Abstract: A fluid damper blade made by bending a sheet of metal into a U and bringing the edges of the U together to form the trailing edge of the blade, the two edges of the U being of castellated form so that they interlock when brought together, with the castellations being bent over so as to embrace a reinforcing locking rod extending the full length of the blade trailing edge. This gives the blade enhanced rigidity and increased resistance to bending and twisting stresses. In addition, welding of the edges of the U is made unnecessary.

Abstract: A spring-powered actuator especially for operating devices such as fire and/or smoke dampers, doors, hatches, vents, traps, valves and other devices having components which are movable between at least two positions. The spring-powered actuator of the invention comprises a longitudinally-displaceable re-wind screw which is rotatable to recharge the spring of the actuator, and a tilting element on the screw which is mounted for tilting movement with respect to the screw axis to allow longitudinal movement of the re-wind screw so as to permit rapid and reliable release of energy stored in the spring. When used in a combination fire and smoke damper, it thus opens or closes the blades of the latter.

Abstract: For releasing and resetting a releasable and resettable device: a spring-motor dual-functioning mechanism comprising release means to release the device, a spring motor to reset the device, and spring-winding means to rewind the spring motor, the spring motor storage power being sufficient for at least two complete resetting operations of the mechanism.

Abstract: A control damper for controlling the flow of air or other gaseous fluid through a duct, comprising a line of blades each of which is so supported for rotation in a surrounding frame that the blades are swingable about parallel axes to open or close an opening in the frame and to be movable at will to intermediate positions between their fully-open and fully-closed positions, in which the blades are of aerofoil shape.

Abstract: A shut-off damper comprising a line of blades which are supported in a surrounding frame for rotary motion about substantially parallel axes to open or close an opening in the frame, and springy sealing strips each provided with a lining or cover of synthetic rubber or other resilient material so that the end portions of the blades make sealing contact with the said linings or covers to reduce or prevent the leakage of fluid past the blades when they are in their fully-closed positions.

Abstract: A shut-off damper having blades of a generally streamlined shape with the trailing edges of the blades comprising fluid sealing means extending along those edges so that a seal is formed between adjacent blades when the blades are in their closed positions.

Abstract: A combination smoke and fire shield damper comprising a line of blades each of which is so supported for rotation in a surrounding frame that the blades are swingable about parallel axes to open or close an opening in the frame, in which the blades are provided with "opened-out" trailing edges so that the leading edge of each blade interlocks with the trailing edge of an adjacent blade when the blades are in their fully-closed positions.