US3325909A

US3325909A - Fabric for pumping fluids

Info

Publication number: US3325909A
Application number: US523463A
Authority: US
Inventors: Raymond C Clark
Original assignee: Huyck Corp
Current assignee: Huyck Corp
Priority date: 1966-01-27
Filing date: 1966-01-27
Publication date: 1967-06-20
Anticipated expiration: 1984-06-20

Description

June 20, 1967 R. c. CLARK FABRIC FOR PUMPING FLUIDS 3 Sheets-Sheet 1 Filed Jan. 2'7, 1966 June 20, W67 R. c. CLARK FABRIC FOR PUMPING FLUIDS 5 Sheets-Sheet 2 Filed Jan. 27, 1966 June 20, 1967 R. c. CLARK 3,325,909

FABRIC FOR PUMPING FLUIDS Filed Jan. 27, 1966 5 $heets-Shee1;. 3

{ XS X x U h [Ff X X W X X X X X United States Patent York Fiied lien. 27, 1966, Ser. No. 523,463 16 Ciaims. (Cl. 34-95) The present invention relates to endless belts made of fabrics of open-weave construction designed to serve a function typical of endless belts as well as the function of pumping or inducing the flow of air, gas or vapors through the fabric from one surface thereof to the other. Fabric belts of the present invention have particular utility, for example, in the field of manufacturing or converting of continuous webs of sheet material wherein the function of supporting, confining or conveying the web is performed in an environment in which the transfer of air, steam, gas or vapors from one side of the fabric to the other becomes desirable.

More specifically, an example of an operation in which fabric belts of the present invention are particularly useful is the removal of moisture from webs of fibrous material such as paper, paperboard and the like either in the course of manufacture of such webs or in the course of removing moisture or other liquids or vapors resulting from coating, printing, laminating and similar operations which may be performed on the web after its manufacturer. For the purposes of the present disclosure the invention will be described in connection with the drying of paper and similar webs in the dryer section of a papermaking machine. From such illustrative disclosure the utility of the invention in other fields will become apparent.

In a typical dryer section of a papermaking machine a web of paper which has been formed and has been partially dewatered in the press section of the machine is conducted over a relatively large number of heated drying cylinders called cans. As a very general statement it may be observed that paper leaving the press section has had removed from it about as much moisture as in practical to remove by mechanical means whereupon the remaining moisture is customarily removed to the desired end point in the dryer section. It is quite customary that for each ton of paper produced approximately two tons of Water must be removed in the dryer section. It will be readily apparent that the evaporation of such a relatively large quantity of water results in the production of a very large volume of water vapor or steam and moisture-laden air which must be scavenged from the paper and carried away from the paper machine. Thus the dryer sections of papermaking machines usually are enclosed or partially enclosed in hoods alfording forced ventilation for removal of the moisture-laden atmosphere and also it is customary to supply large quantities of relatively warm, relatively dry air to replace the air carried away by the hoods.

The paper web is conducted over the dryer cans by a relatively strong fabric which serves to confine the paper in intimate heat-transfer relation with the surface of the drums and which serves also to support and protect it against breakage at least in those portions of the dryer section wherein the moisture content of the paper is still relatively high.

In a typical dryer section of a papermaking'machine heated dryer cans are arranged in upper and lower arrays and the web is conducted sequentially into contact with a can in one of the arrays to a can in the other array and then back to the first array and so on. Ordinarily a dryer felt or fabric is associated with each of the arrays, that is, a dryer fabric is arranged to press the web into contact with several cans in the upper array and another dryer fabric is arranged to press the web into contact with several cans in the lower array. The fabrics are guided into contact with successive cans in the respective arrays by the use of felt rolls and they are returned in an endless path over a suitable number of return rolls. Certain of the felt rolls are positioned between and well below the upper peripheries of successive cans in the upper array so that the upper fabric will be conducted over a substantial portion of the peripheries of such cans. Similarly felt rolls are provided between and substantially above the lower peripheries of successive cans in the lower array for the same purpose. The felt rolls thus positioned between successive dryer cans are usually called pocket rolls inasmuch as the portion of the fabric carried over such rolls, together with the web as it passes from one can to the next, define zones called pockets which are open only at their ends, located at the front and back sides of the machine. The pockets are difficult to ventilate and steam tends to accumulate Within them. Such accumulated steam ordinarily can leave the pockets only by virtue of flowing transversely to the open ends. Such flow of steam is usually promoted by any one of several procedures such as blowing hot air from nozzles directed into the pockets at the opposite ends thereof but considerable difficulty nevertheless is encountered in achieving uniform drying of the Web throughout its width. This problem is well known and has been particularly severe for many years in view of the fact that the fabrics used for holding the web in contact with the drums ordinarily are so-called dryer felts. The dryer felts are rugged and relatively impervious to air, vapors and steam and thereby tend to confine the steam and/or moisture-laden air within the pockets. In recent years there has been a considerable trend toward the use of open-weave porous dryer fabrics, usually made of synthetic materials having the necessary ruggedness and stability under the conditions of heat and moisture which exist in the dryer section. Such open-weave fabrics are readily porous to steam and have reduced to a considerable extent the problems of scavenging of steam from some of the enclosed portions of the dryer section. Neverthless there remains a tendency for the steam and/ or moisture-laden air to become entrapped in the pockets which are formed directly beneath each of the top dryer cans and directly above each of the bottom dryer cans. These pockets are largely enclosed by the paper web and the dryer can surface and there are only relatively small areas where air or steam may flow through the porous dryer fabric to escape from these pockets.

It has been found that by the use of and proper directional disposition of fabric belts made in accordance with the present invention these pockets, as well as other enclosed zones, may be much more effectively and uniformly ventilated as a result of the pumping action of the fabric itself which forces the air and/or steam to flow through the fabric and thus into or out of the heretofore stagnant zones in a uniform manner throughout the width of the paper-making machine. In one preferable embodiment of the present invention the dryer fabrics are so arranged that the movement thereof in the direction of travel of the web will force ambient air and/or vapor to flow through the fabric into the most stagnant portions of the pocket to set the atmosphere within the pocket into motion in a proper direction to flow readily and smoothly out of the opposite side or exit of the pocket where it flows through the fabric into a zone outside the pocket.

Fabrics which will meet the requirements of the present invention may be woven in particular patterns of interlacing of warp and filling yarns whereby the transversely extending yarns will fall into pairs or groups which make up the equivalent of sloping slots with sloping passageways therebetween. Also, in a broader sense they may be made up of combinations of yarns or cables with slats of plastic, wood or metal. Also the equivalent of slats may be made up by the grouping of several transversely extending yarns, cable or monofilaments into bundles having more or less rectangular cross-section and binding such bundles so as to slope with respect to the general plane of the fabric.

Preferred fabrics embodying the present invention and illustrative ways of using such fabrics to best advantage will be described herein and are illustrated in the drawings forming a part of this specification.

In the drawings:

FIG. 1 is a diagrammatic illustration of a typical dryer section of a papermaking machine, or a portion thereof, showing upper and lower arrays of drying cans and associated upper and lower dryer fabrics and in which the web to be dried is moving generally from the right to the left and the fabrics are moving in the directions as indicatedby arrows associated therewith;

FIG. 2 is an enlarged fragmentary diagrammatic showing of a portion of the dryer section illustrated in FIG. 1 wherein the slats of the dryer fabrics are so oriented as to cause movement of ambient atmosphere through the fabrics inwardly of the closed paths through which the fabrics move;

FIG. 3 is a view similar to FIG. 2 but wherein the slats of the dryer fabrics are oriented in the opposite direction;

FIG. 4 is a weave pattern for the production of a particular fabric meeting the requirements of the present invention;

FIG. 5 is a diagrammatic sectional view taken. parallel with the longitudinally extending yarns of a fabric woven in accordance with the pattern illustrated in FIG. 4;

FIG. 6 is a diagrammatic sectional view taken along the line 6-6 in FIG. 5;

FIG. 7 is a diagrammatic illustration of a modified form of fabric meeting the requirements of the present invention;

FIG. 8 is a diagrammatic illustration of another modified form of fabric meeting the requirements of the present invention; and

FIG. 9 is a diagrammatic illustration of still another modified form of fabric meeting the requirements of the present invention.

Referring now to the drawings, in FIG. 1 there is shown an upper array of

dryer cans

10, 12,14 and 16 and a lower array of

dryer cans

18, 20, 22, 24 and 26. Typically, the dryer cans thus identified are smooth, imperforate metal cylinders arranged for rotation upon suitable bearings and supplied with steam at appropriate temperature which is introduced to the interior of each of the cans. In some instances one or more of the cans may be porous and supplied with heated air or other gas under pressure which flows outwardly through the paper anddryer fabrics. Also there is shown a cylinder 28 which may be a baby dryer, guide roll or the like depending upon the type or location of the dryer section or portion thereof illustrated in FIG. 1. A web to be dried is indicated at 30 and for illustrative purposes this may be assumed to be a web of paper which is progressing from the right hand side of the figure and from some preceding portion (not shown) of the papermaking machine. The web 30 is guided over the cylinder 28, downwardly around the dryer can 26, upwardly around the dryer can 16 and sequentially around the remaining lower and upper dryer cans illustrated in FIG. 1. When the web 30 leaves the last illustrated dryer can 18 it may be guided to additional portions of a dryer section or to subsequent parts of the machine, such as a size press, calendar, reel or the like.

An upper dryer fabric 32 is associated with the upper array of dryer cans -16. The fabric 32 is an endless belt conducted through an endless closed path defined byv the dryer cans 1016 and by any suitable combination of devices which illustratively may include felt rolls 34, return rolls 36, tensioning means 38 and

pocket rolls 4t

42 and 44. It will be observed that the pocket rolls 4044 are positioned substantially below the upper peripheries of the upper array of dryer cans and are positioned between successive cans in the upper array whereby the fabric 32 is caused to traverse a substantial portion of the periphery of each of the upper dryer cans 10-16 to hold the web 30 in heat transfer relation with each such portion.

A lower dryer fabric 48 consisting of an endless belt is associated with the lower array of dryer cans 13-26 and illustratively is conducted through such path by felt rolls 5%), return rolls 52, tensioning means 54 and

pocket rolls

56, 58, 6t and 62. The pocket rolls 562 are positioned similarly to those described above in connection with the upper dryer fabric 32 where-by the lower dryer fabric 48 is caused to traverse a substantial portion of the peripheries of the lower dryer cans 18-26 to hold the web 38 in heat transfer relation therewith.

From a consideration of FIG. 1 it will be observed that there are certain enclosed zones which are defined by the

fabrics

32 and 48, the web 30 and the surfaces of the dryer cans. One such zone 64 is enclosed by the upper fabric 32 and lies generally above the dryer section and another zone 66 is enclosed by the lower fabric 48 and lies generally beneath the dryer section. For convenience the

zones

64 and 66 will be referred to herein as loop zones. Usually, the upper loop zone 64 is arranged to exhaust into a hood (not shown) and the lower loop zone 66 is scavenged as an incident to the supply of air to replace that which eventually is exhaused through the hood.

Fabrics constructed and utilized in accordance with the present invention have beneficial ventilating effect on the

loop zones

64 and 66 as will be described below. Use of the invention for this purpose alone may be justified in particular installations wherein ventilation of one or more of the loop zones may be unsatisfactory.

Other enclosed zones which are notoriously difficult to ventilate are the pockets which lie above the

lower dryer cans

20, 22 and 24 as shown in FIG. 1 and beneath the upper dryer cans 10-16 as shown in said FIG. 1. Particular attention will be directed herein to

pockets

68 and 70 which are shown in larger scale in FIGS. 2 and 3 although it will be understood that the same considerations apply to all of the pockets of similar configuration which exist in dryer sections of the general type herein disclosed. The fabrics 32 and .48 are shown in FIGS. 2 and 3 in diagrammatic form with

slats

33 and 49 respectively shown as slanting lines to indicate orientation thereof relative to the direction of movement of the fabrics through the dryer section. The atmospheric currents set up by the fabrics and by the surfaces of other parts in the illustrated zones are indicated by directional arrows which are based upon observation and photographs to smoke flow.

Referring now to FIG. 2 the slats 33 in the upper fabric 32 are sloping forwardly, that is the edge 35 of each slat 33 which terminates in the paper-contacting surface of the fabric 32 is a leading edge and the edge 37 which terminates in the roll-contacting surface is a trailing edge with respect to the direction of travel of the fabric 32. Thus in any portion of the path of the fabric 32 wherein there is nothing in contact with either surface the slats will pump ambient atmosphere through the fabric 33 in a direction leading from the paper-contacting surface to the roll-contacting surface of the fabric 32. The direction of flow of atmosphere thus pumped by the fabric 32 is indicated by arrows 39. Thus, with the slats 35 forwardly oriented as shown in FIG. 2 the fabric 32 will tend to pump the atmosphere of air, water vapor, steam and the like from the outside of the loop zone '64 to the inside thereof.

Also, as shown in FIG. 2, the slats 49 of the lower fabric 48 are oriented forwardly, that is the leading edge of each slat 49 is the edge which terminates in the paper-contacting surface of the fabric 48. Thus, the fabric 48 also will tend to pump atmosphere from the outside of loop zone 66 through the fabric and into that zone.

When considered only from the standpoint of ventilation of the

loop zones

64 and 66 the orientation of the slats in

fabrics

32 and 48 as shown in FIG. 2 may be desirable for use in installations where ventilation of these zones has given rise to particular problems. It will be appreciated that the atmosphere thus pumped into the

zones

64 and 66 will be pumped at a substantially uniform rate throughout the width (from front side to back side) of the dryer section will cause a flow of atmosphere from the interiors of the

zone

64 and 66 outwardly through the open sides of the zones. Because the replacement atmophere is pumped through the full width of the fabrics the atmosphere within the loop zones 64 and 65 in certain dryer sections may 'be continuously scavenged and maintained in a more uniform condition throughout the width of the dryer section than was possible with conventional dryer felts and fabrics.

The fabric orientation illustrated in FIG. 2 is not, however, best calculated for effective ventilation of pockets of the type illustrated at 68 and 70 in said FIG. 2. Thus, in FIG. 2, the web 3%) is shown sandwiched between the fabric 32 and the downcoming surface of the dryer can 16. In common with all rough-textured surfaces which are moved through an atmosphere the fabric 32 will have entrained on the roll-contacting surface thereof an envelope of the adjacent atmosphere which is diagrammatically indicated at 72. The shape of the diagram 72 is intended to indicate that the velocity and volume of the atmosphere thus entrained is greatest near the fabric surface and diminishes as the distance from the fabric increases. The fabric 32 performs no pumping function at this point inasmuch as the paper-contacting surface thereof is closed by the web 34 and can 16. As the fabric approaches the pocket 68 it diverges from the web 30 at point 74 and converges with the pocket roll at point '76. Convergence with the surface of the pocket roll 44 will create a zone of high pressure on the left-hand side of the fabric 32 and divergence from the surface of the web 30 will create a zone of lower pressure on the righthand side of the fabric. Thus, the entrained atmosphere indicated by the diagram 72 will tend to flow through the fabric 32 at the entrance to the pocket 68. However, the orientation of the slats 33 is such that upon divergence of the fabric 32 and web 33 the fabric will tend to pump atmosphere from the entrance of the pocket 68 back through the fabric 32 and towards the loop zone 64, thus opposing and reducing the inward flow of entrained atmosphere from the loop zone 64. The arrow 39 indicates the direction in which the fabric pumps.

The arrangement shown in FIG. 2 results in very little movement of atmosphere in the zone of divergence at the entrance to the pocket 64. As the atmophere within the pocket 64 becomes entrained by the surface of fabric 32 as it bends sharply around the pocket roll 44 it forms a relatively shallow jet which is accelerated and projected in directions tangential to the pocket roll 44. This jet will thus be directed with considerable force upon the inner surface of web 30 in the region indicated by the arrows 78 and is likely to cause a dangerous amount of fluttering of the web 30 in such region. Also, the creation and projection of the jet 78 will tend to lower the pressure in the lower right hand corner of the pocket 68 resulting in the formation of a whorl indicated by arrows 80 and a stagnation zone indicated at 82 in both of which moisture-laden air and/ or steam will be retained.

Still referring to FIG. 2 it will be observed that the pumping action of the fabric 32 is indicated by the arrow 39 at the exit, upper left-hand corner, of the pocket 68. This direction is the same as the direction of flow of atmosphere entrained by the fabric 32 in this region, the latter flow being caused by convergence of the fabric 32 with the web 36 as it moves upwardly to the dryer can 14 and the divergence of the fabric from the upcoming 6 surface of the pocket roll 44. While this agreement in directions of fiow would appear to be favorable to exhaustion of the pocket 68 it will not be effective to break up the whorl or to scavenge the stagnant region 82 throughout the width of the dryer section because there is an inadequate flow of atmosphere through the fabric 32 at the entrance to the pocket 68. Consequently there will be a tendency for outside atmosphere to flow laterally into the pocket 68 from the open sides thereof, leading to uneven drying profile across the width of the web 36.

Although not described in detail herein it will be apparent that the lower fabric 48 will operate in connection with the pocket 70 in the same manner as the fabric 32 operates in connection with the pocket 68.

Much superior results are achieved by the use of the arrangement shown in FIG. 3 wherein the orientation of the

fabrics

32 and 48 is opposite that shown in FIG. 2. Thus, in FIG. 3 the

slats

33 and 49 of the

fabrics

32 and 48 respectively are inclined backwardly with respect to the travel of the fabrics. That is, the edges 35 of the slats 33 which terminate in the paper-contacting surface of the fabric 32 are trailing edges and the edges 37 which terminate in the roll-contacting surface are leading edges. The slats 49 of fabric 48 are similarly oriented. Therefore, when the

fabrics

32 and 48 are driven through their respective endless paths the slats thereof will tend to pump atmosphere from the

loop zones

64 and 66 respectively through the fabrics and outwardly as indicated by the arrows 84 in FIG. 3.

In FIG. 3 the envelope of atmosphere 72 entrained by the roll-contacting surface of the fabric 32 will tend to flow through the fabric 32 from left to right as it approaches the point of convergence 76 with the pocket roll 44. Divergence of the fabric 32 from the web 30 at point 74 will tend to create a zone of low pressure further inducing flow of atmosphere through the fabric 32 in the same direction and thus into the entrance of the pocket 68. In this case the slats 35 of fabric 32 are so oriented that they will pump atmosphere through the fabric 32 as it passes from

points

74 and 76 in this same direction as indicated by the arrows 84.

In FIG. 3 wherein all three factors which cause flow of atmosphere through the fabric 32 work in the same direction the atmosphere enters the pocket 68 from the loop zone 64 in greater volume and at higher velocity than is achieved by the arrangement in FIG. 2. Accordingly the entering atmosphere will be projected downwardly into the pocket 68 and some of it will tend to follow the downwardly moving web 30 thus to reach substantially to the lower right-hand corner of the pocket from whence it will flow in a relatively deep layer entrained in part by the fabric 32 as it turns around the pocket roll 44 with the remainder of the layer flowing in the same direction as a result of the volume and velocity thereof at the entrance to the pocket. The arrows 86 indicate the general pattern of flow of the atmosphere from the entrance of the pocket 68 toward the lower left-hand corner of the pocket from whence it turns upwardly to move with the web 30 toward the exit of the pocket as indicated by arrows 88. The fact that the velocity of the atmosphere in the outermost regions of the layer as indicated by the arrows 90 rather closely approaches that of the atmosphere entrained by the fabric serves to sharply reduce the tendency toward formation of a concentrated high-speed jet such as is formed at 78 in FIG. 2 thus avoiding, in FIG. 3, the danger of fluttering of the web which was discussed above.

A factor which assists in establishing the generally uniform flow of atmosphere through the pocket 68 as shown in FIG. 3 is that at the exit of the pocket 68 the fabric 32 tends to pump atmosphere in a direction opposite to the flow of atmosphere outwardly through the exit. The latter flow is caused by convergence of the fabric 32 with the web 30 as it approaches the dryer can 14 and divergence of the fabric 32 from the surface of the pocket roll 44. Thus from the point 92 to the point 94 the atmosphere from the pocket 68 is caused to flow through the fabric 32 from left to right as indicated by arrows 96 while being resisted by the pumping action of the fabric as it passes between said points 92 and 94. The combined effect is to reduce the velocity at which the atmosphere flows out of the pocket 68 with attendant increase in V atmospheric pressure in the pocket 68 and with a general tendency toward equilization of flow rates of the layers of atmosphere moving through the pocket 68.

Another effect of the arrangement shown in FIG. 3 which is desirable in contrast with the arrangement shown in FIG. 2 is the reduction in the proportionate amount of atmosphere leaving the exit of the pocket 68 which tends to follow the upper surface of the pocket roll 44 and thus to reenter the pocket at the entrance. In FIG. 2 the velocity of the exiting atmosphere is relatively high since all three factors, discussed above, combine to force the atmosphere through the fabric 32. A substantial portion of it thus will be propelled towards the upcoming surface of the pocket roll 44 where there is a zone of low pressure created by divergence of the fabric away from the pocket roll 44. In FIG. 3, however, the reverse pumping action of the fabric 32 not only reduces the velocity of the exciting atmosphere but also tends to pull atmosphere away from the upcoming surface of the pocket roll 44, thereby, reducing the amount of exiting atmosphere which can become entrained with the upper and downcoming surfaces of the pocket roll 44. The reduction 1n short-circuiting of moisture-laden atmosphere is of evident value in the desired increase in drying efficiency.

Although not described in detail herein it will be apparent that the lower fabric -48 arranged as shown n FIG. 3 will operate in connection with the pocket 70 1n the same manner as the fabric 32 operates in connection with the pocket 68,

The operation of the

fabrics

32 and 48 as arranged in FIG. 3 in connection with the

loop zones

64 and 66 is, of course, opposite to that described above in connection with FIG. 2. That is, in FIG. 3, the

fabrics

32 and 48 will pump, where they are open on both surfaces, atmosphere out of the loop zones enclosed thereby. Desirable ventilation of the

loop zones

64 and 66 is accomplished by pumping in either direction since ineither vent the atmosphere enclosed within the loop zones is moved or kept motion by a pumping action which is substantially uniform throughout the widths of the actively pumping portions of the fabrics.

While, as has been made clear above, belts embodying the present invention may take a variety of forms, it is regarded as particularly desirable for many uses and particularly for use in the drying of webs of paper and sunilar fibrous products that the belts consist of a woven fabric. Such belts will resemble in many respects the openweave dryer fabrics with which paper manufacturers are already familiar and thus they comprise a form of the invention which may find more ready acceptance by the industry. A particularly desirable fabric has been selected for illustration herein as a preferred form. This fabric is of the type which is woven from longitudinally extending warp yarns interlaced with transversely extending weft yarns in such a manner that they will fall into pairs lying in a sloping relationship resembling a slat. Each pair of yarns thus forming a slat is spaced from the next adjacent pair by a distance adequate to afford the requisite porosity for the fabric as a whole and to afford sloping passageways between the slats through which the atmosphere such as air, gas or vapors will be induced to flow from one side of the fabric to the other as a result of the pumping action of the slats when the fabric is moved in lengthwise direction. The fabric specifically disclosed is a two-ply fabric with one set of wefts lying in one ply and the other set lying in the other ply. The pairs consist of one weft from each ply. The fabric could comprise three or more plies if so desired but the two-ply 8 fabric herein illustrated has been found to be highly effective for the purposes of the present invention.

The illustrative preferred fabric is woven as a flat twoply fabric. In a flat fabric the warp yarns extend lengthwise of the fabric which is woven to a suitable length after which the ends are joined by any suitable means to form an endless belt in which the warp yarns extends peripherally of the belt and operate in the machine direction when the belt is put into use. In FIG. 4 which is a conventional weave pattern in which the points where warps cross above wefts are indicated by an X. There are two sets of four warp yarns l, 2, 3 and 4 in each repeat which are interwoven with eight weftyarns A, B, C, D, E, P, G and H in each repeat. The weft yarns B, D, F and H of each repeat lie in the upper ply of the fabric while the weft yarns A, C, E and G of each repeat lie in the lower ply. The warp yarn 1 is interwoven only with the wefts in the upper ply and the warp yarn 4 is interwoven only with. the wefts in the lower ply.

Warp yarns

2 and 3 are interwoven with the wefts in both plies in a particular manner to bind the two plies together and also to cause the successive wefts to assumevertically offset paired relationship. The particular weave chosen for illustration is one in which the slanting paired relationship between the weft yarns results from the particular manner in which the

warp yarns

2 and 3 cross the wefts and may be accomplished with all of the warp yarns placed under the same tension and without other departures, from customary loom operation. It will be understood, of course, that the same general result may be accomplished with other specific weaving patterns and loom techniques as may be desired.

FIG. 5 which is a diagrammatic representation of a section taken tranversely of the weft yarns, illustrates the woven relationship, just described, of the weft yarns A through H with one group of the warp yarns 1 through 4. Warp yarn2 crosses under weft A to bind the lower ply and passes between wefts B, C, D and E before it crosses over weft F to bind the upper ply. However, in returning from the upper ply to the lower ply the warp 2 passes between wefts G and H and then crosses under weft A of the next repeat. The length of Warp 2, as diagrammatically shown, which extends upwardly from weft A to weft F is greater than the length which extends downwardly from weft F to weft A in the next repeat. Warp 3 follows a similar path with a length extending upwardly from weft E to weft B of the next repeat which is longer than the length extending downwardly from a weft B to the next weft E. When the fabric is successively beaten up and the warps are crossed in the shedding operations the uneven lengths of the portions of

warps

2 and 3 just discussed will cause the wefts to pair, that is the wefts B and F of the upper ply will be moved toward the left, as viewed in FIG. 5 as a result of the effort of the tensioned uneven spans of warp to equalize themselves. This action of the wefts B and F also causes the previously laid wefts H and D respectively of the upper ply to pair with the lower ply wefts G and C.

In FIG. 6 which is a diagrammatic representation of a section taken transversely of the warp yarns, it will be observed that the weft yarns B and D float under three and over one so as to lie primarily in the lower ply whereas the weft yarns A and C float over three and under one so as to lie primarily in the upper ply. The resultant fabric thus will have its opposite surfaces made up primarily of weft yarns which will lie transversely to the machine direction when the fabric is put into use. Preferably the weft yarns are greater in diameter than the warp yarns. Also, preferably, the warp yarns, at least are made of a material which has great tensile strength and dimensional stability when wet and hot and the weft yarns, at least, are made of a material which is capable of being set in relatively rigid condition. For example, the weft yarns may be made from polyester material such as Dacron which has the requisite characteristics and the warp yarns may be made of a polyamide such as one of the various forms of nylon which upon impregnation with suitably selected heat-settable resin materials can be set by heat into the desirable condition of rigidity. Preferably, the warps and wefts are both of multifilament construction. When the resin is applied to the fabric in the finishing procedure it preferably is a resin which will penetrate deeply into at least the nylon weft yarns and will react with the nylon material in such manner that upon heat setting the formerly supple multifilament structure of each yarn will become quite rigid as a result of binding together of the multifilaments. The longitudinally extending warp yarns may or may not be so drastically affected by the resinous material with which the fabric is impregnated. Many of the resinous materials which have drastic effect upon nylon used as the weft yarns will have considerably less effect upon the polyester materials used as the warp. This is advantageous in the preferred fabric in that the longitudinally extending polyester warp yarns will remain relatively flexible and will permit the fabric to bend about transverse axes incident to travel over the various rolls and dryer cans which define the endless path for the fabric in use.

Woven fabrics useful in connection with the present invention, including the fabric specifically described above, are preferably finished and stabilized in accordance with the teachings of US. Patent No. 2,903,021 granted Sept. 8, 1959 to Holden et al. and U8. Patent No. 3,149,- 003 granted Sept. 15, 1964 to Christie et al. Thus, the fabric is woven to desired length, made endless by joining the ends and is stabilized by resin impregnation and setting while being held in fiat smooth condition under accurate dimensional control in both lengthwise and transverse directions. The resin impregnation procedures which are suitable for the present invention differ from those procedures frequently applied to papermakers felts to make them water repellent, mildew resistant and the like by impregnating them with relatively dilute resinous solutions affording a resin pick-up of a very few percent of the total weight-of the finished felt. For the present invention the resin pickup usually will be from 10% to or more of the weight of the finished fabric and the impregnation materials are applied in relatively concentrated form and frequently in repeated or successive applications of appropriately selected materials. The fabric, when ready for use, more nearly resembles a metal wire screen than it does a traditional fabric such as a papermakers wet felt or dryer felt.

FIG. 7 shows in diagrammatic another form of fabric useful in connection with the present invention. In this form the transversely extending slats 100 are each made up of a plurality of parallel yarns, cords or the like 102 laid up in a staggered stack and secured together, as by an adhesive or settable impregnant to form elongated structures having cross-sections in the shape of parallelograms with inclined sides to establish the desired degree of slant to be assumed in the finished fabric. These slats 1% are interwoven with warp yarns or cords 104 and 1% which cross between each slat much in the manner of a leno-weave fabric. The weaving or forming of the fabric of FIG. 7 may be carried out on simple apparatus similar to that used for manufacture of bamboo shades. Preferably, the finished fabric is stabilized by application of suitable settable resinous material or adhesive to prevent slippage of the warps 104 and 106 relative to those portions of the slats 100 with which they engage as shown in FIG. 7.

In FIG. 8 another useful fabric is shown in which actual slats 108 of wood, plastic or metal, for example, are formed with a cross-section of parallelogram shape with slanting sides so related as to establish desired slope of the slats 108 in the finished fabric. The slats are interwoven with warp yarns, cords or wires 119 and 112 which cross between adjacent slats. This fabric may be formed on apparatus similar to that used for making bamboo shades and preferably is stabilized to prevent slippage of the warps and 112 relative to those portions of the slats 108 which they engage as shown in FIG. 8.

In FIG. 9 there is shown another useful fabric for this invention. In this form slats 114 of generally S- shaped cross section are made of wood, metal, plastic or other suitable material. Preferably the slats 114 are made by extrusion of plastic or metal in known manner. The slats 114 are provided with closely-spaced holes 116 throughout their lengths whereby the slats may be strung upon parallel cables, cords or wires which will extend lengthwise of the finished fabric. Spacers 118 consisting of short lengths of tubular material having outside diameter greater than that of the holes 116 are strung on the cables 120 between each slat 114 to hold the slats in desired longitudinally spaced position upon the cables 120. The tubular spacers preferably are made of plastic or other flexible material whereby they may bend transversely of their lengths as the fabric travels over the rolls, dryer cans or the like which define the endless path through which the fabric is driven in use.

The above detailed description of preferred and modified forms of fabrics and of illustrative manners in which the same may be used is intended to be illustrative rather than limiting in nature inasmuch as it will be apparent that modifications and variations may be made by those skilled in the art without departing from the scope of the claims.

What is claimed is:

1. A dryer fabric comprising an endless belt having longitudinally extending flexible strands interconnected with transversely extending strands arranged in spaced groups of at least two strands lying closely parallel with one another and secured against movement relative to each other and secured against slipping movement relative to said longitudinally extending strands at the points of interconnection between said strands, each of said groups of transversely extending strands being inclined with the surface planes of said fabric so as to form a slat-like body which presents, with respect to the direction of travel of said fabric when it is driven in an endless path, a surface having a leading edge terminating in one surface of said fabric and a trailing edge terminating in the other surface of said fabric; and the space between successive adjacent groups of transversely extending strands defining passageways which extend through the thickness of said fabric.

2. A fabric in accordance with claim 1 in which all of said strands are yarns made of at least one synthetic material, said yarn being interwoven on a loom with the longitudinally extending yarns being warps and the transversely extending yarns being wefts, there being at least two sets of wefts lying in at least two levels within said fabric and said warp yarns being so interwoven with said wefts as to hold said wefts in longitudinally spaced groups of at least two wefts in vertically offset closely parallel relation with each of said groups including one weft from the uppermost set of wefts and one weft from the lowermost set of wefts.

3. A fabric in accordance with claim 2 in which said yarns are secured against slipping by impregnation of said fabric with a heat-settable resinous material heat set in situ.

4. A fabric in accordance with claim 1 in which said longitudinally extending strands are yarns made of at least one synthetic material such as a polyester having great tensile strength and resistance to failure as a result of flexing while moist and at a temperature of at least about 212 F, and said transversely-extending strands are yarns made of at least one synthetic material such as a poylamide having great resistance to abrasion while moist and at a temperature of at least about 212 F., and wherein said yarns are secured against slipping and said transversely extending yarns are rendered relatively rigid by 11 impregnation of said fabric with a heat-settable resinous material heat set in situ.

5. A fabric for pumping fluids comprising an endless belt having longitudinally extending flexible strands interconnected with transversely extending strands arranged in spaced groups of at least two strands lying closely parallel with one another and secured against movement relative to each other and secured against slipping movement relative to said longitudinally extending strands at the points of interconnection between said strands, each of said groups of transversely extending strands being inclined with the surface planes of said fabric so as to form a slat-like body which presents, with respect to the direction of travel of said fabric when it is driven in an endless path, a surface having a leading edge terminating in one surface of said fabric and a trailing edge terminating in the other surface of said fabric; and the spaces between successive adjacent groups of transversely extending strands defining passageways which extend through the thickness of said fabric, whereby upon movement of said endless belt in said direction those portions of said belt which have both surfaces open to a fluid will be effective to pump fluid from said one surface of said fabric through said passageways and outwardly from said other surface of said fabric.

6. A fabric in accordance with claim in which all of said strands are yarns made :of at least one synthetic material, said yarns being interwoven on a loom with the longitudinally extending yarns being warps and the transversely extending yarns being wefts, there being at least two sets of wefts lying in at least two levels within said fabrics and said warp yarns being so interwoven with said wefts as to hold said wefts in longitudinally spaced groups of at least two wefts in vertically offset closely parallel relation with each of said groups including one weft from the uppermost set of wefts and one weft from the lowermost set of wefts.

7. A fabric in accordance with claim 6 in which said yarns are secured against slipping by impregnation of said fabric with a heat-settable resinous material heat set in situ.

8. A fabric in accordance with claim 5 in which said longitudinally extending strands are yarns made of at least one synthetic material such as a polyester having great tensile strength and resistance to failure as a result of flexing while moist and at a temperature of at least about 212 F., and said transversely-extending strands are yarns made of at least one synthetic material such as a polyamide having great resistance to abrasion while moist and at a temperature of at least about 212 F., and wherein said yarns are secured against slipping and said transversely extending yarns are rendered relatively rigid by impregnation of said fabric with a heat-settable resinous material heat set in situ.

9. A dryer fabric suitable for use in a machine for drying webs of material wherein said drying machine has at least one rotatable dryer can over which a web to be dried is guided and wherein said dryer fabric is driven through an endless path to hold said web in heat transfer relation with a substantial portion of the periphery of said dryer can; said dryer fabric comprising an endless porous belt having longitudinally extending elongated flexible strands assembled with transversely extending relatively rigid slat-like bodies spaced longitudinally from one another and secured against movement relative to said strands at the points of engagement between said strands and said slat-like bodies, said slat-like bodies being so contoured with respect to the surface planes of said fabric as to present, with respect to the direction of travel of said fabric in a drying machine, a leading edge terminating in one surface of said fabric, a trailing edge terminating in the other surface of said fabric and an inclined surface extending between said edges; and adjacent spaced slats defining therebetween elongated narrow passageways each of which extends substantially continuously from one edge of said fabric to the other edge thereof and each of which affords a continuous passageway opening into both surface planes of said fabric.

fit. A fabric in accordance with claim 9 in which all of said strands and slat-like bodies are made from yarns made of at least one synthetic material, said yarns being interwoven on a loom with the longitudinally extending yarns being warps and the transversely extending yarns being wefts, there being at least two sets of wefts lying in at least two levels Within said fabric and said warp yarns being so interwoven with said wefts as to hold' said wefts in longitudinally spaced groups of at least two wefts in vertically offset closely parallel relation with each of said groups including one weft from the uppermost set of wefts and one weft from the lowermost set of wefts.

11. A fabric in accordance with claim 10 in which said yarns are secured against slipping by impregnation of said fabric with a heat-settable resinous material heat set in situ.

12. A fabric in accordance with claim 9 in which said longitudinally extending strands are yarns made of at least one synthetic material such as a polyester having great tensile strength and resistance to failure as a result of flexing while moist and at a temperature of at least about 212 F., and said transversely-extending strands are yarns made of at least one synthetic material such as a polyamide having great resistance to abrasion while moist and at a temperature of at least about 212 F., and wherein said yarns are secured against slipping and said transversely extending yarns are rendered relatively rigid by impregnation of said fabric with a heat-settable resinous material heat set in situ.

13. In apparatus for drying webs of material such as paper in a dryer section having a plurality of rotatable dryer cans over which a web of paper to be dried is guided seriatim and means for driving a dryer fabric through an endless path to hold said web in heat transfer relation with a substantial portion of the periphery of at least some of said dryer cans, and wherein said dryer cans are nested in such manner as, with said web of :paper and said dryer fabric, to form enclosed zones open only at the sides of the dryer section; the combination of a dryer fabric comprising an endless porous belt having longitudinally extending elongated flexible strands interconnected with transversely extending relatively rigid slat-like bodies spaced longitudinally from one another and secured against movement relative to said strands at the points of engagement between said strands and said slat-like bodies; said slat-like bodies being so contoured with respect to the surface planes of. said fabric as to prevent, with respect to the direction of travel of said fabric in a dryer section, a leading edge terminating in one surface of said fabric, a trailing edge terminating in the other surface of said fabric and an inclined surface extending between said ed es; adjacent spaced slats defining therebetween passageways each of which extends substantially continuously from one edge of said fabric to the other edge thereof and each of which affords a continuoustpassageway opening into both surface planes of said fabric; and means for guiding said dryer fabric as it is driven through said endless path in a direction such that the trailing edges of each of said slat-like bodies terrnina te in the web-contacting surface of said dryer fabric whereby as said dryer fabric progressively diverges from said web at the entrance to each of said pockets the slat-like, bodies will be effective to pump atmosphere through said fabric and into the pocket.

14. A fabric in accordance with claim 13 which all of said strands and said slat-like bodies are made fro-m yarns made of at least one synthetic material, said yarns being interwoven on a loom with the longitudinally extending yarns being warps and the transversely extending yarns being wefts, there being at least two sets of wefts lying in at least two levels within said fabric and said warp yarns being so interwoven with said wefts as to hold said wefts in longitudinally spaced groups of at least two wefts in vertically offset closely parallel relation with each of said groups including one weft from the uppermost set of wefts and one weft from the lowermost set of wefts.

15. A fabric in accordance with claim 14 in which said yarns are secured against slipping by impregnation of said fabric with a heat-settable resinous material heat set in situ.

16. A fabric in accordance with claim 13 in which said longitudinally extending strands are yarns made of at least one synthetic material such as a polyester having great tensile strength and resistance to failure as a result of flexing while moist and at a temperature of at least about 212 F., said transversely-extending strands are yarns made of at least one synthetic material such as a References Cited UNITED STATES PATENTS 1,333,759 3/1920 Kooy 139-425 FOREIGN PATENTS 80,151 1/ 1951 Czechoslovakia.

FREDERICK L. MA'ITESON, JR., Primary Examiner. A. D. HERRMANN, Assistant Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,325,909 June 20, 1967 Raymond C. Clark It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 1, line 28, for "manufacturer" read manufacture line 40, for "in" read is column 4, line 53, for "to" read of column 5, line 11, after "section" insert and line 19, for "and" read or column 7, line 44, for "vent" read event column 8, line 7, for "extends" read extend line 34, for "tranversely" read transversely column 10, line 49, for "yarn" read yarns column ll, line 32, for "fabrics" read fabric line 67, for "bodies," read bodies; column 12, line 52, for "prevent" read present line 69, after "13" insert in column 13, line 16, before "said" insert and Signed and sealed this 3rd day of September 1968.

(SEAL) Att est:

EDWARD M.FLETCHER,JR. EDWARD J. BRENNER Attesting Officer Commissioner of Patents