Abstract:
A process for producing a colored wood product, comprising the steps of grinding wood in a mill until a wood compact is formed, sieving the wood compact, spraying the sieved wood compact with an aqueous solution of colorant, immersing the wood compact in a bath of aqueous solution of colorant while simultaneously moving the wood compact with a multiplicity of counterrotating augers, and then removing the wood compact from said bath.

Description:
FIELD OF THE INVENTION 
     A process for grinding and coloring wood chips. 
     BACKGROUND OF THE INVENTION 
     U.S. Pat. No. 5,308,653 of Rondy discloses a process for preparing a colored wood product, such as mulch. In the first step of the process of this patent, comminuted wood is fed into a screw conveyor having a first end and a second end, wherein the screw conveyor has a helical auger disposed axially and in close fitting relationship to the internal surface within a generally closed channel, and with a feed port near the first end and a discharge end near the second end, the helical augur being capable of being rotated by a drive means; in this step, the conmminuted wood is fed through the feed port into the first end of the conveyor. In the second step of the process of this patent, the conmminuted wood is contacted with an aqueous color-imparting solution containing at least one color-imparting agent therein for sufficient time to disperse the color-imparting solution onto the surfaces of the comminuted wood to create a colored wood product, such contact occurring at least at the feed port through a feed port nozzle means substantially transversing the feed port and providing a gravity feed sheet of the color imparting solution from a longitudinal slot formed therein. In the third step of the process of this patent, the augur is rotated so that the colored wood product is drawn from the first end to the second end, during which time excess color-imparting solution is drained away from the colored wood product, thereby drying the colored wood product. In the last step of the process, the dried colored wood product is discharged from the screw conveyor (via a discharge chute) and further dried, if necessary. The entire disclosure of thing United States patent is hereby incorporated by reference into this specification. 
     The process of the Rondy patent produces a colored mulch patent with a substantially non-uniform particle size distribution and non-uniformly colored particles. Furthermore, the colored mulch produced by the Rondy patent is not intensely colored. 
     It is an object of this invention to provide a process for producing a colored mulch which has intense color and which is substantially more uniform than the prior art colored mulch products. 
     SUMMARY OF THE INVENTION 
     In accordance with this invention, there is provided a process for producing a colored mulch in which wood is ground by a mill until a compact is formed with at least 80 weight percent of the particles smaller than 4.0 inches, the compact thus formed is sieved to produce a sieved product, the sieved product is then sprayed with a colorant solution while it is being conveyed by a multiplicity of augers to produce a first colored sieved product, the first colored sieved product is immersed in a bath of colorant solution to produce a second colored sieved product, and the second colored sieved product is removed from the bath by a multiplicity of augers and dried. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be described by reference to the specification and the enclosed drawings, in which like numerals refer to like elements, and in which: 
     FIG. 1 is a side view of one preferred apparatus suitable for practicing the process of the invention; 
     FIG. 2 is an exploded view of the apparatus of FIG. 1; 
     FIG. 3 a perspective view of a preferred screening device used in the apparatus of Figure; and 
     FIG. 4 is schematic view of one preferred augur assembly used in the apparatus of FIG.  1 ; 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 is a side view of one preferred color grinder  10  apparatus adapted to practice the process of this invention. One preferred color grinder  10  was produced in accordance with applicant&#39;s specifications and is sold as model number 3600 by Morbark, Inc. of 8507 South Winn Road, Winn, Mich. 
     Referring to FIG. 1, and in the preferred embodiment depicted therein, it will be seen that color grinder  10  is comprised of feed hopper  12 , top yoke  14 , radiator  16 , power unit  18 , hydraulic oil tank  20 , and discharge conveyor  22 . 
     FIG. 2 is a schematic representation of one preferred color grinder  10 . Referring to the embodiment depicted in FIG. 2, it will be seen that wood is fed into hopper  26  onto feed chain  28  which travels in the direction of arrow  30 . 
     The wood used in the preferred process of this invention may be wood in any form and any state of dryness. Thus, e.g., the wood disclosed in U.S. Pat. No. 5,308,653 may be used in the process; the entire disclosure of this patent is hereby incorporated by reference into this specification. Thug, e.g., the wood may be green wood, dry wood with a moisture content of 30 percent of less, etc. 
     In one preferred embodiment, the wood used is substantially pure wood, that is, it contains at least about 90 weight percent of cellulosic material. 
     In one embodiment, the wood used is “curb waste,” i.e., wood from tree trimmings, bushes, construction and demolition waste, wood pallets, etc. 
     Referring again to FIG. 2, the wood  32  is conveyed by feed chain  28  into contact with mill  34 . 
     In one embodiment, e.g., the mill  34  may be one or more of the rotary grinding devices described in U.S. Pat. No. 5,794,866 (a rotatably mounted drum with a plurality of spaced cutter teeth attached to the exterior of the drum), U.S. Pat. Nos. 5,692,689, 5,609,113, 4,470,224, and the like. 
     In another embodiment, the mill assembly  34  may be a hammer mill assembly. Thus, e.g., one may use one or more of the hammer mills described in U.S. Pat. Nos. 4,354,487, 4,215,692, 4,035,217, and the like. The disclosure of each of these United States patents is hereby incorporated by reference into this specification. 
     Referring again to FIG. 2, and in the preferred embodiment depicted therein, mill  34  is comprised of a yoke  36  which feeds the wood into contact with hammer mill  38 . As is known to those skilled in the art, the hammer mill  38  is comprised of a multiplicity of hammers  40  affixed to the exterior of drum  42 . The hammers  40  may be either swing hammers or fixed hammers. In one preferred embodiment, fixed hammers are used. 
     Regardless of which comminuting device is used, the mill  34  preferably grinds wood  32  until substantially at least 80 weight percent of the wood ground by mill  34  has a maximum dimension less than 4.0 inches. In one embodiment, the ground wood produced by mill  34  has a particle size distribution such that at least about 80 percent of its particles are less than 3.0 inches in size. In yet another embodiment, at least about 80 weight percent of the particles produced by mill  34  are less than about 2.2 inches in size. 
     Referring again to FIG. 2, the ground wood produced by mill  34  is then contacted with a sieve  44  which separates all particles greater than 4.0 inches in size such that at least about 98 weight percent of the material percent of the material passing through sieve  44  is smaller than 4.0 inches and, more preferably, smaller than 3.0 inches. In the most preferred embodiment, at least about 98 percent of the sieved material is smaller than 2.0 inches. 
     FIG. 3 illustrates a preferred embodiment of sieve  44 . In the preferred embodiment depicted, sieve  44  is comprised of section  46 , section  48 , and section  50 ; and the sieve openings in each of these sections are preferably circular in cross section. In another embodiment, not shown, the sieve openings have a substantially square shape. 
     Referring to FIG. 3, the sections  46 ,  48 , and  50  are joined to each other by conventional means, such as by a track (not shown) into which these sections slide. In another embodiment, the sections  46 ,  48 , and  50  are integrally joined to each other. In either event, the sieve assembly  44  presents no open area(s) for the passage of wood except for sieve openings  52 . 
     Referring again to FIG. 2, the sieved material  54  passing through sieve  44  is sprayed with a colorant solution passing through a multiplicity of nozzles  56 . 
     The colorant solution passing through the nozzles  56  produces a spray which extends over an area of at least about 4 feet. Thus, although not drawn to scale, width  58  of spray  60  generally extend form the exterior surface  62  of screen  44  past the base  64  of auger system  66 . Residual spray  60  winds up into auger trays  68 . 
     It will be seen thus, that the sieved material is first sprayed with colorant solution and then immersed within auger tray  68  which is filled with colorant solution. 
     FIG. 4 is a schematic representation of auger system  66  which is comprised of a multiplicity of augers  70 ,  72 , and  74 . One may user one or more of the augers described in U.S. Pat. No. 5,308,653, the entire disclosure of which is hereby incorporated by reference into this specification. 
     Referring to FIG. 4, it is preferred to use at least two augers, such as augers  70  and  72 , in process. When such auguers  70  and  72  are used, they preferably are rotated in opposite directions, such as, e.g., in the direction of arrows  76  and  78 . The use of these counter-rotating augers  76  and  78  tends to promote better penetration of the colorant solution into the wood material. 
     It is preferred to use two, or a multiple of two, augers, each adjacent auger rotating in a direction opposite to that of the auger next to it. In one embodiment, illustrated in FIG. 4, each of the augers is comprised of paddles  80  connected to the periphery of one or more sections of one or more of the augers  70 ,  72 , and/or  74 . In general, paddles  80  have a substantially square shape and may be, e.g., approximately 4.0 inches square. 
     Referring again to FIG. 4, the augers  70 ,  72 , and/or  74  are disposed within corresponding trays  82 ,  84 , and  86 , each of which is comprised of colorant solution  61 . A sufficient amount of colorant solution  61  is disposed within each such tray  82 ,  84 , and  86  that the sieved material  54  is immersed within the colorant solution. As will be apparent to those skilled in the art, as augers  70 ,  72  et seq. rotate, they move the sieved material  54  from the base  88  of the trays to the discharge end  90 . 
     Referring again to FIG. 2, the material discharged at discharge end  90  then drops onto stacking conveyor  92  and preferably conveyed upwardly to a point  94  at which it preferably contacts magnetic separator  96 , which removes metallic objects from the sieved material. The metallic objects then can be discharged through chute  97  to bin  98 . 
     The sieved material is then discharged into a truck (not shown) or other suitable container (not shown) and allowed to drop into a heap of material  100 . 
     The colorant material used in the process, which is also used to produce spray  60 , preferably is an aqueous color-imparting solution containing at least one color-imparting agent therein. One suitable solution is described in U.S. Pat. No. 5,308,653, the entire disclosure of which is hereby incorporated by reference into this specification. 
     In one embodiment, the colorant may be an aqueous solution containing iron oxide pigment, carbon black pigment, or am mixture thereof. 
     In one embodiment, the colorant solution is sold as “AMERIMULCH” by the Amerimulch Company of 5549 Canal Road, Valley View, Ohio. In another embodiment, the colorant solution is sold as “MULCH MAGIC” by Becker Underwood Inc. of 801 Dayton Avenue, Ames, Iowa. Alternatively, one can purchase colorant solution from the T. H. Glennan Company. 
     By way of further illustration, one may use one or more of the colorants described in U.S. Pat. Nos. 4,932,156, 2,772,137 (light mahagony staining solution), U.S. Pat. No. 1,043,582 (brown wood coloring solution), U.S. Pat. No. 4,716,060 (colorant with a preservative component), U.S. Pat. No. 3,685,959 (natural wood colors), U.S. Pat. Nos. 2,623,027, 4,530,778, and the like. The disclosure of each of these United States patent applications is hereby incorporated by reference into this specification. 
     Regardless of the colorant solution used, it is preferred to contact the material passing through sieve  44  with at least about two pounds, by weight, of colorant per cubic yard of sieved material; substantially all of such two pounds is then incorporated into the sieved material. In one embodiment, at least four pounds of colorant, by dry weight, are incorporated into the sieved material. The preferred concentration of colorant in the finished product is from about 2.5 to about 4.0 pounds of colorant per cubic yard of dried finished product. 
     It is to be understood that the aforementioned description is illustrative only and that changes can be made in the apparatus, in the ingredients and their proportions, and in the sequence of combinations and process steps, as well as in other aspects of the invention discussed herein, without departing from the scope of the invention as defined in the following claims.