Method for drafting spun yarns in three stages

Abstract

The present invention relates to a method for drafting spun yarns in three stages. The method comprises drafting fiber strips to obtain fiber strands in the first-stage draft zone, drafting fiber strands to obtain non-discrete fiber bands without twist distribution in the second-stage draft zone, and drafting fiber bands to obtain twist less fiber assemblies in the third-stage draft zone. The methods optimize the maximum total draft ratio to obtain twist less fiber assemblies while maintaining evenness and required quality of resultant yarns.

Claims

1. A method for drafting spun yarns in three stages using a drafting mechanism that has an entrance and an exit, four lines of rollers arranged in turn from the entrance to the exit to form a first-stage draft zone, a second-stage draft zone, and a third-stage draft zone, and each draft zone is respectively located between adjacent two lines of rollers; said method comprising: feeding a fiber strip whose twist and weight are detected in advance from the entrance of the drafting mechanism; drafting said fiber strip in the first-stage draft zone to obtain a fiber strand wherein a the twist of said fiber strand is 75% to 95% of that of the fiber strip and the weight of said fiber strand is 71% to 99% of that of said fiber strip and a first-stage draft ratio in said first-stage draft zone is 1.01 to 1.40; drafting said fiber strand in the second-stage draft zone to obtain a non-discrete fiber band without twist redistribution, wherein the twist of said fiber band is 15% to 60% of that of the fiber strip, and the weight of said fiber band is 47% to 98% of that of the fiber strip and a second-stage draft ratio in said second-stage draft zone is 1.01 to 1.52; drafting said fiber band in the third-stage draft zone to obtain a twist less fiber assembly wherein the weight of said fiber assembly is 0.3% to 9.8% of that of the fiber strip, and a third-stage draft ratio in said third-stage draft zone is 10 to 150, and the obtained fiber assembly is output from the exit of the drafting mechanism and is twisted into spun yarns.

2. The method for drafting spun yarns in three stages according to claim 1, wherein the twist and weight of the obtained fiber strand, fiber band, or fiber assembly are respectively detected by a detector in the first-stage draft zone, second-stage draft zone, and third-stage draft zone of said drafting mechanism; the driving of each line of rollers is controlled by a separate servo motor; the revolutions of each line of rollers are respectively adjusted by the separate servo motor according to a detection signal received by a controller from the detector and a corresponding preset value or scope of preset value of each draft zone so that the twist and fiber weight of the obtained fiber strand, fiber band, or fiber assembly can fall within the scope required for each draft zone.

3. The method for drafting spun yarns in three stages according to claim 2, wherein the four lines of rollers of said drafting mechanism are a rear drafting roller pair, a middle-rear drafting roller pair, a middle-front drafting roller pair, and a front drafting roller pair, respectively; the first-stage, second-stage, and third-stage draft zones are respectively formed between said rear drafting roller pair and said middle-rear drafting roller pair, between said middle-rear drafting roller pair and said middle-front drafting roller pair, and between said middle-front drafting roller pair and said front drafting roller pair.

4. The method for drafting spun yarns in three stages according to claim 3, wherein the detector in the first-stage draft zone sends the detection signal containing the twist and fiber weight of the obtained fiber strand to the controller; the controller compares the detection signal with the preset value or scope of preset value of the first-stage draft zone and adjusts a number of revolutions of the rear drafting roller pair and the middle-rear drafting roller pair through the corresponding servo motors according to the comparison result so that the twist of the obtained fiber strand is 75% to 95% of that of the fiber strip and the fiber weight is 71% to 99% of that of the fiber strip.

5. The method for drafting spun yarns in three stages according to claim 3, wherein the detector in the second-stage draft zone sends the detection signal containing the twist and fiber weight of the obtained fiber band to the controller; the controller compares the detection signal with the preset value or scope of preset value of the second-stage draft zone and adjusts a number of revolutions of the middle-front drafting roller pair according to the comparison result and a number of revolutions of the middle-rear drafting roller pair so that the twist of the obtained fiber band is 15% to 60% of that of the fiber strip and the fiber weight is 47% to 98% of that of the fiber strip.

6. The method for drafting spun yarns in three stages according to claim 3, wherein the detector in the third-stage draft zone sends the detection signal containing the twist and fiber weight of the obtained fiber assembly to the controller; the controller compares the detection signal with the preset value or scope of preset value of the third-stage draft zone and adjusts a number of revolutions of the front drafting roller pair according to the comparison result and a number of revolutions of the middle-front drafting roller pair so that the obtained fiber assembly is twist less and the fiber weight is 0.3% to 9.8% of that of the fiber strip.

7. The method for drafting spun yarns in three stages according to claim 3, wherein said rear drafting roller pair consists of a rear upper roller and a rear lower roller, said middle-rear drafting roller pair consists of a middle-rear upper roller with a middle-rear upper apron and a middle-rear lower roller with a middle-rear lower apron, said middle-front drafting roller pair consists of a middle-front upper roller with a middle-front upper apron and a middle-front lower roller with a middle-front lower apron, and said front draft roller pair consists of a front upper roller and a front lower roller.

8. The method for drafting spun yarns in three stages according to claim 7 wherein said rear lower roller, middle-rear lower roller, middle-front lower roller, and front lower roller are respectively driven by corresponding servo motors to rotate; said rear upper roller, middle-rear upper roller, middle-front upper roller, and front upper roller are driven by the corresponding rollers to rotate.

9. The method for drafting spun yarns in three stages according to claim 7, wherein said middle-rear upper apron and middle-rear lower apron, and said middle-front upper apron and middle-front lower apron respectively touch each other closely and rotate reversely to frictionally untwist and draft fiber strands to obtain non-discrete fiber bands without twist redistribution.

10. The method for drafting spun yarns in three stages according to claim 7, wherein a downward-pressing bar is equipped in the third-stage draft zone of said drafting mechanism, said downward-pressing bar touches fiber assemblies, and the detector in the third-stage draft zone of said drafting mechanism is a trace detector.

11. The method for drafting spun yarns in three stages according to claim 1, wherein a maximum total draft ratio of said drafting mechanism is 320.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows the structure of the drafting mechanism of one embodiment of the present invention.

(2) FIG. 2 shows the control system of the embodiment in FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

(3) The following further describes the invention in combination with the drawings and an embodiment. The present is not limited to the given embodiment.

Embodiment

(4) As shown in FIG. 1 and FIG. 2, the drafting mechanism in the embodiment has an entrance and an exit, four lines of rollers are arranged in turn from the entrance to the exit to form the first-stage, second-stage, and third-stage draft zones, and each draft zone is respectively located between the adjacent two lines of rollers.

(5) To be specific, the four lines of rollers of said drafting mechanism are the rear drafting roller pair, the middle-rear drafting roller pair, the middle-front drafting roller pair, and the front drafting roller pair, respectively; the first-stage draft zone (1), second-stage draft zone (2), and third-stage draft zone (3) are respectively formed between said rear drafting roller pair and middle-rear drafting roller pair, between said middle-rear drafting roller pair and middle-front drafting roller pair, and between said middle-front drafting roller pair and front drafting roller pair.

(6) Said rear drafting roller pair consists of a rear upper roller (9) and a rear lower roller (10), said middle-rear drafting roller pair consists of a middle-rear upper roller (11) with a middle-rear upper apron (17) and a middle-rear lower roller (12) with a middle-rear lower apron (18), said middle-front drafting roller pair consists a middle-front upper roller (13) with a middle-front upper apron (19) and a middle-front lower roller (14) with a middle-front lower apron (20), and said front draft roller pair consists of a front upper roller (15) and a front lower roller (16).

(7) Said rear lower roller (10), middle-rear lower roller (12), middle-front lower roller (14), and front lower roller (16) are respectively driven by corresponding servo motors (25, 26, 27, and 28) to rotate; said rear upper roller (9), middle-rear upper roller (11), middle-front upper roller (13), and front upper roller (15) are driven by the corresponding rollers to rotate.

(8) Detectors (21, 22, and 23) are respectively equipped in the first-stage draft zone (1), second-stage draft zone (2), and third-stage draft zone. The signal output ends of the detectors (21, 22, and 23) are respectively connected to the input end of a programmable logic controller (PLC) (29), and the control ends of the servo motors (25, 26, 27, and 28) are respectively connected to the controlling end of the PLC (29). The PLC (29) is equipped with a touch screen (30). A downward-pressing bar (31) is additionally equipped in the third-stage draft zone (3).

(9) In addition, the drafting mechanism has a cradle (24), and a fiber strip feeding device (8) at the entrance.

(10) It should be noted that the detectors (21, 22, and 23) are all products of the prior art in the market. They may be a detector which can simultaneously detect the twist and fiber weight of the target object, or be the combination of a twist detector and a fiber weight detector.

(11) The method for drafting spun yarns in three stages in the embodiment comprises the following steps:

(12) Step 1. A fiber strip (32) whose twist and weight are detected in advance is fed from the entrance of the drafting mechanism, the fiber strip (32) is drafted in the first-stage draft zone (1) to obtain a fiber strand (4); the twist of the fiber strand (4) is 75% to 95% of that of the fiber strip (32) and the weight of the fiber strand (4) is 71% to 99% of that of the fiber strip (32); the draft ratio in the first-stage draft zone (1) is 1.01 to 1.40.

(13) In step 1, the detector (21) in the first-stage draft zone (1) sends a detection signal containing the twist and fiber weight of the obtained fiber strand (4) to the controller (29); the controller (29) compares the detection signal with the preset value or scope of preset value of the first-stage draft zone (1) and adjusts the revolutions of the rear drafting roller pair and the middle-rear drafting roller pair through the corresponding servo motors (25 and 26) according to the comparison result so that the twist and weight of the obtained fiber strand (4) meet the above-mentioned requirements.

(14) Step 2. The fiber strand (4) is drafted in the second-stage draft zone (2) to obtain a non-discrete fiber band (5) without twist redistribution; the twist of the fiber band (5) is 15% to 60% of that of the fiber strip (32), and the weight of the fiber band (5) is 47% to 98% of that of the fiber strip (32); the draft ratio in the second-stage draft zone (2) is 1.01 to 1.52.

(15) In step 2, the detector (22) in the second-stage draft zone (2) sends a detection signal containing the twist and fiber weight of the obtained fiber band (5) to the controller (29); the controller (29) compares the detection signal with the preset value or scope of preset value of the second-stage draft zone (2) and adjusts the revolutions of the middle-front drafting roller pair according to the comparison result and the revolutions of the middle-rear drafting roller pair so that the twist and weight of the obtained fiber band (5) meet the above-mentioned requirements.

(16) In addition, the middle-rear upper apron (17) and middle-rear lower apron (18), and the middle-front upper apron (19) and middle-front lower apron (20) respectively touch each other closely and rotate reversely to frictionally untwist and draft the fiber strand (4) to obtain a non-discrete fiber band (5) without twist redistribution.

(17) Step 3. The fiber band (5) is drafted in the third-stage draft zone (3) to obtain a twist less fiber assembly (6); the weight of the fiber assembly (6) is 0.3% to 9.8% of that of the fiber strip (32); the draft ratio in the third-stage draft zone (3) is 10 to 150; the obtained fiber assembly (6) is output as a prepared fiber body (7) from the exit of the drafting mechanism and is then twisted into spun yarns.

(18) In step 3, the detector (23) in the third-stage draft zone (3) sends a detection signal containing the twist and fiber weight of the obtained fiber assembly (6) to the controller (29); the controller (29) compares the detection signal with the preset value or scope of preset value of the third-stage draft zone (3) and adjusts the revolutions of the front drafting roller pair according to the comparison result and the revolutions of the middle-front drafting roller pair so that the obtained fiber assembly (6) is twist less and its fiber weight meets the above-mentioned requirement.

(19) In addition, the downward-pressing bar (31) touches the fiber assembly (6) to press the fiber assembly (6) down slightly. The detector (23) in the third-stage draft zone (3) can be a trace detector so that it can better detect the fiber weight.

(20) In the above-mentioned method, the controller (29) can adjust the revolutions of all lines of rollers as a whole so that the change of the revolutions of the roller is accurate, timely, and consistent.

(21) Besides the above-mentioned embodiment, the present invention has other embodiments. All technical solutions formed by adopting equivalent replacement or transformation should fall within the scope of the claims of the present invention.