The first stage of size reduction of hard and large lumps of ore is to crush and reduce their size because of this fact crushers are used for breaking of large pieces of solid materials into small lumps.

Crushers Crushers employ compression, slow speed machines hired for coarse reduction of large quantities of solid. A primary crusher is the one which crushes the feed to yield a product 150-250mm in size whereas, secondary crusher is the one which takes the product of a primary crusher and reduces it to particles of about 6mm. The main types of crushers are given as;

Jaw Crusher Smooth Roll Crusher Gyratory Crusher

Jaw Crusher Jaw crusher consist of a set of vertical jaws, one jaw being fixed and the other being moved back and forth relative to it by a pitman mechanism. The jaws are farther apart at the top than at the bottom, forming a tapered force so that the material is crushed progressively smaller and smaller as it travels downward until it is small enough to escape from the bottom opening. The compressive strength of jaw crushers is 320 mega Pascal and the Rpm of jaw crusher is between 200- 400. The jaw crusher is used for crushing trash, making it easy for transportation from one to another location. This is very important because the crushed materials are always easier for transportation, loading and dumping. This machine is heavily used on construction sites where a large amount of hard materials need to be crushed on a daily basis, including stones, rocks, concrete, and other form of debris.

Figure 1 Jaw CrusherDesign of Jaw Crusher As jaw crusher is designed to impart an impact on the solid particles placed between a fixed and a moving plate. The faces of the plate is made up of harden steel, both plates could be flat or the fixed plate and the moving plate convex. The surfaces of both plates could be plain or

corrugated. The moving plate applies the force of impact on the particles held again the stationary plate, plates are bolted on to a heavy block. The moving plate is pivoted at the top end (Blake) or at the bottom end (Dodge) type crusher. In universal crusher the plates are pivoted in the middle so that both the top and the bottom ends can be moved.

Figure 2 Jaw Crusher

Mode of OperationJaw crusher is equipped with one fixed and one moveable crushing jaw (wear parts) forming a wedged shaped crushing area. The side walls of crushing area are made of replaceable wearing sheets. Crushing is carried out between two crushing jaws. The moving jaw of the single toggle jaw crusher moves elliptically. A pendulum motion is being carried out by double toggle jaw crusher. The crushing force is produced by an eccentric shaft, then it is transferred to the crushing area by a toggle plate system and supported by the rear of the housing of the machine. Spring pulley rods keep the whole system in a condition of non-positive connection. Centrifugal masses of the eccentric shaft serve as compensation of heavy loads. A flywheel is provided in the form of pulley. The favorable angle of dip between the crushing jaws has a positive impact on the intake conditions of the feed material. The final grain size distribution is influenced by both the adjustable gap as well as the appropriately selected tooth shape of the crushing plates. One important thing that needs to be closely considered when choosing which jaw crusher to be used, is the size and the length of the crushing chamber. The crushing chamber should be large enough to allow the materials to easily enter inside. As a general rule, a jaw crusher with larger crushing chamber has more crushing power. Long crushing chambers are suitable for hard materials that demand more strength.Parts of Jaw Crusher The parts of a jaw crusher are given as;

Frame Fixed Jaw Moveable Jaw Flywheel Grooved Wheel Spring System Toggle Plate

Toggle Seat Gap Size of set Crushing cavity Pivot Check Plates Adjusting Screw

Working Principle of Jaw Crusher

Types of Jaw Crusher Jaw crusher are divided into two types, both uses compressive force for size reduction;

Blake Jaw Crusher Dodge Jaw Crusher

Figure 3 Types of Jaw Crusher

Blake Jaw Crusher Blake jaw crusher is a type of crusher in which the swing jaw is pivoted at upper position, the amount of motion is at the bottom which means less choking. Blake jaw crusher has a fixed feed area and a variable discharge area. Greatest amount of motion is at the bottom of “V” which means that it have a little tendency to chock. The swinging jaw reciprocates in a horizontal plane usually make an angle of 20-30° with the fixed jaw.

Figure 4 Blake Jaw Crusher

Dodge Jaw CrusherDodge jaw crusher is a type of crusher in which the the swing jaw is pivoted at bottom position, it has a greater tendency to choke. The amount of motion is greatest at the top of “V”. The Dodge jaw crusher has a variable feed area and a fixed discharge area which leads to choking of the crusher hence, it is used only for laboratory purposes and not for heavy duty operations.

Figure 5 Dodge Jaw Crusher

Double Toggle Jaw CrusherDouble Toggle Jaw Crusher is preferred for crushing unusually hard, abrasive rocks and other materials like ferroalloys and glass. In double there is no rotary motion in the crushing cycle and all crushing is done by compression of the feed material between two massive jaws plates. The moving jaw compresses the material against the stationary jaw. Jaw plates can be either smooth or corrugated.

Figure 6 Double Toggle Jaw Crusher

Double Toggle Jaw Crusher have one jaw fixed, while the other pivots about a top hinge. There is no rubbing or grinding. Only compression, which produces a generally cubical product with minimum fines. The moving jaw is very well balanced, so 95% of the drive motor power is used for crushing while 5% of the power is needed to move the jaw itself. As a result of this high mechanical efficiency, double toggle jaw crushers require smaller size motors, keeping power cost down. There are several major advantages to this arrangement;

The horsepower requirement is substantially reduced and only one small diameter flywheel is used.

The eccentric, toggle plates, and shaft bearings run in an oil bath and are protected from dust and other contaminants.

The tramp-iron release mechanism is mounted on the much smaller flywheel and is easily reset.

The swing motion is in a straight line rather than elliptical and the manganese wear plates last longer.

Figure 7 Labelled Diagram of Double Toggled Jaw Crusher

Single Toggle Jaw CrusherIn a single toggle jaw crusher a pitman mounted on an eccentric shaft at the top. At the bottom of the assembly, the pitman is held in position by a toggle plate. The combination of eccentric motion at the top and rocking motion at the bottom provides a positive downward thrust throughout the crushing chamber. Single toggle jaw crushers have better feed acceptance capability than the corresponding double toggle crushers. Jaw crushers are reliable, robust machines, offering a 6:1 reduction ratio in most applications, and will accommodate hard, abrasive materials. Or The single-toggle crusher is the simplest and the lightest of the jaw crushers but is suitable only for producing low crushing forces and therefore used for soft rocks.

Figure 8 Single & Double Toggle Jaw Crusher

Jaw Crusher ProtectionJaw crusher can be kept safe by keeping some points in mind;

Be sure that the crushing chamber is clear. Be sure that all guards and other safety devices are correctly installed and tightly secured

before starting the crusher. Do not allow personnel to be on or near the crusher during operation. Stay clear of feed

and discharge areas to prevent being injured or killed by flying or falling rock. Never attempt to clear jammed material from the crushing chamber while the crusher is

operating. Serious injury or death could result if you are pulled into, or fall inside, the crushing

chamber. Never attempt to adjust the discharge setting during crusher operation. Always wait until

the crusher is completely stopped before making any adjustments.

Always stop the crusher immediately if any gauges show abnormal readings, or if there is a sudden obvious change in operation. Be alert for noises that might indicate trouble.

Industrial Application of Jaw CrusherThe industrial applications of Jaw crusher are given as;

Building stones- water construction- construction industry mobile crushing plant Mining industry- coal industry- rotary dryer Chemical Industry Concrete Recycling Jaw Crusher in Quarry

Building stones- water construction- construction industry mobile crushing plantBuilding stones- water construction- construction industry mobile crushing plant.Since the found of New China, the water conservancy construction develop rapidly, but the water conservancy project that has been built has much low scale, project quality is poor; jaw crusher can be used in the process of water infrastructure.

Mining industry- coal industry- rotary dryerJaw crusher is the most important mining machinery, the mining of ore production, crushing equipment and grinding machine are all can’t do without the crusher machine or spiral ore washing machine. Thus building strong and have competitive machinery industry contributes to China achieve to modernization, revitalization and development of machinery industrialization and our country gradually become the economic powers are inseparable.

Chemical IndustryAt present our country’s crusher device continuous develops and update, develop the crusher equipment to meet the needs of different users. Industry crushing equipment can be used in the cement, chemical, power, metallurgical and other industries to crushing the hard material, such as limestone, slag, coke, coal and other materials.

Concrete RecyclingJaw crushers can be used in concrete recycling. Jaws compress the concrete between a stationary and moveable plate. Concrete is reduced in size as it travels down the length of the wedge between the two plates. Jaws are used as primary crushers and typically produce a 4" to 8" minus product usually used as fill.

Jaw Crusher in QuarryThe primary crushing of the stones is normally carried out by the jaw crushers. Jaw crushers are used on the large scale in this field.

Advantages of Jaw CrusherThe advantages of Jaw crusher are given as;

Following are the different advantages of the jaw crushers:

Simple structure Low cost Maintenance are convenient Reliable work Small machine body Easy to use

Disadvantages of Jaw CrusherThe disadvantages of Jaw Crusher are given as;

Lower productivity Lower power Consumption Bigger vibration Small crushing Ratio Uneven particle size Can’t crowd feeding ore