Elutriation apparatus and method for cleaning granules

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(11)

EP 0 583 924 A3

(12)	EUROPEAN PATENT APPLICATION

(88)	Date of publication A3:
	19.10.1994 Bulletin 1994/42

(43)	Date of publication A2:
	23.02.1994 Bulletin 1994/08

(21)	Application number: 93306247.3

(22)	Date of filing: 06.08.1993

(51)	International Patent Classification (IPC)⁵: B07B 7/01, B07B 11/00, H05F 3/04

(84)	Designated Contracting States:
	DE ES FR GB IT

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Priority:

17.08.1992 US 930811

(71)	Applicant: ILLINOIS TOOL WORKS INC.
	Glenview, Illinois 60025-5811 (US)

(72)	Inventors:
	Rodrigo, Richard D. Line Lexington, Pennsylvania 19932 (US) Good, Timothy A. Royersford, Pennsylvania 19468 (US)

(74)	Representative: Rackham, Stephen Neil
	GILL JENNINGS & EVERY, Broadgate House, 7 Eldon Street London EC2M 7LH London EC2M 7LH (GB)

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References cited: :

(54)	Elutriation apparatus and method for cleaning granules

(57) Apparatus for cleaning granules (10) comprises a hollow vertically-disposed elutriation column (A) into which granules (10), especially small plastic pellets, having adulterating dust, fine particulate and debris entrained therewith are propelled on a stream of ionized air from an upwardly inclined injection tube (B) so that the granules (10) and adulterating dust become temporarily suspended and float within a medial portion (2) of the column (A). Suction imposed from an upper portion of the column (A) draws off the lighter weight particulate at the top of the floating suspension while the larger granules fall to the bottom. Pairs of AC electro-static discharging means (D1, D2) diametrically disposed at opposite portions of the injection tube (B) which is conductive to define a reference electrode (20) isolated from ground are electrically connected to opposite sides of a high voltage AC transformer (G) expose the adulterated granules (10) to a balanced ion emission thereby effecting neutralization and assisting separation of the fines from the coarse granules prior to entry into the elutriation column (A). Fine-from-coarse separation is achieved when the dirty granules with entrained ions are exposed to a high velocity air blast as they are propelled into the elutriation column (A). The entrained ions serve to neutralize the granules (10) and fines suspended within the elutriation column (A) thereby eliminating the possibility of their re-attachment by way of electro-static charging due to friction with the elutriation column wall. A pair of diametrically opposed electro-static discharging means (F₁,F₂) at the lower portion (18) of the elutriation column (A), which is similarly conductive to define a reference electrode in isolated disposition with respect to ground, are also electrically coupled to opposite sides of a second high voltage AC power supply to provide balanced neutralization of the cleansed granules which are then collected for re-cycling or re-use.

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