Plastic and nonmetallic article shaping or treating: processes – Forming continuous or indefinite length work – Shaping by extrusion
Reexamination Certificate
1998-12-31
2001-02-27
Pyon, Harold (Department: 1722)
Plastic and nonmetallic article shaping or treating: processes
Forming continuous or indefinite length work
Shaping by extrusion
C425S377000, C425S384000, C425S385000, C425S392000, C425S325000
Reexamination Certificate
active
06193919
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to the field of producing shaped products from recycled plastic material, and more particularly to a method and apparatus for extruding shaped products from plastic material, particularly recycled materials including plastic.
2. The Prior Art
Plastic materials are sometime recycled by carefully sorting one type of refuse material from another, and ultimately producing granules of pure plastic of a particular type or grade. This is generally not an economical way to recycle plastics from household garbage since it is too costly to adequately separate and sort the different plastics and other materials which are present in household waste. Some uses are known for recycled impure waste plastics, sometimes mixed with other waste products. Typically this involves melting the plastics and pouring the melted plastics into molds to form products such as paving tiles or picnic tables. The process of pouring a mold and allowing the plastic to cure and cool, and then removing the product from the mold is a lengthy process which adds considerably to the cost of the end product and reduces its economic efficiency.
A method of continuously producing an elongated beam from recycled plastic material is disclosed in U.S. Pat. No. 5,413,745, issued to Curt Andersson, in which a mixture of inexpensive waste plastic and dried and heated waste fiber material such as paper is melted and compressed in a machine, and extruded in the form of a beam. The waste plastic material and the waste fiber material are preferably previously shredded or chopped up prior to feeding the same to the machine. In the Andersson process, a mixture of shredded plastic and filler material is fed by a screw feeder to a compression area where a screw conveyor of decreasing pitch further compresses the material, so that it is heated and melted. The molten mixture is continuously forced out of a square or rectangular nozzle in the form of a beam, after which moveable wall sections of a matrix are used to keep the beam shape of the material until it cools. According to Andersson, the beam of material coming out of the nozzle has a low mechanical strength, and the matrix is designed to work and cool the beam to improve its mechanical strength. The Andersson method is suitable for producing continuous elongated beams but the beams are still lacking the rigidity and strength required for structural purposes.
Canadian Patent No. 2,119,512, issued to Roman Evancic, provides a method and apparatus for producing shaped articles from recycled materials. The method comprises: producing a mixture of plastic and fibrous materials wherein the proportion of plastic to the fibrous materials is greater than approximately 10% and less than 60%; heating the mixture to a softened state adapted for extrusion; extruding the materials from an extrusion device through a shaping means to produce a sheet of softened extruded material; cooling and compressing the surface of the sheet to form a skin of relatively harder material on the surface of the extruded material; applying rollers having a low co-efficient of friction to the surface of the sheet under pressure to apply the desired shape to the surface of the sheet; and further cooling the sheet by the application of a cooling liquid.
Other patents of interest are U.S. Pat. No. 5,786,000, issued to Rolf Berner and U.S. Pat. No. 5,788,901, issued to Barnard et al.
SUMMARY OF THE INVENTION
The Andersson patent referred to above already recognizes that the beam of material coming out of the nozzle of the mixer/extruder has a low mechanical strength. To that end Andersson provides a single matrix having moveable walls adapted to contact the surface of the beam. However, the product produced by the Andersson method still has a low mechanical strength. Accordingly, the present invention provides two matrices which are separated from each other and which are positioned downstream of the nozzle of the mixer/extruder. In the present invention, the first matrix is four feet long, for example, and is provided with a plurality of moveable walls which contact and massage the outer surface of the beam as it passes from the nozzle through the first matrix. When the beam of material coming from the mixer/extruder is generally rectangular in cross section, subject to certain deviations in the upper and lower surfaces, the moveable walls can be four in number, and each wall is reciprocated by a separate piston/cylinder combination.
When the beam of material coming form the mixer/extruder is cylindrical in shape, the number of moveable walls can be three, for example, with each moveable wall subtending an arc of approximately 120 degrees; these walls will still be reciprocated by piston/cylinder combinations. In accordance with the present invention, the beam of material coming out of the first matrix referred to above, will pass through a second matrix which is located downstream of the first matrix and spaced therefrom. The second matrix, for example, need only be approximately two feet in length, it being understood that dimensions and shapes indicated herein are for purely illustrative purposes and not intended to be limiting. The second matrix is also provided with four moveable walls which reciprocate horizontally and whose combined inner surface corresponds with the shape of the beam of material passing therethrough. Each of the walls in the second matrix is designed to reciprocate horizontally by virtue of piston/cylinder combinations mounted on the second matrix. Preferably, the piston/cylinder combinations of the first matrix are coordinated with the piston/cylinder combinations of the second matrix such that the moveable walls of the first and second matrices are moved in concert.
Another feature of the present invention involves the use of cooling passageways in the moveable walls of the second matrix. Horizontal ports are provided in each of the moveable walls of the second matrix so that cooling water can flow into one passageway and out the other passageway to cool each of the walls of the second matrix. In this manner, the material passing through the second matrix will be cooled faster than the beam would otherwise be cooled by normal convection.
REFERENCES:
patent: 3776679 (1973-12-01), Hegler
patent: 4212618 (1980-07-01), Hegler et al.
patent: 4361530 (1982-11-01), Peer
patent: 4410474 (1983-10-01), Ahrweiler
patent: 5413745 (1995-05-01), Andersson
patent: 5510071 (1996-04-01), Van Wonderen et al.
patent: 5786000 (1998-07-01), Berner
patent: 5788901 (1998-08-01), Barnard et al.
patent: 2119512 (1995-09-01), None
Dorman William S.
Leyson Joseph
Pyon Harold
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