JPH05192479A - Thread cutter for dual chain-stitch sewing machine - Google Patents

Abstract

PURPOSE:To provide the title cutter which facilitates the adjusting work thereof by varying the position of a lower knife to a looper without shifting the relative positional relation between e lower knife and an upper knife, in the title cutter. CONSTITUTION:A lower knife lever 64, on which a lower knife 65 is fixed, and an upper knife lever 62, on which an upper knife 63 is fixed, are rotatably connected to a cylindrical pivotally-supportable member 86. This member 86 is rotatably fastened on a base plate 61, at a position eccentric to the center of a cylindrical shaft part. The position of the lower knife 65 to a looper 54 is varied by turning and adjusting the member 86, without shifting the positional relation between the lower knife 65 and the upper knife 63.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thread trimming device for a double chain stitch sewing machine, and more particularly to adjusting the position of a lower knife and an upper knife provided on the thread trimming device in a direction orthogonal to the moving direction of the looper with respect to the looper. Regarding the simplification of.

[0002]

2. Description of the Related Art Conventionally, a double chain stitch sewing machine capable of decorative stitching on a work cloth using a looper and one or a plurality of sewing needles, and a lower thread of a looper at the end of decorative stitching in this double chain stitch sewing machine A thread cutting mechanism for cutting the needle thread of a sewing needle is well known. For example, in Japanese Examined Patent Publication No. 61-9080, a pair of curved guide slits are formed immediately below the needle plate, and a slide plate to which a thread holder is attached is arranged parallel to the driving direction of the looper. Further, a carrier having a cutter positioned above the thread holder and a thread clip positioned below the thread holder is arranged in parallel with the thread holder, and the slide plate is moved toward the looper by the rotation of the drive lever. There is described a thread cutting device in which the needle thread is engaged with the thread holder by cutting the needle thread and the needle thread is cut by the cutter while the slide plate is moving to the standby position.

By the way, the inventor of the present application attaches a lower knife having a first hook that engages the lower thread of the looper and a second hook that engages the needle thread of the sewing needle to the lower knife lever, and at the same time, attaches both threads. The upper knife for cutting is attached to the upper knife lever, and the rotation fulcrums of both knife levers are rotatably supported at the same position on the base plate provided on the sewing machine bed, and the thread trimmer drive means waits for the lower knife lever. By reciprocally rotating the position and the lower knife between the working position where the lower knife engages the needle thread and the lower thread, and reciprocally rotating the upper knife lever between the standby position and the thread cutting position, When the female lever is rotated to the operating position, the lower thread and the needle thread engaged with the looper are engaged with the lower knife, and then the lower knife is engaged with the lower knife while rotating to the standby position. Thread The thread cutting apparatus adapted to cut with a scalpel on the cross-sectional position and commercialized.

[0004]

Generally, in this type of thread cutting device, when the lower knife lever moves to the operating position, the lower knife and the needle thread are reliably engaged with the lower knife. In addition, it is necessary to accurately adjust the position of the lower knife in the direction orthogonal to the movement direction of the looper with respect to the looper (hereinafter referred to as the movement orthogonal direction of the looper).
Further, in order to surely cut the lower thread and the needle thread engaged with the lower knife by the upper knife, it is necessary to accurately adjust the position of the upper knife of the thread cutting position to the regular position with respect to the lower knife.

However, in the thread trimming device considered by the inventor of the present application, the upper knife lever and the lower knife lever are rotatably supported by the base plate, and both knife levers are rotated by the thread trimming drive means. Since the needle thread and the bobbin thread engaged with the lower knife are cut, the positional relationship between the upper knife and the lower knife was adjusted to be a normal positional relationship before the thread trimming device was incorporated into the sewing machine. In this state, even if the upper knife is attached to the upper knife lever and the lower knife is also attached to the lower knife lever, the position of the lower knife when the lower knife lever is rotated to the working position when the thread trimming device is installed in the sewing machine If the position of the lower knife is displaced in the direction orthogonal to the movement of the looper, the lower knife must be adjusted in the direction orthogonal to the movement of the looper, and at the same time, the upper knife must be adjusted to the lower knife. Since the position must be adjusted again according to the position change, the position adjustment work of the upper knife and the lower knife with respect to the position of the looper becomes very complicated, and a lot of time is required for this adjustment work. is there.

An object of the present invention is to cut the thread of a double chain stitch sewing machine such that the position adjustment of the lower knife and the upper knife provided on the thread trimming device relative to the looper in a direction orthogonal to the moving direction of the looper can be simplified. To provide a device.

[0007]

A thread trimming device for a double chain stitch sewing machine according to the present invention comprises a needle bar having a lower end to which a sewing needle can be attached, and a needle bar drive mechanism for vertically reciprocating the needle bar.
A double chain stitch sewing machine including a looper for engaging a lower thread with a needle thread, and a looper drive mechanism for reciprocally driving the looper in a direction orthogonal to the cloth feed direction in synchronization with the vertical movement of the needle bar. In the thread cutting device for cutting the bobbin thread and the needle thread when the looper is in the engagement position where the looper is engaged with the needle thread, the first hook engaging the bobbin thread and the second hook engaging the needle thread are provided. A lower knife having a lower knife, a lower knife lever fixed to the lower knife, an upper knife for cutting the threads engaged with the first and second hooks in cooperation with the lower knife, and the upper knife fixed An upper knife lever, a base plate for pivotally supporting the lower knife lever and the upper knife lever respectively, and a standby position of the lower knife lever and an operation position where the lower knife engages the needle thread and the bobbin thread. Rotate back and forth and move the upper female lever to its standby position. A drive means for reciprocally rotating over the disconnection position, and a pivot mechanism for pivotally supporting the rotation fulcrum of the lower knife lever and the rotation fulcrum of the upper knife lever on the base plate, and the position of the lower knife in the operating position of the lower knife lever. Is provided with a pivotal support mechanism for pivotally supporting the lower knife and the upper knife so as to be positionally adjusted in at least a direction orthogonal to the moving direction of the looper in a state where the lower knife and the upper knife are held in a predetermined positional relationship.

[0008]

In the thread trimmer for a double chainstitch sewing machine according to the present invention, the rotation fulcrum of the lower knife lever to which the lower knife is fixed and the rotation fulcrum of the upper knife lever to which the upper knife is fixed are connected to the base plate by a pivot mechanism. Since each is rotatably supported, the position of the lower knife in the operating position of the lower knife lever via this pivot mechanism, at least with the lower knife and the upper knife held in a predetermined positional relationship, The position can be easily adjusted so that the looper is in a normal position in a direction orthogonal to the moving direction of the looper. Moreover, since the lower knife and the upper knife are held in a predetermined positional relationship, the position adjustment of the upper knife with respect to the lower knife can be omitted only by adjusting the position of the lower knife.

When the sewing needle is at the uppermost position and the looper is in the engagement position where the looper is engaged with the needle thread, the lower knife lever is actuated by the driving means from its standby position to the needle thread and the lower thread. The upper knife lever is rotated from its standby position to the cutting position, and at this time, the lower thread is engaged with the first hook of the lower knife and the needle thread is engaged with the second hook. Further, while the lower knife lever is being rotated to the standby position by the driving means, the threads engaged with the first and second hooks are cut in cooperation with the lower knife in the cutting position. After that, the lower knife lever and the upper knife lever are rotated to the standby positions by the driving means.

[0010]

According to the thread trimming device of the double chainstitch sewing machine of the present invention, as explained in the section [Operation], the thread trimming device has the lower knife lever to which the lower knife is fixed and the upper knife. Since the fixed upper knife lever, the drive means for pivoting the both knife levers back and forth and the pivotal support mechanism are provided, the lower knife lever and the upper knife lever are pivoted reciprocally by the driving means, and the bobbin thread engaged with the lower knife Also, the needle thread can be reliably cut.

Further, since the pivotal support mechanism is provided, the position of the lower knife in the operating position of the lower knife lever can be easily and accurately adjusted to the normal position with respect to the position of the looper through this pivotal support mechanism. Moreover, since the lower knife and the upper knife are held in a predetermined positional relationship, the position adjustment of the upper knife with respect to the lower knife can be omitted only by adjusting the position of the lower knife, and the upper knife with respect to the position of the looper can be omitted. The position adjustment work of the knife and the lower knife can be greatly simplified.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. The present embodiment is a case where the present invention is applied to a thread cutting device provided in a decorative sewing machine as a double chain stitch sewing machine. As shown in FIGS. 1 to 9, the decorative sewing machine 1 includes a sewing machine bed portion 2, a pedestal portion 3 erected from the right end portion of the bed portion 2, and the pedestal portion 3 to the bed portion 2.
The bed portion 2 includes an arm portion 4 that extends to the left so as to face the feed tooth. ), The looper drive mechanism 40 for reciprocating the looper 54 in the direction orthogonal to the cloth feed direction, the looper 5
4, a thread cutting device 60 for cutting the needle thread 13 of the sewing needle 11 and the like, and the arm portion 4 are provided with three sewing needles 1
1, a needle bar drive mechanism for vertically moving a needle bar 9 that can be attached to the lower end, a balance drive mechanism (not shown) for vertically moving the balance in synchronization with the vertical movement of the needle bar 9, and a thread cutting device 60 for cutting. A needle thread wiping / holding mechanism 20 for wiping the needle thread 13 above the presser foot 8 and holding the thread end portion of the needle thread 13 is provided.

Since the needle bar drive mechanism is similar to that of a normal sewing machine, a brief explanation will be given without showing it. One end of a connecting lever is attached to a needle bar crank fixed to an upper shaft which is rotationally driven by a sewing machine motor. It is rotatably connected, and the other end of the connecting lever is connected to the needle bar 9 via the needle bar holder, and the needle bar 9 is reciprocally driven up and down via the connecting lever by the rotation of the needle bar crank. A needle mount 10 is fixed to the lower end of the needle bar 9 as shown in FIG.
Three sewing needles 11 are removably attached at a predetermined interval in a direction orthogonal to the cloth feed direction. However, as shown in FIG. 2, the tip of the left sewing needle 11 is lower than the tip of the central sewing needle 11 by a predetermined dimension, and the tip of the right sewing needle 11 is higher than the tip of the central sewing needle 11 by a predetermined dimension. .. Incidentally, reference numeral 12 is a hole.

Next, the thread wiping and holding mechanism 20 will be described with reference to FIGS. 2 to 5. The sewing machine frame 21 of the head 5 of the arm 4 is provided with a fixed plate 22 having a substantially crank shape in a front view. A rotary solenoid (hereinafter, simply referred to as a solenoid) 24 is fixed to the rear surface of the right end portion of the fixing plate 22 by a screw 23, and a thread wiping lever 25 is pivotally mounted on the left end portion thereof with a screw 26. Supported, thread wiper lever 2
The base end of the thread wiping member 27 is fixed to the other end of the screw 5 with a screw 28. Further, a rotary plate 30 is fixed to a drive shaft 29 of the solenoid 24, and the right end portion of a thread wiping link 31 arranged in the left-right direction is rotatably supported by a screw 32 on the rotary plate 30. At the same time, its left end is rotatably supported at one end of the thread wiping lever 25 by a screw 33. However, the rotating plate 30 is always biased in the clockwise direction in FIG. 2 by a winding spring (not shown) incorporated in the solenoid 24.

The tip of the thread wiping member 27 is shown in FIGS.
As shown in FIG. 5, a hook portion 27a having a guide groove 34 and an engagement hole 35 is formed, and the needle thread 13 extending downward from the eyelet 12 can be engaged with the hook portion 27a.
The thread gripping spring 36 made of a thin plate-shaped spring member is fixed to the fixing plate 22 with a screw 37 at the base end thereof, and the hook portion 2 of the thread wiping member 27 is provided near the tip of the thread gripping spring 36.
In order to hold the needle thread 13 in cooperation with 7a, an upwardly curved thread holding portion 36a is formed, and a hook portion 27a is engaged with the tip end portion on the sewing needle 11 side of the thread holding portion 36a. V-shaped guide portion 36 for guiding the needle thread 13 hanging downward
b is integrally formed.

Therefore, when the solenoid 24 is not driven, the rotary plate 30 and the thread wiping link 31 are positioned at the standby position shown by the solid line in FIG.
The hook portion 27a of the thread wiping member 27 is located at a thread holding position shown by a solid line on a substantially lateral side of the sewing needle 11 in the needle up stop state. When the solenoid 24 is driven after the needle thread 13 is cut by the thread cutting device 60 described later, the rotating plate 30
Is rotated to the rotation position shown by the chain double-dashed line, so that the thread wiping member 27 is moved through the thread wiping link 31 and the thread wiping lever 25.
Since it is swung to the position shown by the dotted line, the hook portion 27
a moves to the thread catching position near the bottom of the sewing needle 11 and
The needle thread end portion 13a extending downward from 2 is engaged (see FIG. 3).

After that, when the driving of the solenoid 24 is stopped, the hook portion 27a returns to the thread holding position with the needle thread end portion 13a engaged. At this time, the hook portion 2
The needle thread end portion 13a hanging downward from 7a is connected to the thread holding portion 36a.
Since the guide portion 36a closer to the sewing needle 11 than b is restricted to a narrow V-shaped range, the hook portion 27a and the thread holding portion 36 are
Securely held in cooperation with a. Reference numeral 14 is a presser bar to which the presser foot 8 is detachably attached at the lower end, reference numeral 15 is a needle plate, and reference numeral W is a work cloth.

Next, the looper drive mechanism 40 for driving the looper 54 in the direction orthogonal to the cloth feeding direction will be described with reference to FIG.
It will be explained based on. The lower shaft 41, which is arranged in the bed 2 in the left-right direction and is driven to rotate by a sewing machine motor in synchronization with the rotation of the upper shaft, has a front end portion of a connecting rod 43 extending in the front-rear direction via an eccentric cam 42. And a rear end portion of the connecting rod 43 is pivotally connected to a pivot arm 45 fixed to a pivot shaft 44 arranged in parallel with the lower shaft 41. On the other hand, the looper actuating shaft 46, which is disposed orthogonal to the lower shaft 41 and to which the looper mounting member 53 is fixed, is supported by the machine frame 21 so as to be rotatable and movable in the front-rear direction.

On the looper actuating shaft 46, an engaging body 47 having an engaging groove is rotatably and immovably supported in the front-rear direction, and an engaging piece 49 engaging with the engaging groove is rotatable. It is rotatably attached to the tip of a rotating arm 48 attached to the shaft 44. Further, the upper end of the swing arm 50 which is arranged in the vertical direction and rotates the looper actuating shaft 46 is rotatably fitted to the eccentric cam 51 fixed to the left end of the lower shaft 41, and the lower end thereof. The ball shaft portion 52a of the rotating arm 52 fixed to the looper actuating shaft 46 is fitted and connected to the portion. The base end of a looper 54, which is substantially U-shaped when viewed from the front, is attached to the looper attachment member 53 via a rod 54a.

Therefore, when the lower shaft 41 is rotated by the sewing machine motor, the connecting rod 43 reciprocates in the front-rear direction via the eccentric cam 42, and the pivot shaft 44 reciprocally pivots via the swing arm 45. The looper actuating shaft 46 is reciprocally moved in the front-rear direction through the engagement of the rotating arm 48, the engaging piece 49, and the engaging groove. On the other hand, the rotation of the lower shaft 41 causes the swing arm 5 to move.
Since 0 reciprocates in the substantially vertical direction via the eccentric cam 51, the looper operating shaft 46 is reciprocally pivoted via the pivot arm 52. As a result, the tip portion of the looper 54 is reciprocally moved in a direction orthogonal to the cloth feed direction in proportion to the amount of rotation of the looper operating shaft 46, and reciprocating motion corresponding to the amount of movement of the looper operating shaft 46 in the front-rear direction causes three movements. An elliptical locus is drawn so that the needle thread 13 of the book can be engaged.

Next, the thread cutting device 60 arranged in the bed portion 2 immediately above the looper drive mechanism 40 will be described with reference to FIGS. 7 to 9. A base plate 61 is horizontally arranged in the bed portion 2 and is screwed to a plurality of boss portions provided on the machine frame 21. This base plate 6
1, an upper knife lever 62 having a substantially fan shape in plan view and a lower knife lever 64 having a substantially crank shape are rotatably supported by a pivot mechanism 85 described later. An upper knife 63 is fixed to the protruding portion 62a of the upper knife lever 62. To the lower knife lever 64, a base end of a curved lower knife 65 having a first hook 65a and a second hook 65b formed at its tip is fixed, and a drive connecting rod 66 extending substantially in the left-right direction.
The left end portion of is rotatably connected with a screw 67. The right end portion of the drive connecting rod 66 is the operating shaft 7 of the thread trimming drive mechanism 70.
1 is rotatably connected with a screw 68. A stroke adjusting portion 66a using a turnbuckle is provided at a part of the drive connecting rod 66, and the length of the drive connecting rod 66 can be adjusted by the stroke adjusting portion 66a.

Next, the thread trimming drive mechanism 70 will be described. The operating shaft 71 extending in the left-right direction is supported by a support member 72 attached to the machine frame 21 and having a U-shape in plan view so as to be movable in the left-right direction. An operating lever 73 and a spring receiving member 74 are screw-fastened to the operating shaft 71 located inside the support member 72 with the operating shaft 71 inserted through the operating lever 71 and the spring receiving member 74, respectively. A compression spring 75 is externally mounted on the operating shaft 71. Therefore, the actuating shaft 71 and the actuating lever 73 are always elastically biased to the left (the direction of arrow B) by the spring force of the compression spring 75. Further, the actuating lever 73 is connected to a plunger 77 of a thread cutting solenoid 76 disposed in the left and right direction on the rear side of the machine frame 21, and the thread cutting solenoid 76 is attached to a mounting plate 78 fixed to the machine frame 21. Installed on.

Therefore, when the thread cutting solenoid 76 is not driven, the operating lever 73 and the operating shaft 71 are located at the standby position shown by the solid line, so that the lower female lever 64 is placed at the standby position shown by the solid line via the drive connecting rod 66. Is located in. When the thread trimming solenoid 76 is driven, the operating lever 73 and the operating shaft 71 move in the direction of arrow A and are positioned at the operating position indicated by the chain double-dashed line, so that the lower female lever 64 simultaneously moves through the drive connecting rod 66. The lower knife 65 is rotated clockwise as indicated by the dotted chain line, and the lower knife 65 has its distal end positioned immediately above the looper 54 (see FIG. 8).
Rotate clockwise until. At this time, the first hook 6
The lower thread 55 of the looper 54 is engaged with 5a, and the needle thread 13 is engaged with the second hook 65b.

After that, when the thread trimming solenoid 76 is no longer driven, the operating lever 73 and the operating shaft 71 move and return to the standby position in the direction of arrow B by the spring force of the compression spring 75, and at the same time, the lower female lever 64 moves to the standby position. Turn to. During rotation of the lower knife lever 64 to the standby position, the lower thread 55 engaged with the first hook 65a and the needle thread 13 engaged with the second hook 65b are sequentially cut by the upper knife 63. Here, on the lower surface of the upper knife 63,
As shown in FIGS. 7 and 8, a thread holding spring 79 that abuts from below is fixed to the lower surface of the lower knife 65, and only the lower thread 55 cut by the upper knife 63 and the lower knife 65 and this thread holding spring 79. Held by.

By the way, a circular contact member 80 which contacts the lower female lever 64 is screwed to the upper female lever 62, and the spring receiving portion 62b of the upper female lever 62 and the base plate 61 are linearly bent a plurality of times. The spring 81 is stretched, and the upper female lever 62 is always elastically biased in the clockwise direction by the spring force of the spring 81. Further, in order to regulate the amount of clockwise rotation of the upper female lever 62,
The engaging portion 62c of the upper female lever 62 comes into contact with an engaging portion of a stopper member 82 having a crank shape in a side view which is screwed to the base plate 61.

That is, when the lower knife lever 64 is at the standby position, the upper knife lever 62 is located at the standby position shown by the solid line against the spring force of the spring 81 due to the contact between the contact member 80 and the lower knife lever 64. There is. At this time, the engaging portion 62c
A gap of a predetermined amount is provided between and the locking portion of the stopper member 82. Then, as the lower knife lever 64 rotates to the operating position, the upper knife lever 62 also rotates in the clockwise direction at the same time, but when the engaging portion 62c abuts on the locking portion of the stopper member 82, The rotation of the female lever 62 is restricted at the cutting position indicated by the chain double-dashed line. Further, when the lower knife lever 64 returns to the standby position, the upper knife lever 62 is rotated and returned to the standby position in synchronization with the lower knife lever 64 from the time when the lower knife lever 64 and the contact member 80 abut.

Next, the upper female lever 62 and the lower female lever 6
A pivoting mechanism 85 for pivotally supporting 4 and 4 on the base plate 61 will be described with reference to FIGS. 7 and 9. Shaft holes 62d and 64a are formed at the rotation fulcrum of the upper knife lever 62 and the rotation fulcrum of the lower knife lever 64, respectively.
A cylindrical pivot member 86 having a collar portion is inserted into the d · 64a from above. A screw hole 86a is vertically formed at a position deviated from the center of the cylinder in the pivot member 86, and the pivot member 86 is screwed to the base plate 61 with a screw 87 inserted through the screw hole 86a. .. That is, the female levers 62 and 64 are pivotally supported by the base plate 61 via the pivotally supporting member 86.

Therefore, first, by loosening the screw 87 and rotating the pivot member 86 in the clockwise direction or the counterclockwise direction, the pivot fulcrums of both the female levers 62 and 64 are synchronized with the screw 87. Eccentric movement is performed integrally. That is, with the lower knife 65 and the upper knife 63 held in a predetermined positional relationship, the position of the lower knife 65 at the position where the lower knife lever 64 operates is in a direction including a direction orthogonal to the moving direction of the looper 54. The position is adjustable.

By the way, reference numeral 90 denotes a lower thread feeding mechanism for feeding a predetermined amount of the lower thread 55 from the thread spool at the time of thread cutting so that the lower thread 55 does not come off from the looper 54 at the start of sewing. Since it is not directly related to the invention, its explanation is omitted.

Next, the operation of adjusting the position of the lower knife 65 in the front-rear direction with respect to the looper 54 at the operating position will be described with reference to FIGS. In advance, the lower knife lever 64 and the upper knife lever 62 are assembled to the base plate 61 by the pivot support mechanism 85, and the stopper member 8
2, the contact member 80 and the spring 81 are assembled, and the lower knife 6
The lower knife 65 is fixed to the lower knife lever 64, and the upper knife 63 is fixed to the upper knife lever 62 at the mounting position determined so that 5 and the upper knife 63 have a predetermined positional relationship. Then, the base plate 61 is mounted at a predetermined position in the bed portion 2, and the left end portion of the drive connecting rod 66 is connected to the lower female lever 64 with a screw 67.

Next, as shown in FIG. 7, while the drive connecting rod 66 is manually rotated from the standby position to the operating position, the screw 87 is loosened and the pivot member 86 is rotated clockwise or counterclockwise. Both female levers 62 ・
The rotation fulcrum of 64 makes an eccentric movement integrally with the screw 87 in synchronization. At the same time, both female levers 62 and 64
Since the lower female lever 64 and the drive connecting rod 66 are connected to each other, and the female levers 62 and 64 are integrated by the contact member 80 and the spring 81, a predetermined movement is performed in synchronization with the screw 87. With the knife 65 and the upper knife 63 held in a predetermined positional relationship, the tip of the lower knife 65 on which the hooks 65a and 65b are formed is attached to the looper 5 as shown in FIG.
4, the position can be easily adjusted in a direction orthogonal to the movement direction of the looper 54 (direction of arrow C) (hereinafter, referred to as a direction orthogonal to the movement of the looper indicated by arrow D). Then, finally, the screw 87 is tightened again. Here, by adjusting the length of the drive connecting rod 66 by the stroke adjusting portion 66a, the left limit movement position of these hooks 65a and 65b with respect to the looper 54 can be adjusted to a predetermined position suitable for cutting both yarns 13 and 55. ..

As described above, the thread trimming device 60 includes the lower knife 6
5, the lower female lever 64 to which the upper female 63 is fixed, the upper female lever 62 to which the upper female 63 is fixed, and these both female levers 62 and 64.
Thread cutting drive mechanism 70 and pivot support mechanism 85 for reciprocally rotating
Since the lower knife lever 64 and the upper knife lever 62 are reciprocally rotated by the thread trimming drive mechanism 70,
The lower thread 55 and the needle thread 13 engaged with the lower knife 65 can be reliably cut.

Further, since the pivotal support mechanism 85 is provided, the position of the lower knife 65 in the operating position of the lower knife lever 64 can be easily adjusted to the regular position with respect to the looper 54 via the pivotal support mechanism 85, and Lower knife 65 and upper knife 6
Since it is held in a predetermined positional relationship with 3, the lower knife 6
Only by adjusting the position of 5, the position adjustment of the upper knife 63 with respect to the lower knife 65 can be omitted, and the position adjustment work of the upper knife 63 and the lower knife 65 with respect to the looper 54 can be greatly simplified.

It is also possible to provide a screw hole larger than the outer shape of the screw portion of the screw 87 in the pivot member 86 to form the pivot mechanism 85 so that the position of the pivot member 86 can be adjusted in the direction D orthogonal to the looper movement. is there. The base plate 61 is provided with an elliptical hole parallel to the direction D orthogonal to the movement of the looper, and the pivot member 86
It is also possible to configure the pivot support mechanism 85 so that the position can be adjusted in the direction D orthogonal to the movement of the looper by attaching it to the base plate 61 with a screw 87 and a nut.
Instead of the thread cutting solenoid 76, an air cylinder or various actuators can be used. Needless to say, the present invention can be applied to a thread trimming device for a decorative sewing machine in which a spreader is provided and an upper decorative thread is used, or various other double chain stitch sewing machines.

[Brief description of drawings]

FIG. 1 is a perspective view of a decorative sewing machine provided with a thread cutting device.

FIG. 2 is a partially enlarged front view of an arm section and a sewing machine bed section.

FIG. 3 is a perspective view showing a positional relationship among a needle thread, a thread wiping member, and a thread gripping spring when the thread wiping member moves to a thread catching position.

FIG. 4 is a diagram showing a positional relationship among a needle thread, a thread wiping member, and a thread gripping spring while the thread wiping member is moving to a thread holding position.

FIG. 5 is a diagram when the thread wiping member is moved to a thread holding position.
FIG.

FIG. 6 is a perspective view of a looper drive mechanism.

FIG. 7 is a plan view of a thread cutting device provided in the sewing machine bed.

FIG. 8 is a partial perspective view showing the positional relationship among the looper, the lower knife, and the upper knife when the lower knife moves to the working position.

9 is a vertical cross-sectional view taken along line 9-9 of FIG.

[Explanation of symbols]

 1 Decorative stitch sewing machine 9 Needle bar 11 Sewing needle 13 Needle thread 40 Looper drive mechanism 54 Looper 55 Lower thread 60 Thread trimming device 61 Base plate 62 Upper knife lever 63 Upper knife 64 Lower knife lever 65 Lower knife 66 Drive connecting rod 70 Thread cutting drive mechanism 71 Operation Shaft 73 Actuating lever 76 Thread trimming solenoid 85 Pivoting mechanism 86 Pivoting member 87 Screw

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tsunefumi Ito 15-1 Naedai-cho, Mizuho-ku, Nagoya City Brother Industries, Ltd. (72) Inventor Hiroyasu Iwakoshi 15-1 Naeyo-cho, Mizuho-ku, Nagoya City Brother Industrial Co., Ltd. Company (72) Inventor Kiyoshi Ueda 15-1 Naeshiro-cho, Mizuho-ku, Nagoya City Brother Industries, Ltd.

Claims (1)

[Claims] 1. A needle bar having a lower end to which a sewing needle can be attached, a needle bar drive mechanism for vertically reciprocating the needle bar, a looper for engaging a lower thread with a needle thread, and the looper. A double chain stitch sewing machine having a looper drive mechanism for reciprocally driving in the direction orthogonal to the cloth feed direction in synchronization with the vertical movement of the lower thread, when the looper is in the engagement position where it engages the needle thread, the lower thread And a thread cutting device for cutting a needle thread, a lower knife having a first hook engaging a lower thread and a second hook engaging a needle thread, a lower knife lever having the lower knife fixed thereto, 1
And an upper knife for cutting the thread engaged with the second hook in cooperation with the lower knife, an upper knife lever to which the upper knife is fixed, a lower knife lever and an upper knife lever are pivotally supported respectively. For lowering the lower knife lever to the standby position and the working position where the lower knife engages the needle thread and the lower thread, and the upper knife lever to the waiting position and the cutting position. And a drive mechanism for reciprocally rotating the lower knife lever and a pivot mechanism for pivotally supporting the pivot fulcrum of the lower knife lever and the pivot fulcrum of the upper knife lever on the base plate. With the knife held in a predetermined positional relationship, at least
A thread cutting device for a double chain stitch sewing machine, comprising a pivoting mechanism for pivotally adjusting the position of the looper in a direction orthogonal to the moving direction of the looper.