Plastic and nonmetallic article shaping or treating: processes – Mechanical shaping or molding to form or reform shaped article – To produce composite – plural part or multilayered article
Patent
1997-04-11
2000-02-22
Ortiz, Angela
Plastic and nonmetallic article shaping or treating: processes
Mechanical shaping or molding to form or reform shaped article
To produce composite, plural part or multilayered article
264266, 425577, 4251291, 425130, B29C 4513, B29C 4514
Patent
active
060276789
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a process and a device for manufacturing flat thin-walled moldings with a ground layer made of thermoplastic materials and a covering layer made of prefabricated flat covering materials pressed with the ground layer by a back pressing technique by means of a form tool having a top mold half and a bottom mold half, whereby the ground layer pressed with the covering layer is introduced into the open form tool prior to back pressing with the covering layer into a flat thin-walled molding.
A process of this kind is known from U.S. Pat. No. 4,873,045, wherein the introduction of the ground layer in the bottom mold is done by extrusion, whereby a slotted nozzle attached to a plastifying unit is moved over the lower mold half and applies to the lower mold half a layer of thermoplastic material corresponding to the desired layer thickness. In the subsequent process step, wherein the upper mold half together with the covering layer is pressed against the lower mold half, the extruded and still molten ground layer is pressed with the covering layer.
A process like the one mentioned in the preamble of claim 1 is also known from the German Patent Application P 41 01 106.6, which proposes to produce the ground layer through a preliminary injection molding process in a flat thin-walled form suitable for the subsequent back pressing process, which to a great extent already has the contours of the finished molding.
These known processes have the disadvantage that the finished molding can be produced only with a covering layer connected by back pressing technique, since during the pressing of surface sections without covering layer it is not possible to obtain a satisfactory surface quality.
It has also been proposed to produce single-piece moldings with partially laminated and partially nonlaminated surfaces, in that during the lowering of the upper mold provided with a covering layer, flowable melt is injected into the lower mold half according to the so-called overflow process. However in this case, as can be seen from EP 0 333 198 very definite parameters have to be observed, i.e. the introduction of melt can take place only at a point in time when the mold halves of the form tool are not yet completely closed, but have to complete a remaining form closing path not longer than 100 mm and not shorter than 5 mm, whereby during the introduction of the melt the form closing motion has to be stopped, or slowed down to less than 30 mm/sec. Only when these parameters are observed it can be insured that, at too short a distance, the covering layer is not exposed to and thereby damaged by the mechanical and thermal effect of the intruding melt, while when the distance is too big the danger of skin formation, which leads to the formation of folds in the finished molding, is prevented.
This latter described process is therefore also very expensive for the production of moldings with a partially laminated and partially nonlaminated surface, and can not be used especially for decorative materials with sensitive surface layers on the melt side.
It is therefore the object of the invention to develop a process of the kind mentioned in the introduction and a device for carrying out this process so that single-piece thin-walled moldings can be produced with laminated and nonlaminated sections in a simple way, without the danger of damaging sensitive components of the covering layer and with a high surface quality of the nonlaminated sections of the molding.
In order to achieve this object the invention proposes a process of the kind mentioned in the introduction, which is characterized in that during the or after the back pressing, i.e. during or after the closing of the two mold halves, next to at least one section of the molding having a covering layer laminated through the back pressing technique, at least a further section of the molding is produced through the conventional injection molding technique, i.e. by injecting a melt of thermoplastic material into the cavity of the mold of the section which is not
REFERENCES:
patent: 4335068 (1982-06-01), Hemery
patent: 4873045 (1989-10-01), Fujita et al.
patent: 5256235 (1993-10-01), Howell et al.
patent: 5534216 (1996-07-01), Kamiyama
patent: 5811053 (1998-09-01), Ota et al.
Rehm Guido
Zweig Konrad
Dubno Herbert
Krauss-Maffei AG
Ortiz Angela
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