JPH0632733B2 - Needle bar drive in sewing machine - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a needle bar drive device for raising and lowering a needle bar provided with a sewing needle in a sewing machine. In particular, the present invention relates to a technique of changing the up-and-down stroke of the needle bar in a manner of changing the top dead center position without changing the bottom dead center position of the needle bar.

(Prior Art) Japanese Patent Laid-Open No. 59-2791 discloses a technique in which a needle bar elevating stroke is variable in order to increase or decrease the length of a stitch loop in a sewing machine.
It is disclosed in the publication.

(Problems to be Solved by the Invention) When the lifting stroke is changed by the technique described in the above publication, not only the top dead center position but also the bottom dead center position is changed. For this reason, there remains a technical problem that the loop formation timing varies and the loop formation operation becomes uncertain.

SUMMARY OF THE INVENTION The present invention proposes a lifting stroke changing mechanism in which only the top dead center position is changed and the bottom dead center position is not changed, thereby ensuring the loop forming operation.

(Means for Solving the Problems) In order to achieve the above object, the present invention has developed a needle bar drive device for a sewing machine having the following requirements.

This device is capable of swinging around a needle bar 1 which is supported by a sewing machine head so as to be able to move up and down and has a sewing needle 2 attached to a lower end thereof, and an axis a fixed to the sewing machine head, and the swinging thereof. A needle bar drive member 35 whose end 36 engages with the needle bar 1 to move the needle bar 1 up and down, and a connecting guide 38 formed on the needle bar drive member 35.
And a connecting link 34 that is slidably connected to the same and that swings the needle bar drive member 35 by itself moving up and down, and the connecting link 34 that is connected to the connecting link 34.
Connecting part moving member 3 for sliding the sliding guide 38 onto the connecting guide 38.
2 and 33, and the trajectory drawn by the connecting portion 37 of the connecting link 34 when the connecting guide 38 is located at the bottom dead center with respect to the needle bar drive member 35 in the state of being located at the bottom dead center. It is characterized in that it is formed along.

(Operation) According to the needle bar drive device having this configuration, the needle bar 1 is moved up and down by the swing of the needle bar drive device 35, and the needle bar drive device 3 is moved.
5 is swung by the up and down movement of the connecting link 34. Then, the connection point or the connecting portion 37 of the connecting link 34 slides along the connecting guide 38 with respect to the needle bar driving device 35, so that the connecting link 34 and the needle bar driving member 35 reach the swing center a. Distance changes. That is, when the connecting point or the connecting portion 37 slides along the connecting guide 38, the lever ratio of the swing member changes, and the connecting link 34
The needle bar drive member 35 swings most when the arm moves up and down closest to the swing center a, and the needle bar drive member 35 swings the least when the link link 34 moves up and down farthest from the swing center a. Move. In this way, the lifting stroke of the needle bar 1 is adjusted.

Moreover, according to this configuration, since the connecting guide 38 is formed along the locus drawn by the connecting point when the connecting link 34 is located at the bottom dead center, even if the lever ratio is changed,
The bottom dead center position of the needle bar drive member 35 does not change, and the bottom dead center of the needle bar does not change.

(Embodiment) Next, one embodiment of the present invention will be described with reference to the drawings.
In the figure, 1 is a needle bar supported up and down by a frame F of the sewing machine head, 2 is a sewing needle attached to the lower end of the needle bar, 3
Is a nipple that surrounds the needle bar 1 with respect to the frame F and is vertically and horizontally rotatably supported, and 4 is an elevating member that is vertically slidably supported with respect to the frame F behind the needle bar 1. The upper piece 4a whose upper end is bent in an L shape and extends forward is formed in a bifurcated shape and is movably linked to the connecting member 5 fitted near the upper end of the needle bar 1. Meanwhile,
On the rear side surface near the central portion, a first engaging member 7 having an engaging groove 6 formed laterally in the central portion is provided in a protruding manner.

Reference numeral 8 denotes a nipple rod which is vertically supported on one side of the needle bar 1 so as to be vertically movable with respect to the frame F. The nipple rod 8 is always urged downward by a spring and extends rearward in the vicinity of its central portion. Second
While the engaging member 9 is fixedly attached, the nipple 3 is attached to the lower end of the engaging member 9.
An engaging member 11 that is movably linked is fitted to a connecting member 10 that is fitted to the upper part of the.

Numeral 12 is a cloth pressing rod which is vertically movably supported by the other side of the needle bar 1 so as to be vertically movable with respect to the frame F. The three engaging members 13 are fixedly attached, and below the cloth engaging member 13, a cloth retainer 14 for pressing the needle base of the fabric in an encircling manner at the time of transferring the fabric is provided with a universal joint 15, a spring 16, and a fabric retainer support rod 17.
When the cloth presser bar 14 is vertically moved by the vertical movement of the cloth presser bar 12, the cloth presser bar 14 is horizontally displaced in any direction to transfer the cloth when the cloth presser bar 12 is moved downward, and when the cloth presser 14 is moved upward after the horizontal displacement. Then, the elastic force of the spring 16 automatically returns to the original position in a centripetal manner.

Reference numeral 18 denotes an upper cam shaft horizontally rotatably provided in the rear upper portion of the frame F along the left-right direction. The first cam 30 having a cam groove 30a is fixed to the upper cam shaft 18, and a driving force (not shown) is provided. The rotation of the shaft is transmitted to the upper cam shaft 18, and the upper cam shaft 18 is rotationally driven.

Reference numeral 19 denotes a support shaft that is rotatably provided horizontally below the upper cam shaft 18 in parallel with the upper cam shaft 18. The support shaft 19 has a center b at a position deviated from its rotation center a. The eccentric collar 33 that it has is fixed so as not to rotate relative to it. Support shaft 19
Is rotationally driven by a stroke changing control motor (not shown) whose rotation is controlled based on a stroke changing signal for changing the lifting stroke of the needle bar 1, and when the support shaft 19 rotates, the center b of the eccentric collar 33 moves to the support shaft 19. It revolves around the center of rotation a.

Reference numeral 20 denotes a lower cam shaft which is rotatably and laterally suspended below the support shaft 19, and is rotationally driven by an unillustrated evacuation control motor whose rotation is controlled based on an evacuation signal transmitted when the upper cam shaft 18 is stopped. It

Reference numeral 21 denotes a three-pronged nipple rod driving member which is fitted to the support shaft 19 through an eccentric collar 22 which is fitted to the support 19 so as to be capable of swinging movement. The arm 21a is movably opposed to the second cam 23 fitted to the upper cam shaft 18, while the front arm 21b extended forward is a drive pin 26 fixed to the front end of the front arm 21b. A lower arm 21 which is connected to the second engaging member 9 via the above so as to be capable of pushing up and is further extended downward.
c is driven by a second retracting cam 24 fitted to the lower cam shaft 20 and is spaced apart from the second retracting cam 24, and the upper arm 21a reciprocally swings and the front arm 21 is oscillated by the steady rotation of the second cam 23.
While b reciprocally swings to move the nipple rod 8 up and down, when the lower cam shaft 20 rotates about 90 ° when the upper cam shaft 18 is stopped, the lower arm 21c is pushed forward to move the front arm 2
1b excessively oscillates upward, the nipple rod 8 is pulled up above the top dead center of the steady vertical movement and held at the retracted position above the top dead center, and when the support shaft 19 rotates a predetermined angle, The swing fulcrums of the arm 21a and the front arm 21b are displaced to increase or decrease the vertical movement stroke of the nipple rod 8.

Numeral 25 has substantially the same shape as the nipple rod drive member 21 and has a support shaft 19
On the other hand, an upper arm 2 which is a presser bar driving member fitted so as to be swingable through an eccentric collar and which extends rearward and upward.
5a is drivenly opposed to a third cam (not shown) fitted to the upper cam shaft 18, while the front arm 25b extending forward is a drive fixed to the front end of the front arm 25b. A lower arm (not shown), which is connected to the third engaging member 13 via a pin 27 so as to be capable of pushing up, and extends downward (not shown) is a third retracting cam (not shown) fitted to the lower cam shaft 20. The upper arm 25a is reciprocally oscillated by the steady rotation of the third cam and the front arm 25b is oscillated reciprocally, and the work clamp bar 12 is vertically moved. When the lower cam shaft 20 rotates by approximately 90 ° when the upper cam shaft 18 is stopped, the lower arm is pushed forward, the front arm 25b excessively swings upward, and the work clamp rod 12 becomes the nipple rod 8. Synchronously raised above the top dead center of steady vertical movement Is held at the retracted position above the top dead center, and when the support shaft 19 rotates a predetermined angle in response to the stroke change signal, the swing support point of the front arm 25b is displaced to increase or decrease the vertical movement stroke of the work clamp bar 12. It

Reference numeral 29 denotes a swing lever that is swingably supported in a vertical direction with the rear end portion as a swing center in a state where the rear end portion is pivotally supported by the rear upper end of the frame F and the front end portion extends forward. The pin 31 engaged with the cam groove 30a of the first cam 30 is fixed near the center thereof, and the swing lever 29 is swing-driven in the vertical direction by the rotation of the first cam 30.

Reference numeral 32 denotes an interlocking lever that is fitted to the eccentric collar 33 so as to be freely rotatable, and is swingably fitted to the support shaft 19 via the eccentric collar 33. Protrusion 3
2a is formed.

At the front end of the swing lever 29, the swing lever 29 and the interlocking lever 3
The upper end of a connecting link 34 that connects the two is connected to the lower end of the connecting link 34.
A connecting portion 37 that connects the lower end of the connecting link 34 and the lower end of the connecting link 34 with a connecting pin is formed.

When the swing lever 29 swings, the connecting link 34 is driven in a substantially vertical direction to move up and down, and the connecting portion 37 is displaced in a substantially vertical direction. When the support shaft 19 rotates and the center b of the eccentric collar 33 turns around the rotation center a of the support shaft 19, the connecting portion 37
Moves about the connection fulcrum e between the swing lever 29 and the connection link 34 in an arc in a linear manner toward the rotation center a of the support shaft 19 and the opposite side thereof.

A bifurcated needle that is swingably supported by a support shaft 19 adjacent to the interlocking lever 32 and that swings about a rotation center a of the support shaft 19 (which does not move with respect to the sewing machine head) as a swing center a. The rod drive member 35 is formed with a front arm 35a extending forward and swinging in the vertical direction, and a lower arm 35b extending downward and swinging in the front-rear direction.

At the tip of the forearm 35a of the needle bar drive member 35, a swing end portion 36 that moves up and down while being connected to the needle bar 1 is formed.
The swinging end portion 36 is engaged with the engaging groove 6 of the first engaging member 7 of the elevating member 4. The needle bar 1 is driven up and down by the vertical movement of the swing end 36, and when the swing end 36 is displaced to the bottom dead center, the needle bar 1 descends to the bottom dead center and the swing end 36 moves to the top dead center. When the needle bar 1 is displaced to, the needle bar 1 rises to the top dead center.

A connecting portion 37 of the connecting link 34 is fitted near the proximal end of the front arm 35a of the needle bar driving member 35, and the connecting portion 37 is moved to the swing center a side and the counter swing center side of the needle bar drive member 35. An elongated groove-like fitting groove 38 for guiding the connection point is formed, and the connecting portion 37 is provided on the needle bar drive member 35 at the swing action point c thereof.
Are connected by. When the connecting portion 37 is displaced to the swing center a side and the counter swing center side and the position of the swing action point c is changed, the swing width of the needle bar drive member 35 is changed and the swing end portion 3 is changed.
The vertical movement width of 6 is changed, and the vertical movement stroke of the needle bar 1 is increased or decreased. At this time, the vertical movement width of the swing end portion 36 increases as the connecting portion 37 approaches the swing center a, and the swing end portion 36 increases as the connecting portion 37 moves away from the swing center a.
The vertical movement width of becomes smaller.

The connecting point guide fitting groove 38 of the needle bar driving member 35 swings when the connecting portion 37 and the swinging member 36 are at the bottom dead center when the positions of the connecting portion 37 and the swinging action point c are changed. In the direction in which the gradient of the line segment d1 connecting the center a and the rocking action point c at each position is substantially unchanged, that is, the vertical movement width of the rocking end portion 36 at the bottom dead center is minimized. The portion 36 is formed so as to guide the connecting portion 37 along a direction in which the portion 36 is held at a substantially fixed position at the bottom dead center.

That is, first, the needle bar drive member 35 is placed at the bottom dead center position shown in FIG. Next, the swing lever 29 is placed at the bottom dead center position, and the connection point e between the swing lever 29 and the connection link 34 is placed at the bottom dead center position, whereby the connection link 34 is placed at the bottom dead center.
The connecting link 34 can still move at the bottom dead center around the connecting point e placed at the bottom dead center. Solid and imaginary lines in the figure indicate the posture of the connecting link 34 in the bottom dead center state. The connecting point guide fitting groove 38 is formed along the line drawn by the connecting point or the connecting portion 37 of the connecting link 34 in this state.

When the fitting position of the connecting portion 37 in the fitting portion 38 is changed,
When the connecting portion 37 is displaced to the top dead center and the swing end portion 36 moves upward to the top dead center, the gradient of each line segment d2 connecting each swing action point c and the swing center a changes, and The top dead center position of the moving end 36 fluctuates up and down. Further, the slope of the line segment d1 connecting each swing action point c and the swing center a when the connecting portion 37 is located at the bottom dead center is almost constant at the bottom dead center even if the position of the connecting portion 37 is changed. Held in position. Therefore, the position of the bottom dead center of the needle bar 1 is made substantially constant by changing the position of the connecting portion 37,
The lifting stroke of the needle bar 1 can be changed by changing only the position of the top dead center of the needle bar 1.

As described above, the position of the connecting portion 37 in the connecting point guide fitting groove 38 is displaced by rotating the shaft 19 to eccentrically rotate it. When the center b of the eccentric color 33 is displaced forward, the distance between the connecting portion 37 and the swing center a increases, and when the center b of the eccentric color 33 is displaced rearward, the distance decreases.

That is, in the present embodiment, the eccentric collar 33 and the interlock lever 32 are used to slide the connecting link 34 in the connecting point guide fitting groove 38.

The lower arm 35b of the needle bar drive member 35 always keeps the lower camshaft 2
When the lower cam shaft 20 is rotated about 90 ° by the retract signal when the upper cam shaft 18 is stopped, the lower arm 35b is moved to the forward position. When pushed, the upper arm 35a excessively swings upward, and the needle bar 1 retreats above the steady top and bottom dead center together with the sewing needle 2 in synchronization with the nipple rod 8 and the work clamp drive rod 12. It is held in the retracted state.

Next, the operation and effect of the embodiment having the above configuration will be described.

In this example, the needle bar 1 is movably supported by the sewing machine head and has a sewing needle 2 attached to the lower end thereof, and is swingable around an axis a fixed to the sewing machine head and its swinging end. 36 is a needle bar drive member 35 that engages with the needle bar 1 to move the needle bar 1 up and down, and a connecting guide 38 formed on the needle bar drive member 35.
And a connecting link 34 that is slidably connected to the same and that swings the needle bar drive member 35 by itself moving up and down, and the connecting link 34 that is connected to the connecting link 34.
Connecting part moving member 3 for sliding the sliding guide 38 onto the connecting guide 38.
2 and 33, and the trajectory drawn by the connecting portion 37 of the connecting link 34 when the connecting guide 38 is located at the bottom dead center with respect to the needle bar drive member 35 in the state of being located at the bottom dead center. It is formed along.

Therefore, when the loop length of the stitch loop formed by the vertical movement of the sewing needle 2 is changed, the loop length is expanded and contracted at the upper end side of the stitch loop, and the vertical movement operation of the sewing needle 2 and the winding of the sewing thread around the sewing needle 2 loop the loop. The operation of the loop forming the stitches is always synchronized even if the vertical movement stroke of the sewing needle 2 changes, so that the stitch loop forming operation can be made accurate and stable, and the timing of the looper is readjusted every time the loop length is changed. This has the effect of eliminating labor.

(Effect of the invention) Since the present invention is configured as described above, when changing the loop length of the stitch loop formed by the vertical movement of the sewing needle, the loop length is expanded and contracted on the upper end side of the stitch loop, The vertical movement of the sewing machine and the movement of the looper that forms a loop by winding the sewing thread around the sewing needle are always synchronized even if the vertical movement stroke of the sewing needle fluctuates, and the stitch loop forming operation can be made precise and stable, and the loop This has the effect of eliminating the need to readjust the looper timing each time the length is changed.

[Brief description of drawings]

The drawings show an embodiment of the present invention. FIG. 1 is a side sectional view of a main part, FIG. 2 is a front view of the same, and FIG.
-X line arrow view, FIG. 4 is a YY line sectional view of FIG. 3, and FIG.
The figure is an illustration of the swinging motion of the needle bar drive member. 1 ... Needle bar, 2 ... Sewing needle 35 ... Needle bar drive member, b ... Swing fulcrum c ... Swing action point

Claims (1)

[Claims] 1. A needle bar which is supported by a sewing machine head so as to be able to move up and down and has a sewing needle attached to its lower end, and a swinging end which is swingable around an axis fixed to the sewing machine head. It is slidably connected to a needle bar drive member that engages with the needle bar and moves the needle bar up and down, and a connecting guide formed on the needle bar drive member, and ascends and descends itself. A connecting link for swinging the needle bar drive member, and a connecting part moving member that is connected to the connecting link and slides the connecting link on the connecting guide, wherein the connecting guide is A needle bar drive member in a sewing machine, wherein the needle bar drive member is formed along a locus drawn by a connecting portion of the connecting link when the needle bar drive member is located at the bottom dead center. apparatus