Abstract:
A fluidic control element includes a housing having a fluid space formed between at least two housing parts. First and second flow channels may each have a sealing seat that opens into the fluid space. The fluidic control element may further include a two-armed lever which is configured to swivel in the fluid space. Each arm of the lever may be configured to open and close one of the flow channels in a corresponding end position. Additionally, a valve body may have a load-carrying core including a shaft mounted in the housing. The shaft may be rounded at least in the region in which it is embedded in a sealing ring that surrounds the lever arms.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to German Patent Application Serial No. 202012004020.0, filed on Apr. 20, 2012, the contents of which are herein incorporated by reference in their entirety. 
     FIELD OF THE INVENTION 
     The invention relates to a fluidic control element comprising a housing composed of at least two housing parts, a fluid space being formed between the housing parts and at least first and second flow channels each comprising a sealing seat opening into said fluid space, and comprising a valve body which can be swiveled in the fluid space. 
     The invention particularly refers to fluidic control element being a part of a magnet valve. 
     BACKGROUND 
     A generic control element is known from EP 1 026 407 B1. Such control elements are used in particular for valves with so-called media separation which are used, for instance, in food or analysis technology, in laboratories or in medical engineering. The fluidic control element is part of a so-called direct-acting rocker magnet valve to which a torque, in particular via a magnetic actuator, is immediately applied from outside to the two-armed lever, also referred to as a rocker. 
     Fluidic control elements of the type initially mentioned and hence fluidic control elements according to the invention, too, can be used for blocking, passing, restricting, changing, mixing or distributing fluid flows. 
     The particular aspect of such fluidic control elements of the type initially mentioned is the combined sealing and actuating element. This element is clamped between the two housing parts. Its sealing sheath comprises a sealing ring which is clamped like an O-ring between the housing parts and seals the fluid space in the region of the parting plane of the housing parts. The load-carrying core comprises a shaft which extends through the sealing ring towards outside so that a torque is applied to the shaft from outside. Within the fluid space, the two lever arms stick out from the shaft in opposite directions. Originating from the shaft, the core may also extend into the lever arms in order to give them a higher elasticity. The elastic sealing sheath may completely surround the entire core situated in the fluid space, but this is not compulsory. The sealing sheath, however, is present at least in the region of the sealing seats so as to be able to reliably close the sealing seat with an elastic pressure face. These options do not only apply to prior art, but also for the control element according to the invention explained below. 
     Upon swiveling the lever, the elastic sealing sheath is deformed so that it provides for a restoring force. However, this involves a permanent load on the sealing sheath. 
     The cores used hitherto are formed as punched parts around which the sealing sheath is applied by insert molding or vulcanization. The cross-section of the shaft in the region of the passage through the sealing ring is a rectangular one. In the region where the shaft passes through the sealing ring, the latter is subject to high loads and may tear over the years. 
     It is the object of the invention to improve a fluidic control element such that the valve body possesses a longer product life. 
     SUMMARY 
     The fluidic control element according to the present invention comprises a housing composed of at least two housing parts, a fluid space being formed between the housing parts and at least first and second flow channels each comprising a sealing seat opening into said fluid space, and a valve body defined by a two-armed lever which can be swiveled in the fluid space and defines a combined sealing and actuating element, each arm of the lever being capable of closing and opening its associated flow channel in a corresponding end position. The valve body has a load-carrying core including a shaft mounted in the housing and an elastic sealing sheath surrounding the core in sections, the shaft being embedded in the sealing sheath at least in the region of its mounting in the housing. The sealing sheath comprises a formed-on sealing ring which is clamped between the housing parts and surrounds the lever arms. The shaft is rounded at least in the region in which it is embedded in the sealing ring and adjoins the sealing ring. 
     Whereas rectangular, sharp-edged cross-sectional profiles have usually been used for hitherto existing cores in order to achieve a good embedding in the sealing sheath, the invention chooses the opposite solution. Due to rounding off, there are no sharp edges or borders, i.e. edges or borders defined by immediately intersecting, in particularly flat surfaces, because the edges are always rounded, if present. This means that there will also be no tearing in the sealing sheath originating from these sharp edges. 
     In the control element according to the invention, there are no sharp edges at least in the region where the shaft passes through the sealing ring, preferably in the entire region of the shaft in which it is embedded in the sealing sheath. 
     The preferred embodiment even makes provision that all portions of the shaft which are situated in the sealing sheath and adjoin the sealing sheath are rounded, i.e. do not have any sharp corners or edges. 
     Although the highest loads on the sealing sheath exist in particular in the region of the shaft during swiveling the lever, one embodiment of the invention makes provision that all portions of the core which are situated in the sealing sheath and adjoin the sealing sheath have a rounded design. 
     As already explained, the core may have protrusions which originate from the shaft and stabilize the lever arms. This means that the shaft merges into these protrusions, for instance in one piece, so that a direct torque transmission from the shaft to the lever arms is achieved. 
     The protrusions may be embedded in the sealing sheath on all sides, i.e. the entire region of the valve body which comes into contact with the fluid is covered with the elastic material. 
     Outside the fluid space, at least one actuating arm should be formed on the shaft; it is preferred that two actuation arms pointing in opposite directions are formed on both shaft ends. 
     The actuation arm(s) may comprise an angled stabilization rib which is produced, for instance, by bending the core made of sheet metal. 
     The core can be produced as a punched part and hence at very low cost. 
     The borders of the core are rounded in particular by mechanical, chemical and/or electrochemical or physical ways and means, for instance by means of grinding, sandblasting, etching, eroding or electrochemical machining or combinations thereof. 
     A variant of the processing of the core for rounding it is that the shaft has a multi-layered design in the region of the passage through the sealing ring, including a multi-part design. Here, a load-carrying inner part (also referred to as inner core) is provided, for instance a punched part, to the outside of which a rounded cladding is applied, in particular made of plastic. This cladding can be formed, for instance, by insert-molding the inner part in this region or by coating the inner part, for instance with plastic, or by fastening a prefabricated part. 
     In order to optimize the embedding of the shaft in the sealing sheath and to prevent a gap occurring between the sealing sheath and the shaft during swiveling the valve body, it is preferred that there is a material bond between the sealing sheath and the shaft, preferably even between the sealing sheath and the entire core. 
     The preferred embodiment of the invention makes provision that the sealing ring has a self-reinforcing sealing geometry comprising beads projecting in the region of the surface of contact with the housing parts. These beads produce undercuts in which the fluid exerts a pressure on the bead, pressing the latter against the surface of contact with higher force. 
     With the embodiment in which a sheet metal is used as a load-carrying inner part, it is of advantage to coat it by powder coating technology, in particular with PTFE, prior to embedding it in the sealing sheath. 
     As an alternative to making the core or inner core of metal, it may also be manufactured from hard plastic or can be a bent sheet metal part. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional view through a fluidic control element according to the invention, 
         FIG. 2  is a perspective view of a valve body according to a first embodiment used in the control element according to the invention, 
         FIG. 3  is a top view of the control element according to  FIG. 2 , 
         FIG. 4  is a sectional view along the line IV-IV in  FIG. 3 , 
         FIG. 5  shows various variants of the cross-section of the valve body core which is used with the invention, 
         FIG. 6  shows various variants of the cross-section of the valve body core used in prior art, 
         FIG. 7  is a perspective view through a second embodiment of the valve body core used with the invention, 
         FIG. 8  is a sectional view through the core of the valve body according to  FIG. 7  along line VIII-VIII, 
         FIG. 9  is a third embodiment through a valve body core used with the invention, 
         FIG. 10  shows the shaft which is used with the core according to  FIG. 9 , only the middle region of the shaft being shown, 
         FIG. 11  is a top view of a further embodiment of the valve body used with the invention, 
         FIG. 12  is a sectional view through the valve body according to  FIG. 11  along line XII-XII, 
         FIG. 13  is an enlarged view of the framed region designated with X in  FIG. 12  in the installed state, 
         FIG. 14  is a sectional view through a further valve body used with the invention, 
         FIG. 15  is a sectional view through the valve body according to  FIG. 14  in the installed state, and 
         FIG. 16  is an enlarged detailed cross-sectional view through the valve body in the region of the shaft in the basic state and in a deflected state. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows a fluidic control element in 3/2-way-function, which is part of a 3/2-way-valve. 
     The control element comprises a preferably flat, parallelepiped housing made up of two housing parts  10 ,  12  which are pressed against each other. 
     Formed between the housing parts  10 ,  12  is a fluid space  14  which is defined by recesses in the housing parts  10 ,  12 . 
     Two sealing seats  16 ,  18 , which are also referred to as valve seats, protrude into the fluid space  14 . The sealing seats  16 ,  18  surround the orifices of associated flow channels  20 ,  22  which begin in the fluid space  14  or open into it. 
     The flow channels  20 ,  22  extend through the housing part  10  and are connected to a piping system (not shown). Same applies to a flow channel  24  which is formed without a valve seat and preferably opens into the fluid space  14  between the sealing seats  16 ,  18  or originates from it. 
     Provided in the fluid space  14  is a valve body  26  which is designed as a combined sealing and actuating element and comprises a two-armed lever which can be swiveled about an axle  28 . 
       FIG. 2  illustrates the valve body  26  in more detail. The valve body  26  comprises a middle shaft portion  30  surrounding the axle  28 , the two arms  32 ,  34  originating from said shaft portion. Further, the valve body  26  comprises a closed surrounding sealing ring  36  originating from the shaft portion  30  and extending at a lateral distance from the two-armed lever. 
     The shaft portion  30  extends as far as to outside the sealing ring  36  and has its axial ends each provided with a one- or two-armed actuation arm  38  which is angled relative to the axle  28 . 
     The valve body  26  is a sandwich-type component with a load-carrying core  40  preferably made of sheet metal or hard plastic and surrounded in portions by an elastic sealing sheath made of plastic. 
     According to  FIG. 3 , the core  40  comprises the actuation arms  38  in whose region the core  40  is not surrounded by the sealing sheath  42 , a shaft  44  connecting the actuation arms  38  to each other, as well as two tongue-like protrusions  46  protruding centrally from the shaft  44  in opposite directions and forming the core  40  of the two lever arms  32 ,  34 . The shaft  44  and the protrusions  46  are completely surrounded by the elastic plastic material of the sealing sheath  42  so that they are embedded therein. 
     Apart from the region in which the sealing ring  36  receives the shaft  44 , the sealing ring  36  has no embedded reinforcement, i.e. it is realized without any core  40  and hence is functionally identical to an elastic O-ring or the like. 
     On the side facing the respective sealing seat  16 ,  18 , the sealing sheath  42  may be formed with a somewhat higher thickness, as can be seen in  FIG. 1 . For simplification, the core  40  is not illustrated in  FIG. 1 . It is to be seen, however, that the sealing ring  36  is received in recesses in the housing parts  10 ,  12  and defines the external limitation of the fluid space  14  in the region of the parting plane between the housing parts  10 ,  12 . The sealing ring  36  is axially compressed between the housing parts  10 ,  12 . 
     By the introduction of a torque, for instance by means of electromagnetic actuators acting on the actuation arms  38 , the two-armed valve body  26  is swiveled between two end positions. 
     In the embodiment according to  FIG. 1 , the valve body  26  is swiveled such that the arm  34  closes the sealing seat  18 . Thus, a fluid may flow into the fluid space  14  via the channel  20  and flow out again via the channel  24 . Vice versa, in the other end position a fluid may flow into the control element via the channel  22  and flow out again via the channel  24 . In any intermediate position in which the two sealing seats  16 ,  18  are open, the fluid can be mixed very precisely in quantitative terms. 
     Having clamped the sealing ring  36  between the housing parts  10 ,  12 , the elastic sealing sheath  42  acts like a kind of bearing for the core  40  moving therein, in particular in the region of the shaft  44 . 
       FIG. 4  illustrates a section through the shaft portion  30 . The shaft  44  has an essentially rectangular cross-section with rounded corners or borders  47 . This rounded design of the corners or borders  47  may be produced in different ways. 
     To give an example, the core  40  in the region of its borders and corners can be rounded by a mechanical, chemical and/or electrochemical or physical post-processing. This rounding process is carried out at least in the region of the shaft  44  in which the elastic sealing sheath is embedded. 
     Another possibility of rounding is to provide the shaft  44  with an external coating  48 . Thus, the shaft  44  has a multi-layer design. The coating  48  is realized such that—despite the sharp-edged inner metal or plastic core—the border of the resulting multi-layer core is rounded so that there are no sharp corners or edges adjoined by the elastic material. In this region, the core  40  has a multi-layer design as already stated, comprising the load-carrying inner core and the covering whereby the shaft  44  has an outer circumference which is rounded. 
       FIG. 5  lists most various options for realizing the round shaft  44  as examples. The shaft may be realized without any covering or coating by exhibiting a completely round outer geometry, in the left embodiment an oval one, a circular cross-section or any other, for instance rectangular cross-section with greatly rounded edges. As an alternative to this, the outer surface may also be formed by a covering of the inner core, with the option of realizing the covering as a coating, a part attached by injection molding or as a separately manufactured part which is fastened thereto. By way of example, the inner core can still be realized so as to be rectangular and have a sharp-edged design. These inner cores are illustrated in  FIG. 5  with broken lines and represent examples only. 
       FIG. 6  shows the cross-sections of shafts as usual hitherto in prior art, which were uncoated and formed a portion of a punched part. It can be seen that the cross-sections were realized without rounded edges, even had sharp-edged corners in part, in order to ensure a good anchoring and a form-fitting embedding in the circumferential direction within the sealing sheath. 
       FIG. 7  shows a further embodiment of the core  40  of the valve body according to the invention, in which a sleeve-like covering  148  is provided in the region where the shaft  44  passes through the sealing ring (not shown) realized as in  FIG. 3 . Here again, the shaft has a multi-layer design, comprising an inner core  140  which, for instance, has not been machined and is sharp-edged and has a rectangular cross-section (see  FIG. 8 ), and a covering  148  made of a plastic material and exhibiting a rounded, here circular outer shape. 
     The covering  148  is produced in particular by means of insert-molding the inner core  140  or also by applying a two-part sleeve by gluing. The sealing sheath which will surround the shaft  44  as well as the two-armed lever, is produced in a next step by vulcanizing or insert molding. 
     With this embodiment, too, the core  40  within the fluid space  14  is completely surrounded by the sealing sheath. As an alternative to this, it is also possible, of course, that only portions of the core  40  are embedded in the elastomeric material. 
     In the embodiment according to  FIG. 9 , the core  40  has a two-part design, comprising a U-shaped wire including the shaft  44  and the actuation arms  38  and exhibiting a round, in particular circular cross-section. The wire preferably has, but not necessarily, a flattened portion  52  (see  FIG. 10 ) in the region of the shaft  44 . A two-part lever  54  is either separately produced beforehand and then is fastened to the wire, or the lever  54  is fastened to the wire in the course of the injection molding process. The flattened portion  52  serves for improving the bond and form-fitting embedding in the circumferential direction so that the moment applied via the actuation arms  38  is passed into the two-armed lever  54  in form-fitting manner. 
     The embodiment of the valve body  26  according to  FIGS. 11 to 13  essentially corresponds to the previous embodiments so that only the differences have to be elaborated in the following. Here again, the core  40  is realized as a punched part or plastic part surrounded by a sealing sheath comprising a sealing ring  36 . Here too, the two-armed lever and the shaft  44  are completely embedded in the elastomeric material within the fluid space  14  and in the region of the sealing ring  36 . Laterally outside the sealing ring  36 , the shaft  44  is exposed, for example, i.e. is not embedded in elastomeric material, which would also be possible. 
     Unlike the embodiments which have been described so far, the actuation arms  38  projecting from the same side of the axle  28  are connected with each other in pairs by a bridge  56 . 
     In the illustrated embodiment, the bridge  56  essentially follows the shape of the sealing ring  36  so that a gap  58  occurs between the sealing ring  36  and the bridge  56  as well as the actuation arms  38 . 
     In the exemplary embodiment which is shown, the load-carrying core  40  thus has the shape of the letter omega, and the tongue-like protrusions  46  at its middle leg protruding downwards or upwards. 
     The outer borders of the core  40  are laterally angled and define a stabilization rib  60 . In the design of the core  40  as a punched sheet metal part, the stabilization ribs  60  are merely produced by bending. 
     A further special aspect of the embodiment according to  FIG. 11  which, however, is not limited to the special shape of the core  40 , consists in that the sealing ring  36  has a self-reinforcing geometry. 
       FIG. 12  shows that the sealing ring  36  has laterally protruding (i.e. protruding in axial direction) beads  62 , in the cross-section towards its outer surfaces which come into contact with the housing parts  10 ,  12 . A depression  64  may be present between neighboring beads  62 , but this is not compulsory. 
     In the clamped state (see  FIG. 13 ), the sealing ring  36  will be deformed such that the beads  62  protrude laterally, i.e. inwards toward the fluid space  14  and optionally towards outside. This results in an undercut  66  by the fluid applying a force on the beads  62  which presses the beads  62  against the surface of contact on the housing parts  10 ,  12  even more powerful. Thus, a self-reinforcing effect is achieved. 
     In the embodiment according to  FIGS. 14 and 15 , a bead  62  is realized which in the unloaded state (see  FIG. 14 ) projects upward and downward on the inner side of the sealing ring  36 . In the clamped state (see  FIG. 15 ), the elastomeric material is deformed such that an inwardly oriented bead  62  will be produced which in turn creates the undercut  66  by pressure fluid providing for the self-reinforcing sealing effect. 
     It is to be seen in  FIG. 16  that the shaft  44  in case of a deflection S and a pivoting angle α changes from a horizontal orientation related to  FIG. 16  to a swiveled orientation so that the elastomeric material will be deformed in the region of the sealing ring  36 . However, the round outer geometry of the shaft  44  makes provision that the elastomeric material does not tear and come off from the shaft so that sealing problems could arise.