Patent Description:
The benefits of using a cryogen, such as liquid nitrogen (LIN), to cool and freeze food products are well-known. In addition to dramatically decreasing the time required to freeze a particular food product, in many cases the taste, color, and texture of a cryogenically-frozen food product is superior to conventional, non-cryogenic freezing methods.

Cryogenic tunnel freezers are a common type of cryogenic freezer in the food industry. In a cryogenic tunnel freezer, the food product is cooled by passing the food product through the tunnel along a belt and exposing the food product to the cryogen within the tunnel. Most conventional tunnel freezers include fans located within the tunnel that circulate the cryogen.

For many small and mid-sized food processing operations, use of conventional cryogenic tunnel freezers is not cost-effective, due to their high purchase and operating costs, as well as the fact that they are not well-suited for intermittent use. In addition, most cryogenic tunnel freezers consume LIN at a rate that requires large on-site LIN storage tanks and associated equipment, adding further investment considerations to the customer's overall freezing cost. Therefore, there is a need for a cryogenic tunnel freezer that is better-suited for use in small and mid-sized food processing operations. <CIT> and <CIT> disclose known freezers with a housing, delivery system, belt and driving and tensioning assemblies that support the belt inside and outside the freezer.

According to the present invention there is provided a freezer as claimed in claim <NUM>. The freezer comprises: a housing comprising a plurality of insulated members that define a tunnel, the tunnel having a floor, opposing first and second sidewalls that extend upwardly from the floor, and a ceiling located opposite the floor, the housing having a first opening at a first end of the tunnel that defines an entrance and a second opening at an opposing second end of the tunnel that defines an exit, a length of the tunnel extending from the entrance to the exit; a delivery system adapted to introduce a cryogenic fluid into the tunnel; a belt extending along the length of the tunnel and being continuous, the belt having an upper run that extends through the tunnel and a lower run that extends through the tunnel; and a drive assembly and a tensioning assembly located outside of the tunnel that retain the ends of the belt, wherein the belt is not supported by any other belt guide structures otherthan said drive and tensioning assemblies, the drive assembly being adapted to drive the belt, and the drive assembly, tensioning assembly, belt and housing being configured so that the upper run lies atop the lower run when the belt is operated.

In a preferred embodiment, the belt has first and second side edges defining a width spanning from the first edge to the second edge, the belt comprising: a plurality of chains, each of the plurality of chains comprising a plurality of links, each of the plurality of links comprising a metal body having front and rear holes formed therein, a first chain of the plurality of chains located at the first side edge and a second chain of the plurality of chains located at the second side edge; at least one array of modules, each of the modules being made of a polymeric material and comprising a front row of axially-aligned tubes, a rear row of axially-aligned tubes and a plurality of arms connecting the front row of axially-aligned tubes to the rear row of axially-aligned tubes, each of the at least one array of modules positioned between two of the plurality of chains; and a plurality of metal rods, each of the plurality of metal rods extending across the width of the belt, each of the plurality of metal rods extending through the front row of axially-aligned tubes of one of the modules of each of the at least one array of modules, through the rear row of axially-aligned tubes of another one of the modules in each of the at least one array of modules, through the front or rear hole of one of the plurality of links in each of the plurality of chains, and through the front or rear hole of another one of the plurality of links in each of the plurality of chains.

The ensuing detailed description provides preferred exemplary embodiments of the invention. Rather, the ensuing detailed description of the preferred exemplary embodiments will provide those skilled in the art with an enabling description for implementing the preferred exemplary embodiments of the invention. It being understood that various changes may be made within the scope of the invention, as set forth in the appended claims. Reference numerals that are introduced in the specification in association with a drawing figure may be repeated in one or more subsequent figures without additional description in the specification in order to provide context for other features.

As used herein, the term "cryogenic fluid" is intended to mean a liquid, gas or mixed-phase fluid having a temperature less than -<NUM> degrees C. Examples of cryogenic fluids include liquid nitrogen (LIN), liquid oxygen (LOX), and liquid argon (LAR), liquid carbon dioxide and pressurized, mixed phase cryogens (e.g., a mixture of LIN and gaseous nitrogen). Similarly, as used herein, the term "cryogenic temperature" is intended to mean temperatures at or below -<NUM> degrees C.

Referring to <FIG> and <FIG>, reference numeral <NUM> refers generally to a freezer, of the present invention. The freezer <NUM> includes a belt <NUM>, which carries the product to be cooled or frozen (hereinafter "product") through a tunnel <NUM>. As will be described in greater detail herein, the tunnel <NUM> is preferably chilled using a cryogen, such as liquid nitrogen (hereinafter "LIN"). The belt <NUM> is preferably pervious to liquid and vapor, so that the cryogen can pass through the belt <NUM>.

The tunnel <NUM> comprises an upper section <NUM> and a lower section <NUM>. In this embodiment, the upper section <NUM> is fixed and the lower section <NUM> can be lowered and raised, to move between a closed position (see <FIG>) to an open position (see <FIG>). Referring to <FIG>, the upper and lower sections <NUM>, <NUM> each form a U-shaped construction which, when in a closed position, are joined and define an interior volume having a generally rectangular cross-sectional shape.

In order for the freezer <NUM> to operate efficiently and to prevent escape of cryogenic fluid, it is important that the tunnel <NUM> be insulated and tightly sealed when closed. In this embodiment, the upper and lower sections <NUM>, <NUM> comprise pre-fabricated panels having rigid insulation <NUM>, such as polyurethane having a density of at least <NUM>/m<NUM>, for example, that is bonded to a shell <NUM>. The shell <NUM> is preferably formed from a material that is strong, durable, can be sanitized, and can withstand cryogenic temperatures. In this embodiment, the shell <NUM> is formed from stainless steel, but could be formed of any suitable material. The use of pre-fabricated panels also provides the option to include a coating on the shell <NUM>, such as a plastic coating suitable for food service. Use of such coatings is not practical using traditional, welded construction because the panel material and weld material will have different coefficients of thermal expansion, resulting in delamination of the coating.

Alternatively, the insulation <NUM> could be injected into the shell <NUM> or rigid insulation could be placed into the shell <NUM> after the shell <NUM> is fabricated. Although this construction method is more conventional in the freezer industry, it is more likely to result in gaps and/or voids in the insulation <NUM>, which will reduce the insulating effectiveness of the tunnel <NUM>.

Referring to <FIG>, in order to facilitate shipping and assembly, the upper and lower sections <NUM>, <NUM> each consist of two sidewalls <NUM>, <NUM> that are spanned by a floor <NUM>, which enables the upper and lower sections <NUM>, <NUM> to be shipped flat. In this embodiment the sidewalls <NUM>, <NUM> and floor <NUM> are welded together. Alternatively, each of the sidewalls <NUM>, <NUM> could be bonded to the floor <NUM> using an adhesive that is airtight and will maintain bonding strength at cryogenic temperatures. As will be described in greater detail herein with reference to <FIG>, another alternative construction for the tunnel <NUM> is the use of insulated pre-fabricated panels that are joined by insulated end and corner sections.

The tunnel <NUM> is subject to a wide range of temperatures as it is cooled from ambient temperature (e.g., <NUM> to <NUM> degrees C) to cryogenic operating temperatures (e.g., -<NUM> to -<NUM> degrees C). In order to reduce the likelihood of buckling due to contraction and expansion of the upper and lower sections <NUM>, <NUM>, each preferably includes multiple segments that are joined together when the freezer <NUM> is assembled. Providing the upper and lower sections <NUM>, <NUM> in multiple segments also simplifies assembly of the freezer <NUM>, by reducing the weight and size of the individual parts.

Referring to <FIG>, the upper and lower sections <NUM>, <NUM> of this embodiment consist of three segments <NUM>-<NUM> and <NUM>-<NUM>, respectively. Each segment is secured to adjacent segments using latches (not shown). In order to provide an airtight seal between the segments, gaskets (not shown) are preferably provided at the joints between each of the segments.

An alternative structure for the upper and lower sections is shown in <FIG>. In this embodiment, each of the upper and lower sections preferably comprise multiple interlocking pre-insulated panels that are bonded together only along the length of the sidewall or floor/ceiling. A sidewall <NUM> of the lower section <NUM> is illustrated and consists of four interlocking sections <NUM>-<NUM>. Preferably, small gaps <NUM> are left between each of the sections <NUM>-<NUM> (the gaps <NUM> are exaggerated in <FIG>), which are filled with an adhesive and/or suitable sealant that can withstand cryogenic temperatures. This construction allows the sidewall <NUM> to expand and contract under normal operating conditions without buckling.

A similar construction is also preferably used to join the sidewalls to the ceiling or floor in the upper and lower sections, respectively. Referring to <FIG>, the sidewalls <NUM>, <NUM> and floor <NUM> of the lower section <NUM> are joined using complimentarily-shaped stepped portions. Small gaps <NUM>, which are filled with a bonding agent, are preferably left between the sidewalls <NUM>, <NUM> and the floor <NUM> to allow for expansion and contraction.

Another alternative construction is shown in <FIG>. Sidewalls <NUM>, <NUM> and floor <NUM> of lower section <NUM> interlock in the same manner as the sections <NUM>-<NUM> shown in <FIG>. As in the embodiment shown in <FIG>, small gaps <NUM>, which are filled with a bonding agent, are preferably left between the sidewalls <NUM>, <NUM> and the floor <NUM> to allow for expansion and contraction. This light-weight, simple construction technique allows for reduced manufacturing cost and assembly time. Efficiency benefits can also be realized with regard to cool-down and warm-up times allowing product changes and intermittent production to have minimal effects on the overall freezing operational costs. A further benefit can be realized in the installation time required to install and start-up a new process, as the modular concept allows for quick on-location assembly and installation.

Referring again to <FIG> and <FIG>, the upper section <NUM> is supported by a plurality of legs <NUM>-<NUM>, which are affixed to the upper section <NUM> with mounting brackets. Additional structural rigidity is provided by stabilizing members <NUM>-<NUM>, which extend between each of the legs <NUM>-<NUM>.

The lower section <NUM> is suspended by a lowering assembly comprising steel cables (not shown), which are routed through the legs <NUM>-<NUM> and are extended and retracted (thereby lowering and raising the lower section <NUM>) by turning one of two hand cranks <NUM>, <NUM> (see <FIG> and <FIG>). The hand cranks <NUM>, <NUM> are preferably synchronized by a chain and axle assembly (not shown), which is contained within a cross bar <NUM> that extends across from leg <NUM> to leg <NUM>, across the top of the upper section <NUM>. The hand cranks <NUM>, <NUM> each preferably include a self-locking gearbox (not shown), which reduce the force required to turn the hand cranks <NUM>, <NUM> and prevent the lower section <NUM> from moving when an operator releases one of the hand cranks <NUM>, <NUM>. Other types of assemblies could be used to raise and lower the lower section <NUM>, such as a screw drive driven by a drill or motor, for example.

Referring now to <FIG>, the belt <NUM> consists of six arrays <NUM> - <NUM> of plastic modules that provide the carrying surface for the product, a metal substructure consisting of end chains <NUM>, <NUM> located at the left and right side edges of the belt <NUM>, interior chains <NUM>-<NUM> located between each of the arrays <NUM>-<NUM>, and rods <NUM>-<NUM> that extend from edge-to-edge through each array <NUM>-<NUM> of the plastic modules and each chain <NUM>-<NUM>. In other embodiments, different numbers of arrays of plastic modules and interior chains could be provided. The metal chains and rods provide the tensile strength needed to support the belt <NUM> under the tension loads that are anticipated during operation of the freezer <NUM>. The portion of the belt <NUM> shown in <FIG> repeats along the length of the belt <NUM>, which forms a continuous loop. The plastic modules are used to reduce cost, weight and thermal absorption, and are designed for cryogenic service with adequate allowance included for contraction changes that occur when operating at reduced temperatures. The plastic modules can be made of any polymeric material suitable for cryogenic operating conditions. In this embodiment, the plastic modules are formed of high-density polyethylene (HDPE).

Each of the chains <NUM>-<NUM> consists of overlapping metal links. A link <NUM> is shown in <FIG>. The link <NUM> includes circular front and rear holes <NUM>, <NUM> and an elongated middle hole <NUM>. In this embodiment, each of the chains <NUM>-<NUM> consists of links that are identical to link <NUM>. The front and rear holes <NUM>, <NUM> and elongated middle hole <NUM> are labeled in <FIG> only with respect to link <NUM>. It should be understood that the other links <NUM>, <NUM> have the same orientation.

In order to aid in their description, links <NUM>, <NUM> and <NUM>, rods <NUM>, <NUM>, and <NUM>, and plastic modules <NUM>, <NUM> are numbered in <FIG>. The links <NUM>, <NUM> are arranged so that the rear hole <NUM> of link <NUM> overlaps the front hole of link <NUM>. Similarly, the front hole <NUM> of link <NUM> overlaps the rear hole of link <NUM>. Rod <NUM> includes a hooked end <NUM>, which extends through the middle hole of link <NUM> and the rear hole <NUM> of link <NUM>.

Each plastic module consists of an alternating pattern of cylindrical tubes (through which a rod passes) arranged in front and rear rows (each consisting of axially-aligned tubes) and connecting arms which each connect a tube in the front row to an adjacent tube in the rear row. For example, plastic module <NUM> includes a tube <NUM> through which a portion of rod <NUM> passes. The tubes located in connecting arm <NUM> extends from an end of tube <NUM> to one end of tube <NUM>, which is located on adjacent rod <NUM>. A connecting arm <NUM> extends from the opposite end of tube <NUM> to one end of tube <NUM>, which is located on rod <NUM>. Adjacent connecting arms <NUM>, <NUM> converge slightly (i.e., form a non-zero angle) as they extend from tubes <NUM>, <NUM> to tube <NUM>, which defines a V-shaped pattern and enables adjacent plastic modules <NUM>, <NUM> to overlap. The angle formed by the connecting arms <NUM>, <NUM> is about <NUM> degrees in this embodiment and is preferably between <NUM> and <NUM> degrees. This pattern is repeated along the width and length of the belt <NUM>.

In this embodiment, the front and rear rows of tubes of each of the modules is aligned with the front and rear holes, respectively, of a link. For example, the front and rear rows of tubes <NUM>, <NUM> of module <NUM> are aligned with the front and rear holes <NUM>, <NUM>, respectively, of link <NUM>. In addition, the tubes in the front row of each module are offset from the tubes in the rear row of each module.

In this embodiment, each of the connecting arms (e.g., connecting arm <NUM>) preferably includes a nib <NUM> extending laterally toward the right edge of the belt <NUM> and a second nib <NUM> extending laterally toward the left edge of the belt <NUM>. The nibs <NUM>, <NUM> are provided to prevent a person's finger from being inserted through the belt <NUM>. Connecting arms located adjacent to the chains <NUM>, <NUM> (e.g., connecting arm <NUM>) include only one nib <NUM>, which faces away from the respective chain <NUM>, <NUM> in order to prevent binding.

When installed in the freezer <NUM>, the belt <NUM> forms an endless loop consisting of an upper run <NUM> and a lower run <NUM> (see <FIG>) that each move along linear paths in opposing directions. As is conventional, the ends of the belt <NUM> are retained by a belt drive assembly <NUM> (see <FIG>) and a tensioning assembly <NUM> (see <FIG>). The belt drive assembly consists of a motor <NUM> (see <FIG>) which drives an axle <NUM> (see <FIG>) through a gear reduction assembly <NUM> (see <FIG>). Gears spaced along the axle <NUM> engage the belt <NUM>. The tensioning assembly <NUM> also includes gears which are spaced along an axle <NUM> and engage the belt <NUM>. Axle <NUM> of the tensioning assembly <NUM> is preferably movable along a horizontal axis that is perpendicular to the axle <NUM>, which enables the amount of tension applied to belt <NUM> to be adjusted.

In this embodiment, the belt <NUM> is sufficiently long so as to allow for thermal contraction of the belt <NUM> over its entire length when the tunnel <NUM> is cooled from a temperature of at least <NUM> degrees C (e.g., when non-operational or opened for cleaning) to a temperature of no greater than -<NUM> degrees C, and preferably, no greater than -<NUM> degrees C (e.g., when the tunnel <NUM> is closed and operated), without reducing the distance between the axle <NUM> for the drive assembly <NUM> and the axle <NUM> for the tensioning assembly <NUM>. Optionally, the belt <NUM> could be long enough to include a slack portion (not shown) that would hang downwardly from the axle <NUM> when the belt <NUM> is at ambient temperature (e.g., at least <NUM> degrees C).

In this embodiment, the construction and assembly of belt <NUM> allows for thermal contraction of the belt <NUM> across its width when the tunnel <NUM> is cooled from ambient temperatures (e.g., at least <NUM> degrees C) to operating temperatures (e.g., no greater than -<NUM> degrees C and, more preferably, no greater than -<NUM> degrees C). More specifically, the hooked ends of the rods (e.g., hooked end <NUM> of rod <NUM>) are bent in a manner that provides a compressive force against the end chains <NUM>, <NUM> which, in turn, compresses all of the elements across the width of the belt <NUM>. Accordingly, when the tunnel <NUM> is cooled to operating temperatures and the elements of the belt <NUM> contract, the compressive force exerted by the hooked ends of the rods prevents gaps from forming between the modules and chains.

According to the invention, other than the belt drive assembly <NUM> and a tensioning assembly <NUM>, the belt <NUM> is not supported by any other belt guide structures. When the tunnel <NUM> is in a closed position and the belt <NUM> is operated, the lower run <NUM> of the belt runs atop the floor <NUM> of lower section <NUM> of the tunnel <NUM> and the upper run <NUM> runs atop of the lower run <NUM>. In this embodiment, the upper run <NUM> moves in a direction of travel A (see <FIG>) and the lower run <NUM> moves in the opposite direction. The absence of belt guide structures further reduces the cost and simplifies fabrication and assembly of the freezer <NUM>, and reduces potential hygiene hazards. Due to this construction, belt <NUM> is also relatively light-weight, and therefore, can be removed and replaced relatively easily. In addition, the sandwiched operating configuration of the belt <NUM> (i.e., with the upper run <NUM> located directly atop the lower run <NUM> which, in turn, lays on the floor <NUM>) alleviates a problem with conventional belt designs, in which there are gaps between the upper and lower runs and between the lower run and the floor. In such conventional designs, some LIN is sprayed through and flows beneath the upper run, which results in reduced heat transfer to the product being conveyed atop the upper run and results in a loss of refrigeration. Further losses can also be prevented with this configuration as the warming gas cannot easily pass through the upper run <NUM> and bypass the product to be frozen.

As is conventional, a loading table <NUM> is provided at the infeed end (entrance) <NUM> of the tunnel <NUM>. The infeed end <NUM> and outfeed end (exit) <NUM> of the tunnel <NUM> each preferably include a height-adjustable exhaust hood <NUM>,<NUM>, respectively, which is designed to reduce cooling losses through the openings between the belt <NUM> and the hoods <NUM>, <NUM>. The distance from the infeed end <NUM> to the outfeed end <NUM> defines the length of the tunnel <NUM>. The width of the tunnel <NUM> is transverse and co-planar to the width.

As noted above, the freezer <NUM> has a closed/operating position (see <FIG>), in which the upper and lower sections <NUM>, <NUM> are joined and sealed, as well as an open/cleaning position (see <FIG>), in which the lower section <NUM> is separated from the upper section <NUM> by lowering the lower section <NUM>. When the freezer <NUM> is in the open position, all of the components located inside the tunnel <NUM> are accessible for cleaning. The absence of belt guide structures along the length of the belt <NUM> (as mentioned above) enables clear visible access to the top and bottom sides of both the upper and lower runs <NUM>, <NUM> of the belt <NUM> when the freezer <NUM> is in the open position, which simplifies cleaning/sanitizing of the freezer <NUM>.

Referring now to <FIG> and <FIG>, the cryogen, LIN in this embodiment, is supplied to the freezer <NUM> via a delivery system comprising an inlet <NUM>, which is connected to three nozzle bars <NUM>, <NUM>, <NUM> via a manifold <NUM>. The bars <NUM>, <NUM>, <NUM> are located near the outfeed end <NUM> of the tunnel <NUM>. Each of the bars <NUM>, <NUM>, <NUM> includes a plurality of nozzles which spray the cryogen downwardly onto a tray <NUM>, which is positioned between the upper and lower runs <NUM>, <NUM> of the belt <NUM>, is hinged at the outfeed end <NUM> of the tunnel <NUM>, and preferably extends just beyond the nozzles. The purpose of tray <NUM> is to capture excess cryogen that is not completely vaporized and aid the under product heat transfer performance by cooling the belt <NUM>. A greater or lesser number of bars <NUM>, <NUM>, <NUM> and/or a different number or configuration of nozzles could be provided, depending upon the application and the configuration of the tunnel <NUM>.

In order to provide efficient thermal transfer from the cryogen to the product, it is desirable to create a counter-current flow for the cryogen in the tunnel <NUM> (i.e., in the opposite direction of travel A of the upper run <NUM>). Accordingly, each of the nozzles is preferably oriented to direct its spray against the direction of travel A of the upper run <NUM>. Nozzle angles in the range of zero degrees (vertical) to <NUM> degrees (horizontal) are possible and angles in the range of <NUM> degrees to <NUM> degrees are preferred. The modular design of the freezer <NUM> also allows for the tunnel <NUM> to be assembled for co-current flow by reversing segments <NUM> and <NUM> (see <FIG>) of the upper section <NUM>, which results in the reversal of the inlet <NUM>, nozzle bars <NUM>, <NUM>, <NUM>, manifold <NUM> and exhaust duct <NUM>. In addition, a plurality of baffles <NUM>-<NUM> are spaced along the upper section <NUM> within the tunnel <NUM>, the first baffle <NUM> being located in front of the last nozzle bar <NUM>, extending to an exhaust duct <NUM> (which is located distal to the nozzles), and having the last baffle <NUM> located beyond the exhaust duct <NUM>. In this embodiment, each of the baffles <NUM>-<NUM> is rectangular in shape, is vertically oriented (or could, alternatively, be angled in the direction of flow of the cryogenic fluid) and spans the width of the tunnel <NUM>. As the cryogen exits the nozzles, it expands rapidly and moves toward the infeed end <NUM> of the tunnel <NUM>. The baffles <NUM>-<NUM> increase the velocity of the cryogen by forcing it to pass through the smaller cross-sectional area between the lower end of each baffle and the belt <NUM>. In addition, turbulence is created as the cryogen moves into the spaces between each baffle <NUM>-<NUM> and above the lower edges of the baffles <NUM>-<NUM>. In this embodiment, in order to simplify assembly and allow for interchangeability of parts, all of the baffles <NUM>-<NUM> are identical. Alternatively, the baffles <NUM>-<NUM> could incrementally increase in height from the baffle <NUM> located closest to the nozzle bar <NUM> to the baffle <NUM> located closest to the exhaust duct <NUM>, which would further increase the velocity of the cryogen as it moves from the nozzles to the exhaust duct <NUM>. Optionally, the baffles <NUM>-<NUM> could be removably attached, which would enable the baffles <NUM>-<NUM> to be replaced with baffles having different geometry. Baffles <NUM> and <NUM> reduce refrigeration losses through the infeed end <NUM> and outfeed end <NUM> of the tunnel <NUM>.

Rapid warming and expansion of the cryogen, as well as the exhaust hood <NUM> and an end baffle <NUM>, help direct the cryogen up the exhaust duct <NUM>. In order to enhance counter-current flow, an exhaust fan (not shown) is preferably provided at the top end of an exhaust stack (not shown), which is connected to the upper end of the exhaust duct <NUM>.

The above-described configuration of the tunnel <NUM> provides adequate thermal transfer from the cryogen to the product in a wide range of common applications without the need for turbulence fans located within the tunnel <NUM>. Turbulence fans and other air-moving devices are included in prior art freezer designs to direct the flow of the cryogen through the tunnel <NUM> and are typically driven by electrical power, which introduces heat inefficiencies into the freezer <NUM>. The absence of such fans, or any other type of air-moving device, within the tunnel <NUM> means that the freezer <NUM> of the present invention is able to be operated with lower heat loss than a conventional freezer of similar capacity. The construction can also be dramatically simplified to reduce costs and to allow simple fabrication techniques to be applied. Examples of "air-moving devices" include fans, blowers, ventilators, pneumatic air-movers and the like. As used herein, the term "air-moving device" is not intended to include nozzles, other delivery devices that introduce the cryogenic fluid into the tunnel <NUM>, the belt <NUM>, or any stationary elements in the tunnel <NUM>, such as baffles <NUM>-<NUM>.

Appropriate nozzle configuration (including number of nozzles, angle of the nozzles, nozzle type) is within the skill of one of ordinary skill in the art. It should be noted, however, that the absence of air-moving devices within the tunnel <NUM> increases the importance of proper nozzle configuration because the "momentum" provided by the cryogenic fluid exiting the nozzles is of greater importance to the refrigeration performance of the tunnel <NUM> than in embodiments in which turbulence fans and/or other in-tunnel air-moving devices are used. Of course, the precise "momentum" provided by the Nozzle type selection is made in order to select a nozzle that will allow momentum and directional spray to aid the direction and heat transfer performance.

Another embodiment of a freezer <NUM> is shown in <FIG>. The overall structure of the freezer <NUM> is substantially similar to the freezer <NUM> shown in <FIG>. In this embodiment, the upper and lower sections <NUM>, <NUM> are assembled by joining the insulated members using insulated polymeric corner elements. The insulated members are joined to the corner elements by engaging slots located in the corner elements with cams located in the insulated members. The cams can be engaged and disengaged from the slots by turning an engagement socket using an Allen wrench. The insulated members and corner elements preferably have compressible seals along the surfaces in which they are joined to provide an airtight seal. For example, the floor <NUM> of the lower section <NUM> is joined to the side wall <NUM> by corner element <NUM>. The corner element <NUM> has a slot <NUM> which engages a cam (not shown) located in the floor <NUM> and a slot <NUM> which engages a cam (not shown) located in the side wall <NUM>. Should it be desirable to disassemble the lower section <NUM>, this can be accomplished by disengaging the cams.

The embodiment of the freezer <NUM> also includes a liner <NUM> that is located between the upper and lower sections <NUM>, <NUM> and extends the length of the tunnel. The liner <NUM> includes a floor <NUM> that is parallel to the ceiling <NUM> of the upper section <NUM> (which opposes the floor <NUM>) and the floor <NUM> of the lower section <NUM>. The liner <NUM> also includes sidewalls <NUM>, <NUM> that extend upwardly from the floor <NUM> and over the upper edges of the side walls <NUM>, <NUM> of the lower section <NUM> and attachment posts <NUM>, <NUM>, which enable the liner <NUM> to be attached to the cables <NUM>, <NUM> used to raise and lower the lower section <NUM>. The belt <NUM> (which is identical to belt <NUM>) has a lower run that lies atop the floor <NUM> when the lower section <NUM> is in a closed position (see <FIG>).

In order to facilitate cleaning & sanitizing, the liner <NUM> preferably comprises a single sheet of metal that spans the lower section <NUM>, but may be assembled from multiple segments along its length (like the upper and lower sections). If multiple segments are provided, they are preferably separable for cleaning and sanitation purposes.

In addition, the liner <NUM> is preferably capable of being raised and lowered independently of the lower section <NUM>, to facilitate cleaning of the lower section <NUM>. In this embodiment, the lower section <NUM> and the liner <NUM> are moved from a closed position (<FIG>) to an open position (<FIG>) by turning one of the hand cranks <NUM>, <NUM>, which lengthens the cables <NUM>, <NUM> via a gearbox <NUM>, <NUM>. Referring to <FIG>, the liner <NUM> can be raised without raising the lower section <NUM> by removing the cables <NUM>, <NUM> from attachment posts <NUM>, <NUM> located on the lower section <NUM>, then turning one of the hand cranks <NUM>, <NUM> in the opposite direction used to lower the liner <NUM> and lower section <NUM>.

Use of the liner <NUM> enables the use of insulated members and insulated corner elements in standard commercially, available sizes, while maintaining a preferred tunnel <NUM> profile and location of belt <NUM>.

Claim 1:
A freezer (<NUM>) comprising:
a housing comprising a plurality of insulated members that define a tunnel (<NUM>), the tunnel having a floor (<NUM>, <NUM>, <NUM>), opposing first (<NUM>, <NUM>, <NUM>, <NUM>) and second (<NUM>, <NUM>, <NUM>, <NUM>) sidewalls that extend upwardly from the floor, and a ceiling (<NUM>) located opposite the floor, the housing having a first opening at a first end of the tunnel that defines an entrance and a second opening at an opposing second end of the tunnel that defines an exit, a length of the tunnel extending from the entrance to the exit;
a delivery system adapted to introduce a cryogenic fluid into the tunnel (<NUM>);
a belt (<NUM>) extending along the length of the tunnel (<NUM>) and being continuous, the belt having an upper run (<NUM>) that extends through the tunnel and a lower run (<NUM>) that extends through the tunnel; and
a drive assembly (<NUM>) and a tensioning assembly (<NUM>) located outside of the tunnel (<NUM>) that retain the ends of the belt (<NUM>), wherein the belt is not supported by any other belt guide structures other than said drive and tensioning assemblies, the drive assembly being adapted to drive the belt, and the drive assembly, tensioning assembly, belt and housing being configured so that the upper run (<NUM>) lies atop the lower run (<NUM>) when the belt is operated.