基本原理是油泵把液压油输送到集成插装阀块，通过各个单向阀和溢流阀把液压油分配到油缸的上腔或者下腔，在高压油的作用下，使油缸进行运动.液压机是 利用液体来传递压力的设备。液体在密闭的容器中传递压力时是遵循帕斯卡定律。四柱液压机的液压传动系统由动力机构、控制机构、执行机构、辅助机构和工作介质组成。动力机构通常采用油泵作为动力机构，一般为积式油泵。为了满足执行机构运动速度的要求， 选用一个油泵或多个油泵。低压（油压小于2.5MP）用齿轮泵；中压（油压小于6.3MP）用叶片泵；高压（油压小于32.0MP)用柱塞泵。各种可塑性 材料的压力加工和成形，如不锈钢板的挤压、弯曲、拉深及金属零件的冷压成形，同时亦可用于粉末制品、砂轮、胶木、树脂热固性制品的压制。
Working principle of hydraulic press
Working principle of hydraulic press. The area of large and small plunger is S2 and S1, and the force on plunger is F2 and F1 respectively. According to Pascal's principle, the pressure of closed liquid is equal everywhere, that is, F2 / S2 = F1 / S1 = p; F2 = F1 (S2 / S1). It indicates the gain effect of hydraulic pressure. Like mechanical gain, the force increases, but the work does not gain. Therefore, the movement distance of large plunger is S1 / S2 times of that of small plunger.
The basic principle is that the oil pump delivers the hydraulic oil to the integrated cartridge valve block, and distributes the hydraulic oil to the upper chamber or lower chamber of the oil cylinder through each one-way valve and overflow valve. Under the action of high-pressure oil, the oil cylinder moves. The hydraulic press is a device that uses liquid to transmit pressure. When liquid transfers pressure in a closed container, Pascal's law is obeyed. The hydraulic transmission system of four column hydraulic press is composed of power mechanism, control mechanism, actuator, auxiliary mechanism and working medium. The power mechanism usually uses the oil pump as the power mechanism, which is generally an integral oil pump. In order to meet the requirements of the speed of the actuator, one or more oil pumps are selected. Gear pump for low pressure (oil pressure less than 2.5MP), vane pump for medium pressure (oil pressure less than 6.3mp), plunger pump for high pressure (oil pressure less than 32.0mp). It can also be used for pressing powder products, grinding wheels, bakelite and resin thermosetting products.
Working medium of hydraulic press
The working medium used in hydraulic press is not only to transmit pressure, but also to ensure that the working parts of the machine work sensitively, reliably, with long service life and less leakage.
The basic requirements for working medium of hydraulic press are as follows:
① It has suitable fluidity and low compressibility to improve the transmission efficiency;
② It can prevent corrosion;
③ Good lubrication performance;
④ Easy to seal;
⑤ Stable performance, long-term work without deterioration. At first, water was used as the working medium of hydraulic press, and then a small amount of emulsified oil was added into the water to increase the lubricity and reduce the corrosion.
In the late 19th century, hydraulic press with mineral oil as working medium appeared. The oil has good lubricity, corrosion resistance and moderate viscosity, which is beneficial to improve the performance of hydraulic press. In the second half of the 20th century, a new type of water-based emulsion appeared, which is "water in oil" instead of the original "oil in water". The outer phase of water in oil emulsion is oil, its lubricity and corrosion resistance are close to oil, and the oil content is very small, so it is not easy to burn. However, the high price of water-based emulsion limits its popularization.