US3469384A

US3469384A - Yarn heater

Info

Publication number: US3469384A
Application number: US659181A
Authority: US
Inventors: Nicholas J Stoddard; Robert W Stoddard
Original assignee: Leesona Corp
Current assignee: Leesona Corp
Priority date: 1967-08-08
Filing date: 1967-08-08
Publication date: 1969-09-30
Anticipated expiration: 1986-09-30
Also published as: GB1239816A

Description

Sept. 30, 1969 N. J. STODDARD ET AL YARN HEATER Fild Aug. 8. 1967 2 Sheets-Sheet l mvsu roras, Mam/1s J sraamza Fa in/V. Swap/W0 Sept. 30, 1969 J, STODDARD ET AL 3,469,384

YARN HEATER Filed Aug. 8, 1967 2 Sheets-$heet 2 //V VE/VTOZSI Mae/004s J 57000/2/20 fo s/e714! 570004/20 United States Patent 3,469,384 YARN HEATER Nicholas J. Stoddard and Robert W. Stoddard, Berwyn, Pa., assignors to Leesona Corporation, Warwick, R.I., a corporation of Massachusetts Filed Aug. 8, 1967, Ser. No. 659,181 Int. Cl. Dtllh 13/26; D02g 3/02 US. CI. 57-34 43 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION This invention relates to yarn heaters of the type employed to impart a controlled quantity of heat to strand materials, such as temperature sensitive textile yarns being passed therethrough. In one aspect, the invention relates to yarn heaters for use in conjunction with equipment whereby thermoplastic yarn is textured by a false twsiting operation. The invention also deals with a method of heating twisted yarn.

Techniques for continuously texturing or bulking thermoplastic textile yarn by false twisting are being used with great success. As improvements in various aspects of these techniques make possible the processing of yarn at higher and higher linear speeds, the need to impart heat to the yarn at sufficiently high rates becomes increasingly more critical. Thus one finds that in thermal yarn processing equipment of a given type wherein yarn contact heaters of relatively short length were employed in order to process yarn at given lineal speeds, as improvements are made which permit the processing of yarns at higher lineal s eeds therein it becomes necessary to increase the length of the yarn contact heaters to the point that it becomes awkward to operate this equipment. From a practical viewpoint, of course, yarn heater capacity cannot be increased indefinitely by simply increasing the length of linear contact heaters. Furthermore, insulating and controlling very long contact heaters is far less efiicient than in the case of more compact heating devices.

Moreover, when the thermal treatment to which the yarn is to be subjected is one wherein the yarn is to be heated in a highly twisted condition, as in the case when false-twist bulking or texturing thermoplastic yarn, it is important that the attenuation of twist in the yarn during heating be held to a minimum. The problem of twist attenuation is more pronounced in machines which employ contact heaters.

If the twist is materially attenuated in the yarn along the length of the yarn heater so that there is a considerable twist gradient in the yarn being heated, the bulking, texturing or crimping imparted to the yarn will be of an uneven nature and therefore of a poor quality.

It is an object of this invention to provide a yarn heater which is more compact for a given length of heating surface than those known heretofore.

Another object of this invention is to provide a yarn heater which continuously heats a section of yarn considerably longer than the length of the heater.

ice

Still another object of this invention is to provide improved means for bulking or texturing thermoplastic yarns continuously at very high linear speeds.

Yet another object of this invention is to provide a yarn heater for the continuous heating of yarn being subjected to twisting, which heater will hold to a minimum the degree of attenuation in twist occurring during heating.

Again another object of this invention is to provide an improved method of heating yarns being subjected to twistmg.

The manner in which these and other objects and advantages of the instant invention are realized will be apparent to those skilled in this art from a consideration of this application, especially when taken in conjunction with the accompanying drawing.

SUMMARY OF THE INVENTION According to the instant invention, a yarn heater is provided which has a plurality of yarn heating surfaces and twist propagating means disposed in the yarn path between those surfaces. The yarn, as it passes continuously along this yarn path, is subjected to thermal treatment and twisting so that the twist attenuation along the yarn path is minimal. This yarn heater may be an annular body, generally tubular in shape, having heating surfaces on the outside as well as the inside of the tube and annular twist propagating elements at the top and bottom of the tube. The twist propagating elements may be friction twisters which are rotated as the yarn is advanced along its yarn path, i.e. along the outside of the tube, over the rotating twist-propagating member and then through the inside of the tube, over another rotating twist-propagating member and then again over the outside of the tube, etc., in a number of passes. If desired, a number of axial grooves may be placed on the outside of the tube so that the yarn travels through a different groove in each pass over the outside of the yarn heater.

BRIEF DESCRIPTION OF THE DRAWING FIGURE 1 is a schematic elevation of an embodiment of the apparatus of the instant invention;

FIGURE 2 is a somewhat schematic cross-sectional representation of the same embodiment of the invention as seen on plane 22 indicated on FIGURE 3;

FIGURE 3 is a plan view of the heater of the same embodiment of the invention as is shown in FIGURE 1;

FIGURE 4 is a cross-sectional view as seen on plane 44 shown on FIGURE 2;

FIGURE 5 is a schematic cross-sectional representation, analogous to FIGURE 4, of a somewhat modified embodiment of the heater of the instant invention; and

FIGURE 6 is a schematic cross-sectional representation, analogous to FIGURE 4, of another somewhat modified embodiment of the heater of the instant invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION The embodiment of the heater of this invention depicted in the drawing is shown in combination with elements employed in a false twisting apparatus. It will be understood, however, that the heater of the instant invention is useful in other applications in which yarns are to be heated in a continuous fashion.

The term yarn will be understood to embrace all textile strandlike materials, including staple and multifilament yarns and filaments. Thermoplastic yarns include not only those formed from truly thermoplastic polymers such as nylons, polyesters, polyolefins and mixtures thereof with each other or with non-thermoplastic yarns, but also yarns rendered functionally thermoplastic as by treatment with various solutions.

As may best be seen in FIGURE 1, the overall combination whereby thermoplastic yarn is false-twisted may comprise a creel 11 whereon is mounted yarn supply package 12, pretension control device 13, guide eye 14 which may be mounted on an oscillatable bar, first tension control assembly 15, heater assembly 16, primary false-twisting spindle 17 which includes twist-trapper 18, final tension assembly 19 with associated oscillatably mounted guide eye 20 and take-up assembly 21.

First tension control assembly 15 com-prises a drive roll 31,

idler rolls

32 and 33 and tape 34. Similarly, final tension control assembly 19 comprises drive roll 35,

idler rolls

36 and 37 and tape 38. Yarn take-up assembly 21 comprises drive roll 41, yarn traversing means 42 and take-up package 43.

The twist-trapper is a small cylindrical member of wear resisting material transversely mounted over the central axis of a false twist spindle and adjacent to one extremity thereof, about which the yarn is wrapped one or more times for frictional engagement. All of these elements are conventional components of a present day false-twisting machine.

The yarn heater 16, as may best be seen in FIGURE 2, comprises an annular, generally tubular, heater body 51, the annulus of which defines a central opening or aperture 52 in which is concentrically and rotatably mounted a tube 53 which rides on a plurality of

bearings

54, 55, 55a, and 56. These bearings are of the type capable of operating at elevated temperatures or extended periods without lubrication. Means for rotating this tube 53 about the axis of the opening 52 in the annular heater body 51 are provided in the form of pulley 57 and driving means 58 associated therewith. Driving means 58 may conveniently comprise a belt such as a glass fiber impregnated V-belt, a compact tension spring or a perforated steel band driven by a remote prime mover, or it may comprise a prime mover located right within the heater, such as an air motor or an electric motor adapted to operate at a temperature of ca. 600 F.

Heating elements 59 whereby heater body 51 is heated may be electrical resistance heaters. Also provided, although not shown, are means to control the energy imput to said heating means in order to achieve the desired temperature conditions in the yarn being treated. As is well known in practice, the principal function of such controls is to permit selecting different levels of heater temperatures and to offset the effect of changes in ambient temperature on the selected operating temperature.

Twist propagating elements 60 and 61Which in this embodiment are a pair of friction twistersare fixedly mounted, one adjacent to each of the respective extremities of tube 53, for rotation therewith. The twist propagating elements are positioned adjacent to the respective extremities of the yarn heater body 51 and encircle the respective entrances to the opening 52 formed by the annular heating body and the respective extremities of tube 53. These twist propagating elements may be formed of any convenient heat resistant material such as stainless steel, which may or may not have its yarn-contacting surfaces coated with Teflon. The twist-propagating elements employed in the embodiment shown in the drawing hereof are annular in nature and are, in fact, hemi-toroidal in shape. A hemi-toroidal shape is one which approximates that of a torus bisected by a plane containing the center of the torus and which is oriented so that the trace of the torus thereon is two concentric circles. It will be understood that the term embraces those shapes which are slightly distorted from that of a portion of a true torus, as for instance the shape of

elements

60 and 61 in FIGURE 2. Thus although surface 63 is cylindrical and surface 65 is conical the combined

surface

63, 64, 65 of twist-propagating element 60 performs in this apparatus essentially as if it were hemi-toroidal and Will be so considered for the purpose of this invention. What is important is that the shape of these elements provides a smooth transition for the yarn path from its axial procession through the inside of tube 53 to its axial procession in the opposite direction along the outside of heater body 51.

As may be seen in FIGURE 3, a plurality of

axial grooves

66, 67, 68 and 69, each running substantially the length of heater body 51, may be distributed at any convenient spacing about the outside of heater body 51. The entire heater body assembly may conveniently be insulated with thermal insulation contained within a housing indicated schematically at 70.

In one preferred embodiment of the invention the dimensions of twist-propagating

elements

60 and 61 are such that the internal diameter thereof is slightly smaller than the diameter of the annular opening in the heater, i.e. than the inner diameter of tube- 53. Likewise, the outer diameter of twist-propagating

elements

60 and 61 is such that they slightly overhang the external heat transfer surfaces, i.e. the bottoms of

grooves

66, 67, 68 and 69. As a result, the yarn passing in multiple loops around twist-propagating

elements

60 and 61 under tension are maintained at a slight distance, such as 0.007 inch, from the heat transfer surfaces which they traverse. This results in minimizing the frictional drag to which the yarn is subjected while being heated according to the instant invention.

It will be understood that other heater configurations having a plurality of heating surfaces disposed in compact fashion on a heater body may be employed in this invention. Annular heaters are particularly suited for this purpose because heating surfaces may be disposed in the opening formed by the annulus as well as on the exterior thereof. This permits the establishment of a yarn path which makes several passes through the opening and over the outside of the heater body, the yarn is being heated in each pass. FIGURES 5 and 6 illustrate some cross-sectional configurations of annular heaters which may be used. Thus the heater in FIGURE 5 has a square cross-section and that in FIGURE 6 has an oval crosssection.

Where twisted yarn is being heated, twist-propagating means are disposed in the yarn path in its transition between heating surfaces so that the twist will not be greatly attenuated by the high friction contact which the yarn makes with the heater body as it changes direction. Where these twist-propagating means are friction twisters, their rate of rotation is coordinated with the twisting speed of the primary twisting spindle to maintain the twist attenuation in the yarn at an acceptably low level.

In operation, yarn is drawn from supply package 12 through pre-tension device 13 and guide eye 14 to initial tensioning assembly 15. The slight oscillation imparted to guide eye 14 by the oscillating mounting assures that the yarn will not always follow exactly the same path through initial tensioning means 15 and thereby will avoid grooving driven roller 31 thereof. The tension with which tape 34 is held against driven roller 31 by

idler rollers

32 and 33 assures that the yarn passes through initial control means 15 with substantially no slippage, so that its rate of advance is controlled by the speed of rotation of driven roller 31.

The yarn, now at a controlled, uniform tension, is then passed upwardly over the outer surface of heater 51, as for instance through axial groove 66 thereof, then over yarn twist propagating element 60 and downwardly through the central opening in tube 53, around twist propagating element 61 and again upwardly along the outside of heater body 51, this time through groove 67. In this fashion the yarn continues to make successive passes over different heating surfaces of heater body 51, alternately passing through the opening 52 formed by its annular shape and its outside heating surfaces in

grooves

66, 67, 68 and 69. Each time the yarn passes from one heating surface to another it passes over one of the twist-propagating elements. In thus passing a plurality of complete loops of yarn around the heater, the process of this invention subjects a length of yarn considerably longer than the length of the heater to thermal treatment.

Pulley 57 is driven by driving means 58 at a rate which may be related to the speed of primary twisting spindle 17 and the rate of yarn advance, thereby rotating tube 53 and

twist propagating elements

60 and 61 attached thereto.

The yarn passes upwardly from the heater through primary twisting spindle 17 and around its twist trapper 18. After passing through final tension controlling means 19 the yarn is wound up by take-up assembly 21.

The additional tension applied to the traveling yarn by the multiple passes around the heater surfaces contribute to an increase of yarn tension in the heated Zone. For this reason it is preferable to select from available twist trapper the types which add the least tension to yarns passing around them.

EXAMPLE A stretch yarn having permanent crimp is made from a continuous multifilarnent 70 denier nylon on the apparatus depicted in the drawing. Yarn tension is maintained by tension control elements and 19 at 5 grams, as measured below heater assembly 16, for this 70 denier yarn. Heater temperature is effectively maintained at 450 F. Tube 53 (and thereby twist propagating elements 60 and 61) are rotated at 1000 rpm. The primary twisting spindle 17 is rotated at 400,000 r.p.m. The yarn is advanced through the apparatus at a rate of 415 feet per minute which imparts a twist of 80 turns per inch thereto.

We claim:

1. Means for the continuous heating of twisted yarn comprising a plurality of yarn heating surfaces,

yarn twist-propagating means disposed between pairs of said surfaces whereby a yarn path passing alternately over said yarn heating surfaces and said yarn twist-propagating means is defined,

energy supply means to provide heat at said surfaces,

and

yarn advancing means to move said yarn along said yarn path at the desired rate.

2. The means of claim 1 wherein a plurality of said yarn heating surfaces are generally parallelly aligned surfaces of a single heater body.

3. The means of claim 2 wherein said heater body has an annular configuration and said heating surfaces are disposed in the opening formed by the annulus thereof as well as on the exterior thereof, whereby said yarn path passes alternately through said opening and over the exterior of said heater body.

4. The means of claim 3 wherein said yarn twist-prop agating means are disposed adjacent to the opening formed by said annulus.

5. The means of claim 3 wherein said heater body is generally tubular in shape.

6. The means of claim 3 wherein said heater body is generally square in cross-section.

7. The means of claim 3 wherein said heater body is generally oval in cross-section.

8. The means of claim 4 wherein said yarn twist-propagating means are annular in shape and rotatably mounted.

9. The means of claim 4 wherein said yarn twist-propagating means are annular bodies having an internal diameter slightly smaller that that of the annular aperture of said heater body and an external diameter sufiicient to slightly overhang the exterior heating surfaces of said tubular body.

10. The means of claim 4 further comprising means to separate the various passes of said yarn path over the exterior of said heater body from one another.

11. The means of claim 9 wherein said yarn twist-propagating means are each mounted for rotation in planes generally perpendicular to the axis of said heater body and wherein the yarn-contacting surfaces of said twistpropagating means are adapted, when rotated, to twist said yarn.

12. The means of claim 11 wherein the exterior of said heater body contains a plurality of axial grooves whereby said yarn path passes alternately through said annulus, over one of said yarn twist-propagating means, through one of said axial grooves, over the other of said yarn twist-propagating means and back through said annulus to repeat the cycle, passing through another of said grooves in each cycle.

13. A heater for continuously heating yarn passing therethrough comprising a plurality of highly heat-conductive heat trasfer surfaces disposed in the annular opening and on the exterior of an elongated annular heater body, means to heat said heat transfer surfaces and means to advance said yarn past said heat transfer surfaces.

14. The heater of claim 13 further comprising a number of axial grooves on the exterior of said heater, said number being less than the number of said highly heatconductive heat transfer surfaces, one of said highly heat conductive heat transfer surfaces being disposed in each of said grooves.

15. The heater of claim 13 further comprising means to move the said highly heat conductive heat transfer surface disposed in the annular opening thereof about the axis of said opening while said yarn is being advanced therethrough.

16. Yarn heating means comprising an elongated annular heater body,

a tube mounted for rotation about its axis in the opening formed by the annulus of said heater body,

a pair of annular yarn twist-propagating means fixedly attached to the respective extremities of said tube for rotation therewith,

means to rotate said tube in said heater body,

means to heat said heater body, and

a highly heat conductive surface on the exterior of said heater body.

17. The yarn heating means of claim 16 further comprising a plurality of axial grooves on the exterior of said heater body and a highly heat conductive surface disposed in each of said grooves.

18. A yarn heater for the continuous heating of twisted yarn comprising an elongated annular highly heat-conductive body,

a pair of hemi-toroidal members,

one of said members being rotatably mounted adjacent to each of the respective extremities of said body so as to encircle the entrance to the opening formed by the annulus thereof, and means to heat said body.

19. The yarn heater of claim 18 wherein said hemitoroidal members each have an inside diameter slightly smaller than that of said opening and a body thickness slightly greater than that of said body.

20. The yarn heater of claim 18 further comprising a tube concentrically rotatably mounted in said opening,

means to rotate said tube about the axis of said opensaid hemi-toroidal members being mounted on the respective extremities of said tube for rotation therewith.

21. The yarn heater of claim 16 in combination with yarn twisting means aligned to permit the twist imparted by said yarn twisting means to run backward along the yarn passing through said yarn heater, a twist trapper disposed on said yarn twisting means and on the opposite side thereof from said yarn heater, and yarn advancing means to move said yarn through said combination.

22. The combination of claim 21 further comprising means to rotate said twist-propagating means at a rate correlated with that of said twisting means.

23. The combination of claim 21 further comprising yarn let-off means, yarn take-up means and yarn tension control means, whereby means are provided to let off yarn from a package, to pass said yarn continuously through said heater and said twisting means under controlled tension, and twist running backward through said heater with minimum attenuation and being trapped in the opposite direction, and to rewind said yarn on a package.

24. The combination of claim 23 further comprising means to correlate the rate of operation of said yarn tension control means, said yarn twisting means and said twist-propagating means.

25. The method of continuously heating a yarn while said yarn is being subjected to twisting comprising running a plurality of passes of said yarn around a heater and twisting said yarn between said passes to propagate the twist to all of said passes.

26. The method of claim 25 wherein said yarn makes a plurality of turns through the opening in an annular heater and around the outside thereof and is twisted each time it passes from the outside of said heater into said opening and from said opening to said outside.

27. In the process of continuously crimping thermoplastic yarn by passing said yarn under tension sequentially through a heating zone, a cooling zone and false twisting means whereby there is imparted to said yarn a false twist which runs backward through said yarn into said cooling zone and said heating zone, the improvement comprising passing said yarn in at least one loop through the annular opening and adjacent the exterior of an annular heating means in said heating zone.

28. The improvement of claim 27 wherein said yarn is subjected to additional twisting in said heating zone.

29. In the process of continuously crimping thermoplastic yarn by passing said yarn under tension sequentially through a heating zone, a cooling zone and false twisting means whereby there is imparted to said yarn a false twist which runs backward through said yarn into said cooling zone and said heating zone, the improvement comprising passing said yarn in a plurality of complete loops about heating means in said heating zone wherein each said loop of said yarn is subjected to additional twisting in said heating zone.

30. The improvement of claim 27 wherein said yarn in said heating zone is substantially longer than said heating zone.

31. In the process of continuously crimping thermoplastic yarn by passing said yarn under tension sequentially through a heating zone, a cooling zone and false twisting means whereby there is imparted to said yarn a false twist which runs backward through said yarn into said cooling zone and said heating zone, the improvement comprising additionally imparting twist within said heating zone to said yarn.

32. In the process of continuously crimping thermoplastic yarn by passing said yarn under tension sequentially through a heating zone, a cooling zone and false twisting means whereby there is imparted to said yarn a false twist which runs backward through said yarn into said cooling zone and said heating zone, the improvement comprising additionally twisting said yarn in said heating zone wherein the said additional twisting in said heating zone is of a magnitude to minimize the twist gradient in said yarn.

33. A heater for continuously heating yarn passing therethrough comprising a highly heat conductive heat transfer surface on both the annular interior and the exterior of an elongated annular heater body, at least one of said surfaces on said annular interior and said exterior being characterized by a plurality of heat transfer surface locations, means to heat said heat transfer surfaces and means to advance said yarn past said heat transfer surfaces.

34. The heater of claim 33 further comprising a plurality of axial grooves on the exterior of said heater, one of said heat transfer surface locations being disposed in juxtaposition to each of said grooves.

35. The heater of claim 33 further comprising means to move the said highly heat conductive heat transfer surface disposed in the annular interior thereof about the axis of said interior while said yarn is being advanced therethrough.

36. In the process of continuously crimping thermoplastic yarn by passing said yarn under tension sequentially through a heating zone, a cooling zone and false twisting means whereby there is imparted to said yarn a false twist which runs backward through said yarn into said cooling zone and said heating zone, the improvement comprising looping said yarn about heating means in said heating zone such that said yarn is heated by adjacent but separate heating surfaces on said heating means.

37. The improvement of claim 36 wherein said yarn is subjected to additional twisting in said heating zone.

38. The improvement of claim 37 wherein the said additional twisting in said heating zone is of a magnitude to minimize the twist gradient in said yarn.

39. The improvement of claim 27 additionally comprising minimizing the twist attenuation of said yarn within said heating zone.

40. The improvement of claim 27 additionally comprising minimizing the twist attenuation of said yarn within said heating zone by passing said yarn in contact with twist propagating means.

41. The process of continuously crimping thermoplastic yarn by passing said yarn under tension sequentially through a heating zone, a cooling zone and false twisting means whereby there is imparted to said yarn a false twist which runs backward through said yarn into said cooling zone and said heating zone, the improvement comprising minimizing the twist attenuation of said yarn within said heating zone by passing said yarn in contact with the surface of twist propagating means which move in a direction transverse to the longitudinal axis of said yarn.

42. The improvement of claim 36 additionally comprising minimizing the twist attenuation of said yarn within said heating zone.

43. The improvement of claim 42 wherein said minimizing of the twist attenuation is performed by passing said yarn in contact with twist propagating means located References Cited UNITED STATES PATENTS 2,203,561 6/1940 Broder 2862 2,477,909 8/1949 Stockly 57-l57 XR 2,951,330 9/1960 Bouvet 57l57 XR 2,959,906 11/1960 Richter 5734 FOREIGN PATENTS 901,922 7/1962 Great Britain.

STANLEY N. GILREATH, Primary Examiner WERNER H. SCHROEDER, Assistant Examiner US. Cl. X.R. 2862; 57-157 21% UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,469,384 Datedje t ber 30 1969 Inventor(s) N. J. Stoddard, et al It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Claim 13, line 3; change "trasfer" to-transfer.

Claim 43, line 3; after "located" insert-at the separation of said adjacent heating surfaces.-.

SIGNED AND SEALED JAN 2 0-1970 SEAL) Attest:

WILLIAM E. 50mm.

Attesting Officer