US Patent 10519804 Oil chamber wall

An oil chamber wall arrangement is described as comprising: a chamber wall surrounding a rotor; a plurality of apertures defining through-holes for a flow of oil through the chamber wall, the apertures being defined by a pair of axially separated opposing walls and a pair of circumferentially opposing walls wherein the circumferentially opposing walls are separated by a midline which is radial to the rotational axis of the rotor and at least one of the pair of circumferentially opposing walls is not parallel to the radial midline.