GB274420A - Improvements in and relating to speedometers - Google Patents

Abstract

274,420. Burstyn, W. July 17, 1926, [Convention date]. Electric speed indicators.-In a speedometer of the type in which a dynamo-electric generator is driven from the shaft the speed of which is to be measured, and a current meter functions as the speed indicator, the generator is arranged so that the voltage of the alternating current produced, which is subsequently rectified, has zero value for a finite part of the period. Fig. 5 shows an arrangement in, which the pole-pieces p, q of the permanent magnet N, S are formed with grooves n to secure this result. In Fig. 6, grooves m are provided in addition to the grooves n in order to avoid disturbance by eddy currents. The windings may be arranged upon the armature a or within the grooves m or upon the polepieces p, q. In Fig. 7 the armature is built up of inclined elliptical plates, and the coil s is mounted in a groove m. The commutator may be arranged to give sudden make and break by stepping the contact segments z as shown in Fig. 8. The transmission mechanism may be arranged to drive the spindle x of the armature always in the same direction. As shown in Fig. 9, the spindle carries two toothed wheels u, v coupled to it by free-wheel clutches. The first wheel meshes with a wheel b which is in gear with a driven wheel t, and the second wheel meshes directly with the wheel t. The time constant of the circuit is maintained low so that the current will fall to zero before the expiry of the period of absence of voltage.