PURPOSE: To provide a drop port mechanism of a vacuum loader adapted to suck granular powder in a hopper and to open a damper so as to drop the granular powder in a tank or the like provided in the lower portion when the granular powder reaches a preset quantity.

CONSTITUTION: A drop port mechanism comprises a hopper 1 for sucking and discharging granular powder, a damper nozzle 2 provided in the lower portion, a damper 3 for opening and closing the port, a damper level 4, a damper shaft 6, a balance weight 7, a cam lever 8 provided on the damper shaft, a cam A hitting the roller 9 of the lever to push up the lever, a limit switch 11 for stopping the cam, a limit switch 12 operated by a cam B fixed to the cam lever, and a blower 16 operated by the limit switch 1. The blower 6 is rotated to discharge air through the exhaust pipe 17 of the hopper. The cam A is rotated by a motor, the damper is closed and granular powder is sucked from a pipe 15. When the granular powder reaches its fixed quantity, the blower is stopped, and the damper is opened by the dead load of granular powder.