Hydraulic cylinder
The hydraulic cylinder is operated by a fluid power cylinder.
It is also referred to as a hydraulic linear motor and one of the hydraulic consumers.
He is the most important element in the working hydraulics. In it is the energy from the hydraulic fluid, which is supplied by a hydraulic accumulator or a hydraulic pump, implemented in an easy controllable, straight acting force. Hydraulic cylinders are available in innumerable designs. For the piston and rod diameter, there are DIN / EN standards and internal company standards.
- 2.1 plunger
- 5.1 Example
Double-acting cylinders
For double-acting cylinders, there are two opposing piston faces which are acted upon with hydraulic fluid. The cylinder thus has two active movement directions.
Operating principle of a double-acting cylinder
Differential cylinder
A differential cylinder has only one side face of the piston a piston rod. Characterized it has two differently large effective surfaces: first, the surface on the piston side, which acts fully, and the other, the rod-side area, in which only the annular surface acts. The ratio of piston area to ring surface is denoted by. This extends the differential cylinder normally at two different speeds and a. If the cylinder is operated in closed loop, it runs according to the speed specified by the setpoint.
Rod cylinder
A synchronizing cylinder (also called synchronous cylinder ) has on both sides of the piston area of a piston rod. The volume of the hydraulic oil flowing in and out is therefore always the same and thus, it also runs at the same speed in and out. Rod cylinder can also be implemented with only a piston rod. This provides a special form of the piston rod with internal bores that the area ratios are identical.
Tandem cylinders
In a tandem cylinder, two cylinders are interconnected so that the piston rod of the first cylinder acts through the bottom of the second cylinder on the piston rod therethrough. This due to the increase of the effective piston areas can be reached in spite of small size, a greater force.
Single-acting cylinders
Single-acting cylinders have only one side of the piston which is acted upon by hydraulic fluid. Work can be committed only in one direction. The return movement is carried out by the net mass or a foreign power ( such as a spring ). Lifts often have single-acting cylinders.
Operating principle of a single-acting cylinder
Plunger
A plunger ( plunger or cylinder) does not have an actual piston, but the piston rod serves as a piston. Plunger cylinders have a lower mechanical efficiency, but must be guided axially.
Telescopic cylinder
A telescopic cylinder consists of several reciprocally incorporated cylinders. It is often built in a single-acting design, but also in double-action design. A combination of single-action steps with a double-action stage is possible. The advantage of telescopic cylinders is that they can produce large strokes with relatively small installation lengths.
Designs
The hydraulic cylinder mainly used in industry are cylinders of circular construction according to ISO 6022 and DIN 24333, as well as tie rod according to ISO 6020/2 and DIN 24554th
Forces calculation
The force F on one side and a loss -acting hydraulic cylinder resulting from acting in the cylinder pressure p and the vertical in the direction of area A:
With a diameter dK of the cylinder piston to force FA = extending results to:
With a diameter dS of the piston rod, the retracting force F given by:
Example
A bar loaded with 100 hydraulic cylinder with 70 mm piston diameter and 32 mm rod diameter gives the following extension end strength:
The retracting force of the same cylinder is calculated as:
38.48 kN corresponds approximately to an applied mass of 3.92 tons.
Alternatives
As alternatives for certain areas of application are electric cylinders and pneumatic cylinders.