MXPA99008004A - Sensor assembly for a flu flow meter - Google Patents

Abstract

A sensor assembly for a fluid flow meter, more particularly a gas meter, includes a pressure reservoir made of a non-magnetic matedal and a sensor which is removable from reservoir without depressurizing the fluid line in which it is placed the flow meter. The pressure reservoir is mounted within a bore formed in a protuberance of the body of the meter and, in a preferred embodiment, extends through the inner rotor housing and includes an internal face contoured to conform to the internal wall of the housing. In certain embodiments of the invention, the sensor is formed to cover the mounting screws of the pressure tank so that the tank can not be removed without first removing the sensor. In other embodiments, the mounting screws of the pressure vessel are retained in the pressure vessel by means of spikes, stakes or retaining rings such that the screws must be gradually and sequentially loosened to remove the pressure vessel, in order to avoid improper removal of the pressure vessel from the body bump. In still other embodiments, the pressure reservoir is screwed directly to the body protrusion or includes a threaded collar and a sleeve which is rotatable to facilitate placement of a contoured face relative to the internal wall of the housing. In such embodiments the body protrusion includes an annular depression which allows the pressurized fluid to escape between the pressure reservoir and the protuberance of the body as the pressure vessel is removed, whereby an audible warning is provided that the line in the which is mounted the meter is pressurized

Description

SENSOR ASSEMBLY FOR A FLUID FLOW METER BACKGROUND The present invention relates to fluid flow meters for measuring the proportion of fluid flowing through a pipe or conduit, and more particularly, to gas utility meters that use a rotor with vanes or vanes and a sensor that does not make contact. Flow meters of a type commonly used as commercial utility meters include a housing that encloses a rotor with vanes mounted on an axis connected to a tachometer. The flow of fluid through the meter causes the rotor to rotate at a rate proportional to the flow rate. The tachometer generates a signal proportional to the speed of the rotor to indicate the flow rate of the fluid through the meter. A disadvantage with such meters is that a certain amount of leakage occurs from the bore through which the shaft extends from the meter body. Although this leak is minimized by packing the shaft to seal the hole, this does not completely solve the problem. In addition, such packaging is added to the cost of the meter, has a limited life, and when it fails it can contaminate the liquid or gas flowing through the meter. In addition, packaging can be less effective at relatively high fluid pressures. In response to such problems, fluid flow meters have been designed that do not require a mechanical connection between the rotor and the tachometer and thus can be sealed completely within the housing. This can be achieved either by manufacturing the rotor blades from a magnetic or conductive material, or by mounting a magnetic or conductive element on one or more of the blades of the rotor. A sensor is placed outside the body of the meter which generates a signal or pulse in response to the rotor blades passing through a magnetic or electric field produced by the sensor, and a corresponding fluid flow rate is determined from of the pulse rate generated. Typical systems of this type use magnets mounted on the aluminum pallet or pallets and a sensor that detects a change in magnetic flux caused by a passing pallet. Other systems using radio frequency sensors have been developed. Regardless of the mechanism used, the pulses received from the sensor are processed to determine the volumetric flow rate. Specifically, the pulses are counted to determine the total volume that has passed through the meter. Although such contactless systems for measuring the fluid flow rate solved many problems encountered with the initial mechanically connected flow meters, these systems have disadvantages. Since the accuracy of such magnetic meters or based on radio frequency depends on the ability of the sensor to detect a rotor passing through a magnetic field or FR, the body of the meter is made of a material that does not alter or distorts the field. In addition, these meters are often subjected to highly corrosive environments and must withstand fluid pressures of up to 101 kg / cm2 man. In most cases, these requirements have been met by manufacturing the meter bodies completely from non-magnetic stainless steel or other non-magnetic material. However, the use of stainless steel or other materials for the entire body of the meter increases the cost of material, as well as the cost of manufacturing. Also, the use of some alternative non-magnetic materials react with the fluid being measured, and therefore have an undesirably short lifetime. Attempts have been made to avoid the use of non-magnetic bodies using a sensor enclosed in a non-magnetic receptacle. This receptacle is installed in an opening through the body which can be made of less expensive magnetic material. A seal must be provided between the body and the sensor. A problem encountered with such previous flow meters is thatIf a sensor needs to be removed from the housing for repair or replacement, it is necessary to depressurize the entire line where the meter is placed, since the sensor module itself is part of the meter body and its removal creates an opening. In most cases, this requires downtime. Accordingly, there is a need for a contactless type flow meter that can be made of a conventional material, relatively cheap and robust, but which does not interfere with the magnetic field detected by the sensor, which is resistant to corrosion, can withstand high pressures, which allows the removal of the sensor without requiring the depressurization of the fluid line, and which can be removed safely without endangering the service personnel.

BRIEF DESCRIPTION OF THE INVENTION The present invention is a sensor assembly for a sealed rotor type flow meter which is made of a material that does not interfere with the signals produced by the rotor. Although the preferred embodiments of the fluid flow meters of the present invention described herein are designed for a gas turbine flow meter, the utility of the invention in flow meters designed for water or other fluids or with rotors other than a Turbine impeller will be understood by those skilled in the art. The sensor assembly includes a pressure reservoir received within the bore of a protrusion of the body of the flow meter, and a sensor accommodated within a bore in the reservoir. The reservoir is generally cylindrical in shape and is formed to extend through the cylindrical base of the meter body and internal rotor housing. The housing of the meter is made of a ferromagnetic material. The reservoir includes a face adjacent to the rotor which is sufficiently thin to allow the sensor to detect the passing rotor blades, but is strong enough to withstand internal gas pressures of up to 101 kg / cm2 man. In a preferred embodiment, the face is formed to adjust the contour of the inner face of the inner rotor housing, thereby creating a uniform path for rotor rotation and allowing the sensor to be positioned as close as possible to the path of the blades. of the rotor, thereby increasing the strength of the signal detected by the sensor. A seal device, such as an O-ring, is preferably provided between the pressure reservoir and the protuberance of the flow meter body to ensure a gas-tight seal. The reservoir of the present invention may be attached to the protuberance of the meter body in a number of ways. In one embodiment, the deposit is permanently attached to the protuberance of the body by welding or epoxy. Such permanent bonding eliminates the need for a seal O-ring. However, in some cases removal of the entire sensor reservoir will be required. In these cases, even if the meter can be deflected effectively without a stoppage, it could be difficult to ensure that the line containing the meter has been depressurized and completely purged. Thus, the person performing such maintenance may be exposed to a dangerous release of pressurized gas when the meter body is disassembled. This problem is overcome in another embodiment of the invention in which the pressure vessel is removably connected to the protrusion of the body by screws. The screws pass through the perforations in the pressure vessel and are screwed into the protuberance of the body. In a preferred embodiment, the screws are embedded in the tank body and are retained there during the unscrewing by means of a pin. This requires that all the screws be unscrewed in unison by turning alternately and incrementally each screw. Doing so, the O-ring seal will be broken before any of the screws are removed. If present, the pressurized gas will begin to escape by releasing the seal. The noise will warn the operator to stop the removal of the tank and sensor; a sensor assembly that is resistant to corrosion and capable of withstanding pressures of up to 101 kg / cm2 man; a sensor assembly which allows the easy and safe removal of the sensor for repair and replacement without requiring the depressurization of an associated line; and a sensor assembly that can be safely and easily removed from a fluid line. Other objects and advantages of the present invention will be apparent from the following description, the accompanying drawings and the appended claims.

BRIEF DESCRIPTION OF THE DIAMETERS Figure 1 is a sectional elevation view of a preferred embodiment of the sensor assembly for a fluid flow meter of the present invention; Figure 2 is a sectional elevation view of an alternate embodiment of the sensor assembly of the present invention; Figure 3 is a sectional side elevational view of a second alternate embodiment of the sensor assembly of the present invention; Figures 4A and B are side elevational views in sectional detail of a fastener arrangement in operation for a third alternate embodiment of the sensor assembly of the present invention; Figures 5A, B, and C are side elevational views in sectional detail of fastener arrangements for alternate embodiments of the sensor assembly of the present invention; Figures 6A and 6B are side elevational views in sectional detail of a fourth alternating region of the sensor assembly of the present invention; and Figure 7 is a side elevational view in sectional detail of a fifth alternate embodiment of the sensor assembly of the present invention.

DETAILED DESCRIPTION As shown in Figure 1, a preferred embodiment of the sensor assembly of the present invention, generally designated 8, is mounted on a fluid flow meter, generally designated 20. The flow meter 10 includes a rotor 12 turbine rotatably mounted within a fluid line 14. The rotor 12 includes a hub 16, mounted on an axle 18, and leaves 20 positioned circumferentially around the hub. Preferably, the hub 16 and sheets 20 are made of material such as stainless steel, aluminum, or other electrically conductive material, or with such similar materials arranged in the sheets. The fluid flow meter 10 has a body 22 that can be made of any suitable material, such as cast iron, cast steel, or aluminum, and includes an external main body 23 and an inner rotor housing 25, the latter of which houses the rotor 12 and forms a segment of the fluid line 14. In the embodiment shown in Figure 1, the external main body 23 includes an access closure 24 which is secured to the rest of the main body and includes a seal 26.

The fluid flow meter 10 includes a body protrusion 28 having a bore 29 formed to receive a sensor reservoir 30. The perforation 29 extends through the protrusion 28 and towards the fluid line 14. The reservoir 30 includes a bore 31 formed to receive a sensor 32. The sensor 32 is connected to a similar output gauge or indicator (not shown) by connectors 33. Preferably, the reservoir 30 is made of a non-ferromagnetic material such as stainless steel, although any material that does not interfere with the magnetic field or radio frequency variations detected by the sensor as a result of rotor movement is acceptable. The inner surface of the reservoir 30 and outer surface of the sensor 32 each include cords 34, 36, respectively, for the sensor 32 to be screwed into the reservoir 30. Although the sensor 32 is retained in the reservoir 30 by the cords in a Preferred, anyone of ordinary skill in the art will realize that the sensor 32 could be retained in the reservoir 30 by any number of means including, for example, by holding retainers, by means of a retaining support held in place by a screw, or by a reclining mechanism with resilience, just to name a few. All these modalities could be effective and are considered within the scope of the present invention. The reservoir 30 includes a wall 37 of relatively thin bottom (preferably approximately 0.1016 centimeters thick for a stainless steel reservoir) which protrudes at 10 through the inner rotor housing 25, through the bore 55. The face 54 of the pressure tank 30 is formed to equalize the contour of the inner face 57 of the housing 25. The widening 51 in the rotor housing 25 provides a surface of location for shoulder 39 in reservoir 30 under pressure. This places the contoured face 54 flush with the inner face 57 of the housing 25. The body protrusion 28 contains the threaded bores 38 which align with the uniform holes 40 that extend through the reservoir 30. Fasteners such as threaded screws 42 are inserted through the perforations 40 and include heads 44 and cords 46 that engage with the cords 47, thereby securing the reservoir 30 to the external main body 23. An O 48 ring, preferably made of an elastomeric material, is seated in a channel 50 provided in the sensor reservoir 30. Preferably, the O-ring 48 protrudes from the channel 50 such that when the reservoir 30 is secured in the external main body 23, the O-ring 48 makes contact with the inner walls 52 of the external main body 23, sealing the fluid line 14 of the environmental environment As shown in Figure 2, in an alternate embodiment 8A, the inner wall 52 of the boss 28A of the body is beveled at 51 to receive the ring O 48, which forms a seal between the boss 28A of the body and the reservoir 30A . In the embodiment 8B shown in Figure 3 the reservoir 30B is permanently secured to the external main body 23 by a weld 53 which acts to seal the seal. fluid line 14 of the atmosphere, thereby eliminating the need for an O-ring. As shown in Figures 1, 2 and 3, an opening 55 is formed through the inner rotor housing 25 to allow the face 54 to protrude directly to the fluid line 14. In these embodiments, the face 54 of the reservoir 30 is contoured to align with the inner rotor housing 25 thereby creating a uniform passage for the fluid and avoiding interference with the path A of the rotor blades 20. As shown in Figure 2, the sensor assembly 8A includes a sensor 32A having an elongated head 60 in the shape of a hexagonal nut 62 that allows the sensor 32A to be tightened in the reservoir 30A more easily. The nut 62 is dimensioned such that it covers the heads 44 of fasteners when they are pressed against the reservoir 30A, preventing access to the screws 42. This prevents removal of the reservoir 30A from the external main body 23 without first removing the sensor 32A. A safety aspect included in sensor assembly 8C, shown in Figures 4A and 4B, prevents accidental blasting of reservoir 30C due to the fluid pressure remaining in the fluid line, as represented by arrow B, during 30C tank removal for maintenance. Stoppers 64 are provided on the Heads 44 of the fasteners 42, which capture the fasteners such that all must be removed in unison by alternately and incrementally loosening each fastener. If after the fasteners 42 12 they have been loosened in sufficient quantity, the line is pressurized yet, the fluid, as represented by arrow B, will be released into the atmosphere, creating an audible or visual warning of the residual pressure. Preferably, this leakage will occur while the strings 46 of the fastener are still engaged with at least 3 of the body cords 47, thus providing the warning while the reservoir 30C is still securely connected to the external main body 23. The incorporation of the aforementioned security aspect can take many forms, as long as the fasteners 42 are captured after they are released from the body cords 47. For illustrative purposes, several preferred methods for incorporating this aspect are shown in Figures 5A, 5B and 5C for assembly 8C. As shown in FIG. 5A, a snap ring 66, or alternatively screwed on, is placed on the head 44 of the fastener 42 to capture the fastener when it is loosened from the body cords 47. This prevents removal of the fastener 42 from the perforation 40. In the 8C mode shown in Figure 5B, a portion of the pressure tank 30C is stamped or staked on the head of the fastener 44, creating a lip 68 which captures the 42 and prevents its removal from the perforation 40. And in the 8C mode shown in Figure 5C, a retaining ring 70 is mounted on the lower part of the fastener 42 which prevents the fastener 42 from being removed from the reservoir 30. In this embodiment, the reservoir 30 contains a retention ring bore 72 which it allows space for the retaining ring 70 when the head of the fastener 44 is pressed against its seat 43. Another embodiment of the sensor assembly 8D is shown in Figures 6A and 6B. The pressure reservoir 30D is screwed to the boss 28D of the body, which includes an annular pressure relief groove 79. O-ring seal 48 is positioned such that some turns of the pressure reservoir 30D will displace the reservoir relative to the protrusion 28D of the body, allowing the O-ring seal 48 to enter the depression 79 and remove the seal from the seat while it still maintains a secure rope coupling between the cords 82 of the pressurized container and the cords 80 of the protrusion of the body. A visual and / or audible warning by the fluid B escaping between the boss 28D of the body and the pressure tank 30D will signal that there is still pressure in the lines and will alert a user to stop the removal of the pressure tank. As shown in Figure 7, the sensor assembly 8E includes a reservoir 30E under pressure made of a sleeve 84 having a contoured face 86, formed to conform to the curvature of the internal surface of the internal housing 25, and an internal channel 88 formed to receive the sensor 32 in a threaded connection. The sleeve 84 is preferably made of a non-ferromagnetic material. The sleeve 84 includes a raised, annular rib 90 adjacent to the contoured face 86. A threaded fastening collar 92, having a hexagonal head 94, is screwed to a bore 29E, which has an annular depression 79E. The clamping collar 92 is preferably made of a non-material 14 ferromagnetic, but can be made of a ferromagnetic material without substantially interfering with the operation of the sensor 32. The collar 92 includes a central perforation 95 which slidably and rotatably receives the sleeve 84 therethrough. The clamping collar 92 also includes ring seals O 48, 49, placed between the clamping collar and the protrusion 28E of the body and between the clamping collar and the sleeve 84, respectively. A pressure nut 96 locks the sleeve 84 in position within the clamping collar 92, such that the sleeve is fixed in position and anchored to the collar by engagement of the rib 90 with the end face of the collar and engagement of the clamping nut with the upper surface of the hexagonal head, avoiding with this the relative rotation movement between the sleeve and the collar. The operation of the sensor assembly 8E is as follows. To mount the sensor assembly 8E in a body boss 28E, the collar 92 is first inserted over the sleeve 84 until the end 91 of the collar abuts the rib 90 (at this time the sensor 32 is not inserted in the sleeve) . The collar 92 and sleeve 84 combined are screwed into the bore 29E by rotating the hex head 94 of the collar 92. The sleeve 84 is then rotated relative to the collar 92 until the contoured face 86 conforms to the curvature of the inner surface of the housing. 25 internal. Once the contoured face 86 is properly aligned, the pressure nut 96 is pressed down on the hex head 94 to draw the rib 90 against the end face of the collar and lock the sleeve 84 in position, and the sensor 32 is screwed instead on internal channel 88. Consequently, it is a 15 advantage of this embodiment that the proper orientation of the contoured face 86 is realized without the need to adjust the collar 92, or of cutting ropes in the collar and protuberance of the body with high precision to ensure proper alignment of the contoured face of the reservoir to Pressure. In addition, by removing the collar 92 from the protuberance of the body, the O seal 48 is displaced relative to the protrusion of the body until it reaches the annular pressure groove 79E. The O-ring seal 48 can not maintain a seal in the enlarged space created by the slot 79E and therefore allows the pressurized fluid inside the line to escape through the strings of the perforation 29E and the protrusion 28E of the body, creating a audible warning of the pressurized state of the line. However, at this point, the string of the collar still engages with the corresponding strings of the protrusion 28E of the body, such that the pressurized fluid escaping which creates the audible warning signal can not also urge the collar 92 and the reservoir 30E under pressure of the body's protuberance. The operation of the sensor assembly 8 (Figure 1) is as follows. The flow meter body 22, and in particular the inner rotor housing 25, of the fluid flow meter 10 of the present invention is connected to a fluid line 14. A pressurized gas flows through line 14 colliding with the blades 20 of the rotor 12, causing the rotor to rotate about the axis 18. The sensor 32 is screwed to the reservoir 30 under pressure as close as possible to the path A of the 20 rotor blades. Since the reservoir 30 is made of a material 16 non-magnetic, such as stainless steel, the sensor 32 receives a clear signal of the rotation of the rotor 12. The magnetic fields of the sensor 32 are disturbed and the sensor detects the passage of each leaf 20 of the rotor 12, and transmits this information through from cable 33 to an output indicator (not shown), where the desired output is generated, tai as gas volume, and is displayed. If the sensor 32 needs to be removed from the maintenance flow meter 10, it is simply unscrewed from the cords 34 of the pressure vessel. Since the perforation 31 which receives the sensor 32 is sealed from the fluid line 14, and the pressure tank is capable of safely withstanding pressures of up to 101 kg / cm2 man, this can be done without depressurizing the fluid line 14. If the entire pressure reservoir 30 needs to be removed for maintenance, the fasteners 42 are unscrewed from their respective threaded bores 38 in the protrusion 28 of the body. In a preferred embodiment, the fasteners contain a safety feature that prevents removal of the reservoir 30 from the protrusion 28 of the body while the fluid line 14 is still pressurized. As shown in Figures 4A and B, this is done by providing a stop 64 which retains the fasteners 42 in the perforations 40 by decoupling the cords 47 from the body. When the fasteners 42 are loosened with a certain extension, gas or liquid, as shown by the arrow B, which pressurizes the line 14, will escape from the line 14 of fluid to the environment, creating an audible and possibly visual warning that the line 14 is still pressurized. The leak of gas or liquid around the seal no 17 Seated can be visible if vapor droplets form or if the fluid is colored. An odor can also be detected if the fluid is odorized. These warnings to stop ensure that the tank 30 is removed only when the fluid line 14 is safely depressurized, thereby avoiding dangerous blasting. Although the forms of the apparatuses described herein are preferred embodiments of the invention, it should be understood that the invention is not limited to those precise forms of apparatus, and that changes can be made thereto without departing from the scope of the invention.

Claims (34)

18
1. REVIVAL NAMES 1. A sensor assembly for a fluid flow meter comprising: a rotor; a pressure reservoir made of a non-magnetic material, said reservoir having a cavity formed therein; and a sensor mounted within said cavity and having an internal end positioned adjacent an internal end of said cavity. The sensor assembly of claim 1 wherein said pressurized container is formed to fit within a bore formed in a body protrusion of an associated flow meter. The sensor assembly of claim 2 wherein said pressurized reservoir is formed to protrude through an internal rotor housing of an associated meter when mounted on said body protrusion. 4. The fluid flow meter of claim 2 wherein said pressurized reservoir is releasably attached to said body protrusion. 5. The fluid flow meter of claim 2 wherein said pressure reservoir and body protrusion are both threaded for releasable engagement with each other. 6. The fluid flow meter of claim 2 wherein said pressurized reservoir includes an external threaded nut in said body protrusion; and an internal sleeve threaded in said nut. 19 7. The fluid flow meter of claim 6 further comprising a pressure nut for closing said sleeve in said outer nut. 8. The fluid flow meter of claim 2 wherein said pressurized reservoir is permanently attached to said body protrusion. 9. The fluid flow meter of claim 2 wherein said pressurized reservoir is attached to said body protrusion by a weld or permanent joint. The fluid flow meter of claim 2 wherein said pressurized reservoir includes an internal face formed to provide a uniform contour with said associated internal rotor housing, such that said internal end of said sensor is positioned at a minimum distance of the vane tips of said rotor. The fluid flow meter of claim 2 wherein said pressurized reservoir includes a shoulder formed to engage with a flare in a perforation of the associated sensor reservoir through an internal rotor housing. The fluid flow meter of claim 1 wherein said widening is formed at an internal radially end of said body boss, whereby said pressurized container is prevented from being displaced radially outwardly from said body bore. . The sensor assembly of claim 1 1 further comprising a plurality of mounting screws extending through of said sensor reservoir for attaching said reservoir to said body protrusion; and a fastener for fastening said screws in engagement with said reservoir. The sensor assembly of claim 13 wherein said fastener is selected from the group consisting of a shank pressed into a cross hole formed in said sensor reservoir adjacent to the head of each of said screws, a ring pressed into a widening formed in said sensor reservoir adjacent to a head of each of said screws, a ring screwed into a widening formed in said sensor reservoir adjacent to a head of each of said screws, staked on metal lips adjacent to a widening formed in said sensor reservoir, and a retaining ring mounted on a stem of said screw within a flare formed in said pressurized reservoir adjacent said body projection. 15. The sensor assembly of claim 13 wherein said sensor includes an enlarged head formed such that, when said sensor is mounted in said pressure reservoir, said head covers, and thereby prevents access to said screws. 16. The sensor assembly of claim 15 wherein said enlarged head has a hexagonal shape to facilitate removal of said sensor from said pressurized reservoir. 17. The sensor assembly of claim 2 further comprising a package positioned between said pressurized reservoir and said body protrusion. twenty-one 18. A sensor assembly for a fluid flow meter comprising: a rotor; a pressure reservoir made of a non-magnetic material, said reservoir being formed to fit within a perforation formed in a body protrusion of an associated flow meter and to protrude through an internal rotor housing of an associated meter when it is mounted on said body protrusion, said pressurized reservoir which is releasably attached to said body protrusion and having a cavity formed therein, an internal face formed to provide a smooth contour with said associated internal rotor housing such that said internal end of said sensor is placed at a minimum distance from the vane tips of said rotor, a shoulder formed to engage with a widening in a associated sensor reservoir bore an enlarged head having a hexagonal shape to facilitate the removal of said sensor of said pressure vessel and dimensioned such that when said sensor is mountable In said pressure vessel, said head covers, and thus prevents access to said screws; a plurality of mounting screws extending through said sensor reservoir for attaching said reservoir to said body protrusion; a fastener for fastening said screws in engagement with said tank; 22 a package placed between said pressure reservoir and said body protrusion; and a sensor mounted within said cavity and having an internal end positioned adjacent an internal end of said cavity. The sensor assembly of claim 18 wherein said pressurized reservoir is formed to protrude through an internal rotor housing of an associated meter when mounted on said body protrusion. The sensor assembly of claim 18 wherein said fastener is selected from the group consisting of a pin pressed into a cross hole formed in said sensor reservoir adjacent to the head of each of said screws, a ring pressed into a widening formed in said sensor reservoir adjacent to a head of each of said screws, a ring screwed into a widening formed in said sensor reservoir adjacent to a head of each of said screws, staked on metal lips adjacent to a widening formed in said sensor reservoir, and a retainer mounted on a stem of said screw within a flare formed in said pressurized reservoir adjacent said body projection. 21. A fluid flow meter comprising: a flow meter body; an internal rotor housing; a rotor rotatably mounted within said housing;
2. 2. 3 a sensor assembly including a pressure reservoir made of a non-magnetic material, said reservoir being formed to fit within a perforation formed in a body protrusion of an associated flow meter and to protrude through an internal rotor housing of an associated meter when mounted on said body protrusion, said pressurized reservoir which is fleetably attached to said body protrusion and having a cavity formed therein, an internal face formed to provide a smooth contour with said housing associated internal rotor such that said internal end of said sensor is positioned at a minimum distance from the vane tips of said rotor, a shoulder formed to engage with a countersink in an associated sensor reservoir bore an enlarged head having a shape hexagonal to facilitate the removal of said sensor from said pressure vessel and dimensioned such that when said sensor is mounted in said pressure reservoir, said head covers, and thus prevents access to said screws; a plurality of mounting screws extending through said sensor reservoir for attaching said reservoir to said body protrusion; a fastener for fastening said screws in engagement with said tank; a package placed between said pressure reservoir and said body protrusion; and 24 a sensor mounted within said cavity and having an internal end positioned adjacent an inner end of said cavity. 22. The fluid flow meter of claim 21 wherein said pressurized reservoir is formed to protrude through an internal rotor housing of an associated meter when mounted on said body protrusion. 2
3. 3. The fluid flow meter of claim 21 wherein said fastener is selected from the group consisting of a pin depressed in a cross hole formed in said sensor reservoir adjacent to a head of each of said screws, a pressed ring in a widening formed in said sensor reservoir adjacent to a head of each of said tomjllos, a ring screwed into a widening formed in said sensor reservoir adjacent to a head of each of said screws, staked on metal lips adjacent to a flare formed in said sensor reservoir, and a retainer ring mounted on a stem of said screw within a flare formed in said pressurized reservoir adjacent said body projection. 2
4. 4. A sensor assembly for a fluid flow meter comprising: a sensor; and a pressure reservoir including a sleeve formed to receive said sensor and a collar formed for coupling with an associated flow meter body protrusion and receiving said sleeve therethrough in relatively rotatable coupling, and a nut for securing it. said sleeve in a rotational orientation selected in relation to said collar. The sensor assembly of claim 24 wherein said sleeve includes a contoured face corresponding in shape to an associated internal flow meter housing, whereby said face is rotatably adjustable relative to said collar and said housing associated internal The sensor assembly of claim 25 wherein said sleeve includes a raised, annular rib adjacent an inner end of said collar; and wherein said nut is a snap nut screwed into said sleeve adjacent an outer end of said collar, said sleeve being fixed in axial and rotational position relative to said collar by anchoring coupling between said rib and said inner end of collar and between said pressure nut and said outer end of collar. 27. The sensor assembly of claim 24 wherein said collar includes ropes and is threaded into said associated body protrusion; and said collar includes a seal placed to form a seal between said collar and an internal wall of said associated body protrusion. 28. The sensor assembly of claim 27 further comprising an audible pressure warning means. 29. The sensor assembly of claim 28 wherein said audible pressure warning means includes an annular depression formed in said inner wall of said body boss. associated, placed inside said collar strings, such that unscrewing said collar from said body protrusion displaces said seal toward said annular depression, thereby allowing the pressurized fluid of an associated flow meter to escape between said collar and said protrusion body to create an audible warning sound, while said collar strings remain in engagement with said body protrusion to prevent blasting said collar, sleeve and sensor from said body protrusion. 30. The sensor assembly of claim 24 wherein said sleeve is made of a non-ferromagnetic material. 31 A sensor assembly for a fluid flow meter comprising: a sensor; a pressurized reservoir formed to receive said sensor and formed to engage with an associated flow meter body protrusion, said pressurized reservoir including a seal around an external surface thereof positioned to engage with an internal wall of said protrusion body; and said internal body bulge wall being formed to receive said pressurized reservoir therein and including an annular depression positioned relative to said seal such that the axial displacement of said pressurized reservoir outwardly from a flow meter associated with said reservoir. relation to said body protrusion places said seal in said annular depression, by which it allows the pressurized fluid of said associated flow meter to escape between said pressure reservoir and said body protrusion to create an audible warning sound. 32. The sensor assembly of claim 31 wherein said pressure reservoir includes ropes and is threaded into said associated body protrusion, said pressure reservoir ropes being formed and positioned to remain in engagement with said body protrusion to prevent blasting said collar, sleeve and sensor of said body protrusion when said seal is placed in said annular depression. 33. The sensor assembly of claim 32 wherein said pressure reservoir cords are externally disposed of said seal and said annular depression. 34. The sensor assembly of claim 1 including means for releasably mounting said sensor within said cavity. 28 SUMMARY A sensor assembly for a fluid flow meter, more particularly a gas meter, includes a pressure reservoir made of a non-magnetic material and a sensor which is removable from the reservoir without depressurizing the fluid line in which it is located. placed the flow meter. The pressure reservoir is mounted within a bore formed in a protuberance of the body of the meter and, in a preferred embodiment, extends through the inner rotor housing and includes an internal face contoured to conform to the internal wall of the housing. In certain embodiments of the invention, the sensor is formed to cover the mounting screws of the pressure tank so that the tank can not be removed without first removing the sensor. In other embodiments, the mounting screws of the pressure vessel are retained in the pressure vessel by means of spikes, stakes or retaining rings such that the screws must be gradually and sequentially loosened to remove the pressure vessel, in order to avoid improper removal of the pressure vessel from the body bump. In still other embodiments, the pressure reservoir is screwed directly to the protrusion of the body or includes a threaded collar and a sleeve which is rotatable to facilitate placement of a face contoured with respect to the internal wall of the housing. In such embodiments the body protrusion includes an annular depression which allows the pressurized fluid to escape between the pressure reservoir and the protuberance of the body as the pressure reservoir is removed, whereby a pressure relief is provided. audible warning that the line on which the meter is mounted is pressurized.