Industry News

Types of hydraulic cylinders and design of hydraulic cylinder parameters

2021-07-28

Hydraulic cylinder is a widely used structural form in hydraulic system. In order to correctly design and use this kind of cylinder, we should master its characteristics and related applications and precautions.

(1) Single piston rod hydraulic cylinder this hydraulic cylinder has a piston rod only on one side of the piston, and the effective action areas on both sides of the piston are not equal. The larger the diameter of the piston rod, the greater the difference between the effective action areas on both sides of the piston. When the oil supply pressure is equal, the thrust generated by the side without the piston rod is greater than the tension generated by the side with the piston rod; 1. Under the condition of equal flow, the extension speed of the piston rod caused by the pressure oil on the side without the piston rod is slower than the retraction speed of the piston rod caused by the pressure oil on the side with the piston rod.

Note: it is suitable for the situation that the piston can bear a large thrust in the return direction when there is no-load. The thicker the piston rod, the greater the difference between thrust and tension, slow and fast. The slow work in and fast return of the worktable of hydraulic planer are realized by using a single piston rod hydraulic cylinder.

(2) Double piston rod hydraulic cylinder this kind of cylinder has piston rods on both sides of the piston. When the two piston rods have the same diameter and the oil supply pressure and flow remain unchanged, the reciprocating speed and force of the piston are also equal. Because there are two piston rods, it has good rigidity and stability.

Note: the space occupied during operation is large, and the power range is about 3 times of the effective stroke length. This form of hydraulic cylinder is mostly used in grinder worktable.

(3) Single acting hydraulic cylinder this kind of cylinder is the simplest hydraulic cylinder. It can only supply pressure oil to one side of the piston and output the force in one direction. The movement in the opposite direction is completed according to the external load force, spring force, self weight of the plunger rod or piston rod, that is, there is no hydraulic force in the opposite direction. Its advantage is to save hydraulic power and simplify oil circuit.

Note: the speed and force in the opposite direction cannot be controlled. The self gravity, load force and spring force driving the return movement of the piston rod or plunger rod must be greater than the sum of the back pressure and the friction resistance of various parts of the hydraulic cylinder. For the spring return hydraulic cylinder, the spring must have a certain action space to make its volume larger.

Single acting hydraulic cylinder is widely used in the positioning and clamping of machine tools, the lifting of dump truck, the lifting of elevator, ship cargo boom and so on.

(4) Double acting hydraulic cylinder is more widely used than single acting hydraulic cylinder. The pressure oil can be supplied to both sides of the piston alternately to drive the piston to move back and forth. The movement speed and oil supply pressure in the push and pull directions can be controlled. Double acting hydraulic cylinder can be divided into single piston rod and double piston rod.

Note: the control system is more complex than the single acting hydraulic cylinder. The application of single piston rod double acting hydraulic cylinder is more common than that of double piston rod double acting hydraulic cylinder. The reciprocating hydraulic cylinder of machine tool workbench and various action hydraulic cylinders in engineering machinery all adopt single piston rod double acting hydraulic cylinder.

(5) Plunger hydraulic cylinder most plunger cylinders are single acting cylinders with simple structure and convenient manufacture and maintenance. The plunger of the plunger cylinder is thick, large and heavy, and its rigidity is better than that of the piston rod. Therefore, it is better to use this kind of cylinder in the hydraulic cylinder with large stroke. Because the inner wall of the cylinder block is not in contact with the plunger, but only guided by the contact between the guide sleeve and the plunger, the inner wall of the cylinder block can not be processed or only rough processed, with good process performance and low processing cost.

Note: the volume and weight of the plunger cylinder are relatively large. During horizontal installation, the cold pressure of the column to one side is easy to cause unilateral wear of the seal and guide sleeve. Therefore, the plunger cylinder is suitable for vertical installation. When installed horizontally, the plunger bracket shall be set to prevent the plunger from sagging and avoid "other force" caused by bending and increasing the initial deflection surface.

(6) Telescopic hydraulic cylinder telescopic cylinder is also called multi section cylinder, multi-stage cylinder or composite cylinder. It has two forms: single action and double action. The total stroke of this cylinder is long and the length after contraction is very short. It is especially suitable for occasions with small installation space and long stroke requirements. For the same long stroke, the more sections, the shorter the length after contraction.

Note: the more sections, the greater the deflection when the hydraulic cylinder extends, the more complex the structure, the more difficult it is to manufacture and the higher the cost. Therefore, the number of sections should be increased only in special cases.