Edison, His Life and Inventions [354]
sharply defined, equidistant photographs of successive positions of an object in motion as observed from a single point of view at rapidly recurring intervals of time, such photographs being arranged in a continuous straight-line sequence, unlimited in number save by the length of the film, and sufficient in number to represent the movements of the object throughout an extended period of time."
XVI
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 several feet above a bin having a central partition. Almost midway between the hopper and the bin is placed an electromagnet whose polar extension is so arranged as to be a little to one side of a stream of material falling from the hopper. Normally, a stream of finely divided ore falling from the hopper would fall into that portion of the bin lying to the left of the partition. If, however, the magnet is energized from a source of current, the magnetic particles in the falling stream are attracted by and move toward the magnet, which is so placed with relation to the falling material that the magnetic particles cannot be attracted entirely to the magnet before gravity has carried them past. Hence, their trajectory is altered, and they fall on the right-hand side of the partition in the bin, while the non-magnetic portion of the stream continues in a straight line and falls on the other side, thus effecting a complete separation.
This simple but effective principle was the one employed by Edison in his great concentrating plant already described. In practice, the numerous hoppers, magnets, and bins were many feet in length; and they were arranged in batteries of varied magnetic strength, in order that the intermingled mass of crushed rock and iron ore might be more thoroughly separated by being passed through magnetic fields of successively increasing degrees of attracting power. Altogether there were about four hundred and eighty of these immense magnets in the plant, distributed in various buildings in batteries as above mentioned, the crushed rock containing the iron ore being delivered to them by conveyors, and the gangue and ore being taken away after separation by two other conveyors and delivered elsewhere. The magnetic separators at first used by Edison at this plant were of the same generality as the ones employed some years previously in the separation of sea-shore sand, but greatly enlarged and improved. The varied experiences gained in the concentration of vast quantities of ore led naturally to a greater development, and several new types and arrangements of magnetic separators were evolved and elaborated by him from first to last, during the progress of the work at the concentrating plant.
The magnetic separation of iron from its ore being the foundation idea of the inventions now under discussion, a consideration of the separator has naturally taken precedence over those of collateral but inseparable interest. The ore- bearing rock, however, must first be ground to powder before it can be separated; hence, we will now begin at the root of this operation and consider the "giant rolls," which Edison devised for breaking huge masses
XVI
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 several feet above a bin having a central partition. Almost midway between the hopper and the bin is placed an electromagnet whose polar extension is so arranged as to be a little to one side of a stream of material falling from the hopper. Normally, a stream of finely divided ore falling from the hopper would fall into that portion of the bin lying to the left of the partition. If, however, the magnet is energized from a source of current, the magnetic particles in the falling stream are attracted by and move toward the magnet, which is so placed with relation to the falling material that the magnetic particles cannot be attracted entirely to the magnet before gravity has carried them past. Hence, their trajectory is altered, and they fall on the right-hand side of the partition in the bin, while the non-magnetic portion of the stream continues in a straight line and falls on the other side, thus effecting a complete separation.
This simple but effective principle was the one employed by Edison in his great concentrating plant already described. In practice, the numerous hoppers, magnets, and bins were many feet in length; and they were arranged in batteries of varied magnetic strength, in order that the intermingled mass of crushed rock and iron ore might be more thoroughly separated by being passed through magnetic fields of successively increasing degrees of attracting power. Altogether there were about four hundred and eighty of these immense magnets in the plant, distributed in various buildings in batteries as above mentioned, the crushed rock containing the iron ore being delivered to them by conveyors, and the gangue and ore being taken away after separation by two other conveyors and delivered elsewhere. The magnetic separators at first used by Edison at this plant were of the same generality as the ones employed some years previously in the separation of sea-shore sand, but greatly enlarged and improved. The varied experiences gained in the concentration of vast quantities of ore led naturally to a greater development, and several new types and arrangements of magnetic separators were evolved and elaborated by him from first to last, during the progress of the work at the concentrating plant.
The magnetic separation of iron from its ore being the foundation idea of the inventions now under discussion, a consideration of the separator has naturally taken precedence over those of collateral but inseparable interest. The ore- bearing rock, however, must first be ground to powder before it can be separated; hence, we will now begin at the root of this operation and consider the "giant rolls," which Edison devised for breaking huge masses