DE1157764B - Device for the continuous welding of plastic foils - Google Patents

Description

Bags, storage bags and containers made of plastic films are known to be used by Welding the open end closed. Here one works either according to the heat pulse method, with high-frequency electricity or with hot air. Difficulties arise here when the too Closing parts have heavily dusted inner surfaces, as it is extremely difficult to get dusty Parts, e.g. B. sacks, at a speed customary in the bulk goods industry to weld.

This is especially true when the parts to be closed are made of polyethylene, especially this plastic cannot be welded with high frequency. In contrast to polyvinyl chloride with a dielectric constant of 4 and a heat factor of 0.25 show the corresponding Values for polyethylene of 2.3 and 0.001 indicate that this plastic is insufficient in the high-frequency field can be heated highly. The sealing machines built for films made of polyethylene work therefore mostly according to the heat pulse method.

These devices work discontinuously and are therefore unsuitable for assembly line operation. she are designed as pliers devices, with only one jaw of the pliers a plastic-covered heating wire wearing. Under the pressure of the closed pliers, a current surge briefly heats the wire and with it the film up to the melting point, in order to cool down immediately afterwards. This is the only way to achieve it that the foil separates from the heating wire when the pliers are opened.

When using two heating wires in a clamp device, there is a risk that the heated one Foil is squeezed through under pressure. For this reason, devices with only one heating wire are used. The melted film then, so to speak, partially dissolves the opposite film. At high Working speeds and thick foils is sufficient for a quick transition Amount of heat a two-sided heating is more advantageous, especially since the welding is a heating the inner surfaces, so requires a thorough melting process for the entire thickness of the film. This continuous softening on both sides is also necessary when In the case of dusty filling goods, a fine dust deposit like an insulating layer between those facing each other Sides of the slides. Machines are known in which one instead of the heating tape Metal roller is installed, which presses over a spring-loaded roller made of heat-resistant rubber.

Device for continuous
Welding of plastic foils

Applicant:

Aniline & Soda Factory in Baden

Corporation,

Ludwigshafen / Rhine

Dr. Horst Rosewicz, Ludwigshafen / Rhine,

and Dr. Gernot Manhart, Limburgerhof (Palatinate),

have been named as inventors

These devices work continuously, but because they work on the same principle as the Pliers work, all other mentioned disadvantages of these machines.

In addition, the weldable film thickness and speed are limited because of high speed The heat transfer takes place very quickly during the welding process or, if the film is thick, a lot Heat per surface area must be supplied. This is only due to a high heat transfer coefficient, d. H. to reach a high temperature of the metal tubes. This must protect against sticking Softened foils are constantly moistened with silicone oil, but only up to a certain temperature helps. Since only one film is melted onto the colder opposite side, the closure is secure low with dusty foils.

A device for heat sealing the longitudinal seams of webs made of plastic film is known or paper equipped with a heat-sealable coating. The heat-sealed seams form outwardly protruding edge strips and are carried out in a known manner Hot air heated. The hot air is sent to the two opposite one another to be welded Outside of the tube edge strips brought up in channels. The hot air causes the outer, with the heat-seal coating provided edge strips, while at the same time the inner Area portions of the strips next to the heated zones are cooled by means of air. After that will be the heated edge strips are pressed together with pressure rollers and finally cooled in cooling zones.

309 749/382

When heating heat-sealable coatings, it is therefore sufficient to leave the latter in liquid or liquid form. To make it glued, while the backing made of paper or plastic is still stiff and undeformed remains so that no difficulties arise from the softening of the entire seam can.

It was the object of the present invention to provide a device for continuous welding

solved in that the compressed air takes over the contact pressure necessary for welding.

On the other hand, cooling of the surfaces next to the seams to be heated is not necessary because the 5 on both sides next to the seam, cover the unheated parts of the surface and the steel belts themselves are cooled.

A particular advantage of the device according to the invention is the possibility of the seam next to of plastic films, in particular of Polyäthylen- io to put the outer edge without the film in the Bags of greater wall thickness, to be de-heated by means of hot air or when the seam wraps soften. The device according to the invention is instead collapsed. The superimposed characterized in that in a two-part pairs of steel bands hold the film on both sides for this purpose Frame, the moving part of which is fixed by a hinge of the seam, regardless of whether and a locking lever with the immovable part 15 this remains rigid or softens, ■ connected and by one in a groove of the un- The progressiveness of the invention

Movable part coming to the plant profile strip device is particularly to be seen in the fact that is positively secured against shifting, four it enables it, continuously and automatically to be welded horizontally in pairs in one of the foils of greater wall thickness. at The device can disrupt the weld seam width in a very short time Other lying, switched off by a motor via toothed and bevel gears by shutting off the air supply driven and mutually pressed steel belts, without being affected by subsequent heat such as two heated air preheaters with pipe connections on the Gezur working with heated metal parts Heating the rates necessary for welding, overheating under the heating device Compressed air, two motor-driven seams stuck in one level 25 can come, rotating, in the two gaps between the The amount of heat required for welding

Ribbons for mutual resilient pressure is achieved by heated compressed air on both sides from the outside extending plastic rollers and in a known manner by two opposing, slightly two fixed, on both sides of the ribbons spaced above the film with smaller the respective gaps between each two 30 opening transmitted. The amount of air necessary for welding, one above the other at the weld seam level, has such a speed that the wide flat nozzles attached at a short distance in front of the foils correspond to the width of the weld seam
Openings are arranged.

The steel strips will come into contact with the jaw or roller by resilient means. A pressing devices to compensate for lengthwise sticking of the heated film to the heat transfer medium

so is impossible.

The largely doughy mass is subsequently compressed by compressed air 40 pressed together by ribbed wheels. For this it is necessary to also use the outer foil parts to cool, which are therefore stronger than the inner layers.

To avoid pinching the seam,

Foil parts from the revolving steel belts are grounded by the resiliently mounted, ribbed wheels and transported under mutual pressure to the treatment stations following each other, not during the melting process,
where they first by means of heated compressed air to the
Seam heated and by the pressure of the compressed air
are welded together. During the subsequent, second, stronger pressure through a solid component, which is transported further through room air, the seams that are now frozen on the outside but still inside are briefly cooled from the outside and mutually soft and malleable seams are exerted on the other, mechanically pressed in such a way that the possibly still unconnected Seam parts completely
weld together. Finally, the 55 of plastic foils are described (Fig. 1 and 2). Foil parts in the welded state at the end of the This device consists of a two-part

ejected circumferential steel belts. Frame consisting of a fixed rear part 1

Difficulties can arise when welding in front of and a movable front part 2 together therefore arise because the outer layers are set. The movable part 2 is in a coulter Seam due to its low thermal conductivity 60 nier 3 rotatably arranged. In each of the two parts become much hotter or rather soften than those of the frame are three vertical axes 4 to 6 resp. inner parts that are welded together 7 to 9 are arranged. The outer axes 4, 6, 7 and 9 should. If the horizontally running metal disks 14, 16, 17 are then pressed after they have softened This creates the joint and 19. The metal disks have on the outer outside softer parts as a result of their smaller 65 catch two by a raised web 10 (Fig. 2) of strength easily squeezed, and the wells 11 and 12, which are separated by each other anyway The seam, which is disturbed by internal stresses, becomes four smooth steel strips 21 to 24, which are over-weakened in pairs. According to the invention, this difficulty is arranged, sustained and guided by one another. the

Pressure of the exiting compressed air connects the two parts to be welded without softening them Parts with a solid, act as a pressure body

differentiated excited.

To prevent the continuously rotating steel belts from getting too hot, are on both sides the steel belts arranged cooling devices.

The device according to the invention solves the problem of making plastic films continuously thereby to weld so that the heat can be brought in from outside. For this purpose, the to be welded

which is only then pressed against the seam on both sides. So besides the somewhat resilient pressure the compressed air in the softening zone

In the drawing, for example, the device according to the invention for continuous welding

middle axes 5 and 8 each carry a pressure roller 13 and 15 made of plastic. The belts are moved by a motor 25 which is driven by a gearbox 26 and a bevel gear pair 27, 28 drives the axle 4. From a pulley attached to this axle 29 is the axis 5 via a V-belt 30 and a pulley 31, also via a Gear pair 32, 33 the axis 7 driven. On it there is a pulley 34, which over a V-belt 35 drives the pulley 36 on the axis 8. In this way, the Metal disks 14, 16, 17 and 19 drive the steel belts 21 to 24 evenly.

The four endless steel belts transport and guide the parts to be welded Parts. The one to be welded lies between the two bands that lie one above the other Seam of the foils. Two wide-angle nozzles 37 and 38 are attached at the same height. The nozzles are lying opposite each other. Through them, the heated compressed air jet is perpendicular to the seam connecting parts out. The pressure of the compressed air is 0.5 to 1 atm, depending on the thickness of the foils, the working speed 12 to 30 m / min. The steel belts are after passing through the hot air zone cooled by resiliently pressed metal jaws 39 and 40 through which water flows.

The compressed air is supplied to the two via a pipe 18, a control valve 41 and a pressure gauge 42 adjustable air heaters 43 and 44 passed and heated here to the required temperature. The heating power an air heater is about 1.5 to 2.5 kW.

About 20 cm behind the compressed air nozzles, seen in the running direction of the belts, are the resilient, profiled pressure rollers 13 and 15. There are four tension rollers to tension the four steel belts attached to both parts of the frame, of which only two 45, 46 are shown. This allows the individual belts are tensioned independently and evenly. Through one in a groove of the Fixed frame part coming to the plant profiled strip 20 of the movable frame part is this non-positively secured against shifting. Both frame parts are closed by means of a locking lever 47 set.

The mode of operation of the device is as follows: The parts to be welded are in front of the two Metal disks 16 and 19 abandoned, captured by the four bands 21 to 24 and pressed together and transported to the two wide flat nozzles 37, 38. The heated compressed air supplied here flows on both sides against the seam and heats it until it softens, causing the ligaments to shift the part of the film lying above the softening point. At the same time, the to be welded, exposed parts pressed together. Should the weld occur as a result of intervening If dust particles are imperfect, the weld seam will continue on its way through the Device firmly pressed together by the two pressure rollers 13 and 15 and thus finally welded. The welded parts are finally removed from the conveyor belts that run to the end of the machine promoted near the hinge and ejected here.

Claims (3)

Patent claims: 1. Device for the continuous welding of plastic films, in particular of polyethylene bags of greater wall thickness, by means of hot air, characterized in that in a two-part frame, the movable part (2) by a hinge (3) and a locking lever (47) with connected to the immovable part (1) and secured against displacement by a profile strip (20) coming into contact in a groove of the immovable part (1), four horizontally running, in pairs, one on top of the other at a distance corresponding to the weld seam width, endless, over tooth and bevel gears (27, 28, 32, 33) motor-driven and mutually pressed steel belts (21 to 24), two heated air preheaters (43, 44) with pipe connections for heating the compressed air required for welding, two motor-driven, in one plane rotating plastic rollers ( 13, 15) and, in a known manner, two fixed flat nozzles attached to both sides of the belts (21 to 24) in the respective gaps between the two superimposed belts (21, 22 and 23, 24) at the weld seam level at a small distance in front of the foils (37, 38) are arranged with openings corresponding to the weld seam width. 2. Apparatus according to claim 1, characterized in that the steel strips (21 to 24) tensioned by resiliently pressing devices (45, 46) to compensate for differences in length will. 3. Apparatus according to claim 1, characterized in that on both sides of the steel strips Cooling devices (39) are arranged. Considered publications:
German utility model No. 1798 438. 1 sheet of drawings © 309 749/382 11.63