Dual container

Abstract

The present invention is a dual container including an inner container deformed to reduce a volume according to reduction of accommodated contents, and an outer container in which the inner container is inserted and which is elastically deformable. In the dual container, a mouth portion, a shoulder portion, a drum portion, and a bottom portion are arranged in sequence from top to bottom in a bottle axis direction, an outside air introduction hole configured to introduce outside air between the outer container and the inner container according to reduction of contents is provided, a circumferential groove recessed inward in a radial direction and extending in a circumferential direction is formed in the drum portion, and a longitudinal convex portion configured to disconnect the circumferential groove in the circumferential direction is provided on an inner surface of the circumferential groove.

What is claimed is: 
     
         1 . A dual container comprising:
 an inner container deformed to reduce a volume according to reduction of accommodated contents; and   an outer container in which the inner container is inserted and which is elastically deformable,   wherein a mouth portion, a shoulder portion, a drum portion, and a bottom portion are arranged in sequence from top to bottom in a bottle axis direction,   an outside air introduction hole configured to introduce outside air between the outer container and the inner container according to reduction of contents is provided,   a circumferential groove recessed inward in a radial direction and extending in a circumferential direction is formed in the drum portion, and   a longitudinal convex portion configured to disconnect the circumferential groove in the circumferential direction is provided on an inner surface of the circumferential groove.   
     
     
         2 . The dual container according to  claim 1 , wherein 
 an outer surface of the longitudinal convex portion, the outer surface facing outward in the radial direction, is continuous with an outer circumferential surface of each portion of the dual container, the portion being continuous with the circumferential groove in the upward/downward direction, with no step difference in the upward/downward direction.   
     
     
         3 . The dual container according to  claim 1 , wherein
 at least a lower portion of the drum portion extends outward in the radial direction as it goes downward, and   the circumferential groove is provided in the lower portion of the drum portion.   
     
     
         4 . The dual container according to  claim 2 , wherein 
 at least a lower portion of the drum portion extends outward in the radial direction as it goes downward, and   the circumferential groove is provided in the lower portion of the drum portion.