Method of chilling or freezing products in a cryogenic spiral freezer

Abstract

An upwardly helical flow path of cryogen-rich air inside a cryogenic spiral freezer may be used to chill or freeze products.

What is claimed is: 
     
         1 . A method of chilling or freezing products in a spiral freezer, comprising the steps of:
 introducing a plurality of items onto a conveyor belt that moves in a helical path within a spiral freezer;   injecting cryogen into a flow of chilled air in the spiral freezer to provide cryogen-rich air;   flowing the cryogen-rich air along a helical flow path above and parallel to the helical path of the conveyor belt within the spiral freezer.   
     
     
         2 . The method of  claim 1 , wherein the helical flow of the cryogen-rich air is above and parallel to the helical path of the conveyor belt along the entire helical path of the conveyor belt. 
     
     
         3 . The method of  claim 1 , wherein the helical flow path of the cryogen-rich air is upward and in a same direction as travel of the conveyor belt along the helical conveyor belt path. 
     
     
         4 . The method of  claim 1 , wherein:
 the conveyor belt travels its helical path while supported by an upwardly spiraling conveyor belt support; and   the helical flow of the cryogen-rich air is constrained above and below by adjacent tiers of the conveyor belt support.   
     
     
         5 . The method of  claim 1 , wherein:
 the conveyor belt rotates around and up a cylindrical drum disposed in a center of the spiral freezer along the helical path;   the drum has a continuous outer surface that prevents a flow of gas into an interior of the drum;   the spiral freezer comprises a cylindrical freezing chamber housing that encloses the conveyor belt along its helical path; and   the helical flow of the cryogen-rich air is constrained on one side by the continuous outer surface of the drum and constrained on an opposite side by the freezing chamber housing.   
     
     
         6 . The method of  claim 1 , wherein:
 the conveyor belt travels its helical path while supported by an upwardly spiraling conveyor belt support;   a blower apparatus comprises at least first and second blowers each one of which includes a blower inlet and a blower outlet;   the inlet of the first blower receives cryogen-rich air from a first portion of the spiral freezer in between adjacent tiers of the conveyor belt support and blows it from the outlet of the first blower into a second portion of the spiral freezer in between adjacent tiers of the conveyor belt support; and   the inlet of the second blower receives cryogen-rich air from a third portion of the spiral freezer in between adjacent tiers of the conveyor belt support and blows it from the outlet of the second blower into a fourth portion of the spiral freezer in between adjacent tiers of the conveyor belt support.   
     
     
         7 . The method of  claim 6 , wherein the cryogen-rich air blown from the outlet of the first blower outlet flows along an axis that, when said axis crosses a midpoint of the helical path, said axis is parallel to the tangent line of the helical path. 
     
     
         8 . The method of  claim 6 , wherein the cryogen-rich air blown from the blower outlets is blown in a direction that is never perpendicular to a direction of travel of the portion of the conveyor belt traveling directly underneath the blown cryogen-rich air. 
     
     
         9 . The method of  claim 1 , wherein:
 the conveyor belt has a middle portion in between inner and outer edges;   the conveyor belt rotates around and up a cylindrical drum disposed in a center of the spiral freezer along the helical path through frictional engagement between the inner edge of the conveyor belt and an outer circumferential surface of the cylindrical drum;   the conveyor belt is supported by an upwardly spiraling conveyor belt support forming a ramp underneath the helical path; and   the inner edge and the middle portion of the conveyor belt are continuously supported by the conveyor belt support from a bottom of the helical path to a top of the helical path.   
     
     
         10 . The method of  claim 1 , wherein the cryogen is liquid nitrogen. 
     
     
         11 . The method of  claim 1 , wherein the cryogen is liquid carbon dioxide. 
     
     
         12 . The method of  claim 1 , wherein:
 via a freezing chamber housing outlet, the conveyor belt exits the freezing chamber housing enclosing the helical path and the helical flow path and enters into an interior of a take-up tower housing;   the conveyor belt travels over, under, and/or around a plurality of rollers in a tensioning apparatus inside the take-up tower housing;   via a freezing chamber housing inlet, the conveyor belt exits the take-up tower housing and enters the freezing chamber housing; and   a gaseous atmosphere inside the interior of the freezing chamber housing is isolated from a gaseous atmosphere inside the interior of the take-up tower housing by a wall of the freezing chamber housing except for flow communication via the freezing chamber housing inlet and freezing chamber housing outlet.   
     
     
         13 . The method of  claim 12 , further comprising the steps of:
 via the freezing chamber housing outlet, allowing a portion of the cryogen-rich air exiting the interior of the freezing chamber housing to enter into the interior of the take-up tower housing; and   re-circulating a portion of the cryogen-rich air exiting the freezing chamber outlet back to an interior of the freezing chamber housing via a recirculation passageway and a recirculation blower disposed outside the freezing chamber housing adjacent to the freezing chamber housing outlet.