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Title:
A DEVICE MEANT FOR GRINDING OF FIBROUS MATERIAL
Document Type and Number:
WIPO Patent Application WO/2015/033016
Kind Code:
A1
Abstract:
Grinder meant for grinding fibrous material which grinder comprises a pair of grinding blades comprising grinding surfaces in which case the first of the mentioned pair of blades is a stationary blade surface formed of grooves (13) and ridges (12) and is attached to a stator and the second of the pair of blades is a blade surface which is formed of grooves (13) and ridges (12), which is movable in relation to the previous blade surface and is attached to the rotor between which blade surfaces the grinding occurs and the mentioned ridges are adjusted to direct and control the run of the material to be ground with the attachment plane of the blade surfaces between the parallel ends (15); ( 18) of the ridges (12). The imaginary extension of the front edge of the ridges (12) of the grinding blades of the stator and the rotor is adjusted to form a sharp angle (A); (B) with the attachment plane (20); (21) of the blade surface or with the tangent (22); (23) of the attachment surface and the profile forming the ridge (12) is evenly thick.

Inventors:
KYYTSÖNEN JUHANI (FI)
Application Number:
PCT/FI2014/000021
Publication Date:
March 12, 2015
Filing Date:
September 04, 2014
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
OSTEMS CONSULTING OY (FI)
International Classes:
D21D1/20; D21D1/22; D21D1/30
Domestic Patent References:
WO2004062807A12004-07-29
Foreign References:
US2697966A1954-12-28
US20070210197A12007-09-13
US3305183A1967-02-21
CN202530332U2012-11-14
Attorney, Agent or Firm:
NIEMINEN, Taisto (P.O. Box 65, Tampere, FI)
Download PDF:
Claims:
CLAIMS

1. Grinder meant for grinding fibrous material which grinder comprises a pair of grinding blades comprising grinding surfaces wherein the first of the mentioned pair of blades is a stationary blade surface which is formed of grooves (13) and ridges (17) and is attached to a stator and the second of the pair of blades is a blade surface formed of grooves (13) and ridges (12), is movable in relation to the previous blade surface and is attached to a rotor between which blade surfaces the grinding occurs and the mentioned ridges are adjusted to direct and control the run of the material to be ground with an attachment plane of the blade surfaces between the parallel ends (15); (18) of the ridges (12); (17), characterized in that the sides of the parts which form ridges (12); (17) of the grinding blades of the stator and the rotor are adjusted to a tilted position in relation to the blade surface when the mentioned tilted position is directed backwards in the rotor in relation to the direction of rotation and when the position is directed forward in the stator and that the profile forming the ridge (12) is evenly thick.

2. Grinder according to the claim 1 , characterized in that the sharp angle (A); (B) has an equal magnitude both in the grinding blade of the stator and the rotor.

3. Grinder according to the claim 1, characterized in that the sharp angle (A) is smaller in the grinding blades of the rotor than the angle (B) which is in the grinding blade of the stator.

4. Grinder according to any of the claims 1- 3, characterized in that the sharp angle (A); (B) becomes smaller in the direction of the radius of the grinding surface of the plate grinder and is at its smallest at the outer circle of the grinding surface.

5. Grinder according to any of the claims 1 - 4, characterized in that the grinding surface is divided into two or more (sections) circles which are successive in the direction of the grooves (13) in which circles the mentioned sharp angle (A); (B) has a different magnitude in each circle.

6. Grinder according to any of the claims 1- 5, characterized in that the grinding surface is divided into two or more (sections) circles which are successive in the direction of the grooves (13) in which circles the mentioned sharp angle (A); (B) is at its largest at the feed edge and at its smallest at the removal edge and is smaller in each circle which is closer to the outer edge than in a circle which is closer to the feed edge.

7. Grinder according to any of the claims 5 - 6, characterized in that the surface areas of the mentioned successive circles are of equal size. 8. Grinder according to any of the claims 1 -6, characterized in that the magnitude of the mentioned sharp angle (A); (B) varies in the range of 45 - 85 degrees.

9. Grinder according to any of the claims 1 -7, characterized in that the sharp angle (A); (B) is 5-20 ° smaller in the grinding blades of the rotor than in the grinding blades of the stator.

10. Grinder according to any of the claims 1-8, characterized in that the grooves (13) are wider than the thickness of the ridges (12); (17). 11. Grinder according to any of the claims 1 -9, characterized in that the width of the grooves (13) is 1- 3 times the thickness of the ridges (12); (17).

Description:
A device meant for grinding fibrous material Field of the invention

Object of the invention is a grinder which is meant for grinding fibrous material which invention comprises a pair of grinding blades which comprises grinding surfaces in which case the first of the mentioned pair of blades is a blade surface which is formed of grooves and ridges, is stationary and is attached to a stator and the second of the pair of blades is a blade surface which is formed of grooves and ridges, is movable in relation to the previous blade surface and is attached to a rotor between which blade surfaces the grinding occurs and the mentioned ridges are adjusted to direct and control the run of the material to be ground with an attachment plane of the blade surfaces between the ends of parallel ridges. Background of the invention

Grinders which are meant for grinding of fibrous material are used in order to produce mass which is needed in the manufacturing process of paper and paperboard or are used for processing it in paper and paperboard factories. Grinding occurs in a grinding gap which is located between a stationary stator blade and a rotor blade which moves in relation to it. The commonly used grinders are plate, conical or cylinder grinders. In the plate grinders the grinding occurs between two planar blade surfaces, in conical grinders the grinding occurs between blade surfaces which have a form of a cone and in the cylinder grinders the grinding occurs between two grinding surfaces which have a form of a cylinder. Plate grinders are common especially in producing fibrous material and conical grinders and cylinder and plate grinders are for their part very common in processing fibrous material in order to be suitable for manufacturing paper and paperboard. The blade surfaces in grinders can directly have the form of a plane, cone and cylinder or the grinding surfaces can be formed of separate blade segments which form an uniform grinding surface.

The grinding surfaces are formed of ridges and grooves. The purpose of the ridges and their ends is to defiberize the material and to process it to be suitable for the manufacturing of paper and paperboard. The purpose of the grooves is to convey material on the grinding surfaces and also to direct the material to be defiberized to a blade gap formed by the ends of the ridges of the blade surfaces. Regarding the grinding result in the grinding process it is important to be able to transmit squeezing powers, which loosen the structure of the fibre, into the material to be ground when at the same time one aims to avoid impacts which break the fibres. Excessive breaking of the fibres and formation of fine matter in the material to be ground causes problems in the production of paper and paperboard and weakens the quality features of paper and paperboard. Instead of that grinding processing of fibres during which the structure of the fibres is being processed without harming or breaking the fibres too much improves many quality features of the paper and paperboard and is also advantageous in the manufacturing process of paperboard and paper. In order to boost the grinding and in order to produce good ground material one has aimed to develop the properties of the grinding surfaces in many ways. Blocks which close the blade groove are often located in the blade grooves of the blade surfaces of the grinder. The purpose of the blocks is to prevent the material to be ground from running in the groove and to control the material to run to a blade gap formed by the blade ridges in order to achieve more efficient grinding. Power of the grinding can to a certain extent be increased with this arrangement but the flow control to the blade gap on inadequate and therefore the quality of the end result of the grinding does not always fulfil the

requirements. The utilization of the ridges of the blade surface in order to direct the material to be ground to the blade gap formed by the ends of the ridges of the blade surfaces of the stator and the rotor is not common. A solution is presented in the US patent specification 2012/0012685 in which specification strong, spinous load on the fibrous material to be ground caused by a sharp angle of the ridges is aimed to be reduced by directing the material more efficiently to the blade gap by using various ridges which have a splayed upper surface.

In the publication JPH03113086 a toothing of the grinding surfaces is described in which toothing the surfaces of both grinding blades of the plate grinder comprise a low-gradient inclination surface which directs the mass to be ground towards the surface of a counter blade. The inclination surface stops at a low vertical surface which is in an upright position in relation to the direction of motion of the movable blade. The low vertical surfaces of both blade surfaces meet each other in such a way that a desired grinding gap is formed between them. In this solution the meeting of the low vertical surfaces creates a considerable impact to the blade surfaces and to the mass.

The publication GB 1407712 presents grinding blades which have ridges and grooves. The profiles of the ridges are presented to be widening from the top towards the base. This solution has the disadvantage that due to wearing the ends of the ridges become wider.

Brief description of the invention

The purpose of the invention is to create a new pair of grinding blades which can be adjusted to a grinder with which for example the above mentioned disadvantages can be removed and the grinding efficiency and the quality of the grinding result has been improved.

It is characteristic of the grinder according to the invention what has been presented in the characterising portion of the claim 1.

The essential idea of the invention is the fact that the run of the material to be ground between the ends of the ridges of the blade surfaces to be ground is directed and controlled efficiently with the help of the whole front edge of the ridges. The diagonally positioned front edge of the ridges directs the fibres to have the same direction as the ridge and directs them along the diagonal surface to the blade gap.

Brief description of the figures The embodiments of the invention are described more detailed in the accompanying drawings in which

Figure Fig.1 shows schematically a plate grinder as a side and section view.

Figure Fig. 2 shows schematically a conical grinder as a side and section view.

Figure Fig. 3 shows schematically a blade segment of the blade surface of the rotor of the plate grinder according to the invention seen from the upper oblique.

Figure Fig. 4 shows schematically a pair of blade surfaces of the plate grinder according to the invention as a side and section view.

Figure Fig. 5 shows schematically another pair of blade surfaces of the plate grinder according to the invention as a side and section view.

Figure Fig. 6 shows schematically a pair of blade surfaces of a conical and cylinder grinder as a side and section view.

Figure Fig. 7 shows schematically a blade surface of the rotor of the pair of blade surfaces of the plate grinder according to the invention seen from the direction of the axle of the grinder.

Figure Fig. 8 shows schematically a blade surface of the rotor of the pair of blade surfaces of the conical grinder according to the invention as a side and section view.

Figure Fig. 9 shows schematically a blade surface of the rotor of the pair of blade surfaces of the cylinder grinder according to the invention as a side and section view.

Detailed description of the invention

In the figure 1 the plate grinder is shown as a side and section view. The plate grinder has two opposite grinding surfaces 1 and 2 which form a pair of grinding blades. A grinding gap 3 is formed between the pair of blades in which grinding gap the grinding occurs. The grinding surface 1 is attached to a rotating plate, a rotor 4 which rotor is rotated with a motor through an axle 5. No motor is shown in the figure 1. The grinding surface 2 is attached to a stationary plate, stator 6 which for its part is attached to the body 7 of the grinder.

The material with fibre content which is to be ground is fed through a hole 8 located in the stator to the blade gap 3 formed by the grinding surfaces 1 and 2 which move in relation to each other. The material becomes ground in the blade gap and is removed from the outer edge of the blade surfaces to a grinding chamber 9 and further from there through a removal channel 10 out of the grinder to be processed elsewhere.

In the figure Fig. 2 the conical grinder is shown as a side and section view. The conical grinder has two opposite, cone-shaped grinding surfaces 1 and 2 which form a pair of blades for the grinder. A grinding gap 3 is formed between the pair of blades in which grinding gap the grinding occurs. The grinding surface 1 is attached to a rotating cone, a rotor 4 which is rotated with the help of a motor through an axle 5. No motor 2 is shown in the figure 2. The grinding surface 2 is attached to a stationary cone, a stator 6 which for its part is attached to the body 7 of the grinder.

The material with fibre content which is to be ground is fed through a hole 8 located in the stator to the blade gap 3 formed by the grinding surfaces 1 and 2 which move in relation to each other. The material becomes ground in the blade gap and is removed from the outer edge of the blade surfaces to the grinding chamber 9 and further from there through a removal channel 10 out of the grinder to be processed elsewhere.

There are in a manner known per se devices in the grinders so that the blade gap can be changed to have the desired size. The blade surfaces can be formed of one blade surface assembly or the blade surfaces can be assembled of several blade surface segments which are attached to the stator and to the rotor and thus form a uniform blade surface assembly.

In the figure Fig. 3 a segment 11 of the blade surface of the rotor of the plate grinder according to the invention is shown schematically seen from the upper oblique. In reality there are several ridges 12 in the segment and grooves 13 which are formed between them but for clarity reasons only three ridges of the grinding surface and two grooves which are formed between them are shown in the segment. By using several segments and by attaching them in a manner known per se, such as by welding them to the stator or to the rotor, the whole grinding surface of the stator and the rotor of the grinder can be created. In the figure 3 the direction of motion of the segment is shown with an arrow marked with the letter R. The material to be defiberized is fed from the direction of the feed edge 14 and the material is directed to the blade grooves 13 and further so that they are within reach of the ends 15 of the ridges 12. The ends 15 of the ridges of the blade surface of the rotor form together with the ends of the ridges of the grinding surface of the stator, not shown in the figure 3, a blade gap 3 in which the grinding occurs. In the figure 3 the ridges 12 are in a diagonal position in the relation to the attachment plane 20 of a segment of the blade surface and thus form a sharp angle with the attachment plane of the segment. Due to the diagonal position of the front edge of the ridges the material to be ground can be efficiently directed from the grooves 13 which are formed between the ridges 12 to the blade gap 3 in order to be ground. In the figure Fig. 4 a pair of blade surfaces of the plate grinder according to the invention is schematically shown as a side and section view. The rotor moves in relation to the stator in the direction shown by the arrow R. A grinding gap 3 is formed between the ends 15 of the ridges 12 of the blade surface 1 of the rotor and the ends 18 of the ridges 17 of the blade surface 2 of the stator in which grinding gap the material to be ground undergoes squeezing and cutting powers and becomes ground. The front edges of the evenly thick ridges 12 and 17 of the blade surfaces of the rotor and the stator are in a diagonal position in relation to the attachment planes 20 and 21 of the blade surfaces and the imaginary plane formed by the ends of the ridges is parallel with the attachment plane. In the figure 3 the imaginary extension of the front edge 16 of the ridges of the blade surface of the rotor and the attachment plane 20 of the grinding surface form a sharp angle A. Correspondingly the imaginary extension of the front edge 19 of the evenly thick ridges of the grinding surface of the stator and the attachment plane 21 of the grinding surface form an angle B. The imaginary plane formed by the ends of the ridges is parallel with the attachment plane of the stator. The thickness of the ridges 12 and 17 is constant, in other words they are evenly thick and thus also the grooves which are formed between the ridges are evenly wide.

When the thickness of the ridges is constant, the wearing and lowering of the ridges does not have an impact on the geometry of the blade surface formed by the ridges and the grooves and thus the grinding result stays good in spite of the wearing of the blades. The width of the grooves is typically 1 - 3 times the width of the ridges. The width of the ridges is typically 2 - 6 mm.

The magnitude of the sharp angle between the front edge of the ridges and the attachment plane of the grinding blade has an effect on the direction of the material to be ground to the blade gap. When one wants the grinding rather to process the fibres than break them, a smaller angle is chosen for the sharp angle and when one wants the grinding to reduce the fibres more efficiently, a larger angle is chosen for the sharp angle. Also the properties of the material to be ground have an impact on the choice of the mentioned sharp angle. For short- fibred material one can choose a larger mentioned sharp angle than for long-fibred material. The magnitude of the mentioned sharp angle is thus chosen in the way required by the grinding circumstances and the magnitude of the angle varies between 85° - 45°. Figure Fig. 4 shows an embodiment according to the invention in which the mentioned sharp angles A and B are of equal size.

In the figure Fig. 5 a pair of blade surfaces of the plate grinder according to the invention is shown schematically as a side and section view. In that the angle A between the imaginary extension of the ridges 12 of the grinding surface of the rotor and the attachment plane 20 of the blade surface is smaller than the sharp angle B between the imaginary extension of the front edge 19 of the ridges 17 of the blade surface of the stator and the attachment plane 21 of the blade surface of the stator. A smaller angle can be used for the blade surface of the rotor because the centrifugal force caused by the rotation of the rotor also has an effect on the material to be defiberized and directs it in the grooves which are formed between the ridges towards the outer circle in the direction of the radius and reduces the potential jamming occuring in the grooves of the rotor. With this arrangement the combined effect of the centrifugal force caused by the rotation of the rotor and the front edge of the ridges for directing the fibrous material to the blade gap can be utilized better especially regarding the grinding of long-fibred material. Typically the sharp angle of the blade surface of the rotor can be 10° - 20° smaller than the corresponding angle of the blade surface of the stator.

With the arrangement according to the figure Fig. 5 the directing of the material to be ground to the blade gap can further be boosted and the grinding result can be improved.

In one pair of blade surfaces according to the invention the magnitudes of the mentioned angles A and B change in the direction of the ridges 12 and 17 of the blade surface of the grinder in such a way that the mentioned angles A and B are at their largest at the feed edge 14 and become smaller towards the outer circle of the grinding surface.

In the figure Fig. 6 a pair of blade surfaces of a cone or a cylinder grinder according to the invention is shown schematically as a side and section view. The rotor moves in relation to the stator in the direction shown by the arrow R. A grinding gap 3 is formed between the ends 15 of the ridges 12 of the blade surface 1 of the rotor and the ends 18 of the ridges 17 of the blade surface 2 of the stator in which grinding gap the material to be ground undergoes squeezing and cutting powers and becomes ground. The front edges of the ridges 12 and 17 of the blade surfaces of the rotor and the stator are in a diagonal position in relation to the attachment surfaces 19 and 20 of the blade surfaces. In the figure 6 the imaginary extension of the front edge 16 of the ridges of the blade surface of the rotor and the tangent 22 of the attachment surface 20 of the grinding surface form a sharp angle A. Correspondingly the imaginary extension of the front edge 19 of the ridges of the grinding surface of the stator and the tangent 23 of the attachment surface 21 of the grinding surface form a sharp angle B.

In the figure Fig. 7 a blade surface of the rotor of the pair of grinding blades of the plate grinder according to the invention is shown schematically seen from the direction of the axle of the grinder. There are grooves and ridges at the grinding surface in the direction of the circle of the grinder which grooves and ridges are not shown in the figure. According to the example in this case the grinding surface is divided into two circles with the help of a line 30, into an inner circle 24 and an outer circle 25, which are successive in the direction of the radius in which circles the angle between the imaginary extension of the ridges of the grinding surface and the attachment plane of the blade surface has a different size in each circle. Correspondingly the corresponding angle of the stator of the pair of blades has a different size in successive circles. It is characteristic of a pair of blade surfaces according to the invention that the grinding surface is divided into circles in such a way that the surface areas of the circles are of equal size. In the picture Fig. 7 there are two pieces of circles which have surface areas of equal size, the circles 24 and 25.

In the picture Fig. 8 a blade surface of the rotor of the pair of grinding blades of the conical grinder according to the invention is shown schematically as a side and section view. There are grooves and ridges at the grinding surface. According to the example in this case the grinding surface is divided into two circles 26 and 27 with a line 30 which circles are successive in the direction of the grooves and which circles have the form of a truncated cone in which circles the angle between the imaginary extension of the ridges of the grinding surface and the tangent of the attachment surface of the blade surface has a different size in each circle. Correspondingly the corresponding angle of the stator of the pair of blades has a different size in the successive circles. It is characteristic of a pair of blade surfaces according to the invention that the grinding surface is divided into circles in such a way that the surface areas of the circles are of equal size. In the picture Fig. 8 there are two pieces of circles, the circles 26 and 27, which have surface areas of equal size and have the form of a truncated cone.

In the picture Fig. 9 a blade surface of the rotor of the pair of the blade surfaces of the cylinder grinder according to the invention is shown schematically as a side and section view. There are grooves and ridges at the grinding surface. According to the example in this case the grinding surface is divided into two circles 28 and 29 with a line 30 which circles are successive in the direction of the grooves in which circles the angle between the imaginary extension of the ridges of the grinding surface and the tangent of the attachment surface of the blade surface has a different size in each circle. Correspondingly the corresponding angle of the stator of the pair of blades has a different size in successive circles. It is characteristic of a pair of blade surfaces according to the invention that the grinding surface is divided into circles in such a way that the surface areas of the circles are of equal size. In the picture Fig. 9 there are two pieces of circles, circles 28 and 29, which have surface areas of equal size and have the form of a cylinder.

The grinding surface of the pair of the blade surfaces of the grinder both in the rotor and in the stator can be divided into several circles which are successive in the direction of the grooves in which circles the imaginary extension of the front edge of the ridges of the grinding surfaces and the angle between the attachment plane of the grinding blade or the tangent of the attachment surface has a different size in each circle. The mentioned angle can be the largest at the feed edge and the smallest at the removal edge and is smaller in each circle which is closer to the outer edge than in a circle which is closer to the feed edge. The solution according to the invention can also be modified in such a way that only in the circle which is closest to the outer edge the ridges are in a diagonal position in the way according to the invention. In descriptions above and figures the invention is presented with the help of examples but it is in no way limited to them. The essential thing is the fact that at least in a part of the surface area of the grinding surfaces of the pair of the blade surfaces the imaginary extension of the front edge of the ridges forms a sharp angle with the attachment plane of the blade surface or the tangent of the attachment surface. The invention can be applied in a low consistency and high consistency grinding in plate, conical and cylinder grinders.