METHOD FOR CURVING PLASTERBOARD PANELS, AND COMPONENTS THUS OBTAINED

METHODE DE CINTRAGE DES PLAQUES DE PLATRE ET ELEMENTS AINSI OBTENUS

English Abstract

Platerboard panels (A, B) formed by layers of cardboard (1,3) with a
sandwiched plaster sheet (2) and by layers of cardboard (4,6) with a further
sandwiched plaster sheet (5), are clamped between a female half mold part (C)
and a male half mold part (D) of a forming press, are spread with vinyl
adhesive or other suitable water-based adhesive at the layers of cardboard (3,
4). In each one of the two panels, the plaster sheet (2, 5) is fractured
radially and the layer of cardboard (3) on the outside of the curvature is
stretched and the layer (4) on the inside is compressed. The bonding of the
layer of cardboard (3) of the first panel (A) to the layer of cardboard (4) of
the second panel (B) forces the two panels to a permanent, stable equilibrium
of the respective opposite curving tensions.

French Abstract

L'invention concerne des panneaux de plâtre (A, B) formés de couches de carton (1, 3) comportant une feuille de plâtre intermédiaire (2), et de couches de carton (4, 6) comportant une autre feuille de plâtre intermédiaire (5). Lesdits panneaux de plâtre sont pris entre un demi-moule femelle (C) et un demi-moule mâle (D) d'une presse de formage, et sont recouverts d'adhésif vinylique ou d'un autre adhésif aqueux adapté, au niveau des couches de plâtre (3, 4). Dans chacun des deux panneaux, la feuille de plâtre (2, 5) est fracturée radialement, la couche de carton (3) à l'extérieur de la courbure est étirée, et la couche (4) à l'intérieur est comprimée. Le collage de la couche de carton (3) du premier panneau (A) à la couche de carton (4) du deuxième panneau (B) crée un équilibre permanent forcé des tensions de flexion opposées respectives sur les deux panneaux.

Claims

6
CLAIMS
1. A method for curving plasterboard panels, comprising the steps of:
curving and joining simultaneously, by pressing in a forming press, at least
superimposed plasterboard panels, each formed by a sheet of plaster sandwiched
between two layers of cardboard, after previously spreading a suitable bonding
agent, in order to impregnate and soften more effectively the layers of
cardboard
to be mated and bonded in a curved configuration.
2. The curving method of claim 1, wherein the bonding agent has an
aqueous base.
3. The curving method according to any one of claim 1 and claim 2, wherein
the spreading step of the bonding agent comprises impregnating the cardboard
layers which are to be bonded so as to make them malleable, and to facilitate
curving thereof, while the curving step comprises the formation of a
succession
of radial fractures in the adjacent plaster sheets, which are rigid, the
radial
fractures, divaricating toward the outside of the curve at intervals that vary
depending on the set radius of curvature and the thickness of said plaster
sheets.
4. The curving method according to claim 2, wherein the pressing step
carried out for the plasterboard panels to be curved and joined in a
superimposed configuration, is performed for the time so required for the
evaporation of the aqueous base and for the setting of the bonding agent, and
comprises stabilization of the curving imparted by the forming press, by
subjecting the layers of cardboard of each plasterboard panel to a
deformation,
which is a stretching deformation for the layer on the outside of the curve
and a
compression deformation for the layer on the inside of said curve, to reach
permanent, stable, equilibrium of the opposite curving tensions of the two
layers

7
of cardboard that belong to different panels and are directly subjected to
affect
the bonding.
5. The curving method according to any one of claims 1 to 4, wherein said
spreading step comprises spreading the plasterboard panels so to be joined in
a
curved configuration for bonding, with vinyl adhesive or other suitable water-
based bonding agent.
6. The curving method according to any one of claims 1 to 4, wherein the
retention time of the plasterboard panels inside the forming press during said
pressing step is reduced significantly by way of an additional spreading step
comprising spreading onto the surfaces to be joined bands or strips of water-
based vinyl adhesive alternated with bands or strips of hot melt glue, which
has
shorter setting times than the vinyl adhesive.
7. The curving method according to claim 1, wherein the hot melt glue is a
self-curing urea resin in aqueous solution.
8. The curving method according to any one of claims 1 to 7, wherein the
curving step further comprises, in order to ensure even and exact curving of
the
plasterboard panels to be joined and a substantially uniform distribution of
the
radial fractures in the plaster sheets of said panels, during insertion of
said
panels between a female mold part and a male mold part of the forming press,
arranging laterally, alongside said panels, a flexible metal sheet, which is
arranged so that after the pressing step, the metal sheet lies on the outside
of the
curve formed by the plasterboard panels.
9. The curving method according to claim 8, wherein the method further
comprises the step of providing a plurality of free rollers, arranged at the
margins of the cavity of the female mold part with axes thereof parallel to
the

8
generatrix of the curvature of the female mold part, converting into rolling
friction any of the friction with the flexible metal sheet or with the
plasterboard
panels alone, upon pushing of the plasterboard panels by action of the male
mold part, to forcibly descend the plasterboard panels into the female mold
part
in order to assume the shape that is preset in the forming press.
10. Curved plasterboard panels, constituted by curved components, formed
by the compression bonding of two or more superimposed plasterboard panels,
each comprising at least one sheet of plaster interposed between two layers of
cardboard, having curved portions or profiles of different shapes, said
plaster
sheets comprising a succession of radial fractures which divaricate toward the
outside of the curvature thereof and are arranged at intervals that vary
depending on the radius of curvature and the thickness of said plaster sheets.

Description

CA 02447701 2008-05-13
1
METHOD FOR CURVING PLASTERBOARD PANELS, AND
COMPONENTS THUS OBTAINED
Technical Field
The present invention relates to a method for the mass-production of
curved components for finishing masonry work or other structures, obtained
from normally cornmercially available flat plasterboard panels, which are
already widely used in the building sector for the most disparate uses since
in addition to offering good thermal and acoustic insulation they have an
appreciable structural strength and are particularly suitable to be completed
1o by simply painting or with any other surface treatment or covering.
The plasterboard panels to which the invention relates are those of the
most common type, constituted by a sheet or plate of plaster sandwiched
between two layers of cardboard.
Background Art
Currently such panels can be used not only in the original flat shape but
also as contoured components which are obtained, by way of a method
devised by the same inventor and disclosed in Italian patent application MI
96 A 001586, by bonding together with adhesives two plasterboard panels or
two portions of a same folded panel, subjected beforehand to multiple cuts
2o and/or wedge-shaped incisions formed in the cardboard of the faces to be
joined and in the layer of plaster in order to be able to fold in a hinge-like
fashion, at each one of said cuts and incisions, the intact cardboard of the
exposed surfaces of said coupling.
However, this method, which is already widely appreciated in the
building sector, does not allow to produce curved surfaces, which still
require casting concrete or plaster in appropriate formwork or the use of
elements produced on site with plywood, hardboard or other flexible
material.
Disclosure of the Invention
The method according to the invention arises from the problem of

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providing the workers in the building sector and in the interior-decoration
sector the possibility to easily build, at particularly low cost and without
specific manual skills, curved surfaces that are perfectly executed because
they are formed by means of prefabricated elements to be installed on site
and completed in the same manner required by conventional plasterboard
panels.
Generally speaking, the method according to the present invention is as
simple as it is novel and inventive and consists in curving and joining
simultaneously, in appropriate forming presses, two or more plasterboard
Zo panels that are superimposed after adequately spreading the surfaces in
contact with a suitable bonding agent, which is preferably water-based in
order to impregnate and soften more effectively the layers of cardboard to be
bonded in a curved configuration.
Brief description of the drawings
In order to better describe the new method and the components obtained
thereby, the accompanying drawings show, only by way of non-limitative
example:
Figures 1 and 2, illustrate schematically the method according to the
invention by showing, together with the forming press in partial cross-
section, two plasterboard panels before and after bonding them in a curved
configuration;
Figures 3 and 4, illustrate, by way of partial sectional views of the
forming press before and during bonding of the two curved panels,
additional arrangements for the case in which tighter curves, i.e., having a
smaller radius, are required;
Figure 5, is a transverse sectional view of the curved component
produced with the forming press as shown in Figures 1 and 2;
Figure 6, is a transverse sectional view of the curved component
produced with the forming press as shown in Figures 3 and 4;
Figures 7, 8 and 9, show additional embodiments of components that can

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be manufactured with the method according to the invention.
Ways of carrying out the Invention
With reference to the drawings, the plasterboard panels A and B, which
in the sectional view of Figure 1 are formed respectively by the layers of
cardboard 1 and 3 with the interposed plaster sheet 2 and by the layers of
cardboard 4 and 6 with the interposed plaster sheet 5, before their clamping
between the female mold part C and the male mold part D of the forming
press, are spread with vinyl glue or other suitable water-based bonding agent
in the layers of cardboard 3 or 4, i.e., in the contact faces of the two
panels to
1o be joined by overlapping and compression.
Such spreading, by impregnating the treated cardboard layers and making
them malleable, facilitates their curving, while the plaster sheets 2 and 5,
being rigid, undergo a succession of radial fractures 7 that are more or less
closely spaced depending on the curving radius, the thickness of said sheets
and the consequent difference between the outermost and the innermost
circumferences of each sheet.
Continuing pressing of the two curved and superimposed panels A and B,
all through the time required for the evaporation of the aqueous base and for
the setting of the bonding agent, permanently stabilizes the curving imposed
by the forming press. This occurs because in each one of the two
plasterboard panels to be joined the plaster sheet is fractured radially, and
the layer of cardboard on the outside of the curve is stretched and the layer
on the inside is compressed. Accordingly, the bonding of the cardboard layer
3 of the panel A to the cardboard layer 4 of the panel B forces the two to a
permanent, stable, equilibrium of the respective opposite curving tensions,
i.e., the contraction tension for the cardboard layer 3 and the elongation
tension for the cardboard layer 4.
The retention time of the pairs of curved panels inside the forming press
can be shortened significantly, and production times can be speeded up, by
spreading onto the surfaces to be bonded bands or strips of water-based vinyl

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adhesive alternated with bands or strips of hot-melt adhesive, such as self-
curing urea resin in an aqueous solution, which sets more quickly than vinyl
adhesive.
Figures 3 and 4 show that if the curvature to be imparted by means of the
female mold part F and the male mold part G of the molding press is
particularly significant or marked, the panels A and B to be curved and
bonded simultaneously, after spreading suitable adhesives on the faces 3 and
4 to be joined, are laterally provided, alongside their extension and during
their insertion in the forming press, with a flexible metal sheet E, which by
1o being arranged so as to lie on the outside of the curve to be formed, in
the
specific case in contact with the cardboard layer 6 of the panel B, ensures
perfect curving of the panels and a substantially uniform distribution of the
radial fractures in the plaster sheets 2 and 5.
A further operational advantage, while performing the described method,
Zs can be provided, especially in cases where curving is particularly
significant
or marked, by a plurality of free rollers H which, being arranged at the
margins of the cavity of the mold and so that their axes are parallel to the
generatrix of the curve, convert into a rolling friction the friction of the
flexible metal sheet E or, if said metal sheet is not present, of the
20 plasterboard panels A and B alone when the assembly, pushed by the male
mold part or half-mold G, descends forcibly into the mold part or female
half-mold F to assume the shape provided in the forming press.
Although the illustrated examples of embodiment show the production of
curved elements by joining two plasterboard panels by compression, this
25 does not rule out the possibility of coupling even more than two panels so
as
to meet enhanced requirements of insulation, mechanical strength or other
requirements.
As regards also the profiles =or shapes to be produced, the devised
method, compatibly with the ordinary requirements of compression
30 formation, allows the greatest freedom of choice of radii and extent of the

CA 02447701 2006-07-21
-5-
curves (Figures 5 and 6) and in the succession of curves and countercurves
(Figures 7 and 8) or also in the combination of curved portions with other
straight ones (Figure 9).
Clearly, without altering the general characteristics that have been
illustrated and described, the method according to the invention and the
elements provided thereby are susceptible of further modifications and
variations, which are in any case within the scope of the appended claims.

Representative Drawing