Triangular printing device for screwing position of buttress thread oil casing and accurate printing method of triangular printing device

Abstract

The invention relates to the field of oil casings, in particular to a triangle printing device for the screwing position of a buttress thread oil casing and an accurate printing method thereof, and the printing device comprises a handle, a baffle, a taper lining plate, an arc-shaped positioning frame, a positioning module and a printing module. The taper lining plate of the printing device can be naturally attached to a full-top thread, the positioning module integrates a telescopic base, a compression spring and a replaceable ball head, the ball head makes contact with the thread tooth bottom and the bearing side at the same time, and three-dimensional space positioning is achieved; the distance between the positioning ball head and the baffle and the distance between the bottom edge of the triangular steel seal protrusion and the positioning ball head are designed through a formula, traditional experience positioning errors are avoided, the triangular printing position is accurate, it can be guaranteed that the bottom edge of the triangular steel seal protrusion is exactly located at the tooth top of the thread, marking is clear, and follow-up screwing observation is facilitated.

Description

Technical Field

[0001] This invention relates to the field of oil casing, and specifically to a triangular printing device for printing the screwing position of a trapezoidal threaded oil casing and its precise printing method. Background Technology

[0002] The trapezoidal thread is an important thread type in the API 5B standard. The trapezoidal thread features positive angles on both sides, making it easier to machine. Furthermore, the trapezoidal thread has a larger tooth height, resulting in significantly higher connection strength compared to round threads. Even today, trapezoidal threads are still widely used in oil fields. Trapezoidal couplings do not have internal positioning shoulders for tightening; the proper tightening position is determined by the triangle printed on the pipe body.

[0003] According to the API 5B standard for processing the trapezoidal thread of the sleeve, an equilateral triangle mark with a height of 3 / 8 inch needs to be printed at a position A1 from the end of the pipe. The thread before the base of the triangle is the minimum machine tightening thread, and the thread before the vertex of the triangle mark is the maximum machine tightening thread. By observing or measuring the relative distance between the base of the triangle and the end face of the coupling, a scientific judgment can be made on the tightening status of the coupling.

[0004] It is necessary to print the position of the screwing triangle for observation on the off-trapezoidal threaded joint. Existing printing devices are designed to control the distance from the pipe end to the base of the triangle to be consistent with A1.

[0005] Chinese patent CN202934561U discloses a tool for hammering triangular marks on oil casing threaded joints. This patent provides an adjustable-length hammering tool, solving the problems of inaccurate triangular mark hammering positions and cumbersome hammering operations in current casing joint production. It can accurately hammer out qualified triangular marks at the set positions in a single operation. Chinese patent CN112248661A discloses a batch marking device for triangular marks on oil casing threaded joints. One technical problem it solves is the inefficiency of marking each casing individually in existing technologies, enabling the simultaneous batch printing of triangular marks on a row of flat casings.

[0006] Because the thread has a helix angle, there is a continuous transition from the tooth root to the tooth tip at the same distance from the pipe end in the circumferential direction. Following the operation of patent CN202934561U, although the A1 value of the triangle is strictly ensured, operating this tool cannot guarantee that the base of the triangle will be accurately printed on the observable tooth tip of the pipe body. If the base of the triangle falls at the thread tooth root, the base will not be printed, causing inconvenience for subsequent screwing and observation. Patent CN112248661A mainly focuses on the printing efficiency and clarity of the triangle, but still does not consider how to control the printing position of the triangle base.

[0007] For the eccentric trapezoidal sleeve threaded joint, according to the API 5B standard, a triangular mark indicating the screwing position needs to be printed at a distance of A1 from the pipe end. The existing printing device design only considers the distance A1 of the triangle, and the base of the printed triangle may fall on the bottom of the thread tooth. In this case, the base of the triangle is blurry or even invisible.

[0008] Therefore, there is a need for a triangle printing device for printing the base of a triangle on the top of the thread teeth of an oil casing screwing position. Summary of the Invention

[0009] To address the problems existing in the aforementioned technologies, this invention provides a triangular printing device and a precise printing method for the screwing position of a trapezoidal threaded oil casing. Besides focusing on the A1 distance of the triangle's base, this invention emphasizes that the triangle's base be printed at the top of the thread teeth. A clear triangle base is highly beneficial for judging the screwing condition. Based on determining the A1 length, the positioning of the printed triangle's base was designed, overcoming the drawback of uncertain triangle base position in existing tools.

[0010] The objective of this invention is achieved through the following technical solutions:

[0011] The present invention discloses a triangular printing device for the screwing position of a trapezoidal threaded oil casing, comprising a baffle, an arc-shaped positioning frame, a positioning module and a printing module, for positioning the pipe end;

[0012] The arc-shaped positioning frame is fixedly connected to the baffle and forms a 120° encircling angle. Two tapered inner lining plates that can fit against the threaded conical surface are provided on its inner side. The positioning module is installed along the normal of the arc-shaped positioning frame and has a positioning ball head that can elastically extend and retract along the axial direction. The axial direction of the positioning ball head is perpendicular to the sleeve axis. When the positioning ball head is pressed, it simultaneously contacts the thread tooth root and the bearing side. The distance S1 from the positioning ball head to the baffle is determined with the threaded bearing side as the reference.

[0013] The printing module is fixed to the arc-shaped positioning frame and maintains a fixed position relative to the positioning ball head. The printing module is equipped with a steel stamp punch that can be punched out axially. The axis of the steel stamp punch is perpendicular to the axis of the sleeve. The base of the triangular steel stamp protrusion of the steel stamp punch is at a fixed distance L from the positioning ball head. The distance between the base of the triangular steel stamp protrusion and the end of the tube is A1.

[0014] Where A1 = L + S1, L = (n + 0.75) * P, Lc is the minimum thread length at the screw-in position of the oil casing, and S1 ≤ Lc, where P is the pitch of the trapezoidal thread, and n is the thread length that satisfies the condition... The smallest positive integer is used to ensure that the base of the triangular stamped protrusion always falls on the top of the thread tooth.

[0015] Furthermore, the taper of the tapered inner liner is in the range of 1:6 to 1:36, which is suitable for API specification trapezoidal threads and other special threaded oil casings with tapers. The tapered inner liner naturally fits the full top thread and is designed to match the taper form of the thread. The tapered inner liner is made of resin and will not rub or damage the thread. The tapered inner liner is connected to the arc plate by screws and can be replaced.

[0016] Furthermore, the positioning module includes an adjusting screw, a compression spring, a telescopic base, an end cap, and a positioning ball head. The end cap, fixed to the arc-shaped positioning frame, has a guide hole at its center. A boss protrudes downward from the upper surface of the arc-shaped positioning frame, with a through hole at its center. This through hole is coaxial with the guide hole and together they form a guide channel. The telescopic base slides through the guide channel, and its lower end is connected to the positioning ball head. The compression spring is housed in the through hole, and its lower end abuts against the telescopic base. The adjusting screw is located above the compression spring in the through hole, and the compression amount of the compression spring can be changed by rotating the adjusting screw. The positioning ball head can elastically extend and retract along the axial direction of the guide channel under the action of the compression spring, achieving adaptive positioning.

[0017] Furthermore, the printing module includes a cylindrical cavity, a stamping punch, a cavity end cap, and a shock-absorbing spring. The cylindrical cavity forms a vertically penetrating cylindrical cavity. The cavity end cap is fixedly installed at the upper opening of the cylindrical cavity, and a guide hole is provided at the center of the cavity end cap. The stamping punch is a stepped shaft, with a force-bearing handle at the upper end and an outwardly protruding triangular stamping protrusion integrally formed at the lower end. The stamping punch slides through the guide hole and is limited between the shoulder of the shaft in the cavity and the lower surface of the cavity end cap. The shock-absorbing spring is sleeved on the stamping punch, located on the outer periphery of the shaft section in the cavity. Its upper end abuts against the shoulder of the stamping punch, and its lower end abuts against the inner step of the cylindrical cavity, so that the stamping punch can descend and compress the shock-absorbing spring under the action of external force to complete the stamping, and automatically reset under the action of the restoring force of the shock-absorbing spring.

[0018] Furthermore, the diameter d of the positioning ball head satisfies 3P / 8 < d < P / 2, where P is the pitch. When the triangular printing device is used for sleeves of different specifications, the tangent position between the thread and the tapered inner liner changes, and the extension length of the positioning ball head varies. The adjusting screw ensures that the clamping spring is in full contact with the thread. The arc-shaped positioning frame is designed with an angle of 120°, which, together with the symmetrically arranged tapered inner liner, forms a wrapping effect on the threaded joint.

[0019] Furthermore, it also includes a handle, one end of which is vertically fixed to the baffle, and the other end is provided with an anti-slip knurling or covering layer.

[0020] Furthermore, the triangular stamped protrusion is an equilateral triangle with a height of 3 / 8 in.

[0021] Furthermore, trapezoidal threads are a type of joint widely used in oil casing connections. The thread profile has a tooth root, a bearing side, a tooth tip, and a guide side. Nowadays, various types of trapezoidal threads appear in casing thread joint designs, such as improved trapezoidal threads with better connection performance, where the bearing side angle is negative. The printing device of this invention is used for trapezoidal and improved trapezoidal thread joints, where the bearing side angle α of the thread profile is ±10°.

[0022] Another aspect of the present invention discloses a method for accurately printing triangular marks on a trapezoidal threaded oil casing using the aforementioned triangular printing device for printing the screwing position triangle, the steps of which are as follows:

[0023] S1 Selection: Select a printing device with the corresponding taper according to the specifications of the trapezoidal threaded oil casing to be printed, so that the taper angle of the taper liner plate is consistent with the taper angle of the thread, so as to achieve a natural fit between the taper liner plate and the casing thread around the entire circumference.

[0024] S2 Initial Positioning: Place the baffle against the end face of the sleeve, rotate the adjusting screw to adjust the positioning ball head, and keep the axis of the arc-shaped positioning frame parallel to the axis of the sleeve;

[0025] S3 Locking: Tighten the adjusting screw to allow the positioning ball head to slide in the thread groove until it is in tangential contact with both the thread bearing side and the tooth root. The baffle fits against the tube end for positioning, so that the printing device and the sleeve do not rotate relative to each other.

[0026] S4 Impact Printing: The hammer head impacts the stamping punch axially. As the stamping punch moves downward, the equilateral triangular stamping protrusion at its lower end presses out a triangular mark with consistent depth and clear edges in the thread tooth tip area, and the base of the triangular stamping protrusion falls on the top of the thread tooth.

[0027] The advantages and beneficial effects of this invention are:

[0028] The present invention relates to a triangular printing device and a precise printing method for the screwing position of a trapezoidal threaded oil casing. By designing the distance from the positioning ball to the baffle and the distance from the base of the triangular steel stamp to the positioning ball using formulas, the device solves the positioning error of traditional experience. The triangular printing position is accurate and can ensure that the base of the triangular steel stamp is exactly at the top of the thread tooth, with clear markings, which is beneficial for subsequent screwing observation. Attached Figure Description

[0029] Figure 1 This is a first-view three-dimensional structural diagram of the triangular printing device of the present invention;

[0030] Figure 2This is a second-view three-dimensional structural diagram of the triangular printing device of the present invention;

[0031] Figure 3 This is a schematic diagram of the positioning module structure of the triangular printing device of the present invention;

[0032] Figure 4 This is a schematic diagram of the printing module structure of the triangular printing device of the present invention;

[0033] Figure 5 This is a schematic diagram of the tapered inner liner structure of the triangular printing device of the present invention;

[0034] Figure 6 This is a schematic diagram illustrating the design principle of the axial dimension parameters of the triangular printing device of the present invention.

[0035] Figure 7 This is a schematic diagram of the thread tooth structure applicable to the triangular printing device of the present invention;

[0036] Figure 8 This is a diagram of the key design parameters of the triangular printing device of the present invention in Embodiment 1 (taking Class II in Table 1 as an example);

[0037] Figure 9 This is a schematic diagram of the printing device in use in Example 1;

[0038] Figure 10 This is a schematic diagram of the printing device used in Example 2;

[0039] The attached diagram is labeled as follows: 1-Handle; 2-Baffle; 3-Arc-shaped positioning frame; 31-Boss; 4-Positioning module; 41-Adjusting screw; 42-Compression spring; 43-Telescopic base; 44-End cap; 45-Positioning ball head; 5-Printing module; 51-Stamp punch; 52-Cavity end cap; 53-Cylindrical cavity; 54-Shock-absorbing spring; 6-Tapered inner liner; 7-Tube body. Detailed Implementation

[0040] The present invention will be further described in detail below through specific embodiments. The following embodiments are merely descriptive and not limiting, and should not be used to limit the scope of protection of the present invention.

[0041] Example 1

[0042] A triangular printing device for the screwing position of a trapezoidal threaded oil casing, such as... Figures 1-2 As shown, it includes a handle 1, a baffle 2, an arc-shaped positioning frame 3, a tapered inner lining plate 6 (symmetrically distributed), a positioning module 4, and a printing module 5.

[0043] The handle 1 is a cylindrical rod, with one end vertically fixed to the baffle 2 and the other end provided with anti-slip knurling or a covering layer. The operator holds the part, providing a fulcrum for applying force.

[0044] Baffle 2 is used for positioning the pipe end. The arc-shaped positioning bracket 3 is fixedly connected to baffle 2, forming a 120° surround angle. Its inner side is provided with two tapered inner lining plates 6 that can fit against the threaded conical surface; for example... Figure 5 As shown, the tapered inner liner 6 fits naturally with the full-top thread. Its design is a tapered form that matches the thread, and it can adapt to a tapered range of 1:6 to 1:36. The tapered inner liner 6 is made of resin, which will not rub or damage the thread. The tapered inner liner 6 can be replaced.

[0045] The positioning module 4 can accurately print the tooth tip. The positioning module 4 is installed along the normal direction of the arc-shaped positioning frame 3 and has a positioning ball head 45 that can elastically extend and retract along the axial direction. The axial direction of the positioning ball head 45 is perpendicular to the sleeve axis. In the clamped state, the positioning ball head 45 simultaneously contacts the thread tooth root and the bearing side. The distance S1 from the positioning ball head 45 to the baffle 2 is determined with the thread bearing side as a reference. Figure 3 As shown, the positioning module 4 includes an adjusting screw 41, a compression spring 42, a telescopic base 43, an end cap 44, and a positioning ball head 45. The end cap 44, which is fixed on the arc-shaped positioning frame 3, has a guide hole at its center. The lower surface of the arc-shaped positioning frame 3 has a protruding boss 31, and the boss 31 has a through hole at its center. The through hole and the guide hole are coaxial and together form a guide channel. The telescopic base 43 is slidably inserted into the guide channel, and its lower end is connected to the positioning ball head 45. The compression spring 42 is housed in the through hole, and its lower end abuts against the telescopic base 43. The adjusting screw 41 is located in the through hole at the upper end of the compression spring 42. The compression amount of the compression spring 42 can be changed by rotating the adjusting screw 41. The positioning ball head 45 can elastically extend and retract along the axial direction of the guide channel under the action of the compression spring 42 to achieve adaptive positioning. The diameter d of the positioning ball head 45 satisfies 3P / 8 < d < P / 2, where P is the pitch. When the triangular printing device is used for sleeves of different specifications, the tangent position between the thread and the tapered inner liner 6 changes, the extension length of the positioning ball head 45 is different, the adjusting screw 41 makes the compression spring 42 fully contact the thread, and the arc-shaped positioning frame 3, together with the symmetrically arranged tapered inner liner 6, forms a wrapping effect on the threaded joint.

[0046] The printing module 5 performs high-precision marking, is fixed to the arc-shaped positioning frame 3, and maintains a fixed position relative to the positioning ball head 45. The printing module 5 contains an axially ejectible stamping punch 51, the axis of which is perpendicular to the sleeve axis. For example... Figure 4As shown, the printing module 5 includes a cylindrical cavity 53, a stamping punch 51, a cavity end cap 52, and a shock-absorbing spring 54. The cylindrical cavity 53 forms a cylindrical cavity that runs vertically through the interior. The cavity end cap 52 is fixed to the upper opening of the cylindrical cavity 53, and a guide hole is provided in the center of the cavity end cap 52. The stamping punch 51 is in the shape of a stepped shaft, with a force-bearing handle at the upper end and an outwardly protruding triangular stamping protrusion integrally formed at the lower end. The triangular stamping protrusion is an equilateral triangle with a height of 3 / 8 in. The stamping punch 51 slides through the guide hole, and the shoulder located in the cavity forms a limit between the lower surface of the cavity end cap 52; the shock-absorbing spring 54 is sleeved on the stamping punch 51, located on the outer periphery of the shaft section in the cavity, with its upper end abutting against the shoulder of the stamping punch 51 and its lower end abutting against the inner step of the cylindrical cavity 53, so that the stamping punch 51 can descend and compress the shock-absorbing spring 54 under the action of external force to complete the stamping, and automatically reset under the action of the restoring force of the shock-absorbing spring 54.

[0047] Due to the influence of the outer diameter tolerance and ellipticity of the pipe body 7, at the position where the base of the triangular steel stamp protrusion is equal to A1 from the pipe end, there exists a phenomenon of thread tooth tip, tooth root, and outer surface of the pipe body 7. Since the thread has a helix angle of rotation, there is a continuous transition from tooth root to tooth tip in the thread at the same position from the pipe end in the circumferential direction. The tooth width of the thread is basically the same as the groove width. Dividing a pitch P into four equal parts, there must be a point in the middle of the thread tooth tip within a 180° circumference that satisfies the value of A1. Taking the bearing side of the thread as the reference, when L=(n+0.75)*P, where n is a positive integer, the base of the triangular steel stamp protrusion can fall in the middle of the thread tooth tip. The distance between the base of the triangular steel stamp protrusion, the positioning ball head 45, and the baffle 2 satisfies Equation 1. The base of the triangular steel stamp protrusion falling in the middle of the thread tooth tip must satisfy Equation 2. The relationship between the distance S1 between the positioning ball head 45 and the baffle 2 and the length Lc of the joint full-top thread satisfies Equation 3.

[0048] A1=L+S1……………………………(Equation 1)

[0049] L=(n+0.75)*P……………………………(Equation 2)

[0050] S1≤Lc……………………………(Equation 3)

[0051] In the above formula: A1 is the distance from the bottom edge of the triangular stamped protrusion to the pipe end; Lc is the minimum thread length of the threaded joint; P is the thread pitch; d is the diameter of the locating ball 45; S1 is the distance from the locating ball 45 to the baffle 2; L is the distance from the bottom edge of the triangular stamped protrusion to the locating ball 45.

[0052] Based on equations 1 and 3, the minimum value of L is calculated. Under the constraint that n is a positive integer, n can be chosen to satisfy... The smallest positive integer value.

[0053] The design principle of the axial dimension parameters determined by Equations 1 to 3 is as follows: Figure 6 As shown.

[0054] A schematic diagram of the thread tooth structure applicable to the triangular printing device of the present invention is shown below. Figure 7 As shown.

[0055] For a specific specification of trapezoidal thread, A1, Lc, and P are all fixed values. According to formulas 1 to 3, the minimum value of the positive integer n can be calculated. According to formula 2, the distance L from the bottom edge of the triangular stamped protrusion to the positioning ball 45 is determined. For API specification trapezoidal threads, considering the degree of change and consistency of the taper T and Lc values, all API specification trapezoidal thread joints can be divided into three types: I, II, and III. In the design of the printing device, for API specification trapezoidal thread joints with the same taper, the distance L from the bottom edge of the triangular stamped protrusion to the positioning ball 45 is the same. Among them, each specification of sleeve in type I corresponds to one printing device, and types II and III correspond to one printing device, as shown in Table 1.

[0056] Table 1

[0057]

[0058]

[0059] A unified design for a triangular printing device is presented for Type II trapezoidal thread joints. The arc-shaped positioning frame 3 has an angle of 120°. When the sleeve size varies from 8.625in (219.08mm) to 13.375in (339.72mm), the full top thread is in tangential contact with the tapered inner liner 6, with a vertical position variation range of 34.93mm. On the other hand, the extension of the positioning ball head 45 varies within a range of 9.36mm. The contact force can be adjusted by adjusting the screw 41. The designed printing device can meet the requirements for printing triangles on trapezoidal thread joints with sizes between 8.625in and 13.375in.

[0060] Key design parameters for the printing device of Class II specification off-topic threads are shown below. Figure 8 As shown.

[0061] For the aforementioned API-biased stepped thread, the schematic diagram of the device of the present invention is as follows. Figure 9 As shown.

[0062] The usage steps are as follows:

[0063] S1 Selection: Select the printing device with the corresponding taper according to the specifications of the trapezoidal threaded oil casing, so that the taper angle of the taper liner plate is consistent with the thread taper angle, so as to achieve a natural fit between the taper liner plate and the casing thread around the entire circumference.

[0064] S2 Initial Positioning: Place the baffle against the end face of the sleeve, rotate the adjusting screw to adjust the positioning ball head, and keep the axis of the arc-shaped positioning frame parallel to the axis of the sleeve;

[0065] S3 Locking: Tighten the adjusting screw to allow the positioning ball head to slide in the thread groove until it is in tangential contact with both the thread bearing side and the tooth root. The baffle fits against the tube end for positioning, so that the printing device and the sleeve do not rotate relative to each other.

[0066] S4 Impact Printing: The hammer head impacts the stamping punch axially. As the stamping punch moves downward, the equilateral triangular stamping protrusion at its lower end presses out a triangular mark with consistent depth and clear edges in the thread tooth tip area, and the base of the triangular stamping protrusion falls on the top of the thread tooth.

[0067] Example 2

[0068] For trapezoidal threaded sleeves with sealing structures at the pipe ends, the above method can also be used to design a triangular printing device. For example, for three types of trapezoidal threaded sleeves with different tapers and pitches, A, B, and C, the triangular printing device can be designed according to the above method. According to formulas 1 to 3, the design parameters are shown in Table 2.

[0069] A method for accurately printing triangular marks on non-API casing threads using a triangular marking device for the screwing position of trapezoidal threaded oil casing, similar to Embodiment 1, is illustrated in the schematic diagram below. Figure 10 As shown.

[0070] Table 2

[0071]

[0072] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several modifications and improvements can be made without departing from the concept, and these all fall within the protection scope of the present invention.

Claims

1. A triangular printing device for the screwing position of a trapezoidal threaded oil casing, characterized in that, include: Baffle (2) is used to fit the pipe end for positioning; The arc-shaped positioning frame (3) is fixedly connected to the baffle (2) and forms a 120° encircling angle. Two tapered inner lining plates (6) that can fit against the threaded conical surface are provided on its inner side. The positioning module (4) is installed along the normal of the arc-shaped positioning frame (3) and has a positioning ball head (45) that can be elastically stretched along the axial direction. The axial direction of the positioning ball head (45) is perpendicular to the sleeve axis. The positioning ball head (45) simultaneously contacts the thread tooth root and the bearing side in the clamping state. The distance S1 from the positioning ball head (45) to the baffle (2) is determined with the thread bearing side as the reference. The printing module (5) is fixed to the arc-shaped positioning frame (3) and maintains its position relative to the positioning ball head (45). The printing module (5) is provided with a steel stamp punch (51) that can be punched out axially. The axial direction of the steel stamp punch (51) is perpendicular to the sleeve axis. The base of the triangular steel stamp protrusion of the steel stamp punch (51) has a fixed distance L between it and the positioning ball head (45). The distance between the base of the triangular steel stamp protrusion and the tube end is A1. Where A1 = L + S1, L = (n + 0.75) * P, Lc is the minimum thread length at the screw-in position of the oil casing, and S1 ≤ Lc, where P is the pitch of the trapezoidal thread, and n is the thread length that satisfies the condition... The smallest positive integer is used to ensure that the base of the triangular stamped protrusion always falls on the top of the thread tooth.

2. The printing apparatus according to claim 1, characterized in that, The tapered inner liner (6) has a tapered range of 1:6 to 1:36 and is removable and replaceable.

3. The printing apparatus according to claim 1, characterized in that, The positioning module (4) includes: The end cap (44) fixed on the arc-shaped positioning frame (3) has a guide hole in its center; A boss (31) protrudes downward from the upper surface of the arc-shaped positioning frame (3). The boss (31) has a through hole at its center. The through hole is coaxial with the guide hole and together they form a guide channel. The telescopic base (43) is slidably inserted into the guide channel, and its lower end is connected to the positioning ball head (45); A compression spring (42) is housed in the through hole, with its lower end abutting against the telescopic base (43); The adjusting screw (41) is placed at the upper end of the through hole of the compression spring (42). The compression amount of the compression spring (42) can be changed by rotating the adjusting screw (41). The positioning ball head (45) can elastically extend and retract along the axial direction of the guide channel under the action of the compression spring (42) to achieve adaptive positioning.

4. The printing apparatus according to claim 1, characterized in that, The printing module (5) includes: A cylindrical cavity (53) has a cylindrical cavity that runs vertically through it. A cavity end cap (52) is fixedly installed at the upper opening of the cylindrical cavity (53), and a guide hole is provided at the center of the cavity end cap (52); The stamp punch (51) is in the shape of a stepped shaft, with a force-bearing handle at the upper end and an outwardly protruding triangular stamp protrusion at the lower end. The stamp punch (51) slides through the guide hole and forms a limit between the shoulder in the cavity and the lower surface of the cavity end cap (52). A shock-absorbing spring (54) is sleeved on the stamping punch (51) and located on the outer periphery of the shaft section inside the cavity. Its upper end abuts against the shoulder of the stamping punch (51), and its lower end abuts against the inner step of the cylindrical cavity (53), so that the stamping punch (51) can descend and compress the shock-absorbing spring (54) under the action of external force to complete the stamping, and automatically reset under the action of the restoring force of the shock-absorbing spring (54).

5. The printing apparatus according to claim 1, characterized in that, The diameter d of the positioning ball head (45) satisfies 3P / 8 < d < P / 2, where P is the pitch.

6. The printing apparatus according to claim 1, characterized in that, It also includes a handle (1), one end of which is vertically fixed to the baffle (2), and the other end is provided with anti-slip knurling or a covering layer.

7. The printing apparatus according to claim 1, characterized in that, The bearing-side angle α of the trapezoidal thread is ±10°.

8. A method for accurately printing triangular marks on a trapezoidal threaded oil casing using the printing apparatus described in any one of claims 1 to 7, characterized in that, Includes the following steps: S1 Selection: Select the printing device with the corresponding taper according to the specifications of the trapezoidal threaded oil casing to be printed, so that the taper angle of the taper inner liner (6) is consistent with the thread taper angle, so as to achieve a natural fit between the taper inner liner (6) and the casing thread around the entire circumference. S2 initial positioning: Place the baffle (2) against the end face of the sleeve, rotate the adjusting screw (41) to adjust the positioning ball head (45), and keep the axis of the arc positioning frame (3) parallel to the axis of the sleeve; S3 Locking: The micro-rotating printing device causes the positioning ball head (45) to slide in the thread groove until it simultaneously contacts the thread bearing side and the tooth root. The baffle (2) fits the tube end for positioning, so that the printing device and the sleeve remain without relative rotation. S4 Impact Printing: The hammer head impacts the stamping punch (51) axially. The stamping punch (51) moves downward, and the equilateral triangular stamping protrusion at its lower end presses out a triangular mark with consistent depth and clear edges in the thread tooth top area. The base of the triangular stamping protrusion falls on the top of the thread tooth.

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