Anti-pushing control method for small-stitch-length sewing starting

Abstract

The invention provides a small-needle-pitch sewing starting anti-pushing control method, which comprises the following steps: in a process from a first needle to an Nth needle of sewing starting, controlling a feed lifting driving source and a feeding driving source to run respectively according to an anti-pushing track corresponding to an anti-pushing mode, and in the process, controlling the feed lifting driving source and the feeding driving source to run respectively according to the anti-pushing track corresponding to the anti-pushing mode; the feed dog is always in a state of protruding upwards from the needle plate, a preset distance S is transferred to the sewing starting part of the sewing material, the sewing starting part of the sewing material is squeezed to the position below the presser foot, and the included angle alpha between the presser foot and the horizontal plane meets the condition that alpha is equal to 0 degree or tan alpha is smaller than or equal to mu, the horizontal component force of the acting force F applied to the sewing starting part of the sewing material by the presser foot is not greater than the maximum static friction force between the sewing starting part of the sewing material and the needle plate, so that the subsequent sewing material is prevented from being pushed out by the presser foot. The sewing starting initial position of the feed dog is set, and the preset distance S of the sewing material is achieved through S1 + (N-1) * S2 transferred by the feed dog after N stitches of sewing starting, so that the sewing process that the sewing machine starts sewing at a small stitch length is completed, and the presser foot is reliably prevented from pushing the material.

Description

Technical Field

[0001] The present invention relates to the technical field of sewing machines, and particularly to a control method for preventing material pushing during starting sewing with a small stitch pitch. Background Art

[0002] When a lockstitch sewing machine sews thick materials such as down jackets, the starting sewing process requires the starting point of the thick material to be placed close to the sewing needle, as Figure 1 shown. After that, 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. Due to the relatively thick thickness of the sewing material, the upward tilt angle θ of the presser foot is relatively large, which also makes the horizontal component of the force F exerted by the presser foot on the thick material relatively large. At the same time, based on the linkage relationship between the feed dog and the sewing needle, when the sewing needle is at the upper stop position, the feed dog is at Figure 2 the position A on its movement trajectory as shown, and the feed dog is about to sink below the needle plate; Figure 2 The horizontal line in represents the upper surface of the needle plate. Thus, during the process of lowering the presser foot or during the first stitch of starting sewing, it is very easy for the horizontal component of F to be greater than the friction between the thick material and the needle plate, resulting in the phenomenon of material pushing during starting sewing, that is, the thick material is pushed out after the presser foot is lowered or the thick material is pushed out when sewing the first stitch. The phenomenon of material pushing during starting sewing will cause the thick material to not be sewn normally.

[0003] To solve the problem of material pushing during starting sewing, some sewing machine manufacturers adopt the following control method for preventing material pushing during starting sewing: changing the initial position of the feed dog in the sewing machine when sewing the first stitch of starting sewing, so that the feed dog is at the position B on its movement trajectory, as Figure 3 shown, so as to achieve that when sewing the first stitch of starting sewing, the feed dog sends the thick material out a sufficient preset distance L. This preset distance L can allow the thick material to squeeze under the presser foot, and during the process of feeding the material for a length of L, the feed dog is always above the needle plate; Figure 3 The horizontal line in represents the upper surface of the needle plate. Once the thick material enters under the presser foot, it will reduce the upward tilt angle θ of the presser foot, and thus reduce the horizontal component of F, making the horizontal component of F zero or less than the friction between the thick material and the needle plate, thereby avoiding the thick material being pushed out by the presser foot. However, in the above control method for preventing material pushing during starting sewing, the preset distance is closely related to the stitch pitch of the first stitch of starting sewing. Some sewing processes require small stitch pitch sewing when starting sewing, such as the dense stitch starting sewing process. Then, when sewing the first stitch of starting sewing, the feed dog cannot send the thick material out a sufficient preset distance. Therefore, the above control method for preventing material pushing during starting sewing is only applicable to the sewing process with normal stitch pitch starting sewing, and cannot be applied to the sewing process with small stitch pitch starting sewing. Summary of the Invention

[0004] In view of the above-mentioned disadvantages of the prior art, the object of the present invention is to provide a control method for preventing material pushing during small stitch starting, which can still prevent the presser foot from pushing the material during small stitch starting.

[0005] To achieve the above object, the present invention provides a control method for preventing material pushing during small stitch starting, including the following steps: S1. Configure an electronic control unit, a tooth rack, a feed dog fixed on the tooth rack, a lifting tooth mechanism connected to one end of the tooth rack and driving the tooth rack to reciprocate up and down, and a feeding mechanism connected to the other end of the tooth rack and driving the tooth rack to reciprocate horizontally in a sewing machine. The lifting tooth mechanism has a lifting tooth drive source, and the feeding mechanism has a feeding drive source. The lifting tooth drive source and the feeding drive source are both independently set drive sources and are both communicatively connected to the electronic control unit; S2. Before the first stitch of the sewing machine starts, the electronic control unit controls the outputs of the lifting tooth drive source and the feeding drive source to make the feed dog in the initial starting position. At this time, the feed dog protrudes upward from the needle plate of the sewing machine; S3. Place the sewing material in the state where the presser foot of the sewing machine is lifted. The starting part of the sewing material contacts the feed dog and is next to the sewing needle; lower the presser foot, and the presser foot presses against the starting part of the sewing material; S4. The sewing machine starts the first stitch: During the process that the sewing needle is above the sewing material, the electronic control unit controls the outputs of the lifting tooth drive source and the feeding drive source to make the feed dog keep the state of protruding upward from the needle plate and start to move from the initial starting position, and transfer the starting part of the sewing material along the feeding direction of the sewing machine by a distance S1; during the process that the sewing needle penetrates into the sewing material, the electronic control unit controls the outputs of the lifting tooth drive source and the feeding drive source to make the feed dog keep the state of protruding upward from the needle plate and not move; S5. The sewing machine starts the second stitch, …, until the Nth stitch, N≥2; Each time the Nth stitch starts, during the process that the sewing needle is above the sewing material, the electronic control unit controls the outputs of the lifting tooth drive source and the feeding drive source to make the feed dog keep the state of protruding upward from the needle plate and move at the current stitch pitch of the sewing machine, and transfer the starting part of the sewing material along the feeding direction of the sewing machine by a distance S2; during the process that the sewing needle penetrates into the sewing material, the electronic control unit controls the outputs of the lifting tooth drive source and the feeding drive source to make the feed dog keep the state of protruding upward from the needle plate and not move; After starting the Nth stitch, the total distance △S that the feed dog transfers the sewing material along the feeding 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 part of the sewing material and the needle plate; S6. The electronic control unit controls the lifting tooth drive source and the feeding drive source to operate respectively according to the conventional trajectories corresponding to the conventional sewing mode.

[0006] Further, in the step S4, during the process that the sewing needle moves downward from the upper stop position and has not penetrated into the sewing material, the feed dog moves the starting sewing part of the sewing material by a distance S1.

[0007] Further, in the step S5, each time when starting to sew the Nth needle, during the process that the sewing needle moves downward from the upper stop position and has not penetrated into the sewing material, the feed dog moves the starting sewing part of the sewing material by a distance S2.

[0008] Further, in the step S4 and the step S5, when the sewing machine starts to sew the first needle to the (N - 1)th needle, during the process that the feed dog keeps emerging upward from the needle plate and moves the starting sewing part of the sewing material along the feeding direction of the sewing machine, the electronic control unit controls the lifting tooth drive source to always maintain the current output, so that the feed dog moves horizontally along the feeding direction of the sewing machine.

[0009] Further, in the step S5, when the sewing machine starts to sew the Nth needle, during the process that the feed dog keeps emerging upward from the needle plate and moves the starting sewing part of the sewing material along the feeding direction of the sewing machine, the electronic control unit controls the lifting tooth drive source and the feeding drive source to operate respectively according to the conventional trajectories corresponding to the conventional sewing mode; after the feed dog moves the starting sewing part of the sewing material by a distance S2, the feed dog is at a position flush with the upper surface of the needle plate and at the extreme limit position in the feeding direction of the sewing machine.

[0010] Further, the lifting tooth drive source is a motor, and the lifting tooth mechanism further includes a first lifting tooth crank, a first lifting tooth connecting rod, a lifting tooth shaft rotatably supported in the sewing machine bottom plate, a second lifting tooth crank and a third lifting tooth crank respectively fixed at both ends of the lifting tooth shaft, and a second lifting tooth connecting rod. The first lifting tooth crank is fixed on the motor shaft of the lifting tooth drive source. Both ends of the first lifting tooth connecting rod are respectively rotatably connected with the first lifting tooth crank and the second lifting tooth crank. Both ends of the second lifting tooth connecting rod are respectively rotatably connected with the third lifting tooth crank and the tooth carrier.

[0011] Further, the feeding drive source is a motor, and the feeding mechanism further includes a first feeding crank, a first feeding connecting rod, a feeding shaft rotatably supported in the sewing machine bottom plate, a second feeding crank and a tooth carrier seat respectively fixed at both ends of the feeding shaft, and a tooth carrier pin. The first feeding crank is fixed on the motor shaft of the feeding drive source. Both ends of the first feeding connecting rod are respectively rotatably connected with the first feeding crank and the second feeding crank. The tooth carrier seat is connected with the tooth carrier through the tooth carrier pin.

[0012] As described above, the small stitch starting sewing anti-pushing control method involved in the present invention has the following beneficial effects.

[0013] During the process of sewing the first needle to the Nth needle in this application, the lifter drive source and the feeding drive source are controlled to operate along the anti-pushing trajectory corresponding to the anti-pushing mode respectively. During this process, the feed dog is always in a state of protruding upward from the needle plate and moving the starting part of the sewing material a preset distance △S along the feeding direction of the sewing machine, so that the starting part 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 force of the force F exerted by the presser foot on the starting part of the sewing material is not greater than the maximum static friction force between the starting part of the sewing material and the needle plate. After such a setting, when the lifter drive source and the feeding drive source operate along the conventional trajectories corresponding to the conventional sewing mode respectively later, even if the feed dog sinks below the needle plate, the phenomenon that the sewing material is pushed out by the presser foot will not occur. In this application, by setting the initial starting position of the feed dog and realizing the preset distance △S for moving the starting part of the sewing material along the feeding direction of the sewing machine through S1+(N - 1)*S2 moved by the feed dog after sewing N needles, not only the sewing process of starting sewing with a small stitch pitch is completed, but also it is realized that when the feed dog sinks below the needle plate for the first time, the sewing material has been moved forward by a sufficient distance, thus reliably preventing the presser foot from pushing the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic diagram of pushing the material during starting sewing in the prior art.

[0015] Figure 2 It is a schematic diagram of the position of the feed dog when the needle is at the upper stop position during the first needle sewing in the prior art.

[0016] Figure 3 It is a schematic diagram of the position of the feed dog when the needle is at the upper stop position under the condition that the feed dog sends out the thick material a preset distance L during the first needle sewing in the prior art.

[0017] Figure 4 and Figure 5 It is a schematic diagram of the connection between the tooth carrier, the lifter mechanism and the feeding mechanism in the sewing machine of this application.

[0018] Figure 6 It is a schematic diagram when putting the sewing material in the small stitch pitch starting sewing anti-pushing control method of this application.

[0019] Figure 7 It is a schematic diagram of feeding during the first needle sewing in the small stitch pitch starting sewing anti-pushing control method of this application.

[0020] Figure 8 It is a schematic diagram of piercing the cloth during the first needle sewing in the small stitch pitch starting sewing anti-pushing control method of this application.

[0021] Figure 9 It is a schematic diagram when the needle moves out of the sewing material during the first needle sewing in the small stitch pitch starting sewing anti-pushing control method of this application.

[0022] Figure 10 This is a schematic diagram of the feeding when the second sewing needle starts in the small stitch starting sewing anti-pushing control method of the present application.

[0023] Figure 11 This is a schematic diagram of piercing the cloth when the second sewing needle starts in the small stitch starting sewing anti-pushing control method of the present application.

[0024] Figure 12 This is a schematic diagram of the feeding when the Nth sewing needle starts in the small stitch starting sewing anti-pushing control method of the present application.

[0025] Figure 13 This is a schematic diagram of the movement trajectory of the feed dog in the anti-pushing mode in the first embodiment of the small stitch starting sewing anti-pushing control method of the present application.

[0026] Figure 14 This is a schematic diagram of the movement trajectory of the feed dog in the anti-pushing mode in the second embodiment of the small stitch starting sewing anti-pushing control method of the present application.

[0027] Figure 15 This is a schematic diagram of the operating trajectory of the lifter drive source in the present application.

[0028] Figure 16 This is a schematic diagram of the operating trajectory of the feed drive source in the present application. Detailed implementation manners

[0029] The following specific embodiments illustrate the implementation manners 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.

[0030] It should be noted that the structures, ratios, sizes, etc. shown in the drawings of this specification are only used to cooperate with the content disclosed in the specification for those skilled in the art to understand and read, and are not used to limit the limiting conditions for the implementation of the present invention. Therefore, they do not have technical essence. Any modification of the structure, change of the proportional relationship or adjustment of the size, without affecting the effects that the present invention can produce and the purposes that can be achieved, should still fall within the scope covered by the technical content disclosed in the present invention. At the same time, the terms such as "upper", "lower", "left", "right", "middle" and "one" cited in this specification are only for the convenience of description and are not used to limit the scope for the implementation of the present invention. The change or adjustment of their relative relationships, without substantial change in the technical content, should also be regarded as the scope for the implementation of the present invention.

[0031] It should also be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or there may be an intermediate element at the same time. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or can also be indirectly connected to the other element through an intermediate element.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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).

[0036] 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.

[0037] Step S3, as 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.

[0038] 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 14 As 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 7As shown; that is, the horizontal distance between the initial sewing position E and the position P1 in the front-back direction is S1. At the same time, S1 is also the needle dropping distance of the sewing needle 80 from the front end of the sewing part of the sewing material 120 when the sewing needle 80 starts sewing the first stitch. After that, as Figure 8 shown, the sewing needle 80 continues to move downward and pierces into the sewing material 120, and cooperates with the rotary hook in the sewing machine to complete the actions of piercing the cloth and hooking the thread, thus completing the first stitch sewing. Then, as Figure 9 shown, the sewing needle 80 moves upward to the top dead center position. Therefore, during the process of sewing the first stitch, from the moment the sewing needle 80 pierces into the sewing material 120 until it moves upward to the stop position, the feed dog 20 always remains in the state of protruding upward from the needle plate 90 and does not move.

[0039] Step S5: The sewing machine starts sewing the second stitch, …, until the Nth stitch, N≥2. Each time when starting to sew the Nth stitch, during the process when the sewing needle 80 is above the sewing material 120, the electronic control unit controls the outputs of the lift dog drive source 31 and the feed drive source 41 to make the feed dog 20 remain in the state of protruding upward from the needle plate 90 and move forward to the positions P2, P3, …, PN at the current stitch pitch of the sewing machine. In each such process, the feed dog 20 moves the starting sewing part of the sewing material 120 forward by a distance S2 along the sewing direction of the sewing machine. As Figure 10 shown, the distance S2 matches the current stitch pitch 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 pitch of the sewing machine to complete the Nth feeding. Each time when starting to sew the Nth stitch, during the process when the sewing needle 80 penetrates the sewing material 120, the electronic control unit controls the outputs of the lift dog drive source 31 and the feed drive source 41 to make the feed dog 20 remain in the state of protruding upward from the needle plate 90 and not move, to complete the actions of piercing the cloth and hooking the thread for the Nth stitch. Therefore, after starting to sew the second stitch, as Figure 10 and Figure 13 shown, the feed dog 20 is at the position P2. The total distance △S that the feed dog 20 moves the sewing material 120 forward along the sewing direction of the sewing machine is: △S = S1 + S2; after starting to sew the third stitch, the feed dog 20 is at the position P3, and the total distance △S that the feed dog 20 moves the sewing material 120 forward along the sewing direction of the sewing machine is: △S = S1 + 2*S2; after starting to sew the Nth stitch, as Figure 12 and Figure 14 shown, the feed dog 20 is at the position PN, and the total distance △S that the feed dog 20 moves the sewing material 120 forward along the sewing direction of the sewing machine is: △S = S1 + (N - 1)*S2.

[0040] Specifically, by starting sewing N stitches, the feed dog 20 moves the starting sewing part of the sewing material 120 forward by a distance △S of S1+(N - 1)*S2 in a state of protruding upward from the needle plate 90. This distance △S satisfies that after completing the Nth stitch sewing, the total feeding distance △S can squeeze the starting sewing part of the sewing material 120 under the presser foot 110. At this time, the included angle α between the presser foot 110 and the horizontal plane satisfies: α = 0°, or tanα ≤ μ, where μ is the static friction coefficient between the starting sewing part of the sewing material 120 and the needle plate 90. When α = 0°, the horizontal component force of the force exerted by the presser foot 110 on the sewing material 120 is zero; when tanα ≤ μ, the horizontal component force of the force exerted by the presser foot 110 on the starting sewing part of the sewing material 120 is less than or equal to the maximum static friction force between the starting sewing part of the sewing material 120 and the needle plate 90.

[0041] Step S6: The electronic control unit controls the lifter drive source 31 and the feed drive source 41 to operate along their respective conventional trajectories corresponding to the conventional sewing mode. The lifter drive source 31 and the feed drive source 41 resume their corresponding relationship with the main shaft 50 in the sewing machine. Then, 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. However, even when the feed dog 20 sinks below the needle plate 90 and the presser foot 110 presses against the starting sewing part of the sewing material 120, since the horizontal component force of the force exerted by the presser foot 110 on the starting sewing part of the sewing material 120 is not greater than the maximum static friction force between the starting sewing part of the sewing material 120 and the needle plate 90, there will be no phenomenon of the presser foot 110 pushing the sewing material 120 backward, ensuring the normal progress of sewing.

[0042] In summary, during the process from the first stitch to the Nth stitch at the start of sewing, the lifter drive source 31 and the feeding drive source 41 are controlled to operate along the anti-pushing trajectory corresponding to the anti-pushing mode, so as to adjust the initial starting position E of the feed dog 20 at the start of sewing, the trajectory of the feed dog 20 at the Nth stitch of starting sewing, and the cooperative movement relationship between the feed dog 20 and the sewing needle 80 at the Nth stitch of starting sewing. During this process, the feed dog 20 is always in a state of protruding upward from the needle plate 90 and moving the starting part of the sewing material 120 a preset distance △S along the feeding direction of the sewing machine, so that the starting part of the sewing material 120 is squeezed under the presser foot 110, thereby sending the starting part of the sewing material 120 to a proper 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 force of the force F exerted by the presser foot 110 on the starting part of the sewing material 120 is not greater than the maximum static friction force between the starting part of the sewing material 120 and the needle plate 90. After such a setting, when the lifter drive source 31 and the feeding drive source 41 operate along the conventional trajectories corresponding to the conventional sewing mode respectively later, even if the feed dog 20 sinks below the needle plate 90, the phenomenon that the sewing material 120 is pushed out by the presser foot 110 will not occur. By setting the initial starting position E of the feed dog 20 and realizing the movement of the starting part of the sewing material 120 a preset distance △S along the feeding direction of the sewing machine through S1+(N - 1)*S2 transferred by the feed dog 20 after the Nth stitch of starting sewing, the sewing process of starting sewing with a small stitch pitch by the sewing machine is completed, and it is also realized that when the feed dog 20 first sinks below the needle plate �0, the sewing material 120 has been transferred forward by a sufficient distance △S, thus reliably preventing the presser foot 110 from pushing the material backward.

[0043] Preferably, the first material transfer distance S1 at the first stitch of starting sewing can be equal to the second material transfer distance S2 at the second stitch of starting sewing, or S1 can be slightly less than S2, or S1 can be slightly greater than S2. In this way, the first material transfer distance S1 can also match the current stitch pitch of the sewing machine, avoiding the formation of an obvious blank stitch before the first stitch.

[0044] Furthermore, the preferred structure of the lifter mechanism 30 is: as Figure 4 and Figure 5As shown, the lifting drive source 31 is a motor. The lifting mechanism 30 further includes a first lifting crank 32, a first lifting connecting rod 33, a lifting shaft 34 that extends left and right and is rotatably supported in the sewing machine base plate, a second lifting crank 35 fixed to the right end of the lifting shaft 34, a third lifting crank 36 fixed to the left end of the lifting shaft 34, and a second lifting connecting rod 37. The first lifting crank 32 is fixedly secured to the motor shaft of the lifting drive source 31 by screws. The two ends of the first lifting connecting rod 33 are respectively rotatably connected to the first lifting crank 32 and the second lifting crank 35. The two ends of the second lifting connecting rod 37 are respectively rotatably connected to the third lifting crank 36 and the tooth carrier 10. The end of the third lifting crank 36 rotatably connected to the second lifting connecting rod 37 is a fork-shaped structure, and the end of the second lifting connecting rod 37 rotatably connected to the tooth carrier 10 is also a fork-shaped structure. Thus, when the motor shaft of the lifting drive source 31 rotates, it can drive the tooth carrier 10 and the feed dog 20 to reciprocate up and down, performing the lifting action.

[0045] Further, the preferred structure of the feeding mechanism 40 is as follows: As Figure 4 and Figure 5 shown, the feeding drive source 41 is a motor. The feeding mechanism 40 further includes a first feeding crank 42, a first feeding connecting rod 43, a feeding shaft 44 that extends left and right and is rotatably supported in the sewing machine base plate, a second feeding crank 45 fixed to the right end of the feeding shaft 44, a tooth carrier seat 46 fixed to the left end of the feeding shaft 44, and a tooth carrier pin 47. The first feeding crank 42 is fixed to the motor shaft of the feeding drive source 41. The two ends of the first feeding connecting rod 43 are respectively rotatably connected to the first feeding crank 42 and the second feeding crank 45. The tooth carrier seat 46 is connected to the tooth carrier 10 through the tooth carrier pin 47. Thus, when the motor shaft of the feeding drive source 41 rotates, it can drive the tooth carrier 10 and the feed dog 20 to reciprocate back and forth, performing the feeding action.

[0046] Further, in the above step S5, when starting to sew the second needle, the third needle,..., the Nth needle, during the process of starting to sew the Nth needle each time, the feed dog 20 remains in the state of protruding upward from the needle plate 90 and moves the starting sewing part of the sewing material 120 forward by a distance S2. This can be completed during the process when the needle 80 moves downward from the upper stop position and has not penetrated into the sewing material 120 when starting to sew this needle, or can also be completed during the process when the needle 80 moves upward from the sewing material 120 to the upper stop position after moving out of the sewing material 120 when starting to sew this needle. In this embodiment, it is preferably that during the process when the needle 80 moves downward from the upper stop position and has not penetrated into the sewing material 120 when starting to sew this needle, the feed dog 20 remains in the state of protruding upward from the needle plate 90 and moves forward according to the actual stitch pitch, moving the starting sewing part of the sewing material 120 forward by a distance S2.

[0047] Further, in steps S4 and S5, as Figure 13 or Figure 14As shown, when the sewing machine makes the first to the (N - 1)th stitches during starting sewing, in the process of the feed dog 20 moving the starting part of the sewing material 120 along the feeding direction of the sewing machine while remaining in the state of protruding upward from the needle plate 90, the electronic control unit controls the lifter drive source 31 to always maintain the current output, that is, the lifter drive source 31 does not operate, and its movement trajectory is a straight line, as Figure 15 shown, so that the feed dog 20 translates along the feeding direction of the sewing machine, and the movement trajectory of the feed dog 20 is a straight line.

[0048] Furthermore, in step S5, as Figure 13 or Figure 14 shown, when the sewing machine makes the Nth stitch during starting sewing, in the process of the feed dog 20 moving the starting part of the sewing material 120 along the feeding direction of the sewing machine while remaining in the state of protruding upward from the needle plate 90, the electronic control unit controls the lifter drive source 31 and the feed drive source 41 to operate respectively according to the normal trajectories corresponding to the normal sewing mode, that is, when making the Nth stitch during starting sewing, the movement trajectory of the feed dog 20 accesses the movement trajectory corresponding to its normal sewing; after the feed dog 20 moves the starting part of the sewing material 120 by a distance S2, the feed dog 20 is in a position flush with the upper surface of the needle plate 90 and at the front extreme limit position in the feeding direction of the sewing machine. Therefore, when starting to sew the (N + 1)th stitch, the feed dog 20 sinks below the needle plate 90 and moves backward.

[0049] Furthermore, the following provides two embodiments of the small stitch pitch starting sewing anti-pushing control method.

[0050] Embodiment 1 of the small stitch pitch starting sewing anti-pushing control method: The starting part of the sewing material 120 can be sent to a proper position by making two stitches during starting sewing, and it includes the following steps.

[0051] 1.1. As Figure 6 shown, place the sewing material 120; at this time, the feed dog 20 protrudes from the needle plate 90 at the starting initial position E, the presser foot 110 is lifted, the sewing needle 80 is at the upper stop position, and the starting part of the sewing material 120 is closely adjacent to the rear side of the sewing needle 80.

[0052] 1.2. Make the first stitch: Before the sewing needle 80 moves down and pierces into the sewing material 120, the lifter drive source 31 does not operate, and its movement trajectory is the straight line segment X1 in Figure 15 ; the feed drive source 41 operates, and its movement trajectory is the line segment Y1 in Figure 16 ; thus, the feed drive source 41 drives the feed dog 20 to translate forward by a distance S1. As Figure 7 and Figure 13 shown, the feed dog 20 translates forward from the position E to the position P1, moves the starting part of the sewing material 120 forward by a distance S1, and completes the first feeding. After that, as Figure 8 and Figure 9As shown, the sewing needle 80 continues to move downward and pierces into the sewing material 120, and then moves upward to the top stop position; during this process, neither the lifter drive source 31 nor the feed drive source 41 operates, and the operating trajectory of the lifter drive source 31 is Figure 15 the straight line segment X2 in, and the operating trajectory of the feed drive source 41 is Figure 16 the straight line segment Y2 in. The sewing needle 80 cooperates with the rotary hook in the sewing machine to complete the action of piercing the cloth and hooking the thread, and complete the first stitch sewing. Figure 15 and Figure 16 In, the motor angle A of the main motor 60 corresponds to the moment when the sewing needle 80 just pierces the cloth, and the motor angle B of the main motor 60 corresponds to the completion of piercing the cloth and hooking the thread.

[0053] 1.3. Starting the second stitch: As shown in Figure 13 , the movement trajectory of the feed dog 20 accesses the corresponding movement trajectory during normal sewing at position P1, and position P1 is located above and behind the movement trajectory of the feed dog 20 for the second stitch. Before the sewing needle 80 moves downward and pierces into the sewing material 120 when starting the second stitch, the lifter drive source 31 operates according to its normal trajectory, as shown in Figure 15 ; the feed drive source 41 operates according to its normal trajectory, as shown in Figure 16 ; the feed dog 20 moves from position P1 along the elliptical movement trajectory of the second stitch to position P2, and moves the starting part of the sewing material 120 forward by a distance S2 to complete the second feeding. At this time, the starting part of the sewing material 120 has moved forward by a sufficient distance S1 + S2, and α = 0° or tanα ≤ μ. The lifter drive source 31 and the feed drive source 41 continue to operate according to their normal trajectories, as shown in Figure 15 and Figure 16 , the feed dog 20 sinks below the needle plate 90, and the sewing needle 80 moves downward and pierces into the sewing material 120, as shown in Figure 11 , to complete the second stitch sewing.

[0054] 1.4. Starting from the third stitch, the lifter drive source 31 and the feed drive source 41 continue to operate according to their normal trajectories until the sewing is completed.

[0055] Embodiment 2 of the control method for preventing material pushing during small stitch starting: The difference between Embodiment 2 of the control method for preventing material pushing during small stitch starting and Embodiment 1 of the control method for preventing material pushing during small stitch starting is that Embodiment 2 of the control method for preventing material pushing during small stitch starting requires starting N stitches to send the starting part of the sewing material 120 to a suitable position, and it includes the following steps.

[0056] 2.1. As shown in Figure 6 , put in the sewing material 120, the same as step 1.1 above.

[0057] 2.2. Start the first stitch, as shown in Figures 7 to 9 , and complete the first feeding S1 of the feed dog 20, the same as step 1.2 above.

[0058] 2.3. Second stitch at the start of sewing: As Figure 10 shown, before the sewing needle 80 moves downward and penetrates into the sewing material 120, the lifter drive source 31 does not operate, and the feed drive source 41 drives the feed dog 20 to translate forward by a distance S2. The feed dog 20 translates forward from position P1 to position P2, moving the starting part of the sewing material 120 forward by a distance S2 to complete the second feeding. At this time, the starting part of the sewing material 120 has been moved forward by S1 + S2, but this distance is not sufficient to make α = 0° or tanα ≤ μ at this time. After that, as Figure 11 shown, the sewing needle 80 continues to move downward and penetrates into the sewing material 120, and then moves upward to the top stop position to complete the action of piercing the cloth and hooking the thread. During this process, neither the lifter drive source 31 nor the feed drive source 41 operates.

[0059] 2.4. As Figure 14 shown, repeat step 2.3 to complete the sewing of the third stitch, …, the (N - 1)-th stitch. The feed dog 20 translates forward to position P(N - 1), and the feed dog 20 completes (N - 2) feedings. At this time, the starting part of the sewing material 120 has been moved forward by S1 + (N - 2) * S2.

[0060] 2.5. N-th stitch at the start of sewing: As Figure 14 shown, the movement trajectory of the feed dog 20 connects to its corresponding movement trajectory during normal sewing at position P(N - 1), and position P(N - 1) is located above and behind the movement trajectory of the N-th stitch of the feed dog 20. Before the sewing needle 80 moves downward and penetrates into the sewing material 120 for the N-th stitch at the start of sewing, the lifter 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 movement trajectory of the N-th stitch to position PN, moving the starting part of the sewing material 120 forward by a distance S2 to complete the N-th feeding. At this time, as Figure 12 shown, the starting part of the sewing material 120 has been moved forward by a sufficient distance S1 + (N - 1) * S2, and α = 0° or tanα ≤ μ. After that, the lifter drive source 31 and the feed drive source 41 continue to operate according to their normal trajectories, the feed dog 20 sinks below the needle plate 90, and the sewing needle 80 moves downward and penetrates into the sewing material 120 to complete the sewing of the N-th stitch.

[0061] 2.6. Starting from the (N + 1)-th stitch at the start of sewing, the lifter drive source 31 and the feed drive source 41 continue to operate according to their normal trajectories until the sewing ends.

[0062] Therefore, when the current stitch pitch during the start of sewing by the sewing machine is extremely small, and the feed dog 20 is moved S1 + S2 above the needle plate 90 through the first embodiment of the anti-pushing material control method for starting sewing with a small stitch pitch, and still cannot meet the sufficient material moving distance, then through the second embodiment of the anti-pushing material control method for starting sewing with a small stitch pitch, the feed dog 20 is moved several more stitches above the needle plate 90, that is, several more S2 are moved, until S1+(N - 1)*S2 meets the sufficient material moving distance, and then the feed dog 20 sinks into the needle plate 90 for the first time. In the small stitch pitch start sewing mode, the feed dog 20 in the present application moves intermittently in the first N stitches during start sewing, not continuously. The manifestation form of the intermittent movement is that the feed dog 20 moves the material for the first time, the feed dog 20 stops, the feed dog 20 moves the material for the second time, the feed dog 20 stops, the feed dog 20 moves the material for the third time, the feed dog 20 stops,..., the feed dog 20 moves the material for the Nth time.

[0063] In summary, the present application changes the operating trajectories of the lifter drive source 31 and the feed drive source 41 during the first N stitches before starting sewing, so as to change the cooperative movement relationship between the main motor 60 and the lifter drive source 31 and the feed drive source 41, and enables the feed dog 20 to move the sewing material 120 forward a sufficient distance S1+(N - 1)*S2 in a state of always emerging upward from the needle plate 90, enhancing the support of the feed dog 20 and the static friction force on the thick material in the horizontal direction in the small stitch pitch sewing mode, preventing the problem that the thick material is pushed backward by the presser foot 110 during the start of sewing in the small stitch pitch sewing mode, and broadening the adaptability to sewing thick materials. Moreover, the modification of the overall structure of the existing sewing machine by this structure is small, and even the overall structure of the existing sewing machine can be unchanged. Only by controlling the operating trajectories of the lifter drive source 31 and the feed drive source 41, it can adapt to the anti-pushing material during the start of sewing in the small stitch pitch start sewing process.

[0064] In summary, the present invention effectively overcomes various shortcomings in the prior art and has high industrial utilization value.

[0065] The above embodiments only illustrate the principles and effects of the present invention by way of example, and are not used to limit the present invention. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes completed by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed by the present invention should still 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; 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; 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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