Method of producing core component, and product thereof

Details Method of producing core component, and product thereof Method of producing core component, and product thereof

2002-03-06

2004-07-20

Theisen, Mary Lynn (Department: 1732)

Plastic and nonmetallic article shaping or treating: processes

Forming articles by uniting randomly associated particles

With reshaping or surface embossing of formed article

C264S109000

Reexamination Certificate

active

06764625

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates generally to the production of man-made composite structural and building products molded from a mat of cellulosic fibers produced by the dry process and molded to include one or more interior depressions. More particularly, the invention relates to the production of a cellulosic core component molded to include one or more interior depressions which can be utilized, for example, in an interior space or void formed by a shell or framework of a building product, particularly as a core component that is adhered between opposed doorskins, said core component having one or more interior depressions shaped to receive depressions molded into the doorskins.
2. Brief Description of Related Technology
The invention is described herein is an improvement over the method and articles described in this Assignee's U.S. Pat. No. 5,887,402 ('402). The '402 patent describes a method of manufacturing a core component and then post-press machining or routing one or more interior depressions into at least over major surface of the core component to accommodate interior depressions in the adhered doorskins. In accordance with the present invention, core components are manufactured to include the required interior depressions in the pressing operation to eliminate or substantially reduce any post-press machining.
Man-made boards, such as fiberboard, can be embossed or molded to have three-dimensional shapes and various design and structural features found in natural wood. Types of useful man—man boards are referred to by the following terms, for example: (a) fiberboards such as hardboard (e.g., low-density hardboard), soft board, and medium-density fiberboard and (b) chipboards such as particleboard, medium-density particleboard, and oriented strandboard (“OSB”). Composites of these boards are also useful. Such boards, particularly hardboard, have found widespread use in the manufacture of doorskins, which can be glued together or laminated to form a shell which supports or encloses a structure or a frame.
Commonly, doorskins (also referred to as door faces) are molded from a planar cellulosic mat to include one or more interior depressions or contours, such as one or more square or rectangular depressions which do not extend to the outer edge or periphery of the doorskin product. Doorskins often require inclined molded walls having a plurality of contours that include varied curved and planar surfaces. Where the depressions or contours are included on a doorskin product, this can serve to replicate a more expensive natural wood paneled door. For example, doors having two, three, four, five, and six panel designs are commonly produced. The exterior or visible surfaces of the fiberboard also can be embossed with a design that represents a wood grain pattern found in a natural piece of wood.
The principal processes for the manufacture of wood composites such as doorskins and other structural or building products include (a) wet felted/wet pressed or “wet” processes, (b) dry felted/dry pressed or “dry” processes, and (C) wet felted/dry pressed or “wet-dry” processes. The core components of the present invention are manufactured by the dry process.
In the dry process of the present invention, the cellulosic fibers are generally conveyed in a gaseous stream or by mechanical means rather than a liquid stream. For example, the cellulosic fibers may be first coated with a thermosetting resin binder, such as a phenol-formaldehyde resin. The fibers are then randomly formed into a mat by air blowing the resin-coated fibers onto a support member. The mat may optionally be subjected to pre-press drying. The mat, typically having a moisture content of less than about thirty weight percent and preferably less than about ten weight percent, is then pressed under heat and pressure to cure the thermosetting resin and to compress the mat into an integral consolidated structure.
The fiber mats that are made by the dry process do not have as much fiber intertangling of fibrillated fibers as mats made by the wet or wet/dry processes since the dry process fibers are not slurried in water during water drainage, which enhances fiber intermingling and entangling, and are coated with resin prior to substantial fiber intermingling. As a result, dry process mats that are consolidated by heat and pressure are not as strong as wet or wet/dry process consolidated mats and have been found to suffer from surface peeling when relatively thick dry process core components, e.g., one half inch thickness or more, are roll-coated with adhesive for adherence to opposed doorskins.
Fiber mats have been pressed into pre-selected decorative shapes, typically at a thickness of about one-eighth of an inch, to include one or more panels or depressions and/or other contours in the formation of doorskins, as described above. Two doorskin pieces are typically joined together with an adhesive binder, which is placed at least at the contact points along the periphery of the door assembly formed by the doorskins. Because the doorskin pieces are contoured to include one or more depressions surrounded by co-planar stiles and rails, an open, interior space of varying dimensions is formed by the doorskin assembly.
Doorskin pieces are often not used alone, but in conjunction with (surrounding) some other material(s) disposed on an interior space disposed between two opposed doorskins to add support to the final door product. The doorskin pieces often utilize wood framing at or near the perimeter of the assembled doorskin. It is known to use rails and stiles, which, when attached together, can provide additional structural support for the door. Rails can be generally described as horizontally-oriented beams which provide support for the door. Stiles, on the other hand, can be generally described as longitudinal or vertically-oriented beams which provide support for the door. In addition, a lock block is optionally utilized to provide further support for a door handle and/or a locking mechanism (e.g., a so-called “dead bolt”) at the periphery of the door. The lock block is preferably secured to a stile and/or a rail.
However, although the structure of a man-made composite door product is supported with rails and stiles, often the door still will not perform as well as a natural solid wood door because the interior spaces defined by the opposed doorskins will be substantially hollow or empty. The hollow spaces or voids cause the door to be lighter than is generally preferred. Further, it is often found that the sound insulation provided by such doors may not be satisfactory. Thus, it is often desirable to use a core material (e.g., core pieces or components) to fill these hollow spaces.
A suitable core material should also provide the door product with a desirable weight, for example the weight of a similarly-styled natural solid wood door. A typical, thirty-inch wide solid pine door weighs approximately forty-two pounds. Known core materials and components have the disadvantage, for example, that they often fall far short of the desired weight. In addition, some alternatives to doorskins having a core material (e.g., full thickness particleboard doors) produce a door that is too heavy and/or difficult to manufacture. In addition, a core material should provide the door with a relatively even weight distribution.
The core material should also have characteristics (e.g., size and shape) that allow placement and attachment within the interior spaces formed by the doorskin assembly with very close tolerances required to match the dimensions of the stiles and rails. As described above, doorskins, particularly for paneled doors, are commonly molded to include one or more interior depressions (i.e., on the surface at some distance from the periphery), such as one or more square or rectangular depressions that do not extend to an outer edge of the doorskin. These surface depressions create varying depths (measured from the front face to the back face of the door) of the inter

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