JPH0424088A - Sewing machine with automatic thread cutting mechanism - Google Patents

Abstract

PURPOSE:To make constant the length of end portion of needle thread by providing a needle thread end holding mechanism, a thread holding drive means, a thread holding control means, a spring changeover means and a spring loosening control means to perform thread cutting actions under conditions such that a thread take-up spring has been changed over to an inoperative position at the end of the sewing. CONSTITUTION:When needle thread Ns is cut, the thread Ns is fed toward a movable blade 40 through a thread take-up part 152 by the movement of the blade 40 and hence the part 152 is moved from an operative position to an inoperative position by the sliding friction between the part 152 and the thread Ns. At this moment, a spring rotation regulating member 155 moves to a thread loosening position by the driving action of a thread loosening solenoid, so that an abutment part 153 is situated opposite to an locking part 157. When the needle thread Ns has been cut, the part 153 is engaged with the part 157 and a thread take-up spring 151 is held at its inoperative position. As a result, since the spring 151 is in the inoperative position, the length of the end portion of needle thread between an eyelet 25 and the end of the thread can be made constant regardless of the kind of needle thread Ns.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a sewing machine with an automatic thread trimming mechanism, and in particular 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 device controls a thread take-up spring so that the end of the needle thread remains on the back side of the fabric for a short length of time.

[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 addition to this thread trimming mechanism, it is equipped with a tension release mechanism that releases the resistance force applied to the upper thread by the thread tension mechanism, so that the necessary upper thread can be paid out from the thread supply source when trimming the thread.
Sewing machines are also known in which a tension release mechanism is activated during a thread cutting operation.

Furthermore, Japanese Patent Publication No. 60-47871 provides a thread trimming mechanism, a tension release mechanism, a spring switching mechanism for switching a thread take-up spring to an inactive position, etc., and when the upper thread is cut by the thread trimming mechanism at the end of sewing, An automatic thread trimming sewing machine is described in which a tension release mechanism and a spring switching mechanism are operated to maintain a constant needle thread end length (from the eye of the sewing needle to the thread end) regardless of the type of needle thread. .

On the other hand, Japanese Utility Model Publication No. 61-157487 discloses a device that prevents the end of the needle thread from slipping out of the eye hole at the first stitch at the start of sewing, and that the needle thread and bobbin thread form a bird's nest pattern on the back side of the fabric. In order to prevent the upper thread from becoming tangled, the end of the upper thread that has been cut by the thread trimming mechanism after sewing is caught by the thread catching member above the throat plate, 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 provided with a thread holding device that cooperates with a member to hold the sewing needle at a position considerably distant from the sewing needle.

For reference, the distributor of this application is Patent Application No. 1-285660.
In this issue, we proposed a sewing machine with a thread trimming mechanism equipped with a thread holding mechanism that allows the end of the needle thread to remain briefly on the back side of the fabric.

[Problems to be Solved by the Invention] In the sewing machine equipped with the thread holding device described in the above-mentioned Japanese Utility Model Publication No. 61-157487, the length of the needle thread end is lengthened and cut, and the needle thread end is Since the upper thread Ns and lower thread Bs are held at a position far away from the thread, as shown in Fig. 18, the upper thread Ns and lower thread Bs do not become entangled on the back side of the fabric W, but as shown in Fig. 19, the long upper thread Ns There is a problem that the upper thread remains on the surface of the fabric W, and a thread picking operation is required to manually cut the upper thread end.

In the automatic thread trimming sewing machine described in Japanese Patent Publication No. 60-47871, the length of the needle thread end cut by the thread trimming mechanism can be made uniform; When this is set, the tension release mechanism is not activated at the start of sewing, which prevents the needle thread near the eye hole from moving toward the thread take-up due to the upward movement of the thread take-up, causing the needle thread to come out of the thread take-up, and the thread take-up spring becoming inactive. The spring switching mechanism that holds the device in position is composed of many parts such as a rotating shaft, rotating arm, connecting plate, actuating body, and locking pawl, so the spring switching mechanism becomes complicated. There is.

SUMMARY OF THE INVENTION An object of the present invention is to provide a sewing machine with an automatic thread trimming mechanism that can shorten and make the length of the needle thread end uniform, and that also allows reliable sewing operation from the first stitch and improves the quality of sewing at the beginning of sewing. It's about doing.

[Means to solve the problem]

A sewing machine with an automatic thread trimming mechanism according to the present invention includes 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 shuttle that intertwines upper thread and bobbin thread, and a hook that responds to a thread trimming command. a thread trimming mechanism that automatically cuts the upper thread and bobbin thread between the throat plate and the hook; a thread tension mechanism that applies resistance to the upper thread between the thread supply source and the thread take-up lever; In a sewing machine with an automatic thread trimming mechanism, which is equipped with a tension release mechanism for releasing the resistance force applied to the needle thread by the mechanism, and a thread take-up spring that applies elastic force to the needle thread between the thread tension mechanism and the thread take-up. , a thread holding member that is movable between 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 standby position for releasing the held needle thread. and a needle thread end holding mechanism including a holding force imparting member that cooperates with the thread holding member in the thread holding position to hold the end of the needle thread, and a thread holding member of the needle thread end holding mechanism that is actuated. A thread holding drive means connected to the thread holding member for selectively switching the thread holding member to the three positions, and a thread holding member moving from the standby position to the thread holding position via the thread catching position after the thread cutting operation of the thread cutting mechanism is completed. a thread holding control means for controlling a thread holding drive means to move the thread holding member to a standby position after a predetermined period of time has elapsed after starting the sewing machine motor; and a spring loosening control means that controls the spring switching means so that the thread take-up spring is in an inactive position when a thread trimming command is input and during a period of one to several stitches after starting the sewing machine motor. It is something that

[Effect]

In the sewing machine with an automatic thread trimming mechanism according to the present invention, when a thread trimming command is input, the spring loosening control means controls the spring switching means so that the thread take-up spring is in an inactive position, and activates the tension release mechanism. In this state, the thread trimming mechanism automatically cuts the upper thread and lower thread, so the upper thread necessary for thread trimming is not affected by the thread take-up spring which has been switched to the inactive position, regardless of the type of upper thread. A fixed amount of yarn is paid out from the yarn supply source. After the thread cutting operation is completed, the thread holding control means controls the thread holding drive means so that the thread holding member moves from the standby position, through the thread catching position, to the thread holding position near the side of the sewing needle located at the uppermost position. Therefore, the thread holding member moves to the thread holding position while catching the upper thread end which extends a short certain length from the thread of the sewing needle at the thread catching position, and works with the holding force imparting member to release the upper thread. Hold the ends.

On the other hand, when receiving the sewing machine motor starting start signal, the tension release mechanism is activated and the spring loosening control means switches the spring so that the thread take-up spring is in the inactive position for one to several stitches after the sewing machine motor starts starting. The thread holding control means controls the thread retention control means for a predetermined period of time after the start of the sewing machine motor (for example, when the sewing needle descends from the uppermost position to form a loop of the upper thread and the upper thread and lower thread are intertwined (knot!ff)). After a period of time during which the thread is formed, the thread holding drive means is controlled so that the thread holding member moves to the standby position. Therefore, even though the end of the needle thread is always kept short and constant, the end of the needle thread does not come off from the thread holding mechanism.

〔Effect of the invention〕

According to the sewing machine with an automatic thread trimming mechanism according to the present invention, the needle thread end holding mechanism, the thread holding drive means, the thread holding control means, the spring switching means, the spring loosening control means, etc. are provided, so that when sewing is finished, Since the thread trimming operation is performed with the thread take-up spring switched to the inactive position, the length of the upper thread end can be made constant regardless of the type of upper thread, and this upper thread end can be It can be held by an end holding mechanism.

Since sewing is started with the needle thread end held by the thread holding mechanism and with the thread take-up spring in the inactive position, the needle thread end length does not change, causing skipped stitches and needle stitches. The thread end of the upper thread does not come out from the hole.

The needle thread end holding mechanism is designed to hold the needle thread end at a position near the side of the sewing needle located at the uppermost position, so that the amount of thread from the eye of the sewing needle to the needle thread end is shortened. The upper thread can be cut using the thread cutting mechanism.

Therefore, since the thread amount can be kept short and constant, the end of the upper thread moves to the back side of the fabric and does not remain on the front side of the fabric during the sewing operation from the second stitch onward, and the end of the upper thread does not overlap with the bobbin thread. There is no nest-like tangle of threads, there is no need to pick up threads, and the quality of the sewing at the beginning of each sewing can be significantly improved.

Furthermore, the spring switching means may be of a simple structure that switches the thread take-up spring between an active position and a non-active position.

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

This embodiment is a case where 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 1 is attached to this pivot member 10.
1, a movable thread tension disc 12, a cap-shaped spring rotation regulating member 155, and a compression spring 13 are fitted onto the outside of the pivot member 10.
An adjustment knob 14 for adjusting the resistance force applied to the upper thread Ns is screwed onto the front end of the adjustment knob 1.
4 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 1
4 clockwise or counterclockwise, the spring force of the spring 13 changes, and the resistance force acting on the upper thread Ns sandwiched between the pair of thread tension discs 11 and 12 is adjusted. The fixed system tension plate 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 connected to the third
As shown in the figure, the movable thread tension plate 12 is divided into divided shafts 10a by dividing slits lob extending in the axial direction, and a bridge-like input portion 12a that fits into the dividing slits 10b is formed.
The front end of the thread tension shaft 15 is in contact with the input section 12a,
When the thread tension shaft 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. It has become.

A coil spring portion at the proximal end of the thread take-up spring 151 is accommodated in a spring housing space in the pivot member 10 on the rear side of the fixed thread tension disc 11, and its end portion is fixed to the pivot member 10. 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 position facing the thread tension discs 11 and 12 is located approximately in the center of the tip portion. A thread hook portion 152 is formed which is bent into a substantially U-shape in plan view. The tip of the thread take-up spring 151 has 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 upper thread Ns is supplied to the thread ring catcher 32 by the lower thread of the thread take-up 150, the thread hook portion 152 moves to the working position to absorb the slack of the thread thread Ns, and when the thread thread take-up 150 rises, the upper thread is raised. When the 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, 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. The thread loosening solenoid 20 is fixed to the machine frame 5 with a bracket 22, and the plunger 21 is always biased 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 comes into contact with the stepped part of the cam part 17 and does not push the thread tension shaft 15 forward, so that the movable thread tension disc 12 and the spring rotation are restricted. The member 155 is held at a pressing force applying position shown by a 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. Since the tension shaft 15 is pushed forward, the movable tension disc 12 moves to the tension release position, the spring rotation regulating member 155 moves to the forward position, and the movable thread tension disc 12 is separated from the fixed thread tension disc 11 by a predetermined distance. As a result, the resistance force applied to the upper thread Ns is released.

Next, the rotation regulating mechanism 154 that holds the thread take-up spring 151 in the inactive position will be explained based on FIG. 2, Part 3.

The thread take-up spring 1 is attached to the outer cylinder portion of the spring rotation regulating member 155.
A proximal end portion of a locking member 156 for regulating rotation of the locking member 51 is fixed with a screw 159. The distal end of this locking member 156 is located near the right side of the abutment portion 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 plate 12 in the forward direction. The locking part 157 that the contact part 153 of the thread take-up spring 151 comes into contact with 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 abutting portion 153 abuts against the locking portion 157 and the thread take-up spring 15
1 is held in this inactive position, and when the spring rotation restricting member 155 moves to the retracted position, the abutment part 153 freely passes through the notch 158, and the thread take-up spring 151 moves between the inactive position and the active 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, but since this is similar to the one described in Japanese Patent Application Laid-open No. 5,613,9793, a brief explanation will be provided.

As shown in FIGS. 4 and 5, a sewing needle 24 is provided in the bed portion 7.
A throat plate 27 is attached to which a needle hole (not shown) is inserted, 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 the work cloth W.
It is designed to form a seam.

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 an arc shape up to the point where 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 coiled 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 3B is connected to the fourth
As shown 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, the length of the cut upper thread Ns from the eye hole 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. By shortening the length of the thread catching 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 that hold the needle thread end of the needle thread NsO 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 launching solenoid) is arranged 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, which is generally U-shaped in side view, is rotatably supported on the plate 53 by a pin 65 facing in the front-rear direction, and directly below the second solenoid 54. The second output link 66, which is approximately U-shaped when viewed from the side, is attached to a 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 is rotatably connected to the first output link 62 by fitting a pin 74 fixed to the first arm 72 of the first link 71 into its elongated hole 64a. 1 link 71. At the base end of this first link 7I, a stepped screw 7 is inserted in the front-rear direction via a spacer 75.
6, the mounting is rotatably supported on the plate 53, and the first link 7
The lower end of the second arm 73 of No. 1 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 for attaching a holder is fixed to the front end of the pivot shaft 94, and a thread holding holder 96 is screwed to the plate 95, and a holding force imparting member made of a spring member is attached to the thread holding holder 96. 97 is fixed with a screw. 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 boss portion 9 is provided with a stepped portion at the rear end portion of the pivot shaft 94.
A thread retaining link 91 with 9 is fixed. 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 coiled 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. It is locked by a pin 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 pin 105 oriented 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 generally U-shaped in side view, is fixed to the lower end of the bracket 61 and oriented in the front-rear direction. 109, and the abutting portion 107 of the third output link 106 is always connected to the pin 1.
05 from below, the third output link 106
is biased to rotate clockwise in FIG. 8 by a coiled spring 110 mounted on the pin 109. Third output link 10
The swinging arm 108 of No. 6 is attached to the upper end of the third link 80 with the pin 1
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 upper 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 rotates significantly in the counterclockwise direction, and its hook portion 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 No. 1311D, and the first output link 62, the first link 71, and the The second link 78, the fourth link 81, the thread gripping link member 82, and the thread holding member 100 each move to the position indicated by the dashed dotted line. 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 applying 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.

When the first solenoid 59 is driven by this l, 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 captures the end portion of the needle thread Ns extending downward from the eye hole 25 of the sewing needle 24. 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 coiled 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 and works with the thread pressing portion 98 of the holding force applying 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 constitute 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 FIG. The thread pressing portion 98 of the 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 an input/output interface 130 of the control device C, respectively.

The operation panel 122 is a tension release machine that can be used immediately after starting sewing!
2, the loosening time setting key sets the loosening time (t2) of the upper thread Ns, and the release time setting key sets the release time (t3) from the needle down position to releasing the thread end of the upper thread Ns immediately after the start of sewing. The input/output interface 130 is equipped with keys, etc., and inputs and outputs setting data set by each key operation.
Output to.

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). , a sewing machine stop command signal (L level) is outputted to the input/output interface 130 when the sewing machine is in the neutral position, and a thread trimming signal is outputted when the sewing machine is depressed to the rear pedal position.

The needle-up signal generator 124 detects the rotational position of a metal disk member formed by forming a small opening at a predetermined circumferential position on a sewing machine main shaft (not shown) 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 and the needle up signal generator 124
It is configured similarly to the above, and outputs a needle lower signal to the input/output interface 130 when the sewing needle 24 is at the lowest position.

The control device C includes a CPU 132 and an input/output interface 130 connected to the CPU 132 via a bus 131 such as a data bus. It is composed of 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 needle thread release set time data memo IJ 142 stores the set release time (t3) data for the needle thread Ns.

The thread trimming flag memory 143 stores flag data of a thread trimming flag that is set when the foot pedal 123 is depressed from the neutral position to the rear pedal position and reset when the foot pedal 123 is not depressed to the rear pedal position. 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 denoted by I). 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 by the control device C of the sewing machine M will be described based on the flowchart of FIG. 11 and with reference to FIGS. 12 to 16. however,
To make the explanation easier to understand, the explanation will be given starting from the time when the foot pedal 123 is depressed to the forward position, steps 81 to S13 are executed, and the sewing operation is being executed. In addition, in the figure, Si (i=l, 2.
3...) are each step, and T1 to T9 in FIG. 12 indicate the timing, respectively.

When the foot pedal 123 is operated from the front pedal position to the neutral position and then to the rear pedal position during T1 during sewing, and a stop command signal of rl and J level is input as the pedal pedal signal, the thread trimming flag is set. At T2, when the thread trimming flag in the memory 143 is set (S14: es), two needle lower signals are input from the needle lower signal generator 125, and the counter I becomes "2" (S15: es, S16
, S17: Yes), the thread cutting solenoid 48 and the thread loosening solenoid 20 are respectively driven (S18).

Thereafter, when the sewing machine motor 115 is rotated at a low speed and a needle-up signal is input from the needle-up signal generator 124 (319
:Yes), and the driving of the thread trimming solenoid 48 is stopped (
Further, 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 (S21). Then, at T4, the lower moving solenoid 56 is driven for a predetermined time (for example, 60 m5ec) (S22). Therefore, as described above, the thread gripping link member 82 and the thread holding link 91 move from the solid line position in FIG. Move to position. Subsequently, the first solenoid 59 is driven for a predetermined time (for example, 60 m5ec) (S23). Therefore, only the thread holding member 100 moves to the thread catching position and returns to the thread holding position again with the hook portion 101 catching the thread end of the upper thread Ns extending from the eye hole 25 of the sewing needle 24, thereby increasing the holding force. This needle thread end is held in cooperation with the thread pressing section 98 of the applying member 97. Thereafter, at T5 when the driving of the first solenoid 59 is stopped, the driving of the thread loosening solenoid 20 is also stopped (S24).

Here, a description will be given of the effect of making the length from the eye hole 25 of the sewing needle 24 to the end of the upper thread held by the thread holding member 100 substantially stable and uniform.

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 thread loosening position by driving the thread loosening solenoid 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 in its inactive position. As a result, since the rotation of the thread take-up spring 151 is restricted in the non-acting position, the length of the needle thread end from the eye hole 25 to the needle thread end becomes uniform 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. Therefore, the thread take-up spring 151 is held at its inactive position.

Next, in order to start sewing, when the foot pedal 123 is operated at T6 and is depressed to the forward pedal position (the pedal depression signal is at "H" level) (S2: Yes), the control device C The first timer M1 provided in
For example, 100m5ec) is stored and counting is started (S3), and at T7 when the predetermined time t1 has elapsed, (
S4: ¥es), the sewing machine motor 115 is driven at low speed by the sewing machine motor drive signal (S5), and the setting data 2 of the thread loosening setting time data memory 141 is stored in the second timer M2 in the control device C (S6 ), when the thread loosening solenoid 20 is driven (S7) and the needle lowering signal is manually inputted from the needle lowering signal generator 125 (S8: Yes), the setting data L3 of the needle thread release setting time data memory 142 is set to the controller C. (39), and when the third timer M3 is tied J and up T8 (SIO: Yes
), for example, the sewing needle 24 is moved from the uppermost position to form a loop of the upper thread Ns, and the upper thread Ns and lower thread Bs are intertwined (knotted).
is formed, the upper moving solenoid 55 is driven for a predetermined period of time (for example, 60 m5ec) (Sll). At this time, the thread holding member 100 and the holding force imparting member 97 are at the release position (see FIG. 15) of the thread holding member 100 immediately after starting to move from the thread holding position shown in FIG. 16 to the standby position shown in FIG. 14. Sometimes the upper thread end is released. After that, the second timer M2
When time-up occurs at T9, for example, when several stitches of sewing have been executed and the upper thread Ns and lower thread Bs are definitely intertwined (S12: Yes), the thread loosening solenoid I" 20
is stopped, and the sewing machine motor 115 is driven at high speed (S13) to continue sewing.

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 spring rotation regulating member 155 moves to the forward position.
The thread take-up spring 151 in the non-active position is continuously held in the non-active position. Therefore, the thread take-up spring 151 does not rotate to the operating 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 inserted into the eye hole 25. I can't get out of it.

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.

In this way, the end of the needle thread of a certain length cut off 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 the end of the lower thread does not get entangled with the lower thread Bs in a bird's nest shape, making it easier to pick up the thread. There is no need to do this, and the quality of the sewing at the beginning of each garment can be significantly improved.

Furthermore, since the rotation restriction mechanism 154 is composed of a spring rotation restriction member 155 that moves in conjunction with the tension release mechanism 2,
This mechanism 154 can be greatly simplified. still,
It is also possible to configure the spring rotation regulating member 155 to be selectively switched between an active position and a non-active position using a separately provided solenoid or the like.

Note that the thread tension mechanism 1 and tension release mechanism 2 in the above embodiments
The thread cutting 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. 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 drawings]

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 longitudinal partial side view of the main part of the bed section, Part 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. 8, and FIG. 10 is a sewing machine 11 is a schematic flowchart of the upper thread processing control routine including upper thread holding control and thread loosening control. FIG. 12 is a time chart of various signals.
Fig. 3 is a mechanical diagram of the needle thread end holding mechanism and thread holding drive mechanism, Figs. 14 to 16 are partial front views showing each state of the thread holding mechanism, and Fig. 17 is the needle thread end holding mechanism and thread holding drive mechanism. FIGS. 18 and 19 are enlarged cross-sectional views of the fabric showing the yarn ends of FIGS. 1711J and 1711J, 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 hook, 34. Fixed blade, 40.. Movable blade, 48.. Thread cutting solenoid, 51.. Needle thread end holding mechanism, 52.. Thread holding drive mechanism, 54.. Second
Solenoid, 55・Upper moving solenoid, 56
...Lower moving solenoid, 59...1st solenoid, 7
1...1st link, 78...2nd link, 80...
Third link, 97... Holding force imparting member, 100... Thread holding member, 132... CPIJ, 133... ROM,
140...RAM, C...control device. Patent Applicant: Brother Industries, Ltd.] b4 ・Turn around V Thin Diagram ■- ■-2

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. In a sewing machine with an automatic thread trimming mechanism, which is equipped with a tension release mechanism for releasing force and a thread take-up spring that applies elastic force to the upper thread between the thread tension mechanism and thread take-up, the lower part of the sewing needle located at the uppermost position A thread holding member movable between a nearby thread catching position, a thread holding position near the side of the sewing needle located at the uppermost position, and a standby position for releasing the held upper thread; and a thread holding member located at the thread holding position. a needle thread end holding mechanism having a holding force imparting member that holds the end of the needle thread in cooperation with the thread holding member; a thread holding drive means for selectively switching the thread holding position to the thread holding position; and a thread holding member for moving the thread holding member from the standby position to the thread holding position via the thread catching position after the thread cutting operation of the thread cutting mechanism is completed, and for starting the sewing machine motor. Yarn holding control means for controlling the yarn holding drive means to move the yarn holding member to a standby position after a predetermined period of time has elapsed; and a spring switching means for selectively switching the yarn take-up spring between an active position and a non-active position. 1 at the time of inputting the thread trimming command and after starting the sewing machine motor.
1. A sewing machine with an automatic thread trimming mechanism, characterized in that the sewing machine is provided with a spring loosening control means for controlling a spring switching means so that the thread take-up spring is in an inactive position for a period of one to several stitches.