Patent Description:
Steam cooking (also referred to as steaming) is commonly known as one of the healthiest cooking methods. In particular, steam cooking is often preferred over other cooking methods such as boiling, frying and baking because it results in a lower amount of nutrient destruction.

This is because steam cooking generally operates at a lower temperature, typically below <NUM> degrees Celsius, but nevertheless enables short cooking times due to the wet steam environment. The presence of water as the cooking medium causes a leaching out of water soluble nutrients when boiling, and this is greatly reduced by steam cooking.

A traditional steamer comprises a pan for placing over the hob of a cooker, in which water is boiled. Food to be steamed is mounted over the pan in trays having perforated bases.

Steam cookers are now well known and comprise a steam cooking chamber around which hot air and steam are circulated by a fan. The steam cooker is for example a top-loaded device, rather than a more conventional steam oven with a front door.

Steam is introduced into the cooking chamber, either from an external steam source or else generated internally within the cooking chamber for example by using a vaporizer at the bottom of the cooking chamber. A heating chamber adjacent to the cooking chamber comprises a fan and a heater to generate a circulatory flow of hot air and steam. The steam generation may take place in the heating chamber instead of in the cooking chamber.

The heating chamber is a closed unit next to the main cooking chamber, but it has at least one opening for air intake from the cooking chamber and at least one opening for air delivery into the cooking chamber. The documents <CIT> and <CIT> disclose steam cookers.

It is known for steam cookers of this type to have a non-steam mode, whereby the cooking takes place with no additional humidity, and at a higher temperature, such as <NUM> degrees Celsius. In this case, the steam cooker performs in the manner of an air fryer.

However, the cooking end results when performing this air frying function with a steam cooker are not as good as with a dedicated air fryer.

This invention is based on the recognition that the cooking results in the steam cooker (when used for dry cooking) are worse as a result of the weaker air flow in the steam cooker.

According to examples in accordance with an aspect of the invention, there is provided a steam cooking apparatus, comprising:.

When the steam generator is at the bottom to the cooking chamber, this means some of the flow that would be directed to the steam generator is redirected towards the food support.

The flow redirecting element alters the flow conditions in the cooking chamber to achieve more uniform heating in the region of the food support. This result in increased browning homogeneity (when using the steam cooker in a non-steam mode) for various food types such as fish. It provides an improved heat transfer to the food and an increased local air speed in the vicinity of the food, e.g. above <NUM>/s.

The improved cooking results in reduced protein - albumin leakage for cooking fish, and shorter cooking times for certain food types. The introduction of the flow redirecting arrangement enables a low cost improvement to existing products with significant cooking performance improvement.

The flow redirecting arrangement for example comprises a spoiler. This is a projecting fin, for example with a relatively long length and a short projecting depth.

In one example, the spoiler extends inwardly from an inner surface of a front wall of the cooking chamber. Thus, it interrupts the flow of air down the front surface of the cooking chamber, and redirects that flow at least partially towards the food support.

The spoiler is for example at the level of the bottom of the food support, so that the redirected air flow is directed towards the food.

In another example, the spoiler extends from a front area of the food support. It may project forwardly towards a front wall of the cooking chamber or downwardly towards the bottom. In this case, a modified food support provides the flow altering function.

The spoiler for example has a depth to substantially fill a gap between the food support and the cooking chamber. The spoiler for example has a length between <NUM> and <NUM> times a width of the food support. Thus, the spoiler does not need to extend the full width of the food support to make a significant difference in air flow conditions.

Instead of a projecting spoiler, the flow redirecting arrangement may comprise a step in an inner surface of a front wall of the cooking chamber. Thus, the internal shape of the cooking chamber has a step which performs the same function as the spoiler. Thus, the step is for example at the level of the bottom of the food support, so that the redirected air flow is towards the food.

The apparatus may further comprise upright fins at opposite ends of the flow redirecting element (spoiler or step). These provide further directing of the flow towards the food support, by forming a partially enclosed channel of air.

The apparatus may further comprise a fan in the heating chamber, wherein the vent arrangement comprises an extraction vent between the cooking chamber and the heating chamber at the location of the fan, for drawing air from the cooking chamber to the heating chamber.

In one modification, the apparatus further comprises a barrier ring around the extraction vent. This prevents air entry to the extraction vent from steep angles, and thereby creates a further alteration to the flow conditions, which has again been found to result in more uniform heating in the region of the food support.

The apparatus may further comprise a blocking element spaced over the extraction vent. This prevents air entry to the extraction vent directly from in front, and again thereby creates a further alteration to the flow conditions. This has also been found to result in more uniform heating in the region of the food support.

The blocking element may comprise a disc (i.e. a solid closed shape) or a plate with a central opening.

The vent arrangement for example also comprises a delivery vent between the heating chamber and the cooking chamber, for delivering heated air to the cooking chamber, and a fin arrangement is provided at the delivery vent. Thus, as well as, or instead of, altering the flow conditions from the cooking chamber to the heating chamber, the flow conditions from the heating chamber to the cooking chamber can be controlled to provide more uniform heating.

The invention provides a steam cooking apparatus with a cooking chamber, a steam generator for generating steam to be provided to the cooking chamber and a heating system. A food support is for mounting in the cooking chamber. A flow redirecting arrangement is provided at the front of the cooking chamber for redirecting flow from the front of the cooking chamber away from the stream generator and towards the food support. This improves the uniformity of the cooking process, particularly when the steam cooking apparatus is used in a non-steam mode, and uniform browning of food is desired.

<FIG> shows a known cooking apparatus <NUM>, in particular as disclosed in <CIT>.

The cooking apparatus comprises a cooking chamber <NUM> (i.e. a food chamber in which food to be cooked is placed) in which a food support (basket) <NUM> is mounted. The cooking chamber has a viewing window <NUM> which may also be the openable lid of the apparatus. Food <NUM> to be cooked is placed on the food support which then places the food near the center of the cooking chamber. The food support has air permeable side walls and optionally an air permeable base so that air and steam can circulate through the support to the food.

There is a heating arrangement which in this example comprises a first heater <NUM> for generating steam and a second heater <NUM> for heating air laden with steam. The first heater is used to generate steam (shown as arrow <NUM>) from water which is delivered from a water reservoir <NUM> by a dosing system <NUM>. The dosing system provides water to a feed arrangement <NUM> which delivers water to a surface of the first heater <NUM> to generate steam.

The dosing system may deliver a constant flow of water during cooking or a regularly pulsed delivery of water (so needing no feedback control), but it could also be controlled dynamically during cooking using feedback from a humidity sensor.

A circulation system is provided in the form of a fan <NUM> and motor <NUM>. The circulation system circulates the steam generated by the first heater <NUM> around the cooking chamber. The second heater <NUM> is along the circulation path and thereby further heats the steam to create a high temperature dry steam environment. The circulation system thus moves the saturated air inside the chamber to the food to increase convection and also assists in producing a homogeneous temperature field of all parts inside the cooking chamber, including the viewing window. This is to avoid condensation.

The apparatus is controlled by a controller <NUM>, which controls the heating arrangement <NUM>, <NUM> and optionally also the dosing system <NUM>. The controller receives temperature information from a temperature sensor <NUM>. The temperature of interest is the temperature at the center of the cooking chamber, where the food is located. However, the temperature sensor, which may be a negative temperature coefficient (NTC) temperature sensor, may be located anywhere in the cooking chamber, with a known correlation between the temperature at the sensor location and the temperature in the middle of the chamber.

The temperature is for example regulated by switching on and off the second heater <NUM> of the heating arrangement by the controller. The temperature of the first heater, for steam generation, is regulated by a thermostat again by cycling on and off. These two control mechanisms may be independent.

The cooking chamber is vented to the ambient surroundings by vents <NUM>. Thus, the cooking chamber remains at substantially atmospheric pressure during use.

The controller <NUM> controls the heating arrangement to heat water from the water reservoir to create steam using the first heater <NUM>, and to further heat the steam to create heated steam at a temperature around <NUM> degrees.

The second heater may further heat the steam for example to <NUM> degrees Celsius, or in the range <NUM> to <NUM> degrees Celsius. This approach is explained in <CIT>. Higher temperatures up to <NUM> degrees Celsius could be considered as well.

The circulation system circulates the heated steam around the cooking chamber. The vent or vents of the cooking chamber maintain the pressure at ambient pressure, and thus steam can escape when the maximum possible absolute humidity is reached (for the particular operating temperature), which would otherwise result in an increase in pressure.

The release mechanism provided by the vent or vents means that the steam delivery rate does not need to be controlled, and instead there can be a preset water delivery rate to the first heater <NUM>. The controller may for example implement a control sequence which determines particular points of time when steam generation starts and/or ends. By way of example, a time-delayed start may be used for steam generation. The device is for example in a waiting mode for certain time e.g. <NUM> minutes from the start or else waiting until the cooking chamber temperature reaches <NUM> degrees Celsius. Water is then added to the first water heater <NUM>. This pre-heating improves the avoidance of condensation at the window of the transparent lid as discussed below.

The device also has an operation mode without any steam generation. This invention is in particular aimed at improving the cooking results when used in the operation mode without steam generation, as discussed further below.

The cooking chamber <NUM> comprises a base <NUM>, a rear wall area <NUM>, first and second opposing side wall areas and a front wall area <NUM>. These together define a closed chamber. The rear wall area <NUM> defines a separation wall which separates the cooking chamber <NUM> from a heating chamber <NUM> (behind the rear wall area) in which (at least) the fan blades <NUM> and second heater <NUM> are housed. In the example shown, the motor <NUM>, water reservoir <NUM>, dosing system <NUM>, and controller <NUM> are in a further chamber which is isolated from the heating chamber (i.e. there is no gas or liquid passage between them). However, there may be different components in the different chambers.

<FIG> shows the cooking chamber opened up to show the rear wall area and the first and second side wall areas <NUM>, <NUM> to show one example of vent arrangement.

The circulation system draws air out of the cooking chamber through an extraction vent <NUM> in the rear wall area. This vent leads to the fan blades.

A delivery vent arrangement for delivering air (and steam) comprises a first delivery vent <NUM> at a top region of the rear wall area above the extraction vent <NUM>. It may extend across at least half of the width of the rear wall area, such as across more than <NUM>%, <NUM>% or <NUM>% of that width.

In this example, a second delivery vent <NUM> is at a top region of the first side wall area <NUM> and a third delivery vent <NUM> is at a top region of the second side wall area <NUM>.

It is possible through design of the vents and fan to control the circulation of air and steam within the cooking chamber in a reliable and repeatable way.

Note that the term wall "area" is used because the shape (from above) may not be a polygon, but instead may be a more curved shaped thus not having precisely defined sides, front and back. However, the shape (from above) is generally square or rectangular, so that corresponding front, back and sides may be readily identified. However, this does not imply that other shapes are not possible. Even a circle may be considered to have sides, a front and back by dividing it into quadrants. The front and back face each other to define the cooking chamber volume between them.

The arrangement of vents shown enable a flow of the delivered air to pass over the full area of the underside of the lid <NUM>. The viewing window area of the lid <NUM> has increased heat losses compared to an insulated wall so it is desirable for the window to be exposed to the flow created by the circulation system to maintain the viewing window above the dew point.

To the extent described above, the steam cooking apparatus is as described in <CIT>.

The invention relates to control of the air flow particularly for the no steam cooking mode.

<FIG> shows a simplified diagram of the cooking apparatus including the food support, and showing the flow paths.

It shows the cooking chamber <NUM>, heating chamber <NUM>, the first heater <NUM> (the water heater for generating steam), and the second heater <NUM> (for heating the air laden with steam).

The main circulatory flow is shown as <NUM> from the delivery vent <NUM> to the extraction vent <NUM>. At the front of the cooking chamber, the flow largely follows the internal surface of the cooking chamber, down to the bottom of the cooking chamber. <FIG> also shows that the lid is inclined downwardly from the rear wall to the front wall. This further assists in preventing condensation of steam at the transparent section of the lid via heating.

<FIG> shows a first example of a modification to improve the air flow conditions in the food chamber. The apparatus comprises a flow redirecting arrangement <NUM> at the front of the cooking chamber for redirecting flow from the front of the cooking chamber away from the stream generator and towards the food support <NUM>.

The change in flow paths is schematically shown, and can be seen by comparing <FIG> with <FIG>. The flow redirecting element <NUM> alters the flow conditions in the cooking chamber to achieve more uniform heating in the region of the food support.

This results in increased browning homogeneity (when using the steam cooker in a non-steam mode) for various food types such as fish. It provides an improved heat transfer to the food and an increased local air speed in the vicinity of the food, e.g. above <NUM>/s.

The improved cooking process results in reduced protein - albumin leakage for cooking fish, and shorter cooking times for certain food. The introduction of the flow redirecting arrangement enables a low cost improvement to existing products with significant cooking performance improvement.

In the example of <FIG>, the flow redirecting arrangement <NUM> comprises a spoiler extending widthwise across the front wall of the cooking chamber, and projecting back towards the interior volume of the cooking chamber. The spoiler is a projecting fin, for example with a relatively long length and a short projecting depth. The spoiler is for example at the level of the bottom of the food support, so that the redirected air flow is towards the food. However, it may be slightly raised above the bottom of the food support.

In an alternative but equivalent design, the spoiler projects forwards from the food support (basket) <NUM>. It creates the same flow barrier, essentially closing the gap between the food support and the front wall of the cooking chamber, thereby disturbing a flow around the inside wall of the cooking chamber.

In other alternative designs the spoiler could be a separate part which could be inserted as accessory or as attachment to the chamber or to the food support.

A system could be used for automatically moving or removing (e.g. swing in and out) the spoiler when a specific cooking method requires specific flow conditions.

<FIG> shows the spoiler from above, looking down into the cooking chamber, and for a version where it projects forwardly from a front face of the food support <NUM>.

The spoiler has a length which may correspond to the full width of the food support, but the length may be less than the width of the food support as shown in <FIG>. In this example, the food support has rounded corners, and the spoiler extends only adjacent the central straight section of the front of the food support. The length is for example between <NUM> and <NUM> times the width of the food support <NUM>.

In general, the spoiler or several individual spoilers could be mounted at several position along the width of the food support. Different fans or air intake vent concepts may need different spoiler shapes, such as symmetric or asymmetric designs, to homogenize the flow.

The spoiler has a depth (i.e. the distance by which it extends outwardly from its supporting structure) to substantially fill the gap between the food support and the cooking chamber.

By way of example, the spoiler has a depth of at least <NUM>, i.e. it projects from an underlying generally planar surface by at least <NUM>, for example at least <NUM>. The remaining gap between the outer projecting edge of the spoiler and the adjacent structure is for example less than <NUM>, for example lass than <NUM> for example less than <NUM>, If the spoiler projects from the cooking chamber wall (as in <FIG>), the adjacent structure is the food support. If the spoiler projects from the food support (as in <FIG>), the adjacent structure may be the front wall of the cooking chamber (<FIG>) or it may the the bottom of the cooking chamber (<FIG>).

<FIG> shows a further refinement in which the spoiler <NUM> has upright fins <NUM> at opposite ends of the spoiler. These provide further directing of the flow towards the food support, by forming a partially enclosed channel of air. There may be additional fins along the length of the spoiler.

The fins for example have a height of around <NUM>. Like the spoiler itself, the fin depth corresponds to the gap size between the food support and the cooking chamber, for example around <NUM>. The depth is preferably a small margin less than the space, to prevent scratching.

In <FIG>, the spoiler projects forwardly from the food support towards a front wall of the cooking chamber. <FIG> shows an alternative in which the spoiler <NUM> extends downwardly towards the bottom. The spoiler may then be formed as part of the design of the support feet for the food support or formed as a bent over edge of the food support. Equivalently, the spoiler may project up from the bottom of the cooking chamber rather than down from the food support.

In all cases, the spoiler does not block the passage of air over the steam heater <NUM> - there is for example an air path around the ends of the spoiler.

As shown in <FIG>, instead of a projecting spoiler, the flow redirecting arrangement may comprise a step <NUM> in an inner surface of a front wall of the cooking chamber. Thus, the internal shape of the cooking chamber has a step which performs the same function as the spoiler. The step is again at the level of the bottom of the food support, so that the redirected air flow is towards the food. The step can have the same depth as the spoiler as discussed above.

The step may also perform part of the function of holding the food support. The step does not need to cover the whole cooking chamber width, but may be placed only at a central area, as for the spoiler as described above.

Airflow and airspeed analysis has shown that the airspeed in the center of the food support in the conventional design is around <NUM>/s. Cooking tests have shown that this is the main reason for less food browning and increased albumin leakage e.g. from fish.

The flow redirecting arrangement has been found to increase the airspeed significantly and give improved cooking end-results, especially browning. The central airspeed has been found to increase to <NUM>/s. Cooking speed is also improved for some food types such as salmon and chicken, with a <NUM>% reduction in cooking time recorded.

The spoiler may be attached to the food support or the cooking chamber as explained above. It may be made of metal, silicone or other heat resistant material.

When the spoiler is formed as part of the food support, the food support is preferably designed to fit in the cooking chamber with only one orientation, to prevent a wrongly positioned food support (e.g. with the spoiler at the air inlet side).

The measures above relate to controlling the air flow conditions locally at the front of the food container.

Other measures may be used as well, as will be explained below.

<FIG> shows a blocking element <NUM> spaced over the extraction vent <NUM>. This prevents air entry to the extraction vent directly from in front, and again thereby creates a further alteration to the flow conditions. This has also been found to result in more uniform heating in the region of the food support.

The blocking element <NUM> may comprise a solid disc as shown in <FIG> or or a plate with a central opening as shown in <FIG>. The outer diameter of the plate is then larger than the diameter of the extraction vent.

The blocking element is for example spaced from the extraction vent by a spacing of e.g. <NUM> to <NUM>.

In <FIG>, the blocking element is a disc which is smaller than the size of the extraction vent, so that it only covers a central area of the extraction vent. It may instead be the same size as the extraction vent or indeed larger. The extraction vent for example has a diameter of around <NUM>, and the blocking element may have a diameter of <NUM> to <NUM> or <NUM> to <NUM> or <NUM> to <NUM>.

<FIG> shows a modification with a barrier ring <NUM> around the extraction vent <NUM>. This prevents air entry to the extraction vent from steep angles, and thereby creates a further alteration to the flow conditions, which has again been found to result in more uniform heating in the region of the food support. The barrier ring for example extends forwardly from the rear wall by around <NUM> for example by <NUM> to <NUM>.

Flow guiding parts may also be provided at the delivery vent <NUM> between the heating chamber and the cooking chamber. <FIG> shows a fin arrangement comprising a line of vertical fins <NUM> provided at the delivery vent. The flow conditions from the heating chamber to the cooking chamber can thereby be controlled to provide more uniform heating.

The various flow adaptation measures described above may be used in any combination.

The examples above make use of a heater for generating steam within the cooking chamber, However, the steam generation may instead take place in the heating chamber, or the steam generation may be external to the main body of the steam cooker, with steam delivered by a delivery tube.

The examples above also show a fan in the heating chamber. The fan may instead be in the cooking chamber, or alternative methods may be used for generating the desired circulatory flow so that the heater steam laden air circulates around the cooking chamber.

The examples above have the support (and/or pot) sitting on a base. However, the support may be received directly in the cooking chamber. The support may for example be mounted to sidewalls of the cooking chamber or it may hang down from an upper edge of the cooking chamber or the 1id, with hooks. Similarly, even where there is a base, the base does not need to sit on the base of the cooking chamber. It may instead again hang down from the top of the cooking chamber or lid, or be supported be the side walls.

Claim 1:
A steam cooking apparatus (<NUM>), comprising:
a cooking chamber (<NUM>) having a front (<NUM>) with a front wall, a back (<NUM>) with a rear wall, and sides between the front and the back;
a steam generator for generating steam to be provided to the cooking chamber (<NUM>);
a heating chamber (<NUM>) adjacent the cooking chamber behind the back of the cooking chamber;
a heating arrangement (<NUM>) located within the heating chamber (<NUM>) for heating air laden with steam;
a vent arrangement (<NUM>,<NUM>,<NUM>,<NUM>) formed through the rear wall, between the back of the cooking chamber (<NUM>) and the heating chamber (<NUM>), to allow a circulatory flow of air or steam laden air between the heating chamber and the cooking chamber; and
a food support (<NUM>) for mounting in the cooking chamber,
characterized in that
the apparatus further comprises a flow redirecting arrangement (<NUM>;<NUM>) at the front of the cooking chamber for redirecting flow from the front of the cooking chamber away from the bottom of the cooking chamber.