Removable stopper for a screw-neck bottle
BACKGROUND OF THE INVENTION 
     The present invention relates to screw stoppers in which the screw thread of the bottle neck terminates in a transverse projection forming a positioning stop for a corresponding projection of the screw thread of the stopper, which also comprises a second projection locked behind the stop of the neck. The passage of this second projection over the stop shoulder of the neck requires a certain elasticity of the stopper, failing which said second projection is rapidly destroyed. For decorative purposes, the prior art stoppers are made of plastic material coated with a metal cap which renders the stoppers undeformable. This results in the use of the stopper device described hereinabove being impossible. 
     It is an object of the invention to remedy this drawback both for stoppers covered with a rigid cap and for those whose plastic walls are too thick to obtain sufficient elasticity. 
     SUMMARY OF THE INVENTION 
     The invention therefore relates to a removable stopper for a screwnecked bottle which comprises, at the end of the thread, a transverse stop shoulder, said stopper comprising a transverse projection at the end of the screw thread and a second, spaced-apart projection, parallel to the first, these two projections closely confining between them the stop shoulder of the bottle neck, said stopper being characterised in that the zone of the skirt of the stopper which bears the second projection is weakened. The stopper may be removed and replaced on the bottle neck without damage. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a section through the stopper according to the invention with the bottle neck on which it is to be screwed. 
     FIG. 2 is a section along II--II of FIG. 1. 
     FIG. 3 is a variant of the stopper of FIG. 1. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The stopper shown in FIGS. 1 and 2 is formed by a screw-on stopper 1 made of plastic material covered with a rigid, for example, metallic cap 2. 
     The screw thread 3 of the stopper 1 terminates in a transverse radial projection 4 which abuts against a corresponding radial stop 5 on the bottle neck which receives this stopper. 
     A second radial projection 6 on the stopper is disposed parallel to and spaced from projection 4 and when the stopper is screwed on the bottle, said second projection 6 locks behind the stop 5, which is thus closely confined between the two projections 4 and 6 of the stopper. 
     To allow the projection 6 to pass over stop 5, material is removed from the outer surface of the stopper, forming a notch 7 as it appears in FIG. 2. The position of this notch corresponds to the location of the projection 6 on the inner surface of the stopper. 
     This notch thus gives elasticity to the zone of the stopper which surrounds the projection 6 and enables this projection to yield when passing over the stop 5 on the neck of the bottle. This stopper may thus be removed from and screwed onto the bottle neck any number of times without damage. 
     In the stopper device shown, the stopper 1 comprises a cone 8 which engages in the neck where it is wedged, thus hermetically closing said neck. 
     In this type of stopper, the screw pitch enables the cone to be easily unwedged, which is more difficult in the case of a nonthreaded stopper. 
     In the case of a stopper 1 without the cap shown in FIG. 1, but with an otherwise thick and undeformable skirt, a notch would be unaesthetic. Thus, to render elastic the zone which includes the projection 6, a cut-out 9, as shown in FIG. 3, is made around said projection which determines in the skirt of the stopper a tongue 10 bearing the projection 6, said tongue rising elastically when projection 6 passes over stop 5.