Stitch starting method for preventing material backfeeding in sewing thick material by sewing machine, and sewing machine

Abstract

A stitch starting method for preventing material backfeeding in sewing a thick material by a sewing machine, comprising: on the basis of the size of a thick material (8) and the size of a presser foot (3) and the friction between the thick material and a needle plate (2), setting an anti-pushing reference position and a first stitch minimum stitch length ∆S, wherein when the thick material is located at the anti-pushing reference position, the distance between the front edge of a stitch starting position of the thick material and the central axis of a needle (4) is ∆S, an included angle θ between a lower pressing plane (31) and the surface of the needle plate is 0°, or tan (90°-θ)≥1 / μ; on the basis of the first stitch minimum stitch length ∆S and a placement position of the thick material on the needle plate, determining a position I of a feed dog (1) and a first feeding distance L1; before the thick material is placed, a main shaft (5) not moving, the feed dog first moving to the position I and stopping to place the thick material at the placement position, and the presser foot (3) pressing against the thick material; starting stitching, the feed dog being kept at the position I, and the main shaft first rotating to an angle A; and a feeding driving mechanism (7), a feed dog lifting driving mechanism (6) and the main shaft moving synchronously, the feed dog driving the thick material to move in a cloth feeding direction, and when reaching a position II, the feed dog just sinking below an upper surface of the needle plate, thereby completing first feeding. In the stitch starting method, the movement relationship between the feed dog and the needle is controlled when at the start of stitching, especially at the first stitch, enhancing support of the thick material in the horizontal direction by the feed dog and the friction, and effectively preventing the thick material from being pushed out by the presser foot at the start of stitching. In addition, provided is a se

Description

Methods for preventing fabric slippage when sewing thick materials with a sewing machine, and sewing machine... Technical Field

[0001] This invention relates to the field of sewing technology, specifically to a sewing machine starting method for preventing material slippage when sewing thick materials, and the sewing machine itself. Background Technology

[0002] When sewing thick materials such as down jackets with a flatbed sewing machine, the starting point of the thick material must be placed in front of the needle due to the thickness of the material and the requirements of the starting process. For example, the starting point of the thick material, such as the zipper pull of a down jacket, will have a similar circular shape due to the multiple folds. At the same time, the process requires that the starting point of the thick material should generally be placed directly below the needle (when the needle is in the upper stop position) or next to the needle (when the needle is in the lower stop position), as shown in Figure 2. When placing thick material at the stop position and lowering the presser foot, because the needle is under the needle plate, and according to the synchronization relationship between the needle and the feed dog, the feed dog is also under the needle plate at this time. It does not contact the thick material and does not provide fixed support for the horizontal movement of the thick material. See Figure 3, which shows the state when the presser foot just contacts the material. At this time, the presser foot applies a horizontal force to the thick material. Therefore, when starting to sew, the thick material may be pushed out when the presser foot is lowered or when sewing the first stitch. This pushing phenomenon at the start of the stitch can prevent the thick material from being sewn normally. When this happens, the operator needs to manually push the thick material into the presser foot. Manual pushing makes it difficult to control the force, increasing the difficulty of operation and easily causing needle breakage at the start of the stitch. On the other hand, the power source for the movement of the feed end or the feed dog lifting end of current flatbed sewing machines (including electronic feed flatbed sewing machines) generally comes from the main shaft. The main shaft transmits its power to the feed end or the feed dog lifting end through mechanical transmission. The movement of the feed dog is a combination of the feeding end and the lifting end. This means that the movement of the needle and the movement of the feed dog cannot be completely independent. This limits the position of the feed dog at the upper or lower needle stop position, and makes it impossible to freely control the initial position of the feed dog. It also makes it impossible to control the initial position of the feed dog according to the different thicknesses of the fabric, which leads to the problem of thicker materials being pushed out. Summary of the Invention

[0003] In view of the shortcomings of the prior art described above, the technical problem to be solved by the present invention is to provide a sewing starting method for preventing material from slipping out when sewing thick materials with a sewing machine, and a sewing machine that can effectively prevent thick materials from being pushed out by the presser foot when sewing.

[0004] To achieve the above objectives, the present invention provides a sewing start method for preventing material slippage when sewing thick materials with a sewing machine. The sewing machine includes a feed dog, a feed drive mechanism, a feed dog lifting drive mechanism, a needle plate, a needle, and a presser foot. The movement of the needle plate is driven by a main shaft. The bottom of the presser foot has a downward pressing surface for contacting the sewing material. The feed dog's feed movement in the front-to-back direction is driven by the feed drive mechanism, and its movement in the up-and-down direction is driven by the feed dog lifting drive mechanism. The sewing start method includes:

[0005] S1. Based on the dimensions of the thick material and the presser foot, as well as the friction between the thick material and the needle plate, set the anti-push reference position and the minimum needle distance △S for the first needle. When the thick material is located at the anti-push reference position, its starting front edge is located in front of the needle along the feeding direction and the distance between it and the needle center axis in the feeding direction is △S. The included angle θ between the pressing plane and the needle plate surface satisfies: θ is 0° or tan(90°-θ)≥1 / μ, where μ is the friction coefficient between the thick material and the needle plate.

[0006] S2. Based on the minimum stitch distance △S of the first stitch and the feeding position of the thick material on the needle plate, determine the position I of the feed dog and the first feeding distance L1: When the thick material is placed in the feeding position, the front edge of the starting point of the thick material is located in front of the needle along the feeding direction and the distance between it and the center axis of the needle in the feeding direction is △L. When the feed dog moves from position I along the feeding direction to position II which is just below the upper surface of the needle plate, the feeding distance is L1, and L1-△L≥△S is satisfied.

[0007] S3. Before placing the thick material, the main shaft remains stationary, the feed dog moves to position I and stops at position I; then the thick material is placed at the feeding position on the needle plate, and the presser foot is pressed on the thick material.

[0008] S4. Begin sewing. Keep the feed dog in position I and rotate the spindle to angle A.

[0009] S5. When the main shaft rotates to angle A, the feeding drive mechanism, the lifting drive mechanism and the main shaft move synchronously. The feeding dog drives the thick material to move along the feeding direction. When the feeding dog reaches position II, it sinks just below the upper surface of the needle plate, completing the first feeding.

[0010] Furthermore, in step S2, a normal stitch distance S is also set. If the normal stitch distance S is less than or equal to L1-L0, the feeding distance L1 and position I of the feed dog are determined with L1-L0≥△S as the requirement; if the normal stitch distance S is greater than L1-L0, the feeding distance L1 and position I of the feed dog are determined with L1-L0=S as the requirement.

[0011] Furthermore, in step S1, when μ = 0.15, θ ≤ 10°.

[0012] Furthermore, in step S1, θ is 0°.

[0013] Furthermore, in step S2, when the feed tooth is located at position I, the height difference H1 between its highest tooth and the surface of the needle plate is not less than 0.5 mm.

[0014] Furthermore, in step S2, the spacing L0 = 0.

[0015] Furthermore, in step S4, angle A is the angle corresponding to the synchronous relationship between the main axis and the position I of the feed dog during normal sewing.

[0016] Furthermore, both the feeding drive mechanism and the lifting drive mechanism employ drive sources independent of the main shaft's movement. The movements of the feeding drive mechanism, the lifting drive mechanism, and the main shaft are all controlled by the sewing machine's electronic control system. In step S3, the main shaft stops rotating, and the feeding drive mechanism and the lifting drive mechanism move, causing the feed dog to move to position I. In step S4, the electronic control system acquires the rotation angle of the main shaft while controlling its rotation. After receiving the start-up signal, the electronic control system determines whether the main shaft has rotated to angle A by judging its rotation angle. In step S5, when the electronic control system detects that the main shaft's rotation angle is angle A, it controls the feeding drive mechanism and the lifting drive mechanism to start moving.

[0017] Furthermore, the driving source of the feeding drive mechanism is a feeding motor, the driving source of the tooth lifting drive mechanism is a tooth lifting motor, the main shaft is driven by a main shaft motor, and the electrical control system is connected to the feeding motor, the tooth lifting motor and the main shaft motor respectively.

[0018] The present invention also provides a sewing machine with a thick material anti-backflow start-up mode. When the sewing machine selects the thick material anti-backflow start-up mode, it performs the start-up method as described above.

[0019] As described above, the sewing method and sewing machine of the present invention have the following beneficial effects:

[0020] By modifying the control logic of the feed dog motor, feed motor, and main shaft during the first few stitches of the sewing process, especially the control of the movement relationship between the feed dog and the needle during the first stitch, the horizontal support of the feed dog and friction for thick materials is enhanced. This prevents the problem of thick materials being pushed away by the presser foot when sewing thick materials, thus broadening the adaptability to sewing thick materials. Without changing the sewing machine structure, only by modifying the control logic program and setting relevant parameters, it can adapt to sewing processes involving thick materials, making it more flexible and convenient to use and suitable for various applications. Attached Figure Description

[0021] Figure 1 is a schematic diagram of the structure of the feeding teeth, feeding drive mechanism, tooth lifting drive mechanism and main shaft in this invention.

[0022] Figure 2 is a schematic diagram of the placement of the thick material on the needle plate in this invention.

[0023] Figure 3 is a schematic diagram of the force exerted when the presser foot contacts the thick material in this invention.

[0024] Figure 4 is a schematic diagram of the force exerted on the thick material when the presser foot contacts the thick material in this invention.

[0025] Figure 5 is a schematic diagram of the operation of the feed dog in position I, showing the presser foot contacting the thick material.

[0026] Figure 6 is a schematic diagram of the operation of the feed dog in position II, showing the pressure foot contacting the thick material.

[0027] Figure 7 is a schematic diagram of position I and position II in the feed tooth trajectory of the present invention.

[0028] Figure 8 is a schematic diagram of the synchronous motion relationship between the feeding motor and the spindle motor in this invention.

[0029] Figure 9 is a schematic diagram of the synchronous motion relationship between the tooth-lifting motor and the spindle motor in this invention.

[0030] Attached Figure Numbers Explanation: 1. Feed Dog; 2. Needle Plate; 3. Presser Foot; 3.1 Lower Pressing Plane; 4. Needle; 5. Main Spindle; 6. Feed Dog Lifting Drive Mechanism; 6.1 Feed Dog Lifting Motor; 7. Feed Drive Mechanism; 7.1 Feed Motor; 8. Thick Material; 9. Main Spindle Motor Detailed Implementation

[0031] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification.

[0032] It should be understood that the structures, proportions, sizes, etc., depicted in the accompanying drawings of this specification are merely for illustrative purposes to aid those skilled in the art in understanding and reading the content disclosed herein, and are not intended to limit the conditions under which the invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to the size, without affecting the effects and objectives achieved by the invention, should still fall within the scope of the technical content disclosed herein. Furthermore, the terms such as "upper," "lower," "left," "right," and "middle" used in this specification are merely for clarity and are not intended to limit the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention's implementation.

[0033] Referring to Figures 1 to 9, this invention provides a sewing start method to prevent material slippage when sewing thick materials with a sewing machine. The sewing machine includes a feed dog 1, a feed drive mechanism 7, a lift-up drive mechanism 6, a needle plate 2, a needle 4, and a presser foot 3. The movement of the needle 4 is driven by a main shaft 5. The bottom of the presser foot 3 has a downward pressing surface 31 for contacting the sewing material. The feed dog 1's feed movement in the front-to-back direction is driven by the feed drive mechanism 7, which can adjust the feed distance of the feed dog 1. Its movement in the up-and-down direction is driven by the lift-up drive mechanism 6. Through the coordinated operation of the feed drive mechanism 7 and the lift-up drive mechanism 6, the feed dog 1 is driven to cyclically move along a certain motion trajectory. The preferred motion trajectory of the feed dog 1 is elliptical, but it can also be square or other shapes. The feed dog 1, the feed drive mechanism 7, the lift-up drive mechanism 6, the needle plate 2, the needle 4, and the presser foot 3 can all adopt existing conventional structures.

[0034] The seam-starting method of the present invention includes:

[0035] S1. Based on the dimensions of the thick material 8 and the presser foot 3, and the friction between the thick material 8 and the needle plate 2, set the anti-push reference position and the minimum needle distance △S for the first needle. When the thick material 8 is located at the anti-push reference position, its starting edge is located in front of the needle 4 along the feeding direction, and the distance between it and the central axis of the needle 4 in the feeding direction is △S. The angle θ between the pressing plane 31 and the surface of the needle plate 2 satisfies: θ is 0° or tan(90°-θ)≥1 / μ, where μ is the friction coefficient between the thick material 8 and the needle plate 2. Specifically, as shown in Figure 6, at this time, the pressure F4 of the pressing plane 31 on the thick material 8 and the angle β between the pressing plane 31 and the surface of the needle plate 2 are 90°-θ. At this time, the vertical (perpendicular to the surface of the needle plate 2) component of the pressing plane 31 on the thick material 8 is F4*sinα, and the horizontal component parallel to the surface of the needle plate 2 is F4*cosβ. In actual use, the surface of the needle plate 2 is generally horizontal, that is, the horizontal component F4*cosβ is along the horizontal direction. The horizontal supporting force F6 exerted by the needle plate 2 surface on the thick material 8 is the frictional force, F6=F4*sinβ*μ. If the feed dog 1 and the thick material 8 are not in contact, and the thick material 8 is to be prevented from being pushed on the surface of the needle plate 2, the frictional force must be greater than or equal to the horizontal component F4*cosα, that is, F4*sinβ*μ≥F4*cosβ, i.e., tan(90°-θ)≥1 / μ, or the horizontal component F4*cosβ must be zero, i.e., β=90°, θ=0°.

[0036] When the thick material 8 is below the presser foot 3 and in contact with the pressing plane 31, the value of θ is related to the thickness of the thick material 8, the starting arc and position, and the size and position of the pressing plane. For a specific sewing machine, after the shape and size of its presser foot 3 are determined, the anti-push reference position and the minimum stitch distance △S of the first stitch are different for different thick materials 8. After determining the friction coefficient μ by existing conventional methods, the included angle θ is determined. Then, the thick material 8 is placed on the needle plate 2 and located in an appropriate position below the presser foot 3. The pressing plane 31 of the presser foot 3 is operated to contact and press down on the thick material 8. By adjusting the position of the thick material 8 and measuring the included angle θ between the pressing plane 31 and the surface of the needle plate 2 to the required size, the position of the thick material 8 at this time is taken as the anti-push reference position, and the distance between the starting edge of the thick material 8 and the central axis of the needle 4 in the feeding direction is recorded as △S. Preferably, when μ=0.15, θ≤10°, and when other conditions are met, θ=0° is the most preferred. Of course, the anti-push reference position and △S can also be determined by other appropriate methods. After determining the included angle θ, a geometric image relationship is established based on the thickness of the thick material 8, the starting arc and other dimensions, as well as the size and position of the pressing plane. Through geometric image analysis, it is determined at what position the included angle θ meets the requirements when the starting edge of the thick material 8 changes position.

[0037] S2. Based on the minimum stitch distance △S of the first stitch and the feeding position of the thick material 8 on the needle plate 2, determine the position I of the feed dog 1 and the first feeding distance L1: Refer to Figure 2. When the thick material 8 is placed in the feeding position, the front edge of the starting point of the thick material 8 is located behind the needle 4 along the feeding direction and the distance between the feed dog 1 and the central axis of the needle 4 in the feeding direction is △L. When the feed dog 1 moves from position I along the feeding direction to position II, which is exactly below the surface of the needle plate 2, it will complete one feeding. The feeding distance is L1, and it satisfies L1-△L≥△S.

[0038] In this embodiment, referring to Figure 7, the movement trajectory of the feed dog 1 is an ellipse. Position I is located at the upper rear of the movement trajectory. At this time, preferably, the height difference H1 between the highest tooth of the feed dog 1 and the surface of the needle plate 2 is not less than 0.5mm, which can firmly anchor the feed dog 1 to the bottom surface of the thick material 8, ensuring sufficient lateral support between the feed dog 1 and the thick material 8. When the feed dog 1 moves forward along the feeding direction from position I, it drives the thick material 8 forward, realizing the feeding operation. When the feed dog 1 moves to position II, it sinks below the surface of the needle plate 2, and its movement no longer drives the thick material 8, thus completing the first feeding. The feeding distance is L1, and L1-ΔL is denoted as the first needle distance S1. When the thick material 8 is placed at the feeding position, it is preferably close to the needle 4 (at this time, the needle 4 is at the lower stop position) for easy positioning. At this time, the distance ΔL is equal to the outer diameter r of the needle 4.

[0039] In this embodiment, as a preferred design, a normal stitch length S is also provided. The normal stitch length S is the stitch length of the thick material 8 during the normal sewing process after the start of the sewing. When determining the position I of the feed dog 1 and the first feeding distance L1, the normal stitch length S is used for determination. Specifically, if the normal stitch length S is less than or equal to L1-L0, that is, in order not to push out the thick material 8, the distance required for the first feeding is required to be greater than the normal feeding distance, then the feeding distance L1 and position I of the feed dog 1 are determined with L1-L0≥△S as the requirement. In this way, the first feeding distance is S1, and the subsequent feeding distance is the normal stitch length S. If the normal stitch length S is greater than the first stitch length S1, then the feeding distance L1 and position I of the feed dog 1 are determined with L1-L0=S as the requirement. In this way, the feeding distance of the thick material 8 each time (including the first feeding and subsequent feeding) is S.

[0040] S3. Before placing the thick material 8, the main shaft 5 remains stationary, the feed dog 1 moves to position I and stops at position I; then the thick material 8 is placed at the feeding position on the needle plate 2; the presser foot 3 is lowered and pressed onto the thick material 8.

[0041] In this embodiment, as a preferred design, both the feeding drive mechanism 7 and the lifting drive mechanism 6 employ drive sources independent of the main shaft 5. The feed drive mechanism 7 is driven by a feed motor 71, which, when rotating, drives the feed dog 1 to move back and forth via an intermediate transmission assembly. The lifting drive mechanism 6 is driven by a lifting motor 61, which, when rotating, drives the feed dog 1 to move up and down via an intermediate transmission assembly. The main shaft 5 is driven by a main shaft motor 9. The sewing machine is controlled and connected to the feed motor 71, the lifting motor 61, and the main shaft motor 9, respectively, thereby independently controlling the movements of the feed drive mechanism 7, the lifting drive mechanism 6, and the main shaft 5. Before the thick material 8 is placed, the electronic control system stops the main shaft motor 9, and the feed motor 71 and the lifting motor 61 rotate simultaneously according to a set cooperative relationship. The feed drive mechanism 7 and the lifting drive mechanism 6 move simultaneously, causing the feed dog 1 to move along a certain trajectory. When position I is reached, the feed motor 71 and the lifting motor 61 stop. Of course, in other embodiments, the feeding drive mechanism 7 and the tooth lifting drive mechanism 6 may also adopt other existing suitable design forms, and the two may also share the same drive source.

[0042] Before placing the thick material 8 on the feeding position on the needle plate 2, the up and down position of the needle 4 can be manually controlled by manually turning the handwheel. At this time, the feed dog 1 remains stationary, so that the front edge of the thick material 8 can be placed against the needle 4 to achieve positioning.

[0043] When presser foot 3 is pressed onto the thick material 8, the force situation is shown in Figures 3 and 4. At this time, F1 is the pressure of the spring on the presser foot rod, which is also the power for presser foot 3 to press the cloth. F2 is the horizontal force of the machine housing on the presser foot rod, and F3 is the force of the thick material 8 on the presser foot 3. To make the presser foot 3 balanced, the vector sum of the three forces F1, F2 and F3 needs to be zero, that is, F1=F3*sinα, F2=F3*cosα. Therefore, F3=F1 / sinα. F4 is the force exerted by presser foot 3 on the thick material 8, F4 is the reaction force of F3, F5 is the vertical support force exerted by needle plate 2 and feed dog 1 on the thick material 8 together; F6 is the horizontal force exerted on the thick material 8 by feed dog 1 and needle plate 2 together. Since feed dog 1 is located above the surface of needle plate 2 at this time and has a height H1, it can penetrate more into the bottom surface of the thick material 8. Feed dog 1 will play a fixed support role for the horizontal movement of the thick material 8, and there will be no problem of being pushed backward by presser foot 3. At this time, when feed dog 1 is performing the feeding action, it can give the thick material 8 enough horizontal force along the feeding direction.

[0044] S4. Begin sewing. Keep the feed dog 1 in position I. Press the presser foot 3 onto the thick material 8. The main shaft 5 first rotates to angle A. Preferably, angle A corresponds to the angle between the main shaft 5 and position I of the feed dog 1 in the normal synchronous relationship. That is, if the synchronous movement relationship between the feed dog 1, the needle 4, and the presser foot 3 is not broken, the main shaft motor 9, the feed motor 71, and the dog lifting motor 61 move according to the normally set synchronous movement relationship during normal sewing and starting operations. When the feed dog 1 reaches position I, the main shaft 5 should rotate to angle A. See Figures 8 and 9. As shown, during the start-up of a thick material 8 (corresponding to the main shaft motor 9 angle being 0 degrees), the initial angles of the feed dog and lifting dog differ in the start-up mode, resulting in different initial positions of the feed dog 1. Before angle A, in the normal mode (when sewing thin fabrics), the feed motor 71 and lifting dog motor 61 should swing with the change of the main shaft 5 angle, resulting in the feed dog 1 moving synchronously with the needle 4. However, in the anti-push mode for starting thick material 8 in this invention, the rotation angles of the feed motor 71 and lifting dog motor 61 remain unchanged, resulting in the needle 4 driven by the main shaft 5 moving, while the feed dog 1 remains stationary. Furthermore, angle A can also be set to other suitable positions according to the specific sewing work. The electronic control system acquires the rotation angle of the main shaft 5 while controlling its rotation. After receiving the start-up signal, the electronic control system determines whether the main shaft 5 has rotated to angle A by judging its rotation angle.

[0045] S5. When the electronic control system detects that the rotation angle of the main shaft is angle A, it controls the feeding drive mechanism and the lifting drive mechanism to start moving. The feeding drive mechanism 7, the lifting drive mechanism 6, and the main shaft 5 move synchronously. The feed dog 1 drives the thick material 8 to move along the feeding direction. When the feed dog 1 reaches position II, it sinks exactly below the upper surface of the needle plate 2, completing the first feeding. The needle 4 completes the first stitch. Then, the feeding drive mechanism 7, the lifting drive mechanism 6, and the main shaft 5 work together in a certain synchronous motion relationship to continuously perform sewing work. The electronic control system controls the subsequent feeding distance of the feed dog 1 to be the normal stitch length S.

[0046] The present invention also provides a sewing machine with a thick material anti-back-starting sewing mode. When the sewing machine selects the thick material anti-back-starting sewing mode, it executes the sewing method as described in claim 1, wherein the minimum stitch distance ΔS and the normal stitch distance S of the first stitch are set by the operator in the electronic control system, and the position I of the feed dog 1 and its corresponding first feeding distance L1 are automatically determined by the electronic control system.

[0047] As can be seen from the above, the sewing method and sewing machine of the present invention have the following beneficial effects:

[0048] By modifying the control logic of the coordinated movement of the feed dog motor 61, the feed motor 71, and the main shaft 5 during the first few stitches of the sewing process, especially by controlling the movement relationship between the feed dog 1 and the needle 4 during the first stitch, the horizontal support of the feed dog 1 and friction on the thick material 8 is enhanced. This prevents the thick material 8 from being pushed away by the presser foot 3 when sewing begins, thus broadening the adaptability to sewing thick materials 8. Without changing the sewing machine structure, only by modifying the control logic program and setting relevant parameters, it can adapt to the sewing process of starting with thick materials 8, making it more flexible and convenient to use and suitable for various applications.

[0049] In summary, this invention effectively overcomes the various shortcomings of the prior art and has high industrial application value.

[0050] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can 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 those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A sewing machine method for preventing material slippage during the sewing of thick materials, the sewing machine comprising a feed dog (1), a feed drive mechanism (7), a lift drive mechanism (6), a needle plate (2), a needle (4), and a presser foot (3), wherein the movement of the needle plate (2) is driven by a main shaft (5), the presser foot (3) has a pressing surface (31) at its bottom for contacting the sewing material, the feed dog (1) is driven by the feed drive mechanism (7) in the front-to-back direction and by the lift drive mechanism (6) in the up-down direction, characterized in that: The seam-starting method includes: S1. Based on the dimensions of the thick material (8) and the presser foot (3), as well as the friction between the thick material (8) and the needle plate (2), set the anti-push reference position and the minimum needle distance △S for the first needle. When the thick material (8) is located at the anti-push reference position, its starting edge is located in front of the needle (4) along the feeding direction and the distance between it and the central axis of the needle (4) in the feeding direction is △S. The included angle θ between the pressing plane (31) and the surface of the needle plate (2) satisfies: θ is 0° or tan(90°-θ)≥1 / μ, where μ is the friction coefficient between the thick material (8) and the needle plate (2). S2. Based on the minimum stitch distance △S of the first stitch and the feeding position of the thick material (8) on the needle plate (2), determine the position I of the feed dog (1) and the first feeding distance L1: When the thick material (8) is placed in the feeding position, the front edge of the starting point of the thick material (8) is located in front of the needle (4) along the feeding direction and the distance between the feed dog (1) and the central axis of the needle (4) in the feeding direction is △L. When the feed dog (1) moves from position I along the feeding direction to position II which is just below the upper surface of the needle plate (2), the feeding distance is L1, and L1-△L≥△S. S3. Before placing the thick material (8), the main shaft (5) remains stationary, the feed dog (1) moves to position I and stops at position I; then the thick material (8) is placed at the feeding position on the needle plate (2), and the presser foot (3) is pressed on the thick material (8); S4. Start the sewing action. Keep the feed dog (1) in position I and rotate the spindle (5) to angle A. S5. When the main shaft (5) rotates to angle A, the feeding drive mechanism (7), the lifting drive mechanism (6) and the main shaft (5) move synchronously. The feeding tooth (1) drives the thick material (8) to move along the feeding direction. When the feeding tooth (1) reaches position II, it sinks just below the upper surface of the needle plate (2) to complete the first feeding.

2. The seaming method of claim 1, wherein: In step S2, a normal stitch distance S is also set. If the normal stitch distance S is less than or equal to L1-L0, the feeding distance L1 and position I of the feed dog (1) are determined with L1-L0≥△S as the requirement. If the normal needle distance S is greater than L1-L0, then the feeding distance L1 and position I of the feed dog (1) are determined with L1-L0=S as the requirement.

3. The tucking method according to claim 1, characterized in that: In step S1, when μ = 0.15, θ ≤ 10°.

4. The tacking method according to claim 1 or 3, characterized in that: In step S1, θ is 0°.

5. The method of tucking according to claim 1, wherein: In step S2, when the feed tooth (1) is located in position I, the height difference H1 between its highest tooth and the surface of the needle plate (2) is not less than 0.5 mm.

6. The method of tucking according to claim 1, wherein: In step S2, the spacing L0 = 0.

7. The method of tucking according to claim 1, wherein: In step S4, angle A is the angle corresponding to the position I of the main axis (5) and the feed dog (1) during normal sewing.

8. The method of tucking according to claim 1, wherein: The feeding drive mechanism (7) and the tooth lifting drive mechanism (6) both adopt drive sources independent of the movement of the main shaft (5). The movements of the feeding drive mechanism (7), the tooth lifting drive mechanism (6) and the main shaft (5) are all controlled by the sewing machine's electronic control system. In step S3, the main shaft (5) stops rotating, and the feeding drive mechanism (7) and the tooth lifting drive mechanism (6) move, so that the feeding tooth (1) moves to position I; In step S4, the electronic control system obtains the rotation angle of the main shaft (5) while controlling the rotation of the main shaft (5). After receiving the sewing start signal, the electronic control system determines whether the main shaft (5) has rotated to angle A by judging the rotation angle of the main shaft (5). In step S5, when the electronic control system detects that the rotation angle of the spindle (5) is angle A, it controls the feeding drive mechanism (7) and the tooth lifting drive mechanism (6) to start moving.

9. The method of tucking according to claim 7, wherein: The feeding drive mechanism (7) is driven by a feeding motor (71), the tooth lifting drive mechanism (6) is driven by a tooth lifting motor (61), the main shaft (5) is driven by a main shaft motor (9), and the electrical control system is connected to the feeding motor (71), the tooth lifting motor (61) and the main shaft motor (9) respectively.

10. A sewing machine characterized by: A thick material anti-backflow start-up mode is provided. When the sewing machine selects the thick material anti-backflow start-up mode, the start-up method as described in claim 1 is executed.

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