Abstract:
The present disclosure relates to a retractable assembly for immersion, flow and attachment measuring systems in analytical process technology that includes an essentially hollow cylindrically shaped housing having a service chamber formed in its interior, where the housing includes an encircling groove open to its interior, where the groove includes an expansion space expanding the groove, where the expansion space is arranged on the side of the groove facing away from the interior, and where the housing includes a leakage path, which connects the expansion space with the environment.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    The present application is related to and claims the priority benefit of German Patent Application No. 10 2016 104 921.2, filed on Mar. 16, 2016, the entire contents of which are incorporated herein by reference. 
       TECHNICAL FIELD 
       [0002]    The present disclosure relates to a retractable assembly for immersion, flow and attachment measuring systems in analytical process technology for measuring at least one measured variable of a medium in a containment. 
       BACKGROUND 
       [0003]    Retractable assemblies are sold by the group of firms, Endress+Hauser, in great variety, for example, under the designation “Cleanfit H CPA875.” 
         [0004]    Retractable assemblies are used widely in analytical measurements technology and process automation. They serve to withdraw and reintroduce probes out of and into a process, and thus a medium, without process interruption. The probes are secured in an immersion tube and moved by means of a drive manually or automatically, for example, pneumatically, axially between a process position (measuring) and a service position (maintenance, calibration, washing, probe exchange, etc.). These procedures run within a certain timing cycle or as a function of other determinable or measured parameters. 
         [0005]    Probes in the sense of this present disclosure include probes with at least one accommodation for at least one sensor for measuring one or more physical or chemical, process variables. 
         [0006]    The scope of use of retractable assemblies for measuring physical or chemical, process variables of a medium, e.g. a fluid, especially a liquid, in process technology is broad. Used for determining the process variables are sensors, such as pH-sensors, conductivity sensors, optical or electrochemical sensors for determining a concentration of a substance contained in the medium to be monitored, e.g. O 2 , CO 2 , certain ion types, organic compounds, or the like. 
         [0007]    If retractable assemblies are used for accommodating the sensor for determining at least one process variable, the sensor can be checked, calibrated, cleaned and/or replaced in the service position, wherein the sensor is located, in such case, in the housing interior of the retractable assembly, in the so-called service chamber. In order that the medium not be contaminated by the calibration, rinse or cleaning liquid, in the service position, the service chamber is so sealed from the containment, in which the medium is located, that no exchange of medium/liquid can take place. Usually for this purpose, there is located on the media end of the housing of the retractable assembly a seal, which in interaction with the end region of the immersion tube prevents an exchange of medium/liquid. A seat for the seal is located in the immersion tube or in the housing (i.e., service chamber). Used as seal is frequently an O-ring or a shaped seal. The groove for the seal is, in such case, rectangularly shaped in cross section. In such case, gaps frequently arise when the seal is in place. 
         [0008]    The gaps and edges form dead spaces, where particles can deposit and scale and/or biofilms can form. These are undesirable, since they degrade the functional ability of the retractable assembly. In the worst case, germs and the like can collect, multiply and so contaminate the medium and make it unusable. 
         [0009]    DE 10 2013 111 057 A1 discloses a sealing system and a retractable assembly, which satisfy hygienic requirements. Different hygiene regulations require different types of assembly construction. 
       SUMMARY 
       [0010]    An object of the present disclosure is to provide a hygienic assembly, which satisfies varied regulations. 
         [0011]    The object is achieved by a retractable assembly, comprising an: an essentially hollow cylindrically shaped housing having a service chamber formed in its interior, wherein the housing includes an encircling groove open to its interior, wherein the groove includes at least one, preferably two, expansion spaces, expanding the groove, wherein the expansion space is arranged on the side of the groove facing away from the interior; an immersion tube having an end region, wherein the immersion tube is movable axially in the housing between a service position withdrawn from the medium and a process position run into the medium, wherein in the service position the immersion tube is positioned in the service chamber; and at least one seal, wherein in the service position the seal externally closes and gap-freely seals off the service chamber in that an external end region of the immersion tube lies against the seal. In the retractable assembly, the housing includes a leakage path, which connects the expansion space, especially the expansion spaces, with the environment. 
         [0012]    A lack of sealing, which leads to contamination of a lower expansion space, cannot be detected. The expansion space can only be cleaned appropriately by disassembly. In regular operation, dirt and microorganisms remain therein, and this represents a danger for the process. The leakage path provides a means by which such contamination can be detected. 
         [0013]    The terminology “environment” as used in the present disclosure means the “ambient air,” thus the atmosphere around the retractable assembly. 
         [0014]    In an embodiment, the housing is embodied as at least two parts. In a first embodiment, the housing includes a medium-near process connection part and a medium-far second part, wherein the groove is formed by corresponding cavities in the process connection part and in the second part. In general, the groove is formed by corresponding cavities in the housing. The two-part construction facilitates the manufacturing, and the installation of the seal is simpler. Other embodiments provide three or more parts of the housing. In this way, the housing can be constructed modularly. 
         [0015]    In an embodiment of the leakage paths, these are embodied, for example vertically, by drilling or milling. This is easily done and effectively connects the expansion space with the environment. 
         [0016]    In a further embodiment of the leakage paths, these are so embodied that the housing, for instance the process connection, includes at least one annular insert. This represents another way of providing a path from the expansion space to the environment. 
         [0017]    Advantageously, the housing includes in the process connection part or in the second part or in the insert an axial hole into the expansion space, in order at least partially to form the leakage path. This hole is easy to manufacture, for instance, by machine processing, such as drilling or milling, and achieves the desired goal, namely the providing of the path from the expansion space to the surrounding air. 
         [0018]    In certain embodiments, at least the contacting parts of the process connection and of the insert are of a metal. Mutually contacting metal parts do not, as a rule, seal, so that the desired leakage path results. 
         [0019]    In order to detect possible contamination, a measuring device for detection of medium, liquids and the like is connectable to the leakage path. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]    The present disclosure will now be explained in greater detail based on the appended drawing, the figures of which show as follows: 
           [0021]      FIG. 1  shows a retractable assembly of the present disclosure in a first embodiment; 
           [0022]      FIG. 2  shows a retractable assembly of the present disclosure in a second embodiment; 
           [0023]      FIGS. 3A and 3B  show a process connection and an insert of the retractable assembly of  FIG. 2 ; and 
           [0024]      FIG. 4  shows a retractable assembly of the present disclosure with a rinse chamber. 
       
    
    
       [0025]    In the figures, equal parts are provided with equal reference characters. 
       DETAILED DESCRIPTION 
       [0026]    The retractable assembly of the present disclosure bears the reference character  1  and is shown in  FIG. 1 . Retractable assembly  1  is composed of an essentially cylindrical housing  8 , which can be connected by means of a process connection  19  to a containment (not shown). Process connection  19  can be embodied, for instance, as a flange connection, e.g. of stainless steel. Further details concerning the process connection  19  will be explored below. Located in the containment is the medium  7  to be measured. The containment can be, for instance, a container, vat, tube, pipeline or the like. 
         [0027]    The terms “above”, “over” and related terms in the sense of this present disclosure mean facing away from the medium  7 . The terms “below”, “under” and related terms in the sense of this present disclosure mean facing the medium. The terms “outside”, “external” and related terms in the sense of this present disclosure mean away from the longitudinal axis L of the housing  8 . The terms “inner”, “within” and related terms in the sense of this present disclosure mean toward the longitudinal axis L. 
         [0028]      FIG. 1  shows the retractable assembly  1  in a service position, which will be further explained in greater detail. 
         [0029]    Guided within the housing  8  is an immersion tube  5 . A probe is connected with the immersion tube  5  by a holding means (not shown), for example, by a screwed connection, i.e. the probe is mounted in the immersion tube  5 . The probe in the sense of this present disclosure includes probes having at least one receptacle for at least one sensor  3  for measuring one or more physical or chemical, process variables, for example, pH-value, also via an ISFET, redox-potential, absorption of electromagnetic waves in the medium, for example, waves with wavelengths in the UV-, IR-, and/or visible region, oxygen level, conductivity, turbidity, concentration of metal and/or non-metal substances or temperature. 
         [0030]    When the immersion tube  5  is located in the service position, a portion of the immersion tube  5 , especially the sensor  3 , is located in the interior  9 , in the so-called service chamber  17 , for rinsing, cleaning, calibrating, etc. Located at the lower end region  6  (thus toward the medium) of the immersion tube  5  is a closure element  20  for sealing from the process. Closure element  20  seals the interior  9  from the process, and therewith from the medium  7 . The medium  7  can be hot, poisonous, corrosive or in other manner damaging for humans and the environment. It is, consequently, necessary that the closure element  20  safely and durably seals. For such purpose, a seal  12  is provided on or in the housing  8 , for example a seal in the form of one or more molded sealing units. This will be explained in greater detail below. 
         [0031]    In the service position, the various service tasks, such as cleaning or calibration, can be performed. Cleaning, rinsing and calibration liquids can be fed into the interior  9  via a connection  4 . The liquid can be drained via a corresponding outlet (not shown in  FIG. 1 ). In an embodiment, there is an upper connection (see, for instance,  FIG. 4 ), wherein the retractable assembly  1  is installed inclined relative to the vertical. The rinse, wash and calibration flow direction can also be reversed. 
         [0032]    Immersion tube  5  can be produced of different materials. The state of the art includes immersion tubes  5  of stainless steel, titanium and other chemically resistant materials. Immersion tube  5  can also be produced of a synthetic material such as polyetheretherketone (PEEK), polytetrafluoroethylene (PTFE), a perfluoroalkoxy-polymer (PFA), other synthetic materials or resistant metals, such as, for instance, Hastelloy. The same holds for housing  8 . 
         [0033]    Immersion tube  5  is mounted such that it can be moved axially in the direction of the central axis L toward or away from the medium  7 . Immersion tube  5  is, in such case, run between the service position in the housing  8  (such as described, see  FIG. 1 ) and a process position out of the housing  8 , such that the sensor  3  is in contact with the medium  7  in the process position. 
         [0034]    The shifting of the immersion tube  5  is by way of a manual or automatic drive, for instance, effected by means of a supply energy (not shown). When energy is supplied through a connection (not shown), the immersion tube  5  moves from the service position into the process position. A further connection (likewise not shown) then serves as a drain. If energy is supplied in the reverse direction, the immersion tube  5  moves from the process position into the service position. Pneumatic, hydraulic and electrical drives are known from the state of the art. 
         [0035]    In the process position, the measuring takes place. Via a cage-like opening in the immersion tube  5 , the probe, including the sensor  3 , has access to the medium  7  to be measured. Alternatively or supplementally, the immersion tube  5  tapers upwardly (thus away from the medium), in order to enable rinsing, cleaning and sterilizing of the immersion tube  5 , especially of the closure element  20 . 
         [0036]    In the following, the seal  12  for sealing the interior  9  from the containment, including from the medium  7 , will now be described in greater detail. 
         [0037]    Seal  12  lies in a groove  10  made for it in the housing  8 . Access to the service chamber  17  is blocked by means of the seal  12  and the closure element  20  in the end region  6  of the immersion tube  5 , thus the movable part of the retractable assembly  1 . 
         [0038]    Housing  8  is formed by a process connection part  19  and a second part  22 . Groove  10  is formed by corresponding cavities in the process connection  19  and in the second part  22  of the housing  8 . Groove  10  defines a plane, wherein the normal to the plane extends essentially parallel to the longitudinal axis of the housing  8 . Joining (for instance, by screwed connection) of the process connection part  19  with the second part  22  creates the groove  10  extending around the housing  8  and open to the interior  9 . The shaped seal  12  can be replaced by disassembling process connection part  19  and second part  22  of the housing  8 . The two-part construction of the housing  8  facilitates the manufacturing, and installation of the shaped seal  12  is simplified. Also, the groove  10  can then be produced with the required accuracy, especially surface roughness. 
         [0039]    Seal  12  includes a first section facing the interior  9  and a second section facing away from the interior  9 . In the example, the first section is embodied rectangularly in cross section and the second section circularly in cross section. The first section and the second section form a step where they meet. Various forms, such as, for instance, a wedge shape, embody other options. 
         [0040]    Groove  10  and seal  12  are so embodied that a dynamic sealing surface  15  is formed. The dynamic sealing surface  15  is an internally situated, encircling area of the seal  12 . The dynamic sealing surface  15  is essentially flush with an inner edge of the housing  8 . In an embodiment, the sealing surface  15  is so embodied that a ledge results, whereby a large and therewith cleanable gap of, for example, 1 mm arises. 
         [0041]    Interior  9  is gap-freely sealed from the containment, including from the medium  7 , especially by the dynamic sealing surface  15  interacting with the immersion tube  5 , more specifically the closure element  20 . Thus, no gap can form between housing  8  and shaped seal  12 . In an embodiment, the dynamic sealing surface  15  protrudes into the interior  9 ; this region is then in the case of movement of the immersion tube  5  over the shaped seal  12  pressed slightly outwardly. 
         [0042]    Additionally, groove  10  is so embodied that at least a first static sealing surface  16 . 1  and a second static sealing surface  16 . 2  are formed in the second section. The first static sealing surface  16 . 1  is arranged on the top of the shaped seal  12  in the second section, while the second static sealing surface  16 . 2  is arranged on the bottom of the shaped seal  12  in the second section. The first and second static sealing surfaces  16 . 1 ,  16 . 2  seal the interior  9  gap-freely from the external space. Additionally, the first and second static sealing surfaces  16 . 1 ,  16 . 2  assure that the process connection  19  and the second part  22  of the housing  8  are sealed relative to one another. In order further to guarantee that there are no gaps, the cross section of the groove  10  is embodied smaller than the cross section of the shaped seal  12 . 
         [0043]    The shaped seal  12  is composed, for example, of ethylene-propylene-rubber (EPM), ethylene-propylene-diene-rubber (EPDM), a fluorine containing rubber (FKM), perfluoro rubber (FFKM), polytetrafluoroethylene (PTFE) or a silicone. 
         [0044]    Located at the outer part of the groove  10  is an expansion space  11  expanding the groove  10 . In at least on embodiment, as shown in the example, there are two expansion spaces  11 . The volume of the expansion spaces  11  amounts approximately to 5-20% of the volume of the seal  12 . The region of the seal  12  lying opposite the dynamic sealing surface  15  adjoins the expansion spaces  11 . 
         [0045]    In the case of temperature change, for example, because of a sterilization procedure, the seal  12  can expand into the expansion spaces  11  without reducing the assurance of absence of gaps at the dynamic, first and second static sealing surfaces  15 ,  16 . 1 ,  16 . 2 . In other words, no gap forms at any temperatures. Depending on the material of the shaped seal  12 , temperature changes from −20° C. to +140° C. are possible. 
         [0046]    To meet hygienic requirements, it may be necessary to clean, i.e. to rinse, wash, and, when required, to sterilize the seal  12 . Immersion tube  5  moves into a position, which is located between the service position and the process position. This is locked by a locking apparatus. The locking apparatus is, for instance, a locking element, self-limiting drive or automatically operating mechanism. 
         [0047]    Rinse, cleaning or sterilization medium inflowing through the lower connection  4  flows around the seal  12  and, thus, rinses, cleans or sterilizes it. The inflowing medium can drain into the medium  7  (which, when required, is turned off), respectively into the containment. 
         [0048]    In a first embodiment of the retractable assembly of the invention  1 , such includes a leakage path  30 , which is embodied as a vertical bore or milled passageway. This is shown as a connection of the lower expansion space  11  to the environment  13 , thus to the ambient air. Equally possible is a connection to the upper expansion space or to both expansion spaces. Connected to the leakage path  30  is a measuring device  31  for detection of medium  7 , liquids, etc. Alternatively, a regular visual checking by the user can occur. Thus, it can be detected, when some type of medium is located in the expansion space  11 . 
         [0049]    A second embodiment is shown in  FIG. 2 . In  FIG. 2 , the retractable assembly is in the process position. As has been mentioned, housing  8  is composed of a process connection part  19  and a second part  22 . In contrast to the form of embodiment in  FIG. 1 , the process connection part  19  has been modified; see  FIG. 3A  in this regard. In this case, an annular insert  23  is inserted; see  FIG. 3B . Insert  23  serves as part of the seal geometry. In case the expansion spaces  11 , especially the lower space, are/is contaminated with some type of medium, this medium can flow at the contact surface between insert  23  and process connection  19  outwardly via the leakage path  30  and be detected, for instance, by means of a corresponding detection unit  31  (not shown in  FIG. 2 ). 
         [0050]    At least the contacting parts of the process connection  19  and the insert  23  are metal. The metal contact area between insert  23  and process connection  19  is, thus, embodied as a leakage path  30 . 
         [0051]    As shown in  FIG. 3A , housing  8 , here process connection  19  (or in certain embodiments the second part  22 ), includes an axial blind hole  24  to the expansion space  11  and forms together with a vertical section  25  at least partially the leakage path  30 . In an additional alternative, the insert  23  includes the leakage path  30 , more exactly the blind hole  24 . 
         [0052]    In an embodiment, as shown in  FIG. 4 , there is located in the housing  8  below the service chamber  17 , thus between the service chamber  17  and the containment, another chamber, a rinsing chamber  21 . Especially in the case of hygienic applications, rinsing chamber  21  can be utilized as an additional barrier between the medium  7  and the service chamber  17 , so that in the case of a replacement of the sensor  3 , a double sealing of the containment is assured, as required for certain permits (e.g., EHEDG EL Aseptic Class I). Counting the service chamber  17 , then two different chambers are available for performing work on the probe. An example of such work is sterilization or calibration of the probe in the service chamber  17 . A plurality of rinse/wash connections  4  can be present. Service chamber  17  and rinsing chamber  21  are likewise sealed from one another by seal  12 . Corresponding leakage paths  30  are shown. These can be implemented as above described as vertical bores or by means of inserts.