Abstract:
Multiple shafts are aligned along a frame and configured to rotate in a direction causing paper products to move along a separation screen. The shafts are configured with a shape and spacing so that substantially rigid pieces of the paper products move along the screen while non-rigid pieces of the paper products slide down between adjacent shafts. In one embodiment, the screen includes at least one vacuum shaft that has a first set of air input holes configured to suck air and retain the non-rigid paper products. A second set of air output holes are configured to blow out air to dislodge the paper products retained by the input holes.

Description:
DESCRIPTION OF THE RELATED ART 
   This application is a continuation of U.S. application Ser. No. 10/823,835, filed Apr. 13, 2004, now issued U.S. Pat. No. 7,434,695; which claimed priority to U.S. application Ser. No. 10/264,298, filed Oct. 2, 2002, now issued U.S. Pat. No. 6,726,028, which claimed priority from U.S. Provisional Application No. 60/326,805, filed Oct. 2, 2001 and are all incorporated herein by reference in their entirety. 

   Disc or roll screens are used in the materials handling industry for screening flows of materials to remove certain items of desired dimensions. Disc screens are particularly suitable for classifying what is normally considered debris or residual materials. This debris may consist of soil, aggregate, asphalt, concrete, wood, biomass, ferrous and nonferrous metal, plastic, ceramic, paper, cardboard, paper products or other materials recognized as debris throughout consumer, commercial and industrial markets. The function of the disc screen is to separate the materials fed into it by size or type of material. The size classification may be adjusted to meet virtually any application. 
   Disc screens have a problem effectively separating Office Sized Waste Paper (OWP) since much of the OWP may have similar shapes. For example, it is difficult to effectively separate notebook paper from Old Corrugated Cardboard (OCC) since each is long and relatively flat. 
   Accordingly, a need remains for a system that more effectively classifies material. 
   SUMMARY OF THE INVENTION 
   Multiple shafts are aligned along a frame and configured to rotate in a direction causing paper products to move along a separation screen. The shafts are configured with a shape and spacing so that substantially rigid or semi-rigid paper products move along the screen while non-rigid or malleable paper products slide down between adjacent shafts. 
   In one embodiment, the screen includes at least one vacuum shaft that has a first set of air input holes configured to suck air and retain the non-rigid paper products. A second set of air output holes are configured to blow out air to dislodge the paper products retained by the input holes. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic showing a single-stage de-inking screen. 
       FIG. 2  is a schematic showing a dual-stage de-inking screen. 
       FIG. 3  is a schematic showing an isolated view of vacuum shafts used in the de-inking screens shown in  FIG. 1  or  2 . 
       FIG. 4  is schematic showing an isolated view of a plenum divider that is inserted inside the vacuum shaft shown in  FIG. 3 . 
       FIGS. 5A-5C  show different discs that can be used with the de-inking screen. 
       FIG. 6  is a plan view showing an alternative embodiment of the de-inking screen. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring to  FIG. 1 , a de-inking screen  12  mechanically separates rigid or semi-rigid paper products constructed from cardboard, such as Old Corrugated Containers (OCC), kraft (small soap containers, macaroni boxes, small cereal boxes, etc.) and large miscellaneous contaminants (printer cartridges, plastic film, strapping, etc.)  14  from malleable or flexible office paper, newsprint, magazines, journals, and junk mail  16  (referred to as de-inking material). 
   The de-inking screen  12  creates two material streams from one mixed incoming stream fed into an in feed end  18 . The OCC, kraft, and large contaminants  14  are concentrated in a first material stream  20 , while the de-inking material  16  is simultaneously concentrated in a second material stream  22 . Very small contaminants, such as dirt, grit, paper clips, etc. may also be concentrated with the de-irking material  16 . Separation efficiency may not be absolute and a percentage of both materials  14  and  16  may be present in each respective material stream  20  and  22  after processing. 
   The separation process begins at the in feed end  18  of the screen  12 . An in feed conveyor (not shown) meters the mixed material  14  and  16  onto the de-inking screen  12 . The screen  12  contains multiple shafts  24  mounted on a frame  26  with brackets  28  so as to be aligned parallel with each other. The shafts  24  rotate in a forward manner propelling and conveying the incoming materials  14  and  16  in a forward motion. 
   The circumference of some of the shafts  24  may be round along the entire length, forming continuous and constant gaps or openings  30  along the entire width of the screen  12  between each shaft  24 . The shafts  24  in one embodiment are covered with a roughtop conveyor belting to provide the necessary forward conveyance at high speeds. Wrappage of film, etc. is negligible due to the uniform texture and round shape of the rollers. Alternatively, some of the shafts  24  may contain discs having single or dual diameter shapes to aide in moving the materials  14  and  16  forward. One disc screen is shown in  FIG. 6 . 
   The distance between each rotating shaft  24  can be mechanically adjusted to increase or decrease the size of gaps  30 . For example, slots  32  in bracket  28  allow adjacent shafts  24  to be spaced apart at variable distances. Only a portion of bracket  28  is shown to more clearly illustrate the shapes, spacings and operation of shafts  24 . Other attachment mechanisms can also be used for rotatably retaining the shafts  24 . 
   The rotational speed of the shafts  24  can be adjusted offering processing flexibility. The rotational speed of the shafts  24  can be varied by adjusting the speed of a motor  34  or the ratio of gears  36  used on the motor  34  or on the screen  12  to rotate the shafts  24 . Several motor(s) may also be used to drive different sets of shafts  24  at different rotational speeds. 
   Even if the incoming mixed materials  14  and  16  may be similar in physical size, material separation is achieved due to differences in the physical characteristics of the materials. Typically, the de-inking material  16  is more flexible, malleable, and heavier in density than materials  14 . This allows the de-inking material  16  to fold over the rotating shafts  24 A and  24 B, for example, and slip through the open gaps while moving forward over the shafts  24 . 
   In contrast, the OCC, kraft, and contaminants  14  are more rigid, forcing these materials to be propelled from the in feed end  18  of screen  12  to a discharge end  40 . Thus, the two material streams  20  and  22  are created by mechanical separation. The de-inking screen  12  can be manufactured to any size, contingent on specific processing capacity requirements. 
     FIG. 2  shows a two-stage de-inking screen  42  that creates three material streams. The first stage  44  releases very small contaminants such as dirt, grit, paper clips, etc.  46  through the screening surface. This is accomplished using a closer spacing between the shafts  24  in first stage  44 . This allows only very small items to be released through the relatively narrow spaces  48 . 
   A second stage  50  aligns the shafts  24  at wider spaces  52  compared with the spaces  48  in first stage  48 . This allows de-inking materials  58  to slide through the wider gaps  52  formed in the screening surface of the second stage  50  as described above in  FIG. 1 . The OCC, kraft, and large contaminants  56  are conveyed over a discharge end  54  of screen  42 . The two-stage screen  42  can also vary the shaft spacing and rotational speed for different types of material separation applications and different throughput requirements. 
   Again, some of the shafts  24  may contain single or dual diameter discs to aide in moving the material stream forward along the screen  42  (see  FIG. 6 ). 
   The spacing between shafts in stages  44  and  50  is not shown to scale. In one embodiment, the shafts  24  shown in  FIGS. 1 and 2  are generally twelve inches in diameter and rotate at about 200-500 feet per minute conveyance rate. The inter-shaft separation distance may be in the order of around 2.5-5 inches. In the two-stage screen shown in  FIG. 2 , the first stage  44  may have a smaller inter-shaft separation of approximately 0.75-1.5 inches and the second stage  50  may have an inter-shaft separation of around 2.5-5 inches. Of course, other spacing combinations can be used, according to the types of materials that need to be separated. 
   Referring to  FIGS. 2 ,  3  and  4 , vacuum shafts  60  may be incorporated into either of the de-inking screens shown in  FIG. 1  or  FIG. 2 . Multiple holes or perforations  61  extend substantially along the entire length of the vacuum shafts  60 . In alternative embodiments, the holes  61  may extend only over a portion of the shafts  60 , such as only over a middle section. 
   The vacuum shafts  60  are hollow and include an opening  65  at one end for receiving a plenum divider assembly  70 . The opposite end  74  of the shaft  60  is closed off. The divider  70  includes multiple fins  72  that extend radially out from a center hub  73 . The divider  70  is sized to insert into the opening  65  of vacuum shaft  60  providing a relatively tight abutment of fins  72  against the inside walls of the vacuum shaft  60 . The divider  70  forms multiple chambers  66 ,  68  and  69  inside shaft  60 . In one embodiment, the divider  70  is made from a rigid material such as steel, plastic, wood, or stiff cardboard. 
   A negative air flow  62  is introduced into one of the chambers  66  formed by the divider  70 . The negative air flow  62  sucks air  76  through the perforations  61  along a top area of the shafts  60  that are exposed to the material stream. The air suction  76  into chamber  66  encourages smaller, flexible fiber, or de-inking material  58  to adhere to the shafts  60  during conveyance across the screening surface. 
   In one embodiment, the negative air flow  62  is restricted just to this top area of the vacuum shafts  60 . However, the location of the air suction portion of the vacuum shaft  60  can be repositioned simply by rotating the fins  72  inside shaft  60 . Thus, in some applications, the air suction portion may be moved more toward the top front or more toward the top rear of the shaft  60 . The air suction section can also be alternated from front to rear in adjacent shafts to promote better adherence of the de-inking material to the shafts  60 . 
   The negative air flow  62  is recirculated through a vacuum pump  78  ( FIG. 3 ) to create a positive air flow  64 . The positive air flow  64  is fed into another chamber  68  of the vacuum shafts  60 . The positive air flow  64  blows air  80  out through the holes  61  located over chamber  68 . The blown air  80  aides in releasing the de-inking material  58  that has been sucked against the holes of negative air flow chamber  66 . This allows the de-inking material  58  to be released freely as it rotates downward under the screening surface. In one embodiment, the blow holes over chamber  68  are located toward the bottom part of the vacuum shaft  60 . 
   The second stage  50  ( FIG. 2 ) releases the de-inking material  58  through the screen surface. The stiffer cardboard, OCC, kraft, etc. material  56  continues over the vacuum shafts  60  and out over the discharge end  54  of the screen  42 . The two-stage de-inking screen  42  can also vary shaft and speed. 
     FIGS. 5A-5C  show different shaped discs that can be used in combination with the de-inking screens shown in  FIGS. 1 and 2 .  FIG. 5A  shows discs  80  that have perimeters shaped so that space D SP  remains constant during rotation. In this example, the perimeter of discs  80  is defined by three sides having substantially the same degree of curvature. The disc perimeter shape rotates moving materials in an up and down and forward motion creating a sifting effect that facilitates classification. 
     FIG. 5B  shows an alternative embodiment of a five-sided disc  82 . The perimeter of the five-sided disc  82  has five sides with substantially the same degree of curvature. Alternatively, any combination of three, four, five, or more sided discs can be used. 
     FIG. 5C  shows a compound disc  84  that can also be used with the de-inking screens to eliminate the secondary slot D sp  that extends between discs on adjacent shafts. The compound disc  84  includes a primary disc  86  having three arched sides. A secondary disc  88  extends from a side face of the primary disk  86 . The secondary disc  88  also has three arched sides that form an outside perimeter smaller than the outside perimeter of the primary disc  86 . 
   During rotation, the arched shapes of the primary disc  86  and the secondary disc  88  maintain a substantially constant spacing with similarly shaped dual diameter discs on adjacent shafts. However, the different relative size between the primary discs  86  and the secondary discs  88  eliminate the secondary slot D sp  that normally exists between adjacent shafts for single diameter discs. The discs shown in  FIGS. 5A-5C  can be made from rubber, metal, or any other fairly rigid material. 
     FIG. 6  shows how any of the discs shown in  FIGS. 5A-5C  can be used in combination with the de-inking shafts previously shown in  FIGS. 1 and 2 . For example,  FIG. 6  shows a top view of a screen  90  that includes set of de-inking shafts  24  along with a vacuum shaft  60  and several dual diameter disc shafts  92 . The different shafts can be arranged in any different combination according to the types of materials that need to be separated. 
   The primary discs  86  on the shafts  92  are aligned with the secondary discs  88  on adjacent shafts  92  and maintain a substantially constant spacing during rotation. The alternating alignment of the primary discs  86  with the secondary discs  88  both laterally across each shaft and longitudinally between adjacent shafts eliminate the rectangular shaped secondary slots that normally extended laterally across the entire width of the screen. Since large thin materials can no longer unintentionally pass through the screen, the large materials are carried along the screen and deposited in the correct location with other oversized materials. 
   The dual diameter discs  84 , or the other single discs  80  or  82  shown in  FIGS. 5A and 5B , respectively, can be held in place by spacers  94 . The spacers  94  are of substantially uniform size and are placed between the discs  84  to achieve substantially uniform spacing. The size of the materials that are allowed to pass through openings  96  can be adjusted by employing spacers  94  of various lengths and widths. 
   Depending on the character and size of the debris to be classified, the diameter of the discs may vary. Again, depending on the size, character and quantity of the materials, the number of discs per shaft can also vary. In an alternative embodiment, there are no spacers used between the adjacent discs on the shafts. 
   It will be understood that variations and modifications may be effected without departing from the spirit and scope of the novel concepts of this invention.