WO2008032135A1

WO2008032135A1 - Electrically heated lunch box

Info

Publication number: WO2008032135A1
Application number: PCT/IB2006/002507
Authority: WO
Inventors: Sylvia Cecilia Noronha
Original assignee: GOLDWISE TRADING Ltd
Current assignee: GOLDWISE TRADING Ltd
Priority date: 2006-09-13
Filing date: 2006-09-13
Publication date: 2008-03-20
Anticipated expiration: 2009-03-13

Abstract

A battery powered lunch box (1) includes an electric element (7) extending about a food- receiving dish (3) in the base (2) and an evacuated heat insulating base- chamber (9) surrounding the element (7) , sides and floor of the dish. A lid (11) includes an evacuated heat insulating lid chamber (16) with a plug portion which projects into the mouth of the dish for closing the dish (3) and reducing heat losses.

Description

ELECTRICALLY HEATED LUNCH BOX

Technical field

The present invention relates to electrically heated lunch boxes and, more particularly but not exclusively, to lunch boxes which are battery-operated allowing food to be heated in places remote from an electricity supply.

Background of the Invention

US patent no. 6 144 016 describes an electrically heated lunch box with a food dish heated by radiant elements which may be powered by a battery. The food chamber is a shallow dish with heating elements surrounding its side walls. To prevent heat losses a hinged lid covers the dish and the walls and floor of the dish are surrounded by thermal insulation.

For good performance in places remote from an electricity supply, whether heating food from cold or maintaining an elevated temperature, it will be understood that a high standard of insulation is required as the amount of energy stored in the battery is limited. The design requirements of this application make the achievement of good thermal performance quite challenging. In particular, to avoid heat losses when the hot food is served it is advantageous if the food can be eaten directly from the dish. This requires a shallow dish with a relatively large opening for satisfactory access and with a corresponding relatively large lid. There is therefore a need for a lunch box with improved thermal performance, particularly one for addressing heat loss through the lid.

It is an object of the present invention to meet these needs or more generally to provide an improved electrically heated lunch box. Disclosure of the Invention

According to the present invention there is provided an electrically heated lunch box including:

a base;

a food-receiving dish in the base;

an electric element extending about the dish;

an evacuated heat insulating base chamber surrounding the element, sides and floor of the dish, and

characterised by a lid having an evacuated heat insulating lid chamber for covering the dish.

Preferably the evacuated lid chamber includes a projecting plug-portion which is received in and closes the mouth of the dish.

Preferably one part of a magnetic sealing strip is fixed around the periphery of the dish for cooperating with another part of the magnetic sealing strip fixed to around the lid to fasten the Nd. The lunch box preferably a controller for controlling power supply from a battery pack and to the element, the battery pack being mounted in the base below the dish.

The controller preferably includes a timing circuit, the lunch box having a user- selectable heating temperature and user-selectable time, such that the controller operates the element to achieve the selected temperature by the selected time. This invention provides a portable electrically heated lunch box which is effective and efficient in operational use, reducing heat loss through the lid while still allowing the device to be economically constructed. Providing the high degree of thermal insulation achieved by this design allows satisfactory heating performance from battery alone.

Brief Description of the Drawings

Preferred forms of the present invention will now be described by way of example with reference to the accompanying drawings, wherein:

Figure 1 is a schematic side view (including a part section) of the lunch box of the present invention;

Figure 2 is an enlarged view of detail A of Fig. 1 , and

Figure 3 is a plan view of the open base of the lunch box of Fig. 1.

Description of the Preferred Embodiments

Referring to the drawings an electrically heated lunch box 1 includes a base 2 in which is mounted a shallow dish 3 for receiving the food to be heated. The dish 3 is made of metal and has sides 4, and a floor 5 opposing the open mouth 6. An electric element 7 extends about the dish 3 adjacent the four sides 4 for heating the dish 3. Positioned either side of the element 7 are inner and outer electrical insulating sheets 8a, 8b preferably of mica. A vacuum jacket or evacuated heat insulating base chamber 9 surrounds the element 7, the sides 4 and floor 5. The evacuated chamber 9 is bounded by walls 26 and 27 which may be made from transparent material such as glass and are substantially equidistantly spaced and parallel. The inner faces 10a, 10b of the base chamber 9 may be silvered or otherwise coated to reduce radiant heat transfer, while the substantial vacuum in the chamber works in the known manner to reduce thermal convection and conduction.

The element 7 and insulating sheets 8a, 8b are received in a cavity 13 which extends between the sides 3 and the evacuated chamber 9, as well as between the floor 5 and evacuated chamber 9. In this manner the dish 3 is received in the evacuated chamber 9. The evacuated chamber 9 is in turn mounted in a base housing 18 which may be moulded from plastics.

A lid 11 engages the base 2 to close the top of the dish 3. A magnetic seal of a known type includes two cooperating strips 12a, 12b mounted to the lid 11 and base 2 respectively for sealing therebetween. The two strips may, for example, comprise a magnetised strip within a resilient gasket and a strip of ferromagnetic material. The strip 12b extends peripherally around the mouth 5 of the dish 3. The lid 11 includes a body 15 having a cavity in which an evacuated heat insulating lid chamber 16 is provided for covering the dish 3. Like the base chamber 9, the walls 28, 29 of the chamber 16 may be made from transparent material such as glass with opposing inner surfaces silvered or otherwise coated to reduce radiant heat transfer.

The evacuated chamber 16 is dimensioned to overly the cavity 13, or may alternatively extend to overly the upper face 17 of the base chamber 9. The evacuated chamber 16 includes a projecting plug-portion 19 which projects from the face 21 and is sized to fit within the mouth 6 to close the dish 3. The plug portion 19 the plug portion and mouth include substantially parallel cooperating faces 24, 25 an outermost edge 20 of the plug portion 19 being chamfered to assist in inserting the plug portion 19. The strip 12a extends peripherally around the evacuated chamber 16 adjacent the face 21.

The lunch box further includes an electronic controller (not shown) and user controls (not shown) on a control panel 20. The controls allow a user to select a heating temperature and a time which may be shown on the displays 22, 23 respectively. The controller operates the element 7 to achieve the selected temperature by the selected time.

Aspects of the present invention have been described by way of example only and it should be appreciated that modifications and additions may be made thereto without departing from the scope thereof.

Claims

CLAIMS:

1. An electrically heated lunch box including:

a base;

a food-receiving dish in the base;

an electric element extending about the dish;

2. The lunch box of claim 1 wherein the evacuated lid chamber includes a projecting plug-portion which is received in and closes the mouth of the dish.

3. The lunch box of claim 2 wherein the plug portion and mouth include substantially parallel cooperating faces, an outermost edge of the plug portion being chamfered or radiused to assist in inserting the plug portion.

4. The lunch box of claim 1 wherein one part of a magnetic sealing strip is fixed around the periphery of the dish for cooperating with another part of the magnetic sealing strip fixed to around the lid to fasten the lid.

5. The lunch box of claim 1 wherein the base chamber has walls made from transparent material, the inner faces of the walls being silvered or otherwise coated to reduce radiant heat transfer.

6. The lunch box of claim 1 wherein the lid chamber has walls made from transparent material, the inner faces of the walls being silvered or otherwise coated to reduce radiant heat transfer.