Patent Publication Number: US-6209809-B1

Title: Grinding barrels for pulverizers

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to grinding barrels for use in pulverizers and to methods of grinding material. 
     2. Description of the Related Art 
     For the purpose of assaying core samples obtained by drilling, the core samples are normally firstly broken into pieces and these pieces are then pulverized in a pulverizer. 
     More particularly, the pulverizer is provided with a grinding barrel comprising an upwardly open, dish-shaped grinding barrel body provided with a circular lid for closing the top of the grinding barrel body and a grinding disk located in the interior of the grinding barrel body. The grinding disk has a peripheral diameter which is less than the internal diameter of the grinding barrel body. 
     In use, the broken pieces or core material are placed in the interior of the grinding barrel body, together with the grinding disk, and the lid is then fitted onto the grinding barrel body. The assembly of the lid, the grinding barrel body and the grinding barrel disk are then installed in the pulverizer, which rotates the assembly with a circular motion, thus causing the grinding disk to slide around within the grinding barrel body, and the bottom of the grinding barrel, so that the material to be pulverized is crushed and pulverized between the grinding disk and the internal surface of the grinding barrel body. 
     In conventional grinding barrels, the grinding barrel body has a flat circular bottom surface, and the grinding disk has a flat circular undersurface which slides across the top surface of the bottom of the grinding barrel body. Consequently, the material is pulverized mainly between the peripheral surface of the grinding disk and the annular wall of the grinding barrel body. 
     SUMMARY OF THE INVENTION 
     According to the present invention, there is provided a grinding barrel which has a grinding barrel body formed with an annular peripheral wall and a bottom wall, the annular peripheral wall defining an open top, and grinding barrel lid for closing the open top. The grinding barrel body contains a grinding disk, and an undersurface of the grinding disk, and an upper surface of a bottom of the grinding barrel body, are formed with mutually interengaged recessed and protruding portions. 
     Preferably, the grinding disk and the grinding barrel body are dimensioned so that the disk is displaceable across the upper surface to the peripheral wall of the grinding barrel body at any side of the grinding barrel, and so that the recessed and protruding surface portions are then brought together at an opposite side of the grinding barrel. Consequently, the material is ground between the disk and the barrel both at the periphery of the disk and an internal surface of the peripheral wall and, also, between the recessed and surface portions of the disk and the bottom wall of the grinding barrel body. 
     In a preferred embodiment of the present invention, the recessed and protruding surface portions comprise a central convexly curved protruding portion of the upper surface of the bottom wall of the grinding barrel body and a central, concavely curved recessed portion of the undersurface of the grinding disk. 
     Also according to the present invention, a method of grinding material in a grinding barrel between a grinding barrel body and a grinding disk within the grinding barrel comprises oscillating the grinding barrel body to displace the grinding disk across the grinding barrel body and thereby grinding the material simultaneously between a peripheral portion of the grinding disk and the grinding barrel body and also between a recess in a central portion of the underside of the grinding disk and a raised central portion of a bottom wall of the grinding barrel body protruding loosely into the recess. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be more readily apparent from the following description of embodiments that are given, by way of example, with reference to the accompanying drawings, in which: 
     FIG. 1 shows a view in perspective of a pulverizer; 
     FIGS. 2 and 3 show views taken in vertical cross-section through a grinding barrel according to a first embodiment of the invention; 
     FIGS. 4 and 5 show a plan view and a view in vertical cross-section, respectively, of a grinding disk forming part of the grinding barrel of FIGS. 2 and 3; 
     FIG. 6 shows a view taken in vertical cross-section through a first modification of the grinding barrel of FIGS. 2 and 3; 
     FIG. 7 shows a plan view of a modification of the grinding disk of FIGS. 2 through 5; 
     FIG. 8 shows a plan view of a further modification of the grinding disk of FIGS. 2 through 5; 
     FIG. 9 shows a view taken in cross-section along the line  9 — 9  of FIG. 8; 
     FIGS. 10 and 11 show a plan view, and a view in vertical cross-section, respectively, of a still further modification of the grinding disk of FIGS. 2 through 5; and 
     FIGS. 12 and 13 show views taken in vertical cross-section through a yet further modification of the grinding barrel of FIG.  1 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     In FIG. 1 of the accompanying drawings, there is shown a pulverizer indicated generally by reference numeral  10 . The pulverizer  10  has a housing  11  provided, at its top, a lid  12  which is shown in an open position in FIG. 1 so as to reveal, within the pulverizer  10 , a clamp  14 , which is shown clamping a grinding barrel, indicated generally by reference numeral  16 . The front of the housing  11  includes an access door  15 . Also, the grinding barrel  16  is a conventional grinding barrel having a flat bottomed, cylindrical shape and containing a flat bottomed circular grinding disk (not shown). On energization of the motor of the pulverizer  10 , the clamp  14  and therewith the grinding barrel  16  are oscillated to displace the grinding disk so as to grind material between the grinding disk and the interior surface of the grinding barrel in a manner well know to those skilled in the art. 
     As will be familiar to those skilled in the art, the pulverizer  10  contains an electric motor (not shown) which is employed to oscillate the grinding barrel  16  for the purpose of pulverizing and/or mixing materials contained with the grinding barrel  16 . 
     In FIGS. 2 and 3 of the accompanying drawings, reference numeral  20  indicates generally a grinding barrel  20  according to the present invention for use in the pulverizer  10  in place of the prior art grinding barrel  16 . 
     More particularly, as shown in FIGS. 2 and 3 the grinding barrel  20  comprises a grinding barrel body  22  which is of upwardly-open dish-shaped configuration with a cylindrical peripheral wall  24  extending upwardly from a bottom wall  26 . The bottom wall  26  is provided with a downwardly projecting annular flange  28  forming a support for the grinding barrel  20 . 
     The top of the grinding barrel body  22  is closed by a circular lid  30 , which is sealed to the top of the peripheral wall  24  by a sealing ring  31  recessed n the lid  30 . The grinding barrel body  22  and the lid  30  together define a hollow interior  32 , which contains a grinding disk indicated generally by reference numeral  34 . 
     The bottom wall  26  of the grinding barrel body  22  has, at its uppermost face, an upper surface indicated generally by reference numeral  36 , which comprises a central, convexly curved upwardly protruding or raised surface portion  38 , on an upwardly protruding central portion of the bottom wall  26 , and an annular surface portion  40  extending around and merging smoothly with the central portion  38 . The annular surface portion extends to a frusto-conical surface  42  which, in turn, extends to a cylindrical inner surface  44  of the peripheral wall  24  of the grinding barrel body  22 . 
     The grinding disk  34 , which is radially outwardly displaceable by sliding over the bottom wall  26  to the peripheral wall  24 , is also of upwardly-open dish-shaped configuration, and has a peripheral wall  46  extending upwardly from a bottom  48 . The bottom  48  of the grinding disk  34  has, at its lowermost face opposed to the uppermost face of the bottom wall  26 , an undersurface, indicated generally by reference numeral  50 , which comprises a central, concavely curved, downwardly facing recessed surface portion  52  forming a recess or downwardly facing recessed portion of the grinding disk  34  and an annular surface portion  54 , on a downwardly facing annular portion of the grinding disk  34 , extending around and merging smoothly with the central surface portion  52 . The annular surface portion  54  extends to a frusto-conical surface  56  which, in turn, extends to a cylindrical outer peripheral surface  58 . 
     The peripheral surface  58  of the grinding disk  34  has an outer diameter which is less than the diameter of the inner surface  44  of the cylindrical peripheral wall  24  of the grinding barrel body  22 . 
     The annular surface portion  40  of the surface  36 , the frusto-conical surface  42  and the inner surface  44  of the grinding barrel body  22  together form an outer or first annular grinding surface which has a concave cross-sectional shape complementary to that of a first or outer annular grinding surface formed on the grinding disk  34  by the annular surface portion  58  of the undersurface  50 , the frusto-conical surface  56  and the peripheral surface  58 . 
     The convex central surface portion  38  forms, on the protruding central portion of the bottom wall  26 , an inner or second grinding surface which has a cross-sectional shape complementary to an inner or second grinding surface formed by the recessed central surface portion  52  on the recessed portion of the grinding disk  34 . 
     In a rest position, in which it is shown in FIG. 1, and which corresponds to the state of the grinding barrel  20  when the pulverizer  10  is switched off, the grinding disk  34  is disposed centrally with respect to the grinding barrel body  22  and these two components are dimensioned so that a gap  60  is provided between the grinding disk  34  and the grinding barrel body  22  around the entire periphery of the grinding disk  34 , and a further gap  62  is provided between the central raised and recessed surface portions  38  and  52 . The raised central portion  38  therefore fits loosely into the recessed central portion  52 . 
     When the grinding barrel  20  is in use, and is being oscillated in the pulverizer, the grinding disk  34  is displaced by centrifugal force towards the position, relative to the grinding barrel body  22 , in which it is illustrated in FIG.  3 . Consequently, at the right hand side of the grinding disk  34 , as illustrated in FIG. 3, the grinding disk  34  fits snugly against the grinding disk body  22  along a line of contact. 
     Furthermore, at the side of the grinding disk  34  remote from this side, the outer annular grinding surfaces of the central raised and recessed portions  38  and  52 , also interfit snugly along a line of contact with one another. 
     Therefore, when the grinding barrel  20  is in use, the material to be pulverized is ground between the outer grinding surfaces and also, simultaneously, between the inner grinding surfaces. 
     The grinding disk  34  is also provided with through openings  64 , which are equiangularly distributed about the center of the disk  34 , to allow the material to be ground to flow through the grinding disk  34  during the grinding operation. As seen in FIG. 4, in the present embodiment four of these through openings  64  are provided in the grinding disk  34 . These through openings  64  are of vertical cylindrical shape. 
     Various modifications may be made to the above-described embodiment of the present invention. For example, the central raised portion  38  as illustrated in FIGS. 2 and 3 has a smoothly convexly curved crown  66 . In a modification of the grinding disk  34  indicated generally by reference numeral  34   a  in FIG. 6, the smoothly curved crown  66  is replaced by a flat circular crown  66 . By comparison of FIGS. 2,  3  and  5 , on one hand, and FIG. 6, on the other hand, it will be seen that the shape, including the thickness of the bottom  26  of the grinding barrel body indicated generally by reference numeral  20   a  in FIG. 6 has been modified from that of the bottom  48  shown in FIGS. 2,  3  and  5 . Likewise, in FIG. 6 there is shown a grinding disk  34   a  which is similar to the grinding disk  34  of FIGS. 2 through 5 but has a somewhat greater thickness. 
     While the grinding disk  34  as shown in FIG. 4 is provided with four through openings  64 , it is to be understood that the number of these through openings  64  may be varied and, by way of example, FIG. 7 shows a modified grinding disk  34   b  provided with six through openings  64   b.    
     Furthermore, while the shapes of the through openings  64  shown in FIGS. 2 through 5 are cylindrical, the invention is not restricted to this shape and, as shown by way of example in FIGS. 8 and 9, which show a modified grinding disk indicated generally by reference numeral  34   c , the cylindrical through openings  64  and  64   b  may be replaced by through openings  64   c  each having a frusto-conical upper portion  70  and a cylindrical lower portion  72 . It will also be observed that the grinding disk  34   c  shown in FIGS. 7 and 8 is provided with only three through openings  64   c.    
     FIGS. 10 and 11 show a still further modification of the grinding disk, indicated generally by reference numeral  34   d . This grinding disk  34   d  has four through openings  64   d  which are defined by upwardly convergent frusto-conical surfaces  74 . 
     In FIGS. 12 and 13, there is shown a grinding barrel, indicated generally by reference numeral  20   e , comprising a grinding barrel body  22   e  provided with a lid  30   e  similar to the lid  30  of FIG.  1  and also containing a grinding disk, indicated generally by reference numeral  34   e , in which the center of the underside of the grinding disk  34   e  is downwardly convex and the center of the upper surface of the bottom of the grinding barrel body  22   e  is upwardly concave. 
     More particularly, the grinding barrel body  22   e  has a peripheral wall  24   e  and a bottom wall  38   e , which has a central, convexly curved, upwardly facing, recessed surface portion  38   e.    
     The grinding disk  34   e  has a peripheral wall  46   e  and a bottom  48   e , which is formed, at its lowermost face or undersurface opposed to the uppermost surface of the bottom wall  38   e , with a central, convexly curved, downwardly facing protruding surface portion  52   e  forming a downwardly protruding portion of the bottom  48   e . The undersurface of the bottom  48   e  also includes an annular surface portion  54   e  of ogival cross-section extending around and merging smoothly with the central surface portion  52   e.    
     As shown in FIG. 12, when the grinding disk  34   e  is displaced radially to bring the peripheral wall  46   e  of the grinding disk  34   e  against the peripheral wall  24   e  of the grinding barrel body  22   e , the grinding disk  34   e  and the grinding barrel body  22   e  interfit snugly along a line of contact extending across one side of each of the central surface portions  38   e  and  52   e  and also across the annular surface portion  54   e  and part of the peripheral wall  46   e  of the grinding disk  34   e.    
     As will be apparent to those skilled in the art, various other modifications may be made within the scope of the appended claims.