Articulated Forklift

An articulated forklift is a counterbalance lift truck whose front section pivots relative to the rear body, so the mast can swing sideways to face a rack while the truck itself stays inside a narrow aisle. A conventional counterbalance truck has to turn its whole body to deposit a pallet, which needs an aisle of roughly 3.5 to 4 m. By moving the turning function into a central Articulation Joint, this truck works in aisles of 1.6 to 2.0 m, recovering floor area that would otherwise be spent on turning room. It keeps the reach and stacking flexibility of a counterbalance machine, so the same truck can unload a lorry at the dock and then put the pallet away in a narrow aisle without a load transfer.

Overview

The truck splits into a rear power section and a front load section, joined at the pivot. The Rear Chassis Section carries the traction battery, the cast Cast Counterweight and the drive axle. The Front Swing Section carries the Telescopic Mast and the front load wheel, and swings on the joint. Hydraulics, electrical control, the operator compartment and the safety devices tie the two sections together. The articulation is powered, not free-castoring, so the controller knows the swing angle at all times and can limit travel speed when the mast is turned out.

Articulation joint

The joint is what separates this truck from an ordinary forklift. A hardened vertical Articulation King Pin sets the swing axis, and a large-diameter Slew Ring Bearing carries the radial and tipping loads as the front section turns. Two Articulation Cylinder units swing the front section to either side, reaching up to about 105 degrees so the carriage can face racking on both sides of the aisle. A Pivot Housing locates the pin and the Thrust Washer pair that takes the vertical load, with Ball Bearing supports and Oil Seal units keeping out dirt. An Articulation Angle Sensor reports the swing angle back to the controller, which uses it for the stability and speed interlocks. Hydraulic flow and wiring cross the joint through a Swivel Fitting and a Pivot Cable Track, so the lines are not pinched as the sections move.

Mast and load handling

The Telescopic Mast is a two-stage telescopic frame. A fixed Outer Mast Channel guides a sliding Inner Mast Channel on Mast Guide Roller sets. A single-acting Lift Cylinder raises the inner channel, and a pair of Lift Chain members couple the cylinder ram to the Fork Carriage so the carriage lifts at twice the cylinder speed. Two Tilt Cylinder units tilt the mast fore and aft to cradle a load. The carriage carries two forged Fork Arm members on a hook-bar Carriage Plate, plus a Side-Shift Cylinder that shifts the forks laterally to line up with a pallet without repositioning the truck. Side-shift matters in narrow aisles, where there is little room to correct alignment by driving.

Drive, hydraulics and steering

Traction comes from the Traction Drive Axle, an AC AC Traction Motor feeding a two-stage Drive Gearbox to the front Drive Wheel Hub. An Encoder on the motor closes the speed loop, and a spring-applied Parking Brake holds the truck when stopped or powered down. Hydraulic power for lift, tilt, side-shift, articulation and steering comes from the Hydraulic System: an AC Hydraulic Pump Motor drives a Gear Pump that feeds a sectional Valve Bank. Each Proportional Valve Section is a proportional spool with a Valve Solenoid, so lift and articulation speeds are metered rather than on-off. A Main Relief Valve caps system pressure, and a Pressure Sensor reports it to the controller. The Hydraulic Tank holds the oil with a Suction Strainer and a Return Filter. Steering acts on the rear wheels through a load-sensing Steering Control Unit and a Steer Cylinder on the Rear Steer Axle. The three-wheel layout, one front Drive Wheel and two rear Steer Wheel units on solid Cushion Tire tyres, gives a tight turning circle on smooth warehouse floors.

Electrical, control and battery

The Electrical and Control subsystem runs two inverters, the Traction Inverter and the Pump Inverter, each built around IGBT Power Module switches and DC-Link Capacitor banks. The Vehicle Control Unit coordinates traction, lift, steering and the articulation interlock over a CAN bus, and a DC-DC Converter supplies the 24 V control rail. The Traction Battery is lithium-ion, made of Battery Module blocks of Li-ion Cell, 21700 cells watched by a Battery Management System. The battery sits low and to the rear inside a ballasted Battery Box, so it also contributes to the counterweight. Lithium chemistry suits multi-shift work because it tolerates opportunity charging and does not need a separate charging room, though many fleets still keep lead-acid packs that swap out on the Battery Tray rollers.

Operator compartment and safety

The Operator Compartment gives the operator a suspension Suspension Seat with a presence switch, a Steering Wheel for the rear-wheel steering, a Control Lever Module module for the hydraulics and a Operator Display that shows speed, charge and the live articulation angle. A welded Overhead Guard protects against falling loads. The Safety and Signalling subsystem adds an Emergency Stop, LED work lights, a warning beacon and Proximity Sensor units that watch the rack and aisle near the swung mast.

Materials and use

Structural members, the rear frame and the mast channels are welded and rolled steel, hardened where they slide or pivot. The counterweight and battery box are cast iron and heavy steel plate. Cylinder rods are chrome-plated, and the slew bearing and king pin are case-hardened for wear life. Articulated trucks are bought when an operation needs both dock work and dense storage from one machine, often replacing a pairing of a counterbalance truck and a separate narrow-aisle truck. Typical homes are distribution centres and cold stores where aisle space is expensive and double handling is to be avoided.