Vented check valve

In a post-mix beverage carbonator system including a water supply, a source of carbon dioxide gas, a carbonator tank for mixing the water from the water supply with the carbon dioxide gas and producing a carbonated water mixture, supply pipes for connecting said carbonator tank to said water supply, pumping means for pumping the water from the water supply to the carbonator tank, and check valve means disposed between said carbonator tank and said pumping means, the improvement comprising:

• vented check valve means disposed between said check valve means and said pumping means for passing said water therethrough in one direction during normal operation and preventing the carbonated water mixture in the carbonator tank from backflowing into said supply pipes in an opposite direction in the event of a malfunction in the operation of said check valve means, said vented check valve means including a body portion having a chamber therein containing a movable valve element, an inlet passage and two outlet passages communicating with said chamber, a first of said outlet passages having a first opening on an opposite side of said chamber from said inlet passage and aligned therewith and a second opening communicating with the atmosphere, the walls of said chamber surrounding said inlet passage defining a first valve seat, said first opening of said first outlet passage defining a second valve seat, a second outlet passage communicating with said chamber in a position offset from said inlet and said first outlet passages, said movable valve element connecting only said inlet passage and said second outlet passage though said chamber during said normal operation and connecting only said first and second outlet passages through said chamber during said backflow condition, an improvement in said movable valve element comprising:
• a flexible diaphragm having an annular sealing portion for operative engagement with said first valve seat and a plug-shaped sealing portion extending therefrom and integral therewith for operative engagement with said second valve seat;
• said flexible diaphragm in the absence of fluid flow through said valve body being self-biased in a first shape so that said annular sealing portion firmly seats on said first valve seat and said plug-shaped portion firmly seats in said opening defining said second valve seat;
• said flexible diaphragm during said normal operation having a second shape wherein said annular sealing portion is unseated from said first valve seat and said plug-shaped portion is firmly seated in said second valve seat;
• said flexible diaphragm during said backflow condition having a third shape wherein said annular sealing portion firmly seats on said first valve seat and said plug-shaped portion is unseated from said second valve seat;
• and
• wherein said opening defining said second seat has sloped side walls converging from the walls of said chamber toward said first outlet passage, said opening at the walls of said chamber being larger than the diameter of the tip of said plug-shaped portion, whereby said plug-shaped portion self-centers in said opening.