U.S. patent application number 11/258824 was filed with the patent office on 2006-05-18 for process and device for bending a sheet of synthetic material filled with alumina trihydrate.
This patent application is currently assigned to CREA DIFFUSION. Invention is credited to Francois Provence.
Application Number | 20060105595 11/258824 |
Document ID | / |
Family ID | 34952831 |
Filed Date | 2006-05-18 |
United States Patent
Application |
20060105595 |
Kind Code |
A1 |
Provence; Francois |
May 18, 2006 |
Process and device for bending a sheet of synthetic material filled
with alumina trihydrate
Abstract
A process is provided for bending a board in synthetic material
filled with more than 20% by weight of alumina trihydrate in a
methyl methacrylate matrix: a section of the board is heated so
that it can be bent; the section to be bent is bent while holding
the convex upper surface of the board such that it does not become
elongated. Also provided are a device for implementing such a
process, and a bent board obtained by such a process.
Inventors: |
Provence; Francois; (Metz,
FR) |
Correspondence
Address: |
FLEIT, KAIN, GIBBONS, GUTMAN, BONGINI;& BIANCO P.L.
ONE BOCA COMMERCE CENTER
551 NORTHWEST 77TH STREET, SUITE 111
BOCA RATON
FL
33487
US
|
Assignee: |
CREA DIFFUSION
SOLGNE
FR
|
Family ID: |
34952831 |
Appl. No.: |
11/258824 |
Filed: |
October 26, 2005 |
Current U.S.
Class: |
439/74 |
Current CPC
Class: |
B29K 2033/12 20130101;
B29C 53/84 20130101; B29C 53/04 20130101 |
Class at
Publication: |
439/074 |
International
Class: |
H01R 12/00 20060101
H01R012/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 29, 2004 |
FR |
04 11565 |
Claims
1. A method for bending a synthetic material board filled with more
than 20% alumina trihydrate in a methyl methacrylate matrix, the
method comprising the steps of: heating a section of the board that
is to be bent; and bending the section of the board to be bent,
wherein during the bending step, the upper surface of the board is
held firmly-such that it cannot be elongated during bending.
2. The method in accordance with claim 1, wherein a flexible guide
is positioned along the length of the upper surface and that guide
is clamped against the upper surface during the bending step such
that it does not slip.
3. The method in accordance with claim 1, wherein the board is
heated from the underside.
4. A bending device for bending a synthetic material board filled
with more than 20% alumina trihydrate in a methyl methacrylate
matrix, by heating a section of the board that is to be bent, and
bending the section of the board to be bent, the bending device
comprising: systems for clamping the board so that the upper
surface of the board is held firmly so as to prevent elongation of
its upper surface during bending.
5. The bending device in accordance with claim 4, wherein the
systems for clamping the board comprise: a flexible guide; and a
holding means for holding the guide against the upper surface.
6. The bending device in accordance with claim 5, wherein the
holding means comprises at least one pair of jaws to clamp the
board along the length of an edge of the section to bend, the
flexible guide being secured to an upper one of the jaws.
7. The bending device in accordance with claim 5, wherein the
holding means comprises a flange against which an edge of the board
is intended to abut before the bending step.
8. The bending device in accordance with claim 7, further
comprising a bending beam mounted to move between an initial
position in which the bending beam is above the guide, and an
end-position in which the beam has imparted a bending movement to
guide by applying pressure to flange.
9. The bending device in accordance with claim 6, wherein the upper
jaw comprises a bearing surface intended to apply against the
board, the flexible guide being offset from the bearing surface so
as to allow a boss to form along the length of the upper jaw during
the bending step.
10. A bent synthetic material board that is filled with more than
60% alumina trihydrate, the bent board being obtained by performing
the steps of: heating a section of the board that is to be bent;
and bending the section of the board to be bent, wherein during the
bending step, the upper surface of the board is held firmly such
that it cannot be elongated during bending.
11. The bent board in accordance with claim 10, wherein the bend
radius of the underside surface is between one and four times the
thickness of the board.
12. The bent board in accordance with claim 10, wherein the board
is a board in Corian.TM..
13. The bent board in accordance with claim 12, wherein the bend
radius of the underside surface is between one and four times the
thickness of the board.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is based upon and claims priority from
prior French Patent Application No. 04 11565, filed Oct. 29, 2004,
the entire disclosure of which is herein incorporated by
reference.
FIELD OF THE INVENTION
[0002] The invention concerns a process and device for bending a
sheet of synthetic material filled with alumina trihydrate in a
methyl methacrylate matrix.
BACKGROUND OF THE INVENTION
[0003] A material sold under the name Corian (registered trademark)
is sometimes used in the manufacture of bathroom and kitchen
furnishings. This synthetic material reproduces the appearance of
stones such as marble or granite. It is formed from a methyl
methacrylate polymer filled with pigmented alumina trihydrate. The
proportion of filling can vary from 20 to 85% of the weight, but
preferably exceeds 60%. Document U.S. Pat. No. 3,847,865 describes
the manufacture and the properties of such a material.
[0004] This material can be worked using conventional joinery
methods. It can also be thermoformed. The possibilities of
hot-bending the material are however limited due to the risks of
crazing and discoloration of the material in the event of excessive
bending. This is why the supplier recommends not exceeding a bend
radius of 4 to 6 times the thickness of the sheet of material.
[0005] Document U.S. Pat. No. 5,486,324 proposes producing a
countertop in Corian with a downturned edge at the front and an
upturned edge at the rear of the countertop, with bend radii
relative to the thickness of the board exceeding the limits
mentioned above. To achieve this, it proposes cutting a groove to
reduce the thickness of the board along the length of the bends
between the main body of the countertop and the edges, and then to
hot-bend the material.
[0006] However, although a board with a tight bend radius is
obtained in this manner, the countertop is weakened due to the
local reduction in thickness.
SUMMARY OF THE INVENTION
[0007] The invention aims at providing a process for bending a
Corian board with a tight bend radius without the risk of
discoloration, crazing or weakening the board.
[0008] With these aims in view, an object of the invention is a
process for bending a board in synthetic material with a filling of
more than 20% alumina trihydrate in a methyl methacrylate matrix, a
process whereby the board section that is to be bent is heated and
then bent. During bending, the top convex surface of the board is
held such that its elongation is prevented.
[0009] By proceeding in the manner indicated, that is to say such
that the material has no areas that become elongated during
bending, no discoloration or crazing occurs, even if a bend radius
of less than four times the thickness of the board is produced.
[0010] To achieve this, a flexible guide is placed along and held
firmly against the upper surface without sliding during the bending
stage. The guide provides a bearing surface for the upper surface
and prevents elongation during bending.
[0011] The board is preferably heated from the underside. A
temperature gradient is obtained through the thickness of the
board. The underside area, which is hotter and therefore more
malleable, flows more easily than the upper area, which reduces the
bending stresses, particularly along the upper surface.
[0012] Another object of the invention is also a device for
implementing the abovementioned bending process, this device
comprises means of retaining the board such that it can be bent
while holding the upper surface such that it does not become
elongated.
[0013] The means of retention includes, for example, a flexible
guide and means of holding the guide against the upper surface of
the board.
[0014] In a particular arrangement, the holding means includes at
least one pair of jaws to clamp the board along the length of a
section to bend, the flexible guide being fixed to one of the upper
jaws. When the jaws grip the board, the board is secured between
them and can no longer slide. As the guide is secured to the upper
jaw, a first joint is made between the board and the guide. If two
pairs of jaws are used and positioned on either side of the section
to bend, the two upper jaws are interconnected by the guide and the
board is blocked between the jaws. This arrangement prevents the
top surface of the board from becoming elongated during
bending.
[0015] In another variant, the holding means comprises a flange
against which one edge of the board abuts before the bending step.
The flange is thus another means of blocking the guide with respect
to the top surface of the board.
[0016] In a particular arrangement, the device comprises a bending
beam mounted such that it can move between an initial position in
which the bending beam is above the guide, and a final position in
which the beam has driven the guide in a bending movement by
applying pressure to the flange.
[0017] In a particular application, the upper jaw comprises a
bearing surface provided to apply against the board, the flexible
guide being offset from the bearing surface of thereby allowing a
boss to form along the length of the upper jaw during the bending
step. One can thus obtain a board on which the boss retains any
liquid that might have spilled onto the horizontally positioned top
surface of the board. The boss forms in the space left free beneath
the guide and into which the board material can creep during the
bending operation.
[0018] Another object of the invention is also a bent board
obtained by the previously described process.
[0019] Such a board is of particularly interest when the bend
radius of the underside is between one and four times the thickness
of the board. These bend radius values are smaller than those that
could be obtained until now without the appearance of whitening or
crazing.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] The invention will be better understood, and particularities
and advantages will become apparent on reading the following
description, which makes reference to the appended drawings, in
which:
[0021] FIG. 1 is a cross-sectional schematic view of a device in
conformity with the invention, in a position before bending;
[0022] FIG. 2 is a view similar to FIG. 1 after bending;
[0023] FIG. 3 is a view similar to 1 of a device in conformity with
a second method of production of the invention, in a position
before bending;
[0024] FIG. 4 is a similar view to FIG. 3 after bending; and
[0025] FIG. 5 is a cross-sectional view of a board bent using the
device illustrated in FIGS. 3 and 4.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0026] Preferred embodiments of the present invention will be
described in detail hereinbelow with reference to the attached
drawings.
[0027] A first method of producing a device in accordance with the
invention is shown in FIGS. 1 and 2. This device comprises an upper
jaw 10 and a lower jaw 11 between which is clamped a board 2 that
is to be bent. Jaws 10, 11 are actuated by clamping means, not
illustrated, for example by hydraulic jacks in a conventional
manner. A guide 13 is secured to the upper jaw 10 and extends along
a bearing surface 101 of the upper jaw 10. The guide 12 is for
example a steel sheet of thickness between 0.2 and 0.4 mm.
[0028] The guide 13 is extended by a flange 16 running parallel to
the upper jaw 10, perpendicularly to the face of the guide 13 and,
and towards the lower jaw 11.
[0029] The bending device comprises, among other things, a beam 12
that pivots around a shaft B parallel to the jaws 10, 11, between
an initial position, illustrated in FIG. 1, and an advanced
position, illustrated on FIG. 2. The beam 12 comprises a working
face 121 which is in contact with guide 13 at the flange 16 when
the beam 12 is in the initial position. Beam 12 moreover comprises
a second flange 120 that extends parallel to the pivoting axis B of
the beam 12, perpendicular to the working face 121, and directed
towards jaws 10, 11. When the beam 12 is in the advanced position,
the flange 16 of guide 12 bears against the flange 120 of the beam,
and guide 12 is partially in contact with the working face 121.
Guide 12 then displays a bend between the upper jaw 10 and the
working face 121, through an angle of about 90.degree..
[0030] The device moreover comprises retractable means of heating
14, to heat a surface in the continuation of a bearing surface 111
of the lower jaw 11.
[0031] When this device is used, a Corian board 2 is placed between
jaws 10, 11 of the bending device such that an edge 26 of board 2
abuts against the flange of the guide. After tightening the jaws
10, 11 around board 2, for example with a pressure of 20 to 30
kN/m, the heating means 14 are switched on to heat the Corian board
from the underside 25 opposing the upper side 20 which is in
contact with the guide 13. Once the temperature of the upper side
20 has reached a predetermined threshold, between 135 and
155.degree. C. for example, typically 145.degree. C., the means of
heating is retracted and the beam is made to move from the initial
position to the advanced position. During the bending phase, the
upper side 20 of the board remains in contact with the guide 13
while the edge 26 of the board is blocked against the flange 16 of
guide 13. As a result of this, the upper side of the board does not
suffer any elongation. Guide 13 bends elastically roughly through
an arc of a circle.
[0032] By proceeding in this manner, it has been observed that the
upper side 20 of Corian boards of 12.5 mm thickness, after cooling,
displayed no discoloration or crazing in spite of having a bend
radius of 25 mm in the upper surface.
[0033] In a second method of producing the invention, shown in
FIGS. 3 and 4, the upper jaw 10 is modified with respect to that of
the first method of production in that a shim 15 is added to the
guide 13 on the bearing surface 101 of upper jaw 10. Thus, the
contact with the top surface 20 of board 2 in the initial position
is made through a clamping surface 151 of shim 15. A space 30 is
left free along the edge of the upper jaw 10, between guide 13 and
the top surface 20 of board 2.
[0034] When board 2 is bent by the device in accordance with the
second method of production, the board creeps into space 30 and
thereby creates a boss 23 on board 20. The shape of shim 15 along
boss 23 can be adapted to the desired shape of the boss 23.
[0035] Corian boards of 12.5 mm thickness were bent with a 3-mm
thick shim resulting in a top surface bend radius of 25 mm. No
signs of discoloration or crazing were observed on these
boards.
[0036] FIG. 5 shows an example of a product obtained by the process
according to the invention using the second method of producing the
device. This product is, for example, a countertop 2 for bathroom
facilities. This countertop 2 comprises a main surface 24 designed
to be installed horizontally, and a downturned edge 22, obtained by
bending the board, creating a fascia at the front of the
countertop. The main surface 24 ends with the boss 23 that limits
the flow of any liquid spilled on the main surface 24 towards the
downturned edge 22.
[0037] With both methods of producing the devices, it is possible
to heat the board before it is placed between the jaws. The means
of heating can be radiating elements or a base heated by electrical
heating elements placed in contact with the area to heat.
[0038] The invention is not limited to the methods of production
given purely as examples. The bending angle is not necessarily
90.degree., but can vary from 100 to 180.degree.. The thickness of
the boards can be smaller or larger.
[0039] While there has been illustrated and described what are
presently considered to be the preferred embodiments of the present
invention, it will be understood by those skilled in the art that
various other modifications may be made, and equivalents may be
substituted, without departing from the true scope of the present
invention. Additionally, many modifications may be made to adapt a
particular situation to the teachings of the present invention
without departing from the central inventive concept described
herein. Furthermore, an embodiment of the present invention may not
include all of the features described above. Therefore, it is
intended that the present invention not be limited to the
particular embodiments disclosed, but that the invention include
all embodiments falling within the scope of the appended
claims.
* * * * *