Method for hot-forming a laminated sheet of synthetic resin and

Plastic and nonmetallic article shaping or treating: processes – Mechanical shaping or molding to form or reform shaped article – Shaping against forming surface

Patent

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Details

264295, 264339, 425374, 425397, 72319, 156222, B29G 5304, B21D 1100, B21D 1122

Patent

active

047568631

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL DOMAIN

The invention relates to a method for hot-forming a laminated sheet of synthetic resin composed of several hot-forming laminate layers containing a duromer plastic material and planar carrier materials, between which are inserted layers of a thermoplastic bonding agent, by which method the sheet in at least its region that is to be deformed is heated to the forming temperature which is equal to or higher than the melting temperature of the thermoplastic bonding agent, and whereupon, for the purpose of bending a border region of the sheet that in its final form is flat, it is bent around a cylindrical surface with the aid of a movably guided bending plate, and is cooled, in such a manner that at least during a large part of the bending operation the bending plate will be in planar contact with the border region of the sheet that is to be bent, and the individual laminate layers are mutually displaced in the bending region and in the border region in the direction of the sheet's surface, and whereat, after the bending operation, the bending plate holds the border region in its bent position at least until the resolidification of the thermoplastic bonding agent. In addition, the invention relates to a device for working the method according to the invention.


STATE OF THE ART

Laminated sheets of synthetic resin of the kind described above, as well as methods for hot-forming such sheets are known from German Pat. No. 28 23 669. In this known method, the bending plate executes during the bending operation a rotary motion around an axis that coincides with the axis of the cylindrical surface around which the sheet is being bent, with the bending plate performing a sliding motion relative to the surface of the border region of the sheet that is to be bent, and with which it is in constant planar contact. The frictional forces acting during this sliding motion on the surface of the border range of the sheet that is to be bent counteract a tendency of the sheet to split in the bending region along the bonding agent seams, as the applicant found out later. This splitting is also counteracted in the aforementioned known methods by form-holding parts which after the bending operation hold the bending region or the border region, respectively, in its bent or deformed form, at least until the resolidification of the bonding agent. As a form-holding agent, e.g., a strip-shaped press die with a concave cylindrical pressure surface may be used, which after the bending operation is pressed against the convex surface of the bent sheet region.
Experience has shown that in the aforementioned known methods the pressure surface of the form-holding parts must very precisely match the sheet surface that has a convex bend in the bending region.
With greater thickness tolerances of the sheet, the risk obtains that in the event of a greater thickness deviation upwards, the edges of the pressure surface of the form-holding part will press against the sheet surface in an undesirable manner. In addition, a separate form-holding part is required for each bending radius and each sheet thickness.


DESCRIPTION OF THE INVENTION

It is the object of the invention to indicate a method of the kind mentioned above for the hot-forming of laminated sheets of synthetic resin, which are composed of several hot-forming laminate layers containing a duromer plastic and planar carrier materials, between which are inserted layers of a thermoplastic bonding agent, with the method of the invention making do without the use of special form parts matching the convexly curved.
The problems of the prior art solved by the method of the present invention wherein in the last phase to the invention that is characterized by that in a last phase of the bending operation the bending plate is constantly guided in such a manner that each point of its bending surface has an essential component of motion in a direction parallel to the plane of the bent border region, and that, appropriately, a prebending element is provided connected with the bending

REFERENCES:
patent: 2937689 (1960-05-01), Peterson
patent: 3009201 (1961-11-01), Hansen
patent: 4002049 (1977-01-01), Randolph, Sr.
patent: 4045269 (1977-08-01), Voss et al.
patent: 4350551 (1982-09-01), Michaelson

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