Diaphragm pump is a special type of volume pump. It relies on a diaphragm to change the volume of the studio to suck in and out liquids.

The pneumatic diaphragm pump is mainly composed of the transmission part and the diaphragm cylinder head. The transmission part is the driving mechanism that drives the diaphragm to and fro. Its transmission forms are mechanical, hydraulic and pneumatic, among which the hydraulic transmission is widely used. The working part of the diaphragm pump is mainly composed of crank connecting rod mechanism, plunger, cylinder, diaphragm, pump body, suction valve and discharge valve, among which the driving mechanism consisting of crank connecting rod, plunger and cylinder is very similar to that of reciprocating plunger pump.

When the diaphragm pump is working, the crank-connecting rod mechanism, driven by the motor, drives the plunger to and fro. The movement of the plunger is transmitted to the diaphragm through the working liquid (usually oil) in the cylinder, which makes the diaphragm agitate back and forth.

The cylinder head part of pneumatic diaphragm pump is mainly separated by a diaphragm which separates the transported liquid from the working liquid. When the diaphragm moves towards the drive mechanism, the liquid is sucked in for negative pressure while working in the pump cylinder. When the diaphragm moves to the other side, the liquid is discharged. The transported liquid is separated from the working liquid by a diaphragm in the pump cylinder, and only touches one side of the pump cylinder, suction valve, discharge valve and diaphragm, without touching the plunger and sealing device. This makes important parts such as the plunger work completely in the oil medium and work well.

The diaphragm should have good flexibility and corrosion resistance, usually made of polytetrafluoroethylene, rubber and other materials. The pot bottom parts with mesh holes on both sides of the diaphragm are set up to prevent excessive local distortion of the diaphragm, commonly referred to as the diaphragm limiter. The pneumatic diaphragm pump has good sealing performance and can easily achieve leak-free operation. It can be used to transport corrosive liquids such as acid, alkali, salt and high viscous liquids.

There is a diaphragm in each of the two symmetrical working chambers of the pump, which is connected together by a central link. Compressed air enters the valve from the intake port of the pump, and through the valve mechanism, compressed air is introduced into one chamber, which drives the motion of the diaphragm in the chamber, while the gas in the other chamber is discharged. Once the end of the trip is reached, the valve mechanism automatically introduces compressed air into another working chamber, pushing the diaphragm in the opposite direction so that the two diaphragms move continuously and synchronously to and fro. In the illustration, the compressed air moves from the inlet to the valve and the diaphragm moves to the right. The suction force of the chamber causes the medium to flow from the inlet and pushes the ball valve into the chamber, which is blocked by suction. The media in the chamber is squeezed, the ball valve is pushed open to flow out of the outlet, while the ball valve is blocked and prevented from flow, so the media is continuously sucked in from the inlet and discharged from the outlet through the cycle.