TWI787232B - Method of producing a seam beginning needle thread and sewing machine configured to implement a method of this type - Google Patents

Abstract

A method of producing a seam beginning needle thread and sewing machine configured to implement a method of this type are disclosed. When producing a seam beginning needle thread of a seam to be formed in a piece of fabric such as to have a defined nominal excess thread length, a sewing machine is operated as follows: In a first step, a defined needle thread quantity is provided in the needle thread path between an actuable needle thread clamp (28) and a sewing needle (8) to sew a thread cutting stitch for a needle thread cutting process. In a subsequent step, the needle thread clamp (28) is closed, thus preventing any additional needle thread (9) from being drawn off the needle thread supply once the needle thread clamp (28) has been closed. The thread cutting stitch is now sewn with the needle thread quantity provided in a defined manner. The needle thread (9) is then cut off using a needle thread cutter. As a result, a reproducible seam beginning needle thread is obtained. A sewing machine configured to implement a method of this type may have a displaceable limit stop with which a needle thread feeding unit (24) interacts to set a needle thread quantity to be provided.

Description

Method for producing seam-opening upper thread and sewing machine configured to carry out this method

REFERENCE TO RELATED APPLICATIONS The content of German Patent Application No. DE 102017201240.4 is hereby incorporated by reference. technical field

The invention relates to a method for producing a seam opening top thread of a seam to be sewn in a textile piece, said seam having a defined nominal excess thread length, in particular of at most 10 mm. The invention also relates to a sewing machine configured to carry out a method of this type.

BACKGROUND OF THE INVENTION A sewing machine is known, for example, from document EP 2028311A2. Document DE 3232813 A1 discloses a method for controlling the needle thread in a sewing machine. Document US 4,215,641 discloses electronic control of the upper thread in a sewing machine. Documents DE 102011005198A1 and DE 102010043906A1 also disclose sewing machines and methods for sewing seam openings with such sewing machines. Document DE 10321537 A1 discloses a device for controlling the upper thread of a sewing machine.

SUMMARY OF THE INVENTION It is an object of the present invention to manufacture in a reproducible manner the seam opening top thread of a seam to be sewn in a piece of fabric so as to have a defined nominal excess thread length, i.e. to avoid passing over the end of the seam Undesirably large lateral overhangs.

This object is achieved according to the invention by a method for producing, by means of a sewing machine, the seam-starting upper thread of a seam to be sewn in a textile piece, said seam-starting upper thread having a defined nominal excess thread length. The method comprises the steps of providing, by means of a needle thread supply unit, a defined amount of needle thread in a needle thread stroke between an actuatable needle thread clamp and a sewing needle to perform a tangential stitch for a needle thread cutting process; closing upper thread clamp to prevent any additional upper thread from being pulled out of the upper thread supplier after closing the upper thread clamp; sew tangent stitches with the amount of upper thread provided in a defined manner; and cut the upper thread with the upper thread cutter. The method is carried out by means of a sewing machine comprising: a supply of upper thread; a needle bar comprising a sewing needle for guiding the upper thread through the piece of fabric, the sewing needle being able to be driven to reciprocate up and down; Loop former to capture upper thread during formation; thread lever for forming upper thread loops; actuatable upper thread clamp in upper thread stroke ahead of thread lever; upper thread supply in upper thread stroke behind upper thread clamp Unit; upper thread cutter for cutting the upper thread between two successive seams.

According to the invention it was found that a reproducible amount of needle thread can be provided by means of a needle thread supply unit which interacts with the needle thread clamp. Provides a limited amount of upper thread to perform tangent stitching. In this way, a defined amount of upper thread is provided for preparing the seam end, which on the one hand ensures a reproducible thread cutting process and on the other hand provides a precisely defined amount of upper thread for the seam beginning of successive seams. It is thus possible, for example, to ensure an optimally short upper thread length without impairing the correct looping when sewing the beginning of the seam and/or without impairing the correct production of the corresponding knot when sewing the beginning of the seam. Thus, the beginning of a sewing seam can be easily reproduced and can be carried out with an optimally small amount of upper thread. The upper thread supply unit may be provided in the upper thread stroke between the upper thread clamp and the thread lever. The nominal excess thread length may be up to 10 mm; for certain applications, eg when sewing leather, it may also be significantly higher, eg more than 20 mm, eg in the range of 50 mm. The nominal excess wire length can be in the range of 5 mm.

An embodiment is configured such that the thread resistance between the upper thread supply unit and the sewing needle increases before a defined amount of upper thread is supplied and decreases again before sewing a tangent stitch, which ensures that when a defined amount of upper thread is supplied, this amount is almost completely changed from Pull out the upper thread supplier. The corresponding thread resistance generating unit may be formed by an upper thread clamp device which is usually provided anyway. The thread resistance generating unit may be provided in the upper thread stroke between the upper thread supply unit and the thread bar.

The advantages of a sewing machine configured to carry out the method according to the invention correspond to those already explained above with respect to said method. The sewing machine may have an additional upper thread clamp in the upper thread stroke between the thread rod and the sewing needle. This additional upper thread clamp can also be actuated.

A pivotable thread pulling device that can be driven to perform a pivoting movement has proven to be a suitable needle thread supply unit.

Displaceable stoppers are provided for various modes of operating the upper thread supply unit, thus allowing inter alia to provide various limited amounts of upper thread, with which the upper thread supply unit interacts to set the amount of upper thread to be supplied. For example, this allows the upper thread supply unit to be used on the one hand for the above-mentioned production process and, on the other hand, for example for the method described with respect to document EP 2028311A2. The two methods can also be combined with each other in such a way that in addition to reproducibly providing the amount of upper thread to perform a tangent stitch when sewing the beginning of the seam, when sewing the first stitch as described in document EP 2028311A2 The upper thread is pulled back.

Lifting magnets for restraints have proven useful in practical applications.

The thread resistance generation unit formed by the upper thread tensioning device in the upper thread stroke behind the upper thread supply unit is configured to increase and decrease the thread resistance and can be used to implement a method according to which the upper thread supply unit and The thread resistance between the sewing needles increases before a defined amount of upper thread is provided and decreases again before the tangential stitches are sewn.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A sewing machine 1 has an upper arm 2 and a lower shell-like base 3 interconnected by brackets 4 to form a C-shaped shell. An arm shaft 5 (see FIG. 2 ) is mounted in the arm 2 , which can be driven in rotation by a motor using a belt drive housed in the bracket 4 . A central control unit 6 is connected to the motor, the central control unit is arranged in the upper arm 2 according to the schematic diagram in FIG. Attached to a sewing machine. The needle bar 7 is thus driven by the arm shaft 5 so as to perform a reciprocating up and down motion, and the lower end of the needle bar 7 is provided with a needle 8 . Thread the upper thread 9 through the eyelet of the needle 8 (see Figure 2).

A looper 10 is arranged in the base plate 3 , which can be driven by the arm shaft 5 in such a way as to perform a rotational movement about a vertical axis of rotation 11 (see FIG. 2 ). The supplied lower thread is stored in the lower thread winding case 12 of the looper 10 .

FIG. 2 shows a detailed view of how the upper thread 9 is guided in the sewing machine 1 . Starting from the eye of the needle 8, in the direction opposite to the conveying direction of the upper thread, in other words upstream of the eye of the needle 8, a first upper thread clamp 14 is arranged in the supply side thread stroke, the upper thread clamp 14 has a relative to the first The base body 16 of the needle thread clamp 14 displaces the first clamping plate 15 . The first upper thread clamp 14 is in signal communication with the control unit 6 and is displaceable between the clamping position and the loosening position, in the clamping position, the upper thread 9 is clamped at the position of the first upper thread clamp 14, and In the thread release position, the first upper thread clamp 14 releases the upper thread 9 . In the region of the first needle thread clamp 14 , the needle thread 9 runs in a substantially vertical direction.

The passage of the needle thread 9 through the first needle thread clamp 14 can be defined by means of a plurality of thread openings 17 in the base body 16 . In the embodiment shown in the figures, the upper thread 9 passes from the right through the second threading opening 17 of a total of four threading openings arranged transversely to the thread transport direction.

A wire rod 18 is arranged upstream of the first upper thread clamp 14 , wherein said wire rod's reciprocating up and down movement also comes from the arm shaft 5 in a known manner. According to FIG. 2 , between the thread rod eye 19 provided at the free end of the thread rod 18 and the first needle thread clamp 14 , the needle thread 9 also passes through a guide eye 20 provided at the upper end of the base body 16 .

Upstream of the thread rod 18 , the upper thread 9 passes through the upper thread tensioning elastic unit 20 a and then through the upper thread main gripping device 21 . The upper thread main gripping device 21 has two main tensioners 22 which operate in a known manner and are arranged directly behind each other when viewed in the upper thread transport direction. The upper thread main tensioning device 21 is in signal communication with the central control device 6 . When activated by the control device 6 , the main tensioner 22 provides a preset thread tension to the upper thread 9 .

Between the upper thread main clamping device 21 and the thread rod 18 , the upper thread 9 passes through a further guide eye 23 which is adjustably displaceable transversely to the conveying direction of the upper thread.

A wire pulling device 24 is arranged upstream of the two main tensioners 22 . The thread pulling device 24 functions as a needle thread supply unit in the needle thread stroke. The wire pulling device 24 has a pivotable arm 25 which is articulated to a clamping plate 27 of a second needle thread clamp 28 via a pivot joint 26 . In other words, the wire pulling device 24 is mounted to the clamping plate 27 of the second upper thread clamp 28 . The thread pulling device 24 is arranged in the needle thread stroke behind the second needle thread clamp 28 , in other words downstream of the second needle thread clamp. The boom 25 of the thread pulling device 24 has at its free end a thread hole 29 which can be displaced transversely to the thread of the needle thread 9 between the upstream main tensioner 22 and the second needle thread clamp 28 . The boom 25 is switchable between a neutral position shown in FIG. 2 and a thread pulling position shown in FIG. time, along a thread that is one thread longer than the corresponding thread of the face line 9 when the boom 25 is in its neutral position. In the illustrated embodiment, this thread difference is, for example, 20 millimeters. This thread difference can also have different values, for example, and can range between 10 mm and 100 mm, and can reach 30 mm, 40 mm, 50 mm, 60 mm, 70 mm or 80 mm.

Between the thread hole 29 in the neutral position on the one hand and the upstream main tensioner 22, and on the other hand between the thread hole in the neutral position and the second upper thread clamp 28, the corresponding guide pin 31 is located between the upper thread and the upper thread. The stroke is provided on a mounting plate 30 mounted to the arm 2 . In the thread-drawing position of the jib 25 , the upper thread 9 is passed through the two guide pins 31 and via a meandering path through the thread hole 29 of the jib 25 between the guide pins 31 . The function of the two wire guide pins 31 is that the upper thread 9 passes out of the second upper thread clamp 28 and enters the upstream main tensioner 22 at the same position no matter whether the cantilever 25 is in the pulling position or in the neutral position.

The cantilever 25 can be switched between a neutral position and a wire-pull position by means of an electromagnetic drive, which in turn is in signal communication with the control unit 6 . As an alternative to an electromagnetic drive, the boom 25 can also be driven pneumatically or by means of a stepper motor.

Upstream of the second needle thread clamp 28 is provided a needle thread pretensioning device 32 which operates in a known manner and which can also be in signal communication with the control device 6 . The mounting plate 30 fits not only the guide pin 31, but also the upper thread main tensioner 21 including the two main tensioners 22, the second upper thread clamp 28 including the mounting puller 24, and the upper thread pre-tensioner. Tensioner 32.

Upstream of the upper thread pretensioner 32, the upper thread 9 passes through a threading opening 33 formed in the edge region of the mounting plate 30 shown on the upper side of FIG. 90°. Upstream of the threading opening 33 is provided a needle thread barrel (not shown in detail), which serves as a needle thread supplier.

A hand wheel 34 non-rotatably connected to the end of the arm shaft 5 is provided with an angle scale 35 indicating a complete revolution of the arm shaft 5 divided into 360 degrees.

Figure 2 shows the arm shaft 5 positioned at 205°. In this position, the needle bar 7 has moved a little upwards from its bottom dead center at 180°, so that the upper thread loop is formed next to the eye of the needle 8 . At the 205° position, the looper tip of the looper 10 is able to engage the upper thread loop, thus allowing the upper thread 9 to be brought along.

The components of the sewing machine 1 described above allow the implementation of a method for producing short seam-start top threads.

FIG. 5 shows an exemplary portion 36 in the region of the beginning of a seam 37 on a piece of fabric in which the first stitch is short and subsequent stitches are sewn at regular stitch lengths. The figure shows an upper thread 9 with a seam-starting top thread 38 and a bottom or seam thread 39 , wherein the length of the seam-starting bottom thread of the top thread corresponds to the length of the seam-starting top thread 38 . The two seam opening threads have a nominal excess thread length A of at most 10 mm.

The sewing machine 1 also has an upper thread cutter 40 , only outlined in FIG. 1 , for cutting off the upper thread 9 between successive seams.

In order to produce the seam opening upper thread 38 of the seam 37 in such a way that it has a nominal excess thread length A of at most 10 mm, the sewing machine 1 operates as follows:

In a first step, a defined amount of upper thread is provided in the upper thread stroke between the upper thread clamp 28 and the sewing needle 8 to sew tangential stitches for the upper thread cutting process. This is accomplished with the upper thread supply unit by placing the thread pulling device 24 between the neutral position shown in FIG. switch. The upper thread clamp 28 is then closed, thus preventing any additional upper thread quantity 9 from being pulled out of the upper thread supplier after the upper thread clamp 28 has been closed. After closing the upper thread clamp 28, the thread puller 24 returns to its neutral position shown in FIG. 2 . The tangential stitch can now be sewn with the amount of upper thread provided in a defined manner, which thread bar 28 transfers to the sewing needle 8 . After sewing the tangent stitches, the upper thread 9 is then cut off with the upper thread cutter 40 . In this way, a precisely defined excess length of upper thread is provided to the eyelet 8 of the sewing needle for sewing the beginning of successive seams. The seam opening top thread 38 of the successive seam 37 then has a defined nominal excess thread length A. Thus, an accurately reproducible amount of upper thread is provided both when sewing the end of a seam 37 and when sewing the beginning of a successive seam 37, so that a short excess upper thread length is obtained at the beginning of the thread seam and at the end of the thread seam.

1 and 2 above also allow the upper thread 9 to be pulled back at the beginning of the sewing seam 37, in other words when sewing the first stitch, so that the upper thread 38 at the beginning of the seam can become even more flexible. short. Such a procedure for pulling the upper thread 38 away from the seam is described, for example, in document EP 2028311 A1.

When sewing the beginning of the seam as described above, contrary to this procedure of pulling the thread away from the beginning of the seam, the thread pulling device is actuated before sewing the tangent stitch, in other words when the stitch formation is completed twenty four. These two methods can be combined with each other, in other words the method of pulling the thread away from the beginning of the seam known from the basic principle and the method of cutting and feeding the thread as described in detail above can be combined with each other.

In a variant of the manufacturing method, the thread resistance between the thread pulling device 24 and the needle 8 is increased before a defined amount of upper thread is provided and is reduced again before the tangential stitch is sewn. This is accomplished by correspondingly activating the main tensioner 22 to increase thread resistance before supplying a defined amount of upper thread, and deactivating the main tensioner 22 to reduce thread resistance after providing a defined amount of upper thread and before sewing a tangent stitch. Small line resistance. The thread resistance generating unit is formed by the upper thread main tensioner 21 .

Another embodiment of the components of the needle thread guiding device will be described hereinafter with the aid of FIGS. 3 and 4 , which can be used as an alternative to the solution used in the sewing machine 1 described above with reference to FIGS. 1 and 2 . Components and functions of the embodiment according to FIGS. 3 and 4 which have already been described above with reference to FIGS. 1 and 2 bear the same reference numerals and will not be discussed again in detail.

In the embodiment according to FIGS. 3 and 4 , the thread pulling device 24 and the needle thread clamp 41 are configured as separate components, the function of which otherwise corresponds to that of the needle thread clamp 28 in the embodiment according to FIGS. 1 and 2 . In the embodiment according to FIGS. 3 and 4 , the pivot drive for the suspension arm 25 of the wire pulling device 24 is formed by a rotating magnet 42 .

Instead of the guide pin 31 , the needle thread guide according to FIGS. 3 and 4 is provided with two thread holes 43 .

The needle thread guide according to FIGS. 3 and 4 has a displaceable stop 44 for the respective wire position of the boom 25 . The stop 44 includes a lifting magnet 45 having a lifting piston 46 shown in a fully retracted position in FIG. 3 and in a fully extended position in FIG. 4 . The stop also has a stop member 47 securely mounted to the mounting plate 30 .

Fig. 3 shows the thread pulling device 24, in other words the upper thread supply unit, which is in the thread pulling position to provide the upper thread for the thread cutting function, in other words it is in the thread pulling device 24 as described above to provide a limited amount of upper thread to prepare the tangent stitches position (stop position "line supply"). The thread difference obtained in such a wire feeding and pulling position can be, for example, 50 mm. In this feed position according to FIG. 3 , the lifting piston 46 has been retracted and therefore no longer functions as a stop. In turn, the stop part 47 for the boom 25 now acts as a stop.

FIG. 4 shows the wire position adopted when pulling the wire away from the seam according to the sequence described in document EP 2028311A2 ("wire" position of the stopper). In this thread pulling position, the upper thread is pulled away from the beginning of the seam so that a thread difference of eg 20 mm is obtained. The thread difference in the "wire pull" position of the stop is less than the thread difference in the "wire feed" position of the stop. In the cable position according to FIG. 4 , the lifting piston 46 is already fully extended and thus acts as a stop for the boom 25 . The stop member 47 is inactive.

This feeding process by means of the upper thread feeding unit can be started together with the upper thread cutter 40 . If the upper thread cutter 40 is cam controlled, the thread pulling device 24 can be switched from the neutral position to the thread pulling position as soon as the cam control for the upper thread cutter 40 is activated.

The above-mentioned wire supply and wire drawing methods are controlled by means of a control unit 6 in signal communication with each of the above-mentioned driven parts.

1‧‧‧Sewing machine 2‧‧‧Upper arm 3‧‧‧Lower shell base plate 4‧‧‧Bracket 5‧‧‧Arm shaft 6‧‧‧Central control unit 7‧‧‧Needle bar 8‧‧‧Sewing needle 9‧ ‧‧Upper thread 10‧‧‧Loop forming device 11‧‧‧rotation axis 12‧‧‧Bottom thread winding box 14‧‧‧First upper thread clamp 15‧‧‧First clamping plate 16‧‧‧Basic body 17, 33‧‧‧threading opening 18‧‧‧thread bar 19‧‧‧thread bar eyelet 20a‧‧‧elastic unit for tensioning upper thread 21‧‧‧main clamping device for upper thread; thread resistance generating unit 22‧‧‧tension Device 23‧‧‧guide eyelet 24‧‧‧pull thread device; upper thread supply unit 25‧‧‧cantilever 26‧‧‧pivot joint part 27‧‧‧clamping plate 28, 41‧‧‧needle thread clamp 29, 43‧‧‧Thread Hole 30‧‧‧Installing Plate 31‧‧‧Guide Pin 32‧‧‧Upper Thread Pretensioning Device 34‧‧‧Hand Wheel 35‧‧‧Angle Scale 36‧‧‧Fabric 37‧‧‧ Seam 38‧‧‧Seam opening Upper thread 39‧‧‧Sewing thread 40‧‧‧Upper thread cutter 41‧‧‧Upper thread clamp 44‧‧‧Stop 45‧‧‧Lifting magnet 46‧‧‧From Heavy piston 47‧‧‧Stop part 205°‧‧‧Positioned at 205°A‧‧‧Line length

Exemplary embodiments of the invention will be described in more detail hereinafter with reference to the accompanying drawings, in which: Fig. 1 shows a perspective front view of a sewing machine; Fig. 2 shows a detail of a needle thread guiding device according to the above description, said detail Shown on a larger scale than in FIG. 1; FIG. 3 shows a plan view of a mounting plate comprising parts of another embodiment of the needle thread guide, which can be used in the sewing machine according to FIG. The position stop is in the "thread supply" position; Fig. 4 shows the part according to Fig. 3, the displaceable stop is in the "thread pulling" position; and Fig. 5 shows the thread passing through the double A schematic vertical cross-sectional view of a portion of a ply fabric piece in which the beginnings of seams are visible.

5: arm shaft

7: needle bar

8: Sewing Needle

9: noodles

10: Circulator

11: Axis of rotation

12: Bottom thread winding box

14: The first thread clamp

15: The first clamping plate

16: Matrix

17, 33: threading opening

18: wire rod

19: Rod hole

20: Guide Eyelets

20a: Upper thread tension elastic unit

21: Main clamping device for upper thread; thread resistance generation unit

22: tensioner

23: Guide eyelets

24: Pulling device; upper thread supply unit

25: cantilever

26: Pivot joint

27: clamping plate

28, 41: upper thread clamp

29, 43: wire hole

30: Mounting plate

31: wire pin

32:Upper thread pretensioning device

34: hand wheel

35: Angle ruler

205°: Positioned at 205°

Claims (7)

A method of producing a seam-starting upper thread of a seam to be sewn in a piece of fabric with a sewing machine, the seam-starting upper thread having a defined nominal excess thread length, the sewing machine comprising a supply of upper thread, a needle a bar comprising a sewing needle for guiding the upper thread through the piece of fabric, the sewing needle being drivable for reciprocating up and down movement, a looper for catching the upper thread during stitch formation, a thread lever for forming the loop of the needle thread, an actuatable needle thread clamp positioned ahead of the needle thread lever in the middle of the needle thread stroke, a needle thread supply unit configured as a thread pulling device and located After the upper thread clamp in the middle of the thread stroke, a upper thread cutter is used to cut off the upper thread between two successive seams, the method comprising the steps of: providing the upper thread by means of the upper thread supply unit A defined amount of upper thread in the upper thread travel between the actuatable upper thread clamp and the sewing needle to perform a tangential thread stitch for the upper thread cutting process, wherein the provision is made by operating the thread pulling device Occurs, closes the upper thread clamp to prevent any additional upper thread from being pulled out of the upper thread supply after closing the upper thread clamp, utilizes the upper thread amount provided in a limited manner to sew the tangent stitch, utilizes the upper thread Upper thread cutter to cut the upper thread. The method as claimed in claim 1, wherein the thread resistance between the upper thread supply unit and the sewing needle is increased before the limited amount of upper thread is supplied and decreased again before the tangential stitch is sewn. A sewing machine configured to implement the method as claimed in claim 1 or 2, comprising a supply of upper thread, a needle bar including a sewing needle for guiding the upper thread through the piece of fabric, the sewing The needle can be driven for reciprocating up and down movement, a looper, which is used to capture the upper thread during stitch formation, a thread rod, which is used to form the loop of the upper thread, an actuatable upper thread clamp, which Before the thread rod in the middle of the upper thread stroke, the upper thread supply unit is configured as a thread pulling device and is positioned behind the upper thread clamp in the middle of the upper thread stroke, and the upper thread cutter is used to cut off the The upper thread between two successive seams, wherein the upper thread supply unit is configured in the form of an operable thread pulling device, characterized in that a control unit is used to control the number of successive steps defined in claim 1 Procedure, wherein the operation of the thread pulling device occurs before closing the upper thread clamp. The sewing machine according to claim 3, wherein the upper thread supply unit is configured in the form of a thread pulling device which can be driven to perform a pivotal movement. The sewing machine as claimed in claim 3, which includes a displaceable The stopper, the upper thread supply unit interacts with the displaceable stopper to set an amount of upper thread to be provided. The sewing machine as claimed in claim 5, wherein the stopper has a heavy magnet. The sewing machine according to claim 3, wherein the thread resistance generating unit configured to increase and decrease thread resistance is formed by a needle thread tensioning device positioned after the needle thread supply unit in the needle thread stroke.

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