JPH11227726A - Sterilizing method of plastic container - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely achieve the heat sterilization of the inside of a PET bottle low in heat resistance without thermal deformation. SOLUTION: A steam injection nozzle 42 is inserted from a mouth part 21 of a bottle 20, the steam is injected from the nozzle, the steam is circulated inside the bottle 20, and discharged from the mouth part 21, the steam is surely brought into contact with an inner surface of the bottle to achieve the heat sterilization, and cooling water is sprayed on an outer surface of the bottle to prevent the thermal deformation of a wall surface of the bottle.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for sterilizing plastic containers such as PET bottles. More specifically, the present invention relates to a method for heat sterilizing an inner surface of a plastic container having low heat resistance without heat deformation.

[0002]

2. Description of the Related Art Conventionally, so-called PET bottles have been widely used as plastic containers for filling beverages and the like. By the way, before filling such a PET bottle with a beverage, it is necessary to sterilize the inner surface of the PET bottle. In addition, sterilization treatment of beverage containers includes various treatments such as sterilization in a strict sense to completely kill bacteria and sterilization to reduce or inactivate bacteria to a required level. The entire process is referred to as a sterilization process.

As such a sterilization treatment, there is a treatment in which hot water is injected into the inner surface of a PET bottle to perform a heat sterilization treatment. Such a heat sterilization treatment is generally used alone or in combination with another sterilization treatment such as injection of ozone water. Such heat sterilization has advantages such as simple and reliable steps, but also has the following problems to be solved.

[0004] The first problem is that the container to be sterilized must have heat resistance. Generally, in order to obtain the effect of the sterilization treatment, it is necessary to inject hot water at a temperature of about 65 to 70 ° C. or more. Deformation occurs. For this reason, for example, when the inner surface of a PET bottle is subjected to heat sterilization by jetting hot water, it is necessary to use a PET bottle using a heat-resistant material. For this reason, the cost of the container increases, and the type of the container to be sterilized is limited.

[0005] A second problem relates to the temperature range and safety of hot water. The higher the temperature of the hot water to be injected, the higher the effect of the sterilization treatment. Therefore, the higher the temperature of the hot water, the better. However, since the pressure of the flowing hot water is locally reduced in the piping or valve device for supplying the hot water, the temperature of the hot water is generally about 9
If the temperature is 0 ° or more, boiling may occur at a low pressure generating portion in a pipe or a valve device, and the temperature of the hot water must be 90 ° C or less. It is also conceivable that this hot water is supplied under pressure to prevent boiling in the pipe as described above, but high-pressure, high-temperature hot water scatters far away if the pipe etc. is damaged. At the same time, there is a high risk of sticking to a human body and causing a burn, which is not preferable in terms of safety.

[0006] A third problem relates to the energy cost of producing the above-mentioned hot water. Since the hot water sprayed on the inner surface of the container is discarded as it is,
The cost of energy to generate large amounts of hot water is high.

A fourth problem is that hot water is uniformly sprayed on the inner surface of the container. When the shape of the container to be sterilized is complicated, it is difficult to spray hot water uniformly and evenly on the inner surface. In addition, even a container having a simple overall shape, for example, a PET bottle often has a large number of ribs and irregularities formed on a wall surface in order to improve rigidity and design of the bottle. In the part, there is a possibility that a part that is in the shadow of hot water injection or run-down may be formed, which may impair the reliability of the sterilization treatment. Recently, there has been a demand for a PET bottle that can be crushed at the time of disposal to reduce the volume. However, in such a case, it is expected that the bottle has a complicated wall surface in order to facilitate the crushing. In such a case, there is a possibility that a portion where the hot water is not sufficiently injected is generated.

In order to solve the first problem, recently, hot water is sprayed on the inner surface of the PET bottle,
A method has been proposed in which cooling water is injected onto the outer surface of the bottle to cool the bottle wall surface and prevent deformation of the bottle due to heat. According to such a method, a rise in the temperature of the bottle wall surface is prevented, so that even a non-heat-resistant bottle can be heated and sterilized by jetting hot water.

However, the temperature of the hot water to be injected needs to be 90 ° C. or lower in order to prevent boiling in the piping as described above, and the temperature of the hot water is limited.
The heat transfer from the hot water to the bottle wall is a so-called impingement heat transfer due to the collision of the fluid jet with the wall, which is the most efficient heat transfer method between the fluid and the wall. Transmission method. For this reason, a large amount of heat is transmitted from this hot water to the bottle wall surface, and even if the outer surface is cooled, the effect of preventing the wall surface from rising in temperature becomes insufficient. Therefore, for example, in the case of a non-heat-resistant PET bottle, the temperature of the hot water must be set to a temperature lower than the above 90 ° C. in order to prevent thermal deformation of the bottle. For this reason, the efficiency and reliability of the heat sterilization treatment decrease.

Although the above-described method has an effect of preventing deformation of the container due to heat as described above, the above-mentioned second to fourth problems cannot be essentially solved.

[0011]

DISCLOSURE OF THE INVENTION The present invention has been made based on the above-mentioned circumstances, and it is possible to heat and sterilize the inner surface of a plastic container having relatively low heat resistance effectively and reliably, and to use the heat generated by the heat of the container. Effectively prevent deformation,
Another object of the present invention is to provide a method for sterilizing a plastic container which has high safety and can reduce the cost.

[0012]

According to the present invention, there is provided a method for heat-sterilizing an inner surface of a plastic container, wherein the inner surface of the mouth is provided in the mouth of the container to be heat-sterilized. Forming a gap between the steam ejection nozzle and the step of injecting steam into the container from the steam ejection nozzle, circulating the injected steam in the container, and The method includes a step of discharging the liquid through a gap between the inner surface of the mouth and a step of supplying a cooling medium to the outer surface of the container and cooling a wall surface of the container simultaneously with the step of ejecting steam.

The present invention according to claim 2 is characterized in that the temperature of steam ejected from the steam ejection nozzle is 95 ° C. or higher. Therefore, the heat sterilization treatment can be performed more reliably and efficiently, and the amount of heat transfer from the steam to the container wall surface is small as described above, so that the temperature of the container wall surface is suppressed to be low, and no thermal deformation or the like occurs. .

According to a third aspect of the present invention, in the step of inserting the steam jet nozzle into the mouth of the container, the step of inserting the steam jet nozzle into the mouth of the inverted container with the mouth facing downward from below. In the step of ejecting steam, the steam is ejected upward toward the bottom of the container, and the steam is circulated downward along the inner surface of the wall surface of the container. The container is discharged from the mouth. Therefore, the water condensed on the inner surface of the container is caused to flow down by gravity and can be efficiently discharged from the mouth together with the steam, and the effect of the sterilization treatment is high. There is no obstacle.

The present invention according to claim 4 is characterized in that a step of directly injecting steam into the inner surface of the mouth of the container is added. Since the steam circulating in the container passes through the inner surface of the mouth, it comes into contact with the steam whose temperature has decreased, and the effect of the heat sterilization treatment tends to be reduced, but the steam is directly injected into the inner surface of the mouth. By doing so, the inner surface of the mouth can be more reliably heat sterilized.

The present invention according to claim 5 is characterized in that a step of injecting steam into the outer surface of the mouth of the container is added. Therefore, simultaneously with the heat sterilization of the inner surface of the container, the outer surface of the mouth is also heat sterilized,
The possibility of secondary contamination inside the container after the sterilization treatment can be reliably eliminated.

The present invention according to claim 6 is characterized in that the cooling medium supplied to the outer surface of the container is cooling water. Therefore, the outer surface of the container can be cooled easily and reliably.

The present invention according to claim 7 is characterized in that the cooling medium supplied to the outer surface of the container is cold air. Therefore, the outer surface of the container can be cooled with equipment having a simple structure, and there is no possibility that a problem such as contamination of the inside of the container due to the cooling water occurs, and more reliable sterilization treatment can be performed.

Further, according to the present invention, the steam injected from the steam jet nozzle into the container is pure steam from which impurities in the steam supplied from the boiler have been removed. It is characterized by the following. Therefore, there is no possibility that the inside of the container is secondarily contaminated by the steam, and a reliable sterilization treatment can be performed.

According to a ninth aspect of the present invention, the steam injected from the steam jet nozzle into the container is pure steam generated by heating pure water with a heat exchanger. It is a feature. Therefore, there is no possibility that the inside of the container is secondarily contaminated by the steam, and a reliable sterilization treatment can be performed.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. The first embodiment of the present invention relates to a method for heat sterilizing a plastic container, for example, a PET bottle, and will be described with reference to FIGS. 1 to 12 together with a sterilization apparatus for performing the method.

First, a schematic configuration of the apparatus will be described with reference to FIGS. FIG. 1 is a plan view of the entire apparatus, and FIG. 2 is a front view of the same. Reference numeral 1 in the figure denotes a main body of the apparatus, and the main body 1 is horizontally installed on a floor or the like. On the upper surface of the main body 1, a turntable 2 is provided rotatably in a horizontal plane. The rotary table 2 is driven to rotate clockwise in FIG. 1 by a drive mechanism or the like provided in the main body 1.

At the front end of the main body 1, a carry-in conveyor 3 is provided. A screw conveyor mechanism 4 is provided on the side of the carry-in conveyor 3, and a plastic container, for example, a PET bottle for a beverage is conveyed in an upright state. A carry-in rotor 5 is provided at the end of the carry-in conveyor 3 and transports the conveyed bottles one by one to the rotary table 2.

A large number of gripping mechanisms 6 are provided on the periphery of the rotary table 2 to grip the mouth of the loaded bottle and rotate the bottle 180 ° up and down. To the inverted state. While the rotary table 2 makes one rotation, the interior of the bottle is subjected to a series of sterilization processes of the embodiment of the present invention, such as cleaning with ozone water, heat sterilization by steam injection, finish cleaning, and outer cleaning. Will be

The bottle that has been subjected to the above-described sterilization treatment by rotating the turntable 2 once is returned to the upright state again, transferred to the carry-out conveyor 8 by the carry-out rotor 7, and subjected to the next beverage. Is sent to the filling process. Note that 9
Is a control device for controlling the operation of this device, and 10 is a cover of the turntable 2.

Next, the configuration and operation of each part of such a sterilization apparatus will be described. FIGS. 3 to 7 show the gripping mechanism 6 for gripping the PET bottle 20 and the bottle 2.
0 shows a configuration of a heat sterilization mechanism 40 for performing steam heat sterilization processing on the inside of the bottle 20 and a cooling mechanism 60 for cooling the outer surface of the bottle 20.

First, the gripping mechanism 6 has a chuck mechanism 30, which is rotatably attached to the rotary table 2 about a horizontal axis 31. This check mechanism 30
A pair of check arms 32 and 33 are provided. One check arm 33 rotates about a shaft 36, and these check arms 32 and 33 open and close.

The tip of each of the chuck arms 32 and 33 has a chuck block 3 made of a synthetic resin material or the like.
4 and 35 are provided, and are configured to grip a flange 22 formed at the mouth 21 of the bottle 20. In addition, a notch 37 is formed in one of the check blocks 34 in order to prevent interference of the opening 21 when the bottle 20 is loaded and unloaded.

After the chuck mechanism 30 grips the mouth 21 of the bottle 20 which has been carried in, the drive mechanism (not shown) turns the shaft 31 by 180 ° about the shaft 31 in the direction of the arrow in FIG. The bottle 20 is turned and the held bottle 20 is turned upside down with its mouth 21 down.

The mouth 2 of the inverted bottle 20
As the bottle 20 is turned upside down as described above, the steam jet nozzle 42 of the heat sterilization mechanism 40 is inserted into the bottle 1 upward from below. The diameter of this nozzle 42 is
Is formed smaller than the inner diameter of the opening 21, and a gap is formed between the outer periphery of the inserted nozzle 42 and the inner periphery of the opening 21. In the case of this embodiment, the insertion depth of the nozzle 42 is only the opening 21 of the bottle 20.

The steam jet nozzle 42 has an opening at its tip, and jets steam upward toward the bottom of the bottle 20. In this embodiment, a plurality of side nozzle holes 43 are formed radially on the side surface of the nozzle 42. The nozzle 42 is supplied with steam from a steam supply mechanism 41, and the steam is ejected from the nozzle 42 toward the bottom of the bottle 20 into the bottle 20. The steam is directly injected toward the inner peripheral surface of the.

The steam supply mechanism 41 for supplying steam to the steam ejection nozzle 42 is configured as shown in FIG. 7, for example. That is, reference numeral 44 denotes a boiler as a steam generation source, and the steam supplied from the boiler 44 is sent to a purification mechanism 45. The purifying mechanism 45 has a function of removing the clean can material mixed in the steam supplied from the boiler 44 and impurities in the piping.
Purifies the steam and produces pure steam containing no impurities.

The pure steam is supplied to the pressure regulating valve 46.
And the above-described steam jet nozzle 42 via a pipe 49.
Supplied to The pressure of the pure steam is detected by a pressure detector 47, and based on the pressure signal, a control circuit 48 sends a signal to the pressure regulating valve 46 to maintain the pressure of the pure steam constant. The pure steam pressure may be adjusted by a mechanical pressure adjusting valve.

Each of the steam jet nozzles 42 has the following structure.
Each is provided with an on-off valve 50, which opens and closes in accordance with a step of a sterilization treatment method described later, and ejects steam into the bottle 20. Also, the on-off valve 50 is bypassed and the bypass valve 5
The bypass valves 51 are always opened at a predetermined opening degree. Therefore, even when the above-described on-off valve 50 is closed, a small amount of steam is constantly supplied to the nozzles 42 through the bypass valve 51, thereby preventing contamination inside the nozzles 42.

Further, as shown in FIG. 6, a plurality of positions toward the outer peripheral surface of the mouth portion 21 of the bottle 20 are located at the position where the heat sterilization treatment inside the bottle is performed or at a position thereafter.
For example, two mouth outer nozzles 52 are provided.

These mouth outer nozzles 52 are connected to the piping 49 of the steam supply mechanism 41 via an on-off valve 53 and a bypass valve 54, similarly to the steam jet nozzle 42. Then, steam is ejected from these mouth outer surface nozzles 52 toward the outer peripheral surface of the mouth 21,
The outer peripheral surface of the mouth is subjected to heat sterilization.

As described above, the cooling mechanism 60 for spraying a cooling medium, for example, cooling water, is provided on the outer surface of the bottle 20 held on the outer periphery of the rotary table 2 in an inverted state. The cooling mechanism 60 includes a watering nozzle 61 provided above the bottle 20, and a cooling water supply mechanism 62 that supplies cooling water to the watering nozzle 61. The cooling water supply mechanism 62 supplies tap water or cooling water maintained at a predetermined cleanliness.

Next, a sterilization treatment method according to an embodiment of the present invention, which is performed by such an apparatus, will be described. FIG. 8 shows a flowchart of this sterilization treatment method. First, in step ST1, the bottle 20 is carried in, and the mouth 21 of the bottle 20 is gripped by the gripping mechanism 6 as described above. Next, in step ST2, the bottle 20 is inverted as shown in FIG.

Next, in step ST3, an ozone water cleaning mechanism (not shown) provided in the above-mentioned sterilizing apparatus.
Accordingly, ozone water is sprayed on the inner surface of the bottle 20 for about 1.0 second, and the inner surface of the bottle 20 is preliminarily cleaned. In this embodiment, pure water containing about 1 ppm of ozone is used as the ozone water.

Next, in step ST4, the above-described steam jet nozzle 42 is inserted into the mouth portion 21 of the bottle 20 in the inverted state. And this steam jet nozzle 42
, The pure steam supplied from the steam supply mechanism 41 is jetted. As shown in FIG. 9, this steam is ejected upward toward the inner surface of the bottom of the inverted bottle 20, collides with the inner surface of the bottom, is radially deflected, and descends along the inner surface of the side wall. The excess steam is circulated through the mouth 2
1 is discharged from a gap between the inner peripheral surface of the nozzle 1 and the outer peripheral surface of the nozzle 42. In addition, steam is directly injected from the side nozzle hole 43 of the nozzle 42 toward the inner peripheral surface of the mouth 21.
In the case of this embodiment, the temperature of the steam is preferably 95 ° C. or more, and the jetting is continued for about 4.0 seconds.

In parallel with the above step ST4,
In step ST5, cooling water is sprayed from the spray nozzle 61 to the outer surface of the bottle 20. Therefore, the spray of the cooling water cools the wall surface of the bottle 20 from the outside, suppresses a rise in the temperature of the wall surface, and prevents the bottle 20 from being thermally deformed. Note that the spraying of the cooling water is continuously performed at least while the steam is being injected.

Accordingly, since the inner surface of the wall surface of the bottle 20 is heated and sterilized by the injected steam, and the outer surface of the wall surface is cooled by the cooling water, a rise in the temperature of the wall surface of the bottle 20 is suppressed to a low level. Therefore, even if the bottle has low heat resistance, high-temperature steam can be injected to efficiently and reliably perform the heat sterilization treatment, and the bottle is not thermally deformed.

Due to the contact of such high-temperature steam, the temperature near the inner surface of the bottle wall surface becomes instantaneously high. However, since the steam has a much smaller heat capacity than hot water, the amount of heat transferred from this steam to the container wall surface It is small. Therefore,
The rise in temperature of the bottle wall is kept low, and higher temperature steam can be used. Bacteria and the like existing on the inner surface of the bottle wall surface are instantaneously heated to a high temperature by contact with the steam, so that the effect of the sterilization treatment is not impaired, and the sterilization treatment can be performed efficiently and reliably.

Further, since this steam does not boil like hot water in pipes and valve devices, the temperature of this steam can be increased as far as other conditions permit, and the effect of the heat sterilization treatment is more improved. Large and efficient. Also, even if the pipes or the like are broken, the ejected steam does not reach far away, and even if this steam comes into contact with the human body, it does not cause immediate burns, and it is safer.

Further, in order to generate steam, a larger amount of heat is required by the amount of heat of vaporization than when generating hot water. However, since the density of steam is much smaller than that of hot water, it is used for heat sterilization. The amount of steam generated is small and the amount of heat required is small. Thus, the cost of energy required to generate this steam is reduced.

Also, since steam is a gas, it has high fluidity and diffusivity and is not affected by gravity, so that the steam ejected from the steam ejection nozzle into the bottle circulates through the entire bottle and forms a gap in the mouth. Is discharged from Therefore, even when the shape of the bottle is complicated, or even when complicated unevenness is formed on the wall surface of the bottle, the steam comes into contact with the inner surface of the bottle wall surface, and a reliable heat sterilization treatment is achieved. You.

In this embodiment, the steam jet nozzle 42 is inserted from below the mouth 21 of the inverted bottle 20 with the mouth facing downward, and steam is ejected upward toward the bottom of the bottle. . Therefore, this steam is circulated downward along the inner surface of the wall surface of the bottle and discharged from the mouth, so that water condensed on the inner surface of the bottle flows down by gravity and can be efficiently discharged from the mouth together with the steam. The condensed water does not become an obstacle when the sterilization treatment is more effective and another sterilization treatment is performed later.

In this embodiment, as described above, steam is directly injected from the side nozzle hole 43 of the steam injection nozzle 42 to the inner surface of the mouth 21. As the steam circulating in the bottle passes through the inner surface of the mouth, it comes into contact with the steam whose temperature has decreased, and the effect of the heat sterilization treatment tends to decrease, but steam is directly injected into the inner surface of the mouth. by doing,
The inner surface of the mouth can be more reliably heat sterilized.

As described above, after the heat sterilization of the inner surface of the bottle 20 is completed, in step ST6,
Steam is directly injected from the above-mentioned mouth outer surface nozzle 52 to the outer peripheral surface of the mouth 21, and the outer peripheral surface of the mouth is subjected to heat sterilization treatment. Therefore, it is possible to reliably eliminate the possibility of secondary contamination occurring from the outer peripheral surface of the mouth after the heat sterilization treatment inside the bottle. In this embodiment, the steam is injected to the outer surface of the mouth 21 for about 1.0 second.

Next, in step ST7, ozone water is injected into the inner surface of the bottle, and the inner surface is finish-cleaned. In this embodiment, the ozone water contains about 1 ppm of ozone.
The contained pure water is used, and the ozone water used in this step is collected and regenerated, and used for the preliminary cleaning of the inner surface of the bottle in the above-mentioned step ST3. In this embodiment, the finish cleaning is performed for about 2.0 seconds.

In parallel with this step ST7, in step ST8, disinfecting water such as chlorine water is added to the bottle 20.
And the outer surface of the bottle is washed and sterilized. The step of cleaning the outer surface is performed for about 5.0 seconds in this embodiment.

As described above, this PET bottle 20
After cleaning and sterilizing the inner and outer surfaces of the
In step ST9, the gripping mechanism 6 is inverted,
The grasped bottle is erected, and thereafter, step S
At T10, the bottle is released from being gripped, and the bottle is unloaded to the unloading conveyor 8 by the unloading rotor 7 and sent to the next filling step or the like.

Next, the result of a test on the effect of the heat sterilization treatment by the steam injection will be described. 10 to 1
2 is a bottle 20 at the time of heat sterilization by injection of steam.
FIG. 4 is a diagram showing a temperature change on the inner surface and the outer surface of FIG. In addition,
In this test, in order to clarify the relationship between the circulation of steam in the bottle and the temperature of the bottle wall surface, a steam ejection nozzle without the side nozzle hole 43 described in the above-described embodiment was used. The bottle used for the test had a capacity of 2
It is a 000 ml square non-heat-resistant PET bottle.

FIG. 10 shows the temperature change at point A in FIG. 9, FIG. 11 shows the temperature change at point B in FIG. 9, and FIG. 12 shows the temperature change at point C in FIG. These temperatures were measured by attaching sheet-shaped thermocouples to the inner and outer surfaces of the bottle 20. In these cases, steam having a temperature of 95 to 100 ° C was injected for about 10 seconds, and the temperature of the cooling water was 15 to 16 ° C.

As is clear from FIGS. 10 and 11,
At point A on the bottom side surface and point B on the central side surface of the bottle 20, the temperature of the inner surface of the bottle rises to almost the temperature of the injected steam in a very short time after the start of the injection of the steam, and the temperature of the next 10 The temperature of this inner surface is almost 9 seconds.
It is maintained at 0 ° C. or higher. Therefore, sufficient heat sterilization can be performed.

At the point C at the mouth, as shown in FIG. 12, immediately after the start of the injection, the inner surface temperature rises to about 65 ° C., and thereafter, this temperature is maintained for about 5 seconds. It has risen to about 80 ° C. This is because, immediately after the start of the injection, the cooled steam that comes into contact with the inner surface of the bottle in the low temperature state is discharged through this mouth, and when the temperature of the inner surface of the bottle subsequently rises, the temperature rises. It is presumed that the steam with a small decrease comes to pass through the mouth.

Therefore, if the side nozzle hole is formed in the steam ejection nozzle and the steam is directly injected into the inner surface of the mouth as in the above-described embodiment, the temperature of the inner surface of the mouth becomes lower. Similar to the above points A and B, the temperature rises to a temperature almost equal to the steam temperature immediately after the start of the injection, and more reliable heat sterilization can be performed.

It should be noted that the above-mentioned characteristics of the temperature rise on the inner surface of the mouth are naturally affected by various conditions such as the capacity of the bottle and the amount of steam jetted. For example, if the amount of steam spouted for this bottle capacity is large,
The temperature rise on the inner surface of the mouth is such that it reaches a higher temperature in a shorter time.

At each of these points A, B and C,
The temperature of the outer surface of each bottle is maintained in the range of 20 to 30 °. This temperature is a temperature lower than the glass transition temperature of the resin material of the non-heat-resistant PET bottle, and thermal deformation of the bottle can be reliably prevented. After the test of the heat sterilization treatment was completed, the thermal deformation of each part of the PET bottle was measured. Only a slight thermal deformation having no influence on the use of the PET bottle was observed. there were.

At points B and C in FIGS. 11 and 12, the temperature of the outer surface of the bottle temporarily rises to 30 ° C. or more about 5 seconds after the start of the steam injection. This is because steam is condensed on the inner surface of the bottle, and the condensed hot water flows down the inner surface of the bottle. As described above, since the amount of heat transmitted in contact with hot water is large, the bottle wall surface is heated to a high temperature up to its outer surface. Therefore, from the viewpoint of preventing thermal deformation of the bottle, it is preferable that the hot water condensed on the inner surface of the bottle does not flow down the inner surface of the bottle as described above, that is, the steam injection is performed for 5 seconds or less.

The present invention is not limited to the first embodiment. For example, FIGS. 13 and 14 show an apparatus used in the second embodiment of the present invention. In this embodiment, the above-mentioned bypass valves 51 and 54 are omitted, and on-off valves 50a and 54a each having a bypass passage therein are used. This on-off valve is, as shown in FIG.
The valve body 57 that opens and closes the valve port 56 in the valve hole 5 has a bypass hole 58.
Is formed. Even when the valve body 57 is in a closed state, a small amount of steam is supplied to the nozzle through the bypass hole 58, and the supply of steam to the nozzle is not interrupted. Internal contamination can be reliably prevented.

FIG. 15 shows an apparatus used in the third embodiment. In this apparatus, pure water supplied from a pure water supply source 70 is exchanged with steam from a boiler 72 by a heat exchanger 71 to generate pure water steam.

FIG. 16 shows an apparatus used in the fourth embodiment. This uses cold air instead of cooling water as the cooling medium. That is, the bottle 2 held in an inverted state by the gripping mechanism 6
0 is surrounded by a hood 80 and a cold air supply mechanism 8 is provided.
The cool air supplied from 1 is sent from a blowing nozzle 82 formed at the upper end of the hood 80, and the cool air is circulated along the outer surface of the bottle 20 to cool the outer surface of the bottle 20. In this case, since cooling water is not used for cooling the outer surface of the bottle, the structure of the apparatus is simplified, and there is no possibility of recontamination in the bottle due to the cooling water.

The apparatus used in the above embodiment is the same as the apparatus used in the first embodiment except for the above points. The same reference numerals are given to the portions corresponding to the modes, and the description will be omitted.

Note that the present invention is not limited to the above embodiment, and various features and features disclosed in the above embodiment corresponding to the type of container to be heat sterilized, the level of sterilization, and other specifications. It goes without saying that conditions are appropriately selected and combined.

[0066]

As described above, according to the present invention, the inner surface of the wall of the container is heated and sterilized by the injected steam, the outer surface of the wall is cooled by the cooling medium, and the steam has a heat capacity greater than that of hot water. Since the heat is small and the amount of heat transferred to the wall of the container is small, the temperature rise on the wall of this container is suppressed low, and even for containers with low heat resistance, high-temperature steam is injected to efficiently and reliably heat sterilize. Can be processed.

Since steam does not boil like hot water in pipes and valve devices, the temperature of this steam can be raised as far as other conditions permit, and the effect of the heat sterilization treatment is greater. , And more efficient. Also, even if the pipes or the like are broken, the ejected steam does not reach far away, and even if this steam comes into contact with the human body, it does not cause immediate burns, and it is safer.

Further, in order to generate steam, a larger amount of heat is required by the amount of heat of vaporization than when hot water is generated. However, since the density of steam is much smaller than that of hot water, it is used for heat sterilization. The amount of steam generated is small and the amount of heat required is small. Thus, the cost of energy required to generate this steam is reduced.

Further, since steam is a gas, it has a high fluidity and diffusivity and is not affected by gravity, so that the steam ejected from the steam ejection nozzle into the container circulates through the entire container to form a gap at the mouth. Is discharged from Therefore, even when the shape of the container is complicated, or when complicated unevenness is formed on the wall surface of the container, the steam contacts all over the inner surface of the wall surface of the container, and a reliable heat sterilization treatment is achieved. The effect is great.

[Brief description of the drawings]

FIG. 1 is a plan view of an apparatus used in the method according to the first embodiment of the present invention.

FIG. 2 is a front view of the apparatus of FIG.

FIG. 3 is a schematic side view of a part of a gripping mechanism of the apparatus of FIG. 1;

FIG. 4 is a longitudinal sectional view of a portion of a bottle mouth and a steam ejection nozzle.

FIG. 5 is a view taken in the direction of arrows 5-5 in FIG. 4;

FIG. 6 is a longitudinal sectional view of a portion of a mouth portion of a bottle and a nozzle of a mouth portion outside surface.

FIG. 7 is a schematic diagram showing a configuration of a steam supply mechanism of the apparatus of FIG.

FIG. 8 is a flowchart of a heat sterilization treatment method according to the first embodiment of the present invention.

FIG. 9 is a schematic diagram for explaining the operation of a bottle heat sterilization process by steam injection.

FIG. 10 is a diagram showing a temperature change on the inner and outer surfaces of the bottle at a point A in FIG. 9;

FIG. 11 is a diagram showing a temperature change on the inner and outer surfaces of the bottle at a point B in FIG. 9;

FIG. 12 is a diagram showing temperature changes on the inner and outer surfaces of the bottle at point C in FIG. 9;

FIG. 13 is a schematic diagram showing a configuration of a steam supply mechanism of an apparatus used in the method of the second embodiment.

FIG. 14 is a schematic diagram of the structure of an opening / closing valve mechanism of the apparatus of FIG. 13;

FIG. 15 is a schematic diagram showing a configuration of a steam supply mechanism of an apparatus used in the method of the third embodiment.

FIG. 16 is a schematic side view of a portion of a gripping mechanism of an apparatus used in the method of the fourth embodiment.

[Explanation of symbols]

 2 rotary table 6 gripping mechanism 20 PET bottle 21 mouth 41 steam supply mechanism 42 steam ejection nozzle 43 side nozzle hole 62 cooling water supply mechanism

Claims (9)

[Claims] 1. A method for heat-sterilizing an inner surface of a plastic container, wherein a gap is formed between the mouth of the container to be heat-sterilized and the inner surface of the mouth, and a steam ejection nozzle is inserted. Injecting steam into the container from the steam ejection nozzle, circulating the injected steam in the container, and discharging the steam from the gap between the steam ejection nozzle and the inner surface of the mouth. A process of supplying a cooling medium to the outer surface of the container to cool the wall surface of the container at the same time as the step of ejecting the steam, thereby sterilizing the plastic container. 2. The temperature of steam ejected from said steam ejection nozzle is 95 ° C. or higher.
Sterilization treatment method for plastic containers. 3. The step of inserting the steam ejection nozzle into the mouth of the container includes inserting the steam ejection nozzle from below into the mouth of the inverted container with the mouth down. In the step of ejecting steam, the steam is ejected upward toward the bottom of the container, and the steam is circulated downward along the inner surface of the wall surface of the container and discharged from the mouth of the container. The method for sterilizing a plastic container according to claim 1, wherein 4. The method according to claim 1, further comprising a step of directly injecting steam into the inner surface of the mouth of the container.
Sterilization treatment method for plastic containers. 5. The method for sterilizing plastic containers according to claim 1, further comprising a step of injecting steam into the outer surface of the mouth of the container. 6. The method according to claim 1, wherein the cooling medium supplied to the outer surface of the container is cooling water. 7. The method according to claim 1, wherein the cooling medium supplied to the outer surface of the container is cold air. 8. The plastic container according to claim 1, wherein the steam injected from the steam ejection nozzle into the container is pure steam from which impurities in the steam supplied from the boiler have been removed. Sterilization treatment method. 9. The plastic container according to claim 1, wherein the steam injected from the steam ejection nozzle into the container is pure steam generated by heating pure water with a heat exchanger. Sterilization treatment method.