Apparatus for preventing weaving bar in a loom

Abstract: The apparatus prevents formation of a swelled weaving bar which is caused by interference of the reed and the cloth fell during slow rotation of the loom in forward or reverse direction. The let-off motor (1) is rotated at a slow rate in forward direction in advance of the subsequent slow forward or reverse rotation of the main motor (M) for removal of a faulty weft yarn. Operation of the let-off motor (1) is controlled by a computer control (C) and the motor is forward rotated for a predetermined amount so as to displace the cloth fell (W₁) toward the fabric (W, or retract it away from the swinging area of the reed 6. In restarting the weaving operation, the let-off motor (1) is slow rotated in reverse direction to return the cloth fell to its original position. The rotation of the let-off motor (1) is monitored by the rotary encoder (1a) incorporated therein and connected to the computer control (C 1a) so that the control (C) can determine whether or not the cloth fell displacement is accomplished properly. In the event of any abnormality in the cloth fell displacement, the warp tension detected by the load cell (15) is restored to the tension (F) detected by the load cell immediately before the commencement of the cloth fell displacement.

Description: The present invention relates to an apparatus in a weaving loom for preventing formation of a weaving bar on a woven fabric caused by cloth fell beating by the reed during slow forwgrd or reverse rotation ef the foom which is usually performed subsequently to a stop of weaving operation. Restarting a weaving loom after it is once stopped either manually or automatically in response to a break of any warp tends cause a light weaving bar on a woven fabric because of insufficient force with which the reed beats up the cloth at a start-up of the loom. On the other hand, a heavy weaving bar tends to result when the loom is restarted after it is stopped automatically in response to a failure in weft insertion and then rotated slowly in reverse direction for removal of that faulty weft, because the weave of the fabric adjacent the cloth fell is loosened during the above slow reverse rotation of the loom and hence displaced toward the loom from its normal position. Apparatuses designed specifically to prevent formation of such weaving bars are disclosed, for example, by Publication Japanese Patent Application No. 60-231849 (1985), upon which the preamble portion of Claim 1 is based, Publication of Japanese Patent Application No. 6155241 (1986), Publication of Japanese Patent Application No. 62-263352 (1987} and Publication of Japanese Utility Model Application No. 63-94988 (1988). One form of the weaving bar appearing on the fabric is so-called "Ayamakura (Japanese)", i.e., a weaving bar in which wefts are dislocated alternately up and down with respect to the plane of the fabric, thereby forming a swelled defective portion on the fabric surface. This type of weaving bar, which tends to be formed on a twill fabric, is caused when the cloth fell of a fabric is beaten up by the reed during slow rotation of the loom in either forward or reverse direction. For the purpose of convenience in describing the invention, this kind of weaving defect is referred to as swelled weaving bar hereinafter. None of the above conventional apparatuses are capable of preventing the formation of such swelled weaving bars. Therefore, it is an object of the present invention to provide an apparatus which can prevent successfully the formation of the swelled weaving bar on a woven fabric. To achieve the above object, the present invention, as claimed in Claim 1, provides an apparatus in a jet loom comprising displacing means for displacing the position of cloth fell of a woven fabric along warps by changing the tension of such warps, control means for controlling the driving amount of safd cloth fell displacing means, detecting means for detecting the driving amount of said cloth fell displaying means, and detecting means for detecting the tension of said warps, said control maans having first function of driving said displacing megns to displace the cloth fell for a predetermined distance toward the fabric from the normal position thereof in advance of rotating the loom at a slow rate in forward or reverse direction, second function of driving said displacing means to move the cloth fell back to said normal position after completion of said slow rotation of the loom in the forward or reverse direction, third function of determining whether or not the cloth fell displacement has been accomplished properly from the information from said driving amount detecting means representative of detected driving amount of said cloth fell displacing means and, in the event of a failure in the proper cloth fell displacement, driving said cloth fell displacing means until the warps are tensioned to such an extent that corresponds to the tension detected by said warp tension detecting means immediately before the commencement of said cloth fell displacement. Further embodiments of the invention are claimed in Claims 2-6. When the loom is rotated at a slow rate in forward or reverse direction, its reed is moved swinging in synchronism with the loom rotation. If the cloth fell of a woven fabric is located at its normal position, the cloth fell will be bean by the reed during the above slow forward or reverse rotation of tha loom. By retracting the cloth fell away from its normal position toward the fabric, the cloth fell can be free from the beating action by the reed, with the result that formation of a swelled weaving bar on the fabric can be prevented. If the cloth fell should fail to be displaced for the desired amount, the control means causes the cloth fell displacing means to be driven reverse from the information representative of abnormality and transmitted from the driving amount detecting means. This reverse driving is continued until the warp tension becomes the tension detected by the warp tension detecting means immediately before the commencement of the cloth fell displacement, and the cloth fell is returned to its original position, accordingly. The following will describe in detail an embodiment of the apparatus according to the invention while making reference to FIGS. 1 through 21 which show the following: FIG. 1 is a schematic view showing the weaving loom; FIG. 2 is an enlargad view showing the positional relation between the reed and the cloth fell when the loom is just stopped; FIG. 3 is an enlarged view showing the positional relation between the reed and the cloth fell when the cloth fell is retracted from the beating-up position; FIG. 4 is a graph illustrating the cloth fell displacement controlling; FIG. 5 is a graph illustrating the cloth fell displacement controlling; FIG. 6 is a graph illustrating the cloth fell position shifting control; FIG. 7 is part of a flow chart of the cloth fell displacement controlling program; FIG. 8 is part of a flow chart of the cloth fell displacement controlling program; FIG. 9 is part of a flow chart of the cloth fell displacement controlling program; FIG. 10 is part of a flow chart of the cloth fell displacement controlling program; FIG. 11 is part of a flow chart of the cloth fell displacement controlling program; FIG. 12 is part of a flow chart of the cloth fell displacement controlling program; FIG. 13 is part of a flow chart of the cloth fell displacement controlling program; FIG. 14 is part of a flow chart of the cloth fell displacement controlling program; FIG. 15 is part of a flow chart of the cloth fell displacement controlling program; FIG. 10 is part of a flow chart of the cloth fell displacement controlling program; FIG: 17 is part of a flow chart of the cloth fell displacement controlling program; FIG. 18 is part of a flow chart of the cloth fell displacement controlling program; FIG. 19 is part of a flow chart of the cloth fell displacement controlling program; FIG. 20 is part of a flow chart of the cloth fell displacement controlling program; FIG. 21 is part of a flow chart of the cloth fell displacement controlling program. Referring to FIG. 1 showing a schematic view of a typical weaving loom, reference symbol M designates a main motor whose operation is controlled by a computer control C. Reference numeral 1 depicts a let-off motor provided independently of the main motor M and operable reversibly for driving a warp beam 2. An array of warps T unwound from the warp beam 2 extends over a back roller 3 and tension roller 4 and then are passed through healds 5 and a reed 6 in a known manner. A woven fabric W extends over an extension bar 7, surface roller 8, press roller 9 and crease-removing guide member 10 and is wound round a cloth roller 11. The tension roller 4 is mounted at one end of a tension lever 12, the other end of which has a tension spring 13 to urge the tension roller 4 in such direction that applies a predetermined tension to the warps T. The tension lever 12 is rotatably supported at one end of a detecting lever 14, the other end of which is operatively connected to a load cell 15 for detecting the warp tension. The warp tension is transmitted to the load cell 15 by way of the tension roller 4, tension lever 12 and detecting lever 14, and the load cell 15 is adapted to generate to the computer control C an electrical signal corresponding to the magnitude of the warp tension detected by the load cell. The computer control C is operable to control the rotational speed of the let-off motor 1 according to the information from comparison between a predetermined reference tension and the above electrical signal representativs of the warp tension being detected by the load cell 15 and also to the information of the current warp beam diameter which can bs datermined by a detection signal transmitted from a rotary encoder 16 for mlnitoring the rotational angle of the loom. Because the warp tension is adjusted during the weaving operation by controlling the rotational speed of the let-off motor 1 so as to maintain the tension substantially constant, formation of a weaving bar during the weaving operation can be prevented. A start switch 17 is connected to the computer control C and the latter commands the let-off motor 1 to rotate in forward direction in response to an ON signal from that start switch. A rotary encoder 1a is incorporated in the let-off motor 1 for monitoring the rotational speed thereof and transmitting sfgnals to the control C, which in turn feedback-controls the rotational speed of the let-off motor 1 according to the detection signals from the rotary encoder 1a. The surface roller 8 is operatively connected to a winding motor 18 provided independently of the main motor M and operable reversibly, and the rotational speed of the winding motor 18 is feedback-controlled by the control C in response to detection signals transmitted from a rotary encoder 18a incorporated in the motor for monitoring its rotational speed. An input device 19 is connected to the computer control C for inputting data of cloth fell displacement quantity, and the computer control C is operable to execute the cloth fell displacement controlling program shown by way of flow chart in FIGS. 7 through 21 on the basis of the above input data. The computer control C commands a stop of the main motor M, let-off motor 1 and winding motor in response to a stop signal representative of any abnormglity in the weaving operation and transmitted from a weft inser:tion failure detector 20 or a warp break detector 21, both of which are connected to'ths control C. The control C issues the same stop command in response to an ON signal which is transmitted thereto from a manual stop switch 22. When such stop command is provided, the motors M, 1, 18 are stopped synchronously as indicated by lines C₁, C₂, C₃ in FIG. 4, and the warp letting-off and cloth winding operations ara stopped, accordingly, with the reed 6 brought to a stop at a position immediately before its beat-up position as shown fn FIG. 2. The computer control C stores the data of warp tension F then detscted by the load cell 15. If the stop signal is one from the weft insertion failure detector 20, or stop signal S₁, the computer control C then commands the let-off rotor 1 to rotate at a slow rate in forward direction for a quantity Q′ the data of which has been inputted into the control C from the input device 19. That is, when the stop signal 51 is generated because of a failure in weft insertion, the let-off motor 1 is slow-rotated forward for in advance of the subsequent slow reverse rotation of the main motor M for removal of the faulty weft which has caused the detector 20 to generate the stop signal 51. As the result of this slow forward rotation of the let-off motor 1, the warps T are allowed to be fed forward and the warp tension is reduced, with simultaneous displacement of the cloth fell W₁ for adistance ρ from its normal position toward the fabric W, as shown in FIG. 3. The faulty weft can be removed from the fabric in a known manner by using such an apparatus as disclosed by Publication of Japanese Patent Application No. 2-61138 (1990). That is, the loom is rotated reverse for gbout one turn and a half to allow the faulty weft to be released from the grip by the warps for removal of the weft. It is noted that during this reverse rotation of the loom the reed 6 is movad swinging by way of the normal position of the cloth fell W₁, namaly the beat-up position of the reed. After the above slow forward rotation of the let-off motor 1 for displacement of the cloth fell W₁, the main motor M is rotated reverse at a slow rate for about one turn and a half as indicated by line e₁ in FIG. 4 to place the loom where a warp shed is formed with maximum opening. With the shed thus wide open, the faulty weft on the cloth fell W₁ is released from the warps T, thus making it possible for the faulty weft to be removed easily. In synchronism with the above slow reverse rotation e₁ of the main motor M, the let-off motor 1 and the winding motor 18 are also slow-rotated in the same reverse direction as indicated by lines q₁ and r₁ in FIG. 4. Such synchronous reverse rotation of the motors 1, 18 allows the warps T to be wound back, or rewound, and the fabric W to be moved back, or unwound; for an amount proportional to the reverse rotation of the loom, respectively. Such synchronous rewindirig of the warps T and unwinding of the fabric.W in turn allows the cloth fell W₁ to be shifted for a distance corresponding to the reverse rotation of the loom. As stated earlier, while the loom is.being slow-rotated reverse for about one turn and a half, the reed 6 is moved from its stopped position, shown in FIG. 2, to its most retracted position, shown by phantom line in FIG. 3, by way of the normal cloth fell position P, or the beat-up position of the reed 6. If the cloth fell W₁ were at this beat-up position P, it would be beaten by the reed 6. However, because the cloth fell W₁ is displaced or retracted toward the fabric W from the beat-up position P in advance of the reversing operation of the loom, the cloth fell W₁ is free from beating by the reed 6: Therefore, those wefts which are adjacent the cloth fell W₁ woven only loosely will not be subjected to the disturbance by the reed beating. Thus, formation of the aforementioned swelled weaving bar can be prevented successfully. After the procedure for removing the faulty weft has been completed, the main motor M is rotated at a slow rate in reverse direction again as indicated by line e₂ to move the loom to its weaving-start position immediately before the beatup position to avoid insufficient force in beating-up the cloth at the subsequent start-up of the weaving operation. Though the reed 6 is moved by way of the beat-up position P during this reverse rotatiori of the loom, the cloth fell W1 will receive no beatfng-up action by the reed 6 because the cloth fell is set back from the position P. In synchronism with the above reverse rotation of the main motor M, ths lat-off motor 1 and winding motor 18 are also rotated in the same reverse direction as indicated by lines q₂ and r₂ in FIG. 4. By such reversing operation of the motors 1, 18, the cloth felI W₁ is moved back for a distance corresponding to the slow reverse rotation of the loom to its weavingstart position. As an incidental matter in connection with moving the loom to its weaving-start position, a method is available by which the main motor M may be rotated at a slow rate not in reverse direction but in forward direction to place the loom to the above weaving-start position. In such a case, the let-off motor 1 and the winding motor 18 are both rotated in the same forward direction. After the reversing of the loom to its weaving-start position has been completed, the let-sff motor 1 is rotated reverse at a slow rate for Q⁻ so that the warps T are pulled back thereby to shift the cloth fell W₁ back to its original position P. As it is now apparent from the description so far, the computer control C is provided with a first controlling function of driving the let-off motor 1, as the displacing means, to displace the cloth fell W₁ from its normal position P toward the woven fabric W in advance of the slow reverse rotation of the loom, and a second controlling function of displacing the cloth fell W₁ back to its original position P after completion of the slow reverse rotation of the loom. With the cloth fell W₁ returned to its original position P, the computer control clears the data of the detected warp tension F. Subsequently, the main motor M, let-off motor 1 and winding motor 18 are set into operation synchronously as indicated by lines D₁, D₂, D₃ in FIG. 4, thus the normal weaving operation being resumed. Signal S₂ in FIG. 4 represents a stop signal which is generated by other causes than weft insertion failure, i.e. a stop signal which is generated when a warp break is detected by the warp break detector 21 or when the manual stop switch 21 is turned on. Responding to such stop signal S₂, the control C becomes ready to receive an ON signal from any one of the start switch 17, slow-reversing switch 23 and slow-forwarding switch 24. When a weaving flaw on the fabric W is to be removed, the slow-reversing switch 23 is turned on to generate an ON signal S₄, shown in FIG. 5, to the computer control C. Accordingly, the let-off motor 1 is rotated forward at a slow rate for Q⁺, thereby displacing the cloth fell W₁ toward the fabric W in advance of the subsequent slowreversing of the main motor M so that the cloth fell will not be beaten by the reed 6 when 11 it is moved to swing. After such displacement of the cloth fell W1, the main motor M, let-off motor 1 and winding motor 18 are operated in response to the ON state of the slow-reversing switch 23 to be rotated reverse at a slow rate in synchronism with each other is indicated by lines e₄, q₄, r₄. As the slow-reversing switch 23 is turned off, the motors M, 1; 18 are Stopped, which is then followed by slow reverse rotation of the let-off motor 1 for Q⁻. This reversing operation of the let-off motor 1 pulls back the warps T thereby to shift the cloth fell W₁ back to its original position P. Because the cloth fell.W₁ is thus kept retracted away from the reed's beating-up region during the slow-reversing of the loom for flaw removal, formation of a swelled weaving bar due to interference between the cloth fell : W1 and the reed 6 can be forestalled. In removing the flaws on the fabric W, the slowreversing switch 23 is operated ON/OFF for as many times as the number of defective wefts to be removed and, for the final adjustment of the cloth fell W₁ to move it back to its original position, the slow-forwarding switch 24 may be used. As shown in FIG. 6, the displacement of the cloth fell W₁ is performed in the same way in slow-forwarding the motors M, 1, 18 (as indicated by e₅, q₅, r₅) in response to ON/OFF signals 55 from the slow-forwarding switch 24 as in the slow reversing of the motors by use of the slow-reversing switch 23 as shown in FIG. 5. In case of a loom stop resulting from the weft insertion failure, the reversing operation of the loom to its weavingstart position is performed automatically. In case of a loom stop due to other causes than the weft insertion failure, however, reversing of the loom to its weaving-start position can be initiated by an ON signal S₃ transmitted from the manual start switch 17 to the control C. Displacement of the cloth fell W₁ in advance of the synchronous slow-reversing of the motors M, 1, 18, as inidicated by e₃, q₃, r₃, is done in the same way as in the above case, and it is moved back to its original position after the synchronous slow-reversing of the motors. Because the cloth fell W₁ is thus retrccted away from the beat-up position P, it will not be beaten by the reed 6 moving by way of the position P while the loom is being slow-reversed to its weaving-start position. The distance ρ for which the cloth fell W₁ is displaced from its normal position toward the fabric W depends on the kind of fabric to be woven, but it should be set at a minimum requirement to minimize a possible error in returning the cloth fell W₁ to its original position. If the cloth fell displacement should fail to be performed properly, e.g., if the let-off motor 1 has failed to be slow-rotated forward for the desired quantity Q⁺, as shown by line Q in FIG. 4, this abnormality is determined by the rotary encoder 1a monitoring the rotation of the let-off motor 1. Responding to a signal transmitted from the rotary encoder 1a and representative of such abnormalfty, the computer control C commands the let-off motor to be slow-rotated in reverse direction. Accordingly, the warps T are wound back thereby increasing their tension. The increasing tension is detected continuously by the load cell 15 and the information of such increasing warp tension is sent to the computer control C. Under the controlling of the control C, the slow-reversing of the let-off motor 1 is continued until the warp tension being detected reaches the.tension F which is previously stored in the control C and representative of the warp tension just before the commencement of the cloth fell displacement toward the fabric W: Thus, the computer control C has a third function of determining whether or not the cloth fell displacement has been accomplished properly from the information from the rotary encoder 1a and, in the event of abnormality of the displacement, driving the let-off motor 1 until the warp tension being detected by the lood cell 15 is increased to the stored warp tension F corresponding to the tension detected immediately before the commencement of the cloth fell displacement. As the warp tension is restored to the tension F, the cloth fell W₁ is brought back to its original positfon P. After such restoration of the warp tension, no removal of a weft is followed, but the control C activates an alarming device 25. Because no slow-reversing of the loom for the removal of a faulty weft is done when the cloth fell W₁ stays within the reed swinging area, the cloth fell W₁ will not be beaten by the reed 6. Furthermore, because the cloth fell W₁ is returned to its original position P by the restoration of the warp tension, merely turning on the start switch 17 after manually removing the faulty weft will position the cloth fell W₁ in place and set the loom into weaving operation as in the previous case. Thus, even in case of a possible failure in proper cloth fell displacement, the weaving operation can be restarted without intervention of manual adjustment of the cloth fell position. Also in the event of any abnormality occurring in displacing the cloth fell W₁ back to its original position, the above warp tension restoration is performed in the same manner and the device 25 is energized to alarm the loom operator of the abnormality. Turning on the start switch 17 after the warp tension restoration, the cloth fell W₁ is positioned originally and the loom set into weaving operation. A possible cause of the cloth fell displacement failure, i.e., failure of the let-off motor 1 to rotate forward or reverse for the desired quantity Q⁺ or Q⁻ , includes a control communication error, or such a case in which the cloth fell displacement by feedback controlling has failed to be accomplished in a predetermined time. The slow reverse rotation of the let-off motor 1 for the warp tension restoration is feedback-controlled on the basis of the detected warp tension. The possibility of simultaneous fault with this feedback-controlling and the other feedback-controlling from the rotation detected by the rotary encoder 1a is extremely low. Therefore, the warp tension restoration subsequent to a failure in the cloth fell displacement can be performed with a high degree of certainty and the procedures to be performed subsequent to the failure can be carried out with smoothness. It is to be understood that the present invention is not limited to the above-described embodiment, but it may be practiced in other modifications. For example, an automatic restarting of weaving operation may be substituted with a manual restart by means of the start switch 17. Fear of restarting the weaving operation with a swelled weaving bar formed on the fabric may be forestalled if it is so arranged that the alarming device 25 is activated in case of the abnormality. Additionally, it can be contemplated to provide an apparatus wherein the cloth fell displacement is effected by driving the winding motor. In this case, the cloth fell is displaced toward the fabric by increasing the warp tension. As it would be now apparent from the foregoing description of the embodiment, the apparatus according to the invention, in which the cloth fell is displaced toward the fabric, or retracted away from the swinging area of the reed, in advance of the slow-rotation of the loom in forward or reverse direction so that the cloth fell will not be beaten by the reed moving by way of the beat-up position during the above forward or reverse slow-rotation of the loom, can offer a useful advantage in that the formation of a defective swelled weaving bar to be caused by interference between the reed and the cloth fell can be prevented successfully. Additionally, if the cloth fell displacement should fail to take place properly, the control is operated so as to restore the warp tansion to the tension detected immediately before the commencement of the cloth fell. displacement, so that the cloth fell is free from beating-up by the reed. The apparatus prevents formation of a swelled weaving bar which is caused by interference of the reed and the cloth fell during slow rotation of the loom in forward or reverse direction. The let-off motor 1 is rotated at a slow rate in forward direction in advance of the subsequent slow forward or reverse rotation of the main motor M for removal of a faulty weft yarn. Operation of the let-off motor 1 is controlled by a computer control C and the motor is forward rotated for a predetermined amount so as to displace the cloth fell W₁ toward the fabric W, or retract it away from the swinging area of the reed 6. In restarting the weaving operation, the let-off motor 1 is slow rotated in reverse direction to return the cloth fell to its original position. The rotation of the let-off motor 1 is monitored by the rotary encoder 1a incorporated therein and connected to the computer control C 1a so that the control C can determine whether or not the cloth fell displacement is accomplished properly. In the event of any abnormality in the cloth fell displacement, the warp tension detected by the load cell 15 is restored to the tension F detected by the load cell immediately before the commencement of the cloth fell displacement. DESIGNATION OF REFERBNCE NUMERALS 1 ... Let-off motor as the cloth fell disp!acing means; 1a ... Rotary encoder as the driving amount detecting means; 15 ... Load cell as the warp tension detecting means; C ... Computer control as the control means.

Claims: Apparatus for preventing weaving bar in a loom, said apparatus comprising: displacing means (1, 2, 1a, 8, 18, 18a) for displacing the position of cloth fell (W₁) of a woven fabric along the warp by changing the tension of such warp (W), control means (C) for controlling the driving amount of said cloth fell displacing means (1, 2, 1a, 8, 18, 18a), and detecting means (4, 12, 14, 15) for detecting the tension of said warp, characterised by: detecting means (15) for detecting the driving amount of said cloth fell displacing means (1, 2, 1a, 8, 18, 18a), and said control (C) means having first function of driving said displacing means (1, 2, 1a, 8, 18, 18a) to displace the cloth fell (W₁) for a predetermined distance (ρ) toward the fabric from the normal position thereof in advance of rotating the loom at a slow rate in forward or reverse direction, second function of driving said displacing means (1, 2, 1a, 8, 18, 18a) to move the cloth fell (W₁) back to said normal position after completion of said slow rotation of the loom in the forward or reverse direction, third function of determining whether or not the cloth fell displacement (ρ) has been accomplished properly from the information from said driving amount detecting means representative of detected driving amount of said cloth fell displacing means and, in the event of a failure in the proper cloth fell displacement, driving said cloth fell displacing means until the warp is tensioned to such an extent that corresponds to the tension detected by said warp tension detecting means immediately before the commencement of said cloth fell displacement. Apparatus as claimed in Claim 1, in which the warp (W) is comprised of warps. Apparatus as claimed in claim 1 or claim 2 said control means for controlling the driving amount of said cloth fell displacing means including a software programmable computer (C). Apparatus as claimed in claim 3, said softwar programmable computer (C) storing the value of the warp tension detected by said warp tension means (4, 12, 14, 15) before cloth fell displacement commencement. Apparatus as claimed in any of claims 3 or 4, said displacing means for displacing the portion of cloth fell including motors (1, 18) controlled by said computer (C). Loom, in particular air jet loom, with an apparatus as claimed in any of claims 1 to 5

Inventors: SHINBARA MASAMI C O KABUSHIKI, SHINBARA, MASAMI, C/O KABUSHIKI KAISHA
Applicants: TOYODA AUTOMATIC LOOM WORKS, KABUSHIKI KAISHA TOYODA JIDOSHOKKI SEISAKUSHO
Application year: 1992
Main classification: D03D49
IPC codes: D03D51, D03D49