DE1710274A1 - Weft guard on a loom - Google Patents

Description

Ptl May 30, 1967

OPPENIACHAMMAIN. Ntrwistf. 17 - tel. 185142 öö / ow

Heberlein & 0ο A. (J., OH 9630 Wattwil (Switzerland)

"Weft thread monitor on a loom · ·,

In the case of looms it is necessary »at the Bruoh des Weft thread to turn off the loom immediately so that no further debris can be rorgenoarnen without weft thread and also not calibrate the bed the weft thread can jam again with a subsequent entry «In both cases, errors occur in woven sut. Hur with immediate recognition of the Bohueefadenbruohes and shutdown of the loom know how to avoid mistakes

j To solve this problem, mechanical Sohuas

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171027 *

thread monitor known which during the entry check the weft thread for its mechanical tension · Because of the large mechanicals required The speeds of this scanning device and because of the difficulty in setting the various thread tensions, especially when thick and thin threads are inserted in the same fabric, these mechanical weft thread monitors cause great difficulties during operation known attempts to scan the weft thread electro-optically *

Is also known a weft detector on a weaving loom, emits a accommodated in a protection signal transmitter which different under the influence of the weft thread signals, depending on whether the Paden f is proceeding normally or is broken, and with an attached to) a sley transducer which has a coil which is inductively coupled to the signal generator in the interval between the gate closing movement of the shooter and, when an error signal is received, generates a control pulse which stops the loom. In the case of the well-known thread guard of this type, the Sohuas

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thread over a hell, which he sets in rotation and in which a magnet is contained. As long as the Bolle rotates during the mentioned time interval induces a different signal in the converter bobbin than when it is stationary due to a thread breakage Role. This thread monitor has the disadvantage that the thread has to do a lot of work to get the role to set in rotation, and that this role also does not come to a standstill immediately after a thread break comes, so that brakes still have to be seen.

The present invention avoids these disadvantages in that the signal converter has a high-frequency generator which generates an output voltage via a demodulator, and that its coil is inductively coupled in the time interval mentioned with a coil of the signal generator which is in a circuit, i

whose impedance depends on whether a mechanical {

Vibration system created by friction of the normal Weft thread is set in oscillation, oscillates or not, so that by a thread breakage Changes in the impedance caused by the reaction on the coil of the converter in the output voltage

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of the demodulator causes the control pulse to stop the loom to occur.

The present invention can also be modified in such a way that the coil of the signal converter, which is in the Time interval of the movement past of the sole is inductively coupled to the coil of the signal generator, is a circuit element of the high-frequency generator.

As will be explained in the following description, this results in a simplification of the tuning of the signal converter compared to the former Embodiment.

Measures can also be taken to improve the signal generator, in particular with regard to

) the achievement of a more favorable form of the signal conversion ) former supplied control signal.

In the drawing, embodiments of the invention are object shown schematically. Ss is:

Figure 1: a view of a signal transmitter housed in a shooter, which in the event of breakage of the

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Sohussfadena an electrical signal eyed,

Figure 2 s the electrical circuit diagram dee Signaling device according to fig. 1 and

figur 3 t daa electrical wiring diagram of a signal converter on the sley

mounted iat and from one at Faden- Ä

bruoh TOJB Above received error signal \

a control pulse is generated which is used to stop the lebstuhlea.

Bit Figure 4a and Figure 4b are two diagrams

Clarification of the mode of operation of the signal converter. Furthermore lets

FIG. 5 s the electrical circuit diagram of the signal generator of a weft thread monitor,

Figure 6 ι the electrical circuit diagram of the train j

obeyed signal converter, j

FIG. 7 shows a diagram to explain the mode of operation of the weft thread monitor according to FIG. 1 and 2,

Figure 9 t tine Aueführungsform other of the signal generator and

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Fig. 9 ζ yet another form of the signal transmitter, with a detail variant indicated by dashed lines.

The signal transmitter shown in FIG. 1 has a base plate 1 on which a rod-shaped, piezoelectric crystal 2 is mounted by means of two holders 3 and 4. A vertical leg of a resilient bracket 5 is also attached to the base plate 1, which has a horizontal leg which is connected to the crystal 2 via a coupling link 6 and on which the weft thread 7 lies.The signal transmitter is arranged in the shuttle (shuttle) in which the Torratsspule of the weft thread and is of the sley longitudinally for the insertion of the weft thread between the warp threads will be thrown back and forth w. The thread 7) withdrawn from the bobbin brushes over the bow 5 and causes it to vibrate due to its friction, similar to how the bow of a violin excites the strings to vibrate. In addition to constant friction, the excitation can also take place by periodically striking the running thread during unwinding. The bracket 5, the coupling element 6 and the crystal 2 thereby form a mechanical one

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Vibration system of low damping, which in its resonance frequency oscillates.

The swing of the bracket 5 is a sign that the weft thread 7 is properly withdrawn from the supply spool. In the event of a thread breakage, there is one Bracket 5 still, which - as shown below - leads to the generation of a control pulse that the Loom stops. Ub to prevent the bracket 5 also by forces other than the friction of the thread 7, z. B. by the friction of the protection on the sley or on the warp threads, stimulated to swing can be, the base plate 1 is not rigidly but flexibly mounted in the shooter.

Electrical circuit elements which have been omitted in FIG. 1 are mounted on or in the base plate 1, namely a capacitance diode 8, a resistor 9 »a Capacitor 10 and a coil 11, the circuit of which is shown in FIG. The capacitance diode 8 and the Coil 11 form an oscillating circuit, the resonance frequency of which differs only slightly from that of the capacitance diode The high resistance 9 connected in parallel and that connected in series with the coil 11 has a large capacitance

10ββ4 "2? (Γ377

having blocking capacitor 10 depends on the only separates the piezo crystal 2 from the coil 11 in terms of direct current. Because the capacitance of the capacitance diode 3, however, from the »piezocrystal lying on it 2 depends on the voltage supplied, the resonance frequency V of the LC resonant circuits 8, 11, the is of the order of a few MHz, through which

* Vibrations of the mechanical vibration system 5 » "6.2 modulated, the resonance frequency U) of which is of the order of about 1-2 KHz. that the signal generator 1-11 emits in the event of a thread breakage in that the resonance frequency V is no longer modulated, but assumes a basic value V-j, which corresponds to the capacitance value of the capacitance diode 8 in the absence of a voltage, the one in the event of a broken lead remaining charge at the capacity

) diode 8 via the resistor provided for this purpose ) 9 discharges.

The signal converter attached to the sley, in particular sunk into the same, comprises according to FIG FIG. 3 shows a high-frequency generator 12 which, via a high-resistance resistor 13, has an LC parallel resonant circuit H stimulates vibrations, on its

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Resonance frequency before it is tuned. To the resonant circuit Hf whose coil is denoted by 20 is a Demodulator 15 connected so that a DC output voltage TJ occurs at the output terminals of the signal converter 12-15.

FIG. 4a shows the course of the voltage TI as a puncture of the time t, assuming that the resonance frequency Vo of the resonant circuit 14 is in the range of the modulated resonance frequency V of the resonant circuit 8, 11, but deviates from its basic value Vj. As long as the contactor or the encoder 1-11 is not in the vicinity of the signal converter 12-15, a fixed voltage value TJ ₀ occurs at its output terminals. While the contactor or the encoder flies past the converter, the resonant circuits 8, 11 and 14 are for a short time interval At of z. B. about 5 ms via their coils 18 and 20 coupled to one another. If the piezocrystal 2 is not in oscillation in this interval At, ie if the weft thread 7 is torn off, the oscillating circuit 3, 11 is tuned to the resonance frequency Vi, which _{differs from the resonance frequency V 0 of} the Sohwingkreises 14. The oscillating circuit 8, 11 acts like one connected in parallel to the oscillating circuit 14

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Impedance, so that the voltage at the resonant circuit H decreases with a corresponding increase in the voltage drop in the high-resistance resistor 13. The output voltage thus falls to a value U1, ie a negative pulse 16 of small magnitude _{occurs with respect to the normal level TJ 0.}

If the weft thread 7 strokes normally over the bow 5 and the piezo crystal 2 thus oscillates with the resonance frequency U of about 1-2 KHz, the resonance frequency V of the oscillating circuit 8, 11 assumes the value V ₀ once during each crystal oscillation, in that the The frequency swing in the modulation of the resonant circuit 8, 11 must be so large that the resonance frequency V _{0 is} passed through with each oscillation of the crystal 2. As a result, the resistance of the resonant circuit 8, 11, which represents a series resonant circuit with respect to the voltage induced in the coil 11, becomes very small. As a result, the output voltage IJ then falls within the time interval At several times to a value Ü2 »which is significantly lower than the value TJ-j. During normal work, an output pulse is generated when the encoder flies past the converter. B. is about the same as that

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Impulse 16, and a number of considerably higher, negative peak pulses.

By means of a known pulse duration discriminator, not shown you can define the type of output pulse and the output pulse 16 use as a control impulse to stop the loom *

In the figure 4b shows the voltage TJ is illustrated under the assumption that V ₀ "V-] iet. In the absence of piezo crystal oscillations, the oscillating circuit 3, 11 is thus tuned to the frequency Vo of the oscillating circuit H, so that in the interval Λ t the output voltage falls to the small value TJ 2 and an output pulse 18 of large, negative amplitude is generated. When the thread 7 is drawn off normally, the oscillating circuit 8, 11 is detuned twice with respect to the frequency Vb during each oscillation of the piezoelectric crystal 2, in that its resonance frequency V is once greater and once less than VO. As a result, a pulse 19 appears at the output of the converter during the interval & t, which pulse is composed of a negative basic pulse, which corresponds approximately to pulse 13, and a plurality of positive peak pulses. the

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The peaks of the positive peak pulses are drawn in FIG. 4b approximately at the same level as the normal output level U ₀ } on the assumption that the resonant circuit 8, 11 is detuned from the frequency Vo to such an extent that its resistance becomes very high at this frequency. In practice, however, the peaks should usually be somewhat lower ^. In the case of FIG. 4b, too, the negative output pulse without peak pulses, the duration of which corresponds to a fraction of the interval Δt, is used as a control pulse for shutting down the loom.

The embodiment in which Vf «Vq is preferred because this makes precise coordination superfluous. Of course, mixed forms of the pulses 17 and 19 can also occur if Yi and V _{0 are} not far apart. By the pulse duration discriminator

* But these impulses always become clear from the impulses

* 16 and 18 differentiated.

In a basically very simple embodiment of the thread monitor, which is not shown, there is no error signal generator the piezo crystal 2 and the circuit elements 8-10. Instead, the bracket 5 has a contact bridged by a damping resistor with a mechanical one

Coupled vibration system. The coil 11 is through short-circuited the mentioned contact once for each oscillation of the mentioned system

The coil 11 is in turn inductively coupled to the coil of the resonant circuit H of the unchanged signal converter 12-15 in each time interval Δ χ. If the thread breaks, the bobbin 11 is closed via the damping resistor, and a control pulse similar to the pulse 16 "occurs in the time interval Z ^ t. With normal work, the bobbin 11 is closed several times during the interval Δt, so that an output pulse corresponding to the pulse 17 arises, which does not cause the loom to switch off.

In another embodiment, also not shown instead of the piezocrystal 2 there is an electro- {dynamic device, while the signal generator j and the signal converter otherwise compared to the figures 1-3 are unchanged »

The signal transmitter housed in the shooter, whose circuit eoheaa is shown in Figure 5, is preferably constructed in the same mechanical respect as in FIG

1G 9 Ö kin 3 7 7

Figure 1 is shown. He knows a springy one On the bracket on which the running weft thread slides with friction and the one with a piezo crystal 2 is coupled to a mechanical oscillation system, which with its normal running thread Resonance frequency oscillates. The signal transmitter in turn has a capacitance diode 8, a resistor "9, a blocking capacitor 10 and a coil 11, "whereby the circuit differs from that according to the figure in that between the piezocrystal 2 and the LC resonant circuit 8, 11, a rectifier diode 21 is arranged.

The signal converter according to FIG. 6 in turn knows one High-frequency generator 12a, which consists of an amplifier 22, one arranged in its input circuit, frequency-determining LC element 23 and a feedback ^ coil 20a exists, which also serves for the inductive coupling of the signal converter with the signal generator. The output voltage of the generator 12a is fed directly to a demodulator 15 »Opposite the signal converter According to Figure 5, there is the difference that there is fed from the generator via a high-resistance resistor LC parallel resonant circuit is omitted, because of the inductance is formed by the coupling coil

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In the embodiment according to Figures 1 to 3, it is necessary to tune the generator, or its frequency-determining element, and the LC parallel resonant circuit to the same frequency Yo, which must be in the modulation range of the resonance frequency V of the resonant circuit 8, 11 of the encoder, which has a basic value γ-j for a non-oscillating piezo crystal. G

In the present embodiment according to FIG. 6, it is sufficient to tune only the frequency-determining LC element of the generator 12a, which, moreover, does not necessarily have to be in the input circuit of the amplifier 22, to a corresponding frequency Y _0. Some circuit elements and tuning are thus unnecessary.

Otherwise, the weft thread monitor works according to the figure

5 and 6 as follows: *

As long as the contactor with the signal transmitter is not in the vicinity of the signal converter, its output voltage U has the fixed value U ₀ . If V ₀ = Y 1, and the piezo crystal 2 does not oscillate, that is to say there is a thread breakage, the impedance of the LC oscillating circuit 8, 11 is at the frequency * / o of the converter generator 12a

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great. If the coil 11 is inductively coupled to the coil 20a during the time interval At when the guard flies past the converter, only a small HP current at the frequency V _{0 will} flow in the resonant circuit 11, 8, so that the feedback is only slightly weakened . Bs is thus obtained, only a small negative pulse 24 towards the starting level w TJ _0th If the weft thread runs normally and the w piezo crystal 2 oscillates, the capacitor 10 is charged by the diode 21, i.e. there is a constant voltage drop across the high-resistance resistor 9 * The capacitance of the capacitance diode 8 therefore does not change during an oscillation of the piezo crystal 2 , but has a certain value which is so large that the resonance frequency V of the IC resonant circuit 8, 11 at least approximately coincides with the frequency V ₀ . The impedance of the LC resonant circuit 8, 11 is then low. and in the time interval £ ± t the feedback is greatly weakened, so that a large negative pulse 25 with respect to the output level U ₀ occurs.

To evaluate the pulses 24 and 25, only a simple pulse height discriminator is now necessary. To switch off of the loom serves the control pulse 24, and the

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The discriminator only has to determine that its height does not exceed a certain threshold value.

Of course you can also make Y ₀ »V ·}, in which case the smaller negative pulse 24 occurs with normal thread unwinding and the larger negative pulse 25 i with thread breakage, so that this pulse 25 is the control pulse causing the j disconnection. Since it is simpler and safer to use the larger pulse 25 to switch off ssu, Y ₀ = Vj is preferably selected for the weft thread monitor according to FIGS. 5 and 6, especially since the coordination is considerably easier than in the embodiments described earlier.

The signal converter according to Figure 6 can also be used with the signal transmitter shown in Figures 1 and 2,

1 as well as with the following with reference to FIGS. 8 and 9

descriptive signal heads *

The signal generator according to FIG. 8 differs from that one according to Figure 5 only in that instead of the piezocrystal 2, an already mentioned electrodynamic Device 26 is provided, which in the present case

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consists of a permanent bar magnet 27 and a coil 28 surrounding the same. The magnet 27 belongs to the mechanical oscillation system that through. vibrates the friction of the weft thread and a voltage is induced in the coil 28, which via the rectifier diode 21 of the capacitance diode 8 ) and the condenser 10 is fed. Pie effect) wise is the same as with the signal generator according to FIG. 5.

The signal generator according to FIG. 9 also has an electrodynamic one Device 26, the coil 28 of which, however, lies in a diagonal of a bridge circuit 29, whose four branches consist of diodes 30-53 and in whose other diagonal the coupling coil 11 is arranged. The two diodes t connected to each diagonal point have opposite reverse directions with respect to the same. The device 26 with the diodes 30-31 represents a known ring modulator. When the magnet 27 does not oscillate, i.e. when the weft thread is torn, the resistance of the coil 28 is in the circuit of the coil 11, while with an oscillating magnet 27, as a result of the during a half cycle in the circuits 28, 31, 30 and 28, 32, 33 flowing currents, the diodes 30-32 the coil 11 In this half-cycle, short-circuit the impedance of the circuit for oscillations of the resonance frequency Vo

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this coil 11 is thus changed in the cycle of the oscillations of the mechanical oscillation system.

Compared to an embodiment with a mechanically caused short circuit, this embodiment has the Advantage that no mechanical wear and tear, sensitive short-circuit contact is necessary.

In Figure 9 it is indicated by dashed lines that the coil 11, a capacitor 34 can be connected in parallel, which, under certain circumstances, can be advantageous for achieving suitable impedance values in the circuit of the coil 11.

It should also be noted that it can be advantageous not only to use the signal transmitter housed in the shooter one, but with two signal converters of the same type attached to the sley. While using a single converter, the same is attached approximately in the middle of the sley, then one converter each arranged in the vicinity of the end of a sley. This has the advantage that thread breaks, which only occur at the end of the Schützenweg, before the turnaround the direction of movement of the shooter can be detected

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It is also noted that the mechanical The vibration system is not only stimulated to vibrate by the friction of the running off weft thread can be, but also in that this thread, for. B. as a result of its own vibrations! when expiring repeatedly on one (file of this oscillation system strikes.

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Claims (16)

- 21 claims 1. Weft thread monitor on a loom, with a signal transmitter housed in a shuttle, the emits different signals under the influence of the weft thread, depending on whether the thread runs normally or is torn, and with one on a web-I charger attached transducer that has a coil ( having, which is inductively coupled to the signal transmitter in the time interval of the passage of the contactor is, and on receipt of an error signal generates a control pulse that stops the loom, thereby characterized in that the signal converter (12-15) has a high frequency generator (12) which has a Demodulator (15) generates an output voltage (U), and that its coil (20) in said time interval j (ΔΌ »it a coil (11) of the signal generator (1-11) < is inductively coupled, which is in a circuit (11, 8), the impedance of which depends on whether a mechanical vibration system (2, 51 6), which by Friction of the normally running weft thread (7) is set in oscillation, oscillates or not, so that the change caused by a thread break - 22 - 109642/0377 the impedance by acting on the coil (20) of the converter in the output voltage (TJ) of the Demodulator (15) causes the occurrence of the control pulse (-16 or 18) stopping the loom. 2 weft thread monitor according to claim 1, characterized ^ draws »that the coil (14a) of the converter becomes a . IC parallel resonant circuit (14) belongs to the one Resistor (13) is fed from the high-frequency generator (12), and that the one lying on this resonant circuit Voltage is used to feed the demodulator (15) 3. weft thread monitor according to claims 1 and 2, characterized characterized in that the mechanical vibration system (2, 5 »6) of the encoder has a resilient bracket (5) "on which the running weft thread (7) with ψ friction slides, and with a device (2) is coupled, which generates an electrical voltage when the system oscillates, which is a capacitance diode (8) is supplied so that the resonance frequency (V) of this diode (8) and the coil (11) of the Encoder comprehensive oscillating circuit (8, 11) with the frequency (Q) of the mechanical oscillation system - 23 109842/0377 modulated and thus the impedance of the resonant circuit is changed. 4 · Weft thread monitor according to claims 1 to 3, characterized characterized in that the voltage-generating device is a piezo crystal (2). 5 · Weft thread monitor according to claims 1 to 3, characterized in that the tension-generating Device is an electrodynamic device. 6. Weft thread monitor according to claims 1 to 3, characterized in that the frequency swing of the resonance frequency (Y) of the transducer oscillating circuit (8, 11) is so large that the resonance frequency of the converter oscillating circuit (V ₀ ) falls within its range. 7 · Weft thread monitor according to claim 6, characterized in that { shows that the resonant frequency of the LC parallel resonant circuit (14) of the converter differs from the basic value (V ₁ ) of the resonant frequency of the resonant circuit (8, 11) of the transmitter « 8. weft thread monitor according to claim 1, characterized - 24 109842/0377 draws that the mechanical oscillation eyeetem dee Encoder has a resilient bracket (5) on which the running weft thread (7) slides with friction and which is coupled to a contact bridged by a resistor, which with each oscillation of this System of the transmitter coil (11) short-circuits. 9 · Weft thread monitor according to claim 1, characterized by ™ shows that the signaling device in the shooter is yielding is mounted. 10. Weft thread monitor according to claim 1, characterized in that that the coil (20a) of the signal converter, those in the time interval (At) of the yorbei movement of the Protection is inductively coupled to the coil (11) of the signal generator, a circuit element of the High frequency generator (12a) is. 11. weft thread monitor according to claim 10, characterized in that the high frequency generator (12a) dee Signal converter has a feedback amplifier (22), in whose feedback branch the Coil (20a) is located in the time interval (At) of the Inductive movement of the contactor with the coil (11) - 25 10 98 4 2/037 of the signal generator is coupled, and that the output voltage of the high-frequency generator is directly the demodulator generating the output voltage (U) (15) is supplied (Figure 6). 12. weft monitor according to claim 10, wherein the Coil (11) of the encoder in an LC resonant circuit is, which contains a blocking capacitor (10) and a capacitance diode (8), the capacitance of depends on a voltage that is excited by the mechanical oscillation system, characterized in that, that this voltage of the capacitance diode (8) and the blocking capacitor (10) via a rectifier diode (21) is supplied (Figure 5 and Figure 8). 13. Weft thread monitor according to claims 10 to 12, characterized in that the transmitter has an electrodynamic device (26) consisting of a permanent magnet (27) and a coil (28) inductively coupled to the same, the magnet being part of the mechanical oscillation system belongs, which is caused to vibrate by the friction of the normally running weft thread (Figures 8, 9) _e - 26 109842/0377 14 weft thread monitor according to claim 13, characterized in that that the coil (28) coupled to the magnet in a diagonal of a bridge circuit (29), the four branches of which consist of diodes (30-32) and in the other diagonals the for coupling with the converter serving coil (11) with the two at each diagonal point ™ closed diodes with regard to this point w have opposite blocking direction. 15. Weft thread monitor according to claim 14, characterized in that a capacitor (34) for the coupling coil (11) of the encoder is connected in parallel. 16. Weft thread monitor according to claim 10, characterized in that two cooperating with the signal generator Signal converter of the same type provided t are ever near the ends of the sley are ordered. 109842/0377 Blank page