KR102621331B1 - Thread tensioning device for a machine - Google Patents

Abstract

The thread tension control device 32 for a sewing machine has a tension control shaft 33 configured to allow the sewing thread 13 to be tension adjusted to be wound around the tension control shaft 33. At least one tensioning unit (34, 35) interacts with the tensioning axis (33) to create thread tension in the path of the sewing thread (13) downstream of the tensioning axis (33). The thread path deflecting element 38 is used to deflect the thread path of the sewing thread 13. The thread path of the thread tensioning device (32) first involves the sewing thread (13) being wound around the tensioning axis (33) to create a first thread tension contribution, and then over the thread path deflection element (38), It is then again wound around the tensioning shaft 33 and configured to produce a second yarn tension contribution. As a result, a yarn tensioning device is obtained which has an improved effect on the yarn to be tensioned.

Description

{THREAD TENSIONING DEVICE FOR A MACHINE}

The present invention relates to a thread tensioning device for a sewing machine and to a machine equipped with a thread tensioning device of this type.

A device for adjusting thread tension for a sewing machine is known from DE 196 33 223 C2. DE 2 157 016 A discloses a device for adjusting yarn tension on a yarn-processing machine. DE 20 2012 100 110 U1 discloses an upper thread tensioning device comprising two thread tension disks. DE 103 44 982 A1 discloses a device for adjusting thread tension for a sewing machine. German Patent Specification No. 962 568 discloses a tension control device for needle thread in a two-needle sewing machine. DE 20 2009 004 845 U1 discloses a spool device for a sewing machine.

The object of the present invention is to improve a yarn tensioning device of the type initially mentioned so that the effect on the yarn to be tensioned is improved.

According to the present invention, this object is a thread tensioning device for a sewing machine, which includes at least one tension control shaft configured to allow the sewing thread to be tensioned to be wound around the tension control axis, and a sewing thread downstream of the tension control axis. At least one tensioning unit that interacts with the tensioning axis to create thread tension in the path, and a thread path deflecting element that deflects the thread path of the sewing thread, wherein the thread path of the thread tensioning device is such that the sewing thread first moves along the tensioning axis. This is achieved by means of a yarn tensioning device configured to be wound around the perimeter to create a first yarn tension contribution, then across a yarn path deflection element, and then again around the tensioning axis to create a second yarn tension contribution. do.

According to the present invention, splitting the thread tensioning effect of the thread tensioning device into two thread tensioning contributions, in which the deflection of the thread path is carried out by the thread path deflection element, consists of the force applied by the thread tensioning device on the sewing thread. Help contribute in a desirable way. In particular, it is possible to avoid twisting of the sewing thread, thus preventing any undesirable twisting force from being applied to the sewing thread, and especially preventing accumulation along the thread path of the thread tensioning device (so-called undesirable entanglement). . Splitting the effect of the yarn tensioning device into two yarn tension contributions, each created by forming a loop around one and the same tensioning axis, results in a compact arrangement of the yarn tensioning devices. In particular, it can also be devised to generate a number of different thread tension contributions that can be actuated differently, with the result that the overall thread tension range can be increased in an advantageous manner. Sewing thread can be the upper thread of a sewing machine. The yarn tensioning device also allows more than one yarn tension contribution to occur. A corresponding additional yarn path can be provided by a yarn path deflection element or by another yarn path deflection element providing another yarn path across the tensioning axis to generate said additional yarn tension contribution. The yarn tensioning device may have exactly one tensioning device. Alternatively, the yarn tensioning device may have at least two tensioning units. The tensioning unit may be biased by a bias spring. The bias spring may be a compression spring. Compression springs may consist of helical springs or corrugated springs.

The thread path deflecting member, which consists of a rotatable pin or a roll rotatable about the pin axis, is particularly neutral in terms of the force applied to the sewing thread, the pin being configured such that the sewing thread is wound around the pin. The rotatable pin or rotatable roll can rotate along the sewing thread running on it.

An embodiment considered as a separate embodiment of a tensioning device formed by at least one pair of pressure tensioning disks and at least one actuator, wherein the pressure tensioning disks are arranged in pairs in such a way that the sewing thread to be tensioned passes between the pressure tensioning disks. It is known from the prior art, for example from DE 196 33 223 C2. The pressure tension disk may be configured as a Belleville washer. The tensioning device may have two pairs of pressure tensioning discs or may have more than two pairs of pressure tensioning discs, for example three, four, five or more pairs of pressure tensioning discs. Instead of an electric actuator, a manually operable adjustment element, for example an adjustment screw, can also be used to adjust the tension of the tensioning unit. The pressure tensioning disk may be arranged so that it cannot rotate about the tensioning axis.

a wheel tension disc, a brake body and at least a wheel tension disc, a brake body and at least a wheel tension disc arranged so that the sewing thread to be tensioned passes between the disc portions of the wheel tension disc and the wheel tension disc interacts with an actuator to set the pressure exerted on the wheel tension disc by the brake body. The tensioning unit formed by one actuator has proven to be particularly suitable for generating a yarn tension with a preferably wide tension range and in particular for reproducibly generating a predetermined yarn tension. The disc sections of each wheel tensioning disc, configured to receive the thread to be tensioned, can be rigidly connected to each other, for example welded to each other. The retaining effect of the wheel tension disc can be created by means of a cylindrical retaining section, which can be configured in particular in the manner of a tongue-shaped retaining section. These retaining sections can be interconnected to each other in such a way that a reproducible friction connection is obtained between the retaining section and the tensioned thread. The wheel tension disk may be rotatably mounted on the tension adjustment shaft. In this case, the wheel tensioning disc can co-rotate with the thread to be tensioned when guided around the tensioning axis. The thread tension can then be generated by the actuator pressure by means of a corresponding pressure-dependent braking effect exerted on the wheel tension disc by the actuator-actuated braking body.

The actuator acting on the pair of tension disks may act on the pair of tension disks via wire springs and/or corrugated springs.

The actuator, consisting of a stepper motor, allows particularly fine-tuned and reproducible thread tension settings. The stepper motor can act on at least one tensioning unit by means of a gear unit, which helps to improve the adjustment procedure or the opening speed of the respective tensioning unit or the sensitivity of the influence of the stepper motor on the resulting yarn tension contribution. Linear motors may be used instead of stepper motors. The actuator may have a gear unit. A multi-start screw seal can be used to transfer force between the actuator and the tension disk. Stepper motors can be torque controlled.

At least two tensioning units arranged on the tensioning axis and configured to produce respective yarn tension contributions enable the different yarn tension contributions to be set in a particularly independent manner.

As an alternative to designing the tensioning unit as a pair of tensioning disks, the tensioning unit itself may be formed by at least one stepper motor and the tensioning axis is driven by the stepper motor. The tensioning shaft may form the motor shaft of a stepper motor or may be connected to the motor shaft through a gear device.

The advantages of the sewing machine equipped with the thread tension adjusting device according to the present invention correspond to those already described with reference to the thread tension adjusting device. In addition to the thread tensioning device used as the main thread tensioning device described above, a thread pre-tensioning device may be disposed in the thread path of the sewing thread upstream of the main thread tensioning device.

Below, exemplary embodiments of the present invention will be described in more detail with reference to the drawings, wherein
Figure 1 is a schematic front view showing some internal details of a double lock stitch sewing machine in which the upper thread path is interrupted, i.e. not shown, in areas of thread tensioning components not shown in Figure 1;
Figure 2 is a front view showing further details of the housing part of the sewing machine, in which the components of the thread tensioning device are shown in sections I/II corresponding to sections I/II in Figure 1;
Figure 3 is a cross-sectional view taken along line III-III in Figure 2;
FIG. 4 is a side view of the housing portion seen from observation direction IV of FIG. 2;
Figure 5 is a transparent front perspective view of a portion of the housing as shown in Figure 2;
Figure 6 shows a wheel tension disk with two disk parts that can form the tensioning unit of the main yarn tensioning device instead of a pair of pressure tensioning disks; and
Figure 7 is a side view of an embodiment of a tensioning unit comprising two pairs of pressure tensioning disks with yarn path deflection elements, showing the yarn path in the area of the yarn tensioning device.

The double lock sewing machine (1) has a base plate (2), a stand (3) extending upward therefrom and an inclined arm (4). The arm (6) terminates in the head (5). The arm axis 6 is mounted for rotation within the arm 4. In the head (5), the arm axis (6) drives the crank drive (7) with the thread lever (8). The crank drive (7) is in driving connection with a needle bar (9) mounted on the head (5) in an axially displaceable manner. The needle bar 9 has a needle 10 at its lower end. By means of the crank drive 7, the needle 10 can move up and down along the vertical axis 11.

A Cartesian coordinate system will be used below to simplify the description of positional relationships. The vertical axis 11 extends along the z-direction of this coordinate system. The x-direction runs perpendicularly to the drawing plane of FIG. 1 and runs parallel to the sewing direction of the sewing machine 1 . The y-direction goes to the left in Figure 1.

The needle 10 guides the needle thread 13 into the needle hole, and the needle thread 13 is supplied by an upper thread supply unit composed of a reel 12 through a thread tension control device, as shown in Figure 2, etc. It will be described in more detail with reference to and will also be referred to as an upper thread. The needle thread 13 has a free upper thread starting portion 13a.

The base plate 2 carries a support plate 14 on which the fabric piece 15 rests, and the support plate 14 is fixed by screws. The portion 15 of the support plate 14 consisting of the stitch plate 16 is provided with a recess through which a lower feed dog 17, also called a drop feed, can pass. The feed dog 17 has a stitch hole 18 through which the needle 10 can pass. The feed dog 17 is in drive connection with the sliding and lifting gear unit in a known manner, and the sliding and lifting gear unit is arranged under the base plate 2.

A looper 19 having a looper body 21 having a looper tip 21 is disposed below the support plate 14. A cup-shaped bobbin case is mounted on the looper body 21 to accommodate the supply of looper thread by means of a reel 22 or a thread spool. The reel 22 is the lower thread supply part. Looper thread is also referred to as lower thread.

The looper 19 together with the needle 10 forms a stitch forming tool. The needle 10 is used to guide the upper thread. The looper 19 is used to interlace the upper and lower threads.

The looper 19 is rotatable about a vertical looper axis 23 extending in the z-direction. The looper body 20 is rigidly connected to a shaft 25 extending coaxially with the looper shaft 23. The shaft 25 is mounted to rotate in a bearing block 26 screwed to the base plate 2. On this bearing block 26, a drive shaft 27 is mounted, which is connected to a toothed gear arrangement arranged within the bearing block 26. The toothed gear arrangement has a transmission ratio of 1:2, which means that the looper body 20 placed on the shaft 25 rotates twice for each rotation of the drive shaft 27. The drive shaft 27 is driven and connected to the arm shaft 6 through a belt drive 28.

In sections I/II of FIGS. 1 and 2, the thread tension adjusting device 29 disposed on the housing portion 30 of the arm 4 is configured to adjust a plurality of thread tensions disposed back and forth within the thread path of the upper thread 13. has elements. Following the thread path of the upper thread 13, the reel 12 first leads to a yarn pre-tensioning device, not shown in more detail, which then leads to the main yarn tensioning device 32. . Depending on the design of the sewing machine 1, the thread pre-tensioning device may be omitted.

The main thread tension control device 32 has a tension control shaft 33 (see FIG. 3) around which the upper thread 13 to be tensioned is wound. Two tensioning units (34, 35), each configured to produce a yarn tension contribution, interact with the tensioning axis (33). Each of the tension control units 34 and 35 serves to generate yarn tension or a yarn tension contribution of the upper thread 13 in the path of the upper thread 13 along the tension control axis 33. Depending on the design of the main yarn tensioning device 32, it may also be considered to provide exactly one tensioning unit, for example the tensioning unit 34, which is used to generate yarn tension.

Each tension control unit (34, 35) is formed by a pair of pressure tension disks (36) and an actuator (37). The individual pairs of tension disks (36) are arranged so that the upper thread (13) to be tensioned passes between these pairs of tension disks (36). Each pair of tension disks 36 interacts with an actuator 37 to set the pressure between the tension disks 36. This effect of a pair of pressure tension disks 36 and an actuator 37 is known from the prior art and is described for example in DE 196 33 223 C2 with particular reference to Figure 4.

Actuator 37 may be an electromagnet. Actuator 37 may also be a stepper motor.

The two tensioning units (34, 35) interact with the same actuator (37). The two tensioning devices 34, 35 are arranged directly adjacent to each other in the axial direction on the tensioning axis 33. Between the two tensioning units (34, 35) there is a bearing disk (36) for the tensioning disks (36) of the two tensioning devices (34, 35) to support those placed directly axially adjacent to these bearing disks (37a). 37a) is placed. Like the tension disk 36, the bearing disk 37a is coupled to the tension control shaft 33 and serves to radially support the tension disk 36 facing the bearing disk 37a. For this purpose, the bearing disk 37a has a circumferential bearing groove on each side that is engaged by the edge portion of the respective tension disk 36 facing it.

In addition to the two tensioning units 34 and 35, the main yarn tensioning device has a yarn path deflecting element 38 that deflects the yarn path of the upper thread 13. The thread path of the upper thread 13 in the main thread tensioning device 32 is such that the upper thread 13 first generates the first thread tension contribution on the tensioning axis 33, which is the first of the two tensioning devices 34, 35. It is wound around the tensioning axis 33 in the area of one device and then again around the tensioning axis 33 in the area of the second of the two tensioning devices 34, 35 to create a second yarn tension contribution. It is configured to span the yarn path deflection element 38 before winding. This yarn path within the main yarn tensioning device 32 may also be such that three or more yarn tension contributions are generated. In this case, there may be an additional yarn path wound around the tensioning axis 33 to produce the next yarn tension contribution over the same yarn path deflection element 38 or again over another yarn path deflection element not shown. To this end, the tension control shaft 33 may have an additional tension control unit not shown in the drawings configured in the manner of the tension control devices 34 and 35.

The thread path deflection element 38 is configured as a deflection pin. A deflection pin of this type may be rigidly mounted in the housing portion 30, or alternatively may be configured to be rotatable about the pin axis. In this case, the pin is mounted on the housing part 30 in the manner of a roll via a radial bearing.

Alternatively, it may be considered to design the tensioning devices 34, 35 as each pair of disk portions of the wheel tension disk. For example, a pair of disc parts of a wheel tensioning disc 39 of this type, which can form one of the tensioning units 34 or 35, is shown in FIG. 6 .

The two disc parts 39a of the wheel tension disc 39 are rigidly connected to each other, for example by welding. The outer circumference of the pair of disk portions 39a of the wheel tension disk 39 has an approximately U-shaped or V-shaped groove profile, in which the upper thread 13 is tensioned, for example, within the range of 360°. By winding around the adjusting axis 33 it is guided within the angular range of the circumference.

The external profile of the disc portion 39a of the wheel tension disc 39 is formed by two web rings 40 each having a plurality of webs 41 bent axially outwardly in the +/- x-direction. The arrangement of the web 41 of the two web rings 40 in the circumferential direction is such that the web 41 is coupled to one of the two web rings 40 and then alternately coupled to the other of the two web rings 40. Make it possible. The profile base of the groove profile is formed by the retaining parts 42 of the web 41 overlapping each other in the x-direction. This ensures that the upper thread 13 runs at a precisely defined radius relative to the shaft axis of the tensioning axis 33 when wound around the pair of disc parts 39a of the tension disc 39.

The holding portion 42 may be composed of a tongue portion.

Irrespective of whether the tensioning units 34, 35 consist of a pair of pressure tensioning disks 36 or a pair of disk portions 39a of the wheel tensioning disk 39, at least one of the main yarn tensioning devices 32 One tension control unit may be formed by at least one stepper motor that drives rotation of the tension control shaft 33. The tensioning shaft 33 can then be configured directly as the motor shaft of a stepper motor of this type, or the tensioning shaft can be connected to the motor shaft of the stepper motor via a gear unit. When the tension control unit or tension control units are configured as a stepper motor, the upper thread 13 can be wound around the entire tension control shaft 33, especially more than twice.

As can be seen from Figures 2 to 5, the housing portion 30 is configured to have two main thread tension control devices formed accordingly by guiding the upper thread 13 in the manner of the main tension control device 32 described above. Elements can be mounted. In other words, as shown in these figures, housing portion 30 may carry two main yarn tensioning devices with associated tensioning axes, associated actuators and associated tensioning units as well as associated yarn path deflection elements. .

The actuator 37 acts on the tension disks 36 or 39 of the tension adjustment units 34 and 35, respectively, through compression springs 34. The compression spring 15 34 may be a helical spring, especially a helical wire spring. When using an actuator 37 consisting of a torque-controlled servomotor or stepper motor, this type of tension spring can also be omitted.

In an embodiment of the tensioning units 34, 35 with pressure tensioning disks 36, the yarn tension is determined by the pressure applied by the actuator 37 between each tensioning disk 36 to the yarn disposed therebetween. It is caused by The tension disk 36 may be non-rotatingly disposed on the tensioning axis 33. In embodiments with a disc portion 39a of each wheel tensioning disc 39, each wheel tensioning disc 39 rotates with the winding yarn within its own yarn path and is non-rotating about the tensioning axis 33. The tension is generated through a braking effect exerted by the pressure of the actuator 37 between the braking bodies, which can be arranged as follows. The braking body may be a bearing disk 37a, for example.

In the thread path downstream of the main thread tensioning device 32, the upper thread 13 passes through the thread tightening spring 44 (see Fig. 1) through the thread lever 8 to the hole of the needle 10 before running.

Figure 7 shows the yarn path of the yarn tension adjusting device 32. This figure shows one of two yarn tensioning devices 32 of the embodiment as shown in FIGS. 1 to 5. The thread path in the other thread tensioning device 32 corresponds thereto.

The needle thread 13 first runs from a thread pre-tensioning device, not shown in Figure 7, over a first pair 45 of pressure tensioning disks 36 (first tensioning unit). At this time, the needle thread is wound around the tension control shaft 33 more than 180°, and can also be wound more than once around the entire tension control shaft 33. In the illustrated embodiment, the needle 15 thread is wound around the tensioning axis 33 within an angular range of approximately 270° in the region of the first pair 45 of pressure tensioning disks 36. When the needle thread is wound around the first pair (45), a first thread tension contribution is created to the sewing thread (13).

The needle thread 13 is then wound around the tensioning axis 33 in the same way as for the first pair 45 when the second pair 46 of the pressure tensioning discs 36 of the thread tensioning device 32 It is wound around the yarn path deflection element 38 at a contact angle of approximately 180° before continuing into the (second tensioning unit). When the needle thread is wound around the second pair (46), a second thread tension contribution is created to the sewing thread (13).

Next, the needle thread 13 advances to a thread tightening spring not shown in FIG. 7.

A first pair (45) of pressure tensioning disks (36) is disposed on the housing while a second pair (46) is disposed towards the free end of the tensioning axis (33).

In the embodiment shown in Figure 7, the compression spring 43 is comprised of a corrugated spring. Corrugated spring blocks can also be used here.

The sewing thread 13 may be wound around the tension control shaft 33 in the same or opposite rotation direction in the area of each tension control unit 45, 46. Depending on the yarn type and operating conditions, one of the two directions, “same direction of rotation” or “opposite direction of rotation” may be more preferable to avoid confusion.

Claims (8)

As a thread tensioning device (32) for a sewing machine,
- At least one tension control shaft (33) configured to allow the sewing thread (13) to be tension adjusted to be wound around the tension control shaft (33),
- at least two tension control units (34, 35) interacting with the tension control axis (33) to create thread tension in the path of the sewing thread (13) downstream of the tension control axis (33),
- Equipped with a thread path deflection element 38 that deflects the thread path of the sewing thread 13,
- The thread path of the thread tension adjusting device 32 is the sewing thread 13.
It is first wound around the tensioning shaft 33 to create a first yarn tension contribution,
This then continues over the yarn path deflection element 38,
It is then configured to be wound around the tensioning shaft (33) again to produce a second yarn tension contribution,
- Each of the tension adjustment units (34, 35) is
Formed by at least a pair of pressure tension disks 36 and at least one actuator 37, where the pressure tension disk 36 is configured to allow the sewing thread 13 to be tensioned to pass between the pressure tension disks 36. arranged in pairs, the pressure tensioning disks 36 interact with the actuator 37 to set the pressure between the pressure tensioning disks 36 -, or
Formed by a wheel tension disk 39, a brake body 37a and at least one actuator 37 arranged so that the sewing thread 13 to be tensioned passes between the disk portions of the pressure tension disk 39 - the wheel The tension disc (39) interacts with the actuator (37) to set the pressure applied by the braking body on the wheel tension disc (39),
The at least two tensioning units (34, 35) are arranged on the tensioning axis (33) and are configured to produce respective yarn tension contributions. According to claim 1,
The thread tensioning device is characterized in that the thread path deflection element (38) is configured as a pin rotatable about the pin axis, the pin being configured to allow sewing thread (13) to be wound around the pin. The method of claim 1 or 2,
Yarn tensioning device, characterized in that each tensioning unit (34, 35) has at least two pairs of pressure tensioning disks. The method of claim 1 or 2,
A yarn tensioning device, characterized in that each tensioning disk is comprised of a tongue-shaped retaining portion. The method of claim 1 or 2,
A yarn tension control device, characterized in that the actuator (37) is configured as a stepper motor. The method of claim 1 or 2,
A yarn tensioning device, characterized in that the tensioning unit is configured so that different yarn tension contributions are set in an independent manner. The method of claim 1 or 2,
The yarn tension control device is characterized in that the tension control unit is formed by at least one stepper motor, and the tension control shaft (33) is driven by the stepper motor. A sewing machine equipped with a thread tension adjustment device (32) according to claim 1 or 2.