RU2314381C1 - Milling fittings for disk mill - Google Patents

Abstract

FIELD: pulp-and-paper industry, in particular, milling fittings used for fine milling of material.

SUBSTANCE: milling fittings for disk mill have rotor and stator disks whose working surfaces are divided into sections equipped with parallel rectilinear knives. Cutting edge of one of said knives in each section is aligned with axis of symmetry of this knife. Rotor disk is arranged symmetrically with respect to stator disk.

EFFECT: increased efficiency by providing sign-changing mode of flowing of fibrous suspension during passage thereof through cavity between knives, and reduced angle of intersection of cutting edges.

1 dwg, 1 tbl, 1 ex

Description

The invention relates to grinding sets of disk mills and can be used in the pulp and paper industry at the stage of fine grinding.

Known grinding headset for a disk mill, including a knife grinding mill mounted on a bearing base with knives made in the form of annular sectors evenly distributed on the annular working surface so that the straight lines of their generators converge in its center and are the radial cutting edges of the rotor and stator knives [one].

The disadvantage of this headset is that all the cutting edges of the rotor and stator knives due to the radial design are perpendicular to the vectors of peripheral speeds and peripheral forces. Therefore, their tangent components are equal to zero, and the normal components take maximum values. These factors, together with the sharpness of the cutting edges of the knives and the small size of the inter-knife gap, determine the chopping nature of the force acting on the fibrous material from the side of the contacting cutting edges.

The closest in technical essence to the known solution is the grinding headset of a disk mill, including rotor and stator disks, the working annular surfaces of which are divided into sectors equipped with straight knives parallel to one of the two radial generators of the sector [2].

The disadvantage of this headset is that the tangential components of the peripheral speeds and forces developed by the rotating disk at the intersection points of the cutting edges of the rotor and stator knives, acting along them, move along with the intersection points directed in the same direction with the fibrous fiber moving under the influence of pressure and centrifugal force suspension towards the peripheral peripheral edge of the discs. This reduces the time of exposure to the fibrous material for a single passage of the working intercutaneous cavity.

In addition, due to the identical design of the working annular surfaces of the rotor and stator disks during conjugation, the inclination angles of the cutting edges of the knives to the radii drawn from the center of the disks to the intersection points are opposite in direction, and their sum is equal to the angle of intersection. Therefore, the crossing angles of the cutting edges of the knives always significantly exceed the double angle of friction of the fibrous material about them. As a result of this, the friction forces of the fibrous material on the cutting edges, as a rule, have lower values in comparison with the tangential components of the circumferential forces at the crossing points.

Together, these factors lead to the fact that the layers of milled fibrous material adhering to the cutting edges of the blades of the rotor and stator disks near these points do not jam, and together with them move to the peripheral peripheral edge of the disk. Therefore, especially when using headsets with a partially closed outlet, fibrous material accumulates in the peripheral part of the working inter-knife cavity. Since straight knives are characterized by a decrease in the angle of inclination of the cutting edges of the knives to the radii when moving from the entrance to the periphery, respectively, the angles of their crossing also decrease, i.e. at the periphery, their values approach a double angle of friction. Due to this, the fibrous material accumulated on the periphery is jammed between the cutting edges of the knives, which determines the chopping nature of the force acting on it from the side of the contacting cutting edges. This leads to a shortening of the natural fiber length and to a decrease in the quality of its processing.

This drawback does not allow to intensify the process, improve the quality, productivity and reduce the energy consumption of grinding.

The invention solves the problem of intensification, improving quality, productivity and reducing the energy consumption of the grinding process.

The technical result consists in providing an alternating mode of direction of movement of the fibrous suspension when it passes through the working interknife cavity, as well as in reducing the angle of intersection of the cutting edges.

To achieve the indicated technical effect in a grinding set for a disk mill, including rotor and stator disks, the working annular surfaces of which are divided into sectors equipped with parallel rectilinear knives, according to the invention, the cutting edge of one of the knives of each sector is aligned with its axis of symmetry, and the rotor disk is made inversely relative to the stator.

The proposed design of a grinding headset for a disk mill is illustrated in the drawing, which shows a frontal projection of a fragment of its working annular surface, including two sectors. Knife surfaces are shaded. The circular arrow shows the direction of rotation of the rotor disk. In the left part of the drawing, a wavy line shows a break in the sector of the rotor disk, under which a part of the working surface of the stator disk sector is visible. The following geometric parameters are plotted and labeled:

About - the center of the working annular surface;

OO '- axis of symmetry of a single sector;

LM - the cutting edge is aligned with the axis of symmetry OO ';

AB, CD and EF, GH - two pairs of cutting edges located respectively on different sides of the axis OO ';

φ is the angle of solution of a single sector;

- угол раствора правой и левой частей единичного сектора.

- the angle of the solution of the right and left parts of the unit sector.

The grinding set for a disk mill includes a rotor 1 and a stator 2 disks, the working annular surfaces of which are divided into sectors 3, equipped with parallel rectilinear knives 4 and cells 5 with an inner circumferential edge 6 and an outer edge 7.

The cutting edge 8 (LM) of each unit knife of sector 3 is aligned with the axis OO 'of its symmetry and therefore is radial. The axis of symmetry OO 'divides sector 3 into two equal parts - left and right. The rotor disk 1 is made mirror-like relative to the stator - 2. The cutting edges 9 (AB and EF) of the knives of the rotor disk 1 are located on different sides of the cutting edge 8 (LM).

Grinding headset for a disk mill works as follows. The fibrous semi-finished product under pressure enters through the inner circumferential edge 6 into the working annular interdisk cavity and rims along the cells 5 in the direction of the outer circumferential edge 7. After the rotor disk 1 is rotated through angle β (see drawing), the cutting edges 9 (AB and EF) move to position A'B 'and E'F'. At the points I and N of their intersection with the cutting edges 9 (CD and GH) of the stator disk 2 lying on a circle with an arbitrary radius R _x , the vectors of the peripheral velocity V _o decomposed into tangents V _τ and normal V _n components are selected.

Crossed cutting edges 9 A'B 'and CD of the left side of sector 3 form (see drawing):

, и

;- with radius R _x (OI), respectively, the angles

, and

;

.- angle between each other

.

Crossed cutting edges 9 E'F 'and GH of the right side of sector 3 form (see drawing):

и

;- with radius R _x (ON) respectively angles

and

;

.- angle between each other

.

, см. выше), в предлагаемой угол α_скр существенно снижается на всей площади размалывающей кольцевой межножевой полости, поскольку равен разности углов наклона скрещенных режущих кромок ножей к радиусам, проведенным из центра дисков в точки скрещивания. Поэтому значения углов скрещивания режущих кромок ножей приближаются к двойному углу трения о них волокнистого материала, а силы трения волокнистого материала о режущие кромки принимают большие значения по сравнению с касательными составляющими окружных сил в точках скрещивания. В совокупности эти факторы приводят к тому, что наслойки размалываемого волокнистого материала, налипшие на режущих кромках ножей, заклиниваются между ними.It follows from this that in comparison with well-known headsets (where

, see above), in the proposed angle α _skr significantly decreases over the entire area of the grinding annular inter-knife cavity, since it is equal to the difference in the angles of inclination of the crossed cutting edges of the knives to the radii drawn from the center of the disks to the crossing points. Therefore, the values of the crossing angles of the cutting edges of the knives approach the double angle of friction of the fibrous material about them, and the friction forces of the fibrous material on the cutting edges take large values compared to the tangential components of the circumferential forces at the crossing points. Together, these factors lead to the fact that the layers of milled fibrous material adhering to the cutting edges of the knives are wedged between them.

At the same time, the fibrous semi-finished product passing through the working zone, when it enters into different parts of sectors 3, is subjected to high-frequency exposure to alternating tangential components of peripheral speeds and forces.

This is due to the fact that in the proposed headset in different parts of sectors 3, the direction of the tangent components is opposite (see drawing).

The above-described factors of speed and force impact on the fibrous material can be realized by the fact that the cutting edges 8 (LM) of the knives of individual sectors 3 are aligned with the OO 'axes of their symmetry, and the rotor disk 1 is made mirror-like relative to the stator - 2 (see drawing).

These factors act not only at the intersection of the cutting edges 8 and 9, but also during the subsequent stretching of the fibrous suspension over the entire area of the pair of crossed knives 4 of rotor 1 and stator 2 disks. With this in mind, we can conclude that in the proposed solution, in comparison with the known ones, the processed fibrous semi-finished product receives a more significant mechanical force, consisting in stretching, grinding and, as a consequence, in its increased fibrillation while maintaining the natural fiber length.

It is also of interest that, in contrast to the known solutions in the proposed headset, in the course of its operation, the position with the maximum blocked cells 5 and increased pressure in their cavity alternates with the position when the surface patterns of the rotor and stator 2 disks coincide, and their conjugate cells 5 as open and accessible as possible for a moving fiber prefabricated product with a simultaneous drop in pressure in their cavity. Taking into account the noted factors, this allows us to provide significant pressure drops in the working inter-knife zone (gap), operating in the high-frequency mode and intensifying the process of circulation of fibrous material from cells 5 of rotor disk 1 to cells 5 of stator disk 2 and vice versa. Therefore, with a single passage through the working zone, almost the entire volume of the suspension repeatedly intersects the active region near the intersection points of the cutting edges 8 and 9 of the knives 4, undergoing intense mechanical stress on their part.

The fibrous semi-finished product, having passed the grinding inter-knife cavity, is fed to the next processing stage.

Example. At a laboratory disk mill, at a load of 22 kW, sulfite unbleached softwood pulp was ground. Used:

- the well-known eight-sector knife headset with straight parallel knives, with a single-sector angle of opening of 45 ° [2];

- the proposed knife headset.

The width of the knives and cells of the rotor and stator discs is 4 mm. Comparative performance of both headsets are given in the table. Compared with the known headset [2], the proposed headset allows you to provide the product with high paper-forming properties and physico-mechanical properties of castings with minimal shortening of the fiber.

Using the proposed grinding headset disc mill allows you to:

- to intensify the grinding process by providing alternating mode of direction of movement of the fibrous semi-finished product;

- to improve the quality of processing by reducing the average angle of intersection of the cutting edges of the knives;

- reduce energy consumption due to the fact that almost the entire volume of the suspension with a single passage of the working area repeatedly crosses the inter-knife gap, being subjected to intense impact from the cutting edges of the knives;

- increase productivity by ensuring the optimal number of cycles of passage of the fibrous prefabricated grinding zone.

Information sources

1. SU, No. 502993, IPC D21D 1/30, B02C 7/12, declared 02.01.1974, Bulletin No. 6, published 02.15.1976

2. SU, No. 878847, IPC D21D 1/30, В02С 7/12, notified on 05/03/1979, bulletin No. 41, published on 11/07/1981

Claims (1)

Grinding headset for a disk mill, including rotor and stator disks, the working annular surfaces of which are divided into sectors equipped with parallel rectilinear knives, characterized in that the cutting edge of one of the knives of each sector is aligned with its axis of symmetry, and the rotor disk is made mirror-like relative to the stator.