The invention relates to a tap changer (1) for the uninterrupted switching between winding taps of a tap transformer. Said tap changer comprises an oil vessel (2) which accommodates the components of the tap changer (1) and which comprises an upper oil vessel flange (3), and a tap changer head (4) with a head flange (5). An oil expansion vessel (6) having an upper flange (7) and a lower flange (8) is arranged between the oil vessel (2) and tap changer head (4). Said upper flange (7) of the oil expansion vessel (6) is connected mechanically and in an oil tight manner to the head flange (5), and the lower flange (8) of the oil expansion vessel (6) is connected mechanically and in an oil tight manner to the upper oil tank flange (3).
