Annular motor, mill and method for assembling mill

Abstract

The invention relates to an annular electric machine, comprising: a stator assembly of an annular construction; a rotor assembly of an annular structure, the rotor assembly being arranged inside the stator assembly in the radial direction of the annular motor; and a support assembly, the support assembly being configured to movably mount the stator assembly relative to the rotor assembly along an axial direction of the annular motor. The invention further relates to a mill and a method for assembling the mill.

Description

TECHNICAL FIELD

[0001] The present application relates to a ring motor, a mill and a method for assembling the mill. BACKGROUND

[0002] The mill needs a motor to drive the rotation of the mill barrel in use. The traditional mill driving system is composed of a driving motor, a speed reducer, a pinion shaft and a gear. When driving, the driving motor drives the speed reducer, the speed reducer drives the pinion shaft, the pinion shaft drives the gear, and the gear drives the rotation of the mill barrel to achieve grinding. Such a driving system involves more transmission links. At each transmission link, there will be energy consumption, mechanical consumption, lubrication consumption and space occupation, resulting in low energy utilization rate of the whole driving system, low transmission efficiency, and greatly increased energy consumption, mechanical consumption and lubrication consumption.

[0003] As an improved solution, there is a ring motor that can directly drive the rotation of the mill barrel. However, the stator and rotor of the existing ring motor have a large volume and weight, causing inconvenience in the assembly process. In addition, the high assembly precision requirement for the ring motor also leads to the problem of repeated adjustment of the centering in the assembly process. SUMMARY

[0004] In view of the above problems, according to a first aspect of the present application, a ring motor is provided, comprising: a stator assembly of ring configuration; a rotor assembly of ring configuration, arranged inside the stator assembly along the radial direction of the ring motor; and a support assembly, wherein the support assembly is configured to movably mount the stator assembly relative to the rotor assembly along the axial direction of the ring motor.

[0005] The relative movement between the stator assembly and the rotor assembly is achieved by the support assembly being oriented along the axial direction, which can improve the assembly precision of the ring motor and reduce the operations for centering. In addition, since the stator assembly and the rotor assembly can move relative to each other in the axial direction, the stator assembly and the rotor assembly can be pre-assembled at different positions along the axial direction, respectively, and then the assembled stator assembly and rotor assembly are assembled together. This avoids the risk of mutual adhesion of the stator and the rotor due to magnetic attraction during the installation process.

[0006] According to an embodiment, the support assembly comprises a fixed base fixedly arranged on a support surface of the ring motor and a moving base movable relative to the fixed base along the axial direction, wherein the stator assembly is fixedly connected to the moving base. Optionally, the support assembly can be placed on the support surface by its own weight. Alternatively and preferably, the support assembly can be fixedly connected to the support surface by means of an anchor, such as an anchor, to enhance the stability of the ring motor.

[0007] According to an embodiment, the mobile base is axially slidably supported on the fixed base. The slidable mutual movement simplifies the assembly process. Of course, as an alternative, the axial movement of the mobile base relative to the fixed base can also be realized by means of a directionally guided gear rack engagement or the like.

[0008] According to an embodiment, the fixed base comprises a horizontal section and a pair of guide sections protruding upward from both sides of the horizontal section, the guide sections extending parallel to each other in the axial direction, thereby guiding the movement of the mobile base in the axial direction by means of the guide sections.

[0009] According to an embodiment, the fixed base further comprises a pressing strip arranged at the top end of the guide sections, wherein the pressing strip is configured longitudinally and extends in the axial direction, wherein the pressing strip protrudes beyond the guide sections in the width direction thereof toward the center of the horizontal section.

[0010] According to an embodiment, the support assembly further comprises a centering assembly arranged between the guide sections of the fixed base and the mobile base, the centering assembly comprising two centering pieces arranged axially spaced apart from each other, wherein the two centering pieces are respectively configured wedge-shaped and have their tips facing each other.

[0011] According to an embodiment, the centering pieces comprise guide inclines, thereby adjusting the position of the mobile base in a direction perpendicular to the axial direction by the movement of the centering pieces in the axial direction.

[0012] According to an embodiment, the mobile base comprises a circumferential surface which is shaped to fit the guide inclines.

[0013] According to an embodiment, the end of at least one centering piece opposite to the tip is provided with a cantilever.

[0014] According to an embodiment, the support assembly further comprises a driving device configured to drive the movement of the mobile base in the axial direction relative to the fixed base, wherein the driving device comprises a power source fixedly connected to the fixed base and an actuating piece linearly movable relative to the power source.

[0015] According to an embodiment, the fixed base comprises a mounting seat for fixedly connecting the power source.

[0016] According to an embodiment, the driving device comprises a hydraulic cylinder.

[0017] According to an embodiment, the driving device comprises a linear motor.

[0018] According to one embodiment, the stator assembly comprises a motor housing and stator coils arranged in the motor housing, wherein the motor housing is fixedly connected to the mobile base.

[0019] According to a second aspect of the present application, a mill is provided, comprising a mill barrel and the aforementioned ring motor, wherein the mill barrel is fixedly connected to the rotor assembly and is mounted radially inside the rotor assembly.

[0020] In this embodiment, the ring motor does not require bearings, but uses the mill barrel as the motor output shaft, thereby saving bearing support and truly achieving maintenance-free motor.

[0021] The mill according to the present application also has the advantages described above for the ring motor. Furthermore, the split construction of the stator assembly and the rotor assembly also meets the maintenance requirements of the various components of the mill, thereby ensuring the convenience of mill operation and achieving the most simplified mill drive system.

[0022] According to a third aspect of the present application, a method for assembling the aforementioned mill is provided, comprising the following steps:

[0023] fixedly connecting the rotor assembly to the mill barrel in a torsion-proof manner, wherein the rotor assembly protrudes outward relative to the mill barrel in the axial direction of the ring motor;

[0024] fixedly connecting the stator assembly to the mobile base of the support assembly;

[0025] moving the mobile base relative to the fixed base in the axial direction, thereby arranging the stator assembly radially outside the rotor assembly.

[0026] According to one embodiment, the support assembly comprises a first and a second spacer arranged between a guide section of the fixed base and the mobile base, wherein the first and the second spacer are respectively wedge-shaped and have a pointed end and a wide side end with a cantilever, wherein the first spacer is fixedly connected to the inner side of the guide section before moving the mobile base relative to the fixed base in the axial direction, wherein the wide side end of the first spacer is directed towards the mill barrel, then moving the mobile base in the axial direction, and wherein the pointed end of the second spacer is inserted axially between the guide section and the mobile base, thereby adjusting the position of the mobile base in a direction perpendicular to the axial direction by moving the second spacer in the axial direction. BRIEF DESCRIPTION OF DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings of the embodiments of the present application will be briefly introduced below. The drawings merely serve to show some of the embodiments of the present application, and the present application is not limited to the drawings.

[0028] Figure 1 schematic view of a ring motor according to the present application;

[0029] Figure 2 schematic view of a ring motor according to the present application;

[0030] Figure 3 schematic view of a support assembly of a ring motor according to the present application;

[0031] Figure 4 schematic view of Figure 3 schematic view of the support assembly shown in plan view;

[0032] Figure 5 schematic view of Figure 3 schematic view of the area A shown in enlarged view;

[0033] Figure 6 schematic view of Figure 4 schematic view of the area B shown in enlarged view;

[0034] Figure 7 schematic view of a support slide of the support assembly;

[0035] Figure 8 schematic view of Figure 3 schematic view of the area C shown in enlarged view;

[0036] Figure 9 schematic view of a support assembly of a ring motor according to the present application;

[0037] Figure 10 schematic view of a mill according to a preferred embodiment of the present application. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions of the embodiments of the present application will be described clearly and completely below with reference to the drawings of the embodiments of the present application. The same reference signs in the drawings represent the same components. It should be noted that the described embodiments are part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the described embodiments of the present application, all other embodiments obtained by those of ordinary skill in the art without any creative effort fall within the scope of protection of the present application.

[0039] Unless otherwise defined, technical terms or scientific terms used herein shall have the same meaning to a person having ordinary skill in the art of the present application. The terms "first", "second", and similar terms, used herein do not necessarily mean any order, quantity, or importance, but are used to distinguish different components. The terms "comprising", "including", "containing", and similar terms, mean that the elements or objects listed after the term encompass the elements or objects listed therebefore, and equivalents thereof, without excluding other elements or objects. The terms "connected", "coupled", and similar terms, do not necessarily mean physically or mechanically connected, but can include electrical connection, whether direct or indirect. The terms "upper", "lower", "left", "right", and similar terms, are used only to indicate relative positional relationships, which can change when the absolute positions of the described objects change.

[0040] The present application is described in detail below by way of describing example embodiments.

[0041] Figure 1 A perspective view of a ring motor 100 according to the present application is schematically shown, which can be configured as a ring permanent magnet motor.

[0042] As shown in Figure 1 , the ring motor 100 comprises a stator assembly 2 of ring configuration, a rotor assembly 3 of ring configuration, wherein the stator assembly 2 is arranged radially outside the rotor assembly 3.

[0043] As shown in Figure 1 and Figure 2 , the stator assembly 2 comprises a motor housing 20 configured as a ring and having an inner circumferential surface, not specifically shown, an outer circumferential surface 201, and two annular end surfaces 202 connected with the inner circumferential surface and the outer circumferential surface 201, and defining together with the inner circumferential surface, the outer circumferential surface 201, and the two end surfaces a stator housing inner cavity in which stator coils are arranged.

[0044] In addition, cooling channels, not specifically shown in the drawings, are provided in the stator housing inner cavity, in which any suitable coolant, such as water or oil, can flow in order to output and release operating heat during operation of the ring motor. The cooling channels can be formed in any suitable manner. In the embodiment shown in Figure 1 , interfaces for the cooling channels can be provided on the end surfaces 202 of the motor housing 20. In addition, the stator housing inner cavity comprises an air duct, wherein a fan 5 is provided on the outer circumferential surface 201 of the stator housing 20 in order to blow cooling air into the inner cavity formed by the stator housing, and the inner circumferential surface accordingly comprises air outlet openings in order to communicate the inner cavity with the gap space.

[0045] The rotor assembly 3 is arranged inside the stator assembly 2 along the radial direction of the ring motor 100, and extends axially beyond the end face 202 of the stator assembly 2. The rotor assembly 3 comprises a rotor mounting portion 30 and a rotor core, not specifically shown in the figure, arranged on the rotor mounting portion 30. The rotor mounting portion 30 can be annular, as shown in Figure 1 and Figure 2 The rotor mounting portion 30 comprises an intermediate mounting section 33 arranged on the radially inner surface, which extends perpendicularly to the radially outer surface and the radially inner surface, so that the cross section of the rotor mounting portion 30 is T-shaped. Preferably, the intermediate mounting section 33 is provided with a plurality of axial through holes spaced apart from each other. Fasteners such as bolts can pass through the axial through holes to fixedly connect a driven member, such as a mill barrel described later, with the intermediate mounting section 33 of the rotor mounting portion 30.

[0046] Therefore, the rotor mounting portion 30 is used not only for mounting the rotor core but also for mounting the driven member. It should be understood that the rotor mounting portion 30 can also have other structures and forms according to the specific structure and requirements of the driven member.

[0047] In addition, due to the large volume of the rotor assembly of the ring motor, the magnetic attraction between the rotor and the stator during installation is also very large, making the installation very difficult and prone to safety hazards. Therefore, the ring motor 100 further comprises a support assembly 4. The support assembly 4 is configured to movably mount the stator assembly 2 relative to the rotor assembly 3 along the axial direction x of the ring motor 100. By enabling the relative movement between the stator assembly 2 and the rotor assembly 3 in the axial direction x, the assembly accuracy of the ring motor 100 can be improved, and the operation for centering can be reduced. In addition, since the stator assembly 2 and the rotor assembly 3 can move relative to each other in the axial direction x, the stator assembly 2 and the rotor assembly 3 can be pre-assembled at different positions in the axial direction, respectively, and then the assembled stator assembly 2 and rotor assembly 3 are assembled together. This avoids the risk of mutual attraction of the stator and the rotor due to magnetic attraction during installation.

[0048] As shown in Figures 3 to 9 The support assembly 4 comprises a fixed base 41 fixedly arranged on the support surface of the ring motor 100 and a moving base 42 movable relative to the fixed base 41 in the axial direction x. According to the application occasion, the fixed base 41 of the support assembly 4 can be fixedly connected to the support surface of the ring motor 100, such as the ground, by means of a fixing member not shown in the figure, such as a screw, an anchor bolt, or can be fixedly connected to other equipment. In this embodiment, the moving base 42 is configured to be fixedly connected with the stator assembly 2 and can slide relative to the fixed base 41 in the axial direction x.

[0049] In this embodiment, the support assembly 4 is configured mirror-symmetrically and comprises two identical halves. In an embodiment not shown, the stationary base 41 of the support assembly 4 can also be configured integrally, and the mobile base 42 can also be configured integrally.

[0050] In this embodiment, the stationary base 41 comprises a horizontal section 410, a pair of guide sections 411 and a pressing strip 412 protruding upward from both sides of the horizontal section 410. The two guide sections 411 extend parallel to each other in the axial direction x, so as to guide the movement of the mobile base 42 in the axial direction x by means of the guide sections 411. As shown, the pressing strip 412 is configured longitudinally and extends in the axial direction x. The pressing strip 412 is arranged at the top end of each guide section 411, respectively, and the pressing strip 412 protrudes beyond the guide sections 411 towards the center of the horizontal section 410 in the width direction thereof. Thus, a guide groove extending in the axial direction x is formed by the protruding portion of the pressing strip 412 and the guide sections 411, so as to limit the movement of the mobile base 42 in the height direction. Figure 5

[0051] The support assembly 4 further comprises a centering assembly 43. The centering assembly 43 is arranged between the guide sections 411 of the stationary base 41 and the mobile base 42, and comprises a first centering piece 431 and a second centering piece 432 arranged spaced apart from each other in the axial direction x. As shown, the first centering piece 431 and the second centering piece 432 are configured wedge-shaped, respectively. The first centering piece 431 comprises a guide slope 4310, a tip end 4311 provided at one end of the guide slope 4310, and a wide side end opposite to the tip end, on which a cantilever 4312 is provided. Correspondingly, the second centering piece 432 comprises a guide slope 4320, a tip end 4322 provided at one end of the guide slope 4320, and a wide side end opposite to the tip end, on which a cantilever 4322 is provided. The tip end 4311 of the first centering piece 431 and the tip end 4321 of the second centering piece 432 are opposite to each other and maintain a spacing between the respective tip ends. Figure 6

[0052] Figure 7 A separate view of the mobile base 42 is shown. The mobile base 42 comprises a lower section 421 and an upper section 422. The lower section 421 is configured for being slidably supported on the stationary base 41, and comprises a circumferential surface cooperating with the centering assembly 43. The upper section 422 is configured in the shape of a jaw and is fixedly connected to the motor housing 20 of the stator assembly 2, wherein the outer circumferential surface 201 of the motor housing 20 abuts against the inner side surface of the upper section 422. As shown, the lower section 421 comprises a pair of guide grooves 4211 formed by the protruding portions of the guide sections 411 of the stationary base 41 and the pressing strip 412, and a pair of guide grooves 4212 formed by the protruding portions of the guide slopes 4310 and 4320 of the first centering piece 431 and the second centering piece 432, respectively. Figure 6 and Figure 7 ​​As shown, the circumferential face is substantially trapezoidal in configuration and comprises a first inclined section 4211, a second inclined section 4212 and a flat section 4210 connecting the first inclined section 4211 and the second inclined section 4212. In Figure 6 and Figure 7 As shown in the assembled state, the first inclined section 4211 is shaped to fit the guide slope 4310 of the first centering piece 431, the second inclined section 4212 is shaped to fit the guide slope 4320 of the second centering piece 432 and the flat section 4210 is close to or in contact with the inner wall of the guide section 411 of the fixed base 41.

[0053] By the cooperation of the centering assembly 43 and the sliding base 42, the centering of the sliding base 42 and even of the ring motor 100 is achieved.

[0054] The support assembly 4 further comprises a drive device 44. The drive device 44 is configured for driving the movement of the sliding base 42 relative to the fixed base 41 along the axial direction x and comprises a power source fixedly connected to the fixed base 41 and an actuating member linearly movable relative to the power source. To this end, the fixed base 41 comprises a mounting seat 414 for arranging the power source, as shown in Figure 4 .

[0055] In the embodiment as shown in Figure 9 , the drive device 44 is configured as a hydraulic cylinder, however, in an embodiment not shown, the drive device 44 can also be configured as a linear motor.

[0056] In this embodiment, the drive device 44 comprises a cylinder body 441 fixedly arranged on the mounting seat 414 and an actuating rod 442 telescopically movable relative to the cylinder body 441, the actuating rod 442 passing through and acting on the sliding base 42 along the axial direction x. By the linear movement of the actuating rod 442 relative to the cylinder body 441, the sliding movement of the sliding base 42 relative to the fixed base 41 along the axial direction x is achieved.

[0057] Figure 10 A mill according to the present application is schematically shown. The mill comprises the aforementioned ring motor 100 and a mill barrel 200. The mill barrel 200 is arranged coaxially with the ring motor 100 and fixedly connected with the rotor assembly 3, wherein the mill barrel 200 is mounted radially inside the rotor assembly 3. In this embodiment, the ring motor 100 does not need to support the rotor assembly 3 on the stator assembly 2 by means of bearings, but uses the mill barrel 200 as the motor output shaft, thus saving the bearing support and truly realizing the maintenance-free motor.

[0058] This mill allows an especially advantageous assembly method.

[0059] On one side of the fixed base 41 in the axial direction x, the rotor assembly 3 is fixedly connected to the mill barrel 200 in a torsion-proof manner, wherein the rotor assembly 3 protrudes in the axial direction x of the ring motor 100 relative to the mill barrel 200, in particular in the direction of the fixed base 41. Thereby, the pre-assembly of the rotor assembly 3 with the mill barrel 200 is completed.

[0060] Independently from the pre-assembly of the rotor assembly 3 with the mill barrel 200, on the other side of the fixed base 41 in the axial direction x, a first centring piece 431 of the centring assembly 43 is fixedly arranged on the fixed base 41, wherein the tip 4311 of the first centring piece 431 faces away from the direction of the rotor assembly 3. Here, the stator assembly 2 is fixedly connected to the mobile base 42, wherein the motor housing 20 of the stator assembly 2 is fixedly connected to the inner side of the upper section 422 of the mobile base 42. Thereby, the pre-assembly of the stator assembly 2 on the support assembly 4 is completed.

[0061] Subsequently, by operation of the drive device 44, the mobile base 42 is caused to slide in the axial direction x relative to the fixed base 41 in the direction of the rotor assembly 3, so that the stator assembly 2 is arranged radially outside the rotor assembly 3. During this process, the first inclined section 4211 of the circumferential face of the lower section 421 of the mobile base 42 cooperates with the guide slope 4310 of the first centring piece 431, so that centring of the stator assembly 2 with respect to the rotor assembly 3 is achieved while sliding in the axial direction x.

[0062] In an embodiment of the preferred method, for more precise centring of the stator assembly 2 with respect to the rotor assembly 3, a second centring piece 432 is also arranged between the guide section 411 of the fixed base 41 and the mobile base 42. For this purpose, the tip 4321 of the second centring piece 432 is inserted between the guide section 411 and the mobile base 42 in the axial direction x, and by exerting an external force on the cantilever 4322 of the broad-side end of the second centring piece 432, the second centring piece 432 is caused to move in the axial direction x, so that the position of the mobile base 42 is adjusted more precisely in a direction perpendicular to the axial direction x.

[0063] Certain features, structures, or characteristics of one or more embodiments can be combined in all and / or some embodiments.

[0064] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

[0065] The foregoing is a summary of the application, and is not to be considered as limiting the present application. While several exemplary embodiments of the application have been described, those skilled in the art will readily understand that many modifications can be made to the exemplary embodiments without departing from the novel teachings and advantages of the application. Accordingly, all such modifications are intended to be included within the scope of the application as defined in the following claims. It is to be understood that the application is not to be limited to the particular embodiments disclosed, and that modifications to the disclosed embodiments, and other embodiments, are intended to be within the scope of the application.

Claims

1. A ring motor, characterized in that, The ring motor (100) includes: A stator assembly with a ring structure (2); A ring-shaped rotor assembly (3) is arranged radially within the stator assembly (2) of the ring motor (100); and Supporting components (4) The support assembly (4) is configured to movably mount the stator assembly (2) relative to the rotor assembly (3) along the axial direction (x) of the annular motor (100).

2. The ring motor according to claim 1, characterized in that, The support assembly (4) includes a fixed base (41) fixedly arranged on the support surface of the ring motor (100) and a movable base (42) movable relative to the fixed base (41) along the axial direction (x), wherein the stator assembly (2) is fixedly connected to the movable base (42).

3. The ring motor according to claim 2, characterized in that, The movable base (42) is slidably supported on the fixed base (41) along the axial direction (x).

4. The ring motor according to claim 2, characterized in that, The fixed base (41) includes a horizontal section (410) and a pair of guide sections (411) extending upward from both sides of the horizontal section (410), the guide sections (411) extending parallel to each other along the axial direction (x), thereby guiding the movement of the movable base (42) in the axial direction (x) by means of the guide sections (411).

5. The ring motor according to claim 4, characterized in that, The fixed base (41) also includes a pressure strip (412) disposed at the top of the guide section (411), wherein the pressure strip (412) is constructed longitudinally and extends along the axial direction (x), wherein the pressure strip (412) protrudes beyond the center of the horizontal section (410) in its width direction beyond the guide section (411).

6. The ring motor according to claim 4, characterized in that, The support assembly (4) further includes a centering assembly (43) arranged between the guide section (411) of the fixed base (41) and the movable base (42). The centering assembly (43) includes two centering members (431, 432) arranged at intervals along the axial direction (x), wherein the two centering members (431, 432) are respectively wedge-shaped and their tips (4311, 4321) are opposite to each other.

7. The ring motor according to claim 6, characterized in that, The centering components (431, 432) include guide ramps (4310, 4320), thereby adjusting the position of the movable base (42) in a direction perpendicular to the axial direction (x) by moving the centering components (432) in the axial direction (x).

8. The ring motor according to claim 7, characterized in that, The movable base (42) includes a circumferential surface adapted to the shape of the guide ramps (4310, 4320).

9. The ring motor according to claim 6, characterized in that, At least one centering member (431, 432) has a cantilever (4312, 4322) at the end opposite to the tip.

10. The ring motor according to claim 2, characterized in that, The support assembly (4) further includes a drive device (44) configured to drive the movable base (42) to move along the axial direction (x) relative to the fixed base (41), wherein the drive device (44) includes a power source (441) fixedly connected to the fixed base (41) and an actuator (442) linearly movable relative to the power source (441).

11. The ring motor according to claim 10, characterized in that, The fixed base (41) includes a mounting base (414) for fixing the power source (441).

12. The ring motor according to claim 10, characterized in that, The drive unit (44) includes a hydraulic cylinder.

13. The ring motor according to claim 10, characterized in that, The drive unit (44) includes a linear motor.

14. The ring motor according to claim 2, characterized in that, The stator assembly (2) includes a motor housing (20) and stator coils arranged in the motor housing (20), wherein the motor housing (20) is fixedly connected to the movable base (42).

15. A mill, characterized in that, The mill includes: a mill cylinder (200) and an annular motor (100) according to any one of claims 1 to 14, wherein the mill cylinder (200) is fixedly connected to the rotor assembly (3) and installed on the radial inner side of the rotor assembly (3).

16. A method for assembling a mill according to claim 15, characterized in that, The method includes the following steps: - The rotor assembly (3) is fixedly connected to the mill barrel (200) in a torsion-resistant manner, wherein the rotor assembly (3) protrudes outward relative to the mill barrel (200) along the axial direction (x) of the annular motor (100); - The stator assembly (2) is fixedly connected to the movable base (42) of the support assembly (4); - The movable base (42) moves axially (x) relative to the fixed base (41) so that the stator assembly (2) is arranged radially outside the rotor assembly (3).

17. The method according to claim 16, characterized in that, The support assembly (4) includes a first centering member (431) and a second centering member (432) disposed between the guide section (411) of the fixed base (41) and the movable base (42), wherein the first centering member (431) and the second centering member (432) are respectively wedge-shaped and have tips (4311, 4321) and wide side ends with cantilever (4312, 4322). Before moving the movable base (42) relative to the fixed base (41) along the axial direction (x), a first centering member (431) is fixedly connected to the inside of the guide section (411), wherein the wide end of the first centering member (431) faces the mill barrel (200). Subsequently, the movable base (42) is moved along the axial direction (x), and wherein the tip (4321) of the second centering member (432) is inserted along the axial direction (x) between the guide section (411) and the movable base (42), thereby adjusting the position of the movable base (42) in a direction perpendicular to the axial direction (x) by moving the second centering member (432) along the axial direction (x).

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