Classifying – separating – and assorting solids – Precedent preparation of items or materials to facilitate... – Sorting special items or sorting by methods and apparatus...
Patent
1980-11-26
1982-08-03
Hill, Ralph J.
Classifying, separating, and assorting solids
Precedent preparation of items or materials to facilitate...
Sorting special items or sorting by methods and apparatus...
209 11, 209 39, 209 40, 241 17, 241 23, 241 24, 241DIG31, 241DIG37, B03C 130
Patent
active
043426476
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a method and apparatus for size reduction of a material which is frangible when frozen and for separation of such material from contaminants.
The process and apparatus of the invention are particularly suitable for use in the recovery of scrap rubber, and more particularly to the recovery of uncured rubber process scrap.
BACKGROUND ART
Many rubber articles are provided during manufacture with reinforcements. During manufacture the reinforcing material or materials are emplaced in the article prior to curing the rubber to form the finished article. The term "rubber" as herein used includes both natural rubber and synthetics used as rubber substitutes. The term "uncured rubber" refers to rubber which has not been vulcanised but which may include a minor proportion of reclaimed vulcanised or devulcanised rubber which is sometimes incorporated by blending with new uncured rubber. Examples of rubber articles of the type under discussion are tyres and hoses which may be reinforced with steel, woven fabrics, fibres and the like or by a combination of such reinforcements.
In the manufacture of rubber articles, for any of a number of reasons, the article may be scrapped after incorporation of reinforcing materials but prior to vulcanisation. In the case for example of tyre manufacture, there then results a scrap comprising uncured rubber, contaminated with steel, woven fabric and "cured lumps." The scrap is extremely tacky and agglomerates on contact with other like scrap. It is difficult to handle and hitherto has been disposed of by dumping. Not only the uncured rubber but also the metal and fibrous reinforcements would have considerable commercial value if satisfactorily separable one from each other.
Processes are known for the embrittlement of vulcanised articles such as tyres by use of a cryogenic medium to render the rubber frangible followed by impacting to render the frangible rubber into small pieces. In such processes metal is usually recovered from the impacted rubber by magnetic separation. A limited proportion of the fabric contaminated product can be blended with new rubber the majority being fed instead to chemical plants for chemical removal of fibre and for devulcanisation of the rubber.
In one proposed embrittlement process tyres are dipped in a bath of liquid nitrogen. By virtue of the slow rate of progress through baths required to achieve embrittlement, that process requires a large investment of capital in dip-baths and is wasteful of cryogen. More commonly, cooling tunnels divided into a pre-cooling zone and a liquid nitrogen spraying zone have been employed. The tyres are pre-cooled while being conveyed on belts from the feed-point through the pre-cooling zone towards the spraying zone by means of cryogen boiled off in the spraying zone. U.S. Pat. No. 3,992,899 describes a method of embrittling old tyres which avoids some of the disadvantages of the above methods by pre-cooling the tyres in a rotary tunnel inclined downwardly from the feed end and delivering the tyres to a spraying and draining zone. The apparatus provides a high "feed ratio" at the feed end and a long, convoluted pathway for cooling gases from the cryogen at the spraying zone in order to ensure maximum heat transfer and pre-cooling of the feed material. Neither of the foregoing methods provide for segregation of the rubber from fibrous contaminants.
U.K. Pat. No. 1,334,718 describes a process in which fabric and metal contaminants are segregated from vulcanised rubber articles. In that process the vulcanised articles are first embrittled by conventional means. The embrittled vulcanised articles are then disunited from the vulcanised rubber component by flexing, crushing or comminuting the embrittled material. The fabric component is then removed by screening, for preference but not essentially, under cryogenic conditions.
Alternatively, according to the latter patent, the article may be torn to pieces in a cracker mill prior to embrittlement. In that event the embrittled materi
REFERENCES:
patent: 2471043 (1949-05-01), Schenck
patent: 2919862 (1960-01-01), Beike et al.
patent: 3718284 (1973-02-01), Richardson
patent: 3890220 (1975-06-01), Anderson
patent: 3992899 (1976-11-01), Spahn
Grant, J., Ed., Hackh's Chemical Dictionary, McGraw-Hill Book Co., New York, N.Y., 4th Ed., 1972, p. 272.
Guthrie Graeme J.
McMillan Fraser
Williams David J.
Hill Ralph J.
The Commonwealth Industrial Gases Limited
LandOfFree
Treatment of scrap does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Treatment of scrap, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Treatment of scrap will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1467779