WO2001068976A1

WO2001068976A1 - Method for cutting an edge ship of a continuous web

Info

Publication number: WO2001068976A1
Application number: PCT/FI2001/000257
Authority: WO
Inventors: Mika Viljanmaa
Original assignee: Metso Paper, Inc.
Priority date: 2000-03-16
Filing date: 2001-03-15
Publication date: 2001-09-20
Also published as: FI20000620A0; AU2001246592A1; DE10195910T1; FI110256B; FI20000620A

Abstract

The present invention concerns a method for trimming of a continuous web, such as paper web. As taught by the invention, in order to make the reeling of the web possible, the trim is trimmed intermittently from the web.

Description

Method for cutting an edge ship of a continuous web

The present invention relates to paper machines or equivalent. More specifically, the present invention relates to a method for cutting an edge ship of a continuous web, for instance a paper web or an equivalent.

In order to protect the coatings of the calender rolls of a paper machine, an overwide web is run in relation to the nip width of the rolls on the paper machine for not bringing thermorolls and polymer rolls of the calender into contact with each other in any circumstances.

After the calender, a non-calendered edge strip left outside the nip is cut off prior to a web reeling because the edge strip which is thicker than the rest of the web makes the reeling impossible.

Conventionally, blade cutters are used for cutting the edge strip, the problems caused by which are primarily wearing of blades and break tendency of the web, especially in such cases the starting and ending of the cutting easily causes web breaks. In order to reduce said problems, cutting devices based on high-pressure water jet are developed. This kind of water jet cutting devices are working but their problems are wearing of nozzles, the high price and brief service life of high- pressure pumps both soiling of the web cutting board.

The objective of the present invention is to eliminate or at least to reduce problems related to web trimming known in the art and to provide therethrough an improved web trimming method.

Said aim is achieved using the method mentioned in the preceding, the specific characteristic features of which are presented in the accompanying claims. Thus, the invention is based on the novel and inventive basic idea that a trim is trimmed intermittently so that from a web to be reeled around the reeling core the trim is trimmed intermittently off only on a length corresponding to so many revolutions the reeling of the web is possible.

Preferably, a trim is trimmed intermittently from the web at least on a length equivalent to the percentage value of the thickness difference of the trim and the web by means of water jet, laser or blade.

Of the advantages of the invention, such advantages can be mentioned that an intermittent water jet trimming will not cause a break at the start or at the end; therefore, a trimming can be implemented easily when arranged to be intermittent, for instance so that 10 per cent of the time or the length of the web is trimmed and 90 per cent of the time or the length of a full-width web is reeled. Furthermore, the following aspects may be mentioned among the advantages. For instance, when 20% of the time or a trimmed strip is trimmed, the service time of the high pressure pumps and nozzles will be five times longer, the consumption of water and energy drops to a fifth, and automated cleaning can easily be arranged on the board.

The invention is described below related to an embodiment considered to be advantageous, whereby the trim is trimmed with a water jet.

On a plurality of paper grades, the result of glazing is enchanced up to temperatures of 200 to 250 °C. Thus, web glazing is performed conventionally in a nip between a smooth roll and a metal chilled roll so that the metal roll is heated e.g. by heated oil circulation or induction heating. A typical running temperature of the chilled roll is about 150°C, even above 200°C and, respectively, the web temperature after the nip is about 50°C. The end parts of the shell of the smooth roll are heated, especially when using thin web materials, approximately to the temperature of the metal roll, because the rolls are about to touch each other. Hereby, the surface material of the roll becomes easily damaged because the maximum temperature of a majority of elastomers used as a surface material of the smooth roll is merely 80 to 90 °C. The hardnesses of the coatings of smooth rolls of typical soft calenders vary from 20 P&J up to 93 Shore D, and the elasticity moduli, from 500 MPa to 4000 MPa. The smoothest coatings are used in processes in which a light calendering is sufficient, and endeavours are made to save the paper bulk as much as possible (e.g. folding boxboard). When using the hardest coatings, the paper can considerably be densified, resulting in, for instance, a high degree of smoothness and gloss. On hard coatings, also the duration of also speed and linear pressure is better than on smooth coatings. If the surface material of a smooth roll is damaged, such damaged roll causes damage also on a web edge, especially when running a web of the calender nip width or than narrower than that.

Typically, when protecting the coatings of the calender rolls on a paper machine, a web is run which is excessive in width to the nip width of the calender rolls, in order to make sure that the thermorolls and polymer rolls of the calender would in no situation be in contact with each other, neither to raise the temperature of the polymer rolls too high because of the thermoroll.

After the calendering, in order to enable reeling, or after other forms of finishing the web, such as coating, in which the web edge is exposed to mechanical stress, the trim is removed from the web, the width thereof being typically about 10 to 150 mm. The trimmed strip is drawn either by vacuum through a trim nozzle into the pulper or the trimming apparatus can be so designed that the trimmed strip is by means of gravity guided off from the process.

As taught by the invention, the web is trimmed intermittently, preferably so that for the trimming, an intermittently cutting water jet is used, wherewith from a web to be reeled around a reeling core, that is, a reeling drum iron, a trim is trimmed intermittently off only on a length equivalent to so many revolutions that the reeling of the web is possible. In this manner, trimmed layers and non-trimmed layers are alternately formed in the machine roll.

In a particularly advantageous embodiment of the invention, a continuous web is trimmed intermittently on a length, the length of which compared to the overall length of the web to be reeled is equivalent to at least the percentage value of the thickness difference of the trim and the web which can be calculated from the following formula: l,[%]≥[(d_rn-d_r)/d_r] x 100 in which

Ii = percentage of web trimmed intermittently d_π.= thickness of trim d_r = thickness of calenderized web

When running, according to the invention, a full-width web, that is, a web wider than the nip width, the water jet cutter can be located in the habitual location, so that also the cleansing of the trimming board can be automated to be performed with appropriate means, advantageously utilizing the water jet of a water jet cutter.

The invention is described above with the aid of one embodiment only, being considered to be advantageous. Therewith, the invention is not desired to delimit the invention, and as it is obvious to a person skilled in the art, a number of alternative designs and modifications are conceivable within the protective scope of the novel and inventive idea determined in the accompanying claims. Hence, e.g. laser trimming or blade trimming is also appropriate for the trimming, instead of a water jet.

Claims

1. A method for cutting an edge strip of a continuous web, such as paper web or equivalent, characterized in that to enable a web reeling, an edge strip is cut intermittently from the web.

2. A method according to claim 1, characterized in that water jet is used for cutting intermittently so that the edge strip is cut intermittently off from the web to be reeled around a reeling core only on a length corresponding to so many revolutions that the reeling of the web is possible.

3. A method according to claim 1, characterized in that laser is used for cutting intermittently so that the edge strip is cut intermittently off from the web to be reeled around a reeling core only on a length corresponding to so many revolutions that the reeling of the web is possible.

4. A method according to claim 1, characterized in that a blade is used for cutting intermittently so that the strip is cut intermittently off from the web to be reeled around a reeling core only on a length corresponding to so many revolutions that the reeling of the web is possible.

5. A method according to any one of claims 2 to 4, characterized in that the edge strip is cut from the web intermittently at least on a length corresponding to a percentage value of a thickness difference between the edge strip and the web.

6. A method according to any one of claims 2 to 4, characterized in that the quantity of the portion to be cut intermittently from the web is calculated using the following formula: l,[%]>[(d_m-d_r)/d_r] l00

in which li = %-portion to be cut intermittently from the web d_rn= thickness of the edge strip d_r = thickness of the calendered web

7. A method according to any one of claims 2 to 4, characterized in that when running a full width web, i.e. a web wider than the nip width, the water jet cutter is kept in the habitual location, and that the cleaning of a cutting board is automated to be performed by utilizing the water jet of the water jet cutter.