Form shoulder for paper packaging

Abstract

A forming shoulder (20) is used for forming rectangular paper tubular bag packaging, wherein the forming shoulder (20) comprises a forming shoulder plate (3) with a paper inlet edge (4), an outer boundary edge (2), and a forming edge (1), and a tube-like outlet area (11) with a rectangular cross-section (5). To counteract creasing and wrinkling in paper-based packaging materials, it is proposed that the flank of the rectangular cross-section (10) facing the paper inlet edge (4) has an arcuate curvature (8) pointing towards the paper inlet edge (4), at least in the region of the forming edge (1).

Description

According to the preamble of claim 1, the invention relates to a forming shoulder for forming rectangular tubular bag packages from paper, wherein the forming shoulder comprises a forming shoulder plate with a paper inlet edge, an outer boundary edge and a forming edge and a tube-like outlet region with a rectangular cross section. The forming shoulder is to be used in a vertical tubular bag machine.In the packaging industry, more and more tubular bags made of paper with biodegradable coatings or even without coatings are being demanded. The papers used have very different properties, wherein, in addition to the type and thickness of the coatings already mentioned, for example, the type, length and arrangement of the paper fibers also influence the running behavior in the packaging machine. It has also been shown that the properties themselves deviate significantly within a batch and can also be influenced by hygroscopic behaviour on prolonged storage.As a result, it had to be established that the forming shoulders used in plastic films are not suitable for the use of paper-based packaging, since paper is much more sensitive as packaging material and reacts to the forming process with the formation of defects, wherein, in addition to crease and crease formation, for example in the form of herring-bone patterns, perforation of the material can also occur until tearing occurs. The packaging produced thereby is unusable. During processing on forming shoulders known from the processing of plastic films, the centering of the paper web is also more difficult compared to plastic films; the packaging material tends to run away laterally to a greater extent, with consequent damage and interruptions in the processing operation.Thus, it is usually necessary to carry out first comprehensive test and test tests for each packaging project, in particular if tubular bags with a rectangular cross section are to be produced as a result. A special optimization of the forming shoulder geometry for the special packing material must then take place; a change of the packing material is not readily possible in the known solutions, but entails a renewed test run and optimization measures.Rectangular in the present context means that the cross-sectional shape is generally formed from a rectangle or optionally also a polygon with rounded corners.In principle, the geometry of each forming shoulder consists, in addition to certain main values, of a forming line, an edge curve and the generatrix. The first two elements describe a spatial curve. The forming line is the basis for the physical forming edge at the forming shoulder at which the forming of the flat film web into a tube is carried out. The edge curve describes the external delimitation of the forming shoulder plate, which guides the forming and supports the forming process. The generatrixes are straight lines which connect the two spatial curves to one another according to specific mathematical rules. Together these elements form the characteristically curved surface of the forming shoulder.It is already known to provide elevations in the region of the forming edge of forming shoulders for plastic films and to round them with radii.For packaging materials made of paper, it has been found that a certain web tension of the packaging material is required in order to restrict the tendency to wrinkle. However, the measure of increasing the web tension is counteracted by the tendency of the paper to tear under higher forces, so that it is not easily possible to increase the web tension as desired, for example in the dancer roller system of the packaging material feed.The object of the present invention is to provide a forming shoulder whose geometry is suitable for the processing of a broader spectrum of paper qualities as packaging material.According to the invention, the object is achieved by a forming shoulder of the type mentioned at the beginning, in which the flank of the rectangular cross section facing the paper inlet edge has an arcuate curvature facing in the direction of the paper inlet edge at least in the region of the forming edge, wherein the largest bulge is preferably formed centrally.It has been shown that this central bulge of the rectangular cross section in the direction of the package inlet allows a marked improvement in the packaging quality even with different qualities of the package. The curvature produces a kind of apex in the rectangular forming shoulder similar to that also obtained in round forming shoulders, which apex represents the highest point of the forming curve. Viewed from the center, a convex guide track for the packaging material results, which has a centring effect on the packaging material track and ensures that the tension is maintained transversely to the film running direction, which is not possible by a conventional cross section with a rear forming edge lying purely perpendicularly to the movement path.The solution according to the invention thus offers the advantage that, due to the symmetrical and local increase of the web tension at the apex, possibly present transverse forces become small in relation thereto and centering occurs, which makes lateral run-off less likely. As a result, crease and crease formation are avoided and process safety is increased.In a preferred embodiment of the invention, it is provided that the forming shoulder geometry has an additional geometry at least in regions between the forming edge and an edge curve delimiting the forming shoulder. The forming shoulder plate thus experiences overall an equidistant elevation, including the edge curve itself. The forming edge is to be associated with the forming shoulder tube / or body and experiences an elevation and a rounding.However, a development of the additional geometry is particularly preferred in that it is designed in the form of a bead and has an extension on the forming edge, i.e. an additional geometry is applied which is reminiscent of a shoulder, rim or bead. It has been found that this additional geometry perpendicular to the feed direction of the web further improves the behavior of the paper-based packaging materials used and helps improve the quality of the tubular bag produced.A further measure can provide that the additional geometry and / or the extension of the forming edge decrease towards the outlet region of the rectangular cross section. The effect of these two elements decreases toward the outlet, so that a simplification of the geometry toward the outlet is generally not disadvantageous.Exemplary dimensions for the additional geometry provide that the latter has a height of 0.35 mm, preferably 0.5 mm or more, wherein it can furthermore be provided that the rounding radius of the additional geometry is 0.4 mm, preferably 0.5 mm or more, in the direction of the rectangular cross section.For the geometry of the additional geometry, it has proven advantageous that it has a width of at least 1 mm, preferably 1.5 mm or more, wherein with regard to the maximum height it is preferably provided that the additional geometry has a height of up to 0.6 mm.In a preferred development of the invention, it is provided that the transition region between the bead-like additional geometry and the extension is formed in a straight surface or with a transition radius, wherein the transition region can be formed concave or convex when a transition radius is formed.The transition region between the extension and the forming shoulder plate can be formed with a transition radius, but simple slopes are also possible as a transition at this point.A further advantageous embodiment of the invention provides that the edges forming the cross section are formed slightly shortened in the region of the arcuate curvature, so that the cross-sectional circumference is not substantially enlarged at this point. As a result, the circumference of the rectangular cross section, which is enlarged by the curvature, is compensated in the region of the forming edge, so that the latter remains better adapted to the respective packaging task.In a further possible embodiment of the invention, it is provided that the arc-shaped curvature decreases toward the outlet region or merges into a rectangular cross section in front of the outlet region.Further features, details and advantages of the invention are evident from the wording of the claims and from the exemplary embodiment described below with reference to the drawing. The following are shown: FIG. 1 is an oblique view of a forming shoulder according to the invention;FIG. 2 is a top view of the forming shoulder according to FIG. 1 ; FIG. 3 shows a side view of the forming shoulder according to FIGS. 1 and 2 ; FIG. 4 is a bottom view of the forming shoulder according to FIG. 1; FIG. 5 is an end view of the forming shoulder according to FIG. 1; FIG. 6 shows a detailed view of the geometry of a forming edge of the forming shoulder according to FIG. 1.Referring now to FIG. 1, there is shown a forming shoulder 20 for forming tubular bag packages of rectangular cross-section (not shown) in a vertical tubular bag machine (also not shown). In the region of an inlet edge 4 of a forming shoulder plate 3, the packaging material is supplied in the form of a paper web, which can be coated. An inlet angle α between the tangents of the forming shoulder plate 3 in the region of the inlet edge 4 and a vertical outlet region 11 of the forming shoulder 20 is, for example, in a range of 90 to 70° (see FIG. 3 ) in the case of paper webs as packaging material, wherein this value can be varied. The length of the inlet edge 4 corresponds substantially to the width of the paper web of the packaging material, which is not shown here. Laterally, the forming shoulder plate 3 is bounded by a boundary edge 2.The forming shoulder plate 3 merges at a forming edge 1 into a tubular region 5 which is rectangular in cross section (see FIG. 5 ), wherein rectangular in this context means not a strict rectangular shape but rather a polygonal shape with transition radii 6. The forming of the packaging material web thus begins with a straight inlet edge 4 and ends in a rectangular, tube-like cross section 5.Furthermore, at least in the regions of the corner radii 6, a bead-shaped additional geometry 14 is provided in the development of the forming shoulder body 7.In addition, rounding is carried out in the edge region, for example with a rounding radius of 0.5 mm.In addition, there is the possibility of allowing the elevation along the forming edge 1 to run down steadily up to a specific point.A special feature of the embodiment shown here is that the originally rectangular cross section 5 of the forming shoulder in the region of the forming edge 1 is modified in such a way that the rear straight side, i.e. that which faces the packaging inlet 4, is replaced by an arc 8 with a small curvature. As in the case of the round forming shoulders, this produces a kind of apex which represents the highest point of the forming curve 9. In the front view (see FIG. 5 ), a silhouette with a concave characteristic is thus obtained, which exerts a certain centring effect on the packaging material web and ensures that the tension is maintained transversely to the film running direction, which cannot be achieved in the case of a conventional rectangular cross section in this form.In the context of modifying the curvature of the cross section in the region of the flank facing the inlet 4, it was ensured that the deviation of the cross-section circumference resulting from the arc-shaped curvature is as small as possible with respect to the target circumference of the target cross section. The curved bulge of the rear edge does not have to be continued over the entire length of the tubular cross section, but can be transferred with a continuously emerging transition 12 into a straight line 13, so that a conventional rectangular cross section 5 again results in the region of the outlet 11.In addition to the measure of equidistantly increasing the forming edge 1 by means of the bead-shaped additional geometry 14 and rounding it off with a radius 15 or taking over the applied rounding profile from the round or known rectangular forming shoulders, a further change has been made in the embodiment presented here which, in conjunction with the modified cross section, helps to further reduce wrinkles in the edge regions. For this purpose, a further extension 16 is provided next to the additional geometry 14 on the forming edge 1, wherein a special additional geometry, which in its cross section with the width 19 and the height 18 resemble a type of rounded shoulder, rim or bead, which is applied along the forming edge 1, in conjunction with the modified cross section 10 in the region of the forming edge 1 ensures a particularly wrinkle- and wrinkle-free forming of packaging materials made of paper.The invention is not limited to one of the above-described embodiments, but can be modified in many ways.All features and advantages which emerge from the claims and the description, including structural details, spatial arrangements and method steps, can be essential to the invention both individually and in a wide variety of combinations.List of reference characters1 Forming edge 2 Edge curve 3 Forming shoulder plate 4 Inlet edge 5 Rectangular cross section 6 Corner radii 7 Forming shoulder body 8 Curved region 9 Forming curve (apex) 10 Modified cross section 11 Outlet region 12 Transition region 13 Rectilinear region 14 Bead-shaped additional geometry 15 Rounding radius 16 Extension 17 Transition radius 18 Height (of the additional geometry) 19 Width of the additional geometry 20 Forming shoulder

Claims

Forming shoulder for forming rectangular tubular bag packages from paper, wherein the forming shoulder (20) has a forming shoulder plate (3) with a paper inlet edge (4), an outer boundary edge (2) and a forming edge (1), and a tube-like outlet region (11) with a rectangular cross section (5), characterized in that the flank of the rectangular cross section (10) facing the paper inlet edge (4) has an arcuate curvature (8) facing in the direction of the paper inlet edge (4) at least in the region of the forming edge (1).Forming shoulder according to claim 1, characterised in that the forming shoulder geometry has an additional geometry (14) at least in regions between the forming edge (1) and the boundary edge (2).Forming shoulder according to Claim 2, characterized in that the additional geometry (14) is of bead-shaped design and has an extension (16) in the region of the forming edge (1).Forming shoulder according to claim 2 or 3, characterised in that the additional geometry (14) and / or the extension (16) decrease at the forming edge towards the outlet region (11).Forming shoulder according to one of Claims 2 to 4, characterized in that the additional geometry (14) has a height (18) of 0.35 mm, preferably 0.5 mm or more.Forming shoulder according to one of Claims 2 to 5, characterized in that the rounding radius (15) of the additional geometry (14) is 0.4 mm, preferably 0.5 mm or more.Forming shoulder according to one of Claims 3 to 6, characterized in that the additional geometry (14) has a width (19) of at least 1 mm, preferably 1.5 mm or more.Forming shoulder according to claim 7, characterised in that the extension (16) has a height of up to 0.6 mm.Forming shoulder according to one of Claims 3 to 8, characterized in that the transition region between the additional geometry (14) and the extension (16) is formed in a rectilinear manner or with a transition radius.Forming shoulder according to one of Claims 3 to 9, characterized in that a transition radius (17) is provided between the extension (16) and the forming shoulder plate (3).Forming shoulder according to one of the preceding claims, characterized in that the edges forming the cross section (10) are formed slightly shortened in the region of the arcuate curvature (8), so that the cross-sectional circumference is not substantially enlarged at this point.Forming shoulder according to one of the preceding claims, characterized in that the arc-shaped curvature (8) decreases towards the outlet region or merges into a rectangular cross section (5) upstream of the outlet region (11).

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