Abstract:
In construction of a fluid jet loom equipped with a free weft exchanger and a weft feeler, a weft detection circuit connected to the weft feeler is provisionally disenabled over a predetermined number of picks after every weft exchange and allows continued weft insertion even in case of faulty weft insertion in order to keep high running efficiency of the loom as long as the extent of weaving defect is within a tolerable extent.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to method and apparatus for controlling weft detection on a fluid jet loom, and more particularly relates to method and apparatus for carrying out control on weft detection right after every weft exchange on a fluid jet loom equipped with a free weft exchanger which carries out weft insertion in accordance wth a given weft selection pattern. 
     In general on a fluid jet loom equipped with such a free exchanger, weft insertions at the first and following several picks are quite unstable and tend to cause unnecessary stoppage of the loom on detection of such unstable weft insertions. 
     Such troubles are caused by weft slippage due to abrupt starting of a weft reservoir in turn. The troubles are further caused by a fact that a weft long caught by a clamper, which is located upstream of a main nozzle, can hardly be delivered smoothly due to clinging to the clamper. In the case of a water jet loom, a main nozzle in rest does not initiate its ejection until right before weft exchange and no water exists in the main nozzle. As a consequence, no sufficient ejection of water is obtained as weft insertion of the first pick right after the weft exchange and such insufficient ejection tends to allow undesirable whipping of the leading end of the weft under insertion, thereby causing faulty weft insertion. 
     When a loom is stopped on detection of faulty weft insertion right after every weft exchange, running efficiency of the loom is lowered considerably. When the extent of a weaving defect caused by faulty weft insertion is within a tolerable limit, it is generally better to continue running of the loom in order to keep high running efficiency of the loom. 
     SUMMARY OF THE INVENTION 
     It is the object of the present invenion to raise running efficiency of a loom without stoppage even when weft exchange is followed by faulty weft insertions over several picks. 
     In accordance with the basic concept of the present invention, a weft detection circuit is provisionally disenabled when a faulty weft insertion or insertions are detected within the period of one to two picks right after every weft exchange, thereby allowing continued weft insertion. To this end, the weft detection circuit is accompanied with a detection interceptor circuit which provisionally disenables detection on receipt of a weft selection signal put out by a weft selection circuit. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic view of one embodiment of the apparatus in accordance with the present invention, 
     FIG. 2 is a block diagram of another embodiment of the apparatus in accordance with the present invention, and 
     FIG. 3 is a graph for showing time-functional changes of various signals processed in the apparatus of the present invention and, more specifically, shows signal processing through the circuit section of FIG. 2. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     On the example of the loom shown in FIG. 1 alternate weaving with two different wefts is carried out. One weft from a supply source 1a is passed to a reservoir drum 5a via a nip roller 2a and a feed roller 3a and, after delivery from the reservoir drum 5a, is passed to a main nozzle 7a via a clamper 6a. In a same way, the other weft from a supply source 1b is passed to a reservoir drum 5b via a nip roller 2b and a feed roller 3b and, after delivery from the reservoir drum 5b, is passed to a main nozzle 7b via a clamper 6b. The nip rollers 2a and 2b are linked to a common selection rod 4 which is operated via a lever 4a by a solenoid 8. 
     The electronic part of the apparatus includes a weft selection circuit 30, a detection interceptor circuit 40 and a weft detection circuit 50 connected to each other. 
     The weft selection circuit 30 includes a controller 31 which generates a weft selection signal to control operation of the nip rollers 2a and 2b in accordance with preset pattern, and a solenoid driver 32 which drives the solenoid for operation. When a weft selection signal SA of, for example, level &#34;H&#34; is issued by the controller 31, the solenoid driver 32 urges the solenoid 8 to push up the lever 4a so that the selection rod 4 should move upwards. Then the nip roller 2b is brought into surface contact with the feed roller 3b so that weft insertion should be carried out by the main nozzle 7b. When a weft selection signal SA of, for example, level &#34;L&#34; is issued by the controller 31, the solenoid driver 32 urges the solenoid 8 to pull down the lever 4a so that the selection rod 4 should move downwards. The nip roller 2b is brought out of the surface contact with the feed roller 3b and, conversely, the nip roller 2a is brought into surface contact with the feed roller 3a so that weft insertion should now be taken over by the main nozzle 7a. Though not shown in the illustration, the clampers 6a, 6b and the main nozzles 7a and 7b are also selectively driven for operation by typical circuit control and operating means in response to the above-described weft selection signal SA. The weft exchange mechanism to be employed is not limited to the illustrated example. 
     The detection interceptor circuit 40 includes a preset counter 41 of, for example, a down-type, a one-shot multivibrator 43 and an interlock setter 45. When the weft selection signal SA is put in, the one-shot multivibrator 43 detects rise and fall of the signal and issues a one-shot signal SB to be passed to the preset counter 41. 
     The preset counter 41 has a DATA terminal connected to the interlock setter 45 and a CK terminal connected to a feeler period detector 60. When the rise of the one-shot signal SB from the one-shot multivibrator 43 is put in a PRESET terminal of the preset counter 41, a reference R1 from the interlock setter 45 is set in the peset counter 41. The feeler period detector 60 issues feeler period signals in the form of a train of pulses as shown in FIG. 3. FIG. 3 depicts a graph which explains signal processing through the circuit section shown in FIG. 2. On receipt of every feeler period signal, the preset counter 41 counts fall of the pulse and counts down from the set reference R1. When an instant count value equals zero, the preset counter 41 issues a signal of, for example, level &#34;H&#34;. This signal is passed to the weft detection circuit 50 as a &#34;detection enable signal SC&#34;. 
     The weft detection circuit 50 includes an amplifier 53 for a feeler 51 arranged on the weft arrival side of the loom a comparator 55 which compares the amplified detection signal SD with a given reference R2. When the amplified detection signal SD falls short of the reference R2, the weft insertion is regarded as unsuccessful and a signal SE of level &#34;H&#34; is issued by the comparator 55 in order to indicate faulty weft insertion. The comparator 55 is connected to an AND gate 57 which accept this faulty weft insertion indicative signal SE and the detection enable signal SC from the preset counter 41. The AND gate is also connected to the feeler period detector 60. 
     The AND gate 57 issues a loom stop signal SF when the feeler enable signal SC from the detection interceptor circuit 40 is at level &#34;H&#34; and the faulty weft insertion indicative signal SE is put in by the comparator 55 during the feeler period sensed by the feeler period detector 60. 
     When a weft selection signal SA for weft exchange is issued by the weft selection circuit 30, the one-shot multivibrator 43 accepts the signal to issue a one-shot signal SB which is in turn passed to the preset counter 41. Then the reference R1 from the interlock setter 45 is set in the preset counter 41 which then counts falls of the feeler period signals from the feeler period detector 60 in order to count down from the set reference R1. When an instant count value equals the reference R1 from the interlock setter 45, the preset counter 41 passes a detection enable signal SC to the AND gate 57. No feeler enable signal is put in the AND gate 57 as long as an instant count value exceeds zero so that no AND condition should be established and the AND-gate 57. As a consequence, no loom stop signal is issued by the detection interceptor circuit 50 even when faulty weft insertion signals continue to be issued by the comparator 55. 
     As is clear from the foregoing, the weft detection circuit 50 is provisionally disenabled over a perdetermined period, e.g., a period of one to two picks following weft exchange so that no loom stop signals should be issued during the picks. Similar situation resides in the starting of a loom. As shown in FIG. 3, signals SB1 and H1 are generated by a loom start signal, whereas signals SB2 and H2 are generated by a weft selection signal. It is thus advantageously employed also that the preset counter 41 should not issue the feeler enable signal over the period of one to two picks after starting of the loom. The embodiment shown in FIG. 2 is designed to this end. In this case, the reset counter 41 accepts, via on OR-gate 49, a loom start signal and/or a weft selection signal. A preset signal is passed to the preset counter 41 from the OR-gate 49 when either of the two signals arrives at the OR-gate 49. 
     As long as a weaving defect or defects caused by a faulty weft insertion or insertions following weft exchange are within a tolerable limit, the loom is allowed to continue its operation without causing any serious lowering in running efficiency. Accordingly, the weft detection circuit 50 may be disenabled over a different period depending upon the desired quality of the fabric being produced.