CA2155327A1 - Insulative food container employing breathable polymer laminate - Google Patents
Insulative food container employing breathable polymer laminateInfo
- Publication number
- CA2155327A1 CA2155327A1 CA002155327A CA2155327A CA2155327A1 CA 2155327 A1 CA2155327 A1 CA 2155327A1 CA 002155327 A CA002155327 A CA 002155327A CA 2155327 A CA2155327 A CA 2155327A CA 2155327 A1 CA2155327 A1 CA 2155327A1
- Authority
- CA
- Canada
- Prior art keywords
- container
- food
- liner
- shell
- moisture vapor
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B27/00—Layered products comprising a layer of synthetic resin
- B32B27/32—Layered products comprising a layer of synthetic resin comprising polyolefins
- B32B27/322—Layered products comprising a layer of synthetic resin comprising polyolefins comprising halogenated polyolefins, e.g. PTFE
-
- A—HUMAN NECESSITIES
- A47—FURNITURE; DOMESTIC ARTICLES OR APPLIANCES; COFFEE MILLS; SPICE MILLS; SUCTION CLEANERS IN GENERAL
- A47J—KITCHEN EQUIPMENT; COFFEE MILLS; SPICE MILLS; APPARATUS FOR MAKING BEVERAGES
- A47J47/00—Kitchen containers, stands or the like, not provided for in other groups of this subclass; Cutting-boards, e.g. for bread
- A47J47/14—Carriers for prepared human food
- A47J47/145—Hand carriers for pizza delivery, e.g. with thermal insulation, heating means or humidity control
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B27/00—Layered products comprising a layer of synthetic resin
- B32B27/06—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material
- B32B27/065—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material of foam
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B5/00—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts
- B32B5/18—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by features of a layer of foamed material
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B5/00—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts
- B32B5/22—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by the presence of two or more layers which are next to each other and are fibrous, filamentary, formed of particles or foamed
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
- B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
- B65D81/00—Containers, packaging elements, or packages, for contents presenting particular transport or storage problems, or adapted to be used for non-packaging purposes after removal of contents
- B65D81/38—Containers, packaging elements, or packages, for contents presenting particular transport or storage problems, or adapted to be used for non-packaging purposes after removal of contents with thermal insulation
- B65D81/3813—Containers, packaging elements, or packages, for contents presenting particular transport or storage problems, or adapted to be used for non-packaging purposes after removal of contents with thermal insulation rigid container being in the form of a box, tray or like container
- B65D81/3823—Containers, packaging elements, or packages, for contents presenting particular transport or storage problems, or adapted to be used for non-packaging purposes after removal of contents with thermal insulation rigid container being in the form of a box, tray or like container formed of different materials, e.g. laminated or foam filling between walls
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B2307/00—Properties of the layers or laminate
- B32B2307/30—Properties of the layers or laminate having particular thermal properties
- B32B2307/304—Insulating
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B2307/00—Properties of the layers or laminate
- B32B2307/70—Other properties
- B32B2307/724—Permeability to gases, adsorption
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B2307/00—Properties of the layers or laminate
- B32B2307/70—Other properties
- B32B2307/726—Permeability to liquids, absorption
- B32B2307/7265—Non-permeable
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B2327/00—Polyvinylhalogenides
- B32B2327/12—Polyvinylhalogenides containing fluorine
- B32B2327/18—PTFE, i.e. polytetrafluoroethylene
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B2439/00—Containers; Receptacles
- B32B2439/70—Food packaging
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
- B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
- B65D2585/00—Containers, packaging elements or packages specially adapted for particular articles or materials
- B65D2585/30—Containers, packaging elements or packages specially adapted for particular articles or materials for articles particularly sensitive to damage by shock or pressure
- B65D2585/36—Containers, packaging elements or packages specially adapted for particular articles or materials for articles particularly sensitive to damage by shock or pressure for biscuits or other bakery products
- B65D2585/363—Containers, packaging elements or packages specially adapted for particular articles or materials for articles particularly sensitive to damage by shock or pressure for biscuits or other bakery products specific products
- B65D2585/366—Pizza
Abstract
An improved container for transporting food and similar products is provided. The container employs one or more layers of a breathable material which is permeable to water vapor but repellent to liquid. By enclosing hot food in this container, moisture vapor from the food dissipates away from the food and avoids the soggy texture which often accompanies transported food. The container of the present invention has a wide range of possible applications, including everything from delivery of individual pizzas to large scale relocation of food for institutional purposes.
Description
~1~5327 INSULATIVF FOOD CONTAINER
EMPLOYING BREATHABLE POLYMER LAMINATE
BACKGROUND OF THE INVENTION
1. Field ofthe Invention The present invention relates to apparatus for protecting and preserving ~ood, and especially for protectins hot food during transportation.
EMPLOYING BREATHABLE POLYMER LAMINATE
BACKGROUND OF THE INVENTION
1. Field ofthe Invention The present invention relates to apparatus for protecting and preserving ~ood, and especially for protectins hot food during transportation.
2. Description of Related Art In re~ent years the business of delivering hot food to a home or 10 busir,ess has grown drarnatically. The c~rrent rnarket for pizza deiivery aione is estirnated to compnse billions of dollars irl husiness each year. Moreover, numerous other businesses depend upon indivtdualizad delivery of hot food, including catering businesses. various Asian, Me~ican and other ethnic food restaurants, services providing hot meals to elderly and other shut-ins 15 ser~ices providing hot meals to schools and camps, etc.
In light of the active intetest in such businesses, it is hardly surprising that tremendous activity has centered around means of keeping food hot (or cold) and fresh during transportation. The most common containers in this regard have been primary food packages constructed from waxed paper, ~u plastic or cardboard. Although such containers are inexpensive and convenient. they have proven limited in their ability to preser~e the temperature, freshness and texture of the food.
In response to these concerns, a number of solutions haYe been proposed. For examplel deli~ered piza today is commonly placed in a 25 primary food recept~cie (e.g. a cardboard box) and then inserted into an insulative pDuch for transportation. These pouches are generally constructed from an outer shell of durable ~nit-backed vinyl or similar polymer rnaterial, insulated with approxirnately 3.2 cm (1 1/4 inches) of open cell foarn on eitherside of the piz~a box, and lined ~4ith a nylon coated with vinyl, or simi~ar 30 material.
In order to proteçt '.he insulation frorn becoming wet and/or contaminated with food, the interior liner is norrnally rnade water AM~NI~ED SI~EET
_ WO 94121536 21 S 5 3 2 7 PCT/US93103466 proof to contain moisture within the liner. It is generally recognized that the free flow of liquid through the liner presents a distinct health hazard by allowing bacteria to grow within the insulation and pass back to the food in condensed water vapor.
Additionally, when foam insulation becomes wet, it loses its insulative properties and may even become a heat sink. To address these concerns, recent improvements in this area have included providing a liner of polyester MYLAR-type material which is both heat reflective and almost completely water and water vapor impermeable.
Although such pouches are convenient, relatively inexpensive, and a substantial improvement over the use of a box alone, they are deficient in many respects. The primary problem with these devices is that a sealed interior liner tends to trap moisture vapor given off by the food within the container itself. As the packaging begins to cool, this trapped moisture vapor condenses and leads to the pizza becoming "soggy." The addition of grommetted vent holes in the side of the pouch offers only limited improvement in these conditions. Vent holes free moisture vapor, but they simultaneously release heat--requiring careful proportions to permit liberating some steam while retaining a sufficiently hot and moist pizza. To compound this problem further, the loss of too much moisture is also to be avoided since it can result in the food becoming dry and unappetizing. As a result, these pouches are limited in their utility and service range and present a constant threat of cool and/or damp or dry pizza.
In light of these limitations, a number of far more exotic solutions have been proposed. United States Patents 4,806,736 issued February 21, 1989, to Schirico and 4,816,646 issued March 28, 1989, to Greve each discloses use of pizza delivery containers containing built-in electric resistance heating elements to help keep pizzas hot. To address the problem of moisture build-up specifically, United States Patent 4,922,626 issued May 8, 1990, to Fiddler discloses a pizza delivery container with a motor-driven 3s fan to circulate moist air over a moisture-removing dissicant cartridge. These solutions may function reasonably well for their stated purposes, but they are each considered needlessly complicated and too cumbersome and expensive for widespread use.
Another area of growin~ interest is the delivery of r~la~ively br~e - quantitie~ of hot foods. In addition to normal catering actiYitiss, a number of businesses have sou~ht to expand into ~he delivery of lar~e number of pizas and other foods to schools and camps. In this context, the use of a relaUvely s small pouch is sirnply impractical. Moreover, employing nume-ous pizza boxes or other primary food receptacles is considered both wasteful and a needless expense.
One solution prop,osed in this regard is t~ provide a rack in which multiple reusable trays of food can ~e s~ ked To Insulate the food in the 10 rack~ a padded nylon cover is formed around t~he r~ to help contain the ~ood heat. Wffl a much ~reater quantity of food and much less relative outside surFace a~rea, food tends to stay warmer in this environment. Unfortunately, the problern of rnoisture build-up may be compounded ~,nce the amount of food contained in the rack ;s far greater than the arailable surface area 15 pe,."i:ling moisture dissip~;on. Addltionally, if coYered prim~ry food receptacles are not o"lp'3~r~ in the food rac~s, there is also an increased riskof both liquid precip;td~ onto the food and bacterial contarnination.
Unite~ States Pabnt 4,283,427 to Winters et al. is directed to a microwaYe heatin~ pack~e and a rnethod of microwave heating. The patent 20 is directed to using a l"alenal that b~comes microwave transparent at a given temperature in order to provide an automatic shut off for heatin~ in a microwa~e oven. The mana~ement of heat and rnoJsture in a food t~ansport container is not addressed by this ~-ference.
Patent ~pfic~tion WO 87~04663 to Fo, lapax L~d. is directed to a 2~ foamed p~astic sheet that can be used to insulate food containers. The a,pl.s-tion teaches usin~ an open cell foamed plastic that allows rnoisture to pass thraugh it in arder to keep the moisture away fram faod. The foam plastic shee~ is tau~ht to be appli~d in cont~ct with ~e foad itself. While thisapproach might provide some improvernent owr impenetrable ciosed ccll 30 insulation in sep~c.li,~9 mo~sture frGm ~e food, it c~ntinues to be pl-gu~ bynumerous pr~b'e."s, including inability to ade~uately clean ~e open cell foam between uses, inadequate protec~ion of the food from contamination, insufficient moisture barrier to prevent condensed moisture from passing back to the food, etc.
) Finally, German patent application DE 27 37 756 to W. L. Gore ~
Associates, Inc., is directed to a larninate of microporous PTFE membrane and a fabric material. This laminate is both waterproof and moisture vapor permeable. However, there is no teaching in this reference as to how to use S such a material to produce an improved ~ood transport container.
Finaliy, there are believed to be other applications where a breathable, insulated container for carrying perishables is of use. For example, in the transportation cf certain bio-rnedical products and specimens it is sometimes desirable to keep the product at a constant temperature but allow the lG dissipation of moisture vapor withoul a build up of condensation.
A~-cordingly, it is a pnmary purpose of the present invention to provide an apparatus for protecting food and similar produc-.s which is effective at dissipa'Jng unwanted moisture vapor while retaining heat.
It is a further purpose of the present invention to provide such an , apparatus which provides an effective barrier to liquid entering the storage area through either condensation or seepage from wet weather or other ambient conditions.
It is an additional purpose of the present invention to provide such an apparatus which ~an be adapted to control mois~ure effectively in a Yariety of 2n applications, including instanc~s where relatively large quantities of perishables must be protected.
It is another purpose of the present invenUon to provide such an apparatus which is relatively easy to construc~, use, and transport.
These and other purposes of the present invention will beco ne evident 25 from review of the following specification. These purposes are attained by the container as claimed in the present appliation.
SUMMARY O~ THE INVENTION
The present invention is an improved container for storing and insulating transported food and similar products. The container comprises one 30 or more layçrs of a polymer fabric which is permeable to moisture vapor but resistant to liquid pene~ration. Preferably a laminate of porous polytetrafluoroethylene is ~sed which has proven to be highly effective at se~ectively transmitting water vapor wnile acting as a barrier to transrnission of liquid water. When steaming hot food or other perishable is stored in the 3~ container of the present in~ention, rnoisture vapor freely dissipates fronl the food storage area so as to avoid the detrimental effect of condensation on the food.
In the preferred embodiment of the present invention, the container AMEN~ED Sl~EET
t~
employs multiple layers, with a "breatha~le"/water repellent inner shell directly surrounding the food or food receptacle, an exterior shell pro~ecting ~he outside of the container, and a layer of insulation provided between the inner and exterior shells to help retain heat within the container. As the terrn 5 "breathable" is applied herein, it is meant to encompass any material permitting the passage of moisture vapor. In practice, moisture vapor will pass out of the storage area and either vent to atmosphere or condense between the inner shell ~nd the exterior shell. Since the inner shell is waterproof, condensate is prevented from re-entering the storage ~rea.
lo In a further improvement of the present invention, a temperature maintenance device, preferably compr!sing a phase change material, is employed to assist in maintaining the temperature of the container at a desired level over an extended period of time.
The present invention has proven to be ~uite successful at prup~r,~
II )Fn .~F~T
~ WO 94/21536 215 ~ 3 2 7 PCT/US93/03466 properly transmitting moisture vapor and delivering food which is hot and fresh. The present invention avoids many of the problems previously encountered with some previous insulated storage bags, such as soggy or dry food, and risk of bacterial contamination.
DESCRIPTION OF THE DRAWINGS
The operation of the present invention should become apparent from the following description when considered in conjunction with the accompanying drawings, in which:
Figure 1 is a three-quarter isometric view of a first embodiment of a container of the present invention;
Figure 2 is an enlarged cross-sectional view of an exterior shell, insulative layer, and interior shell of the embodiment of Figure l;
Figure 3 is a three-quarter isometric view of a second embodiment of a container of the present invention, equipped with a rack for stacking multiple layers of food;
Figure 4 is a three-quarter isometric view of third embodiment of a container of the present invention, also equipped with a rack for stacking multiple layers of food; and Figure S is a three-quarter perspective view of a packet of heat emitting material which may be employed in the present invention, the packet being insertable into a pocket provided in the container shown in Figure l.
DETAILED DESCRIPTION OF THE INVENTION
2s The present invention provides an improved container for storing virtually any form of food or similar material. Although the primary intended use of the present invention is for the transportation of food, and the term "food" is applied throughout - this specification for the purpose of simplicity, it should be appreciated that the present invention may be used to store or transport a variety of products, and especially perishable products and specimens, such as those encountered in health care and bio-medical applications.
WO 94/21536 t . - PCT/US93/03466 Shown in Figures 1 and 2 is one embodiment of a container 10 of the present invention. Container 10 is formed as a pouch adapted to receive one or more conventional pizza boxes or similar primary food receptacles and seal around the receptacles to assist in keeping them warm. The container 10 comprises an exterior or secondary shell 12, an insulation layer 14, and an interior shell or liner 16. In order to seal around the receptacles, a flap 18 is provided which can be held in place with any suitable means, such as zippers or hook-and-loop fasteners 20, 22, as shown. The container 10 is also provided with a sealable pocket 24 in the inner liner 16 to receive a heat emitting device as is described below.
As has been explained, in a conventional pouch of this form, a serious problem emerges of condensation from food moisture vapor building up within the pouch and precipitating on the food. This tends to leave the food "soggy" and less appetizing.
However, if the pouch is made from water permeable material, it tends to suffer from numerous other problems. First, the pouch provides insufficient protection from the elements, risking wet and cold food due to seepage of rain or snow. Second, a water permeable inner lining allows water vapor to condense within the insulation layer and lead to heat loss problems. Third, a water permeable inner lining further allows condensation from the insulation layer to pass back through to the food storage area--again making the food wet and cold. Moreover, the passage of condensate from the insulation layer to the food storage area also provides a very undesirable mechanism for bacterial growth from the inaccessible (and thus difficult to clean) insulation layer to contaminate the food. This concern is amplified if the permeable inner lining allows food particles to enter the insulation layer and culture bacterial growth therein.
In order to combat the moisture vapor problem, the present invention uses an inner liner which is moisture vapor permeable but liquid repellent. As is taught in United States Patent 3,953,566 issued April 27, 1976, to Gore, one such material can be formed by heating and rapidly expanding polytetrafluoroethylene (PTFE).
Improvements in this basic process are disclosed in a variety of patents, including United States Patent 4,194,041 issued March 18, ._ WO 94/21536 PCT/US93/03466 1980, to Gore et al., and 5,026,591 issued June 25, 1991, to Henn et al. The resulting product contains a micro-porous lattice of expanded PTFE which is porous enough to allow water vapor to pass through but is hydrophobic and sufficiently dense to repel liquid water. This "breathable"/water repellent material is commercially available from W. L. Gore & Associates, Inc., of Elkton, MD, in a variety of forms, including as a laminated fabric, available under the registered trademark GORE-TEX, which has the expanded PTFE
membrane pre-applied to a polymer fabric material.
Shown in Figure 2 is a more detailed representation of the various components of the container of the present invention. In this embodiment, the inner shell 16 comprises a layer of polymer fabric 26, such as a nylon taffeta. Attached to the fabric 26 with an adhesive layer 28 is a membrane of expanded PTFE 30. The PTFE
membrane 30 comprises a sheet of expanded PTFE made in accordance with the teachings of United States Patent 4,953,566 to Gore with a microporous lattice comprising nodes interconnected with fibrils.
This lattice should provide sufficient pore size for the passage of water vapor while being sufficiently dense and hydrophobic so as to repel liquid water.
Additional water repellency and resistance to contamination of the pores can be achieved by coating the membrane with a variety of substances, such as perfluorosulphonic acid or breathable polyurethane. Processes for providing such coatings are set forth in a number of patents, including United States Patents 4,194,041 to Gore et al., 5,026,591 to Henn et al., and 4,942,214 issued July 17, 1990, to Sakhpara. Although a coating tends to decrease moisture vapor permeability, it significantly increases the durability and liquid repellency of the membrane. Moreover, as is explained below, by varying the type of membrane (e.g. the average pore size therein) and the type and amount of coating applied to the membrane, the precise amount of moisture vapor permeab;lity can be adjusted to produce a customized container with ideal conditions for certain types of foods and for certain service ranges (i.e.
periods of time and conditions under which particular food will stay fresh).
The membrane can be bonded to the fabric through any conventional means, including through the use of an adhesive. The 21~327 8 adhesive may be of any appropriate form which will bind the membrane 30 to the fabric 26 without clogging the pores. Suitable adhesives include, but are not limited to, the class consisting of thermoplastic polymers, thermosetting polymers, or reaction curing polymers. In order to maintain moisture vapor transmission, the adhesive should either be breathable and/or applied only in a non-continuous manner (e.g. through a dot pattern). The adhesives may be applied to the surfaces to be laminated by conventional means, for example by coating or printing methods, or under pressure and lo heat similar to the process disclosed in United States Patent 4,194,041 to Gore et al. Additionally, in embodiments incorporating a coating on the expanded PTFE, as is described above, a hydrophilic polyurethane polymer or similar material can perform a dual role of serving as a protective coating and 15 adhesively bonding the expanded PTFE membrane to the fabric layer.
These and other suitable adhesives are disclosed in United States Patent 4,925,731 issued May 15, 1990, to Driskill et al.
It should be understood that the expanded PTFE membrane, protective coating, and fabric can be arranged in any orientation 20 which will provide the permeability and barrier protection of the present invention. For example, in place of the orientation shown in Figure 2, the expanded PTFE membrane 30 may be oriented facing the interior of the container, with the fabric 26 facing the insulation 14. For this alternative arrangement, it would be 25 preferred to provide an adhesive layer 28 of hydrophilic polyurethane to help improve water repellency and reduce the risk of contamination of the PTFE membrane.
Since the exterior shell 12 must withstand greater abuse, it is preferable that it is constructed from a more durable material, such as vinyl, expanded vinyl, woven nylon (e.g. CORDURA fabric available from E. I. DuPont Co. of Wilmington, DE), etc. As shown, the exterior shell comprises an outer layer 32 of nylon fabric bonded to a coated expanded PTFE membrane 36 (similar to that disclosed in United States Patent 4,194,041 to Gore et al.) and an inner layer 34 of nylon taffeta fabric bonded to an un-coated expanded PTFE membrane (similar to that disclosed in United States Patent 3,953,566 to Gore). Although this construction is not necessary for the proper operation of the present invention, for q some applications it is believed desirabie to provide the exterior shell with a water resistant~breathable layer of expanded PTFE rnembrane 36. Again, the membrane 36 is held in place with a suitable adhesive 38, 40 or similar means.
The insulative layer 14 rnay take any appropriate forrn. It is common today to use an open cell foam (e g. polyurethane) 2.5 to 5 cm (1 to 2 inches) thick. This form of insulation is inexpensive yet has good insulative prope~tiesand good impact resistance. Furthermore, when used in conjunction with the embodiment of the present invention illustrated in Figures 1 and 2, this forrn of insulation tends to breathe sufficiently to permit moisture vapor to pass completely out of the container 10. Additional or alternatiYe insulation can be provided in the form of metallic coatings, and most open or closed cell foams and similar products. including polyesters, puffed polyesters ~e.g.
THERMOLITE insulation available from E.l. DyPont Co. or THINSULATE
insulation available from Minnesota Mining and Manufacturing Co. of St. Paul, s Minnesota), styrene! polyethy~ene, fiberglass, urethanes, and other such produc~s.
Due to the arnount of breathability which can be imparted with the present invention, vent holes can be eliminated from the pouch to provide a more thoroughly sealed container. Nonetheless, for some applications suc,h vent holes may be desira~le (such as to provide further increased air flow or torelease some of the fragrance cf the food as a markeUng tool~ and can be easiiy induded in the container of the present invention. As is known, it is preferred to pro~ide a grornmet or other reinforcement means around such holes.
2c Another embodiment of the present invention tS ~hown in Figure 3. In this configuration, a conbiner 42 is arran~ed in a rack format, providing means to stack a relatively large num~er of separate primary food raceptacles 44. In the illustrated embodiment, the primary food receptacle 44 comprises a cardboard box commonly used for delivered pizzas. Such receptacles 44 work ;o well in the context of the presPnt invention since they are inexpensive yet adequately separate the food from the container 42 while permitting moisture vapor to pass relatively freely from them AMENDED SI~EET
215~327 ._ WO 94/21536 PCTIUS93/03466 To assist in stacking the primary food receptacles 44, one or more shelves 46 may be included to help organize the receptacles and limit the amount of weight imposed on the lower receptacles.
The shelves 46 may be constructed from any suitable material, including a fabric, or semi-rigid or rigid metal or plastic material attached within the container 42.
Like the embodiment of Figures 1 and 2, this container 42 also is constructed from an exterior shell 48, an insulation layer 50a, 50b, 50c in some or all of the sides of the container, and an interior shell or liner 52. Again, the interior shell comprises a breathable moisture vapor permeable material which is resistant to liquid penetration. Due to reduced outside surface area relative to the amount of food which can be stored in this container 42, it is preferred that the liner 52 be constructed from material with a fairly substantial moisture permeability, such as un-coated expanded PTFE material available from W. L. Gore & Associates, Inc., under the trademark GORE-TEX fabric. Additionally, it may be even more desirable in this instance to also construct the exterior shell 48 from similar material, as is shown in Figure 2.
The container 42 is sealed through any suitable means, such as with flap 54. The flap 54 may be constructed from the same material as the rest of the container 42 and should include at least a breathable interior liner 56. The flap may be closed against the rest of the container using hook-and-loop fasteners 58, 60, or other appropriate means.
Shown in Figure 4 for much larger applications is a container 62 constructed to hold very large quantities of food in a rack format. In this form, the container 62 includes multiple shelf channels 64 to receive primary food receptacles, such as cardboard boxes (as have been discussed), or disposable or reusable food trays, etc. Again, the container 62 is constructed with a breathable yet water repellent liner 66, an insulative layer 68, and an exterior shell 70. Like the embodiment of Figure 3, the decreased relative outside surface area compared to the large food carrying capacity of this embodiment requires a liner 66, and perhaps insulation 68 and exterior shell 70, with a high degree of breathability.
A flap 72 is provided to seal the container 62. This flap 72 `_ WO 94/21536 21 S 5 3 2 7 PCT/US93103466 can be insulated and also constructed from breathable material.
The flap 72 may be sealed through use of any suitable means, including hook-and-loop fasteners or zippers 74, 76, as shown.
- Due to the size of the container 62 of this embodiment, it may be desirable to provide casters 78 or similar means to help in transportation.
Further improvement in the present invention can be provided by including some external heat source. Shown in Figure 5 is a temperature maintenance device in the form of a sealed packet 80 containing a phase change material 82. Phase change material comprises a composition which can be activated to cause it to give off heat over a period of time. Alternatively, the material may also be designed to absorb heat over a period of time to provide a cooling effect.
To help maintain food in a hot condition, a phase change material may be provided which can give off a steady amount of heat over an extended period of time. Examples of such material are disclosed in United States Patent 5,070,223 issued December 3, 1991, to Colasante.
Essentially, phase change material includes a solid inert material with an appropriate melting point. By dispersing the inert material within an insulative material and applying heat to melt the inert material, portions of the inert material will slowly cool in stages to return to a solid state. This phase change back to a solid state is an exothermic reaction which provides a steady source of heat.
For use in the present invention, a phase change material with an active ingredient of sodium acetate tetrahydrate or polyethylene glycol is believed suitable. Preferably, the phase change material comprises a mixture of silicone, graphite and polyethylene glycol which is blended to evenly distribute the polyglycol throughout the other ingredients. The material may be packaged within a sealedcontainer to prevent leakage, such as silicone, polyethylene, vinyl, or polyester.
To activate the material, it is exposed to an energy source, such as placing it in a 600 watt microwave oven over a period of approximately 1 minute. When heated in this manner, the phase change material will give off a fairly constant heat of approximately 57 to ~5C (135 to 185 F) over a period of 30 to 60 minutes One such sample tested gave off a temperature of about ~5C (185F) for about 15 minutes after initial equilibrium was reached, then a t~rnperature plateau of about 57C (135F) for another 30 to 45 minutes durin~ phase 5 change, and a steady decline in temperature thereafter. Accordingly, a reliable temperature production could be provided by this material over a period of up to 4~ to 60 minutes or more.
As should be evidenL by placing one or more packets 80 into a container of the present invention, the heat and freshness of the food can be 10 maintained over a significantly extended period of time. The embodiment of Figure 1 includes a pocket 24 adapted to receive such a packet 80. The pocket 24 includes a hook-and-loop sealable flap 84 to help isolate the packet from the f~od storage area. Depending upon the particular effectiveness of such material for a given food, it may be possible to reduce or elirninate the s use of insulation andlor decraase or eliminate the arnount of breathability of the container's fabric.
Although not preferred, without departing from the present invention, other heat or cooling sources may alsa be combined with the present invention for improved operation. Possible exarnples include a battery or fuel powered 20 heating elements, etc.
Even though incorporating a layer of expanded PTFE membrane is the preferred treatment to proYide the properties of the present invention. a number of othertreatrnents may also be effective in ~his regard. For instance, virtually any appropriate material can be en~ployed which will allow passase of 2s moisture vapor while resisting passage of liquid, such as polyethylene glycol-based materials. polyether polyurethanes, polyester polyethers, polyethylene, epoxies, polyimides, polyvinyl alcohol, as well as treated natural rnaterials such as cellulose or cotton.
It should be appreciated tllat the present invention may be adapted for 30 use in many different applications. Depending upan the food material and the environmental canditions, containers may be constructed with a single layer of polymer fabric, with numerous layers of fabric and/or insulation, and with hybrid polymer shells--only a portion of which being constructed frorn a breathable fabric. E:)ue to the present cost of the most effective forms of 35 breathablelwaterproof fabrics, far many ~pp'.c ~;ons it may be preferred to construct the liner from only a portion of breathable fabric in those areas requiring greatest breathability (e.g the top andJar sides) and using a less expensive liquld impermeable fabric for the remainder of the shell.
P~MEN~O S~EE~
215~327 Although the present invention is particula~y applicable to the transportation of steaming hot food, such as piza, as has been noted, it has numerous other possible applications for the transportation andlor short-tenT
storage of other perishables, such as cold foods, bio-medical products or 5 specimens, etc.
Depending upon requirements, the containers cf the present invention may be employed with or without a separate primary food receptacle. Where a primary food receptacle is employed. it should be constnJcted from a materiai which i5 permeable to moisture vapor, such as paper, cardboard, ---o cellulose. etc. With or without a prirnary food r~ceptacle, the material described has proven to be readily cleanable and highly resistant to penetration by food partic~es.
Without intending to limit the scope of the present invention, the following represent examples of how the containers oF the present invention ls may be constructed and ernployed:
Examples A series of containers were constructed and tested to determine the relative effectiveness of the present invention o~er existing food deli~ery containers and variations of designs pursuant to the present invention.
Container 1 - A first container in the form of a pizza pouch was constructed comprising a water impermeable vinyl exterior shell and a nylon taffeta interior liner bonded to an un-coated expanded porous PTFE GORE-TEX membrane acquired from W. L. Gore & Associates, Inc. An insulative layer of 3.2 cm (1 2S 1/4 inches) of open cell polyurethane was provided on the top and bottom ofthe pouch between the shell and the liner. Two c,onventional grornmetted vent holes were provided in the side of the container to permit insertion of a ternperature probe.
AMENDED SI~
21~5327 Container 2 A second con~ainer was constructed identical in form to that of Container 1 but with an exterior shell of nylon taffeta bonded to a polyurcthane coated expanded PTFE GORE-TEX membrane.
Container 3 A third container was constructed identical in forrn to that of Container 1 but with an exterior shell of nylon taffeta bonded to an un-coated expanded PTFE GORE-TEX membrane.
Container 4 o A fourth containerwas constructed identical in form to that of Container 1 but wi~ an exterior shell of nylon taffeta bonded to an un-coated expar,ded PTFE GORE-TEX me,nt,r~ne and a liner of nylor, taffeta bonded to a polyurethane coated expanded PTFE GOR -TEX membrane.
Each of the above containers was testea under the following l~ parameters. First, a strip thermometer (e.g. a THERMOLABEL) was placed on the interior bottom of the food storage areas of each o~ the containers. These thermometers provide a permanent reading of the hi~hest temperature reached. Five identical pizas packaged within a conventional corrugated cardboard boxes were then placed one in each of Ule containers. A second ~0 strip thermometer was placed on the top exteriors of each ~f the piza boxes After 30 minutes, a ~empe,cl-lre probe was inserted within each of the containers and a temperature reading was taken.
The following results were achieved:
Container Tem~. TOD of Piz~a Temp. Bottom of Pizza 1 65.5CC (150F) 71~C (160F) 2 60C (140F) 71 C (160F) 3 82C (180F) 82C ~B0~F) 4 60C (140F) 65.5C (150F~
At this point, the interior ternperature of each of the bags was tested with a temperature probe. Each was aboYe 60C (140F).
Generally pizza deliYery standards call for piza to be approximately 74C ~165F) when removed from an oven, about 68C (1 55F) when delivered to a table within a resburant, and above 49C (1 20F) when transported and delNered after 30 minutes. Accordingly, each of these pizas proved to be well within acceptab~e temperature parameters.
;
c~t3 ~
21~327 When the pizzas were removed, the interior of each of the containers was inspected for condensation. The interior of each of the containers proved to be free of any noticeable moisture.
By way of comparison, a commercially available piz~a deliver,Y container S was simultaneously tested. This container comprised a water and watemJapor impermeable vinyl exterior shell, 1 1t4 inches of polyurethane foam insulation, and an impermeable vinyl interior shell. Two grommetied vent holes were provided in the side ~f the container.
Although the commercial container delivered pizza at or slightiy abo~e 10 the temperatures of the sample containers of the present invention, a visual inspection of the interior of the container after 30 minutes showed substantiai condensation build-up. The amount of water present was so great that the piz~a box had bec~me wet from the condensate. Further, when stored after the test, the commercial container remained wet for an extended period of l5 time--with noticeable moisture still present after two days of na use. This mcisture retention problem is expected to be far worse when the bass are used repeatedly and are not concertedly dried behveen uses.
A subjective taste test of the five pizzas delivered within the five bags tested found them all to be comparabve in temperature, taste and rnoisture 20 content.
It should be evident from the above exampl~s that containers constructed in accordance with the present Invention significantly avoid moisture problems -o~nmonly encountered with presently available delivery containers.
k AN~ND~ ~ET
In light of the active intetest in such businesses, it is hardly surprising that tremendous activity has centered around means of keeping food hot (or cold) and fresh during transportation. The most common containers in this regard have been primary food packages constructed from waxed paper, ~u plastic or cardboard. Although such containers are inexpensive and convenient. they have proven limited in their ability to preser~e the temperature, freshness and texture of the food.
In response to these concerns, a number of solutions haYe been proposed. For examplel deli~ered piza today is commonly placed in a 25 primary food recept~cie (e.g. a cardboard box) and then inserted into an insulative pDuch for transportation. These pouches are generally constructed from an outer shell of durable ~nit-backed vinyl or similar polymer rnaterial, insulated with approxirnately 3.2 cm (1 1/4 inches) of open cell foarn on eitherside of the piz~a box, and lined ~4ith a nylon coated with vinyl, or simi~ar 30 material.
In order to proteçt '.he insulation frorn becoming wet and/or contaminated with food, the interior liner is norrnally rnade water AM~NI~ED SI~EET
_ WO 94121536 21 S 5 3 2 7 PCT/US93103466 proof to contain moisture within the liner. It is generally recognized that the free flow of liquid through the liner presents a distinct health hazard by allowing bacteria to grow within the insulation and pass back to the food in condensed water vapor.
Additionally, when foam insulation becomes wet, it loses its insulative properties and may even become a heat sink. To address these concerns, recent improvements in this area have included providing a liner of polyester MYLAR-type material which is both heat reflective and almost completely water and water vapor impermeable.
Although such pouches are convenient, relatively inexpensive, and a substantial improvement over the use of a box alone, they are deficient in many respects. The primary problem with these devices is that a sealed interior liner tends to trap moisture vapor given off by the food within the container itself. As the packaging begins to cool, this trapped moisture vapor condenses and leads to the pizza becoming "soggy." The addition of grommetted vent holes in the side of the pouch offers only limited improvement in these conditions. Vent holes free moisture vapor, but they simultaneously release heat--requiring careful proportions to permit liberating some steam while retaining a sufficiently hot and moist pizza. To compound this problem further, the loss of too much moisture is also to be avoided since it can result in the food becoming dry and unappetizing. As a result, these pouches are limited in their utility and service range and present a constant threat of cool and/or damp or dry pizza.
In light of these limitations, a number of far more exotic solutions have been proposed. United States Patents 4,806,736 issued February 21, 1989, to Schirico and 4,816,646 issued March 28, 1989, to Greve each discloses use of pizza delivery containers containing built-in electric resistance heating elements to help keep pizzas hot. To address the problem of moisture build-up specifically, United States Patent 4,922,626 issued May 8, 1990, to Fiddler discloses a pizza delivery container with a motor-driven 3s fan to circulate moist air over a moisture-removing dissicant cartridge. These solutions may function reasonably well for their stated purposes, but they are each considered needlessly complicated and too cumbersome and expensive for widespread use.
Another area of growin~ interest is the delivery of r~la~ively br~e - quantitie~ of hot foods. In addition to normal catering actiYitiss, a number of businesses have sou~ht to expand into ~he delivery of lar~e number of pizas and other foods to schools and camps. In this context, the use of a relaUvely s small pouch is sirnply impractical. Moreover, employing nume-ous pizza boxes or other primary food receptacles is considered both wasteful and a needless expense.
One solution prop,osed in this regard is t~ provide a rack in which multiple reusable trays of food can ~e s~ ked To Insulate the food in the 10 rack~ a padded nylon cover is formed around t~he r~ to help contain the ~ood heat. Wffl a much ~reater quantity of food and much less relative outside surFace a~rea, food tends to stay warmer in this environment. Unfortunately, the problern of rnoisture build-up may be compounded ~,nce the amount of food contained in the rack ;s far greater than the arailable surface area 15 pe,."i:ling moisture dissip~;on. Addltionally, if coYered prim~ry food receptacles are not o"lp'3~r~ in the food rac~s, there is also an increased riskof both liquid precip;td~ onto the food and bacterial contarnination.
Unite~ States Pabnt 4,283,427 to Winters et al. is directed to a microwaYe heatin~ pack~e and a rnethod of microwave heating. The patent 20 is directed to using a l"alenal that b~comes microwave transparent at a given temperature in order to provide an automatic shut off for heatin~ in a microwa~e oven. The mana~ement of heat and rnoJsture in a food t~ansport container is not addressed by this ~-ference.
Patent ~pfic~tion WO 87~04663 to Fo, lapax L~d. is directed to a 2~ foamed p~astic sheet that can be used to insulate food containers. The a,pl.s-tion teaches usin~ an open cell foamed plastic that allows rnoisture to pass thraugh it in arder to keep the moisture away fram faod. The foam plastic shee~ is tau~ht to be appli~d in cont~ct with ~e foad itself. While thisapproach might provide some improvernent owr impenetrable ciosed ccll 30 insulation in sep~c.li,~9 mo~sture frGm ~e food, it c~ntinues to be pl-gu~ bynumerous pr~b'e."s, including inability to ade~uately clean ~e open cell foam between uses, inadequate protec~ion of the food from contamination, insufficient moisture barrier to prevent condensed moisture from passing back to the food, etc.
) Finally, German patent application DE 27 37 756 to W. L. Gore ~
Associates, Inc., is directed to a larninate of microporous PTFE membrane and a fabric material. This laminate is both waterproof and moisture vapor permeable. However, there is no teaching in this reference as to how to use S such a material to produce an improved ~ood transport container.
Finaliy, there are believed to be other applications where a breathable, insulated container for carrying perishables is of use. For example, in the transportation cf certain bio-rnedical products and specimens it is sometimes desirable to keep the product at a constant temperature but allow the lG dissipation of moisture vapor withoul a build up of condensation.
A~-cordingly, it is a pnmary purpose of the present invention to provide an apparatus for protecting food and similar produc-.s which is effective at dissipa'Jng unwanted moisture vapor while retaining heat.
It is a further purpose of the present invention to provide such an , apparatus which provides an effective barrier to liquid entering the storage area through either condensation or seepage from wet weather or other ambient conditions.
It is an additional purpose of the present invention to provide such an apparatus which ~an be adapted to control mois~ure effectively in a Yariety of 2n applications, including instanc~s where relatively large quantities of perishables must be protected.
It is another purpose of the present invenUon to provide such an apparatus which is relatively easy to construc~, use, and transport.
These and other purposes of the present invention will beco ne evident 25 from review of the following specification. These purposes are attained by the container as claimed in the present appliation.
SUMMARY O~ THE INVENTION
The present invention is an improved container for storing and insulating transported food and similar products. The container comprises one 30 or more layçrs of a polymer fabric which is permeable to moisture vapor but resistant to liquid pene~ration. Preferably a laminate of porous polytetrafluoroethylene is ~sed which has proven to be highly effective at se~ectively transmitting water vapor wnile acting as a barrier to transrnission of liquid water. When steaming hot food or other perishable is stored in the 3~ container of the present in~ention, rnoisture vapor freely dissipates fronl the food storage area so as to avoid the detrimental effect of condensation on the food.
In the preferred embodiment of the present invention, the container AMEN~ED Sl~EET
t~
employs multiple layers, with a "breatha~le"/water repellent inner shell directly surrounding the food or food receptacle, an exterior shell pro~ecting ~he outside of the container, and a layer of insulation provided between the inner and exterior shells to help retain heat within the container. As the terrn 5 "breathable" is applied herein, it is meant to encompass any material permitting the passage of moisture vapor. In practice, moisture vapor will pass out of the storage area and either vent to atmosphere or condense between the inner shell ~nd the exterior shell. Since the inner shell is waterproof, condensate is prevented from re-entering the storage ~rea.
lo In a further improvement of the present invention, a temperature maintenance device, preferably compr!sing a phase change material, is employed to assist in maintaining the temperature of the container at a desired level over an extended period of time.
The present invention has proven to be ~uite successful at prup~r,~
II )Fn .~F~T
~ WO 94/21536 215 ~ 3 2 7 PCT/US93/03466 properly transmitting moisture vapor and delivering food which is hot and fresh. The present invention avoids many of the problems previously encountered with some previous insulated storage bags, such as soggy or dry food, and risk of bacterial contamination.
DESCRIPTION OF THE DRAWINGS
The operation of the present invention should become apparent from the following description when considered in conjunction with the accompanying drawings, in which:
Figure 1 is a three-quarter isometric view of a first embodiment of a container of the present invention;
Figure 2 is an enlarged cross-sectional view of an exterior shell, insulative layer, and interior shell of the embodiment of Figure l;
Figure 3 is a three-quarter isometric view of a second embodiment of a container of the present invention, equipped with a rack for stacking multiple layers of food;
Figure 4 is a three-quarter isometric view of third embodiment of a container of the present invention, also equipped with a rack for stacking multiple layers of food; and Figure S is a three-quarter perspective view of a packet of heat emitting material which may be employed in the present invention, the packet being insertable into a pocket provided in the container shown in Figure l.
DETAILED DESCRIPTION OF THE INVENTION
2s The present invention provides an improved container for storing virtually any form of food or similar material. Although the primary intended use of the present invention is for the transportation of food, and the term "food" is applied throughout - this specification for the purpose of simplicity, it should be appreciated that the present invention may be used to store or transport a variety of products, and especially perishable products and specimens, such as those encountered in health care and bio-medical applications.
WO 94/21536 t . - PCT/US93/03466 Shown in Figures 1 and 2 is one embodiment of a container 10 of the present invention. Container 10 is formed as a pouch adapted to receive one or more conventional pizza boxes or similar primary food receptacles and seal around the receptacles to assist in keeping them warm. The container 10 comprises an exterior or secondary shell 12, an insulation layer 14, and an interior shell or liner 16. In order to seal around the receptacles, a flap 18 is provided which can be held in place with any suitable means, such as zippers or hook-and-loop fasteners 20, 22, as shown. The container 10 is also provided with a sealable pocket 24 in the inner liner 16 to receive a heat emitting device as is described below.
As has been explained, in a conventional pouch of this form, a serious problem emerges of condensation from food moisture vapor building up within the pouch and precipitating on the food. This tends to leave the food "soggy" and less appetizing.
However, if the pouch is made from water permeable material, it tends to suffer from numerous other problems. First, the pouch provides insufficient protection from the elements, risking wet and cold food due to seepage of rain or snow. Second, a water permeable inner lining allows water vapor to condense within the insulation layer and lead to heat loss problems. Third, a water permeable inner lining further allows condensation from the insulation layer to pass back through to the food storage area--again making the food wet and cold. Moreover, the passage of condensate from the insulation layer to the food storage area also provides a very undesirable mechanism for bacterial growth from the inaccessible (and thus difficult to clean) insulation layer to contaminate the food. This concern is amplified if the permeable inner lining allows food particles to enter the insulation layer and culture bacterial growth therein.
In order to combat the moisture vapor problem, the present invention uses an inner liner which is moisture vapor permeable but liquid repellent. As is taught in United States Patent 3,953,566 issued April 27, 1976, to Gore, one such material can be formed by heating and rapidly expanding polytetrafluoroethylene (PTFE).
Improvements in this basic process are disclosed in a variety of patents, including United States Patent 4,194,041 issued March 18, ._ WO 94/21536 PCT/US93/03466 1980, to Gore et al., and 5,026,591 issued June 25, 1991, to Henn et al. The resulting product contains a micro-porous lattice of expanded PTFE which is porous enough to allow water vapor to pass through but is hydrophobic and sufficiently dense to repel liquid water. This "breathable"/water repellent material is commercially available from W. L. Gore & Associates, Inc., of Elkton, MD, in a variety of forms, including as a laminated fabric, available under the registered trademark GORE-TEX, which has the expanded PTFE
membrane pre-applied to a polymer fabric material.
Shown in Figure 2 is a more detailed representation of the various components of the container of the present invention. In this embodiment, the inner shell 16 comprises a layer of polymer fabric 26, such as a nylon taffeta. Attached to the fabric 26 with an adhesive layer 28 is a membrane of expanded PTFE 30. The PTFE
membrane 30 comprises a sheet of expanded PTFE made in accordance with the teachings of United States Patent 4,953,566 to Gore with a microporous lattice comprising nodes interconnected with fibrils.
This lattice should provide sufficient pore size for the passage of water vapor while being sufficiently dense and hydrophobic so as to repel liquid water.
Additional water repellency and resistance to contamination of the pores can be achieved by coating the membrane with a variety of substances, such as perfluorosulphonic acid or breathable polyurethane. Processes for providing such coatings are set forth in a number of patents, including United States Patents 4,194,041 to Gore et al., 5,026,591 to Henn et al., and 4,942,214 issued July 17, 1990, to Sakhpara. Although a coating tends to decrease moisture vapor permeability, it significantly increases the durability and liquid repellency of the membrane. Moreover, as is explained below, by varying the type of membrane (e.g. the average pore size therein) and the type and amount of coating applied to the membrane, the precise amount of moisture vapor permeab;lity can be adjusted to produce a customized container with ideal conditions for certain types of foods and for certain service ranges (i.e.
periods of time and conditions under which particular food will stay fresh).
The membrane can be bonded to the fabric through any conventional means, including through the use of an adhesive. The 21~327 8 adhesive may be of any appropriate form which will bind the membrane 30 to the fabric 26 without clogging the pores. Suitable adhesives include, but are not limited to, the class consisting of thermoplastic polymers, thermosetting polymers, or reaction curing polymers. In order to maintain moisture vapor transmission, the adhesive should either be breathable and/or applied only in a non-continuous manner (e.g. through a dot pattern). The adhesives may be applied to the surfaces to be laminated by conventional means, for example by coating or printing methods, or under pressure and lo heat similar to the process disclosed in United States Patent 4,194,041 to Gore et al. Additionally, in embodiments incorporating a coating on the expanded PTFE, as is described above, a hydrophilic polyurethane polymer or similar material can perform a dual role of serving as a protective coating and 15 adhesively bonding the expanded PTFE membrane to the fabric layer.
These and other suitable adhesives are disclosed in United States Patent 4,925,731 issued May 15, 1990, to Driskill et al.
It should be understood that the expanded PTFE membrane, protective coating, and fabric can be arranged in any orientation 20 which will provide the permeability and barrier protection of the present invention. For example, in place of the orientation shown in Figure 2, the expanded PTFE membrane 30 may be oriented facing the interior of the container, with the fabric 26 facing the insulation 14. For this alternative arrangement, it would be 25 preferred to provide an adhesive layer 28 of hydrophilic polyurethane to help improve water repellency and reduce the risk of contamination of the PTFE membrane.
Since the exterior shell 12 must withstand greater abuse, it is preferable that it is constructed from a more durable material, such as vinyl, expanded vinyl, woven nylon (e.g. CORDURA fabric available from E. I. DuPont Co. of Wilmington, DE), etc. As shown, the exterior shell comprises an outer layer 32 of nylon fabric bonded to a coated expanded PTFE membrane 36 (similar to that disclosed in United States Patent 4,194,041 to Gore et al.) and an inner layer 34 of nylon taffeta fabric bonded to an un-coated expanded PTFE membrane (similar to that disclosed in United States Patent 3,953,566 to Gore). Although this construction is not necessary for the proper operation of the present invention, for q some applications it is believed desirabie to provide the exterior shell with a water resistant~breathable layer of expanded PTFE rnembrane 36. Again, the membrane 36 is held in place with a suitable adhesive 38, 40 or similar means.
The insulative layer 14 rnay take any appropriate forrn. It is common today to use an open cell foam (e g. polyurethane) 2.5 to 5 cm (1 to 2 inches) thick. This form of insulation is inexpensive yet has good insulative prope~tiesand good impact resistance. Furthermore, when used in conjunction with the embodiment of the present invention illustrated in Figures 1 and 2, this forrn of insulation tends to breathe sufficiently to permit moisture vapor to pass completely out of the container 10. Additional or alternatiYe insulation can be provided in the form of metallic coatings, and most open or closed cell foams and similar products. including polyesters, puffed polyesters ~e.g.
THERMOLITE insulation available from E.l. DyPont Co. or THINSULATE
insulation available from Minnesota Mining and Manufacturing Co. of St. Paul, s Minnesota), styrene! polyethy~ene, fiberglass, urethanes, and other such produc~s.
Due to the arnount of breathability which can be imparted with the present invention, vent holes can be eliminated from the pouch to provide a more thoroughly sealed container. Nonetheless, for some applications suc,h vent holes may be desira~le (such as to provide further increased air flow or torelease some of the fragrance cf the food as a markeUng tool~ and can be easiiy induded in the container of the present invention. As is known, it is preferred to pro~ide a grornmet or other reinforcement means around such holes.
2c Another embodiment of the present invention tS ~hown in Figure 3. In this configuration, a conbiner 42 is arran~ed in a rack format, providing means to stack a relatively large num~er of separate primary food raceptacles 44. In the illustrated embodiment, the primary food receptacle 44 comprises a cardboard box commonly used for delivered pizzas. Such receptacles 44 work ;o well in the context of the presPnt invention since they are inexpensive yet adequately separate the food from the container 42 while permitting moisture vapor to pass relatively freely from them AMENDED SI~EET
215~327 ._ WO 94/21536 PCTIUS93/03466 To assist in stacking the primary food receptacles 44, one or more shelves 46 may be included to help organize the receptacles and limit the amount of weight imposed on the lower receptacles.
The shelves 46 may be constructed from any suitable material, including a fabric, or semi-rigid or rigid metal or plastic material attached within the container 42.
Like the embodiment of Figures 1 and 2, this container 42 also is constructed from an exterior shell 48, an insulation layer 50a, 50b, 50c in some or all of the sides of the container, and an interior shell or liner 52. Again, the interior shell comprises a breathable moisture vapor permeable material which is resistant to liquid penetration. Due to reduced outside surface area relative to the amount of food which can be stored in this container 42, it is preferred that the liner 52 be constructed from material with a fairly substantial moisture permeability, such as un-coated expanded PTFE material available from W. L. Gore & Associates, Inc., under the trademark GORE-TEX fabric. Additionally, it may be even more desirable in this instance to also construct the exterior shell 48 from similar material, as is shown in Figure 2.
The container 42 is sealed through any suitable means, such as with flap 54. The flap 54 may be constructed from the same material as the rest of the container 42 and should include at least a breathable interior liner 56. The flap may be closed against the rest of the container using hook-and-loop fasteners 58, 60, or other appropriate means.
Shown in Figure 4 for much larger applications is a container 62 constructed to hold very large quantities of food in a rack format. In this form, the container 62 includes multiple shelf channels 64 to receive primary food receptacles, such as cardboard boxes (as have been discussed), or disposable or reusable food trays, etc. Again, the container 62 is constructed with a breathable yet water repellent liner 66, an insulative layer 68, and an exterior shell 70. Like the embodiment of Figure 3, the decreased relative outside surface area compared to the large food carrying capacity of this embodiment requires a liner 66, and perhaps insulation 68 and exterior shell 70, with a high degree of breathability.
A flap 72 is provided to seal the container 62. This flap 72 `_ WO 94/21536 21 S 5 3 2 7 PCT/US93103466 can be insulated and also constructed from breathable material.
The flap 72 may be sealed through use of any suitable means, including hook-and-loop fasteners or zippers 74, 76, as shown.
- Due to the size of the container 62 of this embodiment, it may be desirable to provide casters 78 or similar means to help in transportation.
Further improvement in the present invention can be provided by including some external heat source. Shown in Figure 5 is a temperature maintenance device in the form of a sealed packet 80 containing a phase change material 82. Phase change material comprises a composition which can be activated to cause it to give off heat over a period of time. Alternatively, the material may also be designed to absorb heat over a period of time to provide a cooling effect.
To help maintain food in a hot condition, a phase change material may be provided which can give off a steady amount of heat over an extended period of time. Examples of such material are disclosed in United States Patent 5,070,223 issued December 3, 1991, to Colasante.
Essentially, phase change material includes a solid inert material with an appropriate melting point. By dispersing the inert material within an insulative material and applying heat to melt the inert material, portions of the inert material will slowly cool in stages to return to a solid state. This phase change back to a solid state is an exothermic reaction which provides a steady source of heat.
For use in the present invention, a phase change material with an active ingredient of sodium acetate tetrahydrate or polyethylene glycol is believed suitable. Preferably, the phase change material comprises a mixture of silicone, graphite and polyethylene glycol which is blended to evenly distribute the polyglycol throughout the other ingredients. The material may be packaged within a sealedcontainer to prevent leakage, such as silicone, polyethylene, vinyl, or polyester.
To activate the material, it is exposed to an energy source, such as placing it in a 600 watt microwave oven over a period of approximately 1 minute. When heated in this manner, the phase change material will give off a fairly constant heat of approximately 57 to ~5C (135 to 185 F) over a period of 30 to 60 minutes One such sample tested gave off a temperature of about ~5C (185F) for about 15 minutes after initial equilibrium was reached, then a t~rnperature plateau of about 57C (135F) for another 30 to 45 minutes durin~ phase 5 change, and a steady decline in temperature thereafter. Accordingly, a reliable temperature production could be provided by this material over a period of up to 4~ to 60 minutes or more.
As should be evidenL by placing one or more packets 80 into a container of the present invention, the heat and freshness of the food can be 10 maintained over a significantly extended period of time. The embodiment of Figure 1 includes a pocket 24 adapted to receive such a packet 80. The pocket 24 includes a hook-and-loop sealable flap 84 to help isolate the packet from the f~od storage area. Depending upon the particular effectiveness of such material for a given food, it may be possible to reduce or elirninate the s use of insulation andlor decraase or eliminate the arnount of breathability of the container's fabric.
Although not preferred, without departing from the present invention, other heat or cooling sources may alsa be combined with the present invention for improved operation. Possible exarnples include a battery or fuel powered 20 heating elements, etc.
Even though incorporating a layer of expanded PTFE membrane is the preferred treatment to proYide the properties of the present invention. a number of othertreatrnents may also be effective in ~his regard. For instance, virtually any appropriate material can be en~ployed which will allow passase of 2s moisture vapor while resisting passage of liquid, such as polyethylene glycol-based materials. polyether polyurethanes, polyester polyethers, polyethylene, epoxies, polyimides, polyvinyl alcohol, as well as treated natural rnaterials such as cellulose or cotton.
It should be appreciated tllat the present invention may be adapted for 30 use in many different applications. Depending upan the food material and the environmental canditions, containers may be constructed with a single layer of polymer fabric, with numerous layers of fabric and/or insulation, and with hybrid polymer shells--only a portion of which being constructed frorn a breathable fabric. E:)ue to the present cost of the most effective forms of 35 breathablelwaterproof fabrics, far many ~pp'.c ~;ons it may be preferred to construct the liner from only a portion of breathable fabric in those areas requiring greatest breathability (e.g the top andJar sides) and using a less expensive liquld impermeable fabric for the remainder of the shell.
P~MEN~O S~EE~
215~327 Although the present invention is particula~y applicable to the transportation of steaming hot food, such as piza, as has been noted, it has numerous other possible applications for the transportation andlor short-tenT
storage of other perishables, such as cold foods, bio-medical products or 5 specimens, etc.
Depending upon requirements, the containers cf the present invention may be employed with or without a separate primary food receptacle. Where a primary food receptacle is employed. it should be constnJcted from a materiai which i5 permeable to moisture vapor, such as paper, cardboard, ---o cellulose. etc. With or without a prirnary food r~ceptacle, the material described has proven to be readily cleanable and highly resistant to penetration by food partic~es.
Without intending to limit the scope of the present invention, the following represent examples of how the containers oF the present invention ls may be constructed and ernployed:
Examples A series of containers were constructed and tested to determine the relative effectiveness of the present invention o~er existing food deli~ery containers and variations of designs pursuant to the present invention.
Container 1 - A first container in the form of a pizza pouch was constructed comprising a water impermeable vinyl exterior shell and a nylon taffeta interior liner bonded to an un-coated expanded porous PTFE GORE-TEX membrane acquired from W. L. Gore & Associates, Inc. An insulative layer of 3.2 cm (1 2S 1/4 inches) of open cell polyurethane was provided on the top and bottom ofthe pouch between the shell and the liner. Two c,onventional grornmetted vent holes were provided in the side of the container to permit insertion of a ternperature probe.
AMENDED SI~
21~5327 Container 2 A second con~ainer was constructed identical in form to that of Container 1 but with an exterior shell of nylon taffeta bonded to a polyurcthane coated expanded PTFE GORE-TEX membrane.
Container 3 A third container was constructed identical in forrn to that of Container 1 but with an exterior shell of nylon taffeta bonded to an un-coated expanded PTFE GORE-TEX membrane.
Container 4 o A fourth containerwas constructed identical in form to that of Container 1 but wi~ an exterior shell of nylon taffeta bonded to an un-coated expar,ded PTFE GORE-TEX me,nt,r~ne and a liner of nylor, taffeta bonded to a polyurethane coated expanded PTFE GOR -TEX membrane.
Each of the above containers was testea under the following l~ parameters. First, a strip thermometer (e.g. a THERMOLABEL) was placed on the interior bottom of the food storage areas of each o~ the containers. These thermometers provide a permanent reading of the hi~hest temperature reached. Five identical pizas packaged within a conventional corrugated cardboard boxes were then placed one in each of Ule containers. A second ~0 strip thermometer was placed on the top exteriors of each ~f the piza boxes After 30 minutes, a ~empe,cl-lre probe was inserted within each of the containers and a temperature reading was taken.
The following results were achieved:
Container Tem~. TOD of Piz~a Temp. Bottom of Pizza 1 65.5CC (150F) 71~C (160F) 2 60C (140F) 71 C (160F) 3 82C (180F) 82C ~B0~F) 4 60C (140F) 65.5C (150F~
At this point, the interior ternperature of each of the bags was tested with a temperature probe. Each was aboYe 60C (140F).
Generally pizza deliYery standards call for piza to be approximately 74C ~165F) when removed from an oven, about 68C (1 55F) when delivered to a table within a resburant, and above 49C (1 20F) when transported and delNered after 30 minutes. Accordingly, each of these pizas proved to be well within acceptab~e temperature parameters.
;
c~t3 ~
21~327 When the pizzas were removed, the interior of each of the containers was inspected for condensation. The interior of each of the containers proved to be free of any noticeable moisture.
By way of comparison, a commercially available piz~a deliver,Y container S was simultaneously tested. This container comprised a water and watemJapor impermeable vinyl exterior shell, 1 1t4 inches of polyurethane foam insulation, and an impermeable vinyl interior shell. Two grommetied vent holes were provided in the side ~f the container.
Although the commercial container delivered pizza at or slightiy abo~e 10 the temperatures of the sample containers of the present invention, a visual inspection of the interior of the container after 30 minutes showed substantiai condensation build-up. The amount of water present was so great that the piz~a box had bec~me wet from the condensate. Further, when stored after the test, the commercial container remained wet for an extended period of l5 time--with noticeable moisture still present after two days of na use. This mcisture retention problem is expected to be far worse when the bass are used repeatedly and are not concertedly dried behveen uses.
A subjective taste test of the five pizzas delivered within the five bags tested found them all to be comparabve in temperature, taste and rnoisture 20 content.
It should be evident from the above exampl~s that containers constructed in accordance with the present Invention significantly avoid moisture problems -o~nmonly encountered with presently available delivery containers.
k AN~ND~ ~ET
Claims (20)
1. A container for protecting perishable products during transportation which comprises a porous polymer shell adapted to cover the perishable product;
a breathable laminate attached to at least a portion of the polymer shell, the laminate comprising a porous polymer which selectively permits moisture vapor to pass through the polymer shell and restricts liquid from passing therethrough;
wherein the polymer shell and laminate serve to protect the product from condensed moisture vapor by allowing moisture vapor to pass away from the product through the polymer shell and laminate and preventing condensed liquid from passing back through the laminate to contaminate the product.
a breathable laminate attached to at least a portion of the polymer shell, the laminate comprising a porous polymer which selectively permits moisture vapor to pass through the polymer shell and restricts liquid from passing therethrough;
wherein the polymer shell and laminate serve to protect the product from condensed moisture vapor by allowing moisture vapor to pass away from the product through the polymer shell and laminate and preventing condensed liquid from passing back through the laminate to contaminate the product.
2. The container of claim 1 wherein the breathable laminate comprises a membrane of polytetrafluoroethylene (PTFE).
3. The container of claim 2 wherein the breathable laminate comprises a membrane of expanded PTFE with a polyurethane coating applied thereto.
4. The container of claim 1 wherein the polymer shell is encased within a secondary shell; and a thermal insulative layer is provided between the polymer shell and the secondary shell.
5. The container of claim 4 wherein the thermal insulative layer comprises a foam.
6. The container of claim 4 wherein the secondary shell includes a polymer coated with a breathable laminate.
7. The container of claim 1 which further comprises:
an outer secondary shell surrounding the polymer shell, the secondary shell and the polymer shell being formed as a pouch adapted to seal around the perishable product; and a thermally insulative layer oriented between the secondary shell and the polymer shell.
an outer secondary shell surrounding the polymer shell, the secondary shell and the polymer shell being formed as a pouch adapted to seal around the perishable product; and a thermally insulative layer oriented between the secondary shell and the polymer shell.
8. The container of claim 7 wherein the secondary shell includes a moisture vapor permeable material.
9. The container of claim 7 wherein the pouch is adapted to receive a moisture permeable primary receptacle in which the perishable product is stored.
10. The container of claim 1 wherein the container includes a rack adapted to receive multiple layers of perishable product.
11. A container for protecting perishable products which comprises:
an exterior shell;
an interior liner housed within the exterior shell, the interior liner being at least in part permeable to moisture vapor while being resistant to liquid penetration;
wherein the interior liner serves to protect the food from condensed moisture vapor by permitting moisture vapor to pass through the interior liner while in a gaseous state and preventing the moisture from re-entering the liner when it condenses to a liquid state.
an exterior shell;
an interior liner housed within the exterior shell, the interior liner being at least in part permeable to moisture vapor while being resistant to liquid penetration;
wherein the interior liner serves to protect the food from condensed moisture vapor by permitting moisture vapor to pass through the interior liner while in a gaseous state and preventing the moisture from re-entering the liner when it condenses to a liquid state.
12. The container of claim 11 which further comprises a thermally insulative material positioned between the exterior shell and the interior liner to assist in retaining heat within the container.
13. The container of claim 11 wherein the interior liner includes a porous membrane of expanded polytetrafluoroethylene (PTFE).
14. The container of claim 13 wherein the membrane of PTFE includes a coating to improve liquid water penetration resistance of the membrane.
15. The container of claim 11 wherein the container is adapted to receive a moisture vapor permeable primary food receptacle in which the food is stored.
16. The container of claim 15 which further comprises a rack for stacking multiple primary food receptacles.
17. The container of claim 11 which further includes a temperature maintenance device within the container to assist in maintaining the temperature of the food.
18. The container of claim 17 wherein the temperature maintenance device comprises a packet containing phase change material, the phase change material serving to radiate heat when activated.
19. The container of claim 16 wherein a pocket is provided within the liner to house the packet.
20. An improved apparatus for preservation of hot products during transportation which comprises:
a container having an exterior shell, an interior liner, and an insulation layer therebetween, a sealable storage area being formed within the interior liner;
a temperature maintenance device including phase change material which provides a relatively steady source of heat once activated.
wherein the temperature maintenance device is placed within the storage area along with the food in order to assist in maintaining the temperature of the food;
the liner having an interior and an exterior surface, the liner being constructed at least in part from a material which is permeable to moisture vapor and resistant to liquid penetration, the product to be protected being placed within the storage area during transportation;
wherein moisture vapor emitted from the product to be protected dissipates from the interior of the liner by penetrating the breathable liner, and liquid on the exterior of the liner, including condensed moisture vapor, is prevented from entering the interior of the liner by the liquid resistant material.
a container having an exterior shell, an interior liner, and an insulation layer therebetween, a sealable storage area being formed within the interior liner;
a temperature maintenance device including phase change material which provides a relatively steady source of heat once activated.
wherein the temperature maintenance device is placed within the storage area along with the food in order to assist in maintaining the temperature of the food;
the liner having an interior and an exterior surface, the liner being constructed at least in part from a material which is permeable to moisture vapor and resistant to liquid penetration, the product to be protected being placed within the storage area during transportation;
wherein moisture vapor emitted from the product to be protected dissipates from the interior of the liner by penetrating the breathable liner, and liquid on the exterior of the liner, including condensed moisture vapor, is prevented from entering the interior of the liner by the liquid resistant material.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US08/036,306 US5454471A (en) | 1993-03-24 | 1993-03-24 | Insulative food container employing breathable polymer laminate |
| US08/036,306 | 1993-03-24 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2155327A1 true CA2155327A1 (en) | 1994-09-29 |
Family
ID=21887853
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002155327A Abandoned CA2155327A1 (en) | 1993-03-24 | 1993-04-13 | Insulative food container employing breathable polymer laminate |
Country Status (5)
| Country | Link |
|---|---|
| US (1) | US5454471A (en) |
| EP (1) | EP0689517A1 (en) |
| JP (1) | JPH08510429A (en) |
| CA (1) | CA2155327A1 (en) |
| WO (1) | WO1994021536A1 (en) |
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- 1993-03-24 US US08/036,306 patent/US5454471A/en not_active Expired - Fee Related
- 1993-04-13 EP EP93912221A patent/EP0689517A1/en not_active Withdrawn
- 1993-04-13 CA CA002155327A patent/CA2155327A1/en not_active Abandoned
- 1993-04-13 JP JP6520987A patent/JPH08510429A/en active Pending
- 1993-04-13 WO PCT/US1993/003466 patent/WO1994021536A1/en not_active Application Discontinuation
Also Published As
| Publication number | Publication date |
|---|---|
| JPH08510429A (en) | 1996-11-05 |
| EP0689517A1 (en) | 1996-01-03 |
| WO1994021536A1 (en) | 1994-09-29 |
| US5454471A (en) | 1995-10-03 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| FZDE | Discontinued |