JP2910094B2 - Sewing machine balance device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sewing machine balance device that swings a balance according to the movement of a sewing needle according to the rotation of an upper shaft that is driven to rotate.

[Background Art] Generally, a balance that moves up and down in time with the upper shaft of a sewing machine supplies an upper thread to a lower thread bobbin side for sewing with a sewing needle when descending, and a sewing process when ascending. Plays the role of tightening the upper thread loop formed in the eye of the sewing needle and replenishing the upper thread from the thread spool by a predetermined amount for the next sewing.

Conventionally, various types of this balance mechanism are known, for example, as described in Japanese Utility Model Publication No. 63-228,
It is known that a balance is supported on a sewing machine frame by a balance support shaft so as to be swingable, a balance and a crank fixed to an upper shaft are connected by a link, and the balance is moved up and down.
Japanese Patent Application Laid-Open Nos. Sho 63-105788, 63-105789, and 63-105789 disclose that the thread tension can be automatically controlled.
As disclosed in Japanese Patent Publication No. 105790, a balance is supported on a sewing machine frame such that it can swing from a balance support shaft, and a long groove having an arc-shaped groove is formed on the balance, and the long groove rotates with the rotation of the upper shaft. By engaging the crank pin provided on the rotating body to be moved, the balance is moved up and down, when the balance is at the uppermost position, the supply of the upper thread is executed, and the supply of the upper thread is stopped in other periods. Some of them have been proposed.

[Problems to be Solved by the Invention] However, in such a conventional device, a reaction force acts on the thread holding portion of the balance due to the tightening action of the upper thread performed when the balance moves upward. At this time, the crank pin is approaching the balance support shaft, and this reaction force
A large load of (distance from the thread holding portion of the balance to the balance support shaft) / (distance from the crank pin to the balance support shaft) times acts on the crankpin. For this reason, there has been a problem that the crankpin and the long groove need to be robust enough to withstand a large load. Further, since the crank pin slides in the long groove and reciprocates, the crank pin reciprocates once per rotation of the upper shaft. That is, the crankpin slides twice in the long groove, and the durability of the sewing machine that operates at high speed or is frequently used becomes a problem.
In addition, even a relatively high-speed home sewing machine has a problem in that it requires advanced plastic processing technology or the like in order to obtain long groove shape accuracy and wear resistance.

Accordingly, an object of the present invention is to provide a sewing machine balance device with improved durability, with the object of solving the above problems.

[Means for Solving the Problems] In order to achieve the object, the present invention has the following configuration as means for solving the problems. That is, a thread supplied from a thread spool is hung on a thread catcher fixed to a sewing machine frame, the thread is passed through a thread holding portion of a balance, and the hand is moved according to the movement of a sewing needle by rotation of an upper shaft which is driven to rotate. A balance device for a sewing machine that swings a stool, wherein one end of the balance is rotatably supported on a crank pin disposed on the upper shaft eccentric from the axis of the upper shaft, and the balance is swung on the sewing machine frame. A swing lever that is movably supported and swings according to a cam curve of a cam that rotates together with the upper shaft, the swing end of the swing lever being pivotally supported on one end of a connection lever, and The other end of the balance is pivotally supported by the balance, and the movement locus of the thread holding portion of the balance near the uppermost position of the balance is a substantially circular locus about the thread receiver as a center. That is the configuration of the device.

[Operation] In the sewing machine balance device having the above-described configuration, when the upper shaft is driven to rotate, the crankpin rotatably supports the balance while circularly moving around the upper shaft, and rotates together with the upper shaft. The cam swings the swing lever according to the cam curve. Then, the connection lever transmits the swing of the swing lever to the balance, and the movement locus of the thread holding portion of the balance near the uppermost position of the balance is a substantially arc-shaped locus substantially centered on the thread receiving portion. Let Therefore, when the acting force due to the thread tightening acts on the thread holding portion when the balance is raised, the component force acts on the crankpin and the connecting lever. The component force acting on the cam also acts on the swing lever via the connecting lever, and the component force acting on the cam acts on the cam, so that the component force acting on the cam is small.

[Example] Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic perspective view of a balance device of a sewing machine according to an embodiment of the present invention, and FIG. 2 is an exploded perspective view of a main part thereof. 1
The upper shaft 1 is rotatably driven by a sewing machine motor (not shown).
And the counterweight 4 are fitted. A cam groove 2b formed by combining an arc and a straight line shown in FIG. 3 is formed on the end face 2a of the cam 2 on the opposite side of the counterweight 4, and a cam curve 2c, which is the center locus thereof, is indicated by a dashed line. I have.

Further, the counterweight 4 is fixed to the upper shaft 1 by a set screw 6, and a through hole 8 is formed in the counterweight 4 at a position eccentric from the center of the upper shaft 1 (FIG. 2). reference). Then, the shaft portion 12a of the crankshaft 12, into which one end of the crank rod 10 is rotatably inserted, is further fitted into the through hole 8, and
It is fixed by a set screw 14. The tip of the crankshaft 12 penetrates through the through-hole 8 to form a fitting hole formed in the cam 2.
16 and also serves as a stopper for the cam 2.

A needle bar holder 18 is rotatably inserted into the other end of the crank rod 10. The needle bar holder 18 is fixed to a needle bar 20 which is slidably supported in a vertical direction. And
At the lower end of the needle bar 20, a needle holder 22 and a tightening screw 24
26 are supported. Further, in the vicinity of the sewing needle 26, there is provided a presser foot 28 which is supported so as to be able to move up and down and presses the work cloth during sewing.

On the other hand, the crankshaft 12 is provided with a crankpin 12b at a position eccentric from the center of the through hole 8 and parallel to the upper shaft. One end of the balance 30 is rotatably fitted to the crankpin 12b. It is stopped by the screw 31. As a result, one end of the balance 30 is rotatably supported by the crank pin 12b located at a position separated by a predetermined distance L from the center of the upper shaft 1, and when the upper shaft 1 rotates, the balance 30 is One end is formed so as to make a circular motion having a radius equal to the predetermined distance L. The balance 30 has a thread holding portion 32 on which a needle thread 54 to be described later is hung at the tip thereof, and a balance 30 between the crank pin 12b and the thread holding portion 32.
A support shaft 34 is integrally erected in parallel with the upper shaft 1 (see FIG. 2). In this embodiment, the distance between the center of the crank pin 12b and the center of the support shaft 34 is set to about 1.24L (about 1.24 times the predetermined distance L, and so on). In the present embodiment, the shaft portion 12a and the crankpin 12b are integrally formed as the crankshaft 12. However, the crankshaft 12 is not necessarily required to be integrated, and the crankpin 12b makes a circular motion about the upper shaft 1. As described above, the present invention can be implemented by arranging them at the above-described positions.

One end of a connection lever 36 is rotatably fitted to the support shaft 34, and the other end of the connection lever 36 is
It is rotatably fitted to a support shaft 40 parallel to the upper shaft 1 implanted integrally with the shaft, and is prevented from falling off by a stop shaft 42.
In this embodiment, the distance between the centers of the two support shafts 34 and 40 is about 1.6.
It is designed to be 4L. The swing lever 38 is swingably fitted to a swing shaft 46 screwed to a fixed support frame 44, and further has a tip end of the swing lever 38 extended toward the cam 2. A cylindrical engaging portion 50 is formed on the cam 2, and the engaging portion 50 is slidably engaged with the cam groove 2 b of the cam 2. In this embodiment, the center of the support shaft 40 and the swing shaft 46
And the distance between the center of the swing shaft 46 and the center of the engaging portion 50 is about 1.31 L. The angle formed between the line connecting the center of the shaft 46 and the line connecting the centers of the swing shaft 46 and the engagement portion 50 is 105 ° (see FIG. 4).

When the cam 2 is rotated in the direction of arrow A in FIG.
50 slides in the cam groove 2b, and the swing lever 38 swings about the swing shaft 46 according to the cam curve 2c. Then, through the connecting lever 36, the thread holding portion 32 of the balance 30 is raised as shown in FIG. 4 to tighten the upper thread loop formed in the eye 26a of the sewing needle 26 during sewing, and On a locus S1 for replenishing a predetermined amount of the upper thread for sewing, an arc-shaped locus S2 at the uppermost position, and a locus S3 for descending and supplying the upper thread for sewing to the lower thread bobbin side (not shown). In this embodiment, a cam curve 2c is formed as shown in FIGS.

On the other hand, a thread spool provided on the top of a sewing machine frame (not shown)
The upper thread 54 pulled out from the thread 52 is hooked on a thread receiver 56 provided on the front of the sewing machine, and then supplied to the eye 26a of the sewing needle 26 via the thread holder 32 of the balance 30. Have been. Further, the thread receiver 56a of the thread receiver 56 is disposed so as to be located substantially at the center of the substantially arc-shaped locus S2.

Next, the operation of the above-described sewing machine balance device of the present embodiment will be described.

First, the upper thread 54 is pulled out from the thread spool 52, hanged on the thread receiving portion 56a, and passed through the thread holding portion 32 of the balance 30 to form the eye 26 of the sewing needle 26.
The sewing is started through the upper thread 54 through a. The rotation of the upper shaft 1 (the direction of arrow A in FIG. 4) causes the crankshaft 12 to make a circular motion about the upper shaft 1 via the counterweight 4. Thereby, one end of the crank rod 10 inserted into the shaft portion 12a
The sewing needle 26 is moved up and down together with the needle bar 20 via the crank rod 10 and the needle bar holder 18 in a circular motion.

In addition, the rotation of the upper shaft 1 causes the crank pin 12b of the crankshaft 12 to make a circular motion about the upper shaft 1 and one end of the balance 30 to make a circular motion about the upper shaft 1. At the same time as the rotation of the upper shaft 1, the cam 2 is also rotated, so that the engagement portion moves in the cam groove 2b.
The sliding of 50 causes the swing lever 38 to swing about the swing shaft 46 in accordance with the cam curve 2c. The swing of the swing lever 38 is transmitted to the balance 30 via the connecting lever 36, and
Reference numeral 30 denotes a motion obtained by adding a motion according to the cam curve 2c to the circular motion.

As shown in FIG. 4, assuming that the rotation position of the upper shaft 1 is 0 °, the needle bar 20 is at the uppermost position at this time, and the balance 30 is at the position P0 shown in FIG. 32 is the locus S1
Is almost at the end of the rise. Then, by the rotation of the upper shaft 1 in the direction of arrow A, the yarn holding portion 32 moves up on the locus S1 and moves onto the locus S2 on the circular arc. When the upper shaft 1 is rotated by 90 °, the balance 30 is at the position P90, and the thread holding portion 32 substantially moves along the locus S.
It is at the position where it moves from 2 to locus S3. Further, while the upper shaft 1 rotates from 0 ° to 90 °, the needle bar 20 descends from the uppermost position to a position where the sewing needle 26 stabs the work cloth. Only sent.

Then, when the upper shaft 1 rotates from 90 ° to 180 °, the balance 30 moves from the position P90 to the position P180, and the thread holding unit 32
It descends on the locus S3. In this embodiment, the upper shaft 1 is at 40 °.
The cam curve 2c is formed so that the yarn holding portion 32 moves on a substantially arc-shaped trajectory S2 centered on the yarn receiving portion 56a during the rotation from 105 ° to 105 °. Accordingly, the amount of the upper thread 54 does not change due to the movement of the thread holding section 32 during this time.
Next, when the upper shaft 1 rotates from 180 ° to 270 °, the balance 30
Moves from the position P180 to the position P270, and the thread holding portion 32
Go down further on S3.

When the upper shaft 1 rotates from 270 ° to 0 °, the balance 30 moves from the position P270 to the position P0, and the thread holding unit 32 moves from the locus S3 to the locus S1 and rises. By the upward movement of the thread holding section 32, the upper thread loop formed in the eye 26a of the sewing needle 26 is tightened during the sewing process, and the upper thread 54 is threaded for the next sewing.
A predetermined amount is replenished from the thread holding section 32.
Act on. The acting force on the thread holding portion 32 acts as a component force on the crankpin 12b fitted to one end of the balance 32 and on the support shaft 34 of the balance 30.

The component force acting on the support shaft 34 is
The component acts on the swing lever 38 via the support shaft 40, and the component force acts on the pivot shaft 46 and the engaging portion 50 as a component force. A component force that swings the swing lever 38 around the swing shaft 46 acts on the engaging portion 50, and this component force acts as a surface pressure on the cam groove 2b. However, since only the component force for swinging the swing lever 38 acts on the engagement portion 50 and the cam groove 2b, the acting force is small.

Incidentally, the distance L between the center of the upper shaft 1 and the center of the crank pin b, the distance between the centers of the two support shafts 34 and 40, the swing shaft 46
The distance between the center of the engaging portion 50 and the center of the engaging portion 50, the shape of the cam curve, and the like are not limited to the above-described ratios. It may be determined appropriately so that

As described above, when the upper shaft 1 is driven to rotate, the crank pin 12b circularly moves around the upper shaft 1 to rotatably support the balance 30 in the sewing machine balance device of the present embodiment.
The cam 2 rotating together with the upper shaft 1 swings the swing lever 38 according to the cam curve 2c. Then, the connection lever 36 transmits the swing of the swing lever 38 to the balance 30, and the movement locus of the thread holding unit 32 of the balance 30 near the uppermost position of the balance 30 is changed to the thread receiving unit 56.
An oscillating motion is performed with a locus S2 of a substantially circular arc having a substantially center at a.

Therefore, while the yarn holding unit 32 is moving on the locus S2,
The amount of the upper thread 54 is not changed. Further, in order to tighten the upper thread loop formed in the eye 26a of the sewing needle 26 in the sewing process and to replenish a predetermined amount of the upper thread 54 from the thread spool 52 for the next sewing, the thread holding section 32 is moved along the locus S1. When it is raised, the acting force acts on the yarn holding portion 32, and the acting force is
b, acting as a component force on the swing shaft 46 and the engaging portion 50, respectively. However, the component force acting on the engaging portion 50 is a small amount that causes the swing lever 38 to swing, and the acting force acting on the engaging portion 50 and the cam groove 2b becomes small, and the engaging portion 50 And the durability of the cam groove 2b is improved. In addition, crank pin 12
Since b needs only to support the balance 30 so as to be rotatable, it can be firmly formed on the counterweight 4 or the like.
Further, the cam 2 rotates one revolution together with the upper shaft 1 to rotate the swing lever 38.
Is pivoted, so that one rotation of the upper shaft 1 causes the engagement portion 50 to rotate in the cam groove.
Since it only slides once inside 2b, its durability is improved,
Noise is also reduced.

As described above, the present invention is not limited to such embodiments at all, and can be implemented in various modes without departing from the gist of the present invention.

[Effects of the Invention] As described in detail above, in the sewing machine balance device of the present invention, the amount of the upper thread does not change while the thread holding unit moves on the substantially circular locus, and the sewing process is performed. The acting force acts on the thread holding part, but only the component force acting to swing the swing lever acts on the cam, and the acting force acting on the cam is small, and the durability of the cam is improved. Also, the crankpin can be formed firmly. Further, since the cam also makes one rotation with one rotation of the upper shaft and swings the swing lever, the rotation of the upper shaft only slides once along the cam curve, so that its durability is improved and noise is improved. Is also reduced.

[Brief description of the drawings]

1 is a perspective view of a balance device of a sewing machine as one embodiment of the present invention, FIG. 2 is an exploded perspective view of a main part of the embodiment, and FIG. 3 is a front view showing a cam curve of a cam of the embodiment. FIG. 4 is an operation explanatory view schematically showing the configuration of the present embodiment. 1: Upper shaft 2: Cam 2c: Cam curve, 20: Needle bar 12: Crank shaft 12b: Crank pin 30: Balance, 32: Thread holder 36: Connection lever, 38: Swing lever 46: Swing shaft , 56 ... thread catcher 56a ... thread catcher

Claims (1)

(57) [Claims] A thread supplied from a thread spool is hung on a thread catcher fixed to a sewing machine frame, and the thread is passed through a thread holding portion of a balance. A swinging movement of the balance by means of the sewing machine frame, wherein one end of the balance is rotatably supported on a crankpin disposed on the upper shaft eccentric from the axis of the upper shaft, A swinging lever that is swingably supported on the shaft and swings according to a cam curve of a cam that rotates with the upper shaft. The swinging end of the swinging lever is pivotally supported on one end of a connection lever, and The other end of the connecting lever is pivotally supported by a balance, and the movement locus of the thread holding portion of the balance near the uppermost position of the balance is a substantially arc-shaped locus substantially centered on the thread receiver. Balance device.