Empty Container Handler

Overview

An empty container handler is a heavy lift truck built for one repetitive job: picking up, stacking, and shuttling empty shipping containers in a port or depot. Because an empty 20 ft or 40 ft box weighs only a few tonnes, the machine trades the brute lift of a laden handler for height and speed, stacking empties seven or eight high in dense rows so a small footprint of yard holds thousands of boxes. It grips the container from above with a top-lift spreader rather than forks, so it can pick a box off the top of a stack and set it down without threading tines into a pocket.

The truck balances a load held out in front against a heavy rear Counterweight, the same principle as a warehouse forklift scaled up. The Chassis and Counterweight carries that balance, the Lift Mast raises the load, the Top-Lift Spreader grips it, the Diesel Power Pack supplies energy, the Driveline and Axles moves the truck, and the Hydraulic System power every lift and clamp function.

Mast and lift

The Lift Mast is what makes high stacking possible. It is a two-stage telescoping mast: a fixed Outer Mast channel pinned to the frame, and a Inner Mast channel that slides up inside it. A pair of single-acting Lift Cylinder rams drive the inner mast, and over each ram a Lift Chain runs across a sheave so the Lift Carriage climbs faster than the cylinder extends, doubling the reach for a given stroke. The carriage and inner mast are held square against side load by Mast Roller cam rollers, and two Tilt Cylinder rams tilt the whole mast a few degrees forward and back so the operator can set a box flat on an uneven stack.

The spreader

The Top-Lift Spreader is the working attachment, and it matters because the handler grips the container rather than carrying it on forks. A Spreader Frame reaches over the top of the box, and four Twistlock cones drop into the standard corner castings. A small Twistlock Cylinder at each corner rotates its cone ninety degrees to lock the box, and a Landing Sensor confirms the spreader has seated before the locks turn, so a box is never lifted half-engaged. The frame telescopes on Telescope Cylinder rams to fit both 20 ft and 40 ft boxes, shifts left and right on Sideshift Cylinder rams to line up without moving the truck, and folds down Guide Flipper guides that funnel the spreader onto the corners. Many empty handlers carry a double or side-lift spreader that takes two empties at once to raise throughput.

Power pack and driveline

Energy comes from the Diesel Power Pack, built around a turbocharged Diesel Engine of roughly 100-130 kW. The engine feeds both the wheels and the hydraulics, so its Radiator is sized to reject heat from continuous lifting as well as travel, and a Fuel Tank holds a full shift of diesel. The Driveline and Axles uses a Powershift Transmission with a Torque Converter, which lets the truck creep up to a stack and stall against the lift without stalling the engine. Drive goes through a Driveshaft to the Drive Axle, whose Planetary Hub reductions give high torque at the low speeds of yard work, and oil-cooled Wet Disc Brake discs sealed inside the axle resist port grit. The rear Steer Axle steers on a Steer Cylinder for the tight turns of a container row.

Hydraulics and control

Almost every motion on the machine is hydraulic. The Hydraulic System system runs from a Main Pump on the engine through a Control Valve Block of proportional Spool Valve sections, each metering oil to one function so the operator can lift, tilt, sideshift, and lock at once. Relief Valve settings cap the pressure, an Oil Cooler holds temperature in continuous duty, and a Pressure Sensor on the lift circuit feeds the load reading. Coordinating all of it is the Electrical and Control system: a Vehicle Control Unit reads the cab Control Joystick inputs and the Load Weighing Sensor, then commands the valves, while the Operator Display shows lift height, load, and machine status.

Cab and operator

Stacking eight high means the operator must see the top of a tall stack, so the Operator Cab sits high and forward with wide Safety Glazing glazing and an overhead window. An air-suspended Suspension Seat damps the ride over rough yard surfaces, the Cab HVAC keeps the glazed cab usable in a hot or cold climate, and the cab shell is rated to protect the operator from roll-over and falling objects. Modern handlers add height and load indication on the display, camera views down the mast, and twistlock interlocks that block a lift until all four locks confirm engaged.

Use and place in the fleet

Empty handlers work the depot and the empty stacks of a container terminal, where their job is density and speed rather than the raw tonnage of a laden box. They are lighter and cheaper to run than a Laden Container Handler and far more maneuverable than a Rubber-Tyred Gantry Crane, so a terminal uses them to sort, stack, and shuttle the constant flow of empties while the heavier machines handle full boxes. Their limits are weight, since the top-lift spreader and high mast are sized only for empties, and stack stability, since a tall column of light boxes can be pushed over by wind or a careless set. Within those limits they are the workhorse of empty-container yards worldwide.