Classifications

• • D—TEXTILES; PAPER
  • D02—YARNS; MECHANICAL FINISHING OF YARNS OR ROPES; WARPING OR BEAMING
  • D02J—FINISHING OR DRESSING OF FILAMENTS, YARNS, THREADS, CORDS, ROPES OR THE LIKE
  • D02J1/00—Modifying the structure or properties resulting from a particular structure; Modifying, retaining, or restoring the physical form or cross-sectional shape, e.g. by use of dies or squeeze rollers
  • D02J1/22—Stretching or tensioning, shrinking or relaxing, e.g. by use of overfeed and underfeed apparatus, or preventing stretch

Definitions

• the present invention is directed to a drafting system for yarns generally used for textile yarns and particularly is directed to a system for drafting yarns, such as polyester yarns, at speeds greater than 300 meters per minute up to 1500 meters per minute and greater.
• Pretensioning yarn in a drafting system before the yarn contacts any heated device is an important contribution toward obtaining a uniformly dyeable and defect-free yarn.
• U.S. Patent No. 3,539,680 mentioned above recognizes the importance of such pretensioning so as to minimize occurrence of "fluffs" and dyeing unevenness (Col. 4, lines 43-47).
• the patent dis ⁇ cusses an arrangement for obtaining such pretension by providing the combination of a nip roller and a delivery roller, and employing a ratio of peripheral speeds of the delivery roller to the heated feed roller within the range of 1:1.001-1:1.030.
• the patent discloses establishing a pretension zone which is designed to draw the yarn slightly, as indicated by the given ratio range, in order to achieve the required pretensioning.
• the patent indicates alter- natively that 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 quality of the yarn produced on these systems 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. 3,539,680, and the problems of broken filaments and poor dye uniformity have been found to increase as the speed is increased. Broken filaments tend to cause defects, which cause waste and loss of time.
• An object of our invention is to provide a low friction drafting system which provides automatic pretensioning of the yarn before the yarn contacts any heated device and without employing the usual structures upstream from such heated device to provide such pretensioning.
• ⁇ . S. Patent No. 3,919,748 discloses an apparatus for altering the length of a synthetic continuous filament or yarn strand.
• the apparatus comprises a first strand feeding means involving a driven feed roll and a separator idler roll; a first heating means in the form of a heated roll connected to and coaxial with the driven feed roll and having a separator idler roll; a second heating means in the form of a heated plate over which the yarn strand slides; a second feeding means in the form of a driven roller and a separator idler roller; and a driven take-up spool.
• All of the embodiments in the patent, except one, show the "first heating means", which is the heated roll, as being rigidly connected to the first driven feed roll. The exception is the embodiment shown in Fig.
• a "thread guide" 37 is provided between the coaxially aligned driven feed roll and heated roller on one side and the separator idler rollers on the other side which serves to displace the yarn strand from the driven feed roll to the heated roller. Since this is probably a high tension zone, this thread guide in the embodiment of Fig. 4 will tend to damage the yarn strand which will lead to the generation of an exces- sive number of broken filaments in the yarn. The yarn strand filaments which are directly in contact with the surface of the thread guide 37 will be damaged to the extent that they will break in the subsequent drafting of the yarn strand.
• Another object of the invention is to insure that there is no frictional contact made 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 rotatable 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 satisfactorily 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 yarns of equivalent quality to those made by the process disclosed in U.S. Patent No. 3,539,680.
• a drafting system for yarn which has a driven feed roll for feeding the yarn at a predetermined speed; a driven output roll for forwarding the yarn at a second predetermined speed greater than the first-mentioned speed; a low friction freely rotatable heated roll, 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
• the essential features of the above described drafting system are: (a) the steady state resistance to turning of the freely rotatable heated roll plus the separator roll, as measured by stress on the yarn being drafted, is no more than 0.25 grams/denier(drafted yarn) and is preferably ⁇ 0.15 grams/denie (drafted yarn), (b) the start-up resistance, which is primarily the inertia of the freely rotatable heated roll, is is no more than 0.000113 pounds x square foot or denie (drafted yarn)
• the separator roll being located at a position relative to the freely rotatable heated roll and rela- tive 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
• 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 ⁇ .
• 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.
• greater than 60 percent and preferably 80 to 95 percent of the yarn draw tension is transferred 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 friction character of the freely rotatable heated roll that enables the 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.
• the predetermined temperature for the surface of the freely rotatable heated roll will be about 80°C to about 120°C, and the temperature for the device for thermally stabilizing the yarn is such that the yarn temperature is about 120°C to about 220°C as it leaves the thermally stabilizing device.
• 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. 3,539,680;
• 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;
• Figs 4a and 4b are schematic diagrams illustrating preferred locations for the separator roll relative to the freely rotatable heated roll and relative to the direction of the path of yarn movement.
• Fig. 1 represents a prior art drafting system JLQ_ 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 L2_ and a heated godet roll JL4_ and its separator roll 16, and a pinch roll 3J3. 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 2f__r a " d ___ designates the separator roll for the nonheated godet roll 12.
• Fig. 2 represents a prior art drafting system 3_2_ which ..employs a heated stationary pin 3_4_ between a nonheated godet roll 3_6_ and its separator roll _____ and a nonheated godet roll 4Q_ and its separator roll 42, the latter two serving as an output roll arrangement for forwarding the yarn 4_4_ to a winder (not shown) .
• Another nonheated godet roll __6_ and its separator roll 48, as well as yarn guides 50_ and 5_2_ are shown located upstream of the first-mentioned nonheated godet roll 36.
• the yarn may be thermally stabilized by a device such as that represented at ______ 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 120°C to -about 220°C, and the freely rotatable heated roll surface temperature will be about 80°C to about 120°C as the yarn leaves the stabilizing device.
• 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 yarn may be thermally stabilized after it leaves the output roll 70 and its separator roll 72.
• the steady state resistance to turning of the freely 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 is ⁇ 0.15 grams/denier(drafted yarn).
• the steady state resistance to turning has two components: (1) bearing resistance and (2) air drag, with air drag being more sensitive to operating speed.
• the start-up resistance which is primarily the inertia of the freely rotatable heated roll is no more than 0.000113 pounds x square foot or denier(drafted yarn) 4.86xl0" 5 newtons x metres squared and is preferably denier(drafted yarn) approximately 0.000045 pounds x square foot or denier(drafted yarn)
• 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.
• the coefficient of friction between the yarn and the surface of the freely rotatable heated roll is greater than 0.57, and is preferably in the range of 0.75 to 0.95.
• the capstan equation is well-known, but will be mentioned here as being
• T 2 tension of the yarn on side of capstan where yarn is being pulled
• T- ⁇ tension of the yarn on the other side of the capstan
• e base of natural logarithm
• ⁇ coefficient of friction
• the high coefficient of friction insures that the yarn will not slide on the freely rotatable heated roll during the first wrap and thereby undesirably initiate a kind of two-stage drafting. This also helps increase the torque at start-up which minimizes the time for the freely rotatable heated roll to accelerate to steady state.
• the separator roll should be located at a position relative to the freely rotatable heated roll and relative to the direction of the path of the yarn movement such that the angle of contact with the surface of the freely rotatable roll is >_30 o on the first wrap and is , 30° on the last wrap before the yarn leaves the freely rotatable heated roll.
• 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 ⁇ i ct, as ⁇ ⁇ shown in Fig. 4a of the drawings (note path of yarn 56 in Fig. 4a), or so as to be within quadrant "a", as shown in Fig. 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 example, is that the yarn has a longer contact with the heated roll on the last wrap and thereby helps insure that no drafting 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.
• thermocouple would be positioned to assure predetermined surface temperatures
• thermo ⁇ couple internally of the roll with its probe being positioned just beneath the surface of the roll
• the freely rotatable heated roll 66 (Fig. 3) in our invention is wrapped with sufficient wraps to ensure heating of the yarn to approximately the surface temperature of the heated roll. Drafting of the yarn 56 takes place near the point where the yarn leaves the heated roll 66 for the last time on its way toward the output roll 70.
• the output roll may be constructed in the same manner as the input roll, thus costs will be minimized and such construction will be simplified because the godet rolls shown do not require heating; thus maintenance will be reduced as compared to maintenance required for heated godet rolls. Obviously, the latter statement will only be partially true if the thermally stabilizing device should be incorporated in the output roll to make it in effect a heated godet roll.
• a polyester (from polyethylene terephthalate polymer) POY (partially oriented yarn) was used to evaluate the 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.
• no post stabilization device was used in obtaining the results shown in the tables.
• the drafting systems were evaluated with the above-described 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.
• Heated Air Bearing 120 0.67 1.32 0.62 8 wraps • 140* 0.00 0.00 0.78 258/400 m/m 150 2.78 1.56 0.77 160 11.00 4.73 0.79
• Table 1 shows the ⁇ ster uniformity and broken filament results from the different drafting systems and the conditions evaluated using a partially oriented yarn (POY) of polyester (270 denier/30 filaments from polyethylene terephthalate) .
• POY partially oriented yarn
• Table 2 shows the Uster uniformity and broken filament results at various numbers of wraps on the surface of the 70 millimeter diameter heated air bearing or heated roll. Optimum drafting conditions for various POY yarns using the 70 millimeter diameter heated air bearing are shown in Fig. 3.
• 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 150°C. 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 the draw tension before 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 heated air bearing or the pretension was found to be about 42 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.
• One freely rotatable heated roll was constructed using ball bearings.
• the diameter of the roll was 70 mm and its Wk 2 was 0.0045 lbs x ft 2 or 0.00186 newtons x metres squared.
• the roll had a polished chrome surface with a coefficient of friction of 0.85. This roll was used to draft polyester filament yarn under the conditions listed below:
• Another freely rotatable heated roll was constructed using ball bearings.
• the diameter of the roll was 70 mm and its Wk 2 was also 0.0045 ft x lb2.
• 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°.
• 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 roll surface with a higher coefficient of friction
• tions of increased wrap angle and/or increased coefficient of friction between the yarn and the roll surface can be used to eliminate the two-stage drafting.

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• Engineering & Computer Science (AREA)
• Textile Engineering (AREA)
• Yarns And Mechanical Finishing Of Yarns Or Ropes (AREA)
• Artificial Filaments (AREA)
• Spinning Methods And Devices For Manufacturing Artificial Fibers (AREA)

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Citations (4)

• 1984
  • 1984-08-31 CA CA000462235A patent/CA1248741A/en not_active Expired
  • 1984-09-06 DE DE8484903402T patent/DE3467592D1/de not_active Expired
  • 1984-09-06 WO PCT/US1984/001412 patent/WO1985001304A1/en active IP Right Grant
  • 1984-09-06 EP EP84903402A patent/EP0157802B1/en not_active Expired
  • 1984-09-14 IT IT22670/84A patent/IT1175739B/it active
• 1985
  • 1985-05-01 KR KR8570027A patent/KR920002507B1/ko not_active IP Right Cessation

Patent Citations (4)

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