What do you know about our conveyor pulleys? Stokman produces various pulleys for different functions and positions in the conveyor system. In this blog we will tell you about our 5 types of pulleys: the drive pulley, return pulley, tension pulley, deflection pulley and snub pulley. We tell more about the function and properties of these pulleys. Interested? Read more!
In a previous article we already discussed the drive pulley. It is the pulley that drives the conveyor belt. The pulley is driven hydraulically or electrically and the friction between the body of the driving pulley and the conveyor belt causes the belt to move. This friction is an essential functionality of the conveyor belt system, which is why Stokman drive pulleys are fitted with rubber coatings or a combination of rubber and ceramic to increase the friction and remove any water and dirt.
A drive pulley is always single-sided or double-sided, meaning it has one or two drives. Depending on the size of the conveyor system, one or more drive pulleys are used at different positions in the system.
The snub pulley serves to increase the length of the tensioned conveyor belt in order to increase the contact and friction surface between drive pulley and belt. If necessary, this pulley is placed directly behind the drive pulley, in the lower part of the system.
The friction surface has a large effect on the performance of the system because the drive depends on the friction between pulley and belt. In addition, the greater the friction surface between drive pulley and belt, the more grip the pulley has on the belt which will stop the belt from slipping. The snub pulley is therefore particularly suitable for conveyor systems that require very high drive power or systems in highly contaminated environments.
The return pulley is placed where the belt is to change its direction of rotation by 180°. This will often be at the tail end of the conveyor belt. The return pulley often has the same diameter and bearing as the drive pulley. Like all other non-driven pulleys, it can be provided with either external or internal bearings.
A tension pulley is actually a return pulley which is used to tension the conveyor belt. Tensioning the belt leads to high forces on the pulley. Therefore, the tension pulley is often a solid type of pulley.
The tension pulley can also be used as a return pulley at the tail of the belt, and as a tension pulley at any other position in the lower part of the belt. In this case, the preferred position of the tension pulley is as close as possible to the drive pulley where the tensioning forces required for the belt are lowest.
The deflection pulley is used in the lower part in places where the belt has to make a deflection of up to 90°, for example when the belt has to be guided through a structure.
The design of a deflection pulley is similar to a return pulley, but the diameter is often smaller. The pulley design is often lighter, as the smaller length of the tensioned conveyor belt causes less tension.
The correct installation of all pulleys in the conveyor system is essential for their functionality. Part of this is the setup and alignment of the pulleys. A correct set-up and alignment of the pulleys will ensure a perfectly straight conveyor belt and prevent a belt from running sideways off the pulley.
To prevent skewing conveyor belts, pulleys can be equipped with so-called crownings. Because of the crowning, the centre diameter of the pulley is slightly larger than the side diameter, so the circumferential velocity in the centre of the pulley is slightly higher. This causes the belt to tend to move laterally toward that highest point. This is called the centrifugal force. This effect of crowning automatically keeps the belt running in the center of the pulley and prevents the conveyor belt from skewing.
Are you familiar with the quality of Stokman conveyor pulleys and rollers? We are happy to tell you more about our products. Please, contact us. We can tell you more about the possibilities and design of our rollers and pulleys.