Hydraulic cylinder It is a widely used structural configuration in hydraulic systems. To ensure proper operation of hydraulic cylinders, it is essential to understand their characteristics and the associated precautions.

( 1 ) Single-rod piston Hydraulic cylinder This type of hydraulic cylinder has a piston rod only on one side, resulting in unequal effective areas on either side of the piston. The larger the diameter of the piston rod, the greater the difference between the effective areas on the two sides. Under equal supply pressure, the thrust generated on the rodless side is greater than that on the rod‑side. When the flow rate is the same, introducing pressurized oil into the rodless chamber causes the piston rod to extend at a slower speed than when pressurized oil is supplied to the rod‑side to retract the piston rod.

Note: Because the piston rod generates substantial thrust when extended and moves rapidly during retraction, this configuration is ideally suited for applications where the piston rod is subjected to unidirectional loading and requires rapid return under no‑load conditions. The thicker the piston rod, the greater the difference between thrust and pull force; however, this also results in slower speeds overall. A single‑rod hydraulic cylinder is employed to achieve slow advance and rapid return for the hydraulic gantry worktable.

( 2 ) Double-acting piston rod Hydraulic cylinder This cylinder has piston rods on both sides of the piston. When the diameters of the two piston rods are identical and the oil supply pressure and flow rate remain constant, the reciprocating speed and the force acting on the piston are equal. Moreover, with two piston rods, the cylinder exhibits improved rigidity and stability.

Note: The operation requires considerable space, and the working range is approximately equal to the effective length of… 3 times. This type of hydraulic cylinder is commonly used in grinding machine worktables.

( 3 ) Single-acting Hydraulic cylinder This type of hydraulic cylinder is a simple design. It can supply pressurized fluid only to one side of the piston, generating unidirectional force. The return stroke is achieved by external load forces, spring force, or the self-weight of the piston rod, without any hydraulic assistance in the reverse direction. Its advantages include reduced hydraulic power consumption and a simplified hydraulic circuit.

Note: The velocity and force in the opposite direction cannot be controlled. The self-weight, load force, and spring force that drive the piston rod or plunger rod backward exceed the sum of the back pressure and frictional resistance in all parts of the hydraulic cylinder. For spring‑return hydraulic cylinders, the spring must have sufficient travel to allow for a larger overall volume.

Single-acting hydraulic cylinders are widely used in machine tool positioning and clamping, dump truck lifting, elevator lifting, ship crane booms, and other applications.

( 4 ) Double-acting hydraulic cylinders are more widely used than single-acting hydraulic cylinders. Pressurized oil can be alternately supplied to both sides of the piston, driving it in a reciprocating motion, and allowing control over the speed of movement in both the extension and retraction directions as well as the supply pressure. There are two types of double-acting hydraulic cylinders. : Single-rod and double-rod.

Note: Control systems are more complex than those of single-acting hydraulic cylinders. Single-piston‑rod double‑acting hydraulic cylinders are more widely used than double‑piston‑rod double‑acting hydraulic cylinders. Reciprocating hydraulic cylinders for machine tool tables and various actuating hydraulic cylinders in construction machinery all employ single-piston‑rod double‑acting hydraulic cylinders.

( 5 ) Plunger hydraulic cylinders are typically single-acting. They feature a simple structure and are easy to manufacture and maintain. The plunger in such cylinders is thick, large, and heavy, offering superior rigidity compared to the piston rod. Consequently, this type of cylinder is preferred for applications requiring long strokes. Since the cylinder bore does not come into direct contact with the plunger—only the guide sleeve provides guidance—the bore can be left unground or subjected only to rough machining, resulting in excellent manufacturability and low processing costs.

Note: Plunger cylinders have relatively large volume and weight. When installed horizontally, the plunger is pressed off to one side under cold‑pressing conditions, which can lead to uneven wear on the seals and guide sleeves. Therefore, plunger cylinders are best suited for vertical installation. For horizontal installation and operation, a plunger support must be provided to prevent the plunger from sagging, thereby avoiding bending and the enlargement of the initial flexible contact surface. “ No stiffness ” Phenomenon.

( 6 ) Telescopic hydraulic cylinders, also known as multi‑section cylinders, multi‑stage cylinders, or composite cylinders, come in both single‑acting and double‑acting versions. These cylinders offer a long total stroke while maintaining a short retracted length, making them particularly well suited for applications where installation space is limited but a long stroke is required. Moreover, the more stages a cylinder has, the shorter its retracted length will be.

Note: The greater the number of cross‑sections, the larger the deflection of the hydraulic cylinder during extension, the more complex the structure, the higher the manufacturing difficulty, and the greater the cost. Therefore, the number of cross‑sections is increased only in special circumstances.