Pivot door drive device for driving a pivot leaf of a pivot door, comprising the following features: - an electric motor comprising a motor shaft; - a pivot lever that can be pivoted about a pivot lever pivot axis; - the pivot lever is connected or can be connected at the free end thereof to a slide rail fastened to the pivot leaf or to a second lever fastened to the pivot leaf, forming a bell-crank lever for opening the pivot leaf; - the electric motor is operatively connected to the pivot lever by means of a downstream force-transmission apparatus such that rotation of the motor shaft of the electric motor leads to the pivot lever being pivoted about the pivot lever pivot axis thereof and thus to the pivot leaf being pivoted; - the force-transmission apparatus includes a sun gear and a planet gear; - the planet gear can be moved by means of a restraint only at least in a semicircle along a lateral circumferential surface of the sun gear, the teeth of the planet gear engaging with the teeth of the sun gear; - the planet gear is rotatably mounted by means of the pivot lever at an engagement point that is offset with respect to the pivot lever pivot axis; and - the planet gear, as part of the force-transmission apparatus, is operatively connected to the motor shaft of the electric motor such that the rotation of the motor shaft leads to rotation of the planet gear at the lateral circumferential surface of the sun gear, and thus leads to the planet gear rolling on the teeth of the sun gear, taking the pivot lever therewith and pivoting said lever about the pivot lever pivot axis; and the restraint of the planet gear on the sun gear being realised by the following features: - the planet gear is arranged so as to be mounted in a stationary but rotatable manner at the engagement point on the pivot lever; and the pivot lever pivot axis of the pivot lever coincides with a central axis extending through the centre of the sun gear; characterised by the following features: - the restraint of the planet gear on the sun gear is further realised by the following features: a) the sun gear is arranged so as to be stationary and immovable; and b) the force-transmission apparatus has a guide lever that can be pivoted about a guide lever pivot axis; and the guide lever pivot axis of the guide lever coincides with a central axis extending through the centre of the sun gear; and the guide lever is rotatably connected to the planet gear. - an electric motor comprising a motor shaft; - a pivot lever that can be pivoted about a pivot lever pivot axis; - the pivot lever is connected or can be connected at the free end thereof to a slide rail fastened to the pivot leaf or to a second lever fastened to the pivot leaf, forming a bell-crank lever for opening the pivot leaf; - the electric motor is operatively connected to the pivot lever by means of a downstream force-transmission apparatus such that rotation of the motor shaft of the electric motor leads to the pivot lever being pivoted about the pivot lever pivot axis thereof and thus to the pivot leaf being pivoted; - the force-transmission apparatus includes a sun gear and a planet gear; - the planet gear can be moved by means of a restraint only at least in a semicircle along a lateral circumferential surface of the sun gear, the teeth of the planet gear engaging with the teeth of the sun gear; - the planet gear is rotatably mounted by means of the pivot lever at an engagement point that is offset with respect to the pivot lever pivot axis; and - the planet gear, as part of the force-transmission apparatus, is operatively connected to the motor shaft of the electric motor such that the rotation of the motor shaft leads to rotation of the planet gear at the lateral circumferential surface of the sun gear, and thus leads to the planet gear rolling on the teeth of the sun gear, taking the pivot lever therewith and pivoting said lever about the pivot lever pivot axis; - the restraint of the planet gear on the sun gear is further realised by the following features: a) the sun gear is arranged so as to be stationary and immovable; and b) the force-transmission apparatus has a guide lever that can be pivoted about a guide lever pivot axis; and a) the sun gear is arranged so as to be stationary and immovable; and b) the force-transmission apparatus has a guide lever that can be pivoted about a guide lever pivot axis; and