EP3399088B1 - Assembly and sewing machine for producing a starting upper thread with a set protrusion - Google Patents

Description

The invention relates to an assembly for producing an upper seam beginning thread with a nominal seam overhang of at most 10 mm. The invention also relates to a sewing machine with such an assembly.

Sewing machines are known from the EP 1 847 641 B1 , the DE 102 34 251 C1 , the DE 10 2006 019 193 A1 and the DE 101 23 075 C1 . the DE 10 2015 223 194 B3 describes a method for generating an upper seam beginning thread with a short nominal seam protrusion and an assembly for carrying out the method. the DE 34 34 40 874 A1 discloses a thread cutting device for a sewing machine. the U.S. 6,062,152 A discloses an automatic thread cutting device for an embroidery machine. the DE 38 12 092 C2 discloses a buttonhole sewing machine having a thread separating and clamping device. the DE 100 63 003 B4 describes a thread cutter for a sewing machine. the DE 197 19 847 A1 describes a thread trimmer of a sewing machine. the DE 10 2006 059 192 A1 discloses a thread severing device of a sewing machine. the DE 298 11 472 U1 discloses a thread cutting device for a sewing machine for chain stitch sewing work. the DE 10 2007 056 132 A1 discloses a sewing machine having a thread cutting mechanism. the DE 100 55 258 C1 discloses a thread cutter for use in a rotary hook sewing machine.

the CH 704 524 A1 discloses a method for cutting a lower and at least one upper thread for embroidery or sewing. the DE 10 2016 102 024 A1 discloses a sewing machine having a thread cutting device for a sewing start end of a lower thread. the US 2005/0178307 A1 describes a quilting machine. the EP 2 206 820 A1 describes a thread cutting device for a sewing machine.

It is an object of the present invention to develop an assembly of the type mentioned at the beginning in such a way that a reproducible, desired short desired seam projection is achieved. At the same time, safe sewing should be guaranteed.

This object is achieved according to the invention by an assembly having the features specified in claim 1.

According to the invention, it was recognized that an upper thread detection section of an upper thread knife can be used simultaneously for clamping a seam starting upper thread and also for shearing off the seam starting upper thread in order to produce a defined short seam starting upper thread. A compact assembly, which on the one hand ensures a clamping and on the other hand a cutting of the upper thread, is thus made possible. The counter knife can also represent the upper thread clamp. Alternatively, it is possible to design the upper thread clamp as a separate component from the counter knife. The counter knife can be arranged fixed to the frame. Alternatively, it is possible that the counter knife moves relative to a frame of the sewing machine during cutting. The upper thread gripping position, the upper thread clamping position and the upper thread cutting position are mutually different positions of the upper thread gripping section. The upper thread clamping position can be a position of the upper thread gripping section which lies between the upper thread gripping position on the one hand and the upper thread cutting position on the other hand.

A displacement drive according to claim 2 is inexpensive.

A displacement drive according to claim 3 is precise.

The displacement drive can be designed as a lifting cylinder and in particular as a pneumatic lifting cylinder. Alternatively, the displacement drive can be designed as a stepper motor. This stepping motor can be controlled with a corresponding control in such a way that the three positions of the upper thread detection section correspond to corresponding stepping positions of the stepping motor. With such a stepper motor design, stops for presetting the position can be dispensed with.

An adjustable clamping position stop according to claim 4 simplifies the manufacture of the assembly.

A clamping position stop according to claim 5 is inexpensive to manufacture. Self-locking can be achieved by screwing the threaded pin into a plastic body fixed to the frame.

An adjustable cutting position stop according to claim 6 simplifies the manufacture of the assembly.

A stop body according to claim 7 enables precise adjustment of the cutting position stop, a force that is absorbed by the cutting position stop not acting in the direction of displacement of the stop body, which could lead to undesired slippage of the stop.

A suction device according to claim 8 avoids undefined deposition of sections of the upper thread. This prevents undesirably cut thread remnants from collecting in the area of the sewing machine.

The advantages of a sewing machine according to claim 9 correspond to those which have already been explained above with reference to the assembly according to the invention.

Fig. 1

eine Vorderansicht einer Doppelsteppstichnähmaschine;

Fig. 2

eine perspektivische schematische Darstellung eines Stichbildungsbereiches der Nähmaschine;

Fig. 3

eine perspektivische Ansicht einer Grundplatte der Nähmaschine mit abgenommenen Komponenten, so dass eine Baugruppe zum Erzeugen eines Naht-Anfangsoberfadens mit vorgegebenem Soll-Nahtüberstand sichtbar ist;

Fig. 4

eine teilweise geschnittene Seitenansicht der Baugruppe zum Erzeugen des Naht-Anfangsoberfadens, wobei ein Oberfadenmesser mit einem Oberfaden-Erfassungsabschnitt in einer ganz ausgefahrenen Oberfaden-Erfassungsstellung dargestellt ist;

Fig. 5

die Baugruppe nach Fig. 4, gesehen von oben;

Fig. 6

die Baugruppe nach Fig. 4 in perspektivischer Ansicht schräg von oben;

Fig. 7

die Baugruppe nach Fig. 4 mit dem Oberfaden-Erfassungsabschnitt in einer eingezogenen Oberfaden-Klemmstellung;

Fig. 8

die Baugruppe, gesehen aus Blickrichtung VIII in Fig. 7;

Fig. 9

in einer zu Fig. 5 ähnlichen Darstellung die Baugruppe in der Stellung nach Fig. 7;

Fig. 10

in einer zu Fig. 6 ähnlichen Darstellung die Baugruppe in der Stellung nach Fig. 7;

Fig. 11

Die Baugruppe in der Stellung nach Fig. 7, gesehen perspektivisch schräg von unten;

Fig. 12

in einer zu Fig. 4 ähnlichen Darstellung die Baugruppe in einer relativ zur Oberfaden-Klemmstellung weiter eingezogenen Oberfaden-Schneidstellung des Oberfaden-Erfassungsabschnitts;

Fig. 13

einen teilweise gebrochenen Schnitt gemäß Linie XIII-XIII in Fig. 12;

Fig. 14

in einer zur Fig. 5 ähnlichen Darstellung die Baugruppe in der Stellung nach Fig. 12;

Fig. 15

die Baugruppe in einer zu Fig. 6 ähnlichen Darstellung in der Stellung nach Fig. 12; und

Fig. 16

schematisch eine Aufsicht auf eine mit der der Nähmaschine nach Fig. 1 genähte Naht zur Veranschaulichung eines erzeugten Naht-Anfangsoberfadens mit einem vorgegebenen Soll-Nahtüberstand.

Embodiments of the invention are explained in more detail below with reference to the drawing. In this show:

Fig. 1

a front view of a lockstitch sewing machine;

Fig. 2

a perspective schematic representation of a stitch formation area of the sewing machine;

Fig. 3

a perspective view of a base plate of the sewing machine with removed components, so that an assembly for generating a seam start needle thread with a predetermined desired seam projection is visible;

Fig. 4

a partially sectioned side view of the assembly for generating the seam starting needle thread, wherein an upper thread knife with an upper thread gripping portion is shown in a fully extended upper thread gripping position;

Fig. 5

the assembly according to Fig. 4 seen from above;

Fig. 6

the assembly according to Fig. 4 in a perspective view at an angle from above;

Fig. 7

the assembly according to Fig. 4 with the upper thread gripping section in a retracted upper thread clamping position;

Fig. 8

the assembly, seen from viewing direction VIII in Fig. 7 ;

Fig. 9

in one too Fig. 5 similar representation the assembly in the position according to Fig. 7 ;

Fig. 10

in one too Fig. 6 similar representation the assembly in the position according to Fig. 7 ;

Fig. 11

The assembly in the position after Fig. 7 , seen in perspective at an angle from below;

Fig. 12

in one too Fig. 4 In a similar illustration, the assembly in an upper thread cutting position of the upper thread gripping section which is further drawn in relative to the upper thread clamping position;

Fig. 13

a partially broken section along line XIII-XIII in Fig. 12 ;

Fig. 14

in one to Fig. 5 similar representation the assembly in the position according to Fig. 12 ;

Fig. 15

the assembly in one too Fig. 6 similar representation in the position after Fig. 12 ; and

Fig. 16

schematically a plan view of one with that of the sewing machine after Fig. 1 sewn seam to illustrate a generated upper seam thread with a specified nominal seam projection.

A sewing machine 1 designed in particular as a lockstitch sewing machine has a base plate 2 with a stand 3 extending upward therefrom and an angled arm 4. The latter ends in a head 5. In the arm 4, an arm shaft 6 is rotatably mounted. This drives a crank mechanism 7 with a thread lever 8 in the head 5. The crank drive 7 is drivingly connected to a needle bar 9 which is mounted axially displaceably in the head 5. This has a needle 10 at its lower end. The needle 10 can be moved up and down on a vertical axis 11 by the crank mechanism 7.

To simplify the representation of positional relationships, a Cartesian xyz coordinate system is used below. The vertical axis 11 runs along the z direction of this coordinate system. The x-direction runs perpendicular to the plane of the drawing Fig. 1 into this and runs parallel to a sewing direction of the sewing machine 1. The y-direction runs in the Fig. 1 to the left.

The needle 10 guides in an eye a needle thread 13, which is also referred to as the upper thread, which is fed from a bobbin 12 via a thread tensioning device and the thread lever 8. The needle thread 13 has a free upper thread starting section 13a.

The base plate 2 carries a support plate 14 which is fastened with screws and on which a workpiece 15 rests. The support plate 14 has a recess designed for the passage of a lower material slide 17. The latter has a needle hole 18 for the needle 10 to pass through.

Below the support plate 14 there is a gripper 19 which has a gripper body 20 with a gripper tip 21. A cup-shaped bobbin housing 22 for receiving a supply of hook thread in the form of a bobbin 22a is mounted in the hook body 20. Upper edge contours on the one hand of the coil housing 22 and on the other hand of the coil 22a are shown in the schematic illustration according to FIG Fig. 2 indicated by dashed lines. The looper thread is also known as the bobbin thread.

The gripper 19 can be rotated about a vertical gripper axis 23 running in the z direction. A sewing operation direction of rotation 24 of the hook body 20 runs in FIG Fig. 3 clockwise around the gripper axis 23. The gripper body 20 is firmly connected to a shaft 25 which runs coaxially to the gripper axis 23. The shaft 25 is rotatably supported in a bearing block 26 screwed to the base plate 2. In this a drive shaft 27 is mounted, which is connected to a gear mechanism arranged in the interior of the bearing block 26. The gear transmission has a transmission ratio of 1: 2, so that with one revolution of the drive shaft 27, the gripper body 20 located on the shaft 25 rotates twice. The drive shaft 27 is drivingly connected to the arm shaft 6 via a belt drive 28.

A thread-pulling knife 29 (cf. Fig. 3 ), for example from the EP 1 847 641 B1 is known.

To hold and transport the workpiece 15, the sewing machine 1 also has a presser foot 30 and an upper conveyor 31, which interacts with the lower material slide 17 for transporting the workpiece.

The schematic Figure 2 also shows a course of the upper thread 13 from the bobbin 12 to the upper thread starting section 13a. Starting from the bobbin 12, the upper thread 13 is guided to the needle 10 via a thread tensioning device 32 and the thread lever 8 and an upper thread guide clamp 33.

The upper thread guide clamp 33 has a tension washer 34 which is attached to a guide rod 35. The tensioning disk 34 is pulled via a compression spring 36 against an abutment 37, which is fixed to the housing, of the upper thread guide clamp 33 in order to clamp the upper thread 13. At the abutment 37 is a in the Fig. 2 attached schematically shown electromagnet 38, which is controlled via a central control device 39 of the sewing machine 1 in a manner not shown.

Based on Figures 3 to 15 an embodiment of a sewing machine assembly 40 for producing a seam starting thread with a desired seam overhang of at most 10 mm is described below.

Viewed in relation to an xz plane in which the axis of movement 11 of the sewing needle 10 lies, the assembly 40 is arranged on a side of this xz plane opposite the gripper 19 (cf. Fig. 1 and 3 ).

The assembly 40 has an upper thread catcher 41 for grasping a seam starting upper thread at the beginning of a seam to be sewn with the needle thread 13. The upper thread catcher 41 has an upper thread knife 42 (see. Eg Fig. 5 ) with an upper thread gripping section 43 designed as a passage opening. The upper thread catcher 41 also has a counter knife 44 which cooperates with the upper thread knife 42 to cut the needle thread 13. The counter knife 44 is fixedly arranged in relation to a frame of the sewing machine 1.

Furthermore, the upper thread catcher 41 has an upper thread clamp 45. The latter is designed as a U-shaped clamping spring. A contact pressure of the clamping spring 45 against the needle thread knife 42 can be set via a clamping spring adjusting screw 46. A knife pressure, that is to say a contact pressure of the counter knife 44 against the upper thread knife 42, can be set by means of a knife adjusting screw 47.

• einer Oberfaden-Erfassungsstellung zum Erfassen des Naht-Anfangsoberfadens,
• einer Oberfaden-Klemmstellung zum Klemmen des Naht-Anfangsoberfadens zwischen dem Oberfadenmesser 42 und der Oberfadenklemme 45 und
• einer Oberfaden-Schneidstellung zum Abscheren des Naht-Anfangsoberfadens zwischen dem Oberfadenmesser 42 und dem Gegenmesser 44.

The upper thread knife 42 together with the upper thread gripping section 43 can be displaced by means of a displacement drive 48. The displacement drive 48 is designed as a pneumatic lifting cylinder. A displacement movement of the upper thread gripping section 43 runs along the y-direction, that is to say runs linearly. Via the displacement drive 48, the upper thread detection section 43 can be displaced between three positions, namely between

• an upper thread detection position for detecting the seam start upper thread,
• an upper thread clamping position for clamping the seam starting upper thread between the upper thread knife 42 and the upper thread clamp 45 and
• an upper thread cutting position for shearing off the seam starting upper thread between the upper thread knife 42 and the counter knife 44.

The upper thread detection position is in the Figures 4 to 6 shown. The upper thread clamping position is in the Figures 7-11 shown. The upper thread cutting position is in the Figures 12 to 15 shown.

The upper thread gripping position, the upper thread clamping position and the upper thread cutting position are mutually different positions of the upper thread gripping section 43. These three positions can be specified with the displacement drive 48, that is to say with exactly one drive.

A linear guide guides a displacement movement of the upper thread detection section 43 between the three aforementioned positions. The linear guide comprises a guide pin 49 which runs approximately in the z-direction and is attached to a connecting piston 50 which is connected to a piston rod 51 of the lifting cylinder 48 in a tensile manner. The guide pin 49 interacts with an elongated hole 52 in a mounting plate 53 of the assembly 40 to guide the displacement movement of the upper thread gripping section 43 (cf., for example, FIG Figures 4 and 5 ). At an end opposite the mounting plate 53, the upper thread knife 42 is attached to the guide pin 49.

In the upper thread detection position, the upper thread knife 42 is extended in the negative y-direction relative to the counter knife 44 so that the upper thread detection section 43 projects completely over the upper thread knife 42 and the upper thread clamp 45 and is freely accessible for the needle 10 to pass through.

An adjustable clamping position stop is used to preset a relative position of the upper thread knife 42 to the upper thread clamp 45 in the upper thread clamping position. The clamping position stop contains a threaded pin 54 which is screwed into a plastic body 55. This results in a self-locking design of the threaded pin 54. In the stop position of the clamping position stop, i.e. in the upper thread clamping position after the Figures 7-11 , strikes a free end of the threaded pin 54 on the guide pin 49 and thus limits a movement of the upper thread knife 42, starting from the upper thread detection position in the positive y-direction, for example in the Fig. 7 to the left. To set an exact position of the upper thread gripping section 43 in the upper thread clamping position, the threaded pin 54 is correspondingly rotated relative to the plastic body 55. For this purpose, the threaded pin 54 is via a passage opening 56 (cf. Fig. 8 ) in a drive support plate 57 accessible from the outside.

The clamping position stop is between a particular in the Fig. 7 shown stop position and an ineffective neutral position displaceable. This neutral position is for example in the Figure 12 shown. A clamping stop drive 58, which is also designed as a pneumatic lifting cylinder, is used for this displacement of the threaded pin 54 of the clamping position stop. The plastic body 55 is connected to the clamping stop drive 58 via its piston rod 59.

In the stop position of the clamping position stop, the plastic body 55 is supported on the drive support plate 57 against the pretensioning force that the guide pin 49 exerts on the threaded pin 54 (cf. Fig. 7 ).

The clamping stop drive 58 is also mounted on the drive support plate 57. The drive support plate 57 is bent into an L-shape, the upper thread gripping section displacement drive 48 being mounted on a first leg and the clamping stop drive 58 being mounted on a second leg of this L-shape. A displacement movement by the clamping stop drive 58 takes place approximately perpendicular to the displacement movement by the displacement drive 48.

In the upper thread clamping position, the upper thread is clamped between the upper thread clamp 45 and the upper thread knife 42. This clamping position is such that a cutting edge of the upper thread knife 42 does not yet interact with the counter knife for cutting the upper thread 13.

The assembly 40 also has an adjustable cutting position stop for specifying a relative position of the upper thread knife 42 to the counter knife 44 in the upper thread cutting position. The cutting position stop has a stop body 60, which is supported by a stop plate (see Figures 12 and 13 ) is formed. The latter in turn interacts with the guide pin 49 of the assembly 40 in the cutting stop position of the cutting position stop. A contact between the guide pin 49 and the stop plate 60 takes place in the area of an inclined wall section 61 of the stop plate 60, that is to say in the area of a Edge section, which in the plan after Fig. 13 assumes an angle to the x-axis or to the sewing direction.

To set the cutting position stop, a relative position of the stop plate 60 to the mounting plate 53 can be specified via a mounting connection which has an adjusting screw 62 which runs through an elongated hole 63 in the stop plate 60 running along the x-direction (cf. Fig. 13 ). To set the cutting position stop, after loosening the setting screw 62 accordingly, the stop plate 60 is displaced along the x direction so that a contact area between the guide pin 49 and the inclined wall section 61 in the cutting stop position moves accordingly along the y direction.

To specify a relative position of the upper thread knife 42 to the counter knife 44, the stop body 60 can be displaced transversely to a cutting movement direction of the upper thread knife 42, that is to say transversely to the y direction.

In the stop position of the cutting position stop (cf. Fig. 13 ) the stop plate 60 is supported against the pretensioning force by the guide pin 49 on the drive carrier plate 57.

The cutting position stop acts when the clamping position stop has moved into the neutral position.

The assembly 40 also has a suction device 64 for suctioning off a section of the upper thread 13 that has been cut off with the upper thread knife 42 Upper thread knife 42 and the counter knife 44 opens out (cf. Fig. 12 ). An opposite end 66 of the suction pipe 65 is connected to a vacuum source (not shown) of the suction device 64.

In order to generate the seam starting upper thread with the desired seam protrusion of at most 10 mm, a section of the needle thread 13 is first transported from the upper side of the sewing material to a lower side of the sewing material 15 in the upper thread grasping position of the upper thread grasping section 43, the needle 10 passes through the opening of the upper thread engaging portion 43. Then the upper thread starting section 13a is pulled out with the looper 19 until the entire upper thread starting section 13a lies under the underside of the sewing material 15. After a first short stitch, when the thread lever 8 is in the region of the top dead center, the upper thread gripping section 43 is brought out of the upper thread gripping position into the drawn in upper thread clamping position by actuating the displacement drive 48. With the upper thread starting section 13a clamped, a further short stitch is then carried out, the sewing needle 10 then no longer passing through the upper thread gripping section 43. After the second short stitch has taken place, the clamping stop drive 58 is actuated and the clamping position stop is transferred from the clamping position to the neutral position, so that the upper thread gripping section 43 and thus the upper thread knife 42 are now transferred to the further drawn-in upper thread cutting position. In this, a cutting edge of the upper thread gripping section 43 cooperates with the counter knife 44 to cut off the upper thread starting section 13a. The cut part of the upper thread starting section 13a is then sucked off by the suction device 64.

After the two initial short stitches at the beginning of the seam, the seam is then sewn with the normal stitch length. A stitch length is preset with the aid of the control device 39.

Now the further seam with the participation of the upper thread 13 and the lower thread, not shown in detail, can be designed as a lockstitch seam. At the end of the seam, a thread cutting operation of the upper thread 13 and the lower thread with the thread-pulling knife 29 then takes place.

The supervision after Fig. 16 FIG. 10 shows a seam 67 produced with the sewing assembly 40 in a seam starting section. The sewing direction runs along the x-direction in the Fig. 6 to the left. Because of the upper thread section between the upper thread knife 42 and the counter knife 44, the upper thread starting section 13a at the beginning of the seam 67 is so short that a maximum seam protrusion A of 10 mm results.

Is shown in the Fig. 16 also that the first two initial stitches S ₁ , S ₂ are shortened compared to the following stitches S ₃ , ... S _u.

As an alternative to the above-explained configuration of the displacement drive 48 with stops, the displacement drive can also be designed as a stepping motor, the different positions of the upper thread detection section 43 then corresponding to different stepping positions of the stepping motor. These different step positions can be specified via the control device 39.

Claims (9)

1. An assembly (40) for generating a seam starting upper thread with a nominal seam protrusion (A) of at most 10mm

   - with an upper thread catcher (41) for taking up the seam starting upper thread, wherein the upper thread catcher (41) comprises:

   - an upper thread blade (42) with an upper thread take-up section (43),

   - a counter blade (44),

   - an upper thread clamp (45),

   - a displacement drive (48) for the upper thread take-up section (43),

   - characterized in that the upper thread take-up section (43) is displaceable by the displacement drive (48) between

   -- an upper thread take-up position for taking up the seam starting upper thread,

   -- an upper thread clamping position for clamping the seam starting upper thread between the upper thread blade (42) and the upper thread clamp (45) and

   -- an upper thread cutting position for shearing the seam starting upper thread between the upper thread blade (42) and the counter blade (44).
2. An assembly according to claim 1, characterized in that the displacement drive (48) is designed as exactly one drive which displaces the upper thread take-up section (43) between the three positions.
3. An assembly according to claim 1 or 2, characterized in that the displacement drive (48) is designed as a linear drive, wherein a linear guide (49, 52) guides a displacement movement of the upper thread take-up section (43) between the three positions.
4. An assembly according to any one of claims 1 to 3, characterized by an adjustable clamping position stop (54, 49) for presetting a relative position of the upper thread blade (42) to the upper thread clamp (45) in the upper thread clamping position.
5. An assembly according to claim 4, characterized in that the clamping position stop (54, 49) has a self-locking threaded pin (54).
6. An assembly according to any one of claims 1 to 5, characterized by an adjustable cutting position stop (60, 49) for presetting a relative position of the upper thread blade (42) to the counter blade (44) in the upper thread cutting position.
7. An assembly according to claim 6, characterized in that the cutting position stop (60, 49) has a stop body (60) which is displaceable transversely to a cutting movement direction of the upper thread blade (42) for presetting a relative position of the upper thread blade (42) to the counter blade (44).
8. An assembly according to any one of claims 1 to 7, characterized by a suction device (64) for sucking off a cut-off upper thread section.
9. A sewing machine comprising an assembly (40) according to any one of claims 1 to 8,

   - with a driven needle bar (9) with a sewing needle (10) carried thereby for guiding the upper thread (13) and

   - with a shuttle (19) for gripping the upper thread (13) for stitch formation.

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