Sewing – Elements – Starting or stopping
Patent
1983-04-18
1986-12-09
Nerbun, Peter
Sewing
Elements
Starting or stopping
D05B 6922
Patent
active
046273700
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to sewing machine drive devices, and more particularly to a sewing machine drive device which, in order to stop the sewing needle at a desired position, drives the sewing machine at an ultra low speed and changes the speed of the sewing machine to a desired value immediately before the needle is stopped.
BACKGROUND ART
A conventional sewing machine drive device is designed as follows:
The electromagnetic clutch is excited by depressing the foot pedal so that it is electromagnetically coupled to the flywheel which is coupled to the rotor of a sewing machine drive motor which is rotated at all times, and the sewing machine is driven through the electromagnetic clutch thus coupled.
Furthermore, by changing the amount of depression of the foot pedal, an electromagnetic clutch exciting current from the motor speed control circuit is controlled, so that the speed of the sewing machine is controlled to a desired value according to the amount of depression of the foot pedal.
Thus, the conventional sewing machine drive device is disadvantageous in the following points: As the drive motor is rotating at all times whether the sewing machine is driven or stopped, the drive device consumes electric power uneconomically. Since the flywheel has a large moment of inertia, it is difficult to change the direction of rotation of the motor at a desired time. If a friction type electromagnetic clutch is employed, the service life of the drive device is reduced because the clutch is subject to wear.
In order to overcome the above-described difficulties, a sewing machine drive device has been proposed in Japan, in which a print motor is employed as the sewing machine drive motor and is driven by direct current, and the electromagnetic clutch is eliminated, and in which the print motor is directly started or stopped or driven at various speeds according to the operation of the foot pedal. The drive device has an excellent control characteristic because of the employment of the DC motor; however, it is still disadvantage in the following points: The brushes are subject to wear which reduces the service life, thus requiring inspection and maintenance. Since the motor is started and stopped whenever the foot pedal is in operation, the start current is large. Accordingly, a large capacity power source must be employed, and the drive control circuit is bulky, which results in a high manufacturing cost of the drive device.
DISCLOSURE OF THE INVENTION
In view of the foregoing, a first object of this invention is to provide a novel sewing machine drive device in which an AC induction motor is employed as the drive motor, and it is driven by a variable voltage/variable frequency inverter circuit, so that the sewing machine is driven at various speeds, whereby the above-described difficulties accompanying a conventional sewing machine drive device are eliminated.
A second object of the invention is to provide a novel sewing machine drive device in which an AC induction motor is used as the drive motor, and it is driven by an inverter connected in series to a converter, so that the sewing machine is driven at various speeds, and in which, when the speed of the machine is reduced, regenerative braking is effected with the converter being operated as inverter, whereby the above-described difficulties accompanying a conventional sewing machine drive device, and energy is economically used.
The first object of the invention has been achieved by the provision of a sewing machine drive device comprising: a sewing machine drive mechanism having an induction motor and a braking unit; and a position detector connected to the output side of the induction motor, for detecting a sewing needle's position; which, according to the invention, comprises: a stop position control section for causing an inverter circuit to subject the induction motor to variable speed driving and operating the braking unit with the aid of a detection signal from the position detector, to stop the sewing needle at a predetermined po
REFERENCES:
patent: 4137860 (1979-02-01), Yoneji et al.
patent: 4161921 (1979-07-01), Nishida et al.
patent: 4195582 (1980-04-01), Novick
patent: 4530297 (1985-07-01), Fujikawa
Yasukawa Electric Mfg. Co., Ltd., vol. 36, No. 138, Feb. 1972.
Mitsubishi Denki & Kabushiki Kaisha
Nerbun Peter
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