The structure of rotary vane pump is customarily divided into “oil immersed” and “oil sealed”. The former refers to the pump body immersed in the tank, its advantages are: many parts and components that require air tightness can be sealed by oil; easy to set up to prevent pump shutdown and oil return mechanism; easy to set up auxiliary oil circuit to improve the performance of the gas town, but also make the pump work more reliable at a higher inlet pressure. At present, the maximum pumping speed has reached 70L/s. The rest is called “oil seal”, and the purpose is to dip the exhaust valve into the oil. Seal the exhaust port with oil.
According to the location of the rotor eccentricity, there is a distinction between positive eccentric and lateral eccentric. Eccentric on the top is called positive eccentric, called lateral eccentricity on the side. Side eccentricity has the advantages of low oil level, less oil volume, less oil return after shutdown, less starting power and matching power, and easy maintenance of exhaust valve. Attention should be paid to vertical assembly for assembly process. For the positive eccentric structure, the flip chip method can be used for assembling, and the rotor position is used to find the proper position.
For two-stage pumps, the connecting method and supporting method of high and low two-stage rotor are also different: one is four supports, fork connection; the other is two supports. Key link drive. In the Two-Support structure, the low-level rotor is mostly the structure with internal holes, but also with the middle wall of the high-level rotor side journal extension as a low-level rotor. If the outer diameter of the lower rotor is the same as that of the higher rotor, the ratio d/D=b of the outer diameter of the rotor to the cylinder mirror should be larger when the normal groove is not threaded through the shaft. It is desirable to use smaller B when using positive groove. At this time, one end of the rotor is grooved and the other end is provided with a flange. Some people also use different b values, different diameters and rotor diameters for two stages. Or adopt the structural form of the side deflection rotary groove. Because of the different structure, the pump disassembly and assembly are different, users must carefully read the instructions to prevent damage to the pump.
For advanced rotor, for high-speed direct connection structure, considering the influence of dynamic balance, solid form should be adopted. For low speed pumps, when the rotor is large, the hollow form should be adopted to reduce weight.
The rotor has integral, integral wear, shaft, splice, welding and other structural forms. A structure commonly used in China is the two half rotor body plus two rotors with screws and pins. The new structure is joined by a rotor disc and an integral rotor. It has the advantages of good rigidity, low working time and good tolerance precision.
About the stator structure, there are three types of integral, middle wall press in and splice. One of the structures commonly used in China is the same size of the middle wall and the bore diameter. The interference fit is used to press into the stator. The advantage is that the high and low two level cylinder diameter is of good concentricity and the working hours are relatively low. The disadvantage is that the axial displacement can be caused when the interference is small and the shape and position tolerance can be affected when the interference is large; the secondary eccentric circular arc must be processed separately by the secondary clamping; and the depth of the circular arc is difficult to measure.
A new type of middle wall press-in structure has the same outer diameter of the middle wall as that of the rotor. The eccentric and homocentric surface of the high and low two stages can be clamped and processed at one time. The concentricity is good. All tolerances including the depth can be detected by common measuring tools. A small amount of interference is used with a positioning pin, and the middle wall of the stator is smaller, so the middle wall of the stator is thicker. It has good accuracy of geometric tolerance, which provides conditions for achieving high performance and good consistency.
Spliced stator structure, generally can be composed of five parts, parts simple, suitable for automated production, less scrap damage, parts wear more likely to repair, the disadvantage is to reduce the accumulative error of machine tools, more parts, machining surface, pinholes and pins require precision, for large pumps, assembly It is more complex and labor intensive. There are also other forms of splicing.
The integral type is fixed on the structure, just like the 2X type pump under 4L/s produced by Shanghai Vacuum Pump Works in the early stage. It has the advantages of simple maintenance, no moving of the middle wall and no interference deformation of the middle wall. But there are more working hours, higher technological requirements and greater labor intensity.
The structure of exhaust valve is divided into rubber, metal and resin laminate according to material. Rubber valve sheet has a plate, square, triangle and other basic shape, metal valve sheet has a plate shape, multi-layer circular and other basic shape, resin laminate is a plate shape.
For the low speed pump, the exhaust valve can be elastic without any elasticity. For high speed direct connection pumps, the exhaust valve should generally be loaded with elastic force. Therefore, in general, the pumping efficiency of high-speed direct-coupled pumps at inlet pressures above 1.3 kPa will be lower than that of low-speed pumps without elasticity.
The setting of exhaust valve. Because exhaust velocity affects pump power and pumping speed under 1.3kPa inlet pressure, it must be restricted. In the high-speed direct-connection pump, generally high and low two-stage are equipped with exhaust valves, the number of parts depends on the status and exhaust speed. For the two stage suction pump with equal suction volume, only a low level exhaust valve can be provided.