JPH0424090A - Sewing machine with automatic thread cutting mechanism - Google Patents

Abstract

PURPOSE:To prevent in particular tensile forces from being exerted on the end of needle thread, preventing thereby the thread from slipping out of an eyelet by controlling a drive means for use in holding thread in conjunction with the completion of thread cutting action of a thread cutting mechanism and the stating of a machine motor when an operation mode has been set. CONSTITUTION:When an operation mode is set, a tension release mechanism functions at the completion of sewing operation, while, since a control means for holding thread controls a drive means 52 for holding thread operably connected to a thread holding member 100 of a needle thread end holding mechanism 51 so that the member 100 is changed over to a thread holding position from a waiting position through a thread capturing position at the completion of thread cutting action by means of a thread cutting mechanism, the end of the needle thread is held by the member 100 in conjunction with a holding force imparting member 97. When a sewing operation is started, the control means for holding thread controls the means 52, under conditions that a tension release mechanism is in operation, so that the member 100 is positioned at a location above a thread holding position and changed over to a waiting position to release the end of needle thread. On the other hand, for setting an inoperative mode, the member 100 is held at the waiting position.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a sewing machine with an automatic thread trimming mechanism, and particularly to a needle thread end holding mechanism that holds the end of the needle thread that is automatically cut at the end of sewing. This invention relates to a device that can selectively set activation/inactivation mode.

[Prior art]

Conventionally, as described in JP-A-56-139793, for example, when sewing is completed, a movable blade is engaged with a fixed blade between the throat plate and the hook through the drive of a lower shaft, and the upper thread and lower thread are separated. Sewing machines equipped with a thread cutting mechanism that automatically cuts threads at a predetermined timing are already known.

In this sewing machine with a thread trimming mechanism, if the amount of thread from the eye of the sewing needle to the end of the upper thread is short, the end of the upper thread will come off from the eye of the eye on the first stitch at the start of sewing. To prevent this, a large amount of thread is left from the end of the thread to the end when cutting.

However, when sewing with this sewing machine equipped with a thread trimming mechanism, the upper thread can be prevented from slipping out of the thread, but since the amount of thread from the thread to the thread end is long, the needle thread remains on the back side of the fabric for a long time.
There is a problem in that the upper thread Ns and the lower thread Bs get entangled with the bobbin thread after the second stitch, and as shown in FIG. .

In addition, Japanese Utility Model Publication No. 61-157487 discloses a method that prevents the thread end of the needle thread from slipping out of the eye hole at the first stitch at the start of sewing, and also prevents the needle thread and bobbin thread from forming a bird's nest on the back side of the fabric. In order to prevent the upper thread from getting tangled, the end of the upper thread cut by the thread trimming mechanism is caught by the thread catching member above the throat plate after sewing, and the end of the upper thread is transferred between the thread holding member and the thread catching member. A sewing machine has been proposed that is equipped with a thread holding device that works together with the sewing needle to hold the thread at a considerable distance from the sewing needle.

However, with a sewing machine equipped with this thread holding device, the upper thread and bobbin thread do not become entwined in a bird's nest shape on the back side of the workpiece fabric when sewing starts; Since the thread length up to the end of the thread Ns is left long and the end of the upper thread is held at a position quite far from the eye hole, the long upper thread Ns remains on the front side of the fabric W, and the end of the upper thread Ns is manually removed. There are problems such as the need for thread picking work to cut the sections, and the fact that uncut needle thread remains on the surface of the fabric even after the thread picking work is done.

Therefore, in Japanese Patent Application No. 1-285660, the applicant proposed that the upper thread end of the upper thread, which is cut short by the thread cutting mechanism at the end of sewing, be placed at a thread holding position near the side of the sewing needle located at the uppermost position. The end of the upper thread is held at the thread holding position from the start of sewing until the upper thread and lower thread of the first stitch are intertwined. We have proposed a sewing machine equipped with a needle thread end holding mechanism, which allows the needle thread end to remain short on the back side of the fabric without intertwining with the bobbin thread.

[Problem to be solved by the invention]

However, in the sewing machine with a thread trimming mechanism proposed by the applicant, when a special needle thread with high elasticity such as nylon thread is used, the needle thread end that is cut off at the end of sewing is removed by the needle thread end holding mechanism. When you start sewing with the
During the sewing operation, a large tension is applied to the upper thread, especially from the thread of the sewing needle to the upper thread holding part, and this upper thread becomes stretched, and when the upper thread end is released from being held, this upper thread stretches. Since the thread shrinks to its original length, there is a problem that the stitches formed at the beginning of sewing become unraveled or the needle thread comes off from the thread.

The object of the present invention is to provide an automatic thread trimming mechanism that allows the use of a special needle thread with a high degree of elasticity in addition to a general needle thread with a low degree of elasticity, and also allows sewing with clean stitches from the first stitch. Our goal is to provide sewing machines with attached sewing machines.

[Means for Solving the Problems] A sewing machine with an automatic thread trimming mechanism according to the present invention has a sewing needle driven by a sewing machine motor, a thread take-up that is driven up and down in synchronization with the sewing needle, and an upper thread and a lower thread intertwined. A thread cutting mechanism that automatically cuts the needle thread and bobbin thread between the needle plate and the shuttle in response to a thread trimming command, and a thread cutting mechanism that applies resistance to the needle thread between the thread supply source and the thread take-up thread. A thread g-circumfer mechanism to add thread, a tension release mechanism for releasing the resistance force applied to the upper thread by the thread tension mechanism, a thread catching position near the bottom of the sewing needle located at the uppermost position, and a sewing needle located at the uppermost position. A thread holding member that is movable between a thread holding position near the side of the thread holding position and a standby position that is located above the thread holding position and releases the upper thread end, and a thread holding member that cooperates with the thread holding member in the thread holding position. an upper thread end holding mechanism having a holding force imparting member that acts to hold the upper thread end; and an upper thread end holding mechanism that is operatively connected to the thread holding member of the upper thread end holding mechanism and selects the thread holding member between the three positions. A mode for selectively setting an operating mode in which an upper thread end holding mechanism is activated and an inoperative mode in which it is not activated, in a sewing machine equipped with an automatic thread trimming mechanism, which is equipped with a thread holding drive means for automatically switching the thread end holding mechanism. The thread holding drive means is controlled to hold the thread holding member of the upper thread end holding mechanism in a standby position when the inoperative mode is set through the setting means and the mode setting means, and the operating mode is set. A thread holding control means is provided for controlling the thread holding drive means in association with the end of the thread cutting operation of the thread cutting mechanism and the start of activation of the sewing machine motor.

[Effect]

In the sewing machine with an automatic thread trimming mechanism according to the present invention, when the mode setting device sets the operation mode, the tension release mechanism operates at the end of sewing, and the thread holding control device operates the thread cutting mechanism by the thread trimming mechanism. When the thread holding member is completed, the thread holding drive means operatively connected to the thread holding member of the upper thread end holding mechanism is controlled so as to switch the thread holding member from the standby position to the thread catching position and to the thread holding position. The thread holding member cooperates with the holding force applying member to hold the needle thread end at the thread holding position. Further, when sewing is started by starting the sewing machine motor, the thread holding control means positions the thread holding member above the thread holding position and releases the upper thread end while the tension release mechanism is activated. Since the thread holding drive means is controlled to switch to the standby position, the upper thread end is released.

On the other hand, when the mode setting means sets the inoperative mode, the thread holding control means controls the thread holding drive means to hold the thread holding member at the standby position.

[Effects of the Invention] According to the sewing machine with an automatic thread trimming mechanism according to the present invention, since the mode setting means and the thread holding control means are provided, when using a general needle thread with a low elasticity, Since the cut needle thread end is held by the needle thread end holding mechanism, the needle thread end remains short on the back side of the fabric, and the thread does not come out from the eye hole, improving the quality of sewing at the beginning of sewing. .

On the other hand, when using a special needle thread with high elasticity, the mechanism for holding the needle thread end is not operated, so no tension is applied to the needle thread end, and the length of the needle thread end is slightly longer. If you do this, you can sew with clean stitches from the beginning of sewing without the thread coming out from the thread.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

In this embodiment, the present invention is applied to a sewing machine equipped with a thread cutting mechanism and a tension release mechanism.

First, a description will be given of the thread tension mechanism 1 that applies a resistance force to the upper thread NS being let out from the thread spool (path shown in the figure) and the tension release mechanism 2 that removes this resistance force.

Except for the addition of a spring rotation regulating mechanism 154 to the thread tension mechanism 1, this thread tension mechanism 1 has the same structure as an existing general thread tension mechanism, and will therefore be briefly described.

As shown in FIGS. 1 to 3, a pivot member 10 is fixed to a portion of the machine frame 5 at the front end of the head 8 of the arm portion 6 of the sewing machine M, and is movable in the front and rear directions on this pivot member 10. Thread tension axis 1
5 is attached, and a fixed thread tension disc 11 is attached to this pivot member 10.
, a movable thread tension plate 12 and a cap-shaped spring rotation regulating member 1
55 and a compression spring 13 are externally fitted, and an adjustment knob 14 for adjusting the resistance force applied to the upper thread Ns is screwed to the front end of the pivot member 10.
and the spring rotation regulating member 155.

However, the movable thread tension disc 12 and the spring rotation regulating member 155 cannot rotate with respect to the pivot member 10, and the adjustment knob 14
By rotating clockwise or counterclockwise, the force of the spring 13 changes, and the resistance force acting on the needle thread Ns sandwiched between the pair of thread tension discs 11 and 12 is adjusted. still,
The fixed thread tension disc 11 engages with the stepped portion of the pivot member 10 from the front, and the portion in front of the stepped portion of the pivot member 10 is a split sling 10b extending in the axial direction, as shown in FIG. The movable tension disc 12 is divided into a split shaft 10a, and a bridge-like input part 12a that fits into the split slit 10b is formed.The front end of the thread tension shaft 15 is in contact with the input part 12a. 15 is moved forward against the spring force of the compression spring 13, the movable thread tension disc 12 is separated from the fixed thread tension disc 11, and the resistance force applied to the upper thread Ns is released. .

The coil spring portion at the proximal end of the thread take-up spring 151 is accommodated in the spring housing space in the pivot member 10 on the rear side of the fixed thread tension plate 11, and its end portion is fixed to the pivot member IO. The thread take-up spring 151 is extended to the outside from the formed circumferential slit opening, and the tip portion of the thread take-up spring 151 is projected upward, and a substantially central portion of the tip portion faces the thread tension discs 11 and 12. A thread hook portion 152 is formed at the position where the thread hook is bent into a substantially U-shape in plan view. At the tip of this thread take-up spring 151, there is provided a spring rotation regulating member 1, which will be described later.
A contact portion 153 is provided that contacts a locking portion 157 of a locking member 156 fixed to the locking member 55 . This thread hook is part 15
2 is constantly biased by a spring force to the operating position shown by the solid line in FIG. Therefore, when the thread take-up part 152 is supplied with the upper thread Ns to the thread ring catcher 32 by lowering the thread take-up lever 150, it moves to the working position and absorbs the slack of the upper thread Ns, and when the thread take-up lever 150 rises, the upper thread Ns is supplied to the thread ring catcher 32. When the upper thread Ns is taken up from the thread ring catcher 32, it is elastically deformed to the maximum extent to the inactive position shown by the broken line in FIG. 3, thereby allowing the upper thread Ns to be let out.

A cam driven shaft 15A is connected to the machine frame 5 on the rear side of the thread tension shaft 15.
The front end of the cam driven shaft 15A abuts the rear end of the thread tension shaft 15, and the rear end abuts the cam portion 17 of the cam plate 16 which is pivotally connected to the machine frame 5 with a pin 9. are in contact with each other. The cam portion 17 has an actuating portion that pushes the cam driven shaft 15A forward and a stepped portion that is stepped down from the actuating portion. The drive portion 18 of the cam plate 16 is connected to a plunger 21 of a thread loosening solenoid 20 via a connecting rod 19. This thread loosening solenoid 20 is fixed to the machine frame 5 with a bracket 22, and the plunger 21 is constantly urged to the left in FIG. 1 by a compression spring 23. Therefore,
When the thread loosening solenoid 20 is not energized, the cam driven shaft 15A contacts the step-down part of the cam portion 17 and does not push the thread tension shaft 15 forward, so that the movable thread tension disc 12 and the spring rotation regulating member 155 are not energized. is held at the pressing force application position shown by the solid line in FIG. 2, and a resistance force adjusted by the adjustment knob 14 is applied to the upper thread Ns. However, when the thread loosening solenoid 20 is energized, the connecting rod 19 moves to the right in FIG. 1, the cam plate 16 is rotated clockwise, and the cam driven shaft 15A
is pushed by the actuating part of the cam part 17 to push the thread tension shaft 15 forward, so the movable thread tension plate 12 moves to the tension release position and the spring rotation regulating member 155 moves to the forward position, and the movable thread tension The disc 12 is separated from the fixed thread tension disc 11 by a predetermined distance, and the resistance force applied to the upper thread Ns is released.

Next, the rotation restricting mechanism 154 that holds the thread take-up spring 151 in the inactive position will be explained with reference to FIGS. 2 and 3.

A thread take-up spring 1 is provided in the outer cylinder portion of the spring rotation regulating member 155.
The proximal end of a locking member 1560 for regulating the rotation of 51 is fixed with a screw 159. The distal end of this locking member 156 is located near the right side of the abutment part 153 of the thread take-up spring 151 that has moved to the inactive position, and the spring rotation regulating member 155 is located at the distal end along with the movable thread tension disc 12 in the forward direction. The locking part 157 that the contact part 153 of the thread take-up spring 151 contacts when the switch is switched to the forward position and the spring rotation regulating member 155 allows the contact part 153 to pass when the spring rotation regulating member 155 moves to the backward position. A notch 158 is formed.

Therefore, when the thread take-up spring 151 rotates to the inactive position and the spring rotation restriction member 155 moves to the forward position,
The contact portion 153 contacts the locking portion 157 and the thread take-up spring 15
1 is held in this non-working position, and when the spring rotation regulating member 155 moves to the retreat position, the abutting part 153 freely passes through the notch 158, and the thread take-up spring 151 moves between the non-working position and the working position. It becomes elastically deformable over a period of time.

Next, the thread cutting mechanism 3 for cutting the upper thread Ns and the lower thread Bs will be described. Since this mechanism is similar to that described in Japanese Patent Application Laid-Open No. 139793/1983, a brief explanation will be provided.

As shown in FIGS. 4 and 5, the head portion 7 has a sewing needle 24.
A throat plate 27 is attached to the machine frame 5 below the throat plate 27, and a lower shaft 28 is rotatably supported on the machine frame 5 below the throat plate 27. Sword tip 29 and outer pot 3
A fully rotary thread ring catcher 32, generally referred to as a hook, is provided with a thread ring catcher 32, which is generally referred to as a hook, and is equipped with a bobbin case 33 that accommodates a bobbin (not shown). The upper thread Ns and the lower thread Bs are intertwined to form a stitch in the work cloth W.

A fixed blade 34 is screwed to the machine frame 5 on the front side of the thread ring catcher 32 at approximately the front half thereof, and the rear half of this fixed blade 34 is attached to the part near the needle hole of the throat plate 27 along the thread ring catcher 32. It extends in a circular shape until the end, and a blade portion 35 is formed at the tip thereof. still,
Reference numeral 36 is an inner hook stopper that restrains the rotation of the inner hook 31;
Reference numeral 37 denotes a shielding plate that prevents the needle thread Ns that has come off the tip 29 during sewing from becoming entangled with the fixed blade 34 when it is pulled up.

A movable blade holder 38 is rotatably supported on the machine frame 5 on the rear side of the thread ring catcher 32 so as to be able to reciprocate around the same axis as the lower shaft 28. For attachment, a movable blade 40 is fixed to the portion 39 with screws. The arc-shaped left end of the movable blade 40 includes a thread handling part 41 and a thread catching groove part 4.
2 and a blade portion 43 are formed. On the other hand, in order to rotate the movable blade 40, a swing arm 45 is fixed to a swing shaft 44 that is rotated by a cam drive mechanism (not shown). Connection part 4 of blade holder 38
7 are connected. Furthermore, in order to drive the cam drive mechanism by the rotation of the lower shaft 28, the cam drive mechanism is connected to the drive shaft of a thread trimming solenoid 48 (see FIG. 10). Incidentally, reference numeral 49 is a winding spring that biases the swinging arm 45 to rotate counterclockwise in FIG. 4 so as to hold the movable blade 40 in the non-cutting position shown in FIG. Therefore, as will be described later, the thread trimming solenoid 48 is activated at a predetermined timing at the end of sewing.
When energized, the rotation of the lower shaft 28 drives the cam drive mechanism and the swing shaft 44 rotates in the direction of the arrow.
5 and the connecting lever 46, the movable blade holder 38 is connected to the fourth
In the figure, the movable blade 40 is rotated clockwise, and the movable blade 40 is also rotated clockwise, and at the timing when the thread ring of the upper thread Ns comes off the tip 29 of the outer hook 30 and is pulled up, the movable blade 40 connects the upper thread to the work cloth W. The fixed blade 3 captures Ns and bobbin thread Bs at the same time.
It engages with the blade portion 35 of No. 4 and cuts. Here, since the length of the cut upper thread Ns from the eyelet 25 of the sewing needle 24 to the thread end (hereinafter referred to as upper thread end length) is proportional to the length of the thread catching groove 42, the thread By shortening the length of the trapping groove 42, the length of the needle thread end can be shortened.

Next, a needle thread end holding mechanism 51 and a thread holding drive mechanism 52 hold the needle thread end of the needle thread Ns that has been cut after sewing is completed.
I will explain about it.

As shown in FIGS. 6 to 9, a plate 53 is screwed to the rear side of the head 8 of the sewing machine M, and a second solenoid (bistable latching solenoid) is disposed vertically.
The first solenoid 5 54 is fixed to substantially the left half of the plate 53 by a bracket 58 and is arranged vertically.
9 is fixed to approximately the right half of the plate 53 by a bracket 61. The second solenoid 54 is provided with an upper moving solenoid 55 and a lower moving solenoid 56 (see FIG. 13), and when the upper moving solenoid 55 is driven, the plunger 57 moves upward (as shown in FIG. 13). When the lower solenoid 56 is driven, the plunger 57 moves downward (in the direction of the arrow) and is held at the lower position. Immediately above the second solenoid 54, a first output link 62 having a substantially U-shape when viewed from the side is rotatably supported on the plate 53 by a pin 65 facing in the front-rear direction. The second output link 66, which is approximately U-shaped when viewed from the side, is attached to the plate 53 with a pin 69 facing in the front-rear direction.
It is rotatably supported on.

The drive arm 63 of the first output link 62 is connected to the second solenoid 5
Connecting member 70 fixed to the upper end of plunger 57 of No. 4
The swinging arm portion 64 of the first output link 62 has a pin 74 fixed to the first arm 72 of the abbreviated first link 7I fitted in its elongated hole 64a. link 7
1. This first link 71 has a stepped screw 76 extending in the front-rear direction via a spacer 75 at its base end.
The mounting is rotatably supported on the plate 53, and the first link 71
The lower end of the 27th arm 73 is rotatably connected to the right end of the second link 78 with a stepped screw 77. The left end of the second link 78 is rotatably connected to the lower end of the third link 80 by a pin 79, and is also rotatably connected to the upper end of the fourth link 81. A bottle 85 is attached to the right end of the drive arm 83 of the gripping link member 82.
are rotatably connected.

On the other hand, the drive arm portion 67 of the second output link 66 has its elongated hole 6
A pin 87 fixed to a connecting member 86 fixed to the lower end of the plunger 57 of the second solenoid 54 is fitted into the lower end of the plunger 57 of the second solenoid 54 to connect to the connecting member 86. 88 is rotatably connected to the upper end of the fifth link 89, and the lower end of the fifth link 89 is connected to the bin 90.
The first arm 92 of the thread holding link 91 is connected to the first arm 92 of the thread holding link 91 .

For installation, the lower end of the plate 53 has a boss portion 53a facing in the front-rear direction.
is fixed, and a pivot shaft 94 oriented in the front-rear direction is attached to this boss portion 5.
3a and the mounting are rotatably supported through a plate 53,
A plate 95 is fixed to the front end of the pivot shaft 94 for attaching the holder, and a thread holding holder 96 is screwed to the plate 95 for attaching the holder. A member 97 is secured with screws. The distal end portion of the holding force imparting member 97 is formed into a downwardly convex curved thread presser portion 98 (elastic contact portion).

A thread holding link 91 having a boss portion 99 with a stepped portion r5 is fixed to the rear end portion of the predetermined pivot shaft 94. Therefore, as the fifth link 89 moves upward or downward, the thread holding link 91 rotates counterclockwise or clockwise, and the pivot shaft 94 and the holder attachment are held via the plate 95 and the thread holding holder 96. The force applying member 97 rotates counterclockwise or clockwise in synchronization with the thread holding link 91.

On the other hand, a pivot shaft 94 is inserted through the base end of the driving arm 83 and the base end of the swinging arm 840 of the thread gripping link member 82, which is approximately U-shaped in plan view, so that the thread gripping link member 82 is pivoted. A thread holding member 100 is rotatably supported on a support shaft 94, and a thread holding member 100 is attached to the swinging arm portion 84.
is secured with screws. Note that the reference numeral 102 is a spacer. The front end portion of the thread holding member 100 is formed in an arc shape centered on the pivot shaft 94, and the eyelet 25 of the sewing needle 24 is inserted into the left end portion of the arc portion to capture the upper thread Ns extending downward. A hook part 101 (yarn catching part) is formed, and the thread pressing part 98 of the holding force imparting member 97 is attached to this hook part 101.
The hook member 101 is configured to elastically come into contact with a recess on the upper surface of the hook member 101 to hold the end of the upper thread Ns.

Therefore, the upward or downward movement of the fourth link 81 causes the thread gripping link member 82 to rotate counterclockwise or clockwise, and the thread holding member 100 to rotate counterclockwise or clockwise. The swinging arm 84 is attached to the pivot shaft 94 between the plate 53 so that one end of the winding spring 103 is locked to the base end of the thread gripping link member 82, and the other end is attached to the thread holding link member 82. The thread gripping link member 82 is locked to the bin 104 fixed to the second arm 93 of the link 91, and the thread gripping link member 82 is always urged to rotate counterclockwise in FIG. 8 with respect to the thread holding link 91. 91 is always biased clockwise with respect to the thread gripping link member 82, so that the thread pressing portion 98 is pressed against the hook portion 101.
It is designed so that it can surely come into contact with the The drive arm 83 and swing arm 84 of the thread gripping link member 82 have an opening angle of approximately 30 degrees.

A bottle 105 facing in the front-rear direction is fixed to the lower end of the plunger 60 of the first solenoid 59, and a third output link 106, which is approximately U-shaped in side view, is fixed to the lower end of the bracket 61. 109, so that the abutting portion 107 of the third output link 106 is always connected to the bin 1.
05 from below, the third output link 106
is urged to rotate clockwise in FIG. 8 by a winding spring 110 externally attached to the bottle 109. Third output link 10
The swinging arm 108 of No. 6 is attached to the upper end of the third link 80.
They are rotatably connected at 11. Note that 26 is a needle bar, 112 is a presser bar, and 113 is a presser foot.

Next, the upper thread end holding mechanism 51 and the thread holding drive mechanism 52
The operation will be explained based on FIGS. 8 and 13 to 16.

When the upper solenoid 55 is driven, the plunger 57
moves upward to the upward movement position shown in FIG.
, the thread holding member 100 moves to the solid line position. The position of the thread holding member 100 at this time is defined as a standby position. on the other hand,
As the plunger 57 moves to the first movement position, the fifth link 89 and the thread holding link 91 are connected via the connecting member 86.
When the holder is attached, the plate 95, the thread holding holder 96, and the holding force applying member 97 move to the solid line positions, respectively.

The position of the holding force applying member 97 at this time is set as a standby position (see FIG. 14). At this standby position, the thread holding member 10
0 is thick in the counterclockwise direction (rotates, and the hook part 10
1 is a position far above the throat plate 27.

Next, when the lower movement solenoid 56 is driven, the plunger 57 moves downward to the lower movement position shown in FIG.
1. The second link 78, the fourth link 81, the thread gripping link member 82, and the thread holding member 100 each move to the -dotted chain line position. The position of the thread holding member 100 at this time is defined as a thread holding position.

At this thread holding position, the hook portion 10 of the thread holding member 100
1 is a position near the right of the sewing needle 24 at the uppermost position.

On the other hand, as the plunger 57 moves downward, the connecting member 86
The second output link 66, the fifth link 89, the thread holding link 91, the holder mounting plate 95, the thread holding holder 96,
The holding force imparting members 97 each move to the position indicated by the dashed dot line in FIG. 13 (see FIG. 16). At this time, the holding force imparting member 9
The thread presser section 98 of No. 7 engages with the recess of the hook section 101 and can hold the upper thread Ns.

In this state, when the first solenoid 59 is driven, the plunger 60 moves downward and connects the third output link 106, the third link 80, the fourth link 81, the thread gripping link member 82, and the thread through the pin 105. The holding members 100 each move to the position indicated by the two-dot chain line in FIG. At this time, the hook portion 101 of the thread holding member 100 is located near the bottom of the sewing needle 24 at the uppermost position, and the upper thread Ns extends downward from the eye hole 25 of the sewing needle 24.
Capture the end of. The position of the thread holding member 100 at this time is defined as a thread catching position. Further, when the driving of the first solenoid 59 is stopped, the spring force of the winding spring 110 causes the third output link 106, the third link 80, the fourth link 81, and the thread gripping link member 82 to move as shown in the dashed-dotted line in FIG. Since the thread holding member 100 returns to the thread holding position with its hook portion 101 capturing the upper thread end, the thread holding member 100 moves back to the thread holding position in a state where the upper thread end is captured by the hook portion 101, and cooperates with the thread presser portion 98 of the holding horn imparting member 97 to hold the upper thread. The ends are held (see Figure 16).

Further, when the upper moving solenoid 55 is driven, the thread holding member 100 and the holding force applying member 97 move to the standby position, but the second link 78, the third link 80, and the fourth link 8
1 constitutes a four-bar link, so immediately after the start of movement to the standby position, the moving speed of the thread holding member 100 is slower than the moving speed of the holding force applying member 97, as shown in No. 150. Thread pressing portion 98 of holding force imparting member 97
is removed from the hook portion 101, and the needle thread end is released. The position of the thread holding member 100 at this time is the release position.

Next, the overall configuration of the control system of the sewing machine M will be explained based on the block diagram of FIG. 10.

Thread trimming solenoid 48, thread loosening solenoid 20, upper moving solenoid 55, lower moving solenoid 56, first solenoid 5
9 and the sewing machine motor 115 are driven by drive circuits 116 to 12, respectively.
1, and each of the drive circuits 116 to 121 is connected to the input/output interface 130 of the control device c.

The operation lever 122 includes a loosening time setting key for setting the loosening time (t2) of the upper thread Ns by tension release 2 immediately after the start of sewing, and a loosening time setting key for setting the loosening time (t2) of the upper thread Ns by tension release 2 immediately after the start of sewing, and a loosening time setting key for releasing the thread end of the upper thread Ns from the needle down position immediately after the start of sewing. It is equipped with a release time setting key for setting the release time (L3) until the needle thread end holding mechanism 51 is activated, and a setting switch 126 for alternatively setting an operating mode in which the upper thread end holding mechanism 51 is activated and an inoperative mode in which it is not activated. , outputs setting data and switch signals set by key and switch operations to the human output interface 130.

Incidentally, when the setting switch 126 is switched to set the operation mode, the switch signal SS is at the "L" level.
When the switch is switched to set the non-operating mode, it outputs the switch signal SS at the rHJ level.

The foot pedal 123 has three positions: a front pedal position, a horizontal neutral position, and a rear pedal position. When the foot pedal 123 is in the front pedal position depending on the operator's pedal position, it outputs a sewing machine start command signal ("H" level). When the sewing machine is in the neutral position, a sewing machine stop command signal ("L" level) is output, and when it is in the rear pedal position, a thread trimming signal is output to the respective output interfaces 130.

The needle position signal generator 124 uses a proximity switch to control the rotational position of a metal disk member formed with a small opening at a predetermined circumferential position provided on the sewing machine main shaft (path shown in the figure) driven by the sewing machine motor 115.・When the sewing needle 24 is at the uppermost position, a needle-up signal is output to the input/output interface 130. The needle down signal generator 125 also has the needle up signal generator 12.
4, and outputs a needle down signal to the human output interface 130 when the sewing needle 24 is at the lowest position.

The control device C is composed of a CPU 132, an input/output interface 130 connected to the CPU 32 via a bus 131 such as a data bus, a ROM 133, and a RAM 140.

The ROM 133 stores a control program for needle thread processing control including needle thread holding control and thread loosening control.

The set thread loosening time (t2) data is stored in the thread loosening set time data memory 141 of the RAM 140.

The upper thread release set time data memory 142 stores the set upper thread Ns release time (t3) data. The flag memory 143 is reset (data is set to "
Flag data of a non-operation flag F that is set (data is "1") when the non-operation mode is set (data is "1") is stored. The needle down signal counter 144 stores the count value of the needle down signal inputted from the needle down signal generator 125 (its content is represented by ■). Furthermore,
The RAM 140 is provided with various types of memories that temporarily store the results of calculations performed by the CPU 132.

Next, the upper thread processing control routine performed in the control bag WC of the sewing machine M is shown in FIGS. 11(a) and 11(b).
) will be explained with reference to FIGS. 12 to 16. However, to make the explanation easier to understand,
The operation mode is set with the setting switch 126 to use a general upper thread Ns with low elasticity, the foot pedal 123 is depressed to the forward position, steps 81 to S18 are executed, and the sewing operation is being executed. I will explain from. In addition, 5i (i
=1.2.3...) is each step, and T in Figure 12
1 to T9 each indicate timing.

When the foot pedal 123 is operated from the front pedal position to the neutral position and then to the rear pedal position at T1 during sewing, and a stop command signal of "L" level is input as the pedal pedal signal (S19: (Yes), at T2 when two needle down signals are input from the needle down signal generator 125 and the count value I becomes "2" (S20: Yes, 321
．． S22: Yes), the thread cutting solenoid 48 and the thread loosening solenoid 20 are respectively driven (S23). after that,
When the sewing machine motor 115 is rotated at low speed and a needle up signal is input from the needle up signal generator 124 (S24: Yes)
), the drive of the thread trimming solenoid 48 is stopped (S25).
Furthermore, the driving of the sewing machine motor 115 is stopped, and the brake within the sewing machine motor 115 is actuated by the brake signal, so that the sewing machine motor 115 is surely stopped at T4 (S26). Then, at T4, the lower moving solenoid 5
6 is driven for a predetermined time (for example, 60 m5ec) (S
27). Therefore, as described above, the thread gripping link member 82
Since the thread holding link 91 moves from the solid line position in FIG. 13 to the dashed-dotted line position, the thread holding member 100 and the holding force applying member 97 move to the thread holding position shown in FIG. 16. Subsequently, the first solenoid 59 operates for a predetermined period of time (for example, 60 m
5ec) is driven (S28). Therefore, the thread holding member 1
00 moves to the thread catching position and returns to the thread holding position again with the thread end of the upper thread Ns extending from the thread 25 of the sewing needle 24 being caught by the hook part 101, and the holding force imparting member 9
This upper thread end is held in cooperation with the thread presser 98 of No. 7. Thereafter, at T5 when the first solenoid 59 stops driving, the thread loosening solenoid 20 also stops driving (3
29).

Here, the effect of stably making the length from the eye hole 25 of the sewing needle 24 to the end of the needle thread held by the thread holding member 100 constant will be explained.

When the upper thread Ns is cut at T2, the upper thread Ns is cut by the movement of the movable blade 40 via the thread hooking section 152.
0, the thread hook portion 152 moves from the active position to the non-active position due to sliding friction with the upper thread Ns. At this time, the spring rotation regulating member 155 moves to the forward position due to the drive of the thread loosening solenoid T'20, so that the contact portion 153
is a position facing the locking portion 157. And upper thread N
When s is cut, the abutting portion 153 is locked by the locking portion 157, and the thread take-up spring 151 is held at its inactive position. As a result, the rotation of the thread take-up spring 151 is restricted at the non-active position, so that the length of the needle thread end from the eye hole 25 to the needle thread end remains constant regardless of the type of needle thread Ns. On the other hand, even if the driving of the thread loosening solenoid 20 is stopped when the upper thread end is captured by the driving of the first solenoid 59, the upper thread Ns is not connected to the upper thread end holding mechanism 51 and the thread tension mechanism 1. Since the thread take-up springs 151 are held at their inactive positions, the thread take-up springs 151 are held at their inactive positions.

Then, the switch signal SS from the setting switch 126 is read (32), and since the switch signal SS is at "L" level, the flag F is reset (S4), and in order to start sewing, the foot pedal 123 is pressed at T6. When the operator depresses to the front depressing position (depressing signal is rH, level) (S5: Yes), general needle thread N with low elasticity is pressed.
When the operation mode is set to use s (37: Yes), a predetermined time tl (for example, 100m5ec) is set in the first timer M1 provided in the control device C.
is stored and counting is started (S8), and the predetermined time t
1 has elapsed (S9: Yes), the sewing machine motor 115 is driven at low speed by the sewing machine motor drive signal (S10), and the setting data t2 of the thread loosening setting time data memory 141 is transferred to the second It is stored in the timer M2 (S11), and the thread loosening solenoid 20 is driven (S1
2) When the needle down signal is input from the needle down signal generator 125 (S13: Yes), the setting data t3 of the needle thread release setting time data memory 142 is stored in the third timer M3 in the control device C ( S14), when the third timer M3 times out at T8 (S], 5: Yes), for example, the sewing needle 24 is lowered from the uppermost position to form a loop of the upper thread Ns, and the loop between the upper thread NS and the lower thread Bs is When a knot (nodule) is formed, the upper moving solenoid 55 is activated for a predetermined period of time (for example, 60 m5
ec) is driven (S16). At this time, the thread holding member 1
00 and the holding force imparting member 97 are in the release position of the thread holding member 100 immediately after the start of movement from the thread holding position shown in FIG. 16 to the standby position shown in FIG. 14 (see No. 15). is released. After that, at T9 when the second timer M2 times up, for example, when several counts of sewing have been executed and the upper thread Ns and lower thread Bs are surely intertwined (S17
:Yes), the driving of the thread loosening solenoid 20 is stopped, and the sewing machine motor 115 is driven at high speed (318), and sewing continues continuously.

Here, the effect of preventing the needle thread Ns from coming out from the eye hole 25 at the start of sewing will be explained.

At the same time as sewing starts, the thread loosening solenoid 20 is driven, and the flap rotation regulating member 155 moves to the forward position.
As will be described later, the thread take-up cap 151, which has been moved to the non-working position when sewing is stopped, continues to be held at the non-working position. Therefore, the thread take-up spring 151 does not rotate to the working position and sewing is performed at low speed, so that the needle thread end length is held constant and the first and subsequent stitches are sewn, and the needle thread Ns is sewn into the eye hole 25. I can't get out of it.

In this way, the needle thread end portion of the needle thread NsO cut at the end of sewing is held by the thread holding mechanism 51 to the sewing needle 24 located at the uppermost position.
The upper thread end is held at a thread holding position near the side of the upper thread, and this upper thread end is held from the start of sewing until the upper thread Ns and lower thread Bs are intertwined. Due to the sewing operation after the stitch, the end of the upper thread Ns moves to the back side of the fabric W and does not remain on the front side, and furthermore, the end of the upper thread does not get entangled with the bobbin thread Bs in a crow's nest shape, making the thread picking work easier. There is no need to do this, and the quality of the sewing at the beginning of each sewing can be significantly improved.

On the other hand, when sewing is started (S6: Yes), if the inoperable mode is set in the setting switch 126 to use a special needle thread Ns with high elasticity such as nylon thread ( 37: No), the upper moving solenoid 55 is driven for a predetermined period of time, and the thread holding member 100 and the holding force applying member 97 are
is moved to the standby position (330), and thereafter 331 to S4
1, a normal sewing operation is performed in which only the thread trimming mechanism 3 is operated without operating the needle thread end holding mechanism 51 to hold the needle thread end.

Note that a large number of slits are provided at the periphery of a disc-shaped disk attached to the upper shaft driven by the sewing machine motor 115, and a pulse generator is provided to output pulse signals from the sensor through these slits. Thread loosening setting time (t2
) or the needle thread release set time (t3), the number of pulses of this pulse signal may be used.

As explained above, when using the special needle thread Ns with high elasticity, the needle thread end is not held, so no tension is applied to the needle thread end, and the needle thread end length is long enough at the beginning of sewing. By making the sewing needle 24 somewhat longer, the sewing needle 24 can be sewn with clean stitches from the initial stage without the thread coming out from the eye hole 25 of the sewing needle 24.

Note that the setting switch 126 can also be provided at any location other than the operation panel 123 that does not interfere with the sewing operation.

Note that the thread tension mechanism 1 and tension release mechanism 2 in the above embodiments
The thread trimming mechanism 3 is merely an example, and it goes without saying that various existing and well-known configurations may be used in place of it, and the system holding drive mechanism 52 and upper thread end holding mechanism 51 may This is merely an example, and it goes without saying that various existing ones may be used, as well as those obtained by adding various modifications and alterations to the one of this embodiment.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1 is a partially cutaway front view of the arm of the sewing machine, FIG. 2 is a partial side view of the sewing machine, and FIG. 3 is a partially enlarged front view of the sewing machine. Figure 4 is a vertical partial side view of the main part of the bed section, Figure 5 is a partial perspective view of the thread ring catcher and thread cutting device, Figure 6 is a partial side view of the thread holding drive mechanism, and Figure 7 is a partial side view of the thread holding drive mechanism. 8 is a side view of the thread holding drive mechanism and upper thread end holding mechanism, FIG. 8 is a sectional view taken along the line ■-■ in FIG. 7, FIG. 9 is a sectional view taken along the line IX-IX in FIG. Block diagram of the control system of the sewing machine, Figure 11 (a) ・Chapter 11
Figure (b) is a schematic flow chart of the upper thread processing control routine including upper thread retention control and thread loosening control, Figure 12 is a time chart of various signals, and Figure 13 is the upper thread end retention mechanism and thread retention drive. A mechanical diagram of the mechanism, FIGS. 14 to 16 are partial front views showing each state of the thread holding mechanism, FIG. 17 is an enlarged sectional view of the fabric showing the end of the needle thread at the sewing start point, and FIG. 18
19 and 19 are views corresponding to FIG. 17, respectively, according to the prior art. 1. Thread tension mechanism, 2. Tension release mechanism, 3. Thread trimming mechanism, 11. Fixed thread tension disc, 12. Movable thread tension disc, 15. Thread tension shaft, 15A. Cam driven shaft. , 20...Thread loosening solenoid, 30...Outer hook,
31...Inner pot, 34...Fixed blade, 40...Movable blade,
48...Thread trimming solenoid, 51...Upper thread end holding mechanism, 52...Thread holding drive mechanism, 54...Second solenoid, 55...Upper moving solenoid, 56...
Lower moving solenoid, 59... 1st solenoid, 71...
・1st link, 78...2nd link, 80...3rd
Link, 97.. Holding force imparting member, 100.. Thread holding member, 132.. CPU, 133. ROM,
140...RAM, C...control device. Patent applicant: Brother Industries, Ltd. Figure 11 (b)

Claims (1)

[Claims] (1) A sewing needle driven by a sewing machine motor, a thread take-up that is driven up and down in synchronization with the sewing needle, a hook that intertwines the upper thread and bobbin thread, and a hook that intertwines the upper thread and bobbin thread between the needle plate and the hook in response to a thread trimming command. A thread trimming mechanism that automatically cuts the upper thread and lower thread, a thread tension mechanism that adds resistance to the upper thread between the thread supply source and the thread take-up, and a thread tension mechanism that adds resistance to the upper thread by the thread tension mechanism. a tension release mechanism for releasing the force, a thread catching position near the bottom of the sewing needle located at the top position, a thread holding position near the side of the sewing needle located at the top position, and a thread holding position located above the thread holding position. An upper thread end having a thread holding member movable between a standby position and a standby position for releasing the upper thread end, and a holding force imparting member that cooperates with the thread holding member in the thread holding position to hold the upper thread end. and a thread holding drive means operatively connected to the thread holding member of the upper thread end holding mechanism for selectively switching the thread holding member to the three positions. A sewing machine with a sewing machine includes a mode setting means for selectively setting an operating mode in which the upper thread end holding mechanism is activated and an inoperative mode in which it is not activated, and an inoperative mode is set through the mode setting means. When the thread holding member of the needle thread end holding mechanism is set to the standby position, the thread holding drive means is controlled to hold the thread holding member of the needle thread end holding mechanism in the standby position, and when the operation mode is set, the thread cutting operation of the thread cutting mechanism is ended and the sewing machine motor is turned off. 1. A sewing machine with an automatic thread trimming mechanism, characterized in that it is provided with a thread holding control means for controlling a thread holding drive means in connection with the start of startup.