JP2002292173A - Method of sewing at least two sheets of fabric material part together and sewing machine for implementing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To generate seams highly valuable in quality even for a slightly larger range of the number of revolutions derived from the conception that the tension of threads necessary for the generation of the seams highly valuable in quality varies with the number of revolutions because it is not consistent with the number of revolutions. SOLUTION: In a sewing machine (1), a thread tightening device (29) is provided having a thread tightening tool (32) driven by an electromagnet (34). Currents of the electromagnet (34) flowing through a bobbin (33) are altered according to a standardization elapse curve attributively calculated in terms of the number of revolutions of the sewing machine (1). Eventually, this keeps the intersection of needle threads (23) with bobbin threads between the fabric material parts to be sewn together even in the sewing under different numbers of revolutions.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method according to the superordinate concept of claim 1 and a sewing machine according to the superordinate concept of claim 7.

[0002]

2. Description of the Related Art (US Pat. No. 5,363,786;
From DE 41 41 945 C1 (corresponding to 5-253376)
2. Description of the Related Art A general type of sewing machine is known in which a current flowing through a magnet bobbin or a winding frame is changed to change a force for spreading an upper thread by friction. Qualitatively high quality seams in which the intersection of the upper thread and the lower thread are mainly between the fabric material parts cannot be achieved with this. Such valuable seams are required, in particular, in the upholstery or covering of leather upholstery for furniture or automotive cushioning.

[0003] From DE 199 21 516 A1, a thread clamp (thread tight toner) is known in which an electromagnet operated by a control system is controlled in accordance with a thread tension which actually occurs relative to a specified set value. An eigenvalue is calculated from the maximum value of the thread tension in a statistical analysis method for control. Even with this device, the production of a qualitatively valuable seam is not possible in the stated sense.

[0004]

SUMMARY OF THE INVENTION The present invention is based on the recognition that the thread pull required to produce a qualitatively high quality seam is not constant throughout the speed but varies with speed.

[0005] Starting from the above recognition, a general method of producing seams which can be of qualitative value even over a large rotational speed range is described, and a sewing machine for carrying out the method is described. The task of creation forms the basis of the present invention.

[0006]

This object is achieved according to the invention in a general manner by the features of claim 1. The empirical curve of the current calculated and normalized through the rotational speed is calculated based on a series of trials for a given sewing machine type. At this time, the current received by the magnet bobbin or coil is detected. In the current, the intersection has a desired position between the cloth materials. Such a curve generally has a substantially flat roof-shaped profile. Such curves are used as standardized curves in various fabric materials. The curve is adjusted at least at a certain number of revolutions at the beginning of a seam of a very specific textile material. Such an adjustment can be made for two speed ranges with a well-defined spacing, whereby the slope of the curve is also set. Otherwise, the curve is shifted parallel to itself if the stitching ratio changes in a jump-like manner, that is, if the seam has to be overlaid in the course of a seam where a fold or a transverse seam must occur. obtain.

[0007] Advantageous embodiments will become apparent from the dependent claims. The configuration of the characterizing part of claim 6 reproduces a sewing machine for performing the method. The invention will be explained in more detail below on the basis of an embodiment with reference to the drawings.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The sewing area shown in FIG. 1 has a sewing machine 1 whose basic structure is formed as usual.
The sewing machine is simply arranged on a frame 2 shown schematically. The sewing machine 1 has, as usual, a lower part 3, a so-called floor plate (base plate), an upper part 4, a so-called arm, and a stand (standard) 5 connecting the lower part 3 and the upper part 4, so that the whole It becomes the shape of C. An arm shaft 6 is rotatably supported in the upper part 4, and a needle bar 7 having a needle 8 can be driven up and down by the arm shaft. The arm shaft 6 drives a looper 9 supported on the lower part 3 and assigned to the needle 8. In the upper part 4 a foot 10 is further arranged. Upper part 1 of lower part 3
1 is located on the same plane as the support plate 12 belonging to the gantry 2.

The arm shaft 6, and hence the entire sewing machine 1, is driven via a belt transmission 14 by a drive motor 13 mounted on the gantry 2. For the control of the drive motor 13 and therefore of the sewing machine 1, a motor control 15 is provided, which is mounted on the drive motor 13, and for its operation is provided with an operation switch 16, which can be operated by an operator and is only schematically shown. Have been. The sewing machine 1 is further provided with a position transmitter 17 connected to the arm shaft 6. The transmitter is connected to the central computer 1 via line 18
9 and the computer is further connected to a conductor 20.
Is connected to the control unit 15 via the. Computer 1
9 and the motor control unit 15 form a sewing machine control device as a whole.

The position transmitter 17 supplies a signal representing the rotational position of the arm shaft 6 to the computer 19 through a conductor 18 at a predetermined angular distance. Usually, there are 512 signals per rotation of the arm shaft 6. From these signals, the arm shaft 6
And the respective position of the needle 8 can be derived. In addition, the position transmitter 17, which is also referred to as a rotary pulse transmitter, emits a reference signal on each rotation, which represents, for example, a zero position corresponding to the "needle up" position of the needle bar 7.

On the sewing head 21 of the upper part 4, a balance 2 (assigned to the needle bar 7), also driven by the arm shaft 6,
2 are provided. An upper thread (actually also referred to as a needle thread) guided from a stock thread or a thread spool (not shown) is guided to the needle 8 via the balance. Fabric material part on sewing machine 1, first material part 2 in the depicted embodiment
In the sewing machine 1 formed as a double-stitch sewing machine in which the fourth material portion 25 and the second material portion 25 are sewn together, an intersection 27 is formed by the looper 9 between the lower thread 26 and the upper thread 23 which are actually also represented as a looper thread. It is formed. The point of intersection is as far as possible in the piercing area 28 of the material parts 24, 25, ie the material parts 24, 2 sewn together
5 should be located at the center, so that the intersection is not visible from either side as shown in FIG. The sewing machines described so far are generally known as industrial sewing machines and are used extensively in practice.

In order to achieve the above-mentioned desired position of the intersection 27, a thread tightening device 29, shown in detail in FIGS. The device has a carrier plate 31 attached to the sewing head 21 by screws 30. A thread fastener 32 having an electromagnet 34 having a magnet bobbin 33 formed by a winding wire is attached to the carrier plate 31. The electromagnet is arranged in a matching recess 35 of the sewing head 21 on the back surface of the carrier plate 31. A bolt 36 is slidably disposed at the center inside the bobbin 33. A disk 37 (magnetite material, usually iron) which basically covers the electromagnet 34 and is used as a magnet anchor is firmly arranged on the bolt. When the bobbin 33 is energized, the disk
Attracted by The force for attracting the disk 37 depends on the strength of the current flowing through the bobbin 33. Bolt 3
6 passes through the support plate 31. At the end of the carrier plate 31 facing the front side 38, a span disk 39 is fixed by a self-protected nut 40. The spanning disc 39 can move in the longitudinal direction of the bolt 36 together with the bolt 36 and the disc 37 fixed to the bolt, but the pin 4
1 secures against twisting. A fixed span disk 42 fixed to the front side of the carrier plate 31 is assigned to the displaceable or slidable span disk 39.
A gap 43 for accommodating the upper thread 23 is provided between the span disks 39 and 42. The spanning discs 39 and 42 thus form two cooperating pressure or stringing elements.

A ring guide 45 in the form of a retaining ring and a thread guide 46 formed as a bolt are provided on the carrier plate 31 in front of the thread fastener 32 in the upper thread / running direction 44. Behind the thread fastener 32 in the running direction 44, the thread guide 4
Another thread guide 47 formed in the same way as 6 is arranged. 3, the upper thread 23 is guided from a thread winding (not shown) to the thread fastener 32 via the thread guide 45 and the thread guide 46. Here, the upper thread 23 passes through the gap 43 above the bolt 36 and is guided by the thread guide 47. From there it is guided back to the thread fastener 32 and, more specifically, through the gap 43 below the bolt 36. The slidable span disk 39 presses the upper thread 23 on both sides of the bolt 36 against the installation span disk, so that the bolt 36 does not tilt. Upper thread 2 from thread fastener 32
3 is guided to the thread lever 22 via a normal compensation spring 48. The compensating spring 48 is connected to the upper thread 23 beyond the thread lever 22.
Used to compensate for small inaccuracies in guiding the vehicle.

A first rotary potentiometer 49 is further provided on the supporting plate 31.
A second rotary potentiometer 50 and a third rotary potentiometer 51 are attached, and each rotary knob 52 and scale 5
3 is arranged on the front side 38 of the carrier plate 31, and an electric resistor 54 is arranged in the recess 35 of the sewing head 21 on the back side of the carrier plate 31.

The opening and closing and the functional structure will be apparent from FIGS. Computer 19 has a microprocessor 55 with a storage device 56. The microprocessor 55 is supplied with rotation pulses emitted at equal angular intervals via the conductor 18 and the input 57;
A position or reference signal is supplied via 8. As soon as the sewing machine 1 is driven by the drive motor 13, a switching instruction is supplied to the microprocessor via another input unit 59. Microprocessor 55 via input unit 60
Then, a switching instruction of a thick cloth material range such as folding, diagonal stitches or horizontal seams is supplied. Such a switching instruction is given, for example, via a knee (knee) switch 16a operated by the operator. A signal for the thread cutting process is supplied via another input 61. The three potentiometers 49, 50, 51 are connected to another input unit 63 via an analog / digital converter 62.

A pulse width modulator 64 is arranged behind the microprocessor 55. The modulator is further connected to the magnet bobbin 33 of the electromagnet 34 via the amplifier 65.
It is connected to the. The magnet bobbin 33 is in communication with a logical ground (Masse) 67 via a measuring resistor 66. Furthermore, the magnet bobbin is guided to a current regulator 68 which is led back to an amplifier 65.

The storage device 56 stores a curve drawn by a line in FIG. The curve has been empirically calculated. The curve gives information obtained empirically, so that a qualitatively valuable seam in which the intersection 27 of the upper thread 23 and the lower thread 26 is between the fabric materials 24, 25, respectively, This is most easily achieved if the current I supplied to 33 changes substantially in the form of a roof through the speed n. To produce an ideal seam formation, the upper thread 23
Is not constant throughout the rotation speed n. Storage device 56
A program is stored in response to this, which supplies a signal to the pulse width modulator 64 in dependence on the continuous signal coming from the position transmitter 17 and via its output further activates the amplifier 65, From bobbin 3
3 is given a current with a course corresponding to the curve F1 for the speed n.

The specific fabric material portion 24 to be sewn
For 25, the state of the curve F1 is empirically calculated and is, for example, 1000 / min in the range of relatively low speeds n1 and, for example, 3000 / min in the range of relatively high speeds. In the case of a low rotation speed n1,
The current I supplied to the bobbin 33 via the first potentiometer 49 is maintained until the desired sewing formation is reached at this rotation speed n1.
In other words, it is changed all the way until the intersection 27 is at the desired position between the cloth material portions 24, 25. Due to the relatively high rotational speed n2, the current I is calculated in the same way in the second potentiometer 50. Thus, the state of the curve F1 for these fabric material parts which are usually sewn thereafter in large numbers is fixed. By the third potentiometer 51, F2 in FIG.
The shift of the curve F1 in the state indicated by the dotted line and parallel in itself can be set. In the range where the thread tension increased according to this curve is inevitable, for example, in the case of lap sewing such as a horizontal seam or folding in a fabric material portion, the sewing machine is moved. This shift is calculated in the same way for the specific fabric material part to be sewn. When the operator gives a signal to the input unit 59 of the microprocessor 55 via the knee switch 16a or the like,
Sewing is performed according to this curve.

In the case of the above-described embodiment, the control of the current supplied to the bobbin 33 and, consequently, the control of the thread tension of the upper thread through the rotation speed are performed. Instead of in the form of a thread clamp 32 with two spun disks 39, 42, the upper thread is guided via wheels which are braked by electromagnets (corresponding to US Pat. No. 5,363,786).
Thread fasteners according to 4141945 C1 can also be used.

[Brief description of the drawings]

FIG. 1 is a schematic view of a sewing work place.

FIG. 2 is a view of two cloth materials sewn to each other by a double stitch seam;

FIG. 3 is a plan view of the thread fastening device in an enlarged state with respect to FIG. 1;

FIG. 4 is a cross-sectional view of the thread fastening device corresponding to a section line IV-IV in FIG. 3;

FIG. 5 is a block circuit diagram of a first embodiment for controlling the current of the thread fastener.

FIG. 6 is a graph reproducing the progress of the current of the thread fastener with respect to the number of rotations.

[Explanation of symbols]

 Reference Signs List 1 sewing machine 6 arm shaft 7 needle bar 8 needle 13 drive motor 15, 19 sewing machine control device 23 upper thread 24, 25 fabric material portion 26 lower thread 27 intersection 29 thread fastening device 32 thread fastener 34 electromagnet

Continued on front page F term (reference) 3B150 AA01 BA00 CB03 CC04 CD03 CE04 CE27 GD11 GD22 GE05 GE14 GF01 JA02 JA11 LA03 LA40 LA85 NA47 NA72 NB15 NC11 PA03 QA06

Claims (10)

[Claims] An arm shaft (6) and said arm shaft (6)
(13), a sewing machine control device (15, 19), a needle bar (7) with a needle (8) drivable by the arm shaft (6), Sewing machine (1) provided with a thread fastening device (29)
In the upper thread / running direction (44), the fabric material portion (2
At least two cloth material portions (27) are formed using the upper thread (23) and the lower thread (26) supplied to the upper thread (23, 26) to form an intersection (27) between the upper thread (23) and the lower thread (26). 24,2
5) In the method for sewing as described in 5), the thread fastening device includes a thread fastener (32) in contact with the upper thread, and the thread fastener is driven by an electromagnet (34) through which a current (I) flows. The current (I) depends on the number of revolutions (n) of the arm shaft (6), and is calculated recursively and normalized. (I) The upper thread (23) and the lower thread (26) according to the progress curve (F1).
The intersection (27) of the fabric material part is basically (24, 25)
A method for stitching, characterized in that it is changed through the number of revolutions (n), as in 2. A fabric material portion to be sewn (24, 2).
Before the start of the sewing process 5), the curve (F1) is
It is adjusted by the change of the current (I) at least at one predetermined rotation speed (n1, n2), and when the upper thread (23) is tensioned, the intersection (26) basically corresponds to the cloth material portion (24). , 25), wherein the current (I) is set to be between. 3. The method according to claim 2, wherein the curve is adjusted by changing the current at two essentially different rotational speeds. Method. 4. The curve (F1) according to claim 1, wherein said curve (F1) can be moved in parallel with itself by a switching instruction from a sewing machine control device (15, 19). The method described in. 5. The method according to claim 4, wherein the switching instruction is given manually. 6. A sewing machine with a thread tightening device (29) for performing the method according to claim 1, wherein the microprocessor (55) is standardized through the number of revolutions (n). Current (I) curve (F
1) a storage device (56) storing at least one first adjuster (potentiometer 49) for at least the first rotation speed (n1, n3) of the arm shaft (6). A sewing machine provided for adjusting a curve (F1). 7. A second adjuster (50) comprising an arm shaft (6).
Is provided for adjusting the curve (F1) at the time of the second rotation speed (n2), and the second rotation speed (n2) is fundamentally different from the first rotation speed (n1). The sewing machine according to claim 6, characterized in that: 8. The sewing machine according to claim 6, wherein an adjuster (51) is provided for moving the curve (F1) parallel to itself. 9. The at least one regulator comprises a potentiometer (4).
9, 50, 51).
The sewing machine according to any one of the above. 10. The thread fastener (32) is provided with an electromagnet (34).
Pressing elements (39, 4) which can be pressed against each other by
The sewing machine according to claim 6, wherein 2) is provided.