Abstract:
A temperature sensing probe assembly for correcting fluid volume readout of a fluid meter in response to fluid temperature in relation to a standard measurement of temperature for the fluid. A temperature sensitive bimetallic probe is adapted to be immersed in the meter fluid and is enclosed in a tubular metal sheath for protecting the probe against potential injury when handled. Perforations in the sheath enable direct contact between the fluid and the probe.

Description:
FIELD OF THE INVENTION 
     The field of art to which the invention relates comprises meters for measurement of fluid flow volume and having a sensing probe for effecting temperature correction of fluid volume at temperatures deviating from a standard temperature for the metered fluid. 
     BACKGROUND OF THE INVENTION 
     In fluid meters of the type commonly utilized for the volumetric measurement of gaseous fluids, such as gas meters, density of the gas and hence its heating value per unit of volume varies with changes of gas temperature. Consequently, the volume of gas passing through the meter, as recorded on an indicator driven by the meter, does not actually indicate what the volume would measure at a standard temperature used for computing the cost of gas consumed. Variations in gas density due to temperature changes thus result in under-registration of the meter at low temperatures and over-registration at high temperatures. It is therefore necessary, particularly in the case of a large gas-using installation to provide means to compensate for the effect of temperature variation. 
     BACKGROUND OF THE PRIOR ART 
     A mechanism for temperature correction of metered fluid is disclosed for example in U.S. Pat. No. 3,581,566 incorporated herein by reference. Disclosed therein is a mechanical compensating device which automatically compensates for temperature deviations via a volume correction mechanism that controls the drive of a compensated register. By compensating in this manner, the volumetric displacement of the meter is automatically corrected for variations in gas temperature from a standard based temperature so as to establish an accurate measurement for the consumer. 
     Such mechanisms as disclosed in the aforementioned &#39;566 patent includes an elongated temperature probe of a wound bimetallic construction. The probe is emerged in the fluid flow and senses fluid temperature passing through the meter. In response to temperature changes, the probe serves to mechanically vary the counter index for correcting the volume readout to a predetermined standard or base temperature. 
     The probe, in this arrangement, is supported within the meter extending cantilevered into the flow path of the passing fluid. At such time as the probe needs to be serviced or replaced, it is customary to withdraw the probe from its meter support and service or replace it as required. Yet because the probe, is of a wound elongated fragile construction and cantilevered over a substantial portion of its length, handling can prove difficult to avoid injury during repair or replacement that could impair its operational accuracy. At the same time, the distal end of the cantilevered probe being unsupported has a tendency to droop whereby a rubbing contact can be incurred that likewise can adversely affect its operational accuracy. 
     Despite recognition of the foregoing, a ready solution for safeguarding the probe during repair or replacement has not heretofore been known. 
     OBJECTS OF THE INVENTION 
     It is therefore an object of the invention to provide apparatus for protecting the probe unit of temperature correction apparatus for a fluid meter against injury when handled. 
     It is a further object of the invention to utilize a structure that largely encloses and supports the probe against injury at least when serviced, manufactured, shipment, assembly, testing, retrofit, etc. 
     It is a still further object of the invention to effect the previous objects with a structure that is substantially uncostly to fabricate and relatively easy to assemble about the probe. 
     SUMMARY OF THE INVENTION 
     The invention relates to a protective article for a corrective temperature probe of a fluid flow meter. More specifically, the invention relates to a novel construction of such an article that can protect the fragile probe against injury during handling of the probe in situations that could otherwise result in damage producing operational inaccuracies for effecting temperature correction within the meter. 
     The foregoing is achieved in accordance with the invention utilizing a tubular metal sheath closely surrounding the injury prone probe. The sheath is preferably of a weldable metal composition, such as stainless steel, that closely surrounds the probe and is secured at its ends within the meter. The sheath is internally sized to permit arcuate displacement of the bimetallic sensing elements in response to temperature changes to which is exposed along its length. Preferably, the sheath includes a plurality of open slots through which a cross flow of fluid within the meter can contact the sensing element for permitting temperature changes to be encountered. When connected as to an operative reset mechanism of the meter, correction reset occurs continuously on an ongoing basis. Yet by virtue of the surrounding sheath, handling injuries such as has occurred in the past is eliminated so as to benefit from a substantially increased life expectancy and continuing accuracy of the probe unit. 
    
    
     The above noted features and advantages of the invention as well as other superior aspects thereof will be further appreciated by those skilled in the art upon reading the detailed description that follows in conjunction with the drawings. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a fragmentary pictorial view of a prior art compensation device as disclosed in U.S. Pat. No. 3,581,566; 
     FIG. 2 is a diagrammatic cutaway of the braking and driven arm assemblies of the prior art unit of FIG. 1; 
     FIG. 3 is a diagrammatic representation of the prior art device of FIG. 1; 
     FIG. 4 is an isometric view of the probe protector sheath in accordance with the invention hereof; 
     FIG. 5 is a first side view embodiment of a sheath installation utilizing the sheath of FIG.  4 : 
     FIG. 6 is an end view of the apparatus embodiment of FIG. 5; 
     FIG. 7 is a fragmentary and enlarged sectional view as contained in the encircled portion  7  of FIG. 5; 
     FIG. 8 is an enlarged partially broken away fragmentary view of encircled portion  8  of FIG. 5; 
     FIG. 9 is a second side view embodiment of a sheath installation utilizing the sheath of FIG. 4; and 
     FIG. 10 is an end view of the apparatus embodiment of FIG.  9 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     In the description which follows, like parts are marked throughout the specification and drawings with the same reference numerals respectively. The drawing figures are not necessarily to scale and in certain views, parts may have been exaggerated for purposes of clarity. 
     Referring now to FIGS. 1-3 of the drawings, there is illustrated a commercially available temperature correction device, as disclosed for example in U.S. Pat. No. 3,581,566. As therein disclosed, the correction device is designated  10  and is adapted to be self-contained in a conventional fluid meter of the fixed or constant displacement type. Probe  80  provides the sensing of fluid temperature while device  10  includes a fixed throw eccentric mechanism comprising a disc crank  11  on rotatable shaft  12 . A connecting rod  14  is pivotally mounted at a lower end to disc  11  by a pin  15  offset from the axis of shaft  12 . The latter shaft is arranged to be driven by an output element  17  of a constant displacement meter through a conventional gear train so that its rotational movement is a measure of the quantity.of gas passing through the meter. Element  17  is magnetically coupled to the meter rotor shaft which isolates the pressurized meter body on the compensated counter assembly. 
     For translating rotary movement of shaft  12  and disc  11  to the drive mechanism of compensated register  41  of counter assembly  40 , the upper end of connecting rod  14  is pivotally connected by pin  16  to a driving arm  30  mounted on an idler bearing  31  on counter shaft  240  to oscillate accurately about shaft  240 . A driven arm  32  having an adjustable engaging surface  33  pivoted at one end about shaft  240  has a spring  34  forcing opposite end  38  of arm  32  against a cam  35  driving one portion of the cycle. Driving arm  30  includes an L-shaped surface  36  engaging surface  33  of driven arm  32  during a portion of the cycle. In order to actuate compensating register  41 , driven arm  32  carries a suitable over-riding one-way clutch  37  which is drivably associated with counter shaft  240 . 
     In operation of the apparatus, fluid temperature is sensed by a bimetallic temperature sensing probe  80  inserted in the metered fluid. Rotation of the probe is caused by temperature variations that cause rotation of cam  35  about cam shaft  81 . Driving arm  30  is caused to oscillate in a first arc about the idler bearing  31 . The arc of oscillation of driven arm  32  however, is less than that of driving arm  30  with the reduced second arc being limited in one direction by the angle of cam  35  and in the other direction by the limit of the arc of driving arm  30 . Being that the driven arm  32  is held against cam  35  by spring  34  until L-shaped surface  36  engages surface  33 , it causes the L-shaped portion  38  of driven arm  32  to be lifted from the cam. Cam  35 , having an angle dependent upon the temperature of the meter fluid thereby changes the position of cam  35 , and the reduced arc of the driven arm  32  is thus varied. 
     Referring now to FIGS. 4-8 a first embodiment of a temperature sensing unit including a sheath  20  in accordance with the invention hereoffor protecting temperature sensing probe  80  against injury. In a first embodiment, sheath  20  is removable as would be useful with variations in meter well size. Protective sheath  20  is formed in a tubular configuration for connection to a tubular connector flange  22 , and includes a plurality of a parallel, elongated slots  21  through which gaseous fluid can flow in contact with spiral wound bimetallic sensor coil  24 . The distal end of sensor coil  24  is spot welded at a distal end  26  of rotatable shaft  28  and the proximal end of sensor coil  24  is spot welded to the distal end  27  of connector flange  22 . Rotatable shaft  28  extends through both bearings  42  assembled to opposite ends of connector flange  22 .while the distal end  46  of sheath  20  in this embodiment, is fully open. 
     The head or inward end  48  of the compensating unit is comprised of a working cam  50 , a hub  52 , and a dial  54  along with a balance cam  56 . Cam  56  and dial  54  are joined via riveting in a well known manner to form a dial assembly  58  that is secured together with cam  50  and hub  52  in a sandwich relation as by staking. After calibrating sensor  24 , set screw  60  in hub  52  is tightened, locking head assembly  48  firmly to shaft  28 . Excess material of shaft  28  is removed and the head end of shaft  28  is welded at  62  to hub  52  (FIG.  8 ). Reference pointer  64  is affixed to a groove (not shown) of flange  22  aligned with indicia markings thereat on dial  54 . 
     The foregoing, absent sheath  20 , is assembled and secured together after which sheath  20  is added as best seen in FIG. 7 to afford protection against injury of the sensor  24  during mechanical handling. Sheath  20  is preferably comprised of stainless steel or other metal suitable for welding with a wall thickness of about 0.007-0.030 inches, and preferably is of a thickness of about 0.010 inches. A primary use of the sheath is in a field retrofit installation where the installer might inadvertently incur a misalignment in attempting to insert a new probe onto the meter thermo-well such that an injury to the sensor elements could readily occur. The removable feature of the sheath attachment is afforded by an O-ring  66  that provides a frictional fit with the sheath as best seen in FIG. 7, while affording sheath removability such as where insertion resistance is encountered as a result of manufacturing tolerances. 
     By means of the slots  21 , contact between the metered fluid and sensor  20  is readily effected not only by natural gas but also with even more viscous media such as ethylene glycol that impinge directly against the sensor so as to improve heat transfer and subsequent cycle time during calibration testing of the unit. For this embodiment, the sheath is utilized only during installation and then removed during operation or can optionally be left in place where a suitable fit is effected. 
     Referring now more specifically to FIGS. 9 and 10, there is disclosed a second embodiment of sheath which is non-removable and permanent and not intended for removal subsequent to initial installation. It will be noted on comparison, that the two embodiments differ in only minor details such that in the second embodiment, sheath  20  includes a greater length while flange  22  is of a shorter length with a stub  68  to receive sheath  20  in an overfit. Upon receipt, sheath  20  is secured by a weld  70  to flange  22 . Also there is included in the second embodiment a PTFE bearing  72  at an intermediate location within sheath  20 , between the inward end of sensor  24  and the weld  70 . Another difference is the distal end of sheath  20  in the second embodiment is spot or fully welded to a hollow end plug  74  that facilitates draining of test fluids and the like. Moreover, by virtue of the non-removable construction, bearings  72  at both ends of shaft  28  preclude sensor drooping that might otherwise occur. 
     By the above description there is disclosed a novel construction for protecting a temperature sensitive probe of a temperature corrected flow meter installation. With a relatively inexpensive metal sheath installed in an enveloping relation about the probe, the probe is protected against handling injuries such as are commonly encountered during manufacturing, shipment, calibration and retrofitting. While amounting to a relatively simple and inexpensive solution to a long standing problem, previous probe injuries commonly encountered during such occasions have been largely if not completely eliminated by means of the invention. The virtues thereof should be readily apparent to those skilled in the art. 
     Since many changes could be made in the above construction and many apparently widely different embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained in the drawings and specification shall be interpreted as illustrative not in a limiting sense.