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.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

None.

BACKGROUND

Typically, mechanical spiral freezers (spirals) have fans placed in front of one or more heat exchangers. These heat exchangers are a means of using chilled ammonia, or some other compressible fluid, to cool the warmer air. The fans push the warm air through the heat exchanger, and the newly-chilled air exits the heat exchanger with enough velocity and force so as to push this chilled air over a portion of the spiral conveying system. The chilled air picks up heat from food products, so that when the air has passed horizontally through the spiral conveyor, it is now warm air again. This warm air is then re-directed around the side(s) of the spiral conveyor system, and back behind the heat exchanger to the in-feed of the fans. The fans push the warmed air back through the heat exchanger and the cycle is repeated.

The process of removing heat by passing a chilled vapor over a warmer product is called convection. There are three primary elements that impact the food chilling capacity of a refrigeration system using convection:

• • 1. The velocity of the chilled air.
  • 2. The temperature delta between the chilled air and the food product temperature.
  • 3. The amount of exposure the food product has to direct convection while the food product is within the freezing zone of the chilling system.
    Generally speaking, higher velocity air moving over the product removes more heat than slower velocity. The “ideal” velocity is the highest velocity that does not damage or negatively impact product. Also a greater difference in temperature (ΔT) between the air and the product to be chilled removes more heat than less temperature delta. Further, an increase in convection exposure will cause a proportional increase in chilling performance. For example, if we increase the exposure time by 10%, there will be a corresponding 10% increase in refrigeration capacity.

The horizontal airflow of a typical mechanical spiral freezer has two distinct opportunities of improvement: air velocity and increased convection exposure. The chilled air velocity is reduced as the chilled air is pushed across the spiral belt, such that food products closest to the heat exchanger receive higher convection velocity than food products furthest from the heat exchangers. Establishing the highest usable (i.e., ideal) velocity and consistently maintaining that velocity regardless of geographic relationship to heat exchanger would improve system heat removal performance. With regard to increased convection exposure, the food product is moving in a circular fashion. Product moving toward the heat exchanger experiences more air velocity and convection effect than product that is moving away from the heat exchanger. The ideal velocity can only be utilized at the point where product is moving toward the heat exchanger. That being the case, during more than 75% of the time that the product is in the refrigeration system, it is exposed to less than the ideal velocity, thus limiting the performance of the refrigeration system. Establishing the ideal velocity and consistently maintaining that velocity and corresponding convection effect regardless of geographic relationship to heat exchanger would improve system heat removal performance.

As warm air is pushed through the heat exchanger(s), it is chilled. As the spiral belting revolves, a direct and aggressive airflow is directed across the belt at most 70% of the time the product is in the spiral. Since a spiral freezer relies on aggressive airflow to achieve maximum heat transfer between the flowing cold vapor and the relatively warm product, this means that for a significant percentage of time for each revolution of the belt, the product does not receive the full advantage provided by exposure to an aggressive airflow.

Thus, there is a need in the art to provide spiral freezers that allow a greater exposure time of products to an aggressive airflow per belt revolution.

Spiral conveyors are normally enclosed within a large rectangular, insulated structure. The coldest, and therefore densest, air falls to the floor of the spiral. Typically, the conveyor belting entrance to the spiral is located at floor level. Thus, it is the natural tendency of the cold air to escape out that opening (the path of least resistance). As the coldest air leaves the spiral, it causes a “siphon effect” such that warm air is sucked into the enclosure through the exit opening for the spiral conveyor belting. This “warm air infiltration” causes a reduction in the heat transfer rate of the freezer and requires a greater degree of mechanical refrigeration just to maintain the temperature inside the spiral freezer. Warm air infiltration also introduces room air and higher moisture levels in the spiral enclosure, leading to a buildup of highly undesirable water ice on all the cold surfaces within the spiral as well as the product. Warm air infiltration increases the freezing cost and reduces productivity.

Thus, there is a need in the art to provide spiral freezers that avoid or reduce undesired buildup of water ice on product and cold surfaces and increased mechanical refrigeration costs.

SUMMARY

There is disclosed a mechanically refrigerated spiral freezer, comprising: a rotatable drum; a conveyor belt support spiraling up and around the drum to form a spiral ramp; 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; and 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. Each full revolution of the conveyor belt support around the drum constitutes a tier. The conveyor belt support is not connected to the rotatable drum. The freezing chamber housing has 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. 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.

There is also disclosed a method of chilling or freezing products in a spiral freezer, comprising the following steps. A plurality of items is introduced onto a conveyor belt that moves in a helical path within a spiral freezer, each full revolution of the conveyor belt constituting a tier. Air is withdrawn from an upper portion of the helical path. The withdrawn air is chilled with a mechanical refrigeration apparatus to provide a flow of refrigerated air. The flow of the refrigerated air is directed along a helical flow path above and parallel to the helical path of the conveyor belt within the spiral freezer.

The freezer or method may include one or more of the following aspects:

• • the drum has a continuous outer surface that prevents a flow of gas into an interior of the drum.
  • 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.
  • 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.
  • the freezer or system further comprises:
    • 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.
  • the freezer or method further comprises 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.
  • 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.
  • 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.
  • the freezer or method further comprises 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.
  • the conveyor belt support has a dimpled surface.
  • 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.
  • each of said at least one axes extends over the midline of the helical path parallel to a line tangent to the midline.
  • 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.
  • 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.
  • 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.
  • 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.
  • 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.
  • the conveyor belt travels its helical path while supported by an upwardly spiraling conveyor belt support.
  • the helical flow of the refrigerated air is constrained above and below by adjacent tiers of the conveyor belt support.
  • 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.
  • 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.
  • 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.
  • 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.
  • 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.
  • 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.
  • 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.
  • 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.
  • via the freezing chamber housing outlet, a portion of the refrigerated air exiting the interior of the freezing chamber housing is allowed to enter into the interior of the take-up tower housing.
  • a portion of the refrigerated air exiting the freezing chamber outlet back is re-circulated 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.

BRIEF DESCRIPTION OF THE DRAWINGS

For a further understanding of the nature and objects of the present invention, reference should be made to the following detailed description, taken in conjunction with the accompanying drawings, in which like elements are given the same or analogous reference numbers and wherein:

FIG. 1A is an isometric view of an embodiment of the inventive spiral freezer taken from a point of view to the right side of and behind a product exit.

FIG. 1B is an isometric view of the freezer of FIG. 1A taken from a point of view to the right side of and in front of a product entry.

FIG. 2 is an isometric view of an assembly including the drum, drive shaft, drive motor, and support structure of the freezer of FIG. 1A.

FIG. 3 is an isometric view of the assembly of FIG. 2 that also includes a conveyor belt support configured as a spiral ramp.

FIG. 4 is an isometric view of the conveyor belt and rollers of the freezer of FIG. 1A.

FIG. 5A is an isometric view of the assembly of FIG. 3 that also includes the conveyor belt and rollers of FIG. 4 and the mechanical refrigeration apparatus of FIG. 1A.

FIG. 5B is an isometric view of the assembly of FIG. 5A taken from a point of view to the right side of and in front of the product entry.

FIG. 6 is an isometric view of the mechanical refrigeration apparatus of FIG. 5A.

FIG. 7 is a rear elevation view of the assembly of FIG. 3 that also includes the mechanical refrigeration apparatus of FIG. 6.

FIG. 8A is an isometric view of the freezer of FIG. 1A with the take-up tower housing removed.

FIG. 8B is an isometric view of the freezer of FIG. 8A taken from a point of view to the right side of and in front of the product entry.

FIG. 9 is an isometric view of the freezing chamber housing and blower apparatus of FIG. 1A revealing interior features and the helical flow path of refrigerated air that is taken from a point of view to the left side of and in front of a product entry.

FIG. 10 is an isometric view of the freezer of FIG. 8A with the conveyor belt and rollers removed.

FIG. 11 is an isometric view of the take-up tower housing of the freezer of FIG. 1A revealing interior features that is taken from a point of view to the left side of and in front of the product entry.

FIG. 12A is an isometric view of the freezer of FIG. 1A revealing interior features that does not include the mechanical refrigeration apparatus, support legs and arms, conveyor belt, or rollers that is taken from a point of view to the right side of and behind a product exit.

FIG. 12B is an isometric view of the freezing chamber housing and take-up tower housing of FIG. 1A with the assembly of FIG. 2 that is taken from a point of view to the left side of and in front of a product entry

DETAILED DESCRIPTION

The inventive freezer allows products to be chilled or frozen by subjecting them to a flow of refrigerated air inside a spiral freezer. The flow of refrigerated air follows the same helical path as the conveyor belt and thus is co-current to the travel direction of the conveyor belt. The helical flow path of the refrigerated air is produced by a mechanical refrigeration apparatus that receives air from in between adjacent tiers of the conveyor belt from one portion of the freezer, chills the air, and blows or directs the chilled air into a different portion of the freezer in between adjacent tiers of the conveyor belt. The flow of the refrigerated air blown by the mechanical refrigeration apparatus follows a flow path that is tangent to the travel direction of the conveyor belt. The spiral is enhanced or maintained by restricting its ability to flow through the conveyor belt, by restricting its ability to flow through the drum, and by restricting its ability to flow out of an area in between adjacent tiers of the conveyor belt travel.

The inventive freezer may be used to chill or freeze a wide variety of products, including foodstuffs and other industrial products. The foodstuffs include but are not limited to meat, poultry, seafood, produce, sauces, ready-to-eat meals, and ready-to-cook meals.

As best illustrated in FIGS. 1A and 1B, an embodiment of the inventive spiral freezer includes a freezing chamber housing 1 that is connected to a take-up tower housing 5 containing a conveyor belt tensioning apparatus. Inner surfaces of the freezing chamber housing 1 define a freezing chamber. While the freezing chamber and take-up tower housings 1, 5 may be constructed of any material used for such purposes in the field of spiral freezers, typically they are constructed of molded insulated fiberglass for ease of manufacture and lowered material costs.

A conveyor belt 9 receives product to be chilled or frozen at a position adjacent to a product entry 13 and yields chilled or frozen product at a product exit 17. A take-up tower exhaust 21 and an inlet exhaust 25 are used to exhaust refrigerated air to vent. A mechanical refrigeration apparatus 29 induces a spiral flow path for refrigerated air inside the freezing chamber. A recirculation blower (not illustrated) is disposed at an upper portion of a recirculation passageway 33 that re-circulates refrigerated air from an upper portion of the take-up tower housing to the interior of the freezing chamber via a plurality of openings in the freezing chamber housing 1. The refrigerated air is produced by directing a flow of air withdrawn from the freezing chamber past an evaporator (not illustrated) of the mechanical refrigeration apparatus 29.

With continued reference to FIG. 1A and FIG. 1B, a drum motor 41 rotates a drum (hidden) contained within the freezing chamber housing via a spindle 45. The drum is supported by receiving a top portion of the spindle in an upper bearing 49 and a lower bearing (hidden). The upper bearing 49 is in turn supported by a plurality of support arms 53 that lead to a corresponding plurality of support legs 57. The support legs 57 and the lower bearing are secured to a base 69. While FIGS. 1A and 1B illustrated three support arms 53 and legs 57, one of ordinary skill in the art will recognize that more or fewer may be utilized.

As best shown in FIG. 2, a cylindrical drum 42 is rotated by the spindle 45 which is secured to and extending through an axis of the drum 42. The spindle 45 is driven by the drum motor 41 and extends between the upper and lower bearings 49, 73. As best illustrated in FIG. 3, conveyor belt support 77 extends in a spiral path around the drum 42 to form a spiral ramp. The conveyor belt support 77 is not connected to the drum 42 so that the conveyor belt support 77 remains stationary during rotation of the drum 42. Each revolution of the conveyor belt support 77 constitutes one tier. Thus, in FIG. 3, ten tiers are illustrated. As best shown in FIG. 4, the conveyor belt 9 is guided via a plurality of rollers 10 where one or more of the rollers 10 is rotated with a drive motor (not illustrated) to urge travel of the conveyor belt around, over, or under the rollers 10 in a belt travel direction. While the conveyor belt 9 may be constructed of any material used for conveyor belts in the field of spiral freezers, including a metal such as stainless steel, typically it is constructed of polyethylene, such as UHMW, or other polymer material having similar physical properties.

As best illustrated in FIGS. 5A and 5B, a suitable amount of tension is applied to the conveyor belt 9 by maintaining an appropriate amount of space in between at least one pair of adjacent rollers 10. The tension applied to the conveyor belt 9 causes an inner edge of it to frictionally engage a circumferential surface of the drum 42 so that, as the drum 42 is rotated by the drum motor 41 via the spindle 45, the conveyor belt 9 is driven in a spiral path on top of the conveyor belt support 77 around and up the drum 42. The conveyor belt 9 completes several revolutions around the drum 42, each one of which constitutes a tier. While FIGS. 5A and 5B illustrate nine tiers, one of ordinary skill in the art will recognize that more or less tiers may be utilized based upon the residence time desired within the freezing chamber. The conveyor belt support 77 may be constructed of any material used in the field of spiral freezers, including a metal such as stainless steel or a polyethylene (such as UHMW) or other polymer material having similar physical properties. Typically, when the conveyor belt 9 is made of a polymer material, the conveyor belt support 77 is made of stainless steel and when the conveyor belt 9 is made of stainless steel, the conveyor belt support 77 is made of a polymer material.

As best shown in FIGS. 5A, 5B, 6, 7, and 12B, the freezer includes a mechanical refrigeration apparatus 29 having a warm air inlet 65 (disposed at a vertical position in between adjacent tiers of the conveyor belt 9 and conveyor belt support 77) that receives air from an interior of the freezing chamber via a warm air outlet 16 formed in the freezing chamber housing 1. The air received from the interior of the freezing chamber is sucked in by blower apparatus 66 that includes one or more blowers. The blowers may be of any type in the field of gas handling. Typically, they are of the fan type that receives an axial flow of air and ejects it with an axial flow. The air is blown across evaporator tubes in evaporator apparatus 67 and chilled through heat exchange with the refrigerant in the evaporator tubes. The chilled air is directed through a plenum 68A fluidly communicates with refrigerated air outlet 68B. The chilled air is introduced back into an interior of the freezing chamber from refrigerated air outlet 68B (disposed at a vertical position in between adjacent tiers of the conveyor belt 9 and conveyor belt support 77 lower than that of warm air inlet 65) via the freezing chamber inlet 14. One of ordinary skill in the art will recognize that the air received by warm air inlet 65 from the interior of the freezing chamber is typically cold, but not as cold as the refrigerated air.

While FIGS. 5A, 5B, 6, and 7 illustrate that the warm air inlet 65 and the refrigerated air outlet 68B are disposed at radially offset positions, one of ordinary skill in the art will recognize that they need not be spaced apart in the illustrated position. Rather, they may be radially aligned with respect to the center axis of the spindle 45 or be spaced from one another by any angular spacing less than or greater than 180°. However, they are typically spaced from one another by 180° with respect to the center axis of the spindle 45. Moreover, while FIGS. 5A, 5B, 6, and 7 illustrate that the warm air inlet 65 is vertically spaced from the refrigerated air outlet 68B by 8½ tiers of the conveyor belt 9 and conveyor belt support 77, one of ordinary skill in the art will recognize they may be separated by more than or less than this number of tiers. Typically, the warm air inlet 65 is disposed between the uppermost pair of adjacent tiers and the refrigerated air outlet 68B is disposed between the lowermost pair of adjacent tiers. Also, while FIGS. 5A, 5B, 6, and 7 illustrate only a single warm air inlet 65 and a single refrigerated air outlet 68B, one of ordinary skill in the art will recognize that air may be withdrawn from the interior of the freezing chamber by the mechanical refrigeration apparatus 29 via more than one warm air inlet 65 and/or introduced back into the freezing chamber interior via more than one refrigerated air outlet 68B.

As best shown in FIGS. 8A and 8B, the conveyor belt 9 is supported by a plurality of rollers 10. Product (not illustrated) to be chilled or frozen is deposited upon the conveyor belt 9 at a point in between the forward-most roller 10 and an inlet 14 in the freezing chamber housing 1. Inside the freezing chamber housing 1, the conveyor belt 9 with the product is wound around the drum 42 (hidden in FIGS. 8A, 8B) in a spiral path on top of the conveyor belt support 77 (hidden in FIGS. 8A, 8B). The travel direction of the conveyor belt 9 is upwardly counter-clockwise, but one of ordinary skill in the art will recognize that an upwardly clockwise travel direction can instead be utilized with the appropriate arrangement of the conveyor belt support 77 and other related features.

After reaching the top tier of the spiraled conveyor belt support 77, the conveyor belt 9 exits the freezing chamber housing through an outlet 18 and enters the interior of the take-up tower 5 enclosed by the take-up tower housing 5. The conveyor belt 9 then travels out of the product exit 17 (not shown in FIGS. 8A, 8B) where chilled or frozen product is removed from the conveyor belt 9 and around the rear-most roller 10. The conveyor belt returns through the product exit 17 and into an interior of the take-up tower housing 5. After travel through the series of rollers 10 providing the suitable tension, the conveyor belt 9 travels out of the product entry 13 (not shown in FIGS. 8A, 8B) and around a forward-most roller 10 where it is once again loaded with product to be chilled or frozen.

One of ordinary skill will recognize that conveyor belts in spiral freezers actually follow a cylindrical helix path. The refrigerated air inside the freezing chamber of the inventive freezer follows that same helical conveyor belt path in between adjacent tiers of the conveyor belt support 77. As best illustrated by FIG. 9 where the freezing chamber housing 1 is depicted as transparent, the refrigerated air follows an upwardly helical flow path 80 inside the housing 1. The non-annotated arrow at the bottom of the flow path 80 indicates the flow of refrigerated air being introduced into the interior of the freezing chamber by the refrigeration apparatus 29, while the non-annotated arrow at the top of the flow path 80 indicates the flow of air being withdrawn from the interior of the freezing chamber by the refrigeration apparatus 29. When viewed alongside FIGS. 3, 5A, 5B, and 7, it is evident that the upwardly helical flow path 80 of the refrigerated air is above and parallel to the helical path that the conveyor belt 9 takes over the conveyor belt support 77. Thus, the flow path 80 of the refrigerated air is co-current with a travel direction of the conveyor belt 9.

The novel helical flow path 80 for the chilled air provides three main advantages.

First, the product is effectively cooled by the inventive freezer than with conventional spiral freezers for a given level of heat to be removed from the product. Because the flow of refrigerated air is now a continuous helical flow co-current to the direction of the product travel, exposure of the product to an aggressive airflow is significantly increased. As a result, the effectiveness of the heat transfer is increased. Stated another way, for a given amount of mechanical refrigeration, the inventive freezer has a higher chilling or freezing capacity. This allows a processor to increase production. Stated yet another way, for a given amount of product, the almost continuous exposure of the product to an aggressive airflow allows less mechanical refrigeration to be produced for a given amount of heat for lower processing costs.

Second, the product receives higher quality freezing from the inventive freezer than with conventional spiral freezers for a given level of heat to be removed from the product. Because the flow of refrigerated air is not perpendicular to the direction of travel of the conveyor belt, the problem of over-chilling of product placed near an outer edge of the belt and under-chilling of products placed near an inner edge of the belt is avoided. Thus, there is greater uniformity of product freezing from belt edge to belt edge. In the context of the chilling of food products, uniformity of chilling is important for achievement of a desired appearance and texture in the chilled or frozen product.

Third, the inventive freezer tends to reduce the siphon effect experienced by many conventional spiral freezers. Because the inlet of the conveyor belt into the spiral freezer is located at floor level, the cold, denser air wants to escape out that opening. As the coldest air leaves the spiral freezer, warm air is sucked into the outlet of the spiral freezer by a siphoning effect. The warm air infiltration causes a temperature increase in the freezing chamber interior thereby necessitating the production of additional amounts of mechanical refrigeration for purposes other than chilling the product. The inventive freezer works against this problem (that is otherwise experienced by conventional spiral freezers) by creating a flow of chilled air in the direction opposite that of the siphon. Because warm air infiltration also introduces moisture into the freezing chamber, the inventive freezer tends to avoid the degree of highly undesirable water ice buildup on all the cold surfaces that is experienced by conventional spiral freezers.

The helical flow of refrigerated air is created by a pull-push effect of the one or more blowers in the mechanical refrigeration apparatus 29. At a location in between adjacent tiers at one side of the freezing chamber, the refrigerated air is drawn inside the warm air inlet 65 and redirected to a location in between adjacent tiers on another side of the freezing chamber from the refrigerated air outlet 68B at a position lower than where the air was drawn in. This pull-push effect of the mechanical refrigeration assembly 29 induces the helical flow path 80 of the refrigerated air in between adjacent tiers of the conveyor belt support 77 from the bottom-most tier to the top-most tier.

The helical flow path 80 of the refrigerated air is maintained or enhanced by enclosing it in between the outer circumferential surface of the drum 42 and the inner surface of the cylindrical freezing chamber housing 1. In contrast to conventional spiral freezers having drums with porous circumferential surfaces to allow chilled air to pass through the drum 42, the drum 42 of the inventive freezer is for the most part sealed and its outer circumferential surface is continuous. Thus, the momentum of the helical flow of refrigerated air is not decreased by flow of the refrigerated air into the interior of the drum 42 and a restricted channel in between the drum 42 and freezing chamber housing 1 is provided. Utilization of a drum 42 with a continuous outer surface avoids the sanitation issues experienced by conventional cryogenic spiral freezers having porous drums. As discussed in the Background, the inside of a conventional spiral freezer drum is virtually inaccessible. Limited access means that, for the worst cleanup situations, a partial disassembly of the conveyor support rail structure is necessary for conventional cryogenic spiral freezers. The helical flow path 80 of the refrigerated air is further enhanced by only allowing a relatively small gap in between an outer edge of the conveyor belt 9 and an inner surface of the freezing chamber housing 1. Typically, for a conveyor belt 9 having a width W, an inner surface of the freezing chamber housing 1 is spaced from an outer edge of the conveyor belt 9 by no more than a gap of 0.1 W.

The helical flow path 80 of the refrigerated air is also maintained or enhanced by enclosing it in between adjacent tiers of the conveyor belt support 77. In contrast to conventional spiral freezers having a pair of parallel conveyor support rails supporting only the inner and outer edges of the conveyor belt, the conveyor belt support 77 of the inventive spiral freezer substantially supports the entire width of the conveyor belt 9.

Substantially supporting the entire width of the conveyor belt 9 means that most of the surface of the conveyor belt 9 (including its middle portion and portions in between its middle and its inner and outer edges) is supported by the conveyor belt support 77 and that the flow of refrigerated air through the conveyor belt 9 is inhibited. Typically, the conveyor belt support has a continuous upper surface from an inner edge to an outer edge of the conveyor belt 9. The conveyor belt support may optionally have a discontinuous surface whereby an otherwise continuous surface includes a uniform distribution of openings so that, while the surface of the conveyor belt support 77 is not perfectly continuous, it does support the middle of the conveyor belt 9 (as well as portions of the conveyor belt 9 in between the middle and the edges) and also inhibits a flow of the refrigerated air through the conveyor belt 9.

Additionally, one of ordinary skill in the art will recognize that the inner and outer edges of the conveyor belt 9 may project somewhat inwardly and outwardly, respectively, from the conveyor belt support 77 without departing from the invention or impeding the creation of the helical flow path 80 of refrigerated air. Thus, there may be a limited gap in between the drum and an inner edge of the conveyor belt support 77 and/or the outer edge of the conveyor belt 9 may be unsupported.

The conveyor belt support 77 may optionally have a dimpled surface so that wear of the conveyor belt support 77 and conveyor belt 9 is minimized. If that feature is desired, the conveyor belt 9 contacts only the top surfaces of the dimpled portions of the conveyor belt support 77.

Although the conveyor belt support 77 is illustrated as providing continuous support to the conveyor belt in the travel direction of the belt 9 as it travels from the bottom of the drum 42 to the top of the drum 42, one of ordinary skill in the art will recognize that the inventive spiral freezer may utilize individual tiers of conveyor belt supports 7 that sandwich and connect one or more tiers of conventional conveyor belt support rails (a parallel pair of rails that only support the inner and outer edges of the conveyor belt 9). For example, the conveyor belt 9 may be supported across substantially its entire width for one revolution the conveyor belt support 77 immediately upon entry into the freezing chamber. At the termination of this first revolution, the conveyor belt support 77 may connect with a pair of conventional conveyor belt support rails for one or even two or more revolutions around the drum so that the conveyor belt 9 travels upon rails instead of the conveyor belt support 77. At the termination of that revolution or those revolutions, the conveyor belt 9 can once again be supported across substantially its entire width by the conveyor belt support 77. This sequence of conveyor belt support 77 and pair of parallel conveyor belt support rails can be repeated up to the top of the spiral freezer.

As best illustrated in FIGS. 1A, 1B, 10, 11, and 12A, and 12B, a portion of the flow of refrigerated air exiting the freezing chamber outlet 18 is directed downwardly into the re-circulation passageway 33 by the recirculation blower 36. The re-circulation passageway 33 is formed by an outer surface of the freezing chamber housing 1 and an inner surface 32 of a concave, wedge-shaped portion of the take-up tower housing 5. The refrigerated air in the re-circulation passageway 33 is returned to the freezing chamber via a plurality of return air inlets 34 formed in the freezing chamber housing 1.

As best shown in FIGS. 11, 12A, and 12B, the take-up tower housing 5 is adapted and configured to fit together with the freezing chamber housing 1 in complementary fashion. Edges 6 of walls of the take-up tower housing 5 define a front opening 8 that opens into an interior of the take-up tower housing 5. The outer surface of the freezing chamber housing 1 nestles inside the front opening 8 and against the edges 6 to prevent air from infiltrating in between the edges 6 and outer surfaces of the freezing chamber housing 1.

With reference to each of the FIGS, in operation, the conveyor belt 9 travels up and around the forward-most roller 10 after which product to be chilled or frozen is loaded upon it. The loaded conveyor belt 9 with product enters product entry 13 which is an opening in a front face of the take-up tower housing 5. After traversing a short distance, the loaded conveyor belt 9 then enters the inlet 14 of the freezing chamber housing 1.

The refrigerated air outlet 68B is centered on an axis that is parallel to a line that is tangent to a midpoint of the conveyor belt 9 (at the point where the axis and the midpoint intersect at the vertical axis). So, upon entry of the loaded conveyor belt 9 into the inlet 14 of the freezing chamber housing 1, the product on the conveyor belt 9 is immediately subjected to the overhead, co-current flow of refrigerated air from the mechanical refrigeration apparatus 29. One of ordinary skill in the art will recognize that, while the conveyor belt 9 is traveling up and around the drum 42 the product loaded upon it is subjected to a flow of refrigerated air flowing in a helical flow path 80 co-current to the travel direction of the conveyor belt 9. After traveling several revolutions around the drum 42, the conveyor belt 9 reaches the top tier of the conveyor belt support 77 and exits the outlet 18 of the freezing chamber housing 1. At the top tier, air from the freezing chamber interior is withdrawn by the mechanical refrigeration apparatus 29 via the warm air outlet 16 and the warm air inlet 65.

After exiting the outlet 18, the conveyor belt 9 immediately emerges into the interior of the take-up tower housing 5. Upon leaving the outlet 18, the conveyor belt 9 is no longer supported by the conveyor belt support 77 but is instead supported by conventional conveyor belt support rails (not illustrated). Because the conveyor belt 9 is no longer supported by the conveyor belt support, a portion of the refrigerated air at the top of the spiral freezer (which tends to be is colder than the atmosphere inside the take-up tower housing 5) exits the freezing chamber at the freezing chamber outlet 18 and spills down through the conveyor belt 9 to the bottom portion of the interior of the take-up tower housing 5.

By isolating the freezing chamber from the interior of the take-up tower housing 5, the inventive spiral freezer requires a lower amount of mechanical refrigeration for the same degree of chilling of the items in the freezing chamber. It also tends to inhibit the accumulation of ice on surfaces inside the freezing chamber that eventually need to be removed, thereby necessitating shutting down the chilling or freezing process. The mechanisms responsible for these advantages are two-fold.

First, because the interior of the freezing chamber is relatively isolated from the interior of the take-up tower housing 5, there is much lower turbulent air flow in between the two spaces. Thus, the relatively warmer air infiltrating from the ambient atmosphere outside the product exit 17 has a greater tendency to remain trapped at an upper portion of the interior of the take-up tower housing 5 due to its lower density while the relatively colder air spilling from the outlet 18 collects at the lower portion of the interior of the take-up tower housing 5.

Second, because the gaseous atmosphere inside the take-up tower housing 5 does not fully participate in the flow of refrigerated air inside the freezing chamber, the relatively moist air infiltrating into the product exit 17 does not get mixed with the colder refrigerated air to the same degree as in conventional spiral freezers. Because there is less water vapor to condense and freeze inside the freezing chamber (in comparison to conventional freezers), less of the mechanical refrigeration is wasted in condensing and freezing that water vapor.

These two mechanisms result in significant advantages for the inventive freezer. When ice accumulates on surfaces in the inventive freezer, it tends to accumulate more in the interior of the take-up tower housing 5 and less inside the freezing chamber. As a result, the inventive freezer is significantly easier to defrost because there are fewer surfaces to defrost inside the take-up tower housing 5 in comparison to the freezing chamber.

The conveyor belt 9 then emerges from product exit 17 which is an opening in a rear face of the take-up tower housing 5. Product is removed from the conveyor belt 9 after which time the conveyor belt 9 travels down and around the rear-most roller 10. The unloaded conveyor belt 9 then emerges back into the take-up tower housing 5 via the product exit 17. The conveyor belt 9 then travels through the series of rollers 10 providing sufficient tension. Next, the conveyor belt 9 travels out the product entry 13 at the open front face of the take-up tower housing 5 and up and around the front-most roller to complete the cycle.

Apart from the sanitary advantages provided by isolating the freezing chamber from the interior of the take-up tower housing 5, the inventive freezer is easier to clean/sanitize for other reasons. Because the drum 42 is for the most part sealed, it is very difficult for food product to get inside the drum 42 from the sides, the top or the bottom. As a result, it is ordinarily not necessary to take the spiral conveyor belt support 77 off of the drum 42 or to take apart the drum 42 for removal of food particles. Also, a conveyor belt support 77 that extends across the side and middle portions of the conveyor belt 9 from the bottom to the top of the drum 42 reduces the amount of food that falls from the conveyor belt 9 and onto a floor of the freezing chamber. As discussed in the Background, many conventional spiral conveyors have no access doors on narrow ends of the rectangle shape enclosing the freezing chamber and take-up tower. Because these conventional spiral freezers have very limited space for maintenance on the narrow ends of the enclosure, sanitation can only be achieved through a high pressure spray. Because the cylindrical freezing chamber housing 1 is made up mostly of curved doors, all areas of the freezing chamber floor can easily be flushed with minimal water and all areas of the conveyor belt 9 and conveyor belt support 77 are within easy arm reach. As a result, there is no need for an operator to wholly enter the interior of the freezing chamber housing 1—an action that is typically otherwise required in sanitizing conventional cryogenic spiral freezers. Additionally, all belt repairs and maintenance can be completed by an operator while standing outside the freezing chamber housing 1. Thus, the inventive freezer avoids the problems experienced by conventional spiral freezers of inadequate sanitation, excessive volumes of hot water and energy for sanitation, and excessive maintenance time and cost.

Parts List
1   freezing chamber housing
5   take-up tower housing
6   edges (of walls of the take-up tower housing)
8   front opening (opens into an interior of the take-up tower housing)
9   conveyor belt
10  rollers
13  product entry
14  inlet (of freezing chamber housing)
16  warm air outlet
17  product exit
18  outlet (from freezing chamber housing)
21  take-up tower exhaust
25  inlet exhaust
29  blower assembly
32  inner surface (of concave, wedge-shaped portion of take-up tower
    housing)
34  return air inlets
38  vertical conduit (I need to add to specification-oops) for cryogen
39  manifold
33  recirculation passageway
41  drum motor
42  a cylindrical drum
45  spindle
49  upper bearing
53  support arms
57  support legs
65  warm air inlet
66  blower apparatus
67  evaporator apparatus
68A plenum
68B refrigerated air inlet
73  lower bearing
77  conveyor belt support

Preferred processes and apparatus for practicing the present invention have been described. It will be understood and readily apparent to the skilled artisan that many changes and modifications may be made to the above-described embodiments without departing from the spirit and the scope of the present invention. The foregoing is illustrative only and that other embodiments of the integrated processes and apparatus may be employed without departing from the true scope of the invention defined in the following claims.

Claims

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.