Patent Publication Number: US-2010108693-A1

Title: Insulated double-walled disposable plastic cup

Description:
FIELD OF THE INVENTION 
     The present invention generally relates to disposable plastic containers, and more particularly to thermally insulated disposable plastic containers. More specifically, the present invention relates to double-walled thermally insulated disposable plastic containers. 
     BACKGROUND OF THE INVENTION 
     The production and use of thermally insulated disposable containers, such as cups, are well known and highly desirable. Thermally insulated disposable cups are generally useful for both hot and cold beverages. They are designed to maintain the beverage temperature by preventing undesirable heat transfer via the beverage inside the cup to/from the atmosphere or cup holder&#39;s hand. Currently available thermally insulated disposable cups are generally made from paper, polymeric materials or combinations thereof. 
     Paper-based materials are generally favored for disposable cups, because of low cost and high volume production capability. However, paper-based materials generally do not have good barrier properties to liquids. Disposable cups made from such paper-based materials, have a tendency to decompose due to liquid penetration into the paper material, which can cause the cup to loose its structure and become soggy or leak. Furthermore, cups made from paper-based materials generally do not provide adequate thermal insulation and have limited product visibility. 
     There have been many attempts to provide improved thermal insulation to paper-based disposable cups. U.S. Pat. No. 5,226,585 to Varano discloses a double-walled disposable cup made from paper-based materials, which has a smooth walled inner cup and an outer wrap with inwardly directed ribs being useful to maintain a gap between the walls to provide thermal insulation. However, these cups are difficult and expensive to manufacture. They also tend to exhibit liquid barrier problems, which compromise the structural integrity of the cup. 
     U.S. Pat. No. 5,145,107 to Silver et al. teaches a double-walled thermal insulated disposable paper cup having an inner wall connected to an outer wall at the lip and at the base of the cup. The walls have different tapers which define an air pocket between the two walls. The air pocket is meant to provide thermal insulation. However, as with currently available paper-based disposable cups, structural integrity and product visibility remain a disadvantage. 
     Polymeric materials, such as polypropylene, polyethylene terephthalate (PET) based polyesters and polystyrenes have been widely used as container materials for disposable containers because of their improved mechanical and barrier properties. They also provide for product visibility. Numerous methods of producing disposable plastic beverage bottles and cups are disclosed in the prior art. However, containers made from such plastic materials do not provide adequate thermal insulation. Foamed polystyrene cups provide adequate insulation but are not good for recyclability and don&#39;t provide transparency. 
     Accordingly, there is a need for a disposable container that provides excellent thermal insulation and barrier properties and is recyclable. It would also be desirable to see the inside of the container from the sides of the container, thereby having better visibility of the product contained therein. In paper based or foamed polystyrene containers, in order to see the contents inside, it is necessary to look through an opening, for example by removing a lid, which could result in spills or additional heat transfer via the opening. Accordingly, it would be desirable to provide a transparent thermally insulated disposable plastic container. 
     SUMMARY OF THE INVENTION 
     The present invention relates to a thermally insulated double-walled disposable container made from polymeric materials useful for containing hot or cold products and liquids. Thermally insulated double-walled disposable containers in accordance with the invention provide recyclability, enhanced container structural integrity and improved insulation. In addition, a container in accordance with the invention may be transparent. Conventional methods may be used to manufacture a thermally insulated double-walled disposable container in accordance with the invention. The manufacturing of the containers are cost effective. 
     In an aspect of the invention, a thermally insulated double-walled disposable plastic container includes a container body having an inner cup and outer cup fixedly separated by a space. The thermally insulated double-walled disposable plastic container is open at the top and enclosed at the bottom. The space includes a gas for providing thermal insulation. A preferred gas is air. Preferred methods for making the insulated double-walled disposable plastic container includes blow-molding, thermoforming or injecting molding an inner cup and outer cup then fixedly connecting the inner cup and outer cup to define an insulation space there between. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional view of one embodiment of a container in accordance with the invention. 
         FIG. 1A  is an enlarged view of a wall connection in accordance with the invention. 
         FIG. 1B  is an enlarged view of an alternate wall connection in accordance with the invention. 
         FIG. 1C  is an enlarged view of a yet another alternate wall connection in accordance with the invention. 
         FIG. 2  is a cross-sectional view of a tapered walled container in accordance with the invention. 
         FIG. 2A  is an enlarged view of a wall connection of a tapered walled container of the invention. 
         FIG. 2B  is an enlarged view of alternate wall connection of a tapered walled container of the invention. 
         FIG. 2C  is an enlarged view of a yet another alternate wall connection of a tapered walled container of the invention. 
         FIG. 3  is a top view of a container divided into four equal parts having two double-walled portions in accordance with the invention. 
         FIG. 4  is a top view of a container divided into six equal parts having three double-walled portions in accordance with the invention. 
         FIG. 5  is a perspective view of horizontal ribs between walls of a container of the invention 
         FIG. 6  is a perspective view of vertical ribs between walls of a container of the invention. 
         FIG. 7  is a perspective view of one embodiment of a container with both horizontal and vertical ribs between the walls. 
     
    
    
     DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS 
     The present invention provides a thermally insulated double-walled disposable plastic container having excellent insulation properties, recyclability, and optionally transparency. As used herein the term “plastic” refers to a wide range of synthetic or semi-synthetic polymerization products, composed of organic condensation or addition polymers and may contain other substances, including bio materials and recycled content, to improve performance or reduce costs. “Disposable” as used herein is meant to describe articles that are most often discarded after one use. “Double-walled” as used herein refers to a structure that includes an inside wall, an outside wall, and a space defined between the inside wall and outside wall. The term “insulated or insulating” as used here in refers generally to the prevention of reduction of heat transfer from conducting bodies. The term “insulated double-walled disposable plastic container” may alternatively be referred to as ‘container’ for convenience. As used herein the terms inside wall and inside cup generally refer to the same structure and outside wall and outside cup generally refer to the same structure where the container is a cup, and respectively may be used interchangeably. 
     Referring now to  FIG. 1 , there is shown a container  100 . In one embodiment of the invention, the container  100  is preferably a double-walled disposable plastic cup. The container  100  includes an inside wall or cup  102  and an outside wall or cup  104 . The inside wall or cup  102  and the outside wall or cup  104  are fixedly separated by an insulation space  106  between them, and joined at an upper section of the container to enclose the insulation space  106 . The container  100  includes an interior space  110  for containing food or beverages. The inside wall or cup  102  and the outside wall or cup  104  may be any suitable shape, but in a preferred embodiment are frusto-conical in shape with an opening at the top and a base section  108  for providing a closed end. In an embodiment of the invention, the base section  108  is also double-walled. A double-walled base section  108  preferably comprises an inwardly extending protrusion  130  that connects the inside wall or cup  102  and an outside wall or cup  104  to help provide an even distribution of gas or air in the insulation space  106 . In another embodiment of the invention, the base section  108  may be single-walled (not shown). “Single-walled” as used herein refers to a structure that includes only a single layer or a structure that does not have an insulating layer. As shown, the inside wall or cup  102  and outside wall or cup  104  may be formed parallel to each other or any suitable design, including but not limited to tapered. In an embodiment of the invention, vertical ribs are welded on the inside wall or cup  102  and the outside wall or cup  104  for additional strength. 
     The inside wall or cup  102 , the outside wall or cup  104  and the base section  108  may be formed of any suitable plastic. Preferred plastics include polypropylene (PP), polyethylene terephthalate (PET), polylactic acid (PLA), polystyrene (PS) or combinations thereof. It is also preferred that the plastic be food grade plastic. 
     Insulation space  106  preferably comprises a gas. Any suitable gas may be used. It is preferred that such gas provides insulation properties equal to or better than air. Preferred gases include air, nitrogen, and hydrocarbon gases such as pentane or combinations thereof. 
     In accordance with an embodiment of the invention, preferably, the outside wall or cup  104  is preferably of from about 0.005 to 0.030 inches in thickness and more preferably of from about 0.010 to 0.020 inches in thickness; and the inside wall or cup  102  is preferably of from about of 0.001 to 0.012 inches in thickness and more preferably about 0.005 to 0.010. The space  106  between the inside wall  102  and the outside wall  104  is preferably between 0.025 and 0.250 inches, more preferably, between 0.100 and 0.200 inches and even more preferably, between 0.130 and 0.150 inches. 
     In one embodiment of the invention, the container  100  is transparent. In this embodiment it is preferred that at least the inside wall or cup  102  and the outside wall or cup  104  are transparent. The inside wall or cup  102  and the outside wall or cup  104  are preferably formed from any suitable food grade plastic having transparent properties and a transparency value of 80 to 100%. While it is to be understood that the base section  108  also may be transparent, it is not required by the invention. 
     In one embodiment of the invention, the container  100  is translucent. In this embodiment it is preferred that at least the inside wall  102  and the outside wall  104  are translucent. The inside wall  102  and the outside wall  104  are preferably formed from any suitable food grade plastics having translucent properties. While it is to be understood that the base section  108  also may be translucent, it is not required by the invention. The container may be any suitable color and it is also envisioned that the container may be opaque. 
     The container  100  may be of any suitable size. In an embodiment of the invention, the container  100  can also be of the size and shape of a commonly used take-out container to store food or beverages. The take-out container may be of any shape, without limitation, such as a box-type container. In an embodiment of the invention, the container can be put in a microwave or freezer. In various embodiments, the container may have a length larger than the height. In a preferred embodiment of the invention, the base preferably is double-walled. 
     In an embodiment, wherein the container  100  is a cup, the cup may be of any suitable size. For example, the cup can be made in sizes generally used in restaurants and coffee shops, including but not limited to 12, 16, 20, 21, 22, 32 and 44 oz cups. 
     The inside wall or cup  102  and outside wall or cup  104  may be joined or connected by any suitable techniques. A person skilled in the art would appreciate that various chemical or mechanical techniques may be used to join inside wall or cup  102  and outside wall or cup  104  such as, without limitation, welding, ultrasonic welding, adhesive sealants, rim rolling or snap fitting sealing engagement.  FIG. 1A  is an enlarged view of a preferred wall connection  113  by welding or using an adhesive sealant.  FIG. 1B  is an enlarged view of a preferred wall connection, wherein the inside wall or cup  102  and outside wall or cup  104  both have an overhang rim that are rolled together by a conventional rim rolling process to form a curled overturned rim  112 . The upper rim or periphery  114  of the inside wall or cup  102  is curled over the curl of the outside wall or cup  104 . Such double curling also enhances the rigidity of the container  100 . 
       FIG. 1C  is an enlarged view of yet another preferred wall connection technique for a substantially parallel walled container  100 , whereby a snap fitting sealing engagement forms a wall sealing engagement  113 ′ that fixedly attaches the outside wall  104  and inside wall  102 . The snap fitting sealing engagement is advantageous particularly in the case where a lid  120  may be used in connection with the container  100 . In a preferred embodiment, the outside wall  104  is preferably provided with at least two locking protrusions  116  and  118  for engaging the inside wall  102  and a lid  120 , respectively. Preferably, a first outside wall locking protrusion  116  slopes inwardly and downwardly from a top section of the outside wall  104  to provide an engagement section for the inside wall  102 . The inside wall  102  is substantially parallel to the outside wall and extends above and over the top of the outside wall  104 , further extending downwardly to engage an inside wall locking protrusion  116  of the outside wall  104  via an inside wall inner protrusion  117  that slopes inwardly and downwardly to engage and seal with the first outside wall locking protrusion  116 . A second outside wall locking protrusion  118  slopes outwardly and downwardly below the first outside wall protrusion  116  to provide an engagement section for the lid  120 . The lid  120  preferably extends below the first outside wall locking protrusion  116  and has a lid locking protrusion  119  that slopes inwardly to engage the second outside wall locking protrusion  118  and seal the lid to the cup. 
     In another embodiment of the invention, shown in  FIG. 2 , the top section of the outside wall or cup  204  and the inside wall or cup  202  have a difference in taper. Any suitable angle may be used for the taper. As with the previous embodiment, the inside wall or cup  202  and outside wall or cup  204  may be connected by any suitable techniques. In a double-walled base embodiment, there is provided a centering ring  230  that connects the walls or the container to create a concentric gas gap and even distribution of gas between the outside wall or cup  204  and the inside wall or cup  202 . 
       FIG. 2A  is an enlarged view of a cut-out section of a preferred wall or cup connection  213  formed by welding or gluing. The outside wall or cup  204  of the inside wall or cup  202  is sealed via an adhesive or welded in any suitable section of the container from the upper end of the taper to an outwardly extending lip or bend of the outside wall  204 . The upper rim or periphery  214  of the inside wall or cup  202  is preferably formed over and welded to the lip or bend  212  of the outside wall or cup  204 . 
       FIG. 2B  is an enlarged view of a preferred tapered walled connection, where at a suitable point after the taper whereby the inside wall or cup  202  and outside wall or cup  204  meet, the overhang from both the inside wall or cup  202  and outside wall or cup  204  are rolled together by a conventional rim rolling process to form a curled overturned rim  212 . 
       FIG. 2C  is an enlarged view of yet another preferred wall connection technique for a tapered wall container  200 , whereby a snap fitting sealing engagement forms a wall sealing engagement  213 ′ that fixedly attaches the outside wall or cup  204  and inside wall or cup  202 . The snap fitting sealing engagement is advantageous particularly in the case where a lid  220  may be used in connection with the container  200 . In a preferred embodiment, the outside wall or cup  204  is preferably provided with at least two locking protrusions  216  and  218  for engaging the inside wall or cup  202  and a lid  220 , respectively. Preferably, a first outside wall locking protrusion section  216  having an interior surface that slopes inwardly and downwardly from a top section of the outside wall or cup  204  to provide a clasp section for the inside wall  202  having a contact point  221  for a flat outer surface of the inside wall or cup  202  and an inside wall inner protrusion  217  to pinch the first outside wall locking protrusion section  216 . The inside wall or cup  202  tapers toward the outside wall or cup  204  at any suitable position below the first outside wall locking protrusion section and extends above and over the top of the outside wall or cup  204 , further extending downwardly to engage an flat outer surface of the first outside wall locking protrusion section  216  via the inside wall inner protrusion  217  that slopes inwardly and downwardly to pinch the first outside wall locking protrusion section  216 . A second outside wall locking protrusion  218  slopes outwardly and downwardly below the first outside wall protrusion section  216  to provide an engagement section for the lid  220 . The lid  220  preferably extends below the first outside wall locking protrusion section  216  and has a lid locking protrusion  219  that slopes inwardly to engage the second outside wall locking protrusion  218  and seal the lid  220  to the container. 
     In various embodiments of the invention, the double wall is provided only to a portion of the container. The container may be divided into double-walled and single-walled portions. For example, the container may be divided into four parts out of which two are double-walled.  FIG. 3  is a top view of the container  300  in an embodiment of the invention. The circumference of container  300  is divided into four equal parts having two double-walled portions. In a preferred embodiment, two alternate parts  302   a,  and  302   b  are double-walled while the other two  304   a  and  304   b  are single walled.  FIG. 4  is a top view of the container  400  in an embodiment of the invention. The circumference of container  400  is divided into six equal parts having three double-walled portions. In a preferred embodiment, three alternate parts  402   a,    402   b,  and  402   c  are double-walled while the other three  404   a,    404   b,  and  404   c,  are single walled. 
     In an embodiment of the invention shown in  FIG. 5 , the container  500  has horizontal ribs  506  between the inside wall or cup  502  and the outside wall or cup  504 . The horizontal ribs  506  are circular in shape and divide the annular region between the inside wall or cup  502  and the outside wall or cup  504  into number of horizontal sub-regions. The horizontal ribs  506  reduce convection heat loss by blocking air circulation between sub-regions. As a result, the horizontal ribs  506  enhance the thermal insulation performance of the container  500 . In an embodiment of the invention, the horizontal ribs  506  are preferably about 8 mm apart. The horizontal rib thickness is preferably between about 0.001 inch and about 0.010 inch. 
     In another embodiment shown in  FIG. 6 , the container  600  has vertical ribs  606  between the inside wall or cup  602  and the outside wall or cup  604 . The vertical ribs  606  are rectangular in shape and divide the annular region between the inside wall or cup  602  and the outside wall or cup  604  into number of vertical sub-regions. The vertical ribs  606  reduce convection heat loss by blocking air circulation between sub-regions. As a result, the vertical ribs  606  enhance thermal insulation performance of the container  600 . In an embodiment of the invention, the vertical ribs  606  are preferably about 8 mm apart. The vertical rib thickness is preferably between about 0.001 inch and about 0.010 inch. 
     In yet another embodiment shown in  FIG. 7 , the container  700  has both horizontal ribs  706  and vertical ribs  708  that form grids between the inside wall or cup  702  and the outside wall or cup  704 . The grids are preferably square or rectangular. The horizontal ribs  706  and the vertical ribs  708  reduce convection heat loss by blocking air circulation between grids. As a result, the horizontal ribs  706  and the vertical ribs  708  enhance thermal insulation performance of the container  700 . In an embodiment of the invention, the grids are of square shape and are preferably about 8 mm by 8 mm. The thickness of the grids is preferably between about 0.001 inch and about 0.010 inch. 
     A double-walled disposable plastic container in accordance with the invention may be formed by any suitable means. In accordance with another embodiment of the invention the container may be manufactured by conventional blow molding and trimming techniques. Generally a bottle is first formed by a conventional blow molding process. Then the top portion and the body of the bottle are separated into two pieces by a trimming process. The resultant body portion forms a cup. Any thermoplastic polymer can be used to prepare the perform, for example, polypropylene (PP), polyethylene terephthalate (PET), polylactic acid (PLA), polystyrene (PS) or combinations thereof. It is also preferred that the plastic be food grade plastic. Preferred products are polypropylene (PP), polyethylene terephthalate (PET). In yet another embodiment of the invention, the inside and outside walls or cups are formed by a thermoforming process. 
     Injection molding is also a process that may be used to form a container in accordance with the invention. For example, both the inner wall or cup and the outer wall or cup may be formed by injection molding the walls or cups and then joining the walls or cups together by the means described above. The inner wall or cup and outer wall or cup may also be made separately on different molding machines or made on the same machine at different locations. It should also be understood that one or more of the wall forming processes described herein may be used alone or in combination. For example, in accordance with one embodiment of the invention, the outside wall or cup may be injection molded to provide rigidity having a thickness in the range of about 0.005 inch to about 0.020 inch and the inside wall or cup may be blown and trimmed to have a thickness preferably in the range of about 0.001 inch to about 0.010 inch. 
     It should be apparent that the foregoing relates only to the preferred embodiments of the present application and that numerous changes and modifications may be made herein by one of ordinary skill in the art without departing from the general sprit and scope of the invention as defined by the following claims and equivalents thereof.