Berna ?

Description

Unfortunately, this 18 1/2 ligne stopwatch caliber is unmarked, but with a very high certaincy it originates from the swiss manufacturer Berna Watch SA from St. Imier, not least beause of its marked swiss patent number 74234 , which relates to starting and blocking the balance wheel.

All functions are triggered by the crown: Start - Stopp - Reset. Additionally, the movement is wound by the crown, too.

The speciality of this movement is, that its balance wheel oscillates with no less than 360.000 A/h, which allows a measuring resolution of 1/100 second!

Besides the lever pallets, the balance wheel bearings and the ellipse are no jewels used. For a stopwatch, which is only used for short running times, this is sufficient.

Since the movement is an enourmous fast beater, the gear train is made accordingly:

The mainspring barrel drives the decentral seconds(!) wheel at 12 o’clock, which makes one turn every 90 seconds. It is followed by a reduction wheel the central 1/100 seconds wheel, which takes three seconds for a revoltion.

Finally, the steel escape wheel is used, which is controlled by the swiss pallet lever escapement.

As balance wheel, a screw-less, two-leg anular balance is used, which has got a very stiff balance wheel and is deflected only in a small angle.

The precise frequency can be adjusted with a long regulator arm, assumed, you have a timegrapher which can measure 1/100 seconds acoustically.

The whole stopwatch mechanism is located on the dial side with starting and breaking lever, with the reset lever, the switching wheel and the switching lever.

All springs used here are very strong, you can see this on the strong screws and on the two screws, which are used for their fixation.

Technical data

Usage gallery

Patents

• CH74243