Flat wire forming die, forming apparatus, and method of use

Abstract

The present application belongs to the technical field of non-cutting metal mechanical processing, and particularly relates to a die, especially a flat wire forming die, a forming device and a use method, wherein the flat wire forming die comprises: a lower die, a containing area for containing a flat wire is formed on the top surface of the lower die, and a pair of positioning assemblies are arranged on one side of the containing area; a sunken area is formed on the bottom surface of the containing area, and the positioning assemblies are arranged close to the sunken area; and an upper die, a pressing part corresponding to the containing area is arranged on the bottom surface of the upper die; after the flat wire is placed in the containing area, the flat wire in the containing area is pressed down through the pressing part of the upper die, so that the flat wire is formed, and the outer wall of the flat wire is contacted through the positioning assemblies when the flat wire is pressed, thereby limiting the flat wire during the process of pressing down the flat wire to form, and avoiding the flat wire from being raised.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of non-cutting metal machining, and particularly relates to a die, in particular to a flat wire forming die, a forming equipment and a use method. BACKGROUND

[0002] The flat wire needs to be pressed into shape in the production process. The bottom surface of the area for accommodating the flat wire in the lower die of the related die is not a plane. Therefore, the part of the flat wire that is not in the plane will sink more when the upper die presses the flat wire into shape, resulting in the flat wire being raised and failing to meet the forming requirement.

[0003] Therefore, in view of the technical problem that the flat wire is raised when pressed into shape and fails to meet the forming requirement, a flat wire forming die, a forming equipment and a use method need to be designed.

[0004] It should be noted that the above information disclosed in the background section of the present application is only used to understand the background of the present application, and therefore, the above description is not considered to constitute the information of the prior art. SUMMARY

[0005] The present application at least provides a flat wire forming die, a forming equipment and a use method.

[0006] In a first aspect, the present application provides a flat wire forming die, comprising:

[0007] a lower die, a containing area for accommodating the flat wire is formed on the top surface of the lower die, and a pair of positioning assemblies is arranged on one side of the containing area;

[0008] a sunken area is formed on the bottom surface of the containing area, and the positioning assemblies are arranged close to the sunken area;

[0009] an upper die, a pressing part corresponding to the containing area is arranged on the bottom surface of the upper die;

[0010] After the flat wire is placed in the containing area, the flat wire in the containing area is pressed by the pressing part of the upper die, so that the flat wire is formed, and the outer wall of the flat wire is contacted by the positioning assemblies when the flat wire is pressed.

[0011] In an optional embodiment, the positioning assembly comprises a rotating column.

[0012] The rotating column is rotationally arranged on the top surface of the lower die and arranged close to the sunken area;

[0013] a limiting block is arranged on the side wall of the rotating column, and part of the limiting block protrudes from the side wall of the rotating column;

[0014] The rotating column is rotated when the upper die is pressed down, so that the side of the limiting block protruding from the rotating column contacts the outer wall of the flat wire.

[0015] In an alternative embodiment, a groove is formed on the side wall of the rotating column, and the limiting block is partially located in the groove and in sliding connection with the groove;

[0016] A spring is arranged between the inner wall of the groove and the limiting block;

[0017] The part of the limiting block extending out of the groove is provided with a guide angle;

[0018] When the upper die is pressed down to drive the rotating column to rotate, the guide angle contacts the outer wall of the flat wire, so that the limiting block is retracted into the groove and the spring is compressed, so that the limiting block abuts against the flat wire through the spring when the side of the limiting block extending out of the rotating column contacts the outer wall of the flat wire.

[0019] In an alternative embodiment, a spiral groove is formed on the outer wall of the rotating column, the top end of the spiral groove is open, and the directions of the spiral grooves of the two rotating columns are opposite;

[0020] The bottom surface of the upper die is provided with a recess corresponding to the rotating column, and a protrusion is arranged in the recess;

[0021] When the upper die is pressed down, the protrusion enters the corresponding spiral groove to drive the corresponding rotating column to rotate.

[0022] In an alternative embodiment, the rotating column and the lower die are connected by a torsion spring;

[0023] The top surface of the lower die is provided with a mounting block, the side wall of the mounting block is provided with a limiting plate corresponding to the rotating column, and the limiting block is in contact with the side wall outside the rotating column and the limiting plate.

[0024] In an alternative embodiment, the groove stores lubricating oil;

[0025] An oil outlet hole is formed on the side of the limiting block contacting the flat wire, and the oil outlet hole is in communication with the groove.

[0026] In a second aspect, the embodiments of the present disclosure further provide a forming device, comprising:

[0027] A driving device and the flat wire forming die described above;

[0028] The driving device is connected with the flat wire forming die to drive the flat wire forming die to extrude the flat wire, so that the flat wire is formed.

[0029] In an alternative embodiment, the driving device is connected with the top surface of the upper die in the flat wire forming die;

[0030] The driving device is adapted to drive the upper die to press down the flat wire in the lower die.

[0031] In a third aspect, the embodiments of the present disclosure further provide a method for using the flat wire forming die, comprising:

[0032] After the flat wire is placed in the accommodation area, the upper die is used to press down the flat wire in the accommodation area, so that the flat wire is formed, and the outer wall of the flat wire is contacted by the positioning assembly when the flat wire is pressed.

[0033] In an optional embodiment, when the upper die is pressed down to drive the rotating column to rotate, the guide angle contacts the outer wall of the flat wire, so that the limiting block is retracted into the groove and the spring is compressed, so that the limiting block is tightly contacted with the flat wire by the spring when the side of the limiting block protruding from the rotating column contacts the outer wall of the flat wire.

[0034] The flat wire forming die has the advantages that: the flat wire forming die comprises a lower die, an upper die, and the lower die has an accommodation area for accommodating the flat wire on the top surface, and a pair of positioning assemblies are arranged on one side of the accommodation area; the lower die has a depression area on the bottom surface, and the positioning assemblies are arranged close to the depression area; the upper die has a pressing part corresponding to the accommodation area on the bottom surface; after the flat wire is placed in the accommodation area, the upper die is used to press down the flat wire in the accommodation area, so that the flat wire is formed, and the outer wall of the flat wire is contacted by the positioning assembly when the flat wire is pressed, thereby achieving limiting the flat wire during the process of pressing down the flat wire to form, and avoiding the flat wire from being raised.

[0035] Other features and advantages of the present application will be set forth in the following description, and in part will become apparent to those skilled in the art from the description, or can be learned by practice of the application. The objects and other advantages of the present application will be realized and achieved by the structures particularly pointed out in the description and the appended drawings.

[0036] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, the preferred embodiments are described in detail below, and the accompanying drawings are described as follows. BRIEF DESCRIPTION OF DRAWINGS

[0037] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the following will briefly introduce the drawings needed to be used in the specific embodiments or prior art description. Obviously, the drawings in the following description are some embodiments of the present application, and those skilled in the art can also obtain other drawings according to these drawings without creative labor.

[0038] Figure 1 A structural schematic diagram of a flat wire forming die provided by the embodiments of the present disclosure;

[0039] Figure 2 A structural schematic diagram of a depression area provided by the embodiments of the present disclosure;

[0040] Figure 3 A structure schematic diagram of an upper mold provided by an embodiment of the present disclosure;

[0041] Figure 4 A structure schematic diagram of a positioning assembly provided by an embodiment of the present disclosure;

[0042] Figure 5 A sectional view of a positioning assembly provided by an embodiment of the present disclosure;

[0043] Figure 6 A flat wire position schematic diagram provided by an embodiment of the present disclosure.

[0044] In the drawings:

[0045] 1 lower mold, 11 containing area, 12 sunken area, 13 mounting block, 14 limiting plate;

[0046] 2 positioning assembly, 21 rotating column, 22 limiting block, 23 groove, 24 guide angle, 25 spiral groove, 26 oil outlet hole, 27 spring;

[0047] 3 upper mold, 31 pressing part, 32 recessed part, 33 protruding block;

[0048] 4 flat wire. DETAILED DESCRIPTION

[0049] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme of the present application will be described clearly and completely below with reference to the drawings. Obviously, the described embodiments are some of the embodiments of the present application, but not all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of protection of the present application.

[0050] In this document, when it is mentioned that a first component is located on a second component, it can mean that the first component can be directly formed on the second component, or a third component can be interposed between the first component and the second component.

[0051] As used herein, the phrases "in an embodiment," "according to an embodiment," "in some embodiments," and the like generally mean the particular feature, structure, or characteristic following the phrase can be included in at least one embodiment of the present disclosure. Thus, the particular feature, structure, or characteristic can be included in more than one embodiment of the present disclosure, so that the phrases "in an embodiment" and the like do not necessarily refer to the same embodiment. As used herein, the terms "for example," "e.g.," "for instance," "such as," and the like mean "for the purpose of illustration" and are not intended to indicate or imply that a list of features in the phrase that such terms appear is an exhaustive list of possibilities.

[0052] The flat wire needs to be pressed into shape during production. The bottom surface of the area for accommodating the flat wire in the lower mold of the related mold is not a plane. Therefore, during the process of pressing the flat wire into shape by the upper mold, the part of the flat wire that is not on the plane is pressed more and sinks more, causing the flat wire to be raised and unable to meet the shaping requirement.

[0053] It should be noted that similar reference numerals and letters refer to similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0054] Some embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings. The following embodiments and features in the embodiments can be combined with each other without conflict.

[0055] As shown in Figure 1 , Figure 2 , Figure 3 and Figure 6 , at least one other disclosed embodiment provides a flat wire shaping mold, comprising: a lower mold 1, a top surface of the lower mold 1 is provided with an accommodation area 11 for accommodating a flat wire 4, one side of the accommodation area 11 is provided with a pair of positioning assemblies 2; a bottom surface of the accommodation area 11 is provided with a sunken area 12, the positioning assemblies 2 are arranged close to the sunken area 12; an upper mold 3, a bottom surface of the upper mold 3 is provided with a pressing part 31 corresponding to the accommodation area 11; after the flat wire 4 is placed in the accommodation area 11, the flat wire 4 in the accommodation area 11 is pressed down by the pressing part 31 of the upper mold 3, so that the flat wire 4 is shaped, and the outer wall of the flat wire 4 is contacted by the positioning assemblies 2 when the flat wire 4 is pressed, thereby limiting the flat wire 4 during the process of pressing the flat wire 4 into shape and avoiding the flat wire 4 from being raised.

[0056] In this embodiment, during the process of pressing the flat wire 4 into shape, the flat wire 4 is limited by the positioning assemblies 2 contacting the side wall of the flat wire 4, so that when the flat wire 4 located in the sunken area 12 is pressed into the sunken area 12, the other end of the flat wire 4 is prevented from being raised.

[0057] As Figure 4 shown, in an alternative embodiment, the positioning assembly 2 comprises a rotating column 21, which is arranged on the top surface of the lower mold 1 and close to the depression area 12; the side wall of the rotating column 21 is provided with a limiting block 22, part of which extends out of the side wall of the rotating column 21; the rotating column 21 is driven to rotate when the upper mold 3 is pressed down, so that the side of the limiting block 22 extending out of the rotating column 21 contacts the outer wall of the flat wire 4.

[0058] In this embodiment, the rotating directions of the two positioning assemblies 2 are opposite, for example, one rotates clockwise and the other rotates counterclockwise, so that the corresponding limiting blocks 22 gradually approach the flat wire 4 when rotating, and finally the side of the limiting block 22 contacts the side wall of the flat wire 4, completing the limiting of the flat wire 4, and the face-to-face contact between the side of the limiting block 22 and the side wall of the flat wire 4 can ensure the limiting effect.

[0059] As Figure 5 shown, in an alternative embodiment, a groove 23 is formed on the side wall of the rotating column 21, part of the limiting block 22 is located in the groove 23 and is in sliding connection with the groove 23; a spring 27 is arranged between the inner wall of the groove 23 and the limiting block 22; a guide corner 24 is formed on the part of the limiting block 22 extending out of the groove 23; when the upper mold 3 is pressed down to drive the rotating column 21 to rotate, the guide corner 24 contacts the outer wall of the flat wire 4, so that the limiting block 22 is retracted into the groove 23 and the spring 27 is compressed, so that the limiting block 22 tightly abuts against the flat wire 4 when the side of the limiting block 22 extending out of the rotating column 21 contacts the outer wall of the flat wire 4.

[0060] In this embodiment, the limiting block 22 is compressed by the spring 27 when contacting the flat wire 4, and the compressed spring 27 can ensure that the limiting block 22 tightly abuts against the flat wire 4, ensuring the limiting effect.

[0061] In this embodiment, by arranging the guide corner 24, when the guide corner 24 contacts the flat wire 4 during the process of the rotating column 21 rotating and driving the limiting block 22 to gradually approach the flat wire 4, the edge corner of the limiting block 22 will not be stuck with the side wall of the flat wire 4, so that the rotating column 21 can smoothly rotate to make the face of the limiting block 22 contact the side wall of the flat wire 4; when the guide corner 24 of the limiting block 22 contacts the side wall of the flat wire 4, the limiting block 22 can be extruded to retract into the groove 23 to compress the spring 27, so that the side of the limiting block 22 smoothly contacts the side wall of the flat wire 4.

[0062] As Figure 3 and Figure 4As shown in an optional embodiment, a spiral groove 25 is formed on the outer wall of the rotating column 21, the top end of the spiral groove 25 is open, and the spiral grooves 25 of the two rotating columns 21 are in opposite directions; the bottom surface of the upper mold 3 is provided with a recess 32 corresponding to the rotating column 21, and the recess 32 is provided with a protrusion 33; when the upper mold 3 is pressed down, the protrusion 33 enters the corresponding spiral groove 25 to drive the corresponding rotating column 21 to rotate.

[0063] In this embodiment, the spiral groove 25 is provided so that the upper mold 3 can make the rotating column 21 rotate during the pressing process, and the open top end of the spiral groove 25 facilitates the protrusion 33 to enter the spiral groove 25 to make the spiral groove 25 rotate.

[0064] In this embodiment, the spiral grooves 25 of the two rotating columns 21 are in opposite directions to realize that the rotating directions of the two rotating columns 21 are opposite when the upper mold 3 is pressed down.

[0065] In an optional embodiment, the rotating column 21 is connected with the lower mold 1 through a torsion spring; the top surface of the lower mold 1 is provided with a mounting block 13, the side wall of the mounting block 13 is provided with a limiting plate 14 corresponding to the rotating column 21, and the limiting block 22 is in contact with the limiting plate 14 on the side wall outside the rotating column 21.

[0066] In this embodiment, when the upper mold 3 is not pressed down, the torsion spring drives the rotating column 21 to have a tendency to rotate towards the corresponding limiting plate 14 to ensure that the limiting block 22 is in contact with the limiting plate 14 on the side wall outside the rotating column 21, and then the open top end of the spiral groove 25 is positioned, and when the upper mold 3 is pressed down, it ensures that the protrusion 33 can smoothly enter the corresponding spiral groove 25.

[0067] In this embodiment, the top end of the rotating column 21 can be conical to facilitate the extension into the corresponding recess 32.

[0068] As shown in an optional embodiment, the recess 23 stores lubricating oil; one side of the limiting block 22 in contact with the flat wire 4 is provided with an oil outlet hole 26, which is in communication with the recess 23. Figure 4 In this embodiment, when the limiting block 22 rotates and approaches the flat wire 4, when the limiting block 22 is extruded and shrinks into the recess 23, the lubricating oil in the recess 23 is extruded and flows out of the oil outlet hole 26 to be applied on the outer wall of the flat wire 4.

[0069]

[0070] ​In the embodiment, the recess 23 can be connected with an external oil tank through an oil passage, but is not limited thereto, to supplement lubricating oil in the recess 23. An electromagnetic valve can be arranged in the oil passage. When it is necessary to supplement lubricating oil, the electromagnetic valve is opened to allow the lubricating oil to enter the recess 23, and then the electromagnetic valve is closed to allow the limiting block 22 to be extruded to shrink into the recess 23 and extrude the lubricating oil in the recess 23 to flow out of the oil outlet hole 26.

[0071] At least one other disclosed embodiment further provides a forming device, comprising: a driving device, and the flat wire forming die described above; the driving device is connected with the flat wire forming die to drive the flat wire forming die to extrude the flat wire 4, so that the flat wire 4 is formed.

[0072] In an optional embodiment, the driving device is connected with the top surface of the upper die 3 in the flat wire forming die; the driving device is adapted to drive the upper die 3 to press down the flat wire 4 in the lower die 1.

[0073] At least one other disclosed embodiment further provides a method for using the flat wire forming die described above, comprising: after the flat wire 4 is placed in the containing area 11, the flat wire 4 in the containing area 11 is pressed down by the pressing part 31 of the upper die 3, so that the flat wire 4 is formed, and the outer wall of the flat wire 4 is contacted by the positioning assembly 2 when the flat wire 4 is pressed.

[0074] In an optional embodiment, when the upper die 3 is pressed down to drive the rotating column 21 to rotate, the guide angle 24 contacts the outer wall of the flat wire 4, so that the limiting block 22 shrinks into the recess 23 and compresses the spring 27, to make the limiting block 22 abut against the flat wire 4 by the spring 27 when the side of the limiting block 22 that protrudes from the rotating column 21 contacts the outer wall of the flat wire 4.

[0075] In an optional embodiment, when the upper die 3 is not pressed down, the limiting block 22 is in contact with the limiting plate 14 on the side wall outside the rotating column 21.

[0076] In summary, the flat wire forming die comprises: a lower die 1, a containing area 11 for containing a flat wire 4 is arranged on the top surface of the lower die 1, a pair of positioning assemblies 2 are arranged on one side of the containing area 11; a sunken area 12 is arranged on the bottom surface of the containing area 11, and the positioning assemblies 2 are arranged close to the sunken area 12; an upper die 3, a pressing part 31 corresponding to the containing area 11 is arranged on the bottom surface of the upper die 3; after the flat wire 4 is placed in the containing area 11, the flat wire 4 in the containing area 11 is pressed down by the pressing part 31 of the upper die 3, so that the flat wire 4 is formed, and the outer wall of the flat wire 4 is contacted by the positioning assembly 2 when the flat wire 4 is pressed, thereby achieving limiting the flat wire 4 during the process of pressing down the flat wire 4 to form, and avoiding the flat wire 4 from being warped.

[0077] In the description of the embodiments of the present application, unless specifically defined and limited otherwise, the terms "mounting", "connected", "connecting" should be interpreted broadly, for example, can be fixedly connected, can be detachably connected, or integrally connected; can be mechanically connected, or electrically connected; can be directly connected, or indirectly connected through an intermediate medium, or the internal communication of two elements. For those skilled in the art, the specific meanings of the above terms in the present application can be understood according to the specific circumstances.

[0078] In the description of the present application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application. In addition, terms such as "first", "second" and other numerical terms are used herein and do not imply order or sequence unless specifically indicated herein. Therefore, the first element, component, region, layer or section discussed above can be referred to as the second element, component, region, layer or section without departing from the teachings of the example embodiments.

[0079] Spatially relative terms, such as "inner", "outer", "below", "below", "lower", "above", "upper", and the like, can be used herein to facilitate description of the relationship of one element or feature to another element or feature as illustrated in the drawings. In addition to the orientation depicted in the drawings, the spatially relative terms can be intended to cover different orientations of the device in use or operation. For example, if the device in the drawing is turned over, the element described as "below" or "under" the other element or feature will be oriented "above" the other element or feature. Therefore, the example term "below" can cover the above and below orientations. The device can be oriented in other ways (rotated 90 degrees or in other orientations), and the spatially relative descriptors used herein are interpreted accordingly.

[0080] With the above ideal embodiments according to the present application as the inspiration, through the above description, relevant personnel can make various changes and modifications without deviating from the technical idea of the present application. The technical scope of the present application is not limited to the contents of the specification, and must be determined by the scope of the claims.

Claims

1. A flat wire forming die characterized by, The utility model relates to a flat wire forming die which comprises: a lower die (1) having a receiving area (11) for receiving a flat wire (4) formed on the top surface of the lower die (1), and a pair of positioning assemblies (2) arranged on one side of the receiving area (11); a lower recess (12) formed on the bottom surface of the receiving area (11), and the positioning assemblies (2) are arranged close to the lower recess (12); an upper die (3) having a pressing portion (31) corresponding to the receiving area (11) formed on the bottom surface of the upper die (3); after the flat wire (4) is placed in the receiving area (11), the pressing portion (31) of the upper die (3) is used to press the flat wire (4) in the receiving area (11) so that the flat wire (4) is formed, and the positioning assemblies (2) are used to contact the outer wall of the flat wire (4) when the flat wire (4) is pressed; the positioning assembly (2) comprises a rotating column (21); the rotating column (21) is rotatably arranged on the top surface of the lower die (1) and arranged close to the lower recess (12); a limiting block (22) is arranged on the side wall of the rotating column (21), and part of the limiting block (22) extends out of the side wall of the rotating column (21); when the upper die (3) is pressed, the rotating column (21) is rotated, so that the side of the limiting block (22) extending out of the rotating column (21) contacts the outer wall of the flat wire (4); a groove (23) is formed on the side wall of the rotating column (21), and part of the limiting block (22) is arranged in the groove (23) and connected with the groove (23) in a sliding mode; a spring (27) is arranged between the inner wall of the groove (23) and the limiting block (22); a guide angle (24) is formed on the part of the limiting block (22) extending out of the groove (23); when the upper die (3) is pressed to rotate the rotating column (21), the guide angle (24) contacts the outer wall of the flat wire (4), so that the limiting block (22) is retracted into the groove (23) and the spring (27) is compressed, so that the limiting block (22) is tightly pressed against the flat wire (4) through the spring (27) when the side of the limiting block (22) extending out of the rotating column (21) contacts the outer wall of the flat wire (4).

2. The flat wire forming die according to claim 1, wherein a helical groove (25) is formed on the outer wall of the rotating column (21), the top end of the helical groove (25) is open, and the directions of the helical grooves (25) of the two rotating columns (21) are opposite; a recess (32) corresponding to the rotating column (21) is formed on the bottom surface of the upper die (3), and a protrusion (33) is arranged in the recess (32); when the upper die (3) is pressed, the protrusion (33) enters the corresponding helical groove (25) to rotate the corresponding rotating column (21).

3. The flat wire forming die according to claim 1, wherein the rotating column (21) is connected with the lower die (1) through a torsion spring; an installation block (13) is arranged on the top surface of the lower die (1), a limiting plate (14) corresponding to the rotating column (21) is arranged on the side wall of the installation block (13), and the limiting block (22) is in contact with the limiting plate (14) on the side wall outside the rotating column (21).

4. The flat wire forming die according to claim 1, wherein The recess (23) stores lubricating oil; An oil outlet hole (26) is arranged on the side of the limiting block (22) in contact with the flat wire (4), and the oil outlet hole (26) is in communication with the recess (23).

5. A molding apparatus characterized by comprising: The application relates to a flat wire forming die and a forming device thereof. The driving device is connected with the flat wire forming die to drive the flat wire forming die to extrude the flat wire (4) so that the flat wire (4) is formed.

6. The forming device according to claim 5, wherein The driving device is connected with the top surface of the upper die (3) in the flat wire forming die; The driving device is suitable for driving the upper die (3) to press down the flat wire (4) in the lower die (1). The application relates to a flat wire forming die and a forming device thereof.

7. A method of using the flat wire forming die of claim 1, wherein, After the flat wire (4) is placed in the accommodating area (11), the flat wire (4) in the accommodating area (11) is pressed down by the pressing part (31) of the upper die (3), so that the flat wire (4) is formed, and the outer wall of the flat wire (4) is contacted by the positioning assembly (2) when the flat wire (4) is pressed.

8. The using method of the flat wire forming die according to claim 7, wherein When the upper die (3) is pressed down to drive the rotating column (21) to rotate, the guide angle (24) contacts the outer wall of the flat wire (4), so that the limiting block (22) is retracted into the recess (23) and the spring (27) is compressed, so that the limiting block (22) is tightly contacted with the flat wire (4) by the spring (27) when the side of the limiting block (22) protruding from the rotating column (21) contacts the outer wall of the flat wire (4). ​

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