Balanced air return convection oven

Apparatus to heat or cool food products comprising:

• a cabinet;
• front and rear walls extending longitudinally of said cabinet;
• end walls extending transversely of said cabinet, one of said end walls having an entrance opening and the other end wall having an exit opening, said entrance and exit openings having ends adjacent said front and rear walls;
• a dispensing duct in said cabinet;
• a conveyor means for moving food products into said cabinet through said entrance opening, through said cabinet, and out of said cabinet through said exit opening;
• blower means for circulating air in said cabinet, said blower means having a suction passage and an air discharge passage, said discharge passage communicating with said dispensing duct;
• cowling means configured to form an air return duct communicating with said suction passage of said blower means and having at least one return passage through which air discharged into said cabinet through said air discharge passage is drawn toward a central portion of said conveyor substantially midway between edges of said conveyor such that air pressure in said cabinet is substantially balanced across the entrance and exit openings in the end walls of the cabinet, thereby preventing ingress and egress of a substantial volume of air through said entrance and exit openings, and wherein said dispensing duct has openings formed in a first array arranged to project an array of air streams toward the conveyor to heat food products carried on the conveyor;
• and a second array inclined relative to at least one of said end walls adjacent opposite an edge of the opening.

A method of controlling heat transfer to a surface of a food product comprising the steps of:

• moving a conveyor through an opening in a cabinet wall;
• directing a volume of gas through a grid of passages into a dispensing duct, said passages having a length greater than the width of each passage to project generally parallel streams of gas into said dispensing duct, wherein said dispensing duct forms at least one inclined stream of temperature controlled high velocity gas;
• directing said inclined stream across the opening in the cabinet wall at an angle in a range of 3.degree.-30.degree. relative to a vertical plane to separate a boundary layer of entrained ambient air from said inclined stream of temperature controlled gas;
• and directing said inclined stream toward the conveyor such that said inclined stream impinges against a discrete area on the surface of a food product on the conveyor to wipe away a boundary layer of air and moisture from the discrete area against which the inclined stream impinges;
• and moving the food product relative to said inclined stream such that heat is transferred to areas upon which said inclined stream impinges.

A method of controlling heat transfer to a surface of a food product comprising the steps of:

• moving a conveyor through an opening in a cabinet wall;
• directing a volume of gas through a grid of passages into a dispensing duct, said passages having a length greater than the width of each passage to project generally parallel streams of gas into said dispensing duct, wherein said dispensing duct is provided with a first array of openings arranged to project a first array of streams of gas toward the conveyor to heat food products carried on the conveyor, and is provided with a second array of openings inclined relative to a vertical plane for directing a second array of inclined streams across the opening in the cabinet wall at an angle in a range of 3.degree.-30.degree. relative to a vertical plane to separate a boundary layer of entrained ambient air from said second array of inclined streams of temperature controlled gas;
• and directing said second array of inclined streams toward the conveyor such that said second array of inclined streams impinge against discrete areas on the surface of a food product on the conveyor to wipe away a boundary layer of air and moisture from the discrete areas against which the inclined streams impinge;
• and moving the food product relative to said first array of streams such that heat is transferred to areas upon which said streams impinge.