Method for improving seam starting quality of sewing machine

Abstract

The present invention relates to a method for improving the seam start quality of a sewing machine, including a seam start control method, wherein the seam start control method comprises the following steps: S1, before seam start, the thread trimming action has been completed, and the thread take-up lever is located at an initial position of 0.9H to H height; S2, the electronic thread clamp releases the upper thread, the thread take-up lever first moves upward and then downward to release the thread, the machine needle moves downward, and a part of the upper thread end is brought under the needle plate, and when the thread take-up lever reaches a first height position of h1 from its lowest position, h1=0.45H to 0.5 5H, the electronic thread clamp clamps the upper thread; S3, the rotary hook rotates, the thread hooking structure hooks the upper thread end, and further brings the upper thread end under the needle plate, while the thread take-up rod continues to descend from the first height position to the lowest position, and then ascends; S4, when the thread take-up rod ascends and reaches the second height position with a height h2 from its lowest position, h2 = 0.10H ~ 0.15H, the electronic thread clamp releases the upper thread; the thread take-up rod continues to ascend to pull the upper thread for winding, and the upper thread loop enlarged by the rotary hook is tightened and recovered.

Description

Technical Field

[0001] The present invention relates to the technical field of sewing machines, and in particular to a method for improving the seam starting quality of a sewing machine. Background Art

[0002] A sewing machine is a machine that uses one or more sewing threads to form one or more stitches on fabric, interweaving or sewing one or more layers of fabric. A sewing machine is usually composed of a feeder, a base, a transmission, and accessories. Through the reasonable coordination of the movements of each mechanism and the cycle of work, the sewing material is sewn together. Figure 3 As shown, the upper head of the sewing machine is equipped with a thread clamp 11, an electronic thread clamp 13, a thread take-up lever 12, and a needle 7. The upper thread 3 passes through the thread clamp 11, the thread take-up lever 12, the electronic thread clamp 13, and then passes through the needle 7. The thread clamp 11 holds the upper thread 3 and allows it to move. The electronic thread clamp 13 can clamp and release. The thread take-up lever 12 moves up and down to pay out and take up the thread.

[0003] At present, during the thread trimming process of the sewing machine, the thread trimmer will insert the upper thread loop through the thread dividing portion on the movable knife and expand the thread loop. In this way, after the thread trimming, a certain length of upper thread end will be left on the needle 7. In the subsequent seam starting process, the control system controls the electronic thread clamp 13 to bring the remaining upper thread end into the back of the sewing material and repeatedly entangle it in the first few stitches to form a ball-shaped bird's nest. In the existing seam starting process, due to factors such as control timing and unstable response delay of the electronic thread clamp process, the thread take-up lever 12 does not strictly control the coordinated action of the electronic thread clamp 13 during the process of retracting and releasing the upper thread 3. The electronic thread clamp 13 will not be released at the right time during the thread release process of the thread take-up lever 12, and the electronic thread clamp 13 will still keep the upper thread 3 clamped and tightened during the thread retraction process of the thread take-up lever 12, so that the thread end brought into the enlarged thread loop of the rotary hook below the sewing material cannot be retracted, increasing the ball-shaped bird's nest at the seam starting point of the sewing material, thereby affecting the quality of the sewn product.

[0004] On the other hand, in the existing design, see the attached Figure 2 and Figure 3 As shown, when cutting the thread, a dividing tip 52 is provided on the second thread cutting knife 5 (movable knife), and the right side of the dividing tip 52 has a dividing side edge 521 extending to the right. When cutting the thread, the dividing tip 52 is inserted into the thread loop of the upper thread 3 to separate it. The upper thread loop includes three parts: the needle edge thread 32, the cloth edge thread 31, and the connecting line 33 between the needle edge thread needle 32 and the cloth edge thread 31. The needle edge thread 32 moves to the right along the dividing side edge 521, and the needle edge thread 32 and the cloth edge thread 31 are separated, which will expand the upper thread loop, thereby increasing the length of the upper thread loop, and a certain length of upper thread end (35-45mm) will be left. The length of the upper thread end is relatively large, and the longer and thicker the residue is, the smaller the stitch length is, and the larger the ball-shaped bird's nest is, which will further affect the quality of the sewn product. Summary of the Invention

[0005] In view of the shortcomings of the prior art mentioned above, the technical problem to be solved by the present invention is to provide a method for improving the seam start quality of a sewing machine. By controlling the action timing of the electronic thread clamp and the thread take-up rod, the bird's nest thread end effect at the start of seam can be effectively reduced, thereby improving the sewing quality of sewn products.

[0006] To achieve the above-mentioned object, the present invention provides a method for improving the seam start quality of a sewing machine, wherein the sewing machine includes a rotary hook, a thread trimming mechanism, a needle plate, a needle, a thread clamp, a thread take-up lever, an electronic thread clamp, and an upper thread, wherein the upper thread passes through the thread clamp, the thread take-up lever, the electronic thread clamp, and the needle in sequence, and the height between the highest position of the thread take-up lever and the lowest position is H. The improving method includes a seam start control method, wherein the seam start control method includes the following steps:

[0007] S1, before starting to sew, the thread trimming action has been completed, the thread take-up lever is at the initial position, and the height of the initial position from its lowest position is h0 = 0.9H ~ H;

[0008] S2: The electronic thread clamp releases the upper thread, first ascends to the highest position, then descends to release the thread. The needle descends, bringing part of the upper thread end under the needle plate. When the thread take-up lever reaches the first height position of h1 from its lowest position, h1 = 0.65H ~ 0.75H, the electronic thread clamp clamps the upper thread, and the needle switches from the downward state to the upward state.

[0009] S3: The rotary hook rotates, and the thread hook structure on it hooks the upper thread end and further brings the upper thread end under the needle plate. At the same time, the thread take-up rod continues to descend from the first height position to the lowest position, and then ascends;

[0010] S4. When the thread take-up rod moves upward to the second height position h2 from its lowest position, h2 = 0.13H ~ 0.17H, the electronic thread clamp releases the upper thread, and the needle is in the upward state; the thread take-up rod continues to move upward to pull the upper thread for thread rewinding, and during the thread rewinding process, the upper thread loop expanded by the hook structure is tightened and retracted.

[0011] Furthermore, the movement of the needle and the thread take-up rod is driven by the main shaft of the sewing machine, and the sewing machine also includes a control system, which can control the rotation of the main shaft and the loosening and clamping of the electronic thread clamp. The seam start control method also includes: determining the corresponding rotation angle position of the main shaft when the thread take-up rod is at the first height position and the second height position, which are respectively recorded as the first angle position and the second angle position. In step S2, when the control system controls the main shaft to rotate to the first angle position, the electronic thread clamp is controlled to automatically clamp the surface thread; in step S4, when the control system controls the main shaft to rotate to the second angle position, the electronic thread clamp is controlled to automatically loosen the surface thread.

[0012] Furthermore, it also includes a thread cutting method performed before the seam starting control method, the thread cutting method is performed by a thread cutting mechanism, the thread cutting mechanism includes a first thread cutting knife and a second thread cutting knife, the first thread cutting knife is provided with a first cutting edge, the second thread cutting knife is provided with a second cutting edge and a thread dividing tip for inserting into the upper thread loop, the right side of the thread dividing tip has a thread dividing side, the second thread cutting knife can be rotated relative to the first thread cutting knife until the second cutting edge engages with or separates from the first cutting edge, the right side of the thread dividing tip is provided with a V-shaped positioning notch located at the right end side of the thread dividing side, and the left side of the V-shaped positioning notch is connected with the thread dividing side; the thread cutting method includes the following steps: the second thread cutting knife rotates toward the first thread cutting knife, the thread dividing tip enters the upper thread loop, the needle edge thread in the upper thread loop moves to the right along the thread dividing side, enters the V-shaped positioning notch, and reaches the bottom of the V-shaped positioning notch; then the second cutting edge engages with the first cutting edge to cut the thread.

[0013] Furthermore, in the thread trimming method, when the first thread trimmer and the second thread trimmer of the thread trimming mechanism are engaged in the thread trimming state, the distance between the bottom of the V-shaped positioning notch and the needle axis of the sewing machine in the left and right directions and the front and back directions are X and Y respectively, X is 6.5 to 8 mm, and Y is 10 to 12 mm.

[0014] Furthermore, in the thread trimming method, when the first thread trimmer and the second thread trimmer of the thread trimming mechanism are in the engaged thread trimming state, the angle θ between the plane formed by the bottom of the V-shaped positioning notch and the needle axis of the sewing machine and the plane passing through the needle axis and perpendicular to the left and right directions is 33 to 41°.

[0015] Furthermore, in the thread trimming method, the second thread trimmer is arc-shaped and coaxially arranged on the outer peripheral side of the rotary hook, and the second cutting edge is located on the outer arc surface of the second thread trimmer.

[0016] Furthermore, in the thread trimming method, a protruding bulge is provided on the outer arc surface of the second thread trimmer, a through hole is provided on the bulge, the edge of the through hole constitutes a second cutting edge, and when the second thread trimmer and the first thread trimmer are engaged in the thread trimming state, the through hole and the sewing machine needle remain coaxial.

[0017] Furthermore, in the wire cutting method, the second wire cutting knife is provided with a wire cutting hook, and the outer arc surface of the second wire cutting knife is further provided with a wire receiving groove connecting the through hole and the wire cutting hook.

[0018] Furthermore, in the thread trimming method, the first thread trimmer is fixed, and the second thread trimmer can rotate around the rotary hook to engage with or separate from the first thread trimmer.

[0019] As described above, the method for improving the seam start quality of a sewing machine according to the present invention has the following beneficial effects:

[0020] By setting a seam start control method, by controlling the timing of the electronic thread clamp's action at the start of the seam, and coordinating the action and position of the thread take-up lever, the bird's nest thread end effect at the start of the seam can be effectively reduced, thereby improving the sewing quality of sewn products. At the same time, by setting a thread trimming method, a special thread trimming mechanism is designed for thread trimming, and a V-shaped positioning notch is provided on the right side of the dividing tip of the second thread trimmer. When trimming the thread, the bottom of the V-shaped positioning notch will limit the position of the needle edge line, thereby reducing the length of the upper thread loop during occlusal thread trimming, and the length can be kept stable and controllable. The length of the upper thread end formed after the thread trimming is completed is shorter, reducing the bird's nest formed at the start of the seam, and ensuring the quality of the sewn product. By combining the above-mentioned thread trimming method and the seam start control method, the effect of reducing the bird's nest thread end at the start of the seam is achieved from two aspects, thereby improving the sewing quality of sewn products. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a structural diagram of the thread cutting mechanism in the prior art.

[0022] Figure 2 The figure is a schematic structural diagram of a second thread trimmer in a thread trimming mechanism in the prior art.

[0023] Figure 3 This is a schematic diagram of the upper thread in a sewing machine passing through the thread tensioner, thread take-up lever, electronic thread tensioner and needle.

[0024] Figure 4 It is a flow chart of the seam start control method in the thread trimming mechanism of the present invention.

[0025] Figure 5 Schematic diagram of the structure of the second thread cutter in the thread cutting mechanism of the present invention.

[0026] Figure 6 It is a structural schematic diagram of the thread cutting mechanism of the present invention.

[0027] Explanation of Figure Numbers

[0028] 1 bottom plate

[0029] 2 needle bars

[0030] 3. Noodles

[0031] 31 Selvedge

[0032] 32 stitches

[0033] 33 connecting wires

[0034] 4. First Thread Cutter

[0035] 41 First cutting edge

[0036] 5. Second Thread Cutter

[0037] 51 Second cutting edge

[0038] 52 branch line tip

[0039] 521 branch line side

[0040] 53 V-shaped positioning notch

[0041] 531 slot bottom

[0042] 54 Thread trimmer hook

[0043] 55 Wire duct

[0044] 56 Drum

[0045] 57 through holes

[0046] 6. Bottom Line

[0047] 7 Needle

[0048] 8-wire breakout board

[0049] 9 needle plate

[0050] 10 Upper head

[0051] 11 Thread clamp

[0052] 12 thread take-up lever

[0053] 13 Electronic thread clamp DETAILED DESCRIPTION

[0054] The following describes the implementation of the present invention through specific embodiments. People skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification.

[0055] It should be noted that the structures, proportions, sizes, etc. depicted in the drawings of this specification are only used to match the contents disclosed in the specification for people familiar with this technology to understand and read, and are not used to limit the conditions for the implementation of the present invention. Therefore, they have no substantial technical significance. Any modification of the structure, change in the proportional relationship, or adjustment of the size should still fall within the scope of the technical content disclosed by the present invention without affecting the efficacy and purpose of the present invention. At the same time, the terms such as "upper", "lower", "left", "right", "middle", etc. quoted in this specification are only for the convenience of description and are not used to limit the scope of the implementation of the present invention. Changes or adjustments in their relative relationships should also be regarded as the scope of the implementation of the present invention without substantially changing the technical content.

[0056] See also Figures 3 to 6The present invention provides a method for improving the seam quality of a sewing machine, wherein the sewing machine includes a rotary hook, a thread trimming mechanism, a needle plate 9, a needle 7, a thread clamp 11, a thread take-up lever 12, an electronic thread clamp 13 and an upper thread 3. Figure 3 , where the needle 7, thread clamp 11, thread take-up lever 12, and electronic thread clamp 13 are all installed on the upper head 10 on the bottom plate 1 of the sewing machine, and the needle plate 9 is installed on the bottom plate 1 and is located below the needle 7. The upper thread 3 passes through the thread clamp 11, thread take-up lever 12, electronic thread clamp 13 and needle 7 in sequence. The height of the highest position of the thread take-up lever 12 from the lowest position is H. The electronic thread clamp 13 can clamp or loosen the upper thread 3. The thread clamp 11 is used to clamp and stabilize the upper thread 3, and can apply a certain pressure to the upper thread 3. When the upper thread 3 is subjected to a certain tension, it can move in the thread clamp 11.

[0057] The lifting method of the present invention includes a seam start control method, wherein the seam start control method includes the following steps:

[0058] S1. Before sewing, the thread trimming action has been completed. At the initial position, the height of the initial position from the lowest position is h0 = 0.9H~H. At this time, a certain length of the upper thread 3 is formed under the needle 7.

[0059] S2. The electronic thread clamp 13 releases the upper thread 3. The thread take-up lever 12 first ascends to its highest position and then descends to release the thread. The needle 7 descends, bringing part of the upper thread 3 under the needle plate 9. When the thread take-up lever 12 reaches a first height position of h1 from its lowest position, where h1 = 0.65H to 0.75H, the electronic thread clamp 13 clamps the upper thread 3. At this time, the needle 7 transitions from its downward movement to an upward position, meaning it has passed its lowest point. The purpose of this step is to release the thread, allowing the upper thread 3 of appropriate length to be located below the needle plate 9 for subsequent hook hooking.

[0060] S3, the rotary hook rotates, and the thread hooking structure on it hooks the upper thread 3 end located below the needle plate 9, and further brings the upper thread 3 end under the needle plate 9, so that the entire upper thread 3 end is located below the needle plate 9, and at the same time the thread take-up rod 12 continues to descend from the first height position to the lowest position, and then ascends. In this step, the electronic thread clamp 13 remains clamped, so when the thread hooking structure hooks the upper thread 3 end and rotates, the upper thread 3 above the electronic thread clamp 13 will not be pulled down further, while the upper thread 3 below the electronic thread clamp 13 can be smoothly pulled by the thread hooking structure, thereby ensuring that the entire upper thread 3 end is located below the needle plate 9 and its length is controlled within the range.

[0061] S4. When the thread take-up rod 12 moves upward to reach the second height position with a height of h2 from its lowest position, h2=0.13H~0.17H, the electronic thread clamp 13 releases the upper thread 3, and the needle 7 is in an upward state; the thread take-up rod 12 continues to move upward to pull the upper thread 3 for thread winding, and during the thread winding process, the upper thread 3 loop expanded by the hook structure of the rotary shuttle is tightened and recovered. At this time, since the electronic thread clamp 13 is in a loose state, the thread take-up rod 12 will draw out the upper thread 3 on the side of the needle 7 during the thread winding process, that is, the upper thread 3 loop will be tightened and recovered, and the upper thread 3 on the side of the thread clamp 11 will not be drawn out, thereby avoiding extending the thread end of the upper thread 3 and increasing the size of the bird's nest thread ball for sewing.

[0062] In this embodiment, as a preferred design, the movement of the needle 7 and the thread take-up lever 12 is driven by the main shaft of the sewing machine. When the main shaft rotates, the needle 7 and the thread take-up lever 12 are driven to reciprocate through the corresponding transmission mechanism. The sewing machine also includes a control system that can control the rotation of the main shaft and the loosening and clamping of the electronic thread clamp 13. The seam start control method also includes: determining the corresponding rotation angle position of the main shaft when the thread take-up lever 12 is at the first height position and the second height position, respectively recorded as the first angle position and the second angle position. In step S2, when the control system controls the main shaft to rotate to the first angle position, the electronic thread clamp 13 is controlled to automatically clamp the upper thread 3; in step S4, when the control system controls the main shaft to rotate to the second angle position, the electronic thread clamp 13 is controlled to automatically loosen the upper thread 3. That is, by controlling the rotation angle position of the main shaft, the action timing of the thread take-up lever 12 and the electronic thread clamp 13 is determined, which facilitates positioning and enables automatic control.

[0063] The seam start control method of the present invention can effectively reduce the bird's nest thread end effect when starting the seam and improve the sewing quality of sewn products by controlling the action timing of the electronic thread clamp 13 and coordinating the action and position of the thread take-up lever 12.

[0064] The lifting method of the present invention also includes a thread trimming method, which is performed before the seam starting control method. The thread trimming method is performed using a thread trimming mechanism. Figure 5 and Figure 6The thread trimming mechanism is arranged at the rotary hook of the sewing machine. In the sewing machine, the axis of the rotary hook is along the left-right direction, the side where the rotary hook is located is the left side of the sewing machine, and is located below the needle 7. The thread trimming mechanism includes a first thread trimmer 4 and a second thread trimmer 5. The first thread trimmer 4 is provided with a first cutting edge 41, and the second thread trimmer 5 is provided with a second cutting edge 51 and a wire dividing tip 52 for inserting into the upper thread loop. The right side of the wire dividing tip 52 has a wire dividing side edge 521. The second thread trimmer 5 is also provided with a thread trimming hook 54 for hooking the bottom thread 6 and the edge thread 32 in the upper thread 3 and moving toward the first thread trimmer 4. The thread trimming hook 54 and the wire dividing tip 52 share a side edge. The second thread trimmer 5 can rotate relative to the first thread trimmer 4 until the second cutting edge 51 is engaged with or separated from the first cutting edge 41. In the present invention, a V-shaped positioning groove 53 is further provided on the right side of the dividing line tip 52, which is located on the right end side of the dividing line side 521, and the left side of the V-shaped positioning groove 53 is connected with the dividing line side 521, so that the fabric edge line 31 can smoothly enter the V-shaped positioning groove 53 from the dividing line side 521.

[0065] The thread trimming method using the thread trimming mechanism is as follows: Figure 5 and Figure 6 When the thread needs to be trimmed, the second thread trimmer 5 rotates toward the first thread trimmer 4. When the second thread trimmer 5 rotates, the dividing tip 52 enters the upper thread loop, and the needle edge thread 32 moves to the right along the dividing side 521 and enters the V-shaped positioning notch 53. It reaches the bottom 531 of the V-shaped positioning notch 53 and is restricted at the bottom 531 and no longer moves. The selvedge thread 31 then enters the thread trimming hook 54. The thread trimming hook 54 hooks the bottom thread 6 and the selvedge thread 31, and drives the bottom thread 6 and the selvedge thread 31 closer to the first thread trimmer 4, and then engages with the first thread trimmer 4 to cut the thread. During the engaged thread trimming, the needle edge thread 32 is restricted in position by being located in the bottom 531 of the V-shaped positioning notch 53. Therefore, the length of the upper thread loop can remain stable during the engaged thread trimming. Figure 6 As shown, the needle thread 32 and the selvedge thread 31 are now separated, with a certain distance between them. When the first and second cutting edges 41 and 51 cut the selvedge thread 31, they can avoid cutting the needle thread 32. At the same time, compared with existing designs, the length of the upper thread loop is shorter and can be kept stable and controllable. After the thread is cut, the length of the upper thread end formed is shorter, which reduces the bird's nest formed when sewing, thereby ensuring the quality of the sewn product.

[0066] In this embodiment, see Figure 5 and Figure 6The position and depth of the V-shaped positioning notch 53 can be set according to actual thread trimming needs. As a preferred design, when the first and second thread trimmers 4 and 5 are engaged, the distances between the bottom 531 of the V-shaped positioning notch 53 and the sewing machine needle 7 in the left-right and front-back directions are X and Y, respectively, with X ranging from 6.5 to 8 mm and Y ranging from 10 to 12 mm. By setting appropriate values ​​for X and Y, the length of the upper thread loop during engagement can be controlled. Preferably, when the first and second thread trimmers 4 and 5 are engaged, the angle θ between the plane formed by the bottom 531 of the V-shaped positioning notch 53 and the axis of the sewing machine needle 7 and a plane passing through the axis of the needle 7 and perpendicular to the left-right direction is 33 to 41°. The value of θ can be determined by setting the ratio of X to Y. Specifically, X / Y is 0.54 to 0.8. The size of the angle θ can determine the distance between the needle edge thread 32 and the cloth edge thread 31 during thread biting and cutting, so that it is within a suitable range, which helps the needle edge thread 32 avoid the first cutting edge 41 and the second cutting edge 51 and prevent the needle edge thread 32 from being cut.

[0067] In this embodiment, see Figure 5 and Figure 6 As a preferred design, the second thread trimmer 5 is arc-shaped and coaxially positioned on the outer periphery of the rotary hook, maintaining a certain spacing so that the rotary hook does not contact the second thread trimmer 5 during operation. The second cutting edge 51 is located on the outer arc surface of the second thread trimmer 5, and the needle edge 32 is located above the outer arc surface during thread trimming. The first thread trimmer 4 is a fixed blade, stationary and located near the front. The needle 7 is located at the lower end of the needle bar 2. The first cutting edge 41 is located near the needle 7 and below the needle plate 9 hole in the needle plate 9. The second thread trimmer 5 is a movable blade, located behind the first thread trimmer 5. Driven by a corresponding drive mechanism, the second thread trimmer 5 can rotate backward around the rotary hook to engage or disengage with the first thread trimmer 4. Of course, in other embodiments, the second thread trimmer 5 can be located at the rear and the first thread trimmer 4 can be located at the front when not trimming the thread. Alternatively, the first thread trimmer 4 can be a movable blade, capable of rotating toward the second thread trimmer 5.

[0068] In this embodiment, see Figure 5 and Figure 6As a preferred design, the outer curved surface of the second thread trimmer 5 is provided with a protruding bulge 56, and a through hole 57 is provided in the bulge 56. The edge of the through hole 57 constitutes the second cutting edge 51. When engaging the thread, the outer curved surface of the second thread trimmer 5 is inserted into the lower side surface of the first thread trimmer 4 (i.e., the side facing the rotary hook). The second cutting edge 51 on the bulge 56 contacts and engages with the first cutting edge 41, stably shearing the selvedge thread 31 and the bottom thread 6. At this time, the through hole 57 remains coaxial with the sewing machine needle 7, allowing the needle 7 to pass through. In this way, when machining the V-shaped positioning notch 53 on the second thread trimmer 5, the V-shaped positioning notch 53 is determined by the aforementioned distance X, distance Y, and angle θ. At this time, the reference point can be selected at the axis center of the through hole 57 to facilitate machining and positioning.

[0069] In this embodiment, see Figure 5 and Figure 6 The outer arc surface of the second thread trimmer 5 is also provided with a thread accommodating groove 55 connecting the through hole 57 and the thread trimming hook 54. When the thread is engaged and trimmed, the edge thread 31 and the bottom thread 6 are located in the thread accommodating groove 55, thereby stabilizing the positions of the edge thread 31 and the bottom thread 6.

[0070] In this embodiment, see Figure 5 and Figure 6 The thread trimming mechanism also includes a wire dividing piece 8, which is also an arc-shaped structure and is arranged below the second thread trimmer 5, that is, on the side of the second thread trimmer 5 close to the rotary hook. When trimming the thread, the second thread trimmer 5 is inserted above the wire dividing piece 8, and the wire dividing piece 8 is used to better separate the upper thread loops.

[0071] The method for improving the seam starting quality of a sewing machine of the present invention has the following beneficial effects:

[0072] 1. By setting the seam start control method, the timing of the electronic thread clamp 13 is controlled during the seam start, and the action and position of the thread take-up lever 12 are coordinated to effectively reduce the bird's nest thread end effect during the seam start, thereby improving the sewing quality of sewn products.

[0073] 2. By setting a thread cutting method, a special thread cutting mechanism is designed to cut the thread. A V-shaped positioning notch 53 is set on the right side of the dividing tip 52 of the second thread cutting knife 5. When cutting the thread, the position of the needle edge thread 32 will be limited by the bottom 531 of the V-shaped positioning notch 53. On the one hand, the needle edge thread 32 and the cloth edge thread 31 are separated by a certain distance during the bite thread cutting, thereby avoiding the first cutting edge 41 and the second cutting edge 51 from contacting the needle edge thread 32 and avoiding cutting the needle edge thread 32. On the other hand, compared with the existing design, the length of the upper thread loop during the bite thread cutting can be reduced, and the length can be kept stable and controllable. The length of the upper thread end formed after the thread cutting is completed is shorter, reducing the bird's nest formed when sewing, and ensuring the quality of the sewn product. By setting the position of the bottom 531 of the V-shaped positioning notch 53, it is convenient to control the length of the upper thread loop during the bite thread cutting. The thread cutting mechanism has a simple structure and can be improved on the existing thread cutting mechanism, and the cost is low.

[0074] 3. By combining the thread cutting method with the seam start control method, the effect of reducing the seam start bird's nest thread ends can be achieved from two aspects, thereby improving the sewing quality of sewing products.

[0075] In summary, the present invention effectively overcomes various shortcomings in the prior art and has high industrial utilization value.

[0076] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical principles disclosed herein are intended to be covered by the claims of the present invention.

Claims

1. A method for improving the seam starting quality of a sewing machine, the sewing machine comprising a rotary hook, a thread trimming mechanism, a needle plate (9), a machine needle (7), a thread clamp (11), a thread take-up lever (12), an electronic thread clamp (13) and an upper thread (3), the upper thread (3) passing through the thread clamp (11), the thread take-up lever (12), the electronic thread clamp (13) and the machine needle (7) in sequence, the height of the highest position of the thread take-up lever (12) from the lowest position being H, and the method is characterized in that: The lifting method includes a seam starting control method, and the seam starting control method includes the following steps: S1, before starting to sew, the thread trimming action has been completed, and the thread take-up lever (12) is at the initial position, and the height of the initial position from its lowest position is h0=0.9H~H; S2, the electronic thread clamp (13) releases the clamping of the upper thread (3), the thread take-up rod (12) first moves up to the highest position, then moves down to release the thread, the needle (7) moves down, and brings part of the upper thread (3) under the needle plate (9), when the thread take-up rod (12) reaches the first height position of h1 from its lowest position, h1=0.65H~0.75H, the electronic thread clamp (13) clamps the upper thread (3), and at this time the needle (7) changes from the downward state to the upward state; S3, the rotary hook rotates, and the thread hook structure on it hooks the thread end of the upper thread (3), and further brings the thread end of the upper thread (3) under the needle plate (9), while the thread take-up rod (12) continues to descend from the first height position to the lowest position, and then ascends; S4. When the thread take-up rod (12) moves upward and reaches a second height position h2 from its lowest position, where h2=0.13H~0.17H, the electronic thread clamp (13) releases the upper thread (3), and the needle (7) is in an upward state. The thread take-up rod (12) continues to move upward to pull the upper thread (3) for winding up. During the winding process, the upper thread (3) loop enlarged by the hook structure of the rotary shuttle is tightened and recovered.

2. The method for improving the seam start quality of a sewing machine according to claim 1, characterized in that: The movement of the needle (7) and the thread take-up lever (12) is driven by the main shaft of the sewing machine. The sewing machine also includes a control system, which can control the rotation of the main shaft and the loosening and clamping of the electronic thread clamp (13). The seam start control method also includes: determining the corresponding rotation angle position of the main shaft when the thread take-up lever (12) is at the first height position and the second height position, which are respectively recorded as the first angle position and the second angle position. In the step S2, when the control system controls the main shaft to rotate to the first angle position, the electronic thread clamp (13) is controlled to automatically clamp the upper thread (3); in the step S4, when the control system controls the main shaft to rotate to the second angle position, the electronic thread clamp (13) is controlled to automatically loosen the upper thread (3).

3. The method for improving the seam start quality of a sewing machine according to claim 1, characterized in that: The invention also includes a thread cutting method performed before the seam starting control method, wherein the thread cutting method is performed by a thread cutting mechanism, wherein the thread cutting mechanism includes a first thread cutting knife (4) and a second thread cutting knife (5), wherein the first thread cutting knife (4) is provided with a first cutting edge (41), and the second thread cutting knife (5) is provided with a second cutting edge (51) and a thread dividing tip (52) for inserting into the upper thread loop, wherein the right side of the thread dividing tip (52) has a thread dividing side edge (521), and the second thread cutting knife (5) can be rotated relative to the first thread cutting knife (4) until the second cutting edge (51) engages with or separates from the first cutting edge (41), and the thread dividing tip ( A V-shaped positioning notch (53) is provided on the right side of the dividing line side (521), and the left side of the V-shaped positioning notch (53) is connected to the dividing line side (521); the thread cutting method comprises the following steps: the second thread cutting knife (5) rotates toward the first thread cutting knife (4), the dividing line tip (52) enters the surface thread loop, the needle edge thread (32) in the surface thread loop moves to the right along the dividing line side (521), enters the V-shaped positioning notch (53), and reaches the bottom (531) of the V-shaped positioning notch (53); then the second cutting edge (51) and the first cutting edge (41) engage to cut the thread.

4. The method for improving the seam start quality of a sewing machine according to claim 3, characterized in that: In the thread trimming method, when the first thread trimmer (4) and the second thread trimmer (5) of the thread trimming mechanism are in an engaged thread trimming state, the distances between the bottom (531) of the V-shaped positioning notch (53) and the axis of the sewing machine needle (7) in the left-right direction and the front-back direction are X and Y, respectively, where X is 6.5-8 mm and Y is 10-12 mm.

5. The method for improving the seam start quality of a sewing machine according to claim 4, characterized in that: In the thread trimming method, when the first thread trimmer (4) and the second thread trimmer (5) of the thread trimming mechanism are in an engaged thread trimming state, an angle θ between a plane formed by a groove bottom (531) of the V-shaped positioning notch (53) and an axis of a sewing machine needle (7) and a plane passing through the axis of the sewing machine needle (7) and perpendicular to the left and right directions is 33 to 41 degrees.

6. The method for improving the seam start quality of a sewing machine according to claim 4 or 5, characterized in that: In the thread trimming method, the second thread trimmer (5) is arc-shaped and coaxially arranged on the outer peripheral side of the rotary hook, and the second cutting edge (51) is located on the outer arc surface of the second thread trimmer (5).

7. The method for improving the seam start quality of a sewing machine according to claim 6, characterized in that: In the thread trimming method, a protruding bulge (56) is provided on the outer arc surface of the second thread trimmer (5), a through hole (57) is provided on the bulge (56), and the edge of the through hole (57) constitutes a second cutting edge (51). When the second thread trimmer (5) and the first thread trimmer (4) are in an engaged thread trimming state, the through hole (57) and the sewing machine needle (7) remain coaxial.

8. The method for improving the seam start quality of a sewing machine according to claim 7, characterized in that: In the wire cutting method, the second wire cutting knife (5) is provided with a wire cutting hook (54), and the outer arc surface of the second wire cutting knife (5) is also provided with a wire accommodating groove (55) connecting the through hole (57) and the wire cutting hook (54).

9. The method for improving the seam start quality of a sewing machine according to claim 3 or 7, characterized in that: In the thread trimming method, the first thread trimmer (4) is fixed, and the second thread trimmer (5) can rotate around the rotary hook to engage with or separate from the first thread trimmer (4).

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