Apparatus for the continued manufacture of staple fibers from thermoplastic materials

In the process, the strands, which are spun as a fused mass, are initially drawn, then preferably stretched, crimped or textured, and converted into helical windings. The helical windings are laid down on an endless conveyor formed by two conveyor belts laterally spaced from each other. The laid down helical winding turns are then cut between the two endless conveyors to produce two substantially identical fiber lengths from each helical winding turn. The melt spinning of the strands may be effected at such a high speed that the drawing of the filaments or fibers can be omitted. The helical winding turns, prior to cutting thereof, may be subjected to at least one after-treatment. The apparatus includes a rotary distributor into which the crimped strands are supplied substantially axially for conversion into helical winding turns, and includes endless belts tangentially engaging the helical winding turns to move the same downwardly onto the spaced pair of endless conveyor belts. The apparatus also includes clamping devices for clamping the lateral edges of the laid down helical winding turns prior to and during cutting thereof. The cutting devices are interchangeable, and may include two cutters arranged in series and alternately operative, cutter discs, or a revolving mount having several cutters projecting radially therefrom so that successive cutters may be brought into an operative position in succession.

FIELD AND BACKGROUND OF THE INVENTION 
This invention relates to a process and apparatus for the continual 
manufacture of staple fibers from thermoplastic materials, such as fully 
synthetic, filament-forming high polymers, polyethyleneterephthalates, or 
the like, by melt spinning, drawing and cutting in one operating phase at 
melt spinning speeds exceeding 3,000 m/min. 
In presently used processes for the manufacture of staple fibers from 
thermoplastic polymer filaments, two consecutive processing steps are 
required. In the first step, the spun filaments are joined to each other 
to form a cable and the cable is deposited in cans. In the succeeding 
second step, the cables are withdrawn from groups of cans, are joined 
together, after-treated, drawn, fixed, crimped, and finally cut. At the 
present time, spinning speeds range between 1,000 and 4,000 m/min, 
whereas, drawing speeds range only between 100 and 200 m/min. A combined 
process is economically feasible only if these spinning speeds can be 
substantially maintained. 
In one of the processes already proposed, namely, that shown in German 
Offenlegungsschrift No. 2,360,854, filaments, spun at high speed, are 
drawn by injector nozzle means and blown into an inclined cyclone tube, so 
that loops are produced. These loops are pulled out of the discharge end 
of the cyclone tube at a speed which amounts, however, to only one-tenth 
to one-five-hundredth of the speed at which the filaments are supplied to 
the cylone tube. Thus, the loops are laid one above the other and produce 
a cable. This cable is then prepared, as described above, crimped and cut 
in a continual process. 
The proposed process has the drawback that, in accordance with where the 
loop is cut, filament lengths are produced which in the most unfavorable 
case amount to the double length of a cut or, in extreme cases, only to a 
few millimeters. Particularly, excessively long filaments present problems 
for further processing. 
With processes proposed in British Pat. Nos. 824,223 and 796,684, loops are 
also produced but by inserting rods perpendicular to the moving direction 
of the approaching filaments. Aside from the fact that, at very high 
speeds, it becomes difficult to separate the filaments from the rods, in 
this case also both extremely long and extremely short filaments are 
produced. 
Bearing in mind the disadvantages of the known processes or the proposed 
processes, the objective of the present invention is to provide a process 
and apparatus, for the continual manufacture of staple fibers, which 
avoids both extra long and extremely short filaments. 
SUMMARY OF THE INVENTION 
In accordance with the invention, this problem is so solved that, 
initially, the filaments, spun as a fused mass, are drawn, singly or in a 
group, crimped, and then converted into helical windings with the winding 
turns being deposited and cut substantially in half so that two 
approximately identical fiber lengths are produced from each helical 
winding turn. 
In accordance with a development of the invention, a high melt spinning 
speed is provided so that a filament drawing stage can be omitted. 
In accordance with another characteristic of the invention, the filament 
helical windings are subjected to at least one after-treatment prior to 
the cutting stage. 
The present invenion is directed not only to a process but also to an 
apparatus for performing the process. Thus, means are provided for 
subjecting the filaments, which are drawn singly or in groups by 
stretching rollers or the like, to a crimping process by using a device 
for high speed texturing and for converting the filaments to helical 
windings by rotary layer means. After the helical winding turns are 
deposited onto two divided belt conveyors on which they arrive at a 
cutting device, their edges are clamped by pressure rollers or the like 
while the helical turns are engaged by cutters and cut through in the 
middle. Further features of the apparatus will be apparent from the claims 
and from the description of the accompanying drawing. 
With the invention as so far described, there is the considerable advantage 
that the helically coiled strand is cut in a longitudinal direction and 
not a transverse direction, so that extremely long and extremely short 
fibers are avoided and a uniform type of staple fiber is produced. 
An additional advantage of the invention, as compared with known processes, 
is that it is not a cable which is crimped but rather the individual 
filaments or groups of filaments are crimped. By virtue of this, and if 
required, a crimping which is substantially finer scalloped and more 
uniformly distributed over the capillary filaments is effected. 
Aside from a higher jet throughput, for example, higher spinning production 
and investment cost savings, the method and apparatus of the invention 
primarily produces savings in personnel and space requirements, because 
stretching can be omitted. If, based on the tolerable filter load, a 
further increase in spinneret throughput is impossible then, if so 
required, the perforation density in the jet and thus any sticking danger 
can be reduced. Because of reduced space requirements, the process and 
apparatus of the invention are particularly suitable for transferring the 
manufacture of staple fibers to wool or cotton spinning mills, for in such 
cases, it is no problem to plan small scale installations using a modular 
design. The cut-up filament layers can then be directly received, for 
example, through pneumatic means, by the flock mixer installation. Thus, 
formation of a bale in a baling press and the necessity of disintegrating 
the bale in an opener stage, then becomes superfluous. 
An object of the invention is to provide an improved process for the 
continual manufacture of staple fibers from thermoplastic materials. 
Another object of the invention is to provide an improved apparatus for the 
continual manufacture of staple fibers from thermoplastic materials. 
A further object of the invention is to provide such a process and 
apparatus, for the continual manufacture of staple fibers, which avoids 
the production of both super-long and extremely short filaments. 
For an understanding of the principles of the invention, reference is made 
to the following description of typical embodiments thereof as illustrated 
in the accompanying drawing.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring to FIG. 1, by way of example, two sets of four filaments 1, 
discharged from respective spinnerets, are provided with spinning 
preparations by preparation filament guides 2, and are guided around 
deflection rollers 3 and are fed to a stretching device in adjacent 
parallel relation to each other. It is also possible to arrange four or 
eight spinnerets in a circle in approximately the manner disclosed in 
German Offenlegungsschrift No. 2,453,816. Furthermore, instead of four 
individual spinnerets, in applicable cases, one large-scale spinneret can 
be used. 
Stretching preferably is effected between two three-roll sets 4 and 5. It 
will be apparent that, for the residual stretching of rapid-spun 
filaments, only a relatively narrow total looping angle over the rolls is 
required, so that three-roll sets, and possible even two-roll sets, 
generally are sufficient. Also, rapid-spun filaments can be 
cold-stretched. Although, with polyester silks, generally referred to as 
"PES," the extent of shrinking is very high, with a texturing stage 
subsequent to the stretching stage, the PES-filaments are deshrunk. 
However, the filaments can also be hot-stretched or thermally relaxed. 
Then, with very high spinning speeds, stretching can be completely 
omitted. In this latter case, the deflection rolls 3 assure a uniform 
filament draw-off. This results in a distinct qualitative improvement 
relative to an already proposed process, where the filaments are pulled 
off and stretched only by injector spinnerets. 
Following the strecthing stage, the filaments are fed to a high speed 
texturing device 6. For this purpose, for example, a compression-type 
texturing device can be used. However, steamjet, gear belt, and other 
known and suitable high-speed texturing devices also can be used in the 
invention process and apparatus. 
In any particular instance of spinning bi-component or other yarns, the 
crimping device is completely superfluous or may be replaced by a 
shrinking device. With long-staple fibers, for example, worsted yarn 
types, the four filaments grouped together are combined ahead of the 
texturing stage and textured together. Subsequently, they can be deposited 
together, also in a helically wound manner. On depositing short-staple 
types, for example, cotton types, very narrow windings must be produced. 
The total denier, therefor, should not become excessive. For this reason, 
requirements may call for texturing each individual one of the four 
filaments. In such a case, a four-fold texturing device, having four 
adjacent texturing chambers, is used. This is applicable also to 
long-staple fiber cases, where a very fine-scalloped crimping is required. 
From the crimping device 6, the filaments are delivered to a rotary deposit 
device, generally indicated at 9, through the medium of smooth or geared 
rolls 7, 8. These rolls, in any given case, can be omitted, for example, a 
space reduced development of a cable deposit device, already proposed in a 
different context, can be used. Also, other suitable types of rotary 
depositors can be utilized. According to the total denier to be deposited 
and the desired staple length, applicable single or four-fold rotary 
depositors can be used. 
The rotary depositor 9 shown in FIG. 1 substantially comprises a charging 
hopper 10 having a suction jet and a cutter device for feeding in 
filaments, a rotary depositor 11 for producing helical windings, as well 
as a downwardly directing conveyor device 13 comprising several, 
downwardly running conveyor belts 12 for stabilizing and uniformly 
depositing the helical windings. 
The magnitude of the windings and thus of the fiber staple length is given 
by the relationship 
EQU d=(v.multidot.cos.alpha.)/(.pi..multidot.n) 
where: 
d= the winding diameter, 
v= the speed of the fed filament, 
.alpha.= the helix angle (as a function of the speed of the downward 
conveyor device), 
and 
n= the angular velocity of the rotary depositor. 
Two fiber bundles are produced for each winding. The staple length can be 
varied by controlling the angular velocity of the rotary depositor. In 
each case, the downward conveyor device 13 must be adapted to the winding 
diameter, for example, by a coordinated timing of the speed of belts 12. 
Theoretically, it is feasible to set any desired staple-length 
distribution by a programmed variation in and/or control of the angular 
velocity. 
Helical turns 14 are moved on a conveyor device consisting of two parallel 
endless conveyor belts 15 and 15', shown more particularly in FIG. 3, 
which deliver the windings to the cutter stage. In advance of the cutter 
stage, and if required, after-treatment chambers, for example, for the 
deshrinking of bi-component filaments or the fixing of textured filaments, 
can be provided. Just before reaching the cutter device, the edges of the 
helical windings 14 are clamped by belts 16 and 16' engaging these edges 
from above. 
An exemplified embodiment of a cutter device is shown in FIGS. 2 and 3. As 
will be clear from FIG. 2, the cutter device is a dual-cutter type, for 
both winding bands, each consisting of four filaments. If eight filaments 
are to be individually deposited then, accordingly, an eight-fold cutter 
device is required, and this can also be a two-level design. 
Directly at their interface, the belts 15 and 16 and/or 15' and 16' are 
pressed together under high-load pressure by rollers 17 and 18 and/or 17' 
and 18', so that the winding edges are solidly or firmly clamped. The 
pressing belts or rollers are so supported that a free gap is provided 
between the respective pairs of bands 15, 16 and 15', 16'. A knife 19 
extends into this gap and cuts through the windings. To increase the 
knife-edge life, the winding heights can be interchanged or adjusted. 
Because the invention process and apparatus is a continual process, a 
flying type of cutter exchange is required. For this purpose, an interface 
consisting of pressure rollers 20 and 20', 21 and 21', and an interface 
consisting of a knife 22 are additionally provided. For practical reasons, 
the two interfaces are arranged in series and are used in alternation. 
Before removing a used knife for re-grinding, a new unused knife is 
inserted in the gap. By virtue of this, a continual cutting operation is 
assured. 
At the end of the pressing belt assemblies, a pneumatic extraction line 23 
is located. The end of the extraction tube is so arranged that two plates 
24 and 24', effective as lifters, extend into the gap between the belts 
and prevent the cut-up windings from sticking to the run-apart windings. 
FIG. 4 illustrates another embodiment of a cutter device, in which the 
knives 25 are arranged on a revolving or rotating head 26. For boosting 
the knife-edge life equally, the rotating mount 26 can be constructed for 
stepwise rotation. Because unengaged knives are exchanged, no second 
interface is absolutely necessary with the arrangement of FIG. 4. 
FIG. 5 illustrates a cutting arrangement where, instead of stationary 
knives, high-speed rotating cutting discs 27 and 28 are used. This design 
preferably is used if the cutter speeds of stationary and/or slowly 
interchanging knives are not sufficient. High cutter speeds also can be 
obtained by a rapid interchange of knives 19 and/or 22. Furthermore, other 
cutter means, for example, cutter bands, hot knives or wires, or even 
laser beams could be used. 
While specific embodiments of the invention have been shown and described 
in detail to illustrate the application of the principles of the 
invention, it should be understood that the invention may be embodied 
otherwise without departing from such principles.