JP3805969B2 - Sewing machine knife drive mechanism - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sewing machine knife driving mechanism, and more particularly to a sewing machine knife capable of switching between a work of cutting a cloth edge and performing an edge stitching with a main sewing and a work of performing a main sewing without cutting the cloth edge. The drive mechanism.
[0002]
[Prior art]
Conventionally, there is a main stitch in the most basic stitch formed by a sewing machine as a stitch for stitching a plurality of fabrics and the like. The main stitch is formed by crossing the upper thread and the lower thread by scooping the upper thread passed through the needle with the sword tip of the hook that houses the lower thread when the cloth is penetrated by the vertical movement of the needle. Multiple fabrics can be joined together along the seam.
[0003]
On the other hand, there is edge stitching in order to prevent fraying of an edge of a fabric or the like that is easily frayed. Edge stitching is based on the number of threads used to form the stitches and the number of needles that move substantially perpendicular to the fabric surface. Three-needle thread edge stitching (US stitch standard Stitch type 504) and two-needle five thread stitching (US stitch standard Stitch type 516), which is commonly called interlock that combines ring stitching and edge stitching, etc. In both cases, the edge of the cloth is cut by a knife composed of an upper knife that moves up and down and a lower knife that cooperates with the knife. Thus, as in the case of edge stitching, simple edge stitching can be performed in zigzag stitching by cutting the fabric edge with a knife and performing zigzag stitching. For this reason, sewing machines in which a knife cutting function is added to the main stitch have been proposed (Japanese Utility Model Publication No. 57-90056, Japanese Utility Model Publication 57-90057, Japanese Patent Publication No. 58-31950, etc.).
[0004]
[Problems to be solved by the invention]
However, in general, it is desirable that the main sewing machine and the knife cutting mechanism be as close as possible to each other, in addition to the reason that the main sewing machine must be made small. For this reason, there is a limit to incorporating the knife cutting mechanism into the existing structure space of the main sewing machine, and this is the case for the main sewing machine that performs main sewing and cloth edge cutting at once. Realization and commercialization have been difficult due to the mechanism of the main sewing machine.
[0005]
The present invention has been made in order to solve such a conventional problem, and can incorporate a knife cutting mechanism portion into an existing structural space of a sewing machine, cut a cloth edge and perform edge stitching with main sewing. It is an object of the present invention to provide a sewing machine knife drive mechanism capable of easily switching between an operation to be performed and an operation to perform main sewing without cutting the cloth edge.
[0006]
[Means for Solving the Problems]
To achieve this object, the knife driving mechanism of the sewing machine according to the present invention cuts the cloth edge by an upper knife moving up and down via a motion conversion mechanism linked to the rotation axis of the sewing machine and a lower knife cooperating with the upper knife. A knife drive mechanism for a sewing machine that is pivotally supported by the machine frame and slidably guides the upper knife, and the motion conversion mechanism transmits power to the upper knife when the knife is operated. The scalpel drive unit is pivotally moved to the retracted position when the scalpel is inactive and is connected to the top scalpel via a clutch that shuts off power to the top scalpel, and the bottom scalpel is slidably mounted on the scalpel drive unit, Sometimes it has a positioning locking part that positions the knife driving part in the positioning recess of the needle plate with respect to the needle drop position of the needle, and the knife driving part fits the positioning locking part in the positioning recess of the needle plate when operating the knife A positioning lever is provided.
[0007]
Further, the knife driving mechanism of the sewing machine according to the present invention is a sewing machine knife that cuts the cloth edge with an upper knife that moves up and down via a motion conversion mechanism that is linked to the rotation axis of the sewing machine and a lower knife that cooperates with the upper knife. A drive mechanism, which is provided with a knife drive unit that slidably guides the upper knife in the machine frame, and the motion conversion mechanism transmits power to the upper knife when the knife is operated, and the knife drive unit is not It is connected to the upper knife through a clutch that shuts the power to the upper knife when it is in the retracted position, and the lower knife is slidably mounted on the knife drive section. On the other hand, it has a positioning locking part for positioning in the positioning recess of the needle plate, and the scanning drive part is provided with a positioning lever for fitting the positioning locking part to the positioning recess of the needle plate when the knife is operated.
[0008]
Further, the knife driving mechanism of the sewing machine of the present invention is a knife driving mechanism of a sewing machine that cuts the fabric edge by an upper knife that moves up and down and a lower knife that cooperates with the upper knife, and is pivotally supported by a machine frame. A knife drive that guides the knife in a slidable manner is provided. The knife drive transmits power to the upper knife when the knife is activated, and the knife drive is pivoted to a retracted position when the knife is not actuated to cut off power to the upper knife. The lower knife is slidably attached to the knife drive unit, and has a positioning locking part that positions the knife drive unit in the positioning recess of the needle plate with respect to the needle drop position of the needle when the knife is operated. The knife drive unit is provided with a positioning lever for fitting the positioning locking part into the positioning recess of the needle plate when the knife is operated.
[0009]
In the knife drive mechanism of the sewing machine configured as described above, the rotary motion of the rotary shaft of the sewing machine is converted into the vertical motion through the motion conversion mechanism linked to this, and with this vertical motion, the upper knife, the upper knife and The fabric edge is cut with the cooperating lower knife. In this case, the upper knife is slidably guided by the knife drive unit pivotally supported by the machine frame. The motion conversion mechanism is connected to the upper knife through a clutch.
[0010]
Further, the clutch transmits power to the upper knife when the knife of the knife drive unit is operated, and pivots the knife drive unit to the retracted position when the knife is not operated to cut power to the upper knife. At this time, after the positioning locking portion of the lower knife is removed from the positioning recess of the needle plate by the positioning lever of the knife driving portion, the knife driving portion can be pivoted to the retracted position by this positioning lever as it is.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
A preferred embodiment of the sewing machine knife driving mechanism of the present invention applied to a main sewing machine will be described below with reference to the drawings.
[0012]
As shown in FIG. 1, the main sewing machine includes a main sewing forming mechanism 100 and a knife driving mechanism 700.
[0013]
The lock stitch forming mechanism 100 of the lock stitch sewing machine has a known (well-known) structure (Japanese Patent Laid-Open Nos. 49-117148, 52-154448, 53-108547, and Japanese Patent Laid-Open No. 53-108547). 54-60052, JP 54-110049, JP 55-35676, JP 55-113490, JP 55-146190, JP 56-3091 Therefore, detailed description thereof is omitted. However, in brief, the needle 10 pierced with the upper thread 1 and the shuttle 20 having the sword tip 21 (FIG. 2) for storing the lower thread 2 and hooking the upper thread 1 are provided. The needle 10 pierced with the upper thread 1 moves up and down while drawing a locus L10 in a direction perpendicular to the needle plate 8. The sword tip 21 of the hook 20 that houses the lower thread 2 performs a horizontal rotational movement that draws a locus L20 in the same cycle as the vertical movement of the needle 10. The hook (sword tip) 20 may be not only fully rotated but also half-turned. In short, the trajectory L20 and the trajectory L10 of the needle 10 cross each other and the upper thread 1 may be moved by the sword tip 21. It is.
[0014]
Further, in the main sewing machine, linear stitching, zigzag sewing, etc. can be performed by rotating the knob NB and switching the dial DL to various sewing modes in accordance with the respective rotational positions. The main sewing forming mechanism 100 corresponding to the sewing mode is also a known (well-known) structure (Japanese Patent Laid-Open Nos. 48-50853, 49-32754, 50-73754, JP 54-4646, JP 54-6663, JP 54-120057, JP 55-16676, Japanese Utility Model 55-216, Japanese Utility Model 55-4787. Detailed description thereof will be omitted.
[0015]
The needle 10 moves up and down from a rotation shaft supported on the machine frame FR of the main sewing machine, that is, the upper shaft S1 via the motion conversion mechanism MT1. The upper shaft S1 is rotationally driven from the motor M by the timing belt TB1. The shuttle 20 is horizontally rotated through a motion conversion mechanism MT2 from a rotary shaft that is pivotally supported by the machine frame FR of the main sewing machine, that is, the lower shaft S2. The lower shaft S2 is driven to rotate by being synchronized with the upper shaft S1 by the timing belt TB2 and at a double speed (1: 2).
[0016]
The knife driving mechanism 700 of the lockstitch sewing machine, which is a feature of the present invention, moves up and down via a motion conversion mechanism 71 (FIGS. 3 and 4) linked to the rotation axis of the lockstitch sewing machine, in the illustrated example, the upper shaft S1. The cloth edge 5c of the cloth 5 (FIG. 2) is cut by the upper knife 72 and the lower knife 73 cooperating with the upper knife 72.
[0017]
A knife drive mechanism 700 of the main sewing machine is provided with a knife drive unit 710 (FIGS. 1 and 3) that is pivotally supported by the machine frame FR and guides the upper knife 72 in a slidable manner.
[0018]
The motion conversion mechanism 71 transmits power to the upper knife 72 when the knife driving unit 710 is operated, and a clutch 750 that pivots the knife driving unit 710 to a retracted position when the knife is not operated to cut off power to the upper knife 72. It is connected to the upper knife 72 via (FIG. 3).
[0019]
As shown in FIGS. 1, 3, 4, 5, and 7, the motion conversion mechanism 71 includes four links 76, 77 (78), 79, 80 that connect the upper shaft S 1 as a rotation shaft and the machine frame FR. The first four-joint rotation chain LK1, the one link 79 of the first four-joint rotation chain, and the joint N4 of the machine frame FR, and the drive portion 751 of the clutch 750 as one other link 82 And a second four-bar rotation chain LK2 consisting of 79, 81, 82 and 83. In the first four-joint rotation chain LK 1, a link 78 is fixed to the link 77, and the link 78 is connected to the link 80. The link 76 is a fixed link.
[0020]
In the embodiment shown in FIG. 4, the motion conversion mechanism 71 extracts the motion from the mechanism that drives the balance 730 up and down from the upper shaft S <b> 1 as the rotation shaft, converts the motion, and moves the upper knife 72 up and down. However, the motion conversion mechanism 71 may extract the motion from the mechanism that drives the needle 10 up and down from the upper shaft S1 as the rotation axis and convert the motion to move the upper knife 72 up and down. The balance 730 is driven up and down by the four links 76, 77 (78), 79, 80 from the upper shaft S1.
[0021]
As shown in FIG. 3, the clutch 750 includes a pin 84 formed on the other link 82 as the driving unit 751 and a long groove 702 formed on the upper knife 72 as the driven unit 701 and into which the pin 84 is fitted. The pin 84 is screwed with a nut 753 into a mounting hole 752 (FIG. 5) at the bent lower end portion of the other link 82 as the driving portion 751.
[0022]
As shown in FIG. 6, the knife drive unit 710 is provided with a long groove 702 (FIG. 3) to be fitted to the pin 84 of the drive unit 751 and an upper knife drive piece 711 to which the upper knife 72 is fixed, and the upper knife drive. A knife sliding body 712 arranged side by side with the piece 711, a lower knife mounting piece 713 arranged side by side with the knife sliding body 712 and to which the lower knife 73 is fixed, and these three parts from above are an upper knife driving piece 711, a knife sliding piece. The moving body 712 and the lower knife attaching piece 713 are configured to be slidably inserted in this order, and the upper knife 72 and the lower knife 73 are disposed so as to cut the cloth.
[0023]
The female sliding body 712 is formed with a guide groove 712a in which a convex portion 713a formed on the lower knife mounting piece 713 is fitted so as to be slidable in the axial direction of the female sliding shaft 714. A female unit base 715 is fixed for being rotatably fixed to the machine frame FR. Specifically, the upper part 715a of the female unit base 715 is fixed to the machine frame FR with a screwing member such as a screw so as to be rotatable by, for example, a caulking step pin 717. Has been. The step pin 717 is inserted from the female unit base mounting plate 716 side through a spring washer 722 such as a wave spring washer, and can be braked when the female unit base 715 is rotated. In addition, a stopper 715b is formed on the upper end of the female unit base 715, and a protrusion 716a is formed on the side of the female unit base mounting plate 716 where the female unit base 715 is disposed. The horizontal direction in which the female unit base 715 is in the retracted position. When it is rotated vertically downward from, it will not rotate any further. Further, the knife unit base 715 is bent in an L shape so as to cover two predetermined adjacent surfaces of the knife sliding body 712 and the lower knife mounting piece 713. The female sliding body 712 is fixed to the female sliding shaft 714 with a screwing member such as a screw.
[0024]
The lower knife mounting piece 713 has a groove 713b and is engaged with a positioning lever 718 loosely fitted in a slit 715c formed in a bent portion of a knife unit base 715 fixed to the knife sliding body 712. ing. Specifically, the positioning lever 718 is formed with a half-pressing convex portion 718 a as a rotation shaft serving as a fulcrum, and is pivotally supported by a pivoting hole 715 d drilled in the female unit base 715. Further, at one end of the positioning lever 718, a convex portion 718b serving as a load point is formed and engaged with the groove portion 713b of the lower knife mounting piece 713. Accordingly, since the positioning lever 718 is gripped between the knife unit base 715 and the lower knife mounting piece 713, the operation portion 718 c formed at the other end that is the power point of the positioning lever 718 is operated upward. When the rotary knife is rotated, the lower knife mounting piece 713 is lowered while sliding the knife sliding shaft 714. When the operating portion 718c is operated downward to rotate, the lower knife mounting piece 713 causes the knife sliding shaft 714 to move. It will rise while sliding. A concave portion 718c for stopper is formed on the back surface of the convex portion 718b of the positioning lever 718. When the positioning lever 718 is operated upward so that the lower knife 73 is lowered to a predetermined position, it protrudes from the female unit base 715. The stopper convex portion 715e is fitted.
[0025]
As shown in FIGS. 9 and 10, the lower knife 73 fixed to the lower end 713 c of the lower knife mounting piece 713 has a needle plate for moving the knife drive unit 710 with respect to the needle drop position PS of the needle 10 when the knife is operated. 8 has a positioning locking portion 87 for positioning in the positioning recess 86a of the positioning plate 86. The positioning plate 86 in which the positioning recess 86a is formed is configured to be adjustable in position to the left and right so that the sewing width W can be varied with respect to the needle drop position PS. That is, the positioning plate 86 is incorporated in the recess 8a provided in the needle plate 8 so as to be adjustable in the lateral direction so as to be variable in the sewing width W direction, and is fixed by screws or the like after positioning.
[0026]
On the other hand, the upper knife driving piece 711 has a groove portion 711a, and an upper knife spring plate 719 is fitted into the groove portion 711a and fixed by a screwing member 720 such as a screw. The upper knife spring plate 719 is formed in such a length as to extend from the upper knife drive piece 711 and is slidably fitted in the guide groove 712 a of the knife sliding body 712. An upper knife 72 is fixed to a portion 719 a extending from the upper knife driving piece 711 of the upper knife spring plate 719 by a screwing member 721 such as a screw. The extension portion 719 a of the upper knife spring plate 719 is bent so that the upper knife 72 can be pressed against the lower knife 73 by positively applying the elastic force of the upper knife spring plate 719.
[0027]
In the main sewing machine configured as described above, when the edge of the cloth is cut and the edge stitching is performed by the main sewing, the positioning lever 718 of the knife driving unit 710 is lowered to a predetermined position as shown in FIG. When the lower knife 73 is in the non-operating state in which the lower knife 73 is retracted to the retracted position by the lower knife mounting piece 713, the positioning lever 718 is operated upward as shown in FIG. As a result, the lower knife 73 fixed to the lower knife mounting piece 713 having the groove 713b into which the convex portion 718b of the positioning lever 718 is fitted is lowered, and the positioning locking portion 87 of the lower knife 73 is moved to the needle. A knife operating state (FIG. 9) in which the knife driving unit 710 is positioned with respect to the needle drop position PS of the needle 10 by being fitted into the positioning recess 86 a of the positioning plate 86 of the plate 8. At this time, the stopper convex portion 715e protruding from the female unit base 715 is fitted into the stopper concave portion 718c formed in the positioning lever 718 in a state where it can be detached with a predetermined force. Can be prevented.
[0028]
In this operating state of the knife, as shown in FIG. 2, the needle 10 pierced with the upper thread 1 moves up and down with a locus L10 in a direction perpendicular to the needle plate 8 as the upper shaft S1 rotates. The main sewing is the same as in the conventional main sewing, when the upper thread 1 pierced by the needle 10 penetrates the cloth 5 following the vertical movement of the needle 10 and then the needle 10 starts to rise from the bottom dead center. As the lower shaft S2 is synchronized with the upper shaft S1 at the point, the sword tip 21 of the shuttle 20 beats the upper thread 1 so that the upper thread 1 and the lower thread 2 cross each other, and the needle 10 and the balance 730 return further upward (see FIG. When the upper thread 1 is pulled up by 4), the lower thread 2 is pulled up to form the stitches 1a and 2a parallel to the cloth surface on the upper and lower surfaces 5a and 5b of the cloth 5 to be sewn, for example. At the same time, a cross stitch is formed in the vertical direction of the cloth 5 in the vicinity of the center in the thickness direction so as to penetrate the cloth 5 and the above operation is repeated for each cloth feed, thereby performing continuous main sewing. It is formed.
[0029]
The rotary motion of the rotary shaft of the sewing machine, in the illustrated example, the rotary motion of the upper shaft S1 is converted into a vertical motion through a motion conversion mechanism 71 (FIGS. 1, 3, 4, and 7) linked thereto. That is, when the upper shaft S1 rotates, the links 77 and 78 of the first four-joint rotation chain LK1 are used as a crank, the link 80 is used as a connecting rod, and the link 79 is used as a rocker arm. As the link 79 swings, the link 81 of the second four-joint rotation chain LK2 swings, and the link 82, and hence the drive unit 751 of the clutch 750, moves up and down. The movement trajectory of the link 82 draws an elliptical trajectory by the four-joint rotation chain mechanism LK1, LK2, and draws an approximate straight line trajectory in the vertical direction at the suburb PL point of the drive unit 751, and a guide plate 755 fixed to the machine frame FR. The guide pin 754 that passes through the guide elongated hole 755a and is fixed to the PL point of the link 82 supports the reaction from the female drive unit 74. As a result, the drive unit 751 is restricted from moving in the lateral direction, and only the vertical movement is obtained with the stroke t (FIG. 4) for one rotation of the upper shaft S1.
[0030]
The vertically moving motion converted by the motion converting mechanism 71 is passed through a long groove 702 into which the pin 84 of the driving portion 751 of the clutch 750 and the pin 84 of the upper knife driving piece 711 as the driven portion 701 are fitted. Is transmitted to the upper knife 72. The knife operating state in which the positioning locking portion 87 of the lower knife 73 is fitted into the positioning recess 86a of the positioning plate 86 of the needle plate 8 to position the knife driving portion 710 with respect to the needle drop position PS of the needle 10. In FIG. 9, the upper knife 72 is slidable by the guide groove 712 a of the knife sliding body 712 via the upper knife spring plate 719 by the upper knife drive piece 711 pivotally supported by the machine frame FR. Be guided to. In this knife operating state, the knife driving unit 710 is maintained in a vertical state around the step pin 16, and the longitudinal direction of the long groove 702 is oriented in the horizontal direction, so the pin 84 of the driving unit 751 of the clutch 750 and the driven unit 701. The long groove 702 is transmitted with power and transmits power to the upper knife 72 when the knife driving unit 710 operates, and the cloth edge 5c of the cloth 5 is caused by the upper knife 72 and the lower knife 73 cooperating with the upper knife by this vertical movement. Disconnect.
[0031]
By cutting the cloth edge 5c of the cloth 5 and performing zigzag sewing or the like in this manner, the edge over stitching work can be performed in the same manner.
[0032]
Now, when the knife is in an inoperative state where it is desired to perform only the main sewing without cutting the cloth edge 5c of the cloth 5, the positioning lever 718 is operated downward as shown in FIGS. Accordingly, the lower knife 73 fixed to the lower knife mounting piece 713 is raised, and the positioning locking portion 87 of the lower knife 73 is fitted in the positioning recess 86a of the positioning plate 86 of the needle plate 8. Release from the state. The positioning lever 718 directly pivots the knife driving unit 710 around the step pin 717 to the horizontal retracted position, so that the longitudinal direction of the long groove 702 faces the vertical direction, so that the driving unit 751 of the clutch 750 The pin 84 only floats in the long groove 702 of the driven portion 701 and interrupts the power to the upper knife 72. When the knife driving unit 710 is pivoted, a screw 723 having a pan-shaped head fixing the knife sliding body 712 to the knife unit table 715 collides with the knife unit table mounting plate 716, and the knife unit table 715. Is moved over the female unit base mounting plate 716 while being inclined by the buffering action of the spring washer 722 for braking, and is fitted into the recess 716b formed in the female unit base mounting plate 716. Thereby, since the knife drive part 710 is semi-fixed, it can prevent falling down by the vibration of a sewing machine, etc.
[0033]
In this way, only the main sewing is performed without cutting the cloth edge 5c of the cloth 5 by a simple operation by the positioning lever 718 for pivoting the knife driving part 710 from the vertical knife operating position to the horizontal knife retracting position. It is possible to switch to the work to perform.
[0034]
In addition, the knife drive part of the knife drive mechanism of the sewing machine of the present invention is not limited to the one described above, and the positioning is such that the lower knife is slidably mounted and the positioning locking part is fitted into the positioning recess of the needle plate when the knife is operated. Any structure can be used as long as the lever can be provided.
[0035]
In addition, according to the preferred embodiment in which the knife drive mechanism of the sewing machine of the present invention is applied to a lockstitch sewing machine, a horizontal hook that rotates horizontally is used. When the needle is raised from the bottom dead center, the upper thread and the lower thread can be crossed to form a main stitch consisting of a seam parallel to the surface of the workpiece and a vertical seam. Such a hook may be used.
[0036]
【The invention's effect】
As can be seen from the above embodiments, according to the knife driving mechanism of the sewing machine of the present invention, the knife cutting mechanism portion can be incorporated into the existing structure space of the sewing machine, the cloth edge is cut and the edge stitching is performed by the main sewing. The operation of performing the sewing and the operation of performing the main sewing without cutting the cloth edge can be switched and executed.
[Brief description of the drawings]
FIG. 1 is a perspective view showing an embodiment of a lockstitch sewing machine to which a sewing machine knife driving mechanism of the invention is applied.
FIGS. 2A and 2B are explanatory views simply showing the operation of a lockstitch sewing machine to which the knife driving mechanism of the sewing machine of the present invention is applied.
FIG. 3 is a perspective view showing a motion conversion mechanism and a knife drive unit in the knife drive mechanism of the sewing machine of the present invention.
FIGS. 4A and 4B are explanatory views showing an operation state of a motion conversion mechanism in the knife drive mechanism of the sewing machine according to the present invention. FIGS.
FIG. 5 is an exploded perspective view showing a motion conversion mechanism in the knife drive mechanism of the sewing machine of the present invention.
FIG. 6 is an exploded perspective view showing a knife driving portion in the knife driving mechanism of the sewing machine of the present invention.
FIG. 7 is an explanatory view showing the operation of the motion conversion mechanism in the knife drive mechanism of the sewing machine of the present invention.
FIG. 8 is an explanatory view showing the operation of the knife drive unit in the knife drive mechanism of the sewing machine of the present invention.
FIG. 9 is a perspective view showing a knife operating state in the knife drive mechanism of the sewing machine of the present invention.
FIG. 10 is a perspective view showing a state where the knife is not operated in the knife drive mechanism of the sewing machine according to the present invention.
[Explanation of symbols]
5c: Cloth edge 8: Needle plate 10: Needle S1: Rotating shaft of the sewing machine (upper shaft as rotating shaft)
71 ... Motion conversion mechanism 72 ... Upper knife 73 ... Lower knife 86a ... Positioning recess 87 ... Positioning locking part FR ... Machine frame PS ... Needle drop position 700 ... Sewing knife drive mechanism 710 ... knife drive 718 ... positioning lever 750 ... clutch

Claims (3)

A sewing machine knife driving mechanism that cuts a cloth edge with an upper knife that moves up and down via a motion conversion mechanism that is linked to the rotation axis of the sewing machine, and a lower knife that cooperates with the upper knife,
Provided with a knife drive that is pivotally supported by the machine frame and slidably guides the upper knife,
The motion conversion mechanism is configured to transmit power to the upper knife when the knife driving unit is operated, and through a clutch that pivots the knife driving unit to a retracted position when the knife is not operated and cuts power to the upper knife. Connected to the upper knife,
The lower knife is slidably attached to the knife driving part, and has a positioning locking part for positioning the knife driving part in a positioning recess of a needle plate with respect to a needle drop position of the needle when the knife is operated,
The knife driving mechanism of the sewing machine, wherein the knife driving portion includes a positioning lever that fits the positioning locking portion into a positioning recess of the needle plate when the knife is operated. A sewing machine knife driving mechanism for cutting a cloth edge with an upper knife moving up and down via a motion conversion mechanism linked to a rotation axis of the sewing machine and a lower knife cooperating with the upper knife,
A knife drive unit is provided on the machine frame to guide the upper knife in a slidable manner.
The motion conversion mechanism transmits power to the upper knife when the knife drive unit is operated, and places the knife drive unit in a retracted position when the knife is not operated via a clutch that cuts power to the upper knife. Connected to
The lower knife is slidably attached to the knife driving part, and has a positioning locking part that positions the knife driving part in a positioning recess of a needle plate with respect to a needle drop position of the needle when the knife is operated,
The knife driving mechanism of the sewing machine, wherein the knife driving portion includes a positioning lever that fits the positioning locking portion into a positioning recess of the needle plate when the knife is operated. A knife drive mechanism for a sewing machine that cuts a cloth edge with an upper knife that moves up and down and a lower knife that cooperates with the upper knife,
Provided with a knife drive that is pivotally supported by the machine frame and slidably guides the upper knife,
The clutch is configured to transmit power to the upper knife when the knife is operated, and to pivot the knife driver to a retracted position when the knife is not operated to cut power to the upper knife.
The lower knife is slidably attached to the knife driving part, and has a positioning locking part for positioning the knife driving part in a positioning recess of a needle plate with respect to a needle drop position of the needle when the knife is operated,
The knife driving mechanism of the sewing machine, wherein the knife driving portion includes a positioning lever that fits the positioning locking portion into a positioning recess of the needle plate when the knife is operated.

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