Fuel tanks on board vehicles of various kinds generally have to meet sealing and permeability standards in relation to the type of use for which they are designed and the environmental requirements that they have to satisfy. At the present time, both in Europe and throughout the world, there is a substantial tightening of the requirements regarding the limitation of pollutant emissions into the atmosphere and into the environment in general.
To limit these emissions, care is taken in particular to position the components (ventilation lines, valves, baffles, stiffeners, etc.) inside the tank and/or the fill pipe (see in particular application WO 2004/024487 in the name of the Applicant). However, when these components are fastened to the tank after it has been molded, it is generally necessary to make at least one opening in the tank so as to be able to introduce these components into the tank and to fasten them thereto. Hence there may be potential sealing problems near this opening.
Several years ago the Applicant therefore developed a process of initially molding a cut parison (cut into 2 sections) in order to be able to introduce thereinto and fasten thereto components during the actual molding of the tank and to thus avoid piercing openings (see patent EP 1 110 697 in the name of the Applicant).
This process has since been the subject of several improvements targeting particular means for fastening these components: see in particular applications WO 2006/008308 (fastening of components by rivet punching), WO 2006/095024 (fastening of ventilation lines that have a part that can be deformed due to the presence of a bend that is stretched during the attachment of these lines to the parison) and WO 2007/000454 (fastening of components according to an ideal layout and in particular, as regards the ventilation lines, while avoiding the formation of siphons).
These improvements have been able to be made due to the use of a core, i.e. a part of suitable size and shape for being able to be inserted between the cavities of the mold when the parison is located therein and to fasten thereto the components inside the tank without the edges of the parison being welded (since the core must be removed before the final molding of the tank, a step during which the welding of the parison sections is carried out). Such a part (core) is, for example, described in patent GB 1 410 215, the content of which is for this purpose incorporated by reference into the present application.
The installation of the components may be, in certain cases (e.g. when they are components that pass through the wall in order to enable communication with the outside), a difficult undertaking which, when the wall is multilayered, may result in the barrier layer being damaged and/or a connection being obtained that is not very leaktight.