1. Core Principle

A manual hydraulic pallet jack (also known as a pallet truck), its core principle is to use manual lever actuation to drive a hydraulic pump, which pressurizes low-pressure and small-flow hydraulic oil, pushes the piston of the hydraulic cylinder to lift, and realizes the lifting of pallets/cargoes; when the relief valve is opened, the hydraulic oil flows back, and the piston lowers under its own weight/load. It is essentially a combination of Pascal’s Law, lever force saving and hydraulic transmission.

2. Physical Basis: Pascal’s Law

In a confined static liquid, the pressure applied to the liquid will be transmitted equally in all directions (Formula: P₁=P₂, i.e., F₁/S₁=F₂/S₂). The small piston (pump core) has a small area S₁ and a small manual thrust F₁ → generating high pressure P; the large piston (lifting cylinder) has a large area S₂ → obtaining a huge lifting force F₂ (F₂=F₁×S₂/S₁); typical magnification: 20~50 times, with a manual force of dozens of kilograms, it can lift 1~5 tons of heavy objects.

3. Main Components

Manual operating lever (pressure lever + relief handle): Provides lever force and controls lifting/lowering; Hydraulic pump unit (small oil cylinder, pump core, 2 check valves: inlet valve and outlet valve): Generates high-pressure oil; Main lifting cylinder (large piston, cylinder tube, sealing ring): Outputs lifting force and lifts the forks; Hydraulic oil tank (oil storage chamber): Stores hydraulic oil and serves as a return channel; Forks + wheel set: Bears pallets and moves on the ground; Pressure relief valve (oil return valve): Controls the on-off of the oil circuit and realizes lowering.

4. Complete Working Process

4.1 Lifting Phase

1. Press the operating lever down → the lever drives the small pump core to move downward; 2. The pressure in the oil chamber below the pump core rises sharply: the inlet valve closes and the outlet valve opens; 3. High-pressure hydraulic oil flows from the pump chamber → through the outlet valve → into the lower chamber of the main lifting cylinder; 4. The high-pressure oil pushes the large piston to extend upward → drives the forks and pallets to lift synchronously; 5. Release the lever (reset): the pump core moves upward → negative pressure in the pump chamber → the inlet valve opens and the outlet valve closes → the oil in the tank automatically fills the pump chamber to complete one oil suction; 6. Repeat pressing/resetting to continuously supply oil to the main cylinder, and the piston continues to lift until the forks hold the pallet and rise to the desired height.

4.2 Holding Phase

Both the outlet valve and the relief valve are closed, and the high-pressure oil in the main cylinder is completely sealed; the hydraulic oil is incompressible, the piston position is fixed, and the load hovers stably without sliding down.

4.3 Lowering Phase

1. Pull the relief handle on the operating lever backward → the relief valve core opens; 2. The lower chamber of the main lifting cylinder → forms a direct oil return channel with the oil tank; 3. The self-weight of the cargo + the self-weight of the forks → presses the large piston downward, and the high-pressure oil flows back to the oil tank quickly; 4. The piston falls back and the forks lower until they land completely; release the relief handle, the oil return stops, and the pressure holding is restored.

5. Key Details and Supplements

1. Function of check valve: Only allows one-way oil flow and prevents backflow, which is the core of establishing high pressure and holding pressure; 2. Lever amplification: The operating lever is a labor-saving lever, which further reduces the force required for manual pressure (manual force → pump core force is further amplified); 3. Sealing and lubrication: Sealing rings (O-rings, oil seals) prevent oil leakage and ensure pressure; hydraulic oil also lubricates the pump core/piston to reduce wear; 4. Load limit: Use according to the rated load (1t/2t/3t/5t); overloading will cause damage to the sealing ring, deformation of the oil cylinder and loss of pressure relief control.

6. Simplified Principle Diagram (Text Version)

[Manual pressure lever] → [Small pump core pressing down] → [Outlet valve open, inlet valve closed] → [High-pressure oil enters main cylinder] → [Large piston lifts forks]; [Relief handle pulled] → [Relief valve open] → [Oil in main cylinder flows back to tank] → [Piston/forks lower under self-weight]

7. Simplified Version (for Product Manual/Training, ~100 Words)

Based on Pascal’s Law and hydraulic transmission, the pallet jack pressurizes the hydraulic pump by pressing the operating lever, pushing the piston to lift the forks. The check valve maintains pressure, and pulling the relief handle allows oil to flow back, making the forks lower under the load’s self-weight. It has a high force amplification ratio, enabling one person to safely lift several tons of heavy objects.

DIESEL FORKLIFT

ELECTRIC FORKLIFT

ELECTRIC STACKER