Patent EA-002268-B1 (EA)
Title: Threaded connection of two metal tubes with high tightening torque
Inventor: NOEL THIERRY
IPC: F16L15/06
Filed: 1999-09-02
Abstract: 1. A threaded connection of two metal tubes comprising a male element (1) at the flank of the first tube screwed into a female element (2) at the flank of the second tube, the male element has a tapered external threading (3) with trapezoid threads (11,71,31) having two surfaces, one is a carrying surface, the other is an engagement surface (15,75,35), the length (L3) at the thread top is less than that 11, 12) at the base of the threads, said female element (2) has an internal tapered threading (4) with trapezoid threads (12,72,32) the shape of which is conjugated with the shape of said tapered external threading (3), the width (L3, L4) of the external and internal threads (11,12) is greater than that (L6, L5) of the conjugated thread, the width (L3, L4), characterized in that when screwing the male (1) element into the female element (2) both elements are arranged in such a manner that they are beyond the position at which in the process of screwing both surfaces (13,15,73,75,33,35) of the external threading come in contact with both surfaces (14,16,74,34,36) with the internal threading (12,72,32), causing mutual axial reinforcement of both external and internal threadings. 2. The threaded connection according to claim 1, characterized in that diametrical interference between tops (17,20) of the male and female threads (3,4) and bases (18,19) of the conjugated thread (4,3) has a negative or null value when the screwing is over. 3. The threaded connection according to claim 1 or 2, characterized in that the axial clearance (x1,x2), which is at least 0,5 mm, remain between the conjugated tops and the bases, when both flanks (13,5) of the male threads come in contact with the conjugated flanks of the female threading (14,16) in the process of screwing. 4. The threaded connection according to claim 1, characterized in that diametrical interference between tops (77,80) of the male and female threads (3,4) and bases (78,79) of the conjugated thread (4,3) has a positive value when the screwing is over. 5. The threaded connection according any of claims 1 to 4, characterized in that the δ angle between the carrying flank (13,14,73,74,33,34) and the engagement flank (15,16,75,76,35,36) of the male or the female threads is less or equal 20 degree . 6. The threaded connection according to claim 5, characterized in that the δ angle is between 7 and 20 degree . 7. The threaded connection according any of claims 1 to 6, characterized in that the tread tops (17,20,77,80,39,38) of the male and the female threads (3,4) hang over the bases (19,18, 79,78,37,40) from the side of carrying flanks (13,14,73,74,33,34), the α angle between said carrying flanks and a normal to the connection axis is from 0 to -15 degree . 8. The threaded connection according any of claims 1 to 7, characterized in that at least one of threads (3,4) -male and/or female - is provided with a groove (61,62) emerging at the thread top (39,38) on the total length of the thread(s) or on a part of it. 9. The threaded connection according to claim 8, characterized in that the depth of said groove (61,62) does not exceed the thread's height. 10. The threaded connection according to claim 8 or 9, characterized in that the width of the groove (61,62) at the thread top is not more than 2/3 width of the thread measured at half of its height. 11. The threaded connection according to one of claims 8 to 10, characterized in that said groove (61,62) has a U-shaped or a V-shaped profile with a rounded bottom. 12. The threaded connection according any of claims 1 to 11, characterized in that the male and female elements (3,4) comprise at least one sealing surface (5,6), each male sealing surface (5) directed longitudinally and counteracts radially to the conjugated female sealing surface (6) when the screwing is over. 13. The threaded connection according any of claims 1 to 11, characterized in that the male and female elements (3,4) comprise at least one supporting surface (7,8) directed transversely, wherein at least one male support surface (7) butts the female support surface (8) when the screwing is over. 14. The threaded connection (100) according any of claims 1 to 13, characterized in that the male element (1) is disposed at the end of the first metal tube (101) of a large length, and the female element (2) is disposed at the end of the second metal tube of also a large length. 15. Use of two threaded connections (100,100') according one of claims 1 to 13 for connecting two metal tubes (101,101') of large length comprising a male element (1,1') at the end by a metal sleeve (202) provided with a female element at each of its ends.