N. Saati & Cie.，美國羅德島州的普羅維登斯，125 mm，約 1895
N. Saati & Cie., Providence, Rhode Island, 125 mm, circa 1895
A unique ship's chronometer with worm gear movement according the German patent No. 81824 from Januar 9 1894
Case: palisander. Dial: silvered. Movm.: brass movement, lever escapement, bimetallic chronometer balance with 2 weights and 4 screws.
The chronometer by Nowman Micah Saati was an attempt (that was even patented) to replace the normal train of a watch by a mechanism where the large escapement wheel was driven by a worm gear. The construction was intended to improve performance with a simplified mechanism; the latter, however, is doubtful, as a constant transmission of power from the barrel onto the fusee (or the worm gear) was imperative.
The attempt resulted in this construction that essentially corresponds to the patent design: two leverage systems alternately act on the gear wheel on the barrel. The force is diverted in the mounting and used to push a second lever in the spiral upward. When the free lever is caught by the gearing of the barrel, the active part is release and falls downward – it is the part under spring tension that now drives the movement. In another intricate detail the leverage systems as a whole are subject to lateral adjustment, thus avoiding the barrel teeth. The operating noise is unusual in that the usual ticking of a marine chronometer is interspersed by a loud ticktack sound when the levers change.
The mechanism was not really a striking success. We know of another chronometer that uses it, which, however, seems to be a kind of prototype.
Saati was not the only one who tried to fit movements with worm gears: Hans-F. Tölke described that in an amusing article in issues 5 and 6 of "Klassik Uhren" of 1994 and also mentions Saati’s patent.