EP1445365A2

EP1445365A2 - Method and apparatus for detecting weft in loom

Info

Publication number: EP1445365A2
Application number: EP03028141A
Authority: EP
Inventors: Hirohisa Kitamura; Ryosuke Fujimori
Original assignee: Tsudakoma Industrial Co Ltd
Current assignee: Tsudakoma Corp
Priority date: 2003-01-22
Filing date: 2003-12-05
Publication date: 2004-08-11
Anticipated expiration: 2023-12-05
Also published as: KR20040067815A; CN1291087C; JP2004225186A; CN1517463A; EP1445365B1; JP4128458B2; EP1445365A3; DE60321534D1; KR100526048B1

Abstract

There are disclosed a method and an apparatus capable of carrying out an accurate weft detection corresponding to the yarn sort of a weft to be inserted and also capable of judging the presence/absence of a defective weft inserting with accuracy. In the method, at least one of judgment conditions used for judging the presence/absence of the defective weft inserting are set in advance with regard to each yarn sort of the weft, and when carrying out the judgment, at least one of judgment conditions corresponding to each yarn sort of the weft to be inserted are selected and the presence/absence of the defective weft inserting is judged by using the selected judgment condition and a signal from a weft detecting device. The apparatus faithfully carries out this method. <IMAGE>

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a method and an apparatus for detecting a weft by using an output signal from a weft detecting device.

2. Description of the Prior Art

Heretofore, there have been proposed several techniques for detecting the behavior of a weft in the process of the weft inserting by means of a fluid jet loom. For example, one technique wherein any weft detection is suspended for a predetermined period after starting the operation of the fluid jet loom in order to prevent the fluid jet loom from being stopped by unclear reasons such as the earlier or later arrival time of the weft to a predetermined destination and others; another technique wherein a reference threshold value used for detecting the presence/absence of the weft as well as a gain of an amplifier for use in a feeler head signal are decided based on an average value of the signal in the feeler head signal watching period placed prior to the weft watching period (see Patent Document 1); still another technique wherein a signal for stopping the fluid jet loom is generated if the defective weft inserting continuously takes place by predetermined times (see Patent Document 2 ), and so forth.

Patent Document 1: JP Patent Public Disclosure No. 7-11544 (pp. 4 through 5, Fig. 1)

Patent Document 2: JP Patent Publication No. 61-39424 (pp. 2 through 5, Fig. 1)

However, any one of the above prior art techniques fails to think over the fact that the judgment condition including the weft detecting condition with regard to the presence/absence of the defective weft inserting varies every yarn sort of the weft to be weft-inserted (expressed as just "inserted" hereinafter). In other words, in the above prior art techniques, each value of the above predetermined period of time, the signal watching period and the predetermined occurrence times of the defective weft inserting are made constant regardless of the yarn sort of the weft. In short, the above prior art techniques neither consider what value is the most suitable for each yarn sort the weft, nor try to replace the above each constant value by the most suitable value corresponding to alteration of the yarn sort of the weft to be inserted.

Accordingly, there are caused various erroneous weft detections, for instance, one being caused by the loom stoppage due to the above unclear reason at the time of starting the operation of the fluid jet loom after altering the yarn sort; another being caused by the erroneous decision of the reference threshold value and the gain of amplifier due to defecting the flying cotton dusts generated in the process of the weft inserting after altering a yarn to another yarn for instance belonging to the spun yarn system; still another being caused by the erroneous count of the weft inserting times after altering the yarn sort, and so forth, thus the accurate weft detection becoming impossible.

Especially, in the multiple color fluid jet loom in which the yarn sort of the weft is frequently altered, if such erroneous weft detection as mentioned above takes place every alteration of the yarn sort of the weft, the fluid jet loom comes to stop every erroneous weft detection, which results in large extension of the production time of the fabric and the productivity of the fabric is reduced to a great extent. Furthermore, the frequent repetition of stop and restart of the loom worsens if the accuracy of the weft inserting position against the warp shed, the quality of the finished fabric is lowered very much.

Accordingly, an object of the invention is to provide a method and an apparatus capable of surely carrying out the weft detection every sort of the weft to be inserted as well as capable of accurately judging the presence/absence of the defective weft inserting.

SUMMARY OF THE INVENTION

A method of detecting a weft according to the invention includes the steps of setting in advance at least one of judgment conditions for judging the presence/absence of a defective weft inserting with regard to each yarn sort of the weft, and when carrying out the judgment, selecting at least one of judgment conditions corresponding to each yarn sort of the weft to be inserted and judging the presence/absence of the defective weft inserting by using the selected judgment condition as well as a signal from a weft detecting device.

An apparatus for detecting a weft in a fluid jet loom according to the invention includes a weft detecting device for detecting the weft; a judgment condition setting device for setting at least one of judgment conditions as used for judging the presence/absence of a defective weft inserting, with regard to each yarn sort of the weft; and a judgment portion selecting at least one of judgment conditions corresponding to each yarn sort of the weft to be inserted and judging the presence/absence of the defective weft inserting by using the selected judgment condition as well as a signal from the weft detecting device.

For example, the information with respect to each yarn sort of the weft having been inserted is obtainable from a weft selection signal while the judgment condition corresponding to each yarn sort of the weft can be selected from the judgment conditions as set in advance with regard to each yarn sort of the weft.

In case of continuously performing the weft inserting without altering the yarn sort of the weft to be inserted, in other word, continuously repeating a plurality of the weft pickings with the weft of the same yarn sort, the same judgment condition is applicable to the judgment on the presence/absence of the defective weft inserting at each weft picking time. Contrary to this, in case of performing the weft inserting wherein the yarn sort of the weft is altered every weft picking, the judgment condition corresponding to the yarn sort of the weft as altered is selected and used for judging the presence/absence of the defective weft inserting.

Accordingly, as the detection of the weft as inserted is carried out based on each yarn sort of the weft, even if the yarn sort of the weft is altered every weft inserting, the weft detection can be surely carried out, thus the presence/absence of the defective weft inserting being judged with accuracy.

The judgment on the presence/absence of the defective weft inserting may be carried out by comparing a signal from a weft detecting device with a reference threshold value as used for detecting the presence/absence of the weft in the comparator of the comparison portion, or may be carried out based on the above comparison result. Besides, the signal as used for the judgment on the presence/absence of the defective weft inserting, especially the signal to be compared with the above reference threshold value may be the integrated value of the signal from the above weft detecting device.

The judgment conditions include at least one of conditions as selected from a group including a period which is defined over at least one of weft picking periods beginning form the start of the fluid jet loom operation and during which any judgment is not carried out regardless of the presence/absence of the defective weft inserting; a period excluding a weft watching period for use in the above judgment, and watching a signal from the weft detecting device to determine a reference threshold value for detecting the presence/absence of the weft; a judgment mode comparing a signal from the weft detecting device in the weft watching period for the judgment with the reference threshold value; and the occurrence times of the defective weft inserting. Therefore, even if there occurs a certain change in any one of the arrival position of the leading end of the weft, the signal of the weft detecting device, the condition to be compared with the threshold value, the occurrence times of the defective weft inserting, because of altering the yarn sort of the weft in the weft inserting process, the weft detection can be surely carried out.

The weft detecting device includes a weft detecting head which is arranged in the arrival position of the leading end of the weft as normally inserted, and the judgment mode includes at least two modes selected from a group including the mode of judging whether or not the integrated value of a signal from the weft detecting device exceeds the reference threshold value in a predetermined period within the weft watching period; the mode of judging whether or not the integrated value of a signal from the weft detecting device exceeds the reference threshold value within the weft watching period; and the mode of judging whether or not the integrated value of the signal from the weft detecting device exceeds the reference threshold value at the end of the weft watching period.

Instead of the above, the weft detecting device includes a weft detecting head which is arranged in the arrival position of the leading end of such a weft that is cut off by the fluid jet force in the middle of the weft inserting, that is, before the weft inserting is normally completed, and the judgment mode includes the mode of judging whether or not such a state that the integrated value of a signal from the weft detecting device exceeds the above reference threshold within the weft watching period, exceeds a reference time that is determined with respect of each sort of the weft.

The occurrence times of the defective weft inserting includes at least one of the continuous occurrence times of the defective weft inserting and the occurrence times of the defective weft inserting within a predetermined period.

The weft detecting device may include at least one of a weft detecting head of the photoelectric type which detects the weft by having the weft penetrated through a predetermined optical path and a weft detecting head of the contact detection type which detects the weft when the detecting head and the weft make contact with each other due to the fluctuation in the flying course of or the tension applied to the weft.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a block diagram showing an electric circuit of a weft defecting apparatus as an embodiment of the invention.

Fig. 2 is a block diagram showing an electric circuit of a weft defecting apparatus as an embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to Figs. 1 and 2, a weft detecting apparatus 10 uses a H1-feeler head 12 and a H2-feeler head 14 of the photoelectric reflection type. Each of these feeler heads (defecting head) 12 and 14 includes a pair of a light projecting portion and a light receiving portion which are arranged so as to oppose to each other across the groove-shaped weft flying path as formed in a reed of a fluid jet loom. To put it more concretely, the H1-feeler head 12 is provided with a pair of a light projector 16 and a light receiver 20 while the H2-the feeler head 14 is provided with a pair of a light projector 18 and a light receiver 22, and these light projectors and the light receivers are arranged such that the

light receivers

20, 22 receive the light rays emitted by

corresponding light projectors

16, 18 across the weft flying path.

The H1-feeler head 12 is arranged in a position in which the leading end of the weft would arrive while the weft inserting is normally carried out. On the other hand, the H2-feeler head 14 is arranged in a position on the downstream side of and at a distance from the H1-feeler head 12 with regard to the weft inserting direction, and if it happens that the weft is cut off by the fluid jet force in the middle of the weft inserting, the leading end of the weft as cut off would arrive in that position.

While a high frequency pulse current is supplied respectively to

light projectors

16, 18, they repeat blinking and generate light pulses.

Light receivers

20, 22 receive the light from

corresponding light projectors

16, 18 and output electric pulse signals having a level equivalent to the amount of the light incident on weft

signal generating portions

24, 26.

While the weft inserting is normally carried out, as a part of the light emitted by the light projector 16 collides with the weft, the amount of the light incident on the light receiver 20 increases (there is a case where the incident light amount decreases depending on a certain weft color). If no weft as inserted exists in the weft detectable range by the H1-feeler head 12, there is observed no change in the amount of the light incident on the light receiver 20.

While the weft inserting is carried out, if it happens that the weft is cut off on its leading end side by the fluid jet force, a part of the weft as cut off is still blown off by the fluid jet, thus it further flying downstream in the weft inserting direction over the position in which the H1-feeler head 12 is arranged. With this flight of the separated weft including the leading end thereof, as a part of the light emitted by the light projector 18 collides with the separated weft including the leading end thereof, the amount of the light incident on the light receiver 22 increases (there is a case where the incident light amount decreases depending on a certain weft color). If no weft as inserted exists in the weft detectable range by the H1-feeler head 14, there is observed no change in the amount of the light incident on the light receiver 22.

As described in the above, H1- and H2-

feeler heads

12 and 14 output a feeler signal having a level proportional to the amount of the light incident on

light receivers

20 and 22 to weft

signal generating portions

24 and 26, correspondingly. In the example as shown in Figs. land 2, H1- and H2-

feeler heads

12 and 14 and weft

signal generating portions

24 and 26 act as a detector for detecting the weft, respectively.

Each of weft

signal generating portions

24, 26 amplifies an output signal from each of

corresponding light receivers

20, 22 by means of

corresponding amplifiers

28, 30 and detects an output signal from each of these

amplifiers

28, 30 by means of

corresponding detectors

32, 34. Each of the

above amplifiers

28, 30 is a very ordinary amplifier of which the gain is made variable. Each of

detectors

32, 34 has a peak holding circuit in general and converts an output signal from each of

corresponding amplifiers

28, 30 into a direct current, and outputs the converted direct current to a signal processing portion 36, as weft signals S1, S2 of the level capable of telling the presence/absence of the weft.

The rotational angle of the main shaft 38 of the fluid jet loom is detected by an encoder 40 and outputted to a timing signal generating portion 42 of the signal processing portion 36, as an electric crank angular signal .

On one hand, in a judgment condition setting device 70, there are set two periods of which each is used as one of judgment conditions and are defined within the period during which the fluid jet loom completes a unit weaving operation of it. One of these two periods is called a weft presence period, during which the weft is allowed to exist, and the other is called a weft absence period, during which the weft is not allowed to exist, in other words, the weft absence period is the period which begins after the reed beat-up timing (0°) and terminates prior to the above weft presence period. The above two periods are set on the basis of the rotational angle of the main shaft. To put it more concretely, the weft presence period is set at a rotation angle of 200°~290° while the weft absence period is set at a rotation angle of 100°~200°.

Because of this, a timing signal generation portion 42 generates two timing signals H1T and IN1 based on the above two set values for two periods from the judgment condition setting device 70 and the output signal  of the encoder 40, wherein the timing signal H1T corresponds to a weft detecting period for detecting the presence/absence of the weft, that is, the weft presence period while the timing signal IN1 corresponds to a weft absence period in which the presence/absence of the weft is not examined.

The weft absence period indicates a period except the weft presence period, but it may be all the periods in which no weft exists in the position where the H1 feeler head 12 is arranged, or a part of such period.

A weft selection signal generating portion 44 includes a stepping signal generating device 50, a pattern setting device 52, and a selection signal generating device 54, wherein the stepping signal generating device 50 generates a stepping signal in response to the rotational direction of the main shaft of the fluid jet loom, the pattern setting device 52 sets the weft selection contents corresponding to the weft picking number in the form of a pattern, and the selection signal generating device 54 receives stepping signals from the stepping signal generating device 50, counts the weft picking number, and outputs the weft selection signal corresponding to the weft picking number as counted, based on the pattern as set by the above pattern setting device 52.

The stepping signal generating device 50 receives the output from a proximity switch 48 to generate the stepping signal corresponding to the rotational direction of the main shaft 38 of the fluid jet loom.

Various weft selection signals are set in the pattern setting device 52 in the form of various output patterns. For example, these output patterns can be stored i.e. set in advance in the form of a table which classifies the weft selection signals designating the weft used for weft inserting based on the weft picking number (the weft picking order number).

The selection signal generating device 54 counts the weft picking number by means of the stepping signals from the stepping signal generating device 50, reads the weft selection signal corresponding to the counted value from the pattern as set in the patter setting device 52, and then outputs the weft selection signal as read to the signal processing portion 36, a weft inserting unit, a length measuring and storage unit and so forth. The selection signal generating device 54 is constituted such that it increases the count value by +1 or decreases by -1 depending on the stepping signal generated according to the rotational direction of the main shaft, and if the present count value exceeds the weft picking number as set in the above pattern setting device 52, it returns the count value to 1.

The weft selection signal generating portion 44 receives the output signal (picking signal) of the proximity switch 48 detecting every one turn of a dog 46 rotated in synchronization with the main shaft 38, calculates the weft picking number based on the picking signal corresponding to the one turn of the dog, and then selectively generates weft selection signals CL1, CL2, CL3 ... CL_n , which indicate a sort of the weft to be inserted, based on the calculated weft picking number (the weft picking order number).

Each of weft selection signals CL1, CL2, CL3, ..., CLn indicates a sort of the weft as used at the time of carrying out the weft picking for the weft inserting corresponding to the weft picking order number, but it may be possible to use a signal indicative of the order number of the weft inserting nozzle into which the weft is inserted, instead of the above weft selection signal indicative of the sort of the weft.

Weft selection signals CL1, CL2, CL3, ..., CLn are supplied to the signal processing portion 36 as well as to the timing signal generating device 42 and also supplied to the weft inserting unit, the weft length measuring storage unit and so on which are not shown. The weft inserting unit carries out the weft inserting of the weft corresponding to the weft selection signal. The weft inserting pattern may be a small stepping number such as 1*1, 2*2 and so forth.

As shown in Fig. 1, the signal processing portion 36 detects the presence/absence of the weft in each weft detection period of feeler heads 12, 14 based on yarn signals S1, S2, judges the presence/absence of the defective weft inserting based on each of weft detection results by feeler heads 12, 14, and outputs each judgment result to each latch circuit 56 of feeler heads 12, 14.

Each latch circuit 56 receives, through corresponding terminals S1, S2 thereof, a logical signal indicative of the presence/absence of the defective weft inserting at each feeler head from the signal processing portion 36. If the logical signal indicative of the presence of the defective weft inserting is inputted, the latch circuit 56 stores it and outputs a signal S3 indicative of the defective weft inserting and a signal S4 indicative of the weft breakdown due to the blowing off by the fluid jet through corresponding terminals Q1, Q2. These signals S3, S4 act to stop the operation of the fluid jet loom. Furthermore, the latch circuit 50 receives a signal for operating the fluid jet loom which is generated as long as the fluid jet loom is operated. Still further, the latch circuit 50 erases all the stored information by means of the rising operation signal of the fluid jet loom which is generated at the time of beginning the operation of the fluid jet loom and at the same time, turns off each of output signals.

In the example as shown, the signal processing portion 36 is constituted with a pair of circuits for dealing with respective yarn signals S1, S2 from weft -

signal generating portions

24, 26. However, it may be possible to provide the signal processing portion for each feeler head. Besides, one latch circuit 56 may be used in common by feeler heads 12, 14.

In the signal processing portion 36 as shown in Fig. 2, as H1- and H2-feeler heads 12, 14 have the same circuit constitution, the following description will be made about the H1-feeler head 12.

Roughly speaking, the signal processing portion 36 includes a judgment portion 60, and a gain/threshold value calculation portion 58. This gain/threshold value calculation portion 58 calculates an average value of the feeler signal S1 during the input period (100° ~ 200°) of the timing signal IN1, that is, a so-called weft absence period, determines the gain of amplifier 28 as shown in Fig. 1 as well as a reference threshold value for detecting the presence/absence of the weft, based on the above calculated average value, when the timing signal IN1 becomes off (200°), and then outputs the above determined gain signal and reference threshold value to the amplifier 28 and a judgment circuit 62 of the judgment portion 60, respectively.

The judgment portion 60 includes an integrator 64 and an interlock circuit 66 in addition to the judgment circuit 62. The integrator 64 integrates the yarn signal S1 during the input period (2000 ~ 290°) of the timing signal H1T, that is, a so-called weft presence period and outputs the integrated value to the judgment circuit 62.

While the signal for operating the fluid jet loom is inputted, the judgment circuit 62 compares the integrated value of the yarn signal S1 with the reference threshold value from the gain/threshold value calculation portion 58 according to the judgment mode corresponding to each yarn sort of the weft, judges the presence/absence of the weft, in other words the presence/absence of the defective weft inserting, and outputs the judgment result to the interlock circuit 66 when the timing signal H1T becomes off (290°).

The presence/absence of the weft can be detected by comparing the integrated value of the yarn signal S1 with the reference threshold value and determining that the yarn is present (absent depending on a sort of the weft detecting device) if the former is larger than the latter. It is judged that the defective weft inserting has happened when the yarn signal S1 indicates the yarn absence (or yarn signal S2 indicates yarn presence).

The interlock circuit 66 invalidates the judgment output outputted from the judgment circuit 62 for a predetermined period of time from the rising of the loom operating signal (time of beginning the loom operation). The interlock period is set through the judgment condition setting device as will be described later.

A skip processing portion 68 receives the judgment output from the judgment portion 60 and judges the state of the occurrence of the defective weft inserting when the timing signal H1T becomes off (290°). When the occurrence frequency of the defective weft inserting during a predetermined period among a plurality of picking periods reaches a frequency as set, the above skip processing portion gives a judgment output to the latch circuit 56, the judgment output being a logical signal indicative of the defective weft inserting.

The timing signal generating portion 42 outputs two timing signals corresponding to the rotation of the loom main shaft 38 based on the timing set value given from the judgment condition setting device 70 as will be described later. The timing signal generating portion 42 may be externally provided separating from the weft detecting device.

In the judgment condition setting device 70, at least one of judgment conditions are set in advance with regard to every sort of the weft corresponding to the weft selecting signal. This judgment condition setting device 70 is connected with the timing signal generating device 42, the judgment circuit 62, the interlock circuit 66 and the skip processing portion 68 and is able to send each set value of various judgment conditions such as timing signal generating period, judgment mode, interlock period, allowable occurrence frequency of the defective weft inserting and so forth, to each of circuits as described above. As shown in Fig. 3, there are set the following judgment conditions.

1. Interlock period which is defined over at least one of weft picking periods beginning from the start time of the loom operation and during which any judgment as described above is not carried out regardless of the presence/absence of the defective weft inserting. Over one or certain periods immediately after the loom starts up, it sometimes happens the weft flight time up to the feeler head is made different from the normal weft fight time in the steady loom operation, thus the judgment becoming uncertain. The interlock period is prepared in order to prevent the normal weft inserting being erroneously judged to be a defective weft inserting. Accordingly, it will be seen from Fig. 3 that the longer interlock period is set for the weft of such a sort that is apt to generate cotton dusts or the like in the middle of the weft inserting.

2. Period of watching a signal from the H1 feeler head 12 for determining a threshold value except the weft watching period. This period corresponds to the weft absence period. As described above, the signal value in the weft absence period is used in order to determine the reference threshold value. Accordingly, if cotton dusts or the like caused in the middle of the weft inserting are detected during this period, the reference threshold value deviates from a most proper value. As a result, the judgment becomes so uncertain that the defective weft inserting is erroneously judged. This period is included in the judgment conditions for preventing such error. Because of this, as shown in Fig. 3, the stronger the tendency of generating cotton dust or the like becomes, the more this period is made shorter.

3. Comparison Mode comparing a signal value from the H1 feeler head 12 in the weft watching period with the reference threshold value determining whether or not the weft exists within a weft detectable range.

This judgment mode includes the following things to be judged. That is, (i) whether or not the integrated value of the yarn signal S1 exceeds the reference threshold value in a predetermined period within the weft watching period, (ii) whether or not the integrated value of the yarn signal S1 has exceeded the reference threshold value within the weft watching period, (iii) whether or not the integrated value of the yarn signal S1 exceeds the reference threshold value at the end of the weft watching period. At least two things to be judged can be selected corresponding to a sort of the yarn.

As the state of the output signal from the weft detecting device is influenced by the weft flying characteristic (rampage of the weft, presence/absence of weft shrinkage, and others) which varies depends on a sort of the west, the optimum judgment mode can exist for every sort of the weft. In other words, when carrying out the weft inserting with wefts having different characteristics by means of the loom of multicolored type, if the judgment mode is selected so as to meet the characteristic of the most representative weft, it happens that each of other wefts having characteristics different from that of the representative weft comes to be actually judged by an unsuitable judgment mode, thus the judgment becoming uncertain. As a result, there will be made such an erroneous judgment that a normal weft inserting is judged to be a defective weft inserting. Thus, the judgment mode is incorporated in judgment conditions for preventing the erroneous judgment like the above. The term "weft shrinkage" as used in the above indicates a phenomenon in which a weft as once inserted shrinks before it is beaten-up against the cloth fell, thus the leading end of the weft being drawn back toward the upstream side of the weft inserting direction, and this phenomenon will be referred to as "weft shrinkage" hereinafter.

Table 1 indicates an example of judgment mode selection suitably applicable to a spun yarn, a filament yarn, and a yarn easily causing the weft shrinkage. Numerals 1 through 3 as indicated in the column of "H1 Feeler Judgment Mode" corresponds to (i), (ii) and (iii) as described above. Depending on the degree of the weft shrinkage, the weft disappears from the weft detectable range of the weft detecting device, thus coming to lack in the signal.

The above-mentioned judgment mode supposes the case wherein a feeler head which is arranged in an ordinary weft arrival position in the same way as the H1 feeler head 12, judges whether or not the weft arrives at the selvedge, in other words, judges the presence/absence of the defective weft inserting.

Instead of this, in case of judging whether or not the weft as cut off by the fluid jet force in the middle of the weft inserting is detected, in other words, whether or not the weft cut-off by the fluid jet force and the long pick are generated by means of the H2 feeler head 14, which is provided such that it is located in a position on the downstream side of and at a distance from the H1 feeler head 12 in the weft flying direction and if it happens that the weft is cut of by the fluid jet force in the middle of the weft inserting, the leading end of the weft as cut off can fly up to that position, the judgment mode as described before includes the following things to be judged. That is, there is a judgment mode wherein a plurality of periods of time (signal width) are set corresponding to yarn sorts and at the same time, it is judged whether or not the state where the integrated value of the yarn signal exceeds the threshold value within the weft watching period has exceeded the above period of time as set corresponding to the yarn sort.

In a feeler head for use in detection of the weft cut-off by the fluid jet force, dusts such as cotton dusts or the like caused in the middle of the weft inserting are detected if the weft cut-off by the fluid jet force is not generated. The degree of dust generation, in other words, the generation period of the signal from the detective device varies depending on a sort of each weft. If the period of the signal for preventing the erroneous dust detection from being caused is unsuitably set and kept as it is, the judgment of the weft cut-off by the fluid jet force becomes uncertain and it comes to take place that the normal weft inserting is judged as the defective one or vice versa, or the defective weft inserting is overlooked. The feeler head for use in detection of the weft cut-off by the fluid jet force in order to preventing such failures as described above. Accordingly, as shown in Table 1, the stronger the tendency of generating cotton dusts or the like becomes, the more this period of time (signal width) is made longer.

Furthermore, as shown in Tables 2 and 3, the judgment condition for judging the occurrence state of the defective weft inserting including the following things.

(1) Whether or not the defective weft inserting continuously occurs by the number of times as set in advance. Here, it is desirable for this occurrence number of times to be separately set at a different value on the sort by sort basis of the weft for use in weft-inserting.

(2) Whether or not the occurrence number of times of the defective weft inserting within the period as determined in advance has taken place by the number of times as set in advance. Here, this period may be decided by using the number of pickings or the time as a scale.

In the weft detecting apparatus 10, the weft selection signal corresponding to the weft picking is generated every weft inserting, and then each yarn sort of the weft is specified and determined based on that weft selection signal as generated. Furthermore, the judgment condition corresponding to that specified yarn sort is selected, thereby the presence/absence of the weft being detected by the selected judgment condition and the defective weft inserting being judged.

Accordingly, in case of continuously performing the weft inserting without altering the yarn sort of the weft to be inserted, in other word, continuously repeating a plurality of the weft pickings with the weft of the same yarn sort, the same judgment condition is applicable to the judgment on the presence/absence of the defective weft inserting at each weft picking time. Contrary to this, in case of performing the weft inserting wherein the yarn sort of the weft is altered every weft picking, the judgment condition corresponding to the yarn sort of the weft as altered is selected and used for judging the presence/absence of the defective weft inserting.

As described above, the detection of the weft as inserted is carried out based on each yarn sort of the weft as inserted. Accordingly, even if the yarn sort of the weft is altered every weft inserting, the weft detection can be surely carried out, thus the presence/absence of the defective being accurately judged.

The signal processing portion 36 as shown in Figs 1 and 2 is described as hardware i.e. an electric circuit, but it may be replaced by software capable of carrying out the function equivalent to the hardware. Besides, the integrator 64 in the signal processing portion 36 may be replaced by other means, for instance an electric circuit capable of comparatively judging an amplified signal, an electric circuit capable of comparatively judging the result of differentiating a yarn signal, or the like.

With regard to the sorts of the weft, it may be possible to identify and select them by setting as well as using the reference threshold value compared with the feeler signal, the weft watching period, and the gains of

amplifiers

28, 30, respectively.

The feeler head as described above is not limited to that of the photoelectric reflection type and it may be a feeler head of the photoelectric transmission type. Besides, with regard to the type of the weft detecting device, some other types can be considered instead of the type that is arranged facing to the flying path of the weft, for example, the type of generating a signal when the weft transported by the beating-up motion after the weft inserting passes through the weft detectable range, the type of generating a signal when coming in contact with the weft as inserted, and so forth. The later type, that is, the contact detection type may be used as a feeler head of the electro-conductive type, or a sensor of the contact detection type capable of detecting vibration and tension in the water jet loom.

While some embodiments of the invention have been shown and described in the above with reference to the accompanying drawings, the invention is not limited to those embodiments. Various changes and modifications will be possible without departing from the gist of the invention.

Claims

A method of detecting a weft in a loom comprising the steps of.

setting at least one of judgment conditions in advance with regard to each sort of the weft, for judging the presence/absence of a defective weft inserting;

selecting at least one of judgment conditions corresponding to a sort of the weft to be inserted; and

judging the presence/absence of the defective weft inserting by using the selected judgment condition as well as a signal from a weft detecting device (12, 14, 24, 26) for detecting the weft.
A method of detecting a weft in a loom as claimed in claim 1, wherein the judgment of the presence/absence of the defective weft inserting includes the step of comparing a signal from a weft detecting device (12, 14, 24, 26) with a reference threshold value as used for detecting the presence/absence of the weft.
A method of detecting a weft in a loom as claimed in claim 1 or 2, wherein said judgment conditions includes at least one of conditions as selected from a group including a period which is defined over at least one of weft picking periods beginning from the start of the loom operation and during which any judgment is not carried out regardless of the presence/absence of the defective weft inserting; a period excluding a weft watching period for said judgment and watching a signal from said weft detecting device (12, 14, 24, 26) to determine a reference threshold value for detecting the presence/absence of the weft; a judgment mode comparing a signal from said weft detecting device in said weft watching period for said judgment with said reference threshold value; and the occurrence times of the defective weft inserting.
A method of detecting a weft in a loom as claimed in claim 3, wherein said weft detecting device (12, 14, 24, 26) includes a weft detecting head (12) which is arranged in the arrival position of the leading end of the weft as normally inserted, and said judgment mode includes at least two modes selected from a group including the mode of judging whether or not the integrated value of a signal from said weft detecting device exceeds the reference threshold value in a predetermined period within said weft watching period; whether or not the integrated value of a signal from said weft detecting device exceeds said reference threshold value within said weft watching period; and whether or not the integrated value of said signal from said weft detecting device exceeds said reference threshold value at the end of said weft watching period.
A method of detecting a weft in a loom as claimed in claim 3, wherein said weft detecting device (12, 14, 24, 26) includes a weft detecting head (14) which is arranged in the arrival position of the leading end of the weft as cut off by the fluid jet force, and said judgment mode includes the mode of judging whether or not such a state that the integrated value of a signal from said weft detecting device exceeds said reference threshold value within said weft watching period, exceeds a reference time that is determined with respect of each sort of the weft.
A method of detecting a weft in a loom as claimed in any one of claims 3 through 5, wherein the occurrence times of the defective weft inserting includes at least one of the continuous occurrence times of the defective weft inserting and the occurrence times of the defective weft inserting within a predetermined period.
A method of detecting a weft in a loom as claimed in any one of claims 1 through 6, wherein said weft detecting device (12, 14, 24, 26) includes at least one of a weft detecting head of the photoelectric type which detects the weft by having the weft penetrated through a predetermined optical path and a weft detecting head of the contact detection type which detects the weft when the detecting head and the weft make contact with each other due to the fluctuation in the flying course of or the tension applied to the weft.
A method of detecting a weft in a loom as claimed in any one of claims 1 through 7, wherein said loom is constituted to be capable of selectively inserting two or more sorts of wefts in correspondence to a count of a weft inserting pick, and wherein the step of selecting utilizes a weft selection signal to be used in weft inserting for selection of said judgment condition.
An apparatus for detecting a weft in a loom comprising:

a weft detecting device (12, 14, 24, 26) for detecting the weft;

a judgment condition setting device (70) for setting at least one of judgment conditions as used for judging the presence/absence of a defective weft inserting, with regard to each sort of the weft; and

a judgment portion (60) selecting at least one of judgment conditions corresponding to a sort of the weft to be inserted and judging the presence/absence of the defective weft inserting by using the selected judgment condition as well as a signal from said weft detecting device.
An apparatus for detecting a weft in a loom as claimed in claim 9, wherein said loom is constituted to be capable of selectively inserting two or more sorts of wefts in correspondence to a count of a weft inserting pick, wherein said judgment portion (60) is received a weft selection signal, and selects said judgment condition corresponding to the sort of the weft in accordance with said weft selection signal.