Yarn severing and holding apparatus

A yarn severing and holding apparatus for use in a system for changing spinning cans in which synthetic filamentary yarns are deposited. In this apparatus an arm supported, independently of the can transporting means, for rotation at a level between the yarn feeding device and the cans, has a slide mounted thereon for traversing movement lengthwise of the arm. This slide carries a cutting device and also a device for clamping the severed end of the yarn deposited in the full can. This insures that the cut off end of the yarn cannot drop back into the full can and that on the other hand the free end can drop into the still empty can immediately after the cutting operation. Moreover, the severing and holding apparatus is physically divorced from the can-transporting means so that the latter may be designed for either rotational or translational movement.

INTRODUCTION 
The invention, generally speaking, relates to the deposition of synthetic 
continuous threads, yarns, slivers, tows, bands or similar filamentary 
materials hereinafter collectively referred to as synthetic filamentary 
yarns, in spinning cans. More particularly, the invention relates to 
spinning can changing systems and, specifically, to yarn severing and 
holding apparatus for use in such systems. 
BACKGROUND OF THE INVENTION 
Spinning cans--which are also variously known as receiving cans, depositing 
cans or feed boxes--are usually open ended, for example cylindrical, 
containers. The spinning cans may be arranged for uniform rotation about 
their axis and superimposed on or combined with the rotation of the can 
there may be a fluctuating "traversing" or reciprocating movement of the 
can or of a thread guide. A process of this kind has been disclosed for 
example in German Laid-Open Specification (DAS) No. 1 028 736 wherein a 
continuous thread or yarn is deposited in spiral shaped paths into a 
cake-like structure. Another process of the above general kind has been 
described in German Published Specification (DT-OS) No. 2 427 722. 
It is known to arrange spinning can changing systems for at least partially 
automatic operation and this requires that in the changing of the cans the 
continuously fed filamentary yarns must also be automatically severed at 
the full can. 
A number of solutions are known for this kind of problem. Thus, in German 
Published Patent Specification (DT-OS) No. 1 685 580 a device has been 
described in which, after the can has been completely filled, a depositing 
board or plate is shoved into the run of the fibers. An edge of this 
depositing board simultaneously serves as a severing device. The 
filamentary yarn fed during the can changing operation is collected on 
this depositing board. If an empty spinning can has been put in place in 
lieu of the full can, the depositing board is again shoved out of the 
fiber run and the yarns which have been piled up on the depositing board 
in the meantime, all drop into the can. A disadvantage of this device is 
that the severed yarn end drops into the full spinning can so that it can 
be retrieved only with great difficulty. A further drawback of the device 
resides in that in stripping off the material collected on the depositing 
board, entanglements may occur which may later, upon the drawing of the 
yarn from the can, lead to the formation of knots in the strand of yarn. 
Also known is German Pat. No. (DT-PS) 1 091 010 in which the yarn is 
ruptured incident to its transfer from one can to the other. This, 
however, applies to yarns consisting of short, relatively loosely adhering 
fibers particularly natural fibers. In the case of filamentary yarns which 
consist of synthetic continuous fibers, this procedure is impossible. 
Further known is Laid-Open German Patent Specification (DT-AS) No. 2 035 
020 in which three cans are placed on a turntable. Between each of the 
cans there is provided a roof-shaped member in the form of a support 
element. In the rotational axis of the turntable there is provided a 
stationary outrigger arm or boom with a cutting off device in such a way 
that the arm does not impede the run of the yarn. During the can changing 
action the filamentary yarn comes to lie across the roof-shaped member due 
to the rotation of the turntable. After the changing operation has been 
completed, that is, when the empty can stands under the yarn feeding 
device the cutting off device is lowered onto the roof-shaped member and 
the yarn is severed. During the cutting operation the yarn is held by two 
spring-loaded clamping members respectively attached to the two sides of 
the cutting device. Thereupon the cutting off device is lifted again and 
during the final portion of the return stroke of the cutting device the 
two associated clamping members release the corresponding free ends of the 
yarn, thereby permitting them to drop back into the respective cans. 
Here, too, it is disadvantageous that the severed filamentary yarn, that 
is, one end thereof, drops back into the filled can. Also, it is only 
subsequent to the lifting of the boom that the other end of the 
filamentary yarn is released and drops into the can, that is, at a time 
when this can is already being loaded and when several layers have already 
been fed into this can in the meantime; this may also lead to difficulties 
upon drawing off of the filamentary yarn from the can. Another drawback of 
this known cutting off and holding device is that it requires the cans to 
be guided in an arcuate path. 
OBJECTS AND SUMMARY OF THE INVENTION 
It is accordingly the general object of the invention to provide, in a 
system for changing spinning cans in which synthetic filamentary yarns are 
deposited, an improved yarn severing and holding apparatus which avoids 
some or all of the aforementioned disadvantages. 
More particularly it is an object of the invention to provide in such a can 
changing system an improved yarn severing and holding apparatus in which 
upon severing of the filamentary yarn the cut off end is prevented from 
dropping back into the can. 
It is another object of the invention to provide in a can changing system 
of the kind mentioned, an improved yarn severing and holding apparatus of 
simple design and especially one which requires only a minimum of parts 
regardless of the type of can transporting means used. 
Briefly, in the severing and holding apparatus described herein the 
foregoing objects are met by providing this apparatus with an arm which 
extends horizontally between the yarn feeding device and the cans and is 
rotationally supported independently of the can transporting means; and 
with a slide which is mounted on the arm for traversing movement 
lengthwise thereof and which carries a yarn severing device and also a 
device for holding the severed end of the yarn deposited in the full can. 
With the severing and holding apparatus according to the invention it is no 
longer possible that the cut off end drops back into the full can. At the 
same time it is insured that immediately after the cutting operation the 
free end can drop into the still empty can. In this manner the can is 
continuously filled so that entanglements or knot formations are kept from 
occurring. Furthermore, the severing and holding apparatus is physically 
divorced from the can transporting means and, as a result it does not 
matter whether the cans are provided on a turntable or whether they are 
continuously supplied by a conveyor belt. Likewise it is advantageous that 
in the apparatus according to the invention the cutting off function and 
clamping function are carried out simultaneously by the same moving part 
so that the manufacturing costs and the control expenses of the apparatus 
are minimized. 
According to a preferred feature of the invention the severing device 
employs a knife adjustably mounted on one long side of the slide, and the 
holding device uses a pressure element mounted on the other side of the 
slide. In this manner the apparatus can be adapted for use with various 
kinds of fibers and possible wear of individual elements can be 
compensated for without the device becoming inoperative. 
In order to insure that the slide can be traversed fast enough, it is 
proposed according to another feature of the invention, to employ a 
pneumatic device for this purpose; rodless cylinder-piston units generally 
known under the name "ORIGA" may suitably be used; and in order to keep 
the expense for the control of this device at a minimum, it is further 
proposed to control the pneumatic device as a function of the arm 
position. 
According to yet another feature of the invention a variable speed 
transmission is employed for rotating the arm by 360.degree.. The variable 
speed transmission is put in operation -- substantially simultaneously 
with the can transporting means -- in dependence on the degree of fullness 
of the spinning can or, alternatively, by the operating personnel. In this 
fashion, too, low control cost and substantial independence of the type of 
can transporting means employed are insured. 
A further advantage of the invention resides in the fact that it permits 
the use of a single yarn severing and holding apparatus for a multiplicity 
of spinning cans.

DETAILED DESCRIPTION 
In FIG. 1 a filamentary yarn spinning system has been schematically shown. 
Filamentary yarn 1 is drawn off the spinning jet 2 by means of godets 3 
and 4. The yarn then passes, for example, a stretching apparatus 5 and it 
is then supplied to in-feeding godets 6. These in-feeding godets convey 
the filamentary yarn into a deflection device 7 employing a rotatably 
mounted, spatially curved guide tube. By means of this deflection device 
the rectilinearly supplied filamentary yarn is deflected into a helical 
course whereupon it drops in free fall into the spinning can. Deflection 
or "piddling" devices of this kind are known in the art. Reference is made 
for example to allowed U.S. Patent Application, Ser. No. 670,142, filed on 
Mar. 25, 1976, by B. Burow on a "Guide Apparatus for Deflecting a Linear 
Structure". The spinning can 8 may be either round or angular and it may 
be traversable or stationary. At a distance 9 from deflecting device 7 
yarn severing and holding apparatus 10 is mounted, rearwardly displaced 
with respect to the can as shown in FIG. 2. Apparatus 10 must be designed 
in such a way that pulley 15, together with arm 11, can be rotated by 
360.degree. and that in the course of such rotation arm 11 can be brought 
into the position shown in FIG. 2, in which it is located underneath 
deflecting device 7 in line with that device. 
In FIG. 2 a top view of the yarn severing and holding apparatus 10 is 
shown, in which the transporting or conveying means 29 for spinning can 8 
is also visible. Drive motor 44, FIGS. 3 and 4, for this transporting 
means has not been illustrated in FIG. 2. In FIG. 2 apparatus 10 is shown 
in the position in which it just crosses the vertical extension of the 
rotational axis of deflection device 7. 
Yarn severing and holding apparatus 10 comprises L-shaped arm 11 which is 
mounted for rotation in housing 12. The arm is rotated by means of motor 
13' and variable speed transmission 13, by way of V-belt 16 running over 
V-belt pulleys 14 and 15. On V-belt pulley 15 three adjustable switching 
cams 17, 18 and 19 are mounted on three planes. These switching cams 
actuate microswitches 20, 20.1 and 20.2, FIG. 4. Of these switches only 
microswitch 20 is visible in FIG. 2 as the other two switches, as viewed 
in this figure, are disposed behind microswitch 20. The direction of 
rotation of V-belt pulley 15 has been indicated by arrow 21. 
A slide 22 is carried by arm 11 for rectilinear traversing movement. This 
slide is driven by a cylinder piston unit 28. Rodless cylinder piston 
units known under the name "ORIGA" are particularly suitable for this 
purpose because of their small size. These cylinder piston units are 
obtainable from ORIGA CYLINDRAR AB, Kingsor, Sweden. It may be mentioned 
that one example for the use of such units has been described in U.S. 
Patent Application, Ser. No. 785,854, filed on Apr. 8, 1977, by E. Lenk et 
al on "Bobbin Elevators in Bobbin Transport Devices". On slide 22 cutting 
device 23 and holding device or pressure element 24 are mounted one behind 
the other as viewed in FIG. 2 in the direction 26 of can transporting 
means 29. Cutting device 23 and holding device 24 are mounted individually 
adjustable in the slide traversing direction. At its free end arm 11 
comprises an upstanding plate 25 which serves as an abutment element for 
holding device 24 as well as for cutting device 23. 
The operation of the can changing arrangement according to the invention 
shall now be more fully described with reference to FIG. 2, flow chart 
diagram, FIG. 3, and schematic circuit diagram FIG. 4. FIG. 4 shows 
switching logic 41 in its connection to the various system units 
controlling it or controlled thereby, in block diagram form; and in flow 
chart diagram FIG. 3 the resulting changes in the operating conditions of 
the various equipment units of the system have been illustrated as related 
to the switching pulses (SI 1, SI 2, etc.) occurring at various times in 
the operation of the switching logic. In FIG. 4 time delay elements T1, 
T2, FIG. 3, which form part of the switching logic have been indicated but 
other than that the details of the logic have, for the sake of simplicity, 
not been shown in FIG. 4 as any suitable -- electrical and/or pneumatic -- 
implementation of the logic which provides the functions reflected by FIG. 
3, will be readily apparent to those skilled in the art. 
In FIG. 3 it has been assumed that an empty can 8 has been driven by 
transporting means 29 underneath deflection device 7. The can is filled 
with filamentary yarn 1 deposited in loops. Arm 11 is in its rest 
position, that is, switching cam 17 depresses microswitch 20 so that motor 
13 does not receive any current. When can 8 has been filled, this is being 
indicated by a suitable indicating means -- for example a level counter or 
a counting means for the detection of the supplied filamentary yarn 
lengths. This indicating means shown as level detector 42 in FIGS. 3 and 
4, causes switching impulse SI1 to be triggered. As a result of this 
impulse switching logic 41, FIG. 4, causes the traversing or reciprocating 
means 43, if provided, of the spinning can to be terminated (not shown in 
the drawings) and motor 44 of transporting means 29 and motor 13 of yarn 
severing and holding apparatus 10 to be turned on. The speeds of these two 
drives which are thus started substantially simultaneously are timed with 
respect to each other in such a way that arm 11, at the moment it crosses 
the filamentary yarn (FIG. 2), has arrived exactly between the two 
spinning cans, that is, full can 8 and empty can 8.1. Immediately after 
crossing of the fiber run microswitch 20.2 is actuated by cam 19 (SI2) so 
that slide 22 moves into a position where devices 23 and 24 abut against 
plate 25 and is arrested there. The filamentary yarn 1 is cut by severing 
device 23. The severed yarn end of the filled can 8 is clamped between 
holding device 24 and abutment plate 25. 
Due to the fact that arm 11, at the time it crosses the fiber run is 
positioned exactly over the space between the two cans 8 and 8.1 the 
filamentary yarn is prevented from dropping into this space. Another 
result of this is that the filamentary yarn is placed over the arm only 
once so that the yarn is kept from being severed more than once. Inasmuch 
as the yarn is cut immediately after passing the fiber run it is avoided 
that the cut off end drops off only after several yarn layers have already 
been deposited in empty can 8.1. 
The can transporting means 29 are continuously moved until empty can 8.1 
has been advanced to the point of yarn run. Simultaneously arm 11 has been 
rotated far enough to reach its waiting position. This position is 
indicated by the operation of cam 18 of microswitch 20.1 (SI3). Motor 13 
is disconnected. Following this the reciprocating means 43 for spinning 
can 8.1 is switched on. Simultaneously level detector 42 is caused to 
resume is operation. Now, slide 22 is again driven back (SI 4) by the 
operating personnel with the aid of manual control 45 or by means of time 
relay T2. The operating personnel can now secure the freed end of the yarn 
to spinning can 8 so that this yarn end is prevented from dropping back 
into the filled can. 
After this has been done motor 13 is operated (SI 5) by means of time relay 
T1, or by the operating personnel, through the medium of manual control 
45, so that arm 11 is rotated back into its initial position. In this 
position cam 17 actuates microswitch 20 (SI 6). 
After spinning can 8.1 has been filled, the above described operating cycle 
is again resumed. 
In the above description it has been stated that motor 44 of transporting 
means 29 and motor 13 of yarn severing and holding apparatus 10 are timed 
with respect to each other in such a way that arm 11, at the moment it 
crosses the filamentary yarn, arrives midway between the two spinning 
cans. Variable speed transmission 13' is provided to insure this result 
even though cans of different size may be used -- which, in turn, affects 
the time it takes to transport an empty can to the position of a full can; 
for this reason the rotating speed of the arm must be changed 
correspondingly. In order to maintain synchronism between the two drives a 
control connection (not shown in FIG. 4) could be provided between the 
drive of can transporting means 29 and the drive of arm 12; however, in 
practice such a synchronizing connection can be dispensed with. 
It may be added that in the above description of the operation of this 
system the assumption has been spelled out that motor 44 of transporting 
means 29 and motor 13 of apparatus 10 are started substantially 
simultaneously. However, this too is not a necessary requirement as long 
as the operations of the two drive means are started in a predetermined 
mutual time relationship. Thus, it would be possible to design the drive 
of apparatus 10 in such a way that arm 11 will reach the position shown in 
FIG. 2 even when it is started ahead of, or later than, the drive of the 
can transporting means.