Classifications

• • D—TEXTILES; PAPER
  • D03—WEAVING
  • D03D—WOVEN FABRICS; METHODS OF WEAVING; LOOMS
  • D03D47/00—Looms in which bulk supply of weft does not pass through shed, e.g. shuttleless looms, gripper shuttle looms, dummy shuttle looms
  • D03D47/34—Handling the weft between bulk storage and weft-inserting means
  • D03D47/342—Handling the weft between bulk storage and weft-inserting means knot detection
• • D—TEXTILES; PAPER
  • D03—WEAVING
  • D03D—WOVEN FABRICS; METHODS OF WEAVING; LOOMS
  • D03D47/00—Looms in which bulk supply of weft does not pass through shed, e.g. shuttleless looms, gripper shuttle looms, dummy shuttle looms
  • D03D47/34—Handling the weft between bulk storage and weft-inserting means
• • D—TEXTILES; PAPER
  • D03—WEAVING
  • D03D—WOVEN FABRICS; METHODS OF WEAVING; LOOMS
  • D03D51/00—Driving, starting, or stopping arrangements; Automatic stop motions
  • D03D51/14—Driving, starting, or stopping arrangements; Automatic stop motions for reducing speed temporarily

Definitions

• the invention relates to a method for introducing a weft thread in a weaving machine, more particularly in a gripper weaving machine.
• Gripper weaving machines in which a plurality of weft threads are successively introduced into a shed according to a specific pattern by means of grippers are known. With most gripper weaving machines, the weft thread remains connected to the fabric selvedge between the successive introductions and the weft thread is cut by weft scissors from the fabric selvedge at the beginning of the introduction. Weft scissors of this type are described, inter alia, in US 3621885.
• a gripper weaving machine usually comprises a thread monitor in order to detect a broken weft thread, which thread monitor is arranged between a thread stock, such as a spool and the shed.
• a gripper weaving machine may comprise detection means in order to detect irregularities, such as a knot, a relatively thin or thick section in a weft thread and the like.
• a method according to the invention comprises introducing a specific weft thread at a lower speed than the normal speed for this specific weft thread, if a knot or irregularity has been detected in a specific weft thread.
• the invention offers the advantage that it prevents a knot or irregularity in a specific weft thread giving rise to a thread break and thereby stops of the weaving machine as a result of thread breaks are prevented. With certain fabrics, the presence of knots and irregularities in the fabric does not present a problem. Furthermore, the method does not necessarily require additional mechanical or pneumatic means in order to remove a knot before it is woven into the fabric.
• the invention is particularly advantageous for weaving weak weft threads which already contain a significant number of knots due to preparatory processes such as spinning, winding, twisting and the like.
• weft threads of this type the knots are usually also relatively weak and can be pulled apart from a certain yarn tension upwards.
• a method comprises introducing a specific weft thread at a relatively low speed once the knot or irregularity has been detected and before the knot or irregularity is introduced. This makes it possible to reduce the speed only after a certain time or a certain number of introductions after a knot or irregularity has been detected.
• a method comprises introducing a specific weft thread at a relatively low speed at least up to the point in time when the knot or irregularity is introduced. This makes it possible to increase the speed again once it has been ascertained that a knot or irregularity has been introduced.
• a method comprises lowering the speed of the weaving machine after a knot or irregularity has been detected in that specific weft thread.
• This method is particularly suitable for use with a weaving machine in which the speed of the weft thread is determined by the speed of the weaving machine, more particularly with a weaving machine such as a gripper weaving machine.
• a method comprises detecting a knot or irregularity which is located between the thread supply and the fabric selvedge. This may be effected using detection means for detecting a knot or irregularities which comprise a spool switch sensor arranged between two spools and producing a signal when a switch from one spool to the other spool takes place.
• detection means may also comprise a thread sensor which can detect a knot or irregularity in a weft thread.
• An irregularity may consist of a knot, a relatively thin or thick section and the like. If an irregularity is present, the local tensile strength of the weft thread can be assumed to be significantly lower than the nominal tensile strength of the weft thread, i.e. the tensile strength when no irregularity is present. With some weft threads, the irregularities usually consist of knots.
• the invention also relates to a weaving machine, more particularly a gripper weaving machine, which employs a method according to the invention and which comprises a drive unit, for example a drive motor, the speed of which can be controlled.
• a drive unit for example a drive motor
• Fig. 1 shows a gripper weaving machine according to the invention
• Fig. 2 shows the course of the speed of the weaving machine as a function of time
• Fig. 3 shows the course of the break risk of a weft thread and the speed of the weaving machine as a function of the tensile stress in the weft thread.
• Fig. 1 shows a gripper weaving machine comprising a supply 1 for the weft threads 2, 3 and 4.
• the supply 1 comprises, for example, three feeders 5, 6 and 7 for introducing a specific weft thread into the shed 8 during successive introductions.
• the weft thread of each feeder remains connected to the edge 9 between successive introductions and is detached from the edge 9 by means of diagram- matically illustrated weft scissors 10 which are driven by, for example, the weaving machine, at the start of an introduction of a weft thread of a specific feeder.
• the edge 9 is in this case at the first warp thread 11. In the case of weaving without waste, the edge 9 is also the fabric selvedge.
• the weft scissors 10 are arranged at the edge 9 at the beat- up line 12 of the fabric.
• the weft scissors 10 are intended for detaching a weft thread from the edge 9 at the start of the introduction into the shed 8.
• the weaving machine comprises a control unit 14 which, inter alia, controls a thread feeder 13.
• the thread feeder 13 ensures that weft threads are fed from a specific feeder 5, 6 or 7 to a gripper, more specifically to the giving gripper 15. There, the giving gripper
• the supply 1 in this case also comprises a thread monitor
• the feeder 5 comprises two spools 17, 18, the feeder 6 comprises two spools 19, 20 and the feeder 7 comprises two spools 21 , 22. As diagrammatically indicated, the end of the spools
• each feeder 5, 6 or 7 comprises an associ- ated prewinder 23, 24 or 25.
• Spool switch sensors 26, 27 and 28 are arranged between the spools in order to detect a switch from one spool to another spool.
• a thread sensor 29, 30, 31 is arranged in front of every prewinder 23, 24, 25 in order to detect a knot or irregularity in a weft thread.
• the spools are arranged in a fixed position on a spool stand
• the thread feeder 13 comprises a plurality of thread feeder needles 36, 37 and 38 which are each provided with a thread guide.
• the gripper weaving machine comprises a control unit 14 which can interact with detection means which detect when there is a knot or irregularity between a spool and the edge 9, more particularly with the spool switch sensors 26, 27 or 28 and/or the thread sensors 29, 30 or 31.
• the spool switch sensors 26, 27 and 28 produce a signal when a switchover from one spool to another spool takes place, thus making these signals also representative of a knot 39 which is present there.
• the thread sensors 29, 30 or 31 may, for example, use the principle of thickness measurement and are in this case able to produce a different signal when a knot 41 or irregularity in the weft thread passes the thread sensor instead of a normal weft thread.
• Thread sensors 29, 30 or 31 of this type are preferably used when, in addition to the knots produced by connecting two spools, other knots 41 or irregularities are present in the weft thread present on the spools.
• the latter is mainly the case with weak weft threads.
• the abovementioned detection means are preferably arranged in such a manner that the length of weft thread between the detection means and the edge 9 is greater than the length of a weft thread to be introduced. This allows the knot or irregularity to be detected before it is introduced into the shed 8. As there is a certain stock 42, 43 and 44 of weft thread on the prewinder 5, 6 or 7, there will always be sufficient weft length when the abovemen- tioned detection means are arranged in front of the prewinder.
• the giving gripper 15 and the receiving gripper 40 are transported through a shed 8 formed by warp threads 52 by means of gripper belts 50 and 51 in a known manner.
• the warp threads 52 are moved up and down by means of known shed-forming device according to a pattern.
• the gripper belts 50 and 51 are, for example, driven according to a specific movement path by means of a gripper drive 53 and 54.
• Gripper drives 53, 54 of this type are driven by a drive shaft 55 and are known, inter alia, from EP 077.087 A1 and FR 2315558 A1.
• the drive shaft 55 is driven synchronously by means of the drive shaft 56 of the drive motor 57 of the weaving machine.
• the gripper drives 53, 54 impose a movement path on the grippers 15, 40 which is determined by the angular position of the drive shaft 56.
• the movement path of the introduced weft thread is in this case determined by the movement path of the gripper 15 or 40 which interacts with the weft thread.
• the weaving machine comprises a drive unit 45, the speed of which can be controlled.
• the drive unit 45 comprises a drive motor 57.
• An angular sensor 58 is provided in order to determine the angular position of the drive shaft 56 of the drive motor 57.
• This angular sensor 58 is connected to the control unit 14. It is clear that according to a variant, the drive shaft 55 can coincide with the drive shaft 56.
• the drive motor 57 is controlled by means of the control unit 14 in accordance with a specific velocity profile. This may be effected in a manner as described in EP 1.032.867 B1 or WO 03/032481.
• the drive motor 57 can be controlled using a corre- sponding velocity profile. In this manner, a weft thread can be introduced into a shed using a corresponding velocity profile, which is dependent on and determined by the velocity profile of the drive motor.
• the weaving machine comprises an input unit
• each type of weft thread 2, 3 or 4 can also be introduced at a different speed during successive introductions, which operation is to be controlled in a suitable manner by the speed of the drive motor 57.
• the input unit 46 is, for example, used to input the weaving pattern below.
• the weaving machine will then be controlled by the control unit 14, for example according to the pattern below.
• the thread sensor 29 detects, for example, a knot 41 and emits a corresponding signal to the control unit 14, a method according to the invention will be used. As the prewinder 23 still contains a stock 42, the control unit 14 does not have to react immediately.
• the method for introducing a weft thread in a weaving machine comprises introducing a specific weft thread at a lower speed than the normal speed for said specific weft thread when a knot or irregularity was detected.
• the speed for introducing the weft thread 2 is reduced at the fourth, seventh and eighth insertion, for example by limiting the speed of the weaving machine to 500 revolutions/minute and in this way limiting the speed of the corresponding weft thread proportionally.
• the weaving machine is controlled by the control unit 14, for example using the pattern below.
• the speed of 500 revolutions/minute for introducing the weft thread 2 is not reduced at the fourth insertion. This speed is not reduced as this was already at such a low speed before the knot was detected. This speed for the fourth insertion was set at a low speed in order to limit the difference in speed with the previous and/or the next insertion.
• the detection devices 26, 27, 28, are identical to the detection devices 26, 27, 28,
• the speed of the weft thread is determined by the speed of the weaving machine, more particularly by the speed of the drive motor 57. In this case, the velocity pattern of the speed of the weaving machine is adjusted in order to adjust the speed of the weft thread.
• the weaving machine also comprises a storage unit 47 for storing data relating to the speed at which weft threads are introduced, the sequence in which weft threads are introduced and, for example, an abovementioned pattern.
• the data in the storage unit 47 can be input via the input unit 46.
• control unit 14 When one of the detection devices 26 to 31 sends a signal to the control unit 14, the control unit 14 also sends a signal to a counter 48 which counts, for example, the number of introductions from a specific feeder 5, 6 or 7. Depending on the number of insertions counted, the control unit 14 will adjust the pattern as mentioned above and reduce the speed for introducing specific weft threads at a suitable point in time and subsequently increase it again. The number of insertions obviously depends on the stock 42, 43 or 44.
• the counter 48 is able to count the time instead of the number of insertions after such a signal.
• the time taken is dependent on the speed of the weaving machine and on the pattern. This time may be defined as the time required for introducing the number of insertions from a specific feeder.
• the abovemen- tioned number of insertions or the abovementioned time can be set using an input unit 46, for example a keyboard.
• the invention allows weaving to continue from each feeder
• the weaver can also remove the knot or irregularity from the disconnected feeder when repairing the thread breaks and stop the method according to the invention using the input unit 46.
• the feeder in which the knot or irregularity occurred can immediately be restarted and/or an immediate return to weaving at normal speed is possible after the weaving machine has been started.
• the method according to the invention can of course, also be stopped by means of input unit 46, for example if weft threads are woven in which the knots do not result in thread breaks.
• the counter 48 can also be used to record or count the number of knots or irregularities.
• the control unit 14 can also be connected to a display unit or monitor 49.
• the method according to the invention can be used with a weaving machine with any number of feeders.
• the prewinders 23, 24 and 25 may be provided with a known winding detector with which the approximate number of windings on a respective prewinder 23, 24 and 25 can be determined.
• the control unit 14 is able to determine the number of insertions for which the speed has to be reduced and for which the speed can be increased again. This makes it possible to determine in a more accurate way when a knot or irregularity will be introduced into the shed 8 and thus to reduce the time or the number of insertions taking place at reduced speed.
• the speed does not only have to be reduced for a specific weft thread containing knots, but may also be reduced for all other weft threads which do not contain knots. Obviously, the aim will always be to weave at as high a speed as possible. After all, it is advantageous to introduce weft thread at normal speed for as long as possible, as well as to return to introducing weft thread at normal speed as quickly as possible.
• the detection means are not limited to the detection means illustrated. It is likewise possible to provide detection means of this type for detecting knots or irregularities at the output or even downstream of the prewinder. In this case, it is preferable if the speed is reduced immediately after the knot is detected and therefore during the introduction of this weft thread. This allows the risk of a thread break due to a knot to be reduced by decreasing the introduction speed of a weft thread. Should the knot be detected too late and thus already have been partially introduced by the giving gripper 15, it is nevertheless advantageous to reduce the speed during said introduction. As a result, it may, for example, still be possible to prevent the weft thread breaking as a result of the movement of the receiving gripper 40 due to a knot or irregularity.
• the method is particularly suitable for use with gripper weaving machines, in which the speed of the weaving machine determines the speed with which the weft threads are introduced
• the invention can also be used in other types of weaving machines.
• the invention can be used with air weaving machines, in which not only the speed of the weaving machine is then reduced, but also, for example, the pressure of the compressed air is reduced or decreased in order to cause the weft thread to be moved through the shed relatively slowly.
• the invention is particularly suitable for use with gripper weaving machines, the invention can of course also be used with gripper shuttle weaving machines, projectile weaving machines, water jet weaving machines, multiphase weaving machines and other types of weaving machine.
• weaving can continue at a lower speed until the next knot is also definitely weaved in. If, during weaving at reduced speed, a knot is also detected in another feeder, the speed of a weft thread from this other feeder is likewise adjusted according to the invention and the speed of the weft threads of the other feeders can also be adjusted. If two or more thread breaks are detected, weaving can be carried out according to the following pattern, for example. [0053]
• irregularity is understood to mean any irregularity in a weft thread, for example a relatively thin section, a relatively thick section, a nub, a burl, a knot, a splice weld or any other kind of irregularity. It will be clear that where the term knot was used in the above description, every mention relating to a knot also refers to any other kind of irregularity. This means that the term knot can be replaced by the term irregularity throughout the description and that this also forms part of the description of this patent application.
• the invention makes it possible to prevent thread breaks as a result of knots by continuing to weave at a relatively low speed after a knot has been detected until it is highly probable that the knot has been woven in, and subsequently increasing the speed again to the original value.
• the tension of the weft thread is also reduced, as a result of which the risk of a thread break, particularly a thread break at the location of a weak knot, can be prevented.
• the speeds of the weaving machine are only mentioned by way of example.
• the normal speed may be 700, 800, 900, 1000, 1100 and even 1200 revolutions/minute, while a respective associated reduced speed may be between 300 and 800 revolutions/minute.
• the reduced speed may, for example, be 100 to 400 revolutions/minute lower than the normal speed, i.e. the reduced speed is significantly lower than the normal speed.
• This reduced speed can be determined both in absolute and in relative terms, in other words a specific reduction of the speed or a relative or percentage reduction of the speed, for example a speed which is approximately 25% lower than the normal speed.
• the curve 60 in Fig. 3 shows the risk of breakage "f" of a weft thread as a function of the tensile stress "T", which is expressed in cN, for example.
• a thread break commonly occurs at a value tA, whereas the risk of thread break is low at a value lower than tB.
• This value tB is a tensile stress which may be reached at a speed "v" of the weaving machine of, for example, 700 revolutions/minute.
• the risk of breakage follows a curve 61 having a mean break value tC and a value tD below which the risk of thread break is low.
• This value tD is in this case representative of a speed of, for example, 475 revolutions/minute.
• weaving at 700 revolutions/minute or weaving at normal speed are possible and cause no problems, while if a knot is present, weaving without problems is only possible at 450 revolutions/minute or at a relatively low speed.
• the curve 62 for the tensile stress of the weft thread as a function of the associated speed is virtually linear.

Landscapes

• Engineering & Computer Science (AREA)
• Textile Engineering (AREA)
• Looms (AREA)
• Yarns And Mechanical Finishing Of Yarns Or Ropes (AREA)

Priority Applications (4)

Applications Claiming Priority (2)

Publications (1)

Family

ID=36950604

Family Applications (1)

Country Status (6)

Cited By (5)

Families Citing this family (1)

Citations (6)

Family Cites Families (1)

• 2005
  • 2005-06-15 BE BE2005/0303A patent/BE1016639A6/nl not_active IP Right Cessation
• 2006
  • 2006-06-07 DE DE602006019859T patent/DE602006019859D1/de active Active
  • 2006-06-07 CN CN2006800210728A patent/CN101198733B/zh active Active
  • 2006-06-07 WO PCT/EP2006/005406 patent/WO2006133833A1/en not_active Application Discontinuation
  • 2006-06-07 EP EP06754173A patent/EP1891257B1/en not_active Not-in-force
  • 2006-06-07 AT AT06754173T patent/ATE497039T1/de not_active IP Right Cessation

Patent Citations (6)

Non-Patent Citations (3)

Also Published As

Similar Documents

Legal Events