sewing machine

Abstract

To provide a sewing machine which has an enhanced fabric shake suppression function.SOLUTION: A sewing machine includes: a detection part for detecting a position in a cross direction with respect to a feed direction of fabric; a fabric position correction mechanism 62 for correcting the position by moving the fabric in the cross direction, based on the detection of the detection part; a fabric presser part 63 provided opposing to the fabric position correction mechanism 62 in the vertical direction, and being always in contact with the fabric while performing sewing work; energization means 64; a load generation source 65 for generating a forced load in the fabric presser part 63; and a control part. While fabric feeding is stopped, the control part actuates the load generation source 65 so that a forced load is applied on the fabric from the fabric presser part 63, and actuates the fabric position correction mechanism 62, and in the middle of fabric feeding, stops the load generation source 65, thereby applying only a difference between the self-weight of the fabric presser part 63 and the energization force of the energization means 64 to the fabric.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a sewing machine that adjusts the position of a fabric while sewing. [Background technology]

[0002] Conventionally, as described in Patent Documents 1 and 2, for example, there are sewing machines that have a function for adjusting the position of the fabric before it is sewn by the sewing needle. This function is called "edge control" (or sometimes abbreviated as "edge control"), focusing on manipulating the edge of the fabric. In a sewing machine, the fabric is fed intermittently. In other words, the feeding (moving) state and the stopped state are repeated in a short period of time. 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 on the rotating wheel is adjusted by rotating a rotating wheel provided at the tip of a swinging body.

[0003] In the configurations described in Patent Documents 1 and 2, position adjustment is performed only when 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 separated from the moving fabric. In the configuration described in Patent Document 2, the rotating wheel is separated from the moving fabric. The reason for this operation is to prevent the fabric from stretching. However, with these methods, the position adjustment means, such as the claws, engages with the fabric only when the fabric is not being fed. Therefore, the position adjustment means does not engage with the fabric while the fabric is being fed. The fabric is free until it reaches the gap between the needle plate and the fabric presser foot. Therefore, due to vibrations and other factors that occur during fabric feeding, the fabric may become displaced (i.e., become misaligned) before reaching the sewing needle position. As a result, even if a position adjustment means is provided, conventional configurations have sometimes been unable to reliably suppress fabric wobble. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 11-319359 [Patent Document 2] Japanese Patent Application Publication No. 4-132585 Summary of the Invention [Problem to be solved by the invention]

[0005] Therefore, an object of the present invention is to provide a sewing machine with an improved function for suppressing fabric wobble. [Means for solving the problem]

[0006] The present invention is a sewing machine that sews while adjusting the position of a fabric, and is equipped with: a detection unit that detects the position of the fabric in a cross direction that 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 the detection by the detection unit; a fabric presser unit that is arranged 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 that is connected to the fabric presser unit and generates a biasing force that adjusts for the weight of the fabric presser unit; a load generating source that is connected to the fabric presser unit and generates a forced load that presses the fabric presser unit against the fabric position correcting mechanism; and a control unit.The control unit operates the load generating source so that the forced load is applied to the fabric from the fabric presser unit while fabric feeding is stopped, and also operates the fabric position correcting mechanism, and stops the load generating 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.

[0007] According to this configuration, even during fabric feeding, the fabric does not become loose, and the difference between the weight of the contacting fabric pressing part and the biasing force of the biasing means is always applied to the fabric, so that the fabric is less likely to wobble whether fabric feeding is stopped or ongoing.

[0008] The biasing means is two springs provided above the contact position of the fabric pressing section with the fabric, one of the two springs having a constant spring force and the other of the two springs having an adjustable spring force.

[0009] According to this configuration, the spring force of the other of the two springs can be adjusted, so that the load applied to the fabric during fabric feeding can be adjusted to an appropriate value.

[0010] 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.

[0011] According to this configuration, the weight of the fabric pressing portion can be offset by one spring, and then a desired downward load can be applied to the fabric pressing portion by the other spring. [Effects of the Invention]

[0012] According to the present invention, the difference between the weight of the fabric pressing unit and the biasing force of the biasing means can be applied to the fabric, making it difficult for the fabric to wobble, thereby improving the fabric wobble suppression function. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a perspective view showing a sewing machine according to an embodiment of the present invention; [Figure 2] FIG. 2 is an enlarged view of the main part in FIG. [Figure 3] 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 (sewing worker side). FIG. [Figure 4] 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 seen from diagonally below on the rear side (opposite the sewing worker). [Figure 5] 3 is a block diagram showing a configuration related to the position correction of the underlay fabric in the sewing machine; FIG. [Figure 6] 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. [Figure 7] 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. DETAILED DESCRIPTION OF THE INVENTION

[0014] Next, one embodiment of the present invention will be described. In describing the depth direction (front-rear 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)." In addition, in describing 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 FIG. 1, and 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 FIG. 1 and sewn.

[0015] The sewing machine 1 of this embodiment is an overlock sewing machine used for joining two pieces of fabric together, such as sewing fabric to become sleeves to the portions of the body that correspond to the arms of the wearer (for example, attaching sleeves to a T-shirt). The attaching sleeves to a T-shirt is just one example, and the sewing machine 1 of this embodiment can be widely used for 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 one piece of fabric or three or more pieces of fabric stacked together.

[0016] The sewing machine 1 of this embodiment has a conventionally known configuration except for the position correction unit 6 related 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 side to the back side, 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.

[0017] The needle plate 3 is provided on the upper surface of a cylinder portion of the sewing machine 1, and has a needle hole that can receive a 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.

[0018] The sewing machine 1 of this embodiment is configured to perform sewing operations with the upper and lower fabrics overlapping 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 in terms of 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 airflow from the air supply unit 7 onto the upper fabric.

[0019] In the sewing machine 1 of this embodiment, the position correcting unit 6 according to the present invention includes a detecting unit 61, a lower fabric position correcting mechanism 62 as the "fabric position correcting mechanism" set forth in the claims, a lower fabric presser unit 63 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 correcting unit 6 are shown in Figures 3 and 4.

[0020] 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 a direction that intersects with the feed direction. The detection unit 61 has one sensor (only the installed position is shown in FIG. 2 . Note that the portion shown at the base end of the lead line of "61" in FIG. 2 is a nut for fixing the sensor to the sewing machine 1) to the right of the throat 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. A non-contact sensor, specifically an optical sensor, is used as the 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. For example, the plate-shaped portion of the knife mechanism can also serve as the reflector. In the detection state, that is, when the light beam emitted from the sensor does not return to the sensor, the sensor is hidden by the underlying fabric, and the underlying fabric is positioned to the right of the specified position. On the other hand, in the non-detection state, that is, when the light beam emitted from the sensor returns to the sensor, the sensor is not hidden by the fabric but is exposed, and the underlying fabric is positioned to the left of the specified position.

[0021] Based on the detection by the detection unit 61, the lower fabric position correction mechanism 62 corrects the position by moving the lower fabric in the intersecting direction until it reaches the sewing position with the sewing needle 51. The lower fabric position correction mechanism 62 is provided with a belt 621 made of soft resin (specifically, rubber) that moves in a circular motion as shown in the figure. The belt 621 is supported by rollers 622 at two locations at the top and by roller 623 at one location at the bottom. The lower roller 623 is a drive roller connected to a motor 624. The motor 624 is rotated clockwise and counterclockwise by a control unit 66. A tension adjustment roller 625 is in contact with the belt 621 to maintain tension. The belt 621 is configured to move horizontally at its upper end position. The lower fabric position correction mechanism 62 is provided so as to be immovable 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 FIGS. 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 upon receiving 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 edge of the fabric while the sewing machine 1 is in operation, the belt 621 also constantly moves left and right. However, effective position adjustment is only performed 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 located below the lower fabric applies a force of movement to the left and right to the lower fabric that is pressed downward by the lower fabric presser portion 63. On the other hand, when the lower fabric presser portion 63, to which no forced load is applied, is simply on the lower fabric (simply touching the lower fabric 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.The position of the upper fabric is detected by a sensor other than the detection unit 61, and the upper fabric can be moved left and right by controlling the airflow emitted from the air supply unit 7 (see FIG. 2) based on this detection.

[0022] The lower fabric presser 63 is a plate-like portion elongated in the left-right direction and provided above the lower fabric position correcting mechanism 62, separate from the presser mechanism 4 provided above the needle plate 3. In other words, the lower fabric presser 63 is provided facing the lower fabric position correcting mechanism 62 in the up-down direction. Note that the "up-down direction" mentioned above also includes cases where it is inclined. The lower fabric presser 63 can be formed from general steel or stainless steel. Furthermore, in consideration of the balance with the biasing force (spring force) of the biasing means 64 described below, it may be made of light metal or resin (including FRP) to reduce its weight. The lower fabric presser 63 is cantilevered at its right end by the frame 67, is vertically movable relative to the lower fabric position correcting mechanism 62, and is configured to be constantly in contact with the lower fabric during sewing. By being cantilevered, the lower fabric presser 63 left Since there is no need to provide a support member on the other side, it is less likely to obstruct the feeding 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 area where 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, so that it comes into 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.

[0023] The lower fabric pressing section 63 has a spring support section 631 that protrudes upward. In this embodiment, the spring support section 631 is a plate-like body that is smaller than the lower member of the lower fabric pressing section 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 provided on the upper surface of the spring support section 631. Two springs (a first spring 641 and a second spring 642) serving as a biasing means 64 are connected to the lower fabric pressing section 63 above the position where the lower fabric is in contact with the lower fabric. These two springs 641, 642 are configured to generate a spring load that acts on the lower fabric pressing section 63. The biasing means 64 generates a biasing force that adjusts to the weight of the lower fabric pressing section 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.

[0024] The first spring 641 is a coil spring and has a constant spring force. The spring force of this first spring 641 is an upward force and is set to be greater than the weight of the lower fabric holding portion 63. For this reason, the first spring 641 lifts up the lower fabric holding portion 63, so that 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. The first spring 641 in this embodiment is a tension spring used alone, and its upper end is supported by the frame 67 above the lower fabric holding portion 63 and its lower end is connected to the lower fabric holding portion 63.

[0025] 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 screw shaft 632 described above is passed. Therefore, the spring force of the second spring 642 is a downward force. A washer and a nut 633 (for example, having a knurled 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 part 631. The distance from the upper surface of the spring support part 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 changed so that it is smaller when the nut 633 is loosened and larger when the nut 633 is tightened. Therefore, the second spring 642, whose spring force is 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 in a state where almost no downward load is applied (a state where the load is almost 0). The second spring 642 is located to the left of the first spring 641 (i.e., closer to the edge of the base fabric). near Therefore, the second spring 642 is disposed at a position close in the left-right direction to the center of gravity of the lower fabric pressing portion 63. This makes it easy to adjust the spring force against the weight of the lower fabric pressing portion 63 itself.

[0026] 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 pressing portion 63. The reason for using two springs in this manner is that the tension spring (first spring 641) balances the unsprung load including the lower fabric pressing portion 63, and the pressure spring (second spring 642) increases or decreases the pressing force of the lower fabric pressing portion 63 against the lower fabric, thereby adjusting the force 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 feeding can be easily adjusted to an appropriate value depending on, for example, the material of the lower fabric and the fabric feeding speed.

[0027] The load generating source 65 is connected to the lower fabric pressing portion 63 and generates a forced load that presses the lower fabric pressing portion 63 against the lower fabric position correcting 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 pressing portion 63, and an axial plunger 652 extends upward. The plunger 652 is fixed to the lower fabric pressing portion 63. When electricity is applied to this solenoid, the plunger 652 moves so as to be drawn into a 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 pressing portion 63. As a result, the lower fabric pressing portion 63 is pressed against the belt 621 of the lower fabric position correcting mechanism 62 via the lower fabric. When the lower fabric position correcting mechanism 62 is operated in this state, the lower fabric can be reliably moved left and right.

[0028] In this embodiment, the control unit 66 is also a control unit (microcomputer) included in the sewing machine 1 itself. However, this is not limiting and a separate control unit may also be provided. A timing chart is shown in FIG. 6. The upper part of FIG. 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 with the top surface of the needle plate 3 as the reference. 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 FIG. 6 shows the operation of the load generating source 65 (shown as a "solenoid") at the same time as the upper part of the diagram, in a rectangular wave form. "ON" in the diagram corresponds to operation, and "OFF" corresponds to stoppage. As shown in FIG. 6 , while 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, while 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 lower fabric. The value of this difference may be appropriately set so that the lower fabric is unlikely to stretch even while the lower fabric presser unit 63 is in contact with the lower fabric. The value of this difference may be zero, as a result of the weight of the lower fabric presser unit 63 and the biasing force of the biasing means 64 being 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. With this control, the lower fabric does not become free even during fabric feeding, and the difference between the weight of the abutting lower fabric presser portion 63 and the biasing force of the biasing means 64 is constantly applied to the lower fabric, making it less likely for the lower fabric to wobble. If the lower fabric is free, the fabric will move in response to the constant left and right movement of the belt 621, which may cause its position to change before it reaches the sewing position, and this movement is unstable and does not necessarily match the amount of movement of the belt 621, resulting in wobble.By the above control, such fluctuations can be suppressed, and therefore the function of suppressing fluctuations in the fabric can be improved.

[0029] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.

[0030] For example, although the sewing machine 1 in the above embodiment is an overlock sewing machine, it can also be applied to other sewing machines.

[0031] Furthermore, as shown in FIG. 7 (timing chart), the timing for stopping the load source 65 can be delayed compared to the above embodiment. The portion where the width of the rectangular wave portion (the rising portion of which) is wider than in the content of FIG. 6 (the portion with the width indicated by the arrow in the lower part of FIG. 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 source 65 overlap, causing the lower fabric to stretch. By operating the load source 65 as shown in FIG. 7 and sewing in a stretched state with the lower fabric presser unit 63 to which a forced load is applied, it is possible to respond to cases where sewing while stretching the fabric is required. The delay in the timing for stopping the load source 65 can be adjusted as appropriate.

[0032] In addition, while a non-contact sensor such as an optical sensor is used as the detection unit 61 in the above embodiment, a contact sensor can also be used. In addition, while the detection unit 61 includes one sensor in the above embodiment, it can also include two sensors, for example. When two sensors are used, if the fabric is fed with the end of the base fabric folded downward as in the above embodiment, the two sensors can be arranged vertically according to the tolerance range of the end position. Furthermore, while the base fabric position correction mechanism 62 in the above embodiment is configured to move the base fabric only left and right, it can also be configured to move it 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. Although a spring is used as the biasing means 64 in the above embodiment, a pneumatic, hydraulic, or electric actuator can also be used. Furthermore, a combination of a weight and a pulley that can balance the weight of the base fabric presser unit 63 can also be used.

[0033] In addition, although the lower fabric holding portion 63 is provided above the lower fabric position correcting mechanism 62 in the above embodiment, it can also be provided below the lower fabric position correcting mechanism 62. In this case, the load generating source 65 can be provided above the lower fabric holding portion 63.

[0034] Furthermore, although the urging means 64 was provided above the lower fabric pressing portion 63 in the above embodiment, it may also be provided below or at the same height. Furthermore, although the urging means 64 was configured with two springs 641, 642 in the above embodiment, the number of springs used is not limited to this and may be one or more (three or more). Furthermore, various springs such as leaf springs may be used in addition to coil springs. Furthermore, although the two springs 641, 642 were provided above the lower fabric pressing portion 63 in the above embodiment, the vertical installation positions of the springs relative to the lower fabric pressing portion 63 are not particularly limited. [Explanation of symbols]

[0035] 1 sewing machine 2. Feed mechanism 3 Needle plate 4 Presser foot mechanism 5 Needle bar mechanism 51 Sewing needle 6 Position correction section 61 Detection unit 62 Fabric position correction mechanism, lower fabric position correction mechanism 621 Belt 63 Fabric presser, lower fabric presser 64 Actuation means 641 One spring, first spring 642 The other spring, the second spring 65 Load Source 66 Control Unit 67 frames 7 Air supply section

Claims

1. 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.

2. 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.

3. 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.

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