Patent Application
20250043478
The present invention relates to a sewing machine constructed to avoid occurrence of a hitch stitch in forming stitches on a sewing workpiece and also relates to a presser foot device provided in the sewing machine for holding down the sewing workpiece in place.
There have heretofore been known sewing machines which are provided with: a sewing mechanism that performs sewing on a sewing workpiece (such as a fabric workpiece) by moving vertically or up and down a sewing needle with an upper thread passed therethrough, and rotating a rotary hook, having a lower thread housed therein, in synchronism with the vertical or up-and-down movement of the sewing needle to thereby entwine the upper thread around the lower thread; and a feed mechanism that moves a frame (or holding member), having the sewing workpiece held thereon, relative to a needle drop position, to thereby form a stitch in a desired direction on the sewing workpiece. Such sewing machines can form stitches of various lengths in various directions by performing movement control of the sewing workpiece via the feed mechanism on a stitch-by-stitch basis.
It is known in the art that stitches formed by the sewing machines of the aforementioned type come in different quality, namely perfect stitch quality and hitch stitch quality. The perfect stitch is a stitch formed by entwining an upper thread and a lower thread with each other in a mutually balanced state, while the hitch stitch is a stitch formed by entwining an upper thread and a lower thread with each other in such a manner that only the upper thread draws a spiral shape. It is also known that whether the stitch is formed in the perfect stitch quality or in the hitch stitch quality depends mainly on two factors or causes. The first one of the two factors is behavior of the upper thread; more specifically, in this case, the perfect stitch or the hitch stitch is formed depending on in which of counterclockwise and clockwise directions the upper thread, extending through an eye hole of the sewing needle in a front-to-rear direction to connect to the fabric workpiece when the sewing needle with the upper thread passed therethrough pierces the fabric workpiece, is entwined around the sewing needle in accordance with a moving direction of the fabric workpiece (i.e., stitch forming direction) at the time of stitch formation. It is also known that the hitch stitch is formed by the upper thread being entwined around the sewing needle in the clockwise direction.
Note that throughout this description, the term “front” (“in front of”, “forward”, “front side”, and the like) and the term “rear” (“behind”, “rearward”, “rear side”, and the like) respectively refer to the front and rear (back) of the sewing machine as viewed from the front (or in front view) of the sewing machine, the term “left” and “right” respectively refer to the left and right of the sewing machine as viewed from the front (or in front view) of the sewing machine, and the term “leftward twining direction” and “rightward twining direction” respectively refer to counterclockwise and clockwise directions as viewed in top plan view of the sewing machine.
The second one of the two factors is behavior of the lower thread; more specifically, in this case, the perfect stitch or the hitch stitch is formed depending on a relationship between a path of the lower thread 13 extending from the rotary hook (lower thread bobbin), provided beneath a needle plate, and passing through a needle hole of the needle plate to connect to the working fabric located above the needle plate—and the needle drop position of the sewing needle. Namely, it is known that the hitch stitch is formed when the path of the lower thread is located to the right of an up-down movement trajectory of the sewing needle (needle drop position) in accordance with the moving direction of the fabric workpiece (stitch forming direction) at the time of stitch formation.
The hitch stitch is undesirable in that it not only looks unattractive as compared to the perfect stitch but also degrades sewing quality (involving, for example, a problem that the stitch easily gets loosened). Thus, there have been proposed a variety of approaches for avoiding occurrence of a hitch stitch. According to one example of such proposed approaches, a determination is made, per stitch to be formed, as to whether the moving direction of the fabric workpiece (i.e., stitch forming direction) is a perfect-stitch forming direction or a hitch-stitch forming (or occurring) direction, and upon determination that the moving direction of the fabric workpiece (stitch forming direction) is the hitch-stitch forming direction, the position of the upper thread or the lower thread relative to the needle drop position is changed by moving the frame or using a given operating piece.
Patent Literature 1 identified below discloses an invention constructed to avoid occurrence of a hitch stitch due to the behavior of the upper thread. According to the invention described in Patent Literature 1, upon determination that the moving direction of the frame holding the fabric workpiece (i.e., stitch forming direction) is a hitch-stitch forming direction in which a hitch stitch is undesirably formed due to the behavior of the upper thread, the frame is caused to detour leftward of the sewing needle and then move to a target needle drop position (target position) for stitch formation before the tip end of the descending sewing needle reaches the upper surface of the fabric workpiece, instead of the frame being moved directly to the target position. Namely, the invention described in Patent Literature 1 intends to avoid occurrence of a hitch stitch due to the behavior of the upper thread, by entwining the upper thread, connecting to the fabric workpiece, counterclockwise around the sewing needle. However, in order to quickly entwine the upper thread counterclockwise around the sewing needle by causing the frame to detour during the descending movement of the sewing needle, this invention requires an exact match between the time of the descending movement of the sewing needle and the time of the detouring movement of the frame. Thus, if there is any time mismatch between the descending movement of the sewing needle and the detouring movement of the frame, this prior art presents a problem of failing to entwine the upper thread around the sewing needle. Therefore, with the technique described in Patent Literature 1, it is difficult to reliably avoid occurrence of a hitch stitch.
Patent Literature 2 identified below discloses an invention constructed to avoid occurrence of a hitch stitch due to behavior of the lower thread. According to the invention described in Patent Literature 2, a recessed portion is formed behind the needle hole of the needle plate in communication with the needle hole, and upon determination that the moving direction of the frame holding the fabric workpiece (i.e., stitch forming direction) is a hitch-stitch forming direction in which a hitch stitch is undesirably formed due to the behavior of the lower thread, the frame is caused to detour along the shape of the recessed portion and then moved to a target needle drop position for stitch formation (target position), instead of the frame being moved directly to the target position. More specifically, the recessed portion has a distal end portion extending in a left-to-right direction. The frame is moved to detour such that the lower thread enters the distal end portion of the recessed portion from the left of the distal end portion to be engaged in the distal end portion, and that the path of the lower thread passes by the left of the needle drop position and is then stopped behind the needle drop position (i.e., such that the sewing needle drops at a position located to the right and in front of the path of the lower thread). Namely, the invention described in Patent Literature 2 intends to avoid occurrence of a hitch stitch due to the behavior of the lower thread by causing the sewing needle to drop at a position located to the right of the path of the lower thread extending upward to connect to the fabric workpiece. However, because the recessed portion formed behind the needle hole in communication with the needle hole has the distal end portion extending in the left-to-right direction, a protrusion (so-called “peninsular portion”) extending in a right-to-left direction is inevitably formed between the distal end portion and the needle hole. Due to the presence of such a protrusion, this prior art may present a problem of causing an unwanted breakage of the upper thread.
As also known in the art, an upper thread loop captured by a hook point of an outer rotary hook is caused to move while slipping between the outer rotary hook and an inner rotary hook and is then lifted up by a thread take-up lever to move upward along the lower thread while twining around the lower thread. With the construction described in Patent Literature 2, however, the upper thread loop moving upward along the lower thread may undesirably get caught on the protrusion (peninsular portion) adjoining the distal end portion of the recessed portion having the lower thread engaged therein, in which case the upper thread may be undesirably cut or broken. Further, because the lower thread is engaged by entering the distal end portion of the recessed portion, there may be encountered a problem that the lower thread remains engaged in the recessed portion depending on the stitching direction of the next stitch and thus takes a lower thread path different from the normal path.
Patent Literature 3 identified below, too, discloses an invention constructed to avoid occurrence of a hitch stitch due to behavior of the lower thread. According to the invention described in Patent Literature 3, a switch mechanism is provided for switching the path of the lower thread, leading to the needle hole of the needle plate after getting out of the rotary hook, between a left-side route for deviating the path to the left of the up-down movement trajectory of the sewing needle and a right-side route for deviating the path to the right of the up-down movement trajectory. Such lower thread path switching by the switch mechanism is performed through driving of an air cylinder. Upon determination that the moving direction of the frame holding the fabric workpiece (i.e., stitch forming direction) is a direction in which a hitch stitch is formed due to the behavior of the lower thread, the switch mechanism switches the path of the lower thread to either the left-side route or the right-side route before the tip end of the descending sewing needle reaches the upper surface of the fabric workpiece, thereby avoiding occurrence of a hitch stitch. However, the invention described in Patent Literature 3 presents a problem that the construction is complicated, because it is necessary to provide the air-cylinder-driven switch mechanism.
Further, Patent Literature 4 identified below discloses an invention constructed to avoid occurrence of hitch stitches due to behavior of the upper thread and the lower thread. The invention described in Patent Literature 4 includes upper thread control means (needle bar pivoting mechanism) that controls a relationship of the upper thread with the sewing needle and lower thread control means (thread drawing mechanism) that controls a relationship of the lower thread with the sewing needle. With such arrangements, this prior art avoids occurrence of hitch stitches by controlling the individual control means in accordance with the moving direction of the fabric workpiece. Because the needle bar pivoting mechanism as the upper thread control means and the thread drawing mechanism as the lower thread control means each have a complicated construction, this prior art presents a problem that the overall construction of the sewing machine is complicated. Furthermore, in a multi-needle sewing machine where one machine head has a plurality of needle bars, such a complicated construction becomes an even more serious problem.
Furthermore, Patent Literature 5 identified below discloses a sewing machine capable of sewing by individually turning a machine head and a rotary hook housing section. This prior art sewing machine is constructed to achieve enhanced sewing quality by appropriately synchronizing the respective operations of the sewing needle and the rotary hook and respective turning of the machine head and rotary hook housing section. However, this sewing machine presents a problem that the construction is complicated because it has to include a mechanism for turning the machine head and the rotary hook housing section and means for synchronizing the respective operations of these components. The construction described in Patent Literature 5 may be suited for linearly sewing in a given direction, such as sewing running stitches; however, with the construction described in Patent Literature 5, synchronization control is very difficult to perform in the case of embroideries, such as a satin stitch embroidery, where the stitching direction may be reversed, because the turning directions of the machine head and the rotary hook housing section have to be reversed stitch by stitch and the stitching direction, too, changes.
In view of the foregoing prior art problems, it is one of the objects of the present invention to provide a sewing machine that can avoid occurrence of a hitch stitch by use of a construction and control simpler than the conventionally known counterparts and to provide a presser foot device that holds down a sewing workpiece (fabric workpiece) in place and that also has a construction suited for avoiding occurrence of a hitch stitch.
According to a first aspect, the present invention provides a sewing machine and a presser foot device suited for avoiding occurrence of a hitch stitch due to behavior of an upper thread. To accomplish this object, the sewing machine of the present invention includes: a sewing mechanism that performs sewing on a sewing workpiece by moving up and down a sewing needle with an upper thread passed therethrough and rotating a rotary hook, having a lower thread housed therein, in synchronism with the up-and-down movement of the sewing needle to thereby entwine the upper thread around the lower thread; a feed mechanism that displaces a holding member, holding the sewing workpiece, relative to a needle drop position to thereby cause a stitch to be formed in a desired direction on the sewing workpiece; and a pressing member that holds down the sewing workpiece in place around the needle drop position. The sewing machine of the present invention is characterized by including: a guide member provided at the lower end of the pressing member, the guide member having an opening section formed therein in such a manner as to enable the upper thread to pass therethrough substantially in a rotating direction of the rotary hook, the guide member also having a restricting section provided thereon in such a manner as to restrict movement of the upper thread in a direction opposite to the rotating direction of the rotary hook; determination means that determines whether or not a next-stitch forming direction belongs to a predetermined area in which a hitch stitch is undesirably formed; and control means that, upon determination that the next-stitch forming direction belongs to the predetermined area, performs detouring movement of the holding member by actuating the feed mechanism, the detouring movement of the holding member including moving the holding member in such a direction as to cause the upper thread, extending downward from the sewing needle, to move out of the opening section of the guide member and then moving the holding member to a target position corresponding to the next stitch in such a manner that the upper thread having moved out of the opening section abuts against the restricting section.
To be more specific, the rotating direction of the rotary hook is a rotating direction of an outer rotary hook in which a loop of the upper thread is captured (hooked) by a hook point of the rotating outer rotary hook within the rotary hook. Because the rotating direction of the rotary hook is usually the counterclockwise direction, a moving direction of the hook point of the outer rotary hook at the time of capturing the upper thread loop is counterclockwise; such a counterclockwise moving direction of the hook point can be said to be leftward as viewed from the front of the sewing machine. Because the opening section of the guide member is formed in such a manner as to allow the upper thread to pass therethrough substantially in the rotating direction of the rotary hook, the opening section is located to the left of a trajectory of the up-and-down movement (i.e., an up-and-down movement trajectory) of the sewing needle.
As conventionally known, an area in which a hitch stitch is undesirably formed is predictable in relation to a direction of the passage of the upper thread through the eye hole of the sewing needle and on the basis of a moving direction of the sewing workpiece (fabric workpiece) at the time of stitch formation (i.e., stitch forming direction, and the like. Thus, as in the conventionally known technique, the determination means in the present invention can determine whether or not the next-stitch forming direction belongs to the area in which a hitch stitch is undesirably formed. Note that a typical example of the direction of the passage of the upper thread through the eye hole of the sewing needle is, as commonly known, a direction in which the upper thread, paid out downward from an upper thread bobbin, enters the eye hole from the front of the sewing needle and passes rearward through the eye hole to connect to the sewing workpiece (fabric workpiece). In such a typical example, a hitch stitch is undesirably formed due to the behavior of the upper thread when the upper thread twines around the sewing needle in a rightward twining direction, namely in a clockwise twining direction, as noted above. Thus, as an example, when the moving direction of the holding member for forming the next stitch is such a direction as to cause the upper thread to twine around the sewing needle in the rightward twining direction (namely, clockwise direction), the determination means can determine that the next-stitch forming direction belongs to the predetermined area in which a hitch stitch is undesirably formed.
The moving direction of the holding member to a next stitch position (target position) when the upper thread twines around the sewing needle in the clockwise direction is substantially rightward. As well known, the detouring movement of the holding member consists of moving the holding member to the target position while causing the holding member to take a detour such that the upper thread twines around the sewing needle in a leftward twining direction, namely in a counterclockwise twining direction, instead of moving the holding member directly to the target position. In the conventionally known technique, where control for avoiding occurrence of a hitch stitch due to the behavior of the upper thread is performed only by detouring movement control of the holding member, it is necessary to exactly match the time of the moving-down or descending of the sewing needle and the time of the detouring movement of the holding member for entwining the upper thread around the sewing needle in the counterclockwise direction. As a matter of fact, however, such exact operating time matching is extremely difficult to achieve, and thus, the conventionally known technique cannot reliably avoid occurrence of a hitch stitch.
By contrast, by use of the guide member constructed in the aforementioned manner and provided at the lower end of the pressing member, the present invention can compulsorily entwine the upper thread, extending downward from the eye hole of the sewing needle to the sewing workpiece below, around the restricting section of the guide member in the counterclockwise direction when the detouring movement control of the holding member is performed. Namely, in the present invention, the detouring movement control of the holding member is performed with the sewing needle held in a jumped state (i.e., temporarily stopped at an upper position), and this detouring movement control first moves the holding member in such a direction as to cause the upper thread, extending downward from the sewing needle, to move out of the opening section of the guide member (i.e., moves the holding member in the leftward direction). Thus, the upper thread, extending downward from the sewing needle, is guided via the opening section, provided in the guide member, to move out of the opening section (i.e., move further leftward). Then, the detouring movement control moves the holding member to the next stitch position (target position) in such a manner that the upper thread having moved out of the opening section abuts against the restricting section; thus, the upper thread, having been guided to move outward (further leftward) via the opening section can be entwined around the restricting section in the counterclockwise direction.
Then, as the sewing needle pierces through the sewing workpiece to further descend to the rotary hook, the upper thread, having been entwined around the restricting section in the counterclockwise direction, descends together with the piercing sewing needle although the pressing member (guide member) remains on the sewing workpiece, so that the upper thread enters the rotary hook while being located to the left of the sewing needle (while being entwined around the sewing needle in the counterclockwise direction). In this state, the upper thread loop is captured by the hook point of the outer rotary hook within the rotary hook, and the upper thread loop is entwined with the lower thread in a conventionally known manner by a combination of the rotation of the rotary hook and ascending movement of the sewing needle, so that a stitch is formed. Because the upper thread, having moved out of the eye hole of the sewing needle, enters the rotary hook with the upper thread located to the left of the sewing needle (entwined around the sewing needle in the counterclockwise direction), the above-mentioned stitch is formed as a perfect stitch; in this way, the inventive sewing machine can avoid occurrence of a hitch stitch.
Namely, according to the first aspect of the present invention, the control for avoiding the occurrence of a hitch stitch due to the behavior of the upper thread is performed not only by the detouring movement control of the holding member but also with an assistance of a structural action of the guide member provided at the lower end of the pressing member, and thus, it is not necessary to exactly match the time of the descending movement of the sewing needle and the time of the detouring movement of the holding member during the detouring movement control of the holding member. As a result, the present invention achieves a superior benefit that it can avoid occurrence of a hitch stitch through simple control much more reliably than the conventionally known technique.
According to one embodiment of the present invention, when the control means performs the detouring movement of the holding member in order to avoid occurrence of a hitch stitch due to the behavior of the upper thread, a degree or amount of the detouring movement of the holding member may be differentiated in accordance with an area to which the next-stitch forming direction belongs. Namely, in one embodiment, the above-mentioned predetermined area includes first and second areas, the determination means may determine to which of the first and second areas the next-stitch forming direction belongs, and the control means may perform the detouring movement in such a manner that the amount of detour is larger when the determination means determines that the next-stitch forming direction belongs to the second area than when the determination means determines that the next-stitch forming direction belongs to the first area. Further, in a case where the sewing machine is of a type that includes a jump mechanism for jumping the needle bar, the control means may perform jump control of the needle bar via the jump mechanism at the time of the detouring movement. Further, the control means may perform the jump control once (one time) or twice (two times) in accordance with which of the first and second areas the next-stitch forming direction belongs to. A necessary amount of the detour may differ between the different areas; namely, there is an area in which occurrence of a hitch stitch can be avoided by causing the holding member to detour by a relatively small detour amount, and there is another area in which occurrence of a hitch stitch can be avoided by causing the holding member to detour by a relatively large detour amount. Furthermore, time required for the detouring movement of the holding member, too, differs depending on the detour amount. Thus, by changing the detour amount of the holding member depending on the area, it is possible to achieve efficient detouring movement control of the holding member and avoid occurrence of a hitch stitch due to the behavior of the upper thread much more appropriately and efficiently.
Further, in one embodiment of the present invention, the sewing machine may include setting means that sets conditions for the detouring movement to be performed by the control means. As an example, the setting of the conditions by the setting means may include setting whether performing the detouring movement of the holding member by the control means is to be made valid or not; in this case, when it has been set that performing the detouring movement is to be made valid, the detouring movement of the holding member may be performed by the control means. In this manner, ON/OFF of the detouring movement of the holding member by the control means can be set. By setting the detouring movement of the holding member to valid (ON), the detouring movement is performed; thus, occurrence of a hitch stitch due to the behavior of the upper thread can be avoided, with the result that the sewing quality can be enhanced. However, in such a case, an overall production efficiency of the sewing tends to inevitably decrease because extra time is required for the detouring movement of the holding member. Depending on an intended or desired sewn product, it may sometime be more preferable to avoid a decrease of the production efficiency than to avoid degradation of the sewing quality due to occurrence of a hitch stitch. Further, a user may sometimes want to select whether or not to perform the detouring movement control of the holding member, depending, for example, on a type and/or the like of the sewing workpiece (fabric workpiece) or the upper thread. Furthermore, a degree of demand for avoiding occurrence of a hitch stitch may differ between simple straight sewing and complicated embroidery sewing. For these various possible cases, it is useful and beneficial to have a function of setting the detouring movement of the holding member to invalid (OFF), namely a function of selecting between validation (ON) and invalidation (OFF) of the detouring movement of the holding member.
As another example, the setting of the conditions by the setting means may include variably setting a range of the above-mentioned predetermined area; in this case, the determination means may determine whether or not the next-stitch forming direction belongs to the variably set range of the predetermined area, and the control means may perform the detouring movement of the holding member upon determination that the next-stitch forming direction belongs to the variably set range of the predetermined area. Generally, it is difficult to precisely demarcate an area in which a hitch stitch is undesirably formed, and thus, to be on the safe side, it is preferable to perform the detouring movement control of the holding member after setting the predetermined area to a somewhat wider range. However, if the predetermined area is set to a somewhat wider range like this, the overall production efficiency may undesirably decrease as the number of times the detouring movement control of the holding member is performed increases. Further, depending on a desired or intended sewn product, there may arise a case in which the user or the like wants to avoid a decrease of the production efficiency as much as possible by allowing or tolerating occurrence of a hitch stitch in sewing of a part of the sewing workpiece for which it is not necessary to give high priority to the quality of stitches. Further, there may also arise a case in which the user or the like wants to variably set the range of the predetermined area in accordance with a type and/or the like of the sewing workpiece (fabric workpiece) or the upper thread without fixing the range of the predetermined area. For these various possible cases, it is useful and beneficial to have the function of variably setting the range of the predetermined areas for which the detouring movement control of the holding member is to be performed.
In relation to the aforementioned first aspect, the scope of the present invention can be understood also as a component part of a sewing machine, namely as a presser foot device for the sewing machine that is provided with a pressing member and a guide member constructed in the aforementioned manner.
Further, according to a second aspect of the present invention, there is provided a sewing machine which includes, in addition to the aforementioned arrangements according to the first aspect, a construction for avoiding occurrence of a hitch stitch due to behavior of the lower thread and thus can avoid occurrence of any types of hitch stitches and can form perfect stitches over an entire range of stitching directions. Namely, according to the second aspect of the present invention, there is provided a sewing machine which can form stitches as perfect stitches over the entire range of stitching directions, namely can achieve “all-perfect-stitch” sewing.
One embodiment of the sewing machine according to the second aspect of the present invention includes, as a component for avoiding occurrence of a hitch stitch due to the behavior of the lower thread, a needle plate as set forth below. As well known in the art, the needle plate of the sewing machine has a needle hole for passage therethrough of the sewing needle moving up and down, and the needle plate is fixedly provided above the rotary hook. The needle plate disclosed in the present application has a guide hole provided near the front surface of the sewing machine and in communication with the needle hole, and the guide hole is located at a position deviated from the up-and-down movement trajectory of the sewing needle substantially in the rotating direction of the rotary hook. The needle plate provided in the in the inventive sewing machine further has a groove portion provided in front of the needle hole and extending from the guide hole in a direction opposite to the rotating direction of the rotary hook, and the groove portion opens upward and at its part leading to the guide hole and the other portions of the groove portion are defined by a bottom surface and side walls. With such arrangements, the lower thread, having moved out of the rotary hook to extend upward, can be guided to the front of the needle hole through the guide hole and via the groove portion.
Depending on a moving direction of the sewing workpiece at the time of stitch formation (stitch forming direction), double hitch stitches may occur in some area due to the behavior of the lower thread, even if occurrence of a hitch stitch due to the behavior of the upper thread can be avoided. Such double hitch stitches are caused by a path of the lower thread, extending from the rotary hook toward the needle hole of the needle plate, being located behind the up-and-down movement trajectory of the sewing needle, while the sewing needle drops with the upper thread entwined around the sewing needle in the counterclockwise direction. The needle plate constructed in the aforementioned manner avoids occurrence of double hitch stitches due to the behavior of the lower thread, by structurally forcing the path of the lower thread, extending from the rotary hook toward the needle hole of the needle plate, to be located in front of the up-and-down movement trajectory of the sewing needle.
The aforementioned guide hole is located at a position deviated from the up-and-down movement trajectory of the sewing needle substantially in the rotating direction of the rotary hook (leftward direction), and the groove portion is provided in front of the needle hole and extending from the guide hole in the direction (rightward direction) opposite to the rotating direction of the rotary hook, as noted above. Thus, the lower thread is guided to the guide hole as the holding member is moved substantially leftward by the detouring movement control of the holding member. Then, as the holding member is moved substantially rightward to a target position, the lower thread is guided from the guide hole substantially rightward along the groove portion. During that time, the lower thread is received by and kept in engagement with the opposite side walls of the groove portion and thus kept located in front of the up-and-down movement trajectory of the sewing needle without being shifted rearward of the up-and-down movement trajectory of the sewing needle. By the path of the lower thread, extending from the rotary hook toward the needle hole of the needle plate, being kept located in front of the up-and-down movement trajectory of the sewing needle without being shifted rearward of the up-and-down movement trajectory as noted above, occurrence of double hitch stitches can be avoided. Further, because the groove portion has the bottom surface, the upper thread loop, moving upward along the lower thread, can be prevented from getting caught in the groove portion, and thus can be prevented from being cut or broken. Furthermore, because the lower thread is merely received or engaged by the side walls of the groove portion, the lower thread easily comes free or disengage from the groove portion to get back to a normal path as being pulled up in accordance with the upper thread ascending, so that no bad influence is given to the lower thread path at the time of next stitch formation.
Another embodiment of the sewing machine according to the second aspect of the present invention includes a rotary hook as set forth below as a component for avoiding occurrence of a hitch stitch due to the behavior of the lower thread. As well known, the rotary hook of the sewing machine includes a bobbin case rotatably housing a lower thread bobbin having the lower thread wound thereon, an inner rotary hook housing the bobbin case, and an outer rotary hook that rotates around the inner rotary hook in synchronism with the up-and-down movement of the sewing needle, and the inner rotary hook has a needle drop hole formed in an upper front surface portion thereof. The rotary hook disclosed in the present application has a recessed portion formed in the upper front surface portion and at a position deviated from the needle drop hole substantially in the rotating direction of the outer rotary hook, and the recessed portion opens forward and upward and downward and has a rear wall surface. The bobbin case has a thread take-up member provided thereon for directing the lower thread, paid out from the lower thread bobbin, toward the recessed portion of the inner rotary hook, and the lower thread paid out from the lower thread bobbin within the bobbin case is pulled out upward after passing through a hollow space of the recessed portion by way of the thread take-up member.
With such arrangements, the path of the lower thread, extending from the rotary hook to connect to the sewing workpiece above after passing through the needle hole of the needle plate, is caused to be located to the left of the up-and-down movement trajectory of the sewing needle (needle drop position) after passing through the recessed portion of the rotary hook. Namely, the lower thread paid out from the lower thread bobbin is directed, by the thread take-up member, to the recessed portion of the inner rotary hook and then directed to the needle hole of the needle plate after passing through the recessed portion. Because the recessed portion is formed at the position deviated from the needle drop position substantially in the rotating direction of the outer rotary hook (i.e., at a position to the left of the up-and-down movement trajectory of the sewing needle), the path of the lower thread, extending from the rotary hook toward the needle hole, is located to the left of the up-and-down movement trajectory of the sewing needle. In this manner, it is possible to prevent the path of the lower thread, extending from the rotary hook toward the needle hole, from being located to the right of the up-and-down movement trajectory of the sewing needle and thus reduce occurrence of a hitch stitch.
First, with reference to
A base point C located at the center of the diagram represents a current needle drop position (i.e., a position of a needle hole of a needle plate in a sewing machine). Several arrows extending from the base point C denote examples of stitching directions from the base point C to next needle drop positions (i.e., next-stitch forming directions). As well known in the art, a stitching direction of each stitch can be set as desired within an angle range of 360°; typically, the stitching direction of each stitch depends on a sewing pattern. For convenience, in
Further, in
An entire range of the stitching directions can be divided into several areas α to δ according to quality of stitches that are formed in accordance with the stitching directions. The area α is an area to which the stitching directions in which perfect stitches are formed (i.e., perfect-stitch forming directions) belong, and which covers approximately from about 270° to 360° (0°) and to about 85°. As indicated in the sewing needle pictures depicted in overlapping relations to the arrows in this area α, the sewing needle drops with the upper thread, passing from the eye hole of the sewing needle to the fabric workpiece in response to the movement of the holding member (frame), located to the left of the sewing needle, and thus, stitches formed in this area are the perfect stitches. The areas β to δ other than the area α depicted as a blank or white area in
Now, with reference to
A machine shaft 13 is passed through the machine arm 7, and as the main shaft 13 is rotated via a not-illustrated main shaft motor, a needle bar driving member 15 is moved up and down along a base shaft 16 via a not-illustrated cam mechanism, a link 14, and the like provided within the machine arm 7. The needle bar driving member 15 is constructed to engage with a locking pin 17a of a needle bar connecting stud 17 fixed to a predetermined position of the needle bar 9, and the needle bar driving member 15 is switchable between a catch position for catching the needle bar 9 and a non-catch position. In the catch position, the needle bar driving member 15 engages with the locking pin 17a of the needle bar connecting stud 17 as illustrated in
The needle bar 9 selected to be positioned at the operating position is moved up and down, in response to ascending and descending movement of the needle bar driving member 15, while being caught by the needle bar driving member 15. In the course of the up-down movement of the needle bar 9 positioned at the operating position, the sewing needle 11 mounted at the distal end of the needle bar 9 is passed through a needle hole 19a of a needle plate (or throat plate) 19, so that the sewing operation is performed in the well-known manner. Once the above-mentioned jump mechanism is actuated by being driven by the jump motor (not illustrated), the needle bar driving member 15 is set in the non-catch position in such a manner that the needle bar 9 is shifted to a jumped state and held at the top dead point as noted above without being caught by the needle bar driving member 15.
A lifting rod 20 is provided, behind a respective one of the needle bars 9, in the needle bar case 8 in such a manner that the rod 20 is movable up and down. The lifting rod 20 has an axis extending in the up-down direction (vertical direction) similarly to the needle bar 9, and a presser foot device 21 is provided at the lower end of each of the lifting rods 20. Such a presser foot device 21 functions to press and hold down the sewing workpiece in place from above in response to the descending movement of the sewing needle 11, and the presser foot device 21 includes a pressing member 22 and a guide member 23 as will be set forth in detail later. The pressing member 22 is mounted to the lower end of the lifting rod 20, and the guide member 23 is mounted to the lower end of the pressing member 22. One of the lifting rods 20 that corresponds to the needle bar 9 selectively set at the operating position is driven by a fabric pressing motor 24 provided on the machine frame 7, and a link mechanism 25 is connected to the fabric pressing motor 24. As the fabric pressing motor 24 is reciprocatively rotated, a fabric pressing driving member 26 provided on the machine frame 7 is moved up and down via the link mechanism 25. The fabric pressing driving member 26 is constructed to engage with a locking pin 27a of a lifting rod connecting stud 27 fixed to a predetermined position of the lifting rod 20. The locking pin 27a of one of the lifting rods 20, provided in the needle bar case 8, that corresponds to the needle bar 9 selectively set at the operating position engages with the fabric pressing driving member 26, and thus, the lifting rod 20 is moved up and down in its axial direction, together with the presser foot device 21 (the pressing member 22 and the guide member 23), in response to the ascending/descending movement of the fabric pressing driving member 26. When the needle bar 9 is to be jumped by the above-mentioned jump mechanism, the fabric pressing motor 24 is de-actuated in such a manner that the presser foot device 21 (the pressing member 22 and the guide member 23) is stopped at the predetermined upper portion (top dead point).
A combination of the machine head H and the rotary hook 3 corresponding to the machine head H constitutes a sewing mechanism that moves up and down the sewing needle 11 with an upper thread passed therethrough and rotates the rotary hook 3, having a lower thread housed therein, in synchronism with the up-and-down movement of the sewing needle 11 to thereby entwine the upper thread around the lower thread for performing sewing on the sewing workpiece.
The guide member 23, which is of a substantially cylindrical shape, has a hollow portion (opening extending in the vertical direction) communicating with the through-hole 22a of the pressing member 22 in such a manner that the sewing needle 11 having passed through the through-hole 22a can pass through the hollow portion of the guide member 23 vertically or in the up-down direction. The guide member 23 is not of a complete cylindrical shape and has an opening section (recessed section) 29 that opens to the lower end of the guide member 23 and extends over an area from a position opposed to the front left of the sewing needle 11, passing through the opening section 29, to a position opposed to the left side surface of the sewing needle 11, as viewed in front view (see also
In the guide member 23, the front edge and rear edge of the opening section 29 formed generally to the left of the sewing needle 11 correspond respectively to front and rear edge portions 23a and 23b of the guide member 23. Namely, the opening section 29 is demarcated by the above-mentioned front and rear edges, and when the upper thread takes a detour to move in another direction after having moved out the opening of the guide member 23, such detouring movement of the upper thread is restricted by the front or rear edge portion 23a or 23b of the guide member 23. Such a restricting action by the front edge portion 23a plays an important role to avoid occurrence of a hitch stitch due to the behavior of the upper thread. Therefore, a wall portion of the guide member 23 extending forward from the front edge (i.e., front edge portion 23a) of the opening section 29 will hereinafter be referred to as “restricting section 23a”. In the present embodiment, the movement of the upper thread in a direction away from the front edge of the opening section 29, formed generally to the left of the sewing needle 11, which is to be restricted by the restricting section 23a, namely by the front edge portion 23a, is generally rightward movement. Stated differently, the upper thread's movement to be restricted by the restricting section 23a is movement in a direction opposite to the rotating direction (counterclockwise direction) of the rotary hook 3. Therefore, it may be said that the restricting section 23a of the guide member 23 is provided in such a manner as to restrict the movement of the upper thread in the direction opposite to the rotating direction of the rotary hook 3.
As noted above, the opening section 29 is provided to open to the lower end of the guide member 23. Thus, the restricting section 23a defining the front edge of the opening section 29 is provided in such a manner as to restrict the movement of the upper thread, passing through the opening section 29, in the direction opposite to the rotating direction of the rotary hook 3 until the upper thread reaches the lower end of the guide member 23. Thus, the upper thread in the state of being restricted by the restricting section 23a is caused to move along the restricting section 23a to the lower end of the guide member 23 in response to the descending of the sewing needle 11. Then, by passing downward through the opening section 29, the upper thread is released from the restriction by the restricting section 23a. Once the upper thread is released from the restriction by the restricting section 23a, the upper thread twines around the sewing needle 11 in the counterclockwise direction (i.e., in the rotating direction of the rotary hook 3). As an example, the restricting section 23a of the guide member 23 is provided to extend over a suitable area extending forward from the front edge of the opening section 29. As will be described in detail later, the restricting section 23a of the guide member 23 is provided for preventing the upper thread from being located to the right of the sewing needle 11 (in other words, for causing the upper thread to twine around the sewing needle 11 in the counterclockwise direction) when the sewing needle 11 pierces the sewing workpiece, in order to avoid occurrence of a hitch stitch due to the behavior of the upper thread. In
In the embodiment illustrated in
Note that the guide member 23 may be of any suitable outer shape without being limited to the substantially cylindrical shape as described above.
Whereas the guide members 23 illustrated in
In the present embodiment, a novel construction is employed, in relation to the needle hole 19a of the needle plate 19, for avoiding occurrence of a hitch stitch due to the behavior of the lower thread.
In the needle plate construction according to the present embodiment, a guide hole 31 and a groove portion 32 are provided in the needle plate 19 in relation to the needle hole 19a. The guide hole 31 formed through the needle plate 19 is located near the front of the sewing machine and is in communication with the needle hole 19a. Further, the guide hole 31 is located at a position deviated from the up-and-down movement trajectory of the sewing needle 11 substantially in the rotating direction of the rotary hook 3 (i.e., deviated leftward from the up-and-down movement trajectory in
Further, the guide hole 31 is located deviated from the up-and-down movement trajectory of the sewing needle 11 substantially in the rotating direction of the rotary hook 3 (i.e., deviated leftward from the up-and-down movement trajectory) and the groove portion 32 extends, in front of the needle hole 19a, from the guide hole 31 in the direction opposite to the rotating direction of the rotary hook 3 (i.e., extends rightward from the guide hole 31), as noted above. Thus, as the frame 5 is moved generally leftward by later-described detouring movement control (or detour control) of the frame 5, the lower thread D is guided into the guide hole 31. Then, as the frame 5 is moved generally rightward to the needle drop position (target position), the lower thread D is guided from the guide hole 31 generally rightward along the groove portion 32. Because both side surfaces of the groove portion 32 are defined by the side walls 32b, the lower thread D is received or engaged by a rear side surface of the side walls 32b (i.e., rear side wall 32b) and kept in front of the up-and-down movement trajectory of the sewing needle 11 without shifting rearward of the up-and-down movement trajectory of the sewing needle 11. Because the path of the lower thread D extending from the rotary hook 3 toward the needle hole 19a of the needle plate 19 is kept in front of the up-and-down movement trajectory of the sewing needle 11 without shifting rearward of the up-and-down movement trajectory of the sewing needle 11 in the aforementioned manner, it is possible to avoid occurrence of a hitch stitch (particularly, double hitch stitches). Further, because the groove portion 32 has the bottom surface 32a, a loop of the upper thread (upper thread loop), passing through the needle hole 19a to go upward along the lower thread D while reducing the size of the loop, can be prevented from undesirably getting caught in the groove portion 32, and thus, it is possible to avoid occurrence of breakage of the upper thread. Furthermore, because the lower thread D is merely received or engaged by the rear side wall 32b, the lower thread D can readily separate from, or is readily separated or disengaged from, the groove portion 32 to return to a normal path (i.e., a path passing through the needle hole 19a) as the lower thread D is pulled up in response to the upward movement of the upper thread, and thus, formation of the path of the lower thread D at the time of next stitch formation will not be adversely influenced.
In a portion where the guide hole 31 connects to the needle hole 19a, as illustrated by way of example in the top plan view of
In the present embodiment, a novel construction is provided, in relation to the rotary hook 3, for avoiding occurrence of a hitch stitch due to the behavior of the lower thread.
Further, in an upper front surface portion of the inner rotary hook 50, a recessed portion 52 is formed at a position deviated from the needle drop hole 51 in the rotating direction R of the outer rotary hook 60. The recessed portion 52 opens forward and upward and downward and has a rear wall surface 52a that is formed to be located at a substantial limit position where the rear wall surface 52a does not interfere with a movement trajectory of a hook point 61 of the outer rotary hook 60. Because the rear wall surface 52a of the recessed portion 52 is located at the substantial limit position as noted above, the lower thread path leading from the recessed portion 52 to the sewing workpiece (i.e., changing positions of the lower thread from the recessed portion 52 toward the needle hole 19a) can be set as far rearward as possible of the needle drop position (up-and-down movement trajectory of the sewing needle), and thus, a range over which occurrence of a hitch stitch due to the behavior of the lower thread can be avoided can be expanded as much as possible. Left and right side wall surfaces of the recessed portion 52 are respectively surfaces of an upstream side wall 52b located upstream in the rotating direction R of the outer rotary hook 60 and a downstream side wall 52c located downstream in the rotating direction R of the outer rotary hook 60.
On a predetermined position of the bobbin case 40 near the upper end of the bobbin case 40 (preferably, beneath the recessed portion 52), a thread take-up member 41 is provided for directing (guiding) the lower thread, paid out from the lower thread bobbin, toward the recessed portion 52 of the inner rotary hook 50. As will be described in detail later, the lower thread, paid out from the lower thread bobbin within the bobbin case 40, is pulled upward after passing through a hollow space of the recessed portion 52 of the inner rotary hook 50 via the thread take-up member 41. The lower thread having passed through the recessed portion 52 is entwined with the upper thread loop in response to the rotation of the outer rotary hook 60 as conventionally known and then moved upward through the needle hole 19a in response to the ascending movement of the sewing needle 11, thereby forming a stitch. In the aforementioned manner, the recessed portion 52 formed in the inner rotary hook 50 functions to form the path of the lower thread.
With the above-described rotary hook construction, the path of the lower thread leading from the rotary hook 3 to the sewing workpiece, located above the rotary hook 3, through the needle hole 19a of the needle plate 19 is caused to be located to the left of the up-and-down movement trajectory of the sewing needle 11 (needle drop position) after passing through the recessed portion 52 provided in the upper front surface portion of the inner rotary hook 50. Namely, the lower thread paid out from the lower thread bobbin is directed by the thread take-up member 41 to the recessed portion 52 of the inner rotary hook 50 and then directed to the needle hole 19a of the needle plate 19 after passing through the recessed portion 52. Because the recessed portion 52 is formed at the position deviated from the needle drop hole 51 in the rotating direction R of the outer rotary hook 60 (i.e., located to the left of the up-and-down movement trajectory of the sewing needle 11) and the rear wall surface 52a of the recessed portion 52 is formed at the substantial limit position where the rear wall surface 52a does not interfere with the movement trajectory of the hook point 61 of the outer rotary hook 60 as noted above, the path of the lower thread leading from the rotary hook 3 toward the needle hole 19a is located to the rear left of the up-and-down movement trajectory of the sewing needle 11. In this way, it is possible to prevent the path of the lower thread, leading from the rotary hook 3 toward the needle hole 19a, from being located to the right of the up-and-down movement trajectory of the sewing needle 11 and thereby reduce occurrence of hitch stitches.
A further description will be given about the aforementioned arrangements with reference to
For example, in a case where the stitching direction belongs to the area δ of
Preferably, a construction for locking the lower thread at the time of thread cutting may be provided on the downstream side wall 52c of the recessed portion 52. As illustrated in
Next, a description will be given about examples of further improvements of the inner rotary hook 50 and the outer rotary hook 60. As known in the art, the outer rotary hook 60 has, on its outer periphery, the hook point 61 for capturing a loop of the upper thread pulled out of the eye hole 11a of the sewing needle 11. Further, a thread dividing spring (i.e., upper spring part) 62 is fixed to the outer peripheral surface of the outer rotary hook 60 by use of a screw. A distal end portion 62a of the thread dividing spring 62 is formed in a claw shape for guiding the upper thread loop captured by the hook point 61. Further, a front end edge (i.e., front side edge) 62b of the thread dividing spring 62 is formed to be located behind the rear wall surface 52a of the recessed portion 52 in the inner rotary hook 50, as illustrated in
The conventionally known thread dividing spring is shaped to have a projecting portion (fin portion) which extends in the rotating direction of the outer rotary hook and whose front edge end projects forward for pushing forward the upper thread loop captured in response to the rotation of the outer rotary hook. With the front edge end of the thread dividing spring projecting forward like this, the lower thread, directed from the rotary hook toward the needle hole, is also pushed forward, and thus, slackness may occur in the lower thread.
By contrast, in the present embodiment, no such projecting portion (fin portion) is formed on the front end edge 62b of the thread dividing spring 62, therefore, the thread dividing spring 62 does not contact the lower thread guided by the recessed portion 52 and thus slackness does not occur in the lower thread. Namely, in the present embodiment, the thread dividing spring 62 does not push forward the upper thread loop, and thus, the thread dividing spring 62 is referred to more generically as “upper spring part”.
Instead of providing a projecting (fin) portion on the front end edge 62b of the thread dividing spring (upper spring part) 62, the inner rotary hook 50 in the present embodiment has an improved construction as described hereinbelow. As illustrated in
As denoted by two-dot chain lines in
Further, a description will be given about an example of the bobbin case 40 with reference to
The thread take-up member 41 is provided on an upper front surface portion of the bobbin case 40, and more specifically, the thread take-up member 41 is located at a position beneath the opening 42a and deviated a little to the left of the bobbin case 40. As a preferred example, the thread take-up member 41 is in the form of a spring so as to impart tension to the lower thread paid out from the lower thread bobbin and directed toward the hollow space of the recessed portion 52. For this reason, the thread take-up member 41 will hereinafter be referred to also as “thread take-up spring”. The thread take-up spring (thread take-up member) 41 has a ring portion 41a of an annular or curved shape for passing therethrough (or catching) the lower thread paid out from the lower thread bobbin, and the lower thread passed through the ring portion 41a is directed toward the hollow space of the recessed portion 52 of the inner rotary hook 50. The tension imparted by the thread take-up spring 41 functions to not only appropriately guide the lower thread, which is on its way to the needle hole 19a, to pass through the recessed portion 52 (i.e., regulates the path of the lower thread so as to pass through the recessed portion 52) but also absorb slackness occurring in the lower thread. The thread take-up spring 41, which extends generally horizontally on and along the front surface of the bobbin case 40, is fixed at one end (right end), opposite from the above-mentioned ring portion 41a, to the bobbin case 40, and the ring portion 41a constitutes a free end of the thread take-up spring 41. The ring portion 41a is located substantially immediately below the recessed portion 52 of the inner rotary hook 50 and is swingable in the up-down and left-right directions by resilient restoring force of the spring in response to movement of the lower thread passed through the ring portion 41a. In one implementation, a length from the fixed end (right end) of the thread take-up spring 41 to the other end adjoining the ring portion 41a (left end) is relatively long as illustrated in the figures. Thus, a swing range (stroke range) of the thread take-up spring 41 can be made relatively large, so that relatively large slackness of the lower thread can be absorbed. The thread take-up member 41 constituted by a spring member as set forth above can not only function to reliably guide the lower thread toward the recessed portion 52 of the inner rotary hook 50 but also function to prevent slackness of the lower thread under various conditions by imparting tension to the lower thread.
The lower thread pulled out of the pull-out hole 42b of the bobbin case 40 abuts against the thread tension spring 43, passes through the guide groove 42c, passes through the ring portion 41a of the thread take-up lever 41 to move upward, then passes through the recessed portion 52 of the inner rotary hook 50, and then moves out of the rotary hook toward the needle hole 19a. However, the present invention is not so limited, and the lower thread pulled out of the pull-out hole 42b of the bobbin case 40 may be passed through the ring portion 41a of the thread take-up spring 41 by way of the thread tension spring 43 without being passed through the guide groove 42c.
As an option, a guide member 44 may be provided in the bobbin case 40 in front of the thread take-up spring (thread take-up member) 41 as shown in
Further, the guide member 44 has an opening 44b formed in the guide surface 44a so as to extend through the guide member 44 in the front-rear direction in such a manner as to enable a distal end of a picker of a well-known construction (not illustrated) to be inserted therein. The well-known picker is a member that, at the time of cutting of the upper thread by a thread cutting device (not illustrated), holds a portion of the upper thread on the sewing needle and thereby ensures a predetermined remaining length of the upper thread so as to prevent the upper thread from slipping out of the eye hole of the sewing needle. The well-known picker has a pair of left and right distal end portions, and at the time of the thread cutting operation, the two distal end portions are inserted into the opening 42a of the bobbin case 40 to catch and hold the upper thread, passing through the rotary hook 3, and thereby ensure a predetermined (after-cutting) remaining length of the upper thread, so that the upper thread can be prevented from slipping out of the eye hole of the sewing needle. Such a picker can be applied to the present embodiment, too. In the picker (not illustrated) to be applied to the present embodiment, one of the picker's distal end portions must be formed into a length somewhat shorter than that of the conventionally known picker in order to prevent interference to the thread take-up spring 41. The guide surface 44a and the opening 44b of the guide member 44 provide a construction suited for such a special picker. Namely, with the picker set at a predetermined position in the present embodiment, the shorter distal end portion (the left distal end portion) of the picker enters the opening 44b in the guide surface 44a of the guide member 44 but does not abut against the thread take-up spring 41. Thus, when the upper thread loop moves upward along the guide surface 44a of the guide member 44 protruding forward of the thread take-up spring 41, the upper thread loop is reliably caught on the two distal end portions (i.e., caught on the shorter distal end portion as well) of the picker; in this way, it is possible to ensure a predetermined remaining length of the upper thread and thereby prevent the upper thread from slipping out of the eye hole 11a of the sewing needle 11. Note that such a guide member 44 is not necessarily essential and may be dispensed with if the sewing machine is of a type that does not include a picker.
In the present embodiment, in order to avoid occurrence of a hitch stitch due to the behavior of the upper thread, not only the guide member 23 is provided in the presser foot device 21 as set forth above, but also detour control of the frame 5 (frame detour control) is performed. This frame detour control is performed by an electric/electronic control system.
As known in the art, the sewing data of a desired pattern selected by the user are read out from the storage device 103 under the control of the CPU 101 and the drivers 104 to 108 and the like are controlled in accordance with the stitch-by-stitch sewing data, so that a sewing operation is performed to form stitches in a sequential manner. On the basis of the sewing data, a determination can be made as to whether or not a direction in which a next stitch is to be formed, namely a next-stitch forming direction, belongs to any one of the predetermined hitch-stitch forming (occurring areas) (for example, areas β to δ illustrated in
In the present embodiment, upon determination that the next-stitch forming direction belongs to any one of the predetermined hitch-stitch forming areas, detour control for moving the frame 5 in a detouring manner is performed when the frame 5 is to be moved to a target position corresponding to the next stitch, in order to avoid occurrence of a hitch stitch due to the behavior of the upper thread. Such detour control can be performed by a given program executed by the CPU 101. Namely, the CPU 101 and the given program function as means (i.e., detour control means) that, upon determination by the determination means that the next stitch forming direction belongs to any one of the predetermined hitch-stitch forming areas, performs the jump control via the jump mechanism (driver 107 and the like) and performs the detour control of the frame 5 by activating the aforementioned feed mechanism (drivers 105, 106 and the like) to perform detouring movement of the frame 5. Here, the detouring movement of the frame 5 includes moving, with the sewing needle 11 jumped upward to a predetermined upper position, the frame 5 in a particular direction such that the upper thread extending downward from the sewing needle 11 moves out of the opening section 29 of the guide member 23 of the presser foot device 21 and then further moving the frame 5 to the target position corresponding to the next stitch in such a manner that the upper thread, having moved out of the opening section 29, abuts against the restricting section 23a. Such movement of the frame 5 that causes the upper thread, having moved out of the opening section 29, to abut against the restricting section 23a of the guide member 23 is nothing but detouring movement of the upper thread where the upper thread, having moved out of the opening section 29, takes such a detour as to go by way of the restricting section 23a. Namely, the detouring movement is such movement where, with the sewing needle 11 jumped upward, the frame 5 is temporarily moved in such a direction as to cause the upper thread to move out of the opening section 29, then caused to take a detour such that the upper thread, having moved out of the opening section 29, abuts against (i.e., goes by way of) the restricting section 23a and finally moved to reach the target position corresponding to the next stitch, instead of the frame 5 being moved directly to the target position corresponding to the next stitch.
As illustrated as the typical example in
The remaining partial area of the areas β and γ to which the stitching directions in which hitch stitches are formed due to the behavior of the upper thread belong is an area in which occurrence of hitch stitch formation is avoided by causing the frame 5 to make detouring movement of a relatively large detour amount. This partial area will hereinafter be referred to as “second area S2” for convenience sake. This second area S2 includes the remaining portion of the area β and the entirety of the area γ illustrated in
In one embodiment of the present invention, the aforementioned control means may perform the above-mentioned jump control once (i.e., one time), two times or more during the detouring movement of the frame 5. In one implementation, in a case where the next-stitch forming direction belongs to the above-mentioned first area S1, the control means performs the jump control once (one time) during the detouring movement. Further, in a case where the next-stitch forming direction belongs to the above-mentioned second area S2, the control means performs the jump control two times during the detouring movement.
Next, the frame 5 is moved from the mid-point m1 to the target position T1 corresponding to the next stitch. Such movement of the frame 5 is denoted by A2 in
Then, with the sewing needle 9 kept in the jumped state, the frame 5 is moved from the first mid-point m1 to a second mid-point m2. Such movement of the frame 5 is denoted by A2 in
Then, the frame 5 is moved from the second mid-point m2 toward the target position T2 corresponding to the next stitch. Such movement of the frame 5 is denoted by A3 in
In the above-described frame detour control illustrated in
The detouring movement of the frame 5 may be performed continuously rather than intermittently as noted above.
In one embodiment of the present invention, it is preferable to take measures for preventing slackening of the upper thread during the detouring movement control (or detour control) of the frame 5. For that purpose, an upper thread slackening preventing section 200 is provided in a lower portion of the needle bar case 8. Such an upper thread slackening preventing section 200 is disposed above an upper thread locking device 400 of a well-known construction, and opposite end portions of a base plate 201 of the slackening preventing section 200 are fixed by screws to brackets that are mounted to left and right side surfaces of the needle bar case 8. Pressing pieces 203 are fastened to positions of the base plate 201, which correspond to the individual needle bars 9, by screws 202 each having a spring fitted over its stem portion. The upper surface T (not illustrated in
The above-described sewing machine of the present invention can avoid occurrence of hitch stitches due to the behavior of the upper thread and lower thread and thereby achieve all-perfect-stitch sewing in which all stitches are formed as perfect stitches over the entire range of the stitching directions.
The computer program illustrated in
At step St5, a sewing operation for one stitch is performed by moving the frame 5 to a target position corresponding to the stitch movement amount data Pn and causing the needle bar 9 to descend. The detouring movement of the frame 5 is not performed in the sewing operation of step St5. As noted above, the area S0 illustrated in
Note that when the sewing needle 11 passes through the sewing workpiece (fabric workpiece) W, the sewing workpiece may flutter in the up-down direction; thus, undesired slackening may occur in the lower thread D, and the slackened lower thread D may undesirably move rightward beyond the tip of the sewing needle 11. However, the thread take-up member 41 in the present embodiment performs a spring action as noted above; thus, even when the lower thread D has slackened due to the fluttering of the sewing workpiece W or the like, the spring action of the thread take-up member (thread take-up spring) 41 located substantially immediately below the recessed portion 52 of the inner rotary hook 50 quickly absorbs the slackness of the lower thread D. In this way, it is possible to keep the lower thread D in an appropriately taut state and thereby prevent the lower thread D from moving rightward beyond the tip of the sewing needle 11. Further, because the front end edge 62b of the upper spring part (thread dividing spring) 62 of the outer rotary hook 60 is located behind the rear wall surface 52a of the recessed portion 52 of the inner rotary hook 50 as noted above, the front end edge 62b does not push forward the lower thread D by abutting against the lower thread D. Thus, no slackening occurs in the lower thread D due to the behavior of the upper spring part (thread dividing spring) 62 of the outer rotary hook 60. In the above-described manner, the present embodiment takes all possible measures of eliminating a possibility of occurrence of a hitch stitch due to slackness of the lower thread D as well.
Referring now back to
The frame detouring movement control for the first area S1 (one-time jump control) performed at step St9 includes moving the frame 5 to the mid-point m1 with the needle bar 9 kept in the jumped state, then moving the frame 5 to the target position T1, and dropping the sewing needle 11 onto the sewing workpiece W. Details of such control will be given below with reference to
By moving the frame 5 to the mid-point m1 with the needle bar 9 kept jumped to hold the sewing needle 11 at the upper position, the frame 5 is moved as denoted by A1 in
When the eye hole 11a of the further descending sewing needle 11 has reached a position below the needle plate 19 by the further descending sewing needle 11 passing through the sewing workpiece W and the needle hole 19a of the needle hole 19, the portion of the upper thread T, connecting to the sewing workpiece W from the rear portion of the eye hole 11a of the sewing needle 11, extends upward along the left side of the sewing needle 11 to reach the sewing workpiece W after passing through the needle hole 19a of the needle plate 19. In the state where the sewing needle 11 has descended to the rotary hook 3 in the aforementioned manner, the path of the upper thread T leading from the rear portion of the eye hole 11a to the sewing workpiece W (needle hole 19a) above, is held located to the left of the sewing needle 11. In the state where the sewing needle 11 has descended into the rotary hook 3, the upper thread T having moved out from the rear portion of the eye hole 11a to extend upward is captured by the hook point 61 of the outer rotary hook 60 and moved together with the hook point 61, so that a loop of the upper thread is formed (pulled out). Then, the upper thread loop is entwined with the lower thread D through a combination of the rotation of the rotary hook 3, ascending movement of the sewing needle 11, and movement of the thread take-up lever 10; in this manner, a stitch is formed. Because the upper thread T having moved out from the rear portion of the eye hole 11a enters the rotary hook 3 while being located to the left of the sewing needle 11 (entwined counterclockwise around the sewing needle 11), the above-mentioned stitch is formed as a perfect stitch. In the above-described manner, it is possible to avoid occurrence of a hitch stitch in the first area S1 (a part of the area β).
The frame detouring movement control for the second area S2 (two-time jump control) performed at step St10 includes moving the frame 5 to the first mid-point m1 with the needle bar 9 jumped for one stitch, then moving the frame 5 to the second mid-point m2 with the needle bar 9 jumped for another one stitch, and finally moving the frame 5 to the target position T2 and then causing the sewing needle 11 to drop onto the sewing workpiece W. Details of such control will be given below with reference to
By moving the frame 5 to the first mid-point m1 with the needle bar 9 jumped for one stitch to hold the sewing needle 11 at the upper position, the frame 5 is moved at denoted by A1 in
Next, by moving the frame 5 from the first mid-point m1 to the second mid-point m2 with the needle bar 9 still kept jumped (jumped for another one stitch), the frame 5 is moved generally rightward as denoted by the trajectory A2 of
Finally, by moving the frame 5 from the second mid-point m2 to the target position T2, the frame 5 is moved as denoted by the trajectory A3 of
During the course of the movement of the further descending sewing needle 11 to the rotary hook 3 through the sewing workpiece W and the needle hole 19a, the upper thread T is placed in various states similar to those described above with reference to
As described above with reference of
With the frame 5 located at the target position T2, the sewing needle 11 descends further and then ascends, during the course of which a stitch is formed by the loop of the upper thread T twining around the lower thread D in response to the rotation of the rotary hook 3 as noted above. At this stage, the upper thread T having moved out from the rear portion of the eye hole 11a enters the rotary hook 3 with the upper thread T located to the left of the sewing needle 11 (entwined around the sewing needle 11 in the counterclockwise direction), and the path of the lower thread D pulled out of the lower thread bobbin to extend to the needle plate 19 is kept located in front of the up-and-down movement trajectory of the sewing needle 11. With such arrangements, it is possible to achieve desired sewing where occurrence of both a hitch stitch due to the behavior of the upper thread and a hitch stitch due to the behavior of the lower thread (i.e., double hitch stitches) is avoided.
Note that although the lower thread D is also pulled out in response to the detouring movement of the frame 5, slackness of the pulled-out lower thread D is absorbed promptly by the aforementioned spring action of the thread take-up member 41. Namely, in the present embodiment, even though the lower thread D is pulled out in response to the detouring movement of the frame 5, the spring action of the thread take-up member (thread take-up spring) 41 provided in the rotary hook 3 promptly absorbs slackness of the pulled-out lower thread D, and thus, the lower thread D can be kept in a taut state. Therefore, in the present embodiment, the lower thread D can be avoided from getting slackened to come off the receiving or engaging portion (groove portion 32) of the needle plate 19. Namely, in the present embodiment, the thread take-up member (thread take-up spring) 41 functions also as tension imparting means provided below the needle plate 19 for imparting tension to the lower thread pulled out upward from the rotary hook 3 to go toward the needle hole 19a or the guide hole 31 of the needle plate 19.
As well known in the art, the loop of the upper thread T captured by the hook point 61 of the outer rotary hook 60 passes through the inner rotary hook 50 and is then pulled by the thread take-up lever 10 (
By performing the operations of steps St5, St9, and St10 in accordance with the needle moving direction (i.e., the next-stitch forming direction) of the stitch movement amount data Pn, the inventive arrangements achieve desired all-perfect-stitch sewing where occurrence of hitch stitches due to the behavior of the upper thread and due to the behavior of the lower thread (i.e., all types of hitch stitches) is avoided.
Now describing the remaining steps illustrated in
According to one embodiment, the inventive sewing machine may be constructed in such a manner that various data related to the frame detour control (i.e., various conditions for the detour control) can be set and changed or modified as desired by the user.
If the user touches and thereby selects a desired one of the setting items of Nos. 21 to 30 displayed on the parameter setting screen 110, the current setting value of the selected one setting item is displayed on a display section 111. By the user operating a setting value change key 112, the current setting value of the selected setting item can be changed to increase or decrease, and the thus-varied setting value is displayed on the display section 111. By the user depressing an ENTER key 113 after the change of the setting value, the changed setting value is made effective.
The setting item “All Perfect Stitch (Apfs) Use” of No. 21 corresponds to setting means for setting whether performing the frame detouring movement control should be made valid or not. Whether performing the frame detouring movement control should be made valid or not may be set, for example, by setting “Yes” or “No”. The illustrated example denotes a state in which the setting item is set at “Yes”. In an alternative, this setting value “Yes/No” may be replaced with “ON/OFF”.
In order to actually control the validation/invalidation of the detouring movement control of the frame 5 in according with the setting of the No. 21 setting item, it is only necessary to modify a part of the flow of
By enabling such setting as to whether performing the frame detouring movement control should be made valid or not as noted above, the sewing operation can be performed in a variety of manners and with an enhanced efficiency. Although the inventive sewing machine can avoid occurrence of a hitch stitch due to the behavior of the upper thread and enhance the sewing quality by performing the detouring movement of the frame 5 as described above, an overall production efficiency of the sewing tends to inevitably decrease because extra time is required for the detouring movement of the frame 5. Depending on an intended or desired sewn product, it may sometime be more preferable to avoid a decrease of the production efficiency than to avoid degradation of the sewing quality resulting from occurrence of a hitch stitch. For example, in a case where a hidden part of a product invisible on the outer surface of the product is to be sewn, it may be considered to be more preferable to give priority to the production efficiency over the avoidance of occurrence of a hitch stitch. Further, the user may sometimes want to select whether or not to perform the detouring movement control of the frame 5, depending on a type of the sewing workpiece (fabric workpiece), a type of the upper thread, or the like. Furthermore, a degree of demand for avoiding occurrence of a hitch stitch may differ between simple straight sewing and complicated embroidery sewing. For these various possible cases, it is useful and beneficial to provide the function of selecting validation (Yes or ON) or invalidation (No or OFF) of the detouring movement of the frame 5.
The setting items of Nos. 22 to 24 are means for setting parameters a, b, and c prescribing a needle moving direction (stitch forming direction) for the frame detour control and more particularly correspond to setting means for variably setting respective ranges of the aforementioned first and second areas S1 and S2 (see
Generally, it is difficult to precisely demarcate an area in which a hitch stitch is undesirably formed, and thus, to be on the safe side, it may be preferable to perform the frame detouring movement control after setting the areas S1 and S2, for which the frame detouring movement control is to be performed, to somewhat wider ranges. However, if the areas S1 and S2 are set to somewhat wider ranges like this, the overall production efficiency may undesirably decrease as the number of times the frame detouring movement control is performed increases. Further, depending on a desired or intended sewn product, there may arise a case in which the user desires to avoid a decrease of the production efficiency as much as possible by allowing or tolerating occurrence of a hitch stitch in sewing of a sewing workpiece portion for which it is not necessary to give high priority to the quality of stitches. Further, there may arise a case in which the user desires to variably set the ranges of the areas S1 and S2, for which the frame detour control is to be performed, in accordance with a type of the sewing workpiece (fabric workpiece), a type of the upper thread, or the like, without fixing the ranges of the areas S1 and S2. For these various possible cases, it is useful and beneficial to provide the function of variably setting the ranges of the predetermined areas S1 and S2 (values of the individual boundary angles a, b, and c) for which the detouring movement control of the frame 5 is to be performed.
The setting items of Nos. 25 and 26 are means for setting parameters X1 and Y1 that define a first moving direction in the frame detour control (i.e., setting means for variably setting a detouring path of the frame 5); more particularly, the setting items of Nos. 25 and 26 correspond to setting means for variably setting an X-Y displacement coordinate position of the first mid-point m1 (see
By enabling variable setting of the parameters X1, Y1, X2, and X2 defining the moving directions in the detour control of the frame 5 as described above, the detouring path of the frame 5 can be modified as necessary, If a relatively long detouring path of the frame 5 is set, for example, the upper thread can be reliably entwined around the guide member 23 of the presser foot device 21; however, because extra time is required for the detouring movement of the frame 5 in such a case, the overall production efficiency of the sewing decreases. If a relatively short detouring path of the frame 5 is set, on the other hand, the detouring movement of the frame 5 does not take much time, and thus, the overall production efficiency of the sewing can be enhanced. Therefore, the aforementioned setting means of the inventive sewing machine are useful and beneficial because they enable setting of an appropriate detouring path of the frame 5 in consideration of to which of the sewing quality and the production efficiency should be given priority.
Further, the setting items of Nos. 29 and 30 are means for setting an effective minimum stitch length and an effective maximum stitch length that are applied to the above-described frame detour control. The effective minimum stitch length is a minimum value of the stitch length that is applicable to the frame detour control, while the effective maximum stitch length is a maximum value of the stitch length that is applicable to the frame detour control. 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 increasing or decreasing a desired one of these initially-set values as necessary, it is possible to set a user-desired effective minimum stitch length or maximum stitch length. In a case where such setting is to be applied to the frame detour control, the frame detour control may be performed if the length of a stitch to be formed next (next stitch length) is within a range between the set effective minimum stitch length and effective maximum stitch length. For example, a step of determining whether the length of the stitch to be formed next is within the range between the set effective minimum stitch length and effective maximum stitch length may be inserted between step St3 and step St4 of
It should be noted that the construction (or configuration) for enabling the setting of various data related to the frame detour control (i.e., various conditions for the detour control) in the inventive sewing machine is not limited to the above-described construction or configuration where various data are set by user's manual operations via the operation panel 6 of the sewing machine as described above. Namely, an alternative construction may be employed such that at the time of making a desired sewing pattern program or embroidery pattern program, various data related to the frame detour control may be set as desired as detour controlling program data and prestored together with the sewing pattern program or embroidery pattern program. Such a construction in which the various data related to the frame detour control (i.e., conditions for the detour control) are supplied as such programmed data may also be employed in an embodiment of the setting means for variably setting the various data related to the frame detour control (conditions for the detour control).
Note that whereas the above-described embodiments are constructed in such a manner that when the detour control of the frame 5 is to be performed, the needle bar jump control by the jump mechanism is performed together with the frame detour control, the present invention is not so limited, and the present invention may also be practiced in a type of sewing machine that is not provided with the jump mechanism that performs the jump control of the needle bar. In order to perform the detour control of the frame 5 in such a sewing machine not provided with the jump mechanism, it is only necessary to control the operation of the needle bar in such a manner that the sewing needle does not drop during the detouring movement of the frame 5. For example, by reducing the rotation speed of the main shaft 13 during the detouring movement of the frame 5, the needle bar can be controlled in such a manner as to prevent the sewing needle from dropping during the detouring movement of the frame 5.
The embodiments of the present invention have been described above in relation to the case where the present invention is applied to a multi-head and multi-needle type sewing machine. However, the present invention should not be construed as being so limited, and the present invention may also be applied to a single-head type sewing machine or a single-needle type sewing machine. Furthermore, the present invention is applicable to both an embroidery sewing machine and an ordinary sewing machine. In addition, the holding member (or frame) for holding the sewing workpiece in the present invention is not limited to a flat plate type and may be a rotary type like a hat/cap frame. What is more, the rotary hook in the present invention is not limited to a full-rotation vertical rotary hook (DB type) and may be of any other desired type, such as a horizontal rotary hook or a half rotary hook. Furthermore, depending on the type, rotating direction and the like of the rotary hook employed, the areas in which a hitch stitch is undesirably formed may differ from the areas described above in relation to the embodiments of the present invention. In order to deal with such an area difference, it is only necessary to make appropriate modifications that may include making area determinations corresponding to the different areas, modifying the needle bar construction according to the different areas (for example, changing the positions of the guide hole 31 and the groove portion 32), or modifying the rotary rook construction (for example, changing the position of the recessed portion 52) according to the different areas.
What is more, the operation panel 6 employed in the present invention may be either mounted fixedly to the sewing machine or mounted removably to the sewing machine. As a modification, the above-described setting means (i.e., setting device) for manually setting various conditions for the detour control may be implemented by a portable-type operation panel (such as a mobile computer or a mobile terminal) constructed to enable manual setting of various conditions for the detour control as described above with reference to
| Number | Date | Country | Kind |
|---|---|---|---|
| 2021-161554 | Sep 2021 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2022/011961 | 3/16/2022 | WO |
