CN1232895A - Thread clamping device for sewing machine - Google Patents

Abstract

A thread clamping device for a sewing machine, comprising a main thread gripper; on the upstream side of the main thread gripper, a first secondary thread gripper capable of applying a first tension to the upper thread and a second secondary thread gripper capable of applying a second tension tension release mechanism, which can release the tension applied by the main thread tensioner 5; switching device, which switches the first secondary thread tensioner from the tension application state to the tension application release state, and releases the second secondary thread tensioner from the tension application The state is switched to the tension application state; the control mechanism, when the thread cutting process is performed by the automatic thread cutter, releases the tension through the tension release mechanism, and performs state switching through the switcher.

Description

Thread clamping device for sewing machine

The present invention relates to a thread clamping device of a sewing machine which adjusts thread tension by applying tension to an upper thread.

Fig. 7 is an elevational view showing the head of a conventional sewing machine provided with an automatic thread cutter.

In the existing sewing machine, the upper thread 3 wound on the thread reel 2 passes through the sub-tensioner (first tensioner) P4, the main tensioner (second tensioner) 5, the thread take-up spring 6, the thread A7, thread take-up bar 8, clue B9, needle bar guide wire hook 11, needle 12 and arrive at cloth 14 places, cooperate with lower thread 17, form stitches. The lower thread 17 is connected to the stitches on the cloth 14 through the shuttle cover 16 received in the cavity 15 .

In industrial sewing machines, an automatic thread cutter is generally provided. When the sewing ends, the device cuts off the upper thread and the lower thread under the needle plate 13. The movable blade 18 and the fixed blade 19 follow the cutting of the sewing end signal, the upper thread 3 between the cloth 14 and the needle 12, and the lower thread between the shuttle cover 16 and the cloth 14 are cut off.

FIG. 8 shows specific structures of the movable blade 18 and the fixed blade 19 at the time of thread cutting. Fig. 8 (a) ~ (c) are for explaining the flow of the cutting process of sewing machine thread, the sectional view of the vicinity of the needle seen from the side, and Fig. 8 (a') is the sectional view of Fig. 8 ( The top view of the movable blade 18 and the fixed blade 19 in a). 8(a) and (a') show the positional relationship of the movable blade 18, the fixed blade 19, and the upper and lower threads at the moment of cutting the thread.

When in action, the front end 18a of the movable blade 18 is pulled toward the fork-shaped portion 18c along the forward path (direction A) through the part on the wheel caused by the slack of the upper thread 3 between the needle side 3b and the cloth side 3a. Tighten the upper thread 3 while also tightening the lower thread 17.

By the blade portion 18d of the movable blade 18, the concave shape 18b is formed between the fork-shaped portions 18c, which prevents the fixed blade 19 from interfering with the wire therebetween.

Along the retraction line (B direction) of the movable blade 18, the fork-shaped portion 18c pulls out the upper thread 3 and the lower thread 17 through the wire reel 2 and the shuttle cover 16 respectively, and approaches the fixed blade 19 and the blade portion 18d of the movable blade 18 at the same time. The thread is cut by engaging with the blade portion 19a of the fixed blade.

Fig. 8(b) is a diagram showing the state of the thread after cutting. Here, the upper thread from the needle 12 to the cutting portion is referred to as "needle thread 3b".

Fig. 8(c) is a diagram showing the state of the needle thread when the sewing machine is stopped after the thread trimming operation is completed. After thread cutting, before the sewing machine stops, the thread take-up lever 8 pulls the upper thread 3 back, and the final needle thread 3b remains at the needle point. The length of the remaining needle thread 3 b relative to the needle 12 is referred to as "needle thread remaining length L".

When the needle thread remaining length L is short, there is a problem that the thread is pulled out from the needle at the start of the next sewing, or skipped threads occur, and stitches are not formed. When the needle thread remaining length L is too long, when the next stitch is formed, the longer upper thread is sewn in a twisted manner, thereby spoiling the appearance.

In addition, regardless of whether the needle thread remaining length L is long or short, after thread trimming, if the upper thread clamping device is used, the device will greatly affect the success rate of the needle thread clamping process. Here, the above-mentioned upper thread clamping device refers to a device for clamping the thread at the needle point after the thread cutting process, and setting the thread at the needle point at a predetermined position according to a predetermined length during the next sewing.

The remaining needle thread length L is determined simply by the thread passing length of the upper thread 3 from the needle 12 to the position where the movable blade 18 and the fixed blade 19 are engaged. Actually, the above-mentioned length is obtained by the amount bent by the fork-shaped portion 18c of the movable blade 18 .

In addition, since the thread is forcibly pulled out by the fork-shaped portion 18c of the movable blade 18 during the thread cutting operation, the thread is pulled out with a certain margin by virtue of the inertial force of the thread, and the remaining needle thread length L can be increased.

Due to the use of the inertial force of the thread caused by pulling out the movable blade 18, as shown in Figure 9, when cutting the thread, the thread buffer pin 38 in the thread gripper 5 is moved by an actuator or the like, thereby acting on the rotating pulley 5a Spring pressure on the release.

In addition, in order to control the pulling-out amount of the upper thread 3, in the case of being independent from the above-mentioned rotary thread gripper 5 for sewing, the following sub-tensioner P4 is provided, which is used to apply tension to the upper thread when thread cutting. Slight frictional resistance.

However, when sewing thin or soft cloth, if the resistance (tension) exerted by the rotary thread tensioner 5 on the upper thread is very slight, the sub-tensioner P4 cannot be ignored during sewing. Therefore, in the adjustment of the auxiliary thread tensioner P4, the tension during sewing must be given priority.

In addition, when the rotary thread clamp 5 adopts a rotary thread clamp, since the rotary thread clamp must be on the upstream side and in a pre-tensioned state, the adjustment of the auxiliary thread clamp P4 must correspond to the rotary thread clamp device. When the above adjustments are not suitable for the rotary thread tensioner, the tension during sewing is too high, and proper stitches cannot be formed.

When the above method is used, the resistance (tension) of the sub-tensioner P4 is adjusted in such a way that the tension during sewing takes precedence over that during thread cutting, or the resistance (tension) of the sub-tensioner P4 is adjusted in a manner corresponding to the main tensioner ( Tension) when adjusting, the tension at the time of cutting the thread by the automatic thread cutter deviates from the appropriate value, which may cause the following problems, that is, the necessary remaining needle thread length cannot be obtained, or the remaining needle thread length varies and becomes unstable.

Also, on the contrary, when the sub-tensioner is adjusted in such a way that the tension during the thread cutting process is given priority over that during sewing in order to keep the remaining length of the needle thread stable, as described above, sewing with a lower tension is more difficult. In the case of thin items or soft cloth, there is a problem that the tension at the time of sewing deviates from the appropriate value, resulting in poor stitches.

The present invention is proposed in view of the above circumstances, and the purpose of the present invention is to provide a thread clamping device for a sewing machine, which can make the sewing process easier even when sewing thinner items or soft cloth with lower tension. The thread tension is an appropriate value to perform sewing with a good appearance, and the thread tension at the time of thread cutting can also be adjusted to an appropriate value, so that the remaining thread length after thread cutting can be properly kept stable.

In order to solve the above-mentioned problems, the first invention relates to a thread clamping device of a sewing machine, which includes: a main thread clamping mechanism, which applies tension to the upper thread, and adjusts the thread tension during sewing; a secondary thread clamping mechanism, which can be used with The different positions of the above-mentioned main thread clamping mechanism apply auxiliary tension to the upper thread, which is characterized in that the thread clamping device includes:

Tension release mechanism, which can release the tension applied by the above-mentioned main clamping mechanism at any time during the thread cutting process;

The switching mechanism switches the state of the above-mentioned auxiliary thread clamping mechanism from the state of canceling the tension application to the tension application state at any time of the thread cutting process.

According to the above-mentioned first invention, when adopting the main thread tension mechanism that adjusts the thread tension during sewing, there is no need for a thread tensioner (for example, a thread tensioner) with pretension (a small tension applied on the upstream side in advance). In the case of a board), an appropriate tension can be applied to either the thread tension during sewing or the thread tension during thread cutting.

That is, since the tension applied by the main thread tension mechanism is adjusted in a manner corresponding to the time of sewing, and the tension applied by the sub tension mechanism is adjusted in a manner corresponding to the thread cutting process, when sewing Make the above-mentioned tension release mechanism and switching mechanism not function, and make the above-mentioned tension release mechanism and switching mechanism work during the online cutting process. The thread tension at the time of sewing and at the time of cutting the thread is an appropriate value.

Therefore, even in the case of sewing such as thinner items or soft cloth with a lower tension, the thread tension at the time of sewing can be made to an appropriate value, and the sewing with a good appearance can be performed, and it is also possible to reduce the thread tension during the thread cutting process. The thread tension is an appropriate value to keep the remaining thread length at the needle tip stable.

Specifically, the structure for releasing the tension applied by the thread tensioner can be released by, for example, pushing the action piece between the tension plates that press the thread in a clamping manner, so that the tension plates are opened. The structure of pushing the above-mentioned thread, or the structure of pushing back the outer side of the thread tensioner from the inside of the sewing machine frame, and pushing apart the structure of the thread tensioning plates can be realized by various structures. In addition, the operations of the above-mentioned tension releasing structure and switching structure may also be performed according to the timing of the thread cutting process through the control of a control circuit, for example. In addition, it can also be performed according to the time of thread cutting times by an operator's operation. Also, the driving force may be manually driven by an operator using a lever or a pedal in addition to electric power such as a hydraulic or pneumatic piston.

The second invention relates to the thread clamping device of the sewing machine of the above-mentioned first invention, which has the following configuration, and the mode is:

The main thread clamping mechanism includes the main thread tensioner, which must be on the upstream side in advance, so that the upper thread has a smaller tension in order to apply tension. The main thread tensioner applies tension to the upper thread, which affects the thread tension during sewing. Adjustment; the auxiliary thread clamping mechanism, which includes a first auxiliary thread tensioner that can apply a first tension to the upper thread on the upstream side of the above-mentioned main thread tensioner, and a second auxiliary thread tensioner that can apply a second tension;

The above-mentioned switching mechanism can switch the state of the first auxiliary thread tensioner from the state of tension application to the state of tension application release at any time, and can switch the state of the above-mentioned second auxiliary thread tensioner from the state of tension application release to The state of tension.

According to the above-mentioned 2nd invention, when adopting and forming the main thread tensioner that adjusts the thread tension during sewing, it is necessary to require a thread tensioner (for example, a rotating In the case of a thread tensioner, etc.), an appropriate tension can be applied to either the thread tension during sewing or the thread tension during thread cutting.

That is, by adjusting the tension applied to the main thread tensioner and the first sub tensioner in a manner corresponding to the sewing process, and adjusting the tension applied to the second sub tensioner in a manner corresponding to the thread cutting process Make adjustments so that the above-mentioned tension release mechanism and switching mechanism do not function during sewing, the first secondary thread tensioner and switching mechanism act during thread cutting, and the main thread tensioner and the first secondary thread tensioner during sewing , The second secondary thread tensioner acts independently during the thread cutting process, so that the thread tension during sewing and thread cutting process can both be appropriate values.

Therefore, even in the case of sewing thin items or soft cloth with low tension, the thread tension at the time of sewing can be set to an appropriate value, and good-looking sewing can be performed, and it is also possible to make The thread tension at the thread cutting process is an appropriate value to keep the remaining thread length at the needle tip stable.

Here, on the upstream side in advance, there must be a small tension in the upper thread to apply the tension, such as a main tensioner such as a rotary tensioner, but in addition, it may also include a tension plate or the like that prevents the warp of the thread. the clamp. The structure for releasing the tension of the tensioner, or the structure for actuating the tension release mechanism and the switching mechanism may be various structures described in the first invention.

The third invention relates to the thread clamping device of the sewing machine according to the second invention, which is constituted in the following manner, in which the switching mechanism includes:

The first action part switches the state of the first auxiliary tensioner between a tension-applied state and a tension-applied state by reciprocating in a first direction;

The second action part switches the state of the second secondary tensioner between a state of tension application and a state of release of tension application by reciprocating in the second direction;

a drive mechanism having a movable part capable of reciprocating the movable part;

The link transmits the reciprocating motion of the movable part, reciprocates the first operating part in the first direction, and reciprocates the second operating part in a direction opposite to the second direction.

According to the above-mentioned third invention, since only the movable part in the driving mechanism is reciprocated, the switching of the action/non-action of the first auxiliary thread tensioner and the non-action/non-action of the second auxiliary thread tensioner can be carried out. Switching of the action The two kinds of switching can control the operation of the two mechanisms through the movement of the above-mentioned one movable part, so that the timing for operating the switching mechanism can be easily controlled.

The fourth invention relates to the thread clamping device of the sewing machine according to the above-mentioned first to third inventions, which includes a control mechanism that releases the tension by the above-mentioned tension when the thread is cut by an automatic thread cutter installed in the sewing machine. Mechanism for tension release and switching by the switching mechanism above.

According to the above-mentioned fourth invention, due to the control of the above-mentioned control mechanism, when the thread cutting process is automatically performed, the above-mentioned tension release mechanism and the switching mechanism are activated, so that the operator's handling of the sewing process and the thread cutting process can be reduced. Simplification makes the operation content of sewing easier.

Here, the control mechanism can also be the following control circuit. The control circuit can make the above-mentioned tension release mechanism and switching mechanism operate through electrical control. In addition, it can also be the following control mechanism. The control mechanism can be held by the mechanical structure and the thread cutter. Linked to make the tension release mechanism and the switching mechanism act.

Embodiments of the present invention will be described below with reference to FIGS. 1 to 6 . In addition, the same reference numerals as those in the drawings in the prior art are used for the same structures as those in the prior art, so the description thereof will be omitted.

1 is a side view showing a sewing machine head side of a sewing machine including a thread clamping device according to a first embodiment of the present invention;

Fig. 2 shows the specific structure of the auxiliary thread tensioner and the switcher, Fig. 2 (a) represents its elevation view, and Fig. 2 (b) represents the longitudinal section view of the auxiliary thread tensioner;

Fig. 3 is a block diagram showing the circuit structure in the sewing machine in Fig. 1;

Fig. 4 is a time chart showing the operation time of each driving system in the sewing machine;

Fig. 5 is a flowchart showing the sequence of sewing end processing performed by the control circuit in the sewing machine;

Fig. 6 shows the specific structure of the secondary tensioner and switcher of the second embodiment of the present invention, Fig. 6 (a) is its elevation view, and Fig. 6 (b) is a side view including a partial section seen from the side ;

Fig. 7 is a side view showing the head side of a conventional sewing machine;

Figure 8 sequentially shows the thread cutting process performed by the thread cutter, Figures 8(a)-(c) are cross-sectional views viewed from the side near the needle, and Figure 8(a') shows the movable blade of Figure 8(a) Top view with stationary blade;

Fig. 9 is a longitudinal sectional view showing a main thread tensioner provided in the sewing machine.

first embodiment

Fig. 1 is a side view showing the sewing machine head side of the sewing machine comprising the wire clamping device according to the first embodiment of the present invention, Fig. 2 shows the specific structure of the auxiliary thread grippers 21, 25 and the switch 30, Fig. 2(a) Represent its elevation view, Fig. 2 (b) represents the longitudinal sectional view of auxiliary thread tension device.

In Fig. 1, the reference numeral 1 represents the sewing machine frame, the reference numeral 2 represents the thread reel, the reference numeral 3 represents the upper thread, the reference numeral 5 represents the rotary thread clamp as the main thread tensioner, the reference numeral 6 represents the thread take-up spring, and the reference numerals 7, 9 and 11 represent The thread, the number 8 represents the thread take-up lever, the number 10 represents the needle bar, the number 12 represents the needle, the number 13 represents the needle plate, the number 14 represents the object to be sewn, the number 15 represents the cavity, the number 16 represents the shuttle cover, and the number 18 represents the automatic thread trimmer The movable blade in the device, the reference numeral 19 represents the fixed blade in the automatic thread cutter, the reference numeral 21 represents the second secondary thread clamp, the reference numeral 25 represents the first secondary thread clamp, and the reference numeral 30 represents a switch.

The thread clamping device of the present embodiment is constituted by a rotary thread clamp 5 as a main thread clamp provided with a tension releaser therein, first and second sub-thread clamps 21, 25, and a switch 30.

The rotating thread clamp 5 has the same structure as the existing type, so its description is simplified, but as shown in the longitudinal sectional view of Figure 9, it consists of a rotating pulley 5a with a groove guiding the wire at the outer edge, and a The rotating pulley 5a is made up of a sliding contact member 5e that is in sliding contact and applies frictional resistance, a spring 5d that presses the sliding member 5e, and a thread adjusting nut 5b that adjusts the spring force of the spring. By extending the upper thread 3 along the rotating pulley 5a, Tension can be applied to the upper thread 3 by rotating the rotating pulley 5a.

In addition, the structure of the tension release device provided inside the rotary tensioner 5 is also the same as the existing type, so its description is simplified, but it includes a wire connected to the inside of the support shaft 5c of the rotary tensioner 5. The buffer pin 38, and a driving mechanism such as a thread buffer solenoid 98 (FIG. 3) that drives the pin, pushes up the sliding member 5e of the rotary tensioner 5 by the above-mentioned thread buffer pin 38 against the spring 5d. , so as to release the tension of the rotary tensioner 5.

The first and second auxiliary thread tensioners 25, 21 are respectively arranged on the base 20 fixed on the sewing machine frame 1. The base 20 is provided with a thread 20A for feeding the upper thread 3 from the upstream side to the second sub-tensioner 21 and a thread 20B for feeding the upper thread 3 from the first sub-tensioner 25 to the upstream side.

The first auxiliary thread clamp 25 is composed of thread adjusting lever 26, two thread clamping plates 25A, 25A, thread adjusting spring 28, thread adjusting nut 27, etc. The second auxiliary thread tensioner 21 is composed of thread adjusting lever 22, two clips Wire plate 21A, 21A, wire adjustment spring 24, wire adjustment nut 23 etc. constitute.

Thread adjusting rods 22 , 26 are provided with screw rods 22 a , 26 a near their front ends, and the thread adjusting rods 22 , 26 are fixed on the base 20 . The thread clamping plates 25A, 25A are inserted into the thread adjusting lever 26, and the upper thread 3 is sandwiched between the two plates, and the upper thread is exerted frictional resistance by the pressing force of the thread adjusting spring 28. Similarly, the thread clamping plates 21A, 21A are also inserted into the thread adjusting rod 22 to sandwich the upper thread 3 between the two plates, and apply frictional resistance to the upper thread through the pressing force of the thread adjusting spring 24 . The friction force obtained by the above-mentioned first and second auxiliary thread grippers 25, 21 can be adjusted by rotating the thread adjusting nuts 27, 23, respectively.

The adjustment of the tension of the 1st and 2nd auxiliary thread grippers 25, 21 is carried out corresponding to the cutting process for the 1st auxiliary thread gripper 25, in order to obtain an appropriate thread remaining length after the thread is cut, and for the 2nd auxiliary thread gripper For the thread gripper 21, it is carried out corresponding to the rotation of the thread gripper 5, in order to obtain an appropriate tension during sewing.

In addition, even when the positional relationship between the first and second sub tensioners 25 and 21 is replaced with each other, it does not affect the mechanism.

The switcher 30 is composed of a thread tension switching solenoid 31 and a switching arm 34 as a driving mechanism. The switching arm 34 is rotatably mounted on the fulcrum 35 provided on the base 20, and is connected with the plunger core (movable part) 31a in the wire clamping switching solenoid 31 through the pin 32, The wire switches the driving of the solenoid 31 to perform a swinging motion.

The two claw-shaped parts 34aa, 34ab are provided at one end of the switching arm 34, and are moved in the direction in which the plunger 31a is pushed out by the spring 33, whereby the two claw-shaped parts 34aa, 34ab are inserted into the second pair. Between the tension plates 21A, 21A in the tensioner 21, by pulling the plunger 31a in, the two claw-shaped portions 34aa, 33ab can be pulled apart from the second sub tensioner 21.

The other end of the switching arm 34 is provided with the same claw-shaped portion 34bb, 34ba, which moves in the direction in which the plunger 31a is pushed out by the spring 33, thereby opposing the two claw-shaped portions 34bb, 34ba to the second. Pull out the first sub-tensioner 25, and by pulling in the plunger (movable part) 31a, the two claw-shaped parts 34bb, 34ba can be inserted into the tension plate 25A of the first sub-tensioner 25 , 25A between.

That is, the switching arm 34 forms a link, and the claw-shaped portions 34bb, 34ba and the claw-shaped portions 34aa, 34ab form first and second operating portions, respectively.

The above two claw-shaped portions 34aa, 34ab are inserted into the thread clamping plates 21A, 21A so as to float, and the state in which the upper thread 3 is pressed against between the thread clamping plates 21A, 21A is released. The same applies to the other two-pronged claw-shaped portions 34bb, 34ba.

During normal sewing, etc., when the thread tension switching solenoid 31 is in the non-driven state, the plunger 31a is pushed out by the return spring 33, and the upper thread 3 is in the following state. Tension is applied by the first sub-tensioner 25, and no tension is applied by the second sub-tensioner 21.

When the thread tension switching solenoid 31 is driven during thread cutting processing, the plunger 31a is pulled back, and the upper thread 3 is in a state where tension is applied only by the second sub-tensioner 21 , the first secondary tensioner 25 does not apply tension.

Fig. 3 is a block diagram showing a circuit configuration in a sewing machine including the above thread holding device.

A control circuit 80 for controlling sewing processing is provided in the sewing machine. The control circuit 80 consists of a control unit 81 having a CPU (Central Processing Unit), a RAM (Random Access Memory), and a ROM (Read Only Memory), a motor drive circuit 82 that drives a sewing machine motor 93, and a system that operates each drive system. The solenoid driver 83 and the like are constituted.

Through the interface omitted in the figure, the upper shaft angle detector 91 or the pedal sensor 92 is connected with the control unit 81, the thread clearing solenoid 94, the reverse feeding solenoid 95, the automatic push-up solenoid 96, and the thread cutting solenoid 97 , the wire buffer solenoid 98 and the wire clamp switching solenoid 31 are connected to the solenoid driver 83 .

Here, the upper shaft angle detector 91 is used to detect the angle of the upper shaft of the sewing machine, and through this detection, a needle up position signal indicating that the needle 12 is located above, a needle down position signal indicating that the needle is located below, and a signal indicating the speed of the sewing machine. The speed detection signal and the like are output to the control unit 81 . The pedal sensor detects the states of the middle position, the front position, and the rear position of the pedal not shown in the figure, and outputs a sewing machine start signal, a thread trimming signal, a stop signal, and a speed signal to the control unit 81 corresponding to the states. The thread clearing solenoid 94 starts the scraper (not shown) after thread cutting, so that the upper thread 3 falls on the cloth pressing device through the action port. The reverse feed solenoid 95 reverses the feed mechanism when it passes through the action port for back stitching. Automatically push up the solenoid 96 through the action port to make the cloth pressing device rise. The thread cutting solenoid 97 passes through the action port to activate the automatic thread cutter. The thread buffer solenoid 98 is a drive mechanism for rotating the tension releaser inside the thread tensioner 5 .

In addition, the above-mentioned thread cutting solenoid 97 inserts, for example, a roller connected to each mechanism into a cam to activate each mechanism, and the driving force of each mechanism is generally sent from the above-mentioned cam or the like.

Next, the operation of the sewing machine including the thread clamping device having the above-mentioned structure will be described.

Fig. 4 is a time chart showing the operating timing of each drive system in the sewing machine.

During normal sewing, the needle down position signal and the needle up position signal are mutually input from the upper shaft angle detector 91 to the control unit 81 .

In this state, when the operator steps back on the pedal from the front stepping position, as shown in FIG. 4, the thread cutting signal is output from the pedal sensor 92 to the control part 81. Immediately after the input, the thread cutting solenoid 97, the thread buffer solenoid 98, and the thread clamp switching solenoid 31 are respectively driven.

Through the above-mentioned driving, the automatic thread cutter starts the action of thread cutting processing. At the same time, the tension releaser operates to release the tension applied by the rotary thread clamp 5, and the switch 30 operates to release the tension applied by the first sub-tensioner 25. The tension is released, and the second tensioner 21 applies tension.

That is, when the thread cutting process is performed by the automatic thread cutter, only the tension is applied to the upper thread 3 by the second sub-tensioner 21, and the tension held during the thread cutting process is applied, and after the thread cutting process, the remaining thread at the needle tip is The wire remains to the desired length.

The operation content of the thread cutting process performed by the automatic thread cutter is carried out in the manner described in the existing examples.

When the thread cutting process ended, the thread buffer solenoid 98 and the thread tension switching solenoid 31 were not driven, and the rotary thread tensioner 5 and the first and second secondary tensioners 25, 21 returned to the sewing state. Thereafter, the thread clearing solenoid 94 is driven to clean the line by the scraper, after this, the solenoid 96 is automatically driven up, the cloth pressing device rises automatically, and the sewing process ends.

FIG. 5 shows a flowchart of sewing end processing performed by the control unit 81 of the sewing machine.

This sewing end process is started when the operator depresses the pedal during sewing. That is, in step S1, when the pedal sensor 92 detects a signal indicating the rear stepping position, the process proceeds to step S2.

In step S2, through the signal sent by the upper shaft angle detector 91, it is judged whether the sewing machine is operating at a low speed, if it is operating at a low speed, proceed to step S3, but if it is not operating at a low speed (if it is operating at a high speed), repeat step 2 , until it is in a low speed state.

When the sewing machine is in a low speed state and step 3 is performed, it is judged whether the pedal sensor 92 has not yet output the signal of the pedal position, if output, step 4 is performed, but if not output, step S1 is performed.

That is, through the processing of this step S3, the thread cutting processing can be performed only when the sewing machine is stepped back after the sewing machine is in a low speed state.

In step S4, it is judged whether the upper shaft angle detector 91 outputs a needle-down position signal, and this step S4 is repeated until the above-mentioned signal is output, and if it is output, then step S5 is performed.

That is, through the process of step 4, the thread cutting process can be performed when the needle 12 rises from the bottom dead center, and the needle 12 can be controlled so as not to collide with the movable blade 18 in the automatic thread cutter.

In steps S5-7, the thread cutting solenoid 97, the thread buffer solenoid 98, and the thread clamp switching solenoid 31 are excited sequentially, and the process proceeds to step S8.

In step S8, it is judged whether the upper shaft angle detector 91 outputs a needle up position signal, and this step S5 is repeated until the above-mentioned signal is output, and if it is output, the process proceeds to step S9. In step S9, wait for a short set time, and proceed to step S10.

In steps S10-12, demagnetize the thread cutting solenoid 97, the thread buffering solenoid 98, and the thread clamp switching solenoid 31 in sequence, and proceed to step S13. In this step S13, wait for a short set time, Go to step S14.

Thereafter, the thread clearing solenoid 94 is energized (step S14), waiting for the setting time (step S15), demagnetizing the thread clearing solenoid 94 (step S16), waiting for the setting time (step S17), and The solenoid 96 is automatically pushed up for excitation (step S18), and the sewing end process is completed.

Adopt the present invention according to the above-mentioned mode of description, owing to through independent thread gripper (rotary thread gripper 5 and the 1st auxiliary thread gripper 25, the 2nd auxiliary thread gripper 21), when being applied to sewing and thread cutting process, The tension on the upper thread 3 is controlled, so that the tension suitable for each occasion can be applied, and the quality of sewing and the remaining length of needle thread can be satisfied at the same time.

In addition, due to the above-mentioned switch 30, the switching of the action/non-action of the first sub-tensioner 25 and the switching of non-action/action of the second sub-tensioner 21 are temporarily performed, so that Time control for operating the switcher 30 is easily performed.

In addition, the present invention is not limited to the form of the thread clamping device of this embodiment, and the same function and effect as above can be obtained through the following method, the method is: the main thread tensioner adopts a thread tensioner without pretension, and Only one sub-tensioner is provided, and the switching mechanism can perform the same processing on the second sub-tensioner 21 with respect to this sub-tensioner. In addition, the setting or structure of the first and second auxiliary thread tensioners 21, 25, the structure of the main thread tensioner or switching mechanism, etc., the specific structure shown in this embodiment, etc. may not depart from the scope of the essence of the present invention. Make appropriate transformations within.

2nd embodiment

Fig. 6 shows the auxiliary thread gripper and the switcher in the thread gripping device of the second embodiment of the present invention, Fig. 6 (a) is an elevation view, Fig. 6 (b) is a partial longitudinal sectioned side view.

This embodiment shows an example in which the configuration of the switching mechanism is changed, and other configurations and control contents are basically the same as those of the first embodiment.

The structures of the first and second secondary tensioners 42, 51 of this embodiment are basically the same as those of the first embodiment. The different structures are: insertion holes 43b, 52b are respectively formed in the thread adjustment rods 43, 52, and the cable buffer pins 46, 55 are inserted in them, and the contact pieces 42a, 51a respectively connected to the outer clamping plates 42A, 51A It communicates with the inside of the above-mentioned wire adjusting rods 43, 52, and it is in a state of being able to move along the longitudinal direction of the above-mentioned wire adjusting rods 43, 52.

The switcher (switching mechanism) 60 is composed of a thread tension switching solenoid 61 as a driving mechanism, a switching arm 64 as a link, and thread buffer pins 55 and 46 as the first and second operating parts, and is installed on the sewing machine frame. internal. The switch arm 64 is rotatably mounted on the fulcrum 65, and is connected with the plunger core (movable part) 61a in the wire clamp switching solenoid 61 through the pin 62, and is driven by the wire clamp switching solenoid 61. And perform a rocking motion.

When the thread clamp switching solenoid 61 is not driven during normal sewing, the plunger 61a is pushed out by the return spring 63, and the switching arm 64 pushes out the thread buffer pin 46, and the second thread buffer pin 46 is pushed out. The tension plates 42A and 42A in the two secondary tensioners 42 are opened. Therefore, the upper thread 3 is in a state where tension is applied only by the first sub-tensioner 51 and no tension is applied by the second sub-tensioner 42 .

When the thread clamp switching solenoid 61 is driven during thread cutting processing, the plunger 31a is pulled back, the switching arm 64 pushes the thread buffer pin 55, and the first sub-tensioner 51 The clamping plates 51A, 51A are opened. Therefore, the upper thread 3 is in a state where tension is applied only by the second sub-tensioner 42 and no tension is applied by the first sub-tensioner 55 .

The above-mentioned tension adjustment of the first and second auxiliary thread grippers 51, 42 is performed for the first auxiliary thread gripper 51 corresponding to the thread cutting process in order to obtain a suitable thread remaining length after thread cutting. For the thread gripper 42, it is carried out corresponding to the rotation of the thread gripper 5 so as to obtain a suitable tension during sewing.

In the above manner, even if the thread clamping device of the sewing machine of this embodiment is used, the same action and effect as those of the first embodiment can be obtained.

According to the first invention, the main thread tensioner that adjusts the thread tension during sewing is a thread tensioner (for example, a thread tension plate, etc.) that does not require pretension (a small tension is applied on the upstream side in advance). In this case, an appropriate tension can be applied to any one of the thread tension during sewing and the thread tension during thread cutting.

Therefore, even in the case of sewing such as thinner items or soft cloth with a lower tension, the thread tension at the time of sewing can be set to an appropriate value, sewing with a good appearance can be performed, and the thread cutting process can be made The thread tension is an appropriate value to keep the remaining thread length at the needle tip stable.

According to the second invention, the main thread tensioner that adjusts the thread tension during sewing adopts a thread tensioner (for example, a rotary thread tensioner) that must require pretension (small tension applied on the upstream side in advance). etc.), an appropriate tension can be obtained for both the thread tension during sewing and the thread tension during thread cutting.

Therefore, even in the case of sewing such as thinner items or soft cloth with a lower tension, the thread tension at the time of sewing can be adjusted to an appropriate value, and sewing with a good appearance can be performed, and the thread tension at the time of thread cutting For a suitable value, keep the thread remaining length at the tip of the needle stable.

According to the third invention, only by the reciprocating motion of the movable part of the drive mechanism, the switching between the action/non-action of the first sub-tensioner and the switching between non-action/action of the second sub-tensioner are performed. These two kinds of switching can control the actions of the two mechanisms through the movement of one movable part, so that the time for operating the switching mechanism can be easily controlled.

According to the fourth invention, due to the control of the control mechanism, the above-mentioned tension release mechanism and switching mechanism can be activated automatically during the thread cutting process, which simplifies the handling of the operator in the sewing process and the thread cutting process, and makes the sewing process easier. The operation content becomes simple.

Claims (4)

1. A thread clamping device for a sewing machine, which includes: a main thread clamping mechanism, which applies tension to the upper thread, and adjusts the thread tension during sewing; a secondary thread clamping mechanism, which can be in a different position from the above-mentioned main thread clamping mechanism , applying secondary tension to the upper thread, characterized in that the thread clamping device includes: Tension release mechanism, which can release the tension applied by the above-mentioned main clamping mechanism at any time during the thread cutting process; The switching mechanism switches the state of the above-mentioned auxiliary thread clamping mechanism from the state of canceling the tension application to the tension application state at any time of the thread cutting process. 2. The device according to claim 1, characterized in that: The main thread clamping mechanism includes the main thread tensioner, which must be on the upstream side in advance, so that the upper thread has a smaller tension in order to apply tension. The main thread tensioner applies tension to the upper thread, which affects the thread tension during sewing. make adjustments; The sub-tensioner mechanism includes a first sub-tensioner that can apply a first tension to the upper thread on the upstream side of the above-mentioned main tensioner, and a second sub-tensioner that can apply a second tension; The switching mechanism can switch the state of the first auxiliary thread tensioner from the state of tension application to the state of tension application release at any time, and can switch the state of the above-mentioned second auxiliary thread tensioner from the state of tension application release to tension imposed state. 3. The device according to claim 2, wherein said switching mechanism comprises: The first action part switches the state of the first auxiliary tensioner between a tension-applied state and a tension-applied state by reciprocating in a first direction; The second action part switches the state of the second secondary tensioner between a state of tension application and a state of release of tension application by reciprocating in the second direction; a drive mechanism having a movable part capable of reciprocating the movable part; The link transmits the reciprocating motion of the movable part, reciprocates the first operating part in the first direction, and reciprocates the second operating part in a direction opposite to the second direction. 4. The device according to any one of claims 1-3, characterized in that it includes a control mechanism for performing tension by the above-mentioned tension release mechanism during the thread cutting process performed by the automatic thread cutter provided in the sewing machine. Release, and switch through the above switching mechanism.

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