Sterilizing system for filled and sealed articles

An improved sterilizing system for filled and sealed articles which are treated by way of the steps of filling a content into packing means and sealing the filled articles in a filling and sealing station, loading a tray with the filled and sealed articles, building up a tray stack including a predetermined number of loaded trays stacked thereon, sterilizing the tray stacks in a sterilizer and then conveying them to a packing station, wherein the improvement consists in an arrangement of a combination of a tray stack building station for building up a tray stack including a predetermined number of empty trays recovered after the filled and sealed articles are released toward the packing station, a tray stack holding conveyor for holding a plurality of tray stacks built up in said tray stack building station and a tray extracting station in which the empty trays are extracted from the tray stack conveyed from said tray stack holding conveyor one by one and then they are delivered toward the filling and sealing station. The sterilizing system further includes a tray stack holding conveyor having an ample holding capacity, said tray stack holding conveyor being located downstream of the sterilizer. The sterilizing system may be provided with an additional line of conveyance system including a sterilizer which is arranged in parallel to the aforesaid line of conveyance system including the sterilizer.

The present invention relates to an improved sterilizing system for filled 
and sealed articles. 
To facilitate understanding of the present invention a typical conventional 
sterilizing system for filled and sealed articles will be described below 
with reference to FIG. 1. 
In the drawing reference numeral 01 designates a filling and sealing 
apparatus in which various kinds of contents are filled into packing means 
in the form of a bag, envelope or the like (used for retort-pouch 
foodstuff or the like) and the filled articles are sealed. The filled and 
sealed articles (hereinafter referred to simply as articles) are delivered 
therefrom on a conveyor 03 via a transfer mechanism 02 and then they are 
placed on an empty tray 04 on said conveyor 03. Reference numeral 05 
designates a tray stacking apparatus in which a predetermined number of 
trays 06 loaded with the artlces are stacked one above another. One of the 
conventional tray stacking apparatuses is disclosed, for instance, in 
Japanese Patent Laid-Open No. 25090/80 and it is constructed such that the 
loaded trays 06 are stacked from above, one-by-one. Further, reference 
numeral 07 designates a holding conveyor which serves for holding thereon 
a predetermined number of tray stacks 09 including the predetermined 
number of loaded trays stacked in the tray stacking apparatus. Further, 
reference numeral 010 designates a sterilizer in which the plural tray 
stacks 09 are subjected to sterilization under high temperature and 
pressure steam atmosphere or with the use of hot water. After completion 
of the intended sterilization and subsequent cooling the tray stacks 09 
are delivered onto another holding conveyor 011. Further, reference 
numeral 012 designate a tray unloading apparatus in which unloading is 
practiced for the tray stacks 09 in the reverse order relative to the 
aforesaid tray stacking apparatus 05 in such a manner that the sterilized 
trays are unloaded from the upper end of the tray stack 09 one by one and 
then they are placed on a conveyor 013. One of the conventional tray 
unloading apparatuses is disclosed, for instance, in Japanese Patent 
Laid-Open No. 25090/80. Further, reference numeral 014 designate a filled 
article extracting apparatus which serves for extracting the articles from 
the loaded tray 06 conveyed by the conveyor 013 and delivering them toward 
a packing station including a drying apparatus or the like (not shown). 
The empty trays 04 are carried back to a storing or holding area located 
upstream of the filling and sealing apparatus 01 with the aid of wagons, 
carriages or the like (not shown). 
Owing to the arrangement that the conventional sterilizing system for 
filled and sealed articles includes the holding conveyor 07 located 
upstream of the sterilizer 010 and the holding conveyor 011 located 
downstream of the sterilizer 010 so as to temporarily hold a plurality of 
tray stacks 09 prior to sterilizing on the former and temporarily hold a 
plurality of tray stacks 09 after sterilizing on the latter it is ensured 
that supplying of the tray stacks to and discharging of the same from the 
sterilizer 010 are automatically carried out, but it is found that the 
conventional sterilizing system has the following drawbacks. 
(i) The conventional sterilizing system takes about one hour until the 
loaded tray 06 reaches the conveyor 013 via the sterilizer 010 after the 
filling and sealing apparatus 01 starts its operation. The filled article 
extracting apparatus 014 and the packing station including the drying 
apparatus or the like start their operation just when the tray stack comes 
to the end of the conveyor 013. 
This means that there is a so-called time lag relative to starting time of 
operation between the filling and sealing apparatus 01 and the packing 
station. Due to the time lag as mentioned above it becomes necessary to 
make an adjustment for operators who take charge of the filling and 
sealing apparatus 01 and other operators who take charge of the packing 
station separately as to a time when they have to arrive at their factory. 
Obviously, this sort of time adjustment is by no means desirable for 
laborer control in a company. To obviate the problem relative to the above 
time adjustment a remedial measure is usually taken in such a manner as to 
hold the sterilized tray stacks 09 and the sterilized trays 06 on the 
holding conveyor 011 and the conveyor 013 until the next morning. However, 
as is often the case with the conventional sterilizing system, the holding 
conveyor 011 and the conveyor 013 do not have a holding capacity enough to 
obviate the problem relative to the time lag as mentioned above. As will 
be readily apparent, the larger the sterilizer is constructed, the more 
the time lag becomes. Thus, shortage in the holding capacity becomes a 
serious problem. 
(ii) In the conventional sterilizing system there is a necessity for 
manually placing a predetermined number of empty trays 04 on the wagon, 
carriage or the like after the sterilized articles are extracted from the 
tray stack by operating the filled article extracting apparatus 014 and 
then carrying them toward the filling and sealing apparatus 01. Thus, 
automatic recovery of the empty trays fails to be achieved. 
(iii) In the event that any trouble takes place with the filled article 
extracting apparatus 014 or the packing station in the susequent process 
stops its operation, it becomes impossible to continue delivering of the 
empty trays 04 to the filling and sealing apparatus 01 in spite of the 
arrangement for holding the tray stacks 09 and the trays 06 on the holding 
conveyor 011 and the conveyor 013, resulting in stoppage of operation of 
the filling and sealing apparatus 01 and reduced efficiency in production. 
This means that there is no necessity for holding the tray stacks 09 and 
the trays 06 on the holding conveyor 011 and the conveyor 013. 
(iv) Further, when the sterilizer 010 stops its operation due to trouble, 
cleaning, inspection or the like, the articles prior to sterilizing are 
kept on the holding conveyor 07 until the sterilizer 010 starts its 
operation again. The larger the sterilizer 010 is constructed, the longer 
the articles are kept on the holding conveyor 07. As a result the content 
in the article becomes deteriorated and thereby its taste is adversely 
affected. 
Hence, the present invention is intended to obviate the drawbacks inherent 
in the conventional sterilizing system for filled and sealed articles as 
described above. Specifically, the present invention consists in an 
improved sterilizing system for filled and sealed articles which are 
treated by way of the steps of filling a content into packing means and 
sealing the filled articles in a filling and sealing station, loading a 
tray with the filled and sealed articles, building up a tray stack 
including a predetermined number of loaded trays stacked thereon, 
sterilizing the tray stacks in a sterilizer and then conveying them to a 
packing station, wherein the system includes a tray stack building station 
for building up a tray stack including a predetermined number of empty 
trays recovered after the filled and sealed articles are released toward 
the packing station, a tray stack holding conveyor for holding a plurality 
of tray stacks built up in said tray stack building station and a tray 
extracting station in which the empty trays are extracted from the tray 
stack conveyed from said tray stack holding conveyor one by one and then 
they are delivered toward the filling and sealing station. Thus, it is an 
object of the present invention to provide a sterilizing system for filled 
and sealed articles which ensures automatic delivering of the empty trays 
from the filled article extracting station to the filling and sealing 
station and continuous operation of the system without any intermittence 
of operation of the filling and sealing station. 
Further, the present invention consists in an improved sterilizing system 
for filled and sealed articles including a sterilizer in which the filled 
and sealed articles are subjected to sterilization, said sterilizer being 
located between a filling and sealing station and a packing station, a 
tray stack holding conveyor for holding a plurality of tray stacks 
thereon, said tray stack holding conveyor being located upstream of the 
sterilizer, and another tray stack holding conveyor for holding a 
plurality of sterilized tray stacks, said tray stack holding conveyor 
being located downstream of the sterilizer, wherein the system further 
includes a tray stack building station for building up a tray stack 
including a predetermined number of empty trays recovered after the filled 
and sealed articles are released toward the packing station, a tray stack 
holding conveyor for holding a plurality of tray stacks built up in said 
tray stack building station and a tray extracting station in which the 
empty trays are extracted from the tray stack conveyed from said tray 
stack holding conveyor one by one and then they are delivered toward the 
filling and sealing station. Thus, it is another object of the present 
invention to provide a sterilizing system for filled and sealed articles 
which is able to eliminate a time lag in operation between the filling and 
sealing station and the packing station, satisfactorily meet a requirement 
for an enlarged scale of sterilizer and ensure automatic delivering of 
empty trays from the filled article extracting station to the filling and 
sealing station and continuous operation of the system without any 
intermittence of operation of the filling and sealing station. 
Further, the present invention consists in an improved sterilizing system 
for filled and sealed articles in which another line comprising a 
sterilizer, a tray stack holding conveyor upstream of said sterilizer and 
a tray stack holding conveyor located downstream of said sterilizer is 
arranged in parallel to the aforesaid line comprising the sterilizer, the 
tray stack holding conveyor located upstream of the sterilizer and the 
tray stack holding conveyor located downstream of the sterilizer. Thus, it 
is another object of the present invention to provide a sterilizing system 
for filled and sealed article which is able to eliminate a time lag in 
operation between the filling and sealing station and the packing ststion, 
satisfactorily meet a requirement for an enlarged scale of sterilizer and 
ensure automatic delivering of empty trays from the filled article 
extracting station to the filling and sealing station and continuous 
operation of the system without any intermittance of operation of the 
filling and sealing station and moreover without any necessity for 
allowing the filled and sealed articles to be kept for a long periof of 
time on the holding conveyor located upstream of the sterilizer before 
they are subjected to sterilization therein irrespective of stoppage of 
the sterilizer caused due to trouble, cleaning, inspection or the like or 
of any enlarged scale of sterilizer installed. 
Furthermore, the present invention consists in an improved sterilizing 
system for filled and sealed articles in which a tray stack holding 
conveyor located downstream of the sterilizer is constructed of a conveyor 
including plural lines of conveyor units each of which comprises a roller 
conveyor and a corner transfer conveyor. Thus, it is still another object 
of the present invention to provide a sterilizing system for filled and 
sealed articles which is able to eliminate a time lag in operation between 
the filling and sealing station and the packing station, satisfactorily 
meet a requirement for an enlarged scale of sterilizer and ensure 
delivering of the filled and sealed articles from the sterilizer toward 
the packing station at an excellently high efficiency.

Now the present invention will be described in more details with reference 
to FIGS. 2 to 8 which illustrate a sterilizing system for filled and 
sealed articles in accordance with a preferred embodiment of the present 
invention. 
In the drawings reference numeral 1 designates a filling and sealing 
apparatus in which various kinds of contents are filled in packing means 
such as bag or the like (not shown) and after completion of filling of the 
content sealing is effected for the filled packing means. Reference 
numeral 2 designates a loading apparatus adapted to receive the packed and 
filled articles (hereinafter referred to simply as articles) from said 
filling and sealing apparatus 1 and convey them toward a loading conveyor 
3 in the form of a roller conveyor which is driven with the aid of driving 
means (not shown). A predetermined number of articles (16 artlces in the 
illustrated embodiment of the invention (see FIG. 3)) are loaded on each 
of empty trays 4 which are carried by the convyor 3 one after another. 
Reference numeral 5 designates a tray holding conveyor which serves for 
holding a lot of trays 6 loaded with the articles. Further, reference 
numeral 7 designates a tray palletizer which serves for stacking a 
predetermined number of loaded trays 6 on a pallet 8 one above another and 
delivering a tray stack to a pallet holding conveyor 9. 
Reference numeral 10 designates a roller conveyor disposed in the tray 
palletizer 7, said roller conveyor 10 being adapted to be driven with the 
aid of driving means (not shown). The roller conveyor 10 is fixedly 
mounted on a hydraulic cylinder 11 so as to be displaced upward or 
downward. Reference numeral 12 designates a frame for the tray palletizer 
7 which is arranged in parallel to the direction of conveyance of the 
loaded trays 6 and includes a lever 13 pivotally supported therein, said 
lever 13 being formed with a ratch at its lower end. As the loaded tray 6 
is raised up together with the roller conveyor 10, the ratch of the lever 
13 comes in engagement with a rail 6.sub.a of the loaded tray 6 whereby 
the latter is held by the former. Specifically, the lever 13 is rotatable 
about its upper end held on the frame 12 with the aid of a pneumatic 
cylinder 14 so that it is displaced away from the loaded tray 6 so as not 
to cause any interference with upward or downward movement of the latter 
as long as it is inoperative. Reference numeral 15 designates a limit 
switch fixedly disposed on the frame for defining an upper limit of upward 
movement of the roller conveyor 10. Further, reference numeral 16 
designates a pallet conveyor which is constituted of a chain conveyor 17, 
sprockets 18 and 19 and others, said pallet conveyor 16 serving to convey 
a pallet 8 on the roller conveyor 10 as illustrated in FIG. 8. It should 
be noted that the sprockets 18 and 19 are rotatably held by means of 
brackets or the like means (not shown). 
Reference numeral 20 designates a sterilizer in which a tray stack 21 
including a predetermined number of loaded trays stacked on the pallet 8 
is subjected to sterilization under high temperature and pressure steam 
atmosphere and after completion of cooling it is delivered to a pallet 
holding conveyor 22 located downstream of the sterilizer 20. 
The pallet holding conveyor 22 is constituted of roller conveyors 23 and 
corner transfer conveyors 24 and it is designed to have a capacity for 
holding a total number of tray stacks 21 delivered from the sterilizer 20 
for a certain period of time and another tray stacks 21 to be held thereon 
while a packing station stops its operation. In the illustrated embodiment 
of the invention the pallet holding conveyor 22 is constututed of three 
roller conveyors 23 and four corner transfer conveyors 24. 
The corner transfer conveyor 24 is constituted of rollers 25 adapted to be 
rotated by means of a driving mechanism (not shown) and driving chain 
conveyors 26 (see FIGS. 6 and 7). Specifically, the driving chain conveyor 
26 is constituted of sprockets 28, 29 and 30 rotatably supported by means 
of a bracket 27 having an U-shaped cross-sectional configuration, a 
sprocket 31 disposed coaxially relative to the sprocket 30, a chain 35 
extended around the sprocket 31, a sprocket 32 located in the vicinity of 
a motor 32 and a tension sprocket 34, and a hydraulic cylinder 35 having 
the bracket fixedly mounted on the upper end thereof so that it is 
displaced upward or downward in the space formed between the adjacent two 
rollers 25 by means of the hydraulic cylinder 35. Further, reference 
numeral 37 designates a framework which serves for rotatably supporting 
the rollers 25. 
Reference numeral 38 designates a tray depalletizer which is constructed in 
the same manner as the aforesaid tray palletizer 7 but it is operated in 
the reverse order of steps of removing the pallet 8 onto the pallet 
conveyor 16, drawing the loaded trays 6 from the bottom of the tray stack 
one by one and then displacing the drawn one onto the roller conveyor 39. 
Further, reference numeral 40 designates a packed article extracting 
apparatus which serves for receiving the loaded tray 6 conveyed from the 
tray depalletizer 38 via the corner transfer conveyor 24 and the roller 
conveyor 41, extracting the articles therefrom, delivering them to the 
packing station including a drying apparatus and others each of which is 
not shown in the drawings, and delivering the empty trays 4 toward the 
tray palletizer 43 via the corner transfer conveyor 24 and the roller 
conveyor 42. 
The tray palletizer 43 is constructed in the same manner as the aforesaid 
tray palletizer 7 and is operated by way of the steps of receiving the 
pallet 8 conveyed from the tray depalletizer 38 via the pallet conveyor 
16, stacking a predetermined number of empty trays 4 to build up a tray 
stack 44 and then delivering the tray stack 44 onto the pallet holding 
conveyor 45. 
The pallet holding conveyor 45 is arranged between the tray palletizer 43 
and the tray depalletizer 46 and its holding capacity is determined so as 
to ensure continuous operation of the system without any intermittance of 
supply of the empty trays 4 to the filling and sealing apparatus 1 even 
when the packing station stops its operation. 
The tray depalletizer 46 is constructed in the same manner as the aforesaid 
tray depalletizer 38 and is operated by way of the steps of receiving the 
tray stack 44 conveyed from the tray palletizer 43 via the pallet holding 
conveyor 45, separating it into the pallet 8 and the empty tray 4, 
delivering the former onto the pallet conveyor 16, drawing the empty trays 
4 from the bottom of the tray stack one by one and then delivering them 
onto the roller conveyor 47. The empty trays 4 on the roller conveyor 47 
are transferred to the filling and sealing apparatus 1 via the corner 
transfer conveyor 24. 
Next, operations of the sterilizing system for filled and sealed articles 
constructed in the above-described manner will be described step by step 
in the following. 
(a) The predetermined number of articles (not shown) filled with a specific 
content and then sealed in the filling and sealing apparatus 1 are 
delivered therefrom to the loading conveyor 3 via the loading apparatus 2 
and loaded in an empty tray 4 on the loading conveyor 3. Then, the loaded 
tray is transferred to the tray palletizer 7 via the corner transfer 
conveyor 24 and the tray holding conveyor 5. The loaded trays 6 are 
conveyed to the tray palletizer 7 one after another with the aid of 
operating means (stoppers, limit switches and others) each of which is not 
shown in the drawings. 
(b) When the loaded tray 6 is placed on the roller conveyor 10 as 
illustrated in FIG. 5, the hydraulic cylinder 11 starts its upward 
movement. As the hydraulic cylinder 11 continues its upward movement and 
reaches a certain height as illustrated by chain lines where the limit 
switch 15 is actuated, the lever 13 moves forward to the position as 
illustrated by real lines and thereby the ratch on the lever 13 comes in 
engagement with the rail 6.sub.a of the loaded tray 6 whereby the latter 
is supported by the former. After completion of ratch engagement the 
conveyor 10 is lowered and waits for next loaded tray 6. When the next 
loaded tray 6 reaches the roller conveyor 10, the hydraulic cylinder 11 
starts its upward movement again and the loaded tray 6 is brought in 
surface contact with the preceding loaded tray 6 which has been supported 
by the ratch of the lever 13. At this moment the limit switch 15 is 
actuated and thereby the lever 13 is caused to move backward, resulting in 
disengagement from the rail 6.sub.a of the tray 6. Then, the hydraulic 
cylinder 11 is raised up further by a height equal to the thickness of one 
tray and thereafter the lever 13 moves forward again until the ratch of 
the lever 13 comes in engagement with the rail 6.sub.a of the loaded tray 
6. As a result the latter loaded tray 6 is supported together with the 
former loaded tray 6 by means of the lever 13. After completion of the 
second engagement the hydraulic cylinder 11 is lowered. By repeating the 
above-described steps of operations a required number of loaded trays 6 is 
stacked one above another until a tray stack is built up. 
(c) After the predetermined number of loaded trays 6 are stacked, the 
roller conveyor 10 is lowered below the upper surface of the chain 
conveyor 17 and then the latter is driven to receive a pallet 8 at the 
position above the roller conveyor 10. Then, the latter starts its upward 
movement and lifts the received pallet 8. When the upper surface of the 
pallet 8 comes in contact with the bottom surface of the lowermost loaded 
tray 6, the lever 13 is caused to move backward. Thus, the tray stack 21 
is placed on the pallet 8. Next, the roller conveyor 10 is lowered to the 
level as illustrated in FIG. 5. Now the tray stack 21 is ready to be 
delivered onto the pallet holding conveyor 9 located upstream of the 
sterilizer 20 by driving the roller conveyor 10. 
(d) A predetermined number of tray stacks 21 (four stacks in the 
illustrated embodiment of the invention) held on the pallet holding 
conveyor 9 enter the sterilizer 20 and then they are subjected to 
sterilization under high temperature and pressure steam atmosphere. After 
completion of the intended sterilization and subsequent cooling they are 
delivered therefrom onto the pallet holding conveyor 22 located downstream 
of the sterilizer 20. The pallet holding conveyor 22 serves to arrange the 
tray stacks 21 delivered from the sterilizer 20 on the roller conveyors 23 
and the corner transfer conveyors 24 in conformance with such a specific 
order of arrangements as identified by reference numerals I to IV in FIG. 
2. Specifically, the tray stacks 21 are arranged over the pallet holding 
conveyor 22 in such a manner that a tray stack which first enters the 
sterilizer 20 is first delivered to the subsequent process eariest. 
(e) Then, the pallet 8 is first removed from the tray stack 21 by operating 
the tray depalletizer 38 and then it is delivered onto the pallet conveyor 
16, whereas the respective loaded trays 6 are drawn one by one from the 
bottom of the tray stack and then they are displaced toward the roller 
conveyor 39. 
(f) The respective loaded trays 6 are conveyed to the filled article 
extracting apparatus 40 one after another via the corner transfer conveyor 
24 and the roller conveyor 41 and the articles loaded on the tray 6 are 
extracted therefrom by operating the filled article extracting apparatus 
40. After all the articles are extracted from the loaded tray 6, the empty 
tray 4 is conveyed to the tray palletizer 43 via the corner transfer 
conveyor 24 and the roller conveyor 42. 
(g) The tray palletizer 43 is operated in the same manner as the tray 
palletizer 7 such that the empty trays 4 conveyed on the roller conveyor 
42 are stacked one above another on the pallet 8 conveyed on the pallet 
conveyor 16 until a tray stack 44 including the predetermined number of 
empty trays is built up and then the tray stack 44 is delivered onto the 
pallet holding conveyor 45. 
(h) The tray depalletizer 46 is operated in the same manner as the tray 
depalletizer 38 such that the tray stacks 44 conveyed on the pallet 
holding conveyor 45 are separated into the pallets 8 and the empty trays 4 
and the former are delivered onto the pallet onveyor 16 while the latter 
are delivered onto the roller conveyor 47. The respective empty trays 4 
are conveyed to the filling and sealing apparatus 1 one after another via 
the roller conveyor 47. 
Now, advantageous features ensured by the sterilizing system for filled and 
sealed articles constructed in accordance with the present invention will 
be noted below. 
Owing to the arrangement that the pallet holding conveyor 22 is provided 
downstream of the sterilizer 20 it is ensured that an increased holding 
capacity is attained whereby the sterilizing system is not affected by a 
so-called time lag between the filling and sealing station and the packing 
station. Further, since the pallet holding conveyor 22 located downstream 
of the sterilizer is easy to have an enlarged holding capacity, the 
sterilizing system of the present invention can readily meet requirements 
for operation in an increased scale. Furthermore, owing to the arrangement 
that the sterilizing system of the present invention includes the tray 
stack building station 43 where the empty trays conveyed from the packing 
station are stacked one above another, the pallet holding conveyor 45 for 
holding a lot of tray stacks delivered from the tray stack building 
station 43 and the tray extracting station comprising the tray 
depalletizer 46 and the roller conveyor 47 for extracting the empty trays 
from the bottom of the respective tray stacks conveyed from the pallet 
holding conveyor 45 and delivering them to the filling and sealing 
apparatus 1 it is ensured that the empty trays are automatically conveyed 
from the filled article extracting apparatus 41 to the filling and sealing 
apparatus 1. Furthermore, a number of empty trays 4 can be held on the 
pallet holding conveyor 45 in the form of a tray stack, even if any 
trouble takes place with the filled article extracting apparatus 40 or the 
packing station in the subsequent process, filling and sealing operations 
continues without any necessity for stopping operation of the filling and 
sealing apparatus 1. In the above-described embodiment the pallets 8 are 
employed for the sterilizing system but the present invention should be 
not limited only to this. Alternatively, tray stacks may be built up for 
the loaded trays 4 and the empty trays 6 without the use of the pallets 8. 
Further, in the above-mentioned embodiment the palletizers 7 and 43 and 
the depalletizers 38 and 46 are constructed such that stacking and 
extracting of the trays are initiated from the bottom part of the tray 
stacks, but the present invention should be not limited only to this. 
Alternatively, stacking or extracting may be initiated from the upper part 
of the respective tray stacks. 
Next, the sterilizing system in accordance with a modified embodiment of 
the present invention will be described below with reference to FIG. 9. It 
should be noted that same or similar members and components to those in 
FIG. 2 are given the same reference numerals. 
In the drawing reference numeral 50 designates another sterilizer which is 
constructed and functions in the quitely same manner as the sterilizer 20. 
As is apparent from the drawing, the sterilizer 50 is arranged in parallel 
to the sterilizer 20. In addition to the pallet holding conveyor 9 another 
pallet holding conveyor 51 is provided which is operatively connected to 
the corner transfer conveyor 24. By properly operating the corner transfer 
conveyor 24 the tray stacks 21 are alternately delivered to the pallet 
holding conveyors 9 and 51. The pallet holding conveyor 51 is constituted 
of a roller conveyor 52, a corner transfer conveyor 24 and a roller 
conveyor 53. 
Reference numeral 54 designates a pallet holding conveyor which is located 
downstream of the sterilizer 50. Said pallet holding conveyor 54 is 
constituted by a combination of roller conveyors 55, corner transfer 
conveyors 24 and a roller conveyor 56 and it is designed to have a 
capacity of holding a total number of tray stacks 21 corresponding to the 
so-called time lag and tray stacks 21 to be held during stoppage of the 
packing station. A corner transfer conveyor 24.sub.a serves for 
alternately delivering the tray stacks 21 conveyed from both the pallet 
holding conveyors 22 and 54 onto a roller conveyor 23.sub.a. 
Now, operations of the sterilizing system in accordance with the modified 
embodiment of the present invention as described above will be described 
in the following. 
The tray stacks 21 including the predetermined number of trays stacked on 
the pallet 8 are built up in the tray palletizer 7 and then they are 
delivered onto the pallet holding conveyor 9 located upstream of the 
sterilizer 20 via the corner transfer conveyor 24 by driving the roller 
conveyor 10. It should be noted that the corner transfer conveyor 24 
serves for alternately delivering the tray stacks 21 to the pallet holding 
conveyors 9 and 51 both of which are located upstream of the sterilizers 
20 and 50. 
After the predetermined number of tray stacks 21 are held on the pallet 
holding conveyor 9 or 51, they enter the sterilizer 20 or 50 in which they 
are subjected to sterilization under high temperature and pressure steam 
atmosphere, and after completion of the intended sterilization and 
subsequent cooling they are delivered onto the pallet holding conveyor 22 
or 54 each of which is located downstream of the sterilizers 20 and 50. 
The pallet holding conveyor 22 or 54 located downstream of the sterilizer 
20 or 50 serves to arrange the tray stacks 21 delivered from the 
sterilizer 20 or 50 in conformance with the same order of arrangements as 
identified by reference numerals I to IV in FIG. 2 with the aid of a 
combination of the roller conveyors 23 and the corner transfer conveyors 
24 or a combination of the roller conveyors 55 and the corner transfer 
conveyors 24. Specifically, the tray stacks 21 are arranged over the 
pallet holding conveyor 22 or 55 in such a manner that a tray stack which 
enters the sterilizer eariest is delivered to the subsequent process 
eariest. Then, the corner transfer conveyor 24.sub.a receives the tray 
stacks 21 from the pellet holding conveyors 22 and 54 alternately and 
delivers them to the roller conveyor 23.sub.a. 
As will be apparent from the above description, the sterilizing system in 
accordance with the modified embodiment of the present invention has an 
additional advantageous feature that continuous operation of the system is 
ensured with either of the two sterilizers even if the other one stops its 
operation due to trouble, cleaning, inspection or the like. When the 
sterilizing system of the present invention is operated with the use of a 
plurality of sterilizers, it is possible to reduce a waiting time of the 
respective tray stacks prior to sterizing in proportion to the number of 
sterilizers installed. As a result undesirable problems such as 
deterioration of the filled content, changing in taste or the like will be 
effectively obviated. 
As described above, the pallet holding conveyor 22 located downstream of 
the sterilizer 20 serves to arrange the tray stacks 21 delivered from the 
sterilizer 20 on both the roller conveyors 23 and the corner transfer 
conveyors 24 in conformance with such a specific order of arrangement as 
identified by reference numerals I to IV in FIG. 2. Now, the above step of 
operation will be described in a greater detail below with reference to 
FIG. 10. The corner transfer conveyor 24A is alternately operated in such 
a manner as to convey the tray stacks 21 identified by reference numerals 
I and III to the roller conveyor 23A and those identified by reference 
numerals II and IV to the corner transfer conveyor 24B. Specifically, when 
the tray stack 21 identified by reference numeral II is placed on the 
rollers 25 after the tray stack 21 identified by reference numeral I is 
delivered onto the roller conveyor 23A by rotating the rollers 25, the 
driving chain conveyor 26 is raised up above the upper surface of the 
rollers 25 and then the tray stack 21 identified by reference numeral II 
is conveyed to the corner transfer conveyor 24B by operating the driving 
chain conveyor 26. (At this moment the driving chain conveyor 26 on the 
corner transfer conveyor 24B is held at an elevated position and it is in 
operation.) As the driving chain conveyor 26 is lowered to the position as 
shown in FIG. 7, the tray stack 21 identified by reference numeral III is 
delivered from the sterilizer 20. Thus, The tray stack 21 identified by 
reference numeral III is conveyed to the roller conveyor 23A in the same 
manner as that identified by reference numeral I and then the follwoing 
tray stack 21 identified by reference numeral IV is conveyed to the corner 
transfer conveyor 24B in the same manner as that identified by reference 
numeral II. Further, the tray stacks 21 identified by reference numerals I 
and III are conveyed to the corner transfer conveyor 24D via the roller 
conveyor 23A one after another, whereas those identified by reference 
numerals II and IV are to the corner transfer conveyor 24C via the roller 
conveyor 23B one after another. As a result the tray stakcs 21 are 
conveyed to the roller conveyor 23C via the corner transfer conveyors 24D 
and 24C in conformance with the order identified by reference numerals I, 
II, III and IV. 
Finally, FIG. 11 illustrates another preferred embodiment of the present 
invention in which the pallet holding conveyor 22 located downstream of 
the sterilizer 20 is constructed by three lines of combinations of the 
corner transfer conveyors 24 and the roller conveyors 23 and the tray 
stacks 21 are caused to move along the track of a S-shaped real line A in 
the direction as identified by an arrow mark. 
It should be of course understood that the pallet holding conveyor 54 
located downstream of the sterilizer 50 in FIG. 9 may be constructed in 
the same manner as the pallet holding conveyor 22 described above with 
reference to FIG. 11.