A timepiece mainspring is accommodated inside a barrel, an inner end thereof is fixed to a barrel arbor included in the barrel, and an outer end thereof engages with an inner wall of the barrel. The timepiece mainspring includes a helical portion wound in a Bernoulli curve shape from the inner end in a free state having no applied load.

A timepiece power source is provided, including a barrel containing a mainspring mounted between a drum and an arbor rotating integrally with a ratchet wheel, including a differential gear coaxial to the barrel, with a first input driven by the ratchet wheel, a second input which is the drum, and a pivoting output wheel, coaxial to the arbor, arranged to form or to drive a power reserve indicator, the differential gear including balls driving the output wheel, cooperating with an upper surface of the drum, and with a lower surface, which is opposite thereto, of a differential plate forming the first input, pivoting coaxially on the arbor and connected to the ratchet wheel by a friction means cooperating with a plate, and the ratchet wheel forms the cover of the barrel.

A timepiece power source is provided, including a barrel containing a mainspring mounted between a drum and an arbor rotating integrally with a ratchet wheel, including a differential gear coaxial to the barrel, with a first input driven by the ratchet wheel, a second input which is the drum, and a pivoting output wheel, coaxial to the arbor, arranged to form or to drive a power reserve indicator, the differential gear including balls driving the output wheel, cooperating with an upper surface of the drum, and with a lower surface, which is opposite thereto, of a differential plate forming the first input, pivoting coaxially on the arbor and connected to the ratchet wheel by a friction means cooperating with a plate, and the ratchet wheel forms the cover of the barrel.

The timepiece assembly (1) is intended for an arbor (81), in particular a barrel arbor, on a blank (91), in particular a bridge or a plate (91), where the arbor (81) comprises a first axis (A80) and a shoulder (82) extending at least in a radial direction relative to the first axis (A80); and the blank (91) comprises a groove (92) that is oriented along a second axis (A90). The arbor and the blank are configured and/or arranged so as to (i) prevent the arbor from moving in translation along a first axis relative to the blank; and (ii) enable the arbor to slide, during assembly, in translation in a groove along the second axis (A90) perpendicular to the first axis.

The timepiece assembly (1) is intended for an arbor (81), in particular a barrel arbor, on a blank (91), in particular a bridge or a plate (91), where the arbor (81) comprises a first axis (A80) and a shoulder (82) extending at least in a radial direction relative to the first axis (A80); and the blank (91) comprises a groove (92) that is oriented along a second axis (A90). The arbor and the blank are configured and/or arranged so as to (i) prevent the arbor from moving in translation along a first axis relative to the blank; and (ii) enable the arbor to slide, during assembly, in translation in a groove along the second axis (A90) perpendicular to the first axis.