INSULATED FOOD JAR WITH CAMPFIRE OR STOVE HEATABLE INNER CONTAINER

Abstract

An insulated food jar assembly includes an outer insulated container or sleeve having an open mouth and an interior space. The outer insulated container is a double-walled vacuum insulated container. An inner container nests into the interior space of the outer insulated container. The inner container has a collar that extends over the open mouth of the outer container when nested. The collar includes handles and an inner surface that bears against a friction ring about the mouth of the outer container. A lid fastens onto a neck of the inner container. A stopper in the lid fits into the neck and has a gasket to seal against an inward projection of the neck. A gasket at an outer edge of the lid seals against a shoulder of the inner container. The inner container is of a material that may be heated over an open flame heat source.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Patent Application Ser. No. 61/708,417 filed Oct. 1, 2012, which is incorporated herein by reference, and also claims the benefit of U.S. Provisional Patent Application Ser. No. 61/724,652 filed Nov. 9, 2012, which is incorporated herein by reference.

FIELD

Insulated food containers are generally disclosed herein including an insulated food jar with a campfire or stove-heatable inner container.

BACKGROUND

Traditionally, insulated food containers cannot be used to heat food or beverages over a flame or other heat source, such as a campfire or on a stove. Portions of the insulated container would melt or otherwise be damaged by the campfire or stove. Typically, a food or beverage is heated first in a separate pot or other container and then the food or beverage is poured from the pot into the insulated container for storage or transportation. If the food in the insulated container is to be heated, it is generally necessary to remove the food from the insulated container and place it in a container that is safe for heating. Some insulated containers permit heating of the food in a microwave oven, but even these insulated containers cannot themselves be used to heat the food or beverage that is stored therein over open flames from a campfire or a stove.

The user who is camping may choose to eat the heated food, or drink the heated beverage, directly out of the cookware, but in doing so there is little protection from burning oneself on the hot cookware, other than by careful handling of the cookware and careful manipulation of the often flimsy handle attached to the camp cookware.

Accordingly, there is a need for a food or beverage jar that can be used to heat food or beverages contained therein by a variety of heating sources, and thereafter is insulated for heat retention and the safe transportation of the hot food or beverage contained therein, without the worry of burning oneself on the heated container.

SUMMARY

Disclosed herein is an insulated food jar assembly including an insulated outer container, a heatable inner container that is used to heat food or beverages and which slidably engages with an interior of the insulated outer container, and a lid that sealingly mates with the heatable inner container. The insulated outer container helps to retain the heat within the heatable inner container and also permits a user to safely carry the heatable inner container without the risk of being burned by the hot surfaces of the heated inner container.

In one embodiment, the lid includes a stopper that engages a mouth and neck of the heatable inner container. The stopper includes a stopper gasket that forms a liquid tight seal with an inner surface of the heatable inner container. The stopper is itself insulated so as to help prevent heat from escaping the heatable inner container through the lid. The insulated container can also be used to insulate cold items from a warmer environment.

In another embodiment, the heatable inner container includes a collar extending away from the heatable inner container as well as one or more handles connected to the collar for carrying the heatable inner container when the insulated outer container is not being used, such as when the inner container is being placed on the heat source or removed from the heat source. Attaching the handles to the collar and spacing them apart from the sidewalls of the heatable inner container, which sidewalls are heated up by the heat source, allows the handles to remain at a cooler temperature than the hot sidewalls and hot bottom of the heatable inner container.

In another embodiment, the insulated outer container includes a friction ring that engages with an inner surface of the inner container's collar when the inner container is slid inside the outer container, so as to provide a friction fit between the inner and outer containers. In this manner, the inner and outer containers generally cannot slide apart without the user slidably pulling the heatable inner container out from within the interior of the insulated outer container.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an embodiment of an insulated food jar with a campfire or stove-heatable inner container in an un-nested condition.

FIG. 2 is a perspective exploded view of the insulated food jar with a campfire or stove-heatable inner container of FIG. 1.

FIG. 3 is a top view of an embodiment of an assembled insulated food jar with a campfire or stove-heatable inner container.

FIG. 4 is a cross-sectional view of the insulated food jar with a campfire-heatable inner container of FIG. 3.

FIG. 5 is a perspective view of the insulated food jar with campfire or stove-heatable inner container, having the inner container mated to the outer container and the lid of the insulated food jar shown in an unmated exploded position.

DESCRIPTION

While the present invention is capable of being embodied in various forms, the description below of several embodiments is made with the understanding that the present disclosure is to be considered as an exemplification of the claimed subject matter, and is not intended to limit the appended claims to the specific embodiments illustrated. The headings used throughout this disclosure are provided for convenience only and are not to be construed to limit the claims in any way. Embodiments illustrated under any heading may be combined with embodiments illustrated under any other heading.

The subject matter described herein is with the specificity needed to meet statutory requirements. The inventors have contemplated that the claimed subject matter may also take the form of various alternate embodiments, to include different steps or combinations of steps similar to those described herein, in conjunction with other present or future technologies.

One embodiment described herein is an insulated food jar assembly with a campfire or stove-heatable inner container.

Referring to FIG. 1, an insulated food jar assembly 10 is disclosed in an unassembled condition. The insulated food jar 10 includes an outer insulated container 12, an inner food container 14 that slidably mates with the outer container 12, and a lid 16 that seals closed a mouth of the inner container 14.

Referring to FIG. 1, in a preferred embodiment of the disclosure herein, the outer insulated container 12 of the insulated food jar assembly 10 generally takes the shape of a cup having a closed bottom 18, closed sidewalls 20 extending upward therefrom, and an open upper end 22 formed by the sidewalls. The outer container 12 preferably has a circular cylindrical shape, and is made from stainless steel. However, the disclosure of this preferred embodiment should not be read to limit the shape of the cup to only being circular cylindrical or made from stainless steel. In alternate embodiments, the outer container may take alternate shapes, such as having a square cylindrical shape, other cylindrical shapes, or other shapes that are capable of accommodating a nested inner container as will be disclosed further herein. In addition, in alternate embodiments, the outer container may be made of aluminum or other metallic or polymeric materials or other materials without departing from the scope of the present disclosure.

Referring to FIG. 4, in one embodiment, the closed bottom 18 and closed sidewalls 20 of the insulated outer container 12 are both double-walled vacuum-insulated sidewalls. The double-walled, vacuum-insulated bottom and sidewalls are formed by a cup-shaped interior shell 24 being seated inside of a cup-shaped exterior shell 26, which exterior shell 26 is larger than the interior shell 24. The shells 24 and 26 are sealingly connected to each other at their open top ends 28 such that together they define a chamber 30 there between. Any air or other gas may be evacuated from or pumped out of the chamber 30 prior to sealing the two shells 24 and 26 together, thereby creating a double-walled, vacuum insulated outer container. The interior and exterior shells 24 and 26 are both preferably made from stainless steel, aluminum, or another material of suitable rigidity sufficient to resist deforming under the forces placed on the sidewalls by the negative pressures of the vacuum within the chamber. In alternate embodiments, the interior and exterior shells may be sized such that only the sidewalls, and not the bottom, of the outer container are double-walled vacuum insulated walls, without departing from the scope of the present disclosure. The insulating space 30 between the walls of the double walled container may contain a vacuum, partial vacuum or an insulation material or may otherwise be insulated.

Referring further to FIGS. 1 and 4, in one embodiment, the outer container 12 includes a support base 32 affixed over the bottom 18 of the outer container 12. The support base 32 provides the outer container 12 with a stable base upon which the outer container 12 may rest on a table or other flat surface. In one embodiment, the support base 32 may be made of plastic and have the shape of a shallow cup that is snapped or otherwise fastened over the closed bottom of the outer insulated container. In other embodiments, the support base may be made of rubber, rubberized plastic, rubberized metal, or other such materials that may provide the outer insulated container with a non-slip or treaded surface at the bottom end. In still further alternate embodiments, the support base may have a tread pattern imprinted in or on an outer surface thereof to provide further non-slip functionality to the outer insulated container. The support base 32 may also include one or more strengthening ribs or webs 34 projecting from an interior surface 36 thereof. The strengthening ribs 34 provide structural strength to the support base 32 and may rest against or near the bottom surface 18 of the closed bottom of the outer insulated container 12. The support base 32 may be removable so as to facilitate easy cleaning of the outer insulated container 12, or the support base 32 may be permanently affixed to the outer insulated container 12.

In a preferred embodiment, the insulated container 10 includes a recessed groove 38 disposed in an outer surface of the container's sidewall 20. The recessed groove 38 is located near the upper open end of the insulated container 10 and is a continuous groove that extends around the full exterior circumference of the outer container 12. A friction ring or gasket 40 is seated in the recessed groove 38. In one embodiment, this friction ring 40 is a rubber ring having one or more fins projecting radially outward. The friction ring 40 is configured to provide a friction fit between the heatable inner container 14 and the outer insulated container 12 so that, as will be explained in further detail below, when the heatable inner container 14 is nested within the outer insulated container 12, the fins of the friction ring 40 rub against a portion of the heatable inner container 14 and prevent the two containers 12 and 14 from sliding apart without intentionally being pulled apart. The friction ring 40 may maintain its location on the outer container by spring force resulting from the ring 40 being stretched while seated in the recessed groove 38 and an interference fit with various surfaces of the groove. However, the disclosure of the above embodiment should not be read to limit the shape or configuration of the friction ring to a rubber ring with fins seated in a recessed groove. Rather, additional configurations of recessed grooves and friction rings can be used to achieve the same purpose without departing from the scope of the present disclosure. Accordingly, alternate friction ring configurations other than those disclosed herein may be used without departing from the scope of the present disclosure. Furthermore, in alternate embodiments the friction ring may be permanently bonded to the outer container within the recessed groove, or bonded to the outer surface of the outer container without the need for a recessed groove, depending on the configuration, size, and shape of the friction ring and the desired amount of friction between the outer and inner containers. The friction ring may be made of rubber, silicone rubber, or any other polymer that will achieve the purpose and functionality of providing a friction fit between the inner and outer containers.

Referring to FIGS. 1 and 4, the heatable inner container 14 has a closed bottom end 42 and closed sidewalls 44 that extend upward therefrom to form a cup and define a mouth 46 of the heatable container 14. In a preferred embodiment, the sidewalls 44 of the heatable container 14 also define a neck 48 disposed adjacent to the mouth 46 of the inner container 14. In one embodiment, the neck 48 includes one or more threads formed therein that are used to mate with one or more complimentary threads located on the lid 16 of the insulated food jar assembly 10 for sealing the lid 16 to the heatable inner container 14. In this manner, the heatable inner container 14 generally takes the shape of a jar. However, the disclosure of threaded structures should not be read to limit the structures that are used to sealingly mate the lid 16 to the mouth 46 of the heatable inner container 14 of the insulated food jar assembly 10. In alternate embodiments, the neck may include bayonet mounting features that mate with complimentary bayonet mounting structures located on the lid of the food jar assembly, or otherwise use additional mating structures and methods, without departing from the scope of the disclosure herein.

Furthermore, in one embodiment, the heatable inner container 14 includes a transition zone 50 disposed between the main portion of the sidewall 44 and the neck 48. This transition zone 50 is the portion of the sidewall 44 that reduces the diameter of the sidewall 44 from the main food or beverage carrying portion of the inner container 14 to the neck portion 48 of the heatable inner container 14. In one embodiment, the transition zone 50 includes a rigid sealing surface 52 against which a mated stopper gasket 54 disposed in the lid 16 forms a liquid tight seal to seal the inner container 14 closed when the lid 16 is attached to the heatable inner container 14.

In a preferred embodiment the heatable inner container 14 further includes a collar 56 connected to the sidewall 44 and extending outward therefrom. In one embodiment, the collar 56 is connected to the sidewall 44 adjacent to the threads, or other locking feature, disposed in the neck 48 of the heatable inner container 14. In one embodiment, the collar 56 extends radially outward at 58, away from the sidewall 44 of the heatable inner container 14, and then turns downwards at a predetermined angle, for example 90-degrees, and extends at 60 in the direction of the bottom 42 of the heatable inner container 14. In one embodiment, one or more handles 62 are attached to the collar 56. In the illustrated embodiment, a pair of the handles 62 is provided, one on each side of the container 14. By providing handles 62 on the collar 56, the handles 62 are separated from the sidewall 44 of the heatable inner container 14 and are thus insulated to some extent from the sidewalls 44 when the inner container 14 is heated. During use, the handles 62 will thus remain cooler than the sidewalls 44 of the heated inner container 44.

In a preferred embodiment, the inner container 14 is made from stainless steel. However, in alternate embodiments, the container may be made from alternate materials, such as aluminum, copper, or other such materials that permit the heatable inner container 14, as well as the consumable contents that will be stored therein, to be heated over an open flame, such as from a campfire or gas stove, or to be placed on the heating elements of an electric stove or hot plate or on some other heating means without departing from the scope of the present disclosure. The inner container 14 may be formed by draw forming processes and/or other manufacturing methods, including welding of various components, such as the collar 56 and/or handle 62, to the main inner container body.

It will also be appreciated that alternate configurations of the heatable inner container are contemplated without departing from the scope of the disclosure herein. For example, while the depiction of the heatable inner container 14 shown in FIGS. 1, 2, 4, and 5 shows the collar 56 being located between the transition zone 50 and the neck 48 of the inner container 14, it should be appreciated that in alternate embodiments, the collar may be located at alternate locations without departing from the scope of the present disclosure. For example, in an alternate embodiment, the collar may be located about the mouth of the container, extending radially outward therefrom. In this manner, with the collar located at the top of the inner container, the entire inner container, including the collar and handle, may be draw formed from a single sheet of stainless steel without the need to attach separate components thereto by other processes or subsequent steps.

Referring to FIGS. 1, 2, 4, and 5, the lid 16 of the insulated food jar assembly 10 is generally in the shape of an inverted cup. The lid 16 has a closed top 64 and one or more closed sidewalls 66 extending downward from the outer edge of the closed top 64. In a preferred embodiment, the lid 16 has the shape of a circular, cylindrical upside down cup. A continuous backup gasket 68 is attached to and extends downward form the lower free edge of the sidewalls 66. The lid 16 further includes a stopper 70 extending downward from the bottom surface of the closed top 64 in the same direction as the downward extending sidewalls 66. The stopper 70 is centered about the axial center of the lid 16 and has a closed bottom end. The stopper 70 further includes one or more threads 72 disposed in an outer circumferential surface that is configured to mate with complimentary threads disposed in the neck 48 of the heatable inner container 14. However, as will be appreciated, in alternate embodiments the stopper may include bayonet fastening structures that mate with complimentary bayonet structures disposed on the neck of the heatable inner container, as opposed to threaded structures, without departing from the scope of the present disclosure.

The lid 16 further includes the stopper gasket 54 disposed about the lower free end of the stopper 70. In one embodiment, the stopper gasket 54 is seated inside a groove disposed in the outer circumferential surface of the stopper 70 at the bottom free end of the stopper 70. The stopper 70 is configured to mate inside of the neck 48 of the heatable inner container 14, with the stopper gasket 54 being configured to sealingly mate against the rigid sealing surface 50 in transition zone of the heatable inner container 14, so as to form a liquid tight seal there between in order to prevent any fluids from leaking out of the interior space of the inner heatable container 14. It should be appreciated that in alternate embodiments the stopper gasket may be seated in a groove located in the bottom surface of the stopper, with the stopper gasket mating against a complimentary sealing surface located in the heatable inner container, without departing from the scope of the present disclosure. In still alternate embodiments, the stopper gasket may be located at the base (or top) of the stopper 70 and seated in a groove disposed in the bottom surface of the lid's closed top, so that when the lid and inner container are mated, the mouth of the heatable inner container presses against the stopper gasket to form the liquid tight seal. Still further arrangements of the lid's stopper gasket are contemplated which form a liquid tight seal with complementary features in the heatable inner container, without departing from the scope of the present disclosure.

The lid 16 and stopper 70 are preferably made of a heat resistant plastic that will not melt in high heat. Alternatively, the lid 16 and stopper 70 may be made from stainless steel, other metals, or other polymers that can withstand high heat, without departing from the scope of the present disclosure. In one alternate embodiment, the stopper 70 is a hollow cup that has a block of rigid insulation 72 inserted into its open top end. The open end of the stopper 70 is then permanently and sealingly attached to the bottom surface of the lid's closed top 64, so that the insulation 72 is permanently encapsulated there between, with the closed bottom end of the stopper 70 protruding downward from lid's bottom surface 64, as previously disclosed. In this manner, the block of insulation 72 inside the stopper 70 provides thermal insulation, which will help prevent excess heat from the consumable contents located inside the inner container 14 from escaping through the lid 16, and additional structural rigidity to the stopper 70.

Referring to FIG. 1, the insulated food jar assembly 10 is show in its unassembled state. To use the assembly, food or liquid beverages are placed inside the heatable inner container 14 through the mouth 46 of the inner container 14. The inner container 14, which in one embodiment is made of stainless steel, is then placed over (or the bottom surface of the inner container is placed on) a heat source such as a camp fire, camping stove or grill grate, kitchen stove, or other similar heat source. The food or beverage located inside the inner container 14 is thus heated, primarily by conduction of heat through the bottom 42 and/or sidewalls 44 of the inner container 14. The consumable contents in the heatable inner container 14 are heated to the desired temperature, which could be anywhere from room temperature to boiling, or any other desired temperature. When the consumable contents have reached the desired temperature, the user grasps the handles 62 of the inner container 14 and removes the inner container 14 from the heat source. Referring generally to FIGS. 2-5, the inner container 14 is then slid, bottom first, into the insulated outer container 12 so that the inner container 14 is nested inside the outer container 12. The insulated outer container 14 and the heatable inner container 12 are sized such that there is a relatively close fit between the two, with little space between the respective sidewalls of the mated inner and outer containers.

Referring to FIG. 4, when the heatable inner container 14 is slid inside the insulated outer container 12, the downward-extending portion 60 of the inner container's collar 56 also slides over the top 22 of the outer container's sidewalls and around the friction ring 40 disposed therein. Thus, the top 22 of the outer container 12 slides into the space that exists between the exterior surface of the inner container's sidewall 44 and the downward extending portion 60 of the inner container's collar 56. The friction ring 40 disposed at the top of the outer container 12 engages with an interior surface of the downward extending portion 60 of the collar 56 to provide a friction fit there between. In one embodiment, the friction ring 40 includes one or more flexible fins that extend from a main portion of the friction ring 40 and make contact with the interior surface of the downward extending portion 60 of the inner container's collar 56. The fins deflect as they come in contact with the interior surface of the collar 56 and create a friction fit there between. In alternate embodiments, the friction ring 40 may be configured differently but still provide for a friction fit between at least a portion of the inner and outer containers so that they will remain nested until an exterior force is applied to pull them apart. The friction that is created between the inner and outer containers by the friction ring 40 engaging with the collar 56 on the inner container 14 is sufficient to prevent the inner and outer containers 14 and 12 from sliding apart without the user having to intentionally pull the inner and outer containers apart. In this manner, the stainless steel inner container 14 can be used to heat up food or other consumable materials on a stove or over campfire, and can then be inserted into the insulated outer container 12 for heat retention and safe carrying of the inner container 14 by the user. The outer container 12 that holds the heated inner container 14 full of food or other consumable materials provides an insulated barrier to both retain the heat within the inner container 14 and food, thus keeping its contents hot, while at the same time permitting a user to carry the inner container 14 without worrying about getting burned.

If the user does not intend to immediately consume the food or beverage contained inside the inner container 14 that is nested within the insulated outer container 14, the user may sealingly close the inner container 14 by attaching the lid 16 to the mouth 46 of the inner container 14. The lid 16 of the preferred embodiment is screwed onto the top open end of the inner container 14 by inserting the stopper 70 of the lid 16 into the mouth 46 of the inner container 14 and turning the lid 16 to mate the threads 72 disposed in or on the exterior side surfaces of the lid's stopper with the threads formed in the neck 48 of the inner container 14. In an alternate embodiment as previously disclosed, the lid and/or stopper may include bayonet style features that mate with complimentary features located on the inner container, or other such similar mating features that are capable of sealingly closing the inner container with the lid.

In the preferred embodiment, when the lid 16 is mated to the inner container 14 to sealingly close the inner container 14, the stopper gasket 54 that is disposed in the end of the stopper 70 is seated against the rigid sealing surface 52 in the transition zone 50 of the inner container 14 to form a liquid tight seal there between. In this manner the food and/or beverages contained within the inner container 14 are prevented from leaking out of the inner container 14. In addition, because the stopper 70 includes a block of insulation 72 encased within the stopper 70, the act of sealingly mating the lid 16 to the inner container 14 further provides additional heat retention for the food and/or beverage contained therein.

In addition, when the lid 16 is mated to the inner container 14, the backup gasket 68 that extends downward from the free end of the sidewalls 60 of the lid 16 is pressed against an exterior surface of the collar 58 extending from the inner container 14 and forms a liquid tight seal there between. In this manner, should the stopper gasket 54 ever be damaged or wear out over time through excessive or improper use permitting the hot food or beverage to leak into the lid 16, the backup gasket 68 provides an additional seal that will prevent the hot food or beverages from leaking past the lid and potentially burning the user, for example when transporting the insulated food jar assembly 10.

Of course, the insulated food jar 10 may be used to store and transport chilled foods or beverages which are to be consumed in a chilled state or which are to be heated prior to consumption. The present food jar assembly 10 has particular utility when used to store or transport foods or beverages that are chilled during storage and transport and then, prior to consumption, the food or beverage is heated while still in the inner container 14, such as by heating the inner container on a stove or campfire. It is therefore unnecessary to transfer the food or beverage from an insulated transport container to a different container for heating.

The insulated food jar assembly 10 includes grip features that are decorative as well as useful when opening the food jar 10. For example, the base 32 of the outer container 12 has grip contours that aid the user in obtaining a slip-free grip on the outer container during removal of the lid 16 from the jar assembly 10 and/or during removal of the inner container 14 from the outer container 12. The lid 16 has a grip contour 76 that likewise provides a decorative feature that also assists the user in a slip-free grip of the lid 16 during removal of the lid 16 from the inner container 14.

Claims

1. An insulated food jar assembly comprising:

an insulated outer container having an open first end;

a heatable inner container having an open mouth and configured to slidably nest inside said insulated outer container through said first open end, the heatable inner container being of a material and configured for heating over an open flame heating source; and

a lid having a gasket configured to engage the open mouth of said inner container to provide a liquid tight seal between the lid and said heatable inner container.

2. The insulated food jar assembly of claim 1, wherein said lid includes a closed top cover and closed sidewalls extending downward from a perimeter of said closed top cover.

3. The insulated food jar assembly of claim 2, wherein said lid further includes a stopper protruding downward from a bottom surface of said closed top cover, and wherein said stopper is configured to seat within said open mouth of said inner container.

4. The insulated food jar assembly of claim 3, further comprising a gasket disposed about an outer circumference of said stopper.

5. The insulated food jar assembly of claim 1, wherein said insulated outer container is a double walled vacuum insulated outer container.

6. The insulated food jar assembly of claim 5, wherein said insulated outer container includes a support base connected to a lower portion of said insulated outer container.

7. The insulated food jar assembly of claim 1, wherein said heatable inner container includes a collar extending away from a sidewall of said inner container.

8. The insulated food jar assembly of claim 7, wherein said heatable inner container includes one or more handles attached to said collar of said inner container.

9. The insulated food jar assembly of claim 1, wherein said lid and said heatable inner container each include one or more complimentary threaded structures for sealingly fastening said lid to said heatable inner container.

10. The insulated food jar assembly of claim 1, wherein said insulated outer container and said heatable inner container are configured to be selectively positioned in a nested arrangement, wherein when in said nested arrangement at least a portion of said heatable inner container is disposed within an interior of said insulated outer container by a bottom portion of said heatable inner container being slidably engaged through an open top end of said insulated outer container to a fully seated position within said insulated outer container.

11. The insulated food jar assembly of claim 10, further comprising:

a friction ring disposed between an exterior surface of said insulated outer container and a surface of said heatable inner container, wherein said friction ring provides a predetermined amount of sliding friction force between said inner container and said outer container when said containers are in the nested arrangement.

12. The insulated food jar assembly of claim 11, wherein said predetermined amount of friction force between said inner container and said outer container is sufficient to prevent a force of gravity, acting in the direction of sliding movement between said containers, from slidably moving one of said containers beyond the fully inserted position with respect to the other of said containers, when said inner container is fully inserted into said outer container.

13. The insulated food jar assembly of claim 11, wherein said friction ring is disposed about an upper end of said insulated outer container, said friction ring having at least one fin protruding beyond an exterior surface of said outer insulated container, wherein said at least one fin is configured to contact said heatable inner container and apply said predetermined amount sliding friction force against said heatable inner container.