EP0157942B1 - Sewing machine device to maintain a constant distance between needle and looper, by laterally deflected needle - Google Patents

Description

The invention relates to a method for operating a sewing machine, in particular a multi-needle sewing machine, the material being conveyed being conveyed in any direction within the material level.

It often happens on sewing machines that the needle is slightly deflected or bent during the insertion of the sewing material if the sewing material is moved in any direction within the sewing material plane during the insertion of the needle. This deflection or bending of the needle depends on how great the displacement process is while the needle is in the material to be sewn, how stable the needle is and finally how rigid or elastic the material is.

In the classic sewing machine, which is equipped with a feed dog, the deflection or bending of the needle is negligible, since the feed dog generally only moves the sewing material when the needle is not in the sewing material.

In addition, sewing machines are known in which the needle makes a defined movement together with the material to be sewn, namely so-called needle transport machines. However, they only allow the material to be transported or conveyed in one direction, namely in the direction that runs parallel to the plane in which the hook is pivoted. Sewing machines are also known in which both the needle and the gripper make a defined movement, which is derived from one or more cams. These are so-called zigzag or decorative stitching machines. In this case too, the sewing material is only conveyed in the direction that runs parallel to the plane in which the hook is rotated or pivoted.

The more recent developments in the field of automation also for sewing machines, especially for large sewing machine systems, such as multi-needle sewing machines, have resulted in the sewing material being automatically shifted in all directions in the sewing material plane in accordance with mechanical curves or electronic control commands. In this way, any sewing pattern, e.g. Slanted check or check pattern or circular arches and circular patterns or contours of any kind. With these automatic sewing machines, it is often no longer possible, particularly with fast sewing machines, to control the displacement of the sewing material in such a way that it only occurs when the needle is not in the sewing material. The result of this is very often a deflection or bending of the needle in the direction in which the sewing material is moved.

This deflection or bending of the needle is relatively harmless as long as the sewing material is moved parallel to the plane in which the hook is rotated or swiveled. However, it becomes problematic when the material is guided and conveyed transversely to this gripper movement plane, i.e. perpendicular to the gripper movement plane or a smaller angle than 90 ° with a corresponding movement component to this plane. This then also causes the needle to deflect or bend transversely to the gripper movement plane. If the needle is deflected or bent away from the hook, so that the distance between the needle and the hook is greater than normal, there is a risk that the thread loop will no longer be caught by the hook tip. The result is skipped stitches and broken threads. If, on the other hand, the deflection or bending of the needle towards the hook occurs, the hook tip can meet the needle tip. This can result in needle breakage and / or injury to the hook tip.

Attempts have already been made to limit these disadvantageous consequences by making the needle hole through which the needle passes and which is located in the support plate for the material, with the aim of guiding the needle better to be able to. However, this again results in a further disadvantage, namely that needle wear is rapid due to the lateral friction on the wall of the tap hole. In addition, the needle sharpens during the upward and downward movement in the tap hole, so that it becomes unusable for sewing after a relatively short time.

Another attempt to reduce the deflection or bending of the needle has been to enlarge the cross section of the needle. However, this leads to large puncture holes with an unattractive appearance, and very often to bursting of the weaving and knitting threads, especially in the case of sensitive sewing material.

In contrast, the invention is based on the object of creating a working method on a sewing machine by means of which sewing disturbances, such as thread tearing, skipped stitches, caused by the movement of the sewing material and the deflection of the needle caused thereby, are avoided and the sewing properties, in particular sewing safety, are substantially increased will.

The object is achieved according to the invention in that the gripper and / or needle holder is moved in dependence on the needle bending caused by the conveyed sewing material in such a way that the distance between the needle and the plane of movement of the gripper remains essentially the same.

If efforts have so far been taken to take measures to reduce the deflection or bending of the needle or to keep it within limits, the invention is based on the knowledge that the commercially available needles have such great elasticity that they are relatively small anyway Withstand deflections and bends easily over very long operating times without the needles breaking. In the invention, the elasticity of the sewing needle is used in such a way that small displacements of the sewing material during the time,

in which the needle is in the material to be sewn does not cause injuries to the material to be sewn, precisely because the needle can bend elastically by this amount of the small displacement, that is, it moves with the material.

Advantageous refinements of the method according to the invention result from subclaims 2 to 5.

The invention also relates to a device for carrying out the working method on a sewing machine, in particular on a multi-needle sewing machine, in which a drive is provided for conveying the sewing material in any direction within the sewing material plane, and furthermore, the gripper and needle are each attached to a movable holder. Proceeding from this, the device according to the invention is characterized in that a further drive acts on the gripper and / or needle holder, which is designed and controlled in such a way that the gripper and / or needle is dependent on the needle bending caused by the conveyed sewing material Holder is moved so that the distance between the needle and the plane of movement of the hook remains essentially the same.

Advantageous refinements of the device according to the invention result from subclaims 7 to 14.

• Fig. 1 eine perspektivische Ansicht einer Vielnadelnähmaschine;
• Fig. 2 einen Teilquerschnitt in vergrössertem Massstab, und zwar in einer Betriebsstellung, in der die Nadel nicht verbogen und der Greifer demgemäss nicht verschoben ist;
• Fig. 3 einen Teilquerschnitt gemäss Fig. 2, wobei die Nadel nach links verbogen und der Greifer mit seiner Halterung nach links verschoben ist;
• Fig. 4 einen Teilquerschnitt gemäss Fig. 2, wobei die Nadel nach rechts verbogen und der Greifer mit seiner Halterung demgemäss nach rechts verschoben ist;
• Fig. 5 eine vereinfachte perspektivische Darstellung eines Ausführungsbeispiels einer Vorrichtung zum Verschieben der Greiferhalterung, und
• Fig. 6 bis 9 schematische Darstellungen von verschiedenen Ausführungsbeispielen von Vorrichtungen zum Verschieben der Greifer- und/oder der Nadel-Halterung.

Exemplary embodiments of the device according to the invention are shown in the drawing, namely:

• Fig. 1 is a perspective view of a multi-needle sewing machine;
• 2 shows a partial cross section on an enlarged scale, in an operating position in which the needle is not bent and the gripper is accordingly not displaced;
• 3 shows a partial cross section according to FIG. 2, the needle being bent to the left and the gripper with its holder being displaced to the left;
• 4 shows a partial cross section according to FIG. 2, the needle being bent to the right and the gripper with its holder being accordingly shifted to the right;
• Fig. 5 is a simplified perspective view of an embodiment of a device for moving the gripper bracket, and
• 6 to 9 are schematic representations of various embodiments of devices for moving the gripper and / or the needle holder.

Fig. 1 shows a perspective view for reasons of better clarity, a very simplified multi-needle sewing machine 1, in the present case a multi-needle double chain stitch machine, with a fixed base frame 1a and a U-shaped frame on both sides that can be pushed back and forth in the transverse direction Housing parts 1b, 1c and a crosshead 1d connecting them together. The back and forth movement in the direction of the double arrow x is carried out by the electric feed motor 6, which engages with a gear 7 on a rack 8. The rack 8 engages on a slide known per se with a deflection roller 5. This controlled back and forth conveying of the sewing material in the transverse direction x serves, in conjunction with a controlled longitudinal conveying y, any pattern on the sewing material 4, z. B. on a quilted lining, or to quilt with a quilt. In the slide explained above there is a needle plate 3 which is arranged in a fixed manner so that it does not follow the back and forth movement of the slide. There is a known upper thread guide above the needle plate. Furthermore, apparatuses 2 shown are simplified for moving a common needle holder 2a and a needle carrier and a Drük _- kerfusses 2b available. Below the stitch plate 3 there are known devices for the lower thread guide and for the movement of hooks or hooks which are attached in one or possibly several rows per row to a common hook holder, usually a common shaft.

Fig. 2 illustrates a partial vertical cross section through the needle plate 3, on which the material 4 rests. The needle plate 3 is provided with a needle hole 9 for each needle 10, which in practice can also be slightly larger in diameter than shown in the drawing. The upper shaft 11 of the needle is connected to a needle holder (not shown). This sits on a needle carrier or needle bar common to all the other needles of the same row, which is moved up and down during sewing, so that the needle 10, as shown, penetrates the sewing material 4 and the stitch hole 9. When the needle 10 is raised again from the bottom dead center by a small amount to approximately the position shown, a thread loop 12 of the upper thread carried by the needle forms. The tip 13 of a gripper 14 or a gripper hook engages in this thread loop. The hook 14 is connected to a hook holder 15 which, in the case of a multi-needle sewing machine, is fastened together with other hooks of the same row on a shaft 16, which executes a reciprocating movement in the direction of the arrow 17 during sewing, so that the hook 14 performs a pivoting movement in a plane perpendicular to the plane of the drawing according to FIGS. 2 to 4. The distance between the needle 10 on the one hand and the swivel plane of the gripper 14 adjacent to the needle is identified by the reference symbol a. This position of the needle 10 and the gripper 14 relative to one another according to FIG. 2 results when the sewing material 2 either stands still or is conveyed in the direction perpendicular to the plane of the drawing. The position of the needle 10 can each by a fixed sensor 18, for. B. can be measured exactly by an induction or Hall sensor.

If the sewing material 4 according to FIG. 3 is conveyed to the left in the direction of the arrow 19 or with a movement component in this direction, the needle 10 will move to a certain extent bent out on the left. This bending of the needle is drawn in Fig. 3 for better clarity because of very exaggerated. It should also be noted that in practice the needle is not bent in the lower part below the guide plate 3, but within the material 4 and in the area directly above the material. In any case, however, which is important here, the needle is bent so that the distance from the hook 14 is increased, so that the hook tip no longer engages with safety in the needle loop 12. According to the invention, therefore, a drive is provided which engages the gripper holder and which is designed and controlled in such a way that the gripper holder is displaced depending on the needle bending caused by the conveyed sewing material, so that the distance a between the needle and the plane of movement of the gripper 14 remains essentially the same. In this case, the gripper 14 is shifted by a certain amount in the direction of the arrow 20. Instead of shifting the gripper holder 15 and thus the gripper 14 and the gripper tip 13, a corresponding shift of the needle holder can also be carried out, but then by analogy a corresponding dimension in FIG. 3 takes place to the right in order to bring about the essentially constant distance a despite the bending of the needle 10 to the left. Under certain circumstances, it is also conceivable to move both the gripper holder and the needle holder against one another.

The displacement of the hook holders or gripper or the hook tips on the one hand and / or the needle holders and needles on the other hand can be economically easily achieved, in particular in multi-needle sewing machines, because often hundreds and more hooks or hooks are attached to a shaft and needles to a beam. Even if several parallel rows of needles and loops are provided in a multi-needle sewing machine, the needle holders of the individual rows and also the looper holders of the corresponding rows are e.g. B. connected to each other by means of a frame, so that only one drive for moving all gripper holders and grippers and / or all needle holders and needles is then required.

The above statements also apply mutatis mutandis to the case illustrated in FIG. 4 in which the sewing material 4 is conveyed in the direction of the arrow 21 or with a component in this direction. In this case, the needle 10 bends to the right, so that, according to FIG. 4, the gripper holder 15 with the gripper is displaced in the direction of the arrow 22, so that essentially the above-mentioned distance a between the needle and the gripper pivot plane is maintained.

5 to 9 explained below illustrate exemplary embodiments for the drive for displacing the gripper and / or needle holder or the previously explained common gripper shafts 16 or needle bars.

Before going into the device-like design of the exemplary embodiments of the drives, it should be noted in principle that it is advantageous to control the drive for the displacement of the gripper and / or needle holder depending on the conveying speed of the sewing material. This proposal according to the invention is based on the knowledge that the greater the conveying speed of the sewing material, the more the needles are deflected or bent.

A further advantageous inventive idea for the design of the drive device is that the drive for the displacement of the gripper and / or needle holder is controlled as a function of the control commands for the direction and speed of the sewing material. Since these controls, especially for pattern sewing machines, are usually electronic coordinate controls, you can, as I said, their control commands for the direction and speed of the sewing material transversely to the plane of movement of the gripper or grippers to control the displacement of the or use the hook and / or needle holders.

An electric or electrohydraulic servo system is expediently provided for controlling the drive, which is designed in such a way that it generates a displacement of the gripper and / or needle holder proportional to the measured values.

The measured values can also be obtained in that a sensor, for example an induction or Hall sensor, is arranged at a distance from at least one needle and perpendicular to the plane of the pivoting movement of the gripper in question, for measuring the degree of needle bending. It is generally sufficient to measure the needle deflection of only a single needle at the relevant time of sewing or at a specific seam, because it can be assumed that all other needles experience the same deflection at the relevant time of measurement. In this context, it should also be mentioned that the control of the drive does not generally have to cause a change in position of the hook and / or needle holders for every needle stitch of the many needles in a multi-needle sewing machine. If e.g. If a diagonal check has to be sewn, the shift position of the hook and / or needle holders remains unchanged as long as a straight piece of the diagonal check seam is sewn. The hook and / or needle holders are only shifted accordingly at the corner points of the diagonal check seam.

FIG. 5 shows a perspective view and a simplified representation of an exemplary embodiment of a drive for displacing a common shaft 16 for numerous grippers 14, and in this case the drive essentially consists of a lifting magnet 23. FIG. 6 shows an associated functional diagram. Then the electrical voltage of the feed motor 6 or a tachogenerator voltage derived therefrom, preferably fed to the electromagnet or lifting magnet 23 via an amplifier 24, the movable core of which in the direction of the arrow, in cooperation with a return spring 25, generates an adjusting force and brings about the adjustment explained above.

7 illustrates the diagram of a further exemplary embodiment of a drive, specifically an electric servomotor 26 or adjusting motor is provided as the drive, which can be driven via an amplifier 27 by the differential voltage of two electrical voltages, namely on the one hand a first voltage of the feed motor explained above 6 or a tachogenerator voltage derived therefrom and, on the other hand, a second voltage which can be controlled by a potentiometer 28. The potentiometer is directly coupled to the electric servo motor 26 or adjusting motor. The feed motor 6 serves, as stated above, for the conveyance of the sewing material in the transverse direction or perpendicular to the plane of the pivoting movement of the gripper (s). The electric servo motor 26 or adjusting motor acts on the gripper or needle holder, as described above, specifically in accordance with FIG. 7, for example with the interposition of a component 29 which is seated on a spindle 30 driven by the servo motor 26. The mode of operation is therefore that the voltage in the feed motor or on a tachometer generator is compared with a second voltage, the difference between the two voltages being used to drive the servo motor 26 or adjusting motor via the amplifier 27 until the difference between the two Voltages 0 results. As stated, the second voltage is controlled by a potentiometer 28, which in turn is directly coupled to the servomotor or adjusting motor 26.

8 illustrates a diagram of a further embodiment of the drive, specifically the drive is designed as a double-acting pneumatic or hydraulic cylinder 31, in which a displaceable piston 32 is provided. The piston rod 33 of the piston 32 is connected to the gripper or needle holder explained above. The cylinder spaces on both sides of the piston 32 are acted upon by an electro-hydraulic servo valve 34. The servo valve 34 is influenced on the one hand by an electromagnet 35 with the interposition of a spring 36 and on the other hand by a return spring 37. Similar to the previously described exemplary embodiments according to FIGS. 6 and 7, the speed and direction of the conveyance of the sewing material on the corresponding feed motor 6 can also be measured directly in this exemplary embodiment, specifically in the form of the electrical voltage or by measuring a pulse frequency when using a pulse generator or by measuring the voltage on a tachometer generator. If one takes the voltage off the feed motor or the tachogenerator, then the voltage may possibly only need to be guided to the electromagnetic servo valve described, with the aid of the amplifier 38, namely to the electromagnet 35 of this servo valve 34, so that the servo valve corresponds to the adjacent one Tension opens more or less. The downstream pneumatic or hydraulic cylinder 31 will be able to exert more or less great force corresponding to the opening of the servo valve, which force is transmitted via the piston rod 33 of the piston 32 and leads to a defined displacement.

FIG. 9 illustrates a further exemplary embodiment, namely a double-acting pneumatic or hydraulic cylinder 39 with a piston 40 displaceable therein is provided as the drive. The piston rod 41 of the piston is connected to the conveying device of the sewing material in such a way that the displacement paths of the sewing material are transmitted in a direction perpendicular to the plane of the pivoting movement of the hook. The cylinder spaces on both sides of the piston 40 are connected to one another with the interposition of a throttle device 42. Furthermore, the cylinder 39 is connected on the one hand by means of a spring 43 to a fixed part 44 of the machine frame and on the other hand to the gripper or needle holder, as indicated by the double-sided arrow. In this way, it is possible to implement the displacement of the gripper or gripper and / or needle holders purely mechanically. The movement of the sewing material transversely to the plane of the hook pivoting movement is coupled to the piston 40, which transports the air or the oil within the cylinder 39 from one side to the other via the throttle 42. The movement of the cylinder 39 is thus a function of the throttle setting, the spring 43, the operating medium in the cylinder 39, the piston size, etc., but above all also the conveying speed and direction of movement of the sewing material.

In connection with the above exemplary embodiments it was explained how the displacement of the respective gripper and / or needle holder can be carried out very precisely in accordance with the degree of bending of the needle or needles. In the simplest case, it may also be sufficient to control the displacement of the hook and / or the needle only as a function of the direction of movement of the sewing material, i.e. with fixed displacement paths, i.e. with certain uniform displacement paths to one side or the other in the transverse direction. These displacement paths can be gained from practical experience.

Claims (15)

1. Method für operating a sewing machine, in particular a multi-needle sewing machine, in which case the material to be sewn is conveyed in any direction within the plane of the material to be sewn, characterized in that the gripper and/or needle holder is moved depending on the bending of the needles caused by the conveyed material to be sewn, that the distance between the needle and the plane of movement of the gripper remains substantially the same.

2. Method according to claim 1, characterized in that the displacement of the gripper and/or needle holder is controlled depending on the conveying speed of the material to be sewn.

3. Method according to claim 1, characterized in that the displacement of the gripper and/or needle holder is controlled depending on the control demands for conveying direction and speed of the material to be sewn.

4. Method according to one of the preceding claims, characterized in that the bending of the needles is measured by a sensor at at least one -needle.

5. Method according to claim 2, characterized in that the conveying speed of the material to be sewn is measured in an angular region at right angles to the plane of movement of the gripper and that the displacement of the gripper and/or of the needle holder is carried out in proportion to the measured values.

6. Apparatus for carrying out the method according to claim 1 on a sewing machine, in particular on a multi-needle machine, the sewing machine comprising a drive for conveying the material to be sewn in any directions within the plane of the material to be sewn, in which case, furthermore, grippers and needles are attached respectively to a movable holder driven for the formation of the stitch, characterized by a further drive acting on the gripper- and/or needle-holder, which drive is constructed and controlled so that depending on the bending of the needles caused by the conveyed material to be sewn, the gripper- and/or needle-holder is moved, so that the distance between the needle and the plane of movement of the gripper remains substantially the same.

7. Apparatus according to claim 6, characterized in that the drive for the movement of the gripper- and/or needle-holder is controlled depending on the conveying speed of the material to be sewn.

8. Apparatus according to claim 6, characterized in that the drive for the movement of the gripper- and/or needle-holder is controlled depending on the control commands for the conveyance of the material to be sewn a right angles to the plane of movement of the gripper.

9. Apparatus according to claim 6, characterized in that a sensor for measuring the extent of the bending of the needles is located at a distance from at least one needle and at right angles to the plane of the tilting movement of the gripper.

10. Apparatus according to one of claims 6 to 9, characterized in that for controlling the drive, an electrical or electro-hydraulic servo-system is provided, which is constructed so that it produces a movement of the gripper- and/or needle-holder proportional to the measured values.

11. Apparatus according to claim 6, characterized in that provided as the drive is an electromagnet provided with a return spring, to which, possibly with the interposition of an amplifier, the electrical voltage of a feed motor or a tacho-generator voltage derived therefrom is applied, this feed motor being intended for the conveyance of the material to be sewn in the transverse direction or at right angles to the plane of the tilting movement of the gripper and that the electromagnet is connected to the gripper- or needle-holder.

12. Apparatus according to claim 6, characterized in that provided as the drive is a double- end pneumatic or hydraulic cylinder with a piston able to slide therein, that the piston rod of the piston is connected to the gripper- or needle-holder, that the cylinder chambers on both sides of the piston are acted upon by an electro-hydraulic servo-valve, on which a return spring engages and that the electrical voltage of a feed motor or a tacho-generator voltage derived therefrom is applied to the servo-valve, this feed motor being intended for the conveyance of the material to be sewn in the transverse direction or at right angles to the plane of the tilting movement of the gripper.

13. Apparatus according to claim 6, characterized in that provided as the drive is an electrical servo-motor, which can be driven by way of an amplifier by the differential voltage of two electrical voltages, namely on the one hand of a first voltage of a feed motor or a tacho-generator voltage derived therefrom and on the other hand of a second voltage able to be controlled by a potentiometer, that the potentiometer is directly connected to the electrical servo-motor, in which case the feed motor is intended for the conveyance of the material to be sewn in the transverse direction or at right angles to the plane of the tilting movement of the gripper and that the electrical servo- motor acts on the gripper- or needle-holder.

14. Apparatus according to claim 6, characterized in that provided as the drive is a double- ended pneumatic or hydraulic cylinder with a piston able to slide therein, that the piston rod of the piston is connected to the conveying device for the material to be sewn so that the movements of the material to be sewn are transmitted in a perpendicular direction to the plane of the tilting movement of the gripper, that the cylinder chambers on both sides of the piston are connected to each other with the interposition of a restrictor device and that the cylinder is first of all connected by means of a spring to a stationary part of the machine frame and secondly to the gripper- or needle-holder.

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