Flatlock sewing machine bobbin cutter and differential feed adjustment device

Abstract

This invention provides a bobbin thread cutting and differential adjustment device for flatlock sewing machines that eliminates the need for manual adjustment of the differential ratio, which is time-consuming and lacks accurate reproducibility compared to conventional methods, and the need for increased manufacturing costs and complex control when adding new drive components. [Solution] The bobbin cutting and differential adjustment device comprises a single drive motor 70, a bobbin cutting drive member 7 that drives a cutter drive lever 30 in conjunction with the drive motor 70, a differential ratio adjustment member 6 that drives a differential ratio adjustment lever 23 in conjunction with the drive motor 70, and a control device for the drive motor 70. This allows bobbin cutting and differential adjustment to be performed with a single drive device, suppressing cost increases and control complexity, while reducing the number of steps required for differential ratio adjustment and achieving accurate reproducibility.

Description

Technical Field

[0001] The present invention relates to an apparatus for cutting the lower thread and differential adjustment of a flat sewing machine. In the present invention, front and rear refer to the front and rear directions in the fabric feeding direction, left and right refer to the left and right directions when the sewing machine is viewed from the front, and up and down refer to the up and down directions of the sewing machine.

Background Art

[0002] As a lower thread cutting mechanism of a conventional flat sewing machine, a configuration including a thread holder, a cutter, and a drive lever for operating the cutter is known (for example, see Patent Document 1). Also known is a configuration including a thread loosening mechanism that releases the force applied to the thread by a thread conditioner that individually applies tension to a plurality of threads (for example, see Patent Document 2). Further, as a feeding mechanism of a conventional flat sewing machine, a configuration including a main feed amount adjustment lever and a differential ratio adjustment lever is known (for example, see Patent Document 3).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0004] Conventional technologies include a bobbin cutting mechanism operated by a solenoid or air cylinder located near the right side of the rear underside of the sewing machine, and a main feed adjustment lever operated by a drive device located near the left side of the rear underside of the sewing machine. The latter device is used, for example, at the end of sewing, by operating the main feed adjustment lever located near the front of the left side of the underside of the sewing machine to reduce the main feed amount and form a few stitches, thereby preventing the seam from unraveling at the end of the stitching. The differential ratio adjustment lever is located near the front of the right side of the underside of the sewing machine and is adjusted to the required differential ratio by manually rocking it up and down before being fastened to the sewing machine body with a knob-type screw or similar. The differential ratio is adjusted, for example, during easing sewing, and is finely adjusted according to various sewing conditions such as fabric, thread, and part of the garment. (Generally, the differential ratio is expressed as the differential feed amount divided by the main feed amount; for example, 1.0 means the main feed amount and differential feed amount are the same, and 1.2 means the differential feed amount is larger.)

[0005] As described above, adjusting the differential ratio relies on manual labor, which is time-consuming and lacks accurate reproducibility. Furthermore, even if this is operated using a new drive mechanism, it would require adding another drive mechanism in addition to the two mentioned above, resulting in increased manufacturing costs and complex control with three drive mechanisms. The objective of the present invention is to provide a device for bobbin cutting and differential adjustment of a flatlock sewing machine that solves these problems. [Means for solving the problem]

[0006] To achieve the above objective, the invention described in claim 1 is a flatlock sewing machine comprising a bobbin cutting mechanism including a cutter drive lever and a feed mechanism including a differential ratio adjustment lever, characterized in that it comprises one drive motor, a bobbin cutting drive member that drives the cutter drive lever in conjunction with the drive motor, a differential ratio adjustment member that drives the differential ratio adjustment lever in conjunction with the drive motor, and a control device for the drive motor.

[0007] To achieve the above objective, the invention described in claim 2 is a bobbin thread cutting device for a flatlock sewing machine as described in claim 1, wherein the bobbin thread cutting and differential adjustment device comprises a bobbin thread cutting drive cam to which the bobbin thread cutting drive member is fixed to the motor shaft of the drive motor, a driven lever that engages with the bobbin thread cutting drive cam and moves linearly, a driven lever shaft to which one end is fixed to the driven lever and moves linearly and the other end is connected to the cutter drive lever, and a shaft base installed on the sewing machine body that pivotally supports the driven lever shaft.

[0008] To achieve the above objective, the invention described in claim 3 is a bobbin thread cutting device for a flatlock sewing machine as described in claim 2, wherein the bobbin thread cutting and differential adjustment device comprises a differential ratio adjustment cam to which the differential ratio adjustment member is fixed to the motor shaft of the drive motor, a differential ratio adjustment crank that engages with the differential ratio adjustment cam and swings, and a differential ratio adjustment link to which one end is connected to the differential ratio adjustment crank and the other end is connected to a differential ratio adjustment lever.

[0009] To achieve the above objective, the invention described in claim 4 is a bobbin thread cutting device for a flatlock sewing machine as described in claim 3, wherein the bobbin thread cutting drive cam has a cam contour that includes a region in which the cutter drive lever operates and a region in which the cutter drive lever does not operate, and the differential ratio adjustment cam has a cam contour that includes a region in which the differential ratio adjustment lever operates, which acts in the region in which the cutter drive lever does not operate. [Effects of the Invention]

[0010] According to the flatlock sewing machine bobbin cutting and differential adjustment device of the present invention, in a flatlock sewing machine equipped with a bobbin cutting mechanism including a cutter drive lever and a feed mechanism including a differential ratio adjustment lever, by providing a single drive motor, a bobbin cutting drive member that drives the cutter drive lever in conjunction with the drive motor, a differential ratio adjustment member that drives the differential ratio adjustment lever in conjunction with the drive motor, and a control device for the drive motor, bobbin cutting and differential adjustment can be performed with a single drive device, thereby reducing the number of steps required for differential ratio adjustment and achieving accurate reproducibility while suppressing cost increases and complexity of control. [Brief explanation of the drawing]

[0011] [Figure 1] A perspective view from the left rear of the bobbin thread cutting and differential adjustment device of the sewing machine applied to the present invention. The positive direction of the X axis is to the right, the positive direction of the Y axis is to the rear, and the positive direction of the Z axis is to the upward. [Figure 2] A rear view of the bobbin thread cutting and differential feed adjustment device of a sewing machine applied to the present invention. [Figure 3] A left side view of the bobbin thread cutting and differential adjustment device of a sewing machine applied to the present invention. [Figure 4] A right side view of the bobbin thread cutting and differential feed adjustment device of a sewing machine applied to the present invention. [Figure 5] A plan view of the bobbin thread cutting drive cam and differential ratio adjustment cam of the bobbin thread cutting and differential adjustment device of a sewing machine applied to the present invention. [Figure 6] A perspective view from the right rear showing the operation of the bobbin thread cutting and differential feed adjustment device of a sewing machine applied to the present invention. [Modes for carrying out the invention]

[0012] An example of an embodiment of the present invention will be described below with reference to Figures 1 to 5. Figure 1 is a perspective view from the left rear of the bobbin cutter and differential feed adjustment device of a sewing machine applied to the present invention, and Figure 2 is a rear view of the bobbin cutter and differential feed adjustment device of a sewing machine applied to the present invention. In the sewing machine 1, a presser foot (not shown) and a needle plate 12 are positioned above and below the sewing area, which is the part where sewing is performed by the cooperation of the needle 11 and a looper (not shown). The presser foot is movable up and down and is positioned on the upper surface of the needle plate 12 in a state where it is pressed from above, gripping the fabric being sewn by pressing from above.

[0013] The main shaft (not shown) is positioned on the sewing machine body 10 so as to be rotatable in the left-right axial direction and is rotated by a drive device such as a servo motor. The rotation of the main shaft is transmitted through various mechanical elements and becomes the driving force for the up-and-down movement of the needle 11 on the left, the left-right reciprocating movement of the looper, and the movement of the feed mechanism 2. The feed mechanism 2 provides a periodic motion that combines up-and-down and back-and-forth movements, for example, an ellipse when viewed from the side, to the main feed teeth 20 located behind the needle 11 and the differential feed teeth 21 located in front of the needle, which are installed in front of the main feed table (not shown) and differential feed table (not shown).

[0014] The main feed adjustment lever 22 is located on the front of the lower left side of the sewing machine body 10, and the differential ratio adjustment lever 23 is located on the front of the lower right side of the sewing machine body 10. By swinging each of these levers, the main feed amount and differential feed amount can be adjusted individually. If only the main feed adjustment lever 22 is adjusted, both the main feed amount and differential feed amount change while maintaining a constant differential ratio. If only the differential ratio adjustment lever 23 is adjusted, the main feed amount remains unchanged, and only the differential ratio changes.

[0015] The bobbin thread cutting mechanism 3 comprises a thread holder (not shown), a cutter (not shown), and a cutter drive lever 30 for operating the cutter. The rear end of the cutter drive lever 30 protrudes in a branch-like manner from the back of the sewing machine body 10. By swinging this rear end to the right (the positive direction of the X-axis in Figures 1 and 2), the front end of the cutter drive lever 30 swings to the left, pushing the cutter to move to the left and cut the needle thread (extending from the needle 11 to the looper) and the bobbin thread extending from the looper to the stitch. After cutting the bobbin thread, swinging the rear end of the cutter drive lever 30 to the left causes the cutter to move to the right while gripping the bobbin thread extending from the looper with a thread clamp (not shown), and in cooperation with the installed thread holder, it grips the bobbin thread. A cutter drive rod 31 is connected to the rear end of the cutter drive lever 30, and the aforementioned cutting and gripping of the bobbin thread can be performed by operating the cutter drive rod 31 with a drive device.

[0016] The thread loosening mechanism 4 comprises a thread tensioner 40 installed on the right side of the front of the sewing machine body 10, and a thread loosening lever 42 located on the right side of the back of the sewing machine body 10, which releases the tension applied to the thread by the thread tensioner 40. The thread loosening lever 42 releases the tension applied to the thread by the thread tensioner 40 by swinging its lower end to the right (the positive direction of the X axis in Figures 1 and 2). The thread loosening mechanism 4 is used in conjunction with the bobbin thread cutting mechanism 3. After the bobbin thread is cut as described above, the cutter moves to the right while gripping the bobbin thread extending from the looper with the thread clamp, pulling the thread out from the thread tensioner 40. By operating the thread loosening lever 42 at the same time as the bobbin thread is cut, the grip of the bobbin thread by the cutter and thread clamp is prevented from being released.

[0017] The device for lower thread cutting and differential adjustment of the flat sewing machine of the present invention includes a driving motor 70, a lower thread cutting driving member 7 that drives a cutter driving lever 30 in conjunction with the driving motor 70, a differential ratio adjusting member 6 that drives a differential ratio adjusting lever 23 in conjunction with the driving motor 70, and a control device (not shown) of the driving motor 70. A motor mounting bracket 71 is installed on the right side of the back of the lower part of the sewing machine body 10, and the driving motor 70 with its motor shaft facing downward is fixed. The driving motor 70 of this embodiment uses a stepping motor. A lower thread cutting driving cam 72 and a differential ratio adjusting cam 60 are fixedly arranged vertically side by side on the motor shaft of the driving motor 70. This embodiment has a main feed amount adjusting member 5 that drives a main feed adjusting lever 22, and a main feed amount adjusting motor 50 that is interlocked with the main feed adjusting lever 22 is installed on the left side of the back of the lower part of the sewing machine body 10 via a bracket (not shown).

[0018] The sewing machine of this embodiment is a so-called cylinder bed type flat sewing machine, and the driving motor 70 and the main feed amount adjusting motor 50 are installed on the right side of the base of the cylinder part (not shown) on the lower left of the sewing machine body 10. Thereby, space is ensured so that the driving equipment does not get in the way when inserting and sewing a tubular fabric to the base of the cylinder part. Also, even when sewing a flat fabric, the driving equipment is installed at a position where it does not cover the belly of the sewing machine body 10, ensuring space.

[0019] Figure 3 is a left side view of the lower thread cutting and differential adjustment device applied to the sewing machine of the present invention. The main feed amount adjustment member 5 includes a main feed amount adjustment motor 50, a main feed amount adjustment motor crank 51, a main feed amount adjustment link 52, and a main feed amount adjustment lever crank 53. As described above, the main feed amount adjustment motor 50 is installed on the left side of the back of the lower part of the sewing machine body 10 via a bracket. The main feed amount adjustment motor crank 51 is fixed to the motor shaft of the main feed amount adjustment motor 50. One end of the main feed amount adjustment link 52 is connected to the main feed amount adjustment motor crank 51. The main feed amount adjustment lever crank 53 is fixed to the main feed adjustment lever 22 and one end thereof is connected to the other end of the main feed amount adjustment link 52. Thus, when the motor shaft of the main feed amount adjustment motor 50 rotates, the main feed amount adjustment motor crank 51 rotates, the main feed amount adjustment lever crank 53 swings through the main feed amount adjustment link 52, and the main feed adjustment lever 22 swings. The main feed amount adjustment lever crank 53 may be omitted and the main feed amount adjustment link 52 may be directly connected to the main feed adjustment lever 22.

[0020] By rotating the main feed amount adjustment motor 50 through a control device (not shown) as described above, the adjustment of the main feed amount by hand is simplified. Also, by coordinating the operation of the control device and the sewing machine and quickly reducing the main feed amount without stopping the operation after sewing a predetermined length according to the target fabric, fraying prevention at the end of sewing can be performed with less man-hours.

[0021] Figure 4 is a right side view of the bobbin cutting and differential adjustment device of a sewing machine applied to the present invention. The differential ratio adjustment member 6 comprises a differential ratio adjustment cam 60, a differential ratio adjustment crank 61, and a differential ratio adjustment link 62. The differential ratio adjustment cam 60 is fixed to the motor shaft of the drive motor 70. The differential ratio adjustment crank 61 is pivotably mounted on a bracket (not shown) installed on the lower right side of the sewing machine body 10, with one end engaging with the differential ratio adjustment cam 60. One end of the differential ratio adjustment link 62 is connected to the other end of the differential ratio adjustment crank 61. The other end of the differential ratio adjustment link 62 is connected to a pivoting end extending downward from the differential ratio adjustment lever 23. In this embodiment, the engagement between the differential ratio adjustment crank 61 and the differential ratio adjustment cam 60 is made via a driven pin 63 fixed to one end of the differential ratio adjustment crank 61.

[0022] As described above, by rotating the drive motor 70 through the control device, the motor shaft rotates, the differential ratio adjustment cam 60 rotates, the driven pin 63 moves in the front-rear direction, the differential ratio adjustment crank 61 swings, the differential ratio adjustment link 62 moves, the differential ratio adjustment lever 23 swings, and thus the differential ratio is adjusted. In this sewing machine, the differential ratio increases when the lower swinging end of the differential ratio adjustment lever 23 swings forward, as the differential feed amount increases.

[0023] Figure 5 is a plan view of the bobbin cutting drive cam and differential ratio adjustment cam of the bobbin cutting and differential adjustment device of a sewing machine applied to the present invention. In this embodiment, the bobbin cutting drive cam 72 has a cam contour that includes a region 720 in which the cutter drive lever 30 operates and a region 721 in which the cutter drive lever 30 does not operate, and the differential ratio adjustment cam 60 has a cam contour that includes a region 600 in which the differential ratio adjustment lever 23, which operates in the region 721 in which the cutter drive lever 30 does not operate, operates. Figure 5(a) shows how the bobbin cutting drive cam 72, which is fixed to the motor shaft of the driving motor 70, contacts and engages with the driven lever 73 at the boundary between region 720 and region 721 of the cam contour. The driven lever 73 is movable in the left-right direction and is located to the right of the bobbin cutting drive cam 72 and is pressed to the left by a spring (not shown) in the negative direction of the X axis. In this state, the driven lever 73 is in the leftmost position.

[0024] Figure 5(b) shows how the lower thread cutting drive cam 72, which is fixed to the motor shaft of the driving motor 70, contacts and engages with the driven lever 73 in the region 720 of the cam contour. From the state in Figure 5(a), the motor shaft of the driving motor 70 rotates counterclockwise as seen in the figure to reach the state in Figure 5(b). In this embodiment, it rotates approximately 90 degrees, and in this state, the driven lever 73 is in the far right position.

[0025] Figure 5(c) shows how the lower thread cutting drive cam 72, fixed to the motor shaft of the driving motor 70, contacts and engages with the driven lever 73 in the cam contour region 721. From the state in Figure 5(a), the motor shaft of the driving motor 70 rotates clockwise as seen in the figure to reach the state in Figure 5(c). In this embodiment, it rotates by approximately 45 degrees, and in this state, the driven lever 73 is in the leftmost position, the same as in the state in Figure 5(a). Region 721 is made up of a cam contour in the shape of an arc with the center of rotation concentric, and the driven lever 73 does not move within this region. Within this region, the differential ratio adjustment cam 60, fixed to the motor shaft of the driving motor 70, contacts and engages with the driven pin 63, which is pressed by a spring (not shown) in the cam contour region 600. In state 5(a) of Figure 5, the driven pin 63 is in its foremost position. As the state changes from 5(a) to 5(c), the driven pin 63 moves backward (in the positive direction of the Y-axis), causing the differential ratio adjustment crank 61 to oscillate. From state 5(c) of Figure 5, if the differential ratio adjustment cam 60 rotates clockwise as seen in the figure, the driven pin 63 moves further backward, and if it rotates counterclockwise, the driven pin 63 moves forward.

[0026] Figure 6 is a perspective view from the right rear showing the operation of the bobbin cutting and differential adjustment device of a sewing machine applied to the present invention. Figures 6(a), (b), and (c) correspond to Figures 5(a), (b), and (c), respectively. The bobbin cutting drive member 7 comprises a bobbin cutting drive cam 72, a driven lever 73, a driven lever shaft 74, and a shaft base 78. As described above, the bobbin cutting drive cam 72 is fixed to the motor shaft of the drive motor 70, and the driven lever 73 is positioned to the right of the bobbin cutting drive cam 72 and is pressed to the left by a spring to contact and engage with the cam contour of the bobbin cutting drive cam 72. One end of the driven lever shaft 74 is fixed to the driven lever 73 and moves linearly in the left-right direction, and the other end is connected to the cutter drive lever 30. The shaft base 78 is installed on the sewing machine body 10 and pivotally supports the driven lever shaft 74 so that it can move linearly in the left-right direction. In this embodiment, the driven lever 73 and the cutter drive lever 30 are connected via a shaft connecting member 76 fixed to the driven lever 73 and a cutter drive rod 31 connected to the shaft connecting member 76.

[0027] The auxiliary shaft 75 is positioned behind the driven lever shaft 74 and is supported by a shaft base 78, allowing it to move linearly in the left-right direction. One end of the auxiliary shaft 75 is fixed to a shaft connecting member 76, so that when the driven lever shaft 74 moves linearly in the left-right direction, the auxiliary shaft 75 also moves linearly in the left-right direction. One end of the thread loosening bracket 77 is connected to the lower end of the thread loosening lever 42 and the other end is fixed to the auxiliary shaft 75. As a result, when the driven lever 73 moves linearly in the left-right direction, the driven lever shaft 74 and the auxiliary shaft 75 move linearly in the left-right direction, and the cutter drive lever 30 and the thread loosening lever 42 swing in the left-right direction.

[0028] In Figure 6(a), the driven lever 73 is in its leftmost position, and the driven pin 63 is in its foremost position. At this time, the rear end of the cutter drive lever 30 is to the left, so the cutter is gripping the bobbin thread, and the lower end of the thread loosening lever 42 is to the left, so the tension applied to the thread by the thread tensioner 40 has not been released.

[0029] In Figure 6(b), the driven lever 73 is in the far right position. When the state changes from Figure 6(a) to Figure 6(b), the rear end of the cutter drive lever 30 moves to the right, causing the cutter to cut the bobbin thread. Simultaneously, the lower end of the thread loosening lever 42 moves to the right, releasing the tension applied to the thread by the thread tensioner 40. Then, when the state changes from Figure 6(b) to Figure 6(a), the rear end of the cutter drive lever 30 moves to the left, causing the cutter to grip the bobbin thread in cooperation with the thread holder. Therefore, by rotating the motor shaft of the driving motor 70 to transition through Figures 6(a), (b), and (a), the bobbin thread cutting operation becomes possible.

[0030] In Figure 6(c), the driven lever 73 is in its leftmost position, and the driven pin 63 has moved backward from its foremost position. As mentioned above, if the differential ratio adjustment cam 60 rotates from this state, the driven pin 63 moves back and forth, and therefore the differential ratio adjustment lever 23 swings via the differential ratio adjustment crank 61 and differential ratio adjustment link 62. The cutter drive lever 30 is maintained with its rear end on the left, and the gripping of the bobbin thread is also maintained. This state is used when performing normal sewing, and the differential ratio can be adjusted by rotating the motor shaft of the drive motor 70. For example, if the differential ratio is 1.0 in the state of Figure 6(c), the differential ratio can be increased to 1.2, etc. by moving the driven pin 63 backward and swinging the lower end of the differential ratio adjustment lever 23 forward, and the differential ratio can be decreased to 0.8, etc. by swinging the differential ratio adjustment lever 23 in the opposite direction.

[0031] According to the flatlock sewing machine bobbin cutting and differential adjustment device described above, in a flatlock sewing machine equipped with a bobbin cutting mechanism including a cutter drive lever and a feed mechanism including a differential ratio adjustment lever, by providing one drive motor, a bobbin cutting drive member that drives the cutter drive lever in conjunction with the drive motor, a differential ratio adjustment member that drives the differential ratio adjustment lever in conjunction with the drive motor, and a control device for the drive motor, bobbin cutting and differential adjustment can be performed with a single drive device, thereby suppressing cost increases and control complexity, while reducing the number of steps required for differential ratio adjustment and achieving accurate reproducibility.

[0032] The present invention is not limited to the embodiments described above, and those skilled in the art can implement the invention by adding various modifications to the above embodiments without departing from the spirit of the invention, and the present invention also encompasses such modifications. Furthermore, although a flatlock sewing machine was used in this embodiment, the invention is not limited thereto, and can be implemented in, for example, a single-needle or multi-needle double chain stitch sewing machine equipped with a bobbin cutting device similar to that of a flatlock sewing machine. [Explanation of Symbols]

[0033] 1 Sewing machine 2 Feed mechanism 3. Bolt thread cutting mechanism 4. Thread loosening mechanism 5 Main feed amount adjustment member 6. Differential ratio adjustment member 7. Lower thread cutting drive member 10 Sewing machine body 11 needles 12 Needle Plates 20 Main feed teeth 21 Differential feed dogs 22 Main feed adjustment lever 23 Differential ratio adjustment lever 30 Cutter drive lever 31 Cutter drive rod 40 Thread tensioner 41 Tension release member 42. Thread loosening lever 50 Main feed amount adjustment motor 51 Main feed amount adjustment motor crank 52 Main feed rate adjustment link 53 Main feed amount adjustment lever crank 60 Differential ratio adjustment cam 61 Differential ratio adjustable crank 62 Differential Ratio Adjustment Link 63 Driven pin 70 Driving motor 71 Motor mounting bracket 72. Lower thread cutting drive cam 73 Driven lever 74 Driven lever shaft 75 Auxiliary shaft 76 Axle connecting member 77 Thread loosening bracket 78 Axis base 600 (the range in which the differential ratio adjustment lever operates) 720 (area where the cutter drive lever operates) 721 (Cutter drive lever does not operate) area

Claims

1. A flatlock sewing machine comprising a bobbin cutting mechanism including a cutter drive lever and a feed mechanism including a differential ratio adjustment lever, wherein the device for bobbin cutting and differential adjustment of the flatlock sewing machine is characterized by comprising one drive motor, a bobbin cutting drive member that drives the cutter drive lever in conjunction with the drive motor, a differential ratio adjustment member that drives the differential ratio adjustment lever in conjunction with the drive motor, and a control device for the drive motor.

2. The lower thread cutting and differential adjustment device for a flatlock sewing machine according to claim 1 is characterized by comprising: a lower thread cutting drive cam, the lower thread cutting drive member of which is fixed to the motor shaft of the drive motor; a driven lever that engages with the lower thread cutting drive cam and moves linearly; a driven lever shaft, one end of which is fixed to the driven lever and moves linearly, and the other end of which is connected to the cutter drive lever; and a shaft base installed on the sewing machine body that pivotally supports the driven lever shaft.

3. The lower thread cutting and differential adjustment device for a flatlock sewing machine according to claim 2 is characterized by comprising a differential ratio adjustment cam to which the differential ratio adjustment member is fixed to the motor shaft of the drive motor, a differential ratio adjustment crank that engages with the differential ratio adjustment cam and swings, and a differential ratio adjustment link to which one end is connected to the differential ratio adjustment crank and the other end is connected to a differential ratio adjustment lever.

4. The lower thread cutting drive cam has a cam contour that includes a region in which the cutter drive lever operates and a region in which the cutter drive lever does not operate, and the differential ratio adjustment cam has a cam contour that includes a region in which the differential ratio adjustment lever operates that acts in the region in which the cutter drive lever does not operate, characterized in that the lower thread cutting and differential adjustment device for a flatlock sewing machine according to claim 3.

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