GB554410A - Improvements in or relating to air speed indicators - Google Patents

Abstract

554,410. Air speed indicators. HAMSHERE, E. A. Dec. 19, 1941, No. 16411. [Class 106 (ii)] An instrument automatically corrected for altitude changes comprises a rock shaft actuated by a metal capsule responsive to variations in pitotstatic pressure, a second rock-shaft mechanically coupled to the indicator pointer oppositely projecting lever arms carried by the rock shafts, and variable coupling means between the lever arms actuated by means responsive to changes in the static pressure. The pressure fluid from a pitot tube is transmitted through the pipe 2 to a casing 3 secured to the frame plate 1 and acts on a metallic bellows 4 sealed at the upper end to the casing 3. The upward movement of the plate 6 of the bellows with increase of pressure is limited by an adjustable stop 7 carried by a rod 59. Movement of the bellows is transmitted by a rod 8 to an arm 9 on a rock shaft 10. A bracket 12 on the shaft 10 can be adjusted relative to the arm 9 by means of a screw 12a passing through an extension 14 of the arm 9 into the bracket, a spring 13 holding the extension 14 against the head of the screw. The bracket 12 also carries a curved lever arm 15 adjustable axially and radially in the bracket and fixed by a screw 16. Parallel to the rockshaft 10 is a rock-shaft 17 having an arm 19 thereon. A " compensating " arm 20 is mounted on a third rock-shaft 21 approximately at right angles to the shafts 10, 17 the arm passing beneath arm 15 and over arm 19. If the shaft 21 is moved axially to displace the " compensating " arm, the leverage with which the shafts 10, 17 are coupled together will vary, thus altering the magnification of the indicating movement from the bellows 4. The rock-shafts 10, 17, 21 carry counter-balance weights 22, 23, 63. The shaft 17 carries an arm 24 connected by a pivoted link 25 to an arm in one with a toothed wheel gearing with a pinion 24 on the spindle of a pointer 29 moving over a dial 30. A hair spring on the pointer spindle tends to move the pointer from its zero position. " The compensating shaft 21 is mounted so that it can be moved axially in an adjustable carriage 32 by an arm 51 on a fourth rock shaft 33, a ball 52 engaging between collars 53 on the shaft. This shaft is rocked by movements of a rod 37 moved by a bellows 34 against a spring 40. The bellows is acted upon by the static pressure of the atmosphere. The rock shaft 33 carries an independently adjustable pair of curved lever arms 43, 44 and turns against the influence of a spring 48. The carriage 32 is adjustably mounted about the axis 54.