JP2002239280A - Needle thread clamping device for sewing machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a needle thread clamping device capable of surely holding the tip end of a needle thread by increasing the length of the needle thread left after cutting. SOLUTION: The needle thread clamping device comprises tension units 50 and 52 arranged on a thread path leading from a thread supply source to a needle 32 for applying predetermined tension to a needle thread 33, a thread handler 54 arranged on the thread path for drawing up or down the thread through vertical movement, a wiper 60 having a tip end portion 60a capable of intersecting the vertical locus 35 of a needlebar to catch the end of the needle thread thereby after cutting and a holding mechanism 40 for holding the tip end of the needle thread caught by the wiper. The needle thread clamping device further comprises a control means 70 which raises the thread handler before cutting the needle thread to maintain the tension thereof and lowers the same after the completion of cutting the needle thread to release the tension thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a needle thread clamp device for a sewing machine.

[0002]

2. Description of the Related Art In an industrial sewing machine provided with a wiper, upper and lower threads are cut below the sewing cloth after the sewing is completed, and the upper thread is pulled upward by the wiper. When starting the next sewing in this state, since the tip of the upper thread is located near the sewing machine needle, if the sewing is not started while holding the tip of the upper thread, the tip of the upper thread may flap, Its tip is sewn many times to form a so-called bird's nest, which makes it unattractive. For this reason, various needle thread clamp devices for holding the tip of the needle thread have been devised.

FIG. 1 shows an example of such a needle thread clamp device.
This will be described with reference to FIGS. In FIG. 15, an upper thread clamp device 10 is disposed near a sewing needle 2 attached to a lower portion of the sewing machine 1. The needle thread clamp device 10 is entirely attached to a base 1a of a sewing machine via a holding table 11, and a pipe 12 extending horizontally with respect to the base.
Is provided. One end of the pipe 12 communicates with the negative pressure source 4, and a clamp 13 is attached to the other end.

FIG. 16 is an enlarged view of the clamp portion.
As is clear from FIG. 7, an internal space 13a is formed, and two openings 13b and 13c are formed. Opening 13
“b” is connected to the negative pressure source 4 via the pipe 12, and the opening 13 c communicates with the suction nozzle 14. A cylinder 15 having a cylinder rod 15 a is provided above the clamp 13, and a ball 16 is accommodated in an internal space 13 a of the clamp 13. When a negative pressure is generated in the internal space 13a, the ball 16 can float in the internal space 13a.
A conical seating surface 13d on which the ball 16 can be seated is formed in the internal space according to the spherical surface of No. 6. The clamp portion 13 is attached at an oblique angle to the horizontally extending pipe 12, and a suction port 14 a of a suction nozzle 14 attached to a tip of the clamp portion 13 is disposed near a position below the sewing needle 2.

Next, the operation of the sewing machine upper thread clamp device 10 thus configured will be described with reference to FIG. First, as shown in FIG. 18A, after the sewing is completed, the needle thread 3 is cut and pulled up on the upper surface of the sewing cloth by a wiper (not shown), and the tip 3a of the needle thread is placed near the sewing needle 2. positioned. In this state, the negative pressure source 4 is operated to generate a negative pressure in the nozzle 14 through the pipe 12 and suck the tip 3a of the needle thread 3 through the suction port 14a of the nozzle. At this time, the cylinder 15 is not operated yet, and the ball 16 is floating in the internal space 13a of the clamp portion. When the needle thread is sufficiently sucked by the clamp portion 13, the tip 3a of the thread is
It is sucked into the pipe 12 after passing through the space between 6 and the seat 13d.

When such a state is reached, FIG.
, The cylinder 15 is operated, and the cylinder rod 15a is pressed against the ball 16 so that the ball 16 is
Press in the direction of 3d. The ball 16 is pressed against the seat surface 13d while following the seat surface 13d, whereby the needle thread 3 is held between the ball 16 and the seat surface 13d. This state is illustrated in FIG.

[0007] When the thread is securely held, sewing is started. The yarn between the first connection point B and the point A of the nozzle suction port 14a is gradually tightened by the feeding operation (see FIG. 18D).

[0008] As shown in FIG.
A knife 20 is fixed to 4a, and when the point B moves to the point B 'as shown in FIG. 17 by the sewing feeding operation, the needle thread relatively moves with respect to the nozzle suction port 14a. The needle thread 3 is cut obliquely over the edge of the needle 20, and is cut. The cut thread end 3a can be discharged to the outside via the negative pressure source 4 at the time of the next sewing.

[0009]

However, the upper thread clamp device 10 according to the above-mentioned conventional example can suck the upper thread if the remaining length of the upper thread extending from the needle hole of the sewing machine needle 2 after the thread is cut is short. It may not be possible and may cause clamping failure. In particular, in the case of the staggered sewing machine, since the needle moves left and right, the upper thread length after the thread is cut differs depending on whether the final needle position is left or right, so that the possibility of clamping failure increases.

Further, since the distance between the suction port of the clamp device and the needle hole must be shorter than the remaining length of the upper thread, if the remaining length of the upper thread is short, the suction port of the clamp device is arranged at a position close to the needle hole. Inevitably, the area where the operator operates the sewing cloth becomes narrow.

Accordingly, an object of the present invention is to provide an upper thread clamp device capable of securely holding the upper thread end by increasing the remaining length of the upper thread after cutting.

Another object of the present invention is to increase the remaining length of the upper thread after cutting so that the suction port of the clamp device is arranged at a position away from the needle hole, and the operator operates the sewing cloth. An object of the present invention is to provide a needle thread clamp device capable of widening an area at hand.

[0013]

According to the present invention, there is provided a thread tensioner arranged on a thread path from a thread supply source to a sewing needle for applying a predetermined tension to the upper thread, A thread picker that is arranged on the path and raises or lowers the thread by reciprocating, and has a tip that can intersect with the needle bar vertical movement trajectory. The tip can capture the upper thread end after cutting. In a sewing machine upper thread clamp device including a wiper and a holding mechanism for holding an upper thread end captured by the wiper, the thread bobbin is moved forward before the thread cutting operation to maintain the tension state of the upper thread. And a control means for controlling the yarn thread to move backward after the end of the thread cutting operation so as to reduce the tension of the upper thread, thereby providing an upper thread clamping device for a sewing machine.

[0014] It is preferable that the control means controls the wiper to operate after a predetermined time after the thread taker is moved backward.

[0015] It is preferable that the holding mechanism has a tip side suction port disposed so as to face the tip end of the wiper when the wiper is operated.

Further, on the outer peripheral portion of the suction port of the holding mechanism,
It is preferable that a projection for locking the upper thread end is provided outside the wiper movement locus. Further, it is preferable that the projection of the holding mechanism is located above the center of the suction port. The control means can reciprocate the thread taker again after the operation of the wiper.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a needle thread clamp device for a sewing machine according to the present invention will be described with reference to the drawings. First, a schematic configuration will be described with reference to FIG. The present invention is suitable for a staggered sewing machine in which the needle moves left and right, but can also be applied to a normal sewing machine in which the needle does not move left and right.

A lower part of the sewing machine 30 is provided with a presser 31 for pressing a sewing product against a bed surface and a needle bar 34 which can be moved up and down. Needle 32 for passing needle thread 33 through needle bar 34
Is attached, and a suction port 44 provided on one end side of the pipe 42 of the upper thread holding device 40 is arranged near the needle 32.
The other end of the pipe 42 is connected to a negative pressure source 46 (FIG. 8). The operation principle of the upper thread holding device 40 is the same as that of the upper thread clamp device 10 according to the conventional example.

A pretension (first thread tension) 50 and a rotary tension (second thread tension) 52 are arranged on a yarn path from a yarn supply source (not shown) to the needle 32, and apply a predetermined tension to the upper yarn. are doing. A yarn picking device 54 is further disposed on this yarn path. This thread picking device 54
Has a rotatable wire mount 54a and a thread payout wire 54b having one end fixed to the wire mount 54a. The other end of the thread payout wire 54b can be locked with the upper thread, and the other end of the wire mounting base 54a moves up and down by the rotation of the wire mounting base 54a, thereby pulling up or lowering the yarn. More specifically, when the other end of the wire mount 54a rises, tension is applied to the upper thread 33 to make it tension, and when the other end falls, the tension of the upper thread 33 is reduced.

The wiper 60 can be moved so that the tip thereof intersects with the vertical movement locus 35 of the needle bar 34. After catching the end of the yarn 33, the yarn 33 rises and moves in the direction of the suction port 44 of the upper yarn holding device 40. The suction port 44 is disposed so as to oppose the tip of the wiper 60 that has been raised to suck the upper thread end. Further, on the outer peripheral portion of the suction port 44, a projection 44a for locking the upper thread end is provided outside the trajectory of the wiper movement. The protrusion 44 a is located above the center of the suction port 44.

Next, the operation of the wiper 60 will be described with reference to FIGS. FIG. 2 shows a state in which the wiper 60 is at the standby position.
Is located at a position opposing the suction port 44. FIG. 3 shows the wiper 6
0 shows a state in which the leading end 60a of the needle bar 34 has moved away from the suction port 44 of the upper thread holding device 40 and has moved to a position beyond the vertical movement locus 35 of the needle bar 34. Immediately before the wiper 60 starts moving, the upper thread 33 is cut by a thread cutting device (not shown). Thereafter, the wiper 60 performs a return movement toward the suction port 44. FIG. 4 shows a state in which the distal end portion 60a of the wiper 60 intersects with the vertical movement locus 35 of the needle bar 34 to capture the upper thread 33 and attempt to lift it further upward.

The tip portion 60a of the wiper 60 is
After continuing to approach the suction port 44 as shown in FIG. 5, it moves to a position opposing the suction port 44 as shown in FIG. The moving direction A (FIG. 5) of the distal end portion 60 a of the wiper 60 immediately before reaching the state opposing the suction port 44 is substantially the same as the suction direction B (FIG. 6) of the upper thread holding device 40. Is configured. When the state shown in FIG. 6 is reached, the upper thread 33 hits the projection 44a of the suction port 44 and is locked by the projection 44a. Thereafter, the upper thread holding operation is performed by the upper thread holding device 40. The upper thread holding device 40
The principle of the yarn holding operation by the needle is the upper yarn clamp device 1 of the conventional example.
0, and is performed using the same components as the cylinder 15, the ball 16, and the like in FIGS. As a result, FIG.
The upper thread 33 is held by the upper thread holding device 40 as shown in FIG.

As is apparent from FIG.
In order to hold the upper thread 33, the suction port 44 and the needle 3
The distance L between the two needle holes 32a must be shorter than the remaining length of the upper thread 33 extending from the needle hole 32a. Therefore,
If the remaining length of the upper thread is short as described above, the suction port 44 of the clamp device 40 must be arranged at a position close to the needle hole 32a,
The area where the operator operates the sewing cloth is reduced.

Next, the control system of the present invention will be described with reference to the control block diagram of FIG. The control device 70 includes a ROM 71 for storing a program for controlling the sewing machine and data necessary for sewing, a CPU 72 for performing various calculations and processes,
RA in which data calculated by PU 72 is stored
M73 is provided. A start switch 76 and a pedal switch 77 are connected to the CPU 72 via an input / output interface 74.

The main shaft (not shown) of the sewing machine is a sewing machine motor 8.
It is rotatable by 0 and is connected to the CPU 72 via the motor driver 82 and the input / output interface 74. The rotation angle of the rotation axis of the sewing machine motor 80 is detected by an angle detector 84 connected to the CPU 72 via the input / output interface 74. The vertical movement position of the needle bar 34 is uniquely determined according to the rotation angle of the rotation shaft of the sewing machine motor 80. In the context of the present embodiment, the angle detector 84 is used for detecting the upper position and the lower position of the needle bar 34.

The negative pressure source 46 of the upper thread holding device 40 is connected to the negative pressure source C via a negative pressure source operating means 86 and an input / output interface 74.
It is connected to PU72. Further, a clamp cylinder 88 for performing a thread holding operation by the upper thread holding device 40 is connected to the CPU 72 via a clamp cylinder drive solenoid valve 100 and an input / output interface 74.

The thread cutting device (not shown) is operated by a thread cutting cylinder 90, the wire mount 54a of the thread picking device 54 is turned by a thread picking cylinder 92, and the wiper 60 is turned by a wiper cylinder 94. The presser 31 is moved up and down by a presser cylinder 96. These cylinders 90 to 96 are connected to the CPU 72 via respective cylinder drive solenoid valves 102 to 108 and an input / output interface 74.

Next, a timing chart of the operation of each device controlled by the control device 70 will be described with reference to FIG. In the figure, “up position” and “down position” are signals that are detected and changed by the angle detector 84, and are turned off when the upper position and the lower position of the needle bar 34 are detected, respectively. "Thread trimming" is an operation signal of the thread trimming cylinder 90,
Turns on during operation. The thread is actually cut at the end of the operation of the thread cutting cylinder 90, that is, immediately before the operation signal shown changes from on to off.

"Thread picking" is an operation signal of the thread picking cylinder 92, which is turned on during operation. When turned on, the leading end of the thread payout wire 54b rises to apply tension to the upper thread, and when turned off, the leading end descends to relax the tension of the upper thread. The "wiper" is an operation signal of the wiper cylinder 94, which is turned on when the wiper cylinder 94 is operated, and is turned on.
Starts moving. "Presser lift" means presser cylinder 9
With the operation signal of No. 6, it is turned on at the time of operation and the presser foot 31 rises. "Suction" is a signal for operating the negative pressure source 46, and is turned on at the time of operation. “Hold” is an operation signal of the clamp cylinder 88, which is turned on when activated.

First, the lower position is detected by the angle detector 84 and at the same time, the thread cutting cylinder 9
0 and the thread take-up cylinder 92 are turned on, the negative pressure source 46 is operated by the negative pressure source operating means 86, and the clamp cylinder 8 is operated by the clamp cylinder driving solenoid valve 100.
8 turns off.

Next, after a lapse of Ems from the point when the upper position of the needle bar 34 is detected by the angle detector 84, the thread cutting cylinder drive solenoid valve 102 and the thread take-up cylinder drive solenoid valve 1
04, the thread cutting cylinder 90 and the thread picking cylinder 9
2 turns off, the thread trimming ends, and the tip of the thread payout wire 54b descends. When Fms elapses after the end of thread trimming, the wiper cylinder 94 is turned on by the wiper cylinder drive solenoid valve 106. The wiper cylinder 94 is turned off after maintaining the on state for Gms.

Generally, at the same time as the completion of the thread trimming, the wiper 6
In this embodiment, the wiper 60 is operated when Fms has elapsed after the end of the thread trimming. In general, the thread take-off is turned off after a lapse of a predetermined time after the end of the thread cut. And the wiper 60 is operated. The timing of each operation of the thread cutting, thread picking and wiper makes it possible to increase the remaining length of the upper thread. That is, before the thread cutting operation, the tension of the upper thread 33 is maintained by raising the thread payout wire 54b of the thread picking device 54 to maintain the tension of the upper thread 33, and simultaneously lowering the thread payout wire 54b at the end of thread trimming. Then, the wiper 60 is operated, so that the remaining length L of the upper thread 33 increases. Therefore, as compared with the case where the remaining length of the upper thread 33 is short, the suction port 44 of the holding device 40 can be arranged at a position far from the needle hole, and the area where the operator operates the sewing cloth is widened. .

After the wiper cylinder 94 is turned off,
After the elapse of Hms, the presser cylinder 96 is turned on by the presser cylinder driving solenoid valve 108.

After a lapse of Jms from the detection of the upper position, the clamp cylinder 88 is turned on by the clamp cylinder drive solenoid valve 100. After a lapse of Ims from the time when the upper position is detected, the operation of the negative pressure source 46 by the negative pressure source operating means 86 is stopped.

Next, the operation of the present embodiment executed by the control device 70 will be described based on the flowcharts of FIGS. S1, S2,... In the figure indicate the numbers of the processing order (steps). First, in S1, it is determined whether or not a sewing start request is made by an operator. That is, FIG.
The controller 7 determines whether or not the start switch 76 is pressed.
Determined by 0. If there is a sewing start request, the process proceeds to S2, where the clamp cylinder 88 is turned off, and the holding of the upper thread end by the upper thread holding device 40 is released. Next, in S3, the sewing machine 80 is rotated to execute the sewing process.

Next, in S4, it is determined whether or not the operator has requested the thread trimming by stepping on the pedal switch 77. If there is no request, the process returns to S3 to continue the sewing process. If there is a request, the process proceeds to S5, where it is determined whether or not the lower position is detected by the angle detector 84.
The process returns to S3, and if detected, proceeds to S6.

In step S6, the thread cutting device and the thread picking device 54 are driven, and the suction of the upper thread end is started. Thereafter, the process proceeds to S7, where it is determined whether the needle bar 34 has reached the upper position. If it has reached the upper position, the process proceeds to S8, where the rotation of the sewing machine motor 80 is stopped, and the process proceeds to S9.

In S9, it is determined whether or not Ems has elapsed since the needle bar 34 reached the upper position.
The process proceeds to S10 of 1 to stop driving the thread cutting device and the thread picking device, and proceeds to S11.

In step S11, it is determined whether or not Fms has elapsed after the drive stop operation in step S10. When the time has elapsed, the process proceeds to step S12, and the wiper 60 is driven by Gms. At 60a, the upper thread end is captured and moved to a position opposing the suction port 44 of the upper thread holding device 40, and then the process proceeds to S13. In S13, it is determined whether or not Jms has elapsed since the needle bar 34 reached the upper position.
8 is driven to hold the upper thread end by the upper thread holding device 40, and then the process proceeds to S15. In S15, it is determined whether Ims has elapsed after the needle bar 34 has reached the upper position, and when it has elapsed, the process proceeds to S16, in which the operation of the negative pressure source 46 is stopped and suction of the upper thread end is stopped.

Next, another example of the timing chart of the operation of each device controlled by the control device 70 will be described with reference to FIG. This chart differs from the timing chart of FIG. 9 in that the wiper 60 is operated by the wiper cylinder 94 and then the thread take-up cylinder 92 is operated again to raise and lower the yarn feeding wire 54b. Is the same. By driving the thread picking device 54 again in this way and paying out the upper thread from a thread supply source (not shown), the upper thread tension is relieved, so that needle breakage can be prevented.

Next, another example of the suction port 44 of the upper thread holding device 40 will be described with reference to FIGS. On the outer peripheral portion of the suction port 144 shown in FIG. 13, a projection 144a for locking the upper thread end is provided outside the trajectory of the wiper movement. The protrusion 144a is provided at the end surface 144b of the suction port 144.
And a top 144c substantially parallel to. On the outer peripheral portion of the suction port 244 shown in FIG. 14, a projection 244a for locking the upper thread end is provided outside the wiper movement locus. The projection 244a has a top 244c substantially parallel to the end surface 244b of the suction port 244.
Is larger than the top 144c of the suction port 144. Since the suction ports 144 and 244 can reliably lock the upper thread 33 by the tops 144c and 244c, the upper thread 33 can be held more securely than the suction port 44 of FIG. Further, the present invention can be variously modified without being limited to the above embodiment. For example, in the above embodiment, the thread taker is raised (forward movement) before the thread cutting operation, the upper thread path is lengthened to tension the upper thread, and after the end of the thread cutting operation, the thread taker is lowered (returned). ) To reduce the tension of the upper thread. Due to the tension and relaxation of the yarn sandwiching this thread cutting operation, a required amount of the remaining length of the upper yarn could be secured. Instead, the thread taker is lowered (forward movement) before the thread cutting operation, the upper thread path is lengthened to tension the upper thread, and after the end of the thread cutting operation, the thread taker is raised (returned). It is also conceivable to ease the tension of the upper thread. It is also conceivable that the thread is reciprocated in a diagonal direction with respect to the thread path with the thread cutting operation interposed therebetween, thereby tensioning and relaxing the thread to secure a necessary amount of the remaining length of the upper thread.

[0042]

According to the present invention, the thread tension is arranged on the thread path from the thread supply source to the sewing needle to apply a predetermined tension to the upper thread, and the thread tension is arranged on the thread path and reciprocates. A yarn wiper that raises or lowers the needle, a wiper that has a tip that can intersect with the needle bar vertical movement trajectory, and that can capture the upper thread end after cutting with the tip, and the upper thread end captured by the wiper The upper thread clamp device of the sewing machine having a holding mechanism that holds the upper thread in a forward direction before the thread trimming operation to maintain the tension state of the upper thread and to return the thread loop after the end of the thread trimming operation. Control means for controlling the tension of the upper thread so as to relieve the tension of the upper thread, so that the remaining length of the upper thread after the thread is cut becomes longer, and the upper thread end can be reliably held and the holding mechanism Can be installed at a place away from the needle hole, so cloth operation Hand to do is widened, the sewing work becomes easy. .

If the control means is configured to control the wiper to operate after a predetermined period of time after returning the yarn picker, the remaining length of the upper thread after the yarn is cut further increases. The upper thread end can be reliably held.

When the tip end side suction port of the holding mechanism is arranged so as to face the tip end of the wiper when the wiper is operated, the upper thread end is reliably sucked and caught, so that the first stitch is knotted. Is assured.

In the case where a protrusion for locking the upper thread end is provided on the outer periphery of the suction port of the holding mechanism outside the trajectory of the wiper, the upper thread end when the wiper is lifted up is provided. Can be prevented, and the yarn end can be securely held.

Further, when the projection of the holding mechanism is located above the center of the suction port, the hand for performing the cloth operation is widened, so that the sewing operation is facilitated.

When the control means is configured to reciprocate the yarn picker again after the operation of the wiper, the controller can feed out the yarn and prevent the needle from being broken.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an external configuration of a main part of an embodiment of a needle thread clamp device of a sewing machine according to the present invention.

FIG. 2 is a perspective view showing a state in which a wiper of the apparatus according to the present embodiment is at a standby position.

FIG. 3 is a perspective view showing a state in which the tip of the wiper of the device according to the present embodiment has moved away from the suction port of the upper thread clamp device to a position beyond the position of the needle.

FIG. 4 is a perspective view showing a state in which the tip of the wiper of the device according to the present embodiment intersects the vertical movement locus of the needle bar to capture the upper thread and further lift it upward.

FIG. 5 shows a state where the tip of the wiper is further moved from the state of FIG.
FIG. 13 is a perspective view showing a state further raised from the state of FIG.

6 is a perspective view showing a state in which the tip of the wiper has moved to a position opposing the suction port after the state of FIG.

FIG. 7 is a perspective view showing a state where the upper thread is held by the upper thread clamp device of the present embodiment.

FIG. 8 is a block diagram illustrating a control system of the device according to the present embodiment.

FIG. 9 is a timing chart of the operation of each device controlled by the device control device according to the present embodiment.

FIG. 10 is a flowchart illustrating an operation performed by a control device of the device according to the present embodiment.

FIG. 11 is a flowchart illustrating an operation performed by a control device of the device according to the present embodiment.

FIG. 12 is a timing chart illustrating another example of the operation of each device controlled by the device control device according to the present embodiment.

FIG. 13 is a perspective view of another example of the suction port of the upper thread clamp device according to the present invention.

FIG. 14 is a perspective view of still another example of the suction port of the upper thread clamp device according to the present invention.

FIG. 15 is a side view showing a configuration of a device according to a conventional example.

FIG. 16 is an enlarged sectional view showing an internal state of the clamp unit of FIG.

FIG. 17 is a top view of an apparatus according to a conventional example.

FIG. 18 is a cross-sectional view for explaining the operation of the device according to the conventional example with reference to (A) to (D).

FIG. 19 is an explanatory view showing an attached state of a cutter of an apparatus according to a conventional example.

[Explanation of symbols]

 32 Needle 33 Needle thread 34 Needle bar 35 Vertical trajectory of needle bar 40 Needle holding device 44 Suction port 44a Projection 50 Pretension (first thread tension) 52 Rotary tension (second thread tension) 54 Threading device 54b Thread Feeding wire 60 Wiper 60a Wiper tip 70 Control device

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Yoshikatsu Hattori 1-2-2, Kokuryo-cho, Chofu-shi, Tokyo F-term in Juke Corporation (reference) 3B150 AA01 AA07 CE01 CE06 CE23 CE27 FH02 FH03 FH14 FH17 GF02 GF03 JA13 LA04 LA53 LB01 NA48 NA49 NB16 NB17 NC02 NC18 QA04 QA06 QA07

Claims (6)

[Claims] 1. A thread tensioner arranged on a thread path from a thread supply source to a sewing needle to apply a predetermined tension to the upper thread, and a thread tension arranged on the thread path and reciprocating to raise or lower the thread. A wiper having a tip end capable of intersecting with the needle bar vertical movement trajectory, capable of catching the upper thread end after cutting with the tip end, and a holding mechanism for holding the upper thread end captured by the wiper In the upper thread clamp device of the sewing machine, the thread taker is moved forward before the thread trimming operation to maintain the tension state of the upper thread, and the thread taker is moved backward after the thread trimming operation is completed. Control means for controlling so as to reduce the tension state of the thread. 2. The upper thread clamp device according to claim 1, wherein the control means controls the wiper to operate after a predetermined time after the thread taker is moved backward. Needle thread clamp device for sewing machine. 3. The upper thread clamping device according to claim 1, wherein the holding mechanism has a tip side suction port arranged to face a tip end of the wiper when the wiper is operated. Sewing machine upper thread clamp device. 4. The upper thread clamp device according to claim 3, wherein a projection for locking the upper thread end is provided on an outer peripheral portion of the suction port of the holding mechanism, outside the trajectory of the wiper. An upper thread clamp device for a sewing machine, comprising: 5. The upper thread clamp device according to claim 4, wherein the projection of the holding mechanism is located above a center of the suction port. 6. The needle thread clamp device according to claim 2, wherein said control means reciprocates the thread take-up after the operation of the wiper.