Process for making spun-filament fleece from endless synthetic resin filament

The process for making the spun fleece proceeds in a filament-spinning unit having a spinning nozzle system, a cooling shaft, a stretching aperture, a diffuser shaft, a continuously moving fleece recovery conveyor and a device for feeding process air and for drawing outflowing air through the fleece recovery conveyor. The cooling shaft has a shaft wall provided with a plurality of air orifices. That allows process air required for cooling to be fed into the cooling shaft. That air flow at least partially is drawn through the fleece recovery conveyor. The thickness of the spun fleece is measured on the fleece recovery conveyor in the transport direction downstream of the diffuser shaft. The measured value is compared with a predetermined set value. On deviation of the measured value from the set value the setting angle of the air control flap or flaps which are located adjacent the entrance of the stretching aperture is changed. On a positive deviation of the measured value of the thickness from the set value the setting angle is increased, on a negative deviation the set value is reduced.

CROSS REFERENCE TO RELATED APPLICATIONS 
This application is related to the commonly owned applications Ser. Nos. 
119,141, 119,197, 119,398, 119,469, 119,339, all filed 10 Nov. 1987 
FIELD OF THE INVENTION 
My present invention relates to a process for making spun fleece from 
synthetic resin filament. 
BACKGROUND OF THE INVENTION 
A process for making spun fleece or nonwoven mat from endless synthetic 
resin filament using a filament-spinning unit is known. The 
filament-spinning unit includes a spinning nozzle system, a cooling shaft, 
a stretching aperture, a diffuser shaft, a continuously moving fleece 
recovery conveyor and a device for feeding process air and for drawing 
outflowing air through the fleece recovery conveyor. The cooling shaft has 
a shaft wall provided with a plurality of air orifices and process air 
required for cooling is admitted through the air orifices to provide an 
air flow. The air flow is at least partially drawn through the fleece 
recovery conveyor. 
According to the features of the known filament-spinning unit, the process 
parameters such as the flow rate of thermoplastic material, process air, 
the transport speed of the fleece recovery conveyor and the geometric 
parameters of the filament-spinning unit are set up so that the spun 
fleece is produced with as exact and as uniform a given thickness as 
possible. In other words it has a preset surface or area weight. However 
in the existing process and/or in the existing filament-spinning unit it 
is not possible to successfully correct or even control thickness 
deviations from a uniform thickness. The thickness deviations have up to 
now been considered as intrinsic to the system. 
OBJECT OF THE INVENTION 
It is an object of my invention to provide a process for making spun fleece 
or nonwoven mat from endless synthetic resin filament which avoids these 
drawbacks. 
It is another object of my invention to provide a process for making a spun 
fleece from an endless synthetic resin filament in which on deviation of 
the thickness of the spun fleece from a given setpoint value the thickness 
can be easily corrected. 
It is another object of my invention to provide a process for making spun 
fleece from endless synthetic resin filament in which on deviation of the 
thickness of the spun fleece from a setpoint value the thickness can be 
easily corrected over the entire fleece width and which can be easily 
performed in a filament-spinning unit. 
SUMMARY OF THE INVENTION 
These objects and others which will become more readily apparent 
hereinafter are attained in accordance with my invention in a process for 
making a spun fleece from an endless synthetic resin filament in a 
filament-spinning unit including a spinning nozzle system, a cooling 
shaft, a stretching aperture, a diffuser shaft, a continuously moving 
fleece recovery conveyor and a device for feeding process air and for 
drawing outflowing air through the fleece recovery conveyor. The cooling 
shaft has a shaft wall which is provided with a plurality of air orifices 
and process air required for cooling is admitted through the air orifices 
to provide an air flow. The air flow is at least partially drawn through 
the fleece recovery conveyor. 
According to my invention the process further comprises measuring the 
thickness of the spun fleece on the fleece recovery conveyor in the 
transport direction downstream of the diffuser shaft, comparing at least 
one measured or average value of the thickness with at least one 
predetermined setpoint value and on a deviation of the measured value or 
values or the average value from the setpoint value or values a setting 
angle of at least one air control flap which is located adjacent the 
entrance of the stretching aperture is changed so that on a positive 
deviation of the measured value or values or the average value from the 
setpoint value or values (i.e. the measured or average value is larger 
than the setpoint value) the setting angle is made larger and on a 
negative deviation of the measured value or values or the average value 
from the setpoint value or values the setting angle is reduced. 
In one example of the process for making a spun fleece according to my 
invention in the filament-spinning unit having at least one pair of 
opposing air control flaps forming a narrow outlet gap opposite the 
stretching aperture only one of a pair of air control flaps is operable to 
correct the deviation of the measured or average value from the setpoint 
value. 
In another example of my invention in the filament spinning unit having at 
least one pair of opposing air control flaps forming a narrow outlet gap 
opposite the stretching aperture, both of the air control flaps are 
synchronously operable. 
In the scope of my invention several and/or several pair of air control 
flaps are provided in succession in the direction of recovery of the 
endless synthetic resin filament. 
The thickness of the spun fleece can be measured as a mean value over the 
entire spun fleece width or over a portion of the spun fleece width. Then 
in the scope of my invention this measured mean value can be exactly 
adjusted to a suitable setpoint value. 
One particularly advantageous example of my invention however leads to a 
very homogeneous spun fleece thickness over the entire spun fleece width. 
Here the thickness of the spun fleece being measured over the entire spun 
fleece width at different measuring points x.sub.1, x.sub.2, . . . 
,x.sub.n and the setting angle of the air control flap and/or air control 
flaps being adjusted differently at the adjusting points y.sub.1,y.sub.2, 
. . . y.sub.n corresponding to the measuring points x.sub.1, x.sub.2, 
x.sub.n. 
Furthermore the air control flaps can be elastically deformable. The air 
control flaps can also be divided into segments which are each adjustable 
differently. 
In the scope of the process of my invention the measurement of the 
thickness of the spun fleece can occur in an easy way. The simplest 
approach to the thickness measurement involves using transmitted 
radiation, for example produced by radioisotopes. It is understood that 
for adjustment of the air control flaps suitable positioning drives (e.g. 
servomotors) are provided. 
The attained advantages of my invention are such that on deviation of the 
spun fleece thickness from a predetermined set value the thickness can be 
corrected to the setpoint value in an easy way while engaged in the 
filament-spinning apparatus so that a very exact and uniform thickness 
over the entire fleece width can be attained. 
Of specially advantage is the fact that a filament-spinning apparatus 
equipped for performing the process of my invention does not differ 
substantially from the existing fleece-making apparatus when the 
additional measuring devices are included and the air control flap or 
flaps are provided. The finished product, namely the spun fleece made from 
an endless synthetic resin filament, is improved considerably in its 
quality.

SPECIFIC DESCRIPTION 
The unit or apparatus shown in the drawing produces a spun fleece 1 made 
from endless synthetic resin filaments 2. This unit comprises a spinning 
nozzle system 3, a cooling shaft 4, a stretching aperture 5, a diffuser 
shaft 6 and a fleece recovery conveyor 7. 
Devices 8, 9 for feeding process air and for drawing outflowing air through 
the fleece recovery conveyor 7 are provided. 
The cooling shaft 4 has a shaft wall 11 provided with air orifices 10. The 
shaft wall 11 however can also be formed as a flow directing device in the 
form of a screen or grid. Because of this process air required for cooling 
is introducable into the cooling shaft 4. 
The cooling shaft 4 has an upper intensive cooling region 12 and a lower 
additional cooling region 13 as well as suitable air flow dividing guiding 
walls or baffles 14 connected to the shaft wall 11. The air flow dividing 
guiding walls 14 are of adjustable height and the height of the intensive 
cooling region 12 is adjustable because of or by that height 
adjustability. 
Opposing air control flaps 15 on opposite sides of the unit, converging 
like a wedge in the feed direction of the endless filaments 2 and 
connected to the shaft wall 11 are connected in series with the stretching 
aperture 5. These flaps 15 have an outlet gap 16 which opens to the 
stretching aperture 5. In FIG.2 both these air control flaps 15 have an 
adjustable setting angle a (defined between the flap and the adjacent wall 
converging toward the stretching aperture 5) and are movable about a 
horizontal axis 17 as is indicated in FIG. 2 by curved arrows. The 
structure is designed so that the setting angles a and thus the width of 
the outlet gap 16 is adjustable differently over the entire length of the 
air control flap 15. For that appropriate positioning elements can be 
provided. 
The diffuser shaft 6 is provided with pivotable wings 18 defining the flow 
cross section which are movable about a horizontal axis 19. Opposing pairs 
are positioned above each other in this example in several steps and are 
adjustable independently of each other. Also they can be set at different 
setting angles with suitable positioning elements. 
The device 9 for drawing outflowing air has an adjustable damper 20 below 
the fleece recovery conveyor 7 (it can also be above the conveyor) with 
which the width of the outflowing air flow measured in the transport 
direction of the fleece recovery conveyor 7 is adjustable. It can be 
operated with a closed or partially closed air flow for the process air 
and for the outflowing air. 
In any case the apparatus according to my invention does not operate with 
three separate air flows but with a single process air flow which, as 
described, is divided into a partial flow of air for the intensive cooling 
region 12 and a partial air flow for the additional cooling region 13. 
The fleece recovery conveyor 7 which is a wire cloth conveyor is equipped 
with a thickness measuring device for the thickness of the spun fleece 1. 
The thickness of the spun fleece 1 is thus measured over the spun fleece 
width at the measuring points x.sub.1,x.sub.2, . . . , x.sub.n or of 
course at a single measuring point. The air control flaps 15 which are 
located upstream of the stretching aperture 5 and which each have a 
horizontal pivot axis 17 are adjustable relative to or against the air 
flow in regard to their setting angle a according to the deviation of the 
measured thickness value or values or an average thickness value from the 
predetermined setpoint value or value. 
In FIGS. 1 and 2 two opposing air control flaps which are synchronously 
adjustable are provided. The air control flaps 15 are elastically 
deformable and consequently adjustable over their length with different 
adjusting angles a and of course with the adjusting points 
y.sub.1,y.sub.2, . . . ,y.sub.n corresponding to the measuring points 
x.sub.1,x.sub.2, . . . , x.sub.n . Different positioning drives 22 are 
indicated in FIG. 2. 
The thickness measuring device 21, the positioning drives 22 of the air 
control flaps 15 with which the setting angle a is adjustable and the 
setpoint value adjustment are part of a feed back control loop 23 which 
was illustrated in FIG. 2 and to which a controller 24 with a setpoint 
value adjusting device 25 belong. A control of the thickness and thus a 
control of the surface weight results. 
The thickness of the spun fleece 1 is measured on the fleece recovery 
conveyor 7 in the transport direction downstream of the diffuser shaft 6. 
The measured value or values is compared with a predetermined setpoint 
value or values and on deviation of the measured value or values from the 
setpoint value or values the setting angle a of the air control flaps 15 
which are located adjacent the entrance of the stretching gap 5 is 
changed. Of course on a positive deviation of the measured value or values 
from the setpoint value or values (measured value greater than setpoint 
value) the setting angle a is increased, on a negative deviation of the 
measured value from the setpoint value the setting angle a is reduced. 
By the device for feeding process air I mean the shaft wall 11 with the air 
orifices 10, the baffles 14 and other similar members as well as an 
unillustrated air blower or pump. 
FIG. 3 shows an additional example of my invention in which only one of the 
pair of opposing air control flaps 15 on opposite sides of the blower 
shaft adjacent the entrance of the stretching aperture 5 is controlled or 
adjusted by the positioning drive 22.