Method of starting spinning of a yarn in a friction spinning device

In order to start or recommence spinning of a yarn in a friction spinning device, the following method steps are carried out upon start-up of a new spinning operation or upon piecing after a thread break: fibers separated by an opening device are delivered by means of a fiber transporting passage to a rotating friction spinning drum and are twisted to form a twisted fiber structure; when the twisted fiber structure has substantially reached a predeterminate diameter or size, then the twisted fiber structure is transported by an airstream delivered by a pressure duct towards and into a guide tube and is forwarded therein into a convergent space of rotating withdrawal rolls; and the twisted fiber structure is caught at production speed by these withdrawal rolls and delivered on a divergent side of the withdrawal rolls to a receiving suction device which transfers the spun yarn subsequent to the twisted fiber structure to further processing elements.

CROSS REFERENCE TO RELATED APPLICATION 
This application is related to the commonly assigned, copending patent 
application Ser. No. 06/874,521, filed June 16, 1986, now U.S. Pat. No. 
4,646,513 and entitled "METHOD FOR PIECING A YARN IN A FRICTION SPINNING 
DEVICE". 
BACKGROUND OF THE INVENTION 
The present invention broadly relates to a new and improved method of 
starting or recommencing spinning of a yarn in a friction spinning device 
in which freely floating fibers in a fiber feed passage are delivered to a 
friction spinning surface of a friction spinning device or means and are 
forwarded on this friction spinning surface to a yarn formation position 
from which a spun yarn is withdrawn by a yarn withdrawal means. 
The previously known methods and devices for starting or recommencing of 
spinning of a yarn in the aforementioned manner employ a yarn end brought 
back or returned from a package. For purposes of starting or recommencing 
spinning, this yarn end is returned to the stationary friction spinning 
device or means so that thereafter starting of spinning can be carried out 
by feeding fibers to the returned yarn end at reduced speed of the 
friction spinning device or means. It has also been proposed that before 
the start of spinning, that is before the feed of freely floating fibers 
to the inserted yarn end, the latter be untwisted by a corresponding 
motion of the friction spinning device or means in the opposite direction, 
so that the delivered fibers can thus be better bound or interlaced with 
the yarn end. 
Such a device is known from the German Patent Publication No. 3,318,687, 
published Nov. 29, 1984 in which a yarn end from a reverse-rotated package 
is taken up by a suction device, and the yarn thus drawn in is held by 
means of two reciprocating devices in a convergent gap of two stationary 
friction spinning drums. 
Before supplying freely floating fibers to this yarn, the latter is opened 
by reverse rotation of the friction spinning drum, so that the fibers of 
the yarn lie in a substantially twist-free condition in the convergent 
space of the friction spinning drums. Thereafter, the friction spinning 
drums are set in operation at reduced speed in the normal direction of 
rotation, and freely floating fibers are supplied to the opened yarn. The 
yarn thus produced is withdrawn at a correspondingly reduced speed and is 
passed to a joining or knotting means. 
In order to take up the continually delivered yarn during the time required 
for the joining or knotting operation, the yarn is drawn in by a suction 
nozzle functioning as a yarn store. 
After completion of joining or knotting, the complete device is accelerated 
to operating speed and thereafter disconnected from the required auxiliary 
drive means and is driven at operating speed by the normal drive means. 
The disadvantage of such a device lies in the multiplicity of auxiliary 
equipment for the start-spinning procedure. 
SUMMARY OF THE INVENTION 
It is therefore, with the foregoing in mind, a primary object of the 
present invention to provide a method for starting or recommencing 
spinning of a yarn in a friction spinning device which is uncomplicated 
and can be carried out with relatively simple means. 
In order to implement this and still further objects of the invention, 
which will become more readily apparent as the description proceeds, the 
method of starting or recommencing spinning of a yarn in a friction 
spinning device is manifested by the features that it comprises the steps 
of forwarding the freely floating fibers to the yarn formation position 
and twisting the freely floating fibers to form a rotating twisted fiber 
structure of substantially predeterminate size, forwarding the rotating 
twisted fiber structure by a first airstream towards the yarn withdrawal 
means and subsequently catching the rotating twisting fiber structure as 
well as spun yarn adjoining thereon by a yarn take-up means arranged 
subsequent to the yarn withdrawal means. 
The advantages achieved by the invention are substantially that a device 
for carrying out the method can be relatively simple as a result of the 
possibility of performing start-spinning at production speed.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Describing now the drawings, it is to be understood that in order to 
simplify the showing thereof, enough of the structure of the friction 
spinning device or means has been illustrated therein as is needed to 
enable one skilled in the art to readily understand the underlying 
principles and concepts of this invention. Turning specifically to FIG. 1 
of the drawings, the apparatus illustrated therein by way of example and 
not limitation and employed to realize the method as herein-before 
described will be seen to comprise a fiber sliver opening device 1 known 
from the rotor open-end spinning process. The fiber sliver opening device 
1 comprises an opening roller generally indicated by its drive shaft 1.1 
and an infeed opening A provided for receiving a fiber sliver (not shown). 
Freely floating fibers 11 are delivered through a fiber feed or transport 
passage or duct 2 adjoining the opening device 1 by an airstream flowing 
through the fiber transport passage 2 to a perforated friction spinning 
drum 3 which is rotatable and suitably drivable. On this perforated 
friction spinning drum 3, a yarn end 5.1 which is being developed into a 
spun yarn 5, is formed in a known manner at a yarn formation position or 
location 7 (FIG. 2). A counter-roller 4 (which is also rotatable and 
drivable) assists the twisting-in of the fibers 11 located in the 
convergent space of the two rollers defined by the perforated friction 
spinning drum 3 and the counter-roller 4 at the yarn formation position 7. 
The counter-roller 4 does not contact the perforated friction spinning 
drum 3, but is arranged substantially very close thereto (for example at a 
spacing of between 0.05 and 0.15 mm) and substantially parallel thereto. 
The spun yarn 5 is withdrawn by a yarn withdrawal means in the form of a 
rotating withdrawal roller pair 6. 
Such devices are known from previous publications in the patent literature 
and will therefore not be further described in detail. For example, 
British Patent No. 1,231,198 shows a basically similar process in which, 
however, a perforated disc is provided instead of a perforated roller and 
a frusto-conical counter-roller is provided in place of a cylindrical one. 
Furthermore, in addition to the fiber transport passage or duct 2, a 
pressure air duct 8 opens onto the yarn formation position or location 7 
in the convergent space of the two friction spinning drums 3 and 4 (also 
called friction spinning rollers 3 and 4 and also sometimes called 
perforated friction spinning drum 3 and counter-roller 4). The length G of 
an exit opening 9 of the pressure air duct 8 corresponds at least to the 
length F (FIG. 1) of a perforated region of the perforated friction 
spinning drum 3, while the length H of an exit opening 22 of the fiber 
transport passage 2 corresponds at most to the length F of this perforated 
region. The perforated region is designated by the reference character P 
in FIG. 1, and is conveniently illustrated only partially. 
The relation of the distance D or D1 (FIG. 3, FIG. 3a) between the exit 
opening 9 and the yarn end 5.1 located in the yarn formation position 7 to 
the intensity of air flow at this exit opening 9 of the pressure air duct 
8 must be determined empirically on the basis of the subsequently 
described method steps of the start-spinning operation. It will be 
understood that the term "start-spinning operation" as used herein 
includes, when appropriate, both commencement of spinning and 
recommencement of spinning after piecing up a yarn after a yarn or thread 
break. 
The same applies to the width (not referenced) and the form of the exit 
opening 9 of the pressure air duct 8 in order to be able to render 
selectively variable the intensity of the air flow at the exit opening 9; 
the expression "form" of the exit opening 9 refers to the shape of the 
exit opening area. For example, the width of the exit opening 9 can be 
varied within the length G of the exit opening 9 in order to thereby 
obtain differences in the blowing effect along the exit opening 9. 
The pressure air duct 8 also has a connector 10 by means of which this 
pressure air duct 8 can be connected to a non-illustrated suitable 
pressure air supply with all known required elements for regulating the 
air pressure and air quantity and for controlling the air flow. 
In FIG. 3a, the spacing D.1 indicates that the exit opening 9 of the 
pressure air duct 8 can be spaced further from the yarn end 5.1 than the 
exit opening 22 of the fiber transport passage or duct 2 which is spaced 
at the distance K. 
Furthermore, the dash-dotted lines in FIG. 3 schematically indicate a 
further pressure air duct 8.1 showing that the disposition of the pressure 
air duct is not strictly limited to the disposition of the pressure air 
duct 8 represented in full lines in the drawings, without any appreciable 
detrimental effect in the subsequently described blowing action or effect. 
In the following description, the procedure for starting-spinning is 
described both for a new spinning start-up and also for piecing after a 
thread-break i.e. recommencing the spinning operation. 
It is first noted that the previously mentioned air flow or airstream in 
the fiber transport passage 2, for transporting or forwarding the freely 
floating fibers 11 from the conventional opening roller forming part of 
the opening device 1 to the friction spinning drum 3, is created in known 
manner by a suction nozzle 23 located in the friction spinning drum 3. The 
suction nozzle 23 generates a suction air flow or airstream at the surface 
of the friction spinning drum 3 over the length F of the perforated drum 
region or surface P. The yarn end 5.1, on the one hand, and the exit 
opening 22 of the fiber transport passage 2 on the other hand, are located 
within this suction airstream. 
As shown in FIG. 5, during start-spinning, freely floating fibers 11 are 
first supplied or forwarded by means of the fiber transport passage 2 to 
the friction spinning drum 3, initially without withdrawal of these freely 
floating fibers 11 in the form of a yarn or the like, so that a rotating 
twisted fiber structure 12 is formed and becomes steadily larger. 
The counter-roller 4 is not illustrated in FIG. 5 in order to show this 
rotating twisted fiber structure 12 more clearly. 
Now, once this rotating twisted fiber structure 12 has reached a 
predeterminate or desired size then, on the one hand, a suction device 13 
acting as a yarn take-up or removal means is moved toward the divergent 
side of the rotating withdrawal roller pair 6 rotating in the direction of 
the depicted arrows in such manner that this yarn take-up means or suction 
device 13 is able to take up the rotating twisted fiber structure 12 
delivered by the rotating withdrawal roller pair 6. 
On the other hand, after the rotating twisted fiber structure 12 has 
reached the predeterminate or desired size as already mentioned, pressure 
or pressurized air is delivered by the pressure air duct 8. The rotating 
twisted fiber structure 12 is delivered into an entry opening 14 of a 
guide tube 15 or guide means, and passes via this guide tube 15 or guide 
means into the convergent space of the rotating withdrawal roller pair 6. 
As illustrated in FIG. 2, the guide tube 15 is provided between end faces 
of the friction rollers or perforated friction spinning drum 3 and 
counter-roller 4 and the withdrawal rollers or rotating withdrawal roller 
pair 6, in such manner that the axis of symmetry of the guide tube 15 lies 
substantially in an imaginary plane which contains the line of contact or 
nip of the two withdrawal rollers or rotating withdrawal roller pair 6 and 
a location on the perforated friction spinning drum 3 at which the spun 
yarn 5 leaves this perforated friction spinning drum 3. 
The internal diameter of this guide tube or guide means 15 is larger than 
the external diameter of the previously mentioned twisted fiber structure 
or rotating twisted fiber structure 12, for example the internal diameter 
of the guide tube 15 may be, for instance, at least double the external 
diameter of the rotating twisted fiber structure 12. 
A not particularly referenced exit opening of the guide tube 15 can, as 
illustrated in FIG. 2, be provided with cut-outs or coped out in such 
manner that this exit opening substantially conforms or is accommodated to 
the peripheral surface of the withdrawal rollers or rotating withdrawal 
roller pair 6. 
Furthermore, as illustrated in FIG. 4, the guide tube or guide means 15 can 
be formed as an injector guide tube 15.1 with inflow openings or jets 16 
and 17 being provided thereat for inflow of pressure or pressurized air 
of, for instance, a selectable variable intensity. These air blowing-in or 
inflow openings 16 and 17 impart to an airstream guided by these inflow 
openings or jets 16 and 17 a component of force in the yarn withdrawal 
direction Z. The airstream is created by an annular pressure chamber 18 
provided around these inflow openings 16 and 17 and standing under 
pressure. The annular pressure chamber 18 itself is supplied via a 
connector bore 19 with pressurized air from a suitable conventional 
pressure air system generally indicated by a connector tube 20 forming the 
final element thereof. The connector tube 20 or the like is fixedly 
connected to a pressure housing 21 containing the pressure chamber 18 and 
the connector bore 19. 
The pressure casing or pressure housing 21 in turn serves to fixedly 
accommodate the injector guide tube 15.1 and seals the annular pressure 
chamber 18 against the atmosphere. 
Accordingly, in comparison with the guide tube 15, the injector guide tube 
15.1 has the advantage of positively forwarding the previously mentioned 
rotating twisted fiber structure 12 into the convergent space of the 
withdrawal rollers or rotating withdrawal roller pair 6 during the 
start-spinning operation. 
Upon leaving the withdrawal rollers or rotating withdrawal roller pair 6, 
the rotating twisted fiber structure 12 is caught and drawn in by the yarn 
take-up means or suction device 13, as illustrated in FIGS. 6 and 7. 
The spun yarn 5 (see FIG. 7), which is subsequently also drawn in, is 
guided by means of this suction device 13 to the further elements forming 
part of the spinning machine (not shown) but which will not be 
additionally described here. 
As soon as the rotating twisted fiber structure 12 is caught by the suction 
device 13, the airstream in the pressure air duct 8 and the airstream in 
the injector guide tube 15.1 are interrupted or terminated. 
The previously mentioned start-spinning procedure can be carried out at 
full production speed so that the spun yarn 5 delivered or forwarded by 
the withdrawal rollers or rotating withdrawal roller pair 6 corresponds to 
the spun yarn 5 to be produced. 
Clearly, the described method can also be carried out with friction 
spinning devices which, in place of friction spinning drums, have a 
friction spinning disc to which the freely floating fibers 11 are 
transported and by which the spun yarn 5 is formed in a yarn formation 
position or location 7, being withdrawn therefrom by withdrawal rollers or 
a rotating withdrawal roller pair 6. Such a device is illustrated and 
described, for example, in the previously mentioned British Patent No. 
1,231,198. 
It is also possible to use an appropriately perforated belt in place of a 
perforated friction spinning drum or disc, on which perforated belt the 
freely floating fibers 11 are delivered to a yarn formation position or 
location 7 lying at right angles to the direction of belt movement in 
order to produce a spun yarn 5. 
Such a device, with such a band or belt, is illustrated for example in 
French published patent application No. 2,480,799. 
Furthermore, in place of the suction device 13, a mechanical take-up device 
(not shown) can be used. The take-up device must merely be able to receive 
in the aforesaid manner the rotating twisted fiber structure 12 and the 
subsequently following spun yarn 5 at production speed. 
Furthermore, the effect of an airstream or air flow delivered by the 
pressure air duct 8 at predetermined intensity (which on the one hand is 
capable of catching a rotating twisted fiber structure 12 of 
predeterminate size and transporting or forwarding it towards the 
withdrawal rollers or rotating withdrawal roller pair 6) has proved to 
only become operative when the rotating twisted fiber structure 12 has 
attained an adequate size which, however, must be determined empirically. 
It can therefore be concluded that the airstream from the pressure air duct 
8 can also be started before, e.g. by the amount of a predeterminate time 
period, or simultaneously with the transport or forwarding of freely 
floating fibers 11 to the perforated friction spinning drum 3. 
Furthermore it has been found that the airstream does not have a negative 
influence on the spun yarn 5 produced after the start-spinning operation. 
Correspondingly, a selection can be made as to the sequence of starting 
fiber feed and supplying the airstream or of maintaining or switching-off 
the airstream after, i.e. subsequent to the expiration of a predeterminate 
time period, the start-spinning operation. 
Advantageously, the sequence is so selected that first the freely floating 
fibers 11 are supplied or forwarded and the airstream is then switched on 
only after the achievement of a rotating twisted fiber structure 12 of 
desired or predetermined size. 
In addition, the switching-on of the airstream before the delivery or 
forwarding of the freely floating fibers 11 can be used to clean the 
surface of the perforated friction spinning drum 3 and the counter-roller 
4, if necessary. In correspondence with the previously described 
arrangements, this cleaning airstream can selectively be maintained before 
the delivery or forwarding of the freely floating fibers 11, or can be 
switched off prior to such delivery or forwarding. 
In FIG. 2, the dash-dotted line L' indicates the central line of flow of 
the airstream guided in the pressure air duct 8. As indicated by the angle 
.alpha., this line of flow L' is so inclined to the yarn end 5.1 that the 
airstream or air flow creates a component of force R directed towards the 
rotating withdrawal roller pair 6 and acting on the rotating twisted fiber 
structure 12. The angle .alpha. is advantageously selected to be less than 
45 degrees. 
While there are shown and described present preferred embodiments of the 
invention, it is to be distinctly understood that the invention is not 
limited thereto, but may be otherwise variously embodied and practiced 
within the scope of the following claims. Accordingly,