For logistics and material-handling applications, chain engineered for accumulating discrete pieces of product is efficient and durable.
By Gerhard Hartinger • Key Account Manager | iwis Drive Systems
Accumulation chains convey, collect, and separate discrete components. The chains work off electric motors that engage and drive parallel conveyor trains (sometimes called chain strands) on the conveyor edges. The chains run continuously to take conveyed components to set points. At the same time, track rollers support the chain. This is different from traditional drag-chain conveyors that have no rollers.
When pieces of product reach set points, either lift pads, pneumatic pushers, bumpers, conveyor end modules, or other actuators go into action to lift or disengage product from the accumulation conveyor below—and hold, redirect or reorient them for the next production task.
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Accumulation-chain features
Some accumulation chains have transport or accumulation rollers fitted between the chain links. It’s upon these rollers that conveyed products ride.
Accumulation chains can also have low-friction rollers that make chain operation more efficient (for better overall conveying efficiency). Low-friction rollers allow easy positioning of transported material at any point along the transport path—and remove the need to start and stop the chain, which can jostle products into incorrect orientations (or agitate their contents).
Accumulation chain can come with offset accumulation rollers to spread the load distribution. Maintenance-free accumulation chains can also have:
• nickel-plated plates and pins for lubricant-free operation
• covers with protection for fingers and small parts (to boost machine and personal safety)
• side-bow accumulation setups with offset accumulation rollers for conveying systems having extremely small-bend radii.
Higher efficiency through low-friction rollers
Accumulation chains having idler rollers on both sides serve two purposes. Idler rollers engage with the sprocket teeth to transmit power. The idler rollers also support the chain in the profile.
In some cases, slightly protruding bushes in the inner link prevent contact corrosion between the inner link and outer plate. Some accumulation chains also have low-friction sintered metal rollers that provide consistent smooth running conditions not slowed by lubricant adhesion. These low-friction rollers increase the chain efficiency by 30% to decrease motor capacity thanks to lower coefficients of friction—or increased potential conveyor length due to reduced forces.
Offset accumulation rollers for load distribution
Note that many standard accumulation chains have a wide roller on every other pin. In contrast, versions with offset accumulation rollers have transport rollers on every pin, so each works as a load-bearing subcomponent. That means twice as many rollers carry load. Ultimately, this setup reduces wear and strain on the chain guide. The rollers’ offset arrangement also maximizes load distribution and supports the load better (for smoother product advancement). More specifically, it reduces localized load on the chain guides by up to 50% so even plastic guides can convey up to twice the normal load.
Maintenance-free and covered accumulation chain
Chain with nickel-plated plates and pins and low-friction sintered metal rollers are the main features of maintenance-free accumulation chain. These components negate the need for lubrication and further reduce maintenance costs while helping chain resist wear under extreme running conditions. These chains are common in applications where lubrication is impossible or unacceptable due to risk of contamination—for example, when chain conveys food or medical products, electronics, glass or ceramics.
For improved safety, accumulation chains with safety covers shield the space between one transport roller and the next. This prevents the ingress of small parts that jam the rollers or chain links. Plus the covers prevent deliberate or accidental insertion of fingers while the conveyor is operating; that boosts operator safety. Matched to the chain type and required bending radius, protector shields (either jointed or unjointed) totally cover the space between the transport rollers. Plastic clips permanently fit to chain inner links. There is no interference with conveyed goods, workpiece carriers or transport rollers.
Chain versions also exist for side-flexing conveyor applications. Here, side-bow accumulation chains with offset accumulation rollers work in side-flexing conveying systems with tight bend radii down to 350 mm. The roller arrangement provides multiple contact points, which reduces pressure on product through the bend. This can help to prevent marking or damage and also reduces wear on the system.
Case in point: German integrator Schnaithmann makes Modular Transfer Systems (MTS) that use accumulator chains. By combining MTSs with other systems and integrating commercially available parts (such as linear drives, grippers, robotics, processing components, stoppers, positioning devices and turning stations) the company customizes the MTSs. The modules excel in:
• Assembly systems for transmissions conveying to connect machine tools in sequence
• Transportation lines for domestic appliances, hardware and industrial items
• Production cells with integrated robots and processing centers
MTSs handle discrete products to 150 kg, and one version, the BS 11, works for loads to 1,500 N/m. The MTSs use 0.5-in. accumulation chain from iwis to transport workpiece carriers. Hardened-steel accumulation rollers on the chains extend service life and sintered rollers reduce friction (to keep the conveying surface clean and dry).
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I would like to get a rep here to discuss a multi-directional drive chain application on one of our automatic plating lines. This chain will need to go in a circle and then move up and down within the circle.