Belt sander capable of automatically adjusting oscillating position of abrasive belt

A belt sander, comprising:

• a base, including at least one workbench thereon;
• a frame, disposed on one side of the base, the frame having a retaining bracket;
• a rotary unit, including a retaining seat and a motor, the retaining seat and the motor being fixed to the retaining bracket of the frame, a lower wheel being pivotally disposed on the retaining seat, the lower wheel being connected to the motor, one end of a central axle being fixed to the retaining seat, another end of the central axle being fixed to an oscillating seat, a recess being formed on the oscillating seat, an upper wheel being pivotally connected to the oscillating seat, an abrasive belt being mounted on the upper wheel and the lower wheel;
• an oscillating unit, including an electric motor, an eccentric bushing and a bearing, the electric motor being fixed to the retaining seat, the electric motor being connected to an output shaft, the output shaft having a receiving groove, the eccentric bushing being fitted on a periphery of the output shaft, the eccentric bushing and the output shaft being arranged eccentrically, the eccentric bushing having an accommodating groove corresponding to the receiving groove, a pin being inserted in the receiving groove and the accommodating groove, the bearing being fitted on the eccentric bushing and located in the recess;
• an abrasive belt position detector, disposed on the retaining seat for detecting a position of the abrasive belt;
• a first sensor and a second sensor, the first sensor and the second sensor being configured for confirming an oscillating angle of the oscillating seat;
• a control unit, including an electric motor control module, the electric motor control module being electrically connected to the abrasive belt position detector, the first sensor and the second sensor, thereby controlling the electric motor to run or stop running;
• wherein when the electric motor is running, the bearing is rotated eccentrically to drive the oscillating seat to move back and forth.