Patent EA-002698-B1 (EA)
Title: Method for controlling taper pipe thread and corresponding control devices
Inventor: NOEL THIERRY
IPC: G01B5/24
Filed: 2000-02-17
Abstract: 1. A method for controlling male taper pipe thread (3) disposed on an outer peripheral part of the male element (1) located at one end of a metal pipe (101) and comprising at least one sealing means (5,7) located in an immediate proximity to said end to control an mean thread diameter (D1) in the given measuring plane (P1) located at a distance L1 from the plane (P0), using a planar diameter-measuring apparatus (51) which comprises a thrust surface (54,54'), at least two contact surfaces (60,61) located transversely at a distance from each other and an axial distance from the thrust surface and means (55) for measuring the diameter of a circle located in a transversal plane (P1) of measuring and tangent respective to the contact surfaces, said method comprises the steps of: a). adjusting by the planar diameter-measuring apparatus (51) the distance LA between the a thrust surface (54,54') and the plane (P1) in function of the selected distance L1, b). regulating the means for measuring to a predetermined value of transversal distance between the contact surfaces using a reference block (70), the characteristic size of which is determined relative to an estimated value (d1e) of mean diameter in the measuring plane (P1), c). measuring in the measuring plane (P1) the diameter (D1s) of thread between thread crests, wherein the measuring apparatus (51) abuts by its thrust surface (54,54') the free end of the male element, d). comparing the measured diameter (D1s) between thread crests relative to limits of permissible interval, characterized in that the measuring plane (P1) of the mean diameter of male thread (3) is a plane located between the plane (P0) and the first full male thread and that the estimated value of the mean diameter (D1e) in the measuring plane (P1) responds the following equations:   wherein: Dnom is a nominal value of the mean diameter in the plane, TTrepl is a value of male conicity transfer. TTnom is a nominal value of thread conicity, TTmin1, TTmax1, TTmoy1 are respectively minimum, maximum and mean value of conicity of realized male thread, ΔTT1 is an algebraic value of deviation (TTmoy1 - TTnom), (1 is a mean quadratic deviation of value distribution of realized conicity, K1 is the ratio of the male thread length to the distance between the plane (P0) and the first full male thread,  g (u) is a value of normal reduced centered law of distribution for a variable value u. 2. The method according to claim 1, characterized in that the measuring plane (P1) is located substantially on a half distance between the plane (P0) and the plane corresponding to the first full male thread. 3. A method for controlling male taper pipe thread (4) disposed on an internal peripheral part of the female element (2) located at one end of a metal pipe (102) and comprising at least one sealing means (6,8) disposed so as to cooperate with one or several sealing means (5,7) located in an immediate proximity to a free end to control an mean thread diameter (D2) in the given measuring plane (P2) located at a distance L2 from the plane (P0), using a planar diameter-measuring apparatus (51) which comprises a thrust surface (54,54'), at least two contact surfaces (60,61) located transversely at a distance from each other and an axial distance from the thrust surface and means (55) for measuring the diameter of a circle located in a transversal plane (P2) of measuring and tangent respective to the contact surfaces, said method comprises the steps of: a). adjusting by the planar diameter-measuring apparatus (51) the distance LB between the a thrust surface (54,54') and the plane (P2) in function of the selected distance L2, b). regulating the means (55) for measuring to a predetermined value of transversal distance between the contact surfaces using a reference block (80), the characteristic size of which is determined relative to an estimated value (d2e) of mean diameter in the measuring plane (P2), c). measuring in the measuring plane (P2) the diameter (D2s) of thread between thread crests, wherein the measuring apparatus (51) abuts by its thrust surface (54,54') the free end of the female element, d). comparing the measured diameter (D2s) between thread crests relative to limits of permissible interval, characterized in that the measuring plane (P2) of the mean diameter of female thread (4) is located in the zone of female threads and in an intermediate proximity from the plane coinciding with the plane (P1) of measuring mean diameter of a female thread as defined in claim 1 or 2 in case when two male and female threads (3,4) are connected and that the estimated value of the mean diameter (D2e) in the measuring plane (P2) responds the following equations:   wherein: Dnom is a nominal value of the mean diameter in the plane, TTrep2 is a value of conicity transfer. TTnom is a nominal value of thread conicity, TTmin2, TTmax2, TTmoy2 are respectively minimum, maximum and mean value of conicity of realized thread, ΔTT2 is an algebraic value of deviation (TTmoy2 - TTnom), (2 is a mean quadratic deviation of value distribution of realized conicity, K2 is the ratio of the female thread length to the distance between the plane (P0) and the first full female thread,  g (u) is a value of normal reduced centered law of distribution for a variable value u. 4. The method according to any of claims 1 to 3, characterized in that one or several sealing means comprise the sealing thrust surface (5,6). 5. The method according to any of claims 1 to 3, characterized in that one or several sealing means comprise the transversal thrust surface (7,8). 6. The method according to claim 3, taken separately or jointly with claim 4 or 5, characterized in that the mean value of conicity (TTmoy2) of a female thread (4) is less than the mean value of conicity (TTmoy1) associated with it a male thread (3). 7. The method according to claim 1 or 2, taken separately or jointly with claim 4 or 5, characterized in that the mean value of conicity (TTmoy1) of a male thread (3) exceeds the nominal value of conicity (TTnom). 8. The method according to claim 3, taken separately or jointly with claim 4 or 5, characterized in that the mean value of conicity (TTmoy2) of a female thread (4) is less than the nominal value of conicity (TTnom). 9. The method according to any of the preceding claims, characterized in that values of limits of a permissible interval for the diameter between thread crests is obtained by replacing in the formula determining the estimated value of mean diameter in the measuring plane, the values (L1,L2) of distances between the plane (P0) and the measuring plane (P1,P2) for the values (L1min, L1max, L2min, L2max) framing this value. 10. The method according to any of the preceding claims, characterized in that the method is realized using a planar diameter-measuring apparatus (51)which comprises two contact surfaces (60,61), measuring four timesin the same measuring plane (P1,P2), turning the apparatus (51) or a controlled thread (3,4) by1/8 of the full turn around the axis (XX) of the given thread after each measurement and using the mean value of said four measurements as a characteristic of the diameter between the thread crests in said measuring plane. 11. The method according to any of the preceding claims 1 to 9, characterized in that the method is realized using a planar diameter-measuring apparatus (51) which comprises three contact surfaces (60,61), measuring three times in the same measuring plane (P1,P2), turning the apparatus (51) or a controlled thread (3,4) by 40 degree  around the axis (XX) of this thread after each measurement and using the mean value of said three measurements as a characteristic of the diameter between the thread crests in said measuring plane. 12. A planar diameter-measuring apparatus (51) for measuring in the plane (P1,P2) according to any of claims 1 to 12, comprising a thrust surface (54,54'), two contact transversal surfaces, located at a distance from each other and at an adjustable axial distance from the thrust surface and a means (55) for measuring the diameter of a circle located in the transversal measuring plane (P1) and tangent to the contact surfaces (60,61), characterized in that comprises a means for automatic measurement the maximum value of the diameter obtained in the course of measurements. 13. The apparatus according to claim 12, characterized in that comprises a means for effecting static calculations based on obtained values of the diameter between thread crests of a controllable thread. 14. A reference block (70) used for adjusting preset value of a distance between the contact surfaces (60,61) according to claim 1 or 2 using a planar diameter-measuring apparatus having two contact surfaces, characterized in that the block is in the form of a truncated cone and comprises a transversal end surface (72) and two flat surfaces oriented substantially longitudinally, symmetrically inclined relative to the end transversal surface and convergent in the direction of this surface, wherein the angle C between the flat inclined surfaces has a value, equal to 2.arctg (TTmoy1/2) and a transversal distance between flat inclined surfaces has a value, equal to (D1e + h) at a distance (LA) from the end surface, wherein h is a sum of a tooth height (13) of a tread (3) to be controlled and a known factor of geometric correction peculiar to said measuring apparatus (51). 15 The reference block (70) ) used for adjusting preset value of a distance between the contact surfaces (60,61) according to claim 1 or 2 using a planar diameter-measuring apparatus having three contact surfaces, characterized in that the block in the form of a truncated cone and comprises a transversal end surface (72) from the side of the cone crest and a conical peripheral surface with conicity equal to TTmoy1 wherein the diameter of said conical surface at a distance (LA) from the transversal end surface is equal (D1e + h