Abstract: A dashpot has a diaphragm provided for defining a pressure chamber and an atmospheric chamber, and an actuating rod secured to the diaphragm and operatively connected to a throttle valve. A cylindrical supporting member is secured to the diaphragm, opposite to the actuating rod, and a spring loaded valve is provided on an end of the cylindrical supporting member. A pipe secured to the dashpot body and having an opening at an end thereof, is projected into the pressure chamber. The opening is disposed to be closed by the spring loaded valve when the diaphragm is deflected by the throttle valve. A solenoid operated valve is provided to communicate the pressure chamber with the atmosphere through the pipe when opened. the diaphragm and the spring loaded valve are arranged such that the spring loaded valve closes the opening of the pipe at a smaller stroke than that of the diaphragm.