Boots – shoes – and leggings
Patent
1993-06-10
1996-01-16
Envall, Jr., Roy N.
Boots, shoes, and leggings
326 42, 326 44, B65H 2300
Patent
active
054853869
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
A method of calculating and controlling the elongation of a running web, e.g. a web in connection with the preparation of a web in a printing unit and a device for the carrying out of the method.
BACKGROUND ART
In order to obtain a product having a satisfactory quality in the processing of web materials, e.g. in connection with printing, a high accuracy is required as regards an accurate positioning, when the web material is fed into processing machines. When it is the matter of printing, the processing machines can be printing machines.
When the material is fed between rolls, it generally is pretensioned and stretched, which results in a varying length in connection with variations in e.g. web tension and coefficient of elasticity. The elongation of the web material varies with web width, web thickness, moisture, material quality etc. A high product quality requires knowledge of the elongation of the web material in various processing phases and particularly in critical processing phases.
An example of this is the printing on a running paper web, and it is important that the print on forms obtains a predetermined length after the printing. This is particularly important in connection with the preparation of multi-sheet sets, which comprise a plurality of assembled forms, designed e.g. for the simultaneous typing of invoices, shipping notes, order confirmations, etc. Also, in case these multi-sheet sets of assembled forms shall be printed in a remaliner-fed printer, the hole punching for the remaliner-feeding must have an accurate distance between the holes in accordance with the length of the forms. It is difficult to keep the correct length on printed web materials and this is often evident in multi-sheet sets of assembled forms, designed for remaliner-feeding. In these sets some sheets are often stretched and some are wavy, since they are "extended" (in comparison with the rest of the sheets). The sets of assembled forms in this way become unneccesarily thick with air inclusions around the wavy sheets.
BRIEF DISCLOSURE OF THE INVENTION
The object of the invention is to suggest a method and a device, which allow a continuous control and regulation of the elongation of a running moving web material. This object and other goals are achieved according to the method of the invention, which is characterized in that the length change of the web is measured in connection with at least an increase or decrease in the web tension, in that the web tension is measured either before or after the changing of the web tension or after each one of the changing of the web tension and in that the elongation is determined and if it is required corrected through an increase or a decrease in the web tension depending on said length change and web tension measurements.
The changing of the web tension can be done by means of a roll, which accelerates or decelerates the web to a higher or lower web tension than the original one. The web tension can be measured in a way known per se by means of load cells or any other type of web tension meters. The length change can be determined by knowing the web speed of the accelerated or decelerated part of the web and the web speed in that part of the web, which is not influenced by the changing of web tension. The web speed can be measured by counting pulses generated by a roll in contact with that part of the web, which is subjected to a tension change, and by a roll in contact with that part of the web which is not subjected to the tension change.
The braking or acceleration roll can be controlled by a computer, which with constant intervals or by commands carries out a measuring sequence for the determination of the elongation of the web. The computer then receives measuring data from e.g. two pulse generators, provided to determine the web speed, as well as data from the web tension meter. Also, in case the computer is connected to control a tension regulation device, the computer can calculate the required corrections and correct the present tension level in or
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Envall Jr. Roy N.
Oakes Brian C.
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