EDISON'S ORE-MILLING INVENTIONS
THE wide range of Edison's activities in this department of the arts is well represented in the diversity of the numerous patents that have been issued to him from time to time. These patents are between fifty and sixty in number, and include magnetic ore separators of ten distinct types; also breaking, crushing, and grinding rolls, conveyors, dust-proof bearings, screens, driers, mixers, bricking apparatus and machines, ovens, and processes of various kinds.
A description of the many devices in each of these divisions would require more space than is available; hence, we shall confine ourselves to a few items of predominating importance, already referred to in the narrative, commencing with the fundamental magnetic ore separator, which was covered by United States Patent No. 228,329, issued June 1, 1880.
The illustration here presented is copied from the drawing forming part of this patent. A hopper with adjustable feed is supported sever al feet above a bin having a central partition. Almost midway between the hopper and the bin is placed an electromagnet whose