Patent Abstract:
A method and system for manufacturing a consolidated cellulosic article having first and second surfaces of a desired contour, a uniform density and variable caliper and basis weight are disclosed. The method and system employ a primary press having first and second similarly contoured platens to consolidate a mat of cellulosic material and a binding agent to a softboard having first level of density with first and second opposed sides of similar contour. A removal tool is then employed to remove cellulosic material from one or both of the first and second sides in a planar fashion. The resulting mat is then compressed a second time by a secondary press having first and second platens corresponding in shape to a higher density level while maintaining a substantially uniform caliper and basis weight.

Full Description:
CROSS REFERENCE TO RELATED APPLICATIONS AND CLAIM TO PRIORITY 
     This application is a divisional of application Ser. No. 09/995,525, filed Nov. 28, 2001, now U.S. Pat. No. 6,743,318 the disclosure of which is incorporated herein by reference and priority to which is claimed pursuant to 35 U.S.C. § 120. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention generally relates to wood products and, more particularly, relates to methods of manufacturing consolidated cellulosic panels. 
     2. Description of Related Technology 
     Consolidated cellulosic panels, such as fiber board, paper board, particle board, and the like, are typically comprised of wood furnish such as saw dust, shavings, chips, or specially ground fibers, compressed with a binding agent or resin under heat and pressure. Such boards can be used in a variety of applications including, but not limited to, exterior house siding, interior and exterior door facing panels or door skins, cabinet doors, paneling, moulding, etc. 
     It is often desirable to manufacture such panels to a uniform basis weight and caliper. If the panels are flat this can be accomplished by compressing a mat between first and second flat faced dies. However, if one of the faces needs to be deeply contoured, such die compressions have proven to be problematic. For example, if a first die has a contour corresponding to the desired shape of the panel, and the second die has a flat face, the mat compressed therebetween will have a non-uniform caliper, with the thinner areas of the mat being compressed to a higher density than thicker areas. This is especially true with fiberous materials that do not flow under pressure. 
     Current methods of producing such panels therefore typically require that a mat having first and second opposed flat surfaces be compressed according to conventional methods, and that one or more of the surfaces then be machined to have the desired contour. For example, a router may be used to shape the surfaces. U.S. Pat. No. 4,175,106, assigned to the present assignee, discloses such a process. Such tools, however, cannot easily produce sharp inside corners, are relatively slow, and require complex, expensive equipment. 
     Another method requires contoured, complementary, dies on both the top and bottom to produce a substantially uniform thickness through the contoured and non-contoured areas. If one of the top or bottom needs to be flat, or alternatively shaped, the panel must undergo an added machining step adding time, expense and waste to the operation. Shallow contouring of one face is typically done in an embossing operation, or with an embossing die, but the depth of embossing is greatly limited. 
     SUMMARY OF THE INVENTION 
     In accordance with one aspect of the invention, a method for producing a consolidated cellulosic article is provided. The method comprises the steps of providing a mat of cellulosic material and binder resin, providing a first contoured front platen having a first pattern, providing a first contoured rear platen having a pattern generally corresponding to the pattern of the front platen, consolidating the mat between the front platen and the rear platen under heat and pressure to form a molded softboard having a contoured front surface and a correspondingly contoured rear surface, the softboard having a substantially uniform density and a substantially uniform caliper, removing portions of the molded softboard to form a softboard having a front surface and a rear surface with desired contours, providing a second contoured front platen having a contour substantially corresponding to the contour of the front surface, providing a second contoured platen having a contour substantially corresponding to the contour of the rear surface, and consolidating the softboard between the second contoured front platen and the second contoured rear platen under heat and pressure. 
     In accordance with another aspect of the invention, a method of producing a consolidated cellulosic article is provided comprising the steps of compressing a mat of cellulosic material and a binder resin between first and second contoured platens to produce a softboard having first and second opposed contoured sides, removing cellulosic material from the softboard along one of the first or second sides in a planar fashion, and subsequently compressing the mat between third and fourth platens, the third platen being contoured in a manner similar to the first side of the softboard, the fourth platen being contoured in a manner similar to the second side of the softboard. 
     In accordance with another aspect of the invention, a system for producing a consolidated cellulosic article is provided comprising a primary press, a removal tool, and a secondary press. The primary press includes first and second platens and a drive with the first and second platens having opposed, complementarily contoured, die surfaces. The drive is adapted to compress the first and second platens toward one another. The removal tool includes a blade for removal of cellulosic material in a planar fashion. The secondary press has first and second platens and a drive. The first and second platens have opposed die surfaces. The drive is adapted to compress the first and second platens toward one another. 
     These and other aspects and features of the invention will become more apparent upon reading the following detailed description when taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an isometric view of an article constructed in accordance with the teachings of the invention; 
         FIG. 2  is a partial sectional view of an article being compressed by a primary press according to the teachings of the invention; 
         FIG. 3  is a partial sectional view of an article being machined after the primary press according to the teachings of the invention; 
         FIG. 4  is a partial sectional view of an article being compressed by a secondary press according to the teachings of the invention; 
         FIG. 5  is a partial sectional view of an article being machined with an alterative removal plane according to the teachings of the invention; 
         FIG. 6  is a partial sectional view of an article being machined using an alternative tool according to the teachings of the invention; and 
         FIG. 7  is a schematic representation of a system constructed in accordance with the teachings of the invention. 
     
    
    
     While the invention is susceptible to various modifications and alternative constructions, certain illustrative embodiments thereof have been shown in the drawings and will be described below in detail. It should be understood, however, that there is no intention to limit the invention to the specific forms disclosed, but on the contrary, the intention is to cover all modifications, alternative constructions, and equivalents falling within the spirit and scope of the invention as defined by the appended claims. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawings, and with specific reference to  FIG. 1 , an article constructed in accordance with the teachings of the invention is generally referred to by reference numeral  20 . While the article  20  is depicted as a six panel door facing, it is to be understood that the teachings of the invention can be employed in the construction of any number of other consolidated cellulosic articles having a contoured surface. Such articles include, but are not limited to, exterior house siding, flooring, furniture components, paneling, and cabinet doors. 
     As shown in  FIG. 1 , the article  20  includes a first or top surface  22 , a second or bottom surface  24 , first and second side edges  26 ,  28 , and first and second end edges  30 ,  32 . The top surface  22  is contoured, whereas the bottom surface  24  is flat or planar in the depicted embodiment. More specifically, the top surface  22  includes a plurality of indentations  34  of various dimension and depth to provide an appearance desirable for the end application of the article  20 . In the depicted embodiment, the bottom surface  24  is flat to facilitate attachment of the article  20  to a door core, but it is to be understood that the article  20  may include a back surface having a non-flat contour as well. 
     Referring now to  FIG. 2 , a primary press  36  according to the teachings of the invention is depicted compressing a mat  38 . The mat  38  is contemplated to be comprised of cellulosic material, such as wood fiber, mixed with a binding agent or resin. The binding agent may be a thermoset resin such as a phenolic resin or isocyanate. The mat  38  may be formed by sprinkling such fiber and binding agent or a moving conveyor belt. Variations in the height of the mat  38  may be removed with a scalping roller or the like. The belt is often of a mesh or otherwise perforated material to enable a vacuum device to hold the fiber on the belt. The primary press includes an upper platen or die  40 , a lower platen or die  41 , and a drive mechanism  42 . The upper and lower platens are similarly contoured with complementary protrusions  43  and indentations  43   a . The drive mechanism  42  is depicted as a hydraulic cylinder, but may be alternatively provided as with pneumatic actuators, chain and sprocket drives, pulley and belt drives, direct drive couplings to motors or other primary movers, etc. Each die  40 ,  41  is preferably heated, as by a heat source  44 . The heat source  44  may be provided in the form of heat exchanger coils or channels through the dies  40 ,  41 , through which heated fluid, e.g. water, is circulated, or in the form of separate hot platens. 
     The primary press  36  compresses the mat  38  to a first level of density and caliper to result in a softboard  45  as shown in  FIG. 3 . A softboard is defined herein as a compressed mat of cellulosic fiber and a binding agent having a relatively low density, e.g., 10 to 30 lbs. per cubic foot. Such a softboard has sufficient strength to maintain its shape as opposed to being a loose pile of fiber, but would not be suitable for a solid product such as siding or doors. However, since the mat  38  is compressed between upper and lower dies  40 ,  41 , having complementary configurations, the softboard  45  is compressed to a substantially uniform caliper and substantially uniform density. More specifically as noted in  FIG. 3 , zone ∝ is of the substantially same height as zone β. Since the mat  38  begins with a uniform density and basis weight, after compression with such complementarily shaped dies  40 ,  41 , the softboard  45  continues to have a uniform, although greater, density, and a uniform basis weight. 
     Once the softboard  45  is formed, it is machined in a planar fashion to reduce one or both of the top surface  22  or bottom surface  24 . In the embodiment depicted in  FIG. 3 , the bottom surface  24  is machined by a rotary scalper  46 . The rotary scalper  46  includes an axle  47  from which a plurality of blades  48  radially extend. The axle  47  is connected to a suitable drive mechanism (not shown) such as a chain and sprocket drive, a pulley and belt arrangement, or a direct coupling to a primary mover, so as to rotate the axle  47  and blades  48  relative to the softboard  45 . In so doing, the contour of the bottom surface  24  is removed in the depicted embodiment of  FIG. 3 , resulting in a flat or planar surface  50 . 
     In alternative embodiments, the bottom surface need not be completely flattened. The removal tool, be it the rotary scalper  46 , a circular (dado) saw blade ( FIG. 5 ), a band saw blade ( FIG. 6 ), a sander (not shown), or the like, may be controlled to remove all cellulosic material in the softboard  45  up to a predetermined removal plane  49 . For example,  FIG. 5  depicts an alternatively machined softboard  45  wherein the removal plane traverses across the indentations  34 , thereby allowing a portion of the indentation  34  to remain in the bottom surface  24 . One of ordinary skill in the art will readily appreciate that the removal plane  49  can be located at any position within the softboard  45  and affect the ultimate shape of the top surface  22  or bottom surface  24 , accordingly. 
     Referring now to  FIG. 4 , a secondary press  52  according to the teachings of the invention is depicted. The secondary press  52  preferably includes an upper platen or die  54  having a contour matching the contour of the top surface  22 , and a lower platen or die  56  having a surface  58  matching the contour of the bottom surface  24 . In the depicted embodiment, the bottom surface  24  is flattened, and thus the surface  58  is flat, but it is to be understood that if the bottom surface  24  otherwise shaped, e. g., machined to have a shape such as that of  FIG. 4 , the lower die  56  would be similarly shaped. 
     The upper and/or lower dies  54 ,  56  are coupled to a drive mechanism, such as a hydraulic cylinder  60 , to compress the softboard  45  therebetween. The upper die  54  includes protrusions  62  positioned and dimensioned to align with indentations  34  provided within the softboard  45  and further compress the softboard  45  to a lower caliper and higher density. Since portions of the softboard  45  have been removed below the removal plane  49 , the resulting article  20  has a variable basis weight across its length. Steam may be injected into the softboard  45  from an injector  63  during the secondary compression. 
     As indicated above,  FIG. 6  depicts an alternative embodiment according to the teachings of the invention. In  FIG. 6 , rather than employing a rotary scalper  45  to remove cellulosic material from the softboard  45 , a band saw  68  is employed. It is to be understood, that any number of other removal tools may be employed, including but not limited to, circular or dado saw blades and sanders. 
     Not only can the teachings of the invention be used to construct the article  20  having a contoured upper surface  22  and bottom surface  24 , with the article  20  having a uniform density and variable basis weight, but since the article  20  is compressed in dual stages, the cellulosic material removed can be gathered and reused in the creation of subsequent articles  20 . Accordingly,  FIG. 7  depicts a system  70 , which may be constructed in accordance with the teachings of the invention, including the primary press  36 , the removal tool  45 , and the secondary press  52 , as well as recovery mechanism  72 , recycling mechanism  74 , a hopper  76 , and a mat former  78 . The gathering mechanism  72  may be provided in a number of forms, including, but not limited to, a basin or conveyor provided directly below the removal tool  45 . A vacuum may also be employed. Employing a conveyor, gravity may be used to allow  the removal of cellulosic material to fall into the conveyor and be transported back to a reservoir or hopper of cellulosic material (not shown). Alternatively, the vacuum may be provided proximate the removal tool  45  for gathering the cellulosic material immediately upon removal from the article  20 . 
     From the foregoing, one of ordinary skill in the art will appreciate that the teachings of the invention can be employed to construct a consolidated cellulosic article having first and second surfaces contoured as desired, with a substantially uniform density and variable basis weight and caliper. Moreover, the article can be constructed in a manner enabling cellulosic material removed from the article in the process to be recycled and used in the creation of subsequent articles.

Technology Classification (CPC): 8