Tube coupling with clamping effect for the tube and method of mounting a tube coupling

Abstract

The invention relates to a pipe connecting arrangement (1, 30, 36), in particular for connecting thin-walled metal tubes (4), comprising: a tube (4) with a reshaped end portion (3, 31), where the reshaped end portion (3, 31) shows a truncated cone like shape (6) with a decreasing diameter (9) towards the connection end, and a tube end cone angle (α), forming an outer circumferential sealing surface; a connecting member (2) with a receiving recess (13) with a truncated cone like shape with an increasing diameter towards the connection end, and a receiving recess cone angle (β), forming an inner circumferential sealing surface; and a support ring (15, 26, 33) that is arranged circumferentially around at least a part of the tube end (3, 31) of the tube (4). At least a part (24) of the support ring (15, 26, 33) rests against the receiving recess (13) of the connecting member (2).

Description

[0001] Tube coupling with clamping effect for the tube and method of mounting a tube coupling

[0002] The invention relates to a pipe connecting arrangement, in particular to a pipe connecting arrangement for connecting thin-walled metal tubes.

[0003] Transporting gases, liquids and generally fluids between different locations and devices is a standard task in all sorts of industry, research, technology and machinery. The locations and devices that have to be connected may be located close to each other (for example a couple of centimetres or decimetres apart), but may also be very distant from each other (for example hundreds of kilometres). This statement includes all different scales in between, for example distances in the order of metres, tens of metres, hundreds of metres, kilometres and so on. As it is well known to everybody, tubes, pipes and hoses may be used for such a transfer of gases and liquids.

[0004] Depending on the requirements of the particular task in question, appropriate dimensions, wall thicknesses, materials and so on have to be chosen for the tubes and hoses to be used. The requirements include, without limitation, pressure, temperature (of the fluid and of the surroundings), state of matter, chemical composition, fluid throughput rate, presence of vibrations, corrosive conditions, allowable diffusion out of / into the tube, and so on, just to name a couple of requirements. Diffusion can become quite problematic, if, for example, hydrogen is to be transported, due to the high diffusion rate of hydrogen.

[0005] A well-known follow-up problem is the inevitable connection of the tube / hose to a device, and the connection of two tube ends to each other (in particular in light of the finite possible lengths of the tubes and hoses). Here, not only the aforementioned general framework is to be considered, but also easy handability of the various components. It is to be noted that in particular conditions, for example if vibrations do occur, the connections between connected tube ends and between the tubes and the connected devices are particularly prone to leaks, breaks and failures.

[0006] Nevertheless, due to the frequent and almost universal use of tubes and hoses, and consequently of respective connecting arrangements, it is no wonder that a wide variety of suggestions for pipe connection arrangements have already been made.

[0007] An example is the ferrule assembly for conduit fittings that is described in WO 2010 / 068762 A1 . Here, two ferrule-type conduit gripping devices that are to be used in combination are arranged over a tube end. When the tube end is connected to a female connector body by means of a union nut, the two gripping devices that are contacting each other via tapered contact surfaces are moving closer together, causing one of the radially inner gripping devices to cut into the circumferential surface of the tube end, which in turn results in a positive form locking contact that inhibits an axial movement of the gripping devices relative to the tube. Therefore, the respective compound of the tube end and the gripping devices can be tightly screwed onto a female connector device using the union nut. As can be seen from United States patent US 3,103,373 A, the basic design of the assembly disclosed in this application is known for some decades and works quite well in practice. Nevertheless, it is still prone to leakage issues, where the leakage issues become more predominant with gases showing a high diffusion rate, like it is the case with hydrogen. Another problem is the assembly of the arrangement, which is prone to various assembly errors (for example due to wrong placement of the gripping devices). Furthermore, due to the very design concept, this connection arrangement is not suitable for thin-walled tubes, since the tube end has to be able to sustain the high radially inwardly directed pressure force that is extorted by the gripping devices. Another problem that is connected with the design concept is that this type of connection is comparatively prone to leakage issues, and even mechanical failures, when it is used in environments with significant vibrations.

[0008] Another suggestion was made in the European patent EP 2 872 811 B1 . Here, it is suggested to deform the end of the tube in a way that the end forms an inwardly tapered truncated cone-like end portion, where the outer, tapered surface of this end portion is designed to contact a surface with a corresponding inner tapered contact surface of a connecting member. This way, a cone connection with a comparatively large cone-like contact area is established that is quite fluid and gas tight. To further increase the tightness of the connection between the tube and the connecting member, sealing devices like an O-ring or a circumferentially applied sealing material may be provided. To effectuate the required pressure between the tube end and the connecting member, so that a good mechanical contact between the contacting surfaces is established, the tube end is provided with a second bent area with a decreasing diameter (in a direction pointing away from the tube opening). This second bent area forms some kind of a shoulder that is used as a support surface for a union nut. Again, this design has undeniably certain advantages. A disadvantage, however, is that a relatively high mounting force has to be applied between the tube end and the connector member, to realise a sufficiently tight connection between the tube end and the connection member. This limits the applicability of the design. In particular, a certain thickness of the material of the tube has still to be provided.

[0009] EP 1 260 750 B1 suggests a screw pipe connection with a support ring. The screw pipe connection includes a connecting pipe with a socket opening and a screw-on nut. The support ring which fits on the pipeline between a ring bead and a screw part forms with the bead a contact bearing face which forms an angle much greater than 45° relative to the screwing axis so that this area is free of radial force components when the screw connection is tightened up. While this design indeed increases the clamping force of the tube end, it is still far from being perfect, due to the very limited axial extent of the clamping area of the tube end.

[0010] It is therefore obvious that there is a desire for an improved design for a pipe connecting arrangement.

[0011] It is therefore an object of the present invention to propose a pipe connecting arrangement, in particular a pipe connecting arrangement for connecting thinwalled metal tubes, that is improved over pipe connecting arrangements as they are known in the prior art.

[0012] It is another object of the invention to propose a method of connecting a tube end and a connecting member of a pipe connecting arrangement that is improved over such methods as they are known in the prior art.

[0013] A pipe connecting arrangement according to claim 1 solves this object. A method according to claim 14 also solves this object.

[0014] It is suggested, to design a pipe connecting arrangement, in particular a pipe connecting arrangement for connecting thin-walled metal tubes, in a way that the pipe connecting arrangement comprises: a tube with a reshaped end portion, where the reshaped end portion shows a truncated cone like shape with a decreasing diameter towards the connection end (opening end of the tube), and a tube end cone angle a, forming an outer circumferential sealing surface, a connecting member with a receiving recess with a truncated cone like shape with an increasing diameter towards the connection end (opening end of the connecting member), and a receiving recess cone angle , forming an inner circumferential sealing surface, and a support ring that is arranged circumferentially around at least a part of the tube end of the tube, wherein at least a part of the support ring rests against a part of the connecting member, in particular against a part of the receiving recess of the connecting member.

[0015] The notion “pipe connecting arrangement” can relate to an arrangement, where a tube end is to be connected to a machine, a part of a machine or a similar device. Therefore, the respective connecting member may be fixedly attached to the respective piece of machinery or device. It is to be noted that ’’fixedly" can relate to a situation, where the removal of the respective connecting member may not be effectuated without major effort (for example, if the connecting member is soldered, glued or otherwise fixedly attached to the respective part of the machinery and so on). Furthermore, ’’fixedly" can additionally or alternatively relate to a situation, where the respective connecting member may be removed from the respective piece of machinery or device relatively easily, for example when using a threaded connection (possibly using sealing means and the like). However, additionally or alternatively, the notion of a “pipe connecting arrangement" may relate to a situation, where two tube ends are connected to each other, typically using a so-to-say “interceding” or “intermediary” connecting member. This may be understood in a way that a tube end of a first tube connects to the connecting member on a first side and / or at a first position thereof, while another tube end of a second tube is connected to the connecting member at a second side and / or at a second position of the connecting member. It is to be noted that the presently proposed design of a pipe connecting arrangement works with essentially all types of tubes and possibly even hoses. In particular, when it comes to hoses, a design might be possible where a tube-like (“stiff”, not elastically deformable) end is provided at the respective end of the hose. This may be considered as some kind of a plug-like device or a male connector piece at the end of the hose. However, in case the mantle of a hose is sufficiently sturdy, an end of the hose may be used as a so-to-say “direct substitution” of the tube end. Nevertheless, based on the intrinsic advantages of the presently proposed pipe connecting arrangement, it is particularly suitable to be used in combination with thin-walled metal tubes and possibly in combination with other types of tubes and hoses that do not allow for high, radially inwardly directed forces. This may be due to limited mechanical stability of the respective tube or hose (thickness of the mantle, material of the mantle, other influences, et cetera).

[0016] As it is known, tubes (and possibly hoses as well) usually show an essentially circular cross-section. This does not exclude the possibility that different cross sections may be used instead, in particular elliptical cross sections and possibly even triangular, rectangular (quadratic), pentagonal, hexagonal, heptagonal, octagonal or generally n-angled (polygonal) cross sections, in particular in connection with somewhat rounded corners. While (essentially) symmetrical cross sections may be used (n-count symmetry), non-symmetrical cross sections may be envisaged as well. Irrespective of the cross-section, however, the tube or hose typically shows essentially no (significant) variation in cross section along its longitudinal direction (axial direction) when being produced. This is typically due to the production process, where the tube or hose is frequently extruded using a die. It is to be noted that this does not necessarily exclude the possibility of axial variations in thickness, like it is the case with corrugated hoses, just to name an example. Here, the die is typically arranged at an angle relative to an advancing production direction of the tube / hose, so that the production process is sort of spirally winding the corrugated hose. Furthermore, certain type of variations in the axial direction may be introduced in a later production step, for example if an external thread is cut, using a thread cutter type of tool or the like.

[0017] However, presently the tube has to show a reshaped end portion with specified properties. The cross-section of the reshaped end portion of the tube may show essentially the same cross-sectional shape, as the (main part) of the tube itself. However, it is possible as well that the reshaped end portion shows a different cross-section as compared to the (main part of the) tube, in particular a (different) cross-section from the aforementioned list. While the reshaped end portion may be realised by using some kind of mould forms, typically a tube or hose with a ’’straight" tube end (no significant variations in an axial direction) will be reshaped by appropriate manufacturing steps. Such reshaping steps are, as such, known in the prior art and are presently not further elucidated. For completeness, such reshaping processes are described in EP 2 872 811 B1 or WO 2017 / 102190 A1 . It is to be noted that the reshaping process may not only be realised at the production site of the tube or hose, but also by the user of the pipe connecting arrangement. It is to be noted that this is quite often not an end user (although this is possible), but typically another type of production site, where pre-produced parts are connected together (not excluding the possibility of parts that are produced on site). This may also refer to machine shops, performing repairs or the like. For this, usually more or less automated reshaping boxes are produced and sold to the consumer so that he is able to perform the necessary reshaped end portion neighbouring the opening of the tube. It is to be noted that usually such reshaping processes will result in an (essentially) circular cross-section (irrespective of the crosssection of the main part of the tube, at least to a certain extent). Typically, the truncated cone-like shaped part of the reshaped end portion of the tube starts immediately at the tube opening itself. However, this does not exclude the possibility that the beginning of the truncated cone like shaped part of the reshaped end portion is offset from the tube opening by a certain distance. As an example, a cylindrically shaped end part may be foreseen for facilitating the insertion process, for enhancing the tightness, or the like. Typically, the cone angle a is (essentially) the same along the axial extent of the truncated cone like shaped part of the reshaped end portion of the tube.

[0018] It is also possible that a variation of the tapering angle occurs. This may be particularly the case where a tapered surface changes to an untapered surface (for example cylindrical surface). However, changes in the tapering angle even may occur within a tapered section, so that along the axial extent of the respective tapered section, varying tapering angles may be present. In particular, such a variation may be limited to one or both of the end regions of the truncated cone like shaped region of the tube end. This way, a smooth changeover to different parts of the tube end may be realised. In particular, this may reduce mechanical stress in the material of the tube, reducing the possibility of early material fatigue and the like. Typically, the “straight section” of the tapering angle (i.e. a section without a change in the tapering angle) should comprise a significant, particularly the majority of the tapered section of the tube. In particular, the “straight section” should comprise at least 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80% or 90% of the “complete” tapered section (including sections with varying tapering angle). More particularly, typically the “straight section” usually does comprise the section where a major part, or even (essentially) all of the sealing functionally of the pipe connection arrangement and / or of the respective sealing surface is realised.

[0019] The connecting member is provided with a truncated cone like shaped receiving recess, into which the tube end is to be fitted. With increasing diameter towards the connection end (opening end; insertion hole), the receiving recess shows some kind of a funnel like shape. The receiving recess cone angle that forms the inner circumferential sealing surface may be (essentially) the same over the extent of the truncated cone like shaped part of the connecting member. However, variations may occur, similar to the aforesaid in connection with the truncated cone like shape of the tube end portion, at least in analogy. This may particularly relate to variations of the cone angle at the changeover ends of the respective section of the connecting member (in particular where a change from a tapered section to a straight section occurs, or vice versa). Only for completeness, it should be mentioned that usually the truncated cone like shaped receiving recess of the connecting member shows essentially the same cross-sectional shape as the reshaped end portion of the tube. Again, the “straight section” of the tapering angle (i.e. a section without a change in the tapering angle) should comprise a significant, particularly the majority of the tapered section of the receiving recess. In particular, the “straight section” should comprise at least 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80% or 90% of the “complete” tapered section (including sections with varying tapering angle). More particularly, typically the “straight section” usually does comprise the section where a major part, or even (essentially) all of the sealing functionally of the pipe connection arrangement and / or of the respective sealing surface is realised.

[0020] A sealing surface may be understood as (part of) a surface that is intended, designed and / or arranged to come into contact with another (part of) a (sealing) surface in a way that an (essentially) leakage-proof (more particularly liquid tight, fluid tight and / or gas tight) connection may / will be established between the two neighbouring (sealing) surfaces that come into contact with each other. It is possible that at least one of the sealing surfaces shows an advanced surface finishing, like a polished surface. However, it is also possible that the surface shows a standard surface finishing. Usually, however, the surface does not show a distinct surface structure, like ripples, scratches, protruding webs, net like webs or the like. It is to be noted that the respective sealing surfaces may not necessarily come fully into contact with a neighbouring surface to establish a leakage-proof connection. Instead, it is possible that only a part of one or both of the adjacent sealing surfaces will eventually come into a leakage-proof contact. This is usually particularly true for thick-walled tubes. Here, due to the higher required forces for deforming the thick-walled tube, a comparatively short / small contact area usually proves to be sufficient for realising a leakage proof connection.

[0021] Further, a support ring is provided for the pipe connecting arrangement. Support rings are known as such in the state-of-the-art. They are usually arranged by placing it over the tube from one end thereof. In case of a reshaped end portion, the support ring can be placed over the tube before the reshaping occurs (or, in some cases, by placing it over the tube from the other end). Usually, the inner diameter of the support ring and the outer diameter of the undeformed tube / hose (main part of the tube / hose) are approximately the same, where a certain play is foreseen, of course. Furthermore, the cross- sectional shapes of the tube / hose and the support ring are usually chosen to be approximately the same. Support rings are usually used to increase the stability of the connection between the tube and the connecting member against bending forces. Furthermore, when using support rings, the sensitivity of the connected arrangement against vibrations is usually decreased, in particular by clamping at least part of the tube by means of loose parts of the support ring(s). Usually, a good clamping behaviour is advantageous since the various bends in the reshaped end portion of the tube show a decreased strength relative to undeformed parts. This is because cold deformation (which is regularly used for reshaping the reshaped tube end) of materials (metals) typically results in a decreased strength of the material. A clamping usually prevents repetitive small deformations of the bends of the tube due to vibrations, thus usually significantly increasing the lifetime of the arrangement. This is of course advantageous. There are arrangements in the prior art, were a single support ring or a plurality (two, three, four or even more) support rings are used at one end of the tube.

[0022] According to the present suggestion at least a part of the support ring rests against a part of the connecting member. In particular, the support ring may rest against a part of the receiving recess of the connecting member. These statements are usually equivalent to the situation that at least part of the support ring rests against an inner surface part (inner surface of the receiving recess) of the connecting member, typically a part of a truncated cone like shaped part of the connecting member. This, in turn, is usually equivalent to a part of the inner circumferential sealing surface of the receiving recess of the connecting member. It is to be noted that the notion Tests against” may be interpreted in a way that the pipe connection arrangement (or parts thereof) is designed and arranged in a way that a mechanical support is provided for the support ring by means of the connecting member, so that a (radially) outwardly directed movement of (parts of) the support ring is hindered, preferably prevented, more preferably even a (radially) inwardly directed movement of (parts of) the support ring is effectuated during the assembly process of the pipe connecting arrangement and / or when the pipe connecting arrangement is assembled. This may also be interpreted in a way that the connecting member applies at least a part of a force vector onto the support ring that is directed in the (radially) inwardly directed direction during the assembly process of the pipe connecting arrangement and / or when the pipe connecting arrangement is assembled. In a certain sense, this results in an enhancement of the stability of the support ring by external means, i.e. by means of the connecting member. It is to be noted that the connecting member usually shows a somewhat stiff, sturdy and / or undeformable design. Therefore, even if the support ring is designed to be not particularly stiff / sturdy / non-deformable, the support ring can effectuate a strong force in a radially inwardly directed direction. This is because the support ring can stabilise itself by using the solid design of the connecting member (which is usually necessary for performing its purpose). In other words, it is sufficient to design the connecting member sufficiently solid. The support ring, however, may be designed relatively simple and non-solid, but nevertheless may effectively mimic the presence of a solid support ring by using the support of the connecting member. Certainly, the support ring must not be too elastic (like it would be the case for a rubber ring or the like). This is, because the support ring should be able to transfer a certain force. Using the proposed design, a cost-effective design can be realised. Furthermore, the size (wall thickness) of the support ring can also be reduced, which may result in less mounting space. Nevertheless, a very effective support of the tube and within the connecting member can be realised thanks to the present suggestion. Furthermore, in particular when using a tapered surface of the connecting member, it is even possible that an axial movement of (part of) the support ring may be translated into a radially inwardly directed (increasing) force, thus increasing the holding ability of the support ring, and hence the stability of the pipe connecting arrangement.

[0023] Another possible embodiment of the pipe connection arrangement can be realised, when the extent in the axial direction of the truncated cone like shaped section of the end portion of the tube is designed to be smaller than the extent in the axial direction of the truncated cone like shaped section of the receiving recess of the connecting member. When using this design, it is particularly simple to design and arrange the support ring in a way that at least a part thereof rests against a part of the connecting member, particularly against a part of the receiving recess of the connecting member. More particularly, it can rest against a part of the tapered surface of the receiving recess of the connecting member. Then, it is possible that in axial movement of (part of) the support ring can be translated into a radially inwardly directed force. Effectively, for at least certain designs, the generation of such a radially inwardly directed force will “automatically” come up when the (fluid tight, gas tight, liquid tight) connection between the tube end and the connecting member will be established. This way, a single fastening process may result in a plurality (in particular at least two, like fluid tightness / gas tightness / liquid tightness and sound support of the tube relative to the connecting member; the latter in particular with respect to any vibrations occurring) advantageous results.

[0024] Further, it is possible to design the pipe connecting arrangement in a way that the support ring protrudes into a void that is formed between a portion of the end section of the tube and a portion of the receiving recess of the connecting device, wherein the support ring preferably shows an axial protrusion that protrudes into said void. Using this design, the tapering angle of the receiving recess may be used to push at least part of the support ring towards the outer circumference of the tube and / or may create a radially inward directed force towards the outer circumference of the tube. Therefore, the tube can be held tightly in place, so that a particularly high resilience against vibrations may be realised. Furthermore, it is to be noted that the connecting member may usually be designed to be comparatively stiff. Therefore, the directional force (actio = reactio) of (the respective protruding part of) the support ring that pushes the respective annular part of the connecting member radially outwards will usually not widen any parts of the pipe connecting arrangement in a problematic manner / to a problematic extent. Again, it should be mentioned that an axial movement / axial force that is exerted when establishing the tight connection between the tube end in the connecting member will usually result in an inwardly directed radial force that is exerted onto the tube via the support ring, when using this design. The respective protruding part of the support ring may or may not be tapered (in case it is tapered, the tapering angle may or may not be adapted to the tapering angle of the receiving recess). A tapering of the protruding part (surface facing the adjacent surface of the receiving recess) of the support ring may result in a particularly profound radially inwardly directed clamping force, a lower probability of any surface deformations of the receiving recess, and usually a higher possible number of attachment-disconnection-cycles of the pipe connection arrangement is possible. A non-tapered protruding part of the support ring, however, may be advantageous in that a smaller force has to be applied for effectuating the connection of the tube end in the connection member and / or a smaller distance for establishing the connection has to be used (number of turns of the union nut or the like).

[0025] On the axially opposing side of the support ring, the support ring may show a tapered surface (as well). As a tapering angle, in particular a range between 40°, 50°, 60°, 70°, 80°, 85° or 90° (lower limit) and 90°, 95°, 100°, 110° 120°, 130° and 140° (upper limit) might be considered. This tapered surface may be accompanied by a similarly tapered surface that is provided at the tensioning device (union nut) at a corresponding position. In combination, this pair of tapered surfaces may translate an axial movement of the various parts of the pipe connection arrangement into a radially inwardly directed force towards the tube, thus clamping the tube in position in this section as well. Hence, another clamping point is provided. Another possible advantageous effect of this design is that the tapered surfaces will result in a radially inwardly directed deformation of the support ring (clamping state of the support ring) in this section of the support ring. This, however, may bring the elastically deformable member out of contact with (one of) the corresponding surface of the pipe connection arrangement, meaning that the support ring and the tensioning device will become (essentially) independent devices. This is usually advantageous for a reopening of the connection (for example to inspect whether the support ring fits tightly in the receiving recess of the connecting member). Even if the deformation only leads to a partial out-of-contact position, the forces occurring between the support ring and the tensioning device will usually be significantly lower than initially. The same may apply to deformations of the support ring that are induced by other design features, in particular by other tapered surfaces.

[0026] Another possible embodiment of the pipe connecting arrangement can be achieved if the reshaped tube end comprises a mounting collar. Preferably, the mounting collar neighbours the truncated cone like shaped region of the tube end (usually away from the tube opening). The combination of the truncated cone like shaped region and the mounting collar may show a somewhat acorn like appearance. The mounting collar may engage with a part of a force effectuating device (tensioning device; union nut; see below) to establish the connection of the tube end in the connecting member. This way, the axial force that may be exerted by the respective force effectuating device may be transmitted to the tube in an easy and effective way (directly or indirectly; directly usually implies a direct contact between a respective surface of the force effectuating device and a respective surface of the mounting collar; indirectly usually implies that there is some part in between that lies between a respective surface of the force effectuating device and a respective surface of the mounting collar, for example, this part may be a (part of) a support ring). Therefore, a sufficient pushing force of the tube end relative to the connecting member, and hence of the sealing surface of the truncated cone-like shaped tube end against the sealing surface of the truncated cone like shaped receiving recess of the connecting member may be realised. It is to be noted that various angles may be used for the mounting collar. While the surface of the mounting collar may be perpendicular / normal to the axial direction of the tube end / connecting member (being equivalent to an opening angle of 180°), it may enclose an angle (being different from 180°), and in particular it may show a truncated cone like shape as well (with a third, potentially different angle y). In particular, this mounting collar angle y, may lie between 80°, 90°, 100°, 110°, 120°, 130°, 140° and 145° (lower limit) and 150°, 155°, 160°, 165°, 170°, 175° and 180° (upper limit). Using an angle that is different from 180°, the tube can be held particularly tightly in place, since some radially inward directed forces may be generated, so that in turn a particularly high resilience against vibrations may be realised (in particular, this way a second clamping point / a second device that generates a radially inwardly directed force may be easily provided). In this context it is to be noted that a relatively large tapering angle of the mounting collar is usually advantageous to achieve high connection forces between the connecting member and the tube end (without too excessive radially inwardly directed clamping forces that might deform the tube), while it is usually disadvantageous with respect to material weakening due to (usually) significant cold deformation of respective parts of the reshaped end of the tube. Advantageously, a good compromise should be chosen. Preferably, the design of the pipe connecting arrangement should be chosen in a way that the force that is applied by a tensioning device (if present) to the tube end should preferably be directed to less-deformed parts of the tube end, like particularly a straight / flat part of the mounting collar (in particular somewhat displaced from the bends limiting the mounting collar). This is, because here a smaller deformation is usually present, and hence a lower material weakening due to cold deformation of the respective section occured. This does not rule out the possibility that a certain force is applied to relatively strongly bent sections / weakened sections. However, such forces should not be too excessive, keeping in mind the material weakening of those sections. For completeness, it should be mentioned that in case a mounting collar and a support ring with an axial protrusion is used, it is possible that the axial protrusion of the support ring is designed and arranged in a way that it protrudes between a portion of the end section of the tube that is located in the vicinity of the mounting collar and pointing away from the opening end of the end portion of the tube (and being circumferentially placed around the respective tube section), and a portion of the receiving recess of the connecting device.

[0027] It is further suggested to design the pipe connecting arrangement in a way that it further comprises a tensioning device for pressing and / or holding the reshaped end portion of the tube in(to) the receiving recess of the connecting member. While essentially all types of tensioning devices that may be envisaged may be used, in particular a union nut may be used for this purpose. In other words, the tensioning device / union nut may work as a force effectuating device for first pressing the tube end of the tube into the connecting device and / or later holding the tube end of the tube and the connecting device tightly together. When using a union nut, the union nut will typically show a hexagonal outer shape, so that a standard wrench can be used for turning the union nut. Furthermore, on the inside of the union nut, an inner thread may be provided to effectuate an axial force by turning the union nut. In particular, a high axial force may be effectuated with comparatively little effort for the mechanic. Only for completeness, it should be mentioned that the connecting member should be provided with an outer, corresponding thread in this case. Another possible embodiment of the pipe connection arrangement can be realised if the at least a part of the at least one support ring is arranged between the mounting collar of the tube and a force effectuating surface of the tensioning device. Preferably, the support ring may be provided with a radially outward pointing bulge for this. This way, no direct (pushing) contact between the tensioning device (for example a union nut) and the tube end and the connecting member is necessarily established, but only an “indirect” contact via the support ring. Although at first sight this seems to complicate things, the design may be advantageous in a way that the connection becomes more resilient against bending of the connection member relative to the the tube end, which may result in a significantly increased resilience against vibrations. This is, because the support ring may be used to stabilise the tube by limiting its movement in an angular direction. Effectively, the bulge may be a ring-like protrusion that is arranged circumferentially around the support ring (usually limited to a certain axial extent thereof). Typically, the bulge and the remaining support ring form a single piece part. However, different designs are possible as well, like a separately produced bulge that is usually fixedly attached to the usually sleeve-like basic shape of the support ring. The side surfaces of the bulge usually define (part of) the limiting surfaces (as discussed further below). Using this design, a particularly simple preassembly of the pipe connecting arrangement prior to being tightly connected is possible. Further, when using such a bulge, an axial movement of the support ring may be advantageously limited, in particular to a position in the vicinity of the region of the tube end comprising the mounting collar. Even further, using the bulge, a distinct increase in the required mounting force of the tensioning device at a certain point (usually when the attachment movement has reached its optimum value) can be easily realised. By varying the thickness of the bulge (axial extent), it is easy to adapt the point where the mounting force increases to the optimum sealing position of the pipe connection arrangement. It is to be noted that one or two of the side surfaces of the bulge of the support sleeve may show a tapering angle 6, being different from 180° (where 180° is equivalent to the perpendicular arrangement with respect to the axial direction of the support sleeve). In particular, the tapering angle 6 may be chosen from the limits, as described with respect to the tapering angle y of a mounting collar as described above. Using a tapering angle 6 that is different from 180° may provide a clamping effect for the tube by creating a radially inwardly directed force onto the support sleeve and consequently on the tube below the support sleeve.

[0028] An advantageous design of the pipe connection arrangement can be realised, if the pipe connection arrangement is designed and arranged in a way that the tube end cone angle a is smaller than the receiving recess cone angle by at least 1 .5°, preferably by at least 2°, more preferably by at least 3°, even more preferably by at least 4° prior to fixation of the reshaped end portion of the tube within the receiving recess of the connecting device, at least in the region of the sealing surfaces. This may be understood as the situation prior to fixation of the reshaped end portion of the tube within the receiving recess of the connection device. I.e. it relates to the tube end cone angle a of the tube end as it leaves the reshaping machine, as well as to the “mint fresh" (not yet used) connecting member. Is to be noted that even other angles may be envisaged like 0.5°, 1 °, 2.5°, 3.5°, 4.5°, 5°, 5.5°, 6°, 7°, 8°, 9° or 10° (and even more) (lower limit). It is to be understood that when the connection of the tube and the connecting member is established, an at least partial deformation of one or both of the truncated cone like shaped sealing surfaces will have occurred (typically, the sealing surface of the truncated cone like shaped part of the tube end will show a larger extent of deformation). In other words, when the connection is established, a (another) partial deformation of the sealing surfaces (typically, the truncated cone like shaped part of the reshaped end portion will show a larger amount of deformation) will occur. This actually seems to be a very advantageous aspect of the presently proposed design: the insertion movement of the tube end seems to result in some grinding processes, so that the surfaces of the sealing surfaces are adapting to each other, resulting in a particularly snugly fit of the sealing surfaces, which in turn results in a particularly fluid-tight and diffusion-proof contact. When using certain parameters in first experiments, it even seems to be the case that some kind of an initial stage of friction welding may occur, again resulting in a particularly diffusion-proof contact. However, it seems that this does not result in a fully developed positive substance lock contact, at least not to an extent that it is problematic to disconnect the connection at a later point. However, those first experiments indicate that quite often no observable friction welding occurs, but only a very snugly, intimate surface contact. This seems to be particularly advantageous if the connection has to be (re-)opened (disconnected) and (re-)connected later on (possibly for several times). Here, detectable friction welding might alter the surfaces adversely, which might reduce the number of possible (re-)opening and a consequent (re-)attachment cycles of the tube end in the connection member. It is to be noted that due to the proposed design, the contact between the sealing surfaces does not occur at the very same time during the connection process. Indeed, first contact will occur essentially at the tip of the tube end. When continuing the connection process, the resulting deformation process will result in an increasing contacting area between the sealing surfaces of the tube end and of the connecting member.

[0029] It is to be stressed that after establishing the fixation of the reshaped end portion of the tube within the recess of the connecting member, the cone angles of the tube end (tube end cone angle a) and of the receiving recess of the connecting member (receiving recess cone angle ft) will (essentially) show the same angle at positions where a contact of the two sealing surfaces has been established. I.e., in the contact region, the tube end cone angle a is essentially the same as the receiving recess cone angle , when the connection has been established. This final equivalency of the cone angles a, usually (but not necessarily) results mainly from a deformation of the tube end cone angle a. For efficiency reasons, it is typically preferred that the size of the sealing surfaces, where a connection is established, shows a relatively large percentage of the (initial) size of the sealing surfaces (size of the axial extent of the tube end cone angle and / or axial extent of the receiving recess cone angle) prior to establishing the connection (“raw state”). Just to name some numbers: the percentage may be in the order of at least 10%, 15%, 20%, 25%, 30%, 33%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 66%, 70%, 75%, 80% or 85%. As an upper limit, 25%, 30%, 33%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 66%, 70%, 75%, 80%, 85%, 90%, 95% or 100% may be realised. This may relate to the axial extent of the truncated cone like shape of the tube end and / or of the axial extent of the truncated cone like shaped part of the receiving recess (if the sizes are different, usually the smaller one is the relevant one). It is to be noted that the axial extents of the truncated cone like shaped end portion and of the truncated cone like shaped receiving recess of the connecting member may be the same, but may be different as well. As already mentioned, in particular for thick-walled tubes, the respective numbers may be somewhat on the lower side, while for thin-walled tubes, the respective numbers may be somewhat on the higher side.

[0030] It is further suggested that the difference between the tube end cone angle a and the receiving recess cone angle is not larger than 10°, preferably 7.5°, more preferably 5°, even more preferably 3.5°, at least in the region of the sealing surfaces. It is to be noted that different upper limits may be realised as well, like 30°, 25°, 20°, 15°, 12°, 9°, 7°, 6° or 4°. It is to be noted that too large deformations in the course of establishing the connection may be counterproductive with respect to sealing issues and also with respect to early material fatigue that may be induced during the connection process and / or the prior deformation process for reshaping the reshaped tube end. Further, the movement that is required to effectuate the assembly of the pipe connection arrangement (for example the number of turns of the union nut) will not become too excessive, thus speeding up the assembly process.

[0031] First experiments have shown that is also advantageous if the pipe connecting arrangement is realised in a way that the size of the tube end cone angle a and / or of the receiving recess cone angle lies between -15° and 15°, preferably between -10° and 10°, even more preferably between -5° and 5°, yet more preferred between -3° and 3° around a standard cone angle of pipe connection arrangements with truncated cone shapes, at least in the region of the sealing surfaces, wherein the standard cone angle is preferably taken from the group of cone angles, comprising 24°, 40° and 60°. It is to be noted that combinations of the lower and the upper limits of different intervals, as suggested, are deemed to be explicitly disclosed as well, so that a range between -15° and 5° is to be considered as being explicitly disclosed as well. Furthermore, even different lower limiting angles, like -20°, -7.5°, -2° and -1 ° and / or upper limits, like 1 °, 2°, 7.5° and 20° may be used as well (limits possibly in combination with the earlier mentioned ranges, as well). Yet further, it is possible to combine upper and lower range limits (possibly of different ranges) from different standard cone angles. First experiments have shown that the aforementioned ranges seem to result in particularly good connections, showing a very high diffusion resistance / leakage resistance. It is to be noted that pipe connecting arrangements that are using truncated cone like structures for effectuating a leakage-proof connection and that are already available on the market do usually show certain standard values of angles, so as to be interoperable with parts from competitors. Therefore, some standard values attained widespread use, like in particular cone angles of 24°, 40° and 60° value. However, other standard values may also be envisaged (including, but not limited to, other standard values that might evolve in the future).

[0032] In general, it should be mentioned that the cone angles are measured from one flank to the other (full-angle). Therefore, when considering the angle between one flank and the axial direction (centreline, central axis) of the tube and / or of the connecting member, half of the size of the disclosed numbers have to be considered (half-angle).

[0033] Further, it is possible to design the pipe connection arrangement in a way that the ring-like end surface of the end opening of the tube is essentially out of contact with the connecting member. This way any head-to-head contact can be avoided, which may result in a “getting stuck” -effect (movement blocking effect) when pushing the sealing surfaces together. Such a “getting stuck” - effect might lead to a reduced / insufficient size of the contact area between the sealing surfaces of the connecting member and of the tube end, which in turn might result in leakage / diffusion problems. Avoiding such problems is certainly advantageous. Furthermore, another advantage of this design is that usually an interoperability with parts that are already available on the market may be realised. This obviously enhances the marketability of the presently proposed design. In other words, (metallic) sealing surfaces (or possibly all areas where a sealing effect is realised) are (essentially) limited to the sealing surfaces that are provided by the tapered sections (possibly the “straight tapered sections”) that are provided by the truncated cone shaped end portion of the tube and / or the truncated cone like shaped receiving recess of the connecting member. As mentioned in the present disclosure, these sealing surfaces may be reused at least several times. This is contrary to dented surfaces / sharp surfaces that are deformed and / or get stuck, for example by a metal welding. Those may typically be used only once, or at least only for a very limited number of connection / disconnection cycles. It is further to be noted that the limitation of sealing surfaces to the tapered sections (possibly the “straight tapered sections”) may also imply that a single material / material composition is used for sealing purposes (or at least the major part of the overall sealing effect). In other words, additional sealing members like O-rings, metallic sealing rings or the like are not necessary to provide the sealing effect (the major fraction of the sealing effect). This is particularly advantageous for certain gases, like helium or hydrogen which are highly diffusive. Only for completeness it should be noted that the material / material compositions may be different for the sealing surface of the tapered part of the tube and the sealing surface of the receiving recess of the connector (although they might be advantageously essentially the same).

[0034] Even further it is suggested to design the pipe connection arrangement in a way that the contact areas and / or the tapering angles of the tube end and / or of the connecting member and / or of the support ring are dimensioned, designed and arranged in a way that a rotational movement between the connecting device and the tube is reduced, preferably hindered, when the tube is being attached to the connecting device, in particular when actuating the tensioning device, even more particular when turning the union nut. This may be realised in particular by sufficiently high frictional forces between the support ring (if present) and the connecting member, while the frictional forces between the support ring and the tube end, in particular the mounting collar, are reduced. In particular, a suitable choice of the various tapering angles will enable a person skilled in the art to achieve that goal, where the choice of the exact angles and / or sizes of contact areas is obvious to the person skilled in the art.

[0035] Even further, it is suggested to design the pipe connection arrangement in a way that at least the contacting surfaces of the tube and / or of the connecting member and / or of the support ring, preferably at least parts of the tube and / or of the connecting member and / or of the support ring, comprise a material taken from the group that comprises metal, copper, a copper alloy, iron, an iron alloy, steel, hardened steel, stainless steel and aluminium. When talking about stainless steel, in particular V2A and V4A steel may be considered. Using such materials, a particularly diffusion proof and leakage proof arrangement can be realised. Furthermore, the resulting pipe connection arrangement may sustain high pressures, which may be essential for certain applications. Preferably, (at least parts of the) contact surfaces are unstructured, i.e. they do not show any grooves, webs or the like. While it is possible that (at least parts of the) contact surfaces are polished or somehow finished, it is usually sufficient if surfaces are present that result from standard machining operations. Even further, the majority of the sealing surfaces, in particular (essentially) all of the sealing surfaces, might comprise (or essentially consist) of the aforementioned materials.

[0036] Yet further, the pipe connection arrangement may be realised in a way that at least a limiting surface is provided between the connecting member, the support ring and / or the tensioning device, wherein the at least one limiting surface of the pipe connection arrangement is dimensioned, designed and arranged in a way to hinder an axial movement of the tube end of the connecting member relative to each other past a certain point and / or to create a significant increase in the required fixation force past a certain point, in particular for providing a tactile feedback for a user of the pipe connection arrangement when connecting the tube end to the connecting member. Such a design is advantageous over a lot of designs that are known in the prior art. So far it is quite often necessary for the mechanic to attach a tensioning device in a hand-tight way and then to continue the tensioning process by a certain amount. As an example, the mechanic may attach a union nut using his fingers in a hand-tight way. Then he has to turn the union nut for a specified turning angle, like for 500° turning angle (approximately one and a half turns) or for another two full turns (as an example) using a wrench. This approach seems to be suitable, but in practice it is often hard to accomplish, since in case of adverse mounting positions, the mechanic my turn the union nut only by a hard to specify angle each time he repositions the wrench. Therefore, angle size estimation errors / counting errors / overall turning angle errors are hard to avoid, resulting in a significant number of faulty connections by experience (either overtightened or too loose). Further, in case the connecting member and the receiving recess are not well aligned, a relatively high connection force has usually to be applied to reach the “hand tight attachment” position. This is hard to detect, which in turn increases the likelihood of faulty connections. Using the presently proposed design, however, a mechanic with reasonable skills will just turn the union nut using a wrench (for example) until he realises a steep and significant increase in the required torque (fixation force) (change of slope of the torque; change of torque over change of position length unit, in particular change of angle). Then, the mechanic has a tactile feedback that he has to stop further tightening of the tensioning device. It is obvious that this results in a very intuitive operation.

[0037] Just give some numbers for the rapidly increasing required fixation force (in particular torque): the required fixation force may increase by a factor of at least 1 .5, 2, 2.5, 3, 3.5, 4 or even 5 within a short distance (in particular within an angle of up to 2.5°, 5°, 7.5°, 10°, 12.5°, 15°, 20°, 25°, 30°, 35°, 40° or 45°). Additionally or alternatively, the slope of the (change of the required fixation force) versus (the required distance) may change by a factor of at least 1 .5, 2, 2.5, 3, 3.5, 4 or even 5, in particular around the “certain point”. In case of a torque, this may be essentially equivalent to the change in torque over the turning distance, i.e. . Just to give an example from a measurement from a test setup using a 12 mm tube (outer diameter of the tube): the measured required fixation force (torque) changes from 8^ to 22 ^.

[0038] While the support ring and the tensioning device may be provided as separate parts for being assembled separately at the assembly side, it is preferred if the tensioning device and the support ring are preassembled to each other in a reversibly releasable way using an elastically deformable member to form the preassembled tensioning arrangement. The tensioning device may comprise a positive form locking means for connection with the corresponding connection member in a positive form locking way. The extent of the elastically deformable member in a radial direction is smaller than the extent of the positive form locking means of the tensioning device in a radial direction.

[0039] For holding the tensioning device and the support ring in their preassembled state, presently a reversibly releasable fixation using elastically deformable members is suggested. Such elastically deformable members have the advantage that they are quite easy to produce. Another advantage is that even if they are exposed to some unexpected forces during transport and storage (mechanical shock, for example), they usually still remain in a usable (holding) state (which might not be the case with predetermined breaking points). Even more, since the fixation is performed in a reversibly releasable way, the parts may be reattached (or at least readjusted) again to a preassembled state.

[0040] The elastically deformable member may be applied as some kind of a surface coating on (typically) a metal or (hard) plastics surface or as a separate part that is held in place. Typically, the (major) action of holding the support ring and the tensioning device in the preassembled place comes from the exertion of a friction between the two parts by means of the elastically deformable member (the elastically deformable member acting as a friction exerting member; it is to be noted that this usually requires a deformability; as a side note: the (main) elastically deformable member, effectuating the major share of the deformability, may be different from the (main) friction exerting member, effectuating the major share of the frictional force; a spring-loaded break pad is an example for this). Additionally or alternatively, positive form locking techniques (for example an elastic O-ring that is arranged in a circumferential groove) and / or frictional fixation and / or positive substance locking fixation may be used, even in combination. It is to be noted that the positive form locking technique in the present sense is to be performed in a reversibly releasable way. This can be easily done using elastically deformable members for performing this reversible releasable fixation. More particularly, an elastically deformable O-ring that is placed between two adjacent grooves that are provided in the tensioning device and the support ring, respectively, realises a combination of a reversibly releasable form locking technique and a frictional fixation. In case a locking varnish is additionally applied, a positive substance locking technique is used “on top”. It is to be noted that in the present example an O-ring and a locking varnish are only used as exemplary examples.

[0041] Usually, however, the (at least one) elastically deformable member, the tensioning device and / or the support ring (and possibly additional parts) are designed and arranged in a way that the elastically deformable member shows (essentially) only a grinding / frictional contact on at least one side (and hence no positive form lock engagement and / or no positive substance connection). Additionally or alternatively, this may be interpreted in a way that the elastically deformable member, the tensioning device and / or the support ring (and possibly additional parts) are designed and arranged in a way that the elastically deformable member is in contact with a smooth surface on at least one side. This smooth surface may be limited in size in a way that it is smooth within an appropriate range / a distinct and / or predefined range that corresponds to typical displacements of the various parts of the preassembled tensioning arrangement when it is connected to a corresponding part to complete a pipe connecting arrangement. In other words, it may be neighbouring an appropriately dimensioned smooth surface section of a neighbouring surface.

[0042] Typically, a single elastically deformable member is sufficient. However, it is also possible to use two or a plurality of elastically deformable members. Further, the forces that are generated by the elastically deformable member that hinder a relative movement of the support ring and the tensioning device are usually sufficiently low, so that when effectuating a connection of respective parts of the pipe connecting arrangement during assembly, a (then necessary) relative movement of the support ring and of the tensioning device is relatively easily to perform (at least for a certain axial movement). As already discussed, it is advantageous if such an axial movement will be hindered or stopped when reaching a certain (relative) position, however.

[0043] Using a preassembled tensioning arrangement, the combination of a support ring and of a tensioning device may be arranged onto the tube in a single assembly step, facilitating the manufacturing and reducing possible assembly errors.

[0044] It is proposed to design and arrange the preassembled tensioning arrangement in a way that the extent of the elastically deformable member in a radial direction is smaller than the extent of the positive form locking means of the tensioning device in a radial direction. Using this retrospectively surprisingly simple solution, is easily and cheaply possible to avoid any adverse alterations or damages of the surface of the elastically deformable member by parts of the tensioning device (in particular by the positive form locking means) when preassembling the support ring and the tensioning device together. In case a union nut is used as a tensioning device, this usually means that the union nut is designed to comprise (at least) two essentially cylindrical inner surfaces with different radii. In particular, a first radius may be used in a first section (extending in the axial direction) of the union nut, in which the inner thread is provided, while a second radius may be used in a second section (extending in the axial direction) of the union nut, where the elastically deformable member is applied and / or where the elastically deformable member acts upon to effectuate a reversibly releasable fixation, holding the respective parts in the preassembled position of the preassembled tensioning arrangement.

[0045] Additionally or alternatively, it is suggested, to design a pipe connecting arrangement, in particular a pipe connecting arrangement for connecting thinwalled metal tubes, in a way that the pipe connecting arrangement comprises: a tube with a reshaped end portion, where the reshaped end portion shows a truncated cone like shape with a decreasing diameter towards the connection end (opening end of the tube), and a tube end cone angle a, forming an outer circumferential sealing surface, a connecting member with a receiving recess with a truncated cone like shape with an increasing diameter towards the connection end (opening end of the connecting member), and a receiving recess cone angle , forming an inner circumferential sealing surface, a tensioning device, preferably a union nut, for pressing and / or holding the reshaped end portion of the tube in(to) the receiving recess of the connecting member, wherein at least a limiting surface is provided between the connecting member and the tensioning device, and wherein the at least one limiting surface is designed and arranged in a way to hinder an axial movement of the tube end of the connecting member relative to each other past a certain point and / or to create a significant increase in the required fixation force past a certain point, in particular for providing a tactile feedback for a user of the pipe connection arrangement when connecting the tube end to the connecting member.

[0046] A tensioning device is provided for pressing and / or holding the reshaped end portion of the tube in(to) the receiving recess of the connecting member. Therefore, it may be considered (and / or addressed) as a force effectuating device. While essentially all types of tensioning devices that may be envisaged may be used, in particular a union nut may be used for this purpose. Such a union nut will typically show a hexagonal outer shape, so that a standard wrench can be used for turning the union nut. Furthermore, on the inside of the union nut, an inner thread may be provided to effectuate an axial force by turning the union nut. In particular, a high axial force may be effectuated with comparatively little effort for the mechanic. Only for completeness, it should be mentioned that the connecting member should be provided with an outer, corresponding thread in this case. According to the present suggestion, at least one limiting surface is provided between the connecting member and the tensioning device, wherein the limiting surface is designed and arranged in a way to hinder an axial movement of the tube end of the connecting member relative to each other past a certain point and / or to create a significant increase in the required fixation force past a certain point, in particular for providing a tactile feedback for a user of the pipe connection arrangement when connecting the tube end to the connecting member.

[0047] The limiting surface is usually defined by a mechanical contact between two parts of the pipe connection arrangement, in particular between two parts of the pipe connection arrangement that perform, at least in part, an axial movement when the pipe connection arrangement is brought into a leakage proof position, when starting from an initial preassembled (or partially assembled and / or unassembled) state. For this, various realisations may be conceived, for example a contact between a (surface) part of a tensioning device (for example a union nut), a connecting member and / or a surface part of a tube end (like a mountain collar, or the like), either in a direct or in an indirect way (the indirect way using additional pieces in between, as it is described in other parts of the present disclosure).

[0048] In particular, it is proposed that the pipe connection arrangement comprises at least a support ring that is circumferentially arranged around a part of the tube. Using such a support ring, no direct (pushing) contact between the tensioning device (for example union nut) and the tube end and the connecting member has to be necessarily established, but only (or in part) an ’’indirect” contact via the support ring and / or respective surface parts of said parts. It is to be noted that a combination is possible as well, like a partial force transmittal in a direct way and a partial force transmittal in an indirect way. Although providing a support ring seems to complicate things at first sight, the design may be advantageous in a way that the connection becomes more resilient against bending of the connection / the tube end, which may result in a significantly increased resilience against vibrations. This is, because the support ring may be used to stabilise the tube by limiting its movement in an angular direction relative to the connecting member (in particular by “clamping” part of the tube, in particular with respect to angular movements).

[0049] More details of this additional or alternative design are described at different sections of the present disclosure.

[0050] Furthermore, a method of connecting the tube and the connecting member of the pipe connection arrangement according to the present disclosure is suggested, wherein by pushing the tube end of the tube and the receiving recess of the connecting member together in an axial direction, at least one support ring generates a radially inwardly directed force that acts on a part of the tube, preferably clamping the tube in a position relative to the connecting member. Therefore, when the operator of the pipe connection arrangement mounts the various pieces of the pipe connection arrangement together, so as to establish a fluid tight coupling, he automatically establishes a firm clamping fixation of the tube with respect to the connecting member at the same time. Therefore, this will result in a particularly abrasion proof coupling as well, without any additional mounting steps. This is of course very advantageous.

[0051] Additionally or alternatively, a method of connecting the tube and the connecting member of the pipe connection arrangement according to the present disclosure is suggested, wherein the user of the pipe connection arrangement performs a tightening operation by operating the tensioning device, until he detects a significant increase in the required fixation force past a certain point. This triggers the operator to stop further tightening of the tensioning device. Indeed, this a signal to him that the pipe connection arrangement is completed according to specification. When realising such a method, similar features and advantages as already described can be realised, at least in analogy. Furthermore, the method can be modified in the aforementioned sense, resulting in similar or identical features and advantages, as already mentioned, at least in analogy.

[0052] When realising at least one of the proposed methods, similar features and advantages as already described can be realised, at least in analogy. Furthermore, the method can be modified in the aforementioned sense, resulting in similar or identical features and advantages, as already mentioned, at least in analogy.

[0053] Further advantages, features, and objects of the invention will be apparent from the following detailed description of the invention in conjunction with the associated drawings, wherein the drawings show:

[0054] Fig. 1 : a possible embodiment of a pipe connecting arrangement according to the present disclosure in a cut open, schematic view;

[0055] Fig. 2: an enlarged cutaway view of parts of Fig. 1 ;

[0056] Fig. 3: a graph showing the torque in dependence of the turning angle of the union nut of the embodiment of a pipe connecting arrangement according to Fig. 1 ;

[0057] Fig. 4: a second embodiment of a pipe connecting arrangement according to the present disclosure in a schematic cross-sectional view;

[0058] Fig. 5: a third embodiment of a pipe connecting arrangement according to the present disclosure in a schematic cross-sectional view;

[0059] Fig. 6: a schematic cross section through a preassembled tensioning arrangement that may be used for the pipe connection arrangement according to Figs. 1 and 2.

[0060] Fig. 1 shows a possible preferred embodiment of a pipe connecting arrangement 1 in a partially cut open, schematic perspective view. The pipe connection arrangement 1 connects a connecting member 2 and a tube end 3 of a tube 4 together. It is to be noted that the situation in Fig. 1 does not show the fully connected position of the pipe connection arrangement 1 , as will be explained in more detail later on.

[0061] For establishing the connection of the pipe connection arrangement 1 , a preassembled subassembly 27 comprising a support ring 15 and a union nut 14 is used. The support ring 15 and the union nut 14 are movably attached together by means of a friction exerting O-ring 21 , if a certain axial force relative to each other is exceeded. This will be explained in more detail below with reference to Fig. 6.

[0062] Fig. 2 shows an enlarged, cutaway view of the support ring 15 area of Fig. 1 for better visibility. The following detailed description is advantageously read with reference to both Figs. 1 and 2.

[0063] Presently, the connecting member 2 is designed as a double-ended connecting member 2 that shows a connectivity end for connecting a tube end at both sides of the double-ended connecting member 2.

[0064] It is to be noted that the pipe connecting arrangement 1 may show a different design of the connecting member 2 as well, for example in case the connecting member 2 is attached to a machine (not shown), to supply the respective machine with gases or liquids (for example by soldering or by a threaded attachment). In that case, the connecting member 2 would be designed as a single ended connecting member 2 (i.e. only on one side of the connecting member 2 a connectivity end for connection with a tube end 3 would be provided).

[0065] Starting at the tube opening 5 of a tube 4, more particularly of the tube end 3 of tube 4, the tube 4 shows a truncated cone shaped portion 6 neighbouring the tube opening 5. As can be seen in Fig. 1 (and similarly in Fig. 4), the tapering angle of the truncated cone shaped portion 6 at the tube end 4 of tube 4 shows an angle a. In Fig. 1 , due to the view that is shown, only half of the angle a, i.e. is indicated in the Fig. (the angle lies between the central axis 7 of tube 3 and the flange of the truncated cone shaped region 6). This applies to the not yet fully connected state of the pipe connection arrangement 1 . In the region of the truncated cone shaped portion 6, the radius of the tube 4 increases, when going away from the tube opening 5. Presently, the tube opening 5 shows an inner radius that is essentially equivalent to the standard radius 9 of tube 4. However, a different radius could be used as well.

[0066] Going further along the axial length of tube 4 in the direction away from the tube opening 5, adjacent to the truncated cone shaped portion 6, a mounting collar 8 is present. In the region of the mounting collar 8, the radius of the tube 4 decreases again to the size of the standard radius 9 (undeformed radius) of the tube 4.

[0067] As indicated in Figs. 1 (similarly Fig. 4), the tapering angle of the mounting collar 8 of the tube 4 in the proximity the tube end 3 has an angle of y (and hence of as measured with respect to the central axis 7 of the tube 4).

[0068] Following the mounting collar 8 when going away from tube opening 5, the tube 4 finally shows the typical cylindrical shape of tubes (where the standard radius 9 is present). It is to be noted that the tube 4 can certainly be bent or the like. Furthermore, tubes 4 are also of a finite length, so that at a certain distance another tube opening will be present (not shown).

[0069] Corresponding to the tube 4 with its central fluid conduit 10, the connecting member 2 also shows a fluid conduit 12 that presently falls in line with the fluid conduit 10 of tube 4. While in the presently shown embodiment the inner diameter of fluid conduit 12 of connecting member 2 varies somewhat in the axial direction, the diameter could be designed to be essentially constant as well.

[0070] In the presently shown embodiment, the connecting member 2 shows two tube connection sections 11 (only one, namely the one on the right side in Fig. 1 is presently used) that show a receiving recess 13 with a truncated cone shaped recess 13. The receiving recess 13 has a tapering angle (or with respect to the central axis 7).

[0071] In the presently shown embodiment, tapering angle a of truncated cone shaped portion 6 of tube 4 is a = 36°, while the tapering angle of the receiving recess 13 of connecting member is / ? = 40°. An essential point is that the two angles a, ft differ from each other. Presently, the difference is chosen to be 4°, with the tapering angle a of truncated cone shaped portion 6 of tube 4 being smaller than the tapering angle ft of the receiving recess 13 of connecting member 2.

[0072] Again: the indicated values of the angles a, ft are valid before the fluid tight connection between tube end 3 of tube 4 and connection recess 13 of connecting member 2 is established by firmly pressing the tube end 3 into the receiving recess 13. This is the situation of Fig. 1 , where only the very first contact between the tube end 3 and the receiving recess 13 has been established, and before any deformation of any of the parts due to the sealing pressure occurs (by sufficiently tightening the union nut 14). Please note that this is also visible in Figs. 1 and 2 by a small, presently wedge-shaped void that is visible between the outer surface of the truncated cone shaped portion 6 of tube end 3 (later sealing surface) and the inner circumferential surface 35 of receiving recess 13 of connecting member 2 (partially later sealing surface). When the connection between the tube end 3 and the connection member 2 is established by tightly pushing the tube end 3 into the receiving recess 13 (by means of union nut 14 via support ring 15, as explained in detail later on), (usually) the truncated cone shaped portion 6 of the tube end 3 will be deformed so that the respective opposing surfaces of truncated cone shaped portion 6 and receiving recess 13 will snugly fit together after some grinding contact and some deformation work. This grinding contact seems to lead to a corresponding surface finishing of the neighbouring surfaces. While when applying certain parameters possibly a very light, initial stage of friction welding connection may be observable, usually no observable friction welding occurs. This usually increases the number of possible (re-)opening and consequent (re-)attachment cycles of the tube end 3 in the connection member 2. Irrespective of the exact nature of the connection, first experiments have shown that the connection, when being established, is particularly leak-proof and particularly diffusion-proof, even for very diffusive gases like helium or hydrogen under high pressure.

[0073] It is to be noted that typically (as it is the case in the presently depicted embodiment) there is no so to say head-to-head contact / point-to-point contact / line-to-surface contact (or the like) between the ring-like end surface of truncated cone shaped portion 6 of tube end 3 and a corresponding contacting area of the inner surface / receiving surface 13 of connecting member 2. Such a contact of a sharp protrusion with (usually) a flat surface will usually lead to a pressure soldering effect. In turn, the respective sharp protrusion / contacting surface will be not-usable for sealing purposes again, once it has been opened (or at least the sealing effect will be significantly reduced).

[0074] As can further be seen in Figs. 1 and 2, the axial extent arof the truncated cone shaped portion 6 of tube end 3 of tube 4 is smaller than the axial extent b of the receiving recess 13 of connecting member 2. Therefore, a ring-like void 16 will be present between the circumferential outer surface of tube 4 (past the mounting collar 8) and the tapered surface of receiving recess 13 of connecting member 2. The use of this void 16 will be explained in the following.

[0075] A union nut 14 that comprises an inner thread 17 is placed around the tube 4. The union nut 14 is used as a tensioning device for pushing the tube end 3 into the receiving recess 13 by simply turning the union nut 14. To simplify the attachment, the union nut 14 shows a hexagonal shape for attachment of a wrench, as it is known in the art.

[0076] Corresponding to the union nut 14 with its inner thread 17, the outer surface of connecting member 2 is provided with an outer thread 18 with a corresponding design at a corresponding place, as it is obvious to a person skilled in the art. Furthermore, connecting member 2 comprises a section with a hexagonal outer shape, so that another wrench can be used to counter any torque that is introduced by turning the union nut 14; again, this is obvious for a person skilled in the art in the present field of technology.

[0077] The support ring 15 shows tapered pressure surfaces 19a, 19b, 19c for pressure contact with corresponding surfaces of the union nut 14, the mounting collar 8 of tube end 3, and also towards the inner surface 35 of receiving recess 13 of connecting member 2.

[0078] Thanks to the tapered pressure surfaces 19a, 19b, 19c, the support ring 15 will be pushed towards the circumferential outer surface of tube 4 in a direction that points radially inwards, thus holding the tube 4 firmly in place, particularly not allowing any angular movement of the connection member 2 relative to the tube end 3. Thanks to this feature, an early fatigue of the sealing connection can be advantageously avoided. Further thanks to the shapes of the various tapered pressure surfaces 19a, 19b, 19c, and in particular thanks to the pressure surfaces 19a, 19c being directed to the tapered surface 35 of receiving recess 13 and toward union nut 14 (where the connecting member 2 and the union nut 14 are usually designed quite sturdy) an outwardly pushing movement of any weak parts can be avoided, which in turn reduces the disposition for developing any leaks.

[0079] Even more, thanks to the tapered surface 35 of the receiving recess 13 and positioning of the support ring 15, an axial movement of the union nut 14 being screwed onto the connecting member 15 does result in a radially inward directed force that firmly clamps the tube end 3 into position.

[0080] It is to be noted that the tapered pressure surface 19a of the protruding part 24 of the support ring 15 that protrudes into the void 16 between the receiving recess 13 and the truncated cone shaped portion 6 of the tube end 3 of the tube 4 may be designed in a way to show no tapering angle. This is described in more detail further below with reference to Fig. 5.

[0081] As can be further seen in Figs. 1 and 2, the support ring 15 comprises an annular bulge 20. Together with the union nut 14 and the end surface of connecting member 2 around receiving recess 13, the annular bulge 20 functions as a mechanical stop for a connection process of the pipe connecting arrangement 1 . In particular, when a mechanic connects the parts of the pipe connecting arrangement 1 , he will feel the development of the required torque M for turning the union nut 14, as it is shown in Fig. 3.

[0082] Fig. 3 shows the required torque M on the ordinate (y-axis) against the turning angle <p along the abscissa (x-axis). Initially, the mechanic loosely turns the union nut 14 using his fingers (torque M essentially 0; not shown in Fig. 3). Once the very first contact of the various tapered pressure surfaces 19a, 19b, 19c of support ring 15 with corresponding surfaces of tube end 3, connecting member 2 and union nut 14 is established, and further initial contact between truncated cone shaped portion 6 of tube end 3 and receiving recess 13 of connecting member 2 is established (hand-tight tightening), the mechanic will start to use a wrench, since as of now (angle <pQ) a non-negligible torque M starts to be necessary. This is due to the now necessary deformation of tube end 3 when being pushed into the receiving recess 13 of connecting member 2. This results in a slow increase of the required torque M to be applied. Once the side surfaces 23 of bulge 20 contact their corresponding counterparts of union nut 14 and connecting member 2 (end surface around receiving recess 13) at turning angle <pl tthe necessary, required torque M will increase sharply. This can be easily felt by the mechanic. Indeed, this is the indication for him that the connection process is completed and he has to stop turning to avoid any overturning.

[0083] Avoiding any overturning of the connection particularly avoids any possible overpressure in the inwardly directed radial direction that acts on the sections of the tube 4 in the vicinity of the support ring 15. Such an overpressure in the inwardly directed radial direction may lead to a collapse of the tube’s wall or to significantly increased risk of breaks in the tube’s wall over time (something that should be avoided in the first place by using a support ring 15 at all).

[0084] To simplify the work for the mechanic, the union nut 14 and the support ring 15 are presently designed as a preassembled subunit 27 in the presently shown embodiment.

[0085] A possible embodiment of such a preassembled subunit 27 is shown in Fig. 6. In particular, Fig. 6 shows a schematic cross section of the preassembled subunit 27 comprising the union nut 14 and the support ring 15. An O-ring 21 (functioning as a force exerting member) is provided between the radially outer surface of the support ring 15 and the radially inner surface of the union nut 14, as visible in Figs. 1 , 2 and 6. The O-ring 21 effectuates a force fit connection between support ring 15 and union nut 14. This way, the support ring 15 and the union nut 14 may be moved relative to each other in an axial direction, if a certain axial force is exceeded. If no such force is present (like it is the case during shipment or storage of the prearranged tensioning arrangement 27) the two parts will remain in the current position. For completeness: it is certainly possible to provide a circular groove for partially receiving the 0-ring 21 in the support ring 15 and / or in the union nut 14. Presently, however, the groove 37 for the O-ring 21 is only provided in the support ring 15.

[0086] As can be seen, the diameter d of the union nut 14 in the section of the inner thread 17 (and further extending into a smooth surface section showing no threads; first inner dimension of the union nut in the radial direction) is distinctly larger as compared to the diameter d2of the section of the union nut 14 in which the O-ring 21 is located. This way, the preassembly of the union nut 14 and the support ring 15 can be effectuated without any grinding of the outer circumference of the O-ring 21 along the protruding peaks of the inner thread 17 (at least under realistic conditions). Such a grinding that is unavoidable with at least certain arrangements as they are known in the prior art usually causes an adverse alteration or even a damage of the surface of the O-ring 21 . This may result in later occurring leakage issues, or in that the two parts will not hold sufficiently firmly together any more.

[0087] The preassembled subassembly 27 is placed over an undeformed tube end of the tube 4 in a single assembly step. Hence, the tube end of the tube 4 will be reshaped into the reshaped tube end 3 that can be seen in Figs. 1 and 2.

[0088] It is to be noted that in the typical preassembled state of the preassembled subassembly 27, gaps 28 and 29 are present between the corresponding, neighbouring surfaces of the annular bulge 20 of the support ring 15 and of the union nut 14 (gap 28), as well as between the tapered pressure surface 19c of the support ring 15 and of the union nut 14 (gap 29). In particular, the gap 29 neighbouring the tapered pressure surface 19c of the support ring 15 should be somewhat smaller as compared to the gap 28 neighbouring the bulge 20 of the support ring 15. This way, the tapered pressure surface 19c and the corresponding neighbouring tapered surface of the union nut 14 can effectuate a radially inwardly directed force onto the tube 4 to be inserted (to clamp the tube 4 in position) when tightening the final assembly. However, at a certain point a further radially inwardly directed movement near the tapered pressure surface 19c will be hindered. This is the case when the gap 28 near the annular bulge 20 is closed. Thanks to this design, excessive clamping forces may be avoided that may result in a collapsing tube wall of the tube 4. A person skilled in the art may easily design the relative sizes of the two gaps 28, 29.

[0089] Only for completeness it should be mentioned that the presently proposed preassembled tensioning arrangement is not limited to the designs of the various parts according to Fig. 6. in particular, various designs of support ring 15 may be chosen. In particular, a support ring as shown in Fig. 5 may be used analogously.

[0090] In Fig. 4 another possible embodiment of a pipe connection arrangement 30 is shown in a schematic cross section.

[0091] The design is quite similar to the design of the pipe connection arrangement 1 according to Figs. 1 and 2. Therefore, for similar parts identical reference numbers are used, even if the respective parts are not perfectly identical, but only similar with respect to design and / or function.

[0092] As can be seen from Fig. 4, the axial extent a4of the truncated cone shaped portion 6 of tube end 3 is larger than the axial extent h4of the cone shape part of receiving recess 13 of connecting member 32. The support ring 33 is therefore appropriately adapted to fit into the corresponding void between connection member 32, union nut 34 and radially outer area of tube end 31 .

[0093] It is to be noted that no bulge of the support ring 33, similar to the bulge 20 of support ring 15 according to the embodiment of Figs. 1 and 2 is present. Therefore, the force increase is a little bit harder to be observed by the mechanic. Nevertheless, it can still be felt sufficiently well.

[0094] Fig. 5 shows another possible, third embodiment of a pipe connection arrangement 36 in a schematic cross-sectional view. The presently shown third embodiment of the pressure connection arrangement 36 is highly similar to the first embodiment of a pipe connection arrangement 1 , as shown in Figs. 1 and 2. Rather, the essentially only relevant difference of the presently depicted embodiments of pipe connection arrangements 1 , 36 is the design of the support rings 15 (first embodiment) and 26 (presently shown, third embodiment). Namely, instead of a tapered contacting surface 19 a, presently a non-tapered (i.e. cylindrically designed) contacting surface 25 is foreseen for the protruding part 24 of the support ring 26 that is intended to contact the receiving recess 13 of connection member 2.

[0095] The usefulness of this design is somewhat surprising. A big advantage is that usually the torque that is required to turn the union nut 14 for effectuating the connection of the tube end 3 and the receiving recess 13 of the connection member 2 is noticeably lower. Therefore, the connection is easier to realise. Somewhat surprisingly, due to the usually chosen material for the support rings 15, 26, 33 (stiff resin material, soft metallic material or the like), the support ring 15, 26, 33 is typically deformable to a certain extent. Therefore, the protruding part 24 of the support ring 26 will deform when being pressed against the receiving recess 13 of the connection member 2. First experiments indicate that - although a minuscule visible alteration of the surface of the receiving recess 13 of the connection member 2 occurs - no noticeable deformation of the receiving recess 13 of the connection member 2 occurs. Even when scratching along the surface of the receiving recess 13 with a fingernail, no deformations can be felt.

[0096] Therefore, even this design can be used for (re-)opening and (re-)attachment of the tube 4 and the connection member 2 of the pipe connecting arrangement for several times.

[0097] Irrespective of the adapted design of support ring 33, there is still an effect of pushing the support ring 33 radially inwards so as to hold the tube end 31 tightly into place, even if vibrations do occur.

[0098] It is to be noted that a single one or a plurality of the features of one or both of the presently disclosed detailed embodiments may be used in combination with the generic description of the present disclosure.

[0099] Further disclosure can be found in the two applications, filed by the same applicant at the same day under the applicants reference signs DAN2302DEWO (PA18042W001 , claiming priority of DE 10 2023 125 655.6) and DAN2305DEWO (PA18073W001 , claiming priority of DE 10 2023 125 657.2) at the same filing office. The disclosure of these applications is meant to be fully contained in the present application.

Claims

C l a i m s1. Pipe connecting arrangement (1 , 30, 36), in particular for connecting thin-walled metal tubes (4), comprising: a tube (4) with a reshaped end portion (3, 31 ), where the reshaped end portion (3, 31 ) shows a truncated cone like shape (6) with a decreasing diameter (9) towards the connection end, and a tube end cone angle (a), forming an outer circumferential sealing surface, a connecting member (2) with a receiving recess (13) with a truncated cone like shape with an increasing diameter towards the connection end, and a receiving recess cone angle ( / ?), forming an inner circumferential sealing surface, a support ring (15, 26) that is arranged circumferentially around at least a part of the tube end (3, 31 ) of the tube (4), characterised in that at least a part (24) of the support ring (15, 26) rests against a part of the connecting member (2), in particular against a part of the receiving recess (13) of the connecting member (2).

2. Pipe connection arrangement (1 , 30) according to claim 1 , characterised in that the extent in the axial direction of the truncated cone like shaped section (a1;a4) of the end portion (3, 31 ) of the tube (4) is smaller than the extent in the axial direction of the truncated cone like shaped section (bi, b4) of the receiving recess (13) connecting member.

3. Pipe connection arrangement (1 , 30) according to any of the preceding claims, in particular according to claim 2, characterised in that the support ring (15, 26) protrudes into a void (16) that is formed between a portion of the end section (3, 31 ) of the tube (4) and a portion of the receiving recess (13) of the connecting device (2), in particular characterised in that the support ring (15, 26) comprises an axial protrusion (24) that protrudes into said void (16).

4. Pipe connection arrangement (1 , 30, 36) according to any of the preceding claims, characterised in that the reshaped tube end (3) further comprises a mounting collar (8), preferably neighbouring the truncated cone like shaped region of the tube end (3).

5. Pipe connection arrangement (1 , 30, 36) according to any of the preceding claims, characterised by a tensioning device, preferably a union nut (14), for pressing and / or holding the reshaped end portion (3, 31 ) of the tube (4) in(to) the receiving recess (13) of the connection member (2).

6. Pipe connection arrangement (1 , 30, 36) according to any of the preceding claims, in particular according to claim 5, characterised in that the at least a part of at least one support ring (15, 26, 33) is arranged between the mounting collar (8) of the tube (4) and a force effectuating surface (19c) of the tensioning device (14).

7. Pipe connection arrangement (1 , 30, 36) according to any of the preceding claims, characterised in that the tube end cone angle a is smaller than the receiving recess cone angle by at least 1.5°, preferably by at least 2°, more preferably by at least 3°, even more preferably by at least 4° prior to fixation of the reshaped end portion (3, 31 ) of the tube (4) within the receiving recess (13) of the connecting device (2), at least in the region of the sealing surfaces.

8. Pipe connecting arrangement (1 , 30, 36) according to any of the preceding claims, in particular according to claim 7, characterised in that the difference between the tube end cone angle a and the receiving recess cone angle is not larger than 10°, preferably 7.5°, more preferably 5°, if more preferably 3.5°, at least in the region of the sealing surfaces.

9. Pipe connection arrangement (1 , 30, 36) according to any preceding claim, in particular according to any of claims 5 to 8, characterised in that at least a limiting surface (23) is provided between the connecting member (2), the support ring (15, 26, 33) and / or the tensioning device (14), and wherein the at least one limiting surface (23) is designed and arranged in a way to hinder an axial movement of the tube end (3, 31 ) of the connecting member (2) relative to each other past a certain point and / or to create a significant increase in the required fixation force past a certain point, in particular for providing a tactile feedback for a user of the pipe connection arrangement (1 , 30, 36) when connecting the tube end (3, 31 ) to the connecting member (2).

10. Pipe connecting arrangement (1 , 30, 36), in particular for connecting thin-walled metal tubes (4), more particularly pipe connecting arrangement (1.30.36) according to any of the preceding claims, comprising: a tube (4) with a reshaped end portion (3, 31 ), where the reshaped end portion (3, 31 ) shows a truncated cone like shape (6) with a decreasing diameter (9) towards the connection end, and a tube end cone angle (a), forming an outer circumferential sealing surface, a connecting member (2) with a receiving recess (13) with a truncated cone like shape with an increasing diameter towards the connection end, and a receiving recess cone angle ( / ?), forming an inner circumferential sealing surface, a tensioning device, preferably a union nut (14), for pressing and / orholding the reshaped end portion (3, 31 ) of the tube (4) in(to) the receiving recess (13) of the connecting member (2), characterised by at least a limiting surface (23) that is provided between the connecting member (2) and the tensioning device (14), wherein the at least one limiting surface (23) is designed and arranged in a way to hinder an axial movement of the tube end (3) and of the connecting member (2) relative to each other past a certain point and / or to create a significant increase in the required fixation force past a certain point, in particular for providing a tactile feedback for a user of the pipe connection arrangement (1 , 30) when connecting the tube end (3, 31 ) to the connecting member (2).11 . Method of connecting the tube and the connecting member (2) of a pipe connection arrangement (1 , 30, 36) according to any of the preceding claims, characterised in that by pushing the tube end (3) of the tube (4) and the receiving recess (13) of the connecting member (2) together in an axial direction, at least one support ring (15, 26, 33) generates a radially inwardly directed force that acts on a part of the tube (4), preferably clamping the tube (4) in a position relative to the connecting member (2).

12. Method of connecting the tube and the connecting member (2) of a pipe connection arrangement (1 , 30, 36) according to any of claims 1 to 10, in particular method according to claim 11 , characterised in that the user of the pipe connection arrangement (1 , 30, 36) performs a tightening operation by operating the tensioning device (14), until he detects a significant increase in the required fixation force past a certain point.

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