Container for receiving a cryofluid

Abstract

A container (1) for holding a cryofluid comprises an inner container (2) with an outwardly convex cap (7) and an outer container (3) with at least one inwardly concave cap (10), wherein the inner container (2) is supported on the outer container (3) by a first support structure (13) having four rhombus-shaped struts (21-24), the ends (21", 22', 23", 24') of which are located at one of the two diagonally opposite corners (25, 27) of the rhombus are connected to the concave cap (10) and the ends (22", 23', 24", 21') of which are located at the other two diagonally opposite corners (26, 28) of the rhombus are connected to the convex cap (7), each strut (21-24) being connected at one end (21', 22', 23', 24') by a ball joint (29 - 36) and at its other end (21", 22", 23", 24") is connected to the respective cap (7, 10) via a ball or cardan joint (29 - 36).

Description

[0001] The present invention relates to a container for holding a cryogenic fluid, comprising an inner container with at least one outwardly convex cap and an outer container with at least one inwardly concave cap, wherein the inner container is located in the outer container at a distance on all sides, the convex cap projects into the concave cap and the inner container is supported on the outer container via a first support structure and a second support structure which engages the inner container diametrically opposite the first support structure.

[0002] To increase the volumetric energy density of energy sources that are gaseous under normal conditions, they are either compressed and stored in pressure vessels for transport and storage purposes, or cooled to low temperatures, thereby at least partially liquefying them into a cryogenic fluid and storing them in temperature-insulated containers. To power vehicles, liquefied hydrogen or liquefied natural gas (LNG), for example, are stored as high-energy-density cryogenic fluids for subsequent use in what are essentially conventional internal combustion engines or vehicle fuel cells.

[0003] Due to the extremely low temperatures of such cryogenic fluids, e.g., less than -252 °C in the case of liquid hydrogen or less than -161 °C in the case of LNG, the inner vessel experiences significant thermal expansion or contraction during filling. For a cylindrical vessel with a length of approximately 1 m, the expansion can be 5 mm or more, for example. For this reason, at least one of the support structures used to brace the inner vessel to the outer vessel in cryogenic vessels is designed as a floating bearing, which can accommodate changes in the length of the inner vessel.

[0004] However, installing a floating bearing in a cryogenic vessel is complicated because thermal bridges between the inner and outer vessels must be kept as small as possible. Furthermore, while the floating bearing must be able to accommodate changes in length, it must also permanently withstand the radial and torsional forces that occur during operation to prevent the inner vessel from becoming loose in the outer vessel, for example, due to vibrations, acceleration, or deceleration of a vehicle, especially when impacting an obstacle.

[0005] The invention aims to create a container for cryogenic fluids which has an improved support structure for thermally decoupled support of the inner container on the outer container.

[0006] This aim is achieved according to the invention in a container of the type mentioned in the introduction in that the first support structure has four struts forming a rhombus, the ends of which are located at one of the two diagonally opposite corners of the rhombus are connected to the concave cap and the ends of which are located at the other two diagonally opposite corners of the rhombus are connected to the convex cap, each strut being connected at one end via a ball joint and at its other end via a ball or cardan joint to the respective cap.

[0007] The invention thus creates a new type of axially movable, radially stable, and torsionally rigid support for the inner container in the outer container. Thanks to the ball and cardan joints, the diamond-shaped frame formed by the struts can compensate for length changes in the inner container, which manifest themselves in a movement of the convex cap perpendicular to the plane of the diamond. The struts create a temperature gradient across their length to thermally insulate the inner and outer containers. Furthermore, the strut frame engages the convex cap not in its center but around its circumference, resulting in extremely torsionally rigid support for the inner container in the outer container.

[0008] In a particularly advantageous embodiment of the invention, the rhombus is a square. This results in a symmetrical distribution of forces and movement in the support structure.

[0009] Preferably, each strut is connected to the respective cap at both ends via a ball joint, whereby torsional and bending forces on the struts can be minimized when using the frame they form.

[0010] It is particularly advantageous if each ball or universal joint comprises a first part mounted at the respective strut end and a second part articulated to it, mounted on the respective cap. Two second parts located at each corner of the diamond are rigidly connected to each other and mounted together on the respective cap. This means that only two parts need to be mounted on one cap and two parts on the other cap, which reduces the number of parts required and significantly simplifies production.

[0011] Preferably, two rigidly connected second parts can form an angle piece that is screwed, pressed, or welded to the respective cap. Such an angle piece reinforces and stabilizes the connection between the struts and the respective cap.

[0012] Preferably, the diametrical line between the first and second support structures is a longitudinal axis of the inner container, which runs through the apex of the convex cap. In an elongated inner container, the greatest thermal expansion is expected along the longitudinal axis, so the described floating bearing support structure is particularly useful there.

[0013] It is particularly advantageous if the rhombus concentrically surrounds the aforementioned diametrical line. This ensures symmetrical deflection of the struts when the inner container changes length and a movement of the cap along the longitudinal axis, so that the distance between the inner container and the outer container perpendicular to the longitudinal axis does not change.

[0014] Particularly good thermal decoupling between the inner and outer containers is achieved when the struts are made of a thermally insulating material. The struts can be manufactured particularly advantageously from fiber-reinforced plastic, particularly glass-fiber-reinforced plastic. This combines high thermal insulation with additional elasticity to absorb the thermal expansion of the inner container, as well as excellent strength for radial force absorption and torsional rigidity of the support structure.

[0015] The second support structure, which is opposite the first support structure serving as a floating bearing, can be designed as a simple fixed bearing. It can then preferably be used to guide at least one connecting line leading from the exterior of the container into the interior of the container.

[0016] The inner and outer containers can be made of any pressure- and low-temperature-resistant material, such as stainless steel. The inner and outer containers are preferably made of aluminum, which combines low weight with good pressure and low-temperature resistance.

[0017] The invention is explained in more detail below with reference to an embodiment shown in the accompanying drawings. In the drawings: Fig. 1 the container of the invention in a longitudinal section, wherein the first support structure serving as a loose bearing is shown only schematically; the Fig. 2 and3 the convex cap of the inner container and the support structure of the container serving as a loose bearing of Fig. 1 in a frontal view ( Fig. 2 ) or a perspective view ( Fig. 3 ); Fig. 4 Parts of one of the ball joints of the floating bearing of the Fig. 2 and 3 in a perspective view; and Fig. 5 one of the angle pieces of the floating bearing of the Fig. 2 and 3 with two partially shown struts connected by ball bearings in a perspective view.

[0018] Fig. 1 shows a container 1 for holding a cryogenic fluid. The cryogenic fluid can, for example, be hydrogen, which is at least partially liquefied at temperatures of up to -252 °C and below and a pressure of up to 16 bar - or more, depending on the container design - or a comparable cryogenic fluid that can be used for internal combustion engines or fuel cells, e.g. liquefied natural gas (LNG) with a temperature of up to -161 °C and below. The container 1 is mounted, for example, in the manner of a conventional fuel tank on the side of the chassis or frame of a commercial vehicle (not shown in detail), e.g. a truck (lorry) or passenger car (car).

[0019] However, the cryogenic fluid can also be a refrigerant, for example, liquid nitrogen, which is used to operate the cooling system of refrigerated trucks, e.g., food transporters. Accordingly, the container 1 can also be used for storing such refrigerants on trucks or truck trailers.

[0020] For thermal insulation of the cryogenic fluid from the external environment, the container 1 has a double-walled construction, namely an inner container 2 and an outer container 3 surrounding it on all sides with a distance A. The space 4 between the inner container 2 and the outer container 3 is usually evacuated, but can alternatively or additionally be filled with a thermally insulating material.

[0021] Since the cryogenic fluid in the inner container 2 is usually under pressure, (at least) the inner container 2 is designed as a pressure vessel made of metal, for example, stainless steel or aluminum. The outer container 3 can also be made of metal, but also of plastic, since it only has to withstand the ambient pressure compared to the vacuum in the intermediate space 4.

[0022] The inner container 2 has a generally cylindrical shell 5, which is closed at both ends by an outwardly convex cap 6, 7. The term "generally cylindrical" refers to a cylinder with any base or cross-sectional area, be it circular, oval, rectangular, square, square with rounded corners, or otherwise shaped. For maximum pressure resistance, the shell 5 and thus the inner container 2 have a circular cross-section.

[0023] The outer container 3 is essentially adapted to the outer shape of the inner container 2, while maintaining the all-round distance A to create the intermediate space 4. The outer container 3 is also composed, in particular, of a generally cylindrical shell 8 and two inwardly concave caps 9, 10 closing the shell at the ends. It is understood that the distance A does not have to be the same on all sides of the inner container 2. The caps 6, 7, 9, 10 are welded to the respective shell 5, 8, for example, by means of circumferential weld seams 11, 12.

[0024] For caps 6, 7, 9, and 10, any type of domed head with an outwardly convex curvature known in pressure vessel construction can be used, such as elliptical heads, dished heads, basket-arch heads, or the like. For caps 6, 7, 9, and 10, diffuser heads ("reverse-dished ends") can also be used, which have a centrally inwardly curved area surrounded by an outwardly curved edge area. Such diffuser heads are also subsumed here under the term "outwardly convex cap" due to their convex design, at least at the edges.

[0025] To establish the all-round distance A, the inner container 2 is supported on the outer container 3 via two support structures 13, 14, which engage on diametrically opposite sides of the inner container 2. To accommodate thermal changes in length of the inner container 2 in the direction of the diametrical axis D between the first support structure 13 and the second support structure 14, the first support structure 13 is a floating bearing in the direction of the diametrical axis D, i.e., it allows movement of the cap 7 in the direction of the diametrical axis D, while the second support structure 14 is a fixed bearing. Optionally, the second support structure 14 could also be such a floating bearing.

[0026] The Fig. 1 The first support structure 13, shown only schematically, is explained in detail below. The second support structure 14, if designed as a fixed bearing, can be formed, for example, by a sleeve 15 made of thermally insulating material, which tightly penetrates aligned openings of the inner and outer containers 2, 3 and can be used for the sealed passage of connecting lines 16 leading from the container exterior into the inner container 2 and there opening into, for example, a filling opening 17, a removal opening 18, a degassing opening 19, and a heat exchanger 20.

[0027] In the example shown, the two support structures 13, 14 are arranged on the end faces of the elongated inner container 2, so that the diametrical line D is simultaneously the longitudinal axis of the inner container 2. In the case of an inner container 2 that is rotationally symmetrical about its longitudinal axis, the longitudinal axis or diametrical line D passes through the apex S of the caps 6, 7. However, this is not mandatory: the support structures 13, 14 could also engage diametrically on other sides of the inner container 2 (provided the inner container 2 has an outwardly convex cap there for the first support structure 13, as explained further below), in which case the diametrical line D between the support structures 13, 14 no longer coincides with the longitudinal axis of the inner container 2.

[0028] The first support structure 13 serving as a loose bearing is in the Fig. 2 - 5 shown in detail. The construction depicted therein allows thermal expansion and contraction of the inner container 2, more precisely, a displacement of the convex cap 7 in the direction of the diametrical axis D relative to the second support structure 14 and thus relative to the outer container 3, while simultaneously absorbing radial forces normal to the diametrical axis D in the manner of a radial bearing. Furthermore, the support structure 13 is designed to be torsionally rigid, i.e., it prevents rotation of the cap 7 and thus of the inner container 2 about the diametrical axis D or longitudinal axis relative to the outer container 3.

[0029] The support structure 13 has four struts 21-24, which are assembled like a frame to form a rhombus (here: a square). Each strut 21-24 has two ends 21', 21"; 22', 22"; 23', 23"; 24', 24". The struts 21-24 represent the sides of the rhombus. At the corners 25-28 of the rhombus, the facing ends 21" / 22', 22" / 23', 23" / 24', and 24" / 21' of two adjacent struts 21-24 lie next to each other.

[0030] In the example shown, the rhombus formed by struts 21-24 is a flat rhombus, meaning all struts 21-24 lie in a common plane and are of equal length. However, this is not mandatory; struts 21-24 may not lie in a common plane, especially in the case of irregularly shaped caps 7, 10. In the example shown, the rhombus formed by struts 21-24 concentrically surrounds the diametrical line D and the apex S of cap 7.

[0031] The struts 21-24 are in the form of, for example, rods, bars, strips, or bands and are made of a heat-insulating material, e.g., plastic. In particular, the struts 21-24 are each made of a rod or strip of fiber-reinforced plastic, e.g., glass-fiber-reinforced plastic. For example, resin-impregnated, cured fiber mats, e.g., woven, knitted, or non-woven fabrics made of glass, carbon, basalt, and / or stone fibers, etc., can be used for this purpose. These mats are punched, cut, pressed, formed, injection-molded, etc., to form the struts 21-24.

[0032] The ends 21", 22', 23", 24' of the struts 21 - 24 located at one of the two diagonally opposite corners 25, 27 of the rhombus are each connected to the concave cap 10 via a ball joint 29, 30, 33, 34, and the ends 24", 21', 22", 23' of the struts 21 - 24 located at the other two diagonally opposite corners 26, 28 of the rhombus are each connected to the convex cap 7 via a ball joint 31, 32, 35, 36.

[0033] Of the two ball joints 36 / 29, 30 / 31, 32 / 33, 34 / 35, which are each located at the ends 21' / 21", 22' / 22", 23' / 23", 24' / 24" of one and the same strut 21 - 24, one of each can be a universal joint (two degrees of freedom) instead of a ball joint (three degrees of freedom), if desired.

[0034] Each ball or universal joint 29 - 36 is composed of two parts which are connected to one another in an articulated manner, namely a first part A which is mounted on the respective strut end 21' - 24', 21" - 24" and a second part B which is connected to the respective cap 7 or 10 in an articulated manner.

[0035] Fig. 4 shows an example of a ball joint 29 - 39 with a first part A in the form of an eye 37 with a stem 38, which is firmly connected to the respective end 21' - 24', 21" - 24", e.g. clamped, pressed, glued, screwed, welded, integrally formed, etc. The eye 37 has a spherical opening in which a ball 39 is rotatably and pivotably mounted. The ball 39 has a central bore 40, through which a bearing pin 41 of an angle piece 42 ( Fig. 5 ) or 43 ( Fig. 3 ) is passed through.

[0036] The ball 39 with its opening 40, and if applicable the respective angle piece 42, 43 with the bearing pin 41, forms the second part B of the ball joint 29 - 36 in the example shown.

[0037] In the case of the ball joints 29, 30, 33, 34, the angle piece 42 is firmly connected to the concave cap 10, e.g., clamped, pressed, glued, screwed, welded, formed as a single piece, etc. For example, the angle piece 42 has a bore 44 through which it can be screwed to the cap 10 using screws (not shown). In the case of the ball joints 31, 32, 35, 36, the angle piece 43 is firmly connected to the convex cap 7, e.g., clamped, pressed, glued, screwed, welded, formed as a single piece, etc. In the example shown, the angle pieces 43 are welded to the convex cap 7.

[0038] In the example shown, two ball joints 29 / 30, 31 / 32, 33 / 34, 35 / 36 each share a common second part B, i.e. (at the corners 25 and 27) an angle piece 42 with two bearing bolts 41 attached to it at an angle or (at the corners 26 and 27) an angle piece 43 with two bearing bolts 41 attached to it at an angle. It is understood that alternatively each ball joint 29 - 36 could have its own second part B, i.e. can be attached to the respective cap 7, 10 via its own angle piece 42, 43.

[0039] The invention is not limited to the embodiments shown, but includes all variants, modifications and combinations thereof that fall within the scope of the appended claims.

Claims

1. Container for holding a cryogenic fluid, comprising an inner container (2) with at least one outwardly convex cap (7) and an outer container (3) with at least one inwardly concave cap (10), wherein the inner container (2) lies in the outer container (3) with a distance (A) on all sides, the convex cap (7) projects into the concave cap (10) and the inner container (2) is supported on the outer container (3) via a first support structure (13) and a second support structure (14) which engages the inner container (2) diametrically opposite the first support structure (13), characterized in thatthe first support structure (13) has four struts (21-24) forming a rhombus, the ends (21", 22', 23", 24') of which are located at one of the two diagonally opposite corners (25, 27) of the rhombus are connected to the concave cap (10) and the ends (22", 23', 24", 21') of which are located at the other two diagonally opposite corners (26, 28) of the rhombus are connected to the convex cap (7), each strut (21-24) being connected at one of its ends (21', 22', 23', 24') via a ball joint (29-36) and at its other end (21", 22", 23", 24") via a ball or cardan joint (29-36) to the respective cap (7, 10).

2. Container according to claim 1, characterized in that the rhombus is a square.

3. Container according to claim 1 or 2, characterized in that each strut (21 - 24) is connected at its two ends (21', 21", 22', 22", 23', 23", 24', 24") to the respective cap (7, 10) via a ball joint (29 - 36).

4. Container according to one of claims 1 to 3, characterized in that each ball or cardan joint (29 - 36) comprises a first part (A) mounted on the respective strut end (21', 21", 22', 22", 23', 23", 24', 24") and a second part (B) articulated thereto and mounted on the respective cap (7, 10), wherein two second parts (B) located at a corner (25 - 28) of the rhombus are rigidly connected to one another and mounted together on the respective cap (7, 10).

5. Container according to claim 4, characterized in that two rigidly connected second parts (B) each form an angle piece (42, 43) which is screwed, pressed or welded to the respective cap (7, 10).

6. Container according to one of claims 1 to 5, characterized in that the diametrical line (D) between the first and second support structure (13, 14) is the longitudinal axis of the inner container (2), which runs through the apex (S) of the convex cap (7).

7. Container according to claim 6, characterized in that the rhombus concentrically surrounds the diametral (D).

8. Container according to one of claims 1 to 7, characterized in that the struts (21 - 24) are made of a thermally insulating material.

9. Container according to claim 8, characterized in that the struts (21 - 24) are made of fiber-reinforced plastic, preferably of glass-fiber-reinforced plastic.

10. Container according to one of claims 1 to 9, characterized in that the inner container (2) and the outer container (3) are made of aluminum.

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