Soft serve ice cream pump assembly

A pump assembly comprising:

• a diaphragm pump comprising a diaphragm extending across a chamber to define a gas chamber on a first side of the diaphragm and a mixture receiving chamber on a second, opposite side of the diaphragm, and a shaft extending through the diaphragm and moving therewith between a default position and an extended position;
• the mixture receiving chamber configured to receive a liquid mixture via a mixture inlet and pass the liquid mixture to a pressure chamber via a mixture outlet;
• the gas chamber having an inlet port receiving gas of a desired pressure and an outlet port, a sealing ring on the shaft preventing communication between the inlet port and the outlet port until the diaphragm and shaft are in the extended position at which time the gas in the gas chamber passes from the gas chamber to the pressure chamber;
• the pressure chamber having a pressure outlet configured to deliver a pressurized liquid mixture and the gas to a freezing chamber;
• wherein each stroke of the diaphragm causes the pressurized liquid mixture and gas to be passed into the pressure chamber and to the pressure outlet.