Abstract:
An oven for heating food products on a conveyor includes two chambers. A conveyor belt circulates within each chamber and between the chambers. Each chamber includes a drum oriented with a vertical axis, a motor for rotating the drum about the axis, and a conveyor belt having a length helically surrounding the drum. The conveyor belt has an infeed end and outlet end. A plenum is located within the chamber along an outer extent of the chamber and is curved substantially concentrically with the drum. The plenum forms a substantially closed air pathway having an inlet at one end and an outlet at an opposite end passing air into the first chamber. A fan is arranged to circulate air within the chamber and force air into the plenum inlet, through the plenum and out of the plenum outlet. A heat exchanger is arranged in the plenum to heat the air flowing within the plenum.

Description:
[0001]    This application claims the benefit of U.S. Provisional Application 61/591,717, filed Jan. 27, 2012; U.S. Provisional Application 61/591,955 filed Jan. 29, 2012 and U.S. Provisional Application 61/593326, filed Feb. 1, 2012. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    Various spiral oven systems are known. 
         [0003]    For example, U.S. Pat. No. 5,850,781 describes a multi-heating zone, single spiral oven. A spiral conveyor helically winds around a rotating drum. Heating is provided in zones within the oven. The zones are arranged vertically, i.e., an upper zone and a lower zone. Each zone has at least one ventilation device and heating device for circulating hot air through the zone. Each zone preferably has two ventilators, each with a heating device, which cover approximately half of each spiral conveyor winding. 
         [0004]    U.S. Pat. Nos. 7,107,899 and 5,329,916 describe dual spiral ovens. In these patents two rotating drums within the oven are helically surrounded by conveyors wherein the output of one spiral conveyor communicates products onto the input of the next spiral conveyor. Heating elements in U.S. Pat. No. 7,107,899 are arranged as helical electrical coils or hollow tubes that underlie the spiral conveyor. The heating elements in U.S. Pat. No. 5,329,916 are arranged in overhead air ducts. 
         [0005]    The present inventor has recognized that it would be desirable to provide a compact spiral oven that provides an optimized and efficient cooking. 
       SUMMARY OF THE INVENTION 
       [0006]    The exemplary embodiment of the invention provides an oven having a rotating drum and a conveyor surrounding or wrapping the drum helically for transporting products to be cooked along a path from an inlet of the oven to an outlet, a ventilator for circulating air through the oven, and a heat exchanger for heating the air circulated by the ventilator. A housing provides a chamber that surrounds the drum and the conveyor that wraps the drum. A curved plenum is configured adjacent to the chamber wherein the plenum is curved substantially concentrically with the drum. The ventilator forces air in a tangential direction with regard to the drum through the plenum, through a heat exchanger that is configured to curve with the curve of the plenum. The heat exchanger preferably comprises transversely arranged hollow tubes that contain a circulating thermal fluid that is heated outside of the oven. 
         [0007]    Preferably, the oven includes two drums and two spiral conveyors that surround each of the drums respectively. The output of one conveyor delivers product being cooked to an input of the next spiral conveyor. 
         [0008]    The oven is designed for cooking a high amount of meat and chicken products. 
         [0009]    The drums form the largest components of the system, and provide the main source of drive for the conveyor belt, which can be 120 meter in length. The spiral conveyor system can be configured with the conveyor belt entering at the bottom of the drum and exiting at the top. Alternately, the in-feed and out-feed of the spiral conveyors can be the opposite of this arrangement. During the belt&#39;s helical travel, its edge is held in tight contact with the drum, so that the friction created by the wraps of the belt around the drum is sufficient to drive the belt through the system. The drum is driven from underneath by an electric motor and can be either direct or chain-driven. The mechanism that keeps the belt tight against the drum is a secondary drive, or take-up or auxiliary drive. The auxiliary drive provides just enough pull on the belt to keep the belt in tight contact with the drum and to help set belt speed, not to provide the driving force to the belt. This keeps belt tension low. 
         [0010]    Numerous other advantages and features of the present invention will be become readily apparent from the following detailed description of the invention and the embodiments thereof, and from the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  is a front perspective view of the dual spiral oven according to one embodiment of the present invention; 
           [0012]      FIG. 2  is a front perspective view of the dual spiral oven of  FIG. 1  with an outer skin or housing removed to view underlying components; 
           [0013]      FIG. 3  is a schematic top view showing an air flow arrangement for the oven; 
           [0014]      FIG. 4  is a further schematic top view showing the air flow arrangement in the oven; 
           [0015]      FIGS. 5 and 6  are schematic diagrams of spiral oven conveyor belts; 
           [0016]      FIG. 7  is another schematic top view of the oven shown in  FIG. 2 ; 
           [0017]      FIG. 8  is an enlarged perspective view taken generally along line  8 - 8  from  FIG. 7  with some walls removed to view otherwise obscured parts; 
           [0018]      FIG. 9  is a top view taken from  FIG. 8 ; 
           [0019]      FIG. 10  is a perspective view similar to  FIG. 8  but rotated a small amount with some walls removed to view otherwise obscured parts; 
           [0020]      FIG. 11  is a perspective view similar to  FIG. 10  but rotated a small amount with some walls removed to view otherwise obscured parts; 
           [0021]      FIG. 12  is a schematic, partially fragmentary perspective view of a plenum taken from  FIG. 4 . 
       
    
    
     DETAILED DESCRIPTION 
       [0022]    While this invention is susceptible of embodiment in many different forms, there are shown in the drawings, and will be described herein in detail, specific embodiments thereof with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the invention to the specific embodiments illustrated. 
         [0023]    U.S. Pat. Nos. 5,850,781; 7,107,899 and 5,329,916 are all herein incorporated by reference where not inconsistent with the present disclosure. 
         [0024]      FIG. 1  illustrates an oven  30  having a housing  32  and conveyor infeed station  34  and a conveyor discharge station  36 . Products, such as chicken pieces are loaded onto the conveyor infeed station, pass through the housing  32  and are output at the conveyor discharge station  36 . The housing includes a hood  40  that can be raise by four lifting jacks  43 . The housing  32  provides outside walls that substantially enclose the oven. 
         [0025]      FIGS. 2 and 6  illustrate the oven with the housing removed for viewing underlying components. The oven comprises a first drum  44  and a second drum  48 . Preferably, drums  44 ,  48  are solid cylinders. A conveyor belt  54 , such as a stainless steel wire mesh belt, is a continuous belt that moves from the product infeed, and helically wraps around the first drum  44  and the second drum  48  and passes to the discharge station  36 , and over a secondary drive  60  and back to the product infeed station  34 . 
         [0026]    The secondary drive  60  maintains a tension on the belt  54 . The drums  44 ,  48  are rotated by a motor drive (not shown) and engagement of the drums and an inside edge of the belt  54  circulates the belts helically on the drums and between the infeed station  34  and the discharge station  36  and back. 
         [0027]    As shown in  FIGS. 3 and 4 , each drum and associated length of spiral conveyor is arranged in a separate cooking volume of the housing. The drum  44  and a first associated length  54   a  of spiral conveyor  54  are located in a first chamber  66  and the drum  46  and a second associated length  54   b  of spiral conveyor are located in a second chamber  68 . The chamber  66  is heated by at least one ventilator or fan  70  contained in a substantially enclosed fan chamber  71 . The fan  70  is driven by a motor  70   m  from outside the fan chamber. The fan  70  has a rotary axis approximately radially oriented to the circumference of the drum  44 . The fan  70  draws air from chamber  66  in a substantially radial direction R into an inlet  70   a.  The fan  70  is mounted to the fan chamber  71  with the inlet  70   a  in registry with a fan chamber inlet opening  71   a . The fan chamber inlet  71   a  is preferably a funnel or flared inlet, tapered toward the fan inlet, to reduce pressure drop. The air is forced by the fan (s)  70  through an outlet  71   b  of the fan chamber into a curved plenum  72  that has an inner curvature that substantially conforms to the outer circumference of the spiral belt  54   a  within the chamber  66 . The plenum is curved substantially concentrically with the drum  44 . The air is moved through the plenum in a tangential direction T. A curved heat exchanger  76  is located within the plenum that conforms in curvature to the curvature of the plenum  72  to maximize heat exchange surface area in the compact oven. The heat exchanger  76  is preferably comprised of tubes which are transversely oriented and which carry hot heat transfer fluid. The heat exchanger  76  can be made up of vertically aligned exchanger banks  76   a,    76   b,    76   c,  as shown in  FIG. 8 . The heat transfer fluid can be heated outside the oven by a gas or oil fired source, or an electric source, or the like. Heat transfer fluid is conducted to and from the heat exchanger banks  76   a,    76   b,    76   c  by pipes  77 . The plenum  72  is designed to output heated air into the chamber  66  in the tangential direction T so that the air is circulated substantially around the chamber before returning the inlet of the fan  70 . 
         [0028]    Preferably two fans  70  are provided at different elevations but arranged identically when viewed from above, in plan. Both fans force air into the plenum  72  in the same way. 
         [0029]    The chamber  68  is heated by at least one ventilator or fan  80  contained in a substantially enclosed fan chamber  81 . The fan  80  is driven by a motor  80   m  from outside the fan chamber. The fan  80  has a rotary axis approximately radially oriented to the circumference of the drum  48 . The fan  80  draws air from chamber  68  in a substantially radial direction R into an inlet  80   a.  The fan  80  is mounted to the fan chamber with the inlet  80   a  in registry with a fan chamber inlet  81   a . The fan chamber inlet  81   a  is preferably a funnel or flared inlet, tapered toward the fan inlet, to reduce pressure drop. The air is forced by the fan (s)  80  through an outlet  81   b  of the fan chamber into a curved plenum  82  that has an inner curvature that substantially conforms to the outer circumference of the spiral belt  54   b  within the chamber  68 . The plenum is curved substantially concentrically with the drum. The air is moved through the plenum in a tangential direction T. A curved heat exchanger  86  is located within the plenum that conforms in curvature to the curvature of the plenum  82  to maximize heat exchange surface area in the compact oven. The heat exchanger  86  is preferably comprised of tubes which are transversely oriented and which carry hot heat transfer fluid. The heat exchanger  86  can be made up of vertically aligned exchanger banks  86   a,    86   b,    86   c  as shown in  FIG. 8 . The heat transfer fluid can be heated outside the oven by a gas or oil fired source, or an electric source, or the like. Heat transfer fluid is conducted to and from the exchanger banks  86   a,    86   b,    86   c  by pipes  87 . The plenum  82  is designed to output heated air into the chamber  68  in the tangential direction T so that the air is circulated substantially around the chamber before returning the inlet of the fan  80 . 
         [0030]    Preferably two fans  80  are provided at different elevations but arranged identically when viewed from above, in plan. Both fans force air into the plenum  82  in the same way. 
         [0031]    The drums  66  and  68  are rotated clockwise when viewed from above in  FIG. 3 . The belt  54  in the chamber  66  circulates helically up the drum  44  and the belt in the chamber  68  helically circulates helically down the drum  48 . 
         [0032]    The structure of the fans, heat exchangers and plenums are mirror image identical across a vertical center plane CP of the oven  30 . The air flow rotation direction in the chamber  66  is with the drum rotation and belt circulation direction, and the air flow rotation direction in the chamber  68  is counter to the drum rotation direction and belt circulating direction. 
         [0033]    The chambers  66 ,  68  are defined by outside walls of the housing  32  and separated by inside walls  102 ,  104 ,  106 ,  108  ( FIG. 4 ) provided in the housing  32 . The walls  102 ,  104  are curved and form side walls of the plenums  72 ,  82  and extend vertically from a bottom wall of the housing to a top wall of the housing. Opposite sidewalls  103 ,  105  are curved and form side walls of the plenums  72 ,  82 . Different cooking temperatures and conditions can be maintained within the chambers  66 ,  68 , for controlled cooking. Products, such as chicken pieces are input into the infeed station  34 , move on the conveyor  54  up the drum  44  across to the drum 48 , down the drum  48  to the discharge station  36 . Hot cooking gas, such as air is introduced into the first and second chambers  66 ,  68  to cook the products while resident in the respective chambers  66 ,  68 . 
         [0034]      FIG. 7  illustrates that each chamber  66 ,  68  includes an overhead cleaning manifold  202 ,  204 . A pressurized water and soap mixture or solution is provided to the manifolds  202 ,  204  and periodically, during a cleaning procedure, a plurality of nozzles  210  spray water and soap mixture or solution S into the respective chamber. 
         [0035]      FIGS. 8 ,  10  and  11  illustrate construction of the exchangers  76 ,  86  with the walls  102 , 104  removed in the figures. 
         [0036]      FIG. 8  illustrates a further cleaning manifold  230  arranged above the exchanger  76 . A cleaning manifold  250  is arranged above the exchanger  86  and is a mirror image duplicate of the manifold  230  across the vertical center plane CP of the oven. The manifolds  230 ,  250  contain a pressurized water and soap mixture or solution. 
         [0037]    The manifold  230  has a plurality of nozzles  210  for spraying water and soap mixture or solution S onto the top exchanger bank  76   a  during a periodic cleaning procedure. Further manifolds arranged between the banks can be used to spray water and soap mixture or solution S onto the banks  76   b  and  76   c  respectively. The manifold  250  has a plurality of nozzles  210  arranged to spray water and soap mixture or solution onto the top exchanger bank  86   a  during a periodic cleaning procedure. Further manifolds arranged between the banks can be used to spray water and soap mixture or solution onto banks  86   b  and  86   c  respectively. 
         [0038]      FIG. 8  also shows an extension guide plate  260  and an adjustable spoiler plate  266  that is hinged by a plurality of hinges  270  to the extension guide plate  260  arranged between the heat exchanger  76  and the chamber  66 . The extension plate  260  and the spoiler plate  266  can be part of the respective wall  103 ,  105  of an extension thereof and have a vertical length equal to the respective wall  103 ,  105 . An identical extension guide plate and spoiler plate are arranged between the heat exchanger  86  and the chamber  68 , configured as a mirror image duplicate of the guide plate  260  and the adjustable spoiler plate  266  across the vertical center plane CP of the oven. 
         [0039]    The combination of the two plates  260 ,  266 , with proper adjustment thereof allows for fine tuning of the air flow delivered by the fans  70 ,  80  to the chambers  66 ,  68 . The hinges  270  include a portion  271  fixed to the extension guide plate  260  and a portion  272  fixed to the spoiler plate  266 . The portions  271 ,  272  are rotatable with respect to each other about a bolt  273 , when the bolt is loosened for adjustment of the angle between the plates  260 ,  266 . One the angle is adjusted the bolt  273  is tightened which prevents any further rotation of the plates  260 ,  266 . 
         [0040]    Particularly, the air flows circumferentially around the respective drum  44 ,  48  in the respective chambers  66 ,  68 . 
         [0041]      FIGS. 10 and 11  illustrate a vertically arranged steam header  320  that is adjacent the heat exchanger banks  76   a,    76   b,    76   c.  The header  320  contains pressurized steam. The header has a plurality of holes  320   a  arranged spaced-apart in the vertical direction. A mirror image identical header  330  with holes  330   a  is provided at the outlet of the exchanger  86 . Steam under pressure is ejected from the holes  320   a ,  330   a  into the air stream downstream of the exchangers  76 ,  86  such that a proper cooking humidity is maintained in the oven chambers  66 ,  68 . 
         [0042]    The plenums  72 ,  82  are mirror image identical across the vertical center plane CP of the oven. Therefore, only the plenum  82  will be described in detail in  FIG. 12 . 
         [0043]      FIG. 12  illustrates the plenum  82 . The plenum includes the curved vertical sidewalls  102 ,  103  that are substantially concentric with the drum  48 . A top wall  400  substantially closes the space between the walls  102 ,  103  at a top end thereof and a bottom wall  404  substantially closes the space between the walls  102 ,  103  at a bottom end thereof. A fan chamber wall  408  provides at least one and preferably two outlets  81   b ,  81   b  for two fans  80 . Although a flat wall  408  is shown in  FIG. 12 , it is beneficial to provide an expanding or funnel outlet  81   d , expanding in a direction away from the fans and toward the heat exchangers in the direction T ( FIG. 3 ) as shown in  FIG. 7 , to minimize pressure drop. Otherwise, the wall  408  closes an opening defined by the walls  102 ,  103 ,  400 ,  404 . An outlet open face  412  defined by the walls  102 ,  103 ,  400 ,  404 , at an end opposite the wall  408 , allows air to pass from the plenum  82  into the chamber  68 . The extension  260 , and the spoiler  266 , as an adjustable part of inside wall  103 , can be adjusted to most effectively direct forced air flow around the circumference of the drum  48 . The walls  102 ,  103 ,  400 ,  404  form a curved rectangular tube for directing air in a curved path from the outlets  81   b ,  81   b  within the chamber  68 . The heat exchanger  86  is contained within the walls  102 ,  103 ,  400 ,  404 . The walls  400 ,  404  can be regions or portions of an overall housing hood and floor respectively. 
         [0044]    From the foregoing, it will be observed that numerous variations and modifications may be effected without departing from the spirit and scope of the invention. It is to be understood that no limitation with respect to the specific apparatus illustrated herein is intended or should be inferred. 
         [0045]    All references, including publications, patent applications, and patents, cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein, to the extent that the references are not inconsistent with the present disclosure.