Method and machine for forming random fiber webs

Abstract

To form a composite random fiber web containing long and short length fibers, the two types of fibers are fed simultaneously into the same lickerin but with the shorter fibers fed into the lickerin above the longer length fibers, that is, at a point spaced angularly in the direction of rotation of the lickerin in advance of the point at which the longer fibers are fed into the lickerin. The intermingled fibers are doffed from the lickerin by centrifugal force due to the high speed rotation of the lickerin and by an air stream traveling past the lickerin, and are conveyed by the air stream to a moving foraminate condenser on which they are laid down in random fashion. In one embodiment of the invention, two lickerins are provided and two sheets of short length wood pulp fibers are fed into each lickerin angularly in advance of but simultaneously with feed of a mat of longer length textile fibers into each lickerin. A divided air stream sweeps past the two lickerins to doff the fibers therefrom.

Description

The present invention relates to apparatus for producing random fiber webs, and more particularly for producing nonwoven fiber webs from two different types of fibers. In a more specific aspect, the invention relates to apparatus for making random fiber webs from combinations of wood pulp fibers and standard textile fibers.

It has been found that when blending short fibrous materials, such as prefluffed bleached wood pulp fibers, with fibrous materials which have a considerably longer length, such as most man made and natural fibers, normally referred to as textile length fibers, in machines for aerodynamically forming random fiber web structures, there is a strong tendency that these fibrous materials due largely to their greatly dissimilar physical dimensions will separate within the conveying air streams and fractionate to form a non homogeneous blend of components throughout the depth of the web, resulting in various fractions of the components to gravitate towards the condensing surface, and thus giving a nonuniform depthwise arrangement of the various particles, instead of being dispersed with web as a homogeneous blend without separation.

The primary object of this invention is to avoid this tendency of fractionation within the final web and to produce a well dispersed arrangement of the component fibrous materials within the final web structure.

Other objects of the invention will be apparent hereinafter from the specification and from the recital of the appended claims, particularly when read in conjunction with the accompanying drawings.

IN THE DRAWINGS

FIG. 1 is a diagrammatic view illustrating the principle upon which the present invention is based.

FIG. 2 is a detail view on an enlarged scale of the twin feed arrangement of a machine for forming random fiber webs built according to one embodiment of this invention;

FIG. 3 is a vertical sectional view illustrating the structure of a modified form of a machine for performing the present invention;

FIG. 4 is a somewhat similar view illustrating a further modification of the invention; and

FIG. 5 is a vertical sectional view of a still further modification of the invention.

It has been found that to prevent fractionation of short and long length fibrous materials in a random web formed by aerodynamic means, a multiple feed roll nose bar combination feeding to a single lickerin and a single conveying air stream produces a well dispersed final web structure, provided that the shorter fibrous materials are fed to the lickerin before the introduction of the textile length fibers.

The basic principle of the invention is illustrated diagrammatically in FIG. 1. Here pulp fibers and a mat of textile fibers are fed simultaneously to the same lickerin which in its rotation combs off the fibers and delivers them into a duct which conveys them to a foraminate condenser on which the fibers are laid down in random fashion to form the random fiber web. The shorter pulp fibers are fed into the lickerin above the longer textile fibers so that the pulp fibers are properly distributed in the random fiber web.

In FIG. 1, 10 designates a pulp roll from which a pulp web P is fed over a nose bar 11 by means of a feed roll 12 into a rotating lickerin 14. A mat of textile fibers (not shown) is fed over the nose bar 15 by the feed roll 16 into the same lickerin 14 but at a position angularly spaced around the lickerin from the feed roll 12 and nose bar 11 so that the shorter pulp fibers are fed into the lickerin above the longer textile fibers.

The fibers are doffed from the lickerin 14 into a duct 18 by centrifugal force due to the high speed of rotation of the lickerin and by an air stream, which is fed over the saber 17. Duct 18 conveys the air and fibers to an endless screen condenser 19, which moves transversely across the mouth of the duct 18 and over the rolls 20, 21 and 22. The fibers are laid down on this condenser in a random web, and the air passes therethrough.

Referring now to FIG. 2, 30 denotes the feed plate, 32 the conventional feed roll and 34, the conventional nose bar of a conventional textile feed mechanism of a random fiber web forming machine. A mat T of textile fibers is fed by the rotating feed roll 32 over the nose 34 of the feed plate 30 into a conventional rotating lickerin 36. The feed roll may be journaled at opposite ends in a pair of lever arms 38, which are pivoted at 40 on the feed plate 30.

In a machine built according to the present invention, twin pulp drive rolls 44 and 46 are disposed adjacent one another to engage the pulp sheet P travelling from the supply roll 10. These pulp drive rolls are preferaby rubber-covered. The lower one is journaled at opposite ends in brackets 48, which may be integral with or secured to the feed plate 30. The upper feed roll 44 is journaled at opposite ends in another bracket 50 which is mounted at opposite ends by eccentrics 52 on the upright 54 of the machine.

The upper feed roll 44 is continuously spring-pressed toward the lower feed roll 46 by a coil spring 54 which surrounds a stud 56 that is integral with the yoke 57 in which the opposite ends 60 of the feed roll 44 are journaled. This coil spring 54 abuts at its opposite end against a block 58 which is secured to, or integral with an adjusting screw 60 that is adjustable in the block 62 which is fastened to the bracket 50.

The lower feed roll 46 is journaled at opposite ends 62 in plates 64 which are adjustable on a yoke 68 toward and from the lickerin. For this purpose, the bolts 66, which fasten the plates 64 to the yoke 68, pass through elongate slots 70 in the plates 64.

Mounted on the plates 64 and 80 is the feed plate 72. A special nose bar 74 is secured on the feed plate 72 to extend adjacent the lickerin 36.

The feed plate 72 and nose bar 74 are fastened to the plates 64 and plate 80, respectively, by screws 76 and 78. The plate 80 is adjustable also toward and from the lickerin, and for this purpose the screws 82, which fastened the plate 80 to the brackets 48, pass through elongate slots 84 in the plate 80.

A knurled, roll-coin pulp feed roll 90 cooperates with the nose bar 74 to feed the pulp sheet into the lickerin. This feed roll 90 is journaled at opposite ends 92 in a yoke 94 that is spring-pressed toward the nose bar by a coiling spring 96, when is mounted around a stud 98 that is integral with the yoke 94, and which is disposed at its opposite end against the block 100, which is carried by the adjustable screw 102 that threads into the block 104. Block 104 is secured to the feed roll support plate 50.

Air for doffing the fibers from the high speed rotating lickerin is supplied to the space 110 between the block 80 and a plate 112 from a compressed air chamber 114, which is disposed within the block 80. This air feeds to a nozzle 116 adjacent the feed roll 32.

The fibers combed by the lickerin from the sheet P and from the mat T are doffed from the lickerin by the air stream from nozzle 116 and the centrifugal force produced by the high speed rotation of the lickerin.

Adjustment of the opening between the feed roll 90 and nose bar 74 is effected against the resistance of spring 54 by rotation of an eccentric 120, which is journaled at 122 on the feed roll support plate 50. Adjustment of the feed roll 32 toward and from the lickerin is effected by rotation of a screw 121, which passes through the lever 38, and which is carried by a member 123 that is pivoted at 124 on the support 125 for feed plate 30. A coil spring 126, which is disposed between the free end of the lever 38, and a nut 128 serves to resiliently press the lever 38 downwardly; and a coil spring 127, which surrounds the lower portion of the stud 121, counteracts to the desired degree this downward pressure.

In general, the sheet of pulp is fed into the pulp feed assembly via the rolls 44 and 46, guided along the feed plate 72 to the feed roll and nose bar 90, 74, and driven into the lickerin teeth at a low angle. The fluffed pulp fiber is held in the boundary layer of the lickerin 36 and must not be allowed to expand. Hence, the knee formed by the curved end of plate 80 (FIG. 2) is positioned only a few thousandths of an inch from the lickerin teeth, for example, from 0.007 to 0.012. At the lower point of the knee the air nozzle 116 provides an air stream of pressurized air into the nip of the textile feed section, causing the pulp fibers to be forced by this air stream into the advancing textile feed mat T at the same time that the teeth of the lickerin are combing the fibers from the mat T. The air stream also strips the textile feed roll of fibers which tend to collect on the surface of the lickerin due to its counterclockwise rotation. The combining of the two dissimilar short and long fibers is achieved. Blending is achieved by forcing the short pulp fiber into the area between the tips of the lickerin teeth and the outer drum surface of the lickerin. The blended mixture is then conveyed in normal manner to the product condenser 19 of the machine.

A seal 130 is secured to the plate 112 to engage the periphery of the feed roll 32 to prevent wipe off of textile fibers which might possibly be carried around by the feed roll 32 and not stripped therefrom by the teeth of the lickerin.

FIG. 3 is a more or less diagrammatic view looking at the opposite side of the machine from that shown in FIG. 2. Like reference numerals designate the same parts as shown in FIG. 2. The fibers doffed from the lickerin 36 by centrifugal force and the air stream flowing from the nozzle 116 are doffed into the duct 202. The space through which the fibers pass is controlled by the saber 200.

From the mouth of the duct 202, the fibers are carried by the recirculated air stream from duch 204 to an endless screen belt 206, which travels over rollers 208, 209, and 210. The air itself passes through the upper and lower reaches of this condenser screen 206 and the fibers carried by the air stream through the duct 202 are deposited on the upper reach of the belt where it passes transversely across the mouth of the duct 202.

Duct 202 communicates at its lower end, with a vacuum chamber 214. A suction fan 212, which is connected to the vacuum chamber 214 by ducts 216 and 218 and 220, operates through the duct 202 to such the fibers onto the upper reach of the screen 206 where it passes across the mouth of the duct 202.

Pivotally mounted dampers 222, which are adjustable in the duct 218 control the suction force produced by the fan 212. Similar dampers 224, which are disposed in the exhaust side 226 of the fan serve to control the exhaust from the fan to the recirculating duct 204. The exhaust stream passes into a chamber 228 and thence through the duct 204 upwardly across the saber 200. The tubular saber 200 is disposed at the juncture of the duct 202 and the duct 204.

Ports 229 may be provided at one side in the vacuum chamber 214 for pressure release.

A somewhat modified form of machine is shown in FIG. 4. The same reference numerals are employed in this figure to represent like parts as were employed in the figures previously described.

The principal difference between the machine of FIG. 4 and that of FIG. 3 is in the changed arrangement of the vacuum chamber and the suction fan. In FIG. 4 the air drawn from the duct 202 passes through the upper and lower reaches of the condenser 206 into the vacuum chamber 244, and thence through the ducts 250, 248 and 246 to the suction fan 242, which drives this air through the exhaust port 256 into the duct 228. Again dampers 252 in the connecting duct 248 control the rate of flow of air to the suction fan; and the pivoted dampers 254 adjacent the exhaust port 256 control the exhaust from the fan.

Ports 258 may be provided to control pressure release.

The principal difference between the units of FIGS. 3 and 4 and previous web formers is the use of the continuous screen conveyor and the vacuum box positioned below the condensing screen in such wise that the negative air pressure is made to pass through the screen mesh twice, thus allowing a larger area of flow, since in previous designs it was impossible to evacuate enough air due to the mechanical cross area restrictions. This new type of vacuum box also provides a settling chamber for grit to drop out which may pass through the screen and also allows adding dampered outlets so as to bleed the vacuum chamber into atmospheric air, hence using the former as a completely positive pressure machine.

The main difference between the two machines of FIGS. 3 and 4 is, as stated, the location of the vacuum chamber, one forward in the machine, and the other toward the rear. The latter enables the outlet ports to be positioned so that excess air can be returned into the expansion chamber of the machine.

FIG. 5 illustrates a still further modification of the invention in which a pair of lickerins and multiple feed assemblies to each lickerin are provided.

Here two separate rotary lickerins 36, 36' are employed, which are spaced from one another and mounted in parallel relationship with their axes in the same horizontal plane. Two sheets of pulp are fed to each lickerin. The pulp from supply roll 10 being fed to the lickerin 36 between the rolls 44 and 46, which are similar to those previously described, and over the feed roll 90 which feeds the pulp over the nose on the underside of the feed plate 300. Similarly pulp is fed from the supply roll 10' between the two rolls 44', 46' over the nose of the feed plate 303' into the lickerin 36, which is rotating clockwise as indicated by the arrow in FIG. 5.

Similarly pulp is fed from two supply rolls 10.sub.1 and 10.sub.2 to the lickerin 36', the pulp from supply roll 10, passing between the rolls 44.sub.1 and 46.sub.1 and being fed over the nose on the underside of the feed plate 300.sub.1 by the feed roll 90.sub.1 to the lickerin 36', and the pulp from supply roll 10.sub.2 being fed between the rolls 44.sub.2 and 46.sub.2 over the feed plate 303.sub.2 into the lickerin 36'. Compressed air from chambers 301, 301', 301.sub.1 and 301.sub.2 in the feed plate units 300, 300', 300.sub.1 and 300.sub.2 is discharged through nozzles formed in the inner ends of these units to direct air into the nips of the feed sections in the manner of nozzle 116, for example.

Textile fibers are supplied to the lickerin 36 from a tube or chute 302 which communicates with the trumpet 304 that extends partway around the rotary foraminate condenser 306. The textile fibers are doffed from the condenser 306 by the doffing roll 308 and fed by the feed roll 310 over the nose bar 312 of the feed plate 314 to the lickerin at a position disposed angularly around the lickerin 36 beyond the points where the pulp fibers are picked up by the lickerin.

Similarly other textile fibers are fed from the chute 302' into the trumpet 304' which carries them to the condenser 306', from which they are doffed by the doffing roll 308', and fed by the rotating feed roll 310' over the nose bar 312' of the feed plate 314' into the lickerin 36' beyond the point at which the shorter pulp fibers are picked up by the lickerin.

The fibers are doffed from the two lickerins 36 and 36' into a mixing chamber 320 by the centrifugal force due to the high speed rotation of the two lickerins and by streams of air which pass over the teeth of the lickerins. These streams of air originate from the air chamber 322 and are divided by the divider 324 so that they pass between the side walls 326 and 328 of the divider and the feed plates 314 and 314'. Two eccentrically mounted rolls 330 and 330' are in engagement with the flexible sidewalls of the divider 324 to determine the width of the two air streams.

The fibers from the mixing chamber 320 are deposited on an endless screen condenser 334 which passes over the rolls 336 and 338. Roll 336 is driven from a speed changer 340 by the motor 342 through the pulley 344, the belt 346 and the pulley 348.

A fan (not shown) sucks the fibers onto the condenser 334 while the air passes through the screen belt. The exhaust from this fan is through the ducts 350, 352 and 354 back to the air chamber 322.

The mixing chamber is bounded by sidewalls 356 and 358. The sidewall 358 as is well known practice is made in two sections 358' and 358", which are pivoted on one another so that the part 358" can be adjusted by a link 360 to vary the thickness of the web laid down on the endless condenser 334.

The double feed work in all embodiments of this invention results in the shorter pulp fibers being fed above the longer textile fibers but with the shorter fibers kept within the boundary layer flow of the lickerin and held very close to the teeth of the lickerin so that these shorter pulp fibers are forced into the advancing textile feed mat and intermingled into the textile fibers before the two materials are combed out at the lower feed area. Hence, a double combing action is encountered by the pulp fibers.

While the invention has been described in connection with several different embodiments thereof, it will be understood that it is capable of further modification; and this application is intended to cover any modifications of the invention coming within the scope of the invention or limits of the appended claims.

Claims

Having thus described my invention, what I claim is:

1. The method of forming a random fiber web composed of both short length and long length fibers which comprises feeding sheets of the two types of fibers simultaneously into a rotating lickerin with thhe sheet of shorter length fibers being fed into the lickerin at a first feed point disposed angularly around the lickerin, in the direction of rotation of the lickerin, in advance of a second feed point at which the sheet of longer length fibers are fed into the lickerin, pneumatically doffing the short fibers into the second feed point to force the short fibers into the longer fibers being fed at the second feed point, thereby forming a blend of the short and long fibers, doffing the blended fibers from the lickerin by an air stream and the centrifugal force produced by the high speed rotation of the lickerin, and conveying the doffed fibers in the air stream to a moving foraminate condenser to deposit them in random fashion on the condenser.

2. The method according to claim 1, wherein the short length fibers are pulp fibers, and the long length fibers are textile fibers.

3. A machine for forming a random fiber web, comprising

a rotary lickerin,

two feed plates disposed one in advance of the other around the periphery of the lickerin,

means for feeding a sheet of short length fibers over said one feed plate so that the lickerin combs fibers, as it rotates, from said sheet,

means adjacent the periphery of said lickerin to prevent expansion of the combed fibers carried by the lickerin from said one toward the other of said plates,

means for simultaneously feeding a mat of longer length fibers over said other feed plate so that the lickerin also combs fibers as it rotates, from said mat,

means for pneumatically doffing the short fibers from the lickerin and blending them into the longer fibers at the point where the longer fibers are combed from said other feed plate,

further means for doffing the blended fibers from the lickerin, and

means for receiving the doffed fibers and forming a random web therefrom.

4. A machine as claimed in claim 3, wherein the means for feeding said mat into the lickerin includes a rotary feed roll,

said feed roll is rotatably mounted on a support which is adjustable to adjust the nip between the feed roll and said other feed plate, and

pneumatic doffing means comprises an air stream directed into the nip between said said feed roll and said lickerin to doff the shorter length fibers from the lickerin and force them into the mat at the same time that the lickerin is combing fibers from said mat.

5. A machine as claimed for in claim 4, wherein

said receiving means comprises

a moving foraminate condenser, and

said further doffing means comprises means for conducting the fibers, which are doffed from the lickerin, in an air stream to said condenser to lay the fibers down in random fashion on said condenser.

6. A machine as claimed in claim 5, wherein the last-named means comprises

a first duct into which the blended fibers are doffed,

a suction fan for drawing air from said first duct through said condenser, and

a second duct for conveying exhaust air from said fan back to the first-named duct to aid in conveying the doffed fibers through said first-named duct to said condenser.

7. A machine as claimed in claim 6, wherein means are provided in said second duct for adjustably controlling the rate of flow of air therethrough.

8. A machine as claimed in claim 7, wherein a third duct connects said first-named duct with said suction fan, and

means are provided in the last-named duct for adjustably controlling the rate of flow of air from said first-named duct to the suction side of said fan.

9. A machine as defined in claim 3, wherein said means for preventing expansion of the combed fibers carried by the lickerin comprises a knee member adjustably mounted between said two feed plates and having a curved surface disposed in spaced, confronting relation to the perphery of said lickerin between the plates.

10. A machine for forming a random fiber web, comprising

two lickerins mounted for rotation about spaced parallel axes,

a first feed plate associated with each lickerin over which a sheet of wood pulp fibers may be fed into the lickerin,

a second feed plate associated with each lickerin over which a mat of textile fibers may be fed into the lickerin,

each of said first feed plates being disposed angularly in advance of the associated second feed plate in the direction of rotation of the respective lickerin,

means associated with each of said first feed plates for feeding the pulp sheets over said first feed plates,

means associated with each of said second feed plates and operable simultaneously with the first-named feeding means to feed said mats over said second feed plates simultaneously with the feeding of said sheets over their respective feed plates,

means positioned between the first and second feed plates, respectively, of each pair thereof to hold combed wood pulp fibers against expansion during conveyance by the associated lickerin from the first feed plate to the second feed plate of a pair,

means for pneumatically doffing the wood fibers from each lickerin and blending them into the textile fibers at the points where the textile fibers are fed to the associated lickerins, and

further means for doffing the blended fibers from the lickerins.

11. A machine as claimed in claim 10, having

a first duct,

means for directing an air stream into said first duct,

means dividing said first duct into two separate passageways through which the air stream flows past the two lickerins, respectively, to effect the doffing of the blended fibers from the two lickerins simultaneously,

a mixing and expansion chamber, which is open at its lower end, disposed beneath said passageways in communication therewith and into which the fibers doffed from the lickerins are carried by the air streams,

a foraminate condenser movable across the open lower end of said chamber, and

suction means disposed in operative relation to said condenser to cause fibers to be drawn from said chamber and deposited on said condenser to form a random fiber web thereon.