Gravity / Idler Rollers
Materials - Carbon Steel / Stainless Steel
Bearing Housing - Polymide Molded
Sizes - Roller Dia. & Shaft combination as per standard table below
Length - made to order
Load Capacity - reference table below
Carbon steel - Zinc Plated, Chrome plated
SS - Mirror Polished
Coatings - PU Coated, PVC Sleeve
Working Temp - Room Temp.
Standard Sizes available in Type120 Gravity Rollers
This roller construction is similar to Interroll make Series 1700 universal conveyor.
Load Capacity of Conveyor Rollers
The load capacity of conveyor Rollers is as mentioned below. The column headings of the table are lengths in mm. The row headings are roller diameters. It can be seen that the roller capacities of the rollers are in Kgs. The "x" marked shows that, lengths are not recomended that diameter. Want to understand more about load capacity ... read here
*The load capacities are only for reference and indicative, as they are subjected to component material and other working conditions
The roller conveyor designers and users of gravity conveyors need to understand that the load-carrying capacity of rollers is distributive and not concentric. It means that the capacity of the roller is not pointed load capacity.
Load-carrying capacity is inversely proportional to the length of the rollers. As the length of the roller increases, the roller capacity decreases. Accordingly, high-width products need more diameter.
5 types of surface Treatments Or Coatings are available for conveyor rollers
Different types of roller coatings are available to protect the rollers from corrosion.
Below coatings are available for Carbon Steel or MS Rollers.
Zinc Plating is the most used roller coating because it is the fastest and economical process.
Chrome plating is an expensive and time-consuming process.
Powder Coating is also a process that is suitable for gravity rollers.
Polyurethane or PU Coating avoids metal to metal friction. If you are carrying a metallic machined component on a metal roller, the probability of component damage is very high. PU coating prevents this. PU coating protects the roller from corrosion, weathering, and abrasion.
PVC Sleeve is a low-cost alternative to PU coating. PVC sleeves of 1mm or 2mm thickness are applied on the rollers to avoid corrosion and abrasion.
How Gravity Rollers are mounted in the frame?
There are various options for mounting the rollers
Spring-loaded Shaft - The shaft is spring-loaded. While mounting the roller, the shaft is to be pressed and released in the mounting hole. Designers should take note while the design of the roller conveyor that sufficient free distance should be kept between the frames. Lack of the extra distance between the roller mounting frames will make the roller assembly difficult.
Female Tap - The shaft has a female tap in the shaft. and is bolted on the roller mounting frame. When a large number of rollers are to be installed it is very time-consuming work. Pneumatic or electric nut runners are useful in such cases.
Female Tap + Across Flat - Across flat is used most of the time to apply the spanner. As mentioned above, it is laborious work.
Across Flat - The roller shaft has across flat and it is placed in the slot of the roller mounting frame. An "L" frame is used to hold the rollers in place in the frame. This method gives the fastest result.
A conveyor manufacturer has a preset mindset and accordingly the roller mounting option is selected. Across flat option is for applying spanner to the shaft. It is easier to bolt when you can hold the shaft with a spanner. The spanner slot is also important during maintenance. Sometimes due to oil & dirt, the bolt does not open easily. You need to hold the shaft. Across flat is important in such cases.
What are Gravity Roller Conveyor Design Calculations?
Designers make calculations to ensure that the rollers are suitable for the product given.
The product properties should be studied carefully. Before you start the design you should have complete information about the product to be handled and what is the conveyor expected to do.
The shape of the product.
The base of the product should be even at the bottom. Protrusions and projects at the bottom will make the bottom surface uneven. The even surface products are suitable to run on roller conveyors. A refrigerator is not even at the bottom. It has got leveling pads at the bottom. The leveling pads will enter the gap between rollers. So it is not the right product to run on roller conveyors.
Weight of the product.
The product should have evenly distributed weight in it. It might happen sometimes that the product may have unevenly distributed weight inside it. It is called the eccentric weight. In such cases the product behavior is different.
Imagine a box that is half full of soap bars as shown in the image below. In such a case, the center of gravity of the box may change during the travel of the box on the roller conveyor. This is because the box portion ( with weight) will try to enter the gap between the rollers ( since weight is more there). It will result in the shifting and falling of soap bars into the empty space.
To avoid this, a smaller roller pitch is required, so the box may not enter the gap between rollers.
Limitation of gravity rollers & conveyors.
It is challenging to handle higher weights on gravity conveyors. Higher loads get higher speeds with little inclination, which may result in accidental damages at the working place. Proper safety arrangements and speed control rollers or brake rollers reduce unexpected occurrences drastically.
Safety arrangements such as stoppers at unloading ends are a must. Speed control or brake rollers reduce the speed of the rollers. Installation of the speed control rollers is well before the unloading end so that there is sufficient time for the product to stop. There are two types of speed control rollers. Internal speed control rollers, which are inside the roller. Outer speed control roller installation is between 2 rollers. Speed Control Rollers are a must for heavy-duty pallet roller conveyors since they work like gravity roller conveyor brakes.
Similar to higher weights, it is challenging to carry lighter loads. It is because the lighter weights do not slide easily on the rollers, as there is no or very little gravitational force generated.
In such cases, ultra-free rollers are required. Apart from this, a higher inclination is needed to move the product.
Uncontrolled speeds - The speeds may be slow or fast. You cannot stop the product intermittently and then release it. It is difficult to pass the product at the same speed along full gravity conveyor length.
Length Limitations - The gravity conveyor requires a slope to enable the product to slide from top height to lower height. Due to this, for lower product weights and higher inclinations, longer lengths are not suitable.
In spite of all the limitations, gravity roller conveyors are the most widely used conveyors all over the world.
Easy to Use
Easy to maintain
No Power Required.
Easy to move
No Training is required.
Easy for Installation