AU721344B3 - A portable oven - Google Patents

Description

P00012 Regulation 3.2 Revised 2/98

AUSTRALIA

Patents Act, 1990

ORIGINAL

COMPLETE SPECIFICATION PETTY PATENT TO BE COMPLETED BY THE APPLICANT NAME OF APPLICANT: MICHAEL J LONGTON ACTUAL INVENTOR: MICHAEL J LONGTON ADDRESS FOR SERVICE: Peter Maxwell Associates Level 6 Pitt Street SYDNEY NSW 2000 INVENTION TITLE: A PORTABLE OVEN DETAILS OF ASSOCIATED PROVISIONAL APPLICATION NO(S): NIL The following statement is a full description of this invention including the best method of performing it known to me:- The present invention relates to a portable heating oven and, in particular, to an oven that can be used for the home delivery of pre-cooked take away food, such as pizza and Chinese food, and can be powered by the battery of a vehicle used for such delivery.

It is common practice in the home delivery of take away food to cook the food at the store and then have it packed in a cardboard box or plastic food container for transportation by vehicle to the required destination. Home delivery services of this type generally operate for destinations within a prescribed distance from the store to avoid excessive delivery related costs and prevent unduly long transportation times that might cause the food to lose its freshness and/or fall below an acceptable temperature.

The food container and other bag means presently in use for maintaining the temperature of the take away food during delivery at an acceptable temperature above 60 0 C (which is the minimum allowable temperature set by Government health authorities in Australia for protecting against pathogen and bacterial spoilage of cooked food delivered to the consumer), have limited usefulness and fail in circumstances where unexpected delays are experienced during the delivery with the consequence that the take away food may fall to an unacceptable temperature of below 600C.

Even without delivery delays, the need to place a limit on the distance from the store of home delivery destinations, brought about solely by the limited heat retention qualities of conventional food containers, imposes a restriction on the commercial reach, and hence profitability, of the take away food store's business.

Although home delivery of pizzas is effected by placing them in cardboard boxes and then enclosing the box in a partially heat retentive bag for transportation to the required destination, in the instance of home delivery of Chinese food there is presently no means known to the inventor of keeping the food at an acceptable temperature of above 60 0 C, or warm at all. This poses a major health risk as a significant part of Chinese food consists of meat and shellfish, which spoil relatively easily.

Mobile, compact pizza ovens for baking a pizza are known. US Patent No. 4,632,836 describes a pizza preparation and delivery system which is designed to deliver restaurant quality pizzas to the consumer's home or place of business. The system described in that patent includes vehicles which were not only adapted to deliver the pizza, but also adapted to assemble and bake the pizza while in transit. Each vehicle in this system was equipped with a refrigerated case for storing pizza shells, a preparation station with pizza toppings to create an assembled pizza, and a conveyor oven for baking the assembled pizza.

The vehicles used in the preferred embodiment described in that patent included a driver's station and a kitchen area manned by a cook. Although the pizza preparation and delivery system described in that patent enjoyed a measure of success, it was found that the purchase, operating, and maintenance costs of the relatively large vehicles used in the preferred embodiment ran higher than what was desirable.

Further developments of this kind are described in US Patents No.

4,556,046; No. 4,643,167 and No. 4,924,763, the last two of which seek, amongst other things, to provide a smaller sized vehicle that had on board pizza preparation facilities and was more economical to run.

However, none of these patents envisaged a heating oven, rather than a baking oven, and, by seeking to provide full on board pizza preparation facilities, imposed high power demands upon the vehicle used for the delivery.

Clearly, the power demanded for purely maintaining an oven temperature at above 600C but, say, below 1000C for keeping a pizza hot is considerably less than what it would be for baking a pizza in an oven conveyed in a vehicle, where the temperature required is above 200 0

C.

Portable, compact containers for heating a pizza are also known. US Patent No. 4,922,626 discloses a container which is specifically adapted to circulate air over a pizza in the container and remove moisture therefrom so as to prevent the pizza crust from becoming soggy. The container also has a heater powered through a cigarette lighter receptacle of a vehicle to keep the pizza warm. However, the voltage available through the cigarette lighter receptacle is low and just enough to provide a minimal level of heat but not enough to stably maintain the pizza at above 60*C. The container may reach about 600C, but only after considerable time, say in 1 hour or more, which is well beyond a practical time for pizza delivery. Furthermore, if the lid of the container were to be opened at any time during the heating period, a sudden drop in temperature would occur to below 60C. Considerable time would then be required after closing the lid to raise the temperature to above 60 0

C.

Portable pizza baking ovens are known. US Patent No. 5,586,488 discloses an oven that has a cooking chamber defined between upper and lower heating assemblies powered through a domestic power wall outlet.

However, the baking oven is not adapted to be powered by the battery of a vehicle.

It is therefore an object of the present invention to provide a portable heating oven that can be used for the home delivery of pre-cooked food and can be powered by the battery of a vehicle used for such delivery.

It is another object of the present invention to provide a portable heating oven that can also be powered by a mains power supply so that the oven can maintain the food at the acceptable temperature in the store after it has been cooked but before it is required to be taken into the vehicle used for delivery to the required destination.

According to the invention there is provided a portable heating oven adapted for operation in a vehicle comprising, container means defining a chamber for receiving pre-cooked food, said container means including means for providing access to said chamber, handle means mounted on said container means for enabling said oven to be carried, heating means for heating the chamber to a temperature within a temperature range between 600C and 1000C, control means for controlling the supply of power to the heating means when the temperature falls below or rises above the temperature range, fan means for circulating air in the chamber, means for powering the oven from a battery supply of the vehicle whilst the vehicle is mobile, and alternative means for powering the oven from a mains power supply.

In order that the invention may be readily understood and put into practical effect, reference will now be made to the accompanying drawings, in which:- Fig 1 is a perspective view of a portable heating oven according to a preferred embodiment of the present invention, Fig 2 is a cross-sectional view through i I- I of Fig 1 showing some internal detail of the portable heating oven, and Fig 3 is a schematic electrical circuit diagram for the portable heating oven of Figs 1 and 2.

The portable heating oven 10 comprises a container defined by opposed front and rear walls 12, 14, opposed side walls 16, 18, bottom wall 20, and a top surface divided into a lid 22 and an electrical access panel 24. The lid 22 opens and closes on hinges 26 and provides access to a heating chamber 28 adapted to receive therewithin pre-cooked food, such as pizzas arranged in a stack of, say, 6 pizza boxes. The chamber 28 has opposed front and rear walls 30, 32, opposed side walls 34, 36 and a floor wall 38. The roof of the chamber 28 is defined by the lid lower panel 40. The lid lower panel 40 has attached thereto a continuous silicon rubber seal 41 which closes tightly onto a chamber upper rim panel 50. The access panel 24 opens and closes on hinges 25 and provides access to an upper compartment 44 housing the major electrical components. Beneath compartment 44 is a lower compartment 46 housing the fan and heater components. The compartments 44, 46 are spaced apart, in the main, by a hollow wall and are defined by walls spaced apart from the container walls 12, 14, 16 and chamber wall 36.

The container walls 12, 14, 16, 18 and 20, the walls of the lid 22 including the lower panel 40, the chamber walls 30, 32, 34, 36, 38, and rim panel 50, are all fabricated of moulded plastic. The walls of the compartments 44, 46 including the access panel 24, are fabricated of aluminium.

Polyurethane insulation material is located within the walls of the lid 22 and in the hollow wall spaces around the chamber 28 and around the compartments 44, 46, except for the access panel 24.

Each side wall 16, 18 has affixed thereto a handle 42 that enables the oven 10 to be carried by a person. The weight of the oven 10, both when the chamber 28 is full and when it is empty of food, is not beyond the carrying capacity of an average person.

There is a single over centre latch 52 mounted to the front wall 12 of the container, which is adapted to lockingly engage a hook type member 54 mounted to the front wall of the lid 22. A steam vent 56 is located through the lid 22 so as to allow excess steam to escape to atmosphere, thereby preventing food in the chamber 28 from becoming soggy. A strap 58, fixed between the lid lower panel 40 and chamber side wall 34, prevents the lid 22 from swinging open beyond an angle of about 1000 from its closed position.

The chamber 28 has a plurality of spacer bars 29 fixed to its walls to prevent food or its containers from contacting the walls, thereby ensuring that there is an air flow path between the food or its containers and the walls of the chamber. The number and location of spacer bars 29 may vary.

As shown in Fig 2, the lower compartment 46 has two openings 60, 62 to the chamber 28 through which heated air enters and exits the chamber 28.

The openings 60, 62 have grilles 64, 66, respectively, fitted thereto to prevent large particulate matter entering the compartment 46 from the chamber 28 and to prevent anyone tampering with the fan and heater components through the chamber 28.

The fan 68 is located intermediate the openings 60, 62 and propels air in the direction of arrow A towards opening 62 whilst drawing air from opening Air flow is further controlled by mounting the fan 68 to a bracket 70 which divides the compartment 46 into halves, and by positioning the plastic blades 72 of the fan 68 within the circumferential rim of a hole formed through the bracket The heater 74 is located downstream of the air flow from the fan 68 so that fan propelled air is heated before exiting through opening 62 into chamber 28. The coil 76 of a high temperature safety thermostat 78 is located near the opening 62 to monitor or sense the temperature of the air near the heater element 74.

The upper compartment 44 has a plurality of vent holes 80 to atmosphere and is ventilated mechanically and convectionally. The major electrical components mounted on and/or inside the compartment 44 include an electronic temperature controller 82, first and second circuit breakers 84, 86, a 240 volt inlet plug 88, a 12 volt DC inlet plug 90 (commonly referred to as an Anderson plug), first and second relays 92, 94, an inverter 96, a main body 99 of thermostat 78, and a mounting arrangement 98 for the heater 74. Wiring is also present in upper compartment 44 but is not shown in Fig 2 for the sake of convenience, as the schematic circuit diagram of Fig 3 summarizes the wiring connections. A temperature sensor 79, formed of a temperature sensitive resistor in the shape of a bead, hangs from a wire passing through the insulation filled hollow wall separating the upper and lower compartments 44 and 46. The wire is connected to the temperature controller 82 so that the operation of temperature controller 82 is controlled by the temperature sensed by sensor 79.

The oven 10 may be supplied with power from a 240V AC mains power supply or a 12 Volt DC vehicle battery supply, as shown schematically in Fig 3, and can only be operated by one power source at a time.

As far as the mains power supply is concerned, mains power is supplied to the oven 10 via a standard extension lead (suitable for the local power requirements) which is connected to the inlet plug 88. Power travels through Amp circuit breaker 84 and then through the normally closed contact R2/2 on relay 94. The motor of fan 68 starts and runs continuously whilst power is supplied. The electronic temperature controller 82 is energised and will stay energised whilst power is supplied.

If the temperature within the chamber 28 sensed by the temperature sensor 79 falls below the temperature set point, the relay in the temperature controller 82 will close and supply power to the heater 74 via a high temperature safety thermostat 78.

If the temperature within the chamber 28 sensed by the temperature sensor 79 rises above the temperature set point, the relay in the temperature controller 82 will open and stop the supply of power to the heater 74.

If the temperature being sensed by the coil 76 rises to an abnormally high temperature, the high temperature safety thermostat 78 will interrupt power to the heater 74 until it is manually reset. The circuit is completed via the neutral wiring which travels through the normally closed contact R 2/1 on relay 94 and then through 5 Amp circuit breaker 86.

Turning to the 12V DC power supply, the terminals of the vehicle battery are connected to the oven 10 via a purpose made lead 100. The lead 100 is connected to the battery terminals via two.alligator clamps 102, 104, which are colour coded red and black Midway along the lead 100 there is a black plastic control box 106 fitted with an on/off switch 108 with neon indication 110. This switch 108 allows the user to turn the oven 10 on and off from inside the vehicle. A 20 Amp circuit breaker 112 has been fitted to protect the lead 100 from fault currents.

The lead 100 is connected to the oven 10 via the plug 90 which is marked and and can only be connected one way.

With the lead 100 connected to the oven 10, power is fed through fuse 116, which energises R1 relay 92 and R2 relay 94. The 12Volt DC fan 122 is also energised which mechanically ventilates the upper compartment 44. The normally closed contacts R2/1 and R212 on relay 94 open, which stops power from being supplied back through the mains power inlet plug 88.

The normally open contacts RI/1 and R1/2 on relay 92 close causing the inverter 96 to power up. The inverter 96 outputs power through the normally open contacts R2/3 and R2/4 on relay 94 to drive the fan 68, temperature controller 82 and heater 74. The fan motor 68 starts and runs continuously while power is supplied. The electronic temperature controller 82 is energised and will stay energised while power is supplied.

If the temperature within the chamber 28 sensed by the temperature sensor 79 falls below the temperature set point, the relay in the temperature controller 82 will close and supply power to the heater 74 via the high temperature safety thermostat 78.

If temperature within the chamber 28 sensed by the temperature sensor 79 rises above the temperature set point, the relay in the temperature controller 82 will open and stop the power supply to the heater 74.

If the temperature being sensed by the coil 76 rises to an abnormally high temperature, the high temperature safety thermostat 78 will interrupt power to the heater 74 until it is manually reset. The circuit is completed via the neutral wiring which travels through the normally open contact R2/3 on relay 94 and then back to the inverter 96.

It will be apparent from the foregoing that the oven 10 is not adapted to bake or cook food, but rather only to stably heat food to a maximum of 100°C.

Substantially higher temperatures will, for instance, cause melting of componentry, such as the plastic blades of the fan. Such higher temperatures are prevented by the high temperature safety thermostat 78 which is preset to a maximum allowable temperature of, say, 120 0

C.

The oven 10 is also advantageously adapted for use as a portable unit and can be readily supplied with power from either a vehicle battery power supply or a mains power supply.

11 Various modifications may be made in details of design and construction without departing from the scope and ambit of the invention.

Claims (3)

1. A portable heating oven adapted for operation in a vehicle comprising, container means defining a chamber for receiving pre-cooked food, said container means including means for providing access to said chamber, handle means mounted on said container means for enabling said oven to be carried, heating means for heating the chamber to a temperature within a temperature range between 60 0 C and 100C, control means for controlling the supply of power to the heating means when the temperature falls below or rises above the temperature range, fan means for circulating air in the chamber, means for powering the oven from a battery supply of the vehicle whilst the vehicle is mobile, and alternative means for powering the oven from a mains power supply.

2. The portable heating oven of claim 1 wherein the control means comprises an electronic temperature controller which includes a temperature sensor and a relay in the temperature controller adapted to control the supply of power to the heating means, wherein if the temperature within the chamber sensed by the sensor falls below the temperature range, the relay will close and supply power to the heating means, and wherein if the temperature within the chamber sensed by the sensor rises above the temperature range, the relay will open and stop the supply of power to the heating means.

3. The portable heating oven of claim 2 wherein the control means further comprises a high temperature safety thermostat which includes a coil, wherein if the temperature sensed by the coil is above the temperature range and the electronic temperature controller has failed to stop the supply of power to the heating means, the thermostat will interrupt the supply of power to the heating means. Dated this 14th day of March, 2000 MICHAEL J LONGTON Patent Attorneys for the Applicant PETER MAXWELL ASSOCIATES