METHOD FOR PASSING WEB TAIL FROM ONE PAPER MACHINE SECTION TO ANOTHER AND APPARATUS THEREFOR AND CONSTRUCTION THEREOF
The invention relates to a method and apparatus for passing a web tail being threaded from one paper machine section to another by way of guiding the tail with the help of an air jet from a transfer plate. An essential feature of the invention is to employ a construction rising from the surface of the transfer plate to a height with the shape of a linear ramp or a droplet for guiding the web tail in its travel direction thereby minimizing the contact area between the web tail and the transfer plate.
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The invention relates in accordance with the preamble of claim 1 to a method for passing a web tail being threaded from one paper machine section to another by way of guiding the tail with the help of an air jet. Furthermore, the invention relates to an apparatus in accordance with the preamble of claim 9 and the construction thereof in accordance with claim 17.
Tail threading in paper/newsprint or tissue machines is typically implemented with the help of carrier ropes, vacuum-supported belt conveyors or air-assisted transfer surfaces. Of these methods, carrier ropes represent the oldest technology, whereby it also is becoming obsolete due to safety problems. Vacuum-supported belt conveyors are technologically good and safe, but require extremely intensive care and expensive to construct and maintain. Air-assisted transfer plates are gaining ground in the market owing to their generally secure runnability as well as cost-efficient construction and use. However, their most common handicap is a relatively short rope run with respect to machine speed and wide spectrum of web types. If the machine running conditions change in regard to web speed, basis weight or other qualities, generally the system must be readjusted to minimize web broke. Details of prior-art technology are discussed in patent application FI20060757, and in patents FI 123352 and FI 122377.
In the art are known different kinds of arrangements aimed to improve the transfer of web tail from one machine section to the next. Conventional constructions of the prior art have been hampered by a plurality of disadvantages such as, e.g., it has been impossible to achieve a favorable air flow velocity between the transfer plates and the web tail or, alternatively, removal of blown air has disturbed the tail threading process. Resultingly, the performance of state-of-the art apparatus has not seen essential improvements.
It is an object of the present invention to provide a cost-effective and maintenance-free apparatus to perform tail threading in different paper machine sections at various speeds and web types. In practical tests it has been found necessary to create a relatively high vacuum between the web/tail and the web transfer plates by means of an air jet blown in the direction of the web travel, whereby the vacuum is preferably in the range of 5-300 Pa. With the help of induced vacuum, the web/tail is attracted to an immediate vicinity of the transfer plate, that is, at a distance of about 0-5 mm from the plate surface to the tail surface. In this fashion, the tail path can be controlled so that the tail is directed to the desired direction. As to the tail path control, a maximally high vacuum would obviously be advantageous. However, at the same time friction between the threading apparatus and the web should be minimized in order to prevent tail threading speed from falling below the running speed of the process (i.e., machine speed). Inasmuch as the tail/web transfer plate is essentially a fixed accessory while the web travels at machine speed, the mutual speed difference between their surfaces may possibly be very high at this point. Hence, it is necessary to avoid or at least minimize an intimate contact between the tail/web and the transfer plate. Friction is directly related to the attractive force of the induced vacuum and the resultant local contact between the tail/web and the transfer plate. The greater the area of the contact, the higher the generated friction. Resultingly, it is necessary to apply a larger volume and pressure of the air flow to achieve a sufficient attractive force and to compensate for the frictional force.
In regard to the above, the present invention aims to solve three problems:
1. Minimization of possible contact surface area between the tail/web and the transfer plate.
2. Induction of a proper vacuum (5-300 Pa) between the tail/web and the transfer plate.
3. Generation of maximally effective transferring force on the tail/web by means of air jets.
Now the arrangement according to the invention is capable of presenting a comprehensive solution to the above-mentioned prerequisites in a single embodiment that also optimizes the operation of the apparatus. The inventiveness of the present apparatus is based on the unique arrangement of the transfer plate air ducts serving to guide and control the air flow. An essential feature of the air ducts is their entirely novel construction for threading the web tail from one machine section to the next.
More specifically, the invention is characterized by what is stated in the appended claims.
In the following, the invention is described in more detail with the help of appended drawings, wherein
The arrangement illustrated in appended drawings 1-18 now provides a novel approach to a maximally optimal solution capable of overcoming the above-listed problems.
As shown in
In
In the embodiment variants shown in
Obviously, the number of these different variants and combinations can be modified in plural ways. Essential to the invention is that use of different variants or their combinations are selected to suite the point of application. A particular aim of using different variants is to achieve a significant increase in the transfer force moving the tail forward. For instance in accordance with
In accordance with
As shown in
The air exit opening 7 formed into the frog eye 3 is most advantageously located either to above the plate surface 2, parallel to the level of surface 2 or below the level of surface 2 in the fashion shown in
In accordance with the above discussion, the structure of frog eye 3 can be implemented such that it is located entirely flush with the surface 2 of transfer plate 1 or alternatively at the level of surface 2 of transfer plate 1 or just above thereof. An alternative embodiment has a given portion of the frog eye structure 3 situated below the underside 6 of the surface 2 of transfer plate 1.
As shown in
As described above, the number and shape of air exit openings 7 in frog eye 3 can be varied to meet different requirements. As shown in
Analogously, the shape of frog eye 3 proper illustrated in
More particularly, the shape of frog eye 3 and location of air exit opening 7 are dictated by the requirements posed by a specific application. One particularly advantageous embodiment is the frog eye 3 shown in
In the embodiment according to the invention, air flow from frog eye 3 is directed essentially immediately onto the surface of transfer plate 2, parallel to the transfer plate 1 and the travel direction 9 of the web tail as seen from aside the plate. Correspondingly, as seen from above the transfer plate 1, the air flow exits from frog eye 3 essentially directly onto the transfer plate surface 2, either parallel thereto or inclined to transfer plate 1 and the web tail travel direction by −60-+60 deg., most advantageously by −45-+45 deg.
As shown in
According to the invention it is now possible to use a larger air volume and/or speed to create a vacuum. Resultingly, the present arrangement can reduce the effect of friction by way of minimizing the area of contacting surface with the help of higher vacuum. Also the distance of the web tail from the transfer plate surface 2 can be controlled accurately. The web tail makes contact only with the highest point 5 of frog eyes 3 inasmuch as the spaces between the web tail and the transfer plate 1 are filled with the air flow exiting from the frog eyes.
In the manner described above the arrangement according to the invention now is capable of overcoming the three problems listed earlier. Firstly, the area occupied by frog eye 3 seen from above transfer plate 1 is extremely small, whereby the possibly occurring area of contact between the web and the transfer plate remains minimal. Resultingly, as the contact area between the web tail and the transfer plate is minimized, this represents one of the essential features included in the arrangement according to the invention.
A second essential feature of the invention comprises creating an advantageous level of vacuum at 5-300 Pa between the web tail and transfer plate 1. The vacuum between the web tail and transfer plate is dictated by the air flow, i.e., the differential speed of air flow with regard to the web tail speed and amount of injected air. Owing to the structure of frog eye 3, the invention permits the use of a higher air flow rate or speed to establish a greater vacuum. In contrast, arrangements according to prior art inject the air flow from air exit openings at an angle from the transfer table surface. As a consequence, a portion of the air flow induces a lifting effect off the transfer plate on the web tail, while only the remaining portion serves to pull the web tail in the downstream direction of the transfer plate and create a vacuum.
Thirdly, the invention is characterized by providing a maximally great forward-pulling force on the web tail with the help of directed air flow. An essential feature herein is to direct the air flow parallel to surface 2 of transfer plate 1. This can be achieved by locating frog eyes 3 over the entire surface of transfer plate 1 either in an equidistantly spaced, unsymmetrical and/or in a dispersed fashion or only on a selected area of transfer plate 1.
The arrangement according to the invention offers essential improvements in regard with prior-art constructions wherein air is ejected through the transfer plate via holes drilled at an acute angle thereto.
Claims
1. A method for passing a web tail being threaded from one section to another by way of guiding the tail with the help of an air jet from a transfer plate, wherein a structure rising from the surface of the transfer plate to a height with the shape of a linear ramp or a droplet guides the web tail in its travel direction thereby minimizing the contact area between the web tail and the transfer plate.
2. The method of claim 1, wherein, from one or more air exit openings of a frog eye structure arising seamlessly from transfer plate surface, the air flow is directed essentially parallel to the web tail travel direction, whereby simultaneously is created an advantageous level of vacuum at 5-300 Pa between the web tail and transfer plate so that with the help of the vacuum the web tail is kept in the immediate vicinity of surface of the transfer plate, most advantageously at a distance of about 0-5 mm.
3. The method of claim 1, wherein onto the transfer plate are formed a plurality of frog eyes suited to create a maximally high air flow released from air exit openings serving to transfer the web tail forward, whereby the height of frog eye is 0.3-10 mm, most advantageously 3-6 mm, with a width of 2-10 mm, most advantageously 3-8 mm and, in the web tail travel direction over transfer plate, a length of 2-150 mm, most advantageously 10-50 mm, whereby the frog eye has an essentially droplet-like shape wherein the angle of its slanting surface in respect to surface of transfer plate is 10-170 deg., most advantageously 45-135 deg.
4. The method of claim 3, wherein as seen from above the transfer plate, the air flow exits from frog eye essentially directly onto surface of transfer plate, either parallel thereto or inclined to transfer plate and the web tail travel direction by −60-+60 deg., most advantageously by −45-+45 deg.
5. The method of claim 1, wherein the frog eyes are located on surface of the transfer plate interspaced apart from each other by 5-150 mm laterally and by 10-300 mm longitudinally either in an equispaced, unsymmetrical and/or dispersed fashion in the xy-directions at a distance of 30-100 min from each other, either over the entire area or only a given partial area of one or a plurality of transfer plates.
6. The method of claim 1, wherein from the air exit openings the air flow is directed essentially parallel to the web tail travel direction so that the frog eyes are formed either essentially flush with the level of surface of the transfer plate or just above the same or, alternatively, a portion of the frog eye structure extends below the surface of transfer plate.
7. The method of claim 1, wherein the air flow is directed out from one or a plurality of air exit openings of the frog eye so that one or more of the openings are formed either flush with the level of surface of the transfer plate or above the same or alternatively and/or below the surface of transfer plate.
8. The method of claim 1, wherein, in order to improve the direction of the air flow parallel to the surface of the transfer plate, into the frog eye are formed openings from two directions, i.e., from below and from above of the transfer plate so that one opening situated above surface is aligned either parallel to the transfer plate or at an angle of −10-+10 deg. to the plate, most advantageously −5-+5 deg., while as seen from below of the transfer plate the other opening is inclined by 10-170 deg. to the plane of the transfer plate, most advantageously by 45-135 deg., whereafter the air flow path is continued as a duct through the frog eye ending as an air exit opening on the surface of the transfer plate.
9. An apparatus for passing a web tail being threaded from one paper machine section to another by way of guiding the tail with the help of an air jet from a transfer plate, wherein having a structure adapted thereto rising from the surface of the transfer plate to a height with the shape of a linear ramp or a droplet, said structure guiding the web tail in its travel direction thereby minimizing the contact area between the web tail and the transfer plate.
10. The apparatus of claim 9, wherein having onto the surface of transfer plate seamlessly rising from said surface adapted a frog eye structure incorporating one or more air exit openings, wherefrom an air flow is directed essentially parallel to the web tail travel direction, whereby simultaneously is created an advantageous level of vacuum at 5-300 Pa between the web tail and transfer plate so that with the help of the vacuum the web tail is kept in the immediate vicinity of surface of the transfer plate, most advantageously at a distance of about 0-5 mm.
11. The apparatus of claim 9, wherein having onto the transfer plate formed a plurality of frog eyes suited to create a maximally high air flow released from air exit openings serving to transfer the web tail forward, whereby the height of frog eye is 0.3-10 mm, most advantageously 3-6 mm with a width of 2-10 mm, most advantageously 3-8 mm and, in the web tail travel direction over transfer plate, a length of 2-150 mm, most advantageously 10-50 mm, whereby the frog eye has a droplet-like shape wherein the angle of its slanting surface in respect to surface of transfer plate is 10-170 deg., most advantageously 45-135 deg.
12. The apparatus of claim 11, wherein having, as seen from above the transfer plate, the air flow exiting from frog eye is essentially directed onto surface of transfer plate, either parallel thereto or inclined to transfer plate and the web tail travel direction by −60-+60 deg., most advantageously by −45-+45 deg.
13. The apparatus of claim 9, wherein having the frog eyes located on surface of the transfer plate interspaced apart from each other by 5-150 mm laterally and by 10-100 mm longitudinally either in an equispaced, unsymmetrical and/or dispersed fashion in the xy-directions at a distance of 30-100 mm from each other, either over the entire area or only a partial area of one or a plurality of transfer plates.
14. The apparatus of claim 9, wherein having the air flow released from the air exit openings directed essential parallel to the web tail travel direction so that the frog eyes are formed either essentially flush with the level of surface of the transfer plate or just above the same or alternatively and/or below the surface of transfer plate.
15. The apparatus of claim 9, wherein having the air flow directed out from one or a plurality of air exit openings of the frog eye so that one or more of the openings are formed either flush with the level of surface of the transfer plate or above the same or, alternatively, a portion of the frog eye structure extends below the surface of transfer plate.
16. The apparatus of claim 9, wherein having into the frog eye formed openings from two directions, i.e., from below and from above of the transfer plate so that one opening on the surface is aligned either parallel to the transfer plate or at an angle of −10-+10 deg., most advantageously −5-+5 deg., while as seen from below of the transfer plate the other opening is inclined by 10-170 deg. to the plane of the transfer plate, most advantageously by 45-135 deg., whereafter the air flow is continued as a duct through the frog eye ending as an air exit opening on the surface of the transfer plate.
17. A construction of a transfer plate for passing a web tail being threaded from one paper machine section to another by way of guiding the tail with the help of an air jet from a transfer plate, wherein having a guiding construction adapted thereto rising from the surface of the transfer plate to a height with the shape of a linear ramp or a droplet, said construction guiding the web tail in its travel direction thereby minimizing the contact area between the web tail and the transfer plate.
18. The construction of claim 17, wherein having onto the surface of transfer plate seamlessly rising from said surface adapted a frog eye construction incorporating one or more air exit openings, wherefrom an air flow is directed essentially parallel to the web tail travel direction, whereby simultaneously is created an advantageous level of vacuum at 5-300 Pa between the web tail and transfer plate so that with the help of the vacuum the web tail is kept in the immediate vicinity of surface of the transfer plate, most advantageously at a distance of about 0-5 mm.
19. The construction of claim 17, wherein having onto the transfer plate formed a plurality of frog eye constructions suited to create a maximally high air flow released from air exit openings serving to transfer the web tail forward, whereby the height of frog eye is 0.3-10 mm, most advantageously 3-6 mm with a width of 2-10 mm, most advantageously 3-8 mm and, in the web tail travel direction over transfer plate, a length of 2-150 mm, most advantageously 10-50 mm, whereby the frog eye has a droplet-like shape wherein the angle of its slanting surface in respect to surface of transfer plate is 10-170 deg., most advantageously 45-135 deg.
20. The construction of claim 19, wherein having, as seen from above the transfer plate, the air flow exiting from frog eye construction is essentially directed onto surface of transfer plate, either parallel thereto or inclined to transfer plate and the web tail travel direction by −60-+60 deg., most advantageously by −45-+45 deg.
21. The construction of claim 17, wherein having the frog eye constructions located on surface of the transfer plate interspaced apart from each other by 5-150 mm laterally and by 10-300 mm longitudinally either in an equispaced, unsymmetrical and/or dispersed fashion in the xy-directions at a distance of 30-100 mm from each other, either over the entire area or only a given partial area of one or a plurality of transfer plates.
22. The construction of claim 17, wherein having the air flow released from the air exit openings directed essential parallel to the web tail travel direction so that the frog eye constructions are formed either essentially flush with the level of surface of the transfer plate or just above the same or, alternatively, a portion of the frog eye structure extends below the surface of transfer plate.
23. The construction of claim 17, wherein having the air flow directed out from one or a plurality of air exit openings of the frog eye construction so that one or more of the openings are formed either flush with the level of surface of the transfer plate or above the same or alternatively and/or below the surface of transfer plate.
24. The construction of claim 17, wherein having into the frog eye construction formed openings from two directions, i.e., from below and from above of the transfer plate so that one opening on the surface is aligned either parallel to the transfer plate or at an angle of −10-+10 deg., most advantageously −5-+5 deg., while as seen from below of the transfer plate the other opening is inclined by 10-170 deg. to the plane of the transfer plate, most advantageously by 45-135 deg., whereafter the air flow is continued as a duct through the frog eye ending as an air exit opening on the surface of the transfer plate.
Type: Application
Filed: Apr 10, 2015
Publication Date: Jan 26, 2017
Applicant: RUNTECH SYSTEMS OY (Kolho)
Inventors: Kimmo LOIPPO (Kolho), Antti ELO (Keuruu)
Application Number: 15/300,960