while the present invention is susceptible of embodiment in various forms , as shown in the drawings , hereinafter will be described the presently preferred embodiments of the invention with the understanding that the present disclosure is to be considered as an exemplification of the invention , and it is not intended to limit the invention to specific embodiments illustrated . with reference to the figures , the food processing system 1 includes three primary components comprised of an inlet assembly 6 , an intermediate pressurizeable tunnel section 35 , and an outlet assembly 8 . the inlet assembly 6 provides for the introduction of food products into the food processing system without requiring depressurization of the pressurizeable tunnel . similarly , the outlet assembly provides for the expulsion of food products from the food processing system without requiring depressurization of the pressurizeable tunnel . with reference primarily to fig1 - 4 and fig1 - 13 , the inlet assembly 6 includes a pair of inlet screwstacks 7 a and 7 b . as illustrated in fig1 - 4 , the screwstacks 7 a and 7 b may be positioned laterally adjacent to one another relative to the longitudinal path of the food processing system 1 . alternatively , as illustrated in fig1 - 12 , the screwstacks 7 a and 7 b may be positioned longitudinally adjacent to one another relative to food processing system 1 . each of the screwstacks includes a hollow pressure vessel 13 which is preferably vertically aligned . as illustrated best in fig4 , each screwstack further includes an entry opening 17 , openable and closeable by a door 18 , at its upper extremity for the introduction of food products 31 . of importance , the door 18 provides a liquid and gaseous tight seal so that the screwstack can be pressurized . with reference to fig2 , at the bottom of each inlet screwstack 7 a and 7 b , a second opening 19 is provided which is openable and closeable by an exit door . again , the exit door provides a liquid and gaseous tight seal when the door is closed . each of the inlet screwstacks 7 a and 7 b further includes a pair of vertically extending threaded screws 21 positioned within the screwstacks &# 39 ; hollow interior . each screw 21 is rotatable by a motor 15 and includes a plurality of threads 23 . the screws are positioned parallel to one another to provide a space sized so that products can be positioned and maintained between the adjacent threads 23 of the respective screws 21 . the rotation of the screws causes food products 31 to move vertically through the inlet screwstack &# 39 ; s interior . more specifically , food products 31 are introduced into each inlet screwstack &# 39 ; s entry opening 17 when the entry door 18 is in an open condition . rotation of the screws 21 causes food products to be transported downline from the screwstack &# 39 ; s entry opening 17 to the screwstack &# 39 ; s exit opening . as illustrated in fig3 , vertically extending alignment rods or other guide assemblies 16 may be employed to properly maintain the products 31 between the parallel screws while traveling vertically within the screwstack . of importance , the inlet assembly screwstacks are operated so that the first entry opening 17 is closed by the entry door 18 when the respective screwstack &# 39 ; s second exit opening is opened . conversely , the operation of the screwstacks is controlled so that in the event that the entry opening 17 is open then the screwstack &# 39 ; s second exit opening 19 is closed by an exit door 20 . with reference to fig3 and 4 , in order to continuously introduce food products into the food processing system 1 , the operation of the inlet assembly &# 39 ; s respective screwstacks 7 a and 7 b is alternated so that while one screwstack is receiving and loading food products 31 into its interior , the other screwstack is expelling products through a connecting conduit 37 into the pressurizeable tunnel 35 . to introduce food products into the inlet assembly screwstacks 7 a and 7 b , the food processing system preferably includes a conveyor 27 connected to an inlet hopper 23 . the inlet hopper 23 and conveyor 27 transport food products to a sorting chamber 29 which utilizes an internal mechanical actuator ( not shown ) to selectively introduce food products into a screwstack 7 a or 7 b . as illustrated in fig1 , 11 and 12 , preferably the inlet assembly 6 also includes a second sorting chamber 29 connected to the inlet screwstack &# 39 ; s exit openings 19 for receiving food products 31 from the screwstacks 7 a and 7 b for transportation to the pressurizeable tunnel 35 . again , the exit openings 19 of the inlet screwstacks 7 a and 7 b are alternately opened for expulsion of food products 31 into the sorting chamber 29 , which in turn includes an internal mechanical actuator ( now shown ) that transports the food products through a liquid and gaseous tight connecting conduit into the pressurizeable tunnel 35 . the pressurizeable tunnel 35 can take various forms . for example , as illustrated in fig1 and 5 , the pressurizeable tunnel may be subdivided into numerous chambers for product processing . any construction of a pressurizeable tunnel will include at least one heating stage 41 . as illustrated in the figures , the heating stage 41 includes at least one microwave source 43 , preferably including a plurality of microwave generators 45 and wave guides 47 . as illustrated in the figures , a preferred microwave source 43 includes four microwave generators 45 and corresponding wave guides 47 for directing microwave energy downwardly upon the top of food products , and an additional four microwave generators 45 and corresponding wave guides 47 for directing microwaves upwardly upon the bottom of food products . the food products may be conveyed through the heating stage 41 using a wide variety of mechanical apparatus as can be selected by those skilled in the art . as illustrated in fig6 and 14 , in a preferred embodiment , food products 31 are conveyed through the heating stage without any mechanical apparatus engaging the top or bottom of the products by utilizing a pair of parallel belts having elongate slots sized and positioned to receive the edges of product trays effectively eliminating all massive mechanical conveying apparatus from the microwave exposure area 34 . with reference to fig1 , the system for conveying food products through the heating stage preferably employs a conveyor belt system which is mostly disposed within the pressurizeable tunnel &# 39 ; s heating stage 41 . more particularly , the conveyor system 6 consists primarily of a pair of parallel side - by - side belts 60 - l and 60 - r which are spaced apart to engage the sides of packages . preferably , the packages are supported only by the belts 60 and by any buoyancy imparted by the fluid with the heating stage . preferably , all other mechanical supports or other apparatus are eliminated or spaced a significant distance away from the packages to reduce interference to the microwave field . thus , the conveyor belts 60 support packages 31 so that the packages 31 are spaced above any apparatus such as the bottom wall of the pressurizeable tunnel 35 while the packages are conveyed through the microwave field . as illustrated in fig1 , a motor 70 and series of belts , gears , and pulleys are used to drive the pair of conveyor belts 60 in synchronism . in particular , these may include a timing belt 74 and first timing belt pulley 79 coupled to motor 70 via drive gears 78 and drive shaft 80 . a second timing belt pulley 79 on the far side operates belt drive roller 73 . belt drive roller 73 and various belt guide rollers 72 further provide movement and support for the conveyor belts 60 . as illustrated , the motor 70 may be supported by motor bracket 75 above gears 78 , pulley 79 and drive shaft 80 , but it should be understood that other arrangements are possible . in operation , a left hand belt 60 - l is continuously fed around its respective guide rollers 72 and drive roller 73 ( driven by timing belt 74 ), and a respected right hand belt 60 - r is continuously fed around its respective drive roller 73 ( driven by one of the gears 78 ) and its respective guide rollers 72 . left hand belt 60 - l and right hand belt 60 - r are thus kept in alignment with one another via gears 78 , pulleys 79 and timing belt 74 . this is necessary to ensure that the packages 31 are conveyed in an orderly fashion . though not illustrated , a tension measurement device or other device such as a motion transducer may be used in combination with the belts 60 to provide feedback on package location and condition . the tension measurement devices can be located as part of one of the guidance rollers 72 , within the heating stage , or may be part of one of the drive pulleys 72 which may be located outside the heating stage . in addition , belt tensioners may be used to prevent slack in the belts 60 . furthermore , the belts 60 may be perforated to receive sprockets or tabs formed upon drive roller 73 and / or guide roller ( s ) 72 . the sprockets will engage the perforated holes to provide a more positive engagement mechanism between motor 70 and belts 60 . the belts themselves are preferably made of a suitable material that is temperature , fluid and microwave energy insensitive . teflon ™, kevlar ™ and fiberglass are examples of suitable materials . as illustrated in fig6 and 10 , preferably the food products 31 include a bottom tray 34 and a peelable cover 33 for encapsulating a food product 32 . each of the trays include parallel side lips 36 which extend beyond the traditional edge of the tray for being received within the belt slots . the pressurizeable tunnel 35 may include a heat maintenance stage 49 for maintaining food products at a desired temperature for a desired time period to kill pathogenic bacteria , spores , and organisms . the pressurizeable tunnel may also include a product cooling stage 51 for cooling products from high temperatures to lower temperatures for ultimate expulsion from the food processing system 1 . the temperature maintenance stage , including the sub - stages for heating and cooling of products , utilize temperature maintenance screwstacks 11 . as illustrated in fig5 and 7 , each of the temperature maintenance screwstacks 11 preferably include two pairs of screws 21 , as opposed to a single pair of screws within the inlet and outlet assembly screwstacks . within the temperature maintenance screwstacks 11 , a first pair of screws 21 receives the food products 31 which have been introduced into the screwstack through an entry opening 37 . the screws 21 are rotated by one or more motors 15 to transport the food products 31 upwardly to the opposite upper extremity of the screwstack where the food products are moved laterally by a mechanical actuator ( not shown ) to the upper extremity of the other pair of screws 21 . the second pair of screws 21 transport the food products downwardly to the bottom of the screwstack 11 until they are ejected by an additional mechanical actuator to an exit opening 19 where they are expelled to an additional temperature maintenance screwstack 11 or introduced into the outlet assembly 8 . ( see fig7 ). advantageously , the temperature of maintenance screwstacks 11 provide a very small footprint , but a significant travel distance for the food products so that food products are maintained at a proper temperature for a desired time period . as illustrated in fig1 , in a preferred embodiment , the heat maintenance stage 49 includes 3 screwstacks 11 for providing a passageway within which the food products will travel for a sufficiently long time period at a desired temperature sufficient to kill pathogenic microorganisms and spores . meanwhile , a preferred product cooling stage 51 includes 4 screwstacks 11 providing sufficient travel time and distance for the products to cool to a desired temperature before being introduced into the food processing system &# 39 ; s outlet assembly 8 . as illustrated in fig7 and 8 , the outlet assembly 8 receives the food products 31 from the product cooling stage 51 through a connecting conduit 37 . with reference also to fig1 and 13 , the outlet assembly 8 has a construction very similar to the construction of the inlet assembly 6 . specifically , the outlet assembly includes a pair of screwstacks 9 a and 9 b . like , the inlet assembly 6 , the outlet screwstacks 9 a and 9 b may be positioned laterally adjacent to one another relative to the longitudinal path of the food processing system 1 as illustrated in fig1 and 7 . alternatively , as illustrated in fig1 and 13 , the outlet screwstacks 9 a and 9 b may be positioned longitudinally adjacent to one another relative to food processing system 1 . in addition , the outlet assembly includes a sorting chamber 29 which receives the food products from the product cooling stage 51 and conveys the food products to either the first or second outlet screwstack 9 a or 9 b . each outlet screwstack includes a pair of screws 21 for transporting the food products from the screwstack &# 39 ; s bottom extremity to the screwstack &# 39 ; s top extremity . each of the screws is rotated by motors 15 illustrated at the top of the screwstack . after being transported to an outlet screwstack &# 39 ; s upper extremity , a mechanical actuator or the like forces the food products through an exit opening 19 formed in the screwstack sidewall to a sorting chamber 29 . the sorting chamber 29 receives the food products 31 from either the first or second screwstack 9 a or 9 b , which in turn conveys the food products to an exit hopper 25 . a conveyor belt 27 then transports the food products 31 from the exit hopper 25 for distribution . the outlet assembly &# 39 ; s screwstacks &# 39 ; inlet openings 17 near the bottom of the screwstacks and exit openings 19 near the top of the screwstacks are openable and closeable by an entry door 18 and exit door 20 , respectively . each of these doors provide a substantially liquid and gaseous tight seal so that the outlet screwstacks 9 a and 9 b can be filled with a liquid and pressurized . in the event that an outlet screwstack entry opening is open , the respective screwstack &# 39 ; s exit opening is closed by the exit door 20 . conversely , in the event that the exit opening 19 is in an open condition , the outlet assembly &# 39 ; s entry opening 17 is closed by an entry door 18 . thus , at least one of the outlet screwstack &# 39 ; s doors are closed at any one time so as to maintain pressure within the pressurizeable tunnel 35 . in operation , the outlet assembly also operates in similar manner to the operation of the inlet assembly . the outlet screwstacks 9 a and 9 b are operated alternately so that as a first outlet screwstack 9 a receives food products 31 through a sorting chamber 29 from the product cooling stage 51 , the other screwstack 9 b expels food products from its hollow interior to a second sorting chamber 29 for transportation to the exit hopper 25 . in order to control the various conveying apparatus , lever arms , mechanical actuators , and entry and exit doors , the food processing system 1 includes a control processor . the control processor can be designed by those skilled in the art without undue experimentation . the control processor may include one or more computer chips and one or more software programs for controlling the rotation of the screwstack screws , movement of the conveyor belts , movement of the mechanical lever arms and actuators , and opening and closing of the entry and exit doors so as to continuously move food products 31 through the food processing system 1 . in operation , preferably the entire food processing system , including inlet assembly 6 , pressurizeable tunnel 35 , and outlet assembly 8 , is filled with a liquid such as water . as illustrated in fig7 , the water line 53 within the inlet and exit hoppers is sufficiently high so as to be above the chamber &# 39 ; s entry or exit openings so that unwanted air cannot be introduced into the system . in addition , the food processing system includes an active and controllable pressure source ( not shown ) for maintaining the pressurizeable tunnel at an increased pressure , preferably at or above two atmospheres . the active pressure control system may include the use of pressurized cylinders , electric or combustion powered gas compressors , or hydraulic compressors , all of which may be controlled by the control processor . while several particular forms of the invention have been illustrated and described , it will be apparent that various modifications can be made without departing from the spirit and scope of the invention . for example , the inlet , outlet and temperature maintenance screwstacks may be of any length and may store any number of food products . preferably , the screwstacks are sufficiently tall to hold at least 10 food products within its interior . even more preferably , each screwstack is sufficiently tall so as to hold 50 products or more within its interior . in the preferred embodiment , the screwstacks are sufficiently long that each pair of screws 21 which are approximately 8 feet long for storing approximately 60 packaged food products within the screw threads . thus , preferred inlet and outlet screwstacks can store approximately 60 food products within their interior , while each maintenance screwstacks , with their two pairs of screws , can store approximately 120 food products within its interior . various changes to the conveyor system may also be made without departing from the spirit and scope of the invention . for example , the preferred embodiments described herein include a single conveyor belt supplying or retrieving food products to or from a hopper and sorting chamber . however , the sorting chamber may be eliminated by providing the inlet and / or outlet screwstacks with individual belts or the like to supply or receive food products . since changes can be made without departing from the spirit and scope of the invention , it is not intended that the invention be limited except to the following claims . having described my invention in such terms so as to enable persons skilled in the art to understand the invention , recreate the invention and practice it , and having presently identified the preferred embodiments thereof ,
an apparatus and method for processing food products is provided . the product conditioning system includes an inlet assembly , a pressurizeable tunnel and an outlet assembly . the inlet and outlet assembly pressure vessels include a pair of vertically extending parallel screws for transporting food products from one end of the pressure vessel to the other . the pressurizeable tunnel includes a heating stage having microwave sources for irradiating food products so as to pasteurize or sterilize prepackaged food . the pressurizeable tunnel further includes a heat maintenance stage and product cooling stage . both the heat maintenance stage and product cooling stage include vertically extending pressure vessels . within each pressure vessel , two pairs of parallel rotating screws are positioned for moving food products through a liquid environment at a desired temperature for continued pasteurization or sterilization in the heat maintenance stage , and product cooling within the cooling stage .