Backflow preventor for automatic dishwashers

Claim 1

A back flow preventor comprising: a. a tubular shell having a circular open upper end, a vent opening near its upper end, and an internal essentially disposed tube terminating approximately at the upper end of the shell to define with the shell an opening equal to the passage within the internal tube and forming an upwardly directed valve seat, the internal tube and shell forming respectively an inlet duct and an outlet duct; b. a cap member having a closed upper end and a tubular lower portion dimensioned for reception into the upper end of the shell around the inner tube whereby the internal tube discharges upwardly into the cap member for downward discharge into the surrounding shell; c. said cap member also having an internal valve guide channel aligned with the valve seat and an external channel forming with the shell an upwardly directed vent passage to the vent opening; whereby, in the event of suction pressure within the shell, air may be drawn through the vent opening; d. and a ball valve engageable with the internal tube valve seat and movable upwardly therefrom in the guide channel for discharge from the internal tube into the cap member and deflection into the shell.