JPH0957825A - Controlling method of preform forming equipment and preform forming equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a controlling method of preform forming equipment and the preform forming equipment, which enables the continuous operation of an injection molder possible even when the conveyance of a preform to the equipment in a following process becomes impossible temporarily due to the trouble in the equipment in the following process. SOLUTION: At the kicking-off of operation, preforms are discharged out of line through a discharge chute 25. After that, preforms formed in a steady forming mode are conveyed with a tray conveyor 23 or the like in a production line. When troubles occur in an equipment in a following process, preformed trays 13 are accumulated in a tray accumulator 32 and, at the same time, the injection cycle time of injection molders 1 are elongated so as to discharge preforms through the discharge chute 25 when a tray accumulator 32 becomes full of preform trays. When troubles are solved, preforms are sent to the equipment in the following process under the condition that the shortage of preforms is replenished by the accumulated preforms. After all the accumulated preforms are sent out, the injection cycle time is returned to the steady forming mode.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a preform molding equipment control method and a preform molding equipment, and in a preform molding equipment, a container blow molding, and an in-line equipment for filling, a post-process equipment (a container blow molding equipment). It is useful when applied to the case where the injection molding machine of the preform molding equipment is continuously operated without stopping even when the operation of the molding equipment or the filling equipment) is interrupted.

[0002]

2. Description of the Related Art An example of a conventional production line for consistent container blow molding and filling will be described with reference to the layout diagram of FIG. As shown in the figure, first, the raw material pellets of the plastic that is the material of the container are put into the injection molding machine 1, and in this injection molding machine 1, the parison (the test tubular bottomed container shown in part A of FIG. , Also called preform) 10
Then, the parison 10 is taken out of the mold by the unloader 2, separated from the gate associated with the injection into individual units, and put into the parison return box 12 by the chute 15. Returnable boxes 12 filled with parison 10 are stacked in the parison stock area. Parison cooling is performed in the stock of this parison.

After that, the returnable box 12 containing the parison 10
Are transported from the parison stock area to the unscrambler 3 from the parison stock area in accordance with the amount of production required in the subsequent process. In this unscrambler 3, the parison 10 is aligned in a single row and is sent to the heating device 4 of the blow molding machine 5 by the parison conveyor 17. Here, the parison 10 is heated to a temperature at which the glass transition point or higher is easily formed, is mounted in the mold of the blow molding machine 5, and is blow molded into a product container. In this blow molding machine 5, a large number of open and close molds are horizontally arranged at equal pitches on the circumference, and while sequentially rotating horizontally, the parison 10 is sequentially taken in, mold closing, container molding by cleaning air blow, holding cooling, This is a commercially available blow molding machine that performs the steps of mold opening and container removal. FIG. 4B shows a perspective view of the product container 11 blow-molded from the parison 10.

The blow-molded container 11 is carried by a container conveyor 18 into a filling chamber where it is transferred to the rotary filling machine 6 while the delivery timing is adjusted by a star wheel or the like. The rotary filling machine 6 fills the container 11 with the liquid while rotating in the direction of the arrow. The filled container 11 is moved to the capping machine 7 in the next step by the container conveyor 19, where the cap 11 is capped, sealed, and sent to the packaging process by the discharge conveyor 20.

In this equipment, when the liquid to be filled is a beverage, the parison conveyor 17 or the container conveyor 1
In the middle of 8, it is necessary to provide a device for cleaning the parison 10 or the container 11. Further, when the filling liquid requires cold filling of a beverage such as carbon dioxide gas, a sterilizing device is required in the conveyor further upstream.

In such a production line in which the equipment for the parison molding process and the equipment for the blow molding process, which is the next process, are separated from each other, there is an advantage that the parison 10 can be purchased from the outside, but Since the parison 10 is stacked in bulk when stocked, the parison 10 may be deformed, scratched, or dust in the air may be accumulated inside the parison 10, and
Space and trucks for stocking are needed. Especially when the filling liquid is a beverage, wash the container before the filling process,
It needs to be sterilized.

Therefore, in order to reduce the installation area of equipment, work steps, and the number of workers, the parison 10 molded by the injection molding machine 1 and taken out is immediately aligned in a single line and transferred to the parison conveyor 17. By configuring
Unscrambler 3 without the returnable box 12 as above
The parison 10 is cooled while being sent by the parison conveyor 17 and is directly sent from the parison conveyor 17 to the blow molding machine 5, where the container 11 is molded and the filling machine 6 is filled with the liquid. Of course, filling equipment is also conceivable.

[0008]

As described above, the production line in which the equipment for the parison (preform) molding process and the equipment for the blow molding process are separated from each other causes damage and stains on the parison, and an extra washing and sterilization process. The number of workers will increase as necessary. On the other hand, in order to solve this problem, in-line blow molding and filling equipment in which the equipment for the parison molding process and the equipment for the blow molding process are connected in succession, when there is a temporary suspension due to some trouble in the process after blow molding (actual In the manufacturing equipment of (2), the container flow is stagnation within 5 minutes several times a day due to the container clogging such as the container falling, the container jamming, etc.), and the injection molding machine in the parison molding process must be stopped. I won't. When the injection molding machine stops for a few minutes, the properties of the molten resin deviate from the molding conditions, and the resin in the injection cylinder must be extracted when restarting the next operation. There is a loss of material and a large loss of working time.

Therefore, in view of the above-mentioned conventional technique, the present invention is determined even after the operation of the injection molding machine is once started, even if the preform cannot be temporarily transported to the equipment due to a defect in the equipment of the post process. Until the production volume is reached,
An object of the present invention is to provide a preform molding equipment control method and a preform molding equipment capable of continuing the operation of an injection molding machine.

[0010]

Means for Solving the Problems A first method for solving the above problems is described below.
The control method is a control method of a preform molding facility configured to take out a preform molded by an injection molding machine with a unloader and convey the taken out preform to a post-process facility by a conveyor of a production line. When the operation is started, the injection mode is set to the operation start-up mode, and the preform molded by the injection molding machine in this operation start-up mode is produced by the discharge means provided in the unloader for a preset number of shots. When ejected out of the line and when the number of ejected preforms exceeds the set number of shots, the injection mode shifts from the operation start-up mode to the steady molding mode, and the unloader performs the injection in the steady molding mode. The preform molded by the molding machine is controlled to be delivered to the conveyor of the production line. Further, even when the preform cannot be temporarily transported to the same equipment due to a defect in the equipment of the subsequent process, the preform molded by the injection molding machine is discharged by the discharging means to the outside of the production line and the injection molding machine. It is characterized by controlling so that the operation of can be continued.

In the second control method, a preform molded by an injection molding machine is taken out by a take-out machine, the taken-out preform is loaded on a tray, and the tray is transferred to a post-process facility by a conveyor of a production line. A control method for preform molding equipment configured to convey, wherein an injection mode is set to an operation start-up mode when the operation is started, and a preform molded by the injection molding machine is preset in the operation start-up mode. The number of shots is discharged to the outside of the production line by the discharge means provided in the unloader, and when the number of discharges of this preform exceeds the set number of shots, the injection mode is changed from the operation start-up mode to the steady molding mode. Then, the unloader stacks the preforms molded by the injection molding machine in this steady molding mode. The tray is controlled so that it can be transferred to the transfer conveyor of the production line, and if the tray cannot be temporarily transferred to the same conveyor due to a defect in the equipment of the subsequent process, it is installed on the transfer conveyor of the production line. The tray accumulator is loaded with preforms, and the injection cycle time of the injection molding machine is lengthened.When the tray accumulator is full of trays, the storage of this tray is stopped. The preform molded thereafter is controlled so as to be able to continue the operation of the injection molding machine by discharging it from the production line by the discharging means, and further, after the trouble in the equipment of the subsequent step is resolved, While the injection cycle time of the injection molding machine is increased, the accumulated preforms in the tray accumulator are not enough. Complementary, sending the preform to the equipment of the post-process, after all the preforms accumulated in the accumulator has been sent out, the injection cycle time of the injection molding machine is controlled to return to the steady molding mode. And

The first facility is a preform molding system configured to take out a preform molded by an injection molding machine by a take-out machine and convey the taken-out preform to a post-process facility by a conveyor of a production line. In the facility, the unloader is provided with a discharge means for discharging the preform at a place separated from the production line,
A control means for controlling by the first control method is provided.

In the second equipment, the preform molded by the injection molding machine is taken out by the take-out machine, the taken-out preform is loaded on the tray, and the tray is conveyed to the equipment of the subsequent process by the conveyor of the production line. In the preform molding equipment configured as described above, the unloader is provided with a discharge means for discharging the preforms at a place separated from the production line, and the tray on which the preforms are loaded is provided on the transport conveyor of the production line. It is characterized in that a tray accumulator for accumulating is provided and a control means for controlling by the second control method is provided.

Therefore, according to the first control method and the first apparatus, the molding die has the hot runner structure and the deteriorated resin in the hot runner is discharged at the start of the operation, so that the injection molding is performed in the operation start-up mode. A predetermined number of shots of the formed preforms are passed to the discharging means by the discharging machine and discharged out of the line by the discharging means. After that, the injection mode shifts to the steady molding mode, and the unloader delivers the preform injected in this steady molding mode to the conveyor of the production line. In addition, even in the case of equipment failure in the post-process, temporary preforms such as jams of preforms during transport or preformed blow-molded containers, or stagnant molded containers, excess molded preforms are ejected from the unloader. It is then discharged to the outside of the line by this discharging means. In this way, the injection molding machine can be operated continuously without stopping.

According to the second control method and the second equipment, as in the case of the first control method and the equipment,
The preform having a preset number of shots is delivered to the discharging means by the unloader, and is discharged out of the line by the discharging means. After that, the injection mode is changed to the steady molding mode, and the take-out machine delivers the preform injected in this steady molding mode to the conveyor of the production line.

When the preform or the molding container is temporarily stagnant in the post-process equipment, the tray accommodating the preform is accumulated in the tray accumulator and the injection cycle time of the injection molding machine does not change the injection conditions. When the tray accumulator is full, the tray stops accumulating when the tray is full, and the preform molded after that is passed to the discharging means by the unloader and discharged to the outside of the line by this discharging means. To do. In this way, the injection molding machine can continue to operate.

Further, after the stagnation of the preform or the container in the post-process equipment is eliminated, the accumulated preform in the accumulator is used to make up the shortage while the injection cycle time of the injection molding machine is kept long. After sending the preforms to the post-process equipment and sending out all the preforms accumulated in the accumulator, the injection cycle time of the injection molding machine is returned to the time of the steady molding mode.

[0018]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a plan layout view of a preform molding facility according to an embodiment of the present invention and a container blow molding filling facility using a cold, normal temperature or hot filling beverage as a filling liquid.
3 is a flowchart showing a control routine when the preform tray accumulator is not used, and FIG. 3 is a flowchart showing a control routine when the preform tray accumulator is used. It should be noted that in FIG. 1, devices and parts having the same structural functions as those of the conventional example are shown in FIG.
The same reference numerals are given.

In FIG. 1, reference numeral 1 is an injection molding machine for molding a preform. Numeral 22 alternately takes out preforms (the same shape as the parison 10 shown in part A of FIG. 4) from the molds of the two injection molding machines 1, and transfers the preforms to the preform tray 13 in the mold arrangement. It is a machine. Reference numeral 25 is a discharge chute for receiving the molded preform from the unloader 22 according to a command from a control device (not shown) when the injection molding machine 1 is started up or is stagnant due to a trouble in the downstream of the line, and 26 is this discharge chute. It is a defective preform storage box that receives and stores the preform discharged by 25.

Reference numeral 23 denotes an inclined tray conveyor that freely conveys the preform tray 13, and can even out unevenness in the capacity of the front and rear processes. Reference numeral 24 is a cooling casing that surrounds the conveyor 23 and cools the preforms on the preform tray 13. Reference numeral 32 denotes a tray accumulator for stacking preform trays. The tray accumulator 32 is provided with a large number of shelves for accommodating the preform trays 13 with preforms stacked thereon. The preform trays 13 are sequentially pushed into the empty shelves of the tray accumulator 32 and accommodated. The preform trays 13 are sequentially taken out from the shelves of the tray accumulator 32 and are carried to the position of the preform aligning machine 34. In the preform aligning machine 34, the preform tray 1
The preforms are taken out from 3, and these are aligned in a single row and sent to the preform conveyor 35. The preform tray 13 that has been emptied by taking out the preforms is transferred to a return conveyor (not shown), and is sent to the unloader 22 by this return conveyor.

When the preform molding speed of the injection molding machine 1 and the blow molding and filling speeds are synchronized, the preform aligning machine 34 is placed at the downstream end of the tray conveyor 23 without passing through the tray accumulator 32. The preform is taken from the preform tray 13 and transferred to the preform conveyor (free conveyor) 35. Although not shown, this preform conveyor 35 is for suspending the flange of the neck portion of the preform with two parallel bars and sending the preform by the air blown out from the air nozzles. Here, the preform can be stored and the difference in the ability between the front and rear steps can be adjusted.

Reference numeral 4 denotes a heating device for sequentially receiving a single row of preforms from the preform conveyor 35 and heating the preforms. The heating device 4 is an auxiliary mechanism of the blow molding machine 5. The blow molding machine 5 is an apparatus for manufacturing a container (the same shape as the container 11 shown in B of FIG. 4) by blow molding a preform, and includes a large number of blow molding dies arranged in a horizontal annular shape. While rotating, take in the heated preform, close the mold, mold the container by blowing clean air,
Perform the steps of container cooling, mold opening, and container removal. The empty container molded by the blow molding machine 5 is the container conveyor 3
7 (conveyor having a structure in which the flange of the neck of the container is supported from both sides and blows air toward the container to send air), and is then transferred to a table-top container conveyor 38, from which a container transfer mechanism (for example, star wheel) It is moved to the filling machine 6 by the container indexing and delivering mechanism).

The filling machine 6 may be a low temperature liquid filling machine or a high temperature liquid filling machine for carbon dioxide beverages or the like. The container filled with the beverage by the filling machine 6 is sent to the capping machine 7 by the container conveyor 38, where the cap is covered and the container mouth is sealed. After that, the container moves to the transfer conveyor 39, and is sent to the boxing area by the transfer conveyor 39.

This equipment is such that the equipment of each function synchronizes the ability and is directly connected inline by the preform and container feed conveyor. The equipment and conveyor in the line can collapse the container even at one place, bite the container, When a defect such as clogging occurs, it affects the operation of the entire apparatus, and in reality, there is a possibility that the flow of the container will be stagnated within 5 minutes several times a day.

Here, the control of preform molding in this embodiment will be described.

First, the control when the tray accumulator 32 is not used will be described with reference to the flowchart of FIG.

Since the molding die has a hot runner structure and the deteriorated resin in the hot runner is discharged at the start of the operation, the preform injected in the operation start-up mode (preforming condition) is preset. The number of shots n is passed to the discharge chute 25 by the unloader 22 which operates in the discharge mode according to the discharge command, and is discharged to the defective preform storage box 26 outside the line. S1, S2, S3, S4, S
5, S6, S7.

After the discharge of the planned number of shots n is completed, the injection mode is switched to the steady molding mode, and the preform molding is executed under the steady molding conditions. The unloader 22 is also in the steady transfer mode, and the preform injected in this steady molding mode is transferred to the preform tray 13 for each injection rod, and this is transferred to the tray conveyor 2 of the production line.
Hand over to 3. S8, S9, S10, S11, S13,
See S14.

Further, even when the line is interrupted due to a failure of the equipment in the subsequent process, a temporary preform such as a jam of a preform or a molding container during conveyance, or a stagnation of the molding container, the unloader 22 operates according to the discharge command of the control program. The discharge mode is switched to, and the molded extra preform is discharged to the preform storage box 26 outside the line through the discharge chute 25. See S12. In this way, the injection molding machine 1
Can operate continuously without stopping. The molding of the preform is completed when the planned production quantity (shot number = m) is reached. See S15.

Next, the control when the tray accumulator 32 is used will be described based on the flowchart of FIG.

At the start-up of the operation, similar to the control program of FIG. 2, the preset number of shots is passed by the unloader 22 to the discharge chute 25, and the discharge chute 25 discharges it out of the line. S1, S
See 2, S3, S4, S5, S6, S7. After that, the molding mode is shifted to the steady molding mode, and the unloader 22 transfers the injected preform to the preform tray 13 based on this steady molding execution command, and transfers it to the tray conveyor 23 of the production line. S8, S9, S10, S
See 11, S12, S13, S14.

When the line is interrupted due to a temporary preform in a post-process facility or a stagnation of a molding container, the injection cycle of the injection molding machine 1 is set to a mode of deceleration operation in which the injection condition is lengthened within a range where the injection conditions are not broken, and the deceleration molding is performed. While the operation is continued by the execution command, the tray accumulator 32 is set to the loading mode, and the preform tray 13 containing the preform is loaded on the tray accumulator 32. S
16, S17, S18, S21, S22, S23, S2
4, S25. The number of molding shots in this case is added to the number k of steady molding shots. When the tray accumulator 32 reaches the number of possible storages a, the accumulation of the preform tray 13 is stopped, the unloader 22 is switched to the discharge mode, and the preform molded thereafter is stored by the discharge chute 25 outside the line. It is discharged to the box 26. See S26.

After the line interruption is resolved, the unloader 22
Is switched to the steady transfer mode, and the preform tray 13 is passed to the tray conveyor 23 to move the process on the line under the deceleration molding condition (while the injection cycle time is kept long). The accumulator 32 is switched to the take-out mode, detects and confirms that the preform on the preform conveyor 35 has become empty for one injection shot,
One preform tray 13 stored in the tray accumulator 32 is taken out, and the preform tray 1
The preforms loaded on the No. 3 preform aligner 34
The preform conveyor 35 of FIG. S21, S
27, S28, S29, S30, S31. When all the preforms accommodated in the tray accumulator 32 are sent out and the accumulator 32 becomes empty (j = 0), the molding mode returns to the steady molding mode, and the injection cycle time is restored. In this way, the injection molding machine 1 can be continuously operated without stopping. The forming of the preform is completed when the planned production number (shot number = m) is reached. S1
See 5.

The time during which the preform or the container can be allowed to temporarily hold without discharging the preform out of the line is determined by the tray accommodating number a of the tray accumulator 32. Further, in order to increase the injection cycle time of the injection molding machine 1, it is most convenient to extend the time of the step of opening the mold and taking out the preform.

Here, an example of trial calculation of the post-process stagnation time, the number a of accumulators 32 accommodated and the recovery time in the operation cycle is shown below.

Production capacity = injection molding machine (2 units): 200B
PM, blow molding machine, filling machine: 200 BPM, and if the blow molding machine and the filling machine have a stagnation time of 5 minutes and the injection molding machine 1 operates at normal capacity during that time, the number of preform injections is 1,000. Assuming that the number of preforms held by one preform tray is 50, the number of storage shelves a of the tray accumulator 32 may be 20.

Further, the shot cycle of the injection molding machine 1 is 30 seconds, and if the time of the step of taking out the preform is extended by 5 seconds and the one shot cycle is 35 seconds, the production capacity is 171 BPM, and the production capacity of the subsequent step. If there is no change, the number of preforms to be replenished from the accumulator 32 per minute is 29, and the preforms of the tray accumulator 32 are collected in about 35 minutes, at which time the injection molding machine 1 reaches the initial production speed. Can be returned.

Further, the preform conveyor 3 necessary for supplying the preform of the tray accumulator 32
The accumulated amount of preforms in No. 5 requires at least the number of preforms held by one preform tray (for 50 preforms).

[0040]

As described above in detail with the embodiments of the present invention, according to the present invention, the elimination of defective preforms in the preliminary operation at the start of operation is automated, and during normal operation, the equipment for the post-process is installed. Even if the operation is temporarily stopped due to some trouble, the injection molding machine does not need to be stopped and can be operated continuously, so the work process is simplified and the worker can concentrate on restarting the temporarily stopped equipment. Therefore, it is possible to reduce the number of personnel assigned to the line to a smaller number than before. Further, since the preform discharged during the temporary stop can be regenerated, the loss of the resin is reduced as compared with the case where the injection molding machine is stopped.

Further, in the case where the tray accumulator is provided, when the tray accumulator accommodates the preform stacking tray when the apparatus is temporarily stopped due to some trouble in the equipment of the subsequent process, the tray accumulator is molded only when the tray accumulator is full. Since the reforms are discharged outside the line, the amount of preforms discharged due to the interruption of the line is reduced. Also, after the suspension is resolved, the preforms stored in the tray accumulator are completely sent while the injection cycle time of the injection molding machine is extended and the storage preform in the tray accumulator is used to make up for the shortage. After being sent out, it is restored based on the injection cycle time of the injection molding machine. As a result, the injection molding machine can be continuously operated without stopping, so that it is not necessary to remove the resin in the injection cylinder, the loss of the resin material is reduced, and the recovery work time is not lost.

[Brief description of drawings]

FIG. 1 is a plan layout view of a preform molding facility and a container blow molding and filling facility according to an embodiment of the present invention.

FIG. 2 is a flowchart showing a control routine when the accumulator of the preform tray is not used.

FIG. 3 is a flowchart showing a control routine when an accumulator of a preform tray is used.

FIG. 4 is a layout diagram of a conventional container blow molding and filling facility.

[Explanation of symbols]

 1 Injection Molding Machine 4 Heating Machine 5 Blow Molding Machine 6 Filling Machine 7 Capping Machine 13 Preform Tray 22 Extractor 23 Tray Conveyor 24 Cooling Casing 25 Ejecting Chute 26 Bad Preform Storage Box 32 Tray Accumulator 34 Preform Aligning Machine 35 Preform Conveyor

Claims (4)

[Claims] 1. A control method of preform molding equipment configured to take out a preform molded by an injection molding machine by a take-out machine and convey the taken-out preform to a post-process facility by a conveyor of a production line. At the start-up of the operation, the injection mode is set to the operation start-up mode, and in this operation start-up mode, the preform molded by the injection molding machine is produced by the discharge means provided in the unloader for a preset number of shots. When ejected out of the line and when the number of ejected preforms exceeds the set number of shots, the injection mode shifts from the operation start-up mode to the steady molding mode, and the unloader performs the injection in the steady molding mode. The preform molded by the molding machine is controlled to be delivered to the conveyor of the production line. Further, even when the preform cannot be temporarily transported to the same equipment due to a defect in the equipment of the subsequent process, the preform molded by the injection molding machine is discharged by the discharging means to the outside of the production line and the injection molding machine. A method for controlling preform molding equipment, characterized by controlling so that the operation of the preform can be continued. 2. A preform molded by an injection molding machine is taken out by a take-out machine, the taken-out preform is loaded on a tray, and the tray is conveyed by a conveyer conveyor of a production line to a post-process facility. A control method for preform molding equipment, wherein the injection mode is set to the operation start-up mode at the start-up of operation, and the preform formed by the injection molding machine in this operation start-up mode is ejected by the preset number of shots. When the number of shots of the preform exceeds the set number of shots, the injection mode is changed from the operation start-up mode to the steady molding mode, and the unloader is In this steady molding mode, the tray on which the preform molded by the injection molding machine is loaded is If the tray cannot be temporarily transported to the same equipment by controlling it so that it can be delivered to the conveyor conveyor of the production line, the tray accumulator provided on the conveyor conveyor of the production line will be preformed. When the tray accumulator is full and the tray is full, the storage of this tray is stopped, and the trays that have been molded after that are stopped. The reform is controlled so that the operation of the injection molding machine can be continued by discharging it outside the production line by the discharging means, and further, after the trouble in the equipment of the post process is solved, the injection cycle of the injection molding machine While keeping the time long, the accumulated preforms in the tray accumulator are used to make up for the deficiency and Preform molding equipment, characterized in that the preform is sent to equipment, and after all the preforms accumulated in the accumulator have been sent out, the injection cycle time of the injection molding machine is controlled so as to return to the steady molding mode. Control method. 3. A preform molding facility configured to take out a preform molded by an injection molding machine by a take-out machine and convey the taken-out preform to a post-process facility by a conveyor of a production line. The preform molding facility, wherein the unloader is provided with a discharge means for discharging the preform at a place separated from the production line, and a control means for controlling by the control method according to claim 1. 4. The preform molded by an injection molding machine is taken out by a take-out machine, the taken-out preform is loaded on a tray, and the tray is conveyed by a conveyor of a production line to a post-process facility. Reform molding equipment, wherein the unloader is provided with a discharge means for discharging preforms at a place separated from the production line, and a conveyor accumulator for accumulating trays loaded with preforms on the conveyor of the production line. Preform molding equipment, which is provided with control means for controlling by the control method according to claim 2.