Abstract:
The present invention relates to a shear bar, in particular, for a wood chipper for producing wood chips, having at least one cutting edge formed from a hard material and one support surface leading to the cutting edge, wherein the cutting edge is formed from a plurality of hard material elements arranged side by side along the cutting edge on at least one basic body. A strength-optimized realization with a long service life and a simple assembly is achieved as a result of the hard material elements being fastened on the at least one basic body by means of an adhesive bond.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of International Application No. PCT/EP2015/063351 filed Jun. 15, 2015, which designated the United States, and claims the benefit under 35 USC §119(a)-(d) of German Application No. 10 2014 108 607.4 filed Jun. 18, 2014, the entireties of which are incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to a shear bar, in particular, for a wood chipper for producing wood chips, having at least one cutting edge formed from a hard material and one support surface leading to the cutting edge, wherein the cutting edge is formed from one continuous hard material element or from a plurality of hard material elements arranged side by side along the cutting edge on at least one basic body. 
       BACKGROUND OF THE INVENTION 
       [0003]    For shredding bio products, for example, from the agricultural or forestry sectors, but also for waste shredding, shredding units are used where rotating cutters are moved past a fixed shear bar and the product is shredded between the rotating cutters and the shear bar. The material to be shredded is fed to the shredding unit by means of a feeder device. 
         [0004]    The cutters and the shear bars are exposed to a high level of wear, it being possible to increase the service life significantly by using hard metal. In order to achieve a long service life, DE 2014043009164500 provides a shear bar, in particular, to produce wood chips, which comprises at least one cutting edge formed from a hard material. The hard material elements are joined to the basic body as a result of hard soldering. In order to ensure a stress-optimized design for the benefit of a lower breakage risk, the cutting edge is formed from a plurality of hard material elements arranged side by side along the cutting edge on at least one basic body. The object underlying the present invention is, consequently, to provide a strength-optimized shear bar which has a long service life and is simple to assemble. 
       SUMMARY OF THE INVENTION 
       [0005]    The object of the present invention is achieved as a result of the hard material elements being fastened to the at least one basic body by means of an adhesive bond. 
         [0006]    By means of the adhesive bond, the hard material elements can be fastened to the basic body simply and without heat input in a positive locking manner. In this way, an approximately uniform stress distribution can be achieved without thermal distortion which can occur, in particular, in the case of hard soldering during the cooling operation on account of the different thermal expansion coefficients of the different materials. Thus, expenditure on post-treatment is prevented or at least minimized. In addition, a possible structural change inside the metal as a result of heating the basic body, which is produced, in particular, from a hard material, is inhibited. Consequently, a hardened and tempered steel can also be used for the basic body, the strength characteristics of which are not impaired by the joining process. Consequently, a possible decrease in strength as a result of heat input is prevented, which can reduce a breakage risk on the cutting edges. Adhesive bonds are distinguished by short production times and low production costs along with the above advantages. 
         [0007]    An improved hold of the hard material elements on the basic body is achieved as a result of the basic body comprising at least one recess which extends in its longitudinal direction for admitting the hard material elements. In this case, the hard material elements are preferably received in the recess by means of an end portion. The recess facilitates, in particular, the production as the hard material elements can already be aligned therein in a simple manner in the correct position and have taken hold before the adhesive bond is hardened. In addition, as a result of the hard material elements being admitted at least in part into the basic body, a relatively large layer thickness of hard metal can be realized without an excessively large protrusion of material being produced in relation to the basic body. The durability of the cutting edge, which is exposed to a large amount of wear, is able to be extended in this way. 
         [0008]    The recess is preferably developed in such a manner that it comprises at least one counter surface which connects to at least one contact surface of the respective hard material element through the intermediary of the adhesive bond. Consequently, the counter surface and the contact surface form a defined adhesive surface which, as regards its development, can be optimized to the stress. Advantageous in this connection are adhesive surfaces that have as large an area as possible and are aligned in such a manner that they are predominantly subjected to shear when the load is as intended. When the shear bar is used as provided, the force acts on the hard material element chiefly perpendicular to a top surface of the basic body. In a preferred orientation, the adhesive surface consequently runs perpendicular or substantially perpendicular to the top surface. 
         [0009]    It is advantageous for a high level of strength of the adhesive bond when an adhesive gap, which is situated between the at least one counter surface and the respective contact surface, comprises a gap thickness which is defined by at least one spacer. Thus, the formation of regions with different adhesive film thicknesses is avoided during the adhesive operation. These would cause different, undefined strengths. The named development variant allows for the fixing of a defined adhesive film thickness which is decisive to a defined uniform strength of the adhesive bond. In a preferred manner, the thickness d of the adhesive gap is kept as small as possible, for example 0.05 mm&lt;d &lt;0.5 mm. 
         [0010]    The fastening of the respective hard material element to the basic body is facilitated as a result of the spacer being connected in one piece to the hard material element and/or to the basic body. The at least one spacer, in this case, can be realized, for example, in the manner of a pin or a nub. Thus, it is already pre-positioned and does not have to be separately aligned when fastening the hard material element to the basic body. In addition, there is less expenditure on parts. 
         [0011]    The recess preferably comprises an attachment portion at its long-sided ends. This facilitates, on the one hand, the admitting of even the hard material elements located on the outer ends of the cutting edge, as a certain free play is provided in this way. On the other hand, it simplifies the production of the recess. 
         [0012]    A preferred development variant of the shear bar according to the present invention provides that the recess is delimited on opposite sides by means of counter surfaces, wherein the counter surfaces extend in the longitudinal direction of the basic body. In addition, it is provided in this case that the hard material element is bonded with at least one counter surface by way of the end portion, which is inserted into the recess and is realized as a plug-in attachment. The recess thus secures the hard material element additionally against tipping out forward. This simplifies, in particular, the assembly as the respective hard material element can be inserted into the recess first of all in a self-holding manner by means of its end portion that is realized as a plug-in attachment, until the adhesive bond has hardened. 
         [0013]    It has an optimizing effect on costs when the cutting edge is formed by head portions of the hard material elements and when the end portions are set back in relation to the cutting edge transversely with respect to the longitudinal direction of the basic body. A free surface offset to the cutting edge is formed in this manner. The free surface can be formed, for example, by the hard material element itself and/or by the basic body. A possible variant in this case can be in such a manner that allows for space for an edge of the basic body which can be realized simply by the lateral surface of the basic body being lengthened upward in part. The edge can then also comprise a certain wall thickness which almost corresponds to the rear offset of the end portions. In addition, the cross section of the respective hard material element is reduced in the region of the end portion, and as a result its overall volume, which leads to a saving in the material of the cost-intensive hard material. This can occur without impairing the service life of the shear bar, as the material saving is realized on the plug-in attachment which is subjected to less wear, not on the cutting edge which is subjected to heavier wear. 
         [0014]    It is expediently provided according to the present invention that the head portions are supported in relation to the basic body indirectly or directly in a region beneath the cutting edge. This produces additional stability as, in this way, force components acting from above on the respective head portion can be compensated by the basic body at least in part, also, in particular, in a positive locking manner. The end portion and/or the at least one spacer can act in this case, for example, in an indirect manner. In addition, the supporting serves for simplified assembly as it is able to hold the hard material element already in position without the adhesive bond when it is admitted into the recess. 
         [0015]    For favorable force distribution and secure mounting in the recess, the effect is particularly advantageous when the hard material elements are supported in relation to the basic body by means of a positive locking connection. This can be realized, for example, in the form of a counter surface which extends parallel to a top surface and along the basic body. Such a surface progression is advantageous as it is able to absorb in an effective manner the forces introduced in the load state for the most part from the direction of the top surface. 
         [0016]    The shear bar according to the present invention can be formed in a wear-optimized manner by at least one lateral surface of the basic body being set back in relation to a lateral cutting edge portion of the cutting edge which connects indirectly or directly to the cutting edge. Thus, the basic body, which as a rule is produced from less hard material, is protected from excessive wear by the protruding cutting edge. 
         [0017]    A saving in cost-intensive hard material whilst retaining the high level of wear resistance is obtained as a result of the contact surface comprising a shoulder which is set back in relation to the cutting edge and extends in the longitudinal direction of the basic body. The shoulder is in such a manner that the contact surface is divided into a region which protrudes somewhat beyond the shoulder and which includes, in particular, the cutting edge, and a region which is set back in relation to the region, by means of which product to be shredded is fed to the cutting edge. The development makes it possible for the required material strength to be applied in the heavily compressively loaded region of the cutting edge. In contrast, the set-back region, which is generally speaking subjected to expansion, can be provided with a thinner hard material application. This serves as a more flexible loading possibility and saves on material. 
         [0018]    The top surface of the basic body is preferably covered by a cover plate which is fastened on the top surface of the basic body, in particular, by means of a materially bonded connection, for example, a soldered joint or an adhesive bond. The cover plate ensures, on the one hand, a uniform support surface and protects, on the other hand, the basic body against wear. It is preferably realized from a harder material than the basic body. By the cover plate being fastened to the basic body by means of a materially bonded connection, other fastening means, such as, for example, bores which can weaken the basic body, are not required. Adhesive bonds are preferred compared to soldered joints as described above. Depending on the development of the basic body, soldered joints can also be used in the region of the cover plates without weakening the basic body in a significant manner. 
         [0019]    When the hard material elements comprise cover surfaces for the at least partial covering of a top surface of the basic body, this reduces expenditure on parts as there is no need for separate cover plates. Moreover, the cover surfaces can additionally serve as adhesive surfaces, which can additionally stabilize the bond between the corresponding hard material element and the basic body. 
         [0020]    In a further development of the present invention, it is provided that at least one surface of the hard material element and/or at least one corresponding surface on the basic body is treated mechanically, thermally and/or chemically. The surfaces obtain, for example, by means of etching, a roughened surface structure which promotes the arranging of the corresponding surfaces one on top of another by means of an adhesive bond. Mechanical or thermal roughening would also be conceivable here, for example, as a result of a blasting procedure. 
         [0021]    A further advantageous development of the present invention provides that the shear bar comprises at least one recess and/or at least one break-through, wherein the hard material element covers, at least in part, edge regions of the at least one recess and/or of the at least one break-through. An advantageous application is provided for sieve surfaces which are used for shredding and/or sieving solid ground material. In this case, the ground material, on account of its own weight or as a result of corresponding acceleration, impacts on the edges of the recesses or break-throughs, is shredded and sieved. For protection against wear, the edge regions of the recesses or of the break-throughs are covered with hard metal elements which are arranged side by side. 
         [0022]    Furthermore, it is provided in a further advantageous development of the present invention that the shear bar is arrangeable in a static or dynamic manner with reference to the cutting edge of a further cutting element or that the cutting edge of the further cutting element is arrangeable in a static or dynamic manner with reference to the shear bar. For example, the development forms are used in drum shredders, the drum housing being lined with a plurality of strip-shaped shear bars, past which the further cutting element scrapes and shreds the material. It is provided in this case that the drum housing or the further cutting element or the housing and the cutting element carry out a rotational movement. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0023]    The present invention is explained in more detail below by way of exemplary embodiments with reference to the drawings, in which: 
           [0024]      FIG. 1  shows a perspective view of a shear bar with two cutting edges; 
           [0025]      FIG. 2 a    shows the shear bar according to  FIG. 1  along the cutting sequence marked by way of II-II in  FIG. 1 ; 
           [0026]      FIG. 2 b    shows a detail according to  FIG. 2 a    with a hard material element of the shear bar; 
           [0027]      FIG. 3  shows a detail according to  FIG. 1  with the attachment of a cutting edge; 
           [0028]      FIG. 4 a    shows a sectional representation of a shear bar with hard material elements and a cover plate; 
           [0029]      FIG. 4 b    shows a detail according to  FIG. 4 a    with a hard material element of the shear bar; 
           [0030]      FIG. 5 a    shows a sectional representation of a shear bar with hard material elements and a cover plate; 
           [0031]      FIG. 5 b    shows a detail according to  FIG. 5 a    with a hard material element of the shear bar; 
           [0032]      FIG. 6  shows a detail of the shear bar realized according to  FIG. 5 a    with the attachment of a cutting edge; 
           [0033]      FIG. 7 a    shows a sectional representation of a shear bar with hard material elements and a cover plate; 
           [0034]      FIG. 7 b    shows a detail according to  FIG. 7 a    with a hard material element of the shear bar; and 
           [0035]      FIG. 8  shows a detail of the shear bar realized according to  FIG. 7 a    with the attachment of a cutting edge. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0036]      FIG. 1  shows a shear bar  1  with an elongated basic body  10 , which comprises a rectangular cross section in its basic form. It is produced, for example, from a hardened and tempered steel. On its longitudinal ends, which close off in each case by way of end surfaces  14 , mounting surfaces  16  are provided with one bore  11  each and two threaded receiving means  12  for receiving fastening means, preferably screws. The mounting surfaces  16  are cut back over a radius  13  in relation to the basic form of the basic body  10 , and thus allow secure introduction into a mounting which is not shown here. As an alternative to this, the shear bar  1  can also comprise several basic bodies  10  which can be additionally mounted on a carrier. 
         [0037]    The basic body  10  comprises two cutting edges  31  which extend in the longitudinal direction. These are formed by a plurality of hard material elements  30  admitted into two recesses  17 . As an alternative to this, one continuous hard material element, in particular, a continuous hard material element that can be produced in a simple and dimensionally accurate manner, can also be used. This can be realized in particular as an extruded section. Several cover plates  20  are arranged for instance in the axial region of the cutting edges  31  on a top surface  18  of the basic body  10  in such a manner that they form a contiguous part of a support surface  22 . In this case, the abutting edges between the cover plates  20  are placed axially offset with respect to the abutting edges between the individual hard material elements  30  in order to prevent erosions. The part of the support surface  22  formed by the cover plates  20  merges toward the outside surfaces of the top surface  18  into a part formed by the cutting edges  34  which at the same time provides the top cutting edge portions  34  of the cutting edges  31 . The top cutting edge portions  34  are supplemented in each case by a lateral cutting edge portion  33  of the respective cutting edge  31  which extends thereto at an angle preferably within the range of between ≧60° and ≦90°. A lateral surface  15  of the basic body  10  connects in each case to the lateral cutting edge portions. 
         [0038]    Details regarding the hard material elements  30  and the cover plates  20  as well as their arrangement on the basic body  10  can be seen from  FIG. 2 a  and 2 b   . The cover plate  20  rests by way of a bottom surface  23  on the top surface  18  of the basic body  10 . It is fastened by means of an adhesive bond  19  or a soldered joint. As can be seen more precisely in  FIG. 2 b   , the hard material element  30  comprises an almost rectangular cross section with a chamfer  32 , the outside surfaces forming the lateral or the top cutting edge portion  33  or  34 . The oppositely situated surfaces in each case form a first or a second contact surface  301  or  302 , by way of which the hard material element  30  is admitted into the recess  17 . The recess  17  comprises a counter cross section corresponding to the hard material element  30  with a first and second counter surface  171  and  172  which extend in their alignments preferably parallel to the lateral surface  15  or top surface  18  of the basic body, as well as a longitudinal radius  173 . The longitudinal radius  173  facilitates, together with the chamfer  32 , the correct admission of the hard material element  30  in the recess  17 . 
         [0039]    With the cutting edges  31  in the mounted state shown in  FIG. 1 , the contact surfaces  301 ,  302  are joined in each case to the first or the second counter surface  171  or  172  of the recesses  17  as a result of an adhesive bond  19 . It would also be conceivable for just one surface pair, preferably the first contact and counter surface  301  and  171 , to be joined by means of an adhesive bond  19 . As a result of the just two contact and counter surfaces arranged at right angles to one another, the realization shown provides a variant that is particularly simple to produce. 
         [0040]    As shown in  FIG. 2 b   , the hard material element  30  is arranged in relation to the basic body  10  in such a manner that the lateral cutting edge portion  33  of the hard material element  30  is offset forward in relation to the lateral surface  15  of the basic body  10  by a projection V. In the reverse manner, therefore, the lateral surface  15  is set back in relation to the cutting edge, as a result of which the lateral surface  15  is protected from abrasion. The cover plate  20  comprises a shoulder  36  which extends in the longitudinal direction of the basic body close to the hard material element  30 . 
         [0041]      FIG. 3  shows an attachment portion  174  of the recess  17  which is realized with a rounding. The hard material elements  30  which close off the cutting edge  31  toward the outside are also easily able to be inserted into the recess  17  by means of the attachment portion. The geometry of the closing hard material elements  30  can be adapted to the rounding and, for example, fill out the same. Precise positioning can then be performed and the length of the cutting edge can be enlarged. The rounding of the attachment portion  174  additionally provides stress reduction and consequently a diminished risk of breaking. 
         [0042]      FIG. 4 a  and 4 b    show an alternative development variant of the hard material elements  30  and correspondingly of the recess  17 . In this connection, the longitudinally extending recess  17  is inserted at an angle into the basic body as a type of groove. This type of recess  17  creates an edge  177  which comprises a third counter surface  175  which extends parallel to the first counter surface  171  located opposite it. The first, second and a third contact surface  301 ,  302 ,  303  of the hard material element  30  delimit an end portion  312 , which is realized as a type of plug-in attachment. Consequently, the hard material element  30  can already be inserted in a positive locking manner into the recess  17  without an adhesive bond  19 . The three contact surfaces  301 ,  302 ,  303  of the hard material element  30  are joined to the basic body  10  by means of the adhesive bond  19  by way of the three counter surfaces  171 ,  172 ,  175 , which causes a high degree of stability on account of an enlarged adhesive surface. Just as the cover plate  20 , the hard material element  30  can comprise spacers  40  which ensure a defined thickness of the adhesive gap  41 . It is also conceivable for the contact surfaces  301 ,  303  to be at an angle to one another such that a conical end portion  312  is produced. This is then simple to mount in the recess  17 , which is also adapted and realized in a conical manner. 
         [0043]    Above the end portion  312  of the hard material element  30  is situated the head portion  311  thereof which comprises the lateral and top cutting edge portions  33 ,  34  which are preferably arranged at right angles to one another. A good cutting performance with at the same time a high level of stability is produced when the enclosed angle between the cutting edge portions  33 ,  34  is chosen to be within the range of ≧60° and ≦90°. The head portion  311  projects out of the recess  17  in such a manner that it forms the cutting edge  31 . In this case, the lateral surface  15 , in turn, is set back in relation to the lateral cutting edge portion  33  by V such that the lateral surface is protected from wear. The cover plate  20  is set back in relation to the top cutting edge portion  34  for forming a shoulder  36 . 
         [0044]    As regards its stability and simplified assembly, the realization variant shown in  FIGS. 4 a  and 4 b    provides a more favorable but also complex embodiment compared to the first variant. In this case, it is nevertheless relatively simple to produce as a result of the recess  17  which is formed as a type of groove. Stress optimization or improved wear characteristics could be achieved in this variant, for example, by chamfering or rounding of the edges. In particular, the transition between the counter surfaces  171 ,  172  and/or  175  could be formed by means of radii or chamfers and/or the top closure of the edge  177  could be rounded or chamfered. 
         [0045]      FIGS. 5 a  and 5 b    show a further realization variant of a shear bar according to the present invention. In this connection, the first or the second counter surface  171  or  172  of the recess  17  preferably run at least approximately parallel to the lateral surface  15  or to the top surface  18  of the basic body  10 . In addition, the recess  17  is delimited by an outwardly extending edge  177  which comprises the third counter surface  175 . The third counter surface  175  preferably runs parallel or approximately parallel to the first counter surface  171  which is arranged opposite it. A fourth counter surface  176  connects to the third counter surface  175  of the recess  17 , by means of which fourth counter surface the edge  177  slants upward. The hard material element  30  comprises four corresponding contact surfaces  301 ,  302 ,  303  and  304  on its end portion  312  which is realized correspondingly as a plug-in attachment. In this case, the fourth contact surface  304  is realized as an inclination  35  such that the third contact surface  303  is set back in relation to the lateral cutting edge attachment  33 . In this way, space is created for the edge  177  which, in the development of this type, can simply be pulled upward proceeding from the lateral surface  15 . At the same time, the lateral cutting edge portion  33  is offset forward in relation to the edge  177 , which has a favorable effect on the wear resistance as here, a large wear volume is provided in the head portion  311 . In addition, as a result of the inclination  35  the end portion  312  has a smaller cross section than if it were to extend at the same height as the head portion  311 . 
         [0046]    In the example shown in  FIGS. 5 a  and 5 b   , the end portion  312  of the second contact surface  302  rests in a positive locking manner on the second counter surface  172 . The adhesive bond  19  exists between the first, third and fourth contact and counter surfaces  171  and  301 ,  175  and  303  as well as  176  and  304 , which is not directly recognizable in the figures. The cover plate  20  is set back in relation to the top cutting edge portion  34  to form a shoulder  36 .  FIG. 6  shows a further variant of an attachment portion  174 , with a rounding  178 . 
         [0047]      FIGS. 7 a  and 7 b    show a development form according to the present invention, in which the hard material elements  30  comprise cover surfaces  37  which replace the cover plates  20  as regards their function. The transition from the hard material element  30  into the cover surface  37  is realized in a stress-optimized manner by means of a round transition  179 . The attachment of the round transition  179  in the region of the attachment portion  174  is shown in  FIG. 8 . 
         [0048]    As shown in  FIG. 7 a   , the cover surfaces  37  of two oppositely situated hard material elements  30  contact one another in the center of the top surface  18  of the basic body  10  and consequently, in conjunction with the top cutting edge portion  34 , cover the full width of the top surface  18 . The bottom surface  23  of the cover surface  37  is additionally utilized, in this case, as an adhesive surface. It would also be conceivable for it simply to rest thereon and the adhesive bond to be realized in the recess  17  by means of at least one of the contact surfaces  301 ,  302 . 
         [0049]    The described embodiments according to the present invention clarify some of the diverse development possibilities for an adhesive bond of the shear bar  1 . It is thus able to be realized in a strength-optimized manner without additional bores in the region of the cutting edge.