Method for making bags of thermoplastic material.

The invention relates to a method for the manufacture of bags made of thermoplastic material, in which, from a plastic film web by turning of the side parts and the adhesive bonding of the edge regions overlapping each other by a longitudinal seam, a tubular web is formed and separated from the tubular web hose pieces, which the bottomed welds and by filling are provided with head welds.

The blind tube pieces can be provided prior to the attachment of the transverse bottom welds with gussets. Existence of the bags of plastic, so there is the danger of being damaged because the bag walls forming plastic sheets are very susceptible to cracking and the bags are usually subjected to rough handling during loading, transporting and storage. By the turning of the bags resulting damage filling losses up to 50% can occur.

Further bags are known which consist of tubular pieces of a fabric of stretched plastic strips. Such bags have high strength so that they are not damaged even with rough handling and impacts with sharp objects. but made from plastic woven materials bags have the drawback that they can be welded poorly, so that the production of the top and bottom seams considerable difficulties.

The object of the invention is therefore to propose a method of the type described, according to which high-strength sacks can be produced which can be provided with bottom and top welds in a simple manner.

According to the invention this object is achieved by the fact that between two converging plastic foil web pieces of a fabric of stretched plastic strips, which are shorter than the distance of the subsequent bottom and top welds on the flattened sacks are introduced with a mutual distance of the area of ​​the posterior ground bridges and head welds that the webs and the tissue web pieces laterally offset merged and the exposed margins of the webs and tissue web pieces are provided with hot glue orders so that they stick together overlapping margins during the subsequent tube formation, each with its opposite, the hot adhesive applications, and that of the - tubular sheet approximately centrally separating the pieces of tubing between the tissue web pieces and those detected with only the plastic tubing spans transverse bottom welds are provided. Sacks produced by the inventive process thus have three-layered walls, which are formed by the outer and inner plastic sheets which enclose the reinforcing fabric sheet pieces between them. The forming the bag walls composite film has a high density and moreover a high strength because the tissue web pieces are largely insensitive to injury and rißunempfindlich. Since the tissue web pieces are outside the bottom and top welds, these can be easily affixes_D,

The main loads of traps occur in the area of ​​the side walls, which are reinforced by the tissue web pieces, so that an appreciable weakening thus does not occur, that the tissue web pieces each end before the guided through only by the film web sections Floor and Kopfquerschweißnäb.ten.

Sacks produced by the novel process are planning for their filling and after attaching the head welds stand high loads. They are not damaged even at a multiple folding during transport and storage. These bags are not only resistant to cracking, but also against bites, because the ribbon fabric inserts have a tendency to contract again after the penetration of sharp objects.

Appropriately, is provided before the convergence of the plastic film webs one of those multi-spaced parallel adjacent strips of heat sealable adhesive.

This hot glue strip the ribbon fabric inserts with the respective film web are joined. In the regions between the individual woven fabric pieces the Heißklebstoffäufträge adhere the tissue web pieces enclosing sheets together, so that they are sufficiently firmly fixed to each other.

In a further embodiment, it is provided that the length of the tissue web pieces to the height of the side walls of the filled bags corresponds. This configuration is particularly useful in big bags with a capacity of 1 up to 2 tons, as these units of fabric pieces also make up the side walls stiffening lower thirds. Marked with the cross welds ground and head areas make less loaded booths in such bags.

The two-ply tubular film produced by the novel process with the tissue web pieces may be wound to transport rollers are separated from the before filling each bag tube pieces. To substantially cylindrical winding to - get to the edge regions of the flexible tubular web prior to winding: strip of material, such as plastic film, should be drawn up to compensate for the height of the seams formed by the overlap.

In the two-ply provided with the tissue web pieces tubular sheet can be inserted for the production of gusseted bags gussets. Since the gussets compensate for the height of the longitudinal seams and overlaps, a gusseted tubular web without mitgewickelte strips can be wound into cylindrical rolls.

An embodiment of the invention will be explained hereinafter with reference to the drawing. This shows<ul><li>Fig. 1, making a trilayer sheet material,</li><li>Fig. 2 is a plan view in the direction of the arrow II of FIG. 1,</li><li>Fig. 3 is a section through the web along the line III-III of Fig. 1,</li><li>Fig. 4 in perspective a section of tubing made of the inventive three-layer material,</li><li>Fig. 5 a filled bag,</li><li>Fig. 6 in FIG. 5 bag according to the line VI-VI in the section represented and</li><li>Fig. 7 a filled bulk bag in a perspective view, which is not yet closed.</li></ul>

From the film rolls 1 and 2 is continuously drawn off the webs 3 and 4. FIG. spaced apart pieces of fabric 5 are inserted between these two lanes 3 and 4, which are cut from a drawn off from a roll 6 track 7 cyclically. As FIG. 2 shows the individual layers 3, 4 and 5 are offset from each other. About a Leimauftragsaggregat 8 continuous strips are applied 9 of hot melt adhesive, on the one hand, the tissue pieces 5 do not abut one another by, each also connected. From the three-layer flat sheet shown in Figure 2, the formed via a folding device 10 in Figure 3 in cross-section to be recognized hose then. The glue strips required for connecting 11 (Fig. 3) are applied by the hot melt application module 12. The hose 13 is then brought forward by the drawing rollers 14 and further, if necessary, divided by a cutter 15 into individual tube pieces or wound after shutting down the cutter 15 into a roll 16th For this purpose a switch 17 is provided behind the cutting device 15, which is constructed in a known manner. Depending on the intended use, it may be necessary, after the drawing rollers 14 and upstream of the switch 17 to provide a gusseted device, so that the tube then has a cross section which is apparent from Fig. 4. then tube pieces are separated according to FIG. 4 from a gusseted tube, wherein the longitudinal seam is not shown in Fig. 4.

This figure 4 shows that the middle layer 5 is shorter than the other two layers 3 and 4. Although only shown one end of a tube section, then at the other end, the position 5 towards the other layers 3 and 4 is reset , The measure of this offset is denoted by X. An educated from such a piece of hose bag is 5 and 6 shown in Figs.. In particular, from FIG. 6, it can be seen here that the inner layer 5 is not detected from fabric material of the welds 18 and 19. The inner layer 5 is in fact, characterized as in Fig. 4, both ends to that dimension X is shorter than the outer fabric layers 4. A so trained bag may be achieved firstly weld very well and keeps the other mechanical loads extremely well stood. Such bags have a capacity of about 25 to 50 kilos. In them fertilizer is packaged, for example.

The FIG. 7 shows, in contrast to FIG. 5 a large bag with a capacity of 1 up to 2 tons. In this bag, the fabric material 5 extends only over the filling level 20, whereas the required soil formation material is the same as the material needed to close the big bag formed from only two superimposed webs 3 and 4. FIG. The FIG. 2 denoted by Y distance between two pieces of fabric 5 must therefore be large in the manufacture of the bag material to each other, that the two film webs 3 and 4, a tissue piece 5 at both project beyond the extent that there is sufficient material for soil formation (in Fig. 7 already formed) and enough material to necessary to specify the filled big bag of soil remains.