US3414984A - Nozzle-type drying machine for web-like material - Google Patents

Description

Dec. 1o, 196s M. SOININEN 3,414,984

NOZZLE-TYPE DRYING MACHINE FOR WEB-LIKE MATERIAL Filed Nov. 23. 1966 2 Sheets-Sheet 1 INvENTon: /VSoL'n"/7 en ATTORNEBS Dec. 10, 1968 M` solNlNEN 3,414,984

NOZZLE-TYPE DRYING MACHINE FOR WEB-LiKE MATERIAL Filed Nov. 29, 195e 2 sheets-sheet z Iw/Enohfl N- Soa'ninen ATTO United States Patent O 3,414,984 NOZZLE-TYPE DRYING MACHINE FOR WEB-LIKE MATERIAL Mauri Soininen, Turku, Finland, assiguor to Valmet Oy, Helsinki, Finland, a corporation of Finland Filed Nov. 29, 1966, Ser. No. 597,644 3 Claims. (Cl. 34-156) ABSTRACT F THE DISCLOSURE A nozzle-type drying machine for drying a web-like material, such as a paper web, has a cylindrical cover, the web moving over the cover at a distance therefrom supported by a cushion of the drying medium. The drying medium is supplied by at least two rotary impellers situatedV side by side within the cover and each drawing air or other drying medium from its own suction chamber and blowing it into its own pressure chamber surrounding the impeller. Then air is ejected through blow slits in the cover to form the drying cushion. Air is returned through suction slits provided in the cover. The impellers are at least partly enclosed by radiators for heating the air.

The present invention has reference to a nozzle-type drying machine intended for use in drying a web-like material, in particular a paper web, which one desires to dry within the hygroscopic moisture range in such manner that the web is free to contract. It is known for a fact that drying of a paper web in unstressed condition improves the properties of ductility and strength of the paper. No suitable drying machines for the drying of a paper web without stress within the hygroscopic moisture range have been available so far, which is obviously a considerable drawback.

The purpose of the present invention is to provide a suitable drying machine especially for the above-mentioned kind of drying. A drying machine according to this invention is suitable for use in connection with a multipleroller drying machine. When one or several such drying units are installed in the dry part of a multiple-roller drying machine in the region where the drying operation takes place in the range of hygroscopic moisture, in which the greatest shrinkage of the web occurs, s'uch drying of the web is accomplished that its ductility and strength properties improve. Of course, a drying machine according to the present invention is also suitable for other drying purposes. The nozzle-type drying machine according to the present invention may be either revolving or stationary. It is `advantageous if the blownozzles of the machine are fitted to give the air jets from them a direction ldeviating from the normal on the surface in a manner by which a tangential force transporting the web is created. The impellers of centrifugal blowers produce bilateral suction, and each blower section will thus have two suction chambers with a pressure chamber between them. l

The present invention is described in greater detail with reference to the embodiment shown in the attached drawings. FIG. 1 shows a nozzle-type drying machine according to the present invention, partly in section, viewed against the direction of travel of the web; FIG. 2 shows the same nozzle-type drying machine viewed from above and, likewise, partially in section.

The web A passes over the drying unit, supported by the air jets. The surface of the drying unit facing the web is cylindrical, and this cylindrical part of the mantle has blow nozzles, e.g. slit-shaped ones, parallel to the axis of the cylinder, through which air is blown against the web, and in the sections between the rows of blow nozzles it Patented Dec. 10, 1968 has suction nozzles serving to return the air to the suction side of the air-circulating blowers. In the longitudinal direction of the cylinder the unit `consists of one or several blower zones, each zone comprising the impeller of the blower, a suction chamber with attached suction nozzles, and a pressure chamber, to which the blow nozzles are connected. In the embodiment according to FIGS. l and 2 the impellers 2 of the centrifugal blowers mounted on a common shaft 1 provide bilateral suction; each blower zone will then have two suction chambers 3 and 3 and one pressure chamber `4 between them, opposite the blower.

The heating surface necessary in order to provide drying power encircles the blower impellers `as a cylinder. This heating surface may extend over the entire length of the drying unit, as in the embodiment concerned in FIGS. 1 and 2, or it may be provided only at the pressure chambers and omitted at the suction chambers, or vice versa. From the pressure chambers 4 the air flows through the heating surface in substantially radial direction outwards, while the flow is radially inward at the suction chambers 3, 3. In the embodiment shown in FIGS. l and 2 the heating surface consists of a number of tubes 5 on which a number of lamellae 6 parallel to the air flow and shaped like circular arcs have been provided. For improved blower action, furthermore, guide vanes 7 have been placed between the lamellae at the pressure chmaber, these vanes being shaped c g. of the material of the lamellae or alternatively being separate parts. Within the confines of the present invention, the heating surface may equally be designed in many other ways; for instance, the pipes 5 and guide vanes 7 may be integrally combined by manufacturing the pipes transporting the heating medium of a lhollow profile conforming to the shape of the guide vanes and upon which, moreover, heating fins are provided if the profiles are far between or which have no such ns if the proles are closely spaced. The reference numbers 8 and 9 indicate the end-piece chambers of the heating element.

-On the outside of the heating surface, the nozzle unit is placed, its surfaces facing the web combining to form a cylindrical surface. On the surface, blow and suction nozzles alternate, extending over the entire width of the web. One possible design is shown in FIGS. 1 and 2, where the oblong slits 10 form blow slits extending over the entire web, while the consecutive openings 11 of greater width constitute suction slits between each two rows of lblow slits. In the blower 2, the air flows in the direction of the arrows a into the blow slits 10. To the parts of the blow slits opposite the suction chambers 3 and 3 the air is carried by the flow channels 12. The air is discharged in the direction of arrows b into the slitshaped space between web and drying unit. The return air is drawn from this space in the direction of arrows c into the suction slit and through this either directly into the suction chamber 3 or 3', or from the parts of slots opposite to a pressure chamber 4 through flow channels 13 into the suction chamber. The air enters the suction chamber in the direction of arrows d, and the circulating air is further carried into the impellers as shown by arrows e.

In the drawings also the ducts 14 and 15 have been shown, into one of which exhaust air flows from the pressure side of the air-circulating blowers, while new drying air is fed to the suction chambers by the other. These air flows may be controlled in some manner previously known in itself.

Within the scope of the present invention, the nozzletype drying machine may either be stationary or it may be rotatory in its entirety or only as regards the part carrying nozzles. In the former case, the web may be drawn in e.g. by having the blow nozzle jets pointing in the direction of travel transport the end over the drying surface, or there may be separate air jets for drawing-in, or drawing-in is accomplished on a revolving cy lindrical surface at one end of the unit, which surface may have Wire grooves for drawing the end in by wire traction in usual manner. In the latter instance, of course, the nozzles cover the entire circumference of the revolving cylinder and the web is drawn in as in a standard multiple roller machine.

What is claimed is:

1. A nozzle-type drying machine for drying a web, said machine comprising a substantially cylindrical cover, a shaft extending through said cover, at least two centrifugal blower impellers rotatably mounted side by side upon said shaft and having separate pressure and suction chambers, said cover having blow slits for the flow of a drying medium from said pressure chambers, whereby the drying medium forms a cushion around said cover for the web, said cover also having suction slits for withdrawing the drying medium from said cushion to said suction chambers, and radiators mounted within said cover and substantially surrounding said impellers for heating the drying medium.

2. A drying machine in accordance with claim 1, comprising lamellae carried by said radiators and constituting heating ribs,

3. A drying machine in accordance with claim 1, wherein there are two suction chambers on opposite sides of each impeller, whereby each impeller produces bilateral suction.

References Cited UNITED STATES PATENTS 2,964,854 l12/1960 Keifer et a1. 34-115 3,043,018 7/1962 Eleissner 34-115 3,057,079 10/1962 schmidt 34-156 3,085,346 4/1963 Ananda et al. 34-156 XR 3,279,091 10/1966 Ereuier `34--156 FREDERICK L. MATTESON, IR., Primary Examiner.

H. B. RAMEY, Assistant Examiner.

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