US Patent 7321528 Watch movement

The invention relates to a watch movement comprising an annular casing (10), having an external diameter D, which is provided with a central round opening (48) that is defined by an internal diameter d. According to the invention, the gear train (34) comprises a mobile (36) consisting of a minute wheel (36a) and a pinion (36b), a cannon pinion (38), which is driven by the minute wheel (36a) and intended to support a minute hand (40), and an hour wheel (42) which is driven by the pinion (36b) and intended to support an hour hand (44). The cannon pinion (38) and the hour casing (10) and are provided with a central opening that is more or less equal to d. The minute wheel (36a) is provided with a diameter that is slightly smaller than (D−d)/2.