Operating device for electric hoist

An operating device for an electric hoist comprising;

• a DC motor for raising and lowering an object, a control box for the hoist having a two-step push-button switch with two pushed positions where the DC motor is energized at low and high speeds, respectively for raising the object;
• a two-step push-button switch having two pushed positions where the DC motor is energized at low and high speeds, respectively for lowering the object;
• knobs for changing in a stepless manner speeds of said DC motor for raising and lowering the object;
• and a cover for covering said knobs for preventing indiscriminate speed change, said electric hoist further comprising a control circuit for controlling the DC motor, said control circuit comprising an operating circuit including raising and lowering relays for the DC motor, respectively, a high and low speed change relay and variable resistors controlled by said knobs and connected in parallel exchangeable with each other by said high and low speed change relay, a phase control circuit for phase-controlling alternate current from a power source, a full-wave rectifying circuit for full-wave rectifying the phase-controlled alternate current and supplying the rectified direct current to the DC motor, and a normal and reverse rotating circuit including normally opened contact pairs of the raising and lowering relays in the operating circuit.