Plastic and nonmetallic article shaping or treating: processes – Mechanical shaping or molding to form or reform shaped article – Shaping against forming surface
Reexamination Certificate
1996-06-20
2001-06-26
Lorin, Francis J. (Department: 1775)
Plastic and nonmetallic article shaping or treating: processes
Mechanical shaping or molding to form or reform shaped article
Shaping against forming surface
C264S328120, C264S328140, C425S542000, C428S031000, 36
Reexamination Certificate
active
06251326
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a process and an apparatus for manufacturing multilayer molded articles by co-injection molding of two or more different materials to have a final sandwich structure.
BACKGROUND OF THE INVENTION
Many types of processes are known for the manufacture of sandwich molded articles. Generally, said processes enable one to produce only articles having a very simple shape, such as parisons for blow-molded bottles, as disclosed in EP-A-0325440. According to this document, in order to obtain a sandwich parison having an inner layer of PET, an intermediate layer of EV-OH and an external layer of PET, a coaxial injection nozzle is used, and the PET resin is injected before and after injection of the EV-OH resin. A stopping time between first and second injections is provided, while second and third injections are carried out in part simultaneously. The resins, paths are thermally insulated in order to maintain the required different temperatures as far as possible.
U.S. Pat. No. 5,167,896 (Hirota) discloses the coinjection of a resin surface material and a core of fiber-reinforced resin mixture to manufacture a cabinet for use with a display.
Only a portion of the obtained cabinet has a sandwich structure with inner core and two external layers. In fact, coinjection is not an easy process and it becomes even more difficult to control where the required molded article has a geometrically complex shape.
EP-A-93108241.6 discloses an apparatus for coinjection molding provided with several nozzles for one cavity of the mold.
OBJECTS OF THE INVENTION
The object of the present invention is to provide a process and an apparatus for co-injection moulding of sandwich articles having a complex shape.
SUMMARY OF THE INVENTION
Said object is obtained by means of the present invention that relates to a process of preparing a multilayer injection molded article having a sandwich structure according to claim
1
.
The invention also relates to an apparatus to carry out the above process, according to claim
9
.
The invention further relates to the articles obtained by means of the claimed process, and namely to trim panels for autovehicles, characterized according to claim
20
.
According to a preferred embodiment, the mold temperature is controlled to maintain the injected materials in a fluid condition such as to provide along their flow paths optimal temperatures and pressures until the flows of materials meet inside the mold cavity and form a single piece article.
According to another aspect of the invention, two or more injection nozzles are used to simultaneously inject in several points of the cavity said first, second and optionally said further materials.
The advantages of the present invention will be evident to the skilled technician, when considering that it is the first time that complexly shaped articles with a sandwich structure are obtained by coinjection.
The invention will be now described in a more detailed way with reference to the accompanying drawings given by illustrative and non limiting purposes, where:
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“Sandwich moulding—a way to cut car costs?”, Engineering, vol. 225, No. 9, Sep. 1985, London GB p. 483.
Siano Dante
Vecchiarino Luigi
Commer S.p.A.
Lerner David Littenberg Krumholz & Mentlik LLP
Lorin Francis J.
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