Cooking apparatus

Abstract

An oven 310 comprises an oven chamber 370, a port 350 for a demountable heated air source at a rear of the oven, and a flue 330 from the oven chamber. A first heated air source comprising a gas burner (380, figure 5B) and a variable air inlet 346 for use with a second heated air source which comprises a solid fuel carrier 340 may each be demountably receivable by the port, where only the variable air inlet or the first heated air source can be received by the port at the same time. An air flow director 374 may have an upper portion extending downwards, a rear surface that faces the rear of the oven, and a lower portion which directs air flowing down the rear surface more rearwardly, where the air flow director deflects heated air away from the flue and downwards towards the cooking surface. The flue may comprise a valve configured such that, when in a closed position, an open cross-sectional area of the flue through which air can flow out of the oven is at least 25% of the open cross-sectional area of the flue when the valve is in an open position.

Description

Field of the invention The present invention relates to the field of cooking apparatuses comprising an oven, particularly a pizza oven. Background to the invention Cooking apparatuses such as pizza ovens typically have an air inlet into an oven chamber to provide oxygen to fuel the flame used to heat the oven chamber. Heated air circulates in the oven chamber and typically escapes via a flue incorporated into the cooking apparatus. If the heated air escapes the oven too quickly it will not provide efficient heating of the articles to be cooked such as pizzas or dough bases. GB2545929 discloses a device that has previously been incorporated into the roof of pizza ovens to deflect heated air and retain it in the oven chamber. However, these devices can block the access path for large food items into the oven. Some aspects of the invention seek to address this issue. Cooking apparatuses are also known which can receive different types of fuel such as solid fuels like wood and charcoal, as well as gas fuels. Typically the air flow through the oven is not suited to both types of fuel sources and efficiency of cooking in the oven is lower than in single fuel ovens. If a door was to be added to such an oven to increase heat retention and efficiency while burning solid fuels, it could provide a safety hazard when the oven is used with a gas fuel. Some aspects of the invention aim to improve safety and efficiency in ovens which may burn gas or solid fuels. It is in this context that the present inventions have been devised. Summary of the invention In accordance with the present invention, there is provided a cooking apparatus comprising an oven, the oven comprising: an oven chamber having an upper roof surface and a lower cooking surface, opposite to the upper roof surface; an opening for receiving a door at a front end of the oven; a port for receiving a (typically) demountable heated air source at a rear end of the oven, opposite to the front end of the oven; a flue in communication with the upper roof surface of the oven chamber which provides a flow path for air to leave the oven chamber; and an air flow director, the air flow director having an upper portion extending downwards (and typically forwards) and a lower portion (which may also extend downwards and forwards) and a rear surface that faces the rear of the oven, wherein the lower portion of the air flow director comprises a flow direction portion configured to direct air flowing down the rear surface of the upper portion more rearwardly, wherein the oven chamber extends between the port and the flue, thereby defining, in use, a heated air flow path between the port and the flue, and wherein the air flow director is located in the heated air flow path and configured to deflect heated air away from the flue and downwards towards the cooking surface. By directing the air more rearwardly we refer to changing the direction in which the air flows so that its direction of motion has a greater rearward component than before. It may be that the air is redirected to flow in a less forward direction. It may be that the air is redirected to flow in a direction which is rearward (rather than forward). The flow direction portion may extend from the rear surface of the lower portion. The flow direction portion may comprise a region of the rear surface of the lower portion which is concave. The flow direction portion may extend rearward of the direction in which the upper portion extends (i.e. having a rearward component greater than a rearward component of the upper portion). By providing an air flow director in the oven chamber that is configured in this way to deflect heated air downward and towards the cooking surface, recirculation of heated air in the oven chamber is promoted and the cooking surface is suitably heated. Without the air flow director, airflow travels through the oven chamber and out of the flue with a short retention time in the oven chamber itself and the front of the cooking surface can be quite cool, causing uneven heating. Accordingly, the air flow director provides for a greater heat retention in the oven chamber and a greater directed heat flow to the cooking surface where articles to be cooked are placed. The air flow director may as a result create more recirculation than would otherwise be the case for the same vertical extent. In some embodiments, the flow direction portion of the lower portion extends rearwards and downwards relative to an upper portion of the air flow director. It may be that the upper portion of the flow direction portion may define a boundary layer which the air flow in the oven chamber follows and the lower flow direction portion may disrupt this air flow which follows the boundary layer. It may be that the flow direction portion is curved. The flow direction portion may comprise a concave part of the rear surface of the air flow director. The flow direction portion may be incurvate. By curving the air flow director, a better air flow deflection can be achieved whilst maintaining a given vertical gap between the base of the air flow director and the cooking surface. The provision of the curve thus allows for a large proportion of the height of the oven to be accessible in use whilst at the same time achieving efficient deflection of heated air flow downwards towards the cooking surface. For example, the airflow director may be configured such that at least 50%, at least 60%, at least 70%, at least 80% of an oven chamber height (measured from the upper roof surface to the lower cooking surface) is clear for the insertion of or removal of cooking food items. It may be that the airflow director occludes less than or equal to 50%, 40%, 30%, 20% or 10 % of the height of the oven chamber measured from the upper roof surface to the lower cooking surface. Curving the flow direction portion of the air flow director also has the beneficial effect that a sharp edge is removed from an open side which a user may contact (e.g. a sharp edge of the air flow director when formed form a metal sheet which would otherwise be at the lower edge of the air flow director). Accordingly, the curved shape of the flow direction portion provides for increased safety when handling. It may be that the flow direction portion is a curled or folded portion that extends across the breadth of the rear surface of the air flow director. The curvature of the curled portion may be such that a spiral shape is formed or partly formed. The lower portion of the air flow director may be folded once or more than once to form the flow direction portion. For example, the lower portion of the air flow director may be folded, twice, three times or more. The flow direction portion may also be a folded and curled portion. For example, the lower portion of the air flow director may be folded and the curled into the flow direction portion. By incorporating the flow direction portion as a curled or folded portion across the entire breadth, the flow direction portion better deflects air across the whole width of the air flow director for a given height of the air flow director from the cooking surface. Moreover the curled or folded portion can conceal a sharp edge at the end of the air flow director (e.g. from a metal sheet) within the curl or fold so that it is directed away from a user. It may be that the air flow director is configured as a sheet. For example, the air flow director may be formed by bending a sheet of metal. The sheet may be a continuous sheet. The sheet may be configured with features such as holes or perforations included therein. In this way, the whole air flow director can be made from a single material with limited processing steps. Accordingly, the air flow director is easy to manufacture, reducing both time and costs associated with manufacture. It may be that the air flow director is located in an upper region of the oven chamber and slopes downwards (towards the cooking surface) and forwards towards the (front end of the oven). It may be that the air flow director depends from the upper roof surface of the oven chamber. It may be that the air flow director is attached to a side wall of the oven chamber at an attachment point. The air flow director may be positioned beneath and rearward of an opening in the upper roof surface which defines an entrance to the flue. The air flow director may be attached at the attachment point of a side wall and extend into a middle section of the oven chamber directly below or rearward of an opening of the flue defined by the upper roof surface. The provision of the air flow director in an upper region of the oven chamber allows for efficient deflection of heated air in the upper region of the oven chamber towards the cooking surface and promotes recirculation and convection in the oven chamber. It may be that the air flow director causes turbulent air flow. The air flow director may form eddy currents in the heated airflow on deflection of the heated air flow, causing greater recirculation of the heated air in the oven chamber. The turbulent air flow may be formed by disruption of a boundary layer of air following an upper portion of the air flow director by the flow direction portion. The air flow director may be reversibly deployable in the heated air flow path, for example demountable. It may be that the air flow director comprises a connector configured to (e.g. reversibly) attach the air flow director, e.g. to the upper region of the oven chamber. The connector may be an integrated connector configured to reversibly attach the air flow director to the upper region of the oven chamber. For example, the connector may be a screw on the air flow director received into a threaded hole on the oven body. In this way, the air flow director is reversibly deployable in the oven, for example if the oven needed to be used to cook an article which required a very large oven chamber height. As the connector is integrated it will not separate from the air flow director which provides additional safety to the user as this could prevent injuries such as accidental ingestion of connectors. In accordance with a further aspect of the invention, there is provided a cooking apparatus comprising: an oven, the oven comprising: an oven chamber having a cooking surface; a door at a front end of the oven, the door movable between an open and a closed position; a port for receiving a demountable heated air source at a rear end of the oven, opposite to the front end of the oven; and a flue that provides a flow path for air to leave the oven chamber; a first heated air source which is demountably receivable by the port, whereby the first heated air source comprises a gas burner; a second heated air source which comprises a solid fuel carrier; a variable air inlet for use with the second heated air source and which is demountably receivable by the port; wherein only the variable air inlet or the first heated air source can be received by the port at the same time. By incorporating a variable air inlet for use with a second heated air source, rather than relying on air inlets provided in the body of the oven, it is possible to allow a user to control air supply to the second heated air source while ensuring that the first heated air source, a gas burner, can only use its own dedicated air inlet. This is important because of safety risks if the air supply to the gas burner was excessively restricted. This is especially relevant because the oven has a door. The presence of a door enables a user to add or remove food and to decide whether and to what extent to close the door during cooking with solid fuel. The door allows for improved efficiency during cooking, allowing the oven chamber to heat up quickly when closed. However, there could be risks if the door was left closed by a user while the gas burner was in use. Thus, a dual fuel oven with a gas burner option and a closable door can be safely provided. Furthermore, the user has the flexibility to adjust the air supply to the first heated air source. It may be that the variable air inlet is demountably receivable by the port by being inserted through the port or mounted to the port (on the outside or in the port, for example). It may be that the first heated air source is demountably received by the port by being insertable through the port. It may be that the variable air inlet is operable between a range of positions between fully closed and fully open. When fully closed, it may be that the open cross-sectional area of the variable air inlet is less than 25%, less than 10% or less than 5% of the total cross-sectional area of the variable air inlet when fully open. The air inlet may comprise a grating. It may be that the second heated air source is demountably receivable by the port (e.g. mountable to or through the port). Thus, it may be that only the second heated air source, including the variable air inlet, or (only) the first heated air source can be received by the port at the same time. It may be that the second heated air source is demountably receivable through the door. It may be that the second heated air source is fixed to the oven. It may be that the variable air inlet is integral with the second heated air source. It may be that the first heated air source comprises a gas burner air inlet, which may be fixed or variable. By the term fixed it is understood that the inlet cannot be adjusted to vary a cross-sectional area through which air can flow through the inlet. By variable it is understood to mean that the inlet is adjustable such that the cross-sectional area through which air can flow (and so, in use, the flow rate) through the inlet can be changed. The variable air inlet typically comprises a manually operable control which controls the cross-sectional area through which air can flow. For example, it may be that the variable air inlet is integrated into the solid fuel carrier as a panel with apertures defined therein with a manually operable lever which slides a cover occluding a variable cross-sectional area of the apertures depending on the position of the lever. It may be that the gas burner air inlet on the first heated air source is not variable. The gas burner air inlet typically has a fixed cross-sectional area. This ensures appropriate oxygen supply to the gas burner. It may be that the cooking apparatus comprises a further air inlet, which further air inlet is variable. It may be that the cooking apparatus has no air inlet other than the variable air inlet, or one or more inlets integrated with the first or second heated air source, excluding the door and flue. It may be that the variable air inlet, and the gas burner air inlet, when present, are the main inlets for air into the oven chamber to provide oxygen for combustion. For example, it may be that at least 50%, at least 75%, at least 90% or all of the oxygen used for combustion is received through the variable or gas burner air inlet in use. It may be that the solid fuel carrier is configured to receive solid fuel, wherein the solid fuel is at least one of wood, charcoal, and / or fuel pellets. For example, the solid fuel carrier may comprise a perforated tray for receiving wood, charcoal or fuel pellets. The perforations allow air to pass upwards through the fuel to support combustion. The door allows for the opening of the oven which acts as the access point for provision and removal of articles to be cooked and it may optionally be closed during cooking. Closure of the door allows for a greater heat retention in the oven and increases the efficiency of cooking with solid fuel. The door may be demountably mountable or mounted to the body of the oven by way of cooperating formations on the door and on the body, whereby the door is rotatable forwards and backwards around a horizontal axis parallel to the width of the front opening through a range of angles relative to the front opening, between a closed position in which the door closes the oven chamber and a maximally open position, and wherein the cooperating formations are configured such that the door is removable from and mountable to the body, by separation or engagement of the cooperating formations, only in a sub-range of the range of angles and the door is otherwise retained onto the body. By providing the door, a greater efficiency of the oven can be achieved when still safely using a gas burner in the oven. This is because the door can be closed to retain heat more effectively than if open and the oven comprises a flue which remains open to allow for the escape of gas to prevent a gas build up. It may be that the cooking apparatus further comprises the air flow director according to the previous aspect. In a further aspect of the invention, there is provided a method for using the cooking apparatus of the previous aspect, the method comprising the steps of providing the cooking apparatus according to the previous aspect; using the oven with the second heated air source and the variable air inlet present; removing the variable air inlet; mounting the first heated air source; and using the oven with the first heated air source wherein the air flow into the oven is controllable by the variable air inlet. It may be that the method further comprises the steps of removing the first heated air source; replacing the variable air inlet and using the oven with the second heated air source. It may be that the second heated air source is also removed before the oven is used with the first heated air source and replaced after use of the oven with the first heated air source. In a further aspect, there is also provided a method for using the cooking apparatus of the previous aspect, the method comprising the steps of: providing an oven comprising a first heated air source received into the port; demounting the first heated air source from the port; and inserting the variable air inlet, (and if it is demountable, the second heated air source) into the port, wherein the air flow into the oven is controllable by the variable air inlet. The method may comprise causing the air flow into the oven to be controlled (e.g. by the variable air inlet). The method may comprise controlling the air flow into the oven (e.g. by the variable air inlet). It may be that the variable air inlet is integral to the second heated air source. In this way, a user can safely and efficiently use a cooking apparatus which has dual fuel capability and which provides air flow control when using the a solid fuel carrier and which provides increased gas safety when using the gas burner. The oven is efficient in use for both fuel sources as the door can always be closed to retain heat and the flue, particularly when used with the gas burner received into the port, can always be open to prevent gas build up. It may be that the cooking apparatus comprises a flue in fluid communication with the oven chamber. It may be that the flue does not include a valve. The internal cross sectional area of the flue may be fixed. Thus, air flow cannot be excessively restricted when the door is shut and the second, gas burning, demountable heated air source is being used. Thus air flow control takes place at the variable first air inlet (when the first demountable heated air source is being used). The presence of the gas burner air inlet provides at least a minimum, and typically predetermined, air supply when the first demountable heated air source is being used. In a further aspect of the invention, there is provided a cooking apparatus comprising an oven, the oven comprising: an oven chamber having a cooking surface; a door at a front end of the oven, the door movable between an open and a closed position; at least one port for receiving a demountable heated air source at a rear end of the oven, opposite to the front end of the oven; and a flue that provides a flow path for air to leave the oven chamber, wherein the flue comprises a valve operable between an open and a closed position, wherein the valve is configured such that, when the valve is in the closed position, an open cross-sectional area of the flue through which air can flow out of the oven is at least 25 % of the open cross-sectional area of the flue when the valve is in the open position. In this way, the air flow from within the oven chamber and out through the flue can be restricted to control the rate of heating, while still allowing a minimum air flow through the flue. This increases the safety of a cooking apparatus with dual fuel burning capacity. For example, when the cooking apparatus is used with a demountable heated air source that is a gas burner, the cross section of the flue can be varied but will always allow for a sufficient airflow therethrough to prevent gas build up, for example if the flame goes out. At the same time, the oven can be used with a solid fuel source and the flue is substantially closed to maintain the heat required for cooking within the oven chamber. The valve is operable between an open and closed position. The term ‘open’ in this context is understood to mean that, when the valve is open, a maximum airflow through the flue comprising the valve is available. In the same vein, when the valve is closed, a minimum airflow through the flue is available through the flue comprising the valve. This minimum airflow is defined by at least 25% of the open cross-sectional area of the flue. For example, the minimum airflow may be at least 35% and in some preferred embodiments it may be at least 45%. The term open cross-sectional area is understood to mean the cross-sectional area available for air to pass through the flue. The open cross-sectional area may be in the same area of the flue as the valve. The open cross-sectional area may be in a different area of the flue as the valve. For example, the flue may have two channels, one channel comprising the valve and another channel purely defining an exit for air flow. The open cross-sectional area of the flue may therefore be composed of a cross sectional area comprising the valve and a separate cross-sectional area (not comprising the valve). It may be that the valve comprises a movable valve member. For example, the valve member may rotate around a (typically central) axis attached to the flue. Rotation of the valve member may be achieved by a handle connected to the axis and located on an external wall of the flue. The valve member may be slidable between an open position and a closed position. It may be that the valve has a valve member which has a plurality of apertures defined therein and the valve may be in a closed position when all of the holes in the plurality of holes are covered and the valve may be in an open position when at least one of the holes in the plurality of holes is uncovered. The valve member can thus provide for a change in the cross-sectional open area of the flue in a versatile way that gives a large degree of freedom to the user in terms of the extent to which the flue is open to allowing air flow through. It may be that the valve member is a rotatable disc. For example, the valve member may be part of a butterfly valve. It may be that the valve member has a major dimension and a minor dimension that is smaller than the major dimension. For example, the valve member may be configured as a truncated disc with linear sides parallel to its length and curved sides therebetween. It may be that the flue has a circular cross-section and the valve member has a noncircular cross-section. In a further aspect of the invention, a cooking apparatus is provided, wherein the cooking apparatus is according to any of the previous aspects. Optional features of any one aspect of the invention are also, mutatis mutandis, optional features of any other aspect of the invention. Description of the Drawings An example embodiment of the present invention will now be illustrated with reference to the following Figures in which: Figure 1 is a perspective view of a pizza oven according to an embodiment of the invention; Figures 2A and 2B are, respectively, a side cross-sectional view of the pizza oven and a plan cross-sectional view of the flue, according to an embodiment of the invention; Figures 3A - 3C are, respectively, a cross-sectional view of a pizza oven, a perspective view of the air flow director and a further perspective view of the air flow director according to an embodiment of the invention; Figures 4A and 4B are, respectively, a cross-sectional view of the pizza oven and a magnified view of an air flow director and cooking surface, in accordance with an embodiment of the invention; and Figures 5A and 5B are cross-sectional views of a cooking apparatus in accordance with an embodiment of the invention. Detailed Description of Example Embodiments First embodiment - cooking apparatus comprising a flue with a valve As shown in Fig. 1, a pizza oven 100 comprises a pizza oven body 110 supported on legs 120 which extend from a base 112 of the body 110. A flue 130 extends from a top surface 114 of the of the body 110 and a demountable gas burner unit 140 is inserted into a port 150 at the rear of the oven. Fig. 2A shows the same pizza oven 100 in cross-sectional view. Figure 2 shows door 160 received in an opening 162 of the pizza oven body 110 at the front of the oven. The door 160 comprises a door handle (not shown) and the door 160 is shown in an open position allowing access into the oven chamber 170 - i.e. to provide articles for cooking therein or to remove articles for cooking therefrom. The oven chamber 170 is defined by the volume enclosed by the oven body 110, the door 160 and the demountable gas burner 140 when inserted into the port 150 at the rear of the oven. The demountable gas burner 140 comprises a flame safety device 142. The oven chamber 170 comprises cooking surface 172 which is configured to receive articles for cooking. The cooking surface may be a pizza stone. The flue 130 comprises a valve comprising a valve member 132 in the form of a rotatable disc which is connected to the flue 130 by means of an axle 134 around which the disc can rotate. A handle on the outside of the flue 130 (not shown) allows a user to rotate the valve 132 between an open and closed position in order to manually vary a rate of hot air loss from the oven chamber 170. Fig. 2A shows the line A-A along which cross sectional Fig. 2B is taken. Figure 2B is a plan view of the cross-sectional region of the flue 130. Fig. 2B shows the valve member 132 in the closed position - i.e. in a horizontal plane, parallel to the cooking surface 172. In this closed position, space is provided between the flue 130 and the valve member 132, allowing for air flow through the flue 130 even when the valve is closed. Accordingly, the valve is configured such that the open cross-sectional area of the flue through which air can flow out of the oven when the valve is closed is at least 25% of the open cross-sectional area of the flue when the valve is open. Figure 2A also shows the airflow path (represented by the curved arrows) during cooking when the door is closed and the gas burner 140 supplies gas to a flame (e.g. provided by an ignition source, not shown) inside the oven chamber 170. The air from outside the pizza oven 100 enters the pizza oven 100 through a grating 115 on the underside of the gas burner 140 which functions as an air inlet which is integral to the gas burner 140. Heated air from within the oven chamber 170 can leave the oven through the flue 130 and this is the only path through which heated air is lost when the door is closed. When the valve is closed (as shown in Figs. 2A and 2B) at least 25 % of the open cross-sectional area of the flue 130 is available for heated air to leave the oven. In this way, there is a path available to prevent a build up of gas forming inside the oven chamber 170 if the gas burner goes out while the door is closed. This increases the safety of the oven when used with the gas burner. In use, when gas is supplied through demountable gas burner 140 and an ignition source provides a flame, the flame is provided into the oven chamber 170 through the demountable gas burner 140. This flame heats up the oven chamber 170 and the cooking surface 172. When the oven reaches a desired temperature for cooking, for example, in the range of 400 - 500 °C, a user can open door 160 using the handle (not shown) and then place an item to be cooked into the oven chamber 170 and onto the cooking surface 172. During cooking, the gas burner 140 continues to heat air within the oven chamber 170 to reach and maintain optimum temperatures required for cooking. Oxygen received through the air inlet supports combustion to reach these required temperatures and the flue provides a path for hot air and combustion products to escape. Furthermore, by allowing hot air to leave the oven, in the event of the flame going out, the temperature in the oven drops more quickly, triggering the flame safety device to stop the gas flow more quickly than would otherwise be the case. Second embodiment - cooking apparatus comprising an air flow director Fig. 3A shows a cooking apparatus 200 in accordance with a second aspect of the invention. The cooking apparatus 200 is a pizza oven and comprises an oven body 210 with a door 260 located at a front of the oven body 210 and a demountable heated air source in this embodiment is a solid fuel carrier 240 located at a rear of the oven body 210. For example, the solid fuel carrier may be a perforated tray for receiving wood, charcoal, or fuel pellets. The perforations allow air to pass upwards through the fuel to support combustion. The labelled features present in the first embodiment are also present in this embodiment and have the same numbering system where 100 features are replaced by 200 features - for example, 110 in the first embodiment is analogous feature 210 in this second embodiment, 134 is analogous feature 234 etc. In this embodiment, the oven chamber 270 is defined by the volume enclosed by the oven body 210, the door 260 and the demountable solid fuel carrier 240 when inserted into the port 250. Additional features which are included in this embodiment include the air flow director 274. As shown in Fig. 3A, the air flow director 274 is angled forwards and downwards towards a lower cooking surface 272 and depends from an upper roof surface 278 of the oven chamber 270. As shown in Figs. 3B and 3C, the air flow director has a rear surface 279 that faces the rear of the oven. A rearwardly extending flow direction portion 276 is part of a lower region of the air flow director rear surface 279 and this flow direction portion 276 extends rearwardly of the lower portion, towards the rear of the oven. This flow direction portion 276 is a curled portion of the air flow director 274 which extends across a breadth of the air flow director 274. The air flow director 274 is reversibly attached to the top wall 278 of the oven chamber 270 through a screw 277 which is integrated into the air flow director 274. The screw 277 is attached to the upper roof surface 278 via a receiving threaded hole (not shown). The screw 277 fitting in the air flow director 274 allows the air flow director 274 to be reversibly attached to the top wall 278 of the oven chamber 270 but removes any chance of the screw 277 falling out onto the cooking surface 272 in use of the pizza oven 270. Figs. 4A and 4B show the air flow within the cooking apparatus 200 comprising the air flow director 274. In use, when the solid fuel carrier 240 is inserted into port 250 and supplied with solid fuel (not shown), burning of the solid fuel produces a flame which is directed into the oven chamber 270 and provides heat to the oven chamber. As in the previous embodiment, air from outside the pizza oven 200 enters the pizza oven 200 through a grating 215 on the underside of the solid fuel carrier 240. The air flow then travels through the solid fuel carrier 240 and through the port 250 for receiving the demountable solid fuel carrier 240 and into the oven chamber 270. Accordingly, from the port 250 to the flue 230, there is defined a heated airflow path. The air flow path is shown by the arrows. The air flow director 274 deflects the heated air in the oven chamber 270 down towards the cooking surface 272 owing to its angled orientation and position, depending from the upper roof surface 278. The flow direction portion causes air flowing down the rear surface of the air flow director to be deflected more rearwardly / less forwardly than would be the case without the flow direction portion. In this way, heated air is retained in the oven chamber 270 for longer and the cooking surface 272 receives directed heating which improves the cooking efficiency of articles to be cooked such as pizzas on a pizza stone. Fig. 4B shows more specifically the air flow deflection that occurs by the air flow director 274 which comprises the curled protrusion 276. When air travels along the flow path in the oven chamber 270, it reaches the air flow director 274 which is angled towards the cooking surface 272. Owing to the curled flow direction portion 276 on the rear face of the air flow director 274, the air is deflected in a way that it causes an eddy current to be generated which improves recirculation of the heated air in the oven chamber 270. Accordingly, the air is both directed towards the heating surface 272 and recirculated in the oven chamber 270 for longer. This allows for enhanced cooking of articles on the cooking surface owing to a higher proportion of heated air reaching the cooking surface 272 for longer, compared to when no air flow director is present. A portion of the air flow then escapes the oven 200 via the flue 230. As a result, the vertical extent of the air flow director 274 can be smaller than would otherwise be the case. This leaves a larger vertical extent through which food items can be provided into and removed from the oven chamber without being blocked by the air flow director. As the cooking apparatus 200 also comprises the valve comprising valve member 234 which works analogously to the previous embodiment, a controllable air flow path is provided to allow for the escape of air through the flue 230. This is particularly advantageous when using a demountable gas burner 240 as it prevents a build up of gas in the oven chamber 270. Furthermore, as the flue cannot be completely closed off, in the event that the flame is extinguished, the temperature in the oven will decrease quickly, triggering the flame safety device to stop the gas flow. Third embodiment - air flow control system In both Figures 5A and 5B a cooking apparatus 300 is shown in accordance with the invention comprising a pizza oven with oven body 310. A cross-section of the internal volume of an oven chamber 370 is shown that comprises a cooking surface 372 and an air flow director 374. A door 360 is received in an opening 362 at the front end of the oven and comprises a handle (not shown). A flue 330 is provided as a means of escape for hot air to exit the oven chamber 370 and is positioned near the front of the oven. The oven 300 comprises a port 350 at the rear of the oven that is capable of receiving interchangeable gas and solid fuel burners (functioning as demountable heated air sources). In Figure 5A, a solid fuel carrier 340 which is configured to carry wood, fuel pellets and / or charcoal fuel functions as the second heated air source. The solid fuel carrier 340 is inserted into a port 350 on the pizza oven 300 at the oven rear. A variable air inlet 346 is integrated into the solid fuel carrier in this embodiment although it is to be understood that the variable air inlet could be a separate component to the solid fuel carrier. The variable air inlet 346 allows for the introduction of air through the solid fuel carrier into the oven to provide oxygen to the flame produced on burning the solid fuel in the solid fuel carrier. The variable air inlet 346 allows for the amount of air allowed into the oven chamber 370 to be adjusted by a user. In this embodiment the variable air inlet 346 is integrated into the solid fuel carrier 340 as a panel with apertures 347 defined therein with a manually operable lever (not shown) which slides a cover occluding a variable cross-sectional area of the apertures depending on the position of the lever. The solid fuel carrier also comprises an air inlet 348 which is fixed and allows air into the solid fuel carrier. In Figure 5B, the oven is shown with the solid fuel burner replaced with gas burner 380 (functioning as the first demountable heated air source) which comprises a flame safety device 382 that is configured to shut of the gas supply in use if a temperature of the oven chamber is indicative that a flame is no longer burning. The first demountable heated air source further comprises a gas burner air inlet 388. The heated air sources 340, 380 are interchangeable in that they can be swapped depending on which fuel source is preferred for use. Each heated air source 340, 380 comprises an air inlet 348, 388 at the rear of the demountable heated air source (and thus at the rear of the oven) and the flue 330 is completely open to air flow such that it provides an unobstructed exit for air to flow out of the oven. In use, when the solid fuel carrier 340 is inserted into the oven 300 through port 350, air flow enters the solid fuel carrier 340 through rear inlet 348 and then through variable air inlet 346. Air inlet 346 is adjustable in that the flow of air therethrough can be controlled to supply more or less air, depending on what is required. For example, in instances where a high temperature in the oven needs to be achieved quickly, a larger supply of air through variable air inlet 346 can be applied. When the desired temperature is reached and less air is required to be supplied into the oven, the variable air inlet 346 can be adjusted to reduce the air flowing into the oven chamber 370. Accordingly, the air flow into the oven chamber 370 is controlled. This can be achieved in different ways such as by adjusting a grating of the air inlet 346 to block an air flow path through the solid fuel carrier into the oven chamber 370. Gas burner 380 can also be inserted into port 350 in place of the solid fuel carrier 340 and provide a flame to heat the oven chamber. The gas burner air inlet 388 is also provided on the rear of the gas burner 380. Gas burner air inlet 388 is fixed and does not have a built in mechanism to close it. Accordingly, there is always a path for sufficient air to flow into the gas burner for safe combustion. The flame safety device 382 operates to cut off the gas supply in use when a temperature within the oven chamber 370 is indicative that the flame has been extinguished or a flame is not present and this process is speeded up by heat loss through the open flue in use. In combination with the open flue 330, the oven 300 thus displays effective safety controls to prevent risk of gas build up in the oven chamber 370. In each case, using different demountable heated air sources in oven 300, air flow enters the oven 300 from the rear of the oven. This gives the user a greater control over the air flow entering the oven chamber 380 compared to an oven having multiple air inlets for different demountable heated air sources in different parts of the oven. The oven 300 is thus versatile and easy to use for dual fuel capability. Furthermore, the oven may be safely used with the door closed, even with the gas burner present. The gas burner has its own air inlet and the open flue provides a path for hot air to quickly exit the oven chamber in the event that the gas flame goes out. This enables the temperature in the oven to fall quickly and trigger the flame safety device in the gas burner when the flame goes out. In some embodiments, the door will usually only be closed during combustion of solid fuel but if the door is left closed while cooking with gas, safety issues do not arise. It is not necessary for the variable flow inlet to be integrated with the solid fuel burner. The solid fuel burner may, for example, be introduced into the port and the port covered with a panel including the variable flow inlet. The solid fuel carrier may be introduced into and removed from the oven via the door. It may be that it is not necessary to remove the solid fuel carrier. What is important is that the variable flow inlet has to be removed in order to fit the gas burner. Throughout the description and claims of this specification, the words “comprise” and “contain” and variations of them mean “including but not limited to”, and they are not intended to and do not exclude other components, integers, or steps. Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise. Features, integers, characteristics, or groups described in conjunction with a particular aspect, embodiment, or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and / or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and / or steps are mutually exclusive. The invention is not restricted to the details of any foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims

1. A cooking apparatus comprising:an oven, the oven comprising:an oven chamber having a cooking surface;a door at a front end of the oven, the door movable between an open and a closed position;a port for receiving a demountable heated air source at a rear end of the oven, opposite to the front end of the oven; anda flue that provides a flow path for air to leave the oven chamber;a first heated air source which is demountably receivable by the port, whereby the first heated air source comprises a gas burner;a second heated air source which comprises a solid fuel carrier;a variable air inlet for use with the second heated air source and whichis demountably receivable by the port;wherein only the variable air inlet or the first heated air source can be received by the port at the same time, and wherein the first heated air source comprises a gas burner air inlet which is fixed.

2. The cooking apparatus according to claim 1, whereby the second heated air source is demountably receivable by the port.

3. The cooking apparatus according to claim 1 or claim 2, whereby the variable air inlet is integral with the second heated air source.

4. The cooking apparatus according to any of claims 1 to 3, having no air inlet other than the variable air inlet or one or more inlets integrated with the first or second heated air source, excluding the door and flue.

5. The cooking apparatus according to any of claims 1 to 4, wherein the solid fuel carrier is configured to receive solid fuel, wherein the solid fuel is at least one of wood, fuel pellets and / or charcoal.

6. A method for using the cooking apparatus according to any of claims 1 to 5, the method comprising the steps of: providing the cooking apparatus according to123456789101112any of claims 1 to 5; using the oven with the second heated air source and the variable air inlet present; removing the variable air inlet; mounting the first heated air source; and using the oven with the first heated air source wherein the air flow into the oven is controllable by the variable air inlet.

7. The method according to claim 6, further comprising the steps of removing the first heated air source; replacing the variable air inlet; and using the oven with the second heated air source.

8. The method according to any of claims 6 to 7, wherein the variable air inlet is integral to the second heated air source.LO CXI131415

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