A variable pitch drill point screw

Abstract

The utility model discloses a variable diameter type drill tail screw, including screw body, the one end of screw body is set to cutting part, the other end is set to the cap, and the middle part of screw body is the rod piece, and its surface is provided with several circles equal diameter thread tooth, and the area of equal diameter thread tooth is set to the thread area, be provided with variable diameter area between the thread area and cutting part, be provided with several circles variable diameter thread tooth in variable diameter area, and the outside diameter of tooth body in variable diameter thread tooth gradually increases along the direction of cutting part pointing to the cap, and the outside diameter of equal diameter thread tooth set on the thread area is equal with the maximum outside diameter of variable diameter thread tooth in variable diameter area. Through setting the variable diameter thread tooth of gradually increasing outside diameter along the direction of cutting part pointing to the cap between the thread area and cutting part, and cooperating with the synchronous action of chip removal structure and variable diameter thread tooth, realize that the variable diameter thread tooth and hole wall effect more gently when drill tail screw attack, protect the variable diameter thread tooth from damaging, let the hole wall plastic deformation is stable, improve the engagement tightness of equal diameter thread tooth and hole wall internal thread.

Description

Technical Field

[0001] This utility model belongs to the field of fastener technology, specifically a variable diameter self-drilling screw. Background Technology

[0002] Existing self-drilling screws often employ a constant-diameter thread structure. The maximum outer diameter of the constant-diameter thread is significantly larger than the diameter of the shank in the middle of the screw body, resulting in a large thread height. However, the diameter of the hole formed by the cutting part is the same as that of the shank and smaller than the outer diameter of the constant-diameter thread. This leads to excessive interaction force between the starting end of the constant-diameter thread and the hole wall when it enters the workpiece hole, making the thread body extremely prone to damage and deformation, severely affecting the screw's locking reliability and service life. Summary of the Invention

[0003] Purpose of the invention: In order to overcome the shortcomings of the existing technology, this utility model provides a variable diameter self-drilling screw. By setting a variable diameter thread with an outer diameter that gradually increases along the direction of the cutting part towards the nut between the threaded area and the cutting part, and at the same time cooperating with the chip removal structure and the synchronous action of the variable diameter thread, the interaction between the thread and the hole wall is made smoother when the self-drilling screw is driven, the thread is protected from damage, the plastic deformation of the hole wall is stable, and the meshing tightness between the constant diameter thread and the internal thread of the hole wall is improved.

[0004] Technical Solution: To achieve the above objectives, this utility model provides a variable diameter self-drilling screw, comprising a screw body, one end of which is configured as a cutting part, and the other end as a nut. The middle part of the screw body is a rod, and its surface is provided with several turns of equal diameter threads, the area with equal diameter threads being denoted as the threaded area. A variable diameter area is provided between the threaded area and the cutting part, and several turns of variable diameter threads are provided in the variable diameter area. The outer diameter of the thread body of the variable diameter threads gradually increases along the direction from the cutting part to the nut. The outer diameter of the equal diameter threads in the threaded area is equal to the maximum outer diameter of the variable diameter threads in the variable diameter area.

[0005] Furthermore, the pitch of the equal-diameter thread is equal to the pitch of the variable-diameter thread.

[0006] Furthermore, the cutting part is provided with two irregular chip removal structures mirroring the axis of the screw body. Each chip removal structure has an arc-shaped blocking wall and a planar cutting wall. The intersection of each blocking wall and the corresponding cutting wall forms a chip removal groove, and the two chip removal grooves extend in a curved manner.

[0007] Furthermore, the end of the cutting part away from the nut is conical in a radial view. Let the tip of the cone be the tapping point. The two chip discharge grooves meet at the tapping point, and the two cutting walls also meet at the tapping point.

[0008] Furthermore, each of the chip removal structures has a protrusion area that extends into the diameter-changing area and cuts off at least two turns of the diameter-changing thread.

[0009] Furthermore, the nut includes a hexagonal stud and a cap. The cap is integrally connected to the side of the hexagonal stud near the cutting part. The side of the cap away from the hexagonal stud has an insert groove for accommodating a washer. The side of the cap near the hexagonal stud has an arc-shaped umbrella-shaped surface.

[0010] Furthermore, a cylindrical mating groove is coaxially formed at the end of the hexagonal stud away from the cap.

[0011] Beneficial Effects: Compared with existing technologies, this utility model of a variable-diameter self-drilling screw effectively solves the problem of excessive force on the hole wall during tapping caused by the excessive initial tooth height of existing equal-diameter threads, which leads to tooth damage and hole wall cracking. This is achieved by setting a variable-diameter thread with an outer diameter that gradually increases along the cutting direction towards the nut. This allows for a smoother plastic deformation process of the hole wall metal, laying the foundation for tight engagement between the equal-diameter thread and the internal thread of the hole wall, significantly enhancing the tensile and torsional strength of the connection. Simultaneously, the equal-diameter thread and the variable-diameter thread have equal pitch, ensuring precise engagement between the internal thread formed by the variable-diameter thread and the equal-diameter thread, avoiding thread interference and jamming caused by pitch differences, and making the tapping process smoother. In some embodiments, the maximum outer diameter of the first turn of the variable-diameter thread is equal to the diameter of the rod, allowing the variable-diameter thread to engage with the hole wall immediately after the cutting part forms a hole, improving tapping efficiency. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of the structure of a variable diameter self-drilling screw according to the present invention;

[0013] Figure 2 Image C is a magnified view of a portion of the image. Detailed Implementation

[0014] The present invention will be further described below with reference to the accompanying drawings.

[0015] like Figure 1 As shown, a variable diameter self-drilling screw includes a screw body 1, one end of which is configured as a cutting part 2, and the other end as a nut 3. The middle part of the screw body 1 is a rod, and its surface is provided with several turns of equal diameter thread teeth 4. The area where the equal diameter thread teeth 4 are provided is called the thread area 5. A variable diameter area 6 is provided between the thread area 5 and the cutting part 2. Several turns of variable diameter thread teeth 7 are provided in the variable diameter area 6. The outer diameter of the thread teeth 7 gradually increases along the direction from the cutting part 2 to the nut 3. The outer diameter of the equal diameter thread teeth 4 provided in the thread area 5 is equal to the maximum outer diameter of the variable diameter thread teeth 7 in the variable diameter area 6.

[0016] Since the equal-diameter thread 4 is an external thread, the maximum outer diameter of the equal-diameter thread 4 is greater than the diameter of the rod in the middle of the screw body 1, meaning the thread height of the equal-diameter thread 4 is too large. As those skilled in the art should know, in order to ensure the locking effect of the screw, from a radial perspective, the outer contour of the cutting part 2 is the same size as the rod in the middle of the screw body 1. That is, the diameter of the hole cut by the cutting part 2 on the workpiece surface is smaller than the outer diameter of the equal-diameter thread 4. This results in excessive interaction force between the thread body at the starting end of the equal-diameter thread 4 and the hole wall on the workpiece during the driving process, making the thread body easily damaged and deformed. The variable-diameter thread 7 can start from the hole formed by the cutting part 2 on the workpiece surface and gradually squeeze and shape the hole wall, making the plastic deformation process of the workpiece hole wall smoother. This avoids the hole wall from being subjected to excessive stress and breaking due to the excessive thread height when the equal-diameter thread 4 is directly driven in. At the same time, it makes the subsequent equal-diameter thread 4 mesh more tightly with the internal thread of the hole wall, improving the tensile and torsional strength of the connection.

[0017] The pitch of the equal diameter thread 4 is equal to the pitch of the variable diameter thread 7. This ensures that the internal thread formed by the variable diameter thread 7 through extrusion and plastic deformation on the hole wall can be connected with the equal diameter thread 4, avoiding thread interference caused by pitch difference when the variable diameter thread 7 transitions to the equal diameter thread 4.

[0018] The cutting part 2 is provided with two irregular chip removal structures 8 mirrored on the axis of the screw body 1. The cross-section of the two chip removal structures 8 is similar to an irregular cone, that is, each chip removal structure 8 has an arc-shaped blocking wall 9 and a flat cutting wall 10. At the intersection of each blocking wall 9 and the corresponding cutting wall 10, chip discharge grooves 11 are formed. The two chip discharge grooves 11 are arranged in a curved manner. The arc-shaped blocking wall 9 can block the chips cut by the cutting wall 10, so that they are quickly discharged along the curved chip discharge grooves 11, avoiding the accumulation of chips between the thread teeth and the hole wall, preventing chips from hindering the entry of the thread teeth, and at the same time preventing chips from getting stuck between the thread teeth and affecting the forming accuracy of the internal thread.

[0019] The end of the cutting part 2 away from the nut 3 is conical in radial view. Let the tip of the cone be the tapping point 12. The two chip removal structures 8 intersect at the tapping point 12, that is, the two chip removal grooves 11 converge at the tapping point 12, and the two cutting walls 10 also converge at the tapping point 12. When the self-drilling screw of this solution is used to connect the workpiece, the tapping point 12 can destroy the surface of the workpiece. After the surface of the workpiece is destroyed to form a hole, the cutting wall 10 can cut the hole to enlarge its diameter. During the tapping process, the blocking wall 9 can block the chips cut by the cutting wall 10, so that the chips are discharged from the hole along the chip removal groove 11.

[0020] Each of the chip removal structures 8 has a protruding area 13 that extends into the diameter-changing area 6 and cuts off at least two turns of the diameter-changing thread 7. This allows the chip removal structure 8 to engage with the diameter-changing thread 7, enabling simultaneous cutting and tapping during the tapping process. This allows the cutting wall 10 to cut and enlarge the hole while the diameter-changing thread 7 simultaneously squeezes and taps the hole wall, preventing springback deformation of the hole wall when cutting and tapping are performed in separate steps, and ensuring the meshing accuracy of the internal and external threads after tapping.

[0021] like Figure 2 As shown in the embodiment presented in this solution, the variable diameter region 6 is provided with three turns of variable diameter thread 7. These turns of variable diameter thread 7, along the direction from the cutting portion 2 to the nut 3, are sequentially designated as the first variable diameter thread 7a, the second variable diameter thread 7b, and the third variable diameter thread 7c. Let the maximum outer diameter of the first variable diameter thread 7a be D1, the maximum outer diameter of the second variable diameter thread 7b be D2, and the maximum outer diameter of the third variable diameter thread 7c be D3. Then, D1... <D2<D3。

[0022] Assuming there are n turns of reducing thread 7 in the reducing zone 6, the shank diameter of the middle member of the screw body 1 is D0, and the maximum outer diameter of the equal-diameter thread 4 in the thread zone 5 is D4, then D3 = D4.

[0023] In other embodiments not shown, let D1 be the maximum outer diameter of the first turn of the reducing thread 7 in the reducing diameter zone 6 along the direction from the cutting part 2 to the nut 3, and Dn be the maximum outer diameter of the last turn of the reducing thread 7. Then, D4>D0 and Dn=D4 are satisfied. In some embodiments, D1=D0. This design allows the starting point of the reducing thread 7 in the reducing diameter zone 6 to coincide with the outer contour of the cutting wall 10 in the cutting part 2, so that the reducing thread 7 can be inserted into the hole wall immediately after the cutting part 2 cuts a hole on the workpiece surface.

[0024] Furthermore, it should be emphasized here that the variable diameter thread 7 actually changes the tooth height of the tooth body, such as... Figure 2 As shown, if the diameter-changing area 6 is divided into region A and region B by the axis of the screw body 1, and the tooth height difference between two adjacent diameter-changing thread teeth 7 in region A is ΔH1, and the tooth height difference between two adjacent diameter-changing thread teeth 7 in region B is ΔH2, then ΔH1 < ΔH2; therefore, the tooth height of the diameter-changing thread teeth 7 in the diameter-changing area 6 gradually increases or decreases with the increase of its extension distance, but the final result is that the maximum outer diameter of each diameter-changing thread tooth 7 is different.

[0025] The nut 3 includes a hexagonal stud 14 and a cap 15. The cap 15 is integrally connected to the side of the hexagonal stud 14 near the cutting part 2. The side of the cap 15 away from the hexagonal stud 14 has an insert groove 17 for accommodating a washer 16. The side of the cap 15 near the hexagonal stud 14 has an arc-shaped umbrella-shaped surface. More specifically, if the maximum outer diameter of the cap 15 is D5, then D5 ≥ 3D0. The washer 16 accommodated in the insert groove 17 can increase the contact area between the nut 3 and the workpiece surface, disperse the pressure during tightening, and prevent the workpiece surface from being crushed. The arc-shaped umbrella-shaped surface can not only prevent impurities from entering the gap between the nut and the workpiece, but also make the cap 15 fit more tightly with the workpiece surface when the screw is tightened, improving the sealing effect and preventing moisture from seeping into the connection part.

[0026] The cap 15 can be made of metal casting or nylon injection molding, depending on the requirements. When metal casting is used, the cap 15 can withstand a greater tightening torque, which is suitable for high-strength connection scenarios and prevents the nut from deforming due to excessive torque. When nylon injection molding is used, in addition to its waterproof function, the elasticity of nylon can compensate for the difference in thermal expansion and contraction between the screw and the workpiece, reducing the loosening of the connection caused by thermal stress. At the same time, the insulation of nylon can prevent electrochemical corrosion, making it suitable for environments with anti-corrosion and insulation requirements.

[0027] The end of the hexagonal stud 14 away from the cap 15 has a cylindrical mating groove 18 coaxially. When the self-drilling screw of this solution is locked onto the workpiece, the mating groove 18 is used to engage with other fasteners such as locating pins and locking springs. This can prevent the screw from loosening when it is subjected to vibration or other working conditions, improve the anti-loosening performance of the connection, ensure the reliability of long-term use, and is suitable for equipment or structural connections with frequent vibration.

[0028] The above are the preferred embodiments described in this utility model. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of this utility model, and these improvements and modifications should also be considered within the scope of protection of this utility model.

Claims

1. A variable diameter self-drilling screw, characterized in that: The screw body (1) includes a screw body (1), one end of which is a cutting part (2) and the other end is a nut (3). The middle part of the screw body (1) is a rod with several turns of equal diameter thread teeth (4) on its surface. The area with equal diameter thread teeth (4) is called the thread area (5). A variable diameter area (6) is provided between the thread area (5) and the cutting part (2). Several turns of variable diameter thread teeth (7) are provided in the variable diameter area (6). The outer diameter of the thread body of the variable diameter thread teeth (7) gradually increases along the direction from the cutting part (2) to the nut (3). The outer diameter of the equal diameter thread teeth (4) provided on the thread area (5) is equal to the maximum outer diameter of the variable diameter thread teeth (7) in the variable diameter area (6).

2. The variable diameter self-drilling screw according to claim 1, characterized in that: The pitch of the equal diameter thread (4) is equal to the pitch of the variable diameter thread (7).

3. A variable diameter self-drilling screw according to claim 1, characterized in that: The cutting part (2) is provided with two irregular chip removal structures (8) mirrored with the axis of the screw body (1). Each chip removal structure (8) has an arc-shaped blocking wall (9) and a planar cutting wall (10). At the intersection of each blocking wall (9) and the corresponding cutting wall (10), chip removal grooves (11) are formed. The two chip removal grooves (11) extend in a curve.

4. A variable diameter self-drilling screw according to claim 3, characterized in that: The end of the cutting part (2) away from the nut (3) is conical in radial view. The tip of the cone is called the tapping point (12). The two chip discharge grooves (11) meet at the tapping point (12), and the two cutting walls (10) also meet at the tapping point (12).

5. A variable diameter self-drilling screw according to claim 3, characterized in that: Each of the chip removal structures (8) has a protrusion area (13) that extends into the diameter-changing area (6) and cuts off at least two turns of the diameter-changing thread (7).

6. A variable diameter self-drilling screw according to claim 1, characterized in that: The nut (3) includes a hexagonal stud (14) and a cap (15). The cap (15) is integrally connected to the side of the hexagonal stud (14) near the cutting part (2). The side of the cap (15) away from the hexagonal stud (14) has an insert groove (17) for accommodating a washer (16). The side of the cap (15) near the hexagonal stud (14) has an arc-shaped umbrella-shaped surface.

7. A variable diameter self-drilling screw according to claim 6, characterized in that: The end of the hexagonal stud (14) away from the cap (15) has a cylindrical mating groove (18) on the same axis.

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