Safety screw closure

The combination of a safety screw closure and a container having a threaded neck and an annular shoulder arranged below said threads, said closure comprising an inner and outer screw cap located one inside the other, said inner screw cap rotatable about said threaded neck in one direction to close thereon and in an opposite direction to open, said outer cap being rotatable with respect to said inner cap and axially slidable between an outer and inner position, a spring located between said caps to normally urge said outer cap into its axial outer position, said outer cap being movable against said spring into its inner axial position, means for cooperatively coupling said outer cap to said inner cap in any axial position for conjoint rotation with said inner cap in the closing direction and for cooperatively coupling said outer cap with said inner cap in its inner axial position for conjoint rotation with said inner cap in the opening direction, said inner cap having a securing ring attached at its lower end by at least one rupturable connecting bridge member, said securing ring being preshaped to conform to the shape of said annular shoulder, and being radially elastically expandable thereover, said securing ring and the inner cap being provided with intermediate cam members which cooperatingly abut when the closure is screwed on to the container and which are cooperatively ineffective when the closure is unscrewed, whereby only on initially opening of said cap said bridging members are ruptured.