75-85°C and preferably to a temperature of 80°C. A plant for the execution of the method according to the invention comprises a thermostat-regulated oven for the heating of plate-formed PVC-based cellular plastic items, a mould comprising spaced plate pieces extending in a paral- lei manner and which are mutually connected by hinge connections in the lower end, and where the one plate piece is fixedly mounted on a bracket and the other plate piece can be pivoted, and where the external sides of the plate pieces are provided with thermostat -regulated heating elements for the heating of the plate pieces to a preferred working temperature for the mould. In the following, the invention will be explained in more detail with reference to the drawing, where fig. 1 is a side view of a trailer according to the invention, fig. 2 is an end section view of the trailer shown in fig. 1, fig. 3 is the same seen from above, fig. 4 shows a section of the bed of the trailer in detail and showing an axle support moulded into the sandwich construction of the bed, fig. 5 shows the details of an axle suspension with rubber torsion springs, fig. 6 is a perspective view of a mould for use in the forming of core material in curves, fig. 7 shows the same as fig. 6, but where the mould is opened, fig. 8 is a detail view of a rounded transition between plane sections of the construction according to the known technique, and fig. 9 is a detail view of a rounded transition between plane sections of the construction according to the method. Fig. 1 shows a trailer 2 constructed in accordance with the invention, where the undercarriage/bed 4, superstructure 6 and towing arrangement 8 for coupling to a standard tow-bar 10 on a vehicle are built up in one and the same construction of composite materials. As indicated, the superstructure is aerodynamic in shape, which is made possible by the configuration of the trailer as a sandwich construction according to the invention. The sandwich construction is built up as shown in fig. 2 and fig. 3. In the example embodiment shown, the construction, which is self-supporting, consists of an outer shell 12 and an inner shell 14 which consist preferably of formed plastic or glass-fibre plates, between which a core 16 of cellular plastic is provided. From fig. 2 and fig. 3 it will also be seen that the trailer does not have any chassis, which is possible in that the wheels 18 are placed and suspended in transverse rubber torsion springs 20 which are moulded into the bed 22 of the trailer, as shown in fig. 4. Use is hereby avoided of the traditional undercarriage, which would increase the weight of such a trailer to a considerable degree. Moreover, the use of precisely this type of suspension reinforces the loading capacity of the bed 22. As will appear from figs. 4 and 5, the rubber torsion springs 20 comprise an outer axle tube 24 which can be made of extruded composite material, and with a non-circular cross-section inside which there are a number of longitudinal, rod-formed rubber elements 26 which are in abutment with longitudinal cavities 28 in a through-going axle support tube 30 provided with support arms 32, in the free ends of which are placed the wheels 18 with associated brake arrangement 34. In the shown example embodiment, the outer axle tube 24 consists of a glass-fibre reinforced tube with physical characteristics which correspond to those of the sandwich construction of the bed. This is advantageous because of possible temperature variations which can arise, which could otherwise lead to the undesired formation of cracks between the cellular plastic 12 in the cavity between the outer wall 12 and the inner wall 14. In special cases, the outer axle tube 24 can be provided with parts 36, 38 which extend radially, as shown in fig. 4, with the object of distributing the torsional forces from the axle support tube 30 over a greater area within the bed 22. Fig. 6 shows a perspective view of an example embodiment of a work station 50 for use in the moulding of core material 16 of PVC-based cellular plastic. The workstation 50 comprises an oven 52 for heating plates 16 of cellular pla- stic and a mould 54. The oven 52 is thermostat-controlled and the temperature can be regulated by means of the button 56. The mould 54 comprises spaced, curved plate pieces 58, 60 which extend in parallel, and which are mutually con- nected by hinge connections 62 at the lower end. The plate piece 58 is mounted in a fixed manner on a bracket 59, and the mould is opened by lifting the plate piece 60, which hereby swings up by turning around the hinge connection 62, cf . fig. 7. The outsides of the plate pieces 58, 60 are provided with thermostat -regulated heating elements 64 for heating the plate pieces 58, 60 to a preferred working temperature. The workstation is used in the following manner: A plate-formed piece of PVC-based cellular plastic 16 is heated in the oven 52 to a temperature lying within the interval 100-115°, typically between 102-110° and preferably to 108°C. When the preferred working temperature has been reached, the plate 16 of plastic is removed from the oven and is placed between the plates 58, 60 in the mould 54, which by means of the heating elements 64 is preheated to a temperature lying within the interval 70-90°C, typically between 75- 85°C and preferably to a temperature of 80°C. Hereafter, the mould 54 is closed, whereby the plastic plate 16, which in the heated state has become mallea- ble, assumes a shape which is defined by the cavity between the parallel-extending, spaced, curved plate pieces 58, 60.After a relatively short period of time in the mould, where the temperature of the cellular plastic plate 16 is redu- ced and whereby the plastic plate becomes stable in shape, the mould 54 is opened, as already described, and the now shaped -cellular plastic plate 16 is removed from the mould and is ready for use as an assembly element (connection ele- ment) e.g. between two adjacent plane surfaces of cellular plastic . It will be obvious that the method disclosed and the mould 54 can be of other configurations and not least sizes, all depending on the shape of the items which are requi- red to be fabricated, and thus the mould could be of a size corresponding to a complete superstructure for a camping caravan, a sales-car or trailer, merely providing that the oven and the PVC-based plastic plate material used are of sufficient size. Fig. 8 shows a detail section of a rounded transition 70 between plane sections 73, 73' of the construction according to the known technique, where use is made of rectangular-shaped staves 72 sawn from a plate of PVC-based cellular plastic, and which are placed with a certain mutual di- stance between them and glued to a glass-fibre mat 74. As will be seen, there are gaps 76 between the individual staves 72 which give rise to reduced strength characteristics of the finished sandwich construction, comprising an outer and an inner layer 78, 80 of glass-fibre. Moreover, the above- mentioned gaps can also form cold conductors in the finished sandwich construction. Fig. 9 shows a detail section of a rounded transition 82 between plane sections 73, 73' of the construction in accordance with the method according to the invention. As will be seen, no gaps are formed in the PVC-based cellular plastic, and the sandwich construction is therefore more stable and does not comprise cold conductors. With the new construction of a trailer according to the invention, the possibility is thus created for an almost revolutionary change with regard to the choice of trailer configuration. Automobile manufacturers will thus be able to extend their product range with trailers which match their various makes of cars in both shape and colour. Moreover, the trailers will have a considerably greater loading capacity as a consequence of the combination of tare and max. weight limit, and as already mentioned it will be possible to configure said trailers more aerodynami- cally correct, so that the wind resistance is reduced when they are being towed. Both of these conditions will contribute towards a significantly better economy in connection with trailer transport, in that the consumption of fuel is reduced. Furthermore, the trailer thus achieved will be al- most maintenance-free, in that it does not comprise parts which, for example, can be corroded by rust, which will result in a relatively higher resale value and less load on the environment compared with trailers of the known type . Where the load on the environment is concerned, it is worthy of no- te that the materials used in the construction of the trailer according to the invention have a very high re-usability in connection with recycling.

Claims: C L A I M S 1. Trailer (2) or caravan for coupling to a towing vehicle, and comprising a superstructure (6) which comprises t at least one support surface (4) mounted on at least one set of wheels which make it mobile, and means (8) for coupling to the towing vehicle, c h a r -a c t e r i z e d in that the superstructure (6), the chassis (4) and the tow-bar/triangle (8) consist of one and the same self-supporting construction of composite materials, comprising external shells (12, 14) between which a core of suitable core material is placed. 2. Trailer (2) according to claim 1, c h a r a c t e r i s e d in that the construction consists of glass-fibre reinforced sandwich construction parts. 3. Trailer (2) according to claim 1 or 2 , c h a r a c t e r i z e d in that the core material consists of cellular plastic . 4. Trailer (2) according to any of the claims 1 - 3, c h a r a c t e r i s e d in that the wheel suspensions (20) consist of a through-going axle (24) which is an integral part of the self-supporting bed (22) of the construction. 5. Trailer (2) according to claim 4, c h a r a c t e r i s e d in that the through-going axle consists of a rubber torsion-spring suspended axle (20) . 6. Trailer (2) according to claim 4 or 5, c h a r a c t e r i s e d in that the through-going axle (24) or the rubber torsion-spring suspended axle (20) consists of a tube made of extruded composite material . 7. Trailer (2) according to any of the claims 1- 6 and comprising a brake system, c h a r a c t e r i s e d in that the towing and/or the pressure connections between the coupling link and brake mechanism are configured as rod connections consisting of a suitable composite material and led through channels which similarly consist of suitable composite material . 8. Method for the manufacture of curved sections of PVC-based, plate-formed core material (16) , c h a r a c t e r i s e d in that the plate-formed core material (16) is heated to a given temperature, after which the heated material is placed in a mould (54) heated to a preferred temperature, in which over a suitable period of time the material (16) is cooled own to a temperature at which the material becomes stable in shape, after which the formed material is removed from the mould (54) . 9. Method according to claim 8, c h a r a c t e r i s e d in that the plate-formed core material (16) is heated to a temperature lying with the interval 100-115°C, typically between 102-110°C and preferably to 108°C. 10. Method according to claim 8 or 9, c h a r a c t e r i z e d in that the mould (54) is heated to a temperature lying with the interval 70-90°C, typically between 75-85°C and preferably to 80°C. 11. Tool (50) for the execution of the method according to claims 8-11, c h a r a c t e r i s e d in that it comprises a thermostat-regulated oven (52) for the heating of the plate-formed PVC-based cellular plastic items (16) , a mould (54) comprising spaced plate pieces (58, 60) which ex- tend in a parallel manner and are mutually connected by hinge connections (62) , where the one plate piece (58) is mounted in a fixed manner on a bracket (59) and the other plate piece (60) can be pivoted, and where the external sides of the plate pieces (58, 60) are provided with thermostat-regulated heating elements (64) for the heating of the plate pieces (58, 60) to a preferred working temperature for the mould.

Inventors: PEDERSEN JOHN, PEDERSEN, JOHN
Applicants: PEDERSEN JOHN, PEDERSEN, JOHN
Application year: 1999
Main classification: B29C51
IPC codes: B29C51, B29C53, B60G11, B62D29