JPH0473093A - Hook structure for sewing machine - Google Patents

Abstract

PURPOSE:To stabilize the movement of a needle thread and to prevent the generation of roving or thread breakage by forming a guide face on a hook member. CONSTITUTION:When a needle thread 45 is cast off between a recessed part 37 of a hook and a protruding part 38 by a circular arc face 21 toward the direction shown by an arrow 46, a needle thread loop part 48 elevated along a surface 47 of the opening end side of an inner hook of a bobbin case 24 can be guided toward the direction shown by an arrow 49. In other words, when the needle thread 45 is cast off between the recessed part 37 and the protruding part 38, the needle thread 45 is pulle upward by the elevation movement of thread take-up lever (not shown). The needle thread 45 located at the left side of the moving path l of a needle 41 apt to move toward the direction shown by the arrow 46 and the needle thread part 48 located below the moving path l is apt to move toward the direction shown by an arrow 49. At this time, the needle thread 48 located below the moving path is apt to move and to be stabilized on the moving path l of the needle 41 along the guide face 21. The movement at this time is smoothly guided by the guide face 21.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a hook structure for a sewing machine.

Conventional technology For example, in a vertical full-rotation hook installed in a lockstitch sewing machine, the track formed on the outer circumferential surface of the inner hook fits into the track groove of the outer hook, which is driven to rotate around a horizontal axis of rotation. The inner hook is supported by the outer hook, and a bobbin case and a bobbin around which the bobbin thread is wound are removably provided on the inner hook. A locking recess is formed in the flange on the open end side of the inner hook, and a protrusion of a locking member whose base end is fixed to the body of the sewing machine is fitted into the locking recess.
It is configured to prevent the inner hook from rotating as the outer hook rotates.

As shown in FIG. 7, since the free end portion 2 of the hook locking member 1 is parallel to the longitudinal direction thereof, the needle thread loop 4 passed along the outer peripheral surface of the inner hook 3 is attached to a thread take-up lever (not shown). The part 5 is pulled up by the upward movement of , and the part 5 comes into contact with the lower surface 2a of the hook holder 1 due to inertia when it is pulled up, and is pulled out while moving in the direction of the arrow 6 along the lower surface 2a. Thereafter, the thread passes through between the protrusion 7 and the locking recess 8, comes out, engages with the bobbin thread 10 pulled out from a bobbin (not shown) housed in the bobbin case 9, and stitches the first stitch. It is formed.

Problems to be Solved by the Invention In such prior art, when the outer hook 11 is rotated at high speed, the portion 5 of the needle thread loop 4 comes into frictional contact with the lower surface 2a of the free end portion 2, and as the thread take-up moves upward. Loop-shaped part 5
The behavior of the thread becomes unstable, causing variations in the timing and posture of passing between the protrusion 7 and the locking recess 8. Such tricks cause the needle thread loop to become unstable due to variations in the timing and posture of the movement. 4 tension changes undesirably, resulting in looping and yarn breakage.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a hook structure for a sewing machine that can stabilize the behavior of the upper thread and prevent looping and thread breakage.

Means for Solving the Problems The present invention provides a hook lock member whose base end is fixed to the body of a sewing machine and whose end portion is formed with a protrusion that fits into an inner hook lock recess. This hook structure for a sewing machine is characterized by forming a guide surface that is gently curved upward as it approaches the movement path of the needle.

Further, the present invention is characterized in that the hook stop member is coated with a material having low sliding friction over a range including at least the guide surface.

According to the present invention, since the hook stopper member is formed with a guide surface, it is possible to guide the needle thread loop passed along the outer peripheral surface of the inner hook along the guide surface. This makes it possible to stabilize the timing and posture of passing between the hook stop recess and the protrusion of the hook stop member, thereby preventing the generation of undesired tension on the needle thread and preventing looping and thread breakage. It can be prevented.

Further, according to the present invention, since the range including the guide surface of the hook stopper member is covered with a material having good slip properties, the needle thread moving along the guide surface can be guided more smoothly. Generation of undesired upper thread tension can be more reliably prevented, and looping and thread breakage can be even more reliably prevented.

Embodiment FIG. 1 is an enlarged front view showing the vicinity of the guide surface 21 of the rotary rotary hook 20 according to an embodiment of the present invention, and FIG. 2 is a perspective view of the vertical full-rotation rotary rotary rotary rotary rotary rotary rotary rotary rotary rotary rotary rotary rotary rotary rotary rotary rotary rotary rotary rotary rotary rotary rotary rotary rotary rotary rotary rotary rotary rotary rotary rotary rotary rotary rotary rotary rotary rotary rotary rotary rotary rotary rotary rotary rotary rotary rotary rotary rotary rotary rotary rotary rotary rotary rotary rotary rotary rotary rotary rotary rotary rotary rotary rotary rotary wheel rotary rotary rotary rotary rotary rotary rotary rotary-wheel rotary rotary rotary rotary rotary rotary rotary rotary rotary rotary rotary rotary rotary rotary rotary rotary rotary rotary rotary rotary rotary rotary rotary rotary rotary rotary rotary rotary rotary rotary rotary rotary shaft? 3 is a perspective view of the vertical full-rotation hook 22 viewed diagonally from below, and FIG. 4 is a perspective view showing the state in which the bobbin 23 and bobbin case 24 of the vertical full-rotation hook 22 are taken out from the inner hook 28. It is a diagram. An outer hook 26 is fixed by bolts 27 to a lower shaft 25 that is rotationally driven around a horizontal axis of rotation, and an inner hook 28 is housed within the outer hook 26. Inner pot 2
Two rails extending in the circumferential direction are formed on the outer peripheral surface of the outer hook 26, and these two rails are connected to the rail groove 30 formed on the inner peripheral surface of the outer hook 26.
get stuck in.

The inner pot 28 has a bottom portion 32 on which a stud 31 is erected,
It has a cylindrical portion 33 in which the rail 29 is formed, and an outwardly directed seven flange 34 integrally formed at the open end of the cylindrical portion 33. A locking recess 37 is formed in this flange 34, and a locking member 2 made of iron or steel is formed in the locking recess 37.
The protrusion 38 of 0 is fitted. The proximal end of the hook holder 20 is fixed to the body of the sewing machine (not shown), and the free end 39 on which the protrusion 38 is formed is located near the hook holder recess 37 with a slight distance S from the flange 34. It is placed in the open. When the sewing machine is driven with the protrusion 38 of the hook holder 20 fitted into the hook holder recess 37, the lower shaft 25 is rotated around its axis of rotation, thereby locking the outer hook. 26 is rotationally driven in the outer ring rotation direction A around a rotation axis that is common to the rotation axis of the lower shaft 25. When the outer hook 26 starts rotating in this manner, the upper thread brought by the needle 41 is caught by the tip 42 provided on the outer hook 26, and as the outer hook is further rotated downstream in the rotation direction. A needle thread loop is formed and the thread is threaded along the outer peripheral surface of the inner hook 28.

In this manner, when the outer hook 26 is rotationally driven toward the downstream side in the rotational direction A, the protrusion 38 of the hooking member 20 is attached to the end surface 43 of the hooking recess 37 on the upstream side in the rotational direction A.
are in contact with each other, and the rotation of the inner hook 28 due to the rotation of the outer hook 26 is prevented.

A bobbin case 24 is removably attached to the inner hook 28, and a bobbin 23 around which a bobbin thread 48 is wound is housed in the bobbin case 24.

The guide surface 21 of the locking member 20 is formed in an arc shape when viewed from the front side (see FIG. 1). This guide surface 21 is
The free end portion 39 of the hook locking member 20 is formed symmetrically with respect to the central axis l of the protrusion 38 along the longitudinal direction, and its length L is, for example, 20 mm when the outer diameter of the inner hook 28 is 32 mmφ. and the lower surface 44 of the free end 39
The depth d is selected to be approximately 0.4 mm. The protrusion 3
8 is the movement path 11 of the needle 41 and the rotation axis 12
a direction in which the needle thread 45 approaches the movement path 11 downward from the needle hole of the needle 41 when the needle thread 45 is pulled up by the rise of the thread take-up;
That is, it moves in the direction of arrows 46 and 49 in FIG. 1, which will be described later.

By forming such an arcuate surface 21, when the needle thread 45 moves between the hook stop recess 37 and the protrusion 38 in the direction indicated by the arrow 46, the inside of the bobbin case 24 is removed. The portion 48 of the needle thread loop that has risen along the surface 47 on the hook opening end side can be guided along the arcuate surface 21 in the direction of arrow 49. That is, when the needle thread 45 passes between the hook stop recess 37 and the protrusion 38, the needle thread 45 is pulled upward by the lifting movement of the thread take-up (not shown), and the needle 41 travel routes! The needle thread 45 on the left side of FIG. 1 is about to move in the direction of arrow 46, and the moving path is also on! The portion 48 of the upper thread located lower than the upper thread tends to move in the direction of arrow 49. At this time, the needle thread 48 located below moves along the guide surface 21 onto the movement path l of the needle 41 and tries to stabilize, and the movement at this time can be smoothly guided by the guide surface 21.

Moreover, as shown in FIG. 5, the outer surface of the free end portion 39 including the guide surface 21 is coated with a coating layer 5 made of a material with good slipperiness, such as polytetrafluoroethylene (trade name: Teflon).
1 is formed. The polytetrafluoroethylene that constitutes this coating layer 51 is generally wax-like and milky white, has high electrical insulation properties, excellent heat resistance and cold resistance, has an extremely low coefficient of friction, and adheres to other substances. It has properties such as being chemically extremely stable. In addition, when forming the covering layer 51 on the locking member 20, it can be easily formed by vacuum deposition at a low steam pressure, and manufacturing is easy. By forming such a covering layer 51, the sliding friction acting on the upper thread portion 48 can be reduced and the upper thread can be guided even more smoothly. In addition, when forming the coating layer 51, it is not necessary to perform highly accurate surface processing near the free end portion 39 of the locking member 20, and the manufacturing effort can be reduced.

FIG. 6 is a diagram for explaining the thread passing operation of the upper thread 45. First, with reference to FIG. 6(1), the throat plate 52 of the sewing machine
The upper thread 45 is passed through the needle drop hole 53 and brought to the vicinity of the tip 42 of the outer hook 26, and is caught by the tip 42. The bobbin thread 43 pulled out from the bobbin 23 in the bobbin case 24 is interposed between the stacked cloth 54 and the needle plate 52 while being pulled out upward from the needle drop hole 53. When the outer hook 26 is further rotated downstream in the rotational direction A, the loop of the needle thread 45 is expanded in diameter and extends to the vicinity of the lower end of the inner hook 28, as shown in FIG. 6(2). Further, the outer hook 26 rotates downstream in the rotational direction A, as shown in FIG.
As shown in 3), the loop of the needle thread 45 passes through the lower end of the inner hook 28 to form a small diameter needle thread loop at the upper portion of the hook 22. In this state, the upper thread is detached from the tip 42 and pulled upward by the lifting action of the thread take-up (not shown), and as the thread take-up further rises, the needle thread
As shown in Figure (4), the upper thread 45
The portion 48 contacts the arcuate surface. When the thread take-up further rises in this state, the portion 48 moves along the guide surface 21 in the direction of the arrow 49, and the upper thread above the protrusion 38 moves as described in connection with FIG. 45 moves in the direction of arrow 46 and passes between the hook stop recess 37 and the protrusion 38, and the bobbin thread 43 is inserted into the needle thread loop as shown in FIG. 6 (5). One seam is formed as the thread take-up moves upward.

In this way, the upper thread 4 is inserted between the hook stop recess 37 and the protrusion 38.
Since the portion 48 is guided by the guide surface 21 when the rotor 5 passes, the behavior of the portion 48 accompanying the upward movement of the balance can be stabilized, and the locking concave is removed every rotation of the outer hook 26. By making the timing and posture of passing between the location 37 and the protrusion 38 substantially constant, it is possible to prevent undesired changes in needle thread tension. This makes it possible to minimize the occurrence of looping and thread breakage, and to form high-quality seams.

In the above embodiment, the guide surface 21 is formed symmetrically along the longitudinal direction of the roadside portion 39 with respect to the central axis l of the protrusion 38. It may be formed on the starting end side with respect to the axis l, that is, on the right side in FIG. Further, the deepest part P of the guide surface may be located at a position offset from the central axis p of the protrusion 38, for example, the thread extraction of the hook locking recess 37 may be located at the terminal end in the direction 46, and furthermore, the movement path of the needle 41 may be The guide surface 21 may be formed so that the deepest part is at the top.

Effects of the Invention According to the present invention, since a guide surface is formed on the hook stopper member, when the needle thread is pulled out between the hook stopper recess and the protrusion, the needle thread does not move below the guide surface. A certain upper thread can now be guided smoothly along the guide surface, thereby stabilizing the behavior of the upper thread, preventing the generation of undesirable tension, and preventing looping and thread breakage. can be prevented from occurring.

Further, according to the present invention, since the area including the guide surface is covered with a material having low sliding friction, the needle thread moving along the guide surface can be guided even more smoothly. By reliably stabilizing the behavior of the needle thread, it becomes possible to form high-quality seams.

[Brief explanation of drawings]

FIG. 1 is an enlarged front view showing the vicinity of the guide surface 21 of the rotary rotary hook 20 according to an embodiment of the present invention, FIG. FIG. 4 is a perspective view of the vertical full-rotation hook 22 as seen diagonally from below. FIG. 4 is a perspective view of the vertical full-rotation hook 22 with the bobbin 23 and bobbin case 24 removed. FIG. 5 is a cross-section line of FIG. 1. V-
FIG. 6 is an enlarged cross-sectional view as seen from (1), FIG. 6 is a diagram for explaining the thread-crossing operation of the upper thread 45, and FIG. 7 is a front view of a typical prior art. 20... Hook stopper member, 21... Guide surface, 22...
Vertical full rotation hook, 37... Hook locking recess, 38...
Projection, 39... Free end, 42... Tip, 43... Lower thread, 44 Lower surface, 45... Upper thread, 48... Upper thread portion, 5
1. Covering layer agent Patent attorney Number of strokes Keiichi Figure 11 Figure Milo ＾ Figure +-41

Claims (2)

[Claims] (1) The proximal end is fixed to the body of the sewing machine, and the free end is formed with a protrusion that fits into the hook lock recess of the inner hook, and the needle travels along the longitudinal direction of the hook hook member. A hook-clamp structure for a sewing machine characterized by forming a guide surface that is gently curved upward as it approaches. (2) The hook stopper structure for a sewing machine according to claim 1, wherein the hook stop member is coated with a material having low sliding friction over a range including at least the guide surface.