US3081501A

US3081501A - Apparatus for producing nonwoven fabric

Info

Publication number: US3081501A
Authority: US
Inventors: Kalwaites Frank
Original assignee: Johnson and Johnson
Current assignee: Johnson and Johnson
Priority date: 1957-06-12
Filing date: 1957-06-12
Publication date: 1963-03-19
Anticipated expiration: 1980-03-19

Description

March 19, 1963 F. KALWAITES APPARATUS FOR PRODUCING NONWOVEN FABRIC 4 Sheets-Sheet 1 Filed June 12, 1957 mum March 19, 1963 F. KALWAITES APPARATUS FOR PRODUCING NONWOVEN FABRIC 4 Sheets-Sheet 2 Filed June 12, 1957 March 19, 1963 F. KALWAITES Filed June 12. 1957 APPARATUS FOR PRODUCING NONWOVEN FABRIC 4 Sheets-Sheet 3 March 19, 1963 F. KALWAITES 3,081,501

APPARATUS FOR PRODUCING NONWOVEN FABRIC Filed June 12. 1957 4 Sheets-Sheet 4 f J A Mam/ Mum United States Patent 3,081,501 APPARATUS FOR PRODUCING NONWOVEN FABRIC Frank Kalwaites, Highland Park, N.J., assignor, by mesne assignments, to Johnson & Johnson, New Brunswick, N..I., a corporation of New Jersey Filed June 12, 1957, Ser. No. 665,229 6 Claims. (Cl. 19-161) This invention relates to apparatus for producing nonwoven fabrics, i.e., fabrics produced directly from fibers without the use of conventional spinning, weaving, or knitting operations.

Heretofore, nonwoven fabrics have been essentially different in structure from fabrics which have been woven or knitted. In a woven or knitted fabric, the fibers of the material making up the fabric do not occur individually, but are twisted into yarns or threads which in turn are woven or knitted into the fabric. In the well-known spinning operation, fibers are spun or twisted together tightly into mechanical and frictional engagement with one another to form yarns which are substantially circular in cross section. It is these yarns, not the fibers acting individually, which serve as the structural members of the resulting woven or knitted fabrics. Generally speaking, these fabrics comprise reticular structures of intersecting, intertwining yarns which define interstices between them.

Nonwoven fabrics have been of two main types, felts and bonded webs. In each of these, the fibers making up the fabric occur individually and act individually as structural members. This is true even though the fibers in many felts are so highly interlocked and compressed together that it is difficult to identify individual fibers. Hat felts, for instance, are extremely dense, relatively hard fabrics Without apparent interstices, which are quite dissimilar in appearance and qualities to woven or knitted structures.

On the other hand, the fibers in bonded webs are usually flatly assembled in layers, either more or less oriented in one direction as in a card web or arranged in a random manner as in an air laid isotropic web. Various bonding agents have been used to print a binder pattern on such webs or to impregnate them to hold the individual fibers together. In this type of fabric, the fibers may remain relatively straight and overlapping one another with verylittle interlocking between them. They are usually arranged in a more or less uniformly spaced condition in the plane of the Web, in such a way that only very small randomly occurring interstices are apparent between the overlapped fibers and those fibers between interstices remain spaced and more or less flatly arranged, possessing little similarity to the yarns of Woven or knitted fabrics.

The present invention contemplates a nonwoven fabric wherein the fibers are arranged to define a predetermined pattern of holes or openings with most of the fiber segments bordering the holes extending in substantial parallelism with portions of the perimeters of the holes. I11 general, the fibers are arranged in interconnected groupings or web areas extending between the holes in a predetermined pattern corresponding to the aforementioned pattern of holes. The resulting fabric may be made to resemble a particular woven or knitted fabric.

The groupings or groups are connected by fibers extending from one to another in such a way that they are common to a plurality of groupings. It is preferred that the average length of the fibers be considerably greater than the lengths of the groups containing them with the result that the groups predominantly comprise only parts or segments of the fibers passing through them. Preferably, the fibers averagerat least about 4 inch in length and are textile-like in nature. In general, the groupings are connected at junctures wherein the fibers extend in a plurality of diverse directions, while the fiber segments in the groups are relatively parallelized with respect to one another and more closely assembled than at the junctures.

In the foraminous structure formed by the interconnected fiber groupings the fibers are in a state of mechanical equilibrium. The fibers are mechanically and frictionally engaged to the extent that the arrangement of fibers is one of equilibrium.

Due to their structure and appearance and other qualities, fabrics produced by the method and apparatus of this invention are particularly adapted for use in surgical dressings, absorbent dressings such as sanitary napkins and diapers, most suitably for covering sanitary napkins and diapers, in wiping cloths, toweling, filter materials, lining materials, industrial base fabrics, as a substitute for gauze and gauze-like fabrics in general, and a variety of other applications.

The present invention contemplates a method and an apparatus for producing a nonwoven fabric having a predetermined pattern from a layer of irregularly arranged fibers by first wetting the fibrous layer out, then impaling the layer upon a group of prongs, and finally brushing the fibers into fiber accumulating Zones between the prongs.

The layer may be a nonwoven web of fibers, for example, fibers of rayon or cotton. The individual fibrous elements of the layer are capable of movement under the influence of an applied mechanical force. In general, the starting material of the method herein described may be any of the starting materials described in the Kalwaites Patent No. 2,862,251, granted December 2, 1958. The preferred starting material is an unbonded fibrous web.

The preferred method of this invention involves the application of external forces to a continuously moving layer of irregularly arranged fibers impaled upon a group of prongs, by simultaneously brushing the fibers of successive portions of the moving layer longitudinally and transversely of the direction of travel of the layer, thereby moving individual fiber segments into positions within fiber accumulating Zones in the interconnected spaces between the prongs.

In a preferred embodiment of the apparatus of this invention, the prongs or needles are carried on a rotatable cylinder against which a moving layer of irregularly arranged fibers is positioned. The layer of fibers is first passed through a pair of wet-out rolls and then into engagement with the pointed ends of the needles. An embedding brush is reciprocated in a direction normal to the peripheral surface of the cylinder, to press successive portions of the advancing layer of fibers downwardly about the needles. The reciprocation of the embedding brush is controlled by an eccentric bearing which permits only an instantaneous contact with the moving layer of fibers, since the embedding brush must be lifted from the fibers immediately because the needle-bearing cylinder is rotated continuously. The embedding brush is pivoted to permit it to move with the cylinder for the very short interval during which itis in contact with the layer of fibers.

Therotation of the cylinder pulls each portion of the layer of fibers progressively past a seriesof rotary brushes disposed at right angles to the direction of travel of the layer, with their bristles in contact with the layer of fibers embedded about the needles. Alternate brushes are rotated in opposite directions from the direction of rotation of the brushes intermediate the alternate brushes. These rotary brushes press the fibers downwardly about the needles, toward the peripheral surface of the cylinder.

The rotary brushes, which are parallel to the longitudinal axis of the cylinder, are also oscillated longitudinally of the cylinder simultaneously with their rotational movement. The combined rotational and oscillatory movements of the rotary brushes move the individual fibers of the layer along the tapered sides of the needles into contact with the peripheral surface of the cylinder, laterally into the spaces between the needles, and in the direction of their respective longitudinal axes, with respect to the other fibers in the layer, to compact them in fiber accumulating zones between the needles.

The water which is added to the layer of fibers by the wet-out rolls as the layer is moved through the nip between them acts as a lubricant and facilitates the relative movement between the individual fibers in the direction of their respective longitudinal axes. The relative longitudinal movement between individual fibers places the fibers in mechanical equilibrium in their rearranged positions in the resulting nonwoven fabric.

The resulting nonwoven fabric is removed from the needles by passing it through the nip between a pair of doffing rolls positioned beyond the last of the rotary brushes. Either one of the dofiing rolls may be driven to insure continuous movement of the nonwoven fabric away from the cylinder, or suitable means may be provided beyond the dofiing rolls to carry the nonwoven fabric into a drying area. It is obvious that the driven dotfer roll or means for moving the nonwoven fabric from the cylinder to the drying area must be synchronized with the cricumferential speed of the cylinder.

The prongs upon which the fibrous starting layer is impaled before the brushing action is carried out may have rounded, flat, or pointed ends. They are preferably formed with a cylindrical body and long, gradually tapered conical points at their free ends. Conventional card clothing, with the customary burrs removed from the free ends, may also be used. Needles of various sorts are also suitable, including needles having bodies of various cross-sectional shapes, with chisel shaped free ends.

Advantages of the invention other than those generally described above will be apparent from the following description and claims, taken together with the drawings wherein:

FIGURE 1 is a side view, partially in section and partly in elevation, of a machine embodying the invention, with a portion of the frame removed to clarify the illustration, the feed end of the machine being shown on the left and the discharge end on the right side of the figure;

FIG. 2 is a fragmentary cross sectional view, taken along the line 22 of FIG. 1;

FIG. 3 is a fragmentary elevation of the feed end of the machine, with the structure outside the side frame members generally omitted;

FIG. 4 is a fragmentary detail view, partly in elevation and partly in section, showing the embedding brush and the means for reciprocating it along a line normal to the peripheral surface of the cylinder;

FIG. 5 is a cross sectional view, taken along the line 5-5 of FIG. 4;

FIG. 6 is a fragmentary elevational view of the right side of the machine as seen in FIG. 2, showing the driving mechanism for rotating the rotary brushes; and

FIG. 7 is a fragmentary elevational view of the left side of the machine as seen in FIG. 2, showing the mechanism for oscillating the rotary brushes longitudinally of the cylinder.

In the drawings, the reference numeral 2 indicates a supporting frame comprising a pair of vertical posts 3 on opposite sides of the frame at the feed end of the machine and a pair of vertical posts 4 on opposite sides of the discharge end. Longitudinal beams '5 connect each vertical post 3 to the vertical post 4 on the same side of the machine. A transverse beam 5 connects the vertical posts 3 at the feed end of the machine, and a similar transverse beam connects the vertical posts 4-. The frame also includes a side frame plate 6 extending vertically upward from the longitudinal beam 5 at the right side of the frame (as seen from the feed end) and a similar side frame plate 7 extending vertically upward from the beam 5 at the left side of the frame.

A conveyor 8 is positioned adjacent the feed end of the machine to carry a layer 9 of irregularly arranged fibers to the feed end of the machine. The layer of fibers may or may not be self-sustaining. If it is not self-sustaining, a permeable carrier web is provided to carry it until such support is no longer required.

A conveyor 10 is positioned adjacent the discharge end of the machine for carrying the nonwoven fabric, in which the fibers of the layer have been rearranged in a predetermined pattern, from the machine to a suitable bonding or drying area (not shown) of a conventional type. The specific structure of the

conveyors

3 and 10 is not described, since they do not constitute part of the invention and may be of conventional construction.

Wet-out rolls 11 and 12, extending transversely of the machine, are rotatably mounted in vertical alignment at the feed end of the machine. A shaft 13, carrying wetout roll 11, is journalled in bearings 14 mounted on each vertical post 3.

Lower wet-out roll 11 is partially immersed in a water pan 15 supported on brackets 16 mounted on each post 3 below the bearings 14. Upper wet-out roll 12 is carried by a shaft 17 journalled in bearings 18. Each bearing 18 is slidably mounted in a recess 19 extending vertically downward from the upper edge of each vertical post 3. The vertical position of upper wet-out roll 12 is adjustable, and is regulated by hydraulic positioning cylinders 20 mounted on brackets 21 projecting laterally from the top of vertical posts 3. Each positioning cylinder has a two-way piston (not shown) carrying a piston rod 22 connected at its lower end to the bearing 18. By applying hydraulic pressure through conventional control means to one side or the other of the piston of each positioning cylinder, the pressure at the nip between wet-out rolls 11 and 12 may be varied as desired.

The pair of wet-out rolls 11 and 12 cooperate to control the moisture content of the layer 9 of irregularly arranged fibers which is fed from conveyor 8 through the nip between the wet-out rolls. The position of roll 12, relative to roll 11, determines the quantity of water that is applied to the layer 9. The fibers of layer 9 are in mechanical and frictional engagement with one another as the layer passes through the nip between the wet-out rolls. Preferably the layer of fibers contains in the neighborhood of to 200 percent moisture as it leaves the wet-out rolls. The term percent moisture, when used in this specification, refers to the percentage of moisture by weight of the dry layer of fibers.

A main drive shaft 23, extending transversely between

side frame plates

6 and 7, is journalled in bearings 24 each mounted on one of the longitudinal beams 5. The drive shaft projects outside each side frame plate for reasons hereinafter disclosed. A cylinder 25 mounted on drive shaft 23 to rotate therewith is provided with a plurality of needles 26 or similar sharp tapered implements projecting radially from its peripheral surface. The needles are secured to the surface of the cylinder in any suitable manner, and are arranged in accordance with the predetermined pattern of the fabric to be made from the layer of irregularly arranged fibers. During the operation of the machine the drive shaft rotates the needle bearing cylinder 25 continuously.

From the nip between the wet-out rolls 11 and 12, the layer 9 of irregularly arranged fibers is moved into contact with the sharp ends of the needles projecting radially from the peripheral surface of the cylinder. The layer of fibers is pulled into contact with the sharp pointed ends of the needles in an area of the peripheral surface of the cylinder in which pressure means, such a an embedding brush 27, is adapted to impale the layer of fibers on the needles.

The embedding brush 27 extends longitudinally of the needle bearing cylinder and covers substantially the entire width of the cylinder. The working surface of the embedding brush, formed by the ends of the brush bristles, is substantially fiat, but is curved slightly in its transverse direction to allow it to conform to the circumferential curvature of the needle bearing cylinder. The brush 27 comprises a plurality of soft bristles 28 secured to a back 29 which is pivotally secured, as indicated at 30, to a clevis 31 formed on the lower end of a reciprocating rod 32. The axis of the pivot pin 30 is parallel to the longitudinal aXis of main drive shaft 23 for a reason hereinafter disclosed.

A cross bar 33 extending transversely of the machine has its opposite ends secured adjacent the upper edges of the

side frame plates

6 and 7. A plurality of supporting :arms 34 secured to cross bar 33 depend therefrom to rotatably support an embedding brush drive shaft 35 extending parallel to bar 33, as shown in FIGS. 4 and 5. The arms 34, and the associated mechanism, are equivalents, and only one Will be described. The shaft 35 is driven by any suitable driving means (not shown) and carries a pair of eccentric bearings 36 thereon. Each bearing comprises a disk 37 eccentrically keyed to shaft 35, as indicated at 38, and a circular strap 39 fitting around the rim of disk 37. Roller bearings 40, mounted in a race between the peripheral surface of disk 37 and the contiguous inner surface of the circular strap 39, permit the disk 37 to rotate relative to the strap 39, while the eccentricity of the disk relative to shaft 35 causes the circular strap 39 to reciprocate. One end 41 of rod 32 is threaded to fit into a threaded recess 42 formed in the strap 39, whereby rod 32 will be reciprocated by the reciprocating movement of strap 39.

In order to keep reciprocating rod 32 moving back and forth in a fixed path, a guide support cross bar 43-, having its opposite ends secured to

side frame plates

6 and 7, is mounted parallel to embedding brush drive shaft 35, between that shaft and cylinder 25. Cross bar 43 has a guide opening 44, extending normal to the peripheral surface of cylinder 25, which is provided with a guide bearing sleeve 45. Reciprocating rod 32 is positioned in the guide bearing sleeve with a sliding fit so that it can move only in a direction normal to the peripheral surface of needle bearing cylinder 25.

It is seen that rotation of embedding brush drive shaft 35 imparts to the embedding brush 27 a reciprocatory motion having a stroke equal to twice the eccentricity of eccentric bearing 36. Due to the guide support system just described, the reciprocatory motion is confine-d to a path normal to the peripheral surface of cylinder 35.

The reciprocating movement of the embedding brush 27 causes the bristles 28 to engage the layer 9 of fibers and press it downwardly upon the needles 26. The layer of fibers is constantly moving with the needles of cylinder 25, and the bristles of the embedding brush remain in engagement with the layer of fibers for only a very short interval of time. The pivotal joint 30 connecting the bottom end of reciprocating rod 32 and brush 27 permits the embedding brush to pivot and move with the needles the slight distance the needle bearing cylinder rotates during the interval the embedding brush is in contact with the needles. When the embedding brush is lifted out of engagement with the needles by the upward stroke of its reciprocatory improvement, gravity will cause the brush to fall back pivotally, again about joint 30, into it original of fibers produces the major fiber rearrangement as the fibrous layer is impaled upon the needles. In this first rearranging step the fibers are pushed out of the local areas of the layer which are occupied by the advancing needles. As a result, fibers are pushed into closer proximity and increased parallelism in the areas bordering upon the needles. The rearrangement of the fibers is completed by the brushing action of rotary brushes 46, 47, 48, and 49, now to be described.

As the embedding brush 27 moves upwardly out of engagement with the layer of fibers, the layer, which is now impaled firmly on needles 26, is moved by the needles past a series of rotary brushes 46, 47, 48 and 49 mounted on

independent drive shafts

50, 51, 52, and 53, respectively. In the embodiment shown, the rotary

brush drive shafts

50, 51, 52, and 53 are spaced substantially equidistant from main drive shaft 23 and are so positioned relative to the peripheral surface of needle bearing cylinder 25 as to maintain the bristles 54, 55, 56, and 57 of the rotary brushes 46, 47, 4-8, and 49, respectively, in engagement with the fibers of a portion of layer 9 as the layer passes between the needle bearing cyinder and the rotary brushes. The bristles of each of the rotary brushes are very soft so that they may rearrange the fibers of layer 9 without destroying the in tegrity of the layer. As is seen in FIG. 1, some of the bristles are long enough thatexcept as they are pre vented from doing so by the presence of the fibrous web being rearranged-they extend between the spaced needles 26 and below the free side of those needles.

-As shown in FIG. 6,

independent drive belts

58, 59, 60 and 61 extend around a pulley 62 mounted on main drive shaft 23 and pulleys 63, 64, 65, and 66 mounted on rotary

brush drive shafts

50, 51, 52, and 53, respectively. The

drive belts

58, 59, 6t), and 61 drive the

shafts

50, 51, 52, and 53 from main drive shaft 23. -As shown in FIG. 2, the opposite ends of each of the

rotary brush shafts

50, 51, 52, and 53 are mounted in bearings (not shown) carried by bearing

supports

67 and 68 mounted on the outer surfaces of

side frame plates

6 and 7, re- .spectively.

The

drive belts

58 and 60 are each crossed between pulley 62 and their respective pulleys 63 and to drive rotary brushes 46 and 48 in the opposite direction to the direction of rotation of rotary brushes 47 and 4-9. From the, arrows in FIG. 1 indicating the direction of rotation of the needle bearing cylinder and each of the rotary brushes, it is seen that the rotary brushes 46 and 48 are driven in the opposite direction from that in which the needle bearing cylinder 25 is driven, and that rotary brushes 47 and 49 are driven in the same direction as the cylinder 25. Since the rotary

brush drive shafts

50, 51, 52, and 53 are each outside the periphery of the needle bearing cylinder 25, bristles 54 and 56 of rotary brushes 46 and 48, respectively, travel in the same direction as the needles 26 during the portion of their rotational movement while they are in contact with said needles, and bristles 55 and 57 of rotary brushes 47 and 49 travel in the opposite direction from needles 26 While they are in contact with the needles.

The effective fiber rearranging forces exterted by the bristles of each brush as a result of the rotational movement of the brushes depends upon the difference between the linear speed of the bristles and the linear speed of the fibrous layer 9 in the area of contact between them. This difference between the linear speeds of the bristles and the fibers is obtained by subtracting the linear speed of the layer 9 from the linear speed of bristles 54 and 56 which are moving in the same direction, and adding the linear speed of the layer 9 to the linear speed of bristles 55 and 57 which are moving in opposite directions. The rotation of rotary brushes 46 and 48, upon which bristles 54 and 56 are carried, may be speeded up to obtain equal fiber rearranging forces for each of the rotary brushes.

Additional fiber rearranging forces are applied to the fibers of layer 9 by longitudinal oscillation of the shaft of each of the rotary brushes. The mechanism for oscillating the shafts of the rotary brushes longitudinally of their respective axes is shown in FIGS. 2 and 7. The mechanism is the same for each rotary brush, and the description thereof will generally be limited to a single rotary brush for the sake of brevity.

A worm 69 extending laterally from a sleeve 79 is mounted on the end of drive shaft 23 extending outwardly beyond the side frame plate 7. The worm is preferably integral with sleeve 70, but may be formed separately and rigidly secured thereto in any suitable manner. Worm 69 meshes with a worm wheel 71 fixed on oscillator drive shaft 72 which is rotatably mounted in a plurality of bearings 73 extending outwardly from side plate frame 7. Four oscillator earns 74 are rigidly mounted in eccentric relationship on oscillator drive shaft 72. The cams 74 are spaced longitudinally of oscillator drive shaft 72 for a purpose hereinafter described. Collars 75 and 76 are fixed to opposite ends of shaft 72 to prevent displacement of the shaft along its axis relative to worm wheel 71 and bearings 73.

Each bearing support 68 has a pair of fulcrum arms 77 extending outwardly therefrom, and an oscillator lever 78 is pivoted between each pair of fulcrum arms as indicated at 79. The pivot is positioned between the horizontal planes of shaft 72 and the particular rotary

brush drive shaft

50, 51, 52, or 53 which is supported by the bearing in the bearing support 68 from which the fulcrum arms supporting the pivot extend. Each oscillator lever 78 has sufiicient length to extend from a point adjacent oscillator drive shaft 72 to a point adjacent the end of the respective rotary

brush drive shaft

50, 51, 52, and 53.

The lower end of each oscillator lever 78 is bifurcated, as indicated at 30, and a follower roller 81 is mounted to rotate freely on a pin 82 extending across the bifurcated end of the oscillator lever. The cams 74 are spaced in alignment with follower rollers 81, and each roller 81 is normally held in contact with the periphery of one of the earns 74. Each rotary

brush drive shaft

50, 51, 52, and 53 has a mollar 83 secured adjacent its end and a compression spring 84 coiled around the shaft is biased between the collar and a shoulder 85 on the bearing support 68 to exert a constant force against collar 83 to urge the shaft outwardly into contact with the upper end of the respective oscillator lever 78.

As the main drive shaft 23 is rotated, it causes oscillator drive shaft 72 to rotate through the gear linkage, already described, and thereby move each of the oscillator cams 74 through its eccentric orbit. As each cam '74 moves outwardly, it presses against its associated follower roller 81, moving the upper end of the respective oscillator lever '78 and rotary brush drive shaft i Sll, 52, and 53 inwardly against the action of compression spring 84. As the cam 74 moves inwardly, the spring 34 pushes the rotary brush drive shaft outwardly to complete the longitudinal oscillation of the shaft. Each rotary brush completes an oscillatory cycle for every revolution of oscillator drive shaft 72.

If the rearranging forces are applied to an isotropic fibrous web only in a direction parallel to the direction of web travel, they will act most eflectively on fibers extending at right angles to the direction of web travel and will have virtually no effect on fibers extending parallel to the direction of web travel. The effectiveness of the rearranging forces will vary for fibers in intermediate positions, with the effectiveness increasing with any increase in the angle of fiber orientation to the direction of web travel.

It is seen that rearrangement of the fibers could not be uniform if the rearranging forces were applied in only one direction, because of the diminished rearrangement of fibers as the angle of orientation of the fibers approaches the angle of direction of the applied forces. Therefore, the best results are obtained by applying the same rearranging forces in all directions. In the apparatus of this invention rearranging force components having the same effective magnitude are applied to the fibers in all four directions at right angles to each other.

The rearranging force applied by each rotary brush to the fibers of layer 9 is a resultant of forces produced by the above-described oscillation and by the rotation of the shaft on which the rotary brush is mounted. If one plots the motion of each brush with respect to layer 9 due to the oscillation of the brush shaft, the graph will be in the form of a sinusoidal curve. A graph of the motion of a particular group of bristles on the brush with respect to layer 9 due to rotation of the brush will have the form of a straight line. To determine the resultant fiber rearranging force produced by both the rotation and the oscillation of a particular rotary brush 54, 55, 56, or 57, the force due to the circumferential movement of the brush with respect to the fibers, which is of substantially constant magnitude, must be combined with the varying force due to shaft oscillation.

At a given moment, the force applied to the fibers in any particular direction by the rotating and oscillating brush is proportional to the relative speed of movement of the brush in that direction with respect to the fibers. This is true both of the rearranging force produced by relative movement of the brush bristles and the fibers due to retation of the brush, and of the rearranging force produced by relative movement of the brush bristles and fibers due to oscillation of the brush shaft.

The linear speed of movement of the bristles with respect to the fibers which is due to brush rotation may be computed for bristles 54 and 56 on the one hand, and bristles 55 and 57 on the other, in the manner already described above. Since the relative speed of bristles and fibers due to rotation of a given brush remains substantially constant, the magnitude of the resulting fiber rearranging force component likewise remains substantially constant during normal operation of the machine of this invention.

The speed of movement of the brush due to oscillation of its shaft varies, however, as the shaft passes through its oscillatory c cle. This speed may be represented by a sinusoidal curve out of phase with the curve representing the oscillatory morion of the shaft. In the same way, the resulting fiber rearranging force may also be represented by a sinusoidal curve 90 out of phase with the curve showing the oscillatory motion of the shaf During one half the cycle, the force component produced by the oscillation of the rotary brush drive shaft is applied in one direction transverse to the direction of web travel, and during the next half of the cycle it is applied in the opposite direction. The force component is of continuously varying magnitude, increasing from zero at each outer limit of the cycle of oscillation to a maximum when the shaft passes through its middle position and the sinusoidal curve representing the oscillatory movement of the shaft passes through its node. The component of force then decreases until the shaft reaches the opposite outer limit of its oscillation, when the direction of the force component is reversed.

The brushing force component produced by the oscillation of the rotary brush drive shaft is thus generally sinusoidal. However, the nature of the brushes tends to cause the sine curve representing the brushing force component to be flattened out somewhat at each peak. Since bristles 54, 55, 56, and 57 of the rotary brushes are preferably soft and limber, the bristles will tend to bend and their free ends to lag behind the body of the brush as it moves back and forth. When the brush drive shaft reverses its direction of longitudinal movement at each end of its cycle, the bristle ends exhibit an even greater lag, for they then tend to stop altogether, and to remain stationary until the brush body has moved back in the reverse direction far enough to pick up the slack due to the bending of the bristles. Hence the sine curve representing the force component caused by oscillation of the drive shaft must be drawn with each peak flattened out somewhat rather than rising to the maximum value for a perfect sine curve.

It is seen that the effective rearranging force component applied to the fibers in one direction parallel to the axis of each rotary brush may be approximated by determining What may be called a root mean square force, by analogy to the computation of the root mean square voltage of an alternating electric current. By root mean square is meant a quantity equal to 0.707 of the maximum amplitude of the sinusoidal curve representing that rearranging force.

The effective rearranging force component applied to the fibers in the opposite transverse direction has the same magnitude but opposite sign. It is seen that the root mean square or effective transverse rearranging force is applied in each direction parallel to the rotary brush axis during only one half the operation of the machine, and in the opposite direction during the other half of the period of operation. However, the rearranging force in each transverse direction is supplemented, in the embodiment of the machine shown and described, by the force applied by the adjacent rotary brush, which passes through the same cycle of oscillation and produces the same transverse rearranging force first in one direction and then the other.

To produce most nearly uniform rearrangement of the fibers, the rearranging force applied by each rotary brush should have a component parallel to the direction of web travel whose magnitude is substantially equal to the effective magnitude of the force component applied first in one direction parallel to the direction of shaft oscillation and then in the opposite. The force applied to the fibers by the rotary brush at any moment is proportional to the relative speed of movement of the rotary brush with respect to the fibers. Therefore, whenever each rotary brush rotating in one direction (such as brushes 46 and 48 in the embodiment shown and described) is supplemented by another brush (such as brushes 47 and 49) rotating in the opposite direction, the linear circumferential speed of each brush in relation to the fibers being rearranged is preferably equal to 0.707 of the maximum speed of the oscillating rotary brush drive shaft as it passes through the midpoint in its oscillatory path.

As mentioned above, the initial impaling step produces the major rearrangement of the fibers of the fibrous starting layer into a nonwoven fabric 9, having a pattern of openings corresponding to the arrangement of the needles on the needle bearing cylinder. The cumulative effect of brushing the fibers between the needles in different directions, as just described, completes that rearrangement. More specifically, the brushing step supplements the initial lateral movement of the fibers produced by penetration of the prongs or needles, by causing individual fibers to move in the direction of their respective longitudinal axes, with respect to the other fibers in the layer, and thereby to lie in mechanical equilibrium in their final rearranged positions.

After the resulting nonwoven fabric passes the last rotary brush at the discharge end of the machine, it is removed from the cylinder by passing it between the nip of a pair of dofiing rolls 86, 87. The fabric is moved from the doffing rolls to a conveyor 10* which carries it to a suitable drying or other processing area (not shown).

bearings

88, 3 carried by the vertical posts and side frame plates at the discharge end of the machine. One of the dofiing rolls is preferably driven by a motor 90. The motor 90 also drives the main drive shaft 23 through a belt 91 extending around a pulley 92 mounted on one end of the drive shaft.

As used in this specification and claims, the term tapered implements includes not only an implement which is tapered from its base to its free end but also any implement which has uniform cross-sectional dimensions throughout its body portion and gradually di- The dotling rolls are rotatably mounted in 10 minishing cross-sectional dimensions at its free end portion.

The above-detailed description of this invention has been given for clearness of understanding only. No unnecessary limitations should be understood therefrom, as modifications will be obvious to those skilled in the art.

I claim:

1. A machine for continuously producing a nonwoven fabric having holes arranged in a predetermined pattern from a layer of wet, irregularly arranged fibers, said machine comprising a rotatably mounted cylinder, means to rotate said cylinder, a group of prongs mounted on the peripheral surface of said cylinder, said prongs being arranged in said predetermined pattern, means for impaling successive portions of a layer of wet, irregularly arranged fibers upon said prongs to move certain of said fibers laterally into new positions in the layer, a group of brushes rotatably mounted adjacent said cylinder with their longitudinal axes parallel with the longitudinal axis of the cylinder and having soft-bristles extending therefrom some of whose end portions, upon rotation of the brushes, are adapted to extend between said prongs and below the free ends thereof, and means for rotating various of said brushes in different directions to maintain said impaling and move individual fibers in the direction of their respective longitudinal axes, with respect to the other fibers in the layer, so as to permit the rearranged fiber segments to remain in a condition of mechanical equilibrium in their new positions in the areas between the prongs where they define said predetermined pattern of holes.

2. A machine for continuously producing a nonwoven fabric having holes arranged in a predetermined pattern from a layer of wet, irregularly arranged fibers, said machine comprising a rotatably mounted cylinder, means to rotate said cylinder, a group of prongs mounted on the peripheral surface of said cylinder, said prongs be ing arranged in said predetermined pattern, means for impaling successive portions of a layer of wet, irregularly arranged fibers upon said prongs to move certain of said fibers laterally into new positions in the layer, a group of brush-es rotatably mounted adjacent said cylinder with their longitudinal axes parallel with the longitudinal axis of the cylinder and having soft-bristles extending therefrom some of whose end portions, upon rotation of the brushes, are adapted to extend between said prongs and below the free ends thereof, means for rotating various of said brushes in different directions, and means for simultaneously oscillating said brushes longitudinally of their longitudinal axes, to maintain said impaling and move individual fibers in the direction of their respective longitudinal axes, with respect to the other fibers in the layer, so as to permit the rearranged fiber segments to remain in a condition of mechanical equilibrium in their new positions in the areas between the prongs where they define said predetermined pattern of holes.

3. A machine for producing a nonwoven fabric having holes arranged in a predetermined pattern from a layer of wet, irregularly arranged fibers, said machine comprising a rotatably mounted cylinder, means to rotate said cylinder, a group of prongs mounted on the peripheral surface of said cylinder, said prongs being arranged in said predetermined pattern, means for impaling successive portions of a layer of wet, irregularly arranged fibers upon said prongs to move certain of said fibers laterally into new positions in the layer, a group of brushes rotatably mounted adjacent said cylinder with their longitudinal axes parallel with the longitudinal axis of the cylinder and having soft bristles extending therefrom some of Whose end portions, upon rotation of the brushes, are

adapted to extend between said prongs and below the free ends thereof, means for rotating alternate ones of said brushes in a difierent direction from the direction of rotation of the brushes intermediate said alternate brushes, and means for simultaneously oscillating said brushes longitudinally of their longitudinal axes, to maintain said impaling and move individual fibers in the direction of their respective longitudinal axes, with respect to the other fibers in the layer, so as to permit the rearranged fiber segments to remain in a condition of mechanical equilibrium in their new positions in the areas between the prongs where they define said predetermined pattern of holes.

4. A machine for producing a nonwoven fabric having holes arranged in a predetermined pattern from a layerhof wet, irregularly arranged fibers, said machine comprising a rotatably mounted cylinder, means to rotate said cylinder, a group of prongs mounted on the peripheral surface of said cylinder, said prongs being arranged in said predetermined pattern, means for impaling successive portions of a layer of wet, irregularly arranged fibers upon said prongs to move certain of said fibers laterally into new positions in the layer, a group of brushes rotatably mounted adjacent said cylinder with their longitudinal axes parallel with the longitudinal axis of the cylinder and having soft bristles extending therefrom some of whose end portions, upon rotation of the brushes, are adapted to extend between said prongs and below the free ends thereof, means for rotating alternate ones of said brushes in a different direction from the direction of rotation of the brushes intermediate said alternate brushes, the brushes which turn in the same angular direction as the rotating cylinder being rotated less rapidly than the brushes which turn in the opposite direction, and means for simultaneously oscillating said brushes longitudinally of their longitudinal axes, to maintain said impaling and move individual fibers in the direction of their respective longitudinal axes, with respect to the other fibers in the layer, so as to permit the rearranged fiber segments to remain in a condition of mechanical equilibrium in their new positions in the areas between the prongs where they define said predetermined pattern of holes.

5. A machine for producing a nonwoven fabric having holes arranged in a predetermined pattern from a layer of wet, irregularly arranged fibers, said machine comprising a frame, a cylinder rotatably mounted in said frame, means to rotate said cylinder, a group of prongs projecting outwardly from the peripheral surface of said cylinder, said prongs being arranged in said predetermined pattern, means for moving successive portions of a layer of wet, irregularly arranged fibers into contact with the ends of said prongs, an embedding brush mounted in said frame opposite said cylinder, means for reciprocating said brush in a direction normal to the peripheral surface of said cylinder for impaling said successive portions of the layer of fibers on said prongs to move certain of said fibers laterally into new positions in the layer, said embedding brush being pivoted to permit limited movement thereof in the direction of rotation of said cylinder, a group of brushes rotatably mounted adjacent said cylin der and having soft bristles extending therefrom some of whose end portions, upon rotation of the brushes, are adapted to extend between said prongs and below the free ends thereof, and means for simultaneously rotating and oscillating said rotary brushes to maintain said impaling and move individual fibers in the direction of their respective longitudinal axes, with respect to the other fibers in the layer, so as to permit the rearranged fiber segments to remain in a condition of mechanical equilibrium in their new positions in the areas between the prongs Where they define said predetermined pattern of holes.

6. A machine for producing a nonwoven fabric having holes arranged in a predetermined pattern from, a layer of wet, irregularly arranged fibers, said machine comprising a frame, a cylinder rotatably mounted in said frame, means to rotate said cylinder, a group of implements projecting outwardly from the peripheral surface of said cylinder, said implements having sharp free ends and being arranged in said predetermined pattern, means for moving successive portions of a layer of wet, irregularly arranged fibers into contact with the ends of said implements, an embedding brush mounted in said frame opposite said cylinder, means for reciprocating said brush in a direction normal to the peripheral surface of said cylinder for impaling said successive portions of the layer of fibers on said implements, said embedding brush being pivoted to permit limited movement thereof in the direction of rotation of said cylinder, a group of brushes rotatably mounted adjacent said cylinder and having soft bristles extending therefrom some of whose end portions, upon rotation of the brushes, are adapted to extend between said implements and below the free ends thereof, means for rotating alternate ones of said brushes in a different direction from the direction of rotation of the brushes intermediate said alternate brushes, and means for simultaneously oscillating said brushes longitudinally of their longitudinal axes, to maintain said impaling and move individual fibers in the direction of their respective longitudinal axes, with respect to the other fibers in the layer, so as to permit the rearranged fiber segments to remain in a condition of mechanical equilibrium in their new positions in the areas between the prongs where they define said predetermined pattern of holes.

References Cited in the file of this patent UNITED STATES PATENTS 75,906 Haythorn et al. Mar. 24, 1868 355,296 Best Jan. 4, 1887 493,752 Clarenbach et al Mar. 21, 1893 7 1,567,841 Curtin Dec. 29, 1925 1,743,068 Walsh Jan. 7, 1930 1,978,620 Brewster Oct. 30, 1934 2,055,412 Hurst et al. Sept. 22, 1936 2,881,505 Hoffman Apr. 14, 1959

Claims

1. A MACHINE FOR CONTINUOUSLY PRODUCING A NONWOVEN FABRIC HAVING HOLES ARRANGED IN A PREDETERMINED PATTERN FROM A LAYER OF WET, IRREGULARLY ARRANGED FIBERS, SAID MACHINE COMPRISING A ROTATABLY MOUNTED CYLINDER, MEANS TO ROTATE SAID CYLINDER, A GROUP OF PRONGS MOUNTED ON THE PERIPHERAL SURFACE OF SAID CYLINDER, SAID PRONGS BEING ARRANGED IN SAID PREDETERMINED PATTERN, MEANS FOR IMPALING SUCCESSIVE PORTIONS OF A LAYER OF WET, IRREGULARLY ARRANGED FIBRES UPON SAID PRONGS TO MOVE CERTAIN OF SAID FIBERS LATERALLY INTO NEW POSITIONS IN THE LAYER, A GROUP OF BRUSHES ROTATABLY MOUNTED ADJACENT SAID CYLINDER WITH THEIR LONGITUDINAL AXES PARALLEL WITH THE LONGITUDINAL AXIS OF THE CYLINDER AND HAVING SOFT-BRISTLES EXTENDING THEREFROM SOME OF WHOSE END PORTIONS, UPON ROTATION OF THE BRUSHES, ARE ADAPTED TO EXTEND BETWEEN SAID PRONGS AND BELOW THE FREE ENDS THEREOF, AND MEANS FOR ROTATING VARIOUS OF SAID BRUSHES IN DIFFERENT DIRECTIONS TO MAINTAIN SAID IMALYING AND MOVE INDIVIDUAL FIBERS IN THE DIRECTION OF THEIR RESPECTIVE LONGITUDINAL AXES, WITH RESPECT TO THE OTHER FIBRES IN THE LAYER, SO AS TO PERMIT THE REARRANGED FIBER SEGMENTS TO REMAIN IN A CONDITION OF MECHANICAL EQUILIBRIUM IN THEIR NNEW POSITIONS IN THE AREAS BETWEEN THE PRONGS WHERE THEY DEFINNE SAID PREDETERMINED PATTERN OF HOLES.