5 Types of In-Motion Checkweigher Pneumatic Reject Diverts

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Oct 3, 2013

Are you thinking about getting an in-motion checkweigher for your production facility to weigh your product and reject any items that are over or under weight?

Once a product is weighed on the conveyor, a reject device of some sort will be needed to remove the out-of-weight (or out-of-tolerance) items from the line. Most of these devices will need a power source of some sort to activate the reject device. The most common power sources that come to mind are pneumatic, electrical, and hydraulic. For this article, the focus is pneumatically operated devices.

Many types of pneumatically operated devices can be manufactured and installed on an in-motion checkweigher.

Here are five types of pneumatic reject devices:

The first option is a simple air knife or air comb device. These devices simply blow a puff of air at the product and blow it off the line. These are typically used on very light-weight products since they do not physically push or pull the product.

in motion checkweigher

Air-Knife shoots air and blows light product off belt


A second option is a linear thruster.

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Linear thruster physically pushes product off belt

A linear thruster mounts to the side of the conveyor and pushes the product straight off the other side of the conveyor.

A third option is either a pull-off or push-off arm.  An arm of this type has an arm tied to the pneumatic cylinder with a pivot point on the side of the conveyor.   When activated, the cylinder pushes the arm open while the arm pivots about the pivot point.  It either pushes product off the opposite side of the belt or pulls it off to the same side the divert is mounted on.  As it pushes, it also guides the product to the desired side.

in motion checkweigher

Push/pull airm swings out and knocks product off belt

A fourth reject device is an overhead mounted guided cylinder.  A cylinder is mounted between guided rods with a block mounted on the guided rods.  The cylinder moves the block along the guided rods.  A plate of some sort is mounted to the block and hangs down along the side of the conveyor. This plate moves with the block to push product off the side of the conveyor.

in motion checkweigher

Overhead cylinder gate divert

A fifth type of reject is called a drop-down reject.  With this type of divert, the conveyor itself actually has a pivot point located at the beginning of the conveyor and drops down to direct product off the end of the lowered conveyor.

in motion checkweigher

Drop-down divert lowers product to a secondary process

Each of these types of pneumatic reject devices work well when used for the proper applications. If you have any questions about in-motion checkweighers, in-motion sortation, grading, classifiers, etc or whatever reject device would work well for your application, please contact us!


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