ATMOS CLOCK

The 'Atmos' is the brand name of a mechanical clock manufactured by Jaeger LeCoultre in Switzerland which doesn't need to be wound up. It gets the energy it needs to run from small temperature changes in the environment, and can run for years without human intervention.
Inside a hermetically sealed capsule is a mixture of gas and liquid (ethyl chloride), which expands as the temperature rises in the expansion chamber, which then compresses a spiral spring; with a fall in temperature the gas condenses and the spring slackens. This motion constantly winds the mainspring. A variation in temperature of only one degree in the range between 15 and 30 degrees Celsius is sufficient for two days' operation.
To convert this small amount of energy into motion, everything inside the Atmos has to work in as friction-free a manner as possible. For timekeeping it uses a torsion pendulum, which consumes less energy than an ordinary pendulum. The torsion pendulum executes only two torsional oscillations per minute, which is 150 times slower that the pendulum in a conventional clock.
In 1928, an engineer in Neuchatel, Switzerland named Jean-Leon Reutter built a clock driven by a mercury-in-glass expansion device. The device rotated a cylinder which then wound the mainspring by ratchet. The mechanism operated on temperature changes alone. It took the Jaeger-LeCoultre workshop a few more years to convert this idea into a technical form that could be patented.
An early predecessor is Cox's timepiece, a clock developed in the 1760s by James Cox and and John Joseph Merlin. The oldest predecessor still running today is the 1864 Beverly Clock.

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References

References

★ LeCoultre Atmos Clock History

★ Atmos Clock Page