A cutting self-locking screw and a tooth plate mold thereof

Abstract

A self-locking screw includes a screw body and a screw head. The screw body includes a screw shank, a screw tip, a thread, serrations, and protrusions. The screw tip is a square pyramidal shape formed by four flat beveled surfaces. The serrations begin at the connection between the screw shank and the screw tip, spiraling upwards to the middle section of the screw shank with a helix angle of 15°. The crest of the serrations is lower than the crest of the thread. The protrusions are located on the screw shank, with multiple protrusions spiraling upwards from the side near the serrations to the end of the thread away from the screw tip, with a helix angle of 60°. The protrusions are hemispherical, with a flat plane at the end away from the screw shank surface, the height of which is less than the crest height of the thread. The invention also provides a die for cutting a self-locking screw, wherein a stationary die and a movable die form the protrusions through recessed points, and the serrations are formed by the serrations.

Description

Technical Field

[0001] This invention relates to the field of screw manufacturing technology, and in particular to a cutting self-locking screw and its die plate mold. Background Technology

[0002] Screws are tools that utilize the physical and mathematical principles of inclined planes, circular rotation, and friction to gradually fasten objects and machine parts. In the use of screws, ordinary self-tapping screws, or screws, only consist of three parts: a shank, threads, and a head. Their manufacturing process is simple, but their stability is poor. During the self-tapping process, especially with thin metal sheets, plastics, or hardwoods, problems such as chip accumulation, jamming, and workpiece cracking are prone to occur, resulting in the screw not being fully screwed in or insufficient tightening force. For example, Chinese patent CN202022406354.X discloses a flat-head Phillips head self-tapping screw. This self-tapping screw has a self-tapping head fixedly mounted on the top of the shank, a self-tapping threaded portion on the outer wall of the shank, and a self-tapping head fixedly mounted on the bottom of the shank. The self-tapping head has a Phillips head groove inside, with a spare Phillips head groove inside the groove. Both the spare Phillips head groove and the Phillips head groove have positioning holes, with four positioning holes in total. The Phillips head groove has four movable slots on its exterior, and each of the four movable slots has a movable plate inside. The screw's strength is enhanced by reinforcing ribs to prevent breakage due to excessive torque during self-tapping. However, the screw cannot guarantee stability after locking; it is prone to disengagement, its self-locking and anti-loosening capabilities are weak, and its cutting performance needs improvement. Summary of the Invention

[0003] In view of this, the present invention provides a self-locking screw that can be cut to solve the above problems.

[0004] A self-locking screw includes a screw body and a screw head disposed at one end of the screw body. The screw body includes a shank, a screw tip disposed at the end of the shank away from the screw head, a thread on the shank and the screw tip, a serration on the shank, and a plurality of protrusions arranged on one side of the serration. The serration starts from the connection between the shank and the screw tip and spirals upward to the middle section of the shank, with a helix angle of 15°. The crest of the sawtooth pattern is lower than the crest of the thread. The protrusion is located on the screw. Multiple protrusions are arranged spirally from the side near the sawtooth pattern to the end of the thread away from the screw tip, and their helix angle is 60°. The protrusion is hemispherical, and its end away from the screw surface has a flat plane. The height of this plane is less than the crest height of the thread. The root of the sawtooth pattern has a reinforcing groove. The height of this reinforcing groove is less than the crest height of the sawtooth pattern, and its width is less than the root width of the sawtooth pattern.

[0005] Furthermore, the diameter at the connection between the screw and the screw head gradually increases towards the end of the screw head.

[0006] Furthermore, the helix angle of the thread is 15°.

[0007] Furthermore, the main body of the screw tip is a four-sided pyramid shape, which is composed of four flat inclined surfaces joined together, and the connection between the four inclined surfaces is a smooth transition.

[0008] Furthermore, the reinforcing ridges are intermittently arranged along the spiral direction of the serrated pattern, and the cross-section of the reinforcing ridges is triangular with a smooth transition at the top and no sharp edges.

[0009] A die for cutting self-locking screws includes a stationary die and a movable die, the side structures of the stationary die and the movable die being substantially the same. The stationary die includes a protrusion on the surface of the stationary die, a plurality of threaded grooves obliquely disposed on the stationary die, and a plurality of recesses disposed on one side of the threaded grooves.

[0010] Furthermore, the protrusion is located at the edge of the surface of the stationary thread plate, and its width gradually increases towards the screw thread rolling direction. Multiple pits are arranged along the length of the protrusion, and each pit has two mutually symmetrical sides.

[0011] Furthermore, the concave point is located on the surface of the stationary tooth plate and away from one end of the convex strip. Multiple concave points are arranged at an angle of 15°, and the bottom of the concave point has a flat plane.

[0012] Furthermore, the surface of the stationary tooth plate and the screw groove are provided with multiple serrated grooves.

[0013] Furthermore, the tooth tip of the serrated groove is replaced by a hollow groove, which is V-shaped and located on both sides of each serrated groove, with a smooth transition at the bottom and no sharp edges.

[0014] Compared with existing technologies, the self-locking screw provided by this invention forms a double anti-loosening self-locking structure through the geometric locking between the flat bevel of the screw tip and the inner wall of the screw hole, and the friction between the protrusion and the screw hole. This greatly increases the screw's rotation resistance and improves its self-locking and anti-loosening capability. The serrated pattern can pre-cut the thread for subsequent tapping, thereby reducing the tapping torque and improving cutting efficiency. The reinforcing pattern not only reduces the chance of tooth breakage in the serrated pattern but also improves the screw's axial anti-loosening capability. This invention also provides a die for cutting self-locking screws. The stationary die and the moving die form the thread through the provided screw groove, the concave point forms the protrusion, the serrated groove forms the serrated pattern, and the presence of the empty groove can prevent sharp tooth tips from appearing on the serrated groove, thereby improving the service life of the die. Attached Figure Description

[0015] Figure 1 A schematic diagram of the self-locking screw for cutting provided by the present invention.

[0016] Figure 2 for Figure 1 Enlarged diagram of point A in the middle.

[0017] Figure 3 A schematic diagram of the die plate mold for cutting self-locking screws provided by the present invention.

[0018] Figure 4 for Figure 3 Enlarged diagram of point B in the middle.

[0019] Reference numerals: Screw body 10, screw 11, screw tip 12, thread 13, serration 14, protrusion 15, reinforcing groove 16, screw head 20, stationary thread plate 30, ridge 31, thread groove 32, concave point 33, pit 34, serration 35, slot 36, moving thread plate 40. Detailed Implementation

[0020] The following provides a more detailed description of specific embodiments of the present invention. It should be understood that the description of the embodiments of the present invention herein is not intended to limit the scope of protection of the present invention.

[0021] like Figure 1 The diagram shown is a structural schematic of the self-locking screw provided by the present invention. The self-locking screw includes a screw body 10 and a screw head 20 disposed at the end of the screw body 10. It is conceivable that the self-locking screw also includes other functional modules, such as materials for manufacturing the screw, slots for inserting a screwdriver, etc., which are technologies known to those skilled in the art and will not be described in detail here.

[0022] Please see Figure 2The screw body 10 includes a screw 11, a screw tip 12 disposed at the end of the screw 11 away from the screw head 20, a thread 13 disposed on the screw 11 and the screw tip 12, a serration 14 disposed on the screw 11, and a plurality of protrusions 15 arranged on one side of the serration 14.

[0023] The diameter of the connection between the screw 11 and the screw head 20 gradually increases towards the screw head 20, thus strengthening the connection and making it less prone to breakage when the screw is subjected to large torque or lateral impact force, significantly improving the overall structural strength and service life of the screw. The thread 13 starts near the tip of the screw tip 12 and spirals upward to the position of the screw 11 near the screw head 20, with a helix angle of 15°. A small helix angle results in better self-locking performance of the thread, reducing vibration during screw insertion, improving the stability of the screw after locking, and preventing it from falling out.

[0024] The main body of the screw tip 12 is a four-sided pyramid shape, composed of four flat beveled surfaces joined together. The connections between the four beveled surfaces are smoothly transitioned to form four cutting edges for drilling operations. After self-tapping and locking is completed, the four beveled surfaces on the screw tip 12 abut against the sidewall of the bottom of the screw hole, forming a geometric locking and anti-loosening structure. When the screw shows signs of rotation due to vibration, the beveled surfaces on the screw tip 12 interfere with the sidewall of the bottom of the screw hole, forming a resistance to rotation, thereby preventing the screw from rotating and improving the screw's self-locking and anti-loosening ability.

[0025] The serrated pattern 14 begins at the connection between the screw 11 and the screw tip 12, spiraling upwards to the middle section of the screw 11, with a helix angle of 15°. The crest of the serrated pattern 14 is slightly lower than the crest of the thread 13. The serrated pattern 14 performs cutting operations with its relatively sharp crest, resulting in a stronger cutting force compared to a normal continuous thread. This pre-cutting process prepares the thread 13 for subsequent entry, thereby reducing the entry torque and improving cutting efficiency.

[0026] The sawtooth pattern 14 has a ring of reinforcing grooves 16 at its root, which are intermittently arranged along the helical direction of the sawtooth pattern 14. The cross-sectional dimension of each reinforcing groove 16 is smaller than that of the sawtooth pattern 14, and its shape is similar to the tooth profile of the thread 13. The cross-section of the reinforcing groove 16 is triangular, with a smooth, rounded apex and no sharp edges. The height of the reinforcing groove 16 is less than the crest height of the sawtooth pattern 14, and its width is less than the root width of the sawtooth pattern 14. The helix angle of the reinforcing groove 16 is the same as that of the sawtooth pattern 14 (both 15°) to ensure that it is formed synchronously by the mold during the thread rolling process.

[0027] The reinforcing groove 16 effectively prevents the serrated groove 14 from chipping or breaking during high-torque, high-impact self-tapping cutting, ensuring the stable and reliable pre-cutting function of the serrated groove 14 and extending the screw's service life. Furthermore, during thread rolling, the formation of the reinforcing groove 16 also prevents sharp tooth tips from appearing on the thread rolling die, which are prone to wear or chipping during the thread rolling process. Therefore, the formation of the reinforcing groove 16 also improves the service life of the thread rolling die.

[0028] During screwing, the chips generated by the serrated edges 14 accumulate between the two serrated edges 14, thus covering the reinforcing groove 16. When the screw is fully tightened, the compressed material elastically recovers towards the reinforcing groove 16 and compacts the chips covering the reinforcing groove 16, thereby forming a protrusion in the screw hole that matches the shape of the reinforcing groove 16. When the screw is subjected to axial pull-out force or reverse loosening torque, these covered protrusions and the reinforcing groove 16 mechanically interfere, thereby increasing the resistance to axial pull-out of the screw and further improving the screw's self-locking and anti-loosening capability.

[0029] The protrusions 15 are located on the screw 11, and multiple protrusions 15 are arranged spirally from the side near the serrations 14 to the end of the thread 13 away from the screw tip 12, with a helix angle of 60°. The protrusions 15 are hemispherical, and their ends away from the surface of the screw 11 have a flat plane, the height of which is less than the crest height of the thread 13. This allows the smooth outer side of the protrusions 15 to smoothly enter the material, reducing the screw's driving torque and preventing strong interference between the protrusions 15 and the material. The flat surface at the end of the protrusions 15 increases the friction between the screw and the screw hole, thereby increasing the screw's turning resistance and further improving the screw's self-locking and anti-loosening ability.

[0030] like Figure 3 The diagram shows a schematic representation of the die plate mold for cutting self-locking screws provided by the present invention. The die plate mold for cutting self-locking screws includes a stationary die plate 30 and a movable die plate 40 disposed opposite to one side of the stationary die plate 30. It is conceivable that the die plate mold for cutting self-locking screws also includes other functional modules, such as an assembly module, a drive module, etc., which are technologies known to those skilled in the art and will not be described in detail here.

[0031] Both the stationary tooth plate 30 and the movable tooth plate 40 are rectangular blocks. The stationary tooth plate 30 remains stationary, while the movable tooth plate 40 is driven by a drive module to reciprocate horizontally. When the stationary tooth plate 30 and the movable tooth plate 40 overlap, a screw is forced into the space between them, thus completing the tooth rolling process. The long side of the stationary tooth plate 30 is shorter than the long side of the movable tooth plate 40, ensuring a more thorough and complete tooth rolling. The specific operation of the tooth rolling process is existing technology and will not be described in detail here.

[0032] Please see Figure 4 The side structures of the stationary tooth plate 30 and the movable tooth plate 40 are substantially the same, and the stationary tooth plate 30 will be described here. The stationary tooth plate 30 includes a protrusion 31 disposed on the surface of the stationary tooth plate 30, a plurality of threaded grooves 32 disposed obliquely on the stationary tooth plate 30, and a plurality of recesses 33 disposed on one side of the threaded grooves 32.

[0033] The protrusion 31 is located at the edge of the surface of the stationary thread plate 30, and its width gradually increases towards the screw threading direction. Multiple recesses 34 are arranged along the length of the protrusion 31. Each recess 34 has two symmetrical side surfaces, which can form the bevel of the screw tip 12 during the screw threading process. After the screw rolls one revolution, the bevels together form the screw tip 12 with four beveled surfaces. The protrusion 31 is existing technology and also includes smooth surfaces, shear surfaces, etc., which are known to those skilled in the art and will not be described in detail here. The screw groove 32 is distributed on the surface of the stationary thread plate 30, and its inclination angle along the length of the stationary thread plate 30 is 15°. It can form the thread 13 on the screw during the screw threading process. The recesses 33 are located on the surface of the stationary thread plate 30, away from one end of the protrusion 31. Multiple recesses 33 are arranged at an inclination angle of 15°. The bottom of the concave point 33 has a flat surface, and the concave point 33 can form the protrusion 15 on the screw during the screw thread rolling process.

[0034] The surface of the stationary thread plate 30 and the thread groove 32 are provided with multiple serrated grooves 35. These serrated grooves 35 can form the serrated pattern 14 on the screw during the thread rolling process. To avoid sharp tooth tips on the serrated grooves 35, which would increase the wear of the thread plate mold, the tooth tips of the serrated grooves 35 are replaced by a hollow groove 36. The hollow groove 36 is V-shaped and located on both sides of each serrated groove 35. Its bottom is rounded and has no sharp edges, so as to form the reinforcing pattern 16 during the thread rolling process.

[0035] Because the material in the first half of the screw has greater fluidity during the thread rolling process, while the second half is basically stable, to reduce the uncontrollability of screw rolling, the serration 14 can only be a secondary processing of the already formed thread crest. Therefore, the serration groove 35 can only be distributed in the second half of the stationary thread plate 30, thereby improving the imprinting accuracy. Furthermore, the moving thread plate 40 provides pressure and support for the thread rolling operation and needs to reciprocate. Since the position of the serration 14 on the screw is strictly constrained by the thread pitch, to ensure precise positioning of the serration 14 during the thread rolling process, the serration groove 35 is only provided on the stationary thread plate 30.

[0036] Compared with the prior art, the self-locking screw provided by the present invention forms a double anti-loosening self-locking structure through the geometric locking between the flat bevel of the screw tip 12 and the inner wall of the screw hole, and the friction between the protrusion 15 and the screw hole, thereby greatly increasing the screw's rotation resistance and improving its self-locking and anti-loosening ability. The serration 14 can pre-cut the thread 13 that is subsequently driven in, thereby reducing the driving torque of the thread 13 and improving the cutting efficiency. The reinforcing groove can not only reduce the breakage of the serration 14, but also improve the screw's axial anti-loosening ability. The present invention also provides a die for cutting self-locking screws, wherein the stationary die 30 and the moving die 40 form the thread 13 through the provided screw groove 32, the concave point 33 forms the protrusion 15, the serration groove 35 forms the serration 14, and the presence of the empty groove 36 can avoid sharp tooth tips on the serration groove 35, thereby improving the service life of the die.

[0037] The above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions or improvements within the spirit of the present invention are covered within the scope of the claims of the present invention.

Claims

1. A cut self-locking screw, characterized by: The self-locking screw includes a screw body and a screw head located at the end of the screw body. The screw body includes a screw shank, a screw tip located at the end of the screw shank away from the screw head, a thread on the screw shank and the screw tip, a serrated edge on the screw shank, and a plurality of protrusions arranged on one side of the serrated edge. The serrated edge starts from the connection between the screw shank and the screw tip, spirals upward to the middle section of the screw shank, and has a helix angle of 15°. The crest of the sawtooth pattern is lower than the crest of the thread. The protrusion is located on the screw. Multiple protrusions are arranged spirally from the side near the sawtooth pattern to the end of the thread away from the screw tip, and their helix angle is 60°. The protrusion is hemispherical, and its end away from the screw surface has a flat plane. The height of this plane is less than the crest height of the thread. The root of the sawtooth pattern has a reinforcing groove. The height of this reinforcing groove is less than the crest height of the sawtooth pattern, and its width is less than the root width of the sawtooth pattern.

2. The cut self-locking screw according to claim 1, characterized in that: The diameter of the connection between the screw and the screw head gradually increases towards the end of the screw head.

3. The self-locking screw according to claim 1, characterized in that: The helix angle of the thread is 15°.

4. The cut self-locking screw according to claim 1, characterized in that: The main body of the screw tip is a four-sided pyramid shape, which is composed of four flat inclined surfaces joined together, with a smooth transition at the connection of the four inclined surfaces.

5. The cut self-locking screw according to claim 1, characterized in that: The reinforcing ridges are intermittently arranged along the spiral direction of the serrated pattern, and the cross-section of the reinforcing ridges is triangular with a smooth transition at the top and no sharp edges.

6. A die for cutting self-locking screws according to any one of claims 1 to 5, characterized in that: The die mold for cutting self-locking screws includes a stationary die plate and a movable die plate. The stationary die plate includes a ridge on its surface, a plurality of threaded grooves obliquely disposed on the stationary die plate, and a plurality of recesses disposed on one side of the threaded grooves.

7. The die plate mold for cutting self-locking screws according to claim 6, characterized in that: The protrusion is located at the edge of the surface of the stationary thread plate, and its width gradually increases towards the screw thread rolling direction. Multiple pits are arranged along the length of the protrusion, and each pit has two mutually symmetrical sides.

8. The die for cutting a self-locking screw according to claim 6, wherein: The concave points are located on the surface of the stationary tooth plate and away from one end of the protrusion. Multiple concave points are arranged at an angle of 15°, and the bottom of the concave points has a flat surface.

9. The die plate mold for cutting self-locking screws according to claim 6, characterized in that: The surface of the stationary tooth plate and the screw groove are further provided with multiple serrated grooves.

10. The die for cutting a self-locking screw according to claim 9, wherein: The top of the serrated groove is replaced by a hollow groove, which is V-shaped and located on both sides of each serrated groove, with a smooth transition at the bottom and no sharp edges.

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