Patent GB-438137-A (GB)
Title: Improvements relating to indicating instruments such as sensitive altimeters
IPC: G01L7/00
Filed: 1934-05-12
Abstract: 438,137. Indicating instruments. BENDIX AVIATION CORPORATION, 105, West Adams Street, Chicago, U.S.A. May 12, 1934, No. 14424. Convention date, May 13, 1933. Addition to 425,299. [Classes 106 (ii) and 106 (iv)] The instrument includes indicating means which can be preset under one condition for another condition and reference indicating means simultaneously adjustable with the setting of the main indicating means for indicating the condition for which the instrument is preset, and is characterized in that the reference indicating means is calibrated in units different from the units of the main indicating means and having a varying ratio in increments of change to the increments of change in units of the main indicating means. The invention is described as applied to an altimeter of the barometric type indicating in feet the preset indicator indicating the barometric pressure for which the instrument is set in inches of mercury. The Aneroid capsules 7, 8, 9 are carried by a rod 10 secured to a triangular plate 11 spaced from a plate 12 forming with the plate 11 and crossrods 10, 13, 14 a frame carrying the whole mechanism. Movement of the capsules is transmitted by links 22, 23 to a rock-shaft 26. A sleeve 27 adjustably secured on the shaft is connected by a link 31 to a counterweight 33 supported from a leaf spring 38 to damp effect of extraneous vibrations. The sleeve 27 is connected by linkage 41 to a gear sector 39 meshing with a pinion 42 carried by a shaft 43 the ends of which are carried in jewelled bearings in plates 45, 49. The sector 39 is secured to a stub shaft 51 similarly journalled in the plate 12 and a fixed plate 64. Secured to the shaft 43 is a large gear 58 which meshes with a small pinion 59 on a counter shaft 60 carried in jewelled bearings in supporting plates 63, 64 secured to a spacing rod 65 which holds also the plates 45, 49. These are angularly adjustable together about bushings 52, 66 of which the latter is carried by the dial plate 57. On the shaft 43 is a large gear 67 meshing with a pinion 68 carried by a hollow shaft 69 bearing in and extending through the bushing 66 and carrying the pointer 70 showing thousands of feet. A pointer 74 carried on the shaft 60 which passes through the shaft 69 and moves over a concentric scale showing hundreds of feet. A hair spring 75 takes up both lasts in the transmission. Setting means. To set the instrument, say at sea level, to give a correct reading, say when the aeroplane is going to land, the plates 45, 49 are adjusted about the common axis of the pointers. A pin 80 projects from the inner side of the plate 49 into a cut-away portion 81 of an internally threaded block 82 through which passes a threaded shaft 83 journalled in blocks 84, 85, Fig..5, carried by the plate 12. Rotation of the block 82 is prevented by the tongue 86 engaging a slideway. A spring 89 provides a return movement. The shaft 83 is actuated by a knob outside the casing and through bevel gear 96, 97, 100, 101 actuates the screw 83. To indicate the setting in terms of barometric pressure a counter 102 is provided worked from the shaft 83 through bevel gear 105, 106 and indicates in inches of mercury. The increments of pressure correspond with the increments of altitude on the other scale but the increments are unequal. Specification 429,921 is referred to.