EP0142461B1 - Method and device for adjusting the spot of transversal sealing and separating of continuously moving tubular bag packages - Google Patents

Description

The present invention relates to a method for adjusting the transverse sealing and separating position in the case of endless tubular bag packs according to the preamble of patent claim 1 and to an apparatus for carrying out the method according to patent claim 7.

In the case of tubular bag packs, as described, for example, in CH-A 527 090, a film web is drawn through a folding box in order to form a tube from this film web. The items to be packaged are fed continuously to this tube at regular intervals. The filled tube is then divided into individual packages by transverse sealing seams and the packages are usually separated at the same time as the seal. According to this publication, up to about 300 to 400 packs per minute can be produced in this way.

If the film web is printed, it must of course be ensured that the motifs are always arranged the same. In particular when using plastic films, the lengths can change greatly as a result of fluctuations in the tensile stress, so that an exact setting of the sealing and separating position is necessary.

From DE-A 2 951 178 and from EP-A 11 595 it is known to apply a mark to the foils and to evaluate them by means of a sensor in order to always seal and separate them at the right place. According to the first-mentioned arrangement, the deviation in the length of the individual sections is quantized and either the speed of the cutting means and / or the means of transport is changed. For this purpose, a stepper motor is available which acts on a differential gear in order to effect this change together with the mechanical output of the main motor. A differential drive with a stepper motor is also provided in the second publication, but it is assumed here that the packaging is incorrect and must be ejected.

Further devices for continuously correcting an incorrect position of the marks with respect to a cutting point are known, for example, from US Pat. No. 2,529,161 and US Pat. No. 2,599,430.

The US-PS 2529161 describes a device according to the aforementioned method, in which the separating part delivers a wide pulse, the relative position of which is monitored with respect to a narrow pulse from the sensor such that the additional drive stops when these pulses do not overlap and at Overlap, ie if incorrectly set, receives a supply voltage that is used to correct the speed.

US Pat. No. 2,599,430 has a similar device in which the sensor, the transport part and the separating part are provided in a different order. This device comprises a phase detector which supplies two signals «Forward» and «Retard», which follow one another shortly, between which the sensor signal must be located if the separating part cuts at the right moment. This test takes place in a coincidence or mixer and integrator circuit, which consists of two double grid tubes with a downstream transformer with a transmission factor of 1: 1, whereby a positive or negative signal can arise during the test.

These known devices work with monitoring the signals for overlap and are relatively expensive.

It is therefore an object of the present invention to provide a method that works without monitoring the signals for overlap and can be implemented with a less complex arrangement.

According to the invention, this object is achieved by the features in the characterizing part of independent patent claim 1. The device for performing the method is characterized in claim 7.

• Fig. 1 ein Blockschema zur Darstellung des Informationsflusses in einer Vorrichtung zur Durchführung des erfindungsgemässen Verfahrens, und
• Fig. 2 Diagramme zur Erläuterung der Erfindung.

An embodiment of the invention is explained below with reference to the drawing. Show it:

• 1 shows a block diagram for illustrating the flow of information in a device for carrying out the method according to the invention, and
• Fig. 2 diagrams for explaining the invention.

In Fig. 1, triangular closed arrows, when filled, mean the flow of material, and when empty, the flow of energy, open arrows, on the other hand, mean the flow of information. The energy is fed in at N and N '.

From a tubular bag packaging machine, the tubular bag packing part A, a tubular bag transport part B, an optoelectric sensor C and a transverse sealing and separating part D as well as a main drive E, a second drive H, a computer R and an input and display part J are shown schematically.

As important information for the computer R, the machine status MC, namely "stands still" - "runs" - "manual drive" - "machine stop", in addition to the freely selectable parameters from the input and display part J, in addition to the data on the angular position Fi des Foil samples Z and the marks M (Fig. 2) and those entered via the angular position Ms of the hose P and the speed nMi of the machine, the letters i, s behind the device designation, whether it is an actual value or one Target value.

The second drive H receives information from the computer R about the required speed of the transport part B. From the two separately illustrated feed points N and N ', electrical energy flows into the drives E, H, which as mechanical energy with a main shaft on the tubular bag packing part A and is transferred to the transverse sealing and separating part D. The transport part B is directly controlled by the second drive H and the speed is independently kept constant. A disc rotor motor can be used as the drive machine for the second drive.

The information about the angular position Mi is represented by 360 pulses nMi per revolution of the shaft. These can be generated by means of an angle encoder, by means of a step pulse generator or also using an inductive pulse generator.

Tachometers can be used to output the speed information nMi and nFi. A potentiometer for delivering an adjustable constant voltage can be provided for the input of the speed nMs of the machine.

The mode of operation is described with reference to FIG. 2. At the top of the picture is a tubular bag band P, which should move from right to left. The optoelectric sensor C and the transverse sealing and separating part D of the machine are shown. The marks M and the motifs or patterns Z are indicated on the tubular bag band P.

The first line shows the angular position pulses (pMs from the transverse sealing and separating part D, which have a variable distance here. The sensor pulses (pFi in the second line are the pulses from sensor C and coincide with the marks M in time match.

The computer R generates positive pulses + S, the width of which corresponds to the time between the rising edge of a sensor pulse (pFi and the falling edge of the angular position pulse ϕMs assigned to it, as well as negative pulses -S, the width of the time between the rising edge of an angular position pulse (pMs and the Falling edge of the sensor pulse assigned to it (pFi corresponds.

The time difference S of the occurrence of the two pulses ϕMs ―ϕFi is formed in the computer and the error signal and an evaluation signal Sa are obtained by integration U = ∫ςdt, which determines the speed of the additional drive H in order to regulate the advance of the tubular bag packs P. .

This clearly shows that with the invention, all mechanical parts for the speed change are eliminated and only a simple, quickly adjusting pulse control is required.

Claims (8)

1. A method for adjusting the point of transverse sealing and separating of continuous tubular bag packages in a tubular bag packaging machine, which machine is provided with a main drive (E) for driving the packaging element (A) and the transverse sealing and separating element (D), a sensor (C) which generates a sensor pulse (<pFi) when marks (M) on the tubular bag packages pass by it, and an additional drive (H) for a tubular bag conveying element (B), in which an angular position pulse ((pMs) is obtained at the main drive, which pulse defines the position of angular rotation of its shaft with respect to the sensor pulse (ϕFi), and an evaluation signal (Sa) is obtained from the sensor pulse ((pFi) and the angular position pulse ((pMs) in order to determine the rotational speed of the additional drive (H) and thus to control the advance of the tubular bag packages (P), characterised in that a computer (R) is available in which positive pulses (+S) are formed whose width corresponds to the time between the upward slope of a sensor pulse ((pFi) and the downward slope of the associated angular position pulse (ϕMs), or in which negative pulses (-S) are formed whose width corresponds to the time between the upward slope of an angular position pulse (<pMs) and the downward slope of the associated sensor pulse (<pFi), and the computer uses these positive and negative pulses to form, by way of at least an approximate integration, a control voltage (U) from which the evaluation signal (Sa) is produced.

2. A method as claimed in claim 1, characterised in that the respective angular position pulse (<pMs) of the main drive (E) is measured on a shaft which rotates once per working cycle.

3. A method as claimed in claim 2, characterised in that a particular number of angular position pulses (ϕMs) is generated per working cycle and used to determine the accuracy of the desired position.

4. A method as claimed in claim 3, characterised in that a blanking window is defined for the sensor (C) by means of the angular position pulses (ϕMs) in order to activate the sensor (C) in a limited area of the total tubular bag length only.

5. A method as claimed in any of claims 1 to 4, characterised in that, in addition to the angular position pulses ((pMs), signals (nMi) for the rotational speed of the transverse sealing and separating element (D) are fed to the computer (R).

6. A method as claimed in any of claims 2 to 5, characterised in that the shaft rotates in synchronism with the working cycle and, in order to generate a signal for the rotational speed (nMi), a tachometer is coupled to the shaft.

7. A device for implementing the method as claimed in claim 1, characterised in that the tube conveying element (B) with the separate additional drive (H) is located between the packaging element (A) and the transverse sealing and separating element (D) upstream of the sensor (C).

8. A device as claimed in claim 7, characterised in that information about the desired values can be read into the computer (R) and the actual values of the angular position (Fi) and rotational speed (nMi) of the transverse sealing and separating element (D) and information when the mark (M) appears can be fed to it in order to use the time difference determined to alter the evaluation signal (Sa).

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