DEVICE AND METHOD FOR PRODUCING KNITTED FABRIC

Abstract

Knitted fabric is produced with a knitting machine and a roving drawing and strengthening unit. A roving supply unit provides a roving and an auxiliary thread supply unit provides an auxiliary thread. A stretching unit receives the roving and the auxiliary thread. A spinning nozzle following the stretching unit in a roving conveying direction forms a fiber strengthening segment by applying compressed air and an end thread gripping roller pair rotatable in opposite directions provided downstream from the spinning nozzle device in the roving conveying direction delimiting the fiber strengthening segment. A soft knitted fabric is formed by guiding an auxiliary thread through an auxiliary thread gripping roller pair with an adjustable rotational speed before the roving and auxiliary thread enter the stretching unit. The gripping roller pair holds the auxiliary thread so that the auxiliary thread is subjected to tension of no more than 2 cN.

Claims

1-10. (canceled)

11. A device for producing knitted fabric with a knitting machine and a roving drawing and strengthening unit, the device comprising: a roving supply unit with at least one roving; an auxiliary thread supply unit with at least one auxiliary thread; a stretching unit coupled to said roving supply unit for supplying the roving and said auxiliary thread supply unit for supplying the auxiliary thread, said stretching unit including stretching roller pairs arranged one after another in a roving conveying direction; a spinning nozzle device following said stretching unit in the roving conveying direction and forming a fiber strengthening segment by applying compressed air; and an end thread gripping roller pair rotatable in opposite directions and disposed following said spinning nozzle device in the roving conveying direction delimiting said fiber strengthening segment; at least one auxiliary thread gripping roller pair disposed between said auxiliary thread supply unit and said stretching unit, said at least one auxiliary thread gripping roller pair having two auxiliary thread gripping rollers that are rotatable in opposite directions and adjustable with regard to a rotational speed, said auxiliary thread gripping rollers being pressed or capable of being pressed to one another and guiding the auxiliary thread towards said stretching unit, said auxiliary thread gripping roller pair forming a clamping lead-through for the at least one auxiliary thread, and wherein a rotational speed of said auxiliary thread gripping rollers of said auxiliary thread gripping roller pair is adjustable such that a thread tension of the auxiliary thread exiting said auxiliary thread gripping roller pair is smaller than 2 centinewtons.

12. The device according to claim 11, which comprises a device control configured to adjust the rotational speed of at least one of said auxiliary thread gripping rollers and to adjust a rotational speed of said stretching rollers of said stretching unit.

13. The device according to claim 11, wherein said auxiliary thread gripping rollers include a first, profiled auxiliary thread gripping roller and a second, rubberized auxiliary thread gripping roller.

14. The device according to claim 11, further comprising an auxiliary thread oscillation device before said at least one auxiliary thread gripping roller pair in the roving conveying direction of the device.

15. The device according to claim 11, further comprising at least one optical thread sensor following the auxiliary thread gripping roller pair in an auxiliary thread conveying direction.

16. The device according to claim 11, wherein said auxiliary thread supply unit comprises a closed housing formed with at least one opening for exiting the auxiliary thread.

17. A method for producing knitted fabric, the method comprising: supplying at least one roving from a roving supply unit; supplying at least one auxiliary thread from an auxiliary thread supply unit; clamping the auxiliary thread between rollers of at least one auxiliary thread gripping roller pair that rotate in opposite directions, the rollers of the auxiliary thread gripping roller pair having two auxiliary thread gripping rollers that are pressed or capable of being pressed to one another; adjusting the rotational speed of the auxiliary thread gripping rollers such that a thread tension of the auxiliary thread exiting the auxiliary thread gripping roller pair is less than 2 centinewton; guiding the roving and the auxiliary thread to a stretching unit, the stretching unit having stretching roller pairs arranged one after another in a roving conveying direction; subjecting a drawn roving with the auxiliary thread exiting the stretching unit to pressurized air by a spinning nozzle device in a fiber strengthening segment, to thereby strengthen the drawn roving, wherein the fiber strengthening segment is delimited by an end thread gripping roller pair rotating in opposite directions through which the drawn and strengthened roving with the auxiliary thread is led in clamped fashion and an end thread exiting the end thread gripping roller pair is supplied to a knitting machine.

18. The method according claim 17, which comprises supplying the auxiliary thread to the auxiliary thread gripping roller pair oscillating in axis direction of the auxiliary thread gripping rollers.

19. The method according to claim 17, which comprises optically recording a thread tension of the auxiliary thread between the auxiliary thread gripping roller pair and the stretching unit.

Description

[0051] Preferred embodiments of the present invention, including their structure, function and advantages are explained in more detail in the following using figures, wherein

[0052] FIG. 1 schematically shows an embodiment of the device according to the invention in a side view;

[0053] FIG. 2 schematically shows auxiliary thread gripping roller pair of an embodiment of a device according to the invention in a side view; and

[0054] FIG. 3 schematically shows the auxiliary thread gripping roller pair of FIG. 2 in a frontal view.

[0055] FIG. 1 schematically shows an embodiment of the device 1 according to the invention in a side view. Except for the auxiliary thread supply, the shown device corresponds to the device which is described in the document DE 10 2011 053 396 B3 and to whose content it is herewith fully referred.

[0056] The device 1 comprises a roving drawing and strengthening unit 3 for treating a roving 40a under formation of an end thread 40d. The roving drawing and strengthening unit 3 is coupled with a knitting machine 2 for forming a knitted fabric from the end thread 40d on the knitting machine 2. Despite the description end thread it should be noted that the end thread 40d is no conventional yarn, but a drawn, temporarily strengthened roving comprising at least one auxiliary thread 50, as described in detail in the following.

[0057] The roving drawing and strengthening unit 3 comprises a roving supply unit 4 with at least one roving 40a and an auxiliary thread supply unit 5 with at least one auxiliary thread 50.

[0058] The roving supply unit 4 supplies the non-strengthened roving 40a for the roving drawing and strengthening unit 3, which is provided on flyer spools 9 encompassed by the roving supply unit 4. As FIG. 1 shows, the roving 40a is preferably supplied via a transportation shaft 10 to the roving drawing and strengthening unit 3 in a roving conveying direction A. In alternative embodiments of the device 1 according to the invention, the roving 40a can also be supplied to the roving drawing and strengthening unit 3 by means of several or without a transportation shaft 10 situated between the roving drawing and strengthening unit 3 and the roving supply unit 4.

[0059] The roving drawing and strengthening unit 3 further comprises a stretching unit 6 and a spinning nozzle device 70 provided downstream from the stretching unit 6 in roving conveying direction A. The stretching unit 6 illustrated in FIG. 1 comprises stretching roller pairs 601, 602, 603 arranged successively in roving conveying direction A of the roving 40a, especially an inlet roller pair 601, an intermediate roller pair 602 and an outlet roller pair 603. In other embodiments of the device 1 according to the invention, the stretching unit 6 can also comprise more than one intermediate roller pair 602 or no intermediate roller pair 602 at all.

[0060] For drawing and thus for homogenizing the roving 40a, the roving 40a is led through between stretching rollers 60a and 60b of the individual stretching roller pairs 601, 602, 603. By driving the stretching roller pairs 601, 602, 603 with varying speeds that are increasing in the roving conveying direction A, a drawing of the roving 40a to a drawn roving 40b is achieved. The stretching roller pairs 601, 602, 603 are therein driven with such speeds that the outlet roller pair 603 comprises a higher speed than the intermediate roller pair 602 and the intermediate roller pair 602 in turn comprises a higher speed than the inlet roller pair 601. Thus a pre-drawing happens between the inlet roller pair 601 and the intermediate roller pair 602, whereas a subsequent main drawing of the roving 40a is realized between the intermediate roller pair 602 and the outlet roller pair 603.

[0061] For generating the drawing of the roving 40a, the roving 40a has to be transported in clamped fashion between the stretching rollers of the stretching roller pairs 601, 602, 603. This happens preferably by pressing a non-driven stretching roller respectively upper roller 60b to a driven stretching roller respectively lower roller 60a respectively. For pressing the upper rollers 60b to the lower rollers 60a, the upper rollers 60b are connected to an L-shaped stretching unit pressure arm 61. Accordingly, the non-driven stretching rollers 60b can be easily collectively pressed against the driven stretching rollers 60a or removed from them by swinging the stretching unit pressure arm 61. The stretching unit pressure arm 61 can be moved mechanically, pneumatically or hydraulically.

[0062] In order to increase the strength of the drawn roving 40b and to increase the reliability of the process carried out on the device 1, at least one auxiliary thread 50 is supplied according to the invention to the roving 40a. The auxiliary thread 50 is provided by means of an auxiliary thread supply unit 5 typically comprising several supply spools 52.

[0063] In the shown embodiment, the auxiliary thread supply unit 5 comprises a housing 8, which surrounds the supply spools 52 stocking the at least one auxiliary thread 50. The housing 8 of the auxiliary thread supply 5 comprises at least one opening 81, through which the auxiliary thread 50 can be supplied to at least one auxiliary thread gripping roller pair 51 provided downstream from the auxiliary thread supply unit 5 in an auxiliary thread conveying direction B of the auxiliary thread 50. In alternative embodiments of the device 1 according to the invention, the housing 8 can also comprise several openings 81, through which several auxiliary threads 50 can be led out of the housing without tangeling.

[0064] The auxiliary thread 50 removed from the spool 52 and led through the opening 81 of the housing 8 of the auxiliary thread supply unit 5, is supplied carefully and with a desired thread tension to the drawn respectively partly drawn roving 40b by means of the auxiliary thread gripping roller pair 51.

[0065] In the embodiment depicted in FIG. 1, the supply of the auxiliary thread 50 to the drawn roving 40b happens during the drawing of the roving 40a in the stretching unit 6. In the process, the auxiliary thread 50 is supplied particularly preferred between the intermediate roller pair 602 and the outlet roller pair 603 to the stretching unit 6 and thus the roving 40b. Preferably, the auxiliary thread 50 is hereby removed by the outlet roller pair 603 and is, along with the drawn respectively partly drawn roving 40b, conveyed towards a spinning nozzle device 70 provided downstream from the stretching unit in a roving conveying direction A. The rotation speed of the auxiliary thread gripping roller pair 51 can thus be adjusted ideally to the rotation speed of the outlet roller pair 603.

[0066] In other, not shown embodiments of the device 1 according to the invention, the auxiliary thread 50 can be supplied to the not yet drawn roving 4a before traversing the stretching unit 6 or to the drawn roving 40b only after leaving the stretching unit 6.

[0067] By adjusting the tension of the auxiliary thread 50 by means of the auxiliary thread gripping roller pair 51, with which it is supplied to the stretching unit 6, it is possible to significantly influence the softness of the produced end thread 40d and the thereof produced knitted fabric, since the thread tension of the auxiliary thread 50 is inter alia responsible for how many fibers of the drawn roving 40b entwine the auxiliary thread 50 and stick to it in and after the spinning nozzle device 70. In the embodiment of FIG. 1, the auxiliary thread 50 is supplied to the stretching unit 6 with a thread tension smaller than 2 cN, since especially many fibers of the drawn roving 40b wind themselves around the auxiliary thread 50 with such a small thread tension and a particularly high softness of the end thread 40d and thus also of the knitted fabric is generated.

[0068] Furthermore, a tearing of the auxiliary thread 50 and thus an unwanted process interruption can be prevented due to the transport of the auxiliary thread 50 with small tension by means of the auxiliary thread gripping roller pair 51.

[0069] In the embodiment illustrated in FIG. 1, the device according to the invention only comprises one auxiliary thread roller pair 51, however, in further embodiments it can also comprise several auxiliary thread roller pairs 51 arranged successively in auxiliary thread conveying direction B. The use of several auxiliary thread gripping roller pairs 51 in a device 1 has proven to be preferable especially with long transport distances of the auxiliary thread 50 from the auxiliary thread supply unit 5 to the stretching unit 6.

[0070] The drawn roving 40a exiting the stretching unit 6 is, alongside the at least one supplied auxiliary thread 50, supplied to a spinning nozzle device 70 provided downstream from the stretching unit 6 in a roving conveying direction A. In the spinning nozzle device 70, a rotation of the drawn roving 40b comprising the auxiliary thread 50 takes place by means of air jets exiting the spinning nozzle device 70 so that a formation of a so-called false strand ensues.

[0071] In the embodiment of FIG. 1, the spinning nozzle device 70 comprises two air twirling nozzles 70a, 70b arranged successively in roving conveying direction A. The air flow generated in the two air twirling nozzles 70a, 70b comprise opposing rotation directions. The first air twirling nozzle 70a provided downstream from the stretching unit 6, a so-called injector nozzle, causes an untwisting of fiber material of the drawn roving 40b, whereby the peripheral fibers on the drawn roving 40b spread apart. The spread apart peripheral fibers are wound around a fiber core of the roving 40a and/or the auxiliary thread 50 by means of a rotation generation of the second air twirling nozzle 70b provided downstream from the first air twirling nozzle 70a, a so-called swirl nozzle, whereby the false strand is formed. The rotation speeds of the air twirling nozzles 70a, 70b as well as an air flow generated by the respective air twirling nozzle 70a, 70b can be chosen depending on the knitting speed adjustable on the knitting machine 2 and a respective roving conveying speed. Furthermore, the distance of the spinning nozzle device 70 from the stretching unit 6 as well as the distance of the air twirling nozzles 70a, 70b to each other can be chosen application-specific.

[0072] The roving 40b drawn by the stretching unit 6, comprising the at least one auxiliary thread 50 and strengthened in the spinning nozzle device 70 is removed by an end thread gripping roller pair 71 provided downstream from the spinning nozzle device 70 in transport direction A of the roving 40a. The end thread gripping roller pair 71 typically has a driven gripping roller 71a and a non-driven gripping roller 71b pressed against the driven gripping roller 71a. The end thread gripping roller pair 71 can also comprise two driven gripping rollers 71a pressed against each other in alternative embodiments of the device 1 according to the invention. The end thread gripping roller pair 71 enables a speed decoupling of the technical system of the roving drawing and strengthening unit 3 from the technical system of the thread supply to the knitting machine 2. Furthermore, the clamping point realized by the end thread gripping roller pair 71 enables a diversion of the drawn, strengthened roving 40c exiting the end thread gripping roller pair 71 comprising the auxiliary thread 50 to the operational level of the knitting machine 2.

[0073] FIG. 2 schematically shows an auxiliary thread gripping roller pair 51 in an embodiment of the device 1 according to the invention in a side view. The elements in FIG. 2 indicated with the same reference signs as in FIG. 1 correspond to those of FIG. 1, which is why here it is being referred to the above description of these elements.

[0074] In the embodiment shown in FIG. 2, the auxiliary thread 50 stored in the auxiliary thread supply unit 5 is supplied to the auxiliary thread gripping roller pair 51 by means of an auxiliary thread conveying tube 53, whereby a destruction of the auxiliary thread 50 during the transport can be largely excluded. Form, position and dimensions of the auxiliary thread conveying tube 53 can hereby be chosen application-specific.

[0075] The auxiliary thread 50 exiting the auxiliary thread conveying the tube 53 is, before it is supplied to the auxiliary thread gripping roller pair 51 provided downstream in auxiliary conveying direction B, led through an auxiliary thread guiding device 56 arranged between the auxiliary thread conveying tubes 53 and the auxiliary thread gripping roller pair 51. The auxiliary thread guiding device 56 is part of an auxiliary thread oscillation device 57 through which the auxiliary thread 50 is moved sideways back and forth vertically to the auxiliary thread transport direction B, causing that the auxiliary thread 50 does not constantly come into contact with the same contact surfaces of the auxiliary thread gripping rollers 51a, 51b of the auxiliary thread gripping roller pair 51. A shrinkage of the used auxiliary gripping rollers 51a, 51b can thus be prevented.

[0076] The auxiliary thread gripping roller pair 51 preferably comprises, as shown in FIG. 2, two opposing auxiliary thread gripping rollers 51a, 51b working in opposite directions, pressable against each other. In the shown embodiment, the first of the two auxiliary thread gripping rollers 51a is fixed in the device 1, whereas the second auxiliary thread gripping roller 51b is provided in such a way in the device 1 according to the invention that it can be pressed against and detached from the fixedly placed first auxiliary thread gripping roller 51a. According to the embodiment of FIG. 2, for example a spring activated pressing device 54 can be used for this purpose, with which the second auxiliary thread gripping roller 51b can be pressed against the first auxiliary thread gripping roller 51a. In alternative embodiments of the device 1 according to the invention, the pressure device 54 can, however, also be formed differently and can, apart from a mechanical operation, also be positioned hydraulically and pneumatically.

[0077] Size, dimensions, form and texture of the auxiliary thread gripping rollers 51a, 51b can be chosen application-specific. In the shown embodiment, the first auxiliary thread gripping roller is profiled and the second auxiliary thread gripping roller 51b is rubberized. Such a form of the auxiliary thread gripping rollers 51a, 51b prevents a slipping out of the auxiliary thread 50 from the space between the auxiliary thread gripping rollers 51a, 51b and furthermore enables a gentle transport of the auxiliary thread 50. The second auxiliary thread gripping roller 51b can either be formed completely of rubber or only comprise a rubber coating. The profile and material of the profiled auxiliary thread gripping roller 51a can be chosen freely depending on the operation conditions of this auxiliary thread gripping roller 51a. Thus it is for example possible that the profiled auxiliary thread gripping roller 51a comprises a serrated pattern or grooves provided contrary to the auxiliary thread transport direction B.

[0078] In the embodiment shown in FIG. 2, the first auxiliary thread gripping roller 51a is driven, wherein its rotation transmits to the non-driven second auxiliary thread gripping roller 51b. Accordingly, the auxiliary thread gripping rollers 51a, 51b execute opposing rotation movements C, C. In further embodiments of the device 1 according to the invention, however, both auxiliary thread gripping rollers 51a, 51b can be driven, wherein they can either be driven independently of each other or linked to each other or can be linked to each other. What is important here is only that the two auxiliary thread gripping rollers 51a, 51b are driven with opposing rotation directions.

[0079] In the embodiment of FIG. 2, a diversion device 55 is provided downstream the auxiliary thread gripping roller pair 51, which guides the auxiliary thread 50 towards the stretching unit 6. The diversion device 55 prevents a too abrupt diversion and thus a damage of the auxiliary thread 50, whereby the process safety of the device 1 according to the invention can be increased. The diversion device 55 is furthermore formed as an optical fiber sensor in the shown embodiment, which serves for guaranteeing the presence of the auxiliary thread 50 after the auxiliary thread gripping roller pair 51. The detection of the auxiliary thread happens optically and not mechanically at this point in order not to increase the tension level of the thread tension of the auxiliary thread 50 again after the traversing of the auxiliary thread 50 through the auxiliary thread gripping roller pair 51.

[0080] In the shown embodiment, the auxiliary thread 50 exiting the auxiliary thread gripping roller pair 51 and diverted by the diversion device 55 is thereupon transported to the stretching unit 6 or the spinning nozzle device 70 through another auxiliary thread conveying tube 53, whereby a particularly gentle and process-stable transport of the auxiliary thread 50 is enabled.

[0081] FIG. 3 schematically shows the auxiliary thread gripping roller pair 51 depicted in FIG. 2 in a frontal view, wherein here the same reference signs as in the previous figures also indicate the same elements, which is why it is being referred to their previous embodiments at this point.

[0082] FIG. 3 shows the auxiliary thread 50 led through the auxiliary thread conveying tube 53, the auxiliary thread gripping rollers 51a, 51b and the diversion device 55 into the auxiliary thread conveying tube 53.

[0083] Furthermore, it is also apparent from FIG. 3, how the auxiliary thread 50 passes through the auxiliary thread oscillation device 57 comprising the auxiliary thread guiding device 56. By moving the auxiliary thread oscillation device 57 in an oscillation direction D, transverse to the auxiliary thread transport direction B, the contact surface of the auxiliary thread 50 with the surfaces of the auxiliary thread gripping rollers 51a, 51b can be varied, whereby a shrinkage of the auxiliary thread gripping rollers 51a, 51b and their increased wear can be prevented. Especially the guidance of the auxiliary thread 50 by means of the auxiliary thread guiding device 56 of the auxiliary thread oscillation device 57 has proven to be especially preferable with regard to the movement of the auxiliary thread 50 along the surface of the auxiliary thread gripping rollers 51a, 51b, since the auxiliary thread 50 can thus be moved controllably, without shifting, by means of the auxiliary thread oscillation device 57.

[0084] The rotational speed of the auxiliary thread gripping rollers 51a, 51b and/or the movement of the auxiliary thread 50 by means of the auxiliary thread oscillation device 57 can be adjusted by means of a device control 90. By means of this device control 90, the rotational speed of the end thread gripping roller pair 71 and/or the pressure of the compressed air exiting the spinning nozzles 70a, 70b and/or the rotational speed of the rollers of the stretching unit 6 and/or the knitting speed of the knitting machine 2 can be adjusted.

[0085] In the simplest embodiment, the auxiliary thread guiding device 56 is formed as a drill in the auxiliary thread oscillation device 57, which is for example formed as a shaft, however, in other embodiments of the device 1 according to the invention, it can also be formed differently.