Container safety closure

Claim 1

In a closure for containers wherein the application and removal of the closure require forcible axial movement of a closure element relative to the container top, a closure comprising an outer element adapted for manual manipulation and a spring element interposed between the outer element and a portion of the container in a position to resist axial movement of said outer element toward said container, the spring element being of a hollow body of resilient plastic material having convolutions along the length thereof, said element being hollow with at least one end unenclosed, said convolutions having inner and outer ridges, the inner ridges defined on first radii which determine the thickness thereof, the outer ridges defined on second radii, said thicknesses being of unequal dimension whereby the wall portions extending between said ridges are of tapering thickness whereby the radii and varying wall thickness determine the spring characteristics of said spring element, said spring being precompressed along said longitudinal axis to give it a permanent set of decreased axial dimension in an unloaded condition, the predominant preset of said spring occurring in the thinner walled ridges, said convolutions being of essentially annular shape perpendicular to the longitudinal axis, and cooperating means on said closure and container for latching said closure to said container against the bias of said spring, said cooperating means requiring further compression of said spring to unlatch said cooperating means.