Classifying – separating – and assorting solids – Precedent preparation of items or materials to facilitate... – Sorting special items or sorting by methods and apparatus...
Reexamination Certificate
2001-03-27
2002-07-02
Walsh, Donald P. (Department: 3653)
Classifying, separating, and assorting solids
Precedent preparation of items or materials to facilitate...
Sorting special items or sorting by methods and apparatus...
C209S003000, C209S004000, C209S009000, C209S577000, C209S587000, C209S580000
Reexamination Certificate
active
06412642
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to the sorting of metal scrap constituted of a mixture of scrap metal pieces of two or more different alloy compositions, so as to separate the metal pieces of one composition from the other or others. More particularly, it is directed to methods of marking aluminum sheet for scrap sorting purposes.
As used herein, the term “aluminum” refers to aluminum metal and aluminum-based alloys, viz., alloys containing more than 50% by weight aluminum. “Scrap” refers to pieces of metal in solid as distinguished from molten state.
An important and illustrative field of use for such methods (to which, however, the invention in its broader aspects is not limited) is the sorting of manufacturing scrap generated incident to automobile manufacturing operations utilizing aluminum sheet. The production of automobile body components or other automotive parts by forming aluminum sheet generates substantial quantities of metal scrap, i.e., pieces of metal from the sheet stock subjected to the forming and related operations such as trimming. The term “manufacturing scrap” is used herein to differentiate such scrap from post-consumer scrap (generated from used and discarded manufactured articles). Manufacturing scrap differs from post-consumer scrap in that, being generated incident to forming operations, manufacturing scrap does not bear a paint or other permanent opaque coating on its major surfaces, whereas post-consumer scrap often has major surfaces more or less covered with paint or other substances applied after forming.
As is well known, for both environmental and economic reasons it is desirable to recycle sheet metal scrap, including that generated in the manufacture of automotive components from sheet aluminum. In the simplest sense, recycling of the scrap involves remelting the scrap to provide a body of molten metal that can be cast and rolled into useful aluminum sheet.
Frequently, however, automotive manufacturing scrap includes a mixture of scrap pieces of two or more aluminum alloys differing substantially from each other in composition. A specific example of mixed manufacturing scrap of aluminum sheet, generated in certain present-day automotive manufacturing operations, is a mixture of pieces of one or more alloys of the Aluminum Association 5000 series (with four-digit registration numbers between 5000 and 5999) and pieces of one or more alloys of the Aluminum Association 6000 series (with four-digit registration numbers between 6000 and 6999).
The presence of commingled pieces of different alloys in a body of scrap limits the ability of the scrap to be usefully recycled, unless the different alloys (or, at least, alloys belonging to different compositional families such as those respectively designated by the Aluminum Association series 1000, 2000, 3000, etc.) can be separated prior to remelting. This is because, when commingled scrap of plural different alloy compositions or composition families is remelted, the resultant molten mixture contains proportions of principal alloying elements (of the different compositions) that are too high to satisfy the compositional limitations of any particular commercial alloy. While it would therefore be beneficial to be able to sort a mass or body of aluminum sheet scrap containing a mixture of pieces of different alloys, to separate the different alloy compositions or at least different alloy families before remelting for recycling, scrap pieces of different aluminum alloy compositions are not ordinarily visually distinguishable from each other.
Published European Patent Application EP 0 861 910 A2 describes procedures for treating commingled aluminum scrap of two or more wrought aluminum alloys to impart different colors to surfaces of scrap pieces of different compositions for the purpose of sorting by alloy type or family (such as Aluminum Association series). The described procedures involve a separate step for introducing color onto the alloy before sorting, but after the alloy pieces of different compositions have become commingled, via a batch or semi-continuous chemical etch or series of etches. The chemical agents react with alloys of different compositions to produce discernable surface color differences between them. Methods for introducing color proposed include treatment with caustic, acid, oxidizing agents, dyes and combinations thereof.
That is to say, in the process of the European patent application, the marker is applied to every piece of scrap by a chemical treatment process and is subsequently detected by color differentiation. Treating every piece of scrap is inherently an expensive process, involving the performance of special, extra steps after the scrap is collected and before it can be sorted; and since the sortability of the commingled scrap is dependent on the ability of the treatment to react with different alloys to produce discernably different, composition-determined colors, there are limits to the coloring agents that can be used and/or to the types of alloys that can be differentiated.
SUMMARY OF THE INVENTION
An object of the present invention is to provide improvements in the sorting of metal scrap containing scrap pieces of different compositions, affording enhanced convenience and economy. Another particular object is to provide such improvements while avoiding a separate or special step of marking the scrap (i.e., after the scrap has been generated) to differentiate pieces of different compositions for such sorting. A specific object is to provide improved methods, affording the advantages just stated, of marking aluminum sheet to facilitate subsequent sorting of scrap including scrap pieces derived from the sheet together with scrap pieces of sheet of other aluminum alloys or alloy families.
To these and other ends, the invention embraces the application of surface marking to metal stock (i.e., metal produced or prepared in a form for working, cutting, etc., to manufacture articles or components), particularly aluminum sheet, prior to or during the performance of scrap-generating operations such as manufacturing operations.
In certain embodiments of the invention, the marking is performed by application of a marking agent to the stock or sheet during and as a part of procedures for preparing the sheet or other stock for subsequent scrap-generating manufacturing operations. For example, in preparing aluminum sheet for forming into automotive components or the like, it is conventional for the maker and supplier of the sheet to apply lubricant or prelubricant to surfaces of the sheet; in accordance with the present invention, the marking agent may be incorporated in the lubricant or prelubricant prior to application thereof to the sheet surfaces.
It is found that this method, utilizing a conventional sheet-preparing step for applying the marking agent and thereby avoiding any separate or added treatment of either sheet or scrap, can provide a detectable mark on surfaces of manufacturing scrap derived from the marked sheet, the marking agent being initially applied to the sheet in an amount effective to establish a deposit of mark-providing substance that will survive the scrap-generating manufacturing operations to which the sheet is subjected.
The term “mark” as used herein is not limited to a deposit of marking agent which is visible or discernable as a mark on the original sheet; i.e., the marking agent provides a detectable mark on the scrap, not necessarily a visible mark on the sheet. Moreover, while in many instances detection of the mark may be performed by optical scanning, the detectable mark on scrap surfaces contemplated by the invention in its broadest aspects is not limited to a mark that is optically detectable, but also broadly includes a mark that is or can be detected in non-optical ways, e.g. by a sniffing device as used to detect drugs at airports, or by a laser that evaporates surface material in a puff or plume with a short pulse, with immediate analysis of the plume to identify the “mark” substance.
The sheet to which the marking a
Charles David F.
Courval Greg J.
Thomas Michael P.
Wheeler Michael J.
Wilson Ian
Alcan International Limited
Cooper & Dunham LLP
Miller Jonathan R. M.
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