Edison, His Life and Inventions [356]
Thus, this cyclopean operation may be continuously conducted with an amount of power prodigiously inferior, in proportion, to the results accomplished.
The sketch (Fig. 4) showing a large boulder being dumped into the hopper, or roll-pit, will serve to illustrate the method of feeding these great masses of rock to the rolls, and will also enable the reader to form an idea of the rapidity of the breaking operation, when it is stated that a boulder of the size represented would be reduced by the giant rolls to pieces a trifle larger than a man's head in a few seconds.
After leaving the giant rolls the broken rock passed on through other crushing-rolls of somewhat similar construc- tion. These also were invented by Edison, but antedated those previously described; being covered by Patent No. 567,187, issued September 8, 1896. These rolls were intended for the reducing of "one-man-size" rocks to small pieces, which at the time of their original inception was about the standard size of similar machines. At the Edison concentrating plant the broken rock, after passing through these rolls, was further reduced in size by other rolls, and was then ready to be crushed to a fine powder through the medium of another remarkable machine devised by
NOTE.--Figs. 3 and 4 are reproduced from similar sketches on pages 84 and 85 of McClure's Magazine for November, 1897, by permission of S. S. McClure Co.
Edison to meet his ever-recurring and well-defined ideas of the utmost economy and efficiency. The best fine grinding- machines that it was then possible to obtain were so inefficient as to involve a loss of 82 per cent. of the power applied. The thought of such an enormous loss was unbearable, and he did not rest until he had invented and put into use an entirely new grinding-machine, which was called the "three-high" rolls. The device was covered by a patent issued to him on November 21, 1899, No. 637,327. It was a most noteworthy invention, for it brought into the art not only a greater efficiency of grinding than had ever been dreamed of before, but also a tremendous economy by the saving of power; for whereas the previous efficiency had been 18 per cent. and the loss 82 per cent., Edison reversed these figures, and in his three-high rolls produced a working efficiency of 84 per cent., thus reducing the loss of power by friction to 16 per cent. A diagrammatic sketch of this remarkable machine is shown in Fig. 5, which shows a front elevation with the casings, hopper, etc., removed, and also shows above the rolls the rope and pulleys, the supports for which are also removed for the sake of clearness in the illustration.
For the convenience of the reader, in referring to Fig. 5, we will repeat the description of the three-high rolls, which is given on pages 487 and 488 of the preceding narrative.
In the two end-pieces of a heavy iron frame were set three rolls, or cylinders--one in the centre, another below, and the other above--all three being in a vertical line. These rolls were about three feet in diameter, made of cast-iron, and had face-plates of chilled-iron.[31] The lowest roll was set in a fixed bearing at the bottom of the frame, and, therefore, could only turn around on its axis. The middle and top rolls were free to move up or down from and toward the lower roll, and the shafts of the middle and upper rolls were set in a loose bearing which could slip up and down in the iron frame. It will be apparent, therefore, that any material which passed in between the top and the middle rolls, and the middle and bottom rolls, could be ground as fine as might be desired, depending entirely upon the amount of pressure applied to the loose rolls. In operation the material passed first through the upper and middle rolls, and then between the middle and lowest rolls.
[31] The faces of these rolls were smooth, but as three-high rolls came into use later in Edison's Portland cement operations the faces were corrugated so as to fit into each other, gear-fashion, to provide for a high rate of feed.
This pressure was
The sketch (Fig. 4) showing a large boulder being dumped into the hopper, or roll-pit, will serve to illustrate the method of feeding these great masses of rock to the rolls, and will also enable the reader to form an idea of the rapidity of the breaking operation, when it is stated that a boulder of the size represented would be reduced by the giant rolls to pieces a trifle larger than a man's head in a few seconds.
After leaving the giant rolls the broken rock passed on through other crushing-rolls of somewhat similar construc- tion. These also were invented by Edison, but antedated those previously described; being covered by Patent No. 567,187, issued September 8, 1896. These rolls were intended for the reducing of "one-man-size" rocks to small pieces, which at the time of their original inception was about the standard size of similar machines. At the Edison concentrating plant the broken rock, after passing through these rolls, was further reduced in size by other rolls, and was then ready to be crushed to a fine powder through the medium of another remarkable machine devised by
NOTE.--Figs. 3 and 4 are reproduced from similar sketches on pages 84 and 85 of McClure's Magazine for November, 1897, by permission of S. S. McClure Co.
Edison to meet his ever-recurring and well-defined ideas of the utmost economy and efficiency. The best fine grinding- machines that it was then possible to obtain were so inefficient as to involve a loss of 82 per cent. of the power applied. The thought of such an enormous loss was unbearable, and he did not rest until he had invented and put into use an entirely new grinding-machine, which was called the "three-high" rolls. The device was covered by a patent issued to him on November 21, 1899, No. 637,327. It was a most noteworthy invention, for it brought into the art not only a greater efficiency of grinding than had ever been dreamed of before, but also a tremendous economy by the saving of power; for whereas the previous efficiency had been 18 per cent. and the loss 82 per cent., Edison reversed these figures, and in his three-high rolls produced a working efficiency of 84 per cent., thus reducing the loss of power by friction to 16 per cent. A diagrammatic sketch of this remarkable machine is shown in Fig. 5, which shows a front elevation with the casings, hopper, etc., removed, and also shows above the rolls the rope and pulleys, the supports for which are also removed for the sake of clearness in the illustration.
For the convenience of the reader, in referring to Fig. 5, we will repeat the description of the three-high rolls, which is given on pages 487 and 488 of the preceding narrative.
In the two end-pieces of a heavy iron frame were set three rolls, or cylinders--one in the centre, another below, and the other above--all three being in a vertical line. These rolls were about three feet in diameter, made of cast-iron, and had face-plates of chilled-iron.[31] The lowest roll was set in a fixed bearing at the bottom of the frame, and, therefore, could only turn around on its axis. The middle and top rolls were free to move up or down from and toward the lower roll, and the shafts of the middle and upper rolls were set in a loose bearing which could slip up and down in the iron frame. It will be apparent, therefore, that any material which passed in between the top and the middle rolls, and the middle and bottom rolls, could be ground as fine as might be desired, depending entirely upon the amount of pressure applied to the loose rolls. In operation the material passed first through the upper and middle rolls, and then between the middle and lowest rolls.
[31] The faces of these rolls were smooth, but as three-high rolls came into use later in Edison's Portland cement operations the faces were corrugated so as to fit into each other, gear-fashion, to provide for a high rate of feed.
This pressure was