JPS6042751B2 - electric sewing machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electric sewing machine, and more particularly to an electric sewing machine that is most suitable for accurately performing needle alignment at the beginning and end of sewing.

FIG. 1 shows a perspective view of a general electric sewing machine. A sewing machine main body 2 is installed on the top surface of the table 1.

An oil tank 3 containing lubricant for smoothly operating the sewing machine body 2 is attached to the lower surface of the table 1. A pulley 21 and a position detection mechanism 22 are attached to the rotating shaft of the sewing machine body 2. Further, a motor 4 that serves as a driving source for the sewing machine is attached to the lower surface of the table 1. A pulley J-41 is attached to the rotating shaft of this motor 4 via a transmission mechanism 5, and the rotational force of the motor 4 is transmitted via a belt 6 placed between this pulley 41 and pulley 21. The information is transmitted to the sewing machine main body 2. The motor 4 is controlled by a control section 7, and its operation commands are given by operating a foot switch 8. Further, in the transmission mechanism 5, as shown in FIG. 2, a latch plate 53 is disposed between a clutch friction plate 51 and a brake friction plate 52 and is movable in the axial direction of the motor 4. 41 are directly connected. The clutch plate 53 is activated by energizing the clutch coil 54 so that the clutch friction plate 51
and rotate together due to the frictional force. Also, by exciting the brake coil 55, the brake friction plate 5
2 and the clutch plate 53 are in close contact with each other, and the friction force causes the pulley to
Lee 41 stops rotating. Clutch coil 54 and brake coil 55 are connected to transistors 56 and 57, respectively, as shown in FIG. 3, and are driven by their collector currents. The transistors 56 and 57 are driven using a clutch signal CI-S and a brake signal BRS, which are control signals, as base inputs, respectively. The degree of coupling between the clutch friction plate 51 and the clutch plate 53 can be changed by changing the value of the current flowing through the clutch coil 54. The current value flowing through the clutch coil 54 is the clutch signal CI-S.
This can be done by changing the magnitude of CLS or by intermittent clutch signal CLS. The rotation speed of the sewing machine body 2 changes depending on the degree of coupling between the clutch friction plate 51 and the clutch plate 53. When the coupling is strongest, the clutch friction plate 51
and the clutch plate 53 rotate together to obtain the maximum speed,
On the other hand, if the coupling is loose, a slip will occur between the clutch friction plate 51 and the clutch plate 53, making it possible to reduce the rotational speed. In other words, by changing the magnitude of the clutch signal CLS or by making it intermittent, the sewing machine body 2
It is possible to freely change the rotation speed. Furthermore, if the rotational speed is higher than the scheduled speed, the brake can be used to decelerate and operate at a constant speed. Now, in sewing products, it is common practice to perform tacking stitches at the beginning and end of sewing to prevent threads from fraying. The tacking stitch at the beginning of sewing is performed by moving forward a predetermined number of stitches and then moving backward a predetermined number of stitches. Furthermore, for the tacking stitch at the end of sewing, the sewing machine is moved backward by a predetermined number of stitches and then moved forward by a predetermined number of stitches. Sewing machines are generally equipped with a reversing device that reverses the stitch feed (feeding the fabric in the backward direction), and a solenoid is used to operate this device. In other words, the general method is to energize the solenoid of the reversing device to move the vehicle backward, and to turn off the energization of the solenoid to move the vehicle forward. The number of stitches for tacking varies depending on the product to be sewn, but it is necessary for the quality of the product to have a consistent stitch pattern. On the other hand, it is necessary for work efficiency to perform this tacking stitch as fast as possible. Therefore, conventional methods have been used to limit the maximum speed to a certain value or rotate at a constant speed for the tacking stitch at the beginning of sewing, and to rotate at a constant speed for the tacking stitch at the end of sewing. There is. A case will be described in which the starting and ending tacking stitches are sewn at a constant speed and the forward and backward movement of the starting tacking stitch and the backward and forward movement of the ending tacking stitch are set to 4 stitches. Figures 4A, b, c, d, e, f, and g show the sequence of initial tacking stitches. [JPS in Fig. 4a is a signal indicating the upper position of the sewing machine needle, DOWNS in Fig. 4b is a signal also indicating the lower position, BTS in Fig. 4c is a signal that excites the solenoid that operates the reversing device, Figure 4 d(7)B
TM indicates the operation of the solenoid. Also, Figure 4 e (7)
CLSl is a foot operated clutch signal, Fig. 4 f(7)C? 2 is the clutch signal actually input to the transistor 56, and FIG. 4g (7) SPD indicates the number of revolutions of the sewing machine. At the time when sewing starts, the sewing machine needle is stopped at the upper position. When the operator fully depresses the foot switch 8 forward, the speed command from the foot switch 8 becomes NH, which commands the maximum speed NH, as shown in FIG. 4e. As described above, when sewing the initial tacking stitch at a constant intermediate speed NM, a control circuit (not shown) sets the clutch signal to NM during the initial tacking stitch. When the speed of the sewing machine main body 1 is accelerated from a stopped state, the speed is increased to NM by the clutch signal CLS2. Then, when the first tacking stitch is completed, the clutch signal C? 2 rotates at intermediate speed NM until it indicates the maximum speed NH, and then is accelerated to the maximum speed NH. The setting for the initial tacking stitch is 4 stitches as shown in Figure 4, so the lower position signal DOW is used.
When NS is output five times, the four forward stitches are completed (the first lower position signal DOWNS only moves the sewing machine needle from the upper position to the lower position, and no stitches are formed). When the forward movement completes 4 stitches,
Next, solenoid excitation signal BTM to move backward 4 stitches
Turn on. The solenoid contains inductance, and the rise of the solenoid's excitation current is delayed, so
The solenoid BTM starts moving with a delay of time Tl,
It takes Tl to complete the movement. This means that I will be delayed. Also, after completing 4 stitches of reverse movement, the solenoid operation signal BT
When S is turned off, the solenoid BTM returns to its original position after the delay times T2l and T22 have elapsed. Therefore, the actual stitches to be sewn are as shown in Figure 5.
However, due to the delay in the operation of the solenoid BTM, the result becomes as shown in b. In other words, the first stitch in reverse is the solenoid BT.
It takes time Tl for M to finish moving completely. This causes a forward movement, and the return delay time of the solenoid BTM is T22.
Therefore, for the first stitch after the solenoid operation signal BTS is turned off, the reverse signal is turned on when three stitches of forward movement are completed.
Turn off when 7 stitches are completed counting from the start of sewing b
Since the forward movement is one stitch less than the stitch shown in , the desired stitch shown in a is obtained. Conventionally, the number of stitches for tacking stitches was about 4, and the speed NM was 1000 to 1500 r'. P. m
The above method did not cause any problems. However, if a large number of stitches (7 to 8 stitches) are required for the tacking stitch, the time required for the tacking stitch will be longer, so the tacking speed NM should be set at 2000 to 2500 r'. P. It became necessary to raise it to m. Tie stitch speed NM 2000-250
0r'. P. When the value is increased to m, the number of stitches between the solenoid BTM operation and return delay times Tl2 and T22 becomes one stitch or more, and this delay time Tl2 and T22 vary depending on the voltage applied to the solenoid BTM, etc. The stitches of the tacking stitches are not aligned, which poses a quality problem for the sewn product. SUMMARY OF THE INVENTION An object of the present invention is to provide an electric sewing machine in which stitches of tacking stitches are aligned by appropriately adjusting the speed. The present invention utilizes the delay characteristic of the tacking solenoid to reduce the rotational speed of the sewing machine in the moving and returning sections of the reversing device solenoid for tacking, and performs the tacking at high speed in other sections as before. This is what I decided to do.

Each of FIGS. 6A, b, c, d, e, f, and g is a time sequence of starting backtack stitching in the present invention.

In Fig. 6, the set number of stitches is 8 for both forward and backward movement, and the solenoid operation signal BTS is turned on when the first 7 stitches are completed, and the first stitch from the beginning of sewing is completed. This shows the case where it is turned off at this point. Figure 6a (7) UPS is a signal indicating the upper position of the sewing machine needle, Figure 6b (7) DOWNS is a signal similarly indicating the lower position, Figure 6c (7) B'IS operates the reversing device. Fig. 6 d (7) BTM is a waveform indicating the operating state of the solenoid, CLSl in Fig. 6 e is a clutch signal caused by foot pedal operation, Fig. 6 f (7) 0nu 2 is the actual signal to excite the solenoid. The clutch signal inputted to the transistor 56, SPD in FIG. 6g, each indicates the number of revolutions of the sewing machine. The speed at the beginning of sewing is intermediate speed (1) NMl, 6 stitches from the beginning of sewing (DO
command (clutch signal CLS2) until WNS) is completed.
Release NMl. A command NM9 is issued to set the intermediate speed (■) NM9 for the next three stitches as shown in FIG. 6f. Thereafter, a command NMl is issued again to command an intermediate speed (1) NMl from the beginning of sewing to the first stitch, and a command NM2 is issued to command an intermediate speed (■) NM9 for the next three stitches. In this case, for example, the intermediate speed (1
)NML at 2300r. p. m intermediate speed (■) NM2 to 1500 r'. P. If set to m, solenoid B
The time for the TM to move and return is the same as before, 1500r. p
．． Since it is performed at 2300 r.m, it is possible to align the stitches as before, and at the same time, the other sections are 2300 r.m. p. Since the work can be carried out at m, it is possible to greatly improve work efficiency without impairing the quality of sewn products. In addition, especially when strict alignment of the stitches is required, if intermediate speed (1) NMl and intermediate speed NM2 are made adjustable, the operation of the solenoid BTM and the return time can be controlled by the voltage applied to the solenoid BTM. If the stitch size changes, it is possible to adjust the stitches accordingly.

The above explanation has been about the tacking stitch at the beginning of sewing, but it is also possible to align the stitches with the tacking stitch at the end of sewing using the same method. Each of FIGS. 7A, b, c, d, e, f, and g is a time sequence showing tacking stitches at the end of sewing.

The signal contents of each figure correspond to FIGS. 6a-g. When the sewing machine stops or reaches a sufficiently low speed NL of about 200 r''.P.m and the sewing machine needle is in the down position, turn on the solenoid operation signal BTS shown in Fig. 7C. In this case, the sewing machine is a sufficiently low speed NL, so the delay in the operation of the solenoid BTM is not a problem.If the number of backward and forward stitches is set to 8, the solenoid operation signal BTS is turned off when 7 reverse stitches are completed. .on the other hand,
The speed command is set at 2 until 6 backward stitches are completed as shown in Figure 7f.
Issue a command NMl that commands an intermediate speed (1) NMl that indicates approximately 300r″.P.m, and the next 3 stitches are 1300r″.
．． P. Output the intermediate speed (■) NM2 indicating m. Thereafter, a command NMl is issued again to command the intermediate speed (■) NMl. In addition, after finishing the last reverse stitch, the speed should be lowered to a sufficiently low speed and the last two stitches should be done at medium speed (■) again so that it will stop automatically.
A command NM2 is issued to command NM2, and a command N is issued to make the last stitch at a sufficiently low speed n to stop the stitch. The reason for this is that in the case of electromagnetic type, 2300 r. p. Since there is a possibility that one stitch or two stitches may occur before stopping from m, due to variations in the brake force, a command NM2 that commands an intermediate speed NM2 is issued from the second and final stitch. Although the method of varying the speed setting using the stitch signal has been described above, the same effect can be obtained by setting the intermediate speed (■) section based on time instead of the number of stitches. As described in detail above, according to the embodiments of the present invention, sewn products are of high quality and can be sewn efficiently under the best conditions. The forward and backward movement and cloth slippage, which change due to pressure, etc., can always be set to the best conditions by simply adjusting the intermediate speed (1) and intermediate speed (■).

As is clear from the above, according to the present invention, it is possible to accurately match the stitches of the tacking stitch.

[Brief explanation of the drawing]

Figure 1 is a perspective view of an example of an electric sewing machine, and Figure 2 is a perspective view of an example of an electric sewing machine.
Figure 3 is a schematic diagram of the transmission mechanism of the electric sewing machine shown in the figure, and Figure 3 is a circuit diagram of the electric circuit that controls the transmission mechanism of Figure 2 to Figure 4 A9b9.
Each of c9d9e9f9g is a time sequence showing a conventional control operation, FIG. 5 is an explanatory diagram of stitches, and FIG. 6A, b,
Each of c, d, e, f, and g is the tacking stitch time sequence at the start of sewing in the present invention, and Fig. 7A, b, c, d, and e.
, f, and g are the tacking stitch time sequences at the end of sewing in the present invention. 2... Sewing machine body, 4... Motor, 5...
...Transmission mechanism, 7...Control section, 51...
...Clutch friction plate, 52...Brake friction plate, 53...Clutch plate, 54...Clutch coil, 55...Brake coil.

Claims (1)

[Scope of Claims] 1. A motor, a transmission mechanism that includes an electrically controlled clutch and brake and transmits the driving force of the motor to the sewing machine body and controls the speed, and a control device that controls the transmission mechanism. and a reversing device that controls the forward and backward movement of the sewing material using a solenoid,
The tacking stitch at the beginning of sewing is performed by moving backward at a predetermined speed, and the power supply to the solenoid is stopped a predetermined number of stitches before the completion of the backward movement, and until the operation of the solenoid is released,
An electric sewing machine characterized by performing locking stitches at a speed lower than the above-mentioned predetermined speed. 2. The speed lower than the predetermined speed is obtained by issuing a command for a sewing machine rotation speed lower than the predetermined speed for a predetermined period of time one stitch before the energization of the solenoid is stopped. The electric sewing machine mentioned. 3. The electric sewing machine according to claim 2, wherein the low sewing machine rotation speed command issued for the predetermined period of time is issued for three stitches. 4. A motor, a transmission mechanism that includes an electrically controlled clutch and brake and transmits the driving force of the motor to the sewing machine body and controls the speed, a control device that controls the transmission mechanism, and a transmission mechanism for feeding the sewing product. In an electric sewing machine equipped with a reversing device that controls forward and backward movement using a solenoid,
Two stitches before completion of the forward section of the tacking stitch at the end of sewing, issue a speed command intermediate between the above constant speed and a sufficiently low speed when stopping at a fixed position to decelerate, and then issue a sufficiently low speed command for the last stitch. An electric sewing machine that is characterized by the ability to