RU2172248C2 - Method and device for welding foil - Google Patents

Abstract

FIELD: welding foil; making foil bags. SUBSTANCE: welding device includes foil transportation unit and welding unit provided with welding head which may be placed in at least three functional positions: welding position for welding foil, intermediate position at which welding head is kept at first preset distance from welding position and nonworking position at which welding head is kept at second preset distance which exceeds first preset distance; welding unit includes additionally first pneumatic device with whose help welding head may be shifted between and intermediate positions and second pneumatic device with whose help welding head and first pneumatic device may be shifted between intermediate and nonworking positions; both pneumatic devices are connected in series. Method of welding foil consists in positioning the welding head on foil and moving it to first distance and then to second (larger) distance when welding procedure is discontinued; then welding procedure is discontinued; then welding head is shifted between welding position and intermediate position with the aid first pneumatic device, after which welding head and first pneumatic device are shifted between intermediate position and working position by means of second pneumatic device. EFFECT: enhanced efficiency; protection of foil against burning and damage; optimization of welding time. 10 cl, 5 dwg

Description

 The invention relates to a welding device for welding foil, which contains means for supplying foil and welding means, including a welding head, and also to a method for welding foil.

 In a welding device for welding a foil, two or more foil strips are supplied to the welding means and there are welded together using a welding head, which is lowered onto the connected strips and transfers heat to the foil in the right places. The term welding or welding device in this text includes a hot bonding process in which a bonding material is placed between the foil tapes in order to connect them using heat.

 Such a welding process is used, for example, in the manufacture of foil bags, such as beverage bags. Two foil tapes are stacked on top of each other to form the side surfaces of the foil bag. Between them from the edge can be laid foil for the bottom of the package. The foil strips are welded together along two directly superimposed edges of the sides and along the third edge, where the bottom of the bag is usually located. The fourth edge is closed by welding after the foil bag is full.

 Known welding device for welding foil, in particular for the manufacture of foil bags containing means for transporting foil for feeding the welded foil and welding means having a welding head (DE 4331067 A1, 16.03.1995).

 There is also known a method of welding foil, in particular, in the manufacture of packages of foil, in which the welding head is lowered onto the foil for welding, and the welding head is removed from the foil during transportation of the foil further (DE 4331067 A1, 16.03.1995).

 In automated production, foil tapes are fed for welding, and after the welding process, they are torn so as to form separate products. Foil tapes are placed one on top of the other and held under the welding head, which is lowered, while passing a distance of several centimeters. After the head is pressed against the foil, it rises again and the foil tapes are transported further at a distance corresponding to one packet of foil before the welding head is again lowered onto the foil that has been moved further. To achieve high productivity, the welding head is constantly at a high temperature to prevent time-consuming heating and cooling processes. Therefore, it is necessary that in those functional states when the welding operation does not occur, the welding head is so far from the foil that the foil material does not overheat or burn out. Such a distance, for example, is required in cases where the entire welding device is stopped in order to eliminate the malfunction.

 However, in automated production, raising and lowering the welding head to a distance of several centimeters takes an undesirably long period of time with the productivity that is currently possible.

 The objective of the group of inventions is to create a welding device and method for welding foil, which allows you to quickly raise and lower the welding head, ensuring in each functional position that the foil material will not burn and will not be damaged, while optimizing the time during which the welding head remains in the welding and intermediate positions.

This technical result in a welding device for welding foil, in particular for the manufacture of foil bags containing means for transporting the foil for feeding the welded foil and welding means having a welding head, is achieved by the fact that the welding head can allow at least three of the following functional positions:
a) a welding position for performing a foil welding operation;
b) an intermediate position in which the welding head is at a first predetermined distance from the welding position, and
c) a non-working position in which the welding head is located from the welding position at a second predetermined distance that is greater than the first distance,
wherein the welding device further comprises in series connected a first pneumatic device with which the welding head can move between the welding position and the intermediate position, and a second pneumatic device with which the welding head and the first pneumatic device can move between the intermediate position and the idle position.

 The first functional position is the welding position for performing the foil welding operation. In this functional state, the welding head is located directly on the welded foil, thereby heating, or welding, or hot-gluing the foil in those places where the heated surface of the welding head is located. The second functional state is an intermediate position in which the welding head is at a first predetermined distance from the welding position. The welding head is in this intermediate position while the foil advances further by one welded article. The third functional position is the rest position or the inoperative position in which the welding head is removed from the welding position by a second predetermined distance that is greater than the first distance. The welding head is in this idle position to prevent overheating or burnout when the welding device does not transport the foil at a sufficient speed.

 Therefore, the welding device according to the invention provides a quick operation of raising and lowering the welding head moving between the welding and intermediate positions, so that such movement of the welding head will not lead to a loss of time during normal operation, even if the entire welding device is operating at high speed. In the event of a malfunction or at a low speed of the system as a whole, the welding head is in an inoperative position, which corresponds to a greater distance from the foil, so that the foil material will not be damaged by the hot welding head.

 The distance from the welding position to the idle position can be chosen so that damage to the foil material by the heat of the welding head, for example due to burnout, is significantly reduced. However, in the most preferred case, the distance between the inoperative and the welding positions is selected so that the foil material could not be damaged by the heat of the welding head. This ensures that regardless of the length of the break or slowdown of the welding device, the foil material cannot be damaged.

 Particularly preferably, an embodiment of the invention comprises a heat shield which, when inoperative, is placed between the hot welding head and the foil material. When using particularly temperature-sensitive foil materials, such an additional screen ensures that the foil material is not damaged by the heat of the welding head. Such a heat shield may, for example, comprise a rotatable shielding plate.

 Preferred values of the distance from the welding to the idle position are within a few centimeters. This distance is largely dependent on the foil material used, the welding temperature and the geometry of the welding tool used. Between the welding and intermediate positions, it is preferable to choose a distance of several millimeters. Such a short distance guarantees high speed due to the short lifting path.

 The welding head is moved between the intermediate position and the welding position by the first pneumatic device. Due to the short distance to be overcome, the pneumatic device requires only a very small amount of compressed air. The second pneumatic device is used to move the welding head together with the first pneumatic device to the inoperative position.

 The movement of the welding head and the drive connected to it can, for example, be initiated mechanically. Reliable operation is ensured by the control unit, by means of which the transport means is actuated to transport the foil further while the welding head is in an intermediate position.

 The above technical result in the method of welding the foil, in particular in the manufacture of packages of foil, in which the welding head is lowered onto the foil for welding, and the welding head is removed from the foil during further transportation of the foil, achieved by the fact that the welding head during transportation of the foil further removed from the foil by a first distance and the welding head is removed from the foil by a second, greater distance, when the foil welding operation is interrupted, while the welding head is moved between the welding strip position and the intermediate position using the first pneumatic device and move the welding head and the first pneumatic device between the intermediate position and the idle position using the second pneumatic device.

 The inventions are described in detail by way of example of a preferred embodiment and are illustrated by drawings, where in FIG. 1 schematically shows a general view of a device for welding a foil according to the invention; in FIG. 2 is a partial view of FIG. 1, showing welding means in the off position; in FIG. 3 is a partial view of FIG. 1, showing welding means in an intermediate position; in FIG. 4 is a partial view of FIG. 1, showing welding means in a welding position; in FIG. 5 shows a welded unclosed foil bag.

 An embodiment of the invention, which will be considered here, relates to a welding device for the production of foil bags, for example for drinks. Such a foil bag for beverages is shown in FIG. 5. The foil bag 32 contains two side walls of the foil and the bottom of the foil, formed as the base of the package on which it can be placed. A suitable material is, for example, laminated (multilayer) aluminum foil. The foil for the side walls and the foil for the bottom of the bag are welded together along the seams 33. In other cases, a hot gluing operation may be performed. The upper seam 34 is formed at the next processing point after the foil bag has been filled.

 In FIG. 1 is a schematic side view of a welding device made according to the invention and used to make foil bags. Positions 6 and 8 denote, respectively, the feeding drums for feeding the foil. Positions 10 and 12 indicate the appropriate tensioning devices, which ensure sufficient tension of the foil 2, 4. Positions 14 and 16 indicate the deflection rollers, while position 18 denotes the means of drawing of the welded foil 30. Such means of drawing can, for example, be formed by drive rolls which transport the foil further due to frictional gripping. 36 denotes welding means comprising a first pneumatic device 26 acting on a welding head 24 and a second pneumatic device 28 acting on a first pneumatic device. The movement of the welding head 24, which is caused by the pneumatic device 26, is shown by arrow 25, while the movement of the first pneumatic device 26, which is called by the pneumatic device 28, is shown by arrow 27. The control unit 38 controls the movement of the pneumatic devices 26 and 28 and the pulling rolls 18. The movement of the welded foil 30 is shown by arrow 22.

 In FIG. 2 shows a detailed view of the welding means 36 in the idle position. The distance from the foil to the welding head 24 is denoted by "x", "A" and "B" denote the distance from the second pneumatic device 28 to the first pneumatic device 26 and the distance from the first pneumatic device 26 to the welding head 24, respectively.

 FIG. 3 shows the same welding means in an intermediate position. The distance to the welding head 24 is indicated as "y", with "y" being less than "x". “C” denotes the distance from the second pneumatic device 28 to the first pneumatic device 26, wherein “C” is greater than “A” by the same amount by which “x” is greater than “y”.

 FIG. 4 shows the same means of welding in a welding position. The welding head 24 is located directly on the foil. The foil tapes 2 and 4 and the welded foil 30 are respectively located on the support 20. The distance from the pneumatic device 26 to the welding head 24 is “D”, and the distance “D” is greater than the distance “B” by which the welding head 24 is removed from the first pneumatic device 26 in an intermediate or inoperative position.

 The method according to the invention is described by the example of the operation of the welding device discussed above. Foil tapes 2 and 4 come from feed drums 6 and 8, the required tension is maintained by a method that is not related to the present invention, for example, by means of spring tensioning devices 10 and 12. Deflecting rollers 14 and 16 combine the foil tapes. The welded foil tapes 2 and 4 are moved with stops using the pulling rollers 18. The distance covered in one cycle corresponds to the width of the foil bag 32. During the movement of the foil strips 2, 4 and the welded foil 30, respectively, in the direction 22, the welding head 24 is located at a distance "y" from the foil (Fig. 3). As soon as the rotation of the rolls 18 is stopped by the control unit 38, the control unit 38 transmits a signal to the first pneumatic device 26, after which the distance from this pneumatic device 26 to the welding head 24 increases from “B” to “D” (Fig. 4). The welding head 24 is now in direct contact with the welded foil strips 2, 4 and presses them against the support 20. The head is made in a known manner so that it has sufficiently heated sections that cause the foil to be welded along the required seams. These seams later form the side edges 33, as well as the bottom edges of the bag in the case of the foil bag shown in FIG. 5.

 After the welding operation along the desired seams has been completed, and the time interval necessary for this has been determined in advance, the control unit 38 transmits a signal to the first pneumatic device 26 for raising the welding head 24, so that the distance from the pneumatic device 26 to the welding head 24 again becomes equals "B". The welding head 24 is again in an intermediate position. At the same time, the control unit 38 transmits a signal to the pulling rolls 18 in order to advance the foil further by one product, for example, the width of the foil bag 32. When this movement is completed, the control unit 38 transmits a stop signal to the rolls 18 and a signal to the pneumatic device 26 to increase again the distance from the pneumatic device 26 to the welding head 24 from “B” to “D”. When these processes are repeated, the work with stops is obtained, which allows to obtain high productivity, since the welding head 24 requires moving only a short distance, of the order of several millimeters. In addition, the small height "y" that must be overcome requires only a small amount of compressed air to operate the pneumatic device 26.

 It may be necessary for various reasons to interrupt the operation of the entire welding device. Such an interruption is required, for example, during maintenance, during device inspection or during troubleshooting. During this period, it is not always necessary that the heating of the welding head 24 is turned off. This would be disadvantageous in terms of saving energy and time, since re-heating the welding head requires a large amount of energy and takes a lot of time. However, while the foil transport means is at rest, there is a risk that the foil material may be overheated by the hot welding head.

 To avoid possible damage to the foil material, the control unit 38 transmits a signal to the second pneumatic device 28 when the operation of the entire welding device is interrupted. Such a signal can, for example, be sent directly when the operator stops transporting the foil, or can be sent automatically when the transport of foil stops for a predetermined period of time.

 The signal sent to the second pneumatic device 28 causes a decrease in the distance from the second pneumatic device 28 to the first pneumatic device 26 from "C" to "A" (Fig. 2). The distance "x" from the foil 2, 4 and 30 to the welding head 24 thereby increases accordingly, for example, by several centimeters. As a result, damage to the foil material by the heat of the welding head 24 is eliminated.

 In cases where the temperature-sensitive foil material is processed, it is possible to further install a protective plate that is placed between the welding head and the foil material at the same time that the second pneumatic device 28 is activated to protect the foil material from the heat of the hot welding head 24 .When the welding head 24 is again lowered from its idle position, the protective plate is removed.

 In the present embodiment, the foil tapes 2 and 4 are used to form the side walls of the foil pouch 32. For clarity, FIG. 1 and 2, a third foil feeder is not shown for the bottom of the bag, which is placed between the foil strips 2 and 4 and simultaneously welded with a welding device 36.

 The device according to this invention can be used not only with respect to foil bags as described above, but also for processing foil bags in which the side walls are directly welded to each other without additional foil for the bottom of the bag. A third foil feeder is then not necessary.

 A device for directly welding foil tapes to each other has been described above. By selecting the appropriate binder material, it is also possible to perform hot bonding or hot welding using welding means 36.

 The control unit 38 may be configured such that the inoperative position of FIG. 2 may occur not only in cases when foil transportation is interrupted. Preferably, the control unit 38 may be configured such that when selecting a low speed of the pulling rolls 18, the welding head 24 does not allow an intermediate position during transport of the foil further, but allows the inoperative position shown in FIG. 2. In this case, the control unit may be equipped with an input device with which the operator can set the minimum speed at which an intermediate position is allowed according to FIG. 3, and not the inoperative position of FIG. 2, while the foil is transported further.

 Welding means 36 in the above-described embodiment of the inventions sets the various positions of the welding head using two pneumatic devices connected in series.

Claims (10)

 1. A welding device for welding foil, in particular for the manufacture of foil bags, containing means for transporting the foil for feeding the welded foil and welding means having a welding head, characterized in that the welding head can allow at least three of the following functional positions: a) a welding position for performing a foil welding operation; b) an intermediate position in which the welding head is at a first predetermined distance from the welding position, and c) an inoperative position in which the welding head is from the welding position at a second predetermined distance that is greater than the first predetermined distance, wherein the welding device further comprises a first pneumatic device connected in series with which the welding head can be moved between the welding position and the intermediate position and a second pneumatic device with which the welding head and the first pneumatic device can be moved between the intermediate position and the idle position.  2. The welding device according to claim 1, characterized in that the second predetermined distance is large enough so that the foil material cannot be damaged by the heat of the welding head.  3. The welding device according to claim 1 or 2, characterized in that it comprises a heat shield, which in the idle position can be placed between the welding head and the foil.  4. The welding device according to claim 3, characterized in that the heat shield comprises a rotatable shielding plate.  5. A welding device according to any one of claims 1 to 4, characterized in that the second predetermined distance is several centimeters.  6. A welding device according to any one of claims 1 to 5, characterized in that the first predetermined distance is several millimeters.  7. A welding device according to any one of claims 1 to 6, characterized in that an intermediate position is allowed when the welded foil is transported further.  8. The welding device according to any one of claims 1 to 7, characterized in that the inoperative position is allowed when the welding device is interrupted.  9. The welding device according to any one of claims 1 to 8, characterized in that it comprises a control unit that drives transport means for transporting the welded foil further while the welding head is in an intermediate position.  10. A method of welding a foil, in particular in the manufacture of foil bags, in which the welding head is lowered onto the foil to weld it, the welding head being further removed from the foil during transportation of the foil, characterized in that the welding head is further removed during transportation of the foil from the foil to the first distance and the welding head is removed from the foil to a second, greater distance when the welding operation is interrupted, while moving the welding head between the welding position and the intermediate position using the first pneumatic device and move the welding head and the first pneumatic device between the intermediate position and the idle position using the second pneumatic device.

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