Structure analysis of jaw crusher
The structure of the jaw crusher is relatively simple, mainly composed of a frame, a working mechanism, a transmission mechanism, a regulating device, a safety device and a lubrication system. Take the 900mm×1200mm simple pendulum jaw crusher as an example to briefly introduce its structure.
Jaw crushers have two types: integral frame and combined frame. The overall frame is generally welded by castings or steel parts. Domestic small and medium-sized crushers mostly use integral frames. The combined frame is made up of multiple cast iron or welded parts connected by pins or bolts. It is mainly used for large jaw crushers that are difficult to transport (such as underground crushers) or difficult to manufacture.
2. Work organization
The working mechanism (ie, crushing cavity) of the jaw crusher is composed of a fixed jaw (ie, the front wall of the frame in Figure 1 above) and a movable jaw 5. Both jaws are lined with liner plates 2 and 6 made of manganese steel, and the liner plates are fixed on the jaw plates with bolts and wedges. Because it directly participates in the crushing, in order to improve the crushing effect, the surface of the liner has longitudinal corrugations, and the unevenness is opposite. At present, the tooth profile of the liner of the domestic jaw crusher is mostly triangular and trapezoidal.
The surface is vertical and straight. With the application and development of computers, the design of the tooth profile has been developed from the traditional test method and empirical method to the use of computer to optimize the design, so as to obtain a better crushing effect.
Because the wear of various parts of the liner is very uneven during crushing, especially the lower part near the discharge port is more severely worn. For this reason, the liner is generally made up and down symmetrical, and the lower part is worn upside down to extend Its service life. The liner of the large crusher is composed of many pieces, each piece can be interchanged, and the purpose is to extend its service life.
The shape of the crushing cavity of the jaw crusher directly affects its productivity, product particle size composition, particle size, crushing plate service life and power consumption and other technical indicators. At present, most of the crushing chambers of large-scale Jaw crusher produced in my country adopt the old-fashioned linear cavity shape with all teeth. This cavity shape has low productivity, high specific energy consumption, easy clogging, large and uneven product particle size. Recently, a lot of research work has been done on the crushing cavity in China, and a new type of cavity has been used in production.
The two cavity shapes shown in Figure 2a and b have been used in domestic medium and small jaw crushers. Practice has proved that when the swing stroke and swing times of the movable jaw are the same, the curved cavity shape has the advantages of high productivity, large crushing ratio, uniform product size, less over-crushing, small wear of the liner at the lower end of the crushing cavity, and low specific energy consumption. . The advantages of the curved-straight mixed crushing cavity shown in Figure 2c are more obvious.
3. Transmission mechanism
It is mainly composed of a pulley 10, an eccentric shaft 8, a connecting rod 9, and front and rear thrust plates 12, 13 and so on. The eccentric shaft is supported in the main bearing on the side wall of the frame. The upper part of the connecting rod is installed on the eccentric position of the eccentric shaft. When the motor drives the eccentric shaft to rotate, the connecting rod is driven up and down due to the eccentricity, thereby driving the thrust plate to move.
As the thrust plate continuously changes its inclination angle during movement, it drives the movable jaw to periodically swing around the suspended eccentric shaft 8, thereby achieving the purpose of crushing the ore. In order to ensure that the movable jaw and the thrust plate are tightly integrated, a tensioning device composed of two pull rods 15 and two springs 16 is usually used. When the movable jaw swings, it can not only ensure that the movable jaw and the thrust plate are not separated, but also can partially balance the inertial force generated by the movable jaw and the thrust plate.
Since the work of the Jaw crusher is periodic, it will inevitably cause periodic changes in the load of the motor, resulting in a very unbalanced load. Therefore, a large-scale crusher is generally equipped with a flywheel at both ends of the eccentric shaft (one of the flywheels is also used as a belt wheel), and the flywheel of a small and medium-sized crusher can be made one. According to the principle of inertia, the crusher can store energy during the non-working stroke and release it during the working stroke, thereby making the motor load uniform.
4. Adjusting device
The liner of the crusher is constantly worn by the ore during work, which makes the width of the discharge opening gradually larger. In order to ensure the requirements of product particle size, the width of the discharge opening must be adjusted in time. There are the following 3 types of commonly used discharge opening adjustment devices.
(1) Pad adjustment device
17 in Figure 1 above is the pad adjustment device. A set of adjustment pads are placed behind the rear thrust plate support. When the number or thickness of the pads is changed, the rear thrust plate is moved forward or backward to achieve the purpose of adjusting the width of the discharge opening. This kind of adjusting device has a simple and compact structure and does not increase the weight of the whole machine much, so large and medium Jaw crusher are often used. The disadvantage is that it must be stopped during adjustment.
(2) Inclined iron adjusting device
The inclined irons 6 and 7 in Figure 3 are used to adjust the width of the discharge opening. It uses bolts or worm gears or chain drives to lift the rear inclined irons. The front inclined irons are installed in the guide grooves of the two side walls of the frame and can only move horizontally. When the rear inclined iron is lifted, the front inclined iron moves forward along the guide groove due to the relationship of the inclined surface, the thrust plate and the movable jaw move forward, and the width of the discharge opening also decreases.
Conversely, when the rear inclined iron drops, the width of the discharge opening increases. The advantage of this kind of adjustment device is that it can realize stepless adjustment, and there is no need to stop during adjustment. The disadvantage is that the adjustment is very laborious, and the size of the whole machine is increased, so it is only suitable for medium and small jaw crushers.
(3) Hydraulic adjustment device
This adjusting device uses hydraulic cylinders and plungers to adjust the width of the discharge port, and uses manual or electric hydraulic pumps to supply oil to the hydraulic cylinders. The 900mm×1200mm hydraulic simple pendulum jaw crusher shown in Figure 4 uses a hydraulic adjustment device.
When adjusting, first loosen the nut of the tension spring, open the shut-off valve (usually closed), start the hydraulic pump motor, fill the two horizontal hydraulic cylinders at the rear of the frame, and the plunger pushes the wedge iron forward , When moving to the desired position, close the shut-off valve and adjust the thickness of the gasket.
After the adjustment, open the shut-off valve, and press the hydraulic cylinder back to the tank by the backward pressure of the movable jaw, thrust plate and connecting rod of the crusher, and close the shut-off valve after re-compressing the tension spring to a certain position.
5. Safety device
Large objects such as mechanical parts and iron blocks enter the crushing cavity, or the crushing cavity is blocked by materials near the discharge port, etc., which will cause overload of the jaw crusher. At this time, the force of the machine increases rapidly, therefore, a safety device must be installed to prevent accidental damage to the crusher. The commonly used safety devices are as follows.
(1) The thrust plate doubles as a safety device
When designing parts, design the thrust plate as the weakest link, and make it break first when overloaded to protect other parts of the equipment from damage. The thrust plate 13 in the above figure 1 is not only a connecting rod for transmitting force, but also a safety part of the crusher. The thrust plate is generally made of cast iron, and the middle is drilled or cut to reduce its cross-sectional area. The thrust plate can also be combined (Figure 5). The connecting elements such as rivets are made of brittle materials. They are first sheared when overloaded. This kind of safety device is very simple, but the disadvantage is that the handling after the accident is more complicated and the downtime is long.
(2) Overload protection transfer arm
The JC type jaw crusher introduced later (Figure 7), its overload protection adopts the form of overload protection force transmission arm. The device mainly relies on a leaf spring to connect the belt wheel and the main shaft of the crusher, and the torque transmitted is realized by adjusting the shim as needed.
When the overload occurs, the leaf spring is disengaged from the pulley, the pulley is idling on the main shaft, and the main shaft stops rotating, and can be quickly reset when the overload is eliminated. The device is characterized by no damage to any parts, and the insurance has high sensitivity, safety and reliability.
(3) Hydraulic connecting rod as safety device
In Figure 4 above, a hydraulic cylinder and piston are connected to the connecting rod. The hydraulic cylinder is connected with the upper part of the connecting rod, and the piston is connected with the lower part of the connecting rod. During normal operation, the hydraulic cylinder is filled with pressure oil, and the piston and hydraulic cylinder are equivalent to a part of the integral connecting rod. When overloaded, the pulling force acting on the connecting rod increases sharply, causing the oil pressure in the lower oil chamber of the hydraulic cylinder to increase.
When the oil pressure exceeds the pressure specified by the high-pressure relief valve of the combination valve, the pressure oil is discharged through the high-pressure relief valve, the piston and thrust plate stop moving, and the movable jaw stops swinging, thus playing a safety role. When the overload is eliminated, start the hydraulic pump motor to add oil to the lower oil chamber of the connecting rod hydraulic cylinder and the crusher can continue to work.
(4) Hydraulic friction clutch
The 1200mm×1500mm segment-start simple pendulum type Jaw crusher manufactured in my country is equipped with hydraulic friction clutches at both ends of its eccentric shaft (Figure 6). When the crusher is overloaded, the over-current relay activates the hydraulic pump motor through the delay relay to separate the clutch and cut off the main motor at the same time, thereby playing a safety role.
The belt wheel and flywheel of the crusher are connected with the eccentric shaft by a friction clutch. The friction clutch is controlled by the hydraulic system. When starting, the hydraulic pump motor is first activated, so that the pressure oil enters the right side (ie the pulley side) or the left side (ie the flywheel side) of the plunger through the central through hole of the plunger, and pushes the plunger to compress the spring of the friction plate of the friction clutch. The friction plate is separated to disconnect the eccentric shaft from the belt wheel or flywheel. At this time, the motor can be turned on and drive the pulley to rotate.
Then through the electromagnetic reversing valve, the friction clutch between the pulley and the eccentric shaft is closed, and the eccentric shaft and connecting rod start to move. Subsequently, the friction clutch between the eccentric shaft and the flywheel is closed to make the flywheel rotate. The crusher is started in three stages according to the above sequence.
6. Lubrication system
Small jaw crushers generally use rolling bearings, while large and medium jaw crushers generally use sliding bearings with babbitt alloy bearings. Usually the main bearing and connecting rod head bushes are cooled by circulating water when they are overheated. The friction parts of the crusher are lubricated with thin oil or dry oil. The bearings of the eccentric shaft and the connecting rod head adopt the gear hydraulic pump to press in the thin oil for centralized circulation lubrication. The supporting pads of the movable jaw bearing and the liner seat are regularly pressed into dry oil lubrication by manual dry oil lubrication gun.
The structure of the compound pendulum type jaw crusher (picture 3 above) is similar to that of the simple pendulum type, except that the connecting rod, the rear thrust plate and the movable jaw spindle are reduced, and the mechanism is simpler. Since the moving trajectory of the movable jaw is not a reciprocating swing centered on the moving jaw spindle, but a very complicated trajectory, it is called a compound pendulum jaw crusher. The movable jaw 11 is directly suspended on the eccentric shaft 10 through roller bearings, and the lower part is supported by the thrust plate 5.
When the motor drives the eccentric shaft 10 to rotate through the V-belt pulley 13, the movable jaw makes periodic and complex swings to the fixed jaw. The discharge gap of the compound pendulum jaw crusher is adjusted by an inclined iron adjusting device. Compared with the simple pendulum jaw crusher, the compound pendulum jaw crusher has the advantage of simpler and more compact structure;
The bearings of the movable jaw and the frame adopt rolling bearings, which have low friction, convenient start-up and simple lubrication; in addition, the upper horizontal stroke of the movable jaw is large, which can meet the compression required for ore crushing, and the movable jaw can promote the displacement when moving downwards. Because of the role of ore, its productivity is about 30% higher than that of the simple pendulum type. Since 1980, the compound pendulum type fine crushing jaw crusher series have been developed and produced in China.
The disadvantage of the compound pendulum jaw crusher is that the vertical stroke of the movable jaw is large, which speeds up the wear of the crushing plate, aggravates the over-crushing phenomenon of the product, and increases non-productive energy consumption. In order to overcome the above shortcomings, the Beijing Institute of Metallurgical Equipment Research has successfully developed a new type of energy-saving crusher-JC jaw crusher based on the digestion of foreign “Kue-Ken” jaw crushers (Figure 7) The equipment has the following characteristics.
(1) A frictionless crushing mechanism is adopted. During the crushing process, the jaw plate acts as a pure squeezing force on the material without relative sliding. Therefore, the service life of the jaw plate is 5-10 times longer than that of the compound pendulum jaw crusher.
(2) The crushing cavity adopts a variable tooth angle curve cavity shape, and the full cavity crushing is realized by rationally designing the tooth angle and length of each part of the cavity shape, which improves the passing capacity of the crusher and ensures that the crushing particle size of the crusher is uniform .
(3) A simple and practical multifunctional mechanical, hydraulic and electrical protection system is adopted. When the crusher is overloaded, the mechanical protection safety clutch quickly disengages the main shaft and the pulley of the crusher, causing the crusher to run idly, and at the same time, an alarm is issued. Once the overload is released, it can be quickly reset without replacing any parts. In addition, when an abnormal situation occurs in the crusher (such as failure of the lubrication system, damage to the main components, etc.), the multi-functional protection system can quickly cut off the power supply, stop the crusher, and issue an alarm. This greatly improves the safety and reliability of the crusher.
(4) The adjustment of the discharge opening only needs to adjust the front and rear positions of the fixed jaw, without changing the position of the movable jaw. Therefore, adjustment is very convenient and time-saving, and the geometry and size of the thrust mechanism are always kept stable.
(5) The main moving parts of the crusher, such as front and rear thrust plates, thrust plate spindles, connecting rod eccentric shafts, bearings and spindles are all lubricated with fully enclosed thin oil, and the sealing effect is good. Lubricating oil has the dual functions of lubrication and heat dissipation.
(6) The whole machine adopts welding structure, which is light in weight, good in strength, and easy to manufacture and maintain.
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