Plug connector for cryogenic cables

Abstract

A plug-in connector (1) for cryogenic cables is proposed, comprising a coupling socket (3) and a coupling plug (2), in which: the coupling socket (3) and the coupling plug (2) each have an inner tube element (4, 13) and an outer tube element (5, 14) arranged coaxially to the inner tube element (4, 13); in a connected state the coupling plug (2) is inserted into the coupling socket (3); In the connected state, the coupling socket (3) and the coupling plug (2) are detachably connected to each other by a first connection located at one end of their outer pipe elements (5, 7; 14) which is designated as the “hot” end; in the connected state, at another end, referred to as the "cold" end, a joining gap existing between the coupling socket (3) and the coupling plug (2) in the area of ​​their inner pipe elements (4; 13, 15) is sealed by a seal (12); which is characterized by the fact that the outer tube element (5) of the coupling plug (2) is designed as a structured tube element at least in one section and has an outer contour in that section that deviates from a smooth cylindrical shape.

Description

[0001] The invention relates to a plug-in coupling for cryogenic conduits (conduits for conveying cryogenic media, such as liquid helium or hydrogen) according to the preamble of claim 1.

[0002] Such a quick-connect coupling for cryogenic conduits comprises a coupling socket and a coupling plug, wherein the coupling socket and the coupling plug each have an inner tube element and an outer tube element arranged coaxially to the inner tube element. In the connected state, the coupling plug is inserted into the coupling socket. Furthermore, in the connected state, the coupling socket and the coupling plug are detachably connected to each other by a first connection located at one end, referred to as the "hot" end, in the region of their outer tube elements. Additionally, in the connected state, a gap between the coupling socket and the coupling plug in the region of their inner tube elements is sealed by a gasket at another end, referred to as the "cold" end. The coupling socket and coupling plug are typically made of a metal, preferably (stainless) steel.

[0003] Such quick-connect couplings (or simply "couplings") are also known as Johnston couplings. Examples are known from DE 41 07 652 A1 or EP 3 339 713 B1. The seal against the system pressure is located in the so-called "hot" part of the coupling. Such a coupling serves to connect to a piping system consisting of a process pipe (i.e., a media-carrying pipe) and a jacket pipe (i.e., an outer protective pipe). A vacuum is typically drawn within certain compartments of the coupling after connection to the piping system to achieve improved thermal insulation.

[0004] This results in a pressure load on the outer and inner pipe element of the coupling plug or coupling socket.

[0005] Due to the thermal sealing, both insulation pipes—that is, the inner pipe element of the coupling socket and the outer pipe element of the coupling plug—are subjected to ambient pressure (usually atmospheric) due to the aforementioned evacuation. Furthermore, there is also a system pressure from the process line (i.e., the pressure at which the medium is carried through the line or coupling), which can be, for example, 40 or 60 bar. The total pressure then corresponds to the system pressure plus 1 bar (due to the vacuum). In practice, a safety factor is usually incorporated, and the coupling is required to withstand approximately 1.5 times the system pressure. Particularly with the insulation pipe of the coupling plug (hereinafter also referred to simply as "plug"), there is a risk of bulging under such high pressure loads, which is why, according to current best practices, this component had to be designed with a correspondingly robust, thick-walled construction.This has the adverse effect of, among other things, an increased heat input at the cold end of the plug connector.

[0006] Furthermore, a gap formed between the outer tube element of the plug and the inner tube element of the coupling socket (hereinafter also referred to as "socket") is regularly partially filled with cold liquid (the cryogenic medium), and there is a risk that a thermally insulating gas cushion between a sealing element at the warm end and this liquid will be overcome by the liquid, consequently cooling the sealing element. As a result, the sealing element becomes brittle, and the sealing function is no longer guaranteed.

[0007] This means that such couplings must preferably be positioned so that a normal vector of the coupling separation plane has a positive component parallel to the gravitational vector. In other words, the couplings cannot be installed completely horizontally, which correspondingly limits their application possibilities.

[0008] The invention is based on the objective of further developing a plug-in coupling of the aforementioned type in such a way as to achieve a more robust design with regard to buckling due to pressure. Furthermore, the risk of cooling of the "warm" sealing element and the heat input at the cold end of the plug-in coupling are to be reduced.

[0009] This problem is solved according to the invention by a plug-in coupling with the features of claim 1. Advantageous embodiments are defined in the dependent claims.

[0010] A plug-in coupling for cryogenic conduits according to the invention comprises a coupling socket and a coupling plug. The coupling socket and the coupling plug each have an inner tube element and an outer tube element arranged coaxially to the inner tube element. In the connected state, the coupling plug is inserted into the coupling socket. In the connected state, the coupling socket and the coupling plug are also detachably connected to each other by a first connection located at one end, designated as the "hot" end, in the region of their outer tube elements. In the connected state, a gap between the coupling socket and the coupling plug in the region of their inner tube elements is further sealed by a gasket at another end, designated as the "cold" end.The outer tubular element of the coupling plug is designed as a structured tubular element, at least in a partial section, and has an outer contour in that partial section that deviates from a smooth cylindrical shape. Advantageously, said partial section can extend substantially over the entire length of the plug, optionally with the exception of an end connection structure for joining the plug to the socket.

[0011] It is therefore proposed that the insulation pipe (i.e., the outer tube element) of a Johnston coupling connector be designed with a structured outer contour, i.e., one that deviates from a smooth cylindrical shape, in order to counteract buckling and thus allow the insulation pipe to be made thinner-walled than in the prior art. This limits heat conduction and reduces heat input. Furthermore, the structuring also contributes to locally stabilizing the gas cushion, effectively preventing the media from affecting the warm sealing element.

[0012] In particular, the design of the aforementioned insulation pipe as a so-called "bulped pipe" with wave-shaped bulges is advantageous, since the wave-shaped cross-section of the structuring significantly increases the resistance to bulging.

[0013] Furthermore, this method allows for a locally reduced gap between the coupling and the insulation pipe (the inner tube element) of the bushing. With appropriate design, this creates circumferential chambers between the two insulation pipes of the connected coupling, separated only by narrow annular gaps. These annular gaps can be so small that the heat input through the insulation pipes forces the liquid process medium to undergo a phase change in the gap area, thereby forming one or even several localized gas cushions. This allows the coupling to be positioned independently of the direction of gravity.

[0014] An additional advantage is that the wave crests of the "bulped pipe" act as a guide during coupling and effectively reduce friction between plug and socket.

[0015] The required roundness of the pipe elements (insulation pipes) can be achieved by manufacturing them through a forming process (calibration), e.g. by internal high-pressure forming or by rolling or by using a drawing die.

[0016] The following embodiments of the invention have proven to be particularly advantageous: One embodiment of the plug-in coupling according to the invention provides that the outer tube element of the coupling plug has a number of annular protrusions in the relevant section. Preferably, this number is a plurality of protrusions. This allows for the creation of several of the aforementioned narrow annular gaps, which significantly improves the insulating effect.

[0017] One embodiment of the plug-in coupling according to the invention provides that the protrusions are identically designed. This contributes to a further improved insulating effect and allows the advantageous use of a smooth tube as the outer insulation pipe.

[0018] One embodiment of the plug-in coupling according to the invention provides that the protrusions, when viewed in a section along a longitudinal axis of the plug-in coupling, exhibit an axially symmetrical configuration with respect to an axis perpendicular to the longitudinal axis through a vertex of the respective protrusion. This has proven to be particularly advantageous for reasons of stability.

[0019] One embodiment of the plug-in coupling according to the invention provides that the bulges have a continuously curved profile in the direction of the inner tube element of the coupling plug. This also contributes further to stabilization and is additionally advantageous with regard to the aforementioned reduction in friction.

[0020] Another embodiment of the plug-in coupling according to the invention provides that the outer pipe element of the coupling plug has a number of distinct local bulges in the section, which are preferably not continuous throughout. In a specific embodiment, this results in a so-called "dimpled pipe", i.e., a pipe element with a dimpled structure, similar to a golf ball. Such an embodiment is also advantageous for reasons of stability, allowing for less material usage and reduced heat conduction.

[0021] Yet another embodiment of the plug-in coupling according to the invention provides that the local protrusions are arranged in a regular pattern. According to the applicant's findings, this has proven advantageous because it results in a uniform increase in stability. The joining properties are also correspondingly improved.

[0022] Another embodiment of the plug-in coupling according to the invention provides that the outer tube element of the coupling plug has a honeycomb-shaped outer contour in that section. Such a structure is also advantageous for reasons of stability.

[0023] In a further development of this embodiment of the plug-in coupling according to the invention, it can be provided that the honeycomb-shaped design has hexagonal bulges and depressions enclosed by these bulges, or vice versa. This allows comparable advantages to be achieved as with the aforementioned ring-shaped wave structures.

[0024] In another embodiment of the plug-in coupling according to the invention, the outer tubular element of the plug rests against the inner tubular element of the socket, particularly with its protrusions as described in one of the previously described embodiments. This makes it possible to form the aforementioned separate compartments or circumferential chambers between which thermally insulating gas cushions can form, further improving the efficiency of the plug-in coupling.

[0025] In another embodiment of the plug-in coupling according to the invention, the outer tubular element of the coupling plug is axially pre-tensioned, particularly during the actual coupling process, in order to specifically shape the radial outward bulges and to close, or at least minimize, gaps, especially annular gaps, between the outer tubular element of the coupling plug and the inner tubular element of the coupling socket. The advantages associated with this have already been mentioned above.

[0026] In another embodiment of the plug-in coupling according to the invention, it is further provided that a local sealing element insert is arranged between the outer tube element of the coupling plug and the inner tube element of the coupling socket, at least in the area of ​​a subset of the protrusions, preferably in all protrusions. This further improves the closing of the (ring) gap.

[0027] In a further embodiment of the plug-in coupling according to the invention, it is also provided that the sealing element insert consists of a metal, preferably indium. Metallic seals are generally resistant to high vacuums and are durable. The choice of indium, in particular, can ensure that no additional increased thermal conductivity occurs, as would be the case, for example, with the use of copper.

[0028] In another embodiment of the plug-in coupling according to the invention, it is further provided that at least the outer tubular element of the coupling plug is manufactured by forming, preferably internal high-pressure forming or so-called flow forming or pressing. Such processes are known to those skilled in the art. This results in improved roundness and, consequently, improved sealing, as already mentioned.

[0029] In another embodiment of the plug-in coupling according to the invention, it is further provided that at least the outer tube element of the coupling plug has a variable wall thickness in the axial and / or circumferential direction.

[0030] The term "variable wall thickness" means that the wall thickness is not constant, but rather varies in the axial direction (along the longitudinal axis) and / or in the circumferential direction. This characteristic can be used to advantage during the forming process. Furthermore, the applicant has determined that such a variation in wall thickness also increases the stability of the insulation pipe and leads to reduced material usage (resulting in lower thermal conductivity). Flow forming, or pressing, is a particularly suitable manufacturing process for achieving variable wall thicknesses.

[0031] In yet another embodiment of the plug-in coupling according to the invention, the outer tubular element of the coupling plug is stabilized by additional elements, such as stabilizing rings, which are preferably positively locked, and most preferably materially locked. These additional elements are preferably arranged at selected positions along the outer tubular element of the coupling plug. They can help to selectively influence or mitigate its buckling behavior. They preferably consist of materials with poor thermal conductivity, such as PEEK, PTFE, PI, or other, currently unknown plastics or materials with comparable properties.

[0032] Overall, the present invention achieves the following significant advantages over the prior art: lightweight construction with reduced material usage, increased robustness against buckling, enabling installation in any orientation, and reduced heat input. Furthermore, due to improved thermal decoupling, a shorter overall length than previously possible can be achieved.

[0033] Further features and advantages will become apparent from the following description of exemplary embodiments based on the drawing. Fig. Figure 1 shows a plug-in coupling according to the invention in its individual parts; Fig. 2 shows the plug connector from Fig. 1 in longitudinal section; Fig. 3 shows plug connector Fig. 1 in the compound state; Fig. 4 shows the plug connector Fig. 3 in longitudinal section; and Fig. Figure 5 shows an alternative embodiment of the outer tube element of the coupling plug for a plug coupling according to the invention.

[0034] In all figures, the same reference symbols denote identical or at least equivalent elements.

[0035] In the Fig. Figure 1 shows a plug-in coupling 1 according to the invention with longitudinal axis L, shown in its individual parts. Reference numeral 2 designates the coupling plug (plug), and reference numeral 3 designates the coupling socket (socket). The plug comprises two coaxial tube elements, namely an inner tube element 4 and an outer tube element 5. The outer tube element 5 is designed as a structured tube element and accordingly has an outer contour that deviates from a smooth cylindrical shape. In particular, it is structured over most of its longitudinal extent as a "bulbed pipe" with several identical annular protrusions 6, of which only one is explicitly designated. This allows it to be made lighter and thinner while maintaining the same or even improved (pressure) stability. Preferably, the outer tube element 5 of the coupling plug 2 is manufactured by forming, preferably internal high-pressure forming.

[0036] At one end 7 (the so-called "warm end"), the outer pipe element 5 is radially expanded and has no bulges in this area. In a transition area between the bulges 6 and the expanded end 7, an approximately triangular cross-section elevation 8 is provided on the outside, which will be discussed in more detail later.

[0037] Reference numeral 9 shows a V-shaped clamp for the detachable connection of plug 2 and socket 3. Reference numeral 10 denotes a sealing element, preferably made of plastic / elastomer (e.g., NBR or FKM). The use of purely metal sealing elements (e.g., an uncoated metal bead seal) or a composite of a metal carrier and an elastomer or plastic coating (i.e., a coated metal bead seal) is also possible. Reference numeral 11 denotes a stabilizing element of the type of a so-called spacer or standoff for the concentric positioning of the pipe runs connected / welded to the coupling (i.e., inner pipe or process pipe and outer pipe or jacket pipe).Reference numeral 12 shows a further seal, preferably made of a plastic or elastomer suitable for use at cryogenic temperatures, or in the form of a metallic seal, for example made of indium, which serves to seal the inner tube element 4 against its (not shown here) counterpart within the socket 3 when plug 2 and socket 3 are joined together according to the dashed arrow. The stabilizing element 11 ensures that the inner tube element 4 is centered within the expanded end 7; it is preferably made of a poorly thermally conductive material, in particular PEEK, PTFE, PI, or other plastics / materials with similar properties not yet known.

[0038] Elements 7, 9, 10 and the flared end 19 represent a common BICONE V-band connection according to the prior art, which is known to those skilled in the art. Other common detachable flange connections with sealing elements exist that could be used in this context.

[0039] Fig. Figure 2 shows the same situation in longitudinal section. Here it is also evident that the socket 3 comprises two coaxial tube elements, namely an inner tube element 13 and an outer tube element 14. The two coaxial tube elements of the plug 2 and socket 3 are fluid-tightly connected to each other at one end, preferably by a material bond. For the plug 2, this is the case in the right part of the figure in the area of ​​the so-called "cold end"; for the socket 3, this applies to the area on the left of the figure, i.e., at the so-called "warm end". The inner tube element 13 of the socket 3 is tapered in cross-section at its free end and has a tube extension 15, the diameter of which is adapted to that of the inner tube element 4 of the plug 2. The tube extension 15 and the inner tube element 4 of the plug 2 are connected as fluid-tight as possible by means of the seal 12.The pipe extension 15 has an inwardly directed partial pipe extension 15a, which corresponds to a sealing surface for the seal 12, and an outwardly directed partial pipe extension 15b, which is intended for connection to the process pipe (not shown).

[0040] How to Fig. Since the connector 2 is still removed, the connector 2 at reference numeral 15b' also has a kind of partial pipe extension as an integral part of the inner pipe element 4, which is intended for connection to the process pipe (not shown). The opposite end 15a' again corresponds to a partial pipe extension that forms a sealing surface for the seal 12. Functionally, the inner pipe element 4 thus corresponds to a pipe extension extending over the length of the connector, analogous to the pipe extension 15.

[0041] Reference numeral 16 shows a further stabilizing element. The stabilizing element 16 ensures that the inner tube element 13 or the tube extension 15 is centered within the expanded end 7; it is preferably made of a poorly thermally conductive material, such as PEEK, PTFE, PI or other plastics or materials with comparable properties that are not yet known.

[0042] Between the tube elements 4, 5 of the plug 2 or between the tube elements 13, 14 of the socket 3, a so-called superinsulation 17, 18 is arranged, which is usually in the form of a multi-layered, highly (radiation-) reflective film or the like, which is known to those skilled in the art.

[0043] To connect plug 2 and socket 3 at the warm end, which is in the Fig. As shown in Figure 3, the plug 2 has the aforementioned, approximately triangular or conical-shaped elevation 8 on the outside (see Figure 3). Fig. 1 and Fig. 2), to which the socket 3 with its one tufted end 19 is attached (cf. Fig. 1 and Fig. 2) nestles up, see Fig. 4. The sealing element 10 is in the connected state (see Fig. 4) arranged between a flank of the elevation 8 and the tufted end 19 (not visible in the illustration).

[0044] Other sealing methods, such as radial or axial sealing using O-rings, flat gaskets or profile gaskets made of plastics or elastomers or metallic gaskets, are known to the expert and can be used here as an alternative.

[0045] Fig. Figure 4 shows the connected state of the plug-in coupling 1. In this state, the coupling socket 3 and the coupling plug 2 are detachably connected to each other by a first connection located at the hot end in the area of ​​their outer pipe elements 5 and 7 and 14 (by means of the clamp 9). Furthermore, in the connected state, a joint gap at the other, cold end between the coupling socket 3 and the coupling plug 2 in the area of ​​their inner pipe elements 4, 13 and 15 is sealed by the seal 12.

[0046] How to Fig. 4. The bulges 6 of the pipe element 5, in a section along a longitudinal axis of the plug coupling 1, exhibit a symmetrical shape with respect to a plane perpendicular to the longitudinal axis L through a vertex 6a of a respective bulge 6. In addition, the bulges have a continuously curved, i.e., convex, shape in the direction of the longitudinal axis L, pipe element 13 of the coupling plug 2.

[0047] The outer tube element 5 of the coupling plug 2 rests with its bulges 6 on the inside of the inner tube element 13 of the coupling socket 3. To achieve this, the outer tube element 5 of the coupling plug 2 can be axially pre-tensioned during the coupling process, so that in particular the bulges 6 are formed radially outwards to close gaps, especially annular gaps, between the outer tube element 5 of the coupling plug 2 and the inner tube element 13 of the coupling socket 3. In this way, separate annular cavities 20 are formed along the coupling 1, which ensure that no cryogenic fluid reaches the "warm" sealing element 10 ( Fig. 1 and Fig. 2) penetrates and damages it. In any case, any remaining annular gaps between the pipe elements 5 and 13 ensure that any cryogenic fluid that has penetrated evaporates and forms efficient insulating gas cushions, thus preventing further heat input from the outside.

[0048] Although this is not shown in the figures, a local sealing element insert can be arranged between the outer tube element 5 of the coupling plug 2 and the inner tube element 13 of the coupling socket 3, at least in the area of ​​a subnumber of the bulges 6, which sealing element insert consists in particular of a metal, preferably indium.

[0049] Fig. Figure 5 shows an alternative embodiment of only the outer tube element 5 of the coupling plug 2, in which this element has a honeycomb-shaped design of its outer contour over most of its longitudinal extent. The honeycomb-shaped design comprises hexagonal depressions 21 and these surrounding, interconnected hexagonal bulges or projections 22; a reversed embodiment is also possible.

[0050] The pipe element 5 according to Fig. 5 replaces the “bulbed pipe” according to the Fig. 1, Fig. 2, Fig. 3 to Fig. 4, in particular according to the Fig. 1, Fig. 2 and Fig. 4. Other configurations of the pipe element 5 are also possible, e.g. a configuration with isolated (distinct) elevations and / or depressions (so-called dimples) (not shown). QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 41 07 652 A1

[0003] EP 3 339 713 B1

[0003]

Claims

[1] Plug-in connector (1) for cryogenic cables with a coupling socket (3) and a coupling plug (2), wherein: the coupling socket (3) and the coupling plug (2) each have an inner tube element (4, 13) and an outer tube element (5, 14) arranged coaxially to the inner tube element (4, 13); in a connected state the coupling plug (2) is inserted into the coupling socket (3); In the connected state, the coupling socket (3) and the coupling plug (2) are detachably connected to each other by a first connection located at one end of their outer pipe elements (5, 7; 14) which is designated as the “hot” end; in the connected state, at another end, referred to as the "cold" end, a joining gap existing between the coupling socket (3) and the coupling plug (2) in the area of ​​their inner pipe elements (4; 13, 15) is sealed by a seal (12); characterized by, that the outer tube element (5) of the coupling plug (2) is designed as a structured tube element at least in one section and has an outer contour in that section that deviates from a smooth cylindrical shape. [2] Plug coupling (1) according to claim 1, wherein the outer tube element (5) of the coupling plug (2) has a number of annular protrusions (6) in the subsection. [3] Plug-in coupling (1) according to claim 2, wherein the protrusions (6) are identically formed. [4] Plug coupling (1) according to claim 2 or 3, wherein the protrusions (6) in a section along a longitudinal axis (L) of the plug coupling (1) have an axially symmetric design with respect to an axis perpendicular to the longitudinal axis (L) through a vertex (6a) of a protrusion (6) in question. [5] Plug coupling (1) according to one of claims 2 to 4, wherein the protrusions (6) have a continuously curved course in the direction of the inner tube element (4) of the coupling plug (2). [6] Plug coupling (1) according to claim 1, wherein the outer tube element (5) of the coupling plug (2) has a number of distinct local bulges in the subsection. [7] Plug coupling (1) according to claim 6, wherein the local protrusions are arranged in a regular pattern. [8] Plug coupling (1) according to claim 1, wherein the outer tube element (5) of the coupling plug (2) has a honeycomb-shaped design of its outer contour in the subsection. [9] Plug coupling (1) according to claim 8, wherein the honeycomb shape has hexagonal bulges and depressions enclosed by these bulges, or vice versa (21, 22). [10] Plug-in coupling (1) according to one of the preceding claims, wherein the outer tube element (5) of the coupling plug (2) rests on the inside of the inner tube element (13) of the coupling socket (3), in particular with its protrusions (6) according to one of claims 2 to 7 or 9. [11] Plug-in coupling (1) according to one of the preceding claims, wherein the outer tube element (5) of the coupling plug (2) is axially pre-tensioned in order to form, in particular, the bulges (6) according to one of claims 2 to 7 or 9 radially outwards and to close gaps, in particular annular gaps, between the outer tube element (5) of the coupling plug (2) and the inner tube element (13) of the coupling socket (3). [12] Plug-in coupling (1) according to one of claims 2 to 5 or 9, in which a local sealing element insert is arranged between the outer tube element (5) of the coupling plug (2) and the inner tube element (13) of the coupling socket (3) at least in the area of ​​a subnumber of the bulges (6). [13] Plug coupling (1) according to claim 12, wherein the sealing element insert consists of a metal, preferably indium. [14] Plug coupling (1) according to one of the preceding claims, wherein at least the outer tube element (5) of the coupling plug (2) is produced by forming, preferably internal high-pressure forming or most preferably pressing. [15] Plug coupling (1) according to one of the preceding claims, wherein at least the outer tube element (5) of the coupling plug (2) has a variable wall thickness in the axial and / or circumferential direction. [16] Plug coupling (1) according to one of the preceding claims, wherein the outer tube element (5) of the coupling plug (2) is stabilized by additional elements, such as stabilizing rings, which are preferably positively locked, most preferably materially locked.

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