Plastics sorting apparatus

• US 6,365,857 B1
• Filed: 07/31/2000
• Issued: 04/02/2002
• Est. Priority Date: 11/05/1998
• Status: Expired due to Fees

• Current Assignee: Hitachi Zosen Corporation
• Original Assignee: Hitachi Zosen Corporation
• Inventors: Inoue, Tetsuya, Daiku, Hiroyuki, Maehata, Hidehiko, Tamakoshi, Daisuke
• Primary Examiner(s): Walsh, Donald P.
• Assistant Examiner(s): Rodriguez, Joseph C
• Application Number:
  US09/582,562
• Time in Patent Office: 610 Days
• Field of Search: 209/127.3, 209/127.1, 209/128, 209/129, 209/130
• US Class Current: 209/127.3
• CPC Class Codes: B03C 7/006 Charging without electricity supply, e.g. by tribo-electricity or pyroelectricity
• CPC Class Codes: B03C 7/06 with cylindrical material carriers
• CPC Class Codes: B29B 17/02 Separating plastics from other materials
• CPC Class Codes: B29B 2017/0203 Separating plastics from plastics
• CPC Class Codes: B29B 2017/0265 Electrostatic separation
• CPC Class Codes: B29K 2023/06 PE, i.e. polyethylene
• CPC Class Codes: B29K 2023/12 PP, i.e. polypropylene
• CPC Class Codes: B29K 2025/00 Use of polymers of vinyl-aromatic compounds or derivatives thereof as moulding material
• CPC Class Codes: B29K 2027/06 PVC, i.e. polyvinylchloride
• CPC Class Codes: Y02W 30/52 Mechanical processing of waste for the recovery of materials, e.g. crushing, shredding, separation or disassembly
• CPC Class Codes: Y02W 30/62 Plastics recycling; Rubber recycling

Abstract

A conveyor (3) feeds batches of plastic chips (2) in feeding amounts W1 to a charging device (4). After the plastic chips (2) have been stirred and charged inside the charging device (4) for a certain period of time T, they are ejected in batches and fed continuously by a screw feeder (20) to a drum electrode (5) at a feeding amount per unit time W2. The feeding amount per unit time W2 is adjusted so as to satisfy W1/T≦W2≦v×B×H×D where v is the rotation speed of the drum electrode (5), B is a width of the drum electrode (5), H is an average thickness of the plastic chips (2) that have been fed onto the drum electrode (5), and D is a bulk density of the plastic chips (2).

Claims

1. A plastics sorting apparatus comprising:

a charging device for charging a batch of a predetermined amount of different types of fragmented plastic chips while stirring the plastic chips; and

an electrostatic sorting device for sorting plastic chips that have been charged with the charging device by passing them between a pair of sorting electrodes, characterized in that;

the charging device ejects a batch of plastic chips after stirring the plastic chips for a certain period of time T that is necessary to charge the plastic chips;

one of the pair of sorting electrodes is a stationary electrode, and the other of the pair of sorting electrodes is a movable electrode that is arranged to oppose the stationary electrode and adapted to rotate at a peripheral speed v;

the apparatus further comprises

a first feeding device for feeding batches of a feeding amount W1 of the plastic chips to the charging device, and

a second feeding device for continuously feeding onto the movable electrode of the electrostatic sorting device a feeding amount per unit time W2 of the plastic chips that have been ejected in batches from the charging device; and

the feeding amount per unit time W2 is set to satisfy

2. The plastics sorting apparatus as set forth in claim 1, wherein the charging device comprises a rotatable stirring member for stirring the plastic chips, and a feeding amount detector for detecting a feeding amount of the plastic chips that have been fed in batches from the first feeding device;

wherein the first feeding device is a conveyor and the second feeding device is a screw feeder; and

wherein the plastics sorting apparatus further comprises a control unit for controlling driving devices for driving the conveyor, the stirring member, the screw feeder and the movable electrode depending on the feeding amount that is detected by the feeding amount detector.

3. The plastics sorting apparatus as set forth in claim 1, further comprising a shutter for opening and closing an ejection portion of the charging device.

4. The plastics sorting apparatus as set forth in claim 2, further comprising a shutter for opening and closing an ejection portion of the charging device.