Manufacturing container or tube from paper; or other manufacturi – Container making – Pliable container
Patent
1989-04-12
1990-08-21
Terrell, William
Manufacturing container or tube from paper; or other manufacturi
Container making
Pliable container
493 22, 493 24, 493195, B31B 2314, B31B 2364
Patent
active
049502174
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to an arrangement in a bag-making machine for forming bag-defining lines of perforation and weld lines in an elongate web, said machine comprising a driven roller nip including a nip roller and a back-up roller, by means of which the web can be fed into and through the machine, elongate cutting means disposed parallel to said rollers and rotatable about its longitudinal axis, said cutting means being movable into engagement with said back-up roller for making said lines of perforation, and a welding station comprising sealing jaws which are displaceable in the direction of travel of the web and movable into engagement with the web for making said weld lines as the web is moving.
The technique on which this invention is based is represented by a known bag-making machine into the upper part of which an elongate web is fed by means of a roller nip consisting of two rollers. Parallel to one roller, the back-up roller, there is mounted an elongate knife or cutter which is rotatable about its longitudinal axis and whose cutting edge, when rotated, impinges on the back-up roller for producing the lines of perforation in the web passing over the roller. The rotary knife thus impinges on the back-up roller once per revolution and thus produces lines of perforation which, by the continuous feed of the web, will be provided with predetermined spacings for forming bag lengths. After being perforated, the web passes vertically down through the machine past a welding station comprising sealing jaws which are moved in the direction of travel of the web and brought into engagement with the web for making weld lines as the web is moving.
In this known bag-making machine, the knife and the welding station are mechanically interconnected by means of a chain transmission, which entails a number of drawbacks. The operation of the knife and, thus, of the welding station is controlled by an angle sensor connected to the nip roller and measuring the speed of the web or the web length passing the nip roller. Since the knife and the welding station are connected to each other by means of a common chain transmission, it is not possible to set the spacing between the lines of perforation and the weld lines when the machine is in operation. Further, the stop position of the knife before impinging on the backup roller is conditioned by neither the knife nor any sealing jaw being in contact with the web in the stop position. With regard to the rotation of the knife and its cooperation with the sealing jaws of the welding station, the stop position of the knife is limited, in constructional respect, to a maximum so-called impact angle of about 45.degree.. This means that the angle through which the knife edge is decelerated and accelerated before impact varies, which means that at high web speeds the knife will not have time to attain an optimal angular velocity at the impact.
Another drawback is that the knife and the welding station must be arranged relatively close to each other, which entails that the stop position of the knife before the impact is such that the knife edge is situated near the back-up roller and that the angle through which the knife is accelerated becomes limited. A target value of the angle between the stop position of the knife and its impact position is, as stated above, at most about 45.degree..
A further drawback of the known bag-making machine, which has only one knife, is that the minimum bag length that can be produced is mathematically determined, i.e. the circumference of the circular arc which the knife edge describes during its rotation; in mathematical terms, 2.pi. x the distance between the centre of rotation of the knife and the knife edge.
Moreover, the known bag-making machine has proved too slow in operation considering the new bag-making materials which have been developed in recent years. With these materials, the extruder in which the material is extruded into a so-called hose must be run at a higher speed, which means that also the succeeding machines in a producti
REFERENCES:
patent: 3147168 (1964-09-01), Bateman
patent: 3797368 (1974-03-01), Martelli
Fas Converting Machinery Aktiebolag
Terrell William
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