CA1092777A - Method and apparatus for continuously sterilizing flat flexible packages - Google Patents

Abstract

METHOD AND APPARATUS FOR CONTINUOUSLY
STERILIZING FLAT FLEXIBLE PACKAGES

Abstract of the Disclosure The apparatus comprises a sealed chamber including a sterilizing section, a cooling section and a conveyor includ-ing carrier receivers and circulated through the sterilizing and cooling sections. The flat flexible packages containing substances to be sterilized are contained in rotatable carriers. With one side of the sealed chamber is provided a sealing means through which the carriers are charged and discharged into and out of the sealed chamber.

Description

109~77 Back~round of the Invention This invention relates to a method and apparatus for continuously sterilizing substances contained in flat and flexible packages at a sterilizing temperature of higher than 100C and under a pressure higher than atmospheric pressure, said packages being packed with such substance as foodstuff to be sterilized and then sealed, and the innermost layers or portions of the flexible packages being made of heat sealable film.
Various types of continuous sterilization apparatus have been used for sterilizing can~ but batch-type method of sterilization has mainly been used in the past for sterilizing fle~ible packages. The continuous sterilizers utilized to sterilize cans seem to be particularly suitable for mass produc-tion and suitable for the larger output of the products of the same type as in the manufacture of canned food~tuff. The total output of flexible packages such as retortable poucheæ has relatively increased, but it has been rarely the case that ~ large number of such packages are treated in one factory, so that the demand for continuou~ sterilizers have been until recently small.
However, with the recent tendency of mass production of retortable pouches in one factory the continuous sterilizers have been increasing in demand.
Another gr~und of-adopting the continuous sterilizers are based on the consideration of saving energy and labor. With the batch-type method of sterilization, since successive

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109;~777 sterilization cycles are performed independently, the amount~
of the heating medium such as steam are not water, and cooling water required for the sterilization process seem to be larger than that of a continuous method. Further~ore, in the batch-type method, considerable labor is required to load and unloadthe articles to be sterilized. Accordingly, deve~opment of an efficient apparatus capable of continuously sterilizing retortable pouches has long been desired.
A third reaQon for the continuous sterilization is based on the standpoint of food engineering. Usually, cans have been sterilized at a temperature of about 120C, but it has been proved not only theoretically but also experimentally that some foodstuffs have better quality when sterilized in a shorter time at a higher temperature than at a lower temperature for ` 15 a longer time. Various factors that affect the quality of foodstuffs, such as flavour, fragrant, color and nutritive value (vitamines) are chemically unstable and the rate of des-tructio~ of these factors caused by being subjected to heat increases 2 to~3 times for each 10C rise of temperature as doeQ a chemical reaction. On the other hand, the normal rate of destruction of bacteria (saprogenuous bacilluseæ) usually increases 10 to 20 times for each 10C rise of temperature.
From these facts, when sterilized at a high temperature the bacteria like sa~rogenuous--baci-lluses would be de~trcyed in a short time but considerable amounts of vitamines would survive.
With regard to heat penetration, since cans are generally cylindric&l, it requires a relatively long time before the - . .- . . . - . . .
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109;~777 center of the can reaches the pre-determined temperature during which local burning tends to happen. For this rea~on, the can must be kept in violent agitation particularly during steriliza-tion. However, the flexible package iB flat and its thickness is not so lar~e. The~e characterics result in a rapid heat transfer, so that the temperature differential between the central and peripheral portions i9 smaller than that of the can.
Accordin~ly, flat and flexible packages are suitable for high-temperature short-time sterilization.
In the case of high-temperature short-time sterilization, the temperature of the contents needs to be rapidly increased so the sterilization of the canned food requires severe agita-tion for the purpose of averaging the temperatures at the central and peripheral portions since the temperature differential there-between is large as above pointed out. Xowever, in the case of such flexible packages as retortable pouches the packages wou d be damaged (when a severe agitation is applied,) because they do not have s~fficient strength as compared with cans and in certain cases the ste-rilized packages may be damaged and invol~e the risk ~ -of spoilage. Howe~er, as above described, flexible packaes are flat and the temperature differential between the central and peripheral portions is small, so that the flexible packages can be sterilized at a high temperature without applying agitation as in the c&se of cans.
In the high-temperature short-time sterilization, as the hi~h rate of heat penetration into a fooc contained in the rouch is needed, it is desirable that the tem~erature of tile sterilizing .. I -, ~
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10~;~777 at~osphere should reach a predetermined hi~h temperature as fast as ~ossible (come-up time), so that with a conventior.al batch-type method requiring a considerably long come-up +ime, t~Je high-temperature short-time sterilization can not be achieved. ~or this reason, it i9 desirable to provide a sterilizing apparatus capable of reducing the come-up and down time close to zero, that is a continuously sterilizing apparatus.
Among various types of continuous sterilizers which can be used for sterilizing cans, those suitable for the steriliza-tion of flexible packages are hydrostatic-type sterilization apparatus and a sterilization apparatus utilizing a special valve. In the former type, in order to maintain a predetermined pressure in the sterilizing chamber here is provided with a water column com~unicating with the sterilizing chamber at the bottom so as to cause the hydrostatic pressure head in the column to balance with the pressure in sterilizing chamber.
Accordingly~ a high water column must be used in order to maintain a high pressure in the sterilizing chamber meaning the need of instailing a tall column. When steam is used as the heating medium, the pressure is about 1 kg/cm2 at a temperature of 120C, &bout 2.2 k~/cm2 at 135C and about 3.9 kg/cm2 at 150C, so that the hydrostatic-type sterilization apparatus is required to use a water column having 2 height of about 10 m for 120C, about 22 m for 135C and 39 m for 150C. In tnis manner, the high-temperature short-time sterilization using a hydrostatic-type sterilizer is actually limited in terms of - ' ' ~os~m construction. At present, the maximum sterilization temperature of the hydrostatic-type sterilizer is said to be about 128C.
In the sterilization apparatus utilizing a special valve as a sealing means, since a chain conveyor for conveying such con-tainers as cans is passed through the valve, it is impossible toprevent leakage of cooling water through a small gap through which the chain conveyor passes~ Accordingly, pumping means are provided for supplementing the leaked cooling water, and in certain cases a pump having a substantial capacity is needed.
lC The highest sterilization temperature of this type is said to be about 143C.
As described above, these continuous sterilizers are design-ed for mass production, but in some countries where a large number of pouches are not heat-processed in one factory, it is desirable to provide ine~pensive continuous sterilizers having a relatively small size and capacity.
However, in order to save energy and labor a fully auto-mated continuou~ sterilization system must be used in which not only the eterilization apparatus per se but also various equip-ments installed before and after it are suitably connected tooperate automatically. Otherwise, the advantage of fully auto-matio line can not be realized. Different from such rigid containers as cans and bottles, the flexible packages are flexible and have lower mechanical strength so that there are such problems as wrinkling, scratch, folding, warping and welding seam damage.
Thus, there are many problems for establishment of the fully automatic processing system.

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109;~777 Summary of the Invention Accordingly, it i9 an object of this invention to provide a continuous sterilization method capable of automatically sterilizing flexible packages at a high temperature.
Another object of this invention is to provide a novel continuous sterilization apparatus capable of continuously sterilizing flexible packages such as retortable pouches at high temperatures and decreasing the amount of leaking of cool-ing water and enabling sealing of higher pressures.
~ further object of this invention is to provide a novel continuous sterilization apparatus ior flexible packages without ~ -damaging the ~ame, which can efficiently transmit heat to the packages and can readily introduce and discharge the packages into and out of the sterilizing chamber.
~till further object of this invention is to provide a continuous sterilization apparatus wherein the operation of a sealing means and the operations of article admitting and dis-charge mechanism are synchroniized.
Another object of this invention is to provide an improved rotatable carrier capable of containing a plurality of flat fle~ible packages and carry them in a horizontal position during heating and cooling.
According to one aspect of this invention, there is provided a method of continuously sterilizing flat packages comprising the steps of positioning sealed fle~ible packages each packed with substances to be sterillzed in trays, stacking trays one - above the other, accommodating the stacked trays in a rotatable ~ - 7 -; . ~ . ; ~ . - . -. -. .
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carrier, admitting the carrier into a continuous sterilization apparatus, sterilizing the packages in the carrier while the car-rier is conveyed through the sterilization apparatus and while the packages are maintained in a horizontal position, cooling the sterilized packages, discharging the carrier out of the steriliz-ation apparatus, removing the stacked trays from the carrier, separating the stacked trays individually and taking out the sterilized packages from the trays and repeating the steps in the order mentioned.
According to another aspect of this invention, there is : :
provided a carrier for flexible packages comprising a rectangular .
inner container partitioned by partition means into a plurality : :
of compartments each accommodating a flat flexible package, the inner container being provided with vent holes and having a height sufficient to form a space above the flexible packages accommodated in respective compartments, an outer container hav-ing a volume sufficient to accommodate a stack of a plurality of inner containers, the outer container being provided with vent holes and opened at its upper side, a clamping plate biased by spring means for clamping the stack, an operating rod for open-ing said clamping plate against the force of the spring means, and wheels rotatably mounted on both sides of the outer container.
According to still another aspect of this invention, there is provided continuous sterilization apparatus comprising a chamber including a sterilizing section filled with heat medium and a cooling section filled with cooling water, said heating section and said cooling section being in contact each other ... . ,. '. ~ '' :

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1(}5';~777 through a limited contact region, a conveyor provided with a plurality of carrier receivers for receiving carriers to be ster-ilized, each of said carriers comprising a rectangular inner con-tainer partitioned by partition means into a plurality of compart-ments, each accommodating a flat flexible package, said inner container being provided with vent holes and having a height suf-ficient to form a space above the flexible packages accommodated in respective compartments, an outer container having a volume sufficient to accommodate a stack of a plurality of said inner containers, said outer container being provided with vent holes and opened at its upper side, a clamping plate biased by spring means for clamping said stack, an operating rod for opening said clamping plate against the force of said spring means, and wheels rotatably mounted on both sides of said outer container, means .
for moving said conveyor for conveying said carrier receivers successively through said sterilizing section, said cooling sec-tion and said contact region, a sealing means intercepting direct communication between inside and outside of said chamber, an admission mechanism for charging carriers to be sterilized into said carrier receivers via said sealing means, a discharge mech-anism for discharging sterilized carriers to the outside of said chamber from said carrier receivers via said sealing means, sup-porting means arranged between said carrier receivers and said sealing means for supporting said carriers, revolving levers for moving said carriers on said supporting means, and means for op-erating said revolving levers in synchronism with the rotation of said sealing means.

_g_ 109;~777 Each carrier receiver comprises a semi-circular member for holding afore-mentioned rotatable carrier containing a plur-ality of flat flexible packages.
In a preferred embodiment, a water tank is provided on the outside of the sealing means and a conveyor is installed in the water tank for supplying and receiving carriers to and from the sealing means. In this manner the carriers to be sterilized can be also preheated in the water tank.
Brief Description of the Drawings Further objects and advantages of the invention can be more fully understood from the following detailed description taken -9a-. , ' ` , , , ~' ' ` ' ' ;, . ..
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'' lOg~7~7 in conjunction with the accompanying drawings in which:
Fig. 1 is a block diagram for e~plaining the method of sterilization of this invention;
Fig. 2 is a perspective view showing a carrier for carrying flexible packages utilized in this invention;
Fig. 3 is a perspective view showing a container utilized in the carrier;
Fig. 4 is an enlarged longitudinal sectional view of one end of the carrier;
Fig. 5 is a cross-sectional view of the carrier;
Fig. 6 is a side view, partly in section, showing one embodi-ment of the continuoue sterilization apparatus of this invention;
~ig. 7 is a front view, partly broken away, showing the operating shaft utilized in this invention; ~
Fig. 8 i8 a perspective view showing the discharge mechanism ~`
and the carrier;
Fig. 9 is a plan view showing a power transmission mechanism and Flg. 10 's a side view of the power transmission mechanism.
Description of the Preferred Embodiment Referring now to the block diagram shown in Eig. 1, containers of flexible packages 11 are intermittently conveyed to an automatic filling and sealing machine 1 where contents such as foodstuff are sequentlally loaded in the oontainers and the openings thereof are heat sealed to form flexible packages 11. The packages are then positioned in trays 12 at the package loader 2 and the trays 12 containing the packages are discharged from the package loader 2 , . .. . . .

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'' . ' ' "' at a predetermined position thereof. The trays 12 are then stacked one upon the other by a tray stacker 3. The stack of the trays 12 are loaded in a carrier 13 by a tray loader 4. The detail of the carrier 13 will be described later. The carriers are then ad~itted into a continuous sterilization apparatus 5 through a sealing means as will be described later and sterilized continuously at a tem-perature ofhigherthan 100C and under a pressure of higher than the atmo~pheric préssure. ~hen, the carriers are conveyed to a cooling section. After being cooled by water the carriers are discharged to the outside through the sealing means described above.
The carrier discharged from the sterilization apparatus 5 is conveyed to a tray unloader where the trays are removed from the carrier 13 by a fluid pressure cylinder mechanism, for example, and the empty carrier 13 i8 returned to the tray loader 4 by a ~15 conveyor or the like.
Stacked trayæ 12 discharged from the carrier are removed one after one by a tray unstacker 7 and transferred to the succeeding stepe. A package unloader 8 provided with suction cups 8a removes sterilized and.cooled packages 11 from the tray 12 to send them to a drier, not shown, and émpty trays are returned to the package loader 2.
In the system described above, the package loader 2, the tray stacker 3 and the tray loader 4 are disclosed along one line, while the tray unloader 6, the tray unstacker 7 and the package unloader 8 are disposed along other line and by arranging the package loader 2 and package unloader 8 to confront each other and by arranging the tray loader 4 and tray unloader 6 to confront . , ~ '~: :

los~m each other it is not only possible to minimize the space occupied by the continuous sterilization system but also convenient to return the carriers and trays.
As shown in Fig. 2, the carrier 13 for the flexible packages comprises trays that are inner containers 21 and an outer contain- .
er 22. As shown in Fig. 3, each inner container 21 takes the form of a rectangular tray partitioned by partition walls 23 into a plurality of compartments for accommodating a flat flexible pack-age in each compartment. The tray has a height sufficient to form a space above the packages 11 contained therein and is provided with a plurality of vent holes 21a through its side walls, parti-tion walls and bottom wall, and angle shaped stack guides 25 at four corners. As shown in ~igs. 2, 4 and 5, the outer container 22 is provided with an opening at least in the front side for pass-ing the inner container 21 whereas the upper surface of the outer oontainer is opened. The outer container has a volume sufficient to accommodate a stack of several inner containers 21 and is provided with a plurality of vent openings 22a through its bottom plate. A weight 26 is fitted under the bottom wall. A clamping plate 27 for clamping the inner containers is fitted on the upper portion of the outer container 22. To the opposite ends of the clamping plate 27 are secured to guide shafts 28 which slidably extend through the side walls of the outer container 22 to the portion beneath the bottom plate of the outer container 22 where the lower ends of the guide shafts are secured to an operating lever 29 which i9 biased downwardly by coil springs 30 surrounding the lower portions of the guide shafts 28. Shafts 31 are secured .

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to the side walls of the outer container 22 for su~porting wheels 32 which are interconnected by several tie rods 33. As shown in Fig. 5, stop member 34 is provided for the rear side of the bottom plate of the outer container 22 while a stop member 35 is provided on the front side of the clamping plate 27.
When the operating lever 29 i8 pushed upwardly against the force of springs 30, the clamping plate 27 is raised through guide sha~t 28 thereby permitting insertion oi a stack of inner contain-ers 21 (each containing a number of flexible packages). Upon release of the operating lever 29 the clamping plate 27 is urged against the stack by the restoring force of the springs thus forcing the stack against the bottom plate of the outer container 22. The fle~ible packages are conveyed under these conditions for sterilization and cooling.
As shown in Figs. 6 and 7, the continuous sterilization apparatus 5 comprises a sealed chamber 41 with its interior divid-ed by a thermal insulator 45 into a sterilizing section 42 and a cooling section 43, the former being filled with heating medium, for example steam, whereas the latter with cooling water to a le~er 44. A vertical partition wall 45a is provided for the upper portion of the righthand portion of the casing 41 and to the right of this partition wall is provided a sealing means 46 which interupts direct communication between inside and outside of the sealed chamber. The height of the portion of the chamber between the partition wall 45a and the sealing means 46 is smaller than that of the other portion. The thermal insulator 45 is formed with a depending portion so as to form an air space between ... . . . . ..
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~09;~777 the lower surface of the insulator 45 and the level 100 of the cooling water thereby minimizing heat transfer from the heating medium to the cooling water. The pressurized air can be supplied in the air space. The position of the level 100 of the cooling water depends on the amount and pressure of the air contained in the air space.
The sealing means 46 comprises a rotor 47 having a horizontal sha~t 47a and rotated in the counterclockwise direction in the casing 48. There are small gaps of about 0.05 to 0.25 mm between the periphery of the rotor and the inner surfaces of the casing.
Accordingly, when compared with a contact-type sealing members, this construction is more advantageous from the standpoint of wear of the sealing member and driving force required to drive the rotor. The results of experiments show that the leakage of the cooling water in the sterilizing chamber through such narrow gap is very small because of the viscosity of the cooling water, thus it is ~ossible to maintain the atmosphere and the water level in the sterilizing chamber in a stable condition with returning the leakage or supplying fresh water to the cooling section of the chamber. The rotor 47 is provided with three carrier receiving pockets 49 which are e~ually spaced in the circumferential direc-tion. Each pocket 49 has a lever 50 which is rotated to push out the carrier received therein as will be described later.
A chain conveyor 52 is installed in the chæmber 41 for suc-cessively conveying carrier receivers 51 containing the carriers13 through a sterilizing section 42 and a cooling section 43 which are constructed such that the heating medium and the cooling .~ . .
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109~777 water contact with each other at two limited contact regions 44 (the level of the cooling water). The chain conveyor 52 comprises a pair of endless chains 52 between which a plurality of carrier receivers 51 are positioned at a predetermined spacing. Each carrier receiver 51 has substantially semicircular cross-sectional configuration. The conveyor passes over a plurality of wheels 54 and a drive-wheel 5~ to travel along a trapezoidal pass.
As shown in Fig. 6, an admission mechanism 55 and a discharge mechanism 56 are provided. The admission mechanism 55 includes a substantially horizontal supporting member 57 for supporting carriers and a revolving lever 58 mounted thereabove, whereas the discharge mechanism 56 comprises an inclined supporting member 59, and a revolving lever 60. The supporting members 57 and 59 are secured to the inside of the chamber between the conveyor 52 and ,15 the rotor 47 of the sealing means 46 and provided with recesses 57a and 59a for preventing the carrier from rolling in the direc-tion of the rotor and of the chain conveyor, respectively. -To more positively prevent such rolling of the carrier, stops 61a and 61b may be provided. On the outside of the sealing means 46 is disposed a carrier-charge and discharge conveyor 62 having a plurality equally spaced semi-circular carrier receivers 63.
Upper and lower guide plates 64 and 65 extend between the conveyor 62 and the sealing means 46 and turrets 66 and 67 for conveying the carrier are pivotally mounted above and below the guide plates 25, 64 and 65 respectively. A water tank 89 being able to preheat the carrier is disposed to the right of the chamber 41 and a portion of the carrier-charge and discharge conveyor 62, guide plates 64 - - : . .- .. ..

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m and 65, turrets 66 and 67 and revolving lever 68 are immer~ed in the water in the water tank 89. ~he level of the water i~ 101.
As shown in Figs. 6 and 8, the revolving levers 58 and 60 are mounted on operating shafts 69 and 70 to rotate therewith and to be slidable in the radial direction, and the cam-followers 71a, 71b and 72 secured to the revolving levers 58 and 60 engage with cam~ 73 and 74 re~pectively secured to the side wall of the chamber 41. Supporting rollers 75a and 75b are secured on the opposite ends of the upper revolving lever 58 to cooperate with the cam 73 80 as to move the lever 58 in the radial direction once at each one half revolution of the sha~t 69, whereas a supporting roller 76 is mounted on one end of the revolving lever 60 to cooperate with cam 74 80 as to move lever 60 in the radial direction once at each revolution of shaft 70.
As shown in ~igs. 7, 9 and 10, the operating shafts 69 and 70 and the sha~t 47a of the rotor 47 are driven by an electric motor 78 through a transmission mechanism 77. Although not shown in the drawing, the turrets 66 and 67, and the revolving lever 68 - .
are driven synchronously with the shaft 47a of the rotor 47 and the chain conveyor 52.
As shown in ~ig. 6, there are also provided a guide 79 for the chain conveyor 52, guides 80 and 81 for the carrier-charge and discharge conveyor 62, a supply chute 87, and a discharge chute 90.
The method for sterilizing flexible packages with the conti-nuous æterilization appàratus described above by using carriers 13 shown in Fig. 3 is as follows. At first the flexible packages -:, : - ~ ;.
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105~;~777 are positioned horizontally in the trays 21, and a qtack of the trays is positioned in a carrier. The carriers 13 are successive-ly supplied to carrier-receivers 63 of the carrier-charge and discharge conveyor 62 through supply chute 87, to convey the carriers toward one side o~ the sealing means 46. The carriers 1 are then successively received in the pockets 66a of the turrets 66 to be supplied onto the upper guide plate 64. Then, by the rotation of the revolving arm 68, the carriers 13 are sequentially forced into the pocketq 49 of the rotor 47 of the sealing means 46.
As the rotor rotates;in the counterclockwise direction as shown in Fig. 6 and one of the pockets 49 reaches the supporting member 57 of the admitting mechani~m 55, the level 50 i~ rotated to push the carrier received in that pockets on the recess 57a of the supporting member 57. Immediately thereafter, the revolving lever 58 i8 rotated by the operating shaft 69 which rotates in the clock-wise direction to project downwardly the lever 58 thus pushing the carrier 13 to the left as viewed in Fig. 6. Consequently, the carrier 13 on the supporting member 57 i9 positioned in one carrler receiver 51 of the chain conveyor 52 circulating in the counterclockwise direction. The carrier positioned in the carrier receiver i8 conveyed through the cooling water into the steriliz-ing section 42 via contact region 44 by the chain conveyor 52.
In the sterilizing section 42, the fle~ible packages in the carrier are sterilized by the heating medium. Then, the carrier i~ conveyed to the cooling section 43 via contact region 44 where it is cooled by the cooling water. The cooled carrier is then put onto the inclined supporting member 59 of the discharge - . . ~ . . . . .: .

lO9Z7~7 mechanism 56 when the opening of the carrier receiver 51 is directed downwardly. ~he end part 51a of the carrier receiver 51 pushes the carrier on the recess 59a of the SUpPOrtinF
member 59. When the revolving lever 60 rotated by the o~erating shaft 70 which rotates in the clockwise direction i9 projected ' upwardly, the lever 60 rotates in the right direction as viewed a in ~ig. 6 to push the cooled carrier into the pocket 49 where i;
the lever 50 has already been withdrawn after it pushes the carrier to be sterilized on the recess 57a of the supporting member 57. This carrier is discharged to the outside of the '!
chamber 41 by the rotation of the rotor 47 and when pocket 49 reaches a position above the lower guide plate 65, the lever 50 is rotated to push out the carrier from the pocket 49 onto the lower guide plate 65. The carrier is received in the pocket 67a f the turret 67 and then loaded in a carrier receiver 6~ of the carrier-charge and discharge conveyor 62. On the side opposite the sealing means 46 the carrier i9 discharged from the carrier receiver 63 and sent to the tray-unloader through discharge chute 90.
Although in the foregoing description, the desired steriliza-tion and cooling operations were described in connection with a single carrier it will be clear that a plurality of carriers are successively treated in the same manner.
During the above described operations, the levers 50 of the rotor 47 of the sealing means 46 are rotated to project in the pockets for pushing the carriers before sterilization and after cooling out of the pockets, and then the levers 50 are rapidly withdrawn. The rotor 47 of the sealing means 46 is immersed in ,`:, ' ~ . " ' ' ' ' ' ; ". ,' - :
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-1~9;~777 water on the inside and outside of the casing thereby efficiently and safely preventing the leakage of the cooling water. The tràys in the carrier are maintained in a horizontal position during transferring by the weight provided for the outer container 22.
The revolving levers 58 and 60 of the admitting mechanism 55 and the discharge mechanism 56 are guided by cams 73 and 74 to transfer the carrier 13. These levers are projected radially to move the carrier only in regions in which the carrier is to be moved, whereas in the other regions, the levers are retracted not to contact with the next carrier. Stop members 61a and 61b ;~
prevents the carrier from moving on the supporting members 57 and 59 in the directions opposite to the normal directions of trans-ferring thus assuring the movement of the carrier by the revolving levers 58 and 60. ~ -15 In the embodiment de~cribed above, the admission and discharge of ¢arriers ~nto and out of the chamber are performed by a single rotor of the sealing means 46 which prevents a direct communica-tion between the inside and outside o~ the continuous steriliza- j.
tion apparatus so that it is possible to prevent the pressure drop in the chamber 41.
Furthermore, as the rotor 47 is immersed in water by providing the water tank 89 on the outside of the ~ealing means 46, there is 1-no possibility of admitting air into the chamber 41 when the rotor 47 rotates, so that the temperature distribution in the steriliz-25 ~ ing section 42 and the heat transmission to the packages are notaffected. ~oreover, as the packages are preheated in the water tank, it is possible to improve the quality of food in the packages 1 .

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., . . ~ . , 109;~777 and to save energy consumption. It is advantageous to provide a suitable control device for controlling the temperature of the water in the water tank.
As the partition wall is provided for the thermal insulator 45 to form an air space between it and the upper surface 100 of the cooling water, it is possible to decrease the amount of heat transmitted from the heating medium to the cooling water because of low heat conductivity of air, and it iæ possible to decrease or increase the sterilization time by up or down the level 44 of the cooling water.;
It is preferable to rotate operat m g shafts 69 and 70 at different speeds at different portion of one revolution by using an indexing mechanism.

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Claims (13)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A method of continuously sterilizing the contents of flat packages com-prising the steps of containing sealed flexible packages each packed with substances to be sterilized in trays, stacking one above the other a plurality of trays, accommodating said stack in a rotatable carrier, admitting said carrier into a continuous sterilization apparatus, heat sterilizing the pack-ages in said carrier while the carrier is conveyed through said sterilization apparatus and while said packages are maintained in a horizontal position, cooling the sterilized packages, discharging the carrier from said sterili-zation apparatus, removing said stack of trays from said carrier, disassem-bling the stack and taking out sterilized packages from said trays, and re-peating said steps in the order mentioned.

2. The method according to claim 1 which further comprises the steps of returning empty carriers to a station where the stacks of trays are accommodated in said carriers, and returning empty trays to a station where the flexible packages are contained in the trays.

3. The method according to claim 2 wherein a station where the stacks of trays are accommodated in the carriers and a station where the stacks of the trays are removed from the carriers are disposed opposite to each other, and a station where the packages are contained in the trays and a station where the packages are taken out from the trays are arranged opposite to each other.

4. A carrier for conveying flexible packages comprising a rectangular inner container partitioned by partition means into a plurality of compartments, each accommodating a flat flexible package, said inner container being provided with vent holes and having a height sufficient to form a space above the flexible packages accommodated in respec-tive compartments, an outer container having a volume sufficient to accommodate a stack of a plurality of said inner containers, said outer container being provided with vent holes and opened at its upper side, a clamping plate biased by spring means for clam-ping said stack, an operating rod for opening said clamping plate against the force of said spring means, and wheels rotatably mounted on both sides of said outer container.

5. The carrier according to claim 4 which further compris-es a weight secured to the bottom of said outer container.

6. Continuous sterilization apparatus comprising a cham-ber including a sterilizating section filled with heat medium and a cooling section filled with cooling water, said heating section and said cooling section being in contact each other through a limited contact region, a conveyor provided with a plurality of carrier receivers for receiving carriers to be ster-ilized, each of said carriers comprising a rectangular inner con-tainer partitioned by partition means into a plurality of compar-tments, each accommodating a flat flexible package, said inner container being provided with vent holes and having a height suf-ficient to form a space above the flexible packages accommodated in respective compartments, an outer container having a volume sufficient to accommodate a stack of a plurality of said inner containers, said outer container being provided with vent holes and opened at its upper side, a clamping plate biased by spring means for clamping said stack, an operating rod for opening said clamping plate against the force of said spring means, and wheels rotatably mounted on both sides of said outer container, means for moving said conveyor for conveying said carrier receivers successively through said sterilizing section, said cooling sect-ion and said contact region, a sealing means intercepting direct communication between inside and outside of said chamber, an ad-mission mechanism for charging carriers to be sterilized into said carrier receivers via said sealing means, a discharge mech-anism for discharging sterilized carriers to the outside of said chamber from said carrier receivers via said sealing means, sup-porting means arranged between said carrier receivers and said sealing means for supporting said carriers, revolving levers for moving said carriers on said supporting means, and means for op-erating said revolving levers in synchronism with the rotation of said sealing means.

7. The apparatus according to claim 6 which further com-prises rotary shafts, guide means supported by said shafts for said revolving levers to be slidable in the radial direction during rotation and cam means secured to said chamber for moving said levers in said radial direction.

8. The apparatus according to claim 6 wherein said suppor-ting means include means for preventing said carriers from moving in a direction opposite to a predetermined direction.

9. The apparatus according to claim 6 which further com-prises a preheating water tank.

10. The apparatus according to claim 9 wherein an addit-ional conveyor is installed in said preheating water tank for admitting and discharging said carriers to and from said sealing means.

11. The apparatus according to claim 6 wherein said sealing means comprises a tubular casing, and a rotor arranged to rotate within said casing with a narrow gap therebetween, said rotor being provided with a plurality of circumferentially spaced poc-kets for receiving said carriers and means for pushing the car-riers out of said pockets.

12. The apparatus according to claim 7 which further com-prises means for rotating said shafts at different speeds at different portions of one revolution.

13. The apparatus according to claim 6 wherein each carrier receiver comprises a semicircular member and said carrier to be sterilized is a rotatable carrier containing a plurality of flat flexible packages.