A method for controlling the tension of sewing machine thread

Abstract

This invention provides a method for controlling the tension of the sewing machine's top thread, comprising the following steps: during normal sewing, controlling the top thread tension within the normal tension range; during thread trimming, controlling the top thread tension within the low tension range; and after thread trimming, controlling the top thread tension back to the normal tension range. The advantage of this invention is that the drive mechanism controls the movement of the pull rod, allowing the top thread tension to fall within two different value ranges during thread trimming and normal sewing, meeting different needs. Compared to existing technologies that completely loosen the thread to remove tension during trimming, this invention maintains a small top thread tension during trimming and controls the length of the thread end obtained after trimming by changing the magnitude of the top thread tension. This eliminates the need for manual adjustment and testing, improving the machine's intelligence and digitalization level, and further enhancing the product's competitiveness.

Description

Technical Field

[0001] This invention relates to the field of sewing machine technology, and in particular to a method for controlling the tension of the sewing machine thread. Background Technology

[0002] When sewing fabric with a sewing machine, a certain length of thread needs to be left at the eye of the needle to ensure that the thread does not come out of the needle eye when starting to sew. Chinese utility model patent CN204738119U, entitled "Sewing Machine Bird's Nest Removal Device," discloses an arc-shaped swing hook thread clamping device, and a first thread clamp and a second thread clamp set on the thread passage of the sewing machine head. The first thread clamp includes an electromagnet base and a clamping plate, with the top thread passing between them; the second thread clamp includes a clamping plate with a variable-width clamping groove along its circumference. One end of the clamping plate is threadedly connected to a clamping adjustment bolt, which is fitted with a compression spring. The other end of the clamping plate is fixedly connected to a loosening rod, the end of which, away from the clamping plate, corresponds to the loosening electromagnet. The arc-shaped oscillating hook thread clamping device clamps the cut thread end of the needle. When starting to sew again, the timing of the two thread clamping devices is coordinated to provide a sufficiently stable amount of thread for starting sewing. The thread of the starting sewing surface is quickly tightened without the bobbin thread. The clamped thread end is cut off near the needle hole of the fabric, leaving a short thread end.

[0003] Currently, sewing machines equipped with this device energize the electromagnet of the first thread clamp during thread cutting, preventing it from providing thread tension. The length of the thread end remaining on the needle after cutting is entirely controlled by the thread tension provided by the second thread clamp. This is achieved by tightening or loosening the adjusting bolt in the second thread clamp, which changes the compression of the spring. A stronger spring force results in a shorter thread end on the needle after cutting, and vice versa. The entire process relies on manual adjustment of the adjusting bolt to ensure the thread end is at the appropriate length after each cut. This operation is complex, uncontrollable, and requires significant training and skilled workers. Furthermore, the thread passage hole positions and structure of this device are overly complex, significantly affecting the resistance of the thread and causing fluctuations, leading to inconsistent thread lengths on the needle after cutting. Summary of the Invention

[0004] To address the aforementioned shortcomings, this invention provides a sewing machine top thread tension control method, which can automatically adjust the appropriate top thread tension and thread end length according to the thickness of different sewing fabrics.

[0005] This invention provides a method for controlling the thread tension of a sewing machine. The sewing machine includes a mounting shaft fixed in the machine head. A pressure sleeve, a thread-clamping spring, a pressure plate, a first thread-clamping plate, and a second thread-clamping plate are sequentially mounted on the mounting shaft. The two ends of the thread-clamping spring abut against the pressure sleeve and the pressure plate, respectively. The pressure plate abuts against the first thread-clamping plate. A pull rod passes through the mounting shaft. The first end of the pull rod is connected to the pressure sleeve, and the second end is connected to a drive mechanism. The drive mechanism drives the pull rod to move, compressing the thread-clamping spring through the pressure sleeve. The thread-clamping spring acts on the pressure plate, causing the first and second thread-clamping plates to abut against each other, thereby changing the thread tension between the first and second thread-clamping plates. The thread tension range includes a low-tension range and a normal-tension range, with the thread tension in the low-tension range being less than that in the normal-tension range. The sewing machine thread tension control method includes the following steps:

[0006] During normal sewing, the tension of the thread is controlled to be within the normal tension range;

[0007] During thread cutting, the tension of the thread is controlled to be within the low tension range. After the thread cutting is completed, the tension of the thread is controlled to return to the normal tension range.

[0008] Preferably, the driving mechanism includes a motor, and the output shaft of the motor is connected to the pull rod for transmission; the rotation angle of the output shaft includes a first interval and a second interval, when the rotation angle is within the first interval, the surface tension is within the low tension interval; when the rotation angle is within the second interval, the surface tension is within the normal tension interval.

[0009] Preferably, it includes the following steps:

[0010] During normal sewing, the rotation angle of the output shaft is controlled to be within the second range;

[0011] During wire cutting, the output shaft is controlled to rotate into the first interval; after wire cutting is completed, the output shaft is controlled to rotate into the second interval.

[0012] Preferably, the output shaft of the motor is provided with a crank, the crank has a groove, and the second end of the pull rod is connected to a connecting pin, the connecting pin being disposed in the groove.

[0013] Preferably, the sewing machine head is provided with an upper thread hook, and the top thread passes sequentially through the upper thread hook, between the first thread clamping plate and the second thread clamping plate, and through the eye of the sewing machine needle.

[0014] Preferably, it further includes an adjusting seat and a protective cap fixed in the machine head, one end of the mounting shaft is fixed in the adjusting seat and the other end is fixed in the protective cap; the first clamping plate and the second clamping plate are located between the adjusting seat and the protective cap.

[0015] Preferably, the adjusting seat is further provided with a thread-taking spring and an adjusting component for adjusting the compression of the thread-taking spring, and the second clamping plate abuts against the thread-taking spring.

[0016] Preferably, it further includes a guide sleeve and an oil-proof sleeve fixed in the machine head, and a drive shaft is inserted through the guide sleeve and the oil-proof sleeve. The second end of the pull rod is connected to the drive mechanism through the drive shaft.

[0017] Preferably, the sewing machine is equipped with an electronic control module, which is communicatively connected to the drive mechanism.

[0018] The advantages of this invention lie in that the movement of the pull rod is controlled by a drive mechanism, allowing the thread tension to fall within two different value ranges during thread cutting and normal sewing, thus meeting different needs. Compared to existing technologies that completely loosen the thread to remove tension during cutting, this invention maintains a small thread tension during cutting and controls the length of the thread end after cutting by changing the magnitude of the thread tension. This eliminates the need for manual adjustment and testing, improving the machine's intelligence and digitalization, and further enhancing product competitiveness. Compared to existing sewing machines with two thread clamps, this invention improves the structure and position of the thread passage, requiring only one thread clamp and one upper thread hook. This reduces thread resistance fluctuations and makes the thread end length obtained after cutting more stable. Attached Figure Description

[0019] Figure 1 This is a perspective view of the sewing machine head of the present invention;

[0020] Figure 2 This is a schematic diagram of the wire clamp of the present invention;

[0021] Figure 3 It is a timing diagram of the motor;

[0022] Figure 4 This is a front view of the sewing machine head of the present invention.

[0023] Component designation explanation:

[0024] 1. Face line

[0025] 2. Wire clamp

[0026] 21 First clamping plate

[0027] 22 Second clamping plate

[0028] 23 Pressure Plate

[0029] 24 Wire spring

[0030] 25 pull rod

[0031] 26 mounting shafts

[0032] 27 Drive shaft

[0033] 271 Connecting pin

[0034] 281 Guide sleeve

[0035] 282 Oil-proof sleeve

[0036] 291 Adjustment seat

[0037] 292 Protective Helmet

[0038] 293 Pressure sleeve

[0039] 294 push plate

[0040] 295 Thread Take-up Spring

[0041] 3. Top line hook

[0042] 4. Machine head

[0043] 5. Drive mechanism

[0044] 6. Mounting bracket

[0045] 7. Crank

[0046] 71 Slide

[0047] 8 needles Detailed Implementation

[0048] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. These embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0049] In the description of this invention, it should be noted that the terms "upper," "lower," "front," "rear," "left," "right," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0050] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0051] Figure 1 The image shown is a perspective view of the sewing machine head of the present invention. In the following description, it will be referred to as... Figure 1 The attached diagram serves as a reference for orientation, defining the height direction of the machine head 4 as the up-down direction, with the drive mechanism 5 located above the needle 8; defining the length direction of the machine head 4 as the left-right direction, with the drive shaft 27 located to the left of the drive mechanism 5; and defining the width direction of the machine head 4 as the front-back direction, with the drive mechanism 5 located behind the machine head 4.

[0052] like Figure 1 and Figure 2 As shown, this invention employs a thread clamp 2, which is mounted on the sewing machine head 4. The thread clamp 2 includes a mounting shaft 26 fixed within the sewing machine head 4. From front to back, the mounting shaft 26 is movably fitted with a pressure sleeve 293, a thread clamping spring 24, a pressure plate 23, a first thread clamping plate 21, and a second thread clamping plate 22. All these components can move along the axial direction (i.e., the front-to-back direction) of the mounting shaft 26. The two ends of the thread clamping spring 24 abut against the pressure sleeve 293 and the pressure plate 23, respectively, while the pressure plate 23 abuts against the first thread clamping plate 21. A pull rod 25 also passes through the mounting shaft 26. The axial direction of the pull rod 25 is parallel to the axial direction of the mounting shaft 26. The first end (i.e., the front end) of the pull rod 25 is connected to the pressure sleeve 293, and the second end (i.e., the rear end) of the pull rod 25 is connected to the drive mechanism 5. The drive mechanism 5 drives the pull rod 25 to make linear displacement along its own axis, compressing the clamping spring 24 through the pressure sleeve 293. The clamping spring 24 acts on the pressure plate 23, causing the first clamping plate 21 and the second clamping plate 22 to abut against each other, thereby changing the tension of the surface thread between the first clamping plate 21 and the second clamping plate 22. The greater the compression of the clamping spring 24, the greater the pressure acting on the pressure plate 23, the greater the clamping force between the first clamping plate 21 and the second clamping plate 22, and the greater the tension of the surface thread passing through the surface thread between the first clamping plate 21 and the second clamping plate 22. The range of surface thread tension includes a low tension range and a normal tension range, with the surface thread tension in the low tension range being less than that in the normal tension range.

[0053] Based on the above-mentioned adjusting device, the present invention provides a sewing machine thread tension control method, comprising the following steps:

[0054] During normal sewing, the tension of the top thread is controlled within the normal tension range to provide the necessary tension for sewing.

[0055] When cutting the thread, the driving mechanism 5 drives the pull rod 25 to make a linear displacement along its own axis, controls the surface thread tension within the low-tension range, and makes the surface thread tension stable at a certain preset value within the low-tension range. Keeping a small surface thread tension during thread cutting helps to control the length of the thread end obtained after thread cutting. The greater the surface thread tension, the shorter the thread end left on the sewing needle after thread cutting, and vice versa. After the thread cutting is completed, the driving mechanism 5 drives the pull rod 25 to make a linear displacement along its own axis, and controls the surface thread tension to return to the normal tension range.

[0056] The structural form of the driving mechanism 5 is not limited, and it can be an electromagnet or a motor. When using an electromagnet, the iron core of the electromagnet is connected to the pull rod 25. By changing the magnitude of the current passed into the electromagnet, the pull rod 25 can be driven to move forward or backward by different distances, changing the compression amount of the thread clamping spring 24, and thus adjusting the magnitude of the surface thread tension.

[0057] As Figure 2 shown, in an embodiment of the present invention, the driving mechanism 5 includes a motor, and the output shaft of the motor is传动连接 with the pull rod 25 through a transmission mechanism. The transmission mechanism converts the rotational motion output by the motor into the linear motion of the pull rod 25. The motor is specifically a stepping motor. In this embodiment, different rotation angles of the output shaft correspond to different moving distances of the pull rod 25, and thus correspond to different surface thread tensions.

[0058] Combined with Figure 3 it can be known that the value range of the rotation angle of the output shaft includes a first interval and a second interval. When the rotation angle is within the first interval, the surface thread tension is within the low-tension range; when the rotation angle is within the second interval, the surface thread tension is within the normal tension range. Specifically, the rotation angle of the output shaft is θ, the first interval is 0°≤θ<A, and the second interval is A≤θ≤X. The method for controlling the surface thread tension of the sewing machine in this embodiment correspondingly includes the following steps:

[0059] During normal sewing, control the rotation angle of the output shaft to be within the second interval to provide the surface thread tension required for sewing for the surface thread;

[0060] When cutting the thread, control the output shaft to rotate to the first interval. The rotation angle of the output shaft can be adjusted within the first interval according to the different required thread end lengths. The greater the rotation angle of the output shaft within the first interval, the shorter the thread end left on the sewing needle after thread cutting, and vice versa. After the thread cutting is completed, control the output shaft to rotate to the second interval to make the surface thread maintain the surface thread tension required for normal sewing.

[0061] Transmission mechanisms come in various forms. One type includes a crank 7 mounted on the motor output shaft, with a groove 71 on the crank 7. The second end of a pull rod 25 is connected to a connecting pin 271, which is located within the groove 71. Through the cooperation of the groove 71 and the connecting pin 271, the rotational motion output by the motor can be converted into linear motion of the pull rod 25. Another type of transmission mechanism includes a ball screw coaxially connected to the motor output shaft, with a slider on the ball screw. The second end of the pull rod 25 is connected to the slider. The ball screw can convert its own rotational motion into linear motion of the slider and the pull rod 25. Those skilled in the art can also select other types of transmission mechanisms as needed.

[0062] Furthermore, the sewing machine is equipped with an electronic control module, which is connected to the drive mechanism 5. The electronic control module controls the drive mechanism 5 according to the required thread length parameters to adjust the tension of the opposite thread. There is no need for manual adjustment and testing; the working parameters can be directly adjusted and stored digitally.

[0063] like Figure 2 As shown, the wire clamp 2 also includes an adjusting seat 291 and a protective cap 292 fixed in the head 4. One end of the mounting shaft 26 is fixed in the adjusting seat 291, and the other end is fixed in the protective cap 292. The first wire clamping plate 21 and the second wire clamping plate 22 are located between the adjusting seat 291 and the protective cap 292. The adjusting seat 291 is provided with a wire take-up spring 295, and the second wire clamping plate 22 abuts against the front end of the wire take-up spring 295. Those skilled in the art can change the compression of the wire take-up spring 295 by adjusting the adjusting component (such as a knob) provided in the adjusting seat 291, thereby adjusting the clamping force between the first wire clamping plate 21 and the second wire clamping plate 22. The first wire clamping plate 21 can only move between the second wire clamping plate 22 and the protective cap 292. The pressure sleeve 293, the wire clamping spring 24, and the pressure plate 23 are all located inside the protective cap 292. The protective cap 292 can provide protection and prevent external dust and impurities from affecting the normal operation of the wire tension adjusting device. A long groove extending axially is also provided on the side wall of the mounting shaft 26. A push plate 294 is provided in the long groove, and the pull rod 25 is fixedly connected to the pressure sleeve 293 through the push plate 294. When the pull rod 25 makes linear displacement within the mounting shaft 26, the push plate 294 moves linearly in the long groove along with the pull rod 25, pushing the pressure sleeve 293 to compress the clamping spring 24.

[0064] Furthermore, the wire clamp 2 also includes a guide sleeve 281 and an oil-proof sleeve 282 fixed in the head 4. A drive shaft 27 is movably inserted through the guide sleeve 281 and the oil-proof sleeve 282. One end of the drive shaft 27 has a pin hole, and a connecting pin 271 is inserted into the pin hole via a snap ring. The other end of the drive shaft 27 is threadedly connected to the second end of the pull rod 25. Both the guide sleeve 281 and the oil-proof sleeve 282 can limit and guide the drive shaft 27, restricting it to linear displacement only in the forward and backward direction. At the same time, the oil-proof sleeve 282 can also prevent oil inside the head 4 from leaking out.

[0065] like Figure 4 As shown, in the sewing machine of the present invention, the sewing head 4 is further provided with an upper thread hook 3. The top thread 1 passes sequentially through the upper thread hook 3, between the first thread clamping plate 21 and the second thread clamping plate 22, and through the eye of the needle 8. The upper thread hook 3 replaces the first thread clamp in the prior art, and it does not need to provide tension for the top thread, but only serves to guide the thread. This sewing machine simplifies the structure and position of the thread passage hole, reduces the resistance caused by the overall structure when the top thread passes through, and can make the thread length obtained by cutting more stable.

[0066] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and substitutions can be made without departing from the technical principles of the present invention, and these improvements and substitutions should also be considered within the scope of protection of the present invention.

Claims

1. A method for controlling the tension of the thread in a sewing machine, used in a sewing machine, the sewing machine comprising a mounting shaft fixed in the machine head, wherein a pressure sleeve, a thread clamping spring, a pressure plate, a first thread clamping plate, and a second thread clamping plate are sequentially sleeved on the mounting shaft, the two ends of the thread clamping spring respectively abutting against the pressure sleeve and the pressure plate, and the pressure plate abutting against the first thread clamping plate; characterized in that: A pull rod is also inserted through the mounting shaft. The side wall of the mounting shaft is provided with a long groove extending along its own axial direction. A push plate is provided in the long groove. The first end of the pull rod is connected to the pressure sleeve, and the second end of the pull rod is connected to the drive mechanism. A guide sleeve and an oil-proof sleeve are fixedly installed in the machine head. A drive shaft passes through the guide sleeve and the oil-proof sleeve. The second end of the pull rod is connected to the drive mechanism through the drive shaft. The oil-proof sleeve is used to seal and prevent oil from seeping out of the machine head, and the guide sleeve is used to limit the drive shaft to only make linear displacement. The driving mechanism is a stepper motor. The output shaft of the stepper motor is provided with a crank, and the crank has a groove. The rear end of the drive shaft is provided with a connecting pin, which is disposed in the groove to convert the rotational motion of the stepper motor into the linear displacement of the drive shaft. The stepper motor drives the pull rod to move, compressing the wire clamping spring through the pressure sleeve. The wire clamping spring acts on the pressure plate, causing the first and second wire clamping plates to abut against each other, thereby changing the thread tension between the first and second wire clamping plates. The sewing machine thread tension control method includes the following steps: The output shaft rotation angle of the stepper motor A one-to-one mapping relationship is established with the surface tension; the value range of the surface tension includes a low tension range and a normal tension range, and the surface tension in the low tension range is less than the surface tension in the normal tension range. During normal sewing, the output shaft rotation angle of the stepper motor is controlled to be in the second range. This ensures that the tension of the surface line is within the normal tension range; When cutting the wire, the output shaft angle of the stepper motor is controlled to be within the first range. This ensures that the tension of the surface thread is within the low tension range, and the angle is adjusted within the first range according to the required thread length via the electronic control module. After the thread is cut, the tension of the thread is controlled to return to the normal tension range.

2. The sewing machine thread tension control method according to claim 1, characterized in that, The second end of the pull rod is connected to the connecting pin.

3. The sewing machine thread tension control method according to claim 1, characterized in that, The machine head is equipped with an upper thread hook, and the top thread passes through the upper thread hook, between the first thread clamping plate and the second thread clamping plate, and through the eye of the sewing machine needle in sequence.

4. The sewing machine thread tension control method according to claim 1, characterized in that, It also includes an adjusting seat and a protective cap fixed in the machine head, with one end of the mounting shaft fixed in the adjusting seat and the other end fixed in the protective cap; the first wire clamping plate and the second wire clamping plate are located between the adjusting seat and the protective cap.

5. The sewing machine thread tension control method according to claim 4, characterized in that, The adjusting seat is also provided with a take-up spring and an adjusting component for adjusting the compression of the take-up spring, and the second clamping plate abuts against the take-up spring.

6. The sewing machine thread tension control method according to claim 1, characterized in that, The sewing machine is equipped with an electronic control module, which is communicatively connected to the drive mechanism.

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