EP2139773B1 - Bag filling method on a forming, filling and sealing machine - Google Patents

Abstract

The invention relates to a method for filling and sealing a bag, according to which the following steps are carried out: a bag (8) is filled by a filling element (2); the filling element and the bag move in relation to each other while the bag is being filled; parts of the filling element (2) are at least temporarily immersed below the level of the filling product (38) during a first phase (P<SUB>u</SUB>) during the filling of the bag. The weighing cells (26) supply measuring signals at least during a second phase (P<SUB>M</SUB>) comprising at least parts of the first phase (P<SUB>u</SUB>). Said signals are used by the control device for controlling and/or regulating the filling process.

Description

The invention relates to a method for producing, filling and sealing of plastic bags with dusty or granular bulk material and for closing the filled bags.

Such a method is for example from the DE 93 01 355 U known. Here is already a device for producing, filling and closing unilaterally open, preferably provided with gusseted bags of thermoplastic described in which a first welding and separation station to form the bag with bottom seam, a filling station and a second welding station for closing the bag available. Generally, these filling machines are classified in the FFS ( F orm F ill and S eal) category.

When filling dusty bulk materials on machines of the named category by gravity or by free fall, the dusty air displaced by the product must be able to escape from the bag. The escape of air often leads to contamination in the upper edge areas of the bag. Due to the contamination with product dust, the bag can not be securely closed by means of the welding which is generally customary in this type of packaging. In addition, the dust pollutes the environment and must be separately extracted.

Furthermore, the filling of dusty goods according to the known filling method described usually leads to a significantly inflated product volume or to a significant reduction in bulk density, since the product accumulates heavily in the free fall with air. This, in turn, leads to bottling the product initially much more packaging material is needed. In addition, the air must be able to escape from the bag again, otherwise it can not be stacked or stored.

Since the escape of air usually takes a long time, the venting can not take place before closing the bag. The bag must therefore have a perforation. This additionally pollutes the environment, as the fine-grained, dusty products can partially escape through the perforation of the packaging.

Over time, the volume of bulk material decreases again. The sack packaging is now, compared to the packaged bulk material volume, significantly too large. Such filled sacks are difficult to stack on pallets because they are too unstable. The EP 1 459 981 A1 suggests, therefore, to introduce the filler neck of a metering of an FFS machine in the opening of a bag. In the WO 2006/053627 A1 on the other hand, the relative movement between the bag and the filler neck is accomplished by a movement of the bag.

In both of the aforementioned publications Dosierorgane are presented which contain screws. These screws transport the filling material into the bags. The preferred conveying direction in these screws corresponds to the effective direction of gravity. Due to the screws, there is no free fall of the filling material in the bag. Therefore, screws are often used for bagging dusty filling goods. However, their use is by no means mandatory - also in relation to the present invention.

In addition to the above-mentioned mechanical design of the Sackbefüllungsorgane stands in the design of FFS machines that fill especially dusty goods, the weighing process in the center of interest. In prior art FFS machines (see for example DE 199 20 478 C2 and EP 1 201 539 B1 ), which primarily fill less dusty goods, first a hopper is filled with the desired volume of filling material for a bag. The desired volume or the target weight is determined or regulated by weighing the hopper. When the target weight is reached, the filling opening at the bottom of the hopper is opened and the filling material flows by gravity into the designated bag. However, especially in the filling of dusty goods this unsteady process leads to excessive dust. Also in the already mentioned WO 2006/053627 A1 become weighing methods for dusty goods discussed. In general, such weighing methods, when carried out during filling, are also carried out over long periods of time, since the backfilling of dusty filling material without excessive dust development often lasts longer than the filling of an equal amount of conventional filling material. During these - often longer - fillings errors may occur. These errors may include a sack crack, slippage of the sack from the holding tongs, snail breakage or clogging of the worm (if a worm is used). It can be seen that such errors, especially in the case of dusty filling goods, can lead to great contamination of the machine and the machine hall and even damage to the machine park.

Another disadvantage, which manifests itself in particular when filling dusty filling goods, is the limitation of the filling speed. The dusty goods just develop too much dust if they are bottled quickly. Since pre-weighing of the filling material intended for a sack is not an option, the question arises as to how the sack weight should be regulated during filling.

Therefore, the task of the present invention can be summarized as follows: It should be as fast as possible filling process proposed at low dust, in which the weight of the bag can be controlled as accurately as possible. The problem is solved by claim 1.

As a rule, the filling of the bag, the bag formation - often directly from a piece of tubing - immediately precede. To form the pieces of hose, a film tube can be unwound from a settlement.

The invention makes use of the fact that less dust is formed when the mouth of the Befüllorgans is below the Befüllgutsaustrittsöffnung of the metering. It is surprising that meaningful signals can be obtained with load cells, while there is mechanical contact of the filling material in the bag and the metering device.

It is an advantage to filter these signals. In this case, it has been shown that the filling member mainly generates higher-frequency interference signals, which can be eliminated by filtering the signals.

Another measure that can increase filling speed and quality of measurement, is a relative movement of dosing and bag during the filling process. When this relative movement is uniform, spurious signals are limited. This is especially true when the sack is moved uniformly.

The measured values obtained during the submillar filling can advantageously be used as weight measured values for checking or regulating the bag weight during filling. This definition implies that, based on the weight measurements, the time at which the bag filling ends is determined. It also includes that a control of the filling speed and / or the speed of the relative movement between the bag and Befüllorgan is made.

The filling speed, that is, the weight increase per unit time or the first derivative of the weight after the time, can be used to detect errors that occur during the filling process. Such flaws can include a sack crack, which usually results in a rapid decrease in weight gain. The outlined procedure is believed to work best when the control unit emits a warning signal as the weight gain moves out of a desired range. The warning signal can be used by the control unit and / or the machine personnel to correct the error.

Also, monitoring the first derivative of weight gain over time provides insights into the quality of the filling process and early fault detection.

• der Abstand zwischen der Mündung des Befüllorgans und dem Sackboden wird auf einen Mindestabstand eingestellt,
• die Sackbefüllung beginnt, wobei Befüllgut durch die Mündung des Befüllorgans in den Sack strömt,
• der Befüllgutspiegel steigt, wobei entweder keine Steigerung des Abstandes zwischen der Mündung und dem Sackboden durch eine Relativbewegung vorgenommen wird oder diese Relativbewegung langsamer ist als die Geschwindigkeit, mit der der Füllgutpegel steigt,
• ein Beginn oder eine Steigerung der Geschwindigkeit der Relativbewegung zu einem Zeitpunkt, nachdem der Füllgutpegel über der Mündung liegt.

In all the inventive method and also other methods that are performed on machines that change the relative position between the bag and Befüllorgan (the documents EP 1 459 981 A1 and WO 2006/053627 A1 suggest different varieties of such machines), methods are advantageously used in which the control device controls the relative movement between the bag and dosing and the filling as follows:

• the distance between the mouth of the filling device and the bottom of the bag is set to a minimum distance,
• the bag filling begins, with filling material flowing through the mouth of the filling member into the bag,
• the Befüllgutspiegel increases, either no increase in the distance between the mouth and the bag bottom is made by a relative movement or this relative movement is slower than the speed at which the Füllgutpegel increases,
• a start or an increase in the speed of the relative movement at a time after the level of contents is above the mouth.

By these measures, especially the dust formation can be reduced.

If, in addition to the above measures, the beginning or the increase in the speed of the relative movement is made after the Füllgutstand is above the mouth, when a desired distance between the mouth and the Füllgutstand is reached, it is ensured that the mouth of the Befüllorgans not remains far below the Befüllgutstand. In addition, the accelerated relative movement leads to the possibility of measuring the weight of the bag and not the filling pressure of the filling material that comes out of the mouth.

The achievement of the desired distance can again by a weight measurement, d. H. be verified by the evaluation of load cell signals, since it is certainly due to the knowledge of the density of the Befüllstoffes and the bag volume or simply due to empirical values in a position to assign a Sackgewicht a Befüllgutstand. The same applies when measuring the filling speed.

However, a measurement with a radiation sensor can also be used to determine the Befüllgutstandes. Thus, a radiation can be used which penetrates the bag material, but not the filling material. On the side facing away from the radiation emitter side of the bag radiation can only be collected by a suitable sensor when the transmitter and receiver are located above the Füllgutspiegels.

When the nominal distance between the mouth of the filling element and the product level has been reached, the speed with which the product level rises and the speed of the relative movement between the bag and the filling device should be matched to one another. At exactly the same speed, the distance between the mouth and Füllgutspiegel remains constant, which may be desirable.

For the additional observation of the weight increase of the bag per unit of time, the following can be said: If this increase in weight is outside a target or tolerance range, a warning signal is output.

This warning signal, which of course can also lead manually (by the machine operator) or automatically (by a control device) to a control process, can reveal or expose a whole series of errors or failure mechanisms. This teaching also appears to be advantageous for non-dusty filling goods.

The following table contains examples of which measured values or which measured value course can be used to indicate which errors: error detection routine potential hazard hernia (Slope too low or negative slope) Approving the interior of the machine Slipping of the bag from the holding forceps (negative slope) Approving the interior of the machine Disturbance in the product supply line (Slope too low) Formation of an explosive mixture

With the optional use of a screw to fill the filling material, the following error characteristics are added: screw breakage (Slope too low) eg sparking Wrong product (Product specific slope not okay) various dangers Failure of the drive (Slope too low) various dangers Clogging of the snail (Slope too low) various dangers Wrongly adjusted outlet conveyor (ground contact) (Slope too low) Approving the interior of the machine Depending on the type of filling order, it may be advantageous to carry out the monitoring of the weight increase of the bag at the end, in the middle, at the beginning or during the entire filling process. Also in the monitoring of weight gain, it may be advantageous to hide high-frequency interference of the same. These can also be triggered by the Befüllorgan. During a second period of time during the filling process, it is advantageous if the measured values for the bag weight constantly arriving in the control device are not used to control or regulate the bag weight. In this way it is possible to hide the influence of disturbing weight signals on the filling process. Here, the second period may overlap with the first period in which the weight gain is controlled. It may be shorter, longer, or the same as or the first, and may be before, during, or after the first one.

Since the control or regulation of the bag weight during the second period of time is not carried out by an evaluation of the signals of the load cells, it is advantageous to determine this volumetrically or empirically. Volumetric weight determination means, for example, that a measured or known number of screw revolutions is multiplied or otherwise mathematically linked to a known product delivery rate per revolution, so that the weight or volume of the material conveyed into the bag at one time is determined or included can be estimated with sufficient accuracy. At the end of such a second period of time with volumetric measurement, the load cells can again assume the provision of measured values. Incidentally, the term load cells for the purposes of this document covers all suitable weight sensors such as scales and just the load cells themselves. Generally, those skilled in the art will understand as load cells those weight sensors that contain electrical resistances arranged in the form of a Wheatstone bridge. The resistors change their ohmic resistance when deformed. The resistors are mounted on an element that deforms as the weight changes. Accordingly, the electrical output values of the Wheatstone bridge, which underlie the weight measurement change.

Compared to volumetric weight measurement, empirical weight measurement is a measure or estimate that is only or largely due based on empirical values (eg, during a time T, a volume V of a particular filling material is filled).

It is advantageous if the mouth of the Befüllorgans is below the Füllgutgutspiegels during a third period of time. As a rule, this will not be the case at the beginning of the filling process (empty bag). However, tests have shown that this measure (the sub-level filling), the mist formation during filling of the bag leads back. An overlap between the second (no weight control according to load cell signals) and the third time span (bottom mirror filling) is advantageous. The relative movement of Befüllorgan and Befüllgut is suitable to interfere with the Unterspiegelbefüllung the weight measurement. However, these disturbances cease for a second period of time as defined above, because during such a period the weight measurement is not used for weight control. An alternative to this measure is the suppression of interference by a suitable filter. It has been found that the interference signals generated by the Befüllorgan are relatively high frequency, so that this measure is advantageous.

Explicit use can also be made in a fourth period of time, which can again be configured in position and duration as desired at the other time periods. This fourth period of time is advantageous at the end of the filling process.

In a fifth period of time, which can again be designed as desired in position and duration at the other time intervals, the filling can be carried out for the benefit of the overall process, while the outlet of the filling element is located above the filling material level. This phase of filling, for example, can also be found at the end of the filling process and used to enable a sensitive and accurate dosing of the filling material.

As dusty goods, the filling is advantageously carried out with a method according to the invention, among other cement, titanium dioxide and all kinds of plastic dusts into consideration. In general, the expert should understand under dusty goods bulk goods that just can not be filled on an FFS machine, unless a special filling process that often uses screws to guide the bulk material, is used.

Devices for carrying out the method according to the invention are generally controlled and / or regulated by control devices which are loaded with stored command sequences which arrange and / or monitor the methods described above. These control programs are stored either on components of the control device or on other data carriers such as CDs or DVDs. It is also possible to send parts or the entirety of such programs. For all of the abovementioned and known possibilities or media to store and / or transport data and command sequences, the term "data set" is used in the context of this application. This term also includes the sending of the relevant electronic information via networks, for example by e-mail.

Further embodiments of the invention will become apparent from the description and the claims.

Fig. 1

Seitenansicht einer FFS-Maschine

Fig. 2

Detailansicht von Figur 1

Fig. 3

den Verlauf des Sackgewichtes, gegen die Zeit aufgetragen (1. Ausführungsbeispiel)

Fig. 4

den Verlauf des Sackgewichtes, gegen die Zeit aufgetragen (2. Ausführungsbeispiel)

Fig. 5

den Verlauf des Sackgewichtes, gegen die Zeit aufgetragen (3. Ausführungsbeispiel)

Fig. 6

der Verlauf der Sackgewichtszunahme, gegen die Zeit aufgetragen (3. Ausführungsbeispiel)

Fig. 7

den Verlauf des Sackgewichtes, gegen die Zeit aufgetragen (1. Ausführungsbeispiel, Nomenklatur in Bezug auf die Unterspiegelbefüllung)

Fig. 8

den Verlauf des Sackgewichtes, gegen die Zeit aufgetragen (2. Ausführungsbeispiel, Nomenklatur in Bezug auf die Unterspiegelbefüllung)

Fig. 9

den Verlauf des Sackgewichtes, gegen die Zeit aufgetragen (3. Ausführungsbeispiel, Nomenklatur in Bezug auf die Unterspiegelbefüllung)

The individual figures show:

Fig. 1

Side view of a FFS machine

Fig. 2

Detail view of FIG. 1

Fig. 3

the course of the bag weight, plotted against time (1st embodiment)

Fig. 4

the course of the bag weight, plotted against time (2nd embodiment)

Fig. 5

the course of the bag weight, plotted against time (3rd embodiment)

Fig. 6

the course of the bag weight increase, plotted against time (3rd embodiment)

Fig. 7

the course of the bag weight, plotted against time (1st embodiment, nomenclature with respect to the Unterspiegelbefüllung)

Fig. 8

the course of the bag weight, plotted against time (2nd embodiment, nomenclature with respect to the Unterspiegelbefüllung)

Fig. 9

the course of the bag weight, plotted against time (3. Exemplary embodiment, nomenclature with respect to the lower mirror filling)

A tubular film web 15, preferably with inserted gussets, is first conveyed by a preferred roller system 9 in a horizontally movable transport, such as a pair of grippers 18.

The film web 15, after the preference has pulled the section according to the desired bag length, cut by the knife 17. At the same time, the bottom welding takes place 13. The closed at the lower end empty bag 11 is a horizontally displaceable transport, such as a gripper 18, passed and transported to the filling station.

In the filling station takes over a further transport 4, which consists of 3,4,5, the bag section. The empty bag is now opened with a suction system 16. For this purpose, the gripper 4 or be moved in the Z direction (sackeinwärts). The connecting piece of the transport system 3 is moved into the bag and protects the sack inner surfaces from contamination by possible product adherence to the metering tube 2,21.

The opened bag is pulled by the transport system 3,4,5 on the metering tube 2,21 until the lower end of the bag is approximately equal to the Füllgutaustrittsöffnung 31. The bag bottom support device 32,33,34 is driven in the embodiment shown below the sack floor. However, a bag bottom support device 32, 33, 34 is not absolutely necessary. Rather, the relative movement of the bag relative to the Befüllorgan 2,21 mainly caused by the fact that the frame 5 along the guide 6 moves. This is represented by the double arrow 35. In this embodiment of the invention, therefore, the bag is moved relative to the Befüllorgan 2,21. Of course, it is also conceivable to bring about the relative movement between bag 8 and metering element 2 by a movement of metering element 2 or even by a movement of bag 8 and metering element 2. As a rule, it is sufficient in this case if the bag is held by claw-like transport means 4 at its upper end. The mentioned bag bottom support device 32, 33, 34 offers optional, additional protection against a crack of the just welded bag bottom.

The closure tube 21 is lifted and releases the product outlet opening 31. The product / bulk material 24 is filled in the bag. Meanwhile, the transport system 3,4,5 lowers the bag in such a way that the product outlet opening 31 is always below the filling level. However, even before the end of the metering of the product / bulk material 24, the product outlet opening 31 may be located at least once above the filling level 38. After completion of the filling, the closure tube 21 is lowered and closes the product outlet opening 31 by making contact with the closure 20. The connecting piece is pulled out of the bag. The gripper (s) 4 of the transport system 3, 4, 5 is or will now be moved counter to the Z direction (out of the bag) and tightens the opening area at the upper edge 25 of the previously opened bag. Another means of transport takes over the filled bag 8. By means of the closing device 14, the upper edge of the bag 25 is now closed. If necessary, it can be sucked out by the filter integrated in the closure tube 21 together with the dosing process. The required vacuum is introduced via the pipe 23. The integration of the filter in the closure tube allows a very compact design, which makes it possible to fill even relatively small bags. The suction of the air leads to a certain extent to a compression of the bulk material. As a result, a sack size appropriate to the product quantity can be selected.

This effect of product compaction can be enhanced by the additional use of vibration generators / beaters 29. It is advantageous here to set the dosing tube 2, 21 in vibration by means of a vibration generator 29, since it is located within the product at least with parts of its lateral surface during filling. The vibrations are transmitted from the dosing 2.21 to the filling material 24, in which then takes place a compression. Another advantage of the "vibrating metering tube" 2.21 is that the formation of product adherence to the metering 2.21 is thereby largely avoided. The vibrator 29 could also be arranged on the "Sackbodenunterstützungsvorrichtung" 34!

A particularly advantageous embodiment of the carriage is the frame 5 together with the neck 3, transport 4 and the absorption 16 to sensors to store. The sensors send their signal to a weighing electronics, which ultimately controls the dosing process.

To mention is still the guide or support 6, which carries the frame 5 and thus the transport 4. In the metering or pipe 2 is a screw 7, can be promoted with the filling material 24 from the hopper 1 without much dust in the bag 8. The various sensors 26 (in particular weighing sensors or load cells) indicate advantageous locations for attaching such sensors. The conveyor belt 27 transports the filled bags (8). In the vicinity thereof, the checkweigher 30 and the vibration generator 29 are mounted.

The FIGS. 3 to 5 show the time course of the bag weight in three embodiments of the invention. With respect to these figures, the terms previously used with respect to monitoring the filling rate g / t are used. The FIGS. 7 to 9 show the same embodiments and use the terms already used above with respect to the Unterspiegelbefüllung with simultaneous generation of measurement signals. This distinction increases the clarity and facilitates the distinction between inventive and non-inventive filling method.

In the FIG. 2 The following quantities are indicated by the arrows: v _R = relative speed, v _F Speed with which the filling material level rises relative to the bottom of the bag 39, A _soll = desired distance between mouth 31 and product level 38, AM = minimum distance between bottom 39 and mouth 31.

In FIG. 3 the time course of the weight increase of a bag in the execution of a bag filling process is shown. The bag weight g is plotted on the vertical axis and the time t on the horizontal axis. With the first phase P _{1 of} the bag filling fall in this embodiment, the time periods Z ₂ (volumetric or empirical weight control or regulation) and Z ₃ (Unterspiegelbefüllung) together. In this phase P ₁ , therefore, noise signals do not occur in the weight control since the weight signals of the weighing cells 26 are ignored precisely in the case of volumetric or empirical weight control. Interference signals are caused here mainly by the Befüllorgan 2,21 whose Füllgutaustrittsöffnung 31 is yes in the period Z ₃ , which coincides here with the phase 1 and time Z ₂ , below the Befüllgutspiegels 38 is located. As a rule, however, the filling element will be at the beginning of the filling above the filling material level 38, since there is still no or too little filling material in the bag 8. This circumstance is taken into account here by the fact that the time period Z ₃ does not begin at time 0 but at time T ₂ .

When the time T _{1 is reached} , the phase P _{2 of} the bag filling begins. As a rule, in this exemplary embodiment, this point in time will be regarded as having been attained if, on the basis of the volumetric measurement or estimation of the bag weight, it can be assumed that a certain proportion G _{1 of} the bag _target weight G _{target has been} reached. This percentage can be 95%. In the present embodiment (according to FIG. 3 ) now some parameters of the bag filling change: The bag weight is actually monitored by the evaluation of the load cell signals and the filling takes place while the Befüllorgan 2,21 is located entirely above the Füllgutspiegel 38. This improves the quality of the weight measurements. The monitoring of the weight increase, in order to provide an alarm signal if necessary, is carried out during the entire filling process in this embodiment. The filling process ends when the target weight G _{target is} reached. Here, the termination is performed automatically by the control device, not shown, when the load cells 26 report the desired signals to the control device. The filling rate is lower in Phase 2 than in Phase 1.

Another variant of this procedure is in FIG. 4 illustrated. It is sufficient at this point, the differences to the in FIG. 3 To be mentioned embodiment:

The period Z ₄ , in which the signals of the load cells are also used to control / regulate the bag weight, lasts during the entire filling process. There is no volumetric weight control. It is advantageous if the interference signals, which arise in particular during the submillar filling (Z ₃ ), are eliminated by filters on the measuring signals.

In FIG. 5 is dispensed with different phases of the filling process. Throughout the filling process, the weight of the bag is used for weight control (period Z ₄ ). As soon as enough material is in the bag, it will be in the Submirror method filled (period Z ₃ ). A reduction of the bag speed does not occur. These measures can be solved among other things with high demands on the filtering.

In FIG. 6 shows how the in FIG. 5 illustrated embodiment, the first derivative of the weight after the time g / t during the filling operation behaves. It is constant. The curly bracket S indicates the desired range. This does not necessarily have to be symmetrical about the setpoint G / T _nominal . The target range S has a lower S _U and an upper S _O limit. The arrows 36, 37 indicate that the value g / t can leave the target range if an error occurs. A course of the weight change according to the arrow 36 can occur as a result of a blind crack. When the target area S is left, an alarm is triggered, which can trigger measures of the machine personnel and / or the control device.

• a) Das Sollgewicht G_Soll sollte erreicht werden, während die Relativbewegung zwischen Sack 8 und Dosierorgan 2 noch andauert. Wie bereits mehrfach ausgeführt kann diese Relativbewegung durch eine Bewegung eines oder beider dieser beiden Elemente 2, 8 herbeigeführt werden. Es ist auch möglich, dass die Relativbewegung bereits unmittelbar nach dem Zeitpunkt verlangsamt oder beendet wird, an dem das letzte wirklich noch verwertete Messsignal der Wägezellen zustande kommt. Dieses kann vor dem Erreichen des Sollgewichtes sein, und die Zeitspanne zwischen diesem letzten Messsignal und dem Abbruch der Sackbefüllung bei Erreichen des Sollgewichts G_Soll kann aus der Kenntnis der Abfüllgeschwindigkeit allein durch Zeitmesssung und Berechnung gewonnen werden. Alternativ kommt wieder eine kurze volumetrische Messphase Z₂ in Betracht. Wichtig ist, dass gerade die wichtigen letzten Messwerte der Wägezellen nicht durch das Abbrechen der Bewegung, die ja positive oder negative Beschleunigungen hervorruft, verfälscht werden. Schließlich ist die Gewichtsmessung nach der Formel F=gm eine Kraftmessung und die Kraft ist mit der Beschleunigung über das Grundgesetz der Mechanik F=ma verknüpft. Trotz dieser Ausführung erscheint es möglich, insbesondere bei einer Überspiegelbefüllung, auch oben eine Relativbewegung gut zu messen.
• b) Die Relativbewegung zwischen Sack 8 und Dosierorgan 2 sollte während der Befüllung gleichförmig sein. Alternativ ist es auch möglich, wenn zu Beginn des Befüllprozesses eine Beschleunigungsphase stattfindet. Wichtig ist, dass die Relativbewegung gleichförmig ist, während die Wägezellensignale zur Gewichtskontrolle ausgewertet werden (Zeitspanne Z4). Bei gleichförmigen Bewegungen treten eben keine Beschleunigungen des teilweise befüllten Sackes 8 auf, die die Gewichtsmessung verfälschen würden. Eine Alternative zu dieser Vorgehensweise besteht darin, die Relativgeschwindigkeit aufzuzeichnen, etwaige Beschleunigungen zu ermitteln und die durch diese Beschleunigungen entstehenden Fehler gemäß der Formel F=ma aus dem Messwert herauszurechnen. Hierzu sollte auch das augenblickliche Gewicht des Sackes bekannt sein.

In general, tests have shown that even more technical features can be advantageously used in all devices and / or methods according to the invention:

• a) The target weight G _target should be achieved while the relative movement between the bag 8 and metering 2 is still ongoing. As already stated several times, this relative movement can be brought about by a movement of one or both of these two elements 2, 8. It is also possible for the relative movement to be slowed or stopped immediately after the time at which the last really still utilized measuring signal of the weighing cells is produced. This can be before reaching the target weight, and the time span between this last measurement signal and the termination of the bag filling upon reaching the target weight G _target can be obtained from the knowledge of the filling speed solely by time measurement and calculation. Alternatively, a short volumetric measurement phase Z ₂ is again considered. It is important that precisely the important last measured values of the load cells are not falsified by the cancellation of the movement, which indeed causes positive or negative accelerations. Finally, the weight measurement according to the formula F = gm is a force measurement and the force is linked to the acceleration via the fundamental law of mechanics F = ma. Despite this embodiment, it seems possible, especially in a Überspiegelbefüllung, well above a relative movement to measure well.
• b) The relative movement between bag 8 and metering 2 should be uniform during filling. Alternatively, it is also possible if an acceleration phase takes place at the beginning of the filling process. Importantly, the relative motion is uniform while the load cell signals are evaluated for weight control (time Z4). With uniform movements just no accelerations of the partially filled bag 8 occur, which would distort the weight measurement. An alternative to this procedure is to record the relative speed, to determine any accelerations and to calculate the errors resulting from these accelerations according to the formula F = ma from the measured value. For this purpose, the instantaneous weight of the bag should be known.

FIG. 7 shows again the same embodiment as FIG. 3 but additionally uses the terms introduced in relation to the measurement of the bag weight during the filling of the lower mirror. The phase P _U in which the submirror process is filled is equivalent to the third time period Z ₃ . This period is preceded here by the phase P _L , in which the mouth 31 of the Befüllorgans 2 is not below the level of contents 38, since the mouth 31 is a minimum distance AM above the bottom of the bag 39 and there is not enough good in the bag 8 to to cover the mouth 31. In this phase P _L , the relative velocity v _R between the sack 8 and the metering device 2 is set so that it is slower than the speed v _F , with which the filling material rises in the bag. v _R can also be zero here. Therefore, the filling material level 38 "overtakes" the mouth 31 until a desired distance A _setpoint between the level of contents 38 and the mouth 31 is reached. From this point in time T ₂ , the speeds v _R and v _{F are} adjusted, so that the distance A _{target is} maintained.

As mentioned, is filled in the phase P _U in the submirror process. As already too FIG. 3 However, the weight readings are not used here to control the bag weight g. However, in this embodiment, according to the Figures 3 and 7 the load cell signals are used throughout the time Z ₁ to control the filling rate g / t. Therefore, the phase P _M , in which the measured values are utilized in any desired form while being filled in the submirror process, thus lasts between the times T ₂ and T ₁ during the entire submirror filling. The overlap between the periods P _R and P _L indicates that there is still a relative velocity greater than zero in the phase P _L (slowed relative movement v _R between the sack 8 and the metering element 2).

In FIG. 8 in which again that already in FIG. 4 illustrated embodiment, no such overlap between the periods P _R and P _{L is} present. Here, the relative velocity v _R in the period P _{L is} zero. The measurement signals are used during the entire filling process for weight control and for monitoring filling errors, so that the phase P _M lasts again during the entire sub-level filling. This also applies to the view in the Figures 5 and 9 illustrated embodiment. LIST OF REFERENCE NUMBERS 1 funnel 2 metering 3 spigot 4 Mode of Transport 5 frame 6 guide 7 slug 8th Filled sack 9 drawing rollers 10 Mode of Transport 11 empty bag 12 guide 13 bottom weld 14 Kopfnahtschweißung 15 Blown film web 16 sucker 17 knife 18 Mode of Transport 19 unwinding 20 shutter 21 Closing pipe with filter 22 filter 23 Support 24 Product / bulk 25 Upper edge of the bag 26 sensors 27 conveyor belt 28 Directed flow 29 vibration generator 30 checkweigher 31 product discharge opening 32 guide 33 joint 34 Sack ground support 35 Double arrow (movement of the frame 5 with the bag 8) 36 Arrow (deviation from setpoint, sack crack) 37 Arrow (deviation from setpoint) 38 Füllgutpegel 39 bag bottom P ₁ First phase of the filling process up to T1 P ₂ Second phase of the filling process until reaching G _target Z ₁ First time tension (measurement of weight gain) Z ₂ Second time span (volumetric or empirical) Z ₃ Third time span (submirror filling) Z ₄ Fourth time span (monitoring of bag weight) Z ₅ Fifth time span (mirror filling) S _O Upper limit of the target range S _U Lower limit of the target range S Target range of weight gain g / t g / t Weight gain or change per unit time, or even first derivative of the bag weight after the time g / t ² second derivative of the bag weight after the time P _U First phase, bottom mirror filling P _L Start-up phase of filling; Füllgutspiegel 38 not yet over mouth 31st P _M Second phase, measuring the weight during submirror filling P _R Third phase, relative movement between bag and dosing v _R Relative speed between bag and dosing A _M Minimum distance between the bottom of the bag and the mouth of the metering device v _F Speed with which the product level rises

Claims (10)

1. Method for producing a bag, filling the latter with pulverulent or granular contents and closing said bag, in which at least the following measures occur:

   - a bag (8) is filled using a filling element (2),

   - there is relative movement between the filling element and the bag while the bag is being filled,

   - parts of the filling element (2) at least occasionally dip below the contents level (38) during a first phase (P_U) while the bag is being filled,

   - the outlet opening of the filling element is at least occasionally above the contents level (38) during the phase (P₂),

   - the load cells (26) providing measurement signals at least during a second phase (P_M) which comprises at least parts of the first phase (P_U),

   - and these signals being used by the control device to control and/or regulate the filling operation,

   characterized in that
   the filling speed of the contents is lower in the phase (P₂) than in the phase (P_U)
2. Method according to Claim 1,
   characterized in that
   the control apparatus filters the signals provided by the load cells (26), in particular during the second phase (P_M).
3. Method according to Claim 2,
   characterized in that
   higher frequency signals are removed during filtering.
4. Method according to one of the preceding claims, characterized in that
   a relative movement (v_R) takes place between the bag (8) and the metering element (2) at least during a third period of time (P_R) which comprises at least parts of the second period of time (P_M).
5. Method according to the preceding claim, characterized in that
   the relative movement (v_R) is at least occasionally a uniform movement.
6. Method according to one of the preceding claims, characterized in that
   the control device uses the measured values from the load cells (26) at least in one of the following ways or only in one of the following ways:

   - as measured values for monitoring or regulating the weight (g),

   - as measured values of the weight gain (g/t) for detecting an error in the filling process,

   - as a first derivative of the weight gain after the time (g/t²).
7. Method according to one of the preceding claims, characterized in that
   the control device controls the relative movement between the bag (8) and the metering element (2) and the filling operation as follows:

   - the distance between the mouth (31) of the filling element (2) and the bottom (39) of the bag is set to a minimum distance (AM),

   - the bag filling operation begins, contents flowing into the bag (8) through the mouth (31) of the filling element (2),

   - the contents level rises, either the distance between the mouth (31) and the bottom (39) of the bag not being increased by a relative movement or this relative movement being slower than the speed (v_F) at which the contents level (38) rises,

   - the relative movement begins or the speed (v_R) of the relative movement is increased at a point in time after the contents level (38) is above the mouth (31).
8. Method according to the preceding claim, characterized in that the relative movement begins or the speed (v_R) of the relative movement is increased after the contents level (38) is above the mouth (31) if a desired distance (A_Soll) between the mouth (31) and the contents level (38) has been reached.
9. Method according to the preceding claim, characterized in that the reaching of the desired distance (A_Soll) is verified using one of the following methods:

   - a weight measurement (g) by evaluating load cell signals,

   - a measurement of the filling speed (g/t),

   - a measurement using an optical sensor,

   - a volumetric measurement.
10. Method according to one of the three preceding claims,
    characterized in that
    the speed (v_R) of the relative movement and the speed (v_F) at which the contents level (38) rises are matched to one another.

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