Description

[0001] The invention relates to a device for removing weft thread. The invention also relates to a weaving machine having such a device. [0002] It is known that, when a weft thread is inserted into the shed from an insertion side to an opposite side, various irregularities can occur, such as a broken weft thread or a weft thread which does not reach the opposite side of the shed.

[0003] From NL 8602191 A, NL 8602826 A, EP 310804 A2 and EP 534541 A1 , it is known to remove weft thread from a shed. According to one embodiment, the shed is firstly opened so that the weft thread to be removed is free. Next a following weft thread, which is connected to the weft thread to be removed, is inserted into the shed and both weft threads are together removed on the opposite side of the shed. To this end, both pneumatic elements and mechanical elements can be used for the removal of the two weft threads. It is known that the force which pneumatic elements can apply to weft threads is sometimes too small to remove weft threads effectively. Such pneumatic elements are hence especially suitable for removing weft threads which lie sufficiently loose, are nowhere caught in the shed or are nowhere jammed. It is also known that the speed at which mechanical elements can remove weft threads is relatively low, and that the force at which mechanical elements can remove weft threads can be of such magnitude that the force is sufficient to tear the weft threads to be removed. [0004] The object of the invention is a device for removing weft thread, which device allows weft thread to be removed in a reliable and rapid manner.

[0005] This object is solved by a device having the characteristics of Claim 1 and a weaving machine having the characteristics of Claim 5. Preferred embodiments are defined in the dependent claims. [0006] According to the invention, the device comprises a first unit for generating a pneumatic tensile force on a weft thread and a second unit for generating a mechanical tensile force on a weft thread, wherein in the movement direction of the weft thread the first unit is arranged downstream of the second unit, so that weft thread which is guided through the device by the air current generated by the first unit can be clamped by the second unit, and wherein the device comprises a housing having a first bore, which in use extends in the movement direction of the weft thread, and a second bore, which is disposed transversely to the first bore, wherein the second unit is mounted in the area of the second bore. Within the context of the application, by a "pneumatic tensile force" is meant a tensile force generated by an air current on a weft thread, and by a "mechanical tensile force" is meant a tensile force generated by mechanical means, such as clamping elements, on a weft thread. [0007] According to one embodiment, the second unit comprises clamping elements, a first actuator for moving the clamping elements towards each other, and/or a second actuator for rotating the clamping elements.

[0008] According to one embodiment, the device comprises a housing having a first bore for the guidance of a weft thread, wherein the diameter of the first bore is smaller than the diameter of the clamping elements, so that weft thread which is guided through the device can be clamped between the clamping elements of the second unit.

[0009] The invention offers the advantage that the first unit for generating an air current through the device according to the invention is arranged, in the movement direction of the weft thread, downstream of the second unit, so that a suction effect is generated downstream of the me- chanical effect, more particularly in the area of the moveable towards each other and rotatable, drivable clamping elements of the second unit. It is hence not only possible to remove dust in a favourable manner, but it is also possible to remove the mechanically removed portion of weft thread pneumatically from the device according to the invention in a simple and rapid manner.

[0010] The invention also relates to a weaving machine which comprises a device according to the invention. In this case the weaving machine comprises a reed and the device is mounted, in the movement direction of the weft thread, past the reed. According to a preferred embodiment, the weaving machine comprises a weft detector which is mounted between the reed and the device according to the invention, wherein a first actuator, which moves a first clamping element to a second clamping element, moves the first clamping element in a direction towards the reed, so that weft thread is guided to a weft detector.

[0011 ] Embodiments of the invention are described in detail below, based on various schematic figures, in which:

Figure 1 represents a portion of a weaving machine having a device according to the invention;

Figure 2 represents a perspective view of the device according to the invention; Figure 3 represents the device of Figure 2 in the dismantled state;

Figure 4 represents a vertical cross section in the movement direction of the weft thread of the device according to the invention;

Figure 5 represents a vertical cross section transversely to the movement direction of the weft thread of the device according to the invention;

Figure 6 represents a horizontal cross section of the device according to the invention;

Figure 7 represents a variant of Figure 1 ;

Figure 8 represents a variant of Figure 7;

Figure 9 represents a variant of Figure 8. [0012] Throughout the figures, the same or similar elements are indicated by the same reference numerals.

[0013] In Figure 1 , a portion of a weaving machine is schematically shown in the area of the opposite side of the shed (not shown). A device 1 according to the invention, which is fastened via a fastening system 2 to a crossbeam 3 of the weaving machine, is herein shown. A portion of a sley 4, on which a reed 5 and a weft detector 6 are mounted, is further shown.

[0014] When the weft detector 6 detects an incorrectly inserted weft thread, the weaving process is interrupted. According to one embodiment, a following inserted weft thread 10, which is connected to the incorrectly inserted weft thread 1 1 , is next brought in a known manner through the shed to the device 1 according to the invention, for example according to a method as known from NL 86 02191 A. It is here also known, after the detection of an incorrectly inserted weft thread, to release a limited quantity of weft thread in the area of a thread supply and not to cut off the incorrectly inserted weft thread 1 1 from the thread supply. Both weft threads 10, 1 1 are here brought to the device 1 by the blowing effect on the weft threads which is obtained by the successive activation of main blowers (not shown) and auxiliary blowers (not shown). The device 1 is here designed to remove these weft threads 10, 1 1 in an efficient manner from the shed and from the device 1 .

[0015] In order to allow the following inserted weft thread 10 to be brought, together with the incorrectly inserted weft thread 1 1 , via the inlet 7 of the device 1 into the device 1 , the sley 4 is brought into a position wherein the guide channel 8 of the reed 5 is arranged almost in the extension of the inlet 7, as shown in Figure 1 . When both weft threads 10, 1 1 , for example in a loop shape, reach the device 1 according to the invention, these weft threads 10, 1 1 are detected by the weft detector 6. These weft threads 10, 1 1 are hereupon taken up into the device 1 by the suction effect of the device 1 . Next, the following inserted weft thread 10 is cut off from the thread supply, while the device 1 continues to exert a suction effect. In order to enable the following inserted weft thread 10 to be cut off by weft scissors (not shown) arranged near the fell line, the sley 4 is moved with the reed 5 up to the fell line, whereby the weft threads which extend to the device 1 are brought with certainty into the weft detector 6, so that they are with cer- tainty detected. Should both weft threads 10, 1 1 be removed from the shed by the device 1 , the weft detector 6 in this case no longer detects any weft thread, so that the weft detector 6 sends a signal to the control unit 16 of the weaving machine to indicate that the two weft threads have been successfully removed. Should the weft detector 6 during a set time further detect weft thread, a switch is made to a pneumatic and mechanical removal of weft thread, as will be fur- ther described in detail.

[0016] The device 1 according to the invention is shown in detail in Figures 1 to 6. The device 1 according to the invention comprises a first unit 9 for generating an air current, a first actuator 12 for generating a to-and-fro motion, and a second actuator 13 for generating a rotary motion. The first unit 9 is provided via a compressed-air line 14 with compressed air coming from a compressed-air source (not shown), for example a compressed-air source at 1 .5 bar. In order to continuously remove dust, it is preferred to continuously generate an air current through the device 1 by means of the first unit 9. The continuous air current is also advantageous for keeping weft threads taken up in the device 1 stretched in the area of the weft detector 6, for example when the reed 5 moves up to the fell line. The first actuator 12 is provided with compressed air, for example via a valve system 15, for example a double-acting valve system, which, optionally, can move the first actuator 12 in one or the other direction. The valve system 15 is provided via a compressed-air line 17 with compressed air coming from a compressed-air source (not shown), for example a compressed-air source at 6 bar. The second actuator 13 is, for example, a controllable motor. The second actuator 13 and the valve system 15 are controlled by means of the control unit 16 via electrical signals.

[0017] The device 1 according to the invention comprises a housing 20 having a first bore 21 , which in use extends in the movement direction A of the weft thread, and a second bore 22, which is arranged transversely to the first bore 21 . The housing 20 is here designed as a closed block which is provided with bores 21 and 22. The movement direction A of the weft thread is here also the direction from the inlet 7 of the housing 20 to the outlet 49 of the guide pipe 28. The movement direction A of the weft thread is here also the direction from the insertion side to the opposite side of the shed. At one end of the first bore 21 , which also forms the inlet 7, is mounted a guide eye 23. The first unit 9 for generating an air current comprises a blowing device 24, which is mounted at the end 50 of the first bore 21 opposite the inlet 7. The blowing device 24 is designed, for example, as a "venturi". The blowing device 24 is connected via an opening 25 in the housing 20 to the compressed-air line 14, as shown in Figure 1 . By supplying compressed air via the opening 25, an air current is generated through the housing 20 in the movement direction A of the weft thread. The blowing device 24 here generates an air current based on the "Coanda" effect, which is commonly known from the flow theory of compressed air. This air current also gives rise to a suction effect in the area of the inlet 7.

[0018] According to one embodiment, the blowing device 24 comprises a guide pipe 28, which is provided with an external screw thread 27 which is screwed into an internal screw thread 29 of the housing 20, which is mounted in a bore 30 in the housing 20. The bore 30 is arranged in the extension of the first bore 21. In addition, the guide pipe 28 screwed in the housing 20 is fastened via a nut 31 with respect to the housing 20. The blowing device 24 also comprises a profiling 32, which is mounted close to the first bore 21 and in the area of the inlet 26 of the guide pipe 28 for the generation of an air current based on the "Coanda" effect, which profiling 32, to this end, also cooperates with the bore 30 in the housing 20. This allows an air current to be guided in the movement direction A of the weft thread along a weft thread extending through the housing 20, and thus a pneumatic tensile force to be exerted on this weft thread. As can be seen, the internal shape of the guide pipe 28 is divergent in design in order to improve the tensile force exerted on weft threads by the air current. The force exerted on the weft threads by a first unit 9, and also the suction effect, more particularly the suction force exerted on the weft threads from the inlet 7 by the first unit 9, can be set by adapting the pressure of the compressed-air source connected to the compressed-air line 14 and/or by adapting the distance from the profiling 32 to the bore 30.

[0019] The device 1 according to the invention further comprises a second unit 19 for exerting a mechanical tensile force on a weft thread. The second unit 19 is mounted in the area of a second bore 22, which is arranged transversely to the first bore 21 . The second unit 19 comprises, inter alia, a first clamping element 33, a second clamping element 37, a first actuator 12 and a second actuator 13. In the area of the second bore 22 is rotatably mounted a first clamping element 33, which can move to and fro along the second bore 22 in a movement direction B. To this end, the first clamping element 33 is mounted in the shown embodiment on the first actuator 12, which comprises a compressed-air cylinder 38. In the area of this second bore 22 is rotatably mounted a second clamping element 37, which is driven via the second actuator 13. The second actuator 13 comprises a motor 34. This second clamping element 37 is fixedly fastened on the shaft 35 of the motor 34. Between the motor 34 and the second clamping element 37 is mounted a supporting ring 36. The motor 34 is commanded by the control unit 16 of the weaving machine.

[0020] The first clamping element 33 is fastened via a bearing 39 and a fastening element 40, for example a screw, onto the plunger 41 of the compressed-air cylinder 38. The compressed- air cylinder 38 is, for example, double-acting and is moved to and fro by the control unit 16 of the weaving machine, via the valve system 15 shown in Figure 1 , by feeding of compressed air via either the opening 42 or the opening 43. According to a variant embodiment, the compressed-air cylinder 38 can be single-acting, wherein the plunger 41 is commanded in one direction with compressed air and is returned in the other direction by a spring. When the first clamping element 33 is pressed with the aid of the compressed-air cylinder 38 against the second clamping element 37, this second clamping element 37 can be driven together with the first clamping element 33 by the motor 34.

[0021 ] The first actuator 12, viewed in a direction towards the guide channel 8 of the reed 5, is the foremost actuator, meaning that the first actuator 12 for the housing 20 is arranged as shown in Figure 1 . As a result of this arrangement, the first clamping element 33 moves in a direction towards the reed 5 and to the second clamping element 37. This offers the advantage that weft threads which extend through the device 1 according to the invention are pressed into the weft detector 6, while the clamping elements 33 and 37 move towards each other, more particularly while the first clamping element 33 of the first actuator 12 moves rearward. [0022] According to the invention, the first clamping element 33 and the second clamping element 37 are dimensioned such that a weft thread 10 or 1 1 guided through the first bore 21 of the housing 20 can at any moment be clamped with certainty between the clamping elements 33, 37. To this end, according to one embodiment, the diameter of the first bore 21 , and thus also of the guide eye 23, is smaller than the diameter of the clamping elements 33 and 37 in the area of the place where the weft threads are clamped between the clamping elements 33, 37. It is herein ensured that a weft thread 10 or 1 1 can be clamped between the clamping elements 33 and 37 when the clamping elements 33 and 37 move towards each other in the movement direction B. The first clamping element 33 hereupon moves in the movement direction B, while the second clamping element 37 is only rotated and does not move in the movement direction B.

[0023] According to the invention, the clamping elements 33 and 37 are arranged, in the movement direction A of the weft thread, upstream of the first unit 9 for generating an air current. This means that the clamping elements 33, 37 are arranged between the inlet 7 of the housing 20 and the inlet 26 of the guide pipe 28. This offers the advantage that dust present in the housing 20, more particularly dust present in the area of the first bore 21 and the second bore 22, is removed with certainty from the housing 20. Such dust is also named weaving dust and is formed, inter alia, through friction of weft threads with compressed air or with other elements. By the arrangement of the first unit 9, in the movement direction A of the weft thread, downstream of the clamping elements 33 and 37, weft thread, which, by the air current, moves through the device 1 , is also forced almost centrally with respect to the first bore 21 , since the first unit 9 exerts a tensile force on the weft thread. It is also hereby ensured that a weft thread 10 or 1 1 can be clamped with certainty between the clamping elements 33 and 37 when the clamping elements 33 and 37 move towards each other. [0024] According to an exemplary embodiment, the device 1 according to the invention can be applied as follows. When an incorrectly inserted weft thread 1 1 is detected, for example by the weft detector 6, the weaving process is interrupted. Next, the guide channel 8 of the reed 5 is brought by the sley 4 into the extension of the inlet 7, and an incorrectly inserted weft thread 1 1 is brought, together with a following inserted weft thread 10, via the inlet 7 into the device 1 ac- cording to the invention. By the arrangement of the weft detector 6, the weft detector 6 detects weft thread. Next, the incorrectly inserted weft thread 1 1 is cut off from the thread supply. Should the weft detector 6, during a set time, no longer detect any weft thread, this is interpreted by the control unit 16 as all weft thread has been removed. Should the weft detector 6, during a set time, still detect weft thread, this is interpreted by the control unit 16 as weft thread which is stuck or jammed somewhere and cannot be removed by the air current in the device 1 . In this case, the first actuator 12 is commanded so that the clamping elements 33, 37 move towards each other. Next, the second actuator 13 is commanded so that the second clamping element 37 rotates and that also the first clamping element 33 rotates together with the second clamping element 37. Weft thread, which has been clamped between both clamping elements 33, 37, is hereupon drawn via the inlet 7 into the device 1 . After a short time, for example a few milliseconds, the second actuator 13 is no longer commanded, so that the weft threads are not torn or do not break. According to one variant, the clamping elements 33, 37 can be rotated, for example, over a limited angle, for example a limited angle such as a half turn, one full turn or a couple of turns. By the rotation over a limited angle, and thus the movement over a limited dis- tance, it is avoided that weft thread is torn or breaks. When drawn over a limited distance, weft threads can deform with sufficient elasticity and the risk of weft threads being torn or breaking is limited. Next, the first actuator 12 is commanded to move the clamping elements 33 and 37 apart. The portion of weft thread which is hereupon released is removed from the device 1 by the air current. This is successively repeated until the weft detector 6 no longer detects any weft thread. [0025] This mechanical pulling on the weft thread makes it possible to exert a relatively high tensile force, while due to the short-term mechanical pulling on the weft thread or the rotation of the clamping elements 33 and 37 over a limited angle it is avoided that the weft thread is torn or breaks. When the weft thread is no longer stuck or caught, the weft thread can also be removed by the air current while it is not clamped between the clamping elements 33 and 37, so that this weft thread can then be removed relatively quickly. The device 1 according to the invention thus makes it possible both to pull with high force on the weft thread by means of the clamping elements 33, 37 and to rapidly remove weft thread by means of the air current.

[0026] As the second actuator, a DC motor, a step motor, or any type of controllable motor can be applied. According to a variant embodiment, as the second actuator 13 a motor having an settable drive torque can be applied, for example a torque-controlled DC motor, which allows the drive torque of the motor to be adapted to the characteristics of the weft threads, so that it is possible to drive the motor for a longer time and over a larger angle without risk of weft threads being torn or breaking. [0027] Although in the shown embodiment the first actuator 12 is designed as a pneumatic cylinder, according to one variant it is also possible to apply as first actuator another type of actuator, for example a linear actuator and/or an electric actuator.

[0028] According to a preferred embodiment, an air current continuously flows via the compressed-air line 14 through the first unit 9, and thus also through the device 1 . This offers the advantage that dust is removed continuously from the device 1 and no dust accumulation can take place. This also offers the advantage that weft thread which is present in the device 1 is removed continuously from the device 1 . According to one embodiment, an air current only flows continuously through the device 1 if weft threads need to be removed. Should no weft threads need to be removed, it is possible at specific moments to let an air current flow through the device 1 in order to clean the device 1 of dust. According to another possibility, an air current can flow continuously through the device 1 at low flow rate, and an air current can flow through the device 1 at higher flow rate if weft threads need to be removed. To this end, suitable valve devices can be provided in the area of the compressed-air line 14, for example valve devices which are controlled by pulsation. [0029] In Figure 7 is shown a variant wherein the device 1 according to the invention is fastened to the weaving machine in a different way. In this case the device 1 is fastened via a fastening system 2 to a crossbeam 3 of the weaving machine. [0030] In Figures 8 and 9, a variant of, respectively, Figures 1 and 7 is shown, wherein the device 1 according to the invention cooperates with a stretching device 47 as known from WO 2013/1 17564 A2. In this case the stretching device 47 facilitates the guidance of both weft threads 10 and 1 1 to the device 1 according to the invention. Between the weft detector 6 and the stretching device 47, a hook 51 is mounted on the sley 4. Besides, the second weft detector 18, in cooperation with the weft detector 6 arranged next to the reed 5, allows it to determine with certainty when the weft threads 10, 1 1 have been removed. The stretching device 47 can hereby also exert an extra tensile force on the weft threads 10, 1 1 to be removed. The stretching device 47 is hereby fastened with a support 48 to the housing 20 of the device 1 according to the invention.

[0031] It is clear that flat and/or smooth clamping elements 33, 37 do not necessarily have to be provided. According to one variant, clamping elements can also be provided with a surface which can exert a large friction force on weft threads.

[0032] The fastening system 2 is provided with elements which allow the device 1 according to the invention to be arranged in a specific position with respect to the reed 5 or with respect to the stretching device 47. To this end, the fastening system 2, as indicated in Figure 8, can be provided with slots 44, 45, 46 for setting both the device 1 according to the invention and the stretching device 47 in a desired position with respect to the crossbeam 3 and/or the reed 5.

[0033] According to one variant (not shown), the device 1 according to the invention can also be arranged on the insertion side of the shed in order there to remove weft thread there, for example in a way similar to the method described in EP 309 013 A1. An extra blow nozzle can here be provided in order to blow weft thread in the area of the insertion side into a device 1 according to the invention, more particularly via the inlet 7 in the device 1 .

[0034] Within the context of the application, "first" and "second" are used merely to be able to differentiate between the first unit 9 and the second unit 19, between the first clamping element 33 and the second clamping element 37, and between the first actuator 12 and the second actuator 13. The first unit 9 can also be named the pneumatic unit, while the second unit 19 can be named the mechanical unit.