About “Curved” modular belt conveyor / Belt conveyor -5

The following movie is about trial run of a curved modular belt conveyor.Conveyor that can manage both of straight path and curved path with one belt is only modular belt conveyor.

About curved modular belt conveyor

1. About dispersion of force at the curved section of curved belts.
In case of that one belt deals with both of curved path and straight path, which is one of the main characteristics of this conveyor, structure of the conveyor has to be built to adjust that purpose. To find the most effective structure, we believe that it should be understood what kind of force is reacting to the curved section and to each part around the curve.
About the curved belt, large amount of load is applied onto inner part of the curve. The loads are attracted to center of the curve. At the curve section, the belt moves forward along with the rails attached to inner parts of the curve anytime. The rails at the inner parts of curved section are the parts which is worn a lot. The load becomes maximum at the parts where a curve ends and turns to straight, and rails are worn the most at this part. It is the same for returning side of the belt as well.
Pulling force, tension in other words, for the belt is the biggest at outer side of the curved section. Therefore, for the condition of belt selection, maximum allowable tension level has to be considered based on the tension at outer side of the curve section which the most loaded. However, it seems the load or tension is actually dispersed into whole parts of belts because the modular belt is made by plastics and plastics has elasticity as its characteristics. Also, there is limitation in the number of curves that one modular belt can take care of. A belt needs large tension when the number of curves is a lot. Normally, the number of curves that one belt can deal with is two at the maximum. However, some belts can have only one curve and it is because of lack of tension in many cases.

2. Trouble in curved sections
The troubles which can be observed in curved section may be the following two.
1) Belt is lifted up
2) Inner part of belt gets over and derails.
For the solution of 1), belt with tags shaping like hooks is used to prevent the lifting. Rails for belts to run along the tag are built on flame side. However, we have never experience the lifting before.
About 2), the structures of rail have to be considered to prevent the getting over. Actually, we have experienced a case that no problem was found during trial run but the problem was found in returning side in which is difficult to be distinguished. Inner side of the curved section tends to be more loaded than we estimate. Especially, attention need to be payed when distance of straight path before the curved section called tailed side (back side) is short. The above is based on our company’s experience.

3. In case that machine length is short before and after the curved section.
Because of the condition of setting place, machine length of the straight section often becomes shorter than belt manufacturer recommends. In case that machine length for the straight section is short, there tend to be problems on gear meshing between sprocket and belts. Some noise may be heard because of that. Also, it can be observed that there are some unexpected effects to curved section as well. Especially, it has to be careful about the getting over of belt from rail at inner parts of curved section for returning side.

1) In case that machine length is short in tail section which is driven side (back side)
There tend to be problems in gear meshing of sprockets at outer side from the curving direction in the curved section. However, it seems not necessary to worry about it so much. If it is expected to be solved completely to 100%, meshing condition between belts and sprocket need to be adjusted by using tail shafts as a tensioner. However, the effect on the adjustment is still unknown.

2) In case that machine length is short in head section which is driving side (front side)
This structure should be avoided as much as possible. Modular belt can move forwards by being hooked on sprockets of rotating shaft at the driving side. It may cause troubles if machine length is short in head section since meshed condition becomes not appropriate. The phenomenon is the same as the tail section and gear meshing of sprockets becomes not appropriate at outer side from the curving direction in the curved section. Since it is the most loaded part, noise becomes large, and belts or sprocket are worn a lot. As the solution, half to the driving section is used as sprocket and the other half is used as roller. Sprockets are attached only at the inner half of the curve in which meshed condition is good, and no sprocket is attached at the other half and roller are used in stead.In this case, sprockets need to be attached closely each other.

Lifting up prevention
At the curved section, there is possibility that belts are lifted up since they are not evenly loaded and tensioned. Therefore, tags to prevent the lift up are normally attached under the belt and lift up can be prevented with them.However, we have never experienced the lift up before. We always attached the tags just in case.Also, lift up at the returning side has to be concerned.It is rarely paid attention for the returning side though, lift up prevention is necessary as well as carrier side. Normally, rails to hold the belts are attached.


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