The "self-propelled jaw crusher" is a central component among rock crushers. The "jaws" that crush rocks are the "moving teeth" and the "fixed teeth. The moving teeth are directly connected to the eccentric pulleys, which move in waves as the eccentric pulleys rotate in a circular motion. This movement pushes the injected crushed material against the fixed teeth, which grind it down. For this reason, the moving teeth are also called swing jaws. Since the self-propelled jaw crusher is a heavy machine that crushes stone material with extremely high force, the heavy machine itself is also subjected to a large load. Therefore, to prevent damage to the jaw crusher itself when it is overloaded, the "toggle plate" is equipped with a safety device that bends to stop the machine in an emergency. Because of this structure, it is sometimes called a "single toggle crusher. Incidentally, some newer models of self-propelled jaw crushers use a "locking cylinder" system. The "lock cylinder" system is designed to protect the crusher mechanism by denting the cylinder when the hydraulic cylinder is subjected to a certain amount of force.Therefore, the locking cylinder system does not have a toggle plate. (Even if there is, the effect is secondary.)  The lock cylinder also has a gap adjustment function. In conventional jaw crushers, the size of the product is determined by replacing the thickness of the adjustment shim behind the moving teeth to adjust the gap.The locking cylinder system, on the other hand, uses a hydraulic cylinder to allow easy gap adjustment under computer control.

There are two types of mobile jaw crushers, the "direct feeding type" and the "grizzly type," depending on the method of feeding crushed material. 

direct feeding type

This type is common in the old type of mobile jaw crushers. Crushed material is directly fed into the feed port of the crushing chamber using a hydraulic excavator or the like. Feeding a large amount of crushed material at once places a heavy burden on the heavy equipment, and the size of the crushed material discharged will not be uniform, resulting in a decrease in quality. Therefore, the operator is required to have good skills, and the work is very nerve-wracking.

grizzly type

This is the type used in recent self-propelled jaw crushers. The rock to be crushed is once fed into the feed hopper. The vibration of the grizzly sends the rock from the feed hopper little by little into the feed port of the crushing chamber. Since a constant amount of rock is fed into the crushing chamber, crushing efficiency is high and the operator's workload is reduced. In addition, because the grizzly is shaped like a bear's claw, small objects that do not need to be crushed slip through the gaps and fall out. This also reduces unnecessary crushing.

 Since the crushing condition cannot be checked from the cabin of the excavator, the "direct feeding method" requires a skilled operator to feed the material. hen selecting the "direct feeding method" or the "grizzly method," be sure to pay close attention to this point.

Self-propelled jaw crushers have a relatively simple structure, and there is little difference in structure among manufacturers. So what are the criteria for choosing the right one?The following three points should be considered when selecting a self-propelled jaw crusher.

Point 1: Parts availability

Self-propelled jaw crushers are heavy machines with frequent parts replacement. Stability of parts procurement is one of the major points in selecting a self-propelled jaw crusher. 

Point2: Size of feed port

 The size of the feed port indicates the volume of the crushing chamber. The larger the volume, the more crushed material can be fed in, which improves work efficiency. The size of the feed port may be indicated in different ways depending on the manufacturer. Komatsu Construction Machinery's BR380JG-3 is marked as 1065 x 550 mm. Some manufacturers indicate the size in inches, in which case it is written as 3 4 1 2. This means that the long side of the rectangle is 34 inches and the short side is 12 inches. The long side of the jaw crusher feed port tends to get more attention. This is because it is also the size of the dynamic and fixed teeth. However, for efficient crushing, it is also important to know how much the short side is. Since the short side is the opening width of the moving teeth, if the short side is narrow, the movement of the moving teeth in the direction of compression will also be small, and only small crushed material can be fed. Of course, each manufacturer studies the size of the feed opening for efficient crushing, but when selecting a self-propelled jaw crusher, be sure to check the width and length of the feed opening.

Point 3: Compressive strength

 Compressive strength indicates how much force can be applied when crushing stone material.For relatively soft concrete gara, a force of 1900 kg per square centimeter is required. (1900 kgf/cm2) To break a hard natural stone such as granite, 2500 kg per square centimeter is required. (2500 kgf/cm2) For example, if a jaw crusher with a compressive strength of 1900 kgf/cm2 is used to crush granite, the crushing efficiency will be very poor and the jaw crusher will be damaged if it is not used properly. This compressive strength is listed in the performance chart, so it is important to check it carefully. Incidentally, in the case of Komatsu Construction Machinery's BR380JG-3, there is no indication of compressive strength. Maximum feeding mass dimensions. The maximum feeding mass dimensions are shown in the following table. The maximum feed size refers to the maximum size that can be fed by paying attention to the direction of the crushed material to be fed, while the optimum feed size refers to the maximum size that does not require paying attention to the direction of the crushed material. This means that when feeding natural stone, it is necessary to pre-crush it to some small size before feeding.

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