US3351205A

US3351205A - Twisted strands and non-woven filtering media made of such strands

Info

Publication number: US3351205A
Application number: US197168A
Authority: US
Inventors: Clarence A Butler; Lazzaro Dominic Richard
Original assignee: Lindsay Wire Weaving Co
Current assignee: Lindsay Wire Weaving Co
Priority date: 1962-05-18
Filing date: 1962-05-18
Publication date: 1967-11-07
Anticipated expiration: 1984-11-07

Description

NOV. 7, 1967 c BUTLER ET AL 3,351,205

TWISTED STRANDS AND NON'WOVEN FILTERING MEDIA MADE OF SUCH STRANDS Filed May 18, 1962 4 Sheets-Sheet 1 Fi i INVENTORS i I3 CLRREm: R. Bu'rLEmm j lj Dominic R. LRZZHRO A" V A /ans, fig? files 1Q [4 HT OKNEYS Nov. 7, 1967 c. A. BUTLER ET AL 3,351,205 TWISTED STRANDS AND NON-WOVEN FILTERING MEDIA MADE OF SUCH STRANDS Filed May 18, 1962 INVENTORS 4 Sheets-Sheet 2 CLRRENCE B ,ku-ruzn. rmo

Dominic R Lnzzmzo @5028, i HT ORNEY5 Nov. 7, 1967 c. A. BUTLER ET AL' 3,351,205 TWISTED STRA AND NONWOVEN FILTERING MEDIA E OF SUCH STRANDS Filed May 18, 1962 4 Sheets-Sheet 3 /7 mm/ m Fj 14 l5 fj lli $5 1 7 2e 30 32' 6 Q as 30 I 15 F i? EEG "Fail E1 E3 7 T f4 FE .55

INVENTORS K 5 CLHRENCE R. BUTLER, Dommic R. LRZZFIRO Nov. 7, 1967 Q BUTLER ET AL 3,351,205 TWISTED STRANDS AND NON-WOVEN FILTERING MEDIA MADE OF SUCH STRANDS Filed May 18, 1962 4 Sheets-Sheet 4 INVENTORS Cumuce Rjuuap Dominic R. Lnzznao NEYS United States Patent Ofifice 3,351,205 Patented Nov. 7, 1967 3,351,205 TWlSTEl) STRANDS AND NON-WOVEN FILTER- llNG MEDIA MADE OF SUCH STRANDS Ciarence A. Butler and Dominic Richard Lazzaro, Cleveland, Ohio, assignors to The Lindsay Wire Weaving Company, Cleveland, Ohio, a corporation of Ohio Filed May 18, 1962, Ser. No. 197,168 The portion of the term of the patent subsequent to Dec. 1, 1981, has been disciairned Claims. (Cl. 219-490) This invention relates to non-woven filtering media comprised of twisted strands, and the method of making such media. The invention is adapted for use as a filter either for general use or for making belts and the like for use with paper-making machines.

Heretofore, it has been experienced that the wire mesh conventionally used in making Fourdrinier belts for use in paper-making machines must have certain hydraulic characteristics of porosity, as well as sufi'icient wear resistance, corrosion resistance, and durability in order to provide the optimum desired operational conditions for making paper. In the past, the utilization of a coarse wire mesh resulted in a quick tie-watering of the thin fiber mat formed on the belt causing the fine material to flow out as white water before formation of the mat on the belt. Under these conditions, the paper sheet was found to be more dense over the wires than in the area between the wires, resulting in a wire mark in the sheet itself, which could not be brushed or pressed out of the sheet. Thus, it was considered that the ideal sheet forming conditions for uniform structure are to have the thin fiber mat formed rapidly on a belt to prevent the loss of fine material and to keep the stock on the belt fluid for a sufiicient time. In the case of woven wire belts, eiforts to meet these requirements resulted in using finer mesh wires and by attempting to drive more shute wires into the screen to decrease the open area between wires. However, such efforts to make a superior sheet by putting more metal into the belt or making it finer have been unsatisfactory due to the increased expense of finer wire, and relatively shorter life of such wire. More importantly, fabrics, Whether made of natural fibers, synthetic fibers, or metallic wire, when woven, depend on the openings in the weave for porosity, since the fibers or wires generally extend in a direction of One of the planes of the fabric or the belt. Even when the fabric is woven of a twisted yarn, the individual fibers or wires, themselves being non-porous or of low porosity, produce no passageways substantially perpendicular to the plane of the fabric resulting in extremely poor and uncontrolled hydraulic characteristics essential to the production of a superior paper sheet.

Therefore, an object of the present invention is to provide twisted strands for use in making non-woven filtering media having improved characteristics of porosity, wear resistance, corrosion resistance, and durability.

Another object of the present invention is to provide twisted strands comprised primarily from thermoplastic material suitable for use in making non-woven fabric, belts, and the like suitable for use with paper making machines having improved characteristics of porosity, wear resistance, corrosion resistance, and durability.

'A further object of the present invention is to provide a non-woven filtering media comprised of twisted strands and the method of making such media having improved characteristics of porosity, wear resistance, corrosion resistance, and durability.

A still further object of the present invention is to provide a non-woven filtering media comprised primarily of twisted thermoplastic strands, and the method of making such media for use in paper-making machines having improved characteristics of porosity, wear resistance, corrosion resistance, and durability.

Another object of the present invention is to provide a non-woven belt of twisted strands suitable for use with paper-making machines having improved characteristics of porosity, wear resistance, corrosion resistance and durability.

A still further object of the present invention is to provide a non-woven belt made primarily from thermoplastic twisted strands suitable for use with paper-making machines having improved characteristics of porosity, wear resistance, corrosion resistance and durability.

An additional object of the present invention is to provide a more economical, light weight, non-woven fabricor belt, comprised primarily of thermoplastic twisted strands suitable for use with paper-making machines having improved characteristics of porosity, wear resistance, corrosion resistance and durability.

Other and further objects of the present invention will be apparent from the following description and claims illustrated in the accompanying drawings, which, by way of illustration, show a preferred embodiment of the present invention and the principles thereof and what is now considered to be the best mode in which to apply these principles. Other embodiments of the invention embodying the same or equivalent principles may be applied by those skilled in the art in structural changes may be made as desired without departing from the scope of the present invention, in the drawings:

FIG. 1 is an enlarged fragmentary plan view showing a non-woven filtering media comprised of the twisted strands embodying the present invention;

FIG. 2 is a cross sectional view taken along line 2-2 of FIG. 1;

FIG. 3 is an enlarged fragmentary plan view showing a modification of the non-woven filtering media comprised of twisted strands embodying the present invention;

FIG. 4 is a cross sectional view taken along lines 4 4 of FIG. 3;

FIG. 5 is an enlarged fragmentary plan view showing another modification of the non-woven filtering media comprised of a twisted strand embodying the present invention;

FIG. 6 is a cross sectional view taken along lines 6-6 of FIG. 5;

FIG. 7 is an enlarged fragmentary plan view showing another modification of the non-woven filtering media comprised of the twisted strands embodying the present invention;

FIG. 8 is a cross sectional view taken along line 8-8 of FIG. 7;

FIG. 9 is an enlarged fragmentary plan view showing a non-woven filtering media comprised of a plurality of layers of twisted strands embodying the present invention;

FIG. 10 is an enlarged fragmentary plan view showing a modification of a non-woven filtering media comprised of a plurality of layers of twisted strands embodying the present invention;

FIG. 11 is an enlarged fragmentary plan View showing a non-woven filtering media comprised of twisted strands in conjunction with supporting strands embodying the present invention;

FIG. 12 is a sectional view showing a twisted strand having a reinforcing element extending therein;

FIG. 13 is a sectional view showing a modification of the twisted strand having a filler material formed therein as a reinforcing means;

FIGS. 14 through 34 inclusive are vertical cross sectional views showing modified shapes of the twisted strands embodying the present invention;

FIG. 35 is a perspective view of a non-Woven endless belt made in accordance with the principles of the present invention;

FIG. 36 is a diagrammatic illustration showing the filtering media embodying the present invention passing between spaced pairs of rolls for expanding the media longitudinally in accordance with the principles of the present invention;

FIG. 37 is a diagrammatic illustration showing the filtering media embodying the present invention, in another form, mounted intermediate clamping members for expanding the media in transverse and longitudinal directions in accordance with the principles of the present invention;

FIG. 38 is a diagrammatic illustration showing an endless belt made from the filtering media embodying the present invention mounted on stretcher rolls for expanding the belt longitudinally in accordance with the principles of the present invention.

Generally, we have found that a filtering media having improved characteristics of porosity, wear-resistance and corrosion-resistance may be obtained by forming such media of a plurality of twisted thermoplastic strands. By varying the cross sectional configuration, amount and direction of twist of such strands in accordance with the principles of the present invention, we provide a filtering media having a predetermined specific surface area and an improved porosity which is substantially perpendicular to the plane of the media. Accordingly, by forming a filtering media of twisted strands, there is achieved a controlled porosity through the media which is not dependent on the porosity of the strands themselves nor upon intricate weaving techniques, as in the case of conventional fabric constructions. Moreover, in addition to providing a filtering media for general use, we may provide such a media for making endless belts or the like which are suitable for use with paper-making machines. For example, by twisting the thermoplastic strands and maintaining a predetermined ratio of specific surface area to drainage area, there is obtained an endless belt which provides a more efficient utilization of paper stock while incorporating optimum drainage characteristics for producing a superior paper product.

In addition, it has been found that materials, such as thermoplastics, when expanded under controlled temperature condit-ions provide strength and durability highly suitable for making endless belts or the like for paper-making machines. Moreover, expanding of various thermoplastics, such as polycarbonate and nylon, in accord with the principles of the present invention, results in a preferred orientation of the molecular chains comprising the plastic and in the direction of expansion. Such orientation of the plastic not only provides a substantial increase in strength and durability but upon such orientation, the plastic will retain its final dimension, as expanded. Accordingly, we have found that by forming a filtering media of a plurality of such thermoplastic twisted strands and by subsequently expanding the media under controlled temperature conditions, there is achieved a controlled variation in the open area between adjacent twisted strands such as to provide a filtering media having optimum hydraulic characteristics suitable for use, for example, as belts or the like for paper-making machines.

Briefly, to accomplish the objects of providing a filtering media having improved characteristics of porosity, wear resistance, corrosion resistance and durability, there may be provided a non-woven construction made of a plurality of twisted strands having predetermined cross sectional configurations. The twisted strands may be joined together into one or more layers and in a manner to provide a predetermined specific surface area and a porosity through the layer or layers that may be substantially perpendicular to the plane of the media.

To further increase the strength of the media and to maintain a constant porosity through the openings formed between adjacent twisted strands, the filtering media may then be subjected to an expanding operation to orient the strands a predetermined amount in the direction of expansion. In some cases, additional layers of strands of the same and/0r larger cross-sectional dimensions may be utilized in conjunction with the filtering media to provide a more durable construction when utilized, for example, in the environment of paper-making machines.

Referring now more particularly to the drawings, FIGS. 1 to 4 illustrate one form of the invention, wherein fiat strands 1-2-1, respectively, may be formed into a single layer by fusion, solvent cementing or by means of adhesives, such as shown generally at 8 of FIG. 2. In this form, the individual strands, before being bonded together, may be twisted and heat set in a manner and in an amount suflicient to provide the desired specific surface and porosity without overstressing the individual strands. As shown, the alternative strands 1 may be twisted about onehalf or about with about five turns per inch of length in a counterclockwise direction, while the intermediate strands 2 may be twisted the same amount in the opposite or clockwise direction, whereby the openings 9 formed between adjacent strands are aligned in rows extending substantially transversely across the plane of the filtering media. FIGS. 3 and 4 show another form of the invention, wherein the strands 3-4-3, respectively, may be of a generally cross-shape in cross-section, whereby the openings 10 between adjacent strands are considerably more numerous but are of a relatively smaller dimension. In FIGS. 6 and 5, the strands 5-6-5, respectively, may be semicircular in form having a channel portion in vertical crosssection, whereby the openings 11 between adjacent strands may be alternatively spaced or staggered transversely across the width of the filtering media.

In another form, FIGS. 7 and 8 illustrate a construction wherein the L'shaped strands 7-7-7, respectively,

may be twisted with about five turns per inch of length in the same direction either clockwise or counterclockwise. In this forrn, the alternate strands of the layers may also be shifted longitudinally with respect to the intermediate layers by an amount sutficient to produce the openings 12 to obtain a desired porosity. It is to be understood, however, that in some cases, it maybe desirable to, twist the adjacent alternative strands in a manner to vary the relative pitch of the strand rather than by shifting the strands in order to obtain the desired porosity between adjacent strands, as aforementioned. Asshown at FIGS. 9 and 10, the non-woven filtering media may be formed having more than one layer of twisted strands. In such case, the media may include an upper layer of strands 3-4-3, which may extend at an angle with respect to the strands 3 -4 -3 of the lower layer in order to effect the desired degree of porosity through the openings in the layers. In this form, the twisted strands 3-4-3, of the upper layer may extend longitudinally and at right angles. or perpendicularly with respect to the twisted strands 3 -4 -3 of the lower layer, to provide the desired degree of porosity and a predetermined amount of specific surface area, as shown a at FIG. 10.

FIGS. 11 to 13 illustrate another form of the invention, wherein strands 13 may be utilized as supporting or carrying elements for the filtering strands 7 under conditions where the strands of the filtering media do not have sufficient strength to perform the necessary mechanical functions for sufiicient life and durability. Such a condition, for example, may exist where a coarser mesh filtering media is required. As shown, the carrying strands 13 may extend transversely relative to the fabric or media and may be provided, with a reinforcing means, such asmetallic wires, glass strands or the like, shown generally at 15 of FIG. 11. In another form, shown at FIG. 13, the carrying strands 13 may be impregnated with between about 20 to 40 percent, by weight, of a filler material 14, such as glass flakes comprised of borosilicate or the like,.to impart the desired reinforcing strength to the filtering media. In this regard, it is to be understood that the carrying members may extend longitudinally rather than transversely with respect to the filtering media in order to provide the necessary durability for such media. In cases where it is desirable to utilize a supporting layer in conjunction with the filtering media, the strands 13 may be of a greater cross-sectional dimension relative to the strands of the filtering media to thereby impart a greater durability to the media or fabric.

To further control the specific area and porosity through the openings formed between adjacent twisted strands, the filtering media may be provided with additional strands having various cross-sectional configurations, best shown at 19 of FIGS. 1 and 2. As shown, the strands 19 may extend longitudinally between the alternate strands 1 and the intermediate strands 2 in a manner to overlie the openings 9 formed between the adjacent strands. In this manner, in addition to controlling the porosity between openings by a predetermined twisting of the individual strands comprising the media, such porosity may also be controlled by decreasing the area of the openings by the attachment of such additional strands to the media. Moreover, the additional strands 19 are preferably of a finer cross-sectional dimension and may or may not be twisted, as desired, to achieve a predetermined porosity through the filtering media.

The strands comprising the filtering media, fabric, belt or the like, may be formed in any predetermined shape which is suitable for increasing the specific surface area of the belt and which will provide the necessary porosity between adjacent strands of the media. Typical shapes which are useful for such strands are indicated generally at FIGS. 14 through 34, inclusive. FIG. 14 illustrates a quadrilateral configuration in vertical cross-section in the form of a fiat ribbon having

side portions

16 and 17. FIG. 15 shows a similar configuration having rounded ended portions 18. FIG. 16 shows the strands as being generally parabolic, or in the form of a double concave in vertical cross-section, having oppositely disposed concave side portions 20. FIG. 17 shows the strands as comprising two generally

circular portions

22 and 24 bonded together to define a generally figure-eight configuration in vertical cross-section. FIG. 18 shows the strands to be of a generally cross-shaped configuration in vertical crosssection having four oppositely disposed arm portions 26. FIG. 19 shows a similar configuration wherein the arms 26 are generally rounded 28 at their free ends. FIG. 20 shows the strand as being generally star-shaped in vertical cross-section having oppositely disposed points 30. FIG. 21 shows a similar configuration wherein the points 30 may be rounded 32 at their free ends. FIG. 22 shows a modification of the cross-shaped configuration wherein four individual strands 34 may be bonded together to form the desired configuration. Similarly FIG. 23 shows a modification of the star-shaped configuration wherein four individual strands 36 may be equally spaced and bonded together, as illustrated. FIG. 24 shows the strands to be of a generally L-shaped configuration in vertical cross-section having two leg portions 38 extending at substantially right angles to one another, whereas, in FIG. 25 the free ends of the leg portions may be generally rounded, as at 40. FIG. 26 shows a triangular configuration, in vertical cross-section, having two side portions 42 which may be closed across their free ends by a generally surpentine portion 46. FIG. 27 shows a right triangular configuration in vertical cross section having

side portions

48 and 5!} extending at right angles from one another enclosed across their ends by the side portion 52 in the form of a hypotenuse. FIG. 28 shows a modification of the triangular configuration as being generally truncated in vertical cross section having a base portion 54, angularly inwardly extending side portions 56 and a generally fiat or rounded top portion 58. FIG. 29 shows the strand as being generally semi-circular 60 in vertical cross-section, whereas FIG. 30 illustrates the semi-circular configuration as being provided with a generally rounded, longitudinally extending channel portion 62. FIG. 31 shows the strand as being generally U-shaped in vertical cross section, having a base portion 64 and two generally vertical upstanding flange portions 66. FIG. 32 shows the strand as being of a generally star-shaped 68 configuration in radial cross section having six oppositely disposed lobes 70. FIG. 33 shows a similar starshaped configuration 72 having three evenly spaced lobes 74 whose center lines lie at an obtuse angle with respect to one another. FIG. 34 shows the strand to be of a dumbbell configuration 76 having a reduced portion 78 located intermediate two enlarged end portions 80.

In a like manner, where carrying strands are to be used in conjunction or in combination with the filtering media to impart greater durability to the strands, the aforementioned or similarly shaped strands may be utilized as carrying members to obtain the desired specific surface and the required porosity between strands. In this regard, and for purposes of definition, the generally noncircular cross-sectional configuration approximating the circular form may be referred to in terms of a closed plane curve, such as, for example, the elliptical and parabolic configurations. Other regular and/or irregular configurations may be referred to in terms of a closed plane having at least one included angle, such as, for example, the triangular, quadrilateral and polygonal configurations. As applied to the making of non-woven endless belts for paper making machines, the various crosssectional shapes of the twisted strands shown in the drawings are preferably of a size which may be circumscribed by a circle having a diameter of between about 0.010 inch and 0.130 inch. The degree of twist whether in the clockwise or counterclockwise direction may vary with the extent of specific surface area and porosity required in the desired filtering media. For example, a twist embodying five turns per inch of length would be suitable for obtaining a satisfactory ratio of specific surface area to porosity for a filter which would be included within the scope of this invention.

The method of making such filtering media, fabric, belts and the like by attachment of one strand to another may be accomplished by one or several methods. For example, the attachment may be achieved by use of solvent cementing, therrnofusion techniques, or by the use of suitable adhesives, such as those known in the art.

toreover, the thermofusion techniques may be accomplished by direct application of heat through heated platens, rollers, or by generating the heat within the strands themselves, by high frequency dielectric heating, or ultrasonics, or by the use of heated air or liquids. If desired, pressure may be utilized in conjunction with the aforementioned thermoheating techniques, or with solvent cementing. In this connection, it is to be noted that another important advantage may be obtained by fabrication of non-woven media, fabrics, and belts from twisted strands, such as shown at 9% of FIG. 35. For example, the production of an endless belt is facilitated because the ends of the carrying strands, or the filtering strands, as the case may he, need not be joined at the same transverse location, hence, there is no need for a straight line joint or seam extending directly across the transverse portion of the belt. By attaching the ends of the strands together, at staggered points transversely of the belt, such as shown at 72 of FIG. 1, the inherent disadvantages of a single joint, or seam, are eliminated, thereby allowing the production of a fabric or a belt having improved durability and dependability in operation.

In accord with the principles of the present invention, any material, whether made of natural fibers, synthetic fibers, or metallic wires having the desired characteristics of wear resistance, corrosion resistance, and durability, which may be formed and twisted into the desired strand configuration may be suitable for making such non-woven filtering media. We have found, however, that some thermoplastic materials are particularly suitable for making such non-woven filtering media, particularly when utilized in making endless belts for paper making machines. Such thermoplastic materials may include cellulose nitrate, cellulose acetate, cellulose acetate-butyrate, polystyrene, polyethylene, polycarbonate, polypropylene, linear polyethylene, polyvinyl chlorine, vinyl esters, vinylidene chloride, styrene acrylonitrile, styrene butadiene, polytetrafiuorethylene, polychlorotrifluoroethylene, acrylonitrile resin rubber, nylon, methyl methacrylate, ethyl cellulose and the like.

Preferred among the above mentioned thtrmoplastic materials are polycarbonate and nylon which have the property that when expanded under the proper temperature conditions, the molecular chain, of which the plastic is comprised, becomes oriented in the direction of expanding, thus greatly increasing the strength of the material. In order that the desired result be obtained, the molecular chains must have sufiicient mobility so that they are free for movement and become aligned with neighboring molecular chains of the composition. In cases where heat may be applied to the material to promote such mobility, the preferred temperature is commonly referred to as the glass transition temperature. Conversely, when the glass transition temperature is exceeded for a substantial length of time, such as in the normal use of an endless belt, in paper making operations, the orientation and beneficial effects of such orientation become reduced or are lost.

Moreover, when a material, such as polycarbonate, is expanded to produce orientation at temperatures for that material within the glass transition temperature of be tween 250 F. to 310 F. and is subsequently used at temperatures substantially below the lower operating limit of 250 F. for that material, the strength of material is not only increased, but the preferred orientation of the material is retained and the material does not return to its original shape prior to such expansion. Accordingly, to obtain the desired molecular orientation of the material, it is preferable that the glass transition temperature of the material be kept substantially above the maximum temperature at which the material may be subjected in actual use. In this regard, and for purposes of definition, when reference is made to the glass transition temperature, we refer to the temperature demarcation between the lower temperature wherein individual molecules of the plastic material remain relatively fixed and the higher temperature wherein the individual molecules are free for movement relative to one another.

Expanding of the twisted strands to provide the desired molecular orientation of the thermoplastic material may be accomplished in one of several modified forms. As shown at FIG. 36, the individual twisted strands may be attached together to form the desired filtering media, shown diagrammatically at 81. In this form, the media may be stretched longitudinally between a first pair of oppositely disposed rollers 82 and a second pair of similar rollers 83 which may be actuated for rotation in the same direction, but which are coordinated to rotate at higher predetermined speeds relative to the first pair of rollers. Such relative rotational speeds between the respective pairs of rollers allows the thermoplastic filtering media passing between the rollers to be expanded and oriented to any predetermined amount, as desired.

In another form, as shown at FIG. 37, the filtering media 81 may be stretched by gripping the edge portions of the media between pairs of oppositely disposed clamping

members

84 and 86, which may be secured to the media by suitable fastening means 85. To stretch the media, the clamping members may be actuated by suitable mechanical or motor power means (not shown) to cause the members to move away from one another, as shown by the arrows, whereby the media may be expanded in a transverse and/ or longitudinal direction, as desired.

Moreover, in another form, the filtering and/ or carrying strands may be attached together by means of the aforementioned thermofusion or solvent cementing techniques to form an endless belt, shown generally at of FIG. 38. In this form, the belt 90 may be mounted as a unit on oppositely disposed stretcher rolls 92, which are adapted for longitudinal movement toward and away from one another, as shown by the arrows, to impart the desired amount of expansion to the individual thermoplastic strands comprising the belt.

In this regard, though we have illustrated several modilied forms by which the fabric or belt may be expanded, it is to be understood that in some cases it may be desirable to expand the individual strands prior to attaching them together as a unitary filtering media or belt. For example, when the strands are twisted cold or under controlled temperature conditions there results, to some extent, a molecular orientation of the thermoplastic material. We have found it preferable, however, to expand the twisted strands under controlled temperature conditions when attached together either as a fabric, or in the form of an endless belt, whereby we are able to obtain a greater uniformity in orientation of the thermoplastic material. The amount of expanding of the thermoplastic may vary in each case depending upon the desired molecular orientation of the material, and upon the spacing between the twisted strands required to produce hydraulic characteristics suitable for a given paper making operation. We have found, for example, that by attaching a thermoplastic material, such as a polycarbonate, to between about 80 to of its initial length and at a temperature within the glass transition temperature of between 250 to 310 F. for that material, there is obtained desired orientation and drainage characteristics suitable for making Fourdrinier belts.

It can be seen from the foregoing description that the filtering media comprised of non-woven twisted strands, results in many important advantages. Such a filtering media has the important advantage of being constructed to provide the necessary physical strength to insure prolonged life and durability in conjunction with a specific surface, which may be made as fine as desired, depending upon the particular use to which the media may be applied. In such case, by twisting the strands and/ or by arranging the stranded layers into predetermined non-woven.

patterns, there is achieved an increased specific surface area and an improved porosity through the passageways formed by the strands which is substantially perpendicular to the plane of the media.

Accordingly, by twisting strands having cross-sectional configurations other than round, there is achieved a controlled porosity through the openings formed between adjacent strands which is not dependent upon the spacing of the strands themselves but which may be predetermined by the degree of twist given to the individual strands.

In the case of the utilization of such media in the making of endless belts for paper making machines, there results a controlled filtration of the paper stock formed on the belt, while at the same time reducing the loss offine materials through the belt. It can be seen, therefore, that by maintaining a predetermined ratio between specific surface area and drainage area, there is obtained an endless belt which provides a more efficient utilization of paper stock while incorporating optimum drainage characteristics for producing a superior paper product.

Though we have selected to illustrate the principles embodying the present invention with reference to the fabrication of Fourdrinier belts, it is to be understood that the construction may also be applied to other similar applications. The application of such constructions may vary in use from a filter or separator for liquids and solids, to

a construction which may be substantially impervious to moisture but which will allow the easy passage of air or gas.

Thus, while we have illustrated herein a preferred embodiment of our invention, it is to be understood that changes and variations may be made by those skilled in the art without departing from the spirit and scope of the appended claims.

We claim:

1. An endless, non-Woven fabric belt for use with Fourdrinier type of paper making machines adapted for draining fluent material, such as paper stock, formed thereon, said fabric belt comprising a first substantially co-planar layer of polymeric mono-filament strands extending generally parallel to one another and longitudinally of the belt, a second substantially co-planar layer of polymeric mono-filament strands extending generally parallel to one another and transversely at an angle relative to said first layer, said first and second layers of strands being disposed in superimposed relationship and bonded together at their areas of contact between the respective strands in each of said layers, the strands in each of said layers having a non-circular transverse cross-section and being independently twisted a predetermined number of turns in a generally circular direction along their axes, and the strands in each of said layers being disposed in continuous side-by-side relationship and bonded to each other throughout their length at their areas of contact to form longitudinally extending rows of spaced openings between adjacent strands in each of the respective layers.

2. A fabric belt in accordance with claim 1, wherein alternate strands in each of said layers are twisted a predetermined number of turns in one circular direction along their axes, and the intermediate strands are twisted a predetermined number of turns in the opposite circular direction along their axes.

3. A fabric belt in accordance with claim 1, wherein the strands in each of said layers are twisted a predetermined number of turns in the same circular direction along their axes.

4. A fabric belt in accordance with claim 1, including a solid polymeric mono-filament strand disposed between and extending generally parallel between adjacent twisted strands in one of said layers, said solid strands having a substantially reduced transverse cross-sectional dimension as compared to the greatest cross-sectional dimension of said twisted strands in said layer so as to only partially overlie the rows of longitudinally extending openings formed between adjacent of said strands in said layer.

5. A fabric belt in accordance with claim 1, wherein the strands in each of said layers have been twisted approximately five turns per inch in a circular direction along their axes.

References Cited UNITED STATES PATENTS 2,919,217 12/1959 Bobkowicz 16l143 X 3,063,094 11/1962 Warthen 161177 X 3,095,283 6/ 1963 Wheeler 29-191.6 3,158,984 12/1964 Butler 1-61177 X FOREIGN PATENTS 5,762 1897 Great Britain.

MORRIS SUSSMAN, Primary Examiner.

EARL M. BERGERT, ALEXANDER WYMAN,

Examiners.

L. T. PIRKEY, G. D. MORRIS, Assistant Examiners.

Claims

1. AN ENDLESS, NON-WOVEN FABRIC BELT FOR USE WITH FOURDRINIER TYPE OF PAPER MAKING MACHINES ADAPTED FOR DRINING FLUENT MATERIAL, SUCH AS PAPER STOCK, FORMED THEREON, SAID FABRIC BELT COMPRISING A FIRST SUBSTANTIALLY CO-PLANAR LAYER OF POLYMERIC MONO-FILAMENT STRANDS EXTENDING GENERALLY PARALLEL TO ONE ANOTHER AND LONGITUDINALLY OF THE BELT, A SECOND SUBSTANTIALLY CO-PLANAR LAYER OF POLYMERIC MONO-FILAMENT STRANDS EXTENDING GENERALLY PARALLEL TO ONE ANOTHER AND TRANSVERSELY AT AN ANGLE RELATIVE TO SAID FIRST LAYER, SAID FIRST AND SECOND LAYERS OF STRANDS BEING DISPOSED IN SUPERIMPOSED RELATIONSHIP AND BONDED TOGETHER AT THEIR AREAS OF CONTACT BETWEEN THE RESPECTIVE STRANDS IN EACH OF SAID LAYERS, THE STRANDS IN EACH OF SAID LAYERS HAVING A NON-CIRCULAR TRANSVERSE CROSS-SECTION AND BEING INDEPENDENTLY TWISTED A PREDETERMINED NUMBER OF TURNS IN A GENERALLY CIRCULAR DIRECTION ALONG THEIR AXES, AND THE STRANDS IN EACH OF SAID LAYERS BEING DISPOSED IN CONTINUOUS SIDE-BY-SIDE RELATIONSHIP AND BONDED TO EACH OTHER THROUGHOUT THEIR LENGTH AT THEIR AREAS OF CONTACT TO FORM LONGITUDINALLY EXTENDING ROWS OF SPACED OPENINGS BETWEEN ADJACENT STRANDS IN EACH OF THE RESPECTIVE LAYERS.