A thread trimming device for a sewing machine, a thread trimming method, and a sewing machine

Abstract

The application provides a sewing machine thread cutting device, a thread cutting method and a sewing machine. The sewing machine thread cutting device comprises a first thread cutting mechanism and a second thread cutting mechanism. The first thread cutting mechanism comprises a first thread cutting driving source, a thread cutting knife set and a first transmission unit. The thread cutting knife set comprises a movable driving knife. The second thread cutting mechanism comprises a second thread cutting driving source, a first knife edge and a second knife edge which are fixed on the bottom surface of a needle plate and are distributed on both sides of a needle falling hole, a sliding knife blade which is movably installed on the bottom surface of the needle plate, and a second transmission unit. The sliding knife blade is provided with an avoiding groove, a first movable edge and a second movable edge which are distributed side by side along the moving direction of the sliding knife blade, and the first movable edge and the second movable edge are arranged in the avoiding groove. The first thread cutting mechanism cuts the thread after sewing is finished. The second thread cutting mechanism cuts the thread end when sewing is started and cuts the thread end again after the thread is cut when sewing is finished, so that the thread end remaining on the sewing material after cutting is shorter, and the quality of the sewing product is improved.

Description

Technical Field

[0001] This invention relates to a sewing machine thread-cutting device.

[0002] The present invention also relates to a sewing machine thread cutting method using the above-described sewing machine thread cutting device.

[0003] The present invention further relates to a sewing machine that includes the above-described sewing machine thread trimming device. Background Technology

[0004] A sewing machine is a machine that uses one or more sewing threads to create one or more stitches on fabric, allowing one or more layers of fabric to interweave or sew together. A sewing machine typically consists of four parts: a base, a feeding device, a transmission device, and accessories. Through the coordinated movement of these mechanisms, they work in a cyclical manner to sew the fabric together.

[0005] Thread trimming devices are common accessories for sewing machines, used for automatic thread trimming. In some sewing machines, thread trimming devices are used to catch and cut the top thread end when sewing begins, and to cut the top and bottom threads after sewing is completed, such as the thread trimming mechanism disclosed in Chinese Invention Patent Application No. 201811350563.8. However, it uses an electromagnet as the driving source, and its driving structure is complex, making the thread trimming time and position uncontrollable, resulting in defects such as long thread ends, poor stability, and high noise.

[0006] There is another thread-cutting technique where the sewing machine performs small stitch lengths during thread cutting. This eliminates the influence of the sewing machine's stitch length and shortens the distance between the thread-cutting blade and the upper surface of the needle plate, resulting in a short thread tail after a single cut. However, due to factors such as the thickness of the needle plate and the space required for the thread-cutting blade to move beneath it, it is impossible to achieve an even shorter thread tail, thus failing to meet high-end sewing requirements. Summary of the Invention

[0007] In view of the shortcomings of the prior art described above, the purpose of the present invention is to provide a sewing machine thread cutting device that cuts the thread end when sewing begins, and cuts the thread end again after sewing ends.

[0008] To achieve the above objectives, the present invention provides a sewing machine thread cutting device, comprising a first thread cutting mechanism and a second thread cutting mechanism. The first thread cutting mechanism includes a first thread cutting drive source, a thread cutting blade assembly, and a first transmission unit. The thread cutting blade assembly includes a movable active blade, which is distributed below the needle plate in the sewing machine. The first thread cutting drive source is connected to the active blade via the first transmission unit. The needle plate has a needle drop hole and a toothed groove. The second thread cutting mechanism includes a second thread cutting drive source, a first cutting edge and a second cutting edge fixed on the bottom surface of the needle plate and distributed on both sides of the needle drop hole, a sliding blade movably mounted on the bottom surface of the needle plate, and a second transmission unit. The second thread cutting drive source is connected to the sliding blade via the second transmission unit and drives the sliding blade to move along the parallel distribution direction of the first cutting edge and the second cutting edge. The sliding blade has an avoidance groove and a first movable cutting edge and a second movable cutting edge arranged side by side along its moving direction. The avoidance groove communicates with both the needle drop hole and the toothed groove. The first movable cutting edge and the second movable cutting edge are both disposed in the avoidance groove.

[0009] When the sliding blade moves along the first direction, the first movable cutting edge can engage with the first cutting edge;

[0010] When the sliding blade moves in a second direction opposite to the first direction, the second movable cutting edge can engage with the second cutting edge.

[0011] Furthermore, the first and second cutting edges are distributed on both sides of the needle hole along the feeding direction of the sewing machine; there are two clearance grooves, namely the first clearance groove and the second clearance groove. The first clearance groove and the second clearance groove are distributed side by side along the moving direction of the sliding blade and both extend straight along the moving direction of the sliding blade. The first movable cutting edge is located at the end of the first clearance groove near the second clearance groove, and the second movable cutting edge is located at the end of the second clearance groove near the first clearance groove.

[0012] Furthermore, the second thread-cutting mechanism also includes two guide screws fixed on the bottom surface of the needle plate, one of which is inserted into the first clearance groove and the two are slidably engaged, and the other guide screw is inserted into the second clearance groove and the two are slidably engaged.

[0013] Furthermore, the sewing machine thread cutting device also includes a thread suction nozzle, and the active blade has a thread hooking groove that allows the sewing machine needle to pass through; when the active blade is in the initial position, the thread hooking groove is located at the suction port of the thread suction nozzle.

[0014] Furthermore, both the first wire-cutting drive source and the second wire-cutting drive source are motors.

[0015] Furthermore, the first transmission unit includes a first drive crank driven to rotate by a first thread-cutting drive source, a thread-cutting roller rotatably mounted on the first drive crank, a thread-cutting lever with a fixed fulcrum, a first connecting rod, a first thread-cutting shaft rotatable about a fixed axis, a first thread-cutting crank and a second thread-cutting crank respectively fixed at both ends of the first thread-cutting shaft, a second connecting rod, and a movable blade holder rotatable about the lower shaft of the sewing machine. One end of the thread-cutting lever is provided with a thread-cutting groove that can contact and cooperate with the thread-cutting roller. The two ends of the first connecting rod are respectively hinged to the other end of the thread-cutting lever and the first thread-cutting crank. The two ends of the second connecting rod are respectively hinged to the second thread-cutting crank and the movable blade holder. The active blade is fixed on the movable blade holder.

[0016] Furthermore, the second transmission unit includes a second drive crank driven to rotate by a second wire-cutting drive source, a third connecting rod, a second wire-cutting shaft rotatable about a fixed axis, a third and a fourth wire-cutting crank respectively fixed at both ends of the second wire-cutting shaft, a fourth connecting rod, a swing shaft rotatable about a fixed axis, and a fifth wire-cutting crank and a wire-cutting lever both fixed on the swing shaft. The two ends of the third connecting rod are respectively hinged to the second drive crank and the third wire-cutting crank, and the two ends of the fourth connecting rod are respectively hinged to the fourth and the fifth wire-cutting crank. The end of the wire-cutting lever is provided with a pushing part, and the sliding blade is provided with a sliding drive groove for accommodating the pushing part.

[0017] Furthermore, the outer peripheral surface of the pushing part is a cylindrical surface, and the pushing part and the groove wall of the sliding drive groove are in line contact fit.

[0018] Furthermore, the sewing machine thread cutting device also includes a thread sweeping device, which has a thread sweeping drive source, a swingable hook, and a thread sweeping transmission unit connected between the thread sweeping drive source and the swing hook. The end of the swing hook has a hook portion capable of hooking the thread.

[0019] Furthermore, the first and second cutting edges are integrally fixed to the bottom surface of the needle plate.

[0020] The present invention also provides a sewing machine thread cutting method, using the above-described sewing machine thread cutting device, the sewing machine thread cutting method comprising the following steps:

[0021] S1. In the initial state of the sewing machine, the sliding blade is in its initial position, the first and second movable cutting edges are both distributed on the side of the second cutting edge away from the first cutting edge, and the clearance groove is located directly below the needle hole and tooth groove on the needle plate.

[0022] S2. After the sewing machine sets the number of stitches, the second thread cutting drive source is activated, driving the sliding blade to move toward the first cutting edge in the first direction through the second transmission unit, so that the first movable cutting edge and the second movable cutting edge are both distributed on the side away from the first cutting edge; during this process, the first movable cutting edge engages with the first cutting edge and cuts off the thread end passing through the clearance groove.

[0023] S3. The sewing machine continues sewing;

[0024] S4. When sewing is finished and the thread needs to be cut, the first thread cutting drive source is activated, which drives the active knife to move through the first transmission unit. The thread cutting knife group cuts the sewing thread, and the thread end on the sewing material located on the upper surface of the needle plate is passed through the clearance groove. The thread end includes the top thread end and the bottom thread end.

[0025] S5. The second wire cutting drive source reverses its action, driving the sliding blade to move toward the second cutting edge in the second direction through the second transmission unit, so that the sliding blade moves to its initial position; during this process, the second movable cutting edge engages with the second cutting edge, cutting off the top and bottom thread ends that are inserted in the clearance groove.

[0026] Furthermore, the sewing machine thread-cutting device also includes a thread-suction nozzle, and the active blade has a thread-hooking groove that allows the sewing machine needle to pass through; step S2 includes the following sub-steps in sequence:

[0027] S21. The first thread-cutting drive source is activated, driving the active blade to move closer to the needle through the first transmission unit, so that the hook groove is located directly below the needle hole.

[0028] S22. When the first stitch is started, after the needle moves upward from the needle plate, the first thread cutting drive source reverses its action. At the same time, the second thread cutting drive source and the suction nozzle both move. The first thread cutting drive source drives the active blade to reset through the first transmission unit. The active blade moves together with the thread end in the hook groove to the suction port of the suction nozzle. Under the negative pressure formed by the suction nozzle, the thread end is sucked into the suction nozzle. The second thread cutting drive source drives the sliding blade to move towards the first blade edge along the first direction through the second transmission unit, but the first movable blade edge and the first blade edge do not engage.

[0029] S23. The suction nozzle remains in the suction state, and the sewing machine continues to sew the set number of stitches. Then, the second thread cutting drive source continues to operate, and the sliding blade moves towards the first cutting edge along the first direction. During this process, the first movable cutting edge and the first cutting edge bite together to cut off the top thread end. The cut top thread end is sucked away under the negative pressure of the suction nozzle.

[0030] S24, the suction nozzle stops suction.

[0031] Furthermore, the sewing machine thread cutting device also includes a thread sweeping device, which has a thread sweeping drive source, a swingable oscillating hook, and a thread sweeping transmission unit that is driveably connected between the thread sweeping drive source and the oscillating hook.

[0032] In step S5, the sweeping drive source first activates, causing the oscillating hook to swing. The hook at the end of the oscillating hook catches the top thread, pulling the top thread thread threaded in the needle upward from the sewing fabric. Then, the second cutting drive source reverses the action.

[0033] The present invention further provides a sewing machine, wherein the sewing machine is equipped with the above-mentioned sewing machine thread cutting device.

[0034] As described above, the sewing machine thread cutting device, thread cutting method, and sewing machine of the present invention have the following beneficial effects:

[0035] In this application, the first thread-cutting mechanism is used to cut the thread after sewing is completed, and the second thread-cutting mechanism is used to cut the thread end at the start of sewing to prevent the formation of a tangled mess of thread. Simultaneously, the second thread-cutting mechanism is also used to perform a second thread cut after the initial thread cut at the end of sewing, further shortening the thread ends remaining on the fabric to meet high-end sewing requirements. Specifically, the cutting of the thread end at the start of sewing and the second thread cut are achieved through the engagement of the first movable blade with the first cutting edge, and the engagement of the second movable blade with the second cutting edge, respectively. Both the first and second cutting edges are fixed to the needle plate and are very close to the fabric, resulting in shorter thread ends remaining on the fabric after cutting, ultimately reliably and effectively improving the quality of the sewn products. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the sewing machine in this application.

[0037] Figure 2 for Figure 1 A partial schematic diagram from another perspective.

[0038] Figure 3 This is a schematic diagram of the structure of the first wire-cutting mechanism and the second wire-cutting mechanism in this application.

[0039] Figure 4 This is a schematic diagram of the second wire-cutting mechanism in this application.

[0040] Figure 5 This is a schematic diagram of the assembly of the needle plate and the sliding blade in this application.

[0041] Figure 6 for Figure 5 Cross-sectional view at the needle hole.

[0042] Figure 7 This is a schematic diagram of the active blade in this application.

[0043] Figure 8 This is a schematic diagram of the thread-cutting device of the sewing machine in this application when starting the first stitch.

[0044] Figure 9 for Figure 8 A schematic diagram of the active tool after resetting.

[0045] Figure 10 This is a schematic diagram illustrating the second trimming of the thread end after the thread is cut at the end of sewing, as per the application for a sewing machine thread trimming device.

[0046] Figure 11 for Figure 10 A partial schematic diagram.

[0047] Component designation explanation

[0048] 101 casing

[0049] 102 base plate

[0050] 20 needle plates

[0051] 21 needle hole

[0052] 22 tooth grooves

[0053] 30 needles

[0054] 40 First Wire Cutting Mechanism

[0055] 41 First wire-cutting drive source

[0056] 42 Active blade

[0057] 421 Hook groove

[0058] 43 First drive crank

[0059] 44 Wire Cutting Roller

[0060] 45. Wire-cutting lever

[0061] 46 First Link

[0062] 47 First Thread Cutting Spool

[0063] 48 First Wire Cutting Crank

[0064] 49 Second Wire Cutting Crank

[0065] 410 Second Link

[0066] 411 Moving tool holder

[0067] 412 Fixed tool

[0068] 50 Second wire cutting mechanism

[0069] 51 Second wire-cutting drive source

[0070] 52 First incision

[0071] 53 Second cut

[0072] 54 Sliding Blade

[0073] 541 First active cutting edge

[0074] 542 Second active cutting edge

[0075] 543 First clearance slot

[0076] 544 Second clearance slot

[0077] 545 Sliding drive slot

[0078] 55 Guide Screw

[0079] 56 Second drive crank

[0080] 57 Third Link

[0081] 58 Second Thread Cutting Spool

[0082] 59 Third Wire Cutting Crank

[0083] 510 Fourth Wire Cutting Crank

[0084] 511 Fourth Link

[0085] 512 Swing Axis

[0086] 513 Fifth Wire Cutting Crank

[0087] 514 Wire Cutting Lever

[0088] 515 Diversion Section

[0089] 516 First Support

[0090] 517 Second Support

[0091] 60 suction tip

[0092] 70 Line sweeping device

[0093] 71 Scanning Driver Source

[0094] 72 Swinging line hook

[0095] 80 thread ends

[0096] 90 Bottom line end Detailed Implementation

[0097] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification.

[0098] It should be understood that the structures, proportions, sizes, etc., depicted in the accompanying drawings are merely for illustrative purposes to aid those skilled in the art and to facilitate understanding. They are not intended to limit the scope of the invention and therefore have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to size, without affecting the effectiveness and objectives of the invention, should still fall within the scope of the technical content disclosed herein. Furthermore, the terms "upper," "lower," "left," "right," "middle," and "one" used in this specification are merely for clarity and not intended to limit the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention's implementation.

[0099] This invention relates to a sewing machine thread trimming device, a sewing machine thread trimming method using the sewing machine thread trimming device, and a sewing machine including the sewing machine thread trimming device. Figure 1 As shown, the sewing machine includes a housing 101 and a base plate 102, both fixedly mounted; a needle plate 20 fixed on the base plate 102; a main shaft rotatably supported in the housing 101; a needle bar mechanism driven by the main shaft; a lower shaft rotatably supported in the base plate 102; and a rotary hook fixed at the end of the lower shaft. The main shaft is directly driven by the main motor in the sewing machine. The main shaft and the lower shaft are driven by each other and are parallel. The end of the needle bar mechanism is a needle 30 that can move up and down. For ease of description, in the following embodiments, the directions are defined as follows: the axial direction of the main shaft is defined as the left-right direction, and the direction of the main shaft toward the head of the machine is the left direction, and the direction of the main shaft toward the tail of the machine is the right direction. The left end of the main shaft is driven by the needle bar mechanism. The direction of fabric movement when the sewing machine is sewing forward is defined as the forward direction. The direction orthogonal to both the left-right and forward-backward directions is defined as the up-down direction.

[0100] like Figures 1 to 4 As shown, the sewing machine thread cutting device involved in this application includes a first thread cutting mechanism 40 and a second thread cutting mechanism 50. The first thread cutting mechanism 40 is used to cut the thread after sewing is completed, and the second thread cutting mechanism 50 is used to cut the top thread end 80 when sewing begins, and to cut the thread end a second time after cutting the thread at the end of sewing. The thread end includes the top thread end 80 and the bottom thread end 90.

[0101] Specifically, such as Figure 5 and Figure 6As shown, the needle plate 20 of the sewing machine has a vertically penetrating needle hole 21 and several vertically penetrating toothed grooves 22 extending forward and backward. These toothed grooves 22 accommodate the feed dog in the sewing machine. The length of the toothed grooves 22 in the forward-backward direction should meet the travel requirements of the feed dog's reciprocating movement. The feed dog emerges upward from the toothed grooves 22 and contacts the bottom surface of the fabric for feeding. The needle hole 21 has one toothed groove 22 on its front and rear sides. Figure 1 and Figure 3 As shown, the first thread-cutting mechanism 40 includes a first thread-cutting drive source 41, a thread-cutting blade assembly, and a first transmission unit. The thread-cutting blade assembly includes a movable active blade 42, which is located below the needle plate 20 in the sewing machine. The first thread-cutting drive source 41 is connected to the active blade 42 via the first transmission unit and drives the active blade 42 to move. In this embodiment, the active blade 42 moves by rotating around a lower axis. Figure 2 ,as well as Figures 4 to 6 As shown, the second thread cutting mechanism 50 includes a second thread cutting drive source 51, a first cutting edge 52 and a second cutting edge 53 both fixed on the bottom surface of the needle plate 20 and distributed on both sides of the needle drop hole 21, a sliding blade 54 movably mounted on the bottom surface of the needle plate 20, and a second transmission unit. The second thread cutting drive source 51 is connected to the sliding blade 54 through the second transmission unit and drives the sliding blade 54 to move along the parallel distribution direction of the first cutting edge 52 and the second cutting edge 53. The sliding blade 54 is provided with an vertically penetrating clearance groove and a first movable cutting edge 541 and a second movable cutting edge 542 arranged side by side along its moving direction. The clearance groove can communicate with both the needle drop hole 21 and the tooth groove 22. The clearance groove allows the needle 30 to pass through and allows the feed dog to move. The first movable cutting edge 541 and the second movable cutting edge 542 are both set in the clearance groove. When the sliding blade 54 moves back and forth, the direction in which the sliding blade 54 moves toward the first cutting edge 52 is defined as the first direction, and the direction in which the sliding blade 54 moves toward the second cutting edge 53 is defined as the second direction. The first direction is opposite to the second direction. When the sliding blade 54 moves along the first direction, the first movable cutting edge 541 can engage with the first cutting edge 52, thereby cutting the thread end 80 when starting to sew. When the sliding blade 54 moves along the second direction, which is opposite to the first direction, the second movable cutting edge 542 can engage with the second cutting edge 53, thereby performing a second cutting of the thread end after cutting the thread at the end of sewing.

[0102] Furthermore, the present invention also provides a sewing machine thread cutting method, using the above-described sewing machine thread cutting device, the sewing machine thread cutting method comprising the following steps:

[0103] S1. The sewing machine is in its initial state, such as Figure 8As shown, the sliding blade 54 is in its initial position, the first movable cutting edge 541 and the second movable cutting edge 542 are both distributed on the side of the second cutting edge 53 away from the first cutting edge 52, and the clearance groove is located directly below the needle hole 21 and the tooth groove 22 on the needle plate 20.

[0104] S2. After the sewing machine sets the starting stitch count, the second thread-cutting drive source 51 activates, driving the sliding blade 54 to move along the first direction toward the first cutting edge 52 via the second transmission unit. This causes the first movable cutting edge 541 and the second movable cutting edge 542 to be distributed on the side of the first cutting edge 52 away from it. Figure 9 As shown; during this process, the first movable cutting edge 541 engages with the first cutting edge 52 to cut off the thread end 80 passing through the relief groove, thereby cutting the thread end 80 when starting to sew.

[0105] S3. The sewing machine continues sewing;

[0106] S4. When sewing is finished and thread cutting is required, the first thread-cutting drive source 41 is activated, driving the active blade 42 to move via the first transmission unit. The thread-cutting blade assembly cuts the thread, and the thread end on the fabric located on the upper surface of the needle plate 20 passes through the clearance groove. Figure 10 and Figure 11 As shown, the thread ends include the top thread end 80 and the bottom thread end 90;

[0107] S5. The second thread-cutting drive source 51 reverses its action, driving the sliding blade 54 to move toward the second cutting edge 53 in the second direction through the second transmission unit, so that the sliding blade 54 moves to its initial position; during this process, the second movable cutting edge 542 engages with the second cutting edge 53, cutting off the top thread end 80 passing through the clearance groove, realizing a secondary cutting of the thread end and bottom thread end 90 after cutting the thread at the end of sewing.

[0108] Therefore, in the sewing machine thread cutting device involved in this application, the first thread cutting mechanism 40 is used to cut the thread after sewing is completed, and the second thread cutting mechanism 50 is used to cut the thread end 80 when starting to sew, so as to prevent the formation of a bird's nest of thread at the start of the sewing; at the same time, the second thread cutting mechanism 50 is also used to cut the thread end a second time after cutting the thread at the end of sewing, so as to further shorten the thread end remaining on the sewing material and meet the requirements of high-end sewing. In particular, the cutting of the thread end 80 during the initial sewing and the secondary cutting of the sewing thread end are achieved through the engagement of the first movable blade 541 and the first cutting edge 52, and the engagement of the second movable blade 542 and the second cutting edge 53, respectively. Since the first cutting edge 52 and the second cutting edge 53 are both fixed at the bottom of the needle plate 20, the thread cutting positions of the first movable blade 541 and the first cutting edge 52, and the thread cutting positions of the second movable blade 542 and the second cutting edge 53 are very close to the sewing material. This results in a shorter thread end remaining on the sewing material after cutting, ultimately improving the quality of the sewn products reliably and effectively.

[0109] Furthermore, such as Figure 5 and Figure 6 As shown, the first cutting edge 52 and the second cutting edge 53 are distributed on the front and rear sides of the needle hole 21 along the feeding direction of the sewing machine. That is, the first cutting edge 52 is distributed on the front side of the needle hole 21, and the second cutting edge 53 is distributed on the rear side of the needle hole 21. Therefore, the sliding blade 54 moves in a reciprocating linear motion. There are two clearance grooves on the sliding blade 54, namely the first clearance groove 543 and the second clearance groove 544. The first clearance groove 543 and the second clearance groove 544 are arranged side by side along the moving direction of the sliding blade 54 and extend straight back and forth along the moving direction of the sliding blade 54. The first clearance groove 543 is located on the front side of the second clearance groove 544. The first movable cutting edge 541 is located at the rear end of the first clearance groove 543, and the second movable cutting edge 542 is located at the front end of the second clearance groove 544. Preferably, the first cutting edge 52 is preferably located at the rear end of the toothed groove 22 directly in front of the needle hole 21, and the second cutting edge 53 is preferably located at the front end of the toothed groove 22 directly behind the needle hole 21. Thus, the first cutting edge 52, the needle hole 21, and the second cutting edge 53 are arranged in a straight line from front to back. The first clearance groove 543 and the second clearance groove 544 are both distributed on the side directly below the toothed groove 22 in the needle plate 20 that is aligned with the needle hole 21.

[0110] In step S1 above, when the sliding blade 54 is in its initial position, the first movable cutting edge 541 and the second movable cutting edge 542 are both located behind the second cutting edge 53, and the first clearance groove 543 is located below the needle hole 21. In step S2 above, when the sewing machine sets the stitch count, the needle 30 passes through the first clearance groove 543, and the thread end 80 is also inserted into the first clearance groove 543. When the second thread cutting drive source 51 drives the sliding blade 54 to move forward in the first direction, the first movable cutting edge 541 at the rear end of the first clearance groove 543 will move forward with the thread end 80 in the first clearance groove 543 towards the first cutting edge 52, thereby cutting off the thread end 80. After the sliding blade 54 moves forward to its position, the first movable cutting edge 541 and the second movable cutting edge 542 are both located in front of the first cutting edge 52, and the second clearance groove 544 is located below the needle hole 21. In steps S4 and S5 above, the top thread end 80 and bottom thread end 90, cut by the thread cutting blade assembly, are both inserted into the second clearance groove 544. When the second thread cutting drive source 51 drives the sliding blade 54 to move backward in the second direction, the second movable cutting edge 542 at the front end of the second clearance groove 544 will carry the top thread end 80 and bottom thread end 90 in the second clearance groove 544 backward toward the direction close to the second cutting edge 53, thereby cutting off the top thread end 80 and bottom thread end 90. This structure operates stably and can effectively capture the thread end, thus stably achieving the effect of cutting short thread ends.

[0111] Preferably, such as Figure 5 As shown, the second thread-cutting mechanism 50 also includes two guide screws 55 fixed to the bottom surface of the needle plate 20. The guide screw 55 located on the front side passes through the first clearance groove 543 and is slidably engaged with it. The guide screw 55 located on the rear side passes through the second clearance groove 544 and is slidably engaged with it. Thus, in addition to avoiding the needle 30 and the feed dog, the clearance groove also serves as a guide, improving the stability of the sliding blade 54's back-and-forth movement, thereby improving the thread-cutting stability. The first cutting edge 52 and the second cutting edge 53 are integrally fixed to the bottom surface of the needle plate 20. For example, the first cutting edge 52 and the second cutting edge 53 can be integrally machined on the bottom surface of the needle plate 20, or the first cutting edge 52 and the second cutting edge 53 can be integrally fixed to the bottom surface of the needle plate 20 by welding.

[0112] Furthermore, such as Figure 3 , Figure 7 , Figure 8 and Figure 9 As shown, the sewing machine thread-cutting device also includes a fixedly mounted thread suction nozzle 60, and the active blade 42 has a thread hook groove 421 that allows the sewing machine needle 30 to pass through; when the active blade 42 is in the initial position, the thread hook groove 421 is located at the suction inlet of the thread suction nozzle 60. Before sewing the first stitch, the active blade 42 can be rotated backward so that the thread hook groove 421 is located directly below the needle drop hole 21, as shown. Figure 8 As shown; after the first stitch of the sewing machine needle 30 moves upward from the needle plate 20, the active blade 42 rotates forward and resets. The active blade 42 then rotates forward along with the thread end 80 in the thread groove 421, as... Figure 9 As shown, this moves the thread end 80 to the suction port of the suction nozzle 60, ensuring that the suction nozzle 60 can accurately capture the thread end 80. Then, after the first movable cutting edge 541 and the first cutting edge 52 engage and cut the thread end 80, the suction nozzle 60 can suck it away, preventing the thread end 80 from tangling again at the start of the seam and forming a bird's nest. Therefore, the hook groove 421 on the active blade 42 has a capturing function for the thread end 80 during the start-up sequence.

[0113] Furthermore, both the first thread-cutting drive source 41 and the second thread-cutting drive source 51 are motors, preferably stepper motors. The first thread-cutting drive source 41 is fixedly installed at the right end of the machine housing 101, and the second thread-cutting drive source 51 is fixedly installed on the bottom surface of the base plate 102. Both the first thread-cutting drive source 41 and the second thread-cutting drive source 51 are also communicatively connected to the sewing machine's electronic control module and are both controlled by the electronic control module. The first thread-cutting drive source 41 can also be used to drive the presser foot, realizing the simultaneous driving of automatic thread cutting and presser foot lifting at the end of sewing using the same motor.

[0114] Preferably, the first wire cutting mechanism 40 can be a single-moving-blade structure or a double-moving-blade structure. When the first wire cutting mechanism 40 is a single-moving-blade structure, the wire cutting blade assembly also includes a fixed blade 412, which automatically cuts the wire through the engagement of the active blade 42 and the fixed blade 412. When the first wire cutting mechanism 40 is a double-moving-blade structure, the wire cutting blade assembly also includes an auxiliary moving blade that can rotate around a lower shaft, which automatically cuts the wire through the engagement of the active blade 42 and the auxiliary moving blade.

[0115] Furthermore, the preferred structure of the first transmission unit is as follows: Figure 3 As shown, the first transmission unit includes a first drive crank 43 driven to rotate by a first thread-cutting drive source 41, a thread-cutting roller 44 rotatably mounted on the first drive crank 43, a thread-cutting lever 45 with a fixed fulcrum, a first connecting rod 46, a first thread-cutting shaft 47 rotatable about a fixed axis, a first thread-cutting crank 48 and a second thread-cutting crank 49 respectively fixed to the right and left ends of the first thread-cutting shaft 47, a second connecting rod 410, and a movable blade holder 411 rotatable about the lower shaft of the sewing machine. The handle 43 is directly fixed to the motor shaft of the first wire cutting drive source 41 by screws. One end of the wire cutting lever 45 is provided with a wire cutting groove that can contact and cooperate with the wire cutting roller 44. The two ends of the first connecting rod 46 are respectively hinged to the other end of the wire cutting lever 45 and the first wire cutting crank 48. The first wire cutting shaft 47 extends axially to the left and right and is rotatably installed in the base plate 102. The two ends of the second connecting rod 410 are respectively hinged to the second wire cutting crank 49 and the moving blade holder 411. The active blade 42 is fixed on the moving blade holder 411.

[0116] Furthermore, the preferred structure of the second transmission unit is as follows: Figures 2 to 4 As shown, the second transmission unit includes a second drive crank 56 driven to rotate by a second wire-cutting drive source 51, a third connecting rod 57, a second wire-cutting shaft 58 rotatable around a fixed axis, a third wire-cutting crank 59 and a fourth wire-cutting crank 510 fixed to the right and left ends of the second wire-cutting shaft 58 respectively, a fourth connecting rod 511, a swing shaft 512 rotatable around a fixed axis, and a fifth wire-cutting crank 513 and a wire-cutting lever 514 both fixed on the swing shaft 512. The second drive crank 56 is directly fixed to the motor shaft of the second wire-cutting drive source 51 by screws. The two ends of the third connecting rod 57 are hinged to the second drive crank 56 and the third wire-cutting crank 59 respectively. The two ends of the fourth connecting rod 511 are hinged to the fourth wire-cutting crank 510 and the fifth wire-cutting crank 513 respectively. The upper end of the wire-cutting lever 514 is provided with a pushing part 515, and the sliding blade 54 is provided with a sliding drive groove 545 for accommodating the pushing part 515.

[0117] Preferably, such as Figure 3 and Figure 4The second transmission unit also includes a first support 516 and a second support 517, both fixed to the bottom surface of the base plate 102. The second wire-cutting shaft 58 extends axially to the left and right and is rotatably mounted in the first support 516. The swing shaft 512 extends axially to the left and right and is rotatably mounted in the second support 517. The wire-suction nozzle 60 is fixed on the second support 517. The outer peripheral surface of the pushing part 515 is cylindrical. The pushing part 515 and the groove wall of the sliding drive groove 545 are in line contact to reduce friction. The sliding drive groove 545 is integrally disposed on the left side of the front end of the sliding blade 54.

[0118] Furthermore, such as Figure 1 As shown, the sewing machine's thread cutting device also includes a thread sweeping device 70. The thread sweeping device 70 has a thread sweeping drive source 71, a swingable thread hook 72, and a thread sweeping transmission unit connected between the thread sweeping drive source 71 and the swingable thread hook 72. The swingable thread hook 72 is located above the needle 30, and its end has a hook portion capable of hooking the top thread. This hook is used to pull the top thread, which is automatically cut by the first thread cutting mechanism 40 and threaded in the needle 30, upwards from the fabric. Then, the second thread cutting mechanism 50 automatically trims the remaining top thread ends 80 and bottom thread ends 90 on the fabric. The thread sweeping drive source 71 is communicatively connected to the sewing machine's electronic control module.

[0119] In summary, taking the first thread-cutting mechanism 40 as an example of a single-moving blade structure, the working principle of the sewing machine thread-cutting device with the above structure is as follows.

[0120] In the initial state, the active blade 42 and the sliding blade 54 are each in their initial positions. The active blade 42 is separated from the fixed blade 412. The active blade 42 is located in front of the needle 30. The first movable cutting edge 541 and the second movable cutting edge 542 are both distributed behind the second cutting edge 53.

[0121] 2. When the sewing machine starts sewing, the electronic control module controls the first thread-cutting drive source 41 to operate. The first thread-cutting drive source 41 drives the active blade 42 to rotate backward by an angle through the first transmission unit, so that the hook groove 421 on the active blade 42 is located directly below the needle drop hole 21 on the needle plate 20. Figure 8 As shown. When starting the first stitch, the needle 30 sequentially inserts downwards into the needle hole 21 of the needle plate 20, the first clearance groove 543 of the sliding blade 54, and the hook groove 421 of the active blade 42. After cooperating with the rotary hook to complete the hooking action, the needle 30 moves upwards. When the needle 30 moves upwards out of the needle plate 20, the electronic control module controls the first thread-cutting drive source 41 to reverse its movement, controls the second thread-cutting drive source 51 to move, and controls the suction nozzle 60 to perform a suction action. The first thread-cutting drive source 41 drives the active blade 42 to rotate forward and reset via the first transmission unit, as shown. Figure 9As shown, the active blade 42 moves together with the thread end 80 in the hook groove 421 to the suction port of the suction nozzle 60. Under the negative pressure formed by the suction nozzle 60, the thread end 80 is sucked into the suction nozzle 60. At the same time, the second thread cutting drive source 51 drives the sliding blade 54 forward a preset distance through the second transmission unit, but the first movable cutting edge 541 is still located behind the first cutting edge 52 and the two are not engaged.

[0122] 3. The suction nozzle 60 remains in the suction state; the sewing machine continues to sew the set number of stitches, which can be 1-2 stitches; then, the electronic control module controls the second thread-cutting drive source 51 to operate again, and the second thread-cutting drive source 51 drives the sliding blade 54 to continue moving forward through the second transmission unit; during this process, the first movable cutting edge 541 and the first cutting edge 52 will engage, such as... Figure 9 As shown, the top thread end 80 in the first clearance groove 543 is cut off. The cut top thread end 80 was originally held in the suction nozzle 60, and then it is sucked away under negative pressure; the electronic control module controls the suction nozzle 60 to stop sucking. In this way, the sewing thread cutting action is completed, preventing the formation of tangled threads.

[0123] IV. The sewing machine continues sewing.

[0124] 5. As the sewing nears its end, the electronic control module controls the first thread-cutting drive source 41 to operate. The first thread-cutting drive source 41 drives the active blade 42 to rotate backward through the first transmission unit. The active blade 42 engages with the fixed blade 412, cutting the top thread and the bottom thread. Top thread ends 80 and bottom thread ends 90 remain on the fabric. Figure 10 and Figure 11 As shown. Due to the thickness of the needle plate 20 and the normal working space between the needle plate 20 and the active blade 42 and the fixed blade 412, the remaining thread ends 80 and 90 on the sewing fabric will have a certain length. At this time, the electronic control module controls the sweeping drive source 71 to move, and the oscillating hook 72 swings to pull the thread passing through the needle 30 upward from the sewing fabric; then, the electronic control module controls the second thread cutting drive source 51 to move in the opposite direction, and the second thread cutting drive source 51 drives the sliding blade 54 to move backward and reset through the second transmission unit; during this process, the second movable cutting edge 542 and the second cutting edge 53 will engage to cut the thread ends 80 and 90 passing through the needle drop hole 21 and the second clearance groove 544, realizing automatic secondary trimming of the sewing thread ends, which makes the remaining sewing thread ends on the sewing fabric shorter and meets the higher requirements of sewn products.

[0125] In summary, this invention effectively overcomes the various shortcomings of the prior art and has high industrial application value.

[0126] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A thread-cutting device for a sewing machine, comprising a first thread-cutting mechanism (40), the first thread-cutting mechanism (40) comprising a first thread-cutting drive source (41), a thread-cutting blade assembly, and a first transmission unit, the thread-cutting blade assembly comprising a movable active blade (42), the active blade (42) being distributed below the needle plate (20) in the sewing machine, the first thread-cutting drive source (41) being connected to the active blade (42) via the first transmission unit, the needle plate (20) having a needle drop hole (21) and a toothed groove (22), characterized in that: It also includes a second thread-cutting mechanism (50), which includes a second thread-cutting drive source (51), a first cutting edge (52) and a second cutting edge (53) fixed on the bottom surface of the needle plate (20) and distributed on both sides of the needle drop hole (21), a sliding blade (54) movably mounted on the bottom surface of the needle plate (20), and a second transmission unit. The second thread-cutting drive source (51) is connected to the sliding blade (54) through the second transmission unit and drives the sliding blade (54) to move along the parallel distribution direction of the first cutting edge (52) and the second cutting edge (53). The sliding blade (54) is provided with a clearance groove and a first movable cutting edge (541) and a second movable cutting edge (542) arranged in parallel along its moving direction. The clearance groove is connected to both the needle drop hole (21) and the tooth groove (22). The first movable cutting edge (541) and the second movable cutting edge (542) are both set in the clearance groove. When the sliding blade (54) moves along the first direction, the first movable cutting edge (541) can engage with the first cutting edge (52); When the sliding blade (54) moves in a second direction opposite to the first direction, the second movable cutting edge (542) can engage with the second cutting edge (53).

2. The sewing machine thread-cutting device according to claim 1, characterized in that: The first cutting edge (52) and the second cutting edge (53) are distributed on both sides of the needle hole (21) along the feeding direction of the sewing machine; there are two clearance grooves, namely the first clearance groove (543) and the second clearance groove (544). The first clearance groove (543) and the second clearance groove (544) are arranged side by side along the moving direction of the sliding blade (54) and both extend straight along the moving direction of the sliding blade (54). The first movable cutting edge (541) is located at the end of the first clearance groove (543) near the end of the second clearance groove (544), and the second movable cutting edge (542) is located at the end of the second clearance groove (544) near the end of the first clearance groove (543).

3. The sewing machine thread-cutting device according to claim 2, characterized in that: The second wire cutting mechanism (50) also includes two guide screws (55) fixed on the bottom surface of the needle plate (20). One guide screw (55) passes through the first relief groove (543) and the two are slidably engaged. The other guide screw (55) passes through the second relief groove (544) and the two are slidably engaged.

4. The sewing machine thread-cutting device according to claim 1, characterized in that: It also includes a suction nozzle (60), and the active knife (42) has a hook groove (421) that allows the sewing machine needle (30) to pass through; when the active knife (42) is in the initial position, the hook groove (421) is located at the suction port of the suction nozzle (60).

5. The sewing machine thread-cutting device according to claim 1, characterized in that: Both the first wire-cutting drive source (41) and the second wire-cutting drive source (51) are motors.

6. The sewing machine thread-cutting device according to claim 1, characterized in that: The first transmission unit includes a first drive crank (43) driven to rotate by a first wire-cutting drive source (41), a wire-cutting roller (44) rotatably mounted on the first drive crank (43), a wire-cutting lever (45) with a fixed fulcrum, a first connecting rod (46), a first wire-cutting shaft (47) rotatable about a fixed axis, a first wire-cutting crank (48) and a second wire-cutting crank (49) respectively fixed at both ends of the first wire-cutting shaft (47), and a second connecting rod (410). The machine includes a movable blade holder (411) that can rotate around the lower shaft of the sewing machine. One end of the thread-cutting lever (45) is provided with a thread-cutting groove that can contact and cooperate with the thread-cutting roller (44). The two ends of the first connecting rod (46) are respectively hinged to the other end of the thread-cutting lever (45) and the first thread-cutting crank (48). The two ends of the second connecting rod (410) are respectively hinged to the second thread-cutting crank (49) and the movable blade holder (411). The active blade (42) is fixed on the movable blade holder (411).

7. The sewing machine thread-cutting device according to claim 1, characterized in that: The second transmission unit includes a second drive crank (56) driven to rotate by a second wire-cutting drive source (51), a third connecting rod (57), a second wire-cutting shaft (58) rotatable about a fixed axis, a third wire-cutting crank (59) and a fourth wire-cutting crank (510) respectively fixed at both ends of the second wire-cutting shaft (58), a fourth connecting rod (511), a swing shaft (512) rotatable about a fixed axis, and a fifth wire-cutting crank (512) fixed on the swing shaft (512). The third link (57) and the wire cutting lever (513) are respectively hinged to the second drive crank (56) and the third wire cutting crank (59). The two ends of the fourth link (511) are respectively hinged to the fourth wire cutting crank (510) and the fifth wire cutting crank (513). The end of the wire cutting lever (514) is provided with a pushing part (515). The sliding blade (54) is provided with a sliding drive groove (545) for accommodating the pushing part (515).

8. The sewing machine thread-cutting device according to claim 7, characterized in that: The outer peripheral surface of the pushing part (515) is a cylindrical surface, and the pushing part (515) and the groove wall of the sliding drive groove (545) are in line contact fit.

9. The sewing machine thread-cutting device according to claim 1, characterized in that: It also includes a line sweeping device (70), which has a line sweeping drive source (71), a swingable hook (72), and a line sweeping transmission unit that is connected between the line sweeping drive source (71) and the swing hook (72). The end of the swing hook (72) has a hook portion that can hook the face line.

10. The sewing machine thread-cutting device according to claim 1, characterized in that: The first cutting edge (52) and the second cutting edge (53) are integrally fixed on the bottom surface of the needle plate (20).

11. A method for cutting threads on a sewing machine, characterized in that: Using the sewing machine thread-cutting device according to claim 1, the sewing machine thread-cutting method includes the following steps: S1. In the initial state of the sewing machine, the sliding blade (54) is in its initial position, the first movable cutting edge (541) and the second movable cutting edge (542) are both distributed on the side of the second cutting edge (53) away from the first cutting edge (52), and the clearance groove is located directly below the needle hole (21) and tooth groove (22) on the needle plate (20). S2. After the sewing machine sets the number of stitches, the second thread cutting drive source (51) is activated, driving the sliding blade (54) to move along the first direction toward the first cutting edge (52) through the second transmission unit, so that the first movable cutting edge (541) and the second movable cutting edge (542) are both distributed on the side away from the first cutting edge (52); during this process, the first movable cutting edge (541) engages with the first cutting edge (52) to cut off the thread end (80) passing through the clearance groove; S3. The sewing machine continues sewing; S4. When sewing is finished and the thread needs to be cut, the first thread cutting drive source (41) is activated and drives the active knife (42) to move through the first transmission unit. The thread cutting knife group cuts the sewing thread, and the thread end on the sewing material on the upper surface of the needle plate (20) is passed through the clearance groove. The thread end includes the top thread end (80) and the bottom thread end (90). S5. The second wire cutting drive source (51) reverses its action and drives the sliding blade (54) to move toward the second cutting edge (53) in the second direction through the second transmission unit, so that the sliding blade (54) moves to its initial position; during this process, the second movable cutting edge (542) engages with the second cutting edge (53) to cut off the top thread end (80) and bottom thread end (90) that are inserted in the clearance groove.

12. The sewing machine thread-cutting method according to claim 11, characterized in that: The sewing machine thread cutting device also includes a thread suction nozzle (60), and the active blade (42) has a thread hook groove (421) that allows the sewing machine needle (30) to pass through; Step S2 includes the following sub-steps in sequence: S21, the first wire cutting drive source (41) is activated, and the active knife (42) is driven to move towards the needle (30) through the first transmission unit, so that the hook groove (421) is located directly below the needle drop hole (21); S22, starting the first stitch, after the needle (30) moves upward from the needle plate (20), the first thread cutting drive source (41) reverses its action, and at the same time the second thread cutting drive source (51) and the suction nozzle (60) both move. The first thread cutting drive source (41) drives the active blade (42) to reset through the first transmission unit. The active blade (42) moves together with the thread end (80) in the hook groove (421) to the suction port of the suction nozzle (60). Under the negative pressure formed by the suction nozzle (60), the thread end (80) is sucked into the suction nozzle (60). The second thread cutting drive source (51) drives the sliding blade (54) to move towards the first blade edge (52) in the first direction through the second transmission unit, but the first movable blade edge (541) and the first blade edge (52) do not engage. S23, the suction nozzle (60) remains in suction state, the sewing machine continues to sew the set number of stitches, and then the second thread cutting drive source (51) continues to operate, the sliding blade (54) moves along the first direction toward the first cutting edge (52), during this process, the first movable cutting edge (541) and the first cutting edge (52) bite together, cutting off the top thread end (80), and the cut top thread end (80) is sucked away under the negative pressure of the suction nozzle (60); S24, the suction nozzle (60) stops suction.

13. The sewing machine thread-cutting method according to claim 11, characterized in that: The sewing machine thread cutting device also includes a thread sweeping device (70), which has a thread sweeping drive source (71), a swingable swing hook (72), and a thread sweeping transmission unit that is connected between the thread sweeping drive source (71) and the swing hook (72). In step S5, the sweeping drive source (71) first moves to drive the swinging hook (72) to swing. The hook part at the end of the swinging hook (72) hooks the top thread and pulls the top thread in the needle (30) upward from the sewing material. Then, the second cutting drive source (51) moves in the opposite direction.

14. A sewing machine, characterized in that: The sewing machine is equipped with a sewing machine thread cutting device as described in any one of claims 1-10.

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