US3406464A

US3406464A - Ventilation system for a papermaking machine

Info

Publication number: US3406464A
Application number: US637238A
Authority: US
Inventors: Raymond C Clark
Original assignee: Huyck Corp
Current assignee: Huyck Corp
Priority date: 1967-05-09
Filing date: 1967-05-09
Publication date: 1968-10-22
Anticipated expiration: 1985-10-22
Also published as: GB1190331A

Description

Get. 22, 1968 R. c. CLARK 3,406,464

VENTILATION SYSTEM FOR A PAPERMAKING MACHINE Filed May a, 1967 2 Sheets-Sheet 1 INVENTOR. PAV/VO/l/O & [II/PA R. C. CLARK Oct. 22, 1968 VENTILATION SYSTEM FOR A PAPERMAKING MACHINE Filed May 9, 1967 2 Sheets-Sheet 2 R m w m A TTUPIVEU United States Patent 3,406,464 VENTILATION SYSTEM FOR A PAPERMAKING MACHINE Raymond C. Clark, Orange, Conn., assignor to Huyck Corporation, Stamford, Conn., a corporation of New York Filed May 9, 1967, Ser. No. 637,238 9 Claims. (Cl. 34-111) ABSTRACT OF THE DISCLOSURE Background of the invention In the typical so-called Fourdrinier papermaking machine, an aqueous suspension of fibers, called the furnish, is deposited on a travelling forming medium, generally an endless, woven belt of wire and/or synthetic material. As the furnish travels on the moving forming medium, much of the Water is removed therefrom and a somewhat self-supporting continuous web is formed. This removal is facilitated by the use of such well-known devices as hydrofoils, table rolls, and/or suction boxes.

The somewhat self-supporting continuous Web is transferred to a press section where still more of its water content is removed by passing it through a series of nips formed by adjacent press rolls; these press rolls also compacting the web as well as removing additional water therefrom. V

The web is then fed to a dryer section where it is passed about a series of heated, generally cylindrical dryer rolls to remove still further amounts of water therefrom. In most instances, the dryer rolls will have a solid, imperforate surface which contacts the continuous web; however, in some instances it has been found desirable to construct these dryer rolls to have a gas pervious surface through which heated air and/ or steam is blown.

The dryer section of the machine generally includes at least one upper and one lower array of these heated, cylindrical rolls (commonly referred to as dryer cans) with the rolls in each array being arranged in a parallel row. The continuous web is passed between the arrays in a serpentined manner and, as the continuous web passes over each of the dryer cans, it is held in intimate heat transfer relationship therewith by means of a relatively strong, endless, backing fabric or belt. The backing fabric, commonly referred to as a dryer fabric, in most instances will be associated with only one array of dryer cans. In the past, dryer fabrics have generally been impervious blanket-like structures; however, in this instance the dryer fabric will be of a fluid permeable construction so as to readily permit the flow of air and/or vaporized water therethrough. As such, open-weave fabrics are generally desirable for this purpose; however, non-woven structures such as perforated plastic belts and the like have also been found suitable.

In the dryer section of the papermaking machine, the steam and/ or moist air generated as a result of the vaporization of water from the continuous web tends to collect 3,406,464 Patented Oct. 22, 1968 in enclosed areas or pockets formed in the area of the dryer cans. Tent-like pockets are formed in the areas circumscribed by each of the dryer cans, the dryer fabric as it traverses the fabric guide rolls disposed between adjacent dryer cans, and the paper web as it serpentines its way about the dryer cans. Additionally, enclosed pockets are also found in the areas enclosed by each of the dryer fabrics as they travel their respective endless paths. Unless this moist air and/or steam is removed or prevented from building-up in these pockets, vaporization of water from the web will be inhibited.

One method of removing the moist air is to provide heavy-duty air blowers or exhaust fans which force the air transversely through the pockets to the outside portion of the machine. However, with such a method it is diflicult to maintain a uniform moisture profile across the width of the continuous web. Further, this method is also somewhat unsatisfactory on machines of substantial width as it becomes increasingly more diflicult to remove air effectively with increasingly large machine widths, As the tendency today is to further increase the width of the machines, alternative means for removing this moist air must be sought.

Another method of purging the air is to provide means for directing fresh air around or through the fabric guide rolls disposed between adjacent dryer cans into the tentlike pockets to force the moist air therein laterally out of the machine. However, this air has mass and exerts a pressure on the continuous web. If the air is introduced at too high a pressure, the result is often fluttering of the sheet. While sheet flutter may occur along the complete width of the sheets or only at the outer edges thereof, such fluttering cannot be tolerated as it may result in a tear in the sheet with consequent derogation thereof and/ or a jamming of the machine. Therefore, one object of the present invention is to provide an improved means for uniformly drying a continuous web of material.

Another object of the present invention is to provide means for increasing the efliciency of drying a continuous web of material.

Another object of the present invention is to provide means for uniformly drying a continuous web of paper or paper-like material in a papermaking machine.

Still another object of the present invention is to provide an eflicient means for removing the moist air which tends to collect in the pockets of a papermaking machine.

A further object of the present invention is to provide means for uniformly ventilating the dryer pockets of the papermaking machine without fear of damaging the paper web.

Summary of the invention In accordance with the principles of the present invention, in one embodiment thereof there is included in a machine having means for drying a web of material; an endless, fluid permeable belt movable in conjunction with the web of material for guiding it through the machine and arranged to press the web against the drying means. Generally, the drying means comprises heated, cylindrical rolls about a portion of the surface of which the web passes and against the surface of which the web is held in heat transfer relation by the endless belt. The endless belt is also adapted to travel about a plurality of guide rolls which maintain it on its endless path, the result being that the belt travels about both the guide rolls and the dryer cans.

First stationary means are disposed ahead of at least one of the rolls about which the endless belt passes in order to deflect air entrained by the belt away therefrom. This first stationary means, which is positioned on the side of the belt opposite the roll and in close proximity thereto in the direction opposite that in which the belt travels, de-

flects air entrained by the belt away therefrom. Second stationary means, disposed on the same side of the belt as the first stationary means and positioned adjacent the roll, is spaced from the first stationary means in the direction of travel of the belt. The second stationary means is positioned such that air entrained on the underside of the belt, and which is transferred through the belt to the opposite side thereof as the belt travels about the roll, is deflected away from the belt. The second stationary means precludes the transferred air from being drawn back through the permeable belt by the suction force created by the diverging nip at the point where the belt leaves contact with the roll.

To ensure that the air entrained by the permeable belt on the same side thereof as the roll will be transferred through the belt to the other side thereof as the belt travels over the roll, additional stationary means may be provided, this additional means being disposed on the same side of the belt as the roll and positioned in a converging relationship with respect to the belt so as to prevent entrained air from setting up an independent whorl in front of the roll. As such, it may be desirable to position the stationary means such that its converging tip will lie adjacent to, or in some instances in frictional engagement with, the rotatable roll. Thus, substantial amounts of air entrained by the belt will be deflected away therefrom. As this air is generally moist and serves to hinder further removal of water from the web of material, continuous ventilation of the machine results without necessitating the complex and/ or expensive machinery previously required.

Additional objects and advantages of the present invention together with a better understanding thereof may be had by referring to the following detailed description of the present invention together with the accompanying drawings.

Brief description of the drawings FIGURE 1 reveals a simplified diagrammatic view of a portion of the path taken by a dryer fabric as it travels in a papermaking machine and shows one embodiment of the present invention;

FIGURE 2 reveals an alternate embodiment of the invention shown in FIGURE 1;

FIGURE 3 reveals a cabinet view of a dryer section of a papermaking machine in which the present invention may be incorporated;

FIGURE 4 reveals the invention shown in FIGURE 2 and further including an additional modification thereto.

Description of the preferred embodiments Turning now to FIGURE 1 and a description of the present invention, there is shown a portion of the path taken by a dryer fabric as it travels in a papermaking machine. In this instance, and this is done only in order to facilitate discussion of the present invention, there is shown the return run portion of the path of the dryer fabric; that is, the path of travel taken by the dryer fabric after it leaves contact with the last dryer can and before it engages the first dryer can. To further facilitate discussion of the present invention, reference will be made to an upper or topside of the dryer fabric and a lower or underside thereof. These terms are used only to designate respectively the opposite sides of the dryer fabric, as it is not the intention of the present invention to be limited to the specific arrangement hereinafter set forth.

In FIGURE 1 there is shown a dryer fabric 11 travelling from right to left as viewed in the drawings with the upper or topside of the dryer fabric being designated as 13 and the lower or underside of the dryer fabric being designated as 15. As the dryer fabric travels in the machine, it will pass over one or more guide rolls 35 which maintain the fabric about its predetermined endless path of travel. Depending on their position in the machine, these fabric guide rolls may be referred to as pocket rolls, felt rolls, tension rolls and/or return rolls. As seen in FIGURE 1, and for purposes of discussion, there is shown a return roll. However, it is understood that these same principles would hold true for other types of fabric guide rolls and in fact for the dryer rolls themselves as well as for other devices which, while not being in the shape of a roll, will operate in a substantially similar manner to achieve substantially similar results.

As the dryer fabric 11 travels over the roll 35, air entrained by the underside 15 of the dryer fabric 11 will be squeezed or transferred through the dryer fabric to the upper or topside 13 thereof. Thus, a zone of increased pressure will be created on the underside of the dryer fabric in the area of the nip between the roll 35 and the fabric 11. As will be discussed hereinafter, means are provided for deflecting the transferred air away from the dryer fabric 11 and pecluding this transferred air from becoming entrained about the guide roll 35 or otherwise being drawn back through the dryer fabric by the suction force which is created under the dryer fabric just past the point where the fabric leaves contact with the rotating guide roll.

First stationary means are disposed on the topside 13 of the dryer fabric 11 for deflecting air entrained by the upper side of the dryer fabric away therefrom. Specifically, the first stationary means comprises a stationary vane 17 which is disposed adjacent the dryer fabric and extends across the width of the dryer fabric generally transverse to the path of travel of the dryer fabric. The stationary vane 17 is positioned in a diverging relationship with respect to the direction of travel of the dryer fabric and has a leading surface which acts as a knife edge to remove or scrape the air entrained by the topside of the dryer fabric away therefrom. Movement of the dryer fabric 11 past the diverging vane will create a zone of reduced pressure 23 in the area between the diverging vane 17 and the dryer fabric 11; this zone of reduced pressure producing a suction on the dryer fabric to draw further amounts of air entrained by the dryer fabric away therefrom. As seen in FIGURE 1, the first diverging vane 17 is spaced in close proximity to the rotatable guide roll 35 and in a direction opposite that in which the dryer fabric is travelling. Preferably, the zone of reduced pressure will at least partially overlap the zone of increased pressure which will occur at the ingoing nip between the dryer fabric and the guide roll. Thus, as the dryer fabric travels its endless path, it will first travel past the leading edge of the diverging vane 17 and then the rotating roll 35.

In order to remove the air which is transferred through the dryer fabric 11 by the guide roll 35, means are provided for deflecting the transferred air away from the dryer fabric. More specifically, this means comprises a second stationary vane 29 disposed adjacent the guide roll 35 and on the same side of the dryer fabric as the first stationary vane. The second stationary vane 29 is disposed adjacent the dryer fabric 11 and extends across the width of the dryer fabric generally transverse to the path of travel thereof. The second stationary vane is also positioned in a diverging relationship with respect to the path of travel of the dryer fabric with its leading surface acting as a knife edge to scrape or deflect air entrained by the dryer fabric away therefrom. Movement of the dryer fabric 11 past the second diverging vane 29 also creates a zone of reduced pressure 33 in the area between the diverging vane 29 and the dryer fabric 11; the zone of reduced pressure producing a suction on the dryer fabric to draw further amounts of entrained air away therefrom.

Preferably, the second diverging vane will be positioned slightly past the top dead center point of the guide roll 35, or slightly to the left of the guide roll as is shown in FIGURE 1. Thus, any centrifugal forces acting on the air in the fabric as it travels about the guide roll will tend to throw this air away from the roll and fabric. By properly selecting the location of such diverging vane, the maximum amount of transferred air may be deflected away from the dryer fabric. However, it should be reiterated that desirable results may also be obtained by positioning the second diverging vane directly over the top of the guide roll or spaced slight distances on either side thereof. It will be obvious that varying degrees of reduced pressure may be obtained in the

zones

23 and 33 by merely varying the angle at which the vanes 17 and 29 diverge from the fabric 11.

Briefly summarizing the operation of the present invention, air will be entrained by the dryer fabric 11 on either side thereof as it travels through the machine free from contact on the respective sides. If this air is not removed, it will soon become saturated by the moist air and/or steam which is evaporated from the web. This build up, if allowed to persist, will tend to inhibit further removal of water from the web.

As the dryer fabric travels past the first diverging vane 17, the leading surface thereof will act as a scraper and deflect air entrained on the upper side of the dryer fabric away therefrom. In addition, this movement also creates a zone of reduced pressure in the area between the first diverging vane 17, and the dryer fabric 11, this zone producing a suction effect on the dryer fabric to deflect further amounts of entrained air away from the dryer fabric. As the dryer fabric 11 passes over the rotating guide roll 35, air entrained on the underside thereof will be squeezed or transferred through the dryer fabric to the topside thereof, or at the very least be forced into the interstices of the porous dryer fabric. The second diverging vane 29 operates to deflect the squeezed or transferred air away from the dryer fabric 11 exactly in the manner of the first diverging vane. However, as previously mentioned, if the second diverging vane is positioned slightly to one side of the rotating guide roll, and it is preferable to have such spacing done in the direction of travel of the belt, it is possible to take advantage of the centrifugal forces set up by the rotating roll and deflect more of the transferred air away from the dryer fabric. By such means, it is possible to ventilate the pockets in a papermaking machine without producing either a pressure gradient or a non-uniform moisture profile across the web (not shown in FIGURE 1).

Preferably, the stationary vanes will be formed of a material such as sheetmetal, plastic, wood, fiber glass, polyethylene, or other similar material. However, it is not the intention of the present invention to be limited to the specific materials set forth above. Further, the vanes should a least be characterized by being moisture resistant and physically and chemically stable at the elevated temperatures encountered in the dryer section of the machine. Further, while the vanes shown in FIGURE 1 appear to be of a straight contour, as will be explained more fully hereinafter, it is not the intention of the present invention to be limited to such a construction.

Turning now to the embodiment set forth in FIGURE 2, it can readily be seen that the stationary diverging vanes 17 and 29 shown and discussed in FIGURE 1 can be made to assume the shape of an air foil with a convexly curved surface facing the dryer fabric. Specifically, first diverging air foil shaped vane 17a and second diverging air foil shaped vane 29a respectively are substituted for the previously discussed stationary vanes. Each of the foil shaped vanes are disposed in a diverging relationship with respect to the direction of travel of the dryer fabric 11 and each extends across the width of the dryer fabric 11 generally transverse to the path of travel of the dryer fabric. Each is also adjustable to vary the angle of divergence from the dryer fabric and thus vary the amount of entrained air which may be removed therefrom. Movement of the dryer fabric 11 past the vanes creates zones of reduced pressure in the areas between the vanes and the dryer fabric. In this instance though, it should be noted that due to the air foil shaping of the vanes, a greater reduction in pressure is obtained in the areas between the vanes and the dryer fabrics so that a greater suction is produced on the dryer fabric, the result being that more of the air entrained by the dryer fabric is removed.

As a result of the foregoing discussion, it will become readily apparent that the diverging vanes of the present invention may be of any suitable configuration; that is, they may be straight, curved, foil shaped, circular, or of any design which will produce the desirable results of the present invention as it is not the intention of the present invention to be limited to such specific constructions.

Turning now to FIGURE 3, there is shown a simplified dr-yer section of a typical Fou-rdrinier papermaking machine including spaced arrays of horizontally disposed heated dryer rolls; an upper array including rolls 45, 47 and 49 and a lower array including rolls 51, 53 and 55. The rolls may have a solid surface with which a web 57 comes into contact or they may have a gas pervious surface through which heated air and/ or steam may be blown. If a gas pervious surface is desired, the surface of the rolls may be made from suitable materials such as sintered metal fibers, sintered powdered metal, fused glass and the like. Means (not shown) are provided for rotating the cylindrical dryer rolls at a synchronous speed with the continuously formed paper or paper-like web 57 passing in a serpentined manner about the dryer rolls in order that moisture be removed therefrom.

Arranged to guide the paper web through the dryer section, and more specifically to press and maintain the paper web 57 in good heat transfer relationship with at least a portion of each of the dryer rolls 45, 47 and 49 in the upper array, is an endless fluid permeable top dryer belt or fabric 61. This upper dryer fabric 61 may be of a woven construction, of a non-woven perforated construction, or of any other suitable construction. Rotatable pocket guide rolls 63 and 65 are disposed between the dryer rolls 45, 47 and 49 with these pocket guide rolls preferably being positioned somewhat below the center of rotation of the dryer rolls. As seen in FIGURE 3, the dryer fabric 61 will pass over the dryer rolls and under the pocket rolls to ensure that intimate contact is maintained between the paper web 57 and the dryer rolls. A plurality of felt 67 and/or return 68 guide rolls are provided about whose surface the dryer fabric passes (over or under as may be required) in order to define and complete the path of travel of the dryer fabric. Means (not shown) are general- 1y provided for adjusting the tension on the dryer fabric, this means generally being one or more movable tension rolls.

Similarly, a second endless porous belt or dryer fabric 69 is associated with the lower array of dryer rolls, the second dryer fabric 69 being similarly arranged to guide the paper web through the machine as by pressing and maintaining the web 57 against at least a portion of the surface of each of the lower dryer rolls 51, 53, and 55. Rotatable pocket guide rolls 71 and 73 are disposed between and adjacent to the lower dryer rolls 51, 53 and 55 respectively with felt 75 and/or return 76 guide rolls also being provided in order to complete the endless path of travel of the dryer fabric 69.

As the paper web 57 travels through the dryer section of the papermaking machine, it is held in contact with the heated dryer rolls, the result being the generation of steam as the water therein is vaporized. While some of the steam escapes directly through the porous dryer fabrics to the surrounding atmosphere, much of it tends to accumulate in the areas enclosed by the dryer fabrics and also in the tent-like pockets formed between the dryer fabrics, the dryer cans and the paper web as the web travels between adjacent dryer cans. For purposes of discussion, these tent-like pockets are numbered 80, 81, 82 and 83 respectively. Thus, means should be provided for removing this moist air and/ or steam so as not to inhibit further removal of moisture from the web and possibly create a non-uniform moisture profile therein.

Accordingly, a first diverging vane 85 is disposed adjacent the upper side of the dryer fabric 61 between the pocket roll 63 and the dryer can 47. This first diverging vane 85 extends across the width of the dryer fabric 61 and is constructed in a manner as the first diverging v-ane 17a discussed in connection with FIGURE 2. A second diverging vane 87 is positioned adjacent the dryer fabric 61 be.wecn the dryer roll 47 and the pocket roll 65. This second diverging vane 87 is positioned adjacent to the dryer roll 47 and extends across the Width of the dryer fabric generally transverse to the path of travel of the dryer fabric. It can readily be seen that this second diverging vane is constructed in the manner as the second diverging vane 29a also discussed in connection with FIG- URE 2.

Accordingly, the first diverging vane 85 will remove air entrained by the upper side of the dryer fabric 61 whereas air entrained by the underside of the dryer fabric 61 will be forced through the dryer fabric 61 to the topside thereof as the dryer fabric rides over the dryer roll 47 with the interposed paper web 57. The second diverging vane 87 will then deflect away from the dryer fabric 61 the air transferred through the dryer fabric by the squeezing action of dryer roll 47 and the dryer fabric 61. As such, no air is entrained by the dryer fabric as it passes by the second stationary vane 87. Consequently, as the dryer fabric 61 travels with its underside adjacent the dryer pocket 82, moist air from within the dryer pocket 82 will become entrained by the dryer fabric 61 and be removed, as by an identical arrangement (not shown) disposed about dryer roll 49. Thus, it is seen that the present invention effectively purges the moist air from a dryer pocket in a uniform manner, this being accomplished due to the fact that the vanes extend completely across the width of the dryer fabric to remove the entrained air.

Similarly, stationary diverging vanes 89 and 91 might also be positioned before and after the lower dryer roll 53, the elfect being to remove entrained air from the lower dryer fabric 69 and effectively result in moist air from the dryer pocket 83 being pumped out of the pocket by becoming entrained by the dryer fabric. If desired, similar stationary diverging vanes can be positioned about each of the dryer rolls in each array in order to uniformly ventilate each of the dryer pockets.

It can be seen that when moist air is purged from the tent-like pockets 80, 81, 82 and 83, it will be deflected away therefrom into the areas enclosed by the individual dryer fabrics. While it is possible to provide exhaust fans, hoods or other suitable means for removing this moist air, it may be desirable to utilize additional stationary diverging vanes similar to those previously discussed to remove this moist air. If such is desired, and referring now to the return run portion of the upper dryer fabric 61, it is seen that a first diverging vane 17 and a second diverging vane 29 can be positioned about one or more of the return run guide rolls 68. As such, these diverging vanes will operate as previously discussed hereinbefore, the result being that the moist air trapped within the run of the dryer fabric is transferred to the surrounding atmosphere.

It should be pointed out that as used throughout this specification, a stationary diverging vane is positioned adjacent to the dryer fabric when its leading surface or edge or any portion thereof is disposed at least partially Within the layer of gas or air effectively entrained by the moving dryer fabric. In other words, unless some portion of the diverging vane is disposed within the entrained air, it cannot act as a scraper to deflect the air from the fabric.

In order to increase the amount of entrained air transferred from the underside of the dryer fabric to the topside thereof by the rotatable means, and referring now to FIGURE 4, there may further be included a stationary means disposed in in converging relationship with respect to the path of travel of the dryer fabric to ensure that substantially all of the air entrained on the underside of the fabric is transferred therethrough to the topside thereof. Specifically, the stationary means comprises a baffle 95 which is disposed on the underside of the dryer fabric 11 and which extends across the width thereof generally transverse to the direction of travel of the dryer fabric. To ensure that substantially all of the air entrained on the underside of the dryer fabric is transferred therethrough to the topside thereof, the bathe is positioned in a converging relationship with respect to the path of travel of the dryer fabric with the converging portion of the baffle being either in frictional engagement with the rotatable roll 35, or at least positioned as close thereto as practical.

When the converging edge of the baffle engages the roll 35, it may be desired to attach a protective resilient metal, plastic or other suitable tip 97 to the battle in order to reduce wear and tear thereon.

In such a system, air entrained by the bottomside of the dryer felt will collect within the area between the baffle and the dryer fabric and create a zone of increased pressure therebetween. This pressure differential will cause an increase in the amount of entrained air which is transferred through the dryer fabric 11 to the upperside thereof by the roll 35. With such an arrangement, very little, if any, air will be able to escape and set up an independent whorl in front of the roll. The baffle member may be made of plastic, Wood, fiberglass, sheetmetal, polyethylene or any other suitable material having the physical and chemical properties similar to those of the stationary vanes.

Thus, it is readily apparent that an arrangement as has hereinbefore been discussed will provide stationary means for uniformly ventilating dryer pockets and preventing a build up of moist air in these pockets without necessitating the elaborate mechanisms or systems hereinbefore required. Further, such an arrangement provides uniform removal of the moist air thus providing a uniform moisture profile in the -Web.

While I have shown and described only particular embodiments of the present invention, it will be obvious to those skilled in the art that various changes and modificaltions may be made without departing from the invention in its broader aspects. Therefore, it is the intention of the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the present invention.

What I claim as new and novel and desire to secure by Letters Patent of the United States is:

1. In an apparatus for drying a continuous web of material:

(1) an endless porous belt movable with said web to guide said web through said apparatus,

(2) transferring means disposed on one side of said belt and extending substantially in the direction of the width dimension of said belt for transferring air entrained on the one side through said belt to the opposite side thereof, at least a portion of said transferring means lying within the layer of air effectively entrained on said one side of said belt,

(3) first stationary means extending substantially in the direction of the width dimension of said belt on the opposite side thereof from said transferring means and having a surface disposed within the layer of air effectively entrained on said opposite side of said belt to deflect the air entrained by said opposite side away from said belt, said first stationary means being in close proximity to said transferring means and being spaced therefrom in the direction opposite the direction of travel of said belt, and

(4) second stationary means extending substantially in the direction of the width dimension of said belt on the same side thereof as said first stationary means and being spaced therefrom in the direction of the travel of said belt, said second stationary means having a surface disposed within the air transferred through said belt by said transferring means to deflect the air away from said belt.

2. Apparatus as described in claim 1 wherein said first and said second stationary means each comprise stationary vanes disposed in a diverging relationship with respect to the path of travel of said belt with the leading edge of said vanes lying within the layer of air effectively entrained by said belt, movement of said belt past said vanes creating a zone of reduced pressure therebetween to deflect air entrained by said belt away from said belt.

3. Apparatus as described in claim 2 wherein said transferring means comprises rotatable, cylindrical means in contacting relationship with said porous belt as it travels its endless path.

4. Apparatus as described in claim 2 wherein said stationary vanes are substantially air foil in shape and have a convexly curved surface facing said porous belt.

5. Apparatus as described in claim 2 wherein said transferring means comprises a guide roll about a part of the surface of which said porous belt travels.

6. Apparatus as described in claim 2 wherein said transferring means comprises a heated, generally cylindrical roll.

7. Apparatus as described in claim 2 further including third stationary means disposed on the same side of said porous belt as said transferring means, said third stationary means disposed in converging relationship with respect to said transferring means in the direction of travel of said belt.

8. Apparatus as described in claim 7 wherein said third stationary means comprises a converging baffie having its converging tip in engagement with said transferring means.

9. Apparatus as described in claim 7 wherein said stationary means comprises a converging bafile having its converging tip closely spaced from said transferring means.

References Cited UNITED STATES PATENTS 3,314,162 4/1967 Haywood 34-l11 FREDERICK L. MATTESON, JR., Primary Examiner.

A. D. HERRMANN, Assistant Examiner.