British Patent Abridgments

A fluid flow detector comprises a flat plate 1 adapted to be supported in and acted upon by the fluid the flow of which is to be detected, rods, 2 extending from the plate 1 through apertures in a receptacle 4 and being fulcrumed therein by resilient material in the form of sealing rings 9 arranged between the rods 2 and the receptacle means being provided for indicating the degree of flow of the fluid in accordance with the angular position of the member 1. The rods 2 are connected by a cross‐bar 5. The longitudinal axes of the rods 2 intersect the plane of the plate 1. The apertures in the receptacle are provided with bushes 3 of hardened material, the clearance between the rods 2 and the bushes being sufficient to allow the plate‐rod assembly to rock freely between the limits set by the cross‐bar 5 abutting stops 10, 11 which are an integral part of the member 4. A pressure sensitive electric device in the form of a micro‐switch 12 is secured in the member 4. The switch is so arranged that its operating plunger just touches the cross‐bar 5 when the plate‐rod assembly is in its mid‐position. When the device is installed on an air‐craft, air flow acting in the directon of the arrow A will cause the plate‐rod assembly to tilt and so to actuate the switch to hold off a stall warning indicator. If the velocity of the air flow acting in the direction of arrow A falls below a certain predetermined value a spring in the switch 12 will actuate the switch to operate the stall warning indicator and will also push the cross‐bar 5 back to its normal position. To prevent excessive loading of the switch due to a high velocity of air flow in the direction of the arrow A an over‐ride mechanism consisting of a spring‐biassed plunger 13 is provided.