RU2792885C1 - Ball-and-race mill - Google Patents

Abstract

FIELD: material grinding.

SUBSTANCE: ball-and-race mill containing two fixed interconnected hollow halves with a loading opening and a grinding device installed in the cavity between the halves, which is provided with an internal through cavity formed by through holes made in coaxially mounted rotating upper and lower rotors connected to each other by pins with the possibility of limited vertical oscillation relative to each other due to the spring elements installed between them. The upper half is provided with an annular groove with balls placed in it with the possibility of movement and rotation, pressed against the reciprocal annular groove of the upper rotor. The lower rotor is made with an eccentric groove, in which balls are placed with the possibility of rotation and sliding along it, installed in the cells of the hoop pressed against the lower rotor by the inner end surface of the lower half. In the lower part of the lower rotor, through radial holes are made, opened to the internal through cavity, which at the inlet is equipped with a filter connected to the lower rotor, and at the outlet through a branch pipe fixed to the upper rotor, it is hermetically connected to the impeller housing, equipped with an exhaust pipe with installed filter and a container for receiving microparticles. In the lower half there is a hole for the output of product residues.

EFFECT: increasing the productivity.

2 cl, 6 dwg

Description

The invention relates to devices for grinding materials and can be used in construction, paint, chemical, pharmaceutical, mining and other industries.

Known nano-ball mill, which consists of a grinding drum and a horizontal rotating rotor; the material separator is placed between the grinding rotor and the grinding cylinder; a grinding cavity is formed in the inner side of the separator (CN203750625, IPC B02C 17/18, publ. 08/06/2014).

The disadvantage is that the horizontal layout of the mill leads to a large area of occupied space and to a decrease in the quality of grinding, since the material under the weight settles in the lower part of the mill, which leads to low productivity.

A well-known ring-type vertical bead mill for pigment dispersion, which can use a dispersion medium with a very small particle size without causing the problem of clogging the medium, and for which the washing time can be shortened (JP2006000751, IPC B01F3/18; B01F5/10; B01F7/00 ; B01F7/16; B01F7/18; B04B3/00; C09D17/00, published 01/05/2006).

The disadvantage is that this mill is only effective if the material to be ground is properly prepared, i.e. pre-crushed to the proper size.

Colloidal mills are widely known, for example, a separate type mill with three-stage crushing (CN203281268, IPC B01F13/10; B02C7/08; B02C7/12; B02C7/16, publ. 11/13/2013, CN103736550, IPC B02C7/04; B02C7/11; B02C7/17, published 04/23/2014 and others).

Their common disadvantage is that the grinding of materials occurs between the stator and the rotor, which leads to their rapid wear.

The disadvantage of such mills is also the lack of a clear ratio of balls of different sizes in the mass of the ball load, which does not provide maximum productivity and high quality of the resulting commercial products (this problem is described in detail in RF patent No. 2121876 dated 20.11.98).

Known vertical ball mill, consisting of a drive, a tank with a jacket, a frame, loading and unloading devices, a pumping unit and a shaft with blades located on it along a helical line at an angle to each other. The blades are made in the form of rods with a constant cross section, with balls fixed on them with a constant pitch, the diameter of which decreases in the radial direction when approaching the axis of rotation of the shaft, and the distance between the balls is not less than the arithmetic mean value of the ball diameters on the blade. When the blade interacts with the balls in a plane perpendicular to the axis of the blade, there is a force applied to the blade from the side of the ball. Since the upper blades forming the working surface are inclined at some angle to the horizontal, an axial force arises that pushes the balls to the tank wall and to the agitator shaft.

This increases the force of interaction between the balls in both the upper and lower horizontal layers. An increase in the relative slip of the balls with a simultaneous increase in the effort of their interaction significantly increases the productivity of a ball vertical mill per unit volume of its tank and the degree of grinding of the initial product (see - AS USSR No. 354892 of 08/24/1970).

The disadvantage is the complexity of the device and the unreliability of obtaining a product of the required size.

During the patent search, the prototype was not identified.

The technical problem solved by the invention is to ensure the production of a product of a size close to nano-size, of stable quality from a material of a sufficiently large initial fraction without its preliminary preparation.

The technical result of using all the essential features of the invention is to increase productivity while ensuring high-quality grinding.

The technical result is achieved due to the fact that a vertical ball mill has been developed, containing two fixed interconnected hollow half-shells with a loading hole and a grinding device installed in the cavity between the half-shells, connected to an electric drive equipped with a frequency controller, the grinding device is equipped with an internal through cavity formed through holes made in coaxially mounted rotating upper and lower rotors, interconnected by pins with the possibility of limited vertical oscillation relative to each other due to spring elements installed between them; the upper semi-body is provided with an annular groove with balls placed in it with the possibility of movement and rotation, pressed against the reciprocal annular groove of the upper rotor; the lower rotor is made with an eccentric groove, in which balls are placed with the possibility of rotation and sliding along it, installed in the cells of the hoop, pressed against the lower rotor by the inner end surface of the lower half-body; in the lower part of the lower rotor, through radial holes are made, open into the internal through cavity, which at the inlet is equipped with a filter connected to the lower rotor, and at the outlet through a branch pipe fixed to the upper rotor, it is hermetically connected to the impeller housing, equipped with an exhaust pipe with installed in it with a filter and a container for receiving microparticles, while in the lower semi-body there is a hole for the output of product residues.

The upper and lower half-shells are provided with cooling circuits made in the form of tubes with refrigerant wrapped around the outer walls of the shells.

The presence in the vertical ball mill of two motionless interconnected hollow half-shells with a feed opening and a grinding device installed in the cavity between the half-shells, connected to an electric drive equipped with a frequency controller, makes it possible to grind the material loaded through the feed opening.

The presence of a frequency controller of the electric drive allows you to change the frequency of rotation of the rotors of the grinding device during the grinding process, causing vibration of the balls that provide grinding, which improves the efficiency, productivity and quality of grinding.

Execution of a vertical ball mill with a grinding device provided with an internal through cavity formed by through holes made in coaxially mounted rotating upper and lower rotors connected to each other by pins with the possibility of limited vertical oscillation relative to each other due to spring elements installed between them, and the upper semi-body equipped with an annular groove with balls placed in it with the possibility of movement and rotation, pressed against the reciprocal annular groove of the upper rotor, the lower rotor with an eccentric groove, in which balls installed in the cells of the hoop pressed against the lower rotor are laid with the possibility of rotation and sliding along it the inner end surface of the lower half-body provides an increase in the productivity of the mill due to dynamic vibrations caused by the movement of the balls along the eccentric groove when the speed of the upper and lower rotors changes.

The change in the pressure force of the balls to the grooves along which they move in the upper and lower rotors is ensured by using a frequency regulator and spring preloading of the upper and lower rotors to the corresponding semi-bodies, which makes it possible to increase the mill productivity and grinding quality.

Execution in the lower part of the lower rotor of through radial holes open into the internal through cavity, which at the inlet is equipped with a filter connected to the lower rotor, and at the outlet through a branch pipe fixed to the upper rotor, it is hermetically connected to the impeller housing, equipped with an exhaust pipe with installed in it with a filter and a container for receiving microparticles, and the presence in the lower half-body of an opening for the withdrawal of product residues of poor quality, ensures an increase in the quality of the material obtained at the output in the form of microparticles close to nano-size, due to the impossibility of getting particles of larger size inside the through cavity.

The device is shown in the diagrams.

Fig. 1 - general view of the mill installed in the outer casing;

Fig. 2 - explosion diagram of the mill;

Fig. 3 - longitudinal section of the mill along the feed opening;

Fig. 4 - longitudinal section of the lower rotating rotor;

Fig. 5 - view A of Fig. 4;

Fig. 6 is a section B-B of FIG. 4.

The developed vertical ball mill is preferably intended for grinding fluoroplast, which has the lowest coefficient of dry friction among polymers, in particular, fluoroplast-4.

The vertical ball mill 1 is installed in the outer housing 2 and fixed inside it on the frame 3, spring-loaded relative to the outer housing (see Fig. 1). The springing of the frame 3 relative to the housing 2 is necessary in order to prevent the transmission of vibration that occurs in the ball mill 1 to the external environment.

Vertical ball mill 1 (see Fig. 1, 2) contains two fixed interconnected hollow semi-hulls 4, 5. In the upper semi-housing 4, a loading hole 6 is made (see Fig. 2, 3). A grinding device is installed in the cavity between the semi-hulls 4, 5. The grinding device includes two rotating rotors - upper and lower. The grinding device is provided with an internal through cavity 7 formed by coaxially mounted rotating upper 8 and lower 9 rotors. The upper 8 and lower 9 rotors are interconnected by pins 10. In the lower rotor 9 the pins 10 are pressed in, in the upper rotor 8 the pins are seated in the holes in a sliding fit. Installing the pins 10 in the upper rotor 9 on a sliding fit allows a slight vertical movement of the upper 8 and lower 9 rotors relative to each other.

In each of the rotors, coaxial blind grooves are made, located one above the other, in which spring elements 11 are installed. ). In a particular case, a frequency converter made in China, model PST 350-7.5G3, with a power of 7.5 kW, a current of 16.1 A, was used for testing. The upper 8 and lower 9 rotors rotate at the same angular speed.

The upper semi-body 4 is provided with an annular groove 15 with balls 16 placed in it for movement and rotation (see Fig. 2, 3). On the outer surface of the upper rotor 8, facing towards the upper half-body 4, a reciprocal annular groove 17 is made, to which the balls 16 are pressed. The lower rotor 9 is made with an eccentric groove 18, made on the outer side of the lower rotor 9, facing the see Fig. 2, 3, 4, 5). The offset of the X-axis of the eccentric groove is shown in Fig. 5. Balls 19 are placed in the eccentric groove 18 with the possibility of rotation and sliding along it, installed in the cells of the hoop 20. The hoop 20 is pressed against the lower rotor 9 by the inner end surface 21 of the lower half-body 5. The vertical movement of the upper 8 and lower 9 rotors relative to each other allows to ensure the compression of the rotors to the upper 4 and lower 5 half-shells, providing a tight compression of the balls 16 and 19 to the surfaces of the grooves 15, 17 and the eccentric groove 18, respectively.

Upper 8 and lower 9 rotors are made with an internal through hole 22, 23, respectively. In the lower part of the through hole 22 of the upper rotor 8, a groove 24 of a larger diameter is made (see figure 3). The protrusion 25 of the lower rotor 9 is installed in the groove 24 along the sliding fit. Such a landing of the rotors provides a practically sealed internal through cavity 7 formed by through holes 22, 23 of the upper 8 and lower 9 rotors. In the lower part of the lower rotor 9, through radial holes 26 are made, open into the internal through cavity 7 (see Fig.4, 6). At the entrance to the internal through cavity 7, a filter 27 is attached to the lower rotor 9, which ensures the intake of clean air into the through cavity 7 (see Fig. 1). At the outlet, the through cavity 7 through the branch pipe 28, fixed on the upper rotor 8, is hermetically connected to the impeller housing 29, equipped with an exhaust pipe 30 with a filter 31 installed in it and a container 32 for receiving microparticles close to nano-size. In the lower semi-body 5, an opening 33 is made for the output of residues of a product having an increased grain size.

Balls 16 have a larger diameter than balls 19.

The upper 4 and lower 5 half-shells are equipped with cooling circuits made in the form of tubes 34 with refrigerant wrapped around the outer walls of the shells to ensure a stable temperature of the processes and prevent sintering of the crushed material. Water can also be used as a refrigerant.

Vertical ball mill works as follows.

The raw material is poured into the loading device 35, installed on the upper part of the outer casing 2 and equipped with a dispenser, and fed through the loading hole 6, made in the upper half-shell 4, into the cavity between the upper half-shell 4 and the upper rotor 8 of the grinding device (see Fig. 1, 3).

The first coarse grinding is carried out by balls 16, entrained with the possibility of rotation along the annular groove 15 and the reciprocal annular groove 17 of the rotating upper rotor 8. The spring elements 11 push the upper 8 and lower 9 rotors to provide the necessary pressure on the balls 16, 19 located in the annular groove 17 and eccentric groove 18 of these rotors to ensure the required degree of grinding.

A gap 36 is made between the upper rotor 8 and the wall of the upper half-body 4, through which the grinding product flows under its own weight to the eccentric groove 18 of the lower rotor 9.

Balls 19, installed with the possibility of rotation in the cells of the hoop 20 and sliding along the eccentric groove 18, produce finer grinding. Balls 19, sliding along the eccentric groove 18 and rotating in the cells of the hoop 20, pressed against the eccentric groove 18, cause beating and vibration, due to which a better grinding of the incoming product is performed to the required size (close to nano-size). The resulting beat and vibration can be enhanced by changing the speed of the gearboxes by controlling the electric drive through the frequency controller 14.

The resulting vibrations also contribute to the separation of the finer fraction from the large particles that may remain after grinding. The ground product is poured into the gap 37 formed between the lower semi-body 5 and the lower gearbox 9, from where large particles under their own weight and due to the vibration of the mill through the nozzles of the hole 33 for removing product residues are poured into the channel 38 and then into the receiving container 39 (see Fig. 1). From the receiving tank 39 grinding waste can be re-sent for grinding.

The fine fraction is sucked into the specified cavity 7 through the through radial holes 26, open into the internal through cavity 7, and the air flow created by the impeller is entrained in the upper part, enters the exhaust pipe 30 with a titanium filter 31 installed in it with smaller holes, than the milled product. The impeller is driven by its own electric motor, which is not conventionally shown.

Titanium filter 31 cuts off the fine fraction, and it is poured into the container 32 to receive microparticles.

With the proposed multi-stage grinding of the product, particles of fine grinding (approximately nano-sized) are moved by an adjustable air flow, and other fractions are collected in the lower part of the grinding mill and poured out through the nozzles of the outlet 33 for removing product residues.

As tests have shown, the inventive vertical ball mill provides high grinding performance, stable quality of the product obtained when grinding material of a sufficiently large initial fraction.

The device can be manufactured using known devices, modern technologies and materials. In particular, the main elements of the device can be made of the following materials: balls - stainless steel AISI 304, rotors - steel 40X, half-shells - steel 45.

The claimed device can be used in construction, paint, chemical, pharmaceutical, mining and other industries, preferably for grinding fluoroplastic, which has the lowest dry friction coefficient among polymers, in particular, fluoroplast-4.

Claims (2)

1. A vertical ball mill, containing two fixed interconnected hollow half-shells with a loading opening and a grinding device installed in the cavity between the half-shells, connected to an electric drive equipped with a frequency controller, the grinding device is equipped with an internal through cavity formed by through holes made in coaxially mounted rotating upper and lower rotors interconnected by pins with the possibility of limited vertical oscillation relative to each other due to spring elements installed between them; the upper semi-body is provided with an annular groove with balls placed in it with the possibility of movement and rotation, pressed against the reciprocal annular groove of the upper rotor; the lower rotor is made with an eccentric groove, in which balls are placed with the possibility of rotation and sliding along it, installed in the cells of the hoop, pressed against the lower rotor by the inner end surface of the lower half-body; in the lower part of the lower rotor, through radial holes are made, open into the internal through cavity, which at the inlet is equipped with a filter connected to the lower rotor, and at the outlet through a branch pipe fixed to the upper rotor, it is hermetically connected to the impeller housing, equipped with an exhaust pipe with installed in it with a filter and a container for receiving microparticles, while in the lower semi-body there is a hole for the output of product residues. 2. The mill according to claim 1, characterized in that the upper and lower half-shells are provided with cooling circuits made in the form of refrigerant tubes wrapped around the outer walls of the shells.

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