Land vehicles: bodies and tops – Material – Plastic
Reexamination Certificate
1999-03-29
2001-10-09
Pape, Joseph D. (Department: 3612)
Land vehicles: bodies and tops
Material
Plastic
C296S205000, C264S250000
Reexamination Certificate
active
06299246
ABSTRACT:
The present invention relates to a plastic moulding and to a design structure such as a container, casing, gas or liquid tank, pipeline, vehicle frame, cabin, body, etc., as well as to a method for the manufacture of such a plastic molding and design structure for producing car bodies, containers, cable cars, fuel tanks, etc., i.e. moldings, which simultaneously form a load-bearing design structure.
Casings, cabins, bodies, large containers, fuel tanks, etc. are still generally made using metallic materials, such as e.g. metal sheets, steel structures, etc. As a result of the high weight, corrodibility, relatively expensive manufacturing process and complicated handling operations ever increasing efforts are being made to use lighter and more easily processable materials, such as plastics or in general polymers, or plastic structures.
Thus, e.g. for containers, plastic fuel tanks pipelines, vehicle frames, etc. use is made of so-called winding processes, where e.g. liquid resin-impregnated rovings, glass filaments or plastic fibres, fabric tapes, etc. are wound round a core in a mold, where curing takes place. On the one hand shaping is only possible to a very limited extent and on the other the resulting articles can scarcely be machined or finished. They also do not have a smooth surface and in order to obtain an adequate strength relatively large wall thicknesses must be chosen.
According to another known process, in large dies are loosely placed continuous reinforcing fibres, textile fibre structures such as fibre mats, plates and semifinished fibre structures and the like, but only a very limited bearing function can be achieved. Alternatively, there is a whole body fibre reinforcement by incorporating short fibres in the thermoplastic material to be processed. Either these production processes are very complicated and expensive, or the merely short fibre-reinforced plastics nowhere near provide the necessary strength of the design structure to be produced.
According to another variant, mats or plates produced by a deep drawing process from fibre-reinforced duromers are brought into the necessary form or shape and final curing then takes place in a mold or die or by after-annealing. However, this only permits a very limited shaping and only a limited support or bearing function. These parts also do not have an acceptable surface finish and generally the reaction time during curing is also too long.
The problem of the present invention is therefore to overcome the disadvantages of the known processes and to provide a plastic molding and support structure, together with a process for the production thereof, which can be implemented simply and inexpensively using lightweight polymer materials and with which it is possible to carry out further shapings and load-bearing functions.
According to the invention, the set problem is solved by a plastic molding and design structure. Briefly, the invention is directed to a structure which is comprised of a plurality of interconnected fiber-reinforced plastic structural elements defining a load bearing structure and at least one layer of thermolastic polymer material intergrally connecting to and between at least some of the structural elements.
The plastic moulding and design structure is formed from simple, single, high strength, fibre-reinforced structural elements, which are combined to a bearing structure and interconnected and in which a molding-forming polymer material is molded around at least parts of the bearing structure. Thus, in simple manner and from relatively inexpensive material sold by the meter, structural elements and design structures in random form are produced and the desired shaping and surface is obtained in a simple manner by molding or extruding the polymer material. In addition, short cycle times can be achieved. In principle, largely random flat shapes and load-bearing functions of the integrated, bearing structure can be produced. Complete molding or extruding round the bearing structure with the polymer material leads to a completely protected, smooth surface. However, e.g. for large space lattice structures, only partial areas need be molded round with the polymer material and in particular at the junction points of the structural elements.
The reinforcing fibres for the structural elements forming the load-bearing structure are, more particularly, suitable continuous fibre reinforcements of glass fibres, carbon, polypropylene, polyethylene, aramide or other high strength polymer fibres. The matrix for the reinforcing fibres are preferably thermoplastics such as polyamide (PA), polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polycarbonate (PC), polyimide (PI), polyacrylates, polyphenylene sulphide (PPS) and polyether ether ketone (PEEK). At least partly, suitable are duromer materials, such as e.g. polyurethane (PUR), unsaturated polyester resins, epoxy resins, phenolic resins, amino plastics and optionally novolak resins.
In the case of these structural elements forming the load-bearing structure they can e.g. be longitudinally oriented structures such as rods, pipes, longitudinal sections, such as T-sections, L-angles and flat structures such as plates, mats, honeycombs, grids, etc. These structural elements can in general be produced by standard plastics technology manufacturing methods, preferably by pultrusion, extrusion, injection molding or calendering. Preferably these structural elements are produced by cutting to size, finishing and assembling “continuous” material.
For the production of the load-bearing structure, the individual structural elements are joined together by pinning, screwing, bonding, welding, etc. and in the junction area can be located appropriate coupling or connecting elements.
The individual structural elements can be assembled in multilayer form, with at least one high strength core and an outermost layer, which is preferably compatible with the polymer material directly surrounding the element or in which the outermost layer adheres well or can be readily connected to or mixed with the polymer material directly surrounding the element. Good adhesion between structural elements and thermoplastic polymer material is obtained by compatible polymer materials, which diffuse into one another and are consequently microscopically connected, or by chemical bonds.
According to a preferred variant, the outermost layer of the individual structural elements or the surface thereof is at least approximately identical with the polymer material directly surrounding the element. It is also possible to use polymer blends.
The polymer material forming the molding or the design structure at least partly incorporates a thermoplastic polymer such as polyamide (PA), polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polycarbonate (PC), polymide (PI), polyacrylates, polyphenylene sulphide (PPS), or polyether ether ketone (PEEK). In principle, use is made of substantially the same polymers as for the thermoplastic matrix or the coating of the structural elements. The polymer material can have a multi-layer structure with decreasing rigidity and strength from the element to the surface of the molding or design structure. It is also possible for the polymer material to be at least zonally foamed or dyed.
The decreasing rigidity and strength from the structural element towards the outer surface of the polymer material is important, so that if damage occurs or there is deformation to the molding and design structure, a very high energy absorption is guaranteed. Particularly in the manufacture of vehicle frames, car bodies, cabins and the like, it is important that the moldings and design structure forming the body in the so-called crash tests lead to a particularly high energy absorption, so that e.g. a person located in a car or cabin can be given maximum protection.
REFERENCES:
patent: 4045075 (1977-08-01), Pulver
patent: 4491362 (1985-01-01), Kennedy
patent: 4613177 (1986-09-01), Loren et al.
patent: 4976490 (1990-12-01)
Carella Byrne Bain Gilfillan Cecchi & Olstein
Hand, Esq. Francis C.
Pape Joseph D.
RCC Regional Compact Car AG
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