WO2006085317A2

WO2006085317A2 - Combination heating and steaming oven

Info

Publication number: WO2006085317A2
Application number: PCT/IL2006/000166
Authority: WO
Inventors: Zvi Tene
Original assignee: Zvi Tene
Priority date: 2005-02-10
Filing date: 2006-02-09
Publication date: 2006-08-17
Also published as: IL166811A0; WO2006085317A3

Abstract

An oven cooking chamber that includes heating elements, a steam production system with a boiler external to the chamber, a water reservoir, a fan, and a control panel for selecting the heating elements or steam or a combination, used either simultaneously or sequentially.

Description

COMBINATION HEATING AND STEAMING OVEN

FIELD OF THE INVENTION

This invention relates to an oven, particularly one that is capable of cooking food by dry-heat, by steaming, or by a combination of thereof.

BACKGROUND OF THE INVENTION

For high quality cooking, it is often preferable to be able to control the method by which food is heated, including its atmosphere. For instance, food may be baked or grilled (heated from above) using dry intense heat or steamed using hot moist air.

It is also known to use a combination of such heating methods particularly in large-scale (industrial food processing) and medium-scale (e.g. for food catering) applications.

However, it is also often advantageous to have the option of such cooking modes in regard to small-scale cooking as in the home. Accordingly, a number of ovens which provide for heating modes including dry-heating, moist heating and steaming have been suggested.

US 4,700,685 (Miller) discloses a cooking oven for cooking foodstuffs with either steam or forced convection hot air at atmospheric pressure. In the steam mode, steam is continuously generated in the oven cavity. Alternatively, in the convection mode, the amount of moisture supplied to the cavity is controlled. A fan circulates the air or steam in the oven cavity. The steam is generated by means of a slinger cup to which water is supplied and from which water will flow in a thin film over an edge portion of the cup to be slung outwardly and to be atomized thereby by centrifugal force. The atomized water is then caused to flow, by means of the fan, over a heater whereby the atomized water flashes into water vapor or steam. Food juices and condensed steam or water vapor, which collect at the bottom of the oven, can be drained therefrom by means of a drain which is open to the atmosphere. The oven temperature is selectively variable by means of an automatic control.

US 4,810,856 (Jovanovic) describes an infrared cooking oven provided with a rotatable spit which is hollow and is connected to a boiler for producing steam. The steam is fed into the spit and then flows through orifices in the spit and into the meat mounted thereon. The internal steam cooking, coupled with the combined infrared and steam cooking of the exterior, reduces substantially the cooking time while ensuring that the meat will not dry out.

US 4,851,644 and US 4,924,072 (Oslin) and US 4,817,584 (Oslin et al) disclose combination steam and dry ovens that can be operated as a forced-air convection oven, a forced convection oven circulating superheated steam, or a steamer near the boiling temperature of water. Sensors in the oven supply information to a microprocessor that controls heating elements to maintain the oven temperature. The oven circulates superheated steam by blowing its circulating gas over the surface of an internal boiler, which is protected from contamination by a baffle. Water level sensors assure that the water level in the boiler either stays within predetermined limits or else shuts down the oven if the water level is out of limits. Tray stops keep foods and the trays containing them away from the walls of the oven to permit free circulation of air or superheated steam. Water temperature sensors in the boiler and gas temperature sensors in the circulating gas permit the control of relative humidity when the oven is used to proof dough or hold cooked food at a relatively low temperature. Control of the temperature of water in the boiler is aided by blow-down and replacement if the temperature becomes excessive. US '644 and "072 have integral boilers located inside the oven cavity whereas US '582 has a boiler located outside the oven cavity and the cavity and boiler are heated by natural draft gas burners. The oven of US '644 may stand alone or it may be stacked as a combination of units. US 5,619,983 (Smith) discloses a combination convection/steamer oven capable of maintaining an optimum steam saturation level without quenching by equipping the steam generating system of the oven with an adjustable water supply source. When the oven is initially brought up to a pre-selected cooking temperature, a microprocessor controller uses a stored water flow rate profile to calculate the water flow rate required to prevent quenching yet enable a desirable rate of temperature increase. Once the oven has reached operating temperature, the microprocessor controller analyzes temperatures in a drain channel and in the cooking cavity and, based on these parameters, calculates the water flow rate into the steam generating system required to optimize steam saturation in the cooking cavity. The steam generating system also has an improved atomizer including a rotating paddle wheel that is fed water from within by a sprayer fan.

US 5,680,810 (Sham) describes a toaster oven that can heat and steam food, the steam generated in a water tube or a boiling pan placed adjacent the toaster oven's infrared heating coils. Water for making steam is introduced into a reservoir located in the toaster oven's housing. The reservoir can be either permanently situated in the housing, or it can be removable. A microprocessor controls both the steam generation and the heating cycles and is operated via a computer routine that monitors sensors that are positioned about the housing of the toaster oven. The microprocessor also meters the water flowing from the reservoir into the water tubes or boiling pan. A one-way valve ensures that the water flow is positively directed into the water tubes or the boiling pan. A control knob located on the toaster oven's control panel allows a user to select the amount of steam being injected into the cooking chamber.

US 6,000,392 (Stiϊtzl) discloses a gas powered, pressureless steam cooker with a connector tube for ingress of steam into the cooking compartment to minimize the entry of low temperature, wet steam. The connector tube has a small diameter to constrain the entry of steam into the cooker compartment until it has reached at least a minimum velocity. A water reservoir is located alongside the oven compartment to the rear of the cooker and an integrated heat exchange tube and firebox are located in the tank. The connector tube is generally U-shaped and has a lower horizontal leg opening at a mouth outside the water reservoir. An inshot burner fires into the lower horizontal leg and combustion gases flow through the U-shaped tube transferring heat to the water in the reservoir. Additional heat exchange surface may be provided by side to side channels through an upper leg of the U-tube. Flow of combustion gases may be optimized by the shape of the U-tube and a deflecting surface between a vertical web of the U and the upper leg of the U.

US 6,100,502 (Sham et al) discloses a steamer toaster oven with a water tank adjacent it and a steam generating chamber disposed therebetween. The steam generating chamber has a heating element for heating water to become pressurized steam which is conveying to a jet spray nozzle.

SUMMARY OF THE INVENTION

The present invention relates a simply-designed oven capable of dry- heating, steaming or cooking with a combination thereof, in series or parallel suitable for small-scale use in a typical home.

As such, the invention provides an oven for cooking food comprising: a housing defining a cooking chamber; heating elements adapted for heating food in said chamber; a steam production system adapted to operate at essentially atmospheric pressure adapted for steam cooking food in said chamber, said system including a boiler having a heating source, a water reservoir disposed above said boiler and a one-way valve therebetween allowing water to flow from said reservoir to the boiler, the steam producing system being located external to the chamber; piping conveying steam produced in the boiler into the chamber; a fan for distributing heat through out the chamber; and a control panel for controlling heating modes for cooking the food in the chamber which allows heating the food with said heating elements, or heating the food with said steam, or heating the food with a combination of the heating elements and steam, in parallel and/or in series, the oven being adapted for standard home kitchen cooking.

The boiler may comprise an internal sleeve, wherein water within the sleeve is in fluid communication with water within the boiler but external to the sleeve. A heating source is disposed within the sleeve, and an outlet from the boiler drawing steam from within the sleeve. The heating source may be a submerged heating source.

The heating source may be disposed within the boiler such that when the boiler is filled with water, the heating source is submerged.

The boiler may further comprise an internal sleeve, constructed such that when the boiler is filled, water within the sleeve and water external to the sleeve are in fluid communication. The heating source is disposed so as to directly heat the water within the sleeve. The boiler may further comprise a boiler outlet connected to the pipe, wherein the outlet is disposed so as to draw steam from the area within the sleeve.

Thus, the present oven is designed to fit into a typical space suitable for a home oven of the mountable type or of the stand-alone type (on the floor or on a counter). The oven can cook food using either dry heat, steam or a combination of thereof either in parallel or series (i.e. wherein an electric or gas heater and steam are simultaneously used to heat the food or, for example, wherein the food is first steamed and then dry-heated, vice versa or in other combinations). Thus, food can be cooked to retain its juiciness and flavor as well as allowing for crisping of the outside of the food in an affordable home-scale oven.

The design of such oven does not require special integration of a steamer with a diy-heating system, piping from an external water source, a microprocessor or other such complicated and expensive features. Thus, the design is not merely sized for home use, it can be manufactured at a cost appropriate for the home market.

Additional advantages of the oven of the present invention in include: food may be cooked more quickly, as steam has a high heat content and conducts heat better than dry air, and, cooking with steam does not dry out food as does cooking with non-moist heat air.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to understand the invention and to see how it may be carried out in practice, embodiments will now be described, by way of non-limiting examples only, with reference to the accompanying drawings, in which:

Fig. 1 is a cross-sectional front view of an oven according to one embodiment of the present invention;

Fig. 2A is a front view of the oven of Fig. 1 illustrating an exemplary control panel therefor;

Fig. 2B illustrates another exemplary control panel for the oven of Fig. 1 ; and

Fig. 3 is a top view of a modified cooking chamber of a further embodiment of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Referring first to Fig. 1, there is shown a home/kitchen cooking oven 10 according to an embodiment of the invention. The oven 10 includes a housing 12 with compartments 14 and 16 for housing a cooking chamber 18 having heating elements 17, and a steam production system 20, respectively. The present oven 10 may be adapted to be a floor model, counter-top style or a cabinet-mounted type home cooking oven and its outer dimensions are designed to suit such application (e.g., 60x60x90cm for a floor model), mutatis mutandis.

The steam production system 20 comprises a water reservoir 22 which is conveniently fillable via a filling port or lid 24 accessible at the top of the housing 12. Alternatively, the oven 10 can be designed so that the reservoir 22 can be filled via one of its sides (e.g. via a side port - not shown), which may be particularly suitable in the case wherein there is not space over-head the oven 10 such as may be when it is a counter-top or cabinet-mounted type oven. The reservoir 22 may also be adapted to allow for filling via a water pipe (not shown) - for example, analogous to that of a refrigerator designed for ice-making.

The steam production system 20 further comprises a boiler 28 with a heating source 30 (shown as an electric heating element, although the oven may be designed to be gas-fired or use microwave heating technology, etc.), a boiler inlet 31, a boiler outlet 33, a pipe 32 leading from the reservoir 22 to the boiler inlet 31 and a one-way valve 34 in the pipe 32 to prevent backflow of steam produced in the boiler 28.

The heating source 30 may be a submerged heating source, such that it directly contacts the water. This permits faster, more efficient heating. In addition, the submerged heating source 30 may be contained within a sleeve (not illustrated). Water is free to flow between the inside and the outside of the sleeve, all within the boiler 28. However, it will be appreciated that the water within the sleeve, while in fluid communication with the water external thereto, is heated faster than would the quantity of water in the boiler in the absence of the sleeve. This is due to the fact that the sleeve effectively reduces the volume of water to be heated by direct contact with the heating source 30. The boiler outlet 33 draws steam directly from within the sleeve. In this way, the steam production system 20 effectively reaches its operating temperature faster.

The oven 10 further comprises a steam inlet 38 and a fan 40, both typically located at the rear of the cooking chamber 18, as shown, for ensuring uniform temperature within the chamber 18. However, the steam inlet 38 and fan 40 may be located in different locations than those shown (e.g. in side walls or the ceiling of the chamber 18, including being adjacent one another; and the heating elements 17, may be likewise disposed in locations other than that shown.

The steam inlet 38 is in fluid communication with the boiler outlet 33, e.g. via a steam supply pipe 36. The steam inlet 38, the fan 40 and a short portion 37 of the pipe 36 are shown with dashed lines as they are not in the plane of the section of Fig. 1 - rather they are typically disposed along the rear wall of the oven's cooking chamber 18. The fan 40 is typically designed to stop its operation when the oven 10 is open. Power to the heating elements 17 and the boiler 28 may also be designed to stop when the oven 10 is opened.

The steam production system 20 preferably includes a sensor 43 to ensure that the boiler 28 is not operational unless there is a supply of water in the system. The sensor 43 is illustrated schematically in Fig. 1 as may be of any type known per se (e.g. of a type that senses pressure head, etc.). However, such a sensor can be, for example, as simple as a mechanical float switch (not shown) for cutting off the flow of electricity to the boiler's heating source 30.

The steam production system 20 can also comprise a water level indicator (e.g., a sight-glass or a dial indicator - not shown); and optionally include and a water softening unit (not shown)

Located adjacent the bottom of the cooking chamber 18 is a drain pan 42 for draining any condensed water resulting from steam introduced to the chamber and/or oils from the food (illustrated by food F in Fig. 1). The pan 42 may, for example, rest on the bottom of the cooking chamber 18 or be supported in another manner, such as by channels 44, at the sides of the chamber 18. Typically associated with the drain pan 42 is a tray 45 for directing the water/food-oils to the pan through an opening 47 therein. The tray 45 may act as a baffle to keep heat above it and as such may also be designed to reflect heat.

In addition to those elements illustrated in Fig. I₅ it will be appreciated that the oven may comprise other standard elements, including but not limited to, a pressure release valve. This valve is included in order to regulate the amount of steam in the oven, thereby controlling the temperature when steam is used. A humidistat may further be provided.

In operation, water from the reservoir 22 is gravity-fed to the boiler 28 via pipe 32 through one-way valve 34. The water is converted to steam in the boiler 22, which point it flows via steam supply pipe 36 to then enter the cooking chamber 18 at the steam inlet 38. The fan 40 helps distribute the steam - as well as the hot air produced by heating elements 17, if any. For example only, the cooking chamber 18 may be up to 40 liters, say 40cm wide by 40cm deep by 25cm in height, which is estimated to be a size such that a reasonable amount (or sized) food F can fit therein and that a reasonable amount of steam is used. Again, for example only, the reservoir 22 may have a capacity of up to about fifteen liters, which should be suitable for most cooking applications. It should be understood that the chamber 18 and reservoir 22 may be of different sizes, particularly in relation to ovens of different types.

Further, the oven 10 may comprise a pressure sensor (not shown) so that when steam is used (i.e. in the"steam-only" or "combination steam/heating" cooking modes), the boiler 28 is powered off if the pressure in the cooking chamber 18 exceeds a predetermined level. This situation may occur if steam entering the chamber 18 does not condense and/or does not exit the chamber 18 at rate corresponding to the incoming steam rate whereby pressure builds up.

Figs. 2 A and 2B show exemplary control panels 50 and 50a for controlling the cooking modes of the oven 10, i.e. for controlling whether the food is heated by steam, by dry heat or by a combination thereof. Combination cooking can be in series or parallel, or a combination of both. Thus, the cooking can be by steam and heat together (producing superheated steam) or, for example, first steaming the food and then dry heating (or vice versa or back and forth). For example, one may want a chicken cooked to preserve it juiciness, however with crispy skin. In such a case the chicken can be cooked in the oven 10 first by steam (or a combination of heat and steam) and then by dry heat (baking/broiling). The control panel may also work in conjunction with the humidistat and the pressure control valve to regulate the temperature. By gathering information, via the humidistat, about the humidity of the air inside the oven, the control panel may be adapted to determine when and to what degree the pressure release valve should be open.

For such purpose, control panel 50 comprises a cooking mode dial 52 which can be used to program/control a desired cooking program, illustrated by programs A, B, C and D in Fig. 2A. The control panel 50 also includes a temperature control knob 54 and first and second timers 56 and 56a. For situations wherein one would want to use the steam and dry heating cooking modes in series, one after the other, the control knob 54 may be set to a corresponding program and the timers 56 and 56a can be set for first steam cooking to be followed by a cooking time using dry heat - or vice versa - or a more complex cooking scheme. With such control, even foods for which different cooking modes are desired may possibly be cooked together for at least a period of time, thus saving time and energy.

As understood from the above-mentioned possible locations of the steam inlet 38 and the fan 40, dry heat and steam may be introduced at different locations from each other, for example, dry heating from the bottom and steaming from the top. Also, in all of the cooking modes, it is preferable that the fan 40 be operating.

Fig. 2B provides another example of a control panel 50a being a touchpad type control panel and comprising a cooking mode pad 60, a time and temperature input pad 62 and a cooking program display 64. With such a control panel, the cooking mode may be chosen along with a time for that mode and a temperature therefor. It should be understood that if the cooking mode choice is "steam", the resultant temperature is simply that of saturated steam and in such case the temperature is not chosen.

The display 64 allows the user to see what program is being chosen (or was chosen). In the exemplary program shown in the cooking display 64 of Fig. 2B, the display allows the viewing of five cooking modes, and those chosen are, in order, "steam", "combo" (which can be steaming in combination with either baking or grilling), "bake" and finally "grill" - the last display not being used.

It should be understood that the above-described control panels 50 and 50a are merely exemplary, and control panels of many different designs may be employed to achieve the intended heating functions.

Fig. 3 illustrates an alternate cooking chamber 18a particularly useful in the event the food is not cooked on cooking grill, rather on a solid cooking tray. As such, the chamber 18a has channeled walls 70 comprising vertical channels 72 therein for facilitating the distribution of heating media (hot air, steam or combination thereof) throughout the cooking chamber 18a. Thus, the heating media can readily pass up and down the cooking chamber 18a, even if at least partially blocked by a solid heating tray.

It should be understood that many modifications of the oven 10 of the present invention are possible including, for example, that it may comprise more than one steam inlet 38, the compartment- 16 housing the steam production system 20 can be in rear of oven, provided as an add on, and so forth.

Further, there may be a mechanism such that the amount of water in the boiler 28 is controlled - such as a mechanism whereby the one-way valve 34 only allows water to enter the boiler when the water level therein is within a predetermined range.

As such, it will be appreciated by persons skilled in the art that the present invention is not limited by what has been particularly shown by the exemplary embodiments described hereinabove and the combination heating and steaming oven can be embodied by a variety of aspects within the scope of the invention, mutatis mutandis.

Claims

CLAIMS:

1. An oven for cooking food comprising:

- a housing defining a cooking chamber;

- heating elements adapted for heating food in said chamber;

- a steam production system adapted to operate at essentially atmospheric pressure adapted for steam cooking food in said chamber, said system including a boiler having a heating source, a water reservoir disposed above said boiler and a one-way valve therebetween allowing Avater to flow from said reservoir to the boiler, the steam producing system being located external to the chamber;

- piping conveying steam produced in the boiler into the chamber;

- a fan for distributing heat through out the chamber; and

- a control panel for controlling heating modes for cooking the food in the chamber which allows heating the food with said heating elements, or heating the food with said steam, or heating the food with a combination of the heating elements and steam, in parallel and/or in series, the oven being adapted for standard home kitchen cooking.

2. The oven according to claim 1, wherein the chamber has four walls, a top and a bottom, the walls comprising vertical channels therein for facilitating the distribution of heating media throughout the cooking chamber.

3. The oven according to claim 1, wherein the outer dimensions of the oven are designed so that the oven is suitable as a floor-standing model, or as a shelf- top model or as a built-in model.

4. The oven according to claim 1, wherein the boiler has a boiler outlet and the chamber includes a steam inlet for delivering steam produced in the boiler, and a pipe leading from the boiler outlet to the steam inlet.

5. The oven according to Claim 1, wherein the heating source is disposed within the boiler such that when the boiler is filled with water, the heating source is submerged.

6. The oven according to Claim 1, wherein boiler further comprising an internal sleeve, constructed such that when the boiler is filled, water within the sleeve and water external to the sleeve are in fluid communication, the heating source being disposed so as to directly heat the water within the sleeve.

7. The oven according to Claim 6, wherein the boiler further comprises a boiler outlet connected to the pipe, wherein the outlet is disposed so as to draw steam from the area within the sleeve.

8. The oven according to claim 1, wherein the boiler includes an automatic control to shut its power if the level of water therein falls below a predetermined level.

9. The oven according to claim 1, wherein the steam production system further comprises a water level indicator.

10. The oven according to claim 1, wherein the steam production system further comprises a water filtering or water softening unit to limit minerals entering the boiler.

11. The oven according to claim 1, wherein the heating elements and the steam are introduced at different locations one from the other.

12. The oven according to claim 1, wherein the steam production system is adjacent to a side of the oven.

13. The oven according to claim 1, wherein the steam production system is adjacent to a rear portion of the oven.

14. The oven according to claim 1, wherein the reservoir is adapted to be manually fillable.

15. The oven according to claim 1, wherein the cooking chamber has dimensions of less than or substantially equal to 40 liters.