Plastic article or earthenware shaping or treating: apparatus – Distinct means to feed – support or manipulate preform stock... – Extrusion shaping means
Reexamination Certificate
1998-10-16
2001-07-03
Pyon, Harold (Department: 1722)
Plastic article or earthenware shaping or treating: apparatus
Distinct means to feed, support or manipulate preform stock...
Extrusion shaping means
C425S461000
Reexamination Certificate
active
06254369
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to tooling used to make construction materials, and in particular an extrusion die to fabricate a plastic skin on materials used for concrete forms.
2. Description of the Prior Art
Concrete is a widespread and popular building material both in the developed and developing nations. One of the major material costs associated with concrete construction is the cost of the material used to build the form into which the concrete is poured. The traditional material used for concrete forms is lumber and plywood, the cost of which is steadily increasing everywhere, and is particularly acquired at a dear price in many developing nations.
In addition to the lumber and plywood, many other types of materials have been used for concrete forms, including metal sheeting and plastics, the cost of which is substantially higher than plywood and lumber, although such materials are typically more durable and may be reused more times. In most cases, lumber and plywood sheeting can be reused in different concrete forming projects, at the most, two to three times before the material becomes unusable for a variety of factors. While metal is very durable and can be reused many times, metal sheeting and bracing used to support the heavy weight of wet concrete is difficult to work with, and once deformed or bent, becomes practically unusable in any other project. While plastic sheeting and plastic structural components have durability and reusability, and can be easily worked in the field, most of these components lack the strength necessary for heavy concrete form work unless the thickness and, therefore, the cost of such materials is increased beyond the point of economic reason. In addition, many plastic materials are brittle or become brittle after relatively short exposures to the elements.
The extrusion of a plastic or polymer skin onto rectangularly cross sectioned, manufactured lumber in such a manner as to obtain close tolerances of the outer envelope and good adhesion and tight binding of the skin to the underlying lumber or substrate is nontrivial. The problem of obtaining a good lamination becomes particularly difficult when the size of the lumber increases to sizes larger than 2″×4″.
Therefore, what is needed is some type of apparatus and methodology whereby plastic or polymeric skin can be economically laminated on a variety of sizes of material, particularly larger materials such as 2″×6′″s or larger, which material can be repeatedly employed in concrete form work at a low cost similar to plywood and lumber yet with a durability like plastics or metals.
BRIEF SUMMARY OF THE INVENTION
The invention is an extrusion die for providing an extruded skin on a rectangular core of a construction member comprising a die body defining a die cavity through which the core is disposed. An at least partially circumscribing runner is defined in the die body for carrying extrudable material of which the extrusion skin will be formed. An extrusion channel is defined in the die body completely circumscribing the die cavity. A plurality of risers communicates the runner and the extrusion channel so that the extrusion material is provided to the runner and uniformly distributed in the extrusion channel. A mandrel is disposed in the die cavity and forms a continuous enveloping prismatic and conforming cavity between the die body and the mandrel into which the extrusion material is provided by communication of the enveloping prismatic and conforming cavity with the extrusion channel. The enveloping prismatic and conforming cavity has an exit port which circumscribes the core as the core emerges from the die body. The extrusion material is then extruded around and onto the core to form a substantially uniform skin about the core.
The die body is comprised of two die halves. The die cavity is a rectangularly flattened oblong prismatic cavity. The enveloping prismatic and conforming cavity is a rectangularly flattened oblong cavity conformably defined with and exterior to the die cavity. The plurality of risers comprise a subplurality of primary risers and a subplurality of secondary risers. The primary risers provide communication for the extrusion material to center portions of the enveloping prismatic and conforming cavity and the secondary risers provide communication for the extrusion material to opposing side portions of the enveloping prismatic and conforming cavity. The core has a standard construction size of 1″×6″ or larger and preferably a size of 2″×12″ or larger.
The plurality of risers have internal diameters which are sized to permit even flow and distribution of the extrusion material throughout the enveloping prismatic and conforming cavity when the extrusion material is a polyethylene extrusion resin of medium density.
The extrusion channel is defined in the die body adjacent to a land. The extrusion material is communicated from the extrusion channel across the land into the enveloping prismatic and conforming cavity. The land has a width relative to the extrusion channel. The width of the land increases toward opposing side portions of the land as compared to the width of the land in the center of the die body in communication with the primary risers.
The invention is an extrusion die for extruding a substantially uniform skin of plastic onto a rectangular prismatic core. The extrusion die comprises a first and second identical die half. A rectangularly flattened die cavity is defined between the first and second die halves. A mandrel is disposed in the die cavity and has a mandrel body conforming to the shape of the die cavity. An extrusion channel is defined in the first and second die halves and completely circumscribes the die cavity and mandrel beginning at an extrusion feed position and extending to an extrusion port in the first and second die halves. The extrusion channel is spaced apart from the mandrel body by a land defined in the first and second die halves to thereby form an enveloping prismatic and conforming cavity from the extrusion feed position to the extrusion exit ports. A runner is defined in the first and second die halves and communicates with an inlet port defined in the first and second die halves and at least partially circumscribing the die cavity. A plurality of risers communicates the runner with the extrusion channel at a corresponding plurality of azimuthal locations about the die cavity.
The plurality of risers is comprised of a subplurality of primary risers and a subplurality of secondary risers. The primary risers are provided at an azimuthally center position of the die cavity and the secondary risers are provided at opposing azimuthal side positions of the die cavity. The primary risers have a larger inner diameter than the secondary risers. The die has a longitudinal direction and an orthogonal azimuthal direction. The plastic is extruded from the feed position to a longitudinal rearward extrusion position in the die. The die has a center azimuthal location and azimuthal side locations at the feed position. The land is defined at a more forward longitudinal position at the opposing azimuthal side locations than at the azimuthal center location so that flow resistance to the plastic is decreased at the opposing azimuthal side locations of die cavity compared to flow resistance to the plastic at the azimuthal center location.
In the illustrated embodiment the core has at least one cross sectional dimension six inches or greater and preferably 12 inches or greater. The height-to-width ratio of the core is at least 1 to 6 or less.
The invention is also a method of forming an extrusion skin about a rectangular core having a ratio of cross-sectional dimensions of at least six to one comprising disposing the core into a die cavity, and providing extrusion material to an enveloping prismatic and conforming cavity in the shape of a rectangularly flattened oblong. The enveloping prismatic and conforming cavity compl
Blaney Roger A.
Kelly Daniel M.
Risch Richard S.
Del Sole Joseph S
Pyon Harold
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