EP1077875B1 - Packaging machine - Google Patents

Description

The invention relates to a packaging machine for wrapping and / or enclosing products of varying dimensions, size and consistency in packaging material, such as paper, bags, cups and the like. with individual processing units, each of which is assigned a drive with a control unit, through which the specified movement laws (travel-time functions) are processed, as well as sensors for detecting the operating state, and if there are deviations from the synchronicity between the packaging material and the product to be packaged, the movement laws are changed and the resulting path-time law is continuously and continuously differentiable, the resulting speed-time law is continuously differentiable.

Packaging machines are generally extensive systems that consist of a large number of processing units for shaping the packaging, filling, closing and labeling, but also provide units that serve for feeding, filling and closing prefabricated containers. The latter are mainly used for packing bulk goods, but especially for liquid and pasty products from the food sector, e.g. B. drinks, yogurt, cream etc. Their primary areas of application are the pharmaceutical, cigarette, food and beverage industries.
In its basic structure, a packaging machine consists of a mechanically or electronically designed vertical shaft, which serves as a leading axis, and from which drives with control units are connected in the sense of slave axes. The leading position is the input variable for the control unit of the drive that defines the target position of the following axis as the output variable. Each leading axis position is therefore assigned a defined position of the following axis, which is a path-path assignment. The overall movement is divided into individual movement sections, each of which is associated with a movement law by means of which the position of the following axis is assigned to the position of the leading axis.
The entire representation of the movement of the individual processing units takes place in a movement plan. A single work cycle is usually made up of several movement sections. The vertical shaft determines the functional speed as the leading axis, so that the higher the leading axis speed, the higher the cycle performance of the packaging machine.
Packaging machines generally have to incorporate products of different dimensions and external shape into a packaging, so that the machine has to be changed with every product change and adapted to the new packaging conditions. For this purpose, it is known to enter the corresponding laws of motion necessary for the next product to be machined into the machine when the machine is stationary. For this are exchanged cam discs of corresponding shape in mechanical controls; in electronic controls, the laws of motion are adapted to the new conditions by reading in a new program or by replacing a memory module. After commissioning, the control is carried out on the basis of the movement laws entered, but in a disadvantageous manner there is no setting or even a reaction to unforeseen influences. Rather, the motion law is processed exactly according to the specifications. Changes in the geometric conditions occurring during operation, such as z. B. happen under the influence of heat or deviations from the regular process must therefore be disregarded and sometimes lead to significant disruptions that can give rise to manual interruptions. Further reasons for deviations from the target state arise in the case of missing packaging material and / or goods, errors in the packaging material and also in the packaging goods and finally changes in the operating state, such as start, stop, emergency stop and the like.

A control for servo-driven machines, in particular packaging machines, is described in US Pat. No. 5,724,786, in which a transport good to be packaged or filled is conveyed by a conveying device. In order to correct the deviations of the conveyed goods from given path-time laws, it is proposed that a mark is assigned in each case in the conveyed goods and a sensor for detecting the position of the mark is available is, the transport speed can be changed depending on the position of the marking. For this purpose, the target positions are compared with the actual positions and the transport speed is increased or decreased accordingly in order to bring the goods to be conveyed into a desired position at a desired time. For this purpose, the respective position is recorded S times between the start and end of the conveying and the servomotors are controlled accordingly, ie the conveying speed is increased or decreased step by step in order to compensate for deviations of the actual from the target position. As a result, even with a large number of steps S or a reduction in the time intervals at which the positions are recorded, jerky changes in the movement of the conveyed material continue, which means that even with such a control, in which the speed of the Goods to be conveyed can change at any time interval by a finite amount, that is to say inconsistently, acceleration peaks described above can occur, which can lead to increased wear of the machine and / or undesirable noise development.
However, it is also mentioned that the accelerations required to establish the synchronicity can be realized by a sin function.

Proceeding from this, the invention has made the further development of packaging machines the task of changing and adapting the movement laws of the drives to the specific operating conditions during operation becomes possible.

This object is achieved according to the invention in that the laws of motion of the corresponding drive are scaled, i. H. experience stretching or compression with respect to the timeline.

In the sense of the invention, the term “law of motion” means any functional connection between distance and time, whereby distance can be understood to mean a distance / length or an angle. The task of the existing sensors is to record the current operating state (actual state) and to supply it to the control unit for evaluation. For example, it is necessary to apply the wrapping paper provided with images to the goods to be packed, in spite of the stretching and stretching of the paper in the machine itself, in such a way that the image is positioned centrally, ie in the middle of the goods. Moving the packaging paper would be completely unacceptable, with the result that the image would be cut up and only the peripheral areas of the image would be visible in the central area of the goods to be packaged. For this purpose, marginal markings are made on the packaging paper, which are detected by the sensor, so that the stretching, stretching and slippage of the paper can then be compensated for by appropriate control.
The task of the sensor can also be, among other things, to determine the presence of the goods to be packaged and, in the event of defects, to transport the Slow down the packaging material and change the law of movement so that the feed is delayed and adapted to the lack of the packaging good instead of, as is customary in the prior art, the paper transport continues regardless of the missing packaging good and a section of the packaging paper is separated and due to the missing packaging object remains unused.

If the packaging material and the object to be packed are not synchronized, they are adjusted by compressing or stretching the movement laws (= travel-time function) with respect to the time axis. So there follows an adaptation of the laws of motion to the concrete circumstances. In the case of the relative displacement between the packaging material and the goods to be packaged, synchronization takes place in that the path-time dependency, that is to say the advance of the packaging material, is selected such that the assignment to the packaging object is effected in the desired manner.

In another way of changing the laws of motion, the curve shape is changed. For example, when packaging liquid or viscous food in cups, open transport within the packaging machine by a certain distance up to the closure with the lid may be required. In order to ensure that the liquid to be transported does not spill over from the cup, the acceleration during change constantly during this operating phase. When moving open cups, the laws of motion should be chosen so that only low acceleration values and no acceleration peaks occur. When converting the packaging machine to other goods, this requirement can then be waived and new, higher acceleration values motion laws can be used to increase performance.

For all the options described above, the laws of motion and also the transitions between the various laws of motion must be carried out in such a way that there is no significant acceleration in the machine, which would give rise to loads on bearings and increased noise pollution. Particularly high wear on the machine as well as a sudden increase in noise level are always obtained when the acceleration values change suddenly.
Therefore, the invention requires in one of its features that the motion laws of the drives regardless of how the motion law was obtained (upsetting, stretching) and also in the transition areas with regard to the distance-time dependence not only a constant but also represents a continuously differentiable function. Mathematically, this means that the differential is unique and continuous at each function point over time. Another condition is that the resulting speed-time law is continuously differentiable, ie that the acceleration-time law is constant and thus has no cracks. The prerequisite is that the speed-time law can be differentiated in all points. The acceleration changes continuously and without jumps. The transitions will then be smooth.

In the context of the invention, it remains basically arbitrary in what way the motion laws of the drives are concretely generated, that is, whether several generators work in parallel with one another, their outputs are added and thereby the desired motion law arises or whether curve generators are used.

The advantages to be achieved with the invention are numerous:
Due to the appropriate choice of the laws of motion and the "soft" transitions, it can be ensured that only slight accelerations occur at all times. The result is that the packaging machine can be operated smoothly and largely smoothly and therefore gently with regard to the material and the machine itself. The result is an increase in service life and a lower incidence repairs. On the other hand, such a machine can be operated with significantly higher performances compared to the prior art.
It is crucial that the motion laws are changed during continuous operation, ie without a machine stop. This also makes it possible to achieve a further significant increase in economy.

It has already been indicated that the manner of generating the resulting motion law with the above-described properties is basically arbitrary within the scope of the invention. One of the possibilities is to choose mathematical standard functions as output functions, which according to the above-described teachings experience a change due to expansion or compression along the time axis and / or a change in the curve shape and / or linking and / or an overlay and in this way the resulting motion law result. Standard functions are polynomials, exponential functions, logarithmic functions and trigonometric functions (sin, cos, tg, ctg). As a result, only those laws of motion can be obtained that can be derived from the standard functions.

An explicit alternative is that the laws of motion can be generated during operation and without access to output functions. By means of suitable calculation methods, the resulting result fulfilling the aforementioned conditions becomes Law of motion is determined, i.e. a synthesis process carried out that does not require the use of output functions.

A decisive advantage of the packaging machine according to the invention is that the deviations detected by the sensors immediately, i.e. the motion laws of the drives can be changed in real time and adapted to the current situation. Deviations in the manner of a control loop are thus eliminated immediately. However, there is also the basic possibility that not immediately is reacted in real time to the deviations measured with the help of the sensors, but is processed at the movement section currently being processed in accordance with the previous setting and only at one of the next e.g. the immediately following movement section of the drive is only adapted to the new situation with regard to its movement law and is processed by the drive. The drive then responds to the detected deviations with a time delay.

In the case of certain products, particularly high requirements have to be met between the filling phase and the closing of the container in order to ensure that spillage of the filled liquids during the transport phase between filling and closing is reliably prevented. When filling beverages in cups and paper packaging, the above-mentioned complications typically occur. In In such a case, it is recommended in a special embodiment either to select the acceleration-time function below a predetermined value, the threshold value, or to continuously shape the jerk function, which describes the change in the acceleration values. For mathematical reasons, there is always a continuity if the acceleration-time dependence represents a continuously differentiable function. It must be clarified that, in contrast to the most general requirement of the invention, namely the constant differentiability of the path-time profile, only the continuity of the speed-time function results. A constant differentiation of the acceleration-time function is not required in the most general case.

Figur 1

eine Vorrichtung zum Ablängen des Verpackungspapieres,

Figur 2

das Aufbringen von Etiketten auf Flaschen

Further details, features and advantages of the invention can be found in the following description, in which the control unit claimed according to the invention is described in more detail with reference to the schematic diagram shown in the drawing. Show it:

Figure 1

a device for cutting the packaging paper to length,

Figure 2

the application of labels to bottles

In Figure 1, the packaging paper (1) is fed endlessly in the horizontal direction from left to right to a rotating cutting device (2).

In the edge area of the paper there are markings (3) which are detected with the aid of a sensor (4). At the same time, the feed movement (5) is also passed on to the evaluation unit (6).
The drive (7) of the cutting device (2) is controlled via the evaluation unit (6) in accordance with the paper feed and the measured values of the sensor (4). The sensor ensures that despite displacements of the packaging paper in the direction of transport it is always ensured that the cutting device (2) cuts exactly in the desired position. It is crucial that the law of motion of the cutting device (2) is a constant and also continuously differentiable path-time function and the changes in acceleration are kept low, so that "soft" movements are ensured, which with regard to protecting the material, the life of the Machine, as well as the maximum performance bring significant advantages.

FIG. 2 also shows a schematic representation of a part of the packaging machine in which labels are applied to bottles. Here the bottles (8) are successively moved past a label dispenser (9) in the horizontal direction, the respective position of the bottle being detected by a sensor (10) immediately before the label is applied. The movement of the bottle is recorded with the help of the sensor (11).
The position of the supplied label is detected by the label sensor (12) and the information passed on to the evaluation unit (13). From there, appropriate control commands are sent to the drive (14) responsible for feeding the labels. Here too, the evaluation unit (13) ensures that the bottle (8) and the individual label are fed synchronously to one another and are therefore connected to one another with a precise fit. In the event of any deviations, the law of motion of at least one drive, here z. B. the drive (14) for the label feed in its law of motion changed and adapted to the new conditions, such that the path-time function of the law of motion of the motor is a continuous and continuously differentiable function.

It is crucial for the invention that when the synchronicity is lost, the drive's motion law is changed and adapted to the actual situation, it being essential to the invention that the motion law of the travel-time function is always and continuously differentiable in every phase ,

Claims (6)

1. Packaging machine for wrapping and/or enveloping products of changing dimensions, size and consistency in packaging materials such as papers, bags, cups and the like, comprising individual processing unit, to which in each case a drive comprising a control unit is assigned, and by means of which predetermined motions (position-time functions) are executed, and sensors for registering the operating state and, in the event of deviations from the synchronicity between the packaging material and the product to be packaged, the laws of motion are changed and the resulting position-time law is continuous and continuously differentiable, the resulting velocity-time law is continuously differentiable,
   characterised in that
   the laws of motion of the corresponding drive are scaled, that is to say undergo extension or compression with respect to the time axis.
2. Packaging machine according to claim 1,
   characterised in that mathematical standard functions are the initial functions for forming the resulting law of motion.
3. Packaging machine according to claim 1,
   characterised in that the resulting law of motion is generated during operation.
4. Packaging machine according to claims 1 to 3
   characterised in that the changes of the law of motion take place in real time or else with a time delay in one of the following operating cycles.
5. Packaging machine according to one of the preceding claims, characterised in that the acceleration-time function lies below a predetermined value.
6. Packaging machine according to one of the preceding claims, characterised in that the acceleration-time function of the resultants is continuously differentiable.