Abstract:
The invention concerns a cutting shaft for a cutting machine having knife seat grooves distributed so as to be spirally wound on the periphery in the cutting shaft, whereby cutting tools are arranged in the knife seat groove which protrude with a cutting edge beyond the periphery of the cutting shaft and mesh with corresponding counter cutting means of the cutting machine, whereby, to change the cutting contour, cutting tools having at least the same cutting edge length and the same maximum protrusion beyond the cutting shaft, but slighter engagement depth, are arranged with counter cutting means in the shaft. The invention also concerns a cutting tool for a cutting shaft of a shredding machine, whereby knife seat recesses, wound spirally, are distributed on the periphery in the cutting shaft for the cutting tools and the cutting tools have a pointed cutting contour projection beyond the upper and peripheral surface of the cutting shaft, whereby, to extend the cutting edge, the cutting edges of the cutting tool are staggered, stepped or toothed.

Description:
The invention concerns a cutting shaft with cutting tools for a shredding/crushing machine in which cutting tools seated in knife seat grooves spirally wound and distributed on the periphery of a cutting shaft work in opposition to counter cutting edges mounted independently of the shaft. 
     BACKGROUND OF THE INVENTION 
     A shredding/crushing machine, which is the subject of this invention, is shown in FIGS. 23,  24  and disclosed in, DE 42 42 740 A1. The machine is used for cutting and reducing wood, metal parts, plastic material, garbage and other waste materials to small pieces. 
     The shredder/crusher  101  essentially consists of a material hopper  102 , a food 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 this 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  spirally wound and distributed over the periphery (FIG. 23) and are engaged with a first cutting plate  108  and a second cutting plate being used as a scraping bar. 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 fastened below the cutting shaft  106 . A collecting tray  112  is situated below the screen  111 , a worm conveyor  113  being connected to the lowest point of said collecting tray for removing the shredded/crushed material. FIG. 10 shows the cutting shaft  16  in a perspective of a partial view, as seen from the feeding 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  placed into the cutting shaft  106 . The recesses  129  extend from a first edge  140  or 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  131 . The height of the contact surface  131  between the second edge  141  and the base  142  corresponds to the diagonal extension of a cutting tool  107 . 
     The knives  104  which are square in cross section are arranged on the shaft  106  so as to be in a diagonally upward position and form a cutting edge  107   a  in the shape of a pointed roof with a cutting point  107   b  protruding upward. 
     A shredder/crusher of this type has proven successful. 
     In the field of waste recycling 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 shredded or crushed, but also stretch materials, woven synthetic materials, carpets, threads and fibers of all types. In addition, the material to be cut often varies 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 often obtained with respect to the cutting work when using preset a driving power for the cutting shaft and a preset size for the cutting tools. 
     DE-GM 295 15 768.2 discloses cutting tools for shredding machines. The cutting tools consist of several parts, having a cutting tool body and one or two cutting plates. The cutting tool body is an elongated one-piece metal body having, for example, a square cross section, two front surfaces and four similar lateral surfaces. The cutting tool body is somewhat shorter than the cutting tool shown in FIGS. 1 and 2. At the front surfaces, a longitudinally axially tapped hole is placed in the canter into which a screw can engage to fasten a cutting plate. The front surfaces have a contoured surface with two cross-shaped grooves which each extend between the points of the front surfaces. 
     The cutting plates are thin metal plates which can have a corresponding square shape like the front surfaces of the tool body. A hole, through which a fastening screw can pass, is placed in the centre of the cutting plates. On their back side, the cutting plates have webs arranged transversely which are adapted to the shape of the grooves of the cutting tool bodies so that the cutting plates can be fastened in a form-locking and torque resistant manner to the front surfaces of the cutting tool bodies. 
     The cutting tool bodies, each having a cutting plate, form a cutting tool which has the same spatial shape and the same dimensions as the one-piece cutting tool of FIGS. 23 and 24. All four points of the cutting tools can be used as a cutting point, so that a cutting tool with two cutting plates can be used eight times. 
     Cutting tools of this type have proven successful. However, it was found that, with a set cutting tool size of e.g. 40×40×64 mm, it is not possible to efficiently obtain a defined granular, size, in particular of lose than 10 mm. Although an increase in rotational speed and an even larger number of knives on the knife shaft can lead to an increase in cutting speed and a higher cutting sequence and, as a result, a fine granulation, however, this also causes friction and heat, especially in the area of the screen basket area. Moreover, additional suctioning devices are required that draw off the fine material through the screen basket area by suction and prevent unnecessary material rotation about the shaft body and a decrease in throughput. In addition, it was found that, in PVC or stretch foils having a low melting point, the heat formation can be so high that it can result in melting of the material and blockages in the cutting system. 
     The object of the invention is to create a cutting shaft for a shredding machine which can easily and quickly be optimally adjusted to the material to be cut and, moreover, to provide a cutting tool with which it is also possible to produce defined, in particular, small granular sizes without thereby altering the quality of the material to be cut. 
     SUMMARY OF THE INVENTION 
     According to the invention, the cutting shaft is furnished with an easily exchangeable cutting contour. To accomplish this, cutting tools in the form of cutting blocks which are rhombic in cross section are used in enlarged knife seats of cutting shafts which are double the size in comparison to cutting blocks which are rhombic in cross section and customarily used. As a result, the available and inverted V-shaped cutting edge, projecting outward from the cutting shaft, is quadrupled in its length. According to the invention, this solid large cutting block can be replaced by cutting blocks which have the same structure as the large cutting blocks at the knife seat end, however, which are M-shaped on the cutting edge and with a deep V-shaped groove. The two serrations formed hereby and pointing outward are arranged in such a way that they are situated on the same flight circle of the knife, i.e. have the same radial distance from the base of the knife seat in the individual points of large cutting blocks. According to a further advantageous embodiment of the invention, the basic body of the cutting block has two flat recesses, rhombic in a top view, at the front in the area of the two serration, the edge length of which corresponds to the edge length of the serrations. Knife plates can be inserted into the recesses. 
     In addition, it is also possible to furnish cutting blocks having the usual size in conventional knife seats but with the above described finer cutting geometries, i.e. two cutting points. It is thus possible to cut the material of different sizes with a single cutting shaft adjusted to the material to be cut, whereby the cutting contour can be easily and quickly changed. 
     To optimally adjust the cutting power of the shaft or the torque of the shaft to the material to be cut, the number of cutting tools an the shaft can be reduced, whereby the empty knife seats are covered with covering elements in a lid-like manner. As a result the cutting operation can be optimally adjusted to the material to be cut. 
     According to the invention, it was also, found that a fine granulation can be obtained with an elevation of the cutting edge surface or extension of the cutting edge at the same speed, whereby the elevation or extension of the cutting edge surface is obtained with serrated knives. These serrated knives have stopped cutting edges projecting outward in contrast to the conventional cutting tools with straight cutting edges arranged at an angle of 90° to one another. The counter edges of the cutting edges and scraping bars correspond with this cutting contour. The serrated knives can be made similar to the conventional cutting blocks as blocks. To retrofit existing cutting machines, however, it is also possible to bolt the serrated knives as serrated knife plates to the front of the previously used cutting blocks, whereby the cutting blocks Are shortened by the thickness of the plates. 
     It was surprisingly found that, with an unchanged driving power and speed of the cutting shaft, granules of less than 10 mm were produced when using the serrated knives of the invention at the highest throughput capacity, without this resulting in troublesome heat development. If particular, in a cutting machine furnished with the serrated knives of the invention, problematic hollow plastic bodies such as PET bottles or a precompression can also be granulated. Usually, hollow plastic bodies of this type are first compressed into balls and only granulated subsequently. This intermediate step can now be omitted and the hollow bodies can be directly granulated, The granulated hollow body has an optimum bulk density for transport, so that large capacity transport, e.g. in so-called “big bags” is possible. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention shall be described in the following by way of example and with reference to the drawings, showing: 
     FIG. 1 is an enlarged cutting block according to the invention in a partial sectional top view, 
     FIG. 2 is a cutting block according to FIG. 1 in a top view, 
     FIG. 3 is rotating cutting block having two cutting points in a partial sectional top view, 
     FIG. 4 is a cutting block according to FIG. 3, in a top view, 
     FIG. 5 is an insert for a rotating cutting block according to FIG. 3 in a partially cut top view, 
     FIG. 6 is an insert according to FIG. 5 in a view from the top, 
     FIG. 7 is an enlarged cutting tool carrier according to the invention, in a partially cut top view, 
     FIG. 8 is a cutting tool carrier according to FIG. 7, in a view from the top, 
     FIG. 9 is a cutting tool carrier according to FIG. 7 with two mounted knife plates having a straight cutting contour, 
     FIG. 10 is a cutting tool carrier according to FIG. 7 with two mounted knife plates having a staggered cutting contour, 
     FIG. 11 is a cutting tool carrier according to FIG. 7 with a further embodiment of knife plates, 
     FIG. 12 is a cover element for an empty knife seat on a knife shaft in a longitudinal section, 
     FIG. 13 is a cover element according to FIG. 12 in a top view, 
     FIG. 14 is a cover element according to FIG. 12 in a knife a seat in a cross-section, 
     FIG. 15 is a serrated knife according to the invention in a top view, 
     FIG. 16 is a serrated knife according to FIG. 15 in a side view, 
     FIG. 17 is a serrated knife according to FIG. 15 in a view from the top, 
     FIG. 18 is a serrated knife according to FIG. 15 in a front arrangement on a conventional cutting tool, 
     FIG. 19 is a further embodiment of a serrated knife according to the invention in a top view, 
     FIG. 20 is a serrated knife according to FIG. 19 in a side view, 
     FIG. 21 is a serrated knife according to FIG. 19 in a view from the top, 
     FIG. 22 is a serrated knife according to FIG. 19 in a front-end arrangement on a conventional cutting tool, 
     FIG. 23 is a cutting machine with cutting shaft and cutting tools arranged thereon, 
     FIG. 24 is a cutting shaft according to FIG. 23 in a top view. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     An enlarged cutting tool (FIGS. 1,  2 ) according to the invention is a block, rhombic in cross-section, with a lower edge  2  and an upper edge  3  opposite thereto, which, fix a vertical plans  4 . In addition, the block  2  has opposite horizontal edges  5 ,  6  which fix a horizontal plane  7  that is at right angles to the plane  4  and cuts it at the centre. The edges  2 ,  5  define a lower diagonal surface  8 , the edges  2 ,  6  define a lower diagonal surface  9  of the rhombic cutting block. The edges  5 ,  3  define an upper diagonal surface  10 , the edges  6 ,  3  define an upper diagonal surface  11 . The rhombic block  1  designed in this way with four similar surfaces has, in addition, two rhombic front surfaces  12 ,  13 . 
     A cutting tool or cutting block  1  lies in a V-shaped groove or a V-shaped knife seat of a cutting shaft with these surfaces  8 ,  9 . With a front end  13 , the cutting block  1  adjoins a flat knife backing of the cutting shaft, with surface  22 , the cutting block  1  points in direction of rotation, whereby the common edge  11   a  of surface  11  and the front end  12  form a cutting edge in the shape of a pointed roof projecting beyond the periphery of the cutting shaft. 
     Longitudinally in the centre, a vertical bore or a vertical hole  15  is placed in the cutting block  1  from edge  3  to edge  2  which has, from the edges  2 ,  3  to the inside of the cutting block, two wide cylindrical hole areas  16  and an axially aligning narrow hole area  17  connecting the wide hole areas  16  to one another, so that a step  18  each if formed between the wide hole areas  16  and the narrow hole area  17 . The bore  15  or the hole  15  serves to receive a threaded bolt to fasten the cutting block  1  in the groove of a cutting shaft. The steps  18  serve as a bearing for a screwhead of the threaded bolt. 
     In a further embodiment of cutting tool (FIGS. 3 to  6 ), the cutting block  20  has the form of two hexagons, standing on the points and connected with a common vertical side surface, in the cross section, so that the cutting block  20  forms an upper V-shaped groove  21  and a lower inverted V-shaped groove  22  along its longitudinal extension, the bottom edges  21   a ,  22   a  of which are spaced from one another. The cutting block  20  has two upper edges  23  defining the groove  21 , two surfaces  24  sloping outward from the edges  23  and side surfaces  25  extending vertically downward from the surfaces  24 . The groove  22  is limited by edges  26  from which diagonal surfaces  27  extend outward at the top and meet the surfaces  25  with which they form a common edge. The cutting block  20  forms two front surfaces  28 ,  29  corresponding to the cross section, the grooves are formed by two diagonal surfaces  21   b ,  22   b  each at an angle to one another. The distance of the groove bottom  21   a ,  22   a  corresponds to the width of the surfaces  25 , whereby the groove bottom closes vertically with the upper and lower edges limiting the surfaces  25 . A vertical bore  30  is placed in the block  20  on the longitudinal axis, each bore tapering conically from the top and bottom to the vertical centre of the cutting block  20 , so that two receiving cones  31  are formed for accommodating countersunk screws. The slope of the surfaces  27  or surfaces  24  corresponds to the slope of the surfaces  8 ,  9  of a first embodiment, so that the cutting block  20  can be inserted in a form-locking manner in a knife seat groove of a cutting shaft. The edges  23  have the same radial distance from the bottom of the groove of the cutting knife groove as the edge  3  of a first embodiment, so that the cutting tool of the first embodiment may be replaced by a cutting tool of the second embodiment without it being necessary to exchange the shaft, since the radial flight circle of the edges or points projecting beyond the shaft is the same. 
     To enable an optimum seat of the cutting block  20  in a knife groove, a rhombic insert  35  is provided, the length of which corresponds to that of the cutting block  20 . The rhombic insert  35  has an upper edge  36 , a lower edge  37  and two outer edges  30 . The edges  36 ,  37 ,  38  limit four similar surfaces  39  and two rhombic front surfaces  40 . A continuous bore of a continuous hole  41 , which aligns with the hole  31  of a cutting block, is placed in the insert  35  from the edge  36  to the edge  37  on the longitudinal, axis. The surfaces  39  have the same orientation and size as the surfaces  21   b ,  22   b , so that the insert can be fitted in a form-locking manner into the grooves  21 ,  22  of the cutting block  20 . A screw bolt for fastening the cutting block  20  in a knife groove also passes through the bore  41  of the insert  35 . The surfaces  21   b  and  24  as well as  22   b  and  27  formed a cutting edge each at the front, whereby the cutting block  20 , since it is mirror-symmetric, can be turned about a horizontal axis after a cutting edge is worn. 
     In a further embodiment of the cutting block (FIGS. 7,  8 ), only an upper groove  22  is present. The lower diagonal surfaces  27  are continuously extended to the transverse axis at the cutting block and form a single lower edge  26  in the transverse axis of the cutting block. The surfaces  27  and the edge  26  correspond with the surfaces and the groove bottom of a knife seat groove of a cutting shaft. In the area of a front surface  29 , two rhombic knife plate seats  50  are recessed in the front end  29 . The rhombic knife seats  50  have two bearing surfaces  51  for the knife-plates arranged at an angle to one another, whereby a knife plate bearing surface  51  extends diagonally downward on the outside from edge  21   a  and the related second knife plate bearing surface  51  extends diagonally inward at the bottom, parallel to surface  27 , from the edge formed by the surface  24  and  25 . The knife bearing surfaces  51  thus form a flat recess  50  made in the front surface  29  with respect to the longitudinal extension of the block  20 , whereby the lower point or recess is rounded and fluted in the common origin of the surface  51  for accommodating the lower point of a knife plate. The surfaces  21   b ,  24  and  51  defined, at the front end, a rhombic knife bearing surface  53  into whose symmetrical axis a horizontal threaded bore  54  is placed. 
     Rhombic cutting plates  55  (FIGS. 9 to  11 ) may be inserted into the knife seats  50 , whereby the knife plates  55  have horizontal bores  56  in their symmetrical axis, through which a threaded bolt can be inserted and screwed into the threaded bore  54 . The knife a plates  50  are, for example, rhombic knife plates which are dimensioned in such a way that they can be inserted into the press fit  50  so as to be aligned and that they close with the outer contour of the cutting block  20 . Moreover, the knife plates  55  can be inserted (FIGS. 10,  11 ) which have a cutting contour projecting beyond the surfaces  21   b ,  24 , for example, a staggered cutting contour. Contours of this type are used if finer granulated material is to be obtained. 
     The outwardly directed points of the rhombic cutting plates or edges  23  are spaced from a groove bottom of a knife seat groove at the same distance radially as an upper point  3  of a cutting block  1 , so that the radially outermost point of all embodiments is situated on an outer radial knife flight circle. Thus, the cutting edge length in knives with two cutting points is just as large as the length of the cutting edges of a knife with a large cutting point, whereby the depth of engagement into the counter knife plates in a knife with two points is only half as much. 
     The use of the knives is described in the following. 
     Especially for cutting large-sized materials, cutting blocks  1  having a rhombic cross section are inserted into a groove of the knife (not shown), so that the edges  3  or the cutting edges point radially outward. The counter cutting edges of the cutting bar or the scraping bar have a corresponding cutting contour. 
     If smaller material is to be cut with a cutting shaft thus equipped or a cutting machine of this type or if finer granulated material is to be obtained, a cutting block  20  with opposite V-shaped grooves  21 ,  22  is screwed into the V-shaped knife seat groove instead of a cutting block  1 , whereby the groove  22  pointing downward to the cutting shaft is closed with an insert  35 . The surfaces  27  of the cutting block and  39  of the insert  35  provide a common V-shaped surface which is fitted into the V-shaped knife seat groove in a form-locking manner. A screw bolt is bolted into a bore in the knife seat groove through holes  30 ,  41 . The cutting contour of the counter cutting bar or scraping bar is then adjusted to the new cutting contour having two small cutting points per cutting block, so that the cutting contours correspond and mesh. The engagement depth of the cutting contours of the cutting blocks  20  and the corresponding cutting bar is lower in a design of this type, in particular half as much as with an embodiment having cutting blocks  1 . The granulated material is accordingly finer. If the cutting edges  23  are worn, the cutting block  20  can be removed from the knife seat after the screw has been removed, whereby the invert  35  remains in the knife seat. The cutting block  20  is turned horizontally by 180° and placed with the groove  21  on the insert, so that the edges  26  are the outermost projecting cutting edges. If these are worn, the block can then be turned vertically by 180°. 
     When using cutting blocks  20  with only one groove  21  and rhombic press fits  50  for the cutting, knife plates, the cutting block is fitted in a form-locking manner into a V-shaped knife seat groove with the surfaces  27  and edge  26  and bolted with the cutting shaft with a screw bolt which is inserted through the bore  30 . Rhombic knife plates  55  (FIG. 9) may be inserted into the knife plate press fits  50 . In this embodiment, the cutting contour of the counter cutting bar corresponds to the second embodiment of a cutting block. If even finer granulated material is to be obtained, cutting knife plates  53  having a cutting contour (FIGS. 13,  14 ) which may, e.g. be staggered and projecting beyond the surfaces  21   b ,  24 , may be used, whereby the cutting contour of the counter cutting bars must be adjusted to this finer cutting contour i.e. the knife plates of the counter cutting bars must be replaced by the knife plates corresponding to the knife plates  50 . 
     The advantage of the cutting tools of the invention is that a knife shaft or cutting shaft can be provided with another cutting contour, adjusted to the material to be cut, in a very short time, so that many materials that are completely different may be cut with a single cutting machine. For this purpose,both the cutting contour can be altered and the type of knife block or the cutting knife plates used may also be changed, for example, cutting tools can be used which are made from different materials, adjusted to the material to be cut. Of course, conventional cutting tools or cutting tools of conventional size can be exchanged for cutting tools configured according to the invention and having a corresponding smaller cutting contour, so that the cutting contour is refined. Of course, the cutting contour of the counter cutting element must correspond to the respective cutting contour, in particular, ensure a meshed engagement. 
     A cover element  212  (FIGS. 22 to  14 ) according to the invention is, for example, solid, e.g. made of metal or ceramics and has walls  213  corresponding to the diagonal walls  8  of the knife seat and meeting 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 bottom of the groove  206 . The remaining surfaces of the cover element  212  correspond to the groove, so that the cover element  212  is made so as to be in the shape of a semicircular cone in the area of a surface  202   c  of the shaft  201  or the groove end  205   a  and tapers from the semicircular conically shaped and  213  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 a bore  210  in the groove bottom  206 , the cover element  212  has a bore  218  placed in the cover element from the surface  216   b  at right angles 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 in inserted through the bore  218  or hole  18  are screwed into the threaded bore  210  of the shaft in order to rigidly fix the cover element  212  in the groove. The covet element  212  does not have to be a solid, it can also be made as a hollow profile. 
     The angle and size of the surfaces  216  depend on the number of edges and on the diameter of the polygonal shaft. With a smaller diameter the angle of the surfaces to one another becomes greater and reversed. 
     The use of the cover element described in the following. 
     In order to apply an increased force on the individual cutting tools at the same driving power and the same speed of the cutting shaft, in particular with larger cutting tools and greater engagement depth, it may be necessary to reduce the number of knives. Usually several cutting tools, e.g. up to eight, are found on a cutting tool flight circle 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  5  and winding about the shaft without being cut. Moreover, it is advantageous that the cover element may 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 when using cutting tools of various sizes or different cutting geometries. As a result of the form of the cover element corresponding to the groove and the fastening of the caviar element with a screw connection equivalent to the knives, the refitting can be easily and especially quickly accomplished. 
     A cutting tool ( 201 ) according to the invention (FIGS. 15 to  18 ) is, in a top view, an essentially rhombic plate having two lower straight edges  202 , which extent divergently from a common edge  203 . From the lower edges  202 , upper edges  204  extent toward one another and meet at a common upper edge or point  205 . The edges  202  and  204  meet at common side points or edges  206  of the rhombic cutting tool  201 . 
     The upper edges or surfaces  204  of the plate-shaped cutting tool  201  are stepped or a staggered with teeth  208  projecting outward. The edges or surfaces  204  first extend at an angle of about 90° from the points  206  to the edges  202  and then each form two teeth  208 , the one tooth side being directed vertically and the other tooth side horizontally. A single tooth  208  in the shape of a peaked roof is formed in the area of the upper point  205  of the rhombus. 
     A bore  210  is placed at the centre in the cutting tool  201 , in the intersection of the lines between the side points  206  and the lower points  203  and the upper points  205 , said bore tapering conically to the thickness centre of the plate and then expanding conically again from the centre of thickness. The conical bore sections  210   a ,  210   b  serve to accommodate a screw bolt having a countersunk head. 
     The rhombic plate or cutting tool  201  is screwed at the front and an a tool carrier  214  having a rhombic cross section. The rhombic cutting tool carrier  214  has a lower longitudinal edge  215  and an upper longitudinal edge  216  as well as two side longitudinal edges  217 . In a front end  218  of the knife carrier  214 , an axial bore  219  is placed in the centre which aligns with the bore  210  when the plate  201  is placed on the cutting knife carrier. The lower edge  215 , the outer edges  217  and the side surfaces  220  of the knife carrier  214  between the edges  215  and  217  close, with the lower edge  23 , the outer points or edges  206  when the lower edges  203  and the edges  202  of the serrated knife  201  situated between the edges  203 ,  206 . In the area of the upper surfaces  220  of the knife carrier  214 , the teeth  208  of the cutting tool or serrated knife  201  protrude beyond the surfaces  220  and edges  216 . 
     In a further embodiment of the cutting tool (FIGS. 19 to  22 ), a first step or a first tooth  208  with a vertical side  208   a  adjoins the side edges or points  206  of the cutting tool  201 . A horizontal side  208   b  extends from the side  108   a  to inside the rhombus until it meets an imaginary line which extends from the outer points  206  at a 90° angle to the edges  202 . Three further teeth adjoin the toothed edges along this imaginary line continuing upward, whereby the two uppermost tooth of the two upper edges  204  meet and form a plate or flat edges  208   c  in the uppermost area. When screwed onto a knife carrier  214 , the surface or edge  208   c  closes with the uppermost edge  216  of the knife carrier having a rhombic cross section, so that the teeth only laterally project beyond the surfaces  220 . 
     The cutting tool carriers  214  have a vertical bore  225  from edge  216  to edge  214  which extends from the edge  216  at right angles to a longitudinal axis  224  of the carrier. The bore extends with a further bore area  225   a  from edge  216  into the carrier  214  and becomes narrower above the transverse axis with a step  226  to a narrower bore area  225 , which expands again to further bore area  225   a  in the further course to the edge, whereby this bore  225  is mirror symmetric with respect to the narrowing and expansion to the transverse axis. The bore  225  serves to accommodate a screw bolt (not shown) with which a knife carrier  214  is arranged in a cutting tool recess or a cutting tool seat. 
     The cutting tools  201  can be used as rotating knives, so that, once the edges  204  in the area of a front end are worn, the knife in unscrewed from the knife holder  217 , turn and can be fastened to the knife carrier again. 
     The advantage of the cutting tool of the invention is that defined, in particular, small granulated material can be obtained with the cutting tool in the form of a serrated knife at the same driving power and same speed of a shaft. In addition, the knives are simple to manufacture and can also be screwed onto existing knife carriers. 
     The knives do not have to be used as rhombic plates. It is also possible to use one-piece longitudinal knife blocks having a rhombic cross section with toothed, upward pointing surfaces. 
     The cutting contours of the counter cutting or scraping bars must, of course, have a counter cutting edge corresponding to the cutting contour of the cutting tools.