US 3678599 A
In a process for a non-contacting directional control of a web, which is stabilized in a floating state and moves through a treating space, a treating fluid is supplied to said web and the treating fluid is flowed against the rear surface of a guiding surface element which is airfoil-shaped in cross section. Said rear surface is convex toward the web. The treating fluid is sucked from the space between said guiding surface element and said web. This process is adapted to separate a boundary layer from that surface of the web which faces the guiding surface element, and to suck off also said boundary layer.
Description (OCR text may contain errors)
United States Patent Vlts [451 July 25, 1972 54] APPARATUS FOR A NON-CONTACTING 3,231,165 1/1966 Wallin et al ..226/97 STABILIZATION OF A WEB WHICH IS 3,272,415 9/1966 Wallin MQVED IN ITS LONGITUDINAL 3,324,570- 6/1967 1 1mm et al ..34/156 DIRECTION 3,384,282 5/1968 V1ts ..226/97 3,496,648 2/1970 Hermg, Jr ..34/ l 56  Inventor: l-lilmar Vits, Langenfeld, Germany  Assignee: Vits Maschlnenbau Gmbl-l  Filed: Sept. 28, 1970  Appl. No.: 75,949
 Foreign Application Priority Data Oct. 9, 1969 Germany ..P I9 51 002.2
 US. Cl ..34/l56, 226/97  Int. Cl ..F26b 13/00  Field of Search ..34/l0, 156; 226/97, 7, 196
 References Cited UNITED STATES PATENTS 3,041,739 7/1962 Meier-Windhorst ..34/156 Primary Examiner-Frederick 'L. Matteson Assistant Examiner-W. C. Anderson Atlomey-Michael S. Stricker [5 7] ABSTRACT In a process for a non-contacting directional control of a web, which is stabilized in a floating state and moves through a treating space, a treating fluid is supplied to said web and the treating fluid is flowed against the rear surface of a guiding surface element which is airfoil-shaped in cross section. Said rear surface is convex toward the web. The treating fluid is sucked from the space between said guiding surface element and said web. This process is adapted to separate a boundary layer from that surface of the web which faces the guiding surface element, and to suck ofl' also said boundary layer.
6 Claims, 2 Drawing Figures PATENTEML 25 m2 Fig. 2
APPARATUS FOR A NON-CONTACTING STABILIZATION OF A WEB WHICH IS MOVED IN ITS LONGITUDINAL DIRECTION Processes and apparatus for a non-contacting stabilization of a longitudinally moving web through a stream of a blown fluid, which flows over a guiding body, which is disposed on one side of the web and faces it with an airfoil-shaped wall, are already known. The proposals of this kind are based on the recognition that a flow over the convex surfaces of an airfoil section results in subatmospheric pressures, which cause the web to contact the airfoil section. To avoid this, a supporting fluid under superatmospheric pressure has already been introduced into the region between the leading edges of airfoil sections facing each other in mirror symmetry and said fluid has been blown over transverse ribs, which had concave depressions open toward the web. The resulting superatmospheric pressures were used to compensate the subatmospheric pressures. As the web approaches the nozzle(s), the superatmospheric pressure increases; and as the distance increases, the subatmospheric pressure increases, so that the web is automatically stabilized. Besides, an approach of the web to convex portions of an airfoil section will reduce the cross sections for the outflow of fluid from the zone which is under superatmospheric pressure so that the pressure flow from the above-mentioned cross-sectional perforation is automatically increased and the web is lifted more than before from the convex portion of the airfoil section. The web oscillates to assume a stabilized course, which corresponds to a series of sine waves having a small amplitude.
Such apparatus are generally used as nozzle dryers in which warm or hot air is used as a supporting treating fluid. Whereas they embody a basic solution to the problem, it has been found in their operation that phenomena occur which must be eliminated. In web-fed offset printing presses and in multicolor gravure printing, pairs of cylinders are inked in different colors and are contacted in succession with the paper web, preferably on both sides thereof, as said web passes between the cylinders. These inks give satisfactory print only if they have a constant viscosity. The viscosity changes during the printing operation because the supporting fluid can contact the printing cylinders. The offsetor gravure-printing ink forms an extremely thin film, which is subjected to the action of the rapidly flowing supporting fluid on a relatively large surface so that the viscosity of the printing ink increases rapidly. This increases the tendency of the printing paper to adhere to the cylinder as it passes through the nip between the cylinders and to separate from the cylinder only as the tension of the paper web increases. In the meantime, the paper web has been deflected from its central position so that it is no longer in a position in which it is clear of stationary machine elements. These phenomena occur in periodic succession as the cylinder revolves. The resulting enforced vibrations may be at the natural frequency of the paper web so that resonance occurs and the web may move out of the depth of field of optical systems associated with photocells which in response to register marks on the web control the printing mechanisms of said web-fed offset printing machines and multicolor gravure printing machines to maintain a proper register so that the need for difficult manual corrections from the end of the machine is eliminated.
It is an object of the invention to retain all advantages of the stabilization which has been accomplished before and to eliminate the causes and the detrimental results of the disturbing phenomena.
Based on a known process for a non-contacting, stabilized directional control of a longitudinally moved web by means of a stream of supporting fluid which is supplied to the web and applied against the rear surface of a guiding surface element, which rear surface is convex toward the web, said guiding surface element having the shape of an airfoil in cross section, the present invention is characterized in that the treating fluid is sucked from he space between the convex portion of the guiding surface element and the web so that the boundary layer facing the guiding surface element is separated from the web.
This may be effectively accomplished in that the supporting fluid is completely or almost completely sucked off so that the dynamic energy of the supporting fluid acts no longer at the plane of the web but at the rear of the guiding surface element and can be reduced there in that the supporting fluid is sucked off. Undesired, disturbing or directly damaging effects on the web are thus eliminated so that the flow no longer reaches the pressure rolls. The detrimental influences of means disposed in the flow path of the supporting fluid are also eliminated so that the invention gives the desired success, regardless whether the printing mechanisms of web-fed offset printing machines or multicolor gravure printing machines or other kinds of equipment or means are involved which must be withdrawn from the influence of the supporting fluid because such influence would have detrimental results of the kind set forth hereinbefore. For the results which are intended and accomplished by the invention, it will be entirely sufficient to provide the perforations only in that portion of the guiding surface element which, viewed in the direction of flow of the supporting fluid, adjoins the vertex line of the convex guiding surface element, where the distance between the guiding surface element and an imaginary center line of the web is a minimum.
Apparatus for carrying out said processes, which comprise guiding bodies extending over the web transversely to the longitudinal movement thereof and have a perforated guiding surface element which faces and is convex toward the web and has an airfoil section when viewed in the direction of a cross section through the web, are characterized according to the invention in that the guiding body consists of a hollow body having a cavity, which is defined by the airfoil-shaped guiding surface element and which is connected to a vacuum source, preferably to the suction pipe of a blower for pressurizing the fluid to be blown. If the two guiding surface elements which succeed in the direction of movement of the web have confronting leading edge portions defining between them a common inlet for the supporting fluid to be directed against the two guiding bodies, the resulting conditions will be particularly desirable because double nozzles thus formed are particularly simple in structure and may be arranged in any desired number in a row extending in the longitudinal direction of the web, which can thus be subjected to the action of the supporting fluid along a very long path. This results in the special advantage that his sufficient to provide these double nozzles on one side of the web and such arrangement will not adversely affect the stability of the web. This advantage is decisive compared to former proposals, which essentially involved the provision of reciprocally arranged blow nozzles and blow boxes, staggered by one-half pitch, on the other side of the web to ensure that the web can be kept floating between these means. In this connection, the term pitch defines the spacing between two successive nozzles or nozzle groups disposed on one side of the web. If the web must be coated only on one side of the web, the maintenance of the boundary layer on the coated side may be of essential influence on the quality of the final product so that apparatus in which blow nozzles on both sides of the web are required cannot be used in the manufacture of such products whereas according to the invention the coated side of the web faces away from the blow nozzles and is withdrawn from all influences of the blown fluid.
In a known manner, transverse ribs formed with concave depressions and defining nozzles may be disposed between'the web and the guiding bodies and may preferably face the inlets for the supporting fluid; these ribs are preferably also perforated. These transverse ribs providedwith depressions have not only the advantage that they constitute simple means which form one of the two nozzle walls but they result in the formation of a pressure zone also between said ribs and the web, which pressure zone tends to repel the web whereas the web tends to approach the convex portions of the guiding body; this results in the above-described automatic control and automatic stabilization.
BEST AVAILA The drawing shows embodiments of the invention diagrammatically and by way of example.
FIG. 1 is a double nozzle arrangement according to the invention.
FIG. 2 shows that guiding bodies and nozzle members as shown in FIG. 1 may be arranged in rows in any desired manner.
The center line of the web is shown in dash-dot lines in FIG. 1. Guiding bodies generally designated 1, 2 are disposed below the web 0. The confronting boundaries 11, 21 of said guiding bodies define an inlet 3 for a blown fluid, which may consist of air, which by a blower of known type, not shown, is pressurized. This pressure is indicated by a sign. The confronting walls 11, 21 of the guiding bodies face additional walls 12, 22 so that there are cavities or exhaust chambers 13, 23 for supporting fluid to be discharged. These cavities or exhaust chambers are indicated by a sign and are closed toward the'web 0 by head walls 14, 24. Dash-dot-dot lines 15, 25 indicate that the resulting guiding surface elements 14, 24 in conjunction with the rounded inwardly bulging surfaces 16, 26 which are flown against by the supporting fluid from the chamber 3 define airfoil sections, which have rear or trailing ends disposed approximately at 17, 27. The lead lines for the reference numbers 14, 24 extend in such a manner that in a transverse sectional view their far ends coincide with the vertices or, in a three-dimensional system, with the vertex lines, of the airfoil section boundary walls 18, 28 facing the web having the center line 0. The head walls or guiding surface elements 14, 24 have sloping or descending surface portions 'which adjoin the vertices or vertex lines and which are provided with the perforations 19, 29.
A rib 4 formed with a concave depression and with perforations 41 is disposed between each pair of confronting end faces 16, 26 of the guiding body. This rib 4 defines slot-shaped nozzles 51, 52, which receive supporting fluid from the inlet 3. The inflowing supporting fluid flows against the surfaces 14,
28 having the illustrated airfoil sections, which are supplemented by the imaginary surfaces 15, 25. The perforations 19, 29 of the airfoil sections of the guiding bodies 1, 2 open into the resulting vacuum zones at points which viewed in the direction of flow are disposed behind the vertices of walls I4, 24 so that in conjunction with the vacuum in the exhaust chambers 13, 23 the supporting fluid which is present there is more or less removed and separates the boundary layer from the rear surface of the airfoil. The selection of the cross sections of the perforations I9, 29 and of the vacuum in the chambers 13, 23 enables a control ofdesired flow conditions.
FIG. 2 illustrates the arrangement if a plurality of double nozzles in the embodiment shown in FIG. I are disposed one behind the other in a group of row so that the web having the center line 0 can be subjected to the action of the blown fluid along a relatively long path.
FIG. 1 of the U.S. Pat. No. 2,594,299 indicates how nozzles designed according to the invention may be used in a floating dryer and how these nozzles are related to the floating web which moves through the treating chamber and is to be treated in this state.
The invention is directed to each of the features which have been disclosed, even though it may have been mentioned only BLE' COPY in connection with other features, as well as to any practicable combination of part of the features and to the combination of all features, provided that the individualfeatures and the com'- binations of part or all of the features have technical utility and are practicable and useful, even though the novel technical results which may be achieved have not been mentioned and specifically described. All details which are apparent and have been stated in the description and/or claims and/or shown in the drawing, and all combinations of such details, are considered described and claimed as such with their function or functions and in the function relation or functional relations which are obtained in combinations of parts or all of such details.
What is claimed is: I 1. Apparatus for non-contacting guiding a moving web in a stabilized floating manner through a treating space, said apparatus comprising a pair of hollow guiding bodies arranged spaced from each other in the direction of movement of the web and defining between themselves a space, each of said guiding bodies having an end wall facing the web and extending in direction transverse to the movement of the latter over the whole width thereof, each of said end walls having an outer convexly curved guiding surface having an ascending portion starting from said space between said guiding bodies and a descending portion; a rib extending across the width of the web and transversely through the space between said pair of guiding bodies in the region of the ascending portions of the guiding surfaces on the end walls of the two guiding bodies,
spaced therefrom and defining with parts of said ascending portions of said guiding surfaces a pair of diverging nozzles; means for supplying a treating fluid to said space between said guiding bodies so that said treating fluid flows through said nozzles against the web; a plurality of perforations formed through each of said end walls only in the region of said descending portion of said guiding surface; and means for creating an underpressure in the interior of each of said hollow guiding bodies so that treating fluid'blown through said noules against the web is at least in part evacuated from the space between the web and the end walls of the guiding bodies through said perforations and the interior of said hollow guiding bodies.
2. Apparatus as defined in claim I, wherein said guiding bodies in each pair and said rib are mirror-symmetrically arranged with respect to a plane of symmetry between said bodies and at right angles to the direction of movement of the web.
3. Apparatus as defined in claim 1, wherein a plurality of pairs of guiding bodies are arranged spaced from each other in the direction of movement of the web.
4. Apparatus as defined in claim 1, wherein each of said hollow guiding bodies has a wall facing the wall of the other guiding body of said pair of guiding bodies, and wherein each of said facing walls has an inwardly bulging rounded portion blending into the end wall of the respective body.
5. Apparatus as defined in claim 4, wherein said rib has a curved transverse cross section having a convex surface facing said space between said guiding bodies.
6. Apparatus as defined in claim 4, wherein said rib is provided with a plurality of perforations therethrough.