JP2012165849A - Sewing machine and thread cutting method for sewing machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sewing machine and a thread cutting method for a sewing machine that can avoid an increase in power consumption when cutting a thread.SOLUTION: After a thread cutting signal is input, a reverse solenoid is turned on at a timing of t5 to reverse a fabric feed direction. Then, at a timing of t8, a thread cutting solenoid is turned on to cut a needle thread and a bobbin thread. That is to say, the needle position for a last stitch of a seam is put on a position equivalent to the needle position for a second last stitch, and then the needle thread and the bobbin thread are cut. Thereby, it is possible to make even the remaining lengths of the needle thread and the bobbin thread remaining at the end of the seam at a back side of the fabric after cutting thread. Further, since the thread cutting solenoid is turned on after the reverse solenoid is turned off, an ON period of the reverse solenoid and an ON period of the thread cutting solenoid are not overlapped with each other. Thus, it is possible to avoid an increase in power consumption when cutting a thread.

Description

  The present invention relates to a sewing machine and a thread trimming method for the sewing machine.

  There is a sewing machine that automatically performs thread trimming by an operator's operation. The sewing machine cuts the sewing thread composed of the upper thread and the lower thread below the sewing product in a state where the needle is raised from the lower stop position and the needle is in the raised position from the needle plate. In a sewing machine that performs thread trimming of the sewing thread with the cloth feeding direction set to the normal feeding direction, the thread trimming process is performed in the middle of forming the stitch. Therefore, both the upper thread and the lower thread are cut and a stitch cannot be formed. The length of the lower thread out of the sewing thread remaining on the back of the fabric of the sewn product is longer than the upper thread by one stitch, and the quality of the sewn product is deteriorated due to poor appearance. In order to align the remaining lengths of the upper thread and the lower thread, the operator needs to remove the sewing thread remaining on the back of the fabric by hand-kneading. Patent Document 1 discloses a thread trimming method for an automatic thread trimming sewing machine that converts a cloth feed of a sewing machine in a forward feed direction into a reverse feed having a feed amount smaller than that of the forward feed, and has stitches in the reverse feed direction of the first stitch or more. After the formation, the sewing thread is cut below the sewing product in a state where the needle is in the raised position from the needle plate.

JP-A-1-320087

  The automatic thread trimming machine described in Patent Document 1 converts the cloth feed into the reverse feed immediately after the operator performs the thread trimming operation, and performs the thread trimming during the reverse feed. The timing for driving the mechanism that reversely feeds cloth partially overlaps the timing for driving the mechanism that performs thread trimming. Therefore, since the power consumption increases when the driving time overlaps, it is necessary to enlarge the power supply board.

  An object of the present invention is to provide a sewing machine that can avoid an increase in power consumption during thread trimming and a thread trimming method for the sewing machine.

  The sewing machine according to the first aspect of the present invention includes a sewing needle that moves up and down, a needle plate that has a hole through which the sewing product is placed and passes the sewing needle, and the sewing product that is synchronized with the vertical movement of the sewing needle. A feed mechanism for feeding, a feed drive means for driving the feed mechanism to change the normal transfer of the sewing product to reverse feed, and a thread trimmer positioned below the needle plate for cutting the upper thread and the lower thread A sewing machine comprising: a mechanism; a thread trimming drive means for driving the thread trimming mechanism; and an input means for inputting an instruction to drive the thread trimming mechanism by the thread trimming drive means. When there is an instruction to drive the cutting mechanism, the feed driving means is driven to reversely feed the sewing product, and the reverse feed means is used to feed the sewing product in reverse. Reverse feed stop hand that stops the drive of the feed drive means When, after stopping the reverse rotation feed of the workpiece by the reversing feed stop means, and a thread cutting means for driving the thread cutting drive means.

  In the sewing machine according to the first aspect, the reverse feed stopping means stops the drive of the feed drive means after the reverse feed of the sewing product by the reverse feed means. The thread trimming means drives the thread trimming drive means after stopping the reverse feed of the sewing product by the reverse feed stopping means. Therefore, since the driving timing of the feed driving means and the driving timing of the thread trimming driving means do not overlap, an increase in power consumption can be avoided.

  Further, in the first aspect, the reverse feed means sends an amount exceeding half of the feed amount (feed amount of one pitch) of the sewing product per one cycle of the vertical movement of the sewing needle in the feed mechanism. After the transfer, the feed driving means may be driven to feed the sewing product in the reverse direction. If the reverse feed is performed before exceeding half of the feed amount of one pitch, the needle is stuck at the same position as the sewing position one thread before the thread trimming or further on the front side in the sewing product. When thread trimming is performed in this state, after the thread is cut, the stitch before one stitch is unwound, or the upper thread loop S formed by the upper thread is twisted below the needle plate 11 during the thread trimming operation, and the upper thread loop S is Get smaller. For this reason, the moving blade of the thread trimming device may fail to capture the upper thread loop and cannot perform thread trimming. If the reverse feed is carried out after exceeding half of the feed amount of one pitch, the needle will not pierce the same position as the sewing position one stitch before the thread trimming or the front position side in the sewing product. The seam before the first thread trimming is not unraveled, and the upper thread loop S is not twisted during the thread trimming operation. Therefore, it is possible to make the lengths remaining on the back of the upper and lower yarns after cutting the yarn, and to reliably prevent a yarn cutting error. The reverse feed amount is the amount excluding the forward transfer amount of the feed amount.

  The sewing machine thread trimming method according to the second aspect of the present invention includes a sewing needle that moves up and down, a needle plate that has a hole on which a workpiece is placed and through which the sewing needle passes, and is synchronized with the vertical movement of the sewing needle. A feed mechanism that feeds the workpiece, feed driving means that can drive the feed mechanism to change the forward transfer of the workpiece to reverse feed, and an upper thread and a lower thread that are located below the needle plate A thread trimming method performed by a sewing machine comprising a thread trimming mechanism for cutting, a thread trimming driving means for driving the thread trimming mechanism, and an input means for inputting an instruction to drive the thread trimming mechanism by the thread trimming driving means. When the input means instructs to drive the thread trimming mechanism, the feed driving means is driven to reversely feed the sewing product in the reverse feed step, and the reverse feed step in the reverse feed step. After the reverse feed of the sewing product, the feed A reverse feed stopping step of stopping the driving of the driving means, after stopping the reverse rotation feeding of the workpiece in the reverse feeding stopping step, and a thread cutting step of driving the thread cutting drive means.

  In the thread trimming method of the sewing machine according to the second aspect, in the reverse feed stopping step, after the workpiece is reversely fed by the reverse feed means, the drive of the feed drive means is stopped. In the thread trimming step, after the reverse feed of the sewing product is stopped by the reverse feed stop means, the thread trimming drive means is driven. Therefore, since the driving timing of the feed driving means and the driving timing of the thread trimming driving means do not overlap, an increase in power consumption can be avoided.

1 is a perspective view of a sewing machine 1. FIG. 3 is a cross-sectional view showing the periphery of the sewing needle 14 and the periphery of the shuttle mechanism 30. FIG. 3 is a perspective view showing the periphery of a sewing needle 14 and the periphery of a shuttle mechanism 30. FIG. FIG. 4 is a cross-sectional view showing a part of the internal structure of the pedestal 3. 2 is a block diagram showing an electrical configuration of the sewing machine 1. FIG. 3 is a timing chart of a remaining short processing method in the sewing machine 1; It is a flowchart of the remaining short process which CPU71 performs. It is a timing chart of the remaining short process which CPU71 performs.

  Hereinafter, a sewing machine 1 and a thread trimming method according to an embodiment of the present invention will be described with reference to the drawings. The drawings to be referred to are used for explaining the technical features that can be adopted by the present disclosure, and the configuration and flowcharts of the apparatus described are not intended to be limited only to them, but are merely illustrative examples. is there.

  The physical configuration of the sewing machine 1 will be described with reference to FIG. In the following description, the left side, the right side, the upper left side, and the lower right side in FIG. The sewing machine 1 of the present embodiment is characterized in that “remaining short processing” that can make the remaining lengths of the upper thread and the lower thread remaining at the end of the seam on the back side of the cloth after thread trimming can be set.

  The sewing machine 1 is fitted in a recess (not shown) provided in the table 6. A controller 70 that controls the operation of the sewing machine 1 is attached to the lower surface of the table 6. A step-down pedal 91 is connected to the control device 70 via a rod 90. When the operator depresses the pedal 91 to the toe side or the heel side, the switch (not shown) is appropriately turned on and off, and the sewing work 1 starts or stops, or the thread trimming work by the thread trimming mechanism, etc. Is done.

  As shown in FIG. 1, the sewing machine 1 includes a bed portion 2 as a base, a columnar leg column portion 3 erected in the vertical direction on the right end portion of the upper surface of the bed portion 2, and the leg column portion 3. An arm portion 4 is provided extending from the upper end portion to the left side and facing the upper surface of the bed portion 2. A head 49 that protrudes downward is provided at the distal end of the arm portion 4 in the extending direction.

  A needle plate 11 is provided on the upper left end side of the bed portion 2. As shown in FIG. 2, a needle hole 11 </ b> A is provided in the needle plate 11 immediately below the sewing needle 14. Further, the needle plate 11 is provided with a square hole 12 through which a feed dog 32 (described later) moves back and forth. A hook mechanism 30 is provided below the needle plate 11 in the bed portion 2. The shuttle mechanism 30 accommodates a bobbin for lower thread (not shown). Above the shuttle mechanism 30 and below the needle plate 11, a sewing object (hereinafter referred to as the cloth 10 in FIG. 2 as an example) is forward and backward of the sewing machine 1 with a predetermined transfer amount (feed amount). A feed dog 32 is provided for transfer to any of the above. The feed dog 32 is driven by a cloth feed mechanism described later.

  As shown in FIG. 1, a sewing machine motor 87 having a columnar pulley 5 that manually rotates the upper shaft (not shown) of the sewing machine 1 is provided on the upper portion of the right side surface of the pedestal 3. A feed amount adjustment pulley 21 for adjusting the feed amount of the cloth 10 by the feed dog 32 is provided at the center of the front surface of the pedestal 3. A feed amount adjusting motor 22, which is a pulse motor, is fixed to a lower portion of the right side surface of the pedestal portion 3 via a fixing member 25. A drive pulley 23 is fixed to the tip of the output shaft 22A (see FIG. 4) of the feed amount adjusting motor 22. A timing belt 24 is bridged between the feed amount adjusting pulley 21 and the driving pulley 23. The feed amount adjusting motor 22 is connected to a control device 70 (see FIG. 5) via a drive circuit 83 (see FIG. 5) described later. The control device 70 controls driving of the feed amount adjusting motor 22. The driving force of the feed amount adjusting motor 22 is transmitted from the drive pulley 23 to the feed amount adjusting pulley 21 via the timing belt 24. Therefore, the feed amount of the cloth 10 is adjusted with the rotation of the feed amount adjustment pulley 21. A mechanism for adjusting the feed amount of the fabric 10 will be described later. The cloth feed amount can be set on the operation panel 7 described later.

  As shown in FIGS. 1 and 2, a needle bar 13 is provided below the head 49 so as to be movable in the vertical direction. A sewing needle 14 is attached to the lower end of the needle bar 13. A presser foot 15 for pressing the cloth is provided behind the needle bar 13. In the head 49, a needle bar vertical movement mechanism (not shown) for moving the needle bar 13 up and down and a balance mechanism (not shown) for moving the balance 18 (see FIG. 1) for lifting the upper thread 8A up and down are provided. It has been.

  A sewing machine motor 87 (see FIG. 5) for driving the sewing machine 1 is provided below the pedestal 3 shown in FIG. The driving force of the sewing machine motor 87 is transmitted to the upper shaft (not shown) via a joint (not shown). The upper shaft extends in the left-right direction within the arm portion 4. The driving force of the sewing machine motor 87 is transmitted to the lower shaft (not shown) by a transmission mechanism (not shown) provided in the middle of the upper shaft. The lower shaft extends in the left-right direction within the bed portion 2. When the operator depresses the pedal 91, the sewing machine motor 87 is driven, and the elements including the needle bar 13, the balance mechanism, the shuttle mechanism 30, and the feed mechanism are synchronously driven to form a stitch on the cloth.

  As shown in FIG. 1, a rectangular operation panel 7 that is horizontally long when viewed from the front is provided at the center of the upper surface of the arm portion 4. A liquid crystal display 7A (hereinafter referred to as LCD 7A) is provided on the front surface of the operation panel 7. The LCD 7A displays function names and various messages for executing various functions necessary for sewing operations such as selection and editing of a sewing pattern, setting of short remaining processing at the time of thread trimming, and cancellation. A touch panel 7B is provided on the front surface of the LCD 7A. The LCD 7A and the touch panel 7B are connected to the control device 70. The operator selects an item displayed on the LCD 7A with a finger or a touch pen. The touch panel 7B senses the selected item. The operator can input various instructions to the sewing machine 1 via the LCD 7A and the touch panel 7B.

  Next, the cloth feeding mechanism will be briefly described. The cloth feed mechanism of the present embodiment is a conventional well-known mechanism for driving the feed dog 32 shown in FIG. For example, the feed dog 32 is given a forward and backward movement by a horizontal feed shaft (not shown) rotatably supported at both ends of the bed portion 2. Further, vertical movement is given by a vertical feed shaft (not shown) interlocked with a feed base (not shown) to which the feed dog 32 is fixed. The cloth 10 can be fed in the front-rear (forward / reverse) direction by such known means. Switching of the feeding direction of the cloth 10 is determined by the inclination of a switch (not shown) provided in the bed portion 2. The cloth is fed in the reverse direction according to the inclination of the switch, and reverse stitching or the like is performed.

  Next, a known mechanism for adjusting the inclination of the switch will be briefly described. The bed portion 2 shown in FIG. 1 includes a reverse solenoid 58 (see FIG. 5), a solenoid lever (not shown), a reverse stitching lever shaft (not shown), a lever (not shown), and a switching device linkage set ( (Not shown). When the reverse solenoid 58 is turned on, the reverse stitching lever shaft is rotated via a solenoid lever (not shown). The lever (not shown) swings according to the rotation of the reverse stitching lever shaft, and the switch linkage assembly (not shown) swings in the vertical direction. Thereby, the inclination of the switching device is changed to a symmetrical position, and the feed direction of the cloth 10 is switched from the normal feed direction to the reverse feed direction. At this time, the feed amount of the cloth 10 does not change. A reverse stitching lever 9 (see FIG. 1) arranged on the lower side of the front surface of the leg post 3 is connected to the reverse stitching lever shaft. Also by manually operating the reverse stitching lever 9 downward, the reverse stitching lever shaft is rotated to change the inclination of the switch to the symmetrical position, and the cloth 10 is fed in the reverse direction.

  Next, a mechanism for adjusting the feed amount of the cloth 10 will be described. As shown in FIG. 4, the feed adjusting cam 50 is pivotally supported around a shaft 54 at a position facing the feed amount adjusting pulley 21 in the pedestal 3. The feed adjustment cam 50 is connected to a feed adjustment stand 57 via a link 56. The feed adjustment stand 57 is a well-known one connected to a switcher via a link (not shown), and is provided in the bed portion 2 so as to be rotatable. The feed adjustment stand 57 is rotated by the vertical movement of the link 56, and the inclination of the switch is changed. The amount of rocking of the horizontal feed shaft (not shown) is changed by changing the tilt angle of the switch, and the feed amount by the feed dog 32 (see FIG. 2) varies.

  A cam surface 51 having a V-shape in a side view is formed at the front end portion of the feed adjusting cam 50. The rear end portion of the feed adjusting cam 50 is rotatably connected to the upper end portion of a link 56 that is an element constituting the above-described switch linkage group. An adjusting shaft 41 that protrudes rearward from the center of the feed amount adjusting pulley 21 is screwed into the screw hole 3 </ b> A provided in the upper portion of the front surface of the pedestal 3. The distal end portion 42 of the adjustment shaft 41 engages with the cam surface 51 of the feed adjustment cam 50.

The cam surface 51 includes a forward transfer control surface 52 positioned on the lower side and a reverse feed control surface 53 positioned on the upper side. The link 56 is urged downward in FIG. 4 by a spring, and the forward transfer control surface 52 is urged toward the tip end portion 42 of the adjustment shaft 41. When the adjustment shaft 41 is turned, the adjustment shaft 41 appears and disappears, the contact position of the tip end portion 42 with the forward transfer control surface 52 changes, and the swing angle of the switch changes via the link 56. For this reason, the feed amount of one pitch by the feed dog 32 can be adjusted.
The structure using such a feed adjusting cam 50 is the same as the conventional one.

  FIG. 4 shows the state where the reverse solenoid 58 is turned off. The tip end portion 42 of the adjustment shaft 41 contacts the forward transfer control surface 52. In a state in which the reverse solenoid 58 is ON, the link 56 rises against the spring force, and the tip 42 of the adjustment shaft 41 contacts the reverse feed control surface 53. At this time, the swing angle of the switch is switched from the forward feed angle to the reverse feed angle, and the feed direction of the feed dog 32 is reversed.

  Next, the thread trimming mechanism will be briefly described. The thread trimming mechanism is the same as the conventional mechanism. As shown in FIG. 3, the movable blade 61 and the fixed blade 62 are provided so as to be close to the needle hole 11A of the needle plate 11 located above the shuttle mechanism 30 and sandwich the needle hole 11A. The movable blade 61 and the fixed blade 62 cooperate with a thread trimming solenoid 65 (see FIG. 5) housed in the bed portion 2. When the thread trimming solenoid 65 is turned on, the movable blade 61 is movable by a thread trimming cam (not shown). The loop S of the upper thread 8 </ b> A formed when the sewing needle 14 rises from the bottom dead center is captured by the shuttle mechanism 30 and then expanded by the shuttle mechanism 30 to form a triangular loop R. The tip of the moving blade 61 enters into this triangular loop R and separates the upper thread 8A and the lower thread 8B. The upper thread 8A and the lower thread 8B captured by the moving blade 61 are cut at the tip of the fixed blade 62 while being gradually widened by a yarn spreader (not shown) that exhibits a divergent shape of the moving blade.

  Next, the electrical configuration of the sewing machine 1 will be described with reference to FIG. As described above, the sewing machine 1 includes the control device 70. The control device 70 includes a CPU 71. A ROM 72, a RAM 73, an EEPROM 74, and an I / O interface (hereinafter referred to as I / O) 76 are connected to the CPU 71 via a bus 77. The I / O 76 of the control device 70 having such a configuration includes a pedal 91, a touch panel 7B, a drive circuit 81 for driving the LCD 7A, a drive circuit 82 for driving the sewing machine motor 87, and a feed amount. A drive circuit 83 for driving the adjusting motor 22, a drive circuit 84 for driving the reverse solenoid 58, a drive circuit 85 for driving the thread trimming solenoid 65, and the like are connected to each other.

  Next, the remaining short processing method in the sewing machine 1 will be described with reference to the timing chart of FIG. Here, an apparent operation of the sewing machine 1 that performs the remaining short process will be described. In FIG. 6, the needle tip position of the sewing needle 14 is indicated by a solid line, and the vertical feed phase of the feed dog 32 is indicated by a dotted line. The horizontal axis indicates the rotation angle of the upper axis. The operator sets the remaining short process using the operation panel 7.

  First, during the sewing operation, when the operator returns the pedal 91 to the heel side at the timing t1, a thread trimming signal is input. At this time, the needle tip of the sewing needle 14 is located below the needle plate 11, and the feed dog 32 is also located below the needle plate 11. Next, the sewing needle 14 is pulled upward from the needle plate 11 at the timing t2. Furthermore, the feed dog 32 moves above the needle plate 11 at the timing t3. In a state where the feed dog 32 is positioned above the needle plate 11, the cloth 10 is transferred in the forward rotation direction.

  The sewing needle 14 reaches the top dead center at the timing t4. Then, the reverse solenoid 58 (see FIG. 5) is turned on at timing t5 when the upper shaft rotates from the top dead center by a predetermined angle (for example, 35 °). In the present embodiment, the timing t5 at which the reverse solenoid 58 is turned on is adjusted to the timing for positively transferring an amount exceeding half of the feed amount of the cloth 10 per cycle of the sewing needle 14. At this time, the inclination of the switch is changed to a symmetrical position, and the cloth feeding direction is reversed. From t5 timing to t6 timing when the feed dog 32 reaches the needle plate 11, the cloth 10 is transferred in the reverse rotation direction (Q section shown in FIG. 6). The feed dog 32 moves below the needle plate 11 at the timing t6. As a result, the needle drop point of the last stitch of the seam falls to a position near and near one stitch. In the present embodiment, when the sewing needle 14 enters the needle plate 11, the feed dog 32 is adjusted to move below the needle plate 11 almost simultaneously.

  Next, when the sewing needle 14 is positioned near the bottom dead center at timing t7, the needle down signal is turned ON. When the needle down signal is turned ON, the reverse solenoid 58 is turned OFF. As a result, the inclination of the switching device returns to the original, and the cloth feeding direction returns to the normal rotation direction. Then, the thread trimming solenoid 65 is energized at t8 timing when the upper shaft rotates by a predetermined angle (for example, 25 °) from t7 timing when the needle down signal is turned ON. Then, as shown in FIG. 3, the movable blade 61 is moved by a thread trimming cam (not shown). The upper thread loop S formed when the sewing needle 14 rises from the bottom dead center is captured by the shuttle mechanism 30.

  On the lower side of the needle plate 11, the upper thread loop S is enlarged by the shuttle mechanism 30 to become a triangular loop R. In this embodiment, after the yarn trimming signal is input, the fabric 10 is fed forward more than half and then fed backward. As a result, the needle does not pierce at the same position as the sewing position one thread before the thread trimming or the front position side of the sewing product, so that the stitch before the one thread trimming is not unraveled after thread trimming. Further, during the thread trimming operation, the upper thread loop S is caught by the shuttle mechanism 30 in a state where it is not twisted, and a loop R (see FIG. 3) can be formed. Since the tip of the movable blade 61 can surely enter the triangular loop R without the loop R becoming small, it is possible to reliably prevent a thread trimming error. At this time, the balance 18 (see FIG. 1) is at a position slightly elevated from the lowest position. The upper thread 8A and the lower thread 8B captured by the movable blade 61 are gradually spread by the yarn handling (not shown). At this time, the thread is loosened so that an excessive force is not generated on the upper thread 8A. Thus, the upper thread 8A and the lower thread 8B are cut at the tip of the fixed blade 62.

  Next, the remaining short process executed by the CPU 71 will be described with reference to the flowchart of FIG. 7 and the timing chart of FIG. During the sewing work, when the operator returns the pedal 91 to the heel side and a thread trimming signal is input to the control device 70 at the timing t11 in FIG. 8, the CPU 71 stores the “remaining shortage” stored in the ROM 72 (see FIG. 5). This process is executed by calling the “processing program”.

  First, the CPU 71 determines whether or not the remaining short process is set on the operation panel 7 (S10). For example, when the remaining short process is set, the remaining short flag “1” is stored in the RAM 73 (see FIG. 5). When the remaining short process is not set, the remaining short flag “0” is stored. The CPU 71 can determine whether the remaining short process is set based on whether the remaining short flag stored in the RAM 73 is “0” or “1”.

  When the CPU 71 determines that the remaining short process is set (S10: YES), the CPU 71 determines whether or not the needle down signal is ON (S11). When the CPU 71 determines that the needle down signal is OFF (S11: NO), the CPU 71 returns to S11 and enters a standby state. When the CPU 71 determines that the needle down signal is ON at timing t12 (S11: YES), the needle tip position of the sewing needle 14 is located below the needle plate 11, and the feed dog 32 is also below the needle plate 11. positioned.

  Therefore, the CPU 71 determines whether or not the phase of the upper axis is the reverse solenoid ON position (S12). The reverse solenoid ON position is a position obtained by rotating the upper shaft by a predetermined angle (for example, 35 °) from the position where the needle tip position has reached the top dead center. The predetermined angle of the upper shaft that turns ON the reverse solenoid 58 is set to an angle at which more than half of the feed amount of the cloth 10 per cycle of the sewing needle 14 can be forward transferred. In the present embodiment, the needle tip position is set to 35 ° from the position at which the top dead center is reached, but can be changed depending on the operating conditions of the sewing machine (for example, the number of revolutions of the sewing machine motor 87), for example, −55. It is preferable to adjust within the range of ° to + 75 °.

  When the CPU 71 determines that the phase of the upper axis is not the reverse solenoid ON position (S12: NO), the CPU 71 returns to S12 and enters a standby state. If the CPU 71 determines that the phase of the upper axis is the reverse solenoid ON position at timing t13 (S12: YES), the CPU 71 turns ON the reverse solenoid 58 (see FIG. 5) (S13). Thereby, after forwardly transferring an amount exceeding half of the feed amount of the cloth 10 per cycle of the sewing needle 14, the inclination of the switch is changed to a symmetrical position, and the cloth feed direction is reversed. Until the feed dog 32 moves below the needle plate 11, the cloth 10 is transferred in the reverse direction. Thereby, the needle drop point of the last stitch of the seam can be dropped to a position in the vicinity of one stitch before.

  Next, the CPU 71 determines whether or not the needle down signal is ON (S14). When the CPU 71 determines that the needle down signal is not ON (S14: NO), the CPU 71 returns to S14 and enters a standby state. When the CPU 71 determines that the needle down signal is ON at the timing t14 (S14: YES), since the sewing needle 14 is located near the bottom dead center, the reverse rotation solenoid 58 is turned off (S15). As a result, the inclination of the switching device returns to the original, and the cloth feed direction returns to the normal feed direction.

  The CPU 71 determines whether or not the phase of the upper shaft is the thread trimming solenoid ON position (S16). The thread trimming solenoid ON position is a position where the upper shaft has rotated a predetermined angle (for example, 25 °) from when the needle down signal is turned ON. In this embodiment, the angle is set to 25 ° from when the needle down signal is turned on, but the value is not limited to this value depending on the operating conditions of the sewing machine (for example, the rotational speed of the sewing machine motor 87, etc.). If the CPU 71 determines that the phase of the upper shaft is not the thread trimming solenoid ON position (S16: NO), the CPU 71 returns to S16 and repeats the process.

  When the CPU 71 determines that the phase of the upper shaft is the thread trimming solenoid ON position (S16: YES), the CPU 71 turns on the thread trimming solenoid 65 at timing t15 (S17). The thread trimming mechanism starts the thread trimming operation. As described above, on the lower side of the needle plate 11, as shown in FIG. 6, the hook mechanism 30 forms a triangular loop R of the upper thread 8A. In this embodiment, after the yarn trimming signal is input, the fabric 10 is fed forward by an amount exceeding half and then fed backward. As a result, the sewing needle 14 does not pierce at the same position as the sewing position one thread before the thread trimming or the front position side of the sewing product. For this reason, the seam just before one thread trimming cannot be unwound. Since the upper thread loop S is not twisted and is captured by the hook mechanism 30 and becomes the loop R, the loop R is not reduced. Therefore, since the tip of the movable blade 61 can surely enter the triangular loop R, it is possible to reliably prevent a thread trimming error. Thus, the upper thread 8A and the lower thread 8B are cut by the thread trimming mechanism.

  Next, the CPU 71 determines whether or not the needle up signal is ON (S18). When the CPU 71 determines that the needle up signal is not ON (S18: NO), the CPU 71 returns to S18 and repeats the process. When the CPU 71 determines that the needle up signal is ON at timing t16 (S18: YES), the CPU 71 subsequently determines whether the phase of the upper axis is the needle up stop position (S19). The needle up stop position is, for example, a position where the upper shaft has rotated a predetermined angle (for example, 10 °) after the needle up signal is turned ON. In the present embodiment, the angle is set to 10 ° from when the needle up signal is turned on, but the value is not limited to this value depending on the operating conditions of the sewing machine (for example, the rotational speed of the sewing machine motor 87).

  When the CPU 71 determines that the phase of the upper axis is not the needle up stop position (S19: NO), the CPU 71 returns to S19 and enters a standby state. If the CPU 71 determines that the phase of the upper axis is the needle up stop position at timing t17 (S19: YES), the CPU 71 turns off the thread trimmer solenoid 65 and stops the driving of the sewing machine motor 87 (S20). Thus, this process is completed.

  In the above description, the reverse solenoid 58 shown in FIG. 5 corresponds to the “feed driving means” of the present invention, the thread trimming solenoid 65 corresponds to the “thread cutting driving means” of the present invention, and the pedal 91 corresponds to the “input” of the present invention. It corresponds to “means”. The CPU 71 that executes the processes of S12 and S13 shown in FIG. 6 corresponds to the “reverse feed means” of the present invention, and the CPU 71 that executes the processes of S14 and S15 corresponds to the “reverse feed stop means” of the present invention. The CPU 71 that executes the processing of S17 corresponds to the “thread cutting means” of the present invention.

  As described above, in the sewing machine 1 of the present embodiment, the upper thread 8A and the lower thread 8B are cut after the fabric 10 is transferred in the reverse feed direction at a predetermined timing after the thread trimming signal is input. That is, the upper thread 8A and the lower thread 8B are cut after the needle drop point of the last needle is dropped to a position in the vicinity of one stitch before, so the upper thread remaining at the end of the seam on the back of the fabric 10 after thread trimming. The remaining lengths of 8A and lower thread 8B can be made uniform. Therefore, it is possible to save labor for the operator to cut the yarn on the back of the fabric by staking or the like.

  Furthermore, in this embodiment, in particular, the thread trimming solenoid 65 is energized after the reverse rotation solenoid 58 is energized and shut off. That is, after the fabric 10 is transferred in the reverse feed direction, the upper thread 8A and the lower thread 8B are cut. As a result, the ON period (energization period) of the reverse solenoid 58 and the ON period (energization period) of the thread trimming solenoid 65 do not overlap, so that power consumption does not increase during thread trimming.

  Furthermore, in the present embodiment, in particular, after a thread trimming signal is input, the amount of feed of the cloth 10 per one cycle of the sewing needle 14 is positively transferred, and then the reverse rotation solenoid 58 is energized to reverse the rotation. Feeding. As in the past, when the thread feed signal is input and the cloth feed direction is reversed immediately to try to cut the thread, the sewing needle is located at the same position as the sewing position one thread before the sewing machine, or further ahead. 14 will be stabbed. For this reason, the seam before thread trimming after thread trimming is unwound, or the upper thread loop S is twisted and the triangular loop R is formed small during thread trimming by the thread trimming mechanism. According to the present embodiment, since the sewing needle 14 does not pierce at the same position as the sewing position one stitch before the thread trimming in the sewing product or further on the front position side, the stitch before the one thread trimming is not unraveled. Further, since the upper thread loop S is not twisted during thread trimming by the thread trimming mechanism, the triangular loop R is not reduced. Therefore, the tip of the moving blade 61 can surely enter the triangular loop R. Therefore, it is possible to align the lengths of the upper yarn 8A and the lower yarn 8B remaining on the back of the fabric after the yarn is cut, and to reliably prevent a yarn cutting error.

  In addition, this invention is not limited to the said embodiment, A various deformation | transformation is possible. For example, in the above-described embodiment, the thread trimming signal is input when the operator depresses the pedal 91, but the present invention is not limited to this method. The thread trimming signal may be input by the operator pressing the hand switch P (see FIG. 1). As with the automatic reverse stitching program, it is also possible to have a density at which a thread trimming signal is automatically generated after several stitches reverse stitching is automatically performed at the end of sewing. Further, an auxiliary device for feeding the cloth to the sewing machine may be attached, and a thread trimming signal may be input to the sewing machine from the auxiliary device side.

DESCRIPTION OF SYMBOLS 1 Sewing machine 8A Upper thread 8B Lower thread 14 Sewing needle 21 Feed amount adjustment pulley 22 Feed amount adjustment motor 24 Timing belt 32 Feed dog 58 Reverse solenoid 61 Moving blade 62 Fixed blade 65 Thread trimmer solenoid 70 Controller 71 CPU
72 ROM
73 RAM
87 sewing machine motor 91 pedal

Claims (3)

A sewing needle that moves up and down;
A needle plate on which a workpiece is placed and has a hole through which the sewing needle passes;
A feed mechanism for feeding the workpiece in synchronization with the vertical movement of the sewing needle;
Feed driving means capable of driving the feed mechanism to change the forward transfer of the sewing product to reverse feed;
A thread trimming mechanism that is positioned below the needle plate and cuts the upper thread and the lower thread;
Thread trimming drive means for driving the thread trimming mechanism;
A sewing machine comprising input means for inputting an instruction to drive the thread trimming mechanism by the thread trimming drive means,
When there is an instruction to drive the thread trimming mechanism by the input means, reverse feed means for driving the feed drive means to feed the sewing product in reverse rotation;
A reverse feed stop means for stopping driving of the feed drive means after the reverse feed of the sewing product by the reverse feed means;
A sewing machine comprising: a thread trimming means for driving the thread trimming drive means after the reverse feed of the sewing product is stopped by the reverse feed stop means.   The reverse feed means forwards more than half of the feed amount of the sewing product per cycle of the vertical movement of the sewing needle in the feed mechanism, and then drives the feed drive means to drive the feed drive means. The sewing machine according to claim 1, wherein the workpiece is reversely fed. A sewing needle that moves up and down, a needle plate that has a hole through which the sewing product is placed and through which the sewing needle passes, a feed mechanism that feeds the sewing product in synchronization with the vertical movement of the sewing needle, and the feed mechanism A feed driving means capable of changing the forward transfer of the sewing product to a reverse feed, a thread trimming mechanism which is located below the needle plate and cuts the upper thread and the lower thread, and a thread which drives the thread trimming mechanism A thread trimming method for a sewing machine performed by a sewing machine comprising: a trimming driving means; and an input means for inputting an instruction to drive the thread trimming mechanism by the thread trimming driving means.
When there is an instruction to drive the thread trimming mechanism by the input means, a reverse feed step of driving the feed drive means to reversely feed the sewing product,
A reverse feed stop step of stopping driving of the feed drive means after the reverse feed of the sewing product in the reverse feed step;
A thread trimming method for a sewing machine, comprising: a thread trimming process for driving the thread trimming driving means after the reverse feed of the sewing product is stopped in the reverse feed stopping process.

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