Sewing machine hook structure and sewing machine

Abstract

The present invention addresses the problem of avoiding formation of a hitch stitch caused by a bobbin thread. A shuttle (3) includes: a bobbin case (40) for storing a bobbin-thread bobbin; an inner shuttle (50); and an outer shuttle (60). A needle location hole (51) is provided in the front surface of the upper part of the inner shuttle. A recess (52) is formed at a position (e.g., position to the left of the vertical motion line of a sewing needle) offset in the rotation direction of the outer shuttle from the needle location hole in the front surface of the upper part of the inner shuttle. The recess (52) is open at the front side and above and below, and the back side thereof forms a wall surface. The bobbin case is provided with a thread take-up member (41) for directing the bobbin thread delivered from the bobbin-thread bobbin toward the recess. The bobbin thread delivered from the bobbin-thread bobbin passes through the recess via the thread take-up member, and is directed toward a needle hole in a needle plate above the recess. Since the recess is at a position to the left of the vertical motion line of the sewing needle, the path of the bobbin thread from the shuttle to the needle hole is to the left of the vertical motion line of the sewing needle, and hitch stitch formation caused by the bobbin thread can be structurally avoided.

Description

[Technical Field]

[0001] The present invention relates to a hook structure for a sewing machine that is devised to prevent the occurrence of hitch stitches when forming seams on a sewing material, and further to a sewing machine equipped with such a hook structure. [Background technology]

[0002] There are known sewing machines equipped with a sewing mechanism that moves a sewing needle with an upper thread threaded up and down and rotates a shuttle that contains a lower thread in synchronization with the up and down movement of the sewing needle to entangle the upper thread with the lower thread, thereby sewing a workpiece (work cloth), and a feed mechanism that forms stitches in any direction on the workpiece by displacing a frame (holder) that holds the workpiece relative to the needle point. In such sewing machines, the feed mechanism controls the movement of the workpiece for each stitch, making it possible to form stitches of various lengths in various directions.

[0003] The quality of stitches produced by this type of sewing machine is known to be divided into perfect stitches and hitch stitches. A perfect stitch is a stitch formed when the upper and lower threads are intertwined with each other in a balanced manner, while a hitch stitch is a stitch formed when only the upper thread is intertwined with the lower thread in a spiral. It is known that there are two main factors that determine whether a stitch is a perfect stitch or a hitch stitch. One is a factor related to the upper thread. When the sewing needle with the upper thread inserted penetrates the workpiece fabric, the upper thread, which passes through the needle eye from the front to the rear and connects to the workpiece fabric, intertwines with the needle in either a left-handed or right-handed direction, depending on the direction of movement of the workpiece fabric (seam formation direction) when the seam is formed. It is known that a hitch stitch is formed when the upper thread intertwines with the needle in a right-handed direction.

[0004] Throughout this specification, front ("nearby," "foreground," "front side," etc.) or rear ("rear," "rear side," "deep," "rear side," etc.) refers to the front or rear of the sewing machine when viewed from the front, left or right refers to the left or right of the sewing machine when viewed from the front, and left-handed or right-handed direction refers to the direction when the sewing machine is viewed from above (i.e., left-handed is counterclockwise and right-handed is clockwise).

[0005] The other factor is the bobbin thread, and whether a perfect stitch or hitch stitch is formed depends on the relationship between the path of the bobbin thread, which runs from the hook (bobbin thread bobbin) located below the needle plate through the needle hole in the needle plate to the workpiece fabric above, and the needle entry point of the sewing needle.In other words, it is known that a hitch stitch is formed when the path of the bobbin thread is to the right of the vertical movement line of the sewing needle (needle entry point), depending on the direction of movement of the workpiece fabric when the stitch is formed (stitch formation direction).

[0006] Hitch stitches not only have a poorer appearance than perfect stitches, but also have the problem of reducing seam quality by making the stitches more likely to loosen. For this reason, various methods have been proposed to prevent hitch stitches from occurring. One example is a method that determines whether the direction of movement of the workpiece fabric (seam formation direction) is the perfect stitch formation direction or the hitch stitch formation direction during the sewing operation for each stitch, and if it is determined to be the hitch stitch formation direction, changes the position of the upper thread or bobbin thread relative to the needle entry point by moving the frame or using an operating piece, etc.

[0007] Patent Document 1 below discloses an invention for preventing hitch stitches caused by the upper thread. When it is determined that the movement direction of a frame holding a workpiece cloth (the direction of stitch formation) is the direction of hitch stitch formation caused by the upper thread, the frame does not move directly to the target needle entry point (target position) for stitch formation. Instead, before the tip of the sewing needle descending reaches the top surface of the workpiece cloth, the frame detours to the left of the needle and then reaches the target position. This is intended to prevent hitch stitches caused by the upper thread by entangling the upper thread connected to the workpiece cloth to the left around the needle. However, to quickly entangle the upper thread to the left around the needle by detouring the frame while the needle is descending, the timing of the needle's downward movement and the detouring movement of the frame must be precisely matched. Even a slight deviation in timing prevents the upper thread from entangling around the needle. Therefore, the technology disclosed in Patent Document 1 makes it difficult to reliably prevent hitch stitches from occurring.

[0008] Patent Document 2 listed below discloses an invention for avoiding hitch stitches caused by the lower thread, in which a notch is provided adjacent to the back side of a needle hole formed in a needle plate, and when it is determined that the movement direction of a frame holding a workpiece (the direction of stitch formation) is the direction of hitch stitch formation caused by the lower thread, the frame does not move directly to the target needle point (target position) for stitch formation, but instead moves in a detour following the shape of the notch before reaching the target position. Specifically, the notch has a tip extending from left to right, and the frame moves in a detour so that the lower thread enters the tip of the notch from the left side, and the lower thread is caught by the tip of the notch, so that the path of the lower thread passes to the left of the needle point position and is stopped at the back side (i.e., the needle enters on the right and front side of the path of the lower thread). In this way, the needle penetrates to the right of the bobbin thread path that extends upward to connect to the workpiece fabric, thereby preventing the occurrence of hitch stitches caused by the bobbin thread. However, if the notch provided at the back of the needle eye has a tip that extends from left to right, it inevitably forms a protrusion (a peninsula, so to speak) that extends from right to left between the tip and the needle eye, and the presence of this protrusion poses the problem of the risk of the upper thread breaking.

[0009] As is well known, the needle thread loop caught in the hook tip of the outer hook moves between the outer and inner hooks, is pulled up by the action of the take-up lever, and ascends along the bobbin thread while entangled with it. In the structure disclosed in Patent Document 2, the needle thread loop ascending along the bobbin thread may become caught on the protrusion (peninsula portion) adjacent to the tip of the notch that holds the bobbin thread. This causes the needle thread to break. Furthermore, because the bobbin thread enters and is held in the tip of the notch, depending on the sewing direction of the next stitch, the bobbin thread may remain held in the notch, resulting in a problem of the bobbin thread path being different from the normal path.

[0010] Patent Document 3 listed below also discloses an invention for preventing hitch stitches caused by the lower thread. In Patent Document 3, a switching mechanism is provided that selectively switches the path of the lower thread from leaving the shuttle to the needle hole in the needle plate between a left-hand route that biases the thread to the left side relative to the vertical movement line (vertical movement trajectory) of the sewing needle and a right-hand route that biases the thread to the right side, with this switching being performed by an air cylinder. When it is determined that the movement direction of the frame holding the workpiece cloth (the direction of stitch formation) is the direction in which a hitch stitch caused by the lower thread is formed, the switching mechanism switches the lower thread path to either the left-hand route or the right-hand route before the tip of the descending sewing needle reaches the top surface of the workpiece cloth, thereby preventing the occurrence of hitch stitches. However, the need for an air-cylinder-driven switching mechanism results in a complex structure.

[0011] Patent Document 4 below discloses an invention for preventing hitch stitches caused by the upper thread and the lower thread, and includes an upper thread control means (needle bar pivoting mechanism) for controlling the relationship of the upper thread to the sewing needle, and a lower thread control means (thread shifting mechanism) for controlling the relationship of the lower thread to the sewing needle, and controls each control means according to the direction of movement of the workpiece cloth to prevent the occurrence of hitch stitches. In Patent Document 4, the needle bar pivoting mechanism as the upper thread control means and the thread shifting mechanism as the lower thread control means each have a complex structure, which creates the problem of complicating the structure of the sewing machine. Furthermore, in a multi-needle sewing machine having multiple needle bars in one sewing machine head, such a complex structure becomes an even more serious problem.

[0012] Patent Document 5 listed below discloses a sewing machine capable of sewing by rotating the sewing machine head and the shuttle housing separately, and improves sewing quality by synchronizing the timing of the needle and the shuttle and the rotation of the sewing machine head and the shuttle housing with the rotation of the sewing machine head. However, it is necessary to provide a mechanism for rotating the sewing machine head and the shuttle housing and a means for controlling them synchronously, which results in a problem of a complicated structure. Furthermore, while the structure shown in Patent Document 5 is suitable for sewing a straight line in a fixed direction, such as a running stitch, in the case of embroidery in which the stitch direction is reversed, such as satin stitch, the rotation direction of the head and the shuttle housing must be reversed for each stitch, and the sewing direction also changes, making synchronized control extremely difficult. [Prior art documents] [Patent documents]

[0013] [Patent Document 1] Patent No. 2515400 [Patent Document 2] Japanese Patent Publication No. 6-343780 [Patent Document 3] Patent Publication No. 2008-23261 [Patent Document 4] Patent Publication No. 2012-213603 [Patent Document 5] Patent No. 2540051 Summary of the Invention

[0014] The present invention aims to provide a hook structure for a sewing machine that is configured to prevent the occurrence of hitch stitches, and further to provide a sewing machine equipped with such a hook structure.

[0015] According to a first aspect of the present invention, there is provided a hook structure for a sewing machine suitable for preventing the occurrence of hitch stitches due to a bobbin thread. The hook structure for a sewing machine according to the present invention comprises a bobbin case for rotatably storing a bobbin thread bobbin wound with a bobbin thread, an inner hook for accommodating the bobbin case, and an outer hook which rotates around the inner hook in synchronization with the up and down movement of the sewing needle, and a needle hole is provided on the upper front surface of the inner hook. The outer hook has a point portion for capturing the needle thread loop. A recess is formed in the front upper part of the inner hook at a position shifted from the needle hole in the direction of rotation of the outer hook, and the recess is open at the front and top and bottom and forms a wall surface at the back side. The bobbin case is provided with a thread take-up member for directing the lower thread unwound from the lower thread bobbin toward the recess of the inner hook, and the lower thread unwound from the lower thread bobbin in the bobbin case passes through the thread take-up member, passes through the opening of the recess, and is pulled out upward. The movement of the lower thread in the depth direction through the opening of the recess is restricted by the wall surface on the depth side of the recess formed in the inner hook. It is characterized by:

[0016] The rotation direction of the outer hook is the direction in which the tip of the rotating outer hook catches (hooks) the upper thread loop inside the hook. Normally, the rotation direction of the outer hook is counterclockwise, so to clarify the left-right relationship based on that premise, the direction of movement of the tip of the outer hook when capturing the upper thread loop (counterclockwise) is leftward when viewed from the front. In this case, the recess of the inner hook is formed in a position shifted to the left (closer to the rotation direction of the outer hook) from the line of vertical movement of the sewing needle.

[0017] As is well known, in a sewing machine, a holder (sewing frame or embroidery frame) that holds the workpiece is located above the needle plate, and by moving the holder in any direction for each stitch, it is possible to create stitches in any direction on the workpiece. Also, as is well known, a sewing needle with an upper thread threaded therethrough moves up and down, and a shuttle located below the needle plate and containing a lower thread rotates in synchronization with the up and down movement of the sewing needle, entangling the upper thread with the lower thread, thereby sewing the workpiece. The lower thread that emerges from the shuttle and extends upward passes through an opening (needle eye) in the needle plate and is connected to the workpiece. Following the movement of the holder (workpiece) to form the stitch, the lower thread that emerges from the shuttle and is connected to the workpiece also moves. The path of the lower thread relative to the vertical movement of the sewing needle also changes depending on the direction of movement of the lower thread.

[0018] Depending on the direction of movement of the workpiece during stitch formation (seam formation direction), there are regions where hitch stitches due to the bobbin thread occur. Such hitch stitches due to the bobbin thread occur when the bobbin thread path extending from the shuttle to the needle eye of the needle plate is on the right side of the vertical movement line (vertical movement locus) of the sewing needle. In consideration of this point, the shuttle structure according to the present invention is configured to prevent the path of the bobbin thread extending from the shuttle to the needle eye of the needle plate from being on the right side of the vertical movement line (vertical movement locus) of the sewing needle. That is, the bobbin thread unwound from the bobbin thread bobbin is directed by the thread take-up member toward the recessed portion of the inner shuttle, passes through the recessed portion, and heads toward the opening (needle eye) in the throat plate. The recessed portion is formed at a position offset from the needle drop hole in the rotation direction of the outer shuttle (i.e., to the left of the vertical movement line of the needle), so the path of the bobbin thread from the shuttle to the needle eye is on the left side of the vertical movement line of the sewing needle. This prevents the path of the lower thread from running from the shuttle to the needle eye from coming to the right of the vertical movement line of the sewing needle, thereby structurally preventing the occurrence of hitch stitches caused by the lower thread.

[0019] According to a second aspect of the present invention, in addition to the configuration according to the first aspect, a configuration is provided which prevents the occurrence of hitch stitches due to upper thread factors, thereby making it possible to prevent the occurrence of any type of hitch stitch and to produce perfect stitches over the entire range of sewing directions, i.e., a sewing machine which can achieve all-perfect stitches.

[0020] A sewing machine according to a second aspect of the present invention comprises the above-mentioned shuttle structure and a sewing mechanism that moves the needle with an upper thread threaded up and down and rotates the outer shuttle in synchronization with the up and down movement of the needle to entangle the upper thread with the bobbin thread, thereby sewing a workpiece. The sewing machine further comprises a feed mechanism that forms a stitch on the workpiece in any direction by displacing a holder that holds the workpiece relative to a needle point, determination means that determines whether the direction in which the next stitch is to be formed falls within a predetermined area corresponding to a hitch stitch, and detour control means that, when it is determined that the direction falls within the predetermined area, moves the holder by the feed mechanism to detour the upper thread extending downward from the needle in a direction corresponding to a perfect stitch, and then moves the holder to a target position corresponding to the next stitch. By detouring the holder by such detour control means, it is possible to avoid hitch stitches caused by the upper thread. [Brief explanation of the drawings]

[0021] [Figure 1] A diagram showing the relationship between various stitch directions and the quality of the stitches formed in each direction (perfect stitch vs. hitched stitch). [Figure 2] 1 is a front view of a sewing machine according to an embodiment of the present invention; [Figure 3] 3 is an enlarged front view of one of the machine heads in the embodiment shown in FIG. 2. FIG. [Figure 4] FIG. 4 is a side cross-sectional view of the machine head shown in FIG. 3. [Figure 5] FIG. 2 is an enlarged front view showing an embodiment of a presser foot device for pressing down a sewing object. [Figure 6]10A, 10B, and 10C are diagrams showing a modified example of a guide body in a presser foot device, in which FIG. 10A is a perspective view seen from the bottom side, FIG. 10B is a plan view, and FIG. [Figure 7] 10A, 10B, and 10C are diagrams showing another modified example of the guide body in the presser foot device, in which FIG. 10A is a perspective view seen from the bottom side, FIG. 10B is a plan view, and FIG. [Figure 8] FIG. 10 is a perspective view showing another modified example of the presser foot device, in which a cover is provided at the bottom. [Figure 9] FIG. 2 is a perspective cross-sectional view showing an example of a needle plate structure. [Figure 10] 10A is an enlarged view of the pinhole portion in FIG. 9, where (a) is a plan view, (b) is a perspective view showing a cross section taken along line AA, and (c) is a perspective view of a main part illustrating the path of the lower thread. [Figure 11] FIG. 2 is a front view showing an embodiment of a hook structure. [Figure 12] 12 is a plan view of the kettle structure of FIG. [Figure 13] 12A and 12B are left and right side views of the shuttle structure of FIG. 11; [Figure 14] 12 is a perspective view showing an example of a bobbin case included in the shuttle structure of FIG. 11. [Figure 15] FIG. 2 is a block diagram showing an example of a control system for a sewing machine. [Figure 16] 10A and 10B are diagrams illustrating an example of an area where a frame is moved around to avoid a hitch stitch caused by the upper thread. [Figure 17] FIG. 10 is a diagram illustrating an example of a trajectory of a detouring movement of a frame. [Figure 18] FIG. 10 is a plan cross-sectional view showing the relationship between the needle thread and the guide body of the presser foot device when the frame is moving around. [Figure 19] 10 is a flowchart showing an example of a computer program for executing stitch control including all-perfect stitches according to the present embodiment. [Figure 20] 1A and 1B are diagrams illustrating a mechanism for avoiding hitch stitches caused by the bobbin thread using the shuttle structure according to this embodiment, in which (a) is a front view of the shuttle structure, and (b) is an enlarged plan view showing the relationship between the sewing needle and the bobbin thread in the inner shuttle. [Figure 21] 10 is a perspective view illustrating the function of a guide body of the presser device in controlling the bypass movement of the frame. FIG. [Figure 22] 10 is a perspective view illustrating the function of a guide body of the presser device in controlling the bypass movement of the frame. FIG. [Figure 23] FIG. 11 is a perspective view illustrating a mechanism for avoiding hitch stitches using the needle plate structure shown in FIGS. 9 and 10 . [Figure 24] FIG. 10 is a diagram showing an example of setting data for frame detouring control. [Figure 25] 20 is a flowchart illustrating an example of a modification of the computer program shown in FIG. 19. DETAILED DESCRIPTION OF THE INVENTION

[0022] <Area where hitch stitch is formed> First, referring to FIG. 1, we will explain a typical example of the region of the stitch formation direction in which a hitch stitch is formed. FIG. 1 is a diagram listing the relationship between various stitch formation directions and the quality of the stitch formed in each direction (perfect stitch and hitch stitch). The relationship between the stitch formation direction and the quality of the stitch formed varies depending on the orientation and type of hook. FIG. 1 shows this relationship for a fully rotating vertical hook (DB type) commonly used in embroidery sewing machines. Furthermore, as is commonly known, the needle thread is threaded through the eye of the sewing needle in such a way that the needle thread unwound downward from the needle thread bobbin enters the eye from the front of the needle, exits the eye from the rear, and connects to the workpiece (work fabric). Cooperation between the vertically moving needle and the fully rotating vertical hook counterclockwise intertwines the upper and lower threads, forming a stitch on the workpiece (work fabric), as is well known.

[0023] The base point C located at the center of the figure indicates the current needle point (the position of the needle hole in the throat plate of the sewing machine). Several arrows starting from the base point C exemplarily indicate the sewing direction from the base point C to the next needle point (i.e., the direction in which the next stitch is formed). As is well known, the sewing direction of each stitch can be set arbitrarily within a 360-degree range, and the specific direction depends on the sewing pattern. In FIG. 1, for convenience, the direction of the arrow P is set to 0 degrees, and angles are scaled counterclockwise from 0 degrees to less than 360 degrees. Hereinafter, when specifying the region of the sewing direction (i.e., the direction in which the next stitch is formed) by angle, the angle scale in FIG. 1 will be used. In the figure, the directions of the arrows P and P' indicate the left-right direction of the sewing machine, and for convenience, the P direction will be referred to as the positive direction of the X-axis (X+) and the P' direction will be referred to as the negative direction of the X-axis (X-). The direction of the Y-axis, which is perpendicular to the X-axis at base point C, is the front-to-rear direction of the sewing machine, with the direction toward the rear (back) being referred to as the positive direction (Y+) of the Y-axis and the direction toward the front being referred to as the negative direction (Y-) of the Y-axis. As is well known, the movement direction of the holder (frame) that holds the sewing workpiece (workpiece cloth) and the direction of the stitches formed in response to the movement of the holder (frame) are opposite directions. For example, when forming a stitch in the direction of arrow P (0 degrees), the holder (frame) moves in the opposite direction, that of arrow P' (180 degrees).

[0024] In Figure 1, several arrows are overlapped with and surrounded by circled needle diagrams. To facilitate understanding, these needle diagrams are diagrams that show, together with illustrations of the needle eye, typical examples of the relationship between the needle thread and the bobbin thread relative to the sewing needle when a stitch is formed in the direction corresponding to the arrow. Note that the needle diagram shows the needle descending just before entering the needle eye. For convenience, the sewing object (workpiece fabric) is not shown.

[0025] The entire range of sewing directions can be divided into several regions α to δ according to the quality of the stitch formed in accordance with the sewing direction. Region α is the region to which sewing directions that result in perfect stitches belong, and is roughly the region from about 270 degrees to 360 degrees (0 degrees) to about 85 degrees. As shown in the needle diagram overlapping the arrow in region α, as the holder (frame) moves, the needle thread that connects from the needle eye to the workpiece fabric enters the needle while being positioned to the left of the needle, resulting in a perfect stitch. The regions (β to δ) excluding the white region α are regions in which hitch stitches occur. The shaded region β is the region to which sewing directions that result in hitch stitches due to the upper thread belong, and is roughly the region from about 85 degrees to about 180 degrees. As shown by the needle diagram overlapping the arrow in this region β, as the holder (frame) moves, the needle penetration occurs with the upper thread connecting from the needle eye to the workpiece fabric positioned to the right of the needle, resulting in a hitch stitch. The dotted region γ is the region where sewing directions in which hitch stitches occur due to both the upper and lower threads, and is approximately the region between 180 degrees and 210 degrees. The grid-lined region δ is the region where sewing directions in which hitch stitches occur due to the lower thread, and is approximately the region between 210 degrees and 270 degrees. As shown by the needle diagram overlapping the arrow in this region δ, as the holder (frame) moves, the needle penetration occurs with the lower thread connecting from the hook to the workpiece fabric positioned to the right of the needle, resulting in a hitch stitch.

[0026] <Basic configuration of sewing machine> First, with reference to FIGS. 2 to 4, the basic configuration of an example of a sewing machine to which the present invention can be applied will be described. This basic configuration itself is well known, and any configuration can be applied to the present invention, not limited to the illustrated example. FIG. 2 is a front view of a sewing machine according to an embodiment of the present invention, showing an example in which the present invention is applied to a multi-head, multi-needle embroidery sewing machine. A sewing machine frame 1 located above a table 2 has multiple sewing machine heads H arranged longitudinally. Beneath each sewing machine head H, a hook base 4 supporting a hook 3 is provided corresponding to each sewing machine head H. A holder 5 for holding a sewing material (workpiece cloth) such as cloth in a stretched state is placed on the top surface of the table 2. The holder 5 is controlled to move in the X and Y directions (front-back and left-right directions) by a feed mechanism (not shown) located below the table 2. The holder 5 is also known as an embroidery frame or workpiece holding frame, and will hereinafter be referred to as the frame 5. An operation panel 6 for operating the sewing machine and setting various settings is provided on the right side of the sewing machine frame 1. The operation panel 6 is, for example, a touch panel, and is provided with a display section for displaying various information and an input section for entering various instructions. The feed mechanism operates to form stitches in any direction on the sewing material by displacing the frame 5 holding the sewing material relative to the needle drop position, and as this mechanism is well known, a detailed description thereof will be omitted.

[0027] FIG. 3 is an enlarged front view of the sewing machine head H, and FIG. 4 is a side view thereof. A needle bar case 8 is supported on the front of a sewing machine arm 7 attached to the front of the sewing machine frame 1 so as to be slidable left and right. A plurality of needle bars 9 are supported on the needle bar case 8 so as to be movable up and down, and a thread take-up lever 10 corresponding to each needle bar 9 is arranged so as to be able to swing freely. Each needle bar 9 is arranged so that its axial direction extends vertically, and a sewing needle 11 is attached to its lower end. An upper thread T is threaded through the eye 11a of the sewing needle 11 (see FIG. 5, etc.) from the front to the rear (see FIG. 20, etc.). A slide shaft 12 penetrates the needle bar case 8, and the slide shaft 12 is driven by a motor (not shown) to slide the needle bar case 8 left and right. As the needle bar case 8 slides, one of the plurality of needle bars 9 is selectively positioned at an operating position, selecting the needle bar 9 to be operated.

[0028] A main shaft 13 is inserted through the sewing machine arm 7. When the main shaft 13 is rotated by a main shaft motor (not shown), a needle bar driver 15 moves up and down along a base shaft 16 via a cam mechanism (not shown) and a link 14 inside the sewing machine arm 7. The needle bar driver 15 has a structure that engages with a locking pin 17a of a needle bar holder 17 fixed at a predetermined position on the needle bar 9, and is switchable between a catch position where the needle bar 9 is caught and a non-catch position. In the catch position, as shown in FIG. 4, the needle bar driver 15 engages with the locking pin 17a of the needle bar holder 17. In the non-catch position, the engagement between the needle bar driver 15 and the locking pin 17a of the needle bar holder 17 is released, and the needle bar 9 is held at an upper position (top dead center) by the restoring force of a tension spring 18 provided above the needle bar 9. When the needle bar 9 (and the sewing needle 11) is actually moved up and down to perform sewing, the needle bar driver 15 is always set to the catch position. Control that temporarily stops the needle bar 9 (and sewing needle 11) at the top dead center during a sewing operation is known as jump control. When such jump control is performed, the needle bar driver 15 is temporarily set to the non-catch position. To perform such jump control, a known jump mechanism is provided in the sewing machine head H. That is, this jump mechanism is a mechanism that holds the sewing needle 11 at an upper position without lowering it when jump control should be performed during a sewing operation. As an example, the jump mechanism is made up of a jump motor (not shown) provided on the sewing machine arm 7, a drive member (not shown) that sets the needle bar driver 15 to the non-catch position by rotating the needle bar driver 15 about the base shaft 16 by a predetermined angle in response to the drive of the jump motor, the tension spring 18, etc.

[0029] The needle bar 9 selected for the operating position moves up and down in response to the up and down movement of the needle bar driver 15 while it is caught by the needle bar driver 15. As the needle bar 9 selected for the operating position moves up and down, the sewing needle 11 attached to the tip of the needle bar 9 passes through the needle eye 19a of the needle plate 19, and a well-known sewing operation is performed. On the other hand, when the jump mechanism is actuated in response to the driving of the jump motor (not shown), the needle bar driver 15 is set to the non-catch position, and the needle bar 9 is not caught by the needle bar driver 15, but rather jumps as described above and is held at the top dead center.

[0030] The needle bar case 8 is provided with lifting bars 20, each movable up and down, behind each needle bar 9. Like the needle bars 9, the lifting bars 20 are arranged so that their axial direction extends vertically, and a presser foot device 21 is provided at the bottom end of each. The presser foot device 21 is used to press down on the workpiece from above as the sewing needles 11 descend, and includes a presser foot member 22 and a guide body 23, which will be described in detail later. The presser foot member 22 is attached to the bottom end of the lifting bar 20, and the guide body 23 is provided at the bottom end of the presser foot member 22. One lifting bar 20 corresponding to the needle bar 9 selected for the operating position is driven by a presser foot motor 24 provided on the sewing machine arm. A link mechanism 25 is connected to the presser foot motor 24. When the presser foot motor 24 rotates back and forth, a presser foot driver 26, which is provided on the sewing machine arm 7 so as to be able to rise and fall, rises and falls via the link mechanism 25. The presser foot driver 26 has a structure that engages with a locking pin 27a of a lifting bar holder 27 fixed at a predetermined position on each lifting bar 20, and the locking pin 27a of one of the lifting bars 20 provided in the needle bar case 8 that corresponds to the needle bar 9 selected for the operating position engages with the presser foot driver 26, and the lifting bar 20 moves up and down along its axial direction together with the presser foot device 21 (presser member 22 and guide body 23) as the presser foot driver 26 moves up and down. When the needle bar 9 jumps due to the jump mechanism, the presser foot motor 24 stops, and the presser foot device 21 (presser member 22 and guide body 23) stops at a predetermined upper position (top dead center).

[0031] The combination of the above-mentioned sewing machine head H and the corresponding shuttle 3 corresponds to a sewing mechanism that moves the sewing needle 11 with the upper thread threaded up and down, and rotates the shuttle 3 containing the lower thread in synchronization with the up and down movement of the sewing needle 11, thereby entangling the upper thread with the lower thread and sewing the material to be sewn.

[0032] <Structure of the presser foot device> FIG. 5 is an enlarged front view of one embodiment of the presser foot unit 21. A mounting member 28 is provided at the lower end of the lifting rod 20, and the presser foot member 22 of the presser foot unit 21 is detachably attached to the mounting member 28 with screws. The lower end of the presser foot member 22 extends directly below the needle bar 9 and has a through-hole 22a through which the sewing needle 11 passes. When the needle bar 9 descends, the presser foot member 22 also descends to press down on the workpiece from above. The sewing needle 11 then passes through the through-hole 22a and pierces the workpiece, thereby performing sewing. This structure is similar to that of known presser foot units. This embodiment is further characterized by the provision of a guide body 23 protruding downward from the lower end of the presser foot member 22. Each of the components 22, 23 of the presser foot unit 21 may be made of metal or other materials.

[0033] The guide body 23 is generally cylindrical and has a hollow portion (a vertical opening) that communicates with the through-hole 22a of the presser foot member 22, so that the sewing needle 11 passing through the through-hole 22a can pass through the hollow portion and vertically through the guide body 23. The guide body 23 is not a complete cylinder, but has an opening (cutout) 29 that opens to the lower end of the guide body 23, from the left front of the inserted sewing needle 11 to a position opposite the left side of the guide body 23 when viewed from the front (see also Figure 8). The opening (cutout) 29 naturally communicates with the hollow portion of the guide body 23, so that a part of the needle thread (the part that connects to the material to be sewn) that is passed through the eye 11a of the sewing needle 11 that passes through the hollow portion can pass through the opening 29 and exit the guide body 23, depending on the direction of movement of the frame 5. Since the rotation direction (counterclockwise) of the shuttle 3 is, in other words, facing left when viewed from above, the opening 29 formed on the approximate left side when viewed from the front is formed to allow the upper thread to pass in the rotation direction of the shuttle 3. In this way, since the structure allows the upper thread to be let out from the guide body 23 via the opening 29, the upper thread can be wound around the sewing needle 11 counterclockwise (i.e., in the rotation direction of the shuttle 3) depending on the direction of movement of the frame 5 over a wide range, as will be described later.

[0034] The leading and trailing edges of the opening 29 formed on the left side of the guide body 23 correspond to the leading edge 23a and trailing edge 23b of the material wall portion of the guide body 23. In other words, the opening 29 is limited by the leading and trailing edges, and when the upper thread exits the opening and attempts to detour and move in another direction in response to the movement of the frame 5, its movement is restricted by the leading edge 23a or the trailing edge 23b of the material wall portion of the guide body 23. The restricting action of the leading edge 23a plays an important role in preventing the occurrence of hitch stitches caused by the upper thread. Therefore, in this embodiment, the material wall portion of the guide body 23 closer to the front than the leading edge (i.e., leading edge 23a) of the opening 29 is referred to as the restricting portion 23a. The movement of the upper thread in the direction away from the front edge of open portion 29 formed generally on the left side, which is attempted to be restricted by the restricting portion, i.e., front edge portion 23a, is a movement generally to the right, in other words, a movement in the direction opposite to the rotational direction (counterclockwise) of shuttle 3. Therefore, it can be said that restricting portion 23a of guide body 23 is provided so as to restrict the movement of the upper thread in the direction opposite to the rotational direction of shuttle 3.

[0035] As described above, the open portion 29 is provided so as to open all the way to the lower end of the guide body 23. Therefore, the restricting portion 23a defining the front edge of the open portion 29 is provided so as to restrict the movement of the upper thread passing through the open portion 29 in the direction opposite to the rotation direction of the shuttle 3 until it reaches the lower end of the guide body 23. Therefore, when the upper thread is restricted by the restricting portion 23a, as the sewing needle 11 descends, the upper thread moves along the restricting portion 23a to the lower end of the guide body 23 and passes downward through the open portion 29, thereby being released from the restriction by the restricting portion 23a. When the restriction by the restricting portion 23a is released, the upper thread winds counterclockwise around the sewing needle 11 (i.e., in the rotation direction of the shuttle 3). As an example, the restricting portion 23a of the guide body 23 is provided within an appropriate range from the front edge of the open portion 29 toward the front surface. As will be described in detail later, the restricting portion 23a formed on the guide body 23 is intended to prevent the upper thread from coming to the right side of the sewing needle 11 (to wind counterclockwise around the sewing needle 11) when the sewing needle 11 pierces the sewing material, in order to avoid the occurrence of hitch stitches caused by the upper thread. In FIG. 5, the symbol V indicates the vertical movement locus (vertical movement line) of the sewing needle 11. In order to prevent the upper thread from coming to the right side of the sewing needle 11 when the sewing needle 11 pierces the sewing material, the restricting portion (front edge portion) 23a provided on the guide body 23, or at least its lower end (the portion that abuts against the sewing material), is positioned to the left of the vertical movement locus V of the sewing needle 11. In other words, the restricting portion 23a is provided so as to restrict the movement of the upper thread at a position that is offset toward the rotation direction of the shuttle 3 (to the left) from the vertical movement line of the sewing needle 11.

[0036] In the embodiment shown in FIG. 5 (or FIG. 8), the front edge of the open portion 29, i.e., the restricting portion (front edge) 23a formed on the guide body 23, has a shape (recessed portion) that is obliquely cut from above toward the lower left. This inclined shape (recessed portion) causes the upper or middle opening of the open portion 29 to be slightly wider toward the front than the lower opening. Therefore, when the sewing needle 11 and the presser foot 22 descend, if any slack occurs in the portion of the upper thread that has emerged from the open portion 29 and is restricted by the restricting portion 23a, this slack is absorbed by the wider opening, maintaining the upper thread held by the restricting portion 23a as much as possible. This prevents, as much as possible, the upper thread from coming off the restricting portion 23a before the sewing needle 11 penetrates the material to be sewn. However, such an inclination is not essential, and the front edge of the open portion 29, i.e., the restricting portion (front edge) 23a formed on the guide body 23, may be formed vertically.

[0037] The external shape of guide body 23 is not limited to the above-described substantially cylindrical shape, and may be any shape. Figure 6 shows a modified example of guide body 23, where (a) is a perspective view seen from the bottom side, (b) is a plan view, and (c) is a front view. Guide body 23-1 shown in Figure 6 is composed of two side wall surfaces connected at an appropriate angle (for example, approximately 90 degrees), and the space other than these side wall surfaces functions as a space (corresponding to the hollow portion) that allows passage of sewing needle 11 and a space as open portion 29 that allows passage of the upper thread in the rotation direction of shuttle 3. The side wall surface on the front side of guide body 23-1 functions as restriction portion 23a.

[0038] Figure 7 shows another modified example of guide body 23, where (a) is a perspective view seen from the bottom side, (b) is a plan view, and (c) is a front view. Guide body 23-2 shown in Figure 7 is made up of three side wall surfaces connected in sequence at an appropriate angle (for example, approximately 90 degrees), and the space other than these side wall surfaces functions as a space (corresponding to the hollow portion) that allows passage of sewing needle 11 and a space as open portion 29 that allows passage of the upper thread in the rotation direction of shuttle 3. The side wall surface on the front side of guide body 23-2 functions as restriction portion 23a.

[0039] The guide body 23 shown in FIGS. 5 to 7 has a wall portion, and the side edge on the front side of the wall portion functions as the restricting portion 23a. However, this is not limiting. The restricting portion 23a may be formed in the form of a pin-shaped or linear thin pillar member without having a wall portion. For example, two thin pillar members may be arranged to form a space as the open portion 29 between them, with one pillar member (on the front side) functioning as the restricting portion 23a. In this case, an arc-shaped connecting foot may be provided on the opposite side of the open portion 29 to connect the lower ends of the two thin pillar members. As a variation, one or more additional thin pillar members may be provided between the arc-shaped connecting foot members. As another variation, the guide body 23 may be formed of only one thin pillar member functioning as the restricting portion 23a.

[0040] FIG. 8 shows another modified version of the presser foot unit 21, in which a cover 30 is provided below the presser member 22 to cover the guide body 23. The structure of the presser foot unit 21 is the same as that shown in FIG. 5, except for the elements related to the cover 30. The cover 30 has a smoothly rounded convex curved (bowl-shaped) bottom, a relatively large through-hole to loosely accommodate the guide body 23, and a recess on the inside of the upper part that fits the presser member 22. The cover 30 is attached from below the guide body 23 and fastened with screws 31, thereby assembling and fixing the cover 30 to the presser member 22 and covering the side periphery of the guide body 23. Because the guide body 23 is loosely accommodated inside the cover 30 with a gap, the function of the guide body 23 described above is not impaired. As a result, the periphery of the lower end of the guide body 23 is surrounded by the convex curved (bowl-shaped) bottom surface of the cover 30, so that even if the amount of vertical stroke of the presser foot device 21 is reduced to prevent the sewing material from flapping, for example, the guide body 23 can be prevented from getting caught on the stitches on the sewing material as it moves.

[0041] <Thread plate structure> In this embodiment, a novel structure is provided in relation to the needle hole 19a of the needle plate 19 to prevent hitch stitches caused by the bobbin thread. Fig. 9 is a perspective view showing one embodiment of such a novel needle plate structure. Fig. 10 is an enlarged view of the needle hole 19a in Fig. 9, with (a) being a plan view, (b) being a perspective view showing a cross section taken along line AA in (a), and (c) being a perspective view of the essential part illustrating the path of the bobbin thread D. Conventionally known needle holes 19a have generally been simple circular holes, as shown by the dotted lines in Fig. 10(a). The vertical movement path of the sewing needle 11 (V in Fig. 5) passes through approximately the center of this circle.

[0042] In the needle plate structure according to this embodiment, the needle plate 19 is provided with a guide hole 31 and a groove 32 associated with the needle eye 19a. The guide hole 31, which penetrates the needle plate 19, is located near the front of the sewing machine and communicates with the needle eye 19a. The guide hole 31 is offset toward the rotation direction of the shuttle 3 (toward the left in FIG. 10(a)) from the vertical movement line of the sewing needle 11. The needle plate 19 also has a groove 32 extending from the guide hole 31 in the opposite direction to the rotation direction of the shuttle 3 (to the right in FIG. 10(a)) just before the needle eye 19a. The groove 32 is open at its top and in the portion that leads to the guide hole 31, but otherwise forms a bottom surface 32a and a side wall 32b (FIG. 10(b)). As is well known, during sewing, the bobbin thread D coming out of the shuttle 3 passes through the needle eye 19a and extends upward to form a stitch in the sewing object. In this embodiment, the lower thread D coming out of the shuttle 3 is configured to be able to pass not only through the needle eye 19a but also through the guide hole 31 that communicates with it. When the lower thread D passes through the guide hole 31, the portion of the lower thread D coming out above the guide hole 31 can be guided to the front side of the needle eye 19a via the groove 32, depending on the direction in which the frame 5 moves, as shown in Figure 10(c). Because the groove 32 has a bottom surface 32a, the lower portion of the lower thread D remains in the guide hole 31, and the upper portion of the lower thread D is bent and guided into the upper space of the groove 32.

[0043] The guide hole 31 is positioned offset toward the rotation direction of the shuttle 3 (toward the left) from the vertical movement line of the needle 11, and the groove 32 extends from the guide hole 31 in the opposite direction to the rotation direction of the shuttle 3 (to the right) just before the needle eye 19a, so that when the frame 5 is moved substantially leftward by the detour movement control of the frame 5, which will be described later, the bobbin thread D is guided into the guide hole 31, and then, as the frame 5 is moved substantially rightward to the needle drop position (target position), the bobbin thread D is guided substantially rightward from the guide hole 31 along the groove 32. At this time, because the groove 32 is on both sides by side walls 32b, the bobbin thread D is caught by the rear side wall 32b and is maintained on the front side of the vertical movement line of the needle 11 without moving rearward from the vertical movement line of the needle 11. In this way, the path of the bobbin thread D extending from the shuttle 3 to the needle eye 19a of the needle plate 19 is maintained nearer to the up-and-down movement line of the sewing needle 11, rather than toward the rear, thereby preventing the occurrence of hitch stitches (particularly double hitch stitches). Also, because the groove 32 has a bottom surface 32a, the loop of the upper thread that moves upward along the bobbin thread D, passing through the needle eye 19a while shrinking the loop, does not become caught in the groove 32, thereby eliminating the risk of the upper thread breaking. Furthermore, because the bobbin thread D is only retained by the side wall 32b of the groove 32, when the bobbin thread D is pulled up as the upper thread rises, the bobbin thread D easily leaves the groove 32 and returns to its normal path (i.e., the path passing through the needle eye 19a), so there is no adverse effect on the path formation of the bobbin thread D when the next stitch is formed.

[0044] As shown in a plan view in Figure 10(a), for example, at the point where the guide hole 31 connects to the needle eye 19a, the wall surface 31a on the rear side of the guide hole 31 is inclined from the rear toward the front (i.e., toward the left front) closer to the direction of rotation of the shuttle 3. That is, this wall surface 31a is inclined from the rear toward the left front so that the rearmost part is closest to the vertical movement line of the needle 11 and the frontmost part is farthest to the left from the vertical movement line of the needle 11. The inclination of the wall surface 31a at this connection point contributes to smooth transition of the lower thread D along the inclination into the guide hole 31 when the path of the lower thread D is transitioned from the needle eye 19a to the guide hole 31 during the roundabout movement of the frame 5. However, the shape of the connection point between the guide hole 31 and the needle eye 19a is not limited to this, and may be designed in any desired manner.

[0045] <Kettle structure> In this embodiment, a novel structure is provided in relation to the shuttle 3 to prevent hitch stitches caused by the lower thread. FIG. 11 is a front view of one embodiment of such a novel shuttle structure, FIG. 12 is a plan view thereof, FIG. 13(a) is a left side view thereof, and FIG. 13(b) is a right side view thereof. As is well known, the shuttle 3 is disposed below the needle plate 19. As an example, the shuttle 3 is a vertically rotating shuttle (DB type). The shuttle 3 has a bobbin case 40 that rotatably houses a lower thread bobbin (not shown) wound with lower thread, an inner shuttle 50 that houses the bobbin case 40, and an outer shuttle 60 that rotates around the inner shuttle 50 in synchronization with the up and down movement of the sewing needle 11. As is well known, the inner shuttle 50 is fixed to the shuttle base 4 via a shuttle support 70, and the bobbin case 40 is fixed within the inner shuttle 50. The outer shuttle 60 is fixed to a lower shaft (not shown) that rotates in synchronization with the up and down movement of the sewing needle 11, and rotates together with the lower shaft. In a vertical full rotary shuttle (DB type), the rotation direction R of the outer shuttle 60 is counterclockwise. A needle hole 51 is provided on the upper front surface of the inner shuttle 50 to avoid interference with the sewing needle 11.

[0046] A recess 52 is formed on the upper front surface of the inner hook 50 at a position offset from the needle hole 51 in the rotation direction R of the outer hook 60. The recess 52 is open at the front and top and bottom, and has a wall 52a at its rear end. The wall 52a is positioned approximately at the limit where it does not interfere with the path of movement of the needle point 61 of the outer hook 60. By positioning the wall 52a at the rear end of the recess 52 at this approximately limit position, the bobbin thread path connecting the recess 52 to the workpiece (the position of the bobbin thread leading from the recess 52 to the needle eye 19a) can be positioned as far back (rearward) as possible from the needle point (the path of vertical movement). This allows the shuttle structure of this embodiment to maximize the area in which hitch stitches caused by the bobbin thread can be avoided. The left and right walls of the recess 52 are an upstream side wall 52b located upstream of the rotation direction R of the outer hook 60 and a downstream side wall 52c located downstream of the upstream side wall 52b.

[0047] A thread take-up member 41 is provided at a predetermined position near the top of the bobbin case 40 (preferably below the recessed portion 52) for directing (guiding) the lower thread unwound from the lower thread bobbin toward the recessed portion 52 of the inner hook 50. As will be described in detail later, the lower thread unwound from the lower thread bobbin in the bobbin case 40 passes through the thread take-up member 41, passes through the opening of the recessed portion 52 of the inner hook 50, and is pulled out upward. The lower thread that has passed through the recessed portion 52 is entangled in an upper thread loop as the outer hook 60 rotates, in a well-known manner, and emerges from the needle eye 19a as the sewing needle 11 rises, forming a stitch. In this way, the recessed portion 52 provided in the inner hook 50 functions to form a path for the lower thread.

[0048] With this shuttle structure, the path of the lower thread that runs from the shuttle 3 through the needle eye 19a of the needle plate 19 to the upper part of the sewing material passes through the recess 52 provided on the front upper part of the inner shuttle 50, and is located on the left side of the vertical movement line (needle drop position) of the needle 11. In other words, the lower thread that is unwound from the lower thread bobbin is directed by the thread take-up member 41 toward the recess 52 of the inner shuttle 50, passes through the recess 52 and heads toward the needle eye 19a of the needle plate 19. The recess 52 is formed in a position displaced from the needle drop hole 51 in the rotation direction R of the outer shuttle 60 (that is, a position on the left side of the vertical movement line of the needle 11), and its rear wall surface 52a is formed at an approximate limit position where it does not interfere with the movement locus of the blade point 61 of the outer shuttle 60, so that the path of the lower thread that runs from the shuttle 3 to the needle eye 19a is located on the rear left side of the vertical movement line of the needle 11. This prevents the path of the bobbin thread from the shuttle 3 toward the needle eye 19a from coming to the right of the vertical movement line of the sewing needle 11, thereby reducing the occurrence of hitch stitches.

[0049] This point will be further explained with reference to FIG. 1. In the sewing direction corresponding to the region δ where a hitch stitch occurs due to the lower thread, the frame 5 moves 180 degrees in the opposite direction, toward the rear right. Therefore, in a conventional shuttle that supplies the lower thread from below the vertical movement of the needle, the lower thread is pulled by the material to the right of the vertical movement of the needle, resulting in a hitch stitch. In contrast, in this embodiment, when the frame 5 moves toward the rear right to sew in the region δ, the lower thread heading toward the needle eye 19a from the shuttle 3 abuts against the rear wall surface 52a of the recess 52, and the movement of the lower thread toward the right is restricted by the upstream side wall 52b. Therefore, the lower thread coming out of the shuttle 3 passes to the left of the vertical movement of the needle 11 toward the needle eye 19a, and the needle enters on the right side of the lower thread, thereby preventing a hitch stitch.

[0050] For example, in the sewing direction belonging to region δ in Figure 1, when the frame 5 moves in a direction of approximately 70 degrees, the bobbin thread path is reliably to the left of the needle point (the vertical movement path of the sewing needle 11), and hitch stitches are avoided even if the position of the rear wall surface 52a of the recessed portion 52 is shallower than the approximately limit position. On the other hand, when the frame 5 moves in a direction of approximately 40 degrees, if the position of the rear wall surface 52a of the recessed portion 52 is shallower than the approximately limit position, the bobbin thread path is not to the left of the needle point (the vertical movement path of the sewing needle 11) but to the right via the front side, and hitch stitches cannot be avoided. However, as described above, by positioning the rear wall surface 52a of the recessed portion 52 in the approximately limit position, the bobbin thread path can be made to be to the left of the needle point (the vertical movement path of the sewing needle 11), and hitch stitches can be avoided, even when the frame 5 moves in a direction of approximately 40 degrees, for example. In this way, the farther back the rear wall surface 52a of the recess 52 is positioned, the more the area in which hitch stitches caused by the lower thread can be avoided by the shuttle structure of this embodiment can be expanded, and by positioning this rear wall surface 52a at the approximately limit position, the area in which frame bypass control is not required is maximized.

[0051] It is preferable to provide a structure on the downstream side wall 52c of the recess 52 for retaining the bobbin thread during thread trimming. As shown in FIG. 12, the downstream side wall 52c protrudes forward compared to the upstream side wall 52b, and a protrusion 52d is formed at its front end. As is well known, a thread trimming device (not shown) is provided above the shuttle 3. When the thread trimming device performs the thread trimming operation, it catches the portion of the bobbin thread extending from the shuttle 3 to the needle eye 19a and guides it leftward to the cutting position, where it is cut. When the bobbin thread moves leftward in this manner for the thread trimming operation, the bobbin thread abuts against the downstream side wall 52c and can move back and forth along the downstream side wall 52c as appropriate. In this case, if the front edge of the downstream sidewall 52c were flush with the sidewall, the bobbin thread would likely come off the front edge of the downstream sidewall 52c. As a result, the bobbin thread would have to travel a short distance from the shuttle 3 to the thread trimming device. If the bobbin thread were cut in this state, the remaining length of the bobbin thread would be short, which could cause problems with the next operation. To prevent this problem from occurring, a protrusion 52d is provided at the front end of the downstream sidewall 52c, protruding slightly from the wall surface. As a result, when the bobbin thread abutting against the downstream sidewall 52c moves forward during the thread trimming operation, it is retained by the protrusion 52d, preventing the bobbin thread from coming off the front edge of the downstream sidewall 52c. This design ensures that the remaining length of the bobbin thread is sufficient after cutting, preventing problems with the next operation.

[0052] Next, further improvements to the inner hook 50 and the outer hook 60 will be described. As is well known, the outer hook 60 is provided with a point 61 on its outer periphery for capturing the loop of the needle thread pulled out from the eye 11a of the sewing needle 11. A thread dividing spring (i.e., upper spring portion) 62 is fixed to the outer periphery of the outer hook 60 with screws. A tip portion 62a of the thread dividing spring 62 is formed in a claw shape for guiding the upper thread captured by the point 61. A front end edge (i.e., front side edge) 62b of the thread dividing spring 62 is formed so as to be located behind (rearward of) the rear wall surface 52a of the recess 52 of the inner hook 50, as shown in FIG. 13(b). In other words, the front end edge 62b of the thread dividing spring 62 is formed so as not to extend forward of the front side edge (front side edge of the movement locus) of the point 61 of the outer hook 60.

[0053] A conventional thread separating spring has a shape with a protruding portion (fin) at its front edge toward the rear in the direction of rotation in order to push the captured upper thread loop forward as the outer hook rotates. When the front edge of the thread separating spring protrudes in this way, the bobbin thread heading from the hook to the needle eye is also pushed forward, causing slack in the bobbin thread.

[0054] In contrast to this, in this embodiment, the thread dividing spring 62 does not have such a protruding portion (fin) formed at its front end edge 62b so that it does not come into contact with the lower thread guided by the recess 52, thereby preventing slack in the lower thread. In this way, in this embodiment, the thread dividing spring 62 does not push the thread loop forward, and therefore will be referred to in a broader sense as an upper spring portion.

[0055] Instead of providing a protruding portion (fin) on the front edge 62b of the thread separation spring (upper spring portion) 62, in this embodiment, the structure of the inner hook 50 is improved as follows. As shown in Figures 11 and 13(a), etc., a protruding portion 53 is formed on the outer periphery of the front surface of the inner hook 50, extending from the recess 52 in the downstream direction of rotation over a range of approximately 1 / 4 arc angle (i.e., 90 degrees), more specifically, over a range of less than 1 / 4 arc angle (i.e., 90 degrees), particularly over a range of approximately 80 degrees in the illustrated example. More specifically, the protruding portion 53 has a mountain-shaped cross section and is provided with a guide surface 53a that slopes forward as it moves upstream in the direction of rotation, and is formed so that its protruding height decreases as it moves downstream in the direction of rotation. The protruding portion 53 functions to push forward the needle thread loop caught by the point 61 of the outer hook 60. As the outer hook 60 rotates, the upper thread loop is pushed out while moving from below the raised portion 53 upward (from rear to front), and passes around the inner hook 50 while moving along the front surface of the bobbin case 40. In this way, the raised portion 53 of the inner hook 50 can function as a substitute for the fin of a conventionally known thread separating spring.

[0056] 11 and 12, the protrusion 71 of the shuttle support 70 fixed to the shuttle base 4 can fit into the recess 52 of the inner shuttle 50, and in this fitted state the inner shuttle 50 is fixed to the shuttle base 4 and is prevented from rotating together with the outer shuttle 60. A suitable open space is formed between the inner wall surface 52a of the recess 52 and the tip of the protrusion 71 of the shuttle support 70, and the bobbin thread guided into the recess 52 passes through this open space and heads for the needle eye 19a.

[0057] An example of a bobbin case 40 will now be described with reference to FIG. 14. The bobbin thread bobbin housed in the bobbin case 40 is not shown in FIG. 14. As shown in FIG. 14(a), the main body 42 of the bobbin case 40 has an opening 42a at the top front surface to avoid interference with the sewing needle 11 that has fallen into the needle hole. A pull-out hole 42b is formed in the trunk (the outer peripheral side) of the bobbin case main body 42, through which the bobbin thread is pulled out from the bobbin thread bobbin housed therein, and a tension spring 43 is attached to apply a constant tension to the bobbin thread. A guide groove 42c is formed above the pull-out hole 42b to regulate the position at which the bobbin thread passes. The top of the trunk of the bobbin case main body 42 is also open, and this top opening is in communication with the opening 42a.

[0058] The thread take-up member 41 is disposed at the upper front surface of the bobbin case 40, more specifically, at a position below and to the left of the opening 42a. In a preferred example, the thread take-up member 41 is made of a spring material so as to apply tension to the bobbin thread that is unwound from the bobbin thread bobbin and directed toward the opening of the recess 52 of the inner hook 50. Therefore, hereinafter, the thread take-up member 41 will also be referred to as a thread take-up spring. The thread take-up spring (thread take-up member) 41 has an annular or curved ring portion 41a through which (hooks) the bobbin thread unwound from the bobbin is passed, and the bobbin thread passed through the ring portion 41a is directed toward the opening of the recess 52 of the inner hook 50. The tension of the thread take-up spring 41 appropriately guides the bobbin thread toward the needle eye 19a so that it passes through the recess 52 (i.e., it regulates the path of the bobbin thread so that it passes through the recess 52) and absorbs slack in the bobbin thread. The thread take-up spring 41 extends substantially horizontally on the front surface of the bobbin case 40. One end (the right end) opposite the ring portion 41a is fixed to the bobbin case 40, while the ring portion 41a is a free end. The ring portion 41a is located substantially directly below the recess 52 of the inner hook 50, and due to the spring's restoring force, it can swing up, down, left, and right in response to the movement of the bobbin thread threaded therethrough. In one embodiment, the length from the fixed end (the right end) of the thread take-up spring 41 to the end (the left end) on the ring portion 41a side is relatively long, as shown in the figure. This allows the swing range (stroke range) of the thread take-up spring 41 to be relatively large, allowing it to absorb even relatively large amounts of slack in the bobbin thread. By constructing the thread take-up member 41 from a spring material, it not only reliably guides the bobbin thread toward the recess 52 of the inner hook 50, but also applies tension to the bobbin thread to prevent slack in the bobbin thread under various conditions.

[0059] The lower thread pulled out from the pull-out hole 42b of the bobbin case 40 comes into contact with the tension spring 43, passes through the guide groove 42c, passes through the ring portion 41a of the thread take-up spring 41, turns around upward, passes through the recess 52 of the inner hook 50, and comes out into the needle eye 19a. However, this is not limiting, and the lower thread pulled out from the pull-out hole 42b of the bobbin case 40 may be passed through the tension spring 43, and then passed through the ring portion 41a of the thread take-up spring 41 without passing through the guide groove 42c.

[0060] As an option, as shown in Figure 14(b), a guide member 44 may be provided in front of the thread take-up spring (thread take-up member) 41 on the bobbin case 40. The guide member 44 is detachably attached with a screw to the upper left front surface of the bobbin case body 42. The guide member 44 has a guide surface 44a that protrudes forward from the attachment position, and the guide surface 44a is formed so as to be generally continuous with (form a surface that is substantially flush with) the front surface of the bobbin case 40. By providing the guide member 44 in this manner, the upper thread loop that moves to the front of the bobbin case 40 and moves upward as the shuttle 3 rotates can be smoothly guided along the front surface of the bobbin case.

[0061] Furthermore, the guide surface 44a of the guide member 44 is provided with an opening 44b penetrating in the front-rear direction. This opening 44b allows the insertion of the tip of a known picker (not shown). The known picker holds the needle thread on the sewing needle side when the needle thread is cut by a thread cutting device (not shown), thereby ensuring a predetermined amount of remaining thread and preventing the needle thread from slipping out of the needle eye. The known picker has a pair of left and right tips, and during the thread cutting operation, these tips are inserted into the opening 42a of the bobbin case 40 to hook and hold the needle thread passing through the shuttle 3, ensuring a predetermined amount of remaining thread and thereby preventing the thread from slipping out of the needle eye. Such a picker can also be applied to this embodiment. However, in the picker (not shown) applied to this embodiment, the length of one tip (the left tip) of the picker must be slightly shorter than conventional pickers to prevent interference with the thread take-up spring 41. The guide surface 44a and opening 44b of the guide member 44 provide a structure suitable for such a special picker. That is, when the picker is set, the shorter end (the left end) of the picker enters the opening 44b of the guide surface 44a of the guide member 44 but does not come into contact with the thread take-up spring 41. As a result, when the upper thread loop moves upward along the guide surface 44a of the guide member 44 that protrudes forward of the thread take-up spring 41, the upper thread loop is securely hooked on both ends of the picker (i.e., on the shorter end as well), thereby ensuring a predetermined amount of upper thread remaining and preventing the thread from slipping out of the eye 11a of the needle 11. Note that such a guide member 44 is not essential and is not required, for example, in a sewing machine that is not equipped with a picker.

[0062] <Frame bypass control> In this embodiment, in order to prevent hitch stitches caused by the upper thread, in addition to providing the guide body 23 in the presser foot device 21 as described above, a bypass control of the frame 5 is also performed. This frame bypass control is executed by an electric / electronic control system. FIG. 15 is a block diagram showing an example of a control system of a sewing machine (i.e., a sewing machine control device). As is well known, this control system includes a CPU (Central Processing Unit) 101 that controls various processes and drives of the sewing machine, a RAM (Random Access Memory) 102 that serves as the work area for the CPU 101, and a storage device (ROM = read-only memory and / or readable / writable memory such as a flash memory or hard disk) 103 that stores pre-programmed embroidery data (sewing data) of one or more patterns and associated program control data (process control data), as well as various processing programs and data in a non-volatile manner. The control system further includes a driver 104 for a main shaft motor that rotates the sewing machine main shaft 13, drivers 105 and 106 for an X-axis motor and a Y-axis motor that move the frame 5 in the X and Y directions, respectively, a driver 107 for the jump motor that jumps the needle bar 9, and a driver 108 for the presser foot motor 24 that raises and lowers the presser foot device 21, and each driver is connected to a corresponding motor. The control system also includes a user input / output interface 109 including the operation panel 6. As described above, the operation panel 6 is configured with a touch panel that both displays images and accepts user input operations, and various setting and control screens are displayed on the touch panel. A user can perform various operations and settings by touching operation images and the like displayed on the screen of the touch panel. The control system may also include a communication interface (not shown) for communicating with an external device and / or an internal or external communication network.

[0063] As is well known, under the control of the CPU 101, sewing data of an arbitrary pattern selected by the user is read from the storage device 103, and the drivers 104 to 108, etc. are controlled in accordance with the sewing data for each stitch to perform sewing operations and form stitches one after another. This sewing data makes it possible to determine whether the direction in which the next stitch will be formed belongs to a predetermined area in which a hitch stitch will be formed (for example, areas β to δ shown in FIG. 1). This determination can be made by a program executed by the CPU 101. In other words, the CPU 101 and this program function as a determination means that determines, based on the sewing data read from the storage device 103, whether the direction in which the next stitch will be formed belongs to a predetermined area in which a hitch stitch will be formed.

[0064] In this embodiment, in order to prevent the occurrence of hitch stitches due to the upper thread, if it is determined that the direction in which the next stitch is to be formed falls within a predetermined region in which a hitch stitch is to be formed, detouring control is performed to move the frame 5 in a detouring manner when the frame 5 is moved to a target position corresponding to the next stitch. This detouring control can be performed by a program executed by the CPU 101. That is, when the determining means determines that the direction in which the next stitch is to be formed falls within the predetermined region, the CPU 101 and the program function as control means (i.e., detouring control means) that performs the jump control using the jump mechanism (107, etc.) and operates the feed mechanisms (105, 106, etc.) to move the frame 5 in a detouring manner. Here, the detouring movement of the frame 5 consists of moving the frame 5 in a direction in which the upper thread extending downward from the sewing needle 11, with the sewing needle 11 jumping upward, emerges from the open portion 29 of the guide body 23 of the presser foot device 21, and then moving the frame 5 to a target position corresponding to the next stitch so that the upper thread emerging from the open portion 29 abuts against the regulating portion 23a of the guide body 23. The movement of the frame 5 such that the upper thread emerging from the open portion 29 abuts against the regulating portion 23a of the guide body 23 is nothing other than a detouring movement of the upper thread emerging from the open portion 29 so that it passes through the regulating portion 23a. In other words, the detour movement is a movement in which, without immediately moving the frame 5 to the target position corresponding to the next stitch, the sewing needle 11 is made to jump upward, the frame 5 is first moved in the direction in which the upper thread emerges from the open portion 29 of the guide body 23, and then the upper thread emerging from the open portion 29 detours so that it abuts (passes through) the regulating portion 23a, and finally reaches the target position corresponding to the next stitch.

[0065] As shown as a typical example in FIG. 1, the sewing direction in which a hitch stitch occurs due to the upper thread belongs to areas β and γ. A portion of area β around 90 degrees (i.e., an area where the sewing direction is toward the back of the sewing machine) is an area where a hitch stitch can be avoided by moving the frame 5 around with a relatively small detour. For convenience, this area will be referred to as the first area S1. For reference, an example of the first area S1 is shown in FIG. 16. In FIG. 16, as in FIG. 1, the base point C located at the center of the figure indicates the current needle point (the position of the needle hole 19a in the needle plate 19). The sewing direction from the base point C to the next needle point (i.e., the direction in which the next stitch is formed) is determined by an angle from 0 degrees to less than 360 degrees, scaled counterclockwise. The movement direction of the frame 5 corresponding to area S1, which is a sewing direction of around 90 degrees, is the area of ​​around 270 degrees, which is the exact opposite (180 degrees opposite) of area S1. For reference, an example of the target position of movement of the frame 5 corresponding to a stitch in the sewing direction belonging to the first region S1 is shown as T1 in FIG. 16. As can be seen from the figure, the target position T1 corresponding to the next stitch is relatively close to the position where the frame 5 is temporarily moved in the direction where the needle thread emerges from the open portion 29 of the guide body 23 (toward the front left) during the detouring movement of the frame 5. Therefore, the target position T1 can be reached by detouring the frame 5 with a relatively small amount of detouring. The range of this first region S1 is shown in the figure as a range from angle a to b, and is, for example, a range from approximately 85 degrees to less than 112 degrees. However, as will be described later, this range may be variably set as appropriate.

[0066] Of the regions β and γ, which correspond to the sewing direction in which a hitch stitch occurs due to the upper thread, the remaining region S2 is a region in which a hitch stitch is avoided by moving the frame 5 in a detouring manner by a relatively large amount. For convenience, this region will be referred to as the second region. The second region S2 includes the remainder of region β and all of region γ shown in FIG. 1. The movement direction of the frame 5 corresponding to this second region S2 is the region directly opposite (180 degrees opposite) to the second region S2. For reference, an example of the target position of the movement of the frame 5 corresponding to a stitch in the sewing direction belonging to the second region S2 is indicated by T2 in FIG. 16. As can be seen from the figure, when the frame 5 detouring, the target position T2 corresponding to the next stitch may be relatively far and toward the rear from the position where the frame 5 is temporarily moved in the direction in which the upper thread exits the open portion 29 of the guide body 23 (toward the front left). Therefore, to reach the target position T2, the frame 5 must be detouring by a relatively large amount. The range of this second region S2 is shown in the figure as a range of angles b to c, and is, for example, a range of approximately 112 degrees to 210 degrees, but as will be described later, this range may be variably set as appropriate. Note that the regions with different detour amounts are not limited to the two regions (S1, S2) as described above, but may be three or more regions. Also, in Figure 16, S0 indicates a region where no detour movement of frame 5 is performed, and this region S0 includes regions α and δ shown in Figure 1.

[0067] In one embodiment, the control means may perform the jump control one, two or more times during the detour movement. In one embodiment, the control means performs the jump control one time during the detour movement if the direction in which the next stitch is to be formed belongs to the first region S1, and performs the jump control two times during the detour movement if the direction in which the next stitch is to be formed belongs to the second region S2.

[0068] FIG. 17 is a diagram illustrating some of the trajectories of the detouring movement of the frame 5, which are executed by the frame detouring control by the control means. In FIG. 17, as in FIG. 16, C indicates the (current) needle point position (base point) at the start of the detouring movement, and T1 and T2 indicate the needle point positions (target positions) at the end of the detouring movement. In relation to this, FIG. 18 is a plan sectional view showing the relationship between the upper thread T and the guide body 23 of the presser foot unit 21 during the detouring movement of the frame 5, and shows the guide body 23, the sewing needle 11, and the portion of the upper thread T that enters its eye 11a in a horizontal cross section. However, as described above, in the jump state, the sewing needle 11 is positioned higher than the guide body 23, so it should be noted that the cross section of the guide body 23 and the cross section of the sewing needle 11 (and the cross section of the portion of the upper thread T that enters its eye 11a) do not represent cross sections at the same height.

[0069] FIG. 17(a) shows the trajectory of the detour movement when the direction of the next stitch falls within the first region S1. In this example, one jump (for one stitch) is performed during the detour movement. The needle bar 9 (sewing needle 11), which has risen to base point C, is set to a jump state by the jump mechanism and held in an upward position. The presser foot motor 24 stops, and the presser foot unit 21 stops at a predetermined upper position. At the same time, the frame 5 is controlled to move in a direction in which the needle thread T extending downward from the sewing needle 11 exits the open portion 29 of the guide body 23. The movement of the frame 5 at this time is indicated by A1 in FIG. 17(a). The end point m1 of the movement A1 of the frame 5 (i.e., the midpoint of the detour movement) can be set using appropriate X and Y coordinate values. To perform the detour movement efficiently (compactly), it is recommended to set the end point (i.e., the midpoint) m1 of the movement A1 of the frame 5 so that it is diagonally forward and left as shown in the figure. However, the present invention is not limited to this and may be appropriately set within the scope of the present invention. Figure 18(a) shows a state in which the upper thread T comes out diagonally forward left from the open portion 29 of the guide body 23 in accordance with the movement A1 of the frame 5 at this time. When the frame 5 reaches the midpoint m1, the jump control for one stitch ends.

[0070] Next, the frame 5 is moved from the midpoint m1 toward the target position T1 corresponding to the next stitch. The movement of the frame 5 at this time is indicated by A2 in FIG. 17(a). The movement A2 of the frame 5 is diagonally forward to the right as shown in the figure. During this movement A2, the upper thread T emerging from the open portion 29 of the guide body 23 comes into contact with the restricting portion 23a of the guide body 23, and the movement of the upper thread T to the right is restricted by the restricting portion 23a. FIG. 18(b) shows the state in which the upper thread T comes into contact with the restricting portion 23a as a result of the movement A2 of the frame 5 at this time. In this state, the upper thread T emerging from the eye 11a of the needle 11 is positioned to the left of the needle 11. While the frame 5 is moving from the midpoint m1 toward the target position T1, the needle bar 9 (needle 11) and the presser foot 21 descend. Of course, the operation timing is adjusted appropriately so that the frame 5 reaches the target position T1 and completes the detouring movement before the descending sewing needle 11 and presser foot device 21 come into contact with the upper surface of the sewing workpiece.

[0071] FIG. 17(b) shows the trajectory of the detour movement when the direction of the next stitch falls within the second region S2. In this example, two jumps (for two stitches) are performed during the detour movement. The needle bar 9 (needle 11), which has risen to base point C, is set in a jump state by the jump mechanism and held in an upward position. The presser foot motor 24 stops, and the presser foot unit 21 stops at a predetermined upper position (top dead center). At the same time, the frame 5 is controlled to move in a direction in which the needle thread T extending downward from the needle 11 exits the open portion 29 of the guide body 23. The movement of the frame 5 at this time is indicated by A1 in FIG. 17(b) as described above. As described above, the end point m1 of the movement A1 of the frame 5 (i.e., the first intermediate point) can be set using appropriate X and Y coordinate values. As described above, in order to perform the detour movement efficiently (compactly), it is advisable to set the end point (i.e., the first intermediate point) m1 of the movement A1 of the frame 5 so that the movement A1 is in the diagonally forward left direction as shown in the figure. As described above, the state in which the upper thread T comes out of the open portion 29 of the guide body 23 in the diagonally forward left direction as a result of the movement A1 of the frame 5 is as shown in Figure 18(a). When the frame 5 reaches the first intermediate point m1, the first jump control (for one stitch) ends, but in order to maintain the jump state, the second jump control (for one stitch) continues.

[0072] Next, while maintaining the jump state, the frame 5 is moved from the first intermediate point m1 toward the second intermediate point m2. The movement of the frame 5 at this time is indicated by A2 in FIG. 17(b). The movement A2 of the frame 5 is in a direction diagonally forward to the right as shown in the figure. During this movement A2, the upper thread T emerging from the open portion 29 of the guide body 23 abuts against the restricting portion 23a of the guide body 23, and the movement of the upper thread T to the right is restricted by the restricting portion 23a. The state when the upper thread T abuts against the restricting portion 23a during this movement A2 is shown in FIG. 18(b). In this state, the upper thread T emerging from the eye 11a of the sewing needle 11 is positioned to the left of the sewing needle 11. The end point of the movement A2 of the frame 5 (i.e., the second intermediate point m2) can be set using appropriate X and Y coordinate values. Considering that the frame 5 will reliably contact (engage) the target position T2 and the restricting portion 23a, it is advisable to set the end point of the movement A2 (i.e., the second intermediate point m2) so that the movement A2 of the frame 5 is in an appropriate diagonally forward right direction as shown in the figure. When the frame 5 reaches the second intermediate point m2, the second jump control ends. When the frame 5 reaches the end point of the movement A2 (second intermediate point m2), the upper thread T is entangled counterclockwise around the restricting portion 23a.

[0073] Next, the frame 5 is moved from the second intermediate point m2 toward the target position T2 corresponding to the next stitch. The movement of the frame 5 at this time is indicated by A3 in FIG. 17(b). The movement A3 of the frame 5 is in the diagonally rear right direction as shown in the figure. As a result of this movement A3, the upper thread T is further wound counterclockwise around the restricting portion 23a and moves toward the diagonally rear right direction. However, the state is the same as in FIG. 18(b) in that the upper thread T emerging from the eye 11a of the needle 11 is positioned to the left of the needle 11. While the frame 5 is moving from the second intermediate point m2 toward the target position T2, the needle bar 9 (needle 11) and the presser foot 21 descend. As described above, the operation timing is appropriately adjusted so that the frame 5 reaches the target position T2 and completes the detour movement before the descending needle 11 and presser foot 21 come into contact with the top surface of the sewing workpiece.

[0074] In the frame detour control shown in FIGS. 17(a) and 17(b), the detour movement of the frame 5 is performed intermittently. For example, it is preferable to program a combination of stitch data (frame movement data) and a jump control code for each stitch, and to perform a single detour movement by jump control based on a combination of the sewing data of the first stitch (frame movement data to the midpoint m1) and the jump control code, and the sewing data of the next stitch (frame movement data to the target position T1). Furthermore, it is preferable to perform two detour movements by jump control based on a combination of the sewing data of the first stitch (frame movement data to the first midpoint m1) and the jump control code, a combination of the sewing data of the next stitch (frame movement data to the second midpoint m1) and the jump control code, and the sewing data of the last stitch (frame movement data to the target position T2). The number of jump controls in the frame detour control is not limited to one or two, as described above, but may be three or more, or may be only one.

[0075] The detouring movement of frame 5 is not limited to the intermittent movement described above, but may be continuous. Figure 17(c) shows an example of continuous detouring of frame 5, in which the target position is T2 as in (b) and detouring movement is continuously performed along the trajectories A1, A2, and A3 as in (b). For example, a parameter may be set such that frame 5 moves continuously when a jump control code is generated consecutively, and based on this, frame 5 may be continuously detouring to target position T2 while needle bar 9 remains jumping.

[0076] <Prevents upper thread loosening> In one embodiment, measures should be taken to prevent slack in the needle thread T when the bypass movement of the frame 5 is controlled. To this end, as shown in FIG. 3, an upper thread slack prevention unit 200 is provided below the needle bar case 8. The upper thread slack prevention unit 200 is located above a well-known upper thread locking device 400, and both ends of its base plate 201 are fixed with screws to brackets attached to the left and right sides of the needle bar case 8. At positions on the base plate 201 corresponding to each needle bar 9, presser pieces 203 are held by screws 202 with springs fitted to their shafts. The upper thread T (not shown in FIG. 3) hanging from the thread take-up lever 10 is passed between the base plate 201 and the presser piece 203. By adjusting the amount of threading of the screw 202 to change the elasticity of the spring, a slight tension is applied to the upper thread T passing between the base plate 201 and the presser piece 203 through contact resistance. The needle thread T that has passed through the needle thread slack prevention unit 200 passes through the needle thread lock device 400 and is passed through the eye 11a of the corresponding sewing needle 11. The tension applied to the needle thread T by the screw 202 and presser piece 203 of the needle thread slack prevention unit 200 need only be sufficient to prevent the needle thread T, which is caught on (wound around) the guide body 23, from slackening and falling off downward during the bypass movement control of the frame 5. Even if slack occurs in the portion of the needle thread T above the needle thread slack prevention unit 200 when the needle bar 9 jumps or when the take-up lever 10, which moves up and down, descends, the contact resistance of the needle thread slack prevention unit 200 prevents slack from occurring in the portion of the needle thread T below that point, and therefore prevents the needle thread T, which is caught on (wound around) the guide body 23, from slackening and falling off downward during the bypass movement control of the frame 5. The structure of the upper thread slack prevention unit 200 is not limited to that shown in the figure, and any structure may be used as long as it prevents the upper thread T from slackening. Also, a well-known upper thread locking device 400 may be used instead of providing a special upper thread slack prevention unit 200. Since the above-mentioned upper thread slack prevention unit 200 constantly applies tension to the upper thread T, even a slight contact resistance may affect the thread tightness. As a modified example, the upper thread slack prevention unit 200 may be made movable like the upper thread locking device 400, and tension may be applied only when the frame 5 is being controlled to bypass.

[0077] <Sewing control that achieves perfect stitches> The sewing machine shown in the above embodiment can avoid the occurrence of hitch stitches due to upper thread factors and lower thread factors and achieve all-perfect stitches across the entire range of stitching directions. Figure 19 is a flowchart showing an example of a computer program for executing sewing control for all-perfect stitches according to this embodiment. This program is stored in, for example, the storage device 103 shown in Figure 15 and executed by the CPU 101.

[0078] The program shown in FIG. 19 starts when the sewing operation of a pattern (embroidery pattern or other sewing pattern) consisting of multiple stitches selected by the user is started. In step St1, the value of stitch counter n, which indicates the stitch formation order, is set to an initial value of 1. In step St2, stitch movement amount data Pn (XY movement data of frame 5) for forming the stitch of the order (nth stitch) specified by the current value of stitch counter n is obtained. In step St3, the stitch movement direction of the stitch movement amount data Pn (i.e., the direction in which the next stitch is formed) is calculated using the current needle drop position as base point C. In step St4, it is determined whether the calculated stitch movement direction (the direction in which the next stitch is formed) belongs to area S0 shown in FIG. 16 (i.e., the area in which frame detour control is not performed). If YES, proceed to step St5; if NO, proceed to step St8.

[0079] In step St5, the frame 5 is moved to the target position corresponding to the stitch movement amount data Pn, and the needle bar 9 is lowered to sew one stitch. The frame 5 is not moved around during the sewing operation in step St5. As mentioned above, the area S0 shown in FIG. 16 includes the areas α and δ shown in FIG. 1. If the calculated stitch movement direction (the direction in which the next stitch is formed) belongs to area α, a perfect stitch can be formed simply by performing a normal sewing operation. On the other hand, if the calculated stitch movement direction (the direction in which the next stitch is formed) belongs to area δ, the unique shuttle structure mentioned above can be used to prevent hitch stitches caused by the lower thread, and a perfect stitch can be formed. The details are as follows.

[0080] <Avoiding hitch stitching in region δ> FIG. 20 illustrates a mechanism for preventing hitch stitches caused by the bobbin thread using the shuttle structure according to this embodiment, where (a) is a front view of the shuttle structure, and (b) is an enlarged plan view showing the relationship between the needle and the bobbin thread in the inner shuttle 50. The shuttle 3 shown in FIG. 20 is the same as the shuttle 3 described above with reference to FIGS. 11 to 14. When the direction in which the next stitch is to be formed falls within region δ, the frame 5 moves toward the right rear toward the target position corresponding to the next stitch. The bobbin thread D heading from the shuttle 3 toward the needle eye 19a is pulled toward the right rear as the frame 5 moves, but as shown in FIGS. 20(a) and 20(b), the bobbin thread D abuts against the rear wall surface 52a of the recess 52 of the inner shuttle 50, and the movement of the bobbin thread D toward the right is restricted by the upstream side wall 52b of the recess 52. In this way, the lower thread D coming out of the shuttle 3 passes through the left rear side of the vertical movement of the needle 11 toward the needle eye 19a and connects with the workpiece W above, so that when the vertically moving needle 11 is below the needle plate 19, the lower thread D is always located at the left rear side of the needle 11 and never comes to the right of it. This structurally prevents the occurrence of hitch stitches due to the lower thread in the region δ, and the entanglement of the upper thread T and lower thread D achieved in the shuttle 3 forms a perfect stitch.

[0081] When the sewing needle 11 passes through the sewing object (work cloth) W, the sewing object may flap up and down, causing the lower thread D to slacken and possibly moving to the right of the needle tip of the sewing needle 11. However, in this embodiment, the thread take-up member 41 is provided with a spring action, so that even if the lower thread D becomes loose due to flapping of the sewing object W, the spring action of the thread take-up member (thread take-up spring) 41 located almost directly below the recessed portion 52 of the inner hook 50 quickly absorbs the slack in the lower thread D, thereby maintaining the lower thread D in a taut state and preventing the lower thread D from moving to the right of the needle tip of the sewing needle 11. Furthermore, as described above, the front end edge 62b of the upper spring portion (thread separating spring) 62 of the outer hook 60 is located rearward of the back wall surface 52a of the recessed portion 52 of the inner hook 50, so that the front end edge 62b does not come into contact with the lower thread D and push the lower thread D forward. Therefore, the upper spring portion (thread dividing spring) 62 of the outer hook 60 does not cause slack in the lower thread D. In this way, a thorough measure is taken to eliminate the possibility of hitch stitches occurring due to slack in the lower thread D.

[0082] Returning to FIG. 19, in step St8, it is determined whether the stitch moving direction (the direction in which the next stitch is formed) calculated in step St3 above belongs to the first region S1 (part of region β) shown in FIG. 16. If the answer is YES, the process proceeds to step St9. In step St9, frame detour movement control for the first region S1 consisting of a small detour movement trajectory as shown in FIG. 17(a) is executed. If the answer is NO in step St8, this means that the stitch moving direction (the direction in which the next stitch is formed) calculated in step St3 above belongs to the second region S2 (the region including the remainder of region β and region γ) shown in FIG. 16. In this case, the process proceeds to step St10, and frame detour movement control for the second region S2 consisting of a large detour movement trajectory as shown in FIG. 17(b) is executed.

[0083] <Avoiding hitch stitches in area S1> The frame detouring movement control (one jump control) for the first region S1 performed in step St9 consists of moving the frame 5 to the midpoint m1 with the needle bar 9 jumping, as shown in Figure 17(a), and then moving the frame 5 to the target position T1 to cause the needle 11 to drop onto the workpiece W. This will be described in more detail below with reference to Figure 21. Figure 21 is a perspective view illustrating the function of the guide body 23 of the presser foot unit 21 in the detouring movement control of the frame 5.

[0084] When the frame 5 is moved to the intermediate point m1 with the needle bar 9 jumping and the needle 11 held in an upward position, the frame 5 moves as indicated by A1 in FIG. 17(a), and as shown in FIG. 18(a), the upper thread T emerges from the open portion 29 of the guide body 23 of the presser foot unit 21 diagonally forward and to the left. FIG. 21(a) is a perspective view of this state. Next, when the frame 5 is moved from the intermediate point m1 to the target position T1, the frame 5 moves as indicated by the trajectory A2 in FIG. 17(a), and as shown in FIG. 18(b), the upper thread T abuts against the restricting portion 23a of the guide body 23 and is restricted. At the same time, the jump state of the needle bar 9 is released, and the needle 11 and the presser foot unit 21 descend.

[0085] 21(b) shows the state immediately before the descending sewing needle 11 enters the through-hole 22a of the presser member 22 of the presser foot device 21. As can be seen from the figure, the upper thread T, which connects from the rear of the eye 11a of the sewing needle 11 to the workpiece W, is caught by the restricting portion 23a of the guide body 23 (more specifically, the notched portion of the restricting portion 23a), and movement to the right of the vertical movement line of the sewing needle 11 is restricted, and the upper thread T is held on the left side of the sewing needle 11.

[0086] 21(c) shows the state in which the sewing needle 11 further descends and enters the guide body 23 of the presser foot member 22, just before it pierces the workpiece W. The sewing needle 11 descending within the guide body 23 emerges from the rear of the eye 11a and, while being regulated by the regulating portion 23a, passes to the right of the portion of the needle thread T that is connected to the workpiece W. When the guide body 23 of the presser foot device 21 reaches the bottom dead point, the descent of the presser foot device 21 is stopped, and thereafter only the sewing needle 11 continues to descend.

[0087] 21(d) shows the state in which the tip of the sewing needle 11, which is further descending, has passed through the guide body 23 and is pierced into the workpiece W. The portion of the needle thread T which connects from the rear of the eye 11a of the sewing needle 11 to the workpiece W is restricted from moving to the right by the restricting portion 23a of the guide body 23, and is held in a position to the left of the sewing needle 11, and descends along the restricting portion 23a as the sewing needle 11 descends.

[0088] 21(e) shows a state in which the sewing needle 11 is further lowered, so that the portion of the upper thread T that connects from the rear of the eye 11a to the workpiece W reaches below the lower end of the guide body 23. In this state, the portion of the upper thread T that connects from the rear of the eye 11a to the workpiece W comes off the restricting portion 23a and becomes entangled with the sewing needle 11 in the left-handed direction.

[0089] When the sewing needle 11 descends further and passes through the workpiece W and the needle eye 19a of the needle plate 19, with the eye 11a positioned below the needle plate 19, the portion of the upper thread T that emerges from the rear of the eye 11a of the sewing needle 11 and connects to the workpiece W above extends upward along the left side of the sewing needle 11, passes through the needle eye 19a and reaches the workpiece W. In this way, when the sewing needle 11 descends to the shuttle 3, the path of the upper thread T from the rear of the eye 11a to the workpiece W above (needle eye 19a) is held on the left side of the sewing needle 11. With the needle 11 thus lowered into the shuttle 3, as is well known, the needle thread T emerging from the rear of the eye 11a and extending upward is caught by the point 61 of the outer shuttle 60 and moves together with the point 61, forming (pulling out) a loop of the needle thread T, and the combination of the rotation of the shuttle 3, the rise of the needle 11, and the movement of the thread take-up 10 causes the loop of the needle thread T to become entangled with the bobbin thread D, forming a stitch. Since the needle thread T emerging from the rear of the eye 11a enters the shuttle 3 in a position to the left of the needle 11 (winding counterclockwise relative to the needle 11), the stitch is formed as a perfect stitch. As a result, the occurrence of hitch stitches in the first region S1 (part of region β) can be avoided.

[0090] <Avoiding hitch stitches in area S2> The frame detouring movement control (double jump control) for the second region S2 performed in step St10 consists of moving the frame 5 to the first intermediate point m1 with the needle bar 9 jumping one stitch, as shown in Figure 17(b), then moving the frame 5 to the second intermediate point m2 with the needle bar 9 jumping another stitch, and finally moving the frame 5 to the target position T2 to cause the needle 11 to drop onto the workpiece W. This will be described in more detail below with reference to Figures 21(a) and 22.

[0091] By moving the frame 5 to the first intermediate point m1 while the needle bar 9 jumps one stitch and holding the sewing needle 11 above, the frame 5 moves as shown by A1 in Figure 17(b), and as shown in Figure 18(a), the upper thread T extending downward from the rear of the eye 11a of the upper sewing needle 11 emerges diagonally forward and to the left from the open portion 29 of the guide body 23 of the presser foot device 21. The perspective view of this state is shown in Figure 21(a).

[0092] Next, by continuing the jump of the needle bar 9 (jumping another stitch), the frame 5 moves from the first intermediate point m1 to the second intermediate point m2, causing the frame 5 to move generally to the right, as shown by the trajectory A2 in FIG. 17(b). When the frame 5 reaches the second intermediate point m2, the jump control ends. When the frame 5 reaches the end point (second intermediate point m2) of this movement A2, the upper thread T is wound counterclockwise around the restricting portion 23a of the guide body 23. A perspective view of this state is shown in FIG. 22. As can be seen from the figure, the upper thread T, which descends from the sewing needle 11 and connects to the workpiece W, is deeply wound counterclockwise around the restricting portion 23a of the guide body 23. In this way, the frame bypass movement using the double jump control ensures that the upper thread T is hooked around the restricting portion 23a, thereby preventing threading errors.

[0093] Finally, by moving the frame 5 from the second intermediate point m2 to the target position T2, the frame 5 moves as shown by the trajectory A3 in Figure 17(b). As this movement A3 accompanies, the upper thread T further winds counterclockwise around the restricting portion 23a and moves diagonally to the right. In this way, the upper thread T, which connects from the rear of the eye 11a of the needle 11 to the workpiece W, is deeply wound counterclockwise around the restricting portion 23a of the guide body 23, and movement to the right of the vertical movement line of the needle 11 is restricted, and the upper thread T is held to the left of the needle 11. Because the jump control has ended, the needle bar 9 (needle 11) and presser foot 21 descend while the frame 5 moves from the second intermediate point m2 to the target position T2.

[0094] The state of the upper thread T as the needle 11 descends further, passing through the workpiece W and the needle eye 19a and reaching the shuttle 3, is the same as that described above with reference to Figures 21(c) to 21(e). That is, the portion of the upper thread T emerging from the rear of the eye 11a of the needle 11 enters the shuttle 3 while remaining positioned to the left of the needle 11 (winding leftward relative to the needle 11), thereby forming a stitch that avoids the occurrence of hitch stitches caused by the upper thread. In particular, in the region β of the second region S2, a perfect stitch is formed by avoiding the occurrence of hitch stitches caused by the upper thread as described above. In the region γ of the second region S2, hitch stitches caused by both the upper thread and the lower thread coexist, so it is not sufficient to simply avoid the occurrence of hitch stitches caused by the upper thread; it is also necessary to avoid the occurrence of hitch stitches caused by the lower thread. Specifically, even if the frame detouring control causes the needle 11 to be wound counterclockwise, a double hitch stitch occurs if the bobbin thread is positioned behind (rearward of) the vertical movement line of the needle 11. As described above, such a hitch stitch caused by the bobbin thread in the region γ is avoided by the unique needle plate structure related to the needle hole 19a of the needle plate 19. Details are as follows.

[0095] <Avoiding hitch stitches caused by bobbin thread in region γ> As described above with reference to Figures 9 and 10, the needle plate 19 is formed with a guide hole 31 and a groove 32 associated with the needle hole 19a. Figure 23 is a perspective view illustrating a mechanism for avoiding hitch stitches caused by the lower thread by using the structure of the needle plate 19 having the guide hole 31 and groove 32. In Figure 23, for ease of illustration, the frame 5 and the workpiece W present between the presser foot unit 21 and the needle plate 19 are omitted, and accordingly, the lower side of the upper thread T and the upper side of the lower thread D are omitted. Also, for convenience of illustration, the distance between the guide body 23 of the presser foot unit 21 and the needle plate 19 (needle hole 19a) is depicted as if it were constant, but in reality, this distance changes as the presser foot unit 21 moves up and down.

[0096] 23(a) shows the state when the frame 5 has moved approximately to the first intermediate point m1 (diagonally forward left direction) in the frame bypass movement control (two-jump control) for the second region S2 performed in step St10. In this state, the upper thread T extending downward from the rear of the eye 11a of the upper sewing needle 11 emerges diagonally forward left direction from the open portion 29 of the guide body 23 of the presser foot device 21, as described above. The lower thread D extending upward from the shuttle 3 and connected to the workpiece W passed through the needle eye 19a corresponding to the needle drop position before the movement of the frame 5, but is guided from the needle eye 19a to the guide hole 31 as the frame 5 moves to the first intermediate point m1 (diagonally forward left direction).

[0097] 23(b) shows a state when the frame 5 has moved approximately to the second intermediate point m2 (approximately to the right) in the frame detouring movement control (double jump control) for the second region S2 performed in step St10. In this state, the upper thread T extending downward from the rear of the eye 11a of the upper sewing needle 11 is caught on the restricting portion 23a of the guide body 23, as described above, and is restricted from moving to the right of the vertical movement line of the sewing needle 11, and is entangled counterclockwise around the restricting portion 23a. As the frame 5 moves from the first intermediate point m1 to the second intermediate point m2 (approximately to the right), the lower thread D bends from the guide hole 31 and enters the upper space of the groove portion 32, and is guided approximately to the right along the groove portion 32.

[0098] FIG. 23(c) shows the state when the frame 5 has moved approximately to the target position T2 (generally toward the right rear) in the frame bypass movement control (double jump control) for the second region S2 performed in step St10. In this state, the upper thread T extending downward from the rear of the eye 11a of the upper sewing needle 11 is further wound counterclockwise around the restricting portion 23a of the guide body 23, as described above. As the frame 5 moves from the second intermediate point m2 to the target position T2 (generally toward the right rear), the lower thread D is stopped by the side wall 32b (FIG. 10(b)) on the rear side of the groove portion 32 (i.e., closer to the needle eye 19a), and is maintained in front of the vertical movement line of the needle 11 without moving further back than the vertical movement line of the needle 11. This means that the path of the lower thread D, which is drawn upward from the shuttle 3 to the needle plate 19, is maintained in front of the vertical movement line of the needle 11.

[0099] When the frame 5 has reached the target position T2, the needle 11 descends further and then ascends, and in the process, the loop of the upper thread T becomes entangled with the lower thread D as described above in accordance with the rotation of the shuttle 3, forming a stitch. At this stage, the upper thread T emerging from the rear of the eye 11a enters the shuttle 3 in a state where it is positioned to the left of the needle 11 (winding counterclockwise relative to the needle 11), and the path of the lower thread D drawn out from the lower thread bobbin to the needle plate 19 is maintained on the near side of the vertical movement line of the needle 11, as described above. Therefore, sewing is achieved which avoids both a hitch stitch caused by the upper thread and a hitch stitch caused by the lower thread (i.e., a double hitch stitch).

[0100] Note that the bobbin thread D is also pulled out as the frame 5 moves around, but the spring action of the thread take-up member 41 quickly absorbs any slack in the pulled-out bobbin thread D. That is, in this embodiment, by providing the thread take-up member 41 with a spring action, even if the bobbin thread D is pulled out as the frame 5 moves around, the spring action of the thread take-up member (thread take-up spring) 41 provided in the shuttle 3 quickly absorbs the slack in the bobbin thread D, so that the bobbin thread D can be maintained in a taut state. Therefore, the bobbin thread D is less likely to slacken and come off the engagement portion (groove 32) of the needle plate 19. That is, in this embodiment, the thread take-up member (thread take-up spring) 41 also functions (concurrently serves as) tension applying means provided below the needle plate 19 so as to apply tension to the bobbin thread that is unreeled upward from the shuttle 3 and directed toward the needle eye 19a or guide hole 31 of the needle plate 19.

[0101] As is well known, the loop of needle thread T caught by the point 61 of the outer hook 60 passes through the inner hook 50, and when the thread take-up lever 10 (FIG. 4) is pulled up, the loop of needle thread T shrinks as it passes along the bobbin thread D. In this embodiment, the groove 32 is formed to have a bottom surface 32a, so that the loop of needle thread T, which passes upward through the needle eye 19a together with the bobbin thread D while shrinking its loop, does not get caught in the groove 32, and the structure does not cause the problem of upper thread breakage. Furthermore, when the needle enters the target position T2, the bobbin thread D is only engaged with the back side wall 32b (FIG. 10(b)) of the groove 32 of the needle plate 19. Therefore, when the bobbin thread D is pulled up as the upper thread T rises, the bobbin thread D easily leaves the groove 32 and returns to its normal path (i.e., the path passing through the needle eye 19a), and therefore does not adversely affect the path formation of the bobbin thread D when the next stitch is formed.

[0102] As described above, in FIG. 19, by executing the processing of steps St5, St9, and St10 according to the stitch movement direction of the stitch movement amount data Pn (i.e., the direction in which the next stitch is formed), it is possible to achieve sewing consisting of all-perfect stitches that avoid the occurrence of (all types of) hitch stitches due to upper thread factors and lower thread factors.

[0103] Regarding the remaining steps shown in FIG. 19, after the processing of steps St5, St9, and St10, the program proceeds to step St6, where the value of the stitch counter n is incremented by 1. In the next step St7, it is determined whether the value n, which has been incremented by 1, is greater than the "total number of stitches" of the pattern currently being sewn. If the answer is NO, the program returns to step St2, and the processing from step St2 onwards is repeated as described above for the value n, which has been incremented by 1 (i.e., the "next stitch"). When sewing of the pattern currently being sewn is completed, the program determines YES in step St7, and ends the program in FIG. 19.

[0104] <Frame bypass control data settings> In one embodiment, various data related to the frame detouring control (i.e., various conditions for the detouring control) may be configured so that the user can arbitrarily set and change them. FIG. 24 shows an example of a screen display that allows various data related to the frame detouring control (various conditions for the detouring control) to be set and changed using the operation panel 6 (FIG. 2). The operation panel 6 has a touch-operable display screen on which required images and data, etc. are displayed according to various operation modes. When the operation mode is the setting mode, for example, a parameter setting screen 110 as shown in the figure is displayed on the display screen of the operation panel 6. On the parameter setting screen 110, as an example, setting items for the frame detouring control numbered 21 to 30 are displayed together with their respective current setting values. As another example, instead of simultaneously displaying multiple setting items (numbered 21 to 30) on the parameter setting screen 110, at least one setting item may be displayed, and the displayed setting item may be sequentially switched by scrolling or the like.

[0105] When a desired setting item is selected by touching one of the numbers 21 to 30 displayed on the parameter setting screen 110, the current setting value for the selected setting item is displayed on the display unit 111. By operating the setting value switching key 112, the current setting value for the selected setting item is increased or decreased, and is displayed on the display unit 111. After changing the setting value, pressing the confirmation key 113 makes the changed setting value effective.

[0106] The item numbered 21 relating to "Use all perfect stitch (Apfs)" corresponds to a setting means for setting whether or not to enable execution of the frame detouring movement control. For example, by setting Yes / No, it is possible to switch whether or not to enable execution of the frame detouring movement control. In the drawing, the state set to "Yes" is shown. Note that this setting value may be "ON / OFF" instead of "Yes / No".

[0107] In order to actually control whether the detour movement control of frame 5 is enabled or disabled according to this setting, part of the flow in FIG. 19 can be modified as shown in FIG. 25. That is, step St11 is inserted between steps St3 and St4 described above, and in this step St11, it is determined whether or not "Use all perfect stitches (Apfs)" is set to YES (that is, whether or not the execution of the detour movement of frame 5 is enabled). If step St11 is YES, the process proceeds to step St4 described above, and the detour movement control of frame 5 is executed as described above. If step St11 is NO, the process skips step St4 and proceeds to step St5 described above, and the detour movement control of frame 5 is not executed.

[0108] By enabling the setting of whether to enable the detouring movement of the frame 5, a wide variety of sewing operations can be performed and sewing work can be efficiently carried out. As described above, by executing the detouring movement of the frame 5, hitch stitches due to the upper thread can be avoided and sewing quality can be improved. However, the extra time required for the detouring movement of the frame 5 inevitably reduces overall sewing production efficiency. Depending on the target sewing product, there may be cases where it is more important to avoid a decrease in production efficiency than a decrease in quality due to hitch stitches. For example, when sewing hidden parts that are not visible on the surface of the product, it may be preferable to prioritize production efficiency without improving hitch stitches. Furthermore, there may be cases where it is desired to select whether to execute detouring movement control of the frame 5 depending on the type of sewing material (workpiece fabric) or the type of upper thread. Furthermore, the degree of need to avoid hitch stitches may differ between, for example, simple straight stitching and complex embroidery stitching. To accommodate these various situations, it is beneficial to provide a function for selecting whether to enable (Yes or ON) or disable (No or OFF) the detouring movement of the frame 5.

[0109] Items 22 to 24 are means for setting parameters a, b, and c that define the stitching direction (stitch formation direction) for frame detouring control. Specifically, they correspond to setting means for variably setting the ranges of the first and second regions S1 and S2 (FIG. 16). Boundary angles a and b that define the range of the first region S1 are variably set using items 22 and 23. Of the boundary angles b and c that define the range of the second region S2, b is set according to the setting in item 23, and c is variably set using item 24. As an example, the boundary angles a, b, and c are initially set to predetermined values ​​(e.g., a = 85 degrees, b = 112 degrees, c = 210 degrees), and the user manually increases or decreases these predetermined values ​​to variably set them. Based on the settings (values ​​of the boundary angles a, b, and c), the regions S0 and S1 are determined in steps St4 and St8 of FIG. 19.

[0110] Generally, it is difficult to precisely define the area where hitch stitches occur. Therefore, to be on the safe side, it is preferable to set the ranges of the areas S1 and S2 where frame detour control is performed broadly and perform the detour movement control of the frame 5. However, doing so may result in a decrease in overall production efficiency as the number of detour movement controls of the frame 5 increases. Furthermore, depending on the target sewn product, it may be desirable to avoid a decrease in production efficiency as much as possible by allowing hitch stitches in sewing areas where stitch quality is not a priority. Furthermore, it may be desirable to variably set the ranges of the areas S1 and S2 where frame detour control is performed, depending on the type of sewing material (workpiece fabric) or the type of needle thread, rather than fixing them. To address these various situations, it is beneficial to provide a function for variably setting the ranges of the predetermined areas S1 and S2 where detour movement control of the frame 5 is performed (the values ​​of the boundary angles a, b, and c).

[0111] The items numbered 25 and 26 are means for setting parameters X1 and Y1 that define a first movement direction in the frame detouring control (i.e., setting means for variably setting the detouring movement path of the frame 5), and specifically correspond to setting means for variably setting the XY displacement coordinate position (coordinate position relative to the base point C) of the first intermediate point m1 (FIG. 17). The items numbered 27 and 28 are means for setting parameters X2 and Y2 that define a second movement direction in the frame detouring control (setting means for variably setting the detouring movement path of the frame), and specifically correspond to setting means for variably setting the XY displacement coordinate position (coordinate position relative to the first intermediate point m1) of the second intermediate point m2 (FIG. 17). These parameters X1, Y1, X2, and Y2 may also be initially set to predetermined values, and then variably set by the user manually increasing or decreasing each predetermined value. The current values ​​(2.5 mm, -3.8 mm, 1.1 mm) of the parameters X1, Y1, X2, Y2 exemplified in Fig. 24 are expressed in the XY coordinate representation format of the stitch shown in Fig. 1. For example, the XY displacement coordinate position of X1=2.5 mm, Y1=2.5 mm for defining the first intermediate point m1 indicates a stitch position belonging to the X+ and Y+ quadrants in the XY coordinate representation format of the stitch shown in Fig. 1, and the corresponding movement direction of the frame 5 is 180 degrees opposite, so it corresponds to the movement of the frame 5 to the first intermediate point m1 located in the X- and Y- quadrants from the base point C in Fig. 17. Furthermore, the XY displacement coordinate position of X2 = -3.8 mm, Y2 = 1.1 mm for defining the second intermediate point m2 indicates a stitch position belonging to the X- and Y+ quadrants in the XY coordinate representation format of the stitch shown in Figure 1, and the corresponding movement direction of the frame 5 is 180 degrees opposite, so it corresponds to the movement of the frame 5 from the first intermediate point m1 to the second intermediate point m2, which belongs to the X+ and Y- quadrants and is located in the front right direction in Figure 17. Based on the contents set here (the values ​​of the parameters X1, Y1, X2, Y2 that define the first and second intermediate points m1 and m2), the detouring movement control of the frame 5 is performed in steps St9 and St10 of Figure 19.

[0112] In this way, by making it possible to variably set the parameters X1, Y1, X2, and Y2 that define the movement direction in the detouring control of the frame 5, the detouring movement path of the frame 5 can be changed appropriately. For example, if a relatively large detouring movement path is set, the upper thread can be reliably entangled around the guide body 23 of the presser foot device 21, but the detouring movement of the frame 5 takes extra time, which reduces the overall sewing production efficiency. In contrast, if a relatively small detouring movement path is set, the detouring movement of the frame 5 takes less time, which improves the overall sewing production efficiency. Therefore, such a setting means is useful because it allows an appropriate frame detouring path to be set depending on whether priority is given to sewing quality or production efficiency.

[0113] Items 29 and 30 are means for setting the effective minimum stitch length and effective maximum stitch length to which frame detouring control is applied. The effective minimum stitch length is the minimum stitch length (stitch length) to which frame detouring control is applied, and the effective maximum stitch length is the maximum stitch length (stitch length) to which frame detouring control is applied. As an example, the effective minimum stitch length is initially set to 0.0 mm, and the effective maximum stitch length is initially set to 36.0 mm. By appropriately increasing or decreasing these values, the effective minimum stitch length or effective maximum stitch length can be set as desired by the user. When this setting is applied to frame detouring control, for example, if the length of the stitch (stitch length) to be formed next is within the set effective minimum stitch length and effective maximum stitch length, the detouring control of frame 5 can be executed. For example, a step can be inserted between steps St3 and St4 in FIG. 19 (or between steps St11 and St4 in FIG. 25) to determine whether the length of the stitch to be formed next falls within the range between the set effective minimum stitch length and effective maximum stitch length, and if the answer to this step is YES, the process proceeds to step St4, but if the answer is NO, the process jumps to step St5.

[0114] The configuration for setting various data related to the frame detouring control (conditions for detouring control) is not limited to the above-described configuration in which the user manually operates the operation panel 6 of the sewing machine, but may be configured such that when a desired sewing pattern program or embroidery pattern program is created, the data is arbitrarily set as program data for the frame detouring control and stored together with the data for the sewing pattern program or embroidery pattern program. Such a configuration in which various data related to the frame detouring control (i.e., conditions for detouring control) are provided in the form of programmed data is also included in one embodiment of the setting means for variably setting various data related to the frame detouring control (conditions for detouring control).

[0115] In the above-described embodiment, when the frame 5 is moved around, both the frame detouring movement control and the needle bar jump control by the jump mechanism are performed. However, this is not limited to this, and the present invention can also be implemented in a sewing machine that does not have a jump mechanism for jump-controlling the needle bar. In a sewing machine that does not have such a jump mechanism, the detouring movement of the frame 5 can be performed by controlling the operation of the needle bar so that the needle does not drop during the detouring movement of the frame 5. For example, the rotational speed of the main shaft 13 can be reduced during the detouring movement of the frame 5 to prevent the needle from dropping during the detouring movement of the frame 5.

[0116] In the above-described embodiment, the present invention is applied to a multi-head and multi-needle sewing machine. However, the present invention is not limited to this, and can also be applied to a single-head or single-needle sewing machine. The present invention can also be applied to both embroidery machines and regular sewing machines. The holder (frame) for holding the workpiece is not limited to a flat type, but may be a rotary type like a cap frame. The shuttle is not limited to a full-rotation vertical shuttle (DB type), but may be any other type of shuttle, such as a horizontal shuttle or a semi-rotary shuttle. The region where a hitch stitch occurs may differ from that of the above-described embodiment depending on the type and direction of rotation of the shuttle. However, this can be achieved by making appropriate zone determinations, modifying the throat plate structure accordingly (changing the arrangement of the guide hole 31 and the groove 32), or modifying the shuttle structure accordingly (changing the arrangement of the recess 52).

[0117] The operation panel 6 may be fixedly attached to the sewing machine, or may be detachably attached to the sewing machine. As a modified example, the setting means (i.e., setting device) for manually setting the various bypass control conditions may be configured by a portable operation panel (e.g., a mobile computer or a portable terminal) configured to allow manual setting of the various bypass control conditions as described with reference to FIG. 24. In this case, the setting means (i.e., setting device) consisting of such a portable operation panel is equipped with a communication function for communicating with the sewing machine control device, and is configured to enable transmission and reception of setting information / data therebetween. Of course, the setting means (i.e., setting device) for manually setting the various bypass control conditions may be configured to use both the operation panel 6 fixedly or detachably attached to the sewing machine and the portable operation panel.

Claims

1. A hook structure for a sewing machine, comprising: a bobbin case for rotatably storing a bobbin around which a bobbin thread is wound; an inner hook for accommodating the bobbin case; and an outer hook for rotating around the inner hook in synchronization with the up and down movement of the sewing needle, wherein a needle drop hole is provided on the upper front surface of the inner hook, and the outer hook has a point for capturing the needle thread loop, a recess is formed in the front surface of the upper portion of the inner hook at a position shifted from the needle drop hole in the direction of rotation of the outer hook, the recess being open at the front side and at the top and bottom and forming a wall surface at the back side; the bobbin case is provided with a thread take-up member for directing the lower thread unwound from the lower thread bobbin toward the recess of the inner hook, The lower thread unwound from the lower thread bobbin in the bobbin case passes through the thread take-up member, passes through the opening of the recess, and is pulled out upward, A hook structure for a sewing machine, characterized in that the movement of the lower thread toward the rear through the opening of the recess is restricted by the wall surface on the rear side of the recess formed in the inner hook.

2. 2. The hook structure for a sewing machine according to claim 1, wherein the thread take-up member is formed of a spring member.

3. 3. The hook structure of a sewing machine according to claim 1, wherein the thread take-up member has a free end and a fixed end, the thread take-up member is fixed to the bobbin case via the fixed end, and the free end is formed with an annular or curved ring portion through which the lower thread unwound from the lower thread bobbin passes.

4. 4. The hook structure for a sewing machine according to claim 3, wherein the thread take-up member is capable of swinging in accordance with the movement of the bobbin thread passed through the ring portion.

5. 5. The hook structure for a sewing machine according to claim 1, wherein the thread take-up member is disposed below the recess.

6. 6. A sewing machine shuttle structure according to claim 1, wherein the outer shuttle has an upper spring portion arranged around the tip portion, and the front side edge of the upper spring portion is formed so as not to extend forward of the front side edge of the tip portion.

7. 7. The hook structure for a sewing machine according to claim 1, wherein the inner hook has a raised portion formed on the outer periphery of the front surface, the raised portion being provided over a range of less than 90 degrees from the recess in the direction of rotation of the outer hook.

8. 8. A hook structure for a sewing machine according to claim 1, wherein a wall surface at the rear side of the recess of the inner hook is positioned forward of a rotation locus of a front side edge of the point portion of the outer hook.

9. 9. The hook structure of a sewing machine according to claim 1, wherein a guide member is provided in front of the thread take-up member in the bobbin case, and the guide member has a guide surface formed so as to be continuous with the front surface of the bobbin case.

10. 10. The shuttle structure for a sewing machine according to claim 9, wherein the guide surface of the guide member is provided with an opening extending therethrough in the front-rear direction.

11. A hook structure according to any one of claims 1 to 10; a sewing mechanism that moves the sewing needle having an upper thread threaded therethrough up and down and rotates the outer hook in synchronization with the up and down movement of the sewing needle to entangle the upper thread with the bobbin thread, thereby sewing the sewing object; a feed mechanism that forms stitches in any direction on the sewing material by displacing a holder that holds the sewing material relative to a needle drop position; A sewing machine equipped with:

12. a determining means for determining whether the direction in which the next stitch is to be formed belongs to a predetermined area corresponding to a hitch stitch; a detouring control means for, when it is determined that the needle thread is in the predetermined area, causing the holder to be moved by the feed mechanism, thereby detouring the needle thread extending downward from the sewing needle in a direction corresponding to a perfect stitch, and then moving the holder to a target position corresponding to the next stitch; The sewing machine of claim 11 further comprising:

13. The sewing machine further includes a jump mechanism that holds the sewing needle above without lowering it when jump control is to be performed during a sewing operation, 13. The sewing machine according to claim 12, wherein the bypass control means controls the jump by the jump mechanism and also controls the movement of the holder by the feed mechanism.

Images