Patent Publication Number: US-8122570-B2

Title: Apparatus and method for dry forming a uniform non-woven fibrous web

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This is a Continuation-In-Part application of U.S. Ser. No. 12/455,201 filed May 30, 2009, now U.S. Pat. No. 7,886,411, which in turn is a Continuation-In-Part application of U.S. Ser. No. 11/825,331 filed on Jul. 6, 2007, now abandoned. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to an apparatus and method for dry forming a uniform non-woven fibrous web. More particularly, this invention relates to an apparatus and method of dry forming a uniform non-woven fibrous web which has a basis weight of less than about 100 grams per square meter. 
     BACKGROUND OF THE INVENTION 
     Today, various types of textile fibers including: staple fibers, cellulose fibers, defibrated cellulose fibers, and blends of two or more different fibers can be dry formed into non-woven fabrics by a variety of well known methods. Currently, there exist many different kinds of apparatuses for the uniform distribution of air-laid fibers, especially staple textile fibers and cellulose pulp fibers. However, many of these apparatuses are highly complex mechanical devices, some of which are rather cumbersome, that suffer from one or more disadvantages. 
     Many of the non-woven fabrics formed on such machines, especially those formed from cellulosic fibers, exhibited good entanglement and matt structure but have little strength. Most staple fibers provide little strength characteristics. For this reason, such fabrics have usually been utilized in absorbent articles, such as absorbent diapers, absorbent feminine pads, absorbent incontinent articles, etc. where strength is not a requirement. In addition, some of these non-woven fabrics have been used in applications where a certain minimum strength is required but the tactile and absorbency properties are unimportant, for example in various specialty papers. 
     With the development of new and various products, manufacturers would like to run their processes at higher speeds. In addition, some manufacturers would like to use short cellulosic fibers along with the longer staple fibers to improve strength characteristics. The short cellulosic fibers are typically only about 2 to about 3 millimeters in length. Furthermore, many manufacturers would like to be able to form a web that exhibits uniformity in both the machine direction and in the cross direction. Another request from a number of manufacturers is for an apparatus that is capable of making light weight fabrics at current production line speeds, especially those having a basis weight of less than 100 grams per square meter (gsm). Even more so, a number of manufacturers would like to see an apparatus offered for sale that is capable of making light weight fabrics, especially those fabrics having a basis weight of around 75 gsm, 50 gsm, 30 gsm or even a basis weight of about 20 gsm. 
     Now, an apparatus and method for dry forming a uniform non-woven fibrous web has been invented which can accommodate current production line speeds. 
     SUMMARY OF THE INVENTION 
     Briefly, this invention relates to an apparatus and method of dry forming a uniform non-woven fibrous web. The apparatus includes a transport duct having a predetermined cross-sectional area. The transport duct has an entrance and an exit. The entrance is connected to a source of individual fibers and a pressurized gaseous stream. The transport duct is capable of routing a plurality of the individual fibers contained within the pressurized gaseous stream through to the exit. The apparatus also includes a spreading member having an inlet, an outlet and having a length therebetween. The spreading member is a hollow enclosure having first and second major walls connected together by a pair of side walls to form a rectangular cross-sectional configuration having a width and a height. The width constantly increases in dimension along the length from the inlet to the outlet and the height constantly decreases in dimension along the length from the inlet to the outlet. The height is less than the width at the outlet. The inlet of the spreading member is connected to the exit of the transport duct and the exit is aligned at an angle of at least about 15° to the second major wall. The pressurized gaseous stream passing through the spreading member is maintained at a constant or slightly accelerating velocity and with a minimum amount of turbulence. The apparatus further includes a discharge member having an inlet opening, an outlet opening and a length therebetween. The inlet opening is connected to the outlet of the spreading member and has an identical size and cross-sectional configuration as the outlet. The discharge member has first and second major walls connected together by a pair of side walls to form a rectangular cross-sectional configuration having a width and a height. The width is greater than the height. The apparatus further includes a first flexible plate positioned within the discharge member and aligned adjacent to the first major wall. The first flexible plate spans across the outlet opening and has an inner surface and an outer surface. A plurality of screws is positioned across the outlet opening. Each of the screws is capable of being adjusted so as to contact and deflect the outer surface of the first flexible plate and impart a corresponding contour to the inner surface of the first flexible plate. Lastly, a forming zone is located below the outlet opening of the discharge member onto which a uniform dispersion of the fibers can be deposited to form a uniform non-woven fibrous web. 
     The method of dry forming a uniform non-woven fibrous web includes the steps of forming a plurality of individual fibers and then routing the plurality of individual fibers through a transport duct by a pressurized gaseous stream. The transport duct has a predetermined cross-sectional area. The transport duct also has an entrance and an exit. The pressurized gaseous stream has a velocity of at least about 1,000 feet per minute. The method also includes directing the pressurized gaseous stream containing the plurality of individual fibers to a spreading member. The spreading member has an inlet, an outlet and having a length therebetween which is at least 20 times the diameter of the transport duct. The spreading member is a hollow enclosure having first and second major walls connected together by a pair of side walls to form a rectangular cross-sectional configuration having a width and a height. The width constantly increases in dimension along the length from the inlet to the outlet and the height constantly decreases in dimension along the length from the inlet to the outlet. The height is less than the width at the outlet. The inlet of the spreading member is connected to the exit of the transport duct and the exit is aligned at an angle of at least about 15° to the second major wall. The pressurized gaseous stream passing through the spreading member is maintained at a constant or slightly accelerating velocity and with a minimum amount of turbulence. The method further includes directing the pressurized gaseous stream containing the plurality of individual fibers to a discharge member having an inlet opening, an outlet opening and a length therebetween. The inlet opening is connected to the outlet of the spreading member and has an identical size and cross-sectional configuration as the outlet. The discharge member has first and second major walls connected together by a pair of side walls to form a rectangular cross-sectional configuration having a width and a height. The width is greater than the height. The discharge member has a first flexible plate positioned therein and aligned adjacent to the first major wall. The first flexible plate spans across the outlet opening and has an inner surface and an outer surface. A plurality of screws is positioned across the outlet opening. Each of the screws is capable of being adjusted so as to contact and deflect the outer surface of the first flexible plate and impart a corresponding contour to the inner surface of the first flexible plate. Lastly, the method includes depositing the plurality of individual fibers from the outlet opening onto a forming zone to form a uniform non-woven fibrous web. 
     The general object of this invention is to provide an apparatus and method for dry forming a uniform non-woven fibrous web. A more specific object of this invention is to provide an apparatus and method of dry forming a uniform non-woven fibrous web which has a basis weight of less than about 100 grams per square meter. 
     Another object of this invention is to provide an apparatus and method of dry forming a uniform non-woven fibrous web which has a basis weight of from between about 20 gsm to about 75 gsm. 
     A further object of this invention is to provide an apparatus for dry forming a uniform non-woven fibrous web which is void of any baffles which can pivot. 
     Still another object of this invention is to provide an apparatus for dry forming a uniform non-woven fibrous web which is easy to construct and maintain. 
     Still further, an object of this invention is to provide is to provide a continuous method of dry forming a uniform non-woven fibrous web. 
     Other objects and advantages of the present invention will become more apparent to those skilled in the art in view of the following description and the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side elevation view of an apparatus for dry forming a uniform non-woven fibrous web showing a transport duct, a spreading member and a discharge member in cross-section such that the velocity of a pressurized gaseous stream containing a plurality of individual fibers is maintained constant or slightly accelerated through the spreading member while maintaining laminar flow with a minimum amount of turbulence. 
         FIG. 2  is a cross-sectional view of the transport duct taken along line  2 - 2  of  FIG. 1 . 
         FIG. 3  is a perspective view of the apparatus shown in  FIG. 1 , except for the source of the pressurized gaseous stream and the source of the plurality of individual fibers, and depicts the trapezoidal shape of the spreading member. 
         FIG. 4  is a cross-sectional view of the spreading member taken along line  4 - 4  of  FIG. 1 . 
         FIG. 5  is a cross-sectional view of the outlet of the spreading member taken along line  5 - 5  of  FIG. 1 . 
         FIG. 6  is a cross-sectional view of the inlet opening to the discharge member taken along line  6 - 6  of  FIG. 3 . 
         FIG. 7  is a cross-sectional view of the outlet opening of the discharge member taken along line  7 - 7  of  FIG. 1 . 
         FIG. 8  is a perspective view of a flexible plate. 
         FIG. 9  is an enlarged perspective view of an undulating flexible plate secured to the inner surface of first major member and spanning across the outlet opening. 
         FIG. 10  is a cross-sectional view of the outlet opening of the discharge member showing a first flexible plate deflected by a plurality of screws arranged across the outlet opening such that the first flexible plate acquires an undulating contour to further control the basis weight of the to be formed uniform non-woven fibrous web. 
         FIG. 11  is a cross-sectional view of an alternative embodiment of the outlet opening of the discharge member showing first and second flexible plates each being deflected by a plurality of screws arranged across the outlet opening such that both plates acquire an undulating contour to further control the basis weight of the to be formed uniform non-woven fibrous web. 
         FIG. 12  is a chart showing the flow profiles of the discharged fibers exiting the outlet opening of the discharge member. 
         FIG. 13  is a perspective view of an apparatus having identical first and second modular units arranged side by side to form a continuous, monolithic web having double the width of a web produced from the first modular unit alone. 
         FIG. 14  is a flow diagram of a method of dry forming a uniform non-woven fibrous web. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIG. 1 , an apparatus  10  is shown for dry forming a uniform non-woven fibrous web  12 . The apparatus  10  will be described relative to a longitudinal central axis X-X, a vertical central axis Y-Y and a transverse central axis Z-Z. The apparatus  10  includes a transport duct  14  having a predetermined cross-sectional area. The transport duct  14  has a diameter d which can be constant. The transport duct  14  is shown being oriented relative to the vertical central axis Y-Y. However, one can change the orientation of the various components of the apparatus  10  if it suits his needs. The diameter d of the transport duct  14  can vary depending upon the desired flow volume one needs through the transport duct  14 . The diameter d of the transport duct  14  can range from about 1 inch up to about 18 inches or higher. For a pilot line operation, the diameter d of the transport duct  14  can range from between about 1 inch to about 4 inches. For a commercial operation, the diameter d of the transport duct  14  should be at least 6 inches and desirably should be in the range of from between 6 inches to about 18 inches. More desirably, the diameter d of the transport duct  14  is from between about 12 inches to about 16 inches to a commercial operation. 
     As shown in  FIG. 2 , the transport duct  14  has a wall thickness t which can vary in dimension. Desirably, the wall thickness t is at least 0.2 inches. More desirably, the wall thickness t is at least 0.25 inches. Even more desirably, the wall thickness t is at least 0.3 inches. 
     Referring again to  FIG. 1 , the flow through the transport duct  14  can vary depending on the actual construction of the transport duct  14 , the type of fibers utilized and the dimensions, such as the length, width, thickness and the basis weight of the web  12  that one wishes to form. For best results, the transport duct  14  should be linear or straight and have a length that is at least 20 times its diameter d. Typically, the flow through the transport duct  14  is at least about 1,000 feet per minute (fpm) or higher. For a commercial operation, the flow through the transport duct  14  can range from between about 1,000 fpm to about 6,000 fpm. Desirably, the flow through a transport duct  14 , having a diameter d of from between about 12 inches to about 16 inches, is from between about 1,000 fpm to about 5,000 fpm. More desirably, the flow through the transport duct  14 , having a diameter d of from between about 12 inches to about 16 inches, is from between about 2,000 fpm to about 6,000 fpm. Even more desirably, the flow through a transport duct  14 , having a diameter d of from between about 12 inches to about 16 inches, is at least 3,000 fpm. 
     The transport duct  14  has an entrance  16  and an exit  18 . The entrance  16  is connected to a source  20  of individual fibers  22  and to a pressurized gaseous stream  24 . The source  20  of the individual fibers  22  can be a hammermill or other piece of equipment that is capable of separating a sheet or batt of fibers into a plurality of individual fibers  22 . Kamas, M&amp;J, and Famecannica are three companies that make commercial equipment to defibrate pulp into individual fibers  22 . The individual fibers  22  can vary in shape, size and material from which they are formed. The individual fibers  22  can be textile fibers made up of natural or synthetic fibers. The individual fibers  22  can be staple fibers having a length of from between about 1 inch to about 2 inches, short fibers having a length of from between about 2 to about 3 millimeters, or be a blend of both long staple fibers and short fibers. Desirably, the individual fibers  22  can be cellulosic fibers derived from wood pulp, sometimes referred to as cellulosic fluff fibers. Alternatively, the individual fibers  22  can be derived from various parts of plants or trees, such as from the leaves of eucalyptus trees and palm trees, to obtain cellulosic fibers. 
     The pressurized gaseous stream  24  is used to convey or route the plurality of individual fibers  22  into and through the apparatus  10 . Desirably, the gaseous medium is air since it is inexpensive and easy to handle. However, any known gas could be used to convey the plurality of individual fibers  22  through the apparatus  10 . 
     As stated above, it is beneficial to construct the transport duct  14  such that it is linear or has a minimum number of curves or bends. One reason for constructing the transport duct  14  as a hollow linear tube or pipe is to limit pressure drops therein. A straight tube or pipe having a length l that is at least 20 to 1 relative to the diameter d will allow the plurality of individual fibers  22  being carried by the pressurized gaseous stream to acquire the same velocity as the gaseous stream. By “velocity” it is meant rapidity or speed of motion; swiftness. 
     For the purpose of discussion of the invention the term “web” as used herein will include batt and/or substrate. In the case of forming an absorbent web in which the thickness or basis weight of the web  12  is large, in the range of 100 or more grams per square meter (gsm), the aerodynamic characteristics of the fluff forming device, i.e. hammermill, is not critical. However, the aerodynamic and design characteristics of the forming device become more critical when the requirement is to form a web  12  having a basis weight of less than about 100 gsm; or to form a web  12  having a basis weight of less than about 75 gsm; or to form a web  12  having a basis weight of less than about 50 gsm; or to form a web  12  having a basis weight of less than about 30 gsm; or to form a web  12  having a basis weight of about 20 gsm. The challenge becomes taking the plurality of individual fibers  22  that are being conveyed in a round or circular transport duct  14 , at velocities in the range of about 1,000 fpm to about 10,000 fpm or higher, and spreading the individual fibers  22  to a width of about 1.5 meters or greater while achieving a uniformity of the individual fibers  22 . In some cases, the formed web  12  will have a uniform width of from between about 1.5 meters to about 5.4 meters or greater. In the web forming industry, a uniformity ranging from ±10%, measured by accepted standard test methods, is considered normal. 
     The transport duct  14  is capable of routing the plurality of the individual fibers  22  contained within the pressurized gaseous stream  24  through to the exit  18 . It should be understood that the concentration of the plurality of individual fibers  22  in the pressurized gaseous stream  24  within the transport duct  14  can vary. Desirably, the concentration of the individual fibers  22  in the pressurized gaseous stream within the transport duct  14  is at least about 250 cubic feet per pound of fibers  22 . More desirably, the concentration of the individual fibers  22  in the pressurized gaseous stream within the transport duct  14  is at least about 350 cubic feet per pound of fibers  22 . Even more desirably, the concentration of the individual fibers  22  in the pressurized gaseous stream within the transport duct  14  is at least about 400 cubic feet per pound of fibers  22 . Most desirably, the concentration of the individual fibers  22  in the pressurized gaseous stream within the transport duct  14  is greater than about 500 cubic feet per pound of fibers  22 . 
     Still referring to FIGS.  1  and  3 - 5 , the apparatus  10  also includes a spreading member  26  having an inlet  28 , an outlet  30  and having a length l 1  therebetween. The length l 1  is at least 10 times the diameter d of the transport duct  14 . Desirably, the length l 1  is at least 15 times the diameter d of the transport duct  14 . More desirably, the length l 1  is at least 20 times the diameter d of the transport duct  14 . In numerical values, the length l 1  of the spreading member  26  should be at least 20 feet long when the diameter d of the transport duct  14  is 12 inches. The spreading member  26  is a hollow enclosure having first and second major walls,  32  and  34  respectively, connected together by a pair of side walls  36  and  38 . Each of the first and second major walls,  32  and  34  respectively, has a trapezoidal configuration, see  FIG. 3 , which increases in width w from the inlet  28  to the outlet  30 . By trapezoid it is meant a quadrilateral having two parallel sides. 
     In addition, the first major wall  32  is shown angling downward from the inlet  28  to the outlet  30  while the second major wall  34  is aligned parallel to the longitudinal central axis X-X, from the inlet  28  to the outlet  30 . In other words, the first major wall  32  tapers vertically downward from a horizontal plane by an angle phi Ø. The angle phi Ø can vary in degrees. Desirably, the angle phi Ø ranges from between about 1° and about 35°. More desirably, the angle phi Ø ranges from between about 5° and about 30°. Even more desirably, the angle phi Ø ranges from between about 10° and about 25°. Unlike the first major wall  32 , the second major wall  34  is aligned in a horizontal plane. Alternatively, one can construct the spreading member  26  such that each of the first and second major walls,  32  and  34  respectively, converge toward one another as they approach the outlet  30 . 
     It should be understood that the fiber velocity is equivalent to the velocity of the pressurized gaseous stream  24  in the transport duct  14  and the iso-kinetic energy of the individual fibers  22  is dissipated and greatly reduced as the fibers  22  enter the spreading member  26 . This is accomplished by the structure of the transport duct  14  and the angle that it is oriented to the spreading member  26 . This geometry caused the individual fibers  22  leaving the transport duct  14  to strike or hit the inside surface of the first major wall  32  of the spreading member  26 . In this manner, both the velocity and the momentum of the individual fibers  22  are dissipated. This action allows the individual fibers  22  to then be realigned with the airflow profiles in the spreading member  26  that will be developed by the geometries and air velocities used in the design of the spreading member  26 . 
     If the iso-kinetic energy of the individual fibers  22  was not dissipated in the fashion explained above, then the individual fibers  22  could have a tendency to stay in the center of the spreading member  26  and thereby create a heavier basis weight in the center of the to be formed non-woven fabric web  12 . The angle at which the transport duct  14  is aligned with the spreading member  26  can vary as long as the velocity of the individual fibers  22  is dissipated as they strike the inside surface of the first major wall  32 . The angle at which the transport duct  14  enters the spreading member  26  will depend upon the height to width ratio of the spreading member  26 . This angle can vary from between about 15° to about 90°. Typically, it will be closer to about 45° for most applications. Other means of controlling the iso-kinetic energy of the individual fibers  22  at the inlet  28  to the spreading member  26  can be used. Within the spreading member  26  it is important that the plurality of individual fibers  22  have enough residence time to streamline themselves to the airflow that has been developed in the spreading member  26 . This is accomplished by constructing the length l 1  of the spreading member  26  such that it is at a minimum equivalent to 10 times the diameter d of the transport duct  14 . Desirably the length l 1  of the spreading member  26  is at least 20 times the diameter d of the transport duct  14 . Lengths l 1  much shorter than 10 times the equivalent diameter d of the transport duck  14  will result in less efficient fiber spreading in the cross direction and unacceptable profiles. 
     As there may be physical limitations to optimizing the spreading member  26  to lengths l 1  greater than 10 equivalent diameters d of the transport duct  14 , the angle of the exit  18  to the inlet  28  of the spreading member  26  will need to be adjusted accordingly to accommodate this relationship. 
     Referring to  FIGS. 4 and 5 , the four walls  32 ,  34 ,  36  and  38  form a rectangular cross-sectional configuration having a width w and a height h. The width w is measured parallel to the Z-Z axis and the height h is measured parallel to the Y-Y axis. At the inlet  28 , the height h of the pair of side walls  36  and  38  can have a dimension that approaches the width w of the first and second major walls,  32  and  34  respectively. If desired, the four walls  32 ,  34 ,  36  and  38  can form a square configuration adjacent the inlet  28 . The width w at the inlet  28  can be about 10 inches or more and the height h can be about 10 inches or more. Desirably, the width w at the inlet  28  can be about 12 inches or more and the height h can be about 12 inches or more. More desirably, the width w at the inlet  28  can be about 16 inches or more and the height h can be about 16 inches or more. 
     The width w constantly increases in dimension along the length l 1  from the inlet  28  to the outlet  30  and the height h constantly decreases in dimension along the length l 1  from the inlet  28  to the outlet  30 . The height h is less than the width w at the outlet  30 , see  FIG. 5 . This means that at the outlet  30 , the four walls  32 ,  34 ,  36  and  38  form a rectangular cross-sectional configuration with a width w 1  and a height h 1 . The width w 1  at the outlet  30  is much greater than the width w at the inlet  28 , and the height h 1  at the outlet  30  is much less than the height h at the inlet  28 . In addition, at the outlet  30 , the width w 1  dimension is much greater than the height h 1  dimension. Desirably, the width w 1  is greater than about 1 meter. More desirably, the width w 1  ranges from between about 1 meter to about 5.5 meters. Even more desirably, the width w 1  ranges from between about 1 meter to about 3 meters. Most desirably, the width w 1  ranges from between about 1 meter to about 2 meters. Furthermore, at the outlet  30 , the height h 1  is less than about 6 inches. Desirably, at the outlet  30 , the height h 1  is less than about 4 inches. More desirably, at the outlet  30 , the height h 1  is less than about 3 inches. Even more desirably, at the outlet  30 , the height h 1  is less than about 2 inches. Most desirably, at the outlet  30 , the height h 1  is from between about 1 inch to about 2 inches. 
     Referring again to  FIG. 1 , the inlet  28  of the spreading member  26  is connected to the exit  18  of the transport duct  14 . The exit  18  is aligned at an angle theta θ to the second major wall  34 . The angle theta θ can vary in degrees. Desirably, the angle theta θ is at least about 15° to the second major wall  34 . More desirably, the angle theta θ is from between about 15° to about 75° to the second major wall  34 . More desirably, the angle theta θ is from between about 40° to about 50° to the second major wall  34 . Even more desirably, the angle theta θ is around 45° to the second major wall  34 . 
     The function of the spreading member  26  is to transform the pressurized gaseous stream  24  containing the plurality of individual fibers  22  into an extremely uniform flow in cross-section as it approaches the outlet  30 . This is accomplished by maintaining constant or slightly accelerating velocities through the spreading member  26  with a minimum amount of turbulence. As the pressurized gaseous stream  24  passes through the spreading member  26  it is maintained at a constant or slightly accelerating velocity due to the geometrical configuration of the spreading member  26 . In order to accomplish this, the cross-sectional area of the transport duct  14  should be the same or slightly greater than the cross-sectional area of the outlet  30  of the spreading member  26 . This concept of maintaining constant or slightly accelerating gaseous (air) velocities through any cross sectional plane present in the spreading member  26  is important in achieving uniform cross direction gaseous (air) profiles at the outlet  30  of the spreading member  26 . 
     Referring again to  FIGS. 1 ,  3 ,  6  and  7 , the apparatus  10  further includes a discharge member  40  having an inlet opening  42 , an outlet opening  44  and a length l 2  therebetween. The size and configuration of the discharge member  40  can vary. The discharge member  40  can be straight or linear in appearance, be curvilinear, have an arcuate configuration or have some other geometrically configuration. As depicted in  FIGS. 1 and 3 , the discharge member  40  has an arcuate configuration between the inlet opening  42  and the outlet opening  44  which spans an arc of from between about 1° to about 90°. By “arc” it is meant a segment of a circle. 
     Referring to  FIGS. 1 and 6 , the inlet opening  42  of the discharge member  40  is connected to the outlet  30  of the spreading member  26 . Both the inlet opening  42  and the outlet  30  have an identical size and cross-sectional configuration. The discharge member  42  has first and second major walls,  46  and  48  respectively, connected together by a pair of side walls  50  and  52  to form a rectangular cross-sectional configuration having a width w 2  and a height h 2 . The width w 2  is measured parallel to the Z-Z axis and the height h 2  is measured parallel to the Y-Y axis. The width w 2  is greater than the height h 2 . In  FIG. 6 , the first major wall  46  is depicted as being the lower or bottom wall while the second major wall  48  is shown as being the upper or top wall. 
     In  FIGS. 1 and 6 , one will notice that the inlet opening  42  is void of any baffles. In other words, there is no movable baffle that is mounted on a pivot or hinge which can be moved, swung or be partially rotated so as to alter or change the cross-sectional size of the opening between the outlet  30  of the spreading member  26  and the inlet opening  42  of the discharge member  40 . In fact, the outlet  30  of the spreading member  26  is identical in size and cross-sectional shape to the inlet opening  42  of the discharge member  40 . There are no movable components at this location which could obstruct the pressurized gaseous stream  24 . This is an important difference over U.S. Pat. No. 3,812,553 issued to Marshall et al. on May 28, 1974 and entitled: “REORIENTATION OF FIBERS IN A FLUID STREAM”. 
     Referring now to  FIG. 7 , the cross-section of the outlet opening  44  of the discharge member  40  is shown. One will notice that it is a rectangular configuration of identical size and configuration to the inlet opening  42 . In fact, the cross-sectional area of the discharge member  40  remains constant throughout its length l 2 . Alternatively, the cross-sectional area of the discharge member  40  could decrease slightly throughout its length l 2  so as to allow the velocity of the pressurized gaseous stream  24  to slightly increase, if desired. This is an important distinction over U.S. Pat. No. 3,862,867 issued to Marshall on Jan. 28, 1975 and entitled: “PROCESS FOR PRODUCING REINFORCED NONWOVEN FABRICS”. The rectangular cross-sectional configuration of the outlet opening  44  has a width w 3  and a height h 3 . The width w 3  is measured parallel to the Z-Z axis and the height h 3  is measured parallel to the Y-Y axis. The width w 3  is greater than the height h 3 . For example, the width w 3  can range from between about 30 inches to about 90 inches, desirably, about 45 inches to about 70 inches, and more desirably, from between about 50 inches to about 65 inches. The height h 3  can range from between about 0.5 inches to about 4 inches, desirably about 1 inch to about 3 inches, and more desirably, from less than about 2 inches. 
     Referring now to  FIGS. 8-10 , the apparatus  10  further includes a first flexible plate  54  which is positioned within the discharge member  40 . The first flexible plate  54  is aligned adjacent to the first major wall  46  and spans across the width w 3  of the outlet opening  44  of the discharge member  40 . The first flexible plate  54  has an inner surface  56  and an outer surface  58 . The first flexible plate  54  can be constructed from various materials. The first flexible plate  54  can be constructed of a soft but strong flexible metal, plastic or composite material. For example, the first flexible plate  54  can be made from a metal, such as iron, cast iron, steel, stainless steel; a metal alloy such as titanium; a nonferrous metal such as aluminum; a plastic; fiberglass, a thermoplastic such as a polyolefin, polyethylene or polypropylene; a thermoplastic resin such as polytetrafluoroethylene; or from a composite material formed from two or more different materials. The first flexible plate  54  can vary in thickness depending upon the material from which it is constructed. The first flexible plate  54  should be formed such that it can bend as a force is applied to its outer surface  58 . Desirably, the first flexible member  54  is malleable and can be bent multiple times without cracking or breaking. 
     Referring again to  FIG. 8 , the first flexible plate  54  is depicted as a relatively flat, rectangular member. The first flexible plate  54  can vary in size and configuration. The first flexible plate  54  has a width w 4  which is aligned parallel to the width w 3  of the outlet opening  44 . The first flexible plate  54  also has a length l 4  which is aligned perpendicular to the width w 4 . Lastly, the first flexible plate  54  has a thickness t 1 . The width w 4  is slightly less than the width w 3  of the discharge member  40  so that it can fit inside the outlet opening  44 , see  FIG. 7 . In numerical values, the width w 4  can range from between about 30 inches to about 90 inches, desirably, about 45 inches to about 70 inches, and more desirably, from between about 50 inches to about 65 inches. The length l 4  can vary but should be at least about 2 inches. Desirably, the length l 4  can range from between about 2 inches to about 12 inches or more. More desirably, the length l 4  can range from between about 2 inches to about 6 inches. Even more desirably, the length l 4  can range from between about 2 inches to about 4 inches. The thickness t 1  can vary depending upon the material from which the first flexible plate  54  is made. For most application, the first flexible plate  54  should be less than about 0.25 inches thick, desirably, less than about 0.2 inches thick, and more desirably, less than about 0.15 inches thick. 
     The first flexible plate  54  has a leading edge  60  secure to the first major wall  46  and an unsecured edge  62  located downstream from the leading edge  60 . The attachment of the leading edge  60  to the inner surface  56  of the discharge member  40  can be by various means known to those skilled in the art, including but not limited to welding, chemical bonds, adhesives, mechanical fasteners, etc. The junction of the leading edge  60  with the inner surface  56  should be smooth and feathered so that no lip, shoulder or abutment is present. The first flexible plate  54  also has a pair of side edges  64  and  66  aligned perpendicular to the leading edge  60 . These side edges  64  and  66  can be left unattached to the pair of side walls  50  and  52 . Alternatively, one or both of these side edges  64  and  66  can be secured to the adjacent side wall  50  and  52 . In  FIG. 9 , the side edge  66  is depicted as being secured to the inner surface of the side wall  52  by an attachment  68 . The unsecured edge  62  is aligned approximately with the outlet opening  44 . In  FIG. 9 , the unsecured edge  62  is aligned with the terminal end of the inner surface  56  of the discharge member  40 . 
     Referring to  FIG. 10 , a plurality of screws  70  are shown positioned across the width w 3  of the discharge member  40 . Alternatively, the plurality of screws  70  can be positioned across the width of the outlet opening  44 . Each of the screws  70  is threaded into an aperture  72  formed through the first major wall  46 . Each of the screws  70  is capable of being adjusted so as to contact and deflect the outer surface  58  of the first flexible plate  54  and impart a corresponding contour to the inner surface  56  of the first flexible plate  54 . In  FIG. 10 , the first flexible plate  54  is shown having been deformed into an undulating form. However, almost any linear, non-linear or combination linear and non-linear shape can be imparted into the first flexible plate  54  including but not limited to: a shape with flat or straight sections, an arcuate shape, a U-shape, an inverted U shape, a sinusoidal shape, a convex shape, a concave shape, a W shape, etc. 
     The number of screws  70  can vary as well as their location and there arrangement relative to the unsecured edge  62 . The screws  70  should be positioned inward about 0.1 inches to about 3 inches from the edge of the outlet opening  44 . The closer the screws  70  are located relative to the unsecured edge  62  of the first flexible plate  54  the better it is because they can impart a greater distortion to the first flexible plate  54 . The screws  70  can be evenly spaced apart or be unevenly spaced apart. There should be at least 1 screw  70  per foot spaced across the width w 3  of said discharge member  40 . Desirably, there are at least 2 screws  70  per foot spaced across the width w 3  of said discharge member  40 . More desirably, there are from 1 to 3 screws  70  per foot spaced across the width w 3  of said discharge member  40 . Desirably, there are from 1 to 4 screws  70  per foot spaced across the width w 3  of said discharge member  40 . Even more desirably, there are from 1 to 5 screws  70  per foot spaced across the width w 3  of said discharge member  40 . Another guideline is to have from between 2 to 9 screws  70  evenly spaced across the width w 3  of the discharge member  40  when the discharge member  40  has a width w 3  of greater than about 12 inches and less than about 65 inches. 
     Each of the screws  70  has a distance of travel which can range from between about 0.1 inches to about 3 inches. Desirably, the range of travel of each screw  70  is from between about 0.25 inches to about 2.5 inches. More desirably, the range of travel of each screw  70  is from between about 0.5 inches to about 2 inches. The amount of travel capable by one screw  70  does not have to equal the amount of travel capable by another screw  70 . However, to reduce cost, all of the screws  70  should be of the same length and each should be capable of approximately the same amount of travel. In order to fine tune the pressurized gaseous stream  24  exiting the outlet opening  44  of the discharge member  40 , one can adjust certain screws  70  so that they impinge on the outer surface  58  of the first flexible plate  54  and force it to acquire a unique contour. By tightening or threading a screw  70  into the first major wall  46 , one can cause the terminal end of the screw  70  to contact the outer surface  58  of the first flexible plate  54  and cause it to deflect upward. All of the screws  70  do not need to be tightened. As shown in  FIG. 10 , every other screw  70  may be tightened to establish an undulating contour. Measurements can be taken with state of the art flow meters to identify what portions of the first flexible plate  54  needs to be raised or lowered in order to obtain the optimal flow. 
     By deflecting the first flexible plate  54  upward into the outlet opening  44 , one can constrict the cross-sectional area of the outlet opening  44 . By “constrict” it is meant to make smaller or narrower. By constricting the size of the outlet opening  44 , one can influence the trajectory of both the individual fibers  22  and the pressurized gaseous (air) stream  24 . This ability to finely regulate the pressurized gaseous stream  24  containing the plurality of individual fibers  22  permits one to dry form a more uniform non-woven fibrous web  12 . One can create restrictions in the outlet opening  44  of the discharge member  40  in the vicinity of 0.25 inches to about 0.75 inches. These restrictions serve to accelerate the discharge fibers  22  and the pressurized gaseous stream  24  and allow the fibers  22  in these particular areas to spread out causing an adjustment in the basis weight. Adjustments made using the apparatus  10  can result in a correction of ±3 grams per square meter in the fibrous web  12  being formed. By controlling the points of restriction in the flow pattern at the outlet opening  44 , one can fine tune any irregularities to the basis weight profile of the finished dry formed uniform non-woven fibrous web  12 . 
     Even though the discharge member  40  does not have to be constructed in the shape of an arc, by constructing the discharge member  40  to span an arc of approximately 90°, the effect of the first flexible plate  54  can be optimized by the curvature of the full width w 3  of the monolithic discharge member  40 . The curvature of the discharge member  54  tends to cause the individual fibers  22  in the pressurized gaseous stream  24  to hug the first major wall  46  (the bottom wall) of the discharge member  40 . As a result of iso-kinetic and centrifugal forces, the individual fibers  22  become more susceptible to movement and redistribution in the pressurized gaseous stream  24  as a result of the adjustments made to the first flexible plate  54 . 
     The angle at which the individual fibers  22  exit the outlet opening  44  can vary depending on the nature of the forming zone  74  onto which the individual fibers  22  are discharged, as well as the effectiveness of the control exhibited by varying the gap of the outlet opening  44  by the first flexible plate  54 . Consequently, the control originally exhibited on the individual fibers  22  exiting the outlet opening  44  are reduced when the discharge member  40  spans an arc of 90°. As the angle is increased from 90° to 180°, the individual fibers  22  would tend to become more evenly distributed through the entire cross-section of the discharge member  40 . Consequently, a further improvement can be obtained by constricting both the second major wall  48  and the first major wall  46  (the top and bottom walls) of the outlet opening  44 . This will be explained more fully below with reference to  FIG. 11 . 
     Referring again to  FIG. 1 , a forming zone  74  is positioned or located below the outlet opening  44  of the discharge member  40 . The forming zone  74  can vary in design, function and equipment. The forming zone  74  is depicted as having a continuous screen  76  onto which the plurality of individual fibers  22  can be deposited to form a uniform non-woven fibrous web  12 . The screen  76  is advanced in a continuous fashion around two or more rollers  78 , at least one of which is a drive roller. A vacuum box  80  is located beneath the screen  76  and operates by pulling a vacuum such that the plurality of individual fibers  22  are deposited on the upper surface of the screen  76  and the discharged gaseous stream (air) is drawn away by the vacuum box  80 . 
     It should be noted that those skilled in the art are familiar with various forming zones and almost any of them can be employed with the above described apparatus  10 . 
     An important element of this invention is the ability to control the discharge of the plurality of individual fibers  22  into a forming zone  74 . The forming zone can be a foraminous forming screen or other equipment known to those skilled in the art. Alternatively, the plurality of individual fibers  22  can be discharged into another fiber stream or onto a fiber matrix in order for the plurality of individual fibers  22  to blend with different fibers to form a non-woven fibrous web  12 . For example, a plurality of individual cellulosic fibers can be discharged onto a meltblown fiber matrix to form an improved web. The ability to control the discharge of the plurality of individual fibers  22  allows for the formation of a uniform basis weight web. 
     In this case, the angle at which the individual fibers  22  are directed into either type of forming zone  74  is important. This angle may require adjustment. In  FIGS. 1 and 3 , the discharge member  40  turns the plurality of individual fibers  22  through an arc of 90°. This angle can be varied and can be whatever the final forming zone  74  requires. Alternatively, one could tilt the spreading member  26  and the discharge member  40  to an angle which is needed for proper web formation. 
     Referring now to  FIG. 11 , an alternative embodiment is shown wherein a second flexible plate  82  is positioned within the discharge member  40  and aligned adjacent to the second major wall  48 . The second flexible plate  82  can vary in size and configuration. Desirably, the second flexible plate  82  is identical in dimensions to the first flexible plate  54 . The second flexible plate  82  can be constructed from the same material as the first flexible plate  54  or be constructed from a different material. The second flexible plate  82  also has a width w 5  which is equal to the width w 4  of the first flexible plate  54 . The width w 5  of the second flexible plate  82  is aligned parallel to the width w 3  of the outlet opening  44 ′. The width w 5  is slightly less than the width w 3  of the discharge member  40 . The second flexible plate  82  spans across the width of the outlet opening  44 ′ and has an inner surface  84  and an outer surface  86 . A plurality of screws  70 , identical to the screws  70  discussed above, is positioned across said width w 4  of the discharge member  40  or across the width of the outlet opening  44 ′. Each of the screws  70  is capable of being adjusted so as to contact and possibly deflect or distort the outer surface  86  of the second flexible plate  82  and impart a corresponding contour to the inner surface  84  of the second flexible plate  82 . Each of the screws  70  can be adjusted by a similar or by a different amount so that the inner surfaces  56  and  84  of the first and second flexible plates,  54  and  82  respectively, can be distorted as needed and the trajectory of the pressurized gaseous stream  24  containing the plurality of individual fibers  22  can be further controlled. 
     The plurality of screws  70  can be adjusted to cause a deflection of each of the first and second flexible plates,  54  and  82  respectively, up to about 1 inch or more from a flat profile and cause a change in surface contour which can result in a change of as much as ±5 grams per square meter along the width of the uniform non-woven fibrous web  12  formed on the apparatus  10 . 
     Desirably, the second flexible plate  82  is identical in size and dimension to the first flexible plate  54 . The second flexible plate  82  should have a length of at least about 2 inches, a width w 5  slightly less than the width w 3  of the discharge member  40 , and a thickness of less than about 0.2 inches. The second flexible plate  82  also has a leading edge secure to the second major wall  48  and an unsecured edge located downstream of the secured edge. The second flexible plate  82  can be secured to the second major wall  48  in the same fashion as the first flexible plate  54  is secured to the first major wall  46 . 
     Still referring to  FIG. 11 , one can see that the second flexible plate  82  can be deflected or distorted into an undulating pattern similar or identical to the undulating pattern imparted into the first flexible plate  54 . As with the first flexible plate  54 , the second flexible plate  82  can be deflected or distorted into almost any desired geometrical pattern. When the first and second flexible plates,  54  and  82  respectively, are utilized, the vertical opening of the outlet opening  44 ′ is reduced. For example, in  FIG. 11 , at least one point on the second flexible plate  82  can be spaced less than 1.5 inches from a point on the first flexible plate  54 . Desirably, at least one point on the second flexible plate  82  can be spaced less than 1 inch from a point on the first flexible plate  54 . Furthermore, each of the first and second flexible plates,  54  and  82  respectively, can be deflected into an undulating contour by the plurality of screws  70  such that an apex  88  formed in the first flexible plate  54  is vertically aligned with an apex  90  formed in the second flexible plate  82 . The distance between the two apexes can be less than about 1.5 inches, desirably, less than about 1 inch, and more desirably, less than about 0.75 inches. 
     By adjusting the size and shape of the outlet opening  44 ′, one can control the velocity of the pressurized gaseous stream  24  and the individual fibers  22  contained therein. This fine tuning of the pressurized gaseous stream  24  can result in a ±5 grams per square meter adjustment in the cross direction of the finished non-woven fibrous web  12 . By finely adjusting the size and shape of the outlet opening  44 ′, one can dry form a uniform non-woven fibrous web having a basis weight of less than about 100 grams per square meter (gsm) at acceptable production line speeds. In fact, uniform non-woven fibrous webs  12  having a basis weight of about 75 grams per square meter (gsm), about 50 gsm, about 30 gsm, and even webs  12  having a basis weight of about 20 gsm can be produced. Up until now, it has been extremely difficult to dry form uniform non-woven webs of such low basis weights at acceptable production line speeds. 
     Referring now to  FIG. 12 , a chart is depicted that shows the gaseous (air) stream profiles that can be achieved by using the apparatus  10 . This data was obtained without modifying the contour of the inner surface  56  of the first flexible plate  54  by tightening the screws  70 . The second flexible plate  82  was not present in this trial. The gaseous (air) stream profile can be basically made totally flat when the first flexible plate  54 , shown in  FIG. 10 , is implemented by making adjustments to the screws  70 . The gaseous (air) stream profile can also be refined when both of the first and second flexible plates,  54  and  82  respectively, are utilized and each of the first and second flexible plates,  54  and  82  respectively, are deflected by tightening the screws  70 . 
     Referring now to  FIG. 13 , a unitary assembly  10 ′ is shown which consist of two of the apparatuses  10  shown in  FIG. 1 . A first modular unit  92  having a spreading member  26  with an outlet width w 1  of from between about 1 to about 2 meters, and a second modular unit  94 , having a spreading member  26  with an outlet width w 1  of similar or identical construction, is positioned transversely adjacent to the first modular unit  92  to form a unitary assembly  10 ′. The unitary assembly  10 ′ is capable of producing a continuous, monolithic web having double the width of a web  12  produced from the first modular unit  92  alone. By monolithic it is meant constituting or acting as a single, often uniform whole. 
     In  FIG. 13 , the inlet opening  42  of the discharge member  40  is spaced away from the outlet  30  of the spreading member  26  simply for the purpose of representing the double width of the discharge member  40 . In operation, the inlet opening  42  of the discharge member  40  is directly attached to the outlet  30  of the spreading members  26 ,  26  of the first and second modular units,  92  and  94  respectively. 
     It should be understood that any number of modular units, of similar or identical construction, can be positioned side by side to produce a uniform non-woven fibrous web of any desired width. There is no limitation on the number of modular units that can be so arranged. The ability to arrange a required number of modular units allows one to form uniform non-woven fibrous webs having a width of 5 meters or more. For practical purposes, an ideal width w 3  for the outlet opening  44  of an individual discharge member  40  is in the range of about 1 meter to about 1.5 meters. Three, four, five, six or more modular units can be employed in a side-by-side relationship, if needed. 
     In  FIG. 13 , even though the spreading members  26 ,  26 , with their respective inlets  28 ,  28 , are separate units, the discharge member  40  has a continuous, monolithic outlet opening  44 . Because of this, the fibers  22  are gaseous (air) formed with a uniform cross direction when discharged onto the forming zone  74  without any separation as a result of combining the separate spreading members  26 ,  26  through the unitary discharge member  40 . 
     Method 
     Referring now to the flow diagram shown in  FIG. 14 , a method of dry forming a uniform non-woven fibrous web will be described. The method includes the steps of forming a plurality of individual fibers  22  and routing the plurality of individual fibers  22  through a transport duct  14  using a pressurized gaseous (air) stream  24 . The transport duct  14  has a predetermined cross-sectional area with a constant diameter d. The transport duct  14  has an entrance  16  and an exit  18 . The pressurized gaseous stream  24  has a velocity of at least about 1,000 feet per minute. The velocity of the pressurized gaseous stream containing the plurality of fibers can be dissipated at the inlet into the spreading member  26  so that the iso-kinetic energy of the plurality of individual fibers  22  is reduced. 
     The method also includes directing the pressurized gaseous stream  24  containing the plurality of individual fibers  22  to a spreading member  26 . The spreading member  26  has an inlet  28 , an outlet  30  and a length l 1  therebetween. The length l 1  is at least 20 times the diameter d of the transport duct  14 . The spreading member  26  is a hollow enclosure having first and second major walls,  32  and  34  respectively, connected together by a pair of side walls,  36  and  38  to form a rectangular cross-sectional configuration. The rectangular cross-sectional configuration has a width w 1  and a height h 1 . The width w 1  constantly increases in dimension along the length l 1  from the inlet  28  to the outlet  30 , and the height h 1  constantly decreases in dimension along the length l 1  from the inlet  28  to the outlet  30 . The height h 1  is less than the width w 1  at the outlet  30 . The inlet  28  of the spreading member  26  is connected to the exit  18  of the transport duct  14  and the exit  18  is aligned at an angle of at least about 15° to the second major wall  34 . The pressurized gaseous stream  24  passing through the spreading member  26  is maintained at a constant or slightly accelerating velocity and with a minimum amount of turbulence. 
     The method further includes directing the pressurized gaseous stream  24  containing the plurality of individual fibers  22  to a discharge member  40  having an inlet opening  42 , an outlet opening  44  and a length l 2  therebetween. The inlet opening  42  is connected to the outlet  30  of the spreading member  26  and has an identical size and cross-sectional configuration as the outlet  30 . The discharge member  40  has first and second major walls,  46  and  48  respectively, connected together by a pair of side walls  50  and  52  to form a rectangular cross-sectional configuration having a width w 3  and a height h 3 . The width w 3  is greater than the height h 3 . The discharge member  40  has a first flexible plate  54  positioned therein which is aligned adjacent to the first major wall  46 . The first flexible plate  54  spans across the width w 3  of the outlet opening  44  and has an inner surface  56  and an outer surface  58 . A plurality of screws  70  is positioned across the width w 3  of the discharge member  40  or across the width of the outlet opening  44 . Each of the screws  70  is capable of being adjusted so as to contact and deflect or distort the outer surface  58  of the first flexible plate  54  and impart a corresponding contour to the inner surface  56  of the first flexible plate  54 . 
     The method further includes depositing the plurality of individual fibers  22  from the outlet opening  44  onto a forming zone  74  to form a uniform non-woven fibrous web  12 . The forming zone can be a forming screen  74  or any other type of forming mechanism known to those skilled in the art. 
     In this method, it is advantageous to maintain the velocity of the plurality of individual fibers  22  within the pressurized gaseous stream  24  through the transport duct  14 . It is also advantageous to dissipate the velocity of the pressurized gaseous stream  24  containing the plurality of fibers  22  upstream of the inlet  28  into the spreading member  26  so that the iso-kinetic energy of the plurality of individual fibers  22  is reduced. 
     The pressurized gaseous stream  24  containing the plurality of individual fibers  22 , which exits the transport duct  14 , will enter the inlet  28  of the spreading member  26  at an angle of from between about 15° to about 75°. This will cause the plurality of individual fibers  22  to strike an inner surface of the second major wall  34  of the spreading member  26 . This action will allow the velocity and momentum of the plurality of individual fibers  22  to dissipate and the plurality of fibers  22  will be re-aligned with airflow profiles in the spreading member  26 . 
     Alternatively, the method can be used with an apparatus  10  having a discharge member  40  with first and second flexible plates,  54  and  82  respectively. The second flexible plate  82  is positioned within the discharge member  40  and is aligned adjacent to the second major wall  48 . The second flexible plate  82  has a width w 5  which spans across the width of the outlet opening  44 ′ and has an inner surface  84  and an outer surface  86 . A plurality of screws  70  is positioned across the width w 3  of the second major wall  48 . Each of the screws  70  is capable of being adjusted so as to contact and deflect the outer surface  86  of the second flexible plate  82  and impart a corresponding contour to the inner surface  84  of the second flexible plate  82 . 
     While the invention has been described in conjunction with several specific embodiments, it is to be understood that many alternatives, modifications and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, this invention is intended to embrace all such alternatives, modifications and variations which fall within the spirit and scope of the appended claims.