Patent Publication Number: US-8113455-B2

Title: Device for grinding input material

Description:
This nonprovisional application claims priority under 35 U.S.C. §119(a) to German Patent Application No. DE 102006022886, which was filed in Germany on May 15, 2006, and which is herein incorporated by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a device for grinding input material. 
     2. Description of the Background Art 
     Devices of this class are known, for example, from DE 202 16 056, which corresponds to U.S. Pat. No. 7,134,463, or from DE 202 08 606. The disk mills disclosed there are characterized by a grinding chamber, surrounded by a housing, in which grinding tools rotating around a central axis of rotation are arranged. The grinding tools in this case are located at an axial distance, with maintenance of an identical radial distance from the axis of rotation and thus form a rotationally symmetric grinding gap in which the grinding work takes place. 
     The input material is introduced axially into the central area of the grinding chamber and then deflected in a radial direction, where it is taken up and ground by the profiled surfaces of the rotating grinding tools. 
     During the operation of a conventional device of this class, grinding tools are exposed to high mechanical stress, which among other things depends on the type and purity of the input material. As a result, natural wearing of the grinding tools takes place, which with increasing tool lifetime increasingly impairs the quality of the final product. Therefore as a result of wear it is necessary to replace the used grinding tools with new ones at regular intervals. 
     Another reason for the frequent changing of grinding tools is the adaptation of a device of this class to a different material to be ground or a different end product to be achieved. Especially in the case of contract grinding, the input material can vary from one contract to the next, so that adaptation of the grinding tool to the varying input material through the use of suitable grinding tools is necessary. 
     Naturally, each change in the grinding tools is necessarily linked with considerable shutdown times of the grinding device, resulting in production shutdowns for the operator of the device. The shutdown times thus have an important influence on the operating economy of a device of this class. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to minimize the shutdown times caused by changing the grinding tools without restricting the functionality of the invention. 
     It has proven problematic in finding a solution to this task that the extent of the shutdown times required for making changes depends on a number of factors. As examples it is possible to mention the material quality of the grinding tools, the accessibility into the interior of the machine, the manner of fastening of the tools, and the like. This results in the necessity of considering all factors for a suitable solution to achieve acceptable success. It is the achievement of the invention to have discovered a solution that meets these requirements with only minor additional construction expense. 
     Through the arrangement of the grinding tools on an interchangeable ring, all grinding tools are completely changed upon replacement of the interchangeable ring. This advantage is especially felt when individual segments are used as grinding tools, since a considerable expense for installation and removal is linked with the fastening of the individual segments. Thanks to this invention it is possible, when additional interchangeable rings are kept in reserve, to attach the individual segments to the additional interchangeable ring outside of the grinding device without interrupting the grinding operation. Thus the shutdown time is reduced merely to the time span for the replacement of the interchangeable ring, which can be conducted by loosening or tightening a few screws. 
     The use of an interchangeable ring in accordance with the invention also permits wear-optimized design of the device. Whereas in the case of known devices the grinding function and the load removal function were combined in the grinding tools, according to the invention an assignment of this function to different machine components is now provided. The load removal function is completely taken on by the interchangeable ring, which therefore can be of a softer, less high quality steel and therefore has high resistance to dynamic stress. The grinding tools on the other hand no longer have a supporting function within a device in accordance with the invention. Therefore they can be made of an extremely hard and thus wear-resistant material. Such a combination is characterized by longer tool lives and simultaneously lower manufacturing costs. In this process the full functionality of the device in accordance with the invention is maintained, since not only annular grinding tools with simple radial corrugation can be used, but also segmented grinding tools, the corrugation of which can vary for adaptation to the type of material input and the properties of the final product. 
     In a simple embodiment of the invention, an interchangeable ring in accordance with the invention is provided at least in the case of the rotating grinding tools, since the mechanical stress and therefore the wear is higher there. Preferably, however, both of the grinding tools that form the grinding gap are respectively mounted on the interchangeable ring. In this case the invention comprises both embodiments in which both interchangeable rings are fastened to rotating supporting disks, and those in which an interchangeable ring is supported in a fixed location on the device. 
     In an embodiment of the invention, the interchangeable ring is subdivided in a radial direction into an outer circumferential area, which forms the accommodation for the grinding tools, and an inner circumferential area for fastening them to the supporting disk. Therefore the assembly of the grinding tools outside of the grinding device from the rear side of the interchangeable ring is also possible, so that the effective grinding surface will not be reduced or impaired by screw heads or the like. Through a corresponding design of the grinding disks, if desired the screw heads on the rear side of the interchangeable ring are covered by the supporting disk and are thus protected from material accumulations and mechanical stresses which would otherwise make loosening of the fastening screws more difficult. 
     The accommodation of the grinding tools on the interchangeable ring takes place according to an embodiment of the invention through the shape of the indentations corresponding to the grinding tools, so that force-locking is accomplished by means of form-locking. The fastening screws in this process serve essentially for fixing the grinding tools in the indentation. 
     The inner circumferential area that serves for fastening the interchangeable ring to the supporting disk permits the interchangeable ring to be screwed in from the front side of the interchangeable ring facing the grinding gap, since here no coverage by the grinding tools exists. As a result of this type of construction, the accessibility of the fastening means with the housing door open ( FIG. 1 ) is optimized, so that the disassembly and assembly of the interchangeable ring is facilitated and therefore can be conducted more rapidly. 
     Advantageously, the fastening in this area likewise takes place by means of a form lock, which likewise accomplishes centering of the interchangeable ring and thus prevents imbalance. On the other hand, through the elements forming the form lock, advantageous dissipation of force from the grinding tools into the subconstruction is achieved. 
     Also, in an embodiment of the invention, the interchangeable ring with its outer circumference extends beyond the outer circumference of the supporting disk. As a result, the supporting disk can continue to have relatively small dimensions, which leads first of all to material savings and thus cost savings. In addition, with such a design, concentration of mass in the vicinity of the axis of rotation is achieved and thus the kinetic energy of the rotor during rotation of the device in accordance with the invention is kept small. Especially at high rotating speeds with large circumferential velocities, this situation gains importance. 
     In a further development of the concept of weight minimization and weight concentration in the area of the axis of rotation, in accordance with the invention it is suggested that the interchangeable ring be made of plastic, preferably of carbon fiber reinforced plastic, characterized by high strength with low weight. 
     In accordance with an embodiment of the invention, the grinding tools are bonded to the interchangeable ring. In this way full-surface fastening of the grinding tools in the adhesion joint is accomplished, so that the grinding tools can be made extremely thin-walled without breaking during installation. 
     In accordance with another embodiment of the invention it is provided that the adhesive bond be produced with a thermally deactivatable adhesive. In this way by simply heating the interchangeable ring or carrier ring, the grinding elements can be loosened from the supporting construction, so that these are again available for accommodating new, unused grinding tools. 
     Such thin grinding tools are especially suitable in an embodiment of the invention in which the interchangeable ring, on its inside facing the grinding gap, is essentially a flat design. In this way the processing step of machining off an annular recess during the manufacturing of the interchangeable ring is eliminated, with the advantage of cost-effective production. 
     Another embodiment of the invention provides for arranging the grinding tools on a supporting ring, and fastening the unit produced in this way, made of the grinding tools and supporting ring as a whole, on the interchangeable ring. In this manner, the need for having several spare interchangeable rings is eliminated without appreciably increasing the shutdown times. Instead it is sufficient to reserve the simpler-designed and less expensive supporting rings, which need only be placed in the interchangeable ring when needed. 
     In conjunction with adhesive-bonded grinding tools, this embodiment of the invention also offers the possibility for using the grinding tools and supporting ring as a disposable product without reducing the economy of the invention. 
     Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus, are not limitive of the present invention, and wherein: 
         FIG. 1  illustrates a front view of a device in accordance with the invention with the housing door open; 
         FIG. 2  illustrates a front view of the device shown in  FIG. 1  with the housing door closed; 
         FIG. 3  illustrates a vertical section through the device shown in  FIG. 2  along line III-III; 
         FIGS. 4 ,  5 , and  6  illustrate partial sections of different embodiments of the invention in the area of the interchangeable ring, 
         FIG. 7  illustrates a partial view of an interchangeable ring with segmented grinding tools; and 
         FIG. 8  illustrates a partial view of an interchangeable ring in accordance with the invention with an annular grinding element. 
     
    
    
     DETAILED DESCRIPTION 
     On the basis of  FIGS. 1 ,  2 , and  3 , the fundamental structure of a device in accordance with the invention is described. In  FIGS. 1 and 2 , which show a front view with on one hand the housing door  7  open and on the other hand closed, one first sees a machine undercarriage  1 , resting with its feet  2  on a solid base. The top of the machine undercarriage  1  forms a platform on which the grinding device in accordance with the invention is installed. 
     The grinding has an essentially drum-shaped housing  3 , which surrounds a grinding chamber  4 . The housing  3  on its front  5  has a central circular opening  6 , which is closeable with the aid of a housing door  7  that can be pivoted around a vertical axis  8  and locked with locks  9 . 
     The housing door  7  has a central filling opening  10 , followed by, proceeding from the outside, a vertical dropping shaft  11 , opening obliquely into the filling opening  10  in the foot area. Over the thickness of the housing door  7 , the filling opening  10  expands conically to the grinding chamber  4 . The material removal takes place over a material off-take  13 , which in the visualization plane leads tangentially out of the housing  3  and which for example may be connected to a suction system. 
     The rear side  14  of the housing  3  is reinforced to form a horizontal support area  15  with the bearing groups  16 . Through the backside  14  of the housing  3  extends a drive shaft  24  rotatably supported in the bearing groups  16 , the outer end of which supports a multi-grooved disk  18 . The multi-grooved disk  18  is connected over belts with the drive motor  19  shown only in  FIGS. 1 and 2 . The belts travel inside a protective lining  20 . 
     At the opposite end of the drive shaft  24 , located within the grinding chamber  4 , with hubs  29 , is supporting disk  21 , which can be set into rotation around the axis of rotation  31  by means of its drive shaft  24 . The disk  21  has radial distributor ribs  12  on its surface facing the opening  10 . 
     The supporting disk  21  serves for fastening the interchangeable ring  23  within the grinding chamber  4  and for this purpose, on the side facing the grinding gap  36  has an indentation  30 , on the radial delimiting surface of which an annular projection  39  coaxial to the axis of rotation  31  is placed. 
     The projection  39  interacts with a corresponding annular groove  38  on the inner circumferential area of the interchangeable ring  23 , in order to transfer the forces that arise during the grinding operation through the form locking produced in this way. In addition, for fixing the interchangeable ring  23  in the indentation  30  of the supporting disk  21 , six fastening screws  37  distributed uniformly over the circumference are provided, which, originating from the grinding gap plane, extend in the axial direction through the interchangeable ring  23  into the annular projection  39  (also see  FIGS. 4 to 6 ). 
     In the outer circumferential area of the interchangeable ring  23 , on the side facing the grinding gap is an annular disk-shaped recess  28 , which likewise is coaxial to the axis of rotation  31 . The recess  28  serves to accommodate the grinding tools  25  in the form of single segments ( FIG. 7 ) or a whole ring ( FIG. 8 ). By means of the screws  26 , which extend from the reverse side of the interchangeable ring  23  beyond the base of the recess  28 , the grinding tools  25  are retained in the recess  28 . On the other hand, radial forces are led off by the form locking between the interchangeable ring  23  and the grinding tools  25 ; especially the outer contact surfaces of the recess  28  forming the ring shoulder  27  opposes the centrifugal forces operating during use. 
     An interchangeable ring  23 ′ with grinding tools  25 ′ formed as a mirror image to the grinding gap is fastened on the inside of the housing door  7  in a recess  35  forming a form lock with the backside of the interchangeable ring  23 ′ by means of screws  47 ′. In this manner the grinding tools  25  and  25 ′ are axially opposite one another while maintaining a radial grinding gap  36 . 
       FIGS. 4 ,  5  and  6  show partial sections through various embodiments of the invention in the area of the interchangeable ring  23  or  23 ′. For simplicity&#39;s sake, insofar as possible the same reference symbols have been used in the various embodiments for the same or modified parts.  FIGS. 4 and 5  pertain to interchangeable rings that are fastened to the supporting disk  21 , while  FIG. 6  shows an interchangeable ring  23 ′ fastened to the housing door  7 . Naturally, all of the embodiments of interchangeable rings  23 ,  23 ′ shown can be combined with all grinding tools  25  or  25 ′ and can serve for fastening to both the supporting disk  21  and the housing door  7 . 
       FIG. 4  corresponds most closely to the representation in  FIG. 3 . In particular one can see the interchangeable ring  23  with grinding tools  25 , which is anchored over the annular projection  39  to the supporting disk  21 , the annular groove  38  in the interchangeable ring  23  and the screws  47  in the area of the indentation  30 . 
     In contrast to  FIG. 3 , in the embodiment according to  FIG. 4  the supporting disk  21  does not end in the inner circumferential area of the interchangeable ring  23 , but also extends radially outward until coverage of the screws  26  has been accomplished. To receive the heads of the screws  26 , an annular groove  32  has been milled into the supporting disk  21  in the area of the recess, and the heads of the screws  26  lie in this [groove] protected from dirt and mechanical damage. 
     The embodiment of the invention shown in  FIG. 5  is especially suitable for grinding the input material with high rotation speed and thus high circumferential speeds of the grinding tools  25 . Once again an interchangeable ring  23  is seen, which is fastened to the supporting disk  21  in the manner described in  FIG. 3 . The interchangeable ring  23  consists of a carbon fiber-reinforced plastic and therefore has an extremely low weight with high strength. 
     On the side facing the grinding gap  36 , the interchangeable ring  23  has a flat indentation  40  concentrically surrounding the axis of rotation  31 , into which the grinding tools  25  are placed in a form-locking manner. The fastening of the grinding tools  25  in the recess takes place over a large-area bonding joint  33  between the backside of the grinding tools  25  and the base of the recess  40  in the interchangeable ring  23 . It would also be conceivable to bond the grinding tools  25  onto a flat surface of the interchangeable ring  23 . 
     The large-area bonding leads to a fastening method with a uniform application of load over the entire surface of the grinding tools  25 , thus avoiding stress peaks that would otherwise arise in the area of the screws in the case of point fastening. Consequently, the grinding tools  25  can be made substantially thinner and thus lighter. 
     In  FIG. 6  an additional embodiment of the invention is shown with an arrangement of the interchangeable ring  23 ′ on the housing door  7 , but the fastening of this to a supporting disk  21  is likewise possible. The interchangeable ring  23 ′ is fastened to the back side of the housing door  7  as described under  FIG. 3 , wherein once again form locking is produced between the annular projection  39 ′ in the housing  7  and the annular groove  38 ′ in the interchangeable ring  23 ′. The screws  37 ′ then serve for fixing the interchangeable ring  23 ′ in the position predetermined by the form locking. 
     In contrast to the previously described embodiments, in the variants shown in  FIG. 6 , the grinding tools  25 ′ are not fastened directly to the interchangeable ring  23 ′ but rather under intermediate connection of a supporting ring  34 . In this process the supporting ring  34  comes to lie in an annular disk-shaped coaxial recess  41  in the interchangeable ring  23 ′ on the side facing the grinding gap  36  and is held by screws  26 ′ in the recess  41  emanating from the back side of the interchangeable ring  23 ′. The surface  42  of the supporting ring  34  facing the grinding gap  36  is adhered with a thin coating of grinding tools  25 ′ of constant thickness. 
       FIGS. 7 and 8  each show a circumferential section of an interchangeable ring  23  fitted with grinding tools  25 . In  FIG. 7  grinding tools  25  are seen in the form of trapezoidal segments  43 , the effective surface of which is formed by corrugated strips  44 , which travel parallel to one another within a single segment  43 . As a result of the trapezoidal shape of the individual segments  43 , shorter corrugated strips  44 ′ form in the area of the radially traveling abutment joints, with grinding results characteristic for this type of corrugation. 
     In contrast to this, the grinding tools  25  according to  FIG. 8  consist of a single-piece annular disk  45  extending over the entire circumference of the interchangeable ring  23 , in which all corrugated strips  46  are aligned radially. In this way distances of the corrugated strips  45  from one another arise which increase from inside to outside, resulting in a different, likewise characteristic grinding result. 
     During operation of a grinding device in accordance with the invention, the input material is supplied to the dropping shaft  11 , from where it enters centrally through the filling opening  10  into the grinding chamber  4  surrounded by the housing  3 . There it first encounters the central area of the rotating supporting disk  21  and is there carried along by the distributor ribs  12  and subjected to circular movement. The centrifugal forces thus arising guide the input material in the radial direction to the grinding tools  25 ,  25 ′. 
     During passage through the grinding gap  36  formed by the grinding tools  25 ,  25 ′, the input material is broken down on the corrugated strips  44  and  46 . On leaving the grinding gap  36  in the radial direction, the work of grinding is ended and the input material is conveyed to additional processing stages over the tangential material outtake  13 . The arrows  50  shown in  FIG. 3  represent in idealized fashion the material flow through the device in accordance with the invention. 
     If a change in the grinding tools  25 ,  25 ′ becomes necessary because of wear or changing to a different input material, the housing door  7  is opened with the supporting disk  21  standing still, so that the interchangeable rings  23 ,  23 ′ become freely accessible from their side that is otherwise facing the grinding gap. By loosening the screws  47 ,  47 ′ the interchangeable rings  23 ,  23 ′ can be removed and replaced by an interchangeable ring equipped in advance with new grinding tools. After closing and locking the housing door  7 , grinding operation can be resumed after brief shutdown. 
     Thus by keeping two additional grinding rings  23 ,  23 ′ available it is possible to remove the used grinding tools  25 ,  25 ′ from the previously removed interchangeable rings  23 ,  23 ′ while operation continues. This is done either by loosening the screws  26 , or in the case of adhesive bonding, by heating the adhesive in the adhesive joint  23  so that the adhesive loses its retaining force. 
     In the embodiment of the invention shown in  FIG. 6  the interchangeable ring  23 ′ is likewise removed from the grinding device after loosening the screws  47 ′. Outside of the grinding device, after loosening the fastening screws  26 ′, the supporting ring  34  is removed and replaced by a previously prepared new supporting ring  34  with new grinding tools  25 ′. In this way a pair of interchangeable rings  23 ,  23 ′ is suitable for operating a device in accordance with the invention. 
     The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are to be included within the scope of the following claims.