A bearing plastic steel retainer expanding device

Abstract

The application relates to a bearing plastic steel retainer expanding device, belonging to the technical field of bearing assembly, which comprises a chuck, a moving body, an expanding block and a driving mechanism, the moving body is slidably arranged on the chuck, the sliding direction of the moving body is perpendicular to the axial direction of the chuck, a plurality of moving bodies are distributed along the circumferential direction of the chuck, the expanding block corresponds to the moving body one by one, the expanding block is arranged on the corresponding moving body, the expanding block is provided with a circular-arc protruding section, the circular-arc protruding section is used for being clamped and matched with a groove on the retainer, and the driving mechanism is arranged on the chuck and used for driving the plurality of moving bodies to move close to or away from each other. The application has the effect that the roller surface and the inner ring raceway surface are not easily damaged during the installation of the inner ring.

Description

Technical Field

[0001] This application relates to the field of bearing assembly technology, and in particular to a bearing plastic steel cage expansion device. Background Technology

[0002] Railway bearings are components in the running gear of railway vehicles used to support rotating parts and reduce friction. Figure 1 Roller bearings mainly consist of an outer ring, an inner ring 27, a cage 28, and multiple rollers 29. When assembling roller bearings, the multiple rollers 29 are usually installed on the cage 28 first, then the inner ring 27 of the bearing is manually pressed to the inside of the cage 28 and the rollers 29, and then the outer ring of the bearing is installed.

[0003] Currently, in the assembly of tapered roller bearings, after multiple rollers 29 are installed, the space reserved inside the cage 28 is small, which makes it easy to damage the surface of the rollers 29 and the raceway surface of the inner ring 27 when the bearing inner ring 27 is forcibly pressed for installation. Utility Model Content

[0004] In order to avoid damaging the roller surface and inner ring raceway surface during inner ring installation, this application provides a bearing plastic steel cage expansion device.

[0005] The bearing plastic steel cage expansion device provided in this application adopts the following technical solution: A bearing plastic steel cage expansion device, comprising: Chuck; A movable body is slidably disposed on the chuck, the sliding direction of the movable body is perpendicular to the axial direction of the chuck, and multiple movable bodies are distributed along the circumference of the chuck; An expansion block, which corresponds one-to-one with a movable body, is disposed on the corresponding movable body. The expansion block has an arc-shaped protrusion section, which is used to engage with a groove on the retainer. A drive mechanism, which is mounted on a chuck, is used to drive multiple moving objects to move closer to or further apart from each other.

[0006] Preferably, the expansion device further includes a mounting frame, the chuck is mounted on the mounting frame, a limit rod is slidably mounted on the mounting frame, the limit rod corresponds one-to-one with the moving body, the sliding direction of the limit rod is parallel to the sliding direction of the corresponding moving body, the limit rod is used to abut against the side of the corresponding moving body away from the center of the chuck, and the mounting frame is provided with a limiting fitting for limiting the position of the limit rod.

[0007] Preferably, the limiting fitting includes a top block disposed on the mounting bracket and a nut threaded onto the limiting rod. The top block and the limiting rod correspond one-to-one. The limiting rod is a screw rod, which is threaded through the corresponding top block. The nut is located on the side of the corresponding top block away from the moving body.

[0008] Preferably, the mounting frame is provided with multiple support columns, and a top ring plate is provided on the multiple support columns. The chuck is located inside the top ring plate, and the top block is provided on the top ring plate.

[0009] Preferably, the driving mechanism includes a pull rod, a first wedge block, a second wedge block, and a driving source. The pull rod slides along the axial direction of the chuck on the chuck and is located between multiple moving bodies. The first wedge block is disposed on the moving body, and the second wedge block is disposed on the pull rod. The second wedge block corresponds one-to-one with the first wedge block. The first wedge block has a first inclined surface, and the second wedge block has a second inclined surface. The second inclined surface slides in cooperation with the corresponding first inclined surface. The driving source is used to drive the pull rod to move.

[0010] Preferably, the distance from the first inclined plane to the axis of the pull rod decreases toward the direction of the expansion block, and the distance from the second inclined plane to the axis of the pull rod decreases toward the direction of the expansion block.

[0011] Preferably, a connecting shaft is provided on the mounting bracket, the drive source is mounted on the connecting shaft, and the pull rod is located inside the connecting shaft.

[0012] Preferably, the end of the connecting shaft away from the chuck is threaded with a transition flange, and the drive source is connected to the transition flange.

[0013] Preferably, the movable body includes a movable block slidably disposed on the chuck, a locking block disposed within the movable block, and a transition block disposed on the movable block. The expansion block is located above the transition block, and the expansion block is connected to the locking block through the transition block by a connecting screw.

[0014] Preferably, the expansion block is fan-shaped, and when the centers of multiple expansion blocks coincide, the arc-shaped protrusions on the multiple expansion blocks form a ring.

[0015] In summary, this application includes the following beneficial technical effects: In use, the groove on the end face of the cage is inserted into the arc-shaped protrusions of multiple expansion blocks. Then, the rollers are installed on the cage in sequence. After the multiple rollers are installed, the drive mechanism drives multiple moving bodies to move synchronously a certain distance away from the center of the chuck. At this time, the multiple expansion blocks open synchronously, thereby driving the cage to expand until the cage is expanded to the required position, and then the moving bodies stop moving. Then, the bearing inner ring is placed inside the cage and gently pressed into place. Then, the drive mechanism drives multiple moving bodies to drive the expansion blocks to retract synchronously and reset, driving the cage to return to its original shape, thus completing the installation of the bearing inner ring. The inner ring assembly of the cage can then be removed. This application expands the cage when installing the inner ring, thereby facilitating the insertion of the inner ring and preventing damage to the roller surface and the inner ring raceway surface. Attached Figure Description

[0016] Figure 1 This is a planar schematic diagram of the inner ring assembly of the cage in related technologies.

[0017] Figure 2 This is a schematic diagram of the overall structure of an embodiment of this application.

[0018] Figure 3 This is a cross-sectional view of the overall structure of an embodiment of this application.

[0019] Figure 4 This is a partial exploded view of an embodiment of this application.

[0020] Explanation of reference numerals in the attached drawings: 1. Chuck; 2. Moving body; 201. Moving block; 202. Locking block; 203. Transition block; 3. Expansion block; 4. Arc-shaped protrusion; 5. Mounting bracket; 6. Limiting rod; 7. Top block; 8. Nut; 9. Support column; 10. Top ring plate; 11. Tie rod; 12. First wedge block; 13. Second wedge block; 14. Drive source; 15. Connecting shaft; 16. Transition flange; 17. Slide groove; 18. Connecting flange; 20. First hex socket head cap screw; 21. Connecting screw; 22. Third hex socket head cap screw; 23. Fourth hex socket head cap screw; 24. Fifth hex socket head cap screw; 25. Hex socket set screw; 26. External hex socket screw; 27. Inner ring; 28. Cage; 29. ​​Roller; 30. Groove. Detailed Implementation

[0021] The following combination Figures 1-4 This application will be described in further detail.

[0022] Reference Figure 1 To facilitate the installation of the inner ring 27, the cage 28 is made of plastic steel, and the end face of the cage 28 of the tapered roller bearing at the small diameter end has a groove 30, which is opened along the circumference of the cage 28.

[0023] This application discloses a bearing plastic steel cage expansion device. (Refer to...) Figure 2 and Figure 3 The bearing plastic steel cage expansion device includes a mounting frame 5, a chuck 1, a movable body 2, an expansion block 3, and a drive mechanism. The mounting frame 5 stands on the ground and has a center hole on its top surface. A connecting shaft 15 is fixedly inserted through the center hole in the vertical direction. The connecting shaft 15 is fixedly connected to the mounting frame 5 by multiple first hexagon socket screws 20. The connecting shaft 15 is a hollow structure with both ends through it. The chuck 1 is fixedly installed above the connecting shaft 15 by a connecting flange 18 and second hexagon socket screws (not shown in the figure). The cross-section of the chuck 1 is circular, and the chuck 1 and the connecting shaft 15 are concentrically arranged.

[0024] Reference Figure 2 and Figure 3 The movable body 2 is slidably disposed on the chuck 1. The chuck 1 has a sliding groove 17 that slides with the movable body 2. The sliding direction of the movable body 2 is perpendicular to the axial direction of the chuck 1, and multiple movable bodies 2 are distributed along the circumference of the chuck 1. Specifically, in this embodiment, three movable bodies 2 are provided, and the three movable bodies 2 and the chuck 1 form a three-jaw chuck. In other embodiments, the number of movable bodies 2 can be set as needed.

[0025] Reference Figure 2 and Figure 3 Each expansion block 3 corresponds one-to-one with a moving body 2. The expansion block 3 is fixedly installed above the corresponding moving body 2, so that the moving body 2 can drive the corresponding expansion block 3 to move synchronously when it moves. Furthermore, the expansion block 3 is fan-shaped, which facilitates the placement of the retainer 28. Each expansion block 3 has an arc-shaped protrusion 4 on its upper surface. The arc-shaped protrusion 4 is concentrically arranged with the corresponding expansion block 3. The initial position of the expansion block 3 is the position where the expansion block 3 is concentric with the chuck 1, so that when the centers of multiple expansion blocks 3 coincide, the arc-shaped protrusion 4 on multiple expansion blocks 3 forms a ring. The arc-shaped protrusion 4 is used to engage with the groove 30 at the small diameter end of the retainer 28. The size of the ring formed by the arc-shaped protrusion 4 is slightly smaller than the size of the groove 30 on the retainer 28, so as to facilitate the insertion and engagement. The drive mechanism is set on the chuck 1 and is used to drive multiple moving bodies 2 to move closer or further away from each other.

[0026] After the expansion device is installed, the drive mechanism drives multiple moving bodies 2 to move synchronously closer to or further away from the center of the chuck 1, so that the moving bodies 2 drive multiple expansion blocks 3 to move until the circular ring formed by the arc protrusions 4 on the multiple expansion blocks 3 matches the groove 30 at the small diameter end of the retainer 28. At this time, the expansion blocks 3 are in their initial position.

[0027] In use, the groove 30 on the end face of the cage 28 is inserted into the arc-shaped protrusion 4 of the multiple expansion blocks 3. Then, the rollers 29 are installed on the cage 28 in sequence. After the multiple rollers 29 are installed, the multiple moving bodies 2 are driven by the drive mechanism to move synchronously a certain distance away from the center of the chuck 1. At this time, the multiple expansion blocks 3 open synchronously, driving the cage 28 to expand until the cage 28 is expanded to the required position. Then, the bearing inner ring 27 is placed inside the cage 28 and gently pressed into place. Then, the multiple moving bodies 2 are driven by the drive mechanism to drive the expansion blocks 3 to retract synchronously and reset, driving the cage 28 to return to its original shape, thus completing the installation of the bearing inner ring 27. The cage inner ring assembly can then be removed. This application expands the cage 28 when installing the inner ring 27, thereby facilitating the insertion of the inner ring 27 and preventing damage to the surface of the rollers 29 and the raceway surface of the inner ring 27. At the same time, the cage 28 has a certain degree of elasticity and extensibility, and the cage 28 is not easily damaged.

[0028] Reference Figure 2 and Figure 3 To facilitate the movement of multiple moving bodies 2 towards or away from each other, the drive mechanism includes a pull rod 11, a first wedge block 12, a second wedge block 13, and a drive source 14. The pull rod 11 slides through the chuck 1 along its axial direction and is located between the multiple moving bodies 2. The pull rod 11 is concentrically positioned with the chuck 1, and the lower end of the pull rod 11 is located within the connecting shaft 15, thus providing protection. The first wedge block 12 is fixed on the side of the moving body 2 near the center of the chuck 1, and the second wedge block 13 is fixed on the pull rod 11. The second wedge block 13 corresponds one-to-one with the first wedge block 12. The first wedge block 12 has a first inclined surface, and the second wedge block 13 has a second inclined surface. The second inclined surface slides in conjunction with the corresponding first inclined surface. Specifically, the first inclined surface has a guide strip, and the second inclined surface has a guide groove that slides in conjunction with the corresponding guide strip. Through the sliding contact between the guide strip and the guide groove, the sliding contact between the first and second inclined surfaces can be guided.

[0029] Reference Figure 2 and Figure 3 Furthermore, the distance from the first inclined plane to the axis of the pull rod 11 decreases towards the expansion block 3, and the distance from the second inclined plane to the axis of the pull rod 11 also decreases towards the expansion block 3. This causes the second inclined plane to abut against the corresponding first inclined plane when the pull rod 11 moves towards the chuck 1, pushing the moving body 2 to move away from the center of the chuck 1. When the pull rod 11 moves downward away from the chuck 1, the second inclined plane pulls the corresponding first inclined plane to move the moving body 2 towards the center of the chuck 1.

[0030] Reference Figure 2 and Figure 3The drive source 14 is installed at the lower end of the connecting shaft 15 and is located below the chuck 1. The drive source 14 is used to drive the pull rod 11 to move. In this embodiment, the drive source 14 is a cylinder, and the pull rod 11 is threadedly connected to the piston rod of the cylinder. In other embodiments, the drive source 14 can also be an electric cylinder, an electric push rod, etc. Furthermore, the cylinder is connected to an external solenoid valve, so that the cylinder is controlled by the solenoid valve, and the external solenoid valve is controlled by an external solenoid valve switch, so as to facilitate operation by the operator.

[0031] When the cage 28 needs to be expanded, the external solenoid valve switch is activated to energize the solenoid valve. After the solenoid valve vents the cylinder, the piston rod of the cylinder extends, driving the pull rod 11 to move towards the chuck 1. The second inclined surface of the second wedge block 13 on the pull rod 11 abuts against the corresponding first inclined surface, pushing the corresponding first wedge block 12 and the moving body 2 to move away from the center of the chuck 1, thereby realizing the synchronous opening of multiple expansion blocks 3, causing the expansion blocks 3 to drive the cage 28 to expand.

[0032] After the inner ring 27 is placed inside the cage 28, the external solenoid valve switch is closed, causing the solenoid valve to lose power. Then, the piston rod of the cylinder retracts, and the piston rod of the cylinder pulls the pull rod 11 downward. The second inclined surface of the second wedge block 13 on the pull rod 11 will pull the corresponding first inclined surface, causing the first wedge block 12 and the moving body 2 to move towards the center of the chuck 1, thereby causing the multiple expansion blocks 3 to contract synchronously, so as to facilitate the reset of the cage 28.

[0033] In other embodiments, the drive mechanism consisting of the pull rod 11, the first wedge block 12, the second wedge block 13, and the drive source 14 can be replaced by a small bevel gear, a large bevel gear, and a flat threaded disc. The small bevel gear meshes with the large bevel gear, the large bevel gear is connected to the flat threaded disc, and multiple moving bodies 2 are threadedly engaged with the flat threaded disc. By driving the small bevel gear to rotate, the large bevel gear will be driven to rotate, thereby causing the flat threaded disc to drive the three moving bodies 2 to move synchronously toward the center or outward. The traditional three-jaw chuck formed by the chuck 1, the moving bodies 2, and the drive mechanism consisting of the small bevel gear, the large bevel gear, and the flat threaded disc can also achieve the synchronous approach or departure of multiple moving bodies 2.

[0034] Reference Figure 3 A transition flange 16 is threaded onto the end of the connecting shaft 15 furthest from the chuck 1. The transition flange 16 is locked in place by radial hexagonal set screws 25 on the connecting shaft 15. The drive source 14 is fixedly connected to the transition flange 16 by multiple hexagonal screws 26. Since the position of the transition flange 16 on the connecting shaft 15 can be adjusted by rotation, the distance between the cylinder and the chuck 1 can be adjusted as needed.

[0035] Reference Figure 3 and Figure 4Specifically, the movable body 2 includes a movable block 201, a locking block 202, and a transition block 203. The movable block 201 is slidably disposed within the chuck 1, and a connecting groove (not shown in the figure) is formed on the movable block 201. A first wedge block 12 is fixed to the corresponding movable block 201. The locking block 202 is fixed within the connecting groove and is a T-shaped nut. The transition block 203 is fixed to the upper surface of the movable block 201. An expansion block 3 is located above the transition block 203. The expansion block 3 is connected to the locking block 202 by two connecting screws 21 passing through the transition block 203. Specifically, the connecting screws 21 are hexagonal socket head cap screws, thereby fixing the expansion block 3 to the movable body 2. The expansion block 3 is detachably connected to the movable body 2, making it easy to replace the expansion block 3 as needed to accommodate different sizes of cages.

[0036] Reference Figure 2 and Figure 3 Multiple support columns 9 are fixed to the mounting frame 5 by third hexagon socket screws 22. The multiple support columns 9 are arranged at intervals along the circumference of the chuck 1. A top ring plate 10 is fixed to the multiple support columns 9 by fourth hexagon socket screws 23. The chuck 1 is located inside the top ring plate 10, and the top ring plate 10 is concentric with the chuck 1. A limit rod 6 is slidably arranged below the top ring plate 10. The limit rod 6 corresponds one-to-one with the moving body 2. The sliding direction of the limit rod 6 is parallel to the sliding direction of the corresponding moving block 201. The limit rod 6 is located on the side of the corresponding moving block 201 away from the center of the chuck 1. The limit rod 6 is used to abut against the side of the corresponding moving block 201 away from the center of the chuck 1. The mounting frame 5 is provided with a limiting fitting for limiting the position of the limit rod 6.

[0037] Reference Figure 2 and Figure 3 To facilitate limiting the position of the limiting rod 6, the limiting fitting includes a top block 7 and a nut 8. The top block 7 is fixed below the top ring plate 10 by two fifth hexagon socket screws 24. The top block 7 corresponds one-to-one with the limiting rod 6. Further, the limiting rod 6 is a screw rod, and the limiting rod 6 is threaded through the corresponding top block 7. The rotation axis of the limiting rod 6 is parallel to the sliding direction of the corresponding moving block 201. The nut 8 is threaded on the limiting rod 6 and is located on the side of the corresponding top block 7 away from the moving block 201.

[0038] By rotating the limiting rod 6, the limiting rod 6 is moved towards or away from the center of the chuck 1. The limiting rod 6 is moved to a suitable position, that is, when the moving block 201 abuts against the limiting rod 6, the retainer 28 on the expansion block 3 expands to the required position. Then, the nut 8 is rotated so that the nut 8 abuts against the side of the top block 7 away from the chuck 1, thereby locking the limiting rod 6. When the expansion block 3 drives the retainer 28 to expand, the moving block 201 is moved to abut against the limiting rod 6, thereby expanding the retainer 28 to a fixed size position to control the degree of expansion of the retainer 28.

[0039] The implementation principle of this application embodiment is as follows: After the cage 28 and multiple rollers 29 are installed, the drive source 14 is started. The drive source 14 drives the pull rod 11 to move, so that multiple expansion blocks 3 are in the initial position, that is, the ring formed by the arc protrusions 4 on the multiple expansion blocks 3 matches the groove 30 on the cage 28; then the limiting rod 6 is rotated, so that the limiting rod 6 moves towards the center of the chuck 1, and the limiting rod 6 is moved to the appropriate position, that is, when the moving block 201 abuts against the limiting rod 6, the cage 28 on the expansion block 3 expands to the required position.

[0040] Next, the groove 30 on the end face of the retainer 28 is inserted into the arc protrusion 4 of the multiple expansion blocks 3. Then, the rollers 29 are installed on the retainer 28 in sequence. After the multiple rollers 29 are installed, the external solenoid valve switch is activated to energize the solenoid valve. After the solenoid valve vents the cylinder, the piston rod of the cylinder extends and drives the pull rod 11 to move towards the direction closer to the chuck 1. The second inclined surface of the second wedge block 13 on the pull rod 11 will abut against the corresponding first inclined surface, causing the corresponding first wedge block 12 and the moving body 2 to move away from the center of the chuck 1, thereby realizing the synchronous opening of the multiple expansion blocks 3. The expansion blocks 3 drive the retainer 28 to expand until the moving block 201 abuts against the limit rod 6 on the top block 7. At this time, the retainer 28 has been expanded to the required position. Then, the bearing inner ring 27 is placed inside the retainer 28 and gently pressed into place.

[0041] Then, the external solenoid valve switch is closed, the solenoid valve is de-energized, causing the piston rod of the cylinder to retract. The piston rod of the cylinder pulls the pull rod 11 downward. The second inclined surface of the second wedge block 13 on the pull rod 11 will pull the corresponding first inclined surface, causing the first wedge block 12 and the moving body 2 to move towards the center of the chuck 1, thereby causing the multiple expansion blocks 3 to contract synchronously, driving the cage 28 to reset, thus completing the installation of the bearing inner ring 27, and the cage inner ring assembly can be removed. This application expands the cage 28 when installing the inner ring 27, thereby facilitating the insertion of the inner ring 27, and is less likely to damage the surface of the roller 29 and the raceway surface of the inner ring 27. At the same time, the cage 28 has a certain degree of elasticity and extensibility, and the cage 28 is not easily damaged.

[0042] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A bearing plastic retainer expanding device, characterized by, include: Chuck (1); The movable body (2) is slidably disposed on the chuck (1), and the sliding direction of the movable body (2) is perpendicular to the axial direction of the chuck (1). Multiple movable bodies (2) are distributed along the circumference of the chuck (1). Expansion block (3), the expansion block (3) corresponds one-to-one with the moving body (2), the expansion block (3) is set on the corresponding moving body (2), the expansion block (3) has an arc protrusion section (4), the arc protrusion section (4) is used to engage with the groove (30) on the retainer (28); A drive mechanism is provided on a chuck (1) for driving multiple moving bodies (2) to move closer to or further away from each other.

2. A bearing plastic retainer expanding device according to claim 1, characterized in that: The expansion device also includes a mounting frame (5), the chuck (1) is mounted on the mounting frame (5), and a limiting rod (6) is slidably mounted on the mounting frame (5). The limiting rod (6) corresponds one-to-one with the moving body (2). The sliding direction of the limiting rod (6) is parallel to the sliding direction of the corresponding moving body (2). The limiting rod (6) is used to abut against the side of the corresponding moving body (2) away from the center of the chuck (1). The mounting frame (5) is provided with a limiting fitting for limiting the position of the limiting rod (6).

3. A bearing plastic retainer expanding device according to claim 2, characterized in that: The limiting fitting includes a top block (7) set on the mounting bracket (5) and a nut (8) threaded on the limiting rod (6). The top block (7) corresponds to the limiting rod (6) one by one. The limiting rod (6) is a screw rod. The limiting rod (6) is threaded on the corresponding top block (7). The nut (8) is located on the side of the corresponding top block (7) away from the moving body (2).

4. A bearing plastic retainer expanding device according to claim 3, characterized in that: The mounting frame (5) is provided with multiple support columns (9), and a top ring plate (10) is provided on the multiple support columns (9). The chuck (1) is located inside the top ring plate (10), and the top block (7) is provided on the top ring plate (10).

5. The bearing plastic retainer expanding device of claim 2, wherein: The driving mechanism includes a pull rod (11), a first wedge block (12), a second wedge block (13), and a driving source (14). The pull rod (11) slides along the axial direction of the chuck (1) on the chuck (1). The pull rod (11) is located between multiple moving bodies (2). The first wedge block (12) is disposed on the moving body (2), and the second wedge block (13) is disposed on the pull rod (11). The second wedge block (13) corresponds one-to-one with the first wedge block (12). The first wedge block (12) has a first inclined surface, and the second wedge block (13) has a second inclined surface. The second inclined surface slides in cooperation with the corresponding first inclined surface. The driving source (14) is used to drive the pull rod (11) to move.

6. A bearing plastic retainer expanding device according to claim 5, characterized in that: The distance from the first inclined plane to the axis of the pull rod (11) decreases toward the expansion block (3), and the distance from the second inclined plane to the axis of the pull rod (11) decreases toward the expansion block (3).

7. A bearing plastic retainer expanding device according to claim 5, characterized in that: The mounting bracket (5) is provided with a connecting shaft (15), the drive source (14) is mounted on the connecting shaft (15), and the pull rod (11) is located inside the connecting shaft (15).

8. A bearing plastic retainer expanding device according to claim 7, characterized in that: The end of the connecting shaft (15) away from the chuck (1) is threaded with a transition flange (16), and the drive source (14) is connected to the transition flange (16).

9. The bearing plastic retainer expanding device of claim 1, wherein: The movable body (2) includes a movable block (201) slidably disposed on the chuck (1), a locking block (202) disposed within the movable block (201), and a transition block (203) disposed on the movable block (201). The expansion block (3) is located above the transition block (203), and the expansion block (3) is connected to the locking block (202) through the transition block (203) by a connecting screw (21).

10. The bearing plastic retainer expanding device of any one of claims 1-9, wherein: The expansion block (3) is fan-shaped. When the centers of multiple expansion blocks (3) coincide, the arc protrusions (4) on the multiple expansion blocks (3) form a ring.

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