1. Turn on the belt drive
Open belt drives are used with shafts arranged in parallel and rotating in the same direction. In this case, the driver will pull the seat belt from one side and transfer it to the other side.
Therefore, the tension in the lower belt will be higher than the upper belt. The lower belt is called the tight-fitting side belt, and the upper belt is called the slack side belt.
When the distance between the shafts is too far, the bottom of the belt should be the tight side, and the bottom of the belt should be the slack side. In this way, when the upper side becomes a blunt side, it will relax due to its own weight, thereby increasing the arc of contact.
2. Closed or cross belt drive
Cross or twist belt drives are used with rotating shafts in parallel and opposite directions. In this case, the driver pulls the belt from one side and then transports it to the other side.
Therefore, the tension at the bottom of the belt will be greater than the tension at the top of the belt. Because of the high tension, the belt is called the tightened side, and because of the low tension, the belt is called the slack side.
When two parallel shafts must rotate in opposite directions, this type of belt drive uses a belt. At the junction where the belts cross, the belt rubs against itself and wears. To avoid excessive wear, the shafts should maintain a maximum distance between them and run at extremely low speeds.
After a little consideration, you will find that the belts rub against each other at the intersection, which will cause excessive wear. To avoid this, the maximum distance that the shaft must be placed is 20 B, where B is the width of the belt, and the belt speed must be less than 15 m/s.
3. Quickly loose tapered pulley
This type of belt drive will be used when it is necessary to start or stop a driven shaft or machine shaft without disturbing the drive shaft. The pulley locked on the machine shaft is called a fast pulley, and its running speed is the same as the speed of the machine shaft.
The loose pulley slides freely on the machine shaft and cannot transmit any power. When the driven shaft needs to be stopped, the belt is pushed onto the loose pulley through a sliding rod with a belt fork.
4. Stepped cone wheel drive
When the main shaft or drive shaft is moving at a constant speed, a stepper or tapered pulley drive can be used to change the speed of the driven shaft. This is achieved by moving the belt from one part of the step to another.
The stepped cone pulley is an integral casting, which is composed of three or different numbers of pulleys of different sizes adjacent to each other, as shown in Figure 2. A set of driven cone wheels are placed upside down on the drive shaft. The endless belt will be wound on a pair of pulleys.
By moving the belt from one pair of pulleys to another pair of pulleys, the speed of the driven shaft can be changed. The diameter of the driving and operating pulleys should be such that the same belt can also run when transferred on different pairs of pulleys.
5. Horse racing pulley drive.
In an open belt drive device, if the center distance is very small, or the driven pulley is too small, the contact arc between the belt and the driven pulley will be very small, which will reduce the tension in the belt, or if the belt requires stress that cannot pass other The method is obtained, as shown in Figure 3, placing a slow pulley (called a "horse race pulley") on the slack side of the belt.
This increases the contact arc and therefore the stress, which leads to an increase in power transmission.
6. Quarter turn belt drive
Quarter-turn belt drives are also called right-angle belt drives. It is used with shafts arranged at right angles and rotating in a specific direction. To prevent the belt from leaving the pulley, the width of the pulley surface must be greater than or equal to 1.4 b, where b is the width of the belt. If a pulley cannot be set or a reversible speed is required, a quarter-turn belt drive with guide pulley can be used.
7. Composite belt drive
When power is transmitted from one shaft to another through multiple shafts, a composite belt drive will be used.
Factors to consider before using belt drive:
The shaft must be lined correctly to ensure uniform tension in the belt section.
The pulleys should not be too close to make the arc of contact on the small pulleys as large as possible.
The distance between the pulleys should not be too far, so as not to cause heavy objects on the belt shaft, thereby increasing the friction load on the bearing.
A long belt rotates from side to side, causing the belt to exit the pulley, creating curved spots on the belt.
The tight side of the belt should be at the bottom, so any slack on the loose side will increase the contact arc on the pulley.
In order for the flat belt to achieve good results, the maximum distance between the shafts should not exceed 10 m, and the minimum distance should not be less than 3.5 times the diameter of the larger pulley.
