JP7730007B2 - sewing machine - Google Patents

Description

The present invention relates to a sewing machine that adjusts the position of fabric while sewing.

Conventionally, as described in Patent Documents 1 and 2, there are sewing machines that have a function to adjust the position of the fabric before it is sewn by the sewing needle. This function is called "edge control" (or "edge control" for short) because it focuses on manipulating the edge of the fabric. The fabric is fed intermittently in the sewing machine. That is, the feeding (moving) state and the stopped state are repeated in short intervals. In the configuration described in Patent Document 1, the position is adjusted by hooking the upper fabric with the upper claw, and the position is adjusted by hooking the lower fabric with the lower claw. In addition, in the configuration described in Patent Document 2, the position of the fabric abutting the rotating wheel attached to the tip of the oscillator is adjusted by rotating the rotating wheel.

In the configurations described in Patent Documents 1 and 2, position adjustment is only performed while the machine is stopped and the fabric is not being fed. Specifically, in the configuration described in Patent Document 1, the upper and lower claws are moved away from the moving fabric. Also, in the configuration described in Patent Document 2, the rotating wheel is moved away from the moving fabric. The reason for this operation is to prevent the fabric from stretching. However, with this method, the position adjustment means, such as the claws, engages with the fabric only while the fabric is not being fed. Therefore, the position adjustment means does not engage with the fabric while the fabric is being fed, and the fabric is free until it reaches the space between the needle plate and the fabric presser foot. As a result, there is a possibility that the fabric may wobble (i.e., become misaligned) before reaching the sewing needle position due to the influence of vibrations caused by fabric feeding, etc. As a result, with conventional configurations, even if position adjustment means were provided, it was sometimes not possible to reliably suppress fabric wobble.

Japanese Patent Application Publication No. 11-319359 Japanese Patent Application Publication No. 4-132585

The present invention aims to provide a sewing machine with improved fabric wobble suppression capabilities.

The present invention is a sewing machine that sews while adjusting the position of the fabric, and is equipped with a detection unit that detects the position of the fabric in a cross direction, which is a direction that intersects the feed direction; a fabric position correction mechanism that corrects the position by moving the fabric in the cross direction based on detection by the detection unit; a fabric presser unit that is disposed vertically opposite the fabric position correction mechanism and is in constant contact with the fabric while the sewing operation is being performed; a biasing means connected to the fabric presser unit that generates a biasing force that adjusts for the weight of the fabric presser unit; a load generation source connected to the fabric presser unit that generates a forced load that presses the fabric presser unit against the fabric position correction mechanism; and a control unit. The control unit operates the load generation source and the fabric position correction mechanism so that the forced load is applied to the fabric from the fabric presser unit while fabric feeding is stopped, and stops the load generation source during fabric feeding, so that only the difference between the weight of the fabric presser unit and the biasing force of the biasing means is applied to the fabric.

With this configuration, even during fabric feeding, the fabric does not become loose, and the difference between the weight of the contacting fabric presser and the biasing force of the biasing means is always applied to the fabric, making it less likely for the fabric to wobble, whether fabric feeding is stopped or ongoing.

The biasing means may be two springs provided above the contact position of the fabric pressing section with the fabric, one of which has a constant spring force and the other of which has an adjustable spring force.

With this configuration, the spring force of the other of the two springs can be adjusted, making it possible to adjust the load applied to the fabric to an appropriate value while the fabric is being fed.

The spring force generated by one of the two springs is an upward force greater than the weight of the fabric pressing portion, and the spring force generated by the other of the two springs is a downward force.

With this configuration, one spring can offset the weight of the fabric pressing section, and the other spring can then apply the desired downward load to the fabric pressing section.

This invention makes it possible to apply the difference between the weight of the fabric presser and the biasing force of the biasing means to the fabric, making it less likely for the fabric to wobble. This improves the fabric wobble suppression function.

1 is a perspective view showing a sewing machine according to an embodiment of the present invention; FIG. 2 is an enlarged view of the main part of FIG. 1. 2 is a perspective view showing a lower fabric position correcting mechanism, a lower fabric presser section, and a load generating source in the sewing machine, as seen obliquely from above on the front side (the sewing worker's side). FIG. FIG. 2 is a perspective view showing a lower fabric position correcting mechanism, a lower fabric presser section, and a load generating source in the sewing machine, as viewed obliquely from below on the rear side (opposite the sewing operator). 3 is a block diagram showing a configuration related to the position correction of the underlay fabric in the sewing machine; FIG. 5 is a timing chart showing the relationship between the fabric feeding and the operation timing of the load generating source in the sewing machine. 7 is a timing chart showing the relationship between the fabric feeding and the operation timing of the load generating source (extended compared to the case of FIG. 6) in the sewing machine.

Next, one embodiment of the present invention will be described. Note that when referring to the depth direction (front-to-back direction), the side closer to the sewing worker is referred to as the "near side (front side)" and the side further away is referred to as the "rear side (back side)." Furthermore, when referring to up, down, left, and right, they are expressed as the directions when the sewing worker views the sewing machine. Incidentally, the sewing worker is positioned on the right side in Figure 1, and the fabric (top and bottom fabrics in this embodiment) is fed from the right side (lower right side) to the left side (upper left side) in Figure 1 and sewn.

The sewing machine 1 of this embodiment is an overlock sewing machine used for joining two pieces of fabric, such as sewing the fabric that will become the sleeves to the parts of the body that correspond to the wearer's arms (for example, attaching sleeves to a T-shirt). The attachment of sleeves to a T-shirt is merely an example, and the sewing machine 1 of this embodiment can be used for a wide range of tasks, such as sewing two separate pieces of fabric while aligning their edges. The sewing machine 1 of this embodiment can also be used to form flat sewn products that are not cylindrical. In some cases, it can be used for a single piece of fabric, or for three or more layers of fabric stacked together.

The sewing machine 1 of this embodiment has a conventionally known configuration, with the exception of the position correction unit 6, which is relevant to the present invention. As shown in Figures 1 and 2, the sewing machine 1 mainly comprises a feed mechanism 2 located below the fabric and feeding the fabric from the front to the back, a needle plate 3 located above the feed mechanism 2 and receiving a sewing needle 51, a presser mechanism 4 that presses the fabric from above, a needle bar mechanism 5 that sews the fabric with the reciprocating sewing needles 51 (two in this embodiment), and a knife mechanism (not shown) that cuts the edge of the fabric within a set range before sewing and after alignment has been completed.

The needle plate 3 is located on the top surface of the cylinder portion of the sewing machine 1 and has a needle hole that can receive the reciprocating sewing needle 51. The needle plate 3 abuts from below against the lower fabric, which is supported by the cylinder portion, to support it. The presser foot mechanism 4 presses down on the upper fabric above the needle plate 3. Because the lower and upper fabrics are sandwiched between the needle plate 3 and the presser foot mechanism 4, both fabrics are fed to the rear by the feed mechanism 2 during sewing. The right edge of each fabric is sewn.

The sewing machine 1 of this embodiment is configured to sew with the upper and lower fabrics superimposed on top of each other. In the case of fabrics that make up a T-shirt, for example, the fabric for the sleeves can be the lower fabric, and the fabric for the body can be the upper fabric. The sewing machine 1 of this embodiment has been improved with regard to adjusting the position of the lower fabric (corresponding to the "fabric" in the claims). Incidentally, the position adjustment relative to the upper fabric is performed by blowing air from the air supply unit 7 onto the upper fabric.

In the sewing machine 1 of this embodiment, the position correction unit 6 according to the present invention includes a detection unit 61, a lower fabric position correction mechanism 62 serving as the "fabric position correction mechanism" set forth in the claims, a lower fabric presser unit 63 serving as the "fabric presser unit" set forth in the claims, a biasing means 64, a load generating source 65, and a control unit 66. These units are mounted on a frame 67. The main mechanical components of the position correction unit 6 are shown in Figures 3 and 4.

The detection unit 61 detects the position of the base fabric in the cross direction (in this embodiment, the left-right direction perpendicular to the feed direction), which is the direction that intersects with the feed direction. The detection unit 61 has one sensor (only the installed position is shown in Figure 2; the portion indicated at the base end of the lead line of "61" in Figure 2 is a nut for securing the sensor to the sewing machine 1) to the right of the needle plate 3, and detects the edge of the base fabric (specifically, the right edge that is bent downward). The detection results are sent to the control unit 66, which receives the detection results at predetermined time intervals. The sensor is a non-contact sensor, specifically an optical sensor. The optical axis of the sensor is oriented left-right. Although not shown, a reflector is provided directly opposite the sensor to reflect the detection light emitted from the sensor and return it to the sensor. The reflector can also be the plate-shaped portion of the knife mechanism, for example. In the detection state, that is, when the light emitted from the sensor does not return to the sensor, the sensor is hidden by the underlying fabric, and the underlying fabric is to the right of the specified position. On the other hand, in the non-detection state, that is, when the light emitted from the sensor returns to the sensor, the sensor is not hidden by the fabric and is exposed, and the underlying fabric is to the left of the specified position.

Based on the detection by the detector 61, the lower fabric position correction mechanism 62 corrects the position of the lower fabric by moving it in the cross direction until it reaches the sewing position with the sewing needle 51. The lower fabric position correction mechanism 62 includes a belt 621 made of soft resin (specifically, rubber) that moves in a circular motion as shown. The belt 621 is supported by two rollers 622 at its upper part and one roller 623 at its lower part. The lower roller 623 is a drive roller connected to a motor 624. The motor 624 is rotated clockwise and counterclockwise by the control unit 66. A tension adjustment roller 625 contacts the belt 621 to maintain tension. The belt 621 is configured to move horizontally at its upper end. The lower fabric position correction mechanism 62 is fixed in the vertical direction of the sewing machine 1. The base fabric is fed above the belt 621 and between it and the underside of the base fabric presser unit 63 (the position indicated by the symbol "P" in Figures 3 and 4). Therefore, the base fabric is in contact with the belt 621. Therefore, the belt 621 moves in accordance with the direction of rotation of the motor 624, which is controlled by the control unit 66 in response to the detection result of the detection unit 61, and the base fabric is moved left and right. When the detection unit 61 is in a detecting state, the belt 621 moves left and the base fabric is moved left. On the other hand, when the detection unit 61 is in a non-detecting state, the belt 621 moves right and the base fabric is moved right. Since the detection unit 61 constantly detects the fabric edge while the sewing machine 1 is in operation, the belt 621 also constantly moves left and right. However, effective position adjustment is only possible while the base fabric is being pressed by the base fabric presser unit 63, to which a forced load is applied by the load source 65. This is because the belt 621, which is located below the lower fabric, applies a force of movement to the left and right to the lower fabric, which is held down by the lower fabric presser 63. On the other hand, if the lower fabric presser 63, with no forced load applied, is simply on top of the lower fabric (simply touching it with no load applied), even if the belt 621 moves left and right, slippage occurs between the belt 621 and the lower fabric, and the force of movement of the belt 621 is not transmitted to the lower fabric, so the lower fabric does not move left and right. Incidentally, the position of the upper fabric is detected by a sensor separate from the detection unit 61, and the airflow sprayed from the air supply unit 7 (see Figure 2) is controlled based on this detection to move it left and right.

The lower fabric presser 63 is a horizontally elongated plate-like portion provided above the lower fabric position correction mechanism 62, separate from the presser mechanism 4 provided above the needle plate 3. In other words, the lower fabric presser 63 is provided vertically opposite the lower fabric position correction mechanism 62. The "vertical direction" mentioned above also includes cases where the lower fabric presser 63 is inclined. The lower fabric presser 63 can be formed from general steel or stainless steel. Furthermore, considering the balance with the biasing force (spring force) of the biasing means 64 (described later), the lower fabric presser 63 may be made of light metal or resin (including FRP) for weight reduction. The lower fabric presser 63 is cantilevered at its right end by the frame 67, movable vertically relative to the lower fabric position correction mechanism 62, and constantly abuts against the lower fabric during sewing. This cantilevered support eliminates the need for a support member to the left of the lower fabric presser 63, thereby minimizing the obstruction of the feed of the lower and upper fabrics. Unlike the conventional configurations described in Patent Documents 1 and 2, the lower fabric pressing section 63 is not configured to come into contact with or separate from the lower fabric. However, it can be removed from the portion through which the lower fabric is fed during maintenance, etc. The lower surface of the lower fabric pressing section 63 is a flat surface that extends horizontally, and it makes surface contact with the lower fabric. The lower surface of the lower fabric pressing section 63 is a smooth flat surface, so that even when it comes into contact with the lower fabric, it does not get caught on the lower fabric. Incidentally, the upper fabric is configured to pass above the lower fabric pressing section 63.

The lower fabric presser 63 has a spring support portion 631 that protrudes upward. In this embodiment, the spring support portion 631 is a plate-like body that is smaller than the lower member of the lower fabric presser 63 and is integrally connected to the lower member by bolts or the like. A screw shaft 632 for supporting a second spring 642 is integrally formed on the upper surface of the spring support portion 631. Two springs (first spring 641 and second spring 642) serving as a biasing means 64 are connected to the lower fabric presser 63 above the contact position with the lower fabric. These two springs 641, 642 are configured to generate a spring load that acts on the lower fabric presser 63. The biasing means 64 generates a biasing force that adjusts to the weight of the lower fabric presser 63. Each spring 641, 642 is positioned to the right of the range through which the upper fabric is fed so as not to interfere with sewing.

The first spring 641 is a coil spring with a constant spring force. The spring force of this first spring 641 is an upward force that is set to be greater than the weight of the lower fabric holding portion 63. As a result, the first spring 641 lifts the lower fabric holding portion 63, so the weight of the lower fabric holding portion 63 is offset by the first spring 641 and the weight of the lower fabric holding portion 63 is not applied to the lower fabric. In this embodiment, the first spring 641 is a tension spring used alone, with its upper end supported by the frame 67 above the lower fabric holding portion 63 and its lower end connected to the lower fabric holding portion 63.

The second spring 642 is a coil spring, and its spring force is adjustable. In this embodiment, the second spring 642 is a compression spring through which the aforementioned screw shaft 632 passes. Therefore, the spring force of the second spring 642 is a downward force. A washer and nut 633 (e.g., knurled on the outer periphery) are attached to the upper part of the screw shaft 632. The upper end of the second spring 642 abuts against the lower surface of the washer. The lower end of the second spring 642 abuts against the upper surface of the spring support portion 631. The distance from the upper surface of the spring support portion 631 to the lower surface of the washer can be changed by the degree to which the nut 633 is tightened relative to the screw shaft 632. Therefore, the spring force of the second spring 642, which is a compression spring, can be adjusted so that it is smaller when the nut 633 is loosened and larger when the nut 633 is tightened. Therefore, the second spring 642 with its spring force adjusted can apply a desired downward load to the base fabric pressing portion 63. For example, the base fabric pressing portion 63 can be brought into contact with the base fabric with almost no downward load (a state in which the load is almost zero). The second spring 642 is disposed to the left of the first spring 641 (i.e., closer to the edge of the base fabric). Therefore, the second spring 642 is disposed in a position close to the center of gravity of the base fabric pressing portion 63 in the left-right direction. This makes it easy to adjust the spring force to correspond to the weight of the base fabric pressing portion 63.

With the above configuration, the difference between the spring force of the first spring 641, which is a tension spring, and the spring force of the second spring 642, which is a pressure spring, can be applied to the lower fabric presser section 63. The reason for using two springs in this way is that the tension spring (first spring 641) balances the unsprung load including the lower fabric presser section 63, and the pressure spring (second spring 642) increases or decreases the pressure force of the lower fabric presser section 63 against the lower fabric, adjusting it to an appropriate value to deal with flapping of the lower fabric as it is fed. In other words, the two springs have different roles. Furthermore, because the spring force of the second spring 642 is adjustable, the load applied to the lower fabric during fabric feed can be easily adjusted to an appropriate value depending on, for example, the material of the lower fabric and the fabric feed speed.

The load generating source 65 is connected to the lower fabric presser 63 and generates a forced load that presses the lower fabric presser 63 against the lower fabric position correction mechanism 62. In this embodiment, the load generating source 65 is a solenoid that outputs a linear reciprocating motion and generates a downward forced load. This solenoid is fixed below the lower fabric presser 63, and an axial plunger 652 extends upward. The plunger 652 is fixed to the lower fabric presser 63. When electricity is applied to this solenoid, the plunger 652 moves so as to be pulled into the main body 651 equipped with a coil. Therefore, when electricity is applied to the solenoid, a downward forced load is applied to the lower fabric presser 63. As a result, the lower fabric presser 63 is pressed against the belt 621 of the lower fabric position correction mechanism 62 via the lower fabric. When the lower fabric position correction mechanism 62 is operated in this state, the lower fabric can be reliably moved left and right.

In this embodiment, the control unit 66 is also the control unit (microcomputer) included in the sewing machine 1 itself. However, this is not limited to this, and it can also be provided separately. A timing chart is shown in Figure 6. The upper part of Figure 6 shows the operation of the feed mechanism 2. The feed mechanism 2 (specifically, the feed dogs of the feed mechanism 2) moves elliptically, and the up and down movement between the highest and lowest points during this elliptical movement is shown as a sine curve based on the top surface of the needle plate 3. The fabric is fed at the timing of the upper half of the sine curve. In other words, the fabric is fed intermittently. The lower part of Figure 6 shows the operation of the load generating source 65 (shown as a "solenoid") at the same time as the upper part, in a rectangular wave shape. "ON" in the figure corresponds to operation, and "OFF" corresponds to stop. As shown in FIG. 6 , when the feed mechanism 2 is stopped from feeding the fabric (when the feed dog is located below the needle plate 3), the control unit 66 activates the load generating source 65 to apply a forced load to the fabric from the lower fabric presser unit 63, and also activates the lower fabric position correction mechanism 62 to move the belt 621 to the left or right in response to detection by the detection unit 61. On the other hand, when the fabric is being fed (when the feed dog is located above the needle plate 3), the load generating source 65 is stopped so that only the difference between the weight of the lower fabric presser unit 63 and the biasing force of the biasing means 64 is applied to the fabric. The value of this difference may be appropriately set so that the lower fabric is unlikely to stretch while the lower fabric presser unit 63 is in contact with the fabric. The value of this difference may be zero, when the weight of the lower fabric presser unit 63 and the biasing force of the biasing means 64 are perfectly balanced. Preferably, a (small) downward load is set to a level that prevents the lower fabric presser unit 63 from jumping up as the fabric is fed. This type of control prevents the lower fabric from becoming loose even during fabric feeding, and the difference between the weight of the abutting lower fabric presser 63 and the biasing force of the biasing means 64 is constantly applied to the lower fabric, making it less likely to wobble. If the lower fabric were free, the belt 621 would constantly move left and right, causing the fabric to move as well, which could cause its position to change before it reaches the sewing position. Furthermore, this movement is unstable and does not necessarily match the amount of movement of the belt 621, resulting in wobble. The above control can suppress this wobble, thereby improving the ability to suppress fabric wobble.

The above describes an embodiment of the present invention, but the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

For example, although the sewing machine 1 in the above embodiment was an overlock sewing machine, it can also be applied to other sewing machines.

Furthermore, as shown in Figure 7 (timing chart), the timing for stopping the load generating source 65 can be delayed compared to the above embodiment. The portion where the width of the rectangular wave-shaped portion (the rising portion of which) is wider than in Figure 6 (the portion with the width indicated by the arrow in the lower part of Figure 7) is the portion where the timing is delayed. In the portion where the timing is delayed, the fabric feed and the operation of the load generating source 65 overlap, causing the lower fabric to stretch. By operating the load generating source 65 as shown in Figure 7 and using the lower fabric presser unit 63 to apply a forced load, sewing can be performed in a state where the fabric is stretched, which can accommodate situations where sewing while stretching the fabric is required. The delay in the timing for stopping the load generating source 65 can be adjusted as appropriate.

In addition, while the above embodiment uses a non-contact sensor such as an optical sensor as the detection unit 61, a contact sensor can also be used. In addition, while the above embodiment uses a single sensor for the detection unit 61, it can also be configured to use two sensors, for example. When using two sensors, if the fabric is fed with the edge of the base fabric folded downward as in the above embodiment, the two sensors can be positioned one above the other to match the tolerance range of the edge position. In addition, while the above embodiment uses a lower fabric position correction mechanism 62 that moves the base fabric only left and right, it can also be configured to move the base fabric in any two-dimensional direction. Specifically, in addition to the belt 621 in the above embodiment, a roller, a moving arm, or the like can be used. While the above embodiment uses a spring as the biasing means 64, a pneumatic, hydraulic, or electric actuator can also be used. Furthermore, a combination of a weight and pulley that can balance the weight of the lower fabric presser 63 can also be used.

In addition, while the lower fabric holding unit 63 was provided above the lower fabric position correction mechanism 62 in the above embodiment, it can also be provided below the lower fabric position correction mechanism 62. In this case, the load generating source 65 can be provided above the lower fabric holding unit 63.

In addition, while the biasing means 64 was provided above the lower fabric pressing portion 63 in the above embodiment, it can also be provided below or at the same height. In addition, while the biasing means 64 was composed of two springs 641, 642 in the above embodiment, the number of springs used is not limited to this and may be one or multiple (three or more). In addition to coil springs, various springs such as leaf springs can also be used. In addition, while the two springs 641, 642 were provided above the lower fabric pressing portion 63 in the above embodiment, there are no particular limitations on the vertical installation positions of each spring relative to the lower fabric pressing portion 63.

1 Sewing machine 2 Feed mechanism 3 Needle plate 4 Presser mechanism 5 Needle bar mechanism 51 Sewing needle 6 Position correction unit 61 Detector 62 Fabric position correction mechanism, lower fabric position correction mechanism 621 Belt 63 Fabric presser unit, lower fabric presser unit 64 Urging means 641 One spring, first spring 642 Other spring, second spring 65 Load generating source 66 Control unit 67 Frame 7 Air supply unit

Claims (3)

A sewing machine that sews while adjusting the position of the fabric,
A detection unit that detects the position of the fabric in a cross direction that is a direction that intersects with the feeding direction;
a fabric position correcting mechanism that corrects the position of the fabric by moving the fabric in the cross direction based on the detection by the detection unit;
a fabric pressing unit that is provided opposite to the fabric position correcting mechanism in the vertical direction and that is in constant contact with the fabric while the sewing operation is being performed;
a biasing means connected to the fabric pressing portion and generating a biasing force that is adjusted to the weight of the fabric pressing portion;
a load generating source connected to the fabric pressing unit and configured to generate a forced load that presses the fabric pressing unit against the fabric position correcting mechanism;
a control unit,
The control unit
While the fabric feeding is stopped, the load generating source is operated so that the forced load is applied from the fabric pressing unit to the fabric, and the fabric position correcting mechanism is operated;
The sewing machine is configured such that, during the fabric feeding, the load generating source is stopped so that only the difference between the weight of the fabric pressing portion and the biasing force of the biasing means is applied to the fabric. the biasing means is two springs provided above a contact position of the fabric pressing portion with the fabric,
One of the two springs has a constant spring force,
2. The sewing machine according to claim 1, wherein the spring force of the other of the two springs is adjustable. The spring force generated by one of the two springs is an upward force greater than the weight of the fabric pressing portion,
3. The sewing machine according to claim 2, wherein the spring force exerted by the other of said two springs is a downward force.