METHOD FOR OPERATING A HOSE BAG MACHINE

Description

[0001] The invention relates to a method for operating a tubular bag machine according to claim 1. Tubular bag machines of this type are known, for example, from DE 10 2010 028 697 A1, DE 102017 121572 A1, or DE 196 20 560 A1. The tubular bag machine can be a vertically or horizontally operating tubular bag machine, so that the tubular bags are conveyed through the tubular bag machine either vertically or horizontally.

[0002] A wide variety of film materials are known for the production of tubular bags. Due to their ease of processing, plastic films are particularly widely used for the production of tubular bags. These plastic films can also be multilayer films, in which the different layers of the film material are optimized for processing, particularly with regard to the sealing of the film web. Such plastic films typically exhibit high tear resistance and can therefore be processed easily in tubular bag machines, even at high production speeds.

[0003] To ensure the careful use of resources, film materials that enable sustainable and resource-efficient use of materials are increasingly being used to manufacture tubular bags. In particular, film materials with a high paper content are increasingly being used to manufacture tubular bags. This paper material has the particular advantage of being highly recyclable using established recycling systems, such as paper bins.

[0004] The disadvantage of these sustainable film materials is that they have a significantly lower tear resistance. This lower tear resistance of the film material means that when starting up or stopping the flow pack machine, a positive or negative acceleration phase has to be carried out. This phase involves accelerating the machine from an initial speed, for example from a standstill, to the desired target speed or braking it from the target speed to a final speed, for example from a standstill. Through this positive or negative acceleration phase, the mechanical stress on the film web can be limited to a level that reliably prevents the film web from tearing. However, the relatively long acceleration phase when starting up or braking the flow pack machine means that the flow packs are subject to mechanical stress during the positive or negative acceleration phase.negative acceleration phase do not achieve the necessary sealing quality. This is particularly disadvantageous when the acceleration phase is relatively long, resulting in a relatively large number of tubular bags being produced as rejects. In DE 196 20 560 A1 and DE 10 2017 121572 A1, the energy input into the sealing zone is varied depending on the current conveying speed of the film web. However, DE 196 20 560 A1 does not disclose a speed-dependent change in the sealing path along which the cross jaws are in contact with the film web. DE 10 2017 121572 A1 does not disclose a film pull-off within the meaning of the present application.

[0005] Based on this prior art, it is therefore the object of the present invention to propose a new method for operating a tubular bag machine which enables the production of tubular bags with a sufficient sealing quality even during the positive or negative acceleration phase.

[0006] This problem is solved by a method according to the teaching of claim 1.

[0007] Advantageous embodiments of the invention are the subject of the subclaims.

[0008] The method according to the invention is based on the fundamental idea that, during the positive or negative acceleration phase, at least the sealing path, as a sealing parameter of the cross jaws for creating cross seams, is changed depending on the current conveying speed of the film web. This is because the changing conveying speed of the film web during the positive or negative acceleration phase causes an undesirable influence on the sealing parameters, so that the sealing quality can only be maintained by appropriately changing the sealing parameters during the acceleration phase.

[0009] The sealing quality of the transverse seal seams is influenced by a variety of parameters. The sealing time during which the transverse jaws are in contact with the sealing web is particularly important for the sealing quality. If the film web has a significantly lower speed than the target speed during the positive or negative acceleration phase, this can result in an undesirable increase in the sealing time, even if the movement kinematics of the transverse sealing jaws remains constant. This can cause the sealing zone to burn, resulting in unsatisfactory sealing quality.

[0010] In addition to the sealing time, according to the invention the sealing path along which the cross jaws are in contact with the sealing web is also changed depending on the current conveying speed of the film web. If the film web is moving at high speed, in particular at the desired target speed corresponding to the specified cycle time, a correspondingly long sealing path is required in order to introduce the necessary heat through the cross jaws into the sealing zone of the film material. If the film web has a low conveying speed, as is particularly the case in the positive or, in the new negative, acceleration phase, the sealing path must be shortened accordingly in order to prevent the cross jaws from introducing too much heat into the sealing zone. Alternatively or.In addition to the sealing time and the sealing path, the sealing temperature with which the film web is sealed by the cross jaws can also be varied depending on the current conveying speed of the film web. This, in turn, allows the heat input of the cross jaws into the film material to be varied depending on the film web speed, preventing the film material from burning. Furthermore, it is also possible to change the sealing pressure with which the film web is sealed by the cross jaws depending on the current conveying speed of the film web.

[0011] To achieve sufficient sealing quality in the transverse seal seam, the film manufacturer usually specifies optimized sealing parameters from which deviations can only be made within a relatively small tolerance. To ensure sealing quality at all times, even when starting up or braking the flow-wrapping machine, it is particularly advantageous if at least one sealing parameter of the cross jaws for creating transverse seams is changed depending on the current conveying speed of the film web in such a way that the energy input of the cross jaws into the transverse seams remains essentially constant. If, for example, the conveying speed of the film web is reduced, the sealing path of the cross jaws during transverse sealing must also be shortened, since otherwise an excessive amount of heat is introduced into the sealing zone with a constant sealing path.

[0012] A particularly simple process variant results when the sealing pressure and / or the sealing temperature remain unchanged during the positive or negative acceleration phase. This is because these sealing parameters can only be changed with relatively great effort on conventional flow-wrapping machines. In order to keep the heat input into the sealing zone largely constant during the acceleration phases, it is particularly simple to change the sealing path depending on the current conveying speed of the film web so that the effective sealing time remains essentially constant. In particular, the sealing path can be changed in a linear relationship to the current conveying speed of the film web. This means, for example, that if the conveying speed is doubled, the sealing path is extended to twice the length.

[0013] The process according to the invention offers a particularly significant advantage in the continuous production of tubular bags. In particular, the process according to the invention can process a film web with a high paper content, even though these paper films have low tear resistance and can be optimally sealed within a certain parameter range. In particular, the process according to the invention enables the problem-free processing of film webs with a paper content of at least 95%.

[0014] An embodiment of the invention is shown schematically in the drawings and is explained below by way of example.

[0015] They show: Fig. 1 a schematically illustrated tubular bag machine carrying out the method according to the invention in cross-section; Fig. 2 four different sealing parameters for the cross-sealing of the tubular bags in the tubular bag machine according to Fig. 1 when carrying out the method according to the invention.

[0016] Fig. 1 shows a schematically illustrated tubular bag machine 01, in which Fig. 1 Only those parts of the tubular bag machine 01 are shown that are necessary for understanding the invention. A film web 03 is unwound from a supply roll 02 and then formed into a film tube 05 on a forming shoulder 04. The film web 03 is a paper web coated with a sealing layer, with the paper content being higher than 95%.

[0017] The film tube 05 slides down the outside of a format tube 06 driven by a film pull-off 07, whereby the film tube 05 is guided by means of a Fig. 1 The film is sealed longitudinally parallel to its transport direction by a longitudinal sealing device (not shown). The conveying speed of the film web 03 is monitored by appropriate sensors.

[0018] Below the format tube 06 is a cross-sealing device 08 with two cross-jaws 09 for creating cross-sealings, through which the film tube 05 is cross-sealed into individual tubular bags 10. A separating device 11 is integrated into the cross-jaw 09, with which the individual tubular bags 10 can be separated from one another after cross-sealing.

[0019] The filling material 12 for filling the tubular bags 10 is measured using a measuring device, for example, a scale 13, so that the filling quantity intended for each tubular bag 10 is achieved. The measured filling material 12 falls into the funnel 14 below due to an opening impulse of the scale 13. The funnel 14 gathers the filling material 12 to the diameter of the format tube 06.

[0020] The tubular bags 10 are produced continuously in the tubular bag machine 01 at a high cycle rate, meaning at a very high target speed. When starting or decelerating the tubular bag machine 01, the film web 03 must first be accelerated or decelerated sharply from a standstill. To prevent the film web 03 from tearing, the acceleration or deceleration must be limited to a maximum in order to keep the forces occurring during acceleration or deceleration below a tolerable level. This results in a relatively long positive or negative acceleration phase.

[0021] In Fig. 2 Four process parameters of the tubular bag machine 01 are shown schematically during the positive and negative acceleration phases 15 and 16, respectively. The process parameters shown are, in order from top, the conveying speed 17 (V) of the film web 03, the sealing path 18 (XS) of the cross jaws 09, the sealing time 19 (TS) and the amount of heat 20 (QS) introduced into the film web 03 during cross sealing.

[0022] In the top diagram of Fig. 1 , which represents the conveying speed 17 of the film web 03, it can be seen that in the positive acceleration phase 15, the conveying speed 17 is accelerated from a standstill to the specified target speed along a linear ramp. Conversely, in the negative acceleration phase 16, the conveying speed 17 of the film web 03 is decelerated from the target speed to a standstill along a linear ramp.

[0023] The second diagram below schematically shows the sealing path 18 in the positive acceleration phase 15 and the negative acceleration phase 16. It can be seen that the sealing path 18 is increased during the positive acceleration phase 15 and decreased during the negative acceleration phase 16 in a linear relationship to the conveying speed 17 of the film web 03. This shortening or lengthening of the sealing path 18 during the positive acceleration phase 15 and during the negative acceleration phase 16 ensures that the sealing time 19 schematically shown in the third diagram also remains essentially constant during the two acceleration phases 15 and 16.Due to this essentially constant sealing time 19, during which the sealing jaws 09 are in contact with the film web 03 at a constant sealing temperature and constant sealing pressure, the sealing heat 20 introduced during the sealing of the film web 03 is kept essentially constant, as shown schematically in the fourth diagram.

Claims

1. A method for operating a tubular bag machine (01) comprising a film web (03) which is capable of being unwound from a supply reel (02), a forming shoulder (04) for forming the film web (03) into a film tube (05), a film take-off unit (07) acting against the film tube (05) and serving to move the film tube (05) further, a longitudinal sealing device for welding shut the film tube (05) parallel to its transport direction by means of a longitudinal seam, a transverse sealing device (08) which has transverse jaws (09) movable against one another and welding shut the film tube (05) transversely to the transport direction for producing transverse seams, a separating element (11) for separating finished tubular bags (10) from the film tube (05), the tubular bag machine (01) being accelerated in a positive acceleration phase (15) from an initial speed to a target speed when starting or being decelerated in a negative acceleration phase (16) from the target speed to a final speed for stopping, wherein, in the positive acceleration phase (15) and / or in the negative acceleration phase (16), at least one sealing parameter (18, 19, 20) of the transverse jaws (09) for producing tubular bags (10) is changed as a function of the current conveying speed (17) of the film web (03), wherein the sealing path (18) along which the transverse jaws (09) are in contact with the film web (03) is changed as a function of the current conveying speed (17) of the film web (03).

2. The method according to claim 1, characterized in that the sealing time (19) during which the transverse jaws (09) are in contact with the film web (03) is changed as a function of the current conveying speed (17) of the film web (03).

3. The method according to claim 1, characterized in that the sealing temperature with which the film web (03) is sealed by the transverse jaws (09) is changed as a function of the current conveying speed (17) of the film web (03).

4. The method according to claim 1, characterized in that the sealing pressure with which the film web (03) is sealed by the transverse jaws (09) is changed as a function of the current conveying speed (17) of the film web (03).

5. The method according to any one of claims 1 to 4, characterized in that at least one sealing parameter (18, 19, 20) of the transverse jaws (09) for producing transverse seams is changed as a function of the current conveying speed (17) of the film web (03) in such a manner that the sealing heat (20) of the transverse jaws (09) into the transverse seams remains constant.

6. The method according to any one of claims 1 to 5, characterized in that the sealing pressure and / or the sealing temperature (19) remain unchanged in the positive or negative acceleration phase (15, 16), the sealing path (18) being changed as a function of the current conveying speed (17) of the film web (03) in such a manner that the sealing time remains constant.

7. The method according to any one of claims 1 to 6, characterized in that the sealing path (18) is changed in linear dependence on the current conveying speed (17) of the film web (03).

8. The method according to any one of claims 1 to 7, characterized in that the tubular bag machine (01) is continuously driven during the production of the tubular bags (10).

9. The method according to any one of claims 1 to 8, characterized in that the film web (03) contains a high proportion of paper.