Dual drum spiral oven

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.

The invention claimed is: 
     
         1 . An oven comprising:
 a first drum oriented with a first vertical axis and a first motor for rotating the first drum about the axis;   a first length of conveyor belt helically surrounding the first drum, and having an infeed end and outlet end;   a first chamber defined by walls surrounding the first drum and the first length of conveyor belt;   a first plenum positioned within the first chamber, curved substantially concentrically with the first drum, and surrounding at least a portion of the first length of conveyor belt, the first plenum forming 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 first fan arranged to circulate air within the first chamber and force air into the first plenum inlet, through the first plenum and out of the first plenum outlet;   a first heat exchanger arranged in the first plenum;   a second drum oriented with a second vertical axis and a second motor for rotating the second drum about the axis;   a second length of conveyor belt helically surrounding the second drum, and having an inlet end to receive products from the outlet end of the first length of conveyor belt and a discharge end;   a second chamber defined by walls surrounding the second drum and the second length of conveyor belt;   a second plenum within the second chamber and being curved substantially concentrically with the second drum, the second plenum forming a substantially closed air pathway having an inlet and an outlet passing air into the second chamber;   a second fan arranged to circulate air within the second chamber and force air into the second plenum inlet, through the second plenum and out of the second plenum outlet; and   a second heat exchanger arranged in the second plenum;   wherein the first fan is arranged in a first fan chamber that has a radially oriented inlet with respect to the first drum and a tangentially oriented outlet with respect to the first drum that is in substantially enclosed air flow communication with the inlet of the first plenum;   wherein the outlet of the first plenum and the inlet of the first fan chamber are arranged to cause air circulated in the first chamber to substantially circulate around the first drum;   wherein the second fan is arranged in a second fan chamber that has a radially oriented inlet with respect to the second drum and a tangentially oriented outlet with respect to the second drum that is in substantially enclosed air flow communication with the inlet of the second plenum; and   wherein the outlet of the second plenum and the second fan chamber inlet are arranged to cause air circulated in the second chamber to substantially circulate around the second drum.   
     
     
         2 . The oven of  claim 1 , wherein the air circulated in the first chamber substantially circulates around the first drum from the first plenum outlet to the inlet of the first fan chamber, and wherein the air circulated in the second chamber substantially circulates around the second drum from the second plenum outlet to the inlet of the second fan chamber. 
     
     
         3 . The oven of  claim 1 , wherein the first heat exchanger has a curvature to conform to a curvature of the first plenum. 
     
     
         4 . The oven of  claim 1 , wherein the first heat exchanger has a curvature to conform to a curvature of the first plenum and the second heat exchanger has a curvature to conform to a curvature of the second plenum. 
     
     
         5 . The oven of  claim 4 , wherein the first plenum and the first heat exchanger are shaped in mirror image fashion across a vertical center plane of the oven to the second plenum and the second heat exchanger. 
     
     
         6 . The oven of  claim 5 , wherein the first and second heat exchangers comprise tubes for containing a hot heat transfer fluid. 
     
     
         7 . The oven of  claim 6 , wherein the tubes are arranged transversely to an air flow direction across the tubes. 
     
     
         8 . The oven of  claim 1 , wherein the first fan chamber is inside the first chamber, and wherein the first fan is driven by an electric motor outside the first fan chamber. 
     
     
         9 . The oven of  claim 1 , wherein the first plenum is a curved rectangular tube arranged along an outer perimeter of the first chamber. 
     
     
         10 . The oven of  claim 9 , further comprising an additional fan arranged below the first fan, wherein the first fan and the additional fan are arranged in the first fan chamber. 
     
     
         11 . The oven of  claim 1 , further comprising an adjustable spoiler plate that is an extension of an inside wall of the plenum that is closest to the first drum at the plenum outlet and is hinged to the plenum, and wherein the adjustable spoiler plate is adjustable in angle to adjust a direction of re-circulated air flow from the plenum outlet within the first chamber. 
     
     
         12 . The oven of  claim 1 , further comprising a vertically arranged steam header that is adjacent the first heat exchanger, wherein the header has a plurality of holes such that steam under pressure is ejected from the holes into an air stream downstream of the first heat exchanger. 
     
     
         13 . The oven of  claim 1 , further comprising a cleaning manifold arranged above the first heat exchanger, wherein the cleaning manifold is configured to contain and dispense a pressurized water and soap mixture during a cleaning operation, and wherein the cleaning manifold includes a plurality of nozzles for spraying water and soap mixture onto a top of the first heat exchanger. 
     
     
         14 . The oven of  claim 1 , wherein the first plenum is positioned between the first length of conveyor belt and at least one of the walls defining the first chamber. 
     
     
         15 . The oven of  claim 1 , wherein the first length of conveyor belt has an outer circumference and the first plenum has an inner curvature that substantially conforms to at least a portion of the outer circumference of the first length of conveyor belt. 
     
     
         16 . An oven comprising:
 a first drum oriented with a first vertical axis and a first motor for rotating the first drum about the axis;   a first length of conveyor belt helically surrounding the first drum, and having an infeed end and outlet end;   a first chamber defined by walls surrounding the first drum and the first length of conveyor belt, wherein the first chamber has a first cooking condition;   a first plenum positioned within the first chamber and forming an air pathway having an inlet and an outlet, wherein the outlet passes air into the first chamber;   a first heat exchanger arranged in the first plenum;   a second drum oriented with a second vertical axis and a second motor for rotating the second drum about the axis;   a second length of conveyor belt helically surrounding the second drum, and having an inlet end to receive products from the outlet end of the first length of conveyor belt and a discharge end;   a second chamber defined by walls surrounding the second drum and the second length of conveyor belt, wherein the second chamber has a second cooking condition that is adapted to be controlled differently than the first cooking condition of the first chamber;   a second plenum positioned within the second chamber and forming an air pathway having an inlet and an outlet, wherein the outlet passes air into the second chamber; and   a second heat exchanger arranged in the second plenum.   
     
     
         17 . The oven of  claim 16 , wherein the first cooking condition is associated with a first temperature and the second cooking condition is associated with a second temperature, wherein the oven is adapted to be controlled to result in the first temperature being different than the second temperature. 
     
     
         18 . The oven of  claim 16 , wherein the first cooking condition is associated with a first humidity and the second cooking condition is associated with a second humidity, wherein the oven is adapted to be controlled to result in the first humidity being different than the second humidity. 
     
     
         19 . The oven of  claim 16 , wherein the first cooking condition is associated with a first temperature and a first humidity and the second cooking condition is associated with a second temperature and a second humidity, wherein the oven is adapted to control the first cooking condition and the second cooking condition to be different. 
     
     
         20 . The oven of  claim 16 , wherein the first plenum is curved substantially concentrically with the first drum and surrounds at least a portion of the first length of conveyor belt, and wherein the second plenum is curved substantially concentrically with the second drum and surrounds at least a portion of the second length of conveyor belt. 
     
     
         21 . The oven of  claim 16 , further comprising a steam header that is adjacent the first heat exchanger, wherein the steam header has a plurality of holes such that steam under pressure is adapted to be ejected from the holes into an air stream downstream of the first heat exchanger. 
     
     
         22 . The oven of  claim 21 , wherein the first cooking condition is associated with a first humidity, and wherein the steam header is adapted to be controlled to control the first humidity in the first chamber. 
     
     
         23 . The oven of  claim 21 , wherein the steam header is vertically arranged. 
     
     
         24 . The oven of  claim 16 , further comprising a first steam header adjacent the first heat exchanger and a second steam header adjacent the second heat exchanger, wherein the first steam header has a plurality of holes such that steam under pressure is adapted to be ejected from the holes into an air stream downstream of the first heat exchanger and the second steam header has a plurality of holes such that steam under pressure is adapted to be ejected from the holes into an air stream downstream of the second heat exchanger. 
     
     
         25 . The oven of  claim 24 , wherein the first cooking condition is associated with a first humidity and the second cooking condition is associated with a second humidity, and wherein the first steam header is adapted to be controlled to control the first humidity in the first chamber and the second steam header is adapted to be controlled to control the second humidity in the second chamber, wherein the first humidity and the second humidity are adapted to be different. 
     
     
         26 . The oven of  claim 24 , wherein the first and second steam headers are vertically arranged.