Hydraulic cylinder manufacturers--HC

What is the Hydraulic Cylinder?

The hydraulic cylinder is also called linear hydraulic motor. And it is the mechanical executor which is applied to offer a thrust in the limited stroke at the single direction. Hydraulic cylinders are widely used across various industries which are related to machine too, metallurgy, mine, chemical industry, shipping, water and electricity etc.

Hydraulic Cylinder Operating
 

The power of hydraulic cylinder comes from pressurized hydraulic oil which is a kind of special oil. Every hydraulic cylinder has a cylinder barrel where the piston rod can move well with this special oil. And one of the important keys to move is the sealing performance. So the piston rod is connected to a piston. And the piston is combined with sliding rings and o-rings. The inner cylinder is divided into two chambers by piston, the bottom chamber and the piston rod side chamber. The piston rod moves in a linear direction when the oil pressure acts on the piston.

Because hydraulic cylinder is a force supplier, the piston rod is always connected with some other components from machines or tools. When piston rod moves under the oil pressure, the components connected to rod will also start moving.

In the hydraulic linear action system, the hydraulic cylinder is like an actuator and the hydraulic pump is like a generator. The piston can go forth when the pump push the hydraulic liquid into one of nozzles by a high pressure pipe. And then the rod can go back when the pump pushes the hydraulic liquid into the other nozzle. The piston diameter and oil supply’s speed can determine the force and moving speed of hydraulic cylinder.
 

Hydraulic Cylinder Components:

A hydraulic cylinder consists of below components:

a. Hydraulic Cylinder Barrel
The cylinder barrel should use seamless forged steel pipe.
The wall thickness should be determined by pressure requirement.
The inner barrel must be mirror grinded.
The surface finishing should be controlled in 0.05umm.

b. Hydraulic Cylinder Bottom or Cap
Most hydraulic cylinders’ barrels and bottom portions are welded together. If they are not welded well, the inner barrels are easy to be damaged. So the screwed or flanged connections will be designed from the cylinder end cap to barrel. It is a better deign to install and repair hydraulic cylinder.

c. Hydraulic Cylinder Head
The cylinder head is usually connected to barrel with screw or flange, and in some special situations, it will connected with a sort of simple lock. Flange connection is the best methods with the highest price, because the flange must be welded to the pipe before machining. For larger size hydraulic cylinder, it will cause big problem if the cylinder head is not connected with the diameter of 300 to 600mm’s screws, as well as the alignment mounting.

d. Hydraulic Cylinders Piston
The piston, one of important components in hydraulic cylinder, divides the cylinder barrel into two parts. The piston is always machined with grooves to meet elastomeric or metal seals. These seals are often referred to U-cups, O-rings or cast iron rings, which avoid the pressurized hydraulic oil from passing by the piston to the chamber on the opposite side. The different pressures between the two sides of piston can make the cylinder extend and retract.

With the different pressures and temperatures, the piston seal is designed in different and needs various materials. In general, elastomeric seals made from Viton are best in higher temperature environments while seals made from nitrile rubber or other materials are best in lower temperature. And the best seals for high temperature are cast iron piston rings.

e. Hydraulic Cylinder Piston Rod
The piston rod is made of a hard chrome-plated piece of cold-rolled steel. It attaches to the piston and can extend from the cylinder through the rod-end head. In double rod-end cylinders, the actuator has a rod extending and retracting from both sides of barrel. The piston rod connects the hydraulic cylinder to machine component to do work. This connection can be in the form of a machine thread or a mounting attachment such as rod-clevis or rod-eye. These mounting attachments can be welded to the piston rod. And in some special situations, they are installed in the machine part of the rod-end.

f. Hydraulic Cylinders Rod Gland
To avoid the leak of pressurized oil, the cylinder head is always fitted with seals. This area is named rod gland. When the cylinder does the extending and retracting wok, the contaminants are easy to enter the cylinder. So these seals are called rod wiper. Every rod gland has a rod wear ring. This wear ring is like a linear bearing to support the weight of the piston rod and guides it when it goes back and forth through the rod gland. In some situations, especially in small hydraulic cylinders, the rod gland and the rod wear ring are made from a single integral machined part.

g. Hydraulic Cylinders Other Parts
Cylinder bottom connection
Seals
Cushions

A hydraulic cylinder is a supplier of force which is just pulling and pushing. It cannot be transmitted to the piston rod or the cylinder without bending moments or side loads. So the ideal connections of hydraulic cylinder are a single clevis with a spherical ball bearing. They can bring lots of advantages, such as, bear the pushing load, allow for any misalignment between the actuator and make the cylinder move well etc.