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.