Classifications

• • D—TEXTILES; PAPER
  • D05—SEWING; EMBROIDERING; TUFTING
  • D05C—EMBROIDERING; TUFTING
  • D05C11/00—Devices for guiding, feeding, handling, or treating the threads in embroidering machines; Machine needles; Operating or control mechanisms therefor
  • D05C11/08—Thread-tensioning arrangements
  • D05C11/14—Stop motions responsive to thread tension or breakage
• • D—TEXTILES; PAPER
  • D05—SEWING; EMBROIDERING; TUFTING
  • D05B—SEWING
  • D05B69/00—Driving-gear; Control devices
  • D05B69/36—Devices for stopping drive when abnormal conditions occur, e.g. thread breakage
• • D—TEXTILES; PAPER
  • D05—SEWING; EMBROIDERING; TUFTING
  • D05C—EMBROIDERING; TUFTING
  • D05C13/00—Auxiliary devices incorporated in embroidering machines, not otherwise provided for; Ancillary apparatus for use with embroidering machines
  • D05C13/02—Counting, measuring, indicating, warning, or safety devices

Definitions

• the present invention relates to a stitch-forming machine, in particular an embroidery machine, sewing machine or sewing system, with at least one thread for embroidery or sewing, namely with at least one upper thread and with at least one lower thread, and with a device for detecting malfunctions in the area of the thread.
• the present invention further relates to a method for detecting malfunctions in the area of at least one thread for embroidery or sewing, namely at least one upper thread and / or at least one lower thread, a stitch-forming machine, in particular an embroidery machine, a sewing machine or a sewing system.
• two threads are generally used for embroidery according to the step stitch method, namely the so-called upper thread, which is guided through the sewing needle, and the so-called lower thread, which is used for knotting by means of a bobbin case.
• the Stitch formation involves the upper thread and the lower thread equally, so that the absence of one of the two threads leads to an undesirable malfunction of the stitch-forming or embroidery-forming process.
• the stitch-forming machine can even produce an embroidery pattern, but the embroidery pattern produced in this way does not adhere to its carrier because the knotting could not take place. As a result, the embroidery pattern can be destroyed simply by pulling the thread gently.
• measuring devices which automatically detect the absence of the upper thread and / or the lower thread are required in generic stitch-forming machines. Although the absence of the upper thread can be easily recognized by observation, automated detection is required so that, for example, the stitch-forming machine can be stopped immediately if a thread break occurs.
• upper thread monitoring by an electrical switch is also practiced, in that the upper thread is guided over a spring which closes an electrical contact due to the thread tension.
• Non-contact optical methods are mostly used for the bobbin thread monitoring, whereby the bobbin thread monitoring often causes considerable difficulties due to the existing space problems. For this reason, non-contact methods, such as optical methods, are used for this, but are not very reliable due to their sensitivity to dust.
• the present invention has for its object to design a generic stitch-forming machine so that not only the upper thread, but with the device for detecting malfunctions in the area of the thread the bobbin thread can also be monitored in a structurally integrated manner.
• the device has at least one thread rod, by means of which the upper thread is deflected, that the thread rod from the unloaded starting position against a restoring force in the direction of a resulting from the tension of the upper thread , the thread force lying in the plane spanned by the deflected upper thread can be deflected, that the thread rod is assigned at least one detection device for detecting the deflection of the thread rod effected by the thread force and that evaluation means are provided which have at least one mean value generator for forming at least one mean value for each time ranges formed by temporal subdivision of at least one electrical signal emitted by the detection device and at least one comparator for comparing the respective mean values with predetermined threshold values in each case find.
• At least one mean value is in each case formed for the time ranges of the electrical signal which are emitted by the measurement device and which are formed by time division the The presence of a malfunction and / or the type of malfunction is detected by comparing the respective mean values with predefined threshold values.
• the device for detecting malfunctions in the area of the thread can be used to monitor not only the upper thread, but also the lower thread in a structurally integrated manner.
• Detection device essentially outside of an embroidery head of the stitch-forming machine and the areas of the thread facing away from the thread bar
• Detection means are provided essentially within the embroidery head of the stitch-forming machine; that the embroidery head has at least two upper threads; that the upper threads differ in their nature,
• each of the upper threads is assigned a thread feeder; that the upper thread at least partially around the Thread rod is passed around through
• Thread feeder is passed and into a
• Sewing needle is threaded; that the detection device at least two
• each of the detection units comprises: at least one bending element connected to the thread rod and at least one measuring element assigned to the bending element for detecting the bending of the bending element determined by the deflection of the thread rod; that the bending elements are bar, rod or rod-shaped; that the thread rod at an end portion of the
• Bending element is attached; that the bending element has at one end portion a projecting portion on which the
• Thread rod is attached; that the bending of the bending element is essentially proportional to the thread force; that the measuring element is a magnetic measuring element; that the magnetic measuring element at least one
• Bending element is attached; that the magnet on the same end portion of the
• Amplification circuit is assigned; that with high thread force oversteer
• Amplification circuit takes place; that the Hall sensor is provided on a circuit board; that the evaluation means are provided on the board; that the board with the bending element in
• Air gap is provided, the size of which by the
• Bend of the bending element is determined; that by the bending of the bending element certain changes in the size of the
• Air gap in the range of about a few
• Voltage signal is substantially directly proportional to the magnetic field strength; that the detection device at least two
• Processing unit are formed; that the processing unit is designed as a microprocessor; and / or that at least one display unit is provided, by means of which the presence of the malfunction and / or the type of malfunction can be displayed.
• the method according to the present invention can have various advantageous developments, which are characterized independently of one another by the fact that a first electrical measurement signal from a first detection unit of the
• Detection device is emitted and that a second electrical measurement signal from a second
• Detection unit of the detection device is delivered; that the first electrical measurement signal and the second electrical measurement signal for electrical
• Sub-thread is assigned; that the second mean formed for the second time range corresponds to the process of
• Tightening the knot is assigned by a thread feeder provided for the stitch-forming machine; that the following conditions are recognizable: there is no malfunction; there is a malfunction of the upper thread; there is a malfunction of the lower thread; and there is a skipped stitch; that there is no malfunction if the first average is greater than the associated first threshold and if the second average is greater than the associated second threshold; that the upper thread malfunctions if the first mean value is less than that associated first threshold and when the second average is less than the associated second threshold; that the bobbin thread malfunctions when the first average is greater than the associated first threshold and when the second average is less than the associated second threshold; that the lower thread malfunctions if the condition is met that the second mean formed is less than four
• Amplification factor are amplified; that the gain factor is chosen so that the first electrical at low thread force
• Threshold value can be specified with low thread force; that the frequency of occurrence of
• Limit value of the thread force and a respective lower limit value of the thread force are specified; that the thread force is determined by pulling on the free end of the thread; that the determined thread force with the upper
• Limit value of the thread force and / or is compared with the lower limit value of the thread force; and / or that the presence of a thread force above the upper limit value of the thread force and / or below the lower limit value of the thread force is indicated.
• FIG. 1 shows an embodiment of a stitch-forming machine according to the present invention
• FIG. 2 shows a detection unit with a circuit board of the stitch-forming machine from FIG. 1;
• FIG. 3 shows an electrical voltage signal emitted by the Hall sensor of the stitch-forming machine from FIG. 1;
• FIG. 4 shows a diagrammatic representation of the second mean value formed for the second time range as a function of the number of stitches
• FIG. 5 shows a diagrammatic representation of the first mean value formed for the first time range and the second mean value formed for the second time range as a function of time.
• FIGS. 1 and 2 Identical or similar components or features of the invention are provided with identical reference numerals in FIGS. 1 and 2.
• the stitch-forming machine has an embroidery head 1, which is shown with the components essential for the invention.
• the embroidery head 1 has several threads in the form of upper threads 4 with different properties and colors, whereby however, only one upper thread 4 is embroidered at any time.
• the thread transmitter 2 is designated in FIG. 1; for embroidery, the thread feeder 3 is in action in FIG.
• the upper threads 4 are placed around the thread rod 5 and then guided to the thread transmitter 2, 3; the upper threads 4 are then threaded into the sewing needles 7, 8.
• the thread rod 5 is fastened at its two ends in bending elements 6.
• Each of the bending elements 6 has a permanent magnet 9 at its free end, a Hall sensor 10 being located opposite the permanent magnet 9 above an air gap and emitting an electrical voltage signal proportional to the magnetic field strength.
• the Hall sensor 10 is accommodated with the associated amplification circuit on a circuit board 11, the bending element 6 also being fastened to this circuit board 11, so that the air gap between the permanent magnet 9 and the Hall sensor 10 has a clearly defined width (see FIG. 2, in a detection unit with a circuit board 11 of the stitch-forming machine from FIG. 1 is shown schematically).
• the air gap is now increased by the thread force acting on the upper thread 4. Since the Hall sensor 10 is in the stray field of the permanent magnet 9, the magnetic field strength measured at the Hall sensor 10 becomes lower when the Distance of the Hall sensor 10 to the permanent magnet 9 increases. A change in distance of a few millimeters is sufficient to generate an evaluable signal.
• the force distribution on the bending elements 6 depends on the position in which the thread force is on the thread rod 5 works.
• the force on a bending element 6 varies with the position of the working thread.
• the sum of the two forces on the bending elements 6 is equal to twice the thread force.
• the signals of the two measuring elements 9, 10 are summed, the signals being summed in a microprocessor after the analog / digital conversion of the signals.
• the natural frequency of the bending element 6 would have to be significantly higher than the frequency range of the measurement signal. This is achieved in the present invention in that the double thread force is used as the measuring force and the bending element 6 can therefore be selected stiff.
• the natural frequency with which the measuring elements 9, 10 vibrate is a multiple of the useful frequency at the highest speed of the stitch-forming machine, so that the natural frequency of the measuring system is suppressed either by electrical filtering or by an adapted signal processing can be.
• FIG. 3 shows a typical electrical voltage signal emitted by the Hall sensor 10 of the stitch-forming machine from FIG. 1, both the upper thread 4 and the lower thread being present.
• the tension signal which is in a fixed relationship to the machine shaft, shows two maxima, the first maximum occurring when the upper thread 4 is pulled around the bobbin case; the second maximum arises when the thread transmitter 3 tightens the knot.
• both the upper thread 4 and the lower thread are present, however there is no knotting because the looper could not grip the loop of the upper thread.
• the frequency of this condition which arises under various influences in the stitch-forming machine, is a quality criterion in that a rare occurrence of missing stitches speaks for the quality of the stitch-forming machine.
• the first maximum does not occur in the case of a miss stitch, whereas the second maximum is significantly smaller in amplitude than in the normal stitch formation.
• the upper thread 4 is monitored or checked in the first area of the tension signal, which extends to ⁇ / ⁇ .
• the second area of the tension signal which extends from ⁇ ⁇ to ⁇ g, the lower thread is monitored or checked.
• FIG. 4 which shows a diagrammatic representation of the second mean value M2 formed for the second time range as a function of the number of stitches
• FIG. 5 which shows a diagrammatic representation of the for the shows the first temporal range of the first mean Ml and the second mean M2 of the second temporal range as a function of time).
• the state that there is no malfunction FK can be recognized from the fact that both the first mean value M1 lies above the corresponding threshold value S1 and the second mean value M2 lies above the corresponding threshold value S2.
• the state that there is a malfunction FO of the upper thread 4 can be recognized by the fact that both the first average value Ml is below the threshold value S1 assigned to it and the second average value M2 is below the threshold value S2 assigned to it.
• the state that there is a malfunction FU of the lower thread can be recognized on the basis of the mean value M2. If the mean value M2 is below the associated threshold value S2, this need not necessarily be caused by a malfunction FU of the lower thread, but can also be caused by a miss stitch FS. In order to be able to make a decision in this regard, the change in the voltage signal is tracked over several stitches. When the supply of bobbin thread is about to end, the signal of the mean M2 shows the course shown in FIG. 4:
• the signal of the mean value M2 at stitch n-1 is larger than the assigned threshold value S2, but smaller than the signal of the mean value M2 at stitch n-2. If the value falls below the threshold S2 at stitch n, the gradient of the signal of the mean M2 in the last three stages is considered.
• the supply of lower thread has run out. If the lower thread breaks or breaks, the mean M2 remains below its threshold S2 for several stitches without first showing a decreasing tendency in the signal height in the form of a negative gradient. In such a case, the decision can be made after three tricks, for example.
• This first threshold value S1 is selected to be lower than the second threshold value S2 (cf. FIG. 5), the first threshold value S1 being approximately half the size of the second threshold value S2 for the signal of the mean value M2 in the bobbin thread detection.
• the amplification factor caused by the amplification circuit is set in such a way that a sufficient tension level is present with minimal thread force.
• the first threshold value S1 and the second threshold value S2 are then set at this thread force or at this thread tension.
• the amplification circuit can be overridden when the thread force is very high. However, this does not affect the operation of the overall system in any way, because the signals become weaker when errors occur.
• a far more effective variant is to compare the thread force with a lower limit value and with an upper limit value and to provide an indication if the thread force is not in the intended range between the lower limit value and the upper limit.
• the lower limit value and the upper limit value are communicated to the embroidery heads 1 in the setting phase depending on the pattern by the central control;
• the threads 4 can have different lower and / or upper limit values depending on the nature and the type within an embroidery head 1.

Landscapes

• Engineering & Computer Science (AREA)
• Textile Engineering (AREA)
• Mechanical Engineering (AREA)
• Sewing Machines And Sewing (AREA)
• Controlling Rewinding, Feeding, Winding, Or Abnormalities Of Webs (AREA)

Applications Claiming Priority (3)

Publications (2)

Family

ID=7890394

Family Applications (1)

Country Status (4)

Families Citing this family (6)

Family Cites Families (6)

• 1998
  • 1998-12-08 DE DE19856620A patent/DE19856620A1/de not_active Withdrawn
• 1999
  • 1999-12-08 EP EP99961064A patent/EP1100987B1/fr not_active Expired - Lifetime
  • 1999-12-08 AT AT99961064T patent/ATE234954T1/de not_active IP Right Cessation
  • 1999-12-08 WO PCT/EP1999/009657 patent/WO2000034563A1/fr active IP Right Grant
  • 1999-12-08 DE DE59904647T patent/DE59904647D1/de not_active Expired - Fee Related

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events