Holding Container for Cryogenic Liquid

(1.) Field of the Invention

The present invention concerns holding containers for cryogenic liquids of the type comprising an inner casing and an outer casing defining an insulating inner space therebetween and a cryogenic liquid withdrawing pipe in the inner casing including a first portion extending into the inner space between a lower portion of the inner casing and an upper portion of the outer casing, for example, holding containers for distributing liquid nitrogen in particular, which are made self-pressurizable by means of said withdrawing pipe.

(2.) Description of Prior Art

In order to provide a gaseous phase at the outlet of a cryogenic liquid withdrawing pipe, the first portion, or internal portion of the pipe includes a section which is in heat exchange contact with the outer casing at least partially to vaporize the liquid which is withdrawn from the inner casing. Depending on the materials of which the outer casing and the pipe are made, joining of the section and the outer casing by brazing, welding or gluing would cause certain problems, for example deformation of the outer casing, and significantly increases the manufacturing cost.

It is an object of the present invention to provide a holding container for cryogenic liquid of rugged and simplified construction, of reduced manufacturing cost and enabling a large scale of choice of materials of the constitutive elements depending on needs and uses.

For this purpose, according to a characteristic of the invention, the first portion of the pipe includes a section which is kept in resilient contact against the inner face of the outer casing. Typically, this section comprises at least one spiral turn, resilient means cooperating with the spiral turn to tend to produce a radial opening of the latter and therefore to keep it applied against the outer casing.

With such an arrangement, heat exchange contact is maintained notwithstanding the materials with which the pipe and the outer casing are made, and this arrangement enables to highly limit the transmission of shocks or vibrations between the outer casing and the inner casing therefore ensuring an increased life to the holding container.

According to another characteristic of the invention, if for example for considerations of total weight, the withdrawing pipe is made of a light alloy, for example, of aluminum, care should be exercised with such materials that are good heat conductors, to limit heat losses by direct conductivity between the inner casing and the outer casing. For this purpose, according to another characteristic of the invention, the first portion of the withdrawing pipe is connected to an end portion by means of a section of a material with lesser heat conductivity, for example a plastic material.

Other characteristics and advantages of the present invention will appear from the description which follows of an embodiment given by way of illustration without limitation, with reference to the annexed drawings in which:

FIG. 1 is a schematic view in half longitudinal cross-section of a self-pressurizable cryogenic holding container according to the invention;

FIG. 2 is a perspective view of the contact section of the first portion of the withdrawing pipe of the holding container of FIG. 1.

There is illustrated in FIG. 1 a cryogenic container 1 of the self-pressurizable type for the distribution of liquid nitrogen, comprising in known manner an inner casing 2 constituting a holding container for the cryogenic liquid, and an outer casing 3 spaced from the casing 2 to provide an inner space 4 therebetween enabling to provide a multilayer insulation 5 applied against the inner casing 2, the inner space 4 being placed under vacuum by suction through a closeable connector 6. An adsorbing product 7 is advantageously placed in the inner space 4 to catch residual gases that may be present.

In the embodiment illustrated in FIG. 1, the inner casing 2 and the outer casing 3 are both made of aluminum starting from a sleeve 11, 12 and a bottom 13, 14 respectively mounted thereon by welding. The sleeve 12 of the outer casing 3 is advantageously provided with reinforcing ribs 15a, 15b, 15c.

Also in known manner, the holding container comprises a neck 21, typically formed of a tubular element of fiberglass reinforced epoxy resin, which is glued in neck portions of reduced diameter of casings 2 and 3 and joined at the end for example by gluing to a solid element of aluminum 22 having an upper face enabling to receive a plug and a radial duct 24 defining the downstream end of a pressurizing circuit 25 comprising an outer pipe 26 provided with a valve 27 extending between the inlet 24 and a nipple connector 28 of the outer casing 3. The pressurizing circuit comprises an internal part 29, extending into the inner space 4 from the connector 28 to the lower zone of the holding container by first running along, at 30, an internal generating line of the outer casing 3 and providing, in the vicinity of the bottom of the holding container, at least two spiral turns 31, 32, advantageously disposed in one of the ribs (15a) of the outer casing, and which are maintained permanently resiliently pressed against the inner face of the outer casing as will be seen later. If, as illustrated in the example, pipe 29 is made of a material with a good heat conductivity, for example aluminum, the lower end of the pipe portion 29 is connected to a tubular section 33 of a material having a low heat conductivity, for example a plastic material such as a fiberglass reinforced epoxy resin, whose both ends are respectively fixed in a nipple connector 36 to pipe 29 and to nipple connector 37 at a curved end section 38, which itself is connected to a connector 39 which is unitary with the bottom 13 of the inner casing 2.

As better illustrated in FIG. 2, the application under pressure of each spiral turn 31, 32 against the inner face of the outer casing 3 is ensured by at least one resilient spring 41, 42, acting between opposed portions of the spiral turn so as to have a tendency to provide a radial opening of the latter, the anchoring of the ends of the spring on one spiral turn being ensured by self-blocking studs 43, 44.

To use the cryogenic container which has just been described, instead of a plug used for obturation during transportation and storage, there is mounted a tapping device 52 including a dipping tube 53 extending to the vicinity of the bottom of the inner casing 2 and which frees the radial duct 24 towards the gaseous atmosphere of the inner casing 2. To pressurize the holding container, it is then sufficient to open valve 27, which permits to inject gas under pressure withdrawn by circuit 25 into the gaseous atmosphere of the container. The withdrawn cryogenic liquid is then vaporized upon contact with the outer casing 3 at the level of the spiral turns 31 and 32. The withdrawing device 52 additionally comprises a valve 54 for withdrawing cryogenic liquid from the inner casing 2 via dipping tube 53.

In the embodiment represented in FIG. 1, the outer casing 3, the inner casing 2 and the pipe portion 29, and the final section 38 are made of aluminum, the pipe sections being sealingly connected to the connectors 28, 36 and 37 by gluing. As a variant, the pipe portion 29 can be made of stainless steel in which case the tubular section of insulating material 33 can be removed, the stainless steel tube being fixedly mounted on the connectors 28 and 39 by gluing or brazing. Instead of the tubular portion 29 of aluminum, a tubular portion of copper may also be used, which also requires the use of the insulating section 33. Also as a variant, at least the inner casing, as well as advantageously the withdrawing tube may be made of stainless steel. Finally, the holding container according to the invention enables to produce the inner and outer casings as well as the withdrawing tube of plastic material, for example of fiberglass reinforced epoxy resin or polycarbonate.