A method for controlling material push-up at small stitch start

Abstract

The present invention provides a small stitch length seam start anti-pushing control method, in the process of starting the first stitch to the Nth stitch, the feed dog driving source and the feed driving source are controlled to operate according to the anti-pushing trajectory corresponding to the anti-pushing mode, during this process, the feed dog is always in a state of emerging upward from the needle plate, and the seam start position of the sewing material is transferred a preset distance △S, so that the seam start position of the sewing material is squeezed under the presser foot, and the angle α between the presser foot and the horizontal plane satisfies α=0°, or tanα≤μ, so that the horizontal component of the force F applied by the presser foot to the seam start position of the sewing material is not greater than the maximum static friction between the seam start position of the sewing material and the needle plate, thereby preventing the subsequent sewing material from being pushed out by the presser foot. The present application realizes the transfer of the seam material by the preset distance △S by setting the initial seam start position of the feed dog and transferring S1+(N‑1)*S2 by the feed dog after sewing N stitches, thereby completing the sewing process of the sewing machine with a small stitch length seam start and reliably preventing the presser foot from pushing the material.

Description

Technical Field

[0001] The invention relates to the technical field of sewing machines, in particular to a small-stitch-length seam start-up and material-pushing prevention control method. Background Art

[0002] When sewing thick materials such as down jackets on a flat-bed sewing machine, the seam starting process requires that the starting point of the thick material be placed close to the needle, such as Figure 1 As shown. Afterwards, the presser foot of the lockstitch sewing machine is lowered to press against the thick material, causing one end of the presser foot to tilt upward at an angle θ. This angle θ is also the angle between the bottom surface of the presser foot and the horizontal plane. The horizontal component of the force F exerted by the presser foot on the thick material is F*sinθ. Because the thickness of the sewing material is thicker, the upward angle θ of the presser foot is larger, which also makes the horizontal component of the force F exerted by the presser foot on the thick material larger; at the same time, based on the linkage relationship between the feed dog and the needle, when the needle is in the upper stop position, the feed dog is in Figure 2 At position A of its motion trajectory shown, the feed dog is about to sink under the needle plate; Figure 2 The horizontal line in the figure represents the top surface of the needle plate. Therefore, when the presser foot is lowered or the first stitch is sewn, the horizontal component of force F can easily become greater than the friction between the thick material and the needle plate. This can cause the thick material to be pushed out after the presser foot is lowered or during the first stitch. This can cause the thick material to be pushed out at the start of the seam.

[0003] In order to solve the problem of material pushing at the beginning of sewing, some sewing machine manufacturers adopt the following anti-pushing control method: change the initial position of the feed dog in the sewing machine when sewing the first stitch, so that the feed dog is at position B of its motion trajectory, such as Figure 3 As shown, the feed dog can feed the thick material a sufficient preset distance L when sewing the first stitch, and the preset distance L allows the thick material to be squeezed under the presser foot, and the feed dog is always above the needle plate during the feeding process of the length L; Figure 3 The horizontal line in represents the upper surface of the needle plate. Once the thick material enters under the presser foot, the upward angle θ of the presser foot will be reduced, which will also reduce the horizontal component of F, so that the horizontal component of F is zero or less than the friction between the thick material and the needle plate, thereby preventing the thick material from being pushed out by the presser foot. However, in the above-mentioned seam start anti-pushing material control method, the preset distance is closely related to the stitch length of the first stitch of the seam. Some sewing processes require small stitch length sewing when starting the seam, such as the dense stitch sewing process, then the feed dog cannot feed the thick material a sufficient preset distance when the first stitch of the seam is started. Therefore, the above-mentioned seam start anti-pushing material control method is only applicable to sewing processes with normal stitch length, and cannot be applied to sewing processes with small stitch length. Summary of the Invention

[0004] In view of the above-mentioned shortcomings of the prior art, the object of the present invention is to provide a method for controlling material pushing prevention when starting seam with a small stitch length, which can still prevent the presser foot from pushing material when starting seam with a small stitch length.

[0005] To achieve the above object, the present invention provides a method for controlling the material pushing prevention of a small stitch start seam, comprising the following steps:

[0006] S1. A sewing machine is provided with an electronic control unit, a tooth frame, a feed dog fixed to the tooth frame, a tooth lifting mechanism connected to one end of the tooth frame and driving the tooth frame to reciprocate vertically, and a feeding mechanism connected to the other end of the tooth frame and driving the tooth frame to reciprocate horizontally, wherein the tooth lifting mechanism has a tooth lifting drive source, and the feeding mechanism has a feeding drive source, wherein the tooth lifting drive source and the feeding drive source are both independently provided drive sources and are both communicatively connected to the electronic control unit;

[0007] S2: Before the sewing machine starts sewing the first stitch, the electronic control unit controls the output of the feed dog driving source and the feed driving source to place the feed dog in the initial sewing position. At this time, the feed dog emerges upward from the needle plate of the sewing machine.

[0008] S3. With the presser foot raised, place the material for sewing in the sewing machine, with the seam start point in contact with the feed dog and close to the needle; lower the presser foot so that it presses against the seam start point of the material;

[0009] S4. Starting the first stitch of the sewing machine: While the needle is above the material to be sewn, the electronic control unit controls the outputs of the tooth-lifting drive source and the feed drive source so that the feed dog remains in a state of emerging upward from the needle plate and starts to move from the initial sewing position, thereby moving the starting point of the sewing material along the feed direction of the sewing machine by a distance of S1. While the needle is inserted into the material to be sewn, the electronic control unit controls the outputs of the tooth-lifting drive source and the feed drive source so that the feed dog remains in a state of emerging upward from the needle plate and does not move.

[0010] S5, the sewing machine starts sewing the second stitch, ..., until the Nth stitch, N ≥ 2;

[0011] Each time the Nth stitch is started, while the needle is above the sewing material, the electronic control unit controls the outputs of the tooth-lifting drive source and the feed drive source so that the feed dog remains in a state of emerging upward from the needle plate and moves at the current stitch length of the sewing machine, thereby moving the starting point of the sewing material a distance S2 along the feed direction of the sewing machine; while the needle is inserted into the sewing material, the electronic control unit controls the outputs of the tooth-lifting drive source and the feed drive source so that the feed dog remains in a state of emerging upward from the needle plate and does not move;

[0012] After sewing the Nth stitch, the total distance △S that the feed dog moves the sewing material along the feed direction of the sewing machine is: △S=S1+(N-1)*S2;

[0013] At this time, the angle α between the presser foot and the horizontal plane satisfies: α=0°, or tanα≤μ, where μ is the static friction coefficient between the starting point of the sewing material and the needle plate;

[0014] S6. The electronic control unit controls the tooth lifting drive source and the feeding drive source to operate separately according to the conventional trajectory corresponding to the conventional sewing mode.

[0015] Furthermore, in step S4, when the needle starts to move downward from the upper stop position and does not penetrate into the sewing material, the feed dog moves the sewing starting part of the sewing material by a distance S1.

[0016] Furthermore, in step S5, each time the Nth stitch is sewn, while the needle starts to move downward from the upper stop position and does not penetrate into the sewing material, the feed dog moves the sewing starting portion of the sewing material by a distance S2.

[0017] Furthermore, in step S4 and step S5, when the sewing machine starts to sew the first stitch to the N-1 stitch, while the feed dog remains in the state of emerging upward from the needle plate and moves the sewing material to the starting position along the feed direction of the sewing machine, the electronic control unit controls the tooth lifting drive source to always maintain the current output, so that the feed dog moves horizontally along the feed direction of the sewing machine.

[0018] Furthermore, in step S5, when the sewing machine starts to sew the Nth stitch, while the feed dog remains in the state of emerging upward from the needle plate and moves the sewing material to the sewing starting position along the feeding direction of the sewing machine, the electronic control unit controls the tooth lifting drive source and the feed drive source to operate separately according to the conventional trajectory corresponding to the conventional sewing mode; after the feed dog moves the sewing material to the sewing starting position a distance S2, the feed dog is in a position where it is flush with the upper surface of the needle plate and is at the limit position in the feeding direction of the sewing machine.

[0019] Furthermore, the tooth-lifting drive source is a motor, and the tooth-lifting mechanism also includes a first tooth-lifting crank, a first tooth-lifting connecting rod, a tooth-lifting shaft rotatably supported in the sewing machine base, a second tooth-lifting crank and a third tooth-lifting crank respectively fixed at both ends of the tooth-lifting shaft, and a second tooth-lifting connecting rod. The first tooth-lifting crank is fixed on the motor shaft of the tooth-lifting drive source, and the two ends of the first tooth-lifting connecting rod are respectively rotatably connected to the first tooth-lifting crank and the second tooth-lifting crank, and the two ends of the second tooth-lifting connecting rod are respectively rotatably connected to the third tooth-lifting crank and the tooth frame.

[0020] Furthermore, the feeding drive source is a motor, and the feeding mechanism also includes a first feeding crank, a first feeding connecting rod, a feeding shaft rotatably supported in the sewing machine base, a second feeding crank and a tooth rack seat respectively fixed at both ends of the feeding shaft, and a tooth rack pin. The first feeding crank is fixed on the motor shaft of the feeding drive source, and the two ends of the first feeding connecting rod are rotatably connected to the first feeding crank and the second feeding crank respectively, and the tooth rack seat is connected to the tooth rack through the tooth rack pin.

[0021] As described above, the small stitch start and anti-pushing material control method of the present invention has the following beneficial effects.

[0022] In the process of sewing the first stitch to the Nth stitch, the present application controls the tooth-lifting drive source and the feed drive source to operate according to the anti-pushing trajectory corresponding to the anti-pushing mode. During this process, the feed dog is always in a state of emerging upward from the needle plate, and moves the sewing starting point of the sewing material a preset distance △S along the feed direction of the sewing machine, so that the sewing starting point of the sewing material is squeezed under the presser foot. At this time, the angle α between the presser foot and the horizontal plane satisfies α=0°, or tanα≤μ, so that the horizontal component of the force F applied by the presser foot to the sewing starting point of the sewing material is not greater than the maximum static friction between the sewing starting point of the sewing material and the needle plate. After such a setting, when the subsequent tooth-lifting drive source and the feed drive source operate according to the conventional trajectory corresponding to the conventional sewing mode, even if the feed dog sinks under the needle plate, the sewing material will not be pushed out by the presser foot. The present application sets the initial seam starting position of the feed dog, and realizes the preset distance △S of the seam starting position moving the sewing material along the feeding direction of the sewing machine by moving S1+(N-1)*S2 by the feed dog after sewing N stitches. It not only completes the sewing process of the sewing machine with a small stitch length, but also realizes that the sewing material has been moved forward a sufficient distance when the feed dog sinks under the needle plate for the first time, thereby reliably preventing the presser foot from pushing the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of the prior art when starting the seam and pushing the material.

[0024] Figure 2 This is a schematic diagram of the position of the feed dog when the needle is in the upper stop position when sewing the first stitch in the prior art.

[0025] Figure 3 This is a schematic diagram of the position of the feed dog when the needle is in the upper stop position when the feed dog feeds the thick material a preset distance L at the time of sewing the first stitch in the prior art.

[0026] Figure 4 and Figure 5 This is a schematic diagram of the connection between the tooth frame, tooth lifting mechanism and feeding mechanism in the sewing machine of this application.

[0027] Figure 6 This is a schematic diagram of the process of inserting sewing material in the small stitch length seam start and anti-pushing material control method of this application.

[0028] Figure 7 This is a schematic diagram of feeding when starting the first stitch in the small stitch length seam start and anti-pushing material control method of this application.

[0029] Figure 8 This is a schematic diagram of the cloth being pierced when the first stitch is started in the small stitch length seam start and material push-out prevention control method of this application.

[0030] Figure 9 This is a schematic diagram of the needle moving out of the sewing material when sewing the first stitch in the small stitch length seam start anti-pushing control method of this application.

[0031] Figure 10 This is a schematic diagram of feeding when starting the second stitch in the small stitch length seam start and anti-pushing material control method of this application.

[0032] Figure 11 This is a schematic diagram of puncturing the cloth when starting the second stitch in the small stitch length seam start and anti-pushing material control method of this application.

[0033] Figure 12 This is a schematic diagram of feeding when starting the Nth stitch in the small stitch length seam start and anti-pushing material control method of this application.

[0034] Figure 13 This is a schematic diagram of the motion trajectory of the feed dog in the anti-pushing mode of Example 1 of the small stitch start anti-pushing control method of this application.

[0035] Figure 14 This is a schematic diagram of the motion trajectory of the feed dog in the anti-pushing mode of Example 2 of the small stitch start anti-pushing control method of this application.

[0036] Figure 15 Schematic diagram of the operating trajectory of the tooth lifting drive source in this application.

[0037] Figure 16 This is a schematic diagram of the operating trajectory of the feeding drive source in this application. DETAILED DESCRIPTION

[0038] 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.

[0039] 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" and "one" 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.

[0040] It should also be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it may be directly on the other element or there may be an intervening element. When an element is referred to as being "connected to" another element, it may be directly connected to the other element or indirectly connected to the other element through an intervening element.

[0041] In addition, the descriptions of "first", "second", etc. in this application are for descriptive purposes only and should not be understood as indicating or implying their relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined as "first" or "second" may explicitly or implicitly include at least one of such features. In addition, the technical solutions between the various embodiments can be combined with each other, but this must be based on the fact that they can be implemented by ordinary technicians in this field. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by this application.

[0042] The present application relates to the technical field of sewing machines, and in particular to a method for controlling the material push-up prevention during a small stitch start. The method comprises the following steps.

[0043] Step S1: Figure 4 and Figure 5 As shown, the sewing machine is equipped with an electronic control unit, a tooth frame 10, a feed dog 20 fixed to the tooth frame 10, a tooth lifting mechanism 30 connected to one end of the tooth frame 10 and driving the tooth frame 10 to move back and forth, and a feeding mechanism 40 connected to the other end of the tooth frame 10 and driving the tooth frame 10 to move back and forth horizontally. The tooth lifting mechanism 30 has a tooth lifting drive source 31, and the feeding mechanism 40 has a feeding drive source 41. The tooth lifting drive source 31 and the feeding drive source 41 are both independently set drive sources and are both communicatively connected to the electronic control unit. At the same time, the sewing machine is also equipped with a main shaft 50, a main motor 60 that drives the main shaft 50 to rotate, and a needle bar mechanism 70 that is transmission-connected to the main shaft 50. The needle bar mechanism 70 has a needle 80 that can move back and forth. For ease of description, the axial direction of the main shaft 50 is defined as the left-right direction, and the direction of the main shaft 50 toward the needle bar mechanism 70 is the left direction; the horizontal direction perpendicular to the left-right direction is defined as the front-back direction, and the front direction is the feed direction when the sewing machine is sewing; the numerical direction perpendicular to the left-right direction is defined as the up-down direction. Therefore, the tooth lifting mechanism 30 is connected to the rear end of the tooth frame 10 and drives the tooth frame 10 and the feed dog 20 to reciprocate up and down, and the feeding mechanism 40 is connected to the front end of the tooth frame 10 and drives the tooth frame 10 and the feed dog 20 to reciprocate back and forth. Based on the characteristics that the tooth lifting drive source 31 and the feed drive source 41 are independently set drive sources and are independently controlled, the feed dog 20 has multiple motion trajectories.

[0044] The small stitch length seam start anti-pushing control method includes the steps of driving the tooth lifting drive source 31 and the feed drive source 41 to operate in the anti-pushing mode (including the following steps S2 to S5), and the steps of driving the tooth lifting drive source 31 and the feed drive source 41 to operate in the normal sewing mode (including the following step S6).

[0045] Step S2: Before the sewing machine starts sewing the first stitch, the electronic control unit controls the output of the lifting drive source 31 and the feeding drive source 41 to make the feed dog 20 be in the initial position E of sewing. Figure 6 and Figure 13 As shown, or as Figure 6 and Figure 14 As shown, the feed dog 20 emerges upward from the needle plate 90 of the sewing machine, and the feed dog 20 is at the rear limit position within its travel range.

[0046] Step S3: Figure 6 As shown, when the feed dog 20 is in its initial seam start position E, the presser foot 110 of the sewing machine is raised, and the needle 80 is in the upper needle stop position, the sewing material 120 is inserted. The seam start portion of the sewing material 120 contacts the feed dog 20, and based on the requirements of the thick material seam start process, the seam start portion of the sewing material 120 is also close to the rear side of the needle 80. Then, the presser foot 110 is lowered, pressing against the seam start portion of the sewing material 120. Because the seam start portion of the sewing material 120 has a certain thickness, the rear end of the presser foot 110 is tilted upward. However, since the feed dog 20 emerges upward from the needle plate 90, the feed dog 20 has a retaining effect on the seam start portion of the sewing material 120, preventing the presser foot 110 from pushing the seam start portion of the sewing material 120 backward.

[0047] Step S4, the sewing machine starts sewing the first stitch: When the needle 80 is above the sewing material 120, the electronic control unit controls the output of the tooth lifting drive source 31 and the feed drive source 41 to keep the feed dog 20 in the state of emerging upward from the needle plate 90 and move forward from the initial sewing position E to the position P1. During this process, the feed dog 20 moves the sewing starting position of the sewing material 120 forward by a distance S1 along the feeding direction of the sewing machine. Figure 7 and Figure 13 As shown, or as Figure 7 and Figure 14As shown, the first feeding is completed; in the process of the needle 80 being inserted into the sewing material 120, the electronic control unit controls the output of the tooth-lifting drive source 31 and the feed drive source 41 to keep the feed dog 20 in the state of emerging upward from the needle plate 90 and not moving. In this step S4, the feed dog 20 maintains the state of emerging upward from the needle plate 90 to move the seam start position of the sewing material 120 forward by a distance S1. This can be completed in the process of the needle 80 starting to move down from the upper needle stop position and not piercing into the sewing material 120, or it can be completed in the process of the needle 80 moving upward from the sewing material 120 and then moving up to the upper needle stop position. In this embodiment, it is preferred that when the needle 80 starts to move down from the upper needle stop position and before piercing into the sewing material 120 when sewing the first stitch, the feed dog 20 maintains the state of emerging upward from the needle plate 90 and moves forward from the initial seam start position E to position P1. During this process, the feed dog 20 moves the seam start position of the sewing material 120 forward by a distance S1, as shown in FIG. Figure 7 As shown; that is, the horizontal distance between the initial sewing position E and the position P1 in the front-to-back direction is S1. At the same time, S1 is also the needle drop distance between the needle 80 and the front end of the sewing starting position of the sewing material 120 when the needle 80 starts sewing the first stitch. Figure 8 As shown, the needle 80 continues to move downward and penetrates into the sewing material 120, cooperating with the rotary hook in the sewing machine to complete the action of piercing the cloth and hooking the thread, thereby completing the first stitch of sewing. Figure 9 As shown, the needle 80 moves up to the upper stop position. Therefore, during the process of sewing the first stitch, from the time the needle 80 penetrates the sewing material 120 to the time it moves up to the stop position, the feed dog 20 always remains in a state of emerging upward from the needle plate 90 and remains stationary.

[0048] Step S5, the sewing machine starts sewing the second stitch, ..., until the Nth stitch, N ≥ 2. Each time the Nth stitch is started, while the needle 80 is above the sewing material 120, the electronic control unit controls the output of the tooth lifting drive source 31 and the feed drive source 41 to keep the feed dog 20 in a state of emerging upward from the needle plate 90 and move forward to position P2, position P3, ..., position PN at the current stitch length of the sewing machine. Each time during this process, the feed dog 20 moves the starting point of the sewing material 120 forward by a distance S2 along the feed direction of the sewing machine. Figure 10 As shown, the distance S2 matches the current stitch length of the sewing machine, that is, starting from the second stitch, the feed dog 20 moves above the needle plate 90 at the current stitch length of the sewing machine to complete the Nth feed. Each time the Nth stitch is sewn, while the needle 80 is inserted into the sewing material 120, the electronic control unit controls the output of the tooth-lifting drive source 31 and the feed drive source 41 to keep the feed dog 20 in a state of rising upward from the needle plate 90, thus completing the fabric-piercing and thread-hooking action of the Nth stitch. Therefore, after sewing the second stitch, as shown in FIG. Figure 10 and Figure 13As shown, the feed dog 20 is at position P2, and the total distance △S that the feed dog 20 moves forward along the feeding direction of the sewing machine to move the sewing material 120 is: △S=S1+S2; after sewing the third stitch, the feed dog 20 is at position P3, and the total distance △S that the feed dog 20 moves forward along the feeding direction of the sewing machine to move the sewing material 120 is: △S=S1+2*S2; after sewing the Nth stitch, as shown Figure 12 and Figure 14 As shown, the feed dog 20 is at position PN, and the total distance ΔS that the feed dog 20 moves forward along the feeding direction of the sewing machine to feed the sewing material 120 is: ΔS=S1+(N-1)*S2.

[0049] Specifically, by starting the sewing stitch N, the feed dog 20 is caused to protrude upward from the needle plate 90, advancing the seam starting portion of the sewing material 120 forward by a distance ΔS of S1+(N-1)*S2. This distance ΔS satisfies the following conditions: after the Nth stitch is completed, the total feed distance ΔS is sufficient to push the seam starting portion of the sewing material 120 under the presser foot 110. At this time, the angle α between the presser foot 110 and the horizontal plane satisfies the following conditions: α=0°, or tanα≤μ, where μ is the coefficient of static friction between the seam starting portion of the sewing material 120 and the needle plate 90. When α=0°, the horizontal component of the force applied by the presser foot 110 to the sewing material 120 is zero; when tanα≤μ, the horizontal component of the force applied by the presser foot 110 to the seam starting portion of the sewing material 120 is less than or equal to the maximum static friction between the seam starting portion of the sewing material 120 and the needle plate 90.

[0050] In step S6, the electronic control unit controls the tooth-lifting drive source 31 and the feed drive source 41 to operate according to the normal trajectory corresponding to the normal sewing mode. The tooth-lifting drive source 31 and the feed drive source 41 restore the corresponding relationship with the main shaft 50 in the sewing machine, and the movement trajectory of the feed dog 20 is elliptical, moving forward above the needle plate 90 and moving backward below the needle plate 90; but even if the feed dog 20 sinks under the needle plate 90 and the presser foot 110 presses against the seam starting part of the sewing material 120, since the horizontal component of the force applied by the presser foot 110 to the seam starting part of the sewing material 120 is not greater than the maximum static friction between the seam starting part of the sewing material 120 and the needle plate 90, the presser foot 110 will not push the sewing material 120 backward, thereby ensuring normal sewing.

[0051] In summary, in the process of sewing the first stitch to the Nth stitch, the present application controls the lifting tooth drive source 31 and the feeding drive source 41 to operate separately according to the anti-pushing trajectory corresponding to the anti-pushing mode, so as to adjust the initial sewing position E of the feed dog 20 when sewing, the trajectory of the feed dog 20 of the Nth stitch, and the coordinated movement relationship between the feed dog 20 and the machine needle 80 of the Nth stitch. During this process, the feed dog 20 is always in a state of emerging upward from the needle plate 90, and moves the sewing starting part of the sewing material 120 along the feeding direction of the sewing machine by a preset distance △S, so that the sewing starting part of the sewing material 120 is squeezed under the presser foot 110, thereby sending the sewing starting part of the sewing material 120 to the appropriate position. At this time, the angle α between the presser foot 110 and the horizontal plane satisfies α=0°, or tanα≤μ, so that the horizontal component of the force F applied by the presser foot 110 to the sewing starting part of the sewing material 120 is not greater than the maximum static friction between the sewing starting part of the sewing material 120 and the needle plate 90. After such setting, when the tooth lifting drive source 31 and the feed drive source 41 are operated according to the normal trajectory corresponding to the normal sewing mode, even if the feed dog 20 sinks under the needle plate 90, the sewing material 120 will not be pushed out by the presser foot 110. The present application sets the initial sewing position E of the feed dog 20 and transfers S1+(N-1)*S2 by the feed dog 20 after sewing N stitches to achieve the preset distance △S of the sewing starting position along the feed direction of the sewing machine. This not only completes the sewing process of the sewing machine with a small stitch length, but also ensures that the sewing material 120 is moved forward a sufficient distance △S when the feed dog 20 sinks under the needle plate 90 for the first time, thereby reliably preventing the presser foot 110 from pushing the material backward.

[0052] Preferably, the first material shifting distance S1 when sewing the first stitch can be equal to the second material shifting distance S2 when sewing the second stitch, or S1 can be slightly smaller than S2, or S1 can be slightly larger than S2. In this way, the first material shifting distance S1 can also match the current stitch length of the sewing machine, avoiding the formation of obvious blank stitches before the first stitch.

[0053] Furthermore, the preferred structure of the tooth lifting mechanism 30 is as follows: Figure 4 and Figure 5As shown, the tooth-lifting driving source 31 is a motor, and the tooth-lifting mechanism 30 also includes a first tooth-lifting crank 32, a first tooth-lifting connecting rod 33, a tooth-lifting shaft 34 extending left and right and rotatably supported in the sewing machine base, a second tooth-lifting crank 35 fixed at the right end of the tooth-lifting shaft 34, a third tooth-lifting crank 36 fixed at the left end of the tooth-lifting shaft 34, and a second tooth-lifting connecting rod 37. The first tooth-lifting crank 32 is fixed to the motor shaft of the tooth-lifting driving source 31 by screw locking, and the two ends of the first tooth-lifting connecting rod 33 are rotatably connected to the first tooth-lifting crank 32 and the second tooth-lifting crank 35 respectively, and the two ends of the second tooth-lifting connecting rod 37 are rotatably connected to the third tooth-lifting crank 36 and the tooth frame 10 respectively. The end of the third tooth-lifting crank 36 rotatably connected to the second tooth-lifting connecting rod 37 is a fork-shaped structure, and the end of the second tooth-lifting connecting rod 37 rotatably connected to the tooth frame 10 is also a fork-shaped structure. In this way, when the motor shaft of the tooth lifting driving source 31 rotates, the tooth frame 10 and the feed dog 20 can be driven to reciprocate up and down to perform the tooth lifting action.

[0054] Furthermore, the preferred structure of the feeding mechanism 40 is as follows: Figure 4 and Figure 5 As shown, the feed drive source 41 is a motor, and the feed mechanism 40 also includes a first feed crank 42, a first feed connecting rod 43, a feed shaft 44 extending left and right and rotatably supported in the sewing machine base, a second feed crank 45 fixed to the right end of the feed shaft 44, a tooth frame seat 46 fixed to the left end of the feed shaft 44, and a tooth frame pin 47. The first feed crank 42 is fixed to the motor shaft of the feed drive source 41, and the two ends of the first feed connecting rod 43 are rotatably connected to the first feed crank 42 and the second feed crank 45 respectively. The tooth frame seat 46 is connected to the tooth frame 10 through the tooth frame pin 47. In this way, when the motor shaft of the feed drive source 41 rotates, it can drive the tooth frame 10 and the feed dog 20 to reciprocate back and forth to perform the feeding action.

[0055] Furthermore, in the above-mentioned step S5, when starting to sew the second stitch, the third stitch, ..., the Nth stitch, during each process of starting to sew the Nth stitch, the feed dog 20 maintains a state of emerging upward from the needle plate 90 to move the starting point of the seam of the sewing material 120 forward by a distance S2. This can be accomplished during the process of the needle 80 starting to move downward from the upper needle stop position when starting to sew the stitch and not yet piercing the sewing material 120, or it can be accomplished during the process of the needle 80 moving upward from the sewing material 120 and then moving upward to the upper needle stop position when starting to sew the stitch. In this embodiment, it is preferred that during the process of the needle 80 starting to move downward from the upper needle stop position and not piercing the sewing material 120 when starting to sew the stitch, the feed dog 20 maintains a state of emerging upward from the needle plate 90 and moves forward according to the actual stitch length, so as to move the starting point of the seam of the sewing material 120 forward by a distance S2.

[0056] Furthermore, in step S4 and step S5, Figure 13 or Figure 14As shown, when the sewing machine starts sewing the first stitch to the N-1 stitch, while the feed dog 20 keeps emerging from the needle plate 90 and moves the sewing material 120 along the feeding direction of the sewing machine to the starting position of the seam, the electronic control unit controls the tooth-lifting drive source 31 to always maintain the current output, that is, the tooth-lifting drive source 31 does not operate, and its motion trajectory is a straight line, as shown in FIG. Figure 15 As shown, the feed dog 20 is translated along the feeding direction of the sewing machine, and the motion trajectory of the feed dog 20 is a straight line.

[0057] Furthermore, in step S5, Figure 13 or Figure 14 As shown, when the sewing machine starts sewing the Nth stitch, while the feed dog 20 remains protruding from the needle plate 90 and moves the material 120 toward the starting point of the seam in the feed direction of the sewing machine, the electronic control unit controls the dog-lifting drive source 31 and the feed drive source 41 to operate according to the normal trajectory corresponding to the normal sewing mode. That is, the motion trajectory of the feed dog 20 at the start of sewing the Nth stitch is connected to the motion trajectory corresponding to normal sewing. After the feed dog 20 has moved the material 120 toward the starting point of the seam by a distance S2, the feed dog 20 is flush with the upper surface of the needle plate 90 and at its forward limit position in the feed direction of the sewing machine. Therefore, when sewing the N+1th stitch begins, the feed dog 20 sinks below the needle plate 90 and moves backward.

[0058] Furthermore, two embodiments of a method for controlling the material pushing prevention during seam starting at a small stitch length are provided below.

[0059] Example 1 of a method for controlling the material pushing-back at the start of a seam with a small stitch length: The start of a seam of the material 120 can be delivered to a suitable position by just two stitches, and the method includes the following steps.

[0060] 1.1、As Figure 6 As shown, the sewing material 120 is inserted; at this time, the feed dog 20 is at the initial sewing position E, emerging from the needle plate 90, the presser foot 110 is lifted, the needle 80 is at the upper stop position, and the sewing starting point of the sewing material 120 is close to the rear side of the needle 80.

[0061] 1.2, the first stitch: the needle 80 moves down and before it penetrates into the sewing material 120, the tooth-lifting drive source 31 does not operate, and its operating trajectory is Figure 15 The straight line segment X1 in the feeding drive source 41 is running, and its running trajectory is Figure 16 Thus, the feed drive source 41 drives the feed dog 20 to translate forward a distance S1, as Figure 7 and Figure 13 As shown, the feed dog 20 moves forward from position E to position P1, moving the starting point of the sewing material 120 forward by a distance S1, completing the first feeding. Figure 8 and Figure 9As shown, the needle 80 continues to move downward and penetrates into the sewing material 120, and then moves upward to the upper needle stop position; during this process, the tooth lifting drive source 31 and the feeding drive source 41 are not running, and the operation trajectory of the tooth lifting drive source 31 is Figure 15 The straight line segment X2 in the figure, the running trajectory of the feeding drive source 41 is Figure 16 In the straight line segment Y2, the needle 80 cooperates with the rotary hook in the sewing machine to complete the cloth-piercing and thread-hooking action, completing the first stitch sewing. Figure 15 and Figure 16 In the embodiment, the motor angle A of the main motor 60 corresponds to the needle 80 just puncturing the cloth, and the motor angle B of the main motor 60 corresponds to the completion of puncturing the cloth and hooking the thread.

[0062] 1.3, start sewing the second stitch: Figure 13 As shown, the motion trajectory of the feed dog 20 connects to its motion trajectory corresponding to normal sewing at position P1, and position P1 is located above and behind the second needle motion trajectory of the feed dog 20. Before the second needle 80 moves down and penetrates into the sewing material 120, the tooth lifting drive source 31 operates according to its normal trajectory, as shown in FIG. Figure 15 Feed drive source 41 operates according to its conventional trajectory, as shown Figure 16 As shown, the feed dog 20 moves from position P1 to position P2 along the elliptical motion trajectory of the second needle, moving the starting point of the sewing material 120 forward by a distance S2, completing the second feed. At this time, the starting point of the sewing material 120 has moved forward a sufficient distance S1+S2, and α=0°, or tanα≤μ. The lifting drive source 31 and the feed drive source 41 continue to operate according to their normal trajectory, as shown in FIG. Figure 15 and Figure 16 As shown, the feed dog 20 sinks under the needle plate 90, and the needle 80 moves downward and penetrates into the sewing material 120, as shown in FIG. Figure 11 Finish sewing the second stitch as shown.

[0063] 1.4. Starting from the third stitch, the tooth-lifting drive source 31 and the feeding drive source 41 continue to operate according to their normal tracks until the sewing is completed.

[0064] Example 2 of the control method for preventing material push-up at the start of seam with small stitch spacing: The difference between Example 2 of the control method for preventing material push-up at the start of seam with small stitch spacing and Example 1 of the control method for preventing material push-up at the start of seam with small stitch spacing is that Example 2 of the control method for preventing material push-up at the start of seam with small stitch spacing requires N stitches to deliver the seam start part of the sewing material 120 to the appropriate position, which includes the following steps.

[0065] 2.1、As Figure 6 As shown, put in the sewing material 120, same as the above step 1.1.

[0066] 2.2, start sewing the first stitch, such as Figures 7 to 9 As shown, the first feeding S1 of the feed dog 20 is completed, which is the same as the above step 1.2.

[0067] 2.3, start sewing the second stitch: Figure 10 As shown, the needle 80 moves downward and before it penetrates the sewing material 120, the tooth lifting drive source 31 does not operate, and the feed drive source 41 drives the feed dog 20 to move forward by a distance S2. The feed dog 20 moves forward from position P1 to position P2, moving the seam starting point of the sewing material 120 forward by a distance S2, completing the second feed. At this time, the seam starting point of the sewing material 120 is moved forward by S1+S2, but this distance is not enough to make α=0° or tanα≤μ at this time. Afterwards, as shown in FIG. Figure 11 As shown, the needle 80 continues to move downward to penetrate into the sewing material 120, and then moves upward to the upper needle stop position to complete the cloth-piercing and thread-hooking action; during this process, the tooth-lifting drive source 31 and the feed drive source 41 are not running.

[0068] 2.4, such as Figure 14 As shown, step 2.3 is repeated to complete the sewing of the third stitch, ..., and the N-1 stitch, and the feed dog 20 moves forward to position P(N-1). The feed dog 20 completes N-2 feedings; at this time, the starting point of the sewing material 120 is moved forward by S1+(N-2)*S2.

[0069] 2.5, Start sewing the Nth stitch: Figure 14 As shown, the motion trajectory of the feed dog 20 connects to the motion trajectory corresponding to normal sewing at position P(N-1), and position P(N-1) is located above and behind the motion trajectory of the Nth needle of the feed dog 20. Before the needle 80 of the Nth needle moves down and penetrates into the sewing material 120, the tooth-lifting drive source 31 operates according to its normal trajectory, and the feed drive source 41 operates according to its normal trajectory. The feed dog 20 moves from position P(N-1) along the elliptical motion trajectory of the Nth needle to position PN, moving the sewing starting part of the sewing material 120 forward by a distance S2, completing the Nth feeding. At this time, as shown in FIG. Figure 12 As shown, the starting point of the sewing material 120 has moved forward a sufficient distance S1+(N-1)*S2, and α=0°, or tanα≤μ. Afterwards, the feed dog drive source 31 and the feed drive source 41 continue to operate according to their normal trajectory, the feed dog 20 sinks below the needle plate 90, and the needle 80 moves downward to penetrate the sewing material 120, completing the Nth stitch.

[0070] 2.6. Starting from sewing the N+1 stitch, the tooth lifting drive source 31 and the feeding drive source 41 continue to operate according to their normal tracks until the sewing is completed.

[0071] Therefore, when the current stitch length at the start of sewing of the sewing machine is very small, if the feed dog 20 is moved S1+S2 above the needle plate 90 by the first embodiment of the small stitch length anti-pushing control method at the start of sewing still cannot meet the sufficient material shifting distance, the feed dog 20 is moved a few more stitches above the needle plate 90 by the second embodiment of the small stitch length anti-pushing control method at the start of sewing, that is, moved a few more S2, until S1+(N-1)*S2 meets the sufficient material shifting distance, and then the feed dog 20 sinks into the needle plate 90 for the first time. In the small stitch length sewing mode, the feed dog 20 in the present application is intermittent motion, not continuous motion, for the first N stitches of sewing, and the intermittent motion is manifested in the form of the feed dog 20 moving the material for the first time, the feed dog 20 being stationary, the feed dog 20 moving the material for the second time, the feed dog 20 being stationary, the feed dog 20 moving the material for the third time, the feed dog 20 being stationary, ..., the feed dog 20 moving the material for the Nth time.

[0072] In summary, the present application changes the coordinated motion relationship between the main motor 60 and the tooth-lifting drive source 31 and the feed drive source 41 by changing the running trajectory of the tooth-lifting drive source 31 and the feed drive source 41 during the N stitches before starting to sew, so that the feed dog 20 always moves the sewing material 120 forward by a sufficient distance S1+(N-1)*S2 while emerging upward from the needle plate 90, thereby enhancing the horizontal support of the feed dog 20 and the static friction force for thick materials in the small stitch length sewing mode, preventing the problem of thick materials being pushed back by the presser foot 110 when starting to sew in the small stitch length sewing mode, and broadening the adaptability to sewing thick materials. Moreover, this structure makes little change to the overall structure of the existing sewing machine, and may even not change the overall structure of the existing sewing machine. It can adapt to the small stitch length sewing process by only controlling the running trajectory of the tooth-lifting drive source 31 and the feed drive source 41 to prevent the material from being pushed back when starting to sew.

[0073] In summary, the present invention effectively overcomes various shortcomings of the prior art and has high industrial utilization value.

[0074] 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 controlling the material pushing of a small stitch start seam, characterized in that: The following steps are involved: S1. A sewing machine is provided with an electronic control unit, a tooth frame, a feed dog fixed to the tooth frame, a tooth lifting mechanism connected to one end of the tooth frame and driving the tooth frame to reciprocate vertically, and a feeding mechanism connected to the other end of the tooth frame and driving the tooth frame to reciprocate horizontally, wherein the tooth lifting mechanism has a tooth lifting drive source, and the feeding mechanism has a feeding drive source, wherein the tooth lifting drive source and the feeding drive source are both independently provided drive sources and are both communicatively connected to the electronic control unit; S2: Before the sewing machine starts sewing the first stitch, the electronic control unit controls the output of the feed dog driving source and the feed driving source to place the feed dog in the initial sewing position. At this time, the feed dog emerges upward from the needle plate of the sewing machine. S3. With the presser foot raised, place the material for sewing in the sewing machine, with the seam start point in contact with the feed dog and close to the needle; lower the presser foot so that it presses against the seam start point of the material; S4. Starting the first stitch of the sewing machine: While the needle is above the material to be sewn, the electronic control unit controls the outputs of the tooth-lifting drive source and the feed drive source so that the feed dog remains in a state of emerging upward from the needle plate and starts to move from the initial sewing position, thereby moving the starting point of the sewing material along the feed direction of the sewing machine by a distance of S1. While the needle is inserted into the material to be sewn, the electronic control unit controls the outputs of the tooth-lifting drive source and the feed drive source so that the feed dog remains in a state of emerging upward from the needle plate and does not move. S5, the sewing machine starts sewing the second stitch, ..., until the Nth stitch, N ≥ 2; When sewing each of the 2nd to Nth stitches, while the needle is above the sewing material, the electronic control unit controls the outputs of the tooth-lifting drive source and the feed drive source so that the feed dog remains in a state of emerging upward from the needle plate and moves at the current stitch length of the sewing machine to move the starting point of the sewing material a distance S2 along the feed direction of the sewing machine; while the needle is inserted into the sewing material, the electronic control unit controls the outputs of the tooth-lifting drive source and the feed drive source so that the feed dog remains in a state of emerging upward from the needle plate and does not move; After sewing the Nth stitch, the total distance △S that the feed dog moves the sewing material along the feed direction of the sewing machine is: △S=S1+(N-1)*S2; At this time, the angle α between the presser foot and the horizontal plane satisfies: α=0°, or tanα≤μ, where μ is the static friction coefficient between the starting point of the sewing material and the needle plate; S6. The electronic control unit controls the tooth lifting drive source and the feeding drive source to operate separately according to the conventional trajectory corresponding to the conventional sewing mode.

2. The method for controlling the material pushing prevention during the small stitch start according to claim 1, characterized in that: In step S4, when the needle starts to move downward from the upper stop position and does not penetrate into the sewing material, the feed dog moves the sewing starting part of the sewing material by a distance S1.

3. The method for controlling the material pushing prevention during the small stitch start according to claim 1, characterized in that: In the step S5, each time the Nth stitch is sewn, while the needle starts to move downward from the upper stop position and does not penetrate into the sewing material, the feed dog moves the sewing starting portion of the sewing material by a distance S2.

4. The method for controlling the material pushing prevention during the small stitch start according to claim 1, characterized in that: In the steps S4 and S5, when the sewing machine starts to sew the first stitch to the N-1 stitch, while the feed dog remains in the state of emerging upward from the needle plate and moves the sewing material to the starting position along the feed direction of the sewing machine, the electronic control unit controls the tooth lifting drive source to always maintain the current output, so that the feed dog moves horizontally along the feed direction of the sewing machine.

5. The method for controlling the material pushing prevention during the small stitch start according to claim 1, characterized in that: In step S5, when the sewing machine starts to sew the Nth stitch, in the process of the feed dog maintaining the state of emerging upward from the needle plate and moving the sewing material to the sewing starting position along the feeding direction of the sewing machine, the electronic control unit controls the tooth lifting drive source and the feed drive source to operate separately according to the conventional trajectory corresponding to the conventional sewing mode; after the feed dog moves the sewing material to the sewing starting position a distance S2, the feed dog is in a position where it is flush with the upper surface of the needle plate and is at the limit position in the feeding direction of the sewing machine.

6. The method for controlling the material pushing prevention during the small stitch start according to claim 1, characterized in that: The tooth-lifting driving source is a motor, and the tooth-lifting mechanism also includes a first tooth-lifting crank, a first tooth-lifting connecting rod, a tooth-lifting shaft rotatably supported in the sewing machine base, a second tooth-lifting crank and a third tooth-lifting crank respectively fixed at both ends of the tooth-lifting shaft, and a second tooth-lifting connecting rod. The first tooth-lifting crank is fixed on the motor shaft of the tooth-lifting driving source, and the two ends of the first tooth-lifting connecting rod are respectively rotatably connected to the first tooth-lifting crank and the second tooth-lifting crank, and the two ends of the second tooth-lifting connecting rod are respectively rotatably connected to the third tooth-lifting crank and the tooth frame.

7. The method for controlling the material pushing prevention during the small stitch start according to claim 1, characterized in that: The feeding drive source is a motor, and the feeding mechanism also includes a first feeding crank, a first feeding connecting rod, a feeding shaft rotatably supported in the sewing machine base, a second feeding crank and a tooth rack seat respectively fixed at both ends of the feeding shaft, and a tooth rack pin. The first feeding crank is fixed on the motor shaft of the feeding drive source, and the two ends of the first feeding connecting rod are rotatably connected to the first feeding crank and the second feeding crank respectively. The tooth rack seat is connected to the tooth rack through the tooth rack pin.

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