Timepiece drive mechanism

A timepiece drive mechanism comprising a fixed structure on which is pivotally mounted, about a main axis, an arm carrying a planetary gear, which is pivotally mounted on said arm about a first pivot axis remote from said main axis and includes a first wheel pivotally mounted about said first pivot axis or a secondary pivot axis that is parallel thereto, said arm being subjected to the return torque of a first energy source, said drive mechanism further including at least a second energy source arranged to subject to a return torque a third wheel set comprised in said drive mechanism, directly or indirectly via a second wheel set pivotally mounted about a second pivot axis, said first wheel being arranged to roll, under the action of said first energy source, over said third wheel set in a regular forward rolling motion with respect to said structure in a single direction of rotation, wherein said third wheel set is arranged to remain in a fixed position during a first basic travel of said planetary gear and, under the action of said second energy source, to make a rotation in only one direction during a second basic travel of said planetary gear, during which said arm, which is carried by said third wheel set, moves backwards with respect to said fixed structure, and wherein said drive mechanism includes stop means arranged to cooperate with complementary stop means comprised in said third wheel set, or comprised in another external wheel set meshing directly or indirectly with said third wheel set, to hold the latter in position, said stop means being uncouplable under the action of uncoupling control means, comprised in said arm when said arm reaches the end of its forward angular travel, to allow pivoting of said third wheel set in a single direction under the action of said second energy source causing a backward rotation of said arm to the start of its said angular travel.