Zero Pressure Accumulation Conveyors - Accumulation Conveyor

Accumulation conveyors are typically used to transport and accumulate cartons and unit loads so that they are efficiently queued up and fed into sorting, palletizing, strapping, wrapping or many others processes in a distribution or manufacturing operation. They are used to provide a buffer zone where a steady supply of product can be oriented or held back when downstream processes are not ready for additional product. In addition, accumulation conveyors can be used to smooth out fluctuations in production line rates caused by stoppages or machines operating at different speeds.

Depending on the process the accumulation conveyor feeds into, the products will release in singulation or slug fashion.  A singulation release method is when the conveyor zones are controlled such that the product is discharged from one zone only when the immediately adjacent downstream zone is empty. This release method is typically found for most in-process accumulation and release applications, such as packing, weighing or shipping lines. 

Slug release method is when multiple adjacent zones are simultaneously ran in order to provide a large quantity of products to discharge in rapid succession.  This is typically done in a merge zone where several parallel accumulation conveyors are feeding into a single higher throughput takeaway conveyor.

There are two types of accumulation conveyors; minimum pressure and zero pressure.  Minimum pressure accumulation conveyors  do not eliminate the driving force while the products accumulate whereas on zero pressure accumulation conveyors, the driving force is completely eliminated.

Zero Pressure Accumulation Conveyors

In order to ensure that products do not touch each other while they accumulate, zero pressure accumulation conveyor is used.  In zero pressure accumulation conveyor, each zone has a photo-eye sensor sending a product presence signal to a zone controller. If there is a product present in the adjacent downstream zone, then the zone controller keeps the drive rollers from activating. Once the zone controller receives a signal indicating that the next zone is clear of product, the drive rollers are activated thereby conveying the product to the next zone.   

Zero pressure accumulating conveyors are commonly found in distribution centers where there is a wide variety of product width and weight.  Here are two of the most common zero pressure accumulation case conveyors:

Motorized Driven Rollers - Now known as "Green Conveyors" because of their energy efficiency and other environmental advantages over traditional 230/460V AC conveyor, these conveyors use 24V DC technology to drive the motor housed inside the roller that powers its zone. 

Belt Driven Live Roller with Photoeye Sensors - Belt Driven Live Roller (BDLR) with photoeye sensors typically divides the 10' or 12' conveyor section into three or four zones.  Each zone has a photoeye that senses product presence within the zone.  A belt under drive rollers, or carrying rollers, is raised up to engage the drive rollers or lowered to disengage them by pressure rollers that are air or mechanically actuated.  The signal to actuate the pressure rollers is provided by  programmable logic controllers (PLC) or a local zone controller mounted on the conveyor frame.

View Video of Hytrol's Gen3 Zero Pressure Accumulation System Conveyors and Controls Technology

TriFactor is sought out by companies nationwide to provide solutions that reduce inventory and delivery time, lower costs of manufacturing, distribution and transportation, and improve customer service.  If you are looking for an Edge on your competition, discover how TriFactor can make a difference, call today at 1-800-507-4209.

For additional information on Distribution Center Planning, Choosing a Conveyor System Improving Material Handling Efficiency, Costly Conveyor Maintenance Mistakes and related material handling issues visit the TriFactor Learning Center.