Article: Building an Affordable Zero Pressure Accumulation Conveyor

Roller conveyors have probably been around since era of the caveman. Whether made of stone, wood, or metal; roller conveyors all followed in one form or another as a relatively simple and similar means of locomotion. Throughout history, their dominant guiding economic principle has been to minimize the number of rotating power sources since these are typically the most expensive and complex single item associated with the conveyor design.

Even these days, a typical roller conveyor section follows the same basic layout. It uses a large multi-phase electric motor attached to a gearbox which, in turn, rotates a shaft that turns a sprocket that moves a chain or pulley / belt combination. The combo makes contact with all of the rollers in the conveyor section, creating basic transportation for items on the conveyor.

Most conveyor system applications require that the conveyor accumulate items on its rollers; one behind the other with minimal gaps until the discharge of the system needs to stop for a while. Then it re-starts when the discharge is ready to accept items again. And most people want this done without their products plowing into one another and without the conveyor rollers turning and grinding underneath, causing damage while the conveyor is accumulating.

Enter zero pressure accumulation, known as the ‘Holy Grail' of roller conveyor function. With this technique, products queue up in an orderly fashion where the rollers stop driving when you want to accumulate and start to turn when you are done. In order to get the typical conventional roller conveyor work as a zero pressure accumulator usually requires solenoid valves, compressed air utility hook up and a motorized drive train. Conveyor equipment manufacturers have all developed their own versions of the zero pressure accumulation conveyor over the years and most have perfected the technology to where it is mature and predictable.

Up to now, numbers of some small and medium sized businesses that could benefit zero pressure accumulation functionality have shied away from purchasing a conventional conveyor system solution. Not necessarily because of the raw cost of the equipment; but because of the lengthy duration of implementation and associated cost, on-going electric and compressed air utility usage, and skilled labor required for upkeep maintenance. And with business patterns evolving at ever faster rates, owners worry about investing in a conveyor system they need for today's operations becoming obsolete in a short amount of time.

Newer technologies are coming into play to help business combat these issues.

Individual conveyor rollers that utilize their own internal motors, for example, have been around for a few years but are just now being widely considered as viable motive power for conveying systems. Although a single motorized conveyor roller cannot physically perform the same work as one of its large multi-phase electric gear motor counterparts in a conventional design; with the right design concept, it doesn't have to.

Motorized Roller Conveyor sections are, generically, sections that utilize a single motorized conveyor roller that is only mechanically linked with enough free-turning (gravity type) rollers to constitute a controllable zone not much longer than the item to be conveyed. With the proper control system strategy, individual motorized roller conveyor zones can be easily assembled to make zero pressure accumulation conveyor sub systems, particularly for traditional carton type handling applications.

Coming up with the right design concept is key.

Motorized roller conveyor sections with the proper control system can be a complete success. The conveyor equipment industry continues to provide the mechanical building blocks and tools to move materials, but the control system is what makes it go, slow down, speed up, and stop when it is supposed to.

The proper control system for motorized roller conveyors is distributed within each conveyor section because each section only needs to know what is going on in front of it and only needs to inform the section behind it what it is doing. Just now there are new control strategies on the market that allow data and information handling within the control system for motorized roller conveyor. This exciting new scheme opens the door to utilize motorized roller conveyor solutions -and all of the inherent design benefits - for more intelligent functions like product tracking and sorting that until now have been the sole province of conventional conveyor systems with custom control systems.

The proper control system for motorized roller conveyors is distributed within each conveyor section because each section only needs to know what is going on in front of it and only needs to inform the section behind it what it is doing. Just now there are new control strategies on the market that allow data and information handling within the control system for motorized roller conveyor. This exciting new scheme opens the door to utilize motorized roller conveyor solutions -and all of the inherent design benefits - for more intelligent functions like product tracking and sorting that until now have been the sole province of conventional conveyor systems with custom control systems.

Author Pat Knapke is director of engineering for Insight Automation, an Erlanger, Kentucky-based firm which designs and distributes control system solutions for materials handling applications. To reach him visit our Contact us page. Insight Automation is also the exclusive North American provider for PulseRoller Motorized Drive Roller. For more information about PulseRoller, visit Pulse Roller®