16 integral with the intermediate body and having the purpose of insertion into corresponding housing 17 in the first body the first body 10 and the intermediate body 11 are joined by a rotating screw pin 13 with head 13 u2032 housed in the first body abutting against a shoulder which impedes axial movement of the pin without obstructing its rotation the screw pin 13 may be screwed directly to the intermediate body 11 or as shown in the drawings to a threaded element 14 associated with that body in such a way that rotation of the screw pin in one direction causes the approach and in the other direction the distancing of the intermediate body with regard to the first body an anti rotation gasket 15 is mounted around the first body 10 to prevent rotation of the device when it is placed in the chamber for use the contiguous extremities 10 u2032 and 11 u2032 of the two bodies 10 and 11 respectively are in truncated cone form and extend from the respective shoulders 10 u2033 and 11 u2033 together they delimit an annular peripheral housing 18 at which level is envisaged at least one deformable and expandable by compression element such as for example a gasket.