US3087226A - Yarn elasticizing process - Google Patents

Description

April 30, 1963 c. a. EVANS YARN msucfimc PROCESS Original Filed Nov. 18, 1955 2 sheets-sheet 1 FIG.-l-

,a /54 g INVENTOR CYRIL G. EVANS BY mzhw ATTORNEY C. G. EVANS YARN ELASTICI ZING PROCESS Original Filed Nov. 18, 1955 April 30, 1963 2 Sheets-Sheet 2 ATTORNEY United States Patent 3,087,226 YARN ELASTICIZING PROCESS Cyril G. Evans, Spartanburg, S.C., assignor to Deering Milliken Research Corporation, Spartanburg, S.C., a corporation of Delaware Original application Nov. 18, 1955, Ser. No. 547,682, now Patent No. 2,977,661, dated Apr. 4, 1961. Divided and this application Feb. 10, 1961, Ser. No. 38,338 7 Claims. (Cl. 28-72) This invention relates to improved yarn elasticizing processes of the type wherein an end of yarn under tension is conveyed through an angular path while at an elevated temperature. This a division of application Serial Number 547,682, filed November 18, 1955, now U.S. Patent 2,977,661.

It is now well known in the art that, under proper conditions, passing a thermoplastic yarn under tension through a linear path having a sharply angular portion will impart a generally permanent tendency to coil to the yarn if it is at an elevated temperature at the time it passes through the angular portion of the yarn path, and processes for elasticizing yarn in this manner constitute a part of the subject matter of U.S. application S.N. 274,358, filed March 1, 1952. Such processes, as presently practiced and as described in the above mentioned U.S. application, comprise passing the yarn in an angular path about the edge of a blade member or the like with the blade edge positioned at the apex of the angle. The temperature of the yarn is raised to the desired level either by heating the blade and maintaining the same at an elevated temperature or by passing the yarn over a heater positioned in closed proximity to the blade edge Prior to this invention it has generally been considered desirable in processes as above described, to retain the temperature of the yarn at least as nearly constant as possible during its passage through the angular portion of the yarn path or even increase the temperature of the yarn during its passage through this portion of the path. The procedure of heating the blade about which the yarn is passed necessarily results in the temperature of the yarn being greatly increased during its passage through the angular portion of the yarn path, and even where a separate yarn heater is employed it has been conventional to place the blade in such close proximity to the heater that it is maintained at a temperature substantially equal to that of the yarn heating means. In such arrangements the blade edge acts as a supplemental yarn heating means to retain the yarn at substantially the same temperature as that to which it is heated by the primary yarn heating means.

Although it has previously been considered desirable to supply heat to the surface of the yarn in contact with the blade edge during such that the yarn is passing through the angular portion of the yarn path, the possible importance of the temperature of the side of the yarn adjacent the blade edge relative to that of the side of the yarn removed from the blade edge has, as far as is known, not been previously considered. It will be apparent, however, that the methods of the prior art have generally resulted in a differential with the side of the yarn adjacent the blade edge being at a temperature at least slightly higher than that of the side of the yarn removed from the blade edge. Arrangements wherein the yarn is passed about the edge of a heated blade member have inherently resulted in a longitudinally extending portion of the yarn adjacent the blade being at an appreciably higher temperature than the opposite side of the yarn, which is removed from the blade edge, because of the poor thermal conductivity of the yarn, and even in arrangements wherein the yarn is heated before it is passed around the blade edge, a portion of the yarn adjacent the blade edge has un- 3,987,225 Patented Apr. 30, 1963 "ice doubtedly been at a somewhat higher temperature than the opposite side of the yarn since no effort has heretofore been made to cool the blade.

It has now been found that yarn having a higher degree of elasticity than has heretofore been attainable by a blade elasticizing method can be produced by positively exerting a cooling influence on the surface of the yarn in an area extending axially of the yarn at least through the angular portion of the yarn path andperimetrically through at least a substantial portion of the periphery of the yarn. Preferably the cooling conditions are such as to preferentially affect a longitudinally extending portion of the yarn on the inside of the angular portion of the yarn path and according to a preferred embodiment of the invention the cooling influence is provided by retaining a blade member, having an edge about which the yarn is passed, at a mean temperature below that conventionally employed so that the cooling effect is greatest upon the longitudinally extending portion of the yarn surface having a concave curvature axially of the yarn. A further advantage of this arrangement is that the yarn can rapidly be cooled following its passage through the angular portion of the yarn path by contact with one face of the cool blade and it has been found that this results in a further increase in the degree of elasticity imparted to the yarn.

While the exact reason or reasons for the success of the improved process are not fully understood, it seems probable that there are a number of factors involved. During the time a segment of the yarn is passing through the angular portion of the yarn path, the side of the yarn removed from the blade edge is under tension and is stretched rel ative to its condition at a point in the yarn path immediately preceding the angular portion of the yarn path. The opposite side of the yarn is, however, not stretched at this time and, in fact, is under compression. When the yarn segment is subsequently straightened, the stretched side is placed under compression and contracts a percentage of the length it has been stretched in passing through the angular portion of the yarn path. At approximately the same point in the yarn path that the side of the yarn removed from the blade is placed under compression, the opposite side of the yarn is placed under tension and stretched a slight degree relative to its length in the angular portion of the yarn path. The yarn is thereafter cooled with one side under tension and with the other side under compression. When one considers that lowering the temperature widens the creep recovery range and raises the elastic limit of the yarn, it can be seen, in view of the above discussion, that the stretching of the side of the yarn removed from the blade should be accomplished at a relatively high temperature, the stretching of the yarn of the yarn passed in contact with the blade edge should be accomplished at a relatively low temperature and the compressing and contracting of the side of the yarn removed from the blade edge should likewise be accomplished at a relatively low temperature. This would not only explain why improved results might be obtained by uniformly cooling the yarn while it is passing through the angular portion of the yarn path but might also explain why preferably the cooling of the yarn is eifected preferentially on the side of the yarn passing adjacent the blade edge. It should not, however, be inferred from this explanation that the process necessarily results in a net elongation of the yarn being processed since generally the process results in the yarn increasing in denier, and while the explanation appears to be most satisfactory at the present time, it should be emphasized that it is, to some extent, theory and applicants do not wish to be limited thereby.

The invention will now be described in greater detail with reference to the accompanying drawings illustrating two preferred forms of apparatus and in which:

FIGURE 1 is a schematic view in perspective of yarn elasticizing apparatus which can be employed when following the process of this invention showing principal parts in location.

FIGURE 2. is an enlarged front plan view of the blade holding means shown in FIGURE 1 of the drawings.

FIGURE 3 is a cross sectional view taken along the line III, III of FIGURE 2 of the drawings.

FIGURE 4 is a front plan view of a modified form of blade holding means.

FIGURE 5 is a rear elevational view of the blade holder of FIGURE 4.

FIGURE 6 is a cross sectional view taken along the line VI, VI of FIGURE 4 of the drawings.

With particular reference to FIGURES l to 3 of the drawings there is illustrated a yarn supply means 10 mounted on a suitable frame or support member, not illustrated. A yarn end, indicated by the reference numeral 12, passes from supply package 10 through a guide 14, and to a tension regulating device indicated by the reference numeral 16. The tension regulating device 16 serves to remove the fluctuations in tension resulting from the removal of the yarn from supply package 10 and to further tension the yarn 12, while the guide 14 is to permit removal of the yarn from the yarn supply package in an over end manner.

From the tension regulator 16, the yarn passes into contact with a yarn heater 18 which is illustrated as comprises a relatively narrow elongated plate or strip and which may be formed from any suitable material such as stainless steel. As illustrated, the heater strip 18 is provided with a back face 20, a pair of opposed side surfaces 22 and 24, and a yarn engaging upper surface or face 26 which is preferably convexly curved to a radius of from 4 to 10' inches so that continuous contact with the yarn is obtained. The heater strip 18 should be of .sufiicient width to result in an end of yarn drawn thereover being heated to the desired temperature and is preferably as thin as is consistent with the strength and rigidity required. It is adapted to be heated by means of an electric current passed therethrough and is connected by a pair of electric conductors 28 and 30 to a variable transformer 32 which is supplied with power from any suitable source, not illustrated, through leads 34 and 36.

After passing over the face 26 of heater strip 18, the yarn end 12 passes around the edge of a blade member 38 carried by a blade holding means 40 which will subsequently be described in greater detail. The yarn end is then passed in contact with the bottom face of the blade 38, to a guide roller 42 and thereafter to a yarn feeding or transporting device, generally indicated by the reference numeral 44 and illustrated as comprising a pair of driven capstans or rolls 46 and 48. The yarn passes one or more times about rolls 46 and 48, about an idler roll 50 and thereafter through a guide 52 to a conventional yarn take up means 54 here illustrated as comprising a ring and spindle array. The yarn is then collected by the take up means 54 in the form of a conventional yarn package.

The blade holding means 48 comprises an elongated clip member 56 which may be formed of any resilient material such as spring steel and which extends across the back face 20 of heater strip 18. The ends of clip member 56 are in each instance formed with an indentation of such shape as to result in ears 58, 60, 62 and 64 on each corner thereof which are shaped to engage opposite side surfaces 22 and 24 of the heater strip 18 and to precisely position the clip member 56 with respect to the heater element. An elongated heat dissipating member or plate, generally indicated by the reference numeral 66 is attached near one end by any suitable means such as screws 63 to a suitable support surface on clip member 56. A portion of the plate 66 intermediate the two ends thereof is ofiset to form an indentation 72 immediately below one edge of the yarn engaging surface of the heater strip 18. The degree of offset is such that the upper surface of the plate within the indentation 72 is displaced beyond the plane of the lower surface of the secured end of the plate or, in other words, the intermediate portion of the plate is offset an amount at least equal to the thickness of the plate.

The unsupported end of plate 66 is bifurcated to result in a pair of legs 74 and 76 separated by an open ended slot 78 which extends generally parallel to one side of the plate. The slot 78 should be of sufiicient width to easily receive an end of the yarn to be processed and should be of sufficient length to extend at least through the intermediate offset portion of the plate 66 for reasons that will subsequently be seen. Legs 74 and 76 extend outwardly from under heater strip 18 into open convectional contact with the atmosphere and serve as cooling fins to dissipate heat from the entire blade assembly. The total surface area and the mass of the plate 66 are preferably large as compared to that of blade 38 so that the plate may more effectively serve as a heat dissipating means. For example, the mass of the plate should generally be at least about 4 to 10 times that of the blade and the total surface area of the plate should generally be at least about 2. to 5 times that of the blade. Also, the plate 66 is preferably formed of a material having a relatively high specific thermal conductivity, for example, above about 0.1 and preferably above about 0.3 calories per second per degree centigrade, so that the temperature gradient in plate 66 is very small and heat is rapidly removed from the blade member 38. The preferred materials, cost considered, for forming the plate 66 are aluminum and copper, or alloys of either of these two materials, because of the high thermal conductivity by which they are characterized. The distance that legs 74 and 76 extend from under the heater strip will depend upon a number of factors including the total surface area of the plate 66 and the amount of heat that must be dissipated but generally a distance of about A to one inch will be suflicient.

The blade member 38, which may be formed of any suitable material such as blue carbon spring steel or stainless steel, is positioned underneath, as viewed in the drawings, ears 62 and 64, and rests within the indentation 72. Clip member 56 is so formed that cars 62 and 64 extend into the indentation 72 and forcefully contact the bottom surface thereof, as viewed in the drawings, unless they are prevented from doing so by the presence of a blade. It will be seen, therefore, that when a blade is placed in proper position within indentation 72, it is pressed between cars 62 and 64 and plate 66, because of the resilient nature of clip member 56, and is separated from the heater element by a fixed distance as determined by the thickness of ears 62 and 64. The minimum thickness of the ears 62 and 64 at the point of their contact with blade 38 is determined only by the requirement that the ears have sufiicient strength to serve their intended function, although there is generally little or no advantage in making the ears less than about 2 to 5 thousandths of an inch thick at this point. On the other hand, if the ears 62 and 64 are made so thick that the upper surface of the blade is removed from the immediate proximity of the bottom or terminal edge of the yarn heating surface of the heater strip, this requires that the yarn travel a longer distance in passing from the heater to the blade edge and results in premature cooling of the yarn. To compensate for this cooling, the yarn must then be heated to a higher temperature by the heater strip than would otherwise be necessary and this might result in unnecessary yarn deterioration. As a general rule, the thickness of the cars 62 and 64 at the point of their contact with the upper face of the blade should be no more than about 200 to 500 times the diameter of the yarn to be processed and preferably no more than about 25 to 50 times the diameter of the yarn.

It will also be seen from the above discussion that the angle of the blade 38 with respect to a line tangent to the yarn engaging surface of the heater element adjacent its lower edge, as viewed in the drawings, will be determined by the angle which the support surface within the indentation makes with such a line. Since the distance between the point at which the plate is attached to slip member 56 is relatively large as compared to any reasonable thickness for the blade 38, the blade 38 may vary in thickness within reasonably large limits without appreciably varying the angle between the plane of the plate and the yarn path as represented by the above mentioned line tangent to the yarn engaging surface of the heater plate adjacent its lower edge as viewed in the drawings. For example, this angle for a blade which is of an inch thick and for a blade which is 91000 of an inch thick will generally vary less than a degree and this is insuflicient to appreciably affect yarn uniformity. In fact, the angle may be varied as much as one or two degrees without any noticeable variation in the yarn produced so that even with this much variation from unit to unit of the yarn treating apparatus, the yarn produced by the various units is not so different in nature that it cannot readily be combined in the formation of a fabric. This angle is not otherwise extremely critical and as long as all blades are at substantially the same angle to the yarn path, the angle may be varied Within wide limits without resulting in unsatisfactory yarn. For example, the angle may be as much as 90 degrees or more and may be as small as degrees or less. With other factors being equal, it is a general rule that the smaller the angle, the higher the degree of elasticity obtained but when the angle is made very small, it becomes increasingly difficult to retain the plate 66 at a low temperature because of its overall nearness to the heater element. Generally best results can be obtained when the clip member 56 is so formed that the angle between the plane of the blade and a line tangent to the yarn engaging surface of the heater element adjacent its lower edge as viewed in the drawings is from about to 40 degrees.

The width of the blade is relatively unimportant, so long as it is sufiiciently narrow to be accommodated within indentation 72, since the blade is properly positioned by abutment of the yarn engaging edge thereof against the foreward, as viewed in the drawings, boundary surface of the indentation 72. Likewise, the length of the blade is unimportant so long as it is of suflicient length to extend across slot 78, but it is generally advantageous to employ a relatively long blade so that as one point of the yarn engaging edge becomes worn, the blade can be moved lengthwise within indentation 72 to position a new section of the blade edge within the yarn path.

The blade member 38 should generally extend outwardly beyond the heater element of the extent that the yarn engaging edge intersects a line tangent to the yarn engaging surface 26 of the heater element adjacent the lower edge thereof as viewed in the drawings. This results in the most satisfactory yarn path since the yarn remains in contact with the heater element to the termination of the yarn engaging surface and yet is not bent at the point where it leaves the surface. This means that the yarn path approaches the yarn engaging edge of the blade at the minimum possible angle with the blade at any given angle to a line tangent to the yarn engaging surface of the heater element adjacent the lower edge thereof. The above statement, relative to the distance that the blade extends beyond the heater strip, applies, however, only when the heater strip is sufficiently thin that the blade edge is not too far removed from the heater when positioned in the manner described. The blade edge should ordinarily not be at a distance greater than about 300 to 600 times the diameter of the yarn being processed from the yarn engaging surface of the heater element, and if necessary, it is generally advantageous to sacrifice a small approach angle in order to keep the distance of the heater from the blade edge below this upper limit.

It will readily be apparent to those skilled in the art that apparatus of the type described can readily be constructed by modification of a conventional spinning or twister frame. In either instance all that need be added is the yarn heating means including heater strip 18, blade holding means 40, tension regulator 16 and guide means, in some instances, to provide a proper yarn path. In the case of a twister frame, the rolls 46 and 48 can constitute the conventional yarn feed means and in the case of a spinning frame, the feed means can constitute the delivery pair of the drawing rolls. It will also be apparent that a single heater strip of considerable length can serve a multiplicity of blades spaced at intervals corresponding to each position of the frame, although in such an arrangement it is usually desirable for the heater strip to be insulated between the various positions to reduce the heat loss.

In operation, an end of yarn from supply package 10 is threaded through the apparatus in the manner previously described so that it is in contact with the upper yarn engaging surface of heater strip 18 between the cars 58 and 60 and between the ears 62 and 64, passes through slot 78 about the yarn engaging edge of blade member 38 and thereafter passes across the lower surface of the blade member. Since the depth of the indentation 72 is greater than the thickness of plate 66 and since slot 78 extends at least through the offset portion of the plate 66, it will be seen that the yarn at no time need contact any surface of the blade holding means if the yarn is properly centered within slot 78 as it passes around the blade edge. This eliminates the necessity of highly polishing or hardening any of the surfaces of the blade holder and permits the tension in the yarn to be maintained at a minimum value.

Once the apparatus is properly threaded, the heater strip 18 is brought to a proper temperature by adjustment of transformer 32, and even though the heater strip becomes quite hot, blade 38 is retained at a relatively low temperature since it is not in direct contact with the heater element and has a large surface area in contact with plate 66. When the heater strip is at a proper operating temperature, the feed means 44 and collecting means 54 are placed in operation, so that the yarn is drawn through the yarn path at a proper operating linear velocity, and thereafter the tension in the yarn should be checked and regulator 16 adjusted to give a proper value if such is found to be necessary. Proper operating limits for yarn velocity, yarn tension, and heater element temperature, as well as limits for other variables such as the radius of curvature of the blade edge and yarn size, are conventional and are essentially as given in the above mentioned copending United States application, Serial Number 274,358. They will, therefore, not be discussed in detail in this specification.

After the apparatus is in operation, periodic checks should be made on the blade temperature to make certain that sufiicient cooling is achieved. The cooling action necessary for best results will vary with the linear rate of movement of the yarn through the yarn path, since if the linear velocity of the yarn is very high, the yarn is in contact with the blade edge for a shorter time than it would 'be with a lower linear rate of movement. Therefore, to reduce the temperature of the surface of the yarn, during its contact with the blade edge a specified number of degrees below the value at which it would be with no cooling of the blade, the temperature of the blade at the point of contact with the yarn should be lower at higher yarn velocities. Also, since yarn moving at a high velocity will transfer a large amount of heat to the blade edge, it may be necessary that the mean temperature of the blade be considerably below the temperature of the blade at the point where it is in contact with the yarn and for these reasons a very cool blade is generally necessary for best results when the yarn velocity is very high. On the other hand, if the blade is at a very low temperature and the yarn velocity is very slow, it is possible that the yarn might be thoroughly cooled below an operative temperature before the yarn has passed through the angular portion of the yarn path. As a general rule, the benefits of the process of this inven tion are obtained, at least to some extent, if the ratio of the yarn velocity, in yardsper minute, to the difference, in degrees F., between the mean temperature of the blade and the temperature of the yarn on contact with the blade, or of the temperature of the heater element if the arrangement is such that the yarn can be considered to be at approximately the temperature of the heater, is from about 3.0 to 0.05, although the ratio should preferably have a value of from about 0.8 to 0.1. For example, with nylon yarn, which is conventionally processed at a temperature of from about 280 to 340 F, and with conventional yarn velocities of from about 30 to 80 yards per minute, the mean temperature of the blade is preferably from about 60 to 160 F. If, on checking the temperature of the blade, it is found to be too high by the above standards, either the yarn velocity should be reduced, or a blade holding means with greater cooling action should be substituted for the one being employed.

With reference to FIGURES 4 to 6 of the drawings there is illustrated a heater strip 80, similar to that described in connection with the previous drawings, and extending across the back surface of the heater strip is a clip member generally indicated by the reference numeral 82. The clip member 82 is provided with ears 84, 85, 86 and 87 for engaging opposite side surfaces of the heater strip 80 and for precisely positioning the clip 82 with respect to the heater element.

Secured to the clip member 82 by any suitable means such as screws 88 and 90 is an angular heat dissipating member generally indicated by the reference numeral 92. Member 92 is made of a material having a relatively high thermal conductivity and is provided with a pair of depending leg members 94 and 96 extending generally away from heater element 80 into open convective contact with the atmosphere. Leg members 9 4 and 96 serve the same purposes as legs 74 and 76 in the embodiment previously described.

The heat dissipating member 92 extends beyond one side surface of heater element 80 and is provided with an upwardly facing indentation 98 immediately below the side surface of the heater element as viewed in the drawings. Indentation 98 is of sufficient Width to hold a blade member 100, which can be generally similar or identical to that previously described in connection with FIGURES 1 to 3 of the drawings, and provides a recessed support surface against which the blade is operatively positioned. The support surface within indentation 98 should be parallel to the plane of the blade when the blade is at the desired angle with respect to a line tangent to the yarn engaging surface of the heater element 80 adjacent the lower edge thereof as viewed in the drawings while the upper surface of member 92 is preferably at a slightly smaller angle with respect to a similar line for reasons that will subsequently be made clear.

Heat dissipating member 92 is provided with a slot, indicated by the reference numeral 102, which extends from the forward edge of the heat dissipating member, generally perpendicular to the longitudinal axis of blade 100, at least through the indentation 98 to thereby provide a yarn path around the yarn engaging edge of the blade 100. The heat dissipating member 92 is also provided with a groove 104 extending from between leg members 94 and 96 to the slot 102. The base of groove 104 should generally be parallel to the plane of blade 100 and the groove should be of sufiicient depth that an end of yarn drawn across the lower face of the blade 100 can be passed lengthwise of the groove without touching the boundary surfaces thereof. Since the support surface within indentation 98 is at an angle to the plane of the upper surface of member 92, it will be seen that groove 104 may be of less depth toward the rear of member 92, as viewed in the drawings, thereby providing a greater thickness of material above the rear part of the groove for increased strength.

: Ears 86 and 87 extend into indentation 98 and are normally in forceful contact with the bottom surface thereof, in the absence of a blade, due to the resiliency of clip member 82. When a blade member is inserted between ears 86 and 87 and the floor of indentation 98, it is forcefully urged against the heat dissipating member while being retained a fixed distance, equal to the thickness of ears 86 and 87, from the heater element. As in the embodiment previously described, proper alignment of the blade is assured by abutment of its edge against the forward side surface of the indentation 98.

Operation of the embodiment illustrated in FIGURES 4 to 6 is generally similar to that of the embodiment previously described. An end of yarn is drawn over the heater element between ears 84 and 85 and between ears 86 and 8 7. The yarn is then passed through slot 102 into contact with the yarn engaging edge of blade member 100, across the lower surface of the blade and between legs 94 and 96 While within groove 104. The yarn need not contact any surface on the blade holding means and, as in the previous embodiment, the blade member can readily be shifted to present a new portion to the yarn without disturbing the alignment of the blade.

Having thus described my invention what I desire to claim and secure by Letters Patent is:

1. In a yarn elasticizing process wherein an end of yarn is passed under tension about a means providing a sharply angular portion to the yarn path and the yarn is heated so that it reaches the angular portion of the yarn path at an elevated temperature, the improvement which comprises maintaining said means providing the sharply angular portion at a mean temperature such that the ratio of the yarn velocity, in yards per minute, to the difference, in degrees Fahrenheit, between the mean temperature of said means providing the sharply angular portion and the temperature of the yarn immediately prior to its contact with said means providing the sharply angular portion has a value of from about 3.0 to 0.05.

2. A process according to claim 1 wherein the yarn is nylon.

3. In a yarn elasticizing process wherein an end of yarn is passed under tension about the edge of a blade member in an acutely angular path with the edge positioned at the apex of the angle and wherein the yarn is heated so that it is at an elevated temperature at the time it contacts said edge, the improvement which comprises maintaining said blade member at a mean temperature such that the ratio of the yarn velocity, in yards per minute, to the difference, in degrees Fahrenheit, between the mean temperature of the blade and the temperature of the yarn immediately prior to its contact with the blade, has a value of from about 3.0 to 0.05

4. A process according to claim 3 wherein the mean temperature of the blade is such that the ratio of the yarn velocity, in yards per minute, to the difference, in degrees Fahrenehit, between the mean temperature of the blade and the temperature of the yarn at a point immediately preceding its contact with the blade edge is from about 0.8 to 0.1.

5. An improved process as in claim 4 wherein the yarn, following its passage about the blade edge, is passed over one face of the blade member in sliding contact therewith so that the yarn is further cooled in the portion of the yarn path immediately following said acutely angular position.

6. In a process for elastieizing nylon yarn wherein an end of said nylon yarn is passed under tension, at a linear velocity of from about 30 to 80 yards per minute, about the edge of a blade member in an acutely angular path with the edge positioned at the apex of the angle and wherein the yarn is heated so that it is at a temperature of about 280 to 340 F. at a point immediately preceding its cont-act with said edge, the improvement which com- 10 prises maintaining said blade member at a mean temperature of about 60 to 160 F.

10 7. An improved process according to claim 6 wherein the yarn, immediately following its passage about the blade edge, is passed over one face of the blade member in sliding contact therewith.

Australia July 21, 1955 Great Britain Dec. 30, 1943

Claims (1)

1. IN A YARN ELASTICIZING PROCESS WHEREIN AN END OF YARN IS PASSED UNDER TENSION ABOUT A MEANS PROVIDING A SHARPLY ANGULAR PORTION TO THE YARN PATH AND THE YARN IS HEATED SO THAT IT REACHES THE ANGULAR PORTION OF THE YARN PATH AT AN ELEVATED TEMPERATURE, THE IMPROVEMENT WHICH COMPRISES MAINTAINING SAID MEANS PROVIDING THE SHARPLY ANGULAR OORTION AT A MEANS TEMPERATURE SUCH THAT THE RATIO OF THE YARN VELOCITY, IN YARDS PER MINUTE, TO THE DIFFERENCE, IN DEGREES FAHRENHEIT, BETWEEN THE MEANS TEMPERATURE OF SAID MEANS PROVIDING THE SHARPLY ANGULAR PORTION AND THE TEMPERATURE OF THE YARN IMME-

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