JPS6226075Y2 - - Google Patents

Description

[Detailed description of the invention] This invention is a sewing machine that uses a thread take-up to pull up the needle thread to give a predetermined thread tension to the seam. Regarding needle thread feeding devices for sewing machines in which needle thread is continuously fed out from a supply source via a feeding means such as a set of rollers that are in pressure contact with each other by a stepping motor synchronized with the rotation of the It is characterized by being able to reliably supply the required amount of yarn.

In this type of device, if a stepping motor with a small driving force is used, when the upper thread is pulled up from the needle by the thread take-up, the stepping motor will be over-rotated by the strong tension generated in the upper thread, causing the upper thread to There was a drawback that it could be extended beyond the required length.

The object of this invention is to eliminate the above-mentioned drawbacks by providing a needle thread gripping device, and to provide a needle thread supplying device that allows accurate feeding of the needle thread and has high-speed performance.

Examples of this invention will be described below with reference to the drawings.
1 is a needle bar on which a needle 2 with an upper thread T is fixed at the lower end;
It moves up and down in conjunction with the main shaft (not shown) of the sewing machine. Reference numeral 3 denotes a thread take-up, which is linked to the main shaft to support the needle thread T between the needle 2 and the bobbin spool 4 serving as the needle thread supply source, and to tension and relax the needle thread T, and is synchronized with the vertical movement of the needle bar 1. to move up and down between two predetermined positions. 5 is an outer frame (machine frame) of the sewing machine, a thread hook 6 is fixed to the front wall 5a thereof, and a thread guide groove 7 is formed in the upper wall 5b so as to penetrate into the machine frame.

On the front wall 5a, a drive roller 9 fixed to the output shaft of a stepping motor (hereinafter referred to as motor) 8 is disposed on one side of the path of the upper thread T passing through the thread guide groove 7, and on the other side. A driven roller 10 is disposed at , and both rollers 9 and 10 constitute a feeding means. The driven roller 10 is rotatably supported at the free end of an arm 11 whose base end is rotatably supported on the machine frame, and is supported by an elastic body (see FIG. Due to the acting force (not shown),
The outer periphery is always pressed against the outer periphery of the drive roller 9. In the machine frame 5, a pair of clamping plates 12 and 1 are arranged to sandwich the path of the upper thread T between the rollers 9 and 10 and the bobbin winder 4.
3 are arranged facing each other, and one of the clamping plates 12 is fixed to the mover of an electromagnetic solenoid (hereinafter referred to as a solenoid) 14, and both clamping plates 12 and 13 are moved by energizing and de-energizing the solenoid 14 to thread the upper thread T. Constructed to grasp and release. And this solenoid 1
4 is excited by an appropriate detector (not shown) in connection with the detection of the rotational angular position of the corresponding main shaft during the tensioning period of the upper thread T by the thread take-up 3;
The demagnetization is performed in connection with the detection of the rotational angular position of the corresponding main shaft during the relaxation period of the needle thread gripping device.

Note that 15 is a known base tension disposed at the rear of the thread guide groove 7, and always provides a constant resistance to the upper thread T that is weaker than the tension of the lower thread.

Next, the electric circuit of this invention will be explained with reference to FIG.

G1 to G4 are NAND gate circuits (hereinafter referred to as gates), and 11 and 12 are inverters.

2C is a spindle pulse generator, which consists of a disk fixed to the spindle and provided with a plurality of slits at equal intervals on the same circle, and a sensor placed opposite to the rotation path of the slits. A signal is generated in connection with the detection of the slit. A first conversion circuit 21 converts an input signal into a signal with a voltage value corresponding to the frequency and outputs the signal. A second conversion circuit 22 converts an input signal into a signal with a frequency corresponding to the voltage value and outputs the signal. 23 is a variable resistor as a first amplifier circuit, which can be operated manually or based on information recorded electrically or mechanically in advance.
The resistance value is changed in relation to the setting conditions of the setting means that can set different sewing conditions. For example, it is mechanically linked to the mode of manual operation of one or more of a manual device for setting the cloth feed pitch, a manual device for setting the swing width of the needle bar 1, and a manual device for setting the cloth thickness. or related to the information read out from the storage means in electrical connection with aspects of these manual devices, or a stitch previously recorded in a recording device electrically (ROM) or mechanically (cam). The resistance value changes in relation to the information for each eye.

Reference numeral 24 denotes an upper position detector, which consists of a disc fixed to the main shaft and having a cutout corresponding to the rotation angle corresponding to the tension of the upper thread T by the thread take-up lever 8, and a sensor placed opposite to the rotation path of the cutout. , outputs a low level signal (hereinafter referred to as L) during the tension period, and outputs a high level signal (hereinafter referred to as H) during the relaxation period. 25 is a pulse edge generating circuit that instantaneously generates an H signal by aligning the rising edges of the inputs. 2
6 is a counter which is reset by receiving an H signal at its R terminal. 27 is a second amplification circuit, which is interlocked with the first amplification circuit 23; Reference numeral 28 denotes an analog/digital conversion means as a third conversion circuit, which converts the input signal into a binary code corresponding to the voltage value and outputs the binary code. A matching circuit 29 generates an L signal when the output of the counter 26 and the output of the third conversion circuit 28 match. Note that VA is a voltage that is adjusted appropriately through a resistor to the power supply voltage, and can be changed.

30 detects whether the rotational speed of the spindle is above or below a certain speed, and opens/closes gates G2 and G3 so that if it is above the certain speed, gate G2 is opened, and in the following cases, gate G3 is opened. This is a control judgment circuit that consists of multiple elements as shown below. That is, 3
Comparing circuits 1 and 32 generate an L signal when the input voltage at the negative terminal is greater than the input voltage at the positive terminal. 33 is an RS type flip-flop (hereinafter referred to as FF), which outputs an H signal from the Q terminal when an L signal is input to the S terminal, and outputs an L signal from the Q terminal when an L signal is input to the R terminal. Output. Vcc is a power supply voltage, and R1 to R8 are resistors.

This invention has the above structure, and its operation will be explained next. When the sewing machine is driven, the needle bar 1 and the thread take-up lever 3 move up and down in conjunction with the rotation of the main shaft while maintaining a slight phase shift. Furthermore, a signal is output from the main shaft pulse generator 20 every time the main shaft rotates by a predetermined angle, and a signal of L is output from the upper position detector 24 during the tensioning period of the upper thread T by the thread take-up 8.

Therefore, for example, when the sewing machine is driven at a certain speed or less, that is, when the output voltage of the first conversion circuit 21 is lower than the voltage level of P1, the FF 33 receives an L signal at the R terminal. Therefore, an L signal (low speed signal) is output from the Q terminal. This closes the gate G2 and cuts off the output of the second conversion circuit 22. On the other hand, since gates G3 and G1 open at the same time as gate G2 closes, the motor 8 is driven by the output of the spindle pulse generator 20 through the motor drive circuit to the first speed corresponding to the driving speed of the sewing machine.
Rotate clockwise as shown in the figure. To describe this in more detail, the counter 26 is connected to the pulse edge generating circuit 25.
The gate G is controlled by the signal output from the spindle pulse generator 20 until it is reset by the signal
As the motor 8 rotates via G4, G3, and G1, the signal is counted by the counter 26, and when the counted value matches the output code of the third conversion circuit 28, the output of the matching circuit 29 is output. As a result, gate G4 is closed and motor 8 is stopped. Therefore, for example, assuming that the number of signals oscillated from the spindle pulse generator 20 during one reciprocating movement of the balance 3 is 100 pulses, the condition for matching the outputs of the counter 26 and the third conversion circuit 28 is as follows: The condition for closing the gate G4 is that the value of the counter 26 can be set to a maximum value of 100 and any value lower than that by setting the second amplifier circuit 27. For example, if the value is set to 20, the upper thread T is Motor 8 for 20 pulses from the start of relaxation
rotates and stops, and this process is repeated every time the sewing machine forms a stitch.

Contrary to the above, when the sewing machine is running at a certain speed or higher, that is, when the output voltage of the first conversion circuit 21 is higher than the voltage level at point P2, the FF 33 connects the S terminal with an L voltage. Since a signal is input, an H signal (high speed signal) is output from the Q terminal. As a result, the gate G2 opens at the same time as the gate G8 closes, so that the motor 8 rotates clockwise in FIG. 1 via the amplifier circuit 23 at a speed corresponding to the driving speed of the sewing machine. Furthermore, even if the sewing machine is driven at the same speed, if the sewing conditions such as cloth feed pitch, needle amplitude, and cloth thickness are different, the amplification factor of the amplifier circuit 23 will be different, so the rotational speed of the motor 8 will also be different. Become something.

When the motor 8 rotates in this manner, the roller 9
rotates in the clockwise direction in FIG.
With the cooperation of the above, the needle thread T is continuously paid out from the bobbin 4 toward the thread take-up 3 at a speed corresponding to its rotational speed.

Therefore, whether the sewing machine is running at low speed or high speed, the needle thread T of the length required to form each stitch is fixed at thread take-up 3.
The needle thread T is continuously paid out not only when it is relaxed but also when it is tensioned.

Note that when the upper thread T is tensioned by the thread take-up 3, the upper thread T is gripped by the pair of clamping plates 12 and 13, so during that period, the tension between the pair of rollers 9 and 10 and the pair of clamping plates 12 and 13 increases. The needle thread T is stretched, and the stretched amount of the needle thread T is transferred to the clamping plates 12, 13.
When the upper thread is released next time, the upper thread is let out at once from the bobbin winder 4.

As described above, this invention uses an upper thread gripping device that grips the upper thread while the upper thread is being tensioned by the thread take-up, and releases the grip of the upper thread during the relaxation period of the upper thread. Since it is placed on the needle thread path between the means and the supply source or between the feeding means and the thread take-up, a large load is not applied to the stepping motor when the thread take-up tensions (thread tightens) the thread take-up. Since the motor is continuously rotated during the relaxation period and the tension period of the thread by the thread take-up, over-rotation is prevented because it is not affected by inertia unlike intermittent rotation. Therefore, even if a small and inexpensive stepping motor with a weak driving force is used, the required amount of yarn can be accurately supplied.

In addition, a stepping motor that rotates at a speed corresponding to the frequency of a signal generated every time the main shaft rotates by a predetermined angle is used to move the needle thread of the length necessary to form each stitch using a thread take-up during the needle thread relaxation period. Since the sewing machine is configured to supply the sewing machine continuously over the tension period, even if a stepping motor with poor response characteristics is used, it can sufficiently follow the high-speed operation of the sewing machine, increasing the operating speed of the sewing machine and improving sewing efficiency. Effects can be obtained.

Note that FIG. 3 shows another embodiment of the first conversion circuit 21 in this embodiment, and the same elements as in this embodiment are given the same numbers. FIG. 4 is a time chart of FIG. 3. That is, regarding the configuration, 4
0 is a first pulse edge generation circuit that captures changes in the signal of the main shaft pulse generator 20 and instantaneously generates an H signal. Reference numeral 41 denotes a second pulse edge generating circuit which catches the falling edge of the signal from the generating circuit 40 and instantaneously generates an H signal. 42 is a reference pulse generator that always generates a signal at a constant frequency. 4
3 is a counter which clears its contents upon receiving an H signal at its R terminal. 44 is a latch circuit, and H is connected to the R terminal.
It receives the signal and outputs the input state at that time. 4
5 is a digital/analog converter, input (numeric value)
generates a voltage at a level corresponding to G5~G7
is a gate, and 15 is an inverter.

Regarding the operation shown in FIG. 3, when the sewing machine is driven, a signal is generated from the main shaft pulse generator every time the main shaft rotates by a predetermined angle. On the other hand, during the period from the rise to the fall of the signal or from the fall to the rise of the signal, the output signal of the reference pulse generator 42 is counted by the counter 43 via the gate G6 and the inverter 15, and the signal The latch circuit 44 is latched via the gate G7 by the signal from the generating circuit 41 related to the change in the voltage, and the voltage is at a level corresponding to the count value of the counter 43 at that time (when the count value is large, the voltage is at a lower level than when it is small). ) is output from the converter 45.

Further, FIGS. 5 and 6 show separate other embodiments corresponding to FIG. 1, and the same elements as in this embodiment are given the same numbers. That is, FIG. 5 shows the solenoid 14 and the clamping plate 1 as an upper thread gripping device.
2 and 13 are rollers 9 and 1 as feeding means.
0 in the direction in which the upper thread T is fed out, and the clamping plate 1
2 and 13 grip the upper and lower T, thereby preventing a large load from being applied to the motor 8 when tightening the stitches, and preventing the needle thread T from being unwound excessively.

In addition, FIG. 6 shows an example in which the feeding means of this embodiment is replaced with other elements, 50 is a spinning wheel fixed to the output shaft of the motor 8, and the upper T is wound around the outer periphery of the spinning wheel. , 42 is a drag cola that rotates in conjunction with the main shaft. The timing of energizing and de-energizing the solenoid 14 is the same as in this embodiment. Then, when the motor rotates in proportion to the rotational speed of the main shaft, the upper thread T wound around the spinning wheel 50 is paid out toward the thread take-up lever 3. At the same time, the same amount of thread is paid out by the spinning wheel 50, and the needle thread T is pulled out. roller 51,
52, the upper thread T is further fed out to the side of the thread take-up lever 3, so that the upper thread T is always wound around the spinning wheel 50 with a constant tension, and an amount of thread proportional to the rotation angle of the spinning wheel 50 is reliably fed out. It is something.

[Brief explanation of the drawing]

Fig. 1 is a perspective view of the main parts, Fig. 2 is a block diagram of the electric circuit, Fig. 3 is another embodiment of the first conversion circuit,
FIG. 4 is a time chart of FIG. 3, and FIGS. 5 and 6 are other embodiments corresponding to FIG. 1. 3 is a balance, 8 is a stepping motor, 9, 10
are rollers as feeding means, 12, 13, 1
4 is a clamping plate and an electromagnetic solenoid constituting an upper thread gripping device, and 20 is a (main shaft) pulse generator.

Claims (1)

[Scope of claim for utility model registration] A main shaft supported on a machine frame in conjunction with a drive source and rotatable about a fixed axis;
A balance that reciprocates in conjunction with the main shaft so as to relax, a pulse generator that is linked to the main shaft and generates a signal every time the main shaft rotates by a predetermined angle, and a pulse generator that is related to the signal of the pulse generator and is directly proportional to the frequency of the signal A stepping motor that rotates in one direction at a high speed, and a stepping motor that is arranged on the needle thread path between the thread take-up and the needle thread supply source so as to engage the needle thread and pay out the needle thread from the supply source by rotation. A needle thread feeding device comprising: a feeding means rotatably supported on a machine frame; and a needle thread having a length required for forming one stitch is continuously fed out from a supply source when a main shaft rotates, or upper thread gripping in relation to the operation of the thread take-up, which acts by elastic force and grips the upper thread during the tensioning period of the thread take-up, and releases the grip of the upper thread during the relaxation period of the thread take-up. 1. A needle thread supply device for a sewing machine, characterized in that the device is disposed on a needle thread path between a feeding device and a supply source or between a feeding device and a thread take-up.