A double-sided pressure point square nut and its cold heading forming process

Abstract

This invention discloses a double-sided pressure-point square nut and its cold heading process. The square nut body of the double-sided pressure-point square nut has positioning holes, and concave pressure points are provided on both the upper and lower surfaces. The cold heading process of this double-sided pressure-point square nut includes a blanking process, a finishing process, a forming process, and a punching and blanking process. The finishing process completes the first shaping process through the U-shaped cavity bottom of the die assembly, and the second shaping process is completed through the U-shaped cavity bottom of the die assembly and four second large chamfers on each of the four edges. The upper and lower end faces of the finished blank are flat. The forming process uses a multi-layered structure of the front and rear punch cores from the first and second upsetting processes to eliminate the risk of material suction during unloading of the fourth blank after upsetting in the first upsetting process; and completes the third upsetting process through a combination structure of a plug component, a die core, a punch tube, and a core rod; thereby improving the recycling rate of the third upsetting die and reducing costs.

Description

Technical Field

[0001] This invention belongs to the field of fastener manufacturing technology, specifically relating to a double-sided pressure point square nut, its cold heading process, and combined mold. Background Technology

[0002] In the electricity meter manufacturing industry, under normal circumstances, the meter cover is fixed to the meter base by screwing in a sealing screw. The threaded structure on the meter base is often achieved by injection molding the meter base and then inserting a square nut with an interference fit to secure the meter cover to the meter body. With the development of the national economy, in order to solve the supply and demand contradiction of electricity supply at different times, the demand for and quality of electricity meters are increasing, making it increasingly urgent to increase the production and quality of square nuts.

[0003] To address the current shortage of square nuts, the industry has adopted a multi-station cold forging process. This process involves using wire to cold forge square nuts without pressure marks multiple times, and then pressing the marks onto the formed nuts using a punch press to achieve the final product appearance.

[0004] Currently, existing square nuts have a single-sided pressure point. In assembly line production, the orientation of the square nuts often needs to be considered and designed. Furthermore, to reduce the risk of reverse use during injection molding, a testing device needs to be designed, indirectly increasing production costs. Existing square nuts also suffer from limitations in pressure point size, leading to brittle fracture and cracking during forging. Additionally, in assembly line production, the limited processing speed of the punch press results in low production efficiency. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a double-sided pressure-point square nut and its cold-forging process. This invention's double-sided pressure-point square nut is particularly convenient for assembling the meter cover and the meter body, offering superior anti-loosening performance while reducing the frequency and cost of subsequent rust prevention, and decreasing labor input, thus lowering costs. The cold-forging process for the double-sided pressure-point square nut reduces steps and optimizes the process, greatly improving production efficiency and reducing potential defects in the stamping process. It also reduces mold wear costs and increases the frequency of use for high-cost molds.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A double-sided pressure point square nut includes a square nut body with a positioning hole on the square nut body, the positioning hole being a threaded hole located in the middle of the square nut body; the upper and lower surfaces of the square nut body are double pressure surfaces, and each double pressure surface is provided with a concave pressure point.

[0008] A cold heading process for a double-sided pressure-point square nut, wherein the double-sided pressure-point square nut is as described above; the process includes a blanking process, a finishing process, a forming process, and a punching and blanking process; the blanking process involves shearing coiled wire; the finishing process includes a first shaping process and a second shaping process; the forming process includes a first upsetting process, a second upsetting process, and a third upsetting process; wherein,

[0009] The first forming mold for the first forming process includes a first die assembly and a first punch; the die core of the first die assembly forms a U-shaped cavity bottom at the bottom; the first punch has a first inclined portion on its end face so that the end face of the first punch forms a frustum-shaped cone.

[0010] The second forming mold in the second forming process includes a second punch assembly and a second punch; the second punch adopts the same structure as the first punch; the punch core of the second punch assembly forms a U-shaped cavity bottom at its bottom, which is the same as the U-shaped cavity bottom of the first punch assembly. Furthermore, the four edges of the second four corner peripheral walls of the punch core are arc-shaped edges that connect with the U-shaped cavity bottom.

[0011] The first upsetting die for the first upsetting process includes a third die assembly, a third front punch, and a third rear punch. The third die assembly adopts the same die structure as the first die assembly for the first shaping process. The third front punch has two layers of core head structure protruding from its end face to form the third front punch core head. The third rear punch has one layer of core head structure protruding from its end face to form the third rear punch core head. The second upsetting die for the second upsetting process includes a fourth die assembly, a fourth front punch, and a fourth rear punch. The fourth die assembly adopts the same die structure as the first die assembly for the first shaping process. The fourth front punch has the same structure as the third front punch for the first upsetting process. The fourth rear punch has two layers of core head structure protruding from its end face to form the fourth rear punch core head. The third upsetting die for the third upsetting process includes a fifth punch assembly, a fifth front punch assembly, and a fifth rear punch; it also includes a cavity plug component, which is tightly fitted inside the punch core of the fifth punch assembly to form the cavity bottom of the punch core; the upper end face of the cavity plug component is provided with multiple lower protrusions, and the upper end face with multiple lower protrusions corresponds to the lower end face of the fifth blank to be processed; the punch core is a tungsten steel component, and the cavity plug component is a high-speed steel component; the fifth front punch assembly includes a punch tube, in which a mandrel is tightly fitted; the punch tube is a high-speed steel component, and the lower end face of the punch tube is distributed with multiple upper protrusions, and the lower end face with multiple upper protrusions corresponds to the upper end face of the fifth blank to be processed;

[0012] The portion of the mandrel that protrudes from the punch tube forms the fifth front punch mandrel head;

[0013] The fifth rear punch has a protruding core structure on its end face, forming the core of the fifth rear punch.

[0014] The cold heading process for a double-sided pressure point square nut, as described above, involves a coiled wire with four corners. The cross-side dimensions of this coiled wire are smaller than the cross-side dimensions of the second blank formed after the first shaping process. The cutting tool used in the blanking process includes an outer blade and an inner blade holder assembly. The outer blade first cuts from the opposite corners of the coiled wire.

[0015] The cold heading process for a double-sided pressure point square nut, as described above, includes a punching die for the punching and blanking process, comprising a punching punch, a punching die core assembly, and a stripper plate assembly. The punching die core assembly has a protruding locking point on the upper part of the punching die core cavity wall. The stripper plate assembly is a rotating disc with multiple stripping through holes evenly distributed on it. The distance between the lower end face of the stripper plate assembly and the upper end face of the punching die core assembly is greater than the height of the double-sided pressure point square nut.

[0016] As described above, in the cold heading process of a double-sided pressure point square nut, the bottom of the U-shaped cavity is composed of the four corner bottom surfaces of the die core and four large chamfers provided along the four edges of the four corner bottom surfaces. The large chamfers are inclined edges that slope inward from the four corner peripheral walls of the die core towards the four corner bottom surfaces, and the angle of the inclined edges is 30±5°.

[0017] In the cold heading process of a double-sided pressure point square nut as described above, the first inclined portion of the first punch is formed by tilting downward from the first outer edge of the end face toward the first middle part of the end face, and the angle of the first inclined portion is 6 to 10°.

[0018] In the cold upsetting process of a double-sided pressure point square nut as described above, the length of the front punch of the third front punch is 0.55-0.65 times the depth of the countersunk hole of the sixth blank after the third upsetting process; the length of the rear punch of the third rear punch is 0.25-0.35 times the depth of the countersunk hole of the sixth blank after the third upsetting process; and the length of the front punch of the third front punch is 0.65 times the depth of the countersunk hole of the sixth blank after the third upsetting process. The length of the fourth rear punch is 0.70 times the depth of the sixth blank countersunk hole H2 after the third upsetting process; the length of the fifth front punch is 1.45-1.55 mm; the length of the fifth rear punch is 1.40-1.50 mm.

[0019] In the cold heading process of a double-sided pressure point square nut as described above, a groove is provided between the punch tube and the mandrel.

[0020] The technical solution provided above has the following beneficial effects:

[0021] First, the double-sided pressure point square nut of this invention optimizes the existing single-sided square nut by designing the upper and lower surfaces of the double-sided pressure point structure, which objectively reduces the customer's design considerations for orientation selection, and reduces the customer's assembly defect rate and design cost.

[0022] Secondly, in the finishing process of the cold heading forming process of this invention, the first shaping process is completed through the U-shaped cavity bottom of the die assembly. This allows for greater compression and deformation of the shearing tears (and even burrs and sharp angles) generated at the cut surface of the blank after cutting, thereby eliminating these burrs and sharp angles and making the blank inside the die core more uniform and flat. Therefore, the finishing effect on the blank is better.

[0023] Thirdly, in the finishing process of the cold heading forming process of this invention, the second shaping process is completed by setting four second large chamfers on the bottom of the U-shaped cavity of the die assembly and each of the four edges. The first punch with the truncated cone end face can ensure that the upper and lower end faces of the finished blank are flat, which meets the special requirement that the upper and lower end faces of the square nut for the meter have contact conductivity. It is impossible to achieve the same flatness on both sides.

[0024] Fourth, in the forming process of the cold heading process of this invention, the two key processes of nut forming and pressing are combined simultaneously in the production process, reducing the number of processes, optimizing the process, greatly improving production efficiency, and also reducing the adverse risks that may exist in the stamping process.

[0025] Fifth, in the forming process of the cold heading forming process of the present invention, a combination structure of cavity plug component and die core, and a combination structure of punch tube and mandrel are adopted. At the same time, in order to realize the square nut of the product, the key mold structure adopts a combination structure, making full use of material properties, reducing mold wear and the risk of breakage, so as to improve the recycling rate of the third heading die and reduce costs.

[0026] Sixth, in the forming process of the cold heading process of the present invention, the multi-layer structure design of the front and rear punch cores of the first and second heading processes can eliminate the risk of material suction during the unloading of the fourth blank after the first heading process.

[0027] Seventh, the cross-side dimensions of the coiled wire selected in this invention are smaller than the cross-side dimensions of the second blank after the first shaping process, so as to reserve sufficient upsetting allowance for the first blank transferred to the first shaping process, while also taking into account the fact that the cross-side dimensions of the second blank cannot be sufficiently attached to the cavity wall of the first die assembly, which would lead to the phenomenon that the second blank A2 after the first shaping process is not clamped stably.

[0028] Eighth, in the punching and blanking process of the cold heading forming process of the present invention, the punching die core assembly is equipped with a locking protrusion and a stripping disc assembly, which enables the smooth and orderly blanking of the double-sided pressing point square nut of the present invention. Attached Figure Description

[0029] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings:

[0030] Figure 1.1 This is a three-dimensional structural diagram of the invention of the double-sided pressure point square nut;

[0031] Figure 1.2 This is a schematic diagram of the main structure of the invention of the double-sided pressure point square nut;

[0032] Figure 1.3 This is a side view of the invention of the double-sided pressure point square nut;

[0033] Figure 2.1 This is a schematic diagram of the product structure of the cold heading process of the present invention;

[0034] Figure 2.2 This is a schematic diagram of the product structure of the cold heading process of the present invention (Figure 2).

[0035] Figure 3.1 This is a three-dimensional structural diagram of the cutting tool in the material feeding process of the present invention;

[0036] Figure 3.2 This is a cross-sectional view of the cutting tool in the material feeding process of this invention.

[0037] Figure 4.1 This is a cross-sectional structural schematic diagram of the first shaping mold in the first shaping process of the present invention;

[0038] Figure 4.2 This is a three-dimensional exploded view of the first shaping mold in the first shaping process of the present invention;

[0039] Figure 4.3 This is a three-dimensional structural schematic diagram of the first punching die assembly of the present invention;

[0040] Figure 4.4This is a three-dimensional structural schematic diagram of the first punch of the present invention;

[0041] Figure 5.1 This is a cross-sectional view of the second shaping mold in the second shaping process of the present invention.

[0042] Figure 5.2 This is a three-dimensional exploded view of the second shaping mold in the second shaping process of the present invention;

[0043] Figure 5.3 This is a three-dimensional structural schematic diagram of the second punching die assembly of the present invention;

[0044] Figure 6.1 This is a cross-sectional view of the first upsetting die for the first upsetting process of this invention.

[0045] Figure 6.2 This is a three-dimensional exploded view of the first upsetting die for the first upsetting process of this invention;

[0046] Figure 6.3 This is a partial three-dimensional structural schematic diagram of the third front punch 420 of the present invention;

[0047] Figure 6.4 This is a partial three-dimensional structural schematic diagram of the third rear punch of the present invention;

[0048] Figure 7.1 This is a cross-sectional view of the second upsetting die used in the second upsetting process of this invention.

[0049] Figure 7.2 This is a three-dimensional exploded view of the second upsetting die for the second upsetting process of the present invention;

[0050] Figure 8.1 This is a cross-sectional view of the third upsetting die in the third upsetting process of the present invention.

[0051] Figure 8.2 This is a three-dimensional exploded view of the third upsetting die for the third upsetting process of this invention.

[0052] Figure 8.3 This is a two-dimensional exploded view of the third upsetting die in the third upsetting process of this invention;

[0053] Figure 9.1 This is a cross-sectional structural schematic diagram of the punching die for the punching and blanking process of the present invention;

[0054] Figure 9.2 This is a three-dimensional exploded view of the punching die of the present invention. Detailed Implementation

[0055] To make the technical problems, solutions, and beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of the invention.

[0056] Unless otherwise expressly defined, the use of terms such as "first," "second," or "third" in the claims, description, and accompanying drawings of this invention is for distinguishing different objects and not for describing a specific order.

[0057] Unless otherwise expressly defined, in the claims, description, and accompanying drawings of this invention, the use of directional terms such as "center," "lateral," "longitudinal," "horizontal," "vertical," "top," "bottom," "inner," "outer," "upper," "lower," "front," "rear," "left," "right," "clockwise," and "counterclockwise" to indicate orientation or positional relationships is based on the orientation and positional relationships shown in the accompanying drawings and is only for the convenience of describing the invention and simplifying the description, and is not intended to indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as limiting the specific scope of protection of this invention.

[0058] Unless otherwise expressly defined, the terms "fixed connection" or "fixed connection" used in the claims, description and drawings of this invention should be interpreted broadly to refer to any connection in which there is no displacement or relative rotation relationship between the two parties, including non-removable fixed connection, detachable fixed connection, integral connection and fixed connection by other means or components.

[0059] In the claims, description and accompanying drawings of this invention, the terms "comprising," "having," and variations thereof are used to mean "including but not limited to."

[0060] Now combined Figures 1.1 to 9.2 This invention describes a double-sided pressure point square nut and its cold forging process.

[0061] This invention relates to a double-sided pressure-point square nut, which is particularly suitable for fastening the meter cover to the meter body. See also... Figures 1.1 to 1.3The double-sided pressure point square nut A7 includes a square nut body with a positioning hole A701 on it. The positioning hole A701 is a threaded hole located in the middle of the square nut body and extends through the upper and lower surfaces A702 and A703 of the square nut body. The upper and lower surfaces A702 and A703 of the square nut body are double pressure surfaces, each with a recessed pressure point A704. When the double-sided pressure point square nut is installed into the meter base, both the upper and lower surfaces A702 and A703 can serve as contact surfaces with the meter base.

[0062] See Figures 2.1 to 2.2 The cold heading process of the double-sided pressure point square nut of the present invention includes a blanking process S1, a finishing process, a forming process, and a punching and blanking process S7.

[0063] The blanking process S1 cuts the coiled wire 1000; the finishing process includes a first shaping process S2 and a second shaping process S3; effectively shaping the blank. The forming process includes a first upsetting process S4, a second upsetting process S5 and a third upsetting process S6; corresponding to the fourth blank A4, upsetting the front countersunk hole A401 and the rear countersunk hole A402 of the fourth blank A4, upsetting the front countersunk hole A501 and the rear countersunk hole A502 of the fifth blank A5, and upsetting the front countersunk hole A601 and the rear countersunk hole A602 of the sixth blank A6. The punching and blanking process S7 punches out the positioning hole A701 on the blank and completes the blanking process.

[0064] The blanking process involves cutting the straightened coiled wire into segments to obtain a blank of a certain volume. The coiled wire formed by the wire processing technology is a four-cornered wire with four rounded corners.

[0065] See Figure 3.1 and Figure 3.2 The cutting tool 100 used in the blanking process S1 includes an outer blade 110 and an inner blade holder assembly 120, wherein the outer blade 110 is movable. A ratchet mechanism in the feeding system precisely controls the feed length of the coiled wire. The outer blade 110 performs a shearing motion relative to the inner blade holder assembly 120, precisely cutting a section of the first blank A1 from the coiled wire. The outer blade 110 first cuts diagonally from the coiled wire, which reduces wire deformation caused by the shearing motion.

[0066] The inner blade assembly 120 is closed, but the outer blade 110 is open. Therefore, during the cutting process of the coiled wire 1000, the coiled wire will twist and deform towards the "open side," meaning the first blank A1 after cutting is irregular. Furthermore, after the first blank A1 is cut, shearing tears will appear at the cut surface, and even burrs and sharp angles may appear, affecting the quality of subsequent products. Therefore, the opposite side dimensions a and b of the coiled wire 1000 selected in this invention are smaller than the opposite side dimensions of the second blank A2 formed in the first shaping process S2. This provides sufficient upsetting allowance for the first blank A1 transferred to the first shaping process S2, while also preventing the opposite sides of the second blank A2 from not being able to properly adhere to the cavity wall of the first die assembly 200, which would lead to unstable clamping of the second blank A2 formed in the first shaping process S2. In this embodiment, the opposite side dimensions a and b of the selected coiled wire 100 are 0.1-0.4 mm smaller than the opposite side dimensions of the second blank A2. In the first shaping process S2, the first blank A1 is squeezed and deformed by the closed die core of the first shaping mold 200, so that it fills the die core as much as possible, thereby obtaining a more regular blank.

[0067] See Figures 4.1 to 4.4 The first shaping mold 200 of the first shaping process S2 includes a first punch assembly 210 and a first punch 220.

[0068] The die core of the first die assembly 210 forms a U-shaped cavity bottom, which is composed of the first four corner bottom surfaces 211 of the die core and four first large chamfers 212 provided along the four edges of the first four corner bottom surfaces 211. The first large chamfer 212 is an inclined edge that slopes inward from the first four corner peripheral walls 213 of the die core towards the first four corner bottom surfaces 211, and the angle of the inclined edge is 30±5°. The 30±5° inclined edge design of the U-shaped cavity bottom can extrude a larger rounded corner at the outer end of the blank, thereby extruding and removing the larger sharp corners generated by the first blank A1 cut in the blanking process S1.

[0069] The first punch 220 has a first inclined portion 223 on its end face. This first inclined portion 223 is formed by sloping downwards from the first outer edge 221 of the end face towards the first middle portion 222. The angle of the first inclined portion 223 is 6-10°, preferably 8°, to form a frustum-shaped end face of the first punch 220. The design of the first inclined portion 223 on the end face of the first punch 220 not only prevents the end face of the punch from prematurely contacting the gap between the die core of the first die assembly 210 and the first punch 220, thus avoiding the formation of burrs on the blank, but also ensures that when the first punch 220 contacts the original blank, a certain gap exists between the frustum-shaped end face of the first punch 220 and the end face of the blank due to the presence of this inclined portion 223. When the first punch 220 extrudes the blank, the frustum-shaped end face gradually contacts the end face of the blank. As the extrusion deformation process proceeds, the contact area increases until complete contact is achieved. Combined with the first punch 220 die core at the bottom of the shaped cavity, it can be ensured that the two end faces of the second blank A2 are flat after shaping, thus achieving a better finishing effect on the blank.

[0070] Conversely, if the end face of the first punch 220 does not have the 8° bevel 223, or if the end face of the first punch 220 is a flat surface, then the end face of the punch will initially contact the original blank with an excessively large or even the largest flat surface. According to the principle of material extrusion deformation, when the material is extruded in the closed die core, it will extend and deform (flow) along the contact surface in the direction of least resistance. That is, the material will extend outward along the end face of the punch until the blank is upsetting and completely adheres to the die wall. Then, it will begin to be extruded and extended in the reverse direction into the gap between the punch and the die core, and finally, burrs will be extruded from this gap.

[0071] See Figures 5.1 to 5.3 The second shaping mold 300 of the second shaping process S3 includes a second punch assembly 310 and a second punch 320.

[0072] The second punch 320 adopts the same structure as the first punch 220. Specifically, the end face of the second punch 320 has a second inclined portion 323, which is formed by tilting downward from the second outer edge 321 of the end face towards the second middle portion 322 of the end face. The angle of the second inclined portion 323 is 6 to 10°, preferably 8°, so that the end face of the second punch 320 forms a frustum-shaped cone.

[0073] The die core of the second die assembly 310 forms a U-shaped cavity bottom at its bottom, identical to the U-shaped cavity bottom of the first die assembly 210. Specifically, this U-shaped cavity bottom is composed of the second four-corner bottom surface 311 of the die core and four second large chamfers 312 provided along each of the four edges of the four-corner bottom surface 311. The second large chamfer 312 is an inclined edge that slopes inward from the second four-corner peripheral wall 313 of the die core towards the second four-corner bottom surface 311, with an angle of 30±5°. Furthermore, the four edges of the second four-corner peripheral wall 313 of the die core are arc-shaped edges 314 that connect with the U-shaped cavity bottom, further ensuring that the diagonals of the third blank A3 after the second shaping process S3 are uniform, further reducing the impact of blank deformation caused by the shearing process S1.

[0074] See Figures 6.1 to 6.4 The first upsetting die 400 of the first upsetting process S4 includes a third punch assembly 410, a third front punch 420, and a third rear punch 430.

[0075] The third die assembly 410 adopts the same die structure as the first die assembly 210 in the first shaping process S2. Specifically, the die core of the third die assembly 410 forms a U-shaped cavity bottom, which is composed of the third and fourth corner bottom surfaces 411 of the die core and four third large chamfers 412 provided along the four edges of the third and fourth corner bottom surfaces 411. The third large chamfer 412 is an inclined side that slopes inward from the third and fourth corner peripheral wall 413 of the die core towards the third and fourth corner bottom surface 411, and the upper angle of the inclined side is 30±5°.

[0076] The third front punch 420 has two layers of core head structure protruding from its end face, forming the third front punch core head 421; the third rear punch 430 has one layer of core head structure protruding from its end face, forming the third rear punch core head 431. The length L1 of the front punch core head 421 is 0.55-0.65 times the depth H1 of the countersunk hole A601 of the sixth blank after the third upsetting process S6; the length L2 of the rear punch core head 431 is 0.25-0.35 times the depth H2 of the countersunk hole A601 of the sixth blank after the third upsetting process S6. This eliminates the risk of material suction during unloading of the fourth blank A4 after the first upsetting process S4.

[0077] See Figure 7.1 and Figure 7.2 The second upsetting die 500 of the second upsetting process S5 includes a fourth punch assembly 510, a fourth front punch 520, and a fourth rear punch 530.

[0078] The fourth die assembly 510 adopts the same die structure as the first die assembly 210 in the first shaping process S2. Specifically, the die core of the third die assembly 510 forms a U-shaped cavity bottom at the bottom. This U-shaped cavity bottom is composed of the fourth four-corner bottom surface 511 of the die core and four fourth large chamfers 512 provided along the four edges of the fourth four-corner bottom surface 511. The fourth large chamfer 512 is an inclined side that slopes inward from the fourth four-corner peripheral wall 513 of the die core towards the fourth four-corner bottom surface 511, and the angle of the inclined side is 30±5°.

[0079] The fourth front punch 520 adopts the same structure as the third front punch 420 in the first upsetting process S4. Specifically, the fourth front punch 520 has two layers of core head structure protruding from its end face to form the fourth front punch core head 521. The length of the front punch core head 521 is 0.65 to 0.70 times the depth H1 of the countersunk hole A601 of the sixth blank after the upsetting process S6.

[0080] The fourth rear punch 530 has two layers of core head structure protruding from its end face to form the fourth rear punch core head 531. The length of the fourth rear punch core head 531 is 0.75 to 0.85 times the depth H2 of the countersunk hole A602 of the sixth blank after the third upsetting process S6.

[0081] The fourth front punch 520 and the fourth rear punch 530 adopt a two-layer core structure to deepen the two-layer chamfers processed on the fourth blank A4 after the first upsetting process S4, effectively solving the problem of the fourth front punch 520 and the fourth rear punch 530 sucking up material when the fifth blank A5 is unloaded after the second upsetting process S5.

[0082] See Figures 8.1 to 8.3 The third upsetting die 600 of the third upsetting process S6 includes a fifth punch assembly 610, a fifth front punch assembly 620 and a fifth rear punch 630, and also includes a cavity plug 640, which is tightly fitted inside the punch core 611 of the fifth punch assembly 610 to form the cavity bottom of the punch core 611.

[0083] The upper surface of the plug component 640 is provided with multiple lower protrusions 641, which correspond to the lower surface of the fifth blank A5 to be processed, forming the fifth four-corner bottom surface of the die core 611. The die core 611 is a tungsten carbide component, and the plug component 640 is a high-speed steel component with good toughness. During molding, in order to avoid the risk of voids and cracks during mold processing, which would further reduce the impact toughness of the tungsten carbide mold, this invention adopts a combined structure of the plug component 640 and the die core 611. The plug component 640, which is subject to greater impact force and the greatest stress concentration, is designed as a high-speed steel material with good toughness and a certain degree of hardness. Only the plug component 640 can be replaced, avoiding the scrapping of the entire set once the mold is damaged, improving the recycling rate of the die core 611 and reducing costs.

[0084] The fifth front punch assembly 620 includes a punch tube 621, within which a mandrel 622 is tightly fitted. A groove is provided between the punch tube 621 and the mandrel 622, located on the circumferential sidewall of the mandrel 622, facilitating oil drainage and preventing oil expansion and breakage. The punch tube 621 is a high-speed steel component, and its lower end face has multiple upper protrusions 621A, corresponding to the upper end face of the fifth blank A5 to be processed. When the fifth front punch assembly 620 and the fifth rear punch 630 cooperate to punch the fifth blank A5, concave pressing points can be simultaneously pressed onto both the upper and lower surfaces of the fifth blank A5, forming a sixth blank A6. The fifth front punch assembly 620 of the present invention adopts a combination structure of punch tube 621 and mandrel 622. Only punch tube 621 can be replaced, so as to avoid the entire assembly being scrapped once the fifth front punch assembly 620 is damaged, thereby improving the utilization rate of mandrel 622 and reducing costs.

[0085] The portion of the mandrel 622 that protrudes from the punch tube 621 forms the fifth front punch head 622A. The length of the front punch head 622A is 1.45-1.55 mm.

[0086] The fifth rear punch 630 has a protruding core structure on its end face, forming a fifth rear punch core 631. The length of the fifth rear punch core 631 is 1.40-1.50mm. The allowance thickness after the S7 through hole is controlled to be 0.20-0.30 times the total thickness to meet the design principle of "iron grain thickness," that is, the allowance thickness is designed to be approximately 0.20-0.30 times the total thickness, i.e., "allowance thickness" ≈ 0.25 * total thickness. This avoids abnormal punch life caused by collision between the core 622 and the fifth rear punch 630, effectively allows the excess material to be smoothly removed, and makes the double-sided pressure point square nut A7 smooth and neat after the S7 through hole is completed in the punching and blanking process.

[0087] See Figure 9.1 and Figure 9.2 The punching die 700 of the punching and blanking process S7 includes a punching punch 710, a punching die core assembly 720 and a stripper plate assembly 730.

[0088] The upper part of the punching die assembly 720 has a protruding locking point 721 on the upper part of the punching die cavity wall. After the punching and blanking process S7 is completed, the excess material of the double-sided pressing square nut A7 is stuck on the locking point of the punching die and arranged in sequence. As more and more excess material accumulates in the punching die, the previous excess material is pushed towards the punching die holder. There is no locking point on the lower part of the punching die cavity wall, which is in clearance fit with the excess material, so the excess material can be freely removed at this point.

[0089] The stripper disc assembly 730 is a rotating disc with multiple stripping through holes 731 evenly distributed on it. The distance between the lower end face of the stripper disc assembly 730 and the upper end face of the punching die assembly 720 is greater than the height of the double-sided pressure point square nut A7.

[0090] The sixth blank A6 is fed by a robot to the punching die assembly 720 of the punching and blanking process S7, so that the blank surface of the sixth blank A6 is attached to the upper end face of the punching die assembly 720. After the punching punch 710 passes through one of the stripping through holes 731 of the stripping disc assembly 730, it punches the sixth blank A6 with a reserved allowance A603, and pushes the excess material into the protrusion 701 inside the punching die assembly 720, which is then locked. The punching punch 710 carries the double-sided pressure point square nut A7 after the through hole is completed and moves backward until the upper end face of the double-sided pressure point square nut A7 is attached to the lower end face of the stripping disc assembly 730. Due to the obstruction of the stripping disc assembly 730, the double-sided pressure point square nut A7 separates from the punching punch 710. After separation, the double-sided pressure point square nut A7 falls down due to gravity.

[0091] The foregoing description illustrates and describes preferred embodiments of the present invention. As previously stated, it should be understood that the present invention is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. It can be used in various other combinations, modifications, and environments, and can be altered within the scope of the inventive concept described herein through the foregoing teachings or techniques or knowledge in related fields. Any modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the present invention should be within the protection scope of the appended claims.

Claims

1. A cold heading process for a double-sided pressure point square nut, characterized in that the double-sided pressure point square nut includes a square nut body, on which a positioning hole (A701) is provided, the positioning hole (A701) being a threaded hole located in the middle of the square nut body; the upper and lower surfaces (A702, A703) of the square nut body are double pressure surfaces, each with a recessed pressure point (A704); the cold heading process for the double-sided pressure point square nut includes a blanking process (S1), a finishing process, a forming process, and a punching and blanking process (S7); the blanking process (S1) involves shearing coiled wire; the finishing process includes a first shaping process (S2) and a second shaping process (S3); the forming process includes a first upsetting process (S4), a second upsetting process (S5), and a third upsetting process (S6); wherein, The first shaping mold (200) of the first shaping process (S2) includes a first die assembly (210) and a first punch (220); the die core of the first die assembly (210) forms a U-shaped cavity bottom at the bottom; the first punch (220) has a first inclined portion (223) on its end face so that the end face of the first punch (220) forms a frustum-shaped cone. The second shaping mold (300) in the second shaping process (S3) includes a second punch assembly (310) and a second punch (320); the second punch (320) adopts the same structure as the first punch (220); the punch core of the second punch assembly (310) forms a U-shaped cavity bottom at the bottom that is the same as the U-shaped cavity bottom of the first punch assembly (210), and the four edges of the second four corner peripheral walls (313) of the punch core are arc-shaped edges (314) that connect with the U-shaped cavity bottom; The first upsetting die (400) for the first upsetting process (S4) includes a third die assembly (410), a third front punch (420), and a third rear punch (430); the third die assembly (410) adopts the same die structure as the first die assembly (210) for the first shaping process (S2); the third front punch (420) has two layers of core head structure protruding from its end face to form a third front punch core head (421); the third rear punch (430) has one layer of core head structure protruding from its end face to form a third rear punch core head (431); The second upsetting die (500) in the second upsetting process (S5) includes a fourth die assembly (510), a fourth front punch (520), and a fourth rear punch (530). The fourth die assembly (510) adopts the same die structure as the first die assembly (210) in the first shaping process (S2). The fourth front punch (520) adopts the same structure as the third front punch (420) in the first upsetting process (S4). The fourth front punch (520) has two layers of core head structure protruding on its end face to form a fourth front punch core head (521). The fourth rear punch (530) has two layers of core head structure protruding on its end face to form a fourth rear punch core head (531). The third upsetting die (600) for the third upsetting process (S6) includes a fifth die assembly (610), a fifth front punch assembly (620), and a fifth rear punch (630); it also includes a plug member (640), which is tightly fitted into the die core (611) of the fifth die assembly (610) to form the cavity bottom of the die core (611); the upper end face of the plug member (640) is provided with a plurality of lower protrusions (641), and the upper end face with the plurality of lower protrusions (641) corresponds to the part to be processed. The fifth blank (A5) is provided on the lower end face; the die core (611) is a tungsten steel component, and the plug component (640) is a high-speed steel component; the fifth front punch assembly (620) includes a punch tube (621), in which a mandrel (622) is tightly fitted; the punch tube (621) is a high-speed steel component, and a plurality of upper protrusions (621A) are distributed on the lower end face of the punch tube (621), and the lower end face with the plurality of upper protrusions (621A) is provided corresponding to the upper end face of the fifth blank (A5) to be processed; The portion of the mandrel (622) that protrudes from the punch tube (621) forms the fifth front punch head (622A); The fifth rear punch (630) has a core head structure protruding from its end face, forming the fifth rear punch core head (631).

2. The cold heading process for a double-sided pressure point square nut as described in claim 1, characterized in that, The coiled wire is a four-cornered wire with four corners. The opposite side dimensions (a, b) of the coiled wire (1000) are smaller than the opposite side dimensions of the second blank (A2) formed after the first shaping process (S2). The cutting tool (100) used in the blanking process (S1) includes an outer blade (110) and an inner blade holder assembly (120). The outer blade (110) first cuts from the opposite corners of the coiled wire.

3. The cold heading process for a double-sided pressure point square nut as described in claim 1 or 2, characterized in that, The punching die (700) for the punching and blanking process (S7) includes a punching punch (710), a punching die core assembly (720), and a stripper plate assembly (730); the punching die core assembly (720) has a protruding locking point (721) on the upper part of the punching die core cavity wall; the stripper plate assembly (730) is a rotating plate with multiple stripping through holes (731) evenly distributed on it; and the distance between the lower end face of the stripper plate assembly (730) and the upper end face of the punching die core assembly (720) is greater than the height of the double-sided pressure point square nut (A7).

4. The cold heading process for a double-sided pressure point square nut as described in claim 1 or 2, characterized in that, The bottom of the cavity is composed of the four corner bottom surfaces of the die core and four large chamfers set along the four edges of the four corner bottom surfaces; the large chamfers are inclined sides that slope inward from the four corner peripheral walls of the die core to the four corner bottom surfaces, and the angle of the inclined side is 30±5°.

5. The cold heading process for a double-sided pressure point square nut as described in claim 3, characterized in that, The bottom of the cavity is composed of the four corner bottom surfaces of the die core and four large chamfers set along the four edges of the four corner bottom surfaces; the large chamfers are inclined sides that slope inward from the four corner peripheral walls of the die core to the four corner bottom surfaces, and the angle of the inclined side is 30±5°.

6. The cold heading process for a double-sided pressure point square nut as described in claim 4, characterized in that, The first inclined portion (223) of the first punch (220) is formed by tilting downward from the first outer edge (221) of the end face towards the first middle portion (222) of the end face, and the angle of the first inclined portion (223) is 6~10°.

7. The cold heading process for a double-sided pressure point square nut as described in claim 5, characterized in that, The first inclined portion (223) of the first punch (220) is formed by tilting downward from the first outer edge (221) of the end face toward the first middle portion (222) of the end face, and the angle of the first inclined portion (223) is 6~10°.

8. The cold heading process for a double-sided pressure point square nut as described in claim 1 or 2, characterized in that, The length (L1) of the third front punch mandrel (421) is 0.55-0.65 times the depth (H1) of the front countersunk hole (A601) of the sixth blank after the third upsetting process (S6); the length (L2) of the rear punch mandrel (431) is 0.25-0.35 times the depth (H2) of the rear countersunk hole (A602) of the sixth blank after the third upsetting process (S6); the length of the front punch mandrel (521) is 0.55-0.65 times the depth (H2) of the rear countersunk hole (A602) of the sixth blank after the third upsetting process (S6); 6) The depth (H1) of the countersunk hole of the sixth blank after upsetting (A601) is 0.65 to 0.70 times; the length of the rear punch of the fourth rear punch (531) is 0.75 to 0.85 times the depth (H2) of the countersunk hole of the sixth blank after upsetting (A602) in the third upsetting process (S6); the length of the front punch of the fifth front punch (622A) is 1.45-1.55 mm; the length of the rear punch of the fifth rear punch (631) is 1.40-1.50 mm.

9. The cold heading process for a double-sided pressure point square nut as described in claim 4, characterized in that, The length (L1) of the third front punch mandrel (421) is 0.55-0.65 times the depth (H1) of the front countersunk hole (A601) of the sixth blank after the third upsetting process (S6); the length (L2) of the rear punch mandrel (431) is 0.25-0.35 times the depth (H2) of the rear countersunk hole (A602) of the sixth blank after the third upsetting process (S6); the length of the front punch mandrel (521) is 0.55-0.65 times the depth (H2) of the rear countersunk hole (A602) of the sixth blank after the third upsetting process (S6); The depth (H1) of the countersunk hole of the sixth blank (A601) after upsetting (S6) is 0.65 to 0.70 times; the length of the rear punch of the fourth rear punch (531) is 0.75 to 0.85 times the depth (H2) of the countersunk hole of the sixth blank (A602) after upsetting (S6) in the third upsetting process; the length of the front punch of the fifth front punch (622A) is 1.45-1.55 mm; the length of the rear punch of the fifth rear punch (631) is 1.40-1.50 mm.

10. The cold heading process for a double-sided pressure point square nut as described in claim 1 or 2, characterized in that, A groove is provided between the punch tube (621) and the mandrel (622).

11. The cold heading process for a double-sided pressure point square nut as described in claim 3, characterized in that, A groove is provided between the punch tube (621) and the mandrel (622).

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