Shredder

Abstract: A shredder comprises a frame (4); at least two rotatable shafts (1,2) supported (3) in parallel by the frame; a plurality of cutting blades (10) on each shaft, each blade including a mounting (14) which is fixed to the shaft and a number of tips (13) fixed to the periphery of the mounting; and a plurality of spacers (11) mounted on each shaft alternately with the blades (10) such that the blades and spacers on each shaft mesh with the blades and spacers on the or each adjacent shaft. The tips (13) and/or spacers (11) can be replaced when necessary without disassembling the shafts.

Description: This invention relates to a shredder for continuously shredding solid materials, such as plastics, wood, paper, metal, rubber, fiber and skin, by effectively utilising shear force. Shredders of this type are exemplified in Japanese utility model publication S.55-41309, and include two parallel shafts rotatably supported through bearings on a casing, and which rotate in opposite directions. On each shaft is mounted a plurality of one-piece disc-like cutting blades and alternate spacing collars. The blades on one shaft partially mesh with the blades on the other shaft, thereby forming slit cutters. After a certain period of use the blades become worn, and it is then necessary to replace the worn blades with new blades. This is achieved by disassembling the casing and the bearings and removing the blades together with the spacers from the shafts, which is a very complicated and troublesome task. In addition, because the shredder has a considerable number of cutting blades, their replacement is laborious and maintenance is not easy. Another shredder is described in EP-A-0006261. That shredder includes two shafts on which there are mounted shaft collars to which comminuter elements may be fastened to form cutting rings. Between the cutting rings the shafts themselves present smooth cylindrical surfaces acting as "anvils" for the comminuting and cutting action. That device therefore has no spacers mounted on the shaft between adjacent cutting rings. A still further shredding device is described in EP-A-0401620, in which all of the numerous embodiments described with reference to the drawings have alternating rotor discs and spacer rings non-rotatably secured to the shaft by a key, and caps secured to the rotor discs by rods which pass longitudinally through the discs and spacer rings or by welding. If it then becomes necessary to replace the caps, then the axial rods are removed or the weld seams are separated. An alternative arrangement allows for the caps to be released without complete removal of the longitudinal rods, but nevertheless all caps are simultaneously released. The present invention seeks to overcome disadvantages of the known shredders by providing a shredder having blades which are easy to replace and maintain. In accordance with the invention, there is now provided a shredder comprising two counter-rotatable shafts supported in parallel by a frame and a plurality of cutting blades and a plurality of spacers alternately mounted along each shaft, the cutting blades and spacers on one shaft meshing with the cutting blades and spacers on the other shaft and each cutting blade comprising a mounting and plurality of tips separately attached on the radial periphery of the mounting, wherein the circumference of each mounting includes projections which engage recesses in the tips; the tips are identical and are fastened to the mounting with screws whereby the tips are individually removable from the mounting; and the spacers abut the side surface of the adjacent mounting and tips. The invention is described below in greater detail by way of example only, with reference to the accompanying drawings, in which Fig. 1 is a side view, partially in section, showing a cutting blade according to the invention; Fig. 2 is a side view in section showing a spacer for use with the blade; Fig. 3 is a schematic plan view, partially in section, showing a shredder provided with blades according to the invention; Fig. 4 is a schematic side view, partially in section showing the shredder; and Fig. 5 is a sectional view taken along the line of X-X of Fig. 4. Referring first to Figs. 3 to 5, of the drawings, a shredder incorporating the features of the invention comprises a main shaft 1 and a driven shaft 2, both extending horizontally in parallel within a casing 4. Both ends of each shaft 1 and 2 are supported in bearings 3 on the end walls of the casing 4. The casing 4 is formed by two vertically extending side walls and the two end walls, which together form a box open at its top and bottom sides. The main shaft 1 is coupled at one end through a joint 5 to the drive shaft 7 of a drive motor 6 such as an electric motor, and through two spur gears 8 and 9 to one end of the driven shaft 2. The shafts 1 and 2 are rotated by the motor 6 in the opposite directions shown by the arcuate arrows in Fig. 5. A plurality of disc-like cutting blades 10 and a plurality of spacers 11 are mounted on each of the shafts 1 and 2, the blades and spacers on each shaft being tightly interleaved with each other. The radially extending side surfaces of the blades 10 on one shaft closely overlap with the side surfaces of the blades of the other shaft, thereby forming slit cutters, although there is a small clearance between the side surfaces of adjacent blades to prevent friction during rotation. As shown in Fig. 5, the motor 6 is rotated in the direction to cause the portions of the two sets of blades which are between the two shafts 1 and 2 to move downwardly, so that material to be shredded may be introduced through the open top side of the casing 4 and discharged through the open bottom side. Since the gear 9 is larger than the gear 8 (see Fig. 3), the shaft 1 will turn faster than the shaft 2, thereby producing a slitting action of material between adjacent blades. The blades and the spacers are anchored to the shafts so that they rotate together. In the present example, the shafts have a square section and the center holes in the blades and the spacers are square, thus causing the blades and the spacers to rotate with the shafts. As shown in Fig. 1, each blade 10 includes a mounting 14, which is fixed to the shaft 1, 2, and a number of tips 13, which surround the mounting 14 and each of which has a pawl 10a. The mounting 14 is polygonal and has teeth 14a for engagement with the tips 13. Each tip 13 has bolt holes 15 through which bolts 16 are inserted to engage with threaded holes 17 in the mounting 14. The teeth 14a extend into recesses or shoulders 13a of the tips and thereby securely transmit the torque from the shaft 1, 2 to the tips 13, and bear the reaction force when cutting. As shown by the phantom circular line in Fig. 1, the spacer 11 has a diameter large enough to substantially protrude radially from the mounting 14 and overlap the sides of the tips 13. This secures the tips 13 against axial displacement. When each pawl 10a is at its closest approach to the outer periphery of the opposite spacer 11 on the other shaft, the clearance between them is preferably about 0.5 to 1.0 mm. Scrapers 12 (Figs. 3 and 5) are mounted on and project from the side walls of casing 4 towards the blades 10 and spacers 11, and have semicircular ends (Fig. 5) adjacent the tips of pawls 10a and the peripheries of spacers 11. Each spacer 11 is formed by two identical parts 11b which extend around opposite sides of a shaft, and the two parts are secured together by screws 18. As shown in Fig. 2, each part 11b engages one full side and parts of two additional sides of the shaft, thereby enhancing the torque transfer from the shaft to the part. With reference to Figs. 3 and 4, the stack or assembly of spacers and blades is held together by collars 20 which fit between the bearings 3 and the stack. In use, material is thrown from above into the open upper side of the casing 4 and drawn in by the pawls 10a. It is then shredded by the shearing of the slit cutters to have a length equivalent to the interval or space between the pawls 10a, and is discharged downwardly. Because the outer periphery of each mounting 14 is completely surrounded by the tips 13, only the tips 13 wear. The worn tips 13 can be replaced by simply removing the bolts 16, without the necessity of disassembling the casing 4 and the bearings 3 in order to remove the blades 10 from the shaft 1, 2. The outer peripheries of spacers 11 also easily wear. By removing the bolts 18, a spacer 11 can be easily removed from the shaft 1, 2 and replaced.

Claims: A shredder comprising two counter-rotatable shafts (1,2) supported (3) in parallel by a frame (4) and a plurality of cutting blades (10) and a plurality of spacers (11) alternately mounted along each shaft (1,2), the cutting blades (10) and spacers (11) on one shaft meshing with the cutting blades (10) and spacers (11) on the other shaft and each cutting blade (10) comprising a mounting (14) and plurality of tips (13) separately attached on the radial periphery of the mounting (14), wherein the circumference of each mounting (14) includes projections (14a) which engage recesses in the tips (13); the tips (13) are identical; and the spacers (11) abut the side surface of the adjacent mounting (14) and tips (13), characterized in that the tips are fastened to the mounting (14) with screws (16) whereby the tips (13) are individually removable from the mounting (14) A shredder according to claim 1, wherein each mounting (14) has a polygonal outer periphery having outwardly extending teeth (14a) extending into recesses (13a) in the tips (13). A shredder according to claim 1 or claim 2, wherein each shaft (1,2) has a square section and the spacers (11) are formed by two identical parts (11b) each of which engages three of the peripheral surfaces of each shaft.

Inventors: WADA TOSHIHIRO, WADA, TOSHIHIRO
Applicants: KINKI KK, KABUSHIKI KAISHA KINKI
Application year: 1991
Main classification: B02C18
IPC codes: B02C18