KR20020048867A - Upper thread control in a sewing machine - Google Patents

Abstract

PURPOSE: To draw out an end of a needle thread to the underside of a fabric by restricting amount of feeding of the needle thread of the first needle stitch by a simple constitution and to avoid to draw out the needle thread when the fabric is taken out by restricting the amount of feeding of the needle thread when a sewing needle is stopped at the top dead point after the thread is cut. CONSTITUTION: A hook 5 is up and down movably disposed on the front HF of the head part H of a sewing machine and after the thread is cut, before the sewing needle 1 moved to the top dead point, the needle thread T is pinched by the top face 5a and a pinching piece 7 by elevating the hook 5. In addition, when operation of the sewing machine is started and a thread take up lever 4 is lowerd once and then it is elevated to reach the top dead point, the hook 5 is lowered.

Description

UPTH THREAD CONTROL IN A SEWING MACHINE

The present invention relates to a sewing machine that can limit the supply amount of the upper thread.

In general, a technique is known for sewing the upper thread end to the lower surface of the fabric when starting to make the finish of the seam look beautiful.

This sewing machine is shown in Japanese Unexamined Patent Publication No. Showa 62-186892, wherein the upper thread end is drawn to the lower surface of the fabric of the first needle stitch by limiting the supply amount of the upper thread.

Such a sewing machine is threaded to pinch the upper thread between the thread take-up and the needle such that the thread-clamp pinches the upper thread when the thread loop formed at the first stitch of the thread loop formed at the short side of the upper thread where the blade point of the hook extends from the needle. It has a seal-clamp arranged below. After that, while the loop is pulled by the further rotation of the hook without the provision of a thread on the thread take-up side of the needle, tension is applied to the upper thread at the one side that pulls the thread end downward through the needle hole on the cloth and the needle plate. Is applied.

Another type of sewing machine is provided with a high lift of the presser foot to facilitate the processing of the material with a high lift of the needle (large stroke). In other words, the sewing machine generally stops operation with the thread take-up stopped at the upper dead point after thread trimming, where the needle is positioned below the upper dead center where the needle interferes with the possible fabric when the fabric is processed under the presser foot. do. Thus, the upper shaft of the sewing machine rotates in the opposite direction to lift the needle from the stop position to the upper dead center to ensure a high lift of the needle.

In the first aspect of the conventional sewing machine described above, the structure for pinching the upper thread is complicated and expensive. In particular, the seal-clamp should be small in size so that the area in contact with the upper thread is minimized for reasons of poor seam quality. This requires precise parts and incurs high equipment costs.

Such a sewing machine has a thread-clamp in which a user sews a thread for pinching the upper thread, resulting in low working efficiency.

In another form of the sewing machine described above, such as the needle moving in the direction of the upper dead center by reverse rotation of the upper shaft, the take-up machine descends, causing the upper thread between the take-up machine and the needle to loosen. When the fabric is removed under this condition, the loose thread is pulled out with the fabric, so that the end-side thread extending from the needle remains longer than necessary.

Another problem with the first type of conventional sewing machine occurs when the upper thread tip is pulled out to the fabric lower surface of the first needle stitch. Sometimes the sewing machine fails to pull the thread tip under the cloth due to the normal operating speed of the sewing machine at the first stitches. That is, the rapid downward movement of the needle due to the high speed operation of the sewing machine causes the upper thread to be strongly lowered, and force acts out of the thread from the thread-clamp, resulting in a failure to pull out the thread tip under the fabric.

It is therefore an object of the present invention to provide a sewing machine in which the upper thread end is pulled out to the lower surface of the fabric of the first needle by limiting the supply amount of the upper thread with a simple structure.

Another object of the present invention is to provide a sewing machine in which the upper thread is not pulled out when removing the fabric by limiting the supply amount of the upper thread when the needle stops at the upper dead center after thread trimming.

It is a further object of the present invention to provide a sewing machine that operates at low speed at least at the first needle stitch to ensure that the sewing machine is pulled from the first needle stitch to the fabric lower surface.

1 is a partial plan perspective view showing a close up of a sewing machine head used in the present invention.

Fig. 2 is a schematic diagram showing a close proximity to a catching hook according to the first embodiment of the present invention.

3 is a control block diagram of the present invention.

4 is a time graph illustrating the operation of a needle bar and thread take-up in accordance with the present invention.

5 shows a state in which the thread take-up is located in the upper dead center and the locking hook is in the lowered position according to the present invention.

6 is a series of schematic diagrams showing the relationship between a take-up, a needle and a hook in accordance with the present invention.

7 is an acceleration curve showing normal-start and slow-start when the sewing machine starts up.

8 is a schematic perspective view showing a close proximity to a locking hook according to a second embodiment of the present invention.

* Description of Major Symbols in Drawings *

100: sewing machine 1: needle

2: needle bar 3: thread induction part

4 thread take-up 4a thread hole

5: locking hook (locking member, limiting member) 6: air cylinder

7: pinching piece (limiting means) 8: thread tension regulator

10: needle plate C: controller

15: sewing machine controller 16: motor controller

24: D / A converter (driving current limiting means)

25: motor driver (drive current limiting means)

26: comparator (driving current limiting means)

M: Sewing Motor H: Sewing Machine Head

B: Sewing machine bed T: Upper thread

In order to solve the above-mentioned problem, the present invention for a sewing machine is provided. In the first claim of the present invention, the sewing machine has a thread hole through which the upper thread supplied from the upper thread source passes and moves up and down, and the needle moving up and down together with the thread in the thread take-up passing through the needle ear in conjunction with the thread take-up. It includes. The sewing machine further includes a locking member and a driving means. The catching member is disposed adjacent to the thread take-up and movable up and down to fix the upper thread passing through the thread hole at the raised position located adjacent to the upper dead center of the thread take-up by the upper surface. The driving means drives the locking member up and down.

If, for example, the locking member secures the upper thread before the blade point of the hook hooks the loop at the first stitches, the upper thread is tensioned when the hooked loop rotates around the hook. At this time, if the thread supply at the thread take-up side is restricted, the thread is pulled at the thread end side, and the thread end is pulled out to the lower surface of the fabric.

The simple structure of raising the catching member can achieve that the thread tip is pulled out under the fabric from the first stitches, resulting in a reduction in the device cost. In addition, the simple fixing of the upper thread together with the upper surface of the catching member reduces the user's threading of the thread-clamp and improves the working efficiency.

Furthermore, for example, before the fabric after thread trimming is removed under the needle, if the locking member secures the upper thread, the upper thread is not pulled out together with the fabric, so that the upper thread in the needle remains in the proper length.

In this structure, the catching member is selected to be arranged on the upper thread supply side with respect to the thread take-up, and can be arranged on the needle side.

In the second claim of the present invention, the sewing machine further includes a control means for controlling the driving means to secure the upper thread by raising the locking member after the thread is trimmed and before the cloth is removed from under the needle.

In this structure, the proper length of the upper thread remains on the needle.

In the third claim of the present invention, the sewing machine further comprises a hook and control means. The hook has a blade point for hooking a thread loop formed adjacent to the needle ear and interlocks with the needle and the thread take-up. The controller controls the driving means to raise the locking member to secure the upper thread before the blade point hooks the loop at the first stitches.

In this structure, the sewing machine can pull the upper thread end from the first needle stitch to the fabric lower surface.

In the fourth claim of the present invention, the upper surface of the raised engagement member is located somewhat lower than the thread hole on the thread take-up located at the upper dead center.

In such a device, the small amount of upper thread supplied to the needle during the first needle stitching prevents the upper thread from exiting or leaving the needle stitches.

In the fifth claim of the present invention, the sewing machine of any one of the first to fourth claims of the present invention includes a pinching piece for pinching and fixing the upper thread together with the upper surface of the catching member which is disposed on the catching member and rises.

In this structure, the sewing machine ensures the effect of the first to fourth claims of the present invention. In particular, even if the blade point hooks the thread loop and pulls the thread tip down the fabric with the thread tip pressed between the presser foot and the fabric, the thread end does not pull the upper thread out of the thread take-up and the fabric bottom surface for the pinching force between the presser foot and the fabric Can be pulled out stably.

In order to achieve the effect of the fourth claim of the present invention, which applies to the fifth claim in conjunction with the previous claim of the present invention, it is necessary to arrange the catching member and the pinching piece on the side of the upper thread source in relation to the take-up.

In the sixth claim of the present invention, the sewing machine includes a thread take-up, a needle, a hook, and limiting means for limiting the upper thread, and extracts the upper thread end from the first needle stitch to the lower surface of the fabric while limiting the upper thread. The sewing machine includes a thread take-up, a needle, a motor for driving the hook, and a drive current limiting means for limiting the motor driving current for gradually accelerating at least the sewing speed of the sewing machine during the first needle stitching.

The operating speed of the sewing machine is limited by the drive current limiting means for at least the first stitches.

Therefore, the upper thread end can be stably drawn out to the lower surface of the fabric without the upper thread due to the downward operation of the needle is not drawn to the thread-clamp.

A catch hook to be described below, a seal-clamp described in the prior art, or the like is used as the limiting means. Restriction means may be used where it is possible to restrict the upper thread from the first stitches only to pull the upper thread end into the fabric bottom.

First embodiment

As shown in Figure 1, the sewing machine 100 of the present invention has a sewing machine bed (B) to allow the fabric to be positioned above itself, and a sewing machine head (H) facing the sewing machine bed (B).

The needle 1 has a needle ear adjacent to the lower end of the needle, and the upper end of the needle is fixed to a needle bar 2 which is movable up and down. The thread guide 3 attached to the lower end of the jaw portion HA of the head H guides the upper thread T to the needle 1.

The thread take-up 4 has a thread hole 4a through which the thread T passes and is formed vertically on the front surface HF of the head H and is located at the upper right side of the thread guide part 3. Swing up and down. The thread hole 4a is formed in the left-right direction (direction perpendicular to slot H1) in FIG. 1 shows a state where the take-up machine 4 is located at the upper dead point of the take-up machine.

The hook which protrudes from the front surface HF is marked with (5). The hook 5 moves up and down along the slot H2 parallel to the slot H1 and located on the right side. The hook 5 is driven up and down by an air cylinder 6 fixed on the upper surface of the head H. 2, the hook 5 is fixed to the rod 6a of the cylinder 6, and is shown by the double-dashed line and the raised position shown by the solid line as the rod 6a moves up and down. Move between descending positions.

The pinching piece 7 is provided on the locking hook 5 and pinches and fixes the seal T at the right side of the thread take-up 4 together with the hook 5 surface 5a in the raised position. The hook 5 has the surface 5a of the raised position (shown in solid line) slightly lower than the threaded hole 4a of the thread take-up 4 at the upper dead point so that the thread T does not interfere. The surface 5a of the lowered position (shown by the dashed line) is arranged to be lower than the thread hole 4a of the thread take-up 4 at the lower dead point.

The locking hook 5 constitutes a locking means, the locking hook 5 or the locking hook 5 and the pinching piece 7 constitute a limiting means, and the air cylinder 6 constitutes a driving means.

In connection with FIG. 1, the thread tension regulator 8 is mounted on the lower right side of the slot H1 and induces a thread T extending from the spool serving as the upper thread source to the thread take-up 4. The regulator 8 provides tension to the thread T and pinches the thread T between the thread tension disks 8a and 8b.

The needle plate 10 has a needle hole 10a through which the needle 1 passes, the surface of the needle plate is a plane flush with the surface of the bed B, and the fabric (not shown) It is located above.

Although not shown in the drawings, the sewing machine head H drives the needle rod for moving the upper and lower needle rods 2 driven by the sewing motor M (see FIG. 3) up and down. Mechanism and a thread take-up oscillation mechanism for swinging the thread take-up 4 driven by the upper shaft up and down. Since the needle bar 2 and the thread take-up 4 are connected to the upper shaft, the needle 1 and the thread take-up 4 mesh with each other. The bed B receives a hook 11 (see FIG. 6) disposed below the needle plate 10 to form a seam with the needle 1. The hook 11 is also connected to the upper shaft and driven by the upper shaft. Therefore, the needle 1, the thread take-up 4, and the hook 11 interlock with each other.

The bed B further accommodates a thread trimming device (not shown) driven by the thread trimming drive source 21 (see Fig. 3) for trimming the upper thread and the lower thread after the sewing is completed.

The control member related to the flowchart of FIG. 3 is demonstrated.

The controller C is composed of a sewing machine controller 15 and a motor controller 16. The sewing machine controller 15 and the motor controller 16 include a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), and an I / O interface.

The sewing machine controller 15 stores the control program and control data necessary for the sewing operation in the ROM in order to provide a command signal to various devices connected to the motor controller 16 via the I / O interface according to the control program. Store swappable or temporary data in RAM.

The input of the sewing machine controller 15 is connected to the needle position detector 17 and the pedal sensor 18.

The needle position detector 17 is connected to the needle 1 every revolution of the upper shaft so that the detected signals (needle top signal, needle bottom signal) can be provided to the sewing machine controller 15 as well as the motor controller 16. Detects adjacent top dead center and adjacent bottom dead center. The number of stitches is counted as 0, 0.5, 1.0, --- at half the stitches each time, thereby indicating the needle position.

The pedal position 18 is mounted on a foot pedal to send an ON signal to the sewing machine controller 15 when the user operates.

The output of the controller 15 is connected to the electromagnetic valve 19 and the driver 20. The valve 19 is connected to the air cylinder 6. The signal from the controller 15 causes the valve 19 to cause expansion and contraction of the cylinder lud 6a from the cylinder 6 to move the catch hook 5 up and down. The driver 20 is connected to the thread trimming drive source 21 to be driven.

The motor controller 16 is connected to the controller 15 and stores a change in the current value indicating the drive current of the sewing motor M in the ROM.

The input of the controller 16 is also connected to the needle position detector 17, the motor phase detector 22 and the motor speed detector 23. The detector 17 sends the generated needle upper and lower signals to the controller 16. The motor phase detector 22 sends a phase signal to the controller 16 and receives a pulse signal from an encoder attached to the upper shaft. The motor speed detector 23 sends a speed signal to the controller 16 and receives a pulse signal from the encoder described above.

The output of the controller 16 is connected to the D / A converter 24 and the motor driver 25. The D / A converter 24 converts the current value signal of the controller 16, generated according to the control program, into an analog signal and sends it to the comparator 26. In order that the detected value does not exceed the given current value, the comparator 26 compares the current value of the converter 24 with the motor current detection value of the motor driver 25, and supplies the drive current value to the driver 25. .

The motor driver 25 supplies the driving current to the motor M according to the driving current value of the comparator 26, the pulse width modulation (PWM) signal for controlling the motor driving current, and the rotation direction signal of the controller 16. The PWM signal is calculated by multiplying the deviation between the command speed value of the controller 15 and the measured speed value of the speed detector 23 by a given gain.

Operations associated with FIGS. 4-7 are described.

The needle bar 2 and the thread take-up 4 interlock with the rotation of the upper shaft based on the phase relationship as shown in FIG. FIG. 6 shows a series of relations between a needle, a thread take-up, and a hook, corresponding to FIGS. 4A to 4E.

The sewing machine controller 15 causes the thread trimming drive source 21 to cut the upper thread T and the lower thread during the thread trimming period after the sewing is completed.

When the phase detector 22 detects the rotational position of the motor M corresponding to the upper dead center of the thread take-up 4 after finishing the thread trimming, the sewing machine is under the control of the controller 15. The motor stops working with the power cut off (see Fig. 5).

Subsequently, the controller 15 drives the air cylinder 6 through the valve 19 so that the rud 6a lifts the catch hook 5 to the raised position and contracts, so that the upper surface 5a is As shown in Fig. 6 (b), the pin T is pinched and fixed with the pinching piece 7.

Next, as shown in Figure 6 (a), the motor (M) is rotated in the reverse rotation section to move the needle bar (2) to the upper dead center to easily remove the cloth, the sewing machine is to start the pedal The machine remains stopped until the machine stops. When the fabric is removed from underneath the needle 1, the thread T is not pulled out with the fabric because it is fixed between the piece 7 and the surface 5a to prevent the movement of the thread T.

Then, when the pedal is started, an ON signal is sent from the pedal sensor 18 to the controller 15 and drives the motor M to start the sewing machine through the controller 16 and thus passes through the operating section. .

More specifically, when the sewing machine starts to operate, the needle 1 is lowered and the thread take-up 4 moves upward until reaching the upper dead center as shown in Fig. 6 (b). Thereafter, as shown in Fig. 6C, the needle 1 reaches the bottom dead center with the downward motion of the thread take-up 4. At this time, since the thread T is still fixed between the piece 7 and the surface 5a, the thread T remains under tension. And since the upper surface 5a of the raised position is lower than the thread hole 4a of the upper dead center, the thread T is the needle 1 by the length of the height difference when the thread take-up 4 moves downward from the upper dead center. And thus prevents the needle from slipping out or pulling out the needle sweat.

Subsequently, as the needle 1 moves upward from the lower dead center as shown in Fig. 6 (d), the thread loop L is formed adjacent to the upper end of the needle 1, and the blade point 11a Is fixed by. As the hook 11 further rotates into the loop L, as the loop L is widened, the hook 11 is caused by the continuous fixing of the seal T between the hook hook 5 and the piece 7. Does not pull the thread from the side of the needle 1, and pulls the thread from the short side as shown in FIG. 6 (e) to pull the thread end TE downward from below the cloth (lower surface) and the needle hole 10a. .

Thereafter, the needle take-up 4 moves in the direction of the upper dead center as shown in Fig. 6 (b) while the needle 1 moves back to the upper dead point as shown in Fig. 6 (a). When the upper dead center of the thread take-up 4 is detected, the cylinder rud 6a lowers and expands the locking hook 5 as shown in FIG. Since the locking hook 5 descends after the thread take-up 4 is located at the upper dead point, the thread T does not loosen and thus does not interfere with the member adjacent to the thread take-up 4.

After the locking hook 5 is lowered, normal sewing is performed, the thread is cut, the hook 5 is raised again as described above, and the sewing machine is stopped with the needle bar 2 located at the upper dead point and the next pedaling is performed. Wait

In the sewing machine of the present invention, the sewing machine operates slowly during the period between the start of the sewing machine and the lowering of the locking hook 5 so that the thread end is stably drawn out to the lower surface of the fabric. This slow-start control is described below.

When the user starts the pedal, the ON signal of the pedal sensor 18 is sent to the sewing machine controller 15 to instruct the motor controller 16 to output the signal. The controller 16 selects a limited current value for slow-start control among various current values stored in the controller in advance, supplies the selected current value to the D / A converter 24, and the converter converts the converted analog signal into a comparator. Output to (26). The comparator 26 compares the motor current detection value of the motor driver 25 with the limit current value for transmitting the drive current signal to the driver 25 so that the detected value does not exceed the limit current value.

The driver 25 supplies the drive current to the motor M in accordance with the drive current signal of the comparator 26, the PWM signal of the controller 16, and the rotation direction signal. Thus, the sewing machine is gradually accelerated by a slowly rising curve as shown in FIG.

The number of stitches is counted to 1.0 by the signal detected by the needle position detector 17 (after the sewing machine is started, the number of stitches is counted to 0.5 when the needle 1 reaches the bottom dead center, and when the top dead center is reached The number of stitches is counted as 1.0), when the upper dead center of the thread take-up 4 is detected by the motor phase detector 22, the motor controller 16 selects a general current value from various current values, and selects the selected current value. Is supplied to the comparator 26 via the D / A converter 24, and the general current value is larger for general acceleration than the limited current value for the slow-start control.

As a result, the sewing machine is accelerated under normal motor control and relaxes the current limitation.

In Fig. 7, the ordinate indicates the rotational speed of the motor M, and the abscissa indicates the time. Thus, the slope represents the amount of acceleration. The dashed line curve is the acceleration curve under normal motor control, and the solid line curve is the acceleration curve under limit current.

The motor controller 16, the D / A converter 24, the comparator 26 and the motor driver 26 constitute drive current limiting means.

In the above-described first embodiment, the time for raising the catch hook 5 after thread trimming is the time before the motor M reversely rotates after the sewing machine stops, but after the time interval and under the needle 1 As long as it is set to the time before removal, this time is not limited. However, if it is set to the time of sewing machine stop as in the embodiment, the upper thread can be fixed stably.

While the hook 5 is kept fixed in the raised position during the sewing machine regular section of the embodiment to prevent the upper thread from being pulled out when removing the fabric and to simply control the fixing of the thread at the first needle stitch, the hook 5 is transitioned. Once removed, it can be lowered. However, it is necessary to fix the thread T in the raised position before the end of the thread is pulled out from the first needle stitch to the fabric lower surface. However, if the thread T is fixed during the sewing machine stop period as in the embodiment, erroneous pulling of the thread T can be prevented even when the next material is placed under the needle.

The first embodiment uses the pinching piece 7 to pinch the seal T together with the catching hook 5, but the thread T is fixed to some extent using only the hook 5 without the piece 7. It is possible to do For example, if the material is a thin fabric, it may be sufficient to secure the thread T only with the hook 5, since the thread tension is not very strong when removing the fabric. It is also possible to use a high friction material on the hook 5 at the part in contact with the seal T in order to increase the clamping force using only the hook 5.

Regarding the time interval for lowering the hook 5, the first embodiment specifies the time for the take-up machine 4 to reach the top dead center after one cycle of the needle 1 up and down motion, but the end of the thread at the first needle stitch This time period is not limited as long as it can be pulled out to the fabric bottom surface with the contraction of.

The limitation of the motor drive current is relaxed at the same time as the hook 5 is lowered in the embodiment, but may be relaxed, for example, after finishing the lowering of the hook 5.

Second embodiment

A second embodiment of the present invention is described with reference to FIG. 8.

The second embodiment is somewhat different from the first embodiment in the operation of the hook in relation to the hook and the hook. The description is limited to parts different from the first embodiment.

The locking hook 50 has a similar L shape, the center of the hook is supported in the head H and swingable around the rotary shaft 51. One side of the hook 50 is a locking portion 52 for fixing the seal T, and the shaft 51 for moving to the level rising position (of the solid line) and the lowering position inclined downward (of the double dashed line). Swing around. The locking portion 52 protrudes from the head surface HF in the raised position and enters the head H in the lowered position. Here, the slot H1 for the thread take-up 4 and the slot H3 located on the right side (mounting force 8 side) of the slot H1 and parallel to the slot H1 are on the head surface HF. Formed. The catching portion 52 may protrude from the surface HF along the slot H3.

The upper surface 50a of the hook 50 in the raised position is somewhat lower than the thread hole 4a of the thread take-up 4 at the upper dead point as in the first embodiment.

The end of the other side of the hook 50 is rotatably connected to the cylinder lud 60a of the cylinder 60, which acts as the drive means. The contraction / expansion operation of the rud 60a causes the locking portion 52 to move up and down.

The pinching piece 70 is fixed at the top of the slot H3 to pinch and secure the seal T to the upper surface 50a in the raised position.

The operation manner of the second embodiment is described. Initially, the locking portion 52 is in the lowered position together with the pushed out cylinder rud 60a. When the rud 60a contracts, the hook 50 swings around the shaft 51. This operation moves the fixing portion 52 to the raised position to pinch and fix the seal T between the surface 50a and the piece 70.

In the second embodiment, the time interval for fixing or relaxing the seal T is the same as that of the first embodiment, and this description is omitted.

In the second embodiment, the catching hook 50 constitutes the catching member, the catching hook 50 or the pair of catching hooks 50 and the pinching piece 70 constitute the restricting means, and the air cylinder 60 Configure the drive means.

The present invention is not limited to the above embodiments, and various changes and modifications can be made within the spirit and scope of the present invention.

According to the first claim of the present invention, the simple structure of raising the catching member can pull the thread end under the fabric from the first stitches, resulting in a low cost device. In addition, the simple fixing of the upper surface and the upper thread of the locking member prevents the user from threading the thread-clamp, thereby improving the working efficiency.

According to the second claim of the present invention, the proper length of the upper thread remains on the needle.

According to the third claim of the present invention, the sewing machine can pull the upper thread end from the first needle stitch to the fabric lower surface.

According to the fourth claim of the present invention, a small amount of the upper thread is supplied to the needle during the first needle stitching to prevent the upper thread from falling out of the needle or pulling out the needle stitch.

According to the fifth claim of the present invention, the sewing machine ensures the effect of the first to fourth claims of the present invention. In particular, the end of the thread can be stably drawn out to the lower surface of the fabric against the pinching force between the presser foot and the fabric without pulling the thread from the thread take-up.

According to the sixth aspect of the present invention, the upper thread end can be stably drawn out to the lower surface of the fabric without pulling the upper thread from the thread-clamp due to the downward operation of the needle.

Claims (6)

A sewing machine comprising a thread take-up device having a thread hole through which an upper thread supplied from an upper thread source passes, and moving up and down, and a needle moving up and down together with the upper thread passing through the needle ear from the thread take-up in association with the thread take-up device, A catching member disposed adjacent to the thread take-up and movable up and down so that the upper thread passing through the thread hole at the raised position adjacent to the upper dead center of the thread take-up is caught on an upper surface; And Sewing machine comprising a drive means for driving the locking member up and down. The sewing machine according to claim 1, further comprising control means for controlling the driving means to raise the locking member to fix the upper thread before removing the fabric after thread trimming under the needle. The method of claim 1, A hook having a blade point for hanging a thread loop formed adjacent to the needle ear of the needle, the hook for interlocking the needle with the thread take-up; And And sewing means for controlling the driving means to raise the locking member to secure the upper thread before the blade point hooks the loop at the first needle stitch. 4. A sewing machine as claimed in claim 3, wherein said upper surface of said raised locking member is located somewhat lower than said thread hole on said thread take-up located at said upper dead center. 5. The sewing machine as claimed in any one of claims 1 to 4, further comprising a pinching piece for pinching and fixing the upper thread together with the upper surface of the raised locking member and positioned on the locking member. As sewing machine: Thread take-ups having a thread hole through which the upper thread supplied from the upper thread source passes, and moving up and down; A needle moving up and down together with the upper thread passing through the needle ear from the thread take-up in association with the thread take-up; A hook having a blade point for hanging a thread loop formed adjacent to the needle ear of the needle, the hook for interlocking the needle with the thread take-up; And Limiting means for limiting the upper thread, A sewing machine for drawing out the upper thread end to the lower surface of the fabric of the first needle stitch while limiting the upper thread: A motor for driving the thread take-up, the needle, and the hook; And And a drive current limiting means for limiting the motor drive current to gradually accelerate the sewing speed of the sewing machine until at least the upper thread end is drawn out to the fabric lower surface of the first needle stitch.