Dry ice cooler

Information

  • Patent Grant
  • 6212901
  • Patent Number
    6,212,901
  • Date Filed
    Saturday, June 26, 1999
    25 years ago
  • Date Issued
    Tuesday, April 10, 2001
    23 years ago
Abstract
A cooler with a chamber and a cavity in its lid, into which cavity a block of dry ice is inserted. Heat transfers from the chamber through a heat transfer element connecting the chamber to the cavity. The rate of this heat transfer is regulated by covering or uncovering the heat transfer element on the chamber side.
Description




FIELD OF THE INVENTION




Coolers, that is, containers that maintain a lower temperature than the surrounding atmosphere.




BACKGROUND OF THE INVENTION




The earliest cooler may have been a shaded basket. Since then dramatic improvements have been made to the design. These improvements stem from three basic technological advances: Availability of insulating materials, better manufacturing, and the ability to pump heat from liquids or gases which are then used to keep the inside of the container cool.




Insulating materials that are available all reduce heat transfer between their sides, and are built to suit their intended uses. These materials include walls separated by vacuum (to prevent convection) or a solid foam or simply by air. They likewise may include reflective surfaces (to reflect radiated heat).




Construction advances allow the insulating material to fit seamlessly to become a container. Construction also makes coolers practical in a wide variety of uses, despite the relative fragility of insulating materials, because the insulating material is housed in excellent casings.




Cold materials, including most commonly ice, are then put into the cooler to maintain the lower temperature. The cold material will be at a lower temperature than the atmosphere surrounding the cooler. When heat gets through the insulating material into the cooler, raising its temperature, the cold material absorbs that heat. The cooler will therefore reach a stable temperature lying between that of the outside atmosphere and that of the cold material. Where exactly the temperature lies in that range depends on several factors including contents of the cooler, efficacy of the insulating material, and surface areas.




The most effective cold materials are not only cold, but have had the latent heat of a state change extracted from them. For example, to become ice the latent heat of freezing is extracted from water. Thus, the best cold materials change state as they absorb heat Most often this means that they melt, but they may also liquify or even sublimate.




This is only one major problem with ice. It turns back to water, which floods the cooler, and makes it difficult for the remaining ice to keep the cooler cold. The second major problem with ice is that it is not cold enough. That is, because it changes state at 0° Celsius (32° Fahrenheit), this (and only rarely lower) is the temperature that it draws the cooler toward. As explained above, the cooler generally does not reach the temperature of the cold material; and thus, when cooled by ice, the cooler will not keep frozen foods frozen.




The problem that ice turns to water (spillage) has been inadequately solved several ways, including holding the ice within its own container, which reduces its surface area and cooling properties. The relative warmth of ice's freezing point has not been solved.




Colder materials, that is, materials that change state at lower temperatures, obviously will hold the cooler colder. For example, dry ice sublimates at −77.2° Celsius (−107° Fahrenheit). This takes care of any problems with messy melted dry ice spillage but produces CO


2


, which is corrosive.




Another problem with dry ice is too much cooling ability. It can drop temperatures below freezing, as follows from the explanation above, which might be colder than desired. A related problem is its uneven cooling; that is, as a block of dry ice, such as that produced by U.S. Pat. No. 5,528,907, which is incorporated by reference for its information on the properties of CO


2


, shrinks, its cooling ability drops.




What is needed is a way to control the rate of heat transfer to a block of dry ice, and to use such a block in a cooler in a commercial and practical manner, which allows the cooler to hold a temperature below or above freezing, as desired by its owner. This allows a cooler with separate chambers for frozen and not frozen foods, that is, to perform like a fridge.




SUMMARY OF THE INVENTION




A cooling assembly being a structure into which a cold material is inserted in contact with a transfer element through which heat transfers, which heat transfer is adjusted by covering the transfer element more or less.











BRIEF DESCRIPTION OF THE DRAWINGS




Preferred embodiments of the apparatus of this invention will be described in detail below in connection with the following drawings, in which like numbers refer to like components:





FIG. 1

is an orthogonal view of a cooler incorporating features of the present invention;





FIG. 2

is a side elevation of the cooler of

FIG. 1

;





FIG. 3

is a bottom elevation of a lid of the cooler of

FIG. 2

, taken along line


3





3


of

FIG. 2

, showing an example of the heat transfer control feature of the present invention; and





FIG. 4

is a sectional view taken along line


4





4


of

FIG. 3

, showing a cavity in the lid shown in

FIG. 3

, into which cooling material is inserted, including a cover and a controlled heat transfer assembly.











DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS




The present invention is preferably incorporated into a cooler, generally referred to in

FIG. 1

as


10


. A typical cooler


10


which is available from a variety of sources has an outer insulating wall, generally referred to as


12


, and a chamber, generally referred to as


14


, inside these walls. This chamber


14


is preferably suitable to have water ice poured in to it, that is, its inner walls


16


are preferably waterproof.




In this preferred embodiment the cooler


10


has a second chamber, generally referred to as


18


, adapted to use at colder temperatures than chamber


14


. It is practical that the walls


20


of chamber


18


be likewise waterproof. Although a cooler


10


with two chambers, is shown in

FIG. 1

, the present invention is equally suited to single or more than two chambered coolers, and can likewise be used in other situations where convenient, adjustable cooling is required, including soft pouches that need cooling, hard-to-reach places in aircraft, ships, spaceships, electronics and computers, and other applications.




In this two-chambered preferred embodiment, a larger lid


22


is attached by hinges


24


to the walls


12


of the cooler


10


. This lid


22


closes over the opening, generally referred to as


26


, on top of the chamber


14


and insulates and seals that chamber


14


from the surrounding atmosphere.




The lid


22


has an opening or cavity, generally referred to as


28


, preferably through its side, although opening


28


can be through any side of any structure incorporating the cooling assembly being described. This opening


28


has a preferably insulated cover


30


, which is designed to fit snugly inside the opening


28


.




A cold material such as a dry ice block created following U.S. Pat. No. 5,528,907, which is incorporated by reference, is inserted through insertion opening


28


and serves to draw heat from the chamber


14


through an opening, generally referred to as


32


. In this preferred embodiment this heat transfer passes through a plate


34


. This plate


34


may be a {fraction (1/16)} inch thick plate of aluminum, or other material determined through tests and calculations to have heat transmission properties desired for the application to which a cooling assembly is being suited. Plate


34


need not be a plate, but can be any element that has heat transmission properties desired; or plate


34


might simply be omitted.




In this preferred embodiment using a plate


34


, the material and thickness of the plate


34


may be estimated using the formula:








Heat





Flow

=

K



(


t
1

-

t
2


)

Thickness



,










where K is a constant for the material (for example, 237 for aluminum), t


1


is the higher temperature, t


2


is the lower temperature, and thickness is the thickness of the material through which heat is flowing.




Once a material for plate


34


is chosen, the actual heat flow through plate


34


from its exterior surface to its cavity surface may preferably be regulated by adjustable sliding cover


36


adjacent the exterior surface to cover, partially uncover, or completely uncover the plate


34


. Cover


36


travels between an open position substantially uncovering the exterior surface and a closed position in which the exterior surface is at least partially covered by the adjustable cover. Cover


36


is preferably made of insulating material that serves to better prevent heat transfer through it and therefore through the underlying plate


34


.




A two chamber cooler


10


will preferably have a second lid


38


, which again preferably matches the size of the chamber


18


that it closes.





FIG. 2

is a side view of the cooler


10


of FIG.


1


. Commercial coolers


10


commonly have handles


40


for the convenience of their owners. Also, if the cooler


10


is designed to also accept water ice, in combination with other cold materials such as dry ice or alone, then it is convenient to have a pour spout


42


toward the bottom of the cooler


10


for pouring out the inevitable water.





FIG. 3

is a bottom view of the lid


38


taken along line


3





3


of FIG.


2


.

FIG. 4

is a sectional view of the lid


38


taken along line


4





4


of

FIG. 3

, and shows details of the construction of a preferred embodiment of a cooler assembly. In this embodiment the lid


38


is built using a shell


42


of a casing material such as hard plastic, steel, or the like. This shell


42


surrounds, contains, and protects a filling or layer of insulating material


44


such as foam, air, foamed fiberglass, steel, aluminum, or even a vacuum.




A cavity, generally referred to as


46


, is opened into the lid


38


, into which the cold material is inserted, followed by a cover or lid, generally referred to as


48


. Cover


48


is made of an outside shell


50


or casing


50


for which the above materials may be used surrounding an insulating layer


52


or filler


52


selected from the materials likewise listed above. This cover


48


is preferably designed to fit the opening, generally referred to as


54


, of the cavity in the lid


38


snugly to prevent heat transfer into the cold material


56


that is not mediated and regulated by the plate


34


and cover


36


, which themselves block a second opening, generally referred to as


58


, into the cavity


46


.




The cooling assembly is shown in the lid of a cooler. Because of uneven cooling and convection, and well as limiting contact of cooled materials with the plate


34


, thereby excessively cooling the materials in contact with the plate, this is the preferred placement. Those skilled in the art will know to implement equally suitable placements, which may require grilles to distance the cooled materials from the plate


34


, or may require ventilation shafts or even passive or active valve systems.



Claims
  • 1. A cooling assembly comprising:a structure having a cavity therein, said cavity having an insertion opening through said structure for insertion of a cold material and a transfer opening through said structure for transfer of heat into said cavity; a transfer element substantially blocking said transfer opening, having a cavity surface adjacent said cavity and an exterior surface substantially opposite to said cavity surface, such that said cold material will contact said transfer surface substantially on said cavity surface; an adjustable cover over said transfer surface for adjusting between an open position substantially uncovering said exterior surface and a closed position in which said exterior surface is at least partially covered by said adjustable cover, said adjustable cover then being adjacent said exterior surface when in said closed position, whereby a rate of heat transfer into said cavity is regulated; and an active ventilation valve for ventilation of said cold material or said transfer opening, whereby said rate of heat transfer is further regulated.
  • 2. The cooling assembly of claim 1 wherein said adjustable cover slides adjacent said exterior surface between said open position and said closed position along at least one guide in said structure.
  • 3. The cooling assembly of claim 1 further comprising a lid for substantially closing said insertion opening.
  • 4. The cooling assembly of claim 1 wherein said cold material is a block of dry ice, whereby heat transfer is faster than water ice and sublimation prevents spillage.
  • 5. The cooling assembly of claim 1 wherein said transfer element comprises an aluminum plate.
  • 6. A cooler comprising:at least one chamber substantially surrounded on all but an open side by insulated walls; at least one insulated lid openably engaging said open side, said insulated lid travelling between an open position allowing access to said chamber and a closed position preventing said access, said lid having a cavity therein, said cavity having an insertion opening through said lid for insertion of a cold material and a transfer opening through said lid for transfer of heat into said cavity; a transfer element substantially blocking said transfer opening, having a cavity surface adjacent said cavity and an exterior surface substantially opposite said cavity surface, such that said inserted cold material will contact said transfer surface substantially on said cavity surface; an adjustable cover over said transfer surface for adjusting between an open position substantially uncovering said exterior surface and a closed position in which said exterior surface is at least partially covered by said adjustable cover, said adjustable cover then being adjacent said exterior surface when in said closed position, whereby a rate of heat transfer into said cavity is regulated; and an active ventilation valve for ventilation of said cold material or said transfer opening, whereby said rate of heat transfer is further regulated.
  • 7. The cooler of claim 6 wherein said cooler has an upward direction during normal use, and wherein said lid is substantially upward of said chamber.
US Referenced Citations (8)
Number Name Date Kind
537193 Goetz Apr 1895
634791 Bachner Oct 1899
916282 Dunkle Mar 1909
1744890 Hanrahan Jan 1930
3807194 Bond Apr 1974
4537044 Putnam Aug 1985
4561262 Fredrixon Dec 1985
5216900 Jones Jun 1993