Forming method of blind rivet nut, intermediate piece, forming device and blind rivet nut

Abstract

The present invention provides a forming method, an intermediate part, a forming device and a rivet nut of a rivet nut, comprising the steps of upsetting a preset blank twice to form a second preset blank; forming a preset flange and a preset rod portion from the second preset blank and forming a head fixed point in the preset flange; then back-extruding a first hole section of a first blind hole through the head fixed point; back-extruding a second blind hole from an end of the preset rod portion away from the preset flange, and punching the first blind hole to form a second hole section connected to the first hole section, wherein the aperture of the second blind hole gradually decreases from an end of the preset rod portion away from the preset flange toward the preset flange, and the bottom diameter of the second blind hole is smaller than the aperture of the first hole section and larger than the diameter of the second hole section; finishing the preset flange and the preset rod portion to obtain the intermediate part of the rivet nut; separating the waste material between the first blind hole and the second blind hole from the intermediate part of the rivet nut, so that the first blind hole and the second blind hole are connected to obtain a second inner hole and a third inner hole; and then performing necessary processing to obtain a finished part.

Description

Technical Field

[0001] The invention belongs to the field of fastener molding, and in particular relates to a molding method, an intermediate piece, a molding device and a rivet nut. Background Art

[0002] Pull-on rivet nuts, also known as pull-on caps, are nuts that are fastened to connected parts by pull-on rivets. They are widely used in the assembly of electromechanical and light industrial products such as automobiles, aviation, instruments, furniture, and decoration. They are developed to solve the shortcomings of easy melting of welding nuts on metal sheets and thin tubes and easy slipping of internal threads. They do not require internal threads, welding nuts, strong riveting, high efficiency, and are easy to use. However, in the forming method of the rivet nut, some parts need to punch waste materials to form the axial inner hole of the rivet nut, and then tap the inner hole to form a thread. Before the punching waste material process, corresponding blind holes have been formed at both ends of the nut. The blind hole end with a larger aperture is punched to make the hole waste fall from the blind hole end with a smaller aperture, thereby making the corresponding blind holes connected to form the axial inner hole of the rivet nut. However, burrs and steps are likely to remain at the tearing place after the punching waste, or because the blind hole with a smaller aperture has been squeezed back in the previous process, a stacking layer will be formed on the hole wall of the axial inner hole after the punching waste, which will cause burrs after the subsequent tapping of the axial inner hole, resulting in defective products. Summary of the invention

[0003] In view of the problems existing in the above-mentioned prior art, the main purpose of the present invention is to provide a forming method, an intermediate piece, a forming device and a rivet nut for a rivet nut. In the forming method of the rivet nut provided, the intermediate piece is formed by a multi-station cold heading forming machine through six-die six-punching of a preset blank, and includes a rod and a head flange fixedly connected to one end of the rod, the head flange is recessed with a first blind hole at one end away from the rod, and the rod is recessed with a second blind hole at one end away from the head flange, and the aperture of the second blind hole gradually decreases from the end of the rod away from the head flange toward the head flange, and the bottom diameter thereof is larger than the diameter of the second hole section of the first blind hole and smaller than the diameter of the first hole section of the first blind hole. When the waste material is punched from the first blind hole to the second blind hole, the impact of the hole waste on the second blind hole can be completely avoided, so that there is no residual burr or step at the tearing point, and the tearing surface is smooth and without lamination, so as to ensure that there is no burr after tapping and ensure the product quality rate.

[0004] The purpose of the present invention is achieved through the following technical solutions:

[0005] The present invention provides a forming method for a rivet nut. The rivet nut includes a rod portion and a head flange fixedly connected to one end of the rod portion. The rivet nut is provided with an inner hole that penetrates through the head flange and the rod portion along its axial direction. The inner hole at least includes a first inner hole, a second inner hole, and a third inner hole that are sequentially connected. The aperture of the third inner hole gradually decreases from the end of the rod portion away from the head flange towards the head flange, and the apertures of the second inner hole and the third inner hole are both smaller than the aperture of the first inner hole. The method includes the following steps:

[0006] Cut the wire rod to form a preset blank;

[0007] Upsize and shape the preset blank to form a first preset blank;

[0008] Upsize and shape the first preset blank to form a second preset blank;

[0009] Form a preset flange and a preset rod portion on the second preset blank, and form a head fixed point in the preset flange;

[0010] By means of the head fixed point, extrude a first hole section of a first blind hole in the preset flange to obtain the first inner hole;

[0011] From the end of the preset rod portion away from the preset flange, extrude a second blind hole, and punch the first blind hole to form a second hole section connected to the first hole section; wherein,

[0012] The aperture of the second blind hole gradually decreases from the end of the preset rod portion away from the preset flange towards the preset flange; the bottom diameter of the second blind hole is smaller than the aperture of the first hole section; the diameter of the second hole section is smaller than the bottom diameter of the second blind hole;

[0013] Finish sizing the preset flange and the preset rod portion to form the head flange and the rod portion, obtaining an intermediate part of the rivet nut;

[0014] Separate the waste material between the first blind hole and the second blind hole from the intermediate part of the rivet nut, so that the first blind hole and the second blind hole are connected to each other, obtaining the second inner hole and the third inner hole;

[0015] Perform heat treatment, tapping, and electroplating on the preset rivet nut formed with the second inner hole and the third inner hole to obtain a finished rivet nut.

[0016] The present invention also provides an intermediate part of a rivet nut, including:

[0017] The main body comprises a rod and a head flange fixedly connected to one end of the rod; the main body is concentrically provided with a first blind hole and a second blind hole along its axial direction, the first blind hole is formed by the end surface of the head flange facing away from the rod and is recessed inward, and the second blind hole is formed by the end surface of the rod facing away from the head flange and is recessed inward; wherein,

[0018] The first blind hole at least comprises a first hole segment and a second hole segment, and the second hole segment is located between the first hole segment and the second blind hole in the axial direction of the body;

[0019] The diameter of the second blind hole gradually decreases from the end of the rod portion away from the head flange toward the head flange;

[0020] The bottom diameter of the second blind hole is smaller than the hole diameter of the first hole segment and larger than the hole diameter of the second hole segment.

[0021] As a further description of the above technical solution, the bottom diameter of the second blind hole is 1.0 mm-2.0 mm larger than the hole diameter of the second hole section.

[0022] As a further description of the above technical solution, the angle formed by the hole wall of the second blind hole and the axis of the body is 10°-60°.

[0023] As a further description of the above technical solution, the depth of the second blind hole is 0.1 mm-3.0 mm.

[0024] As a further description of the above technical solution, the diameter of the second hole section is 0.1 mm-2.0 mm larger than the nominal diameter of the thread.

[0025] The present invention also provides a forming device for a rivet nut, comprising a cold heading machine and a die assembly installed on the cold heading machine, wherein the die assembly comprises:

[0026] A first die, wherein the first die is used to perform upsetting and shaping on a preset blank to form a first preset blank;

[0027] A second die, wherein the second die is used to perform upsetting and shaping on the second preset blank to form the second preset blank;

[0028] A third mold, the third mold is used to form a preset flange and a preset rod portion of the second preset blank, and to form a head fixed point in the preset flange;

[0029] A fourth die, the fourth die is used to extrude the first hole segment of the first blind hole through the head at a fixed point in the preset flange to obtain a first inner hole;

[0030] The fifth die is used to extrude the second blind hole from the end of the preset rod portion away from the preset flange, and to extend the first hole segment inward to form the second hole segment; wherein,

[0031] The aperture of the second blind hole tapers from the end of the preset rod portion away from the preset flange towards the preset flange; the diameter of the bottom of the second blind hole is smaller than the aperture of the first hole segment; the diameter of the second hole segment is smaller than the diameter of the bottom of the second blind hole;

[0032] The sixth die is used for finishing the preset flange and the preset rod portion to form the head flange and the rod portion, obtaining the intermediate part of the rivet nut;

[0033] The seventh die is used to separate the waste material between the first blind hole and the second blind hole from the intermediate part of the rivet nut, and to connect the first blind hole and the second blind hole to obtain the second inner hole and the third inner hole.

[0034] As a further description of the above technical solution, the first die, the second die, the third die, the fourth die, the fifth die, the sixth die and the seventh die all include a main die and a punching die arranged corresponding to the main die.

[0035] The present invention also provides a rivet nut, including a rod portion and a head flange fixedly connected to one end of the rod portion. The rivet nut is provided with an inner hole penetrating through the head flange and the rod portion along its axis direction. The inner hole at least includes a first inner hole, a second inner hole and a third inner hole. The first inner hole penetrates through the head flange and the rod portion, and the second inner hole is connected between the first inner hole and the third inner hole; wherein,

[0036] The aperture of the third inner hole tapers from the end of the rod portion away from the head flange towards the head flange;

[0037] The apertures of the second inner hole and the third inner hole are both smaller than the aperture of the first inner hole.

[0038] As a further description of the above technical solution, a thread is formed on the hole wall of the second inner hole; a chamfer is formed at the end of the rod portion away from the head flange.

[0039] In summary, the outstanding effects of the present invention are:

[0040] In the forming method of the rivet nut of the present invention, the intermediate piece formed by six-die six-punching of a preset blank by a multi-station cold heading forming machine comprises a rod and a head flange fixedly connected to one end of the rod, the head flange is recessed with a first blind hole at one end away from the rod, the rod is recessed with a second blind hole at one end away from the head flange, and the aperture of the second blind hole gradually decreases from the end of the rod away from the head flange toward the head flange, the bottom diameter of the second blind hole is larger than the diameter of the second hole section of the first blind hole and smaller than the diameter of the first hole section of the first blind hole, and the second blind hole is further processed by the seventh stage of the multi-station cold heading machine. The die separates the waste material between the first blind hole and the second blind hole from the middle piece of the rivet nut, so that the first blind hole and the second blind hole are connected, and a preset rivet nut formed with a second inner hole and a third inner hole is obtained. In this process, the waste material is punched out based on the aperture of the second hole section, and the hole wall of the second blind hole completely avoids the falling track of the waste material, so that no burrs or steps will remain at the tearing point after punching, and the tearing surface is smooth and free of lamination, thereby avoiding burrs after tapping, and the product quality is controllable, ensuring the product quality rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without paying any creative work.

[0042] Figure 1 It is a schematic structural diagram of an intermediate piece of a rivet nut according to an embodiment of the present invention;

[0043] Figure 2 This is a finished product picture of a rivet nut in an embodiment of the present invention;

[0044] Figure 3 It is a schematic diagram of a state in which a rivet nut is punched out of waste by a seventh die in an embodiment of the present invention;

[0045] Figure 4 It is a partial structural schematic diagram of a forming device for a rivet nut according to an embodiment of the present invention;

[0046] Description of Figure Numbers:

[0047] 1. Body; 11. Rod; 12. Head flange; 13. First blind hole; 131. First hole section; 132. Second hole section; 14. Second blind hole; 15. Waste; 21. First inner hole; 22. Second inner hole; 23. Third inner hole; 24. Chamfer; 3. Sixth mold; 4. Seventh mold; 5. Main mold; 51. Main mold cavity; 52. Main mold punch 6. Die; 61. Upset flange punch; 62. Hole protection punch; 63. Waste punch. DETAILED DESCRIPTION

[0048] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0049] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "upper", "middle", "lower", "inner", "outer", etc. is based on the orientation or positional relationship shown in the accompanying drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or component referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. In addition, the terms "first", "second", and "third" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0050] The following will be specifically described with reference to the attached Figure 1 to the attached Figure 4 and embodiments.

[0051] This embodiment provides a forming method for a blind rivet nut. The blind rivet nut includes a rod portion 11 and a head flange 12 fixedly connected to one end of the rod portion 11. The blind rivet nut is provided with an inner hole penetrating through the head flange 12 and the rod portion 11 along its axial direction. The inner hole at least includes a first inner hole 21, a second inner hole 22, and a third inner hole 23 that are sequentially connected. The aperture of the third inner hole 23 gradually decreases from the end of the rod portion 11 away from the head flange 12 towards the head flange 12, and the apertures of the second inner hole 22 and the third inner hole 23 are both smaller than the aperture of the first inner hole 21. The method includes the following steps:

[0052] Cut the wire to form a preset blank.

[0053] Upsize and shape the preset blank to form a first preset blank.

[0054] Upsize and shape the first preset blank to form a second preset blank.

[0055] Form a preset flange and a preset rod portion on the second preset blank, and form a head fixed point in the preset flange.

[0056] By means of the head fixed point, extrude the first hole section 131 of the first blind hole 13 as shown in Figure 1 from the preset flange to obtain the first inner hole 21.

[0057] Extrude the preset rod portion from the end away from the preset flange to form a second blind hole 14 as shown in Figure 1 , and punch the first blind hole 13 to form a second hole segment 132 connected to the lower part of the first hole segment 131; wherein,

[0058] The aperture of the second blind hole 14 tapers from the end of the preset rod portion away from the preset flange towards the preset flange; the bottom diameter of the second blind hole 14 is smaller than the aperture of the first hole segment 131; the diameter of the second hole segment 132 is smaller than the bottom diameter of the second blind hole 14;

[0059] Finish the preset flange and the preset rod portion to form the head flange 12 and the rod portion 11, obtaining the intermediate part of the rivet nut;

[0060] As shown in Figure 3 , separate the waste 15 between the first blind hole 13 and the second blind hole 14 from the intermediate part of the rivet nut, so that the first blind hole 13 and the second blind hole 14 are connected to each other, obtaining the second inner hole 22 and the third inner hole 23;

[0061] Heat-treat, thread, and electroplate the preset rivet nut formed with the second inner hole 22 and the third inner hole 23 to obtain the finished rivet nut.

[0062] By means of the above method, using a multi-station cold heading forming machine for processing, a preset blank is subjected to seven dies and seven punches. The preset blank cut from the wire rod is subjected to two upsetting and shaping operations through the first die and the second die; then, the preset flange, the preset rod portion, and the head fixed point inside the preset flange are formed through the third die; and then, the fourth die is used to perform back extrusion through the head fixed point to form the first hole section 131 of the first blind hole 13, that is, the first inner hole 21 of the blind rivet nut is obtained, and the first inner hole 21 extends from the end face of the preset flange away from the preset rod portion into the preset rod portion; the fifth die will extrude the end of the preset rod portion away from the preset flange to form a second blind hole 14 with a diameter gradually decreasing from the end of the preset rod portion away from the preset flange towards the preset flange, and at the same time, the first blind hole 13 extends inward to form a second hole section 132 connected to the first hole section 131. Among them, although the bottom diameter of the second blind hole 14 is smaller than the aperture of the first hole section 131, it is larger than the aperture of the second hole section 132, so that its hole wall completely avoids the blanking trajectory of the waste 15 in the subsequent waste punching 15 process, thereby ensuring the excellent rate of the product after waste punching 15. The sixth die 3 will finish the blank with the second blind hole 14 formed, mainly finishing the preset flange and the preset rod portion, including their outer diameters and the connection between the two, so as to form the head and the rod portion 11 with various parameters meeting the finished product standards, that is, the intermediate part of the blind rivet nut with preset parameter values is obtained; then, the waste 15 between the first blind hole 13 and the second blind hole 14 is separated from the intermediate part of the blind rivet nut through the seventh die 4, and the first blind hole 13 and the second blind hole 14 are connected to each other, and the preset blind rivet nut formed with the second inner hole 22 and the third inner hole 23 is obtained. Finally, the preset blind rivet nut obtained by cold heading is subjected to necessary heat treatment, tapping, electroplating and other processes to obtain the finished blind rivet nut, wherein tapping is performed on the second inner hole 22; in addition, when processing at the seventh die 4 station, due to the flow characteristics of the metal, the waste 15 will drive the product blank around it to flow downward to a certain extent. Due to the non-straight section setting of the second blind hole 14, the product blank around it will also form a certain angle with the axis of the product blank. Therefore, the length ratio between the second hole section 132 of the first blind hole 13 and the waste 15 can be comprehensively considered and set according to factors such as the nominal diameter of the thread to be formed subsequently, the flow characteristics of the metal, and the forming force of the waste punching 15, so that the angle formed by its flow is less than or equal to the thread angle to be formed. For example, in this embodiment, the angle formed by its flow is less than the 60° thread angle to be formed.

[0063] Specifically, the intermediate part of the blind rivet nut provided in this embodiment includes:

[0064] The body 1 comprises a rod 11 and a head flange 12 fixedly connected to one end of the rod 11; the body 1 is concentrically provided with a first blind hole 13 and a second blind hole 14 along its axial direction, the first blind hole 13 is formed by an end surface of the head flange 12 facing away from the rod 11 and is recessed inward, and the second blind hole 14 is formed by an end surface of the rod 11 facing away from the head flange 12 and is recessed inward; wherein,

[0065] The first blind hole 13 at least includes a first hole segment 131 and a second hole segment 132, and the second hole segment 132 is located between the first hole segment 131 and the second blind hole 14 in the axial direction of the body 1;

[0066] The diameter of the second blind hole 14 gradually decreases from the end of the rod portion 11 away from the head flange 12 toward the head flange 12;

[0067] The bottom diameter of the second blind hole 14 is smaller than the hole diameter of the first hole section 131 and larger than the hole diameter of the second hole section 132 .

[0068] By means of the above structure, the waste material 15 located between the first blind hole 13 and the second blind hole 14 is punched and blanked from one end of the head flange 12, so that the first blind hole 13 and the second blind hole 14 are connected to form the inner hole of the rivet nut. In the process, the waste material 15 is gradually separated from the main body 1 and falls into the waste material 15 dropping core provided in the main mold 5 through the second blind hole 14. Although the aperture of the second blind hole 14 gradually decreases from the end of the preset rod portion away from the head flange 12 toward the head flange 12, the bottom diameter of the hole is smaller than the diameter of the first hole section 131, but larger than the aperture of the second hole section 132. The waste material 15 is punched based on the aperture of the second hole section 132. The hole wall of the second blind hole 14 completely avoids the blanking track of the waste material 15, so that no burrs or steps will remain at the tearing point after punching, and the tearing surface is smooth and free of lamination, thereby avoiding burrs after tapping, and the product quality is controllable, ensuring the product quality rate.

[0069] Specifically, in the present embodiment, the bottom diameter of the second blind hole 14 is 1.5 mm larger than the aperture of the second hole segment 132, and sufficient radial clearance is reserved to ensure that its inner wall is not on the falling track of the waste material 15, thereby ensuring a smooth falling process, no residual burrs or steps are formed at the final tearing point, and also ensuring that the overall tearing surface is smooth and without lamination. Of course, in other embodiments, the bottom diameter of the second blind hole 14 is also larger than the aperture of the second hole segment 132 by any value between 1.0 mm and 2.0 mm, which can be set mainly according to the thickness of the waste material 15 and the factors of metal reverse flow to ensure that the hole wall of the second blind hole 14 is not on the falling track of the waste material 15.

[0070] Specifically, in the present embodiment, the angle formed between the hole wall of the second blind hole 14 and the axis of the main body 1 is 20°, and the depth of the second blind hole 14 is 0.9 mm to adapt to the subsequent tapping specifications. Of course, in other embodiments, according to actual production needs, the angle formed between the hole wall of the second blind hole 14 and the axis of the main body 1 can also be set to any value between 10°-60°, and the depth of the second blind hole 14 can also be set to any value between 0.1 mm-3.0 mm.

[0071] Specifically, in the present embodiment, the second hole segment 132 will be tapped to form a thread, and the aperture of the second hole segment 132 is 0.5 mm larger than the nominal diameter of the thread to be formed subsequently. Of course, in other embodiments, the aperture of the second hole segment 132 can also be set to be 0.1 mm-2.0 mm larger than the nominal diameter of the thread to be formed by subsequent tapping according to actual needs.

[0072] Specifically, in this embodiment, the forming device of the rivet nut provided includes a cold heading machine (not shown in the figure), and a mold assembly (not shown in the figure) installed on the cold heading machine, and the mold assembly includes:

[0073] A first die, wherein the first die is used to perform upsetting and shaping on a preset blank to form a first preset blank;

[0074] A second die, wherein the second die is used to perform upsetting and shaping on the second preset blank to form the second preset blank;

[0075] A third mold, the third mold is used to form a preset flange and a preset rod portion of the second preset blank, and to form a head fixed point in the preset flange;

[0076] A fourth die, the fourth die is used to extrude the first hole section 131 of the first blind hole 13 through the head fixed point in the preset flange to obtain the first inner hole 21;

[0077] A fifth mold is used to extrude the preset rod portion from its end away from the preset flange to form a second blind hole 14, and to extend the first hole section 131 inward to form a second hole section 132; wherein,

[0078] The diameter of the second blind hole 14 gradually decreases from the end of the preset rod away from the preset flange toward the preset flange; the bottom diameter of the second blind hole 14 is smaller than the diameter of the first hole section 131; the diameter of the second hole section 132 is smaller than the bottom diameter of the second blind hole 14;

[0079] The sixth die 3 is used for finishing the preset flange and the preset rod portion to form the head flange 12 and the rod portion 11, so as to obtain an intermediate member of the rivet nut;

[0080] The seventh die 4 is used for separating the waste 15 between the first blind hole 13 and the second blind hole 14 from the intermediate member of the rivet nut, and communicating the first blind hole 13 and the second blind hole 14 to obtain the second inner hole 22 and the third inner hole 23. It should be understood that in this embodiment, the forming device further includes a shearing mechanism (not shown in the figure) for shearing the wire into the preset blank, and a feeding mechanism (not shown in the figure) for moving and feeding between multiple dies.

[0081] Specifically, in this embodiment, the first die, the second die, the third die, the fourth die, the fifth die, the sixth die 3 and the seventh die 4 all include a main die 5 and a punching die 6 arranged corresponding to the main die 5. Please refer to Figure 4 , in this embodiment, the sixth die 3 is on the right side and the seventh die 4 is on the left side. Among them, the punching die 6 of the sixth die 3 includes a flange upsetting punch 61 and a hole protecting punch 62 connected below the flange upsetting punch 61. Its main die 5 includes a main die punch 52 located in the main die cavity 51. The main die punch 52 is opposite to the hole protecting punch 62, and respectively protects the second blind hole 14 and the first blind hole 13, so that the preset flange and the preset rod portion can be finished under the cooperation of the main die cavity 51 and the flange upsetting punch 61. After obtaining the intermediate member of the rivet nut, the punching waste punch 63 included in the punching die 6 of the seventh die 4 punches downward from the orifice of the first blind hole 13 to separate the waste 15 between the first blind hole 13 and the second blind hole 14 from the intermediate member of the rivet nut, so that the first blind hole 13 and the second blind hole 14 are communicated to obtain the second inner hole 22 and the third inner hole 23 of the rivet nut.

[0082] Please refer to Figure 2, specifically, the blind rivet nut provided in this embodiment includes a rod portion 11 and a head flange 12 fixedly connected to one end of the rod portion 11. The blind rivet nut is provided with an inner hole penetrating through the head flange 12 and the rod portion 11 along its axial direction. The inner hole at least includes a first inner hole 21, a second inner hole 22, and a third inner hole 23. The first inner hole 21 penetrates through the head flange 12 and the rod portion 11. The second inner hole 22 is connected between the first inner hole 21 and the third inner hole 23. Among them, the aperture of the third inner hole 23 gradually decreases from the end of the rod portion 11 away from the head flange 12 towards the head flange 12. The apertures of the second inner hole 22 and the third inner hole 23 are both smaller than the aperture of the first inner hole 21. The inner wall of the second inner hole 22 has threads formed by tapping. A chamfer 24 is also formed at the end of the rod portion 11 away from the head flange 12.

[0083] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or perform equivalent replacements for some of the technical features. Any changes, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A forming method of a blind rivet nut, the blind rivet nut comprising a rod portion and a head flange fixedly connected to one end of the rod portion, the blind rivet nut being provided with an inner hole penetrating through the head flange and the rod portion along its axial direction, the inner hole at least including a first inner hole, a second inner hole and a third inner hole that are sequentially communicated, the aperture of the third inner hole tapering from the end of the rod portion away from the head flange towards the head flange, and the apertures of the second inner hole and the third inner hole being smaller than the aperture of the first inner hole, characterized in that, The steps include: Cutting the wire to form a predetermined blank; The preset blank is subjected to upsetting and shaping to form a first preset blank; The first preset blank is subjected to upsetting and shaping to form a second preset blank; Forming a preset flange and a preset stem from the second preset blank, and forming a head fixed point in the preset flange; Extruding the first hole section of the first blind hole through the head at a fixed point in the preset flange to obtain the first inner hole; The preset rod is extruded from one end thereof away from the preset flange to form a second blind hole, and the first blind hole is punched to form a second hole section connected to the first hole section; wherein, The diameter of the second blind hole gradually decreases from the end of the preset rod away from the preset flange toward the preset flange; the bottom diameter of the second blind hole is smaller than the diameter of the first hole section; the diameter of the second hole section is smaller than the bottom diameter of the second blind hole; Finishing the preset flange and the preset stem to form the head flange and the stem to obtain an intermediate piece of the rivet nut; Separating the waste material between the first blind hole and the second blind hole from the middle piece of the rivet nut, so that the first blind hole and the second blind hole are connected to obtain the second inner hole and the third inner hole; The preset rivet nut formed with the second inner hole and the third inner hole is subjected to heat treatment, tapping and electroplating to obtain a finished rivet nut.

2. An intermediate member of a blind rivet nut, characterized in that, include: A body, the body comprising a rod and a head flange fixedly connected to one end of the rod; The body is concentrically provided with a first blind hole and a second blind hole along its axial direction, wherein the first blind hole is formed by an end surface of the head flange facing away from the rod portion and is recessed inwardly, and the second blind hole is formed by an end surface of the rod portion facing away from the head flange and is recessed inwardly; wherein, The first blind hole at least comprises a first hole segment and a second hole segment, and the second hole segment is located between the first hole segment and the second blind hole in the axial direction of the body; The diameter of the second blind hole gradually decreases from the end of the rod portion away from the head flange toward the head flange; The bottom diameter of the second blind hole is smaller than the hole diameter of the first hole segment and larger than the hole diameter of the second hole segment.

3. The intermediate member of the blind rivet nut according to claim 2, characterized in that, The bottom diameter of the second blind hole is 1.0 mm to 2.0 mm larger than the hole diameter of the second hole section.

4. The intermediate member of the blind rivet nut according to claim 3, characterized in that The angle formed between the hole wall of the second blind hole and the axis of the body is 10°-60°.

5. The intermediate member of the blind rivet nut according to claim 2, characterized in that, The depth of the second blind hole is 0.1 mm-3.0 mm.

6. The middle piece of the blind rivet nut according to claim 2, characterized in that, The hole diameter of the second hole section is 0.1 mm-2.0 mm larger than the nominal diameter of the thread.

7. A forming device for a blind rivet nut, comprising a cold heading machine and a die assembly mounted on the cold heading machine, characterized in that, The mold assembly comprises: A first die, wherein the first die is used to perform upsetting and shaping on a preset blank to form a first preset blank; A second die, wherein the second die is used to perform upsetting and shaping on the second preset blank to form the second preset blank; A third mold, the third mold is used to form a preset flange and a preset rod portion of the second preset blank, and to form a head fixed point in the preset flange; A fourth die, the fourth die is used to extrude the first hole segment of the first blind hole through the head at a fixed point in the preset flange to obtain a first inner hole; The fifth die, which is used to extrude a second blind hole from one end of the preset rod portion away from the preset flange, and to extend the first hole section inward to form a second hole section; wherein, the aperture of the second blind hole tapers from one end of the preset rod portion away from the preset flange towards the preset flange; the bottom diameter of the second blind hole is smaller than the aperture of the first hole section; the diameter of the second hole section is smaller than the bottom diameter of the second blind hole; The sixth die, which is used for finishing the preset flange and the preset rod portion to form a head flange and a rod portion, thereby obtaining an intermediate member of the rivet nut; The seventh die, which is used to separate the waste material between the first blind hole and the second blind hole from the intermediate member of the rivet nut, and to connect the first blind hole and the second blind hole to obtain a second inner hole and a third inner hole.

8. The forming device of the rivet nut according to claim 7, wherein the first die, the second die, the third die, the fourth die, the fifth die, the sixth die and the seventh die all comprise a main die and a punching die arranged corresponding to the main die.

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