GB2296415A

GB2296415A - Microwave oven

Info

Publication number: GB2296415A
Application number: GB9426140A
Authority: GB
Inventors: Stephen Marks
Original assignee: Individual
Current assignee: Individual
Priority date: 1994-12-23
Filing date: 1994-12-23
Publication date: 1996-06-26
Also published as: GB9426140D0

Abstract

A microwave oven 115 powered by a low voltage DC supply e.g. from a battery. The battery may be a car battery, the oven being connected for example to a cigarette lighter socket, or an internal battery, e.g. a rechargeable nickel cadmium or lithium ion battery. Heat from the magnetron may be dissipated by a heat sink formed by fins 23 rather than by a fan in order to save energy. A recessed or retractable handle 7 allows portability. <IMAGE>

Description

MICROWAVE OVEN The present invention is concerned with a microwave oven, and more particularly is concerned with a microwave oven for use with a low voltage direct current power supply.

Microwave ovens are conventionally powered from an AC mains supply and are therefore restricted in their use to locations where a suitable power supply is available.

Moreover, conventional microwave ovens require an amount of power, for example 850 watts, which is only readily available from the mains power supply.

There are numerous situations where it would be useful to have a microwave oven which is operable in the absence of mains power. For example, this would benefit travellers, long distance truck drivers and campers, among others, who would then be able to procure a hot meal or a hot drink where such would not otherwise be available or would be inconvenient to procure.

It is therefore an object of the present invention to provide a microwave oven which can be used with a low voltage direct current power supply.

According to the present invention there is provided a microwave oven comprising a housing incorporating a cooking cavity and door means for inserting food into and removing food from the cooking cavity, means for generating microwaves and means for conveying the microwaves to the cooking cavity, means for supplying low voltage DC power to the oven, and means for converting the low voltage DC power for supply to the magnetron.

In order to be able to function from a low voltage direct current supply, such as that available from a vehicle or like battery or from a cigar lighter socket of a vehicle, it is important that the power of the oven should be limited. This in turn can allow the conventional cooling fan to be replaced by a simple heat sink for dissipating the heat generated by the magnetron, for example in the form of a finned assembly secured to the rear of the oven casing.

The means for converting the low voltage DC power may include means for inverting the DC power to an internal AC power and subsequently inverting the internal AC power for supply to the magnetron. Other functions of the oven may be operated with either the low voltage DC power or the internal AC power.

To permit the microwave oven to be readily moved from one location to another, it may be provided with handle means on opposing sides or on the top thereof. For convenience, the handle means may be recessed or retractable.

The oven can be powered from a battery or from a vehicle power supply. If powered from a battery, it is desirable to provide crocodile or like clips or clamps for attaching to the battery terminals. If powered from a vehicle power supply, power can be provided to the oven by way of a cigar lighter socket, by way of a special socket or from the battery terminals. Since connection can be provided to the oven by either of these two ways, this may be accomplished either by providing separate power leads, or by providing a single power lead with an adapter for connection either to the terminals of a battery or to the socket of a cigar lighter or the like.

The battery can alternatively or additionally be provided within the housing of the oven.

The oven may be provided with an AC to DC converter to convert high voltage AC power to low voltage DC power, for use where mains power is available. Alternatively, where the oven is provided with internal AC power which operates at substantially the same voltage and frequency as mains voltage and frequency and the oven may be provided with means for supplying mains power to the internal AC power of the oven where available.

For a better understanding of the present invention and to show more clearly how it may be carried into effect reference will now be made, by way of example, to the accompanying drawings in which: Figure 1 is a perspective view of one embodiment of a microwave oven according to the present invention; and Figure 2 is a perspective view of another embodiment of a microwave oven according to the present invention.

Figure 1 shows a microwave oven comprising a housing 1, a door 3 and a control panel 5. The housing is 1 relatively small for a microwave oven, for example having a substantially uniform side length in the range from 25 to 30 cm, and is provided with recessed carrying handles 7 in opposing sides thereof, although only one such handle is shown. The housing may additionally be provided with one or more brackets (not shown) for mounting the oven in a motor vehicle. The door 3 is hinged and is provided with a handle 9 and with a microwave resistant glass panel 11.

It should be noted that the door may be positioned elsewhere if desired, such as in the top of the housing.

Control panel 5 is provided with a rotary timer 13 and with control buttons 15, such as an ON/OFF button.

Power in the form of a low voltage DC supply, such as 12 volts, is supplied to the oven by way of an adapter 17 and a lead 19. In the illustrated embodiment, adapter 17 is connectible to a cigar lighter plug 21, but the adapter 17 could readily be connectible to a pair of crocodile or like clips or clamps or to any other suitable connector to a source of low voltage DC power. If desired, two separate leads may be provided.

As an alternative, or in addition, to providing the oven with a lead to an external source of low voltage DC power, such as a vehicle power supply or a lead acid battery, the oven may be provided with an internal supply of low voltage power, for example in the form of a rechargeable nickel cadmium or lithium ion battery.

Within the housing 1 is provided a cooking cavity of known construction, to which microwaves are conducted from a magnetron by way of a waveguide. Where the magnetron is of relatively low power, the heat generated by the magnetron can be dissipated by way of a finned heat sink 23 provided at the rear of the housing 1. However, where the magnetron is of relatively high power, the heat generated by the magnetron will be dissipated by blowing cooling air over the magnetron in known manner.

Clearly, it is not possible in a microwave oven of this type to provide the power levels expected of conventional domestic microwave ovens. For example, a low powered domestic microwave oven might employ a magnetron having a power output of some 500 watts. However, even such a low powered magnetron will require at 12 volts a current in excess of 40 amps which can only realistically be provided in a sustained manner by way of a motor vehicle or boat equipped with an alternator. The power of the magnetron in the microwave oven of the present invention is unlikely, therefore, to exceed 600 watts.

Power is supplied to the magnetron from the low voltage DC source by using an suitable converter, for example an inverter to generate internal AC power which is then transformed to the required high voltage power to drive the magnetron. The components of the oven other than the magnetron can then be operated with either the incoming low voltage DC power or with the internal AC power.

The microwave oven shown in Figure 2 is similar to that shown in Figure 1 and the same references are used to denote the same or similar components. However, in the embodiment shown in Figure 2, the carrying handle 25 is provided in the top of the oven housing as compared with in opposing sides as shown in Figure 1.

To extend the use of the microwave oven according to the present invention, it may be provided, for example as an accessory, with converter means for generating the required low voltage DC power from mains AC power, for example by means of a transformer and a rectifier assembly. However, care needs to be taken to ensure the transformer and rectifier assembly can provide the required power.

Alternatively, where provided, the internal AC power described hereinabove, may be at a voltage and frequency substantially identical to mains voltage and frequency thereby enabling mains AC power to be employed where available.

Claims

1. A microwave oven comprising a housing incorporating a cooking cavity and door means for inserting food into and removing food from the cooking cavity, means for generating microwaves and means for conveying the microwaves to the cooking cavity, means for supplying low voltage DC power to the oven, and means for converting the low voltage DC power for supply to a magnetron.

2. A microwave oven as claimed in claim 1 and incorporating a heat sink for dissipating the heat generated by the magnetron.

3. A microwave oven as claimed in claim 2, wherein the heat sink is in the form of a finned assembly secured to the rear of a casing for the oven.

4. A microwave oven as claimed in claim 1, 2 or 3, wherein the means for converting the low voltage DC power includes means for inverting the DC power to an internal AC power and subsequently inverting the internal AC power for supply to the magnetron.

5. A microwave oven as claimed in claim 4, wherein other functions of the oven are operated with either the low voltage DC power or the internal AC power.

6. A microwave oven as claimed in any preceding claim and including handle means, for example on opposing sides or on the top thereof.

7. A microwave oven as claimed in claim 6, wherein the handle means is recessed or retractable.

8. A microwave oven as claimed in any preceding claim and including means for powering the oven from a battery or from a vehicle power supply.

9. A microwave oven as claimed in claim 8, wherein, where the oven is powered from a battery, crocodile or like clips or clamps are provided for attaching to the battery terminals.

10. A microwave oven as claimed in claim 8 or 9, wherein, where the oven is powered from a vehicle power supply, power is provided to the oven by way of a cigar lighter socket, by way of a special socket or from the battery terminals.

11. A microwave oven as claimed in any one of claims 8 to 10, wherein electrical connection is provided to the oven by providing separate power leads, or by providing a single power lead with an adapter for connection either to the terminals of a battery or to the socket of a cigar lighter or the like.

12. A microwave oven as claimed in any one of claims 8 to 11, wherein the battery is provided within the housing of the oven.

13. A microwave oven as claimed in any preceding claim and including an AC to DC converter to convert high voltage AC power to low voltage DC power, for use where mains power is available.

14. A microwave oven as claimed in any one of claims 1 to 12, wherein, where the oven is provided with internal AC power which operates at substantially the same voltage and frequency as mains voltage and frequency, the oven is provided with means for supplying mains power to the internal AC power of the oven.

15. A microwave oven substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.