Technical Field of the Invention

The invention relates to the construction of a pellet mill. The invention falls within the field of briquetting and pelleting of bulk materials of an organic as well as inorganic origin.

Background to the Invention

The common feature of all compaction technologies, which include pelleting, is the compression of materials under high pressure.

A screw extruder is known, in which the screw feeder is also the tool of this mill. The disadvantage of this machine is the need for a cooling system and its low hourly rate of output. Another one is a horizontal pelletizing machine with cylindrical rollers and a cylindrical matrix. The disadvantage of this machine is the uneven supply of material under both rollers. A horizontal pelletizing machine with cylindrical matrix and compression rotor is also similarly designed. The disadvantage of this design is the increased friction between the tool and matrix, and the resulting faster rotor wear. The construction of a horizontal pelletizing machine with gears is also known. Such a pelleting machine comprises a pair of hollow cylinders with gearing around their perimeter. There are holes drilled in the gearing through which the material is extruded into the interior of the cylinders. Cutters located in the interior of the cylinders cut the compressed pellets. The disadvantage of this machine is the small number of teeth on the cylinders, as a result of which which it achieves a low hourly rate of output. There is also a vertical pelleting machine with cylindrical rollers and a flat matrix. The disadvantage of the machine is the high and uneven wear on the rollers.

From the state of technology we know the pellet mill described in Slovak patent SK 286877. For the construction of the mill it is characteristic that the matrix is powered and its drive comes from the drive body. The spherical tool is hollow and the kinetics of the drive mechanism for the matrix passes through the spherical tool. This can be achieved by coupling the matrix with a drive through the cardan joint or pivot joint. An important parameter of the mill is an axial shift of the drive's face from the matrix's face. In this design, the peripheral speed of the spherical tool during each revolution is not constant. This results in the uneven wear of the working tools, reducing the output efficiency of the mill and increasing the cost of the mill's repair due to the need to replace the damaged parts.

As a consequence of the persistent problems with pelleting methods and with the design of pellet mills there is an opening for the design of a pellet mill which would offer reduced energy costs and reduced wear of machine components. The result of this effort is the pellet mill described further in the submitted invention.

Summary of the Invention

The above-mentioned drawbacks are eliminated in a pellet mill according to this invention . The design of the pellet mill is derived from the design where the mill consists of a hollow wedge-shaped body with spherical recesses on its wedge surfaces, while the wedge surfaces are fitted with a punch bearing housing and matrix bearing housing. Furthermore, the punch bearing housing contains a pivoting punch body extending to the first spherical recesses on the hollow wedge body's surface with its face. The matrix bearing housing is fitted with a pivoted matrix extending to the second spherical recesses on the hollow wedge body's surface with its face. The matrix working face and , where appropriate, the punch body working face, have spherical recesses fitted with a spherical body whose radius is equal to the radius of the spherical recesses. The matrix comprises a series of holes on the circumference. The axial deflection of the punch body from the matrix, along with the hollow wedge body and the spherical body, form a compression chamber in the form of a hollow wedge-shaped ring . The axial deflection of the punch body face from the matrix face is δ = 5° to 89°. The essence of the invention further resides in the fact that the matrix is connected to the punch body by intermeshing shaped tools in which the exterior punch body working face is directly or indirectly fitted with shaped protrusions arranged in a regular pattern on its circumference, and the exterior matrix working face is directly or indirectly fitted with a series of holes and/or shaped depressions arranged in a regular pattern on its circumference. There is a direct or indirect kinetic link between the spherical body and the punch body.

In one advantageous option of the pellet mill, the peripheral part of the punch body working face is fitted with a punch ring with shaped protrusions. In a second favourable option of the pellet mill, the peripheral part of the matrix's working face is fitted with a matrix transfer ring with a series of holes and/or shaped depressions.

For the purposes of the present invention it is necessary to understand the term "punch" as the punch body itself, along with the set of shaped protrusions arranged on the circumference of the face of the punch body. The punch body is coupled to a mill drive. Shaped protrusions in the contact wedge area fit into the cavities of the holes and/or shaped depressions, and on the one hand transfer the torque to the matrix and on the other hand help to create pressure inside the cavities of the holes. But it is also necessary to understand the term "punch" as the punch body itself, along with the set of shaped protrusions arranged on the circumference of the face of the punch ring, mounted on the punch body.

A pellet mill according to the invention may be constructed with the spherical body between the punch and the matrix located freely in case of an indirect kinetic link. In this case the spherical body is a spherical tool. The spherical tool is driven by compressed material enslosed in the wedge area of the mill and therefore its speed of rotation is lower than the punch's.

In another independent kinetic link, the spherical body shaped as a spherical tool can be self-propelled where a shaft goes through an axial hole in the punch body. Then the speed of rotation of the punch body may be different from the speed of rotation of the body of the spherical shaped tool. A pellet mill according to the invention can also be constructed so that the spherical body composed of a hemispherical tool forms a block with the punch body in a direct kinetic link, or the spherical body composed of a hemispherical tool is firmly secured to the punch body. The hemispherical tool rotates at the same speed as the punch.

For the purposes of this invention it is necessary to understand the term "spherical body" as a geometrical spherical body or block cylindrical body, whose face is shaped into a hemispherical tool or a cylindrical tool, with a hemispherical tool firmly secured to its face.

The pellet mill design according to the invention is completed by a characteristic feature where, the punch is located in axial and/or radial punch bearings and also where the matrix is located in axial and/or radial matrix bearings, and also where the matrix is fitted to a matrix bearing housing with the first end nut, and/or the punch body is fitted to the punch bearing housing with the second end nut. The pellet mill is supplemented with a feeding hopper connected to the hollow wedge- shaped body.

There is another design option of the pellet mill according to the invention with the characteristics mentioned above, wherein the punch body working face is also fitted with a protruding cover ring on its external surface, with an inner spherical surface. The matrix working face is also fitted on its external surface with a spherical recess, with an outer spherical surface. At the point of the wedge contact between the punch body and the matrix there is a tight connection , achieved by the locating of the inner spherical surface of the cover ring with the outer spherical surface of the spherical recess just before the entrance of the compressed material into the workspace. This closes the workspace, resulting in the elimination of the feed material's friction against the inner surfaces of the punch body and the matrix, because the surfaces of the punch body and the matrix mesh with each other and pull the material under the spherical tool. In doing so, the condition that the axial centre of the inner spherical surface of the cover ring and of the outer spherical surface of the spherical recess and the axial centre of the spherical tool are identical must be satisfied . The protruding cover ring can be a part of the punch's transmission ring or the punch body.

In kinetic reversal, the pellet mill according to the invention with the above basic characteristics can also be designed so that the punch body working face is also fitted on its external surface with a spherical recess with an outer spherical surface. Also, the matrix working face is also fitted on its external surface with a protruding cover ring with inner spherical surface. Then the protruding cover ring can be part of the matrix's transmission ring and/or the matrix.

The function of the pellet mill is based on the fact that bulk organic and/or inorganic material or raw material mixture of the desired size with a maximum water content of 18% passes into the open compression chamber in the shape of a spatial wedge-shaped ring through the wedge feed from the rotating punch and matrix faces, and/or the rotating spherical tool. The open compression chamber is partially surrounded by a rotating spherical body. Subsequently, bulk organic and/or inorganic material or a raw material mixture continues from the compression chamber to the protrusion openings or matrix holes, from which pellets or mouldings of different shapes in general are produced. An important parameter of the mill is the axial shift of the punch's face from the matrix's face, expressed by an angle δ = 5° to 89° .

The advantages of the pellet compression method from bulk organic and/or inorganic material or raw material mixture according to the invention are apparent from its effects, visible to the outside. It is possible to select any angle between the matrix and the punch faces. The pellet mill according to the invention has a simple, compact design. It can also be sized for small to large sizes, depending on the required performance of pellet production. It has a larger active area of material compression compared to existing mill designs, provided that we consider matrixes of the same size. The active area of the material compression (hollow wedge) is actually an area where the material is also compressed through the mechanism of protrusions and depressions to transfer torque from the punch to the matrix, which is a unique solution. It is also a function of the angle of engagement. The size of the angle of engagement depends on the coefficient of friction between the material to be pressed and the design shape of the compression parts.

A very significant advantage of the pellet mill's design according to the present invention lies in the fact that, compared to the pellet production unit, the mill according to the invention requires significantly less power consumption compared with mills at the state of the art. It allows the design of a mill where the contact between the rotating matrix and the punch is almost a point, minimizing the friction between the design parts of the mill and the fed material, also contributed to by the fact that all the elements of the high pressure system are moving simultaneously. The tightness in the compression chamber significantly increases. Also, there is a higher effectiveness of material feed under the spherical tool. I n such a design solution , the peripheral speed of the spherical tool during rotation is already constant, resulting in the even wear of working tools, thereby increasing the life of the whole mill.

Overview of Figures in the Drawings

A pellet mill according to the invention will now be described in more detail in the sections with the accompanying drawings, where Fig . 1 shows the mill mechanism with a freely placed spherical tool in a side cross-section . Fig. 2 shows the mill mechanism with a hemispherical tool in a side cross-section , forming one block with the punch. Fig. 3 is a side cross-section of the mill mechanism with a self-driven spherical tool. Fig . 4 shows the mill mechanism in an axonometric cross-section where the punch body working face is also fitted with a spherical recess with an outer spherical surface on its outer part, and wherein the matrix working face is also fitted with a protruding cover ring with an inner spherical surface on its outer part. Fig. 5 is a side cross-section of the mill mechanism where the punch body working face is also fitted with a spherical recess with an outer spherical surface on its outer part, and wherein the matrix working face is also fitted with a protruding cover ring with an inner spherical surface on its outer part, where the depression radius with the outer spherical surface, and protruding cover ring with an inner spherical surface, are marked.

Invention's Design Examples

It is understood that individual invention examples are presented for illustration and not as limitations to technical solutions. Technology experts would find or be able to discover many equivalents to the specific invention design through no more than routine experimenting. Such equivalents will also fall within the scope of the following claims. Technology experts with a knowledge of the technological state will not have a problem with the system dimensioning and the optimum selection of materials and structural arrangements; therefore these characteristics are not designed in detail.

Example 1

In this example of the invention's specific design, the optimal design of the pellet mill shown in the accompanying Fig . 1 is described . The pellet mill according to the invention consists of a hollow wedge- shaped body 7 with spherical recesses on its wedge surfaces, while the wedge surfaces are fitted with a punch bearing housing 6 and a matrix bearing housing 8. Furthermore, the punch bearing housing 6 contains a pivoting punch body 2, extending to the first spherical recess on the hollow wedge body's 7 surface with its face. The matrix bearing housing 8_ contains a pivoted matrix 5, extending to the second spherical recess on the hollow wedge body's 7 surface with its face. The matrix 5 working face and the punch body 2 working face have spherical recesses fitted with a spherical body 1- a spherical tool, whose radius is equal to the radius of the spherical recesses. The matrix 5 comprises a series of holes on its circumference. The axial deflection of the punch body 2 face from the matrix 5, along with hollow wedge body 7 and the spherical body 1, form a compression chamber in the form of a hollow wedge-shaped ring . The axial deflection of the punch body's 2 face from the matrix 5 is δ = 30°. The matrix 5 is connected to the punch body 2 using intermeshing shaped tools in which the punch body 2 working face is on its outer part independently fitted with shaped protrusions 4 arranged in a regular pattern on the circumference of the punch's embedded ring 3. The matrix 5 working face is on its outer part independently fitted with a series of holes and/or shaped depressions 15 _. arranged in a regular pattern on the circumference of the matrix's 5 embedded ring 4. There is a direct or indirect kinetic link between the spherical body 1 - spherical tool and the punch body 2 where the spherical tool is located freely. The shaped protrusions 4 in the contact wedge area are oriented towards the shaped depressions so that they fit into the cavities of the shaped depressions 1_5 in the series of holes. The punch body 2 is located in the punch's axial and/or radial bearings 9, and also where the matrix 5 is located in the axial and/or radial matrix bearings 10 _. . The matrix 5 is fitted to a matrix bearing housing with the first end nut 1_2, and the punch body 2 is fitted to the punch bearing housing 6 with the second end nut 1_3. The pellet mill is supplemented with a feeding hopper H connected to the hollow wedge body 7.

Example 2

In this example of the invention's specific design, the second pellet mill design is described , as shown in the accompanying Fig. 2. Also in this case, the pellet mill according to the invention is sufficiently described in its basic characteristics in Example 1 . The structural diversity lies in the variation wherein the direct kinetic link of the spherical body 1 formed by a hemispherical tool creates a block with the punch body 2. The hemispherical tool's rotational speed matches that of the punch . The axial deflection of the punch body 2 face from the face of the matrix 5 is δ = 37°. Example 3

In this example of the invention's specific design, the third pellet mill design is described, as shown in the accompanying Fig. 3. Also in this case, the pellet mill according to the invention is sufficiently described in its basic characteristics in Example 1 . The structural diversity lies in the variation wherein the indirect kinetic link of the spherical body 1 formed by a spherical tool has its own drive whose shaft goes through the axial bore in the punch body 2. Then the rotational speed of the punch body 2 may vary from that of the spherical body 1 formed by a spherical tool. The axial deflection of the punch body 2 face from the face of the matrix 5 is δ = 22°.

Example 4

In this example of the invention's specific design , an alternative unshown pellet mill design is described. Also in this case, the pellet mill according to the invention is sufficiently described in its basic characteristics in Example 1 . The structural diversity lies in the variation, where shaped protrusions 14 _. are formed directly on the punch body 2 and shaped depressions 15 _. are formed directly in the matrix 5.

The function of the pellet mill is clear from the method of the pellet compression, where bulk organic and/or inorganic material or raw material mixture of the desired size with a maximum water content of 18% of the bulk passes into the open compression chamber in the shape of the hollow wedge-shaped ring through the wedge feed from the rotating punch and matrix 5 faces, and the rotating spherical body 1, where the torque transfer from the punch to the matrix 5 is ensured by a set of protrusions 4 arranged in a regular parttern on the circumference, fitting into the shaped depressions 15 in the cavities of the series of holes in the matrix 5_,_ in the wedge contact area. Subsequently, the bulk organic and/or inorganic material or a raw material mixture moves from the compression chamber to the matrix 5_ protrusion openings, from which pellets are extruded . Example 5

I n this example of the invention's specific design , an alternative pellet m ill design is described . Also in this case, the pellet mill according to the invention is sufficiently described in its basic characteristics in Example 1 . The structural d iversity lies in the variation where the punch body 2 working face is on its outer part also fitted with a protruding cover ring 16. with an inner spherical surface. The matrix 5 working face is on its outer part also fitted with a spherical recess Y7_ with an outer spherical surface. At the point of wedge contact between the pu nch body 2 and the matrix 5, there is a tight con nection achieved by the locating of the inner spherical surface of the cover ring 16 with an outer spherical surface of the spherical recess 1_7 just before the entry of the compressed material into the workspace. The axial centre of the inner cover ring's 16 spherical surface and the spherical recess' Y7_ outer spherical surface and the axial centre of the spherical body 1 are identical.

Alternatively, the protruding cover ring 16. may be part of the punch's transmission ring 3 or part of the punch body 2.

Example 6

I n th is example of the invention's specific design , there is an alternative pellet mill design in kinetic reversal as shown in Fig ures 4 and 5. Also in this case , the pellet mill accord ing to the invention is sufficiently described in its basic characteristics in Example 1 . The structural diversity lies in the variation where the punch body 2 working face is, on its outer part, also fitted with a spherical recess 17. with an outer spherical surface. Also , the matrix 5 working face is, on its outer part, also fitted with a protrud ing cover ring 16 with an inner spherical su rface. Then , the protruding cover ring 16 can be part of the matrix's transfer ring 4 and/or be part of the matrix 5.

I ndustrial Applicability The pellet mill is usable in manufacture, agriculture, the food industry, and wherever there is a need to process bulk material into a compact solid body with a cylindrical or other shape.