Patent GB-474806-A (GB)
Title: Improvements in altimeters
IPC: G01L11/00
Filed: 1936-05-06
Abstract: 474,806. Altimeters. ETABLISSEMENTS E. JAEGER. May 6, 1936, No. 12820. Convention date, April 1, 1936. [A Specification was placed open to inspection under Sect. 91 of the Acts, Nov. 9, 1936.] [Class 106 (ii)] The instrument is compensated for movement of the capsule due to temperature changes and also for variation in the length of a movement transmitting lever due to temperature change by means either of two bimetallic strips or of one suitably inclined bimetallic strip. In the form shown in Fig. 1, a strip 217<1> is rigidly secured at one end 231 to a right-angled lever 227 pivoted at 218, the other end of the strip being pivoted at 25 to a link 24 pivotally connected at 23 to the diaphragm 2m of a capsule 2. The end of the strip moves from 25 to 25k under temperature and compensates for a movement of the diaphragm from 23 to 23k. Similarly, a second strip 2172 rigidly secured at one end 232 to the lever 227 is pivoted at the other end 233 to the members transmitting movement to the indicating needle 47k and corrects the length l of the lever 227. In alternative forms, one bimetallic strip pivoted to the link 24 and rigidly secured to the lever is suitably inclined to carry out both compensations. The Specification as open to inspection under Sect. 91 comprises also a construction, Fig. 1 (Cancelled), in which the vacuum box has a rigid bottom 1 and strong top constituted by a corrugated diaphragm 2. The bottom is held to a resilient blade 6 by a screw. 5. The ends of the blade 6 engage recesses in rigid pillars 7, 8 connecting the plates 9, 10 carrying the movement. The box 1, 2 rests on the pillar 7 by means of a projection engaging a recess therein, a similar projection entering a recess in the pillar 8 but bearing on a conical pin 18 screwed into a bore of the pillar. This screw serves to adjust the box relatively to the pillar. The movement of the box is transmitted through a bimetallic strip 22 and link 24 to a bell-crank 26 journalled on hard stone bearings in two plates 28, 29 rigidly connected together and to the plate 10. The free end of the arm 34 of the bell-crank is pivoted on hard stone pivots to a link 36 pivoted in turn to a forked member 38 carried by a resilient blade 42 secured to a lever 41 on a shaft 43. From this shaft a rack and pinion 44, 45 transfer the motion to the pointer spindle 46 which is mounted in stone bearings. A screw 48 serves to adjust the transmission ratio. Either the link 36 or blade 42 may be constituted by a bimetallic strip. A spiral spring 53 restores the pointer 47 to zero. In another form, Fig. 8 (Cancelled), the aneroid box 2 has the under face provided with a boss 3 through which the box is evacuated and which is subsequently sealed and protected by a cap 100, the boss being secured to a support 101. The movement of the box is transmitted to indicating means by a link 24, Z-shaped lever 115 pivoted on pivots 26, bimetallic strip 117, link 36 and arm 41 to a shaft 43 in stone bearings, and from the shaft by rack 44, pinion 45a, shaft 46a in stone bearings, toothed wheel 131 to pinion 45 and pointer 47. The amplification ratio is compensated by the strip 117 and can be adjusted by moving the clamp securing the strip to the lever 115 along its arm. A milled knob on the outside of the casing can turn a pinion gearing with teeth on the periphery of the part 129 and thus the whole movement together with the crown 160 carrying the dial 56. A screw acting on the free end of a resilient plate 104 carrying the pivots 26 serves to adjust the zero and a movable abutment 114 limits expansion of the box 2. In a further modification, the disc bearing the barometer scale is not fixed to the part 129 but is turned by gearing from the same knob that turns that part. This subject - matter does not appear in the Specification as accepted.