Abstract:
Apparatus for measuring the rate of flow of a fluid in a conduit includes a receptor assembly arranged on the external surface of the conduit, and a removable external connector assembly including an electromagnet for establishing a magnetic field that extends transversely across the conduit, and a plurality of circumferentially arranged electrodes that are insertable into direct contact at their tips with the fluid in the conduit via sealable gland passages contained in the receptor assembly. A calibration adjustment arrangement is provided for adjusting the calibration factor of the flow signal processing system as a function of the conduit cross-sectional area. In a first embodiment, the glands are self sealable, whereupon the gland passages are automatically closed when the electrodes are removed therefrom. In another embodiment, the gland passages are normally open and are formed in a compressible resilient gland body, whereby radial inward compression of the gland body effects closure of the gland passages. According to a further embodiment, a valve arrangement is provided for opening and closing the gland passages.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     A magnetic flowmeter for measuring the rate of flow in a liquid includes receptor means associated with the conduit, and connector means removably connected with the receptor means, said connector means containing an end-fire electromagnet for generating a magnetic flux field transversely across the conduit, and a plurality of parallel spaced sensing electrodes that extend through sealable gland passages contained in said receptor means for direct engagement at their end tips with the fluid that flows through the conduit. The electrodes are connected with flow signal processing means that include calibration factor adjustment means that are adjusted as a function of the size of the-cross-sectional area of the conduit. 
     2. Brief Description of the Prior Art 
     Flow meters for measuring the rate of flow of a fluid in a conduit are well known in the patented prior art, as shown by the Applicant&#39;s prior U.S. Pat. Nos. 3,885,433, 4,083,246, 4,459,858 and 5,398,552. 
     In the known Faraday-type electromagnetic flow meters, a transverse magnetic field is established in a direction normal to the longitudinal axis of a conduit, and a pair of electrodes in contact with the fluid within the conduit are diametrically arranged along a line normal both to the magnetic field and to the longitudinal axis of the conduit, whereby the velocity of flow is measured by a meter as a function of the potential difference across the electrodes. 
     In the prior patent to Mannherz, U.S. Pat. No. 3,372,589, a side saddle magnetic flow meter is disclosed in which the magnetic field is produced within a relatively large pipe in a region which represents only a portion of the total cross-sectional area thereof. In order to provide an accurate reading of the flow rate through the pipe, the voltage induced in the region produces a signal that is multiplied by a factor that depends on the dimensional relationship of the region to the total cross-sectional area of the pipe. In the patent to Smoll, U.S. Pat. No. 4,195,515, a medical-type flow meter system is disclosed in which an electromagnetic assembly is removably connected by connector means with a tubular member having electrodes mounted in a common transverse plane in contact with the fluid (i.e., blood) flowing through the tabular member. By using a plurality of tubular parts in an extracorporeal circuit, measurements can be made at different points is the circuit.by moving the magnet structure part from one tubular part to another. 
     The Snook, et al., U.S. Pat. No. 4,346,604 discloses a medical electromagnetic flow meter having interchangeable housings and/or magnetic structures, use being made of alignment lugs that automatically effect a desired position and orientation of the lumen and electrode system relative to the magnetic structure., The reluctance of the magnetic circuit may be selectively altered by changing the position of an adjustment keeper, or a Hall probe may be provided for detecting the produced field and for increasing or decreasing the field strength to maintain predetermined values. 
     The aforementioned Marsh U.S. Pat. No. 4,459,858 discloses a flow meter having an electromagnetic probe which is characterized by said probe being mounted within an opening contained in the conduit for generating electrical signals as a function of the velocity of fluid flow. The probe has a debris shedding head portion which protrudes into the interior of the conduit and includes an electromagnet for generating an electromagnetic field in the fluid, the axis of the field extending normal to the direction of fluid flow. The probe further includes a plurality of electrodes arranged beyond the poles of the electromagnet and adjacent the fluid for producing the electrical signals in response to the flow of fluid through the electromagnetic field. Signal processing apparatus is connected with the sensor probe for converting the electrical signals into a flow velocity output signal. The Marsh U.S. Pat. No. 5,398,552, discloses a magnetic flow meter that has a separable magnet assembly that can be joined with a flow tube having a plurality of electrodes embedded within the flow tube. The flow tube is connected in fluid conducting relation between a pair of axially spaced sections of conduit, a first electrical connector being fixed to the outer surface of the flow tube and including first terminals electrically connected with spaced internal electrodes, respectively, that contact the fluid flowing through the tube. A second electrical connector is provided for separable connection with the first connector, which second connector includes an end-fire electromagnet for establishing a transverse magnetic field in the flow tube via the first connector, and second terminals for connecting the electrodes with a flow indicating meter via the first terminals, respectably, and a cable. In order to calibrate the meter for use with flow tubes having different internal cross-sectional dimensions, respectively, the first and second connectors are provided with cooperating size coding and decoding devices, respectively. 
     As distinguished from medical-type instruments for measuring the flow of blood, in the field of industrial process fluid flow such water-supply and waste-fluid removal flow measurement, the conduits are of relatively large size, and it is expensive to provide for each installation a separate flow-indicating meter that is calibrated in accordance with the size of the conduit. Furthermore, pipes or conduits of different internal dimensions have different flow characteristics, owing for example, to the high velocity of fluid flow near the center of the conduit, and a slower velocity near the wall of the conduit where the electrodes are relatively close to each other, so that the sensed velocity is not equal to the average or mean velocity of the flowing fluid. Additionally, as the fluid flows at a variety of velocities, this relationship between the sensed velocity and the mean velocity changes as a finction of fluid velocity. Therefore, for reasonable accuracy there must be an ability to establish a fixed gain multiplier for each pipe size as it relates to sensed velocity vs. mean velocity, and there must be additionally, for situations where higher accuracies are required the ability to have an addition correction factor multiplier that is a function of the velocity of the fluid. 
     Furthermore, the use of a probe with removable electrodes bypasses the problem of electrode fouling that could occur with the Marsh U.S. Pat. No. 5,398,552. Furthermore, having the small diameter electrodes as the only part of the assembly that must be inserted against the pressure of the contained fluid, allows for the use of the flow meter without a need for elaborate insertion hardware as in other insertible designs such as Marsh U.S. Pat. No. 4,459,858. 
     Accordingly, the present invention was developed to provide an improved flow-measuring system wherein a single flow-indicating meter and electrode/magnet assembly may be used to provide accurate flow measurements of fluid flow in a large number of conduits having different internal cross-sectional dimensions. 
     SUMMARY OF THE INVENTION 
     Accordingly, a primary object of the present invention is to provide an improved flowmeter including receptor means arranged on the outer circumferential surface of the conduit, and connector means removably connected with the receptor means, said connector means containing an end-fire electromagnet for establishing a magnetic field transversely across the conduit, and a plurality of parallel spaced sensing electrodes that extend through sealable gland passages contained in said receptor means, the tips of the electrodes being in direct contact with the fluids flowing in the conduit. The other ends of the electrodes are connected with flow signal processing means that include calibration factor adjustment means that are adjusted as a function of the cross-sectional area of the conduit. 
     Another object of the present invention is to provide an electromagnetic flow meter that is automatically calibrated for conduit size upon connection with any one of a plurality of conduits having different internal cross-sectional dimensions, respectively. 
     A more specific object of the invention is to provide an electromagnetic flow measuring system-including a flow tube that is connected in flow-transmitting relation between a pair of axially spaced sections of the conduit, including self-sealing glands and a second separable magnet/electrode assembly with a plurality of electrodes that can be easily inserted through the self-sealing access ports so as to make contact with the fluid contained within a pressurized flow tube, and an attached flow indicating meter for displaying the flow. 
     According to another object of the invention, both the flow tube and the magnet/electrode assembly are equipped with pipe size identifying means that provide for automatically calibrating the meter as a function of the internal cross-sectional dimensions of the associated flow tube. The code means may comprise spaced contacts on both the flow tube and the magnet/electrode assembly, the spacing arrangement which correspond with the cross-sectional dimensions of the flow tube, so that each spacing uniquely defines a particular flow tube size. Alternately, the code means may comprise an electronic chip embedded within the flow tube and a “chip reader” that is part of the magnet/electrode assembly. Other alternate means of coding are electrical terminals on one connector that are read by corresponding code-reading terminals on the other connector. Alternately, the calibration means may simply consist of a size identifying number imprinted on the flow tube where said size identifying number is manually inputted into the flow meter computing electronics via a local user interface. 
     According to a further object of the invention, the transverse magnetic field in the flow tube is produced by an end-fire electromagnet mounted in the magnet/electrode assembly to direct flux that is generally normal to the longitudinal axis of the conduit. 
     Another object of the invention is allow the flow tube self-sealing glands to be penetrated by temperature and pressure probes so that, in addition to flow, a measurement of both the pressure and the temperature of the fluid within the flow tube can be made by probes directly in contact with the fluid. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other objects and advantages of the invention will become apparent from the following specification, when viewed in the light of the accompanying drawings, in which: 
     FIGS. 1 and 2 are diagrammatic views illustrating an electromagnetic flowmeter of the prior art, and 
     FIG. 3 is a sectional view taken along line  3 — 3  of FIG. 2; 
     FIG. 4 is a circuit diagram of the prior art system of FIG. 2; 
     FIG. 5 is a sectional view of an invasive probe arrangement of another prior art flowmeter; 
     FIG. 6 is an exploded perspective view of the improved self-sealing invasive flowmeter of the present invention; 
     FIG. 7 is a sectional view taken along line  7 — 7  of the assembled embodiment of FIG. 6; 
     FIGS. 8-10 are detailed sectional views of applications of the invention of FIGS. 6 and 7 as applied to conduits of varying sizes, respectively, and 
     FIGS. 11-13 are sectional views taken along lines  11 — 11 ,  12 — 12  and  13 — 13  of FIGS. 8-10, respectively; 
     FIG. 14 is a sectional view of a modification of the invention of FIGS. 6 and 7, and 
     FIG. 15 is a sectional view taken along line  15 — 15  of FIG. 14; 
     FIGS. 16 and 17 are detailed sectional views illustrating coding arrangments for us with conduits having diameters of different sizes, respectively; 
     FIG. 18 is a detailed sectional view of a probe having intrusive pressure sensing and temperature sensing intrusive probes, respectively; 
     FIG. 19 is a detailed sectional view of a modification of the invention that is sealable by radially inwardly compressible resilient means; and 
     FIGS. 20 and 21 are detailed sectional views of a sealable valve embodiment of the invention in the open and closed position, respectively. 
    
    
     DETAILED DESCRIPTION 
     Referring first more particularly to FIGS. 1-4, in the prior Marsh U.S. Pat. No. 5,398,552, the known Faraday-type flow measuring system of FIG. 1 for measuring the flow F of fluid in a conduit  2  includes a pair of electrodes  4  and  6  arranged diametrically of the conduit and normal to the magnetic field β that extends transversely of the conduit. The flowmeter measures the potential difference across the electrodes, thereby affording an indication of the velocity of fluid flow. 
     In the embodiment of FIG. 2, a flow tube section  10  is connected between the axially spaced sections  12   a  and  12   b  of the conduit  12 , a first electrical connector  14  being mounted on the outer surface of the flow tube section  10 . As shown in FIG. 3, a first electrical connector  14  is mounted on the outer surface of the conduit, and includes first terminals  16  electrically connected with spaced integral electrodes  18 ,  20 , and  22  that contact the fluid flowing in the conduit. A second electrical connector  24  is separably connected with the first connector  14 , which second connector contains an end-fire electromagnet  28  for establishing the transverse magnetic field β in the conduit, and a plurality of second terminals  26  for connecting the first terminals with the flowmeter  30  via the cable  32 . In order to calibrate the meter for use with a plurality of flow tubes having different cross-sectional dimensions, the first and second connectors are provided with cooperating size coding and decoding devices, respectively. 
     As shown in the aforementioned Marsh U.S. Pat. No. 5,398,552, the first electrical connector means mounted on the flow tube is provided with a plurality of stationary code tabs the arrangement of which corresponds with the internal cross-sectional dimensions of the flow tube. Similarly, as shown in FIG. 4, the corresponding end face of the second electrical connector  124  contains a plurality of openings  148  for receiving the code tabs  146  respectively, thereby to operate the appropriate normally-open switches  150   a ,  150   b ,  150   c ,  105   d  that are connected with the conduit size identifier means  152 . In accordance with the size of the conduit determined by the conduit size identifier means  152 , the calibration factor selector means  154  connects a corresponding calibration factor device CF 1 , CF 2 , CF 3 , or CF 4 , with the flowmeter  130  via gain modifying means  142 , thereby to automatically calibrate the flowmeter  130  in accordance with the internal cross-sectional dimensions of the associated flow tube  110 . If desired, a heat-sensing probe  160  may be provided on a second connector  124  that extends within a corresponding female receptacle  162  that is connected in heat-transmitting relation with a thermal probe that is in contact with, and sensitive to the temperature of, the fluid flowing through the flow tube  110 . Thus, the heat of the fluid as sensed by the probe  164  is transmitted by the male member  160  to the heat processing means  166 , which sends the appropriate heat-responsive signal to the display  131  to adjust correspondingly the reading of the flow meter  130 . 
     Referring now to the prior art embodiment of FIG. 5, the electromagnetic probe. sensor  200  has a tip portion  200   a  that extends into the conduit  202  through a radial opening contained in the wall thereof for direct engagement with the fluid flowing therethrough. The probe includes a pair of sensing electrodes  204  that are connected with the flow signal processing means  206  by means of cable  208 . An end-fire electromagnet (not shown) is contained within the probe body for generating a flux field that extends transversely across the conduit—i.e., generally normal to the longitudinal axis of the conduit. The insertion probe is provided with rather complicated mounting hardware that allows the sensor probe to be inserted into the conduit without stopping the flow of fluid through the conduit., More particularly, the probe body is carried by an end plate  210  that is vertically displaceable by means of threaded bolts  212  and nuts  214 . Rotary valve means  216  close the probe opening as the probes removed, and sealing gland means  218  further seal the opening. It is important to note that owing to the size of the opening in the conduit wall, a substantial amount of force is required to insert the probe into the opening against the fluid pressure force. Furthermore, upon withdrawal of the probe, a substantial amount of sealing force is required. 
     According to the present invention as shown in FIGS. 6 and 7, receptor means  300  are carried by the outer circumferential.surface of a tubular section  302  that is inserted between and in communication with the sections  304   a  and  304   b  of the conduit  304 . Separable connector means  310  are provided that include a connector body  312  containing the end-fire electromagnet  314  that produces the magnet flux β that extends transversely of the conduit, as shown in FIG.  7 . The receptor means contains a plurality of resilient tubular self-sealing glands  318  mounted in parallel though bores contained in the receptor means  300 . Removably extending through the glands  318  are a plurality of parallel sensing electrodes  320  and ground electrode  321  having first end extremities or tips  320   a ,  321   a  that are in direct communication with the fluid flowing though conduit  302 . The other ends  320   b ,  321   b  of the electrodes are carried by the connector body  312  and are electrically connected with the flow meter  324  by conductors  326 . Power supply means  328  provides power to the electromagnetic coil  314  and to the flow meter  324 . 
     In accordance with an important feature of the invention, the flow meter  324  includes calibration factor adjustment means  326  in the form of a gain modifier that may be manually adjusted by keyboard means  328  in accordance with the cross-sectional dimensions of the conduit  304  as determined from visible indicia on the outer surface thereof. Alternatively, the gain modifier may be adjusted by a signal supplied by conductor  330  as determined by coding electrodes  332  that engage corresponding openings  334  in the receptor means to read memory chips carried by the receptor means that are characteristic of the size of the cross-sectional dimensions of the conduit. As distinguished from the prior art embodiment of FIG. 5 having a relative large wall opening requiring great resistance to the fluid pressure force, owing to the relative small diameters of the sensing electrodes (on the order of 0.1 inch), the force resisting the pressure force of the fluid is much smaller according to the invention of FIGS. 6 and 7. In fact, a 1 inch probe would require 100 times the force of a 0.1 inch probe. Thus, the present invention affords the advantage that owing to the insertion of electrodes having only small diameters into the self-sealing gland passages, the insertion of the electrodes can be achieved without expensive valve arrangements and associated hardware, thereby avoiding the safety concerns that are present when large probes are inserted into high pressure lines. 
     Referring now to FIGS. 8-13, there are illustrated three receptor sections  400 ,  402 , and  404  having progressive decreasing diameters d 1 , d 2 , and d 3 , respectively; In these conduits, the circumferential spacing distance between the glands  406 ,  408 , and  410  progressively decreases, respectively. The tubular receptor sections  400 ,  402 , and  404  are-connected between, and are in communication with, the conduit sections  412   a ,  412   b ;  414   a ,  414   b ; and  426   a ,  416   b , respectively. 
     Referring now to FIGS. 14 and 15, the receptor means may be in the form of a separate receptor body  500  that is mounted externally of the unitary conduit  502  by a pair of circumferentially extending straps  504  and  506 . After the receptor body is rigidly mounted in place (as best shown in FIG.  15 ), access holes are drilled through the wall of the conduit by inserting the bit  508  of a drill  510  through the passages of the self-sealing resilient glands  512 ,  514 , and  516 , respectively. 
     Referring now to FIGS. 16 and 17, a coding arrangement is illustrated wherein the gain modifier means of the flow meter is adjusted in accordance with the size of the conduit that contains the fluid being measured. In the illustrated embodiment of connector body  600  contains at one end a recess  602  having a bottom wall  604  that supports a plurality of aligned laterally-spaced electrical contacts  608  that are connected with the respective gain modifying means of the flow meter. Electrode support members  610  (FIG. 16) and  612  (FIG. 17) are insertable within the connector body recess  602 , which support members carry spaced electrodes  614  and  616  having spacing distances d 4  and d 5  that correspond with the size of the fluid conduit. In the FIG. 16 illustration, the electrodes  614  carried by the electrode support body  610  engage a first set of contacts  608   a ,  608   b , and  608   c  to effect a first gain modification corresponding to a conduit having a large cross-sectional area, and in the FIG. 17 embodiment, the electrodes engage a second set of contacts  608   d ,  608   b , and  608   e  to effect a gain modification corresponding to a smaller dimensional conduit. 
     As shown by the embodiment of FIG. 18, in addition to the spaced electrodes  702 , the probe body  700  carries additional probes for measuring other parameters of the fluid flowing through the conduit. More particularly, the hollow fluid pressure sensing probe  704  is connected with the pressure transducer  706  mounted within the connector body for generating a pressure signal VP, and measuring sensor probe  708  is connected with temperature sensor means  710  that produces the temperature responsive signal Vt. These devices, of course, operate independently of the end-fire flux-producing coil  712 . 
     In each of the embodiments described above, the electrodes have a relatively small size (i.e. a diameter on the order of 0.1 inch) relative to the conventional probe of the prior art shown in FIG.  5 . This permits simple manual insertion or removal of the electrodes from the receptor body, the self-sealing resilient glands preventing leakage from the conduit. 
     Of course, other arrangements may be provided that do not include self-sealing glands. In the embodiment of FIG. 19, a resilient radially inwardly-compressible gland body  800  is mounted within a chamber contained in the receptor body  802  that is mounted on the conduit  804 . The receptor chamber has sloped, converging side walls  806  that are engaged by the gland body  800 . The lower surface of the gland body is supported by a stationary support member  8 . 10 , and a rigid operating disk  812  is supported by the upper surface of the gland body. Through passages  816 ,  818 , and  820  for receiving the respective sensing electrodes extend successively through the operating disk  812 , the gland body  800 , the stationary support  810 , and the conduit wall. Annular actuating member  826  is threadably connected with the upper end of the receptor body. Thus, by rotation of the activating rim, the operating disk  812  may be displaced downwardly to effect radial inward compression of the gland body  800 , thereby to close the electrode passages  816 ,  818 , and  820 , and thus seal the conduit against leakage. To install the electrodes, they are partially inserted within the portions of the passages contained in operating disk  812 , whereupon rim  826  is rotated to relieve the forces of compression applied to the gland member  800 , resulting in the opening of the electrode passages that extend therethrough. The electrodes may then be inserted further downwardly through the support body  810  and the conduit wall openings so that the tips of the electrodes come into contact with the fluid in the conduit. 
     In the embodiment of FIGS. 20 and 21, a rotary shut-off valve  900  is provided for opening and closing the electrode passages  902 ,  904 ,  906  that extend through the gland body  910 . Thus, when the valve  900  is in the closed position of FIG. 21, the electrodes may be partially introduced into the upper ends of the electrode passages, whereupon the valve  900  may be rotated to the open position of FIG. 20 to permit full insertion of the electrodes to portions in which the tips of the electrodes engage the fluid within the conduit  916 . 
     While in accordance with the.provisions of the Patent Statutes the preferred forms and embodiments of the invention have been illustrated and described, it will be apparent that changes may be made without deviating from the inventive concepts set forth above.