WO1984003485A1

WO1984003485A1 - A method and device for pressure sealing a passage while a web material is moved therethrough

Info

Publication number: WO1984003485A1
Application number: PCT/DK1984/000016
Authority: WO
Inventors: Kjeld Holbek
Original assignee: Kjeld Holbek
Priority date: 1983-03-03
Filing date: 1984-03-05
Publication date: 1984-09-13
Also published as: DK108383D0; EP0135557A1

Abstract

A flexible web or plate material (10) to be continuously treated within a space or chamber (21, 22) containing a vacuum or a super-atmospheric pressure, may be passed into the treatment chamber through a pressure sealing inlet passage (23) and out from the chamber through a similar outlet passage (24). The pressure sealing passages comprise a plurality of mutually longitudinally spaced, alternatingly oppositely directed web contacting surface parts (40) of opposite, spaced passage defining walls (26, 27). These web contacting surface parts may define a sinuous or tortuous path for the web material (10) passing through the passage in a stretched condition, whereby the web material and the cooperating web contacting surface parts form a kind of labyrinth-seal. A contact pressure between the web material (10) and the web contacting surface parts (40) may be increased by the provision of suction openings, which are formed along the web contacting surface parts (40) and communicate with a vacuum source. In that case, the pressure sealing passage may be defined between a pair of parallel, spaced walls, and the contact pressure between the web material (10) and the web contacting surface parts (40) may then be obtained exclusively by suction.

Description

A METHOD AND DEVI CE FOR PRESSU RE SEALI NG A PASSAGE WH I LE A WEB MATERIAL IS MOVED THERETH ROUGH

The present invention relates to a method of moving a web material through a first passage interconnecting a first space, in which a first pressure level is maintained, and a second space, in which a substan¬ tially different pressure level is maintained .

I n the present specification the term "web material" should be rather broadly interpreted. Thus, this term should comprise any flexible plate or web material including thin plate metal , veneer and other thin wooden plates, woven and non-woven textile web material made from fibres of organic and inorganic materials, such as cotton, iron , cellulose, glass, and plastic.

Processing of web materials may" involve treatment within a vacuum chamber or high-pressu re chamber. Thus, for example, various liquid impregnating means or additives may advantageously be applied to the fibres of a fibrous web material by applying the impregnating means or additives to the web material in an atomized or gaseous condition while the material is exposed to a sub-atmospheric pressu re or va¬ cuum, and the penetration of the liquid additives into the web ma- terial may be improved by subsequently exposing the web material to atmospheric or super-atmospheric pressu re. As another example, it may be desired to apply a protective and/or decorative coating to plate metal or another plate material while exposed to heat under vacuum. Thus, a continuous process involves continuous feeding of a web material through two or more interconnected spaces in which different pressure levels are maintained . I n order to obtain a desired high difference between the pressure levels in successive chambers or spaces, and for the sake of economy and efficiency, an effective pressure seal must be provided in the web-receiving passages inter- connecting the various spaces .

O PI The present invention provides a method of moving a web material through a first passage interconnecting first and second spaces, said method comprising maintaining a first pressure level in the first space, maintaining a substantially different pressure level in the second space, and moving the web material longitudinally in the passage in a stretched condition along a path defined by a plurality of mutually longitudinally spaced, alternatingly oppositely directed web contacting surface parts of opposite, spaced passage defining walls, while maintaining opposite side surfaces of the web material in contact with adjacent web contacting surface parts, each contacting surface part extending transversely over substantially the full width of the web material, whereby each pair of consecutive, oppositely di¬ rected web contacting surface parts and the section of the web mate¬ rial extending therebetween form at least a partial pressure seal . The interconnecting passage preferably includes two or more of such pairs of consecutive, oppositely directed web contacting surface parts, and, consequently, the web sections extending between the web contacting surface parts divide the passage into a number of substantially closed chambers with internal pressures varying between the . first and second pressure levels. The efficiency of the pressure seal obtainable depends on i. a. the gas penetrability of the web material and the tightness obtainable between the edges of the web material and the adjacent inner passage walls. Therefore, the width of the passage is preferably adapted to the width of the web material as closely as possible. This may, for example, be done by replacing detachable inserts defining the transverse extension of the passage. I n some cases, however, it may be desired to provide a controlled air leakage at the side edges of the web material .

Normally, the web material is drawn through the web receiving, sealing passage, and then, of course, the frictional resistance gener¬ ated within the passage has to be substantially smaller than the tensile strength of the web material . I n order to minimize the fric¬ tional resistance the web material may be moved along a substantially rectilinear path . In that case pressure members, such as spring biased roller members may be used for pressing the web material into contact with the respective web contacting surface parts. In the preferred embodiment, however, the web material is sucked into contact with at least some of the oppositely directed web contacting surface parts . This may, for example, be obtained by providing in the web contacting surface parts slots or openings which are in communication with a vacuum source.

According to an alternative embodiment the web material may be moved along a sinuous path , so that the web material may be pressed into contact with the oppositely directed web contacting surface parts by the tensile force applied to the web material in order to move it th rough the pressu re sealing passage.

The said first space may, for example, be a space or a chamber communicating with the atmosphere, and sub-atmospheric or super- atmospheric pressure may be maintained within the said second space. A supply roll of the web material may then be arranged within this second space in which it is exposed to a pressure below or above atmospheric pressure, and it may then continuously be passed th rough said fi rst passage into the first chamber. Normally, however, the web is moved from this first space which communicates with the atmosphere, through the first pasage into the second space in which a pressu re which is substantially below or above atmospheric pressure is maintained, and then from the second space into a thi rd space, which may also communicate with the atmosphere, th rough a second passage, which may be of the same type as the said first passage. Thus, the second space may be a web treatment chamber in which the web material may be exposed to a vacuum or to an increased pres- sure, and the web material may be moved from the second space th rough the said second passage back into the atmosphere.

The web material may, for example, be a fibrous material , the fibres of which are to be impregnated with a liquid impregnating means or additive. I n that case the liquid additive may be applied to the web material within the said second space while a sub-atmospheric pres¬ sure or vacuum is maintained therein so as to evacuate the hollow spaces or internal cavities of the fibres . The liquid additive is pre¬ ferably sprayed onto at least one side surface of the web . The penetration of the liquid additive into the web material may be facilitated if the second space or the web treating space is divided into first and second compartments by the web material passing there¬ through, because the pressure within the first compartment, in which the liquid additive is applied, may then be kept at a slightly higher level than in the other compartment. The pressure increase in the first compartment may, for example, be obtained by supplying nitro¬ gen or another inert gas into that compartment so as to reduce the risk of explosion, in case the liquid additive or impregnating means is of a combustible type. The pressure difference provided through the web material may also promote the penetration of additive into the web material .

According to another aspect the invention also provides a pressure sealing device for cooperating with a web material being passed through the device in a stretched condition between spaces with different pressure levels, said device comprising spaced, oppositely arranged inner surfaces, which define a through-going web receiving passage and which comprise a plurality of alternatingly oppositely directed web contacting surface parts spaced longitudinally along the passage, each web contacting surface part extending transversely over substantially the full width of the passage, and means for main¬ taining the web material in sealing contact with each of the oppositely directed web contacting surface parts .

The oppositely directed web contacting surface parts may be substan- tially plane and parallel, and in that case the contact maintaining means preferably comprise one or more suction openings defined in and extending along the web contacting surface part in question, whereby the web material is kept in sealing engagement with the web contacting surface parts by suction . The inner surfaces defining the web receiving passage may then be substantially plane and parallel wall surfaces arranged with a spacing slightly exceeding the thickness of the web material . The web contacting surface parts may then be defined by the side surface parts closely adjacent to the suction slots or openings defined therein .

itTREXi OMPI Each web contacting surface part may, alternatively, have a convex cross-sectional shape, each intermediate web contacting su rface part on each of the oppositely arranged inner surfaces extending between a pair of adjacent web contacting surface parts on the other opposite inner surface and to a position spaced from a tangential plane common to said pair of web contacting surface parts, less than the thickness of the web material . The web contacting su rface parts will then define a sinuous or tortuous path for the web material, whereby a kind of labyrinthic seal is obtained . The web contacting su rface parts may, of course, extend to a position beyond the said common tangential plane. The web contacting su rface parts may be uniformly spaced . However, if desired, the spaces may vary. For example, the spacing or dis¬ tance between the web contacting surface parts may decrease or increase in the direction of movement of the web material .

The web contacting surface parts may be provided in any suitable manner. Thus, for example, each of the oppositely arranged inner surfaces may have a wavy or sinusodial cross-sectional shape, and the inner surfaces may be substantially uniformly spaced along the length of the passage defined thereby. I n that case, the web con- tacting surface parts are formed by the tops or crests of the waves . The wavy or sinusodial cross-sectional shape of the inner su rfaces of the passage may, for example, be made by molding and/or by ma¬ chining such as milling . Alternatively, the opposite inner surfaces of the passage may be defined by corrugated sheet material such as corrugated sheet metal . I n that case, the corrugation tops may be supported by rods or other elongated supporting members for pre¬ venting substantial deformation of the corrugated sheet material du ring use of the sealing device.

I n another embodiment, each of the inner su rfaces is formed by a substantially smooth wall su rface and by separate, transversely ex¬ tending, longitudinally spaced rod or strip members which are fastened to the smooth wall surface, and which define the web con¬ tacting su rface parts thereon . Such rod or strip members may, for example, be fastened by glueing, bracing, or welding . The contacting surface parts may alternatively be defined by rollers mounted in recesses defined in the smooth wall surfaces .

OMPI The transversely extending web contacting surface parts preferably extend at substantially right angles to the direction of movement of the web material through the web receiving passage. However, these surface parts may, alternatively, extend along oblique directions, and they may even be curved and/or define a herring-bone like pattern, provided that they are all in contact with the web material over the total width thereof.

The convex cross-sectional shape of each web contacting surface part is preferably, but not necessarily, rounded so as to reduce the friction between the web material and the web contacting surface parts . For the same reason, and also in order to obtain an improved seal, the web contacting surface parts are preferably very smooth .

I n principle, the web contacting surface parts may be made from rubber, plastic, or another resilient material of the type which is normally used for tightening purposes . However, such material gives rise to relatively high frictional forces and also to an unacceptable wear. Therefore, it is preferred to use steel, ceramics, silica cement, or another hard material for the web contacting surface parts . These latter materials also allow for a relatively high web treatment tempera- ture, if so desired.

The web receiving passage may follow any desired path, provided that the web material extending through the passage in a stretched condition is in contact substantially only with the web contacting surface parts in the manner described above so as to form a number of pressure seals . Even when the oppositely directed web contacting surface parts are positioned so as to define a sinuous path, it may be desired to minimize the deviation of the web material from a plane condition in order to also minimize the friction between the web ma¬ terial and the web contacting surface parts . This deviation must, however, be sufficient to allow for a certain wear and, nevertheless, ensure a sufficient specific pressure between the web material and the web contacting surface parts to obtain the desired sealing effect. If a sufficient sealing effect cannot be obtained exclusively by the tensile force applied to the web material, grooves or openings, which are in communication with a suitable vacuum source, may be provided in the web contacting surface parts . If the sealing pressure obtainable by the tensile force is sufficient, one or more of the compartments, in which the passage is divided by pairs of consecutive, oppositely directed web contacting surface parts and the sections of the web material extending therebetween, may be communicated with a source of vacuum or pressu rized gas, dependent on which pressure level is maintained in the adjacent space.

The invention will now be further described with reference to the drawings, wherein ,

Fig . 1 is a perspective and partially sectional view of a vacuum impregnating unit for treating a fibrous web material,

Figs . 2a, 2b, and 2c show diagrammatically a fragmentary cross- sectional view of various embodiments of the pressu re sealing pas- sages shown in Fig . 1 ,

Fig . 3 is an end view and partially cross-sectional view of the vacuum impregnating unit shown in Fig . 1 ,

Figs. 4-9 show diagrammatically various other embodiments of pres¬ sure sealing passages which may be used in connection with a unit as that shown in Figs . 1 and 3,

Fig . 10 is a fragmentary sectional view showing a sealing structure which may be used for sealing the wall elements of the unit shown in Figs . 1 and 3 along the edge portions thereof, Fig . 11 is a side view and partially sectional view of a further embo- diment of an impregnating unit comprising a sealing device according to the invention ,

Fig . 12 is an end view and partially sectional view of the impregnat¬ ing unit shown in fig . 11 , and Fig . 13 is a fragmentary sectional view along the line 13-13 in Fig . 12.

Figs . 1 and 3 illustrate a vacuum impregnating unit for impregnating a fibrous web material 10 (Fig . 2c) , such as paper or cardboard, with liquid impregnating means or additives . The vacuum impregnating unit comprises upper and lower wall elements 11 and 12, which may be moved in relation to each other by means of hydraulic or pneu-

O PI matic cylinders 13, which are mounted on the lower wall element 12 and have the free ends of their piston rods 14 connected to brackets 15 mounted on the upper wall element 11 . Guiding rods 16 extending at right angles to the general planes of the wall elements 11 and 12, are mounted on the lower wall element 12 by means of lugs 17, and each of the guiding rods 16 extends through an aligned pair of eye members 18 formed on the upper wall element 11 .

In the closed position of the impregnating unit, longitudinally ex¬ tending, transversely spaced lower edge portions 19 of the upper wall element 11 is in sealingly engagement with a corresponding pair of upper edge portions of the lower wail element 12. The inner, oppo¬ sitely arranged, spaced surfaces of the wall elements 11 and 12 are shaped so as to define therebetween a pair of closely arranged, substantially cylindrical vacuum chambers 21 and 22, a slot-like sinous or tortuous inlet passage 23 connecting the vacuum chamber 21 with the ambient atmosphere, a similarly shaped outlet passage 24 connecting the vacuum chamber 22 with the ambient atmosphere, and a passage 25 interconnecting the vacuum chambers 21 and 22. Each of the passages 23 and 24 is defined between a pair of oppositely ar- ranged, mutually spaced corrugated plates 26 and 27 forming part of the upper and lower wall elements, respectively. Each of the wall elements 11 and 12 also comprises electrical heating means 28 for heating the corrugated plates 26 and 27, and a thermal insulation 29 positioned between the heating means 28 and the outer wall of the respective wall elements . Electrical energy may be supplied to the heating means 28 through an electrical cable 30 (Fig . 1 ) .

The vacuum chambers 21 and 22 are communicating with a suitable vacuum source, such as a vacuum pump (not shown) , through vacuum conduits 31 opening into the bottom parts of the vacuum chambers at 32. Furthermore, a number of spray nozzles 33, which are preferably of the type used as fuel injection nozzles in diesel engines, are mounted in the upper wall element 11 , for continuously supplying a controlled amount of one or more liquid additives or impregnating means into each of the chambers 21 and 22 in an atomized condition . The liquid additives may be supplied to the nozzles 33 from a meter- ing, high-pressure liquid pump, for example of the type used as a fuel pump in a diesel engine. Tubular sensor receiving members 34 extend from an end wall of the cylindrical chambers and allow for insertion of sensors (not shown) into the vacuum chambers for measu ring various physical conditions, such as temperature, oxygen content, humidity, pressure etc. A pair of substantially horizontally extending, vertically spaced upper and lower grid-like web support¬ ing structures 35 and 36 are arranged in each of the vacuum cham¬ bers 21 and 22.

The web treating unit shown in the drawings may be used for im¬ pregnating a fibrous web material 10 with one or more liquid additives or impregnating means, for example of the types described in appli¬ cant's PCT-application published under the international publication number WO 82/04271 , for example in order to impart desired surface characteristics to the fibres of the web material treated . The web material 10 is continuously passed through the inlet passage 23, the spaces defined between the grid-li ke supporting structu res 34 and 35 arranged within the vacuum chambers 21 and 22, and through the outlet passage 24. The web material 10 is preferably supplied to the inlet passage 23 in a heated and substantially dry condition , and the web material is fu rther heated and dried by the heating means 28 when passing the passages 23 and 24. While a relatively low pressure is maintained within the chambers 21 and 22 in order to evacuate the inner cavities of the fibres in the fibrous web material passing there- th rough , metered amounts of liquid additives or impregnating means are applied to the upper surface of the web material in an atomized condition , whereby these additives penetrate into the web material and into the cavities of the single fibres . Due to the vacuum existing within the chambers, the liquid additives may be sprayed or atomized so as to form ultrafine droplets or particles . I n order to promote the penetration of the additives or impregnating means into the fibrous material, metered amounts of an inert gas, such as nitrogen, may continuously be fed into the upper part of the vacuum chambers 21 and 22 through nozzle means (not shown) , in order to maintain in the upper parts of the chambers 21 and 22 a slightly higher pressu re than that in the lower parts of the chambers below the web material . The continuous supply of inert gas or nitrogen to the vacuum cham¬ bers 21 and 22 combined with the supply of air leaking through the inlet and outlet passages 23 and 24, preferably along the edges of the web material, facilitates removal of excessive additives or impreg- nating means, which are preferably in the form of vapour, from the vacuum chambers. The vacuum conduit 31 may then contain an addi¬ tive condensing separator for separating the additives or impregnating means from the mixture of air and inert gas discharged from the chambers 21 and 22.

The supporting structures 36 prevent downward deflection of the web material due to the flow of inert gas and vaporized additives there¬ through . Each of the supporting structures is mainly formed by parallel supporting rods extending substantially in the direction of movement of the web material 10. However, in order to avoid a "lee- effect" which might give rise to a non-uniform impregnating treatment of the web material , the parallel supporting rods preferably define a small acute angle, for example of 15°, with the direction of movement of the web material .

For example in case of maintenance or repair, the wall elements 11 and 12 may be separated by activating the cylinders 13. The relative movements of the wall elements are guided by the guiding rods 16 and the surrounding eye members 18.

The inlet passage 23 and the outlet passage 24 are defined by oppo¬ sitely arranged inner surfaces 37 and 38 (Fig . 2) which have such a shape that the cooperation between the oppositely arranged inner su rfaces 37 and 38 and the web material 10 passing through the passage in question provides an effective pressure seal, which is important for maintaining the desired vacuum within the chambers 21 and 22 without requiring an excessive vacuum source capacity.

As best shown in Fig . 2a-2c, each of the corrugated plates 26 and 27, which define the oppositely arranged inner surfaces 37 and 38, include a number of longitudinally spaced projecting elements or ridges 39, which extend at substantially right angles to the direction

OMPI of movement of the web material 10 through the passages 23 and 24. The elements or ridges 39 on the upper plate 26 are offset in relation to the elements or ridges 39 on the lower plate 27 in the direction of movement of the web material 10. The elements or ridges 39 are shaped and positioned so that the top 40 of each of the elements or ridges is in contact with the web material 10 over its total width , when the web material is passed through the respective passages 23 and 24 in a stretched condition (Fig . 2c) . Because of the tensile stress in the web material 10, the web material is pressed against the top 40 of each of the elements or ridges 39. This means that the web material 10 divides the passage 23 or 24 into a longitudinally extend¬ ing succession of compartments 41 (Fig . 2c) . The pressu re within the compartments 41 located adjacent to the vacuum chambers 21 and 22 may differ slightly from the pressu re of the vacuum chambers, while the pressure within the compartment 41 adjacent to the outer end of the passage may differ only slightly from atmospheric pressure, and the pressu res in the intervening chambers 41 may vary therebetween .

It is understood that in order to obtain the desired pressure seal, the web material 10 passing th rough the inlet and outlet passages 23 and 24 must at least touch the tops 40 of the ridges 39 and should preferably also be pressed thereagainst with a certain pressure. Such pressure might, however, totally or partly be obtained by means of openings or grooves, which are formed along the tops 40 of the ridges 39 and communicate with a vacuum source. I n the embodiments shown in Fig . 2, the desi red contact pressure between the web ma¬ terial and the ridges is obtained by the tensile force applied to the web material being passed through the passage defined between the inner surfaces 37 and 38. I n Fig . 2a a dot-and-dash line 42 indicates a common tangential plane touching the tops of a pair of adjacent ridges 39 formed on the plate 27. It is seen that in order to obtain that a tensile force applied to the web material 10 generates con¬ tacting pressures between the web material and the tops 40 of the ridges 39, the oppositely di rected ridge formed on the plate 26 and extending between the said pair of ridges must - together with the web material in contact therewith - at least touch the tangential plane 42, and preferably extend beyond that common tangential plane. I n

_ OMPI the embodiment shown in Fig. 1 , the spacing between the surfaces 37 and 38 of the plates 26 and 27 may be adjusted by means of adjusting screws 44 extending through the upper wall element 11 .

I n the embodiments shown in Figs . 2a and 2b the ridges 39 are con- stituted by rod-like elements being welded to the opposite surfaces of the plates . I n Fig . 2a the elements 39 have a cross-section formed as a segment of a circle, and in Fig . 2b, the cross-sectional shape of the elements 39 is substantially rectangular with rounded edges . I n Fig . 2c the ridges 39 are formed by a corrugated surface which may be made by moulding and/or machining, such as milling .

Substantial leaks at the edges of the web material 10 may be avoided if the total width of the web material substantially corresponds to the width of the passages 23 and 24. I n order to ensure such correspon¬ dence between the width of the web material and the width of the passages, a cutting blade for cutting the web material may be ar¬ ranged at each side of the inlet passage 23. I n order to adapt the unit shown in Fig. 2 to different widths of web material, filling inserts 43 may be arranged at one or both sides of the inlet and the outlet passages 23 and 24, respectively, as indicated in Fig . 1 . However, as indicated above, it may in some cases be desired to provide a certain controlled leakage of air in order to facilitate re¬ moval of excessive vaporized additives from the chambers 21 and 22.

Figs. 4-9 Illustrate further embodiments of the pressure sealing inlet and outlet passages 23 and 24, and parts similar to parts in Fig . 2 have been designated by the same reference numerals .

In Fig . 4, the pressure sealing passage receiving the web material 10 is defined between a pair of supporting plates 45 to which the pro¬ jecting elements 39 are fastened by means of screws 46. The oppo¬ sitely directed surfaces of the elements 39 define an obtuse-angled profile so as to define a relatively sharp and narrow web contacting top 40. I n order to minimize the frictional forces on the web material 10, the web material follows a substantially rectilinear path, and in order to obtain a sufficient contact pressure between the web material

OMPI 10 and the tops 40 of the elements 39, suction openings may be pro¬ vided along at least some of the tops 40, for example at the inlet and outlet ends of the passage, and these openings may communicate with a suitable vacuum source by means of vacuum conduits 47 indicated with broken lines in Fig . 4. The suction through the vacuum con¬ duits 47 may at least partly replace the suction th rough the vacuum conduit 31 shown in Fig . 3.

I n the embodiment shown in Fig . 5, the projecting elements 39 are in the form of rollers projecting from spaces 48 having trapezium-shaped cross-sections and being defined between plate elements 49, which are fastened to the supporting plates 45 by means of the screws 46. As indicated in Fig . 5, the compartments 41 defined between the plate elements 49 and the web material 10 extending between adjacent roller tops 40 may be connected to a suitable vacuum sou rce by vacuum conduits 47 in order to increase the contact pressure between the web material 10 and the roller tops 40.

I n the embodiment shown in Fig . 6, the roller-like elements 39 have been replaced by strip-li ke elements 39 which are received in cor¬ responding slot-like recesses defined in the supporting plate 45. The projecting tops 40 of the strip-like elements 39 may define a substan¬ tially rectilinear or slightly sinuous path of the web material 10, and in order to obtain a suitable contact pressu re, the compartments 41 may be communicated with a vacuum source as described above.

I n the embodiments illustrated in Figs . 7 and 8, the passage defined between the plates 45 for receiving the web material 10 is defined between a pai r of spaced, substantially plane inner su rfaces 37 and 38. A plurality of transversely extending, longitudinally spaced grooves or channels 50 are formed in each of the surfaces 37 and 38, and each groove or channel in one of the plates 45 is positioned between a pair of grooves or channels 50 in the oppositely arranged plate 45. The grooves or channels 50 communicate with a vacuum source (for example the vacuum chambers 21 and 22 in Fig . 1 ) th rough conduits 47. I n this embodiment the web material 10 is sucked into sealing engagement with the parts of the inner surfaces 37 and 38 extending along and being positioned adjacent to each of the channels or grooves 50. This means that in this embodiment the parts of the inner surfaces 37 and 38 extending along the grooves or channels 50 should be considered "web contacting surface parts" .

The embodiment shown in Fig. 8 corresponds substantially to that of Fig. 7. The main difference is that in Fig . 8 each of the plates 45 contains an inner hollow space 51 which is in communication with the vacuum conduit 47 and serves as a suction box . I n Fig . 8 the chan¬ nels or grooves 50 in Fig. 7 have been replaced by slot-like openings 52 communicating with the hollow space 51 .

The embodiment shown in Fig . 9 corresponds to that shown in Fig. 4. The only difference is that in Fig . 9 the vacuum conduits 47 commu¬ nicate with the compartments 41 defined by the web material 10, and not with the tops 40 of the elements 39. As explained in connection with Fig . 4, the suction through the conduits 47 may contribute to establishing the desired vacuum in the chambers 21 and 22 and there¬ by at least partly replace suction through the vacuum conduit 31 shown in Fig. 3. Furthermore, the conduits 47 need not communicate with all of the compartments 41 .

Fig. 10 illustrates an effective sealing arrangement which may be arranged along the edge portions 19 and 20 of the wall elements 11 and 12 in Fig . 1 . As shown in Fig . 10, the sealing arrangement com¬ prises sealing strips or gaskets 53 and 54 which are made from a heat-resistant, resilient material and fastened to the lower edge portions 19 of the wall element 11 and the upper edge portions 20 of the wall element 12 respectively. The sealing arrangement also com¬ prises a rod-like element 55 having a rhomb-like cross-sectional shape, and when the wall elements 11 and 12 are pressed together, the opposite edges of the rod-like element 55 deform the resilient sealing strips 53 and 54 as shown in Fig . 10 so as to provide an efficient stationary pressure seal .

The vacuum impregnating unit shown in Figs . 11 -13 is mounted in a frame structure comprising vertical columns 56 and horizontally eκ- tending lower and upper beams 57 and 58, respectively . The impreg¬ nating unit comprises lower and upper wall elements 59 and 60, respectively. The lower wall element 59 is supported on the lower beams 57 by means of vertically extending threaded screw members 61 and adjusting nuts by means of which the vertical position of the lower wall element 59 may be adjusted. The upper wall element 60 is suspended from the upper beams 58 by means of vertically extending th readed screw members 63 and adjusting nuts 64 by means of which the vertical position of the upper wall element 60 may be adjusted . The upper and lower wall elements 59 and 60 have adjacent lower and upper, plane, closely spaced, parallel surface parts 65 and 66, respectively, defining a slot-li ke narrow passage 67 between them for receiving a web material 10 to be impregnated in the above described manner in a vacuum chamber 68, which is formed in the wall element 59 and 60. Upper^' ends 69 of the columns 56 have a decreased dia¬ meter and are displaceably received in sleeves 70 which are mounted at opposite ends of the upper beams 58, which are interconnected by a yoke member 71 . This means that a hoist or another lifting device may be connected to the yoke member 71 and may then lift the upper beams 58 and the upper wall element 60 while the sleeves 70 are moved along the upper part 69 of the columns 56, whereby the upper and lower wall elements 60 and 59, respectively, may be separated . I n the lowered position of the upper beams 58, the lower ends of the sleeves 70 are in engagement with a shoulder formed on the cor- responding column 56. I n this position the vertical width of the slot-like passages 67 may be adjusted by means of the adjusting nuts 62 and 64, and the upper wall element 60 has downwardly protecting sealing rim portions 72 for sealing the passages 67 along the opposite side extending parallel with the direction of movement of the web material 10. Atomizing equipment of the type described in connection with Figs . 1 and 3 for atomizing an impregnating liquid in the vacuum chamber 68 is not shown in Figs . 11 and 12, but such equipment may be arranged within a heat insulating housing arranged on the upper wall element 60.

As shown in Fig . 13, the lower and upper wall elements 59 and 60 are a welded structure defining hollow spaces or manifold chambers 74 and 75 therein . The chambers 74 are divided into smaller compart- ments by means of bracing walls 76 each having a circular opening 77 formed therein for interconnecting the compartments of each manifold chamber. Each of the manifold chambers 74 and 75 may be connected to a vacuum pump or another vacuum source (not shown) through connecting openings 78 and 79, and the vacuum chamber 68 may be connected to a vacuum pump or vacuum source through a connecting opening 80. As indicated in Fig. 11 , the openings 78 and 79 in the lower wall element 59 may be connected to the respective vacuum sources through rigid tube connections 81 , while the openings 78 and 80 in the upper wall element 60 are connected to their respective vacuum sources through flexible tube connections or hoses 82. Each of the slot-like sealing passages 67 arranged on either side of the vacuum chamber 68 has two spaced pairs of vacuum openings or slots 83 and 84 interconnecting the passage 67 and the adjacent manifold chambers 74. The vacuum openings or slots 83 and 84 in each pair are substantially identical and are positioned oppositely in the oppo¬ sitely arranged, spaced surface parts 65 and 66. A web material 10 which is passed through the slot-like passages 67 and the vacuum chamber 68 positioned therebetween -divides the vacuum chamber 68 into an upper part and a smaller, lower part. This lower part of the vacuum chamber communicates with the manifold chamber 75 th rough a number of connecting openings 85.

The vacuum openings or slots 83 and 84 extend transversely to the direction of movement of the web material 10, and because the vacuum applied to the opposite vacuum slots 83 and 84 is the same, and because these slots are identical, air is drawn from the ambient atmosphere th rough the very narrow spaces defined in the passage 67 on both sides of the web 10. Thus, even when the width of the passage 67 only very slightly exceeds the thickness of the web 10, the web may float through the passages 67 so that the web may be drawn through the vacuum chamber and the adjoining passages 67 without creating any undue tension in the web material.

By means of the vacuum impregnating unit shown in Figs . 11 -13, a fibrous web material such as a web of paper or board may be impreg- nated under vacuum in a manner described above. The vacuum cham- ber structure shown in Fig . 13 permits the creation of a very high vacuum such as an absolute pressure below 1 millibar.

If the web 10 has a width of 1200 mm and a thickness of 0.64 mm and a water content of 7 per cent, the clearance on either side of the web material between the web material and the adjacent surface parts 65 and 66 may be up to 0. 15 mm, and it will still be possible to maintain a vacuum in the vacuum chamber 68 below 1 millibar under the follow¬ ing conditions :

The distance between the outer end of the passage 67 and the fi rst pair of vacuum slots 83 and 84 and between the first and second pairs of vacuum slots is 70 mm, and the distance between the second vacuum slot and the vacuum chamber 68 is 35 mm. The capacity of the pump connected to the first pair of vacuum slots 83 and 84 is 540

3 m /h so as to obtain an absolute pressure of 180 millibars at these vacuum slots, and the capacity of the vacuum pump connected to the

3 second pai r of vacuum slots is also 540 m /h so as to obtain an abso¬ lute pressure of 6 millibars . The necessary capacity of the vacuum pump connected to the vacuum chamber 68 depends on the partial pressure of impregnating means atomized in the vacuum chamber.

3 However, the capacity of the vacuum pump need not exceed 650 m /h .

This maximum capacity would be able to generate a pressure less than

5 x 10 millibars within the vacuum chamber provided that no water vapour or vapourized impregnating means are present.

It is understood that if the vacuum chamber 68 is replaced by a high pressure chamber, pressurized air should be supplied to the vacuum openings or slots 83 and 84. Furthermore, it is possible to use three or more pairs of such slots or openings in each passage 67 whether the chamber 68 is a vacuum chamber or a high pressure chamber.

It is understood that various modifications of the embodiment de- scribed above could be made without departing from the scope of the present invention . As an example, the vacuum chambers need not be used for impregnation purposes, but could be used for treating two or more layers of material to be laminated, or for applying a protec- tive and/or a decorative coating to a flexible plate material made from wood, metal or another material . Furthermore, the vacuum chambers could be replaced by one or more high-pressure chambers, or by a succession of vacuum and high-pressure chambers with intervening pressure sealing passages according to the invention . Thus, for example, in the vacuum impregnating unit shown in Figs . 1 and 3, the vacuum chambers 21 and 22 could advantageously be followed by a high pressure chamber in order to press the impregnating means into intimate contact with the fibres of the web material 10. It should also be understood that the elements or ridges 39 could have any suitable cross-sectional shape and could be made from any suitable material or materials . As an example, the tops 40 of the ridges 39 could be made from a material which is harder and more wear-resistant than the material from which the remaining part is made.

"g JREAl OMPI Z

Claims

1 . A method of moving a web material through a first passage inter¬ connecting first and second spaces , said method comprising maintaining a first pressure level in the first space, maintaining a substantially different pressure level in the second space, and moving the web material longitudinally in the passage in a stretched condition along a path defined by a plurality of mutually longitudinally spaced, alternatingly oppositely directed web contacting su rface parts of opposite, spaced passage defining walls, while main¬ taining opposite side surfaces of the web material in contact with adjacent web contacting su rface parts , each web contacting surface part extending transversly over substantially the full width of the web material , whereby each pair of consecutive oppositely di rected web contacting su rface parts and the section of the web material extending therebetween form at least a partial pressu re seal .

2. A method according to claim 1 , wherein the web material is moved along a substantially rectilinear path .

3. A method according to claim 1 or 2, wherein the web material is sucked into contact with at least some of the oppositely directed web contacting su rface parts .

4. A method according to claim 1 or 3, wherein the web material is moved along a sinuous path .

5. A method according to any of the claims 1 -4, wherein the web material is moved from the first space into the second space th rough said first passage, and from the second space into a thi rd space through a second passage in a manner similar to movement of the web material through the first passage.

6. A method according to claim 5, wherein atmospheric pressu re is maintained in the first space.

7. A method according to claim 6, wherein a vacuum is maintained in the second space.

8. A method according to claim 7, wherein atmospheric or super- atmospheric pressure is maintained in the third space.

9. A method according to claim 7 or 8, wherein a liquid additive is applied to the web material within the second space.

10. A method according to claim 9, wherein the liquid additive is sprayed onto the web material .

11 . A method according to claim 9 or 10, wherein the second space is divided into first and second compartments by the web material pass¬ ing therethrough, the pressure within the first compartment, in which the liquid additive is applied, being kept at a slightly higher level than in the second compartment.

12. A pressure sealing device for cooperating with a web material being passed through the device in a stretched condition between spaces with different pressure levels, said device comprising spaced, oppositely arranged inner surfaces, which define a through-going web receiving passage and which comprises a plurality of alternatingly oppositely directed web contacting surface parts spaced longitudinally along the passage, each web contacting surface part extending trans¬ versely over substantially the full width of the passage, and means for maintaining the web material in sealing contact with each of the oppositely directed web contacting surface parts .

13. A pressure sealing device according to claim 12, wherein the oppositely directed web contacting surface parts are substantially plane and parallel .

14. A pressure sealing device according to claim 12 or 13, wherein the contact maintaining means comprise one or more suction openings defined in and extending along the web contacting surface part in question .

15. A pressure sealing device according to claim 13 and 14, wherein the inner surfaces defining the web receiving passage are substan¬ tially plane and parallel wall surfaces .

16. A pressure sealing device according to claim 12 or 14, wherein each web contacting surface part has a convex cross-sectional shape, each intermediate web contacting surface part on each of the oppo¬ sitely arranged inner su rfaces extending between a pair of adjacent web contacting surface parts on the other of said inner su rfaces and to a position spaced from a tangential plane common to said pair of web contacting surface parts, less than the thickness of the web material .

17. A pressure sealing device according to claim 16, wherein each of the oppositely arranged inner su rfaces has a wavy or sinusodial cross-sectional shape, and the inner surfaces being substantially uniformly spaced along the length of the passage defined thereby .

18. A pressure sealing device according to claim 16, wherein each of the inner surfaces is formed by a substantially smooth wall surface and by separate, transversely extending, longitudinally spaced roller or strip members, which are projecting from the smooth wall su rface, and which define the web contacting surface parts thereon .

19. A pressure sealing device according to any of the claims 12-18, wherein the web receiving passage is defined between a pai r of wall elements which are in releasable sealing engagement along opposite edge portions .

20. A pressu re sealing device according to claim 19, wherein means are provided for adjusting the spacing between the wall elements .

21 . A pressu re sealing device according to any of the claims 12-20, wherein the web receiving passage includes at least one web treatment chamber between the ends thereof, means being provided for generat- ing a pressure level differing from atmospheric pressu re within said chamber.

22. A pressure sealing device according to claim 21 , further compris¬ ing means for supplying a liquid substance to a first side surface of a web material moving through the treatment chamber of the passage, and means for generating a slightly higher pressure at the said first side surface than at the opposite side surface of the web material .

23. A pressure sealing device according to any of the claims 19-22, wherein the wall elements comprise heating means for heating the web material passing through the passage.

24. A pressure sealing device for cooperating with web material being moved through the device in a stretched condition between a first space substantially at atmospheric pressu re, and a second space with a different pressure level, said device comprising oppositely arranged, substantially plane and parallel inner surface parts with a mutual spacing corresponding substantially to the thickness of the web material so as to define a slot-like web receiving passage interconnect¬ ing said spaces, the opposite surface parts defining at least one pair of oppositely arranged openings extending transversely to the direc¬ tion of movement of the web material, said openings being connected to sources of vacuum when the pressure in said second space is below atmospheric pressure, and to sources of pressurized gas or air when the pressure in the second space is higher than atmospheric pres¬ su e.

25. A pressure sealing device according to claim 24, wherein the oppositely arranged openings in each pair are connected to the same source or to different sources of the same pressure.