Patent Publication Number: US-10788032-B2

Title: Piston arrangement for pumping a liquid

Description:
The present invention relates to a piston assembly for pumping a liquid, in particular in a bottle filling system. 
     For the process of filling liquids into containers such as bottles, various methods for feeding in the filling material are available, depending on the pressure that is required and the measurement method that is used to ensure that each container is filled with a sufficient volume of filling material. 
     One method that can be used with volumetric filling, in particular, involves the use of a piston, which performs stroke movements within a cylinder and displaces a defined volume of liquid with each stroke. For instance, with a first stroke movement of the piston, a defined volume can be drawn from a reservoir through a feed line and into the piston. The feed line is then closed by a shut-off valve, which may also be designed as a non-return valve, so that liquid is prevented from flowing back into the reservoir. 
     The liquid inside the cylinder is then displaced from the cylinder in the opposite direction by a piston stroke and is fed through a line into the container to be filled. Depending on the molding and filling process and on the filling material being bottled, this process can be carried out under various pressures. This method can be used both for filling a container that has already been shaped and for simultaneously molding and filling a preform under high pressure. 
     One problem with the use of such piston pumps is the cleaning process that is involved. Strict hygiene standards must be observed in particular with bottle filling systems for bottling beverages. This includes regular cleaning and disinfection, however it is desirable for these processes to be carried out as quickly as possible in order to avoid long down times for the machine in question. It is also desirable, wherever possible, to avoid external intervention into machinery, such as dismantling parts for cleaning and disinfection, to avoid contaminating the machinery with bacteria introduced from the outside. Areas of a machine that are used for conveying filling material should be isolated from the environment wherever possible and cleaned without being opened up. 
     To allow such machines to be cleaned and disinfected without disassembly wherever possible, various methods for what is known as “cleaning in place” have been developed, in which the components remain in place. 
     However, the cleaning and disinfection of the piston and cylinder in a piston assembly for pumping a liquid remain problematic in that it is typically necessary to dismantle the piston in order to remove contaminants between the piston and the cylinder. In particular, in pistons that are provided with a seal in relation to the cylinder working surface, contaminants in the region of the seal can be removed only inadequately without disassembly. 
     It is therefore the object of the present invention to propose a piston assembly for pumping a liquid, which can be cleaned and/or disinfected without dismantling the piston or carrying out other external interventions into the assembly. 
     According to the invention, a piston assembly for pumping a liquid, in particular in a bottle filling system, is proposed, which comprises a piston that travels within a cylinder and has a working path between a first inversion point and a second inversion point, with the piston forming a tight seal with respect to the cylinder in the region of the working path. The assembly according to the invention is characterized in that, beyond one of the two inversion points, outside of the working path, the diameter of the cylinder is enlarged in one section such that the sealing closure is eliminated there, and the piston can be moved into this area for a cleaning and/or disinfection process. 
     With the assembly according to the invention, liquid can be pumped from a feed line into a container by moving the piston between two inversion points. The volume that is fed to the container is determined by the working path of the piston and by the diameter of the cylinder. Piston and cylinder form a tight seal with one another for this purpose. This can be accomplished without seals by providing precise clearances between piston and cylinder with a non-contact gap seal, or by means of a seal provided on the piston in relation to the working path in the cylinder. 
     According to the invention, beyond one of the two inversion points, outside of the working path, the diameter of the cylinder is to be enlarged in one section. The cylinder diameter is to be enlarged in such a way that the sealing closure is eliminated there. It should further be possible for the piston to be moved into this area for a cleaning and/or disinfection process. 
     During normal operation, the piston describes strokes between the two inversion points, thereby pumping a defined volume of a liquid from a reservoir into a container. For cleaning and/or disinfection, the piston is then moved into the area of the cylinder that has the enlarged diameter, which acts as a cleaning chamber. Depending on the medium that is used, the piston may also be disinfected there. For the sake of simplicity, the term cleaning chamber will be used throughout here, even though the same chamber may be used for disinfection. 
     In the cleaning chamber, the sealing action of the piston in relation to the cylinder wall is eliminated, and a cleaning and/or disinfecting medium can be applied to the piston and cylinder working surface, including any seals that may be provided there. It is no longer necessary to dismantle the assembly or to carry out any other external intervention. 
     Since there is no longer any contact between the piston and the cylinder in the area with the enlarged diameter in the cleaning chamber, it is not necessary for this area to be cylindrical in shape, although this may be advantageous. For the sake of simplicity, the term cylinder will be used throughout here, although it will be obvious to a person skilled in the art that areas in which the piston and cylinder have no contact do not necessarily have to be cylindrical in shape, and may instead also be oval, polygonal or any other desired shape. The crucial feature is that the diameter must be enlarged such that there is no longer any sealing action between the piston and the cylinder. 
     Suitable cleaning and/or disinfecting media are, in particular, liquid or foaming media. It is also possible for steam to be supplied. 
     In an advantageous embodiment of the invention, the diameter of the cylinder is enlarged by means of continuous transitions and/or large radii. This ensures that the piston can be moved from the cleaning position into its working area without becoming caught or jammed. 
     In a further advantageous embodiment of the invention, the section of the cylinder with an enlarged diameter is equipped with nozzles for supplying a cleaning and/or disinfecting medium. These allow cleaning and/or disinfecting medium to be introduced into the cleaning chamber in a targeted manner. This embodiment is particularly advantageous if the piston is provided with a circumferential seal and if cleaning and/or disinfecting medium can be applied directly to this area of the piston in a targeted manner. 
     The piston and the seal can advantageously be designed as integral, so that there are no hidden areas that are difficult to clean and disinfect. In particular, the seal can be a sealing lip that surrounds the piston. The piston and seal can be made of plastic, in particular of polyethylene (PE), polypropylene (PP) or polyethylene terephthalate (PET). 
     According to one embodiment of the invention, beyond the cylinder section with the enlarged diameter, the diameter of the cylinder can return to the diameter of the working path area. More particularly, a tight seal can be formed between piston and cylinder beyond the cylinder section with the enlarged diameter. This design allows a correspondingly configured piston to be moved into the cleaning and/or disinfecting position, in which the cleaning and/or disinfecting medium can be applied to the areas of the piston to be cleaned and/or disinfected, while the piston forms a tight seal with the area that lies beyond the cleaning chamber, thereby preventing any cleaning and/or disinfecting medium from penetrating to the outside. 
     The piston assembly can advantageously have one liquid line and two valves arranged in the liquid line. In particular, at least one of said valves can be embodied as a non-return valve. However, the valves may also be regulated or controlled in any other way, of course. 
     One of the valves may be arranged in the liquid line upstream of the piston and/or one valve may be arranged downstream of the piston. Alternatively, one valve may also be disposed inside the piston. In that case, liquid can be fed in through the piston. 
     It will be obvious to a person skilled in the art that the invention described above and in the following exemplary embodiments is not limited to pistons of pumps. In principle, the invention can be generalized for any application in which a cylindrical body travels within and forms a tight seal with a corresponding sleeve. For instance, the assembly of the invention can be readily applied, for example, to a drawing bar that is movable within a sleeve in a machine for molding containers, or similar applications. These applications are also covered by the subject matter of this application. 
    
    
     
       Various exemplary embodiments of the invention will be explained in greater detail in the following, with reference to the accompanying figures, in which: 
         FIGS. 1 a  and 1 b    are schematic cross-sectional diagrams of a first embodiment of a piston assembly according to the invention for a bottle filling machine, in the working position and in the cleaning and/or disinfecting position, respectively; 
         FIGS. 2 a  and 2 b    are schematic cross-sectional diagrams of a second embodiment of a piston assembly according to the invention, in the working position and in the cleaning and/or disinfecting position, respectively; 
         FIGS. 3 a  and 3 b    are schematic cross-sectional diagrams of a third embodiment of a piston assembly according to the invention, in the working position and in the cleaning and/or disinfecting position, respectively; 
         FIGS. 4 a  and 4 b    are schematic cross-sectional diagrams of a fourth embodiment of a piston assembly according to the invention, in the working position and in the cleaning and/or disinfecting position, respectively; 
         FIG. 5  is a schematic cross-sectional diagram of a fifth embodiment of a piston assembly according to the invention, in which a non-return valve is arranged in the piston; 
         FIG. 6  is a schematic diagram of an alternative embodiment of the piston assembly of  FIG. 5 ; 
         FIG. 7  is a schematic diagram illustrating one solution for a piston-arranged valve; 
         FIG. 8  is a schematic diagram illustrating a further solution for a piston-arranged valve; 
         FIG. 9  is a schematic diagram illustrating one solution for a CIP-suitable seal arrangement in piston and cylinder assemblies; 
         FIG. 10  is a schematic diagram illustrating a further solution for a CIP-suitable sealing arrangement in piston and cylinder assemblies. 
     
    
    
     It will be obvious to a person skilled in the art that the drawings shown here are intended merely to illustrate the principle of the invention and are rendered only schematically and not to scale. In particular, the represented dimensions of the piston and all other dimensions are for illustrative purposes only. The actual dimensions and proportions may be freely determined by a person skilled in the art based on his knowledge in the art. 
       FIG. 1 a    is a schematic diagram of an exemplary embodiment of a piston assembly according to the invention, by means of which liquid filling material can be drawn from a reservoir (not shown) and fed into a container. For this purpose, a piston  1  is arranged in a cylinder  2 . The piston forms a tight seal with respect to the working surface of cylinder  2  by means of lip seal  3 . In the working position, the piston moves along a working path A between a first inversion point U 1  and a second inversion point U 2 . The diameter DZ of the cylinder and the length of working path A are dimensioned such that during the downward movement of piston  1  from first inversion point U 1  to second inversion point U 2 , the piston displaces the volume that is to be filled into the container. 
     In this process, piston  1  may be driven by any type of drive  4 . The force that is required for this purpose is dependent on the amount of pressure that is required for filling the filling material. This process is suitable in principle for all standard filling or molding and filling processes. Non-carbonated beverages can be filled at relatively low pressure, while carbonated beverages require a somewhat higher pressure. If a container will be molded from a preform simultaneously with the filling process, significantly higher pressure is required. 
     As piston  1  moves upward from lower inversion point U 2  to upper inversion point U 1 , and with shut-off valve  7  open, the piston draws filling material from a reservoir (not shown) through non-return valve  5 , with the filling material flowing out of the reservoir in the direction of arrow V. Filling valve  6  is closed during this step. 
     To fill the container, filling valve  6  is opened and the piston is moved from upper inversion point U 1  to lower inversion point U 2 . The filling material flows in the direction of arrow B to the container (not shown here). 
     The assembly is equipped with a cleaning chamber  8 , in this case situated above the working path of piston  1 , in which the diameter DR of the cylinder is enlarged such that the piston no longer forms a tight seal in relation to the cylinder. As is clear from  FIG. 1 b   , in the cleaning chamber piston  1  is freely accessible from all sides and can be acted on by a cleaning and/or disinfecting medium. Nozzles  9  are provided for this purpose in the cleaning chamber. 
     When the piston assembly will be cleaned, the inlet and outlet lines are closed by means of valves  6  and  7 . As illustrated in  FIG. 1 b   , piston  1  is moved upward into cleaning chamber  8 , and cleaning and disinfecting medium is fed in through nozzles  9 . Cleaning and disinfecting may be carried out in multiple steps using various media. The introduced cleaning and disinfecting media flow through the assembly and are removed via drain line  10 , for which purpose valve  11  of drain line  10  is opened. Once cleaning and disinfection are completed, and if necessary following an additional rinsing step, the machine can be returned to operation by lowering piston  1  to the working position, closing valve  11  of drain line  10 , and reopening valve  7  of the feed line. 
     To close off cleaning chamber  8  from the exterior, drive  4  of piston  1  is guided through a bellows  12  that seals off chamber  8 . 
       FIGS. 2 a  and 2 b    show a further exemplary embodiment of the assembly according to the invention, which corresponds largely to the exemplary embodiment shown in  FIGS. 1 a  and 1 b   . Again,  FIG. 2 a    shows the assembly in the working position and  FIG. 2 b    shows the assembly in the cleaning position. 
     In contrast to  FIG. 1 , however, diameter DR of cylinder  2  is enlarged by means of continuous transitions and large radii, so that no edges are formed. Piston  1  can slide downward from its cleaning position to its working position without becoming caught or jammed. 
     In this exemplary embodiment, cleaning and/or disinfecting media are supplied via feed line  13  and shut-off valve  14 . 
       FIGS. 3 a  and 3 b    show an exemplary embodiment similar to the exemplary embodiment of  FIGS. 2 a  and 2 b   , again with  FIG. 3 a    showing the assembly in the working position and  FIG. 2 b    showing the assembly in the cleaning position. 
     In the embodiment of  FIG. 3 , however, piston  1  is designed as longer, and beyond cleaning chamber  8 , the diameter of the cylinder returns to the diameter DZ of the working area. 
     As is shown in  FIG. 3 b   , piston  1  is moved into the cleaning position in such a way that the upper portion of the piston again forms a tight seal with the cylinder, thereby closing off cleaning chamber  8 . The portion of piston  1  around seal  3 , which comes into contact with the filling material, is located within cleaning chamber  8 , and cleaning medium can be applied to said seal by the cleaning nozzles  9  arranged therein. 
       FIGS. 4 a  and 4 b    show an exemplary embodiment similar to the exemplary embodiment of  FIGS. 2 a  and 2 b   , with  FIG. 4 a    again showing the assembly in the working position and  FIG. 4 b    showing the assembly in the cleaning position. 
     In contrast to  FIG. 2 , however, cleaning chamber  8  is located on the opposite side of working position A of piston  1  with respect to filling material line  15 , i.e. piston  1  is lowered into cleaning chamber  8  for cleaning purposes. 
       FIG. 5  is a schematic cross-sectional diagram of a fifth embodiment of a piston assembly according to the invention, in which a non-return valve is arranged in the piston. This assembly allows the liquid to be pumped through the piston. 
     Piston  1  is equipped with a non-return valve  5 , which in the assembly shown here permits a flow of liquid from top to bottom. Here again, filling material is fed in through feed line  20  in the direction of arrow V. As the piston moves downward, and with valve  6  open, the piston pumps filling material in the direction of arrow B, to a container not shown here. After one pumping stroke, valve  6  is closed. The piston moves upward, thereby opening valve  5  and allowing and the filling material located above piston  1  to flow through the piston. During the next pumping stroke, valve  5  closes as soon as the piston moves downward, thereby pumping filling material in the direction of the container. At the same time, fresh filling material flows out of the reservoir. 
     In this assembly, it is also possible to move the piston into a cleaning position in cleaning chamber  8 . A separate infeed of cleaning medium into the chamber is not necessary. Instead, the entire flow path between arrows V and B can be filled with cleaning medium rather than with filling material, thereby allowing a complete cleaning to be carried out without dismantling any components. To allow the feedthrough  21  of drive  4  through the boundary wall of the flow path to also be cleaned without disassembly, a shielding element  22 , for example a bellows as shown in this figure, can be expediently attached as a seal. Alternatively, a diaphragm, a rolling diaphragm or an air bellows may be used. 
     However, a shielding element  22  arranged in the flow path will be exposed to high pressure and thus to high wear. Shielding element  22  can therefore also be arranged on the outside, as shown in  FIG. 6 . In that case, the pressure prevailing in the flow path is absorbed by seal  23 . To also make seal  23  accessible for CIP cleaning, a notch  24  is provided in drive rod  4 , which is located in the region of seal  23  when the assembly is in the cleaning position, allowing cleaning medium to flow around the seal, cleaning it on all sides. Shielding element  22 , configured as a bellows, seals the assembly with respect to the outside. The bellows is required only to withstand the pressure under which the assembly is cleaned. This pressure is considerably lower than the pumping pressure of the piston. 
     Valve  5  in the piston must likewise be suitable for CIP cleaning. Valves of this type may have a variety of designs. 
       FIGS. 7 a  and 7 b    illustrate one such assembly. In this embodiment, piston  1  is hollow and has liquid passages  30  and  31  at its lower and upper ends, respectively. Located below liquid passages  31  at the upper end of piston  1  is a sealing element  32 , in this case a circular plate, which is movable vertically on pin  33 . When the piston moves upward, as shown in  FIG. 7 a   , sealing element  32  is located on the pin at lower stop  34 , and liquid is able to flow through piston  1  in the direction from top to bottom. 
     When the piston moves downward, as shown in  FIG. 7 b   , sealing element  32  moves upward through the incipient flow of liquid and forms a tight seal with the upper end of piston  1 . The liquid passages  31  are thereby closed and the piston is able to displace liquid downward. 
       FIGS. 8 a  and 8 b    show an alternative embodiment of the assembly of  FIGS. 7 a  and 7 b   . Here, sealing element  32  is a ball which forms a tight seal against a seat on a tubular projection  36 . A plurality of such elements may be arranged in one piston. 
     The assemblies of  FIGS. 7 a , 7 b , 8 a  and 8 b    are to be cleaned entirely by the CIP process. All clearances can be selected as large enough to ensure that when a cleaning medium flows through in the cleaning position, all components will be cleaned. In addition, the valve can also be completely cleaned in the normal operating mode by using a cleaning liquid rather than the filling material. 
     One option for the CIP cleaning of circumferential seals on cylindrical bodies such as pistons may also involve providing a plurality of seals spaced apart from one another. The piston can then be brought into a position, as described above, in which the seals are located within a cleaning chamber in which the seals are not in contact with the cylinder that surrounds them in the working position, thereby allowing them to be cleaned. In this case, all seals may be located in a single cleaning chamber, as described above, or each may be located in a separate chamber, which may be a recess, for example in the form of a groove in the cylinder. Cleaning medium can penetrate between cylinder and piston and into the groove to enable cleaning. The recesses may also be arranged offset, so that a single seal can be cleaned in each recess. A solution of this type is shown in  FIG. 9 . 
     Filling valve  6  can advantageously be integrated directly into a filling head  100  so that a minimal flow path is produced between filling valve  6  and the preform or container. An example of a filling head  100  within the scope of the invention is shown in  FIG. 10 . 
     Filling head  100  consists of a filling chamber  102  which via a teed line  104  for pressurized filling material and an annular gap  106 , through which the filling material can be introduced into a preform or container (not shown). 
     Annular gap  106  can be sealed off by means of a valve insert  108 . For this purpose, the valve insert comprises a sealing surface  109 , which cooperates with a complementary sealing surface  109 ′ that surrounds annular gap  106 . Valve insert  108  can be moved in the direction of arrow  110  as shown, in order to close or open up annular gap  106 . 
     Valve insert  108  is mounted on the upper side of pressure chamber  102  in a feedthrough  112  in the side wall of pressure chamber  102 , and is sealed with respect to cylindrical feedthrough  112  by means of a seal  114 . In both of the operating positions for opening up and closing annular gap  106 , seal  114  is always located within feedthrough  112 . 
     A bellows  116  is arranged above feedthrough  112  and is fixedly attached to feedthrough  112  at one end and to valve insert  108  at the other end, in each case forming a tight seal. A closed cleaning chamber  118  with a variable shape is thereby produced above seal  114 . 
     For CIP cleaning, valve insert  108  is brought into a cleaning position in which seal  116  is arranged within cleaning chamber  118 , so that an unsealed gap that connects the filling chamber with cleaning chamber  118  is opened up between feedthrough  112  and valve insert  108 . In this position, filling chamber  102  and cleaning chamber  118  can be jointly flushed with suitable cleaning media, with cleaning medium flowing likewise around the surface of the valve insert, including sealing surface  109  and seal  116 . 
     Also provided is a drawing bar  120 , which is guided within valve insert  108  and is sealed in relation to the valve insert by means of a seal  122 . Seal  122  is positioned so as to enable a travel path of sufficient length for the drawing bar within the valve insert. Between valve insert  108  and drawing bar  120 , a gap is provided, which widens filling chamber  102  up to seal  120 . 
     Above seal  120 , an expansion is provided in valve insert  108 , forming a cleaning chamber  122 . To clean drawing bar  120 , the drawing bar is moved upward until seal  120  is located within cleaning chamber  122  and the gap between drawing bar  120  and valve insert  108  fluidically connects filling chamber  102  with cleaning chamber  122 . In this position, a second seal  124  on the drawing bar seals cleaning chamber  122  toward the top, so that the cleaning chamber, the gap between drawing bar  120  and valve insert  108 , chamber  108  can be flushed and cleaned together using a suitable cleaning medium. 
     Advantageously, prior to the above step, the drawing bar is moved downward until seal  124  is located within cleaning chamber  122 , which is then sealed toward the bottom by means of seal  122 . In this position, cleaning chamber  122 , which is open toward the top, can be flushed with a cleaning medium, simultaneously flushing and cleaning seal  124 .