Apparatus

Abstract

A retaining element 200 (e.g. spacer) for use in a conduit (e.g. cryogenic conduit) arrangement, the retaining element comprising: a main body portion 210 (e.g. a spacer or portion of a spacer), a fir

Description

Technical Field The present invention is concerned with spacers for use in conduits. Specifically, the present invention is concerned with conduits that may transport cryogenic substances with or without electrical current. The present invention may be advantageously used where a first conduit is located within an arrangement and it is not required for that conduit to be strongly held in position. The present invention may be advantageously used where both electrical current and cold fluids are to be transported in one or more conduits. The present invention may be advantageously used inside electrically powered aircraft. Modern systems in aircraft provide electrical conduits that may be assembled using o-rings, nuts and bolts or the like. These systems are widely prevalent and are suitable for the requirements of most modern aircraft. Conduits may undergo thermal expansion and or other movement during use. Modern systems provide stability via holding the conduits strongly in place. This can be effective however it may increase the stress on portions of the conduits. Furthermore, structural elements that hold the conduits in place may provide routes for thermal energy to reach the conduits which is counterproductive to maintaining substances in the conduits at low temperatures. There are aims for electrically powered aircraft to be commercially available in the near future. There are arrangements of such aircraft that provide improved emissions profile alongside being more sustainable than typical fuel powered aircraft. Such electrically powered aircraft may have electrical conduit arrangements that are interfaced in some way with cryogenic fluid conduit arrangements. There are improvements that can be made in the field of electrical conduits for electrically powered aircraft, whether partially or fully electrically powered aircraft. In particular, the present invention is highly advantageous in aircraft that transport cryogenic material or the like. The presently disclosed system may be highly advantageous in aerospace applications however may also be used in any conduit or transmission systems, such as in any vehicles, any machinery or the like. Summary of the Invention Aspects of the invention are set out in the accompanying claims. In accordance with some embodiments described herein, there is provided a retaining element for use in a conduit arrangement, the retaining element comprising: a main body portion; a first moveable portion; a second moveable portion arranged externally to the first moveable portion; and a moveable joining member arranged to connect the main body portion and a portion of at least one of the first moveable portion and the second moveable portion, wherein the moveable joining member is arranged to provide relative movement between at least two of: the main body portion; the first moveable portion; and, the second moveable portion wherein the moveable joining member is moveable along a first axis, wherein the second moveable portion is moveable along the first axis and a second axis, wherein the first axis and the second axis are different. The present disclosure is highly efficient as it provides greater reliability and improved robustness in designs for retaining elements. Furthermore, the present retaining element is straight forward to manufacture while providing a retaining element that allows for great control over the installation and performance when in situ. The present arrangement enables improved handling of movement of conduits during use and better resilience against low temperatures passing through conduits during use. The conduits with which the present retaining element may be used may be suitable for use with electrical current and / or fluids. In examples, the moveable joining member is contractably expandable along a first axis, wherein as the moveable joining member contracts or expands, relative movement is provided between at least two of: the main body portion; the first moveable portion; and, the second moveable portion. The movement of the moveable joining member allows great user control over the arrangement of the retaining element. Specifically, the arrangement disclosed provides high levels of control over the positioning and movement of the arrangement. This can be highly advantageous when the arrangement is employed in situ which may be in poorly accessible locations. Such poorly accessible locations include within conduits for electrical current and / or fluids. In examples, the first moveable portion has a first portion and the second moveable portion has a first portion, wherein the first portion of the first moveable portion and the first portion of the second moveable portion are arranged to abut as the moveable joining member moves along the first axis. In examples, the first axis may be axial and the second axis may be radial. The movement of the moveable joining member may control the relative movement of portions of the retaining element. The present arrangement may have portions that abut during movement. This can be advantageous in preventing over-movement of moveable portions within the arrangement. This in turn improves the reliability of the arrangement and reduces the likelihood of over-movement which may lead to damaging of the retaining element or the conduits within which the retaining element may be placed. Stresses can be controlled within such arrangement and therefore damage risk lowered. In particular, stresses can be reliably modelled as the elements stay broadly in the same place as in the model. One can also reliably model relative movement and bending of the two pipes. As such, it is easier to guarantee contact between the elements does not occur due to spacers moving out of position. In examples, the first portion of the first moveable portion comprises an angled face and wherein the first portion of the second moveable portion comprises a correspondingly angled face, wherein relative movement between the first moveable portion and the second moveable portion along the first axis is arranged to move the angled face of the first moveable portion against the correspondingly angled face of the second moveable portion. Use of angled faces interacting with correspondingly angled faces, in the present arrangement, provides a system that reduces stress between physically abutting and interacting elements. This therefore reduces the likelihood of breaking or otherwise experiencing failures from physical damage. This arrangement therefore provides an improved lifetime of the arrangement. In examples, relative movement of the angled face of the first moveable portion along the correspondingly angled face of the second moveable portion is arranged to move the second moveable portion along the second axis. The present arrangement enables a single direction movement of the moveable joining member to provide a multi-directional movement of other portions of the retaining element. This is particularly advantageous in improving the manoeuvrability of the retaining element during set up (which as noted above may occur in situ) and therefore increasing user control over the element. This may in turn reduce construction time and therefore improve overall manufacture and maintenance of systems comprising the present retaining element. In examples, the moveable joining member is moveable along a first axis between a first position and a second position, wherein in the first position at least two of: the main body portion; the first moveable portion; and, the second moveable portion, are not abutting, and wherein in the second position, the main body portion abuts the first moveable portion and the first moveable portion abuts the second moveable portion. The present arrangement enables a simple movement to control the contraction and expansion of the retaining element. This allows for straightforward installation within difficult to access locations or where access is only along one axis (such as the axis along which the moveable joining member may be moved). This improves installation and removal which in turn improves manufacture and maintenance of larger systems within which the retaining element may be used. In examples, when the moveable joining member is in the first position the retaining element has a first length along the second axis, and wherein when the moveable joining member is in the second position the retaining element has a second length along the second axis, wherein the second length is greater than the first length. The present arrangement allows for a movement along a direction to lead to an expansion or contraction of the moveable joining member. This expansion and contraction has an impact on the size of the retaining element as a whole. This means that the retaining element may be installed in a position or location in a small size and then, by virtue of movement of the moveable joining member, expanded at that position or location. This improves the ease of installation and maintenance of the larger systems within which the retaining element may be used. In examples, when the moveable joining member is in the first position the retaining element has a first length along the first axis, and wherein when the moveable joining member is in the second position the retaining element has a second length along the first axis, wherein the first length is greater than the second length. The present arrangement allows for a movement along a direction to lead to an expansion or contraction of the moveable joining member. This expansion and contraction has an impact on the size of the retaining element as a whole. In arrangements, during movement of the moveable joining member expansion may occur in one direction and contraction may occur in another. This allows the user control over a robustly positioned and sturdy retaining element. This improves the performance of the retaining element when retaining and therefore improves the overall lifetime of the larger system in which the retaining element is used. In accordance with some embodiments described herein, there is provided a conduit for transporting at least one of cryogenic material and electrical current, the conduit comprising: a first conduit portion arranged to carry a cryogenic material; and, a second conduit portion arranged to house a vacuum, the first conduit portion arranged at least partially within the second conduit portion; and the retaining element of any of the above embodiments or examples, wherein the second moveable portion of the retaining element is arranged to abut an inner side of the second conduit portion. This arrangement provides a larger system having great control over the retention of the cryogenic material carrying conduit. Such conduits may move during use for example in response to forces of movement of the cryogenic material through the conduit and / or due to thermal contraction / expansion. As such, a sturdy and easily installed retaining element provides great benefit during the maintenance and construction of such conduits. Conduits using the retaining element disclosed herein have a longer lifetime and are more user friendly in construction. In examples, the second moveable portion comprises a base portion, wherein the base portion is arranged to abut an inner side of the second conduit portion. Use of a somewhat wide base provides greater stability for the retaining element. Such a base provides an anti-tipping mechanism which means the retaining element is less likely to tip during use (unlike modern spacers). In examples, the second moveable portion is arranged towards the second conduit portion and the main body portion is arranged towards the first conduit portion. The second moveable portion may be designed to cooperate with the second conduit portion. The second moveable portion may be designed to interact securely with a surface of the second conduit portion. The main body portion may be designed to cooperate with the first conduit portion. The main body portion may be designed to interact securely with a surface of the first conduit portion. In examples, the main body portion is arranged not to abut the first conduit portion at rest. In this way, contact between the main body portion and the first conduit portion can, at least initially, be avoided. This is advantageous in maintaining the first conduit portion in a significantly thermally isolated position. This allows for the first conduit portion to transport a cryogenic material while losing less thermal energy via conduction through the main body portion of the retaining element. As such, this is a more energy friendly arrangement as it requires less energy to maintain cryogenic material at a low temperature. In examples, the conduit further comprises an electrical conductor for conducting an electrical current, the electrical conductor arranged within the first conduit portion. Electrical signals can be conducted in a highly space- and energy-efficient manner in the present arrangement. The conductors may be maintained in a low temperature environment improving the electrical efficiency of the conductors. Using the first conduit portion to carry both cryogenic material and electrical current is highly space efficient. In examples, the first conduit portion comprises a low friction interface arranged on an outer surface of the first conduit portion. Reducing the friction between the first conduit portion and e.g. the main body of the retaining element is advantageous in arranging the retaining element between the first conduit portion and the second conduit portion. This reduces snagging issues and therefore improves installation and maintenance reducing the cost of handling the system over the lifetime of the system. This also reduces the likelihood of stresses impacting the retaining element during installation, thereby increasing the lifetime of the system. In accordance with some embodiments described herein, there is provided a method for forming a retaining element in a conduit comprising: inserting a first conduit portion at least partially within a second conduit portion, inserting a retaining element into the second conduit portion, the retaining element comprising a moveable joining member moveable along a first axis between a first position and a second position, moving the moveable joining member along the first axis from the first position to the second position to abut the retaining element and the second conduit portion. The method herein is straightforward to conduct and therefore removes a large amount of difficult handling and specialist tools required as for modern systems. The method provides robust locating of the retaining element within the conduit improving the performance of the retaining element in reducing significant movement of portions within the conduit. In turn, this reduces likelihood of damage or other significant stress being provided onto portions of the conduit. In turn, this improves the lifetime of the arrangement formed from the method. In examples, the method further comprises: transporting a cryogenic fluid through the first conduit portion; and providing a vacuum in the second conduit portion. Such a method is highly advantageous for transporting cryogenic fluids and reducing the thermal energy that can access the cryogenic fluids. This therefore maintains the cryogenic fluids at a low temperature and reduces the energy otherwise required to maintain the cryogenic fluid at low temperature. In examples, multi-layer insulation can be used to further reduce the heat leak of the system. In examples, the method further comprises: drawing at least one electrical conductor through the conduit. Allows for an electrical current to be provided through the conduit in advantageously low temperatures. Low temperatures in the present examples may also therefore lead to low electrical resistances. In accordance with some embodiments described herein, there is provided an aircraft comprising the retaining element of any of the above embodiments or examples or the conduit of any of the above embodiments or examples. In examples, the aircraft is at least partially electrically powered. The present arrangement is highly advantageous in at least partially electrically powered aircraft for transporting cryogenic material and / or electrical current. In examples, the aircraft further comprises: a cryogenic material store for storing cryogenic material; and a fuel cell for provision of electrical power for use in the aircraft. In examples, the conduit is arranged to transport cryogenic material from the cryogenic material store to the fuel cell. In examples, the conduit is arranged to conduct electrical power from the fuel cell. 5 In examples, the present retaining element may be used in a closed-loop circuit for cryogenic material. In examples, the present retaining element may be used in a closed-loop circuit for cryogenic material carrying helium. Electrical power current lines may pass through a helium system that is cooled by liquid hydrogen. 10 Fuel cells provide cleaner energy for use in aircraft. This may be in use for thrust or the like. The present arrangement is highly advantageous in aircraft arrangements using transportation of cryogenic material from a cryogenic material store to a fuel cell for use in generating electrical energy. The present arrangement is highly advantageous in transporting electrical 15 energy from a fuel cell to electrical users within the aircraft (such as electrical-to-kinetic energy converters). Brief Description of the Drawings One or more embodiments of the invention will now be described, by way of example only, and with reference to the following figures in which: Figure 1 shows a schematic view of a retaining element for use in a conduit arrangement according to examples of the present disclosure; Figure 2 shows a schematic view of a retaining element for use in a conduit arrangement according to examples of the present disclosure; Figure 3a shows a schematic view of a retaining element for use in a conduit arrangement according to examples of the present disclosure; Figure 3b shows a schematic view of a retaining element for use in a conduit arrangement according to examples of the present disclosure; Figure 4 shows a schematic view of a retaining element in a conduit arrangement according to examples of the present disclosure; Figure 5a shows a schematic view of a retaining element in a conduit arrangement according to examples of the present disclosure; Figure 5b shows a schematic view of a retaining element in a conduit arrangement according to examples of the present disclosure; Figure 6 shows a schematic view of a retaining element in a conduit arrangement according to examples of the present disclosure Figure 7 shows a flow chat of a method for forming a retaining element in a conduit according to some examples; and, Figure 8 shows a schematic view of a retaining element in a conduit arrangement according to examples of the present disclosure. Any reference to prior art documents in this specification is not to be considered an admission that such prior art is widely known or forms part of the common general knowledge in the field. As used in this specification, the words “comprises”, “comprising”, and similar words, are not to be interpreted in an exclusive or exhaustive sense. In other words, they are intended to mean “including, but not limited to”. The invention is further described with reference to the following examples. It will be appreciated that the invention as claimed is not intended to be limited in any way by these examples. It will also be recognised that the invention covers not only individual embodiments but also combination of the embodiments described herein. The various embodiments described herein are presented only to assist in understanding and teaching the claimed features. These embodiments are provided as a representative sample of embodiments only, and are not exhaustive and / or exclusive. It is to be understood that advantages, embodiments, examples, functions, features, structures, and / or other aspects described herein are not to be considered limitations on the scope of the invention as defined by the claims or limitations on equivalents to the claims, and that other embodiments may be 5 utilised and modifications may be made without departing from the spirit and scope of the claimed invention. Various embodiments of the invention may suitably comprise, consist of, or consist essentially of, appropriate combinations of the disclosed elements, components, features, parts, steps, means, etc, other than those specifically described herein. In addition, this disclosure may include other inventions not presently claimed, but which may be claimed 10 in future. Detailed Description The present method and system provides a highly robust and reliable system for stabilising and protecting conduits. Specifically, the present method and system provides robust and reliable handling of conduits that may move or expand / contract during use. Modern systems may use flexible tubing and bellows however associated fatigue and weight issues mean that expansion is not well handled and the system is not overly suited for use in weight-sensitive environments, such as aerospace applications. Furthermore rigid arrangements for conduits that move can lead to the joining elements (spacers) between the conduits and the stabilising elements bearing significant loads during movement of the conduit. The present method and system are particularly advantageous in conduits that are arranged to conduct cryogenic material wherein isolation of the low temperature portion of the conduits is advantageous for maintaining those low temperatures. This system is therefore highly thermally efficient alongside being robust and easily manufactured and installed. Referring to Figure 1, there is shown a schematic view of a retaining element 100 for use in a conduit arrangement according to examples of the present disclosure. The retaining element 100 comprises a main body portion 110. The retaining element 100 comprises a first moveable portion 120. The retaining element 100 comprises a second moveable portion 130 arranged externally to the first moveable portion 120. The retaining element 100 comprises a moveable joining member 140 arranged to connect the main body portion 110 and a portion of at least one of the first moveable portion 120 and the second moveable portion 130. In the specific example shown, the moveable joining member 140 is connected to both the first moveable portion 120 and the second moveable portion 130. The moveable joining member 140 is directly connected to each of the main body portion 110, the first moveable portion 120 and the second moveable portion 130. The moveable joining member 140 is arranged to provide relative movement between at least two of: the main body portion 110; the first moveable portion 120; and, the second moveable portion 130. The moveable joining member 140 is moveable along a first axis, wherein the second moveable portion 130 is moveable along the first axis and a second axis, wherein the first axis and the second axis are different. The arrangement 100 shown in Figure 1 is schematic and is used to provide an understanding of the main parts of the present disclosure. The system 100 has moveable elements that can be moved relative to one another by the movement of the moveable joining member 140 that may be directly or indirectly connected to the main body portion 110, the first moveable portion 120, and the second moveable portion 130. A direct connection may be a connection between two specific elements while an indirect connection may be connection between two specific elements via an intermediary element. The retaining element 100 (or portions thereof) may be used as a spacer in a conduit arrangement or the like. A spacer may be used to provide a space between conduits, such as conduits in close proximity to one another or where conduits may be placed inside other conduits. The use of the retaining element 100 is to hold other elements in place or to retain them to certain positions. Referring to Figure 2, there is shown a schematic view of a retaining element 200 for use in a conduit arrangement according to examples of the present disclosure. The example in Figure 2 has many of the same features (or similar features) as Figure 1, the reference numerals of which are increased by 100 in Figure 2. For example retaining element 200 of Figure 2 has a similar or the same function as retaining element 100 of Figure 1. All such features may not be discussed in detail herein. Such features include main body portion 210, first moveable portion 220, second moveable portion 230 and moveable joining member 240. The arrangement of Figure 2 has a moveable joining member 240 directly in connection with the main body portion 210 and the second moveable portion 230. The moveable joining member 240 may be connected to the first moveable portion 220 indirectly, as explained lower. The moveable joining member 240 is moveable along the axis indicated by double ended arrow A. The moveable joining member 240 may be movable along this axis and / or may be expandable / contractible along the axis. When contracting along the axis A, the moveable joining member 240 provides relative movement between the remaining element in the retaining element 200. Specifically, as the moveable joining member 240 contract, the main body portion 210 may be moved to the left of the image and the second moveable portion 230 may be moved to the right of the image. These two elements therefore move relatively with respect to each other as well as moving relatively to the first moveable portion 220. The shapes of the elements may be broadly as shown. The movement of the moveable joining member 240 results in that, as the elements are pulled together by the moveable joining member 240, the second moveable portion 230 interacts with the first moveable portion 220 which is steadied against the main body portion 210 and the second moveable portion 230 moves along the axis shown by arrow B. Specifically, as the moveable joining member 240 contracts along axis A, the second moveable portion 230 moves along and up first moveable portion 220, thereby moving upwards along the axis B (as well as along the axis A). As the moveable joining member 240 expands along axis A, the second moveable portion 230 moves away from the first moveable portion 220 (along axis A) and therefore moves downwards along the axis B. In examples therefore the moveable joining member 240 is moveable along a first axis (A), wherein the second moveable portion 230 is moveable along the first axis (A) and a second axis (B), wherein the first axis (A) and the second axis (B) are different. In the example shown in Figure 2, the axes are broadly orthogonal. In examples, the main body portion 210 may be a spacer (or a portion of a spacer). In examples, the first moveable portion 220 may be an inner ring of some shape. In examples, the second moveable portion 220 may be an outer ring of some shape. In examples, the moveable joining member 240 may be bolt or other joining element. The moveable joining member 240 may be movable in such a way to contract and expand along the axis A. In this way, the moveable joining member 240 may be movable to be screwed in and out to move. The moveable joining member 240 may be arranged to be moved along a lateral axis (e.g. axis A) via a rotating movement of a portion of the moveable joining member 240. In examples, therefore, the moveable joining member 240 may be a bolt that can be rotationally screwed to provide lateral movement along axis A. The moveable joining member 240 may therefore be contractably expandable along a first axis. As the moveable joining member 240 contracts or expands, relative movement is provided between at least two of: the main body portion 210; the first moveable portion 220; and, the second moveable portion 230. In a specific example, noted above, moveable joining member 240 may be an element that can screw. The element may be able to screw into itself to shorten (contract). The element may be able to screw out of itself to lengthen (expand). This is seen as movement herein. This expansion and contraction may be provided by a screwing motion such that the rotational movement of screwing leads to a lateral movement along axis A. Referring to Figures 3a and 3b, there is shown schematic views of retaining elements for use in a conduit arrangement according to examples of the present disclosure. The example in Figure 3a has many of the same features (or similar features) as Figure 2, the reference numerals of which are increased by 100 in Figure 3a. For example retaining element 300 of Figure 3a has a similar or the same function as retaining element 200 of Figure 2. All such features may not be discussed in detail herein. Such features include main body portion 310, first moveable portion 320, second moveable portion 330 and moveable joining member 340. Figure 3a also shows the axis A and the axis B along which elements may move. As shown in Figure 3a, the moveable joining member 340 may move to provide relative motion between other portions of the retaining element 300. Moving moveable joining member 340 along the axis A may move the main portion 310 towards the second moveable portion 330 and vice versa. The width and length of the retaining element 300 in Figure 3a are shown by W and L respectively. Specifically, the retaining element 300 in the specific example of Figure 3a may be referred to as being at rest or prior to use. At rest, the element 300 has a specific width W and a length L. A further example is shown in Figure 3b, where the moveable joining member 340’ has moved to provide relative movement between portions of the retaining element 300’. The example in Figure 3b has many of the same features (or similar features) as Figure 3a, the reference numerals of which include a ‘. For example retaining element 300’ of Figure 3b has a similar or the same function as retaining element 300 of Figure 3a. All such features may not be discussed in detail herein. Such features include main body portion 310’, first moveable portion 320’, second moveable portion 330’ and moveable joining member 340’. The moveable joining member 340’ has moved the main portion 310’ and the second moveable portion 330’ together. The main portion 310’ is shown abutting the first moveable portion 320’. The first moveable portion 320’ is shown abutting the second moveable portion 330’. The correspondingly sloped faces of the first moveable portion 320’ and the second moveable portion 330’ are shown to interact such that the lateral movement of the second moveable portion 330’ towards the main body portion 310’ leads to an upwards motion of the second moveable portion 330’ along the slanted face of the first moveable portion 320’. The sloped faces may be surfaces or edges or the like. A larger surface area (i.e. a “face” or “surface” rather than an “edge”) may provide a more reliable sliding movement. A larger surface area also spreads out the force between the elements rather than, e.g., concentrating it on an edge or a narrower surface. As such, while edges may be used, it is preferable for surfaces to be used in the retaining element disclosed herein “Corresponding” in this context refers to the cooperating shapes of the relevant faces of the first moveable portion and the second moveable portion. Specifically, as can be seen in Figures 3a and 3b, the two elements have slanted faces at a similar angle such that when the faces meet, the elements can continue to move along the axis A while also moving (by virtue of the interacting faces) along axis B. In the example shown, the first moveable portion is prevented from moving down along axis B when it abuts the main body portion. As such, the second moveable portion moves in response up along axis B against the braced first moveable portion. The faces may correspond without being at precisely the same angle, indeed it is sufficient that the faces allow for reasonably smooth sliding action between the portions. The more different the surfaces are, the more friction will be generated and the increased likelihood of damage between the elements. As such, it is preferred if the faces have a very similar corresponding angles to increase the lifetime of the elements over use. The faces can meet each other in a manner that is broadly flush. If this was not the case, the stresses would be very high between the faces and therefore the system would more be likely to break or experience failure, as such, this arrangement therefore increases the lifetime of the arrangement. In use, specifically, the second moveable portion 330’ moves along the axis A’ due to the moveable joining member 340’ contracting and then, on interaction with the slanted face of the first moveable portion 320’, the second moveable portion 330’ moves along the axis B’. In this way, the second moveable portion 330’ moves both laterally (along A’) and outwardly (along B’). The retaining element 300’ can be deemed to be “in use” in Figure 3b, this will be expanded on below. The “in use” arrangement has a shorter width W than the at rest arrangement width W. The “in use” arrangement has a longer length L’ than the at rest arrangement length L. In this way, the retaining element may be inserted into a space “at rest” and then “expanded” while in that space in one direction (along the axis B, to lengthen L) to become “in use”. This will be highly relevant in the consideration of conduits or the like with which the present system may be used. Referring to Figure 4, there is shown a schematic view of a retaining element 400 in a conduit arrangement according to examples of the present disclosure. The example in Figure 4 has many of the same features (or similar features) as Figure 2, the reference numerals of which are increased by 200 in Figure 4. For example retaining element 400 of Figure 4 has a similar or the same function as retaining element 200 of Figure 2. All such features may not be discussed in detail herein. Such features include main body portion 410, first moveable portion 420, second moveable portion 430 and moveable joining member 440. The arrangement of Figure 4 shows a retaining element 400 in a conduit arrangement 4000. The conduit 4000 may be a pipe or a tube or the like. The conduit 4000 may be arranged to transport or carry relevant materials or the resources from one location to another. This may, in examples, be fuel from a fuel source to a user of that fuel. This may, in examples, be electrical energy from a source of electrical energy to a user of electrical energy. The retaining element 400 has been inserted into the conduit 4000. While the conduit 4000 could be constructed around the retaining element 400 this is not a preferred approach considering the manufacture and installation of these elements. Rather, in the example of Figure 4, the retaining element 400 has been inserted into the conduit 4000 along arrow C (or may be inserted in a similar manner from the left hand side of the drawing). As noted above, the retaining element 400 is inserted into the conduit 4000 in an “at rest” position. The retaining element 400 “at rest” has a larger width W but a shorter length L (noting Figures 3a and 3b) than “in use”. As such, the retaining element 400 is more easily inserted “at rest” into the conduit 4000 considering the shape of the conduit 4000. The conduit 4000 has a narrow “length” (compared to its “width”), using the corresponding dimensions of Figures 3a and 3b. Therefore, inserting the retaining element 400 when it also has a shorter length improves the ease of installation of the retaining element 400. In the example shown, the second moveable portion 430 has a base portion 432. The base portion 432 may be arranged to abut the conduit 4000. Specifically, as the retaining element 400 is inserted into the conduit 4000 (in the example of Figure 4), the base portion 432 of the second moveable portion 430 abuts an inner surface of the conduit 4000. The base portion 432 may preferably have a good connection to the conduit 4000 and so the shape of the base portion 432 may correspond to the shape of the conduit 4000. For example, where the conduit 4000 has a square cross section, the base portion 432 may have a corresponding flat edge. Where the conduit 4000 has a circular cross section, the base portion 432 may have a corresponding curved edge. The base portion 432 may be arranged to be wider than modern spacers to provide a greater stability for the retaining element 400 within the conduit 4000. Greater stability reduces the likelihood of tipping of the spacer and therefore improves the performance of the retaining element 400. As can be seen in Figure 4, the bolt 440 is connected to both the main portion 410 and second moveable portion 430. The moveable portion 430 moves in the direction shown by arrow B. The main portion 410 may not move. The connection for the bolt 440 in at least one of the main portion 410 and the moveable portion 430 may allow for movement of the bolt 440 in the direction shown by arrow B. For example, the connection with the main portion 410 may be a slot within which the bolt 440 may move vertically. This maintains the physical connection between the main portion 410 and the moveable portion 430 while allowing the connecting element 440 to move to reduce the overall stress within the arrangement 400. Modern spacers are often in effect vertical line structures that may be vulnerable to tipping, the present arrangement improves on such elements. Modern spacers are narrow structures to minimise the connection between conduits (specifically where conduit arrangements have two or more conduits arranged somewhat concentrically. Minimising the connection is useful for thermal isolation of the inner conduit. Referring to Figure 5a, there is shown a schematic view of a retaining element 500 in a conduit arrangement according to examples of the present disclosure. The example in Figure 5a has many of the same features (or similar features) as Figure 4, the reference numerals of which are increased by 100 in Figure 5a. For example retaining element 500 of Figure 5a has a similar or the same function as retaining element 400 of Figure 4. All such features may not be discussed in detail herein. Such features include main body portion 510, first moveable portion 520, second moveable portion 530 and moveable joining member 540. The arrangement of Figure 5a differs in the conduit arrangement. Specifically, the conduit arrangement now contains two conduits 5100, 5200. The conduits 5100, 5200 are arranged concentrically (though the corresponding other sides of the conduits are not shown in Figure 5a). In this example, therefore, the retaining element 500 has been inserted between an outer conduit 5100 and an inner conduit 5200. The insertion may occur along a direction indicated by arrow C (as per the above example for Figure 4). The retaining element 500 is inserted “at rest” as noted above as this is easiest for insertion. The second moveable portion 530 has a base portion 532 arranged to abut against a portion of the inner surface of the outer conduit 5100. The retaining element 500 is not intended to abut the inner conduit 5200. To increase ease of installation of the retaining element 500, one or both of the conduits 5100, 5200 may have low friction surfaces along which the retaining element 500 may slide during installation. In the specific example shown, inner conduit 5200 has an outer surface 5202 that may be a low friction outer surface 5202. The low friction outer surface 5202 may be a lubricated outer surface 5202. To increase ease of installation, the retaining element 500 may be of a predetermined size to enable easier insertion. For example, a shorter element 500 may be more easily inserted into the conduit arrangement. In short, the geometry of the retaining element 500 may be altered for improved performance as desired. For example, sloped faces may be steeper or shallower as befits the installation requirements. Suitable lubricants for low temperature and vacuum environments are not straightforward. Traditional lubricants tend to offgas in the vacuum which is undesirable and cryogenic interfaces means many material lose their lubricating properties. Dry lubrication has been found by the present inventors to be highly suitable for arrangements such as those disclosed herein. The retaining element 500 may have a portion formed of G10. G10 has preferable characteristics in relation to strength and thermal conductivity. G10 is strong and a good thermal insulator. These characteristics are suitable for use in the present invention. The main body (which may be formed of e.g. G10) has been designed to have as high length, low area heat paths as possible, to reduce the heat leak. The G10 provides high level of thermal insulation. This provides a freedom of choice of material for the other elements. For example, these may be chosen to be aluminium for a high strength and lightweight solution. Edges of the retaining element 500 may include a thin strip of polytetrafluoroethylene (PTFE) tape or the like. The inner surface of the retaining element 500 may include a thin strip of polytetrafluoroethylene (PTFE) tape or the like. The tape may be feathered and adhered to external surfaces of the retaining element for increased robustness. The conduits may be wrapped in a layer of PTFE tape. The coefficient of friction of this PTFE-PTFE interface is much lower than other solutions and has been found to be around 0.1. This is a considerable improvement on older solutions of around a 0.29-0.48 range expected from a G10-aluminium pipe interaction. A coefficient of friction of around 0.2 or lower may be considered “low” herein. This low friction arrangement is a significant improvement on previous systems, notably an improvement of above 30%. Specifically the example above (where the friction coefficient is as low as 0.1) has an improvement of above 60% over modern solutions. Conduits may be coated in tungsten disulphide (WS2) which further improves the coefficient of friction to around 0.07. Low friction arrangements improve the ease with which the retaining element 500 may be installed into the conduit arrangement 5100, 5200. Lubricants can also be advantageous in providing a surface along which movement can occur during use, when conduits undergo thermal contraction. This in turn reduces the likelihood of damage occurring from bending on the main body portion 510. Bending can lead to delamination and therefore it is preferable to reduce the likelihood of bending on elements such as portion 510. The improvements noted above involve use of a tape or other similar thin coatings. These are therefore extremely lightweight and highly suitable for use in environments where low weight is advantageous. Such environments include use in vehicles such as aircraft or the like where weight savings are highly desirable. The arrangements discussed herein may be produced via additive manufacturing or other similar techniques. Referring to Figure 5b, there is shown a schematic view of a retaining element 500’ in a conduit arrangement according to examples of the present disclosure. The example in Figure 5b has many of the same features (or similar features) as Figure 5a, the reference numerals in Figure 5b have been updated to include a ‘ in them. For example retaining element 500’ of Figure 5b has a similar or the same function as retaining element 500 of Figure 5a. All such features may not be discussed in detail herein. Such features include main body portion 510’, first moveable portion 520’, second moveable portion 530’ and moveable joining member 540’. The example in Figure 5b shows the retaining element 500’ abutting the inner surface of conduit 5100’. Specifically, the base portion 532’ of the second moveable portion 530’ abuts the inner surface of the conduit 5100’. The main body portion 510’ is distanced somewhat from the outer surface 5202’ of the inner conduit 5200’. In use, a lubricant may be applied on the surface 5202’ and the bottom face of main portion 510’. The lubricant may be put onto the inner face of the retaining element 500. The faces to lubricate are those that face one another of the conduit and the inner surface of the retaining element. This allows the main portion 510’ and the surface 5202’ to move past one another should there be contact. If there is contact, which may occur, it is best that the contact is between low friction surfaces to avoid a pulling effect on the main portion 510’. The main portion 510’ may be laminated and is robust against a number of stresses, however a force resulting in a bending action is undesirable. As such, use of lubricant to avoid this is advantageous. The retaining element 500’ in the example of Figure 5b (much like the example of Figure 3b) is “in use”. Specifically, the moveable joining member 540’ has moved along the axis A to pull the main body portion 510’ and the second moveable portion 530’ together. The first moveable portion 520’ abuts against the main body portion 510’. The second moveable portion 530’ is moved towards the first moveable portion 520’ and begins to slide up the slated face of the fist moveable portion 520’. The second moveable portion 530’ therefore moves along both axis A and axis B. The axis B may be a radially outward axis. The retaining element 500’ therefore undergoes contraction in axis A and expansion in axis B. This is useful to secure the retaining element 500’ within the conduit arrangement against the inner surface of the outer conduit 5100’. This movement may be provided by a rotational movement of the moveable joining member 540’ which creates contraction along the axis A. This may be provided, as noted above, by a bolt or the like that contracts along a length in response to a rotational movement. These movements are highly advantageous in conduit arrangements such as those shown as the user has limited space for movement in the B axis and therefore a simple screw mechanism is highly advantageous and leads to improved ease of installation. In the example of Figure 5b, the main body portion 510’ does not touch the inner conduit 5200’. This is advantageous if the inner conduit 5200’ is preferably thermally isolated from the outer conduit 5100’. If the inner conduit 5200’ moves during use or the space between the conduits contracts during transportation of low temperature material (such as cryogenic material) the main body portion 510’ may brace against the inner conduit 5200’ to limit movement and thereby limiting damage that may occur due to unconstrained movement of the inner conduit 5200’. During thermal contraction, the spacers experience touchdown from the conduit. During use, spacer placement is made as required to substantially prevent inner-outer pipework contact. As noted above, the length of the moveable joining member 540’ along axis A is at its shortest when the retaining element is “in use”. Therefore, when the moveable joining member 540’ is at its shortest, the retaining element is at its largest in axis B. While the arrangement shown in the figures are possible, other arrangements are possible that allow for the advantages of the moveable portions disclosed herein. Referring to Figure 6, there is shown a schematic view of a retaining element 600 in a conduit arrangement 6000 according to examples of the present disclosure. The example in Figure 6 has many of the same features (or similar features) as Figure 5a, the reference numerals in Figure 6 have been increase by 100. For example retaining element 600 of Figure 6 has a similar or the same function as retaining element 500 of Figure 5a. All such features may not be discussed in detail herein. The conduit 6000 has a first conduit portion 6100 arranged to carry a cryogenic material and a second conduit portion 6200 arranged to house a vacuum. The first conduit portion 6100 is arranged at least partially within the second conduit portion 6200. In the example shown in Figure 6, a large proportion of the first conduit 6100 is arranged within the second conduit portion 6200. In the example shown in Figure 6, the first conduit portion 6100 has a first end portion 6140 and a second end portion 6160. Each may comprise a bi-metallic joint 6320, 6420. Each bimetallic joint may have a first joint portion formed of a first metallic material and a second joint portion formed of a second metallic material, wherein the second joint portion is larger than the first joint portion. The bimetallic joints may have a first joint portion formed of a first metallic material and a second joint portion formed of a second metallic material joined via at least any one of friction stir welding, explosion bonding, roll bonding, rotary friction welding. Where one portion of the bimetallic joint is aluminium this may advantageously reduce the weight of the structure. Where one portion of the bimetallic joint is steel, this may advantageously be repairable via de-welding. This also improves disassembly and the like. Joining dissimilar metals may also occur via bimetallic additive manufacture. The first conduit portion 6100 is arranged to carry a cryogenic material and this material may be located in portion 6120 indicated in Figure 6. The second conduit portion 6200 is arranged to house a vacuum and this vacuum may be located in portion 6220 indicated in Figure 6. The vacuum 6220 improves the maintenance of a low temperature at conduit portion 6100 which may be arranged to hold a cryogenic material. The vacuum therefore improves the overall reliability of the system and reduces the requirement on re-cooling cryogenic material. The advantage of the present conduit 6000 is that it may be combined with other similar or identical conduits to form a conduit network. The combining can occur in a number of ways. The combining does not require welding. Welding can be used in bi-metallic joints where stainless steel can be used as a material in the weld. The present system may provide leak tight joints that are both strong and durable. The conduits may be joined together by welding, however bolted joints with metal seals may be used. Bolted joints with metal seals may be used for inner conduit which carrying cryogenic material. Joins may be made by metal or polymer seals in the outer conduit or ambient vacuum tube parts. As bolted assemblies are typically slightly heavier than other proposed solutions, bolted assemblies as less preferred for aerospace applications. Noting the above, existing welds on the conduit may be seen to create reduced strength regions. Above mentioned techniques may be advantageous. Friction stir welded transition pieces allows for little or no reduced strength at the bond or materials on either side. Friction stir welding may occur at elevated temperature. This may reduce the strength of aluminium section if it was originally heat treated. Explosion bonded transition pieces allows for little or no reduced strength at the bond or materials on either side. Explosion bonding can avoid strength reductions, as it may be performed at room temperature. Roll bonded transition pieces allows for little or no reduced strength at the bond, but reduced strength of aluminium on one side. Roll bonding may occur at elevated temperature. This may reduce the strength of aluminium section if it was originally heat treated. In the example of Figure 6, the second joint portion of each bi-metallic joint 6320, 6420 is arranged at an end of the conduit portion 6100, 6200. The conduit portions 6100, 6200 have two ends in the arrangement of Figure 6. The joint sections are arranged at the end of the conduits and are well located for connecting to subsequent conduits in a network of conduits. In the example shown in Figure 6, the second conduit portion 6200 has a first end portion 6240 and a second end portion 6260. Each may comprise a bi-metallic joint 6242, 6262. Each bimetallic joint may have a first joint portion formed of a first metallic material and a second joint portion formed of a second metallic material, wherein the second joint portion is larger than the first joint portion. The conduit or conduit arrangements of any of the present examples may use one or more retaining elements to arrange the first conduit (inner conduit) securely within the second conduit (outer conduit). The retaining element 600 is advantageously small in structure to provide a limited thermal conduction path from the second conduit portion to the first conduit portion. The inner conduit portion may be preferably at a very low temperature and therefore thermal isolation, to as great an extent as possible, from the outer conduit portion is advantageous. The inner conduit may be at cryogenic temperatures. The outer conduit may be at any temperature. The outer conduit may be at ambient temperature. The retaining element operates to reduce thermal transfer from one to the other. As noted above, the retaining element 600 of the present examples can provide a secure system for retaining the inner conduit 6100 against movement or contraction during use. The retaining element 600 also significantly reduces thermal transfer to the cold inner conduit 6100 from the warmer outer conduit 6200. The retaining element 600 can be installed easily and the shape can be manipulated once the retaining element 600 is in situ in the conduit arrangement 6000. This is highly advantageous for ease of installation and removal for e.g. maintenance. Retaining elements 600 are advantageous for providing effective stability within the structure. This stable positioning is provided with vastly reduced thermal energy transfer from the outer conduit portion 6200 to the inner conduit portion 61000. The system may have a series of retaining elements 600 to improve ease of locating the inner conduit portion 61000 securely within the outer conduit portion 6200. The formable conduit allows for bent conduits to be adhered to one another and form a long and, where required, winding conduit which otherwise may be difficult to form. In brief, a straight formed conduit can be bent at the required angle. The conduit can then be connected to further conduits (which may be straight). The ends may be welded and therefore the conduit arrangement can be formed from a series of smaller conduit portions. The retaining elements of this disclosure can be inserted from an open end of a conduit prior to welding to further conduit portions. In use, there may be a small a gap between the outer edge of the retaining element 600 and inner edge of the outer conduit 6200 so that a reasonably small turn of the moveable joining element leads to a tight contact. Specifically, it may be advantageous to take this to an extent that the smallest possible gap is present such that the smallest turn of the moveable joining element leads to a tight contact. This improves the installation ease of the retaining element 600 within the conduit arrangement. A larger gap during installation allows for looser tolerances but means that the outer moveable portion needs to move more before the retaining element expands to fill the gap. A smaller gap means a smaller assembly but results in a need for tighter tolerances on the retaining element and the conduits. In a slightly contrasting arrangement, there may be a reasonably large gap between the retaining element 600 and the inner conduit 6100 to allow for movement and forces between the retaining element 600 and the inner conduit 6100. A tight fit between the retaining element 600 and the outer conduit 6200 is advantageous as an active anti-tip system. The retaining element 600 is less likely to rotate within the conduit arrangement if it is strongly held to the inner surface of the outer conduit 6200. Rotations in situ are referred to herein as “tip” or “tipping” of the retaining element and are undesirable as they reduce the effectiveness of the retaining element 600. The arrangement of the retaining element within the conduit arrangement (e.g. tightly to the outer conduit) may reduce the likelihood of tipping as can the shape of the retaining element itself, e.g. having a broad base portion as noted above. Both are advantageous in securing the retaining element within the conduit arrangement. The broad base portion may extend along a portion of the inner side of the second conduit portion. The broad base may have a face or a surface rather than merely an edge that connects to the inner surface of the second conduit portion. Removal of the retaining element may be straightforward in the present arrangement. By e.g. unscrewing the joining member and the spacer comes loose from the arrangement in the conduit and can be removed from the conduit arrangement with a hook or otherwise by the user. The present system is highly suitable for a vacuum outer pipe with a cryogenic material inner pipe. The system is entirely mechanical and does not require glues or other wet lubricants that may offgas to provide a suitable and tight fit in the conduit arrangement. This in turn leads to a system that is very user friendly to install which reduces the requirement for specialist installers or the like. This, in turn, reduces the cost of maintenance. In the example of Figure 6, it can be see that the main body portion of the retaining element is arranged towards the first conduit portion (the inner conduit). Similarly, it can be seen that the second moveable portion is arranged towards the second conduit portion (the outer conduit). The main body portion is an element that is arranged to interact with the first conduit portion only when needed, e.g. during thermal contraction or periods of movement etc. The arrangement reduces the heat transfer between the outer and inner tubes and therefore improves the ability of the inner tube to transport cryogen and maintain it at cryogenic temps. As noted above, the main body portion is arranged not to abut the first conduit portion normally. Rather, the main body portion and the first conduit portion abut during periods of significant movement or during thermal contraction. Thermal contraction may occur at any point during use when cryogenic material flows. The conduit arrangements with which the retaining element may be used are various. While the present retaining element is particularly effective in nested conduits attempting to maintain material at very low temperatures, the retaining element may be used in any conduit arrangement where a retaining element providing an easily installed steadying function is desirable. In particular, the retaining element may be used in a conduit arrangement that carries electrical current or the like. This may be synergistic with the low temperature conduit arrangements as the inner conduit may carry both cryogenic material and an electrical conductor. In this way, the electrical conductor is maintained at a low temperature and therefore the electrical efficiency is maintained at a high level. Referring now to Figure 7, there is shown a flow chat 700 of a method for forming a retaining element in a conduit according to some examples. The method 700 has three steps 705, 710, 715. In a first step 705, a first conduit portion is inserted at least partially within a second conduit portion. In a second step 710, a retaining element is inserted into the second conduit portion. The retaining element comprises a moveable joining member moveable along a first axis between a first position and a second position. In a third step 715, the moveable joining member is moved along the first axis from the first position to the second position to abut the retaining element and the second conduit portion. As noted above, the moveable joining member may be moved in a manner that facilitates easy access and easy movement. This may occur via e.g. a rotational movement that leads to a contraction of the moveable joining member. Typical conduit shapes provide easy movement in a lateral manner along the conduit and reduced movement in a radial direction. As such, the present system is highly advantageous for use in conduit arrangements and provides a robust system for protecting conduits alongside maintaining robust thermal management within the arrangement by reducing contact between the retaining element and the inner conduit where feasible. The present system may advantageously be used within an aircraft or the like where movement of cryogenic material and electrical power occurs. For example, the aircraft may be partially or fully electrically powered. Electrically powered aircraft may use cryogenic material and fuel cells for producing electrical power. These systems may use nested conduit arrangements as noted above. In such cases, the present retaining elements are highly advantageous for easy installation and high performance thermal isolation. The conduits may be part of a conduit network arranged to carry cryogenic material and / or electrical power from one location (e.g. one portion of an aircraft) to another for use. Such an arrangement may be suitable for centralised and / or decentralised power management on aircraft. The retaining element may have a plurality of first moveable portions and second movable portions. See for example, Figure 8 showing an arrangement 800 with similar reference numerals as Figure 5a, where reference numerals for similar elements are increased by 300. For example, retaining element 500 of Figure 5a is similar to retaining element 800 of Figure 8. The arrangement of Figure 8 has a two first moveable portions 820a, 820b and two second moveable portions 830a, 830b. The two second moveable portions 830a, 830b are arranged externally from the main body portion 810 from the two first moveable portions 820a, 820b. It can be seen that there is a symmetry of the retaining element 800. The retaining element 800 is shown in a longitudinally contracted, radially expanded position within an outer conduit 8100. The retaining element 800 is robust and reliable. The retaining element described above may be made of any suitable material. In examples, the main body portion may be formed of a thermal insulator. The first and second moveable portions may be formed of aluminium or the like. The arrangements shown herein may be portions of a retaining element. For example, the retaining element shown herein may be a subsystem within a larger retaining element system. In examples, the retaining element has a plurality of main body portions, first moveable portions, second moveable portions, and moveable joining members. In an example, the retaining element system may comprise 16 moveable joining members each connected in the manner shown herein to a respective main body portion. The retaining element system may be circular for easy insertion into a conduit of a similar shape cross section. Further examples of feature combinations taught by the present disclosure are set out in the following numbered clauses: In an arrangement compared to the above, the main body portion and the first moveable portion may be integral. In which case, the above disclosure holds for an arrangement where the main body portion and the first moveable portion are one element (referred to below as the “main body portion”) and the second moveable portion is then referred to below as the “first moveable portion”. 1. A retaining element for use in a conduit arrangement, the retaining element comprising: a main body portion; a first moveable portion; a moveable joining member arranged to connect the main body portion and the first moveable portion, wherein the moveable joining member is arranged to provide relative movement between the main body portion and the first moveable portion, wherein the moveable joining member is moveable along a first axis, wherein the first moveable portion is moveable along the first axis and a second axis, wherein the first axis and the second axis are different. 2. A retaining element according to clause 1, wherein the moveable joining member is contractably expandable along a first axis, wherein as the moveable joining member contracts or expands, relative movement is provided between the main body portion and the first moveable portion. 3. A retaining element according to clause 1 or 2, wherein the main body portion has a first portion and the first moveable portion has a first portion, wherein the first portion of the main body portion and the first portion of the first moveable portion are arranged to abut as the moveable joining member moves along the first axis. 4. A retaining element according to clause 3, wherein the first portion of the main body portion comprises an angled face and wherein the first portion of the first moveable portion comprises a correspondingly angled face, wherein relative movement between the main body portion and the first moveable portion along the first axis is arranged to move the angled face of the main body portion against the correspondingly angled face of the first moveable portion. 5. A retaining element according to clause 4, wherein relative movement of the angled face of the main body portion along the correspondingly angled face of the first moveable portion is arranged to move the first moveable portion along the second axis. 6. A retaining element according to any preceding clause, wherein the moveable joining member is moveable along a first axis between a first position and a second position, wherein in the first position the main body portion and the first moveable portion are not abutting, and wherein in the second position, the main body portion abuts the first moveable portion. 7. A retaining element according to clause 6, wherein when the moveable joining member is in the first position the retaining element has a first length along the second axis, and wherein when the moveable joining member is in the second position the retaining element has a second length along the second axis, wherein the second length is greater than the first length. 8. A retaining element according to clause 6 or 7, wherein when the moveable joining member is in the first position the retaining element has a first length along the first axis, and wherein when the moveable joining member is in the second position the retaining element has a second length along the first axis, wherein the first length is greater than the second length. 9. A conduit for transporting at least one of cryogenic material and electrical current, the conduit comprising: a first conduit portion arranged to carry a cryogenic material; and, a second conduit portion arranged to house a vacuum, the first conduit portion arranged at least partially within the second conduit portion; and the retaining element of any of clause 1-8, wherein the first moveable portion of the retaining element is arranged to abut an inner side of the second conduit portion. 10. A conduit according to clause 10, wherein the first moveable portion comprises a base portion, wherein the base portion is arranged to abut an inner side of the second conduit portion. 11. A conduit according to clause 9 or 10, wherein the first moveable portion is arranged towards the second conduit portion and the main body portion is arranged towards the first conduit portion. 12. A conduit according to any of clauses 9-11, wherein the main body portion is arranged not to abut the first conduit portion at rest. 13. A conduit according to any of clauses 9-12, further comprising an electrical conductor for conducting an electrical current, the electrical conductor arranged within the first conduit portion. 14. A conduit according to any of clauses 9-13, wherein the first conduit portion comprises a low friction interface arranged on an outer surface of the first conduit portion. 15. A method for forming a retaining element in a conduit comprising: inserting a first conduit portion at least partially within a second conduit portion, inserting a retaining element into the second conduit portion, the retaining element comprising a moveable joining member moveable along a first axis between a first position and a second position, moving the moveable joining member along the first axis from the first position to the second position to abut the retaining element and the second conduit portion. 16. A method according to clause 15, further comprising: transporting a cryogenic fluid through the first conduit portion; and providing a vacuum in the second conduit portion. 17. A method according to clause 15 or 16, further comprising drawing at least one electrical conductor through the conduit. 18. An aircraft comprising the retaining element of clauses 1-8 or the conduit of clauses 9-14. 19. An aircraft according to clause 18, wherein the aircraft is at least partially electrically powered. 20. An aircraft according to clause 18 or 19, further comprising: 5 a cryogenic material store for storing cryogenic material; and a fuel cell for provision of electrical power for use in the aircraft. 21. An aircraft according to clause 20, wherein the conduit is arranged to transport cryogenic material from the cryogenic material store to the fuel cell. 10 22. An aircraft according to clause 20 or 21, wherein the conduit is arranged to conduct electrical power from the fuel cell.

Claims

1. A retaining element for use in a conduit arrangement, the retaining element comprising: a main body portion;a first moveable portion;a second moveable portion arranged externally to the first moveable portion; anda moveable joining member arranged to connect the main body portion and a portion of at least one of the first moveable portion and the second moveable portion,wherein the moveable joining member is arranged to provide relative movement between at least two of:the main body portion;the first moveable portion; and,the second moveable portionwherein the moveable joining member is moveable along a first axis,wherein the second moveable portion is moveable along the first axis and a second axis,wherein the first axis and the second axis are different.

2. A retaining element according to claim 1, wherein the moveable joining member is contractably expandable along a first axis,wherein as the moveable joining member contracts or expands, relative movement is provided between at least two of:the main body portion;the first moveable portion; and,the second moveable portion.

3. A retaining element according to claim 1 or 2, wherein the first moveable portion has a first portion and the second moveable portion has a first portion,wherein the first portion of the first moveable portion and the first portion of the second moveable portion are arranged to abut as the moveable joining member moves along the first axis.

4. A retaining element according to claim 3, wherein the first portion of the first moveable portion comprises an angled face and wherein the first portion of the second moveable portion comprises a correspondingly angled face,wherein relative movement between the first moveable portion and the second moveable portion along the first axis is arranged to move the angled face of the first moveable portion against the correspondingly angled face of the second moveable portion.

5. A retaining element according to claim 4, wherein relative movement of the angled face of the first moveable portion along the correspondingly angled face of the second moveable portion is arranged to move the second moveable portion along the second axis.

6. A retaining element according to any preceding claim, wherein the moveable joining member is moveable along a first axis between a first position and a second position, wherein in the first position at least two of:the main body portion;the first moveable portion; and,the second moveable portion,are not abutting, andwherein in the second position, the main body portion abuts the first moveable portion and the first moveable portion abuts the second moveable portion.

7. A retaining element according to claim 6, wherein when the moveable joining member is in the first position the retaining element has a first length along the second axis, andwherein when the moveable joining member is in the second position the retaining element has a second length along the second axis,wherein the second length is greater than the first length.

8. A retaining element according to claim 6 or 7, wherein when the moveable joining member is in the first position the retaining element has a first length along the first axis, and wherein when the moveable joining member is in the second position the retaining element has a second length along the first axis,wherein the first length is greater than the second length.

9. A conduit for transporting at least one of cryogenic material and electrical current, the conduit comprising:a first conduit portion arranged to carry a cryogenic material; and,a second conduit portion arranged to house a vacuum, the first conduit portion arranged at least partially within the second conduit portion;and the retaining element of any of claim 1-8,wherein the second moveable portion of the retaining element is arranged to abut an inner side of the second conduit portion.

10. A conduit according to claim 10, wherein the second moveable portion comprises a base portion, wherein the base portion is arranged to abut an inner side of the second conduit portion.

11. A conduit according to claim 9 or 10, wherein the second moveable portion is arranged towards the second conduit portion and the main body portion is arranged towards the first conduit portion.

12. A conduit according to any of claims 9-11, wherein the main body portion is arranged not to abut the first conduit portion at rest.

13. A conduit according to any of claims 9-12, further comprising an electrical conductor for conducting an electrical current, the electrical conductor arranged within the first conduit portion.

14. A conduit according to any of claims 9-13, wherein the first conduit portion comprises a low friction interface arranged on an outer surface of the first conduit portion.

15. A method for forming a retaining element in a conduit comprising:inserting a first conduit portion at least partially within a second conduit portion, inserting a retaining element into the second conduit portion, the retaining element comprising a moveable joining member moveable along a first axis between a first position and a second position,moving the moveable joining member along the first axis from the first position to the second position to abut the retaining element and the second conduit portion.

16. A method according to claim 15, further comprising:transporting a cryogenic fluid through the first conduit portion; and providing a vacuum in the second conduit portion.

17. A method according to claim 15 or 16, further comprising drawing at least one electrical conductor through the conduit.

18. An aircraft comprising the retaining element of claims 1-8 or the conduit of claims 9-14.

19. An aircraft according to claim 18, wherein the aircraft is at least partially electrically powered.5 20. An aircraft according to claim 18 or 19, further comprising:a cryogenic material store for storing cryogenic material; anda fuel cell for provision of electrical power for use in the aircraft.

21. An aircraft according to claim 20, wherein the conduit is arranged to transport cryogenic 10 material from the cryogenic material store to the fuel cell.

22. An aircraft according to claim 20 or 21, wherein the conduit is arranged to conduct electrical power from the fuel cell.Application No: GB2414620.1Claims searched: 1-14Examiner: Miss Monika RamelDate of search: 20 March 2025Patents Act 1977: Search Report under Section 17Documents considered to be relevant:Category Relevant to claims Identity of document and passage or figure of particular relevance X,E 1,2,6,7 GB764637 A (LEGRAND PIERRE) Figures 1 and 12 and related passages X 1,2, 9,10,11,1 3 US2003 / 085573 Al (SHUMARD) Figure 7 and related passages X 1,2,9,13 US2022 / 268388 Al (KAMIYAMA) Figures 8 and 10 and related passages X 1,2 DE2917350 Al (FELDER MICHAEL) Figure 1 and related passages A - US3791416A (ZIEMEK ET AL.) A - US3826286 A (BECK)Categories:X Document indicating lack of novelty or inventive step A Document indicating technological background and / or state of the art. Y Document indicating lack of inventive step if combined with one or more other documents of same category. P Document published on or after the declared priority date but before the filing date of this invention. & Member of the same patent family E Patent document published on or after, but with priority date earlier than, the filing date of this application.Field of Search:Search of GB, EP, WO &US patent documents classified in the following areas of the UKCX :www.gov.uk / ipoInternational Classification:Subclass Subgroup Valid From F16L 0059 / 12 01 / 01 / 2006 F16L 0059 / 065 01 / 01 / 2006 F16L 0059 / 135 01 / 01 / 2006

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