Thread trimming mechanism and method for a sewing machine, and sewing machine

Abstract

The present application relates to a thread trimming mechanism and method of a sewing machine, and the sewing machine, the thread trimming mechanism comprises a first thread trimming knife and a second thread trimming knife, the second thread trimming knife is provided with a thread trimming hook for hooking and driving the bobbin thread to move towards the first thread trimming knife, the thread trimming mechanism further comprises a fixedly installed thread trimming catcher, the thread trimming catcher comprises an arc-shaped catching piece arranged along the outer peripheral side of the hook assembly, and the arc-shaped catching piece is located between the hook assembly and the first thread trimming knife, a right-tilted constraint side edge is arranged on the right side edge of the arc-shaped catching piece, and a catching groove is formed on the constraint side edge; when the second thread trimming knife rotates towards the first thread trimming knife, the thread trimming hook intersects with the constraint side edge, and the thread trimming hook drives the bobbin thread to move along the constraint side edge to the catching groove. The thread trimming mechanism of the present application can capture the bobbin thread end after thread trimming is completed, stabilize the position of the bobbin thread end, and improve the stability in the sewing performance.

Description

Technical Field

[0001] This invention relates to the field of sewing equipment, specifically to a thread-cutting mechanism and method for a sewing machine, and a sewing machine itself. Background Technology

[0002] Some existing sewing machines have a function to catch the bobbin thread after thread trimming, such as double-needle sewing machines, buttonhole machines, and bartacking machines with flatbed thread trimming mechanisms. However, all flatbed sewing machines currently produced by sewing machine manufacturers cannot achieve this function. This is because the space under the needle plate of a flatbed sewing machine is extremely small, and the fabric feeding mechanism moves at high speed within this space. Furthermore, the gap between the rotary hook and the thread trimming mechanism is very small. This results in existing flatbed sewing machines not controlling the position of the bobbin thread after trimming. The bobbin thread may fall in any direction. When sewing begins again, the high-speed rotating shuttle hook has a certain probability of hitting the bobbin thread, making its direction of fall even more unpredictable. This leads to several stitches not forming a stitch when starting to sew, commonly known as "starting the stitch without picking up the bobbin thread" or "starting the stitch without thread." Summary of the Invention

[0003] In view of the shortcomings of the prior art described above, the technical problem to be solved by the present invention is to provide a thread cutting mechanism and method for a sewing machine, and a sewing machine that can stabilize the position of the bottom thread end after thread cutting, ensure that the next sewing can be started smoothly, and improve the stability of sewing performance.

[0004] To achieve the above objectives, the present invention provides a thread-cutting mechanism for a sewing machine, used for cutting thread at the rotary hook assembly of the sewing machine. The thread-cutting mechanism includes a first thread-cutting blade and a second thread-cutting blade. The first thread-cutting blade is fixedly installed on the outer periphery of the rotary hook assembly. The second thread-cutting blade is located on the outer periphery of the rotary hook assembly and can rotate around the rotary hook assembly to engage or disengage with the second thread-cutting blade. The second thread-cutting blade is provided with a thread-cutting hook for hooking and driving the bobbin thread towards the first thread-cutting blade. The thread-cutting mechanism also includes a fixedly installed thread-cutting catcher. The thread-cutting catcher includes an arc-shaped catcher plate arranged along the outer periphery of the rotary hook assembly, and the arc-shaped catcher plate is located between the rotary hook assembly and the first thread-cutting blade. The right side of the arc-shaped catcher plate is provided with a rightward inclined constraint side, and a catcher groove is formed on the constraint side. When the second thread-cutting blade rotates towards the first thread-cutting blade, the thread-cutting hook intersects with the constraint side, and the thread-cutting hook drives the bobbin thread to move along the constraint side to the opening of the catcher groove.

[0005] Furthermore, the cutting hook of the second wire cutter is composed of a hooking bevel and a hooking stop. The hooking bevel extends obliquely to the right from the left side of the second wire cutter, and the hooking stop is located on the right side of the hooking bevel. The capturing groove on the arc-shaped capturing plate is located on the left side of the hooking stop. One end of the arc-shaped capturing plate facing the second wire cutter is the A side end, and the other end is the B side end. The side of the constraint side near the A side end extends to the left side of the hooking bevel. When the second wire cutter rotates toward the first wire cutter, the cutting hook and the constraint side intersect to form a closed area, and the capturing groove is located in the closed area.

[0006] Furthermore, when the second wire cutter rotates to engage with the first wire cutter to cut the wire, the closed area formed by the intersection of the wire cutting hook and the constraint side still exists.

[0007] Furthermore, when the second wire cutter rotates to engage with the first wire cutter to cut the wire, the wire cutting hook crosses the constraint side, causing the closed area to disappear.

[0008] Furthermore, the hook-and-stop edge is tilted left and right, with the end closer to the wire-cutting catch located on the left and the end further away from the wire-cutting catch located on the right.

[0009] Furthermore, the angle of inclination of the hook-line guard relative to the front and rear directions is 2 to 4°.

[0010] Furthermore, the angle of inclination of the hook-line guard relative to the front and rear directions is 3°.

[0011] Furthermore, an arc-shaped protrusion is provided on the right side of the arc-shaped capturing plate, and one end of the constraint side near side B extends to the arc-shaped protrusion. The capturing groove is located on the right side of the arc-shaped protrusion.

[0012] Furthermore, the second thread cutter is provided with a thread-separating tip for inserting into the thread loops to separate the threads. The left side of the thread-separating tip is a hook-and-stop edge, and the right side of the thread-separating tip has a first thread-separating oblique edge that is inclined to the right.

[0013] Furthermore, the right side of the arc-shaped capture plate is provided with a second dividing line inclined side that is opposite to the first dividing line inclined side. When the second wire cutter rotates toward the first wire cutter, the first dividing line inclined side and the second dividing line inclined side intersect.

[0014] Furthermore, the first wire cutter is provided with a raised part, and the second wire cutter is provided with a raised part that is inclined toward the side where the rotary hook assembly is located. When the second wire cutter rotates toward the first wire cutter, the raised part is inserted into the lower side of the raised part facing the rotary hook assembly.

[0015] Furthermore, the thread-cutting catch has an installation section connected to the arc-shaped catch plate, and the component in the sewing machine used for the fixed installation of the thread-cutting catch is the catch installation base, and the installation section is fixedly connected to the catch installation base.

[0016] Furthermore, the mounting section is fixedly mounted on the capture component mounting base using fastening screws. The mounting section is provided with a strip-shaped connecting hole extending in the front-back direction, and the fastening screw passes through the strip-shaped connecting hole and is screwed into the capture component mounting base.

[0017] The present invention also provides a method for cutting the thread of a sewing machine, which uses the above-mentioned thread cutting mechanism and includes the following steps:

[0018] S1. Before the cutting operation, the second wire cutter is separated from the first wire cutter;

[0019] S2. When the thread cutting begins, the second thread cutting blade rotates toward the first thread cutting blade, and the thread cutting hook hooks the bottom line. When the second thread cutting blade rotates toward the first thread cutting blade, the thread cutting hook intersects with the constraint side. The thread cutting hook drives the bottom line to move along the constraint side until the bottom line reaches the capture groove, and enters the capture groove under its own tension.

[0020] S3. When the second thread cutter reaches the engagement position, it engages with the first thread cutter to cut the bottom thread, obtaining the bottom thread end; the bottom thread end is located between the second thread cutter and the first thread cutter.

[0021] S4. Before the second wire cutter rotates and retracts, the bottom thread end becomes extended under its own elasticity and remains in the capture groove;

[0022] S5. The second wire cutter rotates and retracts, and the bottom thread end remains stable under the constraint of the capture groove.

[0023] Furthermore, it also includes step S6: when sewing begins again, the rotary hook bobbin in the rotary hook assembly rotates, and its tail pushes the bobbin thread end to the left, so that the bobbin thread end is held in the capture groove and partially pushed out.

[0024] The present invention also provides a sewing machine, including a rotary hook assembly and the above-described thread-cutting mechanism, wherein the thread-cutting mechanism is disposed at the rotary hook assembly to cut the thread.

[0025] As described above, the thread-cutting mechanism and method, as well as the sewing machine, of the present invention have the following beneficial effects:

[0026] By incorporating a thread-catching mechanism, the thread end is captured using a catching groove. During thread cutting, the second thread-cutting blade rotates towards the first thread-cutting blade, pulling the thread end closer to it. The thread end is pulled, exhibiting tension. The thread-cutting hook intersects with the constraint side, causing the thread end to move along the constraint side. When the thread end reaches the opening of the catching groove, it enters the groove under its own tension, thus capturing the thread end and ensuring its stable position. Furthermore, this thread end forms an upward-arching curve, located outside the rotation range of the shuttle assembly's bobbin case, preventing collisions with the rotating bobbin case and thus avoiding erratic movement. This thread-cutting mechanism can capture the thread end after cutting, stabilizing its position and ensuring smooth start-up, thus improving sewing performance stability. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the wire-cutting mechanism of the present invention.

[0028] Figure 2 This is a schematic diagram of the structure of the second wire-cutting blade in the wire-cutting mechanism of the present invention.

[0029] Figure 3 This is a schematic diagram of the structure of the first wire-cutting blade in the wire-cutting mechanism of the present invention.

[0030] Figure 4 This is a schematic diagram of the wire-cutting and capturing device in this invention.

[0031] Figure 5 This is a side view of the wire-cutting catcher in this invention.

[0032] Figure 6 This is a schematic diagram of the thread-cutting mechanism of the present invention during normal sewing and bottom thread capture.

[0033] Figure 7 This is a schematic diagram of the wire-cutting mechanism of the present invention during wire cutting.

[0034] Figure 8 This is a schematic diagram showing the first wire cutter and the wire-catching component of the present invention in state one during wire cutting.

[0035] Figure 9 This is a schematic diagram showing the cooperation of the first wire cutter and the wire-catching component in state two during wire cutting in this invention.

[0036] Figure 10 This is a schematic diagram showing the cooperation of the first wire cutter and the wire-catching component in state three during wire cutting in this invention.

[0037] Figure 11 This is a schematic diagram showing the position of the thread end at the thread-catching component in this invention.

[0038] Figure 12 This is a schematic diagram of the wire-cutting mechanism of the present invention, showing the wire-cutting hook intersecting with the constraint side during wire cutting.

[0039] Figure 13 This is a schematic diagram of the wire cutting mechanism of the present invention during the biting and cutting of wire.

[0040] Figure 14 This is a schematic diagram of the wire-cutting mechanism of the present invention after wire cutting.

[0041] Figure 15 This is a schematic diagram of the bottom line position of the wire cutting mechanism of the present invention before the wire is biting and cut.

[0042] Figure 16 This is a schematic diagram of the bottom line position of the wire cutting mechanism of the present invention after the wire is bitten and cut.

[0043] Figure 17 This is a schematic diagram of the bottom line position of the wire cutting mechanism of the present invention after wire cutting and the retraction of the second wire cutting blade.

[0044] Figure 18 This is a schematic diagram of the thread cutting mechanism of the present invention, in which the shuttle bobbin pushes the bottom thread end after thread cutting.

[0045] Figure 19 This is a schematic diagram showing the position of the surface line loop on the dividing plate in the existing design.

[0046] Component designation explanation

[0047] 01 Splitter

[0048] 1. Casing

[0049] 2. Rotary shuttle assembly

[0050] 2a Rotary shuttle inner liner

[0051] 2b Rotary shuttle skin

[0052] 2c Shuttle frame guide rail

[0053] 3. Rotary hook positioning

[0054] 4 needles

[0055] 5 First Thread Cutter

[0056] 5a First cutting edge

[0057] 5c Elevated section

[0058] 6 Second Thread Cutter

[0059] 6a Second cutting edge

[0060] 6b Wire cutter hook

[0061] 6c Hook line bevel

[0062] 6d outlining edge protection

[0063] 6e tip of the dividing line

[0064] 6f First bisector hypotenuse

[0065] 6g Lifting part

[0066] 7. Wire-cutting catch

[0067] 71 Arc-shaped capture plate

[0068] 711 A side end

[0069] 712 B side end

[0070] 71a Constraint side

[0071] 71b Second bisector hypotenuse

[0072] 71c Capture Groove

[0073] 71d arc-shaped protrusion

[0074] 72 Installation Section

[0075] 72a Strip-shaped connecting hole

[0076] 8. Wire Cutting Drive Component

[0077] 9. Side lines

[0078] 9a Fabric edge line

[0079] 9b Needle edge thread

[0080] 10 bottom lines

[0081] 11 Fastening screws

[0082] A. Rotary shuttle rotation direction

[0083] B. Rotary shuttle skin pushes the bottom thread head direction

[0084] C. Maximum range of motion of the rotary shuttle skin Detailed Implementation

[0085] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification.

[0086] It should be understood that the structures, proportions, sizes, etc., depicted in the accompanying drawings of this specification are merely for illustrative purposes to aid those skilled in the art in understanding and reading the content disclosed herein, and are not intended to limit the conditions under which the invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to the size, without affecting the effects and objectives achieved by the invention, should still fall within the scope of the technical content disclosed herein. Furthermore, the terms such as "upper," "lower," "left," "right," and "middle" used in this specification are merely for clarity and are not intended to limit the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention's implementation.

[0087] See Figures 1 to 18 The present invention provides a tool for cutting thread at the rotary hook assembly 2 of a sewing machine. The rotary hook assembly 2 is positioned and installed by a rotary hook positioning hook 3, which is fixed to the machine housing 1. The outermost part of the rotary hook assembly 2 is a rotating shuttle skin 2b.

[0088] The thread-cutting mechanism of this invention includes a first thread-cutting blade 5 and a second thread-cutting blade 6. Both the first and second thread-cutting blades 5 and 6 can be arc-shaped blades. The first thread-cutting blade 5 is fixedly mounted on the outer periphery of the rotary hook assembly 2. The second thread-cutting blade 6 is disposed on the outer periphery of the rotary hook assembly 2 and can rotate around the rotary hook assembly 2 to engage or disengage with the second thread-cutting blade 6. That is, both the first and second thread-cutting blades 5 and 6 are located on the bobbin 2b with a certain gap, so that the bobbin 2b will not touch the first and second thread-cutting blades 5 and 6 when rotating. The rotation of the first thread-cutting blade 5 is driven by the thread-cutting drive assembly 8. The second thread-cutting blade 6 is provided with a thread-cutting hook 6b for hooking the bottom thread 10 and the top thread 9 towards the first thread-cutting blade 5. (See [reference]). Figure 1 and Figure 6 The thread-cutting hook 6b is located below the needle 4. When the second thread-cutting blade 6 rotates, it will hook the bottom thread 10 and the selvage thread 9a in the top thread loop, and push the bottom thread 10 and the selvage thread 9a to the first thread-cutting blade 5. Then, the second cutting edge 6a on the second thread-cutting blade 6 engages with the first cutting edge 5a on the first thread-cutting blade 5, cutting the bottom thread 10 and the selvage thread 9a at that point.

[0089] The wire cutting mechanism of the present invention also includes a fixedly installed wire cutting catch 7, see [link to documentation]. Figure 4 and Figure 5The wire-cutting catcher 7 includes an arc-shaped catcher 71 arranged along the outer periphery of the rotary hook assembly 2, and the arc-shaped catcher 71 is located between the rotary hook assembly 2 and the first wire-cutting blade 5. The arc-shaped catcher 71 is configured as an arc-shaped thin sheet structure, which can be easily installed in the narrow space, especially in the narrow space between the rotary hook assembly 2 and the first wire-cutting blade 5 (the gap is about 0.7 mm). The right side of the arc-shaped catcher 71 is provided with a rightward inclined constraint side 71a, and a catcher groove 71c is opened on the constraint side 71a. When the second wire-cutting blade 6 rotates toward the first wire-cutting blade 5, the wire-cutting hook 6b intersects with the constraint side 71a, and the wire-cutting hook 6b drives the bottom thread 10 to move along the constraint side 71a to the opening of the catcher groove 71c.

[0090] The basic working principle of the wire-cutting mechanism involved in this invention is as follows: During normal operation, see... Figure 6 The second thread cutter 6 remains stationary, away from the first thread cutter 5, allowing the rotary hook assembly 2 to rotate normally. When thread cutting is required, the thread cutting drive assembly 8 drives the second thread cutter 6 to rotate towards the first thread cutter 5. The thread cutting hook 6b hooks the bottom thread 10 and simultaneously hooks the selvage thread 9a in the top thread loop, bringing the bottom thread 10 and top thread 9 closer to the first thread cutter 5. At this time, the bottom thread 10 is pulled, possessing a certain tension that gradually increases. As the second thread cutter 6 rotates, the thread cutting hook 6b intersects with the constraint side 71a. (See [reference]). Figures 8 to 10 Since the capturing groove 71c is set on the constraint side 71a, the constraint side 71a plays a constraint and guiding role. The thread cutting hook 6b drives the bobbin 10 to move along the constraint side 71a. (See also: In a sewing machine...) Figure 13 and Figure 15 The thread 10 extends from the inner liner 2a of the rotary hook assembly 2, passes through the shuttle guide groove 2c, and extends to the right to the thread-cutting hook 6b. When the thread-cutting hook 6b moves the thread 10 along the constraint side 71a to the opening of the capturing groove 71c, the thread 10 enters the capturing groove 71c under its own tension, thus capturing the thread 10. Then, the second thread-cutting blade 6 rotates to engage with the first thread-cutting blade 5, cutting the thread 10 at the first cutting edge 5a. Before the second thread-cutting blade 6 rotates back, the thread end of the thread 10 extends forward under its own elasticity, see [reference needed]. Figure 13 and Figure 15 Since the bottom thread 10 extends from the shuttle guide groove 2c and then forward to the arc-shaped capturing plate 71, the bottom thread 10 itself has a certain elastic recovery capability. The thread end of the bottom thread 10 tends to extend when bent. After the second thread cutter 6 rotates and retracts, the thread end of the bottom thread 10 will extend forward in the gap between the arc-shaped capturing plate 71 and the first thread cutter 5, forming a forward-falling curved shape. (See [reference]). Figure 16 and Figure 17As shown in the diagram. After the wire cutting operation is completed, the bottom line 10 remains in the capturing groove 71c, constrained in a stable position by the capturing groove 71c, and will not collapse arbitrarily.

[0091] The thread-cutting mechanism of this invention can capture the bottom thread end after thread cutting, stabilize the position of the bottom thread end after cutting, and prevent it from being affected by the rotary hook and bobbin skin, ensuring that the next sewing can be started smoothly, thus improving the stability of sewing performance.

[0092] See Figures 1 to 18 The following specific embodiments further illustrate the wire-cutting mechanism of the present invention.

[0093] In the sewing machine, the axis of the rotary hook assembly 2 is along the left-right direction of the sewing machine, and the rotary hook assembly 2 is located on the left side of the sewing machine. The arc-shaped capture piece 71 has one end facing the second thread cutter 6, which is the A side end 711, and the other end is the B side end 712. In this embodiment, the first thread cutter 5 and the second thread cutter 6 are located on the front and rear sides of the sewing machine, respectively. The front side is the operator's side. When the thread cutter capture piece 7 is installed, the A side end 711 of the arc-shaped capture piece 71 faces the rear side of the sewing machine. At this time, the A side end 711 is the front end, and the B side end 712 of the arc-shaped capture piece 71 faces the front side. At this time, the B side end 712 is the rear end. Of course, in another embodiment, under appropriate circumstances, the positions of the first wire cutter 5 and the second wire cutter 6 can also be interchanged, with the first wire cutter 5 located on the rear side and the second wire cutter 6 located on the front side. In this case, the A-side end 711 is the rear end and the B-side end 712 is the front end. The principle is the same, only the orientation is reversed.

[0094] In existing sewing machines, the thread-cutting mechanism uses a thread separator 01 to separate the thread during cutting. However, see... Figure 19 The thread loop may wrap around the existing thread divider 01, or it may be entirely on one side of the inclined edge of the existing thread divider 01. This will cause the length of the thread end 9 on the right side of the needle to be very unstable after thread cutting. As a preferred design, in this embodiment, see... Figure 2 , Figure 4 and Figure 8The wire-cutting hook 6b of the second wire cutter 6 is composed of a hooking bevel 6c and a hooking stop 6d. The hooking bevel 6c extends obliquely to the right from the left side of the second wire cutter 6, and the hooking stop 6d is located to the right of the hooking bevel 6c. A notch structure is formed between the hooking bevel 6c and the hooking stop 6d, thus forming the wire-cutting hook 6b. The capturing groove 71c on the arc-shaped capturing plate 71 is located to the left of the hooking stop 6d. The constraint side 71a is opposite to the wire-cutting hook 6b, and the side of the constraint side 71a near the A side end 711 extends to the left side of the hooking bevel 6c. Using the above structure, during thread cutting, the second thread cutter 6 rotates towards the first thread cutter 5, and the thread cutting hook 6b hooks the bottom thread 10 and the selvage thread 9a in the top thread loop. Since the constraint side 71a extends all the way to the left of the thread cutting hook 6b, the bottom thread 10 and the top thread 9 will not appear on the left side of the curved capture piece 71, that is, they will not be fitted onto the curved capture piece 71; they will both be located on the right side of the constraint side 71a. See [reference needed]. Figure 11 Then the wire-cutting hook 6b intersects with the constraint side 71a to form a closed area, see [reference]. Figure 9 That is, the hook edge 6c, the hook guard edge 6d, and the constraint side edge 71a form a closed area, and the capturing groove 71c is located within this closed area, meaning that the capturing groove 71c also constitutes part of this closed area. At this time, the bottom thread 10 and the selvage thread 9a are both located within this closed area. As the second thread cutter 6 rotates, the closed area gradually shrinks and gradually approaches the hook guard edge 6d. See [reference needed]. Figures 8 to 10 On the one hand, the bottom thread 10 is constrained to the hook edge 6d, thus approaching the opening of the capture groove 71c, allowing the bottom thread 10 to smoothly enter the capture groove 71c. On the other hand, the selvage thread 9a is constrained by the gradually decreasing closed area. Finally, when the second blade 6a and the first blade 5a of the first thread cutting blade 5 engage, the selvage thread 9a is stably constrained. Therefore, the selvage thread 9a is restricted to a stable position each time the thread is cut, improving the stability of the thread loop during thread cutting and making the length of the thread end 9 after cutting basically consistent.

[0095] In this embodiment, when the second cutting edge 6a and the first cutting edge 5a of the second wire cutter 6 engage to cut the wire, there are two possible solutions. Solution one is that the closed area formed by the intersection of the wire cutting hook 6b and the constraint side 71a still exists. (See [link to relevant documentation]). Figure 10 The enclosed area becomes a very narrow space, which can effectively restrain the selvage line 9a and avoid the problem of breaking the selvage line 9a at this point; the second option is that the thread cutter hook 6b completely crosses the restraint side 71a, making the enclosed area disappear. At this time, the bottom thread 10 and the selvage line 9a will be tightened and restrained at the bottom of the thread cutter hook 6b, that is, at the connection between the hook bevel 6c and the hook guard 6d. This option has the advantage of more stable structure.

[0096] In this embodiment, see Figure 3 and Figure 9 As a preferred design, the hook edge 6d of the thread cutter 6b is tilted left and right, with the front end (the end closer to the thread cutter 7) located on the left and the rear end (the end furthest from the thread cutter 7) located on the right. That is, the hook edge 6d extends from the front left to the rear right, and the tilt angle of the hook edge 6d is small, with a selection of 2 to 4° relative to the front and rear directions, and 3° being preferred. With this slightly tilted hook edge 6d, as the second thread cutter 6 rotates, the closed area becomes smaller and its rightmost position gradually shifts to the right. That is, the rightmost position that the bottom thread 10 and the selvage thread 9a can reach in the closed area will gradually shift to the right, making it easier for the bottom thread 10 to enter the capturing groove 1c. Furthermore, after the bottom thread 10 and the top thread 9 are cut when the first thread cutter 5 pushes, the needle selvage thread 9b has a certain length, preventing the length from being shorter than that of the existing thread cutting mechanism. On the other hand, after the thread is cut, during the rotation and retraction of the second thread cutter 6, the hook edge 6d will slightly push the bottom thread 10 end to the left to ensure that the bottom thread 10 end is located in the capturing groove 1c, thereby ensuring that the bottom thread 10 end can be stably captured. Because the hook edge 6d of the second thread cutter 6 is inclined, as the closed area continuously decreases, it will gradually shift to the right.

[0097] In this embodiment, preferably, see Figure 4 An arc-shaped protrusion 71d is provided on the right side of the arc-shaped capture piece 71. The front end of the constraint side 71a (near the B side end 712) extends to the arc-shaped protrusion 71d. That is, the side of the arc-shaped protrusion 71d is part of the constraint side 71a, forming a guide part. The capture groove 71c is located to the right of the arc-shaped protrusion 71d, that is, to the right of the guide part. With this design, the closed area formed by the intersection of the wire cutter hook 6b and the constraint side 71a gradually becomes smaller and becomes composed of the guide part and the constraint side 71a, making the closed area gradually become more slender. The opening of the capture groove 71c is closer to the hook guard edge 6d and is located in the slender closed area, which makes it easier for the bottom line 10 to enter the capture groove 71c.

[0098] In this embodiment, see Figure 2 , Figure 4 and Figure 8As a preferred design, the second thread cutter 6 is provided with a thread-separating tip 6e for inserting into the thread loops to separate the threads. The left side of the thread-separating tip 6e is a hook-and-stop edge 6d, which is shared with the thread-cutting hook 6b. The right side of the thread-separating tip 6e has a first thread-separating inclined edge 6f that is inclined to the right. When the thread-cutting action begins, the second thread cutter 6 rotates, and the thread-separating tip 6e is inserted into the thread loop, initially separating the thread loop. The fabric edge thread 9a is located to the left of the thread-separating tip 6e, i.e., in the displacement thread-cutting hook 6b, while the needle edge thread 9b is located to the right of the thread-separating tip 6e and moves to the right along the first thread-separating inclined edge 6f as the second thread cutter 6 rotates, thereby gradually separating the thread loops. Further, see Figure 4 and Figure 8 The right side of the arc-shaped capturing plate 71 has a second dividing line inclined edge 71b opposite to the first dividing line inclined edge 6f. When the second thread cutter 6 rotates toward the first thread cutter 5, the first dividing line inclined edge 6f and the second dividing line inclined edge 71b intersect. The second dividing line inclined edge 71b will drive the needle edge thread 9b to move along the first dividing line inclined edge 6f and constrain the needle edge thread 9b at the intersection. See [reference needed] Figure 12 and 13 This design allows for better stability of the top thread loop position. When the second cutter 6a and the first cutter 5a engage, the intersection point of the first dividing line hypotenuse 6f and the second dividing line hypotenuse 71b remains stable each time the thread is cut, meaning the position of the needle edge thread 9b remains stable. Simultaneously, because the fabric edge thread 9a is constrained by the enclosed area, the shape and length of the top thread loop are stable. Therefore, after thread cutting, the length of the resulting top thread 9 end is stable. Furthermore, since the needle edge thread 9b moves a certain distance along the first dividing line hypotenuse 6f, meaning the top thread loop has a certain length, the resulting top thread 9 end after cutting has a certain length and will not be too short.

[0099] In the embodiments, as a preferred design, see [reference needed]. Figure 2 , Figure 3 and Figure 12 The first wire cutter 5 has a raised portion 5c, and the second wire cutter 6 has a raised portion 6g that is inclined towards the side where the rotary hook assembly 2 is located. That is, the raised portion 6g is inclined downward at a certain angle. When the second wire cutter 6 rotates towards the first wire cutter 5, the raised portion 6g first inserts into the lower side of the raised portion 5c, and as it rotates, the raised portion 6g gradually lifts the raised portion 5c. The raised portion 6g functions similarly to a cam, which separates the first wire cutter 5 from the arc-shaped capture plate 71 by a certain distance, facilitating the insertion of the first wire cutter 5. In other embodiments, where certain dimensions allow, before the second wire cutter 6 enters the arc-shaped capture plate 71 and before the second wire cutter 6, the second wire cutter 6 can also press against the arc-shaped capture plate 71 to deform it downward.

[0100] In this embodiment, the wire cutting mechanism can be an improvement on the existing wire cutting mechanism, adding a wire cutting catcher 7 to achieve the functions of surface line 9 constraint and bottom line 10 capture. The wire cutting mechanism can be a circular single-blade wire cutting mechanism, in which case the first wire cutting blade 5 and the second wire cutting blade 6 are respectively the fixed blade and the moving blade in the circular single-blade wire cutting mechanism, both of which are arc-shaped blades. The wire cutting mechanism can also be a circular double-blade wire cutting mechanism, in which case the first wire cutting blade 5 and the second wire cutting blade 6 are respectively the fixed blade and the auxiliary blade in the circular single-blade wire cutting mechanism, both of which are arc-shaped blades.

[0101] In the embodiments, as a preferred design, see [reference needed]. Figure 4 and Figure 5 The thread-cutting catch 7 mainly comprises two parts: an arc-shaped catch plate 71 and an installation section 72 connected to the arc-shaped catch plate 71. The inner diameter of the arc-shaped catch plate 71 is slightly larger than the outer diameter of the rotary hook skin 2b, and they are coaxially arranged to fit the shape of the rotary hook assembly 2 while leaving a gap. The outer diameter of the arc-shaped catch plate 71 is slightly smaller than the second thread-cutting blade 6 to match the second thread-cutting blade 6, ensuring that the second thread-cutting blade 6 can be smoothly inserted into the upper side of the arc-shaped catch plate 71 without interference when cutting the thread. The installation section 72 is used for the fixed installation of the thread-cutting catch 7. In this application, the component in the sewing machine used for the fixed installation of the thread-cutting catch 7 is referred to as the catch mounting base, and the installation section 72 is fixedly connected to the catch mounting base. The catch mounting base can be the machine housing 1 or other fixed components. In this embodiment, the mounting section 72 is fixedly mounted on the capture component mounting base using fastening screws 11. The mounting section 72 has a strip-shaped connecting hole 72a extending in the front-to-back direction. The fastening screw 11 passes through the strip-shaped connecting hole 72a and is screwed into the capture component mounting base. By tightening or loosening the fastening screw 11, the front-to-back position of the thread-cutting capture component 7 can be adjusted, facilitating assembly and making the cooperation between the arc-shaped capture piece 71 and the first thread-cutting blade 5 and the second thread-cutting blade 6 more flexible. Specifically, the mounting section 72 can utilize the mounting position of the thread divider 01 in an existing sewing machine, reducing changes to the existing structure.

[0102] The thread-catching component 7 in this application is located in the core area where the sewing machine thread is formed, and its distance from the rotary hook assembly 2 and the first thread-cutting blade 5 is extremely small. Therefore, the outer edges of the entire component need to be rounded, polished, and hardened to ensure that its shape, toughness, strength, and edges are free from burrs. The arc-shaped catching plate 71 and the mounting section 72 of the thread-catching component 7 are preferably integrated, and their processing method can be ordinary sheet metal stamping, or precision casting, lathe machining, and other modern parts processing techniques.

[0103] The present invention also provides a method for cutting the thread of a sewing machine, which uses the above-mentioned thread cutting mechanism and includes the following steps:

[0104] S1. Before the cutting operation, the second wire cutter 6 is separated from the first wire cutter 5.

[0105] S2. When the thread cutting begins, the second thread cutter 6 rotates towards the first thread cutter 5, and the thread cutting hook 6b hooks the bottom thread 10 and the selvage thread 9a in the top thread loop. As the second thread cutter 6 rotates towards the first thread cutter 5, it inserts between the first thread cutter 5 and the arc-shaped capture piece 71. The thread cutting hook 6b intersects with the constraint side 71a, forming a closed area. The bottom thread 10 and the selvage thread 9a are both located in this closed area. As the second thread cutter 6 rotates, this closed area gradually shrinks. The thread cutting hook 6b drives the bottom thread 10 to move along the constraint side 71a until the bottom thread 10 reaches the capture groove 71c, and enters the capture groove 71c under its own tension. At the same time, the closed area constrains the position of the selvage thread 9a, and the first dividing edge 6f and the second dividing edge 71b constrain the position of the needle edge thread 9b, thereby constraining the position of the top thread loop and making it difficult for the selvage thread 9a to enter the capture groove 71c.

[0106] In this step, when using the wire-cutting mechanism in this embodiment, specifically, the intersection of the wire-cutting hook 6b and the constraint side 71a to form a closed area can be roughly divided into three stages: the first stage, see... Figure 8 The splitting tip 6e is inserted into the top thread loop and separates it. The thread cutter 6b hooks the bottom thread 10 and the selvage thread 9a in the top thread loop. Then, the thread cutter 6b extends between the first thread cutter 5 and the curved capture plate 71. The second thread cutter 6 continues to rotate toward the engagement position. During this process, the second thread cutter 6 pulls the bottom thread 10 and the top thread 9. The bottom thread 10 forms a U-shaped fold at the thread cutter 6b, and is stretched to a certain tension. The top thread 9 is also stretched to a certain tension. Before the second thread cutter 6 rotates to the engagement position, the sewing machine's take-up lever simultaneously lifts up, causing the top thread 9 to move upward a certain distance, further stretching it and giving it greater tension. At this time, a portion of the top thread 9 and bottom thread 10 in the sewn fabric will be pulled out. (See the second stage.) Figure 9 and Figure 12 The thread-cutting hook 6b intersects with the restraining side 71a to form a closed area, which gradually shrinks into a slender shape composed of the guide portion at the arc-shaped protrusion 71d and the hook edge 6d. This confines the bobbin thread 10 and the needle edge thread 9b within the closed area, preventing the top thread loop from getting caught on the thread-cutting catch piece 7. The thread-cutting hook 6b moves the bobbin thread 10 along the guide portion, and the tension of the bobbin thread 10 gradually increases. (See the third stage.) Figure 10As the second thread cutter 6 continues to rotate until the closed area becomes smaller, the bottom thread 10 moves to the opening of the capture groove 71c. Under its own tension, the bottom thread 10 will spring into the capture groove 71c and continue to be driven by the thread cutting hook 6b. It will move slightly in the capture groove 71c until it reaches the bottom of the groove and will not come out of the capture groove 71c. During the rotation of the second thread cutter 6, the first dividing edge 6f and the second dividing edge 71b will intersect. The first dividing edge 6f will drive the needle edge thread 9b to move along the second dividing edge 71b. Because the top thread 9 is pulled upward, the top thread loop is tightened. The fabric edge thread 9a moves close to the hook edge 6d towards the second cutter edge and will not enter the guide wire part 71c, thus not capturing the top thread 9.

[0107] S3. When the second thread cutter 6 reaches the engagement position, it engages with the first thread cutter 5 to cut the bottom thread 10, obtaining the bottom thread 10 end. At the same time, it cuts the fabric edge 9a, obtaining the top thread 9 end. The bottom thread 10 end is located between the second thread cutter 6 and the first thread cutter 5.

[0108] S4. Before the second thread cutter 6 rotates and retracts, the thread end of the bottom thread 10 extends under its own elasticity and remains in the capturing groove 71c. Since the bottom thread 10 extends from the shuttle carriage guide groove 2c and then forward to the arc-shaped capturing piece 71, the bottom thread 10 itself has a certain elastic recovery capability. The thread end of the bottom thread 10 has a tendency to extend when bent. Therefore, the thread end of the bottom thread 10 will extend forward in the gap between the second thread cutter 6 and the first thread cutter 5, forming a forward-falling curved shape. See [reference needed]. Figure 15 As shown, the thread 9 is positioned within the capturing groove 71c. Simultaneously, because the top thread 9 is stretched, it contracts under its own tensile tension immediately after cutting, causing the thread end to move. At this time, the sewing machine's take-up lever also lifts upwards, and the needle moves upwards a certain distance. Besides its own elastic tensile tension, the top thread 9 is also pulled upwards by at least one of the structures—the take-up lever, the needle, and the take-up spring—further ensuring that the thread end of the top thread 9 will not be located in the capturing groove 71c and will not be captured. Furthermore, because the top thread 9 and the bobbin thread 10 have a certain tension during cutting, the remaining thread ends of the top thread 9 and bobbin thread 10 on the fabric will retract to some extent after cutting, thus making the remaining thread ends on the fabric shorter, or even eliminating any loose threads after cutting.

[0109] S5. The second wire cutter 6 rotates and retracts, and the bottom thread 10 remains stable under the constraint of the capture groove 71c; while the top thread 9 does not enter the capture groove 71c and will not be captured.

[0110] Preferably, the thread-cutting method further includes step S6: when sewing begins again, the rotary hook skin 2b in the rotary hook assembly 2 rotates, see [reference]. Figure 18Its tail pushes the end of the bobbin 10 to the left, keeping the end of the bobbin 10 in the capturing groove 71c while pushing it out partially, with the end still captured by the capturing groove 71c. Specifically, after the thread is cut, the bobbin 10 extends from the inner tube 2a of the rotary hook assembly 2, then passes through the shuttle guide groove 2c to reach the capturing groove 71c. When sewing begins again, the tail of the shuttle bobbin 2b will first push the end of the bobbin 10 to the left a certain distance, see [reference needed]. Figure 18 As shown by arrow B, the lead end of the bottom thread 10 is partially pushed out of the capturing groove 71c, but the lead end of the bottom thread 10 remains in the capturing groove 71c, maintaining its captured state. Furthermore, when the lead end of the bottom thread 10 is pushed to the left, it is also restrained by the constraining side 71a, preventing it from overshooting. The pushed-out portion forms a curved segment; that is, this section of the lead end of the bottom thread 10 between the shuttle carriage guide groove 2c and the arc-shaped capturing piece 71 forms an upward-arching curved segment. This curved segment is located outside the rotation range of the tail of the shuttle bob skin 2b in the rotary shuttle assembly 2. Figure 18 The shuttle skin is outside the maximum range of motion C of the rotary shuttle, so the tail of the shuttle skin 2b will not collide with this curved section when rotating, thus preventing erratic movement and ensuring the stability of the bottom thread 10. When sewing begins again, the captured bottom thread 10 forms a locking stitch with the top thread loop. After the bottom thread 10 is released, the capturing groove 71c enters the preparation state for the next bottom thread 10 capture.

[0111] As can be seen from the above, the wire-cutting mechanism and method in this embodiment have the following beneficial effects:

[0112] 1. It can effectively capture the bottom thread 10, stabilize the position of the bottom thread after cutting, and not be affected by the movement of the rotary hook, ensuring that the next sewing can be started smoothly, thus improving the stability of sewing performance;

[0113] 2. While capturing the bottom line 10, the top line 9 thread will not be captured. When the fabric is removed after cutting the thread, the top line will not affect the bottom line 10, thus avoiding the problem of bottom line 10 failing to capture.

[0114] 3. When cutting the thread, the top thread loop can be constrained to a fixed position, improving the stability of the top thread loop during cutting and ensuring that the length of the thread end 9 after cutting is basically consistent, thereby increasing the probability of forming a stitch with the bottom thread 10 when starting to sew again.

[0115] 4. The wire cutting mechanism has a simple structure and can be improved from existing wire cutting mechanisms, resulting in low cost.

[0116] In summary, this invention effectively overcomes the various shortcomings of the prior art and has high industrial application value.

[0117] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A thread trimming mechanism of a sewing machine for trimming thread at a rotating hook assembly (2) of the sewing machine, the thread trimming mechanism comprising a first thread trimming knife (5) fixedly installed at an outer peripheral side of the rotating hook assembly (2) and a second thread trimming knife (6) provided at the outer peripheral side of the rotating hook assembly (2) and rotatable about the rotating hook assembly (2) to engage with or disengage from the first thread trimming knife (5), the second thread trimming knife (6) being provided with a thread trimming hook (6b) for hooking and moving a bobbin thread (10) toward the first thread trimming knife (5), characterized in that: The thread cutting mechanism further comprises a fixedly installed thread cutting catcher (7), which comprises an arc-shaped catching piece (71) arranged along the outer circumferential side of the rotating hook assembly (2), and the arc-shaped catching piece (71) is located between the rotating hook assembly (2) and the first thread cutting knife (5), and a right side of the arc-shaped catching piece (71) is provided with a right-tilted constraint side (71a), and a catching groove (71c) is formed in the constraint side (71a); when the second thread cutting knife (6) rotates towards the first thread cutting knife (5), the thread cutting hook (6b) intersects with the constraint side (71a), and the thread cutting hook (6b) drives the bottom thread (10) to move along the constraint side (71a) to the catching groove (71c).

2. The thread trimming mechanism according to claim 1, characterized in that: The thread cutting hook (6b) of the second thread cutting knife (6) is composed of a thread hooking bevel (6c) and a thread hooking stop edge (6d), the thread hooking bevel (6c) extends rightward from the left side of the second thread cutting knife (6), the thread hooking stop edge (6d) is arranged on the right side of the thread hooking bevel (6c), the catching groove (71c) on the arc-shaped catching piece (71) is located on the left side of the thread hooking stop edge (6d), one end of the arc-shaped catching piece (71) towards the second thread cutting knife (6) is an A-side end (711), and the other end is a B-side end (712), the constraint side (71a) extends to the left side of the thread hooking bevel (6c) on the side close to the A-side end (711); when the second thread cutting knife (6) rotates towards the first thread cutting knife (5), the thread cutting hook (6b) intersects with the constraint side (71a) to form a closed area, and the catching groove (71c) is located in the closed area.

3. The thread trimming mechanism of claim 2, wherein: The closed area formed by the intersection of the thread cutting hook (6b) and the constraint side (71a) still exists when the second thread cutting knife (6) rotates to cut the thread with the first thread cutting knife (5).

4. The thread trimming mechanism of claim 2, wherein: The closed area formed by the intersection of the thread cutting hook (6b) and the constraint side (71a) disappears when the second thread cutting knife (6) rotates to cut the thread with the first thread cutting knife (5).

5. The thread trimming mechanism of claim 2, wherein: The thread hooking stop edge (6d) is arranged leftward and rightward, and one end close to the thread cutting catcher (7) is located on the left side, and the other end away from the thread cutting catcher (7) is located on the right side.

6. The thread trimming mechanism of claim 5, wherein: The inclination angle of the thread hooking stop edge (6d) relative to the front-rear direction is 2-4°.

7. The thread trimming mechanism of claim 6, wherein: The inclination angle of the thread hooking stop edge (6d) relative to the front-rear direction is 3°.

8. The thread trimming mechanism of claim 2, wherein: An arc-shaped protrusion (71d) is arranged on the right side of the arc-shaped catching piece (71), and one end of the constraint side (71a) close to the B-side end (712) extends to the arc-shaped protrusion (71d), and the catching groove (71c) is located on the right side of the arc-shaped protrusion (71d).

9. The thread trimming mechanism of claim 2, wherein: A thread separating tip (6e) for being inserted between the thread loops to separate the threads is arranged on the second thread cutting knife (6), a left side of the thread separating tip (6e) is the thread hooking stop edge (6d), and a right side of the thread separating tip (6e) has a first thread separating bevel (6f) arranged rightward.

10. The thread trimming mechanism of claim 9, wherein: The right side of the arc-shaped catching piece (71) is provided with a second line division bevel (71b) opposite to the first line division bevel (6f), and the first line division bevel (6f) intersects with the second line division bevel (71b) when the second line cutter (6) rotates towards the first line cutter (5).

11. The thread trimming mechanism of claim 1, wherein: The first line cutter (5) is provided with a raised portion (5c), and the second line cutter (6) is provided with a raised portion (6g) inclined towards the side where the rotating hook assembly (2) is located, and the raised portion (6g) is inserted into the raised portion (5c) towards the lower side of the rotating hook assembly (2) when the second line cutter (6) rotates towards the first line cutter (5).

12. The thread trimming mechanism according to claim 1 or 11, characterized in that: The line cutting catching piece (7) has a mounting section (72) connected with the arc-shaped catching piece (71), and the part for fixedly mounting the line cutting catching piece (7) in the sewing machine is a catching piece mounting base, and the mounting section (72) is fixedly connected with the catching piece mounting base.

13. The thread trimming mechanism of claim 12, wherein: The mounting section (72) is fixedly mounted on the catching piece mounting base by means of a fastening screw (11), and the mounting section (72) is provided with a strip-shaped connecting hole (72a) extending in the front-rear direction, and the fastening screw (11) is screwed into the catching piece mounting base through the strip-shaped connecting hole (72a).

14. A thread trimming method of a sewing machine, characterized by: The line cutting mechanism is used, and the method comprises the following steps: S1, before cutting, the second line cutter (6) is separated from the first line cutter (5); S2, when starting to cut, the second line cutter (6) rotates towards the first line cutter (5), the line cutting hook (6b) hooks the bottom thread (10), the line cutting hook (6b) intersects with the constraint side (71a) when the second line cutter (6) rotates towards the first line cutter (5), the line cutting hook (6b) drives the bottom thread (10) to move along the constraint side (71a) to the position where the bottom thread (10) reaches the catching groove (71c), and the bottom thread (10) enters the catching groove (71c) under the action of its own tension; S3, when the second line cutter (6) reaches the occlusion position, it occludes with the first line cutter (5) to cut the bottom thread (10), and the thread end of the bottom thread (10) is obtained; the thread end of the bottom thread (10) is located between the second line cutter (6) and the first line cutter (5); S4, before the second line cutter (6) rotates back, the thread end of the bottom thread (10) becomes an extended state under the action of its own elasticity and remains in the catching groove (71c); S5, the second line cutter (6) rotates back, and the thread end of the bottom thread (10) remains stable under the constraint of the catching groove (71c).

15. The wire trimming method according to claim 14, characterized by: Further comprising step S6, when starting to sew next time, the rotating hook skin (2b) in the rotating hook assembly (2) rotates, the tail portion of the rotating hook skin (2b) pushes the thread end of the bottom thread (10) to the left, so that the thread end of the bottom thread (10) remains in the catching groove (71c) and is pushed out a part.

16. A sewing machine comprising a rotating shuttle assembly (2), characterized in that: Further comprising the line cutting mechanism as claimed in any one of claims 1 to 13, and the line cutting mechanism is arranged at the rotating hook assembly (2) to cut the line.

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