Mechanically refrigerated spiral freezer and method of using same to chill or freeze products

Abstract

An upwardly helical flow path of mechanically refrigerated air inside a spiral freezer may be used to chill or freeze products.

What is claimed is: 
     
         1 . A mechanically refrigerated spiral freezer, comprising:
 a rotatable drum;   a conveyor belt support spiraling up and around the drum to form a spiral ramp, each full revolution of the conveyor belt support around the drum constituting a tier, the conveyor belt support not being connected to the rotatable drum;   an endless conveyor belt disposed on top of the conveyor belt support along a helical path;   a cylindrical freezing chamber housing enclosing the drum and the conveyor belt support, the freezing chamber housing having a conveyor belt inlet through which the conveyor belt travels into an interior of the freezing chamber housing and onto the conveyor belt support, a conveyor belt outlet through which the conveyor belt travels off of the conveyor belt support and out of the interior of the freezing chamber housing, a refrigerated air inlet disposed between adjacent tiers of the conveyor belt support, and a warm air outlet disposed between adjacent tiers of the conveyor belt support at a vertical position higher than that of the refrigerated air inlet;   a mechanical refrigeration apparatus comprising a housing, a warm air inlet in fluid communication with the warm air outlet, a refrigerated air outlet in fluid communication with the refrigerated air inlet, a refrigeration circuit including an evaporator, and a blower, wherein the blower is adapted to:
 draw in warm air from the interior of the freezing chamber housing via the warm air outlet and warm air inlet; 
 direct the warm air past the evaporator to produce refrigerated air; and 
 direct the refrigerated air into the interior of the freezing chamber housing via the refrigerated air outlet and refrigerated air inlet to induce a helical flow path of refrigerated air above and parallel to the helical path of the conveyor belt. 
   
     
     
         2 . The spiral freezer of  claim 1 , wherein the drum has a continuous outer surface that prevents a flow of gas into an interior of the drum. 
     
     
         3 . The spiral freezer of  claim 1 , wherein the conveyor belt has a width W, and the freezing chamber housing is spaced from an outer edge of the conveyor belt by no more than 0.1 W. 
     
     
         4 . The spiral freezer of  claim 1 , wherein the conveyor belt support has a continuous surface that supports at least all portions of the conveyor belt in between inner and outer edges of the conveyor belt and prevents a flow of gas through the conveyor belt support. 
     
     
         5 . The spiral freezer of  claim 1 , further comprising:
 a take-up tower housing;   plurality of rollers disposed within an interior of the take-up tower housing that support travel of the conveyor belt through the take-up tower housing interior, wherein:
 the conveyor belt inlet and conveyor belt outlet are in communication with the take-up tower housing interior; and 
 the interior of the freezing chamber housing is separated from the interior of the take-up tower housing by a wall of the freezing chamber housing. 
   
     
     
         6 . The spiral freezer of  claim 5 , further comprising a pair of parallel conveyor belt support rails supporting inner and outer edges of the conveyor belt as it travels through the interior of the take-up tower housing, the conveyor belt support rails connecting with a top of the conveyor rail support to support travel of the conveyor belt out of the freezing chamber housing and into the take-up tower housing interior. 
     
     
         7 . The spiral freezer of  claim 5 , wherein:
 the take-up tower housing has a first opening communicating with an exterior of the take-up tower housing to allow travel of the conveyor belt out of, and back into, the take-up tower housing interior at a product exit where chilled or frozen product may be unloaded from the conveyor belt;   the take-up tower housing has a second opening communicating with the exterior of the take-up tower housing to allow travel of the conveyor belt out of, and back into, the take-up tower housing interior at a product entry where product to be chilled or frozen may be loaded onto the conveyor belt; and   said spiral freezer further comprises a rear-most roller receives that travel of the conveyor belt therearound at a position located adjacent the product exit and a front-most roller that receives travel of the conveyor belt therearound at a position located adjacent the product entry.   
     
     
         8 . The spiral freezer of  claim 5 , further comprising a recirculation blower disposed adjacent the freezing chamber outlet and a recirculation passageway defined by an outer surface of the freezing chamber housing and an outer surface of a concave portion of the take-up tower housing, the recirculation passageway providing a gas flow passage communicating between the freezing chamber outlet and one or more air return openings formed in the freezing chamber housing, the recirculation blower oriented to draw in a portion of air exiting the freezing chamber outlet and blow the drawn-in portion into the recirculation passageway and thenceforth into the interior of the freezing chamber housing. 
     
     
         9 . The spiral freezer of  claim 1 , wherein the conveyor belt support has a dimpled surface. 
     
     
         10 . The spiral freezer of  claim 1 , wherein:
 the conveyor belt has a midline equidistant from inner and outer edges of the conveyor belt;   the refrigerated air outlet and the warm air inlet are oriented along corresponding axes; and   each of said at least one axes extends over the midline of the helical path parallel to a line tangent to the midline.   
     
     
         11 . The cryogenic spiral freezer of  claim 1 , wherein the induced helical flow of the refrigerated air is above and parallel to the helical path of the conveyor belt along the entire helical path of the conveyor belt. 
     
     
         12 . The method of  claim 1 , wherein:
 the conveyor belt has a midline equidistant between inner and outer edges of the conveyor belt;   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; and   the midline of the conveyor belt is continuously supported by the conveyor belt support from a bottom of the helical path to a top of the helical path.   
     
     
         13 . 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, each full revolution of the conveyor belt constituting a tier;   withdrawing air from an upper portion of the helical path;   chilling the withdrawn air with a mechanical refrigeration apparatus to provide a flow of refrigerated air;   directing the flow of the refrigerated air along a helical flow path above and parallel to the helical path of the conveyor belt within the spiral freezer.   
     
     
         14 . The method of  claim 13 , wherein the helical flow of the refrigerated air is above and parallel to the helical path of the conveyor belt along the entire helical path of the conveyor belt. 
     
     
         15 . The method of  claim 13 , wherein the helical flow path of the refrigerated air is upward and in a same direction as travel of the conveyor belt along the helical conveyor belt path. 
     
     
         16 . The method of  claim 13 , wherein:
 the conveyor belt travels its helical path while supported by an upwardly spiraling conveyor belt support; and   the helical flow of the refrigerated air is constrained above and below by adjacent tiers of the conveyor belt support.   
     
     
         17 . The method of  claim 13 , 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 refrigerated 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.   
     
     
         18 . The method of  claim 13 , wherein:
 the air withdrawn from the upper portion of the helical path is withdrawn from between adjacent tiers of the conveyor belt via a warm air inlet formed in a housing of the mechanical refrigeration apparatus;   the refrigerated air chilled by the mechanical refrigeration apparatus is introduced into the helical pathway in between adjacent tiers of the conveyor belt via a refrigerated air outlet formed in the mechanical refrigeration apparatus housing that is oriented along an axis that crosses a midpoint of the helical path, said axis being parallel to a tangent line of the helical path.   
     
     
         19 . The method of  claim 18 , wherein the refrigerated air is introduced into the helical path by the mechanical refrigeration apparatus in a direction that is never perpendicular to a direction of travel of the portion of the conveyor belt traveling directly underneath where the refrigerated air is introduced into the helical path. 
     
     
         20 . 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.   
     
     
         21 . 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.   
     
     
         22 . The method of  claim 21 , further comprising the steps of:
 via the freezing chamber housing outlet, allowing a portion of the refrigerated 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 refrigerated 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.