US2539978A

US2539978A - Drying yarn

Info

Publication number: US2539978A
Application number: US89449A
Authority: US
Inventors: Pieter Van Dijk
Original assignee: American Enka Corp
Current assignee: Akzona Inc
Priority date: 1949-04-25
Filing date: 1949-04-25
Publication date: 1951-01-30
Anticipated expiration: 1968-01-30

Description

P. VAN DIJK DRYING YARN Jan. 30, 1951 4 Sheets-Sheet 1 Filed April 25. 1949 INVENTOR. I/bm 09k ATTORNEY Pl'eler P. VAN DIJK DRYING YARN Jan. 30, 1951 4 Sheets-Sheet 2 Filed April 25, 1949 INVENTOR. PieterI art 0377c P. VAN DIJK Jan.'30, 1951 DRYING YARN 4 Sheets-Sheet 3 Filed April 25, 1949 P. VAN DIJK Jan. 30, 1951 DRYING YARN 4 Sheets-Sheet 4 Filed April 25, 1949 IN] ENTOR.

pl'e -1 I/aW-BQZ' Patented Jan. 30,

- UNITED STAT S PATENT OFFlCE.

DRYING YARN Pieter van Dijk, Velp, Netherlands, asslgnor to American Enka Corporation, Enka, N. (-3., a

corporation of Delaware characteristics.

.15 Claims.

This invention relates to a method of and apparatus for the continuous drying of synthetic threads in a manner to produce fully shrunk threads having uniformly low residual shrinkage This application is a continuation-in-part of application, Serial No. 12,838 filed March 3, 1948, now abandoned.

Both the viscose and cuprammonium proccesses involve the wet spinning of threads and the use of liquid aftertreating agents with the result that threads so produced must be dried before they can be packaged for shipment. The drying of these threads presents a diflicult problem because they possess a considerable capacity to shrink during drying and, if this tendency is inhibited to any considerable extent, the dried threads possess a residual capacity for shrinkage which deleteriously affects their marketability, particularly to weavers.

In an attempt to overcome the foregoing difliculties it has been proposed to dry wet spun synthetic threads on thread-storage-thread-advancing devices having tapering contours adapted to compensate for the shrinkage and hence to I allow free shrinkage of the thread during drying.

In practice, however, these devices 'have not proved satisfactory due to the fact that every fixed support, even when it is in direct contact with only a limited part of the thread. prevents the thread from shrinking in that localized zone, in consequence of which a residual shrinkage in that zone remains.

Another effort to produce fully shrunk, wet spun synthetic threads involves drawing the threads; in freely supported condition, through a drying zone by a take-up device having a takeup speed less than the delivery speed to the drying zone by an amount corresponding to average anticipated thread shrinkage during travel through the zone. This arrangement has also been disappointingin operation, and it appears that the defects result from the lack of uniformity in the shrinkage potential of wet thread. This difference in ability to shrink or capacity for shrinkage is presumably caused by small variations in the properties of the spinning solution. In any event, a thread which has a tendency to shrink more than average is subjected to some stretch in passage through the drying zone, and it therefore possesses an undesirably high capacity for residual shrinkage, while a thread having a tendency to shrink less than the average causes mechanical difliculties, the shrinkage being less than that for which the take-up is ad- Justed. The latter causes a thread sag of increasing magnitude which interferes with normal operation of the apparatus in the drying zone.

When, however, there is a localized and unpredictable tendency to shrinkage in a portion of the thread, a tension is exerted on the thread in the dryingzone, with the result that the material produced is not fully shrunk. Even if the thread should be homogeneous it is usually impossible to adapt a constant discharge to the constant supply speed, as the ratio of said two speeds often cannot be accomplished by mechanical (gear wheel) transmissions.

It is an object of this invention to overcome the foregoing difficulties and to provide a method and apparatus for drying threads under free shrinkage conditions whereby the tendency to shrink of each thread is continuously analyzed and this analysis is impressed upon the take-up mechanism in a, manner to adjust the take-up from the drying zone to the feed to that zone so that free shrinkage occurs in every case and mechanical difficulties are avoided.

It is proposed according to the present invention to draw each thread to be dried through a drying zone while controlling the draw off rate as a function of the magnitude of thread sag between points of support located exteriorally of the drying zone.

A further and more specific object of this invention is to accomplish the control of the draw off rate by entirely stationary apparatus variously located with respect to the drying chamber and the draw off device in such away as to permit drying in either a vertical or horizontal zone.

Other objects and advantages of this invention will be apparent upon consideration of the following detailed description of several embodiments thereof in conjunction with the annexed drawings wherein:

Figure 1 is a schematic view in side elevation of one embodiment of the present invention;

Figure 2 is a schematic view of a portion of the apparatus of Figure 1 taken from the line 2-2;

Figure 3 is a schematic view in side elevation of a modified draw-off device constructed in accordance with the principles of the present invention;

Figure 4 is a view of the apparatus of Figure 3 taken along the line 44;

Figure 5 is a fragmentary view showing in detail the manner of passage of the thread through the guiding device of Figures 3 and 4;

Figure 6 is a view in side elevation of still another modified form of the present invention.

from the une 1-1 lustrating a further modified form apparatus for controlled shrinkage drying in vertical drying chambers; and

Figure 11 is a view in section taken along the line II-II of Figure 10.

Now referring in greater detail to Figures 1 and 2 of the drawings, the thread to be dried bears reference numeral Ill and it is fed by a propelling device II into a drying tunnel I2 from which it is withdrawn by a pair of rollers I3 and I4. Between the rollers l3 and I4 and the egress mouth of the drying tunnel I: there is located a fixed thread guide I5 and a movable hook guide It pivotaily mounted at I1 in association with a counterweight I8. The counterweight I8 is mounted on an arm I9 which is really one arm of a bell crank, the other arm of which is the hook I8. As stated above, the point of pivotal connection of the bell'crank is at I1. I v

Throughout the drying tunnel I! the thread is entirely unsupported and it comes into-contact with no .structural parts of the drier. Consequently the thread, in its path between the propelling device I] and the thread guide I5, forms a sagging curve somewhat similar to a catenary but not a true catenary in view of the fact that the weight of the thread per-unit length changes as drying occurs. In general, the curve of the thread need not be described'mathematically since it isapparent that the thread passes in a generally horizontal direction through the drying tunnel with the sag being adjusted to maintain the tension at a predetermined low value which will be'sufilciently low so as not to resist materially the tendency of the threadto shrink during drying. For the purposes of this specification substantially horizontal maybe construed to mean almost any direction of passage through the drying tunnel which provides asubstantial horizontal component which, in turn, will produce a sag in the thread. If detailed reference is made to the take-up rollers I3 and I4 it will be noted that, they are frustoconical in shape. The roller I4 is driven at a constant rate of speed by any suitable means not shown, and the axis of this roller is horizontal. The upper roller I3 is driven from the roller It and is mounted in slotted standards, not shown, for vertical adjustment so that it can be raised to permit passage of a thread between rollers I3 and I4 during threading up of the machine. The speed at which the take-up members It and I4 are driven is so adjusted that when the thread contacts those members at or near the mid-point between their ends, thread will be drawn from the drying chamber or tunnel I2 at a rate correlated with the feeding rate of device II in such a way as to permit complete shrinkage.

In view of the fact that threads are non-uniform and will not all have the same shrinkage potential or capacity for shrinkage, the hook guide It is provided to move the thread lengthwise of the rollers I3 and It to adjust the takeup to make it more or less rapid depending upon whether the thread has a greater or a lesser tendency to shrink. This adjustment is eifected entirely automatically since the dry thread leaving the tunnel I2 passes through thread guide I6 and through hook guide I in passing to the rollers. Between guide I5 and hook guide I! the thread exerts a certain tension longitudinally Of its path of movement; Within-certain limits this tension decreases with an increase in sag and increases with a decrease in sag. Accordingly, an increase in tension will move the hook guide I5 toward the guide I5 while'a decrease will move the hook guide It away from the guide II. Accordingly, if the thread exhibits an abnormally high tendency to shrink, the tension between guides I5 and It will be higher than average and the guide I6 will be moved toward the guide I5, thereby displaing the thread toward the small diameter end of the rollers I3 and it where the lower take-up rate adjusts for the unusually high tendency to shrink. If the thread exhibits an unusually low tendency to shrink, the reverse occurs and the guide It moves sion decreases to a certain limit when the sa increases from an almost straight line and it is in this rangethat the arrangement described above operates. The counterweight I8 is so arranged that when no thread is running between the guides I 5 and I6 the guide I6 assumes the broken line position shown in Figure 2. It is noted that the guides I5 and it are located approximately in the plane of contact of the rollers I3 and I4. The thread after passing through the rollers I3 and I4 is. led to a point of collection such as a twister or any other take-up device which can handle thread arriving at variable speeds. I

The drying chamber or drying tunnel I2 in which the thread is heated can be provided with arrangements for blowing hot air-or other hot gases therethrough or can be equipped for infrared drying orhigh frequency electrostatic heating. It is essential however, that in the drying zone the thread hang entirely free in a sort of chain line or catenary entirely free of am! mechanical influence. By doing this the accuracy 01 the response of the adjusting apparatus associated with the take-up rollers I3- and I4 is insured.

It now reference is made to Figures 3, 4 and 5, it will be seen that there is illustrated in those figures another type of apparatus for causing the magnitude of the sag of the thread in its passage through the drying tunnel to adjust the rate at which the thread is taken up. In Figures 3 and 4 there are shown two frusto conical rollers 20 and 2|, the lower roller 20 of which is driven at a constant rate of speed by means not shown. As stated in conjunction with rollers I4, this rate of speed is so correlated with the rate of delivery of thread to the drying zone that in the middle of the take-up rollers between the ends, the takeup surface will have a take-up speed to compensate for the average shrinkage which occurs during a drying operation. In front of the frusto conical draw oi! rollers 20 and 2| and in the thread path between the drying tunnel and those rollers, there is located a fixed thread guide 22 which has

cylindrical tines

23 and 24 which define a thread-guiding slit. The thread-guiding slit between the

tines

23 and 24 slopes with respect to the horizontal plane of the axis of the roller 20 while the thread guide itself lies in a plane parallel to the vertical plane of the axes of rollers 2|! and 2|. The tines are arranged so that the slit rises from the large diameter end of roller 20 to the small diameter end thereof. When working with viscose thread, spun under normal conditions, an angle of 45 between the slit of the guide 22 and the horizontal has given very satisfactory results. The slit extends for sufficient length so that the thread cannot drop off or pull out from between the

tines

23 and 24 during operation. In this regard note that the

tines

23 and 24 are at one end connected by an integral loop 25 and that they are bent to define a vertical threading slit 26 at the upper end of guide 22. operation the thread will pass to the take-up rollers 20 and 2| at about the mid-point between their ends, and the thread, in that position, passes between the

tines

23 and 24 exactly tangent to them, see in this regard, Figure 5.

If, in consequence of increasing shrinkage of the thread during drying, a smaller sag, and

consequently a higher tension of the thread is produced, a force acts between the thread and the top defining tine 23 of the slit. This force exerted upon the tine 23 produces a horizontal component because of the angular disposition of that time. Consequently, the action of the horizontal component is to move the thread upwardly in the slit from left to right as it is viewed in Figure 4. This results in a reduction in the take-up speed due to the fact that the righthand end of the take-up rollers is the end of smaller diameter. As soon as the thread has restored itself to a tangent position with respect to the tine 23, the component urging the thread to the right of Figure 4 ceases to exist and the thread runsat the new speed until other adjustment is necessary.

On the other hand, when sag increasesas a consequence of decreasing shrinkage during drying and tension accordingly decreases, a force is exerted between the thread and the lower tine 24 of the sit of guide22. This force produces a component acting to the left of Figure 4 and shifts the thread to the left of the Figure 4 position, whereby the take-up speed is increased and compensation is effected.

It can be seen by reference to Figures 3, 4 and 5 that the thread returns to the normal position as soon as a temporary deviation from normal sag has passed and that sag and tension in the thread remains practically unchanged from the desired value; that is to say, it fluctuates with small deviation from the position of equilibrium.

While the thread has been shown as passing As stated above, for normal or average between the

tines

23 and 24 tangent thereto, it

is perfectlyapparent that in normal operation the threads can actually pass between the tines without touching either of them. Then, when deviation from normal occurs, they will touch either one or the other of the tines whereby shifting will occur in the desired compensatory direction. Similarly, by modification of the position of the

tines

23 and 24, the thread can touch both tines in normal position and surround them with a certain predetermined angle of wrap. In this case right and left components exist concurrently and in equilibrium are equal. Upon deviation from equilibrium one or the other of the components dominates and the thread is shifted for compensation.

Referring now to Figures 6 and 7, there is shown a still further modification of the present invention whereby thread during drying is maintained at a predetermined angle of sag: -In this form of the invention the thread is not shifted by an auxiliary agency such as the thread guide 22 or hook guide It, but is shifted because of the inclination of the axes of the take-up rollers themselves.

In Figure 6, the take-up rollers are designated by

numerals

21 and 28. It is perfectly apparent that the sagging thread leaving the drying tunnel lies at .all times in a vertical plane. The lower frusto conical roller 21 of the take-up pair is so disposed that its axis 21a lies parallel to the vertical plane of the thread and at an angle 5 with the horizontal. Just as in the other examples, the peripheral speedofthe frusto conical rollers is chosen in such a way that when the thread passes over the rollers at the mid-point between their ends the take-up speed is correlated with the feeding speed of the roller which delivers the thread to the drying zone in a manner to effect compensation for fully shrunk thread. This state of equilibrium is always present when the thread crosses the axis 2M at right angles thereto. Naturally the angle 5 determines the permissible degree of sag of the catenaryin the drying chamber since the angle which the tangent to the catenary makes with the vertical at the point of contact with the roller always equals ,3. This angle is indicated 'a in Figure 6.

If excessive shrinkage occurs during drying the sag decreases in consequence of which the tension in the arriving thread increases and the thread no longer runs at right angles onto the axis of the roller. This causes a component. Whirh acts on the thread to the left of the Figure 6 view and results in migration of the point of contact of the thread to the left of that figure. The migration continues until the angle between the thread and axis 21a again equals Naturally migration to the left of Figure 6 results in decrease in the take-up speed of the

rollers

21 and 28 due to the frusto conical shape of the take-up device. On the other hand, if the sag increases from normal the thread 'migrates to the right of Figure 6 until conpensation has been effected.

In order to prevent the thread from sliding off the ends of the lower roller 21, the thread guides 29 and 3B are provided to limit the side movement of the thread.

After the thread has run round the-lower roller 21 with an angle of wrap of 90, part of the thread can still move around the upper roller, after which it is advanced to a suitable winding arrangement by means of the thread guide 3|.

It has been found that, for practical puposes, a taper of 10% of the frusto conical rollers l3--l4, 2ll-2l, or 21-28 is sufilcient in all cases. Thus, the increase and decrease of the velocity respectively on both sides of the center position of the rollers amounts to 5%.

In order to prevent slippage of the threads on the take-up rollers, it is advisable to cover them with an outer layer which is suitable for such purpose, such as rubber, leather or the like. The surprising practical result of the method. and anparatus of this invention is that during continuous drying a practically fully-shrunk rayon is obtained.

It is believed that the excellent results flow from maintaining the tension in the sagging,

thread, the tension in the thread whenpassing asses-re through the drying chamber should not be 'higher- 1 than one gram per 100 denier and preferably not higher than 0.2 gram per 100 denier. with the arrangements according to Figures 3 to 7, it is possible to adjust the tension on 100 denier thread to a value as low as 0.23 gram.

' In connection with the fact that it isdesirable to be able to set the tension in the drying zone as low as possible, it is important to decrease sible.

is possible without exerting a disadvantageous influence on the full-shrinkage. of the thread. It was found that it is permissible to predry the washed and aftertreated thread, which may often contain more than 200% of water, to a water content of about 70% calculated on dry substance, before this thread ,is supplied to the drying chamber with drawing-or! arrangement according to the invention. This predrying can be executed in the well known way by means of drying rollers. drying reels, thread-advancing rollers, crossedroliers etc. without decrease in velocity.

In the description of the forms of the invention shown in Figures 1 to 7, inclusive, either direct or inferential reference has been made' to a horizontal type drying chamber. It has been found. however. as a part of this invention, that drying under controlled tension conditions can 'be conveniently and efficiently eifected by passing the thread more or less vertically through a vertically disposed drying chamber.

'Referring specifically to Figures 8 and 9, the thread which may be pre-dried to about 70% moisture content is delivered by right

cylindrical rollers

32 and 43 at a constant speed. It is understood of course that the

rollers

32 and 33 will be driven at a constant rate of speed by any type of conventional apparatus not shown. The thread issuing from between the

supply rollers

32 and 33 is allowed to hang or s'ag in a vertically arranged drying chamber 34 in such a way that the lower end of the loop of thread eventually touches a polished plate 35 which is arranged in a sloping position, preferably at an angle of 45 to the horizontal, in the bottom of the drying ehamber.- The relative disposition of the supply rollers 82 and 33 with the plate 35 is such that the vertically sagging thread first touches the sloping plate 35 at'iits highzst side. After touching the plate 35 the thread is drawn upwardly to frusto conical drawofl rollers 36 and.

31, the lower one of which is arranged with its axis horizontal or approximately so and with its center in the axial'sense vertically above the center of the drying chamber 34. The drying chamber 34 is rectangular in horizontal cross section and may be made of any suitable material and supplied with a heated drying medium by known means.

The dimensions and the speed of the draw oil device consisting of the rollers It and is so ll andalso perpendicular to the draw of 8 and 9, ther 8 chosen that the take-up speed at the axial center of the

rollers

34 and 31 is equal to the average speed of the thread in shrunk condition. At the opposite extremities of these two'rollers a peripheral speed 5% higher and lower than average isailorded. Thus it is that, if the dryin thread moves downwardlyperpendicularly from the supply device consisting of the rollers" and device consisting of the rollers '34 and 31, the discharge speed is about 5% lower thanthe average speed of the thread in shrunk condition. Consequently the loop slides down the polished plate 3|. This causes a shift in the point where the thread is drawn on to the rollers It and disc that the thread is gradually taken up at a higher peripheral speed. If the take-up speed then exceeds that required to, compensate for shrinkage, the loop begins to progress up the polished plate 35 so that the axial take-up-point on the

rollers

38 and 31 again moves toward the smaller end of those rollers. By this arrangement in shrinkage due to mun-homogeneity in the thread or other causes.

On both sides of the take-up :device "-31,

rod-shaped guides 38. are provided. The Iunction of these devices is to prevent th'e'thread from running oil the ends of the rollers "-31.

The assembly appearing to the left of the chamber 34 of Figure 8 is a duplicate of the assembly comprised of delivery rollers 32-43. chamber 34 and draw ofl rollers 35-41 and is included in Figure 8 for the purpose 01. showing howa plurality of vertical chambers are to be arranged in a plant assembly.

In the event the drying of thread is eilected by hot air, the vertical chamber renders easier its circulation and the maintenance of the desired temperature. Vertical chambers also afford a considerable measure.of space economy.

Sometimes, it hot. air is used as. the drying medium, the convection currents will displace the thread to such an extent that its coaction with the polished plate 35 becomes too inaccurate to ai'for'd theproper degree of control of draw 0! speed. Should this problem become at all acute under any desired conditions of supply of the heating medium, it can be solved by resort to apparatus of the type shown in Figures 10 and In Figures 10 and 11 a vertical drying chamber 39, similar todrying chamber 34, is divided by a vertically extending partition 40 into two compartments, one for the descending thread and the other for the ascending thread. Between the partition 40 and a sloping plate 4| correspondin to the sloping-plate 35 of Figures is defined a thread slot indicated at 42 the function of which is to receive the loop of thread. In Figures 10 and 11 the thread is fed to the drying chamber by rollers 43 and corresponding respectively to

rollers

32 and 33 of Figure 8 and is collected on frusto

conical rollers

45 and 46 corresponding in structure and function to the rollers 36 and I1. Rod-shaped thread guides 41- are also provided and again these correspond in structure and function to the rods 38.

In the situation illustrated in Figures 10 and 11 where the drying chamber is divided into two compartments by an intermediate vertical partition such as the partition 40. it is desirable to provide the upper portion or the partition with a curving surface such as is shown at so that,

between the feed rollers 43, M andthe take-up device 45-46, will rest on that curving surface and be guided thereby into and through a slot 49 defined between the partition 40 and the vertical wall of the tank and leading to the slot at 42.

In operation, the movement of the bottom of the thread loop in the slot 42 corresponds to the movements described in connection with the plate of Figure 8. In other words, under conditions of increasing shrinkage the lower end of the thread 100p moves along the smoothly rounded surface of the lower edge of the partition in a lateral direction, and at decreasing shrinkage along the plate M inthe opposite lateral direction. .In both cascs the 'change in the discharge speed resulting therefrom compen-v .sates the end speed of the thread produced by the differences in shrinkage, so that a state of equilibrium is established. In contrast to the arrangement of Figures 8 and 9, the thread supply device may be dsposd above the center of the drying chamber.

ures 10 and 11 as compared to those occurring under like conditions in a drying channel without a partition. When drying by circulation of hot air, the air circulation in the first part of the drying channel may be larger than in the second part, whereby the rising thread may run comparatively quietly. 7

Of course, the whole matter of air circulation is avoided in cases where radiant heating is used and, accordingly, the arrangement of Figures 8 and 9 is fully satisfactory under radiant heating conditions.

Again in Figure 10, as in Figure 8, a duplicate chamber is shown to the left of the chamber 39 to demonstrate how multiple chambers are arranged side by side in plant assembly. Also in the case of Figure 10 it is preferable that the slot 42 be disposed at an angle of 45.

Having now particularly described and ascertained the nature of the said invention and in what manner the same is to be performed, it is declared that what is claimed is:

1. In the drying of synthetic thread by the method which involves delivering thread to a drying zone at a constant rate of speed and drawing the thread substantially horizontally through the zone while it is suspended from points outside of the zone to hang with sag in the zone, the

improvement which comprises effecting the drawing of the thread with a frusto conical draw-off roller and controlling the position of the thread axially of the roller as a function of the magnitude of the sag.

. 2. In the drying of synthetic thread by th method which involves delivering thread to a drying zone at a constant -'rate of speed and drawing the thread substantially horizontally through the zone while it is suspended from points outside of the zone to hang with sag in the zone, the improvement which comprises effecting the drawing of the thread with a frusto in threading up the machine, the loop formed 10 drawing the thread substantially horizontally through the zone while it is suspended from points outside of the zone to hang with sag in the zone, the improvement which comprises drawing the thread with a frusto conical drawoff roller having its axis disposed at an angle to the'horizontal equal to the complement of a predetermined angle of sag of the thread and having its end of small diameter above the end of large diameter whereby under normal conditions the thread is received at one point along the length of the roller while deviation from normal sag produces migration of the thread toward an end of the roller thereby to cause variation in the effective take-up rate of the roller.

.4. In the drying of synthetic thread by the method which involves delivering thread to a drying zone at a constant rate of speed and drawing the thread substantially through the zone while it is suspended from points outside of the zone to hang with sag in the zone, the improvement that compriseseffecting the drawing of the 'thread with a frusto conical draw-ofi roller driven at a constant R. P. M. while varying the efiective take-up speed of the draw-off roller by shifting the point of contact of the thread with the roller axially of the roller in response to variations in sag from a pre-determined normal.

5. In apparatus for drying synthetic thread which includes a drying chamber, means for delivering thread to the chamber at a constant. rate of speed and means for withdrawing thread from the chamber so that thread is suspended from points outside of the chamber to hang with sag in the chamber, the improvement which comprises a frusto conical roller for drawing the thread from the chamber, means for driving the roller at a constant R. P. M. and stationary guiding means for varying the point along the axis of the roller at which the thread is received in response to changes in the angle of sag of the thread.

6. In apparatus for drying synthetic thread which includes a drying tunnel, means for de .livering thread to the tunnel at a constant rate of speed and means for withdrawing thread from the tunnel so that thread is; suspended from points outside of the tunnel to hang with sag in the tunnel, the. improvement which comprises a frusto'conical roller for drawing the thread from the tunnel, means for driving the roller at a constant R. P. M. and guiding means intermediate the tunnel and the draw-on rollers for varying the point along the axis of the rollers at which the thread is received'in response to changes in theangle of sag of the thread.

'7. An apparatus as claimed in claim 6 wherein the means intermediate the draw-oil roller and the tunnel is a stationary thread guide in front of the roller defining a slot extending diagonally relative to the face of the roller.

8. An apparatus as claimed in claim 6 wherein the means intermediate the draw-oil? roller and the tunnel comprises a thread guide movably the roller and hence the thread take-up speed.

the tunnel comprises a stationary thread guide adjacent the end of smaller diameter of the roller, a movable thread guide pivotally mounted to shift from one end of the roller to the other which includes a drying-,tunnel and means for delivering thread to the tunnel at a constant speed, the improvement which comprises a frusto conical draw-on roller for drawing the thread from said tunnel, said rollerhaving its axis disposed at 'an'angle to th horizontal and its end of smaller diameter above its end of larger diameter, the thread between said delivering means and said roller hanging with sag in said tunnel, the angle of disposition of said roller being equal to the complement of theaverage angle of sag.

11. An apparatus for'drying synthetic thread which comprises a vertically arranged drying chamber, means for delivering thread to the chamber at a constant rate of speed and a frusto conical roller for withdrawing the, thread from the chamber so that thread is suspended from points outside the chamber to hang with sag in the chamber, means for driving the roller at a to. guide the threadionto the roller surface at any point along its length and a counterweight act-\ the top of the chamber so that the thread is suspended from points outside, of the chamber to hang said sag in the chamber. means for driving the roller at a constant'R. P. M., a stationary plate at the bottom of the chamber disposed at 10. an angle to the horizontal and functioning to.

vary the point along the axis of the rollerat which the thread changes in .the angle of the sag of the thread and a vertically extending partition subdividing the chamber above said plate into two zones that are in communication along the surface of'the plate and along the wall-of the chamber contiguone to the upper end of the plate.

15..Apparatus for drying synthetic threa comprising a vertically arranged drying chamber;

means for delivering thread into the top of the chamber at a constant rate of-ispeed, a frusto 1 conical roller for withdrawing thread from the top of the chamber so that thread is suspended 'zssfrom points outside the chamber to hang with constant R. P. M. and stationary guiding means disposed within the chamber in a position to be engaged by the sagging thread loop for varying the point along the aids of the roller at which the thread is-received in response to changes in the sag of the thread.

12. An apparatus as claimed in claim 11 wherein the stationary guiding means comprises a a plate disposed at an angle to the horizontal and constituting the bottom surface of the chamber.

13. An apparatus as claimed in claim 11 wherein the stationary guiding means is a plate disposed at an angle of 45 to the horizontal and constitutes the bottom surface of the chamber.

14. Apparatus for drying synthetic thread sag in it, mean for driving said roller at a constant R. P. ML, and a sloping'plate in the chamber having its high side vertically below the small end of the roller so that the plate can function to var the point along the axis of the roller at which thread is received in response to changes in the magnitude of sag of the thread.

PIE'I'ER van DIJK.

nnmnnncas crrnn The following referencesare of record in the tile of this patent:

UNITED STATES PATENTS Stanley Apr. 20, 1948 is received'in response to Certificate of Correction Patent No. 2,539,97 8 J anuary 30, 1951 PIETER VAN DIJK It is hereby certified that error appears in the above numbered patent requiring correction as follows:

In the heading to the printed specification line 6, following Serial No. 89,449 insert I n the NetherZrmds May 25, 1.948;

and that the said Letters Patent should be read as corrected above, so that the same may conform to the record of the case in the Patent Oflice.

Signed and sealed this 17th day of April, A. D. 1951.

[SEAL] THOMAS F. MURPHY,

Assistant Commissioner of Patents.