WO2023135362A1

WO2023135362A1 - Adjusting blade gap in processing equipment for processing fibrous material

Info

Publication number: WO2023135362A1
Application number: PCT/FI2023/050014
Authority: WO
Inventors: Juha Aronen; Pekka Saukko
Original assignee: Valmet Technologies Oy
Priority date: 2022-01-11
Filing date: 2023-01-05
Publication date: 2023-07-20

Abstract

A loading device (10), an arrangement and a method for adjusting a size of a blade gap (9) in processing equipment for processing fibrous material. The loading device comprises a gearing (12) to be coupled in connection with a processing element (5, 6) of the processing equipment to move the processing element (5, 6) in respect of another processing element (5, 6) of the processing equipment for adjusting the size of the blade gap (9) between the processing elements, a cage induction motor (14) comprising a shaft (15) coupled to the gearing for operating the gearing, a position sensor (16) for measuring a rotational position (M-RP) of the shaft of the motor for indicating a position of the processing element in respect of the another processing element, and a frequency converter (17) coupled to the position sensor and to the motor for controlling the operation of the motor based on the measured rotational position of the shaft of the motor.

Description

ADJUSTING BLADE GAP IN PROCESSING EQUIPMENT FOR PROCESSING FIBROUS MATERIAL

FIELD OF THE INVENTION

The invention relates to processing equipment for processing fibrous material. Especially the invention relates to adjusting of a size of a blade gap between substantially oppositely positioned processing elements in the processing equipment for processing fibrous material.

BACKGROUND OF THE INVENTION

A refiner, such as a refiner for refining lignocellulose-containing woodbased fibrous material, plant-based fibrous material, or recycled textile material, provides a kind of processing equipment for processing fibrous material. The refiner comprises typically two oppositely positioned refining elements, one of them typically being a stationary refining element and the other one a rotatable refining element that is arranged to be rotated relative to the stationary refining element. Between the opposing refining elements there is a free distance, i.e., a blade gap or a refining chamber, into which the fibrous material to be refined is supplied. In the blade gap the fibrous material is subjected to the refining effect determined by properties of refining surfaces in the refining elements and operational characteristics of the refiner, such as a rotational speed of the rotatable refining element and/or a pressure prevailing in the blade gap.

A prior art arrangement for adjusting a size of a blade gap in a conical refiner comprises a loading device coupled to the rotatable refining element for moving the rotatable refining element in respect of the stationary refining element in an axial direction of the refiner. In this arrangement the loading device comprises a gearing coupled to a shaft of the rotatable refining element and a motor coupled to the gearing to operate the gearing, whereby the gearing and the motor coupled to the gearing together provide a gearmotor for moving the rotatable refining element in respect of the stationary refining element. The actual blade gap adjustment is, however, based on a power control of a main motor of the refiner, i.e., on the control of the power of the motor intended to rotate the rotatable refining element. The power required by the main motor to rotate the rotatable refining element provides an indication about a position of the rotatable refining element relative to the stationary refining element so that the closer the rotatable refining element is to the stationary refining element, the higher the power needed by the main motor to rotate the rotatable refining element because of a pressure increase in the blade gap. In this solution, to prevent the rotatable refining element to be moved too close to the stationary refining element, the loading device is equipped with a mechanical friction coupling that provides a mechanical overload protection for the loading device so that the mechanical friction coupling is arranged to slip in case of force used to move the rotatable refining element towards the stationary refining element rises too high. The mechanical friction coupling thereby limits the force to be applied to move the rotatable refining element towards the stationary refining element. Additionally, this prior art arrangement may comprise a sensor arranged in the refiner to measure the position of the rotatable refining element in the refiner, whereby measurement information provided by this sensor may be applied to prevent the movement of the rotatable refining element too close to the stationary refining element so that they would clash with each other.

Despite of some disadvantages, such as a very high gear ratio of the gearmotor, that being typically over 1000:1, which makes the implementation of the gearing substantially complicate, or of the substantially complicate and expensive implementation of the mechanical friction coupling that also requires a regular maintenance, the prior art arrangement for adjusting the size of the blade gap in the conical refiner is very applicable in typical refining applications, wherein only properties of the fibres are intended to be affected to without substantially affecting to a fibre length of the fibrous material, i.e., without substantially cutting the fibres shorter. However, the power control of the main motor of the refiner is not very applicable way to adjust the size of the blade gap in refining applications wherein especially the fibre length of the fibrous material is intended to be affected to, i.e., wherein the fibres are intended to be cut to have a shorter length, such as in manufacturing of microfibrillar cellulose (MFC) or nanofibrillar cellulose (NFC) wherein very accurate constant blade gap is essential.

BRIEF DESCRIPTION OF THE INVENTION

An object of the present invention is to provide a novel loading device, and an arrangement and method for adjusting a blade gap in processing equipment for processing fibrous material.

The invention is characterized by the features of the independent claims.

The invention is based on the idea of combining the frequency converter, the cage induction motor and the position sensor measuring the rotational position of the shaft of the cage induction motor arranged to operate the gearing of the loading device to move the at least one processing element in respect of the at least one another processing element for adjusting the size of the blade gap between the processing elements.

An advantage of the invention is that it is provided an accurate and simple closed-loop position control application for adjusting the size of the blade gap. The combination of the frequency converter and the cage induction motor allows a substantially low gear ratio, for example between 100:1 and 150:1, which, in turn, simplifies the implementation of the gearing.

Some embodiments of the invention are disclosed in the dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following the invention will be described in greater detail by means of preferred embodiments with reference to the accompanying drawings, in which

Figure 1 shows schematically an arrangement for adjusting a size of a blade gap in a refiner; and

Figure 2 shows schematically a method for adjusting the size of the blade gap in processing equipment for processing fibrous material.

For the sake of clarity, the figures show some embodiments of the invention in a simplified manner. Like reference numerals identify like elements in the figures.

DETAILED DESCRIPTION OF THE INVENTION

Figure 1 is a very schematic side view, partly in cross-section, of a conical refiner 1 for refining fibrous material. The refiner 1 is thus a kind of processing equipment for processing fibrous material. The fibrous material to be refined may for example be lignocellulose-containing wood-based fibrous material, or plantbased fibrous material, or a fibrous material originating from recycled textile material. The fibrous material to be refined is in a form of pulp, i.e., a mixture of water and fibrous material and possibly some additives. A fibre consistency of the fibrous material to be refined may vary depending for example on the raw material of the fibrous material, the fibre consistency being typically between 3-40%.

The refiner 1 has an axial direction as shown schematically with an arrow indicated with the reference sign A and a radial direction as shown schematically with an arrow indicated with the reference sign R. In the axial direction A the conical refiner 1 has a first end El of smaller diameter and a second end E2 of larger diameter.

The refiner 1 comprises a frame 2, at least one supply connection 3 for supplying or feeding at least one flow of the fibrous material to be refined into the refiner 1, as shown schematically with an arrow indicated with the reference sign S, as well as at least one discharge connection 4 for discharging out of the refiner 1 at least one flow of the fibrous material already refined in the refiner 1, as shown schematically with an arrow indicated with the reference sign D.

The refiner 1 comprises a stationary refining element 5, i.e., a stator 5, having a first end of smaller diameter facing towards the first end El of the refiner 1 and a second end of larger diameter facing towards the second end E2 of the refiner 1. Therefore, for the sake of clarity, the reference sign El is also used to denote the first end of the stator 5 and the reference sign E2 is also used to denote the second end of the stator 5. The stator 5 is supported to a frame structure 2 of the refiner 1. The stator 5 thus forms a stationary processing element of the refiner 1.

The refiner 1 further comprises a rotatable refining element 6, i.e., a rotor 6, having a first end of smaller diameter facing towards the first end El of the refiner 1 and a second end of larger diameter facing towards the second end E2 of the refiner 1. Therefore, for the sake of clarity, the reference sign El is also used to denote the first end of the rotor 6 and the reference sign E2 is also used to denote the second end of the rotor 6. The rotor 6 is connected to a shaft 7 that extends substantially in the axial direction A of the refiner 1. The shaft 7 is connected to a main motor 8 of the refiner 1. The main motor 8 is arranged to rotate the shaft 7 and, by the shaft 7, the rotor 6 for example in a rotation direction indicated with an arrow RD in Figure 1. The rotor 6 thus forms a rotatable processing element of the refiner 1.

The stator 5 comprises a refining surface 5a facing to the rotor 6 and the rotor 6 comprises a refining surface 6a facing to the stator 5. The refining surfaces 5a, 6a comprise typically blade bars and blade grooves therebetween, in a manner known by a person skilled in the art. Therefore, for the sake of clarity, the refining surfaces 5a, 6a are not shown in detail in Figure 1. Typically, the refining surfaces are implemented with a set of refining segments attached next to each other in the stator 5 and the rotor 6 so that complete refining surfaces 5a, 6a extending over whole peripheries of the stator 5 and the rotor 6 are provided.

In the conical refiner 1 the rotor 6 is arranged substantially within the stator 5 so that the stator 5 and the rotor 6 are positioned substantially oppositely relative to each other so that there is a blade gap 9 between the substantially oppositely positioned refining surfaces 5a, 6a of the stator 5 and the rotor 6. The blade gap 9, i.e., a refining chamber 9, forms a volume wherein the fibrous material is refined. A free distance D between the opposing stator 5 and the rotor 6 indicates a size of the blade gap 9. The size of the blade gap 9 relative to the other components of the refiner 1 is highly exaggerated in Figure 1.

The operation of the refiner 1 of Figure 1 is as follows.

A flow of the fibrous material is supplied into the refiner 1 through the supply connection 3 at the first end E 1 of the refiner 1, as shown schematically with the arrow indicated with the reference sign S, wherein the fibrous material to be refined flows into the blade gap 9 at the first end El of the stator 5 and the rotor 6. When the rotor 6 is rotated, the fibrous material flows forward in the blade gap 9 from the first end El of the refiner 1 towards the second end E2 of the refiner 1 and is subjected to a refining effect by the opposite refining surfaces 5a, 6a of the stator 5 and the rotor 6 until the fibrous material flows out of the blade gap 9 at the second end E2 of the refiner 1. The flow of the fibrous material in the blade gap 9 is shown schematically with arrows denotes with the reference sign F. The fibrous material refined in the blade gap 9 is discharged out of the refiner 1 for a further processing through the discharge connection 4 at the second end E2 of the refiner 1. The refining effect subjected to the fibrous material in the blade gap 9 may be adjusted for example by adjusting a rotational speed of the rotor 6 and/or by adjusting the distance D between the stator 5 and the rotor 6, i.e., by adjusting the size of the blade gap 9.

Further, Figure 1 shows schematically a loading device 10 which is coupled by a coupling element 11 to the shaft 7 of the rotor 6 of the refiner 1 so that by operating the loading device 10 the rotor 6 may be moved in the axial direction A of the refiner 1 back and forth, as indicated schematically with an arrow AD, to adjust the distance D between the stator 5 and the rotor 6, i.e., to adjust the size of the blade gap 9. When the rotor 6 is moved towards the first end El of the refiner 1, the distance D between the stator 5 and the rotor 6 becomes smaller, i.e., the size of the blade gap 9 is reduced. When the rotor 6 is moved towards the second end E2 of the refiner 1, the distance D between the stator 5 and the rotor 6 becomes larger, i.e., the size of the blade gap 9 is increased. Because of the conical structure of the stator 5 and the rotor 6, an amount of change of the distance D between the stator 5 and the rotor 6, i.e., an amount of change in the size of the blade gap 9, is dependent on the amount of the movement of the rotor 6 in the axial direction A of the refiner 1 and an angle of ascent of the conical structure of the stator 5 and the rotor 6 relative to the axial direction A of the refiner 1. In the embodiment of Figure 1, the rotor 6 thus provides the movable refining element to be moved by the loading device 10 for adjusting the size of the blade gap 9.

The loading device 10 of Figure 1 comprises a gearing 12 having a shaft 13. The shaft 13 of the gearing 12 is coupled in connection with the shaft 7 of the rotor 6 of the refiner 1 by the coupling element 11. The coupling element 11 may also be omitted if the gearing 12 can be connected directly to the shaft 7 of the rotor 6, or to some other part of the rotor 6 so that an operation of the gearing 12 can move the rotor 6 in the axial direction A of the refiner 1 for adjusting the size of the blade gap 9.

The loading device 10 of Figure 1 further comprises a cage induction motor 14 having a shaft 15. The shaft 15 of the cage induction motor 14 is coupled to the gearing 12 for operating the gearing 12 to move the rotor 6 in respect of the stator 5 for adjusting the size of the blade gap 9. The gearing 12 and the cage induction motor 14 coupled to the gearing 12 provide together a gearmotor, wherein the gearing 12 is arranged to multiply the output torque available from the cage induction motor 14. The gearing 12 provides an output torque of the loading device 10 that is needed to move the rotor 6 without substantially increasing a power consumption of the cage induction motor 14 and allowing the size or output power of the cage induction motor 14 to be moderate. The cage induction motor is also inexpensive, has a simple and reliable structure and it is easy to control.

The loading device 10 of Figure 1 further comprises a position sensor 16 in the cage induction motor 14 for measuring a rotational position of the shaft 15 of the cage induction motor 14. The position sensor 16 is typically arranged at the shaft 15 in the cage induction motor 14 but other positions, at which the position sensor 16 can measure the rotational position of the shaft 15 of the cage induction motor 14, are not excluded. The rotational position of the shaft 15 of the cage induction motor 14 may be used to determine the position of the rotor 6 relative to the stator 5 when a geometry of the coupling between the rotor 6 of the refiner 1 and the loading device 10 and a gear ratio of the gearing 12 are known. The output signal of the position sensor 16, i.e., the measured rotational position of the shaft 15 of the cage induction motor 14, is denoted with the reference sign M- RP in Figure 1. The position sensor 16 may for example be a pulse transducer or a pulse sensor.

The loading device 10 of Figure 1 further comprises a frequency converter 17 coupled to the cage induction motor 14 for controlling the operation of the cage induction motor 14 by controlling a power supply to the cage induction motor 14. The frequency converter 17 comprises a position control module PCM configured to determine, based on the measured rotational position M-RP of the shaft 15 of the cage induction motor 14 inputted into the position control module PCM and the known geometry of the coupling between the rotor 6 and the loading device 10 and the gear ratio of the gearing 12, the current position of the rotor 6 relative to the stator 5, i.e., the current distance D between the rotor 6 and the stator 5, i.e., the current size of the blade gap 9. The position control module PCM may be implemented by hardware or software or by a combination thereof.

The position control module PCM of the frequency converter 17 is further configured to receive as an input a set value SET-D for the distance D between the rotor 6 and the stator 5 of the refiner 1, i.e., the set value for the size of the blade gap 9, to be applied in the refining under operation. Based on the measured rotational position M-RP of the shaft 15 of the cage induction motor 14 and the set value SET-D for the size of the blade gap 9, the position control module PCM is further configured to determine a control signal RP-CO to control the operation of the cage induction motor 14 for controlling the operation of the gearing 12 to move the rotor 6 in respect of the stator 5 in the event of the current size of the blade gap 9 differs from the set value SET-D for the size of the blade gap 9.

In the event of the current size of the blade gap 9 being larger than the set value SET-D for the size of the blade gap 9, the frequency converter 17 is configured to control the cage induction motor 14 to cause the rotor 6 to move towards the stator 5 according to the control signal RP-CO provided by the frequency controller 17.

In the event of the current size of the blade gap 9 being smaller than the set value SET-D for the size of the blade gap 9, the frequency converter 17 is configured to control the cage induction motor 14 to cause the rotor 6 to move away from the stator 5 according to the control signal RP-CO provided by the frequency controller 17. Alternatively, in the event of the current size of the blade gap 9 being smaller than the set value SET-D for the size of the blade gap 9, the frequency converter 17 may be configured to not provide any control signal that would cause the cage induction motor 14 to move the rotor 6 relative to the stator 5 if it is expected that for example because of wear of the refining surfaces 5a, 6a of the stator 5 and the rotor 6 the size of the blade gap 9, i.e., the distance D between the rotor 6 and the stator 5, will soon be according to the set value SET-D.

In the event of the current size of the blade gap 9 being substantially same as the set value SET-D for the size of the blade gap 9, any control action to move the rotor 6 relative to the stator 5 is not necessary.

Figure 2 shows schematically an embodiment of the method for adjusting the size of the blade gap in processing equipment for processing fibrous material.

The combination of the cage induction motor 14, the position sensor 16 and the frequency converter 17 provides a closed-loop position control application for controlling the position of the rotor 6 of the refiner 1 relative to the stator 5 of the refiner 1 for adjusting the size of the blade gap 9 in the refiner 1. This closed- loop position control application provides an accurate way to determine and control the current size of the blade gap 9 in a simple way, whereby a sensor possibly arranged in the refiner to measure the position of the rotor 6 in the refiner 1 may be omitted.

The combination of the frequency converter 17 and the cage induction motor 14 provides an accurate control, whereby the gear ratio of the gearing 12 may be selected to be substantially low, for example between 100:1 and 150:1. This, in turn, simplifies the implementation of the gearing 12, leading to cost savings in the implementation of the loading device 10.

The accurate adjustment of the size of the blade gap 9 is especially important in manufacturing of microfibrillar cellulose (MFC) or nanofibrillar cellulose (NFC). The term "nanofibrillar cellulose" refers herein to a collection of separate cellulose microfibrils or microfibril bundles derived from plant-based, and especially wood-based fibrous material. Synonyms for the nanofibrillar cellulose (NFC) are for example nanofibrillated cellulose, nanocellulose, microfibrillar cellulose, cellulose nanofiber, nano-scale cellulose, microfibrillated cellulose (MFC) or cellulose microfibcrils. Depending on the degree of grinding a particle size of the separate cellulose microfibrils or microfibril bundles is of some nanometres (nm) or micrometres (gm). A mean length of the separate cellulose microfibrils or microfibril bundles may for example be 0.2 - 200 gm and a mean diameter may for example be 2 - 1000 nm.

According to an embodiment, the frequency converter 17 is configured to determine a torque TQ of the cage induction motor 14 applied to move the rotor 6 relative to the stator 5 during adjusting the size of the blade gap 9 according to the position control signal RP-CO. The torque TQ may be determined based on the power and frequency used to operate the cage induction motor 14 by the frequency converter 17. The determined torque TQ may be compared with a maximum torque limit value TQMAX whereby in the event of the comparison of the determined torque TQ with the maximum torque limit value TQMAX indicating that the determined torque TQ is equal to or exceeds the maximum torque limit value TQMAX, the frequency converter 17 is configured to cause the cage induction motor 14 to stop, thus causing to interrupt the movement of the rotor 6 relative to the stator 5. The determination of the torque TQ and the comparison thereof to the maximum torque limit value TQMAX provides an electrically implemented overload protection for the cage induction motor 14, whereby the mechanical friction coupling applied in prior art may be omitted. This further provides cost savings in the implementation of the loading device 10.

According to an embodiment, the frequency converter 17 comprises a torque control module TCM that is configured to determine the torque TQ of the cage induction motor 14 applied to move the rotor 6 relative to the stator 5, as well as to compare the determined torque with the maximum torque limit value TQMAX. In response to the comparison of the determined torque TQ with the maximum torque limit value TQMAX indicating that the determined torque TQ is equal to or exceeds the maximum torque limit value TQMAX, the frequency converter 17 is configured to cause the cage induction motor 14 to stop with a specific torque control signal TQ-CO, or by interrupting the power supply to the cage induction motor 14. The torque control module TCM may be implemented by hardware or software or by a combination thereof.

According to an embodiment, the determination of the torque TQ applied in the adjustment of the size of the blade gap 9 is applied during the operation the operation of the refiner 1, for example to prevent an application of excessive load to the fibrous material to be refined and/or to prevent the opposite refining elements 5, 6 to clash to each other. In practice, the determination of the torque TQ applied in the adjustment of the size of the blade gap 9 may be utilized at least at the instants when the rotor 6 is moved towards the stator 5 for reducing the size of the blade gap 9. However, the determination of the torque TQ applied in the adjustment of the size of the blade gap 9 may also be utilized when the rotor 6 is moved away from the stator 5 for increasing the size of the blade gap 9, whereby a possible malfunction in an internal operation of the loading device 10 or its coupling to the rotor 6 may be observed based on the rise of the torque TQ needed by the cage induction motor 14 to move the rotor 6.

According to an embodiment, the determination of the torque TQ applied in the adjustment of the size of the blade gap 9 is utilized for a calibration of the loading device 10 which takes place in an unoperated state of the refiner 1. During the calibration of the loading device 10 the rotor 6 is moved towards the stator 5 until the rotor 6 comes into contact with, i.e., meets, the stator 5, which may be observed based on the determined torque TQ being equal to or exceeding a corresponding torque limit value TQLIMIT, which may be same limit value as the maximum torque limit value TQMAX above or a specific limit value applied during the calibration of the loading device 10. This kind of calibration operation is also called a zero-point calibration. At the point when the rotor 6 meets the stator 5, the rotational position of the shaft 15 of the cage induction motor 14 may be stored into the position control module PCM, for example, and applied later when adjusting the size of the blade gap 9.

According to an embodiment, the loading device 10 comprises a blade gap control module BGCM configured to control the operation of the frequency converter 17 for controlling the adjustment of the size of the blade gap 9. The blade gap control module BGCM may for example be configured to determine the set value SET-D for the size of the blade gap 9 and/or to determine the maximum torque limit value TQMAX for the torque applied in the adjustment of the size of the blade gap 9 during the operation of the refiner 1 and/or the torque limit value TQLIMIT applied during the calibration of the loading device 10. The measured rotational position M-RP of the shaft 15 of the cage induction motor 14 and the determined torque TQ may be input as measuring values into the blade gap control module BGCM and utilized therein for the control of the loading device 10, for example for the determination of the set value SET-D for the size of the blade gap 9. The blade gap control module BGCM may be implemented by hardware or software or by a combination thereof.

In the embodiment of Figure 1 the blade gap control module BGCM is implemented in a higher-level process control system which may be configured to control an operation of an entire fibre mass production compartment, for instance, whereby the blade gap control module BGCM is functionally part of the loading device 10. Alternatively, the blade gap control module BGCM may also be implemented in the frequency converter 17. The higher-level process control system is shown highly schematically in Figure 1 with a box denoted with the reference sign PCS.

The process control system PCS may comprise or receive information related for example to the fibre pulp to be produced, such as a quality or other desired characteristic of the fibre pulp to be produced, a quality or other characteristic of the fibrous raw material to be used as well as additives to be mixed into the fibre pulp to be produced and characteristics thereof. Based on the information received from the process control system PCS, the blade gap control module BGCM may determine setting parameters for the operation of the frequency converter 17, such as the set value SET-D for the size of the blade gap 9 and/or the maximum torque limit value TQMAX to be applied in the adjustment of the size of the blade gap 9 so that desired refining effect is subjected to the fibrous material to be refined.

According to an embodiment, the blade gap control module BGCM is configured to estimate wear of the opposing refining surfaces 5a, 6a during the refining based on for example characteristics of the refining surfaces 5a, 6a, characteristics of the fibrous material to be refined and possibly other characteristics relating to the refining, and to determine the set value SET-D for the size of the blade gap 9 by taking into account also the estimated wear of the refining surfaces 5a, 6a.

According to an embodiment, the loading device 10 comprises a vibration sensor 18 to be arranged to measure a vibration of the refiner 1 during the operation thereof. In the embodiment of Figure 1 the vibration sensor 18 is arranged to the frame 2 of the refiner 1, but other locations of the vibration sensor 18 in the refiner 1 are also applicable if the vibration sensor 18 can detect exceptional vibrations of the refiner 1 that originate from the clashing of the opposing refining elements during the operating of the refiner 1. The vibration sensor 18 provides a vibration measurement signal M-VB that indicates if the stator 5 and the rotor 6 start to clash during the operation of the refiner 1. If the stator 5 and the rotor 6 start to clash during the operation of the refiner 1, the level of the vibration measurement signal M-VB will rise substantially relative to the level of the vibration of the refiner 1 during normal operation of the refiner 1. The vibration measurement signal M-VB may for example be forwarded to the blade gap control module BGCM wherein it may for example be used in the determination of the set value SET-D for the size of the blade gap 9.

In the examples above the rotor 6 is arranged to be moved relative to the stator 5 when adjusting the size of the blade gap 9 but alternatively, the stator 5 may be arranged to be moved relative to the rotor 6 for adjusting the size of the blade gap 9.

Furthermore, in the examples above the disclosed solution for adjusting the size of the blade gap 9 is applied in a conical refiner 1, but the disclosed solution is correspondingly applicable for adjusting the size of the blade gap 9 also in disc refiners comprising disc-like stationary and rotatable refining elements, whereby a change in the size of the blade gap takes place in an axial direction of the refiner.

Furthermore, in the examples above the disclosed solution for adjusting the size of the blade gap 9 is applied in a refiner comprising a stator and a rotor opposite to the stator, but the disclosed solution is correspondingly applicable for adjusting the size of the blade gap 9 also in refiners wherein both opposite refining elements are rotors.

The disclosed loading device 10, as well as its different embodiments above, may alternatively be applied in a disperser which is also a kind of processing equipment for processing fibrous material. The disperser is thus a dispersing device that is intended to disperse the fibrous material in a blade gap between oppositely positioned dispersing elements. The fibrous material to be dispersed may for example be lignocellulose-containing wood-based fibrous material, or plant-based fibrous material, or a fibrous material originating from recycled textile material. The fibrous material to be dispersed is in a form of pulp, i.e., a mixture of water and fibrous material and possibly some additives. A fibre consistency of the fibrous material to be dispersed may vary depending for example on the raw material of the fibrous material, the fibre consistency being typically between 3-40%.

In the disperser the dispersing elements are the processing elements that provide the processing effect, i.e., a dispersion effect, subjected to the fibrous material in the blade gap, and the blade gap forms a dispersing chamber or volume wherein this dispersion effect is subjected to the fibrous material to be processed. The basic construction and operation of dispersers are substantially similar to that of the refiners, despite of some characteristics in dispersing surfaces of the dispersing elements if compared to characteristics in the refining surfaces of the refining elements. Thereby the loading device 10 and different embodiments thereof as disclosed above in connection with the refiner 1 are as well applicable when the loading device 10 is applied in connection with dispersers for adjusting the size of the blade gap in the dispersers.

It will be obvious to a person skilled in the art that, as the technology advances, the inventive concept can be implemented in various ways. The invention and its embodiments are not limited to the examples described above but may vary within the scope of the claims.

Claims

1. A loading device (10) for adjusting a size of a blade gap (9) in processing equipment for processing fibrous material, the loading device (10) comprising a gearing (12) to be coupled in connection with at least one processing element (5, 6) of the processing equipment to move the at least one processing element (5, 6) in respect of at least one another processing element (5, 6) of the processing equipment for adjusting the size of the blade gap (9) between the processing elements (5, 6), a cage induction motor (14) comprising a shaft (15) coupled to the gearing (12) for operating the gearing (12) to move the at least one processing element (5, 6) in respect of the at least one another processing element (5, 6), a position sensor (16) for measuring a rotational position (M-RP) of the shaft (15) of the cage induction motor (14) for indicating a position of the at least one processing element (5, 6) in respect of the at least one another processing element (5, 6), and a frequency converter (17) coupled to the position sensor (16) and to the cage induction motor (14) for controlling the operation of the cage induction motor (14) based at least on the measured rotational position (M-RP) of the shaft (15) of the cage induction motor (14).

2. A loading device as claimed in claim 1, characterized in that the position sensor (16) is arranged at the shaft (15) of the cage induction motor (14).

3. A loading device as claimed in any one of the preceding claims, characterized in that the frequency converter (17) comprises a position control module (PCM) configured to determine a position control signal (RP-CO) for controlling the operation of the cage induction motor (14) based at least on the measured rotational position (M-RP) of the shaft (15) of the cage induction motor (14).

4. A loading device as claimed in claim 3, characterized in that the position control module (PCM) is configured to determine the position control signal (RP-CO) based at least on the measured rotational position (M-RP) of the shaft (15) of the cage induction motor (14) and a set value (SET-D) set for the size of the blade gap (9).

5. A loading device as claimed in any one of the preceding claims, characterized in that the frequency converter (17) comprises a torque control module (TCM) configured to determine a torque (TQ) of the cage induction motor (14) applied to move the at least one processing element (5, 6) in respect of the at least one another processing element (5, 6) and to compare the determined torque (TQ) with a maximum torque limit value (TQMAX) and to cause the cage induction motor (14) to stop in the event of the determined torque (TQ) being equal to or exceeding the maximum torque limit value (TQMAX).

6. A loading device as claimed in any one of the preceding claims, c h a r a c t e r i z e d in that the loading device (10) comprises a blade gap control module (BGCM) configured to determine setting parameters for an operation of the frequency converter (17).

7. A loading device as claimed in claim 6, c h a r a c t e r i z e d in that the blade gap control module (BGCM) is configured to determine at least one of the following parameters: the set value (SET-D) for the size of the blade gap (9) and the maximum torque limit value (TQMAX).

8. A loading device as claimed in any one of the preceding claims, c h a r a c t e r i z e d in that the loading device (10) is configured to be used to adjust the size of the blade gap (9) in a refiner (1) for refining fibrous material or in a disperser for dispersing fibrous material.

9. An arrangement for adjusting a size of a blade gap (9) in processing equipment for processing fibrous material, the arrangement comprising processing equipment for processing fibrous material and comprising at least two substantially oppositely positioned processing elements (5, 6) at least one of which is movable in an axial direction (A) of the processing equipment for adjusting the size of the blade gap (9) between the processing elements (5, 9), and a loading device (10) as claimed in any one of claims 1 to 8 coupled to the processing equipment for moving at least one processing element (5, 6) in respect of at least one another processing element (5, 6) in the axial direction (A) of the processing equipment for adjusting the size of the blade gap (9) between the processing elements (5, 6).

10. An arrangement as claimed in claim 9, c h a r a c t e r i z e d in that the processing equipment is a refiner (1) for refining fibrous material or a disperser for dispersing fibrous material.

11. A method for adjusting a size of a blade gap (9) in processing equipment for processing fibrous material, in which method at least one processing element (5, 6) of the processing equipment is moved in respect of at least one another processing element (5, 6) of the processing equipment by at least one loading 15 device (10) as claimed in any one of claims 1 to 8 for adjusting the size of the blade gap (9) between the processing elements (5, 9 ) , the method comprising measuring a rotational position (M-RP) of the shaft (15) of the cage induction motor (14) for indicating a position of the at least one processing element (5, 6) in respect of the at least one another processing element (5, 6), determining a position control signal (RP-CO) for controlling the operation of the cage induction motor (14) based at least on the measured rotational position (M-RP) of the shaft (15) of the cage induction motor (14), and controlling the operation of the cage induction motor (14) by the frequency converter (17) according to the determined position control signal (RP-CO) to control the position of the at least one processing element (5, 6) in respect of the at least one another processing element (5, 6) for adjusting the size of the blade gap (9) between the processing elements (5, 6).

12. A method as claimed in claim 11, c h a r a c t e r i z e d by determining a set value (SET-D) for the size of the blade gap (9) and determining the position control signal (RP-CO) based at least on the measured rotational position (M-RP) of the shaft (15) of the cage induction motor (14) and the set value (SET-D) determined for the size of the blade gap (9).

13. A method as claimed in claim 11 or 12, c h a r a c t e r i z e d by operating by the cage induction motor (14) the gearing (12) coupled to the at least one processing element (5, 6) for moving the at least one processing element (5, 6) in respect of the at least one another processing element (5, 6).

14. A method as claimed in any one of claims 11 to 13, c h a r a c t e r - i z e d by determining a torque (TQ) of the cage induction motor (14) when the at least one processing element (5, 6) is moved in respect of the at least one another processing element (5, 6), comparing the determined torque (TQ) with the maximum torque limit value (TQMAX), and interrupting the movement of the at least one processing element (5, 6) in respect of the at least one another processing element (5, 6) in response to the determined torque (TQ) being equal to or exceeding the maximum torque limit value (TQMAX).

15. A method as claimed in any one of claims 11 to 14, c h a r a c t e r i z e d by the processing equipment being a refiner (1) for refining fibrous material or a disperser for dispersing fibrous material.