EP1331295A2

EP1331295A2 - Method and apparatus for preventing weft bars in a loom

Info

Publication number: EP1331295A2
Application number: EP03001137A
Authority: EP
Inventors: Nobuhiro Araki; Takeshi Yonenaga; Makoto Takashima
Original assignee: Tsudakoma Industrial Co Ltd
Current assignee: Tsudakoma Corp
Priority date: 2002-01-29
Filing date: 2003-01-20
Publication date: 2003-07-30
Also published as: CN1446964A; EP1331295A3; JP2003221759A

Abstract

A weft bar prevention technique in a loom which moves a cloth fell position by moving a motor 34, 38 prior to starting operation of the loom is characterized in that correction amount data of the cloth fell position is preset per warp tension, and at the time of preparing to start the loom, the correction amount of the cloth fell position is determined according to the warp tension in a state that the loom is stopped on the basis of the correction amount data, and the cloth fell position is corrected on the basis of the correction amount.

Description

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a method and an apparatus for preventing weft bars in a loom which drives a motor and moves a cloth fell position prior to starting the operation.

Description of Prior Art

In a loom, a weft bar is caused as the warp stretches during the stoppage of the loom. To prevent such a weft bar from occurring, a motor is driven prior to starting operation to move (kick back) a cloth fell position in the direction of the warp.

In this type of loom, there is proposed a technique that a correction amount of a cloth fell position is preliminarily set as a function of correction of the cloth fell position with a stoppage period of the loom as a variable, the correction amount of the cloth fell position is calculated from the function of correction of the cloth fell position according to the stoppage period from the time of stopping till immediately before restarting, to correct the cloth fell position on the basis of the calculated correction amount of the cloth fell position (Japanese Patent Appln. Public Disclosure (KOKAI) No. 63-270842). In this conventional art, the correction amount of the cloth fell position is set per weaving condition such as kind of the weft, density of weaving, rotation frequency of a machine, etc.

In a loom, as the tension of the warp (that is, the warp tension) is changed, a stretch amount of the warp changes. The warp tension is sometimes actually changed to meet the operating condition of the loom. If an amount of motion (correction amount) of a correcting motion of the cloth fell position at the time of restarting of the loom is changed in correspondence to this change, a weft bar can be surely prevented.

In the conventional art, however, it is sometimes forgotten to reset the amount of correction of the cloth fell position according to the change in warp tension. In such a case, due to inappropriate set contents, weft bars are continuously generated, with the generation of weft bars or incorrect correction left unnoticed until fabric inspection, causing such a problem as to degrade the quality of the cloth with weft bars generated for a long period of time.

An object of the present invention is to enable to correct, in a loom which moves a cloth fell position in the direction of the warp prior to starting the loom, the cloth fell position before starting the loom to a desired cloth fell position even when the initial position differs according to variation in warp tension.

SUMMARY OF THE INVENTION

The method and apparatus for preventing weft bars according to the present invention is applied to a loom which moves the cloth fell position by driving a motor prior to starting operation of the loom.

Such a method of preventing weft bars includes steps of: presetting a correction amount data of the cloth position per warp tension; determining the correction amount data, at the time of preparing to start the loom, according to the warp tension in stoppage of the loom on the basis of the correction amount data; and correcting the cloth fell position on the basis of the correction amount.

The apparatus for preventing weft bars comprises: a setter for presetting correction amount data on a cloth fell position per warp tension; and a drive amount signal generating section for outputting the drive amount signal according to the correction amount data corresponding to the warp tension signal in the stoppage of the loom when a start preparation signal of the loom, the correction amount data and warp tension signal are inputted and the start preparation signal is inputted. The motor, driven on the basis of the drive amount signal, moves the cloth fell position.

In the above-mentioned method and apparatus for preventing weft bars, even if the cloth fell position is changed when the warp tension is changed or varied, the cloth fell position is corrected at least according to the warp tension in a kickback motion at the start to correct a stretch of the warp, so that the cloth fell position at the first beating is corrected to a predetermined position. Therefore, even if a stretch of the warp due to the warp tension occurs during stoppage of the loom, the cloth fell position is corrected to a predetermined position, thereby preventing occurrence of weft bars.

The correction amount can be determined on the basis of the warp tension immediately before the loom stops. The warp tension here includes anything associated with the tension factor during stoppage of the loom among the warp tension when the loom is under operation, such as the warp tension detected immediately before stopping, target tension immediately before stopping in warp tension control, and the like. By doing so, setting of the correction amount data is simplified.

The correction amount can be determined on the basis of the warp tension detected during stoppage of the loom. By this, since the cloth fell position is controlled based on the actual warp tension, accuracy in correction of the cloth fell position is improved.

The correction data amount can be set in correspondence with the warp tension immediately after the loom stops and a difference between the warp tension immediately after stopping and the warp tension immediately before preparing to start, and the correction amount can be determined on the basis of a difference between the warp tension detected immediately after stopping and the warp tension detected immediately before the preparation to start. By doing so, the cloth fell position is controlled on the basis of, in addition to the warp tension immediately after stopping, the difference in the actual warp tension from immediately after stopping till immediately before preparation to start, so that accuracy in correction of the cloth fell position is improved.

The correction amount data is set in correspondence with the warp tension and the time of stopping of the loom, and the correction amount can be determined on the basis of the warp tension and the time from stopping of the loom till immediately before preparation to start. By doing so, a time factor is further added, so that accuracy in correction of the cloth fell position is improved.

The correction amount data is set in correspondence with the warp tension and the lapse of time, and the correction amount can be determined by obtaining the correction amount data corresponding to the warp tension which acts on the warp from stopping of the loom till immediately before preparation to start at every warp tension and adding the obtained correction amount data. By this, even if the warp tension varies due to the lapse of stoppage time and the stretch amount of the warp changes due to the varying warp tension, more accurate correction amount can be obtained.

The length of action period may be obtained from recorded time by, for example, monitoring the warp tension all the time during stoppage while actuating a timer, recording the time whenever the warp tension changes, or can be obtained by monitoring the warp tension at every given time during stoppage, supposing the count value corresponding to the warp tension at the time of monitoring as +1, and supposing the final count value as the action time.

The method of preventing weft bars further comprises setting a reference cloth fell position correction amount depending on weft bars, and the correction amount can be determined by adding the correction amount data and the reference cloth fell position correction amount. Thus, it is sufficient to correct only the reference cloth fell position correction amount with reference to the state of a fabric, thereby simplifying setting of the correction amount data and the reference cloth fell position correction amount.

The motor may be a drive motor of a cloth take-up device or a drive motor of a warp let-off device.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a block diagram showing an embodiment of the major part of a loom provided with an apparatus for preventing weft bars according to the present invention.

Fig. 2 is a block diagram showing an embodiment of a drive amount signal generating section.

Fig. 3 is a chart showing a waveform of a signal in the embodiment shown in Fig. 1 and showing an embodiment of a kickback motion.

Fig. 4 is a graph and a table showing a first embodiment of the correction amount data.

Fig. 5 is a table showing a second embodiment of the correction amount data.

Fig. 6 is a graph and a table showing a third embodiment of the correction amount data.

Fig. 7 is a table and a graph showing a fourth embodiment of the correction amount data.

Fig. 8 is a block diagram showing another embodiment of the drive amount signal generating section.

PREFERRED EMBODIMENT OF THE INVENTION

Referring to Figs. 1 and 2, in a loom 10, the warp 12 is connected from a let-off beam 14 around which the warp is wound, to a cloth fell 22 via a tension roller 16, a plurality of healds 18 and a reed 20. A woven cloth 24 reaches cloth roller 28 from the cloth fell 22 through a guide roller 26, and is let off to a cloth winding beam 32 by the cloth roller 28 and a pair of press rolls 30, and is taken up by the cloth winding beam 32.

The let-off beam 14, rotated by a let-off motor 34 includes a motor such as an AC servo motor through a decelerator 36, lets off a plurality of warps 12 in a form of a warp sheet. The cloth roller 28, rotated by as take-up motor 38, which is a motor such as an AC servo motor, lets off the woven cloth 24 to the cloth winding beam 32. The

motors

34, 38 are driven in correspondence with rotation of a main shaft (not shown) of the loom.

Though not shown, each heald 18 is reciprocated upward and downward by a motion converting mechanism which receives rotation of a main shaft motor or a motor for exclusive use, and opens the warp 12 vertically. The reed 20 is oscillated by the motion converting mechanism which receives rotation of the main shaft motor or the motor for exclusive use, and beats the weft inserted into the opening or shedding of the warp 12 against the cloth fell 22.

The loom 10 rotates in forward direction or reverse direction the let-off motor 34, reels out the warp 12 from the let-off beam 14 or taking up the warp 12 around the let-off beam 14, the position of the cloth fell 22 (cloth fell position) moves in the moving direction of the warp 12 forward (toward the side of the guide roller 26) or backward (toward the side of the tension roller 16).

The warp let-off device for driving the let-off motor 34 includes an operation control section 40 for controlling the rotation speed of the let-off motor 34, a kickback control section or a drive amount signal generating section 42 for moving the position of the cloth fell 22 forward or backward, and a drive section 44 for driving the let-off motor 34.

An operation signal S1 is a signal representing whether or not the loom 10 is running as shown in Fig. 3(C), and is fed from a main controller not shown to the operation control section 40. The tension acting on the warp 12 can be obtained with the force acting on the tension roller 16 detected by a tension sensor 46, and the obtained tension is fed as a tension signal S2 as shown in Fig. 3(E) to the operation control section 40 and the drive amount signal generating section 42.

The roll diameter of the let-off beam 14, which gradually decreases as the warp 12 is let off, is detected by a roll diameter sensor 48 and fed to the drive section 44 as a roll diameter signal S3. The rotation angle of the let-off motor 34, detected by an encoder 50, is fed to the drive section 44 as a rotation angle signal .

A stop signal S4 is a signal for stopping the loom 10 as shown in Fig. 3(A) and is fed to the correction amount signal generating section 42 from the main controller. A start preparation signal S5 is a signal for having the loom 10 prepare to start as sown in Fig. 3(B) and is fed from the main controller to the correction amount signal generating section 42.

The operation control section 40 is connected to a first setter 52 where necessary data are preliminarily set for tension control of the warp 12 such as a target warp tension, density of beating, rotation frequency of the loom or the like. The operation control section 40 feeds to the drive section 44 a speed instruction signal S6 for settling a deviation between the target warp tension and the tension signal S2 while the loom is running, based on various data set in the first setter 52 and the operation signal S1. An example of the speed instruction signal S6 is shown in Fig. 3(G).

The correction signal generating section 42 is connected to the second setter 54 where the correction amount data of the cloth fell position in the moving direction of the warp 12 is preliminarily set at least per kind of yarn of the warp 12 and per warp tension, and constitutes an apparatus for preventing weft bars together with the second setter 54.

A warp tension T in the loom stoppage for obtaining the correction data, particularly a correction amount ΔP, can be used an actual tension value at an arbitrary time such as immediately before generation of the stop signal, immediately after stopping of the loom, during stoppage, immediately before starting, etc. The time detecting the warp tension T can be preferably an arbitrary time from immediately before the stop signal is generated till immediately before starting. The warp tension T, however, may be a target tension while the loom 10 is running. Details of the correction amount data are explained later with reference to Figs. 4 through 6.

The correction amount signal generating section 42 is provided with a correction amount output section 56 for outputting the correction amount ΔP upon receipt of the tension signal S2, the stop signal S4 as well as the start preparation signal S5, and a signal generating section 58 for outputting a drive amount signal S7 corresponding to the correction amount ΔP upon receipt of the start preparation signal S5 and the correction amount ΔP to the drive section 44.

Further, the correction amount output section 56 is provided with a memory 62 for storing temporary data necessary for outputting the correction amount ΔP as well as time data, and a clock generating section 60 for generating a clock pulse for measuring time.

The correction amount output section 56 starts detection (or calculation) of the warp tension by using the tension signal S2, the warp tension temporarily is stored in the memory 60, reads out from the second setter 52 the correction amount data corresponding to the warp tension detected by inputting of the start preparation signal S5, and outputs the correction amount ΔP corresponding to the warp tension on the basis of the correction amount data readout.

The signal generating section 58, when the start preparation signal S5 is inputted, outputs the drive amount signal S7 corresponding to the correction amount ΔP in a form of the speed instruction signal. Examples of the drive amount signal S7 are shown in Fig. 3(H) through (K).

The drive section 44 sums up the speed instruction signal S6 to be inputted and the drive amount signal S7 in an adder 64, and corrects the addition signal S8 by using the roll diameter signal S3 of the let-off beam 14 in a roll diameter correction circuit 66. The addition signal S8 is corrected so that, for example, the greater the roll diameter d is, the smaller the rotation amount of the let-off motor 34 can become; in other words, regardless of the size of the roll diameter, the warp of a length corresponding to the drive amount signal S7 can be reeled out from the warp beam. The corrected signal S9 is fed to the drive circuit 68 as a final speed instruction signal S9.

The drive circuit 68 feeds the electric current corresponding to the speed instruction signal S9 to the let-off motor 34. The drive circuit 68 constitutes a servo drive circuit upon receipt of the rotation angle signal  of the let-off motor 34. Therefore, the drive circuit 68 outputs the electric current of a phase corresponding to the rotation angle of the let-off motor 34, and upon detection of the rotation amount (or rotation speed) of the let-off motor 34 per unit hour, performs a control to make the rotation amount of the let-off motor 34 approach to the speed instruction signal S9.

When the loom 10 is normally operating, the drive amount signal generating section 42 is maintained in an inoperable state. Therefore, The let-off motor 34 reels out the warp 12 with the speed instruction signal S6 from the operation control section 40 controlled by the speed instruction S9 which was corrected at the roll diameter signal S2 from the roll diameter sensor 48. In the meanwhile, the operation signal S1 is kept to be ON, and the stop signal S4 is kept to be OFF.

If a cause for stopping occurs at a timing as shown in Fig. 3, the stop signal S4 turns ON as shown in Fig. 3(A), while the operation signal S5 turns OFF as shown in Fig. 3(C). By this, the speed instruction signal S6 from the operation control section 40 gradually lowers as shown in Fig. 3(G), the loom 10 enters a stopping motion as shown in Fig. 3(F), and the rotation frequency of the loom 10 gradually lowers as shown in Fig. 3(D). The speed instruction signal S6 and the rotation frequency of the loom 10 finally become zero.

If the cause for stopping is settled and the start button (or start preparation button) is pressed down, the start preparation signal S5 turns ON as shown in Fig. 3(B), so that the drive amount signal generating section 42 works.

By this, the correction amount outputting section 56 out puts the correction amount ΔP according to the tension of the warp 12 at an arbitrary timing from immediately before the loom stops till immediately before starting as well as the kind of yarn and shifts to the start preparation motion or the kickback motion.

During the kickback motion, the speed instruction signal S6 from the operation control section 40 is maintained at zero. As a result, during the kickback motion, only the drive signal S7 from the signal generating section 58 is fed, and the let-off motor 34, controlled by the speed instruction signal S9 corrected at the roll diameter signal S2 from the roll diameter sensor 48, rotates the warp beam 14.

Thereafter, when the operation signal S1 is turned ON as shown in Fig. 3(C), the drive amount signal generating section 42 is switched to an inoperable state, and instead, the operation control section 40 is actuated to gradually increase the speed instruction signal S6 as shown in Fig. 3(G), thereby gradually increasing the rotation frequency of the loom 10 as shown in Fig. 3(D).

The kickback motion is made by selectively rotating in the normal direction and the opposite direction as shown in Fig. 3(H) through (K). In Fig. 3(H) through (K), the solid line shows an example of the drive amount signal for making the kickback motion according to the warp tension (or according to stretch of the warp 12), and the dotted line shows an example of the conventional drive amount signal for making the kickback motion irrespective of the warp tension.

Both drive amount signals S7 as shown in Fig. 3(H) and (I), normally rotating the let-off motor 34, are to correct the cloth fell position and, in more detail, to correct the reverse drive amount in the kickback motion by the warp tension. Both drive amount signals S7 as shown in Fig. 3(J) and (K), reversing the let-off motor 34, are to correct the cloth fell position and in more detail, to correct the reverse drive amount in the kickback motion by the warp tension.

According to the drive amount signal S7 as shown in Fig. 3(H), the let-off motor 34 is rotated by a predetermined amount ΔPa according to the correction amount ΔP only in the direction of the normal (forward) rotation.

According to the drive amount signal S7 as shown in Fig. 3(I), the let-off motor 34 is reversed (rotated in reverse direction ) by the predetermined amount ΔPa and then normally rotated in forward direction by a value (2ΔPa) which is a sum of a value correcting an extra reverse amount (-ΔPa) and the predetermined amount ΔPa. Thus, after raising the warp tension by the reverse drive, the cloth fell position can be more surely moved so as to normally rotate.

According to the drive amount signal S7 as shown in Fig. 3(J), the let-off motor 34 is rotated by the doubled predetermined amount ΔPa (that is, 2 ΔPa) in the reverse direction and then is normally rotated by the predetermined amount ΔPa so as to correct the extra reverse amount (-Δ Pa). Namely, in place of correcting the drive amount toward the normal rotation side as shown in Fig. 3(I), the drive amount toward the reverse side can also be corrected.

According to the drive amount signal S7 as shown in Fig. 3(K), the let-off motor 34 is normally rotated by the predetermined amount ΔPa and then reversed by the doubled predetermined amount ΔPa (that is, 2 Δ Pa) so as to correct an extra normal rotation amount (+ ΔPa). Namely, it is also possible to change the order of the time, which is execute the let-off motor 34 rotating in forward direction before and after at kickback motion.

However, the normal rotation amount and the reverse amount of the let-off motor 34 are not necessarily an integral multitude of the predetermined amount ΔPa according to the correction amount ΔP, but it suffices that, as a result of rotating or reversing the let-off motor 34, the rotation amount of the let-off motor 34, that is, the movement amount of the cloth fell position becomes the predetermined amount ΔPa. Also, in Fig. 3(H) through (K), either one of the rotation side and the reversal side is corrected, but both may be corrected.

In the following, explanation is given about the correction amount data set in the second setter 54 with reference to Figs. 4 through 6.

Fig. 4 shows an example of setting the correction amount A P to correspond to the warp tension per warp tension T without making the loom stoppage time a parameter of the correction amount ΔP. In this case, the warp tension T for obtaining the correction amount ΔP may be, as mentioned already, an actual tension value at an arbitrary timing such as immediately before the stop signal generates, immediately after the loom stops, during stoppage, immediately before starting, or the like, or may be a target tension while the loom 10 is running.

In the embodiment as shown in Fig. 4, the correction amount Δ P may be set, as shown in Fig. 4(A), as a formula per warp tension T to calculate the correction amount A P or, as shown in Fig. 4(B), may be set as a table per warp tension T. Such a group of formulae or tables is provided per kind of warp. The correction amount ΔP is determined by reading out a value corresponding the warp tension at the start preparation time.

The embodiment as shown in Fig. 4 can be applied in case of the warp whose stretch amount does not influence on the length of the stoppage time or in case the time for promptly restarting the loom is not taken into account, which simplifies the constitution of the second setter and facilitates setting of the correction amount data to be set.

In the embodiment as shown in Fig. 4, if the correction amount ΔP is set per actual tension value at an arbitrary time from immediately after stopping of the loom till immediately before starting, the cloth fell position is controlled on the basis of the actual warp tension, and the accuracy in compensating the cloth fell position is improved.

Fig. 5 shows examples of setting the correction amount ΔP, without making the loom stoppage time a parameter of the correction amount ΔP, but by having it correspond to the warp tension immediately after the loom stops and the deviation amount, that is a difference ΔT, of the warp tension immediately before the start preparation relative to the warp tension immediately after the loom stops per warp tension immediately after stopping (or immediately before the start preparation) T1, T2, T3 ....

In the embodiment as shown in Fig. 5, the correction amount Δ P is set as a table per warp tension T1, T2, T3 ... immediately after stopping, but it may be set as a formula per warp tension immediately after stopping for calculating the correction amount ΔP. Such a group of tables or formulae is provided per kind of warp. The correction amount ΔP is determined by reading out, at the start timing a value corresponding to the warp tension immediately after the loom stops and to the difference ΔT in warp tension immediately before the start preparation relative to the warp tension immediately after stopping.

Fig. 6 shows an example of making, in the embodiment shown in Fig. 4, not only the warp tension T but also the time of loom stoppage a parameter of the correction amount ΔP. In this case, the correction amount ΔP is set per warp tension T1, T2, T3 ... in correspondence with the lapsed time t from an arbitrary time point determined for the loom stoppage till immediately before the start preparation. The start point of the lapsed time t can be, for example, immediately after stopping of the loom, the time for detecting the warp tension, starting time of the detection of the warp tension and the like.

In the embodiment as shown in Fig. 6 also, the correction amount ΔP may be set as a formula per warp tension T1, T2, T3 ... for calculating the correction amount ΔP as shown in Fig. 6(A), or may be set as a table per warp tension T1, T2, T3 ... as shown in Fig. 6(B). Such a group or formulae or a group of tables is provided per kind of warp.

In the embodiment as shown in Fig. 6, the correction amount Δ P is determined by reading out a value each corresponding to the warp tension T and the lapsed time t at the time of start preparation. Thus, since a time factor t is further included in the warp tension T to obtaine the correction amount ΔP, the correction accuracy of the cloth fell position is improved.

Fig. 7 shows an example wherein the actual tension of the warp is continuously detected during stoppage of the loom, the time the detected actual tension worked on the warp is measured per detected actual tension; the measured actual tension is stored per the medium value T1, T2, T3 ... within the range of predetermined actual tension as shown in Fig. 7(A); the correction amount ΔP1, ΔP2, ΔP3 ... corresponding to every warp tension is obtained; and the correction amount ΔP is determined by adding the obtained correction amount ΔP1, ΔP2, ΔP3 ...

In the case of the embodiment as shown in Fig. 7, the correction amounts ΔP1, ΔP2, ΔP3 ... are, for example, as shown in Fig. 7(B), set in the form of a formula (or a table) per medium value T1, T2, T3 ... in the range of the predetermined actual tension. Such a formula group (or a table group) is provided per kind of warp.

According to the embodiment as shown in Fig. 7, even if the warp tension changes, the correction amount ΔP corresponding to the change can be obtained, thereby improving the correction accuracy of the cloth fell position and preventing generation of the cloth fell more surely.

As an example of a modification of the embodiment as shown in Fig. 7, it is possible to detect the warp tension at every given time during stoppage of the loom, add1 to the counted value in the range of the actual tension every time the warp tension T1, T2, T3 ... in the same range of the actual tension is detected, obtain the correction amount ΔP1, ΔP2, ΔP3 ... of the warp tension T1, T2, T3 ... , and add them to make the correction amount ΔP.

Namely, by detecting the warp tension periodically, counting the frequency of the warp tension of the same value (medium value) acts on the warp, and replace the period (time) in the embodiment as shown in Fig. 7 with the counted values. In more detail, by shortening the detection cycle of the tension, the same action and effect as the embodiment in Fig. 7 can be obtained.

Referring to Fig. 8, the drive amount signal generating section 70 includes a third setter 72 which enables an operator to set the reference cloth fell position correction amount, seeing the state of the weft bars generated in the cloth at the time of starting preparation. The set reference cloth fell position correction amount is added to the correction amount ΔP outputted from the correction amount outputting section 56 in an adding section 74, and fed to the signal generating section 58.

According to the drive amount signal generating section 70, it suffices for an operator to see the state of the cloth and only correct the reference cloth fell position correction amount, so that setting of the correction amount data and the reference cloth fell position correction amount is simplified. Further, it is not necessary to input all the data every time a cloth fell is generated.

The present invention can be applied not only to a loom which maintains a target tension constant, but also to a loom which positively changes a target tension to correspond to a fabric texture, and not only to a warp let-off device but also to a cloth take-up device. In the case of a cloth take-up device, it is not necessary to input the tension signal S2 to the operation control section 40 in the embodiment as shown in Fig. 1. In this case, it is sufficient to make the speed instruction signal S6 synchronizing with the rotation of the loom outputted from the operation control section and to directly connect the adder 64 and the drive circuit 68, omitting the roll diameter correction circuit 66. Accordingly, the present invention may be applied to at least one of the warp let-off device and the cloth take-up device or to both of them.

In place of controlling the motor for driving the let-off device or the take-up device both during operation of the loom and at the time of kick-back motion, it is possible to provide a motor exclusively used for kick-back controlled by the drive amount

signal generating section

42 or 70 only at the time of the kick-back motion and a motor controlled by the operation control section 40 at the time of operation of the loom.

The present invention is not limited to the above embodiments but can be variously modified without deviating from its purpose.

Claims

A method for preventing weft bars in a loom which moves a cloth fell position by driving a motor 34, 38 prior to starting operation of the loom, comprising steps of: presetting correction amount data of said cloth fell position per warp tension determining the correction amount of said cloth fell position to correct said cloth fell position on the basis of the correction amount and at the time of start preparation of the loom.
A method for preventing weft bars in a loom as defined in claim 1, wherein said correction amount is decided on the basis of the warp tension immediately before the loom stops.
A method for preventing weft bars in a loom as defined in claim 1, wherein said correction amount is determined on the basis of the warp tension detected during stoppage of the loom.
A method for preventing weft bars in a loom as defined in claim 3, wherein said correction amount data is set in correspondence with the warp tension immediately after the loom stops, and a difference between the warp tension immediately after the loom stops and the warp tension immediately before the start preparation, and wherein said correction amount is determined on the basis of the warp tension detected immediately after the loom stops, and a difference between the warp tension detected immediately after the loom stops and the warp tension detected immediately before the preparation to start.
A method for preventing weft bars in a loom as defined in any one of claims 1 through 4, wherein said correction amount data is set in correspondence with said warp tension and the loom stoppage time, and wherein said correction amount is determined on the basis of said warp tension and the time from when the loom stops till immediately before preparation to start.
A method for preventing weft bars in a loom as defined in claim 3, wherein said correction amount data are set in correspondence with said warp tension and the lapsed time, and wherein said correction amount is determined by obtaining said correction amount data corresponding to the warp tension having acted on the warp 12 from the loom stoppage till immediately before the start preparation and the length of its action period per warp tension and adding the obtained correction amount data.
A method for preventing weft bars in a loom as defined in any one of claims 1 through 6, further comprising steps of setting a reference cloth fell position correction amount according to a weft bar, wherein said correction amount is determined by adding said correction amount data and said reference correction amount of the cloth fell position.
A method for preventing weft bars in a loom as defined in any one of claims 1 through 7, wherein said motor is a drive motor of the cloth take-up device or a drive motor of the warp let-off device.
An apparatus for preventing weft bars in a loom for moving a cloth fell position by driving a motor on the basis of a drive amount signal, comprising: a setter 54 with the correction amount data of the cloth fell position preset; and a drive amount signal generating section 42, 70 in which a signal for start preparation and said correction data are inputted, and, by the input of said signal for start preparation, outputting said drive amount signal according to said correction amount data,
wherein, said correction amount data is set per warp tension in said setter 54, and
wherein said drive amount signal generating section 42, 70 outputs said drive amount signal according to the correction amount data corresponding to said warp tension signal in stoppage of the loom, with said signal for the start preparation inputted upon receipt of the warp tension signal.