US3427725A - Sieve drum dryer - Google Patents

Description

Feb 18, 1969 H. FLElssNER 3,427,725

SIEVE DRUM DRYER Filed pril 2v. 1965 lnven for:

Heinz F'leissner- I e7 Q16@ 6W- Arroeney United States Patent O 3,427,725 SIEVE DRUM DRYER Heinz Fleissner, Egelsbach, near Frankfurt, Germany, as-

signor to Anstalt fur Patentdienst, Vaduz, Liechtenstein Filed Apr. 27, 1965, Ser. No. 451,282 Claims priority, application Switzerland, Apr. 29, 1964, 5,578/64; July 1, 1964, 8,648/64 U.S. Cl. 34-115 14 Claims Int. Cl. F26b 13/08 ABSTRACT OF THE DISCLOSURE The present disclosure relates to a heat-treatment apparatus comprising two rows of cylindrical sieve drums disposed in a treatment chamber in a staggered relationship with respect to each other, said sieve drums having a .perforated surface, free from baille means at that portion of said sieve drum not covered with the material being treated and said treatment chamber containing guide means, especially between adjacent sieve drums in the same row.

i tow which, in tensioned condition, is almost impermeable to air and for drying similar materials which are only slightly permeable or impermeable to air. In order to achieve a good circulation of the heated air around the sliver-type material, it has already been tried to place the individual slivers at a certain distance from each other, so that part of the sieve drum jacket is free from material to tbe processed Iand the air can ilow through that free part of the sieve drum jacket.

The air movement takes place preferably from the outside to the inside, i.e., first into the sieve drum from where it is, in general, sucked out again by the fans arranged at the sides of the sieve drum and returned into the treatment chamber by way of heating tubes which reheat the air. However, with materials which can be stressed in longitudinal direction, such as tow and the like in web-form, Ithe .air can also be sucked out of the heating devices by means of the fans or forced into the drums so that an excess pressure is created in the drums and the heated air escapes from the drum interior through the sieve drum jacket. In general, the iirst-mentioned approach will be chosen, with which the air will ilow into the drum from the outside thereof because, in this way, the material to be processed is, at the same time, held onto the drum jacket by the suction draft.

With the known devices, that portion of the sieve drum jacket which is free from lmaterial to be processed is screened against air penetration by means of baille plates because the entire volume of circulated air is to enter the portion of the sieve drum covered by material in order to obtain a good drying eiect. Therefore, the volume of circulated air is relatively small in the case of materials which are impermeable or only slightly permeable to air. Heat transfer or heat absorption of the air when ilowing through the heating devices is corresponding unfavorable. The higher the speed of the air ilow through the heating devices, the better the heat absorption or the heat transfer between heating tubes and air. It has been attempted to ice heat up the air to higher temperatures by providing more heating tubes. However, this results in a further ilow resistance to the air, and thus the air circulation which is already insuilicient in the case of materials which are slightly permeable to air is even further deteriorated. It is a well known fact that the drying eifect is essentially better with materials which are permeable to air than with materials which are slightly permeable to air. Slower drying must be compensated by a larger number of drums. However, this entails the disadvantage that the installations become lar-ger and, as a consequence, more expensive.

In order to improve the air circulation, it has been attempted to place the slivers at a certain distance from each other so that the air can enter through those portions of the drum jackets which are not covered iby the slivers. This impoves the disadvantageous conditions described above but, on the other hand, the working width becomes smaller while the drum length remains the same so that either fewer slivers can be dried simultaneously or longer drums must be constructed which again results in an increase of the costs of the installation.

'According to the present invention, the aforementioned disadvantages are eliminated in a surprisingly simple manner by providing an installation of the above-described kind in which the portion of the sieve drum which is free from material to be processed is totally or partly without baille plates which would otherwise hinder air penetration, i.e., the baille plates which hitherto were usual and considered absolutely necessary are omitted. In this way, part of the air can enter through the said portion of the sieve drum -free from material without a -large resistance where it mixes with the air which has penetrated through the material to be processed and then the air can be forced into the heating devices lor sucked out of them by 4the fans with a considerably higher speed.

A particularly good drying effect is obtained with a device in which two rows of superimposed sieve drums in mutually staggered relationship are provided. In the case of this arrangement of the sieve drums, the air sucked in through the part of the sieve drum free from mateial passes along the mateial to be processed on the adjacent sieve dru-m, arranged at a higher or lower level, with a relatively high speed. Thus, the drying eiect is similar to that obtained with a loop dryer. This loop dryer drying effect is increased by the air penetrating through the material or by the air passing about the material on the sieve drums.

In realization of the present invention, it is proposed in connection with a device in which the heated air ilows into the sieve drums from the outside, i.e., in which the suction draft is created by the fans in the drum interior which suction draft holds the material to be processed onto the sieve drum jacket, to provide a baille plate e.g. in the sieve drum of a drum jacket preferably at that point or lat those places only where the material is to be detached from the sieve drum, which baille plate facilitates removal of the material from the sieve dru-m jacket.

According to a further feature of the present invention, it is suggested to provide shutter-type or louver-type baille plates for controlling the air circulation, which shutter plates can be closed e.g. when starting the device so that the free ends of the slivers are held by the suction draft and the slivers can be automatically fed into and passed through the device. During the subsequent treatment process, the shutter-type baille plates can be more or less opened depending on the quality, nature and/ or air permeability of the material to be processed. In order to obtain optimum drying conditions, conventional automatic regulators and control devices may be installed in the device which open and close, i.e., control the shutter-type baille plates.

According to another aspect of the present invention, it is also conceivable, especially when drying materials with good air permeability, and when using a device with preferably two rows of superimposed sieve drums in mutually staggered arrangement, to provide only part of the `drums with fans, preferably only one row of sieve drums.

According to a further modification of the present invention it is also possible and advantageous, in vparticular when using shutter-type baffle plates, to guide the slivertype material at a certain distance from each other over the sieve drums so that the air can enter through the interspaces of the sieve drums which interspaces are free from material or so that the air can escape from the sieve drums through these interspaces whereby `the air then flows around the material on the sieve drums. However, the distance of the individual slivers from each other can be kept considerably smaller than in a device in which the portion of the sieve drums free from material is screened against air penetration by baille plates. This latter arrangement results in exremely good drying, especially when processing materials impermeable to air, such as paper and cardboard webs.

In `order to increase the flowing speed of the air, the sieve drums of each row should be arranged at a small distance from each other or at least an air guiding element should Ibe provided between each two drlums of one row, so that the air can pass along between these air guiding elements and the material carried and guided on the sieve drturn jacket to the sieve drum in which the suction draft is created, which drum is arranged at a higher or lower level, as the case may be.

In another essential modification of the invention the two rows of sieve drums are arranged at the largest possible distance from each other. Not only that thus the usually available head-room is better utilized but above all, an additional drying effect is obtained similar to that in loop dryers. This effect can even be increased if at least one air guiding element is arranged in the interspace between two adjacent sieve drums so that the speed of the air flow is increased.

The distance between these air guiding elements and the material or the distance between the air guiding sheets, with which the air guiding elements might be provided, and the material should e.g. amount to the one-to-twentyfold thickness of the material.

An air guiding element may be designed as a closed body and/or individual air guiding sheets at equal or varying distances and with equal or varying lengths in direction towards the material may be provided. The air guiding sheets should thereby be so aligned that the air flows towards the material. The walls of the air guiding elements or also the air guiding sheets may be perforated.

It is pointed out that the present invention cannot only be applied to devices with the drums in mutually staggered arrangement but also to devices with the drums arranged in line.

Accordingly, it is an object of the present invention to provide a dryer of the type described above which obviates by extremely simple means the aforementioned disadvantages encountered with the prior art constructions.

Another object of the present invention resides in the provision of a sieve drum dryer which allows greatly improved ciroulation of the drying air without increase in cost in the dryer installation, even when used with materials at best only slightly permeable to air.

Still another object of the present invention resides in the provision of a sieve dnum dryer which exhibits improved drying characteristics without increasing the size of the installation and/ or the cost thereof.

A further object of the present invention resides in the provision of a sieve drum dryer which offers improved heat transfer characteristics of the overall installation without involving complicated encumbering structures.

These and further dbjects, features, and advantages of the present invention will become more obvious from the following description when taken in connection with the accompanying drawing which shows, for purposes of illustration only, two embodiments in accordance with the present invention, and wherein:

FIGURE l is a cross section through a drying device in which differently shaped air guiding elements are arranged between the individual sieve drums of each row, and

FIGURE 2 is a cross section through a drying device in which the individual sieve drums of each row are arranged at a small distance from each other.

In both devices of FIGURES 1 and 2, two rows of mutually staggered sieve drums 2 which carry a material 3 on their perforated jackets are arranged within a casing or drying chamber 1.

The sieve drums of each row have a certain more or less large spacing from one another whereas the distance of the drums of one row with respect to the dnums of the other row is relatively slight and corresponds essentially to the thickness of the material to be dried. It is achieved thereby, especially with an arrangement of shutter-type bale plates 21 which can be completely closed during starting, that the material can be automatically introduced into the installation and/ or guided therethrough.

However, the sieve drums of both rows can also be disposed at a certain distance from one another so that such a dryer approximates a loop dryer in its operation. In FIGURE l, the distance d illustrates a spacing of the sieve drum dryers of adjacent rows whereby the distance therebetween is relatively small. 'It is also within the scope of the present invention to replace one row of sieve drums by guide rollers or smaller sieve dnu'ms whereby a combination of the loop dryer principle with the sieve drum dryer principle results therefrom.

In the dryers illustrated in FIGURES l and 2, shuttertype bale plates 21 are illustrated diagrammatically.

The individual sieve drums are provided only at those places where the material is to be removed from the sieve drum jackets, with a relatively small batile plate 4 in order to facilitate the removal of the material from the sieve drurn jacket.

With the installations 0f FIGURES 1 and 2, fan wheels or blowers (not shown) of conventional construction are arranged at one or both end faces of the drums which suck the air out of the drum inside and guide the thus sucked-out air back to the drying chamber by way of heating pipes 5, serving to heat the drying medium. The flow of air is schematically indicated in both figures by the flow lines provided with arrows.

A relatively large quantity of air is sucked in through those portions of the individual drums which are not covered by material and bafe plates, which air flows with a relatively high velocity along the material to be treated of 'the adjacent sieve drums and thus achieves a good drying effect. The drying of the individual webs takes place from both sides thereof because the webs abut against the sieve drums of one row with one side thereof and against the sieve drums of the other row with the other side thereof so that the air can flow along both sides of the webs.

As maybe seen from FIGURES 1 and 2 the sieve drums 2 at the inlet and outlet of the material to be treated are not surrounded to as great an extent by the material as the remaining drums. In order to achieve llow conditions similar to those as occur at the other drums, i.e., those disposed intermediate the end drums, a further bale plate or plates 2a may be provided at either or both of these two end drums above the inlet or outlet of the material.

In order to favor the air guidance, air guide elements may be provided for example, between two lower sieve drums and/or between the upper sieve drums in such a manner that the interspace is hardly hit by the air flow while the air is guided between the respective guide elements and the sieve drum jacket carrying the material. Such guide elements may be, for example, of V shape or may represent bodies closed upon themselves. These bodies may be of any suitable shape, for example of elliptical cross section. The guide elements of V shape may be arranged staggered several times and having different angles of inclination. As shown in FIGURE 1, the guide elements may be arranged with the leading edge 20 thereof in close proximity to the cylindrical sieve drum 2 in the -adjacent row, more specically, to that portion of the surface of said drum which is not covered by material.

FIGURE 1 illustrates different types of air guide elements 6, 7, 8, and 9 arranged between the individual sieve drums in such a way that an air current impinges on the material 3 which is passed through the device. For example, individual undulations 11 of guide element 9 may have any desired `form and can be placed at varying distances from the sieve drums. The air guiding element 6, is thereby closed upon itself and designed as a bar with elliptical cross section while the air guiding elements 7 consist of staggered V-shaped sheets. One or more of these sheets may be provided with an opening 12 in the middle portion thereof, or the sheets may be perforated. The V- shaped air guide elements 8 produce the desired flow condition within the free space above and below the end sieve drums, respectively. lets are concentrically disposed about a portion of the surface of the sieve drum and extend a predetermined distance between said surface and the heating means 5, thus providing desirable flow conditions.

The device according to FIGURE 2 is similar to FIG- URE 1 except that the air guiding elements between adjacent sieve drums of a respective row are omitted while the desired flow conditions are realized by an appropriate spacing between adjacent sieve `drums of the same row.

The materials to be dried such as slivers in web-form may be disposed at such a distance from one another that, for example, or more of the sieve drum jacket is free from the material to be treated.

While I have shown and described two embodiments in accordance with the present invention, it is understood that the same is not limited thereto but is susceptible of numerous changes and modifications as known to a person skilled in the art, and I therefore do not wish to be limited to the details shown and described herein but intend to cover all such changes and modifications as are encompassed by the scope of the appended claims.

I claim:

1. An apparatus for the heat treatment of material which comprises a treatment chamber, a series of more than two cylindrical sieve drums with perforated surfaces rotatably disposed -within said treatment chamber, said sieve drums arranged in at least two rows and in a staggered relationship with respect to each other, a portion of the cylindrical surface of each of said sieve drums serving as a conveying means and producing a continuous treatment surface in said treatment chamber, means for introducing the material to be treated to said conveying means, vacuum means communicating with the interior of the cylindrical sieve drums, a portion of the surface of each of said cylindrical sieve drums, not covered with said material, being substantially free from baflie means, thus facilitating penetration of the treatment medium into said portion not covered with material and providing tangential ow between adjacent sieve drums with an associated increase in drying effect, wherein guide means are provided between adjacent sieve drums of one row, said guide means accelerating the ilow of the treatment medium which is in contact with the material being treated whereby the drying effect is also accelerated.

2. The apparatus of claim 1, wherein the guide means are perforated.

3. The apparatus of claim 1, wherein the guide means extend a distance of about one to twenty times the thickness of the material from the surface of the material being treated.

4. The apparatus of claim 1, wherein the guide means are variously shaped guide elements or variously shaped guide bodies which close upon themselves.

5. The apparatus of claim 1, wherein the material being treated is in Web-form and is separated from itself such that at least about 20% of the sieve drum jacket is free from said material.

I6. The apparatus of claim 1, wherein said guide means are disposed such that the leading edge thereof is in close proximity to that portion of the surface not covered with material of a cylindrical sieve drum in the row adjacent to said adjacent sieve drums of one row.

7. The apparatus of claim 1, wherein baffle means are provided on the inside of the sieve drums at that portion of the surface of said sieve drums Where the material being treated is being transferred to the next sieve drum.

8. The apparatus of claim 1, wherein only a portion of the sieve drums are provided -with vacuum means.

9. The apparatus of claim 1, wherein shutter-type bafe plates are disposed at that portion of the surface of said sieve drum which is not covered by the material being treated.

10. The apparatus of claim 1, wherein the guide means are effectively formed, at least in part, by sieve drums placed at a relatively small distance with respect to at least some of the adjacent sieve drums.

11. The apparatus of claim 10, wherein said relatively small distance exists between adjacent sieve drums of different rows.

12. 'I'he apparatus of claim 11, wherein said guide means further includes additional guide means disposed at least between some of the sieve drums of the same row.

13. An apparatus for the heat treatment of material which comprises a treatment chamber, a series of more than two cylindrical sieve drums with perforated surfaces rotatably disposed within said treatment chamber, said sieve drums arranged in at least two rows and in a staggered relationship with respect to each other, a portion of the cylindrical surface of each of said sieve drums serving as a conveying means and producing a continuous treatment surface in said treatment chamber, means for introducing the material to be treated to said conveying means, vacuum means communicating with the interior of the cylindrical sieve drums, a portion of the surface o f each of said cylindrical sieve drums, not covered with said material, being substantially free from baffle means, thus facilitating penetration of the treatment medium into said portion not covered with material and providing tangential ow between adjacent sieve drums with an associated increase in drying effect, wherein V-shaped guide means are disposed in the treatment chamber, above and below the end sieve drums providing a restricted passage a-djacent the outer surfaces of said sieve drums whereby the drying effect is thereby accelerated.

14. The apparatus of claim 13, wherein guide means are provided between adjacent sieve drums of one row, said guide means accelerating the ow of the treatment medium which is in contact with the material being treated, whereby the drying effect is also accelerated.

References Cited UNITED STATES PATENTS 2,301,249 11/ 1942 Butterworth et al. 34-115 XR 543,578 7/ 1895 Hartley 34-115 920,351 5 1909 Layland, et a1 34-115 2,964,854 12/ 1960 Kiefer et al 34-115 3,021,608 2/ 1962 Fleissner 34-115 FOREIGN PATENTS 1,110,123 7/ 1961 Germany.

336,540 10/ 1930 Great Britain.

CARLTON R. CROYLE, Primary Examiner.

A. D. HERRMANN, Assistant Examiner.

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