A seam start and material push prevention control method based on bottom feeding function

Abstract

The present invention provides a seam start anti-pushing control method based on a downward feeding function. When the presser foot is raised, the feed dog is sunk under the needle plate by controlling the action of a feed dog lifting drive source, thereby realizing the downward feeding of the feed dog and facilitating subsequent material collection and discharge. Before discharge, the feed dog is moved to a set first preset position under the needle plate. After discharge, before the presser foot is lowered, the feed dog is moved upward, so that the feed dog emerges from the needle plate, and the feed dog has a holding effect on the seam start portion of the sewing material. When the presser foot is subsequently lowered, the presser foot is reliably prevented from pushing the seam start portion of the sewing material backward. Thereafter, before the feed dog sinks into the needle plate when starting the first stitch, the action of the feed dog lifting drive source and the feed drive source is controlled, so that the feed dog feeds the seam start portion of the sewing material forward by a distance L, so that the angle α between the presser foot and the horizontal plane at this time satisfies α=0°, or tanα≤μ. After the feed dog sinks under the needle plate for the first time, the sewing material will not be pushed backward by the presser foot.

Description

Technical Field

[0001] The invention relates to the technical field of sewing machines, in particular to a seam start and material push-off prevention control method based on a lower feeding function. 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 on the movement trajectory shown, the feed dog is about to sink under the needle plate. As a result, 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 addition, in some sewing machines with a bottom feed function, when the presser foot is raised at the end of sewing, the bottom feed assembly in the sewing machine will drive the feed dog to drop below the upper surface of the needle plate, making it easier for subsequent sewing materials to enter and exit between the presser foot and the needle plate. For example, a sewing machine disclosed in Chinese invention patent application No. 201910905844.3. For these sewing machines with a bottom feed function, when the presser foot is lowered before sewing, the feed dog is completely sunk under the needle plate, making it more likely that thick material will be pushed out after the presser foot is lowered, or when sewing the first stitch. Summary of the Invention

[0004] In view of the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide a seam start anti-pushing control method based on the downward feed function, which can prevent the presser foot from pushing the material when the seam starts next time even if the feed dog is downwardly fed when the presser foot is raised.

[0005] To achieve the above object, the present invention provides a seam start-up and anti-pushing material control method based on the bottom feeding function, the seam start-up and anti-pushing material control method 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 move up and down, and a feeding mechanism connected to the other end of the tooth frame and driving the tooth frame to move back and forth, the tooth lifting mechanism having a tooth lifting drive source, the feeding mechanism having a feed drive source, the tooth lifting drive source and the feed drive source being independently provided and being communicatively connected to the electronic control unit;

[0007] S2, the presser foot in the sewing machine is lifted, and the electronic control unit controls the output of the feed dog driving source to make the feed dog sink under the needle plate in the sewing machine;

[0008] S3, the electronic control unit controls the output of the feed dog lifting drive source and the feed drive source, so that the feed dog remains sunk under the needle plate and moves to a first preset position, where the distance between the first preset position and the front limit position of the feed dog in the feeding direction of the sewing machine is L;

[0009] S4. Insert the sewing material, with the starting point of the sewing material close to the back of the needle;

[0010] S5, the electronic control unit controls the feed drive source to always maintain the current output, and controls the tooth lifting drive source to move, so that the feed dog moves upward to the second preset position. The second preset position is higher than the needle plate and is located directly above the first preset position, and the feed dog emerges upward from the needle plate;

[0011] S6. Put down the presser foot, and then press it against the starting point of the sewing material;

[0012] S7. When the sewing machine starts sewing the first stitch, 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 to cause the feed dog to maintain its upward position from the needle plate and move forward from the second preset position to the third preset position. The third preset position is at the same height as the upper surface of the needle plate and is the front limit position of the feed dog. The feed dog then moves the starting point of the sewing material forward a distance L in the feed direction of the sewing machine. 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.

[0013] S8. The electronic control unit controls the tooth lifting drive source and the material feeding drive source to operate separately according to the conventional trajectory corresponding to the conventional sewing mode.

[0014] Furthermore, in step S1, the sewing machine is further provided with a presser foot lifting mechanism connected to the presser foot, the presser foot lifting mechanism has a presser foot lifting drive source, and the presser foot lifting drive source is communicatively connected to the electronic control unit.

[0015] Furthermore, in step S2, the action of lifting the presser foot and the action of sinking the feed dog under the needle plate are performed simultaneously.

[0016] Furthermore, in step S3, the electronic control unit controls the tooth-lifting driving source to always maintain the current output, so that the feed dog moves backward in a direction opposite to the feeding direction of the sewing machine.

[0017] Furthermore, in step S5, the height difference between the second preset position and the upper surface of the needle plate is H, and H is ≥ 0.5 mm.

[0018] Furthermore, in step S7, when the sewing machine starts to sew the first stitch, the main shaft in the sewing machine rotates from the initial angle to the preset angle. During this process, the electronic control unit controls the tooth lifting drive source and the feed drive source to always maintain their current outputs.

[0019] When the spindle rotates to a preset angle, the electronic control unit controls the movement of the tooth lifting drive source and the feeding drive source.

[0020] Furthermore, the preset angle of the main shaft is: the angle of the main shaft corresponding to when the feed dog is at the second preset position in the conventional sewing mode.

[0021] 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.

[0022] 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.

[0023] As described above, the seam start and material push-proof control method based on the bottom feed function according to the present invention has the following beneficial effects.

[0024] The present invention controls the action of the feed dog lifting drive source when the presser foot is raised, so that the feed dog sinks under the needle plate, thereby achieving the downward feed of the feed dog. The feed dog will not emerge from the needle plate, facilitating subsequent material collection and discharge. At the same time, during the material collection and discharge process, the feed dog can be prevented from scratching the sewing material due to the feed dog emerging from the needle plate. In particular, the present invention moves the feed dog under the needle plate to a set first preset position before discharging the material, and moves the feed dog upward before the presser foot is lowered after discharging the material, so that the feed dog emerges from the needle plate, and the feed dog has a holding effect on the seam start portion of the sewing material; when the presser foot is subsequently lowered, the presser foot can be reliably prevented from pushing the seam start portion of the sewing material backward. Then, before the feed dog sinks into the needle plate when starting to sew the first stitch, by controlling the actions of the feed dog lifting drive source and the feed drive source, the feed dog feeds the starting point of the sewing material forward a distance L, thereby allowing the starting point of the sewing material to be squeezed under the presser foot, and making the angle α between the presser foot and the horizontal plane satisfy α=0°, or tanα≤μ. After that, after the feed dog sinks under the needle plate for the first time, the sewing material will not be pushed backward by the presser foot. Therefore, the present application can not only realize the feeding and unloading of material under the feed dog, but also realize 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

[0025] Figure 1 It is a schematic diagram of the prior art when starting the seam and pushing the material.

[0026] 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.

[0027] Figure 3 This is a schematic structural diagram of the sewing machine for this application.

[0028] Figure 4 This is a structural schematic diagram of the sewing machine of this application from another perspective.

[0029] Figure 5 This is a flow chart of the seam start and material push-proof control method based on the bottom supply function of this application.

[0030] Figure 6 This is a schematic diagram of the structure of the sewing machine of this application at the needle plate when the last sewing is completed.

[0031] Figure 7 for Figure 6 Schematic diagram of the structure when the center seam material is removed.

[0032] Figure 8 for Figure 7 Schematic diagram of the structure after the middle feed dog moves horizontally backward under the needle plate.

[0033] Figure 9 For Figure 8Schematic diagram of the structure after the sewing material is placed in the state.

[0034] Figure 10 for Figure 9 Schematic diagram of the structure after the needle plate moves upward and the presser foot is lowered.

[0035] Figure 11 for Figure 10 Schematic diagram of the structure after the middle feed dog moves the starting point of the sewing material forward by a distance L.

[0036] Figure 12 Schematic diagram of the motion trajectory of the feed dog in the bottom feeding and anti-pushing mode in this application.

[0037] Figure 13 Schematic diagram of the operating trajectory of the tooth lifting drive source in this application.

[0038] Figure 14 This is a schematic diagram of the operating trajectory of the feeding drive source in this application. DETAILED DESCRIPTION

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] The present application relates to the technical field of sewing machines, and more particularly to a method for controlling the starting and preventing the material from being pushed back based on the lower feeding function. Figure 5 As shown, the seam start and material push prevention control method based on the bottom feeding function includes the following steps.

[0044] Step S1: Figure 3 and Figure 4 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, or based on the characteristics that the main motor 60, the tooth lifting drive source 31 and the feed drive source 41 are three power sources with independently controllable outputs, the feed dog 20 has multiple motion trajectories. At the same time, the sewing machine is also equipped with a presser foot lifting 110 mechanism connected to the presser foot 110. The presser foot lifting 110 mechanism has a presser foot lifting 110 driving source, and the presser foot lifting 110 driving source is communicated with the electronic control unit; by controlling the action of the presser foot lifting 110 driving source, the presser foot 110 is lifted and lowered.

[0045] The seam start and anti-pushing control method based on the bottom feed function includes the steps of driving the tooth lifting drive source 31 and the feeding drive source 41 to operate in the bottom feed and anti-pushing mode (including the following steps S2 to S7), and driving the tooth lifting drive source 31 and the feeding drive source 41 to operate in the normal sewing mode (including the following step S8).

[0046] Step S2: When the last sewing is finished, Figure 6 As shown, the sewing material 120 is held between the presser foot 110 and the needle plate 90; based on the linkage relationship between the needle 80 and the feed dog 20, the feed dog 20 is in a state of emerging upward from the needle plate 90. At this time, the electronic control unit receives a signal to lift the presser foot 110, and the electronic control unit controls the drive source for lifting the presser foot 110 to operate, lifting the presser foot 110 in the sewing machine; and the electronic control unit controls the output of the tooth lifting drive source 31, and the tooth lifting drive source 31 operates, driving the feed dog 20 to sink under the needle plate 90 in the sewing machine, and the feed dog 20 moves to the lower feed position P1, as shown in FIG. Figure 7 and Figure 12 As shown, the feed dog 20 is fed downward, so that the feed dog 20 will not emerge from the needle plate 90, which is convenient for subsequent material collection and discharge. At the same time, it can also prevent the feed dog 20 from emerging from the needle plate 90 and scratching the sewing material 120 during the material collection and discharge process.

[0047] Step S3, the electronic control unit controls the output of the tooth lifting drive source 31 and the feed drive source 41, so that the feed dog 20 remains sunk below the needle plate 90 and moves backward from the lower feed position P1 to the first preset position P2. Figure 7 、 Figure 8 and Figure 12 The first preset position P2 should meet the following requirements: Figure 12 As shown, in the feeding direction of the sewing machine, that is, in the front-to-back direction, the distance between the first preset position P2 and the front limit position of the feed dog 20 is L, and the distance L is also the feeding distance of the feed dog 20 when it moves forward for the first time to feed the sewing material 120.

[0048] Step S4: Figure 9 As shown, the sewing material 120 is inserted, and the starting point of the sewing material 120 is adjacent to the rear side of the needle 80. At this time, the presser foot 110 is still in the raised position, and the feed dog 20 is still in the lowered position. Therefore, the feed dog 20 is still in the first preset position P2, and the feed dog 20 is still sunk below the needle plate 90, and will not interfere with the placement of the sewing material 120. After the sewing material 120 is placed, the electronic control unit receives the presser foot 110 lowering signal.

[0049] Step S5: First, Figure 9 、 Figure 10 and Figure 12As shown, the electronic control unit controls the feed drive source 41 to always maintain the current output and controls the tooth lifting drive source 31 to operate. Then the feed drive source 41 does not operate, and only the tooth lifting drive source 31 operates, thereby causing the feed dog 20 to move upward from the first preset position P2 to the second preset position P3. The second preset position P3 should meet the following requirements: Figure 12 As shown, the second preset position P3 is higher than the needle plate 90 and is located directly above the first preset position P2, and the feed dog 20 emerges upward from the needle plate 90.

[0050] Step S6, secondly, as Figure 10 As shown, the electronic control unit controls the presser foot 110 to reset its driving source, and the presser foot 110 is lowered. The presser foot 110 then presses against the seam starting point of the sewing material 120. Because the seam starting point 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 protrudes upward from the needle plate 90, the feed dog 20 has a holding effect on the seam starting point of the sewing material 120, preventing the presser foot 110 from pushing the seam starting point of the sewing material 120 backward.

[0051] Step S7, the electronic control unit receives the sewing start signal, and the electronic control unit controls the main motor 60 to operate, and the main motor 60 drives the main shaft 50 and the needle bar mechanism 70 to move, and the sewing machine starts sewing the first stitch. During the process of 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 second preset position P3 to the third preset position P4. The third preset position P4 should meet the following requirements: Figure 12 As shown, the third preset position P4 is at the same height as the upper surface of the needle plate 90 and is the front limit position of the feed dog 20. Thus, as the feed dog 20 moves forward from the second preset position P3 to the third preset position P4, it moves the seam start point of the sewing material 120 forward a distance L along the feed direction of the sewing machine. At this point, 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 start point 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 start point of the sewing material 120 is less than or equal to the maximum static friction between the seam start point of the sewing material 120 and the needle plate 90.

[0052] In step S8, the electronic control unit controls the tooth-lifting drive source 31 and the feed drive source 41 to operate separately according to the conventional trajectory corresponding to the conventional sewing mode, and the tooth-lifting drive source 31 and the feed drive source 41 restore the corresponding relationship with the coordinated movement of the main shaft 50 in the sewing machine, so that 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.

[0053] In summary, before unloading the material, the present application causes the feed dog 20 to move backward under the needle plate 90 to a set first preset position P2, and then to a starting position (i.e., a second preset position P3) in the front-to-back direction to prevent the material from being pushed out. This movement of the feed dog 20 is completed below the needle plate 90, without affecting the sewing experience of the sewing operator. Subsequently, after unloading the material and before the presser foot 110 is lowered, the feed dog 20 is moved upward, so that the feed dog 20 emerges from the needle plate 90. The feed dog 20 has a retaining effect on the seam starting point of the sewing material 120, preventing the seam starting point of the sewing material 120 from being pushed backward when the subsequent tooth holder 10 is lowered. Then, before the feed dog 20 sinks into the needle plate 90 when starting to sew the first stitch, by controlling the actions of the feed dog lifting drive source 31 and the feed drive source 41, the feed dog 20 feeds the starting point of the sewing material 120 forward by a distance L, thereby allowing the starting point of the sewing material 120 to be squeezed under the presser foot 110, and making the angle α between the presser foot 110 and the horizontal plane satisfy α=0°, or tanα≤μ. After that, after the feed dog 20 sinks under the needle plate 90 for the first time, the sewing material 120 will not be pushed backward by the presser foot 110. Therefore, the present application can not only realize the feeding and unloading of the feed dog 20, but also realize that the feed dog 20 has moved the sewing material 120 forward a sufficient distance when it sinks under the needle plate 90 for the first time, thereby reliably preventing the presser foot 110 from pushing the material.

[0054] Furthermore, the preferred structure of the tooth lifting mechanism 30 is as follows: Figure 3 and Figure 4As 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.

[0055] Furthermore, the preferred structure of the feeding mechanism 40 is as follows: Figure 3 and Figure 4 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.

[0056] Furthermore, in step S2, the lifting of the presser foot 110 and the sinking of the feed dog 20 beneath the needle plate 90 can be performed simultaneously, or the lifting of the presser foot 110 can be performed first, or the sinking of the feed dog 20 beneath the needle plate 90 can be performed first. In this embodiment, the lifting of the presser foot 110 and the sinking of the feed dog 20 beneath the needle plate 90 are performed simultaneously. When the electronic control unit controls the operation of the driving source for lifting the presser foot 110, it also controls the operation of the driving source for lifting the presser foot 110. This prevents the feed dog 20 from scraping the sewing material 120 due to the presser foot 110 being lifted too quickly, while also meeting the operator's requirements for the timing of lifting the presser foot 110.

[0057] Furthermore, in the above step S3, while the feed dog 20 remains sunk under the needle plate 90 and moves backward from the lower feed position P1 to the first preset position P2, 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 during this process, so that the feed dog 20 moves backward in a direction opposite to the feeding direction of the sewing machine.

[0058] Furthermore, in the above step S5, the height difference between the second preset position P3 and the upper surface of the needle plate 90 is H, H≥0.5mm, so that the feed dog 20 can be well stuck to the bottom surface of the sewing material 120, ensuring that the feed dog 20 exerts a certain supporting force on the sewing material 120 at this time.

[0059] Furthermore, in step S7, when the sewing machine starts to sew the first stitch, the main shaft 50 in the sewing machine rotates from the initial angle 0° to the preset angle A. During this process, the electronic control unit controls the tooth lifting drive source 31 and the feed drive source 41 to always maintain their respective current outputs, that is, the tooth lifting drive source 31 and the feed drive source 41 do not operate. When the main shaft 50 rotates to the preset angle A, the electronic control unit controls the tooth lifting drive source 31 and the feed drive source 41 to operate. The preset angle A of the main shaft 50 is: the angle of the main shaft 50 corresponding to when the feed dog 20 is in the second preset position P3 in the conventional sewing mode, which can directly connect the synchronous motion relationship between the tooth lifting drive source 31 and the feed drive source 41 and the main motor 60 during subsequent conventional sewing.

[0060] In summary, the motion trajectories of the tooth-lifting drive source 31 and the feed drive source 41 in this application are as follows: when the last sewing is finished, the presser foot 110 is lifted up and the electronic control unit controls the tooth-lifting drive source 31 to move and controls the feed drive source 41 not to move, then the operation trajectory of the tooth-lifting drive source 31 is Figure 13 The trajectory X1 in the figure, the running trajectory of the feeding drive source 41 is Figure 14 The feed dog moves down to the lower feeding position P1. After that, the electronic control unit controls the feed drive source 41 to operate and controls the tooth lifting drive source 31 to not operate. The operation trajectory of the tooth lifting drive source 31 is Figure 13 The trajectory X2 in the figure is a straight line, and the running trajectory of the feeding drive source 41 is Figure 14 The feed dog moves backward to the first preset position P2 according to the trajectory Y2. After that, the presser foot 110 is put down and the electronic control unit controls the tooth lifting drive source 31 to operate and controls the feed drive source 41 to not operate. The operation trajectory of the tooth lifting drive source 31 is Figure 13 The trajectory X3 in the figure, the running trajectory of the feeding drive source 41 is Figure 14The feed dog moves upward to the second preset position P3 along the left section of the trajectory Y3. After that, upon receiving the sewing start signal, the electronic control unit controls the tooth lifting drive source 31 and the feed drive source 41 to remain inactive until the spindle 50 rotates from the initial angle 0° to the preset angle A. During this process, the operation trajectory of the tooth lifting drive source 31 is Figure 13 The trajectory X4 in the feeding drive source 41 is Figure 14 Finally, the spindle 50 rotates to the preset angle A, and the electronic control unit controls the tooth lifting drive source 31 and the feed drive source 41 to operate. The tooth lifting drive source 31 and the feed drive source 41 resume synchronous motion with the main motor 60. The feed dog first moves forward along the elliptical trajectory to the third preset position P4, and then sinks under the needle plate 90. Thereafter, the main motor 60, the tooth lifting drive source 31, and the feed drive source 41 operate according to the normal trajectory corresponding to the normal sewing mode until sewing is completed.

[0061] This application changes the coordination logic of the main motor 60, the tooth lifting drive source 31, and the feed drive source 41 during the feeding and unloading process, thereby enabling the feed dog 20 to feed and unload the material, and reliably preventing the presser foot 110 from pushing the material when starting to sew. This satisfies both the anti-pushing scenario and the ordinary feeding scenario, without the need for identification and judgment, and broadens the adaptability to sewing. Moreover, this structure makes relatively little change to the overall structure of the existing sewing machine, and can even remain unchanged. By simply controlling the operating trajectory of the tooth lifting drive source 31 and the feed drive source 41, it adapts to the anti-pushing of the material when starting to sew during the feeding and unloading process.

[0062] In summary, the present invention effectively overcomes various shortcomings of the prior art and has high industrial utilization value.

[0063] 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 seam start and material push-back based on the bottom feed function, characterized in that: The method for controlling seam starting and material pushing prevention comprises the following steps: 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 move up and down, and a feeding mechanism connected to the other end of the tooth frame and driving the tooth frame to move back and forth, the tooth lifting mechanism having a tooth lifting drive source, the feeding mechanism having a feed drive source, the tooth lifting drive source and the feed drive source being independently provided and being communicatively connected to the electronic control unit; S2, the presser foot in the sewing machine is lifted, and the electronic control unit controls the output of the tooth lifting drive source to make the feed dog sink under the needle plate in the sewing machine; S3, the electronic control unit controls the output of the feed dog lifting drive source and the feed drive source, so that the feed dog remains submerged under the needle plate and moves to a first preset position, where the distance between the first preset position and the front limit position of the feed dog in the feeding direction of the sewing machine is L; S4. Insert the sewing material, with the starting point of the sewing material close to the back of the needle; S5, the electronic control unit controls the feed drive source to always maintain the current output, and controls the tooth lifting drive source to move, so that the feed dog moves upward to the second preset position. The second preset position is higher than the needle plate and is located directly above the first preset position, and the feed dog emerges upward from the needle plate; S6. Put down the presser foot, and then press it against the starting point of the sewing material; S7. When the sewing machine starts sewing the first stitch, 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 to cause the feed dog to maintain its upward position from the needle plate and move forward from the second preset position to the third preset position. The third preset position is at the same height as the upper surface of the needle plate and is the front limit position of the feed dog. The feed dog then moves the starting point of the sewing material forward a distance L in the feed direction of the sewing machine. 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. S8. 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 seam start and material push-back based on the bottom feed function according to claim 1, characterized in that: In step S1 , the sewing machine is further provided with a presser foot lifting mechanism connected to the presser foot. The presser foot lifting mechanism has a presser foot lifting drive source, and the presser foot lifting drive source is communicatively connected to the electronic control unit.

3. The method for controlling seam start and material push-back based on the bottom feed function according to claim 1, characterized in that: In step S2, the presser foot is lifted and the feed dog is sunk under the needle plate simultaneously.

4. The method for controlling seam start and material push-back based on the bottom feed function according to claim 1, characterized in that: In step S3, the electronic control unit controls the feed dog driving source to always maintain the current output, so that the feed dog moves backward in a direction opposite to the feeding direction of the sewing machine.

5. The method for controlling seam start and material push-back based on the bottom feed function according to claim 1, characterized in that: In step S5, the height difference between the second preset position and the upper surface of the needle plate is H, and H is ≥ 0.5 mm.

6. The method for controlling seam start and material push-back based on the bottom feed function according to claim 1, characterized in that: In step S7, when the sewing machine starts to sew the first stitch, the main shaft of the sewing machine rotates from the initial angle to the preset angle. During this process, the electronic control unit controls the tooth lifting drive source and the feed drive source to always maintain their current outputs. When the spindle rotates to a preset angle, the electronic control unit controls the movement of the tooth lifting drive source and the feeding drive source.

7. The method for controlling seam start and material push-back based on the bottom feed function according to claim 6, characterized in that: The preset angle of the main shaft is: the angle of the main shaft corresponding to when the feed dog is at the second preset position in the conventional sewing mode.

8. The method for controlling seam start and material push-back based on the bottom feed function 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.

9. The method for controlling seam start and material push-back based on the bottom feed function 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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