AN APPARATUS FOR SHREDDING FIBROUS MATERIALS SUCH AS STRAW OR PAPER

Abstract: It is known that for the shredding of straw the straw material can be pressed against a rotating cutting or rasping disc (4) which ejects the material to a ring slit (14), wherefrom it is led to a grinding chamber (18) for further comminution. The invention renders the shredding more effective in that a rasping ring (20) is placed at the passage to the grinding chamber and in that the rotating disc (4) comprises projecting knives (24), which cut the material in the ring slit itself. Hereby the apparatus can also shred paper effectively, i.e. be used as a document shredding machine in a highly effective manner and also produce paper shavings from waste paper for advantageous use in gardening and agriculture. An associated problem can be a considerable production of dust, which, however, may be remedied by using a dust exhaust system.

Description: An apparatus for shredding fibrous materials such as straw or paper. The present invention relates to an apparatus for shredding paper, straw, and other fibrous materials and of the type which comprises a receiver chamber of which a bottom surface is constituted by a rotor disc, which at its surface has slightly protruding rib portions for ejecting the material conveyed to the disc, an annular slot being provided along the periphery of the disc and through which the material is introduced into a grinding chamber provided behind or below the disc, in which chamber the material is shredded by the action of rotat¬ ing beater means which cooperate with an annular grind¬ ing screen and eject the shredded material through an exit opening in the grinding screen. Such an apparatus is known from the Danish Patent Application No. 2254/82, and a corresponding apparatus, however of a slightly different type, is known from US Patent Specification No. 3,035,621. In connection with the latter apparatus are not used the slightly protrud¬ ing rib portions, but a number of considerably protrud¬ ing knife blades, which cut the material coarsely with high capacity, whereafter the cut material is let through the annular slot to the grinding chamber, in which the material is additionally shredded; this appa¬ ratus will be well suited for high-capacity production of a rather coarsely shredded material, but for one thing it will operate unreliably for small capacities, which may be desirable in connection with many spreading jobs, for another thing the apparatus will be unable to execute an extremely fine shredding of the material. The former of the known apparatuses is more advan¬ tageous in both said respects, but it is not especially well suited for processing waste paper, which, however, is not relevant in connection with any of the known apparatuses. Recently tests have been made which indicate that rather finely shredded waste paper may find a number of relevant uses, e.g. as bedding for domestic animals and - more importantly - for covering field crops in order to save the heat and humidity .of the soil and to inhibit weed growth. It is well known that also cut straw may be used for the same purpose, but surprisingly it has been observed that potato yield was 40 t/ha by paper covering as opposed to only 15 t/ha by straw covering. This al¬ most sensational result is believed to be due to the reflection of light in the countless white paper sur¬ faces. When small bits of paper are to be used for soil covering and other purposes where they should preferably decompose within a reasonable amount of time, it is essential that the paper bits be torn instead of cut, as the tearing leaves a pronouncedly porous edge which furthers the material communication between the paper bits and their surroundings. Great amounts of waste paper have been accumulated, and it is thus essential to provide an apparatus which may efficiently change the paper into small torn bits. None of the said apparatuses is usable for this, but it has been found that by relatively simple modifi¬ cations they may be useful for the purpose, without being made unusable hereby for processing straw and other materials. It is thus the purpose of the invention to provide an apparatus which is well suited for producing a flow of small torn paper bits from a supplied mass of waste paper, and according to the invention this is obtained by designing the apparatus in the manner indicated in the characterizing clause of claim 1. Thus, when the rotor disc has knife portions which whisk through the said annular slot, the material delivered from the rotor disc will be cut or torn into small bits, which by the further processing in the grinding chamber are shredded into even smaller bits, and by using the said rasping surface it will additionally be ensured that the paper is torn for facilitating its subsequent material commu¬ nication with its surroundings. In general the use of said knife portions will entail that the material is subjected to an additional shredding at the transition from the rotor disc to the grinding chamber, such that the grinding in the chamber may be concentrated to a further shredding of the already finely shredded ma¬ terial. Hereby it is possible in practice to provide a delivery of small bits of torn paper with an extremely compact construction of the apparatus. Hereby large amounts of dust occur which should be separated from the product. In the following the invention is described in more detail with reference to the drawing, in which Fig. 1 is a side view, partially in diametrical section, of an apparatus according to the invention, Fig. 2 is a top view of the apparatus^ Figs. 3 and 4 are detailed sectional views thereof, Fig. 5 is a perspective view of the apparatus com¬ pleted with a necessary dust separator, and Fig. 6 is a sectional view of the dust separator. The apparatus shown comprises a slightly funnel-shaped receiver housing 2, which has a bottom surface consisting of a vaulted rotor plate 4 which is driven by a motor 8 through a shaft 6. At the top side of the disc 4 is fastened a number of radial flat iron pieces 10, which are found only outside the central area, on which is found instead a pair of radial angle iron members having upwardly projecting flanges 12 which project upwardly somewhat above the flat irons 10. Be¬ tween the periphery of the disc 4 and the lower end of the housing wall 2 is an annular slot 14, the lower edge 16 of the housing being located a short distance above the disc periphery and the housing therefrom continuing downwards to a lower housing portion 18 of a slightly increased diameter. The lower, cylindrical edge area of the housing 2 has an annular rasping surface 20 provided with an acutely chattered surface, and on the inside the cylinder wall of the lower housing 18 is coated with an annular screen 22 having an upper and a lower row of holes. At the bottom side of the disc 4 abreast of the upper row of holes is placed a number of protruding fingers in the shape of edge sharpened flat iron members 24 which almost reach the annular screen 22 and which, as indicated, preferably project horizontally outwards, see Fig. 3. Underneath the rotor disc 4 a beater rotor is mounted on the shaft 6, the rotor having a number of protruding blowing and grinding beaters 26, each of which is provided with a wear plate 28 at the extremity, this plate being placed approximately abreast of the lower row of holes of the annular screen 22. The lower housing 18 has a tangential outlet 30, the lower row of holes of the annular screen being com¬ pletely open along the associated arch portion. This outlet may lead to a container for collecting the ejected product, or it may be mounted on a pipe or a hose for ejecting the product. During operation the flat iron pieces 10 will cause the lower layer of the material brought through the housing 2, e.g. waste paper, to be torn off and ejected towards the periphery of the disc 4. Hereby the central upwardly protruding flanges 12 operate to loosening and ejecting the central portion of the material, with a somewhat stronger effect but also at a generally lower operating speed, for further conveying via the ribs 10, whereby the formation of a central, stagnated material plug is prevented. By the combined ejection and rotation of the mate¬ rial layer right above the disc 4, the material will be pressed against and carried along the annular rasping surface 20, which entails a certain shredding of the material, and it will furtherly be conducted out and down through the annular slot 14, which downwards con¬ ducting will be supported by the fact that a suction effect is brought forth by the co-rotation of the blow¬ ing beaters 26,28, which is essential for preventing a clogging of the slot. By this downwards conducting, the material is ex¬ posed to the action of the protruding sharpened flat iron members 24, which will effect a combined cutting and tearing action on the material, in the immediate as well as by the fact that the material is forced around along the upper row of holes of the annular screen 22. During the subsequent downwards conducting, the convey¬ ing of the material is taken over by the beater blades 26,28 which drive the material around along the lower row of holes of the annular screen 22 until the proces¬ sed material is blown out through the outlet 30. The apparatus may be used for an extremely effec¬ tive shredding of paper which is delivered in torn bits after having been subjected to the action of both the annular rasping surface 20 and the radial knives 24 in connection with the grinding along the annular screen 22. The apparatus may be fed with both pressed material bales and with loose material, and in connection with paper the apparatus may be considered not only as a machine for producing the said bedding or soil covering material, but also as an extremely efficient document shredding machine, which will shred the paper far more efficiently than when this is done by cutting the paper into strips; cut paper strips may, though with difficul¬ ty, be reassembled, which will be infinitely more diffi¬ cult in connection with the shredded confetti product delivered by the machine according to the invention. When shredding both straw and paper the problem occurs that the delivered product will contain a consi¬ derable amount of unwanted dust. On this background an apparatus part has been developed in connection with the invention for removing this dust in a simple manner, which is shown in more detail in Figs. 5 and 6. In these figures it is shown that the outlet stub 30 from the grinding chamber is connected to the lower end of an upwardly conducting pipe 34 in which is mounted an upwardly conducting conveyor worm 34 which conveys the received product up to the upper end of the conveyor, where it is delivered, e.g. by being tumbled onto an oblique chute 38 which conveys the product to a collecting container 40. A portion of the pipe 32 is contained in a surrounding cylindrical mantle 42, which at its lower end has an outwardly and downwardly in¬ clined bottom 44 continued by a pipe stub 46 connected to a suction hose 48. Inside the mantle 42 the pipe 32 is provided with relatively fine perforations 50, and it has been found that hereby it is possible to produce an exhaustion of the fine dust in the shredded product, while the coarse particles thereof are conveyed unobstructedly to the delivery end of the pipe 32, the said conveyor worm 34 being rotated by means of a motor driving a lower wheel 52. The suction hose 48 is connected to a non illu¬ strated suction and separating device in which the ex¬ hausted dust may be collected and from which dust por¬ tions may be removed when needed. The conveyor worm 34 should be shaped in such a manner as to have a scraping effect up along the inner surface of the perforated portion of the pipe 32, such that the perforations are not permanently covered by the coarse material shreddings. Hereby it is advantageous to provide the periphery of the conveyor worm with brushes 54, which may keep the holes clean during operation without the conveyor worm having to fit extremely tight¬ ly in the pipe 32.

Claims: C L A I M S : 1. An apparatus for shredding paper, straw, and other fibrous materials, and of the type comprising an upper receiving chamber (2) , in which a bottom surface is constituted by a rotor disc (4) which on its top surface is provided with upwardly projecting portions (10,12) for ejecting the material which has been brought to the disc, an annular slot (14) being provided along the periphery of the disc, through which slot the mate¬ rial is supplied to a grinding chamber (18) behind or below the disc, in which chamber the material is shred¬ ded by the action of rotating beater means (26) which cooperate with an annular screen (22) provided along the wall and eject the shredded material through an outlet opening (30) in the annular screen, characterized in that the rotor disc (4) is provided with a number of protruding knife elements (24) at its periphery, which elements extend radially through the annular slot (14) , the outer slot limiting wall immediately above the outer end of the rotor disc preferably being shaped as a rasp¬ ing ring (20) . 2. An apparatus according to claim 1, characterized in that the outlet opening (30) is connected to the lower end of an upstanding pipe (32) which contains an upwardly conducting conveyor worm (34) and has an open upper delivery end, a partial length of the pipe being surrounded by a cylindrical mantle (42) which is connec¬ ted to an exhaust conduct (48) while the pipe (32) in¬ side the mantle is finely perforated for allowing an exhaustion of dust contained in the material delivered from the outlet opening (30) .

Inventors: JENSEN SVEND, JENSEN, SVEND
Applicants: PRAESTBRO MASKINFAB, APS PRAESTBRO MASKINFABRIK "JIK"
Application year: 1988
Main classification: B02C18
IPC codes: A01F29, B02C13, B02C18, D21B1