pro & con: horizontal vs. vertical coupling - WatchTime

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PRO & CON: HORIZONTAL VS. VERTICAL COUPLINGVERTICALMARC A. HAYEK,CEO OF BLANCPAIN:“Blancpain introduced Caliber 1185,with a height of just 5.5 mm, in 1987,and it remains the world’s slimmest selfwindingchronograph movement. It relieson a vertical coupling to avoid two of themost common problems that beset chronographmovements. On the one hand, agentle interaction between two disksstarts the chronograph. This is unlike thesituation in horizontally coupled devices,in which the gears mesh abruptly whenthe start or stop button is pushed. Ofcourse, if the teeth don’t immediatelymesh perfectly, this abrupt coupling cancause the chronograph’s seconds hand tomake a small but noticeable jump. Furthermore,imperfect meshing can damagethe gears. That’s why the owner’smanuals accompanyingeven thefinest chronographsrecommendthat owners avoid too frequentuse of the stopwatchfunction because the additional energyrequired by the chronograph mechanismcan adversely affect the accuracyof the watch’s rate. Both of these shortcomingshave been rectified in Caliber1185 and in all the successive caliberswith additional functions based on the1185. A sudden jump by the chronograph’shand is eliminated. We have alsoensured that the operation of the chronographexerts only a minimal effect onthe watch’s rate behavior.”Top, right: Blancpain’s Caliber 1185, theforerunner of vertical coupling.Left: Blancpain’s Léman Flyback Chronowith big dateContinued from page 84graph’s center wheel, which causes the chronographhand to begin to move. Analogously,when this connective bridge is removed, thehand instantaneously ceases to move.The chronograph’s center wheel and its teethcease their motion, but the movement (includingthe driving wheel and the intermediatewheel) continues to run.Admittedly, this technical description is a bittheoretical and paints a rosier picture thanwhat takes place in horological reality. A certainamount of play is unavoidable whenevergears transfer force, and this play interfereswith the uniform progress of the chronograph’shand. To prevent the notorious lurchingand trembling of this hand, watchmakersuse a little friction spring that presses against ametal disk bearing the finger that advances theelapsed-minutes counter. This spring minimizesvibrations, but it causes unavoidable frictionand also saps energy from the mainspring.The result is a decline in the amplitude of thebalance whenever the chronograph isswitched on. The art of fine adjustment involvesachieving a well-balanced compromisebetween the braking effect and the loss oftorque.Another difficulty associated with traditionalwheel coupling concerns the meshing of theteeth when the coupling occurs. The tooth ofone gear slips into the space between two adjacentteeth on the other gear, and this causesthe chronograph’s hand to jump a bit when itbegins to move. Furthermore, frequent con-88 WatchTime April 2007
PRO & CON: HORIZONTAL VS. VERTICAL COUPLINGtact between the teeth of the two gears makesthem wear out faster. Watchmakers try to alleviatethis problem by giving each tooth a triangularprofile and by cutting a large number offinely spaced teeth around the rim of thechronograph’s center wheel. The advantagesof the elaborate wheel-couplingsystem include its relativelyflat height and, above all, a visuallyappealing mechanism.The chronograph’s seconds hand (below) onPatek Philippe’s calendar chronograph (bottomright) can also be used as an ordinary secondshand. There is no separate and continuouslyrunning seconds hand.A Simpler SolutionA coupling system thatEdouard Heuer registered forpatent protection on ChristmasEve in 1886 is considerablysimpler. The so-called“rocking pinion” is a moveablymounted arbor with two sprockets.One sprocket, affixed to thedial side, meshes directly with thefourth wheel of the movement. The oppositeone, into which fine teeth have beencut, pivots through a small arc and engageswith the chronograph’s center wheel after thestart button is pushed. When the connection ismade, the chronograph hand begins to run.This mechanism eliminates the need for a drivingwheel and an intermediate wheel. Whenthe button is pressed again, the rocking pinionpivots away from the chronograph’s centerwheel, disconnecting it from the flow of forceand halting the motion of the chronographhand. This system was first used in wristwatchesin 1946. In an effort to produce a more economicalversion, Valjoux constructed columnwheelCaliber 77 ECO with a rocking pinion. Acurrent example of this not-especially-eyecatchingcoupling version is the well-knownand widely used ETA Valjoux 7750.An entirely different type of coupling wasdevised by Manufactures des Montres &Chronographes Pierce S.A., a firm founded inBienne, Switzerland in 1883. This companylaunched its Caliber 130 in 1936. Pierce wasforced to develop its own movement becauseit could no longer obtain movement blanksfrom the classical ébauches factories. Necessitybecame the mother of invention, and PierceVERTICALPHILIPPE STERNPRESIDENT OF PATEK PHILIPPE:“A vertical disk coupling between thecontinually turning axis of the fourthwheel and the pinion of the chronograph’shand allows an interruption ofthe flow of force to the chronographcounters without the need for interruptingthe rotation of the fourth wheel. Atthe same time, this eliminates the dangerof a jump or retrograde motion by thehand because no teeth need to meshwith one another. A conventional solutionwith three chronograph wheels increaseswear. This does not occur in ourcoupling, so the chronograph hand canalso be used as an ordinary seconds handwithout adversely affecting the rate ofthe movement, without reducing thepower reserve and without causing increasedwear.”90 WatchTime April 2007
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pro & con: horizontal vs. vertical coupling - WatchTime

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