JPH0121950B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method for producing gas-filled canned goods by adding a predetermined amount of inert gas to give internal pressure to the canned can in a low-temperature liquefied state immediately before sealing. In a high-speed can production line where the speed of the can production line changes midway through, a predetermined amount of low-temperature liquefied gas is added into the can while it is being moved to the can lid tightening machine after being filled with contents to maintain a predetermined internal pressure. The present invention relates to a method of manufacturing a gas-filled canned food. (Prior art) In cans of beer and carbonated drinks, a portion of the carbon dioxide gas contained in large quantities in the liquid content is released into the head space inside the can, causing the internal pressure to rise below atmospheric pressure. As a result, cans with thin barrel walls can be used without problems. On the other hand, contents that contain almost no carbon dioxide,
For example, in the case of canned fruit juice drinks, fruits pickled in syrup, mandarin orange drinks containing fruit particles, coffee drinks, tea drinks, sake, etc., the internal pressure is below atmospheric pressure (if manufactured by the hot filling method, at room temperature (The pressure is much lower than atmospheric pressure.) Therefore, it was necessary to use cans with thick walls that would not dent due to external forces. However, in recent years, even with such contents, cans with thin body walls have been used. It has been proposed to add a predetermined amount of an inert gas such as nitrogen gas or argon gas to the contents of the can in a liquefied state (low-temperature liquefied gas). In other words, since the low-temperature liquefied gas added to the contents of the can vaporizes in a very short time, the amount sealed in the can can be controlled by a predetermined amount (the volume of the can, the amount of contents filled, the temperature of the contents, etc.). (Determined by the above.) With this, the internal pressure of the can after sealing becomes higher than atmospheric pressure, and this internal pressure supports the can body wall from the inside, so even if a can with a thin body wall is used, it will not dent due to external force. This is because it becomes less likely to occur. An example of a method and apparatus for achieving this objective is disclosed in Japanese Patent Application Laid-open No. 109996/1983. The inert liquefied gas quantitative dropping device described here includes a central tank in which an inert liquefied gas for dropping, an inert liquefied gas for insulation, and a vacuum atmosphere for insulation are each sealed, and an intermediate layer that sequentially surrounds the outer periphery of the central tank. A sealed tank is provided with a triple-layered internal structure formed by an outer tank and an outer tank, and a dripping liquefied gas passage opening/closing valve mechanism is provided at the bottom end of the center tank, which includes a valve seat opening, a valve body, and a valve stem.
This valve stem is connected to an operating mechanism that passes through the central tank and is attached to the outer upper end of the sealed tank, and a liquid level sensor is installed in the central tank to control the liquid level of the dripping liquefied gas in the central tank at a constant level. and a liquefied gas supply pipe with a solenoid valve are inserted or communicated with each other, and a vaporized gas exhaust pipe, a pressurized nitrogen gas supply pipe, and a pressure gauge for controlling the pressure in the central tank are communicated with or attached. There is. In this inert liquefied gas quantitative dripping device, due to the existence of an intermediate tank of inert liquefied gas for heat insulation and an outer tank with a vacuum atmosphere for heat insulation, which are provided around the center tank, the inside of the center tank is affected by heat from the outside air. The vaporization of the inert liquefied gas for dripping is suppressed, and the liquid level and internal pressure of the inert liquefied gas for dripping in the central tank are maintained constant by two control mechanisms. The operating mechanism is actuated by the can detection signal detected just before the can passes directly under the central tank, raises the valve stem and valve body, and opens the valve seat opening for a predetermined period of time. A substantially constant amount of inert liquefied gas is dropped each time. Also, No. 6 in the upper left column of page 4 of JP-A No. 56-4521.
Lines 8 to 8 show that by keeping the on-off valve of the liquid nitrogen dripping device open and constantly dripping liquid nitrogen, and by keeping the moving speed of the cans passing below constant, A method of dropping liquid nitrogen is also described in which the amount of drops is almost the same. (Problems to be solved) In order to reduce the manufacturing cost of canned goods, it is necessary to increase the speed of the canned manufacturing line (i.e., the filling speed of can contents, the speed of tightening can lids, the moving speed of cans, etc.). Desirably, the inert liquefied gas dripping device disclosed in JP-A-56-109996 moves the valve body up and down every time a can passes under it (as the can passes under the valve seat opening). Just before the can passes, the valve element is raised to release the valve seat opening, and just before the can is finished passing, the valve element is lowered to close the valve seat opening, and just before the next can passes under the valve seat opening, the valve element is opened again. (The valve element is lowered just before it finishes passing, and the valve seat opening is closed again.) Therefore, the canning production line is operated at a high speed of 500 cans/min or more. In this case, the opening and closing of the valve seat opening could no longer follow the speed of the can manufacturing line (hereinafter sometimes referred to as line speed), making it impossible to use. On the other hand, in the liquid nitrogen dropping method disclosed in JP-A No. 56-4521, the valve seat opening is always kept open, so the diameter of the valve seat opening is enlarged so that a constant amount (constant By improving the flow of liquid nitrogen so that the amount of liquid nitrogen (per hour) continues to flow down, it becomes possible to handle high-speed canning production lines (hereinafter sometimes referred to as high-speed lines) that can produce more than 500 cans per minute, but it has the following drawbacks: Therefore, it cannot be used for high-speed lines. In other words, among the can lid tightening machines used for can manufacturing,
Its seaming capacity (sealing speed) is approximately 500 cans/min (250ml).
Since it is impossible to operate at full capacity (high-speed operation) immediately after starting operation, it is necessary to operate at low speed for a certain period of time (around 30 minutes) after starting operation (filling speed, can movement speed, etc.). Conventionally, an operating method (the line speed is changed midway) has been adopted in which the line speed is changed at a low speed) and then a high speed operation (generally, the speed is approximately twice that of the low speed operation). In addition, even after shifting to high-speed operation, there may be cases where high-speed filling is unable to supply the liquid in time due to the time it takes to mix the liquid content to be filled into the cans, or there is a problem with the caser that packs manufactured canned goods into boxes. In some cases, such as when an emergency occurs, it may be more convenient to switch the speed of the can manufacturing line to low speed operation from the viewpoint of operating the can manufacturing line. If the liquid nitrogen dripping device disclosed in JP-A-56-4521 is installed in a can manufacturing line where the line speed changes midway,
Since the amount of liquid nitrogen flowing down per certain period of time in this device does not change, if the moving speed of the can increases midway, the amount of liquid nitrogen added into the can will decrease midway (i.e., the amount of liquid nitrogen added into the can will decrease). The amount of liquid nitrogen added to the can opening is the product of the cross-sectional area of the continuing falling liquid nitrogen stream and the time it takes the can opening to cross this liquid nitrogen stream. As the traversal time decreases, in other words as the speed of can movement increases, the amount of liquid nitrogen added into the can decreases.For example, if the speed of movement of the can doubles, the amount of liquid added into the can decreases. (The amount of nitrogen is reduced to 1/2.), resulting in a large number of defective products, making it virtually impossible to use the device disclosed in JP-A-56-4521 on high-speed lines. It is. (Means for Solving the Problem) In order to eliminate the above-mentioned drawbacks, the present invention uses a low-temperature liquefied gas flow-down device equipped with a nozzle section provided with three or more discharge holes through which low-temperature liquefied gas flows down, and a can manufacturing line is operated at a low speed. When the line is in operation, the low temperature liquefied gas is allowed to flow down only from some of the discharge holes (two or more), and when the can manufacturing line is being operated at high speed, the low temperature liquefied gas is allowed to flow down from all the discharge holes. That is, by conveying cans containing liquid one after another, the cans are first passed under the discharge hole of a low-temperature liquefied gas flow device through which low-temperature liquefied gas is continuously flowing down, and into each can. In a method for manufacturing gas-filled canned goods by receiving a predetermined amount of low-temperature liquefied gas, then sending the can to a can lid sealing machine and sealing the can with a can lid, as the low-temperature liquefied gas flowing device. , a nozzle portion having three or more discharge holes and a plurality of valve bodies for opening and closing these discharge holes, and conveying the can at a relatively low first speed. In this case, only some of the plurality of valve bodies are opened to allow the low temperature liquefied gas to flow down only from two or more discharge holes among the three or more discharge holes; When the gas is being transported at a second speed that is higher than the first speed, all of the plurality of valve bodies are opened, and the low temperature liquefied gas is discharged from all of the three or more discharge holes. This is a method for producing gas-filled canned goods, which is characterized by causing gas-filled cans to flow down. (Function) In the present invention, when the can manufacturing line is operated at low speed (that is, when the can movement speed is slow),
When only some of the valve bodies are opened and low-temperature liquefied gas flows down only from some discharge holes, when the can manufacturing line is operated at high speed (i.e., when the cans are moving quickly), all of the If the valve body is opened and the low-temperature liquefied gas flows down from all the discharge holes, and the time it takes for the can to pass under the discharge holes is relatively long, the amount of low-temperature liquefied gas flowing down per unit time is reduced, On the other hand, when the time for the cans to pass under the discharge hole is short, the amount of low-temperature liquefied gas flowing down per unit time is increased, so even if the moving speed of the cans changes, the amount of low-temperature liquefied gas received by each can increases. The amount remains virtually unchanged. Therefore, the internal pressures of the gas-filled cans manufactured before and after changing the speed of the gas-filled can can manufacturing line can be made approximately equal. When the means for increasing or decreasing the amount of low-temperature liquefied gas flowing down per unit time increases the moving speed of the can, the valve body that had closed part of the discharge hole is opened and all the valve bodies are opened. On the other hand, when the moving speed of the can is slowed down, only a part of the valve body is closed, so the operation does not require any skill and can be performed easily and quickly. (Embodiment) An embodiment of the present invention will be described with reference to FIGS. 1 to 5, which show the main parts of a low-temperature liquefied gas flow device. Figures 1 and 2 are longitudinal cross-sectional views of main parts of a low-temperature liquefied gas flow device implementing the method of the present invention. Fig. 2 shows the state of the nozzle part when the canning line is running at a high speed. 3 to 5 are bottom views of the nozzle showing examples of arrangement of discharge holes. Note that the arrow in the figure indicates the direction of movement of the can. Reference numeral 1 denotes a low temperature liquefied gas storage tank with a double-walled heat insulating structure, and a vacuum is created between the inner wall 2 and the outer wall 3. 4 is a nozzle for discharging and flowing down the low temperature liquefied gas 12 formed at the bottom of the storage tank 1;
is a discharge hole provided in the nozzle 4 (this example shows an example in which three discharge holes 5, 5, 5 of the same diameter are provided in a row in two separate nozzles 4, 4). . 6 is a can already filled with liquid; 7
is an endless chain moving at a constant speed (not shown)
These claws are attached at equal intervals to the cans and push the body of the can from behind to transport the can at a constant speed. Reference numeral 8 denotes a guide rail for regulating the movement of the moving can in a direction perpendicular to the traveling direction, and reference numeral 9 denotes a table on which the can slides. 10 is a valve body for opening and closing the discharge hole 5 of the nozzle 4, and 11 is a piston rod for moving the valve body 10 up and down (in this embodiment, a piston rod is provided for each of the separate nozzles 4, 4). (The valve bodies 10 are provided individually.) Here, the relationship between each of the discharge holes 5, 5...5 of each nozzle 4, 4 and the can 6 to be conveyed is shown in the case where the discharge holes 5, 5...5 are lined up in a line as in this embodiment. , each of them should pass through the center of the opening of the can 6 to be transported (i.e., if the cross section of the opening is circular, the diameter line parallel to the direction of travel of the can,
The rows of the discharge holes 5, 5...5 are made to almost coincide with each other from the viewpoint of reducing the loss of the low temperature liquefied gas 12 flowing down and from the viewpoint of reducing the variation in the internal pressure of each can after being sealed. desirable. The liquid level of the low-temperature liquefied gas 12 in the storage tank 1 is at atmospheric pressure, and the liquid level height is determined by a liquid level control sensor (not shown) and a low-temperature liquefied gas supply pipe installed. Since it is kept almost constant by the solenoid valve, the total amount of low-temperature liquefied gas discharged from the discharge holes 5 within a certain period of time will always be almost constant unless the number of open discharge holes 5 is changed. Become. Using this device, unless the number of open discharge holes is changed, the flow rate (ml/S) of low-temperature liquefied gas per unit time will always be approximately constant, so low-temperature liquefied gas can be continuously discharged. below the nozzle
If the top-opening can is made to move at a constant speed,
A certain amount of low temperature liquefied gas will be added into each can. The can into which the low-temperature liquefied gas has been added is immediately sealed to prevent the liquefied gas from evaporating and dissipating and to maintain a constant pressure inside the can. Now, as mentioned above, in the device of this embodiment, two
Discharge holes 5 of the same diameter in each of the nozzles 4, 4
There are three nozzles each, so both nozzles 4, 4
With the valve bodies 10, 10 open, the six discharge holes 5,
When the low-temperature liquefied gas 12 is caused to flow down from 5...5 (see Figure 2), the flow rate (ml/S) of low-temperature liquefied gas per unit time is 3 when only the valve body 10 of one nozzle 4 is opened. When the low temperature liquefied gas 12 is made to flow down only from the discharge holes 5, 5, 5 (see Fig. 1)
This is twice the flow rate of low temperature liquefied gas per unit time. Therefore, the speed ratio between low and high speeds of the can production line (filling speed of can contents, can movement speed, can lid tightening speed) is set to 1:2. When the can manufacturing line is operated at low speed (i.e., the moving speed of the can is slow and the time it takes to pass under the discharge hole is relatively long), the discharge holes 5, 5, 5 of one nozzle 4 are closed. The low temperature liquefied gas is allowed to flow down only from the three discharge holes 5, 5, 5 of one nozzle 4, which is closed by the body 10, while the can manufacturing line is operated at high speed (the moving speed of the cans is slow). (double the operating time), both nozzles 4,
4 valve bodies 10, 10 are opened to open the 6 discharge holes 5,
When low-temperature liquefied gas is allowed to flow down from 5...5, the amount of low-temperature liquefied gas added to can 6 becomes the same in both cases. Therefore, the internal pressure of canned goods manufactured when the line speed is low is almost equal to the internal pressure of canned goods manufactured when the line speed is high, so low-temperature liquefaction is applied to a high-speed canning manufacturing line where the line speed changes midway through operation. A gas-filled can can be manufactured at a predetermined pressure by introducing a gas flow device. Also, when the line speed changes from low to high speed,
Or, to operate the low-temperature liquefied gas flow device in the opposite case, one valve element whose discharge holes are completely closed can be raised to open all the discharge holes, or one valve element can be lowered. All you have to do is close some of the discharge holes completely (no need for fine adjustment).
For example, when the temperature changes, the operator should press the valve body operating button, or the valve body operating device should be linked with a speedometer, etc. of the can conveyor (during high-speed operation, both valve bodies should be in the raised position). The operation is extremely simple and easy, and the operation is extremely simple and easy. In this embodiment, the two nozzles 4, 4 each have three discharge holes 5, but it is preferable to increase the number of discharge holes 5, as shown in FIGS. 3 to 5. In this way, one row of discharge holes is arranged parallel to the direction of travel of the can.
It is most desirable to arrange them in one row, two rows, or three rows from the viewpoint of reducing variations in the internal pressure of each can and reducing the loss of low-temperature liquefied gas. In addition, in the above embodiment, each of the two nozzles has the same diameter and the same number of discharge holes, but even if the diameter and number of discharge holes are changed for each nozzle, A discharge hole may also be provided. However, it goes without saying that the diameter and number ratio of the discharge holes of each nozzle must be changed depending on the speed ratio between low speed and high speed of the can manufacturing line. In addition, in the above embodiment, the nozzle part is composed of two nozzles and two valve bodies, but for example, it is possible to use a nozzle part composed of two nozzles (of course, a plurality of discharge holes). ) and two or more valve bodies, or a nozzle part composed of three or more nozzles and three or more valve bodies may of course be used. In addition, the number of discharge holes provided in the nozzle used in the present invention is set to 2 in order to reduce the variation in the internal pressure of gas-filled cans from one can to another even during low-speed operation.
It is preferable to let the low-temperature liquefied gas flow down from two or more discharge holes, so at least three are required. As a result of research by the present inventors, it has been found that the variation in the internal pressure of canned cans is reduced compared to when the same amount of low-temperature liquefied gas is allowed to flow down from each discharge hole. -Refer to No. 66318). Next, an experimental example of the method of the present invention will be explained. For this experiment, the diameter was approximately 52.6 mm (so-called 202 diameter),
A tin DI can with a height of 132 mm and an internal volume of 250 ml was used. Add 240 g of 95°C water to this DI can at a rate of 450 cans/min during low-speed operation and 900 cans/min during high-speed operation.
(240g±1g) When this can is operated at low speed after filling, only the valve body of one of the two nozzles is raised under the conditions described below, leaving only the discharge hole of one nozzle open. In addition, during high-speed operation, the valve bodies of both nozzles are raised to open all the discharge holes of the two nozzles, and liquid nitrogen flows down from these discharge holes, thereby reducing the discharge of liquid nitrogen from the nozzles of this liquid nitrogen flow device. After liquid nitrogen was added by passing through the holes at different speeds, the can lid was immediately tightened and sealed using a can lid tightening machine. Experimental conditions * Distance (vertical distance) between the bottom surface of the nozzle and the top of the can flange; approximately 5 mm * Liquid level height in the liquid nitrogen storage tank; approximately 110 mm * The number, diameter, and pitch between the discharge holes of each nozzle ( Distance between centers of discharge holes): Flow device A has 5 pieces on each of the two nozzles, 0.8 mm, 2.5 mm, Flow device B has 8 pieces on each of the two nozzles,
0.6mm, 2.5mm In addition, the discharge holes of each of the two nozzles of the flow-down device A are arranged in a row of five, and the discharge holes of each of the two nozzles of the flow-down device B are arranged in two rows of four. , these rows and the diameter line of the opening of the can parallel to the direction of travel were made to almost match or be parallel (the flow down device A could be changed to the flow down device B by replacing the nozzle). (Of course, it is possible to do so.) *Time required from adding liquid nitrogen to tightening the can lid;
1.8 seconds at low speed operation, 0.9 seconds at high speed operation When only one nozzle discharge hole of each flow device A and B is opened (for low speed operation) and two The amount of liquid nitrogen discharged per second was measured when the discharge hole of the nozzle was opened (for high-speed operation). The results are shown in Table 1.

[Table] Next, according to the above conditions, the filling speed of the liquid contents (can movement speed, can lid tightening speed) was changed (from 450 cans/min to 900 cans/min) during operation, and the liquid nitrogen was removed from the liquid nitrogen storage tank. Change the discharge amount of liquid nitrogen (2.56
ml/S→5.17ml/S, 2.58ml/S→5.11ml/S)
After manufacturing canned goods filled with nitrogen gas and cooling them to room temperature, the internal pressure of the canned goods manufactured under each condition was measured.
25 cans each were measured. The results are shown in Table 2.

[Table] As is clear from Table 2, the filling speed (can movement speed, can lid tightening speed) is 450 cans/900 cans/
Even if the amount is changed to 10 minutes, there is almost no difference between the internal pressure of the nitrogen gas-filled canned goods manufactured before the change and the canned pressure of the nitrogen gas-filled canned goods manufactured after the change, and there is also almost no difference in the variation in the can internal pressure. (Effects of the Invention) As described above, in the method of the present invention, even if the speed of the can manufacturing line changes during the process, the internal pressure of the manufactured gas-filled cans hardly changes. Gas filled cans can be manufactured efficiently and therefore at low cost using a variable high speed canning line. Moreover, the operations performed when the line speed changes are also extremely simple.

[Brief explanation of drawings]

Figures 1 and 2 are longitudinal cross-sectional views of main parts of a low-temperature liquefied gas flow device implementing the method of the present invention, and Figure 1 shows the state of the nozzle section when the speed of the can manufacturing line is low; FIG. 2 shows the state of the nozzle section when the speed of the can manufacturing line is high. 3 to 5 are bottom views of nozzles showing examples of arrangement of discharge holes suitable for carrying out the method of the present invention. 4... Nozzle, 5... Discharge hole, 6... Can, 10
... Valve body, 12 ... Low temperature liquefied gas.

Claims (1)

[Claims] 1. By conveying cans containing liquid one after another, the cans are first passed under the discharge hole of a low-temperature liquefied gas flow device through which low-temperature liquefied gas is continuously flowing down. A method for producing gas-filled canned goods by receiving a predetermined amount of low-temperature liquefied gas into each can, and then feeding the can into a can lid sealing machine and sealing the can with a can lid. The low-temperature liquefied gas flow down device is equipped with a nozzle section having three or more discharge holes and a plurality of valve bodies for opening and closing these discharge holes, and the conveyance of the can is carried out using a relatively low-speed first When the flow is carried out at a speed of When the gas is flowing down and the can is being transported at a second speed higher than the first speed, all of the plurality of valve bodies are opened and the three or more discharge A method for manufacturing a gas-filled canned food, characterized in that low-temperature liquefied gas is allowed to flow down from all of the holes.