The invention relates to a method for operating a tubular bag machine for producing bags having a transverse bottom seam and transverse top seam different to the transverse bottom seam according to the preamble of claim 1.
For different packaging tasks in the packaging industry, tubular bags are known in which the transverse bottom seam is formed differently to the transverse top seam. Tubular bags are known, for instance, in which the transverse bottom seam is folded at the side in order to attain a standing surface, for example, whereas the transverse top seam is realized as a simple horizontal transverse seam. The tubular bags differ in regard to their sealing seams at the top and bottom.
In conventional production methods for producing tubular bags, a transverse top seam and a transverse bottom seam are each produced in each work step by means of the bilaterally drivable transverse sealing jaws via a corresponding film sealing method. The thus produced transverse top and bottom seams divide adjacent tubular bags from each other so that the film has to be severed between the transverse bottom and top seams, which are produced together, by means of a severing device, e.g. a cutting knife, for forming the individual bags.
If tubular bags are to be produced which have a transverse bottom seam differing from the transverse top seam, namely a folded transverse bottom seam, producing a transverse bottom seam and a transverse top seam together is not possible in a single work step of the transverse sealing jaws since the film of the tubular bag has to be folded when producing the transverse bottom seam whereas the production of the transverse top seam prohibits folding the film.
To be able to produce such tubular bags having transverse bottom seams and transverse top seams differing from each other, a production method is known from DE 38 24 753 A1, two transverse bottom seams each being formed by adjacent bags in a first work step of the transverse sealing jaws and two transverse top seams each being formed subsequently thereto in a second work step. In this method, the result is that the individual bags are produced in the draw direction of the tube having an alternating orientation so that adjacent bags are each pre-sealed alternatingly at either the transverse top seam or the transverse bottom seam.
When producing tubular bags having folded transverse bottom seams, the use of so-called side folders is necessary, by means of which the film is folded at the side in the desired manner so as to form a side fold before sealing the transverse bottom seam. The quality of the side fold is vastly improved if the side folder interacts with a stationary fold molding, which is disposed on the inner side, when forming the folded transverse bottom seam. By the side folder interacting with the fold molding, the film is ideally guided in the area of the side fold and can be folded in the desired manner. The use of fold moldings on the inner side of the film sheet when forming the side fold, however, causes significant problems when producing tubular bags having differing transverse seams at the top and bottom—for two transverse bottom seams and then two transverse top seams are produced alternatingly by means of the two transverse sealing jaws in these methods. When sealing the folded transverse bottom seams, it is desirable for the transverse sealing jaws to have a particularly small distance to the fold molding so as to warrant an ideal fold formation. Vice versa, a too small distance of the transverse sealing jaw to the fold molding when sealing the unfolded transverse top seam is exceedingly disadvantageous since undesirable folds can be formed in the unfolded transverse top seam if the distance of the transverse sealing jaws to the inner fold molding is too small. In the known method for operating a tubular bag machine for producing bags having folded transverse bottom seams and unfolded transverse top seams, the use of inner fold moldings has been omitted for this reason though this negatively impacts the folding quality when folding the side fold.
Starting from this state of the art, it is therefore the object of the present invention to propose a new method for operating a tubular bag machine for producing bags having folded transverse bottom seams and unfolded transverse top seams, said new method attaining an ideal folding quality when forming the side fold and effortlessly enabling sealing the unfolded transverse top seam at the same time.
This object is attained by a method according to the teachings of claim 1.
Advantageous embodiments of the invention are the subject matter of the dependent claims.
The method according to the invention is first of all characterized by a fold molding being disposed stationarily on the inner side of the film sheet and interacting with the displaceable side folder when forming the side fold. In order to preclude the undesired fold formation in the area of the transverse top seam which is not to be folded, it is intended according to the invention that the distance of the transverse sealing jaws to the stationary fold molding when forming the transverse top seams is different than when forming the transverse bottom seams. In other words, this means that the transverse sealing jaws are each displaced to a different position along the Z-axis depending on whether two transverse top seams or two transverse bottom seams are sealed using the transverse sealing jaws.
In this context, the minimal distance of the transverse sealing jaws to the stationary fold molding is significantly larger when producing the two transverse top seams than the minimal distance of the transverse sealing jaws to the fold molding when producing the transverse bottom seams.
Via the thus attained additional distance of the transverse sealing jaws to the stationary fold molding while sealing the transverse top seams, the undesired fold formation in the area of the transverse top seams—caused by the fold molding—is largely reduced or entirely prevented. When sealing the transverse bottom seams, however, a smaller minimal distance of the transverse sealing jaws to the fold molding is intended so that the functions of the laterally movable side folder can be ideally supported by the stationary fold molding when folding the film in the area of the transverse bottom seam. In other words, this means that the transverse sealing device moves toward a higher position on its closed biaxial movement trajectory when producing the transverse bottom seams than when producing the transverse top seams, provided the draw direction is oriented vertically downward.
In the method according to the invention, the displacement path of the transverse sealing jaws is altered depending on whether two transverse top seams or two transverse bottom seams are to be sealed in the next work step. Nevertheless, most production processes require producing tubular bags having a consistent height between the transverse bottom seam and the transverse top seam, respectively. In order to easily attain this constant bag length of all sealed bags, it is intended according to a preferred method variation for the draw speed of the draw device to correspond to a first speed profile when forming a first tubular bag, said draw speed of the draw device corresponding to a second speed profile, which differs from the first speed profile, when producing a directly following second tubular bag. Unlike in conventional production methods for tubular bags, in which the draw speed of the film sheet follows the same speed profile for all tubular bags, the speed profile of the draw speed is alternatingly altered in this preferred method variation. Owing to the speed profile of the draw speed being alternatingly altered, it is possible to compensate the alteration of the minimal distance of the transverse sealing jaws to the fold molding to the extent that the bag length of all sealed bags is essentially consistent.
In this context, it is particularly advantageous if the draw speed, by means of which the film sheet is drawn in the longitudinal direction, is alternatingly altered between a speed maximum and a speed minimum when forming adjacent bags. Via this alteration of the draw speed, it is possible in a particularly easy manner to compensate the alteration of the minimal distance of the transverse sealing jaws to the fold molding to the extent that the bag length of all sealed bags is essentially consistent.
For which kind of tubular bags the method according to the invention is used is generally arbitrary. The method according to the invention is of particular importance when producing tubular bags in which strip-shaped closing elements, which can be detachably engaged with each other, are fastened transversally to the longitudinal axis of the film sheet in the area of the transverse top seam. For in this kind of tubular bag, producing different transverse top seams and transverse bottom seams is imperative if a standing surface is desired in the area of the transverse bottom seam.
A variation of the method according to the invention is described in the following in an exemplary manner by means of the schematic drawings.
In the following,
In
Each adjacent tubular bag 01 is sealed such that either the two adjacent transverse bottom seams 02 are sealed by means of the transverse sealing jaws or, in the next work step, the two adjacent transverse top seams 03 are sealed by means of the transverse sealing jaws. This is necessary in order to alternatingly fold the film tube, which is made of the film sheet 04, at the side, whereupon the transverse bottom seams 02 are sealed, and to forgo folding the film sheet in the respectively following work step and to seal the unfolded transverse top seam 03.
The method according to the invention for producing tubular bags 01 is to be further explained by means of the illustration in
The tubular bag machine 10 illustrated in
Filling material, which exits the filling tube 14 and enters the interior of the film tube, is poured through the filling tube 14 (process not illustrated). A biaxially drivable transverse sealing device 16 is arranged beneath the filling tube 14. The two transverse sealing jaws 17 can be driven in the Z-direction, i.e. in the conveying direction of the tubular bag 01, and towards each other, i.e. transverse to the conveying direction. When sealing the tubular bags 01, the transverse sealing jaws 17 are pressed against each other and the film sheet 04 is sealed via heat exposure. At the same time, the transverse sealing jaws 17 of the transverse sealing device 16 are displaced in the Z-direction in order to follow the conveying movement of the tubular 01 in order to follow the downward conveying direction of the tubular bag 01 from the top.
In
In order to compensate the additional distance 20 when commencing the sealing for producing the two transverse top seams with regard to the bag length, the draw speed of the two draw bands 15 is altered. By altering the draw speed of the draw bands 15, the change in distance, i.e. the alteration of the Z-coordinates of the transverse sealing jaws 17, can be compensated when commencing the sealing of the transverse bottom seams 02 on the one hand and the transverse top seams 03 on the other hand.
Number | Date | Country | Kind |
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10 2016 213 087.0 | Jul 2016 | DE | national |
Filing Document | Filing Date | Country | Kind |
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PCT/EP2017/067420 | 7/11/2017 | WO | 00 |