The external gear pump is the most widely used gear pump. The general gear pump usually refers to the external gear pump. Its structure is shown in Figure 5-14, which mainly consists of a driving gear, a driven gear, a pump body, a pump cover and a safety valve. The sealed space formed by the pump body, the pump cover and the gears is the working chamber of the gear pump. The axles of the two gears are respectively mounted in bearing holes on the two pump covers, and the driving gear shaft extends out of the pump body and is rotated by the motor. The external gear pump has the advantages of simple structure, light weight, low cost, reliable operation and wide application range.
When the gear pump is working, the driving wheel rotates with the motor and drives the driven wheel to rotate. When the meshing teeth on one side of the suction chamber are gradually separated, the volume of the suction chamber is increased, and the pressure is lowered, and the liquid in the suction pipe is sucked into the pump; the suction liquid is pushed into the discharge chamber by the gear in two directions in the tooth groove. After the liquid enters the discharge chamber, the liquid is squeezed from the discharge chamber into the discharge pipe due to the continuous engagement of the teeth of the two gears. The drive and driven gears rotate continuously, and the pump continuously draws in and discharges liquid.
The pump body is equipped with a safety valve. When the discharge pressure exceeds the specified pressure, the delivery liquid can automatically open the safety valve to return the high pressure liquid to the suction pipe.
The internal gear pump is composed of a pair of intermeshing internal gears and a crescent member, a pump casing, and the like therebetween. The function of the crescent is to separate the suction and discharge chambers. When the driving gear rotates, a partial vacuum is formed at the place where the gear is disengaged, and the liquid is sucked into the pump to fill the teeth of the suction chamber, and then enters the discharge chamber along two sides of the inner and outer sides of the crescent. Where the teeth enter the mesh, the liquid present between the teeth is squeezed and fed into the discharge tube.
In addition to the characteristics of self-priming capacity, flow rate and discharge pressure, the gear pump has no suction valve and discharge valve on the pump casing. It has the characteristics of simple structure, uniform flow and reliable operation, but low efficiency, large noise and vibration, and easy wear. It is mainly used to transport non-corrosive, solid-free particles and lubricating oils. The temperature is generally not more than 70 °C, such as lubricating oil, edible vegetable oil and so on. The general flow range is 0.045~30ms/h, the pressure range is 0.7-20MPa, and the working speed is 1200-4000r/min. https://www.xjetl.com