BEAD MILL

Abstract

The utility model relates to means for grinding pasty materials, in particular paints, and can be used in the design of ball (bead) mills intended for producing paints by grinding and mixing their components. The bead mill comprises a vertical working element with coaxially mounted rubberized disks with through holes and bushings with projections, a drive shaft, and a working cylinder comprising an outer and inner shell equipped with a lining in the form of coaxially mounted individual annular elements made of a highly elastic material. The annular elements are arranged in pairs and symmetrically with the rubberized disks relative to a common diametrical plane perpendicular to the vertical axis of the working element. A cylindrical spring is installed between the drive shaft, which transmits rotation, and the vertical working element.The elasticity of the coils of a cylindrical spring is:where a is the elasticity of the coils of a cylindrical spring, N / m;π is a mathematical constant denoting the ratio of the circumference to its diameter;ν is the rotation frequency, Hz;g is the acceleration due to gravity, m / s;m is the mass of the vertical working element with rubberized disks and bushings, kg.In this case, the through holes of the rubberized disk are covered with a mesh, and each rubberized disk is equipped with four pins installed perpendicular to the plane of the disk and equidistant from each other and from the axis of rotation of the disk, the distance from the axis of rotation of the pin is determined by the expression:r=0.9⋅R,where r is the distance from the axis of rotation of the disk to the axis of rotation of the pin, m;R is the radius of the rubberized disk, m.The technical result of the proposed design of the bead mill is an increase in productivity.

Description

[0001] The utility model relates to means for grinding pasty materials, in particular paints, and can be used in the designs of ball (bead) mills intended for the production of paints by grinding and mixing their components.

[0002] A bead mill is known that contains a vertical working element with coaxially mounted rubberized disks with through holes and rubberized bushings with projections [Patent for invention of the Russian Federation No. 2283181, IPC B02C 17 / 18, published 10.09.2006].

[0003] The reasons that prevent the achievement of the specified technical result include low productivity due to high energy costs associated with achieving the required rotation frequency of the vertical working element.

[0004] A bead mill is known that contains a vertical working element with coaxially installed rubberized disks with through holes and rubberized bushings with projections, as well as a working cylinder that includes an outer and inner shell equipped with a lining in the form of coaxially installed individual ring elements made of a highly elastic material [Patent for invention of the Russian Federation No. 2302902, IPC B02C 17 / 16, published July 20, 2007].

[0005] The reasons that prevent the achievement of the specified technical result include reduced operating efficiency associated with the difficulty of ensuring a normal thermal regime for the technological process taking place in bead mills, which leads to an increase in energy costs for maintaining the optimal temperature of the pigment suspension and a decrease in the quality of the finished product.

[0006] A bead mill design is known, comprising a vertical working element with coaxially mounted rubberized disks with through holes and rubberized bushings with projections, as well as a working cylinder, including an outer and inner shell, equipped with a lining in the form of coaxially mounted individual annular elements made of a highly elastic material, wherein the annular elements and rubberized disks are arranged in pairs and symmetrically relative to a common diametrical plane, perpendicular to the vertical axis of the working element [Patent for invention of the Russian Federation No. 2371253, IPC B02C 17 / 16, published. October 27, 2009].

[0007] The reasons that prevent the achievement of the specified technical result include low productivity due to the low rotation frequency of the vertical working element, while its increase will lead to an increase in energy costs.

[0008] The closest technical solution to the proposed design of a bead mill in terms of a set of features and adopted as a prototype is a bead mill [Patent for Utility Model of the Russian Federation No. 240538, IPC B02C 17 / 16, published. 19.01.2026], comprising a vertical working element with coaxially mounted rubberized disks with through holes and bushings with projections, a drive shaft, and also a working cylinder including an outer and inner shell provided with a lining in the form of coaxially mounted individual annular elements made of a highly elastic material, which are arranged in pairs and symmetrically with rubberized disks relative to a common diametrical plane perpendicular to the vertical axis of the working element, characterized in that between the drive shaft transmitting rotation and the vertical working element a cylindrical spring is installed, the elasticity of the coils of which is:

[0009]

[0010] where is the elasticity of the coils of a cylindrical spring, N / m;

[0011] π is a mathematical constant denoting the ratio of the circumference of a circle to its diameter;

[0012] ν - rotation frequency, Hz;

[0013] g - acceleration of gravity, m / s;

[0014] m - weight of vertical working element with rubberized disks and bushings, kg;

[0015] and the hole of the ring elements is made oval with the following ratio of the length of the major and minor axes:

[0016] L / l = (1.1 ÷ 1.2),

[0017] where L is the length of the major axis of the hole of the ring element, m;

[0018] l - length of the minor axis of the ring element hole, m.

[0019] The reasons that prevent the achievement of the specified technical result include the difficulty of manufacturing oval-shaped ring elements, as well as low circular vibrations with a forced rotation frequency.

[0020] The technical result of the proposed design of the bead mill is an increase in productivity.

[0021] The technical result is achieved in that a bead mill containing a vertical working element with coaxially installed rubberized disks with through holes and bushings with projections, a drive shaft, and also a working cylinder including an outer and inner shell provided with a lining in the form of coaxially installed individual ring elements made of a highly elastic material, which are arranged in pairs and symmetrically with rubberized disks relative to a common diametrical plane perpendicular to the vertical axis of the working element, between the drive shaft transmitting rotation and the vertical working element a cylindrical spring is installed, the elasticity of the turns of which is:

[0022] (1)

[0023] where is the elasticity of the coils of a cylindrical spring, N / m;

[0024] π is a mathematical constant denoting the ratio of the circumference of a circle to its diameter;

[0025] ν - rotation frequency, Hz;

[0026] g - acceleration of gravity, m / s;

[0027] m - weight of vertical working element with rubberized disks and bushings, kg;

[0028] each rubberized disk is provided with four pins installed perpendicular to the plane of the disk and equidistant from each other and from the axis of rotation of the disk, the distance from the axis of rotation of the disk to the axis of rotation of the pin is determined by the expression:

[0029] r=0.9⋅R (2)

[0030] where r is the distance from the axis of rotation of the disk to the axis of rotation of the pin, m;

[0031] R - radius of the rubberized disk, m.

[0032] The installation of four pins on each rubber-lined disc, mounted perpendicular to the disc plane and equidistant from each other and from the disc's rotation axis. The distance from the disc's rotation axis to the pin's rotation axis is determined by expression (2), solves the problem of uniform distribution of beads throughout the bead mill's working cylinder. The velocity of bead particles in the inter-disc space is close to the circumferential velocity of the rubber-lined disc, and under the action of centrifugal force, the beads are thrown toward the walls of the working cylinder. Therefore, stagnant zones form near the vertical working element, leading to ineffective and uneven dispersion of the material being ground. When pins are installed, the beads accumulate and migrate toward the vertical working element, subsequently leading to increased grinding efficiency and increased productivity.

[0033] The choice of the ratio for calculating the distance from the axis of rotation of the disk to the axis of rotation of the pin is justified by the fact that when the value of the coefficient in expression (2) exceeds 0.9, there is an increase in the load on the pin of the rubberized disk itself, as well as the sticking of bead particles in the space between the working cylinder and the pin itself, and when the value of the coefficient in expression (2) is less than 0.9, there is an inappropriate use of the design feature, due to the impossibility of throwing beads and suspension particles to the axis of rotation of the rotor, since the accumulation of suspension particles and the beads themselves under the action of centrifugal force occurs directly near the body of the working cylinder.

[0034] Fig. 1 shows a diagram of a bead mill; Fig. 2 shows a fragment of a bead mill; Fig. 3 shows a section along A-A in Fig. 2.

[0035] The bead mill (Fig. 1) comprises a working cylinder 1 in which a vertical working element, which is a rotor 2, is installed. Rubberized disks 3 with through holes 4 and bushings 5 ​​with projections 6 are mounted coaxially with the rotor 2. A stabilizing disk 7 is installed in the lower part of the rotor 2, which does not touch the walls and bottom of the working cylinder 1. The latter is equipped with pipes 8 and 9 intended, respectively, for the inlet of cooling water and the outlet of used water through a gap 10 of the working cylinder 1. In the working cylinder 1 there is a filter sieve 11 for holding beads (not shown) and openings for feeding the initial components 12 and for draining 13 the finished product. The working cylinder 1 contains an outer 14 and an inner 15 shell made of steel. Gap 10 between shells 14 and 15 is necessary for pumping the cooling medium (water). Inner shell 15 is equipped with a lining made of a set of individual annular rubber elements 16.These annular elements 16 and rubberized disks 3 are arranged in pairs and symmetrically relative to a common diametrical plane perpendicular to the vertical axis of the working element. The height h of the annular elements 16 is (Fig. 2):

[0036] h = (0.5÷0.6)δ, (3)

[0037] where h is the height of the ring elements 16, m;

[0038] δ - installation step of rubberized disks 3, m.

[0039] At the top, rotor 2 receives rotational motion from drive shaft 17 through cylindrical spring 18, the elasticity of whose coils is determined by equation (1). This leads to circular oscillations of rotor 2, with sleeve 5, rubberized disks 3, and stabilizing disk 7, causing additional axial oscillations on cylindrical spring 18 with a forced frequency, rpm:

[0040] n=2n=2⋅ν (4)

[0041] where n is the forced rotation speed, rpm;

[0042] ν - rotation speed, rpm.

[0043] Securing the ring elements 16 to the mill body can be accomplished using various methods. A special adhesive designed for bonding rubber to metal, such as Chemosil or Leuconat, can be used for this purpose. These elements can also be placed in special ring grooves on the inner surface of the mill body (shown in Fig. 1 and Fig. 2), which facilitates their installation and removal.

[0044] On each rubberized disk 3, four pins 19 are installed, located perpendicular to the plane of the disk and equidistant from each other and from the axis of rotation of the disk, the distance from the axis of rotation of the disk 3 to the axis of rotation of the pin 19 is determined by expression (2) (Fig. 2).

[0045] The bead mill works as follows.

[0046] During the manufacturing process (e.g., paint), the required components are fed into the working cylinder 1, and rotational motion is imparted to the working element 2, which features rubberized disks 3 with pins 9 and bushings 5, from the drive shaft 17 via a coil spring 18, which also creates axial vibrations. Due to the presence of through holes 4 and projections 6 in the rubberized disks 3, particles of the bead and grinding mass are entrained in a disordered, turbulent rotational and axial motion. Due to the presence of tangential and centrifugal forces, these particles slide and strike the inner surface of the working cylinder 1 at high speed. Upon colliding with pins 19, they will be thrown, along with the total mass of beads, toward the vertical working element—rotor 2.

[0047] An example of a bead mill in operation.

[0048] The bead mill has a total mass of the vertical working element—rotor 2—with rubberized disks 3 and bushings 5, m = 33 kg. Rotor 2 receives a rotation frequency of ν = 42 Hz from drive shaft 17 through cylindrical spring 18. The elasticity of the spring coils, according to formula (1), is then:

[0049]

[0050] Forced frequency causing additional axial vibrations on the cylindrical spring 18, according to formula (4):

[0051]

[0052] Let's select a spring. A cylindrical spring with a wire diameter of 3 mm has this elasticity. Under a tensile force of F = 40 N, it deforms by ∆k = 1.1 mm per turn, i.e.:

[0053]

[0054] The pitch between the turns is 4.1 mm, the spring diameter D = 16 mm [Anuriev, V. I. Handbook of the mechanical engineer-designer: Vol. 2: In 3 volumes / V. I. Anuryev; edited by I. N. Zhestkova. - 8th ed., revised and enlarged - Mechanical Engineering, 2001. - 900 p.].

[0055] Let's determine the radius at which pins 19 are installed, positioned perpendicular to the disk plane and equidistant from each other and from the axis of rotation of disk 3, and the distance from the axis of rotation of the disk to the axis of rotation of pin (2). Let's assume the diameter of the rubberized disk itself is 300 mm, then we get:

[0056] mm,

[0057] Then, to align the dispersion of the crushed material, it is necessary to install four pins 19 on the rubberized disk 3 with a radius of 135 mm.

[0058] After all the calculated components have been installed and assembled, the feedstock is loaded through the feed port 12. Rotor 2 begins to transmit rotation through coil spring 18, with a spring stiffness of 37 N / mm, to working cylinder 1. The grinding process then begins within working cylinder 1, due to the collision of particles with beads and pins 19 on rubberized disk 3.

[0059] Example.

[0060] Let's calculate the performance of a modernized bead mill operating in an enamel production process. The annual capacity is 700 kg / h. The bead weight is 100 kg, and the bead diameter is 2 mm. The bead density (zirconium ceramic) is ZnO2 - 2.526 kg / l. The effective operating time is 2880 hours. The calculation results and comparison with a typical bead mill are summarized in Table 1.

[0061] As a result of comparative calculations, it can be concluded that with the same productivity of the bead mill, the geometric dimensions of the apparatus decrease (diameter from 0.32 m to 0.296 m, and length from 1.32 m to 1.298 m).

[0062] Thus, the installation of a cylindrical spring 18 between the rotor 2 and the drive shaft 17 with the elasticity of the turns determined by equation (1) leads to circular oscillations of the rotor 2 and causes additional axial oscillations with a forced frequency determined by equation (4).

[0063] Table 1.

[0064] Bead mill calculation results

[0065] № Name of the calculated parameter Dimension Size Preliminary calculation 1 Hourly productivity of the bead mill section kg / h 800 2 Volume of beads m3 0,040 3 Volume of paste in the container m3 0,048 5 Bead mill performance kg / h 543,677 6 Number of bead mills pcs 1 Refined calculation 7 Volume of the mixing device in the mixer m3 0,028 8 Volume of paste in the container m3 0,072 9 Bead mill performance kg / h 813,204 10 Number of bead mills pcs. 1 11 Inner diameter of the bead mill apparatus m 0,371 12 Length of bead mill m 1,298 13 Diameter of disc stirrers m 0,296 14 Disc thickness m 0,030 15 Step between stirrer disks m 0,104 16 Number of disks pcs 9 17 Actual pitch between disks m 0,103 18 Diameter of holes in disks m 0,047 19 Diameter of the center line of the holes in the disks m 0,189 20 Circumferential speed of rotation of disks rad / s 10,702 21 Rotational speed of disks rpm 11,525 22 Power consumption of the bead mill drive kW 36,840 23 Standard electric motor power kW 40,934 24 Thermal energy kW 36 25 Energy losses to the environment kW 7,200 26 The amount of heat required to heat the suspensions kW 12,151 27 Cooling water consumption kg / h 715,248 28 Average temperature for counter-current flow of coolant °C 21,640 29 Required cooling surface m2 0,769 30 Actual cooling surface m2 1,511

[0066] The installation of four pins 19 on each rubberized disk, the installation radius of which is determined by ratio (2), allows for the uniform distribution of beads throughout the working cylinder 1 of the bead mill. This will equalize the speed of bead particles within the inter-disc space of rubberized disk 3. Under the action of centrifugal force, the beads are thrown toward the walls of the working cylinder, and if sufficient beads accumulate near the walls of working cylinder 1, they will be mixed with rotor 2, leading to an increase in overall productivity and improved product quality.

Claims

A bead mill comprising a vertical working element with coaxially mounted rubber-lined disks with through holes and bushings with projections, a drive shaft, and a working cylinder including an outer and inner shell provided with a lining in the form of coaxially mounted individual ring elements made of a highly elastic material, which are arranged in pairs and symmetrically with the rubber-lined disks relative to a common diametrical plane perpendicular to the vertical axis of the working element; a cylindrical spring is installed between the drive shaft transmitting rotation and the vertical working element, the elasticity of the coils of which is: where a is the elasticity of the coils of a cylindrical spring, N / m; π is a mathematical constant denoting the ratio of the circumference of a circle to its diameter; ν - rotation frequency, Hz; g - acceleration of gravity, m / s; m - weight of the vertical working element with rubberized disks and bushings, kg; characterized in that the through holes of the rubberized disk are covered with a mesh, and each rubberized disk is equipped with four pins installed perpendicular to the plane of the disk and equidistant from each other and from the axis of rotation of the disk, the distance from the axis of rotation of the disk to the axis of rotation of the pin is determined by the expression: r=0.9⋅R, where r is the distance from the axis of rotation of the disk to the axis of rotation of the pin, m; R is the radius of the rubberized disk, m.

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