Grinding body separator in mills for triturating and breaking up solids dispersed in liquids

Abstract: Grinding body separator in mills for triturating and breaking up solids predispersed in liquids, which has a truncated cone-shaped stepped support (24), the major base (29) of which has a flange (32) for mounting in the mill and on the steps of which are fitted respective circular rings (25), provided with transverse orifices and which are superposed on one another leaving an outer separation smaller than the smallest thickness of the grinding bodies and an inner separation greater than the former, the assembly of rings being secured by a disk (49), which itself is secured to the minor base (30) of the support and which delimits an outer separation, relative to the smallest ring, equal to that between the superposed rings.

Description: The present invention relates to a grinding body separator in mills for triturating and brewing up solids predispersed in liquids, as set forth in the preamble of claim 1. A separator of this kind is known from FR-A-2 358 928. Known are mills, normally with horizontal shaft and cooled, for products consisting of solids predispersed in liquids of different viscosity, which mills comprise grinding bodies, for example balls, which enter the grinding chamber through the inlet mouth for the product to be treated or through a mouth provided for that purpose; normally the grinding bodies are extracted through an outlet in the bottom of said chamber, which is provided with a double wall for cooling or heating. Said known mills may include a circulation pump for the cooling or heating liquid, and have a shaft on which interchangeable agitation disks are mounted at predetermined spacings to each other, said shaft being driven by a motor via a proper transmission and optionally speed control, and have also a pump, with flow regulator, which impels the product to be treated for its forced and continuous passage through the grinding chamber. Known also are mills, both with horizontal or vertical shaft, with a cylindrical fixed element or stator and a cylindrical rotating element or rotor disposed within the stator, the grinding chamber being formed between the rotor and the cylindrical inner wall of said stator. In those mills the grinding bodies are returned to the grinding chamber through passages, having also at least a cooling chamber in the stator and in some embodiments in the rotor. Also, mills are known like those described before, but in which the grinding chamber is defined by two coaxial cylindrical walls provided with radial lugs and between which a cylindrical jar-shaped rotor is disposed, also provided with lugs on its two parallel surfaces opposite said two walls. In addition, there are known mills with horizontal or vertical shaft, provided with at least one fixed element or stator formed as an annular double cone and with at least one rotor also formed as an annular double cone and introduced in said stator, that is, the rotor has the form of a circular ring of triangular cross section and is introduced into a circular channel of the stator, which is of the same cross sectional shape but somewhat larger; in fact, the configuration of said stators and rotors is that of a torus of substantially triangular, cross section, possibly of a double triangle or other similar form, both for the stator and for the rotor, the transverse section of the latter being inscribed in the interior of that of the stator and leaving therebetween a perimetric space which constitutes the grinding chamber in which the product circulates and in which the balls are enclosed which circulate along a closed path, by means of a return passage of said balls to the beginning of their path. Also the configuration of the rotors in these mills is, sometimes, that of a "disk" of triangular section of revolution with a vertex, normally the most acute, in its peripheral part and, in this case, more than one of such disks can be disposed parallel to each other and transversely to the shaft of the mill, forming a plurality of grinding chambers connected in series or in parallel with respect to the circuit to be followed by the product in treatment. Lastly there are known mills of the type described, formed by one or more plates, which have passages for the recirculation of the balls or grinding bodies in closed circuit, and each of said plates are disposed inside a hollow body or stator of corresponding configuration, so that between each plate or rotor and its stator a grinding chamber is defined more or less in labyrinth form, and each chamber communicates with the next one to cause a circulation of the product in treatment, all plates being actuated by a single shaft. In these known mills there is always a strainer or separator for retaining the grinding bodies inside the grinding chamber, but permitting the passage of the ground product only; such strainers consist of a sieve, eventually rotating with the shaft or being static and fastened to the grinding chamber in the outlet zone of the treated product. There are also mills in which the strainer or separator of the grinding bodies consists of the so-called "gap", defined by a kind of washer of special material fastened transversely on the mill shaft, said washer being disposed at a certain adjustable distance from another washer fastened to the corresponding wall of the grinding chamber and opposite thereto, leaving therebetween a peripheral clearance smaller than the smallest diameter of the grinding bodies, to retain same inside said grinding chamber, but letting the ground product pass as it is being treated in the mill. The grinding bodies may consist of small balls or of other suitable geometric forms and may be of metal, including various alloys, ceramics, glass, etc., but they must always be resistant to wear and to the stresses deriving from the grinding treatment of the respective products to be ground. As has been stated, the grinding bodies may be balls, but no limitation to spherical bodies is intended, but rather bodies of various configurations are included, able to triturate the solid particles of the products to be ground, by impacts and friction between themselves and with the limiting surfaces of the grinding chamber, and said grinding bodies must have dimensions which are a function of the final fineness desired for the solid components of the product to be ground. In general, these mills are used for the treatment of dyes, paints, pesticides or other chemical products, pharmaceutics, foods, cosmetics, electronic products, etc.; having application in the chemical industry in general and, in particular, in the industry of dyes and paints, printing inks, pigments and coatings, paper industry, for grinding the charges to be used in pulps for making paper and other products such as copy paper, in biochemical industries, in the food industry for innumerable products, such as chocolate products, in the electronic industry for coatings of magnetic tapes and of semiconductor products, and in the pharmaceutical and cosmetic industry. In some of the known types of mills described before, the product to be treated circulates through the grinding chamber in a forced and continuous manner, normally impelled by a pump of variable and adjustable flow rate disposed at or near the entrance of the mill. Lastly it is known also that the grinding bodies exert, in these mills, impact and friction streses on the solid particles of the product in treatment, in that innumerable contacts occur between said grinding bodies and the solid particles of the product in treatment. And the grinding bodies occupy a part of the volume of the grinding chamber which is variable and depends on the characteristics of the product to be treated, but the portion of the total volume of said chamber normally occupied by the grinding bodies ranges between 50% and 80%. The materials of which the separators are made must be wear resistant, and often their working surfaces are given hardening treatments. The sieve type separators generally do not allow a very fine adjustment for microballs and produce clogging, being also relatively difficult to clean, hence requiring relatively much labor, and in case of wear they must be replaced, as repair is not economical. Gap type separators involve a certain amount of wear as they have one part movable relative to the other, with relatively complicated disassembly and reassembly as the shaft and other parts of the mill must be disassembled for cleaning, overhaul or replacement. It is the object of the invention to provide a grinding body separator in mills for triturating and breaking up solids predispersed in liquids which eliminates the mentioned disadvantages of the separators of the known mills and permits a fine adjustment for microballs or the like, is easy to clean, simple to install and to disassemble, allows them to be reused as they can be corrected mechanically, requires less treatment time of the products to be ground, has greater efficiency and takes up less space, as well as provides a finer and more uniform finished product more homogeneous in the distribution and size of the solids dispersed in respective liquids, after they have been treated and have passed through the separator in question, and reduces the probability of any clogging or stopping up of the ground product in its passage through the separator. This object is attained by the features of claim 1. Preferred embodiments are subject matter of the dependent claims. The invention is now further explained with reference to the accompanying drawings. In the drawings: Figures 1A and 1B show a view along a longitudinal vertical section of a mill for triturating and breaking up solids predispersed in liquids, which comprises a separator according to the invention; Figure 2 is a front end view of the support of the separator; Figure 3 corresponds to the section III-III of figure 2; Figure 4 represents one of the rings mounted on the support, in an elevation of its rear part, and Figure 5 corresponds to the section V-V of figure 4. As represented in the drawings and specifically in figures 1A and 1B, the grading body separator (1) applies to mills for triturating and breaking up solids predispersed in liquids, such as the one represented in said figures, in this example for a mill which is the invention of the same applicant and which is the subject of European Patent Application No. 91109307.8, published as EP-A-0 483 453, although the separator described in this example could be applied to any other mill of the type which comprises a frame (not shown) on which a stator (2) is mounted, with a jacket (3) for cooling and, if and when applicable, for heating the product in treatment, and having inside the stator a rotor (4) fastened to a shaft (5) disposed along the longitudinal axis of the mill and mounted overhanging on respective supporting and bearing means (6), attached to the frame of the mill, and whose shaft has internal lines (7) for a rotor cooling or heating fluid. The shaft (5) is rotated by driving means and through respective conventional transmission and speed variation means (not shown) attached to the frame. Between said stator (2) and rotor (4) a grinding chamber (8) is defined, in which the grinding bodies initially introduced into said chamber through a closeable inlet (9) of the stator are contained. In the lower part of the stator (2) is an outlet (10), also closeable, for said grinding bodies, and the grinding chamber (8) is traversed by the product in treatment - while the rotor rotates - by conventional means (not shown) impelling said product, which are moved by drive means and through conventional transmission and speed variation means (not shown). The stator (2) has an inlet conduit (11) for the product to be treated, communicating with the exit of the product impulsion means and an outlet conduit (12) for the ground product, in whose exit zone the separator (1) is arranged which prevents the grinding bodies from leaving but lets the ground product pass. Between the stator (2) and the shaft (5) seal means are provided, such as joints (13) and (14), to prevent leakage of the product which circulates continuously and forcedly through the grinding chamber (8). The jacket (3), which may be made of two parts as in the example illustrated, has inlet lines (15), (16) and (17) for a cooling or heating fluid - the latter does not fully appear in figure 1A because of its position but part of its mouth leading to a cooling chamber (18) of the outlet conduit (12) of the ground product can be seen - and outlet conduits (19) and (20), all of which connect with the respective cooling or heating systems. Likewise, the rotor (4) may be cooled or heated by pipes such as pipe (21), which feed the cooling or heating liquid into the interior of the rotor, the liquid returning through conduits such as (22); the pipes and conduits are connected to the respective internal lines (7) of shaft (5), which internal lines lead to the outside in a rotating coupling device (23) of shaft (5) connected to the cooling or heating system. The geometric axis of the type of mill described and illustrated is horizontal but could be vertical. We shall call "front" the part of the separator corresponding to the part of the mill situated more toward the exterior thereof with the outlet of the ground product, and "rear" the opposite part of the mill, that is, the one in contact with the grinding bodies. The separator (1) is composed of a support (24) (figures 1A, 2 and 3) and a series of rings such as (25) (figures 1A, 4 and 5), which may consist of a variable number of rings, four in the example. The support (24) is stepped and preferably hollow; its ideal geometric envelope is a truncated cone and its steps consist of a series of circular rims (27) superposed along parallel planes, normal to the longitudinal axis (28) of the separator and of decreasing diameter from the major base (29) of the support to its free end or minor base (30). Said series of circular rims alternates with another series of short superposed circular cylinders (31), whose centers are disposed in said longitudinal axis (28) and whose diameters are also decreasing in coordination with the respective diameters of said rims (27). The major base (29) has a flange (32) and seal means for its installation in the respective mill, such as joint (33) (figure 1A) disposed in a circular groove (34) (figure 3), said installation being made in the exit zone of the ground product comprising a longitudinal passage (35) which opens into the outlet conduit (12) of the ground product. The stepped support (24) is fastened to the front part of the stator (2) by screws (36) which traversed orifices (37) in the flange (32) of the support (24), so that said flange (32) is on the outside of the mill while the rest of the support (24), together with its rings (25), are disposed toward the interior of the grinding chamber ( 8), as is seen in figure 1A. Obviously other joints may, in some cases and must in others, be provided to assure watertightness between the support (24) of the separator (1) and the stator (2), as well as between the passage (35) of the support and the outlet conduit (12) of the ground product, and also in relation to the cooling chamber (18). Finally, in this example there are orifices such as (38) which connect the cooling chamber (18) and the cooling chamber or chambers defined between the jackets (3) and the body of the stator (2). The mounting of the described separator (1) facilitates its disassembly without having to disassemble, in turn, the stator or the front part thereof. The separator (1) is completed with a series of circular rings (25) of decreasing diameters from the major base (29) of the support (24) to the free end or minor base (30) of the latter, each of said rings being made up of an inner collar (39) and an outer collar (40) (figures 4 and 5), both of square cross section and interconnected by bridges such as (41), the latter defining, together with said two collars, respective transverse orifices or passages such as (42). Each ring (25) fits on a respective step (26), for which the inside diameter (d3 of its inner collar (39) matches, with the necessary fit, the outside diameter of the circular cylinder (31) of the step (26) on which it is mounted. The outside diameter (D) of the outer collar (40) of each of the rings that follow the largest of them coincides with the inside diameter (d1) of the outer collar (40) of the ring (25) on which it is juxtaposed, with the thickness (a) - measured in the direction of the longitudinal axis (28) of the support (24) of the separator (1) - of the inner collar (39) of a ring (25) being somewhat greater than the thickness (b) of its outer collar (40), thus causing a separation (c) between each pair of juxtaposed rings - in the direction of the coincident transverse axis (43) of the rings (25), which coincides with the axis (28) of the support (24) - which is smaller than the smallest of the thicknesses or diameters of the grinding bodies to be retained in the grinding chamber (8). It should be pointed out that the separation (c) between each pair of rings juxtaposed in the manner described coincides exactly with the difference between the thicknesses (a) and (b) of a same ring (figure 5), that is to say, c = a-b, the juxtaposed mounting of the rings being seen in figure 1A. The outer collar (40) of each of the rings that follow the largest of them defines a space, relative to the inner collar (39) of the ring (of greatest diameter D) on which it is juxtaposed, which is greater than said separation (c) between each pair of rings, that is to say, the inside diameter (d1) of the outer collar (40) of the ring of smaller diameter, which is juxtaposed to the following ring of greater diameter (see figure 1A) is greater than the outside diameter (d2) of the inner collar of said ring of greater diameter, establishing or defining between both rings and in this part thereof a circular separation which is greater than said also circular separation (c). Preferably but not necessarily, there is removably fastened on the major base (29) of the stepped support (24) a first circular collar (44) (figure 1A) of square cross section and of greater outside diameter than the diameter (D) of the largest ring (25) of the series of rings, the inside diameter of said first collar coinciding with the outside diameter (D) of the outer collar (40) of said largest ring. Again preferably but not necessarily, there is provided in coplanar and coaxial arrangement with said first circular collar (44) a second collar (45) similar to the first but of smaller diameter, which is practically equal to the inner collar (39) of the larger ring to which it is juxtaposed, the thickness of said second collar - in axial direction - being somewhat greater than the thickness of the outer collar (40) of said largest ring, thus forming between them a separation - in axial direction - which is smaller than the smallest thickness or diameter of the grinding bodies. Between the first and second circular collars a kind of circular channel (46) is defined for the passage of the ground product toward the exit of the mill, which channel communicates with the longitudinal orifice or passage (35) that traverses the flange (32) of the support (24); and it should be pointed out that there may be more than one such longitudinal orifices (35), as needed in the operation of the mill. The first collar (44) is removably fastened to the support (24) by screws (47) which are screwed into threaded holes (48) (figures 2 and 3) of the support; and the assembly composed of the series of rings (25) and the second collar (45) is retained and immobilized by a disk (49) which is applied against the smallest ring and is removably fastened, (for example by a central screw), on the minor base (30) of the stepped support (24) of the separator (1), the outside diameter of said disk being equal to the inside diameter (d1) of the outer collar (40) of said smallest ring, while between the peripheral edge of this disk (49) and the opposite edge of said outer collar of the smallest ring a separation is defined equal to the separation (c) between each pair of juxtaposed rings. The section of the passages for retention of the grinding bodies, defined by the separations between the juxtaposed rings and as described before, is smaller than the section of the rest of the internal passages, thereby reducing the probability of any clogging or stopping up of the ground product occurring in this part of the separator.

Claims: Grinding body separator in mills for triturating and breaking up solids predispersed in liquids, of the type which comprises a frame on which is mounted a fixed element or stator (2), a jacket (3) conducting a cooling or heating liquid, said stator (2) enclosing a rotor (4) fastened to a shaft (5) disposed along the longitudinal axis of the mill and mounted overhanging on respective supporting and bearing means (6) attached to the frame of the mill, which shaft (5) has internal conduits (7) for rotor cooling or heating media and is rotatable by drive means through transmission and speed variation means attached to the frame, a grinding chamber (8) being defined between said stator (2) and rotor (4), in which grinding bodies are enclosed which are initially introduced into said grinding chamber (8) through a closeable entrance (9) of the stator (2), and in whose lower part a likewise closeable outlet (10) for their evacuation is located, the grinding chamber (8) being traversed by the product in treatment while rotating the rotor (4), the stator (2) having an entrance (11) of the product to be treated, and an exit (12) of the ground product, in the exit zone of which are disposed separator means (1) which prevent the grinding bodies from leaving the mill but let the ground product pass, seal means (13, 14) being disposed between the stator (2) and the shaft (5) to prevent leakage of the product which circulates continuously and forcedly through the grinding chamber (8); characterized in that it presents a stepped support (24) whose ideal geometric envelope is a truncated cone, whose steps are formed by a series of circular rims (27) superposed along parallel planes, normal to the longitudinal axis (28) of the separator (1) and of diameters decreasing from the major base (29) of the support (24) to its free end (30), which series alternates with another series of short circular superposed cylinders (31), whose centers are disposed in said longitudinal axis (28) of the separator (1) and whose diameters are also decreasing in coordination with the respective diameters of said rims (27), the major base (29) of the support (24) comprising a flange (32) and seal means (33) for its installation in the respective mill in the exit zone of the ground product; that it presents a series of circular rings (25) of diameters decreasing from the major base (29) of the support to its free end (30), each of them made up of an inner collar (39) and an outer collar (40), both of square cross section and interconnected by bridges (41) which define respective transverse orifices (42), each ring (25) fitting on a respective step (26), for which purpose the inside diameter (d3) of its inner collar (39) matches the outside diameter of the circular cylinder (31) of the step (26) on which it is mounted; that the outside diameter (D) of the outer collar (40) of each of the rings (25) that follow the largest of them coincides with the inside diameter (d1) of the outer collar (40) of the ring (25) on which it is juxtaposed, and the thickness (a) - measured in the direction of the longitudinal axis (28) of the separator (1) - of the inner collar (39) of a ring (25) is somewhat larger than that (b) of its outer collar (40), causing a separation (c) between each pair of juxtaposed rings (25) - in axial direction - which is smaller than the smallest thickness or diameter of the grinding bodies to be retained in the grinding chamber (8); and that the outer collar (40) of each of the rings (25) which follow the largest of them delimits a space, relative to the inner collar (39) of the ring (25) on which it is juxtaposed, which is greater than said separation (c) between each pair of rings (25). A grinding body separator as set forth in claim 1, wherein a first circular collar (44) is removably fastened on the major base (29) of the support (24), said first circular collar (44) being of square cross section and of an outside diameter greater than that (D) of the largest of the series of rings (25) and whose inside diameter coincides with the outside diameter (D) of the outer collar (40) of the largest ring (25). A grinding body separator as set forth in claim 2, wherein in coplanar and coaxial arrangement with said first circular collar (44), a second circular collar (45) similar to the first (44) but smaller and practically equal to the inner collar (39) of the largest ring (25) to which it is juxtaposed, the thickness of said second circular collar (45) - in axial direction - being somewhat greater than that (b) of the outer collar (40) of said largest ring (25), causing a separation - in axial direction - between the two smaller than the smallest thickness or diameter of the grinding bodies, defining between said first and second circular collars (44, 45) a kind of channel (46) for the passage of the ground product toward the exit of the mill, through at least one longitudinal orifice (35) in the flange (32) of the support (24). A grinding body separator a set forth in claim 3, wherein the assembly composed of the series of rings (25) and the second circular collar (45) is retained and immobilized by means of a disk (49) applied against the smallest ring (25) and removably fastened on the minor base (30) of the stepped support (24) of the separator (1), the outside diameter of said disk (49) being equal to the inside diameter (d₁) of the outer collar (40) of the smallest ring (25), and between the peripheral edge of this disk (49) and the opposite edge of said outer collar (40) of the smallest ring (25) a separation is defined equal to that (c) between each pair of juxtaposed rings (25).

Inventors: OLIVER PUJOL CARLOS, OLIVER PUJOL, CARLOS
Applicants: OLIVER & BATTLE SA, OLIVER Y BATLLE S.A.
Application year: 1991
Main classification: B02C17
IPC codes: B02C17