What are the main features of the pulley?

 　 PulleyWhat are the main features?

Pulley is a mechanical transmission that relies on friction to transmit motion and power. Pulleys are widely used. I don't know if you know its characteristics and advantages and disadvantages. Next, let's look at the wheels.

What are the main features of the pulley?

The belt has good elasticity, which can reduce the impact and vibration during work, and the movement is stable and no noise. When the load is too large, the belt slips on the wheels, which can prevent damage to other parts and play a safety protection role. The belt is the middle part. It can select the length within a certain range according to the needs to adapt to the working conditions with large center distance. Simple structure, easy manufacture, convenient installation and maintenance, low cost.

What are the disadvantages of the pulley?

1. It is driven by friction and cannot transmit high power. Sliding into the transmission does not guarantee an accurate transmission ratio.

2. Sliding loss: When the belt is working, the tension difference on both sides of the pulley and the corresponding deformation difference form elastic sliding, resulting in speed loss between the pulley and the driven pulley. Elastic slip is related to load, speed, pulley diameter and belt structure. Some pulleys have geometric slip. Overload will cause slippage, make the belt movement in an unstable state, drop efficiency sharply, increase wear, and seriously affect the life of the belt.

3. Hysteresis loss: The belt will expand and contract repeatedly during operation, especially the winding on the pulley will cause belt friction and cause power loss.

4. Air resistance is: When driving at high speed, the wind resistance in motion will cause torque loss, and the loss value is proportional to the square of the speed. Therefore, when designing high-speed pulleys, the surface area of the belt should be small, try to use thick and narrow belts, the surface of the spokes of the pulley should be smooth, or use spoke plates to reduce wind resistance.

Classification of pulley

According to different uses, pulleys can be divided into general industrial belts, automobile belts, agricultural machinery belts and household appliance belts. Friction transmission belts are divided into flat belts, V belts (also known as V belts) and special belts (V-ribbed belts and synchronous belts) according to their cross-sectional shapes.

The stresses on the pulleys during operation are as follows:

1. Stress caused by tight edge and loose edge tension;

2. The bending stress caused by the bending of the transmission belt.

How to install the pulley

1. Under normal circumstances, try not to tighten the pulley when installing it. If it is necessary to tension the belt, make sure that the edge of the pulley or the installation tool will not damage the wedge teeth and ropes of the belt.

2. Pulley correction requirements: control the deflection angle within 0.25mm, or 2.5mm/500mm (center distance).

3. Due to the pulley andPulleyThere are dimensional tolerances. It is recommended to measure the tension or frequency of the belt when installing each belt, and control the tension or frequency within the specified range by adjusting the distance.

Cut three samples with a length of 250 mm from one PJ V-ribbed belt, and mark a marking line with a spacing of 100mm at the middle position of the PJ V-ribbed belt. When more than three samples cannot be taken from one PJ V-ribbed belt, samples can be cut from the same batch of PJ V-ribbed belt, but must be indicated in the report. 7.4.2 High temperature resistance test method
Place the sample at 100 ℃ ± 2 ℃ for 96 h ± 1 h and then take it out. After standing at laboratory temperature for more than 2h, bend it along a cylinder with a diameter of 20 mm at a contact angle of at least 90 °.