Thread trimming mechanism and sewing machine

Abstract

The utility model provides a thread trimming mechanism and a sewing machine, and belongs to the technical field of sewing machines. The problem that an existing thread trimming mechanism is prone to thread loosening is solved. The thread trimming mechanism comprises a fixed cutter and a movable cutter, the movable cutter is provided with a thread leading hole and a cutting edge capable of being matched with the fixed cutter to trim threads, the thread trimming mechanism further comprises a thread clamping piece capable of abutting against the movable cutter, the movable cutter is located between the thread clamping piece and the fixed cutter, and the face, facing the thread clamping piece, of the movable cutter is provided with a thread loosening face inclining towards one side of the fixed cutter in the direction from the thread leading hole to the cutting edge. The thread guiding hole and the thread loosening face are arranged at an interval, and when the fixed cutter makes contact with the cutting edge of the movable cutter, the thread clamping piece abuts against the position, between the thread loosening face and the thread guiding hole, of the movable cutter. According to the thread trimming mechanism, the trimmed thread end can be smoothly trimmed off while the thread can be prevented from falling off.

Description

Technical Field

[0001] This utility model belongs to the field of sewing machine technology, and relates to a thread-cutting mechanism and a sewing machine. Background Technology

[0002] A sewing machine is a machine that sews fabric together with thread. It includes a needle bar mechanism, thread take-up mechanism, feed mechanism, hook mechanism, pressing mechanism, winding device, and lubrication device. Sewing machines can be classified according to their structure or sewing process into flatbed sewing machines, chain stitch machines, overlock sewing machines, buttonhole machines, and sealing machines. The thread consists of the needle thread that passes through the needle eye and the bobbin thread. The needle thread is also called the top thread, and the bobbin thread is also called the bottom thread. The top thread is drawn from the spool, passes through the thread tensioner, thread decelerator, and right thread hook, then through the take-up lever, and then through the left thread hook before entering the needle eye. The take-up lever's movement feeds the top thread. When starting a sewing machine, the top thread often comes out of the needle eye due to the force applied, causing the sewing to be interrupted. At this time, it is necessary to leave the top thread end long when starting the sewing. However, if the top thread end is too long, it will form a bird's nest structure on the fabric, affecting the appearance of the seam. After the sewing is completed, it must be trimmed manually, which is not only time-consuming but also difficult to trim cleanly, and may even damage the existing stitches.

[0003] Chinese patent literature discloses a device for reducing bird nests in a sewing machine [Application No.: CN202010066459.7; Publication No.: CN111206347A]. The sewing machine includes a needle plate with needle holes. The device includes a fixed blade fixed to the bottom of the needle plate and a movable blade that can be independently driven to cut the thread when the thread take-up lever is at its highest point. Both the fixed blade and the movable blade are located on one side of the needle hole in the needle plate. The blade of the fixed blade faces the needle hole in the needle plate. One side of the movable blade has a thread hook groove, and the other side of the movable blade has a V-shaped cutting edge. The movable blade can swing so that the cutting edge forms a shearing motion with the blade of the fixed blade.

[0004] When starting to sew, the thread is hooked into the groove of the moving blade. The moving blade then guides the thread towards the blade of the stationary blade. Finally, the moving and stationary blades work together to cut the thread when the take-up lever is at its highest point, shortening the initial thread end. The thread end is slack from the moment it is hooked by the moving blade until it is cut. Meanwhile, the sewing machine needle moves upwards to its highest point under the influence of the take-up mechanism. At this point, the thread end can easily move upwards with the needle and detach from the moving blade, causing it to unravel. To prevent this, clamping the thread end between the moving and stationary blades can cause the cut thread end to be trapped and not easily sucked away. Utility Model Content

[0005] The purpose of this invention is to address the aforementioned problems in the existing technology by proposing a thread-cutting mechanism and a sewing machine. The technical problem solved is how to prevent the thread from coming loose while ensuring that the cut thread ends can be smoothly removed.

[0006] The objective of this utility model can be achieved through the following technical solutions:

[0007] A wire-cutting mechanism includes a fixed blade and a movable blade. The movable blade has a wire-leading hole and a cutting edge that can cooperate with the fixed blade to cut wire. The mechanism is characterized by further including a wire-clamping plate that can abut against the movable blade. The movable blade is located between the wire-clamping plate and the fixed blade. The movable blade has a loosening surface on its side facing the wire-clamping plate, which is inclined towards the fixed blade along the direction from the wire-leading hole to the cutting edge. The wire-leading hole and the loosening surface are spaced apart. When the fixed blade contacts the cutting edge of the movable blade, the wire-clamping plate abuts against the movable blade at a position between the loosening surface and the wire-leading hole.

[0008] The fixed blade, moving blade, and thread clamp are installed below the needle plate of the sewing machine and on one side of the needle hole. When the thread-cutting mechanism is working, the moving blade moves to position the thread guide hole directly below the needle hole on the needle plate. The needle, carrying the thread, passes through the needle hole on the needle plate and the thread guide hole of the moving blade. The rotary hook pulls the thread down, placing it inside the thread guide hole. After the needle leaves the thread guide hole of the moving blade, the moving blade, carrying the thread, moves to bring its blade closer to the fixed blade. During this approach, the thread clamp holds the thread on the moving blade, preventing the thread from moving upwards with the needle and thus preventing it from unraveling. The needle then continues to move upwards, and the moving blade continues to move, bringing its blade into contact with the fixed blade. When the fixed and moving blades come into contact to cut the thread, the clamping plate rests against the moving blade between the loosened thread surface and the lead-in hole. At this time, the clamping plate still holds the thread, allowing it to be cut smoothly. After the moving blade completes the cutting, it continues to move, bringing the clamping plate opposite the loosened thread surface. Since the loosened thread surface is inclined towards the fixed blade along the direction from the lead-in hole to the blade, the distance between the clamping plate and the loosened thread surface increases with the movement of the moving blade, thus smoothly releasing the cut thread end and allowing it to come out easily. Therefore, this thread-cutting mechanism can prevent thread from coming off while ensuring that the cut thread end comes out smoothly.

[0009] In the above-mentioned wire cutting mechanism, the moving blade has a clearance groove on the side facing the fixed blade, the cutting edge is located at the edge of the clearance groove, and the wire lead hole is set on the bottom surface of the clearance groove.

[0010] When the thread is threaded through the lead hole and driven by the moving blade, the thread is located in the clearance groove. The clearance groove can prevent the thread from being clamped between the fixed blade and the moving blade, so that the thread end can be smoothly removed after being cut off.

[0011] In the above-mentioned wire cutting mechanism, the clearance groove is V-shaped, and the cutting edge is located at the edge of the groove tip.

[0012] The V-shaped clearance groove not only further prevents the top thread from being trapped between the fixed and moving blades, allowing the thread end to come out smoothly, but also the two side walls of the V-shaped clearance groove have the function of gathering the top thread, so that the top thread can contact the blade of the moving blade to complete the cutting smoothly.

[0013] In the above-mentioned wire cutting mechanism, the side of the moving blade has a V-shaped hook groove at the opening end of the clearance groove.

[0014] When the thread-cutting mechanism is working, the hook groove can also be positioned directly below the needle hole of the needle plate. After the thread passes through the hook groove, it is hooked and driven by the hook groove. Setting up the hook groove provides the moving blade with an additional selectable position for hooking the thread, making the thread-cutting mechanism easier to use.

[0015] In the above-mentioned wire cutting mechanism, the wire clamping piece has a wire clamping part that is bent into the shape of the character "𡿨". The bent part of the wire clamping part forms a protruding ridge, which faces the moving blade and can abut against the moving blade.

[0016] After the thread is cut, the movement of the blade makes the convex edge face the loose thread surface, which can loosen the thread. The clamping part is in the shape of "𡿨", which can prevent the thread from being clamped by the two sides of the convex edge of the clamping part, so that the thread end can be easily removed after being cut.

[0017] A sewing machine includes a needle plate with a needle hole, characterized in that it further includes a thread cutting mechanism as described above, wherein a fixed blade is located below the needle plate and fixedly connected to the needle plate, the fixed blade is located on one side of the needle hole, and a movable blade is movable to position the thread guide hole directly below the needle hole.

[0018] When the thread-cutting mechanism operates, the moving blade moves to position the thread guide hole directly below the needle hole on the needle plate. The needle, carrying the thread, passes through the needle hole on the needle plate and the thread guide hole of the moving blade. The rotary hook pulls the thread down, placing it inside the thread guide hole. After the needle leaves the thread guide hole of the moving blade, the moving blade, carrying the thread, moves to bring the cutting edge closer to the fixed blade. During this approach, the thread clamping plate holds the thread on the moving blade, preventing the thread from moving upwards with the needle and thus preventing the thread from slipping off. The needle then continues to move upwards, and the moving blade continues to move, bringing the cutting edge into contact with the fixed blade. During thread cutting, when the fixed blade and the moving blade come into contact to cut the thread, the thread clamping plate rests against the moving blade between the loose thread surface and the thread guide hole. At this time, the thread clamping plate still holds the top thread, allowing it to be cut smoothly. After the moving blade completes the cutting, it continues to move, bringing the thread clamping plate opposite the loose thread surface. Since the loose thread surface is tilted towards the fixed blade along the direction from the thread guide hole to the blade, the distance between the thread clamping plate and the loose thread surface increases continuously with the movement of the moving blade, thus smoothly releasing the cut thread end and allowing it to come out easily. Therefore, this sewing machine can prevent thread unraveling while ensuring that the cut thread end comes out smoothly.

[0019] In the aforementioned sewing machine, a suction pipe is also included, with its air inlet located below the thread clamp. The suction pipe is used to draw away the cut thread ends, allowing them to smoothly exit the thread-cutting mechanism.

[0020] In the aforementioned sewing machine, the sewing machine also includes a base, the needle plate is fixedly connected to the upper surface of the base, the moving blade is hinged to the needle plate, a motor is fixed inside the base, a drive crank is fixed on the rotating shaft of the motor, a transmission rod is hinged to the base, a pull rod is hinged between one end of the transmission rod and the drive crank, and a connecting rod is hinged between the other end of the transmission rod and the moving blade.

[0021] When the motor is working, it drives the moving blade to rotate by driving the crank, pull rod, transmission rod and connecting rod, thereby realizing the actions of leading the wire, clamping the wire, cutting the wire and loosening the wire, so that the wire cutting mechanism can cut the wire smoothly, and prevent the wire from coming off while allowing the cut wire ends to come off smoothly.

[0022] In the sewing machine described above, an intermediate crank is provided between the transmission rod and the connecting rod. The intermediate crank is coaxially hinged to the base with the transmission rod. A strip-shaped hole is provided on the transmission rod. The intermediate crank and the transmission rod are fixedly connected by screws, with the screws passing through the strip-shaped hole. The connecting rod is hinged to the intermediate crank.

[0023] After loosening the screw, rotate the intermediate crank. The screw moves in the slotted hole, and at the same time, the intermediate crank drives the moving blade to rotate through the connecting rod. When the moving blade is in the correct position, tighten the screw again to fix the intermediate crank to the transmission rod. This allows for fine adjustment of the initial position of the moving blade, enabling the moving blade to coordinate with the motor's movement to perform wire feeding, clamping, cutting, and releasing.

[0024] Compared with the prior art, the present invention has the following advantages:

[0025] A clamping plate is provided to hold the wire, while a loosening surface is provided on the moving blade to prevent wire from slipping and allow the cut wire ends to come out smoothly. An intermediate crank is provided to fine-tune the initial position of the moving blade, allowing the movement of the moving blade and the motor to smoothly perform the actions of wire drawing, clamping, cutting, and loosening. Attached Figure Description

[0026] Figure 1 This is a three-dimensional view of the thread-cutting mechanism installed below the needle plate.

[0027] Figure 2 This is a cross-sectional view of the thread-cutting mechanism installed below the needle plate.

[0028] Figure 3 This is a three-dimensional disassembly of the wire-cutting mechanism. Figure 1 .

[0029] Figure 4 This is a three-dimensional disassembly of the wire-cutting mechanism. Figure 2 .

[0030] Figure 5 This is a 3D view of the thread-cutting mechanism installed on a sewing machine.

[0031] Figure 6 This is a magnified 3D view of the thread-cutting mechanism installed on a sewing machine, behind the hidden needle plate.

[0032] Figure 7 It is a split 3D view of the middle crank and drive rod.

[0033] In the diagram, 1. Base; 2. Needle plate; 2a. Needle hole; 3. Fixed blade; 4. Moving blade; 4a. Lead wire hole; 4b. Blade; 4c. Loosening surface; 4d. Clearance groove; 4e. Hook groove; 5. Wire clamping plate; 5a. Wire clamping part; 5a1. Protruding ridge; 5b. Fixing part; 6. Suction pipe; 7. Motor; 8. Drive crank; 9. Pull rod; 10. Transmission rod; 10a. Strip hole; 11. Connecting rod; 12. Intermediate crank; 13. Screw; 14. Rotary hook. Detailed Implementation

[0034] The following are specific embodiments of the present invention, which are described in conjunction with the accompanying drawings. However, the present invention is not limited to these embodiments.

[0035] like Figure 1 and Figure 2 As shown, a thread-cutting mechanism is installed on a sewing machine, which includes a needle plate 2 having a needle hole 2a. The thread-cutting mechanism includes a fixed blade 3 and a movable blade 4. The movable blade 4 has a thread guide hole 4a and a cutting edge 4b ​​that cooperates with the fixed blade 3 to cut the thread. The fixed blade 3 is located below the needle plate 2 and is fixedly connected to the needle plate 2, with the fixed blade 3 located to one side of the needle hole 2a. The movable blade 4 is located below the fixed blade 3 and is hinged to the needle plate 2. The movable blade 4 can rotate so that the thread guide hole 4a is directly below the needle hole 2a.

[0036] Combination Figure 3 and Figure 4 As shown, the thread-cutting mechanism also includes a thread-clamping plate 5 that can abut against the moving blade 4. The thread-clamping plate 5 is bent into a stepped sheet structure, including a fixing part 5b, a thread-clamping part 5a, and a connecting part connecting the fixing part 5b and the thread-clamping part 5a. The fixing part 5b is fixedly connected to the needle plate 2, and the thread-clamping part 5a is located below the moving blade 4, that is, the moving blade 4 is located between the thread-clamping part 5a of the thread-clamping plate 5 and the fixed blade 3. The side of the moving blade 4 facing the thread-clamping plate 5 has a loosening surface 4c that is inclined towards the fixed blade 3 in the direction from the thread lead hole 4a to the blade 4b, that is, the lower surface of the moving blade 4 has a loosening surface 4c that is inclined upward in the direction from the thread lead hole 4a to the blade 4b. The thread lead hole 4a and the loosening surface 4c are spaced apart, and when the fixed blade 3 contacts the blade 4b of the moving blade 4, the thread-clamping plate 5 abuts against the moving blade 4 at the position between the loosening surface 4c and the thread lead hole 4a.

[0037] like Figure 2 and Figure 3As shown, the moving blade 4 has a relief groove 4d on its upper surface facing the fixed blade 3. The cutting edge 4b ​​is located at the edge of the groove opening of the relief groove 4d, and the lead wire hole 4a is located on the bottom surface of the relief groove 4d. The relief groove 4d is V-shaped, and the cutting edge 4b ​​is located at the edge of the groove opening at the tip of the relief groove 4d. A wire cutting hole is also provided at the tip of the relief groove 4d on the moving blade 4, and the wire debris generated by cutting can fall out of the wire cutting hole and detach from the moving blade 4. A V-shaped hook groove 4e is provided on the side of the moving blade 4 at the opening end of the relief groove 4d. The wire clamping part 5a of the wire clamping piece 5 is bent into a "𡿨" shape, and a protruding ridge 5a1 is formed at the bend of the wire clamping part 5a. The protruding ridge 5a1 faces upward and can abut against the lower surface of the moving blade 4.

[0038] like Figure 1 , Figure 5 and Figure 6 As shown, the sewing machine also includes a base 1, with a needle plate 2 fixedly connected to the upper surface of the base 1. The sewing machine also includes a suction pipe 6 fixed to the base 1, with the air inlet end of the suction pipe 6 located below the thread clamping portion 5a of the thread clamping plate 5. A motor 7 is fixed inside the base 1, and a drive crank 8 is fixed to the shaft of the motor 7. A transmission rod 10 is hinged to the base 1, with a pull rod 9 hinged between one end of the transmission rod 10 and the drive crank 8, and a connecting rod 11 hinged between the other end of the transmission rod 10 and the moving blade 4. An intermediate crank 12 is also provided between the transmission rod 10 and the connecting rod 11, and the intermediate crank 12 is coaxially hinged to the transmission rod 10 on the base 1, meaning the intermediate crank 12 and the transmission rod 10 pass through the same hinge shaft. Figure 7 As shown, a slotted hole 10a is provided on the transmission rod 10. The intermediate crank 12 is fixedly connected to the transmission rod 10 by a screw 13, which passes through the slotted hole 10a. The connecting rod 11 is hinged to the intermediate crank 12, and a hinge pin is fixed on the intermediate crank 12. One end of the connecting rod 11 is fitted onto the hinge pin. After loosening the screw 13, the intermediate crank 12 is rotated, and the screw 13 moves in the slotted hole 10a. At the same time, the intermediate crank 12 drives the moving blade 4 to rotate through the connecting rod 11. When the moving blade 4 is in the correct position, the screw 13 is tightened again to fix the intermediate crank 12 to the transmission rod 10, thereby achieving fine adjustment of the initial position of the moving blade 4.

[0039] When motor 7 is working, it drives the moving blade 4 to rotate via drive crank 8, pull rod 9, transmission rod 10, intermediate crank 12, and connecting rod 11. For example... Figure 2As shown in the diagram, the moving blade 4 first moves to the right, positioning the thread guide hole 4a directly below the needle hole 2a. The needle, carrying the thread, passes through the needle hole 2a of the needle plate 2 and the thread guide hole 4a of the moving blade 4. The rotary hook 14 hooks the thread down, placing it inside the thread guide hole 4a. After the needle leaves the thread guide hole 4a of the moving blade 4, the moving blade 4, carrying the thread, moves to the left, bringing the cutting edge 4b ​​closer to the fixed blade 3. During this approach, the protrusion 5a1 of the clamping plate 5 holds the thread on the lower surface of the moving blade 4, preventing the thread from moving upwards with the needle and preventing it from coming loose. The needle then continues to move upwards, and the moving blade 4 continues to move to the left, bringing the cutting edge 4b ​​into contact with the fixed blade 3 to cut the thread. When the wire is cut by contacting the blade 4b of the moving blade 4, the protruding edge 5a1 of the clamping plate 5 abuts against the moving blade 4 at the position between the loosening surface 4c and the lead hole 4a. At this time, the clamping plate 5 still holds the top thread, allowing the top thread to be cut smoothly. Then, after the moving blade 4 completes the cutting, it continues to move to the left, so that the protruding edge 5a1 of the clamping plate 5 faces the loosening surface 4c. Since the loosening surface 4c is inclined upward along the direction from the lead hole 4a to the blade 4b, the distance between the protruding edge 5a1 of the clamping plate 5 and the loosening surface 4c increases continuously as the moving blade 4 moves to the left, thereby smoothly loosening the cut thread end and allowing it to come out smoothly. After the thread end is loosened, it is sucked away by the suction pipe 6. Therefore, this wire cutting mechanism can prevent the thread from coming off while allowing the cut thread end to come out smoothly.

[0040] The specific embodiments described herein are merely illustrative examples illustrating the spirit of this utility model. Those skilled in the art to which this utility model pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of this utility model or exceeding the scope defined by the appended claims.

Claims

1. A wire-cutting mechanism, comprising a fixed blade (3) and a movable blade (4), wherein the movable blade (4) has a wire-leading hole (4a) and a cutting edge (4b) capable of cooperating with the fixed blade (3) to cut wire, characterized in that, It also includes a clamping piece (5) that can abut against the moving blade (4), the moving blade (4) being located between the clamping piece (5) and the fixed blade (3), the moving blade (4) having a loosening surface (4c) on the side facing the clamping piece (5) that is inclined toward the fixed blade (3) along the direction from the lead hole (4a) to the blade (4b), the lead hole (4a) and the loosening surface (4c) being spaced apart, and when the fixed blade (3) contacts the blade (4b) of the moving blade (4), the clamping piece (5) abuts against the moving blade (4) at the position between the loosening surface (4c) and the lead hole (4a).

2. The wire-cutting mechanism according to claim 1, characterized in that, The moving blade (4) has a relief groove (4d) on the side facing the fixed blade (3), the cutting edge (4b) is located at the edge of the relief groove (4d), and the lead hole (4a) is set on the bottom surface of the relief groove (4d).

3. The wire-cutting mechanism according to claim 2, characterized in that, The clearance groove (4d) is V-shaped, and the cutting edge (4b) is located at the edge of the groove at the tip of the clearance groove (4d).

4. The wire-cutting mechanism according to claim 3, characterized in that, The moving blade (4) has a V-shaped hook groove (4e) at the opening end of the clearance groove (4d) on its side.

5. The wire-cutting mechanism according to any one of claims 1-4, characterized in that, The clamping piece (5) has a clamping part (5a) that is bent into the shape of "𡿨". A protruding ridge (5a1) is formed at the bend of the clamping part (5a). The protruding ridge (5a1) faces the moving knife (4) and can abut against the moving knife (4).

6. A sewing machine comprising a needle plate (2) having needle holes (2a), characterized in that, It also includes a wire cutting mechanism as described in any one of claims 1-5, wherein the fixed blade (3) is located below the needle plate (2) and fixedly connected to the needle plate (2), the fixed blade (3) is located on one side of the needle hole (2a), and the moving blade (4) can move to make the lead hole (4a) located directly below the needle hole (2a).

7. The sewing machine according to claim 6, characterized in that, The sewing machine also includes a suction pipe (6), the air inlet of which is located below the thread clamp (5).

8. The sewing machine according to claim 6, characterized in that, The sewing machine also includes a base (1), the needle plate (2) is fixedly connected to the upper surface of the base (1), the moving blade (4) is hinged to the needle plate (2), a motor (7) is fixed inside the base (1), a drive crank (8) is fixed on the shaft of the motor (7), a transmission rod (10) is hinged on the base (1), a pull rod (9) is hinged between one end of the transmission rod (10) and the drive crank (8), and a connecting rod (11) is hinged between the other end of the transmission rod (10) and the moving blade (4).

9. The sewing machine according to claim 8, characterized in that, An intermediate crank (12) is also provided between the transmission rod (10) and the connecting rod (11). The intermediate crank (12) and the transmission rod (10) are coaxially hinged on the base (1). A strip hole (10a) is provided on the transmission rod (10). The intermediate crank (12) and the transmission rod (10) are fixedly connected by a screw (13). The screw (13) passes through the strip hole (10a). The connecting rod (11) is hinged to the intermediate crank (12).

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