Receptacles – Vehicle mountable tank
Reexamination Certificate
2001-11-06
2003-09-02
Moy, Joseph M. (Department: 3727)
Receptacles
Vehicle mountable tank
C220S004140, C220S004130, C220S062180, C220S062220
Reexamination Certificate
active
06612458
ABSTRACT:
FIELD OF THE INVENTION
The invention concerns a double-wall fuel container of plastic material, for example as a motor vehicle fuel tank.
BACKGROUND OF THE INVENTION
A double-wall fuel container such as a motor vehicle fuel tank of plastic material may typically comprise at least two elements in shell form, which are joined together by joining of the materials thereof.
In the context of fuel containers generally, it is known that single-layer fuel containers consisting of polyethylene are more or less permeable in relation to hydrocarbons, with the result that hydrocarbons diffuse through the wall of the tank and are discharged to the ambient atmosphere, which is undesirable. Fuel tanks are the subject of increasing demands in terms of the permeability thereof in relation to hydrocarbons.
Many attempts have been made to reduce the level of hydrocarbon emissions from fuel tank systems. To further those aims, a fuel tank may be made by a co-extrusion blow molding process, with the wall thereof comprising a laminate with one or more barrier layers which afford a low level of permeability for hydrocarbons. Such tanks generally satisfy the demands in relation to maximum admissible levels of hydrocarbon emissions.
However, problems still arise in this respect in regard to connecting openings in the tank, which are required to form a sealing seat for connection members, valves and the like, while in addition welded seams both in the case of fuel containers which are made up of a plurality of component parts made by an injection molding process and also in the case of fuel containers which were obtained by extrusion blow molding represent a possible source of emissions.
In an attempt to reduce the rate of permeation of a fuel container, for example DE 36 00 177 A1 proposes that the fuel container is made up in a double-wall structure comprising an inner container and an outer enclosure or casing which together form a sealed intermediate space with which there communicates a conduit for the discharge of gas or air. Admittedly, with such an arrangement, a large part of the hydrocarbons which diffuse directly through the tank wall can be trapped in a filter element, but here it is necessary for conduits to be passed through the outer casing a plurality of times, and the points at which the conduits pass through the outer casing in that way also represent sources of hydrocarbon emission. Such conduits and conduit connections which are disposed outside the container have to be optimised in terms of their emissions, and that is highly complicated and expensive and sometimes also encounters limits.
The endeavour therefore is to move as many connecting locations and conduits as possible into the tank or container. For that purpose for example DE 198 49 820 A1 discloses gas-tightly mounting in the region of the tank, on the outside thereof, at least one cover member which in conjunction with the tank wall delimits a space which is screened off with respect to the ambient atmosphere and within which connections, connecting conduits and the like are disposed. That cover member is gas-tightly welded to the wall of the tank. It is also possible to dispose therebeneath for example an activated carbon filter for receiving and separating off any free hydrocarbons which may occur.
A similar design configuration is to be found for example in WO 00/48859 where the tank is also gas-tightly welded to a large-area cover member in the form of a hood.
Endeavours are increasingly being made however to move all the connecting locations and conduits, if possible, into the interior of the container or tank. That is to be implemented particularly well in fuel containers which are made up of large component parts, for example two shell portions.
DE 198 53 097 for example discloses such a fuel container having a wall which is produced by an injection molding process from plastic material and which is of a two-part nature. Each half of the tank in turn comprises shell portions which are arranged one above the other and between which a slit or gap is kept free. Fuel vapors which pass into the gap are discharged therefrom and filtered. With such a tank, all installation components therewithin can be fitted under advantageous and convenient installation conditions, before the shell portions are welded together. Manufacture of such a tank however gives rise to the problem that the permeability properties of the plastic material used can scarcely be improved for example by adopting a multi-layer configuration for the tank wall. It is not possible for multi-layer shell portions of that nature to be produced by an injection molding procedure. Thermoshaping shell portions using a multi-layer semi-manufactured article usually gives rise to difficulties in terms of final manufacture as the processing temperatures for the individual components of the laminates which are usually employed are comparatively far apart.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a fuel container of plastic material, which is of such a design configuration that it can be produced in particular inexpensively while as little fuel vapor as possible is permitted to pass into the ambient atmosphere through the container wall.
Another object of the present invention is to provide an improved fuel container of plastic material of a double-wall configuration, which affords improved resistance to permeability of hydrocarbon fuel vapors therethrough.
Yet another object of the present invention is to provide a plastic fuel container of double-wall structure which can be produced using a simple operating procedure.
In accordance with the principles of the present invention the foregoing and other objects are attained by a double-wall fuel container, for example as a motor vehicle fuel tank, of plastic material, composed of at least first and second elements in shell form, which are joined together by joining of the respective materials thereof. The elements in shell form are each in the form of a double-wall blow molding which are respectively co-extruded in a multi-layer configuration at least in a region-wise manner. A gap is kept free at least in a region-wise manner between the respective walls thereof.
A fuel container or tank produced in that way has various advantages over previous fuel containers, which are to be attributed more particularly to the fact that the individual constituent elements of the fuel container are co-extruded in a multi-layer configuration. On the one hand, that affords the possibility of reducing the permeability of the plastic material used, with measures and procedures which are known for that purpose. On the other hand, the arrangement according to the invention enjoys the advantages of multi-part containers, in terms of mounting and attaching conduits and connecting elements. All visible surfaces of the components can enjoy an outstanding surface nature, which is usually not otherwise the case in regard to the internal surfaces of fuel tanks which are conventionally produced by blow molding. In that situation the plastic material leaves behind otherwise relatively large flow markings, by virtue of the fact that no contact with a molding tool actually takes place in the interior of a blow-molded component. In addition, conventionally blow-molded fuel tanks suffer from irregularities in the wall thickness thereof, by virtue of different expansion distances on the part of different parts of the preform from which the blow-molded tank is produced. The fuel container according to the invention has thereover the advantage that the internal contour of the container has a defined smooth surface.
The elements in shell form may each of such a configuration that they form any division, including an asymmetrically extending one, in the assembled fuel container. For example an element in shell form can be in the form of a trough-like element or a bowl-like element, while the element which is to be fitted thereto to constitute the finished container can form a cover member.
In a preferred feature of the inven
Balzer Martin
Daubenbuechel Werner
Hess Dieter
Kluesener Peter
Pappert Michael
Grossman Tucker Perreault & Pfleger PLLC
Moy Joseph M.
Sig Kautex GmbH & Co. KG
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