A. Lange & Söhne presents LANGE ZEITWERK, the first mechanical wristwatch with a truly eloquent jumping numeral display.
A fresh design concept from the venerable German watch manufacture, the LANGE ZEITWERK offers a mechanical, precisely jumping hour and minute indication of singular clarity.
The German-silver time bridge of the A. Lange & Söhne LANGE ZEITWERK watch unfolds its wings across the entire width of the dial to prominently frame the large numerals of the laterally aligned windows that present the hours and minutes.
It extends down to encircle the subsidiary seconds dial as well, uniting all three levels of time measurement in a harmonious setting. With its easy-to-grip bevelled flutes, the knurled crown points up and away, predicting an upswing movement. The upper part of the dial boasts a power-reserve indicator.
With a whispered click and within fractions of a second, the minute display advances step by step until the watch initiates the big jump at the top of the hour. At this point, all three numeral discs switch forward simultaneously and instantaneously by exactly one unit.
Beneath the extraordinary dial of the ZEITWERK watch, a revolutionary movement with a diameter of 33.6 millimetres fully occupies the space inside the 41.9-millimetre gold or platinum case.
The significant amount of energy required to simultaneously advance all three numeral discs once every hour is delivered by a newly developed barrel with an extra strong mainspring. Its patented design literally turns the venerable wind/unwind principle upside down.
Thus, the mainspring barrel bearing with the higher friction rating is involved when the watch is being wound, but the barrel wheel always turns in the minimised-friction bearing as the mainspring gradually relaxes. This makes more torque available for powering the watch as well as the ensemble of discs with the hour and minute numerals.
A constant-force escapement, also patented, between the barrel wheel and the balance acts as a pacemaker for the jumping advance of the hours and minutes – in its compactness, the mechanism is quite likely unprecedented.
The forces that occur when the numeral discs are accelerated and braked are far beyond the magnitude normally encountered in a movement. To absorb them, a fly governor was integrated in the mechanism. As it rotates, its vanes must displace air like a fan; it is this resistance that dissipates much of the energy and assures gentle switching.
At the same time, the constant-force escapement makes an important contribution to stabilising the rate of the movement: across the entire 36-hour autonomy period, it drives the balance with nearly uniform power, regardless of the state of wind of the mainspring and unaffected by the energy-consuming switching cycles that take place in one-minute intervals. Incidentally, a balance wheel with eccentric poising weights and a hairspring manufactured in-house constitute the high-precision beat controller.
The A. Lange & Söhne LANGE ZEITWERK watch is available in four versions: Yellow gold with champagne dial, Pink gold with argenté dial, White gold with black dial and Platinum with rhodié dial.
A glance through the sapphire-crystal caseback reveals the lavishly decorated Lange L043.1 manufacture calibre that in addition to all its technical novelties of course also features a three-quarter plate, a hand-engraved balance cock, and screwed gold chatons.
The ZEITWERK Jumping Numerals Mechanism
To achieve optimised legibility, the hours and minutes are displayed on the same horizontal axis and in the same large format. The minutes are indicated by two discs. The units disc and the tens disc share the same arbor. A constant-force escapement generates the precise minute steps.
Every 60 seconds, these steps are transmitted to the disc mechanism as abrupt advances by one-fifth of a revolution (72 degrees) via the driving wheel and – seated on the same arbor – the pinion. This incrementally rotating pinion engages with the wheel that carries the units disc. The same wheel is geared to the wheel that via the switching staff is connected to the tens switching wheel which carries a finger with a stone.
Each time the units disc has performed a complete revolution, i.e. every ten minutes, the stone engages with the 6-toothed switching star of the tens arbor and advances it by one-sixth of a full revolution (60 degrees) just when the units disc jumps from 9 to 0. This moves the tens disc forward by exactly one numeral.
To make sure that the tens arbor cannot move freely outside the switching phases, the switching staff and the tens arbor have two safety elements with a form-fit interlock. However, it is not necessary to separately secure the units disc because it is directly connected with the control pinion of the constant-force escapement which itself is blocked outside the switching phases.
After it has performed a complete revolution, the tens arbor switches the large hours ring (with the numerals 1 to 12) forward by one step. For this purpose, it is fitted with a wheel that has only one tooth that engages with the four-toothed switching star of the intermediate hour wheel.
When the tens disc advances from 5 to 0, the intermediate hour wheel is switched forward by a one-fourth of a full revolution (90 degrees). In this case, too, a form fit safety interlock between the tens arbor and the intermediate hour wheel assures that the hours ring cannot advance inadvertently.
This exceptional design approach calls for a novel time setting mechanism: Once the movement is stopped when the crown is pulled, the control lever of the constant-force escapement blocks the entire three-disc set. This blocked state is overcome by an innovative mechanism that distinguishes itself considerably from a classic hand-setting train. While the time is being set, a roller moves over the tips of the contrate hub that is secured to the driving wheel.
Consequently, the arbor to which the roller is connected rotates in accurately defined angular steps, allowing the display to click forward in full one-minute increments. The “hopping” movement of the roller over the contrate hub can be observed through the sapphire-crystal caseback.
The Dual-function Constant-force Escapement
The patent-pending constant-force escapement of the LANGE ZEITWERK handles two crucial functions. On the one hand, it generates the stepper profile for the instantaneous advance of the numerals discs. In this respect, it relies on the strike-train principle with warning followed by drop-and-release that was traditionally implemented in chiming clocks.
On the other hand, it delivers nearly constant torque to the balance across the entire autonomy period and thus enhances the rate stability of the movement. This aspect is particularly important because the LANGE ZEITWERK has a high-performance mainspring with a torque characteristic that varies perceptibly between the fully wound and fully unwound states.
The point of departure is the pretensioned remontoir spring which just received a defined “charge” of fresh energy from the mainspring barrel via the centre wheel and the third wheel pinion and is thus now tensioned.
The driving third wheel is stationary in this phase. In the meantime, the remontoir spring transmits the new charge of energy to the driven third wheel and sets the balance in motion. At this time, the driving third wheel is blocked by the two control pinions.
Their upper ends hold a blocking finger and a blocking disc that alternately block the reciprocations of the two pallet stones in the arms of the Y-shaped control lever. Every 60 seconds, the driving third wheel, when released by the control pinions, advances slightly and thus generates the energy pulse for the switching sequence of the disc mechanism.
The timing of this process is governed by the control lever with its cyclical pivoting motions that takes its kinetic cues from the escapement. The double roller with its impulse pin rotates once a minute together with the fourth wheel because it is riveted to the same arbor.
A few seconds before the top of the minute, the impulse pin moves into the fork of the control lever and slowly pushes it aside against the resistance of the spring. In the quiescent state of the control lever, the blocking finger rests against the pallet stone on the left-hand side.
When the control lever deflects the pallet stone slips away from the finger. Meanwhile, on the other side, the right-hand pallet stone of the control lever has descended into the gap of the blocking disc. As soon as the control lever has deflected to such an extent that the left-hand pallet stone releases the blocking finger, the wheel train can advance by a tiny distance. This corresponds to the warning phase in the strike train of a chiming clock.
The amplitude of this motion is just large enough to let the blocking finger slip behind the pallet stone. At almost the same instant, the right-hand pallet stone drops into the blocking disc gap and the wheel train is stopped again.
As this is happening, the impulse pin increases the deflection of the control lever to such an extent that the pallet fork is suddenly freed. Now, a spring returns the control lever to its original position. This pulls the right-hand pallet stone out of the gap of the blocking disc and releases it. Both control pinions are now free to rotate until the movement of the left-hand pallet stone is once again stopped by the blocking finger.
The left-hand control pinion transmits its motion directly to the driving wheel of the disc mechanism which now instantaneously moves forward by 72 degrees and advances the discs. At the same time, the driving third wheel retensions the remontoir spring.
To absorb the forces that occur during the abrupt advancing and retensioning processes, the excess kinetic energy is dissipated by a fly governor. Thus, a fresh breeze flows through the movement every 60 seconds.
The Patented Mainspring Barrel Bearing System
To use a figure of speech, Lange’s patented mainspring barrel design turns the classic wind/unwind principle upside down. It makes sure that the barrel wheel rotates in the friction minimised bearing while the mainspring is powering the movement but in the bearing with the higher friction rating while the watch is being wound.
Consequently, it takes a bit more effort to wind the watch, but in return, more of the mainspring’s energy remains available to keep it ticking.
The mainspring barrel is geared to the winding mechanism and held by a stop click that engages with the crown wheel. When the crown is turned to wind the watch, this rotates the mainspring barrel seated in the train bridge. At its outer end, the mainspring is hooked to the barrel, so when the watch is being wound, it is entrained by the barrel and gradually tensioned as it wraps around the barrel core. The mainspring barrel arbor is suspended between two bearing jewels.
The upper jewel is located in the mainspring barrel itself, the lower one in the main plate. The barrel arbor is connected to the barrel wheel that in turn is geared to the wheel train of the watch. When the spring is tensioned and powering the movement, the driver pin attached to the barrel arbor and the arched recess in the barrel core constitute a so-called form-fit connection.
This connection allows the spring to transmit its energy to the barrel wheel. So as long as the mainspring is unwinding, the barrel wheel rotates between the two bearing jewels.
The expansion of the barrel core by a barrel arbor represents another design improvement. It simplifies servicing because the mainspring barrel can be lifted out without the need to first remove the train bridge.
The opening in the train bridge and integration of the barrel arbor bearing in the drum create a space large enough to accommodate the 3.32-millimetre high mainspring. It delivers the enormous torque required to simultaneously advance up to three numeral discs and concurrently retension the remontoir spring.
Model: A. Lange & Söhne LANGE ZEITWERK
Lange manufacture calibre L043.1, manually wound, crafted to the most exacting Lange quality standards, decorated and assembled by hand
Precision adjusted in five positions; three-quarter plate made of untreated German silver; balance cock engraved by hand; jumping minutes; constant-force escapement
Number of movement parts: 388
Screwed gold chatons: 2
Escapement: Lever escapement
Oscillation system: Shock-resistant glucydur balance with eccentric poising weights; superior-quality balance spring manufactured in-house with patent-pending attachment system (balance spring clamp), frequency 18,000 semi-oscillations per hour, precision beat adjustment system with lateral setscrew and whiplash spring
Power reserve: 36 hours when fully wound.
Movement dimensions: Diameter: 33.6 millimetres; height: 9.3 millimetres
Jumping hours and minutes, small seconds hand with stop seconds, power reserve indicator
Operating elements: Crown for winding the watch and setting the time
Case, dial & strap
Case material: Yellow gold, White gold, Pink gold or Platinum
Case dimensions: Diameter: 41.9 millimetres; height: 12.6 millimetres
Glass and caseback: Sapphire crystal (hardness 9)
Hands: Rhodiumed gold
Strap: Hand-stitched crocodile strap and Lange prong buckle in solid gold or platinum
Ref.140.021: Yellow Gold case; Solid silver, champagne dial and time bridge in German silver, untreated
Ref.140.029: White gold case; Solid silver, black dial in time bridge in German silver, rhodiumed
Ref.140.032: Pink gold; Solid silver, argenté dial and time bridge in German silver, untreated
Ref.140.025: Platinum case; Solid silver, rhodié dial and time bridge in German silver, rhodiumed
Image Credit: Lange Uhren GmbH