Abstract:
The present invention is a method of forming a compressed product. The method includes introducing a material into a press. The material has a flow direction through the press. The press is arranged to have at least one platen oscillating between a compression phase and a release phase. The at least one platen is configured to impart a compressive force onto the material during the compression phase such that the force is applied initially at an acute compression vector angle relative to the material flow direction. As a function of the angled compressive force, the material is transported a distance through the press and then released during the release phase.

Description:
FIELD OF THE INVENTION 
     This invention relates generally to methods of forming compressed products and, more specifically to a method of forming a compressed composite product with oscillating compression. 
     BACKGROUND OF THE INVENTION 
     Oriented strand board, parallel strand lumber and other engineered wood products produced from discrete wood elements are produced in a press by depositing a mat of resin coated wood elements within the press and applying a compressive force to the mat. Heat from a variety of sources is added to substantially cure the resin while the mat is within the press. The heat may be added in the form of microwave energy, radio frequency energy, steam injection or the like. 
     As depicted in  FIG. 1 , current press systems includes a pair of opposed platens  40   a  configured to continuously compress a material  38   a  into a desired shape. Adjacent each platen  40   a  is a press belt  37  running on roller or ball bearing arrangement  35 . The belt  37  and bearing  35  combination allows movement of the material  38   a  through the platens  40   a  while the platens are continuously applying a compressive force to the material  38   a . This method of forming a composite wood product is problematic in many ways. 
     The current continuous press designs impede the application of energy. The press belt, bearing arrangements and necessary lubrication materials represent a significant barrier for the application of heating energy to the product. The heating of the product via a hot platen technology results into an uneven heating profile which in turn yields an uneven density profile throughout the product. 
     The constant pressure applied also occasionally adversely affects the resulting product. The mat is generally an arrangement of wood elements formed in layers. When pressure is applied, often times there are pockets of air or moisture that gets trapped within the wood layers. As energy is applied, the natural moisture of the wood can form steam pockets in the regions of the trapped air. Subsequently, a blowout or other product defects result, thereby rendering the product unfit for its intended purpose. 
     Still further, the energy required to pull the material through current press systems is considerable. The constant pressure exerted by these press systems requires significant additional energy to move the material through the press system. The excessive amount of additional energy increases the cost of production thereby ultimately affecting market price for the product. 
     SUMMARY OF THE INVENTION 
     The present invention is a method of forming a compressed product. The method includes introducing a material into a press. The material has a flow direction through the press. The press is arranged to have at least one platen oscillating between a compression phase and a release phase. The at least one platen is configured to impart a compressive force onto the material during the compression phase such that the force is applied initially at an acute compression vector angle relative to the material flow direction. As a function of the angled compressive force, the material is transported a distance through the press and then released during the release phase. 
     The present invention further includes a method of forming a compressed wood product. The method includes introducing a mat assembly of resinated wood elements into a press along a material flow direction. The press is arranged to have at least one platen oscillating between a compression phase and a release phase. The at least one platen is controlled to impart a compressive force at a compression vector angle during the compression phase. The compression vector angle includes a lateral motion component and a vertical motion component. The material is transported a distance through the press along the material flow direction. The distance the material is transported is substantially equal to the lateral motion component. Subsequently, the material is released during the release phase such that a relief region is created between said material and said at least one platen, wherein the at least one platen is out of contact with the material. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The preferred and alternative embodiments of the present invention are described in detail below with reference to the following drawings. 
         FIG. 1  is a schematic of a press section according to the prior art; 
         FIG. 2  is a system diagram of the oscillating pressing process according to an embodiment of the present invention; 
         FIG. 3  is a schematic of the oscillating pressing process according to an aspect of the present invention; 
         FIG. 4  is a graphical illustration of the relation between press stroke and material thickness over time in accordance with the present invention; 
         FIG. 5  is a side view of the press platens in accordance with an aspect of the present invention; and, 
         FIG. 6  is a perspective view of an eccentric shaft made in accordance with a further aspect of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention provides a system and method for forming a compressed material product using an oscillating pressing process. By way of overview, and with references to  FIG. 2 , one presently preferred embodiment includes a compressed material forming system  20 . The compressed material forming system  20  includes an oscillating compression system  22  used to apply an oscillating compressive force to the material  38   b . Further, a material temperature control system  24  is used to control the temperature of the material  38   b  during the forming process. A material transport system  26  is included to move the material through the compressed material forming system  20  as desired. Additionally, a material treatment system  28  is optionally present to treat the material  38   b  during the forming process. Specific details of the compressed material forming system  20  are described with more particularity below. 
     The material  38   b  to be subjected to the treatment of the invention desirably comprise a mat assembly  30  ( FIG. 3 ) of resinated discrete wood elements which can be subjected simultaneously to pressure and heat to form consolidated composite wood products  32 . The wood elements may be in any known form. Suitable, non-limiting examples of the wood elements usable with this present invention are wood chips, flakes, strands, veneers, fibers, particles and wafers. 
     The products  32  ( FIG. 3 ) preferably produced by the present invention are any known consolidated composite wood products  32  presently known in the industry. Suitable product  32  examples include but are not limited to particleboard, oriented strand board, fiberboard, waferboard, plywood, laminated veneer lumber, parallel strand lumber, and laminated beams. 
     The moisture content of the material  38   b  prior to treatment by the process of the invention generally will broadly range from about 1% to about 20% by weight. However, this moisture content range is merely a general guideline, and may be departed from. Optimum moisture content for material  38   b  is preferably determined on a case-by-case basis and it is within the skill of the art to correlate moisture levels with mat assembly  30  dimensions in order to make such determinations. It is possible to treat material  38   b  having a moisture content approaching zero, but the limited plasticity of wood under such conditions make this less desirable. The moisture content may be augmented by employing a water-containing adhesive. 
     The resin to be employed in the practice of this invention as it relates to wood is preferably an alkaline phenolic resin. However, it may be any adhesive whose rate of cure is accelerated by the application of heat. Water-soluble and non-water-soluble alkaline and acidic phenolic resins, resorcinol-formaldehyde resins, urea-formaldehyde resins, and isocyanate resins, for example, can be employed. The resin may be applied to material  38   b  in any desired amount. When employing long wood strands, the resin content will often range from about 1 to about 10% of the dry weight of the wood. Most often, the resin will be applied in an amount ranging from about 2 to about 5% of the dry weight of the wood. 
     The oscillating press system  22  is arranged to direct the motion of the platens  40   b . The oscillation is preferably controlled by a drive mechanism  27  ( FIG. 5 ) configured to enable the oscillating motion of the platens  40   b . The drive mechanism  27  includes, among other things, the power sources such as electric motors, petroleum fueled combustion engines, pneumatic or hydraulic power systems or the like along with any suitable connecting structure usable to transmit power to the platens  40   b.    
     Control of the oscillating press system  22  and the drive mechanism  27  is suitably arranged to perform in a number of acceptable manners. For example, in one embodiment, it is performed by a processor or microprocessor (not shown) arranged to perform suitable operations. Any processor known in the art is acceptable, without limitation, a Pentium®—series processor available from Intel Corporation or the like. Alternatively, control of the platens  40   b  is performed by an electronic computer chip, hydraulic control systems or is performed manually. Accordingly, the scope of the present invention shall not be limited by the manner in which the oscillating motion is generated. 
       FIGS. 3 and 4 , illustrate an oscillating press cycle  34  of the oscillating press system  22 . In accordance with the present invention, a single oscillating press cycle  34  includes one full compression phase  44  and one full release phase  46 . The compression phase  44  is the phase of the oscillating press cycle  34  wherein the material  38   b  is under compressive forces from the platens  40   b . Conversely, the release phase  46  is the phase of the oscillating press cycle  34  wherein the material  38   b  is substantially completely free from press applied compressive forces. 
     The release phase  46  is generated by suitably controlling the motion of at least one of the platens  40   b  relative to the material  38   b . More specifically, after the compression phase  44 , at least one of the platens  40   b  is moved away from the material  38   b  at a rate that is faster than the rate at which the material  38   b  is expanding upon release of the compressive forces. During the release phase  46 , the material  38   b  will expand within an elastic region  42  at an expansion rate. The amount of time required for the material  38   b  to expand to substantially a pre-compressed dimension is the compression recovery response time  66 . As will also be appreciated by those skilled in the art, many factors will affect the compression recovery response time  66 . For example, without limitation, material dimension, material composition, resin cure state (if relevant), the amount of compression applied to the material  38   b , and the size of the desired elastic region  42  are all factors having an affect on the compression recovery response time  66 . It will be appreciated by those skilled in the art that material  38   b  will be suitably supported on at least one end of the material  38   b  in order to create the relief region  43  between the material  38   b  and the lower platen  40   b . Additionally, any other known structure are employable to support the material  38   b  through the oscillating pressing system  20 . 
     The oscillating press cycle  34  is preferably selected to occur at a frequency wherein the release phase  46  is less than the compression recovery response time  66  for the material  38   b . More specifically, at least one platen  40  is suitably controlled to release the material  38   b  and subsequently recompress the material  38   b  at a rate faster than the material&#39;s compression recovery response time  66 . As discussed above, a variety of factors affect the material&#39;s compression recovery response time  66 . As such, the determination of a suitable compression recovery response time  66  for a given material is known by those skilled in the art. 
     Although the scope of the present invention is not intended to be limited by the range of frequencies for the release phase  46 , a preferably range of frequencies has been found to achieve desirable results when used in accordance with the present invention. In a particular embodiment, the oscillating press cycle  34  of the present invention is preferably operated between about 1 Hz to about 400 Hz. 
     In accordance with this invention, a relief region  43  is created during the release phase  46  as the platens  40   b  pulls away from the material  38   b  at a rate faster than the material  38   b  is expanding. As best seen in  FIG. 4 , the stroke  62  of the platens  40   b  relative the material thickness  64  is suitably chosen to produce, among other things, the desired relief region  43 . Those skilled in the art will appreciate that the relief region  43  is preferably sized to accommodate a suitable release phase  46 . Additionally, the relief region  43  is sized to allow repositioning of the platens  40   b  without affecting the movement of the material  38   b  through the compressed material forming system  20 . 
     As best seen in  FIG. 3 , a compression vector  36  depicts the resultant motion vector of the platens  40   b  at a moment in time substantially equal to the initiation of the compression phase  44 . In a presently preferred embodiment, the compression vector  36  is suitably at a compression vector angle  37  relative to the material flow direction  50 . The compression vector angle  37  will suitably include a lateral component  39  that reflects instantaneous platen motion in a lateral direction, a direction substantially parallel to the plane of the material flow direction  50 . Additionally, the compression vector angle  37  includes a vertical component  41  indicating similar motion along a vertical direction, a direction substantially perpendicular to the plane of the material flow direction  50 . 
     With reference to  FIG. 3  and to discussions below, a compression vector angle  37  from about 5 degrees to about 85 degrees will be associated with movement of the material  38   b  in a first direction. Further, at a compression vector angle of about 95 degrees to about 175 degrees is associated with movement of the material  38   b  in a second direction, substantially opposite of the first direction. 
     In a presently preferred embodiment the compression vector angle  37  is within a range of about 30 degrees to about 60 degrees. However, smaller and larger compression vector angles  37  are considered within the scope of this invention. More specifically, the present invention has been found to function with a compression vector angle  37  of about 5 degrees to about 85 degrees, relative to the material flow direction  50 . 
     Given the circular motion of the platens  40   b , it has also been determined that a compression vector angle of about 95 degrees to about 175 degrees is also usable with the present invention. Obviously, a compression vector angle  37  within this range would result in the reversal of the material flow direction  50 . More specifically, a second material flow direction  51 , substantially opposite to the first material flow direction  50 , is achieved. It will be appreciated by those skilled in the art, the oscillating pressing system  20  may be controlled in this manner as a means or reheating or recompressing the material  38   b . A more detailed discussion of platen motion and the resulting material transport is discussed below. 
       FIG. 5  depicts an aspect unique to the present invention. The platens  40   b  do not include the press belt and bearing structure (not shown) associated with conventional press configurations. Rather, the platens  40   b  are configured to directly contact the material  38   b  during the pressing process. In this manner, oscillating pressing system  20  does not suffer the thermal losses associated with heating of any bearing structure or press belts (not shown) common to current press system designs. It should be noted, that the platens  40   b  may be lined with a material, such as stainless steel (not shown), to help control microwave energy distribution, if relevant. However, the temperature control system  24 , discussed in more detail below, is suitable configured to eliminate the need for heating of any platen lining material (not shown) to achieve adequate temperature control of the material  38   b.    
     The platens  40   b  are typically aluminum or other metal formed to include a tapered entrance section  48  configured to receive the mat assembly  30  as it enters the oscillating pressing system  20 . The amount of the taper is suitably determined by those skilled in the art. However, in a particular embodiment of the present invention, a taper of about 7 degrees was found to be sufficient. However, platens  40   b  with entrance regions  48  having greater or lesser tapers are considered within the scope of this invention. Additionally, platens  40   b  with entrance regions  48  located at opposed ends of the platens  40   b  are also within the scope of this invention (not shown). 
     The temperature control system  24  is optionally in communication with at least one of the platens  40   b , and includes structure and components used to apply energy to the material  38   b  in order to control the temperature of the material  38   b . For example, the temperature control system  24  may be used to bring the material temperature up to a desired temperature, such as a resin cure temperature. Conversely, the temperature control system  24  may be used to selectively cool the material  38   b . Still further, the temperature control system  24  may be used to both selectively heat and selectively cool the material in accordance with certain aspects of this invention. 
     The temperature control system  24  includes a temperature control unit  54  that is suitably configured to supply the energy to be used in the specific embodiment. The temperature control unit  54  may take many forms commonly known by those skilled in the art. For example, the temperature control unit  54  may be a microwave generator, radio frequency generator, steam injection generator, hot platen, cold platen, hot fluid generator, cold fluid generator or combinations thereof. For simplicity, the temperature control unit  54  is shown in communication with only on of the platens  40   b . However, this configuration is not intended to limit the scope of the invention. Rather, those skilled in the art will appreciate that the temperature control unit  54  may be in communication with either platen  40  or both platens  40   b . Additionally, the temperature control unit  54  may suitably be configured to apply energy along the material&#39;s face or side. Still further, the temperature control system  24  may be employed in a pre-press, in-press or post press arrangement. 
     Those skilled in the art will appreciate, the temperature control unit  54  includes all known structure necessary to utilize the temperature control unit  54 . More specifically, if the temperature control unit  54  is a microwave generator, a suitable wave guide generator with suitable microwave windows (not shown) are part of the temperature control unit  54 . Similar structures will be used where the temperature control unit  54  is a radio frequency generator or the like. When a steam generator is used, suitable hose and fittings (not shown) will likewise be used and are considered within the scope of this invention. 
     With reference to  FIGS. 2 ,  5  and  6 , the material transport system  26  is unique to the design of the present invention. Those skilled in the art will appreciate the function of the material transport system  26  is to move the material  38   b  through the oscillating pressing system  20 . 
     The material transport system  26  is derived from the motion of the oscillating motion of the platens  40   b . More specifically, the motion of the platens  40   b  controls the transportation of the material  38   b  through the oscillating pressing system  20 . As discussed above, and as is best illustrated in  FIG. 3 , the compression vector angle  37  includes both a vertical motion component  41  and a lateral motion component  39 . 
     An oscillating pressing system  20  having platens  40   b  engaging the material  38   b  at a compression vector angle  37  imparts a novel attribute to the present invention. More specifically, when the lateral motion component  39  of the platens  40   b  coincides with a compression phase  44 , the lateral motion component  39  functions to transport the material  38   b  through the press. The material  38   b  is transported through the oscillating pressing system  20  a linear distance that is slightly less than the linear distance traveled by the platens  40   bb  during the compression phase  44 . This transportation occurs one time for each oscillating press cycle  34 . Simultaneously, the vertical motion component  41  suitably compresses the material  38   b  while the material  38   b  is being transported. Accordingly, no other transportation structure, such as an external tractor means, is required to move the material  38   b  through the oscillating pressing system  20 . 
     An optimal manner in which to control the platen  40  motion to achieve an adequate compression vector angle  37  is to drive the platen  40  in a substantially circular motion. With specific reference to  FIGS. 5 and 6 , one presently preferred method of achieving the desired motion is to drive the platens  40   b  on an eccentric shaft  67 , or similar structure. Such a structure will create substantially circular oscillating motion of the platens  40   b  sufficient to proved transportation and oscillating compression of the material  38   b  through the oscillating pressing system  20 . 
     In a presently preferred embodiment, the platens  40   b  are each arranged with at least one bore  47  which is suitably arranged to receive an eccentric shaft  67 . In a particular embodiment, each platen  40  is configured with three bores  47 , each being suitably arranged to receive an eccentric shaft  67 . The eccentric shaft  67  includes a journal region  68  and a lobed region  69 . The journal region  68  is in communication with a drive mechanism  27  via gearing, belt or direct drive means (not shown). The lobed region  69  is configured to remain substantially internal of the platens  40   b  and drive them in a substantially circular motion. The lobed region  69  is preferably sufficiently large enough to create enough of a relief region  43  such that the material  38   b  is not moved in an undesired direction. It is to be noted, however, that although the any give point of the platens  40   b  will transcribe a substantially circular path, the opposed surfaces of the platens remain parallel to one another at all times. 
     With specific reference to  FIGS. 2 and 5 , the material treatment system  28  is preferably configured to treat the material  38   b  while the material  38   b  is within the oscillating pressing system  20 . The material treatment system  28  includes structure arranged to allow the addition of suitable dyes or colorant materials, fire retardant materials, or preservative materials. However, the nature of the product added by the material treatment system  28  is not intended to limit the scope of the present invention. Consequently, any suitable product may be introduced by the material treatment system  28 , including the addition of liquid water. Material treatment systems  28  of the present invention are well known in the art, and as such a detailed description of the structure and methods of operation are not discussed in the present application. 
     A material treatment unit  52  is suitably configured to control introduction of any treatment product. The form of the material treatment unit  52  is not intended to limit the present invention. Thus, any known structure is usable as a material treatment unit  52 . For example, the material treatment unit may be a reservoir with suitable pumps, metering devices, sensing devices etc. commonly used with the temporary storage and disposition of the various treatment products according to this invention. 
     As with the temperature control unit  54  discussed above, the material treatment unit  52  suitably includes any structure necessary to enable the material treatment unit  52  to function as it is intended. For example, the material treatment unit  52  includes any hose, conduit, nozzle, diffuser or pathway utilized by the material treatment unit  52  in the delivery of the treatment product to the material  38   b.    
     In a presently preferred embodiment the material treatment system  28  is configured to introduce the product onto the material  38   b  within the oscillating pressing system  20  during the release phase  46 . However, the material treatment system  28  may be configured to introduce the product before, during or after the material is within the oscillating pressing system  20 . 
     While the preferred embodiment of the invention has been illustrated and described, as noted above, many changes can be made without departing from the spirit and scope of the invention. Accordingly, the scope of the invention is not limited by the disclosure of the preferred embodiment. Instead, the invention should be determined entirely by reference to the claims that follow.