Patent ID: 8042714
Filing Date: 2011-10-25
Classification: A61F,B65D

Abstract:
1. A backflow preventing plug including a thin film resilient membrane defining a flow path and forming an intake port and an outlet port of the flow path, a ball-shaped plug member which is retained by the resilient membrane between the intake port and the outlet port and which is formed with a spherical sealing surface for restricting flow of fluid by coming into resilient contact with a middle portion of the resilient membrane; and clearance forming means comprising at least one of the following: a plurality of projection portions each of which has a shape of projection and which are located at such positions on an inner surface of the resilient membrane as to be closer to the outlet port than to a center of the ball-shaped plug member and to be apart from each other and substantially symmetrically located about a circumferential surface of the ball-shaped plug member; a plurality of projections extending from an outer surface of the ball-shaped plug member toward the resilient membrane, said projections being closer to the outlet port than to a center of the ball-shaped plug member and to be apart from each other and substantially symmetrically located about a circumferential surface of the ball-shaped plug member; and a plurality of recesses formed in a recess shape which are located at such positions on the plug member as to be closer to the outlet port than to a center of the ball-shaped plug member and be apart from each other and substantially symmetrically located about a circumferential surface of the ball-shaped plug member and which communicate with each other at closest positions to the outlet port, wherein said clearance forming means forms a clearance between the outlet port and the plug member, and said resilient membrane is expanded and deformed in a direction away from said plug member by a pressure applied from the intake port.