Pneumatic winding mechanism for a timepiece comprising a mechanical energy source

A pneumatic mechanism for a timepiece comprising a mechanical energy source, said mechanism being arranged to recharge said mechanical energy source, and comprising a sealed chamber capable of alternately expanding and contracting in volume as a function of variations in the surrounding temperature,

• said sealed chamber containing a mixture of reactants comprising a metal alloy arranged in contact with a gas, said mixture being capable of undergoing at least one phase change as a function of variations in the surrounding temperature via reaction between said metal alloy and said gas,
• said mixture of reactants having a coefficient ΔP/ΔT greater than 0.01 bar·° C.−1 in the following operating ranges:
• between about 0 and about 50° C. in temperature, and
• between about 1 and about 50 bar in pressure,
• and being chosen so that the minimum possible difference between temperatures, in said sealed chamber, associated, respectively, with consecutive contrariwise variations in the surrounding temperature, is smaller than or equal to about 4° C.