Method for preventing weft bars in a loom

Abstract

 A method for preventing weft bars from being formed when a loom (1) stops, the loom (1) being operated on the basis of a shedding pattern of which a single repeat includes at least three cycles of a main shaft (23), includes a setting step of setting activation/non-activation of a plurality of kinds of weft-bar-prevention units (44) and activation quantity for when the weft-bar-prevention units (44) are activated in accordance with the combination of the cause of stoppage of the loom (1) and at least one of the cycle number in the repeat of the shedding pattern and a stop time for which the loom (1) has been stopped and a controlling step of controlling the weft-bar-prevention units (44) on the basis of the settings made in the setting step.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

[0001] The present invention relates to a method for preventing weft bars from being formed when a loom stops, the method being suitably implemented in accordance with the cycle in a repeat of a shedding pattern, the cause of stoppage of the loom, etc.

2. Description of the Related Art

[0002] Japanese Unexamined Patent Application Publication No. 2001-172847 discloses a technique for the preventing weft bars from being formed when a loom stops by moving a cloth fell by a set distance before restarting the loom, the distance being determined on the basis of the cycle of the loom's main shaft in a repeat of a shedding pattern at the time of stoppage of the loom and a stop time for which the loom has been stopped.

[0003] According to this technique, however, the distance by which the cloth fell is moved before restarting the loom is determined without taking the cause of stoppage into account, and therefore the weft bars cannot be effectively prevented.

[0004] In addition, Japanese Examined Patent Application Publication No. 2-58382 discloses a technique for preventing heavy filling bars by not activating a weft-bar-prevention unit when weft stop occurs in a loom.

[0005] According to this technique, however, whether or not to activate the weft-bar-prevention unit is determined without taking into account the cycle of the loom's main shaft in a repeat of a shedding pattern and the stop time for which the loom has been stopped, and therefore the weft bars cannot be effectively prevented.

SUMMARY OF THE INVENTION

[0006] Accordingly, an object of the present invention is to provide a method for preventing the weft bars from being formed when a loom stops, the method being suitably implemented in accordance with the cycle number in a repeat of a shedding pattern, the stop time for which the loom has been stopped, and the cause of stoppage of the loom.

[0007] In order to attain this object, according to the present invention, a method for preventing a weft bar from being formed when a loom stops, the loom being operated on the basis of a shedding pattern of which a single repeat includes at least three cycles of a main shaft, includes a setting step of setting activation/non-activation of a plurality of kinds of weft-bar-prevention units and activation quantity for when the weft-bar-prevention units are activated in accordance with the combination of the cause of stoppage of the loom and at least one of the cycle number in the repeat of the shedding pattern and a stop time for which the loom has been stopped and a controlling step of controlling the weft-bar-prevention units on the basis of the settings made in the setting step.

[0008] For example, the activation/non-activation of the weft-bar-prevention units and the activation quantity for when the weft-bar-prevention units are activated may be set in accordance with the combination of the cause of stoppage of the loom, the cycle number in the repeat of the shedding pattern, and the stop time for which the loom has been stopped.

[0009] The weft-bar-prevention units may include a pre-start cloth-fell-moving unit for moving a cloth fell before restart of the loom and a blank-beating unit for performing a beat-up motion without a weft yarn being inserted after the restart of the loom. In such a case, the activation/non-activation of the pre-start cloth-fell-moving unit and the blank-beating unit and the activation quantity for when the pre-start cloth-fell-moving unit and the blank-beating unit are activated are set in accordance with the above-described combination.

[0010] In the case in which a single repeat of the shedding pattern includes three or more cycles of the main shaft, when the loom stops, a shed formed by warp yarns will be open or closed depending on the cycle (cycle number) at the time of stoppage of the loom. Accordingly, the warp tension applied after the loom has stopped differs depending on the cycle number at the time of stoppage of the loom, and therefore the cloth fell moves by different distances depending on the cycle in the repeat. For this reason, it is important to set the conditions of the weft-bar-prevention units (the activation/non-activation of the weft-bar-prevention units and the activation quantity for when they are activated) in accordance with the cycle in view of effectively operating the weft-bar-prevention units.

[0011] The stop time of the loom affects the amount of stretch of the warp yarns. Time ranges for the stop time are set for each of the weft-bar-prevention units, and the activation/non-activation of the weft-bar-prevention units and the activation quantity for when they are activated are set for each time range.

[0012] With respect to the cause of stoppage of the loom, weft stop due to a weft insertion failure, warp stop due to breakage of a warp yarn, and manual stop executed for stopping the loom to replace a cloth roller or to finish the operation are considered. These causes directly affect the process of preventing the weft bar. Normally, the activation/non-activation of the weft-bar-prevention units and the activation quantity for when they are activated are set the same for the warp stop and the manual stop.

[0013] The blank-beating unit, a high-torque-operation unit (also called a rush-start unit), a pre-stop cloth-fell-moving unit, and the pre-start cloth-fell-moving unit (also called a kickback unit) may be provided as the weft-bar-prevention units, and at least two of them are used in combination in accordance with the cycle number in the repeat of the shedding pattern, the stop time of the loom, and the cause of stoppage of the loom.

[0014] The blank-beating unit performs the beat-up motion without the weft yarn being inserted for a set period, that is, for a set number of cycles of the main shaft (a set number of picks) or a set time period after the restart of the loom. The weft insertion is started after the deflection of a reed and a beating force with which the reed beats against the cloth fell have increased and the operational state of the loom has become close to the steady state. Accordingly, the inserted weft yarn is beaten at approximately the same beating force as that in the steady state operation, and therefore the weft bars are effectively prevented.

[0015] The high-torque-operation unit is also called a rush-start unit, and operates a motor for driving the main shaft such that it generates a torque higher than that in the steady-state operation after the restart of the loom. Accordingly, the beat-up motion is performed with a beating force close to that in the steady-state operation immediately after the restart. The high-torque-operation unit may perform two kinds of operations: (1) an operation in which the torque is fixed to, for example, 300% of that in the steady-state operation for a set period, that is, for a set number of cycles of the main shaft (a set number of picks) or for a set time period after the restart; and (2) an operation in which the torque is set to, for example, 300%, 400%, or 500% of that in the steady-state operation for a fixed period, that is, for a fixed number of cycles (for example, two cycles) or for a fixed time period after the restart.

[0016] The pre-stop cloth-fell-moving unit activates around the time when the motor starts to decelerate after the issuance of a stop signal, and rotates a let-off motor and/or a take-up motor in the normal direction so as to move the cloth fell. Accordingly, the cloth fell position is compensated for by taking into account the displacement of the cloth fell (toward a let-off roller) due to the warp tension applied in the stop state, and the beating force applied to the cloth fell in automatic reverse rotation performed after the motor stops will be reduced.

[0017] The pre-start cloth-fell-moving unit is also called a kickback unit, and rotates the let-off motor and/or the take-up motor in the normal or reverse direction so as to move the cloth fell by a set distance before the restart of the loom, thereby preventing a heavy filling bar and a light filling bar from being formed. Activation cycle numbers, causes of activation, time ranges for the stop time, and the activation quantity are set for the pre-start cloth-fell-moving unit.

[0018] According to the present invention, the activation/non-activation of the weft-bar-prevention units and the activation quantity for when they are activated are set in accordance with the combination of the cause of stoppage of the loom and at least one of the cycle number in the repeat of the shedding pattern and the stop time of the loom. In addition, when the loom stops, the weft-bar-prevention units are controlled on the basis of the settings made. Accordingly, the optimum weft-bar-prevention function for the shedding pattern (weave structure) at the time of stoppage of the loom is set and the weft bars are reliably prevented. In addition, since the weft bars are prevented from being formed, various settings of the loom can be made from the viewpoint of increasing the weaving performance of the loom. Therefore, the weaving performance of the loom improves and the stoppage of the loom reduces, so that the operating rate of the loom increases. For example, in the known loom, the area of the shed formed by the warp yarns must be set small and the warp tension must be set low since a noticeable weft bar appears when the loom stops if the shed area is large or the warp tension is high. In comparison, according to the present invention, the weft bars are prevented even when the shed area is large and the warp tension is high. Therefore, the weft insertion performance of the loom can be improved by increasing the shed area or the warp tension, and the weaving performance can be improved accordingly.

[0019] When the activation/non-activation of the weft-bar-prevention units and the activation quantity for when they are activated are set in accordance with the combination of the cause of stoppage of the loom, the cycle number in the repeat of the shedding pattern, and the stop time of the loom, the weft bars are effectively prevented in accordance with all of the cause of stoppage of the loom, the cycle number, and the stop time of the loom.

[0020] When the weft-bar-prevention units include the pre-start cloth-fell-moving unit for moving the cloth fell before the restart of the loom and the blank-beating unit for performing the beat-up motion without the weft yarn being inserted after the restart of the loom and the activation/non-activation of these units and the activation quantity for when they are activated are set in accordance with the above-described combination, the weft bars are effectively prevented in accordance with the cause of formation of the weft bars.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] 

Fig. 1 is a side view showing the main part of the mechanical structure of a loom;

Fig. 2 is a block diagram showing a control system of the loom;

Fig. 3 is a schematic diagram showing the conceptual structure of weft-bar-prevention units; and

Fig. 4 is a diagram showing a weave structure obtained by a single repeat of a shedding pattern.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0022] Fig. 1 shows the main part of a loom 1. In the loom 1 shown in Fig. 1, warp yarns 2 are wound around a let-off beam 3, and a let-off motor 4 rotates the let-off beam 3 so that the warp yarns 2 are unrolled from the let-off beam 3 toward a tension roller 5. The warp yarns 2 are wound around the tension roller 5 and extend through respective droppers 6 and healds which are retained by a plurality of heald frames 7. The heald frames 7 move up and down to form a shed 8, and a weft yarn 10 is inserted through the shed 8 by a weft-inserting member, for example, a weft-insertion nozzle 9 so that the weft yarn 10 is interlaced with the warp yarns 2. Then, the weft yarn 10 is beaten against a cloth fell 11 by a reed 12, and a woven cloth 13 is obtained accordingly. The tension roller 5 is provided with a tension controller 20 which adjusts a tension applied to the warp yarns 2 to a suitable value.

[0023] The woven cloth 13 is wound around a breast beam 14, a guide roller 15, a take-up roller 17, and a guide roller 18, in that order, and is then wound around a cloth roller 19. The take-up roller 17 is directly rotated by a take-up motor 16, and the cloth roller 19 is rotated by the take-up motor 16 with a motion converter 22, such as a speed reducer, provided therebetween.

[0024] The shedding motion of the heald frames 7 and the beat-up motion of the reed 12 are synchronized with the rotation of a main shaft 23 of the loom 1, and the main shaft 23 is driven by a drive motor 24. The rotation of the main shaft 23 is converted into the beat-up motion by a motion-converter 25, and is also converted into the shedding motion of the heald frames 7 by motion-converters 26 and 27 and a dobby 28. The rotation angle of the main shaft 23 is detected by a rotation-angle detector 29, and a rotation-angle signal representing the detected rotation angle is output to a main controller 30 and a shedding controller 42 shown in Fig. 2.

[0025] Fig. 2 shows signals and commands input to the main controller 30 and components of the loom 1 controlled by the main controller 30. The main controller 30 receives the rotation-angle signal from the rotation-angle detector 29; a cycle-specified stop command from a stop-cycle-specifying unit 31; signals representing a cause of activation, an activation cycle number, activation quantity, time ranges for a stop time, the number of cycles, and a start angle at which blank beating is to be started from a setter 32; a manual stop command from a stop button 34; a warp stop signal from the droppers 6; a weft stop signal from a weft feeler 36; and a stop-time signal representing the stop time from a timer 37, the stop time being calculated on the basis of timing start/stop commands output to the timer 37, and controls a drive controller 38 which controls the drive motor 24, a let-off controller 21 which controls the let-off motor 4, a take-up controller 39 which controls the take-up motor 16, and a weft-insertion controller 40 which controls a solenoid valve 41 of the weft-insertion nozzle 9 on the basis of predetermined control programs.

[0026] The rotation-angle signal from the rotation-angle detector 29 is input not only to the main controller 30 but also to the shedding controller 42, as described above. The shedding controller 42 receives the rotation-angle signal from the rotation-angle detector 29 and controls the dobby 28 on the basis of a shedding pattern set in advance by a pattern setter 43, thereby controlling the shedding motion of the heald frames 7. The shedding pattern is set in accordance with a desired weave structure, and is defined by a repeat including a plurality of cycles for each of which the direction and amount of movement of the heald frames 7 are set. The weave structure obtained by a single repeat of the shedding pattern will be described below with reference to Fig. 4.

[0027] The stop-cycle-specifying unit 31 is used in a test for setting conditions used in the process of preventing weft bars. In this test, a manual stop command is issued to the stop-cycle-specifying unit 31 from a stop button 35 when the stop button 35 is operated. Then, the stop-cycle-specifying unit 31 refers to a cycle number set in advance by a setter 33, and issues a cycle-specified stop command to the main controller 30 at that cycle number.

[0028] Fig. 3 shows the conceptual structure of a plurality of kinds of weft-bar-prevention units 44, and the method for preventing the weft bars according to the present invention is applied to looms including the weft-bar-prevention units 44. The weft-bar-prevention units 44 include a blank-beating unit 45, a high-torque-operation unit 46, a pre-stop cloth-fell-moving unit 47 activated during deceleration, and a pre-start cloth-fell-moving unit 48 activated before restart, and at least two of them are provided.

[0029] The blank-beating unit 45 performs the beat-up motion without the weft yarn 10 being inserted for a set number of cycles of the main shaft 23 (a set number of picks) after the restart of the loom 1, and is composed of the main controller 30, the setter 32, the timer 37, and the weft-insertion controller 40. The setter 32 sets time ranges for the stop time, and also sets activation/non-activation of the blank-beating unit 45 in accordance with the combination of the cycle number, the cause of stoppage, and the time range to which the stop time belongs. Alternatively, the setter 32 sets the activation/non-activation of the blank-beating unit 45 in accordance with the combination of the cycle number and the cause of stoppage. Alternatively, the setter 32 sets the time ranges for the stop time, and also sets the activation/non-activation of the blank-beating unit 45 in accordance with the combination of the cause of stoppage and the time range to which the stop time belongs. In addition, the setter 32 also sets the number of cycles (number of picks) for which blank beating is to be performed and the rotation angle at which blank beating is to be started as the activation quantity for when the blank-beating unit 45 is activated.

[0030] Accordingly, when the loom 1 is restarted, the blank-beating unit 45 performs the beat-up motion without the weft yarn 10 being inserted for a set period (period corresponding to a set number of picks). During this time, the drive motor 24 accelerates and deflection of the reed 12 gradually increases, so that a beating force with which the reed 12 beats against the cloth fell 11 increases. Then, after the operational state of the loom 1 has become close to the steady state, the blank-beating unit 45 is stopped and the weft-insertion controller 40 is activated, so that the weft insertion and the beat-up motion are performed together. Since blank beating is performed after the restart of the loom 1, the inserted weft yarn 10 is beaten at approximately the same beating force as that in the steady state operation, and therefore the weft bars are effectively prevented.

[0031] The high-torque-operation unit 46 is also called a rush-start unit, and operates the drive motor 24 such that it generates a torque higher than that in the steady-state operation when the loom 1 is restarted, so that the beat-up motion is performed with a beating force close to that in the steady-state operation immediately after the restart. The high-torque-operation unit 46 may perform two kinds of operations:

(1) An operation in which the torque is fixed to, for example, 300% of that in the steady-state operation for a set number of cycles of the main shaft 23 (a set number of picks) or for a set time period after the restart. More specifically, if the warp stop or the manual stop occurs at the first cycle in a repeat, the increased torque is applied for four cycles irrespective of the stop time. In other cases, the increased torque is applied for one cycle irrespective of the stop time.

(2) An operation in which the torque is set to, for example, 300%, 400%, or 500% of that in the steady-state operation for a fixed number of cycles (for example, for two cycles) after the restart.

[0032] The high-torque-operation unit 46 is composed of the main controller 30, the setter 32, the drive controller 38, and the timer 37. In the present embodiment, the high-torque-operation unit 46 performs the operation of the above item (1), and the timer 37 is not used. More specifically, the setter 32 sets the number of cycles (number of picks) for which the high-torque-operation unit 46 is to be activated as the activation quantity in accordance with the cycle number and the cause of stoppage, irrespective of the stop time.

[0033] The pre-stop cloth-fell-moving unit 47 activates around the time when the drive motor 24 starts to decelerate after the issuance of the stop signal to the main controller 30, and rotates the let-off motor 4 and/or the take-up motor 16 in the normal direction so as to move the cloth fell 11 by a set distance. Accordingly, the cloth fell position is compensated for by taking into account the displacement of the cloth fell 11 (toward the let-off beam 3) due to a warp tension applied in the stop state, and the beating force applied to the cloth fell 11 in automatic reverse rotation performed after the stoppage of the drive motor 24 will be reduced. The pre-stop cloth-fell-moving unit 47 is composed of the let-off controller 21, the main controller 30, the setter 32 which sets the causes of activation and the activation quantity, and the take-up controller 39. The setter 32 sets the activation/non-activation of the pre-stop cloth-fell-moving unit 47 and the activation quantity for when it is activated in accordance with the combination of the cycle number and the cause of stoppage.

[0034] The pre-start cloth-fell-moving unit 48 is also called a kickback unit, and rotates the let-off motor 4 and/or the take-up motor 16 in the normal or reverse direction so as to move the cloth fell 11 by a set distance, thereby preventing a heavy filling bar or a light filling from being formed. The pre-start cloth-fell-moving unit 48 is composed of the let-off controller 21, the main controller 30, the setter 32, the timer 37, and the take-up controller 39. The setter 32 sets time ranges for the stop time independently of the time ranges set for the blank-beating unit 45, and also sets the activation/non-activation of the pre-start cloth-fell-moving unit 48 and the activation quantity for when it is activated in accordance with the combination of the cycle number, the cause of stoppage, and the stop time. Alternatively, the setter 32 sets the activation/non-activation of the pre-start cloth-fell-moving unit 48 and the activation quantity for when it is activated in accordance with the combination of the cycle number and the cause of stoppage. Alternatively, the setter 32 sets the time ranges for the stop time independently of the time ranges set for the blank-beating unit 45, and also sets the activation/non-activation of the pre-start cloth-fell-moving unit 48 and the activation quantity for when it is activated in accordance with the combination of the cycle number and the stop time.

[0035] The method for preventing the weft bars according to the prevent invention is applied to the loom 1 operated on the basis of a shedding pattern of which a single repeat includes three or more cycles of the main shaft 23. In addition, the method includes a setting step of setting the activation/non-activation of the weft-bar-prevention units 44 (the blank-beating unit 45, the high-torque-operation unit 46, the pre-stop cloth-fell-moving unit 47, and the pre-start cloth-fell-moving unit 48) and the activation quantity for when they are activated in accordance with the combination of the cause of stoppage of the loom 1 and at least one of the cycle number in the repeat of the shedding pattern and the stop time for which the loom 1 has been stopped and a controlling step of controlling the weft-bar-prevention units 44 on the basis of the settings made in the setting step so as to prevent a weft bar from being formed in the woven cloth 13 when the loom 1 stops.

[0036] As described above, in the case in which a single repeat of the shedding pattern includes three or more cycles of the main shaft 23, when the loom 1 stops, the shed 8 formed by the warp yarns 2 will be open or closed depending on the cycle at the time of stoppage of the loom 1. Therefore, the displacement of the cloth fell 11 caused by the warp tension differs depending on the cycle in the repeat. Accordingly, the conditions used in the process of preventing the weft bars must be set for each cycle, and such a setting is extremely important for effectively executing the weft-bar-prevention function.

[0037] Fig. 4 shows an example of a weave structure obtained by a single repeat of a shedding pattern (a structural unit repeated in the weave structure), where the repeat includes six cycles. When stoppage of the loom 1 occurs or when an operator manually stops the loom 1 while the loom 1 is operating, the stop signal or the stop command is issued to the main controller 30. Then, the main shaft 23 of the loom 1 starts to decelerate and stops at the cycle subsequent to the cycle at which the stop signal or the stop command has been issued. Then, the main shaft 23 is automatically rotated in the reverse direction, and stops (waits) at a predetermined rotation angle, for example, 320°, in the cycle at which the stop signal or the stop command has been issued. With respect to the weave structure shown in Fig. 4, the shed 8 formed by the warp yarns 2 will be open if the loom 1 stops (waits) at the first, second, fourth, or fifth cycle, and will be closed if it stops (waits) in the third or sixth cycle.

[0038] In the air-jet loom 1 manufactured by the applicant of the present invention (Tsudakoma Kogyo Kabushiki Kaisha), the following operation is performed when the stop signal is issued. That is, when stoppage of the loom 1 occurs while the air-jet loom 1 is operating, for example, when the weft stop occurs, the weft stop signal is detected as the stop signal at the time when the rotation angle of the main shaft 23 is 290°. In both cases of the weft stop and the warp stop, the drive motor 24 starts to decelerate when the main shaft 23 is at 70° in the cycle subsequent to the cycle at which the stop signal has been issued and causes the main shaft 23 to stop at that cycle. Then, the main shaft 23 is automatically rotated in the reverse direction by the drive motor 24 until it reaches 320° in the cycle at which the stop signal has been issued. Then, in the case of the weft stop, the main shaft 23 is further rotated manually in the reverse direction to 180° in the same cycle, where a defective weft yarn is removed, and is still further rotated in the reverse direction to 320° (300° or 160° when blank beating is to be performed) in the cycle previous to the cycle at which the weft stop signal has been issued. Then, the loom 1 is restarted from that position. In the case of the warp stop, a defective warp yarn 2 is repaired while the main shaft 23 is at 320° in the cycle at which the warp stop signal has been issued, and the loom 1 is restarted from that position unless blank beating is to be performed. When blank beating is to be performed, the main shaft 23 is further rotated in the reverse direction to 300° or 160°.

[0039] In a first example (Table 1) described below, time ranges for the stop time are set for each of the blank-beating unit 45 and the pre-start cloth-fell-moving unit 48, and the activation/non-activation of these units and the activation quantity for when they are activated are set for each time range. More specifically, time ranges of 0 to 2 minutes and more than 2 minutes are set for the blank-beating unit 45, and time ranges of 0 to 4 minutes and more than 4 minutes are set for the pre-start cloth-fell-moving unit 48. In the time range of 0 to 4 minutes for the pre-start cloth-fell-moving unit 48, an activation quantity for a stop time of 4 minutes is set, and the activation quantity for a stop time other than 4 minutes is determined proportionally to the stop time. In addition, in the time range of more than 4 minutes for the pre-start cloth-fell moving unit 48, the activation quantity is set the same as that for the stop time of 4 minutes.

[0040] With respect to the cause of stoppage, the weft stop, the warp stop, and the manual stop are considered. The weft stop occurs when the weft feeler 36 detects a weft insertion failure, and the weft stop signal is output at the time when the rotation angle of the main shaft 23 is 290°. The warp stop occurs when a broken or slack warp yarn is detected by the droppers 6. The manual stop occurs when the operator operates the stop button 34 or the stop button 35 to stop the weaving operation or to perform the test. In the first example (Table 1), a second example (Table 2), and a third example (Table 3), which will be described below, the activation/non-activation of the weft-bar-prevention units 44 and the activation quantity for when they are activated are set the same for both the warp stop and the manual stop.

[0041] At least two of the blank-beating unit 45, the high-torque-operation unit 46, the pre-stop cloth-fell-moving unit 47, and the pre-start cloth-fell-moving unit 48 are provided as the weft-bar-prevention units 44, and the activation/non-activation of the weft-bar-prevention units 44 is set in accordance with the combination of the cause of stoppage of the loom 1 and at least one of the cycle number in the repeat of the shedding pattern and the stop time for which the loom 1 has been stopped. Accordingly, three types of combinations are possible: (1) the combination of the cause of stoppage, the cycle number, and the stop time, (2) the combination of the cause of stoppage and the cycle number, and (3) the combination of the cause of stoppage and the stop time. These combinations are determined by taking into account the state of the loom 1 when it is stopped.

[0042] The stop-cycle-specifying unit 31 is used in the test for setting the conditions used in the process of preventing the weft bars. In this test, first, the operator sets a cycle in the repeat at which the loom 1 is to be stopped by specifying a cycle number using the setter 33. Then, the operator presses the stop button 35 while the loom 1 is operating, so as to manually stop the loom 1 for the purpose of the test. At this time, the drive motor 24 does not start decelerating immediately, but starts decelerating after the main shaft 23 reaches the set cycle (cycle number). Then, the drive motor 24 stops, automatically rotates in the reverse direction, and causes the main shaft 23 to stop (wait) at a predetermined rotation angle, for example, 320°, in the cycle set by the operator. As described above, in the test for setting the conditions of the weft-bar-prevention units 44, the main shaft 23 can be stopped at a desired cycle in the repeat, and therefore the test can be performed easily. The optimum conditions determined by this test are used in the examples described below.

First Example

[0043] Table 1 shows an example in which the blank-beating unit 45, the high-torque-operation unit 46, the pre-stop cloth-fell-moving unit 47, and the pre-start cloth-fell-moving unit 48 are provided as the weft-bar-prevention units 44 and the activation/non-activation of these units and activation quantity for when they are activated are set in accordance with the combination of the cycle number in the repeat shown in Fig. 4, the cause of stoppage of the loom 1, and the stop time of the loom 1.

[0044] All of the conditions of the weft-bar-prevention units 44 are set on the basis of the results obtained by the above-described test. In addition, in this example, the weft density (the number of weft yarns per inch) of the woven cloth 13 is one hundred, and therefore the distance corresponding to 1 pick is 0.25 mm. The weft density is set by a weave-structure setter (not shown in Fig. 1), and the main controller 30 calculates the distance corresponding to 1 pick on the basis of a weft-density signal obtained from the weave-structure setter. In addition, according to this example, the pre-start cloth-fell-moving unit 48 rotates the let-off motor 4 and the take-up motor 16 in both the normal and reverse directions. Accordingly, in the table, the activation quantity (distance by which the cloth fell 11 is moved) obtained by rotating the let-off motor 4 or the take-up motor 16 in the normal direction is shown with the positive sign and that obtained by rotating the let-off motor 4 or the take-up motor 16 in the reverse direction is shown with the negative sign.

[0045] With respect to the blank-beating unit 45, the activation/non-activation of the blank-beating unit 45 and the activation quantity (the number of cycles and the start angle of the main shaft 23) for when it is activated are set by the setter 32 in accordance with the cycle number, the cause of stoppage, and the time range to which the stop time belongs (0 to 2 minutes or more than 2 minutes).

[0046] The high-torque-operation unit 46 is always activated irrespective of the cycle number, and the activation quantity (number of cycles) is set by the setter 32 in accordance with the cycle number and the cause of stoppage.

[0047] With respect to the pre-stop cloth-fell-moving unit 47, the activation/non-activation of the let-off controller 21 is set by the setter 32 in accordance with the cycle number and the cause of stoppage (warp/manual stop or weft stop), and the activation quantity for when the let-off controller 21 is activated is set to a distance corresponding to 1 pick. In addition, in this example, it is set by the setter 32 that the take-up controller 39 is not to be activated for any of the cycle numbers.

[0048] With respect to the pre-start cloth-fell-moving unit 48, the activation/non-activation of the let-off controller 21 and the activation quantity for when it is activated are set by the setter 32 in accordance with the cycle number and the cause of stoppage (warp/manual stop or weft stop). The activation quantity is set to a distance corresponding to +1 pick, -1 pick, or -0.7 picks for a normal stop time of 4 minutes, and the activation quantity for a stop time other than 4 minutes is determined as described above depending on the time range to which the stop time belongs (0 to 4 minutes or more than 4 minutes). In addition, the activation/non-activation of the take-up controller 39 and the activation quantity for when it is activated are set by the setter 32 in accordance with the cycle number and the cause of stoppage (warp/manual stop or weft stop). The activation quantity is set to a distance corresponding to +0.2 picks or -0.2 picks for the normal stop time of 4 minutes, and, similar to the case of the let-off controller 21, the activation quantity for a stop time other than 4 minutes is determined as described above depending on the time range to which the stop time belongs (0 to 4 minutes or more than 4 minutes) .

Second Example

[0049] Table 2 shows an example in which the blank-beating unit 45 and the pre-start cloth-fell-moving unit 48 are provided as the weft-bar-prevention units 44 and the activation/non-activation of these units and the activation quantity for when they are activated are set in accordance with the combination of the cycle number in the repeat shown in Fig. 4 and the cause of stoppage of the loom 1.

Table 2.

Activation/Non-activation of Weft-Bar-Prevention Units and Activation Quantity Therefor (Combination of Cycle of Main Shaft and Cause of Stoppage of Loom)
Cycle No.	Cause of Stoppage	Weft-Bar-Prevention Units
		Blank-Beating Unit			Pre-Start Cloth-Fell-Moving Unit
					Let-Off		Take-Up
		Activation/ Non-activation (A/N)	Number of Cycles	Start Angle (°) '	Activation/ Non-activation (A/N)	Quantity (Number of Picks)	Activation/ Non-activation (A/N)	Quantity (Number of Picks)
1	Warp/Manual	N			N		N
	Weft	N			A	+1	A	+0.2
2	Warp/Manual	A	3	160	A	-1	N
	Weft	N			N		N
3	Warp/Manual	A	3	300	N		N
	Weft	A	3	160	A	-1	A	-0.2
4	Warp/Manual	N			N		N
	Weft	N			N		N
5	Warp/Manual	A	3	300	A	-1	A	-0.2
	Weft	N			N		N
6	Warp/Manual	A	3	300	N		N
	Weft	A	3	160	A	-0.7	A	-0.2

[0050] With respect to the blank-beating unit 45, the activation/non-activation of the blank-beating unit 45 and the activation quantity (the number of cycles and the start angle of the main shaft 23) for when it is activated are set by the setter 32 in accordance with the cycle number and the cause of stoppage (warp/manual stop or weft stop). In this example, the stop time of the loom 1 is not taken into account.

Third Example

[0051] Table 3 shows an example in which the blank-beating unit 45 and the pre-start cloth-fell-moving unit 48 are provided as the weft-bar-prevention units 44 and the activation/non-activation of these units and the activation quantity for when they are activated are set in accordance with the combination of the stop time of the loom 1 and the cause of stoppage of the loom 1.

Table 3.

Activation/Non-activation of Weft-Bar-Prevention Units and Activation Quantity Therefor (Combination of Stop Time of Loom and Cause of Stoppage of Loom)
Cause of Stoppage	Weft-Bar-Prevention Units
	Blank-Beating Unit				Pre-Start Cloth-Fell-Moving Unit
					Let-Off		Take-Up
	Stop Time (min)	Activation/ Non-activation (A/N)	Number of Cycles	Start Angle (°)	Activation/ Non-activation (A/N)	Quantity for 4 min. (Number of Picks	Activation/ Non-activation (A/N)	Quantity (Number of Picks)
Warp/Manual	0-2	A	3	160	A	-1	N
	More Than 2	A	2	160
Weft	0-2	N			N		N
	More Than 2	A	2	300

[0052] With respect to the blank-beating unit 45, the activation/non-activation of the blank-beating unit 45 and the activation quantity (the number of cycles and the start angle of the main shaft 23) for when it is activated are set by the setter 32 in accordance with the cause of stoppage and the time range to which the stop time belongs (0 to 2 minutes or more than 2 minutes), irrespective of the cycle number.

[0053] With respect to the pre-start cloth-fell-moving unit 48, the activation/non-activation of the let-off controller 21 is set by the setter 32 in accordance with the cause of stoppage (warp/manual stop or weft stop), irrespective of the cycle number, and the activation quantity for when the let-off controller 21 is activated is set to a distance corresponding to -1 pick for the normal stop time of 4 minutes. Similar to the first example, the activation quantity for a stop time other than 4 minutes is determined as described above depending on the time range to which the stop time belongs (0 to 4 minutes or more than 4 minutes). In addition, in this example, it is set by the setter 32 that the take-up controller 39 is not to be activated irrespective of the cycle number and the cause of stoppage.

[0054] The present invention may be applied not only to the loom according to the above-described embodiment, but also to pile looms and the like. In addition, as described above, the combination of the cause of stoppage of the loom and at least one of the cycle number in the repeat of the shedding pattern and the stop time of the loom and the kinds (functions) of the weft-bar-prevention units are adequately determined in accordance with the functions of the loom and the weave structure.

Claims

1. A method for preventing a weft bar from being formed when a loom (1) stops, the loom (1) being operated on the basis of a shedding pattern of which a single repeat includes at least three cycles of a main shaft (23), the method characterized by comprising:

a setting step of setting activation/non-activation of a plurality of kinds of weft-bar-prevention units (44) and activation quantity for when the weft-bar-prevention units (44) are activated in accordance with the combination of the cause of stoppage of the loom (1) and at least one of the cycle number in the repeat of the shedding pattern and a stop time for which the loom (1) has been stopped; and

a controlling step of controlling the weft-bar-prevention units (44) on the basis of the settings made in the setting step.

2. A method for preventing the weft bar from being formed when the loom (1) stops according to Claim 1, wherein the activation/non-activation of the weft-bar-prevention units (44) and the activation quantity for when the weft-bar-prevention units (44) are activated are set in accordance with the combination of the cause of stoppage of the loom (1), the cycle number in the repeat of the shedding pattern, and the stop time for which the loom (1) has been stopped.

3. A method for preventing the weft bar from being formed when the loom (1) stops according to one of Claims 1 and 2, wherein the weft-bar-prevention units (44) include a pre-start cloth-fell-moving unit (48) for moving a cloth fell (11) before restart of the loom (1) and a blank-beating unit (45) for performing a beat-up motion without a weft yarn being inserted after the restart of the loom (1), and the activation/non-activation of the pre-start cloth-fell-moving unit (48) and the blank-beating unit (45) and the activation quantity for when the pre-start cloth-fell-moving unit (48) and the blank-beating unit (45) are activated are set in accordance with said combination.

Drawing