Sewing machine

Abstract

The present invention comprises: a needle; a needle plate that supports a fabric from below and has a needle drop through which the vertically moving needle penetrates; a looper that reciprocates below the needle plate while holding a looper thread so as to intertwine the looper thread with a needle thread; and a knife part that moves between the needle plate and the looper, and cuts the needle thread and the looper thread connected to the fabric after sewing. The knife part can change, with respect to the needle plate, a cutting position at which the needle thread and the looper thread are cut. Between the needle plate and the looper, a space in which the knife part in a posture before cutting in the position changed state can be disposed is secured.

Description

Sewing machine Cross-reference to related applications

[0001] This application claims priority based on Japanese Patent Application No. 2024-205713, and is incorporated by reference into the description of this application specification.

[0002] The present invention relates to a sewing machine provided with a thread cutting mechanism.

[0003] Conventionally, as a sewing machine provided with a thread cutting mechanism, there exists, for example, a sewing machine described in Japanese Patent Laid-Open No. 61-276597. In this sewing machine, the upper knife and the lower knife for cutting the thread (the needle thread and the looper thread) standby laterally with respect to the looper during the sewing operation. Subsequently, the combination of the upper knife and the lower knife advances to just above the looper. Then, only the lower knife further moves to the left, catches the thread, and then returns to the right. Next, the upper knife and the lower knife engage to cut the thread. After that, the combination of the upper knife and the lower knife returns to the standby position. The thread cutting method of the above-described double-loop sewing machine and the device for implementing the method are described in the above-mentioned document.

[0004] However, in the sewing machine described in the above-mentioned document, the thread was cut at a position that was farther to the right from the needle drop of the needle plate, and the thread that was moved to the right by being caught by the lower knife. In this configuration, since the thread has to be cut at a position away from the needle drop, the length of the thread remaining on the fabric becomes longer by the distance away from the needle drop. Therefore, when the thread cut by the sewing machine is longer than the desired length, the operator may need to perform additional processes such as further cutting the thread manually later to improve the appearance, which has been time-consuming.

[0005] And in the configuration described in the above-mentioned document, even if the cutting position is attempted to be moved to the left with respect to the operator, as shown in FIG. 3 of the above-mentioned document, there is a thickness around the portion where the cutting is performed, which interferes with the looper, making it physically impossible to achieve.

[0006] Furthermore, some sewing machine users have requested the ability to freely adjust the length of the thread left in the fabric, for reasons such as preventing fraying and preventing workers from accidentally damaging the fabric during the aforementioned finishing process.

[0007] Japanese Patent Publication No. 61-276597 (Figure 3)

[0008] Therefore, in view of the above problems, the present invention aims to provide a sewing machine that can freely adjust the thread cutting position.

[0009] The present invention relates to a sewing machine comprising: a needle that moves up and down to penetrate the fabric to be sewn while holding the needle thread; a needle plate that supports the fabric from below and has a needle drop through which the up and down moving needle passes; a looper that moves back and forth below the needle plate to hold the looper thread and entangle the looper thread with the needle thread; and a female part that moves between the needle plate and the looper and cuts the needle thread and the looper thread that are connected to the fabric after sewing, wherein the cutting position of the female part in which the needle thread and the looper thread are cut can be changed relative to the needle plate, and a space is secured between the needle plate and the looper in which the female part can be positioned after the cutting position has been changed before cutting is performed.

[0010] Furthermore, the female part may include a fixed female part that is immovable, and a movable female part that is rotatably mounted relative to the fixed female part so as to perform a scissor-like motion in combination with the fixed female part.

[0011] Furthermore, the position change can be made by adjusting the position of the fixed blade relative to the needle plate in the fabric feeding direction at the time of cutting the needle thread and the looper thread.

[0012] Furthermore, the female part is in a standby state away from the needle drop during sewing, and after sewing is completed, it moves into an advanced state below the needle drop and above the looper, and from that state a cutting operation is performed to cut the needle thread and the looper thread, after which it returns to the standby state.

[0013] Furthermore, the degree of opening of the fixed and movable scalpels when they are open can be adjusted.

[0014] Figure 1 is a perspective view showing the main parts related to thread cutting in a sewing machine according to one embodiment of the present invention, showing the case when the blade is in a standby state. Figure 2 is the same perspective view, showing the case when the blade is in the extended position (before thread cutting). Figure 3 is the same perspective view, showing the point in time when the blade moves further from the extended position to perform thread cutting. Figure 4A is a schematic perspective view showing the relationship between the blade and thread (needle thread, looper thread) in the sewing machine, showing the state immediately before thread cutting. Figure 4B is the same schematic perspective view, showing the state when one of the three needle threads and the looper thread have been cut. Figure 4C is the same schematic perspective view, showing the state when all threads have been cut. Figure 5 is a longitudinal cross-sectional view of the area around the tip (blade edge) of the blade, viewed from the base end to the tip end, showing the vertical relationship between the fixed blade and the movable blade of the blade and the looper in the sewing machine.

[0015] Next, the present invention will be described with reference to one embodiment. Regarding the front-to-back direction, the side closer to the sewing worker is referred to as the "front side," and the side further away is referred to as the "back side." That is, in this embodiment of the sewing machine, the worker is positioned on the front side as indicated in Figures 1 to 3. Furthermore, the up, down, left, and right directions are expressed as those seen from the worker's perspective of the sewing machine. "Horizontal direction" refers to the left-right direction from the worker's perspective. "Directly below" and "directly above" refer to the vertical direction of up and down.

[0016] - Overview of the Sewing Machine - The sewing machine 1 of this embodiment can perform, for example, double chain stitch sewing. However, it is not limited to this, and the present invention is applicable to all sewing machines that can perform sewing with needle thread Y1 and looper thread Y2 (see Figure 4A). Figures 1 to 3 are perspective views of the sewing machine 1 of this embodiment, showing the main parts related to thread cutting rather than the whole machine. For explanatory purposes, the illustrated state is with the cover removed and some of the internal components of the sewing machine exposed.

[0017] The sewing machine 1 of this embodiment includes a needle 2 that moves up and down to penetrate the fabric to be sewn (not shown) while holding the needle thread Y1 (see Figures 4A to 4C), a needle plate 3 that supports the fabric from below on its upper surface and has a needle drop 31 which is a through hole through which the up and down moving needle 2 passes, and a looper 4 located below the needle plate 3 that moves back and forth in a lateral direction perpendicular to the fabric feeding direction to entangle the looper thread Y2 with the needle thread Y1 in order to form a double chain stitch on the fabric. The configurations of these parts can be those of known sewing machines. Note that in Figures 4A to 4C, only a portion of the looper thread Y2 necessary for explaining the cutting process is shown, not the entire thread.

[0018] In this embodiment of the sewing machine 1, three needles 2 are used. The three needles 2 are arranged in parallel in the horizontal direction, and their vertical positions are different. However, the number of needles 2 is not limited to three, and can be arbitrarily set to one or more. The needle plate 3 is provided with a fabric feeding mechanism (not shown), and as the fabric feeding mechanism protrudes above the needle plate 3 and moves in the fabric feeding direction from the front to the back, the fabric is fed while maintaining its vertical position by being pressed down from above by a fabric presser foot (not shown). The driving force for reciprocating the looper 4 is supplied in the sewing machine 1 via a looper shaft 41 that extends horizontally from the pivot shaft for driving each part and moves horizontally while rotating around its axis. The source of the driving force is not particularly limited. Furthermore, the reciprocating range of the looper 4 includes a lateral range that extends to the left and right, including the position directly below the needle drop 31 (in this embodiment, three locations aligned horizontally that coincide with the three needles 2), but can be appropriately set according to the shape of the stitch (double chain stitch in this embodiment) formed by the needle thread Y1 and the looper thread Y2. Note that the aforementioned "lateral movement line" for the looper 4 is the main movement line, and the looper 4 reciprocates in a manner that also includes a secondary movement line related to the swinging of the looper 4 in the fabric feeding direction (forward and backward direction) to entangle the looper thread Y2 with the needle thread Y1. This reciprocating motion of the looper 4 occurs in conjunction with the movement of the looper shaft 41.

[0019] -Knife Mechanism- The sewing machine 1 of this embodiment is equipped with a knife mechanism 5 for cutting the needle thread Y1 and looper thread Y2 at a position below the needle plate 3. The knife mechanism 5 is provided inside the sewing machine 1, covered by a cover. Specifically, as shown in Figures 1 to 3 with the cover removed, the knife mechanism 5 is provided in the area to the right of the needle drop 31 inside the sewing machine 1. The knife mechanism 5 of this embodiment includes a base part 51, a closing start part 52, a first transmission part 53, a second transmission part 54, a knife part 55 (fixed knife 551, movable knife 552), a movable knife operation part 56, and an opening adjustment part 57.

[0020] The base portion 51 is flat and positioned so that its upper surface is horizontal. The base portion 51 is fixed to the horizontal upper surface of the main body portion of the sewing machine 1 by screws and is immovable within the sewing machine 1. The base portion 51 is the part that supports the parts that move relative to the base portion 51.

[0021] The closing activation part 52 is a projection that protrudes upward relative to the base part 51. This closing activation part 52 is provided at the front end of a support plate 511, which is attached to the left end of the base part 51 so as to partially overlap it. The closing activation part 52 is roughly cylindrical in shape, however, it is not limited to this shape. As the second transmission part 54 moves forward towards the side closer to the needle drop 31 (left side), the closing activation part 52 comes into contact with the moving scalpel operating part 56, thereby initiating the closing operation of the scalpel part 55.

[0022] The first transmission unit 53 is positioned above the base unit 51 and is an elongated plate-like body extending in a direction substantially aligned with the front-rear direction. The base end (rear end) of the first transmission unit 53 is rotatably connected to the female actuator A, which reciprocates in the lateral direction. The first transmission unit 53 is supported by a pivot point 531 on the base unit 51 and rotates so that the base end and the tip end (front end) move in an arc-shaped trajectory. The tip end of the first transmission unit 53 has a constricted shape in which the width dimension is reduced, and further towards the tip, it has a substantially circular shape in which the diameter dimension is larger than that of the constricted part.

[0023] The second transmission unit 54, in combination with the first transmission unit 53, constitutes a link mechanism. The link mechanism converts the driving force of the female actuator A into the forward and backward movement of the female part 55 relative to the needle drop 31 and the looper 4. The second transmission unit 54 is an elongated plate-like body positioned on the upper surface of the base unit 51 so as to intersect its longitudinal direction with that of the first transmission unit 53, and extending laterally. The female part 55 is provided at the tip of the second transmission unit 54. The second transmission unit 54 is slidably mounted relative to the base unit 51. The second transmission unit 54 has a recess 541 extending in the width direction formed on its rear side, and the substantially circular portion at the tip of the first transmission unit 53 fits into this recess 541. Preferably, the dimensional relationship between the inner periphery of the recess 541 and the substantially circular portion of the first transmission unit 53 is such that sliding is permitted without causing lateral play. The recess 541 allows for a change in the angle between the longitudinal direction of the first transmission unit 53 and the longitudinal direction of the second transmission unit 54, as the tip of the first transmission unit 53 moves along an arc-shaped trajectory as described above. Therefore, the second transmission unit 54 can be moved laterally as the first transmission unit 53 rotates. A chamfer is formed at the open end of the recess 541 to prevent interference between the first transmission unit 53 and the second transmission unit 54 even when the first transmission unit 53 is tilted relative to the second transmission unit 54. The aforementioned constricted portion of the first transmission unit 53 is also provided to prevent interference.

[0024] The second transmission section 54 has a base-side elongated hole 542, which is a through hole extending laterally, on the base end side (right side) farther from the needle drop 31, and a tip-side elongated hole 543, which is a through hole extending laterally, on the tip side (left side) closer to the needle drop 31. Each elongated hole is formed to be longer than the range of movement of the second transmission section 54. A pin fixed to the base section 51 and protruding upward passes through each elongated hole. The diameter of this pin is enlarged above the second transmission section 54 to prevent the second transmission section 54 from floating upward from the base section 51. The range of movement of the second transmission section 54 in the lateral direction is determined by the combination of each elongated hole and each pin. This range of movement corresponds to the range of movement between the standby position and the extended position of the female section 55, which will be described later. The base-side elongated hole 542 has a shape that extends in the linear direction. On the other hand, the tip-side elongated hole 543 is bent at an obtuse angle, forming a roughly V-shape, with the side closer to the needle drop 31 (left side) facing forward. This shape of the tip-side elongated hole 543 allows the second transmission section 54 to perform a "swinging" motion, where the tip faces backward, as it moves to the right, away from the needle drop 31 (corresponding to the movement of the female section 55 to the standby state, as described later).

[0025] The reason for performing the aforementioned "swinging" motion is that the pivot point 58 of the female part 55, which is the rotation center of the female part 55, is a thick part through which the shaft passes, and therefore it is necessary to avoid interference with the base end (right end) of the looper 4. In addition, an elongated hole can be provided in the base part 51 below the pin (not shown). In this case, the elongated hole is formed to be longer in the direction along the dough feeding direction. Therefore, by adjusting the fixing position of the pin to the base part 51 in the direction along the dough feeding direction using the elongated hole, the range in which the aforementioned "swinging" motion is performed can be adjusted. Accordingly, in this case, even if the movable female part 552 changes position so that it is not directly above the path of movement of the looper 4 when it is extended, as a result of adjusting the opening of the female part 55 with the opening adjustment part 57 described later, the aforementioned "swinging" adjustment can be used to adjust the movable female part 552 so that it is directly above the path of movement of the looper 4 when it is extended. In this adjustment, the positions of both the fixed female part 551 and the movable female part 552 (the position of the entire female part 55) are adjusted.

[0026] The female part 55 moves between the needle plate 3 and the looper 4 as the first transmission part 53 and the second transmission part 54 move relative to the base part 51 as a link mechanism, cutting the needle thread Y1 and looper thread Y2 that are connected to the fabric after sewing. The female part 55 includes a fixed female part 551 that is immovable, and a movable female part 552 that is rotatable around the vertical axis relative to the fixed female part 551 so as to perform a scissor-like operation in combination with the fixed female part 551. The fixed female part 551 and the movable female part 552 are separate components from the second transmission part 54 and are detachable from the tip of the second transmission part 54. In this embodiment, each female part 551 and 552 has a pointed tip, but the shape of the tip is not particularly limited. However, with respect to the movable female part 552, as shown in Figure 4A, it is advantageous for the tip to be pointed so that it can be inserted into the loop portion formed by the needle thread Y1.

[0027] The fixed blade 551 is a long, narrow plate in the horizontal direction and has a blade for cutting thread. The fixed blade 551 is fixed to the tip (left end) of the second transmission section 54. This fixing is done by screw. Therefore, if the blade is worn or damaged, the entire fixed blade 551 can be replaced by removing the screw. The fixed blade 551 moves relative to the needle plate 3 and looper 4 in accordance with the movement of the second transmission section 54. The edge of the blade of the fixed blade 551 is straight in plan view and, as shown in Figures 1 and 2, is inclined to be located towards the rear as it approaches the tip of the fixed blade 551.

[0028] The movable scalpel 552 is a long, narrow plate in the horizontal direction and has a blade for cutting thread. The fixed scalpel 551 and the movable scalpel 552 are stacked on top of each other in the thickness direction. The movable scalpel 552 is rotatably mounted relative to the fixed scalpel 551 around its vertical axis. The blades of the fixed scalpel 551 and the blades of the movable scalpel 552 are positioned so that they can overlap as the movable scalpel 552 rotates, starting from a V-shaped opposing position in a plan view (Figures 1 and 2). The movable scalpel 552 is stacked above the fixed scalpel 551 at the position of the scalpel pivot point 58, which is the center of rotation. Therefore, the rotational trajectory of the movable scalpel 552 around its axis is located above the fixed scalpel 551. Consequently, as shown in Figure 3, when the two scalpels overlap, the movable scalpel 552 is located above the fixed scalpel 551. Similar to commonly used scissors, when the fixed blade 551 and the movable blade 552 are in a closed state with overlapping blades, the blades of both blades overlap, allowing the threads Y1 and Y2, which are sandwiched between the two overlapping blades and extending in the vertical direction, to be cut.

[0029] The movable scalpel operating section 56 functions to rotate the movable scalpel 552 relative to the fixed scalpel 551. The movable scalpel operating section 56 is connected to the base end (right side) of the movable scalpel 552. The movable scalpel operating section 56 has an elongated shape, with a portion bent and curved towards the rear as it extends to the right. The intermediate section 561 of the movable scalpel operating section 56 has a shape that extends diagonally. The closing start section 52 and the opening adjustment section 57 abut against the rear side edge of this intermediate section 561. The return spring 544 provided on the second transmission section 54 abuts against the front end edge of the intermediate section 561. In this embodiment, a torsion coil spring is used as the return spring 544, and the coil portion is pivotally supported in the second transmission section 54 in the lateral and front-rear directions. Furthermore, the tip of the rear arm of the return spring 544, which extends linearly, abuts against the front edge of the intermediate portion 561 of the movable scalpel operating section 56. The tip of the front arm is fixed to the second transmission section 54.

[0030] The movable scalpel 552 and the movable scalpel operating section 56 are integrally connected by a screw. The integrated movable scalpel 552 and the movable scalpel operating section 56 rotate relative to the second transmission section 54 and the fixed scalpel 551. The movable scalpel operating section 56 is slidably mounted relative to the second transmission section 54. Of the rotations of the movable scalpel 552 and the movable scalpel operating section 56, the rotation in the direction of closing the scalpel section 55 occurs when the second transmission section 54 moves to the left toward the needle drop 31. As the movable scalpel operating section 56 moves with the second transmission section 54, it comes into contact with the closing start section 52, which is fixed relative to the base section 51, and receives a pressing force from the closing start section 52 toward the front. Due to this pressing force, the movable scalpel operating section 56 moves toward the front relative to the second transmission section 54, so the movable scalpel 552 on the opposite side of the scalpel rotation pivot point 58 moves toward the rear, opposite to the movable scalpel operating section 56. This closes the scalpel section 55. Furthermore, after each thread Y1 and Y2 is cut, when the second transmission unit 54 moves to the right so as to move away from the needle drop 31, the moving blade operating unit 56 moves away from the closing start unit 52. At that point, the spring force of the return spring 544 acts on the moving blade operating unit 56, returning it to a state where it is in contact with the opening adjustment unit 57.

[0031] In the sewing machine 1 of this embodiment, the relationship between the blade mechanism 5 and the main body of the sewing machine 1 (excluding the blade mechanism 5) is such that, as shown in Figure 2, a space S (see Figure 5) is secured between the needle plate 3 and the looper 4, allowing for the placement of the blade section 55, whose cutting position has been changed before cutting. That is, in the sewing machine 1 of this embodiment, the blade mechanism 5 is positioned such that the blade section 55 (in this embodiment, the part of the movable blade 552 that is thicker than the blade pivot point 58, which has a screw and nut such as a bolt) is located between the needle plate 3 and the looper 4 in the vertical direction (see Figure 2). Here, since a stitch is formed by entangling the looper thread Y2 held by the looper 4 with the needle thread Y1 held by the needle 2, it is difficult to make a design change that would move the looper 4 far away from the needle plate 3. For this reason, the space S between the needle plate 3 and the looper 4 cannot be set to be very large. In other words, the space S is narrow. Even in such a confined space S, the sewing machine 1 of this embodiment makes it possible to position the cutting blade 55 between the needle plate 3 and the looper 4, as described above, by devising the shape of the cutting blade 55 and the trajectory of its movement.

[0032] Furthermore, the second transmission unit 54, the fixed blade 551, the movable blade 552, and the movable blade operating unit 56 are each plate-shaped and are stacked and assembled in the thickness direction. The assembly is done by fastening with bolts or the like. Due to this configuration, the blade unit 55 can move in and out (advance and retreat) into the space S secured between the needle plate 3 and the looper 4. Therefore, the complicated setting of the sewing machine 1 of this embodiment, which, as in the conventional method, only pulls out the threads Y1 and Y2 between the needle plate 3 and the looper 4 and cuts the thread at a position away from the needle drop 31 due to physical interference, is unnecessary.

[0033] - Operation of the Knife Mechanism - The knife mechanism 5 operates as follows. When sewing is performed with the needle 2 and looper 4 working together, the knife part 55 is in the standby state shown in Figure 1. In the standby state, the knife part 55 is located laterally (to the right) away from the needle drop 31 and is at the far right end of its range of movement. After sewing is completed, the operator of the sewing machine 1 operates a switch (not shown) provided on the sewing machine 1, and the knife actuator A is activated. As a result, the knife part 55 moves into an extended state, below the needle drop 31 (directly below the needle drop 31, but not limited to this) and above the looper 4. In the extended state, as shown in Figure 2, the movable knife 552 is located directly above the movement line of the looper 4, and the fixed knife 551 is located behind the movement line of the looper 4. As mentioned above, since the looper 4 swings in the front-to-back direction, the position of the looper 4 in the front-to-back direction at the end of sewing is not fixed but within a range of width. Therefore, assuming that the looper 4 is located in the middle of its oscillation range, the position "directly above the movement line of the looper 4" is defined. The position where the looper 4 is in the middle of its oscillation range corresponds to the position directly below the needle drop 31. In this embodiment, after sewing is completed, at the point when the moving knife 552 enters the loop portion formed by the needle thread Y1 (see Figure 4A), the looper 4 is located at the leftmost position in its reciprocating motion range and in the middle of its oscillation range.

[0034] More specifically regarding the extended state, the plate-shaped portion of the movable blade 552 that is closer to the tip than the pivot point of the blade portion 55 is located directly above the path of movement of the looper 4. Because this portion is plate-shaped and thin, it can be positioned directly above the path of movement of the looper 4 without any obstruction. This allows for the closing operation of moving the movable blade 552 relative to the fixed blade 551 to be performed without any obstruction. On the other hand, as shown in Figure 5, the fixed blade 551 is located in the space S behind the looper 4 without overlapping it above the looper 4, and therefore does not interfere with the looper 4. Furthermore, even if the position of the looper 4 in the front-to-back direction changes due to oscillation, the fixed blade 551 in the extended state is positioned so as not to interfere with the looper 4. In the extended state, as shown in Figure 4A, the movable blade 552 enters into the loop portion formed by the needle thread Y1. The fixed blade 551 is located behind the loop portion.

[0035] As the second transmission unit 54 moves further forward from the aforementioned state, a cutting operation is performed (the female part 55 closes) from the state shown in Figure 4B to the state shown in Figure 4C, thereby cutting the needle thread (upper thread relative to the fabric) Y1 and the looper thread (lower thread relative to the fabric) Y2 below the fabric. From the advancement state to the cutting of the threads, the female part 55 closes as it moves forward (Figures 2 and 3). As a result, the fixed female part 551 moves to the left, and the tip portion of the moving female part 552 moves diagonally to the left and backward. The loop-shaped needle thread Y1 is cut at the rear of the loop portion by the closing female part 55 (see Figures 4B and 4C). At this time, along with the needle thread Y1 (three threads, corresponding to the number of needles 2 in this embodiment), the looper thread Y2, which is entangled with the needle thread Y1 and located near the loop formed by the needle thread Y1, is also cut. At this time, in order for the two blades 551 and 552 to overlap, the movable blade 552 approaches the fixed blade 551, and as the movable blade 552 hooks each thread Y1 and Y2 and moves them backward while cutting them. More precisely, after the movable blade 552 hooks each thread Y1 and Y2 and moves them backward, the blade section 55 closes and cuts each thread Y1 and Y2. In particular with respect to the needle thread Y1, it is shown that between the state shown in Figure 4A and the state shown in Figure 4B, the rear part of the loop bulges backward as the movable blade 552 moves. After cutting each thread Y1 and Y2, the blade section 55 returns to the standby state. With this return, the movable blade operating section 56 separates from the closing start section 52. Because the spring force of the return spring 544 is applied to the movable blade operating section 56, the blade section 55 returns to the open state.

[0036] - Adjustment Mechanism for the Knife Mechanism - Next, the position adjustment of each part will be explained. The closing start unit 52 is adjustable in the front-rear direction relative to the base unit 51. An elongated hole 512 is formed in the support plate 511 on which the closing start unit 52 is provided. This elongated hole 512 is longer in the direction along the dough feeding direction. The support plate 511 is screwed to the base unit 51. By adjusting the fixing position when screwing using the elongated hole 512, the front-rear contact position of the closing start unit 52 with respect to the movable knife operating unit 56, which moves together with the second transmission unit 54, can be adjusted. This makes it possible to adjust the start timing of the closing operation of the movable knife 552 with respect to the fixed knife 551, and the position in the lateral and front-rear directions at which the closing operation begins.

[0037] Here, if the opening degree of the female part 55 is the same when open, if the closing operation of the female part 55 starts earlier, the insertion of the movable blade 552 into the loop portion formed by the needle thread Y1 will be shallower. In this case, as the movable blade 552 approaches the fixed blade 551, the distance over which the movable blade 552 hooks each thread Y1, Y2 and moves them backward increases (because the distance from the blade pivot point 58 to each thread Y1, Y2 is long), and the length of each thread Y1, Y2 remaining in the fabric after cutting increases by the amount they have been moved backward. Conversely, if the closing operation of the female part 55 starts later, the insertion of the movable blade 552 into the loop portion formed by the needle thread Y1 will be deeper. In this case, as the movable blade 552 approaches the fixed blade 551, the distance over which the movable blade 552 hooks each thread Y1 and Y2 and moves them backward becomes shorter (because the distance from the blade pivot point 58 to each thread Y1 and Y2 is shorter). As a result, the length of each thread Y1 and Y2 remaining in the fabric after cutting becomes shorter by the amount they were moved backward. In this way, the length of each thread Y1 and Y2 remaining in the fabric can be adjusted by adjusting the position of the closing start unit 52 relative to the base unit 51.

[0038] Furthermore, by adjusting the start timing of the closing operation of the scalpel section 55 to be earlier, for example, the working time until thread cutting is completed can be shortened. Accordingly, by adjusting the position of the closing starter section 52 relative to the base section 51, the operation of the scalpel mechanism 5 can be optimized to match the desired cutting method.

[0039] The opening degree adjustment unit 57 is attached to the second transmission unit 54 and the fixed blade 551. The opening degree adjustment unit 57 is substantially disc-shaped, with an operating lever 571 protruding radially for gripping during operation. The opening degree adjustment unit 57 has a shape in which the diameter dimension changes in the circumferential direction, and the contact position with the movable blade operating unit 56 can be adjusted by changing the circumferential position when it is fixed to the second transmission unit 54. When the opening degree adjustment unit 57 is fixed at a position with a large diameter dimension, the opening degree of the blade 55 when open (for example, in the standby state, the most open state defined by the return spring 544 and the opening degree adjustment unit 57) can be reduced, and when the opening degree adjustment unit 57 is fixed at a position with a small diameter dimension, the opening degree of the blade 55 when open can be increased. Therefore, the opening degree adjustment unit 57 can be used to adjust the opening degree of the fixed blade 551 and the movable blade 552 when open.

[0040] Here, assuming that the left-right positions of the female part 55 in the female mechanism 5 are the same, a smaller opening of the female part 55 when it is open allows the overlapping position of the blade of the fixed female part 551 and the blade of the movable female part 552 in the closing start state of the female part 55 to be positioned closer to the needle drop 31 in the front-to-back direction compared to when the opening of the female part 55 is larger. More specifically, assuming that the movable female part 552 is positioned directly above the path of movement of the looper 4 when the female part 55 is extended, the position of the edge of the blade of the fixed female part 551 (the part where each thread Y1 and Y2 is cut by the fixed female part 551) just before the closing operation starts can be positioned closer to the needle drop 31 (front-to-back direction). Cutting the threads closer to the needle drop 31 reduces the length of each thread Y1 and Y2 remaining in the fabric. Therefore, by adjusting the opening of the female part 55, the cutting position of each thread Y1 and Y2 can be adjusted.

[0041] Furthermore, a secondary fixing screw 59 for fixing the fixing female 551 to the second transmission unit 54 is provided adjacent to the side (specifically, the left side) of the opening degree adjustment unit 57. Both the opening degree adjustment unit 57 and the secondary fixing screw 59 adjacent to the opening degree adjustment unit 57 can have their fixing positions adjusted by large-diameter holes (not shown). This allows adjustment of the fixing position of the fixing female 551 relative to the second transmission unit 54. Note that the fixing position can also be adjusted using elongated holes instead of large-diameter holes.

[0042] - Summary - In the female mechanism 5 of the present embodiment configured as described above, the female part 55 can change the position of the cutting position for cutting the needle thread Y1 and the looper thread Y2 with respect to the needle plate 3. The position change is made by adjusting the position of the fixed cutter 551 in the fabric feeding direction (front-back direction) with respect to the needle plate 3 at the time of cutting the needle thread Y1 and the looper thread Y2. The position change can be made by changing the opening degree of the female part 55 by the opening degree adjustment part 57.

[0043] Thus, the female part 55 can change the position of the cutting position for cutting the needle thread Y1 and the looper thread Y2 with respect to the needle plate 3. And, a space is secured between the needle plate 3 and the looper 4 in which the female part 55 in the posture before cutting in the changed position can be arranged. For this reason, in the sewing machine 1 of the present embodiment, it is not necessary to perform cutting at a position away from the needle drop 31 as in the prior art, and the position of the cutting position can be changed to a desired position with respect to the sewn fabric, and the needle thread Y1 and the looper thread Y2 can be cut. Therefore, the cutting positions of the respective threads Y1, Y2 can be freely adjusted.

[0044] Since the cutting positions of the respective threads Y1, Y2 can be freely adjusted, by shortening the respective threads Y1, Y2 remaining on the fabric after cutting, operations for improving the appearance such as cutting the remaining threads manually become unnecessary, and thus the labor can be reduced accordingly. Incidentally, in the sewing machine 1 of the present embodiment, the length of each of the threads Y1, Y2 extending from the fabric remaining on the fabric can be made about 3 mm at the shortest. Conversely, it is also possible to easily make the length of each of the threads Y1, Y2 left on the fabric long from the viewpoint of preventing fraying. Therefore, the sewing machine 1 provided with the female mechanism 5 of the present embodiment can meet various demands from users.

[0045] - Modification of the Embodiment - Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various changes can be made without departing from the gist of the present invention.

[0046] For example, the looper 4 of the above embodiment was configured to reciprocate in a horizontal path perpendicular to the fabric feeding direction. However, it is not limited to this. For example, it may be configured to reciprocate in a longitudinal path (vertical direction) along the fabric feeding direction. Also, it may be configured to perform a combined movement of horizontal reciprocation and vertical reciprocation. Further, the reciprocating movement is not limited to a linear movement, and may be an arc-shaped movement.

[0047] Regarding the cutting part 55, in the above embodiment, it was integrally formed in a scissor shape by the fixed cutter 551 and the movable cutter 552 that constitute the cutting part 55. However, it is not limited to this. The fixed cutter 551 and the movable cutter 552 may be separated, and the movable cutter 552 may be configured to move relative to the fixed cutter 551 to cut each thread Y1, Y2. In this case, the moving direction of the movable cutter 552 may be a direction along the fabric feeding direction (front-back direction), or a horizontal direction (left-right direction). Also, in this case, the length of each thread Y1, Y2 left on the fabric can be adjusted by the distance between the blade of the fixed cutter 551 and the blade of the movable cutter 552 in a plan view with respect to the needle drop 31.

[0048] Also, the configurations of the first transmission part 53 and the second transmission part 54 are not limited to those forming a link mechanism as in the above embodiment, and can be variously changed. For example, it may be configured to cause the cutting part 55 to perform a forward and backward movement by a gear, a chain, etc. Further, it may be configured to cause the cutting part 55 to perform a forward and backward movement by electrical control instead of a physical configuration.

[0049] Also, the fixed cutter 551 of the above embodiment was configured to be fixed at a certain position at the tip (left end) of the second transmission part 54. However, it is not limited to this. It may be configured such that the fixing position of the fixed cutter 551 to the second transmission part 54 can be adjusted by a long hole or the like. By configuring it in this way, the overlapping position of the blade of the fixed cutter 551 and the blade of the movable cutter 552 can also be adjusted on the side of the fixed cutter 551.

[0050] The configuration and operation of the above embodiment are summarized below. The above embodiment is a sewing machine 1 comprising: a needle 2 that moves up and down to penetrate the fabric to be sewn while holding the needle thread Y1; a needle plate 3 that supports the fabric from below and has a needle drop 31 through which the up and down moving needle 2 passes; a looper 4 located below the needle plate 3 that moves back and forth to entangle the looper thread Y2 with the needle thread Y1 while holding the looper thread Y2; and a cutting part 55 that moves between the needle plate 3 and the looper 4 to cut the needle thread Y1 and the looper thread Y2 that are connected to the fabric after sewing. The cutting position of the cutting part 55 that cuts the needle thread Y1 and the looper thread Y2 can be changed relative to the needle plate 3, and a space S is secured between the needle plate 3 and the looper 4 in which the cutting part 55 can be positioned after the cutting position has been changed.

[0051] Furthermore, the female part 55 may include a fixed female part 551 that is immovable within the female part 55, and a movable female part 552 that is rotatably mounted relative to the fixed female part 551 so as to perform a scissor-like operation in combination with the fixed female part 551.

[0052] Furthermore, the position change can be achieved by adjusting the position of the fixed blade 551 relative to the needle plate 3 in the fabric feeding direction at the time of cutting the needle thread Y1 and the looper thread Y2.

[0053] Furthermore, the female part 55 is in a standby state away from the needle drop 31 during sewing, and after sewing is completed, it moves into an advanced state below the needle drop 31 and above the looper 4, and from that state a cutting operation is performed to cut the needle thread Y1 and the looper thread Y2, after which it returns to the standby state.

[0054] Furthermore, the degree of opening of the fixed female 551 and the movable female 552 when they are open can be adjusted.

[0055] In the above embodiment, a space S is secured between the needle plate 3 and the looper 4, allowing the cutting section 55, in its repositioned state before cutting, to be positioned. Therefore, unlike in the conventional method, it is not necessary to cut the threads Y1 and Y2 at a position far from the needle drop 31. The cutting position can be changed to a desired position on the fabric after sewing, allowing the needle thread Y1 and looper thread Y2 to be cut. Thus, the cutting positions of the threads Y1 and Y2 can be freely adjusted.

[0056] 1 Sewing machine 2 Needle 3 Needle plate 31 Needle drop 4 Looper 41 Looper shaft 5 Knife mechanism 51 Base part 511 Support plate 512 Slotted hole (support plate) 52 Closing start part 53 First transmission part 531 Pivot part 54 Second transmission part 541 Recess 542 Base end side slotted hole 543 Tip side slotted hole 544 Return spring 55 Knife part 551 Fixed knife 552 Moving knife 56 Moving knife operation part 561 Intermediate part 57 Opening adjustment part 571 Operation lever 58 Knife pivot part 59 Sub-fixing screw A Knife actuator Y1 Needle thread Y2 Looper thread S Space

Claims

1. A sewing machine comprising: a needle that moves up and down to penetrate the fabric to be sewn while holding the needle thread; a needle plate that supports the fabric from below and has a needle drop through which the up and down moving needle passes; a looper that moves back and forth below the needle plate to hold the looper thread and entangle the looper thread with the needle thread; and a female part that moves between the needle plate and the looper and cuts the needle thread and the looper thread that are connected to the fabric after sewing, wherein the cutting position of the female part for cutting the needle thread and the looper thread can be changed relative to the needle plate, and a space is secured between the needle plate and the looper in which the female part can be positioned after the cutting position has been changed before cutting is performed.

2. The sewing machine according to claim 1, wherein the female part comprises a fixed female part which is immovable, and a movable female part which is rotatably provided relative to the fixed female part so as to perform a scissor-like operation in combination with the fixed female part.

3. The sewing machine according to claim 2, wherein the position change is made by adjusting the position of the fixed blade relative to the needle plate in the fabric feeding direction at the time of cutting the needle thread and the looper thread.

4. The sewing machine according to claim 1 or 2, wherein the female part is in a standby state away from the needle drop when sewing is performed, and after sewing is completed, it moves into an advanced state below the needle drop and above the looper, and from that state a cutting operation is performed to cut the needle thread and the looper thread, and then returns to the standby state.

5. The sewing machine according to claim 2 or 3, wherein the opening degree of the fixed blade and the movable blade when open is adjustable.

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