Patent GB-738496-A (GB)
Title: Apparatus for indicating the ratio between the integrals of two independently variable quantities
IPC: G01P11/00
Filed: 1952-06-26
Abstract: 738,496. Speed or ratio indicators. PERROTTI, F., and VALDIVIESO, M. June 26, 1952 [June 26, 1951], No.16138/52. Classes 106 (3) and 106 (4). Apparatus for indicating the ratio between the integrals of two independently variable quantities, such as a distance travelled by a vehicle and the time taken, comprises a differential gearing adapted to be driven by two logarithmic cams which impart to said gearing motions representative of the logarithms of the integrated quantities and an indicator for indicating the differential motion of said gear, means being provided for transforming the logarithmic displacements of the differential gearing into linear displacements of the indicator. A shaft 23, Fig. 1, driven from a vehicle odometer rotates a disc 33 through a worm 24 and gearing comprising a planet carrier 25, planet pinions 28, 29 and sun-wheels 30, 32, the former of which is normally locked and the latter of which is integral with the disc 33. A disc 33<SP>1</SP> above and coaxial with the disc 33 is driven by a clock movement comprising a barrel 43, gears 42, 41, 39 and 38, the gears 41 and 39 being interconnected by a releasable clutch 90, 91. The discs 33, 331 have logarithmic spiral grooves 34, 37 respectively engaged by pins 6 and 4 on gear sectors 2 and 1 which mesh with a planet pinion 3 carried by a planet carrier shaft 7 rotatable on a spindle 5. The extent of movement of the shaft 7 is proportional to the algebraic sum of the logarithms of the rotations imparted to the discs 33, 33<SP>1</SP> and this movement of the shaft 7 is transmitted to a member 9 on a shaft 10 by means of a pin 8 which engages a cam surface of the member 9. The arrangement is such that the movement imparted to the member 9 is directly proportional to the ratio of the movements of discs 33, 331 and is therefore indicative of the speed of the vehicle. The rotation of the member 9 is transmitted via gearing to a spindle 20 carrying a pointer 21 which moves over a linearly calibrated scale 22. The pointer 21 is formed by an index on a transparent disc through which the clock dial 50 and hands 48, 49 may be viewed. An axially-movable spindle 96 rotatable by a knob 78 carries a pinion 79 which may engage the winding or hand-setting gear trains. The discs 33, 33<SP>1</SP> are geared to pinions 53, 55 which normally rotate idly on a spindle 56 on which are mounted two clutch parts 57<SP>1</SP>, 57, the latter of which has a groove which receives the end 58 of one arm of a bell-crank lever 59, the end 62 of the other arm of which is received-by a collar 63 on a shaft 64 rotatable within a hollow shaft 68. A bevel gear 66 is slidably mounted on the shaft 64 and engages a bevel gear 61 on the shaft 56. The shaft 68 is longitudinally movable between two positions as defined by a pin 701 which engages a spiral groove in a collar 70 on the shaft 68. In the inner position of the shaft 68 the bell-crank 59 is so positioned by the collar 63 that the clutch parts 57, 571 are clutched to the pinions 55, 53 under the pressure of a spring 60 so that rotation of the shaft 64 by the knob 67 in the direction of the arrow 75 is transmitted via the bevel gears 66, 61, shaft 56, clutch parts 57, 57<SP>1</SP>, pinions 55, 53 to the discs 33, 33<SP>1</SP> which may thus be zeroized. In this inner position of the shaft 68 a cam 69 positions a lever 73 so that a rod 74 is depressed to disengage the clutch parts 90, 91 in the drive to the disc 33<SP>1</SP>. In the outer position of the shaft 68 the bell-crank 69 is so positioned by the collar 63 that its end 58 effects disengagement of the clutch parts 57, 57<SP>1</SP> from their respective pinions 53, 55. In a modification, Fig. 4, the rotational zeroizing movement is imparted directly to the shaft 56 by a knob 67 and the shaft 64 is controlled by a spring 84 and a cam 82 fixed to the shaft 56.