EP0445157B1 - Sewing machine with transducer and control device - Google Patents

Sewing machine with transducer and control device Download PDF

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Publication number
EP0445157B1
EP0445157B1 EP89912950A EP89912950A EP0445157B1 EP 0445157 B1 EP0445157 B1 EP 0445157B1 EP 89912950 A EP89912950 A EP 89912950A EP 89912950 A EP89912950 A EP 89912950A EP 0445157 B1 EP0445157 B1 EP 0445157B1
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EP
European Patent Office
Prior art keywords
tension
stitch
thread
peak
transducer
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EP89912950A
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German (de)
French (fr)
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EP0445157A1 (en
Inventor
Erich Willenbacher
Bernhard Mertel
Rainer Spickermann
Walter Sinn
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GM Pfaff AG
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GM Pfaff AG
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    • D—TEXTILES; PAPER
    • D05—SEWING; EMBROIDERING; TUFTING
    • D05B—SEWING
    • D05B51/00—Applications of needle-thread guards; Thread-break detectors
    • D—TEXTILES; PAPER
    • D05—SEWING; EMBROIDERING; TUFTING
    • D05B—SEWING
    • D05B47/00—Needle-thread tensioning devices; Applications of tensometers
    • D—TEXTILES; PAPER
    • D05—SEWING; EMBROIDERING; TUFTING
    • D05B—SEWING
    • D05B47/00—Needle-thread tensioning devices; Applications of tensometers
    • D05B47/06—Applications of tensometers
    • D—TEXTILES; PAPER
    • D05—SEWING; EMBROIDERING; TUFTING
    • D05D—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES D05B AND D05C, RELATING TO SEWING, EMBROIDERING AND TUFTING
    • D05D2205/00—Interface between the operator and the machine
    • D05D2205/12—Machine to the operator; Alarms
    • D05D2205/16—Display arrangements

Definitions

  • the invention relates to a thread monitor according to the preamble of claim 1.
  • the thread monitor for displaying missing stitches is known.
  • the thread monitor arranged on a sewing machine in the path of the needle thread has a measuring sensor with a spring clip, to which a strain gauge element, hereinafter referred to as strain gauge element, is attached.
  • the strain gauge element generates an electrical voltage that is proportional to its mechanical deformation caused by the deflection movement of the spring clip.
  • the electrical voltage is fed to evaluation electronics connected downstream of the measuring sensor.
  • a first smaller voltage level is generated when the needle thread loop is widened and a second larger voltage level is generated during the knotting.
  • the voltage levels are monitored in measuring windows, the positioning and size of which are specified by two signal transmitters that monitor the position of the arm shaft.
  • a plurality of actual values is determined from the smaller voltage level and compared with a threshold value, the amount of which depends on the maximum value of the larger voltage level formed in the previous stitch. If all actual values fall below this threshold value, the evaluation electronics issue a warning signal to indicate a missing stitch.
  • the threshold value Since the maximum value of the larger voltage level for each stitch can differ from the corresponding value of the previous stitch and the threshold value depends on this maximum value, the threshold value must be determined anew for each stitch. Such an evaluation of signals is problematic in particular at high sewing speeds and requires complex evaluation electronics.
  • the invention specified in claim 1 or 2 is based on the object of designing the control device of a stitch-forming machine having a transducer in such a way that the measured values supplied by the transducer are used to detect a plurality of different ones from the first stitch with a proper voltage profile, with little circuitry complexity Skipped stitches and thread disturbances on the monitored thread and on the threads to be linked to it via stitch formation can be evaluated.
  • Monitoring the voltage peaks by the comparison device according to claim 1 or 2 is advantageous if at least one of the saving levels has a plurality of voltage peaks. Since not all of these voltage peaks are usually suitable for the detection of a malfunction, only those are identified by which a malfunction can be identified. As a result, the monitoring time can be reduced to a minimum.
  • the display element which can be switched via the switching device can be designed to be optically or acoustically warning.
  • the voltage peaks can be monitored as soon as the first stitch is carried out with a proper voltage profile, since each voltage peak can immediately be assigned the corresponding limit voltage by the comparison device .
  • the value of the voltage below which a malfunction can be identified can be individually adapted to the maximum of the voltage peak, so that a malfunction can be indicated as quickly as possible after its occurrence, however Variations in the voltage peaks caused by sewing do not cause a switching operation.
  • a common limit voltage is set for all voltage peaks regardless of their magnitude, in order to simplify the circuit design.
  • the second piece of information requires the stitch formation phase of the machine, which is fed to the comparison device as a signal.
  • the drop in a voltage peak below the limit voltage serves to demonstrate a malfunction, while the type of malfunction can be determined by the phase of the stitch formation associated with the voltage peak.
  • Claim 3 specifies a particularly advantageous application of the control device according to the invention, after which different missing stitches as a result of a pick-up or a parting-off error and breakage or end of the needle and the looper thread can be identified by monitoring the tension peaks which indicate the corresponding information.
  • the spring element Due to the measure according to claim 5, the spring element has the lowest possible mass at a predetermined bending strength. As a result, the effect of the natural vibrations of the spring element on the values of the thread tension supplied to the control device is negligible even at high sewing speeds.
  • the measure according to claim 6 reduces the vibrations transmitted from the machine to the transducer to a negligibly small extent, so that the values of the thread tension are not falsified by these vibrations.
  • the measure according to claim 7 causes fluctuations in the voltage generated by the stitch formation distortion of the thread tension transmitted to the control device could be reduced to a minimum.
  • a tensioning device (2) for the needle thread coming from a thread supply (not shown) is arranged on the stand (1) of the two-thread chainstitch sewing machine shown in FIG. 1, a tensioning device (2) for the needle thread coming from a thread supply (not shown) is arranged.
  • a sensor (3) which is attached to the sewing machine via a damping element (4) (Fig. 2), for example made of rubber.
  • the transducer (3) has a bending beam (5), the width of which is reduced from the clamping point to the free end. At its free end, the bending beam (5) is formed on the underside with an eyelet (6) receiving the needle thread.
  • strain gauge elements in the following called strain gauge elements, are provided.
  • a first strain gauge element (7) is fastened on the top side and a second strain gauge element (8) on the bottom side of the bending beam (5) close to its clamping point.
  • the strain gauge elements (7 and 8) are applied to a voltage source (Fig. 3) and connected to a half bridge (9) which is connected to an amplifier (10).
  • the output of the amplifier (10) is at one Tension meter (11) with a display (12) and connected to a comparator (13) with an adjusting device (14) serving to set its switching threshold.
  • the output of the comparator (13) is connected to an input of AND gates (15, 16), the second input of which is connected to a position sensor (18) which determines the revolutions of the main shaft (17).
  • This has a light-emitting diode (19) connected to the positive pole of a regulated voltage source, which is connected to ground via a resistor (20) and a photodetector (21) also connected to the positive pole and designed as a phototransistor, which is connected to ground via a resistor (22) is laid on.
  • the position transmitter (18) has a light-emitting diode (23) connected to the positive pole of the voltage source, which is connected to ground via a resistor (24) and a photodetector (25) also connected to the positive pole and designed as a phototransistor Resistor (26) is connected to ground.
  • the output of the AND gate (15) is connected to the set input (S) of a flip-flop memory (30) and that of the AND gate (16) to the set input (S) of a flip-flop memory (31).
  • the AND gates (15 and 16) together with the memories (30 and 31) form a switching device (32).
  • the output (Q) of the memory (30) is connected to a display element (33) which is connected to ground via a resistor (34), while a display element (35) is connected to the output (Q) of the memory (31) which is connected to ground via a resistor (36).
  • a switch (37) is also connected to the outputs (Q) of the memories (30 and 31) and is connected to a shutdown device (38) of a drive motor (39).
  • the drive motor (39) drives the main shaft (17) via a V-belt.
  • the elements (10 to 37) form a control device (40) which is provided for evaluating the thread tension (U F ) measured by the sensor (3).
  • a first thread guide element (42) is attached to the arm (41) of the sewing machine in the thread take-off direction behind the measured value sensor (3) (FIG. 1) and a second thread guide element (44) is attached to the head (43).
  • the needle thread is fed from the thread guide element (44) to the needle (48) via a thread lever (45) and further thread guide elements (not shown) and an eyelet (47) formed on the needle bar (46).
  • a chain stitch gripper (51) is arranged below the needle plate (50) accommodated in the base plate (49).
  • the hook thread is fed to the hook (51) via a tensioning device (52) attached to the stand (1) and via thread guide elements (not shown).
  • the elements (45, 46, 48 and 51) are referred to below as stitch-forming elements (53).
  • the device works as follows:
  • the needle and looper threads are drawn from the thread supply, the tension of the threads changing depending on the movement of the stitch-forming elements (53). Since the needle and looper threads are to be linked in terms of tension by the stitch formation, a sensor (3) in the path of the needle thread is sufficient to determine the course of the thread tension (U F ) formed from the tensions of all threads.
  • the first voltage level (U P1 ) reaches its voltage peak (U1) at the time (t1).
  • the second voltage level (U p2 ) is formed when the thread lever 45 executes an upward movement to tighten the interlacing formed by the needle thread and the hook thread.
  • the voltage level (U P2 ) has two voltage peaks (U 2.1 and U 2.2 ) at times (t2 and t3), the value of the first voltage peak (U 2.1 ) being that of the second voltage peak (U 2, 2 ) exceeds.
  • the gripper (51) misses the needle thread loop, there is a pick-up error.
  • the course of the thread tension (U F ) changes according to FIG. 4b.
  • the first voltage level (U P1 ) takes on the amount of the normal voltage (U N ) or even drops below it, while the second voltage level (U P2 ) is only designed with a voltage peak (U2).
  • the needle (48) misses the loop formed by the hook thread after penetration of the sewing material, there is a parting error. Like a break of the hook thread in the thread pulling direction behind the tensioning device (52), this is indicated by a change in the course of the thread tension (U F ) according to FIG. 4c.
  • the first voltage level (U P1 ) like the first voltage peak (U 2.1 ) of the second voltage level (U P2 ), remains almost unchanged, while the amount of the second voltage peak (U 2.2 ) is greatly reduced.
  • the transducer (9) (Fig. 1) is arranged between the tensioning device (2) and the thread guide element (42) in such a way that the needle thread passes through the eyelet (6) is deflected. This creates a force perpendicular to the direction of extension of the bending beam (5), by means of which the latter is deflected downward.
  • the strain gauge element (7) on the upper side of the bending beam (5) is subjected to tension and the strain gauge element (8) on the underside thereof is subjected to pressure, so that both strain gauge elements (7, 8) change their electrical resistance.
  • the differential voltage (U D ) is fed to the voltmeter (11) indicating its value and to the comparator (13).
  • the switching threshold of the comparator (13) can be adjusted by the adjusting device (14), so that its sensitivity is adapted to the tension of the needle thread.
  • the switching threshold is selected so that it only drops below one of the voltage peaks (U 1, U 2.2 ) when a malfunction, such as a missing stitch or thread break, has occurred.
  • the voltage corresponding to the switching threshold is referred to below as the limit voltage (U G ), which is shown in FIGS. 4a to 4c.
  • the comparator (13) is switched on as long as the differential voltage (U D ) at its input is less than the limit voltage (U G ) and is switched off as soon as the differential voltage (U D ) assumes or exceeds the value of the limit voltage (U G ) .
  • 4d shows the profile of the output voltage (U K ) of the Comparator (13) as a function of the differential voltage (U D ) according to FIG. 4a, while the course of (U K ) according to FIG. 4e follows that of (U D ) according to FIG. 4b and the course of (U K ) according to Fig. 4f which is assigned by (U D ) according to Fig. 4c.
  • the comparator voltage (U K ) is only present at the input of the AND gates (15 and 16) if none of the pulses (I 1 or I 2) shown in Fig. 4g, delivered by the position transmitter (13) ) arrives. This means that no signal can leave the AND gates (15 and 16).
  • the pulse (I1) of the position transmitter (13) from the photodetector (21) arrives at an input of the AND gate (15) when the comparator voltage (U K ) is present. Then a signal is emitted at the output of the AND gate (15) and fed to the set input (S) of the memory (30).
  • the pulse causes the memory (30) to switch on the display element (33) via its output (Q), which indicates a recording error or the breakage of the needle thread.
  • the switch-off device (38) which, depending on the version, switches off the drive motor (39) immediately or prevents it from restarting after the next stopping process.
  • the photodetector (25) of the position transmitter (18) delivers a pulse (12) to one input of the AND gate (16) at the time (t3), while the comparator voltage (U K ) is present.
  • the AND gate (16) is switched through and emits a signal at its output to the set input (S) of the memory (31), so that this switches on the display element (35) via its output (Q), which indicates a cut-off error or indicates the breakage of the hook thread.
  • the output (Q) of the memory (31) like that of the memory (30), simultaneously controls the switch-off device (38) of the drive motor (39) when the switch (37) is closed.
  • the display element (35) is switched off by an electrical pulse on the reset input (R) of the memory (31) and the drive motor (39) is released.
  • FIG. 5 shows a second embodiment of the measuring sensor (3).
  • a permanent magnet (54) is attached to the top of the free end of the bending beam (5).
  • a Hall sensor (56) is attached to the free end of a support arm (55), facing the permanent magnet (54).
  • the distance between the permanent magnet (54) and the Hall sensor (56) is increased, as a result of which the magnetic flux density and thus the Hall voltage of the Hall sensor (56) corresponding to the deflection of the bending beam ( 5) reduced.
  • the Hall voltage is fed to the control device (40) and evaluated.
  • FIG. 6 shows a second embodiment of the control device (40).
  • the output of the amplifier (10) is connected to the voltmeter (11) and, via an A / D converter (57), to the input (E1) of a microprocessor (58).
  • An input device (59) is connected to a second input (E2) of the microprocessor (58).
  • the microprocessor (58) has outputs (A1 and A2), of which the output (A1) with the set input (S) of a flip-flop memory (60) and the output (A2) with the set input (S) of a flip-flop memory (61) is connected.
  • the memories (60 and 61) form a switching device (62).
  • the output (Q) of the memory (60) is connected to the display element (33), that of the memory (61) to the display element (35). Both outputs (Q) are also connected via the switch (37) to the shutdown device (38) of the drive motor (39).
  • the second embodiment of the control device (40) works as follows:
  • the differential voltage (U D ) (Fig. 7) is fed to the A / D converter (57).
  • a digital voltage is present at the output of the A / D converter (57), which is proportional to the differential voltage (U D ) present at its input.
  • the microprocessor (58) converts the digital voltage recorded at input (E1) only into the Time intervals are evaluated in which the voltage levels (U P1 and U P2 ) are formed.
  • the microprocessor (58) determines the value of all digital voltages assigned to the first voltage level (U p1 ) and forms the maximum value (U M1 ) from these values.
  • the maximum value (U M1 ) is compared with a first threshold value which is assigned to a first limit voltage (U G1 ) (FIG. 7).
  • the limit voltage (U G1 ) is to be preselected as a function of the setting of the tensioning device (2) on the input device (59) and is fed to the microprocessor (58) via its input (E2).
  • the microprocessor (58) outputs a pulse to the memory (60) at the output (A1), as a result of which it is switched over and via its output (Q) controls the display element (33) and, when the switch (37) is closed, the shutdown device (38) of the drive motor (39).
  • the maximum value (U M2 ) is formed from the values of the digital voltages assigned to the second voltage peak (U 2.2 ) of the voltage level (U P2 ) and compared with a second threshold value that corresponds to a second limit voltage (U G2 ) (FIG. 7) assigned. Like the first limit voltage (U G1 ), this is to be preselected as a function of the setting of the tensioning device (2) on the input device (59).
  • the microprocessor (58) If the maximum value (U M2 ) corresponds to or exceeds the second threshold value, there is no signal output by the microprocessor (58). If, on the other hand, the maximum value (U M2 ) falls below the second threshold value as a result of a parting error or a fault on the hook thread, the microprocessor (58) outputs a pulse to the memory (61) at the output (A2). This switches it over and controls the display element (35) and the shutdown device (38) of the drive motor (39) via its output (Q).
  • the memories (60 and 61) can each be switched to their initial position via an electrical signal to the reset input (R).
  • the respective threshold value can be optimally adapted to the corresponding maximum value.

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  • Engineering & Computer Science (AREA)
  • Textile Engineering (AREA)
  • Sewing Machines And Sewing (AREA)

Abstract

A known sewing machine has a transducer and an electronic evaluation system. The latter checks the threat tension determined by the transducer by comparing it with a threshold value dependent on the preceding stitch. The evaluation of the stitch tension can therefore only take place after the formation of a stitch by a normal variation in the tension after the sewing machine is brought to a halt. When the threshold value is exceeded, a stitch defect is displayed. The invention, on the other hand, proposes a control device for a sewing machine which makes it possbile to display a plurality of different stitch defects as well as problems associated with the needle thread and gripper thread, starting with the first stitch formed by the machine with normal variation of tension. The control device (40) of the sewing machine has a comparator (13; 58) which compares tension peaks (U1, U2,2) of the thread tension (UF) with a predetermined limiting tension (UG1, UG2; UG), and by means of which a switching device (32; 62) arranged downstream and connected to a cut-off device (38) of the drive motor (39) of the machine, as well as a plurality of display elements (33, 35), can be activated, when a tension peak (U1, U2,2) falls below the corresponding limiting tension (UG1, UG2; UG), in function of the limiting tension (UG1, UG2) or of the phase of stitch formation. The switching device (32; 62) thus brings the machine to a halt and switches on the display element (33, 35) corresponding to the defect function.

Description

Die Erfindung betrifft einen Fadenwächter nach dem Oberbegriff des Anspruches 1.The invention relates to a thread monitor according to the preamble of claim 1.

Aus der US-PS 41 70 951 ist ein Fadenwächter zur Anzeige von Fehlstichen bekannt. Der an einer Nähmaschine im Weg des Nadelfadens angeordnete Fadenwächter weist einen Meßwertaufnehmer mit einem Federbügel auf, an dem ein Dehnungsmeßstreifen-Element, im folgenden kurz DMS-Element genannt, befestigt ist. Das DMS-Element erzeugt eine elektrische Spannung, die proportional zu seiner durch die Auslenkbewegung des Federbügels verursachten mechanischen Verformung ist. Die elektrische Spannung wird einer dem Meßwertaufnehmer nachgeschalteten Auswertelektronik zugeführt.From US-PS 41 70 951 a thread monitor for displaying missing stitches is known. The thread monitor arranged on a sewing machine in the path of the needle thread has a measuring sensor with a spring clip, to which a strain gauge element, hereinafter referred to as strain gauge element, is attached. The strain gauge element generates an electrical voltage that is proportional to its mechanical deformation caused by the deflection movement of the spring clip. The electrical voltage is fed to evaluation electronics connected downstream of the measuring sensor.

Im Verlauf eines Stiches wird bei der Aufweitung der Nadelfadenschlinge ein erster kleinerer Spannungspegel und während der Verknotung ein zweiter größerer Spannungspegel erzeugt. Zum Nachweis von Fehlstichen werden die Spannungspegel in Meßfenstern überwacht, deren Positionierung und Größe durch zwei die Stellung der Armwelle überwachende Signalgeber vorgegeben ist.In the course of a stitch, a first smaller voltage level is generated when the needle thread loop is widened and a second larger voltage level is generated during the knotting. To detect skipped stitches, the voltage levels are monitored in measuring windows, the positioning and size of which are specified by two signal transmitters that monitor the position of the arm shaft.

Von dem kleineren Spannungspegel wird eine Mehrzahl von Istwerten ermittelt und mit einem Schwellwert verglichen, dessen Betrag vom Maximalwert des beim vorangegangenen Stich gebildeten größeren Spannungspegels abhängt. Wenn alle Istwerte diesen Schwellwert unterschreiten, wird durch die Auswertelektronik ein Warnsignal zur Anzeige eines Fehlstiches ausgegeben.A plurality of actual values is determined from the smaller voltage level and compared with a threshold value, the amount of which depends on the maximum value of the larger voltage level formed in the previous stitch. If all actual values fall below this threshold value, the evaluation electronics issue a warning signal to indicate a missing stitch.

Da sich der Maximalwert des größeren Spannungspegels bei jedem Stich von dem entsprechenden Wert des vorangegangenen Stiches unterscheiden kann und der Schwellwert von diesem Maximalwert abhängt, ist der Schwellwert bei jedem Stich neu zu bestimmen. Eine derartige Auswertung von Signalen ist insbesondere bei hoher Nähgeschwindigkeit problematisch und macht eine aufwendige Auswertelektronik erforderlich.Since the maximum value of the larger voltage level for each stitch can differ from the corresponding value of the previous stitch and the threshold value depends on this maximum value, the threshold value must be determined anew for each stitch. Such an evaluation of signals is problematic in particular at high sewing speeds and requires complex evaluation electronics.

Aufgrund seiner Abhängigkeit vom vorangegangenen größeren Spannungspegel kann der Schwellwert nach Anlauf der Nähmaschine beim ersten mit ordnungsgemäßem Spannungsverlauf ausgeführten Stich noch nicht gebildet werden, was eine Verzögerung des Überwachungsvorganges bewirkt. Um diesen Nachteil zu verhindern, sind zusätzliche, in der US-PS 41 70 951 nicht geoffenbarte Steuerelemente erforderlich. Dies erhöht den schaltungstechnischen Aufwand der Auswertelektronik, die ausschließlich zur Anzeige von durch fehlende Aufweitung der Nadelfadenschlinge entstehenden Fehlstichen geeignet ist.Due to its dependence on the previous larger voltage level, the threshold value cannot be formed after the sewing machine starts up on the first stitch executed with a proper voltage profile, which causes a delay in the monitoring process. To prevent this disadvantage, additional control elements not disclosed in US Pat. No. 4,170,951 are required. This increases the circuitry complexity of the evaluation electronics, which is only suitable for displaying missing stitches caused by the needle thread loop not being widened.

Der im Anspruch 1 oder 2 angegebenen Erfindung liegt die Aufgabe zugrunde, die Steuervorrichtung einer einen Meßwertaufnehmer aufweisenden stichbildenden Maschine so auszubilden, daß durch diese die von dem Meßwertaufnehmer gelieferten Meßwerte bei geringem schaltungstechnischen Aufwand vom ersten mit ordnungsgemäßem Spannungsverlauf ausgeführten Stich an zum Nachweis einer Mehrzahl unterschiedlicher Fehlstiche sowie von Fadenstörungen an dem überwachten Faden und an den mit diesem über die Stichbildung zu verknüpfenden Fäden auswertbar sind.The invention specified in claim 1 or 2 is based on the object of designing the control device of a stitch-forming machine having a transducer in such a way that the measured values supplied by the transducer are used to detect a plurality of different ones from the first stitch with a proper voltage profile, with little circuitry complexity Skipped stitches and thread disturbances on the monitored thread and on the threads to be linked to it via stitch formation can be evaluated.

Diese Aufgabe wird bei der stichbildenden Maschine durch die kennzeichnenden Merkmale des Anspruches 1 oder 2 gelöst.This object is achieved in the stitch-forming machine by the characterizing features of claim 1 or 2.

Mit der erfindungsgemäßen Steuervorrichtung nach Anspruch 1 oder 2 besteht die Möglichkeit, unter Verwendung eines einzelnen Meßwertaufnehmers eine Mehrzahl unterschiedlicher Fehlfunktionen am Faden, wie beispielsweise verschiedenartige Fehlstiche oder den Bruch des Nadel- und, bei Doppelsteppstich- sowie bei mehrfädigen Kettenstichmaschinen den Bruch des Greiferfadens zu detektieren, da eine derartige Fehlfunktion durch die Betragsänderung der dieser zugeordneten Spannungsspitze eindeutig nachweisbar istWith the control device according to the invention according to claim 1 or 2, there is the possibility of using a single transducer to detect a plurality of different malfunctions on the thread, such as different types of missing stitches or the breakage of the needle and, in double lockstitch and multi-thread chainstitch machines, the breakage of the looper thread , since such a malfunction can be clearly demonstrated by changing the amount of the voltage peak assigned to it

Die Überwachung der Spannungsspitzen durch die Vergleichsvorrichtung nach Anspruch 1 oder 2 ist von Vorteil, wenn zumindest einer der Sparinungspegel eine Mehrzahl von Spannungsspitzen aufweist. Da zumeist nicht jede dieser Spannungsspitzen zum Nachweis einer Fehlfunktion geeignet ist, werden nur diejenigen überwacht, an denen eine Fehlfunktion erkennbar ist. Dadurch ist die Überwachungszeit auf ein Minimum verkürzbar.Monitoring the voltage peaks by the comparison device according to claim 1 or 2 is advantageous if at least one of the saving levels has a plurality of voltage peaks. Since not all of these voltage peaks are usually suitable for the detection of a malfunction, only those are identified by which a malfunction can be identified. As a result, the monitoring time can be reduced to a minimum.

Da durch Überwachung der Spannungsspitzen eine Mehrzahl unterschiedlicher Fehlfunktionen erkennbar sind, ist es zweckmäßig, bei einer Fehlfunktion die Maschine zu stoppen und die Fehlfunktion durch ein dieser zugeordnetes separates Anzeigeelement kenntlich zu machen. Das über die Schaltvorrichtung schaltbare Anzeigeelement kann optisch oder akustisch warnend ausgebildet sein.Since a plurality of different malfunctions can be identified by monitoring the voltage peaks, it is advisable to stop the machine in the event of a malfunction and to indicate the malfunction by means of a separate display element assigned to it. The display element which can be switched via the switching device can be designed to be optically or acoustically warning.

Durch Vorgabe der der jeweiligen Spannungsspitze zugeordneten Grenzspannung nach Anspruch 1 oder der für alle Spannungsspitzen einheitlichen Grenzspannung nach Anspruch 2 wird bewirkt, daß bereits beim ersten mit ordnungsgemäßem Spannungsverlauf ausgeführten Stich die Spannungsspitzen überwachbar sind, da jeder Spannungsspitze sofort die entsprechende Grenzspannung durch die Vergleichsvorrichtung zuordenbar ist.By specifying the limit voltage assigned to the respective voltage peak according to claim 1 or the limit voltage uniform for all voltage peaks according to claim 2, the voltage peaks can be monitored as soon as the first stitch is carried out with a proper voltage profile, since each voltage peak can immediately be assigned the corresponding limit voltage by the comparison device .

Durch Vorgabe einer an die jeweilige Spannungsspitze angepaßte Grenzspannung durch die Vergleichsvorrichtung gemäß Anspruch 1 ist der Wert der Spannung, unterhalb der eine Fehlfunktion erkennbar ist, individuell an das Maximum der Spannungsspitze anpaßbar, so daß eine Fehlfunktion zwar möglichst schnell nach ihrem Auftreten anzeigbar ist, jedoch nähtechnisch verursachte Betragsschwankungen der Spannungsspitzen keinen Schaltvorgang bewirken.By specifying a limit voltage adapted to the respective voltage peak by means of the comparison device according to claim 1, the value of the voltage below which a malfunction can be identified can be individually adapted to the maximum of the voltage peak, so that a malfunction can be indicated as quickly as possible after its occurrence, however Variations in the voltage peaks caused by sewing do not cause a switching operation.

Bei der Ausführung der Vergleichsvorrichtung nach Anspruch 2 wird zur Vereinfachung des schaltungstechnischen Aufbaues für alle Spannungsspitzen unabhängig von deren Betrag eine gemeinsame Grenzspannung eingestellt. Als zweite Information ist die Phase der Stichbildung der Maschine notwendig, die der Vergleichsvorrichtung als Signal zugeführt wird. Das Absinken einer Spannungsspitze unter die Grenzspannung dient dabei zum Nachweis einer Fehlfunktion, während durch die der Spannungsspitze zugeordnete Phase der Stichbildung die Art der Fehlfunktion bestimmbar ist.When carrying out the comparison device according to claim 2, a common limit voltage is set for all voltage peaks regardless of their magnitude, in order to simplify the circuit design. The second piece of information requires the stitch formation phase of the machine, which is fed to the comparison device as a signal. The drop in a voltage peak below the limit voltage serves to demonstrate a malfunction, while the type of malfunction can be determined by the phase of the stitch formation associated with the voltage peak.

In Anspruch 3 ist eine besonders vorteilhafte Anwendung der erfindungsgemäßen Steuervorrichtung angegeben, wonach unterschiedliche Fehlstiche infolge eines Aufnahme- oder eines Abstechfehlers sowie Bruch oder Ende des Nadel- und des Greiferfadens durch Überwachung der die entsprechenden Informationen anzeigenden Spannungsspitzen erkennbar sind.Claim 3 specifies a particularly advantageous application of the control device according to the invention, after which different missing stitches as a result of a pick-up or a parting-off error and breakage or end of the needle and the looper thread can be identified by monitoring the tension peaks which indicate the corresponding information.

Aus Meßversuchen hat sich ergeben, daß durch Parameter wie Nähgeschwindigkeit, Stichlänge und Fadeneigenschaften das Maximum der Spannungsspitzen nur unwesentlich verändert wird, während sich die Einstellung der Spannvorrichtung maßgeblich auf dieses auswirkt. Um Nachteile bei der Überwachung des Fadens bei geänderter Einstellung der Spannvorrichtung auszuschließen, wird die Grenzspannung und damit die Ansprechschwelle der Vergleichsvorrichtung durch die Stellvorrichtung nach Anspruch 4 an die eingestellte Fadenspannung angepaßt.Tests have shown that parameters such as sewing speed, stitch length and thread properties only slightly change the maximum of the tension peaks, while the setting of the tensioning device has a significant effect on this. In order to rule out disadvantages in the monitoring of the thread when the tensioning device has been changed, the limit voltage and thus the response threshold of the comparison device are adapted to the thread tension set by the adjusting device according to claim 4.

Durch die Maßnahme nach Anspruch 5 weist das Federelement bei einer vorbestimmten Biegefestigkeit die geringstmögliche Masse auf. Dadurch ist die Auswirkung der Eigenschwingungen des Federelementes auf die der Steuervorrichtung zugeleiteten Werte der Fadenspannung auch bei hohen Nähgeschwindigkeiten vernachlässigbar gering.Due to the measure according to claim 5, the spring element has the lowest possible mass at a predetermined bending strength. As a result, the effect of the natural vibrations of the spring element on the values of the thread tension supplied to the control device is negligible even at high sewing speeds.

Die Maßnahme gemäß Anspruch 6 reduziert die von der Maschine auf den Meßwertaufnehmer übertragenen Schwingungen auf ein vernachlässigbar kleines Maß, so daß die Werte der Fadenspannung durch diese Schwingungen nicht verfälscht werden.The measure according to claim 6 reduces the vibrations transmitted from the machine to the transducer to a negligibly small extent, so that the values of the thread tension are not falsified by these vibrations.

Die Maßnahme nach Anspruch 7 bewirkt, daß durch die Stichbildung erzeugte Schwankungen der Spannung, die eine Verfälschung der an die Steuervorrichtung übertragenen Fadenspannung verursachen könnten, auf ein Minimum reduziert werden.The measure according to claim 7 causes fluctuations in the voltage generated by the stitch formation distortion of the thread tension transmitted to the control device could be reduced to a minimum.

Die Erfindung ist anhand eines in der Zeichnung dargestellten Ausführungsbeispieles erläutert. Es zeigt:

  • Fig. 1 eine Seitenansicht einer Nähmaschine mit einem einen Meßwertaufnehmer aufweisenden Fadenwächter;
  • Fig. 2 der vergrößert herausgezeichnete Meßwertaufnehmer nach Fig.1;
  • Fig. 3 eine vereinfachte Steuervorrichtung;
  • Fig. 4 Schaubilder zur Darstellung folgender Verläufe, bezogen auf einen Stich:
    • a) Fadenspannung (UF) ohne Fehlfunktion,
    • b) Fadenspannung (UF) bei einem Aufnahmefehler oder bei einer Störung am Nadelfaden,
    • c) Fadenspannung (UF) bei einem Abstechfehler oder bei einer Störung am Greiferfaden,
    • d) Komparatorspannung (UK) ohne Fehlfunktion,
    • e) Komparatorspannung (UK) bei einer Fehlfunktion gemäß Fig. 4b,
    • f) Komparatorspannung (UK) bei einer Fehlfunktion gemäß Fig. 4c,
    • g) Impulse (I) eines Positionsgebers;
  • Fig. 5 eine vergrößert herausgezeichnete zweite Ausführung des Meßwertaufnehmers;
  • Fig. 6 eine vereinfachte zweite Ausführung der Steuervorrichtung;
  • Fig. 7 Fadenspannung (UF) ohne Fehlfunktion gemäß der zweiten Ausführung der Steuervorrichtung.
The invention is explained with reference to an embodiment shown in the drawing. It shows:
  • Figure 1 is a side view of a sewing machine with a thread monitor having a transducer.
  • 2 shows the magnified marked transducer according to FIG. 1;
  • 3 shows a simplified control device;
  • Fig. 4 graphs to show the following courses, based on a stitch:
    • a) thread tension (U F ) without malfunction,
    • b) thread tension (U F ) in the event of a recording error or in the event of a fault in the needle thread,
    • c) thread tension (U F ) in the event of a parting error or in the event of a fault on the hook thread,
    • d) comparator voltage (U K ) without malfunction,
    • e) comparator voltage (U K ) in the event of a malfunction according to FIG. 4b,
    • f) comparator voltage (U K ) in the event of a malfunction according to FIG. 4c,
    • g) pulses (I) from a position transmitter;
  • 5 shows an enlarged second embodiment of the measurement sensor;
  • 6 shows a simplified second embodiment of the control device;
  • Fig. 7 thread tension (U F ) without malfunction according to the second embodiment of the control device.

Am Ständer (1) der in Fig. 1 dargestellten zweifädigen Kettenstich-Nähmaschine ist eine Spannvorrichtung (2) für den von einem nicht gezeigten Fadenvorrat kommenden Nadelfaden angeordnet. In Fadennachzugrichtung hinter der Spannvorrichtung (2) ist ein Meßwertaufnehmer (3) vorgesehen, der über ein Dämpfungselement (4) (Fig. 2), beispielsweise aus Gummi, an der Nähmaschine befestigt ist. Der Meßwertaufnehmer (3) weist einen Biegebalken (5) auf, dessen Breite von der Einspannstelle ausgehend zum freien Ende hin reduziert ist. An seinem freien Ende ist der Biegebalken (5) an der Unterseite mit einer den Nadelfaden aufnehmenden Öse (6) ausgebildet.On the stand (1) of the two-thread chainstitch sewing machine shown in FIG. 1, a tensioning device (2) for the needle thread coming from a thread supply (not shown) is arranged. In the thread pulling direction behind the tensioning device (2) there is a sensor (3) which is attached to the sewing machine via a damping element (4) (Fig. 2), for example made of rubber. The transducer (3) has a bending beam (5), the width of which is reduced from the clamping point to the free end. At its free end, the bending beam (5) is formed on the underside with an eyelet (6) receiving the needle thread.

Zur Aufnahme der Spannung des Nadelfadens sind Dehnungsmeßstreifen-Elemente, im folgenden kurz DMS-Elemente genannt, vorgesehen. Ein erstes DMS-Element (7) ist an der Oberseite und ein zweites DMS-Element (8) an der Unterseite des Biegebalkens (5) dicht neben dessen Einspannstelle befestigt.To measure the tension of the needle thread, strain gauge elements, in the following called strain gauge elements, are provided. A first strain gauge element (7) is fastened on the top side and a second strain gauge element (8) on the bottom side of the bending beam (5) close to its clamping point.

Die DMS-Elemente (7 und 8) sind an eine Spannungsquelle (Fig. 3) angelegt und zu einer Halbbrücke (9) geschaltet, die mit einem Verstärker (10) verbunden ist. Der Ausgang des Verstärkers (10) ist an einen Spannungsmesser (11) mit einem Anzeigedisplay (12) und an einen Komparator (13) mit einer zur Einstellung von dessen Schaltschwelle dienenden Stellvorrichtung (14) angeschlossen.The strain gauge elements (7 and 8) are applied to a voltage source (Fig. 3) and connected to a half bridge (9) which is connected to an amplifier (10). The output of the amplifier (10) is at one Tension meter (11) with a display (12) and connected to a comparator (13) with an adjusting device (14) serving to set its switching threshold.

Der Ausgang des Komparators (13) ist mit je einem Eingang von UND-Gliedern (15, 16) verbunden, deren zweiter Eingang jeweils an einen die Umdrehungen der Hauptwelle (17) ermittelnden Positionsgeber (18) angeschlossen ist. Dieser weist eine an den Pluspol einer geregelten Spannungsquelle angeschlossene Leuchtdiode (19), die über einen Widerstand (20) an Masse gelegt ist und einen ebenfalls am Pluspol angeschlossenen, als Fototransistor ausgebildeten Fotodetektor (21), der über einen Widerstand (22) an Masse gelegt ist, auf. Weiterhin ist der Positionsgeber (18) mit einer an den Pluspol der Spannungsquelle angeschlossenen Leuchtdiode (23), die über einen Widerstand (24) an Masse gelegt ist und mit einem ebenfalls am Pluspol angeschlossenen, als Fototransistor ausgeführten Fotodetektor (25), der über einen Widerstand (26) an Masse gelegt ist, versehen. Zwischen den Leuchtdioden (19 und 23) und den Fotodetektoren (21 und 25) ist eine drehfest auf der Hauptwelle (17) angeordnete Scheibe (27) vorgesehen, die im Lichtweg zwischen der Leuchtdiode (19) und dem Fotodetektor (21) eine erste Öffnung (28) und, auf einem anderen Radius, im Lichtweg zwischen der Leuchtdiode (23) und dem Fotodetektor (25) eine zweite Öffnung (29) zum Durchgang der Lichtstrahlen aufweist. Bei jedem Durchgang durch die Öffnung (28) wird ein Impuls an das UND-Glied (15) und bei jedem Durchgang durch die Öffnung (29) ein Impuls an das UND-Glied (16) abgegeben, wobei das UND-Glied (16) jeweils um den einer 180°-Drehung der Scheibe (27) entsprechenden Zeitraum nach dem UND-Glied (15) angesteuert wird.The output of the comparator (13) is connected to an input of AND gates (15, 16), the second input of which is connected to a position sensor (18) which determines the revolutions of the main shaft (17). This has a light-emitting diode (19) connected to the positive pole of a regulated voltage source, which is connected to ground via a resistor (20) and a photodetector (21) also connected to the positive pole and designed as a phototransistor, which is connected to ground via a resistor (22) is laid on. Furthermore, the position transmitter (18) has a light-emitting diode (23) connected to the positive pole of the voltage source, which is connected to ground via a resistor (24) and a photodetector (25) also connected to the positive pole and designed as a phototransistor Resistor (26) is connected to ground. Between the light emitting diodes (19 and 23) and the photodetectors (21 and 25) there is a disc (27) arranged on the main shaft (17) in a manner fixed against relative rotation, which has a first opening in the light path between the light emitting diode (19) and the photodetector (21) (28) and, on another radius, in the light path between the light-emitting diode (23) and the photodetector (25) has a second opening (29) for the passage of the light rays. With each passage through the opening (28) a pulse is given to the AND gate (15) and with each passage through the opening (29) a pulse is given to the AND gate (16), the AND gate (16) each by a 180 ° rotation of the disc (27) corresponding period after the AND gate (15) is driven.

Der Ausgang des UND-Gliedes (15) ist mit dem Setzeingang (S) eines Flipflop-Speichers (30) und der des UND-Gliedes (16) mit dem Setzeingang (S) eines Flipflop-Speichers (31) verbunden. Die UND-Glieder (15 und 16) bilden zusammen mit den Speichern (30 und 31) eine Schaltvorrichtung (32).The output of the AND gate (15) is connected to the set input (S) of a flip-flop memory (30) and that of the AND gate (16) to the set input (S) of a flip-flop memory (31). The AND gates (15 and 16) together with the memories (30 and 31) form a switching device (32).

Der Ausgang (Q) des Speichers (30) ist mit einem Anzeigeelement (33), das über einen Widerstand (34) an Masse angeschlossen ist, verbunden, während am Ausgang (Q) des Speichers (31) ein Anzeigeelement (35) angeschlossen ist, das über einen Widerstand (36) an Masse gelegt ist. Mit den Ausgängen (Q) der Speicher (30 und 31) ist außerdem ein Schalter (37) verbunden, der an eine Abschaltvorrichtung (38) eines Antriebsmotors (39) angeschlossen ist. Der Antriebsmotor (39) treibt die Hauptwelle (17) über einen Keilriemen an.The output (Q) of the memory (30) is connected to a display element (33) which is connected to ground via a resistor (34), while a display element (35) is connected to the output (Q) of the memory (31) which is connected to ground via a resistor (36). A switch (37) is also connected to the outputs (Q) of the memories (30 and 31) and is connected to a shutdown device (38) of a drive motor (39). The drive motor (39) drives the main shaft (17) via a V-belt.

Die Elemente (10 bis 37) bilden eine Steuervorrichtung (40), die zur Auswertung der von dem Meßwertaufnehmer (3) gemessenen Fadenspannung (UF) vorgesehen ist.The elements (10 to 37) form a control device (40) which is provided for evaluating the thread tension (U F ) measured by the sensor (3).

In Fadenabzugsrichtung hinter dem Meßwertaufnehmer (3) (Fig. 1) ist am Arm (41) der Nähmaschine ein erstes Fadenführungselement (42) und am Kopf (43) ein zweites Fadenführungselement (44) befestigt. Von dem Fadenführungselement (44) wird der Nadelfaden über einen Fadenhebel (45) und weitere, nicht dargestellte Fadenführungselemente sowie einer an der Nadelstange (46) ausgebildeten Öse (47) der Nadel (48) zugeleitet.A first thread guide element (42) is attached to the arm (41) of the sewing machine in the thread take-off direction behind the measured value sensor (3) (FIG. 1) and a second thread guide element (44) is attached to the head (43). The needle thread is fed from the thread guide element (44) to the needle (48) via a thread lever (45) and further thread guide elements (not shown) and an eyelet (47) formed on the needle bar (46).

Unterhalb der in der Grundplatte (49) aufgenommenen Stichplatte (50) ist ein Kettenstich-Greifer (51) angeordnet. Der Greiferfaden wird dem Greifer (51) über eine am Ständer (1) befestigte Spannvorrichtung (52) sowie über nicht gezeigte Fadenführungselemente zugeleitet.A chain stitch gripper (51) is arranged below the needle plate (50) accommodated in the base plate (49). The hook thread is fed to the hook (51) via a tensioning device (52) attached to the stand (1) and via thread guide elements (not shown).

Die Elemente (45, 46, 48 und 51) sind nachfolgend als stichbildende Elemente (53) bezeichnet.The elements (45, 46, 48 and 51) are referred to below as stitch-forming elements (53).

Die Vorrichtung arbeitet wie folgt:The device works as follows:

Beim Nähbetrieb wird der Nadel- und der Greiferfaden vom Fadenvorrat nachgezogen, wobei sich die Spannung der Fäden in Abhängigkeit von der Bewegung der stichbildenden Elemente (53) ändert. Da der Nadel- und der Greiferfaden durch die Stichbildung spannungsmäßig miteinander zu verknüpfen sind, genügt ein Meßwertaufnehmer (3) im Weg des Nadelfadens, um den Verlauf der aus den Spannungen aller Fäden gebildeten Fadenspannung (UF) zu ermitteln.During the sewing operation, the needle and looper threads are drawn from the thread supply, the tension of the threads changing depending on the movement of the stitch-forming elements (53). Since the needle and looper threads are to be linked in terms of tension by the stitch formation, a sensor (3) in the path of the needle thread is sufficient to determine the course of the thread tension (U F ) formed from the tensions of all threads.

In Fig. 4a ist der Verlauf der Fadenspannung (UF) bei störungsfreier Stichbildung über einen Stich dargestellt.4a shows the course of the thread tension (U F ) with trouble-free stitch formation over a stitch.

Der die Normalspannung (UN) übersteigende erste Spannungspegel (UP1) entsteht, wenn nach Durchgang der Nadel (48) durch ein Nähgut die Schlinge des Nadelfadens von dem Greifer (51) erfaßt und aufgeweitet wird. Der erste Spannungspegel (UP1) erreicht zu der Zeit (t₁) seine Spannungsspitze (U₁).The first voltage level (U P1 ), which exceeds the normal tension (U N ), arises when, after the needle (48) has passed through a sewing material, the loop of the needle thread is gripped and expanded by the gripper (51). The first voltage level (U P1 ) reaches its voltage peak (U₁) at the time (t₁).

Der zweite Spannungspegel (Up2) wird gebildet, wenn der Fadenhebel 45 zum Festziehen der durch den Nadelfaden und den Greiferfaden gebildeten Verschlingung eine Bewegung nach oben ausführt. Der Spannungspegel (UP2) weist zwei Spannungsspitzen (U2,1 und U2,2) zu den Zeiten (t₂ und t₃) auf, wobei der Wert der ersten Spannungsspitze (U2,1) den der zweiten Spannungsspitze (U2,2) übersteigt.The second voltage level (U p2 ) is formed when the thread lever 45 executes an upward movement to tighten the interlacing formed by the needle thread and the hook thread. The voltage level (U P2 ) has two voltage peaks (U 2.1 and U 2.2 ) at times (t₂ and t₃), the value of the first voltage peak (U 2.1 ) being that of the second voltage peak (U 2, 2 ) exceeds.

Wenn der Greifer (51) die Nadelfadenschlinge verfehlt, liegt ein Aufnahmefehler vor. Bei einem derartigen Fehler oder beim Bruch des Nadelfadens in Fadennachzugrichtung hinter der Spannvorrichtung (2) ändert sich der Verlauf der Fadenspannung (UF) gemäß Fig. 4b. Der erste Spannungspegel (UP1) nimmt den Betrag der Normalspannung (UN) an oder sinkt sogar unter diese ab, während der zweite Spannungspegel (UP2) lediglich mit einer Spannungsspitze (U₂) ausgebildet ist.If the gripper (51) misses the needle thread loop, there is a pick-up error. In the event of such an error or if the needle thread breaks in the thread pulling direction behind the tensioning device (2), the course of the thread tension (U F ) changes according to FIG. 4b. The first voltage level (U P1 ) takes on the amount of the normal voltage (U N ) or even drops below it, while the second voltage level (U P2 ) is only designed with a voltage peak (U₂).

Sollte die Nadel (48) nach Durchdringen des Nähgutes die durch den Greiferfaden gebildete Schlinge verfehlen, so liegt ein Abstechfehler vor. Dieser wird, ebenso wie ein Bruch des Greiferfadens in Fadennachzugrichtung hinter der Spannvorrichtung (52), durch eine Veränderung des Verlaufes der Fadenspannung (UF) gemäß der Fig. 4c angezeigt. Der erste Spannungspegel (UP1) bleibt ebenso wie die erste Spannungsspitze (U2,1) des zweiten Spannungspegels (UP2) nahezu unverändert, während der Betrag der zweiten Spannungsspitze (U2,2) stark reduziert ist.If the needle (48) misses the loop formed by the hook thread after penetration of the sewing material, there is a parting error. Like a break of the hook thread in the thread pulling direction behind the tensioning device (52), this is indicated by a change in the course of the thread tension (U F ) according to FIG. 4c. The first voltage level (U P1 ), like the first voltage peak (U 2.1 ) of the second voltage level (U P2 ), remains almost unchanged, while the amount of the second voltage peak (U 2.2 ) is greatly reduced.

Der Meßwertaufnehmer (9) (Fig. 1) ist derart zwischen der Spannvorrichtung (2) und dem Fadenführungselement (42) angeordnet, daß der Nadelfaden beim Durchgang durch die Öse (6) umgelenkt wird. Dadurch entsteht eine Kraft senkrecht zur Erstreckungsrichtung des Biegebalkens (5), durch welche dieser nach unten ausgelenkt wird. Infolge dieser Auslenkung, die proportional zu der Fadenspannung (UF) ist, wird das DMS-Element (7) an der Oberseite des Biegebalkens (5) auf Zug und das DMS-Element (8) an dessen Unterseite auf Druck beansprucht, so daß beide DMS-Elemente (7, 8) ihren elektrischen Widerstand ändern. Dadurch wird eine der Auslenkung des Biegebalkens (5) proportionale Differenzspannung (UD) gebildet, deren Verlauf über einen Stich dem der Fadenspannung (UF) entspricht.The transducer (9) (Fig. 1) is arranged between the tensioning device (2) and the thread guide element (42) in such a way that the needle thread passes through the eyelet (6) is deflected. This creates a force perpendicular to the direction of extension of the bending beam (5), by means of which the latter is deflected downward. As a result of this deflection, which is proportional to the thread tension (U F ), the strain gauge element (7) on the upper side of the bending beam (5) is subjected to tension and the strain gauge element (8) on the underside thereof is subjected to pressure, so that both strain gauge elements (7, 8) change their electrical resistance. This forms a differential tension (U D ) proportional to the deflection of the bending beam (5), the course of which over a stitch corresponds to that of the thread tension (U F ).

Nach Verstärkung durch den Verstärker (10) (Fig. 3) wird die Differenzspannung (UD) dem deren Wert anzeigenden Spannungsmesser (11) sowie dem Komparator (13) zugeleitet. In Abhängigkeit von der Einstellung der Spannvorrichtung (2) ist durch die Stellvorrichtung (14) die Schaltschwelle des Komparators (13) einstellbar, so daß dessen Empfindlichkeit der Spannung des Nadelfadens angepaßt ist. Die Schaltschwelle ist so gewählt, daß sie nur dann von einer der Spannungsspitzen (U₁, U2,2) unterschritten wird, wenn eine Fehlfunktion, wie ein Fehlstich oder Fadenbruch aufgetreten ist. Die der Schaltschwelle entsprechende Spannung ist im folgenden als Grenzspannung (UG) bezeichnet, die in den Fig. 4a bis 4c eingezeichnet ist.After amplification by the amplifier (10) (Fig. 3), the differential voltage (U D ) is fed to the voltmeter (11) indicating its value and to the comparator (13). Depending on the setting of the tensioning device (2), the switching threshold of the comparator (13) can be adjusted by the adjusting device (14), so that its sensitivity is adapted to the tension of the needle thread. The switching threshold is selected so that it only drops below one of the voltage peaks (U 1, U 2.2 ) when a malfunction, such as a missing stitch or thread break, has occurred. The voltage corresponding to the switching threshold is referred to below as the limit voltage (U G ), which is shown in FIGS. 4a to 4c.

Der Komparator (13) ist eingeschaltet, solange die an seinem Eingang anliegende Differenzspannung (UD) kleiner als die Grenzspannung (UG) ist und wird ausgeschaltet, sobald die Differenzspannung (UD) den Wert der Grenzspannung (UG) annimmt oder überschreitet. In Fig. 4d ist der Verlauf der Ausgangsspannung (UK) des Komparators (13) in Abhängigkeit von der Differenzspannung (UD) gemäß Fig. 4a eingezeichnet, während der Verlauf von (UK) nach Fig. 4e dem von (UD) nach Fig. 4b und der Verlauf von (UK) nach Fig. 4f dem von (UD) nach Fig. 4c zugeordnet ist.The comparator (13) is switched on as long as the differential voltage (U D ) at its input is less than the limit voltage (U G ) and is switched off as soon as the differential voltage (U D ) assumes or exceeds the value of the limit voltage (U G ) . 4d shows the profile of the output voltage (U K ) of the Comparator (13) as a function of the differential voltage (U D ) according to FIG. 4a, while the course of (U K ) according to FIG. 4e follows that of (U D ) according to FIG. 4b and the course of (U K ) according to Fig. 4f which is assigned by (U D ) according to Fig. 4c.

Solange keine Fehlfunktion eingetreten ist, liegt die Komparatorspannung (UK) immer nur dann am Eingang der UND-Glieder (15 und 16) an, wenn keiner der in Fig. 4g gezeigten, von dem Positionsgeber (13) gelieferten Impulse (I₁ oder I₂) eintrifft. Dadurch kann kein Signal die UND-Glieder (15 und 16) verlassen.As long as no malfunction has occurred, the comparator voltage (U K ) is only present at the input of the AND gates (15 and 16) if none of the pulses (I 1 or I 2) shown in Fig. 4g, delivered by the position transmitter (13) ) arrives. This means that no signal can leave the AND gates (15 and 16).

Bei einer Fehlfunktion gemäß der Fig. 4b gelangt zur Zeit (t₁) der Impuls (I₁) des Positionsgebers (13) von dem Fotodetektor (21) an einen Eingang des UND-Gliedes (15), wenn an dessen anderem Eingang die Komparatorspannung (UK) anliegt. Daraufhin wird ein Signal am Ausgang des UND-Gliedes (15) abgegeben und dem Setzeingang (S) des Speichers (30) zugeleitet. Der Impuls bewirkt, daß der Speicher (30) über seinen Ausgang (Q) das Anzeigeelement (33) einschaltet, das einen Aufnahmefehler oder den Bruch des Nadelfadens anzeigt. Der Ausgang (Q) des Speichers (30) betätigt bei geschlossenem Schalter (37) gleichzeitig die Abschaltvorrichtung (38), die je nach Ausführung den Antriebsmotor (39) sofort abschaltet oder dessen Wiederanlauf nach dem nächsten Anhaltevorgang verhindert.In the event of a malfunction according to FIG. 4b, the pulse (I₁) of the position transmitter (13) from the photodetector (21) arrives at an input of the AND gate (15) when the comparator voltage (U K ) is present. Then a signal is emitted at the output of the AND gate (15) and fed to the set input (S) of the memory (30). The pulse causes the memory (30) to switch on the display element (33) via its output (Q), which indicates a recording error or the breakage of the needle thread. When the switch (37) is closed, the output (Q) of the memory (30) simultaneously actuates the switch-off device (38) which, depending on the version, switches off the drive motor (39) immediately or prevents it from restarting after the next stopping process.

Nach Betätigen eines nicht dargestellten Rückstellschalters wird in geeigneter Weise ein elektrischer Impuls auf den Rücksetzeingang (R) des Speichers (30) gegeben, so daß dieser das Anzeigeelement (33) abschaltet und den Antriebsmotor (39) freigibt.After actuating a reset switch, not shown, an electrical pulse is given in a suitable manner to the reset input (R) of the memory (30), so that this is the display element (33) switches off and the drive motor (39) releases.

Bei einer Fehlfunktion nach der Fig. 4c liefert der Fotodetektor (25) des Positionsgebers (18) zur Zeit (t₃) einen Impuls (12) an einen Eingang des UND-Gliedes (16), während an dessen anderem Eingang die Komparatorspannung (UK) anliegt. Dadurch wird das UND-Glied (16) durchgeschaltet und gibt an seinem Ausgang ein Signal an den Setzeingang (S) des Speichers (31) ab, so daß dieser über seinen Ausgang (Q) das Anzeigeelement (35) einschaltet, das einen Abstechfehler oder den Bruch des Greiferfadens anzeigt. Der Ausgang (Q) des Speichers (31) steuert wie derjenige des Speichers (30) bei geschlossenem Schalter (37) gleichzeitig die Abschaltvorrichtung (38) des Antriebsmotors (39) an. Das Anzeigeelement (35) wird durch einen elektrischen Impuls auf den Rücksetzeingang (R) des Speichers (31) abgeschaltet und der Antriebsmotor (39) freigegeben.In the event of a malfunction according to FIG. 4c, the photodetector (25) of the position transmitter (18) delivers a pulse (12) to one input of the AND gate (16) at the time (t₃), while the comparator voltage (U K ) is present. As a result, the AND gate (16) is switched through and emits a signal at its output to the set input (S) of the memory (31), so that this switches on the display element (35) via its output (Q), which indicates a cut-off error or indicates the breakage of the hook thread. The output (Q) of the memory (31), like that of the memory (30), simultaneously controls the switch-off device (38) of the drive motor (39) when the switch (37) is closed. The display element (35) is switched off by an electrical pulse on the reset input (R) of the memory (31) and the drive motor (39) is released.

In Fig. 5 ist eine zweite Ausführung des Meßwertaufnehmers (3) dargestellt. An dem freien Ende des Biegebalkens (5) ist an dessen Oberseite ein Dauermagnet (54) befestigt. Am freien Ende eines Tragarmes (55) ist, dem Dauermagneten (54) zugewendet, ein Hallsensor (56) befestigt.5 shows a second embodiment of the measuring sensor (3). A permanent magnet (54) is attached to the top of the free end of the bending beam (5). A Hall sensor (56) is attached to the free end of a support arm (55), facing the permanent magnet (54).

Bei Auslenkung des Biegebalkens (5) unter der Wirkung des Nadelfadens nach unten wird der Abstand des Dauermagneten (54) zu dem Hallsensor (56) vergrößert, wodurch sich die magnetische Flußdichte und somit die Hallspannung des Hallsensors (56) entsprechend der Auslenkung des Biegebalkens (5) reduziert. Die Hallspannung wird der Steuervorrichtung (40) zugeleitet und ausgewertet.When the bending beam (5) is deflected downwards under the action of the needle thread, the distance between the permanent magnet (54) and the Hall sensor (56) is increased, as a result of which the magnetic flux density and thus the Hall voltage of the Hall sensor (56) corresponding to the deflection of the bending beam ( 5) reduced. The Hall voltage is fed to the control device (40) and evaluated.

In Fig. 6 ist eine zweite Ausführung der Steuervorrichtung (40) dargestellt. Der Ausgang des Verstärkers (10) ist mit dem Spannungsmesser (11) und, über einen A/D-Wandler (57), mit dem Eingang (E1) eines Mikroprozessors (58) verbunden. An einen zweiten Eingang (E2) des Mikroprozessors (58) ist eine Eingabevorrichtung (59) angeschlossen.6 shows a second embodiment of the control device (40). The output of the amplifier (10) is connected to the voltmeter (11) and, via an A / D converter (57), to the input (E1) of a microprocessor (58). An input device (59) is connected to a second input (E2) of the microprocessor (58).

Der Mikroprozessor (58) weist Ausgänge (A1 und A2) auf, von denen der Ausgang (A1) mit dem Setzeingang (S) eines Flipflop-Speichers (60) und der Ausgang (A2) mit dem Setzeingang (S) eines Flipflop-Speichers (61) verbunden ist. Die Speicher (60 und 61) bilden eine Schaltvorrichtung (62).The microprocessor (58) has outputs (A1 and A2), of which the output (A1) with the set input (S) of a flip-flop memory (60) and the output (A2) with the set input (S) of a flip-flop memory (61) is connected. The memories (60 and 61) form a switching device (62).

Der Ausgang (Q) des Speichers (60) ist mit dem Anzeigeelement (33), der des Speichers (61) mit dem Anzeigeelement (35) verbunden. Beide Ausgänge (Q) sind außerdem über den Schalter (37) an die Abschaltvorrichtung (38) des Antriebsmotors (39) angeschlossen.The output (Q) of the memory (60) is connected to the display element (33), that of the memory (61) to the display element (35). Both outputs (Q) are also connected via the switch (37) to the shutdown device (38) of the drive motor (39).

Die zweite Ausführung der Steuervorrichtung (40) arbeitet wie folgt:The second embodiment of the control device (40) works as follows:

Nach Verstärkung im Verstärker (10) wird die Differenzspannung (UD) (Fig. 7) dem A/D-Wandler (57) zugeleitet. Am Ausgang des A/D-Wandlers (57) liegt eine digitale Spannung an, die zu der an dessen Eingang anliegenden Differenzspannung (UD) proportional ist.After amplification in the amplifier (10), the differential voltage (U D ) (Fig. 7) is fed to the A / D converter (57). A digital voltage is present at the output of the A / D converter (57), which is proportional to the differential voltage (U D ) present at its input.

Durch den Mikroprozessor (58) wird die am Eingang (E1) aufgenommene digitale Spannung nur in den Zeitintervallen ausgewertet, in denen die Spannungspegel (UP1 und UP2) ausgebildet werden.The microprocessor (58) converts the digital voltage recorded at input (E1) only into the Time intervals are evaluated in which the voltage levels (U P1 and U P2 ) are formed.

Der Mikroprozessor (58) ermittelt von allen dem ersten Spannungspegel (Up1) zugeordneten digitalen Spannungen den Wert und bildet aus diesen Werten den Maximalwert (UM1). Der Maximalwert (UM1) wird mit einem ersten Schwellwert, der einer ersten Grenzspannung (UG1) (Fig. 7) zugeordnet ist, verglichen. Die Grenzspannung (UG1) ist in Abhängigkeit von der Einstellung der Spannvorrichtung (2) an der Eingabevorrichtung (59) vorzuwählen und wird dem Mikroprozessor (58) über dessen Eingang (E2) zugeführt.The microprocessor (58) determines the value of all digital voltages assigned to the first voltage level (U p1 ) and forms the maximum value (U M1 ) from these values. The maximum value (U M1 ) is compared with a first threshold value which is assigned to a first limit voltage (U G1 ) (FIG. 7). The limit voltage (U G1 ) is to be preselected as a function of the setting of the tensioning device (2) on the input device (59) and is fed to the microprocessor (58) via its input (E2).

Solange der Maximalwert (UM1) dem ersten Schwellwert entspricht oder diesen übersteigt, erfolgt keine Signalausgabe durch den Mikroprozessor (58). Wenn dagegen der Maximalwert (UM1) infolge eines Aufnahmefehlers oder einer Störung am Nadelfaden den ersten Schwellwert unterschreitet, gibt der Mikroprozessor (58) am Ausgang (A1) einen Impuls an den Speicher (60) ab, wodurch dieser umgeschaltet wird und über seinen Ausgang (Q) das Anzeigeelement (33) und, bei geschlossenem Schalter (37), die Abschaltvorrichtung (38) des Antriebsmotors (39) ansteuert.As long as the maximum value (U M1 ) corresponds to or exceeds the first threshold value, there is no signal output by the microprocessor (58). If, on the other hand, the maximum value (U M1 ) falls below the first threshold value as a result of a recording error or a malfunction in the needle thread, the microprocessor (58) outputs a pulse to the memory (60) at the output (A1), as a result of which it is switched over and via its output (Q) controls the display element (33) and, when the switch (37) is closed, the shutdown device (38) of the drive motor (39).

Von den Werten der der zweiten Spannungsspitze (U2,2) des Spannungspegels (UP2) zugeordneten digitalen Spannungen wird der Maximalwert (UM2) gebildet und mit einem zweiten Schwellwert verglichen, der einer zweiten Grenzspannung (UG2) (Fig. 7) zugeordnet ist. Diese ist wie die erste Grenzspannung (UG1) in Abhängigkeit von der Einstellung der Spannvorrichtung (2) an der Eingabevorrichtung (59) vorzuwählen.The maximum value (U M2 ) is formed from the values of the digital voltages assigned to the second voltage peak (U 2.2 ) of the voltage level (U P2 ) and compared with a second threshold value that corresponds to a second limit voltage (U G2 ) (FIG. 7) assigned. Like the first limit voltage (U G1 ), this is to be preselected as a function of the setting of the tensioning device (2) on the input device (59).

Wenn der Maximalwert (UM2) dem zweiten Schwellwert entspricht oder diesen überschreitet, erfolgt keine Signalausgabe durch den Mikroprozessor (58). Unterschreitet der Maximalwert (UM2) dagegen den zweiten Schwellwert als Folge eines Abstechfehlers oder einer Störung am Greiferfaden, dann gibt der Mikroprozessor (58) am Ausgang (A2) einen Impuls an den Speicher (61) ab. Dadurch wird dieser umgeschaltet und steuert über seinen Ausgang (Q) das Anzeigeelement (35) und die Abschaltvorrichtung (38) des Antriebsmotors (39) an.If the maximum value (U M2 ) corresponds to or exceeds the second threshold value, there is no signal output by the microprocessor (58). If, on the other hand, the maximum value (U M2 ) falls below the second threshold value as a result of a parting error or a fault on the hook thread, the microprocessor (58) outputs a pulse to the memory (61) at the output (A2). This switches it over and controls the display element (35) and the shutdown device (38) of the drive motor (39) via its output (Q).

Die Speicher (60 und 61) sind jeweils über ein elektrisches Signal auf den Rücksetzeingang (R) in ihre Ausgangsstellung umschaltbar.The memories (60 and 61) can each be switched to their initial position via an electrical signal to the reset input (R).

Durch die Vorgabe unterschiedlich großer Grenzspannungen (UG1, UG2) für die verschiedenen Maximalwerte (UM1 und UM2) ist der jeweilige Schwellwert optimal an den entsprechenden Maximalwert anpaßbar.By specifying differently large limit voltages (U G1 , U G2 ) for the different maximum values (U M1 and U M2 ), the respective threshold value can be optimally adapted to the corresponding maximum value.

Claims (7)

1. Stitch-forming machine, comprising a transducer for determining the tension contained in a thread, which tension assumes higher values during the stitch forming process by the provision of tension levels, and comprising a control device, by means of which the evaluation of this tension is effected, characterised in that the control device (40) has a comparator (50), by means of which each tension peak (U₁, U₂,2) of each tension level (Up1, Up2), which peak is utilisable as evidence of a malfunction, is comparable with a limit tension (UG1, UG2) associated with said peak, and in that, in the event of a tension peak (U₁, U₂,2) falling beneath its associated limit tension (UG1, UG2), a subsequently connected switching device (62), which is connected both to a cut-off device (38) of the driving motor (39) of the machine and to a plurality of indicators (33, 35), is actuatable in dependence on the non-attained limit tension (UG1, UG2), so that the machine can be stopped by the switching device (62), and so that the indicator (33, 35) associated with the non-attained limit tension (UG1, UG2) is switchable
2. Stitch-forming machine, comprising a transducer for determining the tension contained in a thread, and comprising a control device, by means of which the evaluation of the tension is effected within individual phases of the stitch forming process, in which phases the tension assumes higher values by the provision of levels, characterised in that the control device (40) has a comparator (13), by means of which all of the tension peaks (U₁, U₂,2) of each tension level (Up1, Up2) are comparable with a predeterminable common limit tension (UG), which peaks are utilisable as evidence of a malfunction, and, in the event of a tension peak (U₁, U₂,2) falling beneath the limit tension (UG), a subsequently connected switching device (32), which is connected both to a out-off device (38) of a driving motor (39) of the machine and to a plurality of indicators (33, 35), is actuatable in dependence on the phase of the stitch forming process associated with the tension peak (U₁, U2,2) not attaining the limit tension (UG), so that the machine can be stopped by the switching device (32), and so that the indicator (33, 35) associated with this phase of the stitch forming process is switchable.
3. Stitch-forming machine according to claim 1 or 2, for the formation of a chain stitch seam, the thread tension of which has a first tension level with the enlarging of the needle thread loop and has a second tension level with the knotting of the formed loop, characterised in that the switching device (32; 62) is actuatable by the comparator (13; 58) in the event of the tension peak (U₁) of the first tension level (Up1) falling beneath the limit tension (UG1; UG2) for the switching of the first indicator (33) for the evidence of a pick-up error or a fault with the needle thread and in the event of the second tension peak (U₂,2) of the second tension level (Up₂), having two tension peaks (U₂,1 and U2,2), falling beneath the respective limit tension (UG2; UG) for the switching of the second indicator (35) for the evidence of a cutting-off error or, in the case of a multi-threaded chain stitching machine, a fault with the gripper thread.
4. Stitch-forming machine according to claim 1 or 2, characterised in that the comparator (13; 58) has an adjusting device (14; 59), by means of which the limit tension (UG1, UG2; UG) is predeterminable in dependence on the setting of the tensioning device (2) associated with the monitored thread.
5. Stitch-forming machine according to claim 1 or 2, comprising a transducer, which has a resilient element deflectable by the tensioned thread and provided with a sensor, which responds proportionally to its deflection, characterised in that the resilient element is a flexible bar (5), which tapers towards its tree end from the location where it is clamped in position.
6. Stitch-forming machine according to claim 1 or 2 and 5, characterised in that the transducer (3) is mounted on the machine through the intermediary of a damping element (4).
7. Stitch-forming machine according to claim 1 or 2 and 5, 6, characterised in that the transducer (3) is disposed immediately behind the associated tensioning device (2), when viewed with respect to the unwinding direction of the thread.
EP89912950A 1988-11-24 1989-11-17 Sewing machine with transducer and control device Expired - Lifetime EP0445157B1 (en)

Applications Claiming Priority (2)

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DE3839733 1988-11-24
DE3839733A DE3839733C2 (en) 1988-11-24 1988-11-24 Stitch-forming machine with a sensor

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EP0445157B1 true EP0445157B1 (en) 1992-08-05

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EP (1) EP0445157B1 (en)
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JPH05505113A (en) 1993-08-05
DE3839733C2 (en) 1993-12-09
EP0445157A1 (en) 1991-09-11
JP2741952B2 (en) 1998-04-22
KR900702114A (en) 1990-12-05
US5237944A (en) 1993-08-24
DE3839733A1 (en) 1990-05-31

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