Closures for containers

Claim 1

A closure for the neck of a container, which closure is a unitary moulded structure of a resilient material, comprising a top portion, an internally screw-threaded annular skirt portion, which skirt portion is connected to said top portion by a sloping portion, and a downwardly depending annulus portion disposed on the underside of the top portion, said sloping portion having a convexly curved inside surface which joins the underside of the said top portion at a locus near the locus where an outer face of the said annulus portion joins the underside of said top portion, the outer face of said annulus portion having a concavely curved surface, the dimensions between the lower part of the convexly curved inside surface of the sloping portion and the lower part of the concavely curved surface of the outer face of the annulus portion being such as to receive the top of the mouth of a container but the dimension between the upper part of the convexly curved inside surface of the sloping portion and the upper part of the concavely curved surface of the outer face of the annulus portion being such that the top of the mouth of a container is tightly engaged with both the said inside surface of the sloping portion and surface of the outer face of the annulus portion when the said screw-threaded skirt portion is engaged by the screw threads of the container mouth, whereby tHe convexly curved inside surface of the sloping portion is engaged by the outer top portion of the container mouth and moved upwardly and causes the outer face of the annulus portion to pivot outwardly and against the inside top portion of the container mouth and be tightly engaged thereby, and hence effecting a tight seal between the outer top portion of the container mouth and the convexly curved inside surface of the sloping portion and between the inside top portion of the container mouth and outer face of the annulus portion.