Подскажите, пожалуйста, перевод слова Flapper? Это запчасть моторхеда. Перевожу инструкцию по сборке моторхеда.

Контекст такой:
1. Check Valve Cartridge assembly.
Install Seat Seal over lip on Flapper Seat as shown. Install O-ring BS-117 onto Flapper Seat.

Holding the Flapper Insert in the position shown, insert Flapper Pin halfway through the pin hole in the Flapper Housing so the Torsion Spring may be fitted. Push Flapper Pin further, until there is equal spacing between the end of the pin and the outside diameter of the Flapper Housing on both sides. Ensure Flapper Insert is held by the Torsion Spring in the normally closed position.

Заранее большое спасибо!