Patent Application
20230047528
The disclosure relates to a refiner for refining pulps in a fibre pulp suspension, comprising a shaft, a rotor disc attached firmly to the shaft, and a shaft bearing, the rotor disc being disposed between two stator discs and forming a refining chamber between the rotor disc and the stator discs, the shaft being movable in an axial direction, at least one stator disc being slidable in axial direction, the size of the refining chamber being adjustable by means of the spacing between the stator discs, and the rotor disc being movable between the stator discs by moving the shaft in axial direction.
Refiners—or rather the double-disc refiners described—are known with different designs. Typically, a rotor disc rotates between two stationary stator discs, the rotor disc and the stator discs being fitted with refiner plates. The pulp in the suspension is refined in the refining chamber between the rotor disc and the stator discs. Even distribution of the refining pressure in the refining chamber, and thus in the area between the rotor disc and the first stator disc as well as in the area between the rotor disc and the second stator disc, is essential. For this purpose, the rotor must be movable in axial direction. Various solutions are known in the state of the art.
For example, DE 20 2006 002 999 U1 describes a disc refiner for refining a pulp material. Details of the rotor and stator are described, the rotor having a supporting disc that can be displaced on the rotor shaft in axial direction, for example by means of axial toothing. The supporting disc and hence the entire rotor can align freely in axial direction. It is explained that it can also be favourable if the rotor itself can be displaced in axial direction.
Provided herein is a refiner with reduced wear on the rotor discs and stator discs, and, in particular, on the refiner plates on these discs.
This is achieved in that the shaft bearing is connected hydraulically to the refining chamber. In this case, “connected hydraulically” means that a fluid—preferably water—can be transferred between the shaft bearing and the refining chamber. As a result, continuous stream filaments of the fluid—hydraulically speaking—can be shown or are present between the shaft bearing and the refining chamber. Surprisingly, it appears that the shaft can be moved particularly smoothly in axial direction if the shaft bearing is connected hydraulically to the refining chamber. In particular, this smooth movement is also retained when the refiner is in operation. The smooth axial movement of the shaft and thus of the rotor disc firmly attached to the shaft is an essential prerequisite for the pulp present in a suspension being refined evenly in the refining chamber, i.e. in the area between the rotor disc and the first stator disc and in the area between the rotor disc and the second stator disc, because the refining pressure is evenly distributed in the refining chamber. Even distribution of the refining pressure results here from the autonomous and smooth positioning of the rotor disc between the stator discs. Any resistance to positioning, e.g. by friction, is conducive to uneven distribution of the refining pressure, thus directly promoting uneven pulp refining and uneven wear on the rotor discs and stator discs, this wear affecting the refiner plates on the rotor disc and the stator discs in particular. The firm connection between the rotor disc and the shaft means that there is no axial mobility between the shaft and the rotor disc and thus, no relative motion in the axial direction between shaft and rotor disc. However, the connection between rotor disc and shaft can, of course, by designed so as to be detachable, which can be important for service and installation purposes.
A favourable embodiment of the refiner is characterized in that the rotor disc is firmly attached to the shaft inside or outside the shaft bearing. Hence, the shaft is supported on both sides of the rotor disc or has an overhung arrangement. Supporting the refiner shaft on both sides of the rotor disc allows even and distributed bearing load, but not a very compact design as the shaft is supported on both sides of the rotor disc. If it has an overhung arrangement, the rotor shaft is firmly attached to the shaft at a first end of the shaft and the rotor disc is outside the shaft bearing. At a second end of the shaft, the shaft is connected to a motor via a coupling, the coupling being outside the shaft bearing. Advantageously, the overhung arrangement of the rotor disc together with the hydraulically connected shaft bearing disclosed herein allow a very compact design.
An advantageous embodiment of the refiner is characterized in that the shaft is supported entirely on fluid-lubricated plain bearings. This enables particularly smooth shaft movement in axial direction of the shaft. If the shaft is supported on both sides of the rotor disc, only fluid-lubricated plain bearings are disposed on either side of the rotor disc. If the shaft is supported in an overhung arrangement, one end of the shaft is attached firmly to the rotor disc and the shaft is supported entirely on fluid-lubricated plain bearings, the shaft bearing being disposed between the rotor disc and a second end of the shaft. Another favourable embodiment of the refiner is characterized in that the shaft bearing is designed as a fluid-lubricating plain bearing, where a fluid, preferably water, can be fed to the refining chamber via the shaft bearing. Design as a water-lubricated plain bearing is particularly advantageous. In accordance with the hydraulic connection between the shaft bearing and the refining chamber, as described herein, water can be fed to the refining chamber via the water-lubricated plain bearing. Using water as the fluid means that it is possible to support the shaft without using oil, thus excluding the risk of the pulp suspension being contaminated with oil, or rather hydraulic oil. Forced guidance is particularly advantageous in order to ensure that the flow direction of the fluid—preferably water—runs through the fluid-lubricated plain bearing into the refining chamber. Forced guidance of this kind can be achieved easily if the fluid in the shaft bearing has a higher pressure than the fibre pulp suspension in the refining chamber in the area where the fluid enters the refining chamber. Due to the higher pressure of the fluid in the shaft bearing, the fluid flows in the direction of the refining chamber, which has the advantage of effectively preventing the shaft bearing, or rather water-lubricated plain bearing, from being contaminated. Thus, the water-lubricated plain bearing is always flushed through in the direction of the refining chamber and the shaft retains its smooth mobility throughout operations. If the refiner shaft is supported on both sides of the rotor disc, the shaft bearing is designed as a fluid-lubricated plain bearing on either side of the rotor disc, where a fluid, preferably water, can be fed to the refining chamber via the shaft bearing.
Another favourable embodiment of the refiner is characterized in that a seal is disposed between the refining chamber and the shaft bearing. The shaft bearing is designed as a fluid-lubricated plain bearing, where a fluid, preferably water, can be fed through the shaft bearing via the seal to the refining chamber. An advantageous design of the seal comprises a rotary shaft seal or a throttle ring. For example, the seal is disposed between shaft and bearing housing, placed in a cut-out in the bearing housing and secured in the bearing housing by a fastening ring. The shaft passes through the seal, the seal coming into contact with the shaft if it is a rotary shaft seal and a gap being formed between shaft and seal if it is a throttle ring. It is an advantage if the seals have at least one sealing lip.
An advantageous embodiment of the refiner is characterized in that the sealing effect of the seal depends on the flow direction of the fluid. Rotary shaft seals or throttle rings are seals of this kind. The sealing effect dependent on the flow direction can be achieved if the fluid, or rather the fluid pressure, lifts the seal off the sealing surface and/or the seal provides a larger flow cross-section for the fluid when, for example, the fluid flows from the shaft seal to the refining chamber. When the seal lifts off the sealing surface and/or the flow cross-section of the fluid is enlarged, sliding friction in particular between seal and sealing surface is prevented or reduced, enhancing smooth movement of the shaft in the axial direction of the shaft. The seal is designed advantageously with a sealing lip, the sealing lip having a truncated cone shape in order to create a sealing effect that depends on the direction of flow. In order to create a seal towards the rotating shaft, for example between shaft bearing and refining chamber, a seal with a truncated cone-shaped sealing lip can be disposed such that the shaft runs inside the seal, the axial direction of the shaft and the axis of the truncated cone-shaped sealing lip coinciding with one another. In a first example, the seal would be mounted in the bearing housing and the truncated cone-shaped sealing lip would be pressing onto the shaft. Then the fluid flowing from the base to the imaginary tip of the truncated cone-shaped sealing lip would cause the sealing lip to expand and the seal to lift off the shaft, or at least reduce the pressing force of the seal, which is important for the seal and the sliding friction, against the sliding surface, or rather shaft. If the flow direction in this first example is reversed—i.e. the fluid flows from the imaginary tip of the cone to the base of the truncated cone-shaped sealing lip—the fluid would press the sealing lip against the shaft and increase the pressing force of the sealing lip. In a second example, the seal would be mounted on the shaft, for example, and the truncated cone-shaped sealing lip would be facing towards the bearing housing. If the fluid then flows from the base to the imaginary tip of the truncated cone-shaped sealing lip, this would cause the base surface to expand, thus increasing the pressing force of the sealing lip and enhancing the sealing effect towards the bearing housing. Seals with a sealing effect that depends on the direction of flow of the fluid are advantageous because the seal can achieve very little or no friction losses if the fluid flows in the desired direction of flow. However, the best possible seal is obtained if the direction of flow is reversed, and any fluid flow in the opposite direction to the desired direction of flow is reduced or prevented.
A similarly favourable design of the refiner is characterized in that the seal has a lesser sealing effect if the fluid flows through the shaft seal into the refining chamber than if the fluid flows out of the refining chamber into the shaft seal. Seals with a sealing effect that depends on the direction of flow of the fluid are advantageous because they permit very little or no friction losses by the seal if the fluid flows according to the desired direction of flow out of the shaft seal and into the refining chamber. If the direction of flow is reversed, this behaviour is advantageously reversed because the best possible seal is needed if the fluid flows out of the refining chamber and into the shaft seal, particularly to prevent the fibre pulp suspension from flowing out of the refining chamber and into the shaft seal and the shaft seal thus being contaminated by the pulp.
Another favourable embodiment of the refiner is characterized in that a damping element is assigned to the shaft bearing, the damping element being disposed between the rotor disc and a motor, preferably between the rotor disc and a coupling, the coupling being disposed between the rotor disc and the motor. The disclosed bearing permits such smooth movement of the shaft in axial direction that the sudden, abrupt movements by the shaft that can occur during operation are avoided. For example, when the fibre pulp suspension feed to the refiner begins, there can be a resulting force acting on the rotor disc and thus on the shaft that causes an abrupt movement by the shaft. Similarly, there can also be a resulting force acting on the rotor disc or the shaft during operation. The coupling can provide a slight damping effect, e.g. by the action of friction in the coupling. However, this is not enough, so it is an advantage to include a damping element to ensure uniform shaft movements in axial direction.
An advantageous embodiment of the refiner is characterized in that the damping elements are connected hydraulically to the shaft bearing. The damping element comprises a damping area, for example, and a throttling element. The throttling element can be a throttle ring, for example, disposed between shaft and bearing housing and largely covering the gap between shaft and bearing housing. The damping area is formed, for example, by an area between shaft, bearing housing and throttling element, the damping area being disposed between shaft bearing and coupling. Here, the damping element is connected hydraulically to the shaft bearing, i.e. the fluid—preferably water—that can be fed to the shaft bearing is also fed to the damping element, where continuous stream filaments of the fluid can be presented between the shaft bearing, i.e. the fluid feed to the shaft bearing, and the damping element. If the shaft moves in axial direction, the volume of the damping area changes, with fluid flowing into the damping area via the throttle element if the volume increases and out of the damping area via the throttle element if the volume decreases. This results in a damping effect in accordance with the viscosity losses of the fluid when passing through the damping element. It is advantageous to arrange the damping element between the bearing and the coupling because there is no hydraulic influence on the seal when the bearing is disposed between the seal and the damping element.
A similarly advantageous embodiment of the refiner is characterized in that the fibre pulp suspension can be fed to the refining chamber through an inlet area or through the shaft. This advantageous bearing permits shaft diameters that can be used to feed the fibre pulp suspension through the shaft into the refining chamber, and larger shaft diameters can also be implemented in a way that is technically feasible, unlike when using conventional anti-friction bearings.
Another advantageous embodiment of the refiner is characterized in that the rotor disc contains openings, these openings providing even distribution of the fibre pulp suspension in the refining chamber, which can be fed in through the inlet area or shaft. Advantageously, the fibre pulp suspension is fed to the refiner on one side of the rotor disc, the fibre pulp suspension being guided directly into a first gap between a first stator disc and the rotor disc. The fibre pulp suspension can also be fed through the openings in the rotor disc to the second side of the rotor disc, where the fibre pulp suspension can be guided into a second gap between a second stator disc and the rotor disc.
An advantageous embodiment of the refiner is characterized in that the shaft is connected via a coupling to a motor, where the shaft movement in axial direction can be absorbed by the coupling. As the motor is disposed rigidly and the shaft is advantageously movable in axial direction, any relative movement in axial direction between shaft and motor can be absorbed via the coupling.
A particularly advantageous embodiment of the refiner is characterized in that the coupling is designed as a curved teeth coupling and a radial and/or axial movement of the shaft is possible in the curved teeth coupling. Here, the shaft is connected to the motor with external toothing in the area of the coupling and via an intermediate coupling piece with internal toothing. When maintenance is required, very good access to the refiner is obtained by dismounting the intermediate piece. Curved teeth couplings enable the shaft to move in radial direction as well as in axial direction. In addition, curved teeth couplings enable the outer toothing of the shaft and the inner toothing of the intermediate coupling piece to make a swaying movement when the shaft rotates, with permanent sliding friction between the toothings. Thus, there is no initial static friction in the coupling if there is relative axial movement between the shaft and the motor during rotation of the shaft because there is always sliding friction in the coupling between the toothings. As a result, particularly smooth shaft movement is possible in axial direction.
The invention will now be described using the examples in the drawings.
The disclosed embodiments thus offer numerous advantages. The lower wear on the rotor discs and stator discs—especially on the refiner plates on these discs—achieved by very smooth positioning of the rotor disc, which is also retained in continuous operation, is particularly advantageous. Here, the disclosed embodiments prevent any contamination by pulp in the area of the seal and the bearing. Similarly, the disclosed bearing avoids the risk of oil contaminating the fibre pulp suspension because the bearing can be operated without oil, as well as eliminating or minimizing the risk of the pulp contaminating the bearing. The bearing also permits a more compact refiner design and, above all, a shorter overall length.
| Number | Date | Country | Kind |
|---|---|---|---|
| A50275/2020 | Apr 2020 | AT | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2021/056317 | 3/12/2021 | WO |
