Patent Publication Number: US-2005139204-A1

Title: Ventilated gas oven for food products and heat exchanger for said oven

Description:
The present invention relates to a ventilated gas oven for food products and a heat exchanger for said oven.  
      A ventilated oven for the cooking and/or heating of food products, in particular for pizza and possibly other oven-baked products, such as pastry and rotisserie products, composed of a cooking chamber equipped with an electrically or gas supplied heat source.  
      A ventilated oven can be composed of a tunnel type wherein one feeder for the products to be cooked is composed of a conveyor in a material such as a metal grid that crosses the cooking chamber.  
      Alternatively, the ventilated oven cooking chamber can, on the contrary, be closed and equipped with a fixed cooking plate underneath, for example, a plate in refractory material.  
      Moreover, ventilated ovens are also equipped with means for air circulation, in particular, axial or centrifugal fans, as well as air diffusion elements composed of hollow bodies that extend inside the cooking chamber over and beneath the cooking plate. The faces turned towards the cooking plate are perforated with a plurality of small circular conical and funnel-shaped holes, distributed over the total face surface. The diffuser elements formed in this manner take in air from the proximity of the motorised fan and distribute said air in the cooking chamber through the holes.  
      Gas supplied ovens generally introduce the hot fumes produced by gas combustion or some other similar fuels in the burner, directly into the cooking chamber.  
      However, this technical solution can provoke serious pollution in the product to be cooked inside the oven cooking chamber, as well as in the environment where the oven is installed. In fact, the product to be cooked is directly surrounded by the exhaust fumes that are then dispersed into the environment, especially in the case of tunnel ovens.  
      A further problem with ventilated ovens is that the problem concerning homogeneous heat diffusion inside the cooking chamber has not yet been satisfactorily resolved, provoking a negative influence on the quality of the cooked product as well as the energy yield of the oven.  
      A further problem related to ventilated ovens, and in particular, tunnel type ventilated ovens, is the heat loss towards the exterior following the metal grid conveyor action that enters and exits from the cooking chamber, and the hot air that exits from the conveyor entrance and exit openings.  
      The aim of the present invention is to provide a ventilated gas oven for food products, as well as a heat exchanger for said oven that will supply optimised heat distribution in the cooking chamber.  
      A further aim is to provide a ventilated gas oven and a heat exchanger that will avoid pollution of food products in the oven as well as pollution of the environment outside the oven, caused by combustion fumes.  
      Yet another aim of the present invention is to provide an efficient heat exchanger easily interchangeable with other heat exchangers having different characteristics. Another aim is to provide a ventilated gas oven for food products and a heat exchanger for said oven that reduce cooking times as well as energy consumption.  
      A further aim is to provide a ventilated oven that is highly efficient, and easy to transport and install.  
      According to the present invention these aims are achieved with the embodiment of a ventilated gas oven for food products and a heat exchanger for said oven as defined in the independent claims.  
      Further characteristics are defined in the dependent claims. 
    
    
      The characteristics and advantages of a ventilated gas oven for food products and a heat exchanger for said oven according to the present invention will be made more clear in the following description, provided as an example but by no means limitative, with reference to the appended schematic drawings wherein:  
       FIGS. 1 and 2  show perspective views of the front and rear sides respectively, of a ventilated gas oven for food products object of the present invention;  
       FIG. 3  is a perspective view of the rear side of the ventilated oven shown in  FIGS. 1 and 2 , wherein the rear panel has been removed;  
       FIG. 4  shows a perspective view of certain parts of the cooking chamber and the diffuser elements of the oven shown in  FIGS. 1 and 2 , partially disassembled;  
       FIG. 5  is an enlarged perspective view of a diffuser element;  
       FIGS. 6 and 7  are perspective views of a heat exchanger for a ventilated gas oven according to two different embodiments of the present invention. 
    
    
      In reference to said figures, the ventilated gas oven for food products, in particular a tunnel type oven is identified throughout the drawings with reference numeral  10 , and also comprises a cooking chamber  12  crossed in its lower part by a conveyor feeder and cooking plate  13  for food products, a source that supplies heat to the interior of the cooking chamber  12 , a motorised centrifugal fan  15 , arranged in a lateral position to the cooking chamber  12 , as well as air diffusion elements  16  inside the cooking chamber  12 . The heat source comprises a gas burner or burner for some other similar fuel  101 , and a heat exchanger  100  or  100 ′, placed in communication with the burner  101 , and in proximity to the motorised fan  15  and the cooking chamber  12 .  
      The tunnel type ventilated oven shown in FIGS.  1  to  4 , simply as an example, is equipped with a grid type conveyor that also acts as a cooking plate  13 .  
      The cooking chamber  12  of the oven  10  comprises lower  17  and upper  18  walls, a front wall  19  that can possibly be opened, a rear wall  20 , and side walls  21   a ,  21   b , open in order to introduce the products arranged on conveyor  13 . The side walls  21   a  and  21   b  can also possibly have walls that can be adjusted in height to modify the size of the openings and reduce heat dispersion.  
      The rear wall  20  is equipped with a plurality of openings or holes adapted to act as communication between the cooking chamber  12  and a secondary chamber  22 , in which the motorised centrifugal fan  15  is housed, as well as at least part of the heat exchanger  100  or  100 ′.  
      The openings in the rear wall  20  create a supply and return route for the hot air. In fact the diffuser elements  16  are connected to the rear wall  20  at the first rectangular openings  23  which have a complementary size to the section of the diffusers  16  and which extend into the cooking chamber  12  over and beneath the cooking plate  13  as far as the front wall  19 , to form the hot air supply route.  
      The diffuser elements  16  are composed of a hollow box-like body having a decreasing internal section  26  and a panel  27  perforated with a plurality of conical or funnel-shaped holes  24  for air distribution in chamber  12 , as shown in the blow-up detail in  FIG. 5 .  
      The diffuser elements  16  are applied in the cooking chamber  12  using a rapid click-on/release system. Each diffuser element  16  is equipped with two fins bent towards the exterior along the larger edges facing the openings  23  respectively. A first fin  29  in proximity to panel  27  is engaged in the opening  23  of the rear wall  20 , while a second fin  30  is pressure forced elastically against the upper wall  18  and the lower wall  17  of the cooking chamber  12  during diffuser  16  assembly.  
      At the opposite end, the diffuser element  16  is maintained in position by a flexible fixing element  31  attached to the front wall  19  of the cooking chamber  12 . Using said fixing element  31 , it is possible to easily slide the diffuser element  16  in and out without the need for any particular tools.  
      The air sent into the cooking chamber is re-conveyed back to the secondary chamber  22  through further openings in the rear wall  20 . In particular this refers to two openings  33 , one upper and one lower, positioned between the openings  23  for the diffuser elements  16 . Said further openings  33 , connect a perforated compartment  34  to the secondary chamber  22 , and extend from the rear wall  20  through to the front wall  19  of the cooking chamber  12 .  
      The holes  38 , that in the figure are represented as an example on the side walls of compartment  34 , provide a means of communication between the cooking chamber  12  with the interior of compartment  34 , and therefore with the secondary chamber  22 , in this manner creating a return route for the hot air towards the motorised fan  15 .  
      Moreover, a pipe  35  is inserted into the perforated compartment  34 , to recover the hot air in proximity to the side walls  21   a  and  21   b , equipped externally with a collector plate or hood  36 , and/or possibly holes  37 , as shown in a cross-section detail in  FIG. 2 , for the extraction of the air into pipe  35 .  
      FIGS.  1  to  4  show a ventilated gas oven wherein the hermetically sealed heat exchanger  100 , is positioned partially around fan  15  that is applied to a rear panel  40  adapted to close the secondary chamber  22  (shown in  FIG. 2 ) and partially inside the cooking chamber  12 . In a first embodiment shown in perspective in  FIG. 6 , the heat exchanger  100  comprises a combustion chamber  102 , inserted at one end with the burner  101  and at the opposite end with the pipe  103  composed of at least one tubular element, arranged on a plane perpendicular to the motorised fan  15  axis connecting two radiating bodies  104  both to the combustion chamber  102 , and comprising an upper and lower body that extend in a perpendicular manner to the pipe  103  in a direction parallel to the motorised fan axis  15 , for insertion transversally into the cooking chamber  12  of the ventilated gas oven  10 .  FIG. 6  shows the pipe  103  comprising for example, two circular section pipes positioned adjacent to each other, but which could be replaced by a single pipe with a rectangular section for example.  
      Lastly, pipe  103  is inserted into a fume collector chamber  105  that conveys the fumes to a flue  106  shown in  FIG. 2 .  
      The radiating bodies  104  shown in a preferred embodiment in  FIG. 6  comprise a first portion  107  having a concave surface on the side facing the motorised fan  15  to reduce the height volume of the heat exchanger  100 . A second portion  108  of the radiating body  104  has a parallelepiped form adapted for insertion into the hollow compartment  34  that extends from the rear wall  20  of oven  10  to the front wall  19 , and equipped with holes  38  for the recovery of the hot air from the cooking chamber  12 . In fact,  FIG. 4  shows the upper radiating body  104  inserted inside the perforated compartment  34 , while the lower perforated compartment has been removed from the figure to show the position of the lower radiating body  104 .  
      The radiation bodies  104  are divided internally by a dividing panel or partition  109 , extending between the first portion  107  of the said body and a considerable part of the second portion  108  that divides the body  104  into two communicating channels in proximity to the end to form a forced “U-shaped” route for the fumes, as shown schematically by the arrows in  FIG. 6 .  
      The hot combustion fumes produced by the burner  101  in chamber  102  are sent to circulate through pipe  103  and forced to follow through a first channel of the lower radiating body  104  right through to the end in proximity to the front wall  19  of the cooking chamber  12 , to then return towards pipe  103  through the channel on the opposite side. Therefore pipe  103  conveys the fumes that, having radiated heat inside the cooking chamber  12 , flow towards the upper radiating body  104 , that is then crossed by the fumes in the same manner as that described for the lower radiating body. After crossing the radiating body  104 , the fumes are introduced into chamber  105  before evacuation through flue  106 .  
      The radiating bodies  104  that have been crossed completely by the high temperature combustion fumes radiate heat towards the cooking chamber  12 , heating the air and through radiation, also contributing to the cooking of the food products with the circulation of the hot air.  
      Moreover, in the ventilated gas oven  10  object of the present invention, the radiating bodies  104  are inserted inside the compartments  34  through which the hot air from the cooking chamber  12  is recovered and reconveyed to the motorised centrifugal fan  15 . On the return route the air that surrounds the radiating bodies  104  at a very high temperature, extracts heat from the fumes, thus heating the air. Therefore the motorised centrifugal fan  15  sends air at an already high temperature into the cooking chamber  12 , increasing the oven performance considerably.  
       FIG. 7  shows a second possible embodiment of the heat exchanger  100 ′ object of the present invention.  
      In this case, the pipe  103  is composed of two independent tubes  103   a  and  103   b , wherein a first tube  103   a  is connected to the lower radiation body  104 , and a second tube  103   b  is connected to the upper radiating body  104 , both tubes therefore being inserted in the exhaust fume collector chamber  105 .  
      Combustion fume circulation occurs therefore in both radiating bodies  104 , basically as previously described following through a “U-shaped” channel formed by partition  109 . In this case the fumes have basically the same high temperature in both radiating bodies  104 , since they arrive directly from the combustion chamber  102  and have not yet lost their heating capacity.  
      In this second embodiment of a heat exchanger  100 ′ the radiation from the upper body and that from the lower body provide a considerable addition in heat for product cooking.  
      A further embodiment, not shown, of a heat exchanger according to the present invention, foresees the presence of a single radiating body, preferably the lower body.  
      The heat exchangers described as an example can be based on different types of heating and cooking of the food products with different temperature ratios between the upper wall and the bedplate, and are easily interchangeable with each other to adapt the oven to the type of product to be cooked, due to the fact that they are inserted in a manner so that they are easily removable inside the cooking chamber.  
      A further embodiment, (not shown) of a ventilated gas oven object of the present invention, could be equipped with a closed cooking chamber comprising a fixed cooking plate in lower position. The heating and ventilation components will be identical to those described.  
      A further object of the present invention is a heat exchanger as described and illustrated.  
      The main advantage of the ventilated gas oven for food products and the heat exchanger for said oven, object of the present invention, consists in realising the cooking action of food products through the circulation of clean hot air completely separate from the circulating hot combustion fumes which therefore do not enter into contact with the food products to be cooked. Moreover, the products contained in the cooking chamber of the oven object of the present invention are advantageously heated both through radiation, as well as through hot air circulation.  
      A further advantage of the ventilated gas oven for food products and the heat exchanger for said oven according to this invention consists in the circulation of hot air in the cooking chamber that reaches every zone of the chamber in a uniform manner, and is also recovered to minimize thermal dispersion.  
      Moreover during the return route towards the motorised fan, the air is advantageously recalled from a hot zone, thus increasing the oven yield and consequently increasing energy saving.  
      The ventilated gas oven for food products and the heat exchanger for said oven according to this invention, conceived in this manner can be subject to numerous modifications and variants, while remaining within the concept of the invention; moreover all details can be replaced with technically equivalent elements. In particular the materials employed, and their dimensions can be of any type according to technical requirements.