Patent claim: A beverage dispensing system for dispensing a carbonated beverage said beverage dispensing system comprising a beverage container defining an inner space for holding said carbonated beverage at an elevated pressure exceeding the ambient atmospheric pressure a dispensing device for dispensing said beverage from said inner space of said beverage container and a constant flow rate controller having an inlet in fluid communication with said inner space of said beverage container and an outlet in fluid communication with said dispensing device said constant flow rate controller having a first position defining a maximum effective flow area between said inlet and said outlet and a second position defining a minimum effective flow area between said inlet and said outlet said constant flow rate controller shifting gradually during dispensing beverage towards the second position with an increasing pressure difference between said inlet and said outlet and towards the first position with a decreasing pressure difference between said inlet and said outlet.

Related passage: The selfregulating principle of the flow rate control means 5 useful in the present invention is very simple.A section 3 of the dispensing tube 1 is made flexible such that the inner surface of the flexible section facing the interior of the dispensing tube 1 is exposed to a pressure P1 reigning in the duct at that level and the outer surface facing out of the duct 1 is exposed to a pressure substantially equal to the pressure P2 reigning in the container 30 31.When the valve 35 is closed the pressures P1 and P2 in the dispensing duct and the container respectively are substantially equal P1P2 and the flexible section 3 of the dispensing duct 1 is at rest cf.position 3a in Figure 2.Upon opening of the valve 35 a pressure gradient Pab is created between the first opening 1 a of the dispensing duct 1 which is at a pressure P2 and the second opening 1b which is at atmospheric pressure thus driving the flow of beverage out of the container.Consequently the pressure P1 in the dispensing duct 1 at the level of the flexible section 3 becomes lowerthan the pressure P2 reigning in the container 30 31 creating a pressure gradient P21 across the flexible wall 3 of the duct 1.Consequently the flexible wall section will be strained to a geometry 3b such that the crosssection area of the dispensing tube 1 is reduced in this region thus reducing the flow rate Q of the beverage flowing through the dispensing duct 1.Now in case the pressure P2 varies with time for any reason generally P2 will decrease with time in cases such as discussed below but it may increase too the pressure gradient Pab between inlet 1a and outlet 1b of the dispensing duct 1 will vary accordingly and so will the pressure gradient P21 across the flexible wall section 3 of the dispensing duct 1 resulting in a corresponding variation of the cross section area in this region.This mechanism is illustrated in Figure 4 which plots the relative flow rate QQtarget relative to the desired flow rate value Qtarget as well as the relative crosssection area AxAx0 of the dispensing duct at the flexible region 3 with respect to the rest crosssection area Ax0 of the duct in the absence of any pressure gradient P21 as a function of the pressure difference PabP2Patm.