Patent Publication Number: US-4094772-A

Title: Method of and apparatus for sorting light refuse fractions

Description:
FIELD OF THE INVENTION 
     The present invention relates to a method of sorting material including pieces of different rip resistance. More particularly this invention concerns a method of and apparatus for separating flat pieces of textile, foil, and the like from flat pieces of paper and the like. 
     BACKGROUND OF THE INVENTION 
     In the treatment of garbage or refuse it is a standard practice to sort the refuse into a plurality of fractions, usually into a heavy fraction including all of the pieces of relatively great surface density, by which is meant articles having a relatively high ratio of weight to surface area, and a light fraction including all of the pieces of relatively light surface density. Air classifiers, flotation systems, electromagnetic strippers, and the like can be used to separate the heavy fraction into various recyclable subfractions. 
     It has, however, proven a relatively complex task to separate the light fraction into several subfractions. In particular it is highly desirable to separate the synthetic-resin foil and textile pieces on one side from the paper pieces on another. The paper industry requires for making new paper from recovered old paper that the old paper used have a minimum content of foil and textile material. 
     Hitherto the sole method of separating the light fraction into two subfractions as described above has required the use of a large vessel filled with water. The entire light fraction is charged into this water-filled vessel and is separated therein into the desired two subfractions. This system has the considerable disadvantage that is requires an expensive and large installation. Furthermore it is necessary, after the separation, to centrifuge the two subfractions so as to recover the water used in the process. Overall such a procedure is generally so expensive as normally to make it economically unattractive so to separate the light fraction. 
     OBJECTS OF THE INVENTION 
     It is therefore an object of the present invention to provide an improved method of and apparatus for sorting material. 
     Another object is to provide a method of and apparatus for sorting a light fraction as described above so that the foil and textile pieces are separated from the paper pieces. 
     SUMMARY OF THE INVENTION 
     These objects are attained according to the present invention by employing the difference in rip resistance between textile and foil pieces and paper pieces. It has been found that the two fractions vary considerably in this one characterisitc, that is rip resistance, so that the present invention is based on the principle of employing the considerably varying rip resistance between textile and synthetic-resin foil pieces on the one hand and paper pieces on the other. 
     Thus in accordance with the present invention the material including flat pieces of different rip resistance is suspended in a gas stream which is passed over an entrapment element which is oriented relative to the stream in such a manner that pieces of the material catch on it. At the same time the speed of the stream of gas carrying the pieces relative to the element is set so that the less rip-resistant pieces tear free from the entrapment element but the more rip-resistant pieces remain caught on the element. With such a method, therefore, the less rip-resistant pieces, that is, the paper pieces, can be recovered downstream in the stream from the entrapment element. The more rip-resistant pieces will, however, remain caught on the entrapment element and can be stripped therefrom by an arrangement including at least one stripping member or element. 
     With such a method, therefore, it is possible in a relatively small area using a relatively simple piece of equipment to effectively separate the more rip-resistant pieces constituted by pieces of synthetic-resin material and textile, from the less rip-resistant pieces constitued by pieces of paper and the like. 
     According to further features of this invention the apparatus comprises a housing generally constituted as a cyclone. The stream of gas in which the flat pieces to be separated are suspended enters the housing radially tangentially through an upper inlet. A pair of concentric outlets are provided axially eccentric in the housing and both opening downwardly. The central outlet extends down to immediately above the entrapment element and serves only for receiving the pieces of more rip-resistant material stripped therefrom by the stripping member. The other outlet of the cyclone opens downwardly also but at a location axially above and radially spaced outwardly from the outlet for the more rip-resistant material. This outlet serves mainly for carrying away the gas stream and small hard particulate material carried in the gas stream. The less rip-resistant material is collected at the bottom of the housing to be removed therefrom through an airlock-type gate. 
     According to further features of this invention the entrapment element is constituted as a holder lying at the axis of the cyclone and provided with a plurality of radially extending pins. The stripper member is a ring displaceable axially along the holder. To this end pins are associated with means for radially retracting these pins into the holder against the force of respective pin-biasing springs. Thus when it is necessary to strip the more rip-resistant pieces off the entrapment element the pins thereof are retracted and the stripper member is slid along so as to push all of the material caught on the entrapment element into the downwardly open mouth of the outlets for these pieces. 
     It is also within the scope of this invention to form the entrapment element as a drum or holder from which projects a multiplicity of radially extending pins. The drum holder is rotatable about an axis outside the housing, which itself is formed with an aperture or window through which a portion of the holder engages so that the pins thereof project radially into the helical path followed by the gas stream carrying the suspended pieces in the housing. 
     According to yet another feature of this invention the stripping member is constituted as a fixed rod engaged in a groove formed in the holder between the rows of pins. Thus as the holder is rotated past the fixed rod the pieces caught on the pins are pulled radially off them. It is also possible to use a further pin-type roller which is counter-rotated to the entrapment element so as to strip from it the pieces of more rip-resistant material. 
     It is also within the scope of this invention to simply suck the more rip-resistant pieces off the entrapment element. The stream of air used to aspirate such pieces off the entrapment element, formed again as a holder from which extend a multiplicity of radially projecting pins, is thereafter passed through another cyclone so as to separate the gas from the pieces suspended in it. 
     In accordance with yet another feature of this invention the stripper member cooperating with the drum or roller-type entrapment element is an annular body or element spanned over the entrapment element. This annular element can be formed as a rigid drum or perforated belt and in both cases has a multiplicity of apertures through which the pins can engage. A guide is provided so that the stripping member constituted by the annular element lies closely against the holder with the pins projecting fully through it into the housing, yet outside of the housing the annular element separates and moves radially outwardly from the entrapment element in such a manner that the rip-resistant pieces caught on the pins of this entrapment element are moved radially off them so that they can readily be separated from the entrapment element. 
     It is also another feature of this invention that a second housing is provided next to the first housing and the entrapment element, once again formed as a drum with a multiplicity of radially extending spikes or pins, is provided in the second housing. The stripping member is also provided in the second housing. A pump or the like maintains the second housing under slightly lower pressure than the first housing so that leakage around the entrainment element will not prevent proper operation of the cyclone constituted by the first housing. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     The above and other objects, features and advantages of the present invention will become more readily apparent from the following description, reference being made to the accompanying drawing in which: 
     FIG. 1 is a vertical section through an embodiment of the present invention; 
     FIG. 2 is a large-scale sectional view of a detail of FIG. 1; 
     FIG. 3 is a horizontal section through another arrangement in accordance with this invention; 
     FIG. 4a is a top partly sectional view of yet another arrangement according to this invention; 
     FIG. 4b is a section taken along line IVb -- IVb of FIG. 4a; 
     FIG. 5 is a partly sectional view through a further arrangement according to this invention; 
     FIGS. 6 and 6a are sectional views through other devices according to this invention; and 
     FIG. 7 is a vertical section similar to FIG. 1 through yet another arrangement for carrying out the method of the instant invention. 
    
    
     SPECIFIC DESCRIPTION 
     As shown in FIGS. 1 and 2 the apparatus according to the present invention basically comprises a housing 1 constituted as a cyclone having a cylindrical wall 2 forming a chamber 21 centered on an axis A. Opening into the upper region of the chamber 21 is an inlet pipe 4 that is not directed radially of the axis A but tangentially of the inside upper region of the wall 2 so that a stream of gas in which particles and flat pieces are suspended moves helically downwardly in the chamber 2 as indicated by arrow 34. The lower portion of the cyclone housing 1 is tapered frustoconically at 19 and terminates at its lower end at an airlock or gate-type discharge 3. A blower 32 is provided at the upstream end of the inlet conduit 4 into which a supply hopper 31 introduces a mixture of solid material containing, as mentioned above, a small amount of particles and a relatively large quantity of flat pieces of textile material, synthetic-resin foil, and paper. 
     As the suspension descends helically along path 34 in the chamber 21 the flat pieces move radially outwardly and tend to sink slowly or flutter down, The smaller particles remain suspended and can be taken out by means of an upper outlet pipe 5 having a lower mouth which opens axially downwardly in the chamber 21 below the inlet conduit 4. The particles and gas stream coming out of the housing 1 via the outlet 5 are passed through a filter 20 which may be of the cyclone type and thereafter pass along a recycling path 33 to the blower 32 for recycling through the housing 1. This is standard cyclone operation. 
     Received coaxially within the vertical leg of the outlet tube 5 is a smaller-diameter outlet tube 17 having a mouth 16 which opens axially downwardly well below the mouth of the tube 5. Thus the upstream end of the conduit 5 is constituted as a downwardly opening annular mouth surrounding the axial leg of the conduit 17. 
     Provided below the conduit 17 on the axis A is an entrapment element 6 constituted as a holder rod or tube 8 from which project eleven sets of four angularly equispaced and radially extending pins 9. When extended fully radially as shown in FIG. 1 these pins 9 define an imaginary cylinder of a diameter slightly smaller than that of the interior of conduit 17. The holder 8 is carried on a bearing 7 and can be rotated if desired by means of a motor 10. 
     As shown in FIG. 2, each of the pins 9 is radially displaceable within the holder tube 8 by means of a piston 11 inside a cylinder 12 which can be radially pressurized by means of a pump 36. A stop ring 13 carried on each of the pins 9 bears against one end of a compression spring 14 whose other end bears against the interior of the tube 8 so as normally to bias the pin 9 inwardly against the pressure in the cylinder 12. 
     Furthermore there is provided on the holder tube 8 an annular stripping element 15 axially displaceable along the holder 8 when the pins 9 are retracted inwardly by means of an actuator 18 which may be formed as a hydraulic cylinder, screw advance, or other conventional axial-displacement mechanism. 
     In use the flat pieces in the chamber 21 descend downwardly and all become trapped on the pins 9. The motor 10, however, rotates the holder 8 at a sufficient speed that the more easily ripped or torn flat pieces rip loose from the pins 9 and fall downwardly to the outlet gate 3. The less easily ripped pieces remain caught on the pins 9. When these pins 9 become relatively clogged with the less easily ripped pieces they are retracted inwardly and the stripper element 15 is displaced axially along the holder rod 8 so as to push them all into the downwardly open mouth 16 of the conduit 17 which aspirates them. 
     In practice the pieces that exit via the gate 3 are invariably of the relatively rippable paper type. On the other hand the pieces that exit via the conduit 17 are almost entirely flat pieces of textile material as well as syntehtic-resin foil. 
     FIG. 3 shows another arrangement where instead of having a stripper element 6 the housing 2 has a window 37 through which radially engage pins 23 carried on a drum 22. Another spiked drum 38 has pins 39 which interleave with the pins 23. The drum 38 is counter-rotated to the drum 22 so that the pieces picked up by the drum 22 can be stripped from its pins 23. The drum 22 is rotated in a direction against the direction 40 in which the particles and flat pieces move inside the chamber 21. The relative velocities of the pins 23 and of the gas stream in suspension in the chamber 21 are such that paper pieces rip from the pins 23 but the heavier-duty foil and textile pieces are pulled therefrom so that they can be stripped from this by the stripper pins 39. 
     FIGS. 4a and 4b show how instead of the stripper drum 38 with its pins 39 one or more rods 24 may be provided with each engaged in a groove 27a formed in the drum 22 between its pins 23. As the drum 22 rotates past the stationary rod 24 the flat pieces engaged on its pins 23 are therefore automatically stripped from it. 
     In FIG. 5 an arrangement is shown wherein a suction tube 25 has a mouth 25&#39; which opens radially of the drum 22. The other end of the conduit 25 opens tangentially into another cyclone 1a connected at its downwardly open axial outlet to the axial input of a squirrel-cage blower 41. The second cyclone 1a separates out the textile and synthetic-resin foil pieces from the stream in the conduit 25. 
     In FIG. 6 an arrangement is shown wherein the spikes 23 of the drum 22 engage through an opening 28 in the cylindrical wall 2 of the cyclone 1. A belt 26 having a multiplicity of perforations 26&#39; is spanned over the drum 22 and over a pair of idler wheels or cylinders 27. The perforations 26&#39; of the belt 26 are spaced so that the pins 23 can engage through them. Furthermore the belt is engaged tightly over the drum 22 where it reaches through the hole 28 so that the pins 23 project through the belt. Thus these pins 23 can pick up the more rip-resistant pieces in the suspension inside the chamber 21. As the drum 22 rotates, therefore, it will pull these more rip-resistant pieces outside through the hole 28. The pins 23 will then, however, pull out of the holes 26&#39; so that the flat pieces engaged on them will automatically be stripped off. 
     FIG. 6a shows another arrangement wherein the belt 26 is replaced by a perforated drum 26a of cylindrical shape having a center of rotation 26a&#39; set off from the center 22&#39; of the drum 22 radially outwardly from the axis A of the chamber 21. Thus this rigid cylindrical drum 26a will strip flat pieces off the pins 23 in the same manner as the belt 26. 
     Finally FIG. 7 shows yet another arrangement wherein a drum 22 having pins 23 and rotatable by means of a motor 42 extends through a laterally open hole 28 in the side of a frustoconical wall 2&#39; of another cyclone not provided with the outlet 17. A second chamber 29 having its own outlet airlock-type gate 30 is kept under subatmospheric pressure by means of a blower 43. A stripping element 26 or 26a such as shown in FIGS. 6 or 6a can be used on the drum 23 but is not shown in FIG. 7. The chamber 29 ensures that the use of a drum 22 engaging through a hole 28 will not depressurize the chamber 21&#39; which is here of downwardly tapering rather than cylindrical shape as shown in FIG. 1. 
     With the system of the present invention it is therefore a relatively easy matter to separate more rip-resistant flat pieces, thereby automatically segregating paper on the one side and textiles and syntehtic-resin foils on the other. This allows the light fraction recovered in a refuse-sorting plant to be separated into two further subfractions, one of which is eminently usable by a paper plant for making paper again. 
     Any of the elements of any of the embodiments described above can be used in any of the other embodiments described above without in any manner departing from the scope of the instant invention.