FIELD OF THE INVENTION

This invention relates to reinforcement means for rotor poles in a gearless mill.

Specifically, the invention relates to a gearless mill drive with reinforcement means for the rotor poles, to a rotor pole assembly for a gearless mill drive, and to a gearless mill including reinforcement means.

BACKGROUND

Gearless mills are typically driven by a direct drive ring motor around an outer shell of a mill body. The ring motor is generally comprised of a mill body with a flange to which a plurality of rotor poles of the ring motor are directly attached. As the rotor poles are mounted directly onto the mill body, the mill itself becomes the rotor of the ring motor. Each rotor pole is individually exchangeable. A stator ring motor is mounted around the rotor poles leaving an air gap between the rotor and the motor. A driving torque is transmitted via a magnetic field from the motor to the mill body. The transfer of torque from pole to mill flange is only by friction and not by sheer force of the pole bolt. The friction generated by the torque applied to the pole bolts is sufficient for normal operation of the ring motor.

In the ring motor, each rotor pole unit comprises a center plate and pole bolts. Each rotor pole is fixed directly to the flange on the mill body with at least three pretensioned bolts. The outer bolts holding the rotor poles in place are generally equipped with an eccentric bushing to allow air gap adjustment. In addition, the bolts are individually exchangeable.

Figure 4 shows two adjacent rotor poles 212 which are mounted on the flange 214 of the mill body with three bolts, respectively.

Each of the rotor poles is subject to torque and the pole plates act as a cantilever beam. This results in a large amount of stress in the areas around the pole fixation due to the pretension in the bolts and the torque on the pole plates. There is therefore a need to reduce the amount of stress on the poles, particularly for existing ring motors as well as ring motors with more demanding power or power/size ratios.

SUMMARY OF THE INVENTION

According to a first aspect of the invention, there is provided a ring motor mill comprising one or more of the following:

a mill body, wherein the mill body may comprise an outer shell, wherein the outer shell may comprise a flange extending circumferentially around the outer shell;

a ring motor which may comprise a stator and a rotor,

wherein the rotor may comprise a plurality of rotor poles mounted on the flange; wherein the stator may be mounted around the rotor poles;

wherein at least two adjacent rotor poles may be coupled together with a reinforcement member.

In some embodiments, the mill body may comprise an inner and an outer shell.

In a second aspect, the invention provides a rotor pole assembly, particularly for a gearless mill drive, more particularly for a ring motor mill as described herein, comprising one or more of the following:

at least two adjacent rotor poles which may comprise a respective center plate; at least one reinforcement member for coupling together the two adjacent rotor poles; and

fastening means for fastening the reinforcement member to the at least two adjacent rotor poles, particularly to the center plates of the two adjacent rotor poles.

Embodiments described herein further relate to a gearless mill drive including a rotor pole assembly as described herein that is configured to drive a gearless mill (ring motor mill).

A gearless mill drive according to embodiments described herein includes a rotor pole assembly including at least two adjacent rotor poles and at least one reinforcement member as described herein for coupling together the at least two adjacent rotor poles. In some embodiments, the rotor pole assembly includes a plurality of rotor poles to be mounted on a flange, wherein the at least one reinforcement member is configured for coupling together at least two adjacent rotor poles of the plurality of rotor poles. The reinforcement member may be configured in accordance with any of the embodiments described herein.

In a third aspect, the invention provides a method of reinforcing the rotor poles of a ring motor, particularly of a ring motor mill. The method may comprise the step of fitting a reinforcement member as described herein onto adjacent rotor poles with a fastening means, particularly for coupling together the adjacent rotor poles.

In some embodiments, the method comprises positioning the reinforcement member on the adjacent rotor poles such that the adjacent rotor poles are arranged at least partially between a flange and the reinforcement member, and fastening the reinforcement member to the adjacent rotor poles with the fastening means, particularly with two or more bolts extending through the reinforcement member and the flange.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects of the invention will now be further described, by way of example only, with reference to the accompanying figures in which:

Figure 1 shows a gearless mill drive.

Figure 2a shows a cross section of the rotor poles with rotor covers.

Figures 2b and 2c show the forces on two adjacent rotor poles.

Figure 3 is a cross section of a ring motor showing a rotor pole in relation to a mill flange.

Figure 4 shows two adjacent rotor poles attached to a section of the flange of the outer shell of the mill.

Figure 5 shows a perspective view of a connector assembly according to the present invention. Figure 6a shows a perspective view of a connector assembly according to the present invention.

Figure 6b shows an enlargement of the connector assembly of figure 6a.

Figure 7 shows an enlargement of a connector assembly according to the present invention.

Figures 7a, 7b and 7c show perspective views of a connector assembly according to the present invention.

Figure 8 shows a perspective view of a connector assembly according to the present invention.

DETAILED DESCRIPTION

The invention provides a ring motor mill comprising a mill body, wherein the mill body comprises an inner and outer shell, wherein the outer shell comprises a flange extending circumferentially around the outer shell; a ring motor comprising a stator and a rotor, wherein the rotor comprises a plurality of rotor poles mounted on the flange; wherein the stator is mounted around the rotor poles; wherein at least two adjacent rotor poles are coupled together with a reinforcement member.

The invention also provides for a rotor pole assembly for a gearless mill drive, comprising at least two rotor poles comprising a respective center plate; at least one reinforcement member coupling together the two rotor poles; and fastening means for fastening the reinforcement member to the rotor poles, particularly to the center plates.

Figure 1 shows a ring motor mill 100 according to embodiments described herein in a perspective view. The ring motor mill 100 includes a mill body 110 with an outer shell 1 12 and optionally an inner shell, the outer shell 112 including a flange 114 extending circumferentially around the outer shell 112. The ring motor mill 100 further includes a ring motor with a stator 131 and a rotor 132, wherein the rotor 132 includes a plurality of rotor poles 135 mounted on the flange 114, wherein the stator 131 is mounted around the plurality of rotor poles 135.

According to embodiments described herein, the amount of stress on the rotor poles 135 around the pole fixation due to the torque on the pole plates is reduced by providing a reinforcement member (not depicted in FIG. 1) that couples together at least two adjacent rotor poles of the plurality of rotor poles 135.

In some embodiments, a plurality of reinforcement members is provided, each reinforcement member coupling together at least two adjacent rotor poles. The one or more reinforcement members may be fastened to the rotor poles, particularly with fastening means such as bolts. The fastening means may extend from the reinforcement member through at least one of the rotor poles and optionally through the flange. Accordingly, a bolt may not only fix the reinforcement member to a rotor pole, but also the rotor pole to the flange.

Embodiments of reinforcement members 150 coupling together adjacent rotor poles 135 are depicted in enlarged views in figures 5 to 9.

“Coupling together” as used herein may be understood as providing an additional mechanical connection between the two adjacent rotor poles in addition to the fixing of the rotor poles to the mill body via the flange, thereby providing an additional reinforcement of the rotor pole arrangement. In particular, the reinforcement member may span over the two adjacent rotor poles and/or be in contact with both adjacent rotor poles, e.g. being fastened to both rotor poles, thereby mechanically strengthening the rotor pole arrangement.

In one embodiment, the reinforcement member may span across two adjacent poles.

The reinforcement member may comprise a plate. The plate may cover a surface on two adjacent poles. Alternatively, the plate may cover a minimum amount of surface to hold two adjacent poles together. Alternatively, the plate may cover a single pole.

The reinforcement member may be fixed to the rotor poles using fastening means. The fastening means may comprise at least three bolts. The bolts may extend through the reinforcement member, the rotor pole and the flange. The bolts may be aligned, for example in a row. The bolt arrangement may comprise a central bolt and a bolt positioned to each side of the central bolt (i.e. outer bolts). The reinforcement member may be fastened to the adjacent rotor poles with at least one outer bolt of each rotor pole. The reinforcement member may be fastened to the adjacent rotor poles with two outer bolts of each rotor pole. The central bolt may be retained to keep the pole fixed in place on the flange during installation of the plate. Alternatively, the plate may be fixed using adjacent bolts on adjacent rotor poles. The reinforcement member spanning adjacent poles allows the redistribution of stress on the rotor poles due to the torque. This is because it allows a partial ring effect and reduces the pretension specific pressure.

Figure 5 is a perspective view of two adjacent rotor poles 136 mounted on the flange 114 of the mill body and coupled together with a reinforcement member 150 according to embodiments described herein.

As is schematically depicted in figure 5, the reinforcement member 150 may abut against side surfaces of the two adjacent rotor poles 136. In particular, the reinforcement member 150 may include a plate member with a plate surface that abuts against the adjacent side surfaces of the two adjacent rotor poles 136. The plate surface may be essentially flat, and the adjacent side surfaces of the rotor poles may be aligned and extend in the same plane.

In some embodiments, the at least two adjacent rotor poles 136 are arranged at least partially between the flange 114 and the reinforcement member 150. In other words, the at least two adjacent rotor poles 136 may be mounted on the flange 114, such that the flange is arranged on a first side of the at least two adjacent rotor poles 136, and the reinforcement member 150 may be fastened to the at least two adjacent rotor poles 136 on a second side of the rotor poles opposite the first side.

For example, a first bolt may extend through the reinforcement member 150 and through one of the at least two adjacent rotor poles 136, and a second bolt may extend through the reinforcement member 150 and through another one of the at least two adjacent rotor poles 136 for fastening the reinforcement member to the two adjacent rotor poles 135. Hence, the rotor poles are coupled together by the reinforcement member 150 on a second side opposite the first side where the rotor poles are connected to the flange.

In particular, the reinforcement member 150 may be a reinforcing element spanning at least partially or completely across the two adjacent rotor poles and being in contact with the two adjacent rotor poles. The reinforcement member is provided in addition to the flange 114 on which the rotor poles are mounted, particularly on an opposite side of the rotor poles, thereby stabilizing the rotor poles and reducing the amount of stress in the area around the fixation of the pole rotor poles to the flange.

In some embodiments, fastening means 160, e.g., bolts, may extend through the reinforcement member 150, through one of the pole pieces 136, and/or through the flange 114, respectively. Accordingly, the at least two adjacent pole pieces can be reliably held between the reinforcement member 150 and the flange 114 by the fastening means 160, reducing the amount of stress on the pole pieces during the rotation of the rotor.

In some embodiments, which can be combined with other embodiments described herein, the reinforcement member 150 is fastened to the at least two adjacent rotor poles 136 with a fastening means 160, particularly with at least one bolt, more particularly with two or more bolts, e.g. four bolts. For example, the reinforcement member 150 may be fastened to each of the two adjacent rotor poles 136 with one bolt or with two bolts. In particular, each of the two adjacent rotor poles 136 may be mounted to the flange 114 with three bolts, wherein two of the three bolts may additionally extend through the reinforcement member 150 for fastening the reinforcement member to the two adjacent rotor poles 136, as is schematically depicted in figure 5.

In some embodiments, the fastening means 160 includes at least one bolt extending through the flange 114, one of the adj acent rotor poles 136, and the reinforcement member 150. Further, the fastening means may include at least one second bolt extending through the flange 114, the other one of adjacent rotor poles 136 and the reinforcement member 150.

As is schematically depicted in figure 5, the reinforcement member 150 may include a plate 151 spanning partially or entirely over the at least two adjacent rotor poles 136, in particular in a circumferential direction of the ring motor. The plate 151 may have a plate surface being in contact with and optionally being pressed against aligned side surfaces of the two adjacent rotor poles 136. The side surfaces of the two adjacent rotor poles 136 that are in contact with the plate 151 may face away from the flange 114 on which the rotor poles are mounted.

Figure 9 shows an embodiment in which the reinforcement member 150 is a plate member spanning only partially across the two adjacent rotor poles 136 for coupling together the rotor poles 136. In some embodiments, which can be combined with other embodiments described herein, a plurality of reinforcement members 150 may be provided, each of the reinforcement members coupling together at least two adjacent rotor poles. Accordingly, each of the plurality of rotor poles of the ring motor may be coupled together with at least one adjacent rotor pole via at least one reinforcement member 150.

The reinforcement member may be fastened to the rotor poles outside the motor and therefore this can be completed during scheduled maintenance stops and does not require additional downtime for installation. This prevents a loss in profits due to additional inactivity of the mill. In addition, installment of the reinforcement member does not require readjustment of the poles. Also, with such reinforcement members, it is still possible to exchange individual rotor poles, if needed. The ring motor fitted with said reinforcement members also has increased mechanical safety margin.

Adjacent reinforcement members may be linked together by a connecting means 170. The connecting means 170 may have faces reciprocal to the ends of the reinforcement members. The faces may be angular. The connecting means 170 may be fixed to the reinforcement members by pretensioned radial bolts. In this embodiment, the reinforcement member may span across two adjacent poles. Alternatively, the reinforcement member may cover a single rotor pole. The ring motor may comprise a combination of single and double reinforcement members linked together by a connecting means. The connecting means allows a simulation of the full ring effect.

Figures 6a and 6b are perspective views of two adjacent rotor poles 136 mounted on the flange 114 of the mill body. A first reinforcement member 158 is fastened to one of said two adjacent rotor poles, and a second reinforcement member 159 is mounted to the other one of said two adjacent rotor poles. The first reinforcement member 158 may span across one rotor pole, two rotor poles, or more rotor poles (one shown in figures 6a and 6b), and the second reinforcement member 159 may span across one rotor pole, two rotor poles or more rotor poles (one shown in figures 6a and 6b), e.g. similar to the plate 151 depicted in figure 5 that spans across two rotor poles. In particular, the first reinforcement member 158 and/or the second reinforcement member 159 may be a reinforcement member 150 in accordance with any of the embodiments described herein. In some embodiments, adjacent reinforcement members 158, 159 are joined together with a connecting means 170. The connecting means may include a connecting member that is in contact with both adjacent reinforcement members 158, 159, particularly in contact with ends of the adjacent reinforcement members 158, 159 facing each other.

In particular, the connecting means 170 may comprise a first angular face contacting an end surface of the first reinforcement member 158 and a second angular face contacting an end surface of the second reinforcement member 159. For example, the connecting means 170 may include one or two essentially triangularly-shaped connecting members, each connecting member contacting end surfaces of both adjacent reinforcement members 158, 159.

The connecting means 170 may further include at least one pretensioned radial bolt 171 for pressing the connecting members against the ends of the adjacent reinforcement members 158, 159, as is schematically depicted in figure 6b. The positions of the adjacent reinforcement members in the circumferential direction can be stabilized by the connecting means, and a stress on the adjacent rotor poles 136 due to torsional forces can be reduced.

In some embodiments, a plurality of reinforcement members may be provided for coupling together adjacent rotor poles, respectively. Some or all adjacent reinforcement members may be joined together with a connecting means as described herein, in order to stabilize the positions of the reinforcement members in the circumferential direction, maintaining a predetermined ring shape even during the rotation of the rotor.

In one embodiment, the reinforcement members comprise inter-engaging and/or interlocking plates. The plates may be chain-like plates. This allows a full ring effect to be simulated.

Figure 7 is a perspective view of two adjacent rotor poles 136 mounted on the flange 114 of the mill body and coupled together with a reinforcement member 150 according to embodiments described herein, the reinforcement member 150 being an inter-engaging plate 152 configured to inter-engage with at least one adj acent reinforcement member that is likewise configured as an inter-engaging plate 153. In particular, the reinforcement member 150 may be an inter-engaging plate having a first engagement interface configured to inter-engage with a first adjacent reinforcement member arranged at a first circumferential end and a second engagement interface configured to inter-engage with a second adjacent reinforcement member arranged at a second circumferential end opposite the first circumferential end. The inter- engaging plates may be configured as members of a chain that are engaged with each other, providing a ring-shaped chain arrangement that stabilizes the plurality of rotor poles, particularly on a side opposite the side where the flange is arranged.

In one embodiment, the reinforcement member may comprise a screwed assembly that may optionally be welded onto the rotor pole laminations. This reinforcement member arrangement has a high efficiency in reducing stress. This arrangement does not require readjustment of the rotor poles. It also allows for the possibility of exchanging individual poles. However, to install this reinforcement member arrangement, it is necessary to remove the rotor cover to access the pole laminations.

For example, figure 7a shows a reinforcement member 150 that is fixed to the rotor pole laminations of two adjacent rotor poles 136 and thereby couples together the two adjacent rotor poles 136. In particular, the reinforcement member 150 may be mounted to the underside of the mechanical bodies of the two adjacent rotor poles. In the example of figure 7a, the reinforcement member 150 is screwed and/or bolted to the rotor pole laminations of the two adjacent rotor poles 136, as is schematically depicted in enlarged views 7b and 7c. In some implementations, the reinforcement member 150 may be otherwise fastened to the rotor pole laminations or to the underside of the pole bodies of the two adjacent rotor poles 136.

Optionally, the reinforcement member 150 may include two bar elements 161 that are connected to each other, one bar element fastened to each of the two adjacent rotor poles, e.g. via screws or bolts. The two bar elements 161 may be connected to each other in a non- detachable way, e.g. by welding, such that a one-piece or integrally formed reinforcement member 150 is provided that couples together the two adjacent rotor poles 136. In particular, the reinforcement member 150 may include two bar elements that are welded together and thereby extend at least partially across the two adjacent rotor poles, e.g. at an underside of the pole bodies or pole laminations.

In some implementations, the bar elements may extend in an axial direction of the rotor, respectively, and/or may be fixed to the rotor pole laminations at the lower side that is directed toward the mill body, i.e. at a radially inner surface of the pole bodies. In particular, the rotor of the rotor mill may be reinforced by welding together (or otherwise connecting) two bar elements that are fastened to adjacent rotor poles to thereby provide a reinforcement member 150 that couples together two adjacent rotor poles.

A rotor pole, particularly each rotor pole, may have two bar elements fastened thereto (see the rotor poles in figure 7a), such that the rotor pole can be coupled to its two neighboring rotor poles in the circumferential direction by connecting the bar elements to respective further bar elements of the adjacent rotor poles, e.g. by welding, to thereby provide respective reinforcement members.

Each reinforcement member described herein can be combined with any of the other types of reinforcement members or plates described herein.

According to another aspect, a method of reinforcing the rotor poles of a ring motor is described herein. The ring motor may optionally be the ring motor of a ring motor mill including an outer shell with a flange extending circumferentially around the outer shell, wherein the rotor poles of the ring motor are mounted on the flange.

The method includes fitting a reinforcement member 150 onto adjacent rotor poles 136 with a fastening means 160, particularly with one or more bolts, for coupling together the adjacent rotor poles 136.

In particular, the reinforcement member may be positioned on the adjacent rotor poles such that the adjacent rotor poles are arranged at least partially between the flange and the reinforcement member, and the reinforcement member may be fastened to the adjacent rotor poles with the fastening means, particularly with two or more bolts extending from the reinforcement member through the flange.

Any of the embodiments described herein may be used in combination mutatis mutandis.

In particular, embodiments described herein can be summarized as follows:

Aspect 1 : A ring motor mill, comprising: a mill body, wherein the mill body comprises an inner and outer shell, wherein the outer shell comprises a flange extending circumferentially around the outer shell; a ring motor comprising a stator and a rotor; wherein the rotor comprises a plurality of rotor poles mounted on the flange; wherein the stator is mounted around the rotor poles; wherein at least two adjacent rotor poles are coupled together with a reinforcement member.

Aspect 2: A rotor pole assembly comprising: at least one rotor pole comprising a center plate; at least one reinforcement member; and fastening means for fastening the reinforcement member to the center plate.

Aspect 3: The rotor pole assembly of aspect 2, wherein the assembly comprises at least two rotor poles.

Aspect 4: The ring motor mill of aspect 1 or the rotor pole assembly of aspects 2 or 3, wherein the reinforcement member is fastened to the adjacent rotor poles with a fastening means.

Aspect 5: The ring motor mill or the rotor pole assembly of any preceding aspect, wherein the fastening means comprises at least one bolt.

Aspect 6: The ring motor mill or the rotor pole assembly of any preceding aspect, wherein the reinforcement member comprises a plate spanning over at least two adjacent rotor poles.

Aspect 7: The ring motor mill or the rotor pole assembly of any preceding aspect, wherein the reinforcement member comprises inter-engaging plates.

Aspect 8: The ring motor mill or the rotor pole assembly of any preceding aspect, comprising a plurality of reinforcement members.

Aspect 9: The ring motor mill or the rotor pole assembly of any preceding aspect, wherein adjacent reinforcement members are joined together with a connecting means.

Aspect 10: The ring motor mill of aspect 9, wherein the connecting means comprise angular faces reciprocal to the ends of the reinforcement members.

Aspect 11 : The ring motor mill of any one of aspects 9 to 10, wherein connecting means comprise pretensioned radial bolts. Aspect 12: The ring motor mill or the rotor pole assembly of any preceding aspect, wherein the reinforcement members are welded to the rotor pole lamination Aspect 13: A method of reinforcing the rotor poles of a ring motor, the method comprising the step of fitting a reinforcement member according to any preceding aspect onto adjacent rotor poles with a fastening means.

Embodiments of the invention have been described by way of example only. It will be appreciated that variations of the described embodiments may be made which are still within the scope of the invention.

List of reference numerals:

100 rotor mill

110 mill body

112 outer shell

114 flange

131 stator

132 rotor

135 plurality of rotor poles

136 at least two adj acent rotor poles

150 reinforcement member

151 plate

152, 153 inter-engaging plates

158, 159 adj acent reinforcement members

160 fastening means 161 two bar elements

170 connecting means

171 pretensioned radial bolt

212 two adj acent rotor poles

214 flange

301 central fixing bolt

302 bolt with eccentric bushings

303 contact rings

304 rotor cover 305 pole center plate

306 sliding surface teflon rings

307 cooler units

308 mill feed

309 mill discharge

310 electrical stator connection