SE529719C2 - System, machine, procedure and method of manufacture of packaging - Google Patents

Abstract

A system and a process for providing at least one flow of a sterilization agent to at least one sterilization unit in a filling machine is provided. The system includes at least one flow regulator (38, 40) for discharging the flow of sterilization agent, two containers (16, 18) for sterilization agent, each of the containers being interconnected with the flow regulator and alternatingly catering for the supply of sterilization agent to the flow regulator, and a pressure regulator (20) which is connected to each one of the containers and is supplied with an excess pressure in order to pressurise the containers. The system is characterised in that it includes a feedback device (68) which is disposed to read off an actual value of the flow from the flow regulator, compare the actual value with each respective norm value and control the pressure regulator in accordance with the comparison between the actual value and the norm value.

Description

52 25 7 529 719 2 to tubes closed by sealing two opposite edges of each sheet in an overlapping condition. Each tube is then threaded over a respective plastic top and arranged so that the greater part of the plastic top projects outside the tube. After sealing the top and the tube along a contact surface between them, filling, sealing of the open end of the tube to form a sleeve and closing of the package, as well as final forming, await.

The above manufacturing methods are well known and will not be described in detail.

In order to extend the shelf life of the packaged products, it is known to sterilize the packaging material before the filling operation and sometimes also the forming operation. Depending on how long the shelf life is desired and whether the packages are to be distributed and stored in a refrigerated or room temperature environment, different sterilization levels can be selected.

One known way in which packaging material can be sterilized is chemical sterilization. Chemical sterilization can be done, for example, by passing the packaging material through a bath of fl hydrogen peroxide and then a heating station to remove the hydrogen peroxide. This method works excellently when it comes to sterilizing a web of packaging laminate. However, the method is obviously less suitable for sterilizing open cartons before filling. In that case, gas phase sterilization can be applied instead.

A sterilization device for gas phase sterilization of carton bottles is described in the Swedish patent 0203692-9, which is hereby incorporated herein by reference. The patent specification describes how the cardboard bottles are sterilized by allowing those arranged upside down on a conveyor belt to first pass a heating zone, then a sterilization zone and finally a ventilation zone. In the sterilization zone, the carton bottles are exposed to gaseous hydrogen peroxide. To prevent the hydrogen peroxide from condensing on the surface of the cartons in the sterilization zone, which makes subsequent removal more difficult, the cartons are heated in the heating zone to a temperature above the dew point of the hydrogen peroxide gas. In the ventilation zone, the kaitong bottles are exposed to sterile hot air in order to ventilate away hydrogen peroxide that remains in and on the cardboard bottles.

In order for the sterilization to be sufficient, it is important that the carton bottles undergo a sufficiently strong hydrogen peroxide gas exposure. However, the exposure must not be so strong that unauthorized residues of hydrogen peroxide remain in and on the cardboard bottles when they leave the ventilation zone. For this reason, it is important to carefully control the supply of hydrogen peroxide gas to the sterilization zone in order to achieve the desired hydrogen peroxide gas concentration there. 10 15 20 25 30 35 529 719 3 A known packaging machine with a sterilizing device similar to the above comprises two buffer tanks for liquid hydrogen peroxide. The buffer tanks are connected to a pressure regulator which is supplied with an overpressure to pressurize the buffer tanks at a constant predetermined pressure. The buffer tanks are further connected to a flow regulator for discharging a predetermined, substantially constant flow of hydrogen peroxide to an evaporator device in the packaging machine. In the evaporator device, the liquid hydrogen peroxide is evaporated and the resulting hydrogen peroxide gas is introduced into the sterilization zone of the sterilizer. Thus, it is the fl fate regulator that determines the concentration of the hydrogen peroxide gas sterilization zone. In fact, the predetermined fl fate to be discharged from the flow regulator to achieve the desired concentration in the sterilization zone is very small, which places high demands on the flow regulator. There are flow regulators on the market that are specially adapted for applications that involve very small flows. These work excellently as long as the pressure of the hydrogen peroxide supplied from the buffer tanks is substantially constant or varies slowly.

However, due to space reasons in the packaging machine, the buffer tanks have a relatively limited volume and the amount of hydrogen peroxide in a full buffer tank lasts only a relatively short time during normal operation of the packaging machine. Normally, one buffer tank is used at a time to supply hydrogen peroxide to the flow regulator. When the first buffer tank is used and starts to run out, a change must be made to the second buffer tank. After the changeover, when the second buffer tank is used for the supply of hydrogen peroxide to the flow regulator, the first buffer tank is refilled with hydrogen peroxide from a larger storage tank arranged outside the packaging machine.

In connection with a change between the buffer tanks, rapid variations in the pressure of the hydrogen peroxide supplied to the flow regulator can occur. One reason for these rapid variations may be that air enters the connection between the flow regulator and the buffer tanks during the changeover. Another reason may be the acceleration of the hydrogen peroxide from the "new" buffer tank in connection with the changeover from the "old" buffer tank. Today's flow regulators have trouble handling such rapid variations in the pressure of the hydrogen peroxide fed.

This means that the flow out of the flow regulator in connection with a change risks deviating from the predetermined, substantially constant flow of hydrogen peroxide.

Figure 1 is a diagram showing how the hydrogen peroxide flow discharged from the flow regulator can vary with time in connection with a change between the buffer tanks in the known packaging machine. At time zero, the shift is initiated and the diagram shows what the fl fate (A) looks like for 300 seconds after the shift. The bottom line (B) shows the constant pressurization of the buffer tanks by the pressure regulator and the lines (C) and (D) mark the upward and downward tolerances of the hydrogen peroxide flow, respectively. As can be seen from the diagram, the shift causes sharp variations in the hydrogen peroxide flow discharged from the fl fate regulator. After about 65 seconds, the peroxide fl fate is even outside the tolerance line D. Eventually, after about 215 seconds, the flow stabilizes again around the desired, predetermined value.

A deviation in the flow out of the flow regulator means a deviation, from the desired concentration, in the hydrogen peroxide gas concentration in the sterilization zone.

This in turn can result in insufficient sterilization of the cartons or unauthorized residues of hydrogen peroxide in and on the cartons as they leave the ventilation zone. Cardboard boxes that have not been properly sterilized must be discarded. For this reason, the packaging machine is stopped when a sufficiently large deviation in the flow out of the flow regulator is detected. By a sufficiently large deviation is meant a deviation that gives a hydrogen peroxide flow outside the tolerance limits. The machine is restarted only when the pressure of the hydrogen peroxide fed into the fl fate regulator has stabilized and the flow regulator returns the predetermined flow again. However, the packaging that has time to be sterilized incorrectly before the machine is stopped must be discarded. which of course means large financial losses. A machine shutdown also means major financial losses. The problems can be particularly serious because the switching between the buffer tanks has to be done so often.

SUMMARY OF THE INVENTION An object of the present invention is to provide a system, a packaging machine comprising such a system, a method and a method of manufacturing packages comprising such a method, for providing at least one flow of a sterilant to at least one sterilizer. ring unit in a packaging machine, which at least partially eliminates any limitations that may be present in the prior art. The basic concept of the present invention is to provide, at least in connection with a tank change, an opportunity to actively control the pressure regulator based on signals regarding the current flow from the flow regulator to reduce the variations in the pressure of the sterilant supplied to the flow regulator and thus the variations in the flow discharged from the flow regulator.

The system, packaging machine, method and method for achieving the above object are defined in the appended claims and discussed below. A system according to the present invention for providing at least one flow of a sterilant to at least one sterilization unit in a packaging machine comprises at least one flow regulator for discharging the flow of sterilant, two containers for sterilants, which containers each is connected to the flow regulator and alternately provides a supply of sterilant to the flow regulator, and a pressure regulator connected to each of the containers and fed with an overpressure to pressurize the containers. The system is characterized in that it further comprises a feedback means which is arranged to read an actual value of the flow from the flow regulator at predetermined intervals, compare the actual value with a respective setpoint and control the pressure regulator in accordance with the comparison between the actual value and the setpoint.

If the packaging machine is of the type initially discussed in the section on background technology, the sterilization unit comprises the evaporator device and the sterilization device, and refers to the containers for sterilant the buffer tanks.

The term "alternately" means that the sterilant discharged from the flow regulator first comes from one and then from the other of the containers, and so on. Just at the actual change between the containers, the sterilant discharged from the flow regulator can originate from both containers.

The setpoint, which is the desired value of the flow from the flow regulator, is usually constant over time, while the actual value, which is the actual value of the flow from the flow regulator, usually varies more or less with time, especially in connection with a change between the containers. .

The pressure regulator is arranged to limit the overpressure in a suitable manner in order to obtain a desired pressurization of the containers. By controlling the pressure regulator based on actual, current values regarding the flow of sterilant from the flow regulator, the pressurization of the containers can, if appropriate, be changed to reduce variations in the pressure of the sterilant supplied to the flow regulator. This also reduces the variations in the flow from the flow regulator, which entails a considerably reduced risk that the packaging machine must be stopped and packaging must be discarded.

A comparison between the actual value and the setpoint can for example result in a ratio or a difference between the values according to which the pressure regulator is controlled.

The control of the pressure regulator means an increase in the pressurization of the containers if the flow out of the flow regulator is too small and certain conditions are met. Correspondingly, the control of the pressure regulator means a reduction in the pressurization of the containers if the flow out of the flow regulator is too large and certain conditions are met. The feedback means may be arranged to control the pressure regulator so that a first increase of the pressurization is obtained if the difference between the actual value and the setpoint is negative and has an absolute value exceeding a first limit value, which first increase is a function of the absolute value.

The first limit value indicates how much the actual value may deviate from the setpoint before the pressure regulator is controlled to increase the pressurization.

The first increase may, for example, be proportional to the absolute value of the difference between the actual value and the setpoint. The feedback means may be arranged to control the pressure regulator so that a first reduction of the pressurization is obtained if the difference between the actual value and the setpoint is positive and has an absolute value exceeding a second limit value, which first reduction is a function of the absolute value.

The second limit value, which can but does not have to be equal to the first limit value, indicates how much the actual value may deviate from the setpoint before the pressure regulator is controlled to reduce the pressure setting.

The first decrease may, for example, be proportional to the absolute value of the difference between the actual value and the setpoint. The feedback means may be arranged to control the pressure regulator so that a second increase in pressurization is obtained if the difference between the actual value and the setpoint is negative and has an absolute value exceeding a third limit value, and the actual value is decreasing, which second increase is a function of how fast the actual value decreases.

The third limit value, which can but does not have to be equal to the first limit value, indicates how much the actual value may deviate from the setpoint before the pressure regulator is controlled to increase the pressure setting.

The term "decreasing" means that the actual value has a negative trend or derivative, ie that the actual value at the current reading is less than the actual value at the previous reading. In a case where the current reading is the first reading, the actual value “at the previous reading” can be set equal to the setpoint.

The second increase may, for example, be proportional to the absolute value of the difference between the actual value at the current reading and the actual value at the previous reading divided by At, where At = the time difference between the current reading and the previous reading. The feedback means may be arranged to control the pressure regulator so that a second reduction of the pressurization is obtained if the difference between the actual value and the setpoint is positive and has an absolute value exceeding a fourth limit value, and the actual value is increasing, which second reduction is a function of how fast the actual value grows.

The fourth limit value, which may but need not be equal to the first limit value, indicates how much the actual value may deviate from the setpoint before the pressure regulator is controlled to reduce the pressure setting.

The term "growing" means that the actual value has a positive trend or derivative, ie that the actual value at the current reading is greater than the actual value at the previous reading. In a case where the current reading is the first reading, the actual value "at the previous reading" can be set equal to the setpoint.

The second reduction can, for example, be proportional to the absolute value of the difference between the actual value at the current reading and the actual value at the previous reading divided by At, where At = the time difference between the current reading and the previous reading. The feedback means may be arranged to control the pressure regulator so that a third increase of the pressurization is obtained if the ratio between the actual value and the setpoint is less than a fifth limit value which is less than one, which third increase means that the pressurization grows according to a predetermined growth pattern. is less than a sixth limit value and the feedback means reads an actual value which, when compared with the respective setpoint, gives a ratio which is less than a seventh limit value which is greater than the fifth limit value and less than one, that the pressurization is subsequently kept substantially constant until the feedback means reads an actual value which, in comparison with the respective setpoint, gives a ratio which is greater than the seventh limit value, and that the pressurization then drops according to a predetermined sinking pattern independent of the ratio.

The above embodiment thus means that the pressurization grows at a predetermined rate until the pressurization has reached a certain sixth limit value or the ratio between the actual value and the setpoint has increased and reached a certain seventh limit value.

The fifth limit value indicates how much the actual value may deviate from the setpoint before the pressure regulator is controlled to allow the pressurization to grow. Correspondingly, the seventh limit value indicates how much the actual value may deviate from the setpoint before the pressure regulator is controlled to allow the pressurization to drop. The sixth limit value in turn indicates how large the pressurization may be during the third increase.

The fifth limit value may, but need not, be equal to the first limit value.

The growth pattern and the sink pattern can be developed experimentally according to the special conditions for the inventive system. For example, the third increase may be in the form of a parallel trapezoid which lacks a base, i.e. a of the parallel sides. Accordingly, the system may be so constructed that, at the third increase, the pressurization grows from a starting value and then drops back to the starting value.

Of course, the above different embodiments of the feedback means can be combined in any way in one and the same embodiment. According to one embodiment, the feedback means is arranged to control the regulator so that a first, a second and a third increase in the pressurization are obtained if the above respective conditions are met. The resulting total increase in pressurization may then be the sum of the first, second and third increases. According to the same embodiment, the feedback lens means is arranged to control the regulator so that a first and a second pressure reduction are obtained if the above respective conditions are met.

The resulting total reduction in pressurization can then be the sum of the first and second reductions.

It follows from the above that the provisions first to seventh before the words increase, decrease and limit value have nothing to do with order but are only used for distinctive purposes.

According to one embodiment, the feedback means is arranged to be active only during a changeover between the containers and a predetermined time after the changeover.

As described in the introduction, it is precisely in connection with a change between the containers that the feedback function is needed most to minimize variations in the flow out of the system. After the predetermined time, the system is expected to have stabilized and then the feedback means can be made inactive until it is time for the next change.

The system according to the invention can be designed in such a way that one container is arranged to be filled with sterilizing agent when the other container provides for the supply of sterilizing agent to the flow regulator.

The advantage of such a construction is that the system can be operated continuously and does not need to be stopped for filling with sterilant.

According to one embodiment, the system comprises two flow regulators for dispensing, one of which is a flow of sterilant, which flow regulators are each connected to the containers for sterilant. In this embodiment, the feedback means is arranged to read actual values of the flows from the flow regulators, compare the actual values with respective setpoints to obtain a respective difference and control the pressure regulator in accordance with the comparison corresponding to the difference with largest absolute value. flow of sterilant to each of two sterilization units in a packaging machine which may thus have two production lines for the manufacture of twice as many packages. The production lines could be identical and thus require the same flow of sterilant, or be different and therefore require different flows.

The sterilant used in the system can be, for example, liquid hydrogen peroxide which is a well-proven and effective sterilant in the packaging industry.

A packaging machine according to the present invention comprises a system as above.

A method of the present invention for supplying at least one flow of a sterilant to at least one sterilizing unit in a packaging machine comprises discharging the flow of sterilant through at least one flow regulator, supplying sterilant to the flow regulator alternately from two containers for sterilizing means, each container being connected to the flow regulator, and pressurizing the containers by feeding a pressure regulator with an overpressure, which pressure regulator is connected to each of the containers. The method is characterized in that it further comprises at predetermined intervals, through a feedback means, reading an actual value of the flow from the flow regulator, comparing the actual value with a respective setpoint and controlling the pressure regulator in accordance with the comparison between the actual value and the setpoint.

A method according to the present invention for the manufacture of packages comprises a method as above.

The features discussed in connection with the inventive system for providing at least one flow of a sterilant to at least one sterilizer in a packaging machine are, of course, transferable to the inventive corresponding packaging machine and method of making packages and the corresponding method of the invention.

These features can furthermore of course be combined in the same embodiment.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be described in more detail with reference to the accompanying schematic drawings, which show examples of presently non-limiting preferred embodiments of the present invention.

Figure 1 is a diagram illustrating the flow from a flow regulator in a packaging machine according to prior art.

Figure 2 is a schematic diagram illustrating a system according to the present invention.

Figure 3 is a fate diagram illustrating a method according to a first embodiment of the present invention. Figure 4 is a diagram illustrating the flows from the flow regulators in the system of Figure 1 according to the first embodiment.

Figure 5 is a flow chart illustrating part of a method according to a second embodiment of the present invention.

Figure 6 is a diagram illustrating the flows from the flow regulators in the system of Figure 1 according to the second embodiment.

DESCRIPTION OF PREFERRED EMBODIMENTS Figure 2 schematically shows a system 10 according to the present invention. The system is included in a packaging machine (not shown in its entirety) for the manufacture of cardboard bottles as described above in the section dealing with background technology. The packaging machine has two production lines and accordingly the system 10 has the task of providing a respective fl fate of fl liquid hydrogen peroxide to each of two sterilization units, which are also included in the packaging machine. The two production lines are intended for the production of similar packaging and thus the flows provided by the system must be kept as equal as possible. Each of the sterilization units comprises an evaporator device for evaporating the liquid hydrogen peroxide. The evaporator devices are shown in Figures 2 and are designated therein by 12 and 14. The resulting hydrogen peroxide gas is fed to a sterilization zone (not shown) in the machine which is also included in each of the sterilization units. When the cartons pass through the sterilization zone, they are exposed to the hydrogen peroxide gas as part of the sterilization process. Since sterilization in this manner is already known and is further described in the patent specification referred to above, a more detailed description will not be given here.

The system 10 comprises two identical buffer tanks 16 and 18 for liquid hydrogen peroxide and an electronically controllable pressure regulator 20. The buffer tanks are arranged to alternately be responsible for the supply of hydrogen peroxide to the sterilization units.

The pressure regulator is supplied with an overpressure P of 6 bar and is further, via pipelines, connected to each of the buffer tanks 16 and 18 for pressurizing them. The pressure regulator is preset to pressurize the buffer tanks by 1.8 bar during stable operation of the packaging machine. On the pipelines, between each of the buffer tanks 16 and 18 and the pressure regulator 20, are valve means 22 and 24 for regulating the pressurization of the buffer tanks. Each of the buffer tanks further has, through pipelines, a double connection with a drainage tank 26. On the pipelines, between each of the buffer tanks and the drainage tank, there are valve means 28 and 30, respectively 32 and 34, for regulate the drainage of the buffer tanks. A further valve means 36 for drainage control is further arranged between the valve means 32 and 34 and the drainage tank 26.

The buffer tanks 16 and 18 are furthermore each connected, via pipelines, to two flow regulators 38 and 40, which in turn, through further pipelines and a respective valve member 42 and 44, are connected to one of the sterilization units. evaporator devices 12 and 14. The flow regulators 38 and 40, which are marketed by Bronkhorst High-Tech BV, the Netherlands, under the name L | QUl-FLOW®, are specially adapted for applications where it is desirable to dispense very small amounts of liquid with high accuracy, in connection with the system 10, the flow of hydrogen peroxide desired from each of the flow regulators is 4.2 kg / h, i.e. relatively small. With this flow, a concentration of hydrogen peroxide gas is obtained in the sterilization zones which is sufficient to achieve a desired degree of killing without being so great that there is a risk of impermissible residual amounts of hydrogen peroxide 1 and on the carton bottles after completion of sterilization.

Large variations from the desired value of the hydrogen peroxide fl fats discharged from the fl fate regulators can lead to incorrect sterilization of the carton bottles.

For reasons of space, the buffer tanks 16 and 18 have a relatively limited volume and the hydrogen peroxide contained in one of the buffer tanks, for example the buffer tank 18, when it is filled to a certain maximum level is only sufficient to discharge the desired flow from the flow regulators 38 and 40 during a relatively short time. After about eight minutes, the hydrogen peroxide level in the buffer tank 18 has dropped to a certain minimum level and then it is time to switch to the buffer tank 16. Using the buffer tank 16, the buffer tank 18 is filled, etc., as will be described below. In this way it is ensured that hydrogen peroxide is always available for the flow regulators 38 and 40. For checking the hydrogen peroxide level in the buffer tanks there is a sensor means 46 and 48 for detecting the largest level and a sensor means 50 and 52 for detecting the smallest the level arranged in each of the buffer tanks 16 and 18.

The buffer tanks 16 and 18 are connected by pipelines to two similar storage tanks 54 and 56 for liquid hydrogen peroxide. Even if this is not shown in the figure, the storage tanks have a volume that is significantly much larger than the volume of the buffer tanks. The storage tanks are arranged one by one to fill the buffer tanks with hydrogen peroxide. When the hydrogen peroxide in one of the storage tanks, for example the storage tank 56, is used up, a change is made to the storage tank 54.

During use of the storage tank 54, the storage tank 56 can be replaced or alternatively filled. In this way it is ensured that hydrogen peroxide is always available for the buffer tanks 16 and 18 and thus the flow regulators 38 and 40. Valve means 58, 60, 62 and 64 are located on the pipelines to regulate the filling of hydrogen peroxide 10 15 20 25 30 35 529 719 12 from the pre-tank tanks to the buffer tanks. Furthermore, a pump 66 is arranged between the valve means 58, 60 and the valve means 62, 64 for carrying out the actual transfer of hydrogen peroxide from the storage tanks to the buffer tanks.

As mentioned above, large variations from the desired value of the hydrogen peroxide flows discharged from the flow regulators 38 and 40 can lead to improper sterilization of the cartons produced in the packaging machine. The system 10 therefore only allows small variations in the flows to ensure that the sterilization takes place correctly. If the flows from the flow regulators fall outside 4.2 kg / h in 12%, the deviation from the desired flow value is judged to be too great.

As initially described, this leads to the packaging machine being stopped and cardboard bottles having to be discarded with large financial losses as a result.

When the pressure of the hydrogen peroxide supplied to the flow regulators from the buffer tanks 16 and 18 is constant or changes relatively slowly, the flow regulators function satisfactorily and they discharge a substantially constant flow of 4.2 kg / h. However, if the pressure of the hydrogen peroxide supplied to the flow regulators varies relatively quickly, the flow regulators may have problems keeping the respective discharged flows constant and thereby a risk of incorrect sterilization of the cartons may arise. Such rapid pressure variations are particularly common in connection with switching between the buffer tanks 16 and 18. One reason for these rapid variations may be that during the switching air bubbles arise in the pipelines between the flow regulators and the buffer tanks. Another reason may be the acceleration of the hydrogen peroxide from the “new” buffer tank when switching from the “old” buffer tank.

For the sake of clarity, the steps for a change from the buffer tank 18 to the buffer tank 16 are listed below: o Close the valve means 28 o Pressurize the buffer tank 16 o Wait until the pressure is stable in the buffer tank 16 o Open the valve means 32 o Close the valve means 34 o Close the valve means 24 o Open the valve member 60 o Start the pump 66 o Wait until the peroxide level in the buffer tank 18 is equal to the largest level o Close the valve member 60 Otherwise, discussions of system components that do not contribute to the invention tank itself will be omitted. In order to reduce the variations in the hydrogen peroxide flows discharged from the flow regulators and thereby reduce the risk of deviations from the desired flow value which are too large, the system comprises a feedback means 68 which is arranged to communicate with the flow regulators 38 and 40 and the pressure regulator 20 and operate in accordance with the flow chart shown in Figure 3. The feedback means 68 is arranged to read for 100 seconds from a change between the buffer tanks 16 and 18 (step A) an actual value of the flow from each of the flow regulators 38 and 40. The reading is made at predetermined intervals, at intervals of 40 ms, and after each reading differences (step B) are calculated between the actual values and the respective setpoints. As stated above, the setpoints here are constant and equal to 4.2 kg / h. The feedback means is then arranged to compare (step C) the absolute value of the differences in order to control the pressure regulator in accordance with the actual value which deviates most from the setpoint.

If the fumes of hydrogen peroxide from the flow regulators 38 and 40 are too small, the feedback means is arranged to temporarily control the pressure regulator 20 to increase the pressurization of the buffer tanks 16 and 18 to increase the flows. Accordingly, according to a first embodiment of the invention, the feedback means is arranged to examine (step D) whether the ratio between the most deviating actual value and the setpoint is less than a (fifth) limit value = 0.97. If this is the case, the feedback means is further arranged to examine (step E) whether there is room to increase the pressurization of the buffer tanks, ie if the pressurization is less than a (sixth) limit value = 2.3 bar. If the pressurization can be increased, this is done (step F) at a rate of 0.025 bar / s and a status fl agga is set = control to indicate that a (third) increase in the pressurization has been initiated. If, on the other hand, the buffer tanks can no longer be pressurized (step E), the current setting of the pressure regulator 20 is maintained. 0.97, the feedback means is further arranged to examine (step G) if the ratio is less than a (seventh) limit value = 0.98. If this is the case, (step H) the feedback means further investigates whether a (third) increase in the pressurization has been initiated, ie whether the status flag = control. If a (third) increase in pressurization has been initiated and there is (step l) room to increase the pressurization, this is done (step J) at a rate of 0.025 bar / s.

If, on the other hand, no (third) increase has been initiated (step H), or the buffer tanks can no longer be pressurized (step 1), the current setting of the pressure regulator 20 is maintained.

If it is instead determined (in step G) that the ratio between the most deviating actual value and the setpoint is greater than, or equal to, 0.98, the feedback means 10 is further arranged to examine (step K ) if a (third) increase in pressurization has been initiated, ie if the status flag = control. In the event that a (third) pressurization has been initiated and the pressurization of the buffer tanks is greater (step L) than the preset value = 1.8 bar, the pressurization (step M) is reduced at a rate of 0.025 bar / s. If, on the other hand, no (third) increase has been initiated (step K), or the pressurization of the buffer tanks is not greater than 1.8 bar (step L), the current setting of the pressure regulator 20 is maintained. In the latter case, set (step N ) also the status flag = no control to indicate that (the third) increase in pressurization has been completed.

Figure 4 is a diagram illustrating the above process and its effect on the flows of hydrogen peroxide discharged from the flow regulators 38, 40 in connection with a change between the buffer tanks 16, 18. At time zero the change is initiated and the diagram shows how the flows (on, 51 ) appears for 300 seconds after the changeover. The bottom curve (pj) shows the pressure regulator's pressurization of the buffer tanks and the lines (s) and (9) mark the upward and downward tolerances for the hydrogen peroxide fl fate, 4.2 kg / h in 12%. As can be seen from the diagram, the change causes variations in the hydrogen peroxide fl fates output from the flow regulators. In response to these variations, the feedback means controls the pressure regulator so that the pressurization of the buffer tanks changes as shown in the figure. The control means that a (third) increase in the pressurization is initiated when the ratio between the actual value of one of the flow regulators and the setpoint becomes less than 0.97. The pressurization then grows at a rate of 0.025 bar / s, which results in the flows discharged from the fate regulators also starting to grow. The pressurization increases until the maximum pressurization of the buffer tanks of 2.3 bar is reached or the ratio between the actual value and the setpoint has increased to 0.98. As shown in Figure 4, the first of the two alternatives first occurs in this example. When the pressurization reaches 2.3 bar, the pressurization is kept constant until the ratio between the actual value and the setpoint reaches 0.98. Thereafter, the pressurization begins to fall back towards the preset value of 1.8 bari at a rate of 0.025 bar / s.

Thanks to the fact that the feedback means controls the pressure regulator in the above manner, the flow variations in connection with the changeover are greatly reduced. As shown in Figure 4, the control of the pressurization means that the hydrogen peroxide flows from the flow regulators never end up outside the tolerance lines (s) and (8).

In the above embodiment, the feedback means 68 is arranged to temporarily control the pressure regulator 20 to increase the pressurization of the buffer tanks 16 and 18 if the flows of hydrogen peroxide out of the flow regulators 38 and 40 are too small. The feedback means may further be arranged to temporarily control the pressure regulator 20 to reduce the pressurization of the buffer tanks 16 and 18 if the flows of hydrogen peroxide out of the flow regulators 38 and 40 are too large. Accordingly, according to a second, more sophisticated, embodiment of the invention, the feedback means is arranged to operate according to the flow chart shown in Figure 3 + Figure 5. According to the second embodiment, the feedback means operates according to the flow chart shown in Figure 3. and as described above. Thereafter, the feedback means operates according to the flow chart shown in Figure 5. The overall procedure is repeated for 100 s after a change between the buffer tanks at an interval of 40 ms.

As illustrated in Figure 5, the feedback means is thus further (after step AN) arranged to examine (step O) whether the most deviating actual value is less than the setpoint, ie if the difference between the most deviating actual value and the setpoint is negative and has an absolute value exceeding one (first = third) limit value = 0. If this is the case, increase (step P) the pressurization by kl * (setpoint - the most deviating actual value), where k1 is a constant = 0.4. The (first) increase is thus proportional to the absolute difference between the most deviating actual value and the setpoint. The feedback means is then arranged to examine (step Q) whether the most deviating actual value, ie the actual actual value, is less than the previous corresponding actual value, ie whether the actual value is decreasing.

The term "corresponding" means that there are always two actual values from the same flow regulator that are compared in this step. If this is correct, (step R) the pressurization is increased by kg * (previous actual value ~ current actual value) / At, where kg is a constant = 0.1 and At = the time between the readings of the current actual value and the previous the actual value. The (second) increase is thus proportional to the direction coefficient of the actual value.

In the event that it is instead determined (in step O) that the most deviating actual value is not less than the setpoint, the feedback means is arranged to examine (step S) whether the actual value is greater than the setpoint, ie if the difference between the most deviating actual value and the setpoint is positive and has an absolute value that exceeds a (second = fourth) limit value = O. If this is the case, (step T) the pressurization is reduced by kl * (the most deviating actual value - the setpoint), where k1 is a constant = 0.4.

The (first) decrease is thus proportional to the absolute difference between the setpoint and the most deviating actual value. The feedback means is then arranged to examine (step U) whether the most deviating actual value, ie the current actual value, is greater than the previous corresponding actual value, ie whether the actual value is increasing. By the expression "corresponding" is meant, just as above, that there are always two actual values from the same fate controller that are compared in this step. If this is true, the pressure setting (step V) is reduced by k; * (current actual value -previ- previous actual value) / At, where kg is a constant = 0.1 and At = the time between the readings of the current actual value and the previous actual value. The (second) decrease is thus proportional to the direction coefficient of the actual value.

Figure 6 is a diagram illustrating the above procedure and its effect on the flows of hydrogen peroxide discharged from the flow regulators 38, 40 in connection with a change between the buffer tanks 16, 18. At time zero the change is initiated and the diagram shows how the flows (org, ßz ) appears for 300 seconds after the changeover. The bottom curve (pg) shows the pressure regulator's pressurization of the buffer tanks and lines (a) and (6) mark the upward and downward tolerances for the hydrogen peroxide flow, 4.2 kg / h in 12%. As can be seen from the diagram, the change causes variations in the hydrogen peroxide flows discharged from the flow regulators. In response to these variations, the feedback means controls the pressure regulator so that the pressurization of the buffer tanks changes as shown in the figure. The control means that a (first) increase in the pressurization from the preset value of 1.8 bar is obtained as soon as the actual value of one of the flow regulators becomes less than the setpoint, that a (second) increase is obtained when the actual value is less than the setpoint and decreases and that a (third) increase is initiated when the ratio between the actual value and the setpoint becomes less than 0.97. The increase in pressurization results, as can be seen from the figure, in the fact that the flows discharged from the flow regulators increase. The control also means that a (first) reduction of the pressurization from the preset value of 1.8 bar is obtained as soon as the actual value of one of the flow regulators becomes greater than the setpoint and that a (second) reduction is obtained when the actual value is greater than the setpoint and growing . The reduction in pressurization, as shown in the figure, results in a decrease in the flows discharged from the fate regulators.

Thanks to the fact that the feedback means controls the pressure regulator in the above manner, the flow variations in connection with the changeover are greatly reduced. As shown in Figure 6, the control of the pressurization means that the hydrogen peroxide flows from the flow regulators never end up outside the tolerance lines (s) and (6). A comparison between the diagrams in Figures 4 and 6 further shows that the second embodiment of the invention gives significantly less variations in the hydrogen peroxide flows from the flow regulators than the first embodiment.

Thus, as can be seen from the above description, an increase in pressurization may be the result of, at most, three partial increases (first, second and third increases). Correspondingly, a reduction in pressurization may be the result of, at most, two partial reductions (first and second reductions). It should be pointed out that the partial increases, just like the partial reductions, take place at the same time, even if this is not stated in the flow charts. 10 15 20 25 30 529 719 17 During continuous operation of the packaging machine, regular changes are thus made between the buffer tanks to ensure a continuous supply of hydrogen peroxide to the flow regulators. In connection with each changeover, the feedback means is activated which then for 100 s, at intervals of 40 ms, repeats the flow chart shown in figure 3 or figure 3 + 5 depending on which embodiment of the invention is applied. After 100 s, the system is considered to have stabilized sufficiently after the changeover and then the feedback means becomes inactive again. The present invention means that the temporary variations in the fl fates from the fl fate regulators which occur in connection with the changes do not become so great that the packaging machine has to be stopped and packaging discarded. This, of course, means enormous economic and practical benefits.

The embodiments described above are to be considered as examples only. One skilled in the art will appreciate that these embodiments may be modified and varied in a variety of ways without departing from the spirit of the invention.

For example, the packaging machine can of course be arranged for the manufacture of other types of packaging than cardboard bottles. The invention can be applied in all situations where packaging material / packages can be sterilized by means of a gas phase sterilant. Thus, the present invention can be advantageously used in connection with a packaging machine similar to the one initially described, where packages are manufactured by continuous forming, filling and sealing of a tube of packaging laminate.

Furthermore, the packaging machine can be arranged for the production of different types of packaging, for example one variety per production line. In such a case, the setpoints for the two flow controllers may differ. In addition, the setpoints do not have to be constant over time.

Of course, the packaging machine may comprise more than two buffer tanks and more than two production lines and thus flow regulators. The above configuration is just one example.

Finally, it should be pointed out that not all figures are drawn to scale and that all parameter values are only examples and thus can be varied.

Claims (24)

10 15 20 25 30 35 529 719 18 PATENT REQUIREMENTS A system (10) for providing at least one flow of a sterilant to at least one sterilizing unit in a packaging machine, comprising at least one flow regulator (38, 40) for discharging the flow of sterilant, two containers (16 , 18) for sterilants, each container being connected to the flow regulator and alternately providing pre-supply of sterilant to the fate regulator, and a pressure regulator (20) connected to each of the containers and fed with an overpressure to pressurizing the containers, characterized in that it further comprises a feedback means (68) arranged to read an actual value of the flow from the flow regulator at predetermined intervals, compare the actual value with a respective setpoint and control the pressure regulator in accordance with the comparison between the actual value and the setpoint . A system (10) according to claim 1, wherein the feedback means (68) is arranged to control the pressure regulator (20) so that a first increase of the pressurization is obtained if the difference between the actual value and the setpoint is negative and has an absolute value exceeding a first limit value, which first increase is a function of the absolute value. A system (10) according to any one of the preceding claims, wherein the feedback means (68) is arranged to control the pressure regulator (20) so that a first reduction of the pressurization is obtained if the difference between the actual value and the setpoint is positive and has an absolute value exceeding a second limit value, which first decrease is a function of the absolute value. A system (10) according to any one of the preceding claims, wherein the feedback means (68) is arranged to control the pressure regulator (20) so that a second increase in the pressure setting is obtained if the difference between the actual value and the setpoint is negative and has an absolute value which exceeds a third limit value, and the actual value is decreasing, which second increase is a function of how fast the actual value decreases. A system (10) according to any one of the preceding claims, wherein the feedback means (68) is arranged to control the pressure regulator (20) so that a second reduction of the pressurization is obtained if the difference between the actual value and the setpoint is positive and has an absolute value exceeding a fourth limit value, and the actual value is increasing, which second decrease is a function of how fast the actual value grows. A system (10) according to any one of the preceding claims, wherein the feedback means (68) is arranged to control the pressure regulator (20) so that a third increase in the pressure is obtained if the ratio between the actual value and the setpoint is less than a fifth limit value which is less than one, which third increase means that the pressurization grows according to a predetermined growth pattern independent of the ratio as long as the pressurization is less than a sixth limit value and the feedback means reads an actual value which at comparison with the respective setpoint gives a ratio which is less than a seventh limit value which is greater than the fifth limit value and less than one, that the pressurization is then kept substantially constant until the feedback means reads an actual value which when compared with the respective setpoint gives a ratio greater than the seventh limit value, and that the pressure subsequently decreases according to a predetermined decrease pattern independent of the ratio n. A system (10) according to claim 6, wherein the pressurization, at the third increase, grows from a starting value and drops back to the starting value. A system (10) according to any one of the preceding claims, wherein the feedback means (68) is arranged to be active only during a changeover between the containers (16, 18) and a predetermined time after the changeover. A system (10) according to any one of the preceding claims, wherein one container (16) is arranged to be filled with sterilant when the other container (18) provides for the supply of sterilant to the flow regulator (38, 40). A system (10) according to any one of the preceding claims, comprising two flow regulators (38, 40) for discharging each of them a stream of sterilant, which flow regulators are each connected to the containers (16, 18) for sterilization. means, the feedback means (68) being arranged to read the actual values of the flows from the flow regulators, compare the actual values with the respective setpoints for obtaining a respective difference and control the pressure regulator (20) in accordance with the comparison corresponding to the difference with the largest absolute value. A system (10) according to any one of the preceding claims, wherein the sterilant is liquid hydrogen peroxide. A packaging machine comprising a system (10) according to any one of claims 1-11. A method of providing at least one flow of a sterilant to at least one sterilizing unit in a packaging machine, comprising discharging the flow of sterilant through at least one en fate regulator (38, 40), supplying sterilant to the fl fate regulator alternately from two containers (16). , 18) for sterilants, each container being connected to the flow regulator, pressurizing the containers by supplying a pressure regulator (20) with an overpressure, which pressure regulator is connected to each of the containers, 529 719 characterized in that it further comprises reading at predetermined intervals, through a feedback means, (step A) an actual value of fl from the flow controller, comparing (steps D, G, 0, S) the actual value with a respective setpoint and controlling (steps F, J, M, P, R, T, V) the pressure regulator according to the comparison between the actual value and the setpoint. A method according to claim 13, comprising controlling (step P) the pressure regulator (20) so that a first increase of the pressurization is obtained if (step O) the difference between the actual value and the setpoint is negative and has an absolute value exceeding a first limit value, which first increase is a function of the absolute value. A method according to any one of claims 13-14, comprising controlling (step T) the pressure regulator (20) so that a first reduction of the pressurization is obtained if (step S) the difference between the actual value and the setpoint is positive and has an absolute value exceeding one second limit value, which first decrease is a function of the absolute value. A method according to any one of claims 13-15, comprising controlling (step R) the pressure regulator (20) so that a second increase in the pressurization is obtained if (step O) the difference between the actual value and the setpoint is negative and has an absolute value exceeding one third limit value, and (step Q) the actual value is decreasing, which second increase is a function of how fast the actual value decreases. A method according to any one of claims 13-16, comprising controlling (step V) the pressure regulator (20) so that a second reduction of the pressurization is obtained if (step S) the difference between the actual value and the setpoint is positive and has an absolute value exceeding one fourth limit value, and (step U) the actual value is increasing, which second decrease is a function of how fast the actual value grows. A method according to any one of claims 13-17, comprising controlling (steps F, J, M) the pressure regulator (20) so that a third increase in the pressurization is obtained if (step D) the ratio between the actual value and the setpoint is less than a fifth limit value which is less than one, which third increase means that the pressurization grows (steps F, J) according to a predetermined growth pattern independent of the ratio as long as (step E, I) the pressurization is less than a sixth limit value and (steps D, G) feedback the means (68) reads an actual value which, when compared with the respective setpoint, gives a ratio which is less than a seventh limit value which is greater than the fifth limit value and less than one, that the pressurization is then kept substantially constant until (step G) the feedback means reads an actual value which, in comparison with the respective setpoint, gives a ratio which is greater than the seventh limit value, and that the pressurization then drops (step M) according to a predetermined sinking pattern independently of the quota. 10 15 20 21 A method according to claim 18, wherein the pressurization, at the third increase, grows from a starting value and drops back to the starting value. A method according to any one of claims 13-19, comprising allowing the feedback means (68) to be active only during a changeover between the containers (16, 18) and a predetermined time after the changeover. A method according to any one of claims 13-20, comprising filling one container (16) with sterilant when sterilant from the other container (18) is supplied to the flow regulator (38, 40). A method according to any one of claims 13-21, comprising dispensing a flow of sterilant through each of two flow regulators (38, 40), which flow regulators are each connected to the containers (16, 18) for sterilization. and comprising reading (step A) annual values of the flows from the flow regulators at predetermined intervals, comparing (step B) the actual values with the respective setpoints for obtaining a respective dlfferens and controlling (steps F. J, M, P, R, T, V) the pressure regulator (20) according to the comparison corresponding to the difference with the largest absolute value. A method according to any one of claims 13-22, wherein the sterilant is liquid hydrogen peroxide. A method of manufacturing packages, comprising a method according to any one of claims 13-23.