Foot structure and mechanical leg

Abstract

The application relates to the technical field of robots, and particularly discloses a foot structure and a mechanical leg, which comprises a heel piece, a connecting rod, a sole piece and a first driving mechanism; one end of the heel piece is provided with a first rotating shaft, the connecting rod is rotationally arranged on the first rotating shaft, one end of the connecting rod away from the first rotating shaft is provided with a second rotating shaft, and the sole piece is rotationally arranged on the second rotating shaft; the first driving mechanism comprises a bearing frame, a first driving motor and a driving line, the bearing frame is arranged on the heel piece, the first driving motor is arranged on the bearing frame, and the two ends of the driving line are respectively connected with a driving end of the first driving motor and the sole piece. In the application, the connecting rod and the sole piece can be turned in and out as a whole, the sole piece can be turned up and down, and then, after the relative positions of the heel piece and the sole piece are adjusted, the foot structure has sufficient adaptability and stability, and the foot structure can maintain balanced and stable walking.

Description

A foot structure and mechanical leg Technical Field

[0001] This invention relates to the field of robotics, and more particularly to a foot structure and a mechanical leg. Background Technology

[0002] A robot is an intelligent machine capable of semi-autonomous or fully autonomous operation, which can perform tasks such as work or movement through programming and automatic control. The applications of robots are becoming increasingly widespread, with various types of robots visible in fields such as electronics, medicine, semiconductors, metal processing, food processing, and packaging. In recent years, to enable robots to perform even more diverse tasks, many designers have focused on developing humanoid robots, aiming to give them limbs and thus simulate actual human movements.

[0003] In the development of modern robotics and exoskeleton devices, the design and performance of the lower limb structure are particularly important. In existing technologies, the ankle portion of robotic legs only has the functions of pitching and rolling, allowing the foot to move in the vertical plane. However, it fails to fully mimic the complex structure of the human foot. When moving on complex terrain, the existing structure cannot provide sufficient adaptability and stability, making it impossible for the robotic leg to maintain balance and walk stably. Summary of the Invention

[0004] The purpose of this invention is to provide a foot structure and a mechanical leg to solve the problem that existing structures cannot provide sufficient adaptability and stability when moving on complex terrain, making it impossible for mechanical legs to maintain balance and walk stably.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] On one hand, the present invention provides a foot structure, the foot structure comprising:

[0007] A heel piece, one end of which is provided with a first pivot, the first pivot extending along a first direction;

[0008] A connecting rod is rotatably mounted on the first rotating shaft; a second rotating shaft is provided at the end of the connecting rod away from the first rotating shaft, and the second rotating shaft extends along a second direction.

[0009] Foot component, the foot component is rotatably mounted on the second rotating shaft;

[0010] The first drive mechanism includes a support frame, a first drive motor, and a drive line. The support frame is mounted on the heel piece, the first drive motor is mounted on the support frame, and the two ends of the drive line are respectively connected to the drive end of the first drive motor and the foot piece. The first drive motor can drive the drive line to move, so that the drive line pulls the foot piece to rotate around the second rotating shaft. The second rotating shaft can drive the connecting rod to rotate around the first rotating shaft.

[0011] As an alternative to the aforementioned foot structure, the drive end of the first drive motor has a U-shaped drive wheel, the foot piece has a U-shaped fixed wheel, the U-shaped fixed wheel is rotatably mounted on the second shaft, and both ends of the drive line are fixed in the U-shaped groove of the U-shaped drive wheel and the U-shaped groove of the U-shaped fixed wheel; the drive line includes at least two, one end of the at least two drive lines is wound around the U-shaped drive wheel in opposite directions, and the other end of the at least two drive lines is wound around the U-shaped fixed wheel in opposite directions.

[0012] As an alternative to the aforementioned foot structure, the aforementioned first drive motor includes two, and the U-shaped drive wheels on the two aforementioned first drive motors are respectively located at both ends of the aforementioned support frame along the aforementioned second direction. The aforementioned U-shaped fixed wheels include two, and the two aforementioned U-shaped fixed wheels are respectively located at both ends of the aforementioned foot component along the aforementioned second direction. The two aforementioned U-shaped drive wheels correspond one-to-one with the two aforementioned U-shaped fixed wheels.

[0013] As an alternative to the aforementioned foot structure, the aforementioned support frame is provided with first guide wheels at both ends along the aforementioned second direction, the aforementioned heel is provided with second guide wheels at both ends along the aforementioned second direction, and the aforementioned drive line can be wound around the aforementioned first guide wheels and the aforementioned second guide wheels on the same side.

[0014] As an alternative to the aforementioned foot structure, the heel component is further provided with a third guide wheel, which is located between the second guide wheels on both sides of the heel component and is perpendicular to the second guide wheels; the drive lines on both sides of the second guide wheels are all wound around the third guide wheel.

[0015] On the other hand, the present invention provides a mechanical leg, including the foot structure as described above, and the mechanical leg further includes:

[0016] The leg support is provided with a third pivot, which extends along the second direction.

[0017] A connecting block is rotatably mounted on the third rotating shaft; the connecting block is provided with a fourth rotating shaft, which extends along the first direction, and the heel piece is rotatably mounted on the fourth rotating shaft.

[0018] The second drive mechanism is mounted on the leg support; the drive end of the second drive mechanism is connected to the heel member and is used to drive the heel member to rotate around the fourth pivot; the fourth pivot can drive the connecting block to rotate around the third pivot.

[0019] As an alternative to the aforementioned mechanical leg, the second drive mechanism includes a second drive motor, a first link, a second link, and a rotary joint. The second drive motor is mounted on the leg support. The drive end of the second drive motor, the first link, the second link, the rotary joint, and the heel are sequentially rotatably connected, and the second link extends vertically.

[0020] As an alternative to the aforementioned mechanical leg, the aforementioned second drive mechanism includes two, and the second links of the two aforementioned second drive mechanisms are respectively located at both ends of the aforementioned heel member along the aforementioned second direction.

[0021] As an alternative embodiment of the aforementioned robotic leg, the robotic leg further includes a stiffness adjustment mechanism, which comprises:

[0022] The third drive motor is mounted on the support frame.

[0023] A ball screw, wherein the ball screw is connected to the drive end of the third drive motor;

[0024] The slider is slidably disposed on the support frame in the vertical direction, and the slider is connected to the drive end of the ball screw;

[0025] An elastic sheet, one end of which is fixedly connected to the connecting block, and the other end of which is movably inserted through the slider along the vertical direction.

[0026] As an alternative to the aforementioned mechanical leg, the slider is provided with at least two rollers, the at least two rollers are arranged side by side along the second direction, and the elastic sheet rolls through the two rollers.

[0027] The beneficial effects of this invention are as follows:

[0028] The foot structure includes a heel component, a connecting rod, a foot component, and a first drive mechanism. A first pivot is located at one end of the heel component, extending along a first direction. The connecting rod is rotatably mounted on the first pivot. A second pivot is located at the end of the connecting rod furthest from the first pivot, extending along a second direction. The foot component is rotatably mounted on the second pivot. The first pivot allows the connecting rod and foot component to rotate inwards and outwards, while the second pivot allows the foot component to rotate upwards and downwards. By adjusting the relative positions of the heel and foot components, the foot structure achieves sufficient adaptability and stability, enabling it to maintain balance and stable walking. The first drive mechanism includes a support frame, a first drive motor, and a drive line. The support frame is mounted on the heel component, the first drive motor is mounted on the support frame, and the two ends of the drive line are respectively connected to the drive end of the first drive motor and the foot component. The first drive motor can drive the drive line to move, so that the drive line pulls the foot component to rotate around the second rotating shaft. At the same time, the second rotating shaft can drive the connecting rod to rotate around the first rotating shaft, thereby realizing the active adjustment of the relative position of the heel component and the foot component, thereby reducing the difficulty of adjusting the foot structure posture.

[0029] This embodiment also provides a mechanical leg, including the foot structure described above. The mechanical leg further includes a leg support, a connecting block, and a second drive mechanism. The third rotating shaft allows the connecting block and heel component to rotate vertically, and the fourth rotating shaft allows the heel component to rotate inwards and outwards. By adjusting the relative positions of the heel component and the leg support, and further adjusting the relative positions of the heel component and the foot component, the mechanical leg gains multiple degrees of freedom and high flexibility, enabling it to further mimic the complex movements of the human lower limbs. Attached Figure Description

[0030] Figure 1 is a schematic diagram of the foot structure provided in an embodiment of the present invention;

[0031] Figure 2 is a schematic diagram of the mechanical leg provided in an embodiment of the present invention;

[0032] Figure 3 is a partial structural schematic diagram of the mechanical leg provided in an embodiment of the present invention.

[0033] In the picture:

[0034] 1. Heel component; 11. First pivot; 12. Second guide wheel; 13. Third guide wheel; 2. Connecting rod; 21. Second pivot; 3. Foot component; 31. U-shaped fixed wheel; 4. First drive mechanism; 41. Support frame; 411. First guide wheel; 42. First drive motor; 421. U-shaped drive wheel; 5. Leg support; 51. Third pivot; 6. Connecting block; 61. Fourth pivot; 7. Second drive mechanism; 71. Second drive motor; 72. First connecting rod; 73. Second connecting rod; 74. Rotary joint; 8. Stiffness adjustment mechanism; 81. Third drive motor; 82. Ball screw; 83. Slider; 831. Roller; 84. Elastic sheet. Detailed Implementation

[0035] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. The terms "first position" and "second position" refer to two different positions. Furthermore, "above," "on top of," and "over" the first feature in relation to the second feature includes the first feature directly above and diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "under," and "below" the first feature in relation to the second feature includes the first feature directly below and diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0037] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0038] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0039] Example 1

[0040] This embodiment provides a foot structure for balanced and stable walking on complex terrain.

[0041] As shown in Figure 1, the foot structure includes a heel component 1, a connecting rod 2, a foot component 3, and a first drive mechanism 4. A first rotating shaft 11 is provided at one end of the heel component 1, extending along a first direction (i.e., the X direction in the figure). The connecting rod 2 is rotatably mounted on the first rotating shaft 11. A second rotating shaft 21 is provided at the end of the connecting rod 2 away from the first rotating shaft 11, extending along a second direction (i.e., the Y direction in the figure). The foot component 3 is rotatably mounted on the second rotating shaft 21. Thus, the first rotating shaft 11 allows the connecting rod 2 and the foot component 3 to rotate inwards and outwards as a whole, while the second rotating shaft 21 allows the foot component 3 to rotate up and down. By adjusting the relative positions of the heel component 1 and the foot component 3, the foot structure achieves sufficient adaptability and stability, enabling it to maintain balance and stable walking. The first and second directions are perpendicular to each other.

[0042] The first drive mechanism 4 includes a support frame 41, a first drive motor 42, and a drive line. The support frame 41 is mounted on the heel piece 1, and the first drive motor 42 is mounted on the support frame 41. The two ends of the drive line are respectively connected to the drive end of the first drive motor 42 and the foot piece 3. The first drive motor 42 can drive the drive line to move so that the drive line pulls the foot piece 3 to rotate around the second rotating shaft 21. At the same time, the second rotating shaft 21 can drive the connecting rod 2 to rotate around the first rotating shaft 11, thereby realizing the active adjustment of the relative position of the heel piece 1 and the foot piece 3, thereby reducing the difficulty of adjusting the posture of the foot structure.

[0043] Furthermore, the drive end of the first drive motor 42 has a U-shaped drive wheel 421, and the foot piece 3 has a U-shaped fixed wheel 31. The U-shaped fixed wheel 31 is rotatably mounted on the second rotating shaft 21. Both ends of the drive line are fixed in the U-shaped groove of the U-shaped drive wheel 421 and the U-shaped groove of the U-shaped fixed wheel 31. Thus, when the U-shaped drive wheel 421 rotates under the drive of the first drive motor 42, the drive line will be wound circumferentially in the U-shaped groove of the U-shaped drive wheel 421. Then, the other end of the drive line will pull the U-shaped fixed wheel 31, thereby realizing the flipping of the foot piece 3 relative to the connecting rod 2, and the flipping of the foot piece 3 and the connecting rod 2 as a whole relative to the heel piece 1. The fact that both ends of the drive line are fixed in the U-shaped groove of the U-shaped drive wheel 421 and the U-shaped groove of the U-shaped fixed wheel 31 can prevent the drive line from detaching from the U-shaped drive wheel 421 or the U-shaped fixed wheel 31 after movement.

[0044] Specifically, the drive lines include at least two, with one end of each drive line wound in opposite directions around a U-shaped drive wheel 421, and the other end of each drive line wound in opposite directions around a U-shaped fixed wheel 31. This allows the foot component 3 to flip relative to the connecting rod 2 on both sides after the direction of the U-shaped drive wheel 42 driven by the first drive motor 42 is adjusted. Simultaneously, the first drive motor 42 includes two motors, with the U-shaped drive wheels 421 on each motor located at both ends of the support frame 41 along the second direction. The U-shaped fixed wheels 31 also include two motors, located at both ends of the foot component 3 along the second direction, with each U-shaped drive wheel 421 corresponding to one of the two U-shaped fixed wheels 31. This allows the foot component 3 and the connecting rod 2 to be adjusted relative to the heel component 1 on both sides by pulling the two U-shaped fixed wheels 31 on both sides of the foot structure using a differential line drive method.

[0045] Furthermore, the support frame 41 is provided with first guide wheels 411 at both ends along the second direction, and the heel piece 1 is provided with second guide wheels 12 at both ends along the second direction. The drive line can be wound around the first guide wheel 411 and the second guide wheel 12 on the same side, thereby adjusting the winding position and direction of the drive line through the first guide wheel 411 and the second guide wheel 12, thus simulating the muscle and nerve activity of the human foot and improving the flexibility of the foot structure. The heel piece 1 is also provided with a third guide wheel 13, which is located between the second guide wheels 12 on both sides of the heel piece 1 and is perpendicular to the second guide wheels 12. The drive lines on both sides of the second guide wheels 12 are wound around the third guide wheel 13. Thus, by providing the third guide wheel 13, the winding position and direction of the drive line can be further adjusted, and the drive line can be easily pulled out, making the structure more compact and better adaptable to the design of the foot structure.

[0046] Example 2

[0047] This embodiment also provides a mechanical leg, including the foot structure as in Embodiment 1. As shown in Figures 1-3, the mechanical leg further includes a leg support 5, a connecting block 6, and a second drive mechanism 7. The leg support 5 is provided with a third rotating shaft 51, which extends along a second direction. The connecting block 6 is rotatably mounted on the third rotating shaft 51. The connecting block 6 is provided with a fourth rotating shaft 61, which extends along a first direction. The heel component 1 is rotatably mounted on the fourth rotating shaft 61. Thus, the third rotating shaft 51 allows the connecting block 6 and the heel component 1 to rotate up and down as a whole. The fourth rotating shaft 61 allows the heel component 1 to rotate inward and outward. After adjusting the relative position of the heel component 1 and the leg support 5, and further adjusting the relative position of the heel component 1 and the foot component 3, the mechanical leg has multiple degrees of freedom and high flexibility, enabling it to further mimic the complex movements of the human lower limbs.

[0048] The second drive mechanism 7 is mounted on the leg support 5. The drive end of the second drive mechanism 7 is connected to the heel piece 1 and is used to drive the heel piece 1 to rotate around the fourth rotating shaft 61. At the same time, the fourth rotating shaft 61 can drive the connecting block 6 to rotate around the third rotating shaft 51, thereby realizing the active adjustment of the relative position of the heel piece 1 and the leg support 5, thereby reducing the difficulty of adjusting the posture of the mechanical leg.

[0049] Furthermore, the second drive mechanism 7 includes a second drive motor 71, a first connecting rod 72, a second connecting rod 73, and a rotary joint 74. The second drive motor 71 is mounted on the leg support 5. The drive end of the second drive motor 71, the first connecting rod 72, the second connecting rod 73, the rotary joint 74, and the heel piece 1 are sequentially rotatably connected. The second connecting rod 73 extends vertically (i.e., the Z direction in the attached figure), so that the second drive motor 71 can drive the first connecting rod 72 to lift up or down or push the second connecting rod 73. Under the transmission of the rotary joint 74, the second connecting rod 73 enables the heel piece 1 to flip relative to the connecting block 6, and the heel piece 1 and the connecting block 6 as a whole to flip relative to the leg support 5. The first direction, the second direction, and the vertical direction are arranged perpendicular to each other. Specifically, the second drive mechanism 7 includes two, and the second connecting rods 73 of the two second drive mechanisms 7 are respectively located at both ends of the heel piece 1 along the second direction, so that the two second drive motors 71 can drive the two second connecting rods 73 respectively. When the two second connecting rods 73 move up or down simultaneously in the vertical direction, the heel piece 1 and the connecting block 6 as a whole can flip up and down relative to the leg support 5. When the two second connecting rods 73 move in opposite directions in the vertical direction, the heel piece 1 can flip up and down relative to the connecting block 6.

[0050] Furthermore, the mechanical leg also includes a stiffness adjustment mechanism 8, which comprises a third drive motor 81, a ball screw 82, a slider 83, and an elastic plate 84. The third drive motor 81 is mounted on the support frame 41, the ball screw 82 is connected to the drive end of the third drive motor 81, and the slider 83 is slidably mounted on the support frame 41 in the vertical direction and connected to the drive end of the ball screw 82. Thus, under the drive of the third drive motor 81, the slider 83 can move in the vertical direction. At the same time, one end of the elastic plate 84 is fixedly connected to the connecting block 6, and the other end of the elastic plate 84 is movably inserted through the slider 83 in the vertical direction. Thus, the length of the elastic plate 84 between the slider 83 and the connecting block 6 can be adjusted, thereby adjusting the bending stiffness of the elastic plate 84. This adjusts the ease with which the heel 1 can flip inward and outward relative to the connecting block 6, thereby meeting the actual usage requirements of the mechanical leg. Optionally, the slider 83 is provided with at least two rollers 831, which are arranged side by side along the second direction. The elastic sheet 84 is rolled between the two rollers 831. By rolling, the difficulty of moving the slider 83 relative to the elastic sheet 84 can be reduced, and jamming between the slider 83 and the elastic sheet 84 can be avoided.

[0051] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A foot structure, characterized in that, include: Heel component (1), one end of which is provided with a first rotating shaft (11), the first rotating shaft (11) extending along a first direction; connecting rod (2), the connecting rod (2) rotatably mounted on the first rotating shaft (11); the end of the connecting rod (2) away from the first rotating shaft (11) is provided with a second rotating shaft (21), the second rotating shaft (21) extending along a second direction; foot component (3), the foot component (3) rotatably mounted on the second rotating shaft (21); first drive mechanism (4), the first drive mechanism (4) includes a support frame (41), a first drive motor (42) and a drive line; the support frame (41) is mounted on the heel component (1), the first drive motor (42) is mounted on the support frame (41), and the two ends of the drive line are respectively connected to the drive end of the first drive motor (42) and the foot component (3). The first drive motor (42) can drive the drive line to move so that the drive line pulls the foot piece (3) to rotate around the second rotating shaft (21); the second rotating shaft (21) can drive the connecting rod (2) to rotate around the first rotating shaft (11); the drive end of the first drive motor (42) has a U-shaped drive wheel (421), the foot piece (3) has a U-shaped fixed wheel (31), the U-shaped fixed wheel (31) is rotatably mounted on the second rotating shaft (21), and the two ends of the drive line are fixed in the U-shaped groove of the U-shaped drive wheel (421) and the U-shaped fixed wheel (31); the drive line includes at least two, one end of at least two drive lines is wound around the U-shaped drive wheel (421) in opposite directions, and the other end of at least two drive lines is wound around the U-shaped fixed wheel (31) in opposite directions.

2. The foot structure according to claim 1, characterized in that, The first drive motor (42) includes two, and the U-shaped drive wheels (421) on the two first drive motors (42) are respectively located at both ends of the support frame (41) along the second direction. The U-shaped fixed wheels (31) include two, and the two U-shaped fixed wheels (31) are respectively located at both ends of the foot piece (3) along the second direction. The two U-shaped drive wheels (421) correspond one-to-one with the two U-shaped fixed wheels (31).

3. The foot structure according to claim 2, characterized in that, The support frame (41) is provided with first guide wheels (411) at both ends along the second direction, and the heel piece (1) is provided with second guide wheels (12) at both ends along the second direction. The drive line can be wound around the first guide wheel (411) and the second guide wheel (12) on the same side.

4. The foot structure according to claim 3, characterized in that, The heel piece (1) is also provided with a third guide wheel (13), which is located between the second guide wheels (12) on both sides of the heel piece (1) and is perpendicular to the second guide wheels (12); the drive lines on the second guide wheels (12) on both sides are all wound around the third guide wheel (13).

5. A mechanical leg, characterized in that, Including the foot structure as described in any one of claims 1 to 4, the mechanical leg further includes: a leg support (5), the leg support (5) having a third rotating shaft (51) extending along the second direction; a connecting block (6), the connecting block (6) rotatably mounted on the third rotating shaft (51); the connecting block (6) having a fourth rotating shaft (61), the fourth rotating shaft (61) extending along the first direction, the heel member (1) rotatably mounted on the fourth rotating shaft (61); a second driving mechanism (7), the second driving mechanism (7) being mounted on the leg support (5); the driving end of the second driving mechanism (7) being connected to the heel member (1) for driving the heel member (1) to rotate around the fourth rotating shaft (61); the fourth rotating shaft (61) being able to drive the connecting block (6) to rotate around the third rotating shaft (51).

6. The mechanical leg according to claim 5, characterized in that, The second drive mechanism (7) includes a second drive motor (71), a first connecting rod (72), a second connecting rod (73), and a rotary joint (74). The second drive motor (71) is mounted on the leg support (5). The drive end of the second drive motor (71), the first connecting rod (72), the second connecting rod (73), the rotary joint (74), and the heel piece (1) are rotatably connected in sequence, and the second connecting rod (73) extends vertically.

7. The mechanical leg according to claim 6, characterized in that, The second drive mechanism (7) includes two, and the second connecting rods (73) of the two second drive mechanisms (7) are respectively located at both ends of the heel member (1) along the second direction.

8. The mechanical leg according to claim 5, characterized in that, The mechanical leg also includes a stiffness adjustment mechanism (8), which includes: a third drive motor (81) mounted on the support frame (41); a ball screw (82) connected to the drive end of the third drive motor (81); a slider (83) slidably mounted on the support frame (41) in the vertical direction and connected to the drive end of the ball screw (82); and an elastic sheet (84), one end of which is fixedly connected to the connecting block (6) and the other end of which is movably mounted through the slider (83) in the vertical direction.

9. The mechanical leg according to claim 8, characterized in that, The slider (83) is provided with at least two rollers (831), which are arranged side by side along the second direction, and the elastic sheet (84) rolls through the two rollers (831).

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