Screw feeder and fiber structure manufacturing apparatus

A fiber structure manufacturing apparatus, comprising:

• a dry defibrator that pulverizes and defibrates a raw material that contains fibers;
• a transportation unit that transports a defibrated material after defibration by the dry defibrator;
• a material supply unit that supplies a material to the transportation unit;
• a fiber structure forming unit that forms a fiber structure from the defibrated material transported by the transportation unit, wherein
• the material supply unit includes
• a case that includes a material putting-in portion through which a fluff material is put in and a material putting-out portion through which the fluff material is put out below the material putting-in portion;
• and
• a screw that includes a rotational shaft and a blade portion, the rotational shaft being provided rotatably inside the case, the blade portion being spirally mounted on the rotational shaft;
• wherein
• the screw is rotated with repeated alternation of a slope-down direction in which the blade portion slopes downward spirally in a vertical direction and a slope-up direction in which the blade portion slopes upward spirally in the vertical direction.