Plastic and nonmetallic article shaping or treating: processes – Forming articles by uniting randomly associated particles – Autogenously or by activation of dry coated particles
Patent
1995-07-13
1996-12-24
Theisen, Mary Lynn
Plastic and nonmetallic article shaping or treating: processes
Forming articles by uniting randomly associated particles
Autogenously or by activation of dry coated particles
264517, 264122, 425 801, B29C 3502, B68G 1103
Patent
active
055871216
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method and an apparatus for the moulding of a part from a gas-pervious raw material compound in a gas-pervious mould, which at least at one stage of the production is positioned in the gas flow of a flow chamber in such a way that the gas flows through the mould and the raw material. The present invention also relates to a product made by this method.
International Application WO 91/18828 discloses an apparatus for the production of formed parts, such as seat pads, in gas-pervious moulds. The production of the seat pads is carried out by positioning the mould in a flow chamber and filling it with padding material by means of a vacuum pressure, which mould in addition to the padding material contains binding fibres melting under the influence of heat. After the mould has been filled, hot air is passed through the filling chamber, which then also flows through the mould and the layer of padding material contained in it. When the temperature of the padding material has risen to a sufficiently high level, the binding fibres of the padding material melt and form bonds therein. After the heating step, the mould and the moulded part contained in it are caused to cool by leading air through the mould so as to solidify the binding material. The mould can be pressed together after the heating step.
It is sometimes difficult, in the heating step, to heat evenly throughout the part to be moulded, if it is not rectangular, i.e. if the layer of padding material is not of uniform thickness in the direction of the gas flow, but there are both thin and thick portions. When heat energy is led to the mould and the part to be heated contained therein, the hot air used for this purpose passes mainly through those points in which the pressure drop through the mould is smallest, i.e. through those points in which the layer of padding material is the thinnest. The portions of the part to be moulded, through which the main part of the hot gas flows, will then easily overheat, other portions possibly remaining below the moulding temperature.
It is an object of the present invention to provide a method and an apparatus which enable uniform heating and cooling of a part to be moulded in a mould.
It is another object of the invention to provide a method and an apparatus which better than before enable the production of parts of a variety of forms comprising both thin and thick layers of material.
It is a further object of the invention to provide a product produced by the new method, which comprises both thin and thick material layers.
In order to achieve the above mentioned objects, the method according to the present invention for the moulding of a part in a gas-pervious mould positioned in a flow chamber is characterized in that a gas-pervious layer of filling material is disposed in the flow chamber immediately in front of and/or behind the gas-pervious mould.
The apparatus according to the invention for the moulding of a part in a gas-pervious mould is correspondingly characterized in that a gas-pervious filling material chamber filled with filling material is positioned in front of and/or behind the mould, in relation to the flow in the flow chamber.
The product according to the invention is characterized in that the pressure drop caused by the raw material compound which is used to produce it and/or the moulded part in the gas flow depends mainly on the thickness of the layer of raw material compound, i.e. the shape of the part to be moulded, and that the variation of the pressure drop attributable to the shape of the moulded part is compensated during the production by positioning a layer of gas-pervious filling material in front of and/or behind the mould.
The arrangement according to the invention thus makes it possible to adjust the pressure drop in the gas flow over the mould filled with raw material compound and the filling material chamber filled with filling material to a suitable value along the whole width of the "package" to be heated. This ensures when desirable, for instance durin
REFERENCES:
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patent: 4869855 (1989-09-01), Twilley et al.
patent: 5366678 (1994-11-01), Nomizo et al.
patent: 5378296 (1995-01-01), Vesa
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