Compact flowmeter for water, oil, and various liquids.

Figure A.1 shows the schematic cross-section of Flaptor body. The measurement principle of Flaptor is basically the same as that of variable area flowmeter.
When liquid/gas flow hits the flapper, the flapper rotates towards downstream due to the differential pressure, as the pressure in the upstream side is higher than that of the downstream.
The flapper simultaneously receives the force of the spring placed in the hinge so that it rotates towards the upstream. Thus, the flapper is stabilized at the position where the difference pressure force is in balance with the spring force.

As shown in Fig. A.2, the flapper magnetically couples with the pointer in the indicator portion which is placed outside of the body. The flapper angle varies depending on the amount of fluid passing through the space between the flapper and the liner. As the liner is specially designed, the flapper angle and the pointer angle vary proportionally to the flow rate. The mechanism achieves the indicator where the scale spacing of scale plate is almost equal.