Fiber supply arrangement for open-end rotor spinning

In the case of an open-end rotor spinning arrangement, in which the spinning rotor is arranged in a housing which is connected to a vacuum source, a fiber feeding duct is provided which extends from an opening roller to the area of a sliding surface which widens conically to form the fiber collecting surface of the spinning rotor. The smallest cross-section of the fiber feeding duct is situated at a distance from the mouth which is constructed as a slot, the height of which in the axial direction of the spinning rotor is much smaller than the ideal diameter of the smallest cross-section. The ideal diameter is defined as that diameter which corresponds to a circular area corresponding to the smallest cross-section.

BACKGROUND AND SUMMARY OF THE INVENTION 
This invention relates to an arrangement for open-end rotor spinning 
comprising a spinning rotor which has a fiber collecting groove and a 
sliding surface which conically widens to the fiber collecting groove. A 
mouth of a fiber feeding duct is directed toward the sliding surface. The 
fiber feeding duct tapers in the fiber transport direction and starts at 
an opening roller. A housing which receives the spinning rotor is 
connected to a vacuum source and is provided with a covering which has a 
projection which projects into the open end of the spinning rotor while 
leaving an overflow gap for transport air and contains the mouth of the 
fiber feeding duct. The fiber feeding duct starts at the opening roller 
with a width that corresponds to the working width of the opening roller. 
The mouth of the fiber feeding duct is larger in the circumferential 
direction of the spinning rotor than in its axial direction. 
An arrangement of this type represents the state of the art on the basis of 
the German Patent Document DE 37 04 460 A1. In the case of the 
construction of the known arrangement, the mouth of the fiber feeding duct 
has the smallest cross-section which, however, because of its special 
development, is so large that a sufficient amount of transport air can 
flow through the fiber feeding duct. The reason is that the amount of 
transport air is largely determined by the fact that a fly is to be 
avoided in the area of the opening roller. On the one hand, the feeding of 
the supplied fibers onto the sliding surface of the spinning rotor should 
take place at a sufficient distance from the fiber collecting groove and, 
on the other hand, at a safe distance from the open end of the spinning 
rotor. For this reason, in the known arrangement, the height of the fiber 
feeding duct in the axial direction of the spinning rotor should be kept 
as small as possible. However, so that nevertheless a sufficient amount of 
air can flow out through the mouth of the fiber feeding duct, the mouth is 
wider than normal in the circumferential direction of the spinning rotor. 
The problems with respect to the height of the mouth in the axial 
direction of the spinning rotor occur particularly in the case of 
high-speed arrangements for open-end rotor spinning which use particularly 
small spinning rotors of diameters that are partially below 30 mm. The 
known arrangement is a step in the right direction, but is not extensive 
enough. 
Arrangements for open-end rotor spinning comprising so-called fiber guiding 
screens are known, as described, for example, in the German Patent 
Document DE 37 19 959 A1. Fiber guiding screens of this type have the 
purpose of separating the fibers to be fed to the sliding surface from the 
yarn to be withdrawn from the fiber collecting groove of the open-end 
spinning rotor. Even when the fiber feeding ducts are relatively short, 
such fiber guiding screens are capable of guiding the fibers at a secure 
distance from the fiber collecting groove onto the sliding surface. 
However, the fiber guiding screens used in the machines in practice have 
the disadvantage that the fiber feeding ducts connected in front of them 
are so short that the fed fibers are not sufficiently stretched and 
arranged in parallel. 
The invention is based on the object of developing an arrangement of the 
initially mentioned type in such a manner that the spinning can take place 
by means of small spinning rotors, in which case the supplied fibers are 
fed onto the sliding surface of the spinning rotor in a targeted manner 
and in which case the air throughput through the fiber feeding duct is 
sufficient with respect to keeping the opening roller clean. 
As noted above, the present invention is especially advantageous for 
spinning with spinning rotors having a maximum diameter at the collecting 
groove of less than 30 mm. In certain preferred embodiments of the 
invention the maximum diameter of the collecting groove is between 26 mm 
and 30 mm, with optimum practical embodiments having a collecting groove 
diameter of about 28 mm. 
With these small diameter collecting grooves, the rotors contemplated by 
the invention preferably have a rotor open end diameter of between 21 mm 
and 23 mm, with optimum practical embodiments having a rotor open end 
diameter of about 22 mm. The angle of the fiber slide wall, from the fiber 
impact on the rotor wall to the collecting groove with respect to a rotor 
radial plane, is preferably between 76.degree. and 79.degree., with 
optimum practical embodiments having such slide wall inclined at 
77.5.degree. with respect to a rotor radial plane. 
This object is achieved according to preferred embodiments of the invention 
in that the smallest crosssection of the fiber feeding duct is at a 
distance from the mouth and in that the mouth is constructed as a slot the 
height of which, in the axial direction of the spinning rotor, is 
significantly smaller than the ideal diameter of the smallest 
cross-section, in which case the ideal diameter is defined as the diameter 
of a circular area corresponding to the smallest cross-section. 
The smallest cross-section of the fiber feeding duct tapering to this point 
is therefore placed back into an area in which it does not yet present any 
difficulties constructionally to dimension the size of the crosssection 
for a sufficient air throughput. By means of the construction as a slot, 
the height of the mouth of the fiber feeding duct in the axial direction 
of the spinning rotor can be maintained sufficiently small so that, if 
possible, all fibers fed onto the sliding surface still have a 
sufficiently long sliding path to the fiber collecting groove. The outlet 
cross-section on the mouth is nevertheless dimensioned to be sufficiently 
ample because no extreme precision of the fiber feeding is required in the 
circumferential direction of the spinning rotor. It is largely unimportant 
at which angular degree of the circumference the fibers arrive on the 
sliding surface. It is only with respect to the distance from the fiber 
collecting groove and from the open end of the spinning rotor that extreme 
precision is required. 
According to especially preferred embodiments of the invention, the fiber 
feeding duct mouth is disposed and dimensioned so that the fiber impact 
point on the rotor wall is disposed at a position more than two-thirds 
(2/3) of the total axial length of the spinning rotor between the fiber 
collecting groove and the open end of the rotor. This assures a 
sufficiently long travel path from the fiber impact point to the 
collection grooves for all of the supplied fibers, even with the small 
diameter rotors of the type contemplated by the invention. 
In an advantageous development of the invention, the length of the fiber 
feeding duct corresponds at least to twice the medium staple length of the 
fiber material to be spun. A sufficiently long fiber feeding duct has the 
advantage that a certain stretching of the fibers takes place in it. The 
fiber feeding duct has an aligning effect which is also created by the 
fact that the air is accelerated in the transport direction of the fibers. 
The combination is obtained of a good stretching of the fibers with a very 
precise feeding onto the sliding surface without any reduction of the 
available air. 
Advantageously, the slot is bounded on the side facing the fiber collecting 
groove by a fiber guiding surface which extends directly to the sliding 
surface. As a result, the fibers can be transferred to the sliding surface 
of the spinning rotor in a particularly targeted manner. 
Advantageously, the smallest cross-section of the fiber feeding duct has a 
circular area. It was found that round fiber feeding ducts are 
particularly advantageous with respect to the fiber orientation. However, 
after the fibers have been bundled, it is no longer disadvantageous if the 
cross-section of the fiber feeding duct changes directly at the mouth. In 
a further development of the invention, the slot therefore has a 
rectangular cross-section. This results, on the one hand, in the 
sufficient air throughput which is not longer reduced with respect to the 
smallest cross-section and, on the other hand, in the precise target 
direction when the fibers are fed onto the sliding surface. 
In especially preferred embodiments of the invention, the ideal diameter at 
the smallest cross-section of the fiber feeding duct is between 4 mm and 5 
mm, with optimum practical embodiments having an ideal diameter of 4.5 mm, 
resulting in a cross-sectional area of about 17 mm.sup.2. Especially 
preferred embodiments then have a corresponding axial extent of the fiber 
feeding mouth slit of between 2 mm and 3 mm. This configuration of the 
fiber feeding duct facilitates the desired fiber feeding impact point on 
the rotor side wall at a position at least two-thirds (2/3) of the axial 
length of the distance between the collecting groove and the rotor open 
end, while also assuring that the supplied fibers are not spilled over the 
open end of the rotor. 
Advantageously, the length of the slot corresponds to approximately half 
the diameter of the spinning rotor. Thus, the fibers are guided along a 
sufficient length on the fiber guiding surface. 
The fiber guiding surface definitely does not have to be situated 
perpendicularly with respect to the axis of the spinning rotor but may be 
constructed to be askew with respect to this axis. The fiber guiding 
surface may therefore be adapted to the natural moving direction of the 
fibers. 
In a particularly advantageous further development of the invention, the 
mouth is arranged in a separate component containing the end section of 
the fiber feeding duct. As a result, the mouth can be manufactured in any 
manner because it can be produced separately from the fiber feeding duct 
and is subject to virtually no limitations with respect to its shape. The 
reason is that it is difficult to provide a one-piece fiber feeding duct, 
starting from the working width of the opening roller, later with a round 
cross-section and provide it again at the mouth with a rectangular shape. 
However, the separate component allows such a shape. 
The separate component can advantageously be exchanged for an adaptation to 
different fiber materials and/or spinning conditions. Thus, the fiber 
feeding duct, as a whole, can be maintained but the critical area of its 
mouth can nevertheless be adapted to the respective conditions, 
particularly when especially small diameters of spinning rotors are used. 
Expediently, the overflow gap is reduced in the area of the mouth of the 
fiber feeding duct. As a result, it is avoided that in this particularly 
critical area air flows off over the front rotor edge and thus removes fed 
fiber in an undesirable manner instead of having these fibers transported 
to the fiber collecting groove. 
The fiber guiding surface is expediently constructed as a circular segment. 
As a result, the fed fibers can be guided to the sliding surface in an 
approximately tangential direction. 
Preferably, the height of the slot is smaller than half the ideal diameter 
of the smallest cross-section of the fiber feeding duct. On the one hand, 
this permits a high availability of air but, on the other hand, a precise 
feeding of the fiber onto the sliding surface. 
Other objects, advantages and novel features of the present invention will 
become apparent from the following detailed description of the invention 
when considered in conjunction with the accompanying drawings.

DETAILED DESCRIPTION OF THE DRAWINGS 
FIG. 1 shows only the parts of an arrangement for open-end rotor spinning 
which are required for understanding the invention.. The other components, 
which are not shown, may correspond to the design of arrangements for 
open-end rotor spinning which are currently customary. 
The arrangement according to FIG. 1 comprises an opening roller 1 which is 
provided on its circumference with a mounting 2 of needles or saw teeth. 
The opening roller 1 is disposed in a housing 3 and is driven outside the 
housing 3 in a manner which is not shown. On the operating side, the 
opening roller 1 is closed off by a covering 4. 
By way of a feeding device, which is not shown, a sliver is fed to the 
opening roller 1, which sliver is combed out by the opening roller 1 and 
in the process is separated into individual fibers. The fibers which are 
separated by the opening roller 1 are fed by way of a fiber feeding duct 5 
to a spinning rotor 6. The fiber feeding duct 5 starts with a first 
section 7 extending approximately tangentially with respect to the opening 
roller 1 in the housing 3. Part 7 of the fiber feeding duct 5 is continued 
in a straight line from part 8 which is a component of a covering 9. In a 
manner which is not shown, the covering 9 is movably mounted on the 
arrangement for open-end rotor spinning in such a manner that, because it 
is moved away, the spinning rotor 6 can be exposed on its front side. 
Between parts 7 and 8 of the fiber feeding duct 5, a sliding joint 10 is 
disposed, in which a sealing device is provided so that no secondary air 
penetrates into the fiber feeding duct. 
The spinning rotor 6 is arranged in a housing 11 which forms a vacuum 
chamber 12 which is connected to a vacuum pipe 13. The spinning rotor 6 is 
provided with a shaft 14 which penetrates the rear wall of the housing 11 
and which is disposed and driven outside the housing 11 in a manner that 
is not shown in detail. 
The covering 9 closes off the housing 11 containing the spinning rotor 6 on 
the side of the open end 15 of the spinning rotor 6. Between the housing 
11 and the covering 9, a surrounding sealing ring 16 is arranged. The 
covering 9 is provided with a projection 17 which projects into the 
spinning rotor 6. The projection 17 contains the mouth 18 of the fiber 
feeding duct 5 which will be explained in detail in the following. 
Concentrically to the spinning rotor 6, a yarn withdrawal nozzle 19 is 
provided in the projection 17, a yarn withdrawal duct 20 beginning in this 
yarn withdrawal nozzle 16. 
The spinning rotor 6 has a sliding surface 21 which widens from the open 
end 15 of the spinning rotor 6 conically into a fiber collecting groove 
22. During the spinning, the fibers are transported from the opening 
roller 1 by way of the fiber feeding duct 5 in an air current to the 
sliding surface 21. Inside the spinning rotor 6, the air current is 
separated from the fibers. The air current flows off toward the outside by 
way of a ring gap 23 which was left between the open end 15 of the 
spinning rotor 6 and the projection 17 as well as the interior surface of 
the covering 9. 
Because of the high centrifugal force affecting them, the fibers slide on 
the sliding surface 21 into the fiber collecting groove 22 where they are 
collected and bound into a yarn which is withdrawn by way of the yarn 
withdrawal nozzle 19 and the yarn withdrawal duct 20. 
During the spinning, in must be ensured that the fibers arrive on the 
sliding surface 21 at a sufficient distance from the fiber collecting 
groove 22 so that they can slide in such a manner that they are still 
stretched and placed in parallel. In addition, it must be ensured that, if 
possible, no fibers are sucked by way of the open end 15 of the spinning 
rotor 6 through the ring gap 23. This presents a problem especially when 
particularly in the case of high rotational speeds of the spinning rotor 
6--extremely small spinning rotors 6 are used, for example with a diameter 
of approximately 30 mm in the fiber collecting groove 22. The mouth 18 of 
the fiber feeding duct 5 cannot be reduced to the same extent because when 
the required amount of air would no longer flow through the fiber feeding 
duct 5. 
FIG. 1A schematically depicts the radial projection of the mouth 18, having 
the height h in the axial direction and a width w. However, an amount of 
air that is too small would result in fiber fly accumulation on the 
opening roller 1. 
According to the invention, the narrowest cross-section 24 of the fiber 
feeding duct 5 is at a distance from the mouth 18 which is constructed as 
a slot in a manner indicated below. The smallest cross-section 24 
advantageously is a circular area; however, it may also have an oval or 
other design. Based on the smallest cross-section 24, a circular 
cross-section of an equal size can be calculated, the diameter of which is 
called the ideal diameter and must clearly be larger than the height h of 
the slot forming the mouth 18, in the axial direction of the spinning 
rotor 6. 
In the case of the construction according to FIG. 1, the mouth 18 is 
advantageously situated in a separate component 25. This separate 
component 25 is part of the cover 9 which, however, --apart from the mouth 
18--is no longer in one piece with the component containing part 8 of the 
fiber feeding duct 5. As a result, the slot for the mouth 18 can easily be 
designed according to the invention. As it were, an intermediate piece 
which contains the mouth 18 and forms the separate component 25 is 
inserted between the yarn withdrawal nozzle 19 and the actual fiber 
feeding duct 5. This separate component 25 may be considered as a thick 
washer which contains a recess with a fiber guiding surface 26. 
The construction of the fiber guiding surface 26 and the design of the slot 
of the mouth 18 can be determined by testing. Both constructions are such 
that the fibers passing through the fiber feeding duct 5 are kept from 
arriving on the sliding surface 21 too closely to the fiber collecting 
groove 22. The height h of the slot should correspond only to 
approximately half the ideal diameter of the smallest cross-section 24 so 
that the fibers arrive on the sliding surface 21 in a well bundled state. 
As will be illustrated in the following by means of FIGS. 2 to 5, the slot 
is wider in the circumferential direction of the spinning rotor 6. The 
mouth 18 is therefore constructed as a transversely placed loophole. 
The arrangement according to the invention has the advantage that there are 
virtually no more fibers which arrive directly in the fiber collecting 
groove 22 and then result in the feared "balloon fibers". Particularly, 
extremely long balloon fibers lead to very taut "balloon bands". Fibers 
which directly reach the fiber collecting groove 22 without sufficient 
prior contact with the sliding surface 21 are wound up along their full 
length which has a negative effect on the yarn quality. Naturally, it is 
hardly possible to avoid balloon fibers particularly in the case of small 
rotors 6, but the important aspect is the avoiding of extremely long 
balloon fibers. 
FIG. 2 illustrates a separate component 225 with a slot-type mouth 218 and 
a fiber guiding surface 226. Also shown is the smallest cross-section 24 
of the fiber feeding duct 5, as it meets the separate component 225. The 
slot of the mouth 218 already starts in front of the smallest 
cross-section 24 and also continues behind it in the rotating direction A 
so that the air ring rotating along with the spinning rotor 6 promotes the 
fiber movement The fibers coming cut of the mouth 218 therefore receive 
"tail wind". 
When the contour of the component 3 2 5 is constructed corresponding to 
FIG. 3, the fiber guiding surface 326 starts in the area of the narrowest 
cross-section 24 with a wall 328. As a result of this shape, the "nail 
wind" is avoided. 
The "tail wind" is also avoided in the case of the construction according 
to FIG. 4 but, as a result of the design of the wall 428, not as much as 
in the embodiment according to FIG. 3. 
The slot-shaped mouth and the fiber guiding surface 526 according to FIG. 5 
correspond largely to the construction according to FIG. 2, in which case, 
however, a flute 527 is provided in the fiber guiding surface 526 which 
has the purpose of providing the fibers with such 2 direction that these 
arrive on the sliding surface 21 of the spinning rotor 6 as tangentially 
as possible. 
As illustrated in FIGS. 2 to 5, the fiber guiding Surface 226, 326, 426 and 
526 is constructed as a circular segment. Viewed in the fiber transport 
direction, the smallest cross-section 24 of the fiber feeding duct 5 is in 
each case situated in front of the fiber-guiding surface 226, 326, 426 and 
526. From here, the fibers are shot onto the sliding surface 21. 
The separate component 225, 325, 425 and 525 opens up different design 
possibilities without any manufacturing difficulties. According to the 
spinning conditions, the area of the mouth 18 may have variable designs. 
In this case, it is advantageous that the known advantages of a long fiber 
feeding duct 5 are not lost despite the slot-shaped mouth 18. 
If necessary, the described fiber guiding surfaces 226, 326, 426 and 526 
may have very varied surface structures in view of the fact that wear must 
be avoided, but also with the goal of facilitating the sliding of the 
fiber. In particular, it should be endeavored to obtain a smooth 
dirt-repelling surface. 
In the embodiments according to FIGS. 6 and 7, the same components have the 
same references numbers as in the case of the previously described 
embodiments. The description will therefore not be repeated. 
FIG. 6 includes designations for basic dimensions of especially preferred 
embodiments of the invention. These basic dimensions also apply to the 
embodiments of FIGS. 1 and 7 in a corresponding manner as shown in FIG. 6. 
These basic dimensions are as follows: 
(i) The diameter D.sub.G of the fiber collecting groove is between 26 mm 
and 30 mm, with an optimum practical embodiment having a diameter D.sub.G 
of about 28 mm. 
(ii) The angle .alpha. of the rotor fiber slide wall between the fiber 
impact location F (from mouth 18) and the collecting groove, with respect 
to a radial plane P--P, is between 76.degree. and 79.degree., with an 
optimum practical embodiment having an angle X of abut 77.5.degree.. 
(iii) The diameter D.sub.O of the open end of the rotor is between 21 mm 
and 23 mm, with an optimum practical embodiment having a diameter D.sub.O 
of 22 mm. 
(iv) The axial length S.sub.L of the sliding surface between the closest 
fiber impact point F and the collecting groove is at least two-thirds 
(2/3) of the axial length R.sub.L of the rotor. 
(v) The ideal diameter of the fiber feeding duct at section 24 is between 4 
and 5 mm, with an optimum practical embodiment having an ideal diameter of 
4.5 mm. This corresponds to a cross-sectional area of about 17 mm.sup.2 
and produces a mouth of the feeding duct having a height h in the axial 
direction of between 2 and 3 mm. 
In the embodiment according to FIG. 6, the slot type mouth 18 of the fiber 
feeding duct 5 is made still narrower toward its top because of the fact 
that the area of the covering 9 carrying the separate component 25 is 
provided with an elevation 29 which is directed toward the fiber guiding 
surface 26 of the mouth 18. As a result of this design, the slot becomes 
still narrower. The air throughput is nevertheless sufficient because the 
mouth 18 is sufficiently wide in the circumferential direction of the 
spinning rotor 6. 
In the case of the embodiment according to FIG. 7, the ring gap 23 is 
reduced in the area of the mouth 18. In the present case, a type of 
labyrinth seal 30 is provided which extends only in the area of the mouth 
18. As a result, it is prevented that fibers in the area of the mouth 18 
are guided away by way of the front end 15 of the spinning rotor 6. 
In FIG. 7, it is also provided that the fiber guiding surface 26 extends as 
closely as possible to the sliding surface 21. For this reason, when the 
cover 9 is moved away from the spinning rotor 6, the movement must take 
place into a direction which prevents that the fiber guiding surface 16 
comes in contact with the sliding surface 21. A corresponding forced 
guiding must be provided so that the sliding surface 21 is not damaged by 
the fiber guiding surface 26. 
The invention makes it possible to shoot the fibers in a stretched and 
bundled form accurately at a sufficient distance from the fiber collecting 
groove 22 onto the sliding surface 21, despite the sufficient air 
throughput. 
Although the invention has been described and illustrated in detail, it is 
to be clearly understood that the same is by way of illustration and 
example, and is not to be taken by way of limitation. The spirit and scope 
of the present invention are to be limited only by the terms of the 
appended claims.