Patent Document

This application is a U.S. national phase application of PCT International Application No. PCT/FR02/02708 filed Jul. 29, 2002. 
     TECHNICAL FIELD OF THE INVENTION 
     The present invention relates to ovens for cooking food, and more particularly forced convection gas ovens used in institutional kitchens. 
     Forced convection gas ovens for cooking food generally comprise a metal muffle surrounding an interior muffle cavity, with a lower wall forming a floor, an upper wall forming a ceiling, and four vertical peripheral walls. At least one of the peripheral walls is provided with an access door for introducing food to be cooked into the interior cavity of the muffle and extracting it therefrom. 
     In the interior space of the oven, i.e. in the interior cavity of the muffle, convection of air is achieved by a convection turbine, that is driven in rotation by a motor, and that is generally disposed in the vicinity of one of the peripheral walls that has no access door. The turbine is mounted to rotate about a rotation axis perpendicular to the peripheral wall. 
     Gas burners are placed in the flow of air, upstream or downstream of the turbine, and are adapted to heat the air propelled into the muffle by the turbine, encouraging the cooking of the food. 
     In prior art gas ovens, for example as described in the document EP 0 733 862 A, the interior cavity of the muffle is divided into two compartments: a cooking compartment, accessible via the door, and conformed to receive the food to be cooked, and a heating compartment, containing the convection turbine and the gas burners. The cooking compartment is always isolated from the heating compartment by a separating wall, that is generally perpendicular to the rotation axis of the turbine. The separating wall has a double effect of channeling the flow of air propelled by the turbine, and protecting the heating compartment from splashed grease and other materials from the food being cooked. In fact, in prior art ovens, a constant concern is preventing splashes from food being cooked soiling the members inside the heating compartment, namely the turbine, the gas burners and sensors used to control these elements. 
     Despite the presence of the separating wall, manual cleaning operations are periodically required to guarantee that the oven is clean. Cleaning cannot be automated in the prior art oven structures, and necessitates demounting and remounting the separating wall. 
     Another problem that is encountered in gas ovens of this kind for cooking food is the difficulty of ensuring regular cooking of all the food in the oven, regardless of its position within the cooking compartment. It is found in fact that the cooking of the food can vary significantly as a function of the position of the food in the cooking compartment. Some areas of the cooking compartment can overheat the food, while other areas achieve insufficient heating. Also, the evenness of cooking is modified as a function of the type of food to be cooked, and as a function of the quantities of food introduced into the cooking compartment. This results in uneven cooking, and reduced efficiency. 
     SUMMARY OF THE INVENTION 
     A particular object of the present invention is to avoid the drawbacks of prior art structures of forced convection gas ovens for cooking food, with the aim of achieving more even cooking and improved efficiency. 
     The invention stems from the surprising observation that a particular disposition of the gas burner achieves more even cooking and improved efficiency. 
     Accordingly, to achieve the above and other objects, the invention proposes a forced convection gas oven for cooking food, the oven comprising:
         a muffle with a generally parallelepipedal interior cavity delimited by a lower floor wall, an upper ceiling wall and four peripheral walls, at least one of the peripheral walls being provided with an access door for entry of food to be cooked into the interior cavity of the muffle and its exit therefrom,   a centrifugal convection turbine, driven in rotation by a motor, disposed in the interior cavity of the muffle in the vicinity of the center of an adjacent peripheral wall with no access door, mounted to rotate about a rotation axis perpendicular to the adjacent peripheral wall, and adapted to aspirate air axially toward the center of the adjacent peripheral wall and to discharge it radially toward the edges of the adjacent peripheral wall,   a gas burner placed axially in the aspiration inlet of the convection turbine, and adapted to heat the air that is propelled into the muffle by the convection turbine to cook the food,   a cooking volume, reserved in the interior cavity of the muffle to receive food to be cooked;       

     according to the invention, the gas burner is directed toward said peripheral wall of the oven, at which wall the convection turbine is adjacent, and the gas burner is directed toward the center of the convection turbine. 
     The turbine can advantageously have a generally cylindrical structure, with a posterior flange carrying a plurality of short blades at the front and distributed around its periphery. 
     The diameter of the convection turbine can advantageously be greater than one third of the larger dimension of the adjacent peripheral wall. 
     In one advantageous embodiment, the gas burner is generally annular, and its axis is substantially horizontal and perpendicular to said adjacent peripheral wall. 
     For example, the gas burner comprises a posterior heating plate, with holes through which gas can flow distributed over its surface, and shutting off an annular cavity in a burner body. 
     A burned gas evacuation pipe, through which the burned gases escape axially away from the adjacent peripheral wall and are then guided toward the upper portion of the oven, advantageously passes through the central passage of the gas burner. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other objects, features and advantages of the present invention will emerge from the following description of particular embodiments of the invention, which is given with reference to the appended drawings, in which: 
         FIG. 1  is a perspective view of one embodiment of an oven according to the invention; 
         FIG. 2  is a front view of the  FIG. 1  oven; 
         FIG. 3  is a side view of the  FIG. 2  oven, in section taken along the line B—B in  FIG. 2 ; 
         FIG. 4  is a perspective view of one embodiment of the gas burner according to the invention; and 
         FIG. 5  is a side view in diametral section of the  FIG. 4  gas burner. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In the embodiment depicted in the figures, a convection oven according to the invention comprises a muffle  1 , having an interior cavity  8  of generally parallelepipedal shape delimited by a bottom floor wall  2 , a top ceiling wall  3 , two opposite lateral peripheral walls  4  and  5 , an anterior peripheral wall  6  and a posterior peripheral wall  7 . 
     The anterior peripheral wall  6  is fitted with an access door for introducing food to be cooked into the interior cavity  8  of the muffle and extracting it therefrom. 
     The interior faces of the walls of the muffle are generally smooth, to prevent sticking and retention of food particles liable to be separated from food to be cooked. 
     A convection turbine  9  is driven in rotation by a motor  10  supplied with power by an external electrical power supply. The convection turbine  9  is of the centrifugal type, aspirating air axially via its center and discharging air radially via its periphery. To this end it comprises inclined blades, in the usual manner known in the art. The convection turbine  9  is disposed in the vicinity of the center of a peripheral wall with no access door. In the embodiment shown, the convection turbine  9  is disposed in the vicinity of the center of the posterior peripheral wall  7  of the muffle. 
     Alternatively, in an embodiment that is not depicted in the figures, an oven can be provided to have two opposite doors respectively formed in the anterior peripheral wall  6  and in the posterior peripheral wall  7 , with the turbine placed in the vicinity of one of the opposite lateral peripheral walls  4  and  5  of the oven. 
     The convection turbine  9  is mounted to rotate about a rotation axis  11  perpendicular to the posterior peripheral wall  7  to which it is adjacent. 
     Accordingly, the convection turbine  9  aspirates air axially toward the center of the posterior peripheral wall  7  and discharges air radially toward the edges of the posterior peripheral wall  7 . 
     According to the invention, the heating means comprise a gas burner  14 , placed axially in the aspiration inlet of the convection turbine  9 , and adapted to heat the air that is propelled into the muffle by the convection turbine  9 . The gas burner  14  is directed toward the posterior wall  7  of the oven, i.e. directs the flame that it produces toward the posterior wall  7  of the oven. Simultaneously, the gas burner  14  is directed toward the center of the turbine  9 , i.e. directs the flame that it produces toward the center of the turbine  9 . It is supplied via a supply pipe  16 . A pipe  17  for evacuating burned gases passes through its central portion. 
       FIGS. 4 and 5  depict a preferred embodiment of the gas burner  14  according to the invention. 
     The generally annular gas burner  14  comprises a posterior heating plate  30 , with holes through which gas can flow, such as the hole  31 , distributed over its surface. As shown in  FIG. 4 , for example, approximately 60 to 80 radial rows of five holes can be provided and be formed in a posterior heating plate  30  that is relatively thick and in which the length of the holes  31  through which gas can flow exceeds their diameter. 
     The posterior heating plate  30  closes off an annular cavity  32  of a burner body  33  delimited by a hemispherical peripheral wall  34  and by a coaxial tubular central wall  35 . The tubular central wall  35  defines a crossing central passage  36 , through which passes the pipe  17  for evacuating burned gases which is not shown in  FIGS. 4 and 5  but has already been referred to with reference to  FIGS. 1 to 3 . 
     The posterior heating plate  30  comprises at least one ignition electrode  37  and one flame control electrode  38 . 
     The annular cavity  32  of the burner body  33  communicates with the supply pipe  16 , part of which is depicted in  FIGS. 4 and 5 . 
     The electrodes  37  and  38  are advantageously connected to a control device, not shown, by respective connecting lines  39  and  40  disposed inside the supply pipe  16 . 
     As can be seen in  FIGS. 1 to 3 , the annular gas burner  14  is oriented with its axis substantially horizontal and perpendicular to the adjacent peripheral wall  7  or back wall of the oven. The pipe  17  for evacuating burned gases therefore has a first section passing coaxially through the central passage  36  of the gas burner  14 , so that the burned gases exhaust axially away from the adjacent peripheral wall  7  and are then guided toward the upper portion of the oven in the burned gases evacuation pipe  17 . 
     Means for receiving the food to be cooked are also provided inside the muffle  1 . In the embodiment depicted in the figures, a cooking volume  81  is reserved inside the interior cavity  8  of the muffle to receive food to be cooked, and a simple frame is provided to support removable shelves, adapted to enter the muffle through the door provided in the anterior peripheral wall  6 . The shelf support frame comprises uprights connected by top crossmembers to constitute an open and generally parallelepipedal structure allowing free circulation of air inside the oven. The shelf support frame structure carries lateral slideways, for example in the form of U-shaped profiles, perpendicular to the anterior peripheral wall  6 , and conformed to receive in a sliding fashion and to support the lateral edges of horizontal shelves on which food to be cooked can be placed. 
     The convection turbine  9  and the gas burner  14  are placed in the muffle  1  in direct communication with the cooking volume  81 , with no separating wall opposing the flow of air. There is merely provided a mechanical protection grid  22 , which is conformed and interposed between the cooking volume  81  and the combination of the convection turbine  9  and the gas burner  14 , to prevent mechanical contact of a user&#39;s hand with the blades of the rotating turbine or with the gas burner  14 . Thus, the mechanical protection grid  22  is placed on the upstream side of the gas burner  14 . The mechanical protection grid  22  is of closed and enveloping cylindrical shape, with a cylindrical peripheral portion  23  and a plane front portion  24 . The mechanical protection grid  22  has mesh size that is sufficiently large not to impede the flow of air toward or away from the convection turbine  9 , and sufficiently small for a user&#39;s fingers not to pass through them and to encourage the distribution of the convection air flow around the gas burner  14 . 
     In the embodiment shown, the central region of the front portion  24  of the mechanical protection grid  22  carries a filter  29  or a grid of finer mesh, encouraging a more regular flow of convection air around the gas burner  14  to stabilize the flame. 
     Clearly, in the oven structure as defined above, the air discharged radially by the convection turbine  9  is guided only by the peripheral walls of the muffle  1 , and is distributed more freely throughout the cooking volume  81 . This achieves more even cooking. 
     Simultaneously, there is nothing to oppose the free movement of splashed food particles that come from the food to be cooked in the cooking volume  81  and that can propagate into the whole of the interior cavity  8  of the muffle  1 , and especially toward the convection turbine  9  and the gas burner  14 . However, the free flow of air produces an effect of self-cleaning of the oven, and the particles do not remain in the area occupied by the convection turbine  9  and the gas burner  14 . 
     To assure good convection of air, a convection turbine  9  with a generally cylindrical structure can advantageously be used, with a posterior flange  25  in the shape of a disc carrying a plurality of short blades  26  at the front and distributed around its periphery. The diameter D of the convection turbine  9  is preferably more than one third of the larger dimension (width or height) of the adjacent posterior peripheral wall  7 . 
     In the embodiment depicted, the convection turbine  9  has at least twelve blades  26  at the front that have a radial dimension less than one tenth of its diameter D. 
     The embodiment depicted further comprises a cleaning device  27  that sprays water into the muffle  1 . 
     The cleaning device  27  can comprise a horizontal cup adjacent the center of the upper ceiling wall  3 , with central water supply means to produce a flow of water toward the periphery of the cup, parallel to the upper ceiling wall  3 . The water is sprayed radially at the periphery of the cup, preferably when the oven is still relatively warm, and the water then flows over all of the peripheral walls of the oven as well as over the convection turbine  9  and the heating means. 
     The means according to the invention assure correct cooking not only by simple convection of hot gas, but also mixed cooking in the presence of steam. 
     The invention can provide better control of combustion by supplying the gas burner  14  with an appropriate mixture of gas and air at a particular pressure. To this end, a device for producing blown air  16   a  ( FIG. 3 ) is connected into the supply circuit  16  of the gas burner  14 , on the upstream side, to supply the gas burner  14  with blown air. The power of the device for producing blown air  16   a  is advantageously adjustable. 
     The present invention is not limited to the embodiments that have been described explicitly, but includes variants and generalizations thereof within the scope of the following claims.

Technology Category: f