Plastic article or earthenware shaping or treating: apparatus – With apparatus assembly or dismantling means or with idle part – For press shaping surface
Patent
1991-02-08
1992-10-20
Silbaugh, Jan H.
Plastic article or earthenware shaping or treating: apparatus
With apparatus assembly or dismantling means or with idle part
For press shaping surface
156486, 264295, 264322, 264339, 425374, 425394, B29C 5304
Patent
active
051568594
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a method of thermoforming a laminated plastic sheet and to a device for bending thermoplastic laminated plastic sheets.
A method of shaping a laminated plastic sheet is known from the Austrian patent 349 766. In this known method, the region of the sheet to be bent is heated and the sheet is thereupon bent, around a mandrel if necessary, in a bending device. Here, the individual lamellae of the sheet shift relative to one another. Elements serving for shape retention then hold the bent component until the thermoplastic has hardened.
This known method employs a bending toggle which carries a bending plate and is pivoted about a bending mandrel. The bending plate is in constant surface-to-surface contact with the marginal sheet portion to be bent and slides relative to the surface thereof. This sliding motion over a large area is undesired. Since the bending plate lies against the sheet to be bent via an antifriction liner to avoid damage to the surface of the sheet, this bending device cannot hold the bent sheet until the sheet has hardened. Accordingly, a shape retention device is additionally required. The shape retention device includes a pressing die having a concave cylindrical pressing surface which, after the bending procedure, is pressed against the convex surface of the bent sheet portion. This pressing die must be different for each bending radius. Therefore, even the holder of the Austrian patent 349 766 considers the method and device of the patent to be capable of improvement.
A method of this type is known from WO 86/02314. In this known method, the bending device is again in surface-to-surface contact with the marginal sheet portion to be bent throughout at least a large part of the bending procedure. As a result, an undesired shifting of the layers relative to one another occurs at the actual bending location of the sheet to be bent because the bending load is applied far from this actual bending location.
In the device known from the generic WO 86/02314, the pressing member is mounted strictly for up-and-down movement so that only bends of 90 degrees can be obtained, i.e., the method can only be applied to sheets whose margins are to be bent 90 degrees.
OBJECTS AND SUMMARY OF THE INVENTION
It is an object of the invention to improve the known method in such a manner that the actual bending load is uniformly applied to the marginal sheet portion to be bent during the entire bending procedure. A pull towards the free sheet margin is to be exerted on the laminate layers while this bending load is applied so that the sheet is rigidly stressed at the actual bending location.
Another object of the invention is to improve the generic device such that a sheet can be bent in any manner. A single operating device is to contain the arrangement which initiates and performs the bending procedure and such arrangement is to simultaneously exert a pull on the sheet layers to be bent and, following the bending procedure, apply an areal load to the bent section.
BRIEF DESCRIPTION OF THE DRAWING
FIGS. 1 to 4 show a bending device during bending,
FIG. 5 shows a different position of the bending device,
FIGS. 6 and 7 show the region of the bending location of the device according to the invention on a greatly enlarged scale to clarify the design of such region.
DESCRIPTION OF PREFERRED EMBODIMENTS
In the drawings 1 denotes a laminated plastic sheet to be bent. The sheet 1 is of a type known per se and is made up of several thermoplastic laminate layers. Layers composed of thermoplastic binders are interposed between these laminate layers.
The sheet 1 rests in a clamping device 7 which defines an upper clamping surface 8 and a lower clamping surface 9. The free marginal sheet portion 2 of the sheet 1, which is to be bent, projects beyond the upper and lower clamping surfaces in the direction of the arrow F4. In the illustrated exemplary embodiment, the sheet 1 is to be bent approximately 45 degrees in the region of a curved reaction surface 4. The lo
REFERENCES:
patent: 3009201 (1961-11-01), Hansen
patent: 3392074 (1968-07-01), Bartron
patent: 4334947 (1982-06-01), Zaino
patent: 4756863 (1988-07-01), Petershofer
patent: 4777005 (1988-10-01), Miller
Eastley Brian J.
Kontler Peter K.
Silbaugh Jan H.
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