Extrusion Blow-moulding

Mould, moulding machine and method for extrusion blow-moulding

Applicant: PLASTIC OMNIUM ADVANCED INNOVATION & RESEARCH
Inventors: COING JEAN-FRANÇOIS, CHAUSSINAND ANTOINE
Patent application number: WO2022/214462

Mould cavities comprise a multitude of movable rods. A bearing surface is provided at the free end of each movable rod to locally push the parison in the molten state and to bring it into contact with an area of an internal component to form, by pressing, an attachment of the internal component within the parison.

Since the bearing surface of a movable rod is limited by its cross-section, the more zones the internal components must fix, the more movable rods must be provided. Similarly, the more internal components the set contains, the more mobile rods must be provided. This strongly complicates the design of the mould and makes its manufacture more expensive. Furthermore, the parison is pushed by a moving rod toward a zone of an internal component, the material of the parison is stretched toward this fixing zone so that the parison has a reduced thickness at the fixing point. This causes a reduction in the thickness of the material at the location of the attachment and hence a defect in the attachment of the internal component.

In addition, the reduction in thickness observed at the fixing is often accompanied by another deformation, i.e. an undulation of the material around the binding. This is not desirable either because the more the reservoir undergoes deformations during its manufacture, the worse the mechanical strength of the reservoir will be. All these risks are obviously aggravated by the multiplication of the movable rods.

The multiplication of the movable rods leads to a degradation of the homogeneity of the cooling temperature of the mould because the movable rods do not form part of the cooling circuit of the mould. This is not satisfactory because a degradation of the homogeneity of the cooling temperature of the mould is liable to cause deformations of the reservoir during its manufacture.

Another drawback of the above-mentioned mould is that the multiplication of the movable rods leads to the multiplication of the mechanisms for moving the movable rods, leading to an increase in the size and complexity of the extrusion-blow moulding machine equipped.

Therefore, the cost of manufacturing a tank provided with one (or more) internal component(s) increases with the number of mobile rods necessary to fix the internal component(s).

The present invention relates to a mould for manufacturing by extrusion blow moulding a hollow plastic tank body for a motor vehicle from a parison, the reservoir comprising at least one internal component fixed inside the parison during moulding of the hollow body. 

The mould comprising two parts which can be displaced relative to one another delimiting internally, when they are closed against one another, a total moulding surface intended to reproduce a predetermined shape of the hollow body to be manufactured, at least one of the mould parts comprising: at least a first section having a first moulding surface of a first portion of the hollow body to be manufactured, said first moulding surface comprising at least one bearing region configured to form, by pressing, a zone for fixing said at least one internal component inside the parison, a second section having a second moulding surface of a second portion of the hollow body to be manufactured, the second section of the mould part being movable relative to the at least one associated first section of the mould part at least between an intermediate closing position and a final closing position of the mould parts, characterized in that the first moulding surface of the mould part has a plurality of bearing regions and is configured such that the bearing regions simultaneously form, by pressing, a plurality of fixing areas of the at least one internal component inside the parison.