JPH0142229B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to an improvement in the needle bar swinging mechanism of 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. 8 shows a perspective view of an example of a main part of a needle bar swinging mechanism of a zigzag sewing machine such as a conventional industrial lockstitch buttonhole sewing machine.The figure is a conventional known example and details are omitted. To briefly explain, 7 is 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 (not shown) or the like. A counterweight 6 is fixed to the tip of the upper shaft 7. A balance 5 and a crank rod 3 are rotatably fixed on the counterweight 6, and a needle bar crank 16 is attached to a fulcrum screw 18. It is worn. The tip of the crank rod 3 is connected to the needle bar 9.
This engages with a pin on the needle bar holder 8, which is fixedly mounted to hold the needle bar holder 8. 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 mounted on this needle bar rocking base 10.
It is supported so as to be able to reciprocate and slide vertically, and is driven by the crank rod 3 via the needle bar holder 8. On the other hand, the reciprocating movement of the needle bar swing table 10 is caused by a swing cam CM driven by a motor (not shown) via the upper shaft 7, and a needle bar swing rod 12 via the needle bar swing forked rod R. The swinging arm 13 is rotated swingingly.
This is done via 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 needle bar rise amount (departure) (the distance between the hook tip and the lowest point of the needle hole when the needle thread is captured) and the needle bar height (needle bar height) It is known that the absolute value of the distance (distance between the tip of the hook when the thread is captured and the upper edge of the needle hole when the needle thread is captured) changes. FIG. 9 shows a diagram of the main structure, which explains the principle of variation of each of the above values, viewed from the direction of arrow A in FIG. 8. In the figure, S is the center of the hook shaft of the sewing machine, and the rotary hook 20 (indicating the hook tip locus circumference) is rotating in the same direction (clockwise) as the main shaft 7 at twice the rotation speed of the main shaft 7. NP indicates the throat plate surface. The height of the needle bar at the center of the swing and in the left-right direction is indicated by l ₁ , l ₂ , and l _{3 ,} respectively, and the amount of rise of the needle bar is indicated by m ₁ , m ₂ , and m ₃ (units are shown in mm), respectively. Table 1 shows an example of the fluctuation value of each value 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 bar 11 becoming relatively early or late. 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.
This system allows the rotation direction of the rotary hook 20 to be opposite to that of the upper shaft 7 (counterclockwise) so that the needle bar 9 approaches or separates when viewed from the upper shaft rotation direction as described above. As a direction for correcting the relative slowness of the needle bar vertical movement timing, the needle bar height l and the needle bar rising amount m are intended to be less likely to change due to the swinging position of the needle bar 9. . FIG. 10 shows a diagram corresponding to the case where the reverse hook method is applied to the conventional example shown in FIG. 9. Rotary pot 2
The only difference is that the rotation direction of the 0 around the lower axis S is opposite to the upper axis 7 (counterclockwise), and the other components remain unchanged. Table 2 shows the amount of displacement at each position for each equivalent amount of l and m at this time.

[Problem that the invention seeks to solve]

Although the amount of change in l and m values shown in Table 2 has been improved to some extent compared to the case in Table 1, there is a considerable difference in absolute amounts, which is insufficient if only the proposed method is used. However, it is not sufficient to ensure uniform seam quality without skipped stitches. The present invention has been made in view of the above-mentioned problems, and by improving a part of the needle bar swinging mechanism, changes in needle bar height at each needle bar swinging position can be significantly reduced. The purpose is to improve seam quality. [Means for Solving the Problems] Therefore, in the present invention, an auxiliary rod that can slide vertically with respect to the sewing machine frame is provided between the conventional crank rod and the needle bar, and the auxiliary rod is fixed to the auxiliary rod. The crank rod and the rod pivotally mounted on the needle bar holder are connected through respective support shafts of the fixed base so as to reduce changes in the height of the needle bar at each swing position. It is. [Examples] The present invention will be described below based on Examples. FIG. 1 is a perspective view of the main parts of an embodiment of the needle bar swinging mechanism according to the present invention, and is a view corresponding to FIG. 8 of the prior art example, but the drive mechanism part on the right side of FIG. 8 is omitted, and Components that are the same as or equivalent to those in FIG. 8 are indicated by the same reference numerals, and redundant explanation of those portions will be omitted. In FIG. 1, reference numeral 1 denotes an auxiliary rod as a guide means according to the present invention, which is attached to a machine frame (sewing machine head) (not shown) so as to be able to slide back and forth in the vertical direction. This auxiliary rod 1 has a fixed base 4 fixed to its middle part, and a support shaft 4 is mounted on the opposite surface at right angles to the axis of the rod.
a and 4b are provided in a protruding manner. The tip of a crank rod 3 is pivotally engaged with the support shaft 4a, and the rotation of the upper shaft 7 causes the counterweight 6, needle bar crank 16, and crank rod 3 to move the fixed base 4 and the auxiliary rod 1 through the crank movement. Performs up and down reciprocating motion. On the other hand, the rod 2 is pivotally engaged with the other pair of support shafts 4b,
The other end of the rod 2 is configured to be pivotally engaged with a support shaft (not shown) of the needle bar holder 8 in parallel to the support shaft 4b. Numeral 19 is a fixing screw for fixing the needle bar holder 8 to the needle bar 9. 2, 3, and 4 are diagrams showing the main parts as seen from the direction of arrow A in FIG. 1. In FIG. From the position in Figure 2, the needle bar 9 (needle bar oscillating base 10) is to the left of the center position (B)
The state in which the needle has moved by the swing width H on the needle plate NP in the direction shown in FIG.
(Same as before) is shown moved by a width H from the center position to the right (C) direction. In FIG. 2, when the fulcrum screw 18 located at a radius R ₁ from the center of the upper shaft 7 is located at an angle θ ₀ from the center line, the needle 11 is at its lowest point; The upper edge 11a of the needle hole for passing the upper thread (not shown) of 11 occupies the position shown in the drawing. l ₁ is the height of the needle bar, m ₁ is the amount of rise of the needle bar, and L ₁ ~
L ₆ indicates the distance of each division shown. From this, the fulcrum screw 18 is at an angle θ ₁ from the center line.
When the upper edge 11a of the needle hole is located at θ ₁ of the upper shaft 7
By clockwise rotation of -θ ₀ , the needle hole is located at the upper edge 11b of the needle hole located above _m1 . At this time, in the rotating hook 20, each member is adjusted so that the hook tip 20a having a radius R ₂ is aligned with the needle 11 in the left-right (B-C) direction and is located above the upper edge 11b of the needle hole by l ₁ . do. As a result, when the needle 11 is located at the center, the needle thread (not shown) is reliably caught by the hook tip 20a to form the lock stitch, and the lock stitch is performed reliably and stably. Eyes can be formed. Next, when the needle bar 9 (needle bar swing table 10) is moved from the center position to the left (B) direction by a width H, the upper thread catching state corresponding to that in FIG. 2 becomes as shown in FIG. 3. Since the hook tip 20'a is located on the same line as the needle 11 in the left-right direction, the hook tip 20'a rotates clockwise, but is positioned an angle α farther forward than in the case of FIG. 2. At this time, the upper shaft 7 rotates clockwise, but as is well known, the hook 20 is configured to rotate twice for each rotation of the upper shaft 7. Therefore, the hook 20 rotates by an angle α more than in the case shown in FIG. This means that the upper axis 7 is θ ₁ from the center.
The angle is -α/2=θ ₂ , and the fulcrum screw 18 is at the 18' position shown in the figure. Similarly, when the needle rocking table 10 is moved by width H in the right (C) direction from the center position shown in FIG. 2, the needle thread catching state becomes as shown in FIG. 4, and the upper shaft rotation angle The position is at an angle of θ ₁ + α'/2 = θ ₃ from the center, and the fulcrum screw 18 is at the 18'' position shown in the figure. Figure 5 shows an enlarged diagram that combines Figures 2, 3, and 4. .Here, the needle 11 corresponding to FIG.
When the fulcrum screw 18 on the center line and the fixing base 4 fixed to the auxiliary rod 1 are connected via the crank rod 3, the position shown in the figure is obtained. Furthermore, if the fulcrum screw position 18' when the needle 11 swings in the left (B) direction, as shown in FIG. ' position, which is a position moved downward by Δy ₂ from the fixed table position 4 when on the center line. Similarly, the fixed table position 4'' when the needle 11 swings in the right (C) direction, as shown in FIG. 4, is a position Δy ₁ above the fixed table position 4 at the center line position. Here, the hook tip 2 when the needle 11 is on the center line.
0a and the vertical height of hook tip 20'a when swinging in the left (B) direction △l ₂ is △l ₂ = R ₂ - R ₂ COSα needle 1
The vertical height difference △l ₂ ′ between the hook tip 20a when it is on the center line of 1 and the hook tip 20″a when it swings in the left C direction is △
l ₂ ′=R ₂ −R ₂ COSα′. Furthermore, the distance between the needle bar holding position 8 when the needle 11 is on the center line and the upper edge 11b of the needle hole is L ₃ +l ₀ , and the height of the needle bar when the needle 11 swings to the left or right is l ₀ (the tip of the hook 20a and needle hole upper edge 11
distance from b) from needle bar holding position 8″, 8′ to hook tip 2
Let the distances to 0″a and 20′a be L″ ₃ and L′ ₃ , respectively.
Further, the needle bar holding position 8 when the needle 11 is on the center line,
If the difference in height in the vertical direction of the needle bar holding positions 8'' and 8' at the time of left and right rocking is respectively △l ₁ and △l ₁ ', then △l ₁ =
L ₃ +l ₀ +△l ₂ −COSβ(L ₃ ′+l ⁰ ), △l′ ₁ =L ₃ +l ₀ +l
′ ₂
-COSβ′(L″ ₃ +l ₀ )
The position of the fulcrum pin 17, the distance L ₁ from this fulcrum pin 17 to the center S of the hook 20, and the crank rod 3
length L ₄ of rod 2, length L ₅ of rod 2 and auxiliary shaft 1
By determining the distance L ₆ in the left-right direction from the center line of FIGS. 2, 3, and 4, the upper edges 11b, 11' of the needle holes are b, 11″b, that is, the needle bar height (outset) l ₁ , l ₂ , l ₃ , completely the same l ₁
It can be configured so that = l ₂ = l ₃ = l ₀ .
In addition, due to other design constraints, even if they cannot be made completely the same, it is possible to obtain the relationships l ₁ ≒ l ₂ ≒ l ₃ ≒ l ₀ that are substantially sufficient to achieve the purpose of the present invention. For this reason, the amount of change in the height of the needle bar at each position when the needle 11 is swung left and right can be substantially sufficiently reduced. is reliably and evenly captured by the tip of the hook at any swinging position, eliminating the fear of skipped stitches, etc. Also, depending on the type of thread used to form these stitches, such as cotton thread or synthetic fiber thread, the way the needle thread ring carried on the needle 11 is formed differs. By appropriately adjusting and re-fixing the engagement position between the bar holder 8 and the needle bar 9 using the fixing screw 19, the needle bar height characteristic is always uniform.
Regardless of the type of thread, it is possible to form uniform and beautiful stitches without skipped stitches or thread hangnails. Furthermore, in the conventional swinging mechanism of the needle bar 9, various forces in the rotational direction due to the rotational movement of the upper shaft 7 are directly applied in the left-right direction through the needle bar 9 and the needle bar swinging stand 10. However, by interposing the auxiliary rod 1 of the present invention, the above-mentioned influencing force does not directly act on the swinging rod 12, so each member of the swinging mechanism can be made smaller and lighter. Secondary effects can be obtained. [Other Embodiments] FIGS. 6 and 7 show two embodiments in which the lengths and arrangement of each member such as the auxiliary rod 1, rod 2, crank rod 3, etc. of the first embodiment in FIG. 1 are changed. This diagram shows the main part configuration diagram of the needle bar holder at each swing position, 8, 8',
8'' can be constructed in the same way as in the first embodiment, and the same can be done even if the auxiliary rod 1 is fixed to the machine frame and the fixed base 4 is slidable in the vertical direction with respect to the auxiliary rod 1. Furthermore, instead of the round bar-shaped supplementary rod 1, a pair of guide surfaces configured to slidably sandwich the fixed base 4 from both sides are formed on the machine frame, so that the fixed base 4 can be guided in a vertically movable manner. In this embodiment, the support shafts 4a and 4b of the fixed base 4 are shown coaxial, but even if they are different, the same effect can be obtained by determining each component. [Effects of the Invention] As explained above, the needle bar swinging mechanism of the present invention is configured so that substantially the same needle bar height can be obtained at each swinging position of the needle bar. Since the thread ring is constantly and reliably captured by the rotary hook tip, the sewing quality of the zigzag sewing machine can now be improved.

[Brief explanation of drawings]

FIG. 1 is a perspective view of essential parts of an embodiment of the needle bar swinging mechanism according to the present invention, FIGS. 2 to 4 are line diagrams showing the main parts at each position of the needle bar in FIG. , B are composite enlarged diagrams of FIGS. 2 to 4, FIGS. 6 and 7 are main part configuration diagrams of two other embodiments of the present invention, and FIG. 8 is a conventional zigzag sewing machine. FIG. 9 is a perspective view of an example of the main part of the needle swinging mechanism.
Fig. 8 Main part configuration diagram viewed from the direction of arrow A, No. 10
The figure is a diagram corresponding to FIG. 9 when the reverse hook method is applied to FIG. 1... Auxiliary rod, 2... Rod, 3... Crank rod, 4... Fixed base, 4a, 4b... Support shaft,
5... Balance, 6... Counterweight, 7... Upper shaft, 8...
...Needle bar holder, 9...Needle bar, 10...Needle bar rocking base,
11... Needle, 12... Needle bar swinging rod, 20... Rotating hook, 20a... Hook sword tip, S... Lower shaft (center), l
...Needle bar height, m...Needle bar rise amount.

Claims (1)

[Scope of Claims] 1. A needle bar rocking stand rotatably supported on the sewing machine frame around a fulcrum pin and swinging in conjunction with the sewing machine main shaft, and supported so as to be movable up and down on the needle bar swinging stand. A needle bar having a needle at its tip, a rod rotatably supported on the needle bar, a crank rod that moves up and down in conjunction with the main shaft of the sewing machine, a fixed base rotatably supported on the crank rod and the rod, and a machine. A zigzag sewing machine comprising: a guide means supported on a frame and guiding a fixed base so as to be movable up and down along a fixed axis; 2. The zigzag sewing machine according to claim 1, wherein the guide means is supported by the machine frame so as to be movable up and down, and the fixed base is fixed to the guide means. 3. The zigzag sewing machine according to claim 1, wherein the guide means comprises a pair of guide surfaces fixed to the machine frame, and the fixed base is movably held between the guide surfaces.