What kind of options are available to mechanize container filling?

Columns - Technology

January 20, 2011

John W. Bartok Jr.

Container filling is a labor intensive task that needs to be done correctly to get uniform size plants. Besides increasing the number of containers filled per hour, mechanizing this operation can provide an even fill, uniform compaction and a level top surface. Equipment is available that handles multiple size pots, separates the containers, inserts cell packs in trays/flats and dibbles the growing medium for sowing seed or sticking cuttings.

Filling equipment should be adaptable to different growing media. Growing media typically contain peat, vermiculite, perlite, sand, bark, rice hulls, coir, fertilizer and lime. The equipment should be able to convey the media without separating the different components or altering the chemical makeup from container to container. The moisture content of each mix should be adjusted so that after containers are filled there is little settling of the medium.

When filling is done by hand, the medium is usually placed in the containers, vibrated slightly to settle the medium and then leveled or brushed off to even it with the top of the containers. With automated container fillers, these tasks are done mechanically with a scraper or rotating brush.

Large budget solution
There are several types of container filling machines available for growers producing large quantities of plants. One concept originally developed in Europe consists of a hopper on wheels, a soil elevator that lifts the growing medium from the hopper and a horizontal circular chain conveyor.

Empty pots are placed in holders on the chain, carried under the elevating conveyor, filled, dibbled and moved to a location where they are either manually or mechanically removed. Planting can be done as the pots go by or the containers can be placed on carts or pallets for later planting. All operations are timed with a variable speed drive. At least two persons are needed to make the operation efficient. Accessories include twin pot holders for smaller size containers, automatic pot removal and a flat filler.

Another type of machine is designed to move empty containers under a soil hopper. The hopper capacity is usually 1-2 cubic yards and can be filled with a front end loader or belt conveyor. Growing medium is fed by gravity to the containers that move under the discharge chute. Growing medium flow rate is controlled by adjusting the discharge gate.

A belt or chain conveyor is used to move the containers under the bin. A variable speed drive, either electric or hydraulic, allows the feed rate to be adjusted for different size containers. Side guides adjust for different size containers. Feed rates as high as 1,800 flats per hour or 20,000 pots per hour can be achieved.

For certain growing mixes some compaction is needed. This is provided by either an adjustable roller or vibrating plate. Excess soil is removed by an angled scraper or rotating brush.

Some machines have a soil return conveyor that catches excess medium and returns it to the hopper. Other accessories include a dibble, container counter and pot or flat dispenser. Supplying adequate containers to keep the machine full and removing the containers after they have been filled requires either full time employees or conveyors. These machines are usually operated with three employees.

When purchasing a machine, look for heavy duty construction, standard replacement parts that can be sourced locally, easy adjustment for different container sizes and convenient access to controls. Portability is important if the machine is to be moved between greenhouses.

Filling machines mean fewer workers are needed to perform repetitive tasks during critical times of the year. If 10,000 flats or more are filled per year, a flat filler is usually a good investment.

Commercial flat filler

Small budget solution
For a small- to medium-sized grower a low-cost container filling machine can be built from two short, 8-foot belt conveyors. Used conveyors are frequently available from industrial material-handling equipment dealers. The conveyors are placed on a steel frame in an “X” arrangement (Figure 1). One conveyor is fitted with a hopper at the base that holds three to four bags of medium. This conveyor carries the medium up and drops it into a flat or pot placed on a slatted work table in front of the operator. When the container is full, the top is scraped or brushed off and placed on an adjacent cart or conveyor. The excess medium drops into a hopper underneath the work table and is conveyed back up to the soil hopper by the second conveyor.

Operation is controlled by a foot switch. The steel frame can be made transportable by installing casters under the legs. Plans for this filling machine are available from the author.

Have a question? You can write John at jbartok@rcn.com.


A low-cost container filler can be built from two 8-foot belt conveyors