Drafting unit for ring spinning machines

Abstract

Drafting unit for ring spinning machines, comprising an output roller pair (2, 3) downstream of a drafting zone (V) with an output pressure roller (2) and an associated lower cylinder (3) and with a compression zone (D) downstream of the output roller pair (2, 3) and with a delivery pressure roller (5), wherein the output pressure roller (2) is arranged displaced backwards in the direction of the drafting zone (V) relative to a plane (13) perpendicular to the drafting unit plane (14) and passing through the axis of the lower cylinder (3), and wherein the drafting zone (V) is bent downwards.

Description

[0001] The present invention relates to a drafting system for ring spinning machines, with a pair of output rollers arranged downstream of a drafting zone with an output pressure roller and an associated lower cylinder and with a compression zone arranged downstream of the pair of output rollers and with a delivery pressure roller.

[0002] There are drafting systems for ring spinning machines in which the sliver drawn in the drafting zone leaves the drafting system at the nip line between the output pressure roller and the associated lower cylinder, wraps around the lower cylinder by a certain arc, and from there leaves the drafting system as a twisted thread in the direction of the thread guide. If the thread guide moves up and down slightly, the length of the drawn sliver wraps around the lower cylinder also changes within narrow limits. Experience has shown that the length of the wrap around the lower cylinder between the nip line and the run-off tangent, i.e. the line along which the thread releases from the lower cylinder runs, is of great importance for the stability of the spinning process. Both a distance that is too short and too long and the separation point, i.e. the point where the tangent rests on the lower cylinder, lead to increased thread breakage.The maximum and minimum lengths of the wrap commonly used today are based on years of practical experience.

[0003] To improve the strength and hairiness of the yarn, it is now common practice to add a compression zone downstream of the drafting zone. A delivery pressure roller is positioned downstream of the output pressure roller, resting against the lower cylinder. A compressor is arranged between the output pressure roller and the delivery pressure roller, which compresses the fiber sliver emerging from the drafting zone as desired. The compressed fiber sliver leaves the compression zone at the nip line and wraps around the delivery pressure roller until it reaches the detachment point, i.e., the point where the tangent contacts the lower cylinder.

[0004] This significantly increases the length of the wrap between the clamping line and the unwinding tangent, resulting in a decrease in spinning stability and an increase in the frequency of yarn breaks. To keep this disadvantage within acceptable limits, the spinning speed must be reduced, resulting in a reduction in production, which is no less detrimental.

[0005] EP 0 450 361 A1 discloses a drafting system with a stepped guide element. A top apron cage defines a second clamping surface together with the guide element.

[0006] DE 10 2007 024 234 A1 discloses a drafting system with a main drafting zone and a pair of rollers on an outlet side comprising a pressure roller and a lower cylinder. The drafting unit further includes a compression zone. Furthermore, the drafting zone is deflected downward by a fiber deflection element.

[0007] It is an object of the invention to show a solution how the disadvantages associated with the prior art can be avoided or at least greatly reduced.

[0008] This object is achieved by a drafting system according to the invention with the features of claim 1. This is a drafting system for ring spinning machines, comprising a pair of output rollers arranged downstream of a drafting zone, with an output pressure roller and an associated lower cylinder, and with a compression zone arranged downstream of the pair of output rollers and with a delivery pressure roller. The drafting system is characterized in that the output pressure roller is arranged displaced backward in the direction of the drafting zone relative to a plane perpendicular to the drafting system plane and extending through the axis of the lower cylinder. The drafting zone is preferably bent downward.

[0009] Due to the advantageous arrangement of the drafting system according to the invention, the delivery pressure roller moves upward, resulting in the wrapping distance of the untwisted fiber sliver on the delivery pressure roller being approximately the same as the original arrangement without the use of a compactor. The advantageous consequence of this inventive configuration—which will be discussed in more detail elsewhere—is that the spinning stability with a compaction zone is comparable to the spinning stability without a compaction zone.

[0010] The above-described backward displacement of the output pressure roller leads to a further, very positive effect due to the inventive design of the drafting system with a drafting field bent downwards.

[0011] Because the drafting zone is bent downwards, the fiber sliver leaves the top and bottom aprons of the drafting zone, which serve to control draft, not at the drafting system level, but below it, which is essentially determined by the bottom cylinders in front of the output pressure rollers. It wraps around the top apron by a certain arc measure until it separates from the top apron at a tangent to the top apron in the direction of the nip line between the output pressure roller and the associated bottom cylinder. This fiber deflection at the tangent creates considerable friction between the top apron and the fibers of the sliver. This friction advantageously and very effectively prevents edge fibers of the sliver from leaving the fiber structure and becoming lost as fiber fly.The fiber sliver drawn in the drafting zone reaches the nip line between the output pressure roller and the associated lower cylinder in a much more closed configuration than is the case with prior art arrangements. The compression of the fiber sliver in the compression zone is more effective, and the finished yarn is advantageously less hairy.

[0012] The invention is explained in more detail below by way of example with the aid of the figures shown in the drawing. Fig. 1 shows a first drafting system for ring spinning machines in a standard version from the prior art in a schematic side view. Fig. 2 shows a second drafting system for ring spinning machines with a downstream compression zone from the prior art in a schematic side view. Fig. 3 shows a drafting system for ring spinning machines according to the invention in a schematic side view. Fig. Figure 3a shows schematically an enlarged detail A of the drafting system from Fig. 3.

[0013] For the sake of simplicity, components with the same function are generally identified by the same reference numerals in the figures and in the following description.

[0014] The Fig. Figure 1 schematically shows a prior art example of a drafting system for ring spinning machines - general details will not be discussed here as they are known to those skilled in the art - having three pairs of pressure rollers defining a drafting field plane between them. Specifically designated are an output pressure roller 2 and a lower cylinder 3 associated with it. A fiber sliver FB to be drafted runs between the rollers, passing through a drafting zone V comprising upper and lower aprons, up to a nip line 1 and then, wrapping around the lower cylinder 3 up to a release point 4, following a tangent applied to the lower cylinder at the release point 4 to a yarn guide 5.The arrangement is designed such that the fiber sliver FB drawn in the drafting zone V leaves the drafting system at the clamping line 1 between the output pressure roller 2 and the lower cylinder 3, wraps around the lower cylinder 3 up to the detachment point 4 and from there leaves the drafting system as a twisted thread F in the direction of the thread guide 5.

[0015] Since the thread guide 5 moves up and down to a small extent, the length of the wrap around the lower cylinder by the warped fiber band also changes within narrow limits.

[0016] Experience has shown that the length of the wrap of the fiber sliver FB around the lower cylinder between the clamping line 1 and the detachment point 4 is decisive for the stability of the spinning process.

[0017] To increase the yarn strength and to improve its hairiness, the drafting zone V is usually followed by a compression zone D, as in Fig. 2. The output pressure roller 2 is followed by a delivery pressure roller 5, which is supported against the lower cylinder 3 in the area of ​​a nip line 7. Between the pressure rollers 2 and 5, a compressor 6 is arranged, which compresses the fiber sliver FB emerging from the drafting zone V in the desired manner. The compressed fiber sliver FB leaves the compression zone D at the nip line 7 and wraps around the delivery pressure roller 5 up to a tangential point 8. The distance of the wrap between the nip line 7 and the tangential point 8 is thereby greatly extended, as can be seen from a comparison of the situations in Fig. 1 and Fig. 2. However, spinning stability is reduced as a result, and the frequency of thread breaks increases. To mitigate this disadvantage, it is necessary to reduce the spinning speed and accept a reduction in production.

[0018] Fig. Finally, Figure 3 shows an embodiment of a drafting system according to the invention. Here, the output pressure roller 2 is shown displaced backward relative to the plane 13 passing through the axis of the lower cylinder 3 and perpendicular to the drafting field plane 14. The delivery pressure roller 5 then moves—note the difference from the configuration according to Fig. 2 - upwards, and the length of the wrap around the delivery pressure roller by the untwisted fiber band FB then corresponds approximately to the length as shown in Fig. 1. Thus, the spinning stability of a drafting system with a compression zone is comparable to the spinning stability of a drafting system without a compression zone, with a further, very positive effect resulting from the downward bending of the drafting field V ( Fig. 3).

[0019] The draft zone V is determined by the upper and lower aprons 9 and 10, which serve to control the draft. As shown in Fig. 3, Detail A and in Fig. 3a is shown enlarged, the fiber sliver FB leaves the upper and lower aprons 9 and 10 below the drafting system plane formed by the lower cylinders 3 and 11 at the tangential point 12 in the direction of the nip line 1 between the rollers 2 and 3.

[0020] The fiber deflection at the tangential point 12 creates considerable friction between the top apron 9 and the fibers, which prevents edge fibers from leaving the fiber structure and being lost as fiber fly, since the distorted fiber band reaches the clamping line 1 much more closed than in the case of Fig. 1. A more effective compaction of the fiber sliver in the compaction zone can be achieved, resulting in a less hairy finished yarn. List of reference symbols 1 clamping line 2 output pressure roller 3 lower cylinders 4 release point 5 Delivery pressure roller 6 compressors 7 clamping line 8 Tangential point 9 upper straps 10 underlays 11 lower cylinders 12 Tangential point 13 to the stretching field plane 14 vertical plane 14 Stretching field level A Detail D Compaction zone V Delay zone

Claims

[1] Drafting system for ring spinning machines, with a pair of output rollers (2, 3) arranged downstream of a drafting zone (V) with an output pressure roller (2) and an associated lower cylinder (3) and with a compression zone (D) downstream of the output roller pair (2,3) and with a delivery pressure roller (5), characterized by , that the output pressure roller (2) is arranged displaced backwards in the direction of the drafting zone (V) relative to a plane (13) perpendicular to the drafting system plane (14) and passing through the axis of the lower cylinder (3), wherein the draft zone (V) has an upper belt (9) and a lower belt (10), and wherein the drafting zone (V) is designed such that, during operation of the drafting system, the fiber sliver (FB) leaves the upper belt (9) and the lower belt (10) below the drafting system plane (14) at a tangential point (12). [2] Drafting device according to claim 1, wherein the drafting zone (V) is bent downwards. [3] Drafting device according to claim 1 or 2, further comprising three pairs of pressure rollers defining the drafting device plane (14) between them. [4] Drafting system according to one of the preceding claims, wherein the tangential point (12) on the upper belt (9) is designed such that, during operation of the drafting system, a fiber deflection takes place at the tangential point (12). [5] Drafting system according to one of the preceding claims, wherein the delivery pressure roller (5) is arranged downstream of the output roller pair (2, 3). [6] Drafting device according to one of the preceding claims, wherein the delivery pressure roller (5) is supported against the lower cylinder (3) in the region of a clamping line (7). [7] Drafting system according to claim 6, wherein the drafting system is designed such that, during operation of the drafting system, the fiber sliver (FB) leaves the compression zone (D) at the nip line (7). [8] Drafting system according to one of the preceding claims, wherein in an operating position of the drafting system, the axis of the delivery pressure roller (5) is arranged above the axis of the lower cylinder (3).

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