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Title:
REFRIGERATED SHIPPING CONTAINER
Document Type and Number:
WIPO Patent Application WO/1995/015866
Kind Code:
A1
Abstract:
A refrigerated, thin-walled shipping container (8) including a horizontal dividing element (20) forming a compartment (22) for holding CO2 snow created by passing liquid CO2 through manifold (24) along at least one side of the compartment and spraying the CO2 snow against the opposite wall. The charging of the cooling compartment generates gas pressure, and the combination design of the charging manifold and pressure release vents allows the operation to be performed without excessive structural damaging pressure buildup.

Inventors:
THOMSEN VAN E (US)
Application Number:
PCT/US1993/012443
Publication Date:
June 15, 1995
Filing Date:
December 21, 1993
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
THOMSEN VAN E (US)
International Classes:
B60H1/32; F25D3/12; (IPC1-7): B60H3/02; F25D3/12
Foreign References:
US4593536A1986-06-10
US4704876A1987-11-10
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Claims:
Claims
1. A lightweight thinskinned insulated container for transporting frozen goods comprising: a floor, side walls and end walls, each being insulated and having an interior surface permitting the passage of air between the surface and goods placed thereagainst, at least one of the end walls including a closed opening for entrance and egress wherein the closure is insulated and has a conforming interior surface, an insulated top closure, a horizontal barrier forming a separate compartment within the container spanning the distance between the walls intermediate the floor and the top closure, said barrier including a plurality of vents along each of the side walls, a distribution system including C02 snow generating nozzles within the separate compartment along at least one wall, said distribution system adapted to spray C02 snow upwardly and inwardly of the container whereby the vents adjacent the distribution nozzles remain open to permit the escape of flash gasses released during the introduction of the C02 snow.
2. A container as in Claim 1, wherein a vertical barrier is located intermediate the side walls extending the length of the container, dividing the separate compartment into two discrete spaces, and wherein the distribution system extends along each side wall.
3. An insulated container including: side walls, end walls, floor, a ceiling and at least one access door, a horizontal element dividing the container into an upper refrigeration compartment and a lower storage area, a manifold including orifices running the length of the refrigeration compartment adjacent one wall, said orifices oriented to direct the flow of gas escaping therefrom simultaneously toward the opposite wall and the ceiling; vents along each side wall extending through the horizontal element to permit passage of flash gas during the charging of the refrigeration compartment and cooling gas during use, said walls, floor and horizontal element being configured to allow passage of cooling fluid even when the cargo is stacked in contact therewith, and venting means to allow the escape of spent gasses.
Description:
Description

REFRIGERATED SHIPPING CONTAINER

This application is a continuation-in-part application of U.S. Patent Application Serial No. 08/042,891 filed March 24, 1993 which is a file wrapper continuation application of a continuation-in-part application. Serial No. 800,881, filed November 27, 1991 from original U.S. Patent application Serial No. 593,771, filed October 5, 1990.

Technical Field

This invention is directed to refrigerated shipping containers and, more particularly, to a lightweight, thin-skinned container which is capable of maintaining frozen products in a frozen state for several days through the use of carbon dioxide snow and includes a particular apparatus and method for charging the container with carbon dioxide snow without blocking the vents and thus letting the flash gas escape.

Background Art

Carbon dioxide is utilized as a refrigerant in this invention rather than other cryogenic products such as nitrogen or oxygen because, unlike other cryogenic products that exist in only two states, liquid and gaseous, carbon dioxide exists in three forms — liquid, solid and gas. In the solid state, carbon dioxide can be fixedly located or contained to give the cooling effect required. It would be virtually impossible to contain cryogenic products in either liquid or gaseous states in a transportation vehicle.

A study conducted by the American Frozen Food Institute to find an alternative to mechanical methods of refrigeration which require extensive maintenance and labor intensive monitorings concluded that cryogenics.

and especially carbon dioxide, would be a suitable alternative. The Institute created the first prototype railcar utilizing a series of C0 2 tanks placed beneath the floor of the railcar. The carbon dioxide was piped to each end of the railcar and connected to two orifices at each end wall near the ceiling. It was theorized that with the addition of temperature-sensing devices contained within the product environment, injection nozzles triggered by the rising temperature of the product contained therein would be activated and the carbon dioxide in the solid form (snow) would be sprayed upon the product. Because of the direct contact of the CO 2 snow to the product, the temperatures were not uniform and the products that directly contacted the solid CO 2 had a very low temperature and thus certain products would become very brittle. There was also the problem of freezer burn.

In order to keep the solid carbon dioxide from coming into contact with the products contained within the shipping enclosure, the design disclosed in Fink et al, U.S. Patent No. 4,593,536, was developed. This patent utilizes a compartment along the top region of the railcar where the carbon dioxide is deposited in the solid form (snow) and held in reserve. The compartment is able to hold enough of the solid carbon dioxide to last many days. It was therefore possible to charge the car with the amount of snow at the loading location to complete a trip without needing an additional charge, eliminating the need to carry an additional supply of liquid carbon dioxide in the railcar. Sublimation vents were provided along one side wall adjacent to the liquid manifold to allow the sublimation gasses to enter the compartment below to provide the required refrigeration. These vents in the bunker compartment also provide a pressure relief for the flash gasses which are created in the transition from liquid to snow. The cold sublimated gasses theoretically would flow out of these

vents, down the side wall in fluted panels that were provided, across the floor and upwardly in the flutes of the opposite side wall. Because carbon dioxide is heavier than air, the cold gasses did not effectively flow up the opposite side wall, but instead exited down the floor areas to the vents that carried the gasses to the outside, this uneven flow left areas in the compartment not effectively cooled.

A design disclosed by Hill, U.S. Patent No. 4,704,874, theorized that by having a center discharge manifold and providing sublimation openings in the bunker along both side walls and along the end walls, the sublimated gasses would completely envelope the product. The flow of these sublimated gasses down all walls was then channeled along the floor of the compartment. These channels were created by aluminum T- bea s running the length of the rail car which then collected the cold gasses and routed it to a discharge duct to the exterior of the railcar. Because of a basic knowledge that certain perishable products could not be allowed to be contacted by carbon dioxide vapors, and especially those products that require oxygen to exist, an alteration to the previous designs was suggested by Moe, U.S. Patent No. 4,761,969. Moe disclosed a design that was able to operate in a plurality of modes for this purpose. This design was to create the carbon dioxide snow and store it in a flexible bladder located in the bunker compartment. The gasses produced were to be released through a bladder vent and therefore keeping these vapors channeled through the container, not coming in contact with the inner loaded compartment, therefore acting in a manner such as an ice bag. This design has yet to be produced and it is doubtful that any material which could be made into a bladder would be able to withstand the very low temperature of solid carbon dioxide.

Thomsen, Patent No. 4,891,954, was designed to alleviate the problems that have plagued all previous approaches and to control the tremendous pressures that are created in the loading process whereby liquid carbon dioxide is being forced through a small orifice to create the solid form (snow) . The pressure at which liquid carbon dioxide exists in a standard storage vessel and is subsequently transported into the manifold of the storage compartment is approximately 300 p.s.i.g. For each 100 pounds of liquid carbon dioxide that is transformed from a liquid into a solid, only 46.5% becomes the solid and the remainder becomes flash gas. It is this flash gas at the extremely high pressure that is generated during the loading cycle that must be able to exit the bunker compartment, to eliminate the possibility of exploding the bunker or destroying the integrity in the metal in the roof of the vehicle. By creating additional relief ports directly below the center manifold, it was theorized that the snow would be blown toward each wall, therefore allowing at area below the manifold to relive this flash gas pressure.

This design certainly did seem to alleviate the previous problems encountered in the design of the railcars because of their integral strength, but utilizing this same procedure in the manufacture of shipping containers failed drastically. The present invention is directed toward the alleviation of the problems of the flash gas build-up associated with all the previous inventions so that can be successfully utilized in not only railcars but also in ocean shipping containers and trailers.

Disclosure of the Invention

In accordance with the present invention, a carbon dioxide cryogenic refrigeration material is utilized to maintain the required result in keeping the stored products adequately refrigerated. The present

invention includes an insulated lightweight container, intermodal or trailer having a floor, a ceiling, side walls, end walls and loading doors. The side walls determine the length of the container and the end walls being the width. The loading doors could be located in either end wall, or in the side walls. A bunker is provided as a separation of the lower main storage area and the storage area for the snow formed from the cryogenic carbon dioxide. This bunker is a means of supporting the supply of snow and to provide release areas to relieve the sublimated gasses and the flash gas. A plurality of apertures extending through this bunker adjacent to the side walls permit the flow of sublimated gasses from the bunker area to the fluted side walls and also into channels in the floor of the bunker. Each bunker panel has at least one, and preferably two, apertures adjacent each side wall to release those sublimated gasses and flash gasses. These apertures are covered with 1/4-inch stainless steel wire mesh.

In the previous designs that have all been constructed to be used with railcars, it has never been possible to see into the bunker area while charging the compartment with carbon dioxide, therefore it has not been possible to determine exactly the direction of flow or dispersement of the snow. The construction of intermodal containers, using the same center manifold as mentioned in the Hill, Moe, and the previous Thomsen patents, generated the same problems as existed with all previous units designed. The pressure created by the flash gas (up to 300 psi) tends to blow out the bunkers and/or seriously distort the metal in the roof. Even with the relief ports as mentioned in the Thomsen patent, the pressure created is not tolerable. With railcars being constructed with very heavy gauge materials, it is not as critical. However, the shipping containers and trailers are constructed with a maximum

of 14-gauge material and thus are not able to withstand the pressure. The loading doors of a shipping container are located in the rear end wall, making it possible to remove an end bunker compartment and allow visible inspection of the charging procedure. It was determined that, with the center manifold having orifices on each side, the snow was directed to each side wall and the snow in combination with the pressure created by the flash gas completely clogged the apertures that were designed to relieve this pressure, including those center relief ports as described in the Thomsen patent. In order for gasses to penetrate the snow bank being formed above each relief aperture, the snow would have to have a consistency of no more than 30 pounds per cubic foot. The pressure generated by the flash gas, up to 300 psi, however, forced the snow to these points at substantially higher pressure than this and therefore restricted the access of the flash gasses, creating enough pressure to blow out the bunker and distort the metal roof.

As described in the present invention, the manifold with the orifices to discharge the snow is located adjacent to one side wall and directly above the apertures in the bunker. The orifices are therefore directed to the opposite side wall. The snow bank is created at the opposite side wall building backwards toward the manifold.

It is an object of the present invention to provide a manifold and discharge orifice combination for charging containers with CO 2 snow such that the snow freefalls and does not become compacted.

Another object of the present invention is to provide a bunker for supporting and storing CO 2 snow wherein the placement of the charging orifices, the vents and the discharge is such that complete charging and uniform distribution of the cold gas is readily achieved.

Yet another object of the present invention is to provide a shipping container wherein the snow supporting bunker is reinforced, greatly reducing the possibility of structural failure while segregating the snow storage space to improve the efficiency and reduce charging time.

Yet another object of the present invention is to provide a thin-skinned intermodal container such that, knowing the dimension of the container, the amount of insulation and by controlling the sublimation, the container can be charged in the correct amount of CO 2 snow to maintain the desired temperature for the duration of the trip.

Still a further object of the present invention is to provide a container for containing and shipping frozen goods wherein the desired temperature is maintained through the controlled sublimation of CO 2 snow.

Brief Description of the Drawings

Figure 1 is an isometric view of the exterior of a container such as contemplated in the present invention.

Figure 2 is a vertical section through the end of a typical container.

Figure 3 is a plan view of a typical bunker section.

Figure 4 is a vertical view of the bunker of Figure 6. Figure 5 is a vertical view of a typical wall.

Figure 6 is a end view of the wall of Figure 8.

Figures 7, 8 and 9 depict a proposed venting system for a cargo container. Figure 10 is a vertical section through the container illustrating an alternative charging and distribution system including a structure for

segregating the snow-containing space and improving the structural integrity of the unit.

Figure 11 is an alternative charging manifold configuration. Figure 12 is an enlarged view of a gas diffuser.

Figure 13 is an alternative end wall configuration for use in the inventive container.

Figure 14 is a vertical section through the vent structure.

Best Mode For Carrying Out the Invention

As seen in Figure 1, an intermodal shipping container 8 is shown having a pair of front loading doors 18.

Reference is now had to Figure 2 which is a sectional view through the container of Figure 1. The interior of the container 8 includes a fluted floor, preferably aluminum 10, fluted fiberglass side panels 14 and a fiberglass overhead bunker 20 forming a compartment 22 into which the CO 2 snow may be blown. The upper portion of bunker 22 will be faced with a reflective material. The snow is forced into the bunker by means of a manifold pipe 24 having a plurality of nozzle orifices which direct the snow toward the opposite side of the bunker and slightly toward the ceiling. Also seen in this view are the end panels 16, flash gas relief vent 23 as explained hereinafter, and drain members 15. As seen in Figures 3 and 4, the fiberglass bunker 20 includes flanges 27 for resting on top of the walls 14 and also includes vents 25 to allow the cold air to move downwardly into the main compartment. Side wall 14, as seen in Figure 5, likewise includes outwardly projecting elements 2 to hold the cargo somewhat spaced from the wall allowing circulation of the cold air.

Because of the requirements of shipping containers, as set by the International Standards Organization (ISO) , in that the containers be of prescribed dimensions, the vent, as seen as 23 in Figure 1, is also depicted as 23 in Figure 8, which includes the actual opening which is closed by door 30 having an opening so that gauges 17 may be viewed with the door closed. It is to be noted that the door 30 also includes a plug member 34 for filling the opening 23. In order to charge the container, the gaseous CO 2 is pumped into openings 36 and is carried by manifold 24 upwardly to be released as snow in the cargo compartment. As will be obvious, flash gas formed during the charging of the bunker will be able to escape through opening 23, but once the container is fully charged, then door 30 will be closed, sealing opening 23.

Figure 10 depicts the way that the solid CO 2 snow would be formed in the space above the bunker 20, impinging against the divider 13, forming a mound of snow which would then move backwardly toward the nozzle, keeping the vents 25 open for the maximum amount of time, preventing undue pressure and reducing, if not limiting the risk of damaging the container. Figure 11 depicts a plan view of the inventive container showing a vertical section of conduit 40 in communication with two horizontally placed, outwardly extending conduits 42, which in turn are connected with conduits 44 extending the length of the container. A plurality of nozzles 46 are distributed along the length of the container which, as pointed out hereinabove, extend outwardly and upwardly, impinging the CO 2 snow against the barrier 13. As seen in this view and as seen more clearly in Figure 12, the nozzles 46 include a gas diffuser 48 which is in the form of a truncated cone. The nozzle 46 has a vertical vent 50, allowing some of the flash gas to escape upwardly and be

diffused rearwardly, whereas the CO 2 snow exits through the end of the nozzle as at 52 and is projected across the container to impinge against barrier 13.

Figure 13 depicts an alternative end wall system, including vertical support members 54 intersected by angle support members 56, which terminate adjacent the upper portion of the container, giving additional strength and reserving a place for the vent 58, which as explained hereinbefore and described in greater detail hereinafter, allows for the venting of gases during the sublimation and cooling of the product. The warm gases from the floor move up the interior side of the hull and when the pressure is great enough to release the magnetic catch, exit to the atmosphere. As seen in Figure 14, vent 58 is closed by a door 60 having insulation 62 and a hinge 64 at the upper portion thereof. In addition to the sealing gaskets, the lower portion of the door includes a magnetic strip interaction to keep it closed until sufficient internal pressure is reached.