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1996 Cedarapdis-El-Jay C54 Portable Cone Crusher
Crushers are machines used to crush various materials, namely rocks, ore, and other aggregates for the purpose of rock-fill for landscaping, road building, erosion control, and mining ores. There are several different types of crushers, all suited for different construction and mining applications and used to crush rocks of various forms and sizes.


[edit] History

[edit] Early Crushing Methods

The crushing of rocks and aggregates has been a progressively demanding industry for at least the last three centuries. Originally, mining materials such as gold, silver, and copper were crushed by hand. When it was not possible to use brute force, heavy rocks were raised, either by groups of men or with the help of animals, and dropped. When irrigation systems were invented, men used water to raise rocks for crushing. Other methods included the use of sledgehammers.[1]

Before the use of steam machines, stone getters would get into groups of two to four to blast and break rocks, drilling small holes into rock and filling them with straw and explosives. With steam power going strong in the 19th century, methods of drilling and crushing changed drastically. Machines that ran on electric or gas diesel were produced.[2]

[edit] The First Crushing Machines

The first hint of a crushing machine appeared in 1830. An idea was posited about a drop hammer, which later was used in stamp mills. In the 1840s, a second patent was issued: a wooden box and a wooden cylindrical drum that revolved at 350 revolutions per minute. Neither device was developed enough to have an impact on the crushing industry.

Although he never developed a line of manufactured crushers, Thomas Edison helped develop a primary crusher when he was trying to reduce magnetic iron ore. He discovered that crushing rocks would be more economical than using explosives. 

Eli Whitney Blake produced the first successful jaw crusher in 1858, a prototype that all subsequent crushers would follow. Philters W. Gates patented the gyratory crusher, another primary crusher machine, in 1883. Both Blake's and Gates' models were engaged in a contest to measure which machine was most successful and productive. Having to crush nine cubic yards (6.9 m3) of stone, the Gates model completed the task in just 20 ½ minutes and the Blake model finished at 64 ½ minutes.

Cedarapids 5066 Portable Impact Crusher

[edit] Smith and Post's Contributions

Thomas L. Smith and Paul W. Post, the original owners of what is now Telsmith, knew in 1906 that with the production of cars becoming more widespread, and with legislation for better road conditions, there would be a market for aggregate, and thus they launched one of the biggest crusher manufacturers worldwide.

The first crusher produced by Smith and Post was the Symons, "Pillar Shaft" gyratory crusher, selling 50 units. By 1910, they were also producing jaw crushers like the "Dodge."

With the demand for smaller aggregate, Telsmith decided that another type of machine, the tertiary crusher, was needed to further reduce the rocks to ½ inch (1.3 cm). Smith Engineering (later to be known as Telsmith) developed a cone crusher called the reduction crusher, as well as the Telsmith Cone, the Intercone and perhaps one of the most successful crushers in history, the Gyrasphere crusher in the mid 1930s.[3]

[edit] Growing Crushers

Gate’s gyratory crushers kept getting bigger with time. His second machine had an 18-inch (46-cm) receiving opening and by 1910, the gyratory crusher had a receiving opening as large as 48 inches (122 cm).

Other crusher manufacturers were in the race to produce bigger and more productive machines. Power & Mining Machinery Co. built the 84 x 60 jaw crusher and the sledging roll crusher, a primary crusher with 84 x 60 inch (213 x 152 cm) machine, which could only be used for select applications but proved to be very popular.

[edit] The Dawn of the Hammer Mill

The hammer mill crusher first appeared in 1920 and was used to break stone by impact force. The box-shaped device consisted of a shaft in the center, which rotated mounted hammers and a set of grates. The premise of the hammer mill was to break stone by creating high-speed impact. Hammer mills evolved mostly between 1920 and 1950, when impactors were included to the list, which meant no more grates.

[edit] Taylor's Crushers

One of the largest crushers was a model produced by Taylor Engineering in 1919. It had a 60-inch (152-cm) receiving opening and remained in first place until Taylor produced the 72-inch (183-cm) gyratory crusher in 1969. It served as the world’s biggest and only machine at that size until 2001, when the machine was downsized in order to perform underground mining applications.

Perhaps the biggest development in crushers since Taylor’s size revolution was the birth of low-speed sizers and roll crushers—machines best suited for soft to medium materials.[4]

[edit] Building Highways

Telsmith also upgraded its crusher selections. With the building of the interstate highway, large equipment was needed and as a result, the 4248 jaw crusher and 66-inch (168-cm) Gyrasphere crushers were produced in 1960s.[5]

[edit] Features/How it Works/Types

The crushing of materials occurs in three stages: primary, secondary, and tertiary. Rocks can pass through as many as four crushers to achieve the desired size. When a rock passes through a crusher its size is reduced, an expression referred to as the ratio of reduction.

The types of crushers include:

[edit] Jaw Crusher

2002 Lippman 3042 30x42 in. Portable Jaw Crusher
The jaw crusher consists of a frame, eccentric shaft, big belt pulley, flywheel, movable jaw, side guard plate, toggle plate, rear seat of toggle plate, modulation gap screw, returning spring, fixed jaw plate, and a movable jaw plate.

The jaw crusher is one of the most widely used primary crushers and is suited for materials that range from soft to extremely hard. It receives the stone between two jaws; a stationary jaw and a movable piece that moves vertical and horizontal when rotated. The Blake model, a double-toggel crusher,  has a movable jaw hanging from a shaft that sits on a frame of bearings. It achieves sufficient crushing by rotating the shaft, raising and lowering the pitman, and utilizing the two toggles. As the toggles ascend, the swing jar closes slightly and high pressure is exerted. When the stones are small enough, they fall through the bottom of the jaw. The reduction ratio for jaw crushers range from 3/1 to 5/1. Jaw crushers range in sizes from 12 inches (30 cm) to 1.5 inch (38 mm).[6]

Jaw crushers can come in two toggle types: the double toggle (DT jaw crusher) and the single toggle (ST jaw crusher). The difference between the two is that the single toggle requires a feeder and can typically only produce 27,500 pounds per square inch (189,605 kPa), crushing only light to medium materials. The double toggle, however, can crush 90,000 pounds per square inch ( 620,528 kPa) and tends to feature hydraulic toggle adjustment attachments.[7]

[edit] Gyratory Crusher

The cone-shaped gyratory crusher is another example of a primary machine. This type of crusher comprises of a cast iron or steel frame with a chamber that is wide at the top and narrow on the bottom and lined with steel concaves. A crushing head gyrates the fulcrum point. When rock passes through the top, it is crushed when it enters the crushing chamber and is reduced in size until it passes through the bottom of the chamber. It is capable of producing 350 to 10,000 MTPH and a crushing hardness of as much as 900,000 pounds per square inch (6,205,281 kPa).[8]

[edit] Cone Crusher

Also known as a reduction crusher, the cone crusher is a secondary or tertiary device used to produce finely crushed stone from medium to hard, abrasive material. It is similar in style to the gyratory crusher but differs because it has a smaller cone and smaller receiving opening. The cone’s rotating speed is higher than the gyratory, at 430 to 580 revolutions per minute. The cone head, made of manganese steel, sits on a shaft, which is also one of the crushing surfaces. The process of crushing is repeated until the pieces are small enough to disappear into the crusher’s bottom opening.[9]

[edit] Hammer Mill

Predominately used as an impact crusher in secondary crushing, the hammer mill (or crusher) can crush medium to hard materials with a slight abrasion. The rotor consists of a hammer and is moved by a motor resulting in high-speed rotation. Materials such as cement and coal are fed through the upper slot and successfully crushed by shearing and grinding caused by the hammer.

[edit] Roll Crusher

The roll crusher is best used for crunching soft to medium material when further reductions must be made. The structure consists of a cast-iron frame and two steel rolls, each sitting on a horizontal shaft. Rocks are crushed finely on a v-belt sheave. This machine is generally slow and high maintenance.

[edit] Rod and Ball Mill

The rod and ball mill is used in the final stages and helps produce a finished product of uniformly fine aggregate, such as sand. The rod mill is a circular device with a steel outer shell and a mineral interior, and uses driver gears to move stone along. As the mill rotates in a slow manner, the stone is grinded by tumbling rods. The ball mill uses steel balls instead of rods and can grind aggregate even finer and smaller than that of the rod mill.[10]

[edit] Impact Crusher

Impact crushers are used in the aggregate and mining industries to crush rock. However, very hard rock is not ideal for this type of crushing because of the high cost of its parts. The impact crusher is available in a variety of configurations: vertical shaft impact crushers can have a shoe and anvil, rotor and anvil, or rotor and rock shelf; horizontal shaft impact crushers can have a 2,3, or 4 bar fixed rotor, or high speed hammers.

The rock falls onto/into the rotor and breaks. It is then propelled against breaker bars inside the crushing chamber.

[edit] Common Manufacturers

[edit] Additional Photos

2006 Extec C12 Plus Track 800mm x 1100 mm Jaw Crusher
Telsmith 36FC Skid Mounted Cone Crusher
2001 BL Pegson 428 Crawler Impact Crusher
2003 El-Russ-Sandvik H4800 Hydrocone Portable Cone Crusher

[edit] References

  1. Mular, Andrew L. et al. Mineral Processing Plant Design, Practice and Control. SME: 2002.
  2. Aggregate Production Through The Ages. Wainwright. 2008-09-24.
  3. Telsmith History. Telsmith. 2008-09-24.
  4. Mular, Andrew L. et al. Mineral Processing Plant Design, Practice and Control. SME: 2002.
  5. Telsmith History. Telsmith. 2008-09-24.
  6. Peurifoy, R.L Construction Planning, Equipment and Methods. McGraw-Hill: New York, 1970. 564-591
  7. Mular, Andrew L. et al. Mineral Processing Plant Design, Practice and Control. SME: 2002.
  8. Mular, Andrew L. et al. Mineral Processing Plant Design, Practice and Control. SME: 2002.
  9. Jaw Crusher. Stone Crusher. 2008-09-24.
  10. Peurifoy, R.L Construction Planning, Equipment and Methods. McGraw-Hill: New York, 1970. 564-591