Package making – Wrapping machines – Cover-wiping passage or pocket for initial wrap
Reexamination Certificate
2000-09-11
2003-04-08
Kim, Eugene (Department: 3721)
Package making
Wrapping machines
Cover-wiping passage or pocket for initial wrap
C053S373600, C053S373700
Reexamination Certificate
active
06543202
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a device for welding two films, with a heated sealing or welding arrangement cooperating with an opposed tool, the films being arranged between the sealing or welding arrangement and the opposed tool and the sealing or welding arrangement and the opposed tool being movable relative to each other.
Devices of the above-mentioned type are known. The sealing or welding arrangement is usually moved upwardly from below while the opposed tool is moved downwardly from above and, in particular, is integrated into the arrangements which are required for forming loops.
It is pointed out that it is of lesser importance for the device just described, and for the invention, whether the arrangement which joins the ends of the films is formed as a sealing arrangement or as a welding arrangement, so that in this context the one procedure or configuration is entirely interchangeable with the other procedure or configuration.
It is also inessential to the application of the invention whether the device is used for welding two films or two film ends, or both ends of one film, and so on. It is also possible, using the device, to weld together both ends of two areas of the same film, for example, to form a hose or similar part, in order to benefit from the effect according to the invention, and this can apply, for example, to pieces of film as understood in accordance with the invention. It is also possible according to the invention to weld together more than two films or pieces of films.
In the known devices the sealing or welding device comprises a heating blade the upper edge of which has a wedge-like configuration. This heating blade has the function of severing the films as it makes contact with them and at the same time of welding together the film ends produced by the severing action. In this process the film ends forming the loop are firstly to be welded together, so that an endless form is produced. Secondly, the film ends fed from above and below are to be re-connected after separation of the loop, so that a curtain is produced and the work cycle can be repeated. Such devices as those described at the outset are known, for example, in bandolier machines.
For welding of PE films, temperatures of approximately 250° C. are usually necessary. The heating blade or heating mirror is either permanently heated or intermittent heating of these arrangements for short periods is provided, in which case the relatively large mass of the heating blade entails a corresponding thermal inertia. For this reason the sealing process requires a certain time.
In known devices, an interval of about 0.5 sec. is required for sealing, half of this time being needed for heating and the other half for cooling, and in particular for bonding the film ends.
For example, if a bandolier machine of the type in question executes 35 work cycles per minute, a time of 1.71 sec. is available for one work cycle. The time interval required for the complete welding process therefore accounts for about one-third of the total time.
Furthermore, the heating blade used in such machines is a source of danger or injury, as it is usually heated to a temperature of more than 200° C.
In the known machine the heating blade, as already described, is moved upwardly from below during the work process. In the upper part of the movement the blade acts on the films. The not inconsiderable mass of the heating blade and the associated arrangements requires a sufficiently powerful drive system to which the corresponding machine parts must be adapted. In addition, means for aligning or fixing the films one above the other are necessary in the known machines. For this purpose suitable tensioning elements or clamping devices are used, the operation of which must be incorporated in the periodically-occurring welding procedure, which operation, of course, takes time. Furthermore, the use of these additional elements is correspondingly expensive and also requires additional space, which is difficult to provide, especially because the welded seam, for example, on a ready-packed product, must be arranged as close as possible to the product.
BRIEF SUMMARY OF THE INVENTION
It is an object of the present invention to provide an improved device for welding films/pieces of film of the type described above in which the above disadvantages are reduced or substantially obviated. It is a further object to provide a device in which that a higher cycle frequency is achieved.
The present invention provides a device for welding two films or pieces of film, with a heated sealing or welding arrangement cooperating with an opposed tool, the films being arranged between said sealing or welding arrangement and said opposed tool and said sealing or welding arrangement and said opposed tool being movable relative to each other, wherein said opposed tool has elastic material on its front face facing towards said film and/or said front face of said opposed tool facing towards said film is of elastic configuration, and in that said elastic material and/or said front face yields elastically at least partially when said sealing or welding arrangement and said opposed tool are moved together.
In the device according to the invention, when said opposed tool necessary to the welding process is advanced, said films are also fixed in place, one upon the other, by the same movement, either simultaneously or before or afterwards. By combining two operations of fixing the films and advancing said opposed tool for the welding process, time is saved in the periodic welding process and it is possible, in principle, to operate the device at higher cycle frequencies.
According to the invention the device is used for welding, that is, for joining two pieces of film without having to destroy said film. In a preferred embodiment of the invention combined cutting and welding, that is, a process in which the film is severed, is also possible.
In order to join the films, the opposed tool and the sealing or welding arrangement are movable relative to each other. Through the elastic configuration of the face of the opposed tool facing the film, it is ensured that, regardless of the exact thickness of the films or the relative position of the sealing or welding arrangement in relation to the opposed tool, sufficient pressure or force is always exerted on the film so that the desired function, for example, welding or combined cutting and welding, is achieved. In the prior art, complex adjustment of the precise final positions of the moving parts in relation to each other was necessary in order to avoid, in particular, shearing of the films by the moving parts without cutting and welding being achieved. Conversely, adjustment was also necessary to ensure that no gap was left between the opposed tool and the sealing arrangement, which gap would make it impossible to join the films. The design advantage as described above also makes possible a further advantage, in that the complex adjustment processes otherwise needed, especially when changing films or carrying out maintenance work, can be omitted.
In a preferred embodiment of the device according to the invention said opposed tool includes means by which the degree of elasticity of said opposed tool and/or of said front face is varied and, in particular, is reduced, so that this zone exerts increased pressure on said film when said sealing or welding arrangement and said opposed tool are brought together. The bringing together of said sealing or welding arrangement and said opposed tool causes said material to yield towards said opposed tool, because of its elasticity. As a result of this springing effect, an essentially predetermined force is produced between said opposed tool and said sealing or welding arrangement. In the further development according to the invention this force is varied locally in order to achieve special effects, for example, by applying increased pressure to certain portions in order to provide better thermal contact or to exert corresponding shear forces on said film
Jacobson & Holman PLLC
Kim Eugene
Skinetta Pac-Systeme Kiener GmbH & Co.
Tawfik Sameh
LandOfFree
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