Automatic pressing device for battery top cover

Abstract

An automatic battery top cover pressing device comprises a workbench, a rotating disc device arranged on the workbench, a planishing device, a pressing deviation correcting device and a pressing plate storage device, the rotating disc device comprises a shell, a motor is fixed in the shell and penetrates through the shell, a rotating disc is fixed to the motor, a limiting groove is formed in the side wall of the rotating disc, a connecting hole is further formed in the rotating disc, and the rotating disc is connected with the planishing device through the connecting hole. The motor drives the turntable to synchronously rotate; the planishing device comprises a supporting rod, the supporting rod is connected with a planishing assembly, the planishing assembly comprises a connecting rod, and the connecting rod is connected with a planishing roller in a rolling mode; the press-fit deviation rectifying device comprises a cylindrical support, a base, a deviation rectifying mechanism and a press-fit mechanism, the deviation rectifying mechanism comprises a clamping jaw air cylinder and a deviation rectifying assembly, two deviation rectifying pieces in the deviation rectifying assembly are matched, a telescopic air cylinder in the press-fit mechanism is connected to the top of the clamping jaw air cylinder, and a press-fit plate is connected to a connector. And for a battery top cover pressing process, the labor cost is reduced, and the production efficiency and the production qualification rate are improved.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of batteries, in particular to an automatic pressing device for a battery top cover. BACKGROUND

[0002] A battery refers to a cup, a groove or other container or part of a composite container containing electrolyte solution and metal electrodes to generate current, a device capable of converting chemical energy into electric energy, having positive and negative electrodes, and generally referring to a small device capable of generating electric energy. The performance parameters of the battery mainly include electromotive force, capacity, specific energy and resistance. Using a battery as an energy source can obtain a current with stable voltage, stable current, long-time stable power supply, little influence from the outside world, simple battery structure, convenient carrying, easy charging and discharging operation, little influence from the outside world, stable and reliable performance, and plays a great role in various aspects of modern social life.

[0003] However, in the production process of the battery, the top cover of the battery needs to be pressed on the opening position on the upper side of the battery cup. The prior art is to manually correct and press the position of the battery cover, resulting in high labor cost, and also affecting the working efficiency and consistency of the product, so that the battery cover assembly error occurs, thereby causing the problem of battery scrap, or the problem of incomplete battery cover assembly and local protrusion. These problems have an impact on the performance, size and appearance of subsequent welding, therefore, the existing battery top cover pressing device cannot meet the production needs of the present age. CONTENT OF THE INVENTION

[0004] The embodiment of the utility model provides a kind of automatic pressing device for battery top cover, realize the process of battery top cover pressing in production process, reduce artificial cost, improve production efficiency and production qualified rate.

[0005] To achieve the foregoing object, the application adopts the following technical solutions:

[0006] An automatic pressing device for battery top cover, characterized by comprising

[0007] Workbench;

[0008] Rotating disc device is arranged on the workbench, the rotating disc device includes a shell, a motor arranged in the shell and a rotating disc fixed to the motor, the motor is fixed in the shell and penetrates the shell, a limiting groove is arranged on the side wall of the rotating disc, a connecting hole is further arranged on the rotating disc, and the motor drives the rotating disc to rotate synchronously;

[0009] The leveling device comprises a support rod and a leveling assembly connected to the support rod, the leveling assembly comprises a connecting rod and a leveling roller connected to the connecting rod, one end of the connecting rod is connected to the support rod, and the other end is connected to the leveling roller;

[0010] The pressing and correcting device comprises a cylindrical support, a base connected to the cylindrical support, a correcting mechanism fixed to the base, and a pressing mechanism fixed to the top of the correcting mechanism, the correcting mechanism comprises a jaw cylinder and a correcting assembly connected to the jaw cylinder, the correcting assembly comprises at least two correcting pieces, the two correcting pieces are matched to simultaneously form a ring around the battery cover and the battery cup body, the pressing mechanism comprises a telescopic cylinder and a connecting head connected to the telescopic cylinder, the telescopic cylinder is connected to the top of the jaw cylinder, and the end of the telescopic cylinder is connected with the connecting head, and the connecting head is connected with the pressing plate;

[0011] The pressing plate storage device connected to the pressing and correcting device.

[0012] In some optional embodiments, an included angle α is formed between the support rod and the leveling assembly, and 70°<α<90°.

[0013] In some optional embodiments, the leveling roller comprises a roller body and a flexible protective layer arranged on the outer wall of the roller body.

[0014] In some optional embodiments, the correcting piece comprises a connecting part and a correcting part.

[0015] In some optional embodiments, one side of the correcting part is provided with an arc-shaped correcting groove, and the arc of the arc-shaped correcting groove is β, and 30°<β<70°.

[0016] In some optional embodiments, the pressing plate storage device comprises a rotating shaft, at least one group of extension rod assemblies connected to the outer wall of the rotating shaft, and a storage assembly connected to the extension rod assemblies.

[0017] In some optional embodiments, one group of the extension rod assemblies comprises at least six extension rods, and the six extension rods are uniformly distributed on the outer wall of the rotating shaft.

[0018] In some optional embodiments, the storage assembly comprises at least six storage racks, and the number of the storage racks in the storage assembly corresponds to the number of the extension rods in the extension rod assembly.

[0019] In some optional embodiments, the inside of the storage rack is further provided with an annular bottom support.

[0020] In some alternative embodiments, the limiting groove is in the shape of a U.

[0021] The battery top cover automatic pressing device provided by the application has the following beneficial effects:

[0022] In the technical scheme adopted by the application, the battery top cover automatic pressing device is provided with a turntable device, a flattening device, a pressing and correcting device and a pressing plate storage device on the workbench. The motor is fixed in the interior of the shell of the turntable device and penetrates the shell. The motor is fixed with a turntable. The limiting groove is arranged on the side wall of the turntable. The motor drives the turntable to rotate synchronously. The flattening assembly is connected to the supporting rod of the flattening device. The flattening assembly comprises a connecting rod and a flattening roller. The pressing and correcting device comprises a cylindrical support, a base, a correcting mechanism and a pressing mechanism. The correcting mechanism comprises a clamping jaw cylinder and a correcting assembly. The two correcting members in the correcting assembly are matched. The telescopic cylinder in the pressing mechanism is connected to the top of the clamping jaw cylinder. The connecting head is connected with the pressing plate. The process of pressing the battery top cover in the production process of the battery is realized. The labor cost is reduced. The production efficiency and the production qualification rate are improved. BRIEF DESCRIPTION OF DRAWINGS

[0023] Other features, objects and advantages of the application will become more apparent from the following detailed description of non-limiting embodiments made with reference to the accompanying drawings:

[0024] Figure 1 is a perspective view of a battery top cover automatic pressing device according to the application;

[0025] Figure 2 is a schematic view of a turntable device in a battery top cover automatic pressing device according to the application;

[0026] Figure 3 is a schematic view of a flattening device in a battery top cover automatic pressing device according to the application;

[0027] Figure 4 is a sectional view of a roller body and a flexible protective layer in a battery top cover automatic pressing device according to the application;

[0028] Figure 5 is a partial structure schematic view of a correcting member in a battery top cover automatic pressing device according to the application;

[0029] Figure 6 is a perspective view of a pressing mechanism in a battery top cover automatic pressing device according to the application;

[0030] Figure 7 is a position schematic view of a telescopic cylinder, a correcting assembly and a battery cup in a battery top cover automatic pressing device according to the application;

[0031] Figure 8is a perspective view of a battery top cover automatic pressing device in the application;

[0032] Figures 9-11 respectively are schematic diagrams of a battery top cover pressing process in an embodiment of a battery top cover automatic pressing device of the application.

[0033] Reference signs:

[0034] 10, workbench;

[0035] 20, turntable device; 21, shell; 22, motor; 23, turntable; 23A, connecting hole; 24, limiting groove;

[0036] 30, flattening device; 31, support rod; 32, flattening assembly; 321, connecting rod; 322, flattening roller; 3221, roller body; 3222, flexible protective layer;

[0037] 40, pressing and correcting device; 41, cylindrical support; 42, base; 43, correcting mechanism; 431, clamping jaw cylinder; 432, correcting assembly; 4321, correcting piece; 43211, connecting part; 43212, correcting part; 43212A, arc-shaped correcting groove; 44, pressing mechanism; 441, telescopic cylinder; 442, connecting head; 4421, pressing plate;

[0038] 50, pressing plate storage device; 51, rotating shaft; 52, extension rod assembly; 521, extension rod; 53, storage assembly; 531, storage rack; 531A, annular bottom support;

[0039] 60, battery cup; 61, battery cover. DETAILED DESCRIPTION

[0040] The specific embodiments of the application will be described below in conjunction with the drawings and examples, and through the content recorded in the description, those skilled in the art can clearly and completely understand the technical solutions of the application, the technical problems solved, and the technical effects produced. It can be understood that the specific embodiments described herein are only used to explain the application, but not to limit the application. In addition, in order to facilitate the description, only the parts related to the application are shown in the drawings.

[0041] It should be noted that the structures, proportions, sizes, etc. shown in the drawings of the specification are only used to cooperate with the content recorded in the specification, so that those skilled in the art can understand and read, and do not have technical substantial significance, any modification of the structure, change of the proportion relationship or adjustment of the size, without affecting the effects and purposes that the application can produce, should fall within the scope of the technical content disclosed by the application.

[0042] The terms "first", "second", "the", "this", and similar terms, as used herein, do not denote any quantity limitation, but rather distinguish one entity from another. The terms "comprises", "comprising", "includes", "including", "has", "having", and the like, as used herein, are specifically intended to be open-ended and to mean including, but not limited to. The terms "connected", "coupled", or the like, unless otherwise contradicted, are not limited to physical or mechanical connections or couplings, but can include electrical connection or couplings.

[0043] It should be further noted that the embodiments of the present application correspond to the longitudinal section in the corresponding front view direction, the transverse section in the corresponding right view direction, and the horizontal section in the corresponding top view direction.

[0044] In addition, the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0045] Reference Figure 1 , Figure 1 is a perspective view of a battery top cover automatic pressing device. As shown in Figure 1 , a battery top cover automatic pressing device includes a workbench 10, a turntable device 20 arranged on the workbench 10, a flattening device 30 and a pressing and correcting device 40, and a pressing plate storage device 50 connected to the pressing and correcting device 40.

[0046] Continuing to refer to Figure 1 , and referring to Figure 2 , Figure 2 is a schematic view of a turntable device in a battery top cover automatic pressing device. As shown in Figure 1 and Figure 2 , the turntable device 20 includes a housing 21, a motor 22 arranged inside the housing 21, and a turntable 23 fixed to the motor 22. The motor 22 is fixed inside the housing 21 and penetrates the housing 21. The side wall of the turntable 23 is provided with a limiting groove 24. The turntable 23 is further provided with a connecting hole 23A. The connecting hole 23A arranged on the turntable 23 corresponds to the connecting hole 23A of the connecting end of the motor 22. Specifically, the connecting hole 23A of the connecting end of the motor 22 and the connecting hole 23A on the turntable 23 are sequentially penetrated by bolts, and the bolts and nuts are cooperated with each other to realize the fixed connection between the motor 22 and the turntable 23, so that the motor 22 drives the turntable 23 to rotate synchronously. Further, the limiting groove 24 is in the shape of a U.

[0047] Continuing to refer to Figure 1, refer to Figure 3 and Figure 4 , Figure 3 is a schematic view of a flattening device in a battery top cover automatic pressing device, Figure 4 is a sectional structure schematic view of a roller body and a flexible protective layer in a battery top cover automatic pressing device. As shown in Figure 1 , Figure 3 and Figure 4 , the flattening device 30 comprises a support rod 31 and a flattening assembly 32 connected to the support rod 31, and an included angle α is formed between the support rod 31 and the flattening assembly 32, 70° < α < 90°, the flattening assembly 32 comprises a connecting rod 321 and a flattening roller 322 rollingly connected to the connecting rod 321, one end of the connecting rod 321 is connected to the support rod 31, and the other end is connected to the flattening roller 322, specifically, a bearing (not shown in the figure) is embedded on one end of the flattening roller 322 connected to the connecting rod 321, and the end of the connecting rod 321 connected to the flattening roller 322 is sleeved in the bearing to realize the rolling connection of the flattening roller 322 and the connecting rod 321, the flattening roller 322 comprises a roller body 3221 and a flexible protective layer 3222 arranged on the outer side wall of the roller body 3221, here, the flattening roller 322 is rollingly connected to the connecting rod 321, and the flexible protective layer 3222 is arranged on the outer side wall of the roller body 3221 of the flattening roller 322, so as to avoid rigid collision on the battery cover 61 during the flattening process of the flattening roller 322 on the battery cover 61, thereby avoiding damage to the battery cover 61 and effectively improving the qualified rate in the battery production process.

[0048] continue to refer to Figure 1 , refer to Figure 5 , Figure 5 is a partial structure schematic view of a deviation correcting member in a battery top cover automatic pressing device. As shown in Figure 1 and Figure 5 , the pressing deviation correcting device 40 comprises a cylindrical support 41, a base 42 connected to the cylindrical support 41, a deviation correcting mechanism 43 fixed to the base 42, and a pressing mechanism 44 fixed to the top of the deviation correcting mechanism 43; the deviation correcting mechanism 43 comprises a clamping jaw air cylinder 431 and a deviation correcting assembly 432 connected to the clamping jaw air cylinder 431, the deviation correcting assembly 432 comprises at least two deviation correcting members 4321, and the two deviation correcting members 4321 cooperate to simultaneously form a ring around the battery cover 61 and the battery cup 60, thereby correcting the deviation of the battery cover 61, the deviation correcting member 4321 comprises a connecting part 43211 and a deviation correcting part 43212, one side of the deviation correcting part 43212 is provided with an arc-shaped deviation correcting groove 43212A, the arc of the arc-shaped deviation correcting groove 43212A is β, 30° < β < 70°, so as to facilitate the mutual cooperation of the two deviation correcting members 4321, and the ring around the battery cup 60 and the battery cover 61 is more complete, avoiding the situation that one side does not contact the inner side wall of the arc-shaped deviation correcting groove 43212A.

[0049] With reference to the drawings Figure 1 With reference to the drawings Figure 6 And Figure 7 , Figure 6 is a perspective view of a pressing mechanism in a battery top cover automatic pressing device according to the present application, Figure 7 is a position schematic view of a telescopic cylinder, a deviation rectifying assembly and a battery cup in a battery top cover automatic pressing device according to the present application. As shown in Figure 1 , Figure 6 and Figure 7 , the pressing mechanism 44 comprises a telescopic cylinder 441 and a connecting head 442 connected to the telescopic cylinder 441, further, the telescopic cylinder 441 is connected to the top of the clamping jaw cylinder 431, and the end of the telescopic end of the telescopic cylinder 441 is connected with the connecting head 442, the connecting head 442 is connected with the pressing plate 4421, the connection mode between the connecting head 442 and the pressing plate 4421 comprises but is not limited to magnetic attraction type connection, embedded bolt type connection and the like, in addition, the center of the telescopic cylinder 441, the deviation rectifying part 43212 on the two deviation rectifying parts 4321 in the deviation rectifying assembly 432, the center of the combined arc-shaped deviation rectifying groove 43212A after the combination, and the center of the cross section of the battery cup 60 are located on the same vertical line, so as to realize that during the whole working process of the pressing plate 4421 for pressing the battery cover 61, the work efficiency and accuracy are improved when the corrected battery cup 60 and the battery cover 61 are pressed by the pressing plate 4421 driven by the telescopic cylinder 441, thereby reducing the qualified rate.

[0050] With reference to the drawings Figure 1 With reference to the drawings Figure 8 , Figure 8 is a perspective view of a pressing plate storage device in a battery top cover automatic pressing device according to the present application. As shown in Figure 1 and Figure 8 , the pressing plate storage device 50 comprises a rotating shaft 51, at least one set of extension rod assembly 52 connected to the outer side wall of the rotating shaft 51, and a storage assembly 53 connected to the extension rod assembly 52, the rotating shaft 51 is sleeved on the cylindrical support 41, the extension rod assembly 52 comprises at least six extension rods 521, the six extension rods 521 are uniformly distributed on the outer side wall of the rotating shaft 51, the storage assembly 53 comprises at least six storage racks 531, the number of the storage racks 531 in the storage assembly 53 corresponds to the number of the extension rods 521 in the extension rod assembly 52, the shapes and sizes of the storage racks 531 in the storage assembly 53 are different, so as to adapt to the pressing of the battery cover 61 with different shapes and sizes, further, the inside of the storage rack 531 is also provided with an annular bottom support 531A, so as to lift the pressing plate 4421 and realize storage, thereby being able to adapt to the pressing of the battery top cover and the battery cup 60 with different sizes and shapes, and improve the convenience of use and the adaptability of the device.

[0051] Here, the turntable device 20, the flattening device 30, the pressing and correcting device 40 and the pressing plate storage device 50 arranged on the workbench 10, the motor 22 is fixed in the inside of the shell 21 of the turntable device 20, and penetrates the shell 21, the motor 22 is fixed with the turntable 23, the side wall of the turntable 23 is provided with the limiting groove 24, the turntable 23 is further provided with the connecting hole 23A, the motor 22 drives the turntable 23 to rotate synchronously; the support rod 31 of the flattening device 30 is connected with the flattening assembly 32, the flattening assembly 32 includes the connecting rod 321, the connecting rod 321 is rollingly connected with the flattening roller 322; the pressing and correcting device 40 has the cylindrical support 41, the base 42, the correcting mechanism 43 and the pressing mechanism 44, the correcting mechanism 43 includes the jaw cylinder 431 and the correcting assembly 432, the two correcting pieces 4321 in the correcting assembly 432 cooperate, the telescopic cylinder 441 in the pressing mechanism 44 is connected to the top of the jaw cylinder 431, and the connecting head 442 is connected with the pressing plate 4421, which realizes the process of pressing the battery top cover during the production of the battery, reduces the labor cost, and improves the production efficiency and the production qualified rate.

[0052] Reference Figures 9-11 , Figures 9-11 Respectively, an embodiment of the battery top cover automatic pressing device is a schematic diagram of the battery top cover pressing process.

[0053] Reference Figure 9 , the battery cup 60 and the battery cover 61 are provided, after the battery cover 61 is positioned by the preliminary welding process, the positional relationship between the battery cover 61 and the battery cup 60, the battery cover 61 is welded upright on the top of the battery cup 60, and the electrode protrusion of the battery cover 61 faces the inside.

[0054] Reference Figure 10 , the battery cover 61 is flattened by the flattening device 30, at this time, the electrode protrusion of the battery cover 61 faces the outside.

[0055] Reference Figure 11 , the position of the battery cover 61 is corrected and pressed by the pressing and correcting device 40.

[0056] For the convenience of understanding, the working principle of the present application is further described as follows: during the working process of the battery top cover automatic pressing device, the battery cup 60 and the battery cover 61 which have completed preliminary welding positioning are sent to the limiting groove 24 through the external feeding device, and after the material is sensed by the external inductor, a signal is sent to the external automatic control switch to make the rotating disc device 20 rotate. During the rotating process, the battery cover 61 which has completed preliminary welding positioning is flattened by the flattening device 30, and until the battery cup 60 and the battery cover 61 are brought to the position directly below the pressing and correcting device 40 under the action of the rotating disc device 20, and after the material is sensed by the external inductor, a signal is sent to the external automatic control switch, the correcting mechanism 43 simultaneously embraces the battery cover 61 and the battery cup 60 to correct the battery cover 61, and after correction, the battery cover 61 is reset, and a signal is again sent to the external automatic control switch to make the pressing mechanism 44 press the battery cover 61, that is, the pressing of the battery top cover is completed.

[0057] In addition, during use, the storage assembly 53 is rotated by dialing the storage rack 531, so that the appropriate pressing plate 4421 required is selected to be installed on the connecting head 442, which further improves the convenience and reliability of the equipment in use, and avoids the problem that the pressing plate 4421 cannot be quickly replaced according to the specifications of the battery cover 61 and the battery cup 60 during the working process.

[0058] Although the present application has been described and illustrated with reference to specific embodiments thereof, these descriptions and illustrations are not limiting. As one of ordinary skill in the art will readily appreciate, various changes, modifications, and substitutions can be made without departing from the true spirit and scope of the application as defined by the appended claims. The drawings can not be to scale. There can be differences between the technology as actually produced and the technology as described in the specification. Other embodiments of the application not specifically described can be apparent to one of ordinary skill in the art. The specification and drawings should be considered as illustrative only, and not restrictive. Modifications can be made to adapt a particular situation, material, composition of matter, method, or process to the objective, spirit, and scope of the application. All such modifications are intended to be within the scope of the claims appended hereto. Although methods disclosed herein have been described with reference to particular sequences for performing certain operations, it will be readily appreciated that these operations can be combined, subdivided, or reordered to form an equivalent method, without departing from the teachings of the present application. Accordingly, unless specifically indicated herein, the order and grouping of operations are not limitations of the application.

Claims

1. An automatic pressing device for a battery top cover, characterized in that, The utility model relates to a battery cover and battery cup body synchronous pressing device which comprises a workbench (10); A turntable device (20) is arranged on the workbench (10), the turntable device (20) comprises a shell (21), a motor (22) arranged inside the shell (21) and a turntable (23) fixed to the motor (22), the motor (22) is fixed to the inside of the shell (21) and penetrates the shell (21), a limiting groove (24) is arranged on the side wall of the turntable (23), a connecting hole (23A) is further arranged on the turntable (23), and the motor (22) drives the turntable (23) to rotate synchronously; A flattening device (30) comprises a supporting rod (31) and a flattening assembly (32) connected to the supporting rod (31), the flattening assembly (32) comprises a connecting rod (321) and a flattening roller (322) rotatably connected to the connecting rod (321), one end of the connecting rod (321) is connected to the supporting rod (31), and the other end of the connecting rod (321) is connected to the flattening roller (322); A pressing deviation rectifying device (40) comprises a cylindrical support (41), a base (42) connected to the cylindrical support (41), a deviation rectifying mechanism (43) fixed to the base (42) and a pressing mechanism (44) fixed to the top of the deviation rectifying mechanism (43), the deviation rectifying mechanism (43) comprises a clamping jaw air cylinder (431) and a deviation rectifying assembly (432) connected to the clamping jaw air cylinder (431), the deviation rectifying assembly (432) comprises at least two deviation rectifying pieces (4321), the two deviation rectifying pieces (4321) are matched to simultaneously form an embrace for the battery cover and the battery cup body, the pressing mechanism (44) comprises a telescopic air cylinder (441) and a connecting head (442) connected to the telescopic air cylinder (441), the telescopic air cylinder (441) is connected to the top of the clamping jaw air cylinder (431), the telescopic end of the telescopic air cylinder (441) is connected with the connecting head (442), and the connecting head (442) is connected with a pressing plate (4421); A pressing plate storage device (50) is connected to the pressing deviation rectifying device (40). An included angle alpha is formed between the supporting rod (31) and the flattening assembly (32), and 70° < alpha < 90°.

2. The battery top cover automatic pressing device according to claim 1, wherein The flattening roller (322) comprises a roller body (3221) and a flexible protective layer (3222) arranged on the outer side wall of the roller body (3221).

3. The battery top cover automatic pressing device according to claim 2, characterized in that, The deviation rectifying piece (4321) comprises a connecting portion (43211) and a deviation rectifying portion (43212).

4. The battery top cover automatic pressing device according to claim 2, characterized in that, One side of the deviation rectifying portion (43212) is provided with an arc-shaped deviation rectifying groove (43212A), and the arc of the arc-shaped deviation rectifying groove (43212A) is beta, and 30° < beta < 70°.

5. The battery top cover automatic pressing device according to claim 4, wherein The pressing plate storage device (50) comprises a rotating shaft (51), at least one group of extension rod assemblies (52) connected to the outer side wall of the rotating shaft (51) and a storage assembly (53) connected to the extension rod assemblies (52).

6. The battery top cover automatic press bonding device according to claim 1, wherein ​ 7. The battery top cover automatic pressing device according to claim 6, wherein, The set of extension rod assemblies (52) comprises at least six extension rods (521), which are evenly and uniformly distributed on the outer sidewall of the rotating shaft (51).

8. The battery top cover automatic pressing device according to claim 7, wherein, The receiving assembly (53) comprises at least six receiving racks (531), the number of the receiving racks (531) in the receiving assembly (53) corresponding to the number of the extension rods (521) in the extension rod assembly (52).

9. The battery top cover automatic pressing device according to claim 8, wherein, The inside of the receiving rack (531) is further provided with an annular bottom support (531A).

10. The battery top cover automatic press bonding device according to claim 1, wherein, The shape of the limiting groove (24) is U-shaped.

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