Greenhouse Mechanization and Material Handling
Plant Handling Systems
Reducing plant handling costs is a goal of most greenhouse businesses. Moving plant material is time-consuming, heavy work, and expensive in terms of labor costs. There are many plant handling systems that can be used to reduce this task and its cost. The following are some typical plant handling systems used in greenhouses to improve productivity and efficiency.
Conveyors
Moving materials is one of the most labor-intensive jobs in the production of plants. Although carts are becoming more popular as a method of moving container plants, conveyors are more versatile in that they can quickly move cartons, bags, bales, bulk soil as well as plants. Conveyors are available in any width or length needed. They can be installed permanently or set up temporarily.
Belt Conveyors
The major advantage of a belted conveyor line is motorization; it will keep the product moving. Coupled with speed control and directional (forward and reverse) control, the operator can create a smooth-flowing movement of product that will determine the pace for the workers on the line and also create a predictable product output. Conveyors are often equipped with electric motors. A belt conveyor works well for moving boxes, bags, bales, pots, flats, and bulk materials (Figure 4.6).
Gravity Conveyors
Gravity conveyors are ideal for moving boxes, bales, and flats, either manually by workers pushing the material down the line or by allowing the material to move by gravity. Because of the bumpy ride the rollers create, this conveyor is better suited for products with long, flat bottoms, such as flats of boxes, rather than individual pots. There are two basic types of gravity conveyors: wheel and roller (Figure 4.7). The rolling surface of a wheel conveyor is a series of small-diameter skate wheels supported by a metal frame. Light loads and items with solid bottoms work best on this conveyor.
Chain Conveyors
Chain conveyors are used for moving materials horizontally or between floors. They are also used in potting machines and bale breakers to move the soil vertically. The simplest system uses a single endless chain to carry pots from a potting machine to carts or trailers for transferring to the growing area. Motorized conveyors are available, but these are more expensive. Speed can be fixed or variable. Sprockets power the chain, unlike rollers, which are used with belt conveyors. Motorized conveyors are used in packing areas for roses, bulbs, and growing mixes that may be placed in bags or boxes.
Auger Conveyors
Auger conveyors are used to convey or elevate granular materials, such as growing mixes, peat, vermiculite, sawdust, or chips. Augers are preferred for these applications to other types of conveyors because of their simplicity, low cost, durability, and versatility.
Gantry Conveyors
Gantry conveyors are common in gutter-connected greenhouses (Figure 4.8). A gantry is a beam or frame with wheels on both ends that is supported on rails. It spans over a bay of plants and is pushed by hand. The rails, usually pipe or angle iron, are attached to the sidewall posts and extend the length of the bay. Frequently, pipe rails are also heat pipes. A gantry can be built with one or multiple shelves to carry the plants.
Overhead Monorail Conveyors
An overhead monorail conveyor can be used to eliminate the time-consuming and backbreaking job of moving plants from the transplanting area to the growing area and onto the shipping area (Figure 4.9). This system consists of a tubular or angle iron track suspended from the greenhouse frame and a trolley-mounted rack that is pushed along manually.
Carts
All sizes of greenhouse operations can benefit from carts (Figure 4.10). They increase labor efficiency by allowing one person to move more material at one time than could be carried by hand. Most carts have variable shelf spacing to handle different-sized plants and containers. Typically, a cart for moving bedding plants will hold 25 to 30 flats. They usually work best over distances of less than 200 feet (61m) but will work well for longer distances if a garden tractor or electric cart pulls several at a time.
Forklifts
Forklifts or lift trucks are efficient in moving material, but their main purpose is for lifting and stacking. Ubiquitous in warehousing operations, forklifts are commonly used in greenhouses, as warehousing or similar operations often occur here to some degree to receive, store, and distribute the supplies needed for plant production, harvesting, and transport. Most greenhouses use some degree of palletization.
Front-End Loaders
Front-end, or bucket, loaders come in three basic types: skid-steer, wheel, and articulated-body loaders. The skid-steer loaders tend to be smaller but are used to take advantage of their size. The skid-steer method of turning enables the vehicle to turn within its own length, an advantage in tight spaces.
Tractors, Trailers, and Other Vehicles
Although many more methods are possible for moving plants in a greenhouse, the tractor-and-trailer method is a widely used one. Farm tractors are commonly referred to as motorized units because they are widely available, but many other types of vehicles are used to pull trailers.
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