A combination punch that facilitates venting

Abstract

A combined punch for easy venting includes an inner punch and an outer punch. The inner punch includes a cylindrical inner punch body with a top plate at its rear end and an inner punch head at its front end for forming a tightening groove for screw heads. The outer punch includes a cylindrical outer punch body with an inner hole in its central axis. The inner punch body is interference-fitted into the inner hole, and the rear end of the outer punch body abuts against the top plate. The front end face of the inner punch body is aligned with the front end of the inner hole, and the front end of the outer punch body has a forming groove. The inner punch head and the forming groove together form a cavity. This invention forms a microscopic venting channel through the assembly gap between the inner and outer punches, effectively venting gas from the cavity during cold heading, avoiding the "bulging" and rounded corner phenomena caused by air compression, significantly improving the dimensional accuracy and edge clarity of the internal hexagonal tightening groove, and ensuring the forming quality and connection reliability of the screw head.

Description

Technical Field

[0001] This utility model relates to the field of bolt processing technology, and in particular to a combined punch that facilitates venting. Background Technology

[0002] Screw head tightening grooves include slotted, Phillips, square, and hexagonal types. Screws with hexagonal tightening grooves, such as socket head cap screws and countersunk head screws, are among the most widely used fasteners in the machinery industry. The head forming quality of these screws, especially the dimensional accuracy, form and position tolerances, and mechanical properties of the hexagonal tightening groove, directly affects the ease of assembly, the reliability of the connection, and the safety of use.

[0003] Currently, the main manufacturing process for this type of product is cold heading. In existing technologies, punches are mostly one-piece structures with a forming cavity at the front end, used to simultaneously form the outer contour of the screw head and the internal hexagonal tightening groove.

[0004] However, during the instantaneous impact of the punch on the blank to form the internal hexagonal tightening groove, the air inside the punch cavity must be rapidly and completely expelled. However, due to the high-speed compression between the punch and the blank, the air expulsion channel is easily blocked by the metal material itself, causing the air to be compressed and trapped inside the cavity. The compressed high-pressure air then acts in the opposite direction on the metal material that has not yet fully deformed, causing irregular expansion of the hexagonal hole wall, commonly known in the industry as "big belly." This results in the internal hexagonal groove having an excessively large opposite side dimension, failing the go / no-go gauge inspection and leading to product failure and scrap. Simultaneously, the compressed high-pressure air also causes the edges of the internal hexagonal tightening groove to form a rounded shape, making it prone to slippage with the wrench during use, failing to achieve the tightening torque required by the customer, resulting in connection failure and completely failing to meet usage requirements.

[0005] Therefore, in view of the shortcomings of the existing technology, it is necessary to design a combined punch that facilitates venting to solve the above problems.

[0006] It should be noted that the above introduction to the technical background is only for the purpose of providing a clear and complete explanation of the technical solution of this utility model and facilitating the understanding of those skilled in the art. It should not be assumed that the above content is known to those skilled in the art simply because it has been described in the background section of this utility model. Utility Model Content

[0007] To overcome the shortcomings of the prior art, the present invention aims to disclose a combined punch that facilitates venting.

[0008] This utility model discloses a combined punch that facilitates venting, comprising:

[0009] The inner punch includes a cylindrical inner punch body, a top plate at the rear end of the inner punch body, and an inner punch at the front end for forming a screw head tightening groove.

[0010] The outer punch includes a cylindrical outer punch body, which has an inner hole along its axis that mates with the inner punch body. The inner punch body is inserted into the inner hole with an interference fit, and the rear end of the outer punch body abuts against the top plate.

[0011] The front end face of the inner punch body is aligned with the front end of the inner hole, and the front end of the outer punch body is provided with a forming groove for forming the outer contour of the screw head. The inner punch and the forming groove together form a cavity for forming the screw head.

[0012] Preferred technical solution: The inner punch body is a cylindrical structure formed by centerless grinding, and the inner punch is a hexagonal punch used to form an inner hexagonal tightening groove.

[0013] Preferred technical solution: The inner hole is a cylindrical hole formed by wire cutting.

[0014] Preferred technical solution: The diameter of the inner punch body is 0.4 to 0.6 mm larger than the diagonal length of the hexagonal punch.

[0015] Preferred technical solution: The interference fit between the inner punch body and the inner hole does not exceed 0.02mm.

[0016] Preferred technical solution: The inner hole is a tapered hole whose diameter gradually increases from its front end to its rear end.

[0017] Preferred technical solution: The inner wall of the inner hole is provided with at least one first venting groove along its axial direction.

[0018] Preferred technical solution: The outer wall of the inner punch body is provided with at least one second venting groove along its axial direction.

[0019] Preferred technical solution: The inner edge of the rear end of the inner hole is chamfered.

[0020] Due to the application of the above technical solution, the beneficial effects of this utility model compared with the prior art are as follows:

[0021] This invention designs the punch as an inner and outer combined structure, utilizing the tiny gap at the assembly interface between the two to form an exhaust channel. This effectively avoids the problem of gas not being able to escape from the cavity during cold heading, thereby improving the forming accuracy of the screw head tightening groove, ensuring complete edges and corners, avoiding curvature, and thus improving the connection stability of the screw head during use. Attached Figure Description

[0022] To more clearly illustrate the specific embodiments of this utility model or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this utility model. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0023] Figure 1 This is a schematic diagram of the structure of a combined punch that facilitates venting according to the present invention;

[0024] Figure 2 This is a longitudinal sectional view of a combined punch for facilitating venting according to the present invention;

[0025] Figure 3 This is an exploded view of a combined punch for facilitating venting according to the present invention.

[0026] In the above attached figures, 1 is the inner punch; 11 is the inner punch body; 12 is the top plate; 13 is the inner punch head; 2 is the outer punch; 21 is the outer punch body; 22 is the inner hole; and 23 is the forming groove. Detailed Implementation

[0027] The following specific embodiments illustrate the implementation of this utility model. Those skilled in the art can easily understand other advantages and effects of this utility model from the content disclosed in this specification.

[0028] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be used interchangeably where appropriate for the purposes of describing embodiments of this application herein. Furthermore, the terms "comprising" and "having," and their synonyms, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0029] In this application, the terms "upper," "lower," "left," "right," "front," "back," "top," "bottom," "inner," "outer," "middle," "vertical," "horizontal," "lateral," and "longitudinal" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are primarily for the purpose of better describing this utility model and its embodiments, and are not intended to limit the indicated device, element, or component to having a specific orientation, or to be constructed and operated in a specific orientation.

[0030] Furthermore, in addition to indicating direction or positional relationship, some of the aforementioned terms may also have other meanings. For example, the term "above" may also be used in some cases to indicate a certain dependency or connection relationship. Those skilled in the art can understand the specific meaning of these terms in this utility model according to the specific circumstances.

[0031] Furthermore, the terms "installation," "setting," "equipped with," "connection," "linking," "fitting," and "fitting" should be interpreted broadly. For example, "connection" 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 a direct connection or an indirect connection through an intermediate medium, or it can be an internal connection between two devices, components, or parts. Similarly, "fitting" can mean completely or partially fitted. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0032] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0033] like Figure 1 , Figure 2 and Figure 3 As shown, this utility model discloses a combined punch for easy venting, including an inner punch 1 and an outer punch 2. The main components of this utility model will be described in detail below:

[0034] The inner punch 1 includes a cylindrical inner punch body 11 that has been precision machined by a centerless grinder. The rear end of the inner punch body 11 is provided with a top plate 12, and the front end is provided with an inner punch 13 for forming a screw head tightening groove.

[0035] The outer punch 2 includes a cylindrical outer punch body 21. The outer punch body 21 has an inner hole 22 that mates with the inner punch body 11 along its axis. The inner hole 22 is machined by wire cutting. The front end of the outer punch body 21 is provided with a forming groove 23 for forming the outer contour of the screw head. The inner punch 13 and the forming groove 23 together form a cavity for forming the screw head.

[0036] In use, the cylindrical inner punch body 11 of the inner punch 1 is pressed axially into the rear end inlet of the inner hole 22 of the outer punch 2. Because the inner hole 22 and the inner punch body 11 are designed with an interference fit, the force between the inner punch body 11 and the inner hole 22 gradually increases during the pressing process, ensuring a secure assembly. After pressing, the top plate 12 at the rear end of the inner punch 1 abuts tightly against the rear end face of the outer punch 2, thereby limiting and supporting the built-in inner punch axially and preventing it from moving backward during operation. Simultaneously, it is necessary to ensure that the front end face of the inner punch body 11 is strictly aligned with the front end face of the inner hole 22, forming a flat joint front working surface. Alternatively, subsequent grinding can ensure that the front end face of the punch body 11 is strictly aligned with the front end face of the inner hole 22.

[0037] The method and principle of this utility model are as follows: During cold heading, the combined punch and the metal blank are punched at high speed. Under great pressure, the blank flows into the cavity formed by the inner punch 13 and the forming groove 23, thereby forming the outer contour of the screw head and the inner hexagonal tightening groove.

[0038] During this process, the precise interference fit between the inner punch 1 and the outer punch 2 actually forms extremely small gap channels. These micro-gaps are large enough to allow air molecules to pass through under high pressure, but because they are so small, they effectively prevent metal material from flowing in and blocking the cavity during extrusion. The air trapped in the cavity is driven by pressure to flow backward along these micro-gaps between the outer wall of the inner punch body 11 and the inner wall of the inner hole 22, and finally escapes smoothly from the rear end of the punch to the outside of the mold. This avoids the high-pressure air being sealed in the cavity, thus eliminating the back expansion force caused by air compression. Therefore, the formed internal hexagonal tightening slot has straight walls without a "bulge" phenomenon, and the side dimensions are stable and meet the tolerance requirements. At the same time, the corners can be completely filled with metal material, forming clear and sharp edges, avoiding the formation of rounded corners, ensuring the engagement of the screw with the wrench during use, preventing slippage, and meeting the specified tightening torque requirements.

[0039] In some embodiments, such as Figure 1 , Figure 2 and Figure 3 As shown, the diameter of the inner punch body 11 is 0.4 mm larger than the diagonal length of the hexagonal punch. This prevents the metal squeezed out during the forming of the inner hexagonal tightening groove from entering the connection gap between the inner punch 1 and the outer punch 2 along the side wall of the hexagonal punch.

[0040] In some embodiments, such as Figure 1 , Figure 2 and Figure 3As shown, the inner hole 22 is a tapered hole with a diameter that gradually increases from its front end to its rear end, and the interference fit between the inner punch body 11 and the inner hole 22 does not exceed 0.02 mm. This tapered hole structure forms a natural diffusion channel. When gas flows from the narrow front space to the rear, the airflow velocity is smoothly reduced as the channel space gradually increases, which helps the gas to exit more smoothly and reduces the resistance to gas flow. In addition, the micro-tapering also slightly reduces the resistance when pressing the inner punch, making the assembly process easier to control.

[0041] Meanwhile, the inner edge of the rear end of the inner hole 22 is chamfered, which serves to guide and center the inner punch 1 during press-fitting, preventing damage to the surface of the inner punch body 11 or the interference fit surface; furthermore, it can serve as a collection port for the final gas outflow to the external space, optimizing gas outflow efficiency. By optimizing the shape of the airflow channel, the smoothness and stability of exhaust are further improved, while also taking into account the convenience and reliability of assembly.

[0042] In some embodiments, such as Figure 1 , Figure 2 and Figure 3 As shown, a first venting groove is formed along the axial direction of the inner wall of the inner hole 22; a second venting groove is formed along the axial direction of the outer wall of the inner punch body 11. These specially machined shallow grooves, together with the original micro-gaps, constitute a more efficient and unobstructed venting network. It provides a clear, low-resistance path for gas discharge, especially in high-volume, high-speed continuous production, ensuring that gas is instantly discharged during each impact molding. This further reduces the venting resistance inside the cavity, making the venting process faster and more thorough, providing a double guarantee for the continuous and stable production of high-quality products under high production cycles.

[0043] Finally, it should be noted that the above are merely preferred embodiments of the present utility model and are not intended to limit the present utility model. Although the present utility model 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 make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A combination piercing needle facilitating venting, characterized in that, include: The inner punch (1) includes a cylindrical inner punch body (11), the rear end of which is provided with a top plate (12), and the front end is provided with an inner punch (13) for forming a screw head tightening groove. The outer punch (2) includes a cylindrical outer punch body (21), the outer punch body (21) has an inner hole (22) that mates with the inner punch body (11) through its axis, the inner punch body (11) is inserted into the inner hole (22) with an interference fit, and the rear end of the outer punch body (21) abuts against the top plate (12); The front end face of the inner punch body (11) is aligned with the front end of the inner hole (22), and the front end of the outer punch body (21) is provided with a forming groove (23) for forming the outer contour of the screw head. The inner punch (13) and the forming groove (23) together form a cavity for forming the screw head.

2. The combination punch pin of claim 1, wherein: The inner punch body (11) is a cylindrical structure formed by centerless grinding, and the inner punch (13) is a hexagonal punch used to form an inner hexagonal tightening groove.

3. The combination punch pin of claim 2, wherein: The inner hole (22) is a cylindrical hole formed by wire cutting.

4. The combination punch pin of claim 3, wherein: The diameter of the inner punch body (11) is 0.4 to 0.6 mm larger than the diagonal length of the hexagonal punch.

5. The combination punch pin of claim 4, wherein: The interference fit between the inner punch body (11) and the inner hole (22) does not exceed 0.02 mm.

6. The combination punch pin of claim 1, wherein: The inner hole (22) is a tapered hole whose diameter gradually increases from its front end to its rear end.

7. The combination punch pin of claim 1, wherein: The inner wall of the inner hole (22) is provided with at least one first venting groove along its axial direction.

8. The combination punch pin of claim 1, wherein: The outer wall of the inner punch body (11) is provided with at least one second exhaust groove along its axial direction.

9. The combination piercing needle of claim 1, wherein: The inner edge of the rear end of the inner hole (22) is chamfered.

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