GB964588A - Pressure sensing flow control means - Google Patents

Abstract

964, 588. Fluid-pressure servomotor systems. NORMALAIR Ltd. Nov. 9, 1961 [Nov. 16, 1960; Dec. 23, 1960], Nos. 39330/60 and 44288/60. Heading G3P. Means for controlling the amount of air or gas flowing through apparatus, such as a fan 23, enclosed in a duct 10 comprises butterfly valve or shuttering means 24 actuated by a spring biased diaphragm 16 in response to signals from a pressure sensing device 1. The latter comprises a casing divided by a flexible diaphragm 6 into two chambers 4, 5 containing an aneroid bellows 9 and a bellows 7, respectively. A valve 25 actuated by the diaphragm 6 and controlling the pressure on the diaphragm 16 is mounted inside the bellows 7 which communicates with the chamber 4 and with the duct 10 at a point upstream of the fan while the chamber 5 is subjected to the duct pressure downstream of the fan. As the pressure difference across the latter increases the valve 25 and the shuttering means 24 are closed. In a further embodiment, the flow through a heat exchanger is controlled by a butterfly valve, the bellows 8 is connected to the downstream side of the exchanger, and the control valve co-operates with a seat arranged beneath it in the conduit leading to the diaphragm 16. The bellows 9 acts as an altitude compensating means and has its sensitivity limited by a spring 22.