US20080022993A1

US20080022993A1 - Gas conveyor oven with differentiated air flow

Info

Publication number: US20080022993A1
Application number: US11/728,370
Authority: US
Inventors: Marco Moretti
Original assignee: Moretti Forni SpA
Current assignee: Moretti Forni SpA
Priority date: 2006-07-27
Filing date: 2007-03-26
Publication date: 2008-01-31
Also published as: EP1882416A2; EP1882416B1; EP1882416A3; ITPS20060024A1

Abstract

A gas conveyor oven has a conveyor belt for conveying an item through a heating chamber in which separate parts or sides of the item are to be concurrently heated at different temperatures. A blower draws heated air from a gas burner into a ventilation chamber in which a first baffle directs a first fraction of the heated air from the blower into a first portion of the heating chamber; and a second baffle directs a second fraction of the heated air from the blower into a second portion of the heating chamber. The second fraction of the heated air has a different rate of flow than the first portion, because the first and second baffles are positioned asymmetrically with respect to the heater, so that the fraction of air deflected by each baffle onto a different part or side of the item differs in volume and flow rate.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention is directed to the field of conveyor ovens and, more particularly, to a gas conveyor oven for use in baking food with forced air circulation that provides an adjustable and differentiated air flow.
2. Description of the Related Art
The commercial bakery industry is extremely competitive. This is especially true with respect to that segment of the industry in which food is baked and then immediately served for consumption, such as pizza. Commercial pizzerias use different types of ovens; some, for example, use a static oven in which a pizza is placed in the oven and then watched until it is ready to be served. Alternatively, some commercial pizzerias employ a conveyor oven, in which pizzas are placed on a conveyor belt to move them through the oven at a controlled rate so that each pizza is maintained in the oven for a predetermined period of time and exits the oven fully cooked.
Conveyor-type pizza ovens have heating chambers which must be heated to the desired temperature for baking pizza, either through radiant heat that is electrically generated or generated by flame-producing burners supplied with natural gas or liquefied petroleum gas (LPG). To minimize the cooking time and optimize the results, conveyor ovens commonly employ forced air heating, in which air heated to the desired temperature is blown over the pizza and then recycled to the heating element so that the pizza is continuously maintained at the proper cooking temperature with advantageous efficiency.
The cooking of pizza presents a special problem as compared to other types of baking. Optimum preparation of pizza calls for the bottom crust to be cooked at a higher temperature than the toppings, so it is preferred that pizza ovens provide different heating environments for the top and the bottom of the pizza.
In electric ovens, this may be accomplished by providing separately controllable, distinct heating elements for each of the top and bottom of the pizza. In one such known electric pizza oven disclosed in published European Patent Application No. 1,442,660 A1, air is circulated through upper and lower diffusers, in which separate upper and lower heating elements are disposed. The upper and lower heating elements heat the air in their respective diffusers to different temperatures, so that the air forced over the toppings is slightly cooler than the air forced onto the crust, thereby yielding an optimum cooking performance for this use.
This procedure is not, however, practical for ovens which employ a gas burner to generate heat, because it is preferred in such ovens that only one burner be used as the heat source, rather than two. Such ovens moreover sometimes require on and off cycling of the burner to maintain the desired cooking temperatures, which is an inefficient use of the burner and may lead to uneven cooking results. It is preferred that the burners remain “on”, but this can lead to too much heat on the toppings and known ovens do not always adequately handle the need to maintain different cooking temperatures.
There is accordingly a need in the art for a gas conveyor oven which can provide a differentiated heating environment for the top and bottom of an item being cooked, while using only a single burner.
There is a further need in the art for a gas conveyor oven which can efficiently use a single burner to provide differentiated heat to the top and bottom of an item being cooked, without the need for supplemental heating elements.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a gas conveyor oven which addresses the needs of the art and is simple, safe, economical and efficient.
It is another object of the invention to provide a gas conveyor oven that provides differentiated forced air flow, and therefore differentiated heat, to two different regions of a cooking chamber.
Briefly stated, a preferred embodiment of the invention is implemented in a gas conveyor oven that has a conveyor belt for conveying a food item through a heating chamber. A blower draws heated air from a gas burner into a ventilation chamber in which a first baffle directs a first fraction of the heated air from the blower into a first portion of the heating chamber; and a second baffle directs a second fraction of the heated air from the blower into a second portion of the heating chamber. The second fraction of the heated air has a different rate of flow than the first portion of the heated air, because the first and second baffles are positioned asymmetrically with respect to the heater, as a result of which the fraction of air deflected by each baffle differs in both volume and rate of flow.
Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. It should be further understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is illustrated in the attached drawings, in which like numerals designate like elements, and wherein:

FIG. 1 is a cross-section of a gas conveyor oven constructed in accordance with a preferred embodiment of the invention, taken across the direction of travel of the conveyor;

FIG. 2 is a top plan view, partially broken away and in partial cross-section, of the gas conveyor oven of FIG. 1; and

FIG. 3 is a cross-section of the gas conveyor oven of FIGS. 1 and 2, taken parallel to the direction of travel of the conveyor

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

In FIG. 1, there is shown, generally at 100, a gas conveyor oven constructed in accordance with the present invention. A mesh conveyor belt 1 carries items to be heated through a heating chamber 2, which can be inspected through a glass front door 3 and is insulated on all sides with thermal insulation material 4 stored in interspaces in oven 100.
A gas fed burner 5 (FIG. 2) supplies heat to heating chamber 2 with a flame column 6 positioned parallel to the direction of movement of conveyor 1, which is situated in front of and at essentially the same level as flame column 6.
Burner 5 is equipped with a continuous flame modulator, preferably composed of a gas supply valve connected to a Venturi air intake tube serving a variable speed electronically adjustable electric fan, for automatic regulation of the gas flow to burner 5 based on the incoming flow of air and adjusted by the variable speed fan and consequent mixing of the two fluids in order to optimize the stoichiometric combustion ratios.
A partition 7 is displaced behind flame column 6 and between flame column 6 and a blower 8 within heating chamber 2. Blower 8 is centrally positioned with respect to flame column 6. Blower 8 is preferably a left rotating centrifugal fan located on the side of flame column 6 opposite heating chamber 2. Blower 8 centrally draws in air heated by flame column 6 and evenly expels it peripherally into a ventilation chamber 10 extending parallel to the length of heating chamber 2.
Blower 8 includes a motor 9 located in the rear of oven 100, externally of ventilation chamber 10, and operates a second external coaxial centrifugal fan 11. Fan 11 circulates forced air outside of heating chamber 2 and within a peripheral space 12 delimited by a sheet metal covering 13 on the exterior of oven 100 to keep the exterior of oven 100 at a safe temperature.
Left and right angular baffles 14 and 15 (FIG. 3) are located on the vertical sides of ventilation chamber 10 and have respective apices 14A, 15A. Left baffle 14 has its apex 14A located higher than the axis of rotation of blower 8, while the apex of right baffle 15A is roughly level with the axis of rotation of blower 8.
Three radial deflectors 16A, 16B and 16C are positioned within ventilation chamber 10. A first deflector 16A is positioned below the left angular baffle 14, and the other two deflectors 16B and 16C are positioned respectively below and above right angular baffle 15.
Ventilation chamber 10 opens into lower feeder channel 17 and upper feeder channel 18, which each have their respective openings along the entire length of ventilation chamber 10 (see FIG. 3). As explained hereinbelow, the opening of lower feeder channel 17 is larger than the opening of upper feeder channel 18 (see FIG. 1).
Lower and upper feeder channels 17, 18, extend respectively below and above flame column 6 and then diagonally into heating chamber 2 respectively below and above conveyor belt 1 along the entire length of conveyor belt 1 within heating chamber 2. Lower and upper feeder channels 17, 18 empty into heating chamber 2 through respective lower and upper diffusers 19, 20 which define respective series of lower and upper calibrated holes 19A, 20A.
Lower and upper splitters 21, 22 are positioned in respective lower and upper feeder channels 17, 18.
The article or item to be heated is transported by conveyor belt 1 through a transport canal 23. Transport canal 23 is bounded by conveyor belt 1, upper diffuser 20 and front door 3, and is partially closed at its rear by a deflector 24 that includes a lower opening 25 extending along the length of deflector 24.
Positioned rearward of deflector 24 is the convex face of a curved partition 26. Partition 26 extends substantially parallel to flame column 6 along its entire length within lower and upper feeder channels 17, 18. The space between the outer extent of partition 24 and lower and upper feeder channels 17, 18 respectively defines lower and upper gaps 27, 28.
Disposed within heating chamber 2, and preferably located in upper output feeder channel 18, are electronic temperature sensors 29 that are operatively connected to burner 5, as further explained below.
In the operation of gas conveyor oven 100, blower 8 draws hot air from around flame column 6, and expels it peripherally outward by its counter-clockwise rotation. The expelled heated air is intercepted by left and right angular baffles 14, 15, which are configured with respective apexes 14A, 15A defined above and alongside the horizontal disposition of fan 8 (see FIG. 3). In relation to the rotation of fan 8, the flow of heated air is shaped and directed by the asymmetrical orientation of baffles 14, 15, and magnified by deflectors 16A, 16B and 16C, to split the flow of heated air into two streams that are respectively channeled into lower and upper feeder channels 17, 18. The heated air that is directed downward has a higher flow rate, by virtue of the relatively greater volume of lower feeder channel 17 as compared to upper feeder channel 18, since the positioning of apex 14A above the center of blower 8 causes a relatively greater proportion of the otherwise evenly distributed heated air to flow downward into lower feeder channel 17.
In this manner, through lower and upper feeder channels 17, 18, the flow of heated air reaches and crosses diffusers 19, 20 and is forced below and above conveyor belt 2. The greater flow of heated air to lower feeder channel 17 provides more heat to the bottom of the pizza crust transported on conveyor belt 2, while at the same time providing less heat to the upper feeder channel 18 to properly cook the toppings carried on the top of the crust.
After circulating over and under the conveyor belt 2 for cooling the transported article, the flow of air coming through diffusers 19, 20 is centrally drawn into transport canal 23 and passes through opening 25 below deflector 24 and into curved partition 26. The heated waste air is then split and channeled through lower and upper gaps 27, 28, thus returning to flame column 6 for reheating and return to the forced air cooling operation. Recycling of the already-heated air back to flame column 6 efficiently decreases the overall cost of operation of conveyor oven 100.
Even with just one burner and one blower, as is preferred, this labyrinthian structure can achieve uniform and optimal cooking of pizzas by directing the heat where it is needed, the proper temperatures being maintained without shutting off flame column 6. The intensity of the flame is instead modulated by adjusting the parameters to achieve the optimum mixture of combustible gas and air, thus resulting in more efficient use of gas as compared to the normal waste of gas in “on-off” systems, while offering uniform cooking of pizzas.
In particular, in a currently preferred embodiment of the invention, temperature sensors 29 located in upper feeder channel 18 monitor the temperature of the heated air where it is at its maximum temperature. The temperature of the heated air may then be electronically controlled based on preset optimization parameters such as regulation of the variable speed electric fan serving a Venturi air intake tube that is connected to the gas supply valve of the continuous flame supply modulator of burner 5. This valve suitably increases or decreases the supply of combustible gas to flame column 6 based on the temperature detected by sensors 29, and thus increases or decreases the intensity of flame column 6. The desired temperature is accordingly maintained by constantly optimizing the stoichiometric ratio for the air-gas mixture.
There are of course alternative ways of achieving these functions, while using the innovative construction herein described. The system presented here can be realized with structures equivalent to those described as would be appreciated by those of ordinary skill in the art, and those of ordinary skill would also appreciate that the parameters and structures hereof may be varied without under experimentation to realize the benefits provided by the invention.
For example, the structure of the ventilation chamber can be modified to change the running direction of the blower to thereby provide a more sustained flow in the lower duct than in the upper duct. In other embodiments, the relative flow of air to the lower and upper feeder channels 17, 18 can be adjusted by providing means for varying the orientation and positioning of at least one of the baffles 14, 15, such as a motor 30 operative to raise and/or lower the baffle.
As should now be apparent, the preferred system and contemplated variations offer numerous advantages, including the provision of an implementation that successfully yields a gas conveyor food oven with only a single burner and a single blower while achieving high efficiency and desirable adjustability.
It will also be appreciated that the gas conveyor oven of the invention will have utility in any heating application in which it is desired to use a single heater to heat two sides of an item at different temperatures or heat levels, even where the two sides are not top and bottom but, rather, left and right, or front and back. One of ordinary skill in the art can readily modify the constructions described herein without undue experimentation to adapt the inventive gas conveyor oven for a particular application or utility.
It will also be appreciated by those of ordinary skill in the art that the relative rate of heated air flow to the upper and lower feeder channels may be adjusted or set by the relative positioning of apices 14A and 15A with respect to each other and to blower 8, to thereby set the relative heated air flow rates through the feeder channels to the desired proportion.
Thus, while there have shown and described and pointed out fundamental novel features of the invention as applied to preferred embodiments thereof, it will be understood that various omissions and substitutions and changes in the form and details of the devices illustrated, and in their operation, may be made by those skilled in the art without departing from the spirit of the invention. For example, it is expressly intended that all combinations of those elements which perform substantially the same function in substantially the same way to achieve the same results are within the scope of the invention. Moreover, it should be recognized that structures and/or elements shown and/or described in connection with any disclosed form or embodiment of the invention may be incorporated in any other disclosed or described or suggested form or embodiment as a general matter of design choice. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto.

Claims

1. A gas conveyor cooking oven, comprising:

a heating chamber;

means for conveying through said heating chamber, an article to be cooked in said oven;

a gas heater;

means for drawing heated air from said gas heater;

means for directing into said heating chamber heated air from said means for drawing and for splitting said directed heated air into first and second fractions of the directed heated air, such that said second fraction of the heated air has a different rate of flow than said first fraction of the heated air; and

means for recycling said heated air to said gas heater after said heated air passes through said heating chamber; and

wherein said first fraction of the heated air is directed into a first portion of said heating chamber and said second fraction of the heated air is directed into a second portion of said heating chamber so that each fraction of the heated air cooks a different part of the conveyed article at a different cooking heat as the article is conveyed through said heating chamber.

2. The gas conveyor oven of claim 1, wherein said means for conveying comprises a conveyor belt for conveying the article to be cooked in said oven through said heating chamber.

3. The gas conveyor oven of claim 2, wherein said conveyor belt comprises a mesh material.

4. The gas conveyor oven of claim 1, wherein said article is a food to be cooked.

5. The gas conveyor oven of claim 4, wherein said article is pizza, and wherein said first portion of the heating chamber is disposed above said means for conveying so that the first fraction of the heated air cooks toppings of the pizza and said second portion of the heating chamber is disposed below said means for conveying so that the second fraction of the heated air cooks the crust of the pizza.

6. The gas conveyor oven of claim 1, wherein said gas heater comprises a burner.

7. The gas conveyor oven of claim 1, wherein said means for drawing comprises a blower.

8. The gas conveyor oven of claim 1, wherein said means for directing includes at least a first baffle.

9. The gas conveyor oven of claim 8, wherein said first fraction of the heated air is directed into a first feeder channel and said second fraction of the heated air is directed into a second feeder channel.

10. The gas conveyor oven of claim 9, wherein said first feeder channel is larger than said second feeder channel.

11. The gas conveyor oven of claim 10, wherein said means for directing further comprises a second baffle, said first baffle directing said first fraction of the heated air into said first feeder channel and said second baffle directing said second fraction of the heated air into said second feeder channel.

12. The gas conveyor oven of claim 11, wherein said first baffle is angled and defines a first apex, and said second baffle is angled and defines a second apex, said first and second apices being positioned asymmetrically with respect to said gas heater.

13. The gas conveyor oven of claim 12, wherein said first apex is positioned lower in height than said second apex.

14. The gas conveyor oven of claim 11, further comprising means for adjusting a position of at least one of said first and second baffles.

15. The gas conveyor oven of claim 1, wherein said first portion of said heating chamber is below said means for conveying, and said second portion of said heating chamber is above said means for conveying.

16. The gas conveyor oven of claim 1, further comprising a temperature sensor within said heating chamber for monitoring a temperature within said heating chamber; and

means for controlling at least one of said gas heater, said means for drawing and said means for directing in response to said temperature sensor to adjust the temperature in at least one of said first and second portions of said heating chamber.

17. The gas conveyor oven of claim 1, wherein said means for directing further comprises a deflector for directing the heated air to at least one of said first and second portions of said heating chamber.

18. A gas conveyor oven, comprising:

a heating chamber;

a conveyor belt for conveying through said heating chamber a food item to be cooked in said oven;

a gas heater;

a blower for drawing heated air from said gas heater;

a first baffle for directing a first fraction of the heated air from said blower into a first portion of said heating chamber;

a second baffle for directing a second fraction of the heated air from the blower into a second portion of said heating chamber, at a different rate of flow than said first portion of said heated air; and

wherein said first and second baffles are positioned asymmetrically with respect to said heater, so that each fraction of the heated air cooks a different part of the conveyed food item at a different cooking heat as the food item is conveyed through said heating chamber.

19. The gas conveyor oven of claim 18, wherein said food item is pizza.

20. The gas conveyor oven of claim 18, wherein said conveyor belt is formed of a mesh material.

21. The gas conveyor oven of claim 18, wherein said first fraction of the heated air is directed into a first feeder channel and said second fraction of the heated air is directed into a second feeder channel.

22. The gas conveyor oven of claim 21, wherein said first feeder channel is larger than said second feeder channel.

23. The gas conveyor oven of claim 22, wherein said first baffle directs said first fraction of the heated air into said first feeder channel and said second baffle directs said second fraction of the heated air into said second feeder channel.

24. The gas conveyor oven of claim 23, wherein said first baffle is angled and defines a first apex, and said second baffle is angled and defines a second apex, said first and second apices being positioned asymmetrically with respect to said gas heater.

25. The gas conveyor oven of claim 24, wherein said first apex is positioned lower in height than said second apex.

26. The gas conveyor oven of claim 18, further comprising means for adjusting a position of at least one of said first and second baffles.

27. The gas conveyor oven of claim 18, wherein said first portion of said heating chamber is below said conveyor belt, and said second portion of said heating chamber is above said conveyor belt.

28. The gas conveyor oven of claim 18, further comprising a temperature sensor within said heating chamber for monitoring a temperature within said heating chamber;

and means for controlling at least one of said gas heater, said blower, said first baffle and said second baffle in response to said temperature sensor to adjust the temperature in at least one of said first and second portions of said heating chamber.

29. The gas conveyor oven of claim 18, further comprising a deflector for directing heated air to at least one of said first and second portions of said heating chamber.