DRIVE DEVICE COMPRISING A ROLL FOR TRANSPORTING MATERIAL AND A VARIABLE RELUCTANCE MOTOR

Field of the Invention

The present invention relates to a drive device, and in particular to a drive device comprising a roll used in, e.g., fibre machine.

Related background Art

In fibre machines such as paper, board or tissue

machines, fibre is transported via a plurality of rolls, for example in a dryer section of such a machine. In the prior art, the rolls are driven by electro motors such as asynchronous motor, synchronous motors or DC motors.

With respect to the construction of the machine as well as to the maintenance thereof, these kinds of motors comprise several disadvantages: For example, for

transmitting the mechanical drive power of these motors to the rolls, power transmissions are required. This requires some effort in the construction, and also leads to a complicated maintenance during operation.

Summary of the Invention

Thus, it is an object of the present invention

overcome the above problems of the prior art.

According to a first aspect of the present invention, this object is solved by a drive device as set out in the independent claim 1. In particular, the drive device comprises a roll for transporting material, and a

variable reluctance motor including a stator and a rotor, wherein the rotor comprises salient poles, and the roll comprises a shaft part and the rotor.

According to a second aspect of the invention, the above object is solved by a roll for transporting material as defined in claim 12. In particular, the roll for

transporting material comprises a shaft part and a rotor, wherein the rotor comprises salient poles and is

insertable into a stator of a variable reluctance motor.

According to a third aspect of the present invention, the above object is solved by a variable reluctance motor as set out in claim 21. In particular, the variable

reluctance motor comprises a stator and a rotor

comprising salient poles, wherein the rotor is part of a roll for transporting material. Thus, according to several aspects of the present

invention, a rotor of a variable reluctance motor is formed such that it is part of a roll for transporting material. Hence, an easy direct drive device is provided, which can be realized without power transmission shafts or gears, so that costs can be reduced and maintenance can be facilitated.

Advantageous developments are set out in the dependent claims .

For example, the rotor and the shaft part may be directly connected with each other. In this way, both parts can be separately manufactured, but easily be connected together to form one unit. Alternatively, the rotor and the shaft part may be integrally formed. That is, a roll can be formed from one piece . The salient poles (in the following also referred to as teeth) of the rotor may be provided over the whole length or a part of the roll.

The spaces between the salient poles may be filled with a material having a lower permeability than the material of the rotor.

The roll may be made of iron or a low-alloy iron

material .

The rotor may be provided inside the stator, or,

alternatively, the stator may be provided inside the rotor . The stator may be provided as a full circle or as a segment of a circle.

The material to be transported by the roll may be a web, a paper or a board.

The roll may be usable as a part of a paper or board machine .

Brief Description of the Drawings

These and other objects, features, details and advantages will become more fully apparent from the following detailed description of embodiments of the present invention which is to be taken in conjunction with the appended drawings, in which:

Fig. 1 shows a sectional view in longitudinal direction of a roll according to a first embodiment,

Fig. 2 shows a cross sectional view of a rotor part of the roll according to the first embodiment, Fig. 3 shows a sectional view in longitudinal direction of a roll according to a second embodiment,

Fig. 4 shows a sectional view in longitudinal direction of a roll according to a third embodiment,

Fig. 5 shows a sectional view in longitudinal direction of a roll according to a fourth embodiment,

Fig. 6 shows a sectional view in longitudinal direction of a roll according to a fifth embodiment,

Fig. 7 shows a sectional view in longitudinal direction of a roll according to a sixth embodiment, Fig. 8 shows a sectional view in longitudinal direction of a roll according to a seventh embodiment,

Fig. 9 shows a cross sectional view of a shaft part of the roll according to a modification, and

Fig. 10 shows a cross sectional view of a shaft part of the roll according to a further modification. Detailed Description of embodiments

In the following, description will be made to embodiments of the present invention. It is to be understood, however, that the description is given by way of example only, and that the described embodiments are by no means to be understood as limiting the present invention thereto . According to embodiments of the present invention, a drive device for fibre machine, such as a paper, board or tissue machine is provided. In particular, the drive device drives a roll for transporting material such as fibre. According to these embodiments, a variable

reluctance motor is applied as a drive source, wherein the rotor of the variable reluctance motor is part of the roll .

Variable reluctance motors are gradually breaking through in the speed-controlled drives of manufacturing. They will possibly replace frequency converter driven short- circuit motors (asynchronous motors) and are a good alternative for permanent-magnet motors (dc motors or synchronous motors) .

In general, applications for variable reluctance motors in the paper industry are all recent speed- and moment- controlled drives. These can be old direct-current drives or newer frequency-converter drives. Advantages of the variable reluctance motor in these applications are:

durable and simple structure, good cooling

good efficiency in the whole operating range

fault tolerance

constant power range is wide

- no permanent magnets, still close to a disc motor operates as a generator in a regenerative drive small rotor inertia, rapid moment control

more cost-effective than a permanent magnet motor ecological structure, friendly to the environment - energy savings

no dependence on permanent magnet material

The drive device including the variable reluctance motor can be applied in traditional drives of a fibre machines, such as:

paper-machine line drive

coating-machine line drive

calender line drives

winder drives

- slitter-winder line drive

brake generator

According to the present embodiments, the roll is

directly driven by the variable reluctance motor. That is, the drive device does not need a transmission

(gearbox) , and is cheaper and easier to service than a permanent-magnet motor, since, for example, no effective cooling is necessary and the rotor is no magnetic during servicing .

As will be explained in the following in more detail, the rotor of such a variable reluctance motor can be

connected directly to a roll, such that a part of the roll, on the outer surface or inner surface, has been toothed similar to the rotor of the variable reluctance motor. Preferably, this part of the roll is iron or a low-alloy iron material. Typically, all low-alloy iron materials have a good permeability required. Preferably, the rotor and also the stator are made from laminated steel in order to reduce eddy currents. The rotor of a variable reluctance motor comprises salient poles (which are also referred to as rotor poles or teeth) . The stator of a variable reluctance motor comprises salient poles, at which stator coils are wound. The magnetic poles of the rotor are formed by the salient poles through magnetic reluctance. Therefore, the rotor of a variable reluctance motor can be formed rather simply, so that no bars, cage, magnets, windings or the like on the rotor are necessary.

Between the salient poles, there are gaps (also referred to as grooves), which may be left empty, i.e., are air gaps. Alternatively, the gaps can be filled with some material having low permeability, such as common

plastics .

The stator can be inside or outside the rotor. The distance and number of stator poles fulfils the

conditions defined for the rotation of the VR motor.

Preferably, the number of rotor poles is not the same as that of the rotor poles (typically less) . If required by the structure or maintenance, the stator can be made of segments. The stator can operate only on a part of the rotor circle. Those parts of the rotor, which are not close to the stator, are passive roll or shaft parts without having any magnetic pull. This latter case is not possible if a permanent-magnet rotor is used. In the following, several embodiments of the present invention are described in more detail by referring the enclosed drawings.

Fig. 1 shows a first embodiment for a drive device according to the present invention. In particular, a roll 10 is shown, which comprises a rotor part 10A and a shaft part 10B. In the present embodiment, the shaft part 10B and the rotor 10A are provided as one piece, i.e. are integrally formed. Over the whole lengths of the roll, salient poles (also referred to as teeth) 30A are formed, which are indicated in the drawing by a hatched area. Thus, according to the first embodiment, the roll 10 can easily be formed by machining. Reference number 20 denotes the stator of the variable reluctance motor, wherein according to the present embodiment the rotor is provided inside the stator.

Fig. 2 shows a cross sectional view of the roll, taken at the rotor part 10a.

The roll 10 is made of iron or a low-alloy iron material. The spaces between the salient poles (gaps) are filled with a material 30a which has a lower permeability than a material of the rotor. For example, common plastics or the like can be applied for this. By filling the gaps with such a material, it is possible that the roll has a smooth surface, so that the fiber can be easily

transported by the roll. According to the present

embodiment, the spaces are filled with the material over the whole length of the roll 10. However, alternatively it would be possible to provide the material only in the gaps in the shaft part, so that the gaps in the rotor part 10A will be left empty.

Fig. 3 shows a second embodiment for the drive device. The second embodiment differs from the first embodiment in that the salient poles 31 are not provided over the whole length of the roll 10. The gaps between the salient poles can be made by machining such as milling, for example. Depending on the manufacturing process, the gaps can be made in a slightly rounded form, as it is

indicated in Fig. 3. Similar as according to the first embodiment, also here the gaps can be filled with a material having a low permeability such as common

plastics. Otherwise, the second embodiment is similar to the first embodiment, that is, the stator 21 of the variable reluctance motor is provided outside the stator 11.

As a modification of the second embodiment, it is also possible to provide the salient poles only at the rotor part 11A, so that the shaft part 11B would have a uniform surface. In this case, it would not be necessary to fill the gaps between the salient poles.

Fig. 4 shows third embodiment for the drive device.

According to the third embodiment, the rotor 12A and the shaft part 12B a separated, but directly connected to each other, for example by welding or the like, or by a detachable connection or joint (such as screws or bolts or the like) . According to the third embodiment, the salient poles 32 are provided only at the rotor part. Similar as in the first and the second embodiment, the stator 22 is provided outside of the rotor. Similar as in the above-described modification of the second

embodiment, it is also not necessary to fill the spaces between the salient poles with a material having a lower permeability .

Fig. 5 shows a fourth embodiment for the drive device. As shown in Fig. 5, according to this embodiment the stator 23 is provided inside the stator part 13A. According to the fourth embodiment, the rotor part 13A and the shaft part 13B of the roll 13a integrally formed. For example, the opening in the roll 13 for the stator part can be made by machining such as drilling or the like. The salient poles 33 are provided inside the roll. Fig. 6 shows a fifth embodiment of the drive device. The fifth embodiment is the similar to the fourth embodiment, and differs in that here the rotor part 14A and the shaft part 14B are separate elements, which are connected to each other for example by welding or the like, or by a detachable connection or joint (such as screws or bolts or the like) . The rotor part 14A and the shaft part 14B form together the roll 14. Otherwise, the fifth

embodiment is similar to the fourth embodiment, that is, the stator 24 is provided inside the rotor, and the rotor part 14A comprises salient poles 34 on the inner side.

Fig. 7 shows a sixth embodiment for the drive device. According to the sixth embodiment, the rotor part 15A and the shaft part 14B are integrally formed to the roll 15, and the salient poles 35 are provided over the whole length of the roll 15. Similar as in the fourth and fifth embodiments, the stator 24 is provided inside the rotor.

Fig. 8 shows a seventh embodiment for the drive device. The seventh embodiment is similar to the sixth

embodiment, and differs in that the salient poles 36 are provided only over a part of the roll 16. Depending on the manufacturing method, also here the salient poles 36 can be rounded, similar as in case of the second

embodiment. Furthermore, also according to the seventh embodiment, the stator 26 is provided inside the rotor.

According to the seventh embodiment, the roll 16 is provided as a hollow tube, similar as in case of the sixth embodiment. However, it would be possible to use solid roll, wherein the space for the stator 26 is provided by machining (e.g., drilling) or the like, similar as in case of the fourth embodiment. According to the fourth to seventh embodiments, the rotor salient poles are provided inside the roll, so that the outer surface of the roll is uniform and smooth. Hence, it is not necessary to provide a material having a lower permeability than the rotor in the gaps between the salient poles. However, depending on the need, for example with respect to maintenance and the like, also here this material could be provided in the gaps.

Furthermore, according to the embodiments described above, the stator is provided as a full circle. However, depending on the need or the specific construction for the paper machine, it is also possible to provide the stator only as a segment of the circle. In this way, maintenance can be facilitated.

According to the first to third embodiments, in the gaps between the salient poles of the rotor preferably the material having a low permeability is filled. This can be modified such that this material is provided over the whole surface of the shaft part (10b, lib, 12b), so that a smooth and uniform surface of the roll is provided.

This is illustrated in Fig. 9 as a modification to the first embodiment, but can be appropriately applied to all embodiments. As shown, the material (plastics) 30b is provided over the whole surface also over the salient poles 30 of the shaft part 10b. If the construction of the variable reluctance motor permits this (i.e., when the gap (air + plastics) between rotor and stator poles is small enough) , it is also possible to provide the material in this way over the rotor part 10a as well.

Alternatively, a tube or a hollow cover can be fitted over the shaft part in order to provide a uniform

surface. This is illustrated in Fig. 10, wherein the tube is denoted by reference number 30c. In this case, the material 30a can also be omitted. Thus, according the embodiments described in the

following in more detail, following advantages can be achieved :

- A rotor section can be made in an ordinary roll only by machining

- Costs of replacement rolls are low

- The rotor section is not magnetic nor vulnerable to corrosion or temperature

- No power transmission shafts or gears are required - The solutions according to the embodiments gives new possibilities to cost-effective structures.

It is noted that the embodiments and general and specific examples described above are provided for illustrative purposes only and are in no way intended that the present invention is restricted thereto. Rather, it is the intention that all variations and modifications be included which fall within the spirit and scope of the appended claims.