Wrenching bolt, manufacturing technology of wrenching bolt, bolt assembly and bolt screwdriver

Abstract

The invention provides a wrenching bolt and a preparation process thereof, a bolt assembly and a bolt screwdriver, and the wrenching bolt comprises a screw rod, the outer wall of the screw rod is provided with an external thread; the bolt head is located at one end of the screw rod, the end of the bolt head is provided with a concave pulling and screwing groove, a plurality of grooves extending in the radial direction are distributed in the inner wall of the pulling and screwing groove, the grooves comprise a plurality of spline tooth grooves and a plurality of rectangular grooves, and the inner wall of each spline tooth groove comprises a concave curved surface. Convex curved surfaces formed by outer round corners are arranged at the radial inward root parts of the flower tooth grooves and the rectangular grooves; wherein the number of the flower tooth grooves is larger than that of the rectangular grooves, the radial depth of the flower tooth grooves is smaller than that of the rectangular grooves, and the number of the rectangular grooves is at least two. In this way, on the premise that the structural strength of the bolt head is considered, the wrenching bolt can exert larger twisting torque when needed through the special-shaped wrenching groove.

Description

Technical Field

[0001] The present application relates to the field of bolts, and particularly to a wrenchable bolt, its preparation process, a bolt assembly, and a bolt screwdriver. Background Art

[0002] For existing bolt products such as hexagon socket head cap screws, Phillips head screws, and slotted head screws, they mainly rely on the wrenching grooves at the shaft ends to contact and limit with the bit and screwdriver, so as to realize the rotation of the bolt.

[0003] For example, as Figure 1 , Figure 2 shown, it shows a bolt 1 known to the inventor. It sequentially includes a conical head 101, a cylindrical section 102, a thread finishing section 103, and a thread section 104 along the axial direction. The shaft end of the conical head 101 has a recessed wrenching groove 105. The wrenching groove 105 is a hexagon socket head cap groove, and the inner wall of the hexagon socket head cap groove is mainly composed of curved surfaces.

[0004] The Chinese utility model patent with the publication number of "CN209687887U" discloses "a new type of hexagon socket head cap screw". The hexagon socket head cap screw of this utility model patent includes a nut, and a boss is integrally formed on the upper surface of the nut. A screw fastening hole is provided on the boss. The screw fastening hole has a three-layer hole type structure. The first layer of hole type is a hexagon socket head cap hole, which is similar to the bolt 1 known to the inventor. The second layer is a regular hexagon hole matching an inner hexagon wrench, and the third layer is a conical hole with a cross-shaped bottom. This screw can be suitable for different tools to tighten or loosen it during installation, and will not damage the installation surface.

[0005] By arranging different groove shapes in a progressive manner along the axial direction, this bolt (screw) can indeed adapt to different wrenching tools. However, compared with ordinary bolts, a lot of the axial space inside this bolt is used to layout these three layers of holes, which will also reduce the structural strength of the bolt in this part to a certain extent.

[0006] The depth of the groove of the bolt will affect the installation of the entire bolt and the bearing capacity of the head. If the depth is relatively shallow, the torque that the bolt can withstand for wrenching the bolt is small, the pre-tightening force generated is small, the anti-loosening performance is poor, and it is easy to slip. If the depth is relatively deep, the installation torque that the bolt can withstand is large, but when the thickness of the bolt head is certain, an excessive groove depth will cause the bearing capacity of the bolt head to decrease and reduce the mechanical properties of the product. There is a contradiction in the product. Summary of the Invention

[0007] In view of the state of the above-mentioned prior art, this application is made. In a first aspect, the purpose of this application is to provide a wrenchable bolt.

[0008] The technical solution adopted in this application includes: a screw rod, the outer wall of the screw rod has an external thread; a bolt head, the bolt head is located at one end of the screw rod, the end of the bolt head has a recessed wrenching groove, and a plurality of grooves extending radially are distributed on the inner wall of the wrenching groove. The grooves include a plurality of spline grooves and a plurality of rectangular grooves. The inner wall of the spline groove includes a concave curved surface. At the radially inward roots of the spline groove and the rectangular groove, there are convex curved surfaces formed by external rounded corners; wherein, the number of spline grooves is greater than the number of rectangular grooves, the radial depth of the spline groove is less than the radial depth of the rectangular groove, and there are at least two rectangular grooves.

[0009] As a further improvement of this application, the inner wall of the rectangular groove includes: a pair of parallel side faces, and an outer end face connected to the pair of side faces and located radially outside the pair of side faces. A right-angled internal corner is formed at the junction of the side face and the outer end face; the distance between the pair of side faces in the same rectangular groove is equal to the distance between the two ends of the concave curved surface; the convex curved surface is tangent to the concave curved surface for a smooth transition, and the external rounded corners of the spline groove and the external rounded corners of the adjacent spline groove or the rectangular groove form a continuous convex curved surface.

[0010] As a further improvement of this application, the radial depth of the rectangular groove is 1.5 to 2.5 times the radial depth of the spline groove.

[0011] As a further improvement of this application, the number of rectangular grooves is two, and the two rectangular grooves are arranged symmetrically in a mirror image.

[0012] As a further improvement of this application, the radius of the rounded corner corresponding to the convex curved surface is greater than the radius of the rounded corner corresponding to the concave curved surface, and the central angle corresponding to the convex curved surface is less than the central angle corresponding to the concave curved surface; the tops of all the convex curved surfaces are located on the same tooth root circle, and the bottoms of all the concave curved surfaces are located on the same tooth top circle.

[0013] As a further improvement of this application, the number of rectangular grooves is two, the number of spline grooves is four, the included angle between the spline groove and the adjacent spline groove is 60°, and the included angle between the spline groove and the adjacent rectangular groove is 60°.

[0014] In a second aspect, a bolt assembly is provided, including the above-mentioned wrenching bolt. The bolt assembly includes: a wrenching bolt; a nut, and the nut is threadedly assembled with the screw rod.

[0015] In a third aspect, a screwdriver is provided, which has a head including a plurality of teeth arranged circumferentially and protruding radially. The plurality of teeth include a plurality of spline teeth and at least one rectangular tooth. The radially outer portion of the rectangular tooth is rectangular, and the radially inner portion of the rectangular tooth has the same shape as the radially inner portion of the spline teeth.

[0016] As a further improvement of the present application, the number of the rectangular teeth is two, and the two rectangular teeth are arranged symmetrically in a mirror image. The head can be inserted into the wrenching groove of the wrenching bolt described above. The spline teeth and the rectangular teeth are respectively in shape fit with the spline tooth groove and the rectangular groove for wrenching the wrenching bolt.

[0017] In a fourth aspect, a manufacturing process for a wrenching bolt is provided for manufacturing the above wrenching bolt. The manufacturing process for the wrenching bolt includes: Step S1: providing a bolt blank, where the bolt blank is a cylindrical blank; Step S2: performing a upsetting process on the bolt blank to upset the bolt blank into a mushroom head blank, where the mushroom head blank includes a swollen head and a smooth rod, further upsetting the mushroom head blank, and machining the wrenching groove at the end of the swollen head to form a preformed blank; Step S3: performing machining on the preformed blank, turning the preformed blank to form a stepped shaft, where the stepped shaft includes a first shaft section and a second shaft section, and the diameter of the first shaft section is greater than the diameter of the second shaft section; Step S4: performing thread rolling on the second shaft section to form the external thread, and the major diameter of the external thread after thread rolling is equal to the diameter of the first shaft section.

[0018] The beneficial effects of the wrenching bolt of the present application include:

[0019] First, different from the wrenching groove of the existing bolt which is a tooth groove with the same shape in one circle, the inner wall of the wrenching groove of the present application is distributed with spline tooth grooves and rectangular grooves. The inner wall of the spline tooth groove is mainly composed of a curved surface, and the inner wall of the rectangular groove is mainly composed of a flat surface. The whole wrenching groove constitutes a special-shaped groove. Relying on its own plane and larger radial depth, the rectangular groove can provide more contact area and lever arm, so it is not easy to slip in occasions where a large tightening force is used.

[0020] Second, the number of spline tooth grooves is greater than the number of rectangular grooves, and the radial depth of the spline tooth grooves is less than the radial depth of the rectangular grooves, so that the rectangular grooves do not interfere with the contact between the ordinary bit and the wrenching bolt, and it can also be applicable to the occasion of small tightening force of the ordinary bit.

[0021] Again, a greater radial depth of the rectangular groove is equivalent to increasing the force arm. On the premise that the axial depth of the wrenching groove is unified, it can provide a greater torque than an ordinary bolt. Or, on the premise of achieving the same torque, the groove depth of the wrenching groove can be reduced, reducing the material equivalent to being dug out from the bolt head, thereby improving the load-bearing capacity of the bolt head and enhancing the reliability of wrenching the bolt.

[0022] Secondly, the convex surface formed by the outer fillet is equivalent to increasing the opening width of the spline groove and the rectangular groove, and at the same time, it is also convenient to unify the local shape here, so that different bit heads can be positioned and contacted with the wrenching bolt of the present application.

[0023] In a preferred manner, the rectangular groove includes at least two arranged in mirror symmetry. This symmetric distribution can make the torque transmission more balanced, reduce the situation of eccentric load, and thus improve the torsional strength of the bolt head.

[0024] The beneficial effects of the bolt assembly of the present application include:

[0025] The wrenching bolt and the nut in the bolt assembly are assembled by threads. The screw rod can pass through the workpiece to be fixed, and the bolt head and the nut can be located on both sides of the workpiece to be fixed, so as to fix the plate-shaped workpiece.

[0026] The beneficial effects of the screwdriver of the present application include:

[0027] Both the spline teeth and the rectangular teeth can contact and engage with the wrenching bolt. The design of the rectangular teeth is convenient for increasing the upper limit of the torque that the screwdriver can apply to the wrenching bolt. The beneficial effects of the preparation process of the wrenching bolt of the present application include:

[0028] The preparation process of the present application processes the wrenching groove at the end of the enlarged head of the bolt blank through upsetting treatment, mainly relying on the overall upsetting forming rather than the processing method of completely removing materials. First, a stepped shaft is processed, and the relatively thin shaft section in the stepped shaft is rolled to form an external thread. Let a part of the material be radially extruded inward to form the root of the thread, and let a part of the material be radially extruded outward to form the crest, which helps to ensure the processing accuracy and forming quality of each part structure of the wrenching bolt. Brief Description of the Drawings

[0029] In order to more clearly illustrate the technical solutions in the embodiments, the accompanying drawings of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0030] Figure 1 It is a front view of a partially-sectioned bolt known to the inventor;

[0031] Figure 2is an axial view of a bolt known to the inventor;

[0032] Figure 3 is a partial cross-sectional front view of an embodiment of the wrenching bolt of the present application;

[0033] Figure 4 is an axial view of an embodiment of the wrenching bolt of the present application;

[0034] Figure 5 is a front view of a special bit of an embodiment of the present application;

[0035] Figure 6 is an axial view of a special bit of an embodiment of the present application;

[0036] Figure 7 is a schematic diagram of the application of an embodiment of the bolt assembly of the present application;

[0037] Figure 8 is a front view of a bolt blank of an embodiment of the preparation process of the wrenching bolt of the present application;

[0038] Figure 9 is a front view of a mushroom head blank of an embodiment of the preparation process of the wrenching bolt of the present application;

[0039] Figure 10 is a partial cross-sectional front view of a preformed blank of an embodiment of the preparation process of the wrenching bolt of the present application;

[0040] Figure 11 is an axial view of a preformed blank of an embodiment of the preparation process of the wrenching bolt of the present application;

[0041] Figure 12 is a front view of a stepped shaft of an embodiment of the preparation process of the wrenching bolt of the present application;

[0042] Figure 13 is an axial view of a stepped shaft of an embodiment of the preparation process of the wrenching bolt of the present application;

[0043] Figure 14 is the cross-sectional profile of the inner wall of the wrenching groove of an embodiment of the wrenching bolt of the present application;

[0044] Figure 15 is a schematic diagram of the use of a wrenching bolt and a hexagon socket bit in an embodiment of the installation method of the wrenching bolt of the present application;

[0045] Figure 16 is a schematic diagram of the use of a wrenching bolt and a special bit in an embodiment of the installation method of the wrenching bolt of the present application;

[0046] Figure 17 is a flowchart of an embodiment of the preparation process of the wrenching bolt of the present application;

[0047] Figure 18 is a flowchart of an embodiment of the installation method of the wrenching bolt of the present application.

[0048] Explanation of the reference numerals

[0049] 1 - bolt; 101 - tapered head; 102 - cylindrical section; 103 - thread run - out section; 104 - thread section; 105 - wrenching groove;

[0050] 2 - wrenching bolt; 201 - tapered head; 202 - cylindrical section; 203 - thread run - out section; 204 - thread section; 3 - special bit; 301 - working end; 3011 - flower teeth; 3012 - rectangular teeth; 4 - fixing plate; 5 - bolt blank; 6 - mushroom head blank; 601 - enlarged head; 602 - smooth rod; 7 - pre - formed blank; 8 - stepped shaft; 801 - first shaft section; 802 - second shaft section; 9 - wrenching groove; 901 - cylindrical cavity; 902 - flower tooth groove; 9020 - convex surface; 9021 - first outer fillet; 9022 - concave surface; 903 - rectangular groove; 9031 - second outer fillet; 9032 - side elevation; 9033 - outer end face; 904 - chamfer; 905 - conical cavity; 10 - nut; 1001 - external hexagonal section; 1002 - axially elongated section; 11 - bottom circle of tooth; 12 - top circle of tooth; 13 - hexagon socket head bit; 14 - clearance space Detailed implementation manners

[0051] The exemplary embodiments of the present application will be described below with reference to the accompanying drawings. It should be understood that these specific descriptions are only used to teach those skilled in the art how to implement the present application, rather than to exhaust all feasible ways of the present application, nor to limit the scope of the present application.

[0052] Refer to Figure 3 、 Figure 4 、 Figure 14 , an embodiment of the present application provides a wrenching bolt 2. The bolt includes a screw rod and a bolt head. Among them, the outer wall of the screw rod has an external thread. The bolt head is located at one end of the screw rod, and the end of the bolt head has a recessed wrenching groove 9. The wrenching groove 9 is a blind hole. A number of grooves extending radially are distributed on the inner wall of the wrenching groove 9. The grooves include a number of flower tooth grooves 902 and a number of rectangular grooves 903. The inner wall of the flower tooth groove 902 includes a concave surface 9022. At the root of the flower tooth groove 902 and the rectangular groove 903 facing radially inward, there are convex surfaces 9020 formed by outer fillets. Among them, the number of flower tooth grooves 902 is greater than the number of rectangular grooves 903. The depth of the flower tooth groove 902 along the radial direction is less than the depth of the rectangular groove 903 along the radial direction. The rectangular groove 903 includes at least two. The number of the rectangular grooves 903 can also be one.

[0053] The beneficial effects of adopting the above embodiments include: Through the special shape design of the wrenching groove 9, when wrenching the bolt 2, the bit wrenching groove 9 forms more surface contacts, reducing the risk of slipping during the wrenching process. Since the longer radial depression dimension of the rectangular groove 903 correspondingly enlarges the inner wall area of itself, and the characteristic of the rectangular groove 903 is that its inner wall is composed of flat surfaces, the flat surface is more conducive to forming the surface contact phenomenon. As long as a bit matching the wrenching bolt 2 is used and the cross-sectional contour thereof also matches the cross-sectional contour of the rectangular groove 903, it is conducive to generating more surface contacts when the bit contacts the wrenching groove 9. The radial depth of the rectangular groove 903 is larger, which is equivalent to increasing the force arm. When the axial depth of the wrenching groove 9 is unified, the wrenching bolt 2 of the present application can provide a greater torque than an ordinary bolt. Or on the premise of achieving the same torque, the groove depth (i.e., the axial dimension) of the wrenching groove 9 can be reduced, thereby improving the bearing capacity of the bolt head and the reliability of the wrenching bolt 2. Additionally, when the pre-tightening force is small, an ordinary hexagon socket bit 13 (see Figure 15 ) can be inserted into the wrenching groove 9 to normally wrench the wrenching bolt 2. When the pre-tightening force is large, a special bit can be used to engage with the rectangular groove 903 of the wrenching groove 9 (see Figure 16 ), thereby applying a greater pre-tightening force.

[0054] Figure 14 is the cross-sectional contour of the inner wall of the wrenching groove 9. In one embodiment, as shown in Figure 14 , the inner wall of the rectangular groove 903 includes: a pair of parallel side faces 9032, and outer end faces 9033 connected to the pair of side faces 9032 and located radially outside the pair of side faces 9032. A right-angled internal corner is formed at the junction of the side face 9032 and the outer end face 9033. It can be understood that, optionally, a chamfer, for example, a rounded corner, can be provided at the right-angled internal corner. The distance between the pair of side faces 9032 within the same rectangular groove 903 is equal to the distance between the two ends of the concave curved surface 9022. The convex curved surface 9020 and the concave curved surface 9022 are tangentially transitioned. The outer rounded corners of the flower tooth grooves 902 form a continuous convex curved surface 9020 with the outer rounded corners of the adjacent flower tooth grooves 902 or rectangular grooves 903. As shown in the cross-section in Figure 14 , the cross-section of the convex curved surface 9020 is a relatively long arc, while the outer rounded corners of the flower tooth grooves 902 or rectangular grooves 903 are relatively short arcs, and the two short arcs can be spliced into a long arc. Both the convex curved surface 9020 and the concave curved surface 9022 are arc surfaces.

[0055] The beneficial effect of adopting the above embodiments is that the continuous convex curved surface 9020 and concave curved surface 9022 can enhance the structural strength and avoid stress concentration.

[0056] In another embodiment, as shown in Figure 14As shown, the outer rounded corner of the flower tooth groove 902 is the first outer rounded corner 9021, the outer rounded corner of the rectangular groove 903 is the second outer rounded corner 9031, the side vertical surface 9032 is tangent to the adjacent second outer rounded corner 9031, and an obtuse positive corner is formed at the junction of the side vertical surface 9032 and the adjacent second outer rounded corner 9031. The convex curved surface 9020 is composed of two adjacent first outer rounded corners 9021, or composed of one adjacent first outer rounded corner 9021 and one second outer rounded corner 9031.

[0057] In one embodiment, as Figure 14 shown, the radius of curvature corresponding to the convex curved surface 9020 is greater than the radius of curvature corresponding to the concave curved surface 9022, and the central angle corresponding to the convex curved surface 9020 is less than the central angle corresponding to the concave curved surface 9022. The tops of all the convex curved surfaces 9020 are located on the same tooth bottom circle (or inscribed circle) 11, and the bottoms of all the concave curved surfaces 9022 are located on the same tooth top circle (or circumscribed circle) 12. The tooth bottom circle 11 and the tooth top circle 12 are virtual circles. Figure 14 The tooth bottom circle 11 and the tooth top circle 12 are represented by dashed lines in

[0058] The beneficial effects of adopting the above embodiment are as follows: optimizing the geometric shape of the wrenching groove 9 makes the torque distribution more uniform and improves the bearing capacity. The tooth bottom circle 11 and the tooth top circle 12 make the shape and size of each flower tooth groove 902 unified, enhancing standardization.

[0059] In another embodiment, the range of the central angle corresponding to the concave curved surface 9022 is 150° to 160°, and the range of the central angle of the convex curved surface 9020 is 85° to 95°.

[0060] In one embodiment, the number of rectangular grooves 903 is two, the number of flower tooth grooves 902 is four, the included angle between adjacent flower tooth grooves 902 is 60°, and the included angle between the flower tooth groove 902 and the adjacent rectangular groove 903 is 60°.

[0061] The beneficial effects of adopting the above embodiment are as follows: the symmetrical distribution can make the torque transmission more balanced, reduce the off-load situation, improve the anti-torsion strength of the bolt head, and also facilitate the positioning and operation of the bit.

[0062] In one embodiment, as Figure 3 shown, the bottom of the wrenching groove 9 has a conical cavity 905, and the conical cavity 905 makes the axial depth of the wrenching groove 9 gradually deeper in the radially inward direction. Additionally, as Figure 4 shown, the opening of the wrenching groove 9 has a chamfer 904, and the chamfer 904 is a chamfering treatment. If there is no chamfer 904, the opening edge of the wrenching groove 9 will be relatively sharp, and the chamfer 904 also expands the opening area of the wrenching groove 9.

[0063] The beneficial effects of adopting the above embodiments are as follows: The conical cavity 905 can ensure that the center of the bottom surface of the wrenching groove 9 is relatively the most sunken, ensuring that there will be no situation of bulging in the middle due to machining accuracy problems. Therefore, if an external bit enters the wrenching groove 9, the bit can fully contact the flower tooth grooves 902 and the rectangular grooves 903, without being affected by the possible bulging of the bottom surface of the wrenching groove 9. The chamfer 904 facilitates the alignment of the bit and reduces the alignment accuracy during insertion.

[0064] In another embodiment, as Figure 4 shown, the arc edge formed by the chamfer 904 is equal to the diameter of the tooth top circle 12.

[0065] In one embodiment, the wrenching groove 9 of the wrenching bolt 2 can be applied to bolts such as external hexagonal head bolts, square head bolts, and T-shaped head bolts. As Figure 3 shown, the wrenching bolt 2 is preferably a countersunk head bolt, and the bolt head is a conical head 201. Along the direction away from the bolt head, the screw rod sequentially includes a cylindrical section 202, a thread end section 203, and a thread section 204. The thread section 204 and the thread end section 203 have external threads on the outer wall of the screw rod.

[0066] The beneficial effects of adopting the above embodiments are as follows: Countersunk head bolts are suitable for assembly occasions where the surface needs to be kept flat. The segmented structure of the screw rod facilitates optimizing the strength distribution of the screw rod and ensuring the reliability of the threaded connection.

[0067] In another embodiment, combining Figure 3 and Figure 4 shown, the cavity surrounded by the wrenching groove 9 is a special-shaped cavity. It can be understood that the central body of the wrenching groove 9 is a cylindrical cavity 901. A plurality of flower tooth grooves 902 and a plurality of rectangular grooves 903 are circumferentially distributed on the cylindrical cavity 901, and a conical cavity 905 is also provided at the axial end of the cylindrical cavity 901.

[0068] In another embodiment, as Figure 3 and Figure 4 shown, the axial depth of the wrenching groove 9 is less than the inner diameter of the wrenching groove 9. The axial depth of the wrenching groove 9 is not greater than half of the axial length of the conical head 201, and the maximum inner diameter of the wrenching groove 9 is not greater than half of the outer diameter of the conical head 201. This ensures that less material is equivalently removed from the conical head 201 by the wrenching groove 9, and the negative impact of the wrenching groove 9 on the structural strength of the conical head 201 is smaller.

[0069] In another embodiment, as Figure 14 , the radial depth of the rectangular groove 903 is 1.5 to 2.5 times the radial depth of the flower tooth groove 902.

[0070] As Figure 14As shown, the radial depth of the spline groove 902 is the radial distance from the bottom center of the spline groove 902 (i.e., the deepest part in the radial direction, i.e., the outermost part in the radial direction) to the bottom circle 11 of the tooth. The radial depth of the rectangular groove 903 is the radial distance from the bottom center of the rectangular groove 903 (i.e., the deepest part in the radial direction, i.e., the outermost part in the radial direction) to the bottom circle 11 of the tooth.

[0071] In another embodiment, the semi-apex angle of the conical head 201 is 45°, that is, the included angle between the generatrix of the outer wall of the conical head 201 and the axis of the wrenching bolt 2 is 45°. The range of the semi-apex angle of the conical cavity 905 is from 70° to 75°, that is, the range of the included angle between the generatrix of the inner wall of the conical cavity 905 and the axis of the wrenching bolt 2 is from 70° to 75°.

[0072] In another embodiment, the number of the rectangular grooves 903 is two, and the two rectangular grooves 903 are arranged in mirror symmetry.

[0073] This application provides a bolt assembly, which includes the above-mentioned wrenching bolt 2. As Figure 7 shown, the bolt assembly includes a wrenching bolt 2 and a nut 10, and the nut 10 is threadedly assembled with the screw rod.

[0074] The beneficial effects of adopting the above embodiments are as follows: The cooperation of the two can improve the fastening and anti-loosening performance of the connection, and is suitable for application scenarios with different pre-tightening force requirements.

[0075] In another embodiment, as Figure 7 shown, along the axial direction, the nut 10 can be composed of an integral outer hexagonal section 1001 and an axially elongated section 1002. The outer hexagonal section 1001 and the axially elongated section 1002 increase the overall axial length of the nut 10. There are internal threads on the inner walls of the outer hexagonal section 1001 and the axially elongated section 1002, that is, it is equivalent to increasing the travel of the internal thread of the nut 10 and improving the assembly firmness of the nut 10 and the wrenching bolt 2. In addition, the outer diameter of the outer hexagonal section 1001 is greater than the outer diameter of the axially elongated section 1002, that is, the relatively thin axially elongated section 1002 plays the role of controlling the overall material consumption of the nut 10 as much as possible. The outer hexagonal section 1001 is convenient for contacting with a wrench and turning the nut 10 with the help of the wrench.

[0076] This application provides a wrenching screw. The wrenching screw forms a sharp part at one end of the screw rod of the wrenching bolt 2, that is, a sharp part is formed at the end of the screw rod away from the bolt head. The wrenching screw can be directly screwed into the internal part of the connected part through the threaded section 204.

[0077] This application provides a manufacturing process for a wrenching bolt, which is used to manufacture the above-mentioned wrenching bolt 2. As Figure 17 shown, the manufacturing process includes: Step S1: Provide a bolt blank 5, as Figure 8As shown, the bolt blank 5 is a cylindrical blank. Step S2: Upsetting treatment is performed on the bolt blank 5. As Figure 9 shown, the bolt blank 5 is upset into a mushroom head blank 6. The mushroom head blank 6 includes a bulged head 601 and a smooth rod 602. The mushroom head blank 6 is further upset, and a wrenching groove 9 is machined at the end of the bulged head 601, thereby forming a preformed blank 7. Step S3: Machining is performed on the preformed blank 7 to turn out a stepped shaft 8. The stepped shaft 8 includes a first shaft section 801 and a second shaft section 802. The diameter of the first shaft section 801 is larger than that of the second shaft section 802. Step S4: Thread rolling is performed on the second shaft section 802 to form an external thread. As Figure 3 , Figure 12 shown, the external thread is formed on the thread section 204 and the thread end section 203.

[0078] The beneficial effects of adopting the above embodiment are as follows: It mainly relies on integral upset forming instead of solely relying on the processing method of removing materials. In mass production, this processing method is beneficial to reducing waste and lowering production costs.

[0079] In one embodiment, the bolt blank 5 in step S1 is a cylindrical blank with chamfers at both ends. The outer diameter of the bolt blank 5 is 0.3 mm larger than that of the screw rod, and the axial length tolerance of the bolt blank 5 is controlled within 0.1 mm. The surface roughness of the turning in step S3 is at least 3.2 μm. The major diameter of the external thread after thread rolling in step S4 is equal to the diameter of the first shaft section 801. The axial length of the thread end section 203 is not greater than twice the pitch of the thread section 204.

[0080] The beneficial effects of adopting the above embodiment are as follows: The dimensional tolerance control of the bolt blank 5, the requirements for the surface roughness of turning, and the axial length limitation of the thread end section 203 can ensure the processing accuracy, and the appropriate surface roughness can improve the assembly performance.

[0081] The present application provides a method for installing a wrenching bolt, which uses the above wrenching bolt 2. As Figure 18 shown, this installation method includes: Step T1: As Figure 7 shown, the wrenching bolt 2 is passed through the fixing plate 4. A nut 10 is arranged on one side of the fixing plate 4. The nut 10 is threadedly assembled with the wrenching bolt 2. The nut 10 can be a self-locking nut 10. The wrenching bolt 2 is screwed into the thread section 204 of the self-locking nut 10 without screwing into the thread end section 203.

[0082] It can be understood that the fixing plate 4 here is only illustrative and can represent two or more components fixed by the wrenching bolt 2 and the nut 10.

[0083] Step T2: Select a bit and install the bit on the power tool. Step T3: Use the power tool and tighten the wrenching bolt 2 with the bit. When the torque is reached, separate the bit from the wrenching bolt 2.

[0084] Among them, step T2 includes: Step T201: When the (required) pre-tightening force is small, a hexagon socket bit 13 can be selected as the bit. As Figure 15 shown, the shape profiles of each tooth of the hexagon socket bit 13 are the same. Each tooth of the hexagon socket bit 13 is in concave-convex fit with the flower tooth groove 902, but not in concave-convex fit with the rectangular groove 903. A gap space 14 as Figure 15 shown will be formed between the hexagon socket bit 13 and the rectangular groove 903. Use a power tool equipped with the hexagon socket bit 13 to press against the wrenching groove 9 of the wrenching bolt 2 and tighten. Step T202: When the pre-tightening force is large, as Figure 16 shown, a special bit 3 is selected as the bit. As Figure 5 and Figure 6 shown, the special bit 3 has a working end 301 responsible for the operation. The cross-sectional profile of the outer wall thereof is in concave-convex fit with the cross-sectional profile of the inner wall of the wrenching groove 9. The special bit 3 includes a flower tooth 3011 in concave-convex fit with the flower tooth groove 902 and also includes a rectangular tooth 3012 in concave-convex fit with the rectangular groove 903. Use a power tool equipped with the special bit 3 to press against the wrenching groove 9 of the wrenching bolt 2 and tighten.

[0085] When the tooth of the hexagon socket bit 13 is located in the rectangular groove 903, only the first outer fillet 9031 of the rectangular groove 903 is in surface contact with the tooth of the hexagon socket bit 13. When the rectangular tooth 3012 of the special bit 3 is located in the rectangular groove 903, the side vertical surface 9032 and the outer end surface 9033 of the rectangular groove 903 are both in surface contact with the surface of the rectangular groove 903.

[0086] The beneficial effects of adopting the above embodiments are: The wrenching bolt 2 can be directly installed on the base by using power tools such as electric drills. The present wrenching bolt 2 can adapt to two installation working conditions. In the case where the (required) pre-tightening force is small, or when there is no special installation tool (i.e., the special bit 3), the ordinary hexagon socket bit 13 can be used to install the wrenching bolt 2. In the case where the (required) pre-tightening force is large, the special bit 3 is used. After the special bit 3 is matched with the wrenching groove 9, a larger contact area and a larger force arm can be generated, so as to achieve a larger tightening force.

[0087] The method for installing the wrenching bolt of the present application is provided with two optional bit heads, so as to adapt to different pre-tightening force requirements. When the pre-tightening force is small or there is a lack of special tools, it can be installed with a common hexagon socket bit head 13, which improves the adaptability and convenience of the installation scenario. Moreover, the wrenching groove 9 of the wrenching bolt 2 of the present application does not affect the insertion of different bit heads. The tightening operation is carried out by using a power tool in cooperation with the bit head. When the pre-tightening force is large, the bit head has more surface contact and a larger lever arm with the wrenching groove 9. When the pre-tightening force is small, the contact area and lever arm between the bit head and the wrenching groove 9 are relatively small. In these two cases, the forces applied to the wrenching bolt 2 do not differ significantly, so the wrenching groove 9 of the wrenching bolt 2 is not easily damaged by screwing, ensuring the service life of the wrenching bolt 2.

[0088] The embodiment of the present application also provides the above-mentioned special bit head 3. The bit head can also be called a screwdriver bit. The embodiment of the present application also provides a screwdriver, which can be a common straight screwdriver with a handle, or an L-shaped right-angle elbow screwdriver. The screwdriver has a head that cooperates with the above-mentioned wrenching groove 9. The head can have, for example Figure 5 , Figure 6 the structure shown.

[0089] A bolt screwdriver has a head, and the head includes a plurality of teeth arranged circumferentially and protruding radially. The plurality of teeth include several flower teeth 3011 and at least one rectangular tooth 3012. The radially outer part of the rectangular tooth 3012 is rectangular, and the radially inner part of the rectangular tooth 3012 has the same shape as the radially inner part of the flower tooth 3011.

[0090] The head of the bolt screwdriver can cooperate with the above-mentioned wrenching groove 9 to tighten or loosen the above-mentioned wrenching bolt 2. The flower teeth 3011 and the rectangular teeth 3012 are respectively in shape fit with the flower tooth groove 902 and the rectangular groove 903 for screwing the wrenching bolt 2. The wrenching bolt 2 can be in the form of the above-mentioned special bit head 3, screwdriver, etc.

[0091] The above embodiments are only for illustrating the technical concept and features of the present application, and the purpose is to enable those skilled in the art to understand the content of the present application and implement it. It should not be used to limit the protection scope of the present application. Any equivalent changes or modifications made according to the spirit of the present application should be covered within the protection scope of the present application.

Claims

1. A wrenching bolt, characterized in that, Comprising: A screw, the outer wall of the screw having external threads; A bolt head located at one end of the screw, the end of the bolt head having a recessed wrenching groove (9), the inner wall of the wrenching groove (9) being distributed with a plurality of grooves extending radially, the grooves including a plurality of spline grooves (902) and a plurality of rectangular grooves (903), the inner wall of the spline groove (902) including a concave curved surface (9022), and both the radially inward roots of the spline groove (902) and the rectangular groove (903) having convex curved surfaces (9020) formed by external rounded corners; Wherein, the number of the spline grooves (902) is greater than the number of the rectangular grooves (903), the radial depth of the spline groove (902) is less than the radial depth of the rectangular groove (903), and the rectangular groove (903) includes at least two.

2. The wrenching bolt according to claim 1, wherein: The inner wall of the rectangular groove (903) includes: a pair of parallel side faces (9032), and an outer end face (9033) connected to the pair of side faces (9032) and located radially outside the pair of side faces (9032), and a right-angled internal corner is formed at the junction of the side face (9032) and the outer end face (9033); The distance between a pair of the side faces (9032) within the same rectangular groove (903) is equal to the distance between the two ends of the concave curved surface (9022); The convex curved surface (9020) and the concave curved surface (9022) are in tangential transition, and the external rounded corners of the spline groove (902) and the external rounded corners of the adjacent spline groove (902) or the rectangular groove (903) form a continuous convex curved surface (9020).

3. The wrenching bolt according to claim 1, wherein: The radial depth of the rectangular groove (903) is 1.5 to 2.5 times the radial depth of the spline groove (902).

4. The wrenching bolt according to claim 1, wherein: The number of the rectangular grooves (903) is two, and the two rectangular grooves (903) are arranged in mirror symmetry.

5. The wrenching bolt according to claim 1, characterized in that: The radius of the rounded corner corresponding to the convex curved surface (9020) is greater than the radius of the rounded corner corresponding to the concave curved surface (9022), and the central angle corresponding to the convex curved surface (9020) is less than the central angle corresponding to the concave curved surface (9022); The tops of all the convex curved surfaces (9020) are located on the same tooth bottom circle (11), and the bottoms of all the concave curved surfaces (9022) are located on the same tooth top circle (12).

6. The wrenching bolt according to claim 1, wherein: The number of the rectangular grooves (903) is two, the number of the spline grooves (902) is four, the angle between the spline groove (902) and the adjacent spline groove (902) is 60°, and the angle between the spline groove (902) and the adjacent rectangular groove (903) is 60°.

7. A bolt assembly, characterized in that, Including the wrenching bolt according to any one of claims 1 to 6, the bolt assembly comprising: A wrenching bolt (2); A nut (10), the nut (10) being threadedly assembled with the screw.

8. A screwdriver having a head, characterized in that, The head includes a plurality of teeth arranged circumferentially and protruding radially, the plurality of teeth including a number of flower teeth (3011) and at least one rectangular tooth (3012), a radially outer portion of the rectangular tooth (3012) being rectangular, and a radially inner portion of the rectangular tooth (3012) having the same shape as a radially inner portion of the flower tooth (3011).

9. The screwdriver for bolt according to claim 8, characterized in that, The number of the rectangular teeth (3012) is two, the two rectangular teeth (3012) being arranged symmetrically in a mirror image, the head being capable of being inserted into the wrenching groove (9) of the wrenching bolt according to any one of claims 1 to 6, the flower teeth (3011) and the rectangular teeth (3012) being in shape fit with the flower tooth grooves (902) and the rectangular grooves (903) respectively for wrenching the wrenching bolt.

10. A preparation process for a wrenching bolt, characterized in that, For manufacturing the wrenching bolt according to any one of claims 1 to 6, the manufacturing process of the wrenching bolt includes: Step S1: Providing a bolt blank (5), the bolt blank (5) being a cylindrical blank; Step S2: Upsetting the bolt blank (5) to upset the bolt blank (5) into a mushroom head blank (6), the mushroom head blank (6) including a swollen head (601) and a smooth rod (602), further upsetting the mushroom head blank (6) and machining the wrenching groove (9) at an end of the swollen head (601) to form a preformed blank (7); Step S3: Machining the preformed blank (7), turning the preformed blank (7) to machine a stepped shaft (8), the stepped shaft (8) including a first shaft section (801) and a second shaft section (802), a diameter of the first shaft section (801) being greater than a diameter of the second shaft section (802); Step S4: Thread rolling the second shaft section (802) to form the external thread, a major diameter of the external thread after thread rolling being equal to a diameter of the first shaft section (801).

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