Double-movable cutter thread trimming mechanism of sewing machine, and thread trimming method

Abstract

A double-movable cutter thread trimming mechanism of a sewing machine. The sewing machine comprises a frame, a thread trimming mechanism, and a shuttle mechanism. The thread trimming mechanism comprises a first movable cutter assembly, a second movable cutter assembly, and a driving assembly; a first thread trimming movable cutter of the first movable cutter assembly and a second thread trimming movable cutter of the second movable cutter assembly are both rotatably arranged on the outer side of the shuttle mechanism; the first thread trimming movable cutter rotates around the shuttle mechanism between a first position and a second position, and the second thread trimming movable cutter moves around the shuttle mechanism between a third position and a fourth position; and the first thread trimming movable cutter is provided with a thread slot for allowing a needle to pass through and hooking a sewing thread in the sewing starting stage, and a first thread hooking recess for hooking the sewing thread in the completion stage. The first thread trimming movable cutter cooperates with the second thread trimming movable cutter to cut off the sewing thread, thereby reducing thread heads and improving the production efficiency.

Description

Double-action knife thread cutting mechanism and thread cutting method of sewing machine TECHNICAL FIELD

[0001] The technical scheme relates to the field of sewing machines, and particularly relates to a double-action knife thread cutting mechanism and thread cutting method of a sewing machine. BACKGROUND

[0002] A sewing machine is a machine that forms one or more stitches on a workpiece by sewing thread, and interweaves or stitches one or more workpieces together. The sewing machine generally comprises a base, a needle bar mechanism, a feeding mechanism, a thread hooking mechanism, a presser foot mechanism, a thread cutting mechanism and an accessory part, and the mechanisms cooperate to work in cycles.

[0003] For example, Chinese patent CN117926509A discloses a sewing machine thread cutting structure, a sewing machine thread cutting method and a sewing machine. The thread cutting mechanism comprises a driving knife, and the driving knife has a driving knife split thread tip, a first split thread edge, a second split thread edge, a driving knife thread storage groove, a driving knife blade and a bottom surface thread split thread port. The thread cutting structure comprises a split thread hook fixedly arranged with the driving knife. The split thread hook has a thread hooking tip portion. The thread hooking tip portion is arranged on the inner circumferential side of the driving knife and on the side of the bottom surface thread split thread port away from the driving knife thread storage groove. There is a thread passing space between the thread hooking tip portion and the driving knife. There is a split thread storage groove between the thread hooking tip portion and the bottom surface thread split thread port. The split thread storage groove is communicated with the thread passing space.

[0004] During the starting and ending stages of the sewing operation, long thread ends are often left on the surface of the cloth, especially the thread ends formed during the starting stage, which often have a bird's nest shape, damaging the neatness and beauty of the surface of the clothes and lowering the overall quality standard of the finished product. Therefore, the excess thread ends need to be finely trimmed manually or automatically to ensure that the final quality of the clothes is good.

[0005] The above-mentioned sewing machine thread cutting structure, sewing machine thread cutting method and sewing machine can cut the excess thread ends and are suitable for general clothes processing. However, the problem of thread ends left on the surface of the cloth has not yet reached an ideal state and cannot meet the requirements of high-quality clothes production. The thread ends are still obvious and need to be trimmed again to achieve a shorter thread cutting effect, which needs to be improved. SUMMARY

[0006] The technical scheme is provided to solve the problem of achieving a shorter thread cutting effect without secondary trimming, and provides a double-action knife thread cutting mechanism and thread cutting method of a sewing machine.

[0007] The purpose of the technical scheme is achieved as follows.

[0008] The utility model provides a double-action knife thread cutting mechanism of a sewing machine, which is suitable for thread cutting in the starting stage and the ending stage of the sewing machine; the sewing machine comprises a frame, a thread cutting mechanism and a rotating hook mechanism; the thread cutting mechanism is arranged on the frame and below the needle;

[0009] The thread cutting mechanism comprises a first action knife assembly, a second action knife assembly and a driving assembly;

[0010] The first action knife assembly comprises a first transmission assembly and a thread cutting action knife one;

[0011] The second action knife assembly comprises a second transmission assembly and a thread cutting action knife two;

[0012] The driving assembly drives the thread cutting action knife one through the first transmission assembly, and the thread cutting action knife one rotates around the axis of the rotating hook shaft of the rotating hook mechanism between a first position and a second position; the driving assembly drives the thread cutting action knife two through the second transmission assembly, and the thread cutting action knife two rotates around the axis of the rotating hook shaft of the rotating hook mechanism between a third position and a fourth position;

[0013] The thread cutting action knife one is provided with a thread hole slot for the needle to pass through and hook the sewing thread in the starting stage and a thread hooking slot one for hooking the sewing thread in the ending stage, and a first blade edge is further arranged on the front side of the thread cutting action knife one;

[0014] A second blade edge is arranged on the front side of the thread cutting action knife two;

[0015] During the process that the driving assembly drives the thread cutting action knife one to rotate from the second position to the first position, the driving assembly simultaneously drives the thread cutting action knife two to rotate from the third position to the fourth position; the thread cutting action knife two abuts against the surface of the thread cutting action knife one during the rotation process of the thread cutting action knife two, so that the first blade edge of the thread cutting action knife one cooperates with the second blade edge of the thread cutting action knife two to cut the sewing thread.

[0016] In the initial state, the thread cutting action knife one and the thread cutting action knife two are located on the same side of the frame, and the thread cutting action knife one and the thread cutting action knife two rotate in the same direction to approach the needle; during the process that the thread cutting action knife one rotates from the first position to the second position, the thread hole slot gradually approaches the needle; during the process that the thread cutting action knife two rotates from the third position to the fourth position, the second blade edge gradually approaches the needle.

[0017] A thread holder is arranged on the frame, located between the first position and the second position and close to the first position; during the process that the thread cutting action knife one resets to the first position, the thread hole slot drives the sewing thread to the position of the thread holder, and the thread cutting action knife one clamps the sewing thread in the thread hole slot in cooperation with the thread holder. The frame is further provided with a thread suction device, and the discharge suction port of the thread suction device is connected to the thread hole slot; when the excess sewing thread is cut and the thread cutting action knife one leaves the thread holder, the thread suction device sucks the cut sewing thread.

[0018] Through the above technical scheme, after the first cutting knife hooks the sewing thread to the second position, the thread clamp presses the thread in the inner wall of the thread hole groove, and then releases the thread after cutting, at this time the thread suction device sucks the cut thread into the collection and processing through the discharge suction port, avoiding scattering in the working area, and ensuring the normal operation of the equipment.

[0019] Preferably, the first cutting knife is also provided with a second thread hooking groove, and the second thread hooking groove and the first thread hooking groove are respectively located on both sides of the width of the first cutting knife; when cutting the sewing thread in the finishing stage, the first cutting knife moves towards the needle, and the tip of the first cutting knife penetrates through the thread loop of the sewing thread; the first thread hooking groove and the second thread hooking groove hook the sewing thread on both sides of the first cutting knife respectively; a guide groove is arranged between the thread hole groove and the first cutting edge of the first cutting knife, and the first thread hooking groove is located in the middle of the guide groove. Through the above technical scheme, the second thread hooking groove hooks the sewing thread on the other side of the thread loop, increases the length of the cut thread on the first cutting knife, avoids the sewing thread from being separated from the needle, reduces the operation of re-threading, improves the use efficiency, and the guide groove is used for accommodating the sewing thread, avoiding the pressure on the sewing thread when the second cutting knife is attached to the first cutting knife.

[0020] Preferably, the first transmission assembly includes a first crank, a first connecting rod, and a first ring portion, the two ends of the first connecting rod are respectively hinged between one end of the first crank and the first ring portion, the first cutting knife is arranged on the first ring portion, and the first ring portion is rotationally connected relative to the rack to drive the first cutting knife.

[0021] The second transmission assembly includes a second crank, a second connecting rod, and a second ring portion, the two ends of the second connecting rod are respectively hinged between one end of the second crank and the second ring portion, the second cutting knife is arranged on the second ring portion, and the second ring portion is coaxially arranged with the first ring portion to drive the second cutting knife.

[0022] The driving assembly has various structures. The first structure is that the driving assembly includes a first driving member, a second driving member, a third transmission assembly, a fourth transmission assembly, and a sleeve rod structure. The sleeve rod structure includes a transmission rod one and a transmission rod two arranged inside or outside the transmission rod one. The first driving member drives the transmission rod one through the third transmission assembly, and the transmission rod one drives the first transmission assembly. The second driving member drives the transmission rod two through the fourth transmission assembly, and the transmission rod two drives the second transmission assembly. The nested sleeve rod structure design not only effectively saves space, but also improves the compactness and stability of the structure.

[0023] Preferably, the third transmission assembly is used to drive the transmission rod to rotate, and the fourth transmission assembly is used to drive the transmission rod to rotate; the first driving member drives the third transmission assembly, and the second driving member drives the fourth transmission assembly. Through the above technical scheme, the two transmission assemblies are arranged on the two driving members respectively, so that the motor output shaft directly or indirectly transmits power to the transmission assembly, so as to directly and efficiently transmit power to the two transmission rods respectively, reduce energy loss and mechanical wear in the power transmission process, and ensure that the transmission rod can rotate according to the predetermined trajectory and speed.

[0024] Preferably, the third transmission assembly comprises a first curved arm and a second curved arm movably arranged on the first curved arm; one end of the first curved arm is fixed on the motor shaft of the first driving member, and the other end of the second curved arm is fixed on the transmission rod one; the end face of the second curved arm close to the first curved arm is provided with a sliding groove, and the swinging end of the first curved arm is correspondingly provided with a sliding block arranged in the sliding groove to realize sliding guidance; the swinging of the first curved arm drives the transmission rod one to rotate, and the other end of the transmission rod one directly or indirectly drives the first cutter assembly.

[0025] Through the above technical scheme, the third transmission assembly is connected between the transmission rod one and the first driving member for power transmission, the motor shaft of the first driving member drives the first curved arm to swing, the sliding block is fixed on the other end of the first curved arm and slides along the sliding groove to guide the movement of the second curved arm, so that the transmission rod one rotates with the movement of the second curved arm, thereby realizing that the transmission rod one drives the first cutter assembly.

[0026] Preferably, the second curved arm is provided with a limiting portion fixed to one end of the sliding groove away from the fixed end of the second curved arm, for limiting the sliding block from falling out of the sliding groove.

[0027] Through the above technical scheme, the limiting portion of the second curved arm is fixed to one end of the sliding groove away from the fixed end connected with the first curved arm, so as to prevent the sliding block from accidentally falling out of the sliding groove due to various factors (such as vibration, impact, etc.) during transmission, avoid the risk of falling out, and thus ensure the continuity and safety of transmission.

[0028] Preferably, the fourth transmission assembly comprises a third curved arm and a driving cam arranged on the third curved arm; one end of the third curved arm is fixed on the motor shaft of the second driving member, and the other swinging end close to the driving cam is provided with an adjusting portion acting on the driving cam, so that the third curved arm transmits power to the transmission rod two.

[0029] Through the technical scheme, the fourth transmission assembly is arranged between the transmission rod two and the second driving member to realize efficient power transmission, the motor shaft of the second driving member serves as a power source to drive the third crank arm to periodically swing, the adjusting part arranged at the end of the third crank arm is closely matched with the driving cam, relative movement is generated between the adjusting part and the driving cam through rolling, sliding or rotating of the adjusting part, thereby realizing efficient power transmission, and the transmission rod two is driven to rotate, thereby realizing driving of the second knife assembly by the transmission rod two.

[0030] Preferably, the transmission rod two is provided with an elastic member, which is sleeved at one end of the transmission rod two provided with a second crank; the second crank is provided with a connecting block, and the elastic member is arranged between the connecting block and the rack, and the elastic force of the elastic member is used for resetting of the second cutting knife; the transmission rod one is arranged in the transmission rod two, and the length of the transmission rod one is greater than that of the transmission rod two, so that both ends of the transmission rod one protrude from both ends of the transmission rod two, and are used for connecting the first crank and the second crank arm; the second driving member has two motor shafts, one of which is used for connecting the third crank arm, and the other is used for connecting the presser foot to realize stitch length adjustment.

[0031] Through the technical scheme, the elastic member on the transmission rod two is connected between the connecting block and the rack, the connecting block two provides stable support, and the elastic force of the elastic member makes the fourth transmission assembly have a resetting movement trend, so that the second cutting knife is returned to the initial position, and the continuity and accuracy of the cutting action are ensured.

[0032] The transmission rod two is a hollow shaft sleeve, and the transmission rod one is a core rod; the transmission rod one is arranged in the transmission rod two to be concentric with each other, and the transmission rod one protrudes from both ends of the transmission rod two to be connected with the first crank and the second crank arm, so that the transmission structure is simplified, and the precision of transmission is facilitated.

[0033] One side of the motor shaft is specially used for connecting the third crank arm, as a power source of the fourth transmission assembly, to realize corresponding mechanical action, and the other side is provided with a motor shaft having other purposes, which is used for connecting a presser foot mechanism to realize stitch length adjustment to meet different sewing requirements, and two motor shafts are designed to improve the overall performance of the driving member.

[0034] The structure of the second driving assembly is as follows: the driving assembly includes a first motor and a second motor; the first motor drives a first transmission assembly; the second motor drives a second transmission assembly;

[0035] The first transmission assembly includes:

[0036] A first swing arm is arranged at the output end of the first motor, and a first sliding block is protrusively arranged at the end side of the first swing arm;

[0037] A linkage crank is hinged on the end cover of the first motor, and the front end of the linkage crank has a first sliding slot, and the first sliding block is movably connected in the first sliding slot;

[0038] A first connecting rod is arranged at the rear end of the linkage crank;

[0039] A first ring part is rotatably arranged on the hook mechanism and connected with the rear end of the first connecting rod, and the first ring part is provided with the first cutting knife.

[0040] The linkage crank is in a V shape, and the lower side of the middle part of the linkage crank is provided with a first hinge shaft, and the first hinge shaft is rotatably arranged on the end cover of the first motor;

[0041] One side wall of the linkage crank is provided with the first sliding slot, and the other side wall is provided with the first output rod, and the upper end of the first output rod is hinged with the first transmission rod.

[0042] The third driving assembly is provided with only one power source, and the power source simultaneously outputs power to the first transmission assembly and the second transmission assembly;

[0043] During the rotation of the first cutting knife from the first position to the second position, the second transmission assembly isolates the power transmission between the driving assembly and the second cutting knife; during the rotation of the first cutting knife from the second position to the first position, the second transmission assembly transmits the power of the driving assembly to the second cutting knife.

[0044] The second transmission assembly comprises a shifting cam and a swing rod assembly;

[0045] The shifting cam is driven by the driving assembly;

[0046] The swing rod assembly is rotatably arranged on the frame, the lower part of the swing rod assembly is matched with the shifting cam, and the upper part of the swing rod assembly drives the second connecting rod and the second ring part;

[0047] The lower part of the swing rod assembly is provided with a guide slot, and a moving rod and an elastic part are arranged in the guide slot; the elastic part is used for resetting the moving rod;

[0048] When the shifting cam applies force to the end part of the moving rod, the moving rod is retracted into the guide slot and isolates the power transmission; when the shifting cam abuts against the side part of the moving rod, the shifting cam drives the second connecting rod through the moving rod.

[0049] The sewing machine further provides a thread cutting method, and the sewing machine comprises the double-cutting-knife thread cutting mechanism, and the thread cutting method comprises thread cutting in a starting stage and thread cutting in a finishing stage, and the steps are as follows:

[0050] Step S1, initial state, both the cutting knife one and the cutting knife two are located on the same side of the frame, the cutting knife one is in the initial first position, and the cutting knife two is in the initial third position; the fabric to be sewn is placed;

[0051] Step S2, the stage of starting sewing, the cutting knife one moves towards the direction of the needle, the cutting knife one rotates until the thread hole groove is located directly below the position of the needle, and the cutting knife one is in the second position; the needle first passes through the thread hole groove downward, then leaves the thread hole groove upward and is lifted to a suitable position above the frame, completing the first needle-down action of the needle;

[0052] Step S3, the cutting knife one moves to the first position, and the cutting knife two moves to the fourth position; the cutting knife one retreats towards the position close to the cutting knife two; the thread hole groove of the cutting knife one approaches the second blade edge of the cutting knife two; the cutting knife two slides on the surface of the cutting knife one, and the first blade edge and the second blade edge approach each other;

[0053] Step S4, the needle continues to sew, and the thread on the needle is locked with the bobbin thread in the rotating hook mechanism;

[0054] Step S5, the cutting knife one continues to reset to the first position, and the cutting knife two continues to move to the fourth position; when the second blade edge of the cutting knife two and the first blade edge of the cutting knife one coincide, the sewing thread in the thread hole groove is cut off; the cutting knife one is reset; after the cutting knife two reaches the fourth position, it is reset to the third position; the sewing thread is cut off in the stage of starting sewing;

[0055] Step S6, the needle continues to sew until the current sewing operation is completed, and the needle is lifted above the frame;

[0056] Step S7, the sewing thread in the stage of finishing is executed, the cutting knife one moves to the second position, and the cutting knife one rotates until the thread hook groove one is directly below the needle; after the thread hook groove one hooks the sewing thread, the cutting knife one is reset to the first position, and the cutting knife two moves to the fourth position; the cutting knife one and the cutting knife one move towards each other, the thread hook groove one of the cutting knife one approaches the blade edge of the cutting knife two with the sewing thread, the cutting knife two slides on the surface of the cutting knife one, and when the blade edge of the cutting knife two and the blade edge of the cutting knife one coincide, the sewing thread in the thread hook groove one is cut off;

[0057] Step S8, the cutting knife one is reset; after the cutting knife two reaches the fourth position, it is reset to the third position; the sewing thread in the stage of finishing is cut off.

[0058] In step S3, when the cutting knife one moves to the first position, the thread hole groove passes through the thread clamp, the thread in the thread hole groove is pressed by the thread clamp, and the thread is in the thread locking state and cannot exit the thread hole groove; then step S4 is executed.

[0059] The technical scheme has the advantages of:

[0060] 1、The technical scheme drives the first cutting knife assembly and the second cutting knife assembly to rotate through the driving assembly, so that the first cutting knife and the second cutting knife rotate around the outer side shaft of the rotating hook mechanism; the first cutting knife and the second cutting knife are located on the same side of the rack, which can realize thread hole slot thread hooking and thread cutting in the starting stage, and can realize thread hooking and thread cutting in the ending stage, thereby reducing thread residue and improving production automation and production efficiency.

[0061] 2、The technical scheme adds a thread hooking groove two on the first cutting knife, and the thread hooking groove one and the thread hooking groove two cooperate to cut the sewing thread in the ending stage, and reserve the sewing thread on the needle, thereby avoiding the phenomenon of thread breakage due to too short sewing thread in the next starting stage.

[0062] 3、In the technical scheme, the first mode of the driving assembly is a sleeve rod structure transmission, which includes a transmission rod one and a transmission rod two, the transmission rod one is arranged in the transmission rod two, and the two transmission rods are arranged in a concentric manner and correspond to the first cutting knife assembly and the second cutting knife assembly, which simplifies the transmission structure and improves the precision of transmission.

[0063] 4、In the technical scheme, the second mode of the driving assembly is a linkage crank with a "V" type design, the linkage crank is hinged to the end cover of the first motor, and the space below the sewing machine rack is very narrow, this structure can realize the transmission of the first transmission assembly, and can make the first motor realize the same trajectory of the first cutting knife when rotating forward and reversing.

[0064] 5、In the technical scheme, the third mode of the driving assembly is that one power source drives the first cutting knife and the second cutting knife, which reduces the cost of one power source and further optimizes the structure and cost. DETAILED DESCRIPTION

[0065] Fig. 1 is a schematic view of the structure of the embodiment 1 installed on the rack.

[0066] Fig. 2 is another perspective view of the embodiment 1 installed on the rack.

[0067] Fig. 3 is a schematic view of the transmission structure of the embodiment 1.

[0068] Fig. 4 is a schematic view of the installation of the first cutting knife and the second cutting knife in the embodiment 1.

[0069] Fig. 5 is a schematic view of part of the structure of the first cutting knife assembly and the second cutting knife assembly in the embodiment 1.

[0070] Fig. 6 is a schematic view of the partial explosion of the first cutting knife assembly in the embodiment 1.

[0071] Figure 7 is a partial exploded view of the second knife assembly of Example 1.

[0072] Figure 8 is a view of the cooperation of the first and second cutting knives of Example 1.

[0073] Figure 9 is a view of the operation of the thread hole hooking of Example 1.

[0074] Figure 10 is a view of the operation of the hooking of the first and second thread hooking grooves of Example 1.

[0075] Figure 11 is an exploded view of the third and fourth transmission assemblies of Example 1.

[0076] Figure 12 is a view of the transmission structure of Example 2.

[0077] Figure 13 is a view of the transmission of the first motor driving the first cutting knife of Example 2.

[0078] Figure 14 is a view of the transmission of the second motor driving the second cutting knife of Example 2.

[0079] Figure 15 is a view of the transmission structure of Example 3.

[0080] Figure 16 is a view of the transmission structure of Example 3.

[0081] Figure 17 is a view of the swing rod assembly of Example 3.

[0082] Reference: 1, rack; 2, first moving knife assembly; 3, second moving knife assembly; 4, driving assembly; 5, sleeve rod structure; 6, wire hole groove; 8, third transmission assembly; 9, fourth transmission assembly; 10, sliding groove; 11, sliding block; 12, limiting part; 13, adjusting part; 14, elastic member; 15, connecting block; 16, wire clamping device; 17, wire suction device; 21, first cutting knife; 22, first transmission assembly; 31, second cutting knife; 32, second transmission assembly; 41, first driving member; 42, second driving member; 51, transmission rod one; 52, transmission rod two; 61, preparatory wire groove; 71, wire hooking groove one; 72, wire hooking groove two; 81, first curved arm; 82, second curved arm; 91, third curved arm; 92, driving cam; 100, rotating shuttle mechanism; 101, first motor; 102, second motor; 103, first swing arm; 104, first sliding block; 105, linkage crank; 106, end cover; 107, first sliding groove; 108, first output rod; 109, first hinged shaft; 110, return spring; 111, transmission crank; 181, wire guide groove one; 182, wire guide groove two; 200, needle; 201, linkage input shaft; 202, actuating cam; 203, swing rod assembly; 205, moving rod; 2051, side of moving rod; 2052, end of moving rod; 206, guide groove; 207, elastic member; 208, adjusting nut; 209, positioning pin shaft; 210, limiting block; 211, first blade edge; 212, knife tip; 221, first crank; 222, first connecting rod; 223, first ring part; 311, second blade edge; 322, second connecting rod; 323, second ring part. DETAILED DESCRIPTION

[0083] The specific embodiments of the technical solution will be described in further detail below with reference to the accompanying drawings.

[0084] Embodiment 1: Referring to FIGS. 1 and 2, a double-moving-knife wire cutting mechanism is installed below a rack 1 of a sewing machine, the rack 1 in the figure is provided with a rotating shuttle mechanism 100 and a needle 200 above the rack 1, the rotating shuttle mechanism 100 is a prior art and will not be described here, the needle 200 is used to pass through sewing thread and can be lifted up and down or lowered.

[0085] Referring to FIGS. 3 and 5, the wire cutting mechanism comprises a first moving knife assembly 2, a second moving knife assembly 3 and a driving assembly 4; the first moving knife assembly 2 comprises a first transmission assembly 22 and a first cutting knife 21; the second moving knife assembly 3 comprises a second transmission assembly 32 and a second cutting knife 31;

[0086] The first cutting blade 21 of the first cutting assembly 2 is used to hook the sewing thread, and the second cutting blade 31 of the second cutting assembly 3 is used to cut the sewing thread in cooperation with the first cutting blade 21; the driving assembly 4 comprises a first driving member 41 and a second driving member 42, both of which can be a stepping motor; the first driving member 41 and the second driving member 42 are indirectly driven by the sleeve rod structure 5 to drive the first cutting assembly 2 and the second cutting assembly 3 respectively.

[0087] The second driving member 42 can be a double-shaft motor, the two ends of the motor shaft of which extend outward, one end of the motor shaft is used to drive the second cutting assembly 3, and the other end is used to drive another set of mechanism, such as a presser foot lifting mechanism or a stitch length adjusting mechanism, etc., and the technical solution of how to share one motor between the two sets of mechanisms is the prior art, which will not be described here.

[0088] Referring to FIGS. 5 and 6, the first transmission assembly 22 comprises a first crank 221, a first connecting rod 222 and a first ring 223; the lower end of the first crank 221 is fixedly sleeved on the end of the transmission rod 51 away from the first driving member 41, the upper end of the first crank 221 is hingedly connected to the lower end of the first connecting rod 222, the other end of the first connecting rod 222 is hingedly connected to the first ring 223, forming two hinged points, and the first ring 223 is rotatably sleeved on the rotating hook mechanism 100; when the first driving member 41 drives the transmission rod 51 to rotate, the transmission rod 51 drives the first crank 221 to swing, the first crank 221 drives the first connecting rod 222, and the first connecting rod 222 drives the first ring 223 to rotate; the first ring 223 is provided with the first cutting blade 21, which is used to switch the first cutting blade 21 between different positions; the first cutting blade 21 is in the shape of an arc.

[0089] Referring to FIGS. 5 and 7, the second transmission assembly 32 comprises a second crank 321, a second connecting rod 322 and a second ring 323; the lower end of the second crank 321 is fixedly sleeved on the end of the transmission rod 52 away from the second driving member 42, the upper end of the second crank 321 is hingedly connected to the lower end of the second connecting rod 322, and the other end of the second connecting rod 322 is hingedly connected to the second ring 323, forming two hinged points; the second ring 323 is rotatably sleeved on the rotating hook mechanism 100 and adjacent to the first ring 223; when the second driving member 42 drives the transmission rod 52 to rotate, the transmission rod 52 drives the second crank 321 to swing, the second crank 321 drives the second connecting rod 322, and the second connecting rod 322 drives the second ring 323 to rotate; the second ring 323 is provided with the second cutting blade 31, which is used to switch the second cutting blade 31 between different positions; the second cutting blade 31 is in the shape of an arc.

[0090] The second crank 321 is provided with a connecting block 15 located above the second crank 321, and the end of the transmission rod two 52 close to the second crank 321 is sleeved with an elastic element 14, which is preferably a torsion spring; the torsion spring is arranged between the connecting block 15 and the rack 1 respectively, and the elastic force of the torsion spring acts on the second crank 321, so that the second crank 321 can quickly reset after the transmission rod two 52 is separated from the inner surface of the driving cam 92, so that the cutting line moving knife two 31 remains in the initial position reset tendency.

[0091] The first ring part 223 and the second ring part 323 are rotatably sleeved on the outer circumferential side of the adapted shuttle mechanism 100, and the shuttle mechanism 100 is used as the rotation axis.

[0092] As shown in FIG. 11, the sleeve rod structure 5 includes a transmission rod one 51 and a transmission rod two 52, the transmission rod two 52 is arranged inside or outside the transmission rod one 51, in this embodiment, the transmission rod one 51 is arranged inside the transmission rod two 52, the transmission rod two 52 is a sleeve structure, the transmission rod one 51 is a rod core structure, the transmission rod one 51 and the transmission rod two 52 can rotate independently and are concentrically arranged, and the two ends of the transmission rod one 51 pass through the two ends of the transmission rod two 52 respectively.

[0093] As shown in FIG. 11, the third transmission assembly 8 is arranged between the first driving element 41 and the transmission rod one 51, the third transmission assembly 8 transmits the rotation of the motor shaft of the first driving element 41 to the rotation of the transmission rod one 51, the third transmission assembly 8 includes a first curved arm 81, a second curved arm 82 and a sliding block 11; one end of the first curved arm 81 is fixed on the motor shaft of the first driving element 41, the second curved arm 82 is located on the side of the first curved arm 81 away from the first driving element 41, and the first curved arm 81 swings to drive the second curved arm 82 to run synchronously; the sliding block 11 is protruded from the other end of the first curved arm 81 towards the second curved arm 82, the sliding block 11 is a rectangular block, a sliding groove 10 is arranged on the end face of the second curved arm 82 close to the first curved arm 81, the sliding groove 10 penetrates through both ends along the length direction of the second curved arm 82, and the width size of the sliding block 11 is matched with the groove width of the sliding groove 10, so that the sliding block 11 can be embedded in the sliding groove 10 and slide along the length direction of the sliding groove 10 to push the second curved arm 82 to swing, and based on the other end of the second curved arm 82 being fixed on the transmission rod one 51, the transmission rod one 51 is driven to rotate. The transmission is in the form of the sliding block 11 and the sliding groove 10 assembly, and the forward rotation and reverse rotation of the first driving element 41 realizes the same trajectory when the cutting line moving knife one 21 rotates.

[0094] The second curved arm 82 is provided with a limiting part 12 fixed in the sliding groove 10 and located at one end of the groove away from the fixed end of the second curved arm 82, in this embodiment, the limiting part 12 is preferably a bolt, which is used for abutting the sliding block 11 and limiting the sliding block 11 from accidentally separating from the through end of the sliding groove 10, thereby improving the guiding stability.

[0095] The fourth transmission assembly 9 is arranged between the second driving member 42 and the second transmission rod 52, and is configured to transmit the rotation of the motor shaft of the second driving member 42 to the rotation of the second transmission rod 52. The fourth transmission assembly 9 comprises a third curved arm 91 and a driving cam 92. One end of the third curved arm 91 is locked on the motor shaft of the second driving member 42, and the other end of the third curved arm 91 is fixed with the adjusting part 13. The adjusting part 13 protrudes towards the driving cam 92. The adjusting part 13 can be in rolling, sliding or rotating relative motion with the driving cam 92. In the embodiment, the driving cam 92 is provided with a cam groove. The protrusion degree of the inner wall of the cam groove is not uniform. The adjusting part 13 is embedded in the driving cam 92 and in contact with the inner wall of the cam groove. When the third curved arm 91 rotates to drive the adjusting part 13, the adjusting part 13 is in contact with the inner wall of the cam groove to drive the driving cam 92 to move intermittently. Since one end of the driving cam 92 is fixed on the end of the second transmission rod 52, the second transmission rod 52 is driven to rotate.

[0096] Referring to FIG. 8, the cutting knife 21 is provided with a thread hole groove 6, a thread hooking groove 71, a thread hooking groove 72 and a standby thread groove 61. Each groove penetrates the thickness direction of the cutting knife 21. The thread hole groove 6 and the thread hooking groove 71 are arranged along the rotation direction of the cutting knife 21. The thread hole groove 6 is located away from the cutting tip of the cutting knife 21. The cutting tip is provided with a first blade edge 211 with uneven flatness. The thread hole groove 6 is used for the needle 200 to pass through and hook the sewing thread in the starting stage. The standby thread groove 61 is a standby thread hole groove. For the part of the fabric that does not need to reserve the sewing thread with the thread clamp, the standby thread groove 61 can be used as a thread hole groove by adjusting the rotation position of the cutting knife 21 through the driving assembly.

[0097] The thread hooking groove 71 and the thread hooking groove 72 are respectively and correspondingly located on the opposite sides of the middle part of the cutting knife 21, and each has an opening outward. In the cutting process in the ending stage, the cutting tip 212 of the cutting knife 21 penetrates the thread loop of the sewing thread in the process of rotating to the second position. The thread loop is stretched and slides to the two openings. The process of stretching the thread loop completes the thread storage action of the sewing thread. The sewing threads on the two sides are hooked into the corresponding thread hooking groove 71 and thread hooking groove 72. In the embodiment, the cutting knife 21 is provided with two guide grooves for containing the sewing thread, including a guide groove 181 and a guide groove 182. The guide groove 181 is located between the thread hole groove 6 and the first blade edge, and covers the thread hooking groove 71 to guide the sewing thread to the thread hole groove 6. The front end edge of the guide groove 181 is provided with the first blade edge. The front end of the guide groove 181 can be a through groove or a non-through groove. The through groove forms the standby thread groove 61. The other guide groove 182 is arranged corresponding to the thread hooking groove 72 to guide the sewing thread to the thread hooking groove 72.

[0098] The second cutting knife 31 is arranged above the outer side of the first cutting knife 21, the front end of the second cutting knife 31 abuts against the upper surface of the first cutting knife 21 and slides, the front end of the second cutting knife 31 is provided with a second cutting edge 311, when the second cutting knife 31 and the first cutting knife 21 approach each other, the sewing thread is led to the second cutting edge 311 by the thread hole groove 6 in the starting stage, and the sewing thread is led to the second cutting edge 311 by the thread hooking groove 71 in the ending stage; the sewing thread is not cut off under the pressure of the first cutting edge until the sewing thread is cut off when the sewing thread coincides with the second cutting edge, thereby ensuring the cut thread in the starting stage and the broken thread in the ending stage.

[0099] Referring to FIG. 11, the frame 1 is further provided with a thread clamping device 16 which is arranged on the inner side of the first cutting knife 21 and can be aligned with the thread hole groove 6, when the sewing thread is ready to be cut in the starting stage, the thread clamping device 16 clamps the sewing thread which passes through the thread hole groove 6 against the inner wall of the first cutting knife 21, thereby locking the thread and stopping the supply of the thread to the needle 200 (the thread which passes through the needle 200 of the sewing machine is the top thread, and the thread in the rotating hook mechanism 100 at the bottom of the sewing machine is the bottom thread), so that the subsequent second needle sewing thread is stable and is not easy to be separated after sewing.

[0100] The frame 1 is further provided with a thread suction device 17, the discharge suction port of the thread suction device 17 is connected to the thread hole groove 6, and the thread suction device 17 is used to suck the thread after cutting.

[0101] The application also claims to protect a thread cutting method of a double-cutting-knife sewing mechanism, the method is realized by the double-cutting-knife thread cutting mechanism, and the thread cutting method comprises a starting stage and an ending sewing stage, and the steps are as follows:

[0102] S1, initial state, in the starting stage, the first cutting knife 21 is in the initial first position, and the second cutting knife 31 is in the initial third position; the first cutting knife and the second cutting knife are located on the same side, the same side referred to herein is that the frame is divided into front and back sides with the needle as the boundary, the moving area of the cloth towards the needle during sewing is the front side, and the moving area of the cloth away from the needle is the back side; in this embodiment, both are located on the front side of the frame; as shown in FIG. 3, in the initial state, the first cutting knife and the second cutting knife are relatively rotated to the right side of the rotating hook mechanism, and are slightly staggered at this position and do not require to be in the same position; the cloth to be sewn is placed;

[0103] S2, the first driving member 41 drives the thread cutting knife 21 to move towards the needle, and the thread cutting knife 21 is located at the second position; the electric control system of the sewing machine controls the needle to perform the first needle lowering action in the thread starting stage, the needle first passes through the needle plate and the sewing material downward, then passes through the thread hole groove 6 and enters the rotary hook mechanism to hook the bottom thread, and then exits the thread hole groove 6 upward and rises to a suitable position above the machine frame 1; the thread passing through the needle is the face thread, and the thread in the rotary hook mechanism at the bottom of the sewing machine is the bottom thread; the thread tensioner of the sewing machine pulls the face thread on the needle upward and makes the face thread retreat, and in this process, the face thread storage is completed; the thread end of the sewing thread on the needle remains in the thread hole groove 6; the bottom thread in the rotary hook mechanism may be brought into the thread hole groove 6 from below to above, and in the subsequent movement of the thread cutting knife 21, the bottom thread will automatically separate from the thread hole groove 6 or be cut off together, and the bottom thread does not affect the subsequent action;

[0104] S3, the thread cutting knife 21 moves to the first position, and the thread hole groove 6 of the thread cutting knife 21 approaches the blade edge of the thread cutting knife 31; the thread cutting knife 31 moves to the fourth position, the second driving member 42 drives the thread cutting knife 31 to slide on the surface of the thread cutting knife 21, and the first blade edge and the second blade edge approach each other; when the thread hole groove 6 passes through the thread clamp 16, the thread cutting knife 21 retreats to the specified position and pauses with the thread cutting knife 31 at the existing position, and the thread clamp 16 locks the face thread and cannot exit the thread hole groove 6.

[0105] S4, as shown in FIG. 9, the needle performs the second needle lowering action, the face thread on the needle is locked with the bottom thread in the rotary hook mechanism 100, the thread tensioner of the sewing machine moves upward to the highest point and tightens the face thread, avoids the second needle from being lifted to be taken out of the thread hole groove 6, ensures that the subsequent cut thread is not easy to loosen, and ensures that the second needle locking ends; during the upward movement of the thread tensioner, when the length of the face thread is insufficient, the thread loosener will automatically loosen the thread and supplement a certain length of the face thread, which can ensure that the face thread can maintain a certain tight state every time the thread starting is started, and the sewing quality is improved;

[0106] S5, the thread cutting knife 21 continues to reset to the first position, the thread cutting knife 31 continues to advance to the fourth position, the two driving members continue to drive the thread cutting knife 31 to approach the thread cutting knife 21, continuously slide forward on the surface of the thread cutting knife 21, and the thread cutting knife 21 is reset; after the thread cutting knife 31 reaches the fourth position, the blade edge of the thread cutting knife 31 and the blade edge of the thread cutting knife 21 approach and coincide with each other, cut the sewing thread in the thread hole groove 6, and complete the length of the thread end of the face thread on the needle in the thread starting stage; the thread cutting knife 31 resets to the third position and separates from the thread clamp, and the thread suction device 17 sucks away the cut sewing thread through the air suction port;

[0107] S6, the needle continues to sew until the end of the sewing operation, and the needle is lifted above the frame 1;

[0108] S7, the thread cutting in the finishing stage is performed, the first driving member 41 drives the thread cutting moving knife one 21 to move towards the needle until the tip of the thread cutting moving knife one 21 passes through the thread loop of the sewing thread and reaches the second position, at the second position, the thread loop is opened by the thread cutting moving knife one 21 and slides into the openings of the thread hooking groove one 71 and the thread hooking groove two 72; the bobbin thread is twisted with the sewing thread in the thread hooking groove one 71 and the thread hooking groove two 72; the first driving member 41 drives the thread cutting moving knife one 21 to retreat, the second driving member 42 drives the thread cutting moving knife two 31 to move towards the thread cutting moving knife one 21, the thread hooking groove one 71 with the sewing thread approaches the blade of the thread cutting moving knife two 31, the thread cutting moving knife two 31 slides on the surface of the thread cutting moving knife one 21, and the blade of the thread cutting moving knife two 31 and the blade of the thread cutting moving knife one 21 cut the sewing thread in the thread hooking groove one 71 when they coincide;

[0109] S8, the thread cutting in the finishing stage is completed, the second driving member 42 drives the thread cutting moving knife two 31 to reset, and the first driving member 41 drives the thread cutting moving knife one 21 to reset, and the thread cutting is completed.

[0110] In the step S3, when the thread cutting moving knife one 21 moves to the first position, the thread hole groove 6 first passes through the thread clamp 16, and the bobbin thread in the thread hole groove 6 is pressed by the thread clamp 16, so that the bobbin thread is in the thread locking state and cannot exit the thread hole groove 6; and then the step S4 is performed.

[0111] It should be noted that the second position in the step S2 refers to the position of the thread cutting moving knife one 21 when the thread hole groove 6 is directly below the needle, and the second position in the step S7 refers to the position of the thread cutting moving knife one 21 when the sewing thread is hooked into the opening of the thread hooking groove one 71.

[0112] Subsequently, the above thread cutting operation is repeated to reduce the thread residue, and the subsequent manual processing step is omitted, thereby improving the production automation and production efficiency.

[0113] In embodiment 2, as shown in FIGS. 12-14, the embodiment is basically the same as embodiment 1, and the difference is that the driving assembly 4 includes a first motor 101 and a second motor 102; the first motor 101 drives a first transmission assembly; and the second motor drives a second transmission assembly.

[0114] The first transmission assembly includes:

[0115] A first swing arm 103 is arranged at the output end of the first motor 101, and a first sliding block 104 is protrusively arranged at the end side of the first swing arm 103.

[0116] A linkage crank 105 is hinged on the end cover 106 of the first motor 101, and the front end of the linkage crank has a first sliding groove 107, in which the first sliding block 104 is movably connected;

[0117] A first connecting rod 222 is arranged at the rear end of the linkage crank 105;

[0118] A first ring part 223 is rotatably arranged on the hook mechanism 100 and connected to the rear end of the first connecting rod 222, and the first ring part 223 is provided with the first cutting knife 21.

[0119] The linkage crank 105 is in a "V" shape, and the lower side of the middle part of the linkage crank 105 is provided with a first hinge shaft 109, which is rotatably arranged on the end cover 106 of the first motor;

[0120] One side wall of the linkage crank 105 is formed with the first sliding groove 107, and the other side wall is formed with a first output rod 108, and the upper end of the first output rod 108 is hinged to the first connecting rod 222. The swinging process of the linkage crank 105 realizes power transmission.

[0121] The linkage crank is designed in a "V" shape and is hinged on the end cover of the first motor. The space below the sewing machine frame is very narrow. This structure can realize the transmission of the first transmission assembly, and can also make the same trajectory of the first cutting knife when the first motor rotates forward and reversely. The first motor 101 and the first transmission assembly form a structure similar to an independent module, which is more convenient to assemble, occupies less space, and has better stability.

[0122] As shown in FIG. 12, the structure of the second motor driving the second transmission assembly is similar to that of embodiment 1. A third crank arm 91 is arranged on the motor shaft of the second motor 102, and an adjusting part 13 is arranged on the third crank arm. The adjusting part 13 cooperates with a driving cam 92 to transmit power to a transmission rod 51. The transmission rod 51 drives a transmission crank 111, which drives a second connecting rod 322 and a second ring part 323. The sizes and shapes of the components of the second transmission assembly are different from those of embodiment 1, and the functions and effects are the same.

[0123] Embodiment 3, as shown in FIGS. 15-17, is basically the same as embodiment 1, except that the driving assembly 4 has only one power source, and the power source simultaneously outputs power to the first transmission assembly and the second transmission assembly.

[0124] The second transmission assembly isolates the power transmission between the driving assembly 4 and the second cutting blade 31 when the first cutting blade 21 rotates from the first position to the second position; the second transmission assembly transmits the power of the driving assembly 4 to the second cutting blade 31 when the first cutting blade 21 rotates from the second position to the first position.

[0125] The second transmission assembly comprises a shifting cam 202 and a swing lever assembly 203.

[0126] The shifting cam 202 is driven by the driving assembly; the outer contour of the shifting cam 202 is similar to the number "6".

[0127] The swing lever assembly is rotatably installed on the frame; the lower part of the swing lever assembly 203 cooperates with the shifting cam, and the upper part of the swing lever assembly 203 drives the second connecting rod 322 and the second ring part 323.

[0128] The lower part of the swing lever assembly is provided with a guide groove 206, and a moving lever 205 and an elastic part 207 are installed in the guide groove 206; the elastic part is used for resetting the moving lever 205; when the shifting cam 202 applies force to the end part 2052 of the moving lever, the moving lever 205 is hindered by the elastic part 207 and is retracted into the guide groove 206, thereby isolating the power transmission; when the shifting cam 202 rotates to a certain angle, the shifting cam 202 abuts against the side part 2051 of the moving lever, and at this time, the shifting cam 202 is reversely rotated, so as to drive the second connecting rod 322 through the moving lever. The inner end of the moving lever 205 is provided with an adjusting nut 208, which can adjust the position of the moving lever 205. A shock-absorbing limiting block 210 is further arranged beside the swing lever assembly, so as to realize the silence during operation.

[0129] The power source is a stepping motor, and the motor shaft transmits power to the linkage input shaft 201; as shown in FIGS. 15 and 16, the linkage input shaft 201 drives the first crank 221 and the shifting cam 202 at the same time; the first crank 221 drives the first connecting rod 222, and the first connecting rod 222 drives the first ring part 223 to rotate, and the first ring part 223 is provided with the first cutting blade 21.

[0130] One power source drives the first cutting blade and the second cutting blade at the same time, which reduces the cost of one power source, and further optimizes the structure and cost. Reducing one power source further reduces the space requirement below the frame, and the remaining space can be matched to other functional modules, so that the sewing machine has more powerful functions.

[0131] The above describes the basic principles and main features of the technical solution and the advantages of the technical solution, and the protection scope of the technical solution is defined by the appended claims and their equivalents.

Claims

1. A double-action knife thread cutting mechanism of a sewing machine, the sewing machine comprising a machine frame (1), a thread cutting mechanism and a rotating hook mechanism; the thread cutting mechanism is arranged on the machine frame (1) and below the needle; characterized in that: the thread cutting mechanism comprises a first knife assembly (2), a second knife assembly (3) and a driving assembly (4); the first knife assembly (2) comprises a first transmission assembly (22) and a thread cutting knife one (21); the second knife assembly (3) comprises a second transmission assembly (32) and a thread cutting knife two (31); the driving assembly (4) drives the thread cutting knife one (21) to rotate between a first position and a second position through the first transmission assembly (22); the rotation of the thread cutting knife one (21) is around the axis of the rotating hook mechanism; the driving assembly (4) drives the thread cutting knife two (31) to rotate between a third position and a fourth position through the second transmission assembly (32); the rotation of the thread cutting knife two (31) is around the axis of the rotating hook mechanism; the thread cutting knife one (21) is provided with a thread hole slot (6) for the needle to pass through and hook the sewing thread in the starting stage and a thread hooking slot one (71) to hook the sewing thread in the ending stage; a first blade edge (211) is further arranged on the front side of the thread cutting knife one; a second blade edge (311) is arranged on the front side of the thread cutting knife two (31); in the process of the driving assembly (4) driving the thread cutting knife one (21) to rotate from the second position to the first position, the driving assembly (4) simultaneously drives the thread cutting knife two (31) to rotate from the third position to the fourth position; the thread cutting knife two (31) abuts against the surface of the thread cutting knife one (21) in the rotation process, so that the first blade edge of the thread cutting knife one (21) cooperates with the second blade edge of the thread cutting knife two (31) to cut the sewing thread.

2. A double action knife thread trimming mechanism for a sewing machine as defined in claim 1 wherein, in the initial state, the thread cutting knife one (21) and the thread cutting knife two (31) are located on the same side of the machine frame (1); in the process of the thread cutting knife one (21) rotating from the second position to the first position, the thread hole slot (6) gradually moves away from the needle; in the process of the thread cutting knife two (31) rotating from the third position to the fourth position, the second blade edge gradually moves close to the needle.

3. The double action knife thread trimming mechanism of a sewing machine according to claim 1, wherein a thread holder (16) is further arranged on the machine frame (1) and close to the second position; in the process of the thread cutting knife one (21) moving from the second position to the first position, the thread hole slot (6) drives the sewing thread to the position of the thread holder (16); the thread cutting knife one (21) cooperates with the thread holder (16) to hold the sewing thread in the thread hole slot (6); the machine frame (1) is further provided with a thread suction device (17), the discharge suction port of the thread suction device (17) is connected at the thread hole slot (6), which is used to suck the thread end after cutting the thread; 4. The double action knife thread trimming mechanism of a sewing machine according to claim 1, wherein: the thread cutting knife one (21) is further provided with a thread hooking slot two (72), the thread hooking slot two (72) and the thread hooking slot one (71) are respectively located on the two sides of the width of the thread cutting knife one (21). The wire guide groove one (181) is arranged between the wire hole groove (6) of the first moving cutter (21) and the first blade edge.

5. The double action knife thread trimming mechanism of a sewing machine according to claim 1, wherein: The first transmission assembly (22) comprises a first crank (221), a first connecting rod (222) and a first ring part (223), two ends of the first connecting rod (222) are respectively hinged between one end of the first crank (221) and the first ring part (223), the first moving cutter (21) is arranged on the first ring part (223), and the first ring part (223) is rotationally connected relative to the rack (1) and used for driving the first moving cutter (21); The second transmission assembly (32) comprises a second crank (321), a second connecting rod (322) and a second ring part (323), two ends of the second connecting rod (322) are respectively hinged between one end of the second crank (321) and the second ring part (323), the second moving cutter (31) is arranged on the second ring part (323), and the second ring part (323) is coaxially arranged with the first ring part (223) and used for driving the second moving cutter (31).

6. The double action knife thread trimming mechanism of a sewing machine according to claim 1, wherein: The driving assembly (4) comprises a first driving member (41), a second driving member (42), a third transmission assembly (8), a fourth transmission assembly (9) and a sleeve rod structure (5); The sleeve rod structure (5) comprises a transmission rod one (51) and a transmission rod two (52) arranged inside or outside the transmission rod one (51); The first driving member (41) drives the transmission rod one (51) to rotate through the third transmission assembly (8), and the transmission rod one (51) drives the first transmission assembly (22); The second driving member (42) drives the transmission rod two (52) to rotate through the fourth transmission assembly (9), and the transmission rod two (52) drives the second transmission assembly (32); The third transmission assembly (8) comprises a first curved arm (81) and a second curved arm (82) movably arranged on the first curved arm (81); The other end of the first curved arm (81) is fixed on a motor shaft of the first driving member (41), and the other end of the second curved arm (82) is fixed on the transmission rod one (51); An end face of the second curved arm (82) close to the first curved arm (81) is provided with a sliding groove (10), and a swing end of the first curved arm (81) is correspondingly fixed with a sliding block (11) arranged in the sliding groove (10) to realize sliding guidance; The swing of the first curved arm (81) drives the transmission rod one (51) to rotate, and the other end of the transmission rod one (51) directly or indirectly drives the first moving cutter assembly (2); The second curved arm (82) is provided with a limiting part (12) fixed to one end of the sliding groove (10) away from the fixed end of the second curved arm (82), used for limiting the sliding block (11) from falling out of the sliding groove (10); The fourth transmission assembly (9) comprises a third curved arm (91) and a driving cam (92) arranged on the third curved arm (91). One end of the third swing arm (91) is fixed on the motor shaft of the second driving member (42), and the other swing end is provided with an adjusting part (13) near the driving cam (92), the adjusting part (13) acts on the driving cam (92), so that the third swing arm (91) transmits power to the transmission rod two (52).

7. A double action knife thread trimming mechanism for a sewing machine as defined in claim 1 wherein, Comprise: The driving assembly (4) comprises a first motor (101) and a second motor (102); The first motor (101) drives the first transmission assembly; the second motor drives the second transmission assembly; The first transmission assembly comprises: A first swing arm (103) is arranged at the output end of the first motor (101), and a first sliding block (104) is arranged on the end side of the first swing arm (103); A linkage crank (105) is hinged on the end cover (106) of the first motor (101), and the front end of the linkage crank has a first sliding groove (107), and the first sliding block (104) is movably connected in the first sliding groove (107); A first connecting rod (222) is arranged at the rear end of the linkage crank (105); and A first ring part (223) is rotatably arranged on the swing lever mechanism (100) and connected with the rear end of the first connecting rod (222); the first ring part (223) is provided with the first cutting knife (21).

8. A double action knife thread trimming mechanism for a sewing machine as defined in claim 7 wherein: The linkage crank (105) is "V"-shaped, and the lower side of the middle part of the linkage crank (105) is provided with a first hinge shaft (109) which is rotatably arranged on the end cover (106) of the first motor; One side wall of the linkage crank (105) forms the first sliding groove (107), and the other side wall forms a first output rod (108), and the upper end of the first output rod (108) is hinged with the first connecting rod (222).

9. The double action knife thread trimming mechanism of a sewing machine according to claim 1, wherein: The driving assembly (4) has only one power source; one power source simultaneously outputs power to the first transmission assembly and the second transmission assembly; During the rotation of the first cutting knife (21) from the first position to the second position, the second transmission assembly isolates the power transmission between the driving assembly (4) and the second cutting knife (31); during the rotation of the first cutting knife (21) from the second position to the first position, the second transmission assembly transmits the power of the driving assembly (4) to the second cutting knife (31).

10. A double action knife thread trimming mechanism for a sewing machine as defined in claim 9 wherein: The second transmission assembly comprises a shifting cam (202) and a swing lever assembly (203); The shifting cam (202) is driven by the driving assembly; The swing lever assembly is rotatably arranged on the rack; the lower part of the swing lever assembly (203) cooperates with the shifting cam, and the upper part of the swing lever assembly (203) drives the second connecting rod (322) and the second ring part (323); The lower part of the swing lever assembly is provided with a guide groove (206), and a moving rod (205) and an elastic part (207) are arranged in the guide groove (206); the elastic part is used for resetting the moving rod (205). The toggle cam (202) exerts force on the end of the moving rod (2052), the moving rod (205) retracts into the guide slot (206) and isolates power transmission; when the toggle cam (202) abuts against the side of the moving rod (2051), the toggle cam (202) drives the second connecting rod (322) through the moving rod.

11. A thread trimming method of a sewing machine, characterized by, The double-action knife thread cutting mechanism of a sewing machine comprises the thread cutting method according to claim 1, and the thread cutting method comprises thread cutting in a starting stage and thread cutting in a finishing stage, and the steps are as follows: Step S1, initial state, the thread cutting knife one (21) and the thread cutting knife two (31) are located on the same side of the machine frame (1), the thread cutting knife one (21) is in the initial first position, and the thread cutting knife two (31) is in the initial third position; the cloth to be sewn is placed; Step S2, starting stage, the thread cutting knife one (21) moves towards the direction of the needle, the thread cutting knife one (21) rotates until the thread hole slot (6) is located directly below the needle, the thread cutting knife one (21) is in the second position; the needle first passes through the thread hole slot (6) downward, then leaves the thread hole slot (6) upward and is lifted to a suitable position above the machine frame (1), and the first needle lowering action of the needle is completed; Step S3, the thread cutting knife one (21) moves to the first position, and the thread cutting knife two (31) moves to the fourth position; the thread cutting knife one (21) retreats towards the thread cutting knife two (31); the thread hole slot (6) of the thread cutting knife one (21) approaches the second blade edge of the thread cutting knife two (31); the thread cutting knife two (31) slides on the surface of the thread cutting knife one (21), and the first blade edge and the second blade edge approach each other; Step S4, the needle continues to sew, and the thread on the needle is locked with the bottom thread in the rotating hook mechanism; Step S5, the thread cutting knife one (21) continues to reset to the first position, and the thread cutting knife two (31) continues to move to the fourth position; when the second blade edge of the thread cutting knife two (31) and the first blade edge of the thread cutting knife one (21) coincide, the sewing thread in the thread hole slot (6) is cut off; the thread cutting knife one (21) is reset; after the thread cutting knife two (31) reaches the fourth position, the thread cutting knife two (31) is reset to the third position; the thread cutting in the starting stage is completed; Step S6, the needle continues to sew until the current sewing operation is completed, and the needle is lifted above the machine frame; Step S7, thread cutting in the finishing stage is performed, the thread cutting knife one (21) moves to the second position, and the thread cutting knife one (21) rotates until the thread hooking slot one (71) is directly below the needle; after the thread hooking slot one (71) hooks the sewing thread, the thread cutting knife one (21) is reset to the first position, and the thread cutting knife two (31) moves to the fourth position; the thread cutting knife one (21) and the thread cutting knife one (21) move towards each other, the thread hooking slot one (71) of the thread cutting knife one (21) approaches the blade edge of the thread cutting knife two (31) with the sewing thread, the thread cutting knife two (31) slides on the surface of the thread cutting knife one (21), and when the blade edge of the thread cutting knife two (31) and the blade edge of the thread cutting knife one (21) coincide, the sewing thread in the thread hooking slot one (71) is cut off; Step S8, the cutting line dynamic knife one (21) is reset, and the cutting line dynamic knife two (31) is reset to the third position after reaching the fourth position; the cutting line is completed in the finishing stage.

12. The thread trimming method of a sewing machine according to claim 11, wherein In the step S3, when the cutting line dynamic knife one (21) moves to the first position, the thread hole groove (6) first passes through the thread clamp (16), and the thread in the thread hole groove (6) is pressed by the thread clamp (16), so that the thread is in the thread locking state and cannot exit the thread hole groove (6); then the step S4 is executed.

Images