JPH0880392A - Needle thread lead quantity adjusting device for sewing machine - Google Patents

Abstract

PURPOSE: To freely adjust the binding point and release point of needle thread with an easy operation in a device which adjusts the lead quantity of the needle thread by adjusting those binding point and release point. CONSTITUTION: A thread binding cam 47 and a thread release cam 48 are fixed on a principal axis 14 with a screw 49 so that their positions can be adjusted, respectively, and the needle thread 36 can be bound/released by rocking a first arm (driven body) 50 and a movable wheel 40, etc., according to the motion of both cams 47, 48. The lead quantity of the needle thread 36 can be adjusted by adjusting the binding point and release point of the needle thread by changing the mounting angles of both cams 47, 48 on the principal axis 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a needle thread withdrawal amount adjusting device for a sewing machine, which adjusts the amount of needle thread withdrawn from a thread supply source in accordance with a sewing operation.

[0002]

2. Description of the Related Art In a sewing machine, an upper thread located between a thread spool and a thread take-up is clamped in order to adjust the amount of the upper thread pulled out from the thread spool in accordance with the feeding operation of a work cloth and the swinging operation of a sewing needle. The upper thread withdrawal amount adjusting device is provided for setting the restraining timing for restraining and the releasing timing for releasing the clamping force according to the movement of the balance or the sewing needle. FIG. 9 is a conventional example showing a sewing machine provided with this type needle thread withdrawal amount adjusting device,
This is disclosed in JP-A-63-105789.

Here, 1 is a rotatable movable plate, 2 is a fixed yarn path regulating plate, and the movable plate 1 is a stepped screw 1.
When it rotates in the direction of arrow C about a, the upper thread 3 is clamped and restrained between the movable wheel 1b of the movable plate 1 and the yarn path regulating plate 2.
Further, when the movable plate 1 rotates in the direction opposite to the arrow C, the movable wheel 1
The distance between b and the yarn path regulating plate 2 is increased, and the clamping force for the upper thread 3 is released.

In this case, the operation of the sewing needle 4 and the balance 5 is set according to the rotational phase angle of the main shaft 6. Therefore, by fixing the rotary cam 7 to the main shaft 6, engaging the arm 8 with the cam groove 7a of the rotary cam 7, and rotating the arm 8 following the cam groove 7a, the link arm 9 is stepped. Screw 1
When the contact wheel 1c of the movable plate 1 is pressed by the contact portion 9a of the link arm 9 by rotating the needle 4a about the sewing needle 4a.
The movable plate 1 is rotated according to the movement of the balance 5 and the balance 5.

A solid line MD in FIG. 10 is an operation curve of the movable wheel 1b, the horizontal axis represents the rotation phase angle of the main shaft 6, and the vertical axis represents the release amount of the movable wheel 1b (the amount of movement in the direction opposite to the arrow C). Show. Here, when the movable wheel 1b reaches the release point F, the distance between the movable wheel 1b and the yarn path restricting plate 2 increases, and the clamping force for the upper thread 3 is released. When the movable wheel 1b reaches the restraint point C, the distance between the movable wheel 1b and the yarn path regulating plate 2 becomes small, and the upper thread 3 is clamped and restrained. Therefore, when the distance between the release point F and the restraint point C becomes smaller, the release time of the upper thread 3 becomes shorter, and the amount of the upper thread 3 pulled out from the thread spool according to the swinging operation of the sewing needle 4 and the work cloth feeding operation. As the number of threads decreases, the thread tension becomes tense.

[0006]

In the case of the above conventional configuration,
There are the following two methods for moving the release point F and the constraint point C. (1) Adjust the mounting angle of the rotary cam 7 to the spindle 6,
As shown by the alternate long and short dash line in FIG. 10, the entire operation curve MD is moved. (2) By using the eccentric contact wheel 1c and changing the mounting angle of the contact wheel 1c, as shown by the broken line in FIG.
The height of the motion curve MD is changed.

However, both of the operations (1) and (2) move both the release point F and the constraint point C (the moved release point is indicated by F'and F '', Points are indicated by C ′ and C ″), for example, if the release point F is moved to the right without moving the constraint point C in order to tension the thread tension, the operations of (1) and (2) are performed. It is necessary to perform a laborious and skilled operation such as performing in parallel. Due to such circumstances, conventionally, it is difficult to adjust the release point F and the constraint point C, and there is a restriction on the setting of the release point F and the constraint point C.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a needle thread withdrawal amount adjusting device for a sewing machine which can freely adjust the restraining point and the releasing point by a simple operation. .

[0009]

A needle thread withdrawal amount adjusting device of a sewing machine according to the present invention clamps a portion of an upper thread from a thread supply source through a balance to a sewing needle, the portion being located between the thread supply source and the balance. A restraining position for restraining and a pair of sandwiching bodies movable to a releasing position for releasing the sandwiching force are provided, and the restraining timing for moving the sandwiching body to the restraining position and the releasing timing for moving the sandwiching body to the releasing position are set to the balance and the sewing needle. A timing adjusting means for individually adjusting the restraint timing and the release timing is provided in the case of adjusting the amount of the upper thread drawn from the thread supply source in accordance with the sewing operation by adjusting according to the operation. It is characterized by the fact (claim 1).

In this case, the timing adjusting means is provided between the thread restraining cam and the thread releasing cam, which are provided on the main shaft for operating the balance and the sewing needle, and rotate in conjunction with the main shaft, and these cams and the sandwiching body. The rotation movement of the thread restraining cam is transmitted to the sandwiching body by contacting the thread restraining cam to move the sandwiching body to the restraining position, and the rotation movement of the thread releasing cam is brought into contact with the thread releasing cam. And a follower for moving the holding body to the release position, and the binding timing is adjusted by adjusting the mounting angle of the thread restraining cam with respect to the main shaft, and the main axis of the thread releasing cam is adjusted. The release timing may be adjusted in accordance with the adjustment of the mounting angle with respect to (2).

Further, when the driven body comes into contact with both the yarn restraining cam and the yarn releasing cam, a gap larger than the maximum usable upper thread thickness is formed between the sandwiching bodies. Good (Claim 3).

[0012]

According to the first aspect of the present invention, the timing adjusting means can individually adjust the restraint timing and the release timing, so that the rotary cam mounting angle adjustment and the contact wheel mounting angle adjustment are performed in parallel. It becomes possible to easily adjust the release point and the constraint point as compared with the conventional method.

According to the second aspect of the invention, the restraint timing is adjusted by adjusting the mounting angle of the yarn restraining cam with respect to the main shaft, and the release timing is adjusted with the adjustment of the mounting angle of the yarn releasing cam with respect to the main shaft. adjust. Therefore, the timing can be adjusted by a simple operation such as changing the mounting angle of the cam.

According to the third aspect of the present invention, when the driven body comes into contact with both the yarn restraining cam and the yarn releasing cam, a gap larger than the maximum usable upper thread thickness is formed between the sandwiching bodies. To be done. Therefore, the upper thread can be always released in response to the replacement of the upper thread.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to an electronically controlled lockstitch sewing machine will be described below with reference to FIGS. First, in FIG. 5, a pedestal portion 12 is erected on the right end portion of the bed portion 11, and an arm portion 13 is provided on the upper end portion of the pedestal portion 12. The arm portion 13 extends in the horizontal direction so as to face the bed portion 11, and the main shaft 14 is housed therein as shown in FIG. 6. The main shaft 14 is connected to a sewing machine motor (not shown) and is driven to rotate by the sewing machine motor. Reference numeral 15 denotes a bush metal that rotatably supports the main shaft 14.
Is fixed to the machine frame 16 of the sewing machine.

A balance crank 17 is fixed to the left end of the main shaft 14, and the balance crank 17 is provided with a crank pin 17a. A connecting plate 18 is fixed to the crank pin 17a, and when the main shaft 14 rotates, the crank pin 17a and the connecting plate 18 rotate about the main shaft 14. Also, as shown in FIG. 5, a head portion 19 is provided at the tip of the arm portion 13, and inside the head portion 19, as shown in FIG.
0 is provided. This needle bar support 20 has a pin 20a.
Is attached to the machine frame 16 of the sewing machine, and swings in the direction of arrow A about the pin 20a.

A needle bar 21 is provided on the needle bar support 20 so as to be vertically movable. A sewing needle 21a is attached to the lower end of the needle bar 21, and when a swing mechanism (not shown) is driven, the needle bar support 20 swings in the direction of arrow A about the pin 20a, As a result, the needle bar 21 and the sewing needle 21a swing together with the needle bar support 20 in the arrow A direction. Also,
A needle bar crank 23 is attached to the connecting plate 18 by a pivot pin 22.
Is rotatably attached. The needle bar 21 is rotatably connected to the needle bar crank 23, and when the balance crank 17 rotates, the needle bar crank 23 causes the needle bar crank 23 to rotate.
The needle bar 21 and the sewing needle 21a are configured to move up and down with respect to the needle bar support 20.

The solid line MA1 in FIG. 3 is a movement curve showing the displacement of the eye of the sewing needle 21a with the rotational phase angle of the spindle 14 as a parameter, and the solid line MA2 is the movement curve showing the displacement of the lower end of the sewing needle 21a.

Inside the arm portion 13, as shown in FIG. 6, an auxiliary shaft 24 is housed at a position diagonally rearward of the main shaft 14. The auxiliary shaft 24 is arranged in parallel with the main shaft 14, and is rotatably attached to the sewing machine frame 16. A swing lever 25 is rotatably connected to the auxiliary shaft 24, and one end of the swing lever 25 extends between the balance crank 17 and the connecting plate 18.

As shown in FIG. 7, a cam hole 26 is formed at one end of the swing lever 25, and a crank pin 17a of the balance crank 17 is inserted in the cam hole 26.
A balance 27 is integrally formed on the other end of the swing lever 25. Then, when the balance crank 17 rotates,
As the sewing needle 21a moves up and down, the crank pin 17a
Presses the inner surface of the cam hole 26 of the rocking lever 25, and the balance 27 of the rocking lever 25 reciprocates in the vertical direction (arrow B direction) about the sub shaft 24. The uppermost position of the balance 27 is shown by a solid line in FIG. 7, and the lowermost position is shown by a chain double-dashed line.

The cam hole 26 has an arc portion 26a and an arc portion 26.
It is composed of two straight portions 26b formed on both sides of a, and the curvature of the arc portion 26a is the crankpin 1
It is set to be the same as the rotational curvature of 7a. Therefore, FIG.
As shown in, while the crank pin 17a is located in the arc portion 26a, the rotational movement of the crank pin 17a is not transmitted to the swing lever 25. Solid line MB in FIG.
Is a balance 27 using the rotational phase angle of the spindle 14 as a parameter.
3 is a motion curve showing the displacement of As is clear from the figure, the balance 27 is stopped at the uppermost position in the range of the phase angle of 41 ° to 115 ° where the crank pin 17a is located in the arc portion 26a.

As shown in FIG. 7, the head portion 19 is provided with a presser bar 28, and a presser bar 28a is attached to the presser bar 28. Further, the operation lever 2 is provided on the head portion 19.
9 is rotatably provided, and the moving position of the presser bar 28 is adjusted in accordance with the operation position of the operation lever 29, and the work clamp foot 28a is moved to a lower position for pressing the work cloth or an upper position separated from the work cloth. It is configured to move.

The bed portion 11 has a needle plate 30 and a feed dog 3
1 is provided. The feed dog 31 penetrates through the needle plate 30 and is exposed on the bed portion 11. When the cloth feed mechanism (not shown) is driven in conjunction with the main shaft 14, the feed dog 31 is activated and the work clamp foot is pressed. The work cloth (not shown) pressed by 28a is fed by the feed dog 31 to form a predetermined stitch on the work cloth. A solid line MC in FIG. 3 is a motion curve showing the horizontal displacement of the feed dog 31. Here, except for the initial stage of cloth feeding, the balance 27 is stopped at the uppermost position during the period from when the main shaft 14 rotates about 40 ° to when the eyelet of the sewing needle 21a reaches the upper surface of the needle plate 30. The feeding is substantially executed.

In the arm portion 13, as shown in FIG.
A plate member 32 is provided on the left side of the main shaft 14. The plate member 32 constitutes a part of the machine frame 16 of the sewing machine, and a U-shaped thread guide body 33 is provided at an upper end portion of the plate member 32. The thread guide 33 is composed of an upper plate portion 33a, a left guide plate portion 33b extending downward from the left side of the upper plate portion 33a, and a right guide plate portion 33c extending downward from the right side of the upper plate portion 33a. The left guide plate portion 33b is fixed to the upper end portion of the plate member 32 by the screw 34.

Left guide plate 33b and right guide plate 3
As shown in FIG. 1, a left guide groove portion 33d and a right guide groove portion 33e are formed in 3c so as to face each other, and the upper thread 3 drawn from a thread spool 35 (see FIG. 3) corresponding to a thread supply source.
6 is inserted into the right guide groove 33e from the rear opening of the right guide groove 33e, then inserted into the left guide groove 33d from the rear opening of the left guide groove 33d, and is led to the left side of the left guide plate 33b. Has been done. A guide groove 33f is formed in front of the left guide groove 33d in the left guide plate 33b, and the needle thread 36 led out from the left guide groove 33d is inserted into the guide groove 33f. After that, it is bent downward.

A yarn path restricting plate 37 is fixed to the lower end of the plate member 32. A movable plate 38 is rotatably attached to the lower end of the plate member 32 by a stepped screw 39. A movable wheel 40 is rotatably attached to the movable plate 38, and a V-shaped groove 40a is formed on the outer peripheral surface of the movable wheel 40.
(See FIG. 8) are formed. And the guide groove 33
The upper thread 36 bent downward from f is provided with a thread guide plate 37.
And the movable wheel 40, and when the movable plate 38 rotates around the stepped screw 39 in the direction of arrow C, the movable wheel 4 moves.
The groove portion 40a of 0 is fitted into the yarn path regulating plate 37 (see FIG. 8), and the upper thread 36 is clamped and restrained by the yarn path regulating plate 37 and the movable wheel 40. That is, the yarn path regulating plate 37 and the movable wheel 4
0 corresponds to the pair of holding bodies 41 in claim 1.

The needle thread 36 inserted between the yarn path restricting plate 37 and the movable wheel 40 is bent upward by the yarn path restricting plate 37 (see FIG. 8), and the thread holding portion 27a of the thread balance 27. , And is bent downward and inserted into the eyelet of the sewing needle 21a through the thread guide portions 42a and 42b.

A sleeve 43 is rotatably fitted to the outer peripheral surface of the auxiliary shaft 24 and located on the left side of the swing lever 25. The swing lever 25 is connected to the sleeve 43. A crank-shaped operating arm 44 is fixed to the sleeve 43 so as to be located between the left guide plate portion 33b and the right guide plate portion 33c, and a thread catching portion 44a is formed at the tip of the operating arm 44. Has been done.

When the swing lever 25 swings around the counter shaft 24 and the balance 27 of the swing lever 25 moves to the uppermost position, the swing lever 25 rotates the sleeve 43 and the operating arm 44 moves. The auxiliary shaft 24 is rotated rearward (in the direction of arrow D). As a result, the yarn catching portion 44a of the operating arm 44 is located behind the upper yarn 36. Further, when the balance 27 is moved to the lowest position, the operating arm 44 rotates in the direction opposite to the arrow D (forward) as shown by the chain double-dashed line in FIG. 7, and the yarn catching portion 44a moves forward of the upper yarn 36. The needle thread 36 is positioned and the upper thread 36 is captured by the thread catching portion 44a.

As shown in FIG. 6, a pretensioning device 45 is provided on the left side of the plate member 32. The pretensioning device 45 includes a pair of tone discs 45a, a spring (not shown) that presses one of the tone discs 45a, and an operation dial 45b. An upper thread 36 located between the yarn path restricting plate 37 and the balance 27 is inserted between the pair of tension discs 45a, and the upper thread 36 is sandwiched between the pair of tension discs 45a. As shown in FIG. 5, when the operation dial 45b is rotated from the outside, the spring expands and contracts, the pressing force against the tension disc 45a changes, and the clamping force of the needle thread 36 by the pair of tone discs 45a changes. It is supposed to do.

As shown in FIG. 1, a thread restraining cam 47 and a thread releasing cam 48 corresponding to the timing adjusting means 46 according to claim 1 are fixed to the main shaft 14 by screws 49.
As shown in FIG. 2, elliptical cam surfaces 47a and 48a are formed on the outer peripheral surfaces of the yarn restraining cam 47 and the yarn releasing cam 48, respectively. Further, as shown in FIG. 1, a first arm 50 corresponding to the follower according to claim 2 is fixed to the sub shaft 24, and a contactor 50a is provided at the tip of the first arm 50. . Then, the cam surface 47 of the thread restraining cam 47
As shown in FIG. 2, the cam surface 48a of the yarn releasing cam 48 and the cam surface 48a of the thread releasing cam 48 are formed with overlapping portions a and b. The overlapping portions a and b are formed at the overlapping portions a and b. Are cam surfaces 47a and 48a
Contact both sides.

Further, the cam surface 48a of the yarn releasing cam 48 is formed with a protruding portion (c) which is located between the overlapping portions (a) and (b) and protrudes from the cam surface 47a. The contact 50a contacts only the cam surface 48a. Further, on the cam surface 47a of the yarn releasing cam 47, there is formed a protruding portion D located between the overlapping portion B and the protruding portion D and protruding from the cam surface 48a.
a contacts only the cam surface 47a.

That is, as shown in FIG.
Is both the cam surfaces 47a and 48a or the cam surface 47a.
a and 48a are always in contact with each other, and as a result, the rotation of the main shaft 14 is transmitted from the cam surfaces 47a and 48a to the first arm 50 through the contact 50a, and the first arm 50 swings. Accordingly, the sub shaft 24 is adapted to rotate.

A second arm 51 is fixed to the left end of the sub shaft 24. When the first arm 50 swings and the sub shaft 24 rotates, the second arm 51 rotates about the sub shaft 24. It is designed to move. The link arm 52 is rotatably attached to the lower end of the second arm 51 by a pin 52a, and the lower end of the link arm 52 has a stepped screw 3a.
It is rotatably attached to the plate member 32 by 9. Therefore, when the second arm 51 rotates about the counter shaft 24,
The link arm 52 rotates about the stepped screw 39.

A tension coil spring 53 is interposed between the plate member 32 and the movable plate 38, and the tension coil spring 53 urges the movable plate 38 in the direction of arrow C. And
A circular contact ring 38a is provided on the movable plate 38, and a contact portion 52b is formed on the lower end of the link arm 52. The contact ring 38a of the movable plate 38 is formed by the tension coil spring 5.
The spring force of 3 makes contact with the contact portion 52b.

In this case, as shown in FIG. 2, since the distance from the cam surfaces 47a and 48a to the main shaft 14 is short in the overlapping portion a, when the contact 50a of the first arm 50 contacts the overlapping portion a. 1, the first arm 50
Rotates in the counter-arrow D direction around the counter shaft 24, and the second arm 51 rotates in the counter-arrow D direction via the counter shaft 24. Therefore, the connecting portion between the second arm 51 and the link arm 52 rotates in the direction opposite to the arrow E. Then, the contact portion 52b of the link arm 52 rotates in the direction opposite to the arrow E and there is no member for receiving the contact wheel 38a, so that the movable plate 38 rotates in the direction of arrow C by the spring force of the tension coil spring 53. The distance between the yarn path regulating plate 37 and the movable wheel 40 is minimized.

A solid line MD in FIG. 3 is an operation curve of the movable wheel 40 using the rotational phase angle of the main shaft 14 as a parameter. Here, the contact 50a of the first arm 50 comes into contact with the overlapping portion a in the range excluding the mountain-shaped portion located in the range of the rotation phase angle of 40 ° to 115 °, and the yarn path regulation plate 37 and the movable wheel 40. The distance between and is minimal. Hereinafter, the case where this interval is the minimum is set as the reference position of the movable wheel 40, and the release amount of the movable wheel 40 is "0", and the description will proceed.

Further, as shown in FIG. 2, in the overlapping portion b, the distance from both cam surfaces 47a and 48a to the main shaft 14 is long, so that the contact 5 of the first arm 50 contacts the overlapping portion b.
When 0a comes into contact, in FIG. 1, the first arm 37 rotates in the arrow D direction, and the second arm 51 rotates in the arrow D direction via the sub shaft 24. Therefore, the connecting portion between the second arm 51 and the link arm 52 rotates in the arrow E direction. Then, the contact portion 52b of the link arm 52 rotates in the direction of the arrow E and resists the spring force of the tension coil spring 53 to cause the contact wheel 3 to rotate.
Since 8a is pressed in the direction opposite to the arrow C, the movable wheel 40 rotates in the direction opposite to the arrow C, and the distance between the yarn path restricting plate 37 and the movable wheel 40 becomes maximum.

In the solid line MD of FIG. 3, the contact portion 50a of the first arm 50 contacts the overlapping portion B at the flat portion α of the mountain portion located at the rotation phase angle of 40 ° to 115 °, and the yarn path The distance between the regulation plate 37 and the movable wheel 40 is maximized. In the present embodiment, the maximum usable upper thread thickness is "0.3 mm", so the maximum value (that is, the amount of release of the movable wheel 40) is equal to or greater than the maximum usable upper thread thickness,
For example, it is set to "0.7 mm".

Further, as shown in FIG. 2, in the protruding portion C, the contact 50a of the first arm 50 is connected to the thread releasing cam 48.
Contact only the cam surface 48a. Therefore, as the main shaft 14 rotates in the direction of the arrow F and the contact point of the contact 50a with respect to the cam surface 48a moves from the overlapping portion B toward B, the distance between the yarn path regulating plate 37 and the movable wheel 40 is increased. The movable plate 38 is rotated in the direction opposite to the arrow C so that is from the minimum to the maximum. In the solid line MD in FIG. 3, it is the inclined portion β that indicates that the movable wheel 40 is moved by the protruding portion C.

Further, as shown in FIG. 2, in the protruding portion D, the contact 50a contacts only the cam surface 47a of the thread restraining cam 47. Therefore, as the main shaft 14 rotates in the direction of the arrow F and the contact point of the contact 50a with respect to the cam surface 47a moves from the overlapping portion B to B, the distance between the yarn path regulating plate 37 and the movable wheel 40 is increased. The movable plate 38 rotates in the direction of the arrow C so that is from the maximum to the minimum. In the solid line MD in FIG. 3, it is the inclined portion γ that indicates that the movable wheel 40 is moved by the protrusion d.

Next, the operation of the above configuration will be described mainly with reference to FIG. (1) When the balance 27 is at the lowest position, the contact 50
a contacts the overlapping portion B of the cam surfaces 47a and 48a, and the amount of release of the movable wheel 40 is "0". Therefore, the upper thread 36 is restrained by the movable wheel 40 and the yarn path restricting plate 37. Therefore, as the operating arm 44 rotates in the direction opposite to the arrow D, the upper thread 3 is moved by the thread catching portion 44a of the operating arm 44.
When 6 is captured, the upper thread 36 is pulled out from the thread spool 35. In addition, the needle thread 36 extending from the thread path regulation plate 37 to the sewing needle 21a
Is in a relaxed state.

(2) Until the balance 27 is raised from the lowermost position to the uppermost position, the contact 50a contacts the overlapping portion B of the cam surfaces 47a and 48a, and the movable wheel 40 and the yarn guide plate 3
7, the upper thread 36 is restrained. Therefore, the needle thread 36 from the thread path regulating plate 37 to the sewing needle 21a is tightened as the balance 27 moves up.

(3) At the initial stage when the balance 27 is held at the uppermost position, the contact 50a is located at the protruding portion C,
It comes into contact with the cam surface 48a of the thread releasing cam 48. Therefore, the movable wheel 40 is rotated so as to release the upper thread 36 which is clamped and restrained, and when the movable wheel 40 reaches the release point (diameter 0.1
The release point for the thin upper thread 36 of about mm is indicated by F1 and the release point for the thick upper thread 36 of about 0.3 mm in diameter is indicated by F2), and the upper thread 36 by the movable wheel 40 and the thread guide plate 37.
Is released.

(4) In the middle stage when the balance 27 is held at the uppermost position, the contact 50a contacts the overlapping portion B of the cam surfaces 47a and 48a, and the movable wheel 40 and the yarn guide plate 3
The distance from 7 is maximum. Therefore, the upper thread 36 is held in the released state, and the upper thread 36 is pulled out from the thread spool 35 in accordance with the feeding operation of the work cloth and the swing operation of the sewing needle 21a. still,
The pretensioning device 45 imparts a passing resistance to the pulling operation of the upper thread 36, and the upper thread 36 is provided depending on the thickness and material of the work cloth.
It is for fine adjustment of the withdrawal amount of. Further, as shown by the solid line MC in FIG. 3, the work cloth feeding operation is executed before the release of the upper thread 36. The consumption of the upper thread 36 accompanying this feeding operation is the elastic elongation of the upper thread 36. When the amount of the upper thread 36 is replenished and the restraint of the upper thread 36 is released, the elongation is canceled.

(5) In the latter stage when the balance 27 is held at the uppermost position, the contact 50a is located at the protruding portion d,
It comes into contact with the cam surface 47a of the thread restraining cam 47. Therefore, the movable wheel 40 rotates so as to clamp the released upper thread 36, and when the movable wheel 40 reaches the constraint point (the constraint point for the thin upper thread 36 is C1, the constraint point for the thick upper thread 36 is To C
2), the upper thread 36 is restrained by the movable wheel 40 and the yarn path restricting plate 37. Along with this, the sewing needle 21a is attached to the needle plate 30.
Since the upper thread loop is formed on the lower thread bobbin side, unnecessary upper thread 36 can be prevented from being pulled out from the thread spool 35.

In general, the state in which the upper thread 36 is restrained by the time when the cloth feeding and the needle swing are completed with the restraint of the upper thread 36 being released and the sewing needle 21a reaches the needle plate 30, the upper thread 36 is restrained again. The sewing operation is executed at, and the upper thread loop is formed on the lower thread bobbin side. Therefore, the constraint timing and the release timing of the upper thread 36 are automatically controlled according to the thickness of the upper thread 36, and the feed amount of the work cloth and the sewing needle 21a are controlled.
The required amount of the upper thread 36 determined by the swing amount of the upper thread 36 is surely replenished, and the optimum thread tension according to the upper thread 36 is obtained.

According to the above embodiment, the cam surfaces 47a and 48a are formed on the thread restraining cam 47 and the thread releasing cam 48, respectively, and the movable wheel 40 is moved by transmitting the rotational movement of the cam surface 47a to the movable wheel 40. Move to the restraint point and move the cam surface 48
The movable wheel 40 is moved to the release point by transmitting the rotational motion of a to the movable wheel 40. Therefore, as shown in FIG. 4, the operation curve MD of the movable wheel 40 includes the operation curve MD1 of the movable wheel 40 by the cam surface 47a (indicated by a chain line) and the operation curve MD2 of the movable wheel 40 by the cam surface 48a (in a solid line). (Shown) and are combined.

Therefore, in FIG. 1, if the screws 49 are loosened and the attachment angles of the yarn restraining cam 47 and the yarn releasing cam 48 with respect to the main shaft 14 are changed, the operation curves MD1 and M are obtained.
D2 horizontally moves independently, and the rotational phase angles of the restraint points C1 and C2 and the release points F1 and F2 are adjusted. Therefore,
It is possible to freely adjust the constraint point and the release point by a simple operation, as compared with the conventional case in which the operation of moving the entire motion curve MD of the movable wheel 40 and the operation of changing the height of the motion curve MD are performed in parallel. It will be possible. Moreover, when the contact 50a comes into contact with the overlapping portion B of the yarn restraining cam 47 and the yarn releasing cam 48, a gap larger than the maximum usable upper thread thickness is present in the contact ring 4.
Since it is formed between 0 and the yarn path regulating plate 37, the upper thread 36 can be always released in response to the replacement of the upper thread 36.

In the above embodiment, the operating curve M
Although the flat portion α is formed in D, the present invention is not limited to this, and the interval between the release points F1 and F2 and the restraint points C1 and C2 (that is, the withdrawal amount of the needle thread 36) is set to a predetermined value. If so, the flat portion α may be eliminated. Incidentally, this kind of operation curve can be realized by shortening the length of the overlapping portion B of the cam surfaces 47a and 48a.

Further, in the above-described embodiment, the movable wheel 40 and the yarn guide restricting plate 37 are caused by the contact 50a coming into contact with both the cam surfaces 47a and 48a in the overlapping portion B.
Although a gap of "0.7 mm" is formed between the upper thread 3 and the upper thread 3 that can be used, the present invention is not limited to this.
It is sufficient if the maximum thickness is 6 or more. When the maximum thickness of the upper thread 36 is “0.3 mm” as in this embodiment,
If the gap of about “0.4 mm” is formed, the upper thread 36 can be pulled out smoothly.

In the above embodiment, the pretensioning device 45 is used to provide passage resistance to the needle thread 36. However, the pretensioning device 45 may be provided if necessary.

Further, in the above embodiment, except for the initial stage of the cloth feeding, while the cloth feeding is substantially executed,
Although the configuration is such that the balance 27 is held at the uppermost position, the present invention is not limited to this, and the cam hole 26 may be formed so that the balance 27 is held at the uppermost position from the start of cloth feeding.

[0054]

As is apparent from the above description, the needle thread withdrawing amount adjusting device of the present invention has the following excellent effects. According to the means of claim 1, since the restraint timing and the release timing can be adjusted individually, compared to the conventional case in which the rotation cam mounting angle adjustment and the contact wheel mounting angle adjustment are performed in parallel. It is possible to easily adjust the release timing and the restraint timing.

According to the second aspect, the restraint timing can be adjusted by adjusting the mounting angle of the yarn restraining cam with respect to the main shaft, and the release timing can be adjusted with the adjustment of the mounting angle of the yarn releasing cam with respect to the main shaft. Since it can be adjusted, the timing can be adjusted by a simple operation such as changing the mounting angle of the cam.

According to the third aspect of the present invention, when the driven body comes into contact with both the yarn restraining cam and the yarn releasing cam, a gap greater than the maximum usable upper thread thickness is formed between the sandwiching bodies. Therefore, the upper thread can be always released in response to replacement of the upper thread.

[Brief description of drawings]

FIG. 1 is a perspective view of a main part showing an embodiment of the present invention.

FIG. 2 is an enlarged side view showing a thread releasing cam and a thread restraining cam (a sectional view taken along the line EE in FIG. 6).

FIG. 3 is a timing chart showing movements of a balance, a sewing needle, a movable wheel, and a feed dog.

FIG. 4 is a diagram showing a principle of adjusting release timing and restraint timing.

FIG. 5 is a perspective view showing the external appearance of the sewing machine.

FIG. 6 is a front view of the main part

FIG. 7 is a side view of the main part.

FIG. 8 is a view showing a state in which the upper yarn is clamped and restrained by a yarn path restricting plate and a movable wheel (a cross-sectional view taken along the line of FIG. 7)

FIG. 9 is a view corresponding to FIG. 1 showing a conventional example.

FIG. 10 is a view corresponding to FIG.

[Explanation of symbols]

14 is a spindle, 21a is a sewing needle, 27 is a balance, 35 is a thread spool (thread supply source), 36 is an upper thread, 41 is a nipping body, 46 is a timing adjusting means, 47 is a thread restraining cam, 48 is a thread releasing cam, Reference numeral 50 indicates a first arm (driven body).

Claims (3)

[Claims] 1. A restraint position for pinching and restraining a portion of the needle thread, which is located between the yarn source and the balance, of the needle thread from the thread source to the sewing needle, and a releasing position for releasing the holding force. By providing a pair of clamps, and adjusting the constraint timing for moving the clamps to the constraint position and the release timing for moving the clamps to the release position in accordance with the operation of the balance and the sewing needle, the thread supply is performed with the sewing operation. A needle thread withdrawal amount adjusting device for adjusting the amount of the upper yarn withdrawn from a source, wherein a timing adjusting means for individually adjusting the restraint timing and the release timing is provided. 2. A timing adjusting means is provided on a main shaft for operating a balance and a sewing needle, and is provided between a thread restraining cam and a thread releasing cam which rotate in conjunction with the main shaft, and between these cams and a sandwiching body. The rotation movement of the yarn restraint cam is transmitted to the sandwiching body when it comes into contact with the yarn restraining cam, and the sandwiching body is moved to the restraining position. A follower for transmitting the nipping body to the release position to move the nipping body to the release position, and adjusting the attaching timing of the yarn restraining cam with respect to the main shaft, the restraining timing is adjusted, and the yarn releasing cam is attached to the main shaft. The needle thread withdrawal amount adjusting device according to claim 1, wherein the release timing is adjusted in accordance with the adjustment of the angle. 3. When the driven body comes into contact with both the yarn restraining cam and the yarn releasing cam, a gap larger than the maximum usable upper thread thickness is formed between the sandwiching bodies. The needle thread withdrawing amount adjusting device according to claim 2, which is characterized in that.