Sewing machine and presser device

Abstract

The present invention addresses the problem of avoiding the occurrence of hitch stitching with a simple configuration and control. A presser device (21) comprises: a presser member (22) that moves up and down in synchronization with a sewing operation to press a sewn article; and a guide body (23) provided at the lower end of the presser member. The guide body is provided with an open part (29) to allow passage of a needle thread toward the direction of rotation of a hook (3) and a regulating part (23a) to regulate the movement of the needle thread in the opposite direction of the direction of rotation of the hook. When it is determined that the direction in which to form the next stitch belongs to a predetermined area in which a hitch stitch is to be formed, a detour movement of a frame (5) holding the sewn article is performed. The detour movement causes the frame to move in the direction in which the needle thread extending downward from the sewing needle exits the guide body from the open part, and then causes the frame to move to a target position corresponding to the next stitch so that the needle thread that has exited from the open part contacts the regulating part.

Description

Technical Field

[0001] The present invention relates to a sewing machine devised to avoid the occurrence of hitch stitches when forming stitches on a workpiece, and further relates to a presser device for pressing the workpiece in the sewing machine.

Background Art

[0002] A sewing machine is conventionally known, which has a sewing mechanism that moves a sewing needle passed through an upper thread up and down and rotates a bobbin storing a lower thread in synchronization with the vertical movement of the sewing needle to entwine the upper thread with the lower thread, and stitches a workpiece (fabric to be processed), and a feed mechanism that relatively displaces a frame (holder) holding the workpiece with respect to the needle drop position to form stitches in an arbitrary direction on the workpiece. In such a sewing machine, by controlling the movement of the workpiece by the feed mechanism for each stitch, stitches of various lengths in various directions can be formed.

[0003] It is known that the quality of stitches formed by this type of sewing machine includes perfect stitches and hitch stitches. A perfect stitch is a stitch formed by entwining the upper thread and the lower thread in a well-balanced state, and a hitch stitch is a stitch formed by entwining only the upper thread with the lower thread in a spiral pattern. It is known that there are two main factors that determine whether the formed stitch becomes a perfect stitch or a hitch stitch. One is the factor of the upper thread. When the sewing needle passed through the upper thread pierces the fabric to be processed, the upper thread that passes from in front of the eye of the sewing needle to the rear and connects to the fabric to be processed is wound around the sewing needle in either a left-handed or right-handed direction depending on the moving direction (stitch forming direction) of the fabric to be processed during stitch formation, and a perfect stitch or a hitch stitch is formed accordingly. It is known that a hitch stitch is formed when the upper thread is wound around the sewing needle in the right-handed direction.

[0004] Throughout this specification, "front" ("in front", "forward", "front side", etc.) or "rear" ("rearward", "rear side", "back", "back 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 the left winding direction or right winding direction refers to the direction when the sewing machine is viewed from above (that is, left winding is counterclockwise and right winding is clockwise).

[0005] Another is the factor due to the lower thread, which depends on the relationship between the path of the lower thread that extends from the bobbin (lower thread bobbin) placed below the needle plate through the needle hole of the needle plate to the upper processing cloth and the needle drop position of the sewing needle, and a perfect stitch or a hitch stitch is formed. That is, it is known that a hitch stitch is formed when the path of the lower thread is on the right side with respect to the vertical movement line (needle drop position) of the sewing needle according to the moving direction (stitch forming direction) of the processing cloth during stitch formation.

[0006] The hitch stitch not only has a worse appearance than the perfect stitch, but also has problems such as the stitch being prone to loosening, which deteriorates the sewing quality. Therefore, various methods for avoiding the occurrence of hitch stitches have been proposed conventionally. As an example, during the sewing operation for each stitch, it is determined whether the moving direction (stitch forming direction) of the processing cloth is the perfect stitch forming direction or the hitch stitch forming direction. When it is determined to be the hitch stitch forming direction, a method has been proposed to shift the position of the upper thread or the lower thread with respect to the needle drop position by moving the frame or operating piece, etc.

[0007] Patent Document 1 below discloses an invention for avoiding hitch stitches caused by the upper thread. When it is determined that the moving direction of the frame holding the processed fabric (seam formation direction) is the hitch stitch formation direction caused by the upper thread, instead of directly moving the frame to the target needle drop position (target position) for seam formation, before the tip of the descending sewing needle reaches the upper surface of the processed fabric, the frame is detoured to the left of the needle and then made to reach the target position. By this, it is intended to avoid the occurrence of hitch stitches caused by the upper thread by winding the upper thread connected to the processed fabric around the sewing needle in a left-handed manner. However, in order to quickly wind the upper thread around the sewing needle in a left-handed manner by detouring the frame during the descent of the sewing needle, it is necessary to accurately match the timing of the descending movement of the sewing needle and the detouring movement of the frame. There is a problem that if the timing is off even slightly, the upper thread cannot be wound around the sewing needle. Therefore, with the technique disclosed in Patent Document 1, it was difficult to reliably avoid the occurrence of hitch stitches.

[0008] The following Patent Document 2 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 moving direction of a frame holding a work cloth (stitch formation direction) is the hitch stitch formation direction caused by the lower thread, the frame is not moved directly to the target needle drop position (target position) for stitch formation, but is moved 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 is moved 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, and the path of the lower thread passes to the left of the needle drop position and is stopped at the back side (i.e., the sewing needle drops to the right and front side of the path of the lower thread). In this way, the needle is caused to drop to the right of the path of the bobbin thread that extends upward and connects to the work cloth, thereby preventing the occurrence of hitch stitches caused by the bobbin thread. However, the fact that the notch connected to the back side of the needle hole has a tip that extends from left to right inevitably creates a protrusion (a peninsula, so to speak) that extends from right to left between the tip and the needle hole, and the presence of this protrusion creates the problem that it may cause the upper thread to break.

[0009] As is known, the upper thread loop caught by the tip of the outer hook moves while passing between the outer hook and the inner hook, is pulled up by the action of the take-up lever, and ascends along the lower thread while entangled with the lower thread. In the structure disclosed in Patent Document 2, the upper thread loop ascending along the lower thread may get caught on the protrusion (peninsula portion) adjacent to the tip of the notch that holds the lower thread. If this happens, the upper thread breaks. In addition, since the lower thread enters and is held at the tip of the notch, depending on the sewing direction of the next stitch, the lower thread may remain held at the notch, which may cause a problem that the lower thread path may differ from the normal path.

[0010] Patent Document 3 below also discloses an invention for avoiding hitch stitches caused by the lower thread factor. In Patent Document 3, a switching mechanism is provided to alternately switch the path of the lower thread from the bobbin to the needle holes of the needle plate to a left route biased to the left side and a right route biased to the right side with respect to the vertical movement line (vertical movement locus) of the sewing needle, and this switching is performed by air cylinder drive. When it is determined that the moving direction of the frame holding the work cloth (sewing line forming direction) is the hitch stitch forming direction caused by the lower thread factor, before the tip of the descending sewing needle reaches the upper surface of the work cloth, the switching mechanism switches the path of the lower thread to the left route or the right route, thereby avoiding the occurrence of hitch stitches. However, since it is necessary to provide an air cylinder drive type switching mechanism, there is a problem that the structure becomes complicated.

[0011] Patent Document 4 below discloses an invention for avoiding hitch stitches caused by the upper thread factor and the lower thread factor, and includes upper thread control means (needle bar rotation mechanism) for controlling the relationship of the upper thread with respect to the sewing needle and lower thread control means (thread pulling mechanism) for controlling the relationship of the lower thread with respect to the sewing needle. Each control means is controlled according to the moving direction of the work cloth to avoid the occurrence of hitch stitches. In Patent Document 4, since the needle bar rotation mechanism as the upper thread control means and the thread pulling mechanism as the lower thread control means each have a complicated structure, there is a problem that the structure of the sewing machine becomes complicated. Further, in a multi-needle sewing machine having a plurality of needle bars in one sewing machine head, such complication of the structure becomes an even more serious problem.

[0012] Patent Document 5 below discloses a sewing machine capable of sewing by rotating a sewing head and a bobbin case respectively. Along with the rotation of the sewing head, the sewing quality is improved by synchronizing the timing of the sewing needle and the bobbin and the rotations of the sewing head and the bobbin case. However, it is necessary to provide a mechanism for rotating the sewing head and the bobbin case and means for synchronously controlling them, which causes a problem that the structure becomes complicated. In addition, the structure shown in Patent Document 5 is suitable for sewing in a straight line in a certain direction such as a running stitch, but in the case of embroidery where the sewing direction is reversed like a satin stitch, it is necessary to reverse the rotation direction of the head and the bobbin case for each stitch, and since the sewing direction also changes, synchronous control is very difficult.

Prior Art Documents

Patent Documents

[0013]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Summary of the Invention

[0014] The present invention has been made in view of the above points, and aims to provide a sewing machine capable of avoiding the occurrence of hitch stitches with a simpler configuration and control than conventional ones. Furthermore, it aims to provide a presser device for a workpiece (processed fabric) having a structure suitable for avoiding the occurrence of hitch stitches.

[0015] According to a first aspect of the present invention, there is provided a sewing machine and a presser device suitable for avoiding the occurrence of hitch stitches due to upper thread factors. For this purpose, the sewing machine according to the present invention includes a sewing mechanism that moves a sewing needle up and down through an upper thread and winds the upper thread around a lower thread by rotating a bobbin that stores the lower thread in synchronization with the up and down movement of the sewing needle, and performs sewing on a workpiece; a feeding mechanism that forms a seam in an arbitrary direction on the workpiece by relatively displacing a holding body that holds the workpiece with respect to a needle drop position; and a presser member that presses the workpiece around the needle drop position. In the sewing machine, a guide body provided at a lower end of the presser member, the guide body being provided with an opening portion so as to allow the passage of the upper thread in the rotation direction of the bobbin, and a regulating portion being provided so as to regulate the movement of the upper thread in a direction opposite to the rotation direction of the bobbin; a determining means for determining whether the direction of forming the next seam belongs to a predetermined region where a hitch stitch is formed; and a control means for performing a detour movement of the holding body by operating the feeding mechanism when it is determined that the region is the predetermined region, the detour movement comprising moving the holding body in a direction in which the upper thread extending downward from the sewing needle exits from the opening portion of the guide body, and then moving the holding body to a target position corresponding to the next seam so that the upper thread exiting from the opening portion abuts against the regulating portion.

[0016] The rotation direction of the bobbin is, specifically, the rotation direction of the outer bobbin, and is the direction when the tip of the rotating outer bobbin captures (hooks) the upper thread loop inside the bobbin. Usually, since the rotation direction of the bobbin is counterclockwise, when rephrasing on the premise of this so that the left-right relationship becomes clear, the direction of movement of the tip of the outer bobbin when capturing the upper thread loop (counterclockwise) is leftward in a front view. Therefore, since the opening portion formed in the guide body is formed so as to allow the passage of the upper thread in the rotation direction of the bobbin, the opening portion will be located on the left side of the up and down movement line (up and down movement locus) of the sewing needle.

[0017] As is conventionally known, a region where a hitch stitch is formed can be predicted in relation to the threading direction of the upper thread through the eye of the sewing needle and depending on the moving direction (sewing direction) of the workpiece (fabric to be processed) during seam formation. Thus, similar to the prior art, the determination means can determine whether the direction for forming the next seam belongs to a predetermined region where a hitch stitch is formed. Note that a typical example of the threading direction of the upper thread through the eye of the sewing needle is, as is commonly known, a direction in which the upper thread fed downward from the upper thread bobbin enters the eye from the front side of the sewing needle, exits to the rear, and is connected to the workpiece (fabric to be processed). In such a typical example, as described above, in terms of the upper thread factor, a hitch stitch occurs when the upper thread winds around the sewing needle in a right-handed direction. Thus, as an example, when the moving direction of the holder for forming the next seam is a direction in which the upper thread winds around the sewing needle in a right-handed direction, the determination means may determine that the direction for forming the next seam belongs to a predetermined region where a hitch stitch is formed.

[0018] The moving direction of the holder to the next seam position (target position) when the upper thread winds around the sewing needle in a right-handed direction is substantially to the right. As is well known, the detour movement of the holder does not directly move the holder to the target position, but rather moves the holder to the target position while detouring the holder so that the upper thread winds around the sewing needle in a left-handed direction. In the prior art, the hitch stitch avoidance control for the upper thread factor was performed only by the detour movement control of the holder. Therefore, it was necessary to precisely match the timing of the detour movement of the holder for winding the descending sewing needle and the upper thread in a left-handed direction. In practice, such a precise match was difficult, and thus a hitch stitch could not be reliably avoided.

[0019] In contrast, in the present invention, by providing a guide body having the above-described structure at the lower end of the pressing member, when controlling the detour movement of the holding body, the upper thread extending from the eyelet of the sewing needle to the lower sewing material can be forced to wind leftward around the restricting portion of the guide body. That is, the detour movement of the holding body is performed with the sewing needle in a jumped state (temporarily stopped upward), and the upper thread extending downward from the sewing needle first moves the holding body in the direction of exiting from the open portion of the guide body (that is, leftward). In this way, the upper thread extending downward from the sewing needle is guided to exit outward (more to the left) through the open portion due to the presence of the open portion provided in the guide body. Then, by moving the holding body to the position of the next stitch (target position) so that the upper thread exiting from the open portion abuts against the restricting portion, the upper thread guided outward (more to the left) through the open portion can be wound leftward around the restricting portion.

[0020] From this state, when the sewing needle further penetrates the sewing material and descends into the bobbin case, the pressing member (guide body) stays on the sewing material, but the upper thread wound leftward around the restricting portion descends together with the penetrating sewing needle, and the upper thread comes to be positioned on the left side of the sewing needle (left winding with respect to the sewing needle) and enters the bobbin case. In this state, the upper thread loop is captured by the sword tip of the outer bobbin case in the bobbin case, and by the combination of the rotation of the bobbin case and the upward movement of the sewing needle, the lower thread is wound around the upper thread loop and a stitch is formed as known. Since the upper thread exiting from the eyelet of the sewing needle enters the bobbin case in a state of being positioned on the left side of the sewing needle (left winding with respect to the sewing needle), the stitch is formed as a perfect stitch, and the occurrence of a hitch stitch can be avoided.

[0021] Thus, according to the present invention that follows the first aspect, the hitch stitch avoidance control for the upper thread factor is not performed only by the detour movement control of the holding body, but is performed with the assistance of the structural action of the guide body provided at the lower end of the pressing member. Therefore, it is not necessary to precisely match the timing of the downward movement of the sewing needle and the detour movement of the holding body in the detour movement control of the holding body. Compared with the prior art, it has an excellent effect that it is possible to avoid the occurrence of hitch stitches with easy control and reliably.

[0022] According to one embodiment, when the control means performs the detour movement of the holding body to avoid the occurrence of hitch stitches due to the upper thread factor, the degree of the detour movement of the holding body may be varied according to the region to which the direction of forming the next seam belongs. That is, in one embodiment, the predetermined region includes a first region and a second region, the determination means determines whether the direction of forming the next seam is in the first region or the second region, and the control means performs the detour movement so that the detour amount is larger when it is determined to be the second region than when it is determined to be the first region. Further, in a type of sewing machine provided with a jump mechanism for jumping the needle bar, the control means may perform jump control of the needle bar by the jump mechanism when performing the detour movement. Also, the control means may perform jump control once or twice according to whether it is the first region or the second region. There is a region where hitch stitches can be avoided by detouring the holding body with a relatively small detour amount, and there is also a region where hitch stitches can be avoided by detouring the holding body with a relatively large detour amount, and the required detour amount can vary depending on the region. Also, the time required for the detour movement of the holding body varies depending on the amount of the detour. Therefore, by switching the degree of the detour amount of the holding body according to the region, it is possible to realize efficient detour movement control of the holding body, and it becomes possible to more appropriately and efficiently avoid the occurrence of hitch stitches due to the upper thread factor.

[0023] Furthermore, as an example, a setting means for setting the conditions for the detour movement performed by the control means may be provided. As an example, the conditions for the detour movement set by the setting means include setting whether or not the control means enables the detour movement of the holding body. When it is set to enable the detour movement, the detour movement of the holding body by the control means may be performed. Thereby, it is possible to set ON / OFF of the detour movement control of the holding body by the control means. By setting it to valid (ON), the hitch stitch caused by the upper thread factor can be avoided by performing the detour movement of the holding body, and the sewing quality can be improved. However, since it takes extra time for the detour movement of the holding body, it is inevitable that the overall production efficiency of sewing will decrease. Depending on the intended sewn product, there may be a case where it is desired to avoid a decrease in production efficiency rather than a decrease in quality due to hitch stitches. Also, depending on the type of the workpiece (fabric to be processed) or the upper thread, etc., there may be a case where it is desired to select whether or not to execute the detour movement control of the holding body. Also, for example, the requirement for avoiding hitch stitches may be different between simple straight sewing and complex embroidery sewing. In preparation for these various cases, it is beneficial to have a function of setting the detour movement of the holding body to invalid (OFF), that is, a function of selecting valid (ON) or invalid (OFF) of the detour movement of the holding body.

[0024] As another example, the conditions for the detour movement set by the setting means include variably setting the range of the predetermined area. The determination means determines whether the direction of forming the next seam belongs to the range of the variably set predetermined area. When it is determined that the direction belongs to the range of the variably set predetermined area, the control means may execute the detour movement of the holding body. Generally, it is difficult to precisely define the area where hitch stitches occur. From a safety perspective, it is better to set the range of the predetermined area wider and perform the detour movement control of the holding body. However, if this is done, the overall production efficiency will decrease as the number of detour movement controls of the holding body increases. Also, depending on the target sewn product, there may be cases where it is desired to avoid a decrease in production efficiency as much as possible by allowing hitch stitches in the sewing of parts where seam quality is not emphasized. In addition, there may be cases where it is desired to variably set the range of the predetermined area according to the type of the workpiece to be sewn (processed fabric) or the upper thread without fixing it. In preparation for these various cases, it is beneficial to have a function of variably setting the range of the predetermined area for which the detour movement control of the holding body should be performed.

[0025] In relation to the first aspect, the scope of the present invention can also be grasped as a sewing machine part, that is, as a presser device for a sewing machine including a presser member and a guide member having the structure described above.

[0026] Furthermore, according to a second aspect of the present invention, in addition to the configuration according to the first aspect, by providing a configuration for avoiding the occurrence of hitch stitches due to the lower thread factor, it is possible to avoid the occurrence of any type of hitch stitches and to make the seams over the entire range in the sewing direction perfect stitches, that is, to provide a sewing machine capable of realizing all perfect stitches.

[0027] In an embodiment of the sewing machine according to the second aspect, as a configuration for avoiding the occurrence of hitch stitches due to the lower thread factor, a needle plate as described below is provided. As is well known, the needle plate of a sewing machine has a needle hole for passing a reciprocating sewing needle and is fixed above the bobbin case. The needle plate disclosed in the present application is provided closer to the front surface of the sewing machine and has a guide hole communicating with the needle hole, and the guide hole is disposed offset toward the rotational direction of the bobbin case rather than the vertical movement line of the sewing needle. Further, the needle plate has a groove portion extending from the guide hole in a direction opposite to the rotational direction of the bobbin case in front of the needle hole, and the groove portion has an open upper portion and a portion communicating with the guide hole, but the bottom surface and side walls are formed otherwise, so that the lower thread extending upward from the bobbin case can be guided to the front side of the needle hole through the guide hole and via the groove portion.

[0028] Depending on the moving direction (stitch forming direction) of the work cloth during stitch formation, even if hitch stitches due to the upper thread factor are avoided, there is a region where double hitch stitches due to the lower thread factor occur. Such double hitch stitches occur when the upper thread falls off the needle with the left side (left-handed winding) with respect to the sewing needle, while the lower thread path extending from the bobbin case to the needle hole of the needle plate is located behind the vertical movement line (vertical movement locus) of the sewing needle. The needle plate configured as described above is structured to force the lower thread path extending from the bobbin case to the needle hole of the needle plate to be in front of the vertical movement line (vertical movement locus) of the sewing needle, thereby avoiding hitch stitches due to the lower thread factor.

[0029] The guide hole is offset and arranged closer to the rotation direction of the bobbin (closer to the left side) than the vertical movement line of the sewing needle, and the groove portion extends from the guide hole in the direction opposite to the rotation direction of the bobbin (to the right direction) in front of the needle hole. Therefore, when the holding body is moved substantially to the left by the detour movement control of the holding body, the lower thread is guided to the guide hole, and then as the holding body moves substantially to the right to the target position, the lower thread is guided substantially to the right along the groove portion from the guide hole. At this time, since both sides of the groove portion are side walls, the lower thread is locked by the side walls and is maintained on the front side of the vertical movement line of the sewing needle without moving to the back side of the vertical movement line of the sewing needle. In this way, the lower thread path extending from the bobbin to the needle hole of the needle plate is maintained on the front side without going to the back side of the vertical movement line of the sewing needle, so that the occurrence of double hitch stitches can be avoided. Further, since the groove portion has a bottom surface, the upper thread loop rising along the lower thread is not caught by the groove portion, and thus there is no risk of causing upper thread breakage. Furthermore, since the lower thread is only locked to the side walls of the groove portion, when the lower thread is pulled up as the upper thread rises, the lower thread easily detaches from the groove portion and returns to the normal path, so that it does not adversely affect the lower thread path during the formation of the next stitch.

[0030] In a further embodiment of the sewing machine according to the second aspect, as a configuration for avoiding the occurrence of hitch stitches due to the lower thread factor, a bobbin as described below is provided. As is well known, the bobbin of a sewing machine has a bobbin case that rotatably houses a lower thread bobbin wound with the lower thread, an inner bobbin that houses the bobbin case, and an outer bobbin that rotates in synchronization with the vertical movement of the sewing needle around the inner bobbin. A needle drop hole is provided in the upper front surface of the inner bobbin. The bobbin disclosed in the present application forms a recess at a position offset from the needle drop hole in the rotation direction of the outer bobbin on the upper front surface of the inner bobbin. The recess is open at the front side, top, and bottom, and forms a wall surface at the back side. The bobbin case is provided with a thread taking member for directing the lower thread fed out from the lower thread bobbin toward the recess of the inner bobbin, and the lower thread fed out from the lower thread bobbin in the bobbin case passes through the opening of the recess via the thread taking member and is pulled upward.

[0031] With this configuration, the path of the lower thread that connects from the kettle through the needle holes of the needle plate to the upper sewing material above becomes to the left of the vertical movement line (needle drop position) of the sewing needle through the concave portion of the inner kettle. That is, the lower thread fed out from the lower thread bobbin is directed by the thread take-up member toward the concave portion of the inner kettle, passes through the concave portion, and heads toward the needle holes of the needle plate. Since the concave portion is formed at a position shifted in the rotation direction of the outer kettle from the needle drop hole (that is, a position to the left of the vertical movement line of the sewing needle), the path of the lower thread from the kettle toward the needle holes becomes to the left of the vertical movement line of the sewing needle. Thereby, it is possible to prevent the path of the lower thread from the kettle toward the needle holes from coming to the right side of the vertical movement line of the sewing needle, and thus, the occurrence of hitch stitches can be reduced.

Brief Description of the Drawings

[0032]

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MODE FOR CARRYING OUT THE INVENTION

[0033] <Region where a hitch stitch is formed> First, referring to FIG. 1, a typical example of the region in the seam formation direction where a hitch stitch is formed will be described. FIG. 1 is a diagram listing the relationships between various seam formation directions and the quality of the seams (perfect stitches and hitch stitches) formed in each direction. Note that the relationship between the seam formation direction and the quality of the formed seam varies depending on the orientation of the sewing machine and the type of the sewing machine. FIG. 1 shows the above relationship in a fully rotating vertical hook (DB type) commonly adopted in embroidery machines. Also, as is normally known, the way the upper thread is passed through the eye of the sewing needle is such that the upper thread fed downward from the upper thread bobbin enters the eye from the front side of the sewing needle, passes through to the rear, and is connected to the workpiece (fabric to be processed). By the cooperation of the vertically moving sewing needle and the vertically rotating hook that rotates counterclockwise, the upper thread and the lower thread are intertwined as is well known, and a seam is formed on the workpiece (fabric to be processed).

[0034] The reference point C located at the center of the figure indicates the current needle drop position (the position of the needle hole on the needle plate of the sewing machine). Several arrows starting from the reference point C exemplarily show the sewing direction from the reference point C to the next needle drop point (i.e., the direction of forming the next stitch). As is well known, the sewing direction of each stitch can be arbitrarily set within a range of 360 degrees, specifically depending on the sewing pattern. In FIG. 1, for convenience, the direction of arrow P is set as 0 degrees, and the angles from 0 degrees to less than 360 degrees are marked counterclockwise from there. In the following, when specifying the area of the sewing direction (i.e., the direction of forming the next stitch) by an angle, it shall follow the angle scale in FIG. 1. In the figure, the directions of arrows P and P' are the left - right direction of the sewing machine. For convenience, the direction of P is the positive direction of the X - axis (X+), and the direction of P' is the negative direction of the X - axis (X -). The direction of the Y - axis orthogonal to the X - axis at the reference point C is the front - back direction of the sewing machine. The direction towards the back (rear) is the positive direction of the Y - axis (Y+), and the direction towards the front is the negative direction of the Y - axis (Y -). As is well known, the moving direction of the holding body (frame) holding the workpiece (fabric to be processed) and the direction of the stitch formed according to the movement of the holding body (frame) are in an inverse relationship. For example, when forming a stitch in the direction of arrow P (0 - degree direction), the holding body (frame) moves in the direction of arrow P' (180 - degree direction), which is exactly the opposite.

[0035] In FIG. 1, overlapping some of the arrows, there is a needle diagram enclosed in a circle. This needle diagram is a figure that schematically shows, together with the picture of the needle hole, a typical example of the relationship between the upper thread and the lower thread with respect to the sewing needle when a stitch in the direction corresponding to the arrow is formed, for the purpose of assisting understanding. Note that this needle diagram depicts the sewing needle during its downward movement just before entering the needle hole. For convenience, the workpiece (fabric to be processed) is not shown in the illustration.

[0036] The entire range of the sewing direction can be divided into several regions α to δ according to the quality of the seam formed according to the sewing direction. Region α is the region to which the sewing direction that results in a perfect stitch belongs, and is generally the region of approximately 270 degrees to 360 degrees (0 degrees) to approximately 85 degrees. As shown in the needle diagram drawn overlapping the arrow in this region α, as the holding body (frame) moves, the upper thread connected to the work fabric from the eye of the sewing needle falls while being positioned on the left side of the sewing needle, so the seam formed is a perfect stitch. The regions (β to δ) excluding region α shown in white are the regions where hitch stitches occur. The shaded region β is the region to which the sewing direction in which hitch stitches occur due to the upper thread factor belongs, and is generally the region of approximately 85 degrees to approximately 180 degrees. As shown in the needle diagram drawn overlapping the arrow in this region β, as the holding body (frame) moves, the upper thread connected to the work fabric from the eye of the sewing needle falls while being positioned on the right side of the sewing needle, so the seam formed is a hitch stitch. The dotted region γ is the region to which the sewing direction in which hitch stitches occur due to both the upper and lower thread factors belongs, and is generally the region of approximately 180 degrees to approximately 210 degrees. The region δ marked with grid lines is the region to which the sewing direction in which hitch stitches occur due to the lower thread factor belongs, and is generally the region of approximately 210 degrees to approximately 270 degrees. As shown in the needle diagram drawn overlapping the arrow in this region δ, as the holding body (frame) moves, the lower thread connected to the work fabric from the bobbin falls while being positioned on the right side of the sewing needle, so the seam formed is a hitch stitch.

[0037] <Basic Structure 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 is applicable will be described. Such a basic configuration itself is well-known, and not limited to the illustrated example, and those of any configuration can be applied in the present invention. FIG. 2 is a front view of a sewing machine according to an embodiment of the present invention, and as an example, it shows an embodiment applied to a multi-head and multi-needle type embroidery sewing machine. A plurality of sewing machine heads H are arranged in the longitudinal direction on a sewing machine frame 1 located above a table 2. Below each sewing machine head H, a bobbin base 4 supporting a bobbin 3 is provided corresponding to each sewing machine head H. Further, on the upper surface of the table 2, a holding body 5 for holding a workpiece to be sewn (processed cloth) such as a cloth in an extended state is placed. The holding body 5 is controlled to move in the X and Y directions (front-back and left-right directions) by a feed mechanism (not shown) provided below the table 2. The holding body 5 is known as an embroidery frame or a processed cloth holding frame, etc., and hereinafter will be referred to as a frame 5. On the right side of the sewing machine frame 1, an operation panel 6 for operating the sewing machine and performing various settings is erected. The operation panel 6 is, for example, a touch panel, and includes a display unit for displaying various information and an input unit for giving various instructions. Note that this feed mechanism operates to form stitches in an arbitrary direction on the workpiece to be sewn by relatively displacing the frame 5 holding the workpiece to be sewn with respect to the needle drop position, and since it is well-known itself, a detailed description thereof will be omitted.

[0038] 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 surface of the front of the sewing machine arm 7 attached to the front surface of the sewing machine frame 1 so as to be slidable in the left-right direction. A plurality of needle bars 9 are supported on the needle bar case 8 so as to be vertically movable, and a balance 10 corresponding to each needle bar 9 is swingably disposed. Each needle bar 9 is arranged such that its axial direction extends in the vertical direction (perpendicular direction), and a sewing needle 11 is attached to the lower end of each. The upper thread T is passed through the eyelet 11a of the sewing needle 11 (see FIG. 5 etc.) from the front side to the rear side (see FIG. 20 etc.). A slide shaft 12 is provided through the needle bar case 8, and the needle bar case 8 slides in the left-right direction by sliding the slide shaft 12 in the lateral direction by driving a motor (not shown). In accordance with the slide of the needle bar case 8, any one of the plurality of needle bars 9 is selectively positioned at the operating position, and one needle bar 9 to be operated is selected.

[0039] The main shaft 13 is penetrated through the sewing machine arm 7. When the main shaft 13 is rotated by a main shaft motor (not shown), the needle bar driver 15 moves up and down along the base shaft 16 via a cam mechanism (not shown) and a link 14 etc. within 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 to a predetermined position of the needle bar 9, and can be switched between a catch position for catching the needle bar 9 and a non-catch position. At 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. At 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 the upper position (top dead center) by the restoring force of a tension spring 18 provided at the upper part of the needle bar 9. When actually moving the needle bar 9 (and the sewing needle 11) up and down to perform sewing, the needle bar driver 15 is always set to the catch position. The control for temporarily stopping the needle bar 9 (and the sewing needle 11) at the top dead center during the sewing operation is known as jump control. When performing such jump control, the needle bar driver 15 is temporarily set to the non-catch position. In order 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 upward without lowering it when jump control should be performed during the sewing operation. As an example, the jump mechanism includes 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 by a predetermined angle around the base shaft 16 in response to the drive of the jump motor, and the tension spring 18 etc.

[0040] The selected needle bar 9 at the operating position moves up and down in accordance with the lifting and lowering movement of the needle bar driver 15 while being caught by the needle bar driver 15. During the process of the selected needle bar 9 at the operating position moving up and down, the sewing needle 11 attached to its tip penetrates through the needle hole 19a of the needle plate 19, and a well-known sewing operation is performed. On the other hand, when the jump mechanism operates in response to the drive of the jump motor (not shown), the needle bar driver 15 is set to the non-catch position, the needle bar 9 is not caught by the needle bar driver 15, and it enters the jump state as described above and is held at the top dead center.

[0041] In the needle bar case 8, lifting rods 20 are respectively provided behind each needle bar 9 so as to be vertically movable. Similar to the needle bar 9, the lifting rods 20 are arranged such that their axial directions extend in the vertical direction (perpendicular direction), and pressing devices 21 are provided at their lower ends respectively. The pressing device 21 is for pressing the workpiece from above as the sewing needle 11 descends, and includes a pressing member 22 and a guide body 23 which will be described in detail later. The pressing member 22 is attached to the lower end of the lifting rod 20, and the guide body 23 is provided at the lower end of the pressing member 22. One lifting rod 20 corresponding to the needle bar 9 selected at the operating position is driven by a cloth pressing motor 24 provided on the sewing machine arm. A link mechanism 25 is connected to the cloth pressing motor 24. When the cloth pressing motor 24 is driven to rotate back and forth, a cloth pressing driving body 26 provided on the sewing machine arm 7 so as to be vertically movable moves up and down via the link mechanism 25. The cloth pressing driving body 26 has a structure that engages with a locking pin 27a of a lifting rod holder 27 fixed at a predetermined position of each lifting rod 20. The locking pin 27a of one lifting rod 20 corresponding to the needle bar 9 selected at the operating position among the plurality of lifting rods 20 provided in the needle bar case 8 engages with the cloth pressing driving body 26, and the lifting rod 20 together with the pressing device 21 (pressing member 22 and guide body 23) moves up and down along its axial direction due to the up and down movement of the cloth pressing driving body 26. When the needle bar 9 jumps by the jump mechanism, the cloth pressing motor 24 stops, and the pressing device 21 (pressing member 22 and guide body 23) stops at a predetermined upper position (top dead center).

[0042] The combination of the above-described sewing machine head H and the bobbin 3 corresponding thereto corresponds to a sewing mechanism that moves the sewing needle 11 through which the upper thread is passed up and down, rotates the bobbin 3 storing the lower thread in synchronization with the up and down movement of the sewing needle 11 to twist the upper thread around the lower thread, and sews the workpiece.

[0043] <Structure of the pressing device> FIG. 5 is an enlarged front view showing an embodiment of the pressing device 21. An attachment member 28 is provided at the lower end of the lifting rod 20, and a pressing member 22 of the pressing device 21 is detachably attached to the attachment member 28 by screws. The lower end of the pressing member 22 extends directly below the needle bar 9 and is provided with a through hole 22a through which the sewing needle 11 is inserted. Therefore, when the pressing member 22 also descends when the needle bar 9 descends and presses the workpiece from above, the sewing needle 11 that further descends passes through the through hole 22a and pierces the workpiece, and sewing is performed. The structure up to here is the same as that of a well-known cloth pressing device. In this embodiment, further, a guide body 23 protruding downward is provided at the lower end of the pressing member 22. Each component 22, 23, etc. of the pressing device 21 may be made of a material such as metal.

[0044] The guide body 23 has a substantially cylindrical shape and has a hollow portion (an opening in the vertical direction) communicating with the through hole 22a of the pressing member 22, and the sewing needle 11 passing through the through hole 22a can pass through the hollow portion and pass through the guide body 23 in the vertical direction. The guide body 23 does not form a complete cylinder, and in a front view, an open portion (notch) 29 that opens to the lower end of the guide body 23 extends from the left front of the inserted sewing needle 11 to a position opposite to the left side surface (see also FIG. 8). The open portion (notch) 29, of course, communicates with the hollow portion of the guide body 23, and a part of the upper thread passed through the eyelet 11a of the sewing needle 11 passing through the hollow portion (the portion connected to the workpiece side) can pass through the open portion 29 and exit the guide body 23 depending on the moving direction of the frame 5. Since the rotation direction of the bobbin 3 (counterclockwise) is leftward when viewed from above, it can be said that the open portion 29 formed generally on the left side in the front view is formed to allow the passage of the upper thread in the rotation direction of the bobbin 3. Thus, since it is a structure in which the upper thread can be led out of the guide body 23 through the open portion 29, the upper thread can be wound around the sewing needle 11 in a left-handed manner (that is, in the rotation direction of the bobbin 3) as will be described later according to the moving direction of the frame 5 over a wide range.

[0045] In the guide body 23, the front edge and the rear edge of the opening 29 formed generally on the left side correspond to the front edge portion 23a and the rear edge portion 23b of the material wall portion of the guide body 23. That is, the opening 29 is bounded by the front edge and the rear edge. When the upper thread tries to move in a different direction after coming out of the opening according to the movement of the frame 5, its movement will be restricted by the front edge portion 23a or the rear edge portion 23b of the material wall portion of the guide body 23. In order to avoid the occurrence of hitch stitches due to the upper thread factor, the restricting operation by the front edge portion 23a plays an important role. Therefore, in this embodiment, the material wall portion of the guide body 23 closer to the front surface from the front edge of the opening 29 (that is, the front edge portion 23a) is referred to as the restricting portion 23a. The movement of the upper thread in a direction deviating from the front edge of the opening 29 formed generally on the left side, which the restricting portion, that is, the front edge portion 23a, tries to restrict, is generally a rightward movement. In other words, it is a movement in the direction opposite to the rotation direction of the bobbin 3 (counterclockwise). Therefore, it can be said that the restricting portion 23a in the guide body 23 is provided so as to restrict the movement of the upper thread in the direction opposite to the rotation direction of the bobbin 3.

[0046] As described above, the opening portion 29 is provided so as to open to the lower end of the guide body 23. Therefore, the regulating portion 23a that defines the front edge of the opening portion 29 is provided so as to regulate the movement of the upper thread passing through the opening portion 29 in the direction opposite to the rotational direction of the bobbin 3 of the upper thread until it reaches the lower end of the guide body 23. Therefore, in a state where the upper thread is regulated by the regulating portion 23a, as the sewing needle 11 descends, the upper thread moves along the regulating portion 23a to the lower end of the guide body 23 and passes through the opening portion 29 downward, thereby releasing the regulation by the regulating portion 23a. When the regulation by the regulating portion 23a is released, the upper thread winds around the sewing needle 11 in a left-handed direction (i.e., in the rotational direction of the bobbin 3). As an example, the regulating portion 23a in the guide body 23 is provided in an appropriate range closer to the front surface from the front edge of the opening portion 29. As will be described in detail later, the regulating portion 23a formed on the guide body 23 is for preventing the occurrence of hitch stitches due to the upper thread factor, so that when the sewing needle 11 pierces the workpiece, the upper thread does not come to the right side of the sewing needle 11 (so that it winds around the sewing needle 11 in a left-handed direction). In FIG. 5, the symbol V indicates the vertical movement locus (vertical movement line) of the sewing needle 11. For the purpose of preventing the upper thread from coming to the right side of the sewing needle 11 when the sewing needle 11 pierces the workpiece, the regulating portion (front edge portion) 23a provided on the guide body 23 or at least its lower end (the portion in contact with the workpiece) shall be positioned to the left of the vertical movement locus V of the sewing needle 11. That is, the regulating portion 23a is provided so as to regulate the movement of the upper thread at a position offset toward the rotational direction of the bobbin 3 (left side) from the vertical movement line of the sewing needle 11.

[0047] In the embodiment shown in FIG. 5 (or FIG. 8), the front edge of the opening portion 29, that is, the regulating portion (front edge portion) 23a formed on the guide body 23 has a shape (recessed portion) that is obliquely cut out from above toward the lower left direction. Due to such an inclined shape (recessed portion), the upper or middle opening in the opening portion 29 is widened somewhat more forward than the lower opening, so that when the sewing needle 11 and the pressing member 22 are descending, if there is slack in the portion of the upper thread that comes out of the opening portion 29 and is regulated by the regulating portion 23a, this slack is absorbed at the location of the wider opening, and the state of holding the upper thread by the regulating portion 23a is maintained as much as possible, thereby being able to prevent as much as possible the upper thread from coming off the regulating portion 23a before the sewing needle 11 pierces the workpiece to be sewn. However, such an inclination is not essential, and the front edge of the opening portion 29, that is, the regulating portion (front edge portion) 23a formed on the guide body 23 may be formed vertically.

[0048] Note that the external shape of the guide body 23 is not limited to the substantially cylindrical shape as described above, and it may be any shape. FIG. 6 is a diagram showing a modified example of the 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. The guide body 23-1 shown in FIG. 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 that allows the sewing needle 11 to pass through (corresponding to the hollow portion) and a space as the opening portion 29 that allows the upper thread to pass through in the rotational direction of the bobbin 3. The side wall surface on the front side of the guide body 23-1 functions as the regulating portion 23a.

[0049] FIG. 7 is a diagram showing another modified example of the 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. The guide body 23-2 shown in FIG. 7 is composed of three side wall surfaces sequentially connected at an appropriate angle (for example, approximately 90 degrees), and the space other than these side wall surfaces functions as a space that allows the sewing needle 11 to pass through (corresponding to the hollow portion) and a space as the opening portion 29 that allows the upper thread to pass through in the rotational direction of the bobbin 3. The side wall surface on the front side of the guide body 23-2 functions as the regulating portion 23a.

[0050] Note that the guide body 23 shown in FIGS. 5 to 7 has a wall surface portion, and the side edge portion on the front side of the wall surface portion functions as the restricting portion 23a. However, it is not limited to this. Without having a wall surface portion, the restricting portion 23a may be formed in the form of a pin-shaped or linear thin column member. For example, two thin column members may be arranged to form a space as the opening portion 29 therebetween, and one of the (front side) column members may be made to function as the restricting portion 23a. In that case, an arc-shaped connecting foot portion for connecting the lower ends of the two thin column members may be provided on the opposite side of the opening portion 29. As a modification, one or more other thin column members may be provided in the middle of the arc-shaped connecting foot portion. As another modification, the guide body 23 may be composed of only one thin column member that functions as the restricting portion 23a.

[0051] FIG. 8 is a view showing another modification of the pressing device 21, in which a cover 30 for covering the guide body 23 is provided below the pressing member 22. The structure of the pressing device 21 is the same as that shown in FIG. 5 except for the elements related to the cover 30. The cover 30 has a smooth, rounded convex curved surface (bowl-shaped) on the bottom surface side, and a through-hole with a relatively large diameter is provided so that the guide body 23 can be loosely accommodated. The upper inner side forms a recess that conforms to the pressing member 22. By mounting the cover 30 from below the guide body 23 and tightening it with a screw 31, the cover 30 is assembled and fixed to the pressing member 22, thereby covering the periphery of the side surface of the guide body 23. Since the guide body 23 is loosely accommodated with a gap inside the cover 30, 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 bottom surface of the convex curved surface (bowl-shaped) of the cover 30. Therefore, even if the vertical stroke amount of the pressing device 21 is reduced to prevent the sewing object from fluttering, for example, it is possible to prevent the guide body 23 from being caught on the seam on the sewing object to be moved.

[0052] <Needle plate structure> In this embodiment, a novel structure is provided in relation to the needle holes 19a of the needle plate 19 to avoid the occurrence of hitch stitches due to lower thread factors. FIG. 9 is a perspective view showing an embodiment of such a novel needle plate structure. FIG. 10 is an enlarged view showing the portion of the needle hole 19a in FIG. 9, where (a) is a plan view, (b) is a perspective view showing a cross section along the line A-A in (a), and (c) is a perspective view of the main part exemplifying the path of the lower thread D. The conventionally known needle hole 19a was generally a simple circular hole, as exemplified by the dotted line in FIG. 10(a). The vertical movement line (V in FIG. 5) of the sewing needle 11 passes through the approximate center of this circle.

[0053] In the needle plate structure according to this embodiment, in the needle plate 19, a guide hole 31 and a groove portion 32 are provided in relation to the needle hole 19a. The guide hole 31 formed to penetrate the needle plate 19 is provided closer to the front of the sewing machine, communicates with the needle hole 19a, and is displaced and arranged closer to the rotation direction of the bobbin case 3 (closer to the left side in FIG. 10(a)) than the vertical movement line of the sewing needle 11. Further, the needle plate 19 has a groove portion 32 extending from the guide hole 31 in the direction opposite to the rotation direction of the bobbin case 3 (right direction in FIG. 10(a)) in front of the needle hole 19a. The groove portion 32 is open at the upper part and the part communicating with the guide hole 31, but the bottom surface 32a and the side wall 32b are formed otherwise (FIG. 10(b)). As is well known, during the sewing operation, the lower thread D coming out of the bobbin case 3 passes through the needle hole 19a and extends upward to form a stitch in the workpiece. In this embodiment, the lower thread D coming out of the bobbin case 3 is configured to be able to pass not only through the needle hole 19a but also through the guide hole 31 communicating therewith. And when the lower thread D passes through the guide hole 31, depending on the direction in which the frame 5 moves, as shown in FIG. 10(c), the portion of the lower thread D coming out upward from the guide hole 31 can be guided to the front side of the needle hole 19a through the groove portion 32. Since the groove portion 32 has a bottom surface 32a, the lower part of the lower thread D remains in the guide hole 31, and the upper part of the lower thread D is bent and guided to the upper space of the groove portion 32.

[0054] The guide hole 31 is disposed offset toward the rotation direction of the bobbin 3 (toward the left side) from the vertical movement line of the sewing needle 11, and the groove portion 32 extends from the guide hole 31 in the direction opposite to the rotation direction of the bobbin 3 (to the right direction) in front of the needle hole 19a. Therefore, when the frame 5 is moved substantially leftward by the detour movement control of the frame 5 described later, the lower thread D is guided to the guide hole 31. Then, as the frame 5 is moved substantially rightward to the needle drop position (target position), the lower thread D is guided substantially rightward from the guide hole 31 along the groove portion 32. At this time, since both sides of the groove portion 32 are side walls 32b, the lower thread D is locked by the inner side wall 32b and is maintained on the front side of the vertical movement line of the sewing needle 11 without shifting to the back side of the vertical movement line of the sewing needle 11. In this way, the path of the lower thread D extending from the bobbin 3 to the needle hole 19a of the needle plate 19 is maintained on the front side without going to the back side of the vertical movement line of the sewing needle 11, so that the occurrence of hitch stitches (particularly double hitch stitches) can be avoided. Further, since the groove portion 32 has a bottom surface 32a, the loop of the upper thread that passes through the needle hole 19a while shrinking the loop and goes upward along the lower thread D is not caught by the groove portion 32, and thus there is no risk of causing upper thread breakage. Furthermore, since the lower thread D is only locked to the side wall 32b of the groove portion 32, when the lower thread D is pulled up as the upper thread ascends, the lower thread D easily detaches from the groove portion 32 and returns to the normal path (that is, the path passing through the needle hole 19a), so that it does not adversely affect the formation of the path of the lower thread D during the formation of the next stitch.

[0055] As shown in a plan view in FIG. 10(a), as an example, at the location where the guide hole 31 connects to the needle hole 19a, the inner wall surface 31a of the guide hole 31 is inclined from the back to the front direction closer to the rotation direction of the bobbin 3 (that is, to the left front direction). That is, this wall surface 31a is inclined from the back to the left front direction such that the rearmost part is closest to the vertical movement line of the sewing needle 11 and the foremost part is farthest to the left from the vertical movement line of the sewing needle 11. The inclination of the wall surface 31a at such a connection location contributes to smoothly guiding the lower thread D to the guide hole 31 along the inclination when shifting the path of the lower thread D from the needle hole 19a to the guide hole 31 during the detour movement of the frame 5. However, it is not limited to this, and the form of the connection location between the guide hole 31 and the needle hole 19a may be arbitrarily designed.

[0056] <Kettle Structure> In this embodiment, in relation to the kettle 3, a novel structure is provided to avoid the occurrence of hitch stitches due to the lower thread factor. FIG. 11 is a front view showing an embodiment of such a novel kettle 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 kettle 3 is disposed below the needle plate 19. As an example, the kettle 3 is a vertically fully rotatable kettle (DB type). The kettle 3 has a bobbin case 40 that rotatably houses a lower thread bobbin (not shown) wound with the lower thread, an inner kettle 50 that houses the bobbin case 40, and an outer kettle 60 that rotates in synchronization with the vertical movement of the sewing needle 11 around the inner kettle 50. The inner kettle 50 is fixed to the kettle base 4 via a kettle support 70 as is well known, and the bobbin case 40 is fixed within the inner kettle 50. The outer kettle 60 is fixed to a lower shaft (not shown) that rotates in synchronization with the vertical movement of the sewing needle 11 and rotates together with the lower shaft. In the vertically fully rotatable kettle (DB type), the rotation direction R of the outer kettle 60 is counterclockwise. On the upper front surface of the inner kettle 50, a needle drop hole 51 is provided to avoid interference with the sewing needle 11.

[0057] On the upper front surface of the inner kettle 50, a recess 52 is formed at a position shifted from the needle drop hole 51 in the rotation direction R of the outer kettle 60. The recess 52 is open at the front side and the upper and lower sides, forms a wall surface 52a at the back side, and the wall surface 52a at the back side is formed so as to be disposed at a substantially limit position where the wall surface 52a does not interfere with the movement locus of the sword tip 61 of the outer kettle 60. By disposing the wall surface 52a at the back side of the recess 52 at the substantially limit position in this way, the lower thread path (the position of the lower thread from the recess 52 toward the needle hole 19a) leading from the recess 52 to the workpiece to be sewn can be made as far as possible to the back side (rear) from the needle drop (vertical movement locus), and thereby, the region where the hitch stitches due to the lower thread factor can be avoided by the kettle structure according to this embodiment can be extended as far as possible. The left and right wall surfaces in the recess 52 are an upstream side wall 52b located on the upstream side in the rotation direction R of the outer kettle 60 and a downstream side wall 52c located on the downstream side thereof.

[0058] At a predetermined position near the upper part of the bobbin case 40 (preferably, below the recess 52), a thread guide member 41 is provided for guiding (directing) the lower thread drawn from the lower thread bobbin toward the recess 52 of the inner pot 50. As will be described in detail later, the lower thread drawn from the lower thread bobbin in the bobbin case 40 passes through the opening of the recess 52 of the inner pot 50 via the thread guide member 41 and is drawn upward. The lower thread passing through the recess 52 is wound around the upper thread loop as is well known in accordance with the rotation of the outer pot 60, comes out upward from the needle hole 19a as the sewing needle 11 rises, and forms a stitch. In this way, the recess 52 provided in the inner pot 50 functions to form the path of the lower thread.

[0059] With such a pot structure, the path of the lower thread leading from the pot 3 through the needle hole 19a of the needle plate 19 to the upper workpiece to be sewn comes to the left side with respect to the vertical movement line (needle drop position) of the sewing needle 11 through the recess 52 provided on the upper front surface of the inner pot 50. That is, the lower thread drawn from the lower thread bobbin is directed toward the recess 52 of the inner pot 50 by the thread guide member 41, passes through the recess 52, and heads toward the needle hole 19a of the needle plate 19. The recess 52 is formed at a position shifted in the rotation direction R of the outer pot 60 from the needle drop hole 51 (that is, at a position on the left side with respect to the vertical movement line of the sewing needle 11), and the inner wall surface 52a on the back side thereof is formed at a substantially limit position where it does not interfere with the movement locus of the sword tip 61 of the outer pot 60. Therefore, the path of the lower thread from the pot 3 toward the needle hole 19a becomes the left back side of the vertical movement line of the sewing needle 11. Thereby, the path of the lower thread from the pot 3 toward the needle hole 19a can be prevented from coming to the right side of the vertical movement line of the sewing needle 11, and thus the occurrence of hitch stitches can be reduced.

[0060] This will be further described with reference to FIG. 1 in this regard. In the region δ to which the sewing direction in which the hitch stitch is generated due to the lower thread factor belongs, the frame 5 moves in the right back direction opposite to it by 180 degrees. Therefore, in a conventional bobbin which is configured to supply the lower thread from below the vertical movement line of the sewing needle, the lower thread is pulled by the workpiece to be sewn and the path of the lower thread becomes on the right side of the vertical movement line of the sewing needle, and thus the needle drops, generating a hitch stitch. On the other hand, in this embodiment, when the frame 5 moves in the right back direction for sewing in the region δ, the lower thread going from the bobbin 3 toward the needle hole 19a abuts against the inner side wall surface 52a of the recess 52, and the movement of the lower thread in the right direction is restricted by the upstream side wall 52b. Therefore, since the lower thread coming out of the bobbin 3 passes through the left side of the vertical movement line of the sewing needle 11 and heads toward the needle hole 19a, the generation of the hitch stitch can be suppressed by the needle dropping on the right side of the lower thread.

[0061] For example, in the sewing direction belonging to the region δ in FIG. 1, when the frame 5 moves in a direction of approximately 70 degrees, the lower thread path surely becomes on the left side of the needle drop (the vertical movement line of the sewing needle 11). Therefore, even if the arrangement of the inner side wall surface 52a of the recess 52 is shallower than the approximately limit position, the generation of the hitch stitch is avoided. On the other hand, for example, when the frame 5 moves in a direction of approximately 40 degrees, if the arrangement of the inner side wall surface 52a of the recess 52 is shallower than the approximately limit position, the lower thread path does not become on the left side of the needle drop (the vertical movement line of the sewing needle 11), but becomes on the right side via the front side, so that the hitch stitch cannot be avoided. However, as described above, by setting the arrangement of the inner side wall surface 52a of the recess 52 to the approximately limit position, even when the frame 5 moves in a direction of approximately 40 degrees, for example, the lower thread path can be made to be on the left side of the needle drop (the vertical movement line of the sewing needle 11), and the hitch stitch can be avoided. Thus, the deeper the arrangement of the inner side wall surface 52a of the recess 52 is, the more the region in which the hitch stitch due to the lower thread factor can be avoided by the bobbin structure according to this embodiment can be expanded. Also, by setting the arrangement of this inner side wall surface 52a to the approximately limit position, the region that does not require the frame detour control is maximized.

[0062] Note that a structure for locking the lower thread during thread cutting may be provided on the downstream side wall 52c of the concave portion 52. 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 the front end. Above the bobbin 3, a known thread cutting device (not shown) is provided. When the thread cutting device performs a thread cutting operation, the portion of the lower thread extending from the bobbin 3 to the eyelet 19a is captured and guided leftward to the cutting position, where it is cut. When the lower thread moves leftward for the thread cutting operation in this way, the lower thread abuts against the downstream side wall 52c and can move appropriately back and forth along the downstream side wall 52c. In that case, if the front edge of the downstream side wall 52c is on the same plane as the side wall, the lower thread is likely to come off from the front edge of the downstream side wall 52c. Then, the lower thread will reach the thread cutting device from the bobbin 3 at a short distance. When cut in that state, the remaining length of the lower thread after cutting will be short, which may cause problems when working next. To prevent such inconveniences, a protrusion 52d is provided at the front end of the downstream side wall 52c so as to protrude somewhat from the wall surface. Thereby, during the thread cutting operation, when the lower thread abutting against the downstream side wall 52c moves forward, it is locked by the protrusion 52d, and the lower thread does not come off from the front edge of the downstream side wall 52c. By this device, the remaining length of the lower thread after cutting can be ensured to be necessary and sufficient, and problems can be prevented when working next.

[0063] Next, further improved examples of the inner pot 50 and the outer pot 60 will be described. As is well known, the outer pot 60 is provided with a sword tip 61 on its outer periphery for capturing the loop of the upper thread drawn out from the eyelet 11a of the sewing needle 11. Also, a thread separating spring (i.e., the upper spring portion) 62 is fixed to the outer peripheral surface of the outer pot 60 by screws. The tip portion 62a of the thread separating spring 62 is formed in a claw shape to guide the upper thread captured by the sword tip 61. Further, the front edge (i.e., the front side edge portion) 62b of the thread separating spring 62 is formed so as to be located deeper (rearward) than the back wall surface 52a of the recess 52 in the inner pot 50 as shown in FIG. 13(b). In other words, the front edge 62b of the thread separating spring 62 is formed so as not to protrude in front of the front side edge portion (the front side edge of the movement locus) of the sword tip 61 of the outer pot 60.

[0064] A conventionally known thread separating spring has a shape provided with a portion (fin) in which the front edge end protrudes forward in the rearward direction of the rotation direction in order to push out the captured upper thread loop forward as the outer pot rotates. When the front edge end of the thread separating spring protrudes in such a manner, the lower thread going from the pot to the needle hole is also pushed forward, resulting in slack in the lower thread.

[0065] On the other hand, in the present embodiment, such a protruding portion (fin) is not formed at the front edge 62b so that the thread separating spring 62 does not come into contact with the lower thread guided by the recess 52, and thus, it is configured so that no slack occurs in the lower thread. In this way, in the present embodiment, since the thread separating spring 62 does not push out the thread loop forward, more broadly, it will be referred to as the upper spring portion.

[0066] Instead of providing a protruding portion (fin) at the front edge 62b of the yarn separating spring (upper spring portion) 62, in this embodiment, the structure of the inner pot 50 is improved as described below. As shown in FIGS. 11 and 13(a), etc., on the outer peripheral portion of the front surface of the inner pot 50, over a range of approximately a quarter arc angle (i.e., 90 degrees) in the downstream direction of rotation from the recess 52, specifically over a range less than a quarter arc angle (i.e., 90 degrees), and particularly in the illustrated example over a range of approximately 80 degrees, a raised portion 53 protruding forward is formed. Specifically, the raised portion 53 has a mountain-shaped cross-section and is provided with a guide surface 53a that slopes forward as it goes upstream of rotation, and is formed such that the protruding height decreases as it goes downstream of rotation. The raised portion 53 functions to push the upper yarn loop caught by the sword tip 61 of the outer pot 60 forward. As the outer pot 60 rotates, the upper yarn loop is pushed out while moving from below the raised portion 53 to above (from the rear to the front), and passes around the inner pot 50 while moving along the front surface of the bobbin case 40. Thus, the raised portion 53 of the inner pot 50 can function as a substitute for the fin of a conventionally known yarn separating spring.

[0067] Note that, as shown by the two-dot chain line in FIGS. 11 and 12, the protrusion 71 of the pot support 70 fixed to the pot base 4 can be fitted into the recess 52 of the inner pot 50. In the fitted state, the inner pot 50 is fixed to the pot base 4 and is prevented from rotating together with the outer pot 60. An appropriate opening space is configured to be formed between the rear wall surface 52a of the recess 52 and the tip of the protrusion 71 of the pot support 70, and the lower yarn guided into the recess 52 passes through this opening space and heads towards the needle hole 19a.

[0068] Furthermore, an example of the bobbin case 40 will be described with reference to FIG. 14. In FIG. 14, the lower thread bobbin housed in the bobbin case 40 is not shown. As shown in FIG. 14(a), the main body 42 of the bobbin case 40 has an opening 42a at the upper part of its front surface to avoid interference with the sewing needle 11 that has fallen. On the body part (outer peripheral side surface) of the bobbin case main body 42, a drawing hole 42b for drawing the lower thread from the lower thread bobbin housed inside is formed, and a thread tension spring 43 for applying a certain tension to the lower thread is attached. And above the drawing hole 42b, a guide groove 42c for regulating the passing position of the lower thread is formed. Also, the upper part of the body part of the bobbin case main body 42 is open, and this upper opening communicates with the opening 42a.

[0069] The thread take-up member 41 is disposed at the upper front portion of the bobbin case 40, more specifically, at a position shifted to the left below the opening 42a. As a preferred example, the thread take-up member 41 is made of a spring material so as to apply tension to the lower thread fed from the lower thread bobbin and directed toward the opening of the recess 52 of the inner pot 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 the lower thread fed from the lower thread bobbin passes (is hooked), and the lower thread passed through the ring portion 41a is directed toward the opening of the recess 52 of the inner pot 50. Due to the tension of the thread take-up spring 41, the lower thread going toward the needle hole 19a is appropriately guided so as to pass through the recess 52 (that is, the path of the lower thread is regulated so as to pass through the recess 52), and the slack of the lower thread is absorbed. The thread take-up spring 41 extends substantially horizontally on the front surface of the bobbin case 40, and one end (right end) on the side opposite to the ring portion 41a is fixed to the bobbin case 40, and the ring portion 41a is a free end. The ring portion 41a is located substantially directly below the recess 52 of the inner pot 50, and can swing in the vertical and horizontal directions along with the movement of the lower thread passed therethrough by the restoring force of the spring. In one embodiment, the length from the fixed end (right end) of the thread take-up spring 41 to the end portion (left end) on the ring portion 41a side is relatively long as shown in the figure. Thereby, the swing range (stroke range) of the thread take-up spring 41 can be relatively increased, and relatively large slack of the lower thread can also be absorbed. Thus, by configuring the thread take-up member 41 with a spring material, not only the function of reliably guiding the lower thread toward the recess 52 of the inner pot 50, but also the function of preventing the lower thread from sagging under various conditions by applying tension to the lower thread can be provided.

[0070] The lower thread drawn out from the lead-out hole 42b of the bobbin case 40 abuts against the thread tension spring 43, passes through the guide groove 42c, reverses upward through the ring portion 41a of the thread take-up spring 41, passes through the recess 52 of the inner pot 50, and exits through the needle hole 19a. Note that this is not restrictive, and the lower thread drawn out from the lead-out hole 42b of the bobbin case 40 may be passed through the ring portion 41a of the thread take-up spring 41 without passing through the guide groove 42c after passing through the thread tension spring 43.

[0071] As an option, as shown in FIG. 14(b), in the bobbin case 40, a guide member 44 may be provided in front of the thread take-up spring (thread take-up member) 41. The guide member 44 is detachably attached to the upper left front portion of the front surface of the bobbin case main body 42 by screws. The guide member 44 is provided with a guiding surface 44a that protrudes forward from its attachment site, and the guiding surface 44a is formed so as to be generally continuous with (form a substantially coincident surface with) the front surface of the bobbin case 40. By providing the guide member 44 in this way, the upper thread loop that moves to the front surface of the bobbin case 40 and shifts upward as the bobbin 3 rotates can be smoothly guided along the front surface of the bobbin case.

[0072] Furthermore, an opening 44b penetrating in the front-rear direction is provided in the guiding surface 44a of the guide member 44. This opening 44b is for enabling the tip of a well-known picker (not shown) to be inserted. The well-known picker is for holding the upper thread on the sewing needle side when cutting the upper thread by a thread cutting device (not shown), thereby ensuring a predetermined amount of remaining thread and preventing the upper thread from coming out of the eyelet of the sewing needle. The well-known picker has a pair of left and right tips, and during the thread cutting operation, both these tips are inserted into the opening 42a of the bobbin case 40, and the upper thread passing through the bobbin 3 is hooked and held at both tips to ensure a predetermined amount of remaining upper thread, thus preventing the thread from coming out of the eyelet of the sewing needle. Such a picker can also be applied in this embodiment. However, in the picker (not shown) applied to this embodiment, in order to prevent interference with the thread take-up spring 41, the length of one tip (the left tip) of the picker must be made slightly shorter than that of the conventional one. The guiding surface 44a and the opening 44b of the guide member 44 provide a structure suitable for such a special picker. That is, in a state where the picker is set, the shorter tip (the left tip) of the picker enters the opening 44b of the guiding surface 44a of the guide member 44 but does not contact the thread take-up spring 41. Thereby, when the upper thread loop moves upward along the guiding surface 44a of the guide member 44 protruding in front of the thread take-up spring 41, the upper thread loop is surely hooked by both tips of the picker (that is, also by the shorter tip), thus ensuring a predetermined amount of remaining upper thread and preventing the thread from coming out of the eyelet 11a of the sewing needle 11. Note that such a guide member 44 is not essential, for example, it is unnecessary in a type of sewing machine not equipped with a picker.

[0073] <Frame bypass control> In this embodiment, in order to avoid the occurrence of hitch stitches due to the upper thread factor, in addition to providing the guide body 23 in the presser device 21 as described above, the frame 5 is subjected to detour control. This frame detour control is executed by an electrical / electronic control system. FIG. 15 is a block diagram showing an example of a sewing machine control system (that is, 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 is a working area of the CPU 101, and one or more pre-programmed embroidery data (sewing data) and program control data (procon data) related thereto, as well as various processing programs and data, which are stored non-volatilely in a storage device (ROM = Read Only Memory and / or Flash Memory, a readable memory such as a hard disk, etc.) 103. Further, the control system includes a driver 104 for the main shaft motor that rotates the sewing machine main shaft 13, drivers 105 and 106 for the X-axis motor and the Y-axis motor for moving the frame 5 in the X direction and the Y direction, respectively, a driver 107 for the jump motor for jumping the needle bar 9, and a driver 108 for the cloth presser motor 24 for raising and lowering the presser device 21, and the corresponding motors are connected to the respective drivers. Further, the control system includes a user input / output interface 109 including the operation panel 6. As described above, the operation panel 6 is configured by a touch panel that doubles as an image display and a user input operation receiver, and various setting / control screens are displayed on the touch panel. The user can perform various operations / settings by touching an operation image or the like displayed on the screen of the touch panel. Further, it may include a communication interface (not shown) for communicating with an external device and / or an internal or external communication network.

[0074] As is well known, in accordance with the control of the CPU 101, arbitrary pattern sewing data selected by the user is read from the storage device 103, and each driver 104 to 108 etc. is controlled in accordance with the sewing data for each stitch, and a sewing operation is performed, and stitches are sequentially formed. Based on this sewing data, it is possible to determine whether the direction of forming the next stitch belongs to a predetermined region (for example, the regions β to δ shown in FIG. 1) where a hitch stitch is formed. This determination can be performed by a program executed by the CPU 101. That is, the CPU 101 and the program function as determination means for determining whether the direction of forming the next stitch belongs to a predetermined region where a hitch stitch is formed, based on the sewing data read from the storage device 103.

[0075] In this embodiment, in order to avoid the occurrence of hitch stitches due to the upper thread factor, if it is determined that the direction of forming the next stitch belongs to a predetermined region where hitch stitches are formed, when moving the frame 5 to the target position corresponding to the next stitch, detour control for moving the frame 5 in a detour manner is performed. This detour control can be performed by a program executed by the CPU 101. That is, the CPU 101 and the program function as control means (i.e., detour control means) for performing the detour movement of the frame 5 by performing the jump control by the jump mechanism (such as 107) and operating the feed mechanism (such as 105, 106) when it is determined by the determination means that the direction of forming the next stitch belongs to the predetermined region. Here, the detour movement of the frame 5 means moving the frame 5 in the direction in which the upper thread extending downward from the sewing needle 11 exits from the opening portion 29 of the guide body 23 of the presser device 21 in a state where the sewing needle 11 jumps upward, and then moving the frame 5 to the target position corresponding to the next stitch so that the upper thread exiting from the opening portion 29 abuts against the regulating portion 23a of the guide body 23. The movement of the frame 5 such that the upper thread exiting from the opening portion 29 abuts against the regulating portion 23a of the guide body 23 is nothing but a movement in which the upper thread exiting from the opening portion 29 detours via the regulating portion 23a. That is, the detour movement means that, without immediately moving the frame 5 to the target position corresponding to the next stitch, in a state where the sewing needle 11 jumps upward, the frame 5 is first moved in the direction in which the upper thread exits from the opening portion 29 of the guide body 23, and then, the upper thread exiting from the opening portion 29 detours so as to abut (pass through) the regulating portion 23a, and finally, the frame 5 reaches the target position corresponding to the next stitch.

[0076] As shown as a typical example in FIG. 1, the regions to which the sewing directions in which hitch stitches are generated due to the upper thread factor belong are region β and region γ. A partial region around 90 degrees in region β (that is, the region where the sewing direction is on the back side of the sewing machine) is a region where hitch stitches can be avoided by moving the frame 5 around with a relatively small amount of detour. For convenience, this is referred to as the first region S1. As a reference, an example of the first region S1 is shown in FIG. 16. In FIG. 16, similar to FIG. 1, the reference point C located at the center of the figure indicates the current needle drop position (the position of the needle hole 19a of the needle plate 19), and the sewing direction from the reference point C to the next needle drop point (that is, the direction in which the next stitch is formed) is specified by the angle from 0 degrees to less than 360 degrees marked counterclockwise. The moving direction of the frame 5 corresponding to the region S1 in the sewing direction around 90 degrees is the region around 270 degrees, which is exactly the opposite (180 degrees opposite side). As a reference, an example of the moving target position of the frame 5 corresponding to the stitch in the sewing direction belonging to the first region S1 is shown as T1 in FIG. 16. As can be understood from the figure, when the frame 5 moves around, the target position T1 corresponding to the next stitch is relatively close from the position where the frame 5 is once moved in the direction in which the upper thread comes out from the opening 29 of the guide body 23 (to the left front side). Therefore, the target position T1 can be reached by moving the frame 5 around with a relatively small amount of detour. The range of this first region S1 is shown as the range of angles a to b in the figure, and as an example, it is a range of about 85 degrees to less than 112 degrees. However, as will be described later, this range may be variably set as appropriate.

[0077] Of the regions β and γ to which the sewing direction in which hitch stitches are generated due to the upper thread factor belongs, the remaining region S2 is a region that avoids hitch stitches by moving the frame 5 around with a relatively large amount of detour. For convenience, this will be referred to as the second region. The second region S2 includes the remainder of the region β shown in FIG. 1 and all of the region γ. The moving direction of the frame 5 corresponding to this second region S2 is the region directly opposite (180 degrees opposite) thereto. As a reference, an example of the target position of the movement of the frame 5 corresponding to the seam of the sewing direction belonging to the second region S2 is indicated by T2 in FIG. As can be understood from the figure, when the frame 5 makes a detour movement, from the position where the frame 5 is once moved in the direction in which the upper thread exits from the opening 29 of the guide body 23 (to the left front side), the target position T2 corresponding to the next seam is relatively far and may be closer to the back side. Therefore, in order to reach the target position T2, it is necessary to move the frame 5 around with a relatively large amount of detour. The range of this second region S2 is shown in the figure as the range of angles b to c, and is, for example, in the range of about 112 degrees to 210 degrees. However, as will be described later, this range may also be variably set as appropriate. Note that the regions with different amounts of detour are not limited to the two regions (S1, S2) as described above, and may be three or more regions. Also, in FIG. 16, S0 indicates a region where the frame 5 does not make a detour movement, and this region S0 includes the regions α and δ shown in FIG. 1.

[0078] In one embodiment, the control means may perform the jump control one time, two times, or more times during the detour movement. In one embodiment, when the direction of forming the next seam belongs to the first region S1, the control means performs the jump control one time during the detour movement, and when the direction of forming the next seam belongs to the second region S2, the control means performs the jump control two times during the detour movement.

[0079] FIG. 17 is a diagram illustrating some of the trajectories of the detour movement of the frame 5 executed by the frame detour control by the control means. In FIG. 17, similar to FIG. 16, C indicates the (current) needle drop position (base point) at the start of the detour movement, and T1 and T2 indicate the needle drop positions (target positions) at the end of the detour movement. In this regard, FIG. 18 is a plan sectional view showing the relationship between the upper thread T and the guide body 23 of the presser device 21 during the detour movement of the frame 5, and shows the guide body 23 and the portion of the upper thread T that enters the sewing needle 11 and its eyelet 11a in a horizontal cross section. However, as described above, in the jump state, the sewing needle 11 is at a position 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 the eyelet 11a) do not show cross sections at the same height.

[0080] FIG. 17(a) shows the trajectory of the detour movement when the direction of forming the next seam belongs to the first region S1. In this example, jump control for one time (for one stitch) is performed during the detour movement. The needle bar 9 (sewing needle 11) that has risen at the base point C is set to the jump state by the jump mechanism and held upward. Also, the cloth presser motor 24 stops, and the presser device 21 stops at a predetermined upper position. At the same time, the frame 5 is controlled to move in a direction in which the upper thread T extending downward from the sewing needle 11 exits from the opening 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 of the movement A1 of the frame 5 (that is, the intermediate point of the detour movement) m1 may be set with appropriate X-Y coordinate values. Considering performing the detour movement efficiently (compactly), the end point (that is, the intermediate point) m1 of A1 may be set so that the movement A1 of the frame 5 is in the direction diagonally forward to the left as shown in the figure. However, it is not limited to this, and it may be set appropriately within the scope not departing from the gist of the present embodiment. FIG. 18(a) shows a state in which the upper thread T exits from the opening 29 of the guide body 23 in the direction diagonally forward to the left along with the movement A1 of the frame 5 at this time. When the frame 5 reaches the intermediate point m1, the jump control for one stitch ends.

[0081] Next, the frame 5 is moved from the intermediate point m1 toward the target position T1 corresponding to the next seam. 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 in the diagonally forward right direction as shown in the figure. In the process of this movement A2, the upper thread T that has come out of the opening 29 of the guide body 23 abuts against the restricting portion 23a of the guide body 23, and the rightward movement of the upper thread T is restricted by the restricting portion 23a. FIG. 18(b) shows the state in which the upper thread T abuts against the restricting portion 23a as the frame 5 moves with the movement A2 at this time. In this state, the upper thread T that has come out of the eyelet 11a of the sewing needle 11 is located on the left side of the sewing needle 11. While the frame 5 is moving from the intermediate point m1 toward the target position T1, the needle bar 9 (sewing needle 11) and the presser device 21 descend. Of course, appropriate operation timing adjustment is made so that the frame 5 reaches the target position T1 and the detour movement is completed before the descending sewing needle 11 and the presser device 21 contact the upper surface of the workpiece to be sewn.

[0082] FIG. 17(b) shows the trajectory of the detour movement when the direction of forming the next seam belongs to the second region S2. In this example, two (for two stitches) jump controls are performed during the detour movement. The needle bar 9 (sewing needle 11) that has risen at the base point C is set in a jump state by the jump mechanism and held upward. Also, the cloth presser motor 24 stops, and the presser device 21 stops at a predetermined upper position (top dead center). At the same time, the frame 5 is controlled to move in the direction in which the upper thread T extending downward from the sewing needle 11 comes out of the opening 29 of the guide body 23. The movement of the frame 5 at this time is also indicated by A1 in FIG. 17(b) as described above. Similarly to the above, the end point (i.e., the first intermediate point) m1 of the movement A1 of the frame 5 may be set with appropriate X-Y coordinate values. Similarly to the above, considering performing the detour movement efficiently (compactly), the end point (i.e., the first intermediate point) m1 of A1 is set so that the movement A1 of the frame 5 is in the diagonally forward left direction as shown in the figure. The state in which the upper thread T comes out of the opening 29 of the guide body 23 in the diagonally forward left direction as the frame 5 moves with the movement A1 is as shown in FIG. 18(a) as described above. When the frame 5 reaches the first intermediate point m1, the first (for one stitch) jump control ends, but the second (for one stitch) jump control is continued to maintain the jump state.

[0083] Next, while maintaining the jump state, move the frame 5 from the first intermediate point m1 toward the second intermediate point m2. The movement of the frame 5 at this time is shown as A2 in FIG. 17(b). The movement A2 of the frame 5 is in the direction of diagonally forward to the right as shown in the figure. In the process of this movement A2, the upper thread T that has come out of the opening 29 of the guide body 23 abuts against the restricting portion 23a of the guide body 23, and the rightward movement of the upper thread T is restricted by the restricting portion 23a. The state when the upper thread T abuts against the restricting portion 23a in the process of this movement A2 is the same as that in FIG. 18(b). In this state, the upper thread T that has come out of the eyelet 11a of the sewing needle 11 is located on the left side of the sewing needle 11. The end point of the movement A2 of the frame 5 (that is, the second intermediate point m2) may be set with appropriate X-Y coordinate values. Considering that it surely abuts against (applies to) the target position T2 and the restricting portion 23a, it is advisable to set the end point of A2 (that is, the second intermediate point m2) so that the movement A2 of the frame 5 is in an appropriate diagonally forward to the right direction as shown in the figure. When the frame 5 reaches the second intermediate point m2, the second jump control ends. Note that when reaching the end point (the second intermediate point m2) of the movement A2, the upper thread T is in a state of being wound around the restricting portion 23a in a left-handed manner.

[0084] Next, move the frame 5 from the second intermediate point m2 toward the target position T2 corresponding to the next seam. The movement of the frame 5 at this time is shown as A3 in FIG. 17(b). The movement A3 of the frame 5 is in the direction of diagonally backward to the right as shown in the figure. Along with this movement A3, the upper thread T is further wound around the restricting portion 23a in a left-handed manner and heads in the direction of diagonally backward to the right. However, the point that the upper thread T that has come out of the eyelet 11a of the sewing needle 11 is located on the left side of the sewing needle 11 remains the same as the state in FIG. 18(b). While the frame 5 is moving from the second intermediate point m2 toward the target position T2, the needle bar 9 (sewing needle 11) and the presser device 21 descend. Similar to the above, appropriate operation timing adjustment is made so that the frame 5 reaches the target position T2 and the detour movement is completed before the descending sewing needle 11 and presser device 21 contact the upper surface of the workpiece to be sewn.

[0085] In the frame bypass control shown in FIGS. 17(a) and (b) described above, the bypass movement of frame 5 is performed intermittently. For example, a program is prepared by combining stitch-by-stitch sewing data (frame movement data) and jump control codes. The bypass movement by one jump control may be performed based on the combination of the sewing data of the first 1 stitch (frame movement data to intermediate point m1) and the jump control code, and the sewing data of the next 1 stitch (frame movement data to target position T1). Also, the bypass movement by two jump controls may be performed based on the combination of the sewing data of the first 1 stitch (frame movement data to first intermediate point m1) and the jump control code, the combination of the sewing data of the next 1 stitch (frame movement data to second intermediate point m1) and the jump control code, and the sewing data of the last 1 stitch (frame movement data to target position T2). Note that the number of jump controls in the frame bypass control is not limited to 1 or 2 as described above, and may be 3 or more, or may be only 1 time.

[0086] The bypass movement of frame 5 is not limited to the example of performing it intermittently as described above, and may be performed continuously. FIG. 17(c) shows an example of continuously performing the bypass movement of frame 5. Similar to (b), the target position is T2, and an example of continuously performing the bypass movement along the same trajectories A1, A2, A3 as in (b) is shown. For example, when the jump control codes are continuous, parameters such as making frame 5 move continuously may be set, and based on this, the bypass movement of frame 5 may be continuously performed up to the target position T2 while keeping the needle bar 9 in the jumped state.

[0087] <Upper thread slack prevention> In one embodiment, measures may be taken so that the upper thread T does not become slack during the detour movement control of the frame 5. For this purpose, as shown in FIG. 3, an upper thread slack prevention portion 200 is disposed below the needle bar case 8. The upper thread slack prevention portion 200 is disposed above a well-known upper thread locking device 400, and both ends of its base plate 201 are fixed to brackets attached to the left and right side surfaces of the needle bar case 8 with screws. At positions corresponding to each needle bar 9 on the base plate 201, a presser piece 203 is held by a screw 202 having a spring fitted on its shaft portion. The upper thread T (not shown in FIG. 3) hanging from the balance 10 is passed between the base plate 201 and the presser piece 203. Thereby, by adjusting the screwing amount of the screw 202 to change the elastic force of the spring, a slight tension is applied to the upper thread T passing between the base plate 201 and the presser piece 203 by contact resistance. The upper thread T that has passed through the upper thread slack prevention portion 200 passes through the upper thread locking device 400 and is passed through the eyelet 11a of the corresponding sewing needle 11. The tension applied to the upper thread T by the screw 202 and the presser piece 203 of the upper thread slack prevention portion 200 may be such that it can prevent the upper thread T caught (wound) on the guide body 23 from slipping downward due to slack during the detour movement control of the frame 5. With this upper thread slack prevention portion 200, even if slack occurs in the portion of the upper thread T above the upper thread slack prevention portion 200 when the balance 10 that moves up and down during the jump of the needle bar 9 descends, the contact resistance in the upper thread slack prevention portion 200 prevents the upper thread T below it from becoming slack, and it is possible to prevent the upper thread T caught (wound) on the guide body 23 from slipping downward due to slack during the detour movement control of the frame 5. Note that the structure of the upper thread slack prevention portion 200 is not limited to that shown in the figure, and any structure may be used as long as it can prevent the upper thread T from becoming slack. Also, instead of providing a special upper thread slack prevention portion 200, a well-known upper thread locking device 400 may be used as a substitute. Since the above-described upper thread slack prevention portion 200 always applies tension to the upper thread T, it is conceivable that even a slight contact resistance may affect the thread tightening. As a modification, the upper thread slack prevention portion 200 may be made movable like the upper thread locking device 400, and tension may be applied only during the detour control of the frame 5.

[0088] <Sewing control for realizing all perfect stitches> The sewing machine shown in the above embodiment can avoid the generation of hitch stitches due to the upper thread factor and the lower thread factor, and realize a sewing in which stitches over the entire range in the sewing direction are all perfect stitches. FIG. 19 is a flowchart showing an example of a computer program for executing sewing control consisting of all perfect stitches according to this embodiment. This program is stored, for example, in the storage device 103 shown in FIG. 15 and executed by the CPU 101.

[0089] The program shown in FIG. 19 starts when starting the sewing operation of a pattern (embroidery pattern or other sewing pattern) consisting of a plurality of stitches selected by the user. In step St1, the value of the stitch counter n indicating the formation order of the stitches is set to the initial value 1. In step St2, stitch movement amount data Pn (X-Y movement data of frame 5) for forming the stitch at the order (n-th stitch) specified by the current value of the stitch counter n is acquired. In step St3, the sewing direction of the stitch movement amount data Pn (that is, the direction for forming the next stitch) is calculated with the current needle drop position as the base point C. In step St4, it is determined whether or not the calculated sewing direction (the direction for forming the next stitch) belongs to the region S0 shown in FIG. 16 (that is, the region where no frame detour control is performed). If YES, proceed to step St5; if NO, proceed to step St8.

[0090] 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 perform a single-needle sewing operation. In the sewing operation in step St5, the frame 5 does not perform a detour movement. As described above, the region S0 shown in FIG. 16 includes the regions α and δ shown in FIG. 1. If the calculated sewing direction (the direction for forming the next stitch) belongs to the region α, a perfect stitch can be formed simply by performing a normal sewing operation. On the other hand, when the calculated sewing direction (the direction for forming the next stitch) belongs to the region δ, the occurrence of hitch stitches due to the lower thread factor can be avoided by the above-described unique bobbin structure, and a perfect stitch can be formed. The details are as follows.

[0091] <Avoidance of hitch stitches in region δ> FIG. 20 is a diagram for explaining a mechanism for avoiding hitch stitches due to the lower thread factor by the bobbin structure according to the present embodiment. (a) is a front view of the bobbin structure, and (b) is an enlarged plan view showing the relationship between the sewing needle and the lower thread in the inner bobbin 50. The bobbin 3 shown in FIG. 20 is the same as the bobbin 3 described above with reference to FIGS. 11 to 14 and the like. When the direction for forming the next stitch belongs to the region δ, the frame 5 moves in the right rear direction toward the target position corresponding to the next stitch. The lower thread D from the bobbin 3 toward the needle hole 19a is pulled in the right rear direction as the frame 5 moves. However, as shown in FIGS. 20(a) and (b), the lower thread D abuts against the back wall surface 52a of the recess 52 of the inner bobbin 50, and the movement of the lower thread D in the right side direction is restricted by the upstream side wall 52b of the recess 52. Thus, the lower thread D that has come out of the bobbin 3 passes through the left rear side of the vertical movement line of the sewing needle 11 and heads toward the needle hole 19a, and is connected to the upper workpiece W above. Therefore, in a state where the sewing needle 11 moving up and down is below the needle plate 19, the lower thread D is always located on the left rear side of the sewing needle 11 and does not come to its right side. This structurally avoids the occurrence of hitch stitches due to the lower thread factor in the region δ, and the entanglement of the upper thread T and the lower thread D realized in the bobbin 3 forms a perfect stitch.

[0092] When the sewing needle 11 passes through the workpiece (processed fabric) W, the workpiece may flutter up and down, causing the lower thread D to slacken, and the slackened lower thread D may move to the right side of the tip of the sewing needle 11. However, in this embodiment, by providing the thread take-up member 41 with a spring action, even if the lower thread D slackens due to the fluttering of the workpiece W or the like, the spring action of the thread take-up member (thread take-up spring) 41 located substantially directly below the concave portion 52 of the inner pot 50 quickly absorbs the slack of the lower thread D, so that the lower thread D can be maintained in a taut state, and the lower thread D can be prevented from moving to the right side of the tip of the sewing needle 11. Further, as described above, since the front end edge 62b of the upper spring portion (thread separating spring) 62 of the outer pot 60 is located behind the rear side wall surface 52a of the concave portion 52 of the inner pot 50, the front end edge 62b does not contact the lower thread D and push the lower thread D forward. Therefore, the slack of the lower thread D due to the upper spring portion (thread separating spring) 62 of the outer pot 60 does not occur. In this way, all possible measures are taken to eliminate the possibility of hitch stitch generation due to the slack of the lower thread D.

[0093] Returning to FIG. 19, in step St8, it is determined whether or not the sewing direction (the direction for forming the next stitch) calculated in step St3 belongs to the first region S1 (a part of region β) shown in FIG. 16. If YES, the process proceeds to step St9. In step St9, a frame detour movement control for the first region S1 consisting of a small detour movement locus as shown in FIG. 17(a) is executed. If the determination in step St8 is NO, it means that the sewing direction (the direction for forming the next stitch) calculated in step St3 belongs to the second region S2 (the region including the rest of region β and region γ) shown in FIG. 16. In this case, the process proceeds to step St10, and a frame detour movement control for the second region S2 consisting of a large detour movement locus as shown in FIG. 17(b) is executed.

[0094] <Avoidance of hitch stitch in region S1> The frame bypass movement control (one-time jump control) for the first region S1 performed in step St9 consists of moving the frame 5 to the intermediate point m1 with the needle bar 9 in a jumped state, and then moving the frame 5 to the target position T1 to drop the sewing needle 11 onto the workpiece W. Specifically, as described below with reference to FIG. 21. FIG. 21 is a perspective view illustrating the function of the guide body 23 of the presser device 21 in the bypass movement control of the frame 5.

[0095] With the needle bar 9 jumped and the sewing needle 11 held upward, by moving the frame 5 to the intermediate point m1, the frame 5 moves as shown at A1 in FIG. 17(a), and as shown in FIG. 18(a), the upper thread T comes out from the opening 29 of the guide body 23 of the presser device 21 in the direction of the front left obliquely. FIG. 21(a) shows this state in a perspective view. Next, by moving the frame 5 from the intermediate point m1 to the target position T1, the frame 5 moves as shown in 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, by releasing the jumped state of the needle bar 9, the sewing needle 11 and the presser device 21 descend.

[0096] FIG. 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 device 21. As can be seen from the figure, the upper thread T connected to the workpiece W from behind the eyelet 11a of the sewing needle 11 hangs on the restricting portion 23a of the guide body 23 (specifically, the notch portion in the restricting portion 23a), the movement of the upper thread T to the right side of the vertical movement line of the sewing needle 11 is restricted, and it is held on the left side of the sewing needle 11.

[0097] FIG. 21(c) shows the state immediately before the sewing needle 11 further descends and enters the guide body 23 of the presser member 22 and pierces the workpiece W. The sewing needle 11 descending in the guide body 23 passes through the right side of the portion of the upper thread T that comes out from behind the eyelet 11a of the sewing needle 11 and is connected to the workpiece W while being restricted by the restricting portion 23a. When the guide body 23 of the presser device 21 reaches the bottom dead center, the descent of the presser device 21 is stopped, and thereafter only the sewing needle 11 further descends.

[0098] FIG. 21(d) shows a state in which the tip of the further descending sewing needle 11 passes through the guide body 23 and pierces the workpiece W. The portion of the upper thread T connected to the workpiece W from behind the eyelet 11a of the sewing needle 11 is restricted from moving rightward by the restricting portion 23a of the guide body 23, and thus is held at the left position of the sewing needle 11 and descends along the restricting portion 23a as the sewing needle 11 descends.

[0099] FIG. 21(e) shows a state in which as the sewing needle 11 further descends, the portion of the upper thread T connected to the workpiece W from behind the eyelet 11a reaches below the lower end of the guide body 23. In this state, the portion of the upper thread T connected to the workpiece W from behind the eyelet 11a comes off the restricting portion 23a and becomes entangled with the sewing needle 11 in the left-handed winding direction.

[0100] In a state where the further descending sewing needle 11 passes through the workpiece W and the needle hole 19a of the needle plate 19 so that the portion of the eyelet 11a is located below the needle plate 19, the portion of the upper thread T that comes out from behind the eyelet 11a of the sewing needle 11 and is connected to the upper workpiece W extends upward along the left side of the sewing needle 11, passes through the needle hole 19a, and reaches the workpiece W. Thus, in a state where the sewing needle 11 has descended to the bobbin 3, the path of the upper thread T from behind the eyelet 11a to the upper workpiece W (the needle hole 19a) will be held on the left side of the sewing needle 11. In a state where the sewing needle 11 has descended into the bobbin 3 in this way, as is well known, the upper thread T that comes out from behind the eyelet 11a and extends upward is caught by the sword tip 61 of the outer bobbin 60, and by moving together with the sword tip 61, an upper thread loop is formed (drawn out). By the combination of the rotation of the bobbin 3, the upward movement of the sewing needle 11, and the movement of the balance 10, the loop of the upper thread T is entangled with the lower thread D, and a stitch is formed. Since the upper thread T that comes out from behind the eyelet 11a enters the bobbin 3 while being located on the left side of the sewing needle 11 (left-handed winding with respect to the sewing needle 11), this stitch will be formed as a perfect stitch. As described above, the occurrence of hitch stitches in the first region S1 (a part of the region β) can be avoided.

[0101] <Avoidance of hitch stitches in region S2> The frame bypass movement control (two - jump control) for the second area S2 performed in step St10, as shown in FIG. 17(b), moves the frame 5 to the first intermediate point m1 with the needle bar 9 jumped by one stitch. Next, with the needle bar 9 jumped by another stitch, the frame 5 is moved to the second intermediate point m2. Finally, the frame 5 is moved to the target position T2 and the sewing needle 11 is dropped onto the workpiece W. Specifically, as will be described below with reference to FIGS. 21(a) and 22 together.

[0102] With the needle bar 9 jumped by one stitch and the sewing needle 11 held upward, by moving the frame 5 to the first intermediate point m1, the frame 5 moves as shown at A1 in FIG. 17(b). As shown in FIG. 18(a), the upper thread T extending downward from behind the eyelet 11a of the upper sewing needle 11 comes out from the opening 29 of the guide body 23 of the presser device 21 in the direction of the front left - diagonal. The state at this time is as shown in FIG. 21(a) in perspective view.

[0103] Next, with the jump of the needle bar 9 continued (in the state of being jumped by another stitch), by moving the frame 5 from the first intermediate point m1 to the second intermediate point m2, the frame 5 moves generally rightward as shown in the trajectory A2 of FIG. 17(b). When the frame 5 reaches the second intermediate point m2, the jump control ends. When reaching the end point (the second intermediate point m2) of this movement A2, the upper thread T is in a state of being wound left - handedly around the regulating portion 23a of the guide body 23. The state at this time is as shown in FIG. 22 in perspective view. As can be seen from the figure, the upper thread T descending from the sewing needle 11 and connected to the workpiece W is deeply wound left - handedly around the regulating portion 23a of the guide body 23. In this way, the frame bypass movement by the two - jump control can surely wind the upper thread T around the regulating portion 23a, so that the winding error can be prevented.

[0104] 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 locus A3 in FIG. 17(b). Along with this movement A3, the upper thread T is further wound counterclockwise around the regulating portion 23a and heads in the direction of the rear right diagonal. Thus, the upper thread T connected to the workpiece W from behind the eyelet 11a of the sewing needle 11 is deeply caught counterclockwise by the regulating portion 23a of the guide body 23, and its movement to the right of the vertical movement line of the sewing needle 11 is restricted and it is held on the left side of the sewing needle 11. Since the jump control has ended, while the frame 5 is moving from the second intermediate point m2 toward the target position T2, the needle bar 9 (sewing needle 11) and the presser device 21 descend.

[0105] The state of the upper thread T in the process of the further descending sewing needle 11 passing through the workpiece W and the needle hole 19a and reaching the bobbin case 3 is the same as described above with reference to FIGS. 21(c) to (e). That is, the portion of the upper thread T emerging from behind the eyelet 11a of the sewing needle 11 enters the bobbin case 3 while maintaining a state of being located on the left side of the sewing needle 11 (counterclockwise with respect to the sewing needle 11), and a stitch that avoids the occurrence of hitch stitches due to the upper thread factor can be formed. In particular, in the portion of the second region S2 that is the region β, by avoiding the occurrence of hitch stitches due to the upper thread factor as described above, a perfect stitch is formed. In the region γ of the second region S2, since hitch stitches due to the upper thread factor and hitch stitches due to the lower thread factor are mixed, it is not sufficient to simply avoid the occurrence of hitch stitches due to the upper thread factor, and it is also necessary to avoid the occurrence of hitch stitches due to the lower thread factor. Specifically, this is because a double hitch stitch occurs when the lower thread is located behind (rearward) the vertical movement line of the sewing needle 11 even when it is wound counterclockwise around the sewing needle 11 by the frame detour control. Such hitch stitches due to the lower thread factor in the region γ are avoided by the specific needle plate structure related to the needle hole 19a of the needle plate 19 as described above. Details are as described below.

[0106] <Avoidance of hitch stitches due to the lower thread factor in the region γ> As described above with reference to FIGS. 9 and 10 etc., in the needle plate 19, a guide hole 31 and a groove portion 32 are formed in relation to the needle hole 19a. FIG. 23 is a perspective view illustrating a mechanism for avoiding hitch stitches as a cause of the lower thread by the structure of the needle plate 19 having the guide hole 31 and the groove portion 32 in this way. In FIG. 23, for ease of illustration, the frame 5 and the workpiece W existing between the presser device 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, the distance between the guide body 23 of the presser device 21 and the needle plate 19 (the needle hole 19a) is depicted as being constant, but actually, this distance changes according to the vertical movement of the presser device 21.

[0107] FIG. 23(a) shows a state in which, in the frame detour movement control (two - jump control) for the second region S2 performed in step St10, generally, when the frame 5 has moved to the first intermediate point m1 (in the diagonally forward left direction). In this state, the upper thread T extending downward from behind the eyelet 11a of the upper sewing needle 11 is, as described above, in a state of coming out from the opening portion 29 of the guide body 23 of the presser device 21 in the diagonally forward left direction. The lower thread D extending upward from the bobbin 3 and connected to the workpiece W passes through the needle hole 19a corresponding to the needle drop position before the movement of the frame 5, but is guided from the needle hole 19a to the guide hole 31 as the frame 5 moves to the first intermediate point m1 (in the diagonally forward left direction).

[0108] FIG. 23(b) shows a state in which, in the frame detour movement control (two - jump control) for the second region S2 performed in step St10, generally, when the frame 5 has moved to the second intermediate point m2 (generally in the right direction). In this state, the upper thread T extending downward from behind the eyelet 11a of the upper sewing needle 11 is, as described above, caught by the regulating portion 23a of the guide body 23, and the movement to the right side of the vertical movement line of the sewing needle 11 is restricted, and it winds around the regulating portion 23a in a left - hand twist. The lower thread D enters the upper space of the groove portion 32 by bending from the guide hole 31 as the frame 5 moves from the first intermediate point m1 to the second intermediate point m2 (generally in the right direction), and is guided substantially in the right direction along the groove portion 32.

[0109] FIG. 23(c) shows the state when the frame 5 has generally moved to the target position T2 (generally in the direction of the upper right back) 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 behind the eyelet 11a of the upper sewing needle 11 is further wound counterclockwise around the regulating portion 23a of the guide body 23 as described above. The lower thread D is locked by the side wall 32b (FIG. 10(b)) on the inner side of the groove portion 32 (that is, closer to the needle hole 19a) as the frame 5 moves from the second intermediate point m2 to the target position T2 (generally in the direction of the upper right back), and is maintained in front of the vertical movement line of the sewing needle 11 without shifting to the back side of the vertical movement line of the sewing needle 11. This means that the path of the lower thread D drawn upward from the bobbin 3 and reaching the needle plate 19 is maintained in front of the vertical movement line of the sewing needle 11.

[0110] In the state where the above-mentioned frame 5 reaches the target position T2, the sewing needle 11 further descends and then ascends. In this process, as the bobbin 3 rotates, the loop of the upper thread T is wound around the lower thread D as described above, and a stitch is formed. At this stage, the upper thread T coming out from behind the eyelet 11a enters the bobbin 3 in a state where it is located on the left side of the sewing needle 11 (counterclockwise with respect to the sewing needle 11), and the path of the lower thread D drawn from the lower thread bobbin and reaching the needle plate 19 is maintained in front of the vertical movement line of the sewing needle 11 as described above. Therefore, sewing that avoids both the hitch stitch due to the upper thread factor and the hitch stitch due to the lower thread factor (that is, double hitch stitch) is realized.

[0111] Incidentally, although the lower thread D is also pulled out as the frame 5 moves circuitously, the spring action of the thread take-up member 41 described above quickly absorbs the slack of the pulled-out lower thread D. That is, in this embodiment, by providing the thread take-up member 41 with a spring action, even if the lower thread D is pulled out as the frame 5 moves circuitously, the spring action of the thread take-up member (thread take-up spring) 41 provided in the bobbin 3 quickly absorbs the slack of the lower thread D, so that the lower thread D can be maintained in a taut state. Therefore, it is less likely that the lower thread D will become slack and come off from the locking portion (groove portion 32) of the needle plate 19. That is, in this embodiment, the thread take-up member (thread take-up spring) 41 also functions (doubles as) a tension applying means provided below the needle plate 19 so as to apply tension to the lower thread fed upward from the bobbin 3 and heading toward the needle hole 19a or the guide hole 31 of the needle plate 19.

[0112] As is well known, the loop of the upper thread T caught by the sword tip 61 of the outer bobbin 60 passes through the inner bobbin 50, and the upper thread T is pulled up along the lower thread D while reducing its loop by the lifting of the balance 10 (Fig. 4). In this embodiment, since the groove portion 32 is formed to have a bottom surface 32a, the loop of the upper thread T that passes through the needle hole 19a together with the lower thread D while reducing the loop does not get caught in the groove portion 32, and the structure does not cause the problem of upper thread breakage. Further, when the needle drops at the target position T2, since the lower thread D is only locked to the side wall 32b (Fig. 10(b)) on the inner side of the groove portion 32 of the needle plate 19, when the lower thread D is pulled up as the upper thread T rises, the lower thread D easily detaches from the groove portion 32 and returns to the normal path (i.e., the path passing through the needle hole 19a), so that it does not adversely affect the path formation of the lower thread D during the formation of the next stitch.

[0113] As described above, in Fig. 19, by executing the processes of steps St5, St9, and St10 according to the needle moving direction of the stitch movement amount data Pn (i.e., the direction of forming the next stitch), it is possible to realize a stitch composed of all perfect stitches that avoids the occurrence of (all types of) hitch stitches due to upper thread factors and lower thread factors.

[0114] Regarding the remaining steps shown in FIG. 19, after the processing of steps St5, St9, and St10, it goes to step St6, and the value of the stitch counter n is incremented by 1. In the next step St7, it is determined whether the incremented value n is greater than the "total number of stitches" of the pattern currently executing the sewing operation. If NO, it returns to the above-mentioned step St2, and for the incremented value n (i.e., the "next stitch"), the processing after step St2 is repeated as described above. When the sewing of the pattern currently executing the sewing operation is completed, in step St7, it is determined as YES, and the program in FIG. 19 is terminated.

[0115] <Frame bypass control data setting> In one embodiment, various data related to the frame bypass control (i.e., various conditions for the bypass control) may be configured to be arbitrarily set and changed by the user. FIG. 24 shows an example of a screen display in which various data (various conditions for the bypass control) related to the frame bypass control can be set and changed using the operation panel 6 (FIG. 2). The operation panel 6 is provided with a touch-operable display screen, and on the display screen, required images, 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 frame bypass control numbered 21 to 30 are displayed together with their current set values. As another example, instead of simultaneously displaying a plurality of setting items (numbers 21 to 30) on the parameter setting screen 110, at least one setting item may be displayed, and the displayed setting items may be sequentially switched by a scroll operation or the like.

[0116] When a desired setting item among numbers 21 to 30 displayed on the parameter setting screen 110 is touched and selected, the current set value regarding the selected one setting item is displayed on the display unit 111. By operating the set value switching key 112, the current set value regarding the selected setting item is incremented or decremented and is displayed on the display unit 111. After changing the set value, when the confirmation key 113 is pressed, the changed set value becomes valid.

[0117] The item related to "Use of All Perfect Stitch (Apfs)" No. 21 corresponds to setting means for setting whether to enable the execution of frame bypass movement control. For example, by setting Yes / No, it is switched whether to enable the execution of frame bypass movement control. In the illustration, the state set to "Yes" is shown. Note that this setting value may be "ON / OFF" instead of "Yes / No".

[0118] In order to actually control the enabling / disabling of the bypass movement control of frame 5 according to this setting, a part of the flow in FIG. 19 may be changed as shown in FIG. 25. That is, step St11 is inserted between the aforementioned steps St3 and St4, and in this step St11, it is determined whether "Use of All Perfect Stitch (Apfs)" is set to YES (that is, whether to enable the execution of the bypass movement of frame 5). If step St11 is YES, it proceeds to step St4, and as described above, the bypass movement control of frame 5 is executed. If step St11 is NO, it jumps to step St4 and proceeds to step St5, and the bypass movement control of frame 5 is not executed.

[0119] By enabling the setting of whether to execute the detour movement of the frame 5 in this way, a diverse sewing operation can be performed, and efficient operation of the sewing work can be achieved. As described above, by executing the detour movement of the frame 5, hitch stitches due to the upper thread factor can be avoided, and the sewing quality can be improved. However, since the time required for the detour movement of the frame 5 takes extra time, it is inevitable that the overall production efficiency of sewing decreases. Depending on the intended sewn product, there may be cases where it is desired to avoid a decrease in production efficiency rather than a decrease in quality due to hitch stitches. For example, when sewing a hidden part that is not visible on the surface of the product, it seems preferable to prioritize production efficiency without improving hitch stitches. Also, depending on the type of the material to be sewn (processed fabric) or the upper thread, etc., there may be cases where it is desired to select whether to execute the detour movement control of the frame 5. Also, for example, in simple straight sewing and complex embroidery sewing, the required degree of avoiding hitch stitches may be different. In preparation for these various cases, it is beneficial to have a function to select whether the detour movement of the frame 5 is effective (Yes or ON) or ineffective (No or OFF).

[0120] Items numbered 22 to 24 are means for setting parameters a, b, and c that define the sewing needle direction (seam formation direction) for performing frame detour control. Specifically, it corresponds to setting means for variably setting the ranges of the first and second regions S1 and S2 (FIG. 16). The boundary angles a and b that define the range of the first region S1 are variably set in items numbered 22 and 23. Among the boundary angles b and c that define the range of the second region S2, b follows the setting in item numbered 23, and c is variably set in item numbered 24. As an example, predetermined values (for example, a = 85 degrees, b = 112 degrees, c = 210 degrees) are initially set as each boundary angle a, b, c, and these predetermined values a, b, c are variably set by increasing or decreasing them by manual operation by the user. Based on the content set here (the values of each boundary angle a, b, c), the determination of regions S0 and S1 in steps St4 and St8 of FIG. 19 is performed.

[0121] Generally, since it is difficult to precisely demarcate the area where hitch stitches occur, it is advisable to set the ranges of regions S1 and S2 where frame bypass control is executed more broadly and perform the bypass movement control of frame 5 from a safety perspective. However, if this is done, there is a risk that the overall production efficiency will decrease as the number of bypass movement controls of frame 5 increases. Also, depending on the target sewn product, there may be cases where it is desired to avoid a decrease in production efficiency as much as possible by allowing hitch stitches in the sewing of areas where the quality of the seam is not emphasized. Additionally, there may be cases where it is desired to variably set the ranges of regions S1 and S2 where frame bypass control is executed, without fixing them, according to the type of the workpiece to be sewn (fabric to be processed) or the upper thread. In preparation for these various cases, it is beneficial to have a function to variably set the ranges (the values of respective boundary angles a, b, c) of the predetermined regions S1 and S2 where the bypass movement control of frame 5 should be performed.

[0122] Items numbered 25 and 26 are means for setting parameters X1 and Y1 that define the first movement direction in frame bypass control (i.e., setting means for variably setting the bypass movement path of frame 5). Specifically, it corresponds to setting means for variably setting the X-Y displacement coordinate position (relative coordinate position with respect to the reference point C) of the first intermediate point m1 (Fig. 17). Items numbered 27 and 28 are means for setting parameters X2 and Y2 that define the second movement direction in frame bypass control (setting means for variably setting the bypass movement path of the frame). Specifically, it corresponds to setting means for variably setting the X-Y displacement coordinate position (relative coordinate position with respect to the first intermediate point m1) of the second intermediate point m2 (Fig. 17). For these parameters X1, Y1, X2, and Y2, predetermined values may be initially set respectively, and these predetermined values may be variably set by increasing or decreasing them through manual operations by the user. Note that the current values (2.5 mm, -3.8 mm, 1.1 mm) of the respective parameters X1, Y1, X2, and Y2 illustrated in Fig. 24 are represented in the X-Y coordinate expression format of the seam shown in Fig. 1. For example, the X-Y displacement coordinate position of X1 = 2.5 mm and Y1 = 2.5 mm for defining the first intermediate point m1 indicates the seam position belonging to the quadrants of X+ and Y+ in the X-Y coordinate expression format of the seam shown in Fig. 1. Since the movement direction of frame 5 corresponding to this is the opposite by 180 degrees, it belongs to the quadrants of X- and Y-, corresponding to the movement of frame 5 from the reference point C to the first intermediate point m1 located in the left front direction in Fig. 17. Also, the X-Y displacement coordinate position of X2 = -3.8 mm and Y2 = 1.1 mm for defining the second intermediate point m2 indicates the seam position belonging to the quadrants of X- and Y+ in the X-Y coordinate expression format of the seam shown in Fig. 1. Since the movement direction of frame 5 corresponding to this is the opposite by 180 degrees, it belongs to the quadrants of X+ and Y-, corresponding to the movement of frame 5 from the first intermediate point m1 to the second intermediate point m2 located in the right front direction in Fig. 17. Based on the content set here (the values of the respective parameters X1, Y1, X2, and Y2 that define the first and second intermediate points m1 and m2), the bypass movement control of frame 5 in steps St9 and St10 of Fig. 19 is performed.

[0123] By enabling the variable setting of the parameters X1, Y1, X2, and Y2 that define the moving direction in the bypass control of the frame 5, the bypass movement path of the frame 5 can be appropriately changed. For example, if a relatively large bypass movement path is set, the upper thread can be reliably wound around the guide body 23 of the pressing device 21. However, since it takes extra time for the frame 5 to move in a bypass, the overall sewing production efficiency decreases. On the contrary, if a relatively small bypass movement path is set, the time required for the frame 5 to move in a bypass is not excessive, and the overall sewing production efficiency is good. Therefore, an appropriate frame bypass path can be set according to the balance of whether to prioritize sewing quality or production efficiency, so such a setting means is beneficial.

[0124] Items numbered 29 and 30 are means for setting the effective minimum stitch length and the effective maximum stitch length to which the frame bypass control is applied. The effective minimum stitch length is the minimum value of the length (stitch length) of the seam to which the frame bypass control is applied, and the effective maximum stitch length is the maximum value of the length (stitch length) of the seam to which the frame bypass control is applied. As an example, 0.0 mm is initially set as the effective minimum stitch length, and 36.0 mm is initially set as the effective maximum stitch length. By appropriately increasing or decreasing this value, the user-desired effective minimum stitch length or effective maximum stitch length can be set. When this setting is applied to the frame bypass control, for example, if the length (stitch length) of the seam to be formed next is within the range of the set effective minimum stitch length and effective maximum stitch length, it may be configured to execute the bypass control of the frame 5. For example, between steps St3 and St4 in FIG. 19 (or between steps St11 and St4 in FIG. 25), a step for determining whether the length of the seam to be formed next falls within the range between the set effective minimum stitch length and effective maximum stitch length is inserted. When this step determines YES, it goes to step St4, but if it is NO, it may be configured to jump to step St5.

[0125] Note that the configuration for enabling the setting of various types of data related to the frame bypass control (bypass control conditions) is not limited to the configuration in which it is performed by manual operation by the user using the sewing machine operation panel 6 as described above. When creating a desired sewing pattern program or embroidery pattern program, it may be arbitrarily set as program data for frame bypass control and stored together with the data of the sewing pattern program or embroidery pattern program. A configuration in which various types of data related to the frame bypass control (that is, bypass control conditions) are provided in the form of such programmed data is also included in one embodiment of the setting means for variably setting various types of data related to the frame bypass control (bypass control conditions).

[0126] Note that in the above-described embodiment, when performing the bypass movement of the frame 5, the needle bar jump control by the jump mechanism is performed together with the frame bypass movement control. However, the present invention is not limited to this, and the present invention can also be implemented in a type of sewing machine that does not include a jump mechanism for performing jump control on the needle bar. In a sewing machine not provided with the jump mechanism, in order to perform the bypass movement of the frame 5, the operation of the needle bar may be controlled so that the needle does not drop during the bypass movement of the frame 5. For example, by reducing the rotational speed of the main shaft 13 during the bypass movement of the frame 5, it is possible to control so that the needle does not drop during the bypass movement of the frame 5.

[0127] In the above-described embodiments, examples of applying the present invention to multi-head and multi-needle type sewing machines have been described. However, the present invention is not limited to this, and the present invention can also be applied to single-head type sewing machines or single-needle type sewing machines. Further, the present invention can be applied to either embroidery sewing machines or ordinary sewing machines. Further, the holding body (frame) for holding the workpiece to be sewn is not limited to a flat type, and may be a rotary type such as a hat frame. Further, the bobbin is not limited to a fully rotating vertical bobbin (DB type), and may be any other type of bobbin such as a horizontal bobbin or a semi-rotating bobbin. Although the region where the hitch stitch occurs may be different from that in the above-described embodiments depending on the type of bobbin adopted and its rotation direction, etc., region determination corresponding thereto may be performed, or the needle plate structure may be deformed accordingly (changing the arrangement of the guide holes 31 and the groove portion 32), or the bobbin structure may be deformed accordingly (changing the arrangement of the concave portion 52), etc.

[0128] The operation panel 6 may have a structure fixedly attached to the sewing machine, or may have a structure detachably attached to the sewing machine. As a modification, a portable operation panel (for example, a mobile computer or a mobile terminal, etc.) configured to be able to manually set various bypass control conditions as described with reference to FIG. 24 may be used to configure setting means (that is, a setting device) for manually setting the various bypass control conditions. In that case, the setting means (that is, the setting device) composed of such a portable operation panel has a communication function for communicating with the control device of the sewing machine, and is configured such that setting information / data can be exchanged between the two. Of course, as the setting means (that is, the setting device) for manually setting the various bypass control conditions, both the operation panel 6 fixedly or detachably attached to the sewing machine and the above-described portable operation panel may be configured to be used in combination.

Claims

1. A sewing mechanism that stitches a sewing object by moving a sewing needle up and down through an upper thread and rotating a bobbin that stores a lower thread in synchronization with the up and down movement of the sewing needle to wind the upper thread around the lower thread, A feeding mechanism that forms a seam in an arbitrary direction on the sewing object by relatively displacing a holding body that holds the sewing object with respect to the needle drop position, A pressing member that presses the sewing object around the needle drop position In a sewing machine comprising, A guide body provided at the lower end of the pressing member, the guide body being provided with an opening portion so as to allow the passage of the upper thread in the rotational direction of the bobbin, and a regulating portion being provided so as to regulate the movement of the upper thread in a direction opposite to the rotational direction of the bobbin, Determining means for determining whether the direction in which the next seam is formed belongs to a predetermined region where a hitch stitch is formed, Control means for performing a detour movement of the holding body by operating the feeding mechanism when it is determined that the region is the predetermined region, the detour movement moving the holding body in a direction in which the upper thread extending downward from the sewing needle exits from the opening portion of the guide body, and then moving the holding body to a target position corresponding to the next seam so that the upper thread exiting from the opening portion abuts against the regulating portion, A sewing machine characterized by comprising.

2. The opening portion is provided so as to open to the lower end of the guide body, The sewing machine according to claim 1, wherein the regulating portion is provided so as to regulate the movement of the upper thread in a direction opposite to the rotational direction of the bobbin until it reaches the lower end of the guide body as the upper thread passes through the opening portion.

3. The sewing machine according to claim 1 or 2, wherein the regulating portion is provided so as to regulate the movement of the upper thread at a position offset closer to the rotational direction of the bobbin than the up and down movement line of the sewing needle.

4. The sewing machine according to any one of claims 1 to 3, wherein the control means is configured to set a path of the detour movement so that the upper thread exiting from the opening portion of the guide body is locked by the regulating portion before the holding body reaches the target position.

5. The predetermined region includes a first region and a second region, the determining means determines which of the first region and the second region the direction in which the next seam is formed is in, The sewing machine according to claim 4, wherein the control means performs the detour movement such that the amount of detour is larger when it is determined to be the second region than when it is determined to be the first region.

6. When jump control should be performed during the sewing operation, it further includes a jump mechanism that holds the sewing needle upward without lowering it. The sewing machine according to any one of claims 1 to 5, wherein the control means performs the jump control by the jump mechanism when performing the detour movement. **Claim 7** The sewing machine according to claim 6, wherein the control means performs the jump control one or two times during the detour movement. **Claim 8** The sewing machine according to any one of claims 1 to 7, wherein the restricting portion of the guide body has a recessed portion suitable for locking the upper thread. **Claim 9** The sewing machine according to any one of claims 1 to 8, wherein in the sewing mechanism, a member for preventing the slack of the upper thread is arranged on the path of the upper thread from the balance to the sewing needle. **Claim 10** The sewing machine according to any one of claims 1 to 9, further comprising setting means for setting the conditions of the detour movement performed by the control means. **Claim 11** A needle plate having a needle hole for passing the vertically moving sewing needle is provided above the bobbin. The needle plate is provided near the front surface of the sewing machine and has a guide hole communicating with the needle hole, and the guide hole is disposed offset toward the rotation direction of the bobbin from the vertical movement line of the sewing needle. Furthermore, the needle plate has a groove portion extending in a direction opposite to the rotation direction of the bobbin from the guide hole in front of the needle hole, and the upper part and the part communicating with the guide hole of the groove portion are open, but the rest are the bottom surface and the side wall. The sewing machine according to any one of claims 1 to 10, wherein the lower thread extending upward from the bobbin can be guided to the front side of the needle hole through the guide hole and the groove portion. **Claim 12** The bobbin includes a bobbin case that rotatably houses a lower thread bobbin around which the lower thread is wound, an inner bobbin that houses the bobbin case, and an outer bobbin that rotates in synchronization with the vertical movement of the sewing needle around the inner bobbin. A needle drop hole is provided on the upper front surface of the inner bobbin. On the upper front surface of the inner bobbin, a recess is formed at a position shifted from the needle drop hole in the rotation direction of the outer bobbin. The recess is open at the front side and vertically, and the back side forms a wall surface. The bobbin case is provided with a thread guiding member for guiding the lower thread fed out from the lower thread bobbin toward the recess of the inner bobbin. The sewing machine according to any one of claims 1 to 11, characterized in that the lower thread fed from the lower thread bobbin in the bobbin case passes through the opening of the recess via the thread take-up member and is drawn upward.

13. A presser device for pressing a workpiece in a sewing machine, wherein the sewing machine includes a sewing mechanism that moves a sewing needle passing through an upper thread up and down and rotates a bobbin storing a lower thread in synchronization with the up and down movement of the sewing needle to twist the upper thread with the lower thread and sew the workpiece, and the presser device includes a presser member that presses the workpiece around the needle drop position, a guide body provided at the lower end of the presser member, the guide body being provided with an opening portion so as to allow the passage of the upper thread in the rotational direction of the bobbin, and a regulating portion being provided so as to regulate the movement of the upper thread in the direction opposite to the rotational direction of the bobbin, and the presser device is characterized by comprising the same.

14. The opening portion is provided so as to open to the lower end of the guide body, The presser device according to claim 13, wherein the regulating portion is provided so as to regulate the movement of the upper thread passing through the opening portion in the direction opposite to the rotational direction of the bobbin until it reaches the lower end of the guide body.

15. The presser device according to claim 13 or 14, wherein the regulating portion is provided so as to regulate the movement of the upper thread at a position offset closer to the rotational direction of the bobbin than the up and down movement line of the sewing needle.

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