Method for preventing a stop streak in a jet loom

Abstract

 To provide a method of preventing a stop streak caused by beating a faulty weft in a jet loom.
STRUCTURE
A weft (Y) ejected from a weft inserting main nozzle (19) is assisted by air jets issued from a plurality of auxiliary nozzles (20-23) in flying throughout a warp shed. A plurality of weft arrival detectors (F₁-F₇) are arranged at spaced intervals between any paired auxiliary nozzles and also between any two adjacent pairs of such nozzles. If a control computer (C) fails to receive a weft arrival signal from any of the weft arrival detectors (F₁-F₇) later than the latest permissible arrival time, it causes a loom drive motor (M) to be stopped immediately with simultaneous application of brake (B).

Description

DETAILED DESCRIPTION OF THE INVENTION

INDUSTRIAL FIELD OF UTILTZATION

[0001] The present invention relates to a method of preventing formation of a stop streak on a fabric in a jet loom.

PRIOR ART

[0002] If a weft fails to be inserted properly throughout a warp shed in a jet loom, it may be detected by a weft detector located at the downstream end of weft flying passage beyond the weaving width of the loom and adapted to detect the leading end of each inserted weft. Alternatively, weft insertion may be monitored by use of a plurality of weft detectors arranged within the range of weaving width of a jet loom along weft flying passage, as disclosed by Publications of unexamined Japanese patent applications 55-142750 (1980), 58-36242 (191983) and 62-250248 (1987).

[0003] It is so arranged in the conventional apparatus disclosed by Publication 55-142750 that a signal representing a failure in weft insertion is generated when at least one of the plural weft detectors fails to detect the leading end of an inserted weft.

[0004] In the apparatus of Publication 58-36242, a failure in weft insertion is recognized when a weft-detected signal fails to be generated by a weft detector in a predetermined time after its preceding weft detector has detected an inserted weft.

[0005] In the apparatus of Publication 62-250248 for use in a jet loom having a plurality of auxiliary nozzle, each auxiliary nozzle is a activated at a time when the air jetting zone of that auxiliary nozzle is anticipated to be reached by the leading end of an inserted weft, on the basis of the time at which the leading end has been detected by a weft detector located immediately upstream of the auxiliary nozzle. That is, if the leading end of an inserted weft fails to be detected by a weft detector even after elapse of an anticipated time as measured after its preceding weft detector has detected the weft, a signal is generated which is indicative of a failure in proper weft insertion.

PROBLEMS THAT THE INVENTION IS TO SOLVE

[0006] When a failure in weft insertion is recognized by a weft detector located at the downstream end of weft flying passage along the weaving width of a jet loom, the loom is brought to a complete stop with the faulty weft, i.e. the weft resulting from failure in weft insertion, woven to the cloth fell of woven fabric. This is because the loom drive motor is rotated further under the influence of inertia even after it is stopped and braked. Because the faulty weft is beaten by a reed and pressed against its preceding weft insertion just previously, the cloth fell formed after the faulty weft has been removed therefrom will not become straight. That is, part of the cloth fell pressed by the beating reed with the faulty weft held therebetween will not be aligned straight after removal of the faulty weft from the cloth fell with respect to the remaining part of the clothfell having no such faulty weft. Even if the loom operation is resumed after the cloth fell position adjustment, this poor straightness of the cloth fell causes a defective stop streak appearing on the resulting woven fabric. It is, noted that such stop streak becomes more conspicuous if the faulty weft is looped when it is beaten-up by the reed.

[0007] The apparatuses according to Publications 58-36242 and 62-250248 equipped with plural weft detectors arranged within the weaving width may detect a failure in weft insertion earlier than an apparatus having a weft detector located at the downstream end of weft flying passage beyond the weaving width. However, it has been customary heretofore, that the loom is stopped at a predetermined crank angle on the basis of the time at which the weft insertion failure is detected by the weft detector at the extremity end beyond the weaving width. Thus, the faulty weft is inevitably beaten by the reed against the cloth fell and formation of a stop streak could not be prevented by these apparatuses.

[0008] Therefore, it is an object of the present invention to provide a method of preventing a stop streak which is caused by application of different forces to the cloth fell due to the presence of a faulty weft resulting from failure in proper weft insertion.

MEANS SOLVING THE PROBLEMS

[0009] In order to achieve the above object, the first embodiment of the invention provides a method comprising detecting the leading end of an inserted weft by means of a plurality of weft arrival detectors arranged within the range of weaving width of the jet loom and causing the loom to be stopped if any weft arrival times detected by the weft arrival detectors are later than the latest permissible arrival times established for the respective weft arrival detectors, said causing the loom to be stopped being effected immediately in response to the earliest detected time of said detected weft arrival times.

[0010] The second embodiment of the invention provides a method comprising detecting the leading end of an inserted weft by means of the above plurality of weft arrival detectors and causing the loom to be stopped immediately if weft arrival times detected by the weft arrival detectors shows a specific tendency in progressive delay of weft arrival times with reference to the latest permissible arrival times established for the respective weft arrival detectors.

[0011] The third embodiment of the invention provides a method comprising detecting the leading end of an inserted weft by means of the above plurality of weft arrival detectors and causing the loom to be stopped and substantially simultaneously causing the cloth fell of woven fabric to be shifted away from the weft beat-up position a reed of the loom if any weft arrival times detected by the weft arrival detectors are later than the latest permissible arrival times set for the respective weft arrival detectors said causing the loom to be stopped and the cloth fell to be shifted being effected immediately in response to the earliest detected time of said detected weft arrival times.

OPERATION THE INVENTION

[0012] According to the first embodiment of the invention, the loom driving motor is stopped and braked immediately in response to a delayed weft arrival detected by a weft arrival detector. This can bring the loom to a complete stop after rotation by inertia before the beat-up position reached by the reed, so that the faulty weft will not be beaten against the cloth fell during the rotation of the loom by inertia. Therefore, a stop stream resulting from beating the faulty weft against the cloth fell can be prevented successfully.

[0013] According to the second embodiment of the invention, the loom drive motor is stopped and braked immediately upon recognition of a tendency of the weft arrival times detected by the weft arrival detectors being delayed at such a rate that a failure in weft insertion will eventually occur.

[0014] There is a fear that the loom rotation by inertia may not be stopped before the beat-up position is reached by the reed in the method according to the first embodiment of the invention if a delayed weft arrival is detected by a weft arrival detector located closer to the downstream end of the weaving width. In order to avoid such a situation, it is so arranged according to the third embodiment of the invention that shifting of the cloth fell away from the beat-up position of the reed is effected together with stopping and braking of the loom drive motor in response to a delayed weft arrival detected by a weft arrival detector. The shifting of the cloth fell can help prevent the faulty weft from being beaten against the cloth fell.

EMBODIMENTS

[0015] The following will describe the method for preventing a stop steak in a jet loom while referring to the accompanying drawings including Figs. 1 through 8, that show embodiments that are operated according to the invention and parts thereof.

FIG. 1

is a diagrammatic front view showing a weft inserting apparatus of a jet loom incorporating therein a circuit for preventing a stop streak.

FIG. 2

is a diagrammatic side view of the jet loom.

FIG. 3

is a view similar to FIG. 2, but showing specifically a faulty weft in the form of a loom.

FIG. 4

is an enlarged side view showing a reed of the loom moved as far as it will go with the loom stopped, and a cloth fell in its retracted position.

FIG. 5

is a flow chart showing part of the program for disposing of a faulty weft and preventing a stop streak.

FIG. 6

is a flow chart showing the remaining part of the program.

FIG. 7

is a flow chart showing the program for disposing of a faulty weft and preventing a stop streak according to modified embodiment of the invention.

FIG. 8

is a graph illustrating prediction of a delay in weft arrival.

[0016] The following will describe an embodiment of the present invention while having reference to FIG. 1-6 in the accompanying drawings.

[0017] Referring firstly to FIG. 2 showing diagrammatically a jet loom in side view having an apparatus for performing the method of the invention, reference symbol M designates a loom drive Motor the operation of which is controlled by a control computer C. The motor M has a brake B. Reference numeral 1 designates a reversible let-off motor provided independently of the loom drive motor M for driving a warp beam 2. Warp yarns T unwound from the warp beam 2 are guided toward healds 5 and a reed 6 through a back roller 3 and a tension roller 4. Woven fabric W guided is guided by an expansion bar 7, a surface roller 8 operatively connected to the motor M, a press roller 9 and a stretching guide 10 and then wound up by a cloth roller 11.

[0018] The tension roller 4 is mounted to one end of a tension lever 12 which has at the other end thereof a spring 13 acting to urge the tension roller 4 in pressing contact with the warp yarns T thereby applying tension thereto. The tension lever 12 is rotatably supported by one end of a detecting lever 14 whose other end is connected to a load cell 15. In such an arrangement, the warp tension is transmitted to the load cell 15 through the tension roller 4, tension lever 12 and detecting lever 14, thereby causing the load cell 14 to generate to the control computer C an electrical signal representative of the current magnitude of warp tension being applied to the tension roller 4.

[0019] The control computer C is operatively connected to the warp let-off motor 1 to control its rotational speed according to comparison between warp tension setting and the actual warp tension that is represented by the output electrical signal from the load cell 15 and also to the current warp beam diameter which can be monitored by a rotary encoder 16 for detecting the angle of rotation of the loom. Thus, the warp tension is adjusted properly during normal weaving operation by controlling the rotational speed of the motor 1 and weaving defects such as weaving bar can be prevented from being formed in the woven fabric W.

[0020] The control computer C is connected to a start control switch 17 which, when energized, generates an ON signal to the control computer which, then responding to such signal, transmits a forward rotation command signal to the motor M through an inverted I and a forward rotation command signal to the let-off motor 1. The control computer C provides a feed-back control for controlling the rotational speed of the let-off motor 1 from detection signals transmitted from a rotary encoder 1a incorporated in the motor 1.

[0021] Now referring to FIG. 1 showing diagrammatically a weft inserting apparatus of the jet loom having a circuit for preventing a stop streak from being formed on a fabric woven by the jet loom, reference numeral 18 designates a weft measuring and storage device of known winding type. A predetermined length of weft Y measured and stored by the device 18 is inserted into a warp shed by an air jet issued from a weft inserting main nozzle 19. The inserted weft Y is assisted in flying through the shed by air jets issued from pairs of auxiliary nozzles 20, 21, 22, 23 for accelerating the weft. These auxiliary nozzles 20-23 are arranged within the range of weaving width of the loom. There are provided weft detectors S₁, S₂ of optical reflection type located at predetermined positions at the downstream end of the weft flying passage remote from the weft inserting main nozzle 19 and beyond the range of weaving width of the loom for detecting the leading end of each inserted weft and generating to the control computer C signals representing presence or absence of the weft.

[0022] The weft measuring and storage device 18 has a stop pin 24a which is driven by a solenoid 24 to be engaged with a weft winding surface 18a of the device 18 for winding and storage of the predetermined length of weft Y and to be disengaged therefrom for releasing the same weft. Operation of the solenoid 24 is controlled from a command signal transmitted by the control computer C according to the information of angle of rotation of the loom.

[0023] Adjacent the weft winding surface 18a is provided a weft detector 25 of optical reflection type for detecting a weft being released from the weft winding surface 18a. In operation, the control computer C deenergizes the solenoid 24 when the number of detections by the weft detector 25 becomes a predetermined number setting, thereby moving the stop pin 24 into engagement with the weft winding surface 18a to stop weft releasing therefrom.

[0024] Injection of air jet from the weft inserting main nozzle 19 is controlled by a solenoid-operated valve V₁, while injection of air jets from the pairs of auxiliary nozzles 20-23 is controlled by similar solenoid-operated valves V₂, V₃, V₄, V₅, respectively. The valve V₁ is connected to an air tank 26 for holding therein air under pressure and supplying the air to the valve. The valves V₂-V₄ are connected to a common air tank 11 for holding therein air under pressure and supplying the air to the respective valves. The valve V₅ is connected to a separate air tank 28 for holding therein air under pressure and supplying the air to the valve.

[0025] The solenoids for the valves V₁-V₅ are operated to open or close their associated valves according to a command from the control computer C which provides such command in response to information of the current angle of rotation of the weaving loom being monitored by the rotary encoder 16. In normal operation, the valves V₁-V₅ are activated successively starting with the first valve V₁.

[0026] As shown in FIG. 1; between any paired auxiliary nozzles and also between any two adjacent pairs of such nozzles are provided weft detectors F₁, F₂, F₃, F₄, F₅, F₆, F₇ of optical reflection type at spaced intervals for detecting the arrival of the leading end of each inserted weft.

[0027] Immediately above the main weft inserting nozzle 19 is provided a known device 29 for disposing of a faulty weft. This device 29, which is disclosed, e.g. by Publication of unexamined Japanese patent application 2-61138 (1990), functions to prevent insertion of a weft in the event of occurrence of failure in proper insertion of its preceding weft and then to remove a resulting faulty weft on the cloth fell W₁ of the woven fabric W with the aid of the weft succeeding the faulty weft. As indicated by connection between the device 29 and the control computer C, operation of the former device is controlled by the latter.

[0028] FIGS. 5 and 6 provide flow charts showing a program according to which the above-described apparatus operates to prevent formation of stop streak.

[0029] As the leading end of a weft Y ejected through the weft inserting main nozzle 19 reaches the detector F₁ to be detected thereby, the same detector generates a weft-arrival signal to the control computer C. If the time of signal generation, hence the time at which the weft has arrived at the detector F₁, is at or earlier than the latest permissible arrival time T₁ set for that detector, the control computer C monitors whether or not the weft-arrival signal generation by the next detector F₂ takes place at or earlier than the latest permissible arrival time T₂ for the detector F₂.

[0030] Likewise, the control computer C monitors the generation of weft-arrival signals from the remaining weft detectors F₃, F₄, F₅, F₆, F₇ with reference to their latest permissible arrival times T₃, T₄, T₅, T₆, T₇, respectively. If the weft-arrival signals have been generated at or earlier than the respective latest permissible arrival times T_m (m=1-7) for the weft arrival detectors F_m (m=1-7), the control computer C then monitors the weft arrival by means of the weft detectors S₁, S₂ outside the range of weaving width. When the detector S₁ detects arrival of the weft while the detector S₂ detects no weft, the control computer C commands the loom to continue its weaving operation. If the detector S₁ fails to detect arrival of the weft, the control computer C commands the loom drive motor M and the let-off motor 1 to stop and application of the brake B thereby to cause the loom to stop at a given crank angle. If both of the detectors S₁, S₂ detect the weft, the control computer provides the same command as in the above case so that the loom is caused to stop at the given crank angle. Incidentally, the failure in weft insertion in the latter case can be considered to be caused by a cut-off in the inserted weft.

[0031] If any of the weft detectors F_m detect the weft arrival later than their latest permissible arrival times T_m, the control computer C commands a stop of the loom drive motor M and application of the brake B in response to the firstly detected delayed arrival. If the signal of such firstly detected delay is generated by any one of the detectors F₄-F₇, the control computer C also commands the let-off motor 1. to be accelerated for a predetermined length of time before it is stopped. This acceleration of the motor 1 allows the warp yarns T to be unwound faster than normal rate and, therefore, the cloth fell W₁ of the woven fabric W is shifted away from the beat-up position of the reed 6. On the other hand, if the signal of the above firstly detected delay is generated by any one of the detectors F₁-F₃, the control computer C commands the let-off motor 1 to be stopped without being accelerated.

[0032] After the loom operation has been thus stopped, the device 29 is operated to prevent a weft succeeding the faulty weft Y₁ from being inserted. Then, the motors M and 1 are rotated reverse and a maximum opening of a warp shed is formed. In this position, the faulty weft Y₁ at the cloth fell W₁ is released from the grip by upper and lower warp sheets T and then pulled out from the cloth fell W₁ by the aid of its succeeding weft portion in a known manner.

[0033] In case of a stop of the loom because of the detection of delayed weft arrival by any one of the detectors F₁-F₃, the reed 6 will be stopped before making a beat-up of the cloth fell W₁ as shown in FIG. 4, so that the faulty weft Y₁ as shown in FIG. 3 will not be beaten against the cloth fell W₁. Therefore, weft Y_o inserted just previously will not receive beating force of the reed 6 by way of the weft Y₁.

[0034] As referred to earlier herein, when the faulty weft Y₁ remains between the upper and lower warp sheets T in a looped state as shown in FIG. 3, part of the weaving width is free from a weft and some other part thereof has looped weft corresponding in thickness to two strands of weft. Unless the cloth fell W₁ is free from beat-up by the reed 6 as shown in FIG. 4, the previously inserted weft Y_o would receive beating force of different magnitudes depending on whether it receives the force directly or via a single strand of weft or double strand of looped weft. As a result, straightness of the cloth fell W₁ would be disturbed when the faulty weft Y₁ is removed, and the resulting non-straight line of the cloth fell W₁ would produce a defective stop streak in the woven fabric.

[0035] According to above-described embodiment of the invention, however, because the reed 6 can stop before making a beat-up in case when the delayed weft arrival is detected by any one of the detectors F₁-F₃, formation of the above stop streak in the resulting woven fabric can be prevented.

[0036] In case of a stop of the loom due to detection of a delayed weft arrival by the weft arrival detectors F₄-F₇, beating of the faulty weft Y₁ may not be avoided safely unless some provision is made to make the cloth fell W₁ free from the beating. For this reason, according to the above embodiment, the cloth fell W₁ is shifted or retracted away from the beat-up position of the reed 6 simultaneously with stopping of the loom operation so as to reduce the influence of the beating-up by the reed 6. This shifting of the cloth fell W₁ can effectively prevent the woven fabric from having a defective stop streak.

[0037] It is so arranged in the above-described embodiment that shifting of the cloth fell W₁ is not effected when the delayed weft arrival is detected by the first to third detectors F₁-F₃, but it is noted that the cloth fell shifting may be effected in response to a delayed weft arrival detected by the second detector F₂ or the third detector F₃, or even by the first detector F₁.

[0038] After removal of the faulty weft Y₁ subsequent to a loom stop due to detection of a weft arrival delay by the weft arrival detectors F₁-F₃, the main motor M and the let-off motor 1 are started to rotate forward synchronously to resume the weaving operation of the loom.

[0039] In case of a loom stop due to detection of a weft arrival delay by the weft arrival.detectors F₄-F₇, firstly the let-off motor 1 is rotated reverse for a predetermined amount and thereafter the main motor M and the let-off motor 1 are started to rotate forward synchronously, thereby resuming the weaving operation of the loom. The reversing of the let-off motor 1 is done so as to offset the previous forward acceleration of the motor thereby to move the cloth fell W₁ back to its original position with respect to the beat-up position of the reed 6. It is noted that present invention is not limited to the above-described embodiment but it can be practiced in other ways as exemplified by flow chart shown in FIG. 7.

[0040] Even when a weft arrival detector F_m (m=1-6) detects the leading end of an inserted weft at or earlier than its latest permissible arrival time T_m (m=1-6), the loom may be stopped and the cloth fell W₁ retracted away from the beat-up position of the reed 6 if the weft arrival time t_m detected by the detector F_m and the time t_m-1 of the preceding detector F_m-1 do not fulfill the equation (1) below.


where, H_m is a constant, or a value of ratio of the delay at a given weft arrival detector F_m to the delay at the detector F_m-1 that precedes F_m.

[0041] Referring to the graph in FIG. 8 in connection with the modified embodiment, the points P_m-1, P_m, P_m+1 represent the latest permissible arrival time T_m-1, T_m, T_m+1 of the weft arrival detectors F_m-1, F_m, F_m+1, respectively; the points Q_m-1, Q_m, Q_m+1 represent the weft arrival times t_m-1, t_m, t_m+1 actually detected by the detectors F_m-1, F_m F_m+1, respectively. Therefore, (T_m - t_m) and (T_m-1 - t_m-1) in the above equation (1) represent the distances corresponding to the time differences between the points Pm and Q_m, and the points P_m-1 and Q_m-1, respectively. When the ratio of the distance (T_m - t_m) to the distance (T_m-1 - t_m-1), as expressed in the above equation (1), is smaller than a given value, an extension from the line L connecting the points Q_m-1 and Q_m will pass below the point P_m-1 as shown in the graph. The constant H_m in the equation (1) is defined as the above-mentioned given value. As seen from the graph in FIG. 4, if the ratio (T_m - t_m)/(T_m-1 - t_m-1) is smaller than this constant Hm, it can be predicted that the weft arrival time t_m-1 to be detected by the detector F_m+1 would be later than latest permissible arrival time T_m-1 for that detector F_m+1. That is, it is so controlled according to the above modified embodiment that the loom operation is stopped and the cloth fell W₁ is shifted if the relationship between the detected times t_m and t_m-1 of the detector F_m and its preceding detector F_m-1 respectively, do not fulfill the requirement of the above equation (1). By predicting a failure in weft insertion by a possibly delayed arrival time at the detector F_m+1, the loom stop can be effected early enough to forestall a defective stop streak to be produced otherwise.

[0042] To provide a method of preventing a stop streak caused by beating a faulty weft in a jet loom. A weft Y ejected from a weft inserting main nozzle 19 is assisted by air jets issued from a plurality of auxiliary nozzles 20-23 in flying throughout a warp shed. A plurality of weft arrival detectors F₁-F₇ are arranged at spaced intervals between any paired auxiliary nozzles and also between any two adjacent pairs of such nozzles. If a control computer C fails to receive a weft arrival signal from any of the weft arrival detectors F₁-F₇ later than the latest permissible arrival time, it causes a loom drive motor M to be stopped immediately with simultaneous application of brake B.

EFFECT OF THE INVENTION

[0043] As it would be now apparent from the foregoing description, the first embodiment of the invention, according to which the loom operation is stopped immediately in response to the earliest detected time of delayed weft arrival times detected by the weft arrival detectors, can provide an effect in that beat-up of a faulty weft by the reed against the cloth fell can be avoided, thereby preventing a stop streak.

[0044] According to the second embodiment of the invention, it is possible to predict an impermissible delay of weft arrival time at a weft detector before it actually detects the leading end of the weft by monitoring the tendency of delay in weft arrival time. Therefore, a loom stop can be effected early enough to prevent a stop streak on the woven fabric.

[0045] The third embodiment of the invention, according to which the cloth fell is retracted away from the beat-up position of the reed, as well as the loom is stopped, is effective in such a case that beat-up of a faulty weft cannot be avoided merely by stopping the loom operation.

DESIGNATION OF REFERENCE NUMERALS

[0046] F₁-F₇ .... Weft arrival detectors, M .... Loom drive motor, C .... Control computer, Y₁ .... Faulty weft resulting from failure in weft insertion

Claims

1. Method of preventing formation of a stop streak on a fabric in a jet loom comprising detecting the leading end of an inserted weft by means of a plurality of weft arrival detectors arranged within the range of weaving width of the jet loom and causing the loom to be stopped if any weft arrival times detected by the weft arrival detectors are later than the latest permissible arrival times established for the respective weft arrival detectors, said causing the loom to be stopped being effected immediately in response to the earliest detected time of said detected weft arrival times.

2. Method of preventing formation of a stop streak on a fabric in a jet loom comprising detecting the leading end of an inserted weft by means of a plurality of weft arrival detectors arranged within the range of weaving width of the jet loom and causing the loom to be stopped immediately if weft arrival times detected by the weft arrival detectors shows a specific tendency in progressive delay of weft arrival times with reference to the latest permissible arrival times established for the respective weft arrival detectors.

3. Method of preventing formation of a stop streak on a fabric in jet loom comprising detecting the leading end of an inserted weft by means of a plurality of weft arrival detectors arranged within the range of weaving width of the jet loom and causing the loom to be stopped and substantially simultaneously causing the cloth fell of woven fabric to be shifted away from the weft beat-up position of a reed of the jet loom if any weft arrival times detected by the weft arrival detectors are later than the latest permissible arrival times established for the respective weft arrival detectors, said causing the loom to be stopped and the cloth fell to be shifted being effected immediately in response to the earliest detected time of said detected weft arrival times.

4. Loom with means for preventing formation of a stop streak on a fabric and operated according to the method as claimed in any of claims 1 to 3.

Drawing