Abstract:
The invention concerns a knife seat arrangement on a cutting shaft of a shredding machine, having a knife seat groove and cutting tool arranged therein, whereby the cutting tool, fastened so as to be detachable in the knife seat groove, adjoins a flat back surface on a flat front surface of a stop element and the stop element adjoins a corresponding end surface of the knife seat groove with a semicylindrical rear wall, whereby the stop element has a protrusion, situated in a form-locking manner in a corresponding recess of the groove bottom and directed inward, in the area of the groove bottom of the knife seat groove, said protrusion partially gripping under the cutting tool and adjoining it, so that the stop element is supported radially in the groove by the cutting tool. In addition, the invention concerns a knife seat arrangement in a shredding machine with knife seat recesses distributed about the periphery, spirally wound, whereby cutting tools can be placed in the knife seat recesses and a number of knife seat recesses are placed on a common radial shaft plane, so that several cutting tools are situated on a common, radial cutting tool flight circle, whereby, adjusted to the desired cutting force, the knife seat recesses of a common radial plane of the shaft are uniformly furnished with cutting tools and that knife seat recesses not furnished with cutting tools are covered or filled with cover elements.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This application is a continuation application of U.S. patent application Ser. No. 09/310,496, filed on May 12, 1999, now abandoned, which claims priority to German Application Nos. 19821205.4 filed on May 12, 1998 and 19821207.0 filed on May 12, 1998. 
    
    
     BACKGROUND OF THE INVENTION 
     The invention concerns an arrangement of seats for knives on a cutting shaft in a shredding machine according to one embodiment. 
     A known shredding machine is shown in FIG.  16  and disclosed in DE 42 42 740 A1 and can be used to shred and reduce wood, metal parts, plastic material, garbage and other waste materials. 
     The shredder  101  essentially consists of a material hopper  102 , a feed unit  103  and a cutting tool  104 . The three machine components  102 ,  103 ,  104  are connected to one another so as to be detachable by flanged couplings and, when assembled, form a feeding chamber  105 . In the feeding chamber  105 , a cutting shaft  106  driven by an electromotor engages in the lower area opposite the feed unit  103 . The cutting shaft  106  is octagonal or polygonal in shape and is equipped with a number of cutting tools  107 . The cutting tools  107  are fastened to the cutting shaft  106  and spirally wound and distributed over the periphery and are engaged with a first cutting plate  108  and a second cutting plate being used as a scraping bar  109 . The upper side of the first cutting plate  108  is simultaneously part of the floor of the feed chamber  105 . A perforated screen  111  fastened to reinforcing rings  110  is provided below the cutting shaft  106 . A collecting tray  112  is situated below the sieve  111 , a worm conveyor  113  being connected to the lowest point of said collecting tray for removing the crushed or shredded material. FIG. 17 shows the cutting shaft  16  in a perspective of a partial view, as seen from the feed chamber  105 . The cutting shaft  106  has a number of cutting tools  107  which are attached to the cutting shaft  106  in a thread-like manner. The cutting tools  107  sit in the recesses  129  made in the cutting shaft  106 . The recesses  129  extend from a first edge  140  of the cutting shaft  106  to the second edge  141  following in direction of rotation. The base  142  of the recess  129  deepens uniformly relative to a cutting shaft surface  139  over its entire longitudinal extension. The base  142  or the supporting area  131  forms a right angle with the contact surface  130 . The height of the contact surface  130  between the second edge  141  and the base  142  corresponds to the diagonal extension of a cutting tool  107 . 
     A known shredding machine of this type is also shown in the brochure “Holzmag Zerkleinerungstechnik” [Holzmag Shredding Technology] of Holzmag AG. In particular, a polygonal rotor shaft is shown which has knife seats and cutting tools inserted into the knife seats. The cutting tools are blocks rhombic in cross-section which are arranged in essentially V-shaped grooves which are distributed about the periphery of the shaft. The grooves are made in the shaft with bevelled cutters, which is why the end of the groove found in the shaft has a semicircular shape. The cutting tools, which have a flat rhombic front surface and a flat rhombic back surface, require a flat emplacement on the back of the knives in order to ensure an impact resistant fit in the grooves. To this end, semicircular positioning elements are inserted into the semicircular or semicylindrical groove ends and welded with the material of the shaft. 
     A shredding machine of this type has proven successful. 
     In the field of waste recyling and disposal of waste materials, disposal firms must respond more and more flexibly to the various materials to be processed. Thus, for example, not only hard materials such as plastic housings, plastic products, electronic parts or other breakable materials have to be crushed but also stretch materials, woven synthetic materials, carpets, threads and fibers of all types. In addition, the material to be cut can vary considerably in size and volume; for example, small-sized hollow plastic bodies (PET bottles) and plastic barrels must be handled. Experience has shown that unsatisfactory results are obtained with respect to the cutting operation when using a preset driving power or the cutting shaft and a preset size for the cutting tools. 
     SUMMARY OF THE INVENTION 
     The object of the invention is to create an arrangement of seats for knives on a cutting shaft with which different demands with respect to the cutting operation of the cutting shaft can be easily met. 
     According to the invention, the groove for the knife seat is designed in a such a way that knife positioning elements can be loosely inserted in the rear end area of the groove and are loosely mounted. The knife positioning elements or stop elements are kept radially covered by the cutting tool screwed into the knife seat and, in addition, centered by the back of the cutting tool. 
     The positioning surface or the positioning element can have a contour protruding beyond the shaft, which is preferably adapted to the contour of the knife, so that the knife is supported by the positioning element over the entire rear surface of the knife. 
     The knife positioning elements according to the invention are, like the knives, easily and quickly exchangeable, so that they can be exchanged for other knives having knife positioning elements adapted accordingly. In addition, it is advantageous that, when there is a damaging impact stress on the knife which e.g. leads to a deformation of the knife seat, the knife positioning element can be exchanged because it is merely inserted in a corresponding recess of the shaft and is not welded with the shaft. As a result, the energy expended when changing the knife position is considerably reduced. 
     According to the invention, a cutting shaft can also be equipped in such a way that, at a preset maximum driving power, it can be optimally designed for the material to be shredded. 
     According to the invention, at a constant driving power, a cutting shaft can be adjusted to the material to be shredded in such a way that cutting tools can be removed at certain points from the cutting tools that are spirally wound and distributed on the periphery of the cutting shaft and replaced by cover elements of the invention which cover the knife seat in a lid-like manner. This enables a reduction or increase of the number of tools at a constant driving power of the cutting shaft, i.e. the torque of the cutting shaft is distributed to different numbers of knives and thus adapted to the material to be chopped. With difficult-to-shred materials, as e.g. carpets or woven plastics, the force on the individual cutting tools can be appropriately increased by reducing the tools, whereby the cover elements of the invention ensure that no chopped materials accumulate in the knife seats and contaminate the knife seats or that thread-like material to be chopped winds about the shaft in the area of the empty knife seats without being cut. With hard materials to be cut, the cover elements ensure that the grooves for the knife seats are not damaged. 
     The invention shall be described in the following by way of example and with reference to drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 illustrates the design of a knife seat groove according to one embodiment of the invention in a polygonal knife shaft in a sectional view through the shaft, 
     FIG. 2 illustrates a top view onto the knife seat groove according to FIG. 1, 
     FIG. 3 illustrates a section along the line A—A in FIG.  2  through the knife seat groove, 
     FIG. 4 illustrates a knife seat arrangement according to the invention having a knife positioning element and an inserted cutting tool in a section diagonal to the shaft, 
     FIG. 5 illustrates the arrangement of FIG. 4 in a top view onto the shaft, 
     FIG. 6 illustrates the arrangement of FIG. 4 in a section along the line A—A in FIG. 1, in a top view onto the bearing surface of the knife positioning element, 
     FIG. 7 illustrates a knife seat placed in a cutting shaft, in a longitudinal section diagonal to the longitudinal extension of the shaft, 
     FIG. 8 illustrates a knife seat according to FIG. 7 in a top view, 
     FIG. 9 illustrates a knife seat according to FIG. 7 in a section along line A—A in FIG. 8, 
     FIG. 10 illustrates a cover element according to the invention in a knife seat according to FIG. 7, 
     FIG. 11 illustrates a cover element of the invention in a knife seat according to FIG. 8, 
     FIG. 12 illustrates a cover element of the invention in a knife seat in a section along line A—A in FIG. 11, 
     FIG. 13 illustrates a further embodiment of the cover element according to the invention in a knife seat according to FIG. 7, 
     FIG. 14 illustrates a further embodiment of a cover element according to the invention as a hollow profile having reinforcing ribs in a knife seat as per FIG. 8, 
     FIG. 15 illustrates a cover element according to the invention in a knife seat in a section along line A—A in FIG. 14, 
     FIG. 16 illustrates a known shredding machine having a cutting shaft and cutting tools attached thereto, 
     FIG. 17 illustrates a cutting shaft of a shredding machine as per FIG. 16, in a top view. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A cutting shaft  1  (FIGS. 1 to  3 ) for accommodating cutting knives or cutting tools is, for example, a cutting shaft  1  having a polygonal cross section. Flat surfaces  2 , which meet one another with edges  3 , are formed by the polygonal cross section, whereby the edges  3  extend parallel to a longitudinal axis, preferably uniformly distributed about the periphery of the polygonal cutting shaft  1 . Uniformly or regularly distributed knife seats  4  are mounted spirally wound on the periphery of the cutting shaft  1 . The knife seats  4  are grooves  5  that are funnel-shaped in cross section with a flat groove bottom  6 . The groove bottom  6  or the grooves  5  extend as hexagons from a surface  2  into the cutting shaft  1 . The groove  5  begins at about the transverse axis of a surface  2   a , and extends over the entire width of the next surface  2   b  and ends at approx. the transverse axis of the next surface  2   c  but one. Due to the hexagonal arrangement of the groove bottom  6 , the groove  5  becomes deeper from the first surface  2   a  to the last surface  2   c . The groove  5  which is funnel-shaped in cross section ends in the area of surface  2   c  with a semicylindrical rounded end  5   a . In the conical area of the end  5   a , the groove  5  has a flat groove bottom  6  and short walls  7  extending tangentially upward from the flat groove bottom  6 , so that the groove  5  above the groove bottom  6  is a rectangular or square groove. The groove  5  expands with diagonal walls  8  from the short walls  7 . Tangential straight walls  9  extend from the diagonal walls  8  to the surface of the cutting shaft  1  or the surface  2   c . In the area of the surface  2   c , the groove  5  has a constant height. The groove depth decreases successively from the edge  3  between the surface  2   c  and surface  2   b  to the edge  3  between the surface  2   b  and surface  2   a , so that the height of the walls  9  of the groove  5  becomes less and less until the walls  9  disappear in the area of the edge  3  between surfaces  2   b  and  2   a . The depth or height of the groove  5  continues to decrease from the edge  3  between the surface  2   b  and surface  2   a  to the emergence of the groove bottom  6  in the surface  2   a  and increasingly about the slope of surface  2   a  to surface  2   b.    
     In the area of surface  2   b , a bore  10  is placed in the groove bottom  6  at right angles to the groove bottom  6 . The bore  10  serves to accommodate a setscrew (not shown) for cutting tools. 
     In the area of the end  5   a , the groove  5  is formed from the upper surface  2   c  to the level of the groove bottom  6  as a cylindrical bore  12 , so that the groove  5  has a semicylindrical wall  13  at right angles to the surface  2   c  in the area of end  5   a . Adjacent to the walls  8 , pointing in direction of the outlet of groove  5 , cylinder casing sector-shaped walls  15  are formed on both sides of the transverse axis  14  of groove  5  and adjacent to wall  13 . The flat groove bottom  6  opens at the end into a circular groove bottom  16 . A cylindrical recess or bore  17  is placed in the bottom  16  so as to be axially aligned to the bore  12 . 
     Referring to FIGS. 3-6, the stop element or positioning element  20  of the invention has a cylindrical foot plate  21  with a circular disk-shaped cylinder bottom wall  22  and a cylinder jacket wall  23 . A semicylindrical section  24  of the element  20  extends from the foot plate  21  away from the foot plate  21 . The semicylindrical section  24  has a flat front surface  25  and a casing wall or back surface  26  which is semicircular in cross section. The flat surface or wall  25  aligns with an axial plane of the foot plate  21 , whereby the radius of the cylinder casing wall  26  is larger than the radius of the jacket wall  23  of the foot plate  21 , so that the semicylindrical section  24  forming a step  27  protrudes beyond half of the cylindrical foot plate  21 . The casing wall  26  of the semicylindrical section  24  tapers in from of a cone-shaped shell wall  28  up to a point  29 , so that the flat wall  25  tapers via-à-vis the foot plate  21  in a inversed V-shaped manner to the point  29 , forming an edge  30 . 
     The foot plate  21  corresponds with the bore  17  and fits into it in a form-locking manner, at the top, it closes with the groove bottom  6 . The casing wall  26  corresponds with the wall  13 , so that the stop element  20  is disposed in the end area  5   a  of the groove  5 , whereby the foot plate  21  rests in the bore  17  and the casing wall  26  adjoins the wall  13  in a form-locking manner. Step  27  rests in a form-locking manner on surface  16 . 
     A cutting tool  35  to be placed in the groove  5  is a longitudinal block  35 , rhombic in cross section, having a lower longitudinal edge  36  pointing into the groove  5 , an upper longitudinal edge  37 , two side longitudinal edges  38  and four surfaces  39  that have the same angle to one another. The rhombus forms a cutting tool face surface  40  pointing out of the groove  5  and a cutting tool rear surface  41  pointing toward the groove end  5   a . The surfaces  39  and surface  40  form an inverse V-shaped cutting edge  42  that points outward. Extending from edge  37  to edge  36 , a bore  45  is placed at about the longitudinal axis of the cutting tool  35 , which has a wide bore area  45   a  in the vicinity of edge  27  that becomes narrower with a step  46  to form a narrower bore area  45   b.    
     The arrangement of the stop element  20  and a cutting tool  35  in a groove  5  or in a knife seat  4  will be described in the following. First, the stop element  20  is inserted into the bore  17  with the foot plate  21 , so that the cylinder casing wall  26  of area  24  adjoins the wall  13 . A cutting tool  35  is then pushed into the groove  5  until the cutting tool surface  41  or rear knife surface adjoins surface  25  in a form-locking manner. The cutting tool  35  lies on the surfaces  8  of the groove  5  and, with the longitudinal edge  36 , on the groove bottom  6  and, at the top, on the foot plate  21 , radially covering the latter. A screw bolt (not shown) is then inserted through the bore or the hole  45  and then screwed into the bore  10  of the cutting shaft  1  which is aligned with the bore  45 . By fastening the cutting tools  35  to the cutting shaft  1 , the stop element  20  is also fastened to the cutting shaft  1  due to the pressure of the longitudinal edge  36  on the foot plate  21 . The edge  30  of the stop element  20  closes with the surfaces  39  and the upper longitudinal edge  37  of the cutting tool  35 . 
     In a further embodiment, the upper side of the footplate  21  is designed V-shaped, protruding beyond the groove bottom  6 , whereby the groove bottom  6  horizontally aligns or seals with the base of the V-shaped protrusion. In this embodiment, the footplate  21  holohedrally adjoins the lower diagonal surfaces and the edge  36  of a cutting tool  35  in a form-locking manner. As a result, a centering or alignment of the stop element  20  is obtained when the cutting tool  35  is inserted. 
     If the surfaces  39  of the cutting tool  35  are contoured, for example, contoured with teeth that point outward, the edge  30  of the stop element  20  can be formed accordingly, so that the cutting tool  35  is holohedrally supported by the stop element  20  in the area of the surface  39  adjacent to the longitudinal edge  37 . 
     The stop element  20  can, adjusted to the material of the cutting tool  35 , consist of hard metal, metal, ceramics or the like. In addition, various stop elements  20  can be used for different cutting contours of the cutting tools  35 , which are exchanged when the knives are exchanged. Furthermore, protrusions can be formed on the rear surface  26  of the stop element  20 , said protrusions fitting in appropriate corresponding recesses of the rounded end wall  13  of the groove  5 , so that the stop elements  20  are hereby radially secured. 
     If the number of cutting tools  35  on the cutting shaft  1  is reduced, the setscrew is unscrewed and the cutting tool  35  removed. The stop element  20  is then removed, after which a cover piece (not shown) is pushed onto the empty groove  5  or into the empty knife seat  4  and screwed in the bore  10 . 
     In the design of a knife seat  4  according to the invention and the stop elements  20  of the invention, it is advantageous that the stop elements can be easily removed. As a result, the stop elements  20  can be easily removed when there is damage. In addition, the stop elements  20  can be adjusted to the various forms of the cutting tool  35  or materials and be inserted together with the knives. Furthermore, it is advantageous that the stop elements  20  do not have to be unwelded after damage has occurred. 
     In the embodiment of the invention according to FIGS. 7 to  15 , a cutting shaft  201 , for example a cutting shaft  201  having a polygonal cross section, is shown for accommodating cutting knives or cutting tools. Due to the polygonal cross section, flat surfaces  202  are formed which meet at their edges  203 , whereby the edges  203 , extending parallel to a longitudinal axis of the shaft  201 , are preferably uniformly distributed on the polygonal cutting shaft  201 . Uniformly or regularly distributed knife seats  204 , wound spirally, are placed on the periphery of the cutting shaft  201 . The knife seats  204  are grooves  205 , funnel-shaped in cross section with a flat groove bottom  206 . The groove bottom  206  or the grooves  205  extend as hexagons from a surface  202  into the cutting shaft  201 . The groove  205  begins at about the transverse axis of a surface  202   a , extends over the entire width of the next surface  202   b  and ends approx. at the transverse axis of the next surface  202   c  but one. Due to the hexagonal arrangement of the groove bottom  206 , the groove  205  becomes deeper from the first surface  202   a  to the final surface  202   c . The groove  205 , funnel-shaped in cross section, ends in the area of the surface  202   c  with a semi-tapered funnel-shaped, rounded end  205   a . The groove  205  has the flat groove bottom  206  and short walls  207  extending tangentially upward from the flat groove bottom  206  in this area, so that the groove  205  is a rectangular or square groove above the groove bottom  206 . The groove  205  expands from the short walls  207  with diagonal walls  208 . Straight walls  209  extend tangentially from the diagonal walls  208  to the surface of the cutting shaft  201  or surface  202   c . In the area of surface  202   c , the groove  205  has a constant height. The groove depth declines successively from the edge  203  between the surface  202   c  and surface  202   b  to the edge  203  between the surface  202   b  and surface  202   a  and increasingly declines from edge  203  between surface  202   b  and surface  202   a  to the bottom of the groove where the groove ends at surface  202   a , again by the slope of surface  202   a  to surface  202   b.    
     The diagonal walls  208  serve as bearings for cutting tools. In the area of surface  202   b , a bore  210  is placed in the groove bottom  206  at right angles to the groove bottom  206 . The bore  210  serves to accommodate a setscrew for cutting tools. 
     The cover element  212  of the invention (FIGS. 10 to  12 ) is solid, e.g. made of metal or a ceramic, and points to walls  213  corresponding to the diagonal walls  208  which meet at a common edge  214 . When the cover element  212  is placed in the groove  205 , the edge  214  is situated between the short walls  207  and is preferably slightly spaced from the groove bottom  206 . The remaining surfaces of the cover element  212  correspond to the groove  205 , so that the cover element  212  is made so as to be in the shape of a semicircular cone end  215  in the area of a surface  202   c  or the groove end  205   a  and tapers from the semicircular conically shaped end  215  along the groove  205 , whereby the cover element  212  has surfaces  216   a ,  216   b  and  216   c  pointing outward and oriented at an angle to one another, which each align or close with the surfaces  202   a ,  202   b  and  202   c  of the polygonal cutting shaft  201 . 
     Aligned with the bore  210 , the cover element  212  has a bore  218  made in the cover element from the surface  216   b  at a right angle to the edge  214  and which becomes narrower from a further area  218   a  with a step  219  to a narrower area  218   b . A threaded bolt is inserted through the bore  218  or hole  18  and screwed into the threaded bore  210  of the shaft  201  in order to rigidly fix the cover element  212  in the groove  205 . 
     In a further embodiment of the cover element  212  (FIGS. 13 to  15 ), the cover element  212  is shaped like a hollow profile in the form of a plate  220  that is bent twice, whereby three surfaces  221   a ,  221   b  and  221   c  are formed by the bending, which meet at the crease edges  222 . The outer form of the plate  220  corresponds to the form of the groove  205  or the shaft  201 , adjacent to the surfaces  202   a ,  202   b ,  202   c , so that, when the cover element  212  has been pushed into the groove  205 , the plate  220  seals in a form-locking manner on the outside. 
     The plate  220  has a cylindrical formation  225  in direction of the bore  210  in the groove bottom  206  which is formed, in the area of the diagonal walls  208  of the groove  205 , with diagonal supporting walls  226  corresponding to the walls  208 . A bore  218  for accommodating a screw bolt is also placed in this plate  220  in the area of the formation  225 . In a further embodiment (FIG.  14 ), a reinforcing rib  227  is situated on the underside and a transverse reinforcing rib  228  diagonally thereto, following the longitudinal slope of the cover element  212 . 
     The use of the cover element is described in the following. 
     In order to apply an increased force on the individual cutting tools at a preset driving power and the constant speed of the cutting shaft, it is necessary to reduce the number of knives. Usually several cutting tools, e.g. up to eight, are found on a cutting tool flight circle or a common, radial plane of the shaft with cutting tools generally spirally wound and distributed over the periphery, so that during a rotation of the shaft a cut is made eight times in this flight circle. The number of knives can, for example, be halved on a knife flight circle, so that only four cuts are made during a rotation. The empty four knife seats or grooves are covered with the cover element of the invention, whereby it is advantageous that the cover elements prevent material from accumulating in the groove or prevent difficult-to-cut material, such as e.g. carpets, from catching on empty grooves  205  and winding about the shaft without being cut. With hard material to be cut, the cover elements prevent the knife seat grooves not equipped with knives from being damaged by the plate  220  seals in a form-locking manner on the outside. 
     The plate  220  has a cylindrical formation  225  in direction of the bore  210  in the groove bottom  206  which is formed, in the area of the diagonal walls  208  of the groove  205 , with diagonal supporting walls  226  corresponding to the walls  208 . A bore  218  for accommodating a screw bolt is also placed in this plate  220  in the area of the formation  225 . In a further embodiment (FIG.  15 ), a reinforcing rib  227  is situated on the underside and a transverse reinforcing rib  228  diagonally thereto, following the longitudinal slope of the cover element  212 . 
     The use of the cover element is described in the following. 
     In order to apply an increased force on the individual cutting tools at a preset driving power and the constant speed of the cutting shaft, it is necessary to reduce the number of knives. Usually several cutting tools, e.g. up to eight, are found on a cutting tool flight circle or a common, radial plane of the shaft with cutting tools generally spirally wound and distributed over the periphery, so that during a rotation of the shaft a cut is made eight times in this flight circle. The number of knives can, for example, be halved on a knife flight circle, so that only four cuts are made during a rotation. The empty four knife seats or grooves are covered with the cover element of the invention, whereby it is advantageous that the cover elements prevent material from accumulating in the groove or prevent difficult-to-cut material, such as e.g. carpets, from catching on empty grooves  205  and winding about the shaft without being cut. With hard material to be cut, the cover elements prevent the knife seat grooves not equipped with knives from being damaged by the materials. Moreover, it is advantageous that the cover element can be manufactured in an especially simple and easy manner, for example, by metal casting. 
     By providing cover elements, it is thus possible to quickly refit a conventional cutting shaft to various types of materials. As a result of the form of the cover element corresponding to the groove and the fastening of the cover element with a screw connection equivalent to the knives, the refitting can be easily and especially quickly obtained.