US2890526A - Sieve drum drier for drying a continuous fleece of fibrous material - Google Patents

Description

June 16, 1959 J. FLElssNER SIEVE DRUM D 2,890,526 RIER FoR DRYING A CONTINUOUS FLEECE oF FIBRoUs MATERIAL 2 Sheets-Shee't 1 Filed Jan. 17, 195e ,0 (Pho/P ART) r il., ...I2 E

June 16, 1959 J. FLExssNl-:R 2,890,526 SIEVE DRUM DRIER FOR DRYING A CONTINUOUS FLEECE OF FIBROUS MATERIAL Filed Jan. 17, 1956 2 Sheets-Sheet 2 United States Patent @mee Y '2,850,526 Patented June V16, 1959` SIEVE DRUM DMR FOR DRYING A CONTINU- GUS FLEECE F FIBROUS MATERIAL Johann Fleissner, Egelsbach-Frankfurt am Main, Germany, assigner to Fleissner & Co. G.m.b.H., Frankfurt am Main, Germany Application January 17, 1956, Serial No. 559,697

1 Claim. (Cl. 3ft-115) This invention relates to sieve drum driers for drying continuous fleeces of fibrous material of varying thickness or having great permeability to air and comprising a number of sieve drums staggered vertically in an upper and a lower row, and in particular to such driers of the type in which no perforated stationary casing is provided adjacent the drum surfaces to ensure that the flow of air through the fleece and the surfaces is substantially normal to the surfaces.

An object of the invention is to be able to construct in any given instance a sieve drum drier having, on the one hand, as short an over-all length as possible, but which, on the other hand, is so designed that, depending on the weight and permeability to air or perforated nature of the material to be dried, a flow of fair which does not destroy said material can be obtained.

The known sieve drum driers, so far as they have come into practical use, are only useful for drying ra strip( of material which has a certain strength in the direction in which it is passed through the drier and which is relatively light and of low moisture content. ln order to obtain a large angle of engagement around the sieve drumls and to make the entire machine as compact as possible, the sieve drums are arranged in two rows, adjacent drums in each row being separated from one another by a distance of up to abount one fifth of the drum diameter. In such an arrangement, however, the permissible strength of the induced draught is limited. Air sucked into the drums through their Sieve surfaces to hold the fleece thereon is drawn through between the drums` disposed close to one another and where the space between the drums is narrowest, it flows substantially tangentially to the surface of the drum, then to /Veer round and pass through the fibrous web and the drum. If the induced draught is strong, the air flowing tangentially to the surface of the drums tears out portions of the fibrous fleece and destroys its uniformity. Because of the limited draught, the field of application of such known sieve drum driers is therefore limited to light material to be dried having ra low moisture content and a certain strength in the direction in which it passes through the drier.

Attempts have been made to overcome the difliculties involved where heavier or extremely air-permeable material to be dried is concerned by arranging stationary, perforated casings around the rotating sieve drums and spaced at a constant distance therefrom, said casings being intended to cause the strong air currents impinging on the surface of the sieve drums to be baflled and equalised and to cause the air to flow evenly out of the pressureL chamber formed by the stationary casings and at right angles to the sieve drums proper, so that it should thereby become possible to avoid the blowing away `and destruction of the fleece of material to be dried. The distance between the sieve drums in that case is greater than one quarter of the drum diameter, but this construction has not led to any useful result, because after only a short period of running iibres deposited on the sieve drums and on the stationary, perforated cylindrical casings form a troublesome coating to which the projecting fibres of the brous fleece adhere and thus lead to the destruction of the web and to blocking `of the space between the sieve drums and the casings. Cleaning of the space between the sieve drums and the stationary cylindrical casing is very difficult, because, owing to the width of the drum, which is always considerable, the restricted intermediate space is diflicult of access.

According to the invention, in different sieve drum driers in which the distance between the sieve drums disposed side by side in each row is greater than one quarter of the diameter of the drums, the sieve drums disposed in one row are arranged at `a different distance apart, according to the thickness and permeability to air of the material to be dried. In the case of thicker and heavier material to be dried and greater permeability to air and generally when relatively high induced draught's become necessary, the drums in one row are arranged at a greater distance from one another, while when the necessary induced draught is smaller a smaller distance from one another is used for the drums in one row. In each case, it is thereby possible, while obtaining the most favourable induced draught, to maintain the shortest over-all length of the machine. Accordingly, with the maximum induced draught the distance between the drums is greatest and the limit case is obtained, according to the invention, when, on increasing the distance between the sieve drums beyond the diameter of said drums, the two rows of sieve drums are combined in one row.

In order to obviate interference with the fibrous fleece from the side as it passes through the machine, side covers are fitted to the sieve drums. So as to apply the beginning of a fibrous fleece properly, a leading strip of material irnpermeable to air is passed through the sieve drum. drier, said leading strip providing for the beginning of the fibrous web to be likewise conveyed through the machine properly.

The invention will be explained in det-ail hereinafter with reference to the drawings, in which embodiments of the invention are shownV diagrammatically. Inv the drawings:

Figure 1 shows: an arrangement of the sieve drums of `a known form of drum drier,

Figures 2 and 3 illustrate two yarrangements of the sieve drums of a drum drier in accordance with the invention,

Figure 4 is a longitudinal section and a part-cross-section of the line A--B of a sieve drum drier with a fibre feeding arrangement for forming a fibrous fleece, using three sieve drums, and

Figure 5 shows the fibrous fleece.

In Figure 1 are shown drying drums 10, l1v and 12 which rotate uniformly in the direction of the arrows 19 and to the periphery of which the fleece material to be dried, 18, is applied and is held by the induced draught of the `drying medium. This construction is in accordance with the state of the art. The material to be dried is supplied byan endless lattice belt 13 and is taken over by the drum 1t) owing to the induced draught prevailing in the interior thereof and remains on the cylindrical surface of the drum 1d until the induced draught is interrupted bythe cover plate 20 fitted inside the drum. At that point, the induced draught of the drum 11 -acts on the material to be dried and the llatter passes automatically on to the drum 11. The same process is repeated as the material passes from the drum 11 to the drum 12 and, after the induced draught has been terminated by the cover plate 22, the drum 12 delivers the material to the endless lattice belt 14.

The embracing or looping angle 15 of the three drums is equal and is about 280. The drums 10 and 12, on the one hand, and the drum 11, on the other hand, are

application of a leading strip for a located in different horizontal rows and, while only three drums are illustrated, as many drums as desired may be arranged in each row.

The induced draught arrangement is not shown. A fan of conventional type 'sucks the air from the interior of the drums in the axial direction, so thatY the air ow 17 is produced which, of course, also completely covers f Y" y2,890,526

the periphery of the drums 10, 11 and 12 except in the regions of the cover plates 20,21 and 22. In Figure 1, the drums and 12 in one row are at the distance e1 from one another, as has heretofore been customary in sieve drum driers for obtaining the smallest over-all length and a relatively large embracing angle. This distance is about one fth of the diameter of the drums. It has been seen from the figure that the ow lines 17 between the sieve drums run almost parallel to the surfaces of the drums before they bend round to penetrate into the brous eece and the sieve drum. Owing to this course of the flow lines, it may easily happen that the fibrous eece is destroyed by libres or fibrous portions being torn out of the fleece. In addition, the formation of eddies which is possible here obstructs the ow of air and has a disadvantageous effect. In this construction, it is therefore only possible to employ a comparatively small induced draught, so that only light tleeces with a low moisture content can be dried. Any increase in the induced draught results in destruction of the ibrous fleece.

' Figure 2 showsl an arrangement of the sieve drums according to the invention. The distance e2 between two sieve drums in one row, which distance is chosen to be greater than one quarter of the diameter of the drums, is adjusted dilferently according to the thickness and permeability to air of the material to be dried and the figure shows that in this way the ow lines are not subjected to such a sharp curvature or bending effect as in the case of the construction according to Figure 1. Owing to this, the ow lines do not run at the surface of the sieve drum and cannot tear any libres or pieces out of the fleece, since the air which impinges on the fibrous web ows in a direction normal to the movement of 4said brous web. Thus, in view of this distance between the drums, a more powerful induced draught can be employed. Added to this there is the fact that in the arrangement of the drums 10 and 12 with respect to the drum 11 shown in Figure 2 the embracing angle 15 is considerably reduced, in fact to about 246. Owing to this, the area over which the air passes through the sieve drums is considerably reduced for a given width of drum and the velocity of the air in the sieve drum and in the brous web is increased at one and the same time, which has a favourable effect on the adhesion even of rather heavy brous fleeces or on the adhesion of material which is very permeable to air or material full of holes.

In Figure 3, all the sieve drums are arranged in a row at a distance e from one another. Fans 24 are mounted adjacent the drums as shown in Figure 2 of the patent to Fleissner et al., No. 2,835,047, to draw air out from the interior of the drums. Suitable means are provided, as is also shown in said patent, for rotating the fans and the drums in the directions illustrated by the arrows. 'Ihe increased distance e is brought about owing to the fact that the lower sieve drum 11 has been raised to the level of the upper sieve drum. 'I'he distance e is as great as the diameter of each drum, plus twice the thickness of the brous web. The embracing angle of the fibrous Web is only so that the free cross-section for the induced draught in the sieve drum has been reduced still further. Owing to this, the air velocity is increased still further, so that the adhesion is still greater than in the case of the construction according to Figure 2. The ow lines in this case run substantially atter than in Figure 2, so that this construction is suitable for drying the heaviest material or material which is very permeable to air, without fear that the fleece will be destroyed.

Owing to the increase in the distance between two drums, the over-all length of the machine is increased. In order to obtain the most economical point, the smallest distance between the `drums and the air velocity are so adjusted to one another in any given case that the velocity of the air through the periphery of the sieve drums amounts at the most to one eighth of the minimum value, to be indicated in percent by the drum diameter, of the distance between two drums. In this there lies a rough formula for dimensioning a sieve drum drier so as to obtain an economical over-all length.

Figure 4 shows a sieve drum drier with sieve drums 10, 11 and 12 and a drawing-in sieve drum 22 and two steel bands 23, which are led round the edges of the sieve drums and drive said drums. The band 23 is endless. End cover plates 24 are provided laterally of the sieve drums. These cover plates 24 prevent eddies by which the fibrous web is destroyed from the edge from being formed at the side between the sieve drums. Above and below the sieve drums there is provided a perforated plate 25, by which the stream of inflowing suction air is rendered uniform in the direction of ow.

In spite of the strong induced draughts according to the invention, care must also be taken that an adequate suction is maintained in the brous eece when it is introduced into the drum drier and only partly covers the sieve drums. For this purpose, a leading strip 26 (Figure 5) consisting of material impermeable to air is secured to the driving bands 23 by means of steel bands 27 and 28. The driving bands carry the strip 26 over the sieve drums, so that a suitable induced draught is maintained in the brous eece from the start and even rather heavy fibrous webs adhere from the beginning to the sieve drums.

What is claimed is:

A drum drier for drying heavy fleece comprising a plurality of sieve drums aligned side by side with parallel axes in a single row and with adjacent drums rotatable in opposite directions, a semi-cylindrical interior cover plate mounted adjacent the periphery of each drum and below the axis in one drum and above the axis in an adjacent drum for blocking air passage through one half of one drum and the opposite half in an adjacent drum,`

' References Cited in the tile of this patent UNITED STATES PATENTS 347,360 Y -Lorimer Aug. 17, 1886 1,377,793 Schwartz May 10, 1921 FOREIGN PATENTS 1,110,078 France Oct. 5, 1955

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