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   Hydraulic cylinders are a widely used structural form in hydraulic systems. Therefore, to correctly design and use these cylinders, it is necessary to understand their characteristics, applications, and precautions.

　　(1) Single-rod hydraulic cylinders have a piston rod on only one side of the piston, resulting in unequal effective areas on both sides of the piston. The larger the piston rod diameter, the greater the difference in effective area on both sides of the piston. With the same supply pressure, the thrust on the side without the piston rod will be greater than that on the side with the piston rod. With the same flow rate, the outflow speed on the side without the piston rod is slower than that on the side with the piston rod.

　　(2) Double-rod hydraulic cylinders have piston rods on both sides of the piston. When their diameters are the same, and the supply pressure and flow rate remain unchanged, the reciprocating speed and force of the piston are also the same. Because there are two piston rods, the stiffness and stability are both very good.

　　Note: The occupied space during operation is very large, approximately 3 times the effective stroke length. Most grinding machine worktables use this type of hydraulic cylinder.

　　(3) Single-acting cylinders are simple hydraulic cylinders. Pressure oil is supplied to only one side of the piston, outputting a unidirectional force. The return stroke depends on factors such as load force, spring force, and the weight of the piston rod or plunger. In other words, there is no oil pressure in the opposite direction. Its advantages are saving hydraulic power and simplifying the oil circuit.

　　Note: The speed and force of the return stroke cannot be controlled. The self-weight, load force, and spring force that cause the piston rod to return must be greater than or equal to the sum of the pressure and the frictional resistance of various parts of the hydraulic cylinder. Spring-return hydraulic cylinders require a certain operating space, thus increasing the volume.

　　Single-acting hydraulic cylinders are more suitable for applications such as machine tool positioning, dump truck lifting, lift platform lifting, and ship loading booms.

　　(4) Double-acting hydraulic cylinders have much wider applications than single-acting hydraulic cylinders. Pressure oil can be alternately supplied to both sides of the piston, causing the piston to reciprocate. The speed and pressure in both directions can be adjusted.

　Note: The control system is more complex than that of single-acting hydraulic cylinders, and its applications are more extensive. The reciprocating hydraulic cylinders of machine worktables and various hydraulic cylinders of engineering machinery all use single-rod double-acting hydraulic cylinders.

(5) Plunger hydraulic cylinders are mostly single-acting cylinders. They have a simple structure and are easy to manufacture and maintain. The plunger is thicker, larger, heavier, and has better stiffness than the piston rod, so it is recommended to use this cylinder in large-stroke hydraulic cylinders. The inner wall of the cylinder does not contact the plunger; it only relies on the guide bushing and plunger contact guide components. Therefore, the inner wall of the cylinder only needs rough machining or finishing, resulting in good process performance and low processing cost.

　Note: Plunger cylinders have a relatively large volume and weight. During horizontal installation, if the plunger is cooled on one side, unilateral wear of the seals and guide bushings is likely to occur. Therefore, vertical installation is recommended.