GB217214A - Improvements relating to speed indicators - Google Patents

Abstract

217,214. Fabriques des Montres Zenith, (Successors to Fabriques des Montres Zenith G. Favre-Jacot et Cie). June 9, 1923, [Convention date]. Differential speed indicators of the type in which the speed indication is effected by two members, one of which is driven at a speed corresponding to that to be measured, and the other is arranged to move periodically at a speed following a predetermined law. The element 3 is driven by a pinion 3<a> at a speed equal or proportional to that to be measured and drives through a coiled spring 5 a balance-wheel 4. Once every revolution the balance-wheel is arrested and its spring coiled up by the engagement of an arm 32 upon it with a pin 18 carried by a spring-pressed lever 17 pivoted to the casing at 16. After an interval it is released when a pin 19 on the disc 3 engages the arm 17. This position is shown in Fig. 3, the relative position of the parts when stationary being shown in Fig. 2. Upon release the wheel 4 accelerates under the action of the spring 5 and moves forward until a pin 23 upon it catches up to and engages an arm 22 of a lever 10 pivoted at 9 to the rotary disc 3. Means are provided for positioning the indicating pointer 40 when this engagement occurs. Upon the pointer spindle, movement of which is restrained by a spring 41, is fixed a toothed wheel 6<a> meshing with a loosely mounted toothed disc 6. A spring-pressed pawl 14 mounted between the 6 and a bridge-piece 12 carries a bar 15 one end of which engages the teeth of a fixed ratchet 7, the other end being adapted to be engaged by a second arm 24 of the lever 10. The lever 10 has also a nose-piece 25 adapted to engage a projection 26 on the bridge-piece 12. When the speed to be measured is increasing the nose 25 engages the projection 26 for a period before the pin 23 engages the arm 22 and displaces the nosepiece. In this way a movement is transmitted to the disc 6 through the bridge 12, the pawl bar 15 meanwhile riding over the ratchet 7. When the speed is decreasing, the pin 23 catches up to the arm 22 before the parts 25, 26 have engaged, and the arm 24 is caused to lift the bar 15 off the teeth of the ratchet 7 so as to permit a backward movement of the pointer 40 under the influence of the spring 41. A clip 31 mounted on the disc 3 is engaged by the blade 32 and provides a deadening stop for the balance wheel 4 at the end of its relative movement. In order to prevent the instrument from being damaged should the speed exceed the maximum for which it is constructed, the pivot 9 carrying the lever 10 is adapted to be rocked by the engagement of a pin 27 with a fixed cam 28 and disengage the parts 25, 26 if this has not already been effected by the pin 23. Modifying scale of readings.-The form of the meshing toothed wheels 6, 6a is not circular, but is selected so that the movement of the pointer 40 is proportional to the speed of the wheel 3. Registering distance upon counters.-An odometer is actuated by a lever 45 which has a finger engaging a circular cam groove 34 in the wheel 3.