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  Process and device for bending a sheet of synthetic material filled with alumina trihydrateUSPTO Application #: 20060105595Title: 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. (end of abstract) Agent: Fleit, Kain, Gibbons, Gutman, Bongini & Bianco P.l. - Boca Raton, FL, US Inventor: Francois Provence USPTO Applicaton #: 20060105595 - Class: 439074000 (USPTO) Related Patent Categories: Electrical Connectors, Preformed Panel Circuit Arrangement, E.g., Pcb, Icm, Dip, Chip, Wafer, Etc., With Provision To Conduct Electricity From Panel Circuit To Another Panel Circuit, Overlying Second Preformed Panel Circuit, Both Adapted To Be Electrically Connected The Patent Description & Claims data below is from USPTO Patent Application 20060105595. Brief Patent Description - Full Patent Description - Patent Application Claims
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 Continue reading... Full patent description for Process and device for bending a sheet of synthetic material filled with alumina trihydrate Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Process and device for bending a sheet of synthetic material filled with alumina trihydrate patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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