Counterbalance Forklift

Overview

A counterbalance forklift is the most common lift truck in any warehouse, and its whole design follows from one principle: balance. When the forks pick up a load at the front of the truck, that weight tries to tip the truck forward over its front wheels. To stop that, the truck carries a heavy mass at the rear, so the front wheels act as a pivot with the load on one side and the counterweight on the other, like a seesaw. Getting that balance right at every lift height and reach is what the rest of the machine is built around, because the forks reach straight out from the front with no outriggers in the way, which is what lets the truck drive right up to a pallet.

The truck is built on a Chassis & Counterweight that carries the Counterweight. Mounted on it are the Mast Assembly that lifts, the Hydraulic System that powers the lift, the Powertrain that drives the truck, the Steering Axle, the Braking System, the Operator Station, and the Electrical System system that ties everything together.

Chassis and counterweight

The Chassis & Counterweight starts with a heavy welded Truck Frame that takes the concentrated loads from the mast and spreads them into the axles. At the rear sits the Counterweight, a large cast-iron block whose only job is to balance the load. On electric trucks the Battery Tray and battery double as part of this mass, which is why electric forklift batteries are so heavy. An Overhead Guard cage protects the operator from anything that might fall off a raised load. The front Drive Axle both drives and carries the bulk of the weight, riding on Forklift Tire units chosen for the floor: solid cushion tires for smooth indoor concrete, pneumatic tires for rough yards.

Mast and forks

The Mast Assembly is the lifting structure at the front. It is made of nested channels: a fixed Outer Mast Rail bolted to the truck and an Inner Mast Rail that telescopes up out of it. A Fork Carriage rides up these rails on Mast Roller bearings, and the two Fork Arm tines that go under the pallet hang from the carriage. Lifting is done by hydraulic cylinders working through Lift Chain leaf chains over sheaves, which multiplies a short cylinder stroke into a much longer carriage travel, so the truck can lift several meters with a compact cylinder. A Load Backrest keeps tall loads from tipping back toward the driver, and the whole mast can be tilted slightly to cradle the load or set it down level.

Hydraulics

The Hydraulic System is the muscle behind both lifting and steering. A Hydraulic Pump driven by the powertrain pressurizes oil from the Oil Reservoir, and the operator's levers move spools in a Control Valve Bank bank that directs that oil. To lift, oil flows to the Lift Cylinder units; to tilt the mast, it goes to the Tilt Cylinder units; to steer, it feeds the steering cylinder. A Relief Valve caps the pressure so an overload cannot burst anything, Hydraulic Hose lines carry the oil to each cylinder, and a Hydraulic Filter keeps the oil clean on its way back to the tank, since dirty oil is the main killer of hydraulic components.

Powertrain and steering

The Powertrain moves the truck. On an electric model, a Traction Motor draws from the Traction Battery through a Motor Controller and drives the front axle through a Transmission; engine-powered models swap the motor and battery for an engine and torque converter but keep the same layout. A Cooling Package package keeps the controller and powertrain from overheating during a hard shift.

The Steering Axle is at the rear, which is what gives a counterbalance truck its tight turning circle. A single Steering Cylinder swings the rear Steer Wheel units through a wide angle on their Steering Knuckle pivots, linked by Tie Rod arms. Steering from the rear lets the front of the truck, where the load is, swing into a pallet position while the tail pivots tightly, so the truck works in aisles only a little wider than its length plus the load.

Brakes, operator station, and electrical

The Braking System has to stop a truck that may weigh several tonnes with a load up high. A Master Cylinder driven by the Brake Pedal sends fluid to Wheel Brake drum brakes on the drive axle, and a Parking Brake holds the truck on grades. The Operator Station is built so one person can drive and lift at once: a suspended Operator Seat with a presence Seat Switch that cuts travel when nobody is sitting, a Steering Wheel, a row of Control Lever handles for lift and tilt, a Pedal Set, and a Instrument Display showing battery or fuel, hours, and warnings. A Seat Belt is critical, since the safest place in a tip-over is staying in the seat under the guard.

The Electrical System system links it all. A Vehicle Controller reads the operator inputs and the Sensor Set, which includes a Tilt Angle Sensor for mast tilt and a Speed Sensor that lets the truck slow itself when lifted high. A Wire Bundle harness, Work Light lamps, a Horn, and a Fuse & Relay Box complete the system. Variants run from compact three-wheel electric trucks for narrow indoor aisles to large pneumatic-tire diesel trucks that handle heavy loads outdoors, but the seesaw balance, the telescoping mast, and the rear-wheel steering are common to all of them.