Sliver preparation

Abstract

A drafting system for conveying a sliver to an inlet opening of a vortex chamber of an air-jet spinning device, for a drafting system having an exit roller pair and at least one additional drafting system roller pair and/or apron roller pair. A sliver is supplied at a spinning station of an air-jet spinning machine for the production of a thread to the vortex chamber. The exit roller pair can be driven decoupled from the at least one additional pair of drafting system rollers and/or apron rollers. In the method, the roller pair is driven for combing the sliver end after a spinning interruption at a predetermined combing speed and the at least one stretching mill roller and/or belt roller pair upstream of the starting roller pair is stopped or operated at a holding speed associated with the combing speed, which is at most 10% of the combing speed.

Claims

1. A method for operating a drafting system having an exit roller pair and at least one additional drafting system roller pair and/or apron roller pair, the method comprising: supplying a sliver to a spinning station of an air-jet spinning machine for producing a thread to a vortex chamber of an air-jet spinning device of the spinning station; decoupled driving of the exit roller pair from the at least one additional drafting system roller pair and/or the apron roller pair; driving the exit roller pair at a predetermined combing-out speed for combing out the sliver after an interruption of spinning; wherein the at least one additional drafting system roller pair and/or the apron roller pair located upstream of the exit roller pair in the sliver running direction is stopped or operated at a holding speed which is associated with the combing-out speed and which amounts to a max. 10% of the combing-out speed; and stopping the drafting system combing and then powering up the drafting system for piecing.

2. The method according to claim 1, wherein driving the exit roller pair occurs before the at least one additional drafting system roller pair and/or the apron roller pair when the drafting system is powered up during piecing.

3. A drafting system for conveying a sliver in the direction of an inlet opening of a vortex chamber of an air-jet spinning device, the drafting system comprising: an exit roller pair which can be driven decoupled from at least one additional drafting system roller pair and/or apron roller pair; and a control unit for carrying out the method for operating the drafting system according to claim 2 after an interruption of spinning.

4. The drafting system according to claim 3, wherein the control unit is integrated into a central control unit of the air-jet spinning machine.

5. The drafting system according to claim 4, wherein the control unit is designed to variably adjust the combing-out speed and/or the holding speed.

6. The drafting system according to claim 3, wherein the control unit is designed to variably adjust the combing-out speed and/or the holding speed.

7. A drafting system for conveying a sliver in the direction of an inlet opening of a vortex chamber of an air-jet spinning device, the drafting system comprising: an exit roller pair which can be driven decoupled from at least one additional drafting system roller pair and/or apron roller pair; and a control unit for carrying out the method for operating the drafting system according to claim 1 after an interruption of spinning.

8. The drafting system according to claim 7, wherein the control unit is integrated into a central control unit of the air-jet spinning machine.

9. The drafting system according to claim 8, wherein the control unit is designed to variably adjust the combing-out speed and/or the holding speed.

10. The drafting system according to claim 7, wherein the control unit is designed to variably adjust the combing-out speed and/or the holding speed.

Description

(1) An exemplary embodiment of the invention is explained below with reference to the drawings. In the drawings:

(2) FIG. 1 shows a front view of an air-jet spinning machine with workstations that each having a workstation-specific thread take-up device and a thread preparation device for supplying its air-jet spinning device, and

(3) FIG. 2 shows a sectional view in a schematic representation of an air-jet spinning device during the piecing process.

(4) FIG. 1 schematically shows, in a front view, a textile machine that is usually referred to as a cross-wound bobbin 9, producing an air-jet spinning machine 1 in the present case. Such textile machines 1 have a plurality of spinning stations 2 between machine frames 13A, 13B arranged at the end of the machine. A spinning can 3 is positioned at each of the spinning stations 2 and is equipped with a supply of feed material, for example with a sliver 25.

(5) The spinning stations 2 furthermore each have a drafting system 4, an air-jet spinning device 5, a draw-off device 6, a thread cleaner 7 and a thread-checking device 8 which ensures that the thread 36 spun or produced from the sliver 25 in the air-jet spinning device 5 is wound in crossing layers onto a take-up bobbin 9. The so-called cross-wound bobbin 9 produced during the spinning process is in each case held in a bobbin frame (not shown), as is customary, and is rotated by a bobbin drive (also not shown).

(6) Each of the spinning stations 2 is also equipped with a thread take-up device 39 which makes it possible to take up a thread end 37 of a manufactured thread 36 that has run onto the cross-wound bobbin 9 after an interruption of spinning and to transfer it to a so-called thread preparation device 40 arranged in the region of the draw-off device 6.

(7) FIG. 2 shows, in a side view and a larger scale, an air-jet spinning device 5 suitable for carrying out the method according to a preferred embodiment during the piecing process.

(8) As can be seen, the drafting system 4 for drafting the sliver 25 is upstream form the air-jet spinning device 5 shown in section. Downstream from the air-jet spinning device 5 in the sliver running direction R is a take-off device 6 which can be driven reversibly by an individual motor and ensures that the finished thread 36 can be conveyed in the direction of the take-up bobbin 9 and in the opposite direction thereto.

(9) In addition, the thread preparation device 40, which is not shown in more detail here, is arranged in the region of the thread take-off device 6 which prepares the thread end 37 of the finished thread 36, which has been retrieved by the yarn take-up device 39, for the subsequent piecing process.

(10) As shown in FIG. 2, the air-jet spinning device 5 basically consists of a two-part outer housing 14, 15, an expansion housing 16, a nozzle block 17, a sliver guide 18 and a hollow spinning cone 19.

(11) In this case, the expansion housing 16, in conjunction with the front housing part 14 of the outer housing, forms a front annular space 20 which is connected to an overpressure source 22 via a pneumatic line 21 and is connected to the expansion space 28 arranged in the rear housing part 15 of the outer housing.

(12) While the expansion space 28 is indirectly connected to the ambient atmosphere via an exhaust air channel 29, the annular space 20 is pneumatically continuously connected to at least one blowing air nozzle 23 which are arranged in the nozzle block 17.

(13) The blowing air nozzle 23 opens into a vortex chamber 33 in the region upstream from the inlet opening 35 of the spinning cone 19 and is thus directed onto the head 24 of the spinning cone 19 in such a way that a rotating air flow is created on the latter. The spinning cone 19 is preferably made of a highly wear-resistant material, for example a technical ceramic material.

(14) To control the supply of compressed air, the pneumatic line 21 is equipped with a valve 32, the actuation of which preferably takes place by a spinning station's control unit 38 which is connected to the valve via corresponding control lines.

(15) During the normal, previously known spinning process, which is not shown here, the sliver 25, which is stored in a spinning can 3, first passes through the drafting system 4 on its way to the cross-wound bobbin 9, where it is strongly drafted. Via the exit roller pair 26 of the drafting system 4, the stretched sliver 25 is then transferred into the region of the inlet opening 27 of the air-jet spinning device 5 and is sucked into the vortex chamber 33 of the air-jet spinning device 5 under the influence of a negative pressure flow present there. Inside the air-jet spinning device 5, the stretched sliver 25 passes via the sliver guide 18 and the nozzle block 17 to the inlet opening 35 of the hollow spinning cone 19 and is drawn into the spinning cone 19 by the thread 36 forming within the spinning cone 19. In so doing, the sliver 25 is exposed to the influence of a rotational flow in the region of the head 24 of the spinning cone 19 which is generated by the air flow exiting the nozzle block 17.

(16) The valve 32 is open for the defined supply of this air flow to the nozzle block 17 initiated by the overpressure source 22. In order to enable the outflow of the air flow flowing in via the nozzle block 17 through the exhaust air duct 29 to the ambient atmosphere or to the machine's own suction during the spinning process, a valve 34 connected to the control unit 38 via a corresponding control line is open.

(17) During the spinning process, due to the continuous movement of the sliver 25 in the sliver running direction R, the sliver 25 is continuously drawn into the hollow spinning cone 19, wherein the edge fibers are wound helically around the core fibers of the sliver 25. The thread 36 produced thereby is pulled out of the air-jet spinning device 5 by means of the thread withdrawal device 6 and subsequently wound into a cross-wound bobbin 9.

(18) If an interruption of spinning occurs during the spinning process, for example due to a breaking of the sliver 25 or due to a controlled cut of the already spun thread 36 by the thread cleaner 7, a piecing process must first be carried out before a restart of the spinning process.

(19) As is known, to carry out a piecing process, on the one hand the stretched sliver 25 and on the other hand the already finished thread 36 which has run onto the cross-wound bobbin 9 are required.

(20) After an interruption of spinning, the spinning station's thread take-up device 39 of the relevant spinning station 2 first retrieves the thread end 37 of the already completed thread 36 from the cross-wound bobbin 9 and transfers it to a thread preparation device 40 arranged downstream from the air-jet spinning device 5 in the sliver running direction R.

(21) There, the yarn end 37 is freed from twist and loose fibers as far as possible and then transferred to the vortex chamber 33 for piecing and positioned there.

(22) To prepare the sliver 25, during the return of the thread end 37 into the vortex chamber 33, the drafting system 4 is operated by the control unit in a combing mode in which the first drafting system roller pair 42, the second drafting system roller pair 43, and the apron roller pair 41 are at a standstill, whereas the exit roller pair 26 is operated at a combing-out speed, and the free end of the sliver 25 is thereby prepared in an optimal manner for the piecing process.

LIST OF REFERENCE SIGNS

(23) 1 Air-jet spinning machine 2 Spinning position 3 Spinning can 4 Drawing system 5 Air-jet spinning device 6 Take-off device 7 Thread cleaner 8 Thread traversing device 9 Take-up bobbin 13A, 13B Machine frame 14 Outer housing 15 Outer housing 16 Expansion housing 17 Nozzle block 18 Sliver guide 19 Spinning cone 25 Sliver 26 Exit roller pair 28 Expansion space 29 Exhaust duct 32 Valve 33 Vortex chamber 34 Valve 35 Inlet opening 36 Thread 37 Thread end 38 Control unit 39 Thread take-up device 40 Thread preparation device 41 Apron roller pair