STEAM COOKING OVEN

TECHNICAL FIELD

The present invention relates to a cooking oven, and especially to a cooking oven provided with means for generating steam.

BACKGROUND ART

In common steam ovens today, the steam is generated by injecting or dripping water onto the heating means of the cooking chamber. A problem with such ovens is that the amount of water cannot be adjusted properly in relation to the temperature of the heating means. Commonly too much water is fed into the oven, wherein the oven must be provided with a drainage. Another common solution of steam ovens today is that they are provided with a separate steam generating device, having its own heating means and that feeds steam directly into the cooking chamber of the oven. The oven thereby becomes more complex and the amount of steam into the oven is difficult to control.

There is thus a need for an improved steam oven, removing the above mentioned disadvantages of the prior art.

DESCRIPTION OF THE INVENTION

A first object of the present invention is to provide an inventive cooking oven enabling the use of steam during the preparation of food. It is a second object of the present invention that said oven has a simple construction and is safe and reliable in its use. A third object of the present invention is to provide a method to control said oven. These objects are achieved by the oven defined in claim 1 and the method defined in claim 10. Said cooking oven comprising a cooking chamber, a water supply line and valve means.

The cooking chamber is adapted to have an adjustable cooking temperature, i.e. the temperature in the cooking chamber is, in ordinary fashion, possible to regulate within a temperature interval used for preparation of food.

The water supply line extends into the cooking chamber in order to feed water into the cooking chamber through a water nozzle. Further, the valve means is arranged to regulate the feed of the water out of said water nozzle. When the cooking temperature in the cooking chamber is high enough, i.e. above a water evaporation temperature, water fed into the cooking chamber will evaporate, wherein steam is generated within the cooking chamber. The inventive cooking oven is characterised in that the water nozzle mouth inside a steam box. The steam box comprises steam generating means arranged inside the steam box and adapted to adapt said ambient cooking temperature. The steam generating means and the water nozzle are arranged such relative each other, that water injected into said steam box through said water nozzle are lead to said steam generating means.

When the cooking temperature in the cooking chamber is above a water evaporation temperature and said steam generating means have adapted that temperature, water injected through the water nozzle will evaporate when it comes in contact with the steam generating means. Due to the contact between the steam generating means and the water, the evaporation of the water is faster and more effective than if the water would evaporate just by the heat convection from the air in the cooking chamber. Further, due to the arrangement of the steam generating means inside the steam box and relative the water nozzle such, that water injected into the steam box comes in contact with the steam generating means, it is facilitated that all the injected water is evaporated effectively. A temperature sensor is arranged such in the cooking oven that it can sense the temperature within the cooking chamber. An electronic control unit receives information about the temperature in the cooking chamber. The electronic control unit further controls the valve means dependent at least upon said temperature within the cooking chamber.

Further, the steam box is provided with side walls, bottom wall and a top wall, whereby the geometrical shape of the box can be of the art that two or more of these elements can be integrated with each other and the bottom wall can (but must not) be the bottom of the cooking chamber. Hence, the steam box defines an essentially closed volume, within which the steam generating means is arranged, whereby it is assured that the injected water does not pour out in to the surrounding cooking chamber.

The valve means is adapted to inject a predetermined amount of water in each injection. The predetermined amount of water is adjusted such, that the whole water amount can be evaporated. A drain is not needed in the inventive cooking oven, since all the water injected therein is evaporated. The steam box is however provided with outlet means, through which the steam can exit the steam box out to the surrounding cooking chamber. The outlet means is preferably provided distance from the bottom of the steam box, such that the water cannot pour out of the steam box before it has been evaporated. It is preferred that the outlet means is a plurality of orifices, which are arrange on a plurality of sides of the steam box, in order to spread the steam in a plurality of directions. The outlet means can be arranged in the side walls and/or in the top wall of the steam box, just as long as they are arranged in an upper part of the steam box, i.e. distanced from the bottom wall. The steam generating means comprises a material which after a temperature drop, e.g. caused from an evaporation of water, fast recovers after a cooling down, and adapts a surrounding temperature. Such a material is for example aluminium, which has a high heat transfer coefficient.

The steam box can be arranged on different places within the cooking chamber, depending of the design of the cooking chamber. The steam box is suitable to arrange on a bottom, a side wall or a top wall of a cooking chamber. The specific design of the steam box must thereby be adapted to where the steam box is arranged within the cooking chamber.

It is preferred that the steam generating means only is heated by the surrounding in the cooking chamber, i.e. through heat convection. No additional heating unit is thereby needed to heat the steam generating means. It would however be possible to provide the steam generating means with separate heating means in order to fast raise the temperature in the steam generating means.

Further, it is preferred that the steam box is provided with spreading means. The spreading means has the purpose to spread the water injected into the steam box to the steam generating means, such that the water has a large contact surface to the steam generating means. The spreading means is thereby arranged such, that water injected into said steam box strikes the spreading means first after leaving the water nozzle, whereby the water is spread among the steam generating means. A faster and more effective generating of steam is thereby achieved. The spreading means can thereby be an object placed distance from the water nozzle, the spreading means is alternatively arranged close to the water nozzle or even as a mouthpiece attached to the water nozzle.

There are alternative arrangements of the steam generating means relative the water nozzle. The steam generating means and the water nozzle is preferably adapted to the arrangement of the steam box in the cooking chamber. If the steam box is arranged on a bottom or a top surface of the cooking chamber it is preferred that the steam generating means is arranged essentially in the same horizontal plane as the water nozzle. The steam box can thereby be made as flat as possible in order to save space on the cooking chamber.

If the steam box is arranged on a vertical surface in the cooking chamber, it is preferred that the steam generating means is arranged below the water nozzle and in a vertical plane, such that the injected water can be spread among the steam generating means. The spreading means thereby preferably comprises a gutter in which the injected water can flow out to the steam generating means, which are located distanced from said water nozzle. The gutter is preferably arranged at least partially above the steam generating means.

The steam box is possible to arrange such, that a heating means of said cooking chamber passes through said steam box, even though not necessary. However, an arrangement of the heating means of the cooking chamber can be suitable to avoid a rearrangement of the heating means in order to fit the steam box in to the cooking chamber.

In order to have full control of the injected amount of water in to the steam box, it is preferred that a pressure regulator is provided in the water supply line, in order to regulate the water pressure upstream of said valve means to a predetermined pressure. The injected amount of water is thereby easily regulated, through the valve means. The water supply line can thereby be connected to any suitable water supply such as a common water conduit or an external water supply reservoir feeding the water supply line. The pressure regulator is preferably a throttle, throttling the water flow, such that a predetermined pressure is achieved downstream of the pressure regulator. When having a throttle as a pressure regulator, the water pressure upstream of the pressure regulator must be higher than the water pressure downstream of the pressure regulator.

The water regulator achieves a predetermined steady pressure downstream of the pressure regulator itself. The ECU can thereby be provided with information about the pressure downstream of the pressure regulator and thereby achieve a predetermined injection of water in to the steam box, i.e. predetermined amount of steam into the cooking chamber. Further the pressure regulator facilitates that the steam regulation can be made exact independently of the pressure in the water supply line upstream of the pressure regulator. Whereby, the water supply line of the cooking oven can be connected to essentially any water supply available without interfering with the precision in the amount of generated steam. It is further provided that the water supply line is provided with a safety valve adapted to only let a predetermined amount of water through. If a water leakage would occur somewhere in the water supply line, e.g. in the valve means regulating the flow of water through the water nozzle, the safety valve stops the water flow when a predetermined amount of water has past the safety valve. The predetermined amount of water is preferably equal to or just above the amount of water that is injected into the steam box during actuation of the valve means. The safety valve thereby protects the cooking oven and prevents an overflowing of the steam box, and thereby protects against water damages upon the cooking oven and/or the facility it is located in, e.g. in the case of a leaking inlet valve.

The third object of the present invention is achieved through a method to control the inventive cooking oven. According to the method the valve means is controlled to inject a predetermined amount of water into said steam box upon receiving of an actuating signal. It is preferred that said actuating signal causes one or a plurality of subsequent injection pulses. The actuating signal is preferably send by an electronic control unit (ECU). The electronic control unit can be one for solely controlling the steam generation or be the same which already controls the temperature and other functions of the oven.

By injecting the water in a plurality of subsequent injection pulses instead of in one long pulse, a fast evaporation of the water is achieved. This, because when a to large amount of water is injected into the steam box at once, a gas film is formed between the steam generating means and the still not evaporated water, wherein the evaporation process takes a longer time. By applying injection pulses instead, each pulse of injected water is allowed to evaporate before the next pulse of water is injected. The water volume in each pulse is thereby controlled such that an immediate evaporation can be achieved. The amount of water in each pulse can optionally be dependent and varying with the cooking temperature, i.e. the temperature of the steam generating means. A higher temperature means a faster evaporation.

It is further preferred that the valve means is controlled such by the ECU, that the valve means only can be actuated to inject the predetermined amount of water if the cooking temperature is above a first predetermined threshold temperature. It is thereby secured that the temperature in the cooking chamber is high enough to evaporate the full amount of water injected.

It is further advantageous, that the ECU controls the valve means such that an actuating signal is send to the valve means if the cooking temperature has been above a second predetermined threshold value during a first predetermined time period. The first time period, during which the cooking chamber must have had the second predetermined temperature, assures that the steam generating means have had time to adapt the temperature of the surrounding cooking chamber. It is further advantageous that the ECU controls the valve means such, that when the valve means has been actuated to inject a predetermined amount of water a first time, it can only be actuated to inject a predetermined amount of water a second time after a second predetermined time period. A recovery of the steam generating means is thereby facilitated. The time of the recovery of the steam generating means is among others dependent of the temperature in the cooking chamber and the material of the steam generating means.

It is further preferred that said actuating signal is initialised by a manual operation of a press button, wherein the ECU reacts thereupon, if the circumstances allows it, i.e. temperature and timing allows it. A fully automatic control of the steam generation is also possible. The ECU could thereby also get information about an actual humidity in the cooking chamber from a humidity sensing means and a preferred humidity in the cooking chamber, whereby a regulation of the humidity in the cooking oven is performed automatically, however still dependent upon the temperature and timing.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described in detail with reference to the figures, wherein:

Figure 1 discloses a schematic drawing of the invention.

Figure 2 discloses a schematic view of a cooking oven according to the invention.

Figure 3 discloses schematic view of an alternative embodiment of the invention.

Figure 4 discloses schematic view of a cut out of steam box according to the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

The following only embodiments of the invention are shown and described, simply by way of illustration of different modes of carrying out the invention. Figure 1 discloses a schematic view of a cooking oven 100 according to the invention. Now the working principle of the cooking oven 100 provided with the steam device according to the invention will be described in conjunction with figure 1 . The cooking oven 100 is provided with a cooking chamber 1 10 in which a steam box 121 is provided. A water supply line 124 extends into the steam box 121 and is provided with in a water nozzle 120. The water nozzle 120 is arranged such that water fed out there from is led to the steam generating means 122 arranged within the steam box 121 . The steam generating means 122 comprises aluminium blocks arranged in rows inside the steam box 121 . Other materials and different arrangement for the steam generating means 122 is also possible, as long as the material used has a suitable heat transfer coefficient, i.e. able to fast adapt to a surrounding temperature. The cooking chamber 1 10 is heated by heating means 1 13 (not shown in figure 1 ) in conventional manner. The heating means 1 13 can be electric heating means, gas heating means or any other suitable type used for cooking ovens. The type of heating means for the cooking chamber 1 10 is however not an issue of the invention.

The water supply line 124 is connected to any suitable water supply (not shown), such as common water tap, having a high enough water pressure. In the shown and preferred embodiment of the invention, the water supply line 124 is provided with a water safety SV. The water safety SV can be set to let through a predetermined amount of water, and if that predetermined amount of water is exceeded, the water safety closes, whereby no more water is let through. Water damages to the oven and/or the facility the oven is located in are thereby prevented. The water supply source delivers water with a first pressure p2, whereby after passing a pressure regulator R arranged in the water supply line 124 the water pressure is regulated such, that the water pressure after the pressure regulator R is a second pressure p2. The water pressure regulation is preferably made such, that the second water pressure p2 is held constant. Valve means V is arranged between the pressure regulator R and the water nozzle 120. When the valve means V is open, water is injected into the steam box 121 through the water nozzle 120 and when the valve means V is closed, no water is injected into the steam box 121 . A pressure sensor P is arranged to sense the second pressure p2 downstream of the pressure regulator R.

Because the second water pressure p2 is constant, a simple regulation of the amount of water injected through the water nozzle 120 is facilitated by opening the valve means V during a specific time period. The amount of water injected into the steam box 121 is adapted to the size of the steam box 121 .

A cooking oven is normally provided with an electronic control unit (ECU) in order to control the cooking temperature, and optionally other features of the cooking oven. It is preferred that the ECU also is used to control the steam generation. Steam is generated when water is injected in the steam box 121 and the water comes in contact with the steam generating means 122, if the steam generating means has a high enough temperature.

A temperature sensor T is arranged within the cooking chamber 1 10, the temperature sensor T provides the ECU with information about the temperature in the cooking chamber 1 10, whereby the ECU can control the heating means 1 13 of the cooking chamber 1 10 such that a desired temperature is achieved.

The cooking oven 100 is further provided with a press button 1 12, with which the steam function of the cooking oven 100 is controlled. When the press button 1 12 is actuated a signal is send to the ECU to actuate the valve means V, whereby an actuating signal is send from the ECU to the valve means V, which thereby injects a predetermined amount of water into the steam box 121 , if a set of predetermined conditions are fulfilled, i.e. correct temperature over a correct amount of time. Now, when the cooking oven 100 is started for the first time of the day, it needs a certain time to heat up to a desired cooking temperature. And further time is needed to heat the whole mass of the cooking chamber 1 10 and the object arranged therein, e.g. cooking plate 1 15, steam box 121 with steam generating means 122. If water is injected into the steam box 121 before the right temperature is achieved, i.e. a first predetermined threshold temperature, all of the injected water might not get evaporated. A first and a second predetermined threshold temperature are thereby defined in the ECU. The first predetermined threshold temperature is lower than the second predetermined threshold temperature. It is thereby provided that the ECU does not allow the valve means V to inject any water into the steam box 120 until the temperature in the cooking oven 100 has been equal to or above a second predetermined threshold value for a first predefined time period.

The ECU will thereafter send an actuating signal to the valve means V upon an actuating of the press button 1 12, as long as the temperature in the cooking chamber 1 10 is above the first predetermined threshold temperature.

This since, it is now ensured that the steam generating means 122 has a high enough temperature for evaporating the injected amount of water.

However as soon as the temperature in the cooking chamber 1 10 sinks below the second predetermined threshold value, the ECU want allow any opening of the valve means V.

The first predefined time limit is set dependent on mass of the steam generating means 122 and how fast the steam generating means 122 adapt to the surrounding temperature in the cooking chamber 1 10, i.e. the heat transfer coefficient of the steam generating means 122. The first predetermined threshold temperature is preferably 200 degree C. The second predeternnined threshold temperature is preferably 160 degree C. These example temperatures are however just examples and other common cooking temperature are just as suitable, as long as they are above the evaporation temperature of water.

The first predetermined time period is dependent of the size of the cooking chamber 1 10, the heating means 1 13, the steam box 121 , the steam generating means 122 and any other factors influencing the temperature and temperature gradient of the cooking chamber 1 10.

When water is injected into the steam box 121 , the temperature in the cooking chamber 1 10 in general and the temperature of the steam means 122 specifically is lowered, because of energy (heat) needed to evaporate the injected water. It is thereby provided that the ECU does not allow the valve means V to inject a second pulse of water into the steam box 121 until the temperature of cooking chamber 120 has been above the first predetermined threshold value during a second predetermined time period. The second predetermined time period is preferably shorter than the first predetermined time period.

A cooking oven 100 according to the invention is disclosed in figure 2. The steam box 121 is provided at a bottom of the cooking chamber 1 10. The steam box 121 is further provided below a cooking plate 1 15 (only partially disclosed) arranged in the cooking chamber 1 10. The cooking plate 1 15 can for example be a stone plate, which is common in baking ovens or be a built up of a plurality of plates; the type of cooking plates 1 15 is however not important for the invention. It should be said though, that when the steam box 121 is arranged below the cooking plate 1 15, the cooking plate 1 15 is arranged such in the cooking chamber 1 10, that steam can pass up above the cooking plate 1 15 into upper part of the cooking chamber 1 10. The steam can for example pass in splices between two adjacent plates or in splices between the cooking plate 1 15 and the side walls of the cooking chamber 1 10.

The cooking oven 100 disclosed in figure 2 is provided with two cooking chambers 1 10, 210. Both or just one of the cooking chambers 1 10,0 210 can be provided with a steam a steam device according to the invention. A separate press button 1 12, 212 is provided for each cooking chamber 1 10, 210. In figure 3 is a close up view of a design of a steam box 121 according to the invention disclosed. As can be seen, the steam box 121 in figure 3 is square shaped, other shapes is however just as possible. The steam box 121 is provided with steam generating means 122, which in this case are aluminium bars arranged in two columns adjacent to each other. The water nozzle 120 is arranged in the middle between the two columns of steam generating means 122. In front of the water nozzle 120 a spreading means 123 is provided. In the disclosed version of the steam box 121 , the spreading means 123 is a steam generating means 122 arranged perpendicular to the other steam generating means 122. When the water injected from the water nozzle 120 hits the spreading means 123, it is spread within the steam box 121 . The spreading means 125 thereby facilitates a faster evaporation of the water, because it gets fast spread within the steam box 121 .

The steam box 121 is further provided with a lid 126. The lid 126 extends between all the four side walls of the steam box. The lid 126 prevents water injected into the steam box 121 to splash out of the box until it has evaporated. The lid 126 is provided with outlet means in the form of orifices 125, through which the steam can pass out to the surrounding cooking chamber 1 10. The orifices 125 can however alternatively be arranged on the side walls of the steam box 121 . It is however important that the outlet means 125 is arranged above the bottom of the steam box 121 , such that it is just steam that flows through the orifices 125 and not liquid water. In the embodiment of the steam box 121 shown in figure 2 and 3, the steam box 121 is arranged such, that the heating means 1 13 of the cooking oven 100 passes through the steam box 121 . This might increase the speed of the heating of the steam generating means, but is not a requirement of the invention; instead it is the flexibility of the invention that allows the steam box 121 to be placed such, that the heating means 1 13 can be placed in the same manner as in a conventional cooking oven. An alternative arrangement of the steam box 121 is shown in figure 4; here the steam box 121 is arranged upon one of the side walls of the cooking chamber 1 10. The function of the steam box 121 is however equivalent with the steam box 121 disclosed in figure 2 and 3, i.e. functions according to the inventive idea explained in conjunction with figure 1 .

The construction of a steam box 121 arranged on a side wall of the cooking chamber 1 10 becomes however slightly different. The steam generating means 122 is arranged in one or a plurality of rows and essentially below the water nozzle 120. The water nozzle 120 can be arranged in the middle of the steam box 121 , whereby the injected water thereby has to be spread out to the steam generating means located furthest away. A gutter can there act as a spreading means 123, in which the injected and water can flow out to the distanced steam generating means 123 arranged at the ends of the steam box 121 . However, the water nozzle 120 can also be arranged such that it injects essentially horizontally and parallel to the side wall of the cooking chamber 1 10, in order to achieve a sufficient spread of the injected water over the steam generating means 122. Also such a parallel arrangement can be combined with a suitable spreading means 123. It should be clear that the specific arrangement of the water nozzle 120 in relation to the steam generating means 122 is not important, as long as the steam generating means 122 and the water nozzle are arranged such relative each other, that water injected into the steam box 121 through the water nozzle 120 is lead to the steam generating means 122.

Reference signs mentioned in the claims should not be seen as limiting the extent of the matter protected by the claims, and their sole function is to make claims easier to understand.

As will be realised, the invention is capable of modification in various obvious respects, all without departing from the scope of the appended claims. Accordingly, the drawings and the description thereto are to be regarded as illustrative in nature, and not restrictive.