Pot spinning machine

A pot spinning machine holds a yarn rewinding tube in ready position during the spinning operation for immediate movement to an operative rewinding position in the event of a yarn break so that the broken end of yarn is not lost by winding onto the yarn cake already formed in the spinning pot and the yarn cake may then be properly rewound. The yarn break is detected with the aid of a yarn sensor which then emits a signal for immediately moving the rewinding tube into the rewinding position and clamping the yarn end. The rewinding operation can begin, even in the absence of a loose end of the yarn, if the yarn has assumed the form of a chord-like yarn segment extending substantially in the circumferential direction against the inner face of the yarn cake deposited onto the inside wall of the pot, which can be grasped and utilized to initiate the rewinding operation.

FIELD OF THE INVENTION 
The present invention relates to a pot spinning machines and methods 
utilizing spinning pots that rotate during spinning and rewinding, wherein 
the fiber material to be spun is delivered from a drafting arrangement to 
a tubular yarn guide associated with each spinning pot which delivers the 
spun yarn via a mouth in the yarn guide to progressively form a yarn cake 
in the spinning pot. After the conclusion of the spinning operation or 
upon a yarn break, the yarn cake must be wound up onto a rewinding tube 
held in readiness during spinning at the mouth of the yarn guide spaced 
apart from its rewinding position. 
BACKGROUND OF THE INVENTION 
Pot spinning is also known as centrifugal spinning, and hence the apparatus 
utilized for performing such spinning are referred to as pot or 
centrifugal spinning frames or machines. Such machines either have tubular 
pots both ends of which have openings of virtually equal size, suspended 
pots which have a downward opening on the underside of the pot for 
removing the spun yarn, or standing pots with an upward opening for 
removal of the spun yarn located at the top of the pot. Reference in this 
respect is made to German Patent Disclosure DE 41 08 929 A1. There are 
also pot spinning machines wherein, once the yarn cake in the pot has been 
finished, the yarn guide is first pulled out of the pot and a tube is then 
inserted into the pot to initiate the rewinding operation (see Swiss 
Patent CH 360 004). Other pot spinning machines have a cylindrical 
spinning pot open at the top and bottom, with a yarn guide introduced 
through the upper opening during spinning and with a corresponding bobbin 
tube inserted through the lower opening for rewinding (see German Patent 
Disclosure DE 43 24 039 A1). Finally, there are pot spinning machines in 
which the rewinding tube is predisposed in a ready position during 
spinning coaxially on the yarn guide or yarn guide tube. These machines 
may utilize either standing spinning pots or spinning pots that are 
cylindrical with openings at each end (see East German Patent DD 21 834 
and German Patent Disclosure DE 43 24 039 A1). 
There are also pot spinning machines with substantially cylindrical pots 
that lack any top and bottom, known as tube centrifuges, both ends of 
which have an opening of virtually the same size. Such tubular spinning 
pots may be magnetically-supported as in German Patent Disclosure DE 42 08 
039 A1. According to German Patent Disclosure DE 43 24 039 A1, it is also 
possible with a standing tubular spinning pot of the kind known from East 
German Patent DD 21 834, that during spinning, the rewinding tube (onto 
which the yarn cake is to be wound) is predisposed on the tube of the yarn 
guide above the mouth thereof and locked thereat to prevent its being 
lowered. In this reserve position, the tube does not touch the rotating 
loose end of the yarn. 
In these known cases, the rewinding tube can be held in readiness either 
above or below the spinning pot and thrust into the path of the loose end 
of the yarn as needed. If the rewinding tube is not thrust forward at the 
correct time in the event of a yarn break, then the torn end of the yarn 
in the pot runs along the inner wall of the yarn cake and can no longer be 
located and manipulated automatically with known devices. In that case, 
the rewinding operation can be initiated only from outside, generally 
manually, by relatively complicated procedures (see Swiss Patent CH 348 
346 or German Patent DE 842 916). 
In German Patent Disclosure DE 26 21 900 A1, an optical yarn monitor is 
disclosed to be located quite close to the point at which the yarn is 
created and records not only the presence but also the proper motion of 
the yarn. This known yarn monitor, which is preferentially used in ring 
spinning machines, is positioned adjacent an associated drafting 
arrangement at the base of the balloon forming above the spindle. The yarn 
sensor is intended to initiate protective provisions in the event of a 
yarn break, such as shutting off the following processing station. 
As mentioned above, to initiate the rewinding operation, the rewinding tube 
is placed in the pot. In this connection, it has long been known for the 
loose end of the yarn furnished from the mouth of the yarn guide to be 
caught with the aid of a groove provided on the lengthwise end of the 
rewinding tube (see U.S. Pat. No. 802,161, page 2, lines 58/59). 
Mechanical means are also known for grasping the inner yarn layers of the 
yarn cake in the event of a yarn break, to enable the rewinding operation 
to be initiated, either by hand (see Swiss Patent CH 348 346, page 1, 
lines 18 ff.) or via a swiveling mechanism (see German Patent DE 842 916, 
page 4, lines 13-23). 
In all of these known devices that initiate the rewinding operation after a 
yarn break, some layers of yarn are deposited randomly onto the rewinding 
tube which can lead to considerable problems in the later winding process 
in that it is generally not possible to unwind these random yarn layers 
from the tube. This produces additional waste, and the tubes require 
special cleaning. 
In German Utility Model DE-GM 76 25 081, a tubular bobbin tube is disclosed 
that is entirely cylindrical and has a yarn catching slit with an 
associated yarn retaining element at a lengthwise end on the outer 
circumferential surface of the tube. A similar cylindrical bobbin tube 
with an encompassing yarn catching slit is disclosed in German Patent 
Disclosure DE 27 17 189 A1. In the latter case, the yarn catching slit may 
also be provided on the face-end edge of the tube (page 7, paragraph 4). A 
yarn catching slit with integrated yarn clamping means at a lengthwise end 
of a cylindrical bobbin tube is disclosed in European Patent Disclosure EP 
0 524 545 B1. All of these known yarn catching slits are intended to be 
able to grasp and hold only a yarn that is pressed approximately radially 
with tension into the respective slit. 
OBJECT AND SUMMARY OF THE INVENTION 
In view of the above-described known pot spinning machines, it is an object 
of the present invention to provide a means to rescue or retrieve for 
purposes of further processing the already-spun yarn cake or the yarn 
contents of the centrifuge in a pot spinning machine, even in the event of 
a yarn break. 
Basically, the present invention provides a yarn sensor associated with the 
transport path of the yarn in a pot spinning operation to detect the 
occurrence of a yarn break, and an associated means connected with the 
sensor for shifting the rewinding tube into a rewinding position when a 
yarn break is detected. Accordingly, when a yarn break during the pot 
spinning operation is detected by the yarn sensor, the rewinding tube may 
thereupon immediately be moved into its rewinding position, preferably 
with the broken yarn end being clamped at the same time, so that the yarn 
cake already located in the pot is immediate rewound to the rewinding 
tube. In this manner, the invention makes it possible to move the 
rewinding tube into its rewinding position before the broken yarn end has 
left the mouth of the yarn guide. As a result, it is assured that the 
contents of the pot will be rewound even if there is a yarn break, and 
that the yarn end cannot be deposited irretrievably on the yarn cake. 
In the present invention, the rewinding tube is preferably locked on the 
tube of the yarn guide in a reserve position above the mouth of the yarn 
guide during the normal ongoing spinning operation. In the event of a yarn 
break, all that is needed to initiate rewinding is to release the locking 
means, so that the rewinding tube drops past the mouth of the yarn guide. 
Conversely, if the rewinding tube is normally located below the mouth of 
the yarn guide tube during the spinning operation, for instance, in the 
case of a suspended or tubular spinning pot, then the rewinding operation 
can likewise be initiated instantaneously in the event of a detected yarn 
break by quickly thrusting the rewinding tube upwardly beyond the yarn 
guide mouth. In both cases, the end of the rewinding tube adjacent to the 
yarn guide mouth should be held in readiness as close as possible to the 
mouth, so that the extraordinarily short time available from the time a 
yarn break is detected until the yarn end emerges from the mouth of the 
yarn guide will suffice to catch the yarn end for the sake of rewinding. 
For the above purpose, the adjacent end of the rewinding tube is 
positioned only far enough away from the yarn guide mouth as to not impede 
the operation of spinning or winding the yarn cake. 
According to another aspect of the invention, the yarn sensor signal 
produced in the event of a yarn break is utilized to initiate not only the 
described movement of the rewinding tube past the yarn guide mouth, but 
also clamping of the broken yarn end in the region of the yarn guide tube 
or at the forward-moving end of the rewinding tube, so that continued 
rotation of the pot unchanged must necessarily rewind the yarn cake 
contained in the pot onto the tube. 
Preferably, the rewinding tube is moved with sufficient quickness upon a 
yarn break to reach the rewinding position before the torn yarn end leaves 
the mouth of the yarn guide tube. Since only a fraction of a second is 
available for this purpose, it is advantageous if the yarn sensor is 
located upstream along the yarn path as far as possible in advance of the 
yarn guide mouth. A position in the vicinity of a preceding fiber drafting 
arrangement, i.e., immediately following the triangular conformation of 
the fibers being spun as they exit the drafting arrangement in direction 
of the yarn travel, is preferred. The fiber spinning triangle is not only 
located relatively far from the yarn guide mouth but also represents an 
especially difficult region in that yarn breaks during the spinning 
operation in pot spinning machines occur predominantly in the region of 
the spinning triangle. A yarn sensor disposed below the spinning triangle, 
preferably still upstream of the adjacent entrance to the yarn guide tube, 
can therefore detect a yarn break quickly enough that the rewinding tube 
may be brought into its rewinding position long before the yarn end leaves 
the mouth of the yarn guide tube, so that the still-rotating loose end of 
the yarn may be fixed in notches or clamping devices at the base of the 
rewinding tube. 
Because of this provision for the early detection of a yarn break in the 
same region where such breaks typically occur, enough time remains to 
initiate the associated emergency provision of rapidly raising or lowering 
of the rewinding tube from the reserve position held in readiness above or 
below the spinning pot into the rewinding position. From an energy 
standpoint, it is more favorable to allow a tube to drop rather than to 
raise the tube, it is preferable for the rewinding tube to be held in 
readiness in an upper position on the tube of the yarn guide above the 
yarn guide mouth. 
In this reserve position, the rewinding tube can be fixed, for instance 
with the aid of a magnet. Since the release of a thusly suspended 
rewinding tube can occur very quickly, and the distance the tube must 
travel from the reserve position to the rewinding position is short, the 
rewinding operation can be initiated virtually instantaneously, not only 
at the end of yarn cake buildup but in the interim as well in the event of 
a yarn break or some other interruption in the spinning operation. Almost 
equally quickly, a rewinding tube held ready below the yarn guide mouth 
can be raised from its reserve position to the rewinding position, for 
instance by spring force. 
According to a further feature of the invention, the described reserve 
position of the rewinding tube on the yarn guide enables not only a yarn 
break to be detected quickly by the yarn sensor and the direct release of 
the rewinding tube thereupon, but also accomplishes the particular 
advantage of enabling the locking of the rewinding tube to be designed 
such that upon its release the rewinding tube simultaneously clamps the 
yarn end sliding through the yarn guide tube, preferably by means of one 
and the same motion. In other words, one and the same mechanism, such as a 
control magnet initiated by the yarn sensor, locks the rewinding tube in 
the reserve position, and in the other position it clamps the yarn end 
sliding through the tube of the yarn guide. 
In a particular embodiment of the invention, provision is made for 
initiating the rewinding operation, especially after a yarn break, even if 
there is no longer any revolving loose end of the yarn between the yarn 
guide mouth and the yarn cake such that all the fiber material deposited 
in the spinning pot or centrifuge is wound onto the rewinding tube and 
later can be unwound from it again without any loss. In normal spinning 
operation, a loose end of the yarn extends radially between the mouth of 
the yarn guide tube and the spun yarn cake. However, in the event this 
loose end of yarn is no longer available, the present invention 
advantageously serves instead to initiate the rewinding operation by 
utilizing a different starting length of yarn, namely a length of yarn 
that has already left the deposition path radially extending from the yarn 
guide and has already applied itself loosely to the inner wall of the yarn 
cake. Specifically, the rewinding operation may be initiated utilizing a 
broken yarn end that has been applied to the inner wall of the yarn cake 
not exactly circularly but rather partly in the orientation of a chord 
relative to the interior of the pot and which therefore extends 
essentially in a radial plane of the pot approximately along the 
circumference of the rewinding tube. 
According to a further feature of the invention, at least one of the 
lengthwise ends of the rewinding tube has a radially protruding flanged 
portion with a yarn catching notch therein partially covered by a spring 
element, the widened portion being positioned to project into close 
adjacency with the yarn cake almost close enough to touch the inside 
surface of the yarn cake. As a result, a yarn chord segment utilized such 
as above-mentioned for initiating the rewinding operation will extend 
essentially parallel to the circumferential direction, or in the plane of, 
the radially protruding widened portion and can be firmly retained. 
This outcome is surprising. Conventional catching notches on rewinding 
tubes are known not to be able to properly hold a chord-like yarn end 
firmly and to use such a yarn end for ordered rewinding of a yarn cake. 
This is because the applicable chord-like yarn segment rests only loosely 
and without tension (in the radial plane of the catching means) on the 
inside face of the yarn cake. The known catching means are designed such 
that the chord segment, if it is touched at all, passes only loosely 
through the yarn catching notch. 
However, the functional integration of the characteristics preferably 
employed to construct the present apparatus, namely the maximum possible 
radius of the radially protruding widened end portion of the rewinding 
tube, the catching notch located on the edge of the widened end portion, 
and the spring element of the catching notch, lead to complete success 
that could not have been expected in advance from these individual 
characteristics. 
As noted, it is preferably provided that the catching notch is positioned 
as close as possible to the inside diameter of the yarn cake, so that it 
can reliably grasp any chord-like yarn segment that develops. In 
accordance with a preferred embodiment, it is especially favorable for the 
plate-like widened portion to be inwardly recessed at its axial end face 
for receiving the spring element, and for the spring element to partially 
cover the catching notch at a distance, measured from the axial end of the 
widened portion, that is equal to or greater than a yarn diameter. A snap 
ring is preferably provided as the spring element. 
Thus, the present invention accomplishes a pot spinning method by which it 
is assured that the yarn cake in the spinning pot will be automatically 
rewound properly even in the event of a yarn break, without requiring a 
search for the yarn end on the yarn cake. That is, in the event of a yarn 
break, if against expectation the loose end of the yarn extending from the 
yarn guide mouth to the yarn cake should prove not to have been grasped, 
then the present invention assures by means of the method carried out by 
the described apparatus that a yarn end applied circumferentially in the 
form of a yarn chord segment onto the inside face of the yarn cake is 
utilized to initiate the rewinding operation. Various conventional devices 
are possible as the yarn sensor, which by way of example may function 
optically or capacitively. One example of an optical yarn sensor or yarn 
monitor is disclosed in German Patent Disclosure DE 26 21 900 A1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring now to the accompanying drawings and initially to FIG. 1, a 
representative spinning station of a pot spinning machine is shown. In 
advance of the spinning pot is a drafting arrangement 1, typically having 
a series of drafting roller pairs but symbolized in FIG. 1 only by the 
last pair of drafting rollers, wherein a sliver 2 is drawn and as it 
emerges from the last roller pair is twisted under the influence of the 
revolving spinning pot 9 so as to converge in a spinning triangle 3 into a 
yarn 17. The yarn 17 then immediately passes through a yarn sensor 4 
located directly following the spinning triangle 3 and enters an entrance 
end to a tubular yarn guide 5. The yarn 17 emerging from the exit mouth 6 
of the yarn guide 5 is applied to the inner wall 8 of the spinning pot 9 
and wraps centrifugally thereagainst to progressively form a yarn cake 10. 
During the spinning operation, a rewinding tube 11 is located coaxially on 
the yarn guide 5, immediately above and spaced from its mouth 6, from 
which position the rewinding tube 11 can be lowered past the mouth 6 of 
the yarn guide 5 to initiate a rewinding operation (as indicated by the 
position 12 shown in broken lines and discussed more fully below). 
A rewinding operation may be initiated for several reasons. On the one 
hand, if the yarn cake 10 in the spinning pot 9 has been completed, or on 
the other hand, if an interruption in the spinning operation has occurred, 
for instance from yarn breakage, rewinding will be initiated. The base of 
the rewinding tube preferably has suitable clamping or retaining devices. 
Thus, when the rewinding tube 11 is lowered outwardly past the mouth 6 of 
the yarn guide 5 into the rewinding position 12 shown in broken lines, the 
rotating loose trailing end 7 of the yarn 17 forming the yarn cake in the 
spinning pot can be grasped by clamping or retaining devices and fixed 
such that the yarn cake 10 is automatically or by compulsion wound onto 
the rewinding tube 11 as the spinning pot 9 continues to rotate. 
The rewinding tube 11, once wound with the yarn from yarn cake in the 
spinning pot, can then be transferred to a caddy 13, having a flat base 15 
and an upstanding spindle 14 for coaxially supporting the rewinding tube 
11, that is held ready at a suitable spacing below the spinning pot 9. 
After being lowered in the direction of the arrow 16, the wound tube 11 
can be carried away together with the caddy 13 for further processing, 
while a new empty tube is brought with a further caddy (not shown) and 
fixed below the yarn guide 5 in the reserve position. 
The rewinding tube 11 is held in the reserve position on the yarn guide 5 
above its exit mouth 6 during normal ongoing centrifugal winding of the 
yarn cake in the spinning pot by a locking means 19 shown in FIG. 2. If 
the yarn sensor 4 detects a yarn break, the yarn sensor 4 transmits a 
signal to the locking means 19 to release the rewinding tube 11. The 
locking means 19 thereupon disengages from the rewinding tube 11, so that 
the rewinding tube 11 drops downwardly and the rewinding operation is 
initiated. For initiating the rewinding operation, it is advantageous if 
the rotating loose end 7 of the yarn between the yarn guide mouth 6 and 
the yarn cake 10 has a sufficient tension to catch the yarn end on the 
tube and fix it. An adequate tension for this purpose may under some 
circumstances already exist if the yarn end is long enough. It is 
especially advantageous, however, for the yarn end to be clamped or 
otherwise firmly held or caught and for the rewinding operation to be 
initiated immediately thereafter. 
The locking means 19 shown in FIG. 2 is a preferred exemplary embodiment 
that is suitable both for keeping the rewinding tube 11 in its reserve 
position on the tube of the yarn guide 5 and in the event of a yarn break, 
by switchover of the locking means, for clamping the yarn 17 or its 
trailing yarn end, in the axial interior channel 18 of the yarn guide 5. 
To that end, the locking means 19 includes an electromagnet 22 which is 
switchable by the supply of electrical current to its electromagnetic 
windings in response to signals furnished by the yarn sensor 4 to act upon 
and displace a locking pin 20 or the like to move between the position 
indicated by solid lines, wherein the pin 20 extends radially outwardly 
into engagement within an interior recess in the rewinding tube 11 to lock 
the rewinding tube 11 in its reserve position, and a position 21 
represented by broken lines, wherein the locking pin 20 extends radially 
inwardly into the channel 18 of the yarn guide 5 into clamping engagement 
with the yarn end 17 therein. During a switchover from the tube locking 
position to the yarn clamping position, the rewinding tube 11 is released 
to slide downwardly into its rewinding position which is predetermined by 
means of a stop 23 affixed to the yarn guide 5 that is preferably biased 
outwardly by spring force to engage in another interior recess within the 
rewinding tube 11 as it drops into the rewinding position. It is equally 
possible for the stop 23 to have an electromagnetic drive 24, to enable 
the stop 23 to be retracted and the rewinding tube 11 thus to be released. 
FIG. 3 shows another embodiment of a spinning station of a pot spinning 
machine, which is substantially identical to the spinning station of FIG. 
1 except that, in this embodiment, the rewinding tube 11 is introduced 
into the spinning pot from beneath. 
In pot spinning machines according to the present invention in which the 
rewinding tube is already held in readiness in a reserve position during 
the spinning operation so that the rewinding tube can be immediately 
brought to the rewinding position, the rewinding tube should be moved into 
the rewinding position in the event of a yarn break so quickly that the 
yarn cake already formed in the spinning pot can still be properly 
rewound. Thus, according to the present invention, the yarn break is 
detected with the aid of the yarn sensor 4, which thereupon sends a signal 
for instantaneously moving the rewinding tube into the rewinding position 
and for clamping the yarn end. 
FIG. 1A schematically shows a spinning station of another pot spinning 
machine wherein a spinning pot 9 rotates in bearings 25 about an axis 26. 
The type of bearings are of no significance with respect to the present 
invention; however, it is known to use magnet bearings, for instance to 
support single-motor-driven spinning pots. 
A sliver drawing device, such as a drafting mechanism 1 to which is 
supplied a sliver 2, is installed above the spinning pot 9. The yarn 17 
created by the action of the revolving spinning pot 9 is applied into the 
interior of the spinning pot 9 via a yarn guide tube 5 supported for axial 
movement and the yarn is thereby wrapped centrifugally onto the inner wall 
27 of the rotating spinning pot, forming a yarn cake 10. 
A rewinding tube 11 is fixed in a ready position on the yarn guide tube 5 
by means of a latching device 19, which is triggerable in a defined 
fashion to shift the rewinding tube 11 downwardly beyond the mouth of the 
yarn guide 5 into a rewinding position (not shown). 
As can be seen from FIGS. 4 and 5, the rewinding tube 11 has a flange-like 
portion 28 projecting radially outwardly from its lower end, with at least 
one yarn catching notch 30 formed in the flange 28. The radial flanged 
portion 28 is recessed on its interior to receive a spring element 34, 
preferably embodied as a snap ring or the like, that partially covers the 
yarn catching notch 30 at a distance a from the lower edge 35. The 
distance a should preferably be the same as or greater than the diameter 
of the yarn to be caught. 
In the event of a yarn break below the yarn sensor 4, the trailing yarn end 
that emerges from the mouth of the yarn guide 5 is not as a rule applied 
securely flush against the annular interior surface of the yarn cake 10 
but instead loosely forms in chord-like segments 36, 37 relative to the 
previously wound layers of the yarn cake 10. If such a chord-like segment 
36 or 37 of a yarn end located on the yarn cake 10 enters the region of 
the radial flange portion 28 of the rewinding tube 11, then as the 
spinning pot continues rotating the notch 30 acts as a yarn catching 
device in which the chord-like yarn segment becomes engaged to be grasped 
and clamped by the spring element 34, without any necessity for the yarn 
segment to have been tensioned or otherwise held taut beforehand. Because 
the spinning pot continues rotating during this yarn end catching 
operation, a rewinding operation is automatically initiated causing the 
entire yarn cake 10 deposited in the spinning pot to then be wound in 
ordered fashion onto the rewinding tube 11 for subsequent unwinding from 
the tube 11 without loss. 
It will therefore be readily understood by those persons skilled in the art 
that the present invention is susceptible of a broad utility and 
application. Many embodiments and adaptations of the present invention 
other than those herein described, as well as many variations, 
modifications and equivalent arrangements, will be apparent from or 
reasonably suggested by the present invention and the foregoing 
description thereof, without departing from the substance or scope of the 
present invention. Accordingly, while the present invention has been 
described herein in detail in relation to its preferred embodiment, it is 
to be understood that this disclosure is only illustrative and exemplary 
of the present invention and is made merely for purposes of providing a 
full and enabling disclosure of the invention. The foregoing disclosure is 
not intended or to be construed to limit the present invention or 
otherwise to exclude any such other embodiments, adaptations, variations, 
modifications and equivalent arrangements, the present invention being 
limited only by the claims appended hereto and the equivalents thereof.