Matsushita Electric Industrial Co., Ltd.

Takashi Dohi

Shigeo Neki

Nozomu Shinozaki

Kenichi Ohara

Nobuho Shibata

Isamu Yasunobu

Iwao Gotoh

Shinji Yamazaki

In apparatus for controlling the rotational speed of a synchronous motor arranged to be driven by an inverter having switches for selectively energizing respective windings of the motor, a current detector is provided to an input of the inverter for detecting input current to the inverter to thereby interrupt energization of the switches by using an output of a first timer circuit when the current exceeds a predetermined value, and a second timer circuit is provided for interrupting energization of the switches on switching between respective phases of the motor. An interrupting time duration by the second timer circuit may be varied in accordance with the rotational speed of the motor and by the plugging state thereof.

Apparatus for controlling AC servo motor

A motor controller for a sewing machine starts to count the number of pulse signals issued during rotation of a motor after reception of a stop signal and the detection of the needle position, and thereby sets a speed value for controlling the rotation speed of the motor so that it gradually slows based on the result of the counting of the pulse signals and so that the rotation speed of the motor goes to zero when it reaches a predetermined low value.

Motor controller for a sewing machine

In a sewing machine, a variable speed setting device generates a variable reference speed signal which is applied to a controller. A tachogenerator produces speed pulses at a frequency proportional to the speed of a motor which drives a needle armshaft. The speed pulses are counted during the interval between successive ones of low-frequency clock pulses and a first actual speed signal proportional to the speed of rotation of the motor is derived from the count. High-frequency clock pulses are counted during the interval between successive ones of the speed pulses and a second actual speed signal proportional to the speed of rotation of the motor is derived from the count. The first actual speed signal is enabled when the reference speed signal is higher than a predetermined value and the second actual speed signal enabled when the reference speed signal is lower than the predetermined value. The controller responds to the enabled signal by controlling the speed of the motor so that the enabled signal substantially equals the reference speed signal.

Variable speed control with selectively enabled counter circuits

In a control device for a sewing machine control apparatus wherein an electric motor generates a reverse torque against a torque due to a load on the sewing machine in abeyance state, to hold a sewing needle in an upper or a lower position, the reverse torque reaches a maximum value by a known feedback system at its turn to a predetermined revolution angle. The control apparatus is devised such that, when it is further turned in excess of the predetermined revolution angle, the reverse torque falls to zero, hence the driving motor remains at the position turned to the predetermined revolution angle.

Sewing machine control apparatus

Sewing machine driving apparatus

In a motor control apparatus arranged to drive a motor by rectifying a.c. voltage and smoothing a rectified voltage by a capacitor, a voltage across the capacitor is detected to see if the voltage is below a reference voltage or not by a first comparator (24), and if so, an output voltage (V) is produced. This output voltage (V) is used to change another reference voltage of another comparator (21) used for detecting if current to the motor (5) or a motor drive circuit (4) is greater than the reference. When the current is larger than the reference, the comparator (21) produces a low level output causing a control circuit (23) to control the drive circuit (4) to reduce the current to motor (5).

Circuit arrangement for controlling starting current of a motor

A sewing machine comprises a multiplier for multiplying an operator-controlled variable reference speed value by a multiplying factor, a tachogenerator for generating speed-related pulses at a rate proportional to the speed of rotation of a motor pulley and an angular position detector for generating a position pulse in response to a predetermined position of an armshaft pulley which is coupled by a belt to the motor pulley. A ratio detector is provided for counting the speed-related pulses present during the interval between successive ones of the position pulse to generate a count as a representation of the diameter of the armshaft pulley and deriving a ratio value between the count and a value representative of the diameter of the motor pulley. The ratio value is applied to the multiplier as the multiplying factor to alter the reference speed value. A speed control circuit is responsive to the speed-related pulses for deriving an actual motor speed value and controls the speed of the motor in accordance with a difference between the actual motor speed value and the altered reference speed value.

Sewing machine with reference speed correction by dimensional ratio

A speed setting arrangement for a sewing machine comprises a permanent magnet mounted for unitary rotation with the foot pedal of the sewing machine, and a magnetic sensor including a plurality of magnetoresistors arranged in pairs to form a bridge circuit on a stationary plane spaced a distance from the plane of rotation of the magnet. The magnetic sensor provides an output signal which is exclusively a function of the magnetic orientation of the magnet and thus serves as a valid indication of the amount of pedal depression. An analog to digital converter is coupled to the magnetic sensor to convert its output into a digital signal for speed control purposes.

Speed setting arrangement for sewing machines

A sewing machine comprises a pedal position detector for detecting the position of the manually operated foot pedal of the machine and generating therefrom a pedal position indicating digital signal comprising a set of a predetermined number of binary digits. The sets of binary digits are organized into a plurality of command signals each comprising a plurality of sets of binary digits corresponding to adjacent positions of the pedal for indicating a specified operating condition of the sewing machine. The sewing machine is operated in response to the command signal.

Sewing machine having a digital command circuit

Disclosed is a sewing machine having a tachogenerator for generating pulses at a frequency proportional to the speed of the sewing machine and a position detector for detecting the position of a foot pedal. A sewing condition detector is provided for detecting the operating conditions of the sewing machine in which it is to be subsequently operated and generating therefrom a corresponding condition indicating signal and a manually adjustable binary code generator for generating a speed indicating binary code in response to the condition indicating signal. Further included is a digital memory responsive to the position indicating signal and the speed indicating binary code for generating a speed control digital signal. The pulses generated by the tachogenerator are processed in accordance with the speed control digital signal to control the amount of motive power transmitted from a motor to the sewing machine.

Sewing machine having a memory for generating a speed signal in response

A speed setting device for an industrial sewing machine comprises a lever pivotally mounted at one end thereof on a stationary wall and adapted to be pivotally moved in response to the foot pedal of the sewing machine. An arm is pivotally mounted at one end to the stationary wall and operatively engaged with the lever so that they rotate in unison about respective pivot points thereof. The pivot point of the second member is between the lever pivot point and the engagement point between the lever and arm. Thereby, the arm is rotated through an angle greater than the angle through which the lever is rotated in response to the angular displacement of the foot pedal. An angular displacement sensor detects the angular displacement of the arm to generate a speed setting signal.

Speed setting device for a sewing machine

A sewing machine comprises a pedal position detector for detecting the position of a manually operated foot pedal and generating therefrom a pedal position indicating signal. A predetermined position of the armshaft of the sewing machine is detected for generating an armshaft position signal. A soft-start speed setting circuit is provided for successively generating a soft-start speed setting signal of an increasing value as a function of time in response to the occurrence of the armshaft position signal. The soft-start speed setting signal is enabled when it is smaller in magnitude than the pedal position indicating signal and conversely the pedal position indicating signal is enabled when the latter is smaller than the soft-start speed setting signal. The enabled signal is used to control the speed of the sewing machine.

Sewing machine having a soft-starting circuit

A needle position detector for a sewing machine includes a pair of disk-like members axially mounted on a rotary shaft coupled to the armshaft of the sewing machine. Each of the disk-like members is provided with an optically nonreflective portion occupying a greater area of its circumference and an optically reflective portion occupying a smaller area of the circumference. The disk-like members are adjusted so that the angular positions of the respective reflective portions correspond to the upper and lower needle positions. A light emitting element is associated with each of the disk-like members to emit light in a radial direction thereto. A light sensitive element is also associated with each disk-like member to receive light reflected from the reflective portion of the associated disk-like member to generate a needle position signal.

Needle position detector

A speed detector comprises a rotary shaft for rotation with a sewing machine, a ring-shaped permanent magnet uniformly magnetized in a direction parallel to the axis of the rotary shaft, at least one ring-shaped, internally toothed ferromagnetic member or stator and an externally toothed ferromagnetic circular member or rotor which is secured to the rotary shaft inside the stator to form a varying air gap between the opposing teeth. The permanent magnet and the two ferromagnetic members are disposed to form a closed loop magnetic circuit in which a ring-shaped coil is disposed. The air gap and hence the reluctance of the magnetic circuit changes periodically with the revolution of the rotary shaft so that a voltage is generated in the coil which varies at a frequency proportional to the operational speed of the sewing machine.

Speed detector for sewing machines

An electromagnetic clutch for use with a motor having a fixed bracket and a rotatable motor shaft which comprises a flywheel attached to the motor shaft and an output shaft rotatably supported by the bracket. A clutch rotor is attached to the output shaft so as to extend between the flywheel and a radial portion of the bracket. A clutch section is provided which includes a clutch ring axially movable with respect to the flywheel when a clutch solenoid is energized. A brake section is also provided which includes a brake ring axially movable with respect to the bracket when a brake solenoid is energized. Both the clutch and brake rings are mounted on sliding members which may be axially displaced relative to pins secured to the flywheel and bracket, respectively. Buffer members are interposed between the rings and sliding members.

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Hirakata, Japan

Takashi Dohi