| 摘要 |
A self-closing valve for a packaging container, especially a thin-walled plastics bottle, has an outwardly concave valve head (22) joined to an outer margin (20) by a flexible connecting wall (24). The connecting wall has a frustoconical outer portion (56) and a cylindrical inner portion (57) joined together at an elbow (58). The inner portion (50) is joined to the valve head at a thin, inturned flange (60). The outer portion (56) of the connecting wall is frustoconical and moves between downwardly inclined and upwardly inclined positions as the valve advances to its dispensing position. The outer portion (56) accordingly imparts a bistable operating characteristic to the valve. The elbow (58) of the connecting wall (24) acts as a spring to retract the valve head (22) quickly after dispensing. The flange (60) acts as a living hinge, with substantially no flexural stiffness, so that subsequent deformation of the valve head (22) to allow venting is not resisted. |
