An assembly for closing a tube, said assembly comprising: - a tube head comprising a neck and a seal closing off said neck - a cap comprising a punch adapted to cut said seal, said neck and said cap being configured to allow maintaining said cap fixed on said neck in a first position, known as the standby position, in which the punch is held away from the seal, in a second position, known as the use position, in which said punch pierces said seal and in a third position, known as the closing position, in which said neck and said cap ensure that said tube is sealed, said cap being configured to move from the standby position to the use position and/or from the use position to the closing position by at least one rotational movement, said cap and said neck defining a longitudinal axis Z-Z, said cap being configured to move from the standby position to the use position and/or from the use position to the closing position further by an axial movement along the axis Z-Z said neck comprising at least one first locking means cooperating with said cap to keep said cap in the standby position, said one or more first locking means being one or more projecting elements (37a, 37b, 37c) located on an outer surface of said neck said neck comprising at least one guide groove configured to cooperate with said cap to allow rotational movement and/or the axial movement for the passage of said cap from the standby position to the use position and/or from the use position to the closing position, said assembly being characterised in that said groove has successive guide portions of which a first portion is vertical with respect to the axis Z-Z and ensures the standby position, followed by a second portion which is helical of slope x and allows said plug to be removed from the standby position, then followed by a third portion which is helical with a slope y and allowing the passage of said cap to the use position, then followed by a last portion which is horizontal with respect to the axis Z-Z and allowing the passage of said cap to the closing position, the slope y of the third helical portion being greater than the slope x of the second helical portion. - a tube head comprising a neck and a seal closing off said neck - a cap comprising a punch adapted to cut said seal, said neck and said cap being configured to allow maintaining said cap fixed on said neck in a first position, known as the standby position, in which the punch is held away from the seal, in a second position, known as the use position, in which said punch pierces said seal and in a third position, known as the closing position, in which said neck and said cap ensure that said tube is sealed, said cap being configured to move from the standby position to the use position and/or from the use position to the closing position by at least one rotational movement, said cap and said neck defining a longitudinal axis Z-Z, said cap being configured to move from the standby position to the use position and/or from the use position to the closing position further by an axial movement along the axis Z-Z said neck comprising at least one first locking means cooperating with said cap to keep said cap in the standby position, said one or more first locking means being one or more projecting elements (37a, 37b, 37c) located on an outer surface of said neck said neck comprising at least one guide groove configured to cooperate with said cap to allow rotational movement and/or the axial movement for the passage of said cap from the standby position to the use position and/or from the use position to the closing position, said assembly being characterised in that said groove has successive guide portions of which a first portion is vertical with respect to the axis Z-Z and ensures the standby position, followed by a second portion which is helical of slope x and allows said plug to be removed from the standby position, then followed by a third portion which is helical with a slope y and allowing the passage of said cap to the use position, then followed by a last portion which is horizontal with respect to the axis Z-Z and allowing the passage of said cap to the closing position, the slope y of the third helical portion being greater than the slope x of the second helical portion.