Plastic and nonmetallic article shaping or treating: processes – Carbonizing to form article – Agglomeration or accretion
Patent
1980-03-28
1983-08-02
Silbaugh, Jan H.
Plastic and nonmetallic article shaping or treating: processes
Carbonizing to form article
Agglomeration or accretion
156 731, 156245, 264 26, 264513, 264515, 264516, B29C 1707, B29D 300, B32B 110
Patent
active
043965628
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a method of producing a hollow monobloc body by expanding a parison made of a thermoplastic material using a blowing process, such as extrusion-blowing or injection-blowing, the body having a further element dispoed on one of its interior walls.
There are numerous cases where it is necessary to provide a further element inside a hollow body, either as a characteristic feature of the body or as a point of attachment or connection to the interior wall. When the hollow body is formed from two shells or two complementary members, such as a metal container formed by stamping or a container produced by injection moulding, it is convenient to put in place a further element which will form the desired projecting portion and to fix it to the inside of one of the shells before closing the assembly. It is not possible to use this method for one-piece containers by expanding a soft hollow parison of thermoplastic material as the size of the further element does not allow it to be introduced inside the hollow body through one of its original orifices.
2. Description of the Prior Art
It has been suggested to place the further element into the mould before the blowing process and to keep it spaced from the walls of the parison by means of a retractable support or mandrel, see, for example, French Pat. No. 1 317 649 in the name of Kautex. The further element can consequently be fixed to the interior wall after the blowing step. In all known cases, such as in the patent cited hereinbefore, the element is fixed by utilising a hole through the interior wall or the hole left behind by the support or the mandrel.
The hollow body is often used as a container or reservoir which must be air or water-tight. There is no guarantee that the spot where the element passes through the wall of the container or the reservoir is properly sealed and even less where the hole is made by the mandrel. Such a risk can not be taken as the container or the reservoir may have to be used for inflammable liquids.
SUMMARY OF THE INVENTION
The invention provides a satisfactory solution to the problem of attaching a further element to the interior of a hollow body produced in one piece by expanding a hollow parison of thermoplastic material by means of a blowing process, even if the hollow body is a container or a reservoir as it is not necessary to make a hole in the wall.
The solution is based on the conventional blowing method and the element is maintained between the shells of the mould, and is characterised by the fact that its support does not leave any trace in the wall of the hollow body. According to the invention the end of the support opposite the end carrying the further element terminates in an insert which is made beforehand of a thermoplastic material identical or compatible with that of the hollow body, so that, after moulding the insert through the wall of the body, there is an intermolecular cohesion of the materials, and the insert and the wall form a block.
More specifically, the invention comprises a method of producing a hollow monobloc body in a mold having a pair of separable shells. The method includes the steps of separating the shells of the mold from each other; interposing an element between the shells, the element being positioned by a support attached thereto; forming a parison between the shells and around the element; bringing the shells together to enclose the parison and the element; producing by blowing a hollow monobloc body having an orifice therein, the body surrounding the element and having its interior wall spaced therefrom, the element being maintained at a distance from walls of the parison before and during blowing; removing the body from the mold; freeing the element from the support; and welding the element to the interior wall of the body using an electrode or sonotrode inserted through the orifice in the body.
BRIEF DESCRIPTION OF THE DRAWINGS
Further features and advantages of the invention are given in the description
REFERENCES:
patent: 3061104 (1962-10-01), Schuffner
Creaplast
Silbaugh Jan H.
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