[0034] The present invention will be further elaborated below in conjunction with the accompanying drawings and specific embodiments.
[0035]A threaded joint based on position control, including a male thread and a female thread. The cross-sectional shape of the male thread and the female thread is a trapezoidal thread, a rectangular thread or an inverted trapezoidal thread; in the thread structure, the tooth top is parallel to the tooth bottom, and the tooth side is parallel to the tooth The angle between the top or tooth bottom is ≥80°, the thread taper is 1:8~1:14, the thread tooth height is 1.0mm~1.6mm, and the pitch is 6mm/tooth~8mm/tooth. The section of the male thread and the female thread gradually changes along the helical direction of the thread, showing that the tooth height remains unchanged, the tooth width of the male thread gradually increases, and the tooth width of the female thread gradually decreases. The change rate of the tooth width of the male thread and the female thread is the same, which is 0.2 mm/tooth~1.0mm/tooth, that is, the tooth width of the male thread increases by 0.2mm~1mm every time it rotates toward the big end, and the tooth width of the female thread decreases by 0.2mm~1mm every time it rotates toward the big end.
[0036] like figure 2 , taking the cross-sectional shape of the male thread and the female thread as a rectangular thread as an example, a section of the thread is intercepted, in which the male thread and the female thread have a gradual tooth shape and mesh with each other;
[0037] In a section of the intercepted thread, dp is the tooth width corresponding to the meshing position of the male thread, db is the tooth width corresponding to the meshing position of the female thread, do is the backlash between the front and rear female threads, d is the thread pitch, then:
[0038] db+do=d;
[0039] Male thread in screwing direction dp tapering; female thread db Gradually larger, thread pitch d is a fixed value, corresponding to the female thread do slowing shrieking,
[0040] As the thread progressively advances, when dp and db Rotate to the corresponding position so that:
[0041] db+dp=d;
[0042] which is dp=do , at this time, the male and female threads fit together, because the gradual tooth shape of the male and female threads forms a wedge effect, the threads cannot be screwed in further, and the male and female threads reach the ideal screwing position and stop screwing;
[0043] Take appropriate points on the male and female threads, so that the points correspond to the tooth width of the male and female threads dp , db Satisfy:
[0044] db+dp=d;
[0045] The distance from this point to the end face of the shoulder of the male thread is LP , the distance from this point to the end face of the female thread is Lb , making LP more than the Lb ,set up
[0046] Δd=Lp-Lb;
[0047] In the process of actually buckling the pipe, it is judged whether the pipe is screwed in place by observing the gap between the shoulder end face of the male thread and the end face of the female thread after the screwing. Δd , indicating that the tube is screwed in place; otherwise, it is judged that the tube is not screwed in place.
[0048] Specific case: select the specification of 101.6mm×7.8mm, and use inverted trapezoidal thread in the design. The top of the tooth is parallel to the bottom of the tooth, and the angle between the side of the tooth and the top or bottom of the tooth is 84.5°. The thread taper is 1:2, the thread tooth height is 1.475mm, and the thread pitch is 7mm/teeth. The change rate of the tooth width of male and female threads is 0.3mm/tooth, that is, the tooth width of the male thread increases by 0.3mm every time it rotates toward the big end, and the tooth width of the female thread decreases by 0.3mm every time it rotates toward the big end.
[0049] Pick a point on the thread such that: ;
[0050] db=dp=3.5mm;
[0051] Meet the pipe tightening thread fit requirements.
[0052] According to the thread structure relationship, the measured LP =37.3mm, Lb =37mm. but Δd =0.3mm.
[0053] In the actual pipe screwing, observe the gap between the shoulder end face of the male thread and the end face of the female thread after screwing to judge whether the pipe screwing is in place. If the gap between the male and female ends of the pipe is less than or equal to 0.3mm, it indicates that the pipe is screwed in place; otherwise, it is judged that the pipe is not screwed in place.
[0054] The above are preferred embodiments of the present invention. For those of ordinary skill in the art, according to the teachings of the present invention, without departing from the principle and spirit of the present invention, the changes, modifications, Alternatives and modifications still fall within the protection scope of the present invention.
