Powder transport screw, and development device, process unit and image-forming apparatus comprising this powder transport screw

A development device, comprising:

• a development part;
• a toner hopper for holding a toner supplied to the development part;
• and
• a toner transport screw disposed inside the development part, the toner transport screw comprising:
• a rotating shaft;
• helical blades comprising a first blade part and a second blade part disposed on a circumference of the rotating shaft, a spiral of the first blade part and the second blade part being in opposite directions;
• at least one spiral direction reversal part formed on the rotating shaft in between respective ends of the first blade part and the second blade part;
• and
• a passage formed in the spiral direction reversal part around the circumference of the rotating shaft between respective ends of the first blade part and the second blade part, the passage allowing a powder to pass through a width of the passage formed in an axial direction of the rotating shaft,
• wherein the first blade part and the second blade part do not overlap with each other in the circumferential direction of the rotating shaft to allow the powder to pass there between without contacting the first and second blade parts.

An image-forming apparatus that comprises a toner transport screw, the toner transport screw comprising:

• a rotating shaft;
• helical blades comprising a first blade part and a second blade part disposed on a circumference of the rotating shaft, a spiral of the first blade part and the second blade part being in opposite directions;
• at least one spiral direction reversal part formed on the rotating shaft in between respective ends of the first blade part and the second blade part;
• and
• a passage formed in the spiral direction reversal part around the circumference of the rotating shaft between respective ends of the first blade part and the second blade part, the passage allowing a powder to pass through a width of the passage formed in an axial direction of the rotating shaft,
• wherein the first blade part and the second blade part do not overlap with each other in the circumferential direction of the rotating shaft at the passage to allow the powder to pass there between.