Patent GB-425299-A (GB)
Title: Improvements in and relating to indicating instruments such as sensitive altimeters
IPC: G01L7/00
Filed: 1933-06-08
Abstract: 425,299. Indicating-apparatus; barometers. BENDIX AVIATION CORPORATION, 105, West Adams Street, Chicago, U.S.A. June 8, 1933, No. 16464. Convention date, June 9, 1932. [Classes 106 (ii) and 106 (iv)] In an indicating-instrument a differential gear system is included in the transmission means between the indicating- means and the actuating device so as to be effective to produce relative movement between the pointers and scale of said indicating-means during the indicating action and for setting the instrument for a predetermined condition. As applied to a sensitive altimeter, the casing 8 has secured to its back plate 9 by a screw and nut, a braced frame 12, 13 carrying aneroid chambers 22, 24, the movement of which is conveyed through a temperature compensating element and pivoted linkage 30 to a rock-shaft 34. The movement of this shaft is transmitted through a quadrant 42 and multiplying gearing 43, 45, 46 to a spindle 47. A large pointer 49 moving over a dial 50 having a scale to indicate hundreds of feet is mounted on a spindle 48. Concentric with this scale is another scale graduated in thousands of feet over which moves a small pointer 53 which is geared to the pointer 49. For this purpose a pinion 54 on the shaft 48 meshes with a gear 55 in one with a gear 58 which meshes with a gear 59 on a hollow shaft 60 carrying the pointer 53. A hair spring 61 prevents backlash in the transmission. Interposed in the transmission is a planetary differential gear through which relative movement between the pointers and their scales may take place for setting the instrument to read zero when the instrument reaches the height for which it was set; and also through which the pointer may be operated by the aneroid capsules during indicating action. A pair of meshing planet gears 63, 63a are carried by a pair of shafts 64, 65. A planet pinion 73 rigid with the gear 63 meshes with a sun gear 74 on a hollow hub 75 through which the spindle 47 extends. A planet pinion 76 is rigid with the gear 63a and meshes with a pinion 77 integral with the shaft 48 of the large pointer. A large gear 78 secured to the hub 75 is journalled on a bushing 79 rigidly secured to the fixed frame member 36. The gear 78 meshes with a pinion 80 gearing with a wide pinion 82 secured to a manually-operated shaft 83. The shaft 47 to which movement of the aneroids is transmitted has fixed to it a frame 87 which carries the cage 67, 66 of the planetary gears and thus drives the pointer spindle 48. To impart a setting to the pointers, the shaft 83 is moved to the left against the influence of a spring 95 and the pinion 82 disengaged from a fixed tooth 88 and rotated to turn the gear 78 and thus the pointers. This movement of the shaft 83 moves a blade spring 92 against a fixed wedge 97 and a friction member 91 at the end of the spring is forced against a brake disc 90 carried on the shaft 47 so as to prevent rotation of the latter. The brake mechanism may be dispensed with. The setting given to the pointers may be read on a Veeder counter 98 driven through gears 100, 101, 102, 103.