keeping the widget pressurized by avoiding sudden pressure changes which would allow gas in the widget to escape liquid inlet line 416 runs from the beer supply bowl 424 to the fill head 410 notice that variable valve 436 may be used to carry out the beer filling operation without undue sudden pressure variations which would discharge the widget after the can and widget have been pressurized on off valve 407 is opened while pinch valve 434 is allowed to gently release pressure from the can and fill head pressure in the beer supply bowl 424 drives beer or other product up line 416 and into the can as shown previously in fig5 but without any pressure spikes or dips which would cause the co2 or n2 previously charged into the widget see fig3 and 4 to become discharged beer supply bowl 424 has above the actual beer in the head space 424 of the bowl pressurized co2 this pressurized co2 is not only used to drive beer up line 416 it is also used for the counterpressure step see fig4 when the gas line not visible in this view see 332 and 362 of fig7 for an example from the top of the bowl to the fill head is opened the head to bowl co2 line not visible in this view allows equalization of pressure between the can and the beer supply bowl when the valve controlling this conduit is open pressure may equalize and gas may in fact flow in either.