Thread trimming mechanism of sewing machine and double-needle sewing machine

Abstract

The thread trimming mechanism comprises a fixed cutter, a movable cutter and a movable cutter driving part, a cutter part through hole is formed in the movable cutter, a movable cutter blade is formed by the edge of one side of an orifice in the upper end of the cutter part through hole, and the movable cutter driving part can drive the movable cutter to move to an initial position and a sewing starting extending position. When the movable cutter is located at the sewing starting extending position, the cutter part through hole is located under a machine needle of the sewing machine, and when the movable cutter moves to the initial position, the blade of the movable cutter can be meshed with the blade of the fixed cutter. When the movable cutter is located at the initial position, a bottom thread retaining structure is formed between the bottom thread retaining part and the bottom thread retaining spring, the adsorption assembly is provided with an adsorption opening capable of generating a suction effect, and the adsorption opening is located on the lower side of the cutter part through hole when the movable cutter is located at the initial position; the thread clamping piece is arranged on the upper side of the movable cutter, an upper thread maintaining structure is formed between the upper thread clamping part and the thread clamping piece when the movable cutter is located at the initial position, and the movable cutter driving part comprises a thread trimming motor.

Description

Technical Field

[0001] The invention relates to the technical field of sewing machines, and in particular to a thread trimming mechanism of a sewing machine and a double-needle sewing machine. Background Art

[0002] The conventional thread trimming mechanism in a double-needle sewing machine is driven by an electromagnet in cooperation with a thread trimming cam to drive the moving knife to move forward and backward to achieve the thread trimming function. In this design, the movement stroke of the moving knife is fixed, and the trajectory of the thread trimming cam directly determines the movement stroke of the moving knife. Figure 1 As shown, the thread trimming electromagnet is fixed on the bottom plate. When the thread trimming electromagnet is energized and attracted, the ball of the main rod assembly will be stuck in the groove of the thread trimming cam. As the thread trimming cam rotates, the main rod assembly and the intermediate transmission mechanism composed of multiple transmission parts drive the movable knife driving slider to slide back and forth. The movable knife driving slider drives the movable knife 3 fixed thereon to move back and forth. Therefore, the movable knife also moves back and forth under the drive of the thread trimming cam. After engaging with the fixed knife, the suture thread can be cut.

[0003] The principle of the existing thread cutting mechanism cutting the thread is as follows: Figure 1 and attached Figure 4 As shown, the movable knife has a hook and a movable knife blade. When the movable knife starts to return and prepare to cut the thread, the upper thread and the lower thread have been hooked by the hook on the movable knife. At this time, the upper thread and the lower thread are still a complete thread. When the thread above the movable knife blade of the movable knife contacts and engages with the fixed knife blade on the fixed knife, the sewing thread will be cut. After the thread is cut, the upper thread and the lower thread on the outside of the fixed knife blade are connected to the sewing material, the upper thread on the inside is connected to the needle, the lower thread is connected to the bobbin, and the lower thread is also clamped by the lower thread clamp under the passive knife to prevent it from falling off.

[0004] After the existing double-needle sewing machine cuts the thread, the upper thread ends are relatively long. Therefore, when sewing next time, the longer upper thread ends are easy to intertwine and entangle with the bottom thread or itself on the back of the sewing material, forming a raised thread ball, which is commonly known as a "bird's nest". The bird's nest is not only ugly in appearance, but if this part of the bird's nest is located close to the human body, it will cause skin itching and discomfort. Therefore, how to remove the bird's nest is often a pain point and difficulty in the clothing industry, especially in double-needle sewing machines, which have a rotary shuttle on the left and right. The existing single-needle flat sewing machine can not be used on double needles. At the same time, due to the narrow left and right space in the double-needle sewing machine, the installation space is also extremely limited. Summary of the invention

[0005] In view of the above-mentioned shortcomings of the prior art, the technical problem to be solved by the present invention is to provide a thread trimming mechanism of a sewing machine and a double-needle sewing machine, which can reduce the size of the sewing material bird's nest and effectively prevent the problem of sewing thread coming off.

[0006] To achieve the above-mentioned purpose, the present invention provides a thread trimming mechanism of a sewing machine, comprising a fixed knife, a movable knife and a movable knife driving part, wherein the movable knife is provided with a hook part, and the movable knife is also provided with a knife through hole, and one side edge of the opening at the upper end of the knife through hole constitutes a movable knife blade, and the movable knife driving part can drive the movable knife to move to an initial position and a seam start extension position, and when the movable knife is in the seam start extension position, the knife through hole is located directly below the needle of the sewing machine, and when the movable knife moves from the seam start extension position to the initial position, the movable knife blade can engage with the fixed knife blade of the fixed knife, and the thread trimming mechanism also includes a bottom line holding spring, a thread clamping piece and an adsorption component, and the bottom line holding spring is arranged below the movable knife, and the lower side surface of the movable knife A bottom line holding portion is provided, and a bottom line holding structure for stabilizing the bottom line is formed between the bottom line holding portion and the bottom line holding spring when the movable knife is in the initial position, the adsorption component is provided with a suction port, and can generate a suction effect at the adsorption port, and the adsorption port is located at the lower side of the knife through hole when the movable knife is in the initial position; the thread clamping piece is arranged on the upper side of the movable knife, and a surface thread clamping portion is provided on the movable knife, and when the movable knife is in the initial position, the surface thread clamping portion is located on the side of the knife through hole close to the needle, and a surface thread holding structure for stabilizing the surface thread is formed between the surface thread clamping portion and the thread clamping piece, the movable knife driving portion includes a thread cutting motor and an intermediate transmission assembly, and the thread cutting motor and the movable knife are connected via the intermediate transmission assembly.

[0007] Furthermore, the movable knife moves linearly along the front-rear direction of the sewing machine, and the knife through hole is a strip-shaped hole extending along the front-rear direction.

[0008] Furthermore, it also includes a movable knife guide frame and a movable knife driving slider, the movable knife guide frame is fixed in the sewing machine, the movable knife guide frame is provided with a guide groove extending along the front-to-back direction, the movable knife driving slider is installed in the guide groove, and the movable knife is fixed on the movable knife driving slider.

[0009] Furthermore, the movable knife is also provided with a guide groove connecting the hook portion and the through hole of the knife portion.

[0010] Furthermore, it also includes a fixedly installed support spring sheet, which is supported on the lower side of the bottom line retaining spring.

[0011] Furthermore, the adsorption component comprises a straw, and a port of the straw constitutes a adsorption port.

[0012] The present invention also provides a double-needle sewing machine, including two rotary shuttles and two machine needles, and the two rotary shuttles cooperate with the two machine needles respectively, and also includes the above-mentioned thread cutting mechanism, wherein there are two thread cutting mechanisms, and the two thread cutting mechanisms are respectively used for thread cutting of the two machine needles.

[0013] Furthermore, the two thread trimming mechanisms share one thread trimming mechanism.

[0014] Furthermore, the two thread trimming mechanisms share an intermediate transmission assembly, which includes a rotating crank, a driving connecting rod, a first thread trimming lever, a synchronous connecting rod, a second thread trimming lever, a first movable knife shaft and a second movable knife shaft. The rotating crank is fixed on the output shaft of the thread trimming motor, and the first movable knife shaft and the second movable knife shaft are rotatably installed in the sewing machine. The first thread trimming lever is fixedly connected to the first movable knife shaft, and the second thread trimming lever is fixedly connected to the second movable knife shaft. One end of the driving connecting rod is hinged to the rotating crank, and the other end is hinged to the first thread trimming lever. Both ends of the synchronous connecting rod are respectively hinged to the first thread trimming lever and the second thread trimming lever. The first movable knife shaft is provided with a first swing arm connected to the movable knife of one thread trimming mechanism, and the second movable knife shaft is provided with a second swing arm connected to the movable knife of the other thread trimming mechanism.

[0015] Furthermore, the lengths of the synchronization connecting rod and the driving connecting rod are adjustable.

[0016] As described above, the thread trimming mechanism and the double-needle sewing machine according to the present invention have the following beneficial effects:

[0017] 1. It provides an innovative method to solve the problem of bird nests, realizing the function of a small bird nest when starting to sew. When starting to sew, the surface thread is shortened by the thread cutting mechanism. After the sew, the bird nest on the sewing material is small in size and more beautiful in appearance. It solves the problem that the original bird nest is large in size and causes discomfort after contact with the human body, and meets the user's use needs.

[0018] 2. It can effectively improve the thread rate at the start of sewing. Since the thread behind the start of sewing is clamped by the thread clamp and the movable knife, the surface thread will not be pulled out from the sewing material due to the movement of the thread take-up rod or the needle, thus avoiding the problem of thread derailment at the start of sewing.

[0019] 3. The action of the thread trimmer motor is highly controllable and can well control the action sequence of the moving knife, so as to facilitate the coordination with the action of the sewing machine to realize the action of sewing the bird's nest and the thread trimming action.

[0020] 4. The thread trimming mechanism has a compact and reasonable structure. It does not use any large additional devices to interfere with the user's operation or affect the replacement of the bobbin. It can drive the two moving knives to move synchronously through a thread trimming motor and an intermediate transmission assembly. The moving knife is installed on the shuttle frame. Even if the user changes the needle position and moves the shuttle frame, there is no need to adjust the position of the moving knife because the relative positions of the rotary shuttle and the needle thread hook remain unchanged. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a structural schematic diagram of an existing thread trimming mechanism.

[0022] Figure 2 It is a structural schematic diagram of the thread cutting mechanism of the present invention.

[0023] Figure 3 for Figure 2 Enlarged view of circle A in .

[0024] Figure 4 It is a structural schematic diagram of the movable knife in the present invention.

[0025] Figure 5 It is a schematic diagram of state 1 during the working process of the thread trimming mechanism of the present invention.

[0026] Figure 6 It is a schematic diagram of state 2 during the working process of the thread trimming mechanism of the present invention.

[0027] Figure 7 It is a schematic diagram of state three during the working process of the thread trimming mechanism of the present invention.

[0028] Figure 8 It is a schematic diagram of state 4 during the working process of the thread trimming mechanism of the present invention.

[0029] Fig. 9 It is a schematic diagram of state five during the working process of the thread trimming mechanism of the present invention.

[0030] Fig.10 It is a schematic diagram of state six during the working process of the thread trimming mechanism of the present invention.

[0031] Fig.11 It is a schematic diagram of the surface thread position at six states during the working process of the thread trimming mechanism of the present invention.

[0032] Fig.12 It is a schematic diagram of the seam starter stitch in the present invention.

[0033] Fig.13 It is a schematic diagram of the structure of the intermediate transmission component in the present invention.

[0034] Description of Figure Numbers

[0035] 1 Hook

[0036] 2 Fixed knife

[0037] 2a Fixed blade

[0038] 3. Cutting

[0039] 3a Hook

[0040] 3b Knife through hole

[0041] 3c Moving knife blade

[0042] 3d upper thread clamping part

[0043] 3e Boot Slot

[0044] 4 Thread trimming cam

[0045] 5. Thread trimming electromagnet

[0046] 6 Bottom thread holding spring

[0047] 7. Straw

[0048] 7a Adsorption port

[0049] 8 Wire clamp

[0050] 9 Support spring

[0051] 10 Needle plate

[0052] 10a Adjusting bolt

[0053] 11 Feed dog

[0054] 12 Needle

[0055] 13 Noodles

[0056] 14 Bottom Line

[0057] 15 Moving knife drive slide

[0058] 16 Moving knife guide frame

[0059] 17 Thread trimmer motor

[0060] 18 Turn the crank

[0061] 19 Driving connecting rod

[0062] 20 First Tangent Lever

[0063] 21 First moving knife axis

[0064] 22 Synchronous connecting rod

[0065] 22a First Shot

[0066] 22b Second shot

[0067] 23 Second tangent lever

[0068] 24 Second moving knife axis

[0069] 24a Second swing arm

[0070] B Head seam DETAILED DESCRIPTION

[0071] The following is a description of the implementation of the present invention by means of specific embodiments. Those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification.

[0072] It should be noted that the structures, proportions, sizes, etc. drawn 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 limiting conditions for the implementation of the present invention, so they have no substantial technical significance. Any modification of the structure, change of 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 effects and purposes that can be achieved by the present invention. At the same time, the terms such as "upper", "lower", "left", "right", "middle" and so on 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. The change or adjustment of their relative relationship should also be regarded as the scope of the implementation of the present invention without substantially changing the technical content.

[0073] See also Figures 2 to 13 The present invention provides a thread trimming mechanism of a sewing machine, comprising a fixed knife 2, a movable knife 3 and a movable knife driving unit, wherein the movable knife driving unit is used to drive the movable knife 3 to move. The movable knife 3 is provided with a hook portion 3a, and the hook portion 3a is used to hook the upper thread 13 and the lower thread 14 when trimming the thread. In the thread trimming mechanism of the present invention, the movable knife 3 is also provided with a knife portion through hole 3b, and one side edge of the upper end opening of the knife portion through hole 3b constitutes a movable knife blade 3c. The movable knife driving unit can drive the movable knife 3 to move to an initial position and a seam start extension position. When the movable knife 3 is in the seam start extension position, the knife portion through hole 3b is located directly below the sewing machine needle 12. When the movable knife 3 moves from the seam start extension position to the initial position, the movable knife blade 3c can engage with the fixed knife blade 2a of the fixed knife 2. The thread trimming mechanism also includes a bottom line holding spring 6, a thread clamping piece 8 and an adsorption assembly. The bottom line holding spring 6 is arranged below the movable knife 3. A bottom line holding portion is provided on the lower side of the movable knife 3. When the movable knife 3 is in the initial position, the bottom line holding portion and the bottom line holding spring 6 directly form a bottom line holding structure for stabilizing the bottom line 14. The adsorption assembly is provided with a suction port 7a and can produce a suction effect at the suction port 7a. When the movable knife 3 is in the initial position, the suction port 7a is located at the lower side of the knife through hole 3b; the thread clamping piece 8 is arranged on the upper side of the movable knife 3. A surface thread clamping portion 3d is provided on the movable knife 3. When the movable knife 3 is in the initial position, the surface thread clamping portion 3d is located on the side of the knife through hole 3b close to the needle 12, that is, between the needle 12 and the knife through hole 3b, and a surface thread holding structure is formed between the surface thread clamping portion 3d and the thread clamping piece 8. The movable knife driving portion includes a thread trimming motor 17 and an intermediate transmission assembly. The thread trimming motor 17 is connected to the movable knife 3 through the intermediate transmission assembly.

[0074] The thread trimming mechanism of the present invention can be used in a double-needle sewing machine or a single-needle sewing machine. The thread trimming mechanism cooperates with a machine needle 12 and a rotary hook 1 to work. The thread trimming motor 17 and the adsorption component are controlled by the electronic control system of the sewing machine. The thread trimming mechanism can effectively realize a small-volume bird's nest and effectively prevent the problem of sewing seams and thread derailment. The specific working process and principle are as follows:

[0075] (1) Initial state before seaming, see Figure 5 As shown, at this time, the thread end of the surface thread 13 is located on the needle 12, the movable knife 3 is in the initial position, the bottom line holding part is in contact with the bottom line holding spring 6, and a bottom line holding structure is formed therebetween. The bottom line 14 extending from the bobbin is clamped by the bottom line holding structure to maintain stability.

[0076] (2) See Figure 6 , start sewing. At this time, you can adjust the lower stitch length first so that the stitch length is smaller than the stitch length during normal sewing. The electronic control system of the sewing machine controls the action of the thread trimming motor 17, and the movable knife driving unit drives the movable knife 3 to move from the initial position to the sewing start extension position. The knife through hole 3b is located directly below the needle 12 of the sewing machine. At this time, the bottom line 14 originally clamped below the movable knife 3 may fall off from the bottom line holding spring 6 due to the movement of the movable knife 3. Therefore, the adsorption component is started, and the adsorption port 7a generates negative pressure. The position of the adsorption port 7a is also just below the bottom line 14. Once the bottom line 14 falls off, it will be sucked by the mouth of the suction pipe 7 to ensure that it does not fall off, avoiding the problem of sewing without threading. By controlling the action of the thread trimming motor 17, the movable knife 3 can accurately reach the sewing start extension position and maintain it for a period of time.

[0077] (3) See Figure 7 At this time, the shuttle 1 hooks the thread. At this time, the needle 12 has descended to enter the knife hole 3b of the movable knife 3, and the surface threads 13 on both sides of the hole of the needle 12 also enter the knife hole 3b. At the same time, the tip of the shuttle 1 passes through the thread loop of the surface thread 13.

[0078] (4) See Figure 8 After the shuttle tip of the rotary shuttle 1 enters the loop of the upper thread 13, it continues to move to expand the loop of the upper thread 13. At this time, the needle 12 has moved upward to above the feed dog 11. On the one hand, the rotary shuttle 1 has a certain pulling force on the loop of the upper thread 13. On the other hand, the upper thread 13 is not a complete loop when the first stitch is just started. Therefore, as the rotary shuttle 1 continues to move and the loop expands, the loop of the upper thread 13 breaks, and the thread head of the upper thread 13 detaches from the rotary shuttle 1, and finally the thread head of the upper thread 13 passes through the knife through hole 3b of the movable knife 3 and remains under the movable knife 3.

[0079] (5) The thread take-up lever is in an upward motion. The thread take-up lever of the sewing machine will bring a portion of the upper thread 13 out from under the feed dog 11 until the thread take-up lever is at the highest point (that is, the upper needle stop position). Then the upper thread 13 will no longer be brought out. Fig. 9 Then the movable knife 3 starts to retreat, moving from the seam start extension position toward the initial position, and during the retreat process, the movable knife 3 drives the upper thread 13 toward the fixed knife 2, while the upper thread 13 is continuously driven by the thread take-up rod.

[0080] (6) When the thread take-up lever moves to the upper needle stop position, the movable knife 3 completes the reset action and reaches the initial position. Fig.10 and Fig.11 As shown, the movable knife blade 3c will mesh with the fixed knife blade 2a to cut the face thread 13. When the movable knife 3 reaches the initial position, the face thread clamping portion 3d on the movable knife 3 contacts the thread clamping piece 8, forming a face thread holding structure therebetween, and at this time, the face thread clamping portion 3d is located between the knife through hole 3b and the needle 12, so the part of the face thread 13 connected to the needle 12 will be clamped by the face thread holding structure and will not fall off, while the cut part of the face thread 13 will be sucked away by the suction port 7a located below the movable knife 3.

[0081] At this point, the process of sewing the first stitch is completed. Through the above process, on the one hand, the length of the thread end of the surface thread 13 on the needle 12 can be shortened, and the cut thread end has been sucked away by the suction port 7a and will not accumulate under the oil pan. On the other hand, after the surface thread 13 is cut off, the part of the surface thread 13 connected to the needle 12 will be stably clamped by the thread clamping piece 8 above the passive knife 3 and will not fall off.

[0082] Then the double-needle sewing machine continues to run the second stitch of the seam. Since the upper thread 13 on the needle 12 has been clamped by the thread clamp 8 and the movable knife 3, the thread loop after the second needle is inserted into the rotary shuttle 1 can continue to expand, so the upper thread 13 can bring the lower thread 14 to the sewing material to form a stitch. At the same time, since the thread head of the upper thread 13 is shorter and the current stitch length can be smaller than the normal stitch length during sewing, the bird's nest presented will be very small and will only accumulate to a point, which looks more like a thread cutting and tight stitching effect. At the same time, since the upper thread 13 is clamped during the second stitch, the upper thread 13 will not be brought out of the sewing material due to the movement of the thread take-up rod, which can effectively prevent the seam from coming off. For the stitch of the head of the seam when sewing a small bird's nest, refer to Fig.12 As shown, it is similar to the state of cutting the thread at the end of sewing. Of course, even if the upper thread 13 and the lower thread 14 are intertwined and entangled, the volume of the bird's nest will not be very large because the length of the upper thread 13 has been effectively shortened.

[0083] The thread trimming mechanism of the present invention, when the thread trimming operation is performed after the normal sewing operation is completed, the movable knife 3 extends to the bottom of the needle 12 and exceeds the sewing start extension position by a certain distance to the thread trimming extension position, and then returns to hook the upper thread 13 and the lower thread 14 through the hook portion 3a to reach the fixed knife 2, and then the movable knife blade 3c and the fixed knife blade 2a engage with each other to complete the thread trimming operation. After the thread trimming is completed, the lower thread 14 extending from the rotary hook 1 is located below the movable knife 3 and is clamped by the lower thread holding structure formed by the lower thread holding portion and the lower thread holding spring 6, and the thread trimming mechanism returns to the state before the sewing operation, that is, returns to the state before the sewing operation. Figure 5When the movable knife 3 cuts the thread and comes out of the knife, the suction component works, so that the suction port 7a sucks for a while, to prevent the surface thread 13 cut off during the seaming action of the bird's nest from being sucked away.

[0084] The thread trimming mechanism of the present invention independently drives the movable knife 3 to move through the thread trimming motor 17. The stroke of the movable knife 3 is controllable. When starting to sew, it can cooperate with the bottom thread holding spring 6, the thread clamping piece 8 and the adsorption component to work, and cooperate with the action of the sewing machine needle 12 and the thread take-up rod to shorten and clamp the surface thread 13, which can effectively realize a small-volume bird's nest and effectively prevent the problem of thread derailment at the start of sewing.

[0085] See also Figures 2 to 13 The present invention is further described below with a specific embodiment:

[0086] In this embodiment, see Figure 3 and Figure 4 As a preferred design, the movable knife 3 moves linearly along the front-to-back direction of the sewing machine, and the knife through hole 3b is a strip hole extending along the front-to-back direction. When used in a double-needle sewing machine, since the needle bar of the double-needle sewing machine will swing back and forth during sewing, the length of the knife through hole 3b along the front-to-back direction is determined according to the size of the sewing machine working stitch length and the size of the front-to-back swing range of the needle 12, so as to ensure that the needle 12 can smoothly enter the knife through hole 3b when sewing the first stitch, and the needle 12 will not hit the movable knife 3 when swinging back and forth.

[0087] In this embodiment, see Figure 2 and Figure 5 As a preferred design, the thread trimming mechanism also includes a movable knife guide frame 16 and a movable knife driving slider 15. The movable knife guide frame 16 is fixed on the shuttle frame of the sewing machine. The movable knife guide frame 16 is provided with a guide groove extending in the front-to-back direction. The movable knife driving slider 15 is installed in the guide groove. The movable knife 3 is fixed on the movable knife driving slider 15. The movable knife driving part is connected to the movable knife driving slider 15, and can drive the movable knife driving slider 15 to move straightly forward and backward in the guide groove to realize the knife out and retract.

[0088] In this embodiment, see Figure 4 As a preferred design, the movable knife 3 is also provided with a guide groove 3e connecting the hook portion 3a and the knife through hole 3b. When cutting the thread, the movable knife 3 retreats from under the needle 12 to the initial position, and the hook portion 3a hooks the upper thread 13 and the lower thread 14 and moves toward the fixed knife 2. The upper thread 13 and the lower thread 14 will be located in the guide groove 3e, which plays a role in stabilizing the position of the upper thread 13 and the lower thread 14.

[0089] In this embodiment, see Figure 2 and Figure 4As a preferred design, the bottom line holding spring 6 is an elastic clip. When the movable knife 3 moves, the bottom line holding spring 6 can be in good contact with the lower side of the movable knife 3 to ensure that the bottom line 14 can be stably clamped. The thread trimming mechanism also includes a fixedly installed support spring sheet 9, which is supported on the lower side of the bottom line holding spring 6 and can provide an upward elastic force to the bottom line holding spring 6, further ensuring that the bottom line holding spring 6 and the movable knife 3 can stably clamp the bottom line 14.

[0090] In this embodiment, see Figure 2 and Figure 4 As a preferred design, the adsorption assembly includes a suction pipe 7 and a suction component (not shown in the drawings), the end of the suction pipe 7 constitutes a suction port 7a, the suction pipe 7 is located below the support spring sheet 9, and is tilted, and the suction port 7a is in a horizontal state. The suction pipe 7 is connected to the suction component, and the suction port 7a generates negative pressure through the suction of the suction component, thereby achieving adsorption.

[0091] In this embodiment, see Figure 2 , Figure 3 and Fig.11 The thread clamping piece 8 is an elastic thin sheet structure, which is located below the needle plate 10 and fixed to the needle plate 10 by screws. An adjusting bolt 10a is screwed on the needle plate 10. The adjusting bolt 10a is located above the thread clamping piece 8, and its lower end is used to abut against the thread clamping piece 8. The deformation degree of the thread clamping piece 8 can be adjusted by adjusting the bolt 10a, that is, the contact pressure between the thread clamping piece 8 and the surface thread clamping part 3d of the movable knife 3 can be adjusted, thereby adjusting the thread clamping force on the surface thread 13.

[0092] The present invention also provides a double-needle sewing machine, see Figure 1 , including two rotary hooks 1 and two machine needles 12, the two machine needles 12 are arranged front and back, the two rotary hooks 1 are respectively located on the left and right sides of the two machine needles 12, and one rotary hook 1 works in conjunction with one machine needle 12. It also includes the above-mentioned thread trimming mechanism, correspondingly, there are two thread trimming mechanisms, and the two thread trimming mechanisms are respectively used for the thread trimming work of the two machine needles 12, that is, one thread trimming mechanism works in conjunction with one machine needle 12, and the other thread trimming mechanism works in conjunction with the other machine needle 12.

[0093] In this embodiment, preferably, see Figure 2 and, Figure 3 and Fig.13 The two thread trimming mechanisms share a moving knife driving unit, and a thread trimming motor 17 in the moving knife driving unit drives the two moving knives 3 to move synchronously. Figure 2 and Fig.13The intermediate transmission assembly includes a rotating crank 18, a driving connecting rod 19, a first thread trimming lever 20, a synchronous connecting rod 22, a second thread trimming lever 23, a first movable knife shaft 21 and a second movable knife shaft 24. The rotating crank 18 is fixed to the output shaft of the thread trimming motor 17. The first movable knife shaft 21 and the second movable knife shaft 24 are both rotatably installed in the sewing machine. The first thread trimming lever 20 is fixedly connected to the first movable knife shaft 21, the second thread trimming lever 23 is fixedly connected to the second movable knife shaft 24, and the driving connecting rod One end of 19 is hinged to the rotating crank 18, and the other end is hinged to the first thread cutting lever 20, and the two ends of the synchronous connecting rod 22 are respectively hinged to the first thread cutting lever 20 and the second thread cutting lever 23, the first movable knife shaft 21 is provided with a first swing arm connected to the movable knife 3 of one thread cutting mechanism, and the second movable knife shaft 24 is provided with a second swing arm 24a connected to the movable knife 3 of another thread cutting mechanism. Specifically, the first swing arm and the second swing arm 24a are both transmission connected to the movable knife driving slider 15 where the movable knife 3 is located.

[0094] When the movable knife driving unit in this embodiment is working, the thread trimming motor 17 drives the rotating crank 18 to rotate, and drives the first thread trimming lever 20 to rotate through the driving connecting rod 19. When the first thread trimming lever 20 rotates, it drives the first movable knife shaft 21 to rotate. The first movable knife shaft 21 drives the movable knife driving slider 15 where one movable knife 3 is located to move through the first swing arm thereon, thereby driving the movable knife 3 to move. The first thread trimming lever 20 will also drive the second thread trimming lever 23 to rotate through the synchronous connecting rod 22. When the second thread trimming lever 23 rotates, it drives the second movable knife shaft 24 to rotate. The second movable knife shaft 24 drives the movable knife driving slider 15 where another movable knife 3 is located to move through the second swing arm 24a thereon, thereby driving the movable knife 3 to move, thereby realizing the synchronous movement of the two movable knives 3 in one movable knife driving unit.

[0095] In this embodiment, see Fig.13 As a preferred design, the driving connecting rod 19 is a telescopic rod with adjustable length. The synchronous connecting rod 22 includes a first rod 22a and a second rod 22b. The first rod 22a is provided with a strip hole, and a bolt is passed through the strip hole and screwed into the second rod 22b, so that the first rod 22a and the second rod 22b are fixedly connected. The first rod 22a is hinged to the first tangent lever 20, and the second rod 22b is hinged to the second tangent lever 23. When the position of the bolt in the strip hole is changed, the effective working length of the synchronous connecting rod 22 can be changed. By using the length-adjustable synchronous connecting rod 22 and the driving connecting rod 19, the lengths of the synchronous connecting rod 22 and the driving connecting rod 19 can be adjusted according to the structural conditions of the sewing machine and the working conditions of the movable knife 3, so as to meet the use conditions in various occasions and facilitate assembly.

[0096] In the present invention, the thread trimming motor 17 adopts a stepping motor, and the thread trimming motor 17 is ensured to be at the same zero point each time it is assembled by a limit pin. The moving knife driving sliders 15 of the two thread trimming mechanisms are installed on the shuttle frame where the corresponding rotary hook 1 is located, and the first moving knife shaft 21 and the second moving knife shaft 24 are also installed in the corresponding shuttle frame. Even if the user changes the needle position and moves the shuttle frame, the relative position of the rotary hook 1 and the needle 12 for hooking the thread remains unchanged, so there is no need to adjust the position of the moving knife 3.

[0097] As can be seen from the above, the thread trimming mechanism and the double-needle sewing machine of the present invention have the following beneficial effects:

[0098] 1. An innovative method for solving the bird's nest problem is provided, which realizes the function of a small bird's nest when sewing. When sewing, the surface thread 13 is shortened by a thread cutting mechanism. After sewing, the bird's nest on the sewing material is small in size and more beautiful in appearance. The problem that the original bird's nest is large in size and causes discomfort after contact with the human body is solved, and the user's use needs are met.

[0099] 2. It can effectively improve the thread rate at the start of sewing. Since the surface thread 13 at the start of sewing is clamped by the thread clamping piece 8 and the movable knife 3, the surface thread 13 will not be pulled out from the sewing material due to the movement of the thread take-up rod or the needle 12, thereby avoiding the problem of thread derailment at the start of sewing.

[0100] 3. The action of the thread trimming motor 17 is highly controllable and can well control the action sequence of the movable knife 3, thereby facilitating the coordination of the action of the sewing machine to achieve the action of sewing the bird's nest and the thread trimming action.

[0101] 4. The thread trimming mechanism has a compact and reasonable structure. It does not use any bulky additional devices to interfere with the user's operation and affect the replacement of the bobbin core. It can drive the two movable knives 3 to move synchronously through a thread trimming motor 17 and an intermediate transmission assembly. The movable knife 3 is installed on the shuttle frame. Even if the user changes the needle position and moves the shuttle frame, the relative positions of the rotary hook 1 and the needle 12 for hooking the thread remain unchanged, so there is no need to adjust the position of the movable knife 3.

[0102] In summary, the present invention effectively overcomes various shortcomings in the prior art and has high industrial utilization value.

[0103] 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 familiar with 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 a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A thread trimming mechanism for a sewing machine, comprising a fixed knife (2), a movable knife (3) and a movable knife driving unit, wherein the movable knife (3) is provided with a hook portion (3a), characterized in that: The movable knife (3) is also provided with a knife through hole (3b), and one side edge of the upper end opening of the knife through hole (3b) constitutes a movable knife blade (3c). The movable knife driving unit can drive the movable knife (3) to move to an initial position and a seam start extension position. When the movable knife (3) is in the seam start extension position, the knife through hole (3b) is located directly below the needle (12) of the sewing machine. When the movable knife (3) moves from the seam start extension position to the initial position, the movable knife blade (3c) can engage with the fixed knife blade (2a) of the fixed knife (2). The thread trimming mechanism also includes a bottom line holding spring (6), a thread clamping piece (8) and an adsorption component. The bottom line holding spring (6) is arranged below the movable knife (3). A bottom line holding portion is provided on the lower side of the movable knife (3), and when the movable knife (3) is in the initial position, the bottom line holding portion and the bottom line holding spring (8) are in contact with each other. 6) to form a bottom line holding structure for stabilizing the bottom line (14); the adsorption component is provided with an adsorption port (7a) and is capable of generating a suction effect at the adsorption port (7a); when the movable knife (3) is in the initial position, the adsorption port (7a) is located at the lower side of the knife through hole (3b); the thread clamping piece (8) is arranged on the upper side of the movable knife (3); the movable knife (3) is provided with a surface thread clamping portion (3d); when the movable knife (3) is in the initial position, the surface thread clamping portion (3d) is located at the side of the knife through hole (3b) close to the machine needle (12); and a surface thread holding structure for stabilizing the surface thread is formed between the surface thread clamping portion (3d) and the thread clamping piece (8); the movable knife driving portion comprises a thread cutting motor (17) and an intermediate transmission component; the thread cutting motor (17) and the movable knife (3) are connected via the intermediate transmission component.

2. The thread trimming mechanism according to claim 1, characterized in that: The movable knife (3) moves linearly along the front-rear direction of the sewing machine, and the knife through hole (3b) is a strip-shaped hole extending along the front-rear direction.

3. The thread trimming mechanism according to claim 1, characterized in that: The invention also comprises a movable knife guide frame (16) and a movable knife driving slider (15), wherein the movable knife guide frame (16) is fixed in the sewing machine, a guide groove extending in the front-rear direction is provided in the movable knife guide frame (16), the movable knife driving slider (15) is installed in the guide groove, and the movable knife (3) is fixed on the movable knife driving slider (15).

4. The thread trimming mechanism according to claim 1, characterized in that: The movable knife (3) is also provided with a guide groove (3e) connecting the hook portion (3a) and the knife portion through hole (3b).

5. The thread trimming mechanism according to claim 1, characterized in that: It also includes a fixedly installed support spring sheet (9), which is supported on the lower side of the bottom line retaining spring (6).

6. The thread trimming mechanism according to claim 1, characterized in that: The adsorption component comprises a suction tube (7), and the end of the suction tube (7) constitutes a suction port (7a).

7. A double-needle sewing machine, comprising two rotary hooks (1) and two machine needles (12), wherein the two rotary hooks (1) cooperate with the two machine needles (12) respectively, and characterized in that: It also comprises a thread cutting mechanism as claimed in any one of claims 1 to 6, wherein there are two thread cutting mechanisms, and the two thread cutting mechanisms are respectively used for thread cutting work of two machine needles (12).

8. The double-needle sewing machine according to claim 7, characterized in that: The two thread trimming mechanisms share one thread trimming mechanism.

9. The double-needle sewing machine according to claim 8, characterized in that: The two thread trimming mechanisms share an intermediate transmission assembly, the intermediate transmission assembly comprising a rotating crank (18), a driving connecting rod (19), a first thread trimming lever (20), a synchronous connecting rod (22), a second thread trimming lever (23), a first movable knife shaft (21) and a second movable knife shaft (24), the rotating crank (18) is fixed on the output shaft of the thread trimming motor (17), the first movable knife shaft (21) and the second movable knife shaft (24) are both rotatably installed in the sewing machine, the first thread trimming lever (20) is fixedly connected to the first movable knife shaft (21), The second thread cutting lever (23) is fixedly connected to the second moving knife shaft (24); one end of the driving connecting rod (19) is hinged to the rotating crank (18), and the other end is hinged to the first thread cutting lever (20); the two ends of the synchronous connecting rod (22) are respectively hinged to the first thread cutting lever (20) and the second thread cutting lever (23); the first moving knife shaft (21) is provided with a first swing arm connected to the moving knife (3) of one thread cutting mechanism; the second moving knife shaft (24) is provided with a second swing arm (24a) connected to the moving knife (3) of another thread cutting mechanism.

10. The double-needle sewing machine according to claim 9, characterized in that: The lengths of the synchronous connecting rod (22) and the driving connecting rod (19) are adjustable.

Images