US Patent 7357172 Check valve with a spiral coil seal

A seal for a check valve for a metal molding machine. The seal is provided by the combination of a peripheral groove in an outer surface of the check valve and a helically wound core in the groove. The helically wound coil is expandable into sealing engagement with a cylindrical wall of the molding machine. The helically wound coil may be movable laterally in the groove between a melt channel open position and a melt channel closed position to open or seal the melt channel.