JPS5811238B2 - Sewing machine thread cutting mechanism - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thread trimming mechanism for a sewing machine, and in particular to a thread trimming cam fixed to a drive shaft such as a main shaft of a sewing machine or a shaft that rotates in synchronization with the main shaft of the sewing machine and formed with a cam groove. The driven body connected to the mechanism is moved in the axial direction against elastic force and connected to the cam groove of the thread trimming cam, and then the driven body is reciprocated around the fixed axis by the rotation of the thread trimming cam as the drive shaft rotates. This invention relates to a thread cutting mechanism that rotates to reciprocate the thread cutting mechanism to cut the thread.

This type of thread cutting mechanism is known, for example, from Japanese Patent Publication No. 49-45349.
This type of thread trimming mechanism is known in the art as described in No. 1, etc., and in this type of thread trimming mechanism, a driven body that reciprocates by a thread trimming cam is reciprocated by a cam groove, so the thread trimming knife is forcibly rotated in a reciprocating manner to cut the thread. The large force makes it possible to cut the thread reliably, and the return movement is also reliable, eliminating accidents caused by collisions between the needle and the knife.Also, the shape of the cam groove allows the reciprocating speed of the knife to be set to any desired position. There are advantages such as reliable thread cutting.

However, the power device that moves the driven body in the axial direction against elastic force and connects the driven body to the cam groove of the thread trimming cam uses the electromagnetic force of the electromagnet activated by the thread trimming signal. It requires a large capacity, consumes a lot of power, and requires the use of a large size.Also, due to a slight increase in frictional resistance and moment, the electromagnet's operating time is delayed, causing problems with the driven body and thread trimming. This results in disadvantages such as not being able to interlock with the cam and thread trimming becomes impossible.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-described drawbacks of the conventional sewing machine by providing a connecting cam for connecting a thread trimming cam to a driven body of a drive shaft such as a main shaft of a sewing machine or a shaft synchronously interlocked therewith.

Embodiments of the present invention will be described below with reference to the drawings. A sewing machine 1 shown in FIG. 1 includes a pair of needle thread tension devices 1a.

1b and a pair of horizontal pots 2a and 2b as shown in FIG.
This sewing machine 1 is a well-known two-needle sewing machine with a constant low pressure for a certain period of time at the initial stage of operation of the sewing machine, regardless of the amount of toe depression of the pedal 3, as shown in Japanese Patent Laid-Open No. 54-97136. After driving the sewing machine at a high speed, the sewing machine is driven at a high speed by a speed control device as a sewing machine driving means, and by pressing the heel of a well-known pedal, a needle up signal causes the sewing machine to rotate for half a cycle, and a needle down signal causes the sewing machine to rotate for another half cycle. A stop device is provided for stopping the needle in the upper position.

First, the drive section of the thread cutting mechanism will be explained.

FIG. 6 is a partially omitted plan view of only the thread cutting mechanism provided on the underside of the bed 5 of the sewing machine, as seen from above the bed 5. Reference numeral 6 indicates a horizontally disposed hook shaft as a drive shaft, and the main shaft of the sewing machine ( (not shown) in a 1:1 ratio.

γ is a cam body fixed to the hook shaft, and has a cam groove 8 for thread cutting.
A thread cutting cam 9 formed with a thread trimming cam 9 and a connecting cam 10 formed of an outer circumferential cam provided on one end surface are integrally formed.

A support 11 is fixed to the lower surface of the bed 5 and supports a vertical driven shaft 12.

Reference numeral 13 denotes a driven body, which is supported rotatably and movably in the axial direction by the driven body shaft 12, and has an arm 13b extending in a direction substantially orthogonal to an arm 13a extending downward from the cam body, and an engaging claw 13.
c, and is always pressed downward by a spring 61.

A roller shaft 16 is provided at the tip of the arm 13a, and forms an engagement shaft 15 that extends downward with the upper roller 14 that can be loosely fitted into the cam groove 8 of the thread trimming cam 9.

The engaging pawl 13 is opposed to two step portions 17 a and 17 b formed on the support body 11 as shown in FIGS. 6 and 7.

Reference numeral 18 denotes an electromagnet as a power device, which is supported by a counter plate 19 fixed to the lower surface of the bed 5, and its armature 20 (not shown) is always pressed to the left in FIG. 6 by elastic force.

21 is a connecting body, which forms an arm 21a extending above the connecting cam 9 and an arm 21b having a pressing part 21c facing the lower end surface of the arm 13b of the driven body 13 as shown in FIG. Armature 2 is bent into a U-shape as shown in Figure 6.
0 and two E-rings 22a, 2.
2b so as to move in conjunction with the movement of the armature 20.

Further, as shown in FIG. 8, the projection 21d of the connecting body 21 is brought into contact with the lower surface of the supporting plate 19 by the action of a spring 230 provided between the connecting body 21 and the supporting plate 19, thereby maintaining the connecting body 21 in the state shown in FIG. .

As shown in FIGS. 6.8 and 9, reference numeral 24 denotes a connecting roller as a connecting follower, which is fixed to the tip of the arm 21a of the connecting body 21 toward the connecting cam 9.

Reference numeral 25 denotes a thread loosening body, whose base is bent so as to sandwich the support part of the support body 11 as shown in FIGS. 10 and 11, and rotatably supports the driven body shaft 12. An engaging end surface 25a and a locking end surface 25b are formed opposite to the mating shaft 15, and two needle thread tension devices 1a of the sewing machine are provided at the tips.

Flexible wire 2 as an interlocking mechanism connected to a known mechanism for applying and releasing tension to the needle thread by 1b
Fix 6.

Reference numeral 27 denotes a locking body, the base of which is rotatably supported on the end surface of the support body 11 by a stepped screw 28, as shown in FIGS.
a and an upwardly facing locking step 27b facing below the locking end surface 25b of the thread loosening body 25, and the upper end of the contact portion 27a is moved by the force of the spring 29 provided between the support body 11 and the arm 13a. It is in pressure contact with the lower end surface of.

Next, the portions having the horizontal hooks 2a, 2b and the thread cutting knife will be explained with reference to FIGS. 2 to 5.

FIG. 2 is a plan view of a pair of horizontal hooks 2a and 2b, each of which has the same mechanism on the left and right, and only the side of the horizontal hook 2a will be described below.

Reference numeral 30 denotes a pot base, which is fixed to the bed 5 through its elongated hole 31.

2a is a well-known horizontal full-rotation hook, except for a part, which is supported by a hook base, rotates in conjunction with the hook shaft 6, and has an outer hook 33 with a tip 33a for catching a needle thread loop, and a bobbin with hook thread. 3
4, and a cap 36 that is removably attached to the inner hook 35 so as to cover the upper surface and periphery of the bobbin 34.
It is composed of.

The cap 36 also has a brake piece 37 shown in FIG.
8, and a pressing portion 3γa extending slightly away from the outer periphery of the cap 36, and a pressing portion 3γa whose tip is bent and extends inward from the notch 36a of the cap 36, as shown in FIG. A brake piece 37b is formed opposite to the outer periphery of the brim, and this brake piece 37 is normally operated by its own elastic force.
The pressing part 37a separates from the outer periphery of the cap 36, and the brake element 3
7b is away from the outer periphery of the bobbin, and the pressing part 37a
The brake element 37b is provided so as to come into contact with the collar of the bobbin and perform braking by pressing the bobbin from the outside against an elastic force.

Reference numeral 39 shown by a two-dot chain line in FIG. 3 is a thread cutting shaft, which is rotatably supported perpendicular to the hook base 30, and forms a moving knife stand 40 at its upper end.

Reference numeral 41 denotes a moving knife, whose base is fixed to the moving knife stand 40 with screws 42, and whose tip extends to the vicinity of the needle thread catching portion of the horizontal hook 2a and forms a thread catching hook 43 there. As shown in FIG. 2, when the needle thread moves forward in the clockwise direction, it crosses and passes through one of the needle thread loops that revolve around the bobbin and the yarn, and during the backward movement, these threads are captured by the catching hook 43, The threads are sheared with a fixed knife 44 fixedly arranged near the end of the thread.

As shown in FIG. 3, the thread cutting shaft 39 below the movable knife table 40 has a main pressing body 45 bent in the shape of an opening and placed inside.
A subordinate pressing body 46 disposed on the outside thereof is provided rotatably.

The main pressing body 45 is provided with a downwardly extending portion 45a and an upwardly extending portion 45b, and the downwardly extending portion 45a is provided with a movable scalpel table 40.
An engagement bent part 45c and a spring catch 45d are formed, which are bent upward so as to face the side end surface of the forward rotation direction, and the upper extending part 45b has a tip part bent upward. Later, a horizontally extending locking portion 45e is formed.

The subordinate pressing body 46 is formed with a lower extending portion 46a and an upper extending portion 46b bent along the upper extending portion 45a of the main pressing body 45, and a spring hook 46c is formed on the lower extending portion 46a. The tip of the upwardly extending portion is bent in the horizontal direction and then bent upward to form a contact 46d facing outwardly from the pressing portion 37a of the brake piece 37.

Further, a spring hook 45f extending outward is formed on the main pressing body 45, and a spring 47 is passed between the spring hook 45f and the hook base 30, and the spring hook 45f is pressed against a pin 48 provided on the hook base 30. The main pressing body 45 is maintained in the position shown in FIGS. 2 and 3.

Furthermore, spring hooks 45d and 46 of the main and subordinate pressing bodies 45 and 46
An interlocking spring 49 whose strength is weaker than that of the spring 47 of the main pressing body 45 is placed between the main pressing body 45 and the main pressing body 45.

Reference numeral 50 denotes a support fixed to the upper surface of the pot base 30, and an upwardly extending portion 45b of the main and subordinate pressing bodies 45 and 46.

An electromagnet 51 is supported at a position corresponding to the lower part of the tip of 46b.

Reference numeral 52 designates a magnetic plate, which is bent downward on both sides and loosely fitted into the protrusion 50a of the support 50 through a hole 52a formed at the base, and the magnetic body 52 is inserted into the second As shown in Figure 5, the yoke 51 of the electromagnet 51 is always
a Separate from the top edge.

Reference numeral 54 denotes a locking plate, which has a mouth shape as shown in FIG. 3 and is fixed to the upper surface of the magnetic plate 52 with a screw. The upper part of the locking part 54a is bent by the spring 53 acting on the magnetic plate 52 to form the locking part 54a of the main pressing body 45.
e It is in pressure contact with the lower surface.

In addition, thread cutting shafts 39 are supported separately on a pair of hook bases 30.
are each connected to a drive mechanism as shown in FIG.

That is, an L-shaped bar 55 is fixed to one thread cutting shaft 39, and one arm 55a of the L-shaped bar 55 is connected to the arm 13b of the driven body 13 described above via a pair of ball connecting rods 56at56b.

The other arm 55b of the L-shaped bar 55 has a pair of elongated holes 58, respectively, in an interlocking arm 57 fixed to the other thread cutting shaft 39.
a, screw 6 through connecting levers 58, 59 with 59a.
Connect by 0.

The present invention has the above configuration, and the operation will be explained next.

The conditions shown in each drawing are as follows: The sewing machine is driven at high speed by stepping on the pedal 3 in Fig. 1, and two parallel lock stitches are formed using needle thread and yarn using two needles and a pair of hooks. are doing.

When the heel of the pedal 3 is pressed from this state, a thread trimming signal is first generated by well-known electrical control, but at this stage there is no thread trimming output, and the sewing machine gradually slows down to a moderate speed until it stops at a fixed position. After this is detected, when a needle lower position detection signal is output around the main shaft rotation angle of 210 degrees as shown in FIG. 12, a thread trimming signal is output.

As a result, the electromagnet 18 shown in FIG. 6 is actuated to move the armature 20 to the right, move the connecting body 21 from the unconnected position to the connected position via the E IJ ring 22b, and move the connecting roller 24 to the eighth position. At the position shown in the figure, the connection cam 10 enters the rotation locus.

When the hook shaft 6 and the cam body 7 in FIG. 8 rotate clockwise from this state, the connecting roller 24 is pushed up by the connecting cam 10, and the connecting body 21 rotates clockwise around the armature 20. Due to the movement, the pressing part 21c pushes up the lower end surface of the arm 13b and raises the entire lower driven body 13 in the inoperative position against the spring 61 to the activated position. enters the cam groove 8 of the thread trimming cam 9, the engaging pawl 13c rises vertically from the solid line position in FIG. 7, and the locking body 27 in FIG. The upper portion of the stop step portion 27b is pressed against the lower surface of the locking end surface 25b of the thread loosening body 25.

The main shaft further rotates and the main shaft rotation angle is 270 degrees as shown in Fig. 12.
If the angle exceeds 10°, the cam groove 8 of the thread trimming cam 9 will cause the roller 14 to
Through this, the driven body 13 begins to rotate clockwise around the driven body shaft 12 in FIG. 6.

As the driven body 13 is rotated clockwise in FIG. 6, the engaging claw 13c first moves above the upper step 17b of the support 11 as shown by the dashed line in FIG.
4 and the cam groove 8 of the thread trimming cam 9 is ensured.

Further, due to the forward rotation of the driven body 13, the engagement shaft 15 of the roller shaft 16 is moved to the engagement end surface 25a of the thread loosening body 25 shown in FIG.
, and rotates the thread loosening body 25 as shown by the two-dot chain line.
Pull the flexible wire 26 to release the tension applied to the needle thread by the two needle thread tension devices 1a and lb of the sewing machine,
In connection with this rotation of the thread loosening body 25, the engaging end surface 25 of the thread loosening body 25 is
b moves to the left of the locking step 27b of the locking body 27 in FIG. Toe surface 25b
As a result, the thread loosening body 25 is maintained at the position indicated by the two-dot chain line in FIG.

Further, due to the forward movement of the driven body 13, one thread cutting shaft 39 is rotated counterclockwise via the ball connecting iron 56 a t b and the L-shaped lever 55 shown in FIG.
The other thread cutting shaft 39 is rotated in the same direction via the arm 55b of No. 5, the connecting levers 58 and 59, and the interlocking arm 57.

As the driven body 13 rotates in the forward direction, the pair of thread cutting shafts 390 rotate in the counterclockwise direction, so that the pair of horizontal hooks 2a
, 2b, the forward movement of the movable knife 41 and the bobbin braking are performed, but since they are the same mechanism, one of the horizontal hooks 2a will be described below.
The effect of the side will be explained.

As shown in FIGS. 2 and 3, when the thread trimming shaft 39 starts rotating counterclockwise, the side end surface of the movable knife table 40 engages with the bending engagement portion 45c of the main pressing body 45, and the main pressing The body 45 begins to rotate counterclockwise against the spring 47, and this rotation causes the subordinate pressing body 46 to rotate in the same direction via the interlocking spring 49, and the contact 46d of the main pressing body 45 5 The brake 37b presses the pressing portion 37a of the brake piece 37 as shown by the dashed line in Figure 5, and the brake 37b
Contact the outer periphery of the collar of No.4.

When the contactor 46d comes into contact with the pressing part 37a, as shown in FIG. after passing in the rotational direction of the horizontal hook.

Then, when the main and subordinate pressing bodies rotate to the positions indicated by chain lines in FIG. The left end surface of the main pressing body 45 engages with the right end surface of the locking portion 45e of the main pressing body 45 to prevent the main pressing body 45 from moving back by the spring 47, so that the contact 46d of the secondary pressing body 46 is moved by the interlocking spring 49. The braking piece 37 is pressed by the acting force.

After passing around 340° of the spindle rotation angle shown in Fig. 12,
The cam groove 8 of the thread trimming cam 9 causes the driven body 13 to rotate counterclockwise in FIG. 6 via the roller 14, and the rotation of the thread trimming shaft 390 causes the movable knife 41 to rotate counterclockwise in FIG. The hook 43 captures one of the needle thread loops and the yarn that are rotating around the bobbin.

Due to this backward rotation of the driven body 13, the engaging pawl 13c indicated by the two-dot chain line in FIG. The engagement shaft 15 of the shaft 16 moves to the right at the same time, but the thread loosening body 25
does not return to the solid line position because the locking step portion 27b of the locking body 27 engages with the locking end surface 25b, and the needle thread tension device 1a,
The state in which the needle thread tension applied by 1b is released is maintained.

The return rotation of the driven body 13 also causes the thread trimming shaft 39 to return, and the needle thread and thread caught in the catching hook 43 are pulled out from the needle thread supply source and the bobbin. 1a,
1b is released, it is easily pulled out, and the return rotation of the thread trimming shaft 39 causes the movable knife table 40 to rotate clockwise, but the main pressing body 45 is not engaged with the locking plate 54 shown in FIG. Stop part 5
4a is locked at the position shown by the two-dot chain line, and the braking piece 37 brakes the collar of the bobbin 34, so that the bobbin 34 does not rotate excessively when the thread is pulled out by the moving knife 41.

Then, the needle thread and yarn caught by the catching hook 43 of the moving knife 41 are pulled out in the above state and sheared by the moving knife 41 and the fixed knife 44.

As the main shaft of the sewing machine rotates, the driven body 13 continues to rotate further, and as shown in FIG. The right end surface of the engaging pawl 13 indicated by the dashed dotted line is to the left of the upper step portion 17b, the connecting roller 24 of the connecting body 21 is released from being pushed up by the connecting cam 10, and a needle upper position signal is generated.

As a result, the driven body 13 is moved to the eighth position by the acting force of the spring 30.
10, the roller 14 is moved out of the cam groove 8, and the upper end of the contact portion 27a of the locking body 27 is pressed down against the spring 29 to release the thread loosening body 25 by the locking stepped portion 27b. The thread loosening body 25 shown by the dashed line in Figure 11 moves back to the position shown by the solid line, and tension is again applied to the needle thread by the needle thread tension devices 1a and 1b.

Furthermore, the electromagnet 18 is also deactivated by the thread trimming signal, and its armature 20 moves to the left as shown in FIG. As it moves out of the trajectory, the protrusion 2 moves around the armature due to the acting force of the spring 23, as shown in FIG.
The rotation is restored in the counterclockwise direction until the upper end of 1d contacts the support plate 19.

Furthermore, as shown in FIG. 12, a wiper signal is generated with a delay from the needle top position signal, and the wiper device (not shown) pulls out the cut needle thread end to the upper surface of the cloth, and this signal causes the electromagnet shown in FIG. 51 for a short time.

Due to the action of the electromagnet 51, the left side of the magnetic plate 52 moves down against the spring 53, releasing the locking of the main pressing body 45 by the locking portion 54a of the locking plate 54, and the main pressing body 45 is moved by the spring 47. Due to the acting force, the spring hook 45b moves back to the position shown in FIG. The reverse pressing body 46 also moves back to release the suppression of the brake piece 37 by the contactor 46d, and the braking of the bobbin 34 is released.

Further, the motor that drives the sewing machine is stopped by the above-mentioned needle up position signal, and the sewing machine stops when the needle is in the up position, and each part returns to its original position as shown by the solid line in each figure.

Next, when you step on the pedal 3 with your toe, the sewing machine starts rotating at a constant low speed for a certain period of time at the beginning of the sewing machine operation regardless of the amount of pedal operation due to the action of the speed control device 4, and the cut end of the needle thread passes through the thread hole of the needle. After the seam is reliably formed without coming out, the degree of rotation is gradually increased and the seam is formed.

As described above, the present invention operates a coupling electromagnet as a power device to place the coupling body in the coupling position and rotates the drive shaft, thereby rotating the coupling body with the coupling cam provided on the drive shaft and responding to this rotation. By providing a driven body that is interlocked and connected to the thread trimming mechanism and connected to the cam groove of the thread trimming cam,
Since the driven body and the thread trimming cam are connected via the thread trimming cam by the power of the motor, which is the driving force of the sewing machine, it is possible to reduce the capacity of the thread trimming power device and the connecting electromagnet. This has the effect of reducing power consumption and cost, making it highly economical, and also making it possible to downsize the thread trimming mechanism.In addition, the connection between the driven body and the thread trimming cam is fixed to the drive shaft. Since it is done by
Compared to the conventional method using the electromagnetic force of an electromagnet, the driven body is always reliably connected to the predetermined angular position of the thread trimming cam, regardless of increases in frictional resistance in various parts or decreases in voltage, etc. It has the advantage of being able to cut accurately.

Next, other embodiments of the invention will be described.

In the illustrated embodiment, the present invention is applied to a sewing machine with a horizontal hook, but the same effect can be obtained even if the invention is applied to a sewing machine with a vertical hook.

Further, the same effect can be obtained even if the cam body 7 of the illustrated embodiment is provided on the main shaft of the sewing machine.

Further, the connecting cam 10 of the illustrated embodiment may be formed by forming a cam groove on the end surface of the cam body 7, or forming a cam groove on the outer periphery of the cam body 7 in the same way as the cam groove 8 of the thread cutting cam 9. A similar effect can be obtained even if the connecting body 21 is provided so as to be controlled by.

In addition, in the illustrated embodiment, during thread cutting, the roller 1
4 and the cam groove 8 is connected to the driven body 13.
The connecting body 21 is rotated by the connecting cam 10 until the thread cutting is completed, and the connecting rollers move the connecting body 21 during the 100-rotation trajectory of the connecting cam 10. It is also possible to provide it between the connecting body 21 and the bed 5 etc. so as to maintain the same.

Further, the electromagnet 18 as a power device can be replaced with an air cylinder or the like.

[Brief explanation of drawings]

Fig. 1 is an overall perspective view, Fig. 2 is a plan view of a pair of horizontal hook sections, Fig. 3 is a perspective view of one hook base, Fig. 4 is a perspective view of the brake piece, and Fig. 5 is a plan view of a pair of horizontal hook sections. Fig. 6 is a plan view of the thread trimming mechanism drive section seen from the top of the bed, and Fig. 7 is a v-■ sectional view of
Figure 8 is a cross-sectional view along ■-■ in Figure 6, Figures 9.10 and 11 are ix-■t x in Figure 8
-x, the XI-XI sectional view, and FIG. 12 are approximate time charts. In the figure, 9 is a thread cutting cam, 13 is a driven body, 41 is a moving knife as a thread cutting mechanism, 10 is a connecting cam, 21 is a connecting body, 18
is an electromagnet as a power device.

Claims (1)

[Scope of Claims] 1. A thread trimming cam fixed to a drive shaft such as a sewing machine main shaft or a shaft that rotates in synchronization with the sewing machine main shaft and having a cam groove formed therein, and supported rotatably about a fixed axis relative to the sewing machine frame. and a driven body capable of axial movement along its axis between an operating position where it is connected to the thread trimming cam and rotates back and forth due to its rotation, and an inoperative position where the connection is released by elastic force; In a sewing machine equipped with a thread cutting mechanism that captures, pulls out, and cuts thread in conjunction with the reciprocating rotation of a driven body, 1. Connecting cams such as an outer circumferential cam, an end face groove cam, an outer circumferential groove cam, etc. fixed to a drive shaft; A suppressing portion facing the axially movable end surface of the driven body and a connecting follower facing the cam portion of the connecting cam are formed, and are rotatable about a fixed axis with respect to the sewing machine frame and connected to one side in the axial direction. The connecting follower and the connecting cam are connected by moving to the connecting position, and the connecting follower is pushed by rotation of the connecting cam to rotate around the fixed axis. A connecting body that moves the driven body in the axial direction by a pressing part to set it to the operating position and releases the connection by moving it to the uncoupled position, and a connecting body that operates in response to a thread trimming signal to move the coupled body to the coupled position. A thread trimming mechanism for a sewing machine, comprising: a power device that moves a coupling body to an uncoupled position in connection with completion of thread trimming by the thread trimming mechanism.