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Although his machines never came into general use in the industry, Thomas A, Edison ranks as a pioneer in the development of the large primary breaker; in fact, Edison is credited with the promulgation of a very interesting and constructive bit of reasoning, with the development of a deposit of lean magnetic iron ore at Edison, N. J., he was using a number of the small jaw crushers then available for his initial reduction. Realizing that to concentrate this ore at a cost to permit marketing it competitively meant cutting every possible corner, he studied the problem of mining and crushing the ore as one of the steps susceptible of improvement.
In approaching the problem, Edison reasoned that the recoverable energy in a pound of coal was approximately equal to the available energy in one pound of 50 percent dynamite; but the cost per pound of the coal. Furthermore, a large part of the dynamite used in his mining operation was consumed in secondary braking to reduce the ore to sizes that the small primary crushers would handle. The obvious conclusion was that it would be much cheaper to break the large pieces of ore by mechanical rather than by explosive energy.
With that thesis as a starting point, he set out to develop a large primary breaker, a development which culminated several years later in the huge and spectacular 8- X 7-ft. Edison rolls. A description of the action of this machine will be found in a later section of this series. During the early years of the present century these giant machines created considerable interest, and several were installed in this country. However, they never became popular, and interest swung back to the more versatile gyratory and jaw types. Edison rolls were also developed in smaller sizes for use as secondary and reduction crushers. In his own cement plant Edison used dour sets of rolls operating in series to reduce the quarry-run rock to a size suitable for grinding.
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