Vane and exhaust valve in vane pump of function
The vane always contacts with the inner wall of the pump chamber during the operation of the pump. Therefore, the vane should have certain strength and wear resistance. Generally speaking, cast iron, graphite and polymer composite materials are used as rotary vane materials, and polymer composite materials are used for direct coupled pump.
Exhaust valve is one of the main vulnerable parts of vane pump, which will affect the pumping performance and produce noise. There are two types of exhaust valve: one is to use rubber pad as valve plate, the other is to use cloth phenolic laminate or spring steel sheet as valve plate. The exhaust valve must be immersed in pump oil. In the process of exhaust, compressed gas pushes the exhaust valve. After passing through the pump oil, it is discharged. The pump oil acts as a seal.
In a two-stage pump, when the cavity of high vacuum stage is different from that of low vacuum stage, an auxiliary exhaust valve should be set between the two stages. The function of the auxiliary exhaust valve is to open the auxiliary exhaust valve when the inlet pressure is high and the compressed gas from the high vacuum stage chamber has reached the exhaust pressure. Part of the gas is discharged by the auxiliary exhaust valve, and part of the gas is pumped away by the low vacuum stage chamber. With the decrease of pump population pressure, the discharge of auxiliary exhaust valve gradually decreases until it is finally closed.