JPH0135725Y2 - - Google Patents

Description

[Detailed explanation of the idea]

[Field of Industrial Application] The present invention relates to an improvement of the needle bar swinging mechanism in a so-called lockstitch zigzag sewing machine which has a mechanism for swinging the needle from side to side like a zigzag or buttonhole sewing machine. [Prior Art] FIG. 4 is a perspective view of an example of the main parts of the needle and swing mechanism of a zigzag sewing machine such as a conventional industrial lockstitch button sewing machine. The figure is a conventional example, so the details will be omitted for a brief explanation. Reference numeral 7 denotes an upper shaft (main shaft) of the sewing machine, which is rotationally driven in the direction of the arrow shown in the figure via a pulley P by a motor or the like (not shown). A counterweight 6 is fixed to the tip of the upper shaft 7, and this counterweight 6
A balance 5 and a crank rod 3 are rotatably fixed on the top, and a needle bar crank 16 is pivotally attached to a fulcrum screw 18. The tip of the crank rod 3 engages with a pin on a needle bar holder 8 that is fixedly arranged to hold the needle bar 9. Reference numeral 10 denotes a needle bar rocking table that swings back and forth in the direction of arrow B-C in the figure around a fulcrum pin 17 fixed to the machine frame (head, not shown) of the sewing machine, and holds the needle 11 at the lower end. The needle bar 9 is attached to this needle bar swing base 1.
0 so as to be able to reciprocate in the vertical direction, and is driven by the crank rod 3 via the needle bar holder 8. On the other hand, the reciprocating motion of the needle bar rocking table 10 is
A swing cam CM driven by a motor (not shown) via the upper shaft 7 swings the needle bar swing rod 12 via the needle bar swing forked rod R, and further swings the swing arm 1.
3, a pin 14 fixed thereto, and a square piece 15 that engages with the pin 14 and is rotatably disposed at the lower part of the needle bar swing table 10. In the figure, W indicates an oil wick. In the conventional needle bar swing mechanism as described above,
When the needle 11 is swung left and right (B-C direction), the amount of needle bar rise (the amount of rise of the needle bar from the bottom dead center of the needle bar until the needle meets the hook tip) and the height of the needle bar (the needle bar height) It is known that the absolute value of the distance (distance between the tip of the hook and the upper edge of the needle hole when the thread is caught) changes. FIG. 5 shows a diagram illustrating the principle of variation of each value as viewed from the direction of arrow A (front of the sewing machine bed) in FIG. 4. In the figure, S is the lower axis (the hook axis, the center) of the sewing machine, and the rotary hook 20 (representing the trajectory circumference of the hook tip) runs in the same direction as the upper axis ( (clockwise). The axes of the upper shaft 7, the lower shaft S, and the swing fulcrum pin 17 of the needle bar swing stand 10 are parallel to each other within a plane perpendicular to the bed surface (throat plate surface) NP of the sewing machine. It is located in That is, when viewed from the front of the sewing machine bed, the three axes are on a straight line perpendicular to the bed surface NP. The needle bar heights at the center of the needle bar swing and in the left and right directions (B, C) are l ₁ , l ₂ ,
l ₃ , similarly, the needle bar rise amounts are indicated by m ₁ , m ₂ , and m ₃ , respectively. Table 1 shows an example of the fluctuation values of each of the above values when the swing amplitude of the needle is 3 mm on each side.

[Table] As shown above, depending on the left and right position of the needle bar 9,
The reason why the value changes is that when the needle bar is swung while the upper shaft 7 is rotating in a certain direction, the needle bar 9 moves closer or further apart when viewed from the direction of rotation of the upper shaft.
This is caused by the timing of the vertical movement of the needle 11 becoming relatively early or late. Figure 6 a and b are the dotted circles a and b in Figure 5, respectively.
This is an enlarged view of the part, and it can be understood from the figure that l ₂ ≫ _{l 3} . In this way, if the needle bar height l changes significantly depending on the needle bar swing position, the hook tip 2 will change at each position.
It will be appreciated that the timing at which the 0 will capture the needle thread loop will be different. In this way, if the needle bar height l changes significantly depending on the needle bar swing position, the hook tip 20 will change at each position.
Since the timing at which the sewing machine catches the needle thread loop is different, it is not possible to form uniform stitches without skipped stitches at each position. In order to improve the above-mentioned drawbacks, a so-called reverse hook method (reverse hook method) has been proposed, for example, in Japanese Patent Laid-Open No. 56-52089.
In this method, the rotation direction of the rotary hook 20 is reversed (opposite direction) to the upper shaft 7, so that the needle bar 9 approaches or separates when viewed from the upper shaft rotation direction as described above. In order to correct the relative delay relationship in the timing of the vertical movement of the bar, it is intended that the needle bar height l and the needle bar rising amount m are less likely to change due to the swinging position of the needle bar 9. FIG. 7 shows a diagram corresponding to the case where the reverse hook method is applied to the conventional example shown in FIG. 5. Reverse the direction of rotation around the lower shaft S of the rotary pot 20 (opposite direction)
The other components are left unchanged. Table 2 shows the amount of change in each equivalent l and m amount at each position at this time.

[Problem that the invention attempts to solve]

As shown in Table 2, the amount of change △l in the needle bar height at the left-right swing position is reversed in magnitude compared to the case in Table 1, and the absolute value is almost halved. ,However, in such a proposal example,
Since the rotation direction of the lower shaft is opposite to the conventional one, significant changes are required to the lower shaft drive system, rotary pot, and related mechanisms, and there are also major restrictions on the ability to share parts with other models and other design changes. expected to receive. The present invention was developed in view of the above-mentioned problems, and it is possible to improve the amount of change in needle bar height to the same extent as the conventional proposal without making any major changes to the main mechanism of the sewing machine. The purpose is to make it possible. [Means for Solving the Problems] Therefore, in the present invention, the above-mentioned arrangement position is displaced from the conventional position by a slight distance from a plane perpendicular to the sewing machine bed surface including the lower shaft center axis. This is what I did. [Example] The present invention will be described below based on an example.
FIG. 1 is an operational diagram of the essential parts of the needle bar swinging mechanism showing the upper shaft arrangement position according to the present invention, and FIG. 2 is a slightly more substantial view of FIG. 1. In the figure, above-mentioned figures 4 and 5
Components that are the same or equivalent to those in the figures are indicated by the same or equivalent symbols, and redundant explanation will be omitted. As in the conventional mechanism, the straight line connecting the center of the fulcrum pin 17, which is the center of swing of the needle bar swing table 10, and the center S of the lower shaft is perpendicular to the bed surface (throat plate) NP, and is the center of the upper shaft 7a. is swung by a distance e from the vertical line in the right c direction in the figure. In this embodiment, e=5 mm is selected. H represents the outline of the sewing machine head. FIG. 3 shows the center position of the upper shaft 7a, respectively.
This is a diagram showing the change in the needle bar bottom dead center position when the needle bar is moved to the A 1 , A ₂ , and A ₃ positions, and it is a geometric diagram that shows that the change _in the needle bar height when the needle bar 9 swings left and right decreases. This is a diagram for scientific proof. When the upper shaft 7a position is shifted from A ₁ to _{A 3} as described above, the lowest point of the needle bar on the left and right swinging straight line becomes different between the right and left needle bars. It is assumed that the lowest end is when the needle bar crank 16 and the crank rod 3 (see FIG. 4) form a straight line.
Naturally, as shown in FIG. 6, the left B swing in which the hook tip 20a and the needle bar 9 come together more quickly is farther from _A1 to _A3 , so the lowest point position is shallower. Also, the right C swing is
Since it is close to A ₁ to _{A 3} , the lowest point is slightly deeper than when swinging to the left. The advantage of this method is that the position of the lowest point (needle bar bottom dead center) is different when swinging to the left and right. The reason for this is that when swinging to the left, the tip of the hook is 20a.
The bottom dead center of the needle bar does not need to be far away because the bottom dead center of the needle bar matches quickly, but when swinging to the right, the hook tip and the needle bar match at different times, so in order to obtain a certain level of needle bar height, it is necessary to set the needle bar's bottom dead center farther away. It is necessary to lower the needle bar until Due to the geometry described above, the amount of change Δl in the height of the needle bar when the needle bar 9 swings left and right acts in the direction of decreasing. The dimensions and mechanisms related to the needle bar and needle bar oscillation table in the conventional example shown in FIGS. 4 and 5 remain the same, and the position of the upper shaft 7a is set to e=e as in the embodiment described above.
Table 3 shows the change in needle bar height l when the needle bar height is 5 mm. The swing amplitude shall be 3 mm on each side, as in Table 1.

[Effect of idea]

As explained above, according to the upper shaft arrangement position according to the present invention, the amount of change in the needle bar height at each horizontal swing position of the needle bar can be adjusted without major changes to the main mechanism of the zigzag sewing machine. Therefore, it is possible to form uniform stitches without skipped stitches or the like at a constant needle bar height close to a predetermined value, thereby improving the sewing quality.

[Brief explanation of the drawing]

Fig. 1 is an operating diagram of the essential parts of the needle bar swing mechanism showing the upper shaft arrangement position according to the present invention, Fig. 2 is a slightly more substantial view of Fig. 1, and Fig. 3 is the upper shaft position. Geometric explanatory diagram showing changes in needle bar bottom dead center position due to movement of
FIG. 4 is a perspective view of an example of the main part of the needle bar swinging mechanism of a conventional zigzag sewing machine, FIG. 5 is a configuration diagram as seen from direction A in FIG. 4, and FIGS. FIG. 5 is an enlarged view of portions a and b of the dotted line diagram, and FIG. 7 is a corresponding view when the reverse hook method is applied to the conventional example of FIG. 5. 9...Needle bar, 10...Needle bar rocking base, 11...
Needle, 17...Fully pin, 20...Rotary hook, 20a
... Hook tip, S ... Lower shaft (shuttle shaft), NP ... Bed surface (throat plate surface), l ₁ , l ₂ , l ₃ ... Needle bar height, m ₁ ,
m ₂ , m ₃ ...needle bar rise amount.

Claims (1)

[Scope of utility model registration request] In a zigzag sewing machine where the axis of the lower shaft (hoot shaft) and the axis of the swing fulcrum pin of the needle bar rocking table are arranged in a plane perpendicular to the sewing machine bed surface, the upper shaft ( A zigzag sewing machine characterized in that an axial center line of a main shaft (main shaft) is disposed at a position displaced by a small distance from the vertical plane.