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Title:
COOKING APPARATUS AND AIR DELIVERY AND CIRCULATION DEVICE THEREFORE
Document Type and Number:
WIPO Patent Application WO/2016/124789
Kind Code:
A2
Abstract:
The present invention relates to an air delivery and circulation device for a cooking apparatus comprising a duct member mountable in a cooking chamber of the cooking apparatus, the duct member comprising an airflow inlet for receiving heated air and at least one opening into the cooking chamber, in which the duct member operable to channel the heated air from the airflow inlet to the opening. An aerofoil shaped extension member projects externally from the duct member at or adjacent to each opening and is operable to direct streams of heated air from the opening into the cooking chamber to thereby heat or cook a food product in the cooking chamber. The present invention further relates to a cooking apparatus comprising such an air delivery and circulation device.

Inventors:
MCINTYRE, Michael, James (Boyne Hill, Navan, County Meath C15 K8FW, C15 K8FW,, IE)
Application Number:
EP2016/052645
Publication Date:
August 11, 2016
Filing Date:
February 08, 2016
Export Citation:
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Assignee:
MCINTYRE, Michael, James (Boyne Hill, Navan, County Meath C15 K8FW, C15 K8FW,, IE)
International Classes:
A21B1/02; A21B1/26; F24C15/32; H05B3/00; H05B6/64
Other References:
None
Attorney, Agent or Firm:
MACLACHLAN & DONALDSON (2b Clonskeagh Square, Clonskeagh Road, Dublin D14 VON2, D14 VON2, IE)
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Claims:
CLAIMS

1. An air delivery and circulation device for a cooking apparatus comprising: a duct member mountable in a cooking chamber of the cooking apparatus, the duct member comprising an airflow inlet for receiving heated air and at least one opening into the cooking chamber, in which the duct member is operable to channel the heated air from the airflow inlet to the opening, and an aerofoil shaped extension member that projects externally from the duct member into the cooking chamber at or adjacent to each opening, and whereby the aerofoil shaped extension member is operable to direct streams of heated air from the opening into the cooking chamber to thereby heat or cook a food product in the cooking chamber.

2. An air delivery and circulation device as claimed in Claim 1 , in which the aerofoil shaped extension member comprises a pair of spaced apart extension member wings each having an aerofoil profile.

3. An air delivery and circulation device as claimed in Claim 1 or Claim 2, in which each extension member wing is configured as a plate member formed from one or more of: metal, polymer, ceramic, glass or other materials configured to withstand high heat. 4. An air delivery and circulation device as claimed in any one of the preceding claims, in which each opening of the duct member is provided as a slot having an elongate top edge and an elongate bottom edge spaced apart by a pair of side edges, and one of the pair of extension member wings is provided at or adjacent the top edge of the slot, and the other of the pair of extension member wings is provided at or adjacent to the bottom edge of the slot.

5. An air delivery and circulation device as claimed in any one of the preceding claims, in which each extension member wing comprises a top surface and a bottom surface, and the top surface of each extension member wing is profiled with an aerofoil shape such that the top surfaces of the pair of extension member wings when arranged at or adjacent an opening together define a substantially arc-like or curve-like profiled surface.

6. An air delivery and circulation device as claimed in any one of the preceding claims, in which the aerofoil shaped extension member is integrally formed with the duct member

7. An air delivery and circulation device as claimed in any one of the preceding claims, in which the duct member comprises a plurality of openings and an aerofoil shaped extension member extends into the cooking chamber at or adjacent to each opening. 8. An air delivery and circulation device as claimed in any one of the preceding claims, in which the air delivery and circulation device comprises connection means for connecting the airflow inlet to an outlet of an air heating chamber of the cooking apparatus. 9. An air delivery and circulation device as claimed in any one of the preceding claims, further comprising connection means for connecting the airflow inlet to an outlet of an air recirculation chamber of the cooking apparatus.

10. An air delivery and circulation device as claimed in any one of the preceding claims, further comprising connection means for connecting the airflow inlet to an outlet of an air heating chamber and air recirculation chamber of the cooking apparatus such that heated air from the air heating chamber and air recirculation chamber are combined at the airflow inlet of the duct member. 11. An air delivery and circulation device as claimed in any one of the preceding claims, in which the duct member is mountable to baffle means provided between an air heating chamber and the cooking chamber of the cooking apparatus.

12. An air delivery and circulation device as claimed in any one of the preceding claims, in which the duct member is mounted slightly below a ceiling surface of the cooking apparatus.

13. An air delivery and circulation device as claimed in any one of the preceding claims, in which the duct member comprises an arrangement of interconnected or integrally formed tube members, the tube members extending into the cooking chamber in the direction of flow of air through the duct member.

14. An air delivery and circulation device as claimed in any one of the preceding claims, in which the duct member comprises a pair of side tube members that extend substantially perpendicularly to baffle means of the cooking apparatus.

15. An air delivery and circulation device as claimed in any one of the preceding claims, in which the side tube members are spaced apart in the cooking chamber by one or more cross tube members that extend substantially perpendicular between the side tube members, and at least one opening is provided in each of the side and cross members.

16. An air delivery and circulation device as claimed in any one of the preceding claims, in which the duct member comprises one or more regions of converging or reducing cross-sectional internal diameter.

17. An air delivery and circulation device as claimed in any one of the preceding claims, in which a metering valve is disposed in the duct member.

18. A cooking apparatus comprising: a cooking chamber for cooking a food product therein; an air recirculation chamber, an airflow delivery and circulation device comprising a duct member is mounted in the cooking chamber, the duct member comprising at least one opening into the cooking chamber and an airflow inlet for receiving heated air from the air recirculation chamber, in which the duct member is operable to channel the heated air from the airflow inlet to the opening, and an aerofoil shaped extension member that projects externally from the duct member into the cooking chamber at or adjacent to each opening, and whereby the aerofoil shaped extension member is operable to direct streams of heated air from each opening into the cooking chamber to heat or cook a food product in the cooking chamber.

19. A cooking apparatus comprising: a cooking chamber for cooking a food product therein; an air heating chamber; an air recirculation chamber, and an airflow delivery and circulation device comprising a duct member mounted in the cooking chamber, the duct member comprising at least one opening into the cooking chamber and an airflow inlet for receiving heated air from both of the air heating chamber and the air recirculation chamber, and in which the duct member is operable to channel the combined heated air from the air heating chamber and the air recirculation chamber from the airflow inlet to the opening, and an aerofoil shaped extension member that projects externally from the duct member at or adjacent to each opening, and whereby the aerofoil shaped extension member is operable to direct streams of heated air from the opening into the cooking chamber to heat or cook a food product in the cooking chamber.

20. An airflow delivery and circulation device substantially as herein described with reference to and as shown in the accompanying drawings.

21. A cooking apparatus substantially as herein described with reference to and as shown in the accompanying drawings.

Description:
COOKING APPARATUS AND AIR DELIVERY AND CIRCULATION DEVICE

THEREFORE

The present invention relates to a cooking apparatus and an air delivery and circulation device for a cooking apparatus.

Various types of ovens for cooking food items are known to circulate a turbulent or irregular airflow through a cooking chamber to heat or cook a food item. However, nonuniform surface browning of food items cooked by these ovens is typical, and localised hot or burn spots frequently occur due to changes in the slope and flow direction of the airflow within the cooking chamber.

A further problem that exists is that these ovens are inefficient due to the manner in which heated air used to cook a food item is reheated and recirculated within the cooking chamber of the cooking apparatus.

It is therefore an object of the present invention to provide an air circulation and delivery device for a cooking apparatus which goes some way towards overcoming the above problems and/or provides the public and/or industry with a useful alternative.

Further aspects of the present invention will become apparent from the ensuing description which is given by way of example only.

According to one embodiment the present invention provides an air delivery and circulation device for a cooking apparatus comprising: a duct member mountable in a cooking chamber of the cooking apparatus, the duct member comprising an airflow inlet for receiving heated air and at least one opening into the cooking chamber, in which the duct member operable to channel the heated air from the airflow inlet to the opening, and an aerofoil shaped extension member projects externally from the duct member at or adjacent to each opening, and whereby the aerofoil shaped extension member is operable to direct streams of heated air from the opening into the cooking chamber to thereby heat or cook a food product in the cooking chamber.

Preferably, the aerofoil shaped extension member comprises a pair of spaced apart extension member wings which project into the cooking chamber at or adjacent to each opening.

Preferably, each extension member wing is configured as a plate member formed from one or more of: metal, polymer, ceramic, glass or other material configured to withstand high heat up to temperatures of about between 400 to 500 degrees Celsius.

Preferably, each opening of the duct member is provided as a slot having an elongate top edge and an elongate bottom edge spaced apart by a pair of side edges, and one of the pair of extension member wings is provided at or adjacent the top edge of the slot, and the other of the pair of extension member wings is provided at or adjacent to the bottom edge of the slot, in which heated air flows out of an opening between the extension member wings.

Preferably, each extension member wing comprises a top surface and a bottom surface, and the top surface of each extension member wing is profiled with an aerofoil shape such that the top surfaces of the pair of extension member wings when arranged at or adjacent an opening together define a substantially arc-like or curve-like profiled surface.

Preferably, the aerofoil shaped extension member is integrally formed with the duct member. Alternatively, the aerofoil shaped extension member is connectable to the duct member.

Preferably, the duct member comprises a plurality of openings and an aerofoil shaped extension member extends into the cooking chamber at of adjacent to each opening. Preferably, the air delivery and circulation device comprises connection means for connecting the airflow inlet of the duct member to an outlet of an air heating chamber of the cooking apparatus.

Preferably, the air delivery and circulation device comprises connection means for connecting the airflow inlet of the duct member to an outlet of an air recirculation chamber of the cooking apparatus.

Preferably, the air delivery and circulation device comprises connection means for connecting the airflow inlet of the duct member to an outlet of an air heating chamber and air recirculation chamber of the cooking apparatus such that heated air from the air heating chamber and air recirculation chamber are combined at the airflow inlet of the duct member.

Preferably, the duct member is mountable to baffle means provided between an air heating chamber and the cooking chamber of the cooking apparatus.

Preferably, the duct member is mounted slightly below a ceiling surface of the cooking apparatus. Preferably, the duct member comprises an arrangement of interconnected or integrally formed tube members, the tube members extending into the cooking chamber in the direction of flow of air through the duct member.

Preferably, the duct member comprises a pair of side tube members that extend substantially perpendicularly to baffle means of the cooking apparatus.

Preferably, the side tube members are spaced apart in the cooking chamber by one or more cross tube members that extend substantially perpendicular between the side tube members. The cross tube members that extend substantially perpendicular between the side tube members act as a balancing mechanism, by way of restrictive means, to substantially equalise the pressure and airflow of through/within each tube member.

Preferably, the duct member comprises one or more regions of converging or reducing cross-sectional internal diameter.

Preferably, a metering valve is disposed in one of or in each of: the side tube members and the cross tube member.

According to a further aspect of the present invention there is provided a cooking apparatus comprising: a cooking chamber for cooking a food product therein; an air heating chamber; baffle means for separating the cooking chamber and the air heating chamber, and an airflow delivery and circulation device comprising a duct member in the cooking chamber, the duct member comprising at least one opening into the cooking chamber and an airflow inlet for receiving heated air from the air heating chamber, in which the duct member is operable to channel the heated air from the airflow inlet to the opening, and an aerofoil shaped extension member projects externally from the duct member into the cooking chamber at or adjacent to each opening, and whereby the aerofoil shaped extension member is operable to direct streams of heated air from the opening into the cooking chamber to heat or cook a food product in the cooking chamber.

According to a still further aspect of the present invention there is provided a cooking apparatus comprising: a cooking chamber for cooking a food product therein; an air recirculation chamber, baffle means for separating the cooking chamber and the air recirculation chamber; and an airflow delivery and circulation device comprising a duct member is mounted in the cooking chamber, the duct member comprising at least one opening into the cooking chamber and an airflow inlet for receiving heated air from the air recirculation chamber, in which the duct member is operable to channel the heated air from the airflow inlet to the opening, and an aerofoil shaped extension member projects externally from the duct member into the cooking chamber at or adjacent to each opening, and whereby the aerofoil shaped extension member is operable to direct streams of heated air from the opening into the cooking chamber to heat or cook a food product in the cooking chamber.

According to a still further aspect there is provided a cooking apparatus comprising: a cooking chamber for cooking a food product therein; an air heating chamber; an air recirculation chamber, and an airflow delivery and circulation device comprising a duct member mounted in the cooking chamber, the duct member comprising at least one opening into the cooking chamber and an airflow inlet for receiving heated air from both of the air heating chamber and the air recirculation chamber, and in which the duct member is operable to channel the combined heated air from the air heating chamber and the air recirculation chamber from the airflow inlet to the opening, and an aerofoil shaped extension member projects externally from the duct member at or adjacent to each opening, and whereby the aerofoil shaped extension member is operable to direct streams of heated air from the opening into the cooking chamber to heat or cook a food product in the cooking chamber.

The present invention provides an air delivery and circulation device for a cooking apparatus, such as an oven, toaster or other cooking device used for heating or cooking a food product. The present invention comprises a duct member or tubing, and an aerofoil shaped extension member that projects externally from the duct member at or adjacent to each opening thereof for the delivery of heated air into a cooking chamber of the cooking apparatus. It will be understood that the cooking apparatus of the present invention also includes conventional means for radiant convection cooking including one or more fan- assisted convection elements and/or one or more quartz heating elements.

The present invention ensures that heated air travels smoothly in regular paths through the duct member and exits via the aerofoil shaped extension member, which operates to deliver heated air into the cooking chamber of the cooking apparatus. The resultant laminar flow or streamline flow ensures that the velocity, pressure, and other flow properties of the air at each point in the cooking chamber remains relatively constant.

Laminar air flow over the aerofoil shaped extension member further causes a decrease in pressure consisting of thin parallel layers or laminae of air. The air in contact with the top surface of the aerofoil shaped extension members is substantially stationary, but other layers of heated air slide over each other thus bringing air from the top and sides of the cooking apparatus (using the differential pressure that is created) creating a recirculation effect inside the cooking apparatus. The present invention provides a self-perpetuating recirculated airflow that provides consistent results in terms of browning when cooking a food item for minimum energy input.

The present invention further provides a cooking apparatus with an air heating chamber, an air circulation device and a baffle plate which cooperate to extract maximum energy from the airflow for a given input power.

The duct member circulates the airflow into and around the cavity, expelling airflow over the aerofoil shapes to deliver a laminar airflow with a substantially constant pressure and velocity. By recirculating air back to the duct member over a reflector provided in the recirculation chamber housing quartz heating tubes provides further energy efficiency as excess energy is absorbed from the reflectors into the recirculated air. Such absorption improves the efficiency of the reflectors and the quartz tubes and ensures that they are maintained at a constant temperature, which extends the working life of the tubes.

The provision of filtration means at the inlet port of the air re-circulation chamber is advantageous, and further extends the working life of the quartz tubes. Airflow over the reflectors is provided by a venturi effect, not a dedicated motor and fan, which contributes to a further energy efficiency.

Recirculating the heated air from the inside of the cooking chamber by establishing differential pressure inside the cooking chamber by use of the aerofoil shapes and not high powered fans, contributes to a further energy efficiency. The retention of moisture in the product and cooking chamber improves the quality of cooking process and the resultant cooked product. Using software to control the cooking process by measuring power draw at each stage and the cycling of power to heating elements, quartz tubes and adjusting time accordingly, contributes to a further energy efficiency and improvement in the cooking process.

The invention will be more clearly understood from the following description of some embodiments thereof, given by way of example only, with reference to the accompanying drawings, in which:

Fig. 1 is a diagrammatic of a cooking apparatus incorporating an air delivery and circulation device according to the invention; Fig. 2 is perspective view from above of a duct member of the air delivery and circulation device according to the invention;

Fig. 3 is a perspective view from above of a section of the duct member shown in Fig.2;

Fig. 4 is a perspective view from above of a further section of the duct member shown in Fig. 2;

Fig. 5 is a perspective view from above showing air flow through the duct member of Fig. 2;

Fig. 6 is an end view of the of the duct member of Fig. 2 showing air flow over a section thereof;

Fig. 7 is a front view showing a cooking chamber of a cooking apparatus in which is mounted the duct member shown in Fig. 2; and

Fig. 8 is a perspective view of a baffle plate according to the invention; Fig. 9 is a diagrammatic of an air heating chamber for a cooking apparatus according to the invention;

Fig. 10 is a diagrammatic of a section of the air heating chamber shown in Fig. 9, and

Fig. 11 is a diagrammatic of a cooking apparatus in which is mounted the duct member shown in Fig. 2 showing air flow into an air inlet of the duct member according to the invention. Referring to the drawings, and initially to Fig. 1 , there is shown a cooking apparatus 1 for cooking a food item. The cooking apparatus 1 comprises a cooking chamber 2 into which is placed a food item to be cooked, and the cooking chamber 2 is closable by a door 3. The cooking apparatus 1 includes an air heating chamber 4 for supplying heated air into the cooking chamber 2. The air heating chamber 4 houses an impeller fan 5 which is driven by a motor 6 and a heating element 26 for heating air drawn into the heating chamber 4 by the impeller fan 5. A baffle means or baffle plate 7 is provided for separating the cooking chamber 2 and the air heating chamber 4. An air re-circulation chamber 9 is provided in the upper region of the cooking chamber 2 and comprises quartz heating tubes 11 housed in reflectors 10 which radiate heat into the cooking chamber 2. The quartz tubes reflectors 11 are maintained at the cooking chamber pre-set temperature and heat up to a temperature in the range of about 300 - 500 degrees Celsius when activated. An inlet port 18 channels air from the cooking chamber 2 back to the air recirculation chamber 9.

Also shown is a duct member 8 of an air delivery and circulation device according to the invention, which will be further described with reference to Figs. 2 to 11. The cooking chamber 2, the air heating chamber 4, the air re-circulation chamber 9 and the duct member 8 are contained in a housing 20 of the cooking apparatus 1.

As shown in Figs. 2 to 4, the duct member 8 comprises an airflow inlet port 14 for receiving heated air and a number of openings 12 which face into the cooking chamber 2. The duct member 8 is operable to channel the heated air from the airflow inlet 14 to the openings 12. The duct member 8 will be understood to be an arrangement of interconnected or integrally formed conduits or tubes providing a passageway for the transfer of a heated fluid, such as heated air, from the air heating chamber 4 via the duct member 8 and out of the openings 12 into the cooking chamber 2 to cook a food item placed therein.

The duct member 8 comprises an aerofoil shaped extension member, indicated generally by the reference numeral 13, that projects externally from the duct member 8 at or adjacent to each opening 12. The aerofoil shaped extension member 13 provided at each slot opening 12 is operable to deliver and to direct streams of heated air from the opening 12 into the cooking chamber 2 to thereby heat or cook a food product in the cooking chamber.

As shown, each aerofoil shaped extension member 13 comprises a pair of spaced apart aerofoil extension member wings 13a, 13b which project into the cooking chamber 2 at or adjacent to each opening 12. In the instance shown, each extension member wing 13a, 13b is configured as a plate member formed from one or more of: metal, polymer, ceramic, glass or other material configured to withstand high heat. Each extension member wing also comprises a top surface 40 having an aerofoil profile and a bottom surface 41, and the top surfaces 40 of the pair of extension member wings when arranged at each opening 12 together define a substantially arc-like or curve-like profiled surface. Each opening 12 provided on the duct member 8 is formed a slot having an elongate top edge and an elongate bottom edge spaced apart by a pair of side edges, in which one of the pair of extension member wings 13a is provided at or adjacent the top edge of the slot 12, and the other of the pair of extension member wings 13b is provided at or adjacent to the bottom edge of the slot 12. Heated air thus flows out of each opening slot 12 between the extension member wings 13a, 13b. The slots may optimally have a height of the order of about 1 mm to 5mm, and preferably 2mm, based on cooking chamber volume and airflow requirements.

The inlet port 14 of the duct member 8 is provided by the open ends of the duct member 8, each of which is connected to the baffle means 7 of the cooking apparatus 1 to provide a passage for heated air to pass through.

In the instance shown, the duct member 8 comprises a pair of side tube members 15 spaced apart and in communication with a pair of cross tube members 16. It will be understood that the side tube members 15 and cross tube members 16 extend in the direction of flow of air through the duct member, such airflow indicated by the dotted arrows TV. In use, the side tube members 15 extend substantially perpendicularly to the baffle means 7, and the cross tube members 16 extend substantially parallel to the baffle means 7.

The duct member 8 comprises convergent regions or ducts 17 in which the side tube members 15 and/or the cross tube members 17 have a tapered section merging to form a reduced cross-sectional diameter. A metering valve may optionally be disposed in one of or in each of: the side tube members and the cross tube member to regulate and/or monitor air flow through the duct member 8

Fig. 8 shows the baffle means 7 of a cooking apparatus in further detail. The baffle means 7 is positioned between the cooking chamber 2 and the air heating chamber 4. The baffle means 7 may be formed as a plate comprising an air intake opening 21 disposed therein through which air is drawn from the cooking chamber 2 into the air heating chamber 4 by the centrifugal impeller fan 5. The air intake opening 21 of the baffle means 7 comprises a rounded or defined curved edge 22 on the air heating chamber side 24 and also the cooking chamber facing side 25 to improve the efficiency. Also provided are air outlet ports 23 which are provided as openings in the plate 7 through which heated air is channelled to the cooking chamber 2. More specifically, the inlet ports or open ends 14 of the duct member 8 are coupled to the ports 23 to enable the transmission of heated air from the air heating chamber 4 to the cooking chamber 2.

Figs. 9 and 10 show the air heating chamber 4 of the present invention. The air heating chamber 4 comprises an impeller fan 5 to draw air from the cooking chamber 2 via the air intake opening 21 of the baffle plate 7 into the air heating chamber 2, and a heating element 26 for heating the intake air. The fan 5 is further operable for circulating and propelling the heated air within and out of the air heating chamber 4 via the air outlet ports 23 of the baffle plate 7 to the duct member 8 and into cooking chamber 2. The air heating chamber 4 further comprises a back plate 27 onto which are mounted the heating element 26 and the impeller fan 5. The plate 27 comprises an upstanding side wall 28 and receiver plate 30 which extends around the chamber 4 to enable the baffle means 7 to be secured to the open face of the air heating chamber 4 such that the impeller fan 5 is positioned substantially opposite the air intake opening 21 of the baffle means 7.

Optionally, an arrangement of guide members 29 may be provided on the plate backing plate 27. The guide members 29 may be integrally formed or releasably interconnected up stands on the backing plate 27 and are positioned between to the impeller fan 5 and the heating element 26. The guide members 29 are provided as curved vanes or fins, and in use, as the airflow directed from the impeller fan 5 passes over the surfaces of the guide members 29 an increase in the speed of the airflow is observed, with a resultant decrease in pressure at exit. The fan guide members fulfil a number of extra functions such as causing areas of differential pressure within the air heating chamber thereby creating a rush of air to the air outlet exit ports 23. Further guide members 30 are provided adjacent to the heating element 26 and opposite each air outlet port 23 of the baffle plate 7. The guide members 30 are provided as a curved vane or plate or fin on the plate 27, and in operation, as the heated airflow passes over the surfaces of the guide members 30 an increase in the speed of the airflow is observed, with a resultant decrease in pressure attracting air from other sections of the heat chamber. A further effect is an increase in the exit airspeed at the air outlet port 23 and has a still further effect of stabilising the exit airflow entering duct member 8.

The operation of the air delivery and circulation device according to the invention will now be described with specific reference to Figs. 5 to 7 and Fig. 11.

Heated air, indicated by arrows TV, is channelled from one or both of the air heating chamber 4 and the air re-circulation chamber 9 and mixed as it passes through a convergent conduit 42 and into the duct member 8. The heated air exits the duct member 8 via the openings 12, indicated by the arrows 'B', passing over the top surface 40 of the aerofoil shaped extension member wings 13b as it flows into the cooking chamber 2.

As the airflow Ή passes over the aerofoil shaped wing member 13b its speed will increase, with a resultant decrease in pressure. In consequence, heated air within the upper regions of the cooking chamber 2, indicated by the arrows 'C (Fig. 6 and 7), which has a higher pressure and temperature relative to the airflow 'Β', then moves down toward the region of the chamber 2 comprising lower relative pressure heated air. Cooler air at the sides of the cooking chamber 2 is also drawn around the duct member 8 in the cooking chamber 2 and the associated aerofoil shaped extension member wings 13a, 13b causing a recirculation of air within the cooking chamber 2. It will be understood that the airflow 'C is moist as it contains moisture that has evaporated from the surface of the food item being cooked and it has not at that stage of the cycle been re-circulated back to the air heating chamber 2 or recirculation chamber 9 to be dried.

As the airflow 'C passes over the top surfaces 40 of the aerofoil shaped extension member wings 13a, 13b an increase in the speed of the airflow 'C is observed, with a resultant decrease in pressure, and the airflows 'B' and 'C are mixed and directed toward the food item to thereby heat and/or cook the food item. The airflow in the cooking chamber 2 is thus a function of the differential pressure being created by the aerofoil shapes since air flowing over the aerofoil shapes increases in speed with a resultant decrease in pressure.

Air from within the cooking chamber 2 is then drawn back into the heat chamber 4 by the impeller fan 5 and into the re-circulation chamber 9 from the cooking chamber 2 via the inlet 18 at the front of the roof of the cooking chamber 2 and this air is recirculated back to the cooking chamber 2 by repeating the above cycle. The heat from the reflectors 10 is absorbed by the air as it is drawn through the air recirculation chamber 9 and expelled back to the cooking chamber 2 via the openings 12 of the duct member 8 and over the aerofoil shaped extension member 13 to cook or heat food within the cooking chamber 2.

A built in venturi or constriction is provided in the recirculation duct 19 which causes a decrease in pressure thereby drawing air over the reflectors 10 absorbing heat from them and keeping them at a substantially constant temperature in the region of 230 degree Celsius (which is the nominal cavity temperature). Making use of the air recirculation chamber 9 in this manner provides a significant energy saving when the quartz tubes are activated which will avoid the need to power the conventional heating elements of the cooking apparatus 1 during a short cook stage of about between 30 and 90 seconds.

For example, if heating elements were on they would draw up to about 2000 watts and since the quartz tubes draw about 2000 watts the combined energy draw would be about 4000 watts, excluding all the other items such as the motors, fans, magnetrons and the like. Moreover, the provision of the air recirculation chamber 9 which uses the otherwise wasted energy of the quartz reflectors 10 to heat recirculated air from the cooking chamber 2 to cook a product enables the cooking apparatus 1 to be operated using a 13amp AC supply (2990 watts). The reflectors 10 are also maintained at a constant temperature which improves their overall efficiency and extends their working life. When the cooking apparatus 1 is not cooking and the quartz tubes 11 are powered off, then the oven cooking chamber 2 is maintained at a pre-set temperature, such as 230 degrees Celsius by the heating elements in the air heating chamber 4 cycling on and off.

The present invention thus involves the re-circulation of moist air. The moisture in this recirculated air in the cavity is absorbing stray microwave energy and radiant energy from the quartz tubes and metal of the oven and in the process the moisture which is relatively dry steam is converted into superheated steam by absorbing this stray energy, which otherwise would be lost in the air heating chamber 4, and with a gain of an increase in temperature. Aspects of the present invention have been described by way of example only and it should be appreciated that additions and/or modifications may be made thereto without departing from the scope thereof as defined in the appended claims.