Patent Publication Number: US-2013233878-A1

Title: Dispensing unit and method for dispensing a liquid under pressure

Description:
The present invention relates to a dispensing unit and a method for dispensing a liquid under pressure. 
     The document EP 1064221 discloses a device for dispensing a liquid, wherein the device comprises a container having a first compartment, and a second compartment, the first compartment being arranged for receiving the liquid to be dispensed, and the second compartment being arranged for receiving a propellant gas, wherein, at least during use, an opening is provided between the first and the second compartment. The device further comprises a pressure control means arranged for controlling, during use, the pressure of the propellant gas flowing from the second compartment into the first compartment. The pressure in the second compartment, at least prior to use, is between 4 and 16 bar, preferably about 10 bar, measured at application temperature, whereas the regulated pressure in the first compartment, at which the liquid is dispensed via the dispensing means, is such that an overpressure of 0.1 to 1.5 bar, preferably about 0.7 bar, relative to the surroundings is maintained in the first compartment. This device has the drawback that the pressure in the first compartment is regulated so that a constant pressure is always maintained therein, which means that in case of gaseous beverages, where an overpressure of about 0.6-0.8 bar should be maintained depending on the equilibrium pressure of the particular beverage, a substantial overpressure prevails in the first compartment during dispensing the liquid. The flow rate of the liquid during dispensing can be controlled solely by adjusting the cross-sectional flow area of a dispensing duct or outlet of the dispensing device. Decreasing the flow area of the liquid at a constant pressure, however, results in an increase of the flow velocity of the liquid, which may cause the development of undesired turbulences in the liquid in the region of the restricting member. This leads to excess frothing of the dispensed liquid and, in particular for gaseous beverages, a substantial release of gas from the liquid. 
     The present invention is based on the inventive idea that during dispensing, instead of maintaining a regulated constant pressure in the liquid container and controlling the flow rate of the liquid by controlling the flow area of the dispensing channel or dispensing outlet for the liquid, the flow area of the dispensing channel or outlet is rather maintained at a constant value, preferably at a maximum value, and the pressure in the liquid container is controlled within a predetermined pressure range so as to control the flow rate of the liquid being dispensed. This novel approach of dispensing allows to apply a relatively low pressure at dispensing for any kind of liquid, including both gaseous and non-gaseous beverages, while keeping the possibility to adjust the flow rate of the liquid by simply adjusting (or even varying) the desired pressure of the propellant gas in the liquid container. A further advantage of this solution is that by controlling the pressure prevailing in the liquid container during dispensing, the flow path of the liquid from the liquid container through the dispensing unit may be formed free of any obstacle of flow, thus allowing to avoid the development of undesired turbulences in the liquid during dispensing. 
     It is therefore an object of the present invention to provide a dispensing unit adapted for adjusting the pressure of the propellant gas in the liquid container by the consumer during dispensing within a predetermined range of pressure. Another object of the present invention is to provide a dispensing unit adapted to establish a predetermined regulated pressure for storing the liquid in the container after dispensing. 
     It is yet another object of the present invention to provide a method for dispensing a liquid at a low and adjustable pressure. 
     These and other objects are achieved by providing a dispensing unit as defined in claim  1 . The above objects are further achieved by providing a method as defined in claim  12 . Preferred embodiments of the dispensing unit and the method according to the present invention are defined by the dependent claims. 
    
    
     
       The present invention will now be described in more detail through preferred embodiments thereof with reference to the accompanying drawings, in which: 
         FIG. 1   a  is a perspective view of a first preferred embodiment of the dispensing unit according to the invention in its initial state, 
         FIGS. 1   b ,  1   c  and  1   d  are a top plan view, a side view and a bottom plan view of the dispensing unit shown in  FIG. 1   a , respectively, in an unfolded state, 
         FIG. 2  is top plan view of the dispensing unit shown in  FIG. 1  in its initial state, 
         FIG. 3  is a cross sectional view of the dispensing unit shown in  FIG. 1  taken along the line A-A, 
         FIG. 4  is a cross sectional view of the dispensing unit shown in  FIG. 1  taken along the line B-B, 
         FIG. 5  is a cross sectional view of the dispensing unit shown in  FIG. 1  taken along the line C-C, 
         FIG. 6  is a cross sectional view of the dispensing unit shown in  FIG. 1  taken along the line H-H, 
         FIG. 7  is perspective view of a dispensing device comprising the dispensing unit shown in  FIG. 1 , 
         FIG. 8  is a cross-sectional view of the dispensing device shown in  FIG. 7  taken along the line A-A of  FIG. 2 , with the operating lever being in its initial position, 
         FIG. 9  is a partial cross-sectional view of the dispensing device shown in  FIG. 7  taken along the line H-H of  FIG. 2 , with the operating lever being in its initial position, 
         FIG. 10  is a partial cross-sectional view of the dispensing device shown in  FIG. 7  taken along the line A-A of  FIG. 2 , with the operating lever being in a first operating position, 
         FIG. 11  is a partial cross-sectional view of the dispensing device shown in  FIG. 7  taken along the line H-H of  FIG. 2 , with the operating lever being in the first operating position, 
         FIG. 12  is a partial cross-sectional view of the dispensing device shown in  FIG. 7  taken along the line G-G of  FIG. 2 , with the operating lever being in the first operating position, 
         FIG. 13  is a partial cross-sectional view of the dispensing device shown in  FIG. 7  taken along the line H-H of  FIG. 2 , with the operating lever being in a second operating position, 
         FIG. 14  is a partial cross-sectional view of the dispensing device shown in  FIG. 7  taken along the line H-H of  FIG. 2 , showing a second embodiment of the dispensing unit with the operating lever being in the initial position, 
         FIG. 15  is a partial cross-sectional view of the dispensing device shown in  FIG. 7  taken along the line H-H of  FIG. 2 , showing the second embodiment of the dispensing unit with the operating lever being in its first operational position, and 
         FIG. 16  is a partial cross-sectional view of the dispensing device shown in  FIG. 7  taken along the line H-H of  FIG. 2 , showing the second embodiment of the dispensing unit with the operating lever being in its second operating position. 
     
    
    
     In  FIG. 1   a , a first preferred embodiment of the dispensing unit  10  according to the invention is illustrated in a perspective view. Although the dispensing unit  10  in  FIG. 1  is shown as a cap for a bottle, the dispensing unit may be designed in any other way, for example as a taping unit for a beer keg. The illustrated first embodiment of the dispensing unit  10  comprises a lower mounting part  11  and an upper covering part  12 . The lower mounting part  11  and the upper covering part  12  are connected via a flexible hinge  13 . The upper covering part  12  comprises a pivotable operating lever  14  used to control the flow rate of the liquid during dispensing. The operating lever  14  is provided with several once breakable joints  15  for fixing the operating lever  14  to an adjacent portion of the upper covering part  12 . These joints  15  also have the function to demonstrate that the dispensing unit  10  has not been tampered with. Before the first use of the dispensing unit  10 , these joints  15  are to be broken so that the operating lever  14  can be moved. 
     In  FIGS. 1   a ,  1   b  and  1   c , the lower mounting part  11 , the upper covering part  12 , the operating lever  14  and the once breakable joint  15  of the dispensing unit  10  can be seen in different views of an unfolded state. In  FIG. 1   d , a flexible dispensing tube  16  and a membrane  22  of a pressure regulating means are also shown, although these elements are arranged inside the dispensing unit  10 . 
     In  FIG. 2 , the dispensing unit  10  can be seen in a plan view using the same reference numbers as in  FIGS. 1   a  to  1   d . This figure also indicates sectioning lines A-A, B-B, C-C and H-H along which cross-sectional views are taken and illustrated in the following  FIGS. 3 to 6 , in which the dispensing unit  10  is shown in its initial state, i.e. in the storage state, when the operating lever is in its initial position. 
       FIG. 3  illustrates the dispensing unit  10  in a cross-sectional view taken along the line A-A indicated in  FIG. 2 . Inside the dispensing unit  10 , a dispensing tube  16  is arranged under the operating lever  14 . The dispensing tube  16  is secured to the lower mounting part  11  and comprises an opening  17  that establishes a fluid communication with the internal space of the liquid container (not shown) to which the dispensing unit  10  is coupled. The dispensing tube  16  has an outer end portion  19  provided with an opening  19 ′ to allow the liquid to flow out from the liquid container during dispensing. In  FIG. 3 , the outer end portion  19  of the dispensing tube  16  is entirely compressed by an eccentric front projection  18  of the operating lever  14 , thereby the flow path of the liquid is closed. 
     As can be seen in  FIG. 4 , the upper covering part  12  of the dispensing unit  10  is secured to the lower mounting part  11 , for example, by snap fitting between a downward projection  20  of the upper covering part  12  and the rim  21  of a corresponding through-hole of the lower mounting part  11  adapted to receive said projection  20 . 
     The dispensing unit  10  also comprises a pressure regulating means to generate a constant regulated pressure for the propellant gas in the liquid container. In the illustrated preferred embodiments of the dispensing unit  10 , the pressure regulating means comprises a resilient membrane  22 , preferably made of rubber, a valve stem  23  joined to a central portion of the membrane  22  at is one end, a valve head  24  formed at the other end of the valve stem  23  and a fluid communicating path for the propellant gas, said fluid communicating path connecting the internal space of the gas container and the internal gas space of the liquid container (also referred to as head space) through the pressure regulating means. In the illustrated embodiments of the dispensing unit  10 , the fluid communicating path includes a first gas channel  25   a  in which the valve stem  23  is guided, and a second gas channel  25   b  (shown in  FIG. 6 ). The operation of the pressure regulating means of the dispensing unit  10  will be described later. 
     As shown in  FIG. 5 , the operating lever  14  has two coaxial pivots  26   a  and  26   b  serving as a shaft for the operating lever  14  around which it can be pivoted. On the lateral surface of the inner pivot  26   a , there is a stud  27  arranged extending into a guiding hole  29  (shown in  FIG. 6 ) of a slide  28 . The slide  28  is guided so that it can move horizontally between two end positions defined by the two end positions of the operating lever  14 . When the operating lever  14  is pivoted, the stud  27 , which is arranged eccentrically with respect to the rotational axis of the pivots  26   a ,  26   b , moves along a circular path, thus forcing the slide  28  to move toward the central portion of the dispensing unit  10  or in the opposite direction, while the stud  27  moves up or down in the guiding hole  29 . 
     As clearly shown in  FIG. 6 , the slide  28  partly covers the membrane  22 , the extent of coverage depending on the position of the operating lever. Under the coverage area of the membrane  22 , there is a third gas channel  30  formed to connect the internal space of the gas container with the head space of the liquid container through the pressure regulating means. The slide  28  is formed so as to be capable of varying the area of an upper aperture  31  of the third gas channel  30 , thereby adjusting the amount of the propellant gas flowing from the gas container into the liquid container. By adjusting the flow rate of the gas flowing through the third gas channel  30 , the pressure of the propellant gas can be varied in the liquid container during dispensing. Since the pressure regulating means of the dispensing unit  10  is adapted to generate a predetermined pressure in the liquid container, the variable pressure range has an upper limit defined by said preset pressure of the pressure regulating means. On the other hand, the lower limit value of the variable pressure range can never decrease below the ambient pressure since the closure of the third gas channel  30  will terminate the outflow of the liquid and also prevent the ambient air from entering the liquid container. 
     The mechanism including the operating lever, the slide, the third channel and pressure regulating means together constitute a means for adjusting the flow rate of the propellant gas flowing from the gas container into the liquid container. By varying the flow area of the third gas channel by said mechanism, the desired pressure may be adjusted in the liquid container, and thereby the flow rate of the liquid may also be set during dispensing. 
       FIG. 7  schematically illustrates an assembled dispensing device  30  comprising a liquid container  36  (indicated by dashed line), for example, a bottle containing a beverage, a gas container  33  containing a propellant gas, for example carbon dioxide or nitrogen, at a high pressure, a dispensing unit, such as the dispensing unit  10  according to the present invention, and preferably a dip tube  35 . The dispensing unit  10  is coupled to the liquid container  36  and the gas container  33  in a gas-tight sealed manner. Although in  FIG. 7 , the gas container  33  is shown inside the liquid container  36 , the gas container  33  may equally be arranged externally to the liquid container  36 . The dip tube  35  is arranged inside the liquid container  36  and connected to a corresponding dispensing channel of the dispensing unit  10 . 
     In  FIG. 8 , a cross-sectional view of the dispensing device  30  shown in  FIG. 7  is illustrated with the operating lever  14  of the dispensing unit  10  being in its initial position. The cross-section is taken along the line A-A of  FIG. 2 . In the dispensing device  30 , the operating lever  14  is in its initial position that is normally applied during storage of the dispensing device  30 . In this case, the front projection  18  of the operating lever  14  closes the outer end portion  19  of the dispensing tube  16 , thereby preventing the dispensing of the liquid  32  from the liquid container  36 . Due to the overpressure of the propellant gas  34  prevailing in the head space of the liquid container  36 , the dispensing tube  16  also contains liquid  32  under pressure. The liquid  32  can enter the dispensing tube  16  through the opening  17  of the dispensing channel (not shown) formed within the dispensing unit  10 . 
     In the partial cross-sectional view of  FIG. 9 , an exemplary way of coupling the dispensing unit  10  to the liquid container  36  and the gas container  33  can be seen in more detail. According the present invention, the dispensing unit  10  has a first coupling means for coupling to the liquid container  36 . As illustrated in the embodiment shown in  FIG. 9 , the first coupling means may comprise a snap fitting portion  40  formed in the lower mounting part  11  of the dispensing unit  10 , said snap fitting portion  40  being adapted to be sealingly attached to a corresponding coupling part of the liquid container  36 . To this end, the first coupling means may comprise an elastic sealing ring  38  against which the corresponding coupling portion of the liquid container  36  bears after mounting the dispensing unit  10  onto the liquid container  36 . Although in  FIG. 9 , only a preferred embodiment of said first coupling means is illustrated, the dispensing unit may according to the present invention may be coupled to the liquid container in other ways as well, for example by threaded fitting or gluing, the implementation of which alternative coupling modes is obvious for those skilled in the art. 
     According the present invention, the dispensing unit  10  further comprises a second coupling means for coupling to the gas container  33 . As illustrated in the embodiment shown in  FIG. 9 , the second coupling means may comprise a snap fitting portion  42  formed also in the lower mounting part  11  of the dispensing unit  10 , said snap fitting portion  42  being adapted to be sealingly attached to a corresponding coupling part of the gas container  33 . It is preferred that the first coupling means comprises an elastic sealing ring  43  against which a corresponding coupling portion of the gas container  33  bears after attaching the gas container  33  to the dispensing unit  10 . Although in  FIG. 9 , only a preferred embodiment of said second coupling means is illustrated, the dispensing unit may be coupled to the gas container in other ways as well, for example by threaded fitting or gluing, the implementation of which alternative coupling modes is obvious for those skilled in the art. 
       FIG. 9  shows the dispensing unit  10  in its storage state when the operating lever (not shown) is in its initial position. The slide  28  is now in its inner end position where it presses the whole coverage area of the membrane  22  onto an upper surface of the lower mounting part  11 , thereby entirely closing the upper aperture  31  of the third gas channel  30 . Under this condition, the membrane  22  takes the form like a dome, and the valve head  24  closes the lower aperture of the first gas channel  25   a . The pressure of the propellant gas  34  acting to the bottom surface of the valve head  24  is compensated by the counteracting resilient force of the elevated membrane  22 . In the gas space defined by the membrane  22  and the upper surface of the lower mounting part  11  of the dispensing unit  10 , the pressure is equal to the pressure of the gas container  33 , and due to the fluid communication path between the gas container  33  and the head space of the liquid container  36  through the second gas channel  25   b , this pressure is also equal to the pressure prevailing in the liquid container  36 , also referred to as a first pressure. 
     After finishing the dispensing of the liquid, the operating lever is moved again into its initial position, resulting in the same arrangement of the parts within the dispensing unit as shown in  FIG. 9 . If the dispensing pressure was lower than said first pressure when the dispensing was terminated, the propellant gas tends to flow from the gas container  33  into the liquid container  36  through the second gas channel  25   b  until the first pressure is reached and set in the liquid container  36  by the pressure regulating means of the dispensing unit  10 . 
     In  FIG. 10 , the dispensing unit  10  can be seen with its operating lever  14  being in a vertical position wherein the dispensing tube  16  is open to the maximum extent, i.e. the outer end portion  19  of the dispensing tube  16  presents the largest possible flow area for the liquid. In this case, however, the third gas channel (not shown) is still closed. The liquid flows out from the liquid container  36  through the dispensing channel (not shown), then via the opening  17  and finally through the dispensing tube  16 . If a dip tube  35  is also used (as shown in  FIG. 10 ), the liquid  32  is driven into the dispensing channel through the dip tube  35 . 
       FIG. 11  shows the same state of the dispensing unit  10  as shown  FIG. 10 , but in a cross-sectional view of the dispensing device  30  taken along the line H-H indicated in  FIG. 2 . The pressure regulating means is still under the same condition as described for the initial state of the dispensing unit  10 , that is, the membrane  22  is elevated and the third gas channel  30  is closed. In the first preferred embodiment of the dispensing unit  10 , this vertical operating position of the operating lever  14  shown in  FIGS. 10 to 12  (also referred to as a first operating position) defines a boundary position between a first operating range of the operating lever  14  and a second operating range thereof, wherein the first operating range is associated with the control of the flow area of the dispensing channel or outlet for the liquid (i.e. the dispensing tube  16 , in the first embodiment), whereas the second operating range is associated with the control of the flow area of the third gas channel  30  for the propellant gas. By continuing to pivot the operating lever  14  counter-clockwise in  FIG. 11 , the upper aperture  31  of the third gas channel  30  becomes gradually opened as the slide  28  moves toward the periphery of the lower mounting part  11 . 
     As can be seen in the cross-sectional view of the dispensing device illustrated in  FIG. 12 , the dispensing channel  44  establishes a fluid communication path for the liquid  32  between the internal space of the liquid container  36  and the flexible tube  16 . To the lower end of the dispensing channel  44 , a dip tube  35  may optionally be connected. 
     In  FIG. 13 , the dispensing device  30  is shown in a partial cross-sectional view, wherein the operating lever  14  is moved to a second operating position to at least partially open the upper aperture  31  of the third gas channel  30 . In the illustrated embodiment of the dispensing unit  10 , this position of the operating lever  14  belongs to the second operating range of the operating lever  14 , wherein the flow rate of the liquid  32  is controlled during dispensing by controlling the pressure of the propellant gas  34  in the liquid container  36 . The more downward the operating lever  14  is pushed in the direction F indicated by an arrow in  FIG. 13 , the larger area of the upper aperture  31  of the third gas channel  30  is released by the displacement of the slide  28 , thus causing the elevation of an increasing area of the coverage portion of the membrane  22  above the aperture  31 . Hence, by varying the opened area of the aperture  31 , the amount of gas flowing from the gas container  33  into the liquid container  36  through the third gas channel  30  and, consequently, the driving force for the liquid  32  may be varied. 
     In order to minimize or even entirely to terminate the gas flow through the second gas channel  25   b  during dispensing, the second gas channel  25   b  is to be closed or alternatively, it is to be restricted so that a substantial delay be presented at the generation of the first pressure in the liquid container  36  by the pressure regulating means. To this end, in the first preferred embodiment of the dispensing unit  10 , the second gas channel  25   b  has a restricted section  25   c  in which the gas flow rate, under normal operating conditions, is so small that only a negligible amount of propellant gas can flow therethrough into the liquid container  36 , and therefore the regulated first pressure can be generated by the pressure regulating means within a relatively long time with respect to the time period normally needed to dispense the desired amount of liquid. For example, if the first regulated pressure is 1.7-2 bars absolute, a diameter of approximately 100 urn for the restricted section  25   c  allows a regulation delay of approx. 5 to 15 minutes, which is a much longer time than the usual duration of filling a glass. After finishing the dispensing of the liquid, however, such a delay has no significance if the next dispensing action starts even later. Moreover, the regulated first pressure is in the liquid container  36  is greater than the equilibrium pressure of the liquid  32  stored in the liquid container  36 , preferably only by a few tenths bar, thus providing an appropriate long term storage pressure for the liquid in the liquid container during storage. 
     On the other hand, the pressure regulating means of the first embodiment of the dispensing unit  10  also limits the maximum pressure of the pressure range associated with the second operating range of the operating lever. When the third gas channel  30  is entirely opened, the pressure in the liquid container  36  increases quickly due to the large flow are of the aperture  31 , but the pressure can rise only up to the first pressure since the pressure regulating means prevents the pressure of the head space of the liquid container  36  from increasing further. In fact, upon reaching the first pressure in the liquid container  36 , the valve head  24  will close the first gas channel  25   a , thereby blocking the flow of any more propellant gas  34  from the gas container  33  into the liquid container  36 . 
     In  FIG. 14 , a partial cross-sectional view of a dispensing device  30 ′ is illustrated with a second embodiment of the dispensing unit  110  according to the present invention. In this example, the operating lever  114  (indicated by dashed line) of the dispensing unit  110  is in its initial position used for storage of the liquid container  136 . This second embodiment of the dispensing unit  110  comprises a common gas channel  130  providing the function of both the first gas channel and the second gas channel used in the first embodiment of the dispensing unit. In order to properly control the gas flow through this common gas channel  130 , the slide  128  is designed to have a recess  129  on its bottom sliding surface which allows the membrane  122  to have a local elevation  123  above the upper aperture  131  of the common gas channel  130 . Under this local elevation  123 , a limited flow rate for the propellant gas  134  is allowed, thus providing a substantial delay in the development of the first pressure in the liquid container  136 . 
     As can be seen in  FIG. 15 , which illustrates the second embodiment of the dispensing unit  110  with the operating lever  114  being in its first operating position, the slide  128  is moved to a position where it entirely closes the common gas channel  130 . Similarly to the first embodiment of the dispensing unit (but not shown in  FIG. 15 ), in this position the operating lever  114  entirely opens the flexible dispensing tube of the dispensing unit  110 . 
       FIG. 16  illustrates the second embodiment of the dispensing unit  110  with the operating lever  114  being in a second operating position during dispensing where the inner end portion of the slide  128  at least partly opens the common gas channel  130  by allowing the main part of the membrane  122  to elevate above the upper aperture  131  of the common gas channel  130 . In the second operating range of the operating lever  114 , the common gas channel  130  is used only for controlling the pressure of the propellant gas in the liquid container  136  and thus also the flow rate of the liquid being dispensed. As the second embodiment of the dispensing unit  110  has no separate gas channel with a restricted section to feed propellant gas  134  from the gas container  133  into the liquid container  136 , the relatively large flow area of the common gas channel  130  allows a rather quick development of the regulated first pressure in the liquid container  136  after finishing the dispensing of the liquid. 
     In a second aspect, the present invention also relates to a novel method of dispensing a liquid under pressure from a liquid container in which the liquid is stored under pressure by a propellant gas having at a first regulated pressure. Preferably, the first pressure exceeds the equilibrium pressure of the liquid by a few tenths bar. So as to provide the first regulated pressure in the liquid container, additional propellant gas is stored in a gas container at a second pressure substantially higher than the first pressure. The propellant gas stored in the second gas container is also used for controlling the flow rate of the liquid during dispensing. 
     In the method according to the invention, the dispensing is started by reducing the first pressure of the liquid container to a third pressure, wherein the third pressure is at least the ambient pressure. Depending on the design of the particular dispensing apparatus used for dispensing, the third pressure may be higher than the ambient pressure. After the overpressure of the liquid container is partly or wholly released, the dispensing path for the liquid is opened and the flow area of the entire dispensing path is settled. Opening of the dispensing path of the liquid may be carried out along an internal dispensing duct or at a dispensing outlet. 
     Finally, while keeping the settled flow area of the dispensing path for the liquid unchanged, the pressure of the propellant gas in the liquid container is controlled within a pressure range defined by the first pressure and the ambient pressure, thereby dispensing a first amount of liquid. This first amount preferably corresponds to the entire dose of the liquid to be dispensed at one run. It is preferred that the overpressure prevailing in the liquid container during dispensing does not exceed the ambient pressure by a few tenths bar, e.g. 0.1-0.2 bar, in order keep the flowing rate of the liquid at a rather low level and thereby not to allow excess frothing of the liquid. 
     Alternatively, the step of reducing the overpressure in the liquid container and the step of opening and settling the flow area of the dispensing path for the liquid may be executed simultaneously. In this case a second amount of liquid may additionally be dispensed in this step, but this second dispensed amount of liquid should be very limited. It is preferred that the second amount is smaller than 10 to 15% of the entire amount of liquid to be dispensed in one dose. 
     In a particularly preferred embodiment of the method according to the present invention, during dispensing, the dispensing pressure of the propellant gas in the liquid container is controlled by controlling the flow rate of the propellant gas flowing from the gas container into the liquid container. For controlling the pressure in the liquid container during dispensing may, however, be carried out in other ways as well, for example by using an additional gas supply, optionally an external gas container, to provide the necessary amount of gas for this purpose. 
     Although in the foregoing, several preferred embodiments of the dispensing unit and the dispensing method according to the invention have been illustrated, the present invention is not in any way limited to the exemplary embodiments shown in the description and the drawings and many variations thereof are possible within the scope of the invention defined by the attached claims. 
     In particular, the single operating lever of the dispensing unit may be carried out by providing two independent operating levers for each operating range mentioned above, i.e. a first operating lever for controlling the flow area of the dispensing path for the liquid and a second operating lever for controlling the flow are of the third gas channel (or the common gas channel) for the propellant gas. Moreover, instead of levers, any other kind of tool, such as a push button, a rotatable knob, etc. may be used as an operating means for controlling the flow rate of the liquid. 
     The pressure regulating means may also be designed differently from the exemplary pressure regulator described above with reference to the drawings, while providing the same function of generating a regulated first pressure in the liquid container. Such pressure regulating means are well-known in the art.