Abstract: A liquid flow control device (20) comprises a variable orifice (28/30) in a conduit (15), and branch lines (41, 42) above and below a flow restriction, which may be the variable orifice itself. The orifice is controlled to maintain a predetermined relation between the pressures (P.sub.1, P.sub.2) in the two branches. A metering valve (60) for a second liquid to be injected into the conduit may be controlled simultaneously to maintain a preset ratio between the flow coefficients of the valve and the orifice, so that if the pressures above and below the metering valve are the same as the pressures above and below the variable orifice, the respective flow rates will stay in the same proportion, and the proportion of second liquid injected into the liquid in the conduit will be constant at all flow rates.

Abstract: A connector for high pressure fluid conduits, such as fire hoses, has a chamber (10) with an inlet (4) and outlet (6) and between them a resilient ring (18), having an outer diameter close to the width of the chamber, on a dished support (14). The ring has a generally rectangular section except for a chamfer (24) on the inner upstream edge. The support has a central flow passage (16) aligned with the central passage (20) in the ring and carries two intersecting trapezoidal fins (22) projecting through the ring. When connected to a complementary coupling, the inlet and outlet bores of the connector correspond to the diameter of the chamfered portion of the ring. The device controls transient pressure peaks by deformation of the resilient ring without excessive reduction in flow.