Abstract:
A system for separating pieces of plastic bag from ground yard debris and the like, e.g., asphalt shingles. A conveyor conveys the debris material along a conveyor path and an agitator bounces the conveyor to cause the lighter plastic to reposition to the top of the material on the conveyor. A suction tube end is positioned over the debris material following agitation to draw the plastic off the top of the material. The tube end is selectively adjustable to enable discriminate suction effect to draw off a maximum amount of plastic and a minimal amount of nonplastic recyclable debris.

Description:
FIELD OF THE INVENTION 
     This invention relates to a system that removes plastic from recycled materials and more particularly the removal of pieces of plastic film resulting from shredding of plastic bags, e.g., during a recycling of yard debris. 
     BACKGROUND OF INVENTION 
     It is common practice for communities to provide for recycling of yard debris such as grass, weeds, bush trimmings, tree branches and so on. These materials are collected e.g. from home owners, shredded, screened and redistributed e.g. as ground cover, rather than filling in-ground disposal sites. However, a constant problem with this recycling process is the presence of plastic film among the yard debris. This is believed due to the practice of homeowners collecting yard debris in large plastic bags and dumping the bags filled with the yard debris into designated recycling bins. Plastic bags get shredded and screened with the yard debris and if not removed gets deposited with the yard debris for redistribution as ground cover. Such plastic is detrimental for such use and it is desirable if not essential that the plastic be removed from the yard debris as feasible. Prior to the present invention, the ground up yard debris was conveyed through an extensive hood-like enclosure wherein upwardly directed air movement separated out a major portion of the lighter plastic material. The lighter plastic is drawn away from the heavier yard debris materials and suctioned off through a duct and to a disposal receptacle while the heavier yard debris is separately conveyed out of the hood to be collected and recycled. Such separation involves a substantial expenditure and an object of the present invention is to accomplish such removal of plastic at reduced cost. 
     BRIEF DESCRIPTION OF THE INVENTION 
     A problem with the procedure currently in use for separating out the plastic, is the dependency on relative mass as between the plastic and the various types of yard debris. It is perhaps unavoidable that the air suction draw for removing the plastic also draws off a portion of the otherwise quite acceptable yard debris material. The undesirable factor is exaggerated by the desired objective to remove, e.g. in the order of 80% of the plastic. The different types of debris and the different condition of the debris being subjected to the separation process e.g. wet versus dry, mostly wood versus mostly leaves, etc., dictates that the suction process be set at a rate that ensures plastic removal under worst case conditions. Such criteria results in a high volume of separated and removal of a quantity of the lighter yard debris along with the desired plastic. 
     As previously discussed, the existing process and machinery therefore is also undesirably expensive and both these issues are addressed by the present invention. 
     In a preferred embodiment of the present invention, the yard debris with plastic film i.e. plastic bags, is ground and screened. The overs of the screening process, which includes the major portions of the plastic, is conveyed from the screen to a collection point via a belt conveyor e.g. a trough-type belt conveyor. A flexible hose e.g. 10 inches in diameter is connected at one end to a suction fan and the other end is positioned with the open end overlying the conveyor belt. This latter end is mounted so as to be adjustable relative to the material being conveyed on the conveyor belt e.g. between 6 and 12 inches over the material. 
     Just prior to the point where the material on the belt passes under the vacuum hose end e.g. a couple of feet prior, the material is agitated e.g. using a roller or rotor with slats or flutes that rapidly bumps the bottom of the belt and bounces the material conveyed on the top of the belt. Because the plastic is lighter than the vegetation material being conveyed, it rises to the top and is most susceptible to the overlying vacuum. The drawing and vacuuming effect from the material of the belt underlying the hose end is determined by the air flow through the tube and the spacing of the hose end from the material on the belt. The top most material i.e. the closest to the tube end, is thus most effected. 
     An operator stationed at the open end of the tube overlying the belt can view the effect of the suction and adjust the spacing of the tube end. The operator thus is able to maintain a delicate balance as between allowing too much plastic to cross the tube end (the tube end needs to be lowered) and having too much of the vegetation drawn into the tube end (the tube end needs to be raised). 
     The invention as briefly described will be more fully understood and appreciated upon reference to the following detailed description having reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view of a plastic removal apparatus in accordance with the present invention; 
         FIG. 2  is a perspective view of a suction producing apparatus forming part of the apparatus of  FIG. 1 ; and 
         FIGS. 3 and 4  are front and side views of an alternate embodiment. 
     
    
    
     DETAILED DESCRIPTION 
       FIGS. 1 and 2  illustrate an embodiment of the invention.  FIG. 1  shows a trough-type conveyor belt  10  conveying ground up yard debris  12 . The yard debris  12  typically has been through prior processing step(s) including a grinding process that e.g. reduces tree limbs and the like to chunks of vegetation referred to herein sometimes as bark chips. The bark chips have further been separated into size categories by screening which typically includes placing the bark chips on one end of an inclined vibrating screen where small bark chips pass through the screen and the larger size chips are vibrated along the screen length and deposited off the screen end. This latter debris-type is referred to as bark chip overs or simply as overs. Plastic bags that have been shredded by the prior grinding operation are largely contained in the bark chips&#39; overs. It is the bark chip overs with plastic pieces that make up the material  12  of  FIG. 1  and the operation of the apparatus of  FIGS. 1 and 2  is intended for the removal of such plastic from the bark chip overs. 
     In  FIG. 1 , placed under the trough belt  10  just prior to a removal apparatus, generally indicated by reference arrow  14 , is an agitation rotor  16 . The rotor  16  includes bumper flutes  18  which engage the underside of the conveyor belt  10 . The rotor  16  is adjustable up and down as indicated by adjustment arrows  21 . Thus, the flutes  18  are adjusted into greater or lesser contact with the underside of the belt  10  and as the belt is driven, the belt engages the flutes to rotate the rotor and in the process causing bumping-type agitation of the material  12  being conveyed by the belt  10 . This agitation induces rearrangement of the material  12 , the lighter portions tending to somewhat float to the top and the heavier material gravitating to the bottom. Plastic being lighter in weight tends to rise to the top and is set up for removal by a suction hose which will now be explained. 
     Reference is made to  FIG. 2  where a conventional suction fan  22  is illustrated. Air is sucked into the fan  22  via an inlet nozzle  24  and out of the fan via outlet nozzle  26 . Any debris contained in the air is screened and deposited in a removable/replaceable debris bag  28 . Connected to the inlet nozzle  24  is a flexible tube  30 . 
     The same flexible tube  30  is shown in  FIG. 1  and as shown extends from the fan  22  up and over the conveyor belt  12  with the open end  32  facing downward and positioned in spaced relation over material  12  being conveyed on the conveyor belt  10 . The tube end is held in place over the conveyor belt by an adjustable holder  34 . The holder  34  includes a sleeve portion  36  strapped onto a positioning shoe  38 . A fixed support  40  includes a cross bar  42 . A vertical pipe  44  fixed to the cross bar  42  slidably supports a pivotal dual stemmed bracket  46 . A tubular handle  48  extends through a second stem of the bracket  46  and one end of the handle is connected to shoe  38 . It will be observed that pivotal movement of the handle  48 , as indicated by arrow  50 , generates raising and lowering of shoe  38  secured to the tube  30  and thereby raises and lowers tube end  32  in spaced relation to material  12  on conveyor belt  10 . Note that the connection between the shoe  38  and handle  48  may be pivotal to accommodate the angular shift of the handle and maintain a vertical orientation of the tube end. 
     OPERATION 
     There are a number of factors which effect the process of vacuum separation of the plastic and bark. Certain of the bark may be heavier or lighter e.g. due to size and/or moisture content and/or height of material  12  on the belt, and similar variables may apply to the plastic. Thus, a particular setting of the spaced relationship of the tube end  32  over the material  12  (or belt  10 ) will not produce the same results over any length of time. To accommodate such variables and so as to improve separation, the height of the tube end  32  can be varied and thereby increasing the suction (lowering the tube end  32 ) or decreasing the suction (raising the tube end  32 ). 
     A determination of the satisfactory separation of bark material from plastic can be observed by an operator represented by arrow  52 . He can observe how much bark is being sucked into tube end  32  and how much plastic remains on the material as it passes tube end  32 . He can readily adjust the height of the tube end to increase or decrease the suctional effect on material  12 . The operator may also determine that the agitation is too great or too little and adjust the height of the rotor  16  (arrows  21 ). A further adjustment is available by moving the bracket  46  up or down on the vertical pipe  44  by unlocking and relocking lock screw  56  as indicated by arrow  54 . 
     It may be desirable to have a second or greater number of the removal stations of the type illustrated and described above, the stations spaced along the reach of the conveyor belt. Further, the raising and lowering of the tube end  32  may be accomplished by the use of motors and sensors to reduced dependency on operator manipulation. It has been observed that often the bark material is heated and gives off steam as it is conveyed under the tube end  32  and one can observe the effect of the vacuum by noting the extent to which that steam is drawn into the tube end. The spacing of the tube end is generally sufficiently above the material  12  to allow for a funnel-like suction draw on the material allowing for a greater width of the material  12  on the belt than the diameter of the tube end. 
     An alternate embodiment is illustrated in  FIGS. 3 and 4 . In this alternate embodiment, the suction station is provided at the end of a screen  58 . Such a screen is referred to at the outset of the brief description of the invention and as explained provides for the overs being transferred off the end of the screen and onto a troughed conveyor belt, e.g. conveyor belt  10 . 
     It is recognized, however, that the screen itself is a form of conveyor that typically relies on vibration/agitation of the materials to induce movement of the materials along the screen while performing a separating action of those materials. Yard debris is placed on the input end of an upper screen deck and, by vibration/agitation, moves the debris along the length of the screen. Smaller size material passes down through the screen openings and onto lower screen decks having smaller screen sizes which repeat the separating process. Material on the upper deck that does not pass through the upper screen (the overs) gets moved by vibration/agitation along the deck to the output end of the deck and transferred off the screen and onto a conveyor, e.g. a conveyor  10 . 
     It is further recognized that the vibration applied for facilitating movement of the debris also performs the operation of bouncing the lighter materials to the top of the debris pile on the screen. Accordingly, the position of a vacuum tube or tubes  32  at the exit end of the overs screen deck will perform the desired suctioning off of the lighter plastic materials. 
     With reference to the schematic illustrations of  FIGS. 3 and 4 , item  58  is a vibrating screen with multiple screen decks  60 ,  62 ,  64 . The upper screen deck, e.g.  60 , carries the “overs” material  12 . That is, the openings through the screen decks diminish in size to separate input material by size. The larger size screen at or near the top (upper screen deck  60  in  FIGS. 3 and 4 ) has screen openings of a size that will retain the larger material, e.g. bark chips and plastic pieces (overs material  12 ). These are typically vibrated off the end of the screen  60  and onto a conveyor belt  10 ′. 
     In this embodiment of the invention and primarily because the screen deck  60  is substantially wider than the typical trough belt  10 , multiple tubes  30 ′ are provided, each connected to a manifold  68  and each fitted with a suction nozzle  66 . Suction is provided to the manifold via suction hoses  70  which in turn are connected to e.g. a fan or fans  22 . (See  FIG. 2 .) 
       FIGS. 3 and 4  further illustrate the manner of manual adjustment closer to and farther from the material  12  on the output end of the screen deck  60 . As illustrated, each suction nozzle  66  is secured to a tubular handle  73  that is connected to a holder  72  similar to holder  34  of the prior embodiment. The three holders  72  are mounted on vertical pipes  76 . The handles  73  are projected through holder  72  and then tied to cross bar  74  via holder  75 . Raising and lowering of cross bar  74  simultaneously lowers and raises the three nozzles  66 . Individually, each nozzle  66  can be adjusted relative to each other as provided by adjustment of holders  72  relative to vertical pipes  76 . Alternatively, the suction nozzles need not be tied together and each nozzle adjusted manually via raising and lowering of bar  73 , i.e., cross bar  74  being eliminated. 
     The above descriptions are intended as preferred embodiments of the invention and there are numerous modifications/variations that will become obvious to those skilled in the art. An example is found in the practice of recycling asphalt shingles which are ground into chunks and used for paving, e.g. roads. Again, plastic is a problem and the invention can be used to separate the plastic from the ground up asphalt chunks. It is therefore to be understood that the invention as claimed is not limited to any particular embodiment or particular features of the embodiments illustrated. Accordingly, the claim terms are intended to have a broad meaning and to be interpreted in accordance with common understanding of those terms as used in the art.