Guiding air-borne webs

Jan. 1, 1963 c. allander etal 3,070,901

GUIDING AIR-BORNE WEBS

Filed Feb. 16, 1960

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ATTYS.

3,070,901

Patented Jan. 1, 1963

United States Patent Office forth -hereinafter with reference to the accompanying drawings illustrating a suitable embodiment of the present invention -and wherein;

FIG. 1 is a -fragmentary view in perspective showing diagrammatically the air -forces blowing against a web in accordance with the present invention;

FIG. 2 is a longitudinal section through a dryer embodying one form of apparatus for practicing the present invention;

FIGS. 3 and 4 are sectional views taken on lines 3—3 and 4—4 respectively of FIG. 2;

FIGS. 5 -and 6 are plan and elevational views of the dryer embodying the present invention with portions broken away to more clearly illustrate construction; and

FIG. 7 -shows a modified form of lower wall for the upper distributing boxes.

Referring now to the drawings, FIG. 1 illustrates a web W which is supported in its travel by jets of air directed against the underside -of the web -in a direction longitudinal thereof as indicated by the arrows 11. Air or other drying -medium is -directed against -the upper surface of the web alternately to the right and left, transversely of the direction of travel of the web as indicated by the arrows 12 and 13 respectively.

A suitable -apparatus for directing the flow from the fans is disclosed in our Patent No. 2,848,820 and may consist of a series of upper -boxes 14« and 145 arranged in spaced relation longitudinally of the web and lower boxes 15 underlying the web in longitudinally spaced relation -as shown in FIG. 2. The surface of the boxes 14α and 145 which confront the web W are fora-minous, as shown -in FIGS. 2-5 being louvered as indicated at 16α and 16 b, and the end walls of the boxes 14« and 14b are extended downwardly closely adjacent -the web alternately on opposite sides as indicated at 17« and 17b respectively in FIGS. 3 and 4. If desired the confronting surfaces of -the upper boxes may be perforated as indicated at 16c in FIG. 7. Thus, the box 14« shown in FIG. 3, directs the air downwardly against the web W and the air flows to the right -as indicated by the arrows 12. The box 145 shown in FIG. 4, on the other hand, directs the air downwardly against the web W and the air flows -to the left as indicated by the arrows 13.

In normal operation of the apparatus, the forces exerted by the air streams indicated by the arrows 12 and 13 balance one another and maintain the web- in the center of its path during its longitudinal travel through the dryer. However, when threading the apparatus, or at other times, the web may have a tendency to move to the left or the right of the path, and to overcome this tendency, means is provided to regulate the forces exerted by the respective air streams indicated at 12 and 13. To this end, in -accordance with one feature of the invention, dampers are provided at 21 to throttle the flow of air into the box 14α -and thereby change the quantity of air flowing to the right of the apparatus, indicated by the arrows 12. Reduction of this quantity of air reduces the force on the web tending to displace -the same to the right thereby permitting it to travel towards the left under the influence of the adjacent air streams 13. Similar dampers 22 are mounted in the box 145 to throttle the air flow indicated at 13 -and reduce the force tending to move the material to the left, thereby permitting the material to move back towards the right. The dampers may be operated manually or by conventional control devices responsive to the lateral position of the edges of the web.

The -invention is characterized by the fact that rightward and leftward flow o-f air through the boxes 14α and 145 and transversely over the upper surface of the web W, is effected -by separate axial-flow propeller fans 23 -and 24 respectively. The fans 23 and 24 -are operated counterdirectionally, -so that if the fans 23 rotate clock3,070,901

GUIDING AIR-BORNE WEBS

Claes Allander, Sodra Angby, and Sven Wallin, Jonkoping, Sweden, assignors to Aktiebolaget Svenska Flaktfabriken, Nacka, Sweden ⁵

Filed Feb. 16, 1960, Ser. No. 9,078

Claims priority, application Sweden Feb. 1, 1956 4 Claims. (Cl. 34—156)

The present invention relates to apparatus for drying iq or similar treatment of webs in which the web is conveyed completely or partly air-borne by means of a gaseous medium blown against the under side of the web, and has particular application to means for guiding the web through the apparatus. The present application is 15 a continuation-in-part of our application Serial Number 636,521, filed January 28, 1957.

In apparatus of the stated type, gaseous medium is directed preferably perpendicularly against the under surface of the web and is conducted away longitudinally of 20 the web, and other gaseous medium is blown across the top of the web and is caused to flow transversely alternately to the right and the left sides of the web during its passage through the apparatus. Webs conveyed in this manner often have a tendency to move sideways in 25 one direction or the other in spite of the fact that the medium blown against the top of the web is conducted away in alternating directions. This sideways movement is especially pronounced when feeding the leading edge of a new web, i.e., while threading the web, for instance, 30 into a cellulose dryer.

The present invention provides apparatus for eliminating this disadvantage by employing separate fans and varying the quantity of the medium conducted away in alternating transverse directions by said fans individually 35 in order to regulate the forces of the transverse medium currents acting upon the web.

The necessary variation of the medium quantity may be effected either by throttling the medium current, for example by adjustable dampers or the like in the path of' 40 the circulating medium from each fan, or by individually regulating the current, for example by changing -the speed of the respective circulating fans effecting the transverse flow. The regulation may in both cases be performed either manually or entirely automatically by means of conventional control means operated by impulse devices-, photoelectric cells or the like which are responsive to the lateral position of the edges of the web. The apparatus of the present invention can preferably be used for guiding webs in accordance with our Patent No. 2,848,820 ₅θ which was copending with out parent application Serial No. 636,521. Th w'ebs are conveyed and stabilized by means of -a medium which is blown against the web and is conducted away in different ways at the upper and lower sides of the web. The apparatus according to- the present invention is operated in such a manner that the variation of the medium quantity only influences the guiding forces occasioned by the medium blown -against the upper side of the web, but does not change the guiding forces of the medium which is blown against the lower θθ side -of the web and is conducted away longitudinally of the web.

In -the practice of the invention, the circulating means for the medium consists of propeller fans operating counter-directionally alternately at opposite sides of the web. The design and -arrangement of the -throttling or regulating means may be varied without departing from the invention.

AU of the objects of the invention are more fully set wise, the fans 24 rotate counterclockwise. Specifically there is a separate gas supply system for each of the opposite surfaces of the web; the one system for one surface

3,070,901 supplying gas directed along the direction of movement of the web at spaced points therealong and thereacross; and the other system for the other surface supplying gas directed across the direction of movement of the web and, including. alternate boxes along the length of the web, each box having its individual blower fan with the fan axis aligned with the flow of gas in the box, and alternate boxes supplying gas respectively from opposite side edges of the web by fans which rotate in opposite directions respectively when viewed from behind the fans in the direction of gas flow.

In addition to providing for regulation of flow of air into the upper boxes 14 by the dampers 21 and 22, further regulation of the quantities of air is accomplished by changing the speeds of the motors 25 and 26 of the respective fans 23 and 24, for example, by speed control devices 27 and 28 responsive to the lateral position of the web W, as determined by sensing devices 29 and 30 operatively associated with the side edges of the web.

It has been found that, in accordance with the invention, by using separate fans operating counterdirectionally at each side of the web, the forces exerted by the respective fans are more readily balanced and the adverse effect of certain unknown factors is entirely eliminated, and it has been possible to accurately guide a web having a width of seventeen feet.

While a particular embodiment of the present invention has been herein illustrated and described, modifications are possible within the scope of the present invention as defined in the appended claims.