This device in the general sense is a three-dimensional engine with reciprocating or reciprocating movements. The operating principles of the hydraulic cylinder are widely used in astronautics, aviation, road construction, as well as on hoisting machines and in the earth moving industry. The mechanism has found application in various equipment, including forging machines and metal cutting machines.
Device description
If we consider the simplest case, then we can say that the hydraulic cylinder is a sleeve in the form of a cylindrical tube with an internal surface that has undergone careful processing. Inside the device there is a special piston with cuffs in the form of rubber seals. The latter serve to ensure that the working fluid does not flow through the divided cavity of the cylinder. In operation, special mineral oils are used. The device and the principle of operation of the hydraulic cylinder mean the flow of fluid into the cavity. The piston receives a certain pressure and begins to move.
Correct selection of the device requires knowledge of some important characteristics. To begin with, you should choose a suitable piston diameter, that is, the value of the pushing or pulling force of the hydraulic cylinder. A significant role is also played by the value of the diameter of the rod. This parameter is selected depending on the required load capacity and the level of dynamic load. If the value is incorrectly selected, the rod may bend during operation. The piston stroke, in turn, affects the direction of movement of the working body and the overall dimensions of the device in the unfolded state. When assembled, the dimensions are determined by the distances in the centers. The method of mounting the hydraulic cylinder depends on its design.
General principle of work
On the polished surface of the rod, the force is transmitted from the piston through the rod. The correct direction is determined by the helpbook. The processes for supplying and discharging the working fluid in the cylinder occur through two caps fixed in the sleeve. Also, the stem has a seal of several cuffs. The first of them serves to prevent leakage of the working fluid from the hydraulic cylinder, and the second collects dirt that gets inside. The movable mechanism and the stem on the thread are connected by a special part or eye, which provides movable fastening of the unit body.
There are two main principles of hydraulic cylinder operation - with control by means of a control valve or thanks to certain means for adjusting the hydraulic drive. At the same time, all operating mechanisms are manufactured with increased strength and reliability. Structural elements like a cylinder and a control unit operate at high pressures up to 32 MPa. In order to better understand the mechanisms of action of such aggregates, their main relevant varieties should be considered.
Single acting hydraulic cylinders
In such devices, the rod extends through the pressure of the working fluid in the piston cavity. Returning to the starting position is carried out by spring force. When compared with the principle of operation of a double-sided hydraulic cylinder, one important nuance can be noted. Other things being equal, less force is created in a one-sided unit. This is due to the fact that the direct stroke of the rod implies the need to overcome the spring force of the spring in the mechanism under consideration.
A striking example of a single-acting hydraulic cylinder is an ordinary jack. In this case, the spring is used as the main return element. However, in some cases there is no need to use this part. For example, the return can occur due to the gravity of the lifted load, another unit, or through a drive mechanism.
Double-acting hydraulic cylinders
Here, the working fluid also creates pressure on the stem. As the cavity of the hydraulic cylinder is selected, respectively, a piston or rod. A direct stroke is able to create more effort, but the speed of the working fluid is less. With the reverse movement, the picture is exactly the opposite.
This principle of operation of a double-acting hydraulic cylinder is based on the difference in areas to which the direct application of the pressure force of the working fluid occurs. Similar devices are found everywhere, for example, during operations of raising and lowering dumps in most bulldozers. The main role is played by the effective cross-sectional area.
Function of the hydraulic locks
The design of this element is based on what type the hydraulic cylinder belongs to. A one-way device is characterized by the presence of a saddle, a locking and regulating element in the form of a ball, a piston with a pusher, and also a spring. The principle of operation of the hydraulic cylinder and its lock is that in the absence of pressure in the control line, the working fluid flows from one channel to another, thereby shifting the ball. However, the reverse stroke does not occur, because under the action of the flow, the locking-regulating element is firmly pressed against the saddle. If pressure is present in the control line, then the working fluid moves freely between the two channels.
In a double hydraulic lock two check valves are combined at once. They are located in one housing so that the control line of each of them is connected to the input of the other. The principle of operation of the hydraulic lock of the hydraulic cylinder in this case is based on the fact that the working fluid moves in the opposite direction only when there is pressure in the compartment. Moreover, each of the two sides of the mechanism works independently.
Design options
Among the main types are plunger, piston and telescopic devices. The principle of operation of the plunger hydraulic cylinder implies the supply of working fluid into the cavity, where the plunger begins its displacement due to the action of high pressure. The unit is able to return to its original state due to the action of external force on the end of the rod.
Piston cylinders are the most common. The main difference between such devices from plunger ones is the ability to create a pushing or pulling force. The stock cavity communicates through the breather with the atmosphere, however, dust and dirt particles do not enter the work surface.
Telescopic hydraulic cylinders
These devices got their name due to their external resemblance to telescopes or telescopes. The versatility of these hydraulic cylinders makes it possible to use both unilateral and bilateral mechanisms in their basis. Most commonly used for lifting and lowering dump truck bodies. The principles of operation of a telescopic type hydraulic cylinder imply the presence of a large piston stroke with relatively compact overall dimensions of the device itself.