I. Manual Hydraulic Forklift Structure
Power Unit Structure
Comprising an operating handle, a lever mechanism, and a plunger hydraulic pump. The hydraulic pump consists of a pump body, piston chamber, and oil inlet and outlet ports. The oil tank is connected to the pump body via oil pipes. The handle is hinged to the pump body lever via a pin, forming the manual input interface.
Actuator Structure
The main unit is a single-acting hydraulic cylinder, consisting of a cylinder barrel, piston rod, end cap, and seal assembly. The forks are secured by two L-shaped alloy steel fork arms via a crossbeam. The lifting frame is connected to the mast guide rails via rollers, forming a vertical kinematic pair.
Control System Structure
The unloading valve is integrated into the pump body or a separate valve block and consists of a valve body, valve core, return spring, and operating handle. The overload protection valve is connected in parallel with the main oil circuit and features a built-in pressure-regulating spring and steel ball seal.
Transmission Structure
The lifting chain is anchored to the vehicle frame and lifting frame at both ends, with the middle section passing over an alloy sprocket at the top of the piston rod. The sprocket is rigidly connected to the piston rod via a keyway, and chain guide grooves are provided on both sides of the mast.
Load Frame Structure
The frame is welded from channel steel into a U-shaped frame, and the mast is riveted together with vertical guide rails and transverse support beams. The base of the forks is hinged to the lifting frame via a slew axis, transmitting the load through the frame to three bearing points.
Travel System Structure
The two front load wheels have a nylon-coated steel core structure, with the axles fixed to the frame. The rear steering wheel is equipped with a universal bearing and a foot brake, and is connected to the steering linkage via a vertical shaft.
II. Working Principle of Manual Hydraulic Forklifts
Lifting Energy Transmission
When the handle is manually pressed, a lever mechanism drives the hydraulic pump piston to compress the oil. The high-pressure oil pushes open a check valve and enters the lower chamber of the cylinder, pushing the piston rod out. The sprocket at the top of the piston rod rotates to reel in the chain, forcing the lifting frame to rise along the mast track.
Static Load Mechanism
When the handle is released, the hydraulic pump check valve automatically closes. The lower chamber of the cylinder forms a closed pressure chamber, and the piston rod is supported by hydraulic reaction force, allowing the forks to hover at the target height. The weight of the cargo is balanced by the hydraulic support force.
Controlled Lowering Process
When the unloading valve handle is loosened, the valve core shifts, opening the oil return channel. The weight of the forks compresses the piston rod, causing the oil in the cylinder to flow back to the tank through the orifice of the unloading valve. Gravitational potential energy is converted into thermal energy in the oil, and throttling damping achieves a slow descent.
System Cycle Logic
The oil discharged during the descent is cleaned by a filter and stored in the tank. During the next lift, the hydraulic pump draws oil from the tank and re-pressurizes it, forming a closed hydraulic cycle of "suction-pressurization-action-return."
