A cutting device for large-diameter steel pipes

Abstract

This utility model relates to the technical field of steel pipe cutting equipment, specifically to a cutting device for large-diameter steel pipes. Its features include a base frame, a clamping seat, a clamping rotation device, a roller device, a fixed plate, and moving cutting devices. The fixed plate, roller device, and clamping seat are all located on the upper part of the base frame and are arranged sequentially at intervals from one end to the other. The fixed plate has a circular through hole in its center. The clamping rotation device is located on the clamping seat and is used to clamp one end of the steel pipe and drive the steel pipe to rotate slowly. The other end of the steel pipe is supported on the roller device and passes through the circular through hole in the fixed plate. Multiple moving cutting devices are located on the fixed plate and are evenly spaced along the rotation direction of the clamping rotation device. The moving cutting devices can move radially along the circular through hole to cut the steel pipe. This utility model can simultaneously cut the steel pipe from multiple positions on its outer circumference, greatly improving the overall cutting efficiency and significantly reducing the cutting time.

Description

Technical Field

[0001] This utility model relates to the technical field of steel pipe cutting equipment, specifically to a cutting device for large-diameter steel pipes. Background Technology

[0002] Large-diameter thick-walled steel pipes refer to steel pipes with an outer diameter typically exceeding 325mm and a wall thickness exceeding 20mm. They are mainly used in various industrial fields, such as machinery manufacturing, automobile manufacturing, energy industry, petrochemicals, and municipal construction. Currently, when processing such large-diameter thick-walled steel pipes, a cutting saw is usually used to position and cut the steel pipe. However, in actual use, although cutting the steel pipe with a single cutting blade is simple and convenient, when dealing with such large-diameter and thick-walled steel pipes, the cutting time of a single cutting blade is relatively long, and its cutting efficiency is relatively average. Utility Model Content

[0003] The technical problem to be solved by this utility model is to provide a cutting device for large-diameter steel pipes that can simultaneously cut steel pipes from multiple positions on the outer circumference of the steel pipe, which can greatly improve the overall cutting efficiency and greatly reduce the cutting time.

[0004] To solve the above-mentioned technical problems, the technical solution adopted by this utility model is as follows: A cutting device for large-diameter steel pipes includes a base frame, a clamping seat, a clamping rotation device, a roller device, a fixed plate, and a moving cutting device. The fixed plate, roller device, and clamping seat are all located on the upper end of the base frame and are arranged sequentially at intervals from one end to the other. The fixed plate has a circular through hole in the center that allows the steel pipe to pass through. The clamping rotation device is located on the clamping seat and is used to clamp one end of the steel pipe and drive the steel pipe to rotate slowly. The other end of the steel pipe is supported on the roller device and passes through the circular through hole of the fixed plate. Multiple moving cutting devices are located on the fixed plate and are evenly spaced along the rotation direction of the clamping rotation device. The moving cutting devices can move radially along the circular through hole and cut the steel pipe.

[0005] Furthermore, the clamping and rotating device includes a rotating plate, a rotating shaft, a rotating drive assembly, and a clamping assembly. The rotating shaft is arranged laterally and rotatably mounted on the clamping seat via a first bearing. A rotating plate is fixedly mounted on one end of the rotating shaft. The rotating plate is located on the clamping seat near the roller device. The rotating drive assembly is located on the clamping seat and is connected to the other end of the rotating shaft. A circular positioning block adapted to the opening at one end of the steel pipe is fixedly mounted at the center of one side surface of the rotating plate. Multiple clamping assemblies are mounted on the rotating plate and evenly spaced along the circumference of the circular positioning blocks.

[0006] Furthermore, the rotary drive assembly includes a rotary motor and a reducer. Both the rotary motor and the reducer are fixedly mounted on the clamping seat. The motor shaft of the rotary motor is connected to the input shaft of the reducer via a first coupling, and the output shaft of the reducer is connected to one end of the rotary shaft via a second coupling.

[0007] Furthermore, the clamping assembly includes an adjusting screw, a clamping block, and a fixing block. The fixing block is fixedly mounted on the rotating plate. The fixing block has a first threaded hole that matches the adjusting screw. The adjusting screw is threaded into the first threaded hole and its end is rotatably connected to the clamping block. The clamping block has a clamping groove that matches the steel pipe, and a clamping pad is fixedly mounted on the inner surface of the clamping groove.

[0008] Furthermore, the mobile cutting device includes a cutting motor, a cutting blade, a moving block, a mounting plate, and a linear drive. The mounting plate has a strip-shaped slot that extends through its outer circumference. Guide rails are formed on both inner sides of the strip-shaped slot on the mounting plate. The moving block has two symmetrically arranged guide grooves that are adapted to the guide rails. The moving block is slidably embedded in the two guide rails through the two guide grooves. The cutting motor is fixedly mounted on the moving block. The cutting blade is fixedly mounted on the motor shaft of the cutting motor and located on the side of the mounting plate away from the roller device. The mounting plate is fixedly mounted at the opening of the strip-shaped slot on the mounting plate. The linear drive is located on the mounting plate and is used to drive the moving block to move.

[0009] Furthermore, both the fixed plate and the roller device are fixedly installed. The clamping seat is slidably connected to the base frame through a sliding component and can slide towards or away from the fixed plate. The base frame is equipped with a sliding drive device for driving the clamping seat to slide.

[0010] Furthermore, there are two sliding components arranged at intervals. Each sliding component includes a slide rail and at least one slider. The slide rail is fixedly installed on the upper end of the base frame, and the slider is fixedly installed on the bottom end of the clamping seat. The slider and the slide rail are adapted to each other and slide together. Limiting blocks are fixedly installed on both ends of the slide rail on the upper end of the base frame.

[0011] Furthermore, the sliding drive device includes a drive motor, a transmission screw, and a slide. The two ends of the transmission screw are rotatably mounted on the base frame via second bearings. The drive motor is fixedly mounted on a motor base, which is also fixedly mounted on the base frame. The motor shaft of the drive motor is connected to one end of the transmission screw via a third coupling. The slide is sleeved on the transmission screw, and the two are threadedly engaged. The slide is fixedly connected to the lower end of the clamping seat.

[0012] Furthermore, the idler roller device includes a mounting base and idler roller assemblies. The mounting base is fixedly installed on the upper end of the base frame. Multiple idler roller assemblies are arranged on the mounting base. The multiple idler roller assemblies together form a groove that is compatible with the steel pipe. The steel pipe is rotatably and movablely supported in the groove.

[0013] Furthermore, the idler assembly includes a rotating idler and an idler seat. The idler seat is fixedly mounted on a mounting base, and the rotating idler is rotatably mounted on the idler seat. Several rolling grooves are evenly distributed on the outer circumferential surface of the rotating idler, and matching balls are provided in the rolling grooves. Multiple sealing plates for sealing the rolling grooves are also installed on the outer circumferential surface of the rotating idler. The multiple sealing plates are evenly arranged along the circumferential direction of the rotating idler, and multiple circular slots are provided on the sealing plates that allow one side of the ball to pass through. The circular slots are matched with the ball.

[0014] As described above, the large-diameter steel pipe cutting equipment provided by this utility model has the following beneficial effects: by clamping and rotating the steel pipe at one end and cooperating with the roller device to stably support the other end of the steel pipe, the stability of the support at both ends of the steel pipe is ensured, thus ensuring the smooth progress of the steel pipe cutting process. By using multiple moving cutting devices, the steel pipe can be cut simultaneously from multiple positions on the outer circumference of the steel pipe. The moving cutting devices can first move and cut along the radial direction of the circular perforation and cut through the thick wall of the steel pipe. Then, in conjunction with the clamping and rotating device, the steel pipe is slowly rotated and rotated at a certain angle, thereby realizing the full circle cutting of the steel pipe by multiple moving cutting devices. This can greatly improve the overall cutting efficiency and greatly reduce the cutting time, thereby increasing the overall production capacity. Attached Figure Description

[0015] Figure 1 This is a three-dimensional structural diagram of a cutting device for large-diameter steel pipes according to the present invention.

[0016] Figure 2 for Figure 1 A magnified view of a portion of point A in the middle.

[0017] Figure 3 This is a schematic diagram of the structure of a large-diameter steel pipe cutting device according to the present invention.

[0018] Figure 4 for Figure 3 A magnified view of a portion of point B in the middle.

[0019] Figure 5 This is an exploded view of the three-dimensional structure of the idler roller assembly.

[0020] Figure 6 This is a schematic diagram of the three-dimensional structure of the movable block.

[0021] Figure 7 This is a schematic diagram of the cutting state of a large-diameter steel pipe cutting device according to the present invention.

[0022] Figure 8 for Figure 7 A magnified view of a portion of point C.

[0023] In the diagram: 1-Base frame; 2-Clamping seat; 3-Clamping rotation device; 31-Rotating plate; 311-Circular positioning block; 32-Rotating shaft; 33-Rotating drive assembly; 331-Rotating motor; 332-Reducer; 34-Clamping assembly; 341-Adjusting screw; 342-Clamping block; 343-Fixing block; 4-Idler roller device; 41-Mounting seat; 42-Idler roller assembly; 421-Rotating idler roller; 4211-Rolling groove; 422-Idler roller seat; 423-Ball bearing; 424- 4241-Circular slot; 5-Fixing plate; 51-Circular perforation; 52-Strip slot; 53-Guide rail; 6-Moving cutting device; 61-Cutting motor; 62-Cutting blade; 63-Moving block; 631-Guide groove; 64-Mounting plate; 65-Linear drive component; 7-Sliding assembly; 71-Slide rail; 72-Slider; 73-Limit block; 8-Sliding drive device; 81-Drive motor; 82-Transmission screw; 83-Slide table; 84-Motor base; 9-Steel pipe. Detailed Implementation

[0024] The present invention will be further described below through specific embodiments.

[0025] like Figures 1 to 8 As shown, the present invention discloses a large-diameter steel pipe cutting device, comprising a base frame 1, a clamping seat 2, a clamping rotation device 3, a roller device 4, a fixed plate 5, and a moving cutting device 6. The fixed plate 5, the roller device 4, and the clamping seat 2 are all located on the upper end of the base frame 1 and are arranged sequentially at intervals from one end to the other. The fixed plate 5 has a circular through hole 51 in its center, through which a steel pipe 9 can pass. The clamping rotation device 3 is located on the clamping seat 2 and is used to clamp one end of the steel pipe 9 and drive the steel pipe 9 to rotate slowly. The other end of the steel pipe 9 is supported on the roller device 4 and passes through the circular through hole 51 of the fixed plate 5. Multiple moving cutting devices 6 are located on the fixed plate 5 and are evenly spaced along the rotation direction of the clamping rotation device 3. The moving cutting devices 6 can move radially along the circular through hole 51 and cut the steel pipe 9.

[0026] The clamping and rotating device 3 clamps and fixes one end of the steel pipe 9, and the roller device 4 provides stable support for the other end of the steel pipe 9, thereby ensuring the stability of the support at both ends of the steel pipe 9 and ensuring the smooth progress of the cutting process. By using multiple moving cutting devices 6, the steel pipe 9 can be cut simultaneously from multiple positions on its outer circumference. The moving cutting device 6 can first move and cut along the radial direction of the circular perforation 51 and cut through the thick wall of the steel pipe 9. Then, in conjunction with the clamping and rotating device 3, it drives the steel pipe 9 to rotate slowly and at a certain angle, thereby realizing the full circle cutting of the steel pipe 9 by multiple moving cutting devices 6. This can greatly improve the overall cutting efficiency and greatly reduce the cutting time, thereby increasing the overall production capacity.

[0027] Preferably, the number of the movable cutting devices 6 is 3-5. When there are 3 movable cutting devices 6, the clamping and rotating device 3 drives the steel pipe 9 to slowly rotate 120 degrees, which can achieve full-circle cutting of the steel pipe 9 by 3 movable cutting devices 6. When there are 4 movable cutting devices 6, the clamping and rotating device 3 drives the steel pipe 9 to slowly rotate 90 degrees, which can achieve full-circle cutting of the steel pipe 9 by 4 movable cutting devices 6. When there are 5 movable cutting devices 6, the clamping and rotating device 3 drives the steel pipe 9 to slowly rotate 72 degrees, which can achieve full-circle cutting of the steel pipe 9 by 5 movable cutting devices 6.

[0028] The clamping and rotating device 3 includes a rotating plate 31, a rotating shaft 32, a rotating drive assembly 33, and a clamping assembly 34. The rotating shaft 32 is arranged laterally and rotatably mounted on the clamping seat 2 via a first bearing. One end of the rotating shaft 32 is fixedly provided with the rotating plate 31. The rotating plate 31 is located on the clamping seat 2 near the idler roller device 4. The rotating drive assembly 33 is located on the clamping seat 2 and is connected to the other end of the rotating shaft 32. A circular positioning block 311, which is adapted to the opening at one end of the steel pipe 9, is fixedly provided at the center of one side surface of the rotating plate 31. The end surface of the circular positioning block 311 is frustum-shaped, which facilitates the quick and accurate insertion of the circular positioning block 311 into the opening at one end of the steel pipe 9. The clamping components 34 are multiple and are arranged on the rotating plate 31 and are evenly spaced along the circumference of the circular positioning block 311. Thus, with the cooperation of the circular positioning block 311 and the multiple clamping components 34, the steel pipe 9 can be well clamped and fixed. At the same time, when the rotation drive component 33 drives the rotating plate 31 to rotate slowly, the steel pipe 9 can be rotated slowly in sync. Preferably, the number of clamping components 34 is 3-5.

[0029] The rotary drive assembly 33 includes a rotary motor 331 and a reducer 332. Both the rotary motor 331 and the reducer 332 are fixedly mounted on the clamping seat 2. The motor shaft of the rotary motor 331 is connected to the input shaft of the reducer 332 via a first coupling. The output shaft of the reducer 332 is connected to one end of the rotary shaft 32 via a second coupling. Preferably, the rotary motor 331 is a servo motor.

[0030] The clamping assembly 34 includes an adjusting screw 341, a clamping block 342, and a fixing block 343. The fixing block 343 is fixedly mounted on the rotating plate 31. The fixing block 343 has a first threaded hole that matches the adjusting screw 341. The adjusting screw 341 is threaded into the first threaded hole, and its end is rotatably connected to the clamping block 342. Correspondingly, the adjusting screw 341 and the clamping block 342 are rotatably connected through a third bearing. The clamping block 342 has a clamping groove that matches the steel pipe 9. A clamping pad, which is a rubber pad, is fixedly mounted on the inner surface of the clamping groove. Thus, when the adjusting screw 341 is tightened, the clamping block 342 can be driven to press against the outer circumference of one end of the steel pipe 9. With the cooperation of multiple clamping blocks 342, the clamping and fixing of one end of the steel pipe 9 can be achieved.

[0031] The mobile cutting device 6 includes a cutting motor 61, a cutting blade 62, a moving block 63, a mounting plate 64, and a linear drive component 65. The mounting plate 5 has a strip-shaped slot 52 extending through its outer periphery. Guide rails 53 are formed on both inner sides of the strip-shaped slot 52 on the mounting plate 5. The moving block 63 has two symmetrically arranged guide grooves 631 that are adapted to the guide rails 53. The moving block 63 is slidably embedded in the two guide rails 53 through the two guide grooves 631, thereby guiding the movement of the moving block 63. The cutting motor 61 is fixedly mounted on the moving block 63. The blade 62 is fixedly mounted on the motor shaft of the cutting motor 61 and located on the fixed plate 5 on the side away from the roller device 4. The mounting plate 64 is fixedly mounted at the opening of the strip groove 52 of the fixed plate 5. The linear drive member 65 is provided on the mounting plate 64 and is used to drive the moving block 63 to move. In this way, the cutting motor 61 can drive the cutting blade 62 to rotate at high speed, and the linear drive member 65 can drive the moving block 63 to move radially, so as to drive the cutting blade 62 to move radially synchronously, thereby realizing the movement along the radial direction of the circular perforation 51 and cutting the steel pipe 9.

[0032] Preferably, the linear drive component 65 is a hydraulic cylinder, a pneumatic cylinder, or an electric push rod.

[0033] Correspondingly, both the fixed plate 5 and the roller device 4 are fixedly installed. The roller device 4 is located near the fixed plate 5. The clamping seat 2 is slidably connected to the base frame 1 through the sliding assembly 7 and can slide towards or away from the fixed plate 5. The base frame 1 is provided with a sliding drive device 8 for driving the clamping seat 2 to slide. Thus, after one cut is completed, the sliding drive device 8 can drive the clamping seat 2 to slide towards the fixed plate 5, thereby realizing that the entire steel pipe 9 slides towards the fixed plate 5 so that the remaining part of the steel pipe 9 can be cut again.

[0034] Two sliding components 7 are arranged at intervals. Each sliding component 7 includes a slide rail 71 and at least one slider 72. The slide rail 71 is fixedly installed on the upper end of the base frame 1, and the slider 72 is fixedly installed on the bottom end of the clamping seat 2. The slider 72 is adapted to the slide rail 71 and the two slide in a sliding fit. Limiting blocks 73 are fixedly installed at both ends of the slide rail 71 on the upper end of the base frame 1, thereby effectively ensuring the stability and smoothness of the clamping seat 2 when sliding.

[0035] The sliding drive device 8 includes a drive motor 81, a transmission screw 82, and a slide 83. Both ends of the transmission screw 82 are rotatably mounted on the base frame 1 via second bearings. The drive motor 81 is fixedly mounted on a motor base 84, which is also fixedly mounted on the base frame 1. The motor shaft of the drive motor 81 is connected to one end of the transmission screw 82 via a third coupling. The slide 83 is sleeved on the transmission screw 82, and the two are threadedly engaged. Correspondingly, the slide 83 has a second threaded hole to facilitate threaded engagement with the transmission screw 82. The slide 83 is fixedly connected to the lower end of the clamping seat 2. Thus, the drive motor 81 drives the transmission screw 82 to rotate, and through the threaded engagement between the transmission screw 82 and the slide 83, as well as the guiding effect of the sliding assembly 7, the slide 83 can move relative to the transmission screw 82, thereby causing the clamping seat 2 to move synchronously.

[0036] The idler roller device 4 includes a mounting base 41 and an idler roller assembly 42. The mounting base 41 is fixedly installed on the upper end of the base frame 1. Multiple idler roller assemblies 42 are arranged on the mounting base 41. The multiple idler roller assemblies 42 together form a groove that is adapted to the steel pipe 9. The steel pipe 9 is rotatably and movablely supported in the groove.

[0037] The idler roller assembly 42 includes a rotating idler roller 421 and an idler roller seat 422. The idler roller seat 422 is fixedly mounted on the mounting base 41, and the rotating idler roller 421 is rotatably mounted on the idler roller seat 422. A plurality of rolling grooves 4211 are evenly distributed on the outer circumferential surface of the rotating idler roller 421. Matching balls 423 are provided within the rolling grooves 4211. A plurality of sealing plates 424 for sealing the rolling grooves 4211 are also installed on the outer circumferential surface of the rotating idler roller 421. The sealing plate 424 is evenly arranged along the circumference of the rotating roller 421. The sealing plate 424 is provided with a plurality of circular slots 4241 that allow one side surface of the ball 423 to pass through. The circular slots 4241 are adapted to the ball 423. Thus, when the steel pipe 9 is supported on the ball 423 in the groove, the free rolling of the ball 423 in the rolling groove allows the steel pipe 9 to rotate or move smoothly in the groove under the action of external force.

[0038] The above are only some specific embodiments of this utility model, but the design concept of this utility model is not limited thereto. Any non-substantial modifications made to this utility model using this concept shall be considered as an infringement of the protection scope of this utility model.

Claims

1. A cutting device for large-diameter steel pipes, characterized in that: The device includes a base frame, a clamping seat, a clamping and rotating device, a roller device, a fixed plate, and a moving cutting device. The fixed plate, the roller device, and the clamping seat are all located on the upper end of the base frame and are arranged sequentially at intervals from one end to the other. The fixed plate has a circular through hole in its center, through which a steel pipe can pass. The clamping and rotating device is located on the clamping seat and is used to clamp one end of the steel pipe and drive the steel pipe to rotate slowly. The other end of the steel pipe is supported on the roller device and passes through the circular through hole in the fixed plate. Multiple moving cutting devices are located on the fixed plate and are evenly spaced along the rotation direction of the clamping and rotating device. The moving cutting devices can move radially along the circular through hole and cut the steel pipe.

2. The cutting equipment for large-diameter steel pipes according to claim 1, characterized in that: The clamping and rotating device includes a rotating plate, a rotating shaft, a rotating drive assembly, and a clamping assembly. The rotating shaft is arranged laterally and rotatably mounted on the clamping seat via a first bearing. One end of the rotating shaft is fixedly provided with the rotating plate, which is located on the clamping seat near the idler roller device. The rotating drive assembly is located on the clamping seat and is connected to the other end of the rotating shaft. A circular positioning block adapted to the opening of one end of the steel pipe is fixedly provided at the center of one side surface of the rotating plate. Multiple clamping assemblies are provided on the rotating plate and are evenly spaced along the circumference of the circular positioning blocks.

3. The cutting equipment for large-diameter steel pipes according to claim 2, characterized in that: The rotary drive assembly includes a rotary motor and a reducer. Both the rotary motor and the reducer are fixedly mounted on the clamping seat. The motor shaft of the rotary motor is connected to the input shaft of the reducer via a first coupling, and the output shaft of the reducer is connected to one end of the rotary shaft via a second coupling.

4. The cutting equipment for large-diameter steel pipes according to claim 2, characterized in that: The clamping assembly includes an adjusting screw, a clamping block, and a fixing block. The fixing block is fixedly mounted on the rotating plate. The fixing block has a first threaded hole adapted to the adjusting screw. The adjusting screw is threaded into the first threaded hole and its end is rotatably connected to the clamping block. The clamping block has a clamping groove adapted to the steel pipe, and a clamping pad is fixedly mounted on the inner surface of the clamping groove.

5. The cutting equipment for large-diameter steel pipes according to claim 1, characterized in that: The mobile cutting device includes a cutting motor, a cutting blade, a moving block, a mounting plate, and a linear drive. The mounting plate has a strip-shaped slot extending through its outer circumference. Guide rails are formed on both inner sides of the strip-shaped slot on the mounting plate. The moving block has two symmetrically arranged guide grooves that are adapted to the guide rails. The moving block is slidably embedded in the two guide rails through the two guide grooves. The cutting motor is fixedly mounted on the moving block. The cutting blade is fixedly mounted on the motor shaft of the cutting motor and located on the side of the mounting plate away from the roller device. The mounting plate is fixedly mounted at the opening of the strip-shaped slot on the mounting plate. The linear drive is located on the mounting plate and is used to drive the moving block to move.

6. The cutting equipment for large-diameter steel pipes according to claim 1, characterized in that: Both the fixed plate and the roller device are fixedly installed. The clamping seat is slidably connected to the base frame through a sliding component and can slide towards or away from the fixed plate. The base frame is provided with a sliding drive device for driving the clamping seat to slide.

7. The cutting equipment for large-diameter steel pipes according to claim 6, characterized in that: The sliding components are two and spaced apart. Each sliding component includes a slide rail and at least one slider. The slide rail is fixedly installed on the upper end of the base frame, and the slider is fixedly installed on the bottom end of the clamping seat. The slider is adapted to the slide rail and the two slide in a sliding fit. Limiting blocks are fixedly installed on both ends of the slide rail on the upper end of the base frame.

8. The cutting equipment for large-diameter steel pipes according to claim 6, characterized in that: The sliding drive device includes a drive motor, a transmission screw, and a slide. The two ends of the transmission screw are rotatably mounted on the base frame via second bearings. The drive motor is fixedly mounted on a motor base, which is fixedly mounted on the base frame. The motor shaft of the drive motor is connected to one end of the transmission screw via a third coupling. The slide is sleeved on the transmission screw, and the two are threadedly engaged. The slide is fixedly connected to the lower end of the clamping seat.

9. The cutting equipment for large-diameter steel pipes according to claim 6, characterized in that: The idler roller device includes a mounting base and idler roller assemblies. The mounting base is fixedly installed on the upper end of the base frame. Multiple idler roller assemblies are arranged on the mounting base. The multiple idler roller assemblies together form a groove that is adapted to the steel pipe. The steel pipe is rotatably and movablely supported in the groove.

10. The cutting equipment for large-diameter steel pipes according to claim 9, characterized in that: The idler assembly includes a rotating idler and an idler seat. The idler seat is fixedly mounted on the mounting base, and the rotating idler is rotatably mounted on the idler seat. A plurality of rolling grooves are evenly distributed on the outer circumferential surface of the rotating idler, and matching balls are provided in the rolling grooves. A plurality of sealing plates for sealing the rolling grooves are also installed on the outer circumferential surface of the rotating idler. The plurality of sealing plates are evenly arranged along the circumferential direction of the rotating idler, and the sealing plates are provided with a plurality of circular slots that allow one side surface of the balls to pass through. The circular slots are adapted to the balls.

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