GB653246A - Improvements in aircraft speed indicators - Google Patents

Abstract

653,246. Aircraft safe-speed indica tors BELL AIRCRAFT CORPORATION. July 18, 1947, No. 19321. Convention date, March. 29, 1944. [Class 106 (ii)] An aircraft instrument comprises a fluid - tight housing 10 and pointers 15, 55 moving over an indicating face 14, the pointer 15 being actuated by means responsive to the difference between impact and static air pressure to indicate airspeed, and the pointer 55 being actuated by means responsive to changes in static air pressure to indicate maximum safe airspeed. As shown, the housing interior has a connection 52 to the static pressure portion of a Pitot-tube device (not shown), and the pointers 15, 55 are actuated respectively by a bellows 40, whose interior has a connection 45, 48 to the impact pressure portion of the Pitot-tube, and a sealed evacuated bellows 80. The shaft 16 for pointer 15 is mounted in a sleeve 18 and has a zero-return spring 19. A pinion 20 on the shaft meshes with a toothed sector 22 pivoted at 24 and carrying a crank-arm 26 which engages an arm 28 extending from a rock-shaft 30. This shaft also carries a crank 34 which engages an arm 36 connected to bellows 40. The bellows action is controlled by a variable resistance spring device 50. The sleeve 18 carries the pointer 55 and is connected by similar transmission mechanism to the bellows 80 which is carried by a rotatable boss 82 connected by an arm 90 and strut 88 to a nut 86 threaded on a screw 85. The screw can be adjusted in accordance with a scale 95 carrying index numbers corresponding to maximum permissible mack numbers for different aircraft.