Method for processing a warp sheet of yarns

A method for processing a warp sheet of synthetic multifilament yarns wherein the yarns may be withdrawn from supply packages and advanced along a path of travel in warp sheet form, heated and drawn while in advancing warp sheet form to orient the filaments, and then wound for example on a warp beam. Upon detection of a yarn break, the advance of the warp sheet is terminated, and means are provided for interrupting the application of heat to the sheet while the advance is terminated so as to avoid damage to the remaining yarns from a continued application of heat.

Referring more particularly to the drawings, FIG. 1A and 1B schematically 
illustrate a preferred embodiment of an apparatus in accordance with the 
present invention. In this embodiment, the apparatus is adapted to process 
a warp sheet 10 of yarns, and it comprises an upstream pair of delivery 
rolls 12 and a downstream pair of delivery rolls 14, which serve to 
advance the warp sheet 10 along a horizontal path of travel, while drawing 
the warp sheet. Heating means is positioned along the path of travel for 
applying heat to the advancing sheet, and the heating means comprises two 
heated rolls 15a and 15b which extend transversely across the warp sheet 
and are arranged parallel to each other. The two rolls 15a, 15b are 
rotatably mounted on a lever arm 16, which is adapted to pivot about an 
axis 18 which extends transversely across the sheet 10 and parallel to the 
rotational axes of the rolls 15a, 15b. As illustrated, the axis 18 lies in 
the plane defined by the two rotational axes of the rolls 15a, 15b, and it 
also lies in the plane 19 defined between the pairs of delivery rolls 12 
and 14. 
In addition to the pair of heated rolls 15a, 15b, there is also provided an 
unheated pair of rolls 20a, 20b which are of like design. In particular, 
the pair of rolls 20a, 20b are mounted at the ends of a second lever arm 
22 which is adapted to pivot about an axis 24 which is parallel to the 
axis 18 of the arm 16. Both pairs of rolls 15a, 15b and 20a, 20b are 
positioned in the draw zone between the delivery rolls 12 and 14. The 
lever arms 16 and 22 extend parallel to each other as illustrated, or they 
may be arranged in mirror symmetry with respect to each other. 
As indicated above, the pivot axes 18 and 24 of the two lever arms 
preferably lie in the plane defined between the two pairs of delivery 
rolls 12 and 14. This arrangement permits one of the rolls of each pair to 
be positioned above the warp sheet 10, and the other roll of each pair to 
be positioned below the sheet. Thus one roll of each pair of adapted to 
move into the sheet of yarns 10 from the bottom, and the other roll moves 
into the sheet from the top. During advance of the sheet, the heated pair 
of rolls 15a, 15b assumes the position illustrated in FIG. 1A so as to 
deflect the sheet 10 along a generally Z-shaped path 26. The unheated 
rolls 20a, 20b are then essentially out of contact with the sheet. When 
the sheet is slowed down, the pivoting movement of both pairs of rolls 
initiated in the indicated direction, preferably concurrently with the 
start of the braking. In so doing, the heated pair 15a, 15b is withdrawn 
from the sheet of yarns and the unheated pair 20a, 20b moves into 
engagement with the sheet so that the path of the sheet becomes changed to 
that indicated at 27 in FIG. 1B. Both paths 26 and 27 have the same 
length, so that the sheet of yarns remains under the same tension in both 
conditions. Advantageously, this operation is controlled as a function of 
the tension on the sheet of yarns, and so that the tension does not 
substantially change during movement of the two pairs of rolls. With a 
parallel arrangement of the lever arms 16 and 22 as illustrated, the arms 
will be seen to move in opposite directions. However, when the arms are 
arranged in mirror symmetry, their movement would be in the same 
direction. 
Rather than mounting the rolls 15a, 15b, and 20a, 20b to pivotal lever arms 
as illustrated in FIG. 1, the rolls may alternatively be arranged 
independently of each other. For example, one heated and one unheated roll 
may be located below the sheet, and the other heated and unheated roll may 
be mounted above the sheet. However, in such an arrangement, separate 
guiding and operating mechanisms are required for each of the rolls, which 
is more complicated than the above described embodiment. Nonetheless, the 
separate guidance and control of the rolls may be desirable in that it 
enables a very sensitive control of the yarn heating, by the extent of the 
entry of the rolls into the sheet, and whereby the respective looping 
angles may be changed. 
In the above described embodiments, the various rolls represent relatively 
large masses which must be moved rapidly by reason of the normally rapid 
braking of the advance of the sheet. This can led to substantial inertial 
forces being generated when the rolls are moved. This problem is avoided 
by another embodiment of the invention, in which the heating means is not 
moved, but rather, the sheet of yarns is separated from the heating means 
to thereby interrupt the heating of the sheet of yarns. One embodiment of 
this design is illustrated in conjunction with FIGS. 2-5. 
In FIG. 2, there is illustrated an arrangement in which a hot plate 30 is 
mounted at a fixed location below the sheet of yarns 43. The upstream and 
downstream yarn delivery systems for the sheet of yarns each comprises a 
series of three rolls about which the sheet is threaded. The innermost 
rolls 47, 48 of the two delivery systems and which are closest to the hot 
plate 30 are heated, and each such roll includes a lifting cover 33 which 
is adapted to move between the sheet of yarns and the associated roll upon 
the slowing of the advance of the sheet. The covers 33 on the rolls 47, 48 
thereby act to lift the sheet from the surface of the hot plate 30, and 
from the surfaces of the rolls 47, 48, as illustrated in dashed lines, to 
the solid line position. Thus the heating effect on the sheet is rendered 
negligible. 
FIGS. 3 and 4 illustrate two different embodiments of a lifting cover 33 
for the heated rolls 47, 48 as shown in FIG. 2. In the embodiment of FIG. 
3, the pivoting axis 45 of the cover 33 coincides with the axis of the 
roll 47, so that the lifting cover is spaced a uniform distance from the 
roll surface during its movement. As illustrated, the angular extend 49 of 
the area covered by the lifting cover 33 extends beyond the looping angle 
44 of the sheet of yarns 43 on the heated roll. As shown in solid lines, 
the cover 33 is in its operative position between the sheet of yarns 43 
and the roll surface, and it is adapted to shield the sheet from the 
underlying roll. When the sheet of yarns is advancing, the lifting cover 
33 is in the inoperative position 33A, shown in dashed lines. The area to 
be covered by the lifting cover 33 depends upon the respective looping 
angle 44, and if possible, the area 49 should be four to twenty percent 
larger than the looping angle 44. This of course is only possible when the 
looping angle 44 is less than 180 degrees, which is the normal case. 
FIG. 4 illustrates an embodiment which may be used in the case of a 
cantilevered heating roll. In this embodiment, the axis of rotation 45 of 
the lifting cover 33 is relocated spaced from and parallel to the axis 50 
of the roll a distance 36. The axis 45 is also arranged in a plane 35 
which is defined by the roll axis 50 and the bisector of the looping angle 
44. This arrangement is advantageous in that the distance 37 between the 
roll surface and the inside of the lifting cover 33 is smaller in the 
lifting or operating position, than is the distance 38 in its inoperative 
position 33A. As a typical example, the minimum distance 37, which is also 
a function of the relative size of the apparatus, measures about 0.5 to 2 
mm in the operating position, and the distance 38 measures about 10 to 25 
mm in the inoperative position. 
In instances where the rolls 47, 48 are heated, the effect of the lifting 
cover 33 will be aided when it is composed of a heat insulating material, 
as is shown in FIG. 5. In this embodiment, the cover 33 is composed of an 
inner reflective layer 41, an insulating intermediate layer 40, and a wear 
resistant yarn contact layer 39. The edges 42 extending transversely to 
the sheet are preferably composed of a wear resistant material. 
In some cases, it may be desirable to cool the rolls of the downstream 
delivery system 14, so as to avoid possible changes in the yarn structure 
caused by the heat, such as an uncontrolled subsequent condensation. Also, 
the preheating of the sheet of yarns 43 as it enters the draw zone may be 
advantageous. To be able to closely control the heating of the sheet, 
there is also provided the possibility of adapting the effect of the heat 
on the sheet to the momentary speed of the sheet. This may be accomplished 
by a change of the effective looping angle 44, or the partial covering of 
the heated roll by the cover 33. In the embodiment of FIG. 1, the above 
object may be accomplished by coordinating the pivoting of the two pairs 
of rolls 15a, 15b, and 20a, 20b since the looping angle may be 
substantially varied as a function of the depth of entry of the rolls into 
the sheet, between a minimal surface contact to a maximum looping. 
FIG. 6 illustrates a further embodiment of the invention. In this 
embodiment, the cover is a flexible sheet 80 of material. There is shown 
one heated roll 60 which is rotatably supported in bearings (not shown) 
and driven by a drive (not shown). The roll 60 is partly wrapped by the 
yarns 3 which form a warp. A lever arm 81 or 82 is freely rotatably 
mounted to the axis 45 of the roll at respective ends thereof. Each lever 
arm is connected to a gear wheel 83, which is driven via the gear wheel 84 
and motor 85. It should be noted that a gear wheel identical with 84 and a 
motor identical with 85 are provided at the other end of the roll. Both 
motors are synchronously driven in the same direction of rotation as is 
roll 60. In case of yarn breakage, the brakes of the apparatus are set 
into operation. 
At the free ends of lever arms 81, 82, there is mounted a hook 86, 87, 
respectively, and the isolating sheet of material 80 is supported between 
these hooks. The sheet of material is flexible, so that it is able to 
conform to the curved surface of the roll 60. The flexible sheet of 
material is, for example, a cloth, a foil, a mat or the like. It should 
have sufficient heat resistance to bear the temperature of roll 60, which 
is up to 200.degree. C. On the other hand, it should have sufficient 
insulating properties to prevent the flow of heat from roll 60 to the 
warp, or to at least essentially impede the flow of heat. In case of yarn 
breakage or upon putting the brakes into operation, the motors 85 are 
operated for a short time, until the leading edge 88 of the sheet of 
material reaches the nip formed between the surface of the roll 60 and the 
warp. There it is clamped between the surface of the roll and the warp, 
and it is then transported by the roll 60 or the warp 3. 
It should be noted that the hooks 86 and 87 are positioned outside the 
length of the roll, and essentially on the same radius as that of the roll 
60. The length 89 of the sheet of material 80 is such that it is 
essentially identical with the running length of the yarns extending from 
the application of the brakes and to reaching a standstill (i.e. the 
braking distance). That means that in case of yarn brakage and upon 
application of the brakes, lever arms 81, 82 move the sheet of material 80 
from the illustrated non-operative position and so that the leading edge 
88 moves into the nip between the surface of the roll 60 and the warp 3. 
Here the sheet of material is clamped and then wrapped around the roll, so 
that it completely covers that part of the surface which is in contact 
with the warp. Furthermore, the length should be such that when restarting 
the apparatus, the heating of the warp, i.e. the direct heat-conducting 
contact between roll 60 and warp, is started again at a suitable point of 
time. It may be useful, if the length of the sheet of material is greater 
than the length of the yarn between the application of the brakes and 
reaching a standstill (braking distance). Preferably, however, the length 
of the sheet of material corresponds to this braking distance. 
It can be seen that a flexible cover of the described type may also be used 
with rolls which are contacted by the warp sheet which loops around the 
bottom of the roll, such as is the case with the second roll 60 shown in 
FIGS. 7A and 7B. In this case, the flexible sheet of material hangs at the 
lever arms 81, 82. By moving the levers downwardly, the leading edge which 
is opposite the edge which is held by the lever arms falls by its gravity 
into the nip between the warp 3 and the surface of the roll. The sheet is 
then clamped and transported to cover the surface of the roll. Upon 
restarting the apparatus, the sheet of material is transported by the 
roller, until it leaves the gap and the lever arms 81, 82 are moved 
without being driven by their motors 85. 
A further embodiment of an apparatus for processing a sheet of yarns in 
accordance with the present invention is illustrated in FIGS. 7A and 7B. 
As illustrated, a creel 51 is provided which accommodates a plurality of 
feed yarn packages 52, such as one thousand such packages. The yarns 53 
are withdrawn from the packages via suitable yarn guides, tensioners, and 
yarn detectors (not shown). The yarns are withdrawn by a first pair of 
rolls 54 and subsequently fanned into groups of yarns, with each group 
then being guided through elongate air jet beams 57. The beams 57 each 
comprise an elongate hollow rectangular section, and they are supported by 
a frame 55, 56 so as to be disposed in horizontal, vertically spaced apart 
rows. Each beam includes an air passageway extending horizontally through 
its hollow section, and a plurality of yarn ducts which extend 
transversely to the longitudinal direction of the beam and which are 
aligned in a longitudinally spaced apart relation. Also, an air jet 
aperture communicates between the central air passageway of the beam 
section and each yarn duct for providing an impinging airstream upon 
respective ones of the yarns. The advancing yarns are thereby entangled by 
the air jet, so as to improve the yarn cohesion, as well as improve the 
smooth running properties and stretchability of the yarn. A further 
description of a beam of this type may be obtained from the commonly owned 
copending application Ser. No. 676,723, now U.S. Pat. No. 4,592,119, and 
entitled Air Jet Yarn Entangling Apparatus. 
Each air jet beam 57 is preceeded and followed by a guide bar 81, which is 
suitably mounted to the associated beam. Subsequent to the air jet 
entanglement, all of the yarns are brought together into one plane, by 
means of the two guide rolls 58. The yarns are then withdrawn by the feed 
rolls 59 of the drawing system. Heated rolls 60 follow the feed rolls 59, 
and the rolls 60 are heated to about 90 degrees C. in the case of 
polyester yarns. The yarns then travel over a hot plate 61 upon which they 
are heated to about 120 degrees C. or more. The hot plate 61 is pivotally 
mounted on a support bracket 62, and the plate is adapted to be removed 
from the sheet of yarns by a pneumatic cylinder piston assembly 63. The 
assembly 63 may be controlled as a function of yarn detectors (not shown). 
A deflecting roll 64 is mounted downstream of the plate 61, and is 
followed by delivery rolls 65. The circumferential speed of the delivery 
rolls 65 is greater than the circumferential speed of the feed rolls 59, 
by the draw ratio. The sheet of yarns is then guided via a reed or comb 68 
to the warp beam 67 on the beam winder 66. 
The present invention provides that covers as per FIGS. 3-6 may be provided 
for thermally isolating the heated rolls 60 from the warp sheet during a 
non-advance or standstill of the sheet, or that the rolls 60 may be heated 
with a fluid, and that valve means is provided through which the heated 
fluid may be rapidly exchanged with an unheated fluid. In this latter 
case, the valve means is preferably operatively connected with the yarn 
monitoring system of the drawing apparatus. Water is usually a suitable 
hot fluid, since temperatures up to 100 degrees C are usually sufficient. 
Water is also suitable as the cooling fluid, with cool being here 
understood to mean a temperature at which the yarns are not subject to 
damage. 
It should also be noted that the surface speed of the rolls 60 may be 
adjusted independently of that of the rolls 59 and 65, respectively, which 
is known per se from the drawing technology for man made filament yarns, 
and in particular polyester filament yarns. 
FIG. 8 illustrates the heating and cooling circuit for the rolls 60 of the 
embodiment of FIGS. 7A and 7B. The rolls 60 are hollow, and are connected 
to a fluid conduit via conventional slip ring couplings. The heating 
circuit includes a pump 70, and upon operation of the pump 70, a heating 
fluid circulates through the heater 71 which holds the fluid at a 
predetermined temperature. Upon a break of even one of the yarns of the 
sheet 10 being detected by the yarn sensor 72, an output signal is 
generated causing the three way valves 73 and 74 to be reversed so that 
the heater is disconnected from the fluid circuit and the cooler 75 is 
connected to the circuit in its place. The cooler 75 may be an active 
cooler, however under certain circumstances it may comprise a sufficiently 
large fluid container in which the fluid is held at room temperature. For 
this purpose, a heat exchanger may be provided if necessary. The fluid is 
then transported from the cooling container or cooler 75 into the interior 
of the hollow roll 60. In so doing, it will often suffice that the roll 60 
receives a single filling of the cooled fluid, however, this depends on 
the mass and thermal characteristics of the roll 60, as well as its 
temperature, the temperature of the fluid pumped from the cooling 
container, and also the desired temperature decrease. 
Instead of replacing the heated fluid of the roll 60 with a single filling 
of cooling fluid, it is also possible that the cooling fluid may be 
continuously circulated. In this case, a temperature sensor 76 may be 
positioned in the circuit upstream of the pump 70, with the sensor 76 
being designed to disconnect the drive 77 of the pump 70 upon a desired 
temperature having been reached. 
Referring again to FIG. 7B, it will be recalled that the rolls 60 of the 
feed system and the plate 61 are heated. Also, it will be understood that, 
depending upon the degree of the spun orientation of the advancing yarns, 
a change in length, i.e. flow, will occur between the last roll 60 and the 
hot plate 61. It may also be assumed that the flow zone will extend to the 
hot plate 61. As a result, in the even of a shut down, an undrawn length 
of the yarn will rest upon the heated roll 60 and the initial portion of 
the hot plate 61. For this reason, the apparatus may be temporarily 
operated in the reverse direction after a shut down of the apparatus, with 
the transmission ratio between all rolls 59, 60, 65 being changed to one 
to one. This reverse movement continues until no undrawn yarn is left in 
contact with any heating means. When the rolls 60 are not cooled, the 
return movement should thus continue until the flow zone has arrived at a 
point upstream of the rolls 60. If however the rolls 60 are cooled in the 
manner described above, the return movement needs to proceed only so far 
that the flow zone comes to a position between the rolls 60 and the entry 
side of the heating plate 61, which means that a shorter return distance 
will be adequate. When proceeding in this manner, the cooling of the rolls 
and/or the lifting of the hot plate from the yarns may be avoided. 
However, it should be noted that this procedure is applicable only when 
the drawn yarn material can withstand the temperatures required for the 
drawing, without damage during the anticipated time of the breakdown. The 
ability to withstand such temperature depends on the particular yarn 
composition. Likewise, the level of the temperature is dependent on the 
yarn composition, as well as the other drawing parameters and the desired 
end product. It has been found that the described method is easily 
applicable to and advantageous with the processing of polyethylene 
therephthalate multifilament yarns which have been spun at a delivery 
speed of more than 3500 m/min, which imparts a relatively high spun 
orientation. 
To restart the apparatus after correction of the breakdown, the rolls 59, 
60 and 65 first start to rotate at a transmission ratio of one to one 
until the yarns, i.e. the flow zone, has again reached the position at 
which the shut down occurred. The number of forward revolutions of the 
rolls 59, 60, 65 at a transmission ratio of one to one thus corresponds to 
the number of the rearward revolutions previously carried out at a 
transmission ratio of one to one. It should be noted also that the warp 
beam must perform these backward and forward revolutions. and it is 
necessary to adapt its speed to the permissible yarn tension. 
In the drawings and specification, there has been set forth preferred 
embodiments of the invention, and although specific terms are employed, 
they are used in a generic and descriptive sense only, and not for 
purposes of limitation.