Spiral conveyor and filter unit

A spiral conveyor comprising:

• a tray into which chips or scrapes discharged from a cutting machine are thrown together with cutting fluid,
• a discharge duct for discharging the chips or scrapes,
• a filter unit connected between the tray and the discharge duct,
• a conveyance spiral mounted within the tray and the filter unit and driven in a predetermined rotating direction for conveying the chips or scrapes in a predetermined direction, and
• a cutting fluid tank for receiving the cutting fluid falling down from the tray and the filter unit,
• wherein the filter unit comprises
• a primary filter fixed at a position close to an outer periphery of the conveyance spiral,
• a secondary filter rotating on the outside of the conveyance spiral and the primary filter, the primary filter comprising a pair of filter members, each having a more rough texture than the secondary filter and being arranged on opposite sides of the conveyance spiral with small qaps between the filter unit and the outer periphery of the conveyance spiral, and
• a washing nozzle for spraying washing liquid onto the secondary filter, wherein the chips or scrapes captured by the primary filter is scraped by the rotating conveyance spiral and delivered back to a conveyance path, whereas the chips or scrapes passing through the primary filter and captured by the secondary filter are removed by the washing nozzles and delivered back to the conveyance path.