What is the structure and working principle of a hydraulic cylinder?

[DeWalker]

Introduction to the structure and working principle of hydraulic cylinders: As an actuating element, a hydraulic cylinder is essentially an energy conversion device. It converts the pressure energy of the input fluid into the mechanical energy of the piston's linear motion. The so-called input hydraulic energy refers to the flow rate and pressure of the input fluid, while the output mechanical energy is the speed v (m/s) and traction force f during piston movement. Hydraulic cylinders come in various structural forms and can be classified in multiple ways: 1. Piston type: Piston cylinders can be divided into single-rod and double-rod structures, with fixed methods including cylinder body fixation and piston rod fixation. Based on hydraulic force application, they can be single-acting or double-acting. 2. Plunger type: Plunger cylinders are single-acting hydraulic cylinders where hydraulic force only enables movement in one direction, with return stroke relying on external forces or the plunger's weight. The plunger is supported by but doesn't contact the cylinder sleeve, making the sleeve easy to machine and thus suitable for long-stroke applications. 3. Telescopic type: Telescopic cylinders have two or more stages of pistons. The extension sequence is from large to small, while the retraction sequence is typically from small to large. Telescopic cylinders achieve long strokes while maintaining compact retracted lengths, making them common in construction and agricultural machinery. 4. Rotary type: Rotary cylinders output torque and achieve reciprocating motion, coming in single-vane, double-vane, and helical rotary forms. In vane types: The stator block is fixed to the cylinder body while the vane and rotor are connected. Depending on oil inlet direction, the vane drives the rotor to perform reciprocating rotation.