An oil transfer unit has a rotating part extending along an axis, a stationary part provided with an oil mouth, and a floating part having a cylindrical surface fitted onto an outer cylindrical surface of the rotating part in a non-contact configuration; an annular groove is provided between the floating part and the rotating part to put the oil mouth into communication with an inner chamber of the rotating part; both sides of the groove are sealed by a hydrostatic seal defined by a radial gap between the cylindrical surfaces; the unit has at least one oil transfer tube, coupled to the stationary part and the floating part in a fluid-tight manner and with freedom of movement, and a connecting rod to prevent rotation of the floating part; the opposite ends of the connecting rod are coupled to the stationary part and floating part by respective spherical joints.