Gravity Conveyor Systems

What is a gravity conveyor?

A gravity conveyor is a system that uses gravity or physical force to move items from one location to another. Chutes, skatewheel conveyors, and roller conveyors are all examples of gravity conveyors. These simple machines don’t need electrical power. All it takes is a slope or a push to slide an item from one end to the other.

Heavy-duty gravity roller conveyors are usually made of steel or aluminum. There are also composite and PVC options to move lighter loads. It’s important to choose a material strong enough to handle the weight of the items you plan to move.

Benefits of gravity conveyors

Why choose a gravity conveyor over other types of conveyor systems? Here are a few benefits to consider.

• Easy to  maintain. You won’t need a mechanic to keep your system running. Even a heavy-duty gravity roller conveyor has only three parts  – a frame, supports, and rollers.
• Low-cost way to increase your handling capacity. Gravity rollers move items fast and with little effort. This frees up worker time and energy. They’re an inexpensive way to boost productivity and throughput.
• Suitable for a variety of uses. These machines can be applied in almost any industry. Common uses include shipping and receiving, order fulfillment, and kitting or light assembly. Roller conveyors can branch off other lines or merge them together. Curved sections even let gravity conveyors go around corners.
• No electric parts to wear out. The non-powered nature of a gravity conveyor means no noise or heat from a running motor. There are no motorized or electrical parts to wear out or become obsolete. It’s a low-maintenance solution that won’t add to your facility’s electrical bill.

How do gravity conveyors work?

The simple answer is in the name. Gravity conveyors are installed on an incline. The force of gravity carries items from the head of the conveyor down the line. It might take a gentle push to get items started when the slope is slight.

In some applications, like order fulfillment, the conveyor is installed on a flat grade. A worker’s push provides the force needed to put the package in motion. This keeps the order from sliding past a workstation that wasn’t ready for it yet.

Heavy-duty gravity roller conveyors consist of carefully spaced rollers in a steel frame. The rollers have individual spring-loaded axles. They are mounted on a round or hexagonal shaft and supported by oil-sealed bearings. Each roller shaft is held in the frame by springs or retaining pins. Damaged rollers are easy to remove and replace without affecting their neighbors.

How many rollers you need depends on the size of the items you plan to move. Consider the smallest parcel that might travel down the line. To keep the line moving smoothly, there should never be fewer than three rollers under a load at any time. Otherwise, packages get stuck in the gap between rollers.

Heavy-duty roller conveyors are ideal for large containers difficult to move by forklift. Containers with uneven, open, or rimmed bottoms – like wire bins, wooden crates, or barrels – move easily down a roller line.

As flexible as gravity conveyors are, they’re not ideal in every situation. If you need to stop items from moving down a powered conveyor you simply cut the power. But there’s no turning off gravity. The downside to a non-powered conveyor is the inability to control movement.

If you’re already using a powered system, adding roller conveyors can make it more effective. A roller line is an inexpensive way to connect powered lines. Rollers at the end of a powered conveyor can slow fast-moving loads to a safe speed before they reach human workers.

Installing a gravity roller conveyor

Our expert installers can set up your gravity roller conveyor in any part of your facility. Their simple construction makes these devices flexible and scalable so we can work within the constraints of your facility’s footprint.

If you should modify your layout or add a new product line, no problem. Your heavy-duty gravity roller conveyor has only three parts: the rollers that move the product, the frame that contains the rollers, and the supports that hold the whole thing up. We can easily take apart your existing conveyor to reconfigure it or move it to a new part of the building.

Temporary supports stand on the floor like a piece of furniture. These make the conveyor easy to move. For very heavy applications, you may want to fix the feet to the facility floor.

Move items safely

• Watch out for possible pinch points between frame sections. Workers can get caught between sections or between the conveyor and loads. Prevent injuries by reducing these pinch points.
• Train workers to never stand or lean on a gravity roller conveyor system. The low-friction surface will roll out from under them and cause them to fall.
• Consult an experienced professional about the appropriate grade for your gravity conveyor’s incline. A roller conveyor does not have to be steep to move products quickly. A 5-degree slope might be great for light loads, but heavy loads start out fast and then accelerate. If you don’t address this by gradually leveling out the grade, the parcel could fly off the end of the line at dangerous speeds. At the same time, a grade that’s not steep enough will slow down your throughput. Workers will have to walk to stalled products and give them a push to get them going again.

Our materials handling experts can find the incline where products move at a speed that is “just right.” We consider the layout of your facility, the design of your conveyor, and the size and weight of your loads. We may suggest adding special speed-control rollers. These rollers act as a brake to slow down fast-moving items.

Choosing the best gravity roller conveyor

Once you decide to add a gravity conveyor to your workplace it’s time to consider the features you will need. As simple as these conveyors are, there are still decisions to make. We take the guesswork out of the process by listening to your needs and providing expert recommendations rooted in more than 60 years’ materials handling experience.

Your expert consultant will start with the dimensions of your products. For best results, your frame should provide at least one inch of clearance on each side of a load. You can add side guides to reduce the risk of items sliding sideways off the gravity conveyor.

Next, we’ll consider the weight of your loads. We’ll make sure the conveyor you choose is sturdy enough to handle the heaviest package you might send down the line. Even if most of the loads will be lighter, we want you to be prepared for the odd heavy item. If your loads are mixed weight, be careful with the pitch of your gravity conveyor’s incline. Your consultant might recommend speed-control rollers to keep heavy items from moving too fast. A motorized conveyor may be a better choice for facilities where heavy loads are the norm.

A gravity conveyor installed at the wrong pitch can be disastrous - and dangerous. Rely on your consultant’s expertise to keep your people and your products safe.

What goes into your gravity conveyor

Rollers. Standard roller sizes are 1.5-inch, 1.9-inch, 2.5-inch, and 3.5-inch diameters.

• Light-duty: We use 1.5-inch rollers for loads less than 100 pounds
• Medium-duty: We recommend 1.9-inch rollers in a medium-duty frame for loads between 100 and 250 pounds
• Heavy-duty: We use 2.5-inch or 3.5-inch rollers in a heavy-duty frame for very heavy loads

Larger rollers can carry more weight, but they are more expensive. Smaller parcels need rollers spaced closer together. Our recommendation will ensure every load rests on at least three rollers at a time.

Frame. Steel frames are the strongest and most durable. If a lightweight solution is important, aluminum can be substituted. Your consultant will recommend the material strong enough to support your heaviest loads. Heavy-duty loads need heavy-duty gravity roller conveyors.

Most frames come in 5-foot or 10-foot sections that connect to customize the length of your conveyor. Curved sections can carry items around obstacles. They can also be used to branch or merge lines.

If you are using gravity to move heavy loads, plan on extra length. A flat stretch at the end of the incline gives items time to slow down before they come off the line.

Frames are available with and without side guides. We recommend side guides if your packages are small, light, or may slide sideways as they move down the line.

Supports. Your supports are made of the same material as your frame. We typically  position support legs every 8 feet along the length of the conveyor. If you’re moving very heavy items, your consultant might plan to position supports closer together.

Working with our experts ensures all pieces of your gravity conveyor – rollers, frame, and supports – are rated to handle the heaviest loads they might encounter.

We help you build solutions that last for years

A heavy-duty gravity roller conveyor is a workhorse that will benefit your facility for years. To get the full value from your purchase, take time at the beginning to set yourself up for success. Miscalculating the size, type, or layout you need will yield disappointing results.

Luckily, you don’t have to make this decision alone. ISS Material Handling has the top team in the nation for gravity conveyor systems. We’ve been helping businesses design custom gravity conveyor solutions since 1961. Reach out for answers to all your questions and insights into questions you haven’t thought to ask.