US 3272415 A
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S. WALLlN Sept. 13, 1966 APPARATUS FOR STABILIZED TRANSPORT OF WEB- 0R SHEETLIKE MATERIALS Filed March 16, 1964 FIGI.
mvam'onz SVEN WA LLI N United States Patent 3,272,415 APPARATUS FOR STABILIZED TRANSPORT ()F WEB- OR SHEET-LIKE MATERIALS Sven Wallin, Taby, Sweden, assignor to Alrtiebolaget Svenska Flaktfabriken, Stockholm, Sweden Filed Mar. 16, 1964, Ser. No. 352,721 Claims priority, application Sweden, Mar. 17, 1963, 3,004/63 8 Claims. (Cl. 226-97) This application is a continuation-in-part of the application of this inventor, Sven Wallin, Serial No. 289,467, filed on June 19, 1963, now Patent No. 3,206,092, dated September 14, 1965, and claiming priority from an earlier filed Swedish application dated June 21, 1962.
The present invention relates to an apparatus for stabilized transport of a sheet-like material such as a web which is supported by means of air or other gaseous medium.
In the present instance the apparatus comprises a plurality of distribution ducts for supplying the medium, these ducts having a surface facing the material forming a guide plane for the material and provided with a plurality of medium supply ports, arranged in pairs and primarily directed in opposite directions. Typically, the supply ports are arranged having the shape of pressed-down eye-lid perforations, and constructed so that the medium is caused to flow from these in streams essentially parallel to the plane of the transported material. Further, exhaust ducts having exhaust ports are also arranged in the guide plane acting in conjunction with the supply ports in order to extract the medium from the space between the material and the plane. The invention is intended to provide an improvement of recently-produced apparatus of the kind based on the principle or concept that the flow or venturi effect, which principle states that when a gaseous medium flows between two surfaces, a force will be exerted which will tend to move these surfaces towards each other, can be utilized to produce a stabilized carrier with the material floating without tension at a fixed distance from the guide plane.
In previously known apparatus the medium is supplied by means of a number of distribution boxes presenting one side facing the web of material and located on the transport plane, each provided with rows of discharge ports grouped along the centre line of the box and with the space between the boxes acting as exhaust ducts for the medium.
The invention, which is based on the concept that the application of the effect is not limited by the above-mentioned constructional shape of the distribution elements, is characterized in that the supply and exhaust openings are arranged in relation to each other so that the medium supplied therefrom has time to form a continuous film of medium before being exhausted. Further, as the medium is being extracted it is divided up into a number of separate streams.
The invention will permit a choice of location of both supply ports for medium supply and exhaust ports for its extraction. Thus, for example, a plurality of supply ports can be arranged in one and the same distribution duct while in the same way the exhaust ports may be located between the supply ports assuming that the conditions set forth above are fulfilled. In order to ensure that the material is not acted upon in a disturbing manner by the medium leaving through the exhaust ports, according to a suitable embodiment of the invention, the total area of the exhaust ducts may constitute between 20 times, preferably 10 times, the total area of the supply ports to ensure that extraction takes place without the generation of a difference in static pressure on the medium on both sides of the material. This permits a fixed position of the material in relation to the guide plane. For the same reason, according to a second suitable embodiment of the invention, the exhaust ducts are provided with a grating, in which the area of free flow constitutes 50-90% of the areas of the exhaust ducts and the remaining part of the grating forms the supporting plane for transmitting two streams of medium directed towards each other so that the said streams form a film of medium along the centre part of the grating stably supporting the material. These gratings may be designed in the shape of an are or made convex.
The invention may also be utilized for stabilizing a webor sheet-like material which is driven forward by mechanical conveyors or airborne through a plant with air distribution elements of other design, in that the material on a part of the transport path is carried over a separate distribution duct constructed according to the invention. In a similar manner the invention may be used in applications where transport is to take place vertically or at an angle inclined to the horizontal plane. In that instance the distribution ducts may be located on an arbitrary side of the material, such as, if suitable, above the material. Due to the fact that the material transported according to the invention will be driven completely without tension, the utilization of the invention in, eg dryers for paper, means that the finished product will possess excellent values as regards longitudinal elongation, transverse elongation and strength.
Other objects and a fuller understanding of the invention may be had by referring to the following specification and claims taken in conjunction with the accompanying drawing in which:
FIG. 1 is a fragmentary perspective view of a portion of apparatus constructed in accordance with the present invention;
FIG. 2 is a perspective view of another embodiment of the present invention; and
FIG. 3 is a fragmentary perspective view of another embodiment of apparatus constructed according to the invention.
In the drawing, a web-like material 1 is driven forward above a transport or guide plane comprising a plurality of air distribution ducts 2, which supply air or other gaseous medium from supply means, in the present instance fans (not shown). In the surface 2a of the ducts 2 facing the material, are gaseous medium supply ports 3a and 3b respectively, made, in the present instance in the form of pressed-down eye-lid perforations directed principally in opposite directions and constructed so that the medium is caused to flow substantially in opposite directions in streams essentially parallel to the transport plane. As illustrated, the ports 3a of one row are staggered with respect to the ports 3b of the other row. The medium is extracted through exhaust ducts 4 located so as to prevent collision between the undivided streams of medium before being exhausted. In order to comply with this condition, the distance between supply ports and corresponding exhaust ducts should be such that the velocity of the stream of medium in the space between material and transport plane is reduced to 0.2-0.8 times, preferably 0.5 times, the medium supply velocity. Gratings 5 arranged in the exhaust ducts are provided with exhaust ports 6, the total area of which amounts to 5090% of the exhaust duct area. In the case shown in FIG. 1, where the distribution ducts are provided with bevelled edges 7, the grating 5 has been made in the shape of an arc in order to obtain an unaltered level for the material.
FIG. 2 illustrates another embodiment of the invention with the web of material removed. In this embodiment a plurality of ducts 12 having surfaces 12a and 12b are provided with gaseous medium supply ports 13 and 23 respectively. For purposes of identification, the ports 13 have been designated as rows, 13a and 13b while the ports 23 have been designated as rows 23a and 23b. Although the eye-shaped ports 23 and 13 are somewhat dissimilar they serve the same function as the ports 3a and 3b as heretofore described. Further, as may be noted in FIG. 2, the corresponding rows of ports are aligned and not staggered as those illustrated in FIG. 1. In a manner similar to that above-described, the medium is extracted through exhaust du-cts 14 having gratings 15 and exhaust ports 16 therein, and positioned with respect to the supply ports so as to prevent collision between the undivided streams of medium as it flows therebetween. The various limits as to distance, area and velocity are as heretofore described.
In the embodiment shown in FIG. 3, a plurality of gaseous medium supply ports 8a, 8b, are arranged in one and the same distribution duct 9, and the exhaust ports are located in this instance between the supply ports and are connected to an exhaust duct through passages 11.
As distinguished from earlier known transport apparatus, where the material is supported by jets of air at right angles to it, the invention may be used to transport materials with great differences in area per weight without any ditficulties whatsoever in producing the desired material level.
Without departing from the concept of the invention, the distribution ducts could be arranged so that they combine to form an arched transport plane or a plane following an arbitrary arc.
What I claim is:
1. Apparatus for the stabilized transport of web or sheet, like material supported by a gaseous medium, said apparatus comprising: at least one distribution duct for supplying said medium, said duct having a surface confronting said material and forming a guide plane therefor, gaseous medium supply ports arranged in pairs in said plane and each port of a pair directed oppositely to the other port of the pair, said supply ports including means whereby said medium is caused to flow therefrom in streams substantially parallel to said transport plane, exhaust ports in said guide plane spaced from the acting in conjunction with said supply ports to extract the medium from the space between said material and said plane, said supply and exhaust ports being positioned in relation to each other so that the medium supplied from said supply ports forms a continuous film of medium prior to being exhausted through said exhaust ports, and means to divide said continuous film into a plurality of separate streams upon being exhausted.
2. Apparatus in accordance with claim 1 including a plurality of distribution ducts arranged transverse to the direction of transport of said material, and wherein said supply ports are located along the centerline of said ducts, said ducts being spaced one from the other in the direction of transport so as to define exhaust ducts therebetween,
and a grating covering said exhaust duct, said grating including said exhaust ports.
3. Apparatus in accordance with claim 1 wherein said guide plane comprises a continuous medium distribution duct having equally spaced rows of supply ports substantially transverse to the direction of material transport, and wherein said exhaust ports are separate ports and pass through said distribution duct, said exhaust ports located adjacent each other and arranged in rows parallel to said supply ports.
4. Apparatus in accordance with claim 3 where-in said rows of exhaust ports lie transverse to the direction of material transport and are laterally alternating with said supply ports.
5. Apparatus in accordance with claim 1 wherein the area of said exhaust ports is five to twenty times the total area of said supply ports thereby insuring extraction of said medium without generation of differences in static pressure of the medium on both sides of the material thereby allowing the material to be fixedly located relative to said transport plane.
6. Apparatus in accordance with claim 5 wherein said total area of the exhaust ports is ten times the total are-a of said supply ports.
7. Apparatus in accordance with claim 1 including at least two supply ducts spaced from each other so as to define an exhaust duct therebetween, and wherein said surface confronting said material and forming a guide plane therefor includes a transverse bevel to impart a deviation from the surface of the material being conveyed, said exhaust duct having a grating defining said exhaust ports and an intermediate portion between said ports, the area of said exhaust ports being at least 50 to percent of the cross section-a1 area of said exhaust duct whereby the said 7 intermediate portion of said grating forms the supporting plane for transmitting two streams of medium directly towards each other so that the said streams form a pressurized cushion stably supporting the material along the center portion of said grating.
8. Apparatus in accordance with claim 7 wherein said grating over said exhaust ducts is outwardly convex in cross section.
References Cited by the Examiner UNITED STATES PATENTS 713,787 11/1902 McKone 30231 2,848,820 8/1958 Wallin et al. 22697 X 2,905,768 9/1959 Cronquist. 3,070,901 1/ 1963 Allander et al. 3,206,092 9/1965 Wallin 22697 FOREIGN PATENTS 945,309 12/ 1963 Great Britain.
M. HENSON WOOD JR., Primary Examiner.
A. N. KNOWLES, Assistant Examiner.