CN110485070B

CN110485070B - Thread tensioning device for a sewing machine and sewing machine with a thread tensioning device

Info

Publication number: CN110485070B
Application number: CN201910354681.4A
Authority: CN
Inventors: 格特·兰格莱克; 佛罗莱恩·舒尔茨; 乔纳斯·埃克斯纳
Original assignee: Duerkopp Adler AG
Current assignee: Dukepu Aihua Co ltd
Priority date: 2018-05-14
Filing date: 2019-04-29
Publication date: 2021-03-30
Anticipated expiration: 2039-04-29
Also published as: CN110485070A; JP2019198647A; JP7304201B2; EP3569754B1; EP3569754A1; TWI803631B; KR20190130503A; KR102621331B1; DE102018207426A1; TW201947079A

Abstract

A thread tensioner for a sewing machine and a sewing machine having the thread tensioner are disclosed. The thread tensioning device (32) has a tensioning shaft (33) which is configured in such a way that the sewing thread (13) to be tensioned is allowed to wind around the tensioning shaft (33). At least one tensioning unit (34, 35) interacts with the tensioning shaft (33) to generate a thread tension in the path of the sewing thread (13) downstream of the tensioning shaft (33). The thread path deflecting element (38) is used for deflecting the thread path of the sewing thread (13). The thread path of the thread tensioning device (32) is such that the sewing thread (13) is first wound around the tensioning shaft (33) to generate a first thread tension effect, then wound over the thread path deflecting element (38) and then wound around the tensioning shaft (33) again to generate a second thread tension effect. As a result, a wire tensioning device is obtained which has an improved influence on the wire to be tensioned.

Description

Thread tensioning device for a sewing machine and sewing machine with a thread tensioning device

Technical Field

The present invention relates to a thread tensioner for a sewing machine and to a machine having such a thread tensioner.

Background

A thread tensioning device for a sewing machine is known from DE 19633223C 2. DE 2157016 a discloses a device for tensioning threads on a thread processing machine. DE 202012100110U 1 discloses an upper thread tensioner comprising two thread tensioning disks. DE 10344982 a1 discloses a thread tensioning device for a sewing machine. German patent specification No. 962568 discloses a tensioning device for a needle thread in a two-needle sewing machine. DE 202009004845U 1 discloses a bobbin arrangement for a sewing machine.

Disclosure of Invention

The object of the present invention is to improve a thread tensioning device of the type described above in such a way that its influence on the thread to be tensioned is improved.

According to the invention, this object is achieved by a thread tensioner for a sewing machine, having: at least one tensioning shaft configured to allow a sewing thread to be tensioned to wrap around the tensioning shaft; at least one tensioning unit interacting with the tensioning shaft to generate thread tension in the path of the sewing thread downstream of the tensioning shaft; a thread path deflecting element to deflect a thread path of the sewing thread; wherein the thread path of the thread tensioning device is such that the sewing thread is first wound around the tensioning shaft to generate a first thread tensioning action, then wound over (extended by) the thread path deflecting element, and then wound again around the tensioning shaft to generate a second thread tensioning action.

According to the invention, it was found that the thread tension effect of the thread tensioning device is divided into two thread tension effects, between which the thread path deflecting element performs a deflection of the thread path, which assists in an advantageous manner in distributing the force exerted by the thread tensioning device on the sewing thread. In particular, twisting of the sewing thread can be avoided, thereby preventing any undesired torsional forces from being exerted on the sewing thread, in particular from building up along the thread path of the thread tensioning device (so-called undesired tangles). The effect of the wire tensioner is divided into two wire tensioning actions, each generated by forming a loop around the same tensioning shaft, resulting in a compact arrangement of the wire tensioner. It is also conceivable to generate a number of different thread tensioning actions, which are in particular differently performable, with the result that the overall thread tension range can be increased in an advantageous manner. The sewing thread may be an upper thread of a sewing machine. The wire tensioning device also allows more than two wire tensioning actions to be generated. Then, a corresponding additional line path may be provided by the line path deflecting element or by another line path deflecting element providing another line path above the tensioning axis to generate said additional line tensioning effect. The thread tensioning device can have exactly one tensioning unit. Alternatively, the thread tensioning device can also have at least two tensioning units. The tension unit may be biased by a biasing spring. The biasing spring may be a compression spring. The compression spring may be configured as a coil spring or a wave spring.

The thread path deflecting element is configured as a rotatable pin or as a roller rotatable about a pin axis, the pin being configured such that the sewing thread is allowed to wind around the pin, which is particularly neutral in terms of the forces exerted on the sewing thread. The rotatable pin or rotatable roller can then rotate with the sewing thread extending thereon.

Considered separately, an embodiment of the tensioning unit formed by at least one pair of pressure-tensioning discs and at least one actuator, the pressure-tensioning discs being arranged in pairs such that the sewing thread to be tensioned passes between the pressure-tensioning discs, the pressure-tensioning discs interacting with the actuator to set the pressure between the pressure-tensioning discs, is known from the prior art, for example from DE 19633223C 2. The pressure tension disc may be configured as a Belleville washer. The tensioning unit may have two pairs of pressure-tensioning discs or even more than two pairs of pressure-tensioning discs, for example three, four, five or even 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 tensioning force of the tensioning unit. The pressure tensioning disc may be arranged so as to be non-rotatable with respect to the tensioning shaft.

The tensioning unit formed by the wheel-type tensioning disc, the brake body and the at least one actuator, which is arranged such that the sewing thread to be tensioned passes between the disc portions of the wheel-type tensioning disc, the wheel-type tensioning disc interacting with the actuator to set the pressure exerted by the brake body on the wheel-type tensioning disc, proves to be particularly suitable for generating thread tensions with an advantageously large tension range, in particular reproducibly generating predetermined thread tensions. The disc sections of the respective wheel-type tensioning disc, which are configured to accommodate the wire to be tensioned, may be rigidly connected to each other, e.g. welded to each other. The retaining effect of the wheel-type tensioning disk can be produced by a circumferential retaining section, which can be configured in particular in the manner of a tongue-shaped retaining section. These retaining segments can engage one another in such a way that a reproducible frictional connection is obtained between the retaining segments and the thread to be tensioned. The wheel-type tension disc may be rotatably fitted on the tension shaft. In this case, the wheel-type tensioning disc can rotate jointly with the wire to be tensioned, while the tensioning disc is guided around the tensioning shaft. A line tension can then be generated by the actuator pressure through a corresponding pressure-dependent braking effect exerted on the wheel tensioner disc by the brake body operated by the actuator.

The actuators acting on the pair of tensioning discs may act on the pair of tensioning discs via wire springs and/or wave springs.

An actuator configured as a stepper motor allows for a particularly fine-tuned and reproducible setting of the line tension. The stepping motor can act on the at least one tensioning unit by means of a gear unit, which contributes to increasing the sensitivity of the stepping motor to the influence of the generated wire tensioning effect or to adjusting the speed of the program or the opening of the respective tensioning unit. A linear motor may be used instead of the stepping motor. The actuator may have a gear unit. A multi-start sewing thread can be used to transmit force between the actuator and the tensioning disc. The stepper motor may be torque controlled.

At least two tensioning units, which are arranged on the tensioning shaft and are configured such that a respective line tension effect is generated, allowing different line tension effects to be set in a particularly independent manner.

As an alternative to designing the tensioning unit as a pair of tensioning discs, the tensioning unit itself may be formed by at least one stepper motor, the tensioning shaft being driven by the stepper motor. The tensioning shaft may form the motor shaft of the stepper motor, or may be connected to said motor shaft via a gear unit.

The advantages of the sewing machine with the thread tensioning device according to the invention correspond to those already described above with reference to the thread tensioning device. In addition to the thread tensioning device described above (which then serves as main thread tensioning device), the thread tensioning device can be arranged in the thread path of the sewing thread upstream of the main thread tensioning device.

Drawings

Exemplary embodiments of the invention will be described in more detail below with reference to the accompanying drawings, in which:

fig. 1 shows a schematic front view showing some internal details of a double lock stitch sewing machine, wherein the upper thread path is interrupted in the region of the thread tensioning member not shown in fig. 1, in other words not shown;

FIG. 2 shows a front view showing additional details of a housing portion of the sewing machine, with components of the thread tensioning device shown in section I/II, which corresponds to section I/II in FIG. 1;

FIG. 3 shows a cross-sectional view along the line III-III in FIG. 2;

fig. 4 shows a side of the housing part seen from the viewing direction IV in fig. 2;

FIG. 5 shows a perspective oblique front view of the housing portion as shown in FIG. 2;

FIG. 6 shows a wheel-type tension disc with two disc portions that may form a tension cell of a main line tensioner of a line tensioner instead of a pair of pressure tension discs; and

fig. 7 shows a side view of one embodiment of a tensioning unit comprising two pairs of pressure tensioning discs and a wire path deflecting element, which shows the wire path in the region of the wire tensioning device.

Detailed Description

The double lockstitch sewing machine 1 has a frame 1a comprising a base plate 2 having a support 3 extending upwardly therefrom and an angled arm 4. The arms terminate in a head 5. An arm shaft 6 is mounted for rotation in the arm 4. In the head 5, an arm shaft 6 drives a crank driver 7 through a wire rod 8. The crank drive 7 is in driving connection with a needle bar 9, which is mounted in the head 5 in an axially displaceable manner. The shank 9 has a needle 10 at its lower end. The needle 10 is movable up and down along a vertical axis 11 by means of a crank drive 7.

A cartesian xyz coordinate system will be used below to simplify the illustration of the positional relationship. The vertical axis 11 extends along the z-direction of the coordinate system. The x-direction extends perpendicular to and into the plane of drawing of fig. 1 and parallel to the sewing direction of the sewing machine 1. The y direction extends to the left in fig. 1.

The needle 10 guides a needle thread 13 into the eye, which needle thread 13 is fed by an upper thread supply configured as a reel 12 and also called upper thread via a thread tensioning device and a thread rod 8, which thread tensioning device will be explained in more detail with reference to fig. 2 and the following. The needle thread 13 has a free upper thread starting section 13 a.

The base plate 2 carries a support plate 14 on which a piece of fabric 15 is placed, the support plate 14 being fastened by means of screws. A portion of the support plate 14 configured as a stitch plate 16 is provided with a recess that allows a lower feed dog 17 (also referred to as a drop feed) to pass through. The feeder dog tacker 17 has suture holes 18 that allow the needle 10 to pass through. The feeder dog 17 is in driving connection in a known manner with a sliding and lifting gear unit, which is arranged below the bottom plate 2.

Below the support plate 14, a ring former 19 is provided, which has a ring former body 21 with a ring former tip 21. In the looper body 21, a cup-shaped spool housing is mounted, which receives a looper thread supply in the form of a spool 22 or spool. The spool 22 is a supply of bobbin thread. The looper thread is also referred to as a bobbin thread.

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

The circulator 19 is rotatable about a vertical circulator axis 23 extending in the z-direction. The annulator body 20 is rigidly connected to a shaft 25 extending coaxially with the annulator axis 23. The shaft 25 is mounted for rotation in a bearing block 26 screwed to the base plate 2. In this bearing housing 26, a drive shaft 27 is mounted, which is connected to a toothed gear unit arranged within the bearing housing 26. The tooth gear unit has 1: 2, which means that the looper body 20 arranged on the shaft 25 rotates twice per revolution of the drive shaft 27. The drive shaft 27 is drivingly connected to the arm shaft 6 via a belt drive 28.

The thread tensioning device 29 in the I/II section of fig. 1 and 2, which is arranged on the housing part 30 of the arm 4, has a plurality of thread tensioning members which are arranged one after the other in the thread path of the upper thread 13. Seen along the thread path of the upper thread 13, after the reel 12 there is first a thread pretensioning device, not shown in detail, which is followed by a main thread pretensioning device 32. Depending on the design of the sewing machine 1, the thread pretensioning device can also be omitted.

The main thread tensioner 32 has a tension shaft 33 (see fig. 3), and the upper thread 13 to be tensioned is wound around the tension shaft 33. Two tensioning

units

34, 35, each configured to generate a wire tensioning action, interact with the tensioning shaft 33. Each of the

tension units

34, 35 serves to generate a line tension or a line tension effect of the upper thread 13 in the path of the upper thread 13 after the tension shaft 33. Depending on the design of the main thread tensioning device 32, it is also conceivable to provide precisely one tensioning cell, for example the tensioning cell 34, which is used to generate the thread tension.

Each of the

tensioning units

34, 35 is formed by a pair of pressure tensioning discs 36 and an actuator 37. The pressure-tensioning discs 36 of the respective pair of tensioning discs are arranged such that the upper thread 13 to be tensioned passes between the pair of tensioning discs 36. The respective pair of tension discs 36 interact with an actuator 37 to set a pressure between the tension discs 36. This effect of a pair of pressure-tensioning discs 36 and actuators 37 is known from the prior art and is described, for example, in DE 19633223C 2, in particular with reference to fig. 4.

The actuator 37 may be an electromagnet. The actuator 37 may also be a stepper motor.

Both tensioning

units

34, 35 interact with the same actuator 37. The two

tensioning units

34, 35 are arranged directly axially adjacent to one another on the tensioning shaft 33. Between the two tensioning

units

34, 35, a bearing disc 37a is arranged for those tensioning discs 36 of the two tensioning

units

34, 35 to bear against the tensioning disc 36 arranged directly axially adjacent to this bearing disc 37 a. Like the tension disc 36, a bearing disc 37a is fitted on the tension shaft 33 and serves to radially support the tension disc 36 facing the bearing disc 37 a. For this purpose, the bearing disc 37a has a circumferential bearing groove on either side, which engages with an edge portion of the respective tensioning disc 36 facing the bearing groove.

In addition to the two tensioning

units

34, 35, the main thread tensioning device has a thread path deflecting element 38 to deflect the thread path of the upper thread 13. This thread path of the upper thread 13 in the main thread tensioning device 32 is such that the upper thread 13 is first wound around the tensioning shaft 33 in the region of the first of the two tensioning

units

34, 35 to generate a first thread tensioning action of the tensioning shaft 33 and then, before being wound again around the tensioning shaft 33 in the region of the second of the two tensioning

units

34, 35, is passed over the thread path deflecting element 38 to generate a second thread tensioning action. This wire path in the main wire tensioner 32 may also be such that more than two wire tensioning actions are generated. In this case, there may be an additional line path above the same line path deflecting element 38 or above another line path deflecting element not shown, and then again around the tensioning shaft 33 to generate the next line tensioning action. For this purpose, the tensioning shaft 33 can carry a further tensioning unit configured in the manner of tensioning

units

34, 35, which is not shown in the figures.

The line path deflecting element 38 is configured as a deflecting pin. This type of deflector pin may be fixedly mounted to the housing portion 30 or, alternatively, may be configured so as to be rotatable about its pin axis. In this case, the pin is mounted in the housing part 30 in the manner of a roller via a radial bearing.

Alternatively, it is conceivable to design the

tensioning units

34, 35 as a respective pair of disc portions of a wheel-type tensioning disc. For example, a pair of disc portions of a wheeled tension disc 39 of this type, which may form one of the

tension units

34 or 35, is shown in fig. 6.

The two disc portions 39a of the wheel-type 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-type tension disk 39 has an approximately U-shaped or V-shaped groove profile in which the upper thread 13 is guided in an angular range of the circumference, for example, by winding it around the tension shaft 33 in a range of 360 °.

The outer contour of the pair of disc portions 39a of the wheel-type tension disc 39 is formed by two band rings 40, which each have a plurality of bands 41 bent axially outwards in the +/-x direction. The arrangement of the bands 41 of the two band rings 40 in the circumferential direction is such that the bands 41 are associated with one of the two band rings 40 and then with the other of the two band rings 40 in an alternating manner. The contour base of the groove contour is formed by the retaining portions 42 of the strip 41, which overlap one another in the x-direction. This ensures that the upper thread 13 extends at a precisely defined radius relative to the axis of the tension shaft 33 when wound around the pair of disc portions 39a of the tension disc 39.

The holding portion 42 may be configured as a tongue portion.

Whether or not the

tension units

34, 35 are configured as paired pressure tension discs 36 or paired disc portions 39a of the wheel type tension disc 39, at least one tension unit of the main line tension device 32 may be formed by at least one stepping motor that drives rotation of the tension shaft 33. Then, the tension shaft 33 may be directly configured as a motor shaft of this type of stepping motor, or the tension shaft may be connected to the motor shaft of the stepping motor via a gear unit. When the tension unit is configured as a stepping motor, the upper thread 13 may be completely wound on the tension shaft 33, particularly wound on the tension shaft 33 more than once.

As can be seen from fig. 2 to 5, the housing part 30 can be equipped with means which, by correspondingly guiding the upper thread 13, allow the formation of two main thread tensioners in the manner of the above-described main tensioner 32. In other words, as shown in these figures, the housing part 30 may carry two main line tensioners with associated tensioning shafts, associated actuators and associated tensioning units and associated line path deflecting elements.

The actuator 37 acts via the compression spring 34 on the

tensioning disc

36 or 39 of the

tensioning unit

34, 35, respectively. The compression spring 34 may be a coil spring, in particular a helical wire spring. This type of tensioning spring may also be omitted when using an actuator 37 configured as a torque-controlled servo motor or stepper motor.

In the embodiment of the

tensioning units

34, 35 with pressure tensioning discs 36, the line tension is generated by the pressure exerted on the line arranged therebetween by the actuator 37 between the respective tensioning discs 36. The tensioning disk 36 may be arranged non-rotatably on the tensioning shaft 33. In the embodiment with a disc portion 39a of the respective wheel-like tensioning disc 39, the tension is generated by the braking effect exerted by the pressure of the actuator 37 between the respective wheel-like tensioning disc 39, which rotates together with the wire wound thereon in its wire path, and the brake body, which in turn may be non-rotatably arranged with respect to the tensioning shaft 33. For example, the braking body may be a bearing disc 37 a.

In the thread path downstream of the main thread tensioning device 32, the upper thread 13 passes through the thread fastening spring 44 (see also fig. 1) to the eye of the needle 10 before extending via the thread lever 8.

Fig. 7 shows the wire path of the wire tensioning device 32. This figure shows one of the two wire tensioners 32 of the embodiment shown in figures 1 to 5. The wire path in the other wire tensioning device 32 then corresponds to it.

The needle thread 13 is first passed over a first pair 45 of pressure-tensioning disks 36 (first tensioning unit) from a thread pretensioning device, not shown in fig. 7. In doing so, the needle thread is wound more than 180 ° around the tensioning shaft 33 and may also be wound more than once completely around the tensioning shaft 33. In the illustrated embodiment, in the region of the first pair 45 of pressure-tensioning disks 36, the needle thread is wound around the tensioning shaft 33 over an angular range of approximately 270 °. When the needle thread is wrapped around the first pair 45, a first thread tension effect is generated on the sewing thread 13.

The needle thread 13 is then wound around the thread path deflecting element 38 with a contact angle of approximately 180 ° and around the tensioning shaft 33 in the same way as the first pair 45, before extending into the second pair 46 of pressure tensioning discs 36 (second tensioning unit) of the thread tensioning device 32. When the needle thread is wrapped around the second pair 46, a second thread tensioning action is generated on the sewing thread 13.

The needle thread 13 then extends to a thread tightening spring, not shown in fig. 7.

A first pair 45 of pressure tensioning discs 36 is arranged on the housing, while a second pair 46 is arranged towards the free end of the tensioning shaft 33.

In the embodiment shown in fig. 7, the compression spring 43 is configured as a wave spring. Corrugated spring blocks may also be used here.

The sewing thread 13 can be wound around the tensioning shaft 33 in the region of the

respective tensioning unit

45, 46 in the same rotational direction or in the opposite rotational direction. Depending on the type of thread and operating conditions, one of the two directions "same direction of rotation" or "opposite direction of rotation" may be more advantageous to avoid entanglement.

Claims

1. A thread tensioner (32) for a sewing machine having:

-at least one tensioning shaft (33) configured to allow a sewing thread (13) to be tensioned to wind around the tensioning shaft (33),

-at least one tensioning unit (34, 35) interacting with the tensioning shaft (33) to generate a thread tension in the path of the sewing thread (13) downstream of the tensioning shaft (33),

-a thread path deflecting element (38) to deflect the thread path of the sewing thread (13),

-wherein the thread path of the thread tensioning device (32) is such that the sewing thread (13)

-first wound around a tensioning shaft (33) to generate a first line tension effect,

then bypassing over the line path deflection element (38), an

-wrapping again around the tensioning shaft (33) to generate a second wire tensioning action.

2. The thread tensioning device according to claim 1, characterized in that the thread path deflecting element (38) is configured as a pin rotatable about a pin axis, the pin being configured to allow a sewing thread (13) to be wound around the pin.

3. Thread tensioning device according to claim 1, characterized in that the respective tensioning unit (34, 35) is formed by at least one pair of pressure tensioning discs (36) and at least one actuator (37), the pressure tensioning discs (36) being arranged in pairs such that the sewing thread (13) to be tensioned passes between the pressure tensioning discs (36), the pressure tensioning discs (36) interacting with the actuator (37) to set the pressure between the pressure tensioning discs (36).

4. Thread tensioning device according to claim 1, characterized in that the respective tensioning unit (34, 35) is formed by a wheel-type tensioning disc (39), a brake body (37a) and at least one actuator (37), which are arranged such that the sewing thread (13) to be tensioned passes between disc portions of the wheel-type tensioning disc (39), the wheel-type tensioning disc (39) interacting with the actuator (37) to set the pressure exerted by the brake body on the wheel-type tensioning disc (39).

5. The wire tensioning device according to claim 3 or 4, characterized in that the at least one actuator (37) is configured as a stepper motor.

6. The wire tensioning device according to claim 3, characterized by comprising at least two tensioning units (34, 35) arranged on a tensioning shaft (33), the tensioning units (34, 35) being configured to generate a respective wire tensioning action.

7. The wire tensioning device according to claim 1, characterized in that the tensioning unit is formed by at least one stepper motor, by which a tensioning shaft (33) is driven.

8. A sewing machine with a thread tensioning device (32) according to claim 1.