DE2702542A1 - HEAT RESET, HOLLOW METALLIC COUPLING - Google Patents

Description

Patent attorneys

Dr.-lng. Walter Abltf January 21, 1977

Dr. DiciG- Γ. M ο rf
Dipl.-Miys. M. Li Schneder
Munich 86, Pienzenauerstr. 28

RAYCHEM CORPORATION

300 Constitution Drive, Menlo Park, Calif. 9 ^ 025,

V.St.A.

Heat-recoverable, hollow metallic coupling

The invention relates to couplings, in particular for line elements such as pipes.

Many types of couplings for connecting and terminating pipes and lines have been proposed over the course of time, many of which were complex in construction and required considerable time and effort to assemble.

However, recently it has been proposed the so-called To use "memory metals" to make couplings much simpler. For example, in the British Patent specification 1 327 44-1 discloses a tubular coupling element described and claimed from such a metal, which on its inner surface with an inward directed tooth or several inwardly directed protrusions

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is provided, wherein the coupling element when heated to the transition temperature of the metal in question radially is shrinkable. Other such couplings can be provided with smooth or ribbed bores.

According to the Belgian patent specification 820 880 it is proposed that composite coupling is to be produced, in which an insert under the restoring force of a heat-resettable metallic, tubular actuating element in contact with the line component, such as a pipe. The insert can be provided with protrusions or ribs be and / or consist of a material which is compatible with the line material, for example from a easily worn material. These composite couplings have advantages in certain applications because they without damaging their structural features, such as a projection arrangement, are easier to manufacture and have difficulties avoid regarding the incompatibility between certain memory metals and deca metal pipe.

Such resettable metal couplings are particularly suitable for connecting pipes of, for example, hydraulic ones Systems in aircraft. In these applications, the couplings are often designed to be tapered towards their end, so that the stress on the hydraulic pipe under bending loads is reduced. By rejuvenating the At the ends of the coupling, this can more easily experience a bend and thus the load over a larger area of the pipe to distribute. In this way, failure of the tubular member as a result of high stress concentration is prevented or noticeably reduced.

Although high bending stresses can be reduced significantly in this way, the bending of the Pipe within the coupling relative movement between the ends of the coupling and the enclosed pipe. These

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Relative movement, which in aircraft construction and other applications, where vibrations occur over long periods of time, is of particular importance, runs essentially in the longitudinal direction and causes chafing and wear on the pipe. The roughened and pitted ones produced in this way Areas result in a high concentration of stress in the pipe, which is caused by repeated bending cycles Expansion of the cracks through the pipe wall and ultimately leads to a complete break.

Attempts have been made to reduce chafing at the pipe / coupling interface. For example lubricants were used to reduce the friction at the interface between pipe and coupling, however, these attempts were unsuccessful and the problem of pipeline failure in the area of the coupling ends as a result of a relative movement between the components remained unsolved.

The present invention provides a heat recoverable, hollow, metallic coupling is available which has a main section and has at least one end voltage distribution section with an opening for receiving a line element, the thickness of the coupling in the end Stress distribution section is generally less than in the main section, and the coupling is characterized is that the end-side stress distribution section at its end facing away from the main section with an outer Collar is provided with increased wall thickness.

In certain advantageous embodiments of the invention The end-side stress distribution section has the approved coupling in addition to the said collar a section with a substantially constant wall thickness, which is preferably by a tapered section connected to the main section is, where the strength of the tapered section in

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Increases towards the main section and these two sections together cause the stress distribution. The length of the section with an essentially constant wall thickness is preferably in the range from 20 % to 100 % of the outer diameter.

In other advantageous embodiments, the section with an essentially constant wall thickness can be omitted, in which case the collar is then connected to the main section by a tapered section, which alone is responsible for distributing the tension. In these embodiments, the tapered portion is substantial preferably longer and less tapered than the tapered portion in the embodiments that also have a thin-walled section with constant wall thickness.

The collar is preferably made in one piece with the end-side stress distribution section and is expediently located at the extreme end of it; However, it is obvious that although the arrangement of a large, thin-walled Coupling section beyond the collar in practice would negate the function of the collar, however in some cases it may be useful to move the collar slightly inwards opposite the outermost end of the coupling to arrange. The wall thickness of the collar is greater than that of the end-side stress distribution section in FIG the immediate vicinity of the same, but it is generally not as great as the wall thickness of the main section.

In the preferred embodiments of the invention, the hollow metallic coupling is generally cylindrical Opening, d. H. the wall thicknesses of the main section and the stress distribution section or the stress distribution sections are due to changes in the shape of the outer surface influenced. The hollow element is preferably designed to be substantially tubular. The term "tubular"

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how it is used in this context is not restricted to hollow cylinders, but also includes, for example Items with a non-circular cross-section, such as T-links, X-links, and Y-links. The clutch therefore includes generally at least two end-side stress distribution sections, each of which has an opening for receiving it of a line element, but the invention also comprises a coupling for terminating an individual line element, which only has a voltage distribution section having an opening for this line element.

In many applications, the couplings according to the invention are designed as one-piece arrangements and can be used in unison with the teaching of British patent specification 1 327 44-1 with be provided with one or more inner projections, which get stuck on resetting in the line element or in the line elements, for example a hydraulic pipe. Such protrusions are preferably provided in the interior of the main section, although it is also shown in FIG In some cases it may be advantageous to arrange them in the interior of the end section or the end sections.

In other applications it can be useful to use the coupling to be designed as a composite component, in accordance with the teaching of Belgian patent 820 880, where in In this case, the coupling has an insert which, for example, itself is provided with an internal projection can be and / or made of an easily damaged material. Such an insert can be provided, for example in order to prevent a corrosive effect between the heat-recoverable metal element and the pipe element, it is advantageous that the insert extends over the end or ends of the heat recoverable coupling extends out. In such a case, the insert is expediently made of a flexible or structurally weak material, so that the effect of the collar or collars is not reduced.

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The heat recoverable metallic couplings of the present invention can be made from any suitable memory metal, the type of material used depending on the particular application of the coupling. Suitable memory metals are, for example, various alloys of titanium and nickel, according to z. U.S. Patents 3,17,851, 3,351,463, 3,753,700, 3,759,552, and also British Patents 1,327,441 and 1,327,442, and NASA Publication SP 110, "55-Nitinol-The Alloy with a Memory, etc. ^11. (US Government Printing Office, Washington, DC 1972) .Heat recovery is not limited to such titanium-nickel alloys, for example, various β-brass alloys also have this property, including N. Nakanishi et al, Scripta Metallurgica 5 433-440 (Pergamon Press 1971), reference is made, and such materials can be doped by known methods to their transition temperatures to reduce at cryogenic temperatures. Furthermore, in stainless steel 30 ¹ I such properties have been observed, as pointed out by E. Enami et al, in the latter publication on pages 663-68.

In general, these metals have a transition temperature within a range between -196 ° C and + 135 ° C and especially between -196 ° C and -70 ° C (whereby this is the represents the lowest temperature that commonly occurs in daily life), so they are by immersion brought into their martensitic state in liquid nitrogen can be. However, recently it has become possible to precondition memory metal so that in a transition process, their transition temperature increases can be. In this way, objects made from such alloys can be exposed before they are used Room temperature, being restored to heat by heating. Such processes for preconditioning by storage and transport with the aid of liquid nitrogen are unnecessary

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for example in German patent applications 2,603 2,603,863 and 2,603,878.

The aforementioned nickel-titanium alloys are particularly suitable for use in connection with the present invention.

From the foregoing it can be seen that the present invention aims to provide relative movement at the ends of heat-resettable metal couplings to eliminate chafing and wear of the tubular element and thus Finally, to prevent failure of the tubular element- To achieve this, the heat-recoverable metallic Couplings equipped with voltage distribution sections, which have rigid end collars. The overall arrangement can be recovered from heat and is usually constructed in one piece, although in certain applications it is advantageous to have composite structures that incorporate an insert from a use another metal or material, for example in those cases where the pipe element contains a substance that is corrosive to the heat-recoverable metal.

In the preferred embodiments, the stress distribution sections of the couplings have tapered sections, which a transition from the preferably cylindrical, thick-walled main section to the thin-walled End sections, if any, and form the collar. In most cases the coupling is on the main section made more rigid than the tubular element used with the coupling. At the outer ends of the voltage distribution sections, the walls of the coupling are thin and the coupling is preferably at least as flexible as the tubular element. In this way, the design of each coupling end ensures that it fits into the coupling tube element extending into it experiences stress as a result of a bend which extends over a wide Area is distributed and not concentrated on the rigid edge.

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The stress distribution sections result in a strength gradient with regard to the tensile and compressive loads, wherein the tensile and compressive strength of the coupling differ from the relatively rigid, preferably cylindrical main sections the coupling towards the collar If the coupling has thin-walled end sections, the compressive and tensile strength of the coupling is in these sections preferably less than in the line elements, such as a pipe section with which the coupling is used.

The collars of the stress distribution sections have a wall thickness that is significantly greater than that of the adjacent ones thin-walled sections. The thickness and internal dimension of each collar obtained after recovery result in the resetting of such a ring strength that the coupling firmly embraces the tubular element. This ring strength sufficient to reduce the linear bending force of the stress distribution section to overcome. The linear bending force is understood to mean that force which tends to to generate a relative longitudinal movement between the coupling and the tubular element comprised by this when the tubular element is subjected to a bend. In other words, the tubular element is detected in such a way that the Collars cannot slide in the longitudinal direction of the pipe during a bending process. Pressure is thus applied and stretching inwardly the collars in the stress distribution sections. As a result, there is little or no relative longitudinal movement between the coupling and the tubular element and chafing and wear and tear are switched off or significantly reduced in size.

The invention will then be explained using exemplary embodiments in conjunction with the drawings. It demonstrate:

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1 shows a plan view of a coupling according to the invention with the associated pipe arrangement,

FIG. 2 shows a cross section along the line 2-2 of FIG. 1, FIG. 3 shows an end view of the coupling,

Fig. 4 is a front sectional view along the line 4-4 of Fig. 2,

5 shows a cross section of a second embodiment of a coupling according to the invention,

Fig. 6 is a partially sectioned illustration of a non-reset clutch provided with an insert is and

7 is a partially sectioned view of FIG Embodiment according to FIG. 6, which has been reset by the tubular element.

According to Fig. 1, the coupling consists of a one-piece, hollow coupling element 10 made of heat-restorable metal.

The coupling element 10 contains a substantially cylindrical, hollow main portion 14 which has a substantially cylindrical opening 12 extending over its entire Length extends. Two annular teeth or protrusions 13 are provided on each side of the coupling to provide sealing properties to improve the same.

The stress distribution sections 15 and 17 extend in the longitudinal direction, extending from each end of the main section 14 to the collars 26 and 28. The stress distribution sections 15 and 17 have tapered sections 16 and 18 and thin-walled sections 20 and 22. The eich tapered sections 16 and 18 distribute the coupling

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element 10 exerted resistance to bending, when they extend into the coupling element 10 Tube elements experience bending stress. The tapered portions 16 and 18 set that of the tubular members exerted load against a decreasing resistance, which is due to the decreasing cross-section of the walls this tapered sections is conditional. This allows the load to be distributed over a larger one Pipe length and avoids a fatigue fracture at a certain highly stressed point on the edge of a stiff not tapered coupling element.

The thin-walled sections 20 and 22 each extend from the tapered sections 16 and 18 to the collars 26 and 28. The length of each thin-walled section is approximately between 20 and 100 % of its outer diameter. The inner wall of each thin-walled section is substantially smooth, although properly shaped, inwardly directed projections may be present. The thin-walled sections 20 and 22 cause the relatively flexible ends of the tapered sections 16 and 18 to be elongated, thereby eliminating the edges that are present in known couplings at the end of similarly designed tapered sections. The known couplings tend to promote chafing and wear because of the relative longitudinal movement at the ends of the coupling between the latter and the enclosed raw element. The thin-walled sections bring the coupling ends further away from the more strongly developed areas of the tapered coupling section.

The collars 26 and 28 are each at the ends of the thin-walled Sections 20 and 22. The cross-section of the collars 26 and 28 is made much stronger than that thin-walled sections 20 and 22. These collars 26 and 28 are also made of heat-recoverable metallic work-

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material and are dimensioned in such a way that they can withstand their heat recovery firmly encompass the tubular element located within the coupling. The collars 26 and 28 can have a thickness which corresponds to the strength of the main section of the coupling. However, in most cases it is not necessary that the collar is made as thick as the main section of the coupling.

The holding force of the collars 26 and 28, which is effective against a longitudinal movement and which is based on the gripping force of the collars 26 and 28 and the force induced by the resetting of the collar around the tubular element is dimensioned in such a way that that it withstands the longitudinal force generated by elastic deformation of the thin-walled sections 20 and 22 can be. Therefore, the collars 26 and 28 remain independent of the deflection of the tubular element relative to this in their location. If the tubular element is subject to bending stress, the thin-walled sections experience 20 and 22 an elastic deformation, whereby the tubular element relative to the cylindrical main section 14-without Shifting the collar can sag. The thin-walled sections 20 and 22 preferably have a flexural strength which is no larger than that of the tubular element with which the coupling is used. If the strength the thin-walled sections 20 and 22 would be larger than that of the tubular element, the tubular element could be subjected to extreme stress at the ends of the coupling which could lead to failure of the tubular element. A gradual decrease in the bending moment in the pipe, starting from a maximum stress at the ends of the coupling up to a stress which decreases towards zero near the center of the coupling element required for a long service life under bending loads. It is therefore evident that the task of the thin-walled sections between the tapered sections and the collar serves to enable the collars to move: ait the tube during its bending, and furthermore

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impart linear stress to the tapered sections so that they move with the pipe.

In this way, any or almost any relative movement between the tube and the coupling is eliminated.

The heat recovery properties of the coupling element 10 are for both the main section 14 and the collar and 28 an advantage. The main section 14 prevents its return to the tubular elements 30 and 32 pulling out the tubular elements from the coupling and provides a seal to an escape of high pressure fluid, which may be present inside the pipe to prevent. At the same time, the collars 26 and 28 are reset ensure that there is no wear and tear and no chafing.

A particular embodiment of this coupling made of a nickel-titanium alloy was for connecting pipes with determined an outer diameter of 1.27 cm, the compound obtained for hydraulic pressures up to 550 bar (8000 ρ si) was suitable. The finished coupling was 4.13 cm total length prior to its heat recovery, the length of the central main section Was 1.9 cm, the length of each tapered portion was 0.64 cm, the length of each thin-walled portion 0.32 cm and the length of each collar 0.16 cm. The outside diameter of the main section was 1.80 cm and its thickness about 0.27 cm. The thin-walled sections had an outside diameter of 1.26 cm and a thickness of about 0.025 cm. The wall thickness of each collar was about 0.13 cm.

Fig. 5 shows a second embodiment of the coupling. The coupling 40 has a main portion 44 and two end portions Sections used for stress distribution, which are made up of the tapering sections 46 and 48 and the collar 56

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land 58 exist. A series of inner, circumferential projections 43 are provided on the inner surface of the central portion of the coupling. In this coupling, no thin-walled sections with constant wall thickness are provided between the tapered sections 46, 48 and the collars 56, 38. An embodiment of this coupling, which again consisted of a nickel-titanium alloy and was intended for the connection of drilling with an outer diameter of 1.27 cm at hydraulic pressures of up to 550 bar, had a total length of 4.19 cm in the non-reset state wherein the length of the main section was 1.27 ^cm , the length of each tapered section was about 1.21 cm, and the length of each collar was 0.25 cm. The outer diameter of the main section was 1.85 cm and the thickness of this section was about 0.31 cm. The thickness of the tapered portion adjacent to the collar was about 0.060 cm and the wall thickness of the collar was 0.178 cm. As can be seen, in this coupling the tapering sections 46 and 48 are longer and taper less than the corresponding sections in the coupling according to FIGS. 1 to 4.

Figures 6 and 7 show the use of an assembled device having a generally cylindrical insert 34 with inwardly directed teeth or projections. The inwardly directed protrusions serve to to further deform the captured tubes 30 and 32, as can be seen from FIG. 6. Thus the insert 34 becomes it used to increase the holding force of the clutch. Inserts that fulfill other functions, for example a Frictional action on the inner ends of tubes 30 and 32 will be also used. A more detailed description of such inserts can be found in the previous one Belgian Fatetnschrift 820 880. The depicted insert is shorter in length than the total length of the heat-recoverable coupling element. However, is the stake intended to have a corrosive effect between the heat return

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To prevent adjustable coupling and the tubular element, it is advantageous that the insert extends over the ends of the heat-resettable coupling extends addition. Iai the latter Case, the insert is preferably flexible or consists of a weak material, so that the arrangement of the rigid collar 26 and 28 advantages obtained are not impaired.

As can be seen, the coupling described reduces or prevents longitudinal movement between a deflecting one Bohr and the coupling and reduces the maximum bending stresses occurring in the area of the coupling on the Bohr. In this way, chafing and wear of the tube at the outer ends of the coupling is substantially avoided.

The invention also relates to a method of completion of a single line element or for the production of a Connection between two or more line elements using the coupling described.

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Claims (22)

262 27Q2t> «» 2 Claims Heat recoverable, hollow, metallic coupling, with a main section and at least one end-side stress distribution section with an opening for Receiving a line element, the wall thickness of the coupling in the end-side stress distribution section is substantially less than in the main section, characterized in that the end-side stress distribution section has an outer collar (26, 28) with increased wall thickness. 2. Coupling according to claim 1, characterized in that the end-side stress distribution section has a section (20) with a substantially constant wall thickness, which has a tapered section (16) is connected to the main section (14), the wall thickness of the tapered section increasing increased towards the main section too. 3. Coupling according to claim 2, characterized in that the section with a substantially constant wall thickness has a length which varies between 20% to 100 % of its outer diameter. 4. Coupling according to claim 1, characterized in that the end-side stress distribution section a has tapering section (46, 48), the wall thickness of which increases towards the main section (44), the collar (56, 58) lying adjacent the narrow end of the tapered portion. 5. Coupling according to one of Claims 1 to 4, characterized in that that the collar is at the extreme end of the stress distribution section. - 15 - 709830 / 03A7 ORlGiNAL INSPECTED 262 6. Coupling according to one of claims 1 to 5t, characterized in that the collar has a wall thickness which is less than the wall thickness of the main section (14, 44). 7. Coupling according to one of claims 1 to 6, characterized in that that the inner opening of the coupling is essentially cylindrical. 8. Coupling according to one of claims 1 to 7> characterized in that the coupling has at least two end tension distribution sections (I5i 17). 9- coupling according to claim 8, characterized in that the main portion (14) is substantially cylindrical and has an opening at each end. 10. Coupling according to one of claims 1 to 9 »characterized in that that the coupling is made of a nickel-titanium alloy. 11. Coupling according to one of claims 1 to 10, characterized in that that the coupling is designed in one piece. 12. Coupling according to claim 11, characterized in that the main section (14) has a device (13 »43, 36) which protrudes inwardly to engage the tubular member upon heat recovery. 13- coupling according to claim 12, characterized in that said device consists of one or more internal projections consists. 14. Coupling according to claim 12 or 13, characterized in that the inner wall of the stress distribution section is smooth and continuous. - 16 709830/0347 262 15 · Coupling according to one of Claims 1 to 10, characterized in that that the coupling is constructed as a composite device and has an insert (3 * 0. 16. Coupling according to claim 15, characterized in that the insert (2 ^ 0 is provided with internal projections The sleeve is and / or consists of a wearable material. 17- Procedure for obtaining a degree or a Connection with at least one line element characterized by (a) Placing the conduit element within a heat-recoverable , hollow, metallic coupling that has a main section and at least one end Has voltage distribution section with an opening for receiving the line element, the wall thickness of the coupling in the end-side section is substantially less than in the main section and the end-side Section at its end facing away from the main section with an outer collar with a raised Has wall thickness, and (b) V / arm reset of the heat recoverable, hollow, metallic coupling while grasping the line element. 18. The method according to claim 17, characterized in that the end-side stress distribution section of the coupling has a section with a substantially constant wall thickness which is connected to the main portion by a tapered portion, wherein the strength of the tapered section increases towards the main section. 19 · The method according to claim 18, characterized in that the thin-walled portion has a bending strength which is not greater than that of the conduit element is. - 17 - 709830/0347 20. The method according to claim 17, characterized in that the end-side stress distribution section is one tapering section on v / eist, the wall thickness of which increases towards the main section and the collar is next to the narrow end of the tapered section. 21. The method according to any one of claims 17 to 20, characterized in, that the main section has a significantly greater flexural strength than the line element. 22. The method according to any one of claims 17 to 21, characterized in that that the inside dimension of the collar after resetting is smaller than the corresponding outside dimension dec line element. 23- The method according to any one of claims 17 to 22, characterized in that that the line element is a pipe element. -18 709830/0347