Abstract:
A mold for use in a rotary compactor in order to form compacted mass products (e.g., briquets) from a compactable material, the mold having at least one roll pocket that is provided with a surface configuration adapted to impart corresponding grooves to the respective mass surface, and in turn, to provide a physical barrier to the flow of the compactable material adapted to impart an optimal balance between releasability and wear resistance as compared to a pocket previously known in the art.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention relates to the formation of compacted mass products, such as briquets formed from charcoal and other solid (e.g., particulate) biomass materials. More particularly, the present invention relates to the formation of generally pillow-shaped briquets by means of roller or rotary molding. 
       BACKGROUND OF THE INVENTION 
       [0002]    Compacted masses can be formed from a variety of materials, and into a corresponding variety of forms (e.g., briquettes or compacted sheets). Such sheets, for instance, can be subsequently gound and screened to achieve desired particle sizes for a particular end use or need (e.g., as fertilizer or cat litter). 
         [0003]    Briquettes formed of charcoal and other materials (e.g., biomass) are often configured in a generally pillow-shape. This configuration provides for both reasonable ease of manufacturing by the supplier, and handling by the consumer. See, for instance, U.S. Pat. No. 5,049,333 (Briquet Forming Apparatus and Method), as well as U.S. patent application Ser. No. US 2006/0064926 (Charcoal Briquet Having a Grooved Surface), the disclosures of both of which are incorporated herein by reference. The &#39;926 application, in turn, describes a briquet having a generally pillow-shaped briquet having a generally convex upper surface, a generally convex lower surface, and a periphery wherein at least one of the upper or lower surfaces has located thereon enhanced surface textured features in the form of at least one groove, channel, trench or the like. As described therein, “when two or more grooves are present on one or both surfaces, the grooves are preferably parallel to each other, parallel to two opposing sides of the briquet, and perpendicular to two other opposing sides of the briquet. The presence of one or more grooves on or both surfaces increases the surface area to volume ratio thereby enabling more of the briquet to be exposed to oxygen.” 
         [0004]    Generally, the roll pockets for use in a rotary compactor need to be replaced when their useful service life has been expended, thereby adding to the corresponding cost of manufacturing the corresponding material (e.g., briquettes). In turn, it would be quite beneficial to be able to improve the service life of roll pockets, particularly if it can be done without detrimental impact on their overall use or other desireable properties relating to either the pockets themselves, or the compacted masses thus formed. 
       SUMMARY OF THE INVENTION 
       [0005]    In one preferred embodiment, the present invention provides a mold for use in a rotary compactor, the mold comprising a plurality of roll pockets adapted to form a compacted mass (e.g., briquet) from a compactable material. In a preferred embodiment, the mold provides a plurality (e.g., pair) of replaceable, opposing roll pockets, adapted to form a compacted mass, the pockets comprising:
       a) a first pocket adapted to impart a substantially convex upper surface to the compacted mass, and   b) a second pocket adapted to impart a substantially convex opposite (lower) surface to the compacted mass;   c) at least one of the first and second pockets comprising a surface configuration adapted to impart corresponding grooves to the respective compacted mass surface;   d) the surface configuration of at least one roll pocket providing a physical barrier to the flow of the compactable material adapted to impart an optimal balance between releasability and wear resistance as compared to pockets previously known in the art.       
 
         [0010]    In turn, a roll pocket of the present invention provides an improved combination of both service life and economy, as compared to roll pockets previously known. 
         [0011]    In one preferred embodiment, for instance, at least one roll pocket comprises one or more reliefs, positioned in a manner that is sufficiently offset from the direction of material flow. The relief(s), in turn, is sufficient to provide a damming effect, thereby impeding the flow of material, in a manner sufficient to lessen abrasion of the pocket surface by the material itself, and thereby improve the useful working life of the pocket. In addition to its damming effect, however, the relief is also sufficient (e.g., in terms of its size, dimensions, and orientation) to permit suitable release of the compacted material, once formed. 
         [0012]    In a particularly preferred embodiment, the pocket comprises a plurality of such relief portions, e.g., in the form of parallel lines, or cross-hatched lines (e.g., as in the general form of an “X”, a “K”, or an inverted chevron), wherein at least one such line is offset from the path of material flow. 
         [0013]    In a particularly preferred embodiment, a pair of opposing roll pockets is provided (also referred to as a pocketed roll), adapted to form a briquet having grooves on both major convex surfaces, the pockets having improved wear resistance, sufficient to permit significantly more feed material to be formed, as compared to roll pockets previously used. For instance, the improved wear resistance preferably corresponds to between about 10 and about 50% longer life before replacement of a roll pocket, and preferably 25 to 35% longer life, as compared to a pocket without such surface configuration. In a particularly preferred embodiment, the mold comprises a pair of opposing roll pockets, each of which provide at about 10% or more, and preferably about 15% or more longer life for either or both pockets as previously known and described (e.g., as described in U.S. patent application Ser. No. US 2006/0064926 cited above). 
         [0014]    Without intending to be bound by theory, it appears that the surface configuration provided by a roll pocket of this invention is sufficient to grab feed material, on the one hand, thereby slowing or “damming” the flow of material through the pocket (and in turn, lessening abrasive wear), while at the same time, facilitating release of the formed briquette. 
         [0015]    In turn, those skilled in the art, given the present description, will appreciate the manner in which the geometric configuration of either or both pockets, and corresponding surface configurations, can be determined, based on such considerations as the particle size, moisture content, compaction pressure, and release characteristics of the feed material itself. 
         [0016]    Those skilled in the art will further appreciate, given the present description, the manner in which various factors can be determined in order to achieve the goals and improvement described herein. These include, for instance, the orientation of reliefs (e.g., offset parallel lines, cross-hatched lines, etc.), the dimensions of any particular relief (e.g., height, length, radii), the operational conditions (e.g., material velocity, pressure), and the material itself (e.g., particle size, moisture, density, abrasiveness). 
         [0017]    In turn, the mold of the present invention can be used to compact any suitable material, including for instance, powdered or granular charcoal, biomass, steel mill byproducts, fertilizer, and the like. 
         [0018]    In an other aspect, the present invention provides a compacted mass (e.g., briquet) formed using a pocket roll and corresponding method of this invention. Such a briquet will generally have a generally pillow-shaped briquet having a generally convex upper surface, a generally convex lower surface, and a periphery wherein at least one of the upper or lower surfaces has located thereon enhanced surface textured features in the form of at least one groove, channel, trench or the like, generally corresponding to the surface configuration on the pocket rolls used to form the compacted mass. 
         [0019]    In yet another aspect, the invention provides replacement parts, in the form of roll pockets, individually or in pairs, for use with a rotary mold in accordance with this invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]    The following drawings are illustrative of particular embodiments of the present invention and therefore do not limit the scope of the invention. The drawings are not to scale (unless so stated) and are intended for use in conjunction with the explanations in the following detailed description. Embodiments of the present invention will hereinafter be described in conjunction with the appended drawings, wherein like numerals denote like elements. 
           [0021]      FIG. 1  is a side view of a rotary compactor according to some embodiments of the invention. 
           [0022]      FIG. 2  is a schematic diagram illustrating engagement of opposing roll presses according to some embodiments of the invention. 
           [0023]      FIG. 3  is a partial side cut-away and cross-sectional view of a press roll according to some embodiments of the invention. 
           [0024]      FIG. 4A-4C  are various views of a prior art roll pocket including parallel reliefs, having lengths substantially parallel to the flow of material. 
           [0025]      FIGS. 5A-5D  are various views of a roll pocket including parallel reliefs according to some embodiments of the invention. 
           [0026]      FIGS. 6  is a partial side cut-away and cross-sectional view of a press roll according to some embodiments of the invention. 
           [0027]      FIGS. 7A-7C  are various views of a prior art roll pocket including a K-shaped relief. 
           [0028]      FIGS. 8A-8C  are various views of a roll pocket including a K-shaped relief according to some embodiments of the invention. 
           [0029]      FIGS. 9A-9B  are various views of a roll pocket including corner relief portions according to some embodiments of the invention. 
           [0030]      FIGS. 10A-10B  are various views of a roll pocket including angled relief portions according to some embodiments of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0031]    The following detailed description is exemplary in nature and is not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the following description provides some practical illustrations for implementing exemplary embodiments of the present invention. Examples of constructions, materials, dimensions, and manufacturing processes are provided for selected elements, and all other elements employ that which is known to those of ordinary skill in the field of the invention. Those skilled in the art will recognize that many of the noted examples have a variety of suitable alternatives. 
         [0032]    Briquetting can be performed using various approaches. Roll type briquette machines apply pressures to particles by squeezing them between two rolls rotating in opposite directions. In turn, pockets (e.g., including or in the form of cavities or indentations) can be cut into the surfaces of the rolls for use in forming the briquettes. 
         [0033]    Modern briquette machines usually have only one roll in a fixed position in the frame. The other roll is moveable, but is restrained by hydraulic cylinders. The rolls may be arranged horizontally or side by side in the frame, or they may be arranged vertically or one above the other as in rolling mills. The rolls additionally may be located symmetrically between the bearings or they may be mounted outside the bearings at the end of cantilevered shafts. Each of these four arrangements has certain unique properties. Other features of the machines as well can be varied to satisfy special process conditions. Six characteristics in all determine the behavior of roll type briquette machines. 
         [0034]    Briquette machine rolls are classified according to their construction as integral, solid or segmented. Integral rolls, as the name implies, are made integral with the shafts. These rolls usually have a band of stainless steel or some corrosion or abrasion resistant material welded to their circumference or working face. Since they have no joints or mating surfaces, integral rolls are frequently used for briquetting food or pharmaceutical products where cleanliness is of primary concern. Integral rolls can easily be steam heated or water cooled. They are not generally suitable for abrasive materials. 
         [0035]    Solid rolls or tires are the most commonly used briquetting rolls and consist of replaceable rings keyed or shrink fitted to the shafts. The rolls are made from a variety of abrasion and corrosion resistant materials. Unlike integral rolls, which require some compromise in materials of construction, solid rolls and shafts can each be made from the most suitable material. 
         [0036]    Segmented rolls are made in a series of sections or segments which are mechanically clamped to the shafts. The advantages of segmented rolls are obvious to anyone who has ever changed conventional rolls, so rolls of this type have been the subject of continuing investigation since the beginning of the briquetting industry. Segmented rolls are recommended for briquetting hot or abrasive materials and are made from materials suitable for such applications. 
         [0037]    The mechanical construction of the rolls determines such important characteristics as reliability, ease of maintenance and cost of operation. The effect that the rolls will have upon materials passing through them, however, depends on their geometry. In most briquette machines, the moveable roll is pressed against a fixed roll by hydraulic cylinders. Stops located between the bearing blocks prevent the rolls from coming in contact with each other. Material passing between the rolls attempts to spread them apart. The hydraulic cylinders resist this effort until the force exerted by the material exceeds that exerted by the cylinders. The moveable roll is then displaced and in turn displaces the pistons in the hydraulic cylinders until both efforts become equal. The oil displaced by the pistons is stored under pressure in a gas filled accumulator. It returns from there as needed to push the moveable roll back against the stops. 
         [0038]    The hydraulic system acts like a spring. The initial force holding the rolls together can be adjusted by the pressure of the oil in the cylinders. The incremental force necessary to displace the moveable roll is also adjustable by the volume of the gas in the accumulator. The success of the modern roll type briquette machine is due in no small part to this ability of the hydraulic system to match the slope of the force-displacement curve of the moveable roll to the requirements of the briquetting process. When roll type briquette machines were limited to compacting materials, which were mixed with binders, the simple gravity type feeder was usually adequate. Briquetting in this case is primarily a forming or molding process and little change in the density of the product occurs as it passes through the rolls. The pressure required for such applications is low and the virtue of simplicity frequently outweighs the advantages possible from more sophisticated control. 
         [0039]    Gravity type feeders consequently are still used for some purposes. For dry or finely divided materials, screw or auger type feeders are commonly used. These feeders in addition to controlling the mass of material passing between the rolls, frequently have important secondary effects. They may precompress the material before it reaches the rolls. They may crush the particles to achieve a more favorable size consistency. There is speculation that the mobility of the particles in the feed screw allows the crystal axes to align themselves more favorably so as to produce better quality briquettes. Heating of the particles in the screw feeder may also have a significant effect. Whatever the mechanisms may be, briquettes of better quality frequently can be made by using a screw feed. 
         [0040]      FIG. 1  is a side view of a rotary compactor  100  (also referred to herein as a “briquette machine”) according to some embodiments of the invention. The general design and construction of rotary compactors is well known in the art, and for the sake of clarity only a brief overview of the rotary compactor  100  is provided herein. Those skilled in the art will appreciate that rotary compactors are complex machines including numerous components not included in the discussion herein. The roll compactor  100  generally includes opposing roll assemblies  104 ,  106  that are mounted and engaged within the compactor  100  in a manner that facilitates the briquetting functionality of the compactor  100 . The compactor  100  further includes a feeder assembly  102  positioned above the roll assemblies  104 ,  106  that receives briquette material and feeds the material to the roll assemblies. The roll assemblies  104 ,  106  comprise a number of components familiar to those skilled in the art, including press rolls or molds that include a number of roll pockets configured to receive the material from the feeder assembly  102  and form it into briquettes. 
         [0041]      FIG. 2  illustrates at least a portion of this process.  FIG. 2  is a schematic diagram illustrating engagement of opposing roll presses  200 ,  202  according to some embodiments of the invention. Each roll press  200 ,  202  includes a number of roll pockets  204  (shown in cross-section). As the first press roll  200  rotates in direction  208  (clockwise in  FIG. 2 ) and the second press roll  202  rotates in direction  210  (counterclockwise in  FIG. 2 ), briquette material is introduced to the rolls in the direction of material flow  206 . The roll pockets  204  in the opposing press rolls come together and form a mold that receives the briquette material. The press rolls and pockets then press together to compact the material into a briquette (or other compactable mass) having a desired shape. 
         [0042]    As conventional press rolls rotate together and compact the briquette material, there is a tendency for the briquette material to expand and push out of the roll pockets in direction  212  due to the pressure and continuous rotation of the press rolls. This is sometimes referred to as material “washout.” The washed out material often abrades the press roll pockets, leading to undesired wear and poor performance along the trailing edge of the roll pocket, among other places. Embodiments of the invention provide one or more of the roll pockets with an improved surface configuration that provides an improved damming effect, thereby impeding the flow of washed out material in direction  212 , in a manner sufficient to lessen abrasion of the pocket surface. This improves the useful working life of the pocket. 
         [0043]      FIG. 3  is a partial cut-away and cross-sectional view showing a portion of a press roll  300  according to some embodiments of the invention.  FIG. 3  is a view of the press roll  300  from an orientation perpendicular to the axis of rotation  306 , and shows a portion of the outer surface or “face”  302  of the press roll  300 . The press roll  300  includes a number of roll pockets  304  arranged on the face  302  of the press roll  300 . While  FIG. 3  shows two rows of roll pockets  304  extending across the face  302  of the roll  300 , it should be appreciated that in some embodiments the roll pockets cover substantially the entire face  302  of the press roll in the form of consecutive rows. 
         [0044]    As shown near the top of  FIG. 3  in cross-section, the pockets  304  are formed as depressions or hollowed-out portions in the face  302  of the press roll  300 . In some embodiments the pockets  304  may be formed integrally within the surface of the press roll. In some embodiments the pockets  304  may be formed in mold segments that can be fixed to the surface of the press roll. Returning to  FIG. 3 , the roll pockets  304  have a surface configuration including two substantially parallel reliefs  314  that are angled with respect to the direction of compactable material flow  308  (and also with respect to the direction of material washout  212  shown in  FIG. 2 ). The rotation of the press roll  300  around the axis of rotation  306  defines a direction of rotation similar to the direction  308  of compactable material flow. The rotation also defines leading edges  310  and trailing edges  312  of each roll pocket  304 . 
         [0045]      FIG. 4A-4C  are various views of a prior art roll pocket  400  including a pair of parallel reliefs  412  oriented substantially parallel to a direction of flow  422  of the compactable material.  FIGS. 4A-4C  show the bottom, contoured surface  404  of the roll pocket  400  as it is formed in the press roll  402  (shown in dotted lines) with the pocket opening  406  positioned at the face of the roll.  FIG. 4A  shows a top view of the roll pocket  400 , illustrating the two reliefs  412 . The reliefs  412  are formed in the roll pocket  400  with a fillet  414  providing a smooth transition between the surface of the pocket  404  and portions of the reliefs  412 . The roll pocket  400  has a leading edge  408  and a trailing edge  410  determined by the direction of rotation of the press roll.  FIG. 4B  illustrates an end view of the roll pocket  400  taken along line BB shown in  FIG. 4A , showing a profile view of the reliefs  412 . Various dimensions of the roll pocket surface configuration are also denoted, including the pocket depth  416 , the relief height  418  as measured from the maximum pocket depth, and the relief depth  420  defined from the surface of the press roll. 
         [0046]      FIGS. 5A-5D  are various views of an improved roll pocket  500  according to some embodiments of the invention. The roll pocket  500  has a surface configuration including substantially parallel reliefs  512  oriented at an angle  526  with respect to a longitudinal axis  524  of the reliefs and the direction of material flow and press roll rotation  522 .  FIG. 5A  shows a top plan view of the pocket  500 . As shown in  FIG. 5B , which is a side view of  FIG. 5A  taken along line BB, the roll pocket  500  is formed as a depression in the press roll  502 , having a contoured bottom surface  504  and an opening  506  in the face of the press roll  502 . As shown in  FIGS. 5A and 5C , the reliefs  512  are formed as elongated, raised ridges having a curved surface. Fillets  514  provide a stepped transition between the reliefs and the surrounding surface  504  of the roll pocket  500  that improves the releasability characteristics of the pocket. 
         [0047]    Returning briefly to  FIG. 2 , when compactable material is introduced to the mold formed by the opposing roll pockets  204  and the roll pockets compress together as the press rolls  200 ,  202  rotate, the compactable material tends to be pushed out of the pockets in a direction  212  opposite the direction of rotation  208 ,  210 . Accordingly, the material is pushed from the leading edge to the trailing edge of the pocket, and in some cases out of the pocket proximate the trailing edge. Returning to  FIG. 5A , according to some embodiments the surface configuration (e.g., reliefs  512 ) of the roll pocket  500  provides a physical barrier to this backflow or washout of the compactable material as it is pushed from the leading edge  508  of the pocket to the trailing edge  510  of the pocket  500 . The physical barrier reduces the amount of material being washed out of the pocket, thus reducing wear on the pocket and extending the useful life of the roll pocket  500 . 
         [0048]    Accordingly, one or more reliefs can effectively trap some of the compactable material as it is pushed back out of the pocket, reducing washout and wear on the pocket. In the example shown in  FIGS. 5A-5D , the two reliefs  512  provide trapping edges  528  that act as physical barriers to the flow of the compactable material toward the trailing edge  510  of the pocket. The reliefs  512  thus create “trap zones”  530  between the leading edge  508  of the pocket and the trapping edges  528 . Turning to  FIGS. 4A-4C , the example of the prior art roll pocket  400  does not provide a surface configuration that forms a barrier to movement of the compactable material toward the trailing edge  410  of the pocket  400  (opposite the direction of material flow  422 ). Instead, the roll pocket  400  includes reliefs  412  that are substantially parallel to the direction  422  of material flow, allowing material to move more freely toward the trailing edge  410  of the pocket. 
         [0049]    Returning to  FIGS. 5A-5D , in some embodiments of the invention, the dimensions of the various contours and reliefs on the surface  504  of the roll pocket  500  can also provide an improved capability to trap or “dam” compactable material within the roll pocket. For example, in some embodiments the reliefs  512  of the roll pocket  500  have an increased height  518  with respect to the pocket depth  516  than in previous roll pockets. The increased height of the relief  512  presents a higher physical barrier to material moving within the pocket, thus decreasing wear and increasing the useful life of the pocket  500 . 
         [0050]    Accordingly, one or more aspects of the roll pocket  500  provide improved performance over the prior art roll pocket  400 . For example, it is believed that improvements in the surface configuration of the improved roll pocket  500  can increase the serviceable life of the roll pocket  500  by about 30% with respect to the prior art roll pocket  400 . Similarly, it is estimated that a typical, improved roll pocket  500  can process about 30% more compactable material than previous roll pockets before needing replacement. 
         [0051]      FIG. 6  is a partial cut-away and cross-sectional view showing a portion of a press roll  600  according to some embodiments of the invention.  FIG. 6  is a view of the press roll  600  from an orientation perpendicular to the axis of rotation  606 , and shows a portion of the outer surface or “face”  602  of the press roll  600 . The press roll  600  includes a number of roll pockets  604  arranged on the face  602  of the press roll  600 . While  FIG. 6  shows two rows of roll pockets  604  extending across the face  602  of the roll  600 , it should be appreciated that in some embodiments the roll pockets cover substantially the entire face  602  of the press roll in the form of consecutive rows. 
         [0052]    As shown near the top of  FIG. 6  in cross-section, the pockets  604  are formed as depressions or hollowed-out portions in the face  602  of the press roll  600 . In some embodiments the pockets  604  may be formed integrally within the surface of the press roll. In some embodiments the pockets  604  may be formed in mold segments that can be fixed to the surface of the press roll. Returning to  FIG. 6 , the roll pockets  604  have a surface configuration including a K-shaped relief  614  having relief portions angled with respect to the direction of compactable material flow  608  (and also with respect to the direction of material washout  212  shown in  FIG. 2 ). The rotation of the press roll  600  around the axis of rotation  606  defines a direction of rotation similar to the direction  608  of compactable material flow. The rotation also defines leading edges  610  and trailing edges  612  of each roll pocket  604 . 
         [0053]      FIG. 7A-7C  are various views of a prior art roll pocket  700  including a K-shaped relief  712 .  FIGS. 7A-7C  show the bottom, contoured surface  704  of the roll pocket  700  as it is formed in the press roll  702  (shown in dotted lines) with the pocket opening  706  positioned at the face of the roll.  FIG. 4A  shows a top view of the roll pocket  700 , illustrating the K-shaped relief  712 . The relief  712  is formed in the roll pocket  700  with a fillet  714  providing a smooth transition between the surface of the pocket  704  and portions of the relief  712 . The roll pocket  700  has a leading edge  708  and a trailing edge  710  determined by the direction of rotation of the press roll.  FIG. 7B  illustrates an end view of the roll pocket  700  taken along line BB shown in  FIG. 7A , showing a profile view of the relief  712 . Various dimensions of the roll pocket surface configuration are also denoted, including the pocket depth  716 , the relief height  718  as measured from the maximum pocket depth, and the relief depth  720  defined from the surface of the press roll. 
         [0054]      FIGS. 8A-8D  are various views of an improved roll pocket  800  according to some embodiments of the invention. The roll pocket  800  has a surface configuration including a K-shaped relief  812  having portions of the relief oriented at an angle with respect to the direction of material flow and press roll rotation  822 .  FIG. 8A  shows a top plan view of the pocket  800 . As shown in  FIG. 8B , which is a side view of  FIG. 8A  taken along line BB, the roll pocket  800  is formed as a depression in the press roll  802 , having a contoured bottom surface  804  and an opening  806  in the face of the press roll  802 . As shown in  FIGS. 8A and 8C , the relief  812  is formed as a group of connected, elongated, raised ridges having curved surfaces. Fillets  814  provide a stepped transition between the relief and the surrounding surface  804  of the roll pocket  800  that improves the releasability characteristics of the pocket. 
         [0055]    According to some embodiments the surface configuration (e.g., relief  812 ) of the roll pocket  800  provides a physical barrier to the backflow or washout of the compactable material as it is pushed from the leading edge  808  of the pocket to the trailing edge  810  of the pocket  800 . The physical barrier reduces the amount of material being washed out of the pocket, thus reducing wear on the pocket and extending the useful life of the roll pocket  800 . 
         [0056]    Accordingly, the K-shaped relief (or one or more portions of the relief) can effectively trap some of the compactable material as it is pushed back out of the pocket, reducing washout and wear on the pocket. In the example shown in  FIGS. 8A-8D , the two angled “legs” of the relief  812  provide trapping edges  828  that act as physical barriers to the flow of the compactable material toward the trailing edge  810  of the pocket. The relief  812  thus creates “trap zones”  830  between the leading edge  808  of the pocket and the trapping edges  828 . 
         [0057]    In some embodiments of the invention, the dimensions of the various contours and reliefs on the surface  804  of the roll pocket  800  can also provide an improved capability to trap or “dam” compactable material within the roll pocket. For example, in some embodiments the relief  812  of the roll pocket  800  has an increased height  818  with respect to the pocket depth  816  than in previous roll pockets. The increased height of the relief  812  presents a higher physical barrier to material moving within the pocket, thus decreasing wear and increasing the useful life of the pocket  800 . With respect to  FIG. 7B , for example, the prior art roll pocket  700  may have a relief height  718  of about 0.117 inches above the bottom of the pocket, while the improved embodiment shown in  FIG. 8B  can include a relief height  818  of about 0.202 inches. When compared with pocket depths of 0.455 inches and 0. 432  inches for the prior art pocket  700  and the improved pocket  800 , respectively, the improved surface configuration of the pocket  800  provides a relief height  818  that is about 47% of the pocket depth  816 , while the prior art pocket  700  only provides a relief height  718  of about 26% of the pocket depth  716 . The substantial increase in relief height in proportion to pocket depth can provide improved trapping or damming characteristics. 
         [0058]    Accordingly, one or more aspects of the roll pocket  800  provide improved performance over the prior art roll pocket  700 . For example, it is believed that improvements in the surface configuration of the improved roll pocket  800  can increase the serviceable life of the roll pocket  800  by about 15% with respect to the prior art roll pocket  700 . Similarly, it is estimated that a typical, improved roll pocket  800  can process about 15% more compactable material than the previous roll pocket  700  before needing replacement. 
         [0059]      FIGS. 9A-9B  are various views of a roll pocket including a plurality of reliefs according to some embodiments of the invention. The roll pocket  900  has a surface configuration including raised corner reliefs  912  having portions oriented at an angle with respect to the direction of material flow and press roll rotation  922 .  FIG. 9A  shows a top plan view of the pocket  900 . As shown in  FIG. 9B , which is a front perspective view of  FIG. 9A , the roll pocket  900  is formed as a depression in the press roll  902 , having a contoured bottom surface  904  and an opening  906  in the face of the press roll  902 . As shown in  FIGS. 9A and 9B , the reliefs  912  are formed as a group of raised corner portions having curved surfaces configured to form a raised cross or t shape in a compactable mass. Fillets provide a stepped transition between the reliefs and the surrounding surface  904  of the roll pocket  900  that improves the releasability characteristics of the pocket. 
         [0060]    According to some embodiments the surface configuration (e.g., one or more of the reliefs  912 ) of the roll pocket  900  provides a physical barrier to the backflow or washout of the compactable material as it is pushed from the leading edge  908  of the pocket to the trailing edge  910  of the pocket  900 . The physical barrier reduces the amount of material being washed out of the pocket, thus reducing wear on the pocket and extending the useful life of the roll pocket  900 . 
         [0061]    Accordingly, one or more of the corner relief portions can effectively trap some of the compactable material as it is pushed back out of the pocket, reducing washout and wear on the pocket. In the example shown in  FIGS. 9A and 9B , the two upper corner reliefs  912  near the trailing edge  910  of the pocket provide trapping edges  928  that act as physical barriers to the flow of the compactable material toward the trailing edge  910  of the pocket. The reliefs  912  thus creates “trap zones”  930  between the leading edge  908  of the pocket and the trapping edges  928 . 
         [0062]    While  FIGS. 9A and 9B  show a surface configuration adapted to form a raised cross in the compactable mass, a corresponding inverted configuration is also possible in some embodiments. For example, the pocket  900  could include a single cross shaped relief that rises above the pocket surface  904  that is adapted to form a raised cross shape with depressed dimples in the compressed mass. 
         [0063]      FIGS. 10A-10B  are various views of a roll pocket including a plurality of reliefs according to some embodiments of the invention. The roll pocket  1000  has a surface configuration including raised angled reliefs  1012  having portions oriented at an angle with respect to the direction of material flow and press roll rotation  1022 .  FIG. 10A  shows a top plan view of the pocket  1000 . As shown in  FIG. 10B , which is a front perspective view of  FIG. 10A , the roll pocket  1000  is formed as a depression in the press roll  1002 , having a contoured bottom surface  1004  and an opening  1006  in the face of the press roll  1002 . As shown in  FIGS. 10A and 10B , the reliefs  1012  are formed as a group of raised angled portions having curved surfaces configured to form a raised X shape in a compactable mass. Fillets provide a stepped transition between the reliefs and the surrounding surface  1004  of the roll pocket  1000  that improves the releasability characteristics of the pocket. 
         [0064]    According to some embodiments the surface configuration (e.g., one or more of the reliefs  1012 ) of the roll pocket  1000  provides a physical barrier to the backflow or washout of the compactable material as it is pushed from the leading edge  1008  of the pocket to the trailing edge  1010  of the pocket  1000 . The physical barrier reduces the amount of material being washed out of the pocket, thus reducing wear on the pocket and extending the useful life of the roll pocket  1000 . 
         [0065]    Accordingly, one or more of the raised relief portions  912  can effectively trap some of the compactable material as it is pushed back out of the pocket, reducing washout and wear on the pocket. In the example shown in  FIGS. 10A and 10B , the three upper reliefs  1012  provide trapping edges  1028  that act as physical barriers to the flow of the compactable material toward the trailing edge  1010  of the pocket. The reliefs  1012  thus creates “trap zones”  1030  between the leading edge  1008  of the pocket and the trapping edges  1028 . 
         [0066]    While  FIGS. 10A and 10B  show a surface configuration adapted to form a raised X shape in the compactable mass, a corresponding inverted configuration is also possible in some embodiments. For example, the pocket  1000  could include a single X-shaped relief that rises above the pocket surface  1004  that is adapted to form a raised X-shape with depressed dimples in the compressed mass. 
         [0067]    According to some embodiments, the surface configuration of a particular roll pocket may include one or more reliefs oriented at a variety of angles with respect to the directions of material flow/washout. For example, in some cases the surface configuration may include a single, horizontal relief (or groove made from e.g., two horizontal reliefs) oriented substantially perpendicularly to the direction of material flow. In some embodiments different angular configurations such as an inverted V- or chevron-shaped relief can be incorporated into the surface of the roll pocket. Those skilled in the art will appreciate that a variety of surface configurations are possible that have properties similar to those of the described embodiments for providing an improved damming effect on the flow of material out of a roll pocket. 
         [0068]    Thus, embodiments of the invention are disclosed. Although the present invention has been described in considerable detail with reference to certain disclosed embodiments, the disclosed embodiments are presented for purposes of illustration and not limitation and other embodiments of the invention are possible. One skilled in the art will appreciate that various changes, adaptations, and modifications may be made without departing from the spirit of the invention and the scope of the appended claims.