RU2548879C1 - Cutting unit for grinding of plastic materials - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to structural elements of grinders used mainly in preparation of clay stock at enterprises of construction materials. Cutting unit comprises rotary blade knife (3). Every blade of the latter is composed of a replaceable cutting adapter directed along cutting edge by a through hole. Said adapter is fitted on axle rigidly secured at knife boss (3). Said axle features wedge-like cross-section converging in direction of knife rotation. Cutting adapter through hole featured mating shape with wedge point directed towards cutting edge. Bores are made in said cutting adapter on wedge base side for bolts to fit therein to press the adapter to said axle.

EFFECT: higher reliability, higher quality of material grinding.

7 cl, 9 dwg

Description

FIELD OF THE INVENTION

The invention relates to the structural elements of grinding devices used mainly in the preparation of clay raw materials at the enterprises of the building materials industry, in the production of fine ceramics, etc.

State of the art

A device for grinding and mixing plastic materials, mainly clay, comprising a housing with a loading hopper, a screw and a cutting unit, including perforated plate-grids installed in the housing and blade blades placed between them, mounted on the drive shaft (see patent for the invention RU 2297324 IPC B28C 1/14, published on 04/20/2007). A knife placed between the gratings, provides cutting material from the first, in the direction of movement of the material, gratings and its movement in the direction of the subsequent grating. In the process, the knife is subjected to significant impacts from the processed ceramic material, as a result of which its surfaces wear out quickly.

A significant drawback of the mentioned solution is the implementation of a solid cast knife. Such knives can be subjected to a limited number of edits, after which they will need to be completely replaced, which is uneconomical in terms of metal consumption.

More economical and technologically more advanced in maintenance are knives with interchangeable cutting tips fixed to the base of the knife by means of fasteners (see patent SU 1719071, IPC B02C 18/18, publ. 15.03.92, patent US 6029917, IPC B02C 18 / 30, op. 29.02.2000, patent DE 802044, 12.21.1950).

However, in all the above-mentioned solutions for cutting meat, only cutting inserts (blades) are fixed on the three-petal base of the knife. In devices designed for grinding clay, the entire front (frontal) surface of the blade of the knife is exposed to abrasion from the ceramic material.

As the closest, by the presence of similar structural features, analogue to the claimed technical solution, the cutting unit adopted in German patent DE 1276492, IPC B02C 18/36, publ. 08/29/1968

According to the materials of the aforementioned patent, the cutting unit includes a rotating blade knife interacting with perforated plate-grids, in which each blade is made in the form of a replaceable cutting nozzle with a through hole oriented along the cutting edge, mounted by this hole on an axis fixed in the knife hub.

As a disadvantage of the closest analogue, it is possible to note the free landing of the knife on an axis made in the form of a conventional bolt passed through the through hole of the nozzle. With this fastening, the knife does not have a rigid fixation and can freely rotate on the axis. The possibility of cutting is ensured by the fact that during operation the cutting edge of the knife is pressed against the plane of the lattice by the material itself.

Such a cutting unit can only be used in small low-speed devices designed for cutting food products, where the reaction forces from the side of the transported material are negligible. In devices designed to grind materials such as clay, where the knife is subjected to high loads from the side of the crushed material, the absence of a rigidly fixed position of the knife relative to the grids can lead to the squeezing of the knife from the desired cutting plane along the grill, as a result of which high-quality grinding will not be ensured material.

Disclosure of invention

The task to be solved by the claimed invention is directed is to increase the reliability of the device under increased loads and the quality of grinding material by ensuring a fixed position of the cutting elements of the knife relative to the grids interacting with it.

This problem is solved due to the fact that in the cutting unit for a device for grinding plastic materials containing at least one rotary blade knife located between flat grids, each blade of which is made in the form of a replaceable cutting nozzle with a through hole oriented along the cutting edge, fitted with this a hole on the axis fixed in the hub of the knife, according to the claimed invention, the axis is rigidly fixed in the hub and is made with a wedge-shaped cross-section, tapering in the direction ascheniya knife cutting through-hole nozzle configured mating shape of the wedge tip facing towards the cutting edge, the wedge from the base in the cutting nozzle is provided with holes for the bolts, ensuring its preload to the axle.

Used in the formula, the term "interchangeable cutting nozzle" hereinafter for brevity, can be replaced by "nozzle" or "cutting nozzle".

The above set of essential distinguishing features allows you to get a new positive technical result, namely, to ensure a reliable fixed position of the cutting elements of the knife relative to the grids interacting with it during operation, while maintaining the simplicity of manufacture and change of cutting nozzles.

The proposed fixing of the cutting nozzle on the axis using a wedge-shaped connection with preload by means of bolts is characterized by high reliability and simplicity. The wedge-shaped trapezoidal cross-section of the axis eliminates the nozzle turning on the axis and at the same time ensures reliable fixation of the nozzle against displacement along the axis under the action of centrifugal forces during knife rotation, due to the considerable friction forces between the inclined faces of the axis and the nozzle forming a wedge with a simple compression of the nozzle to the axis with bolts.

The holes are made only in the nozzle. The axis has no holes. In order to increase the reliability of the connection, only a longitudinal open groove is possible, made in the axis from the side of the wedge base and designed to accommodate the end part of the bolt.

The absence of the need to combine the holes, which would be necessary for a threaded connection of the nozzle and the axis, helps to reduce the accuracy requirements for the geometric dimensions and position of the nozzle holes, which simplifies the process of manufacturing nozzles.

Another positive aspect of the proposed design solution is the ability to reduce the thickness of the nozzle while maintaining the necessary strength and rigidity of the cutting tool. Reducing the thickness of the replaceable part of the knife, subjected to wear, helps to save metal.

Particular preferred cases of the implementation of the proposed device are also aimed at solving the aforementioned problem.

The angle between the side faces of the axis interacting with the surfaces of the nozzle and forming a wedge is preferably 30 °. This ensures a secure fit of the cutting nozzle on the axis when tightening with bolts and helps to reduce the thickness of the walls of the nozzle due to the convergence of the cross-sectional shape of the axis and the nozzle.

The front (or frontal) surface of the blade of the knife is the working surface, because it is she who acts on the processed material cut off by the cutting edge from the input grate. By “input” is meant the first lattice located in the direction of movement of the material, i.e. grill in front of the knife. By “output” is meant the second lattice located in the direction of movement of the material, i.e. grill behind the knife.

The working surface of the interchangeable cutting nozzle forming the blade is preferably made in the form of a cylindrical surface, characterized in that at its input section adjacent to the cutting edge, the angle α between the tangent drawn to this surface and the normal drawn to the plane of the input grating is 20 -30 °, and at its exit section, the angle β between the tangent drawn to this surface and the plane of the output lattice is 5-10 °.

This form of the working surface not only provides movement of the material cut from the input grate in the direction of the output grate, but also improves the rubbing of the processed material through the openings of the output grate into the subsequent cutting compartment. The material is drawn into a smoothly tapering wedge-shaped gap formed between the working surface of the nozzle and the outlet grill, and is wiped with an end portion of this surface through the holes of the grill.

A steeper bend of the working surface of the blade in the inlet section (α <20 °) will make it difficult to move clay along it to the outlet grate. Too gentle bending of the surface (α> 30 °) will contribute to a good cutting of the clay tows entering the compartment through the inlet grate, but will not allow the material to linger in front of the knife, which is desirable since some accumulation of material in front of the knife contributes to an additional “washing” of clay.

An increase in the bending of the working surface at the exit section (β> 10 °) will lead to a significant decrease in the contact area between the blade and the grating and, as a result, the effect of forcing the material through the grating. Reducing the angle β to 0 ° is also undesirable, because will lead to a sharp decrease in the amount of material falling under the pushing part of the knife.

Thus, the said shape of the working surface of the cutting nozzle provides the ability to fulfill the purpose of the nozzle and helps to improve the quality of grinding material.

The mentioned conditions correspond to a cutting nozzle made in the form of a half disk segment, the cylindrical surface of which forms the working surface of the nozzle. The execution of the nozzle in the form of a part of a disk segment contributes to an additional approximation of the geometric shapes of the cross section of the axis and the nozzle and to a decrease in the wall thickness of the nozzle while maintaining sufficient tool stiffness.

Replaceable cutting nozzle can be made integral in thickness (size along the cutting edge) and consist of several identical cutting elements mounted on an axis in a row. Moreover, each cutting element has at least one hole for the bolt, ensuring its fastening on the axis.

In the zone of fixing the axis on the hub of the knife, a platform is made for supporting the replaceable cutting nozzle. To further increase the reliability of the device, it is advisable to perform on the site from the side opposite to the rotation of the knife, a persistent protrusion for the cutting nozzle. The presence of a persistent protrusion allows to reduce the load on the axis during operation due to its transfer through the nozzle to the protrusion formed directly in the hub. This prevents the “slice” of the axis during overloads and further improve the reliability of the device.

For the manufacture of interchangeable cutting nozzles, the method of waterjet cutting can be applied.

Brief Description of the Drawings

The invention is illustrated by an example of a specific implementation, illustrated by the drawings, which depict:

figure 1 - cutting unit for grinding plastic materials;

figure 2 - knife, General view, isometry;

figure 3 - knife, partially disassembled, isometry;

figure 4 - replaceable cutting nozzle, isometry;

figure 5 - section aa from figure 1, is rotated;

figure 6 is an example of cutting blanks for the manufacture of nozzles;

Fig.7 is an example of a knife with a hub with stops;

in Fig.8 - the hub of the knife of Fig.7, isometry;

figure 9 is an example of a knife with composite nozzles.

The implementation of the invention

The proposed cutting unit for a device for grinding plastic materials contains (see Fig. 1) a rotary blade knife 3 located between the flat grids 1 and 2. Each blade of the knife 3 is made in the form of a replaceable cutting nozzle 4 with a through hole 5 oriented along the cutting edge 6, mounted on the axis 7, rigidly fixed in the hub 8 of the knife (see figure 2-4). Axis 7 is made with a wedge-shaped cross-sectional shape, tapering in the direction of rotation of the knife. The through hole 5 of the cutting nozzle 4 is made in the reciprocal form, facing the tip of the wedge in the direction of the cutting edge 6. On the side of the base of the wedge in the cutting nozzle 4 there are holes 9 for installing bolts 10, ensuring its compression against the axis 7.

The angle φ between the side faces of the axis 7 forming a wedge is preferably 30 ° (see FIG. 5).

Replaceable cutting nozzles 4 are made in the form of a half disk segment, the cylindrical surface of which forms the working surface 11 of the nozzle.

The working surface 11 is characterized in that the angle α formed between the tangent drawn to the surface 11 at the input portion near the cutting edge and the normal drawn to the plane of the input grill 1 is 20-30 °. In this case, the angle β between the tangent drawn to the surface 11 in the output section and the plane of the output lattice 2 is 5-10 °.

For the manufacture of interchangeable cutting nozzles 4 was applied the method of waterjet cutting. An example of cutting a disk billet of high strength steel is shown in Fig.6.

In the zone of fixing the axis 7 on the lateral surface of the hub 8 of the knife, a platform 12 is made for supporting the replaceable cutting nozzle. From the side opposite to the rotation of the knife, the supporting platform 12 can be limited by a persistent protrusion 13 (see Fig.7, 8).

Figure 9 shows an example of the execution of the cutting nozzle composite, of the same cutting elements 14, mounted in a row on the axis 7. For fixing on the axis, each cutting element 14 has at least one hole 9 for the bolt 10.

Such an implementation of the nozzle 4 can pursue various goals. In some cases, the need to make a composite nozzle may arise due to the limited capabilities of waterjet cutting. For example, the thickness of the nozzle may be limited by the thickness of the sheet from which it is cut.

To reduce the friction forces between the knife 3 and the input grill 1, the lower face 15 of the cutting nozzles 4 is inclined to the plane of the grill 1 at an angle γ of 5-10 °. With a closer location of the face 15 to the plane of the grating 1, the friction forces between the knife and the grating will increase significantly, and an increase in the said angle of more than 10 ° will reduce the resistance and reliability of the cutting part of the knife.

For greater reliability of the location of the bolts 10 in the axis 7, a groove 16 can be made to accommodate the end of the bolt.

The cutting unit operates as follows.

In the process, the cutting nozzles 4 of the knife 3 cut off the pressed material from the input grill 1 and move it in the direction of the output grill 2, acting on the material with the working surface 11. Near the grill 2, the crushed material falls into a smoothly tapering wedge-shaped gap between the working surface 11 and the plane of the grill 2 where it is rubbed by the end portion of the surface 11 through the holes of the lattice 2.

For its part, the transported material exerts a counter-pressure force on the cutting nozzle, which is transmitted from the nozzle 4 to the axis 7 and from the last to the hub 8 of the knife, part of the force is perceived by the persistent protrusion 13 (which is true for each blade of the knife). Despite significant impacts from the material side, nozzles 4 are reliably held in a predetermined position, while preserving predetermined location angles (α, β, γ), which ensure the operation of cutting elements and high-quality grinding of the material.

As the working surface 11 of the nozzle 4 and its cutting edge 6 wear out, the nozzle is replaced. Unscrew the bolts 10 and remove the worn cutting nozzle 4 (or cutting elements 14, Fig. 9, forming the nozzle). A new nozzle 4 is mounted on the axis 7. Install bolts 10 in the holes 9 of the nozzle 4 (cutting element 14) and press the axis 7 against the walls of the hole 5 of the nozzle 4 (cutting element 14), press the wedge, ensuring a reliable connection of the replaceable cutting nozzle with the axis and its fixed position during the operation of the knife.

Claims (7)

1. A cutting unit for a device for grinding plastic materials, comprising at least one rotary blade knife located between flat grids, each blade of which is made in the form of a replaceable cutting nozzle with a through hole oriented along the cutting edge, mounted on an axis fixed in the hub of the knife characterized in that the axis is rigidly fixed in the hub of the knife and is made with a wedge-shaped cross section tapering in the direction of rotation of the knife, the through hole of the cutting nozzle is made reciprocal rmy facing edge of the wedge in the direction of the cutting edge, the wedge base side in the cutting nozzle is provided with holes for the bolts, ensuring its preload to the axle. 2. The cutting unit according to claim 1, characterized in that the angle between the side faces of the axis forming the wedge corresponds to 30 °. 3. The cutting unit according to claim 1, characterized in that the working surface of the interchangeable cutting nozzle is made in the form of a cylindrical surface, characterized in that at its input section adjacent to the cutting edge, the angle between the tangent drawn to this surface and the normal, drawn to the plane of the input grate, is 20-30 °, and on its output section, the angle between the tangent drawn to this surface and the plane of the output grate is 5-10 °. 4. The cutting unit according to claim 3, characterized in that the replaceable cutting nozzle is made in the form of a half disk segment, the cylindrical surface of which forms the working surface of the nozzle. 5. The cutting unit according to claim 1, characterized in that the interchangeable cutting nozzle is made integral. 6. The cutting unit according to claim 1, characterized in that on the hub of the knife in the zone of attachment of the axis, a support platform for a removable cutting nozzle is formed, limited on the side opposite to the rotation of the knife by a thrust protrusion. 7. The cutting unit according to claim 1, characterized in that the interchangeable cutting nozzles are made by hydroabrasive cutting.

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