Reciprocating vacuum pump, also known as piston vacuum pump, belongs to one of the low vacuum acquisition equipment. Compared with the rotary vane vacuum pump, it can be made into a pump with large pumping speed, and the efficiency is slightly higher than that of the water ring vacuum pump. The main drawbacks of this kind of pump are its complex structure, large volume and large vibration in operation. It can be replaced by liquid ring vacuum pump in many cases.

The working principle of reciprocating vacuum pump:

The structure and working principle of the reciprocating pump are shown in the figure. The main components are cylinder 1 and piston 2, in which the reciprocating linear motion is made. The driving of the piston is accomplished by crank connecting rod mechanism 3 (including cross head). In addition to the main components mentioned above, there are important components such as exhaust valve 4 and suction valve 5, as well as auxiliary components such as seat, crankcase, dynamic seal and static seal.

When running, driven by the motor, the piston in the cylinder moves to and fro through the role of crank and connecting rod mechanism. When the piston moves from the left end to the right end of the cylinder, the density of the gas in the cylinder decreases as the volume of the left chamber of the cylinder increases, thus forming the process of pumping. At this time, the gas in the suction container passes through the suction valve 5 and enters the left chamber of the pump body. When the piston reaches its rightmost position, the left chamber of the cylinder is completely filled with gas. Then the piston moves from the right to the left, when the suction valve 5 closes. The gas in the cylinder is gradually compressed as the piston moves from right to left. When the pressure of the gas in the cylinder reaches or slightly exceeds one atmospheric pressure, the exhaust valve 4 is opened, and the gas is discharged into the atmosphere to complete a working cycle. When the piston moves left to right again, it repeats the previous cycle, and so on, and finally achieves a stable equilibrium pressure in the pumped container.

In order to improve the efficiency of air extraction, suction valves and exhaust valves are usually installed at both ends of the cylinder, and then the suction and exhaust ports at both ends of the cylinder are connected in parallel by pipelines.