Abstract: A slide-type potentiometer for speed control of electric motors under control of a foot-pedal actuator mechanism comprising an actuating rod reciprocatably movable in the longitudinal directions thereof, a spring member for urging the actuating rod in one of the longitudinal directions, a contact supporting member having an electrical contact secured thereto and mounted on the actuating rod so as to be movable in the longitudinal directions along with the actuating rod, a resistor element positioned such that the electrical contact member is slidably moved on the resistor element upon movement of the actuating rod, and a housing for enclosing the contact supporting member and the resistor element, the housing has a through-hole through which one end portion of the actuating rod extends outwardly.

Abstract: There is provided a DC motor speed control system comprising a main motor circuit which supplies a motor current from an AC source through a full-wave rectifying circuit and a semiconductor element having a control electrode to a DC motor, a manually variable voltage setting means which is connected with the full-wave rectifying circuit, a charging circuit which is connected with the manually variable voltage setting means, a switching element having a control element which is connected with the charging circuit and, when the charged voltage in the charging circuit reaches a predetermined value, is made conductive to discharge the charging circuit thereby to supply a discharge current to the semiconductor element as a triggen current, a constant voltage element which is connected with the full-wave rectifying circuit, and a detecting means which detects the counter electromotive force induced in the motor.

Abstract: A speed control circuit arrangement for controlling a rotational speed of an AC commutator motor by an AC controlled rectifier element. The speed control circuit arrangement comprises a pulse transformer which is connected at the secondary winding to the control electrode of the AC controlled rectifier element and one of two main electrodes of the controlled rectifier element and supplies a trigger pulse to the control electrode, a variable resistor for adjusting the rotational speed of the motor, a first capacitor connected at one end through the variable resistor to the other main electrode and at the other end to one end of an AC power source, a pulse generating element connected across said first capacitor with the primary winding of the pulse transformer intervening therebetween, and a first resistor connected at one end to the one main electrode and at the other end to the other end of the AC power source through the first capacitor.

Abstract: A speed control system for a motor comprising a main motor circuit supplying motor current to the motor from an A.C. power source through a semiconductor element provided with a control electrode, trigger voltage supplying means supplying trigger voltage to the control electrode of the semiconductor element, motor voltage detecting means for detecting voltage induced in the motor, and automatically variable resistance means having its resistance value varied automatically depending on the detected motor voltage. In the system, the trigger voltage supplied by the trigger voltage supplying means is controlled depending on the variation in the resistance value of the automatically variable resistance means, and the firing angle of the semiconductor element is retarded in response to an increase in the detected motor voltage and advanced in response to a decrease in the detected motor voltage.

Abstract: A motor driven sewing machine comprises pulse generator means for generating a first pulse associated with the first predetermined angular position and a second pulse associated with the second predetermined angular position of the main-shaft of the machine, and state-alternating means for alternatively changing its states between first and second states in response to the first and second pulses. The needle position and cloth feed are controlled in accordance with the states of the state-alternating means.

Abstract: A control apparatus for an electrically driven sewing machine with stitch pattern producing means comprises an electric signal generator for generating an electric signal related to at least one predetermined angular position of a main shaft of the sewing machine, set board means capable of setting therein a desired stitch pattern by means of a probe, and pattern detecting means for reading out cloth feed operation information and needle position information of the stitch pattern set at the set board means. The needle bar is set at a predetermined position in dependence upon the needle position information as read out, while cloth feed is effected in dependence upon the cloth feed operation information, whereby sewing operation is performed in the same stitch pattern as the one stored in the set board means.

Abstract: A motor speed control apparatus for an electrically-driven sewing machine capable of effecting single stitch comprises a main motor circuit for supplying a motor current to a motor from an AC power supply through a main switch and a semiconductor element with a controlled electrode, a first control means for controlling the semiconductor element in order to effect normal operation, a controller adapted to change between its first and second state so as to control the speed of the motor continuously when the first control means is energized, a second control means for controlling the semiconductor element for effecting single stitch, and a change-over means for changing over the operation between the first and second control means. The second control means includes means for setting the trigger voltage for conducting the semiconductor element, a switching element coupled with the trigger-voltage setting means, a bias means for energizing the switching element, and a charge-discharge circuit.

Abstract: A motor control apparatus for driving a power sewing machine comprises a main motor circuit for supplying a motor current to a DC motor from an AC power supply through a main switch and a semiconductor element with a control electrode, a controller for controlling the speed of the motor, a first control means for effecting normal stitching by controlling the conduction state of the semiconductor element, a second control means for effecting a single stitch by controlling the conduction state of the semiconductor element, and a means for switching the operation between the first and second control means. The second control means includes a needle position detector means for detecting the needle to reach predetermined positions, a switching means connected in series to the needle position detector means, a trigger voltage supply means for applying a trigger voltage to the control electrode of the semiconductor element, and a switch-operating means.