US3320684A

US3320684A - Driers for treatment of a web by a gaseous medium

Info

Publication number: US3320684A
Application number: US427375A
Authority: US
Inventors: Leckner Borje Valentin
Original assignee: Individual
Current assignee: Individual
Priority date: 1964-02-03
Filing date: 1965-01-22
Publication date: 1967-05-23
Anticipated expiration: 1984-05-23

Description

y 967 B. v. LECKNER 3,320,684

DRIERS FOR TREATMENT OF A WEB BY A GASEOUS MEDIUM Filed Jan. 22, 1965 2 Sheets-Sheet 1 y 1967 B. v. LECKNER $320,684

DRIERS FOR TREATMENT OF A WEB BY A GASEOUS MEDIUM Filed Jan. 1965 2 Sheets-Sheet 2 /Z/J' F1 0 1,22 \F27 5137i 4 4 4 mm a United States Patent DRIERS FOR TREATMENT OF A WEB BY A GASEOUS MEDIUM Biirje Valentin Leckner, Linnegatan 20, Jonkoping, Sweden Filed Jan. 22, 1965, Ser. No. 427,375 Claims priority, application Sweden, Feb. 3, 1964, 1,280/64; Jan. 9, 1965, 260/65 Claims. (Cl. 34-156) This invention relates to arrangements in such driers, conditioning apparatuses and the like for the treatment of a substantially horizontal, continuously advancing web by means of a gaseous treatment medium blown towards the web, as comprise at least one treatment zone extending in the horizontal direction of travel of the web and within which the blowing of the fluid takes place, means being provided for maintaining the web within the zone floating, wholly or in part, by means of a statical overpressure on the underside of the web with respect to the pressure on the upper side of the web. Driers and the like of this kind should not be mixed up with virtually alike drieis, in which the web is carried by air jets directed from below against the undereath surface of the web and exerting a lifting action by means of their dynamic or velocity pressure.

A general object of the invention is to provide a drier or the like in which the web to be treated is not subject to wear and friction from a supporting surface diminishing the carrying off of moisture from the web, while it is being advanced.

A specific object of the invention is to provide a drier or the like in which the supply of drying and/or heating medium or the like to different sections of the treatment zone may be easily and individually controlled while the web is being advanced.

With these and other objects in view the apparatus according to the invention is primarily characterized in that the treatment zone thereof is divided, in the direction of travel of the web, into a plurality of preferably equal sections, each comprising a blowing box or header in the shape of a flat pocket which is substantially parallel to the web.

The pocket extends transversely to the web below the same and has its opening connected to a pressure chamber for the medium beside one edge of the web. The upper side of the pocket is provided with apertures, slots or perforations for the directing of the medium against the underneath side of the web, which apertures may be designed in a manner known per se. In addition thereto the pocket is, however, provided with slots or perforations along its edges for blowing or blasting a continuous edge curtain of the medium against the web. This edge curtain dams up the medium or fluid blown from the surface perforations and thereby creates a gas cushion having a statical overpressure under the web, on which cushion the web can float.

These and other features and advantages will appear from the accompanying drawings, illustrating, as a nonlimiting example, a preferred embodiment of the invention and in which:

FIGURE 1 is a plan view, partly in section on the line I-I in FIG. 2;

FIGURE 2 is a front view, partly in vertical, longitudinal section on the line 11-11 in FIG. 1;

FIGURE 3 ,is a vertical cross section on the line III-III in FIGURE 2;

FIGURE 4 illustrates a blowing box of such kind as is comprised in a drier according to FIGS. 1-3 and seen from above;

FIGURE 5 is a vertical longitudinal section on the line VV in FIGURE 4;

FIGURE 6 is an end view of the blowing box according to FIGURES 4-5 as seen from the line VIVI in FIG- URE 4;

FIGURE 7 illustrates, diagrammatically and in principle, the slots of a blowing box as seen in cross section on the line VIIV-II in FIGURE 4;

FIGURE 8 illustrates an alternative to the embodiment according to FIGURE 7;

FIGURE 9 is an enlarged cross section of a blowing slot;

FIGURE 10 is an enlarged detail view of the encircled portion X of FIGURE 5 and illustrates a blowing slot in the end of the blowing box.

FIGURES 46 are drawn on a larger scale than FIG- URES 1-3, and FIGURES 7-8 are drawn on a still larger scale.

Referring to FIGURES 13 the casing of the drier is designated 1 and consists of a bottom wall 2, a top wall 3 and two

longitudinal walls

4 and 5. The drying medium is circulated by blowers 6 driven by motors 7. The impeller 6 of each blower is arranged in a circular opening in a partition wall 8 in front of which a pressure chamber 9 is located which is separated from a suction chamber 10 by means of the partition wall 8. The suction chamber 10 communicates with two adjacent suction chambers 11 through air heaters 12. The web passes through the drier in several horisontal layers parallel to each other and is indicated by doted lines. It is designated M in FIGURES 2 and 3. The means for advancing the web, such as driving and idling rollers, are not shown in the drawings since they are not essential to the invention. Blowing boxes 13 are arranged between two adjacent layers of the web M. Above the uppermost layer of the web and under the lowermost layer thereof blowing

boxes

14 and 15 respectively are also arranged. All blowing boxes project from the pressure chamber 9 (FIGURE 3).

In the embodiment according to FIGURES 1-3 there are two blowers above each other within every section of blowing boxes connected in parallel. In the longitudinal direction the sections are arranged alternatingly in such a manner, that the blowers in every second section are located on one and the same side and the remaining blowers are located on the opposite side. This alternating orientation is not necessary for the invention but merely a suitable mode of construction. The blowing boxes 13-15 operate to blow the blowing medium against the upper as Well as the lower surface of the different layers of the web. The blowing boxes have the shape of flat, thin pockets which are parallel to the different layers of the web and extend across their respective parts of the web. Within each section they project from a common pressure chamber 9 to which they are connected by means of a funnel-shaped inlet piece 16. Each blowing box has an upper side 17 and an underneath side 18. The upper side 17 may be a substantially plane surface according to FIGURE 7 or ridged according to FIGURE 8. The underneath side of the blowing box is suitably ridged according to FIGURES 7 and 8. The longitudinally extending valleys 19 which become deeper towards the end wall 20 of the blowing box operate to carry away the drying medium to that suction chamber 11 which is located immediately opposite to the above-mentioned pressure chamber 9 on the other side of the drier. The end walls 20 are preferably provided with inspection openings having covers 21 which may easily be removed.

FIGURE 9 is a cross section illustrating how a blowing slot 22 may be designed. The blowing box is assumed to be made of sheet iron of uniform thickness. Two plates 23 may have their marginal portions 24 bent or folded inwards along a respective folding line 25 forming an edge. The marginal portions 24 are preferably bent and shaped in such a way, that they diverge somewhat, as shown in FIGURE 9. Spacers 26 are attached to the edges 25 therebetween at intervals to define the width of the slot 22. At the same time the spacers may serve as braces by interconnecting slot edges located on opposite sides of the blowing box, as is indicated in FIG. 5. The outermost slots 27 along the two upper edges of the blowing box are preferably adapted for inclined blowing upwards-inwards as is evident from FIGURES 7-8. Also .at the end of the blowing box there is an edge slot 28 formed between an inclined rail 29 and a flexible tongue or flap 30 (FIGURE 10).

The spacing between the rail 29 and the tongue 30 forms the slot 28, the width of which may be adjusted by means of a set screw 31. According to FIGURE 10 most blowing box 15, however, has to carry a layer of the web and consequently has its upper side shaped in the same way as the blowing boxes 13, its underneath side being tight.

The apparatus operates in the following way. To facilitate the explanation only air is considered as a treatment medium in the following description. The blowers 6 blow the air into the pressure chambers 9 from where it flows into the blowing

boxes

13, 14 and 15. Through the slots or

perforations

22, 27, 28 the air flows from the blowing boxes and strikes the web M on its upper side as well as its underneath side. During the drying operation the drying air hereby carries away part of the water or moisture contents of the web. After its contact with the web the air flows into that suction chamber 11 which is located just opposite to that pressure chamber 9 from which the air previously escaped. From the suction chamber 11 the air divides up into two branch streams, each of which flows into an adjacent suction chamber 10 through the air heaters 12. Then, the procedure is repeated with the air flowing in the opposite direction, and so on. The flow of the air across the web after having been in contact therewith is facilitated by the valleys 19 between the ridges. Means for the supply of dry air and carrying off of moist air are not shown in the drawings, since they are irrelevant tothe invention.

Through the air curtain from the

slots

27 and 28, air which is blown out through the slots 22 from the upper surface of the blowing box is surrounded or confined, where a damming up takes place under the web and an air cushion having a statical over-pressure is created and maintained within the surrounded area. On this air cushion the web M within the section and the area in question can float freely. On the upper side of the web such an air cushion is not formed, since no curtain blowing takes place there.

Towards the pressure chamber side such an air curtain is not necessary, if the structure is designed in such a way, that the funneled connection 16 thereforms a damming wall or the like. If the pocket should not have such a funneled opening, a damming baflle or the like may be inserted in lieu thereof. Of course, a damming curtain may be blown out also on this side.

Only small overpressures are required under the web to keep it floating. An overpressure of only 1 millimeter water guide of manometer corresponds to a lifting power of 1 kilogramme/square meter which is more than sufficient for lighter webs. There are no difficulties in creating an overpressure of eg 5 millimeters water, guide of manometer, and that is suflicient to keep floating even a very heavy web. In practice, so heavy webs are rather rare.

According to FIGURES 7, 8 and 10 the

slots

27 and 28 are inclined upwards-inwards. This is not absolutely necessary, but the obliqueness increases the damming action at a certain curtain flow rate of a certain velocity. The lateral slots 27 may be adjustable, too, but in practice the adjustability of the end slot 28 has proved quite suflicient for the control of the lifting power. This fact simplifiies the setting of the drier, since the end slots 28 may easily be made .accessible by shaping the lateral panels 32 in front of the suction chambers as doors; they may also be shaped as hinged flaps or be made removable. Thereby, also the inspection covers 21 become accessible.

When a web advances through a drier, it becomes progressively lighter when drying. On account hereof it is necessary that the lifting power of the air cushions should be adjustable in accordance with the weight of the web. By dividing each treatment zone into fields or sections according to the invention, such an adjustment may easily be carried out. To this end it may be suitable to provide thelateral panels or doors 32 with inspection windows. It is also. possible to make the means for the adjustment of the width of the slots accessible from the exterior of the drier, e.g. by providing a rotatable excenter which engages the tongue 30.

Even though the invention to. particular advantage may be applied to driers and the like, the blowers of which are arranged alternatingly according to FIGURES 13, it is not restricted tosuch embodiments but may be successfully applied to driers, conditioning apparatuses and the like in which the treatment medium follows other trajectories. Thus, all blowers may be arranged on one and the same side of the apparatus, the treatment medium flowing back through a return channel on the upper and/ or underneath side of the apparatus and so on.

It has proved suitable to utilize slits or slots for the blowing, but also other forms of holes, e.g. circular apertures, may be used. It is also possible to combine different kinds of openings, i.e. circular apertures or perforations for the blowing within the dammed area and slots for the curtains; For the curtains slots are particularly well suited, since they create a continuous curtain already at the openings and since they also permit a simpler and more reliable directing of the outflowing medium. If circular apertures are utilized for the blowing of the curtains, the individual jets merge only at a distance from the outlet opening.

A borderline case arises if adjacent blowing boxes are made in such a way, that their edges extend in immediate contiguity to each other. Then the edge curtainsfrom the laterial slots 27 may merge and then separate again towards the underneath side of the web. This may be further extended to the case, where only one of two adjacent blowing boxes is provided with such a lateral slot.27.

While the invention has been particularly shown and described with reference to one preferred embodiment thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention. Thus, part of the elements comprised in the apparatus described may be omitted or replaced by equivalents.

I claim:

1. In a conditioning apparatus for the treatment of a movable web my means of a gaseous treatment medium blown towards the web: at least one treatment zone having a substantial extension in the direction of travel of said web and through which said web is positively advanced; at least one substantially flat and horizontal pocket-like blowing box having its principal extension and two opposing walls substantially parallel to the surface of said web; a plurality of alternating ridges and valleys, which extend transverse to the direction of travel of the web and are arranged in at least one of said opposing walls of said pocket-like blowing box; at least one pressure chamber, into which said pocket-like blowing box opens; at least one blower for creating an overpressure in said pressure chamber and said blowing box; a plurality of openings in said opposing walls of said blowing box for directing medium jets from below against the adjacent surface of said web; those of the medium jet forming openings which are arranged in said ridged wall of said blowing box being located on the edges of said ridges; and means for creating and maintaining, under the travelling web, a gas cushion in which an overpressure exists and on which the web may float.

2. In a conditioning apparatus for the treatment of a movable web by means of a gaseous treatment medium blown towards the web; at least one treatment zone having a substantial extension in the direction of travel of said web and through which said web is positively advanced, said treatment zone comprising a plurality of sections, located adjacent to each other in a file extending in the direction of travel of said web; at least one substantially flat and horizontal pocket-like blowing box having its principal extension substantially parallel to said web and an upper wall facing the underneath surface thereof in each treatment section; at least one pressure chamber, into which said pocket-like blowing box opens, in each treatment section; at least one blower for creating an overpressure in each of said pressure chambers and blowing boxes; a plurality of openings in the upper wall of each of said blowing boxes for directing medium jets from below against the underneath surface of said web; and narrow slots extending along those of the edges of the upper wall of said pocket-like blowing box, which do not define its opening, for creating a substantially continuous gas curtain confining a horizontal gas cushion in which an overpressure exists and on which the web floats.

3. Apparatus according to claim 2, in which the underneath surface of at least the majority of said pocketlike blowing boxes are also provided with jet forming openings.

4. Apparatus according to claim 2 characterized in that said upper wall of each blowing box is substantially planar and in that a plurality of alternatng ridges and valleys, extending transverse to the direction of travel of the web are arranged in any blowing box underside, which faces said web.

5. Apparatus according to claim 2 further comprising at least one flexible side wall portion having an edge which defines, together with an adjacent edge of said upper wall of said blowing box, one of said slots; and adjustment means adapted to deflect said side wall edge towards and away from said adjacent edge for controlling the width of said slot.

6. Apparatus according to claim 2, characterized by the provision of means associated with said narrow slots for directing said curtain forming jets upwards-inwards in respect of said blowing box to make said jets approximately from three sides of a truncated pyramid sloping upwards.

7. Apparatus according to claim 6 characterized in that said upper wall of each blowing box is substantially planar and in that a plurality of alternating ridges and valleys, extending transverse to the direction of travel of the web are arranged in any blowing box underside, which faces said web.

8. Apparatus according to claim 6 further comprising at least one flexible side wall portion having an edge which defines, together with an adjacent edge of said upper wall of said blowing box, one of said slots; and adjustment means adapted to deflect said side wall edge towards and away from said adjacent edge for controlling the width of said slot.

9. In a conditioning apparatus for the treatment of a movable web by means of a gaseous treatment medium blown towards the web; at least one treatment zone having a substantial extension in the direction of travel of said web and through which said web is positively advanced, said treatment zone comprising a plurality of sections, located adjacent to each other in a file extending in the direction of travel of said web; at least one substantially flat and horizontal pocket-like blowing box having its principal extension substantially parallel to said web and an upper wall facing the underneath surface thereof in each treatment section; at least one pressure chamber, into which said pocket-like blowing box opens, in each treatment section; at least one blower for creating an overpressure -in each of said pressure chambers and blowing boxes; a plurality of openings in the upper wall of each of said blowing boxes for directing medium jets from below against the underneath surface of said web; and narrow slots which extend along those of the edges of the upper wall of said pocket-like blowing box, which do not define its opening, and are directed upwards-inwards in respect of said blowing box, for creating a horizontal, truncated upwardly tapering gas cushion in which an overpressure exists and on which the web floats; said blowers and pressure chambers of adjacent sections being located alternatingly on opposite sides of the longitudinal edges of the travelling web.

10. In a conditioning apparatus for the treatment of a movable web by means of a gaseous treatment medium blown towards the web: at least one treatment zone having a substantial extension in the directon of travel of said web and through which said Web is positively advanced; at least one substantially flat and horizontal pocket-like blowing box having its principal extension substantially parallel to the surface of said web; at least one pressure chamber into which said pocket-like blowing box opens; at least one blower for creating an overpressure in said pressure chamber and said blowing box; a plurality of openings in the upper surface of said blowing box for directing medium jets from below against the underneath surface of said web; and means for creating and maintaining, under the travelling web, a gas cushion in which an overpressure exists and on which the web may float; means defining alternating ridges and vallevs extending transverse to the direction of travel of the web being arranged in at least one of the horizontal surfaces of said pocket-like blowing box; said medium jet forming openings being located on the edges of said ridges.

References Cited by the Examiner UNITED STATES PATENTS 1,487,362 3/1924 Rice 34l59 X 2,402,545 6/1946 Frum 34-160 3,070,901 1/1963 Allander et al 34156 3,070,902 1/1963 Oholm 34159 X 3,127,080 3/1964 Allander et al 34l56 X FOREIGN PATENTS 158,493 4/ 1957 Sweden.

FREDERICK L. MATTIESON, IR., Primary Examiner. JOHN J. CAMBY, Examiner.