Thread trimming and presser foot lifting device and sewing machine

Abstract

The present invention provides a thread trimming and presser foot lifting device and a sewing machine. The thread trimming and presser foot lifting device comprises a motor, a transmission crank, a presser foot lifting driving assembly, a thread trimming driving assembly, a presser foot assembly and a thread trimming assembly. The transmission crank is connected to the rotating shaft of the motor and moves synchronously with the rotating shaft of the motor. The transmission crank has a first driving part and a second driving part. The first driving part is connected to the presser foot lifting driving assembly, and the presser foot lifting driving assembly is connected to the presser foot assembly. The second driving part is detachably connected to the thread trimming driving assembly, and the thread trimming driving assembly is connected to the thread trimming assembly. When the motor rotates forward, the first driving part drives the presser foot assembly to move through the presser foot lifting driving assembly, and the second driving part is in a separated state from the thread trimming driving assembly. When the motor rotates reversely, the second driving part drives the thread trimming assembly to move through the thread trimming driving assembly. By designing a transmission crank with two driving parts, the actions of thread trimming and presser foot lifting of the sewing machine are realized, the structure is compact, and the assembly and debugging requirements are low.

Description

Technical Field

[0001] The invention relates to the technical field of sewing, in particular to a thread trimming and presser foot lifting device and a sewing machine. Background Art

[0002] Sewing machines can be divided into household sewing machines, industrial sewing machines and sewing machines for service industries according to their uses. Most of the industrial sewing machines are general-purpose sewing machines, including lockstitch machines, chainstitch machines, quilting machines, overlock machines and interlock machines. During the use of sewing machines, in order to increase the work efficiency of operators and reduce labor intensity, the use of automatic presser foot lifters has become more and more frequent.

[0003] The automatic thread trimmer and presser foot lifting device of the existing sewing machine are separate, and the automatic thread trimmer and presser foot lifting device are driven by electromagnets or cylinders to trim and reset the thread. The pneumatic presser foot lifting and thread trimmer take a long time to execute the entire action, react relatively slowly, and make a loud noise. The electromagnet presser foot lifting and thread trimmer take a short time to execute the entire action, react quickly, and make a small noise. However, when working for a long time, the electromagnet is easy to get hot, resulting in slow and weak presser foot lifting and thread trimmer reaction.

[0004] The Chinese invention patent with the authorization announcement number CN 207452400 U discloses a thread trimming, thread loosening and presser foot lifting action driving device for a flat sewing machine and a flat sewing machine, comprising a motor, a thread trimming driving member and a presser foot driving member; the thread trimming driving member comprises a thread trimming cam and a thread trimming driving rod; the thread trimming cam is connected to the motor shaft of the motor; the thread trimming driving rod is in contact with the circumferential surface of the thread trimming cam, and the thread trimming driving rod can move under the drive of the thread trimming cam to drive the thread loosening device and the thread trimming device to move; the presser foot driving member comprises a presser foot lifting cam and a presser foot connecting rod; the presser foot lifting cam is connected to the motor shaft of the motor; the presser foot connecting rod is in contact with the circumferential surface of the presser foot lifting cam, and the presser foot connecting rod can move under the drive of the presser foot lifting cam to drive the presser foot device to move; the position of the protruding portion of the presser foot lifting cam in the circumferential direction of the motor shaft has a specified angle difference relative to the position of the protruding portion of the thread trimming cam in the circumferential direction of the motor shaft, so that the action of the thread trimming device precedes the action of the presser foot device.

[0005] Although the above structure solves the defects of electromagnet-driven presser foot lifting and thread trimming, and realizes one motor to drive thread trimming and presser foot lifting, the actions are driven by the thread trimming cam and the presser foot lifting cam respectively, which has the defects of complex structure and high assembly difficulty. Summary of the invention

[0006] The purpose of the present invention is to provide a thread trimming and presser foot lifting device and a sewing machine, which realize the thread trimming and presser foot lifting actions of the sewing machine through a transmission crank, have a compact structure, and have low assembly and debugging requirements, and can effectively improve the production efficiency of the whole machine and reduce production costs.

[0007] In order to achieve the above-mentioned purpose, the present invention provides a thread trimming and presser foot lifting device, comprising a motor, a transmission crank, a presser foot lifting drive assembly, a thread trimming drive assembly, a presser foot assembly and a thread trimming assembly, the transmission crank is connected to the rotating shaft of the motor and moves synchronously with the rotating shaft of the motor, the transmission crank has a first driving part and a second driving part, the first driving part is connected to the presser foot lifting drive assembly, and the presser foot lifting drive assembly is connected to the presser foot assembly, the second driving part is detachably connected to the thread trimming drive assembly, and the thread trimming drive assembly is connected to the thread trimming assembly, when the motor rotates forward, the first driving part drives the presser foot assembly to move through the presser foot lifting drive assembly, and the second driving part is in a separated state from the thread trimming drive assembly, when the motor rotates reversely, the second driving part contacts the thread trimming drive assembly, and the second driving part drives the thread trimming assembly to move through the thread trimming drive assembly.

[0008] Optionally, the presser foot lifting drive assembly includes a first connecting member, a second connecting member, a pull rod, a third connecting member, a first transmission shaft, a connecting crank and a fourth connecting member connected in sequence, one end of the first connecting member is connected to the first driving part, and the fourth connecting member is connected to the presser foot assembly. When the motor rotates forward, the first driving part drives the first transmission shaft to rotate through the first connecting member, the second connecting member and the connecting rod, and the first transmission shaft drives the fourth connecting member to move downward through the connecting crank, thereby driving the presser foot assembly to move.

[0009] Optionally, the fourth connecting member is provided with a sliding groove, and the presser foot assembly includes a presser foot and a presser foot rod connected to each other, the presser foot rod is sleeved with a first shaft hoop, and the shaft hoop is connected to the sliding groove through a fastener, when the motor rotates forward, the fourth connecting member drives the first shaft hoop and the presser foot rod to move downward through the fastener, and then drives the presser foot to move downward, when the motor rotates reversely, the fourth connecting member moves upward, drives the fastener to move along the sliding groove, and the presser foot assembly does not move.

[0010] Optionally, the two ends of the second connecting member are respectively connected to the first connecting member and the casing of the sewing machine, and the second connecting member is provided with a plurality of connecting holes, each of which has a different distance from the two ends of the second connecting member, and the pull rod is connected to the second connecting member through the connecting holes.

[0011] Optionally, a second shaft hoop is sleeved on the first transmission shaft, and the second shaft hoop is connected to the third connecting member to limit the axial movement of the third connecting member along the first transmission shaft.

[0012] Optionally, the thread trimmer drive assembly includes a transmission rod, a crank slider mechanism and a second transmission shaft, the top of the transmission rod is detachably connected to the transmission crank, the bottom of the transmission rod is connected to the crank of the crank slider mechanism, the crank and the housing of the sewing machine have a connection point, the crank can rotate around the connection point, and the two ends of the second transmission shaft are respectively connected to the thread trimmer assembly and the slider of the crank slider mechanism. When the motor rotates forward, the transmission crank moves in a direction away from the transmission rod. When the motor rotates reversely, the transmission crank contacts the transmission rod and drives the transmission rod to move downward. The transmission rod drives the second transmission shaft to move horizontally through the crank slider mechanism, thereby driving the thread trimmer assembly to operate.

[0013] Optionally, a return spring and a stopper are further sleeved on the second transmission shaft, one end of the return spring abuts against the stopper, and the other end abuts against the housing in a detachable manner.

[0014] Optionally, the bottom of the second driving portion has a groove, and the shape of the groove is adapted to the shape of the top of the transmission rod.

[0015] Optionally, the motor is a stepper motor or a grating motor.

[0016] Based on this, the present invention also provides a sewing machine, comprising the thread trimming and presser foot lifting device.

[0017] In a thread trimming and presser foot lifting device and a sewing machine provided by the present invention, at least one of the following beneficial effects is achieved:

[0018] 1) By designing a transmission crank with two driving parts, the actions of thread trimming and presser foot lifting of the sewing machine are realized. The structure is compact and the assembly and debugging requirements are low, which can effectively improve the production efficiency of the whole machine and reduce the production cost;

[0019] 2) When the motor rotates forward, the first driving unit drives the presser foot assembly to move through the presser foot lifting driving assembly, and the second driving unit is separated from the thread trimming driving assembly. When the motor rotates reversely, the second driving unit drives the thread trimming assembly to move through the thread trimming driving assembly. The two actions of thread trimming and presser foot lifting are realized through the forward and reverse rotation of one motor. The structural design is ingenious and the operation is convenient.

[0020] 3) The height of the presser foot can be adjusted by controlling the speed of the motor, and debugging is simple and convenient; BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1-Figure 2 A schematic structural diagram of a thread trimming and presser foot lifting device provided in an embodiment of the present invention;

[0022] Figure 3 A three-dimensional diagram of a transmission crank provided by an embodiment of the present invention;

[0023] Figure 4 A front view of a transmission crank provided by an embodiment of the present invention;

[0024] Wherein, the accompanying drawings are marked as follows:

[0025] 10-motor; 20-drive crank; 21-first drive unit; 22-second drive unit; 31-first connecting piece; 32-second connecting piece; 33-pull rod; 34-third connecting piece; 35-first transmission shaft; 36-connecting crank; 37-fourth connecting piece; 41-presser foot rod; 42-presser foot; 51-first shaft hoop; 52-second shaft hoop; 60-knife disc; 71-drive rod; 72-crank slider mechanism; 73-second transmission shaft; 74-reset spring; 75-stop block. DETAILED DESCRIPTION

[0026] In order to make the purpose, advantages and features of the present invention clearer, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that the drawings are all in a very simplified form and are not drawn to scale, and are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention. In addition, the structure shown in the drawings is often a part of the actual structure. In particular, the emphasis of each drawing is different, and sometimes different scales are used.

[0027] As used in the present invention, the singular forms "one", "an", and "the" include plural objects, unless the content clearly indicates otherwise. As used in the present invention, the term "or" is generally used in a sense that includes "and / or", unless the content clearly indicates otherwise. As used in the present invention, the term "several" is generally used in a sense that includes "at least one", unless the content clearly indicates otherwise. As used in the present invention, the term "at least two" is generally used in a sense that includes "two or more", unless the content clearly indicates otherwise. In addition, the terms "first", "second", and "third" are used only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, the features defined as "first", "second", and "third" may explicitly or implicitly include one or at least two of the features.

[0028] Please refer to Figure 1 and Figure 2 , Figure 1-Figure 2The present invention is a structural schematic diagram of a thread trimming and presser foot lifting device provided in an embodiment of the present invention. The present embodiment provides a thread trimming and presser foot lifting device, comprising a motor 10, a transmission crank 20, a presser foot lifting drive assembly, a thread trimming drive assembly, a presser foot assembly and a thread trimming assembly. The transmission crank 20 is connected to the rotating shaft of the motor 10 and moves synchronously with the rotating shaft of the motor 10. The transmission crank 20 has a first driving part 21 and a second driving part 22. The first driving part 21 is connected to the presser foot lifting drive assembly, and the presser foot lifting drive assembly is connected to the presser foot assembly. The second driving part 22 is detachably connected to the thread trimming drive assembly, and the thread trimming drive assembly is connected to the thread trimming assembly. When the motor 10 rotates forward, the first driving part 21 drives the presser foot assembly to move through the presser foot lifting drive assembly, and the second driving part 22 is in a separated state from the thread trimming drive assembly. When the motor 10 rotates reversely, the second driving part 22 contacts the thread trimming drive assembly, and the second driving part 22 drives the thread trimming assembly to move through the thread trimming drive assembly.

[0029] In this embodiment, the thread trimming and presser foot lifting device is applied to a flat sewing machine, and can also be applied to other types of sewing machines such as an overlock sewing machine and a lockstitch sewing machine. In addition, the thread trimming and presser foot lifting device can be applied to an integrated sewing machine or a non-integrated sewing machine, and this application does not impose any restrictions on this.

[0030] Please refer to Figure 3-Figure 4 , Figure 3 A three-dimensional diagram of a transmission crank provided by an embodiment of the present invention; Figure 4 The front view of the transmission crank provided in the embodiment of the present invention. The transmission crank 20 has a first driving part 21 and a second driving part 22, and the first driving part 21 and the second driving part 22 are used to drive the presser foot lifting driving assembly and the thread trimming assembly respectively, that is, in this embodiment, by designing a transmission crank 20 with two driving parts, the actions of thread trimming and presser foot lifting of the sewing machine are realized, the structure is simple, easy to assemble, and can effectively improve the production efficiency of the whole machine and reduce the production cost.

[0031] In this embodiment, the first driving part 21 can be fixedly connected to the presser foot lifting driving assembly by means of thread connection, pin connection, etc. When the rotating shaft of the motor 10 rotates, the transmission crank 20 is driven to rotate, thereby driving the presser foot lifting driving assembly to move. The second driving part 22 is detachably connected to the thread trimming driving assembly. The detachable type can be understood as that the second driving part 22 is not fixedly connected to the thread trimming driving assembly. When the motor 10 rotates forward, the second driving part 22 will move in a direction away from the thread trimming driving assembly. At this time, the presser foot lifting driving assembly drives the presser foot assembly to move and complete the presser foot lifting action, and the thread trimming driving assembly and the thread trimming assembly do not move. Only when the motor 10 reverses, the second driving part 22 will contact the thread trimming driving assembly and drive the thread trimming assembly to complete the thread trimming action. At this time, the presser foot lifting driving assembly moves, but the presser foot assembly does not move.

[0032] Please continue to refer to Figure 1-Figure 2 The presser foot lifting drive assembly includes a first connecting member 31, a second connecting member 32, a pull rod 33, a third connecting member 34, a first transmission shaft 35, a connecting crank 36 and a fourth connecting member 37 connected in sequence. One end of the first connecting member 31 is connected to the first driving part 21, and the fourth connecting member 37 is connected to the presser foot assembly. When the motor 10 rotates forward, the first driving part 21 drives the first transmission shaft 35 to rotate through the first connecting member 31, the second connecting member 32 and the connecting rod. The first transmission shaft 35 drives the fourth connecting member 37 to move downward through the connecting crank 36, thereby driving the presser foot assembly to move.

[0033] In this embodiment, the presser foot assembly includes a presser foot rod 41, a presser foot 42 and other parts well known to those skilled in the art, one end of the first connecting member 31 is threadedly connected to the first driving portion 21 of the transmission crank 20, the other end of the first connecting member 31 is fixedly connected to one end of the second connecting member 32, the other end of the second connecting member 32 is connected to the housing of the sewing machine, one end of the pull rod 33 is connected to the connecting hole on the second connecting member 32, the other end of the pull rod 33 is connected to one end of the third connecting member 34, the other end of the third connecting member 34 is sleeved on the first transmission shaft 35 and fixedly connected to the first transmission shaft 35, the other end of the first transmission shaft 35 is fixedly connected to the connecting crank 36, the other end of the connecting crank 36 is fixedly connected to one end of the fourth connecting member 37, and the fourth connecting member 37 is connected to the presser foot rod 41 through the first shaft hoop 51. In this embodiment, the fixed connection includes but is not limited to a threaded connection and a pin connection.

[0034] When the motor 10 rotates forward, the transmission crank 20 rotates counterclockwise ( Figure 1(seen from left to right in the figure), the first driving part 21 rotates to drive the first connecting member 31 to move downward, one end of the second connecting member 32 moves downward, and then drives the third connecting member 34 to rotate clockwise through the pull rod 33, and the transmission crank 20 rotates clockwise to drive the fourth connecting member 37 to move upward, and then drives the presser foot rod 41 to move upward, realizing the presser foot lifting action 42.

[0035] Please continue to refer to Figure 1-Figure 2 , the fourth connecting member 37 is provided with a sliding groove, the presser foot 42 assembly includes a presser foot 42 and a presser foot rod 41 connected to each other, the presser foot rod 41 is sleeved with a first shaft hoop 51, and the shaft hoop is connected to the sliding groove through a fastener. When the motor 10 rotates forward, the fourth connecting member 37 drives the first shaft hoop 51 and the presser foot rod 41 to move downward through the fastener, thereby driving the presser foot 42 to move downward. When the motor 10 is reversed, the fourth connecting member 37 moves upward, driving the fastener to move along the sliding groove, and the presser foot 42 assembly does not move. The purpose of setting the sliding groove is that when the motor 10 is reversed, although the presser foot lifting 42 driving assembly follows the action, the fourth connecting member 37 moves downward along the sliding groove, which is an empty stroke for the fourth connecting member 37, and the presser foot rod 41 does not move. In this embodiment, the fastener is, for example, a pin. In an initial state, the fastener may be located at the top of the sliding groove. When the motor 10 reverses, the fastener slides from the top of the sliding groove to the bottom of the sliding groove.

[0036] Please continue to refer to Figure 1-Figure 2 , the two ends of the second connecting member 32 are respectively connected to the first connecting member 31 and the housing (not shown) of the sewing machine, and the second connecting member 32 is provided with a plurality of connecting holes, each of which has a different distance from the two ends of the second connecting member 32, and the pull rod 33 is connected to the second connecting member 32 through the connecting holes. It can be understood that by connecting the pull rod 33 to different connecting holes on the second connecting member 32, the stroke of the pull rod 33 is changed, thereby changing the stroke of the third connecting member 34, the first transmission shaft 35, the connecting crank 36 and the fourth connecting member 37, thereby changing the height of the presser foot lifter 42.

[0037] Further, a second shaft hoop 52 is sleeved on the first transmission shaft 35, and the second shaft hoop 52 is connected to the third connecting member 34 to limit the axial movement of the third connecting member 34 along the first transmission shaft 35. Specifically, the second shaft hoop 52 is fixed on the first transmission shaft 35, and a slot can be set on the top of the third connecting member 34, and a block can be set on the top of the second shaft hoop 52, so that the block is stuck in the slot to limit the third connecting member 34.

[0038] Please continue to refer to Figure 1 The thread trimming assembly includes a knife disc 60, and the knife disc 60 includes a bottom plate, a movable knife holder, a movable knife, a fixed knife holder, a fixed knife and a push plate and other parts well known to those skilled in the art. The thread trimming drive assembly includes a transmission rod 71, a crank slider mechanism 72 and a second transmission shaft 73. The top of the transmission rod 71 is detachably connected to the transmission crank 20, and the bottom of the transmission rod 71 is connected to the crank of the crank slider mechanism 72. The crank has a connection point with the housing of the sewing machine, and the crank can rotate around the connection point. The two ends of the second transmission shaft 73 are respectively connected to the thread trimming assembly and the slider of the crank slider mechanism 72. When the motor 10 rotates forward, the transmission crank 20 moves in a direction away from the transmission rod 71. When the motor 10 rotates reversely, the transmission crank 20 contacts the transmission rod 71 and drives the transmission rod 71 to move downward. The transmission rod 71 drives the second transmission shaft 73 to move horizontally through the crank slider mechanism 72, thereby driving the thread trimming assembly to move.

[0039] When the motor 10 reverses, the transmission crank 20 rotates clockwise, the second driving part 22 presses the transmission rod 71 downward, and the crank of the crank slider mechanism 72 rotates counterclockwise, so that the slider of the crank slider mechanism 72 moves to the left, thereby driving the second transmission shaft 73 to move to the left, and the second transmission shaft 73 drives the shearing assembly to move, thereby completing the thread cutting action.

[0040] Furthermore, a return spring 74 and a stopper 75 are sleeved on the second transmission shaft 73, one end of the return spring 74 abuts against the stopper 75, and the other end abuts against the housing in a detachable manner. When the second transmission shaft 73 moves to the left, the other end of the return spring 74 abuts against the housing, so that the return spring 74 is compressed. After the thread trimming action is completed, the motor 10 rotates forward, and the second transmission shaft 73 moves to the right under the action of the return spring 74, completing the reset of the thread trimming drive mechanism.

[0041] Further, the bottom of the second driving part 22 has a groove, and the shape of the groove is adapted to the shape of the top of the transmission rod 71, so that the second driving part 22 and the transmission rod can better contact each other, thereby facilitating the transmission of force. In this embodiment, the groove is arc-shaped, and the arc surface of the groove is adapted to the top surface of the transmission rod 71.

[0042] In this embodiment, the motor 10 is a stepper motor or a grating motor, which has high positioning accuracy and fast response, and will not cause the presser foot 42 to be lifted or the thread trimmer to be powerless, thereby effectively improving the production efficiency of the entire machine and reducing production costs.

[0043] Based on this, the present embodiment further provides a sewing machine, which includes the above-mentioned thread trimming and presser foot lifting device.

[0044] In summary, the embodiment of the present invention provides a thread trimming and presser foot lifting device and a sewing machine. When the motor rotates forward, the first driving unit drives the presser foot assembly to move through the presser foot lifting driving assembly, and the second driving unit is in a separated state from the thread trimming driving assembly. When the motor rotates reversely, the second driving unit drives the thread trimming assembly to move through the thread trimming driving assembly. The two actions of thread trimming and presser foot lifting are realized by the forward and reverse rotation of a motor. By designing a transmission crank with two driving parts, the actions of thread trimming and presser foot lifting of the sewing machine are realized. The structure is compact and the design is ingenious. The assembly and debugging requirements are low, which can effectively improve the production efficiency of the whole machine and reduce the production cost. In addition, the height of the presser foot lifter can be adjusted by controlling the speed of the motor, and the debugging is simple and convenient.

[0045] The above is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any technician in the relevant technical field, without departing from the scope of the technical solution of the present invention, makes any form of equivalent replacement or modification to the technical solution and technical content disclosed in the present invention, which does not depart from the content of the technical solution of the present invention and still falls within the protection scope of the present invention.

Claims

1. A thread trimming and presser foot lifting device, characterized in that: The invention comprises a motor, a transmission crank, a presser foot lifting driving assembly, a thread trimming driving assembly, a presser foot assembly and a thread trimming assembly, wherein the transmission crank is connected to the rotating shaft of the motor and moves synchronously with the rotating shaft of the motor, the transmission crank has a first driving part and a second driving part, the first driving part is connected to the presser foot lifting driving assembly, and the presser foot lifting driving assembly is connected to the presser foot assembly, the second driving part is detachably connected to the thread trimming driving assembly, and the thread trimming driving assembly is connected to the thread trimming assembly, the detachable type means that the second driving part is not fixedly connected to the thread trimming driving assembly, when the motor rotates forward, the first driving part drives the presser foot assembly to move through the presser foot lifting driving assembly, the second driving part and the thread trimming driving assembly are in a separated state, when the motor rotates reversely, the second driving part contacts the thread trimming driving assembly, and the second driving part drives the thread trimming assembly to move through the thread trimming driving assembly; Wherein, the presser foot lifting driving assembly comprises a first connecting member, a second connecting member, a pull rod, a third connecting member, a first transmission shaft, a connecting crank and a fourth connecting member connected in sequence, one end of the first connecting member is connected to the first driving part, and the fourth connecting member is connected to the presser foot assembly, when the motor rotates forward, the first driving part drives the first transmission shaft to rotate through the first connecting member, the second connecting member and the connecting rod, and the first transmission shaft drives the fourth connecting member to move downward through the connecting crank, thereby driving the presser foot assembly to move; The thread trimmer drive assembly includes a transmission rod, a crank slider mechanism and a second transmission shaft, the top of the transmission rod is detachably connected to the transmission crank, the bottom of the transmission rod is connected to the crank of the crank slider mechanism, the crank and the housing of the sewing machine have a connection point, the crank can rotate around the connection point, the two ends of the second transmission shaft are respectively connected to the thread trimmer assembly and the slider of the crank slider mechanism, when the motor rotates forward, the transmission crank moves in a direction away from the transmission rod, when the motor rotates reversely, the transmission crank contacts the transmission rod and drives the transmission rod to move downward, the transmission rod drives the second transmission shaft to move horizontally through the crank slider mechanism, and then drives the thread trimmer assembly to move; The second transmission shaft is also sleeved with a return spring and a stopper, one end of the return spring abuts against the stopper, and the other end abuts against the housing in a detachable manner; The bottom of the second driving part has a groove, and the shape of the groove is adapted to the shape of the top of the transmission rod.

2. The thread trimming and presser foot lifting device according to claim 1, characterized in that: The fourth connecting member is provided with a sliding groove, and the presser foot assembly includes a presser foot and a presser foot rod connected to each other. The presser foot rod is sleeved with a first shaft hoop, and the shaft hoop is connected to the sliding groove through a fastener. When the motor rotates forward, the fourth connecting member drives the first shaft hoop and the presser foot rod to move downward through the fastener, thereby driving the presser foot to move downward. When the motor rotates reversely, the fourth connecting member moves upward, driving the fastener to move along the sliding groove, and the presser foot assembly does not move.

3. The thread trimming and presser foot lifting device according to claim 1, characterized in that: The two ends of the second connecting member are respectively connected to the first connecting member and the casing of the sewing machine. The second connecting member is provided with a plurality of connecting holes, and the distances from each connecting hole to the two ends of the second connecting member are different. The pull rod is connected to the second connecting member through the connecting holes.

4. The thread trimming and presser foot lifting device according to claim 1, characterized in that: A second shaft hoop is sleeved on the first transmission shaft, and the second shaft hoop is connected to the third connecting member to limit the axial movement of the third connecting member along the first transmission shaft.

5. The thread trimming and presser foot lifting device according to claim 1, characterized in that: The motor is a stepping motor or a grating motor.

6. A sewing machine, characterized in that: It comprises the thread trimming and presser foot lifting device as described in any one of claims 1-5.

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