Patent Document

BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to an apparatus for comminuting, grinding and dispersing flowable grinding stock. 
     2. Background Art 
     Apparatuses of the generic type are known in many forms as so-called agitator mils. These agitator mills have a grinding receptacle that defines a grinding chamber, in which a rotor and auxiliary grinding bodies are disposed. The grinding stock passes through the grinding chamber, and is essentially comminuted, ground and dispersed by the movement of the auxiliary grinding bodies. 
     These apparatuses are also known as so-called roller mills; in these machines, two or more rollers form a grinding gap, which can be adjusted between two rollers. In the grinding gap, the grinding stock is subjected to high shearing stresses, and is thereby comminuted, ground and dispersed. Roller mills of this type are used in the production of printing inks, among other things. A drawback of these machines is that the grinding stock must be collected after each passage through the roller mill, and supplied to it again. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to create an apparatus of the generic type, in which the grinding stock can be repeatedly subjected to shearing actions by structurally simple means, 
     In accordance with the invention, his object is accomplished in an apparatus for comminuting, grinding and dispersing flowable grinding stock, comprising 
     a stand; 
     a grinding receptacle, 
     which is rotatably seated on the stand, 
     which has an axis of rotation, 
     which has an interior that is prodded with an opening that is open toward the top, 
     which is drivable to rotate about the axis of rotation, and 
     which has an inner, first grinding surface, 
     which is rotationally symmetrical relative to the axis of rotation, and 
     defines the interior of the grinding receptacle; 
     a grinding stock feed line for the supply of grinding stock the opening; 
     a grinding stock discharge, which discharges from the opening; 
     a grinding roller, 
     which is rotatably seated on the stand, 
     which has a central longitudinal axis, 
     which is drivable to rotate about the central longitudinal axis, and 
     which has a second grinding surface, 
     which is rotationally symmetrical relative to the central longitudinal axis, and 
     which cooperates with the first grinding surface to define a grinding gap. 
     The crux of the invention is the configuration of the apparatus such that the material to be ground is supplied to the grinding gap multiple times in one passage, because the rotational forces at the first grinding surface cause the material to move along approximately helical paths to the material discharge. The basic action of the apparatus according to the invention can best be compared to that of a roller null having a hollow roller, inside which an inner roller is disposed, forming a grinding gap. In this regard, the grinding receptacle could also be characterized as a hollow roller. Unlike agitator mills, the apparatus according to the invention operates without auxiliary grinding bodies. 
     Further features, advantages and details of the invention ensue from the following description of an exemplary embodiment illustrated in the drawing. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 is a vertical longitudinal section through an apparatus according to the invention; 
     FIG. 2 is a vertical longitudinal section through the grinding receptacle and the grinding roller of the apparatus of FIG. 1, in a schematic representation for explaining the function; 
     FIG. 3 is a plan view of FIG.  2 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     As can be inferred from FIG. 1, an apparatus according to the invention has a stand  1 , in which an electric drive motor  2  is seated. The motor has a lower, first power take-off  3  and an upper, second power take-off  4 , which is driven by the motor  2 , by way of a gear  5  having an infinitely-variably-adjustable transmission. A grinding receptacle  6  is rotatably seated on the stand  1  by means of a lower bearing journal  7  in bearings  8 . The first power take-off  3  employs a belt drive  9  in driving the receptacle to rotate. 
     A grinding roller  10 , which is mounted to a roller drive shaft  11 , is disposed in the grinding receptacle  6 . The drive shaft  11  is extremely sturdy, and is seated in two bearings  12 ,  13 , which are spaced as far apart as possible in a bearing slide element  14 . In the upper region of the stand  1 , the bearing slide element  14  is seated in a guide  15  so as to be displaced with the grinding roller  10  in the direction  17 , which extends transversely to the essentially vertical, central longitudinal axis  16  of the drive shaft  11 . The drive shaft  11 , and therefore the grinding roller  10 , can be driven by the second power take-off  4  of the motor  2  by way of an articulated shaft  18  and a belt drive  19 , with the articulated shaft  18  being coupled to the second power take-off  4  by way of a sliding bearing  20 , so displacements of the bearing slide element  14  in the direction  17  can be compensated. The bearing slide element  14  can be moved into a desired position by hydraulically-actuatable adjusting drives  21 , e.g., in the form of hydraulically-actuatable piston-cylinder drives, then secured or blocked in this position. 
     The adjusting drives  21  are articulated to the stand  1 . They can also be actuated individually for reasons that will be explained below. 
     The grinding receptacle  6  is approximately frustoconical, and is embodied to be rotationally symmetrical relative to an axis of rotation  22  extending through the bearing journal  7 . The receptacle has a bottom  23  and a frustoconical receptacle wall  24 , which widens toward the top. The grinding receptacle  6  has an upper opening  25 ; near this opening, on the outside of the receptacle wall  24 , is an annular, preferably cylindrical-ring-shaped, support surface  26 , against which support rollers  27  rest, the rollers being supported in turn in the stand  1 . 
     A grinding stock supply line  29  leads into the interior  28  of the grinding receptacle  6 , namely in the open region between the bottom  23  and the grinding roller  10 . Provided in the region of the opening  25  is a grinding stock discharge  30 , the discharge surrounding the opening  25 . The material to be ground is guided through the line  29  in the supply direction  31 , and is carried off in the discharge direction  32 . 
     The inside surface of the receptacle wall  24  forms a polished, frustoconical, first grinding surface  33 . The surface of the grinding roller  10  also forms a polished, cylindrical, second grinding surface  34 . 
     The axis of rotation  22  of the grinding receptacle  6  and the axis  16  of the grinding roller  10  form an angle a, which corresponds, entirely or at least essentially, to one-half of the opening angle of the frustoconical first grinding surface  33 . The two grinding surfaces  33  and  34  can also be slightly convex. 
     Also provided on the stand  1  is a sensor  35 , which can be used to detect the fullness level  36  of the material in the grinding receptacle  6 . The signals of this sensor  35  are transmitted to a central control  37 , which influences the drive motor  2 , the gear  5 , and thus the speeds of the grinding receptacle  6  and the grinding roller  10 . This central control  37  also actuates a grinding stock pump  38 . The control  37  is freely programmable. 
     The apparatus functions as follows. 
     The first grinding surface  33  and the second grinding surface  34  define a grinding gap  39 , which extends essentially parallel to the axis  16 , as can be seen in FIGS. 1 and 2. The overlap of the first grinding surface  33  and the second grinding surface  34  in the direction of the axis  16 , that is, the length b of the grinding gap  39 , extends essentially from the bottom  23  to the opening  25  of the grinding receptacle  6 . The diameter c of the grinding roller  10  is always smaller than the projection of the diameter d of the inside bottom surface  40  onto the diameter c. The following applies: c&lt;d×cos a. The following preferably applies: 
     
       
         0.2 d× cos  a≦c≦ 0.9×cos  a.    
       
     
     The adjusting drives  21  have moved the bearing slide element  14 , with the drive shaft  11  and the grinding roller  10 , into a position in which the grinding gap  39  has a desired width and, if applicable, a desired extension, 
     The grinding receptacle  6  is driven in the direction of rotation  41 , and the grinding roller  10  is driven in the direction of rotation  42 —in other words, as can be seen in FIG. 3, in the same direction—so the material is conveyed through the grinding gap  39  in the same conveying direction  43 . As can be seen from FIGS. 1 and 2, the fullness level  36  of the grinding stork is very low, so the grinding roller  10  only dips slightly into the material. When the grinding receptacle  6  and the grinding roller  10  are inoperative, therefore, the majority of the grinding gap  39  is located above the fullness level  36  of the material. Upon rotary actuation, the frustoconical widening of the first grinding source  33  toward the opening  25  located at the top causes the grinding stock to be conveyed upward on helical paths  44 ; consequently, the material passes through the grinding gap  39  multiple times until it reaches the opening  25 , and thus the discharge  30 . For cleaning purposes, a closable outlet  45  is provided in the bottom  23 . 
     Because of the at least essentially frustoconical embodiment of the first grinding surface  33  and the at least essentially cylindrical embodiment of the second grinding surface  34 , relative speeds exist in the grinding gap  39  between the grinding surfaces  33  and  34 ; in theory, identical circumferential speeds of the grinding surfaces  33  and  34  can dominate at a single location. This is the case when a&gt;0, that is, when the first grinding surface  33  is actually frustoconical and the second grinding surface  34  is cylindrical. In general, 0&lt;a≦45°. Preferably, 10°≦a≦30°. If the first grinding surface  33  is also cylindrical, that is, a=0, which is entirely possible, the above-described conveying actions still take place, i.e., the grinding stock moves upward toward the opening  25  in an approximately helical movement, relative to the first grinding surface  33 . Generally, the relative speeds can be significantly influenced if the grinding receptacle  6  and the grinding roller  10  are driven at different, variable rpms. 
     The angle a can be modifiable such that the width of the grinding gap  39  changes over its length b. For example, the arrangement can be such that the grinding gap  39  has its greatest width downwards, i.e., where it begins in the vicinity of the bottom  23 , and the width continuously decreases toward the top. This can be achieved in that the grinding receptacle  6  is seated to pivot by a small angle in the region of its bearing  8 . In particular, this can be achieved simply by actuating the adjusting drives  21  slightly differently, which effects a corresponding change in the width of the grinding gap  39  over its length b. Because such changes in the width of the grinding gap  39  over its length b lie within a range of thousandths of millimeters, this can be achieved by the corresponding different actuation of the adjusting drives  21  based on the unavoidable play present in the guide  15 . In addition, changes in the width of the grinding gap  39  with a frustoconical embodiment of the first grinding surface  33  can also be effected by the relative displacement of the grinding receptacle  6  and the grinding roller  10  in the direction of the axis  16 . The width of the grinding gap  39  lies in a range of 3 to 500 μm preferably in a range of 5 to 50 μm.

Technology Category: 7