Patent Publication Number: US-2021161073-A1

Title: Cracker roller disc

Description:
BACKGROUND 
     Field 
     This invention relates to a cracker roller assembly on a forage harvester or similar agricultural harvesting machine and, more specifically, to discs for use in such an assembly, to a method for the manufacture of such discs, and to discs produced by the method. 
     Description of Related Art 
     Forage harvesters are used to harvest different kinds of crops which may require different harvesting processes. If, for example, grass is harvested the forage harvester cuts the grass from the field, compresses the grass in the compression rollers before chopping the harvested material into smaller parts in a chopper drum. The chopped grass is then discharged by a blower via a spout into an accompanying trailer. If, for example, a kernel crop such as maize, is harvested the harvesting process requires an additional step to crack the closed skin of the kernels, therefore, a cracker unit is provided between the chopper drum and the blower to crush each kernel. 
     Cracker units typically comprise two longitudinal cracker rollers which are arranged with a roller gap (longitudinal space) between them through which harvested crop is fed. As shown in International Patent Application WO 2012/010396 (commonly assigned with the present application) the cracker rollers may be formed by an arrangement of multiple cracker roller discs mounted on a common shaft. Another example is the disc cracker offered by Maschinenfabrik Bernard Krone GmbH (illustrated at http://landmaschinen.krone.de/index.php?id=2548&amp;L=1). Such a multi-disc arrangement has a number of advantages compared to a unitary roller in terms of manufacturing and maintenance costs. For example, foreign object damage occasioned by a solid object passing through the roller gap may be remedied by the replacement of just a few of the discs rather than a complete, and much more expensive, roller. 
     Each disc typically has an arrangement of radial cutting surfaces across each face to assist in breaking up the material. With a large number (between 20 and 40) of discs in a typical cracker roller assembly, an efficient method of manufacture is clearly desirable. One current technique involves casting the individual discs followed by individual dressing of the cutting surfaces. An alternative technique comprises lathe turning of a blank of material to generate a disc shape and then milling the surface of the blank to cut in the individual cutting edges. Manufacture of cracker roller discs is discussed further in commonly-assigned European patent EP-B-2666348. 
     An object of the present invention is to provide an improved cracker roller disc. 
     SUMMARY 
     According to a first aspect of the present invention there is provided a cracker roller disc, having an axial bore through the centre, a first portion radially outward of the centre of substantially constant thickness, a second portion radially outward of the first portion which second portion tapers towards the periphery, and further comprising a plurality of conical machined surfaces forming radially extending edges on opposed faces of the disc; 
     characterised in that the edges are interrupted by grooves extending substantially perpendicular to said edges. 
     The grooves, which may be in the form of a spiral, a circle, or a series of concentric circles, extend the effective length of each edge and improve performance of the disc. 
     In further aspects, the present invention provides a method of manufacturing the cracker roller disc, and cracker roller comprising a plurality of the discs axially aligned and mounted on a common shaft. 
     Preferred features of the invention are set out in the dependent claims attached hereto and will be described below with reference to exemplary embodiments of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will now be described, by way of example only, with reference to the following drawings in which: 
         FIG. 1  is a schematic view showing functional components of a forage harvester; 
         FIGS. 2 and 3  show respectively end view and perspective view of the cracker unit of  FIG. 1 ; 
         FIG. 4  is a flow chart representation of a method according to the invention; 
         FIG. 5  is a perspective view of a forged disc blank; 
         FIG. 6  is a perspective view of a machined disc; 
         FIGS. 7 and 8  show respectively plan and sectional views of a forged disc blank; 
         FIGS. 9 and 10  show sectional views through the disc blank at different stages in the manufacturing process; 
         FIGS. 11, and 12  show respectively plan and half-sectional views of a finished cracker roller disc; 
         FIG. 13  is a sectional view through a part of the disc of  FIG. 11 ; 
         FIG. 14  is a perspective view of a machined disc; 
         FIG. 15 a , 15 b    are details of views of  FIG. 12 ; 
         FIG. 16  is a plan view of a further embodiment of finished cracker roller disc; and 
         FIG. 17  is a half-sectional views of a forged roller disc. 
     
    
    
     DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS 
       FIG. 1  shows a forage harvester  1  provided with a front attachment  2  which contains cutting equipment for cutting a crop. The cut crop is fed through a series of compression rolls  3   a  in a compression roller housing  3  to a chopper drum  4  where the crop is chopped into smaller pieces. The chopped crop passes through duct  5  and is fed through the cracker unit  6  where the crop is further crushed and threshed. The harvested crop is then blown upwards along duct  5  by accelerator  8  and exits through spout  9 . In  FIG. 1  the cracker unit  6  is shown in an operational position: in a non-operational position, the cracker unit  6  is pivoted to the side of the duct  5  and therefore harvested crop by-passes the cracker roller assembly  7  as it moves through duct  5 . 
       FIGS. 2 and 3  show a cracker roller assembly  7 . The cracker roller assembly  7  comprises two frame parts  10  and  11  (not shown in  FIG. 2 ). Two cracker rollers  12  and  13 , each formed from seventeen discs  30  mounted on respective roller shafts  12   a ,  13   a , are mounted to a respective frame part  10 ,  11 . The cracker roller discs  30  are provided with teeth for cracking/crushing the harvested crop which can be seen more clearly in  FIGS. 6 and 11 . The cracker rollers  12 ,  13  are mounted parallel to each other and are rotatable about their longitudinal axes. A longitudinal space between the rollers, the roller gap, allows the cut crop to pass between the rollers. 
     As will be understood, the dimensions of each of the discs  30 , and the number of discs per roller, may be varied. One factor affecting potential variation is the characteristics of the material to be harvested. 
     The method of manufacture of the cracker roller discs  30  may be considered as a three-stage process, as represented by  FIG. 4 . The first stage  40  comprises forming a disc blank, the second stage  41  comprises machining of ridges on the surfaces of that blank, and the third stage  42  comprises machining of peripheral features to create further cutting edges. Each of these steps is described in more detail below. 
       FIGS. 5 and 6  respectively show perspective views of the disc blank  29  and machined disc  30 .  FIG. 7  shows the disc blank  29  in plan view, and  FIG. 8  is a sectional view through the disc blank taken on line AA of  FIG. 7 . The blank has an axial bore  50  through the centre, a first portion  52  radially outward of the centre of substantially constant thickness, and a second portion  54  radially outward of the first portion which second portion tapers towards the periphery of the disc blank providing each of the second portions with a frusto-conical profile. A suitable taper angle is 21.8 degrees, although variation is possible as mentioned above. 
     The disc blank  29  is a steel body which may be machined from a plain block of material but is preferably formed by forging. C45 steel is a suitable material, although other forgeable steels may be used instead. As part of the blank forming step, the forging process creates a plurality of upstanding ridges  56  extending radially outward across the second portion  54  on each face of the disc. 
       FIGS. 9 and 10  are sectional views through the disc blank and the machined disc taken on line BB in  FIG. 8 . From  FIG. 9  it can be seen that the radial ridges  56  have a generally rounded profile in their upper (furthest from the disc body) portion. The lands  58 , defined as the portions of disc surface between the ridges  56 , are sloped from one ridge to the next to give a generally sawtooth profile. The disc blank  29  shown has 48 ridges of substantially constant width. It will be recognised that greater or fewer ridges may be provided, with the ridge height and separation being determined by the need to accommodate grain and other material of the particular crop being handled. 
     As can be seen from  FIG. 9 , the step of forming (first stage  40 ) includes circumferentially aligning each ridge  56  on a first face of the disc blank  29  with a corresponding ridge on the opposing face of the disc blank. Furthermore, the step of forming includes aligning the distal ends of each corresponding pair of ridges  56  with radial projections  60  spaced around the periphery of the disc blank  29 , as can be seen particularly in  FIG. 7 . Adjacent radial projections  60  are connected via a contour  61  which is inclined radially inwards in the direction of crop flow (indicated by arrow CF) to give a generally sawtooth profile in the direction of crop flow. 
     Reverting to  FIG. 4 , the second stage  41  of the process comprises machining each of the opposed faces of the disc blank to remove the top part of each ridge  56  and leave at least one sharp edge  62  providing a cutting edge extending along each ridge 
     Additionally, this stage removes parts of the radial projections  60 . The surface of the second portion  52  and the inner surface of the bore  50  may also be machined in this operation. The section view of  FIG. 10  shows one (upper) face of the disc having been machined to produce machined surfaces  64  and the edges  62 . Preferably the second stage  41  is done by turning on a lathe, but may also be provided by milling in a radial direction. 
       FIG. 11  is a plan view of the machined disc  30 ,  FIG. 12  is a half section through the disc of  FIG. 11  taken on line CC, and  FIG. 13  is a part section through the disc of  FIG. 11  taken on line DD. As best seen in  FIGS. 10 and 11 , the machined surfaces  64  include a conical (frusto-conical) machined surface  640  which extends radially along the ridges  56  and forms the outer contour of second portion  54 . 
     The conical machined surface  640  is further provided with a groove  650  which extends from the conical machined surface  640  towards the symmetry plane E 1 . Groove  650  radially extends along a spiral path (indicated with dotted line  651 ) and is substantially perpendicular to the ridges  56 . 
     In this way, the conical machined surface  640  provides edges  620  which are interrupted by groove  650  to form further edges described with the perspective view in  FIG. 14 . 
     First groove edges  621  are formed by the intersection of the conical machined surface  640  and groove  650  and extend substantially perpendicular to edges  620 . Second groove edges  622  extend at an angle to the edges  620  towards the towards the symmetry plane E 1 . At the grove base third groove edges  623  which are formed substantially perpendicular to edges  620  and fourth groove edges  624  which are substantially parallel and offset to edges  620 . It will be noted that the groove edges  621 ,  623  increase the number of edges by adding edges perpendicular to edges  620  while groove edges  622  and  624  extend the length off the overall edges provides. 
     In the shown embodiment and further indicated with  FIG. 15 a   , second groove edges  622  extend substantially perpendicular to edges  620  to form a rectangular cross section. Alternatively and as best seen in  FIG. 15 b   , second groove edges  622  may be provided in an angle to edges  620  to form a trapezoid cross section. More alternatively, the grove may be provided with a triangular cross section as indicated by dotted line  622 ″. It will be recognised that the geometry of the grooves  650 ,  652   a ,  652   b ,  652   c ,  652   d  (depth, width, height and inclination of edges relative to each other) may vary depending on the need to accommodate grain and other material of the particular crop being handled, e.g. to avoid that crop kernels are trapped in the groove and not released from cracker roller assembly  7  so that crop flow would become blocked. 
     In the shown embodiment of  FIG. 11 , the spiral groove  650  is provided which extends radially outwards in the direction of the crop flow indicted with arrow CF (REM: Please reverse the arrow in  FIG. 11 ) in  FIG. 11  to enable that crop trapped in groove  650  is pushed outwards. Alternatively and shown in  FIG. 16 , concentric grooves  652   a ,  652   b ,  652   c ,  652   d  may be provided, the path indicated with dotted line  653   a  to  653   d  concentric to the axis of rotation of disc  30  indicated with Axis A 1 . 
     In the shown embodiment of  FIGS. 7 and 8 , the forged ridges  56  are radially extending at a constant height relative to the lands  58 . Alternatively, as shown in  FIG. 17 , the ridges  56  may be provided with indentations  57  which match with the path of the grooves  650 ,  652   a ,  652   b ,  652   c ,  652   d  to be machined subsequently (indicated with dotted line  655 ) to reduce the material to be machined. 
     Comparing particularly  FIGS. 7, 11 and 13 , it can be seen that the third stage  42  step of machining includes removing a portion of each radial projection  60  from either side of the disc blank and creating a machined area  70  of the lands  58 . The machined area  70  is provided by a milling step whereby the milling cut is made at an angle inclined to the symmetry plane E 1  shown in  FIG. 8  so that the machined surfaces  70  of the opposing faces theoretically meet in a sharp radial inclined edge  67 . Due to tolerances, this radial inclined edge  67  may be interrupted, so that contour  61  is partly present as shown in  FIG. 11  with line  61   a . This is not deleterious to the functioning of the disc. 
     In the illustrated embodiment, the design of ridges  56  is such that the machined surfaces  70  are of constant width so that, in order to create them, a milling tool with one diameter need only be moved once in between the ridges  56 . 
     As can be seen in  FIGS. 11 to 13 , the machined surfaces  64 , respectively the conical machined surface  640 , of each ridge meet in a sharp radial edge  66 . All edges  66 ,  67 ,  620 ,  621 ,  622 ,  623 ,  624  assist in the cutting of crop kernels together with leaves and stalk parts that have not been cleanly cut by the chopping drum  4  ( FIG. 1 ). 
     This is preferably accomplished by turning the disc blank  29  in a second stage  41  of the process on a lathe using a single cutting tool to remove the upper part of all ridges  56  and peripheral portions  60  on a first side of the disc blank in a single turning operation, before reversing the disc blank on the lathe and machining the second side. Alternatively, a milling tool could be used to be moved along the ridges  56 . 
     The third stage  42  of the process is preferably accomplished on a milling machine. As will be recognised, it is a further particular benefit that all of the cutting edges  67  are provided by milling the machined surface  70  which extends only partly into the lands  58 , so that time on the machining tool can be greatly reduced compared to prior art techniques. In the embodiment shown, third stage  42  requires one-eighth of the conventional machining time as the movement of the machining tool is only 10 mm instead of 80 mm when machining the complete land  58 . Furthermore, machining the complete land  58  would require a more complex pattern of movement of the tool as the machined surface would be more of a triangular shape, preventing the machining with a larger tool in the radially inward parts of the land  58 . 
     If the second stage  41  and third stage  42  of the process are accomplished by using a milling machine in one step (one clamping required for each side), there is still a time saving due to the partial machining of land  58  to create machined surface  70 . Alternatively the second stage  41  may be split into two steps, a first step to machine the conical machined surface  640  and a subsequent step to machine grooves  650 ,  652   a ,  652   b ,  652   c ,  652   d.    
     Furthermore, if using a lathe to carry out the second stage  41  it may be possible to effect the third stage  42  on the same machinery if the lathe is equipped with driven tools and positionable (milling) spindle. 
     As used herein in relation to the invention, the term “machining” means every kind of operation in which a cutting tool or the part itself is pivoted to cut contours from said part. 
     The process of milling may include known milling techniques, e.g.
         End/Face milling: characterised in that the tool penetrates the part along its rotational axis whereby the end face can be completely used to cut the part. In the case of stage  41 , the machined surface  64  is approximately perpendicular to the rotational axis of the milling tool.   Cylindrical or plain/peripheral milling: characterised in that the tool penetrates the part perpendicular to its rotational axis whereby the circumferential face can be completely used to cut the part. In the case of stage  41 , the machined surface  64  is approximately parallel to the rotational axis of the milling tool.       

     Furthermore, grinding (end grinding or plain grinding) could also be used according to the procedures described for milling above, although this is not a preferred option due to the typically much higher costs involved. 
     Referring to the first stage  40 , the above embodiment describes the disc blank as a forged part. However, it will be understood that any procedure to provide a disk blank, e.g. steel casting and hardening afterwards, may be used instead. In such a case, the second stage  41  and/or third stage  42  may require the usage of grinding. Even with such a method, the partial machining of lands  58  still results in a time saving. 
     In the shown embodiment, the cracker disc is made of a disc blank  29  which already contains pre-shaped ridges  56  and lands  58 . Alternatively, current further technique may be used which comprises lathe turning of a blank of material to generate a disc shape and then milling the surface of the blank to cut in lands  58  to form ridges  56  with a conical machined surface  640  which extends radially along the ridges  56  and forms the outer contour of second portion  54 . The conical machined surface  640  may then further provided with a groove  650  which extends from the conical machined surface  640  towards the symmetry plane E 1 . 
     Referring back to  FIG. 3 , the present invention also provides a cracker roller  12 ,  13  made up of discs  30  manufactured as described above and mounted on a roller shaft  12   a ,  13   a . To assist this, an axially extending keyway  68  is cut in the wall of the bore  50  through the disc blank: when mounted on a roller shaft  12   a ,  13   a , a radially extending key or projection (not shown) from the shaft engages the keyway  68  to prevent the discs  30  rotating relative to the shaft. 
     From reading of the present disclosure, other modifications will be apparent to those skilled in the art and the scope of the invention is limited only by the following claims.