DRAFTING SYSTEM FOR YARNS

TRAIN D'ETIRAGE POUR FILES

English Abstract

Drafting System for Yarns
Abstract
Drafting system for textile yarns and including a
driven feed roll, a driven output roll, a low friction
freely rotatable heated roll located between the
driven feed roll and the driven output roll and
operating at essentially the same surface speed as the
driven feed roll, the freely rotatable heated roll
being driven by engagement with the yarn and whereby
sufficient yarn tension automatically is transferred
upstream of the freely rotatable heated roll to
pretension the yarn before it contacts the freely
rotatable heated roll with drafting taking place near
the location where the yarn leaves the freely rotata-
ble heated roll to pass toward the driven output roll.
TR0436B

Claims

We Claim:
1. A drafting system for yarn comprising:
driven feed means for feeding said yarn at a
predetermined speed driven output means for
forwarding said yarn at a second predetermined
speed greater than said first-mentioned pre-
determined speed; a low friction freely rotatable
heated roll, the surface of which is heated to a
predetermined temperature, said freely rotatable
heated roll being located between said driven feed
means and said driven output means and a separator
roll spaced adjacent to said freely rotatable
heated roll and wherein said yarn is wrapped a
plurality of times around said freely rotatable
heated roll and said separator roll: and the
surface speed of said freely rotatable heated roll
is operating slightly faster than the surface speed
of said driven input means, with said freely
rotatable heated roll being driven by engagement
with said yarn and whereby sufficient yarn tension
automatically is transferred upstream of said
freely rotatable heated roll to pretension said
yarn before it contacts said freely rotatable
heated roll with drafting taking place near the
location where said yarn leaves said freely
rotatable heated roll to pass toward said driven
output means, and wherein:
(a) the steady state resistance to turning of the
freely rotatable heated roll plus separator
roll, as measured by stress on the yarn being
drafted, is no more than 0.25 grams/denier
(drafted yarn),
27

(b) the start-up resistance, which is primarily
the inertia of the freely rotatable roll, is
no more than <IMG>
or <IMG>
as obtained from the equation
<IMG>
wherein
T = torque (length x force)/per unit
denier
C = constant depending on units selected
k = radius of gyration (units of length)
a = angular acceleration (radians per
second squared)
W = weight (units of mass),
(c) the coefficient of friction, between the yarn
and the surface of the freely rotatable heated
roll as measured on a Rothschild Friction
Tester (based on capstan equation) using 180°
contact at a yarn speed of 10 metres/minute,
is greater than 0.57,
(d) the separator roll being located at a position
relative to the freely rotatable heated roll
and relative to the direction of the path of
yarn movement such that the angle of contact
of the yarn with the surface of the freely
rotatable heated roll is >30° on the first
wrap and is >30° on the last wrap before the
yarn leaves the freely rotatable heated roll,
and
28

(e) there is no frictional contact made with the
yarn in the area where pretension occurs
between the location where the yarn exits from
the driven feed means and the location where
the yarn makes initial contact with the freely
rotatable heated roll.
2. A drafting system as defined in Claim 1 wherein
said steady state resistance to turning of the
freely rotatable heated roll plus separator roll,
as measured by stress on the yarn being drafted. is
<0.15 grams/denier(drafted yarn), and said
start-up resistance is no more than
<IMG>
<IMG>
3. A drafting system as defined in Claim 1 wherein
said coefficient of friction is in the range of
0.75 to 0.95.
4. A drafting system as defined in Claim 1 wherein
said separator roll is located at a position
relative to the freely rotatable heated roll and
relative to the direction of the path of yarn
movement so as to be within the angular
specification designated <IMG> shown in Fig. 4a
of the drawings.
5. A drafting system as defined in Claim 1 wherein
said separator roll is located at a position
relative to the freely rotatable heated roll and
relative to the direction of the path of yarn
movement to so as to be within quadrant "a" shown in
Fig. 4b of the drawings.
29

6. A drafting system as defined in Claim l and
including means for thermally stabilizing the
yarn.
7. A drafting system as defined in Claim 6 wherein
said means for thermally stabilizing the yarn is
located between said freely rotatable heated roll
and said driven output means.
8. A drafting system as defined in Claim 6 wherein
said means for thermally stabilizing the yarn is a
means for heating said driven output means.
9. A drafting system as defined in Claim 1 wherein
greater than 60 percent of yarn draw tension is
transferred upstream of said freely rotatable
heated roll.
10. A drafting system as defined in Claim l wherein 80
to 95 percent of yarn draw tension is transferred
upstream of said freely rotatable heated roll.
11. A drafting system as defined in Claim 1 wherein
said low friction freely rotatable heated roll is
supported for rotation on an air bearing.
12. A drafting system as defined in Claim l wherein
said low friction freely rotatable heated roll is
supported for rotation on ball bearings.
13. A drafting system as defined in Claim 6 wherein
said yarn is a polyester yarn and said predeter-
mined temperature for said surface of said freely
rotatable heated roll is about 80°C to about 120°C
and the temperature for said means for thermally
stabilizing said yarn is such that the yarn

temperature is about 120°C to about 220°C as the
yarn leaves said means for thermally stabilizing
said yarn.
31

CLAIMS SUPPORTED BY THE SUPPLEMENTARY DISCLOSURE
S.D. 14. A drafting system as defined in claim 1 wherein
said steady state resistance to turning of the freely rotatable
heated roll plus separator roll, as measured by stress on the
yarn being drafted, is <0.15 grams/denier (drafted yarn), and
said start-up resistance is
<IMG>
no more than or
<IMG>
S.D. 15. A drafting system as defined in claim 1 wherein
said steady state resistance to turning of the freely rotatable
heated roll plus separator roll, as measured by stress on the
yarn being drafted, is <0.15 grams/denier (drafted yarn), and
said start-up resistance is
<IMG>
no more than or
<IMG>
32

Description

De6criPtion
Drafting Sy6tem for Yarns
Technical Field
The present invention is directed to a drafting
eystem for yarns generally used for textile yarn6 and
particularly i6 directed to a ~ystem for draf~ing
yarn~, 6uch a~ polyester yarns, at speeds greater than
300 meters per minute up to 1500 meters per minute and
greater.
Background
There is con~iderable prior art in the drafting of
yarns, and particularly for polyester yarn~. U.S.
Patent No. 3,539,680 discloses one system where 6peed~
disclosed are around 600 meters per ~inute to 1500
meter~ per minute: however, rela~ively ~peaking, this
is a very expen~ive system requiring equipment and
main~enance thak we think can be omitted with the
system that we propose herein.
Pretensioning yarn in a drafting ~ystem before ~e
yarn contact~ any heated device~ whether ~uch device be
a fixed pin, a rotating roll, a stationary contact
heater or other type of device, i6 an important
contribution ~oward obtaining a uniformly dyeable and
defect-free yarn. U.S. Patent No. 3,539,G~0 mentioned
abo~e recogni~e~ the importance of æuch preten~ioning
~o a6 to minimize occurrence of "fluff~" and dyeing
unevennes~ ~Col. 4~ lines 43-47). The patent discu~ses
an arrangement for obtaining such preten6ion ~y
providing the combination of a nip roller and a
, .

delivery roller, and employing a ratio of peripheral
~peeds of the delivery roller to the heated feed roller
within the range of l:l.OOl-1:1.030. Thus the patent
discloses e~tablishing a pretension zone which i6
designed to draw the yarn slightly, as indicated by the
given ratio range, in order to aehieve the required
pretensioning. The patent indicates alternatively ~hat
a thread brake or guide may be used if it can impart
uniform and predetermined tension.
Other types of drafting systems employ heated pins,
heated plates, and heated plates with separator rolls,
all of which are well known. The quali~y of the yarn
produced on these systems, however, has been found to
be generally poor due to the high level of broken
filaments and poor dye uniformity than that produced on
a system such as represented by the above-mentioned
U.S. Patent No. 3,539,68Q, and the problems of broken
filaments and poor dye uniformity have been found to
increa~e as the speed is increased. Broken filamentæ
tend to cause defects, which cause waste and los8 of
time~
An objec~ of our invention is to provide a low
~ri~tion drafting ~y~em which provides au~omatic
pretensioning of the yarn before the yarn contac~s any
heated device and without employing t~e usual
structures upstream from such heated device to provide
~uch pretensioning.
U.S. Patent No. 3,919,748 discloses an apparat~g
for altering the length of a &ynthetic continuou~
filament or yarn strand. ~h~ apparatus co~prises a
first strand feeding means involving a driven feed roll
and a separa~or idler roll; a f ir~t heating means in
~he form of a heated roll connec~ed to and coaxial with
the driven feed roll and having a ~eparator idler roll:
a second heating mean~ in the form o~ a heated pla~e
over which ~he yarn strand slides: a second feeding
means in the form o~ a driven roller and a ~eparator
A

~2a ~74~
idler roller; and a driven take-up spool. All of the
embodiments in the patent, except one, show the "fir~t
heating means", which is the heated roll, as being
rigidly connected to the fir~t driven feed roll. The
excep~ion i~ the embodiment ~hown in Fig. ~ where the
"heated roller 20"' turn~ freely on stud 23 of the
swinging arm 26 and is thus turned only by the yarn
strand a~ the yarn strand loops around the heated
roller. The pa~entee does not give any reason for t~e
purpo~e of thi~ exception nor does he offer any
advantage~. There i6 no recognition by the patentee,
therefore, that preten~ioning of the yarn would
automatically occur upstream of the heated roller 20
in the area between the exit of the yarn fitrand from
the driven feed roll 17 ~Fig. 4) and the initial
contact of the yarn strand with the heated roller 20l.
Although Fig. ~ does not illu6trate a separator idler
roller, it i8 as6umed that it would be po~itioned as
illustrated in Fig. 6. Also, although the patentee
doe~ not indicate in his ~iscu~6ion of the embodimene
of Fig. 4 that the separator idler roller for heated
roller 20' would need to be independently rotatable
from the 6e~arator idler roller for th~ driven ~eed
roll 17, it is assumed that thi~ would be desirable.
In reference to Fig. 6, therefore, a "thread guide" 37
is proYided between the coaxially alisned driven feed
roll and heated roller on one side and the ~eparator
idler roller~ on the other 6ide which ~erves to
displace the yarn ~trand from the driven feed roll to
the heated roller. Since thi~ is probably a hig~
tension zone, thi6 ~read guîde in the embodiment of
Fig. 4 will tend to damage the yarn strand which will
lead to the generation of an excessive number oP broken
filament~ in the yarn. The yarn 6trand filaments which
are ~irectly in contact with t~e 6urfacs of the thre~d
guide 37 will be damag~d to the
~} .

~2gi~317~
extent that they will break in the subsequent drafting
of the yarn strand.
Another object of the invention, therefore, is to
insure that there is no frictional contact ~ade with
the yarn in the area between the exit of the yarn from
the input feed roll and the initial contact of the yarn
with the freely rota'able heated roll.
Still another object of our invention is to provide
a low maintenance drafting system.
A further object of our invention is to provide a
drafting system which will operate satisfac~orily from
a mechanical quality and dye uniformity standpoint, at
speeds up to 1500 meters per minute and greater.
A still further object is to provide a less
expensive drafting system for providing textile yaxns
of equivalent quality to those made by the process
disclosed in U.S. Patent No. 3,539,680.
.
Disclosure of In~ention
In accordance with the present invention, we
provide a drafting system for yarn which has a driven
feed roll for feeding the yarn at a predetermined
speed; a driven output roll for ~orwarding the yarn
at a second predetermined speed greater than the
first-mentioned speed; a low friction freely rotatable
heated rollr the surface of which is heated to a pre-
determined temperature, the freely rotatable heated
roll being located between the driven feed roll and the
driven output roll; and a separator roll spaced
adjacent to the freely rotatable heated roll and
wherein the yarn is wrapped a plurality of times around
the freely rotatable heated roll and the separator
roll. The surface speed of the freely rotatable heated
roll is operating slightly faster than the surface
speed of the driven input roll with the freely
rotatable heated roll being driven by engagement with

~L2~37'~
the yarn. As a result. sufficient yarn ten6ion
automatically is tran~ferred upstream of ~he freely
rotatable heated roll to pretension ~he yarn before it
contacts the freely rotatable heated roll. Drafting
takes place near the loca~ion where the yarn leaves the
freely rotatable heated roll to pass toward the driven
output roll.
The e~sential feature~ of the above described
drafting system are:
(a) the steady ~tate resi6tance t~ turning of the
freely rotatable heated roll plus the separator roll,
as measured by stress on the yarn being drafted, i6 no
more than 0.25 grams/denier(drafted yarn) and is
preferably <0.15 grams/denier(drafted yarn),
(b) t~e start-up resistance. which is primarily the
inertia of the freely rotatable heated roll, i6
no more than 0.000113 Pounds x s~uare foot or
denier(drafted yarn~
4.B6xlQ-5 newtons x metres sauared and is preferably
denier(drafted yarn)
approximately 0.000045 pounds x sQUare foot or
denier(drafted yarn)
1.86xlO-5 ne~tons x metres squared a8 obtained from
denier(drafted yarn)
the equation
T = CWk2a
denier ~drafted yarn~
wherein
T - torque (length x force~per unit denier
C = constan~ depending on units selected
k = radius of gyration (unit~ of len~th~
a = angular acceleration (radian6 per
second squared)
weight (units of mas6~,
.
(c~ the coefficien~ of friction betwee~ the yarn
and the sur~ace of the ~reely rotatable heated roll, as
mea~ured on a Rothschild Friction Te~ter (ba~ed on
; :
,
:
.

capstan equation) using 180 cGntact at a yarn speed
of 10 metres/minute, is greater than 0.57,
(d) the separator roll being located at a position
relative to the freely rotatable heated roll and rela-
tive to the direc~ion of the path of yarn movementsuch that the angle of contact of the yarn with the
surface of the freely rota,able heated roll is > 30
on the first wrap and is >30 on the last wrap
before the yarn leaves the freely rotatable heated
roll, and
(e) there is no frictional contact made with the
yarn in the area where pretension occurs between the
location where the yarn exits from the driven feed
roll and the location where the yarn makes initial
contact wi~h the freely rotatable heated roll.
More specifically, the separator roll is located
at a position relative to the freely rotatable heated
roll and relative to the direction of the path of yarn
movement so as to be either within the angular
specification designated 2 + 6 ~ as shown in Fi~. ~a
of the drawings, or so as to be within quadrant ~a",
as shown in Fig. 4b of the drawings.
A device for thermally stabilizing the yarn may be
located between the freely rotatable heated roll and
the driven output roll, or the driven output roll may
be heated so as to thermally stabilize the yarn, or
the yarn may be thermally stabilized after the yarn
leaves the driven output roll.
In the drafting system disclosed herein, greater
than 60 percent and preferably 80 to 95 percent of the
yarn draw tension is trans~erred upstream of the
freely rotatable heated roll to pretension the yarn
before the yarn touches the heated roll. It is impor-
tant to realize that in the proposed drafting system
of this invention it is the low ~riction character o~
the freely rotatable heated roll that enables the

~2~
transmission of a significant portion of the draw
tension upstream of the freely rotatable heated roll,
thereby providing automatic or inherent pretensioning
of the yarn.
The drafting system may include a low friction
freely rotatable heated roll that is an air bearing,
or it may be a ball bearing or any other low friction
bearing arrangement. "Air bearing~ and ~ball bearing~
are expressions used herein to describe a heated roll
that may be supported for rotation either by an air
bearing arrangment or a ball bearing arrangement.
~ here the yarn being processed is polyest~r yarn,
the predetermined temperature for the surface of the
freely rotatable heated roll ~ill be about 80C to
about 120C, and the temperature for the device or
thermally stabilizing the yarn is such that the yarn
temperature is about 120C to about 220C as it leaves
the thermally stabilizing device.
Brief Description of the Drawings
The details of our invention will be described
in connection with the accompanying drawings, in which
Fig. 1 is a schematic elevational view of a prior
art drafting system employing a pinch roll such as
that disclosed in the above-mentioned U.S. Patent
No. 3,539,~80;
Fig. 2 is a schematic elevational view of a prior
art drafting system employing a heated pin;
Fig. 3 is a schematic elevational view of the
drafting system of the present invention employing
a low friction freely rotatable heated roll and a post
stabilizing device; and
Figs 4a and 4b are schematic diagrams ill~strating
preferred locations for the separator roll relative to
the freely rotatable heated roll and relative to the
direction o~ the path o yarn movement.
. . .

~2~
Best Mode for Carrying Out the Invention
Fig. 1 represents a prior art drafting system 10
such as disclosed in U.S. Patent No. 3,539,680 in
which a pretension zone for the yarn being processed
is established between a nonheated godet roll 12 and a
heated godet roll 14 and its separator roll 16, and a
pinch roll 18 bearing against the heated godet roll 14
serves to minimize variability of the yarn drafting by
preventing the drafting of the yarn 20 from extending
upstream of the location of the pinch roll 18. The
godet roll 22 and its separator roll 24 serve as an
output roll arrangement for forwarding the yarn to a
winder (not shown). Guides for the yarn are shown at
26 and 28, and 30 designates the separator roll for
the nonheated godet roll 12.
Fig. 2 represents a prior art drafting system 32
which employs a heated stationary pin 34 between a
nonheated godet roll 36 and its separator roll 38 and
a nonheated godet roll 40 and its separator roll 42,
the latter two serving as an output roll arrangement
for forwarding the yarn 44 to a winder (not shown).
Another nonheated godet roll 46 and its separator
roll 48, as well as yarn guides 5~ and 52 are shown
located upstream of the first-mentioned nonheated
godet roll 36.
The drafting systems of Figs. l and 2 will be
discussed later in relation to the drafting system of
the present invention following a discussion of the
essential features of the invention.
In Fig. 3, which represents the proposed drafting
system 54 o the present invention, the yarn 56 is
shown being guided over yarn guides 58 and 60 to a
nonheated godet roll 62 and its adjacent separator
roll 64. The yarn then passes ~o a low friction
freely rotatable heated roll 66 and its adjacent
separator roll 68 to be wrapped a plurality of times

therearound before passing to the nonheated godet roll
or output roll 70 and its adjacent separator roll 72
to be forwarded to a winder (not shown).
The yarn may be thermally stabilized by a device
such as that represented at 74, which may be a slit or
plate heater having either contact or noncontact with
the yarn. Typical temperatures to be employed with a
contact heater, when the yarn being processed is poly-
ester, are such that the yarn temperature will be
about 120C to about 220C, and the freely rotatable
heated roll surface temperature will be about 80C to
about 120C as the yarn leaves the stabilizing
device.
Alternatively the device for thermally stabilizing
the yarn may be a device for heating the driven output
roll; thus the driven output roll may be a heated
godet roll. It is also within the scope of the inven-
tion that such heated godet roll may be a stepped
godet roll such that controlled shrinkage may take
place during thermal stabilization, or the ya~n may be
thermally stabilized after it leaves the output
roll 70 and its separator roll 72.
As heretofore pointed out, we have discovered so~e
essential features that must be present in our draft-
ing system in order for our system to be effective.We have not found these features present in the prior
art nor recognized by the prior art.
First, the steady state resistance to tuxning of
the ~reely rotatable heated roll plus the separator
roll, as measured by stress on the yarn being drafted,
must be no more than 0.25 grams/denier(drafted yarn)
and preferably ~s <0.15 grams/denier(drafted yarn).
Obviously, the steady state resistance to turning has
two components: (1) bearin~ resistance and (2) air
drag, with air drag being mor~ sensitive to operatiny
speed.

-- 10 --
Second, ehe start-up resi~tance, w~ich is primarily
the inertia of the ~reely rotatable heated roll, i5
no more than 0.000113 pounds x ~quare foot or
denier(drafted yarn)
5 4.86x10-5 newton6 x metres s~uared and i~ pre~erably
denier(drafted yarn)
approximately O.Q00045 ~ounds x square foot or
denier(drafted yarn)
1.86xlO-5 newtons x metre6 sq~red a~ obtained from
denier(drafted yarn)
the equation
T - CWk2a
denier (drafted yarn)
wherein
T = torque (length x force)~per unit denier
C = constant depending upon the units 6eleceed
k = radius of ~yration (unit~ of length)
= angular acceleration (radian~ per
6econd squared)
W = weight (unit~ of ma~s)~
For a given yarn at stare-up, the torque iB
approxima~ely constant and i8 generated by sliaing
frictional contact with the free~y rotatable ~ea~ed
roll. Thus, the re~istance to turning i~ directly
proportional to Wk . The torque generated ~o
accelerate the freely rotatable heated roll iP also
proportional to denier because the area in contact with
the heated roll increase~ as the denier increa~e~.
Thu6, ~pecifying that the pound~ x ~quare
foot/denier(drafted yarn) ~newton6 ~ metres squared~-
denier~drafted yarn)] 6hould not exceed a given number,
i~ equivalent to caying that ~he angular acceleration
will equal or exceed a minimum value and thereby
35 minimi~e ~tare-up time for the freely ro~at~ble ~eated
roll.

7~L
Third, the coefficient of friction between ~he yarn
and the surface of the freely rotatable hea~ed roll, a~
mea6ured on a Roth~child Friction Tester (ba6ed on
capstan equation~ u6ing 180 contact at a yarn 6peed of
10 metres~minute, is greater ~han 0.57, and i6 prefer-
ably in the range of 0.75 to 0.95. The capstan equa-
tion i~ well-known, but will be mentioned here a6
bein~
T2 = e~
T
wherein
T2 = ten~ion of the yarn on the side of the
capstan where yarn i6 being pulled
Tl = tension of the yarn on ~he other ~ide
of the capstan
e = base of natural logarithm
= coefficient of friction
~ = angle of wrap in radians
The high coefficient of friction insures that t~e
yarn will not slide on ~.he freely rotatable heated roll
during the fir~t wrap and thereby undesirably initiate
a kind of two-stage drafting. Thi6 also hel~s increa~e
the ~orque at star~-up which minimizes the ~ime for ~he
freely rotatable heated roll ~o accelerate ~o steady
~tate.
Fourth, the separator roll 6hould be located at a
~06ition relative to the freely rotatable heated roll
and relative to the direc~ion of the path of the yarn
movement ~uch that the angle of contact with the
6urface o~ the freely rotatable roll i6 ~30 on the
fir~t wrap and i6 230~ on ~he la~t wrap before the
yarn leaves the freely rotatable heated roll, Note,
for example, the angle of contact llxll, which would be
on the firfit wrap in Fig6. ~a and gb, and the angle of
contact "y", which would be on the last wrap in Figs.
4a and 4b.
.

- 12 -
As also heretofore pointed out, the separator roll
is located at a position relative to the freely
rotatable heated roll and relative to the direction of
the path of yarn movement so as to be either within
the angular specification designated + , as
shown in Fig. 4a of the drawings (no'e path of yarn 56
in Fig. 4a), or so as to be within quadrant "a~, as
shown in Eig. 4b of the drawings (note path of yarn 56
in Fig. 4b). The reason for the yarn being in
quadrant ~a~ in Fig. 4b, for èxample, is that the yarn
has a longer contact with the heated roll on the last
wrap and thereby helps insure that no drating will
take place before the yarn leaves the freely rotatable
heated roll. The distance between the separator roll
and the freely rotatable heated roll should be mini-
mized with about one (1) to two (2) inches ~2.54
centimeters to 5 centimeters) being reasonable~
Fifth, there is no frictional contact made with
the yarn in the area where pretension occurs between
the location where the yarn exits from the driven feed
roll and the location where the yarn makes initial
contact with the freely rotatable roll. This ~eature
is quite essential hecause any interference in this
critical area, such as shown by the thread guide 37 in
Fig. 6 of U.S. Patent No. 3,919,748, as heretofore
discussed, will cause damage to the yarn resulting in
filament breakage in the subsequent drafting of the
yarn.
The drafting systems of the prior art will
now be discussed and compared with the drafting system
of the present invention. Be~ore doing so, however,
we want to point out that the feed system for our
inven~ion does not have to be powered godetsl as is
often true in the prior art, but can be of any o~ the
lesser-costing devices used on false twist texturing
machines, (i.e. rubber cots on shafts, casablancas)O

- 13 -
U.S. Patent No. 4,053,27~ discloses a hea~ed air
bearing that in principle would be suitable Por
practice ~f t~e ~resen~ invention. ~lthough t~ere i6
no disclo~ure in the patent where the thermocouple
would be positioned to assure pre~etermined ~urface
temperatures, we would ~uggest employing a thermocouple
internally of the roll with its probe being positioned
just beneath the surface of the roll such as disclosed
in U.~. Patent No. 3,879,594 or Patent No. 3,296,418,
for example. Air bearings or rolls are al~o shown in
U.S. Patent~ No. 4,013,326, No. 3,753,517, and No.
3,560,066. Ball bearing rolls may also be used and are
conventional in the art, ~uc~ as shown in U.S. Patent
No. 3,296,418. The design o~ such roll, ~owever, must
be o~ very low friction.
The freely rotatable heated roll 66 (Fig. 3) in our
invention i6 wrapped with sufficient wraps to ensure
heating of the yarn to approximately ~he surface
temperature of the heated roll~ Drafting of the yarn
56 takes place near the point where the yarn leaves t~e
heated roll 66 for the last time on it~ way koward t~e
outpu~ roll 70.
The output roll may be con6tru~ted in the same
manner a the input roll, thus costs will be mini~i~ed
and ~uch construction will be simpli~ied because the
godet rolls shown do not reguire heating thu~
maintenance will be reduced a~ compared to maintenance
required for heated godet rolls. Obviously, ~he latter
statement will only be partially true if the thermally
stabilizing device should be incorPorated in t~e output
roll ~o ma~e it in effect a heated godet roll.
The following drafting sy8tem8 were evaluated:
(1) a drafting sy6tem including a heated godet roll
~aving a 0.5 meter circumference and a pinch xoll ~uch
a6 disclosed in U.S. Patent No. 3,539,680 and illus-
'~
-, ;. ,~ , , .

~24B74~
- 14 -
trated in Fig. 1; (2) the same drafting system as in
(1) except the pinch roll was removed (not shown in
the drawings); (3) a drafting system including a
stationary 40 millimeter diameter heated stationary
pin having a flame-coated ceramic surface, such as
disclosed in Fig. 2; (4) the same drafting system as
in (3) except that a stationary 80 millimeter diameter
heated stationary pin was used; (5) a drafting system
including a 70 millimeter diameter freely rotatable
heated roll was used, such as is illustrated in
Fig. 3.
A polyester (from polyethylene terephthalate
polymer) POY (partially oriented yarn) was used
to evaluate ~he drafting systems. See U.S. Patent
No. 4,245,001 for a description of the polymer and
spinning conditions for making the POY. The numbers
shown in the tables below are highly dependent upon
the quality of the polymer from which the yarns were
spun and the spinning process from which they were
made. Thus the true significance of these numbers
is determined only by looking at the relative values
among the systems as opposed to the absolute numbers.
As noted in the tables, no post stabilization device
was used in obtaining the results shown in thé tables.
The drating systems were evaluated with the
above-aescribed yarn to determine optimum drafting
conditions for each system at 400 meters per minute
and at 1000 meters per minute drafting speeds~ The
drafting system of our invention ran so smoothly at
1000 meters per minute that we see no problems in
running it up to 1500 meters and greater. After
optimum drafting conditions were determined for each
system~ the systems were then compared to each other,
as shown by the tables below.

~2~7~
Table 1
Drafting Conditions for Polyesler POY
270 denier/30 filaments
Preheating Broken Filaments
Temperature(ct./1000 m) %
Set Pt., C X** S*** Uster
Heated Air Bearing100 2.33 1.66 3.12
8 wraps 120 1.89 1.17 1.95
645/1000 m/m 140 0.33 0.50 0.66
150* 0.11 0.33 0~67
160 0.11 0.33 0.7~
Heated Air Bearing120 0.67 1.32 0.62
8 wraps 140* 0.00 0.00 0v78
258/400 m/m 150 2.78 1.56 0.77
160 ll.OU 4.73 0.79
80 mm Hot Pin 70 9.67 3.00 6.92
1-360 wrap 80 14.11 3.98 7.23
645/1000 m/m 90 19.67 3.~0 7.18
80 mm Hot Pin 70 4.89 2.09 5.60
`1-360 wrap 80 2.67 2.34 5.20
258/400 m/m 100* 4.00 2.34 2.24
120 14.22 4.27 1.00
40 mm Hot Pin 80 12.87 3O94 6.97
1~360 wrap 90 28.33 6.40 7.25
645/1000 m/m 100 45-44 8.68 7.20
120 100.33 10.6~ 6.62
140 127.67 14.57 5.40
40 mm Hot Pin 70 3.44 1.81 6.78
1-360 wrap 80 6.44 3.50 6.R3
258/400 m/m 90 5.44 2.40 6.20
100 4.44 2.60 ~.20
Heated Godet (no pinch) 80 1~33 1.41 3.33
8 wraps 95 1.00 1.32 ~.72
645/1000 m/m 100 0.56 0.73 1.82
110* 1.56 0.88 0.73
120 43.3 8.66 U.68

7-~
- 16 -
Table 1 continued
Heated Godet (with pinch) 105 0.00 0.00 0.93
8 wraps 110* 0.00 0.00 0.73
645/1000 m/m 115 0.33 0.50 0.72
Heated Godet (no pinch) 60 17.77 7.97 2.65
8 wraps 80 9.56 2.96 2.60
258/400 m/m 90 0.11 0.33 1.31
95* 0.44 0.53 0.86
100 4.33 2.45 0.95
110 102.20 17.75 0.93
120 393.10 63.07 1.45
Heated Godet (with pinch) 90 0.22 0O44 1.40
8 wraps 95* 0.11 0.33 0.88
258/400 m/m 100 0.78 1.64 0.80
*optimum conditions
**mean of nine (9) separate measurements on
1000 meters of drawn yarn
***standard deviation
no post stabilization was used in obtaining
,hese results

7~1
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- 19 -
Table 1 shows the Uster uniformity and broken
filament results from the different drafting systems
and the conditions evaluated using a partially
oriented yarn (POY) of polyester (270 denier/3
filaments from polyethylene terephthalate)D
Table 2 shows the Uster uniformity and broken
filament results at various numbers of wraps on the
surface of the 70 millimeter dia~eter heated air
bearing or heated roll. Optimum drafting conditions
for various POY yarns using the 70 Inillimeter diameter
heated air bearing are shown in Fig. 3.
In reference to Table 1 again, in general as the
temperature of the drafting device increases, the
level of broken filaments for the yarn decreases,
passes through a minimum and then increases. The Uster
uniformity behaves similarly. The drafting conditions
which gave the minimum Uster uniformity and broken
filament level was chosen as the optimum drafting
condition, and it is indicated with a single asterisk
in Table 1. The 70 millimeter diameter heated air
bearing was found to perform as well as the heated
godet with the pinch roll and better than either of
the t~o heated pins or the heated godet roll without a
pinch roll.
The number of wraps on the heated air bearing was
found to be an important variable as shown in Table 2.
The optimum number of wraps was found to be eight for
a drafting speed of 1000 meters per minute, draw ratio
of 1.55X and a set point of the heated air bearing of
150C Increasing the number of wraps above eight did
not appear to lower the Uster uniformity or the broken
filament level. Also shown in Table 2 is th~ draw
tension be~ore and after the heated air bearing as a
function of the number of wraps. For the above condi-
tions and eight wraps, the tension before the heatedair bearing or the pretension was found to be about 42

7~
- 20 -
grams with the tension after the heated air bearing
being about 100 grams. Obviously, this particular
combination of yarn, number of wraps, speed, etc.,
causes an unusually large drag to exist on the heated
roll. In this case a tension of 60 grams or higher
would be preferred. It will be noted that as the
wraps increased after eight, the pretension increased.
A speed check with a Strobe light showed the heated
air bearing or freely rotatable heated roll surface to
be moving only slightly faster than the feed roll.
This was very surprising to us. This feature occurs
because the dynamic stress strain curve of the undrawn
yarn was found to be Hookean over the tension ranges
encountered before the yarn makes contact with the
heated roll and under these conditions the yarn
exhibits a very high dynamic modulus.
The best operating temperatures for the yarns
when drafting on the 70 millimeter diameter heated air
bearing using eight wraps are shown in Table 3.
Higher speed or larger total deniers were found to
require higher operating temperature o~ the heated air
bearing or heated roll. Therefore, each yarn wi~l
have its own particular optimum temperature settings.
Actual surface temperature of the heated air
bearing or heated roll, as measured with a contact
thermocouple (not shown) immediately after stopping
the ro.ating surface ~see Table 3), was lower than the
set point temperature. "Set point temperature~ is the
temperature established within the heated roll, and
does not mean the surface temperature of the roll~
This difference was caused by the location of the
thermocouple which was in the unit core rather than in
the rotating surface.
Dyed socks made from the yarns which were drawn
on the heated air bearing or heated roll at 1000
meters per minute bad exce-llent uniformity. They were

found to be superior to the yarns produced on ~he fixed
heat pins and equivalent to those produced on the
heated godet sy~t~m without a pinch roll.
The following is an example of an ef~ective draft-
ing system as disclosed herein.
~AMPLE 1
One freely rotatable heated roll was constructed
using ball bearings. The diameter of the roll was
10 70 m~ and it6 Wk was 0.0045 lb6 x ft or O.OQl86
newtons x metres 6quared.
The roll had a poli~hed chrome surface wi~h a
coefficient of friction of O.~S. This roll was used to
draft polyester filamen~ yarn under the ~onditions
listed below:
Draw ra~io - 1.60X
Pin temperature (6et point) - 100C
Stabilizatio~ plate temperature - 160C
Speed - 300 m~min
The measured percent of draw ~ension
transferred upstream into the pretension
zone was about 92S.
The feed yarn wa6 22~(140)/25 POY
The yarns produced dyed uniformly and con~ained les~
25 than 0.3 bro~en filamPnts per pound of yarn. Start-up
was also adegu~te.
The following exampl~ are used to determine and
define important variables related to the ~ucces~ul
operation of the drafting ~ystem di~closed herein.
~AMPLE 2
Another freely rotatable heated roll wa6 con-
6tructed u~ing ball bearing~. The diame~er of the roll
was 70 mm and its Wk2 was al~o 0.0045 1~6. X ft.2.
35 The surface, however, was plas~a coated ceramic with

- 22 -
a coefficient of friction of 0.29. When running a
temperature series on the roll, an unusual phenomenon
was observed. The feed yarn was 225(140)/25
polyester POY.
Draw ratio - 1.6GX
Stabilization plate temperature - 140C
Speed - 800 m/min
The measured percent of draw tension
transferred upstream into the pretension
zone was about 85%.
The separator roll was located as shown in
Figure 3 such that the wrap angle for the
first wrap was approximately 30.
Set Point on In Out Speed SurEace Speed
15Roll C M/Min of Roll M/Min
500 510
- 80 500 510
100 500 510
110 50n S48
20 120 500 607
128 500 658
Notice that at 100C and below the surface speed
of the roll differs from the input speed by about 2%.
This 2~ represents the elastic ex~ension o~ the POY
under the pretension load. This elastic extension is
the reason the roll operates slightly faster than the
feed roll speed. However, at llO~C and above, there
is some obvious drafting of the yarn taking place
3Q before it establishes good frictional contact wi~h the
surface of the roll. This two stage drafting behavior
is undesirable.
Two ways were found to eliminate this undesirable
behavior. The first was to increase the wrap angle on
the first wrap to 270 or more. This is not a very
practical method. The second approach was to use a

~2~
- 23 -
roll surface with a higher coefficient of friction. A
polished chrome surface roll was constructed with a
coefficient of friction of 0.85. No two-stage draft-
ing was observed with this surface. Thus, combina-
S tions of increased wrap angle and/or increasedcoefficient of friction between the yarn and the roll
surface can be used to eliminate the two-stage
drafting.
The invention has been described in detail with
particular reference to preferred embodiments thereof,
bu~ it will be understood that variations and modifi-
cations can be effected within the spirit and scope of
the invention.

7~
SUPPLEMENTARY DISCLOSURE
As taught in the principal disclosure a drafting system
is pro~ided for yarn which has a driver feed roll for feeding
yarn at a predetermined speed; a driven output roll for
forwarding the yarn at a second predetermined speed ~reater
than the first-mentioned speed; a low friction freely rotatable
heated roll, the surface of which is heated to a predetermined
temperature, the freely rotatable heated roll being located
between the driven feed roll and the driven output roll; and
a separator roll spaced adjacent to the freely rotatable
heated roll and wherein the yarn is wrapped a plurality of
times around the freely rotatable heated roll and the separator
roll. The surface speed of the freely rotatable heated roll
is operating slightly faster than the surface speed of the
driven input roll with the freely rotatable heated roll being
driven by engagement with the yarn. As a result, sufficient
yarn tension automatically is transferred upstream of the
freely rotatable heated roll to pretension the yarn before it
contacts the freely rotatable heated roll. Drafting takes
place near the location where the yarn leaves the freely
rotatable heated roll to pass toward the driven output roll.
One of the essential features of the above described
system is the start-up resistance, which is primarily the
inertia of the freely rotatable heated roll, which is
0 000113 pbunds x square foot
no more than denier ~drafted yarn) or
4.86 x 10 5 newtons x metres squared and is preferably
denier tdrafted yarn)
0 000075 pounds x square foot
no more than denier (drafted yarn) or
3 10 x 10- newtons x metres squared, still more preferably
denier (drafted yarn
0 000045 pounds x square foot
is no more than denier (drafted yarn) or
-S.D. 24-

::IL2~
denier ~drafted yarn)
0.000030 pounds x square foot
no more than denier (drafted yarn) or
.
1.24 x 10 5 newtons x metres squared as obtained from
denier (drafted yarn)
CWk2a
the equation T = denier (drafted yarn)
wherein
T = torque (length x force)/per unit denier
C = constant depending on units selected
k = radius of gyration (units of length)
a = angular acceleration (radians per second squared)
W = weight (units of mass).
For a given yarn at start-up, the torque is approximately
constant and is generated by sliding frictional contact with
the freely rotatable heated roll. Thus the resistance to
turning is directly proportional to Wk2. The torque generated
to accelerate the freely rotatable heated roll is also
proportional to denier because the area in contact with the
heated roll increases as the denier increases. Thus, specifying
that the pounds x square foot/denier (drafted yarn) ~newtons x
meters squared/denier (drafted yarn)] should not exceed a
given number, is equivalent to saying that the angular
acceleration will equal or exceed a minimum value and thereby
minimize start-up time for the freely rotatable heated roll~
Obviously, start-up performance, as the denier of the
feed yarn is decreased, becomes poorer unless the Wk2 sf the
freely rotatable heated roll is reduced correspondingly.
The following additional example is provided of an
effective drafting system as disclosed.
EXAMPLE 3
One freely rotatable ~eated roll was constructed using
ball bearings. The diameter of the roll was 70 mm and its Wk2
was 0.0045 lbs. x ft 2 or 0.00186 newtons x meters squared.
-S.D. 25-
~ .

37~
The roll had a polished chrome surface with a co-efficient
of friction of 0.85. This roll was used to draft polyester
filament yarn under the conditions listed below:
Draw ratio - 1.60 x
Pin temperature (set point) - 100C
Stabilization plate temperature - 160C
Speed - 300 m/min.
The measured percent of draw tension transferred upstream
into the pretension zone was about 92%.
The feed yarn was 96(60)/20 POY.
The yarns produced dyed uniformly and contained less than
0.3 broken filaments per pound of yarn. Start-up was marglnal.
B S.D. 26-