EP1394310B1 - Method for determining the underthread supply and sewing machine with monitoring of the underthread supply - Google Patents

Method for determining the underthread supply and sewing machine with monitoring of the underthread supply Download PDF

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Publication number
EP1394310B1
EP1394310B1 EP03405536A EP03405536A EP1394310B1 EP 1394310 B1 EP1394310 B1 EP 1394310B1 EP 03405536 A EP03405536 A EP 03405536A EP 03405536 A EP03405536 A EP 03405536A EP 1394310 B1 EP1394310 B1 EP 1394310B1
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EP
European Patent Office
Prior art keywords
light
bobbin
light receiver
thread
receiver
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP03405536A
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German (de)
French (fr)
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EP1394310A3 (en
EP1394310A2 (en
Inventor
Hans Flückiger
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BERNINA International AG
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Fritz Gegauf AG
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Publication date
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Publication of EP1394310A3 publication Critical patent/EP1394310A3/en
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Classifications

    • D—TEXTILES; PAPER
    • D05—SEWING; EMBROIDERING; TUFTING
    • D05B—SEWING
    • D05B59/00—Applications of bobbin-winding or -changing devices; Indicating or control devices associated therewith
    • D05B59/02—Devices for determining or indicating the length of thread still on the bobbin
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
    • B65H—HANDLING THIN OR FILAMENTARY MATERIAL, e.g. SHEETS, WEBS, CABLES
    • B65H63/00—Warning or safety devices, e.g. automatic fault detectors, stop-motions ; Quality control of the package
    • B65H63/08—Warning or safety devices, e.g. automatic fault detectors, stop-motions ; Quality control of the package responsive to delivery of a measured length of material, completion of winding of a package, or filling of a receptacle
    • B65H63/082—Warning or safety devices, e.g. automatic fault detectors, stop-motions ; Quality control of the package responsive to delivery of a measured length of material, completion of winding of a package, or filling of a receptacle responsive to a predetermined size or diameter of the package
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
    • B65H—HANDLING THIN OR FILAMENTARY MATERIAL, e.g. SHEETS, WEBS, CABLES
    • B65H2701/00—Handled material; Storage means
    • B65H2701/30—Handled filamentary material
    • B65H2701/31—Textiles threads or artificial strands of filaments
    • D—TEXTILES; PAPER
    • D05—SEWING; EMBROIDERING; TUFTING
    • D05B—SEWING
    • D05B57/00—Loop takers, e.g. loopers
    • D05B57/08—Loop takers, e.g. loopers for lock-stitch sewing machines
    • D05B57/10—Shuttles
    • D05B57/14—Shuttles with rotary hooks

Definitions

  • the invention relates to a method for determining the lower thread supply and a sewing machine with a lower thread supply monitoring according to the preamble of claims 1 and 4.
  • the upper thread is supplied by a arranged on or next to the sewing machine spool whose size is essentially arbitrary.
  • the second thread, called lower thread is wound on a spool, which is inserted into the interior of the rotatably mounted and driven gripper of the sewing machine and is held freely rotatable there.
  • the size of the gripper consequently determines the maximum size of the bobbin.
  • the wound up Unterfadenmenge or the Unterfadenvorrat is in any case in relation to the upper thread supply on the outside
  • the coil arranged in the machine housing is many times smaller and must therefore be filled or replaced more frequently.
  • the bobbin when sewing from the outside is not visible because it is located within the gripper housing, which is located in the lower arm. For this reason, it is difficult to monitor the current lower thread stock and the lower thread take-off during the sewing operation. To make matters worse, often when sewing smaller pieces of cloth by the operator, a partially already filled bobbin is wound with another thread, because no empty bobbin more is available. This other thread is not connected to the already existing on the coil. After consumption of this outer thread no seam can be produced, although on the spool core, for example, still 50% or 70% of another thread is wound up.
  • Measuring devices are already known from the prior art with which attempts to determine the end or the remaining amount of the lower thread on the lower thread bobbin rotatably held in the gripper and stop the sewing machine before the end of the lower thread is pulled out of the upper thread through the sewing material and in particular before more stitches are sewn, which are therefore not held on the bottom of the fabric by a bobbin thread.
  • a device for detecting the amount of residual thread on a bobbin of a sewing machine is known.
  • a light beam is sent from a light transmitter substantially tangentially through the annulus between the two spool flanges and the spool through to a light receiver.
  • diagonally opposite holes are provided in the gripper housing and in the coil housing, through which the light beams are sent through.
  • the light rays are passed very close to the spool, so that the end of the thread supply can be detected as soon as the light rays can penetrate this area. If the bobbin is still filled with thread, no light signal can be received by the receiver.
  • a second sensor detects the movements of the gripper, so that it is clearly recognizable whether the thread supply is now used up or whether only the gripper is stationary. With such a device, the thread supply can be detected only shortly before the complete emptying of the coil.
  • Object of the present invention is to provide a method for determining the Unterfadenvorrats and a sewing machine with a lower thread supply monitoring, with the instantaneous amount of thread on the lower thread bobbin can be determined at any time. Another object is to calculate the time of the end of the lower thread on the lower thread bobbin from the amount of thread consumed per unit time.
  • Light source can be directed tangentially to the axis of rotation of the coil or the gripper directed light rays through the gripper body on a photosensitive element and there compared the time of arrival of the first light beam with the current rotation angle of the gripper and thus accurately determined the diameter of the current thread supply on the spool become.
  • the location of the incidence of the light beam can be compared with the knowledge of the instantaneous angle of rotation of the gripper and thus the diameter of the yarn supply can be determined.
  • the bobbin diameter and hence the yarn supply can be determined.
  • the possible measurement parameters could also be used in combination for determining the thread supply in order to increase the measurement accuracy.
  • the accuracy can be significantly affected neither by small lint, dust, abrasion or other influences.
  • inexpensive elements a light-emitting diode and a photosensitive element
  • the end of the latter can be calculated.
  • the free-arm sewing machine 1 shown purely schematically in the example in FIG. 1 comprises a base 3, an upper arm 5, a lower or free arm 7 and the machine housing 9 connecting the three parts.
  • a needle bar 11 and the presser foot bar 13 attached in the upper arm 5 are a needle bar 11 and the presser foot bar 13 attached in the lower arm 7 .
  • the lower arm 7 is schematically indicated by a circle of the gripper 15 in the cut area. The details of the gripper 15 are shown enlarged in Figures 2 to 4.
  • the gripper 15 described in the example comprises, among other elements a gripper body 17 which sits on a drive shaft 19 and by a pinion 21 in drive connection with the main shaft of the sewing machine drive is (main shaft not shown). It does not matter if the gripper is a rotating one fixed to the drive shaft is attached, or an oscillating, which is loosely inserted in the gripper driver and consequently not fixedly arranged on the drive shaft 19.
  • a bobbin 27 for receiving a bobbin case 28 for a bobbin - short spool 29 - freely rotatably mounted on the gripper body 17.
  • the bobbin case 28 is held by means of a shutter 31 at the front end 33 of a coil end 27 coaxial with the drive shaft 19 secured stub shaft 20.
  • FIG. 2 only a small section of the front flange 35 of the coil 29 is visible.
  • flange 35 annularly arranged openings 37 are recessed.
  • the rear flange 39 of the coil 29 is visible in Figure 3. There, the front flange 35 is covered by the bobbin case 28.
  • the bobbin case 28 is peripherally surrounded only over an arc of about 180 degrees of a mantle.
  • a view through the gripper 15 is in each case possible if the two recesses 45 ', 45 "on the gripper body 17 and attached to the coil support 27 slots 49', 49" and the omitted part in the shell of the bobbin case 28 are in overlap.
  • the cross section of the per gripper rotation once possible view depends in addition to the once structurally fixed geometry of the gripper 15 and the dimensions of the recesses 45 ', 45 "and slots 49', 49" only from the current packing diameter D of the coil 29 in the annular packing area 47th wound up thread.
  • the cross-sectional view is the smallest (see Figure 5a); when empty the largest (see Figure 5c).
  • the lower limit of the cross-sectional view in the fixed recess 45 " is given by the apex 41 of the coil pack or the spool core 43, the upper by the respective position the front in the direction of rotation P edge 61 of the recess 45 ".
  • the rotational angle position of the gripper 15, at which the beam passage or passage per revolution is detected, is directly usable as a measure for the calculation of the actual coil diameter D.
  • the measuring method will now be explained in more detail: At a radial distance from the periphery of the gripper 15, the light source 51 and on the other side of the gripper 15, that is substantially diagonally opposite, a light receiver 53 having a receiving region extending at least over a length a 0 -a 3 (vertical line in Figs. 5) capable of receiving the beams 57a-57b of the beam 57 emitted from the light source 51.
  • the light beams 57a-57b penetrate both the two recesses 45 ', 45 "in the gripper body 17 and the slots 49', 49" in the coil carrier 27, when they briefly reach mutual overlap.
  • An overlap of the recesses 45 ', 45 “and the slots 49', 49” thus takes place once per complete revolution of the gripper body 17 or once during a cycle in oscillating grippers 15.
  • Figure 4 which shows a cross section through the gripper 15, is the geometric position of the recesses 45 ', 45 "and the slots 49', 49” shown clearly.
  • the light beams 57a, 57b emanating from the light source 51 and bounding the beam 57 at the top and at the bottom can be seen which fall through the gripper 15 onto the light receiver 53.
  • the light beam 57a represents a tangent between the light source 51 and the spool core 59.
  • the light beam 57b is also a tangent, namely a tangent to the package of a full spool whose diameter is approximately equal to the diameter of the flanges of the bobbin 29.
  • the two light beams 57a, 57b in FIG. 4 and also in FIG. 5c consequently represent the two extreme values of the beam 57.
  • a CCD element, a photodiode or phototransistor or other photosensitive element may be used as the light receiver 53.
  • the light emitted by the light source 51 passes in the illustrated examples as a divergent beam 57 through the gripper 15 to the light receiver 53 as soon as the forward edge 61 of the recess 45 "releases the passage of light rays is determined by the thread package, is the first that can be detected by the light receiver 53.
  • the gripper body 17 rotates in the counterclockwise direction, ie in the direction of the arrow P.
  • the "first" light beam is denoted by 57x. Is the coil 29 empty, the first light beam 57x corresponds to the light beam 57 a and reaches the light receiver 53 at the point a 3 (compare FIGS. 4 and 5c).
  • FIG. 5b shows the situation with a half-filled coil 29.
  • the first light beam 57x impinges on the point a 2 , which lies between the two extremes a 1 and a 3 .
  • a light beam with parallel rays can also be used.
  • the instantaneous position of the front edge 61 of the recess 45 is assumed to be known in Example 2. Its position can be calculated from the rotational position of the main shaft of the sewing machine 1.
  • the light receiver 53 detects the location a 1 to a 3 of the impingement of the first light beam 57x impinging on the light receiver 53 as soon as the front edge 61 of the recess 45 '' passes through the light beam 57x allowed.
  • the knowledge of the location (a 1 to a 3 ) of the impingement of the first light beam 57x on the light receiver 53 directly enables the calculation of the packing diameter D because there is a direct geometrical relationship (FIGS. 5a-5c).
  • the location of the last light beam could be detected before the trailing edge 62 on the recess 45 "begins to close the light cone (FIGS. 6a-6c).
  • the time t 1 of the light beam 57x is detected on impact and compared with the rotational angle position alpha of the front edge 61 on the gripper body 17. From these two parameters, the diameter D of the packing can also be calculated ( Figures 5a-5c, Figures 6a-6c).
  • the diameter D of the coil packing can also be calculated (width of the light cone in FIGS. 6a-6c).
  • Example 3 Instead of the time duration t x - t o as described in Example 3, the amount of light or light energy (mW), which impinges on the receiver 53, detected and used to calculate the diameter D. However, the accuracy of this measurement is less than that in Example 3, since flaws and aging of the light source 51 make flaws unavoidable (area of the light cone in FIGS. 6a-6c).
  • the aforementioned examples for the acquisition of data for calculating the packing diameter D can also be combined in order to be able to increase the accuracy.
  • the four possible types of measurement not only the instantaneous diameter D can be determined, but also the per unit time resulting decrease in the diameter D and thus the consumption of thread and the time in which the thread on the coil 29 is completely used up.
  • the continuous measurement of the diameter D of the coil package 47 thus makes it possible to determine the instantaneous yarn consumption, regardless of the thickness of the yarn.
  • the average speed n of the coil 29 is required in this case.
  • known means are available for the detection of the speed n of the coil.
  • the knowledge of the thread consumption can be further used to control the thread tension of the upper thread. Namely, the yarn consumption per stitch is greater than the known theoretical value resulting from the type of stitch and the stitch length and the thickness of the fabric, the upper thread tension is too large and it is drawn too deep in the sewing material. By loosening the upper thread tension, the threading of the lower thread into the sewing material can be brought to the desired degree. Analogously, too small a lower thread consumption compared to the theoretical value is an indication that the upper thread tension is too low and consequently must be increased.
  • the known means as described for example in DE-A-4 116 638, find use.
  • a reliable measurement of the speed n of the bobbin 29 can also be achieved with a device as disclosed in Swiss Patent Application No. 00893/02 of 30.05.2002. With the measuring method or device disclosed there, the speed n of the bobbin 29 can be reliably detected at any time, in particular, a standstill of the bobbin 29 can be detected immediately. Even if vibrations of the sewing machine make the bobbin 29 vibrate, which may be misinterpreted as "non-stop".

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  • Engineering & Computer Science (AREA)
  • Quality & Reliability (AREA)
  • Textile Engineering (AREA)
  • Sewing Machines And Sewing (AREA)
  • Filamentary Materials, Packages, And Safety Devices Therefor (AREA)

Abstract

A light beam (57a, 57b) is projected from a light source (51) through apertures (49', 49) in the bobbin carrier (27) and hook body (17) on to a receiver (53). The angle of rotation of the hook body (17) when light is detected by passing both the aperture edge and the surface of the thread package is used to calculate the package diameter. An Independent claim is also included for a sewing machine with this method of underthread sensing, the receiver (53) being connected to the machine control. Alternative methods involve measuring the position on the receiver where the initial or final light ray is detected, measuring the duration of light reception, or measuring the amount of light received. The corresponding receivers detect the position or the amount of light received.

Description

Gegenstand der Erfindung ist ein Verfahren zur Bestimmung des Unterfadenvorrats und eine Nähmaschine mit einer Unterfadenvorrats-überwachung gemäss Oberbegriff der Patentansprüche 1 und 4.The invention relates to a method for determining the lower thread supply and a sewing machine with a lower thread supply monitoring according to the preamble of claims 1 and 4.

Beim Nähen und Sticken mit einer Nähmaschine werden bekanntlich zwei Fäden, der Oberfaden und der Unterfaden, miteinander verschlauft. Der obere, Nadelfaden genannt, wird von einer auf oder neben der Nähmaschine angeordneten Spule geliefert, deren Grösse im wesentlichen frei wählbar ist. Der zweite Faden, Unterfaden genannt, ist auf eine Spule gewickelt, welche in das Innere des drehbar gelagerten und antreibbaren Greifers der Nähmaschine eingelegt wird und dort frei drehbar gehalten ist. Durch die Grösse des Greifers wird folglich die maximale Grösse der Unterfadenspule bestimmt. Die aufgespulte Unterfadenmenge bzw. der Unterfadenvorrat ist in jedem Fall im Verhältnis zum Oberfadenvorrat auf der ausserhalb des Maschinengehäuses angeordneten Spule ein Vielfaches kleiner und muss folglich häufiger aufgefüllt oder ausgetauscht werden. Zudem ist die Unterfadenspule beim Nähen von aussen nicht einsehbar, da sie sich innerhalb des Greifergehäuses befindet, das im Unterarm angeordnet ist. Aus diesem Grunde ist das Überwachen des momentanen Unterfadenvorrats und des Unterfadenabzugs während des Nähvorgangs schwierig. Erschwerend kommt hinzu, dass häufig beim Nähen kleinerer Nähgutstücke durch die Bedienungsperson eine teilweise bereits gefüllte Unterfadenspule mit einem anderen Faden überwickelt wird, weil keine leere Spule mehr vorhanden ist. Dieser andere Faden ist mit dem bereits auf der Spule vorhandenen nicht verbunden. Nach Verbrauch dieses äusseren Fadens kann keine Naht mehr erzeugt werden, obwohl auf dem Spulenkern beispielsweise noch 50% oder 70% eines anderen Fadens aufgewickelt ist.When sewing and embroidering with a sewing machine, two threads, the upper thread and the lower thread, are known to be looped together. The upper, called needle thread, is supplied by a arranged on or next to the sewing machine spool whose size is essentially arbitrary. The second thread, called lower thread, is wound on a spool, which is inserted into the interior of the rotatably mounted and driven gripper of the sewing machine and is held freely rotatable there. The size of the gripper consequently determines the maximum size of the bobbin. The wound up Unterfadenmenge or the Unterfadenvorrat is in any case in relation to the upper thread supply on the outside The coil arranged in the machine housing is many times smaller and must therefore be filled or replaced more frequently. In addition, the bobbin when sewing from the outside is not visible because it is located within the gripper housing, which is located in the lower arm. For this reason, it is difficult to monitor the current lower thread stock and the lower thread take-off during the sewing operation. To make matters worse, often when sewing smaller pieces of cloth by the operator, a partially already filled bobbin is wound with another thread, because no empty bobbin more is available. This other thread is not connected to the already existing on the coil. After consumption of this outer thread no seam can be produced, although on the spool core, for example, still 50% or 70% of another thread is wound up.

Aus dem Stand der Technik sind bereits Messvorrichtungen bekannt, mit denen versucht wird, das Ende oder die Restmenge des Unterfadens auf der im Greifer drehbar gehaltenen Unterfadenspule festzustellen und die Nähmaschine anzuhalten, bevor das Ende des Unterfadens vom Oberfaden durch das Nähgut herausgezogen wird und insbesondere bevor weitere Stiche genäht werden, die auf der Nähgutunterseite folglich nicht von einem Unterfaden gehalten werden.Measuring devices are already known from the prior art with which attempts to determine the end or the remaining amount of the lower thread on the lower thread bobbin rotatably held in the gripper and stop the sewing machine before the end of the lower thread is pulled out of the upper thread through the sewing material and in particular before more stitches are sewn, which are therefore not held on the bottom of the fabric by a bobbin thread.

Aus der GB-A 2 296 721 ist eine Vorrichtung zum Erfassen der Restfadenmenge auf einer Unterfadenspule einer Nähmaschine bekannt. Dabei wird ein Lichtstrahl von einem Lichtsender im wesentlichen tangential durch den Ringraum zwischen den beiden Spulenflanschen und dem Spulendorn hindurch zu einem Lichtempfänger geschickt. Dazu sind im Greifergehäuse und im Spulengehäuse diagonal gegenüberliegend Löcher angebracht, durch die die Lichtstrahlen hindurch geschickt werden. Die Lichtstrahlen werden sehr nahe am Spulendorn vorbeigeleitet, so dass das Ende des Fadenvorrats festgestellt werden kann, sobald die Lichtstrahlen diesen Bereich durchdringen können. Ist die Spule noch mit Faden gefüllt, so kann vom Empfänger kein Lichtsignal empfangen werden. Ein zweiter Sensor detektiert die Bewegungen des Greifers, damit eindeutig erkennbar ist, ob nun der Fadenvorrat aufgebraucht ist oder ob nur der Greifer stillsteht. Mit einer solchen Vorrichtung kann der Fadenvorrat nur kurz vor dem vollständigen Leeren der Spule erfasst werden.From GB-A 2 296 721 a device for detecting the amount of residual thread on a bobbin of a sewing machine is known. In this case, a light beam is sent from a light transmitter substantially tangentially through the annulus between the two spool flanges and the spool through to a light receiver. For this purpose, diagonally opposite holes are provided in the gripper housing and in the coil housing, through which the light beams are sent through. The light rays are passed very close to the spool, so that the end of the thread supply can be detected as soon as the light rays can penetrate this area. If the bobbin is still filled with thread, no light signal can be received by the receiver. A second sensor detects the movements of the gripper, so that it is clearly recognizable whether the thread supply is now used up or whether only the gripper is stationary. With such a device, the thread supply can be detected only shortly before the complete emptying of the coil.

Aus der US-A 4,825,789 ist eine weitere Vorrichtung zum Erfassen des Fadenendes auf einer Unterfadenspule einer Nähmaschine offenbart. Auch bei dieser Vorrichtung wird ein Lichtstrahl von einem Lichtsender tangential über den Spulendorn zu einem Lichtempfänger gerichtet. Solange Fadenvorrat auf der Spule vorhanden ist, kann der Lichtstrahl den Lichtempfänger nicht erreichen. Erst kurz vor dem Fadenende kann durch diese Sensoren dem Bediener der Maschine ein Signal übermittelt werden, das auf das Ende des Fadens in der Unterfadenspule hinweist.
Mit beiden bekannten Vorrichtungen kann folglich nur das Fadenende bzw. der Zeitpunkt, bevor das Fadenende erreicht ist, erkannt werden. Fadenbrüche oder eine Bestimmung der momentan vorhandenen Fadenmenge und damit der Zeitpunkt, in dem das Fadenende erreicht wird, lässt sich mit den bekannten Vorrichtungen nicht erkennen.From US-A 4,825,789 another device for detecting the yarn end on a bobbin of a sewing machine is disclosed. Also in this device, a light beam is directed by a light transmitter tangentially over the bobbin to a light receiver. As long as thread supply is present on the bobbin, the light beam can not reach the light receiver. Only briefly Before the thread end, these signals can be used to send a signal to the operator of the machine that indicates the end of the thread in the bobbin.
Consequently, only the thread end or the time before the thread end is reached can be detected with both known devices. Yarn breaks or a determination of the currently existing amount of thread and thus the time at which the thread end is reached, can not be seen with the known devices.

Aufgabe der vorliegenden Erfindung ist die Schaffung eines Verfahrens zur Bestimmung des Unterfadenvorrats und einer Nähmaschine mit einer Unterfadenvorrats-Überwachung, mit der jederzeit die momentane Fadenmenge auf der Unterfadenspule feststellbar ist.
Eine weitere Aufgabe besteht darin, den Zeitpunkt des Endes des Unterfadens auf der Unterfadenspule aus der pro Zeiteinheit verbrauchten Fadenmenge zu errechnen.Object of the present invention is to provide a method for determining the Unterfadenvorrats and a sewing machine with a lower thread supply monitoring, with the instantaneous amount of thread on the lower thread bobbin can be determined at any time.
Another object is to calculate the time of the end of the lower thread on the lower thread bobbin from the amount of thread consumed per unit time.

Gelöst werden diese Aufgaben durch ein Verfahren zur Bestimmung des Unterfadenvorrats und eine Nähmaschine mit einer Unterfadenvorrats-Überwachung gemäss den Merkmalen der Patentansprüche 1 und 4.
Weitere vorteilhafte Ausgestaltungen der Erfindung sind in den abhängigen Ansprüchen wiedergegeben.These objects are achieved by a method for determining the lower thread supply and a sewing machine with a lower thread supply monitoring according to the features of claims 1 and 4.
Further advantageous embodiments of the invention are given in the dependent claims.

Mit einer radial vom Greiferkörper beabstandeten Lichtquelle können tangential zur Drehachse der Spule bzw. des Greifers gerichtete Lichtstrahlen durch den Greiferkörper hindurch auf ein lichtempfindliches Element gesendet und dort der Zeitpunkt des Eintreffens des ersten Lichtstrahls mit dem momentanen Drehwinkel des Greifers verglichen und damit exakt der Durchmesser des momentanen Fadenvorrats auf der Spule festgestellt werden. Mit der gleichen Vorrichtung, nämlich der Lichtquelle und einem lichtempfindlichen Element, das sich über eine endliche Länge erstreckt, kann auch der Ort des Auftreffens des Lichtstrahls zusammen mit der Kenntnis des momentanen Drehwinkels des Greifers verglichen und damit der Durchmesser des Fadenvorrats festgestellt werden. Weiter kann mit der gleichen Anordnung durch Messen der Zeitdauer, während der ein Lichtstrahl auf das lichtempfindliche Element fällt, der Spulendurchmesser und damit der Fadenvorrat bestimmt werden. Selbstverständlich könnten die möglichen Messparameter auch in Kombination zur Bestimmung des Fadenvorrats herangezogen werden, um die Messgenauigkeit zu erhöhen. Die Genauigkeit kann weder durch kleine Flusen, Staub, Abrieb oder andere Einflüsse wesentlich beeinträchtigt werden. Es können zudem kostengünstige Elemente (eine Leuchtdiode und ein lichtempfindliches Element) verwendet werden. Zusammen mit einer kontinuierlichen Messung der mittleren Spulendrehzahl mit geeigneten Mitteln und dem zeitlichen Verlauf der Durchmesserabnahme und dem Unterfadenverbrauch pro Stich kann, unabhängig von der Dicke des Fadens, das Ende des letzteren errechnet werden.With a radially spaced from the gripper body Light source can be directed tangentially to the axis of rotation of the coil or the gripper directed light rays through the gripper body on a photosensitive element and there compared the time of arrival of the first light beam with the current rotation angle of the gripper and thus accurately determined the diameter of the current thread supply on the spool become. With the same device, namely the light source and a photosensitive element extending over a finite length, the location of the incidence of the light beam can be compared with the knowledge of the instantaneous angle of rotation of the gripper and thus the diameter of the yarn supply can be determined. Further, with the same arrangement, by measuring the period of time during which a light beam is incident on the photosensitive member, the bobbin diameter and hence the yarn supply can be determined. Of course, the possible measurement parameters could also be used in combination for determining the thread supply in order to increase the measurement accuracy. The accuracy can be significantly affected neither by small lint, dust, abrasion or other influences. In addition, inexpensive elements (a light-emitting diode and a photosensitive element) can be used. Together with a continuous measurement of the mean reel speed with suitable means and the time course of the diameter decrease and the lower thread consumption For each stitch, regardless of the thickness of the thread, the end of the latter can be calculated.

Anhand illustrierter Ausführungsbeispiele wird die Erfindung näher erläutert. Es zeigen

Figur 1
eine Seitenansicht einer schematisch dargestellten Nähmaschine mit im Bereich des Greifers aufgeschnittenem Freiarm einer Freiarmnähmaschine,
Figur 2
eine Ansicht eines Greifers in Achsrichtung,
Figur 3
eine Ansicht des Greifers in Figur 2 in Seitenansicht (teilweise aufgeschnitten),
Figur 4
ein Querschnitt längs Linie IV-IV in Figur 3,
Figur 5a
eine schematische Darstellung eines umlaufenden Greifers mit darin angeordneter Spule, mit annähernd maximaler Fadenmenge, wobei die vordere Kante der Ausnehmung den Beginn einer Messung darstellt,
Figur 5b
eine schematische Darstellung eines umlaufenden Greifers mit darin angeordneter Spule, mit halber Packung,
Figur 5c
eine schematische Darstellung eines umlaufenden Greifers mit darin angeordneter Spule, Spule leer,
Figur 6a
eine schematische Darstellung eines umlaufenden Greifers mit darin angeordneter Spule, mit annähernd maximaler Fadenmenge, wobei die hintere Kante der Ausnehmung den Beginn der Messung darstellt,
Figur 6b
eine schematische Darstellung eines umlaufenden Greifers mit darin angeordneter Spule mit halber Packung,
Figur 6c
eine schematische Darstellung eines umlaufenden Greifers mit darin angeordneter Spule, Spule leer.
Based on illustrated embodiments, the invention will be explained in more detail. Show it
FIG. 1
a side view of a schematically illustrated sewing machine with cut open in the region of the gripper free arm a Freiarmnähmaschine,
FIG. 2
a view of a gripper in the axial direction,
FIG. 3
a view of the gripper in Figure 2 in side view (partially cut away),
FIG. 4
a cross section along line IV-IV in Figure 3,
FIG. 5a
a schematic representation of a rotating gripper with arranged therein coil, with approximately maximum amount of thread, wherein the front edge of the recess represents the beginning of a measurement,
FIG. 5b
a schematic representation of a rotating gripper with arranged therein coil, with half package,
FIG. 5c
a schematic representation of a rotating gripper with arranged therein coil, coil empty,
FIG. 6a
a schematic representation of a rotating gripper with arranged therein coil, with approximately maximum amount of thread, wherein the trailing edge of the recess represents the beginning of the measurement,
FIG. 6b
a schematic representation of a rotating gripper with arranged therein coil with half package,
FIG. 6c
a schematic representation of a rotating gripper with arranged therein coil, coil empty.

Die im Beispiel in Figur 1 rein schematisch dargestellte Freiarm-Nähmaschine 1 umfasst einen Sockel 3, einen Oberarm 5, einen Unter- oder Freiarm 7 sowie das die drei Teile verbindende Maschinengehäuse 9. Im Oberarm 5 sind eine Nadelstange 11 und die Nähfuss-Stange 13 befestigt. Im Unterarm 7 ist im aufgeschnittenen Bereich schematisch durch einen Kreis der Greifer 15 angedeutet. Die Einzelheiten des Greifers 15 sind in den Figuren 2 bis 4 vergrössert dargestellt.The free-arm sewing machine 1 shown purely schematically in the example in FIG. 1 comprises a base 3, an upper arm 5, a lower or free arm 7 and the machine housing 9 connecting the three parts. In the upper arm 5 are a needle bar 11 and the presser foot bar 13 attached. In the lower arm 7 is schematically indicated by a circle of the gripper 15 in the cut area. The details of the gripper 15 are shown enlarged in Figures 2 to 4.

Der im Beispiel beschriebene Greifer 15 umfasst nebst anderen Elementen einen Greiferkörper 17, der auf einer Antriebswelle 19 sitzt und durch ein Zahnritzel 21 in Antriebsverbindung mit der Hauptwelle des Nähmaschinenantriebs steht (Hauptwelle nicht dargestellt). Es spielt keine Rolle, ob es sich beim Greifer um einen rotierenden handelt, der fest auf der Antriebswelle befestigt ist, oder um einen oszillierenden, der lose im Greifertreiber eingelegt und folglich nicht fest auf der Antriebswelle 19 angeordnet ist.The gripper 15 described in the example comprises, among other elements a gripper body 17 which sits on a drive shaft 19 and by a pinion 21 in drive connection with the main shaft of the sewing machine drive is (main shaft not shown). It does not matter if the gripper is a rotating one fixed to the drive shaft is attached, or an oscillating, which is loosely inserted in the gripper driver and consequently not fixedly arranged on the drive shaft 19.

Auf dem Greiferkörper 17 sitzt peripher ein Fadenschutzoder -fangblech 23 mit einer Mitnehmerspitze 25. Im Innern des Greiferkörpers 17 ist auf dem vorderen Ende der Antriebswelle 19 ein Spulenträger 27 zur Aufnahme einer Spulenkapsel 28 für eine Unterfadenspule - kurz Spule 29 - frei drehbar gelagert. Die Spulenkapsel 28 wird mittels eines Verschlusses 31 am vorderen Ende 33 eines im Spulenträger 27 koaxial zur Antriebswelle 19 befestigten Wellenstummels 20 festgehalten. In Figur 2 ist von der Spule 29 nur ein kleiner Ausschnitt von deren vorderen Flansch 35 sichtbar. In Flansch 35 sind ringförmig angeordnete öffnungen 37 eingelassen. Der hintere Flansch 39 der Spule 29 ist sichtbar in Figur 3. Dort ist der vordere Flansch 35 von der Spulenkapsel 28 verdeckt. Ebenfalls ist dort der Scheitel 41 des Spulenkerns 43 der Spule 29 teilweise sichtbar. Die beiden letztgenannten Elemente sind sichtbar, weil im Greiferkörper 17 Ausnehmungen 45' und 45" und im Spulenträger 27 Schlitze 49',49" angebracht sind, welche einen tangentialen Durchblick durch den Greifer 15 hindurch erst ermöglichen.In the interior of the gripper body 17 is on the front end of the drive shaft 19, a bobbin 27 for receiving a bobbin case 28 for a bobbin - short spool 29 - freely rotatably mounted on the gripper body 17. The bobbin case 28 is held by means of a shutter 31 at the front end 33 of a coil end 27 coaxial with the drive shaft 19 secured stub shaft 20. In FIG. 2, only a small section of the front flange 35 of the coil 29 is visible. In flange 35 annularly arranged openings 37 are recessed. The rear flange 39 of the coil 29 is visible in Figure 3. There, the front flange 35 is covered by the bobbin case 28. Also, there is the apex 41 of the spool core 43 of the coil 29 partially visible. The latter two elements are visible because in the gripper body 17 recesses 45 'and 45 "and in the coil carrier 27 slots 49', 49" are mounted, which allow a tangential view through the gripper 15 therethrough.

Um den Durchblick, d.h. das Durchleiten von Lichtstrahlen 57 einer peripher angeordneten Lichtquelle 51 zu ermöglichen, ist auch die Spulenkapsel 28 peripher nur über einen Bogen von ca. 180 Winkelgraden von einem Mantel umgeben.
Ein Durchblick durch den Greifer 15 ist jeweils dann möglich, wenn die beiden Ausnehmungen 45',45" am Greiferkörper 17 und die am Spulenträger 27 angebrachten Schlitze 49',49" sowie der weggelassene Teil im Mantel der Spulenkapsel 28 in überdeckung liegen. Da beim Nähen der Spulenträger 27 bezüglich des Nähmaschinengehäuses 9 stillsteht, wird der Durchblick durch die Ausnehmung 45' am Greiferkörper 17 möglich, wenn die beiden gegenüber liegenden Ausnehmungen 45',45" und Schlitze 49',49" oberhalb der Drehachse A der Antriebswelle 19 liegen (wie in Figur 4 dargestellt).In order to see through, ie the passage of light rays 57 to a peripherally arranged light source 51 to allow, the bobbin case 28 is peripherally surrounded only over an arc of about 180 degrees of a mantle.
A view through the gripper 15 is in each case possible if the two recesses 45 ', 45 "on the gripper body 17 and attached to the coil support 27 slots 49', 49" and the omitted part in the shell of the bobbin case 28 are in overlap. Since when sewing the bobbin 27 is stationary with respect to the sewing machine housing 9, the view through the recess 45 'on the gripper body 17 is possible if the two opposite recesses 45', 45 "and slots 49 ', 49" above the axis of rotation A of the drive shaft 19th lie (as shown in Figure 4).

Der Querschnitt der pro Greiferdrehung einmal möglichen Durchsicht hängt nebst der einmal konstruktiv festgelegten Geometrie des Greifers 15 und den Abmessungen der Ausnehmungen 45',45" und Schlitze 49',49" nur noch vom momentanen Packungsdurchmesser D des auf der Spule 29 im kreisringförmigen Packungsbereich 47 aufgewickelten Fadens ab. Bei voller Packung ist der Durchblicks-Querschnitt am kleinsten (vgl. Figur 5a); bei leerer Packung am grössten (vgl. Figur 5c). Die jeweils untere Begrenzung des Durchblick-Querschnitts in der feststehenden Ausnehmung 45" ist durch den Scheitel 41 der Spulenpackung oder des Spulenkerns 43 gegeben; die obere durch die jeweilige Lage der in Drehrichtung P vorderen Kante 61 der Ausnehmung 45".The cross section of the per gripper rotation once possible view depends in addition to the once structurally fixed geometry of the gripper 15 and the dimensions of the recesses 45 ', 45 "and slots 49', 49" only from the current packing diameter D of the coil 29 in the annular packing area 47th wound up thread. When fully packaged, the cross-sectional view is the smallest (see Figure 5a); when empty the largest (see Figure 5c). The lower limit of the cross-sectional view in the fixed recess 45 "is given by the apex 41 of the coil pack or the spool core 43, the upper by the respective position the front in the direction of rotation P edge 61 of the recess 45 ".

Die Drehwinkellage des Greifers 15, bei der der Strahlendurchgang oder -durchtritt pro Umdrehung erfasst wird, ist direkt als ein Mass für die Berechnung des aktuellen Spulendurchmessers D nutzbar. Das Messverfahren wird nun näher erläutert:
In einem radialen Abstand von der Peripherie des Greifers 15 ist die Lichtquelle 51 und auf der andern Seite des Greifers 15, d.h. im wesentlichen diagonal gegenüber liegend, ein Lichtempfänger 53 mit einem sich mindestens über eine Länge a0-a3 erstreckenden Empfangsbereich (vertikale Linie in den Figuren 5), der die Strahlen 57a - 57b des von der Lichtquelle 51 ausgesandten Strahlenbündels 57 zu empfangen in der Lage ist, angeordnet. Die Lichtstrahlen 57a - 57b durchdringen sowohl die beiden Ausnehmungen 45',45" im Greiferkörper 17 als auch die Schlitze 49',49" im Spulenträger 27, wenn diese kurzzeitig in gegenseitige Überdeckung gelangen. Eine Überdeckung der Ausnehmungen 45',45" und der Schlitze 49',49" erfolgt folglich einmal pro vollständige Umdrehung des Greiferkörpers 17 oder einmal während eines Zyklus' bei oszillierenden Greifern 15. In Figur 4, welche einen Querschnitt durch den Greifer 15 darstellt, ist die geometrische Lage der Ausnehmungen 45',45" und der Schlitze 49',49" übersichtlich dargestellt. Im weiteren sind die von der Lichtquelle 51 ausgehenden, das Strahlenbündel 57 oben und unten begrenzenden Lichtstrahlen 57a,57b zu erkennen, welche durch den Greifer 15 hindurch auf den Lichtempfänger 53 fallen. Der Lichtstrahl 57a stellt eine Tangente zwischen der Lichtquelle 51 und dem Spulenkern 59 dar. Der Lichtstrahl 57b ist ebenfalls eine Tangente, und zwar eine Tangente an der Packung einer vollen Spule, deren Durchmesser annähernd dem Durchmesser der Flanschen der Unterfadenspule 29 entspricht. Die beiden Lichtstrahlen 57a,57b in Figur 4 und auch in Figur 5c stellen folglich die beiden Extremwerte des Strahlenbündels 57 dar.
Als Lichtempfänger 53 kann ein CCD-Element, eine Fotodiode oder Fototransistor oder ein anderes lichtempfindliches Element verwendet werdenThe rotational angle position of the gripper 15, at which the beam passage or passage per revolution is detected, is directly usable as a measure for the calculation of the actual coil diameter D. The measuring method will now be explained in more detail:
At a radial distance from the periphery of the gripper 15, the light source 51 and on the other side of the gripper 15, that is substantially diagonally opposite, a light receiver 53 having a receiving region extending at least over a length a 0 -a 3 (vertical line in Figs. 5) capable of receiving the beams 57a-57b of the beam 57 emitted from the light source 51. The light beams 57a-57b penetrate both the two recesses 45 ', 45 "in the gripper body 17 and the slots 49', 49" in the coil carrier 27, when they briefly reach mutual overlap. An overlap of the recesses 45 ', 45 "and the slots 49', 49" thus takes place once per complete revolution of the gripper body 17 or once during a cycle in oscillating grippers 15. In Figure 4, which shows a cross section through the gripper 15, is the geometric position of the recesses 45 ', 45 "and the slots 49', 49" shown clearly. In the further the light beams 57a, 57b emanating from the light source 51 and bounding the beam 57 at the top and at the bottom can be seen which fall through the gripper 15 onto the light receiver 53. The light beam 57a represents a tangent between the light source 51 and the spool core 59. The light beam 57b is also a tangent, namely a tangent to the package of a full spool whose diameter is approximately equal to the diameter of the flanges of the bobbin 29. The two light beams 57a, 57b in FIG. 4 and also in FIG. 5c consequently represent the two extreme values of the beam 57.
As the light receiver 53, a CCD element, a photodiode or phototransistor or other photosensitive element may be used

Das von der Lichtquelle 51 emmitierte Licht gelangt in den dargestellten Beispielen als divergierendes Strahlenbündel 57 durch den Greifer 15 hindurch auf den Lichtempfänger 53, sobald die jeweils in Drehrichtung P vordere Kante 61 der Ausnehmung 45" den Durchtritt von Lichtstrahlen freigibt. Der Lichtstrahl 57x, der durch die Fadenpackung bestimmt wird, ist der erste, der vom Lichtempfänger 53 erfasst werden kann.
In den Figuren 5a bis 5c dreht der Greiferkörper 17 im Gegenuhrzeigersinn, d.h. in Richtung des Pfeils P. Der "erste" Lichtstrahl ist mit 57x bezeichnet. Ist die Spule 29 leer, so entspricht der erste Lichtstrahl 57x dem Lichtstrahl 57 a und erreicht den Lichtempfänger 53 an der Stelle a3 (vgl. Figuren 4 und 5c). Ist die Spule 29 jedoch mit Faden vollständig gefüllt, so ist der überwiegende Teil des Packungsraums 47 für Licht nicht durchlässig. Der erste Lichtstrahl 57x kann folglich erst weiter oben durchtreten und trifft an der Stelle a1 auf den Lichtempfänger 53 (vgl. auch Figur 5a). Figur 5b zeigt die Situation mit einer zur Hälfte gefüllten Spule 29. Hier trifft der erste Lichtstrahl 57x auf die Stelle a2 auf, welchen zwischen den beiden Extremen a1 und a3 liegt. Alternativ zu einem divergierenden Lichtbündel kann auch ein Lichtbündel mit parallel verlaufenden Strahlen verwendet werden.The light emitted by the light source 51 passes in the illustrated examples as a divergent beam 57 through the gripper 15 to the light receiver 53 as soon as the forward edge 61 of the recess 45 "releases the passage of light rays is determined by the thread package, is the first that can be detected by the light receiver 53.
In FIGS. 5a to 5c, the gripper body 17 rotates in the counterclockwise direction, ie in the direction of the arrow P. The "first" light beam is denoted by 57x. Is the coil 29 empty, the first light beam 57x corresponds to the light beam 57 a and reaches the light receiver 53 at the point a 3 (compare FIGS. 4 and 5c). However, if the bobbin 29 is completely filled with thread, the major part of the packing space 47 is not permeable to light. Consequently, the first light beam 57x can only pass further upwards and strikes the light receiver 53 at the point a 1 (see also FIG. 5a). FIG. 5b shows the situation with a half-filled coil 29. Here, the first light beam 57x impinges on the point a 2 , which lies between the two extremes a 1 and a 3 . As an alternative to a divergent light beam, a light beam with parallel rays can also be used.

Im folgenden werden vier Möglichkeiten der Vorrichtung, den Durchmesser D der Fadenpackung festzustellen, aufgezeigt. Die momentane Position der Vorderkante 61 der Ausnehmung 45" wird im Beispiel 2 als bekannt vorausgesetzt. Deren Lage ist aus der Drehlage der Hauptwelle der Nähmaschine 1 errechenbar.In the following four ways of the device to determine the diameter D of the thread package, shown. The instantaneous position of the front edge 61 of the recess 45 "is assumed to be known in Example 2. Its position can be calculated from the rotational position of the main shaft of the sewing machine 1.

Beispiel 1 (Ort) Example 1 (location)

Der Lichtempfänger 53 erkennt den Ort a1 bis a3 des Auftreffens des ersten Lichtstrahls 57x, der auf den Lichtempfänger 53 auftrifft, sobald die vordere Kante 61 der Ausnehmung 45" den Lichtdurchtritt des Lichtstrahls 57x erlaubt. Die Kenntnis des Ortes (a1 bis a3) des Auftreffens des ersten Lichtstrahls 57x auf dem Lichtempfänger 53 ermöglicht direkt die Berechnung des Packungsdurchmessers D, weil ein direkter geometrischer Zusammenhang vorliegt (Figuren 5a-5c). Alternativ könnte der Ort des letzten Lichtstrahls erfasst werden, bevor die hintere Kante 62 an der Ausnehmung 45" den Lichtkegel zu schliessen beginnt (Figuren 6a-6c).The light receiver 53 detects the location a 1 to a 3 of the impingement of the first light beam 57x impinging on the light receiver 53 as soon as the front edge 61 of the recess 45 '' passes through the light beam 57x allowed. The knowledge of the location (a 1 to a 3 ) of the impingement of the first light beam 57x on the light receiver 53 directly enables the calculation of the packing diameter D because there is a direct geometrical relationship (FIGS. 5a-5c). Alternatively, the location of the last light beam could be detected before the trailing edge 62 on the recess 45 "begins to close the light cone (FIGS. 6a-6c).

Beispiel 2 (Zeit) Example 2 (time)

Es wird der Zeitpunkt t1 des Lichtstrahls 57x beim Auftreffen erfasst und mit der Drehwinkellage alpha der vorderen Kante 61 am Greiferkörper 17 verglichen. Aus diesen beiden Parametern lässt sich ebenfalls der Durchmesser D der Packung errechnen (Figuren 5a-5c; Figuren 6a-6c).The time t 1 of the light beam 57x is detected on impact and compared with the rotational angle position alpha of the front edge 61 on the gripper body 17. From these two parameters, the diameter D of the packing can also be calculated (Figures 5a-5c, Figures 6a-6c).

Beispiel 3 (Belichtungsdauer) Example 3 (exposure time)

Es werden die Zeitpunkte tx bis to des Auftreffens des ersten Lichtstrahls 57a bis zum Verschwinden des letzten auf dem Empfänger 53, d.h. die Beleuchtungsdauer erfasst. Zusammen mit der bekannten Drehzahl n des Greifers 15 und der Grösse der Ausnehmung 45" kann ebenfalls der Durchmesser D der Spulenpackung errechnet werden (Breite des Lichtkegels in Figuren 6a-6c).The times t x to t o of the impact of the first light beam 57 a until the disappearance of the last on the receiver 53, ie the illumination duration, are detected. Together with the known rotational speed n of the gripper 15 and the size of the recess 45 ", the diameter D of the coil packing can also be calculated (width of the light cone in FIGS. 6a-6c).

Beispiel 4 (Lichtmenge) Example 4 (amount of light)

Statt der Zeitdauer tx - to wie in Beispiel 3 beschrieben, kann die Lichtmenge oder Lichtenergie (mW), welche auf den Empfänger 53 auftrifft, erfasst und zur Berechnung des Durchmessers D herangezogen werden. Die Genauigkeit dieser Messung ist allerdings geringer als diejenige im Beispiel 3, da durch z.B. Verflusung und Alterung der Lichtquelle 51 Fehler unvermeidbar sind (Fläche des Lichtkegels in Fig. 6a-6c).Instead of the time duration t x - t o as described in Example 3, the amount of light or light energy (mW), which impinges on the receiver 53, detected and used to calculate the diameter D. However, the accuracy of this measurement is less than that in Example 3, since flaws and aging of the light source 51 make flaws unavoidable (area of the light cone in FIGS. 6a-6c).

Die vorgenannten Beispiele zur Erfassung von Daten zur Errechnung der Packungsdurchmessers D lassen sich auch kombinieren, um die Genauigkeit erhöhen zu können.
Durch die vier möglichen Messarten kann nicht nur der momentane Durchmesser D festgestellt werden, sondern auch die pro Zeiteinheit resultierende Abnahme des Durchmessers D und damit auch der Verbrauch von Faden sowie der Zeitpunkt, in dem der Faden auf der Spule 29 vollständig aufgebraucht ist.The aforementioned examples for the acquisition of data for calculating the packing diameter D can also be combined in order to be able to increase the accuracy.
By the four possible types of measurement, not only the instantaneous diameter D can be determined, but also the per unit time resulting decrease in the diameter D and thus the consumption of thread and the time in which the thread on the coil 29 is completely used up.

Die kontinuierliche Messung des Durchmessers D der Spulenpackung 47 ermöglicht es also, den momentanen Fadenverbrauch unabhängig von der Dicke des Fadens zu ermitteln. Als zusätzlicher Parameter wird in diesem Fall die mittlere Drehzahl n der Spule 29 benötigt. Für die Erfassung der Drehzahl n der Spule stehen bekannte Mittel zur Verfügung.The continuous measurement of the diameter D of the coil package 47 thus makes it possible to determine the instantaneous yarn consumption, regardless of the thickness of the yarn. As an additional parameter, the average speed n of the coil 29 is required in this case. For the detection of the speed n of the coil known means are available.

Die Kenntnis des Fadenverbrauchs kann weiter zur Regelung der Fadenspannung des Oberfadens benutzt werden. Ist nämlich der Fadenverbrauch pro Stich grösser als der bekannte theoretische Wert, der sich aus der Stichart und der Stichlänge sowie der Dicke des Nähguts ergibt, so ist die Oberfadenspannung zu gross und es wird der Unterfaden zu tief in das Nähgut eingezogen. Durch Lösen der Oberfadenspannung kann der Einzug des Unterfadens ins Nähgut auf das gewünschte Mass gebracht werden. Analog ist ein zu kleiner Unterfadenverbrauch gegenüber dem theoretischen Wert ein Hinweis, dass die Oberfadenspannung zu gering ist und folglich erhöht werden muss.The knowledge of the thread consumption can be further used to control the thread tension of the upper thread. Namely, the yarn consumption per stitch is greater than the known theoretical value resulting from the type of stitch and the stitch length and the thickness of the fabric, the upper thread tension is too large and it is drawn too deep in the sewing material. By loosening the upper thread tension, the threading of the lower thread into the sewing material can be brought to the desired degree. Analogously, too small a lower thread consumption compared to the theoretical value is an indication that the upper thread tension is too low and consequently must be increased.

Zum Feststellen der Drehzahl n der Unterfadenspule 29 können die bekannten Mittel, wie sie beispielsweise in der DE-A-4 116 638 beschrieben sind, Verwendung finden. Eine zuverlässige Messung der Drehzahl n der Unterfadenspule 29 kann auch mit einer Vorrichtung, wie sie in der CH Patentanmeldung Nr. 00893/02 vom 30.05.2002 offenbart wird, erreicht werden. Mit der dort offenbarten Messmethode bzw. Vorrichtung kann die Drehzahl n der Unterfadenspule 29 jederzeit zuverlässig erfasst werden, insbesondere kann ein Stillstand der Unterfadenspule 29 sofort erkannt werden. Sogar dann, wenn Erschütterungen der Nähmaschine die Unterfadenspule 29 vibrieren lassen, was als "Nichtstillstand" missgedeutet werden kann. Dies ermöglicht es, einen Fadenbruch oder das Ende eines auf einen bereits vorhandenen Faden aufgewickelten Faden auf der Unterfadenspule 29 festzustellen und die Nähmaschine anzuhalten, bevor der Unterfaden die Stichplatte verlassen kann. Ein weiterer Vorteil der Drehzahlmessung ist, dass die Drehrichtung der Spule 29 erkannt werden kann. Ein Signal ergeht bei falsch eingelegter Spule.To determine the speed n of the bobbin 29, the known means, as described for example in DE-A-4 116 638, find use. A reliable measurement of the speed n of the bobbin 29 can also be achieved with a device as disclosed in Swiss Patent Application No. 00893/02 of 30.05.2002. With the measuring method or device disclosed there, the speed n of the bobbin 29 can be reliably detected at any time, in particular, a standstill of the bobbin 29 can be detected immediately. Even if vibrations of the sewing machine make the bobbin 29 vibrate, which may be misinterpreted as "non-stop". This makes it possible to detect a thread break or the end of a wound on an already existing thread on the lower thread bobbin 29 and stop the sewing machine before the lower thread can leave the throat plate. Another advantage of the speed measurement is that the direction of rotation of the coil 29 can be detected. A signal is issued when the coil is inserted incorrectly.

Claims (5)

  1. Method for determining the lower thread supply on the lower thread bobbin (29) of a sewing machine (1) having a light transmitter (51) and a light receiver (53), a light beam bundle (57) from the light transmitter (51) being guided through slots (49', 49") provided in the bobbin carrier (27) and through peripheral recesses (45', 45") disposed in the hook body (17), tangentially relative to the bobbin core (43) and to the thread packing, through the packing space (47) between the flanges (35, 39), and at least one of the light beams (57x) being received by the light receiver (53) and the received signal being forwarded to the machine control unit for calculating the bobbin packing diameter (D), characterised in that the momentary angle of rotation (alpha) of the hook body (17) and/or the point in time (t) is detected when a light beam (57x) is registered by the light receiver (53).
  2. Method according to claim 1, characterised in that the location (ax) of the first and/or last light beam (57x) is detected on the light receiver (53).
  3. Method according to claim 1, characterised in that the duration of the light reception and/or the light quantity which is incident on the light receiver (53) is detected during one hook rotation.
  4. Sewing machine having a lower thread supply monitoring system, comprising a hook (15) with a hook body (17), a bobbin carrier (27) disposed in the hook body (17) and a freely rotatable lower thread bobbin (29) which is disposed in the bobbin carrier (27) in a bobbin capsule (28), a light transmitter (51) and a light receiver (53), slots (49', 49") and recesses (45', 45") being provided in the periphery of the hook body (17) and in the casing of the bobbin carrier (27) which permit a tangential passage of light beams (57) from the light source (51) to the light receiver (53) through the packing space (47) on the bobbin (29), characterised in that a CCD element, a photocell or a phototransistor is used as light receiver (53), which light receiver (53) registers the location of incidence of the first and/or last light beam (57) on the light receiver (53) and is connected to the machine control unit.
  5. Sewing machine according to claim 4, characterised in that the light receiver (53) comprises means which detect the received light quantity and/or the illumination duration.
EP03405536A 2002-09-02 2003-07-15 Method for determining the underthread supply and sewing machine with monitoring of the underthread supply Expired - Lifetime EP1394310B1 (en)

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CH149102 2002-09-02
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CN105821596B (en) * 2016-06-01 2018-11-16 杰克缝纫机股份有限公司 A kind of bobbin thread for sewing machine excess detection method
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EP1394310A3 (en) 2006-03-29
US6863007B2 (en) 2005-03-08
EP1394310A2 (en) 2004-03-03
ATE358202T1 (en) 2007-04-15
US20040040482A1 (en) 2004-03-04
DE50306893D1 (en) 2007-05-10

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