Patent Publication Number: US-9902603-B2

Title: Method and filling machine for filling cans or the like containers with liquid contents

Description:
RELATED APPLICATIONS 
     This application is the national stage under 35 USC 371 of international application PCT/EP2014/000534, filed on Mar. 1, 2014, which claims the benefit of the Mar. 13, 2013 priority date of German application DE 102013102547.1, the contents of which are herein incorporated by reference. 
     FIELD OF INVENTION 
     This invention relates to packaging, and in particular, to filling machines. 
     BACKGROUND 
     Filling machines for filling containers are known. It is also known to purge the inside of a container before filling it. This is done by sealing the container against a filling element and allowing a purgative gas to fill the container. A typical purgative gas is carbon dioxide. It is also known to introduce the purgative gas along a vertical filling element axis and into the bottle interior, and to conduct away such gas from the bottle interior via a controlled gas-path. 
     SUMMARY 
     An object of the invention is to provide a method that also allows a container, and in particular, a can, to have its interior purged. 
     A particular feature of the invention is that of purging a container by introducing purgative gas takes place exclusively through a constricted gas path with reduced flow cross-section, and draining purgative gas from the container via an unconstricted gas path with a substantially larger flow cross-section. As a result, purgative gas flows into a container with both low pressure and high throughput. 
     In some practices, the pressure above atmospheric pressure is only 0 bar to 3.0 bar. In others, it is between 0 bar to 2.0 bar. In yet other practices, it is between 0.5 bar to 1 bar. At least during filling, the unconstricted gas path exhibits its full flow cross-section, without any reduction as a result of a choke. This results in a rapid pre-loading and filling of the containers. 
     In one aspect, the invention features a method for operating a filling machine for filling containers with liquid contents. Such a method includes sealing the container against a filling element, conducting purgative gas via a first controlled gas-path from a first ring channel common to all filling elements of the filling machine to the container&#39;s interior via a controllable choke arrangement that can switch between a first choke-state in which the controllable choke arrangement chokes gas flow and a second choke-state in which the controllable choke arrangement allows free gas flow, the controllable choke arrangement being in the first choke-state, thereby reducing pressure of the purgative gas to a purge pressure, draining the purgative gas from the container, which is flowing at a purge pressure of between 0 bar and 2 bar above ambient pressure, out of the container&#39;s interior through first and second return-gas openings of the filling element and into first and second return-gas channels of a second controlled gas-path of the filling element, the first and second return-gas channels being controlled by corresponding first and second control valves that are operable independently of each other, and pressure-filling the container with the liquid contents. 
     Practices of the invention include those in which the first ring channel is maintained at an under-pressure. 
     Other practices include those in which draining the purgative gas comprises draining the purgative gas through openings that are offset by 180° around a filling element axis of the filling element. 
     Yet other practices include those in which sealing the container comprises sealing a mouth of the container against a ring seal. 
     Some practices include causing the controllable choke arrangement to switch into the second choke-state. In these practices, wherein pressure filling the container comprises causing the liquid contents to force the purgative gas out of the container&#39;s interior via the second controlled gas-path and into a second ring channel. These practices include those in which the controllable choke arrangement comprises a non-return valve arranged parallel to a choke, wherein, except for flow into the second ring channel, the non-return valve prevents flow, those in which the choke arrangement comprises a choke having a changeable flow cross-section, and those in which the controllable choke arrangement comprises a control valve and a choke arranged parallel to the control valve. 
     Yet other practices include those in which pressure-filling the container comprise comprising causing the choke arrangement to be in the second state when a liquid-dispensing valve of the filling element permits liquid content to flow into the container. 
     Some practices of the invention include controlling choke-state of the choke by causing motion of a valve tappet that moves in response to opening and closing of the liquid-dispensing valve. 
     Yet other practices include closing the first and second control valves of the return-gas channels during pre-loading of the container before filling the container. 
     As used herein, “container” includes cans, such as those normally used for beverages, and can-like containers, such as kegs for beer, including PET kegs, and containers in which the cross-section of the container opening is only slightly smaller than the cross-section of the container interior. 
     The method disclosed herein is not limited to liquid filling-material but can also be used for inert gas purging of bottles. 
     As used herein, “pressure filling” refers to a filling method in which the containers to be filled are sealed against a filling element. Usually, before the actual filling phase, i.e. before the opening of a liquid-dispensing valve, the containers are pre-loaded via at least one controlled gas-path formed in the filling element. 
     Pre-loading involves filling with a purgative gas under pressure. Typical purgative gases include inert gas or CO2 gas. Liquid contents flowing into the container force the gas out of the container&#39;s interior via a controlled gas-path formed in the filling element. 
     As used herein, expressions such as “essentially” or “some” indicate deviations from an exact value by ±10%, preferably by ±5%, and/or deviations that are not of significance to function. 
     Further embodiments, advantages, and application possibilities of the invention derive from the following description of exemplary embodiments and from the figures. In this context, all the features described and/or pictorially represented are in principle the object of the invention, alone or in any desired combination, regardless of their combination in the claims or reference made to them. The contents of the claims are likewise made a constituent part of the description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features of the invention will be apparent from the following detailed description and the accompanying figures, in which: 
         FIG. 1  shows a view from above a filling machine for the filling of cans with liquid filling-material; 
         FIG. 2  shows a filling position of the filing machine from  FIG. 1 , together with a can arranged in a sealed position at the filling element; 
         FIGS. 3 and 4 , show controlled gas-paths of the filling element of the filling position from  FIG. 2 ; 
         FIG. 5  shows the filling position from  FIG. 2  configured for a CIP cleaning and/or CIP disinfection; 
         FIG. 6  shows a further embodiment of the filling position in  FIG. 2 ; 
         FIGS. 7 and 8  show controlled gas-paths of the filling element from  FIG. 6 ; and 
         FIGS. 9 and 10  show a controlled gas-path in different operating states. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows a filling machine  1  for pressure filling containers  2  with filling-material. Examples of filling-material include beer and soft drinks. An example of a container is a can. 
     The filling machine  1  includes a rotor  3  that rotates about a vertical machine-axis MA. The rotor&#39;s periphery has filling positions  4  disposed thereon. Empty containers  2  are conducted to the filling points  4  via a container inlet  5 . Filled containers are removed at a container outlet  6 . 
     Filling takes place within an angle range of the rotational movement A of the rotor  3 . The angle range extends between the container inlet  5  and the container outlet  6 . During filling, containers  2  are arranged with their container axes parallel to a vertical machine-axis MA and coaxially with a filling-point axis FA of the filling point  4 . 
     This process described herein is for rotational filling machines. However, a similar process can be carried out with linear filling machines. As a result, large PET containers, such as those used as beer kegs, can also be filled in this manner. 
     Referring to  FIG. 2 , a filling point  4  includes a filling element  7 . This filling element  7 , together with the filling elements  7  of the other filling points  4 , is arranged at the periphery of the rotor  3 . 
     Also located at the rotor  3  is a filling-material tank  8 . In the illustrated embodiment, the filling-material tank  8  is a ring tank. During the filling operation, the filling-material tank  8  is partially filled with the filling-material. The filling material defines a liquid-filled portion  8 . 1  that holds liquid. Inert gas above the liquid-filled portion  8 . 1  forms a gas-filled portion  8 . 2  that holds a gas. The inert gas is maintained at a filling pressure PF. In some embodiments, the filling pressure is between 3 bar and 5 bar. Suitable choices for an inert gas include CO2 gas and nitrogen. 
     A product line  10  with an in-line flow meter  9  connects the liquid-filled portion  8 . 1  to the filling element  7 . Similar product lines connect the liquid-filled portion  8 . 1  to other filling elements. As a result, the filling-material tank  8  is common to all the filling points  4  on the rotor  3 . 
     The rotor  3  also supports upper and lower ring-channels  11 ,  12  that surround the vertical machine-axis MA. Like the filling-material tank  8 , the upper and lower ring-channels  11 ,  12  are common to all the filling points  4  and filling elements  7 . 
     During filling, the upper ring-channel  11  conducts inert gas. The lower ring-channel  12  accumulates return gas collected from the filling elements  7  during the purging of the container  2 . The pressure in the upper ring-channel  11  is equal, or essentially equal or slightly less than the filling pressure PF in the gas-filled portion  8 . 2 . The pressure in the lower ring-channel  12  is atmospheric pressure or below. 
     The filling element  7  is formed in a filling-element housing  13  with a liquid-carrying channel  14 . An upper region of the liquid-carrying channel  14  connects to the product line  10 . A lower end of the liquid-carrying channel  14  terminates on an underside of the filling element  7 , where it forms a ring-shaped outlet opening  15  that concentrically surrounds the filling-point axis FA and through which liquid filling-material flows into a container  2  during filling. 
       FIG. 2  shows a liquid-dispensing valve  16  in the liquid-carrying channel  14  upstream of the outlet opening  15 . The liquid-dispensing valve  16  is formed from a valve body  18  that is arranged at a valve tappet  17 . As shown in  FIG. 2 , the valve body  18  of the liquid-dispensing valve  16  contacts a valve surface in the liquid-carrying channel  14 . In this state, the liquid-dispensing valve  16  is closed. To open it, an actuator  19  raises the valve body  18  with the valve tappet  17 . Preferably, the actuator  19  is a pneumatically controlled actuator  19 . 
     The valve tappet  17  includes a gas channel  20  that is coaxial with the filling-point axis FA. The gas channel  20  opens on the underside in the region of the outlet opening  15 . An upper end of the valve tappet  17  opens into a gas-filled chamber  21  formed in the filling-element housing  13 . 
     During the pressure filling of the containers  2 , it is useful to control the different phases of the filling process. To achieve this, the apparatus includes a first control-valve  23 , a second control-valve  24 , a third control-valve  29 , and a fourth control-valve  30 . These control valves  23 ,  24 ,  29 ,  30  are disposed along first and second controlled gas-path s  22 ,  26  formed in the filling-element housing  13 . In one implementation, the control valves  23 ,  24 ,  29 ,  30  are pneumatically actuated valves. 
       FIGS. 3 and 4  show the topologies of the connections between the first and second controlled gas-path s  22 ,  26  and the upper and lower ring-channels  11 ,  12 . 
     Referring to  FIG. 3 , the first controlled gas-path  22  connects the gas-filled chamber  21  and the upper ring-channel  11  in a controlled manner. Control over the connection comes from placing control elements in series along a flow path extending between the gas-filled chamber  21  and the upper ring-channel  11 . One control element is the first control-valve  23 . Another control element is the parallel combination of a second control-valve  24  and a choke  25 . 
     The choke  25  has a fixed reduced flow cross-section. When the second control-valve  24  is closed, the choke  25  allows a gas flow through a parallel bypass that bypasses the closed second control-valve  24 . As a result, by opening and closing the second control-valve  24 , it is possible to change the effective flow cross-section of the first controlled gas-path  22 . 
     Referring back to  FIG. 2 , the filling-element housing  13  has first and second return-gas channels  27 ,  28  that extend vertically through the filling-element housing  13  in a direction parallel to the filling-point axis FA. The first and second return-gas channels  27 ,  28  are part of the second controllable gas path  26 . The third control-valve  29  is along the first return-gas channel  27 . The fourth control-valve  30  is along the second return-gas channel  28 . 
     The first return-gas channel  27  ends, at its lower end, at a first return-gas opening  27 . 1 . Similarly, the second return-gas channel  28  ends, at its lower end, at a second return-gas opening  28 . 1 . The first and second return-gas openings  27 . 1 ,  28 . 1  are at the underside of the filling element  7  opposite the outlet opening  15 . They are offset both radially outwards in relation to the filling-point axis FA, and axially above the outlet opening  15  along the direction of the filling-point axis FA. In the embodiment represented, the first and second return-gas openings  27 . 1 ,  28 . 1  are offset by 180° about the filling-point axis FA. 
     Referring to  FIG. 4 , the second controlled gas-path  26  connects the first and second return-gas openings  27 . 1 ,  28 . 1  to the lower ring-channel  12 . As shown in the figures, the inlets of the third and fourth control-valves  29 ,  30  connect to the corresponding first and second return-gas channels  27 ,  28  respectively. The outlets of both the third and fourth control-valves  29 ,  30  connect to the lower ring-channel  12 . 
     Referring back to  FIG. 2 , the filling element  7  further comprises a centering cone  31  and an associated ring seal  31 . 1 . During purging, pre-loading, and filling, the ring seal  31 . 1  seals the centering cone  31  against an opening edge of a container  2  that is standing on a container carrier  32 . This results in a sealed space into which the outlet opening  15 , the lower end of the gas channel  20 , the first return-gas opening  27 . 1 , and the second return-gas opening  28 . 1  all open. 
     A bellows  33 , which is subjected to the filling pressure PF, acts, via a linkage  34 , to pre-tension the centering cone  31  into its lower position so that it is located tightly against the container  2 . Interaction of a curved roller  35  provided at the linkage  34  with an outer lifting curve that does not circulate with the rotor  3  either lifts or lowers the centering cone  31  to either seal the container or facilitate its removal. 
     Electro-pneumatic actuators  36  actuate the pneumatically actuated control-valves  23 ,  24 ,  29 ,  30 . These actuators  36  are controlled by a machine control-system of the filling machine  1 . The process by which the filling element  7  carries out pressure filling of containers  2  is described as follows. 
     An initial step is that of pushing the container  2  into the filling point  4 . This is carried out by closing the liquid-dispensing valve  16 , the first control-valve  23 , and the second control-valve  24 . Then, the third control-valve  29  and the fourth control-valve  30  are opened. This opens the second controlled gas-path  26 . The centering cone  31  is also raised against the effect of the bellows  33 . 
     The next step is that of purging the container interior with inert gas. During this process, the container  2  is located in the sealed position at the filling element  7 . In this sealed position, the centering cone  31  is lowered with its ring seal  31 . 1  pressed tightly against the container  2 . 
     The liquid-dispensing valve  16  is then closed, and the first control-valve  23 , the third control-valve  29 , and the fourth control-valve  30  are all opened. The second control-valve  24 , however, remains closed. As a result, purgative gas from the upper ring-channel  11  flows via the choke  25  into the gas-filled chamber  21 . From there, the purgative gas continues through the gas channel  20 , which sends it along a path straight down the central zone of the container&#39;s interior. Upon reaching the base of the container  2 , the gas is deflected back upwards along the periphery of the container  2 . This results in a circulating flow  37 . 
     The purgative gas, together with any air purged from the container  2 , enters the first and second return-gas openings  27 . 1 ,  28 . 1  and the now-opened second controlled gas-path  26  to be carried away by the ring channel  12 . As noted above, the lower ring-channel  12  is maintained at or slightly below atmospheric pressure. This promotes flow through the second controlled gas-path  26   
     Because of the choke  25  in the first controlled gas-path  22  and the parallel first and second return-gas channels  27  and  28 , the flow cross-section of the second controlled gas-path  26  is significantly greater than the effective flow cross-section of the first controlled gas-path  22 . As a result, air carried into a container at a purging pressure, Ps, that is between the atmospheric pressure and an overpressure of some 0.5 bar to 2.0 bar, preferably of some 1.0 bar, is forced in a very short time out of the container interior and replaced by inert gas (for example CO 2  gas or nitrogen). 
     There are three factors that contribute to this advantage. 
     First, purgative gas is conducted to the container interior via the choke  25  of the first controlled gas-path  22 . As a result, the pressure of the purgative gas flowing to the container  2  is perceptibly reduced in relation to the pressure in the upper ring-channel  11 . 
     Second, as a result of the choke  25 , the flow cross-section of the second controlled gas-path  26  is greater than the effective flow cross-section of the first controlled gas-path  22 . As a result, high gas-throughputs are obtained inside the container  2  at reduced purge pressure Ps. This high gas-throughput is further enhanced by under-pressure in the lower ring-channel  12 . 
     Third, the configuration avoids formation of a significant vortex of purgative gas with air. Such a vortex would otherwise impair the purge process. 
     Fourth, the first and second return-gas openings  27 . 1 ,  28 . 1  are offset by 180° about the filling-point axis FA and are located inside the ring seal  31 . 1  directly at its sealing point and therefore directly at the inner side of the opening edge of the container  2 . As a result, the radial distance from the return-gas openings  27 . 1  and  28 . 1  to the filling-point axis FA is equal to or only slightly smaller than the corresponding distance between the inner side of the ring seal  31 . 1  and the filling-point axis FA. 
     The reduction in purge time means that the filling machine  1  can fill more containers  2  per unit time. Additionally, the shorter purge time means lower gas consumption. 
     The next step is to pre-load the container&#39;s interior with inert gas. This is carried out with the container  2  still being sealed against the filling element  7  and with the centering cone  31  lowered. 
     To carry out this pre-loading step, the liquid-dispensing valve  16 , the third control-valve  29 , and the fourth control-valve  3  are all closed. The first and second control-valves  23  and  24  are opened. This increases the effective flow cross-section of the first controlled gas-path  22  by allowing inert gas as pre-loading gas to at least partially bypass the choke  25 . The container&#39;s interior is thus promptly pre-loaded with inert gas at a pressure that is the same or essentially the same as the filling pressure PF. 
     Next comes the actual pressure filling. This is carried out with the container  2  still in the sealed position at the filling element  7 . 
     In this step, the third and fourth control-valves  29 ,  30  are closed, thus closing the second controlled gas-path  26 . Meanwhile, the first and second control-valves  23 ,  24  are opened. 
     Then, the liquid-dispensing valve  16  opens to begin the filling phase. This causes liquid filling-material to flow via the outlet opening  15  into the container, and specifically through the conical formation of the liquid-carrying channel  14  in the region of the outlet opening  15  along the inner surface of the container. Meanwhile, the completely open gas channel  20  and the completely opened first controlled gas-path  22  conduct inert gas that has been forced out of the container  2  back into the upper ring-channel  11 . The flow meter  9  monitors the quantity of the filling-material flowing to the container  2 . Once the required filling quantity is reached, the flow meter  9  sends a signal that causes the actuator  19  to close the liquid-dispensing valve  16 . 
     The next step is to relieve pressure from the interior of the now-filled container  2 . 
     With the container  2  still located in the sealing position at the filling element, and with the liquid-dispensing valve  16 , the first control-valve  23 , and the second control-valve  24  all closed, at least one of the third and fourth control-valves  29 ,  30  is opened. In a preferred embodiment, both the third and fourth control-valves  29 ,  30  open. This allowed excess pressure in the head space of the container  2  to be relieved into the lower ring-channel  12  by the second controlled gas-path  26 . 
     Finally, the filled container  2  is released. This is carried out with the liquid-dispensing valve  16  closed, the first and second control-valves  23 ,  24  closed, and with the third and fourth control-valves  29 ,  30  open. The centering cone  31  is raised by the control curve interacting with the curve roller  35  such that the filled container  2  can be removed at the container outlet  6 . 
     In some embodiments, the filling element  7  can carry out further process steps. For example, the filling element  7  can also carry out a slow top-up filling and/or a slow filling before closing the liquid-dispensing valve  16 . To do so, the first control-valve  23  is open and the second control-valve  24  is closed. 
       FIG. 5  shows the filling element  7  in a cleaning and/or disinfection operating state or CIP mode (CIP cleaning and/or disinfection) of the filling machine  1 . In this state, there is a purge cap  38  on the underside of each filling elements  7 . This forms a purge space  39  closed to the surroundings and into which outlet opening  15 , the lower, open end of the gas channel  20 , and the first and second return-gas openings  27 . 1  and  28 . 1  open. 
     During this CIP cleaning and/or disinfection, the filling-material tank  8  is filled with a liquid cleaning and/or disinfection medium or CIP medium respectively. The first and second control-valves  23 ,  24  are closed, thus closing the first controlled gas-path  22 . The third and fourth control-valves  29 ,  30  are opened, such that the CIP medium can flow out of the tank  8 , through the liquid-carrying channel  16 , through the outlet opening  15 , through the purge space  39 , through the first and second return-gas channels  27 ,  28 , and into the ring channel  12 , from which the CIP medium is drained off. 
     During CIP cleaning and/or disinfection, opening the third and fourth control-valves  29 ,  30  forms a wide open second controlled gas-path  26  having a large effective flow cross-section for the CIP medium and therefore a high CIP medium throughput. This promotes intensive CIP treatment. 
     It is also possible to close the third and fourth control-valves  29 ,  30  and open the first and second control-valves  23 ,  24 . With the liquid-dispensing valve  16  still opened, the first controlled gas-path  22  can also be treated with the CIP medium from the filling-material tank  8 , which is then drained off via the upper ring-channel  11 . 
     Among the particular features of the filling machine  1  is that, during the purging of a container, purgative gas exits via a gas path that has a greater cross-section than that gas path that it used to enter. In particular, purgative gas enters via the choke  25  and exits via the second controlled gas-path  26  with a substantially greater flow cross-section. As a result, despite a high throughput, purgative gas flows to the container  2  at a reduced purgative gas pressure. An overpressure predominates in the container  2 . This overpressure is lower than the filling pressure PF. In some embodiments, it is lower by as much as 2.0 bar. Embodiments also include those in which it is lower by between 0.5 bar and 2.0 bar, and those in which it is lower by 0.5-1.0 bar. Both during pre-loading, as well as during filling, the first and second control-valves  23 ,  24  are opened, thus giving the first controlled gas-path  22  its full flow cross-section. This results in rapid pre-loading and filling of the containers  2 . 
     In some embodiments, all the control valves  23 ,  24 ,  29 ,  30  have the same design. Each one is pre-tensioned by internal spring means into a first state. To cause transition into a second state, a control pressure overcomes the bias of the internal spring. In the first and second control-valves  23 ,  24 , the first state is one in which the valves are open. In contrast, in the case of the third and fourth control-valves  24 ,  29 , the first state is one in which they are closed. 
     With the foregoing configuration, only the first control-valve  23  needs an independent electropneumatic actuator  36 . A common electropneumatic actuator  36  actuates the second, third, and fourth control-valves  24 ,  29 ,  30 . During purging, the common electropneumatic actuator  36  imposes a control pressure that closes the second control-valve  24  and opens the third and fourth control-valves  29 ,  30 . During pre-loading and filling, the common electropneumatic actuator  36  remains inactive. Therefore, the first and second control-valves  23 ,  24  are in their default open state and the third and fourth control-valves  29 ,  30  are in their default closed states. A third electropneumatic control actuator  36  actuates the actuator  19 . This considerably simplifies actuation of the control-valves  23 ,  24 ,  29 ,  30  by the electropneumatic actuators  36   
       FIG. 6  shows as a further embodiment of a filling machine  1   a  having an alternative filling element  7   a . The further embodiment filling machine  1   a  features a further ring tank  40  at the rotor  3 . The further ring tank  40  serves as a common relief channel for all the filling elements  7   a.    
     As shown in  FIGS. 7 and 8 , the alternative filling element  7   a  has a somewhat different topology for connecting the upper ring-channel  11  to the gas-filled chamber  21  and for connecting the lower ring-channel to the first and second return-gas openings  27 . 1 ,  28 . 1 . In particular, the first controlled gas-path  22  of  FIG. 3  is replaced by an alternative first controlled gas-path  22   a  in  FIG. 7 , and a third controlled gas-path  42  is added as shown in  FIG. 8 . 
     As shown in  FIG. 7 , the alternative first controlled gas path  22   a  has only a first control-valve  23 . Instead of another control valve parallel to the choke  25 , the alternative first controlled gas-path  22   a  has a non-return valve  41 . The non-return valve  41  is closed for flow out of the upper ring-channel  11  and opened for flow into the upper ring-channel  11 . 
     The method steps of purging and pre-loading of containers  2  with inert gas under a filling pressure PF from the upper ring-channel  11  and pressure filling of the containers  2 , with return feed of the inert gas which is thereby forced out of the containers  2  both take place in a manner analogous to the corresponding steps described in connection with the filling element  7 . 
     During purging, with the first control-valve  23  opened and with the non-return valve  41  blocking, once again, by way of the choke  25  in conjunction with the first and second controlled gas paths  27 ,  28 , the purgative gas is conducted out of the upper ring-channel  11  with reduced purge pressure Ps in the container  2 , and flows through with high throughput. With the first control-valve  23  open, the pre-loading of the containers  2  takes place solely via the choke  25 . 
     During the pressure filling of the containers  2 , the inert gas forced out by the inflowing filling-material, with the first control-valve  23  open, is conducted back into the upper ring-channel  11  both via the choke  25  and via the now open non-return valve  41 . The greater part of the flow is, however, via the non-return valve  41 . 
     As shown in  FIG. 8 , a second controlled gas-path  26  provides a connection between the first and second return-gas openings  27 . 1  in a manner already described in connection with  FIG. 4 . The first return-gas opening  27 . 1  connects to the lower ring-channel  12  via a second control-valve  29  in the first return-gas channel  27 . Similarly, the second gas opening  28 . 1  connects to the lower ring-channel  12  via a third control-valve  30  in the second return-gas channel  28 . 
     However, unlike the embodiment shown in  FIG. 4 , the embodiment shown in  FIG. 8  features a third controlled gas-path  42  that connects the further ring tank  40  to the first return-gas opening  27 . 1  by way of a fourth control-valve  24 . This third controlled gas-path  42  provides a way to vent excess gas into the further ring tank  40  during pressure release of a filled container  2 . 
     During the pressure relief phase, the first, second, and third control-valves  23 ,  29 ,  30  are closed, and the fourth control-valve  24  is opened. This opens the third controlled gas-path  42  so that pressure relief takes place into the further ring tank  40 . 
     With the alternative filling element  7   a , therefore, the flow of the inert gas during the purging, pre-loading, and filling also takes place via the first controlled gas-path  22   a . This flow occurs with reduced flow cross-section during purging and pre-loading, but with the entire flow cross-section during filling. 
       FIGS. 9 and 10  show the filling-element housing  13  in the region of the gas-filled chamber  21  with a filling element  7   b  according to a further embodiment of the invention, and specifically with a first controlled gas-path  22   b  in the connection between the upper ring-channel  11  and the gas channel  20 . In this embodiment, the gas-filled chamber  21  is a part of a first controlled gas-path  22   b  having a changeable choke  43  that is arranged in the first controlled gas-path  22   b  in operational effect in series with a first control-valve  23 . 
     The changeable choke  42  is controllable between a first state, shown in  FIG. 10 , and a second state, shown in  FIG. 9 . In the first state, the changeable choke  43  has a reduced choke cross-section. In the second state, the changeable choke  43  has an enlarged choke cross-section. 
     The changeable choke  43  is formed at an upper end of the valve tappet  17 , and specifically at a choke opening  20 . 1  of the gas channel  20 . The changeable choke  43  is formed in such a way that raising the valve tappet  17  enlarges the choke opening  20 . 1  and lowering the valve tappet  17  constricts the choke opening  20 . 1 . 
     As a result of this automatic change in the choke opening&#39;s cross-section, there is no need for a further control-valve. Instead, the choke opening  20 . 1  changes automatically. 
     During purging and pre-loading from the upper ring-channel  11  that takes place via the second gas path  22   b  with the choke opening  20 . 1  at its reduced flow cross-section, as shown in  FIG. 10 . In contrast, the return of inert gas forced out by the filling filling-material during pressure filling takes place with the choke opening  20 . 1  at its enlarged cross-section, as shown in  FIG. 9 . 
     In one embodiment, the changeable choke  43  has a choke body  44  that does not move with the valve tappet  17 . Instead, the choke body  44  is secured to the filling-element housing  13  so that it is coaxial with the filling-point axis FA. This choke body  44  extends into the choke opening  20 . 1 . 
     The choke body  44  is shaped like a mushroom head. In particular, the choke body  44  has a first cylindrical section having a first radius and a second cylindrical section having a second radius that is greater than the first radius. In the first state, shown in  FIG. 10 , the second section is in the choke opening  20 . 1 . In the second state, as shown in  FIG. 9 , the first section is in the choke opening  20 . 1  while the second section is accommodated within an extension of the gas channel  20 . 
     The invention has been described by way of exemplary embodiments. It is understood that numerous modifications and derivations are possible without departing from the inventive concept on which the invention is based.