Clark Equipment Company has introduced a new "Hydro-Mechanical" steering system for its C25 series internal combustion counterbalance forklifts. In traditional forklifts, the steering ratio is fixed, requiring many turns of the wheel to turn the rear axle. This can be tiring for operators working in tight aisles, yet a "quick" steering ratio can be dangerous at high travel speeds.
The Clark system uses a "Dual-Flow Orbitrol" (steering control unit). The unit has two internal hydraulic circuits: a "Low-Flow" circuit for high-speed driving (requiring more steering input) and a "High-Flow" circuit for low-speed maneuvering. The system uses a "Vehicle Speed Sensor" to switch between these modes automatically.
The engineering highlight is the "Variable Steering Ratio Logic." When the forklift is stationary or moving below 5 km/h, the system activates the "High-Flow" circuit. The operator can turn the rear wheels from lock-to-lock with just 2.5 turns of the steering wheel, allowing rapid maneuvers for loading trucks. When the forklift accelerates above 10 km/h, the system electronically switches a solenoid valve to the "Low-Flow" circuit. This increases the number of turns required for full lock, providing a "heavier" and more stable steering feel, preventing accidental over-correction that could cause a tip-over. Additionally, the system features an "Auto-Centering" assist. When the operator releases the wheel, hydraulic pressure assists the return of the rear axle to the straight-ahead position, reducing driver fatigue.
