History of crushers

 Crushing and breaking of rock, ore and minerals is one of the oldest industries undertaken by man. The earliest crushing known was by hand on "native" ores (gold, silver, and copper) or on ores containing lapis lazuli, garnet, diamond, jade, etc. Glass making may have required breaking of agglomerates.

If hand crushing was impractical a heavy rock or weight was raised by men or animals with a rope and allowed to drop onto the rock to be crushed. Irrigation led to invention of waterpower to raise the weight. The lnvcntion of the cam and cogwheel allowed the operation to be continuous.

Crushing is the essential function in the treatment of all rocks and minerals, whatever is their and use. The primary crushing of rocks does not appear compatible with high tech engineering of 21 Century. However, we have come a long way from the beginning of the 1800's when crushing was carried out by hundreds of men and women equipped with sledgehammers.

The earliest U.S. patent for a crushing machine was issued in 1830. It covered a device, which, in a crude way, incorporated the drop hammer principle later used in the famous stamp mill, whose history is so intimately linked with that of the golden age of American mining. Eli Whitney Blake invented the first successful mechanical rock breaker - the Blake jaw crusher patented in 1858. Blake adopted a mechanical principle familiar to all students of mechanics, the powerful toggle linkage. That his idea was good is attested to by the fact that the Blake type jaw crusher is today the standard by which all jaw crushers are judged. In 1881, Philters W. Gates was granted a patent on a machine that included in its design all of the essential features of the modem gyratory crusher.

An interesting sidelight of these early days occurred in 1883 at Meriden, Connecticut, where a contest was staged between a Blake jaw crusher and a Gates gyratory crusher. Each machine was required to crush nine cubic yards of stone, the feed-size and discharge settings being similar. The Gates crusher finished its quota in 20 % minutes, the Blake crusher in 64 '/2 minutes. For some years after these pioneer machines were developed, requirements remained very simple. All mining and quarrying, whether underground or open-pit, was done by hand; tonnage's generally were small, and product specifications simple and liberal.

Even the largest commercial crushed stone-plants were small, consisting of one crusher, either jaw or gyratory, one elevator and one screen. When demand grew beyond the capabilities of one crusher, it was generally a simple matter to add a second machine. When the business outgrew the capacity of this sort of plant, it was not unusual to double up, either in the same building, or by erecting an entirely separate plant adjacent to the original one.

The steam shovel began to change the entire picture of open-pit mining. With the steam shovel came the really "huge" gyratory crusher, with its 18 inch receiving opening. This turn toward really large primary crushers started just a few years before the turn of the century, and in 1910 crushers with 48 inch receiving openings were being built.

About this time the jaw crusher suddenly came back to life and stepped out in front with a great contribution to the line of mammoth sized primary crushers: the 84 inch x 60 inch machine built by the Power and Mining Machinery Company for a trap rock quarry in eastern Pennsylvania.

During the same years the industry was concerned with development of larger and still larger primary crushers, another member of the family was born: the single, sledging roll crusher. The machine quickly achieved a high degree of popularity, and although its field of application was relatively limited, quite a number of these machines were installed for primary crushing service. The line was expanded to also include the 84 inch x 60 inch machine. The double roll crushers had limited popularity in the mining industry.

In 1919, Traylor Engineering manufactured the largest gyratory crusher yet built. This was a 60 inch gyratory sold to Michigan Limestone and Chemical Company in Rogers City, Michigan. This size stood until 1969 when Traylor Engineering built the first 72 inch gyratory crusher. This crusher was sold to Johns Manville of Canada. It was in service as the world's only operating 72 inch machine until 2001 when the mine went underground and the gyratory was replaced with low speed sizers.

By 1920, the harnmer mill had been developed to produce a fine product in a single pass machine. These machines employ the impact principle of breaking stone. The hammermill is a simple mechanism. The machine comprises a box-like frame, a centrally located, horizontal shaft rotating element on which hammers are mounted., and a set of circumferentially arranged grates in the lower part of the housing. The shaft rotates at high velocity, which break the stone by impact. From the 1920's through the 1950's the hammerrnills were modified to include impactors that broke the rock with fixed breaking bars and the elimination of the grates on certain machines. The double toggle jaw crusher was supplemented by the single toggle jaw crusher where the pitman/toggle arrangement was eliminated and the motion was derived from an eccentric drive shaft.

In 1960, the feeder-breaker was developed for underground coal mining to follow the continuous miners. These are low-headroom machines that consist of a flight bar feeder and a rotating breaking drum with teeth or picks. The material is transferred to the tailend of the feeder, is dragged toward the headend and crushed in-line as the material passes under the drum. These machines have now been modified and upgraded to handle limestone and other non-abrasive materials. Some manufactures identify the rock machines as impact horizontal roll crushers.

In the early 1980's, low speed sizers were introduced. This represented one of.the only fundamental developments in primary crushers in three-quarters of a century.

Conventional roll crushers are suitable for crushing soft to medium strength materials and can provide accurate reduction of >10:1. Roll crushers, both smooth and toothed, are generally designed with high peripheral speeds, and uneven wear can be a major problem. The main feature of the low speed sizer, which can broadly be considered a variety of toothed roll, is that it,exploits the fact that the ratio of compressive strength to tensile and shear strength in the majority or rocks is approximately 10:1. The low speed sizers breaks the rock in tension or in shear by its "snapping" and chopping action rather than in compression as conventional crushers do.

Additionally, the positioning of the teeth on the rolls allows undersize to fall directly through the machine resulting in high throughputs at very low rotational speeds that leads to greatly reduced wear, energy savings, better control of discharge size in three dimensions, and greatly reduced fines.