Fruit Grading Line

Overview

A fruit grading line takes loose fruit from the orchard or cold store, cleans it, measures each piece, and drops it into the outlet lane that matches its grade. The grade is set by three measurements taken while the fruit moves: weight, size, and surface color. Packhouses run these lines to turn a mixed harvest into uniform packs that meet a buyer's size and color band, which is what fixes the price the fruit fetches. A typical machine handles apples, citrus, stone fruit, tomatoes, or similar round produce at 8 to 12 tonnes per hour across a bank of lanes.

Fruit enters through the Infeed Section, is cleaned in the Washing Section and dried in the Drying Section, then the Singulation Section places one piece into each cup of the Weigh-Cup Carrier carrier. As the cups move, the Optical Sizing Unit unit reads color and size and the load cells read weight. The Drop-Cup Ejection system tips each cup over the right lane of the Outlet Lanes. The Drive System keeps every section in step and the Control Cabinet runs the logic.

Infeed and washing

Bins arrive full and are emptied by the Bin Tipper, which cradles a bulk bin and rotates it with a pair of Hydraulic Ram cylinders so fruit rolls out without bruising. Many lines tip into a wet Water Dump Tank, where fruit floats out of the bin on a cushion of water before climbing the Roller Elevator. From there a bed of Metering Roller units spaces the fruit forward at an even rate.

The Washing Section runs the fruit across a bed of turning Brush Roller units while a row of Spray Bar manifolds wets it through many Spray Nozzle tips. Each brush uses a stainless Brush Core Tube wound with a soft nylon Brush Bristle Set set that scrubs without marking the skin. Water drains to the Wash Sump Tank, passes a Debris Screen, and is sent back up by the Wash Pump units so the line uses little fresh water.

Drying and singulation

Wet fruit cannot be read cleanly by a camera, so the Drying Section removes the surface film. A bed of Sponge Roller units, each wrapped in an absorbent Sponge Cover, soaks up most of the water, and an Air Knife fed by the Drying Blower blows off the rest. The blower uses a balanced Blower Impeller driven through a Servo Motor so its speed can be trimmed for delicate fruit.

The Singulation Section then turns a loose stream into a single file. A set of Singulating Belt lanes running at staggered speeds pulls fruit apart, Aligner Roller pairs center each piece, and a Loader Cup hands one fruit to each grading cup. Good singulation matters because every later step assumes one fruit per cup.

Weighing and vision

The heart of the line is the Weigh-Cup Carrier carrier: a pair of Cup Conveyor Chain strands carry a long row of Weigh Cup Module units, each a pivoting Cup Body on a Cup Pivot Pin held level by a Coil Spring. As a cup passes the weigh station it rides briefly on a Load Cell, which reads the fruit weight in motion to about one gram. A Line Tachometer tracks the position of every cup so the controller always knows which fruit is where.

The Optical Sizing Unit unit looks down at the cups from inside a Light Tunnel lit evenly by several LED Light Array banks built from high-CRI LED Strip sources. Four Camera Head units, each an CMOS Image Sensor behind a Lens Assembly in a sealed Camera Housing, image the fruit from several angles. The Vision Processing PC computes diameter, projected area, color band, and visible defects, triggered in step with the line by the Encoder Trigger Board board.

Ejection and outlet lanes

Once the controller has a weight, a size, and a color for a given cup, it assigns a grade and a target lane. The Drop-Cup Ejection system carries one Trip Actuator per lane, each a Eject Solenoid that swings a Trip Finger into the path of the cup follower at the right moment. The finger trips the Trip Roller under the cup, the cup tips, and the fruit drops. The Ejection Controller fires each solenoid with millisecond timing so fruit lands in the correct Lane Chute.

The Outlet Lanes lanes catch the graded fruit gently. A spiral Lane Chute lowers each piece in a slow descent onto a Padding Belt and into a Collection Bin or onto a packing table. With 16 lanes a line can split a harvest into several size bands and a few color or quality grades at the same time.

Drive and control

Every section is kept in step by the Drive System system. Six Gearmotor units, each pairing a stator and rotor with a Gearbox Housing and Helical Gear Pair, turn the brushes, the cup chain, and the outlet belts through a set of Drive Shaft lines and Drive Belt reductions. Shafts run in Ball Bearing supports sealed with Oil Seal rings to keep washdown water out.

The Control Cabinet holds the brains. A PLC reads the load cells, the tachometer, and the vision result, then commands the Variable Frequency Drive drives and the ejection solenoids. The operator sets size bands, color grades, and lane mapping from the Operator HMI touchscreen. The whole frame is built from 304 stainless on stainless Leveling Foot supports so the line can be hosed down at the end of each shift.

Variants and use

Lines scale from a single grading channel for a small packhouse to wide multi-lane machines that feed automatic baggers and tray fillers. Stone fruit and tomato lines run more cameras and softer cups because the fruit marks easily, while citrus lines add a waxing stage after the Drying Section. Weight-only versions drop the Optical Sizing Unit unit and grade on the Load Cell reading alone, which suits crops sold by count and size rather than color. In every form the job is the same: clean the fruit, measure it, and send it to the lane that matches its grade.