GB247314A - Improvements in or relating to calculating mechanism - Google Patents

Abstract

247,314. Legros, L. A. Nov. 20, 1924. Logarithmic apparatus. - ,Calculating mechanism of the kind which enables the value of a function of two variable quantities to be indicated comprises a differential gear, two of the wheels of which are each coupled to the driven sector of a pair of interengaging toothed cam-like members to impart an angular movement to the wheels proportional to the logarithm of the angular movement of the driving sectors. As shown in Figs. 1, 2, and 3, applied to a motor vehicle for giving the rate of fuel consumption in miles per gallon, the indicating spindles 10, 12 of the two measuring instruments are coaxial and drive through gearing 13, 14, 19, 20 respectively the logarithmic spiral sectors 16, 22. The sector 16 gears with a similar sector 17 rotatably mounted on a spindle 11, Fig. 3, but integral with a sun wheel 18 gearing with a pinion 30 of a pair of planet wheels 30, 32 secured to a spindle 28 in a differential gear frame 26 freely mounted on the spindle 11. Similarly the sector 22 through a sector 23 and pinion 24 drives a pair of planet wheels 29, 31 on a spindle 27 in the differential gear frame. A flexible connection 42 consisting preferably of a bent elastic link of spring or wire serves to maintain engagement of the camgears. The gear frame 26 and the spindles 10, 12 carry indicating drums 33, 38, 39 respectively for co-operation with a fixed index line extending across the reading aperture 40, Fig. 2; the drum 33 is graduated logarithmically .and the drums 38, 39 uniformly. As an alternative. the frame and spindles may carry pointers movable over fixed graduated drums or dials arranged on separate spindles. In the latter case where the graduations do not follow in uniform divisions a variable motion gear 53, 55, Fig. 5, is utilized to transmit uniform increments of movement to the driving sector. The condition to be observed in forming the teeth of the sectors is that the teeth must touch on the pitch line at the point midway between the centres of rotation, a shrouding extending to the pitch line being formed at one side to ensure the proper meshing of the interengaging sectors. A servomotor or " follow up " device may be employed to drive the mechanism from one or both instruments. Such a device is shown in Fig. 9 wherein the spindle 10 carries an arm 62 provided with two brushes 63 adapted to co-operate with a drum 64 having two pairs of contacting segments 68 - - 71, in circuit with a source of current 79, and a pair of solenoids 84, 85. The arm 82 of the solenoids rotates a commutator drum 76 on which bears two pairs of brushes 74, 75, 80, 81 respectively connected to the brushes 73 of the armature winding of a motor 67 and to the source 79. The motor 67 through worm gearing 65, 66 drives the drum 64 in one or other direction. Specification 194,124 is referred to.