FI77812B - FOGNINGSANLAEGGNING, FOERFARANDE FOER FOGNING OCH FOGBALK FOER SAECKAR. - Google Patents

Description

The present invention relates to the manufacture of plastic bags in which the bags are formed from a tubular web by heat sealing. In particular, the invention relates to the sealing of the corners of a sack.

5 The term plastic bag is used herein to mean all kinds of bags or sacks for packaging made of heat-sealable plastics.

Plastic bags are normally made from a tubular web by heat-sealing the hose at a desired location across the web 10 and cutting the web next to the seam thus made.

The result is a rectangular sack that is closed on three sides and open on one side, from the mouth of the sack.

When filling the above-mentioned sack with the material to be packed, especially when strong plastics are used, due to the geometry of the ra-15 field, sharp, protruding corners, the so-called "Ears". These sharp corners are harmful. For example, they tend to break the stretch film commonly used to tie stacks stacked on a pallet. To eliminate said disadvantage, triangular areas are separated from the corners of the base by sau-20. The substance to be packaged is thus unable to fill and stiffen the corners of the base and form said harmful "ears".

Efficient sealing machines have transverse grooving beams along the track for a certain distance, with 25 resistance wires or similar members required for heat sealing. However, current machines only provide straight seams. Therefore, the sealing of the corners must be performed with a separate, stationary sealing member. The web must thus be stopped during the sealing of the corners, which significantly slows down the process.

It is an object of the present invention to provide a sack sealing apparatus in which both the bottom and the corners of the bottom can be sealed without stopping the web.

The apparatus of the present invention comprises a sealing beam 35 movable with the track, with resistance wires or similar members stretched obliquely over the beam at the edges of the track, by means of which corner seams are formed when the beam is pressed against the track for the required time.

2 77812

In particular, a sealing beam is used which has a single resistance wire for forming both corners, which is suitably tensioned obliquely at the corner seams and isolated in the area between them from contact with the track. Preferably, the insulation is performed by placing a resistance wire in the distance between the corners to run inside the beam off the surface.

The resistance wires required for corner sealing are best placed in the same beam as the resistance wire forming the bottom seam. However, if desired, the resistance wires can also be placed in different beams.

Compared to the equipment currently in use, the equipment now invented is faster because the track does not have to be stopped during the sealing of the corners.

Some embodiments of the invention are described in more detail below. In the drawings included in the description, Fig. 1 shows in a simplified manner the entire sealing apparatus and Fig. 2 shows the various sealing beams used in the apparatus, and Fig. 3 shows the finished sealed sack.

With the apparatus according to Figure 1, transverse seams 2 are formed in the tubular heat-sealable plastic track I. The track is then cut across in front of each transverse seam to obtain the sacks according to Figure 3.

To form the transverse seam 2, the apparatus has a rod; a spice beam 3 with a transverse tensioned resistance wire 4 so that the wire presses against the surface of the track. For the sake of clarity, only one sealing beam is drawn in Figure 1, but in practice there are always several. The required counter-beam is also not drawn in the figure. The sealing beams are attached at their ends to chains 5 that rotate indefinitely. The chains are driven in the same direction and at the same speed as the track. The resistance wire of the beam is in contact with the track for such a long time that a seam 2 is formed.

• * _ The sealing beam also has an angle-sealing resistance wire 6. Its ends are tensioned obliquely to the surface of the beam so that when they press against the track, corner seams 7 are formed behind the transverse seam (relative to the direction of travel) separating triangular areas from the bottom corners of the sack. The part between the sealing parts of the corner seam wire is taken inside the beam, so 3 77812 it is not able to make unnecessary seams on the track. Both wires have a spring that compensates for thermal expansion.

The corner seams 7 necessary to prevent the formation of sharp corners are provided by the devices without adjusting the path py-5. If corner seams are not required, only the cross-joint wire 4 can be heated.

Alternatively, the cross-sealing wire 4 'and the corner-sealing wire 6' can also be placed in different beams, as in the beams 31 and 32 of Fig. 2. In principle, these beams can also be placed in different equipment, whereby the track is run successively through both.

If desired, devices for diagonally sealing the corners of the mouth part of the sack can, of course, also be placed in the apparatus.

Claims (7)

1. A plastic bag sealing system, by means of which a joint is formed in a hose-like hot-sealable web, and in which the system at least one, a certain distance with the web following, printed against its surface, joints on which one surface is at least one facing the web pressurizing heated joints or a corresponding means, characterized in that the joints or part of it is placed on the joints (3/32) at the edge of the web as an obliquely angular joints (6) directed over the web, the joints of which are substantially shorter than the width of the web. Plant according to claim 1, characterized in that the plant has a corner joining tree (6) at each edge of the web. i15 3. Plant according to claim 2, characterized in that the corner jointing trees consist of a tree (6) which is isolated from the web in the area between its joining parts. Installation according to claim 3, characterized in that the corner jointing trees (6) in the area between each joint; y; 20 parts were isolated from the web by placing the insulated part of the trees into the beam (3/32). Installation according to any one of claims 1 to 4, characterized in that the joint beam (3) also has at least the same length of cross-jointing tree (4) as the angular position of the web. "25 to the direction of travel of the web, thus, that the cross-joining trees ·; * [· 'are placed immediately next to the inner end of the joining portion of the corner-joining tree (6). 6. A method of joining plastic bags, in which a joint is formed in a hose-like web of hot-insertable plastic so that, at least one, a certain amount of pressure is pressed against the surface of the web. seam beam, on the surface of which there is at least one bonding tree pressing against the web or a corresponding means, and heated the seaming trees while being pressed against the surface of the web, characterized in that a seaming tree in the seam beam (3/32) is used. tree (6), which is substantially shorter than the width of the runway and which is pushed towards the runway starting from the runner obliquely in the crosswise direction of the runway.