Spraying device for lithium battery diaphragm

Abstract

The invention discloses a spraying device for a lithium battery diaphragm, and relates to the technical field of battery diaphragm spraying, the spraying device comprises a base and two groups of edge position frames arranged on the base, the base is provided with a swing spraying mechanism for driving a spraying pipeline to swing back and forth above the diaphragm in a fan-shaped track to perform spraying operation on the diaphragm, and the swing spraying mechanism is arranged on the base. The swing spraying mechanism comprises a transverse shaft arranged between the two sets of side position frames, the two ends of the transverse shaft are each coaxially and fixedly provided with a set of shaft position discs, swing rods which freely deflect in the vertical direction are arranged below the shaft position discs, the swing rods rotate on the side position frames in a fixed-axis mode, and lower position shafts are coaxially fixed to the swing rods. By arranging the swing spraying mechanism, the spraying pipeline can be driven to swing back and forth above the diaphragm in a fan-shaped track, comprehensive spraying of the diaphragm is achieved, the swing spraying mechanism is small in movement amplitude and does not need to occupy a large space size, and therefore the spraying device can be flexibly arranged in a limited production site, space is saved, and the production cost is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of battery separator spraying, and specifically provides a spraying device for lithium battery separators. Background Art

[0002] Lithium batteries have been widely used in many fields. The performance and safety of lithium batteries largely depend on the quality of their internal components, and the battery separator is one of the key components. The main function of the battery separator is to separate the positive and negative electrodes of the battery to prevent short circuits caused by contact between the two poles, while allowing lithium ions to freely pass through during the charging and discharging process, thereby completing the electrochemical reaction of the battery.

[0003] Chinese Patent (Publication No.: CN116493180B), this solution specifically includes a main body structure, a translation structure, and a spraying structure. The translation structure is fixedly arranged on the main body structure, and the spraying structure is fixedly arranged on the translation structure and is located above the main body structure. The separator can be fixed through a limiting component, and can be flipped 180 degrees for turning in cooperation with the surface-changing component, and then promoted to dry with the help of a drying component; the translation structure can drive the spraying structure to move, and with the linkage of the nozzles in the spraying structure, a relatively large area can be directly sprayed, shortening the spraying time, and it can be adjusted according to the horizontal length of the spraying; it can also quickly achieve single and double uniform spraying over a large range with the spraying structure, improving the overall spraying efficiency.

[0004] For the lithium battery separator spraying device in the above patent, a translation structure is used to drive the nozzle to move to achieve full spraying of the separator. However, in actual applications, when the separator size is large, the translation structure needs to move a long distance, which not only increases the space requirement of the device, but also may reduce the spraying efficiency. In addition, in order to meet the movement range of the nozzle, the entire spraying device needs to occupy a large space, which brings many inconveniences to actual applications when the production site is limited. Therefore, a spraying device for lithium battery separators is proposed. Summary of the Invention

[0005] The purpose of the present invention is to provide a spraying device for lithium battery separators, which has the advantages of quickly covering a large area of the separator region without occupying a large space size, and solves the problem that the spraying device needs to occupy a large space.

[0006] To achieve the above purpose, the present invention provides the following technical solution: A spraying device for lithium battery separators includes a base and two sets of side frames arranged thereon, and further includes a spray pipe arranged on the side frames and multiple sets of nozzles arranged on the spray pipe. A swing spraying mechanism is provided on the base to drive the spray pipe to reciprocally swing in a fan-shaped trajectory above the separator for spraying operations. The swing spraying mechanism includes a transverse shaft disposed between two sets of side frames. Both ends of the transverse shaft are rotatably fixed on a set of side frames respectively. A set of shaft position discs are coaxially fixed at both ends of the transverse shaft. And a swing rod that can freely deflect in the vertical direction is provided below the shaft position disc. The swing rod is rotatably fixed on the side frame and coaxially fixed with a lower shaft. The lower shaft and the spray pipe are fixedly connected to each other. A lifting component for adjusting the horizontal height of the side frame is provided on the base. And a speed change component for adjusting the time taken for the swing rod to complete a single reciprocating swing cycle when the height of the side frame changes is provided on the side frame.

[0007] Preferably, a two-way connection clamping ring is provided between the lower shaft and the spray pipe. And two incomplete cavity grooves integrally formed in the two-way connection clamping ring are respectively used for clamping and fixing the lower shaft and the spray pipe.

[0008] Preferably, the swing rod is in a vertical state in the initial state, and the nozzles fixedly penetrated on the spray pipe are vertically downward.

[0009] Preferably, a positioning pin is fixedly connected to one end of the shaft position disc facing the swing rod. A positioning groove for the positioning pin to slide and connect is provided on the swing rod.

[0010] Preferably, the speed change component includes a U-shaped cranked frame fixedly connected to the side frame. A spline shaft that can freely rotate driven by a motor is rotatably fixed on the U-shaped cranked frame. A friction wheel is slidably sleeved on the spline shaft. The friction wheel moves freely along the laying direction of the spline shaft. A conical cylinder is fixedly sleeved on the transverse shaft. The conical cylinder includes an integrally formed annular conical surface. The annular conical surface and the friction wheel are in frictional contact with each other.

[0011] Preferably, the spline shaft and the annular conical surface are arranged parallel to each other in the vertical cross-section.

[0012] Preferably, a freely rotatable threaded rod is provided on the U-shaped cranked frame. And the threaded rod is rotatably fixed on the U-shaped cranked frame. A same-position seat is threadedly connected to the threaded rod. And a same-position sliding groove for the same-position seat to slide and connect is provided on the U-shaped cranked frame. A clamping groove for accommodating the friction wheel is provided on the same-position seat. The outer side surface of the friction wheel is in sliding contact with the inner wall of the clamping groove.

[0013] Preferably, the lifting component includes a driving shaft that can freely rotate in the vertical direction driven by a motor. The driving shaft is rotatably fixed on the side frame. And a universal joint for drivingly connecting the driving shaft and the threaded rod is provided on the side frame. A worm is coaxially fixed on the driving shaft. The worm is meshed with a worm gear and the worm gear is rotatably fixed on the side frame. The worm gear is meshed with an inclined rack. The inclined rack is fixedly connected to the base. A turning sliding groove for the side frame to vertically slide is provided on the base.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows: By providing a swing spraying mechanism, the present invention can drive the spraying pipeline to reciprocally swing in a fan-shaped trajectory above the diaphragm, realizing comprehensive spraying of the diaphragm. This spraying method can quickly cover a large area of the diaphragm region, significantly improving the spraying efficiency. Moreover, the movement amplitude of the swing spraying mechanism is small, without occupying a large space size. Thus, the spraying device can be flexibly arranged within a limited production site, achieving the purpose of saving space.

[0015] By providing a variable-speed component, the present invention can adjust the swing speed of the spraying pipeline to ensure that the coating material can evenly cover the surface of the diaphragm during the spraying process. Especially when the spraying area increases, by appropriately reducing the spraying speed, the non-uniformity of the coating thickness can be reduced, thereby improving the coating quality. The variable-speed component can dynamically adjust the swing speed of the spraying pipeline according to the change of the spraying range. This dynamic adjustment function enables the device to adapt to different spraying requirements, ensuring the consistency of the spraying thickness, and further improving the uniformity of the coating. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a schematic diagram of the overall structure of the present invention; Figure 2 is a schematic diagram of the component where the U-shaped crank of the present invention is located; Figure 3 is of the present invention Figure 2 enlarged view at A in; Figure 4 is a schematic diagram of the component where the swing rod of the present invention is located; Figure 5 is of the present invention Figure 4 enlarged view at B in; Figure 6 is a schematic diagram of the component where the inclined rack of the present invention is located; Figure 7 is a schematic diagram of the component where the two-way connecting clamp of the present invention is located; Figure 8 is a schematic diagram of the relationship between the rotation angle of the positioning pin and the deflection amount of the swing rod of the present invention; Figure 9 is a schematic diagram of the relationship between the deflection angle of the spraying pipeline and the spraying length of the present invention.

[0017] In the figure: 1, base; 2, horizontal axis; 3, conical cylinder; 4, U-shaped bracket; 5, spline shaft; 6, friction wheel; 7, threaded rod; 8, coaxial seat; 9, clamping groove; 10, coaxial sliding groove; 11, side bracket; 12, shaft position disc; 13, positioning pin; 14, swing rod; 15, positioning groove; 16, lower shaft; 17, bidirectional connection clamp; 18, spray pipe; 19, driving shaft; 20, worm; 21, worm gear; 22, helical rack; 23, turning sliding groove. Detailed implementation manners

[0018] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0019] Please refer to Figures 1 to 9 , the present invention provides a technical solution: a spraying device for a lithium battery separator, including a base 1 and two groups of side brackets 11 arranged thereon, and further including a spray pipe 18 arranged on the side brackets 11 and a plurality of nozzles arranged on the spray pipe 18. A swing spraying mechanism for driving the spray pipe 18 to reciprocally swing in a fan-shaped trajectory above the separator to perform spraying operations on the separator is provided on the base 1; The swing spraying mechanism includes a horizontal axis 2 arranged between the two groups of side brackets 11. The two ends of the horizontal axis 2 are respectively rotationally fixed on a group of side brackets 11. A group of shaft position discs 12 are coaxially fixed at both ends of the horizontal axis 2. And a swing rod 14 that freely deflects in the vertical direction is arranged below the shaft position disc 12. The swing rod 14 is rotationally fixed on the side bracket 11 and coaxially fixed with a lower shaft 16. The lower shaft 16 and the spray pipe 18 are fixedly connected to each other; A lifting component for adjusting the horizontal height of the side bracket 11 is provided on the base 1, and a speed change component for adjusting the time taken for the swing rod 14 to complete a single reciprocating swing cycle when the height of the side bracket 11 changes is provided on the side bracket 11.

[0020] As Figure 1 and Figure 4 shown, when spraying the battery separator, the battery separator to be sprayed is driven to be conveyed below the spray pipe 18, and the central position of the spraying area is made to correspond to the spray pipe 18. Among them, the swing rod 14 is in a vertical state in the initial state, and the nozzles fixedly penetrated on the spray pipe 18 are vertically downward. Therefore, by making the plurality of nozzles on the spray pipe 18 correspond to the midline position of the area to be sprayed in the initial state, the problems of missed spraying and repeated spraying are ensured to be avoided.

[0021] Meanwhile, when the axial disc 12 rotates freely in the vertical direction, it can drive the two groups of axial discs 12 arranged at its upper end to rotate synchronously. Among them, the rotation process of the axial disc 12 can drive the swing rod 14 to deflect reciprocally, and a lower shaft 16 is coaxially fixed on the swing rod 14, thereby driving the lower shaft 16 to rotate reciprocally in the vertical direction.

[0022] At the same time, a two-way connecting clamp 17 is provided between the lower shaft 16 and the spray pipe 18, and the two incomplete cavities integrally formed in the two-way connecting clamp 17 are respectively used for clamping and fixing the lower shaft 16 and the spray pipe 18. Therefore, when the lower shaft 16 rotates reciprocally in the vertical direction, it can drive the spray pipe 18 to swing through the two-way connecting clamp 17, that is, drive the nozzle provided on the spray pipe 18 to swing in a fan-shaped trajectory during the discharging process to achieve the purpose of spraying the diaphragm.

[0023] Meanwhile, the horizontal height of the base 1 is changed through the lifting component, and then the distance between the spray pipe 18 and the battery diaphragm in the initial state is changed. Thus, when the spray pipe 18 swings reciprocally, the coverage range of the spray pipe 18 on the battery diaphragm can be expanded, and then the spraying area of the spray pipe 18 is increased.

[0024] Among them, in order to ensure the uniformity of spraying, the required time for the swing rod 14 and the spray pipe 18 to complete a single reciprocating motion is changed through the speed-changing component. Thus, when the spraying area of the battery diaphragm increases, the spraying speed can be appropriately reduced to drive the paint to evenly cover the surface of the diaphragm, reduce the non-uniformity of the coating thickness, and achieve the purpose of improving the coating quality.

[0025] Furthermore, a positioning pin 13 is fixedly connected to one end of the axial disc 12 facing the swing rod 14, and a positioning groove 15 for the positioning pin 13 to slide and connect is formed on the swing rod 14.

[0026] As Figure 4 、 Figure 5 、 Figure 7 、 Figure 8 and Figure 9 shown, when the transverse shaft 2 rotates freely, it can drive the axial disc 12 arranged at its end to rotate synchronously, and the positioning pin 13 fixedly arranged on the axial disc 12 is slidably connected to the swing rod 14 through the positioning groove 15. Thus, when the axial disc 12 drives the positioning pin 13 to rotate continuously, it can drive the swing rod 14 to swing reciprocally in the vertical direction, and then drive the spray pipe 18 to swing reciprocally through the lower shaft 16 to complete the spraying operation on the battery diaphragm.

[0027] It should be noted that when the positioning pin 13 rotates continuously at a constant speed, the swing amplitude change of the swing rod 14 per unit time is determined by the displacement H of the positioning pin 13 in the horizontal direction. That is, when the positioning pin 13 rotates by a unit angle W, the displacement H of the positioning pin 13 in the horizontal direction is different. Thus, when driving the swing rod 14 and the spray pipe 18 to swing reciprocally, there are differences in their instantaneous swing speeds.

[0028] Among them, when the spray pipe 18 makes a single forward swing and its swing speeds are the same, that is, when the swing angle of the spray pipe 18 per unit time is M, the spraying length N on the battery separator is different. That is, when the angle between the spray pipe 18 and the vertical bisector gradually increases, during the process of swinging by a unit angle M, the spraying length N on the battery separator gradually increases.

[0029] Therefore, to ensure the uniformity of the battery separator coating, when the positioning pin 13 rotates following the axial disc 12, when the positioning pin 13 rotates by a unit angle W, its horizontal displacement H gradually decreases. Further, when driving the swing rod 14 and the angle between the swing rod 14 and the vertical bisector gradually increases, its instantaneous swing speed gradually decreases. Combined with Figure 9 In other words, when the angle between the spray pipe 18 and the vertical bisector gradually increases, its swing speed gradually slows down. Further, it drives the swing angle of the spray pipe 18 per unit time to become smaller. At the same time, since the spray pipe 18 gradually moves away from the vertical bisector, the spraying length N in a unit angle M gradually increases. Thus, by gradually reducing the swing speed of the spray pipe 18, during the process of reciprocating swing spraying of the spray pipe 18, it can relatively uniformly coat the battery separator, thereby ensuring the uniformity of the coating. When the spray pipe 18 swings, the lower shaft 16 is its swing center point, and thus the movement amplitude is small and does not require a large space size.

[0030] In a relatively preferred embodiment, the speed-changing assembly includes a U-shaped crank frame 4 fixedly connected to the side frame 11. A spline shaft 5 driven by a motor to rotate freely is rotatably fixed on the U-shaped crank frame 4. A friction wheel 6 is slidably sleeved on the spline shaft 5, and the friction wheel 6 moves freely along the laying direction of the spline shaft 5; A tapered cylinder 3 is fixedly sleeved on the transverse shaft 2. The tapered cylinder 3 includes an integrally formed annular conical surface, and the annular conical surface is in frictional contact with the friction wheel 6. The spline shaft 5 and the annular conical surface are parallel to each other in the vertical cross-section.

[0031] A threaded rod 7 that rotates freely is provided on the U-shaped crank frame 4, and the threaded rod 7 is rotatably fixed on the U-shaped crank frame 4. A co-location seat 8 is threadedly connected to the threaded rod 7, and a co-location sliding groove 10 for the co-location seat 8 to slide and connect is provided on the U-shaped crank frame 4; The co-seat 8 is provided with a clamping groove 9 for accommodating the friction wheel 6, and the outer side surface of the friction wheel 6 is in sliding contact with the inner wall of the clamping groove 9.

[0032] As Figures 1 - 3 shown, the first motor is fixedly arranged on the U-shaped bracket 4, and the spline shaft 5 is driven by the first motor to rotate freely, thereby driving the friction wheel 6 sleeved thereon to rotate synchronously. The friction wheel 6 is in frictional contact with the annular conical surface integrally formed in the conical cylinder 3. Therefore, when the friction wheel 6 rotates, the transverse shaft 2 can be driven to rotate freely in the vertical direction through the conical cylinder 3.

[0033] Meanwhile, when the transverse shaft 2 rotates, the swing rod 14 is driven to swing reciprocally in the vertical direction through the shaft position disc 12 and the positioning pin 13 arranged at its end, thereby driving the spray pipe 18 to swing reciprocally in the vertical direction to complete the spraying operation on the battery separator.

[0034] Wherein, when the horizontal height of the side seat 11 changes, since the U-shaped bracket 4 is fixedly connected to the side seat 11, the horizontal height of the U-shaped bracket 4 is driven to change synchronously. When the heights of the side seat 11 and the U-shaped bracket 4 change, the threaded rod 7 can rotate freely on the U-shaped bracket 4, thereby driving the co-seat 8 in threaded cooperation with the U-shaped bracket 4 to move along the laying direction of the U-shaped bracket 4.

[0035] At the same time, the threaded rod 7, the spline shaft 5 and the annular conical surface are parallelly arranged in the vertical cross-section. Therefore, when the co-seat 8 moves with the rotation of the threaded rod 7, the friction wheel 6 can be pushed to slide on the spline shaft 5 through the clamping groove 9 opened thereon, thereby changing the relative position between the friction wheel 6 and the annular conical surface.

[0036] It should be noted that since the sizes of the annular conical surface in different cross-sections are different, when the friction wheel 6 moves along the laying direction of the spline shaft 5, the perimeter ratios of the friction wheel 6 to the conical cylinder 3 at the corresponding positions are different. When the U-shaped bracket 4 and the side seat 11 move upward to increase the initial height of the spray pipe 18, the reciprocating swing amplitude of the spray pipe 18 in the vertical direction remains unchanged at this time. The increase in the distance between the spray pipe 18 and the battery separator will drive the spraying range of the spray pipe 18 to increase. Therefore, by dynamically adjusting the position of the friction wheel 6, when the rotational speed of the spline shaft 5 remains unchanged, the rotational speed of the transverse shaft 2 can be adaptively adjusted to ensure that the spray pipe 18 requires a longer time to complete a single reciprocating swing cycle, thereby effectively ensuring the consistency of the spraying thickness while increasing the spraying range of the battery separator, and further improving the spraying effect.

[0037] Based on the embodiment of the speed-changing assembly, the lifting assembly includes a driving shaft 19 that is driven by a motor to rotate freely in the vertical direction. The driving shaft 19 rotates about a fixed axis on the side frame 11, and a universal joint for drivingly connecting the driving shaft 19 and the threaded rod 7 is provided on the side frame 11; A worm 20 is coaxially fixed on the driving shaft 19. The worm 20 is meshed with a worm gear 21, and the worm gear 21 rotates about a fixed axis on the side frame 11. The worm gear 21 is meshed with an inclined rack 22, and the inclined rack 22 is fixedly connected to the base 1; A turning chute 23 for the vertical sliding of the side frame 11 is formed on the base 1.

[0038] As Figure 1 and Figure 6 shown, the driving shaft 19 is driven by a second motor fixedly provided on the side frame 11 to rotate in the vertical direction. A worm 20 is fixedly provided on the driving shaft 19, and the worm 20 is meshed with a worm gear 21. Thus, the worm gear 21 can be driven to rotate freely on the side frame 11. At the same time, the worm gear 21 is meshed with an inclined rack 22, and the inclined rack 22 is fixedly provided on the base 1. Therefore, when the driving shaft 19 rotates, the worm gear 21 can be driven to rotate synchronously, and the horizontal height of the worm gear 21 and the side frame 11 can be changed through the meshing relationship between the worm gear 21 and the inclined rack 22.

[0039] Meanwhile, the driving shaft 19 and the threaded rod 7 are drivingly connected through a universal joint. Thus, when the rotation process of the driving shaft 19 raises the horizontal height of the side frame 11, the perimeter ratio between the friction wheel 6 and the corresponding position of the tapered cylinder 3 can be increased through the rotation process of the threaded rod 7. Therefore, when the rotational speed of the spline shaft 5 remains unchanged, the rotational speed of the transverse shaft 2 can be reduced. Furthermore, when it is necessary to spray a larger range of battery diaphragms in a single time, the time used by the spray pipe 18 in a single reciprocating cycle can be increased, thereby ensuring the consistency of the spraying thickness and improving the spraying quality.

[0040] It should be noted that the universal joint used to drive the driving shaft 19 and the threaded rod 7 in this article is an existing device. The purpose of the universal joint is to drive the threaded rod 7 to rotate synchronously with the driving shaft 19 and to synchronously change the rotation direction with the change of the rotation direction of the driving shaft 19. At the same time, the universal joint is a well-known technical means for those skilled in the art, so it is not illustrated.

[0041] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirits of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A spraying device for lithium battery separator, comprising a base and two sets of side frames arranged thereon, a spraying pipe arranged on the side frames and a plurality of nozzles arranged on the spraying pipe, characterized in that: The base is provided with a swing spray mechanism for driving the spray pipe to swing back and forth in a fan-shaped trajectory above the diaphragm to spray the diaphragm; The swing spray mechanism comprises a transverse shaft arranged between two sets of side frames, the two ends of the transverse shaft are respectively fixedly rotated on a set of side frames, the two ends of the transverse shaft are respectively coaxially fixed with a set of shaft disks, and a swing rod freely deflected in the vertical direction is provided below the shaft disk, the swing rod is fixedly rotated on the side frames and coaxially fixed with a lower shaft, and the lower shaft is fixedly connected to the spray pipe; The base is provided with a lifting component for adjusting the horizontal height of the side frame, and the side frame is provided with a speed changing component for adjusting the time taken by the swing rod to complete a single reciprocating swing cycle when its own height changes.

2. A spraying device for lithium battery separator according to claim 1, characterized in that: A two-way connecting clamp is provided between the lower shaft and the spray pipe, and two groups of incomplete cavities integrally formed in the two-way connecting clamp are respectively used for clamping and fixing the lower shaft and the spray pipe.

3. A spraying device for lithium battery separator according to claim 1, characterized in that: The swing rod is in a vertical state in an initial state, and the nozzle fixed through the spray pipe is vertically downward.

4. A spraying device for lithium battery separator according to claim 3, characterized in that: A positioning pin is fixedly connected to one end of the axial position disc facing the swing rod, and a positioning groove for the positioning pin to be slidably connected is provided on the swing rod.

5. A spraying device for lithium battery separator according to claim 4, characterized in that: The speed change assembly comprises a U-shaped bracket fixedly connected to the side frame, a spline shaft driven by a motor to rotate freely is fixedly rotated on the U-shaped bracket, a friction wheel is slidingly sleeved on the spline shaft, and the friction wheel moves freely along the laying direction of the spline shaft; The fixed sleeve on the transverse shaft is provided with a conical cylinder, the conical cylinder includes an integrally formed annular conical surface, and the annular conical surface and the friction wheel are in friction contact; The U-shaped frame is provided with a freely rotatable threaded rod, and the threaded rod is fixedly rotated on the U-shaped frame, a co-position seat is threadedly connected to the threaded rod, and a co-position sliding groove for sliding connection of the co-position seat is provided on the U-shaped frame; The lifting assembly includes a driving shaft driven by a motor to rotate freely in a vertical direction, the driving shaft rotates on a side frame, and a universal joint for transmission connection between the driving shaft and the threaded rod is provided on the side frame; A worm is coaxially fixed on the driving shaft, the worm is meshedly connected with a worm wheel, and the worm wheel is fixedly rotated on the side frame, the worm wheel is meshedly connected with a bevel rack, and the bevel rack is fixedly connected to the base.

6. A spraying device for lithium battery separator according to claim 5, characterized in that: The spline shaft and the annular cone surface are both arranged in parallel on a vertical section.

7. A spraying device for lithium battery separator according to claim 6, characterized in that: The base is provided with a turning slide groove for the side frame to slide vertically.

8. A spraying device for lithium battery separator according to claim 7, characterized in that: The same seat is provided with a clamping groove for accommodating the friction wheel, and the outer side surface of the friction wheel is in sliding contact with the inner wall of the clamping groove.

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