US 3706192 A
A system is provided to false twist and simultaneously draw a linear synthetic high polymer yarn. The yarn is first heated and then false twisted in a novel false twister wherein the diameter of the twisting chamber is considerably greater than the yarn feeding and discharge channels.
Description (OCR text may contain errors)
United States Patent Leibbrand et al. 1 Dec. 19, 1972 PROCESS AND APPARATUS FOR  References Cited FALSE TWISTING SYNTHETIC YARNS UNITED STATES PATENTS  Inventors: Bertus Leibbrand, Elst; Johan J. 3 079 745 311963 B t I 57177 3 x reen e a 21:??? figzis iih gz' g' 2,515,299 7/1950 Foster et al ..s7/77.3 A E L d A d 2,863,280 12/1958 Ubbelohde ....57/77.3 x m e 3,022,566 2/1962 Daniels et al. ..57/34 B Arnhem of Netherlands 3,206,922 9/1965 Nagahara et 8].... .....57/34 HS x  Assignee: Akzona incorporated, Ashevme 3,237,392 3/1966 Crouzet ..57/34 HS X N.C. Primary Examiner-Donald E. Watkins  Flledz Oct. 8, 1970 Attorney-Albin F. Knight 21 A 1. No.1 79 231 1 pp 57 ABSTRACT  Foreign Application Priority Data A system is provided to t'alse twist and simultaneously draw a lmear synthetic high polymer yam. The yarn is Oct. 14, 1969 Netherlands ..69l5479 fi t heated and then f l twisted in a novel f l 1969 Netherlands twister wherein the diameter of the twisting chamber Oct. 14, 1969 Netherlands ....691548] is considerably greater than the yam f di and Oct. 14, Netherlands discharge channels  U.S. CI. ..57/34 HS, 57/34 B, 57/77.3,
57/157 TS, 57/157 F  1m. (:1 ..D02g l/16, D02g 1/02 11 C 1 Drawmg Figures  Field of Search.57[ 34 R, 34 HS, 51, 77.3,77.45,
PATENTEDBEB 1' W2 3.706.192 sum 1 or 2 L L .l
20 1 INVENTORS BERTUS LEIBRAND JOHAN J. MERTENS HARM A. PLOEGER ROBERT SLUI JTERS LEENDERT van ASSENDELFT ATTORNEY PKTENTED 19 I97? 3. 708. 192
sum 2 BF 2 FIG. 3
I8 [16 17 29 72:41 Ei t EEE 2 23 H 24 INVENTORS BERTUS LEIBRAND JOHAN J. MERTENS HARM A. PLOEGER ROBERT SLUIJTERS LEENDERT van ASSENDELFT Mi-M ATTORNEY PROCESS AND APPARATUS FOR FALSE TWISTING SYNTHETIC YARNS The present invention relates to a process and apparatus for false twisting synthetic linear high polymer yarns, threads and the like. More particularly, the invention relates to an improved system for false twisting yarn in pneumatic jets while drawing the same to several times its original length.
Apparatus of this general type is known in the art but has not been commercially satisfactory. The systems used did not give the yarn a sufficiently high angular velocity to obtain in the yarn a temporary twist of the high level required. This was found to be particularly true as the trend in the industry was to the application of ever increasing linear speeds of the yarn.
US. Pat. Nos. 3,009,309; 3,069,836, and 3,206,922 all disclose pneumatic jets for imparting a false twist to the yarn. However, in each case the yarn is twisted after the drawing operation and under a decreased tension or let-off in order to produce a crimped or bulked yarn.
It is therefore an object of the present invention to overcome the shortcomings and deficiencies in the prior art.
It is a further object to provide a system for producing a false twisted yarn that is stable, compact, and of high quality for use in the knitting and weaving trades.
Another object is to correlate the several elements in the system to provide an improved process.
Still another object is the provision of a unique false twisting apparatus.
These and other objects and advantages will become apparent when considered in conjunction with the accompanying drawings wherein:
FIG. 1 shows a schematic view of an improved arrangement of apparatus for carrying out the process of the invention as a continuous operation;
FIG. 2 is an enlarged sectional view of the pneumatic false twister;
FIG. 3 is a modified version of FIG. 1; and
FIG. 4 shows an enlarged -modified section of the pneumatic chamber with portions of the channels shown on each end of the chamber.
Referring now to the drawings, undrawn yarn is conveyed from a supply package 11 via pigtail guide 12 to a pair of constant-speed feed rolls 13. The yarn is then passed to a hot pin 14 heated to about 140 C. and makes at least one wrap therearound and after passing around the hot pin is led through a tubular oven 15 of from 2 to 3 meters in length and heated to a temperature of about 175 C. The oven 15 is surrounded by a steam jacket 16.
After leaving the oven 15, the yarn is passed through an opening provided in a baffle 17 and then enters a pneumatic false twister generally shown at 18, an enlarged view of which is shown in FIG. 2.
The pneumatic false twister 18 consists of a substantially cylindrical chamber 19 into which compressed air is blown in a tangential direction through a slot 20 via air inlet 21 At one end of chamber 19 there is disposed a yarn feed channel 22 and at the other end of the chamber a discharge channel 23. The yarn feed and discharge channels are of equal length, which length L is of from 25 to 150 times as large as their inside diameter d. The length L may, for instance, be 25, 50, 75, 100, 125 to 150 times as large as the diameter d. It is preferred that the inside diameter D of the chamber is at least approximately 1.2 to 1.5 times the inside diameter d of the feed and discharge channels 22 and 23.
On the inside of, and adjacent to, the chamber 19 the connections to channels 22 and 23 are. suitably rounded off. The baffle l7 is located at an adjustable distance from feed channel 22.
After leaving false twister 18, the yarn passes on to a draw roll 24 provided with separator roll 25. Depending on the desired draw ratio of the yarn, the circumferential velocity of the draw roll may be chosen to be, for instance, 1.5 to 4 times that of feed rolls 13. Finally, the drawn and false twisted yarn 26, after passing through a top pigtail guide 27, is taken up on a ring twister 28.
The adjustable distance A between feed channel 22 and oven 15 is not more than approximately 250 mm., but preferably between 20 to 35 mm. The baffle 17 is located at an adjustable distance B from feed channel 22.
The embodiment according to FIG. 3 differs from that according to FIG. 1 in that downstream of the pneumatic false twister l8 and at some distance therefrom there is provided a second mechanical false twister 29. The second false twister 29 may be constructed in different ways known in the art and is therefore represented in the drawing only schematically. After the yarn has left the second false twister 29, it passes on to a roll 24 with separator roll 25 FIG. 4 is a partial view of a modified embodiment of a false twister, like parts being indicated by like numerals. Near the end of the yarn inlet side, the wall of chamber 19 is provided with an annular zone 30 whose diameter is larger than that of the adjoining wall portion of chamber 19. Via a narrow slit 31 the annular zone 30 connects with a collecting space 32 which communicates with the ambient air via a channel 33. Under the influence of the centrifugal force, dust, for instance in the form of titanium dioxide, coming from the yarn will be forced into the collecting space 32, from where it will be discharged into the ambient atmosphere via channel 33.
By the use of the foregoing apparatus according to the invention, it is possible to give the yarn an angular velocity of as high as a few million revolutions per minute. This makes it possible to give the yarn a temporary twist, that is, a false twist, of customary level, in combination with a yarn transport velocity of from 300 to 800 meters per minute, which velocity is very high for a false twisting process.
By way of example, the apparatus according to the invention was used for the false twisting of a six-filament polyamide yarn having a total denier of 20. While traveling at a speed of 700 meters per minute, the yarn was, in the pneumatic false twisting device, caused to rotate at a rate of 3.5 million revolutions per minute. This led. to the formation in the yarn of a temporary twist, or false twist, of the order of 3.5 X 10 /700 5000 turns per meter.
the circumference thereof and in tangential direction, escapes to the surrounding atmosphere through the coaxial feed and discharge channels provided at the end surfaces of chamber. The feed and discharge channels have a much smaller diameter than the chamber, so that the velocity of rotation of the air is increased considerably as it enters the feed and discharge channels.
Since the inside diameter of the feed and discharge channels is considerably larger than the diameter of the yarn to be treated, which may have a denier of, say 20, the rolling of the yarn against the inside of the channels takes place at a high transmission ratio, which is another factor contributing to a high rotational velocity of the yarn.
In spite of the high rotational velocities, the process can readily be started andkept running smoothly if the apparatus is further equipped with a second false twister downstream of the pneumatic first false twister. In other words, there is provided another mechanical false twister which serves to impart to the yarn at least 5 to percent, more particularly 30 to 40 percent, of the total amount of twist temporarily present in the yarn. The 'apparatus,.according to the invention, has advantage in that said mechanical false twister is formed by a driven false twisting spindle or a friction disc, or a yam-wrapped rotating roller or tube whose longitudinal axis is at an angle with the longitudinal direction of the yarn.
High speeds required for economic reasons can be applied and the correct draw ration be chosen which is necessary to finallyobtain a yarn of a particular denier if the apparatus according to the invention locates both the pneumatic first false twister and the second false twister between the feed rolls and the draw rolls.
With the false twisting apparatus, the yarn is, in a known manner, successively heated upstream of the pneumatic twister and cooled.
The cooling is effected in such a manner that after leaving the heating member the yarn is over a relatively long distance, say 400 to 500 mm., passed through the ambient air before it'arrives at the false twister.
In known apparatus the very high economic valve of the yarn speed because of the combination with the drawing process will call for an even longer cooling zone between the heating member and the false twisting member, which is difficult to realize because of the available height and space.
According to the present invention, the false twisting apparatus is unique in that the distance between the pneumatic false twister and the heating member is not more than approximately 250 mm. With a preferred embodiment of the apparatus according to the invention, the distance between the pneumatic false twister and the heating member is approximately to 35 mm. Despite the short length of the cooling zone between the false twister andthe heating member, it has surprisingly been found that even at speeds of from 500 to 1,000 meters per minute, which are uncommonly high for false twisting processes, the apparatus according to the invention provides a satisfactory cooling and that a longer cooling zone even has an adverse influence on the quality of the yarn. In a preferred embodiment of the apparatus according to the invention, the distance member is adjustable.
The results obtained with the apparatus, according to the invention, can be improved in a simple manner by disposing a shield or baffle between the pneumatic false twister and the heating member. This shield is provided with an opening for passage of the yarn and protects the yarn against the heat on one side and air on the other. An efficacious construction is also obtained if the apparatus is constructed so that the longitudinal axes of the yarn feed channel of the pneumatic false twister and the heating member are not positioned coaxially.
Internal wear of the pneumatic false twister can be inhibited if at or near the circumference of the chamber wall of the pneumatic false twister, on its inside it is locally provided with a narrow discharge opening. According to the invention, the narrow discharge opening has the advantage that in the annular zone the diameter is greater than that of the adjoining portion of between the pneumatic false twister and the heating the chamber wall. In a preferred embodiment of the apparatus, the narrow discharge opening connects with a collecting space which is located at a larger radial distance from the center of the chamber, the collecting space being in open communication with the ambient atmosphere via a narrow channel.
It is preferred that the annular zone should be formed at the yarn inlet side of the chamber. It surprisingly has been found that in spite of the high air velocities, the internal wear of the pneumatic false twister according to the invention is negligibly small, which is probably to be attributed to the face that under the influence of the centrifugal forces the hard particles, such as titanium dioxide, coming from the yarn, collect in the annular zone of relatively large diameter from where they are discharged into the ambient atmosphere.
What is claimed is:
1. Apparatus for false twisting synthetic yarns which comprises yam feeding means and yarn drawing means for transporting the yarn from a source of supply to a take-up device, a pneumatic false twister formed with a cylindrical chamber and provided with means to supply compressed air in a tangential direction along the circumference of the chamber, feed and discharge channels rigidly mounted on each end of the chamber, the inside diameter of the chamber being substantially greater than the inside diameter of the channels, and the length of each channel being at least 10 times that of their inside diameter.
2. Apparatus according to claim 1 in which the inside diameter of the chamber is at least 1.2 to 1.5 times the inside diameter of the feed and discharge channels.
3. Apparatus according to claim 1 in which the length of the feed and discharge channels is 25 to times that of their inside diameter.
4. Apparatus according to claim 1 which further comprises a mechanical false twister disposed downstream of the pneumatic false twister.
5. Apparatus according to claim 4 in which the pneumatic false twister and the mechanical false twister are both located between the yarn feeding means and the yarn drawing means.
6. Apparatus according to claim 1 which further comprises heating means disposed between the yarn feeding means and the false twister.
7. Apparatus according to claim 6 in which the distance between the pneumatic false twister and the heating means is approximately 20-35 mm.
8. Apparatus according to claim 1 which further comprises a shield or baffle disposed between the pneumatic false twister and the heating means to provide passage for the yarn.
9. Apparatus according to claim 1 which further 5 comprises a narrow discharge opening at or near the circumference of the chamber wall of the pneumatic false twister.
10. Apparatus according to claim 9 in which the narrow discharge opening is connected to a collecting 10 space located at a larger radial distance from the center of the chamber, the collecting space being in open