The invention relates to a device for packaging comprising a forwardly transported foil web, two sealing jaws for welding of the foil web, whereby the shaped foil web is clamped between the sealing jaws and is welded in this manner, and the first sealing jaw can be moved toward the foil web, with the foil web and away from said foil web, and comprising a cutting device for cutting the welded foil web.
It is known in tubular bagging machines that two sealing jaws are moved toward one another in order to weld a tubular or lengthwise folded foil web transversely with respect to its transport direction. Such welded areas of the foil web can be filled and can be welded lengthwise with respect to the transport direction by means of a further welding device, or it is possible to create bag areas open on one side. The areas are cut off from the foil by means of the cutting device so that bags are created. These bags can be filled and welded bags, or empty bags open on one side.
Two sealing jaws of a vertical tubular bagging machine are known from EP 0 469 105, which sealing jaws rotate in opposite direction each about axes, and which each describe a D-shaped path, and which along the straight section of the path in a co-moving manner weld a continuously forwardly moved foil web transversely with respect to its transport direction in order to create in this manner a head seam of a bag and a bottom seam of a following bag in the longitudinally welded foil web. The foil web is cut between these seams.
Furthermore a horizontal tubular bagging machine is known, in which a foil web is folded lengthwise and along its centerline. The foil web is moved forwardly in cycles. Two vertically aligned sealing jaws are moved toward one another during each foil standstill in order to create during one welding operation a side seam of a bag and one side seam of a following bag. The foil web is cut between these side seams in order to separate a created bag from the foil web.
The known devices for packaging have the disadvantage that the mechanics for pressing the sealing jaws against one another is relatively complicated since both sealing jaws are moved away from the foil web and thereafter again toward said foil web. This mechanics is even more complicated when the sealing jaws are over stretches co-moved with the moved foil web in order to weld the foil web during the foil transport.
The basic purpose of the invention is to reduce in the above-described device the technical requirements for effecting a welding of a moving foil web.
The purpose is attained by supporting the second sealing jaw for a co-movement with the first sealing jaw, the path of co-movement extending coextensively with the foil web, and the second sealing jaw can be moved back against the transport direction of the foil web.
The device of the invention has the advantage that the technical requirement for welding a moving foil web is reduced since merely the first sealing jaw must be moved by means of a jaw drive and by a relatively uncomplicated set of mechanics initially along a sealing stretch with the foil web and must thereafter be removed from the foil web and returned into its initial position. The second sealing jaw is merely co-moved along the sealing stretch on a path synchronously with the first sealing jaw and hereby fulfills its purpose to apply together with the first sealing jaw a sealing pressure onto the foil and to bring heat into two foil areas which lie one on top of the other in order to weld these together. While the first sealing jaw is, at the end of the sealing stretch, removed from the foil web perpendicularly with respect to the transport direction and is thereafter again moved back toward the foil web into its original position in order to act there again against the foil web, the second sealing jaw is moved back by means of a simple set of mechanics against the transport direction of the foil web. Thus, while the first sealing jaw rotates in a plane, the second sealing jaw performs, for example, only a back and forth movement, whereby the latter is moved parallel with respect to the first sealing jaw during the sealing operation.
When the path extends parallel with respect to the transport direction, then the tension in the foil web is constant during the sealing operation. In addition a straight web can be realized in a simple manner. The second sealing jaw can extend on the centerline of the foil web. A welding of the foil takes place only when together with the first sealing jaw a sealing pressure is applied to the foil. However, in order not to influence the foil transport too much during the moving back of the second sealing jaw, a spacing is provided between the sealing surface of the second sealing jaw and the centerline, which spacing is preferably 1 to 4 mm. A good sealing result with a secure foil path is achieved with this spacing. A path can be defined by a rail, along which a carriage is moved, on which the second sealing jaw is fastened. The rail can be straight and can extend parallel to the centerline, however, it could also be curved or circular. In the case of a circular path, the second sealing jaw carries out a circular movement.
The second sealing jaw does not need a separate drive but is co-moved with the movement of the first sealing jaw when a carrier connection is provided between the sealing jaws, which connection takes along the second sealing jaw in correspondence with the movement of the first sealing jaw, which movement occurs in transport direction and opposite thereto. In principle only one carrier would be sufficient. The second sealing jaw could then be moved back into its initial position by means of spring force.
When the transport direction extends horizontally, then it is possible for the foil web to be folded along its centerline and to be sealed in this manner transversely with respect to the transport direction. It is hereby possible to place the second sealing jaw relatively close to the centerline without interfering with the foil pathway.
Relatively high packaging speeds can be achieved when the first sealing jaw rotates about an axis. Whereas if a circular path is not chosen for the first sealing jaw, but a D-shaped one, then a relatively long path with closed sealing jaws is available along the straight D-section in order to carry out a foil welding. A D-shaped circular path is achieved, for example, when the first sealing jaw rotates about two axes of rotation, which are arranged parallel to one another, by means of a four-bar mechanism, whereby the sealing surface is held parallel with respect to the transport direction during the sealing operation by said mechanism. The straight section of the D-shaped circular path is achieved by a cushioning of the first sealing jaw perpendicular with respect to the transport direction.
A relatively high packaging speed is in addition achieved by the first sealing jaw rotating continuously. A servomotor is used for this purpose and also for the purpose that the rotational speed of this sealing jaw must not be constant. The packaging speed is further increased when the first sealing jaw is moved back faster than the sealing jaws are moved during the welding operation.