The area of the large and small plunger is S2 and S1 respectively, and the force on the plunger is F2 and F1 respectively.
According to PASCAL’s principle, the pressure of the confined liquid is equal everywhere, that is, F2/S2=F1/S1=p; F2=F1(S2/S1).
The gain effect of hydraulic pressure is the same as that of mechanical gain. The force is increased, but the work is not gained. Therefore, the motion distance of large plunger is S1/S2 times of that of the small plunger.
The basic principle is:
The oil pump transfers the hydraulic oil to the integrated cartridge valve blocks, and assigned to the upper chamber or lower chamber of the cylinder through the one-way valve and relief valve. Under the action of high pressure oil, the oil cylinder starts to move up and down.
The hydraulic press is a device that makes use of liquid to transfer pressure. The law of PASCAL is applied to the transfer of pressure in a closed container.
The hydraulic drive system of four-column hydraulic press consists of power mechanism, control mechanism, executive mechanism, auxiliary mechanism and working medium.
Usually, the oil pump is used as the power mechanism. One or more pumps are selected to meet the requirement of running speed of the actuator.
- Gear pump for low pressure (oil pressure less than 2.5mp);
- Blade pump for medium pressure (oil pressure less than 6.3mp);
- Plunger pump for high pressure (oil pressure less than 32.0MP).
The function of working medium used in a hydraulic press is not only to transfer pressure but also to ensure the working parts of the hydraulic press machine are sensitive, reliable, long life and less leakage.
The basic requirements of hydraulic press for working medium are:
① Suitable fluidity and low compressibility are available to improve transmission efficiency.
③ Good lubrication performance;
④ Easy to seal;
⑤ Stable performance, long-term work without deterioration.
The hydraulic press uses water as the working medium at first and then uses emulsified liquid by adding a small amount of emulsified oil into the water to increase the lubrication and reduce corrosion.
The oil press with mineral oil as a working medium appeared in the late 19th century. The oil has good lubricity, anti-corrosive and moderate viscosity, which is beneficial to improve the performance of the hydraulic press.
In the second half of the 20th century, a new type of water-based emulsifying solution was developed, which was characterized as “oil inclusion water” rather than “water inclusion oil”.
The outlook of the ” water inclusion oil ” is oil, its lubricity and corrosion resistance are close to oil. Besides, it contains little oil and is not easy to burn. However, water-based emulsions are more expensive, which limiting its spreading.