Abstract
The present disclosure relates to a magnetically inductive flowmeter for determining flow velocity and/or volume flow of a medium, the flowmeter including a measuring tube for conveying the medium, a magnetic field producing means and at least one electrode assembly, which is installed in the measuring tube in such a manner that it forms a galvanic contact with the medium, wherein the electrode assembly has an electrode body, wherein the electrode body is stylus shaped and has a front end surface, wherein a pressure measuring transducer is coupled with the electrode body, and wherein the pressure measuring transducer is contactable with the pressure acting on the front end surface.
Claims
1-15. (canceled)
16. A magnetically inductive flowmeter for determining flow velocity and/or volume flow and pressure of a medium, the flowmeter comprising: a measuring tube adapted to convey the medium; a magnetic field producing means; and at least one electrode assembly disposed in the measuring tube as to form a galvanic contact with the medium, the at least one electrode assembly comprising an electrode body, which is generally stylus-shaped and has a front end surface, and a pressure measuring transducer coupled with the electrode body, wherein the pressure measuring transducer is configured to be acted upon by a pressure acting on the front end surface.
17. The flowmeter of claim 16, wherein the pressure measuring transducer includes a measuring membrane.
18. The flowmeter of claim 16, wherein the electrode body includes a bore open to the measuring tube.
19. The flowmeter of claim 18, wherein the bore defines a passageway that forms an integrated pressure supply duct for conveying the medium.
20. The flowmeter of claim 16, wherein the electrode body is connected terminally with a hollow body.
21. The flowmeter of claim 20, wherein the at least one electrode assembly further comprises a housing containing the pressure measuring transducer, the housing connected to the hollow body by material bonding.
22. The flowmeter of claim 21, wherein an electrical contacting of the electrode body is effected via the hollow body and/or the housing.
23. The flowmeter of claim 21, wherein the housing includes at least one contacting apparatus via which the electrode assembly is electrically contacted with a measurement and/or evaluation unit.
24. The flowmeter of claim 16, wherein the magnetic field producing means comprises at least one coil and at least one coil core disposed in an interior of the at least one coil, wherein the at least one coil core is embodied as a hollow cylinder, and wherein the at least one electrode assembly is disposed in the interior of the at least one coil core.
25. The flowmeter of claim 24, wherein the at least one coil core has an interior surface, and wherein the at least one electrode assembly further comprises insulation disposed between the interior surface and the housing, which is disposed within the at least one coil core.
26. The flowmeter of claim 16, wherein the electrode body includes an electrode head, wherein the electrode head has a contour.
27. The flowmeter of claim 16, wherein the electrode body comprises a fill level monitoring electrode and/or a reference electrode and/or a measuring electrode configured to sense a measurement voltage in the medium.
28. The flowmeter of claim 16, wherein the electrode body is configured as a peg electrode, a pointed electrode or a mushroom electrode.
29. The flowmeter of claim 20, wherein the electrode body has a basic terminal shape embodied as a cone or a frustum, and wherein the hollow body includes a seat adapted for the electrode body, which seat is configured complementary to the basic terminal shape of the electrode body.
30. The flowmeter of claim 29, wherein the basic terminal shape includes a surface element and a cone axis, which together form an angle of between 5° and 25°.
Description
[0050] The invention will now be explained in greater detail based on the appended drawing, the figures of which show as follows:
[0051] FIG. 1 a schematic view of a tube cross section of a magnetically inductive flowmeter of the state of the art;
[0052] FIG. 2 a schematic, exploded view of an electrode assembly of the invention;
[0053] FIG. 3 a schematic view of a longitudinal section of a magnetically inductive flowmeter of the invention;
[0054] FIG. 4 a longitudinal section of the hollow body of the invention and a detail view; and
[0055] FIG. 5 a longitudinal section of the electrode body of the invention and a detail view.
[0056] FIG. 1 shows a known magnetically inductive flowmeter. The construction and the measuring principle of magnetically inductive flowmeters are basically known. An electrically conductive medium is conveyed through a measuring tube (1). A magnetic field producing means (7) is so arranged that its magnetic field lines extend perpendicularly to a longitudinal direction defined by the measuring tube axis. Suited as magnetic field producing means (7) is preferably a saddle coil or a pole shoe (26) with superimposed coil (23) and coil core (24). In the case of applied magnetic field, there arises in the measuring tube (1) a flow dependent potential distribution, which is sensed with two measuring electrodes (3, 4) mounted at the inner surface of the measuring tube (1). As a rule, the electrodes (3, 4) are arranged diametrically opposite one another and form an electrode axis, which extends perpendicularly to the magnetic field lines and to the longitudinal axis of the tube. Based on the measured voltage and taking into consideration the magnetic flux density, flow velocity and the tube cross sectional area, volume flow of the medium can be determined. In order to avoid short-circuiting of the measurement voltage on the measuring electrodes (3, 4) through the tube (8), the inner surface is lined with an insulating material e.g. in the form of a plastic liner (2). The magnetic field produced by a magnetic field producing means, for example, an electromagnet, results from a direct current of alternating polarity clocked by means of an operating unit. This assures a stable zero-point and makes the measuring insensitive to influences resulting from multiphase materials, inhomogeneities in the medium or low conductivity. A measuring unit reads the voltage between the measuring electrodes (3, 4) and outputs flow velocity and/or volume flow of the medium calculated by means of an evaluation unit. Usual magnetically inductive flowmeters have supplementally to the measuring electrodes (3, 4) two other electrodes (5, 6). On the one hand, a fill level monitoring electrode (5), which is mounted optimally at the highest point in the tube (8) and has only a minimum distance to the tube inner surface, serves to detect a partial filling of the measuring tube (1). This information is forwarded to the user and/or taken into consideration for ascertaining volume flow. Furthermore, a reference electrode (6), which is mounted usually diametrically opposite the fill level monitoring electrode (5), serves to assure a sufficient grounding of the medium.
[0057] As shown in FIG. 2, the pressure measuring transducer (12) is a part of the electrode assembly (10), which supplementally comprises at least one electrode body (11). The pressure measuring transducer (12) is, in such case, located in a housing (16), which is conductive and, thus, provides an electrical contact between electrode body (11) and a contacting apparatus (18) mounted terminally on the pressure measuring transducer (12) manufactures. Thus, the entire electrode assembly (10) is in galvanic contact with the medium. In a further development, a hollow body (14) forms a hollow space (19) between the pressure measuring transducer (12) and the electrode body (11), or the outlet of the bore (15) embodied as pressure supply duct. Thus, the pressure of the medium acting on the front end surface of the electrode body (11) is led via the pressure supply duct to the measuring membrane (13), where it is detected. Furthermore, the housing (16) is connected by material bonding with the hollow body (14). The electrode body (11) includes an electrode head (17), wherein the electrode head (17) has a contour. The contacting apparatus (18) serves for tapping the pressure of the medium converted into an electrical, or digital, signal for a measurement- and/or evaluation unit (9). In such case, the contacting apparatus (18) includes at least one pin, which is in an electrical contact with the housing (16) and, thus, with the electrode body (11). The hollow body (14) is embodied in such a way that it forms, on the one hand, a hollow space (12) between measuring membrane (13) and electrode body (11) and, on the other hand, seals the electrode body (11) in such a manner that the medium flowing through the pressure supply duct cannot escape via the contact area. The electrode body (11) includes an external screw thread, which serves to secure the electrode body (11) to the measuring tube (1) and to connect to the hollow body (14), which has an internal thread.
[0058] The magnetically inductive flowmeter shown in FIG. 3 includes an electrode assembly (10), which comprises a stylus shaped electrode body (11) having an electrode head (17) having a contour (20), an insulating sleeve (21), a nut (22), a hollow body (14) and a pressure measuring transducer (12). The electrode body (11) includes a screw thread, which serves, on the one hand, for securing the electrode body (11) to the measuring tube (1) with a nut (22), and, on the other hand, for connecting to the hollow body (14) and/or the pressure measuring transducer (12). For mounting the electrode assembly (10) to the measuring tube (1), the electrode body (11) is led through an opening provided in the tube (8) and liner (2) and secured with an insulating sleeve (21) and a nut (22) outside of the tube. The hollow body (14) has an internal thread, such that the hollow body (14) with the shape interlocked pressure measuring transducer (12) can be screwed onto the screw thread of the electrode body (11). The hollow body (14) is embodied to produce a sealed contact to the electrode body (11), so that the medium flowing through the bore cannot escape at the contact location between the two components. The seal is preferably embodied as a conical seal. The electrode assembly (10) shown in FIG. 3 is embodied as a fill level monitoring electrode (5) and is arranged in the interior of a coil (23), especially in the interior of a coil core (24). For this further development, it is necessary to provide the coil core (24) as a hollow cylinder and to insulate the electrode assembly (10) electrically from the magnetic field producing means (7), especially the coil (23) and the coil core (24). The insulation (25) can be implemented by a coating of the inside of the coil core (24) with an electrically insulating material or by the introduction of an electrically insulating, hollow cylinder between the coil core (24) and the electrode assembly (10).
[0059] The hollow body (14) shown in FIG. 4 has a first end and a second end. Provided on the first end is an opening, which forms together with the housing of the pressure measuring transducer a hollow space (19). The second end includes a seat (29) for the electrode body. The seat (29) includes an internal thread (32), which serves to connect the hollow body (14) releasably with the electrode body. The seat (29) is at least partially cylindrically embodied and includes a region, which tapers conically narrower in the direction of the hollow space (19) and which is formed complementary to the terminal region of the electrode body. In the tapering region of the seat (29), seat (29) assumes the shape of a frustum. Seat (29) can have on its inlet end an additional region, which is embodied conically, in order to facilitate introduction of the electrode body. The hollow space (19) and the seat (29) are connected together via a passageway (33). The passageway (33) and the seat (29) have a shared axis (34) of symmetry.
[0060] The detail view shows a section of the longitudinal section of the hollow body (14). The seat (29) has an inner diameter, which continuously decreases in the direction of the hollow space (19). In this way, the seat (29) assumes in the region at least partially the shape of a frustum. The seat (29) includes a stop surface (35) for the electrode body. The conical tapering includes a surface element (30), which intersects the stop surface (35). A vertical line from the stop surface (35), or the cone axis (31), and the surface element (30) form an angle ϕ.sub.H, which preferably lies between 5° and 25°. In the case of the shown embodiment, ϕ.sub.H=10°, with a dimensional tolerance of −1°.
[0061] FIG. 5 shows an electrode body (11) of the invention with a bore (15), which is embodied as a pressure supply duct. The electrode body (11) is at least partially embodied as a hollow cylinder. In a region, the electrode body (11) has an external thread (36), which serves to connect the electrode body (11) releasably with the hollow body (14). In a terminal region of the electrode body (11), which goes into the seat of the hollow body (14), the outer diameter of the electrode body (11) becomes less in the direction of the hollow body (14). The terminal region is conically shaped and assumes the basic terminal shape of a frustum having a bore (15), wherein the bore (15) and the frustum have a shared axis of symmetry (34). In the assembled state, the lateral surface (37) of the terminal region is in contact with the hollow body. Upon the screwing together of the electrode body (11) and the hollow body, the lateral surface (37) comes into contact with the inner lateral surface 38 of the hollow body (14). If further force is exerted on the electrode body (11), then a deformation of the terminal region of the electrode body (11) in the direction of the symmetry axis (34) results. The electrode body (11) does not necessarily have to contact the stop surface (35). A gap can remain between the stop surface of the hollow body and the electrode body (11).
[0062] The detail view shows the terminal region of the electrode body (11). The outer diameter of the electrode body (11) decreases in the direction of the terminal end, while the diameter of the bore (15) remains constant. The result is a decrease of the wall thickness in the terminal region. The transition from the terminal end surface to the lateral surface (37) of the electrode body (11) is rounded. A surface element (30) and the cone axis (31) of the basic terminal shape form an angle ϕ.sub.E, which preferably lies between 5° and 25°. The angles ϕ.sub.H and ϕ.sub.E are so tailored to one another that the difference ϕ.sub.E−ϕ.sub.H lies between 0° and 4°. In the illustrated embodiment, the angle ϕ.sub.E=10° with a dimensional tolerance of +1°.
LIST OF REFERENCE CHARACTERS
[0063] 1 measuring tube [0064] 2 liner [0065] 3 first measuring electrode [0066] 4 second measuring electrode [0067] 5 fill level monitoring electrode [0068] 6 reference electrode [0069] 7 magnetic field producing means [0070] 8 tube [0071] 9 measuring-, operating- and/or evaluation unit [0072] 10 electrode assembly [0073] 11 electrode body [0074] 12 pressure measuring transducer [0075] 13 measuring membrane [0076] 14 hollow body [0077] 15 bore [0078] 16 housing [0079] 17 electrode head [0080] 18 contacting apparatus [0081] 19 hollow space [0082] 20 contour [0083] 21 insulating sleeve [0084] 22 nut [0085] 23 coil [0086] 24 coil core [0087] 25 insulation [0088] 26 pole shoe [0089] 27 field-guide material [0090] 28 basic terminal shape [0091] 29 seat [0092] 30 surface element [0093] 31 cone axis [0094] 32 internal thread [0095] 33 passageway [0096] 34 symmetry axis [0097] 35 stop surface [0098] 36 external thread [0099] 37 lateral surface [0100] 38 inner lateral surface
