Patent ID: 7197883

Claim:
Apparatus useful for cooling or freezing a product, comprising (A) a housing comprising an elongated tunnel having a product entrance and a product exit, a conveyor belt for carrying product inside and through said tunnel from said entrance to said exit, said belt having upper and lower surfaces and first and second side edges and, within said housing, (B) liquid cryogen injection apparatus for applying liquid cryogen to product on the upper surface of said belt; (C) an exhaust port, including an exhaust fan, through which cryogen vapor can be withdrawn from said housing by the action of said exhaust fan, (D) upper impingement structure above said belt, and a unitary plenum that comprises the space above said upper impingement structure and the space outside the first side edge of said belt; (E) return space outside the second edge of said belt; (F) the upper impingement structure comprising a plurality of concave troughs opening toward the belt and terminating at trough edges aligned side by side across the direction of travel of said belt so that between each pair of adjacent troughs there is a flow space having a top that is in fluid communication with said plenum, sides that are between respective ends of adjacent troughs, and an impingement slot that is between terminal edges of adjacent troughs, wherein terminal trough edges terminate a distance above the belt surface to define impingement zones, located between the impingement slot of a flow space and the belt surface, through which product to be cooled or frozen can pass on said belt; (G) barrier structure between said plenum and said return space that prevents vapor flow through the sides of said flow spaces that are closer to said second side edge of said belt into the return space and that prevents vapor flow through the sides of said impingement zones that are closer to said second side edge of said belt into the return space; and (H) a plurality of circulation fans located along the length of the housing which can draw cryogen vapor from said return space and impel the cryogen vapor through said fans into said plenum.