Throttle flap valve 3 turns about fixed axis A. Rigidly attached to valve 3 is pulley 4 over which flexible cord 5 runs. One end of cord 5 is attached at point B to bell member 2 and the other end at point C to counterbalancing weight 6. When the pressure changes in pipeline 1, connected to the space under bell member 2 by tube 7, the bell member rises or descends. This turns throttle flap valve 3 and continues until the pressure in the pipeline approaches the preset value again.
$3766$SHP,Rg$