WO1996005462A1 - Pipe connector - Google Patents

Abstract

The invention concerns a pipe connector comprising a bush component with a conical internal thread and an internal component with a conical external thread such that these two components can be screwed together. The threaded sections can adjoin a smooth section which is optionally in the form of a metal sealing seat. One component (6, 21, 43) has a known thread flank line (17, 24, 31, 39, 40) of constant inclination and the other component (1, 22, 44) has a thread flank line (16, 23, 30, 41, 42) which deviates therefrom with respect to the contour and/or cone.

Description

 Pipe connector

The invention relates to a pipe connector according to the preamble of the main claim.

Pipe connectors are used to connect tubular elements, for example pipelines, which in particular convey fluids under pressure, such as gas or oil. When searching for oil or gas, these pipes are used as casing or production pipes.

The pipe connections considered here are usually made with threads, an external thread on a pin element and a

Internal threads in a socket element that are screwed together. Regarding the clear positioning after screwing

A distinction is made between pipe connectors with an applied marking and those that have an additional joint element as an inner or outer shoulder. This shoulder element can also act as a seal. The shoulder essentially consists of

annular surfaces, for example at the free end of the

Pin element and the inside of the sleeve element are arranged and are firmly pressed together by screwing them together. In the case of an inner shoulder, the pin element is pressed together between the shoulder and the thread and the sleeve element is stretched between the shoulder and the thread. In the case of an outer shoulder, the pin element is stretched between the shoulder and the thread and the socket end is pressed together between the shoulder and the thread. The stresses in the socket and spigot caused by the surface pressure in the shoulder are predominantly absorbed only by the last few thread teeth of the thread, which are adjacent to the shoulder surfaces. The other thread lengths are only extremely lightly loaded.

Accordingly, the loaded thread teeth are highly stressed. These high tensions in the thread are caused by external stress on the

Connection, in particular increased by axial tension or pressure, but also by internal and external pressure and by bending, so that the

Total stress can reach a value that is greater than the permissible yield strength. Axial tension can cancel the preload in the joint and thus its effect of positioning and sealing, axial pressure can lead to plastic deformation in the shoulder area and, with subsequent tensile loading, render the sealing function ineffective by lifting off the joint.

To the forces acting on the sealing surfaces (impact) as

Distributing reaction forces to the largest possible number of thread teeth is a specially trained method in DE 3431 808 AI

Pipe connector disclosed. In this proposal, the pipe connector has an intermediate portion of the thread between the ends of the male and female threads in which both elements have the same pitch. In the end sections are the slopes between tenon and

Socket thread different, depending on the position of the joint: If the annular sealing surfaces (butt) are on the inside of the pipe, then the thread of the pin element has a greater pitch than the thread of the sleeve element; if the sealing surface is on the outside of the pipe, it is the other way round. The proposed arrangement is intended to transmit the reaction force resulting from the impact evenly to the thread teeth. However, loads such as axial compression and bending continue to a large extent in the impact that is already significantly pre-stressed by the screw connection

initiated.

The object of the invention is to provide a pipe connector that is easy to manufacture and with which a load bearing for all external

Loads on the connection are mainly achieved via the thread. Loads that particularly endanger known pipe connectors with a butt shoulder, such as axial compression, bending and excessive screwing moments, should no longer be caused solely by the butt to

predominantly part of the thread. In addition, an even distribution of all loads on the thread is sought.

This object is achieved with the features specified in the characterizing part of claim 1 and claim 9. Advantageous further developments are part of subclaims.

The pipe connector according to the invention is characterized in that an element, preferably the pin element, as is known

Thread flank line with a constant taper pitch in the usual range of 1: 6 to 1:16. The other element, i.e. in the

As a rule, the sleeve element has one with regard to

Taper inclination and the contours deviating thread flank line. When the two elements are connected, the result is in

Screw position at least in a certain area, be it the Thread center area or more the edge areas an oversize of

Thread flank diameter. In addition to the radial bracing, this thread overlap essentially creates an axial bracing in the thread due to the Poisson effect. The axial

With a suitable design, bracing occurs due to local expansion due to overlap and due to the axial contraction of the sleeve as well as correspondingly due to the local constriction and the associated transverse expansion of the pin element.

According to a further feature of the invention, thread forms cause the axial bracing to be negative due to their profile design

Load flank in combination with the flank line of the socket thread that deviates from the thread flank line of the journal. The proposed conventional design of the pin element has the great advantage that a damaged pin thread can be cut with the usual simple means. The sleeve element, which is manufactured with greater technical effort, must be replaced if damaged. From the inventive point of view, however, is a special embodiment of the

Thread flank line also possible in the pin element. The idea of the invention can also be applied to integral connectors.

The structural design of the sleeve element can be in different

Way, but always with the aim that in

 Screwing position an axial bracing is generated in the thread. The main variants are; the convex contour of the

 Thread flank line, and in combination with a clearly pronounced negative load flank a steeper or flatter socket cone in the

Compared to the cone. About 3 positive flank inclinations are common, but according to the invention a flank inclination in the range from -7 ° to -12 ° is selected. A special feature is the freely designed socket thread flank line, for example in the form of a flat sinus curve. This contour has a diameter for the socket thread flank line, which is partly larger and partly smaller and at certain locations the same as the locations of the journal flank line corresponding to the screwing position. As a result, different tensions can be achieved at several locations, distributed over the entire thread length.

The construction does not rule out an impact as a positioning element or as an additional support element for absorbing extreme axial pressure loads or bending. However, axial compression and the pressure component of the bend are also taken over by the thread in this case, thus preventing the shoulder from being overloaded.

The combination options described above can also be applied to a two-stage thread, preferably with a centrally located metallic sealing seat, possibly in combination with a shoulder. The combination of different, respectively constant cone inclinations has also proven to be particularly advantageous in terms of producibility

exposed.

By uniformly loading the thread areas, the tooth height of the thread can be reduced compared to conventional connectors. To the same extent, the pipe connector is smaller in its height, which leads to an enlargement of the annular space cross-sections in bores and permits slimmer piping. On the other hand, if the tooth height is maintained, the axial pressure or bending strength of the connection can be increased, as can the screwing torque. Increased bending strength and increased screwing torque are of particular advantage e.g. at

rotating installation or cementing of casing pipes, with deflected or horizontal bores. This allows the high

Frictional resistance of the borehole wall or of the cement can be overcome without overloading or damaging the connection.

In the drawing, the

Pipe connector according to the invention explained in more detail.

Show it:

Fig. 1 shows a longitudinal section through a pipe connector with a sleeve

Figure 2 is a longitudinal section through a pipe connector as

 Integral connection

3 shows a longitudinal section through a threaded area with a

 Thread with convex socket thread flank line in

Screw position

Figure 3a, the thread of the sleeve element

Figure 3b, the thread of the pin element

4 shows a longitudinal section through a threaded area with a

 Threads with different taper inclinations in the socket and spigot combined with a negative load flank

Figures 4a,

 4b, 4c enlarged sections from FIG. 4

5 shows a longitudinal section through a threaded area with a freely shaped sleeve thread flank line in the screwing position. FIG. 5a shows the thread of the sleeve element

Figure 5b, the thread of the pin element

Figure 6 shows a two-stage thread with different taper inclinations in

 Combination with a negative load edge

Figures 6a,

6b, 6c enlarged sections from FIG. 6 To clarify the wording and accuracy of the

 Descriptions set forth below are some explanations of technical terms for threads that have been used to describe the invention.

Load flank: the surface of the thread, the axial

 Transfer form-fitting from the spigot to the sleeve.

 Leading flank: The flank of the same thread tooth opposite the load flank. The guide flank is usually not loaded with screwed threads under tension.

 Note: Axial compression leads to a load on the leading edge and

 Relief of the load flank. However, the designations are also retained for this load case.

 Flank angle: The angle that the flank forms with a normal to the thread axis in the thread profile

includes. A flank angle is said to be positive if the angle in the thread gap between the flank and the thread root adjoining the flank is greater than the angle in the thread gap between the normal to the thread axis and the same thread root, this angle is smaller than the angle between the normal to the thread axis and the thread root, the flank angle is called negative. Flank diameter line: jacket line of an imaginary, coaxial to the

 Threaded body, usually a cylinder or a truncated cone, which cuts the flanks such that the sections formed for the sewing head and thread base are the same size.

 Outer diameter line: jacket line of an imaginary, coaxial to the

 Threaded body, usually a cylinder or a truncated cone, the jacket of which touches the thread heads of the external thread or the thread root of the internal thread.

 Core diameter line: surface line of an imaginary, coaxial to the

 Thread lying body, usually a cylinder or a truncated cone, the jacket line touches the thread root of the external thread or the thread tips of the internal thread.

 Coverage: Coverages are assigned to oversizes

 Dimensions, e.g. Lengths or diameters of two parts to be connected, the body with a larger dimension being mounted by applying an external force within the body with a smaller dimension. One speaks z. B. from

 Coverage if the pin outer diameter is locally larger than the corresponding sleeve outer diameter. Overlaps can also exist in the axial direction.

 Overlaps lead to drawing

Penetrations of two parts assembled into each other. Because solid body penetrations are not mechanically possible, must

 Joining the parts, the dimensional differences are compensated for by deformations that cause tension within the assembled parts.

In Figures 1 and 2, pipe connectors are shown in a longitudinal section, namely in Figure 1 with a sleeve and in Figure 2 as an integral connection. The first-mentioned pipe connector consists of a sleeve 1, which is provided with two conical threaded sections 2, 3 and has a sealing seat and a joint on both sides in the central area. The details of the sealing seat and joint are not shown here since these are not essential to the invention. The two pipes 4, 5 to be connected are designed in the end region as pin elements 6, 7 and, in addition to the thread of the sleeve 1, also have conical thread sections 8, 9. In contrast to FIG. 1, the one shown in FIG. 2 does not apply

Integral connection the sleeve. The two pipes 10, 11 to be connected are designed in their end regions on the one hand as a pin element 12 and on the other hand as a sleeve element 13. The two elements 12, 13 each have a complementary conical design

Threaded section 14.15. The depiction of the joint and sealing seat has been omitted.

FIG. 3 shows the longitudinal section of a threaded area in the screwed position with a convex socket-thread fill line 16

(Individual illustration in FIG. 3a), combined with a pin thread with a conical thread flank line 17 (individual illustration in FIG. 3b)

shown. The overlap can be seen here as a penetration in the central region 18 of the thread. Because of the convex shape of the socket thread flank line 16, there is no edge regions 19, 20 Overlap and thus no axial bracing.

4 shows a longitudinal section of a threaded area with a pin 21 and a socket thread 22 in the screwed position. The thread flank lines 23, 24 have different taper inclinations. Both threads have a negative load flank 25. FIGS. 4a, 4b, 4c show enlarged sections of FIG. 4. Overlaps are again shown as penetrations. The principle of the tensioning of the load flank 26 against the guide flank 27 in FIG. 4b of the thread can be seen in FIG. 4c.

In Figure 5, the thread is shown schematically in a longitudinal section with a free-formed sleeve flank line in the screwing position. To simplify matters, there is no detailed representation of the thread, but only a representation with the course of the thread outer diameter lines 28, 29, the thread flank diameter lines 30, 31 and

Thread core diameter lines 32.33. Figure 5a shows the thread of the sleeve element 1 in an individual representation, 5b the thread of the

Pin element 6. The exemplary representation shows areas 34 with radial overlap, areas 35 with radial play, which necessitate axial bracing (analogous to FIG. 4), and areas 35 free of play and tension.

An example shows in FIG. 6 how the idea according to the invention in various forms is divided into two thread stages 37, 38. Both stages have this thread

Different taper inclinations, in the example the taper inclinations 39.40 of the pin thread 43 are the same in both stages 37.38

Taper 41 in the outer thread step 37 of the socket thread 44 is flatter than the slope 39 of the complementary pin thread 43, whereas the slope 42 in the inner thread step 38 of the Socket thread 44 is steeper than that of the complementary pin thread 43. FIGS. 6a, 6b and 6c show enlargements of the cutout analogous to the cutout enlargements of FIG. 4, with overlaps leading to tension being shown again as penetrations.

Claims

claims 1. Pipe connector with a socket element that is a conical  formed internal thread and with a pin element, which has a conical external thread that can be screwed to it, wherein a thread-free section, which is optionally designed as a metallic sealing seat, can be connected to the threaded sections,  characterized ,  that one element (6,21,43) has a known thread flank line of constant inclination (17,24,31,39,40) and the other element  (1,22,44) with respect to the contour and / or the taper deviating thread flank line (16,23,30,41,42). 2. Pipe connector according to claim 1,  characterized ,  that the sleeve element (1) is convex  Threaded refueling line (16), wherein in the screwed position there is a thread overlap in at least one area. 3. Pipe connector according to claim 1,  characterized ,  that the pin element (21) is a straight straight  Threaded refueling line (24) and the sleeve element (22) one in With regard to the contour and / or the cone, the thread flank line deviates therefrom and the thread additionally has a clearly pronounced negative load flank (25). 4. Pipe connector according to claim 3,  characterized ,  that both elements (21, 22) have a thread flank line of constant inclination (23, 24) with a strongly pronounced negative load flank (25), the inclinations of the two  Thread flank lines (23, 24) are different. 5. Pipe connector according to claim 4,  characterized ,  that the difference in taper is at least 0.01 mm / inch and at most half a tooth height per inch. 6. Pipe connector according to claims 4 and 5,  characterized ,  that when arranging an inner sealing seat, the inclination of the  Socket thread flank line is flatter than that of the pin and with an external sealing seat the inclination of the socket thread flank line is steeper than that of the pin. 7. Pipe connector according to claim 1,  characterized ,  that the pin element (6) has a thread flank line (31) of constant inclination and the sleeve element (1) has a freely shaped thread flank line (30), the diameter of the  Socket thread flank line (30) is partly larger, partly smaller and partly the same as the diameter of the corresponding pin-thread flank line (31). 8. Pipe connector according to claim 7,  characterized ,  that the thread of both elements (1,6) has a clearly pronounced negative load flank. 9. Pipe connector with a socket element, which is a two-stage  conical internal thread and with a pin element which has a two-stage conical external thread which can be screwed to it and, if appropriate, with a metallic sealing seat and arranged between the two stages  possibly a shoulder,  characterized ,  that both stages (37, 38) of an element (43) were known  Thread flank lines of constant inclination and at least one step (37, 38) of the other element (44) has a thread flank line which deviates therefrom with regard to the contour and / or the cone (41, 42). 10. Pipe connector according to claim 9,  characterized ,  that both elements (43.44) in both stages (37.38)  Have thread flank lines of constant inclination with a clearly pronounced negative flank, the inclination of the respective thread flank lines of sleeve (44) and pin (43) differing from one another in at least one step (37, 39). 11. Pipe connector according to claim 9,  characterized , that the thread flank line (41) of the sleeve (44) of the outer first stage (37) is flatter than that of the pin (43) and the thread flank line (42) of the sleeve (44) of the inner second Step (38) of the two-stage thread is steeper than that of the pin (43). 12. Pipe connector according to claim 3 to 6, 8, 10 and 11,  characterized ,  that the negative flank has an angle in the range of -7 ° to -12 °.