The internal structure of the mechanical water meter can be divided into three parts: shell, sleeve and inner core. The shell is made of cast iron, and the water passes through the lower ring space of the shell after coming out of the water inlet, which is called the “lower ring chamber”. The “upper ring chamber” in this annular space communicates with the water outlet. The bottom of the sleeve has a filter screen to filter the debris in the water. There are two rows of round holes on the side of the sleeve, and the position of the round holes is opposite to the upper and lower ring chambers of the shell. Obviously, the lower row is the water inlet hole, and the upper row is the water outlet hole. These two rows of holes are made diagonally along the tangent direction of the circle, and the upper and lower rows of holes are in opposite directions. The water flows in the tangential direction from the lower discharge hole, which is bound to form a rotating water flow, which is very important for the work of the water meter.
Take a look at the inner core, the inner core of the mechanical water meter is divided into upper, middle and lower three layers, we see from the window is the upper layer, only the pointer and the dial. In fact, the most critical is the lower layer, which has a plastic wheel, there are many plastic blades on the edge of the wheel, called the “impeller”.
The position of the impeller of the mechanical water meter is just in the rotating flow formed by the lower hole of the casing, the water shocks the blades around the wheel, produces torque, and makes the impeller rotate. The bigger the tap, the faster the water flows, and the faster the impeller spins.
The shaft of the impeller reaches the middle layer vertically, and there is a small gear on the shaft, which is engaged with the “decimal number gear” to achieve the purpose of accumulating the number of revolutions. The function of the “decimal number gear” is that every time the single-digit gear makes ten revolutions, the ten-digit gear makes one revolution. In other words, a one-digit gear makes one revolution, and a ten-digit gear makes one tenth of a revolution. The single-digit gear is the driver, which drives the ten-digit gear. In fact, each level of the decade is completed with two pairs of gears to make the rotation direction consistent, one pair of transmission ratio is 9:30, the other pair is 10:30, the two pairs are connected together, the total transmission ratio is the product of the two, that is, 0.099999, can be approximated to 0.1.