Abstract:
A static deck oven has a flat conducting element ( 17 ) located between a cooking shelf ( 13 ) and lower heaters ( 15 ) The conducting element is connected to and in heat transfer relationship with a water-containing trough ( 18 ) inside the oven space Heat passes through the element to the trough and converts the water into steam, which provides a beneficial surface effect to the products being cooked. A computerised controller ( 22 ) determines extra energy required to convert a particular dose of water into steam, and controls the energy input to the heaters accordingly.

Description:
FIELD OF THE INVENTION 
   The Present invention relates to deck ovens. 
   BACKGROUND TO THE INVENTION 
   Some existing deck ovens have a steam generator located outside the oven space which supplies steam into the oven via an inlet pipe. The external steam generator includes a steel or aluminium mass which is heated by heating elements that are dedicated solely to heating the mass. The mass defines a cavity into which a water spray pipe directs a mist or spray of water to produce steam for the deck oven. 
   SUMMARY OF THE INVENTION 
   Such a deck oven has the disadvantage that it requires separate heating elements for cooking the products and for producing the steam. Other disadvantages include heat loss and the requirement for control gear for the external steam generator. The external steam generator and the supply pipe require lagging to operate efficiently. Installing the lagging can be a time consuming and expensive operation, and having the steam generator separate from the oven requires extra space and adds to assembly costs. The insulation layer also means that it is difficult and time consuming to maintain or fix internal elements of the steam generator, which is susceptible to lime scale build up. 
   Other existing ovens have a direct water injection system which sprays water into the oven by means of one or more nozzles located in the oven. It is believed that these types of oven do not significantly reduce the amount of energy used to produce steam even though droplets are heated rather than a large single body of water. This kind of existing oven is also susceptible to limescale build up, especially in the nozzles, and requires pumps and header tanks. Furthermore, the glass, doors and lights within the oven may be susceptible to damage caused by direct impact of water droplets and the baked product may suffer if impacted by unvapourised water droplets. Although it does not require external steam elements and therefore there is no external heat loss, this steam generator does not tend to produce satisfactory “shine” on certain food products such as loaves. 
   Embodiments of the present invention are intended to provide a more efficient and smaller deck oven without loss of steam quality. Space is often at a premium in the design of ovens, especially for example where the oven is to be fitted in an existing cooking area, e.g. in a supermarket. Preferred embodiments of the present invention produce steam without the need for specialised heating elements. 
   According to a first aspect of the present invention there is provided a deck oven including: 
   at least one heater; 
   a steam generator including a conducting element located in a lower part of the oven, the element being in heat transfer relationship with the heater, and 
   a water container in heat transfer relationship with the conducting element, such that in use, the water in the container is heated to produce steam. 
   The container may be internal or outside the oven. The container may be a trough. The container can be placed at an end of the oven remote from the oven door. Water may be supplied to the container by means of a pipe. A shield may be located between the container and the main cooking area, possibly abutting the container, to help prevent splashing and distribute the steam evenly in the oven. 
   The conducting element may either be integral with or connected to the water container. The conducting element and/or the container may be formed of a plurality of aluminium plates. 
   The oven typically further includes a heat distribution shelf abutting or adjacent the heater. The steam generator can be located between the shelf and the heater. The heat distribution shelf can be formed of at least one ceramic or metallic tile. In an alternative embodiment, the conducting element and heat distribution shelf can be a single body formed of suitable material. In yet another embodiment the water container and heat distribution shelf may be a single integral body. In this case, water may be supplied from under the shelf. 
   The conducting element may be substantially planar and may have dimensions substantially similar to those of the main cooking area. The element may be rectangular and may have dimensions similar to those of the shelf. The conducting element can be formed of aluminium or other good heat transfer material. 
   The heater may include a plurality of heating elements. The heating elements may be spaced apart at intervals along the conducting element. The intervals between the elements may be smaller near the container than the spaces between the elements further from the container. The heating elements may be intended for combined use for baking and heating the water container, or may be dedicated to one or the other. 
   The oven may further include a controller, which may be configured to keep either all the heating elements or only the heating element(s) nearest to the water container on for substantially longer than required for baking. The controller may control the power to the heating elements so that the heat input rate is at a higher level for a specified time period. The specified time period or power level may be a function of the amount of steam and/or water to be supplied into the oven. There may be at least one additional heating element located near the container. 
   The controller may include a program selection component for selecting the temperature and duration of baking and, optionally, steaming. The controller may be configured to implement a warm-up procedure in which the oven space reaches a desired temperature before cooking begins. A thermocouple component may be used to monitor the oven temperature and output from this can be used by the controller to control the heater during the warm-up. The controller can determine the number of heating elements that are switched on during the warm-up. Alternatively or additionally, the controller may control the period of time for which all or some of the elements are switched on/off during the warm-up. For example, the controller may switch all the elements on for 50% of the warm-up period and then switch them off for 50% of the period. 
   The controller may require a user to input a Start command before commencing the baking and, optionally, the steaming, after the warm-up. 
   If steam is to be used then the controller may calculate the amount of energy required to produce the desired level of steam in addition to the energy required for the heater to bake. A thermocouple component may be used to monitor the oven temperature and output from this can be used by the controller to control the heater during the baking and, optionally, steaming. The controller may be implemented by software. A thermocouple component may be used to perform at least some of the functions of the controller. 
   The deck oven may include a plurality of shelves, each shelf having a corresponding respective conducting element and container. The oven may be a static oven. 
   According to another aspect of the present invention there is provided a deck oven including: 
   a shelf for receiving products to be cooked; 
   at least one heater located beneath the shelf; 
   a steam generator including a conducting element located in the oven between the heater and the shelf, the element being in heat transfer relationship with the heater, and 
   a water container in heat transfer relationship with the conducting element, such that in use, the water in the container is heated to produce steam. 
   According to another aspect of the invention there is provided a method of producing steam in a deck oven, the method including steps of: 
   supplying water to a container in the oven, the container being in heat transfer relationship with a conducting element located in a lower part of the oven, the conducting element being in heat transfer relationship with at least one heater, and 
   heating the conducting element such that the water in the container is heated to produce steam. 
   Whilst the invention has been described above, it extends to any inventive combination of the features set out above or in the following description. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention may be performed in various ways and, by way of example only, an embodiment thereof will now be described, reference been made to accompanying drawings in which: 
       FIG. 1  is a section side view of a deck oven according to a preferred embodiment; 
       FIG. 2  illustrates a detailed view of a conductive element and trough for use in the oven of the preferred embodiment; 
       FIG. 3  illustrates schematically the steps which can be performed in connection with a computerised controller of the oven, and 
       FIG. 4  illustrates a front view of part of an oven including a plurality of conductive elements and troughs. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring to  FIG. 1 , a deck oven generally indicated at  10  includes a swing door  11  at one end, which is opened to transfer products  12  such as loaves into and out of the oven space. The products are placed on an oven shelf  13  formed of a ceramic tile. Beneath the ceramic tile  13  there is a cavity  14  in which there is a plurality of lower heating elements  15 , which can operate by gas or electricity. Although four pairs of elements  15  are shown in  FIG. 1 , it will be appreciated that any reasonable number or arrangement of heaters may be provided. In particular, the spaces between the heaters may be smaller at the end of the oven remote from the door  11  so as to be beneficial for the production of steam as will be described below. As with conventional ovens, the heating elements  15  can be used to supply heat to bake the products  12 . The ceramic tile  13  is intended to distribute the heat produced by the lower heating elements  15 . There is also a plurality of upper heating elements  16  located near the ceiling of the oven space. 
   Also located in cavity  14  is a substantially flat rectangular aluminium heat collector  17 . The heat collector  17  is located above the lower heating elements  15  (i.e. between the heating elements  15  and the lower surface of the tile  13 ). It will understood that the heat collector  17  could be placed beneath the heating elements  15 , although it is believed that the heat transfer will not tend to be as effective. The collector  17  has substantially the same width as the ceramic tile  13  but has a longer length so that it extends from the door end of the oven to the remote end of the oven beyond the edge of the ceramic tile  13 , thereby covering substantially the same area as the oven floor. As the heat collector covers a large proportion of the area under the tile  13 , local hot spots are reduced or eliminated. 
   A container  18  is formed integrally with the remote end of the collector  17  inside the end of the oven remote from the door. Having the container in this location is preferred for smaller ovens; however, it will be appreciated that the container could be located near the door or along the side of the oven space. It may also be desirable to have more than one water container. In an alternative embodiment the container  18  is located outside the oven body, although this is likely to result in more heat loss and insulation may be required for it. 
   The container  18  is a trough formed from a substantially rectangular block narrower in width than the tile  13  with a cavity extending substantially across its width (see FIG.  2 ). The container  18  has a depth of approximately 50 mm. A rectangular shield  19  is fixed vertically inside the oven, adjacent the container  18  and between it and the door  11  to reduce the possibility of the oven contents being exposed to fluid droplets or spitting. The shield  18  can also assist with balancing the distribution of steam within the oven space. 
   A water pipe  20  enters through the wall of the oven remote from the door  11  to deliver water into the trough  18 . The pipe  20  has a diameter of typically around 8-22 mm, to help avoid build up of scale inside it. In addition, the pipe  20  is inclined to ensure that little or no water remains in it after steaming. 
   In use, the aluminium collector  17  absorbs part of the heat generated by the lower heating elements  15 . The heat is conducted along the collector  17  to the trough  18 , thereby converting the water in the trough into steam. The steam rises and moves into the oven space as indicated by arrows  21 . 
   The heating elements  15  are switched on/off by a computerised controller  22 , possibly in response to a temperature sensor/thermocouple  23  located near the ceiling of the oven by the door  11 . 
   In one embodiment, the controller functions as follows: 
   1. If the programme selected uses steam, the bottom elements stay full on for a fixed time after the baking is started, ignoring the bottom heat setting. It is intended that the time is fixed for all products, initially around 8 minutes, adjustable in increments of approximately less than 0.5 minutes. The time could be a programmable variable or be linked with the bake/steam time for certain products. 
   2. When a Stop button on the controller is pressed after a program that uses steam, the bottom elements can be controlled to stay on full power for a fixed time between 0 and 5 minutes, e.g. 2 minutes. 
   3. To attempt to ensure that the steam system is warmed up before the first bake, upon power up the bottom elements can be running at between sixty and one hundred percent of their full power. They can stay on until a fixed temperature below the selected baking temperature is reached, for example 25° C. below. 
     FIG. 3  illustrates the steps performed in connection with the computerised controller  22  in one embodiment of the oven. At step  301  the oven is switched on and one or more cooking programs can be selected by a user by means of an interface  25  on the controller  22 . The programs typically specify the temperature and duration of the baking and, optionally, steaming. 
   At step  302  the controller controls the periods for which the top and/or bottom heating elements are switched on/off and so the amount of time sets of elements spend creating an optimum temperature in accordance with the selected bake/steam programme. This “pre-cooking” step allows the oven to warm up quickly to the optimum temperature, ideally always in substantially the same period of time, thereby saving energy over long warm-up times. Feedback from the thermocouple  23  may be used by the controller to prevent overheating (step  303 ). 
   When the oven has reached the desired temperature, the oven is ready and the operator may press a Start button (indicated at  24  in  FIG. 1 ) at step  304  to begin cooking. 
   At step  305  the controller computer checks whether the selected programme uses steam. If this is not the case then at step  306  the oven bakes using the heating elements without steam for the required length of time and baking stops at step  307 . 
   When the cooking is over, at step  308  the controller analyses the next programme that has been selected by the user. The controller then creates a profile for the on/off periods of the independently controlled top and bottom heating elements at step  309  so that the temperature needed for the next programme can be achieved in the oven. Doing this between programmes means that when steam is not needed the waiting time between bakes is reduced. Furthermore, the collector plate can be set at an optimum temperature. 
   If the controller check of step  305  indicates that steam is to be used then at step  310  the controller calculates the amount of energy used during the required steaming. This can involve determining the extra amount of energy required to convert a particular dose of water (data regarding the flow rate of water into the oven can be obtained by the controller computer) into steam and controlling all or some of the heaters to adjust the temperature accordingly. This can be achieved by the controller  22  by calculating the period of time for which the bottom heating elements need to remain on to achieve the temperature and adjusting the state of the heaters accordingly. 
   The controller can calculate how far the current oven temperature is from the desired temperature and adjusts the on/off time of the bottom heating elements (and/or the top elements in an alternative embodiment) until the target temperature is substantially achieved. As the oven temperature gets nearer the target temperature, the “off” time of the heating elements will typically get longer so that the temperature is reached without overheating. The software used by the controller can take into account how the presence of the extra mass (e.g. the container and water) within the oven may affect the temperature change. 
   If the steaming is stopped part way through the programme then the controller may note the elapsed time into the program and can then calculate the time for which the bottom heating elements are required to stay on to complete the programme as if it had not been stopped. 
   At step  311  the calculated energy is put into the collector plate in addition to the energy required to bake the product. Approximately 2 minutes may be is added to the heating time to even up the temperature. The thermocouple loop may be used to maintain the collector plate at a temperature suitable for the product being baked (step  312 ). When the cooking has finished (step  313 ) control is passed on to step  308  as described above. 
   As can be seen in  FIG. 4 , if an oven contains a plurality (e.g. three) trays/shelves side by side, then each shelf can have its own heat collector and trough, each working in the way described above. It will be appreciated that arrangements of multiple shelves other than side by side can also work in substantially the same way. 
   The embodiments described above have several advantages over conventional deck ovens. The ones lacking an external steam producer means that the ovens take up less space, thereby reducing the number of parts and lagging operations required on conventional ovens and thereby reducing assembly costs. Having an integral steam generator means that heat loss from an external steam generating unit is eliminated. The aluminium collector  17  can be easily removed for cleaning and so is more resilient to lime scale build up. As the water is supplied into the heated trough  18 , a greater volume of water comes directly into contact with a heated surface than by conventional spray/mist pipes and so vaporisation of the water is assured. 
   The embodiments described above do not need a dedicated heater to create steam, as the heat can be taken from the heating elements that can also bake. Also, if steaming is not required, there is little or no heat loss attributable to the steam generator. Other advantages of the embodiments include reduced manufacturing costs as the amount of insulation, support brackets, elements, control system, wiring and sheeting associated with an external steam generator is reduced. Improved maintenance and reliability is also an advantage as the embodiments tend to be more resistant to limescale, especially as there are no nozzles present, and even if limescale does build up then it is more easy to maintain than earlier arrangements. However, tests have shown that little lime scale builds up on the collector  17  as the conversion of the water into steam involves quite “violent” boiling and so the water is scattered and can be blown out of the oven. Furthermore, no pumps, thermocouples, contactors, air compressors, water tanks, float valves, etc are essential. The internal steam generator also means that the oven has a smaller foot print, thereby saving space, and the oven depth can also be reduced. 
   The oven can also have a reduced power (kW) rating as the same heating elements are used for producing steam as for baking. As well as this reduced energy consumption, the amount of water needed by the oven to steam is also less than for conventional ovens. 
   Having separate tiles and heat collectors has the advantage of being easy to remove and clean. They can also be modular for the production of ovens having different widths. They provide even steam distribution and even heat collection. It is also possible that the collector and shelf could be combined into a single shelf formed of suitable material. 
   Our results show that this method of producing steam provides a more reliable and better shine on products such as bread than conventional direct water spray systems, comparable to that produced by a conventional deck oven with an external steam generator, only without the disadvantages associated with the external steam generator. It is thought that having the water flow relatively slowly onto the small surface area of the container allows some of the water to keep boiling after part of it has been converted to steam, which helps improve the “shine”.