Abstract:
The invention is directed to a low-temperature cooler using dry ice as a cooling agent. The cooler has two compartments, one for the dry ice and one for chilled storage. The cooler self-regulates via an aqueous filled temperature-regulating valve to maintain a desired temperature in the storage compartment such that the products stored therein are stored at an optimum temperature. Upon achieving a predetermined temperature in the storage compartment, the valve closes, thereby maintaining the predetermined temperature in the storage compartment.

Description:
FIELD OF THE INVENTION  
       [0001]     The invention is generally directed to a portable cooler for storing and containing perishable items for transport. The invention is more specifically directed to a portable cooler comprising a first compartment for cooling and a second compartment for storage. A self-regulating valve acts to allow entry of cooling vapor from the coolant compartment into the storage compartment until a desired temperature in the storage compartment is reached.  
       DESCRIPTION OF THE PRIOR ART  
       [0002]     Portable coolers have become ubiquitous in modern culture. As personal transport has become commonplace in society, so too has society&#39;s desire to take their portable coolers, containing perishable products, with them. While some portable coolers are quite sophisticated and made of expensive material, others are very simple, disposable coolers made of inexpensive polymer foam or other insulated material. However, while the construction of portable coolers may vary greatly, the means of cooling items stored within them does not.  
         [0003]     Most portable coolers are adapted to use ice as the cooling agent. In its most simplified form, a cooler has but one compartment containing both the ice and products to be cooled. When the cooling agent is ice, this arrangement can lead to waterlogged products, as well as a large volume of water when the ice melts. Alternatively, the cooling agent can be in a separate compartment from the products to be cooled. When ice is the cooling agent, the temperature of the products will not be maintained at about the freezing point of water (0° C.), as segregation of the ice from the stored products engenders higher temperatures in the storage compartment. Consequently, there exists a dilemma between maintaining the product at the lowest temperature and keeping the products dry.  
         [0004]     There have been several efforts to solve these problems. For example, U.S. Pat. No. 4,577,475 to Herrera describes a portable cooler having multiple compartments wherein an upper compartment will hold ice, along with beverages and foodstuffs, while lower compartments can be used to hold other products as well. In the design taught by Herrera, the water from the melted ice drains either from a tap in the top compartment or a tap in the bottom compartment.  
         [0005]     Other efforts to design coolers have resulted in portable refrigeration units such as those described in U.S. Pat. No. 3,585,813 to Hansen, U.S. Pat. No. 3,959,982 to Denis et al. and U.S. Pat. No. 5,555,740 to Stevenson, to name a few. The Hansen, Denis, and Stevenson patents describe the use of double-chambered coolers where one chamber is adapted to hold a liquid refrigerant while a series of coils passes through the walls of the second compartment, thereby maintaining a reduced temperature in the storage compartment.  
         [0006]     Other attempts to maintain a maximally-reduced temperature in a portable cooler rely on frozen carbon dioxide or dry ice as the cooling agent. U.S. Pat. No. 2,610,472 to Maxwell describes a double-chambered cooler where one chamber is adapted to store dry ice and an adjacent chamber is a storage chamber for items to be chilled. The storage compartment is designed with one or more cooling coils running through the bottom so as to absorb heat from the storage compartment. The dry ice chamber is designed to have a grate or grill suspended above the floor of the chamber so that gas from the sublimation of the dry ice collects underneath the grate and is forced through the coils.  
         [0007]     U.S. Pat. No. 3,820,355 to Olivares describes a three-chambered cooler. The first chamber comprises an insulated containment for dry ice. The second chamber comprises an empty or secondary “step-up” container sharing a common floor with the first chamber that is made of a suitable heat-transferring material. The third chamber comprises the storage chamber. The storage chamber also has a conduit or coil passing from the first chamber through the third chamber and vented to the outside.  
         [0008]     U.S. Pat. No. 4,195,491 (the &#39;491 patent”) and U.S. Pat. No. 4,288,996 (the &#39;996 patent”) to Roncaglione describe some similar dry ice coolers. The &#39;491 patent describes a conversion kit for traditional ice chest coolers. The kit comprises a small container that is placed in the middle of the cooler and a pair of refrigeration coils that are displaced on the front and back sides of the cooler. The coils are designed to vent to the outside through a side drainage opening. The &#39;996 patent describes a dry ice cooler essentially as results from the conversion of the traditional cooler with the kit of the &#39;491 patent.  
         [0009]     U.S. Pat. No. 6,212,901 to Pint et al describes a dry ice cooler having two chambers and a two-piece lid. One smaller chamber is for dry ice while a second, larger storage chamber is for items to be cooled. The covers or lids for the cooler fit over each of the chambers such that the lid for the large chamber is larger than the lid for the smaller chamber. The lids each have a heat transfer element on their inner end such that when the lids are in the closed position, the heat transfer elements come together such that the heat from the large storage container is absorbed by the cooled element connected with the dry ice chamber. The temperature of the storage chamber is regulated by covering the element to a greater or lesser degree.  
         [0010]     As may be appreciated, the use of portable coolers comprising liquid cooling units is neither economical nor disposable. The units described above, using dry ice as a coolant, are generally quite complicated and depend on cooling coils to transfer heat which also adds considerable expense to their manufacture. Moreover, there is generally very little ability to control the temperature, except for venting the collected gas to the outside or, as in Pint, covering the heat transfer element. However, as the activity in the field illustrates, there is an unmet need for an inexpensive yet efficient cooler that maintains low storage temperatures and does not result in melted ice and water-logged food products. In addition, the cooler should be portable and reusable but also disposable, if desired.  
       SUMMARY OF THE INVENTION  
       [0011]     It is therefore an object of the present invention to provide a portable, low-temperature cooler comprising an insulated container having a first chamber and a second chamber. The cooler will act to maintain the temperature in the storage compartment at a desired temperature, such as, for example, at about at least 0° C., and provide a method for self-regulating the temperature so as to maintain the temperature in the first chamber at the predetermined temperature.  
         [0012]     In one preferred version of the invention, the cooler comprises an insulated container having a first chamber and a second chamber. The first chamber comprises a coolant chamber and contains a cooling agent, and the second chamber is a product storage compartment. The invention also includes a coolant tube leading from the first chamber to the second chamber. In addition, the coolant tube includes a temperature-regulating valve, the temperature-regulating valve controlling the entry of gaseous vapors produced by the cooling agent into the second chamber from the first chamber via the coolant tube.  
         [0013]     In another preferred version, the cooler comprises an insulated container having a top, a bottom, opposing front and back sides and two opposing ends. The interior space of the cooler further comprises two chambers separated from each other by an internal wall. The first chamber comprises a coolant chamber and the second chamber a product storage compartment. In addition, the first chamber further includes a pressurization container for holding a cooling agent. The pressurization container has a top so that the cooling agent inside the pressurization container remains enclosed. Inside the pressurization container is also a vapor space. A coolant tube, having a lumen and leading from the vapor space of the pressurization container to the product storage compartment, is also included. The coolant tube allows vapors from the cooling agent to enter the product storage compartment from the pressurization container. Further, the coolant tube includes a temperature-regulating valve, the temperature-regulating valve situated inside the product storage compartment. The temperature-regulating valve occludes the lumen of the coolant tube at a predetermined temperature and thereby stops the flow of vapor from the cooling agent. An exit-relief valve is also used to facilitate the flow of the vapor from the product storage compartment.  
         [0014]     The advantages of the invention are several. First, the invention allows the temperature of the storage compartment to be kept at a specific temperature. Second, the invention allows the product in the storage compartment to be separated from the cooling agent so as not to be immersed in it. Third, the invention allows much colder temperatures to be achieved in the storage compartment than is currently possible with most disposable coolers. Fourth, the cooler is much more economically constructed than other cooling units achieving similar temperatures.  
         [0015]     The cooler of the present invention can be used at multiple temperatures. For example, the cooler provides a container which can be used to ship perishable goods at about a temperature of 0° C., thereby keeping the produce fresh but unfrozen. The invention also allows the maintenance of colder temperatures in the storage compartment by changing the set point of the temperature-regulating valve and by changing the cooling agent. By manipulating these two variables, the temperature of the storage compartment can be maintained at, at least, about −80° C.  
         [0016]     The objects and advantages of the invention will appear more fully from the following detailed description of the preferred embodiment of the invention made in conjunction with the accompanying drawings.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]      FIG. 1  is a perspective view of the cooler with the top open and the interior revealed.  
         [0018]      FIG. 2  is a front section view of the cooler of the present invention taken along lines  2 - 2  of  FIG. 1 .  
         [0019]      FIG. 3  is a perspective view of one embodiment of the valve of the present invention.  
         [0020]      FIG. 4  is a perspective view of another embodiment of the valve of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0021]     The invention is directed to a low-temperature, portable ice chest or cooler  10 . The cooler  10  uses cooling agents  12  with a lower temperature than conventional ice, thereby allowing the temperature of products  14  stored in the cooler  10  to be maintained at temperatures approximating the temperature of the cooling agent  12 . This allows the cooler  10  to be essentially self-regulating at that temperature.  
         [0022]     Referring now to  FIG. 1 , the cooler  10  is shown with its top  20  open, revealing the interior  22  of the cooler  10 . The cooler  10  is formed from two opposing sides  24  and  26 , a front side  28 , a rear side  30  and a bottom  32 . The sides  24 ,  26 ,  28  and  30  have an upper edge  34  on which the top  20  securely rests. While in some versions the top  20  may be removable, in other versions the top  20  has hinges (not shown) which attach the top  20  directly to the rear  30  of the cooler  10 . When the top  20  is hingedly attached to the cooler  10 , the top  20  can be secured by a latch or other fastener (not shown). When the top  20  is removable, the top  20  fits securely into the openings formed by the upper edges  34  of the sides  24 ,  26 ,  28  and  30 . Further, the top  20  of the cooler  10  may comprise a two-part article having a separate cover for the storage compartment  40  and the coolant chamber  38 . However, it is within the scope of the invention that the top  20  may be a single unit such that removing the top  20  exposes both the storage compartment  40  and coolant chamber  38 .  
         [0023]      FIG. 1  also shows the internal wall  36  which divides the interior  22  of the cooler  10  into a coolant chamber  38  and a storage compartment  40  for products  14  to be cooled. The internal wall  36  can be of various thicknesses, depending on the products  14  stored and the cooling agents  12  (shown in  FIG. 2 ) used. Further, the cooler  10  can be formed as a unitary article such that the internal wall  36  is an integral part of the cooler  10 . It is also an aspect of the invention that the cooler  10  can be assembled with the internal wall  36  being added after the cooler  10  is fabricated.  
         [0024]     The cooler  10  can be made of any insulated material. For example, more permanent coolers  10  may be made from durable polymers and metal alloys while less expensive coolers  10  may be made of disposable foam polymers, cardboard or other inexpensive materials.  
         [0025]     Referring to both  FIGS. 1 and 2 , the coolant chamber  38  of the cooler  10  includes a pressurization container  42 . The cooling agent  12  is contained within the pressurization container  42 . The pressurization container  42  comprises a closed container suitable for containing a low-temperature cooling agent  12 . The pressurization container  42  is configured to fit within the coolant chamber  38 . The pressurization container  42  has walls  44 , a bottom and a removable top (not shown). The pressurization container  42  is further configured to be air-tight when the top is secured in place. In some versions, the pressurization container  42  may be square while in other versions the pressurization container  42  is rectangular. In some versions, the top of the pressurization container  42  fits snugly into corresponding grooves (not shown) formed by the walls  44  of the pressurization container  42 . In other versions, the pressurization container  42  is cylindrical and the top may be attached to the pressurization container  42  via a threaded neck (not shown).  
         [0026]     The pressurization container  42  also includes a vapor space  50 . The vapor space  50  collects vapor  52  released from a cooling agent  12 . The vapor  52  released from the cooling agent  12  collects in the vapor space  50  and is maintained under pressure due to the air-tight design of the pressurization container  42 . In some preferred versions, the pressurization container  42  is fabricated of an insulating material such as foam, insulated metal or insulated glass.  
         [0027]     Also illustrated in  FIG. 2  is a coolant tube  54 . The coolant tube  54  is hollow and has a first end  56  and a second end  58 . The first end  56  originates in the pressurization container  42  of the coolant chamber  38 . The coolant tube  54  passes through an opening in the top of the pressurization container  42  and through an opening in the internal wall  36 , where the second end  58  of the coolant tube  54  terminates in the storage compartment  40 .  
         [0028]     An aqueous filled temperature-regulating valve  64  is fitted around the circumference of the coolant tube  54  after it enters the storage compartment  40 . By using a cooling agent  12  that vaporizes, the vapor  52  collecting in the vapor space  50  of the pressurization container  42  is forced into the first end  56  of the coolant tube  54  and passes through the coolant tube  54  into the storage compartment  40  via the second end  58  of the coolant tube  54 .  
         [0029]     Illustrated in  FIG. 3 , the temperature-regulating valve  64  is designed to regulate the amount of cooling vapor  52  entering the storage compartment  40  and thereby maintain the temperature in the storage compartment  40  at a desired level. The donut-shaped temperature-regulating valve  64  contains a fluid (not shown), which, upon freezing, expands. When expanded, the fluid closes the coolant tube  54  by occluding the lumen  68 . By closing the coolant tube  54 , vapor  52  from the cooling agent  12  is prevented from entering the storage compartment  40 , thereby allowing the temperature in the storage compartment  40  to rise. The freezing point of the fluid in the temperature-regulating valve  64  determines the temperature set point of the storage compartment  40  in which the temperature-regulating valve  64  is situated. For example, when the fluid in the temperature-regulating valve  64  is pure water, the set point is 0° C., the freezing point of water. When the fluid in the temperature-regulating valve  64  is water plus a solute, the freezing point of the solution is depressed according to the concentration of the solute used to prepare the fluid. In some instances, the outer surface of the temperature-regulating valve  64  will be covered with a thin layer of insulating material (not shown) such as foam or rubber, thereby allowing the fluid in the temperature-regulating valve  64  to equilibrate with the ambient temperature of the storage compartment  40  rather than allowing the temperature-regulating valve  64  to become super-cooled by direct contact with the coolant tube  54 .  
         [0030]     In instances where different temperatures are desired in the storage compartment  40 , the temperature at which the temperature-regulating valve  64  closes can be varied. For example, the set point of the temperature-regulating valve  64  can be altered by adding solutes to the fluid contained in the temperature-regulating valve  64 , thereby decreasing the temperature at which the temperature-regulating valve  64  closes. For example, while dry ice has a melting point of −78° C., liquid nitrogen has a boiling point of −195.8° C. The freezing point of a liquid may be lowered by adding a solute to the fluid in accord with the equation for freezing point depression: 
 
 T=iK   f   m  
 
 where the change in the melting point (T) is a function of: i (the van&#39;t Hoff factor, the number of particles into which the solute dissociates); m (the molality of solute in the liquid); and K f  (the freezing point constant for the liquid). By making use of the solute effect on the freezing point, the set-point of the temperature-regulating valve  64  can be lowered from 0° C. This method for depressing the freezing point of a liquid is routinely practiced by automobile owners when using a mixture of antifreeze and water in their cars&#39; cooling systems. 
 
         [0031]     Also illustrated in  FIGS. 1 and 2  is a pressure-release valve  53 . As the cooling agent  12  produces vapor  52 , the vapor  52  increases the pressure within the pressurization container  42 . Including a pressure-release valve  53  in the pressurization container  42  prevents the vapor  52  from creating unnecessarily or dangerously high pressure levels. The pressure-release valve  53  is inserted into the vapor space  50  of the pressurization container  42 . The pressure-release valve  53  can be inserted through the walls  44  or the top of the pressurization container  42 . In some versions of the invention, the pressure-release valve  53  vents excess vapor  52  from the pressurization container  42  into the coolant chamber  38  of the cooler  10 . In other versions of the invention, the pressure-release valve  53  vents excess vapor  52  to the outside environment. When the pressure-release valve  53  vents to the outside, it may enter through the walls  44  of the pressurization container  42 .  
         [0032]     In addition, by situating the pressure-release valve  53  in the vapor space  50 , the force of the vapor  52  entering the coolant tube  54  can be regulated. Regulating the force of the vapor  52  allows the pressure-release valve  53  to serve as an auxiliary temperature control. By lowering the tolerance of the pressure-release valve  53 , increased vapor  52  is drawn off of the vapor space  50 . This lowers the force of the vapor  52  as it passes into the storage compartment  40  and allows the temperature in the storage compartment  40  to increase. By increasing the tolerance of the pressure-release valve  53 , less vapor  52  is drawn off of the vapor space  50 , thereby increasing the force of the vapor  52  entering the coolant tube  54 . As will be apparent to those of skill in the art, the temperature resulting in the storage compartment  40  is a function of the overall force of the vapor  52  as it enters the storage compartment  40 . The force of the vapor  52  is determined by the pressure of the vapor  52  produced and the resistance provided by the pressure-release valve  53 . Pressure-release valves  53  similar to those described are commercially available as both preset valves and as adjustable valves from Cole-Palmer Instrument Co., Vernon Hills, Ill., and Aldrich Chemicals, Milwaukee, Wis.  
         [0033]     The cooler  10  of the present invention may also contain an exit-relief valve  55 , as shown in  FIG. 2 . The exit-relief valve  55  may be located on the opposing side of the storage compartment  40  from the temperature-regulating valve  64 . The exit-relief valve  55  facilitates the flow of the cooling vapor  52  as it exits the storage compartment  40 . The exit-relief valve  55  may be positioned through the wall  24  of the cooler  10 . The exit-relief valve  55  must be set at a lower level than the pressure release valve  53  to allow the cooling vapor  52  to flow throughout the product storage chamber  40 .  
         [0034]     Referring again to  FIG. 3 , a first embodiment of the temperature-regulating valve  64  can be seen. In this embodiment, the temperature-regulating valve  64 , referred to as a “Donut” valve, comprises an insulation layer  68  around the coolant tube  54  to prevent conduction from prematurely freezing the temperature-regulating valve  64 . The temperature-regulating valve  64  surrounds the coolant tube  54  and may be encased in a flexible membrane, such as plastic (not shown). In this embodiment, the temperature-regulating valve  64  contains a fluid and acts as a membrane through which the vapor  52  passes. As discussed previously, the fluid can be water. As the fluid in the “donut” temperature-regulating valve  64  freezes, it compresses the coolant tube  54  and discontinues the flow of the coolant  12  from the coolant chamber  38  to the storage compartment  40  via the opening in the internal wall  36 .  
         [0035]     Referring now to  FIG. 4 , a second embodiment of the temperature-regulating valve  64  is shown. In this embodiment, the temperature-regulating valve  64 , in the form of a “Pincer” valve, comprises a base cylinder  72 . The base cylinder  72  includes a first closed end  74 , sides  76  and a second open end  78 . Attached to the first closed end  74  is the first pincer  80 , which includes a base arm  82 , an extension arm  84  and a cross arm  86 .  
         [0036]     The temperature-regulating valve  64  also includes a nested sliding cylinder  88 . The sliding cylinder  88  includes a first closed end  90 , sides  92  and a second open end (not shown). The sliding cylinder  88  is designed to be slidably nested with the open end  78  of the base cylinder  72 . Attached to the first closed end  90  of the nested sliding cylinder  88  is a second pincer  94 , which also includes a base arm  96 , an extension arm  98  and cross arms  100 . Within the base cylinder  72  and sliding cylinder  88  is a membrane-filled expansion fluid sac  104 , filled with fluid. The cross arms  100  are crossed such that when the base cylinder  72  and the sliding cylinder  88  expand, the arms  100  come together to pinch the coolant tube  54  shut. This design incorporates a spring  108  connected to the pincers  80  and  94  that opens the pincers  80  and  94 , thereby allowing fluid to flow through the coolant tube  54 . When the pincers  80  and  94  move together, the spring  108  is stretched. When the fluid in the sac  104  melts, the spring  108  pulls the pincers  80  and  94  open, resetting the cylinders  72  and  88  and allowing fluid to flow through the coolant tube  54 .  
         [0037]     Different uses for the cooler  10  may require different set points for the temperature of the storage compartment  40 . For example, if the cooler  10  is used for transporting fresh produce, it would be desirable to keep the temperature in the storage compartment  40  close to 0° C. so as to keep the products  14  in the storage compartment  40  unspoiled but also unfrozen. In this instance, the fluid in the temperature-regulating valve  64  would be pure water and the pressurization container  42  would contain dry ice so as to rapidly chill the storage compartment  40  while maintaining the temperature of the storage compartment  40  above freezing. However, if the stored products  14  were biological samples, it would be desirable to keep them very cold. Typically, biological samples such as reagents, cells or tissues are shipped packed in dry ice. However, by using the current invention, the temperature in the storage compartment  40  could be maintained at the desired temperature by using dry ice as the cooling agent  12  and a water-solute mixture for the fluid in the temperature-regulating valve  64 . Therefore, temperatures in the storage compartment  40  can be set lower than 0° C. In addition, while other cooling agents  12 , such as liquid nitrogen, may be used, dry ice is the safest and most easily available sub-zero cooling agent  12 .  
         [0038]     It will be appreciated by those of skill in the art that there are alternative configurations to the temperature-regulating valve  64 . All that is necessary is a configuration that harnesses the energy derived from the expanding fluid contained within the temperature-regulating valve  64 . For example, the temperature-regulating valve  64  may comprise a “donut” fitting on the inside of the coolant tube  54 , whereby the temperature-regulating valve  64  expands, thereby occluding the lumen  68  of the coolant tube  54 . In another preferred version (not shown), the temperature-regulating valve  64  includes a large marble-shaped, aqueous-filled sphere made of a distensible material such as rubber, latex, silicone or other material. In this version, the distensible sphere sits inside a tube and is held in place by internal radial rabbets. Upon freezing and expansion of the sphere, the sphere seats firmly against the grooves of the walls of the pressurization container  42 , thereby occluding the lumen  68  and stopping the flow of vapor  52  into the storage compartment  40 .  
         [0039]     It is understood that the invention is not confined to the particular construction and arrangement of parts herein illustrated and described but embraces such modified forms thereof as come within the scope of the following claims.