JPS6248511B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD The present invention relates to an automatic thread tension device in which a pair of rollers pulls up an upper thread for thread tightening in a sewing machine.

Purpose of the Invention An object of the present invention is to provide an automatic thread tension device that can automatically and accurately set the thread tension and always obtain the correct stitches, despite its simple structure. .

Embodiment Hereinafter, an embodiment of a lockstitch zigzag sewing machine embodying the present invention will be described based on the drawings.
As shown in FIG. 1, this sewing machine consists of a base 1, a pillar 2, and a head 3, and near the left rear end of the base 1 is a lower arm 4 having a work cloth support surface 4a.
is provided protrudingly, and an auxiliary table 5 having a substantially L-shape in plan is attached near the front left side. The throat plate 6 is attached to the left upper surface of the lower arm 4.

Near the front of the upper surface of the base 1, there is a holding type power-on switch 7, and three holding type speed setting switches 8, 9, for low speed operation, medium speed operation, and high speed operation.
A speed setting switch group 11 consisting of 10 speed setting switches is arranged.

A display panel 12 is provided on the front surface of the head 3, and the display panel 12 has rows of a large number of figures 13 showing various stitch patterns, and each figure 13.
There are provided a large number of rows of light emitting diodes 14, respectively corresponding to the light emitting diodes 14, and a large number of rows of automatic return type pattern selection switches 15 corresponding to each of the light emitting diodes 14, respectively. An automatic return type start/stop switch 16 is located below one side of the display panel 12.
is provided. Then, when one of the stitch patterns is selected using the shape 13 and one of the pattern selection switches 15 corresponding to the selected shape 13 is pressed, the light emitting diode 14 corresponding to the pattern selection switch 15 lights up. to indicate the selected state, and the selected stitch pattern becomes ready to be sewn.

Further, when the start/stop switch 16 is pressed once, a sewing machine motor (not shown) inside the sewing machine is driven, and when it is pressed again, the sewing machine motor is stopped. The sewing machine main shaft, which will be described later, is rotated by the drive of the sewing machine motor, and in conjunction with the rotation, the sewing machine needle 17 reciprocates up and down linearly or while oscillating, and the feed dog ( (not shown) is adapted to perform a predetermined feeding movement. Further, in conjunction with the rotation of the main shaft of the sewing machine, a hook (not shown) provided in the lower arm 4 rotates in synchronization with the up and down reciprocating movement of the needle 17, thereby forming and enlarging the thread loop of the needle thread. They are starting to do more exercise. Note that the pot in this embodiment is a full-rotation pot.

As shown in FIG. 2, the presser foot 19 supported at the lower end of the presser bar 18 presses the work cloth c with a predetermined pressing force, and can be raised and lowered by a presser foot lifting lever (not shown). ing. A rack member 20 is fixed to the upper part of the presser bar 18, and a pinion 22 operatively connected to a movable terminal of a potentiometer 21 is attached to the rack member 20.
are meshing. The pinion 22 is rotated by the vertical movement of the presser bar 18, and the potentiometer 21 outputs an analog voltage corresponding to the rotation angle of the pinion 22. The cloth thickness detector 60 including the potentiometer 21 is configured to convert the analog voltage from the potentiometer 21 into a digital signal and output the signal as the thickness of the work cloth c.

A spool 23 as an upper thread supply source shown on the right side of FIG. 2 is provided in the sewing machine head 3, and the upper thread Y
It is starting to supply

A sewing machine main shaft 24 provided in the sewing machine head 3 has a large diameter bevel gear 25 and a circular control cam body 2.
6 is fixed.

a support shaft 27 supported within the head 3 of the sewing machine;
A small-diameter bevel gear 28 that meshes with the bevel gear 25 is fixed to one end. Its support shaft 2
A large diameter drive roller 29 is fixed to the other end of the roller 7.
It is always rotated in the direction of arrow P in synchronization with the rotation of the sewing machine main shaft 24. Further, this driving roller 29 is arranged in the upper thread path between the needle 17 and the bobbin winder 23.

Inside the head 3, a transmission member 30 is rotatably supported at its intermediate portion by a shaft 31, and at one end thereof a small-diameter driven roller 32 that can move toward and away from the drive roller 29 is supported. When the transmission member 30 is rotated in the direction of arrow Q against the action of a spring means (not shown), the driven roller 3
2 is in contact with the circumferential surface of the drive roller 29, and the upper thread Y is sandwiched between the two rollers 32, 29. In this upper thread pinching state, the upper thread Y is rotated by the rotation of both rollers 9, 32 based on the rotation of the sewing machine main shaft 24. The thread Y is pulled up in a direction opposite to the feeding direction, and the needle thread loop is tightened. And these two rollers 29,
32 constitutes an upper thread pulling mechanism. Note that one of the rollers 29 and 32 is made of metal, and the other is made of rubber.

The cam body 2 is provided on one side of the control cam body 26.
A control cam surface 33 consisting of a low portion 33a and a high portion 333b is formed in the rotational direction of the rotor 6, and the cam surface is formed such that the width of the high portion 33b differs in the direction intersecting the rotational direction.

At one end of a connecting shaft 34 supported in the head 3 of the sewing machine, a contact 35 is swingably supported at an intermediate portion by a stepped screw 36. The control cam body 26 is always in contact with the control cam surface 33, and the engaging portion 35b at the other end is in contact with the transmission member 30.
When the contact portion 35a engages with the high portion 33b of the control cam surface 33 as the control cam body 26 rotates, the engagement portion 35b
is engaged with the other end of the transmission member 30, the transmission member 30 is rotated in the direction of arrow Q, and the driven roller 32 comes into contact with the drive roller 29. Therefore, while the high portion 33b of the control cam surface 33 and the contact portion 35a of the contactor 35 are engaged, the upper thread Y is pulled up.

Further, as shown in FIG. 3, the engagement start side edge 33c of the high portion 33b of the control cam surface 33 extends in the radial direction of the control cam body 26, and the engagement end side edge 33d has a quadratic function. line (e.g. parabola)
The length L of the high portion 33b in the rotational direction increases toward the outer circumference. On the other hand, as the connecting shaft 34 rotates, the contact portion 35a of the contactor 35 is brought into contact with the control cam body 26.
The control cam body 26 is moved in a direction perpendicular to the rotational direction of the control cam body 26, so that the contact position with respect to the control cam surface 33 is changed in the radial direction of the control cam body 26. Therefore,
When the contact portion 35a is moved to the outer circumferential side of the control cam body 26, the end of the engagement between the contact portion 35a and the high portion 33b of the control cam surface 33 is delayed, and the upper thread Y
The lifting time will be correspondingly longer.

As shown on the upper left side of FIG. 2, a motor shaft 39 of a positioning motor 38, which is a step motor fixed in the head 3 of the sewing machine and is rotatable in forward and reverse directions, has a rotating disk 40 having a slit 40a. A positioning cam body 41 is fixed. An origin detector 42 consisting of a light emitting diode 42a and a phototransistor 42b, which sandwich the disk 40, is arranged near the rotating disk 40, and the slit 40a corresponds between the light emitting diode 42a and the phototransistor 42b. When this happens, an origin detection signal is output to stop the positioning motor 38 from rotating in reverse.

The other end of the connecting shaft 34 is connected to the cam surface 4 of the positioning cam body 41 by the spring force of the spring 43.
A contact body 44 that engages with 1a is fixed, and the positioning cam body 4 is based on the forward rotation of the positioning motor 38.
1 is rotated in the direction of arrow S, and the contactor 35 is rotated in the same direction. Then, the positioning motor 3
8. By the positioning cam body 41 and contact body 44,
A positioning mechanism is configured to change the setting of the contact position of the contact 35 with respect to the control cam surface 33. Further, the contact body 44 and the connection shaft 34 constitute a connection body for transmitting the amount of displacement of the cam surface 41a of the positioning cam body 41 to the contactor 35.

A drive roller 45 is arranged between the rollers 29, 32 and the thread winding 23. This drive motor 45 is constantly rotated while the start/stop switch 16 is turned on. Drive motor 4
Two circular rotary plates 47 are attached to the drive shaft 46 of No. 5 so as to be located in the needle thread path.
There is a spacer 48 between them as shown in FIG.
are interposed to form a void 49. Then, the rotating plate 47 is rotated by the drive motor 45 in the direction of arrow N, which follows the pulling direction of the upper thread Y, and as the rotating plate 47 rotates, the upper thread Y, which has been picked up by the rollers 29 and 32 and loosened, enters the gap 49. It is now being stored. Moreover, the void 49
The width is determined to be slightly larger than the diameter of the upper thread Y based on the thickness of the upper thread Y, and the width can be increased or decreased by appropriately replacing the spacer 48.

A pair of thread guides 50 are arranged in the upper thread path sandwiching the rotary plate 47, and one of the thread guides 50
A tensioner 51 for applying tension to the upper thread Y is arranged between the upper thread Y and the thread winder 23.

Further, as shown in FIG. 5, in this sewing machine, a needle position detection device for detecting the position of the needle 17 is installed on a pulley provided on the main shaft 24 of the sewing machine or at a location where a motor drive shaft or the like is rotationally driven. The vessel 61 and
A data reading timing pulse generator 62 and a cloth thickness detection timing pulse generator 63 are provided. The needle position detector 61 receives a needle position detection signal SG1, which rises when the needle 17 moving vertically moves downward with respect to the needle plate 6 as a reference, and falls when it moves upward, as shown in FIG. The data read timing pulse generator 62 outputs:
A timing pulse SG2 is output that rises a short time after the needle 17 sinks below the throat plate 6 from above and falls a short time after the needle 17 moves upward from below the throat plate 6. Further, the cloth thickness detection timing pulse generator 63 is adapted to output the cloth thickness timing pulse SG3 with a slight delay from the rise of the timing pulse SG2.

The arithmetic circuit 64 is composed of a central processing unit 65, a read-only program memory 66, and a working memory 67 for reading and writing. The drive amount of the positioning motor 38 is calculated in relation to the vertical reciprocating movement of the needle 17.

Next, the operation of the sewing machine thus constructed will be explained with reference to the block circuit diagram shown in FIG. 5 and the timing chart shown in FIG. 6. Now, in order to operate the sewing machine at a predetermined speed, any switch 8, 9, 10 of the speed selection switch group 11 is selected.
After selecting and operating the power on switch 7, turn on any pattern selection switch 1.
5, select and operate start/stop switch 16
When turned on, the arithmetic circuit 64 discriminates the output signal from the speed selection switch group 11 and operates the sewing machine motor drive circuit 68, the sewing machine motor 69 is rotated at a predetermined number of rotations, and the needle 17 moves up and down. . Further, output signals from the pattern selection switch group 15 and the start/stop switch 16 are sent to the arithmetic circuit 6.
4, when straight stitching is selected, the amplitude drive circuit 70 is not activated, the feed drive circuit 71 is activated, the feed actuator 72 is driven, and the feed dog is set to a predetermined feed amount and feed. direction. When pattern stitching is selected, the amplitude drive circuit 70 is activated, the amplitude actuator 73 is driven, the needle 17 is positioned at a predetermined swing position, and the feed drive circuit 71
The feeding actuator 72 is driven via the
The feed dog is activated. These selected patterns are displayed by lighting up one of the light emitting diodes 14 based on the operation of the pattern indicating device 74.

When the sewing machine is operated in this manner, the control cam body 26 is rotated together with the sewing machine main shaft 24, and each time the high portion 33b of the control cam surface 33 and the abutting portion 35a of the contactor 35 engage, a contact occurs. The child 35 is rotated in the direction of the arrow T, the transmission member 30 is rotated in the direction of the arrow Q, the driven roller 32 comes into contact with the rotating drive roller 29, and the upper thread is synchronized with the vertical movement of the needle 17. Y is pulled up.

The amount by which the upper thread Y is pulled up is determined as follows. That is, as shown in FIG. 6, when the needle 17 sinks downward from the throat plate 6, the needle position detector 61 outputs the pulse signal SG1, and a little later than that, the data reading timing pulse generator 6 outputs the pulse signal SG1.
A pulse signal SG2 is outputted from the pulse signal SG2, and a timing pulse signal SG3 is outputted from the fabric thickness detection timing pulse generator 63 with a slight delay from the pulse signal SG2. In response to this timing pulse signal SG3, the central processing unit 65 inputs a digital cloth thickness detection signal from the cloth thickness detector 60.

The central processing unit 65 receives the cloth thickness detection signal, a stitch forming signal drawn out from the program memory 66 in response to the output signal from the pattern selection switch group 15, and a working memory 66 corresponding to the input signal. Based on the calculation result, the thread pulling drive circuit 75 is operated, and the positioning motor 38 is rotated by a predetermined amount in the positive direction from the origin position, and the positioning cam body 41 causes the contact 35 to rotate by a predetermined amount. For this reason, the high portion 33 of the control cam surface 33
The engagement time between the contact portion 35a and the contact portion 35a of the contactor 35 is set to be optimal, and the upper thread Y is pulled up by an amount most suitable for the seam to perform correct thread tightening.

Further, during operation of the sewing machine based on the ON operation of the start/stop switch 16, the thread storage drive circuit 7 is turned on.
6 is activated, and the drive motor 45 is continuously rotated. As a result, the loosened portion of the upper thread Y pulled up by the rollers 29 and 32 is wound up and stored in the gap 49 between the rotating plates 47 attached to the drive motor 45. That is,
Since the gap 49 is slightly larger than the diameter of the upper thread Y, the upper thread Y tends to move together with the rotating plate 47 due to contact with the rotating plate 47.
Furthermore, since the gap 49 has a spacing that is only slightly wider than the needle thread Y, the air within the gap 49 rotates together with the rotating plate 47, and the needle thread Y is pulled in the direction of rotation. In this way, the upper thread Y is stored in the gap 49 as it is naturally wound up without being applied with tension. Therefore,
It is possible to reliably prevent the loosened portion of the pulled-up needle thread Y from becoming entangled with the components of the sewing machine.

When the upper thread Y has been pulled up in one stitch of sewing in this manner, that is, when the contact portion 35a of the contactor 35 is separated from the high portion 33b of the control cam surface 33, a signal is input to the thread pulling drive circuit 75. Then, the positioning motor 38 is reversely rotated, and the origin detector 42 and the slit 40a of the rotary disk 40 are stopped at the corresponding origin position.

This completes the operation of the thread pulling device in one stitch of sewing.

In this way, in this automatic thread tension device, when an arbitrary stitch pattern is selected by the pattern selection switch 15 and the sewing machine is started, the optimum amount of upper thread is automatically adjusted in conjunction with the up and down reciprocating movement of the needle 17. A raise is carried out.

In the above embodiment, a circular cam body was used as the control cam body, but a cylindrical cam body having a cam surface or a cam groove on the outer periphery may also be used. Engagement start side edge 33c
The upper thread can be changed to have a quadratic curve line, etc., so that the upper thread pull-up start timing can also be changed, or the engagement end side edge 33d can be made into a straight line that does not pass through the center of the control cam body 26. It's okay.

Effects of the Invention As exemplified in the embodiments above, the present invention is configured such that a driving roller and a driven roller that approaches and separates from the driving roller nip the upper thread and pull up the upper thread. The approach and separation movement of the driven roller is controlled by the engagement between the control cam body and the contact element, and the contact position of the contact element with respect to the control cam body is controlled by a positioning mechanism including a positioning motor. Therefore, in order to obtain the upper thread pulling amount suitable for each stitch formation, the driving amount of the positioning motor is calculated based on the calculation of the calculation circuit. To provide an excellent effect of automatically and accurately setting thread tension and always obtaining correct stitches.

[Brief explanation of the drawing]

The drawings show an embodiment embodying the present invention, in which Fig. 1 is an external view of the sewing machine, Fig. 2 is a perspective view showing the main parts of the invention and related mechanisms, and Fig. 3 is a control diagram. 4 is a sectional view showing the needle thread storage mechanism, FIG. 5 is an electric block circuit diagram, and FIG. 6 is a curve showing the needle thread supply amount curve using a full rotary hook and a conventional thread take-up. 2 is a timing chart showing output waveforms of signals from a needle position detector, a data reading timing pulse generator, and a cloth thickness detection timing pulse generator. Needle...17, Thread winder...23, Sewing machine spindle...24,
Bevel gear...25, control cam body...26, drive roller...29, driven roller...32, control cam surface...3
3, Connection shaft...34, Contactor...35, Positioning motor...38, Positioning cam body...41, Cam surface...41
a. Contact body...44, Arithmetic circuit...64, Needle thread...Y.

Claims (1)

[Claims] 1. The upper thread is placed at an appropriate position in the upper thread path from the upper thread supply source 23 to the needle 17, and is pulled out from the upper thread supply source 23 as the needle 17 moves up and down. A drive roller 29 that always rotates in one direction in synchronization with the rotation of the sewing machine main shaft 24 to pull up the thread Y.
The needle thread Y drawn out from the needle thread supply source 23 as the needle 17 reciprocates up and down is transferred to the drive roller 29.
a driven roller 32 rotatable to pinch and pull up the sewing machine main shaft 24; a control cam body 26 having a control cam surface 33 formed in the direction of rotation thereof and having different control cam surfaces 33 in a direction crossing the direction of rotation; and a control cam of the control cam body 26. A contactor 35 is always in contact with the surface 33 and is configured to change its contact position in a direction perpendicular to the direction of rotation of the control cam body 26; a transmission member 30 for transmitting contact/separation motion of the driven roller 32; and a positioning motor 38 driven to change the setting of the contact position of the contactor 35 in a direction intersecting the rotational direction of the control cam body 26. including;
Positioning mechanism 3 operatively connected to the contactor 35
4, 41, 44, etc., and an arithmetic circuit 6 that calculates the drive amount of the positioning motor 38 in relation to the up and down reciprocating movement of the needle 17 in order to obtain the upper thread pulling amount suitable for each stitch formation.
4. An automatic thread tension device for a sewing machine having 4. 2. The control cam body 26 is a circular cam body with the control cam surface 33 formed on one side thereof, and by changing the contact position of the contactor 35 in the radial direction of the circular cam body, the driven 2. The automatic thread tension device for a sewing machine according to claim 1, wherein the control cam surface 33 is formed so that the approaching and separating movements of the roller 32 are changed. 3 The positioning mechanism includes the positioning motor 3
a positioning cam body 41 rotationally driven by 8;
A claim in which the cam body 41 has a connecting body 34, 44 for transmitting the amount of displacement of the cam surface 41a of the cam body 41 to the contact 35, and the contact 35 is positioned at a contact position corresponding to the amount of displacement. An automatic thread tension device for a sewing machine according to item 1.