Patent Publication Number: US-9403168-B2

Title: Device for comminuting feedstock

Description:
This nonprovisional application claims priority under 35 U.S.C. §119(a) to German Patent Application No. DE 20 2010 006 173.3, which was filed in Germany on Apr. 27, 2010, and which is herein incorporated by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a device for comminuting feedstock. 
     2. Description of the Background Art 
     Devices of this type belong to the field of mechanical process engineering, particularly the conversion of a feed material into an end product of predefined shape and size by way of comminution. Such devices include, inter alia, disc mills, such as those disclosed, for example, by German Utility Pat. No. DE 202 16 056 U1, which corresponds to U.S. Pat. No. 7,134,463. Such disc mills have a rotor, which works together with a stator within a housing. The rotor includes a carrier disc, which is equipped along its outer circumferential area with grinding tools lying within the disc plane. The grinding tools lie opposite to stationary stator tools, arranged at the inner housing wall concentrically around the axis of rotation, at an axial distance with the maintenance of a grinding gap. 
     Both the rotor and stator tools can be formed by segments and are screwed onto the carrier disc or to the housing wall. This very time-intensive work increases not only the assembly costs during wear-related tool replacement, but also concurrently increases the length of downtimes of the disc mill, which conflicts with efficient utilization. For this reason, rotor and stator tools, which have a complete ring that can be replaced as a whole unit, are already in use in disc mills. This does in fact shorten the tool replacement times, but the profile of the grinding tools is limited in terms of manufacturing technology to a substantially radial fluting. 
     The conventional art also includes mills, such as those described, for example, in European Pat. Appl. No. EP 2 070 596 A1. The mill disclosed therein has a cone-shaped housing, whose inner circumference is provided with a grinding bed insert, shaped like a hollow truncated cone, to form a stator. Arranged coaxially within the grinding bed insert is a rotor, whose rotor tools are formed by radially oriented impact plates, which are suspended in a pendular manner and with maintenance of the grinding gap strike along the inner circumference of the stator tools. The grinding bed insert, shaped like a hollow truncated cone, forms the stator tools and is inserted as a whole unit into the housing, whereby a clamping ring at the larger-diameter front end of the housing assures the securing against axial positional changes of the grinding bed insert. As in the case of the previously mentioned one-piece tool rings in disc mills, based on the monolithic design of the grinding bed insert here as well only a substantially coaxial fluting on the inner circumference of the grinding bed insert is possible. Variations in the geometry of the fluting, to match the stator tool active surface for comminution to specific feedstock or to achieve a specific processing result, are not possible. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the invention to develop further conventional devices in regard to shortest possible downtimes during tool replacement and greatest possible flexibility in matching the stator tools to the feedstock and to the end product requirements. 
     Due to the invention, it is possible to satisfy simultaneously the thus far mutually exclusive requirements in the prior art for the most rapidly possible replacement of comminuting tools, on the one hand, and a greatest possible freedom during the selection of the type of fluting of the comminuting tools, on the other, within a device. 
     By means of the segment-like design of the stator tools it is possible for two successive segments to have a different fluting, as a result of which both the intensity of the comminution and the residence time of the feedstock within the comminution area can be controlled. At the same time, for assembly, the segments are merely placed in the stator and then fixed in their position with a clamping element. Extremely short downtimes caused by tool replacement can be achieved in this way. The invention therefore makes possible a more economic operation of the device of the invention by means of a simplified tool replacement with simultaneous qualitative improvement of the processing result due to the possibility of being able to better match the stator tools to the specific general conditions. 
     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  shows a vertical section through a device of the invention along the line I-I depicted in  FIG. 2 ; 
         FIG. 2  shows a horizontal section through the device shown in  FIG. 1  along the line II-II there; 
         FIG. 3  shows a detail of the device shown in  FIG. 1  in the areas designated by III; 
         FIGS. 4 to 6  show alternative embodiments to the solution shown in  FIG. 3 ; and 
         FIGS. 7 to 13  show corresponding detail solutions in conjunction with the devices of the invention in the form of disc mills. 
     
    
    
     DETAILED DESCRIPTION 
       FIGS. 1 and 2  depict a vertical and horizontal section through a device of the invention in the form of a mill  1 . A frame-like base  2  can be seen, which is made of steel profiles and with its top side forms a horizontal platform  3  with central opening  4 . Base  1  supports mill  1  of the invention, whose axis of rotation  5  is oriented perpendicular to platform  3  and extends through central opening  4 . 
     Mill  1  comprises a housing  6  with a bottom part  7 , which is formed by a cylindrical trough. Bottom  8  of the trough has a circular opening  9  concentric with the axis of rotation  5 . Bottom part  7  is open upwards, the edge being formed by a circumferential annular flange  10 . Annular flange  10  is used to support and attach a concentric bearing ring  11 , which is formed angular in cross section and whose horizontal leg is connected to annular flange  10 . 
     Housing  6  continues upward in a bell-shaped upper part  12 , which is shaped like a hollow truncated cone and whose larger-diameter bottom side is open and associated with bottom part  7  and whose smaller-diameter top side has an opening  14 , which is limited by a circumferential collar  13  radially facing inward. A removable cover  15  is bolted together removably with collar  13  and has a concentric feed opening  16 , to which a feed connecting piece  17  is attached. Arrow  18  represents the feedstock which is fed axially into mill  1  through feed connecting piece  17 . 
     The larger-diameter bottom side of upper part  12  has a circumferential annular flange  19  at the outer circumference, said flange which is supported via adjusting screws  20  on the vertical leg of bearing ring  11 . In the housing section between annular flange  19  and the larger-diameter front end of upper part  12 , the outer housing covering is formed cylindrically, in order to be guided with an accurate fit and axially movable within bearing ring  11 . The distance between bottom part  7  and top part  12  can be adjusted by adjusting screws  20 . 
     Upper housing part  12  with its inner circumference forms the stator, along which fifteen segments  21  forming the comminuting surface are arranged. The long sides  22  of segments  21  are formed for this purpose so that they run in each case within the axial planes relative to the axis of rotation  5 . Segments  21  butt-jointed in the circumferential direction in this way form the stator tools of the rotor-stator system. To secure the relative position of segments  21  relative to one another, it is also possible to provide the mutually associated long sides  22  of two adjacent segments  21  with positive-fit elements, for example, in the form of a tongue and groove, which is not illustrated, however. 
     The cross section of segments  21  is evident primarily from  FIG. 2 . Accordingly, segments  21  have a planar rear side  23  and lie only with their longitudinal edges formed by rear side  23  and long sides  22  in each case linearly against the conically extending inner jacket of upper part  12 , which results in a polygon-like course of the rear side of the comminuting surface. The linear mounting along the longitudinal edges, moreover, makes assembly easier compared with flat mounting, because manufacturing-related inaccuracies within the bearing surface would impede a snug seating of segments  21 . Because the inner side of upper housing part  12  has a constant curvature, hollow spaces  58  which have a cross section in the form of circular segments and can be used, for example, for conveying a cooling medium, form between upper housing part  12  and the rear sides  23  of segments  21 . The front side  24  of segments  21  has an arcuate curvature and is provided with fluting. 
     The size of the hollow spaces  58  resulting between segments  21  and the inner side of upper housing part  12  depends, inter alia, on the number of segments  21 . The invention prefers a number of segments between 12 and 20, preferably between 15 and 18. A segment  21  therefore extends over 1/12 to 1/20, preferably over 1/15 to 1/18 of the inner circumference of the stator. 
     The particular formation of the two short sides  25  of segments  21  will be described in greater detail in regard to  FIGS. 3 to 6 . 
     A rotor  26  rotating around the axis of rotation  5  is evident within housing  6 . Rotor  26  comprises a shaft  27 , which is retained within a cylindrical shaft bearing  28  in bearing assembly  29  coaxially with the axis of rotation  5 . In this regard, shaft bearing  28  is inserted over part of its length into opening  9  in bottom  8  of bottom part  7 , whereby an annular flange  30  outwardly surrounding shaft bearing  28  is used for the positionally precise attachment of rotor  26  relative to housing  6 . A multiple-groove pulley  31 , which is coupled to a drive not shown in greater detail, is seated on the end of shaft  27  lying outside housing  6 . 
     An impact plate  32  is attached on the face side to the opposite end of drive shaft  27  concentric with the axis of rotation  5 . Hammering blocks  33 , arranged in the circumferential area, at their top side facing feed opening  16  form a first comminuting stage for the feedstock entering mill  1  via feed connecting piece  17 . 
     There is a first carrier disc  34  also seated concentrically on shaft  27  at an axial distance to impact plate  32 ; rotor tools are arranged in pairs in the form of impact plates  35  at the circumference of the carrier disc. In this case, the effective edges of impact plates  35  run parallel to the surface lines, forming the front side  24  of segments  21 , with maintenance of a radial working gap. A first retarding disc  36  is arranged concentrically plane parallel and at an axial distance on drive shaft  27  in the direction of bottom part  7 . The first retarding disc  36  is used to control the residence time and the material stream through mill  1  of the invention. 
     Another comminuting stage is formed by a second carrier disc  37  attached concentrically to shaft  27  and is equipped like the first carrier disc  34  with impact plates  35  at its circumference. Finally a second retarding disc  38 , seated concentrically on shaft  27 , follows in the flow direction through mill  1 . 
     Details of the attachment of segments  21  to upper part  12  of housing  6  emerge from  FIG. 3 . In this regard,  FIG. 3  shows a section, as indicated with III-III in  FIG. 2 , and thereby is within the butt joint of two adjacent segments  21 . 
     Each segment  21  for its attachment to upper part  12  along both short sides  25 . 1  and  25 . 2  in each case has an arcuate ledge section  39 . 1  and  39 . 2 . In the installed state, ledge sections  39 . 1  and  39 . 2  of all segments  21  form a circular ledge, which runs concentrically around the axis of rotation  5 . 
     For the positive-fit receiving of ledge section  39 . 1  at the first short side  25 . 1  an annular groove  40 , likewise concentrically surrounding the axis of rotation  5 , is arranged in upper housing part  12  on the inner side of collar  13 . This enables the insertion of segments  21  with their ledge sections  39 . 1  into annular groove  40  in upper part  12  employed for assembly. In so doing, segments  21  reach the inner side of upper part  12  only with the longitudinal edges formed by long sides  22  and rear side  23 . 
     To attach segments  21  in the area of the larger-diameter bottom side of upper part  12 , a likewise concentric clamping ring  41  is provided, which can be clamped by means of screws  42  against the front end of upper part  12 . Clamping ring  41  extends with its inner circumference radially inward via the opening to the bottom side of upper part  12  and has an annular shoulder  43  emerging axially from the ring plane, which during setting of clamping ring  41  on upper part  12  already equipped with segments  21  engages behind ledge section  39  at the second short side  25 . 2  of segments  21  and thereby assures their positionally precise position. 
     In comparison with the embodiment shown in  FIG. 3 , the embodiment illustrated in  FIG. 4  shows a simplified solution with respect to the manufacture of the device. In this case, the positive fit in the area of the first short side  25 . 1  is not produced by a tongue and groove construction. Instead, the first short side  25 . 1  and upper housing part  12  are formed in the common contact area and lie within a radial plane relative to the axis of rotation  5 . In the area of clamping ring  41 , the two embodiments according to  FIGS. 3 and 4  are similar, so that the foregoing statements apply here as well. 
     In the embodiment according to  FIG. 5 , the bracing of the first short side  25 . 1  in upper housing part  12  corresponds to that described in regard to  FIG. 3 . In contrast, the second short side  25 . 2  has a planar area within a radial plane, said area on which a clamping ring  41 . 1  with a correspondingly planar form acts. 
     The embodiment according to  FIG. 6  shows the greatest degree of simplification. Both the first top side  25 . 1  and second top side  25 . 2  of segments  21  are formed as planar here and are held in the axial direction by correspondingly planar bearing surfaces in upper housing part  12  or at clamping ring  41 . 1 . The embodiment according to  FIG. 6  shows to a certain extent a combination of the embodiments shown in  FIGS. 4 and 5 . A securing of the position of segments  21  in the radial direction results from the ring-shaped arrangement of segments  21  around the axis of rotation  5 , whereby segments  21  are mutually braced via their long sides  22  and radially inward movements due to arching are prevented. 
       FIGS. 7 to 13  relate to embodiments of different arrangements of segments  21  at stationary or also rotating bearing elements, whereby the planes of attachment are each within a radial plane relative to the axis of rotation  5 . Such solutions are suitable for implementing the invention in disc mills, for example, according to German Utility Pat. No. DE 202 16 056 U1 mentioned in the introduction to the description. 
     In  FIG. 7  a bearing element is designated with reference character  44 , for example, a rigid or rotating bearing disc or a rigid housing wall. The comminuting tools, arranged in a circle around the axis of rotation  5 , in the form of segments  21  are visible on the side of carrier element  44 , said side facing the grinding gap. To attach segments  21 , a recess  45  with a rectangular cross section, surrounding the axis of rotation  5  concentrically, is arranged in the surface of carrier element  44 ; the recess is formed by a bottom  46 , an outer wall  47 , and an inner wall  48 . 
     Recess  45  is used for receiving segments  21 , which with their rear side  23  rest with their entire surface against bottom  46  and with their first short side  25 . 1  with their entire surface against outer wall  47 . The radial size of recess  45  is selected such that an annular space, which is used to receive a clamping ring  41 . 3 , results between inner wall  48  and segments  21 . In this regard, clamping ring  41 . 3  rests with its inner circumference against inner wall  48 , whereas the outer circumference decreases in the direction toward the side facing bottom  46  to form a sloping circumferential surface. Clamping ring  41  acts via this sloping surface together with segments  21 , whose second short side  25 . 2  widens linearly with the formation of a correspondingly inclined surface toward the rear side  23 . In this way with the tightening of screws  42  a clamping force, acting radially outward against outer wall  47  and axially against bottom  46 , is transmitted to segments  21  via the clamping ring  41 . 3 . 
       FIG. 8  differs from this embodiment only in that outer wall  47  is undercut toward bottom  46 . The first short side  25 , formed complementary thereto, of segment  21  engages behind the undercut wall  47  and is secured in this way in addition against axial lifting. 
     The embodiment of the invention as shown in  FIG. 9  differs from the two previously described embodiments in that carrier element  44  has no channel-like recess  45 , but a substantially planar surface, which has a circular wall  50 , projecting from the plane, only at the outer circumferential area; the radially inwardly facing side  49  of said wall is undercut so that these areas correspond to the corresponding outer circumferential area of the embodiment shown in  FIG. 8 . 
     Clamping ring  41 . 4  has an outer circumference, corresponding to that described in  FIG. 8 , and therefore works together with the sloping second short side  25 . 2  as described in  FIG. 8 . In contrast, the inner circumference of clamping ring  41 . 4  is greatly widened in the direction toward carrier element  44  with the formation of an incline  57 , to achieve as large a support area  56  as possible of clamping ring  41  at the planar top side of carrier element  44 . 
     The embodiment according to  FIG. 10  corresponds in many parts to that described for  FIG. 7 . There are differences in the area of the second short side  25 . 2  of segments  21 , which widens in steps toward the rear side  23  of segments  21  with the formation of a rectangular ledge section  39 . 1 . Clamping ring  41  has an outer circumference, formed complementary thereto, with an annular flange  51 , which clamps ledge section  39 . 1  axially against bottom  46 . 
     The embodiment according to  FIG. 11  is similar to that described for  FIG. 10  with the difference that segments  21  widen in steps also in the area of the first short side  25 . 1  toward rear side  23  and thereby form a ledge section  39 . 2 , which engages with a positive fit in a corresponding groove  52  in outer wall  47 . Segments  21  therefore have an axially symmetric cross section. 
     The embodiment of the invention shown in  FIG. 12  differs from this in a clamping ring  41 . 6  axially symmetric in cross section. Clamping ring  41 . 6  has, as described in  FIG. 11 , a circumferential annular flange  51  at the outer circumference. In addition, there is a second annular flange  53 , which is arranged in an analogous manner at the inner circumference of clamping ring  41 . 6 . Inner wall  48  has a geometry complementary thereto with a ring-shaped recess  55 , so that upon tightening of screws  42  clamping ring  41 . 6  rests both on ledge section  39 . 1  of second short side  25 . 2  and on recess  55  in inner wall  48  and is therefore stressed symmetrically. 
     A variant of this is the subject of the embodiment disclosed in  FIG. 13 . Here, short sides  25 . 1  and  25 . 2 , widening in the direction of rear side  23 , each have ledge sections  39 . 3  and  39 . 4 , with incline  54  sloping toward the outer circumference or the inner circumference in the direction of rear side  23 . Upon clamping of the complementary formed clamping ring  41 . 7 , in the contact area to segment  21 , a radially outwardly directed component is generated in addition to the clamping force directed against bottom  46 . An axially symmetric embodiment of clamping ring  41 . 7  in cross section and a complementary shape of wall  48  ensure a symmetric stress on clamping ring  41 . 7 . 
     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.