Abstract:
Failure in a weft inserting motion of a weaving loom is detected if a weft yarn, which is shot into a shed of warp yarns, separates from electrodes, a predetermined number of times, within one picking motion to stop the weaving loom.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to a method of and a device for controlling a weft inserting motion of a weaving loom for stopping the loom in response to failure in the weft inserting motion. 
     Several methods and devices have been proposed for stopping a weaving loom in response to failure in a weft inserting motion. According to one of the conventional methods and devices, a failure in a weft inserting motion is detected by checking whether or not an electrical current flows through two electrodes by means of a weft yarn contacting the two electrodes. 
     However, a defect can be pointed out in the above described conventional methods and devices. That is, when the weft yarn, which is properly shot into a shed of warp yarns, separates from one of the two electrodes even for an instant during a detecting time period, a failure in the weft inserting motion is undesirably detected regardless of a proper picking. 
     SUMMARY OF THE INVENTION 
     It is therefore a primary object of the present invention to provide an improved method of removing the aforementioned defect of the prior art, according to which method failure in a weft inserting motion is detected only if the number of connections of the weft yarn with the two electrodes reaches a predetermined number within one picking motion. 
     Another object of the present invention is to provide an improved device for removing aforementioned defect of the prior art, which device detects failure in the weft inserting motion only if the number of connections of the weft yarn with the two electrodes reaches a predetermined number within one picking motion. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other objects, features and many of the attendant advantages of this invention will be appreciated more readily as the invention becomes better understood by the following detailed description, when considered in connection with the accompanying drawings, wherein like parts in each of the several figures are identified by the same reference characters, and wherein: 
     FIG. 1 is a block diagram illustrating a first embodiment of the present invention; 
     FIGS. 2A-2J show wave forms of various signals appearing at various parts of the block diagram of FIG. 1; 
     FIG. 3 is a block diagram illustrating a second embodiment of the present invention; and 
     FIGS. 4A-4G show wave forms of various signals appearing at various parts of the block diagram of FIG. 2. 
    
    
     Reference is now made to FIG. 1, which illustrates a first embodiment of the present invention in a block diagram. 
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Two electrodes 1 and 2 are provided on a reed 4 at the opposite side with respect to a suitable yarn shooting means (not shown), wherein it is preferable that the electrodes 1 and 2 are sufficiently spaced in order to avoid an undesirable electrical connection due to shooting-water although a weft yarn 3 does not touch the electrodes. As shown, the electrode 1 is connected at one end thereof to one end of a d.c. power source 6, and the other end of the d.c. power source 6 is connected to a detector 5. The electrode 2 is connected at one end thereof to the detector 5. The weft yarn 3 serves, in picking, to electrically contact the electrodes 1 and 2, thereby to allow a d.c. current to flow a series circuit consisting of the electrodes 1 and 2, the detector 5, and the d.c. power source 6. The signal from the detector 5, which represents whether or not the weft yarn 3 contacts the electrodes 1 and 2, is fed to a wave form shaping circuit 7. A shaped signal from the circuit 7 is then fed to an AND gate 9 through an inverter 8 and an input terminal 9a. 
     An arm 11 is fixedly attached to a rotatable axis 10 which rotates in synchronism with motion of a weaving loom (not shown). As shown, a piece of iron 12 such as a permanent magnet is fixedly attached to the arm 11. In the vicinity of the locus of the movement of the piece of iron 12, a suitable switching means including a coil is provided to generate a signal indicative of a logic &#34;1&#34; when the piece of iron 12 comes in the neighborhood of the switching means 13. The signal from the switching means 13 represents a time period of a weft yarn inserting motion and is fed to the AND gate 9 through an input terminal 9c. The AND gate 9 is connected through an input terminal 9b to a pulse generator 14 which always generates a train of pulses at a predetermined time intervals after a weaving loom starting switch 15 is switched on. Once the starting switch 15 is switched on, a hook-type switch 17 is closed and retains its condition as long as left alone to close an interlocked contact 18, thereby to supply the pulse generator 14 with an electrical energy from a power source (not shown) connected to a terminal 25a. On the other hand, the hook-type switch 17 closes a plurality of interlocked contacts 21 to energize a weaving loom driving motor 19. 
     The pulses from the pulse generator 14 is fed to a counter 22 through the AND gate 9 only when the three inputs each denotes a logic &#34;1,&#34; as is well known in the art. The counter 22 generates a signal when the number of the pulses from the pulse generator 14 reaches a predetermined number within one detecting time period, allowing a monostable multivibrator 23 to generate a control signal. The control signal thus produced is then fed to a relay circuit 24 to allow the same to open a switch 25 connected in series with a manual stop switch 33. This means that the driving motor 19 is deenergized to stop the loom. In the above, it is preferable to determine the one detecting time period such that it corresponds to a time period indicated by the signal from the switching means 13. Whilst, if the number of the pulses from the pulse generator 14 does not reach the predetermined number within one detecting time period, the counter 22 does not generate any signal therefrom. In the above two cases, the number of the pulses stored in the counter 22 is cleared by a reset signal from a reset signal generator 26 at the end of the detecting time period. 
     In the above, the pulse repetition rate of the pulse generator 14 and the predetermined number of the counter 22 should be changed in accordance with a kind of a weft yarn, for example. 
     In the following, the operation of the first preferred embodiment of FIG. 1 will be described in connection with FIGS. 2A--2J. When the starting switch 15 is switched on, the motor 19 is energized to start the loom (not shown) and the pulse generator 14 begins to generate a train of pulses at a predetermined repetition rate. If the weft yarn 3 contacts the electrodes 1 and 2 during all the detecting time period, the signal from the detector 5 has a wave form as shown in FIG. 2G. In this case, the signals from the shaping circuitry 7 and the inventer 8 have wave forms as shown in FIGS. H and I, respectively. On the other hand, the wave form of the signal from the generator 14 is denoted in FIG. 2c, and the wave form of the signal from the switching means 13 is denoted in FIG. 2D. In the above case, that is, when the weft yarn 3 contacts the electrodes 1 and 2 during all the detecting time period, the AND gate 9 does not generate any output in that the signal from the inverter 8 indicates a logic &#34;0.&#34; 
     Whilst, if the weft yarn 3 separates two times, for example, while the signal from the switching means 13 indicates a logic &#34;1,&#34; the signal from the detector 5 has a wave form as shown in FIG. 2A. The signal from the detector 5 is then fed to the shaping circuitry 7 in which the signal is shaped. Therefore, it is understood that the output of the AND gate has a wave form as shown in FIG. 2E. This means that the counter 22 counts two pulses for the detecting time period. 
     On the other hand, if the weft yarn 3 does not contact the electrodes 1 and 2 while the signal from the switching means 13 indicates a logic &#34;1,&#34; as shown in FIG. 2D, the signal from the detector 5 does not indicate a logic &#34;1.&#34; Therefore, the AND gate receives a logic &#34;1&#34; for the detecting time period at the input terminal 9a. This means that the counter 22 receives 8 pulses from the pulse generator 14 through the AND gate 9. In the above, even if considering a phase shift between the inputs to the AND gate, the counter 22 counts at least 7 pulses during the detecting time period. As a result, when the predetermined number of the counter 22 is set to 7, the counter 22 generates a signal as shown in FIG. 2F, which signal triggers the monostable multivibrator 23, thus stopping the weaving loom as already referred to. 
     In the above three cases, the reset signal generator 26 generates the reset signal in response to a trailing edge of the signal from the switching means 13, as shown in FIG. 2J. The reset signal is fed to the counter 22 to clear the same. Thus, the loom continues to operate. 
     In the foregoing, the inverter 8 cam be omitted wherein the counter 22 generates its output when the number of the pulses from the pulse generator 14 is less than a predetermined number. 
     Reference is now made to FIG. 3, which illustrates a second preferred embodiment of the present invention. In the following, the same parts as those of FIG. 1 will not be referred to in detail for brevity. An amplifier 27 receives the signal from the detector 5 to amplify the same to a predetermined level. The amplified signal is then fed to a wave form shaping circuitry 28 to be shaped as shown in FIG. 4B. The signal from the shaping circuitry 28 is then fed to an AND gate 29 through an input terminal 29a. The AND gate receives the signal from the switching means 13 at an input terminal 29b. The output terminal (no numeral) of the AND gate 29 is connected to an integrator 30 which integrates the magnitudes of the pulses from the circuitry 28. As shown, the reset signal generator 26 is interposed between the switching means 13 and the integrator 30, resetting the integrator 30 just as already referred to in connection with FIG. 1. The signal from the integrator 30 is then fed to the next stage, viz, a comparator 31 which compares the magnitude of the supplied signal with that of a reference signal to generate a signal indicative of a logic &#34;1&#34; if the former is less than the latter. The comparator 31 is connected to an AND gate 32 through an input terminal 32a. On the other hand, a switching means 13&#39;, which is similar to the switching means 13, is connected to the AND gate 32 through an input terminal 32b, supplying the same with a signal indicative of a logic &#34;1&#34; at the end of the time period of the signal from the switching means 13. The output terminal (no numeral) of the AND gate 32 is connected to the relay circuit 24. 
     In the following, the operation of the second preferred embodiment of FIG. 3 will be described in connection with FIGS. 4A-4G. If the weft yarn 3 separates from one of the electrodes 1 and 2, two times, for example, while the signal from the switching means 13 (FIG. 4C) indicates a logic &#34;1,&#34; then the signal from the detector 5 has a wave form as shown in FIG. 4A. The signal from the detector 5 is fed to the amplifier 27 to be amplified thereat to a predetermined level. The signal (not shown) from the amplifier 27 is fed to the shaping circuitry 28 from which the signal having a wave form as shown in FIG. 4B is generated to be fed to the AND gate 29 through the input terminal 29a. Therefore, the AND gate 29 generates a signal with a wave form as shown in FIG. 4D, which signal is then fed to the integrator 30 to be integrated therein. The wave form of the output of the integrator 30 is shown in FIG. 4E. The signal from the integrator 30 is then fed to the comparator 31 which compares the magnitude of the supplied signal with that of the reference signal (&#34;L&#34; in FIG. 4E), wherein, when the latter is more than the former, the signal from the comparator 32 indicates a logic &#34;1,&#34; on the other hand, otherwise, the signal from the comparator 32 indicates a logic &#34;0,&#34; as shown in FIG. 4F. Whilst, the AND gate 32 receives a signal indicative of a logic &#34;1&#34; at the end of the time period of the signal from the switching means 13 as shown in FIG. 4G. Therefore, in the above case, the AND gate 32 does not generate a control signal which is to be fed to the relay circuit 24 to open the switch 16. 
     It is understood that, if the magnitude of the signal from the integrator 30 does not exceed the reference level &#34;L&#34;, the AND gate 32 generates the signal indicative of a logic &#34;1&#34; therefrom to open the switch 16 to deenergize the weaving loom. 
     It is apparent from the foregoing that according to the present invention the defect inherent in the prior art can be removed. 
     While the invention has been described in connection with two exemplary embodiments thereof, it will be understood that many modifications will be readily apparent to those of ordinary skill in the art; and that this application is intended to cover any adaptation or variations thereof. Therefore, it is manifestly intended that this invention be only limited by the claims and the equivalents thereof.