Auxiliary weft yarns drawing-off device and process, weaving loom equipped with such a device |
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申请号 | EP08166242.1 | 申请日 | 2008-10-09 | 公开(公告)号 | EP2175057B1 | 公开(公告)日 | 2011-06-15 |
申请人 | SCHÖNHERR Textilmaschinenbau GmbH; | 发明人 | Burkert, Martin; Pietzonka, Dieter; | ||||
摘要 | |||||||
权利要求 | |||||||
说明书全文 | This invention relates to a device for drawing auxiliary weft yarns out of a fabric on a loom, that is when the fabric is being woven. This invention also relates to a loom equipped with such a device and to a process for drawing auxiliary weft yarns out of a fabric on a loom. In the field of weaving machines, and as shown on The invention aims at solving these problems with a new device for drawing auxiliary weft yarns out of a fabric, without needing to cut the auxiliary weft yarns in the middle, whereas the quality of the fabric can be improved. The invention concerns a device for drawing auxiliary weft yarns out of a fabric on a loom, this device comprising at least one draw-off unit located next to a first longitudinal edge of the fabric and having means to exert, on at least one auxiliary weft yarn, a drawing effort, and at least one locking unit adapted to hold the fabric in its position along a direction substantially parallel to the weft yarns in the fabric. This device is characterized in that the locking unit comprises a gripper sub-unit and driving means adapted to move the gripper sub-unit along a direction substantially parallel to the weft yarns in the fabric. Thanks to the invention, the locking unit holds the fabric in position, which enables it to resist the friction forces induced by the drawing-off movement of the auxiliary weft yarns on the totality of their length. In other words, the locking unit prevents the fabric from going along an oblique way that could result from the shear stress induced by friction forces generated by the displacement of the auxiliary weft yarns within the loops of the fabric. According to further aspects of the invention, which are advantageous but not compulsory, the device for drawing auxiliary weft yarns might incorporate one or several of the following features:
The invention also concerns a weaving loom equipped with a device as mentioned here above for drawing auxiliary weft yarns out of a fabric when such a fabric is being woven on this loom. Such a loom is more reliable and produces fabrics of higher quality than the looms of the prior art. According to an advantageous aspect of the invention, such a loom may comprise dedicated means, preferably Leno heddles, to weave a special false selvedge whose weft yarns are formed exclusively by auxiliary weft yarns. Finally, the invention concerns a process according to claim 10 which can be implemented with a device as mentioned here-above for drawing auxiliary weft yarns out of a fabric on a loom. According to further aspects of the invention, which are advantageous but not compulsory, this process might incorporate one or several of the following features:
The invention will be better understood on the basis of the following description which is given in correspondence with the annexed figures and as an illustrative example, without restricting the object of the invention. In the annexed figures
A carpet weaving loom 1 is partially and schematically represented on Jacquard heddles 15 are driven by a non represented Jacquard mechanism and cooperate with pile warp yarns 16 in order to form the pile shed. Lancets 17 are arranged within the shed and form a support for some auxiliary weft yarns 31 which are introduced within the pile shed by a second non represented rapier whose movement is represented by arrow A3. One lancet 17 is represented on Warp yarns 13 and ground weft yarns 14 form together the backing of a fabric 2, for instance a carpet provided with loops. 21 and 22 denote respectively the longitudinal edges of fabric 2 shown respectively on the left and on the right of this fabric on A-A' denotes the direction of progression of fabric 2 within loom 1. This direction is rectilinear and vertical on a part of the path of fabric 2 on A device 20 is provided on loom 1 and devoted to the weaving of a special false selvedge 25 for fabric 2. Device 20 is represented in a schematic way on As known by the people skilled in the art of weaving, device 20 may include two heddles, each provided with lifting heddle and one doup. These two heddles are advantageously driven by the Jacquard mechanism. Device 20 can also be formed of a mechanism having discs oscillating about a weft wise axis and provided with apertures for warp yarns 19, or any kind of mechanism that permits to cross warp yarns between them in a weave. As explained here-after with respect to Non represented means are also used to weave standard false selvedges next to each longitudinal edge 21 or 22 with dedicated warp yarns and with ground weft yarns 14. The standard false selvedge 26 close to edge 21 is separated by non represented cutting means downstream the draw-off unit. The standard false selvedge close to edge 22 is not represented since it is cut at the level of the beating point. Once fabric 2 has been woven, auxiliary weft yarns 31 extend in the main part of fabric 2, between edges 21 and 22, and up to false selvedge 25. They lie perpendicularly to direction A-A'. A device 50 is provided on loom 1 in order to draw-off or pull the auxiliary weft yarns 31 out of fabric 2. This device 50 comprises a draw-off unit 51 mounted next to longitudinal edge 21 of fabric 2 and a locking unit 52 mounted next to longitudinal edge 22. Draw-off unit 51 comprises an elongated guide bracket 53 whose longitudinal axis X53 is substantially parallel to the weft yarns 14 and 31 in fabric 2, that is perpendicular to direction A-A' and parallel to direction B-B'. A servomotor 54 is mounted on bracket 53 next to its extremity opposite to fabric 2 and drives a belt 55. Belt 55 goes around a idle pulley 56 mounted on bracket 53 in the vicinity of edge 21. A carriage 58 is fast with belt 55 and can be moved between the positions represented respectively on Device 50 also includes an electrical winder 59 adapted to wind the special false selvedge 25 when it comes out of a guide member 60 located next to edge 21 and held in position by a bracket 62. In other words, the false selvedge 25 enters guide member 60 and is then pulled by winder 59, which enables to separate false selvedge 25 from the main part of fabric 2. False selvedge 25 can then be directed towards a bin 61. On Carriage 58 is provided with a hook-forming gripper 65 which comprises an arm 66 fixed by screws 67 on carriage 58 and a hook part 68 located at the end of arm 66 directed towards edge 21 and where an idle pulley 69 is rotatively mounted around an axis X69 which is oblique with respect to the longitudinal axis X66 of arm 66. Axis X69 is defined by a support member 70 fast with arm 66. Pulley 69 is mounted with respect to member 70 thanks to a roller bearing 71, which facilitates rotation of pulley 69 around axis X69. Instead of roller bearing 71, one can also use a needle bearing or a ball bearing. On A deflector 72 is also mounted at the end of arm 66 next to pulley 69, at the level of hook part 68. Deflector 72 aims at guiding an auxiliary weft yarn 31 towards the radial external surface 69A of pulley 69 when carriage 58 moves arm 66 towards edge 21, in such a way that deflector 72 comes into contact with this yarn. In other words, due to the binding of false selvedge 25 at the level of guide member 60, one auxiliary weft yarn extending between this false selvedge and the main part of fabric 2 is on the path of hook part 68, so that it can be partly wounded around surface 69A after it has been guided by deflector 72. Then, when carriage 58 is moved by belt 55 towards servomotor 54, auxiliary weft yarn 31 is pulled by hook part 68 out of fabric 2. Since a part of this auxiliary weft yarn is fast within false selvedge 25, the traction effort T1 exerted on a weft yarn 31 by pulley 69 is such that the part of the yarn 31, which is still engaged in the loops of fabric 2, is pulled out of these loops. Effort T1 is substantially parallel to weft yarns in fabric 2, that is to direction B-B', which facilitates pulling of auxiliary weft yarns 31 out of fabric 2. When the carriage 58 moves from the position of Carriage 58 is provided with no positively driven accessory. Therefore, carriage 58 does not need to be fed with power and can be very light, as compared to the case where it would carry a clamp. Friction forces resist the extraction of a weft yarn 31 out of fabric 2. These friction forces could locally deform fabric 2 and cause it to deviate from its path. In order to avoid this, locking unit 52 comprises two rollers 81 and 82 respectively mounted on two arms 83 and 84 of a clamp 85. Both rollers rotate around axes X81 and X82 that are parallel to direction B-B'. Clamp 85 can press rollers 81 and 82 one against the other. Roller 81 lies against the front side 23 of fabric 2, whereas roller 82 lies against its backside 24. Roller 82 is provided with needles 82A which can at least superficially penetrate within fabric 2, thus ensuring efficient guiding of fabric 2 by the pair of rollers 81 and 82. When they are pressed against each other, rollers 81 and 82 exert a locking effort E on fabric 2 that can only move along direction A-A' but is locked along direction B-B'. This effort E prevents the fabric to run obliquely due to the friction forces occurring when one yarn 31 is pulled out of the loops of a row of loops on front side 23. Effort E is basically a pinching effort. In other words, thanks to unit 52, it is possible to resist friction forces between yarns 31 and loops of fabric 2 that could be prejudicial to the handling of the fabric 2 in the loom. However and since the effort E must be limited to avoid that the needles 82A damage the fabric 2, clamp 85 forms a gripper sub-unit which is movable parallely to direction B-B' and is piloted by a linear actuator 86 in order to correct the position of the fabric along the direction B-B' in case it deviates from its normal path. A contact sensor 90 is provided on bracket 53. Sensor 90 delivers to an electronic control unit 100, a signal S90 representative of the position of edge 21 along direction B-B', next to pulley 56. Unit 100 generates, on the basis of signal S90, an electronic control signal S100 which is sent to actuator 86 in order to position clamp 85 along direction B-B' in relation with the actual position of edge 21. The clamp 85 is moved by the actuator 86 along direction B-B' with the amount of the shift of position of edge 21 so that edge 21, recovers its normal position. In other words, it is possible to react, with unit 52, to a movement of edge 21 towards servomotor 54 by sending to actuator 86 a signal S100 to pull clamp 85 backwards on Thanks to effort E, it is possible to pull on fabric 2, in order to resist the friction forces that tend to deviate fabric 2 towards bracket 53. By successively applying this shift of position of unit 52, clamp 85 moves towards edge 22 and comes to a point where it is necessary to bring it back to a position that is closer to the opposite edge 21 of fabric 2, in order to avoid that the rollers 81 and 82 leave the fabric, which would make effort E inefficient. To this end, unit 52 is periodically deactivated and clamp 85 is opened. Then rollers 81 and 82 are moved by actuator 86 towards a center zone of fabric 2, that is towards edge 21. Clamp is then closed so that effort E is exerted closer to the center of fabric 2. Alternatively, a sensor, e.g. a switch, can be used to detect when rollers 81 and 82 come close to edge 22 and send a signal to unit 100 which then controls clamp 85 and actuator 86 to deactivate unit 52 and move the rollers towards the center of fabric 2. A protecting cover 87 is arranged between a beam 88 supporting actuator 86 and the back side 24 of fabric 2, in order to avoid direct contact with the needles 82A. Draw-off unit 51 and locking unit 52 are offset from each other along direction A-A'. More precisely, rollers 81 and 82 are offset with respect to hook-forming part 68 along direction A-A', so that locking effort E is exerted on a part of fabric 2 whose auxiliary weft yarns 31 have already been pulled out. One notes Δ5 the distance between items 68, next to edge 21, and 81-82, next to edge 22, along direction A-A'. Distance Δ5 can have a value between 10 and 40 mm, for a fabric having a width ℓ2 between 2 and 4 m. Unit 52 is located upward of unit 51, so that effort E is exerted on a part of fabric 8 where auxiliary weft yarns 31 have already been drawn-off by unit 51. Therefore, effort E does not brake or lock weft yarns 31 when they are pulled out of fabric 2 by gripper 65. In particular, needles 82A do not interfere with weft yarns 31. In order for the hook part 68 of arm 66 to efficiently pull a weft yarn 31 out of fabric 2, it is necessary that the part of this weft yarn that belongs to false selvedge 25 is not pulled out of this false selvedge. In other words, false selvedge 25 must hold one end of each yarn 31 strongly enough to resist the traction T1 exerted by the hook part 68. To this purpose, and as shown on A second series of warp yarns 19B extend around weft yarns 31 and warp yarns 19A. More precisely, each warp yarn 19B crosses each weft yarn 31 on the side opposite to warp yarns 19A. That is, if the warp yarns 19A are on the backside of the weft yarns 31 on If one weaves a false selvedge 25 in the way represented on As shown on After a predetermined period of time Δt1 which corresponds to the first part M1 of its movement, carriage 58 reaches a maximum speed Smax where weft yarn 31 can be pulled out rapidly from the loops since only a relatively small part of each weft yarn 31 is still engaged within some of the loops. Carriage 58 keeps this maximum speed during a second part M2 of its movement, for a period of time Δt2. In a third part M3 of the carriage movement, the carriage reverses its direction of travel and, in a fourth part M4, it decelerates on its way back to the position of On As shown by curve P, the position of carriage 58, and hence of gripper 65 and hook part 68, has smooth transitions. At the end of the first part M1 of the movement, the carriage 58 reaches an intermediate position PA which is closer to position P2 than to position P1. The path between positions P1 and PA corresponds to more than 50% of the total path between position P1 and position P2. In other words, the carriage 58 and the gripper 65 reach their maximum speed Smax after Δt1, that is when the carriage has reached position PA where it has travelled more than 50% of its path between the end positions P1 and P2. With such velocity and position profiles, each auxiliary weft yarn 31 is progressively drawn out of the fabric 2, in particular in part M1 of its movement where it undergoes a high tension since it goes through many loops. Since the path between P0 and PA represents more than 50% of the total path between P1 and P2, an auxiliary weft yarn reaches its maximum extraction speed Smax when it is already more than 50% out of the fabric, that is when its tension has decreased. Heating of the auxiliary weft yarns is thus relatively low, as compared to what happens with looms of the prior art, and the risk that the auxiliary weft yarn cuts one or several loops, which can result from the speed and tension of the weft yarns in the prior art, is reduced. In the second embodiment of the invention represented on This invention induces several advantages. The carriage 58 is "passive", in so far as it does not carry any actuator to drive a clamp or anything similar. Therefore, carriage 58 can be light and move at a high speed. One does not need a cutting device to be used in the middle of the fabric, which avoids quality problems in the center of the fabric. Thanks to the locking unit 52, no movement along the direction B-B' results from the friction forces induced by the sliding movement of the auxiliary weft yarns 31 within the loops. The movement of the carriage is inline with the auxiliary weft yarns 31 in the fabric, so that friction between the auxiliary weft yarns and the loops can be minimized. The use of a roller bearing 71 between items 69 and 70 induces lower friction forces on the weft yarn 31 at the level of hook part 68 and, hence, relatively low forces on the false selvedge 25, so that the risk of brakeage of yarns 31 is diminished. The fact that one uses a hook forming gripper 65 induces that the total path L58 of the carriage can be roughly half the width ℓ2 of the fabric 2. Only one special false selvedge 25 is provided next to one edge 21 of the fabric which induces that not much material is wasted. Thanks to the speed profile M1-M4 adapted for the movement of carriage 58, the draw-off cycle is not twice as long as in the case where only half of an auxiliary weft yarn is taken out of the fabric next to each longitudinal edge. Moreover, as explained here-above, overheating of the auxiliary weft yarns is prevented, and risks to cut the loops with the auxiliary weft yarns are low. According to some embodiments of the invention, the draw-off unit can be located on the taker-rapier side of the weaving machine, whereas the locking unit is located on the bringer-rapier side. Alternatively, the draw-off unit can be located on the bringer-rapier side, whereas the locking unit is located on the taker-rapier side. The invention has been represented on a single-piece loom 1. It can also be implemented with a face-to-face weaving loom where loop-carpets or loop-and-pile carpets can be woven. In the case of face-to-face weaving, the device can include two draw-off units next to one edge of the fabric and one or two locking unit next to the other edge. The contact sensor 90 may be located next to edge 21 or next to edge 22 or two sensors can be used. Sensor 90 is represented on the figures as a mechanical sensor. However, other kinds of sensor can be used, e.g. optical sensors. Instead of one weft yarn 31, the gripper 65 can pull several such yarns at a time, e.g. five or six. Instead of, or in addition to, the special weaving pattern for false selvedge 25, one can use melt-yarns or ultrasonic welding to make the auxiliary weft yarns fast with this selvedge. Instead of a servomotor 54 and a belt 55, any other type of electrical, hydraulic or pneumatic linear actuator may be used to drive the hook forming gripper 65. |