a support element;

at least one sealing contact face and a closure apparatus centre axis;

at least one operating apparatus with at least one adjusting element which can be moved from a first position to a second position relative to the support element,

at least two transmission elements;

wherein the closure apparatus is in a sealing position in the second position of the adjusting element;

wherein the adjusting element is pivotable or rotatable about an operating axis relative to the support element, wherein the operating axis is parallel to but radially spaced apart from the closure apparatus centre axis; and

wherein the operating apparatus comprises an eccentric element associated with the at least one adjusting element, wherein the eccentric element can be pivoted about the operating axis, wherein a sliding surface of the eccentric element, which is averted from the operating axis, is at a varying distance from the operating axis;

wherein at least when the adjusting element is in the first position, two adjacent transmission elements of the at least two transmission elements overlap by way of in each case one side section when the said transmission elements are viewed along the closure apparatus centre axis;

wherein at least when the adjusting element moves to the second position, each transmission element moves radially away from the closure apparatus centre axis, thereby placing the closure apparatus into the sealing position when the adjusting element is in the second position; and

wherein at least in the sealing position, pressing faces of the at least two transmission elements form a circle when viewed along the closure apparatus centre axis.