Constant jumps

RICHARD LANGE JUMPING SECONDS and pocket watch with seconde morte by A. Lange & Söhne

Technical addendum for the RICHARD LANGE JUMPING SECONDS
The RICHARD LANGE JUMPING SECONDS conceals three technical highlights beneath its puristic regulator dial: the namesake jumping seconds, the constant-force escapement that assures uniform power management and the ZERO-RESET mechanism for resetting the seconds hand. These are three reasons for a look backstage and into the construction of Lange’s L094.1 manufacture calibre.

Jumping seconds
The jumping seconds is an A. Lange & Söhne tradition that dates back nearly 150 years. In 1867, Saxon watchmaking pioneer Ferdinand Adolph Lange crafted a pocket watch with a seconde morte. Its large sweep seconds hand circumscribed a minute in exactly 60 steps. The hand could be started and stopped but not reset to zero. His sons Richard and Emil evolved the system and in 1877 filed a patent application for the mechanism they mounted on the three-quarter plate, naming it “seconds movement with jumping seconds”. 

The functional principle of the RICHARD LANGE JUMPING SECONDS, launched in January 2016, is similar: as in the historic mechanism, a flirt and a star were the elements that controlled the seconds jump, the conversion of the six semi-oscillations of the balance into one hand step per second.

The modern jumping seconds mechanism

The star that rotates beneath a transparent sapphire bearing jewel is attached to the escape wheel arbor. Together with the escape wheel, it rotates about its own axis once every five seconds. After each full second, one of the tips of the star liberates the tensioned lever arm, which watchmakers refer to as the “flirt”. It performs an abrupt rotation through 360 degrees before being stopped by the next tip again. This motion sequence causes the seconds hand to advance by precisely one marker.

Constant-force escapement
A. Lange & Söhne has been intensively investigating ways to offset the difference between the high initial torque and low final torque of mainsprings. With the fusée-and-chain transmission first introduced in 1994, and three different constant-force escapements, A. Lange & Söhne has meanwhile developed four separate constant-power delivery systems.

In the LANGE 31, the constant-force escapement delivers a constant amount of torque in ten-second intervals across a period of 31 days. In the ZEITWERK, it harnesses the force of the powerful mainspring and instantaneously advances the numeral discs once every minute. In the RICHARD LANGE JUMPING SECONDS, the mechanism fulfils a dual function: on the one hand, it offsets the waning power of the mainspring barrel, and on the other, it prevents a loss of amplitude during the seconds jump. The mechanism utilises the switching impulse of the jumping seconds integrated in the wheel train to deliver fresh energy to the remontoir spring of the constant-force escapement, which is visible through an aperture in the train bridge. In a separate wheel train between the mainspring barrel and the escapement, the constant-force escapement compensates the dwindling torque of the mainspring. The remontoir spring of the constant-force mechanism delivers virtually constant torque to the escapement, so the amplitude of the watch remains stable during the entire power reserve period of up to 42 hours. In combination with the cam-poised balance, excellent rate stability is guaranteed by a free-sprung hairspring, which, like the remontoir spring, is made in-house.

ZERO-RESET mechanism
The ZERO-RESET device first integrated into the SAX-0-MAT movement in 1997 was refined for the RICHARD LANGE JUMPING SECONDS and endowed with a multidisc clutch. Its purpose is to reliably steady the large seconds hand with its comparatively high moment of inertia, especially during the sudden acceleration and braking phases associated with the seconds jump. Additionally, the clutch makes it possible to isolate the wheel train when resetting the seconds hand to zero.

When the crown is pulled, a complex set of levers triggers three processes within fractions of a second: the arresting spring is gently pivoted into the balance and holds it, and the clutch discs are separated with a clamp, disconnecting the seconds hand from the wheel train. 

The reset hammer contacts the heart cam, advancing it and the seconds hand to the zero position. When the crown is pushed home, the seconds hand is re-engaged with the wheel train and the balance is released. It immediately starts oscillating again. 

About A. Lange & Söhne
Dresden watchmaker Ferdinand Adolph Lange laid the cornerstone of Saxony’s precision watchmaking industry when he established his manufactory in 1845. His precious pocket watches remain highly coveted among collectors all over the world. The company was expropriated after World War II, and the name A. Lange & Söhne nearly vanished. In 1990, Ferdinand Adolph Lange’s great-grandson Walter Lange had the courage to relaunch the brand. Today, Lange crafts only a few thousand wristwatches in gold or platinum per year. They are endowed exclusively with proprietary movements that are lavishly decorated and assembled by hand. With 54 manufacture calibres developed since 1994, A. Lange & Söhne has secured a top-tier position among the world’s finest watch brands. Brand icons, such as the LANGE 1 with the first outsize date in a regularly produced wristwatch and the ZEITWERK with its precisely jumping numerals display, rank among the company’s greatest successes. Sophisticated complications such as the RICHARD LANGE PERPETUAL CALENDAR “Terraluna”, the ZEITWERK MINUTE REPEATER and the DATOGRAPH PERPETUAL TOURBILLON reflect the manufactory’s determination to achieve ever new pinnacles in horological artistry.