Steel bar positioning device

Abstract

The utility model discloses a reinforcing steel bar positioning device, which belongs to the field of building manufacturing, and comprises a reinforcing steel bar matching piece which is of a plate-shaped structure and comprises a plurality of longitudinally arranged clamping parts, the clamping parts are provided with clamping holes, and notches are formed in the clamping holes, so that reinforcing steel bars are clamped into the clamping holes from the notches; the mold matching part is located at one end, in the longitudinal direction, of the steel bar matching part and comprises a first supporting arm and a second supporting arm, an included angle a is formed between the first supporting arm and the second supporting arm, and the included angle a ranges from 85 degrees to 95 degrees so that the mold matching part can be clamped into an external corner of a stair mold forming face. According to the steel bar positioning device, the shape structure of a stair mold is fully utilized, the mold matching piece with the splayed bottom is clamped with the stair mold, and the steel bar positioning device is combined with the external corner of the forming surface of the stair mold to limit steel bars, so that the movement range of the steel bars is effectively limited, and a steel bar layer does not slip as far as possible under various disturbances; and the protection layer is controlled accurately.

Description

Technical Field

[0001] The utility model relates to the field of construction, and more specifically, to a steel bar positioning device. Background Art

[0002] During the production process of staircase components, during construction, the staircase can be constructed with a horizontal mold or a vertical mold. For the matching protective layer control technology, plastic stirrups, concrete stirrups, plastic pads, etc. are generally used. The height supported by the stirrups is used to determine the position of the steel bars, and then the self-weight of the steel bars is used to press the stirrups to prevent the stirrups from displacing or falling off. The steel bars are placed on the stirrups or pads to lift the steel bars, without reliable restraint for limiting, resulting in ineffective control of the protective layer and ultimately unqualified inspection.

[0003] For example, the Chinese patent document (Publication No.: CN 219471541 U) provides a detachable steel pipe support stirrup structure for staircases, including a fixed support column, a threaded sleeve, a threaded support rod, a bottom platform, and a bottom plate. The bottom plate is arranged on the upper side of the lower mold, a bottom platform is arranged on the upper side of the bottom plate, a threaded support rod is arranged on the upper side of the bottom platform, a threaded sleeve is sleeved on the circumferential side of the threaded support rod, and a support sleeve is arranged on the upper side of the threaded sleeve. In the utility model, the threaded sleeve can be rotatably connected with the threaded support rod, and then the fixed support column can be driven to move up and down by the rotation of the threaded sleeve, so that the height of the fixed support rod can be adjusted, facilitating the adjustment of the overall height of the stirrup assembly, and capable of supporting staircase steel bar skeletons with different thickness requirements. By arranging the first transverse support rod, the first longitudinal support rod, the second transverse support rod, and the second longitudinal support rod, the upper layer steel bar mesh and the lower layer steel bar mesh can be limited and fixed.

[0004] Although the above device has a certain degree of flexibility, essentially it does not have an effective limiting function. Due to the complexity of the construction environment, various disturbances may occur, and it is extremely easy to produce deviation, resulting in the displacement of the steel bars and the failure of the protective layer control.

[0005] In view of the above problems, the related technology does not provide an effective solution. Summary of the Utility Model

[0006] In order to solve the problems that may exist in the related technology, some embodiments of the present application provide a steel bar positioning device, including: a steel bar fitting, having a plate-like structure and including a plurality of longitudinally arranged clamping parts. The clamping parts have clamping holes, and a notch is formed on the side wall of the clamping parts, so that the steel bar can be clamped into the clamping hole from the notch; a mold fitting, located at one end of the steel bar fitting in the longitudinal direction, including a first support arm and a second support arm. An included angle a is formed between the first support arm and the second support arm, and the included angle a is 75° to 95°, so as to be clamped into the external corner of the forming surface of the staircase mold.

[0007] Furthermore, a restraining rod is provided in the middle of the inner wall of the clamping hole, and the restraining rod extends transversely to the notch to divide the inner space of the clamping hole into two parts.

[0008] Furthermore, the constraint rod is arranged with a plurality of positioning protrusions on two opposite side surfaces in the longitudinal direction; the positioning protrusion comprises a blocking surface and a guiding surface for contacting the surface of the steel bar; the blocking surface is located on the side of the positioning protrusion away from the notch, and the guiding surface is opposite to the blocking surface; the angle between the guiding surface and the cross-section of the constraint rod is less than 30°, and is inclined toward the inner side of the clamping hole; the blocking surface is perpendicular to the cross-section of the constraint rod.

[0009] Furthermore, the guiding surface and the blocking surface are connected via a connecting surface, the connecting surface is parallel to the cross section of the restraining rod, and the positioning protrusion is in a prism shape.

[0010] Furthermore, both ends of the notch are respectively connected to guide arms, and the guide arms extend toward the outside of the clamping hole; and the outer end of the restraint rod protrudes from the outer end of the guide arm.

[0011] Furthermore, the guide arm comprises a guide surface facing the constraint rod; the guide arm opens outward, and an angle between the guide surface and a cross section of the constraint rod is 3° to 10°.

[0012] Furthermore, an anti-slip portion protruding from the inner wall of the clamping hole is formed at one end of the guide arm close to the clamping hole, the anti-slip portion is in the shape of a quadrangular pyramid, and a surface of the anti-slip portion facing the restraining rod is a part of the guide surface.

[0013] Furthermore, it also includes a movable gap, which extends from the outer side of the notch to the circumference of the clamping hole and covers more than half of the circumference of the clamping hole.

[0014] Furthermore, a reinforcing rod is connected between two side walls of the movable gap that are opposite to each other in the longitudinal direction.

[0015] Furthermore, the inner wall of the clamping hole is formed with a plurality of anti-slip portions protruding upward along the circumferential direction; the anti-slip portions are regular quadrangular pyramid structures and extend along the axial direction of the clamping hole; and the ratio of the top surface area to the bottom surface area of ​​the anti-slip portions is less than 1:5.

[0016] Further, it includes a mold fitting. The mold fitting has a V-shaped clamping interface, the clamping interface faces the longitudinal direction, an included angle a is formed in the clamping interface, and the included angle a is 75° to 95°. The clamping interface is used to attach to the outer corner of the forming surface of the staircase mold; one side of the mold fitting is connected with a plate-shaped steel bar fitting. A notch is formed on the side of the steel bar fitting, the notch faces the transverse direction, and a clamping hole is connected to the inner side of the notch. The radial cross-section of the clamping hole is parallel to the longitudinal direction and is used to accommodate the steel bar.

[0017] Further, the angle bisector of the included angle a is not parallel to the radial cross-section of the clamping hole.

[0018] Further, a plurality of the notches arranged along the longitudinal direction are formed on the side of the steel bar fitting, and the clamping hole is connected to the inner side of each notch.

[0019] Further, the clamping interface is composed of a first support arm and a second support arm, and the first support arm and the second support arm are asymmetric.

[0020] Adopting the technical solution provided by the present utility model, compared with the prior art, it has the following beneficial effects:

[0021] The steel bar positioning device makes full use of the shape structure of the staircase mold, is clamped with the staircase mold through the "eight-shaped" mold fitting at the bottom, and the combination of the steel bar positioning device and the outer corner of the forming surface of the staircase mold limits the steel bar. The activity range of the steel bar is effectively restricted, so that the steel bar layer can also be as non-slip as possible in the face of various disturbances, and the protection layer control is accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The drawings constituting a part of this application are used to provide a further understanding of this application, making other features, purposes, and advantages of this application more obvious. The schematic embodiments and descriptions of the drawings of this application are used to explain this application and do not constitute an improper limitation to this application. In the drawings:

[0023] Figure 1 It is a schematic diagram of the overall structure of the steel bar positioning device according to an embodiment of this application;

[0024] Figure 2 It is a schematic diagram of the overall structure of the steel bar positioning device according to an embodiment of this application;

[0025] Figure 3 It is a schematic diagram of the overall structure of the steel bar positioning device according to an embodiment of this application;

[0026] Figure 4 It is a schematic diagram of the partial enlarged structure of the steel bar positioning device according to an embodiment of this application;

[0027] Figure 5 Schematic diagram of the partial enlarged structure of the steel bar positioning device according to an embodiment of the present application;

[0028] Label description:

[0029] 100, steel bar fitting;

[0030] 110, clamping part; 111, clamping hole; 111a, anti-slip part; 1111, notch; 112, restraint rod; 113, positioning protrusion; 1131, guiding surface; 1132, blocking surface; 1133, connecting surface; 114, guiding arm; 1141, guiding surface; 1142, anti-disengagement part; 115, moving gap; 1151, strengthening rod;

[0031] 200, mold fitting; 200a, clamping interface; 210, first support arm; 220, second support arm. Detailed implementation manners

[0032] In order to enable those skilled in the art to better understand the solutions of the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present application.

[0033] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and do not have to be used to describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances so as to describe the embodiments of the present application here.

[0034] In the present application, the orientation or positional relationship indicated by the terms "upper", "lower", "left", "right", "front", "rear", "top", "bottom", "inner", "outer", "middle", "vertical", "horizontal", "lateral", "longitudinal", etc. is based on the orientation or positional relationship shown in the accompanying drawings. These terms are mainly used to better describe the present application and its embodiments, and are not used to limit that the indicated device, element or component must have a specific orientation, or be constructed and operated in a specific orientation. And, in addition to being able to represent the orientation or positional relationship, some of the above terms may also be used to represent other meanings. For example, the term "upper" may also be used to represent a certain attachment relationship or connection relationship in some cases. For those of ordinary skill in the art, the specific meanings of these terms in the present application can be understood according to specific circumstances.

[0035] The present application provides a steel bar positioning device. Specifically, the steel bar positioning device can be used for precast stairs. During the manufacturing process of the precast stairs, a stair mold is required. The stair mold includes a forming surface, which is used to form the tread surface of the stairs and faces the steel bars. The mold has a protruding external corner on one side of the forming surface. It should be noted that the protruding external corner corresponds to the internal corner of the precast stair finished product.

[0036] As shown in Figure 1 , the steel bar positioning device includes a steel bar fitting 100 and a mold fitting 200. The mold fitting 200 is located at one end of the steel bar fitting 100 along the longitudinal direction. The steel bar positioning device is preferably made of plastic material, such as nylon with relatively high strength.

[0037] As a solution, as shown in Figure 1 、 2 , the steel bar fitting 100 has a plate-like structure and includes a number of longitudinally arranged clamping parts 110. The clamping parts 110 have clamping holes 111, and notches 1111 are formed on the side walls of the clamping parts 110, so that the steel bars can be clamped into the clamping holes 111 from the notches 1111, thereby restricting the relative positions of the steel bars in different layers. Optionally, the number of clamping parts 110 is 2, 3, 4, etc., and the number of clamping holes 111 corresponds to the number of clamping parts 110.

[0038] Among them, as shown in Figure 1 、 3 , the mold fitting 200 includes a first support arm 210 and a second support arm 220. An included angle a is formed between the first support arm 210 and the second support arm 220. Optionally, the included angle a is 75° to 95°, such as 76°, 79°, 82°, 88°, 89°, 90°, or 91°, etc., so as to be clamped into the external corner of the forming surface of the stair mold.

[0039] As other solutions, as shown in Figure 1 , the mold fitting 200 of the steel bar positioning device has a V-shaped clamping interface 200a. An included angle a is formed in the clamping interface 200a, and the included angle a is 75° to 95°. The clamping interface 200a is used to attach to the external corner of the forming surface of the stair mold. A plate-like steel bar fitting 100 is connected to one side of the mold fitting 200. Notches 1111 are formed on the side edges of the steel bar fitting 100. The notches 1111 face the transverse direction. Clamping holes 111 are connected to the inside of the notches 1111. The radial cross-section of the clamping holes 111 is parallel to the longitudinal direction and is used to accommodate the steel bars.

[0040] Preferably, the angular bisector of the included angle a is not parallel to the radial cross-section of the clamping hole 111, that is, there is an included angle greater than 0 between the angular bisector of the included angle a and the radial cross-section of the clamping hole 111, so as to further increase the stability of the steel bar assembly.

[0041] In detail, in some cases, such as during the construction of a horizontal mold, in order to ensure the comfort of the user when using the prefabricated staircase product, the angle bisector of the external angle of the staircase mold is generally inclined relative to the plumb line. If the mold fitting 200 is to be snap-fitted with the external angle of the staircase mold, the angle bisector of the angle a also needs to be inclined relative to the plumb line. If the angle bisector of the angle a is parallel to the radial section of the clamping hole 111 at this time, the steel bar fitting 100 will also be inclined relative to the plumb line, and when supporting the steel bar, the stability of the force transmitted by the steel bar positioning device to the staircase mold will be reduced.

[0042] Specifically, the card interface 200a is composed of Figure 1 The card interface 200a is composed of a first support arm 210 and a second support arm 220. More specifically, with one first support arm 210 and one second support arm 220 as a group of support arms, the card interface 200a can be composed of multiple groups of support arms to make the card interface 200a lightweight.

[0043] Furthermore, the first support arm 210 and the second support arm 220 are asymmetric to accommodate the sizes of different surfaces of the entrance staircase mold.

[0044] Preferably, a plurality of notches 1111 arranged along the longitudinal direction are formed on the side of the steel bar fitting 100 , and a clamping hole 111 is connected to each inner side.

[0045] In this way, the steel bar positioning device makes full use of the shape structure of the stair mold, and is clamped with the stair mold through the "eight-shaped" mold matching piece 200 at the bottom. The steel bar positioning device and the positive angle combination of the stair mold forming surface limit the steel bars, effectively limiting the range of movement of the steel bars, so that the steel bar layer can be misaligned as much as possible in the face of various disturbances, thereby allowing accurate control of the protective layer.

[0046] Specifically, when the steel bar positioning device is applied to horizontal mold construction, it uses the positive corner of the stair mold as support through the mold fitting 200, and the multiple layers of steel bars are clamped into the steel bar fitting 100 to prevent dislocation; when the steel bar positioning device is applied to horizontal mold construction, one side of the steel bar layer is the stair mold, and the other side is the matching plate for combined molding with the stair mold. One end of the steel bar positioning device, that is, the mold fitting 200, supports the positive corner of the stair mold, and the other end supports the matching plate, and the steel bar is clamped into the clamping hole 111 of the middle steel bar fitting 100, and it can also serve as a limiting device for the cross-sectional size of the component.

[0047] Optionally, the above-mentioned steel bar positioning device is provided with more hollow structures. For example, a plurality of triangular slots are provided between adjacent clamping parts 110, so that the steel bar positioning device has a certain strength while meeting a certain lightness, which is convenient for user operation.

[0048] Optionally, the steel bar fitting 100 and the mold fitting 200 are integrally formed, which reduces the manufacturing cost, and the overall steel bar positioning device can relatively evenly bear the stress applied by the steel bar.

[0049] Preferably, as Figure 4 shown, a restraining rod 112 is provided in the middle of the inner wall of the clamping hole 111. The restraining rod 112 extends horizontally to the notch 1111 to divide the internal space of the clamping hole 111 into two parts. The steel bar can be clamped above or below the restraining rod 112 to adjust the spacing between the steel bar layer and its adjacent steel bar layer. Thus, the design of the restraining rod 112 between the clamping holes 111 enables the user to clamp the steel bar at different positions of the clamping hole 111 according to the differences between different precast stairs, so as to adapt to the steel bar spacing and cover layer requirements of different slab thicknesses.

[0050] Since the restraining rod 112 has a certain toughness, preferably, as Figure 4 shown, a number of positioning protrusions 113 are arranged on the opposite sides of the restraining rod 112 in the longitudinal direction. The positioning protrusion 113 can further prevent the steel bar from slipping between the inner wall of the clamping hole 111 and the restraining rod 112 after the steel bar is clamped above or below the restraining rod 112.

[0051] Specifically, as Figure 4 shown, the positioning protrusion 113 includes a guiding surface 1131 and a blocking surface 1132 for contacting the surface of the steel bar. The blocking surface 1132 is located on the side of the positioning protrusion 113 away from the notch 1111, and the guiding surface 1131 is opposite to the blocking surface 1132. The included angle between the guiding surface 1131 and the cross-section of the restraining rod 112 is less than 30°, and it is inclined towards the inside of the clamping hole 111. Since the angle of the guiding surface 1131 is relatively gentle, the steel bar will not be blocked during the process of entering the clamping hole 111. The blocking surface 1132 is perpendicular to the cross-section of the restraining rod 112, which can effectively prevent the steel bar from slipping after entering the clamping hole 111.

[0052] More specifically, as Figure 4 shown, the guiding surface 1131 and the blocking surface 1132 are connected by a connecting surface 1133. The connecting surface 1133 is parallel to the cross-section of the restraining rod 112, and the positioning protrusion 113 is in the shape of a frustum of a pyramid. If the guiding surface 1131 and the blocking surface 1132 are directly connected, the positioning protrusion 113 will be in the shape of a sharp angle, which will cause greater wear of the restraining rod 112 and reduce its service life during the contact with the steel bar.

[0053] Preferably, as Figure 5On the inner wall of the clamping hole 111 shown, a number of anti-slip portions 111a protruding upward are formed circumferentially. The anti-slip portion 111a has a regular quadrangular frustum structure and extends along the axial direction of the clamping hole 111, so that the anti-slip portion 111a has a certain strength. The ratio of the top surface area to the bottom surface area of the anti-slip portion 111a is less than 1:5, which can generate a large frictional force with the surface of the steel bar, further making it difficult for the steel bar to slip out after entering the clamping hole 111.

[0054] Preferably, as Figure 4 , 5 shown, guiding arms 114 are respectively connected to both ends of the notch 1111. The guiding arms 114 extend outward from the clamping hole 111, enabling users to quickly insert the steel bar into the clamping hole 111. Further, the outer end of the restraining rod 112 protrudes beyond the outer end of the guiding arm 114, facilitating users to accurately place the steel bar on the upper side or the lower side of the restraining rod 112.

[0055] Specifically, as Figure 5 shown, the guiding arm 114 includes a guiding surface 1141 facing the restraining rod 112. The guiding arm 114 opens outward, and the angle between the guiding surface 1141 and the cross-section of the restraining rod 112 is 3° to 10°, such as 4°, 6°, 8° or 9°, etc.

[0056] At one end of the guiding arm 114 close to the clamping hole 111, an anti-disengagement portion 1142 protruding beyond the inner wall of the clamping hole 111 is formed. The anti-disengagement portion 1142 has a quadrangular pyramid shape, and the surface of the anti-disengagement portion 1142 facing the restraining rod 112 is a part of the guiding surface 1141, which is used to further restrict the displacement of the steel bar.

[0057] Preferably, as Figure 4 , 5 shown, the steel bar positioning device further includes a movable gap 115. The movable gap 115 extends circumferentially from the outside of the notch 1111 to the clamping hole 111 and covers more than half of the circumferential side area of the clamping hole 111. In this way, especially when the notch 1111 of the clamping hole 111 is small, the clamping hole 111 can have a large deformation space. Specifically, during the process of the steel bar being inserted into the notch 1111, the notch 1111 deforms and expands outward. After the steel bar enters the clamping hole 111, the notch 1111 resets and retracts, thereby restricting the steel bar from moving around.

[0058] Further, as Figure 4 , 5 shown, a reinforcing rod 1151 is connected between the opposite side walls of the movable gap 115 in the longitudinal direction to increase the structural strength.

[0059] Generally speaking, the steel bar positioning device of the present application is connected and interacts with the staircase mold and the steel bars at the same time, making the control of the steel bar protection layer a holistic measure. It can stably restrict the steel bars, has high strength, can withstand certain construction disturbances or concrete vibration, and does not displace when facing construction loads, which is more effective for the control of the protection layer.

[0060] In the present application, the terms "install", "set", "provided with", "connected", "connected to", "socketed" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral structure; it can be a mechanical connection or an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, or there is internal communication between two devices, components or parts. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific circumstances.

[0061] The above are only the preferred embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A steel bar positioning device, characterized in that: include: The steel bar matching piece is a plate-like structure, comprising a plurality of longitudinally arranged clamping parts, each of which has a clamping hole, and a notch is formed on the side wall of the clamping part so that the steel bar can be inserted into the clamping hole through the notch; The mold fitting is located at one end of the steel bar fitting along the longitudinal direction, and includes a first support arm and a second support arm. The first support arm and the second support arm form an angle a, and the angle a is 75° to 95° to fit into the positive angle of the stair mold forming surface.

2. A steel bar positioning device according to claim 1, characterized in that: A restraining rod is arranged in the middle of the inner wall of the clamping hole, and the restraining rod extends transversely to the notch to divide the inner space of the clamping hole into two parts.

3. A steel bar positioning device according to claim 2, characterized in that: The restraining rod is provided with a plurality of positioning protrusions on two opposite sides in the longitudinal direction; The positioning protrusion includes a blocking surface and a guiding surface, which are used to contact the surface of the steel bar; the blocking surface is located on the side of the positioning protrusion away from the notch, and the guiding surface is opposite to the blocking surface; the angle between the cross-section of the guiding surface and the constraint rod is less than 30°, and is inclined toward the inside of the clamping hole; the blocking surface is perpendicular to the cross-section of the constraint rod.

4. A steel bar positioning device according to claim 3, characterized in that: The guiding surface and the blocking surface are connected via a connecting surface, the connecting surface is parallel to the cross section of the restraining rod, and the positioning protrusion is in a prism shape.

5. A steel bar positioning device according to any one of claims 2 to 4, characterized in that: Both ends of the notch are respectively connected with guide arms, and the guide arms extend toward the outside of the clamping hole; The outer end of the restraining rod protrudes from the outer end of the guide arm.

6. A steel bar positioning device according to claim 5, characterized in that: The guide arm comprises a guide surface facing the restraining rod; The guide arm opens outward, and an angle between the guide surface and the cross section of the restraint rod is 3° to 10°.

7. A steel bar positioning device according to claim 6, characterized in that: An anti-slip portion protruding from the inner wall of the clamping hole is formed at one end of the guide arm close to the clamping hole. The anti-slip portion is in the shape of a quadrangular pyramid, and a surface of the anti-slip portion facing the restraining rod is a part of the guide surface.

8. A steel bar positioning device according to claim 1, characterized in that: It also includes an active gap, which extends from the outside of the notch to the circumference of the clamping hole and covers more than half of the circumference of the clamping hole.

9. A steel bar positioning device according to claim 8, characterized in that: A reinforcing rod is connected between two side walls of the movable gap which are opposite to each other in the longitudinal direction.

10. A steel bar positioning device according to claim 1, characterized in that: The inner wall of the clamping hole is formed with a plurality of anti-slip portions protruding upward along the circumferential direction; the anti-slip portions are regular quadrangular pyramid structures and extend along the axial direction of the clamping hole; the ratio of the top surface area to the bottom surface area of ​​the anti-slip portions is less than 1:

5.

11. A steel bar positioning device, characterized in that: It includes a mold matching piece, the mold matching piece has a V-shaped card interface, the card interface faces the longitudinal direction, the card interface forms an angle a, the angle a is 75° to 95°, and the card interface is used to be attached to the positive angle of the molding surface of the staircase mold; A plate-shaped steel bar fitting is connected to one side of the mold fitting, a notch is formed on the side of the steel bar fitting, the notch faces the transverse direction, a clamping hole is connected to the inner side of the notch, the radial section of the clamping hole is parallel to the longitudinal direction, and is used to accommodate the steel bar.

12. A steel bar positioning device according to claim 11, characterized in that: The bisector of the angle a is not parallel to the radial cross section of the clamping hole.

13. A steel bar positioning device according to claim 11 or 12, characterized in that: The side edge of the steel bar matching piece is formed with a plurality of notches arranged along the longitudinal direction, and the inner side of each notch is connected with the clamping hole.

14. A steel bar positioning device according to claim 11, characterized in that: The card interface is composed of a first supporting arm and a second supporting arm, and the first supporting arm and the second supporting arm are asymmetrical.

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