The belt of Z type bucket elevator is supported by the upper and lower rollers, and the upper rollers are active rollers, which are fixed on the frame of the upper fuselage and cannot be moved arbitrarily; The lower rollers are driven rollers, and the bearing seat of the lower rollers are placed in the slide of the lower frame, and the adjusting screw is installed to facilitate the balance weight of the tension device can be adjusted and connected with the lower roller when the belt deviation and so as to make the belt tension.
When the rollers rotate, the belt rotates with the roller by the friction force with roller. At this moment, the friction force becomes the main active force of the belt. Since the upper rollers are active rollers, the lower rollers can slide in the slide according to the stress of the upper roller and the belt. The first is the weight of the belt and the materials on the belt and the downward force of gravity, which causes the bearing reaction of roller to the belt. And then is the friction force between the rollers and the belt along the circumference. The friction force becomes the main force for the belt to move around the roller and generate the turning torque. When the roller is horizontal, the gravity and the bearing reaction are equal and in opposite directions. The two forces balance each other, and no component force is generated on the belt. The belt will run normally on the roller and will not deviate. However, when the drum is tilted, gravity and bearing reaction are not in balance, and the bearing reaction will produce a force that makes the belt move to the side of the roller. When the force is greater than the axial friction force between the belt and the roller, the belt will slide on the roller, that is the belt deviation.

The analysis and treatment of the belt deviation of Z type bucket elevator
1.The rollers are not in the horizontal position. From the force analysis of the belt, it can be drawn that the upper and lower rollers must be horizontal, otherwise the belt by the elastic force will produce a component force, resulting in belt deviation. And the lower rollers can slide in the slide, so the installation must ensure the levelness of the upper rollers firstly.
2.The installation center line is not straight.
Because the belt is supported by the upper and lower rollers, there are certain requirements for the relative position of the upper and lower rollers, otherwise the belt will be distorted, while the upper and lower rollers are placed on the frame, the perpendicularity and distortion of frame must meet the requirements. After ensuring the perpendicularity and torsion resistance of frame, it is necessary to measure the torsion resistance of the upper and lower rollers and the coincidence of the center line. Due to the certain torsion resistance of the frame, the measurement must be based on the roller itself in stead of the frame, otherwise it will cause error increase multiply.
3.The belt itself is bent or the joint is not straight.
The belt bolt hole nails are crooked or the belt cut and bandwidth are not right angles, which will make the tension force of the belt is uneven. When running, the place where the joint turns will deviation. For this case, the belt can be cut straightly and the screw hole can be punched again.
Above three kinds of reasons all need to pay close attention to when installing. When the belt deviation is not large, it can also be rectifies by adjusting the adjusting screw of the lower roller, but this causes uneven stress on the belt, the belt is easy to be worn and damaged, shortening the service life of the belt. During operation, it is also necessary to pay attention to that if the surface of the roller is bonded with urea, which makes the roller a cone surface, the belt will also deviate to one side, which requires regular cleaning of the roller.
Through the above analysis, it can be seen that the main reason for the belt deviation of Z type bucket elevator is installation. After the frame is adjusted when installing, the first thing to do is to ensure the horizontal of the upper roller, so that the elastic force received by the belt is vertical upward, and the belt has no force to both sides of the roller. And then, adjusting the torsion resistance of the upper and lower rollers and the coincidence degree of the center line. After qualified adjustment, fixing the slide of the bearing seat of the lower rollers, so as to ensure that the adjusted upper and lower rollers will not distort and the belt will not deviate.