JPH0124517B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for automatically setting the tension of upper thread and lower thread of a sewing machine, and its purpose is to:
In an electronic sewing machine that electronically controls the amount of needle lateral runout and the amount of material feed, the needle thread and bobbin thread are automatically set to an appropriate tension at the same time depending on the type of sewing selected, and both tensions can also be manually adjusted. It attempts to make it possible.

To adjust the thread tension on a sewing machine, generally, adjust the bobbin thread tension appropriately by taking into account the fabric thickness, etc., and then try using the thread tension device to adjust the needle thread tension under that bobbin thread tension. The mesh between the upper thread and the lower thread is adjusted by sewing, for example, so that it is in the middle of the fabric thickness. A method has been proposed in which the needle thread tension is automatically set according to the type of sewing, but since the optimum value of the needle thread tension has a correlation with the bobbin thread tension,
Automatic setting of only the upper thread does not necessarily adjust the interlace between the upper thread and the lower thread to an appropriate position for the fabric thickness.

The present invention was devised to solve the above-mentioned drawbacks, and it is possible to form suitable seams by appropriately setting the tension of the upper thread and lower thread at the same time according to the type of sewing and the thickness of the fabric. At the same time, the tension of both the upper thread and the bobbin thread is increased using a twin needle to reduce the fabric shrinkage between the two stitches, so-called pin-tuck stitching, and buttonhole stitching in particular, as shown in Figure 6 below. By setting only the thread tension to a low level so that the intertwining of the upper thread and bobbin thread appears on the upper surface of the fabric, the looped bobbin thread wraps around the edge of the buttonhole fabric cut to strengthen the edge. This makes it possible to form so-called purl stitch buttonholes using automatic settings.

Embodiments of the present invention will be described below with reference to the drawings. In the drawings, 1 is the main body of the sewing machine, 2 is the front panel, and 3 is a semi-transparent decorative plate that displays various patterns including straight stitches and buttonhole stitches. Part 4 is printed (in FIG. 1, part of the pattern display part is shown and the rest is omitted). Display lamps are arranged corresponding to these patterns, and by selecting one of the plurality of pattern selection buttons 5, the pattern is selected, the thread tension is automatically set, and the selected pattern is selected. The display part of the pattern is illuminated from the back side of the decorative plate 3. These selection buttons 5
Of these, 5 _A is for straight stitching, and 5 _B is for scallop pattern sewing. A thread tension switching button 6 is provided for increasing the thread tension for both stitches. After operating selection button 5 _A or 5 _B , When the switching button 6 is operated, both the upper and lower threads of the selected pattern are set strongly, the display lamp 7 indicates that the setting has been made, and when any of the selection buttons 5 is operated again, the setting is changed. is about to be cancelled. Selection buttons _5M and _5N are used to select a set of a lower bar tack and a left line tack, and a set of an upper bar tack and a right line tack, respectively, for purl stitch buttonholes. 8 is a needle thread tension manual adjustment dial. By pressing this dial, the manual setting is enabled, the display lamp 9 lights up, and by rotating this dial, the needle thread tension can be adjusted to select a pattern. is adjusted independently of If any of the selection buttons 5 is operated again, the automatic setting of the selected pattern is returned to. 10 is a lower thread tension manual adjustment dial, and 11 is a display lamp thereof, which is switched and displayed in the same manner as the above-mentioned upper thread tension setting. 12, 13, 1
4 are operation buttons for specifying thread tension for thick, medium, and thin fabrics; 12', 13'1
Reference numeral 4' indicates an indicator lamp that indicates the specified status.

Fig. 2 shows the structure of the upper thread tension device, in which 15 is a plunger type solenoid and stator 16 is the sewing machine body 1.
Fixed. Reference numerals 17 and 18 indicate thread tension discs serving as upper thread tension members, which are fitted into the small diameter portion 20 of the plunger 19 of the solenoid 15, and are held between the support plate 21 and presser plate 22, which are fitted in the same way, so that the stator 16 The sewing machine body 1 can be moved slightly in the axial direction between the side surface of the sewing machine body 1 and the sewing machine body 1. Reference numeral 23 denotes a stopper which is screwed to the small diameter portion 20 so as to restrict the relative movement of the small diameter portion 20 in the axial end direction and to make the axial mounting position adjustable. The mounting is performed by providing a slight gap in the axial direction between the stopper 23 and the large diameter portion 24 of the plunger 20 so that the thread tension discs 17 and 18 are not pinched.
25 is a coil of the solenoid 15, and its excitation current is controlled. These installations described above are performed when the plunger 1 is installed when the solenoid 15 is energized and the thread tension discs 17 and 18 are clamped.
9 is made adjustable by the mounting bracket 23, and when the movement amount G is made larger in the same excitation, the clamping pressure of the thread tension discs 17 and 18 is adjusted to be smaller. . In this case, the solenoid 15 is such that the suction force changes gradually in response to changes in the residual movement amount G in order to facilitate adjustment of the clamping pressure.

FIG. 3 is a perspective view of the hook portion of the horizontal hook, and FIG. 4 is a sectional view thereof including a lower thread tension adjustment section. In FIGS. 3 and 4, an outer hook 26 is attached to a hook shaft 27 made of a magnetic material, and is rotated by transmitting the movement of a lower shaft 28 through gears 29 and 30. Reference numeral 31 denotes an auxiliary shaft made of a non-magnetic material, which is coaxially connected to the hook shaft 27 using a screw 32. 33 is a bearing integrated with the sewing machine main body 1. Reference numeral 34 denotes an excitation coil, which is attached to the sewing machine body 1 coaxially with the hook shaft 27 and rotatable about the shaft, so that its excitation current can be controlled. In FIG. 3, the excitation coil 34 is shown partially in section. 35 is an inner pot, the main part of which is made of synthetic resin, but an inner pot bottom 36 made of a magnetic material is inserted. The inner hook 35 is prevented from rotating by a swing-type rotation stopper 37, and the bottom of the inner hook has a slight gap from the hook shaft 27, so that even when the outer hook 26 is rotating, the inner hook 35 is prevented from rotating. It has almost stopped. Reference numeral 38 denotes an eccentric cam for swinging the rotation device, and is made of a non-magnetic material fixed to the shuttle shaft 27. 3
9 is a bobbin made of a magnetic material, and the state in which the bobbin thread is wound thereon is shown by a chain line. 40 is the lower thread end. The bobbin 39 rotates on the inner hook bottom 36 as the bobbin lower thread 40 is drawn out. The hook shaft 27, inner hook bottom 36, and bobbin 39 made of the magnetic material form a magnetic path that passes through the center of the excitation coil 34, and the magnetic path extends from both ends to the outside of the excitation coil by a space. It is designed to pass through. As the excitation current of the excitation coil 34 increases or decreases, its magnetic flux increases or decreases, and therefore the frictional force between the inner pot bottom 36 and the bobbin 39 increases or decreases depending on the magnetic attraction force therebetween. The reason why the auxiliary shaft 31 and the like are made of non-magnetic material is to eliminate adhesion of sliding surfaces and the like.

FIG. 5 is a control circuit diagram, and MC is a microcomputer, for example, a commercially available 8080 system is used, and the microcomputer stores each pattern selected by the pattern selection button 5 in its built-in electronic storage device. The sewing machine stores stitch control signals, upper thread and lower thread tension designation signals necessary for each stitch, and performs various controls as described later. DA ₁ is a digital-to-analog converter, and the microcomputer MC receives operation signals from the pattern selection button 5 and cloth thickness specification buttons 12, 13, and 14, or the operation of the thread tension switching button 6 following the operation of the pattern selection button. From the combination of these operation signals, the microcomputer converts the 3-bit digital signal for specifying needle thread tension into an analog signal. S ₁ is an analog switch, and when the pattern selection button 5 is operated, the contact piece means C ₁ is moved to the lower side in the figure, and when the needle thread tension manual adjustment dial 8 is subsequently pressed, the switch 8 _S is operated. The output of the digital-analog converter DA 1 is enabled when the contact means is below with respect to the non-inverting input terminal + of the operational amplifier OP ₁ , and the output of the digital-analog converter DA ₁ is enabled when it is above. The variable resistance VR ₁ , which is adjusted by turning the thread tension manual adjustment dial 8, is enabled. The variable resistor receives a control power supply _Vcc at one end, and its output includes the range of data output by the digital-to-analog converter _DA1 , making it possible to adjust even weaker tension. When the pattern selection button 5 is operated as input data to the digital-to-analog converter DA ₁ , the microcomputer MC makes the same specification as when the cloth thickness medium specification button 13 is operated. The bobbin thread has a moderate tension, and the upper thread has a tension within a range that is not particularly strong, and the tension is specified for each selected pattern. When the thread tension switching button 6 is also operated, both thread tensions are specified to be relatively large. Further, the cloth thickness designation buttons 12, 13, and 14 designate the lower thread tension as strong, medium, or weak, respectively, and the needle thread tension is also automatically set in connection therewith. The output terminal of the operational amplifier OP ₁ is connected to the base of a transistor Tr ₁ , and the collector of the transistor is connected to an excitation coil 25 for needle thread tension control receiving a power supply +V,
The emitter is grounded via a resistor _R1 and connected to the inverting input terminal of the operational amplifier _OP1 .
The control circuit for the excitation coil 34 for lower thread tension control has the same configuration as the upper thread tension control circuit, and although the details are omitted, the DA ₂ is a digital
The analog converter _S2 is an analog switch, and the contact piece means _C2 similarly moves up and down based on the operation of the pattern selection button 5 and the operation of the switch _10S by pressing the bobbin thread tension manual adjustment dial 10. VR ₂ is a variable resistance that is adjusted by rotating the bobbin thread tension manual adjustment dial 10. OP ₂ is an operational amplifier, Tr ₂ is a transistor, and R ₂ is a resistor. Said digital-
Similarly, for input data to the analog converter DA ₂ , a relatively small value is specified when only the pattern selection button 5 is operated, and a relatively large value is specified when the thread tension switching button 6 is also operated. .

In the above configuration, 5 of the 5 pattern selection buttons
When either _M or 5 except _N is operated, the specified pattern is selected, and the display lamp from the lower part of the pattern display section 4 displays the selected pattern. Although not shown in the control circuit of FIG. 5, the microcomputer MC outputs a stitch control signal for the selected pattern to a stitch forming device (not shown). At the same time, the microcomputer is adapted to the specification of medium material thickness, and each digital
A 3-bit signal is output to analog converters DA ₁ and DA ₂ for specifying upper thread tension and lower thread tension appropriate for the selected pattern. That is, this signal is used to set the needle thread tension to a value suitable for the pattern depending on the type of pattern, and specifies that the intertwining line between the needle thread and the bobbin thread be located at the center of the fabric thickness. This data is converted into analog values by digital-to-analog converters DA ₁ and DA ₂ , which are input to operational amplifiers OP ₁ and OP ₂ , and the coils 25 and 34 of each solenoid generate current values based on the analog values. The tension of the upper thread and bobbin thread is adjusted by excitation.

When pattern selection button 5 _M or 5 _N is selected,
This is a designation for purl buttonholes, and the microcomputer MC sets the lower thread tension to a weaker one and the upper thread to a stronger one. Therefore, during seam formation, as shown in Figure 6, the lower thread T _L is pulled up by the tension of the upper thread T _U to the point where the interlocking stitch P is visible on the upper surface of the fabric, and the lower thread T _L is used to cut the buttonhole fabric. The embossed edge E is bent to strengthen it to prevent it from fraying. Next, if the cloth is thick, the thread tension will need to be increased because the friction of the thread passing through the cloth will increase.
After operating the pattern selection button 5, when operating the thick material specification operation button 12, the microcomputer
MC specifies a higher bobbin thread tension and also sets an appropriate upper thread tension. Furthermore, when the fabric is thin, it tends to shrink, so it is necessary to weaken the thread tension, and when the thin fabric specification operation button 14 is operated, the lower thread and upper thread are similarly set to weaker values. The operation button 13 for specifying inside items is the same as the operation buttons 12 and 14.
This resets the designation to the normal cloth thickness, and can be replaced by operating the pattern selection button 5 again. After operating the pattern selection button _5A or _5B , when the thread tension switching button 6 is operated, the microcomputer MC sets the tension of both the upper thread and the lower thread to be strong. This is especially true when sewing with two needles, in which the stitches are formed using two upper threads on the top surface of the fabric, but since the lower thread is common, the strong setting allows the stitches to be stitched in parallel. The strong tension of the upper and lower threads acts between the two stitches that make up the fabric, causing the stitches to shrink, resulting in what is called a pintuck stitch. When the pattern selection button 5 is operated again, sewing with the normal thread tension is resumed. Next, when you press the upper thread tension manual adjustment dial 8 (or lower thread manual adjustment dial 10), the microcomputer
MC is switch S ₁ or S ₂ contact means C ₁ or C ₂
Move upward to enable variable resistance VR ₁ or VR ₂ and switch to manual adjustment of each thread tension. In particular, the needle thread tension manual adjustment dial 8 is designed to be able to adjust the needle thread tension to a very low level for use in basting and the like. When the pattern selection button 5 is operated again, the thread tension returns to the normal automatic setting.

As described above, according to the present invention, the upper thread tension and the lower thread tension are set in relation to each other by a pattern selection operation or a simple push button operation. Useful innovations include being able to form beautiful seams without fear of cloth shrinkage when the sewing machine is in the appropriate position, and automatic setting of special thread tension combinations for pintuck sewing and purl sewing buttonholes. It is.

[Brief explanation of drawings]

Fig. 1 is a schematic front view of a sewing machine showing an embodiment of the present invention, Fig. 2 is a sectional view of the needle thread tension adjustment device, and Fig.
The figure is a perspective view of the hook part of the horizontal hook, and FIG. 4 is its sectional view.
FIG. 5 is a control circuit diagram, and FIG. 6 is an explanatory diagram of the stitches to be formed. In the figure, 5 is a pattern selection operation section, 12, 13, 14
25 is an electromagnetic coil that is a main element of the upper thread tension adjustment section; 34 is an electromagnetic coil that is a main element of the lower thread tension adjustment section; MC is an electronic storage device and a thread tension setting means. It is a microcomputer that exists everywhere.

Claims (1)

[Claims] 1 A sewing machine that electronically controls the relative position of the fabric and the needle has a pattern selection operation section for selecting a desired pattern from among a plurality of sewing patterns, and a fabric thickness specification operation section for specifying the thickness of the fabric to be sewn. , an electronic storage device storing a set of thread tension signals of upper thread tension and lower thread tension appropriate for the combination of the designation by the pattern selection operation section and the designation by the cloth thickness designation operation section; , an upper thread tension adjustment section that automatically adjusts the upper thread tension; a lower thread tension adjustment section that automatically adjusts the lower thread tension; and a lower thread tension adjustment section that automatically adjusts the upper thread tension; An automatic thread tension setting device for a sewing machine comprising a thread tension setting means for setting each thread tension of an adjusting section and a bobbin thread tension adjusting section.