Thread trimming mechanism

Abstract

The present application provides a thread cutting mechanism for cutting the thread in the needle hole of the needle plate, which comprises a moving cutter holder under the needle plate, a moving cutter and a fixed cutter on one side of the needle hole. The top wall of the moving cutter is provided with an obliquely extending blade face. The fixed cutter is located above the moving cutter, and comprises a cutter handle part away from the needle hole and a blade part close to the needle hole. The cutter handle part is detachably attached to the bottom wall of the needle plate. The blade part obliquely extends from the bottom wall of the needle plate to the directly below of the needle hole. The thickness of the blade part gradually decreases in the extending direction. The end surface of the blade part close to the needle hole is perpendicular to the horizontal plane. The lower edge of the end surface is the lowest point of the blade part, and forms a cutting edge parallel to the horizontal plane. The thread can be vertically cut by the contact between the cutting edge and the highest point of the blade face. The rigidity of the blade part is improved, the elastic retreat is reduced, the thread cutting action is crisp and smooth, the thread cutting effect is good, the adjustment is convenient and easy, and the thread cutting mechanism is durable.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of sewing machines, and particularly relates to a thread cutting mechanism of an automatic sewing machine. BACKGROUND

[0002] An automatic sewing machine is a sewing machine capable of automatically completing a sewing process under the control of a computer. After sewing is completed, the thread needs to be cut so as to take down the sewing material. Common thread cutting mechanisms of automatic sewing machines are mostly arranged on one side of a needle plate. The thread cutting position is far away from the needle hole on the needle plate. After the thread is cut, the thread end remaining on the sewing material is long, the sewing thread is wasted, the quality of the sewing material is affected, manual trimming is required, the production efficiency is low, and the labor intensity is large.

[0003] To solve this problem, a thread cutting mechanism with a short thread end has appeared on the market. For example, Chinese patent CN108457015A discloses such a thread cutting mechanism of an automatic sewing machine. The fixed knife of the scheme is a 7-shaped sheet, which is vertically folded. The lower end of the fixed knife is fixed on a fixed knife seat, and the upper end of the fixed knife is provided with a fixed knife edge and is suspended outside the moving knife. The fixed knife edge cuts off the sewing thread by contacting the outer wall surface of the moving knife. Such a setting causes at least the following problems in use of the scheme:

[0004] 1. The folded part of the fixed knife actually constitutes a rotating shaft of the fixed knife edge, and the rotating shaft is perpendicular to the rotating plane of the moving knife. When the thread is cut, the fixed knife edge will rotate around the folded part in a direction away from the outer wall surface of the moving knife due to the pushing of the outer wall surface of the moving knife and the elastic force of the fixed knife itself, forming elastic retreat. The thread cutting action is not crisp and smooth, and the phenomenon of seeming to be cut but not being cut may occur, and the thread cutting effect is poor.

[0005] 2. When the fixed knife and the moving knife are adjusted, the angle of the fixed knife and the position of the fixed knife need to be adjusted, which is difficult. After the angle and / or position of the fixed knife are changed, the degree of elastic retreat of the fixed knife will also change, which will affect the cooperation between the fixed knife and the moving knife. Therefore, multiple adjustments are required, and the operation is not convenient.

[0006] 3. The contact surface (or line) between the fixed knife edge and the outer wall surface of the moving knife is parallel or approximately parallel to the axial direction of the sewing thread. When the thread is cut, the fixed knife edge is greatly worn, and the service life is short. SUMMARY

[0007] The present application aims to overcome the shortcomings of the prior art and provide a thread cutting mechanism with crisp and smooth thread cutting action, good thread cutting effect, convenient and small difficulty in adjustment, and long service life. The thread cutting mechanism cuts a short thread end, wastes little sewing thread, does not affect the quality of the sewing material, does not require manual trimming, has high production efficiency and small labor intensity, and is particularly suitable for use in an automatic sewing machine.

[0008] To achieve the above object, the technical scheme provided by the present application is that a thread cutting mechanism is used to cut the thread arranged in the needle hole of a needle plate, the thread cutting mechanism comprises a moving knife holder, a moving knife and a fixed knife, the moving knife holder is arranged below the needle plate, the top wall of the moving knife is provided with an obliquely extending blade surface, the fixed knife is arranged above the moving knife, the fixed knife comprises a handle part away from the needle hole and a blade part close to the needle hole, the handle part is detachably attached to the bottom wall of the needle plate, the blade part obliquely extends from the bottom wall of the needle plate to the position directly below the needle hole, the thickness of the blade part gradually decreases in the extending direction, the end surface of the blade part close to the needle hole is perpendicular to the horizontal plane, the lower edge of the end surface is the set of lowest points of the blade part, and forms a cutting edge parallel to the horizontal plane, and the cutting edge vertically cuts the thread by contacting the highest point of the blade surface.

[0009] Preferably, the handle part is embedded in the positioning groove provided in the bottom wall of the needle plate, and the groove opening of the positioning groove is higher than the lower surface of the handle part.

[0010] Further preferably, the needle hole penetrates the top wall of the positioning groove downward.

[0011] Further preferably, the groove depth of the positioning groove is less than or equal to 20% of the thickness of the needle plate.

[0012] Further preferably, the positioning groove is an arc-shaped groove, and the center of the arc-shaped groove is located on the extension line of the rotation axis of the rotating hook.

[0013] Preferably, the distance between the cutting edge and the needle hole is 3±0.5mm.

[0014] Preferably, the thickness of the thickest part of the blade part is 2.4-2.8 times the thickness of the handle part, and the thickness of the thinnest part of the blade part is 1.1-1.3 times the thickness of the handle part.

[0015] Preferably, the fixed knife further comprises a connecting part for connecting the handle part and the blade part, and the thickness of the connecting part gradually increases from the handle part to the blade part.

[0016] Preferably, the thread cutting mechanism further comprises a limiting boss for limiting the position of the rotating hook, and the limiting boss is formed by the end part close to the needle hole of the transverse rib plate connected to the inner wall of the needle plate seat.

[0017] Further preferably, the thread cutting mechanism further comprises a thread clamping plate, the thread clamping plate is in the shape of a Chinese character "7", the upper end part of the thread clamping plate is used for clamping the thread in cooperation with the upper surface of the limiting boss, and the lower end part of the thread clamping plate is located on one side of the moving knife and connected to the outwardly protruding longitudinal rib plate of the needle plate seat.

[0018] Due to the above technical scheme, the present application has the following advantages compared with the prior art:

[0019] 1. By arranging the fixed knife above the moving knife, the blade portion of the fixed knife extends obliquely from the bottom wall of the needle plate to directly below the needle hole, which can shorten the distance between the cutting edge of the fixed knife and the needle hole in the horizontal direction as much as possible, thereby further reducing the length of the thread remaining on the fabric.

[0020] 2. By gradually reducing the thickness of the blade portion in the extension direction, the end face of the blade portion near the needle hole is perpendicular to the horizontal plane, which can enhance the rigidity of the blade portion, greatly reduce the degree of elastic retreat of the blade portion, make the thread cutting action crisp and smooth, the thread fracture flat, and the thread cutting effect good, and form a gap between the blade portion and the needle plate, thereby reducing the contact area with the thread and reducing the wear of the thread and the fixed knife.

[0021] 3. By arranging the inclined blade face on the top wall of the moving knife, the lower edge of the end face of the blade portion near the needle hole is the lowest point of the blade portion, and a cutting edge parallel to the horizontal plane is formed, which can realize vertical cutting of the thread by the contact between the cutting edge and the highest point of the blade face during the rotation of the moving knife, thereby reducing the wear of the cutting edge of the fixed knife during thread cutting, prolonging the service life, and being durable.

[0022] 4. Since the cutting edge of the fixed knife and the blade face of the moving knife are in an upper and lower cooperation mode, and the degree of elastic retreat of the fixed knife is extremely small and almost negligible, only the height of the blade face of the moving knife in the vertical direction needs to be adjusted during the cooperation adjustment of the fixed knife and the moving knife, which is easy to adjust and convenient to operate. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 、 Figure 2 、 Figure 3 is a perspective view of a preferred embodiment of the present application.

[0024] Figure 4 、 Figure 5 、 Figure 6 is an assembly and disassembly schematic view of a preferred embodiment of the present application.

[0025] Figure 7 is Figure 1 a front view schematic view.

[0026] Figure 8 is Figure 7 an enlarged sectional view in the direction of A-A in

[0027] Wherein: 10. moving knife holder; 20. moving knife; 21. blade face; 22. positioning boss; 23. line hooking part; 24. avoiding face; 30. fixed knife; 31. knife handle part; 32. blade part; 321. end face; 322. cutting blade; 33. connecting part; 34. screw; 40. needle plate; 41. needle hole; 42. positioning groove; 50. needle plate holder; 51. transverse rib plate; 52. longitudinal rib plate; 60. limiting boss; 70. thread clamping plate; 71. waist-shaped hole; 72. screw. DETAILED DESCRIPTION

[0028] The preferred embodiments of the present application are described in detail below with reference to the accompanying drawings, so that the advantages and features of the present application can be more easily understood by those skilled in the art, and the scope of protection of the present application is more clearly defined.

[0029] The up-down, left-right, front-rear directions described in the present application refer to Figure 1 the up-down, left-right, front-rear directions in the

[0030] As shown in Figures 1 to 8 , the thread cutting mechanism provided by the present application is used to cut the thread passing through the needle hole 41 in the needle plate 40, and the thread cutting mechanism comprises a moving knife holder 10, a moving knife 20 located below the needle plate 40, and a fixed knife 30 located on one side of the needle hole 41. The end of the moving knife 20 away from the needle hole 41 is supported on the top of the moving knife holder 10, and the end of the moving knife 20 close to the needle hole 41 is provided with a blade face 21, a positioning boss 22, and a line hooking part 23. The blade face 21 is arranged on the top surface of the moving knife 20 and extends obliquely, the positioning boss 22 is arranged on the bottom wall of the moving knife 20 and protrudes downward, and the line hooking part 23 is connected to the outer wall of the moving knife 20 for hooking the thread passing through the needle hole 41. When the moving knife holder 10 rotates, it can drive the moving knife 20 to rotate, and the rotation plane of the moving knife 20 is parallel to the horizontal plane, so that the blade face 21 cooperates with the fixed knife 30 to cut the thread. The fixed knife 30 is located above the moving knife 20, and the fixed knife 30 comprises a knife handle part 31 away from the needle hole 41 and a blade part 32 close to the needle hole 41. The knife handle part 31 is detachably attached to the bottom wall of the needle plate 40, and the blade part 32 extends obliquely from the bottom wall of the needle plate 40 to the directly below the needle hole 41. The thickness of the blade part 32 gradually decreases in the extending direction, the thickness of the thickest part of the blade part 32 is 2.4-2.8 times the thickness of the knife handle part 31, the thickness of the thinnest part of the blade part 32 is 1.1-1.3 times the thickness of the knife handle part 31, the inclination degree of the upper surface of the blade part 32 is greater than the inclination degree of the lower surface of the blade part 32, and intuitively, the slope of the upper surface of the blade part 32 is steeper. The end face 321 of the blade part 32 close to the needle hole 41 is perpendicular to the horizontal plane, the lower edge of the end face 321 is the collection of the lowest points of the blade part 32, and the lower edge forms a cutting blade 322 parallel to the horizontal plane. When the moving knife 20 rotates with the moving knife holder 10, the cutting blade 322 vertically cuts the thread by contacting the highest point of the blade face 21.

[0031] The advantage of this setting is that:

[0032] 1. It can minimize the horizontal distance between the fixed blade and the needle hole, thereby further reducing the length of thread residue on the sewing fabric.

[0033] 2. It can enhance the rigidity of the cutting edge and significantly reduce the degree of elasticity of the cutting edge, making the thread cutting action crisp and clean, the thread break flat, and the thread cutting effect good. It can also create a gap between the cutting edge and the needle plate, reducing the contact area with the thread, thereby reducing the wear of the thread and the fixed blade.

[0034] 3. It can form a cutting edge parallel to the horizontal plane. When the moving blade rotates, it achieves vertical shearing of the seam through the contact between the cutting edge and the highest point of the blade surface. The wear on the fixed blade is small when cutting the thread, resulting in a long service life and durability.

[0035] 4. Since the fixed blade and the moving blade are fitted together vertically, and the fixed blade shank is attached to the bottom wall of the needle plate, the degree of elastic yielding of the fixed blade in the vertical direction is extremely small and can be almost ignored. When adjusting the fixed and moving blades, it is only necessary to adjust the height of the moving blade in the vertical direction. The adjustment is simple and convenient.

[0036] A positioning groove 42 is provided on the bottom wall of the needle plate 40. The knife handle part 31 is embedded in the positioning groove 42 and fixed by screws 34. The depth of the positioning groove 42 should not be too large, as this would reduce the strength of the needle plate 40, nor should it be too small, as this would not serve the positioning function. Preferably, the depth of the positioning groove 42 is 10%-20% of the thickness of the needle plate 40. In this embodiment, the thickness of the needle plate 40 is 1.7mm, and the thickness of the positioning groove 42 is 0.3mm. The opening of the positioning groove 42 is higher than the lower surface of the knife handle part 31. The advantage of this setting is that the thickness of the knife handle part 31 is not affected by the depth of the positioning groove 42, thereby ensuring the strength of the fixed knife 30.

[0037] In this embodiment, the positioning groove 42 is an arc-shaped groove, and the center of the arc-shaped groove is located on the extension line of the rotation axis of the rotary hook. The advantage of this setting is that when the cutting edge 32 is impacted by the cutting edge surface 21, the impact force can be evenly distributed on the inner wall of the positioning groove 42 that contacts the handle 31, thereby reducing the wear of the positioning groove 42. Even if the screw 34 is loosened due to frequent impacts, the handle 31 can be stuck by the inner wall of the positioning groove 42, and its position in the horizontal direction is not easily changed.

[0038] In the embodiment, the pinhole 41 vertically penetrates the top wall of the positioning groove 42 downward, the pinhole 41 is a waist-shaped hole extending in the left-right direction, and the cutting edge 322 extends horizontally in the front-rear direction. The advantage of the arrangement is that when the hooking part 23 rotates along with the moving cutter 20 to drive the suture to advance, the cutting edge 322 can be arranged on the advancing route of the suture, thereby further optimizing the cutting effect of the suture.

[0039] In the embodiment, the distance between the cutting edge 322 and the pinhole 41 is 3±0.5 mm, which is much smaller than the distance between the pinhole 41 and the end surface of the needle plate 40 (in the prior art, the distance is usually greater than 10 mm), and the technical effect of controlling the length of the residual thread to about 3 mm can be achieved.

[0040] In the embodiment, the fixed cutter 30 further comprises a connecting part 33 for connecting the cutter handle part 31 and the cutting edge part 32, and the thickness of the connecting part 33 gradually increases from the cutter handle part 31 to the cutting edge part 32. The advantage of the arrangement is that the fixed cutter 30 can be made more smooth as a whole.

[0041] In the embodiment, the needle plate 40 is fixed on the top of the needle plate seat 50, the needle plate seat 50 is provided with a transverse rib plate 51 and a longitudinal rib plate 52 to increase the strength, the transverse rib plate 51 is squeezed between the moving cutter 20 and the rotating hook, and the end portion close to the pinhole 41 constitutes a limiting boss 60 for limiting the protruding position of the rotating hook. The longitudinal rib plate 52 extends outwardly and protrudes from the end surface of the needle plate seat 50.

[0042] The thread cutting mechanism further comprises a thread clamping plate 70, which is in the shape of a Chinese character “7”, the upper end portion of the thread clamping plate 70 is used for clamping the thread in cooperation with the upper surface of the limiting boss 60, and the lower end portion of the thread clamping plate 70 is movably connected to the end surface of the outwardly protruding longitudinal rib plate 52 of the needle plate seat 50. Specifically, the lower end portion of the thread clamping plate 70 is provided with a waist-shaped hole 71 extending in the up-down direction, and a screw 72 is arranged in the waist-shaped hole 71 to fix the thread clamping plate 70 to the longitudinal rib plate. The advantage of the arrangement is that the lateral fixing space can be left by the position change of the fixed cutter 30, which facilitates the fixation and height adjustment of the thread clamping plate 70.

[0043] In order to further prolong the service life of the cutting edge part 32 of the fixed cutter 30, in the embodiment, the upper surface of the moving cutter 20 is further provided with an avoiding surface 24 lower than the lowest point of the cutting edge surface 21, and the avoiding surface 24 is arranged on both sides of the cutting edge surface 21.

[0044] The thread cutting mechanism provided by the application can realize the transformation of the existing thread cutting mechanism by only replacing the needle plate, the needle plate seat, the fixed cutter and the thread clamping plate. The change of the existing mechanism is small, the replaced parts are convenient to disassemble and assemble, the operation is simple, and the transformation cost is low.

[0045] The above examples are only for illustrating the technical concept and characteristics of the present application, and the purpose is to enable those skilled in the art to understand the content of the present application and to implement it, and cannot limit the protection scope of the present application. Any equivalent changes or modifications made according to the spirit and essence of the present application shall be covered within the protection scope of the present application.

Claims

1. A thread cutting mechanism for cutting a thread passing through a needle hole in a needle plate, the thread cutting mechanism comprising a moving knife holder, a moving knife and a fixed knife located on one side of the needle hole, the moving knife having a top wall with an obliquely extending blade face, characterized in that: the fixed knife is located above the moving knife, the fixed knife comprising a handle portion away from the needle hole and a blade portion close to the needle hole, the handle portion being detachably attached to a bottom wall of the needle plate, the blade portion obliquely extending from the bottom wall of the needle plate to directly below the needle hole, the blade portion gradually decreasing in thickness in the direction of its extension, an end surface of the blade portion close to the needle hole being perpendicular to the horizontal plane, a lower edge of the end surface being a set of lowest points of the blade portion and forming a cutting edge parallel to the horizontal plane, the cutting edge perpendicularly cutting the thread by contacting the highest points of the blade face; the handle portion is embedded in a positioning groove provided in the bottom wall of the needle plate, an opening of the positioning groove being higher than a lower surface of the handle portion; the fixed knife further comprises a connecting portion for connecting the handle portion and the blade portion, the connecting portion gradually increasing in thickness from the handle portion to the blade portion; the needle hole passes through a top wall of the positioning groove downwardly; a groove depth of the positioning groove is less than or equal to 20% of a thickness of the needle plate; the positioning groove is an arc-shaped groove, a center of the arc-shaped groove being located on an extension line of a rotation axis of a rotating hook; a distance between the cutting edge and the needle hole is 3±0.5 mm; a thickness of the thickest part of the blade portion is 2.4-2.8 times of a thickness of the handle portion, and a thickness of the thinnest part of the blade portion is 1.1-1.3 times of the thickness of the handle portion; the thread cutting mechanism further comprises a limiting boss for limiting a position of a protrusion of the rotating hook, the limiting boss being formed by an end portion of a transverse rib plate connected to an inner wall of a needle plate holder and close to the needle hole; the thread cutting mechanism further comprises a thread clamping plate, the thread clamping plate being in a 7-shaped form, an upper end portion of the thread clamping plate being used for clamping a thread in cooperation with an upper surface of the limiting boss, and a lower end portion of the thread clamping plate being located on one side of the moving knife and connected to a longitudinally extending rib plate protruding outwardly from the needle plate holder. ​ ​ ​ 2. The thread trimming mechanism according to claim 1, characterized in that: ​ 3. The thread trimming mechanism of claim 1, wherein: ​ 4. The thread trimming mechanism of claim 1, wherein: ​ 5. The thread trimming mechanism of claim 1, wherein: ​ 6. The thread trimming mechanism of claim 1, wherein: ​ 7. The thread trimming mechanism of claim 1, wherein: ​ 8. The thread trimming mechanism of claim 7, wherein: ​

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