A flow-through screw and method of use thereof

Abstract

The application discloses a flow screw and a use method thereof in the technical field of threaded fasteners, and the flow screw comprises a screw body, the screw body is mainly composed of a screw rod segment and a screw cap segment integrally formed on the screw rod segment, the screw rod segment is sequentially provided with a threaded segment and a drill tip segment from top to bottom, the screw cap segment is mainly composed of a flange and an end head, the drill tip segment is provided with a conical surface for centering and guiding, and the end head is integrally formed with a protrusion for transmitting torque; the four-square conical tip structure formed by the four conical surfaces arranged on the drill tip segment can generate multi-point friction with the plate and rapidly generate heat to soften the base material at high speed, and the hot melting penetration is completed under the axial pressure, the bottom hole does not need to be pre-processed, the connecting process is simplified, and the hole drilling deflection problem is avoided.

Description

Technical Field

[0001] This invention relates to the field of threaded fastener technology, and in particular to a rotary screw and its method of use. Background Technology

[0002] With the advancement of lightweighting of new energy vehicle bodies, the demand for connecting high-strength steel, aluminum alloy and other metal sheets continues to increase. The hot-melt self-tapping fastening process, which does not require pre-drilled bottom holes and can be constructed on one side, has been widely used in the assembly of various sheet metal components due to its simplified process and high connection strength.

[0003] Existing flow drill screws rely on high-speed rotation and friction to generate heat and soften the plates to be connected. They can simultaneously complete drilling, internal thread extrusion molding, and locking, completing the entire connection process in one go, effectively improving the construction efficiency of plate assembly.

[0004] However, in actual use, this type of screw still has some prominent defects: On the one hand, the centering and guiding performance of the front drilling structure is insufficient, which easily leads to drilling deviation when working on high-strength hard plates. The plate's heat-melting softening efficiency is also low, directly resulting in poor forming accuracy and unstable meshing strength of the subsequent internal threads. On the other hand, the anti-torsion and anti-slip performance of the screw head's driving engagement structure is limited. Under the high-speed and high-torque conditions of servo tightening equipment, slippage and disengagement are likely to occur. At the same time, the transition structure design of the thread forming section is unreasonable, which easily leads to insufficient load-bearing strength of the formed thread, making it difficult to meet the connection reliability requirements under high-load conditions. Therefore, we urgently need a rotary screw and its usage method to solve the above problems. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a rotary screw that achieves pre-hole-free hot-melt centering drilling through the square conical tip structure of the drill tip section. It utilizes a large-diameter tapered thread section to progressively compress the softened base material for flanging to form a high-strength internal thread. A conical groove is provided at the bottom of the flange to accommodate the front flanging and ensure a tight fit, thereby completing the drilling, flanging, tapping, and locking processes in one go.

[0006] The objective of this invention is achieved as follows: it includes a screw body, which is mainly composed of a screw section and a nut section integrally formed on the screw section. The screw section is provided with a threaded section and a drill tip section from top to bottom. The nut section is mainly composed of a flange and an end. The drill tip section is provided with a tapered surface for centering and guidance. The end is integrally formed with a protrusion for transmitting torque.

[0007] Optionally, the major diameter of the external thread of the threaded section decreases tapered from top to bottom to form a progressive compression bearing engagement zone for the internal thread of the plate flange bushing.

[0008] Optionally, the conical surface is mainly composed of two sets of first conical surfaces and second conical surfaces. The first conical surfaces and the second conical surfaces are arranged in annular staggered arrangement along the axis of the screw section. The first conical surfaces and the second conical surfaces cooperate to form a square conical tip structure for softening the metal sheet.

[0009] Optionally, both sets of second cone surfaces are integrally formed with raised ridges, and the height of the arc point of the first cone surface is greater than the height of the raised ridge of the second cone surface.

[0010] Optionally, the bottom of the flange is provided with a tapered groove, and the angle between the inclined side of the tapered groove and the screw section is in the range of 45°-60°.

[0011] Optionally, the protrusion is mainly composed of an inner ring post and an outer ring post, the inner ring post and the outer ring post are integrally formed, and the inner ring post is provided with a groove for adapting to external equipment.

[0012] Optionally, the outer ring post is provided with arc-shaped grooves, and the number of arc-shaped grooves is at least six sets. The six sets of arc-shaped grooves are arranged equidistantly in a ring along their axis, and the six sets of arc-shaped grooves form a six-petal structure on the outer ring post to prevent slippage.

[0013] A method for using a rotary screw and its application includes the following steps:

[0014] S1: Clamping and alignment, aligning the protrusion at the end of the screw with the drive structure of the external tightening tool, so that the groove on the inner ring column matches the tool positioning structure, and the arc groove on the outer ring column engages with the tool drive tooth groove, aligning the drill tip with the preset penetration position of the metal plate to be connected.

[0015] S2: Pressing contact, applying axial pressure to the screw, causing the highest point of the arc of the first conical surface on the drill tip to abut against the surface of the plate;

[0016] S3: High-speed spinning hot melt, driving the screw to rotate at high speed around its own axis and continuously apply axial feed pressure, and through the friction between the first conical surface of the drill tip and the plate, the contact area of ​​the plate is heated and softened.

[0017] S4: Penetrating the forming bushing, the screw continues to be fed axially until the drill tip completely penetrates the plate. The heated and softened plate material is squeezed and extended to the back of the plate to form a cylindrical flanged bushing.

[0018] S5: Speed ​​reduction extrusion tapping, reduce screw speed and maintain axial feed, the external thread major diameter enters the flange bushing in a tapered decreasing thread section from top to bottom, continuously extruding the inner wall of the flange bushing, forming an internal thread on the inner wall of the flange bushing.

[0019] S6: The end face is fitted and locked. The screw continues to rotate and feed. The lower end face of the flange abuts against the surface of the plate. The tapered groove at the bottom of the flange accommodates the flange allowance on the front of the plate, completing the locking connection.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] 1. The rotary screw and its method of use are provided with a square cone tip structure consisting of two sets of first cone surfaces and two sets of second cone surfaces arranged in annular interlacing at the drill tip section. The second cone surface has a raised ridge, and the arc height of the first cone surface is higher than the height of the raised ridge. This can form a pre-loosening-deep grinding alternating friction mode during high-speed rotation, pre-peeling the plate and concentrating friction to generate heat, so that the base material is rapidly heated and softened. Under axial pressure, it can achieve near-chip-free hot melt penetration hole formation, eliminating the need for pre-drilling. Furthermore, the force balance of the circumferentially distributed cone surfaces suppresses swaying and ensures hole position accuracy.

[0022] 2. This type of rotary screw and its method of use involves setting the major diameter of the external thread of the threaded section to decrease in a tapered manner from top to bottom. After the flanged bushing is formed, the screw is introduced without resistance through the small diameter end thread. As it rotates and advances, it applies continuous radial extrusion from shallow to deep to the inner wall of the bushing, which is still in a softened state, gradually forming a full-tooth profile and uniform pitch internal thread, and forming a large-area helical surface contact engagement area, thereby improving the tensile strength, tooth engagement accuracy and anti-loosening performance of the threaded connection.

[0023] 3. This type of rotary screw and its usage method involves creating a tapered groove at the bottom of the flange with an angle of 45°-60° between the inclined edge and the axis of the screw section. During the locking stage, it accommodates a small amount of flange allowance on the front side of the plate. The inclined groove wall guides and gathers the flange allowance into the bottom of the groove and presses it against the mating surface, making the lower end face of the flange fit tightly against the plate, avoiding loose tightening. It also forms a through-type double-sided clamping structure with the flange bushing on the back, ensuring the stability of axial load and long-term service reliability. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0025] Figure 1 This is a first-view schematic diagram of the overall structure of a rotary screw.

[0026] Figure 2 This is a schematic diagram of the overall structure of a rotary screw from a second perspective.

[0027] Figure 3This is a third-view schematic diagram of the overall structure of a rotary screw.

[0028] Figure 4 This is a top view schematic diagram of a rotary screw.

[0029] Figure 5 This is a cross-sectional structural diagram of a rotary screw.

[0030] Figure 6 This is a schematic diagram of the convex ridge structure of a rotary screw.

[0031] Figure 7 This is a flowchart illustrating a method for using a rotary screw.

[0032] The following are marked in the diagram: 1. Screw body; 2. Threaded section; 3. Drill tip section; 4. Flange; 5. End; 6. Tapered surface; 7. Protrusion; 8. Tapered groove; 9. Inner ring post; 10. Outer ring post; 11. Groove; 12. Arc groove; 13. Raised ridge. Detailed Implementation

[0033] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] Example 1: As Figures 1-5 The rotating screw shown includes a screw body 1, which is mainly composed of a screw section and a nut section integrally formed on the screw section.

[0035] Here, the screw body 1 is made of high-strength alloy material and is integrally molded, so that there is no connection interface between the screw section and the nut section, avoiding assembly gaps and stress concentration, and improving the overall load-bearing capacity and fatigue life.

[0036] Furthermore, the integrally formed screw section and nut section obtain uniform core hardness and surface reinforcement layer after heat treatment, which can withstand the centrifugal force and axial feed pressure generated by high-speed rotation without deformation.

[0037] Furthermore, the transition area between the screw section and the nut section can be provided with rounded corners or tapered transitions to reduce abrupt changes in cross-section, improve torque transmission efficiency, and reduce notch sensitivity.

[0038] The screw section is provided with a threaded section 2 and a drill tip section 3 from top to bottom. The major diameter of the external thread of the threaded section 2 decreases in a tapered manner from top to bottom to form a progressive extrusion bearing engagement zone for the internal thread of the flange bushing of the plate.

[0039] Here, the major diameter of the external thread of thread segment 2 gradually decreases in the direction away from flange 4, forming a tapered external thread. When this tapered external thread enters the flange bushing, the minor diameter end thread is the first to contact the inner wall of the flange.

[0040] Furthermore, as the screw body 1 rotates and advances, the gradually increasing thread diameter continuously compresses the softened inner wall of the bushing, causing the metal material to gradually flow and form a tooth profile that closely fits the thread section 2, thus achieving progressive extrusion tapping without cutting.

[0041] Furthermore, the pitch of thread segment 2 remains constant, resulting in a uniform pitch and full tooth profile in the formed internal thread, forming a long surface contact engagement area with thread segment 2, thereby ensuring tensile strength and thread anti-loosening performance.

[0042] The nut section mainly consists of a flange 4 and an end 5. A tapered groove 8 is provided at the bottom of the flange 4. The angle between the inclined side of the tapered groove 8 and the screw section is in the range of 45°-60°.

[0043] Here, the tapered groove 8 at the bottom of the flange 4 expands outward from the root of the screw section to form an annular recess. The angle between its inclined edge and the axis of the screw section is controlled between 45° and 60°, so that the tapered groove 8 has a suitable accommodating space.

[0044] Furthermore, during the locking process, the slight flange caused by the penetration of the drill tip 3 on the front of the plate is contained in the tapered groove 8, which prevents the flange material from raising the flange 4 and causing a loose fit, thereby ensuring the fit between the lower surface of the flange 4 and the plate.

[0045] Furthermore, the selection of the included angle range takes into account both the strength of the groove and the capacity of the flange to accommodate it. If the included angle is too small, the groove wall will be too thin, which may affect the stiffness of the flange. If the included angle is too large, the space to accommodate it will be insufficient. The range of 45°-60° is conducive to achieving a balance between structural strength and functional requirements.

[0046] The conical surface 6 is mainly composed of two sets of first conical surfaces and second conical surfaces. The first conical surfaces and the second conical surfaces are arranged in a ring-shaped staggered arrangement along the axis of the screw section 2. The first conical surfaces and the second conical surfaces cooperate to form a square conical tip structure for softening metal plates.

[0047] Here, four conical surfaces 6, formed by two sets of first conical surfaces and two sets of second conical surfaces arranged in a strict 90° circumferential staggered pattern, converge at the end of the screw segment 2, forming a square conical tip structure with distinct edges and strong piercing capability. Each conical surface 6 has a symmetrical tilt angle relative to the axis of the screw body 1, so that the four conical surfaces are not only evenly distributed circumferentially, but also exhibit perfect central symmetry in axial projection. When the tip initially contacts the plate, the four edges of the square conical tip will first embed into the plate surface in the form of line contact. This multi-point edge embedding method can provide stable mechanical restraint at the moment of contact, so that the drill bit axis quickly coincides with the normal of the plate surface, thereby achieving reliable centering and preventing slippage or deviation in the initial stage of drilling.

[0048] Furthermore, under high-speed rotation, the four conical surfaces 6 of the square cone tip form an alternating sliding multi-point friction pair with the sheet metal. The friction path covers the perimeter of the cone tip, and the generated frictional heat is highly concentrated in a small area near the cone tip, causing the temperature of the metal base material at that location to rise rapidly to a softened or thermoplastic state in a very short time. Under continuous axial pressure, the square cone tip, in a high-temperature softened state, can force the sheet material to undergo plastic flow and be squeezed to the perimeter of the hole by gradually pressing it in, rather than forming chips through traditional cutting methods. This achieves a near-chip-free penetration and hole-forming process. This process not only reduces axial drilling resistance but also avoids the generation of large chips, making it particularly suitable for flanging drilling of thin plates or ductile metals.

[0049] Furthermore, the four sets of conical surfaces 6 formed by the circumferentially staggered arrangement of the first and second conical surfaces can generate mutually symmetrical radial forces in real time when in contact with the plate during rotary drilling. These radial forces achieve dynamic equilibrium due to their circumferential distribution, effectively offsetting the lateral forces caused by material inhomogeneity or external interference, thereby significantly suppressing swaying and vibration during drilling. The stable drilling posture ensures the connection between the formed bottom hole and the flange bushing of the screw section 2.

[0050] The end 5 has an integrally formed protrusion 7 for transmitting torque. The protrusion 7 is mainly composed of an inner ring post 9 and an outer ring post 10. The inner ring post 9 and the outer ring post 10 are integrally formed. The inner ring post 9 has a groove 11 for adapting to external equipment. The outer ring post 10 has an arc-shaped groove 12. There are at least six sets of arc-shaped grooves 12. The six sets of arc-shaped grooves 12 are arranged equidistantly in a ring along their axis. The six sets of arc-shaped grooves 12 form a six-lobed structure on the outer ring post 10 to prevent slippage.

[0051] Here, the inner ring post 9 of the protrusion 7 is connected to the top of the end 5, and the outer ring post 10 surrounds the inner ring post 9 and forms an integral part therewith. The groove 11 on the inner ring post 9 is used to cooperate with the positioning pin or positioning boss of the external servo tightening device to achieve circumferential positioning.

[0052] Furthermore, the arc-shaped groove 12 on the outer ring post 10 forms a six-petaled profile similar to a plum blossom, and the inner contour of the special sleeve matches it. When the sleeve is driven, the torque is evenly transmitted through the six-petaled surface, which not only increases the contact area but also effectively prevents slippage and disengagement during the driving process.

[0053] Furthermore, the multi-faceted contact of the six-lobed structure can reduce the unit pressure of a single lobe, reduce local plastic deformation caused by torque fluctuations during connection operations, and the groove 11 of the inner ring post 9 can act as a guide during installation, ensuring quick alignment and engagement of the sleeve and the protrusion 7, and improving assembly efficiency.

[0054] Example 2, see attached document Figure 6 A type of rotary screw:

[0055] A rotary screw includes a screw body 1, which is mainly composed of a screw section and a nut section integrally formed on the screw section. The screw section is provided with a threaded section 2 and a drill tip section 3 from top to bottom. The nut section is mainly composed of a flange 4 and an end 5. The drill tip section 3 is provided with a tapered surface 6 for centering and guidance. The end 5 is integrally formed with a protrusion 7 for transmitting torque. The major diameter of the external thread of the threaded section 2 decreases taperedly from top to bottom to form a progressive extrusion bearing engagement zone for the internal thread of the flange bushing of the plate.

[0056] The conical surface 6 is mainly composed of two sets of first conical surfaces and second conical surfaces. The first conical surfaces and the second conical surfaces are arranged in annular staggered arrangement along the axis of the screw section 2. The first conical surfaces and the second conical surfaces cooperate to form a square conical tip structure for softening the metal sheet. The two sets of second conical surfaces are integrally formed with protruding ridges 13. The height of the arc of the first conical surface is greater than the height of the protruding ridge 13 of the second conical surface.

[0057] Here, four conical surfaces 6, formed by two sets of first conical surfaces and two sets of second conical surfaces arranged in a strict 90° circumferential staggered pattern, converge at the end of the screw section 2, forming a square cone tip structure with height difference characteristics. Unlike the smooth, uniformly high conical surface in Embodiment 1, in this embodiment, the two sets of second conical surfaces are integrally formed with a protruding ridge 13 extending along the generatrix of the conical surface. This ridge gradually rises from the root of the cone tip, reaches its peak in the middle section of the conical surface, and then smoothly transitions to the edge of the conical surface, forming a linear reinforcing ridge with an arc-shaped convex cross-section. The two sets of first conical surfaces maintain a complete arc surface shape, and the height of the arc point exceeds the height of the protruding ridge 13 of the second conical surface by a preset difference, thereby forming a first conical surface on the circumferential contour of the square cone tip. The high-position and low-position of the second conical surface protrusions are arranged in a sawtooth pattern. When the cone tip initially contacts the plate, the two sets of high-position first conical surface arc apexes first touch the plate surface in a double-point contact form, providing the initial positioning reference for the drill bit. As the axial feed proceeds, the two sets of second conical surface protrusions 13 follow and embed into the plate. Their linear protrusions form two parallel indentation grooves along the plate surface, which together with the double-point contact of the first conical surface constitute a four-point coordinated centering mechanism of two-point positioning first and two-line locking. This mechanism can effectively compensate for the micro-unevenness of the plate surface at the moment of contact, so that the drill bit axis is accurately coincided with the plate normal direction under multiple constraints. The centering accuracy is more reliable than the edge embedding method of Embodiment 1.

[0058] Furthermore, under high-speed rotation, the height difference between the high point of the first conical surface arc and the convex edge 13 of the second conical surface creates a pre-loosening-deep grinding alternating friction mode that differs from that in Embodiment 1. Within one rotation cycle, when the high point of the first conical surface arc passes over the plate, the contact arc length between its high-position profile and the plate is relatively short, generating a scratching effect with instantaneous high contact stress, pre-peeling the oxide layer and hardened film on the plate surface, and simultaneously generating initial frictional heat to preheat the material in a shallow layer; when the rotation reaches the point where the convex edge 13 of the second conical surface contacts the plate, its linear protruding top surface forms a narrow and long strip contact band with the plate, the contact pressure is concentrated and the duration of action is relatively long, generating deep friction on the surface of the plate that has been preheated by the first conical surface, causing the frictional heat to be rapidly conducted into the interior of the plate along the linear contact trajectory of the convex edge 13. The cyclical alternation of pre-loosening and deep grinding causes the sheet metal in the cone tip region to experience a stepwise temperature increase under the cumulative effect of alternating frictional heat, reaching a softened or thermoplastic state within a shorter number of rotations than in Example 1. Under continuous axial pressure, the softened sheet material is crushed layer by layer by the square cone tip and flows plastically along the cone surface to the outside of the hole edge. The protruding rib 13 also guides the material flow during this process, causing the flanged material to flow out along both sides of the rib, ultimately forming a nearly chip-free through hole. Furthermore, the surface roughness of the hole wall is better than in Example 1 due to the pressing effect of the protruding rib 13.

[0059] Furthermore, based on the staggered conical surface configuration formed by the high point of the first conical surface arc and the convex edge 13 of the second conical surface, the radial force system generated between the square conical tip and the plate during rotary drilling is richer and has an active correction capability than in Embodiment 1. Due to the different surface curvature and contact stiffness of the two sets of first conical surfaces arc surfaces and the two sets of second conical surfaces convex edges 13, they each generate radial force components with different amplitudes and directions when in contact with the plate: the arc surface of the first conical surface generates a relatively gentle radial pushing force, while the convex edge 13 generates a higher peak pulse-like radial impact force due to its linear protrusion structure. These four sets of radial forces with unequal amplitudes form an asymmetrical but self-balancing dynamic force system due to their circumferential 90° even distribution, causing the drill tip to experience four regular force fluctuations in each revolution. This controlled force fluctuation endows the drill tip with the ability to actively yield to local hard points or uneven structures in the plate and adaptively center itself, which can more effectively overcome drilling path deviation than the uniform force balance in Embodiment 1. Meanwhile, when rotating, the convex ridge 13 embeds itself into the plate in a linear protrusion, generating a circumferential biting effect similar to that of a gear hobbing, which greatly enhances the rotational traction adhesion of the drill tip to the plate, effectively avoiding slippage and free spin during high-speed drilling. Under the synergistic effect of the above-mentioned active correction force system and circumferential biting effect, the drilling skew and vibration amplitude are further reduced compared to the first embodiment. The coaxiality of the formed bottom hole and the flange bushing of the screw section 2 is significantly improved, providing a better guiding reference for the subsequent progressive extrusion tapping of the thread section 2, and ultimately ensuring the meshing accuracy and fatigue life of the threaded connection.

[0060] The bottom of the flange 4 is provided with a tapered groove 8, and the angle between the inclined side of the tapered groove 8 and the screw section is in the range of 45°-60°.

[0061] The protrusion 7 is mainly composed of an inner ring post 9 and an outer ring post 10. The inner ring post 9 and the outer ring post 10 are integrally formed. The inner ring post 9 has a groove 11 for adapting to external equipment.

[0062] The outer ring post 10 is provided with an arc-shaped groove 12. There are at least six sets of arc-shaped grooves 12. The six sets of arc-shaped grooves 12 are arranged equidistantly in a ring along their axis. The six sets of arc-shaped grooves 12 form a six-petal structure on the outer ring post 10 to prevent slippage.

[0063] The difference from Embodiment 1 is that Embodiment 2, based on the square cone tip structure of Embodiment 1, adds a protruding ridge 13 and sets the height difference between the first cone surface and the second cone surface protruding ridge 13, thereby achieving an upgrade from single embedding to staged embedding in initial centering, from uniform friction to pre-scraping-concentrated friction in frictional heat generation, and from single force balance to complex force system self-balancing in the drilling process, further optimizing drilling efficiency, centering accuracy and process stability.

[0064] Reference manual attached Figure 7 A method for using a rotary screw and its application includes the following steps:

[0065] S1: Clamping and alignment: Align the protrusion at the end of the screw with the drive structure of the external tightening tool, so that the groove on the inner ring post matches the tool positioning structure, and the arc groove on the outer ring post engages with the tool drive tooth groove, aligning the drill tip with the preset penetration position of the metal plate to be connected.

[0066] Here, the groove 11 on the inner ring post 9 of the protrusion 7 is aligned and embedded with the positioning pin or positioning boss of the external servo tightening tool or special sleeve, so that the screw and the tool are circumferentially positioned to prevent relative rotational misalignment during clamping; at the same time, the six-lobed structural contour formed by the six sets of arc grooves 12 on the outer ring post 10 is engaged with the inner six-lobed cavity of the tool drive end to achieve reliable engagement of the torque transmission interface. At this time, the square cone tip of the drill tip section 3 is aligned with the preset entry position mark on the surface of the metal plate to complete the clamping and alignment preparation.

[0067] Furthermore, the groove 11 can be fitted with a clearance fit or a transition fit to facilitate quick insertion and removal. Simultaneously, the groove wall can withstand circumferential shear force during torque transmission, preventing circumferential slippage between the inner ring post 9 and the tool. The six-lobed structure formed by the arc-shaped groove 12, by replacing the traditional hexagonal corner contact with arc-shaped surface contact, increases the load-bearing area for torque transmission and reduces the contact stress per unit area, thereby reducing the risk of wear between the tool and the screw head.

[0068] Furthermore, on automated assembly lines, the groove 11 of the inner ring post 9 can also serve as a positioning feature for visual recognition or mechanical guidance, making it easier for robots or automatic tightening mechanisms to quickly identify the circumferential posture of the screw and complete automatic alignment, thereby improving assembly efficiency; the multi-faceted symmetry of the six-lobed structure allows the tool to be quickly inserted at any 60° integer multiple angle, reducing the time consumed for clamping and alignment.

[0069] S2: Press-fit contact, applying axial pressure to the screw so that the highest point of the arc on the first conical surface of the drill tip abuts against the surface of the plate.

[0070] Here, the external tightening tool applies initial axial pressure to the screw body 1 through the protrusion 7, causing the square cone tip of the drill tip 3 to feed towards the surface of the plate. Since the height of the arc of the first cone surface is greater than the height of the ridge 13 of the second cone surface in this embodiment, when the square cone tip contacts the plate, the arc vertices of the two sets of first cone surfaces first abut against the plate surface in a double-point contact form, forming an initial contact state; at this time, the ridge 13 on the second cone surface has not yet contacted the plate and is in a suspended and ready state.

[0071] Furthermore, the initial contact method using two points allows the screw axis to obtain two symmetrical support points at the moment of contact. These two support points are symmetrically distributed 180° circumferentially, which can initially constrain the lateral degree of freedom of the drill tip within the plane of the plate. Compared with single-point contact or uncertain multi-point contact, this deterministic two-point contact can provide a more stable initial attitude reference for subsequent drilling, reducing centering errors caused by microscopic unevenness of the plate surface or initial screw misalignment.

[0072] Furthermore, the axial pressure applied at this stage should be controlled within a certain range to ensure that the arc height of the first conical surface is pressed into the plate surface at a very shallow depth, avoiding excessive impact or excessively deep indentation on the plate at initial contact. This shallow indentation can also serve as a guide trajectory for the subsequent embedding of the second conical protrusion 13, providing a preset benchmark for the collaborative centering mechanism of "two-point initial positioning and two-line follow-up locking" in stage S3.

[0073] S3: High-speed spinning hot melting, driving the screw to rotate at high speed around its own axis and continuously applying axial feed pressure, and through the friction between the first conical surface of the drill tip and the plate, the contact area of ​​the plate is heated and softened.

[0074] Here, the external tightening tool drives the screw to rotate at a preset high speed around its own axis while continuously applying axial feed pressure. During rotation, the high point of the first conical surface arc at the tip of the square cone and the convex edge 13 of the second conical surface form an alternating pre- and deep grinding friction mode due to the height difference: In each rotation cycle, the high point of the first conical surface arc first sweeps across the plate, generating a high contact stress scraping action with a shorter contact arc length, pre-peeling the oxide layer and hardened film on the plate surface and generating initial frictional heat; subsequently, the convex edge 13 of the second conical surface follows in a line contact manner, generating concentrated friction on the preheated plate surface, causing the frictional heat to be conducted into the plate along the linear contact trajectory of the convex edge.

[0075] Furthermore, under the continuous action of alternating pre-loosening and deep grinding friction, the metal temperature in the contact area of ​​the sheet metal increases in a stepwise manner. The scraping and pre-loosening of the first conical surface reduces the surface hardness of the sheet metal, providing softening conditions for the subsequent deep grinding of the protruding ridge 13; the linear contact zone of the protruding ridge 13 has a small contact area and concentrated pressure, resulting in a high frictional heat flux density, which can quickly heat the contact area of ​​the sheet metal cone tip to above the recrystallization temperature, causing the metal base material to enter a softened or thermoplastic state. This alternating friction mode has a higher heat generation efficiency and a faster heating rate than the uniform friction mode.

[0076] Furthermore, as the temperature in the contact area of ​​the sheet continues to rise and reaches a thermoplastic state, the yield strength of the material decreases significantly. At this point, under the action of axial feed pressure, the square cone tip begins to gradually press into the softened sheet interior, causing the sheet material to undergo plastic flow and be squeezed to both sides of the cone surface. In this process, in addition to generating frictional heat, the protruding ridge 13 also plays a role in guiding the flow of plastic material, causing the squeezed material to flow orderly along both sides of the ridge and migrate towards the periphery of the hole edge, laying the foundation for the material flow path for the formation of a regular flange bushing in stage S4.

[0077] S4: Penetrating the forming bushing, the screw continues to be fed axially until the drill tip completely penetrates the plate. The heated and softened plate material is squeezed and extended to the back of the plate to form a cylindrical flange bushing.

[0078] Here, under the combined action of continuous high-speed rotation and axial feed pressure, the square cone tip gradually penetrates the entire thickness of the plate. When the drill tip 3 completely penetrates the plate, the heated and softened metal material around the cone tip is squeezed and extends axially towards the back of the plate, forming a cylindrical flange bushing that protrudes towards the back side around the penetration hole on the back of the plate. This flange bushing is made of a single piece of material with the plate body, without a connecting interface, and has continuous metal flow lines.

[0079] Furthermore, during the penetration process of the four conical tips, the circumferentially distributed configuration of the four conical surfaces 6 ensures uniform compression of the plate hole wall, resulting in a flange bushing with a basically consistent wall thickness in all circumferential directions. The convex ridge 13 continues to play a material diversion role during the penetration stage. Its linear protrusion guides the plastically flowing material in an orderly manner to the arc surface area of ​​the adjacent first conical surface when rotating, avoiding material accumulation on the conical surface or defects such as uneven circumferential thickness in the flange bushing, thereby obtaining a cylindrical flange bushing with regular geometry and uniform wall thickness.

[0080] Furthermore, during the forming process, the flanged bushing, being in a thermoplastic state and subjected to continuous pressing by the conical surface, exhibits a smooth inner wall surface and increased material density, providing a high-quality base material for the extrusion tapping in stage S5. Simultaneously, the height of the flanged bushing can be adjusted by controlling the axial feed stroke to accommodate different plate thicknesses and connection strength requirements. The slight flanged allowance generated on the front of the plate due to the cone tip pressing is temporarily retained around the hole on the front of the plate, to be accommodated by the conical groove 8 at the bottom of the flange in stage S6.

[0081] S5: Speed ​​reduction extrusion tapping, reducing screw speed while maintaining axial feed, the external thread major diameter enters the flange bushing in a tapered decreasing thread section from top to bottom, continuously extruding the inner wall of the flange bushing, forming an internal thread on the inner wall of the flange bushing.

[0082] Here, after the drill tip 3 has completely penetrated the plate and formed the flange bushing, the external tightening tool reduces the screw speed to the preset tapping speed while maintaining axial feed pressure. At this time, the threaded section 2, located above the screw section 2, begins to enter the flange bushing. The major diameter of the external thread of this threaded section tapers away from the flange 4, so the minor diameter thread enters the flange bushing first. Its outer diameter is smaller than the inner diameter of the flange bushing, allowing for resistance-free entry.

[0083] Furthermore, as the screw continues to rotate and advance, the gradually increasing external thread diameter on threaded section 2 exerts a continuous radial compression on the inner wall of the flange bushing, progressing from shallow to deep. Due to the preheating in stages S3 and S4 and the residual temperature from plastic deformation, the flange bushing material remains in a low yield strength state. Under the compression of the thread profile, it undergoes plastic flow, gradually filling the tooth groove of the threaded section and forming a closely fitting tooth profile along the outer contour of the threaded section, thus creating a non-cutting extruded internal thread. This forming process generates no chips, has high material utilization, and produces a full and rounded internal thread profile.

[0084] Furthermore, because the pitch of thread segment 2 remains constant, the pitch of the formed flanged bushing's internal thread remains uniform throughout the extrusion process as the tapered major diameter gradually increases, without any pitch deviation due to changes in the major diameter. A long helical surface contact engagement area is formed between the extruded internal thread and the external thread of thread segment 2. This surface contact method has a higher load-bearing area and tensile strength than the line contact method of traditional cutting threads, and also provides superior thread anti-loosening performance under vibration conditions. In addition, the tapered design of thread segment 2 ensures that the tapping torque increases gradually along the axial direction, avoiding the peak torque impact at the initial stage of tapping and reducing the risk of flanged bushing cracking during the tapping process.

[0085] S6: The end face is fitted and locked. The screw continues to rotate and feed. The lower end face of the flange abuts against the surface of the plate. The tapered groove at the bottom of the flange accommodates the flange allowance on the front of the plate, completing the locking connection.

[0086] Here, after the threaded section 2 completes the extrusion forming of the internal thread of the flange bushing, the screw continues to rotate and feed until the lower end face of the flange 4 abuts against the front surface of the plate. As the flange approaches the plate, the tapered groove 8 at the bottom of the flange 4 is aligned with the flange allowance area around the front opening of the plate. As the flange is axially fed, the tapered groove gradually accommodates the flange allowance within its annular recessed space, preventing the flange allowance from raising the flange and causing gaps or looseness between the flange and the plate.

[0087] Furthermore, the angle between the inclined side of the tapered groove 8 and the axis of the screw section 2 ranges from 45° to 60°. This angle design allows the tapered groove to accommodate the flange allowance while the inclined groove wall guides and gathers the flange allowance inward, pressing it into the bottom of the groove and making it adhere to the annular area between the lower end face of the flange and the plate. This accommodating process eliminates the interference of the flange allowance on the connection interface, allowing the lower end face of the flange to achieve a large-area fit with the front of the plate, ensuring that the clamping force is evenly distributed on the mating surface.

[0088] Furthermore, after the lower end face of the flange is fully fitted with the front face of the plate, tightening torque is continued to achieve the preset preload. At this point, axial clamping of the plate and flange bushing is formed between flange 4 and threaded section 2. The flange bushing provides support from the back, while the flange applies pressure from the front, forming a through-type double-sided clamping connection structure. This connection method incorporates the flange bushing of the plate material as part of the connection and participates in load bearing, resulting in higher tensile strength and vibration loosening resistance compared to traditional connection methods that rely solely on thread engagement. Simultaneously, the tapered groove 8's containment of the flange allowance prevents preload attenuation due to the flange allowance being crushed, ensuring the reliability of the connection for long-term use. Thus, the rotary screw completes all connection procedures from clamping and alignment to end-face fitting and locking.

[0089] The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A rotary screw, comprising a screw body (1), characterized in that: The screw body (1) is mainly composed of a screw section and a nut section integrally formed on the screw section. The screw section is provided with a thread section (2) and a drill tip section (3) from top to bottom. The nut section is mainly composed of a flange (4) and an end (5). The drill tip section (3) is provided with a tapered surface (6) for centering and guiding. The end (5) is integrally formed with a protrusion (7) for transmitting torque.

2. The rotary screw according to claim 1, characterized in that: The external thread major diameter of the threaded section (2) decreases tapered from top to bottom to form a progressive extrusion bearing engagement zone for the internal thread of the plate flange bushing.

3. A rotary screw according to claim 2, characterized in that: The conical surface (6) is mainly composed of two sets of first conical surfaces and second conical surfaces. The first conical surface and the second conical surface are arranged in a ring-shaped staggered arrangement along the axis of the screw section (2). The first conical surface and the second conical surface cooperate to form a square conical tip structure for softening metal plates.

4. A rotary screw according to claim 3, characterized in that: The two sets of second cone surfaces are integrally formed with protruding ridges (13), and the height of the arc high point of the first cone surface is greater than the height of the high point of the protruding ridge (13) of the second cone surface.

5. A rotary screw according to claim 4, characterized in that: The bottom of the flange (4) is provided with a tapered groove (8), and the angle between the inclined side of the tapered groove (8) and the screw section is in the range of 45°-60°.

6. A rotary screw according to claim 5, characterized in that: The protrusion (7) is mainly composed of an inner ring post (9) and an outer ring post (10). The inner ring post (9) and the outer ring post (10) are integrally formed. The inner ring post (9) has a groove (11) for adapting to external equipment.

7. A rotary screw according to claim 6, characterized in that: The outer ring post (10) is provided with an arc-shaped groove (12), and the number of the arc-shaped groove (12) is at least six sets. The six sets of arc-shaped grooves (12) are arranged equidistantly in a ring along their axis, and the six sets of arc-shaped grooves (12) form a six-petal structure on the outer ring post (10) to prevent slippage.

8. A method of using a rotary screw and the same method of using the same, for implementing the rotary screw according to any one of claims 1-7, characterized in that: Includes the following steps: S1: Clamping and positioning, aligning the protrusion (7) of the screw end (5) with the drive structure of the external tightening tool, so that the groove (11) on the inner ring post (9) is adapted to the tool positioning structure, and the arc groove (12) on the outer ring post (10) is engaged with the tool drive tooth groove, and aligning the drill tip (3) with the preset penetration position of the metal plate to be connected. S2: Pressing contact, applying axial pressure to the screw, so that the arc high point of the first conical surface on the drill tip section (3) abuts against the surface of the plate; S3: High-speed spinning hot melting, driving the screw to rotate at high speed around its own axis and continuously applying axial feed pressure, through the first conical surface of the drill tip (3) to rub against the plate, so that the contact area of ​​the plate is heated and softened; S4: Penetrate the forming bushing, the screw continues to be axially fed to the drill tip section (3) to completely penetrate the plate. The heated and softened plate material is squeezed to extend to the back of the plate, forming a cylindrical flanged bushing. S5: Reduce speed extrusion tapping, reduce screw speed and maintain axial feed, the external thread major diameter enters the inside of the flange bushing in a tapered decreasing thread section (2) from top to bottom, continuously extruding the inner wall of the flange bushing, forming an internal thread on the inner wall of the flange bushing. S6: The end face is fitted and locked, the screw continues to rotate and feed, the lower end face of the flange (4) abuts against the surface of the plate, the tapered groove (8) at the bottom of the flange (4) accommodates the flange allowance on the front of the plate, and the locking connection is completed.

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