STORAGE TANK FOR CRYOGENIC LIQUID

Abstract

A storage tank for cryogenic liquid having an outer tank constructed of a rigid material and an inner tank contained within and spaced inwardly from the outer tank. A first fill line for cryogenic liquid has a first end open exteriorly of the outer tank and a second end open inside the inner tank. The first fill line is fluidly sealed to both the inner tank and the outer tank and the first fill line has a first predetermined flow rate at a set filling pressure. A valve is associated with the first fill line to selectively open and close the first fill line. A second fill line for cryogenic liquid has a first end open exteriorly of the outer tank and a second end open inside of the inner tank. The second fill line has a second predetermined flow rate at the predetermined filling pressure. Furthermore, the first and second lines are sized so that the first flow rate is several times the second flow rate.

Claims

1. A storage tank for cryogenic liquid comprising: an outer tank constructed of a rigid material, an inner tank contained within and spaced inwardly from said outer tank, a first fill line for cryogenic liquid having a first end open exteriorly of said outer tank and a second end open inside said inner tank, said first fill line being fluidly sealed to both said inner tank and said outer tank, said first fill line having a first predetermined flow rate at a predetermined filling pressure, a valve associated with said first fill line to selectively open and close said first fill line, a second fill line for cryogenic liquid having a first end open exteriorly of said outer tank and a second end open inside said inner tank, said second fill line having a second predetermined flow rate at said first predetermined filling pressure, wherein said first flow rate is several times said second flow rate.

2. The invention as defined in claim 1 wherein said second end of said first fill tube is positioned adjacent a bottom of said inner tank.

3. The invention as defined in claim 2 and comprising at least one flow baffle contained in said inner tank.

4. The invention as defined in claim 3 and comprising at least two baffles contained in said inner tank.

5. The invention as defined in claim 1 and comprising a valve arrangement to fill and discharge the inner tank through said second fill line.

Description

BRIEF DESCRIPTION OF THE DRAWING

[0013] A better understanding of the present invention will be had upon reference to the following detailed description when read in conjunction with the accompanying drawing, wherein like reference characters refer to like parts throughout the several views, and in which:

[0014] FIG. 1 is a front view illustrating a preferred embodiment of the storage tank of the present invention;

[0015] FIG. 2 is a longitudinal sectional view thereof; and

[0016] FIG. 3 is an elevational sectional view thereof.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE PRESENT INVENTION

[0017] With reference to the drawing, a preferred embodiment of a cryogenic storage tank 10 according to the present invention is shown. The cryogenic storage tank 10 stores cryogenic liquid, such as liquid nitrogen, for many different purposes. One such purpose, for example, is to provide the liquid nitrogen to cryogenic freezers of the type used to store biological specimens.

[0018] The cryogenic storage tank 10 includes an outer tank 12 which is generally cylindrical in shape having a closed top 14 and closed bottom 16. The outer tank 12 is typically constructed of stainless steel although other materials may be used without deviation from either the spirit or scope of the invention.

[0019] With reference now to FIG. 2, the cryogenic storage tank 10 includes an inner tank 18. The inner tank is completely contained within the interior of the outer tank 12. The inner tank 18 is generally cylindrical in shape and

[0020] an inner tank 18 is contained within the interior of the outer tank 12. This inner tank 18 is also preferably made of stainless steel and is spaced inwardly from the outer tank 12. As such, a space 20 is created between the inner tank 18 and the outer tank 12. In the conventional manner, this storage space 20 is typically evacuated and/or filled with a thermal insulating material.

[0021] As best shown in FIGS. 1 and 2, a conventional valve assembly 22 is mounted to the top 14 of the outer tank 12. This valve assembly 22, furthermore, is fluidly connected by a fluid line 24 which is open at its lower end 26 adjacent a bottom 28 of the inner tank 18.

[0022] The valve assembly 22 is conventional in construction and includes various valves to not only monitor, but also release excess pressure from the interior of the inner tank 18. The valve assembly 22 is also fluidly connected to supply cryogenic liquid to the cryogenic freezer 30, or other cryogenic equipment, by a supply line 32.

[0023] In operation, only a small volume of cryogenic liquid from the interior of the inner tank 18 is used to supply the cryogenic equipment 30. As such, only a very small flow rate of the cryogenic liquid from the inner tank 18 is required to operate the cryogenic equipment 30. Consequently, the supply line 32 typically has a very small diameter, e.g. one quarter of an inch.

[0024] Although the cryogenic tank 10 may be refilled with the cryogenic liquid by fluidly connecting a source of cryogenic liquid to the valve assembly 22 and ultimately to the small diameter tube 24, the fill time required for the cryogenic tank 18 is very slow. In order to provide a rapid fill for the inner tank 18 of cryogenic liquid, a second fill line 50 has one end which extends outwardly from the top 14 of the cryogenic outer tank 12. The second fill line 50, furthermore, extends through both the outer tank 12 and inner tank 18 and has an inner end 52 adjacent the bottom of the inner tank 18. A conventional fluid valve 54, furthermore, is fluidly connected in series with the second fill line 50 and further provides the benefit of being able to supply and refill the tank concurrently.

[0025] The second fill line 50 has an inside diameter greater than the inside diameter of the primary or first fill/supply line 24. As such, the cross sectional area of the interior of the supply line 50 is several times the cross sectional area of the first supply line 24. This greater area, furthermore, allows a much greater flow rate through the second supply line 50 than the first supply line 24 with pressure provided by the refill source 60.

[0026] With references no to FIG. 3, the cryogenic storage tank 10 includes baffles 56. The baffles 56 are generally disc shaped and are contained with the inner tank 18

[0027] As best shown in FIG. 3, one or more liquid baffles 56 are contained within the interior of the inner tank 18 and are axially spaced from each other. These baffles 56 include through openings 58 to minimize sloshing of the cryogenic liquid during a refill operation.

[0028] In operation, when refilling of the cryogenic tank 10 is required, a refill source 60 of cryogenic liquid is first fluidly connected to the second fill line 50. Thereafter, the valve 54 is open and which allows the cryogenic liquid from the refill source 60 to flow through the second refill line 50 and into the interior of the inner tank 18.

[0029] Any conventional means, such as valving on the valve assembly 22, may be used to determine when the inner tank 18 is filled. Once this occurs, the valve 54 is closed and the refill source 60 disconnected from the second line 50.

[0030] Since the inside diameter of the second refill line 50 is greater, and preferably several times greater than the primary refill/supply line 24, a refilling of the inner tank 18 may be rapidly accomplished in a few minutes.

[0031] From the foregoing, it can be seen that the cryogenic storage tank of the present invention provides a storage tank which enables rapid refilling of the storage tank as required. Having described my invention, however, many modifications thereto will become apparent to those skilled in the art to which it pertains without deviation from the spirit of the invention as defined by the scope of the appended claims.