Abstract:
An automatable measuring, cleaning and calibrating device for pH-electrodes or electrodes for measuring redox potentials, specifically in process engineering, having an electrode armature which keeps the measuring electrode in an operating position or in a maintenance position, whereby the electrode is retained in the maintenance position in a rinsing chamber in which a cleaning and calibration procedure can be performed. The device has a pump device to supply cleaning fluid and calibration solutions to the rinsing chamber over a delivery line connecting the pump device and the rinsing chamber. In order to configure the device more compactly, the pump device includes several feeds on its intake side, and a device is furnished to selectively activate a particular feed, and the media (cleaning fluid, calibration solution, etc.) brought selectively over the particular feeds to the pump device reach the rinsing chamber over the common delivery line.

Description:
BACKGROUND  
         [0001]    The invention relates to an automatable measuring, cleaning and calibration device for pH-electrodes or electrodes for measuring redox potentials, specifically in process engineering, having an electrode armature which maintains the measuring electrode in an operating position or in a position for maintenance, where the electrode is retained in the maintenance position in a rinsing chamber in which a cleaning and calibration procedure can be carried out, and having a pump device to supply cleaning fluid and calibration solutions to the rinsing chamber by way of a delivery line connecting the pump device and the rinsing chamber.  
           [0002]    Electrochemical sensors and their electrodes are only conditionally consistent with respect to their measurement characteristics as a result of the effects of temperature, type and concentration of ions in the test medium, contamination and ageing, and for this reason they should be cleaned at appropriate intervals and checked through the use of standardized calibration solutions. In an inspection of this kind sensor, parameters such as zero point and steepness of the sensor curve are captured through measurements and saved in the appropriate measurement and evaluation device for consideration during sensor operation.  
           [0003]    An electrode armature for a measuring, cleaning and calibration device is described, for example, in DE 39 27 282 A. Using an electrode armature of this type, a pH-electrode, for example, can be moved from its operating position in a process container and brought into a position for maintenance in a rinsing chamber, where it is exposed to cleaning and calibration solutions.  
           [0004]    Further efforts are being made to automate this cleaning and calibration process, which is hereafter described as maintenance. The known method is to supply cleaning fluids and calibration solutions through pump equipment to the rinsing chamber of the measuring, cleaning and calibrating device. A separate pump device is used for each medium to be supplied.  
           [0005]    The object of the present invention is to design a more compact version of an automatable measuring, cleaning and calibration device of the type described above.  
         SUMMARY OF THE INVENTION  
         [0006]    This object is achieved under the invention in the case of a device by which the pump device comprises several feeds on its intake side, by which a device for selectively activating a particular feed, and by which the media selectively brought over the particular feeds to the pump device, i.e. cleaning fluid, calibration solutions or rinse water, reach the rinsing chamber through the common delivery line.  
           [0007]    It is therefore proposed with the present invention that specifically only a single pump device be used, which is then connected to several feeds, for example, to several feed lines, which for their part are connected to various receiving containers for different calibration solutions and for different cleaning or rinsing solutions furnished directly at the device or at a remote location. By means of the device for selectively activating a particular feed, the feed desired at the time in accordance with the preselected cleaning and calibration cycle can be activated so that the appropriate cleaning fluid can be delivered through the pump device to the rinsing chamber.  
           [0008]    The cleaning and calibration sequence is designed such that cleaning fluids and calibration solutions, but also rinsing solutions and compressed air if needed, can be delivered alternately to the rinsing chamber in order to service the sensor, its pH-electrode or its redox electrode, respectively.  
           [0009]    A typical cleaning and calibration cycle for a pH-measuring electrode could run as follows: First, the measuring electrode, which has been moved from the operating to the maintenance position, is pre-rinsed with water. This is followed by a cleaning step by rinsing the chamber with cleaning fluid. Immediately afterwards water is used to provide a second rinse. The rinsing chamber is then blown dry with compressed air. A first calibration solution is introduced in the form of a pH-buffered primary solution, and the corresponding values for the sensor are determined, processed metrologically and saved. Another rinse with water is performed, followed by further blowing dry with air. Then a second calibration solution is introduced as the sensor signal is recorded, and then a water rinse is carried out, followed by an air rinse.  
           [0010]    It must be pointed out that the operational position and the maintenance position of the sensor are not necessarily different from one another, as is customary with an switching armature, and thus do not have to be located, for example, inside or outside a process container, but it would be possible, at least in principle, for telescoping housing components or similar to be furnished, which seal off the process, while retaining the position of the measuring electrode.  
           [0011]    In any case it proves advantageous if only a single pump device is provided, which comprises the several feeds, specifically a first means of supply to provide a cleaning fluid and a second and a third means of supply to provide a first and a second calibration solution, respectively.  
           [0012]    Furthermore, it proves to be advantageous if the pump device is a metering pump device, with which specified quantities can be supplied to the rinsing chamber. This proves to be especially advantageous with respect to the calibration solutions which, for cost reasons, should be consumed only in the required quantity.  
           [0013]    The pump device could comprise extensive intake ducts equipped with a plurality of selectable valves. However, in a further development of the invention it is proposed that the pump device comprises a first component which can be connected to the several feeds, which has one opening per feed, which openings can be connected selectively to one specific individual intake duct of the pump device.  
           [0014]    To achieve this it is further proposed that the device for selectively activating a particular feed has a second component, which is adjustable with respect to the first component, comprising the intake duct, and that the first and the second component are adjustable relative to each other in such a way that one intake port of the intake duct can be selectively connected to a particular feed. Thus the two components are adjusted to each another, specifically rotated, such that a cross-section of the openings on both sides communicate with each other to create a fluid connection between a particular feed and the intake duct of the pump device.  
           [0015]    In order to be able to furnish means of supply for the several feeds permanently in place, it proves advantageous if the first component, which is connected to these feeds, is a rigidly mounted component. However, this is not absolutely necessary, since flexible means of supply can also be used for the feeds. Accordingly, it proves to be advantageous if the second component is an actuator moveable with respect to the first rigidly mounted component. The two components under the invention can be rotated with respect to each other, so that it is possible to achieve selective actuation of the particular feeds.  
           [0016]    In a further embodiment of the invention the intake duct, which is formed in the second component, is tilted with respect to a rotational axis. Preferably it runs radially inward, but is tilted at the same time. This creates open installation space in the area of the intake port of the intake duct inside the second component, in which control devices, specifically valve control devices, which will be described in detail below, can be housed  
           [0017]    To selectively activate the feeds, the first and the second component specifically and preferably have flange-shaped contact surfaces, lying against one another and specifically rotatable with respect to each other, in which the openings of the first component and the intake ports of the second component open and communicate with one another. In order to rotate the two components relative to each other, a positioning device is provided which is preferably computer controlled.  
           [0018]    The positioning device comprises in a preferred embodiment of the invention a positioning means which is moveable linearly, where its adjusting motion runs specifically tangentially to the rotational circle of one component and provides progressive adjustment therefor about one or more rotational positions.  
           [0019]    With respect to automation it proves to be advantageous if the device for selectively activating a particular feed comprises furthermore a position control device with which the position of the first and second components can be determined one to the other. In this way the adjusting means can be moved for as long a time until the position control device reports reaching the next following activation position for the particular feed.  
           [0020]    In order to realize selective activation of the several feeds it would be conceivable, for example, for the two components to be moveable with respect to each other with adequate sealing. Instead, it has proven to be achievable advantageously, more reliably and involving lower design costs if the openings of the first component can be closed in each instance by valves preloaded in the closing direction, which can then be opened when the appropriate feed is activated.  
           [0021]    It is proposed that the valves comprise valve bodies which can be lifted from a valve seat opposite to the feed direction, when the appropriate feed is activated.  
           [0022]    Lifting of the valve body could be accomplished per se in any way, for example, electromagnetically. However, it proves to be advantageous if a plunger device is furnished in the second component in the area of the intake opening of the intake duct, which lifts the valve body from its valve seat. The plunger device can, for example and preferably, be furnished in the region above, that is, axially behind the intake port, specifically when the intake duct runs at an angle radially inward-as was already indicated previously. The plunger device is preferably configured in the form of a piston with a push rod, whose free end extends preferably through and beyond the intake port in the direction of the first component. The free end of the push rod can then project into the opening in the first component and lift the valve body from its valve seat. To do this, the plunger piston is preferably preloaded in the opposite direction, so that in its non-activated state its open end does not project beyond the contact surface of the second component. When a feed is to be activated, with the first and second component correctly positioned relative to each other, the plunger piston can be moved against the preload, specifically and preferably pneumatically, so that it opens the valve and creates a communication for flow between the intake duct and the appropriate feed, so that in the following intake stroke by the pump device a preferably predetermined volume of fluid can be drawn in.  
           [0023]    In accordance with a preferred embodiment of the invention, the intake duct runs basically radially inward and there opens into a cylindrical chamber, in which an intake and displacement piston can be moved. During the intake stroke, a selected appropriate feed must communicate with the intake port of the intake duct, so that a preferably predetermined volume of transported medium, namely, cleaning fluid or calibration solution or rinsing fluid, is drawn into the cylindrical chamber. In the subsequent displacement stroke, a non-return valve, preferably furnished in the feed, is closed. Moreover, the previously mentioned push rod device, which was furnished as necessary, is activated such that the valve in the opening of the first component closes this opening again. But if the aforementioned non-return valve is additionally furnished, the preload of these valves does not need to be set particularly high.  
           [0024]    The intake and displacement piston of the pump device is preferably connected by means of a piston rod means to a moveable control piston in a preferably pneumatic control cylinder. In a preferred embodiment, this control piston is under spring tension in one direction, preferably in the direction of displacement of the intake and displacement piston. This means that only a single pneumatic control connection has to be furnished, with which the piston is moved in the intake direction. The subsequent displacement stroke is carried by spring preloading of the control piston. The pump device can be driven by cycled bursts of compressed air with a piston stroke frequency which can be preset and thus with presettable volumetric displacement. The aforementioned push rod device is driven in exactly the same cycle, which further simplifies the realization of the pump device design. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0025]    Additional features, details and advantages of the invention are found in the attached patent claims and the drawings and following description of a preferred embodiment of the invention. In the drawings:  
         [0026]    [0026]FIG. 1 shows a schematic representation of the inventive measuring, cleaning and calibration device;  
         [0027]    [0027]FIG. 2 shows a view of a control unit for the device from FIG. 1 with a pump device;  
         [0028]    [0028]FIG. 3 shows a longitudinal section of the pump device depicted in FIG. 2;  
         [0029]    [0029]FIG. 4 shows a side view of the pump device from FIG. 1; and  
         [0030]    [0030]FIG. 5 shows an isometric view of the pump device from FIG. 3 and  4 . 
     
    
     DETAILED DESCRIPTION  
       [0031]    [0031]FIG. 1 shows a schematic representation of an automatable measuring, cleaning and calibration device for pH-electrodes  2  or electrodes  2  for measuring redox potentials. The electrode  2  is held in an electrode armature  4 , called a “switching armature”, and connected by a cable  6  to a transducer  8  which is computer-controlled or which comprises a process control computer. A control unit  10  is also shown having a pump unit  12  which can be seen in FIGS.  2  to  5 . The pump device  12 , which is configured as a metering pump, lifts a cleaning fluid  16 , a first and a second calibration solution  18 ,  20 , water under pressure  22  and compressed air  24  from storage containers  14  over a common delivery line  26  into a rinsing chamber  28  for the electrode armature  4  in a manner to be described in greater detail hereafter.  
         [0032]    Furthermore, pneumatic control lines  30  lead from the control unit  10  to the electrode armature  4  to move the electrode  2  from, or into, its operating position inside a process container  32 , or into or out of a maintenance position shown in FIG. 1. Pneumatically actuated end switches are also provided. Also shown is a rinse block arrangement  34  in the delivery line  26  with a plurality of valves. Through the valves, water under pressure  22  or compressed air  24  can be supplied directly to the electrode armature  4  instead of the medium delivered by the pump device  12 . Two additional connections  36  are furnished for additional media, for example, superheated steam, organic cleaner or an additional cleaning agent or cooling air.  
         [0033]    [0033]FIG. 2 shows the inside of the control unit  10 , where the single pump device  12  for delivering cleaning fluid  16  and calibration solutions  18  and  20  is housed.  
         [0034]    The control unit  10  comprises a housing  38  in which mounting plates are located, such as mounting plates  40 , which carry an electronic module  42 . Also shown is a piezo-pneumatic valve arrangement  44  for activating the electrode armature  4 . The control unit  10  converts commands from the transducer  8 , which represents the control center of the measuring arrangement, into pneumatic signals to control the electrode armature  4 . Feedback signals about armature position, meaning the position of the electrodes  2 , about the fluid level in the canisters  14 , and monitoring data for compressed air  24  and water under pressure  22  are processed in the control unit  10 . Conversely, measurement signals from the measuring electrode  2 , which are sent over the electrode cable  6  to the transducer  8 , are also processed there. The transducer  8  is the communications center for the device. The transducer  8  includes a process control computer or is connected to a process control computer and an input device. It controls signal paths and is linked over an RS 485 bidirectional interface to the control unit, where the signals and control commands from the process control computer are converted into pneumatic magnitudes to control the pump device  12  and to activate the electrode armature  4 , or these signals and commands are carried out. As already mentioned, feedback, such as armature position, canister fluid level and monitoring of compressed air and water is sent over this interface to the process control computer.  
         [0035]    As already indicated, feed lines  48  lead from the supply containers  14  to the single pump device  12 . Additional feed lines  48  carry water under pressure  22  and compressed air  24 . The connection of the feed lines  48  to the pump device  12  cannot be seen from FIG. 1. FIG. 2, however, shows three of a total of five connectors  50  positioned concentrically in a circle for the feed lines  48 . This means that all the feed lines  48  discharge into this single pump device  12 , which will described in more detail below. The pump device  12  is configured such that the five connections  50  can be activated selectively, so that the pump device  12  can selectively lift the particular media—cleaning fluid, calibration solutions, compressed air, water—through the five feed lines  48  and through the common delivery line  26  to the electrode armature  4 . A pump output  52  leads inside the concentrically arranged connections  50  in FIG. 2 down and away and forms an angled connection for the delivery line  26 .  
         [0036]    Construction and operation of the single pump device  12  are explained below with the aid of FIGS. 3 and 4. FIGS. 3 and 4 show a sectional view and a side view of the single inventive pump device  12 . The pump device  12  comprises a first rigidly attached component  54 , into which the connections  50  are threaded into axial bores  56  as male parts. The specific axial bores  56  form transverse ports  58  running in an axial direction through the first component  54 . However, the transverse ports  58  narrow through the first component  54  and form a conical valve seat  60  for a valve body  59 . All five transverse ports  58  open into the connection to the particular valve seat  60  in the form of orifices  61  in a flange-shaped connecting surface  62  in the first component  54 . The pump device  12  includes a second rotatable component  64  opposite the first component  54 . This second component  64  lies against the contact surface  62  with a contact surface  66  complementary to the contact surface  62 .  
         [0037]    In the second component  64 , which can be rotated about a longitudinal center axis  68  of the pump device  12 , a second intake duct  70  is formed, which, starting from an intake port  72  in the contact surface  66 , runs radially inward but is inclined at an angle to the longitudinal center axis  68  and angled upward and opens into a central cylindrical chamber  74 .  
         [0038]    By rotating the second component  64  with respect to the first component  54 , one of the connections  50  and thus one of the feed lines  48  can be selectively activated, by performing the rotation such that the intake port  72  of the intake duct  70  coincides with the orifices  61  of the transverse ports  58  in the contact surface  62 , so that a fluid communication path exists. The rotation of the second component  64  with respect to the first component  54  is carried out by a device  76 , which will be described in more detail below and which engages steps or pins  80  furnished on the circumference  78  of the second component  64  and thus rotates the second component  64 .  
         [0039]    In order to achieve a fluid communication between the transition ports  58  in the first component and the intake duct  70  in the second component  64 , the valve body  59  has to be lifted from the conical valve seat  60 , in other words against the direction of feed. This is done by a push rod device  82 , which comprises a pneumatically actuatable piston  84  and a push rod  86 . The piston  84  with the push rod  86  is housed in an offset axial bore  88  in the second rotatable component  64 , such that the free end  90  of the push rod  86  protrudes beyond the contact surface  66  through the intake port  72 . The free end can then extend into the opening  61  of the transition port  58  and lift the valve body  59  from its valve seat  60 , so that a fluid communication with the intake duct  70  is created. It should be mentioned that the piston  84  with the push rod  86  is driven by pneumatic control pressure which is supplied through a connecting opening  92  in a cover  94 , which cover  94  closes the axial bore  88  in a pressure-tight manner. When pneumatic pressure is removed, the piston  84  and the push rod  86  are returned by a spring  96 , so that the valve body  59  is pushed against the valve body  60  again by spring preload in a sealing fashion.  
         [0040]    When, while a fluid communication exists, an intake and displacement piston  98  is moved upward, that is, into the position shown in FIG. 3, the particular fluid medium is drawn out of the feed line  48  into the cylindrical chamber  74  through the intake port  70 , the transverse port  58  and the connections  50 . In the ensuing displacement stroke of the piston  98 , basically the entire volume of the cylindrical chamber  74  filled with fluid is moved, or displaced, through a central axial outlet pipe  100  to the pump outlet  52 . In the outlet pipe  100 , a valve  104  is preloaded against the direction of flow, the closing effort of which is calculated such that the valve  104  opens under the displacement pressure of the piston  98 . The delivery line  26  is attached to the open end of the angled pump outlet  52 .  
         [0041]    It should be mentioned that during the displacement stroke of piston  98 , the specific non-return valve  106  furnished in the connection  50  closes anyway, but it still proves advantageous if the valve body  59  is also again seated against its valve seat  60  in a sealing fashion by moving the push rod  86  back. After completion of the displacement stroke a further feed line  48 , or a further connector  50  respectively, can be activated without fluid medium present in the transition ports  58  escaping into the area between the contact surfaces  62  and  66 .  
         [0042]    The intake and displacement piston  98  is connected through a piston rod  108  running in an axial direction to a second actuating piston  100 , which can be moved in a control cylinder  112 . The control cylinder  112  is located in an axial direction on the side of the second component  64  opposite the first component  54 . The control cylinder  112  is activated by a pneumatic connection  114  axially opposite the pump outlet  52 . The pneumatic connection  114  provides compressed air over a tube  116  screwed to the control piston  110  through the control piston  110  and over a transverse bore  118  in a part  120  of the control piston  112  facing the first component  64 , so that when pressure is applied, the control piston  110  and with it the piston rod  108  and the intake and displacement piston  98  is moved upward, in the intake direction. A return spring  124  is located in the other part  122  of the control cylinder  112 , which is supported against one side of the control piston  110  and moves the latter downward when pressure is removed, in the displacement direction, whereby the displacement stroke of the piston  98  is carried out.  
         [0043]    It should be mentioned that compressed air is applied to the push rod device  82  in the same cycle as to the pneumatic connection  114 , and thus the control piston  110 . The result of this is that the appropriate valve body  59  is always lifted from its valve seat  60  at the moment of the intake stroke of the piston  98 , so that a fluid communication is present. On the ensuing displacement stroke, on the other hand, the free end of the push rod  86  is pulled back again below the contact surface  66 , so that the valve body  59  again lies in a sealing fashion against its valve seat  60 .  
         [0044]    The aforementioned device  76  for rotating the second component  64  with respect to the first rigidly attached component  54  shall now be explained. As can be seen from FIG. 4, the device  76  comprises a pneumatic positioning device  125  having a pneumatic cylinder  126  with a compressed air connection  128  and a linearly moveable positioning means  130  inside the cylinder  126 . As can be seen from the isometric view in FIG. 5, the direction of adjustment of the positioning means  130  is aligned tangentially to the direction of rotation and to the circumference  78  of the second component  64 . The positioning means  130  has a rack-like carrier  132  on the side facing the circumference of the rotatable component  64 , which engages the previously mentioned steps or pins  80  on the circumference  78  of the component  64  and, as result of the motion of the positioning means  130 , rotates the component  64  around its longitudinal center axis  68 .  
         [0045]    Furthermore, a position control device  136  is provided (FIG. 3), which comprises two microswitches  138 ,  140  positioned one above the other for position feedback and for the zero position.  
         [0046]    When a maintenance process is performed according to set programs, a corresponding command is given by the process control computer in the transducer  8  to the control unit  10 , and from there the measuring electrode  2  is moved from its operational position into the maintenance position shown in FIG. 1 by means of the pneumatic control lines  30 . A maintenance program, as was mentioned at the beginning, can then be carried out by selectively activating the feed lines  48 . To do this, the component  64  is rotated with respect to component  54  by means of the pneumatic positioning device  125  such that a suitable connection  50 , and thus over the appropriate feed line  48 , a specific container  14  is selected. It is also possible that a rinse with water under pressure  22  is carried out and only then is the container  14  with the cleaning fluid  16  selected and fed to the rinsing chamber  28  for the electrode armature  4  over the single pump device  12  and the delivery line  26 .  
         [0047]    Cleaning or calibration programs can be freely adapted to the specific requirements by means of the process control computer. Cleaning and calibration media can be selected, if necessary, additional media can be supplied over the rinsing block arrangement  9 , and the number and sequence of the steps can be varied as desired.  
         [0048]    Program-controlled maintenance procedures can be carried out, for example, according to specifiable time intervals. It is also possible that a sensor test device in the transducer is operated, which gives a signal to perform a maintenance procedure in the event that the sensor deviates too quickly, and that such a maintenance program is subsequently performed. It is furthermore conceivable that following each mains power outage, a maintenance procedure is automatically performed.