WO1995001552A1

WO1995001552A1 - Flow meter with cantilevered-mounted turbine

Info

Publication number: WO1995001552A1
Application number: PCT/US1994/007212
Authority: WO
Inventors: Zaki D. Husain; Franklin D. Goodson; Helmut Zenger
Original assignee: Daniel Industries, Inc.
Priority date: 1993-06-29
Filing date: 1994-06-27
Publication date: 1995-01-12
Also published as: AU7178894A

Abstract

A miniaturized turbine meter is disclosed. While the size of the turbine meter is small, it performs all the functions of prior turbine meters and has a large rangeability over a very large range of pressure. The turbine meter includes a body (13) which is bilateral and sometimes symmetrical, permitting the turbine meter to be installed in either orientation in a flow line. A first diffuser (15) is included with the turbine meter which maintains the rotor of the turbine meter in position by having a cantilevered shaft extending from the diffuser. A second diffuser or shroud is placed over the end of the cantilevered shaft farthest from the first diffuser and is spaced so as to avoid forcing engagement with the end of the cantilevered shaft, whereby the clearances of the two diffusers are non-critical and misalignment is avoided.

Description

FLOW METER WITH CAN ILEVERED-MOϋNTED TURBINE

Field of the Invention The invention relates to flow measurement devices and in particular, to flow measurement devices using turbine meters as a basis of the flow measurement.

Background of the Invention Pipes are used to transport fluids of all sorts. Because the measurement of these fluids is important, various types of fluid measuring devices such as orifice plates, flow meters, turbine meters, etc. are installed in-line with pipe sections. The use of such a measurement for flow has been known since ancient times. The present invention relates in general to turbine flow meters. Turbine flow meters usually include a measuring chamber having a flow guide in the front of such chamber, a measuring wheel supported for rotation in the chamber and includes a magnetic device which counts the blade turnings for blades mounted on the hub of the measuring wheel.

The basic theory with regard to electronic turbine meters is that fluid flow through the meter impinges upon the turbine blades which are free to rotate about an axis along the center line of the turbine housing. The angular (rotational) velocity of the turbine rotor is directly proportional to the fluid velocity through the turbine. The output of the turbine meter is measured by an electrical pickup mounted in the meter body. The output frequency of this electrical pickup is proportional to the flow rate. Also, each electrical pulse is proportional to a small incremental volume of flow. This incremental output is digital in form, and as such, can be totalized with a maximum error of one pulse regardless of the volume measured. Problems with existing turbine meters include a shift in the meter factor curve over pressure change, rangeability over a large range of pressures, large size, and the intrusion of dirt. It is the object of the present invention to avoid the meter factor curve change over the operating pressure of the meter, to permit high flow rangeability over a large range of pressure, such as substantially ambient to 5000 p.s.i. or higher. It is a further object of the present invention to substantially reduce the size of the meter. An additional object of the present invention is to inhibit intrusion of dirt within the mechanism of the measuring wheels supported for rotation in the chamber. A further object of the present invention is to reduce the criticality of clearances and avoid misalignment problems.

Summary of the Invention The present invention discloses a turbine meter that is suitable for either liquid or gas flow which can be installed for use over a large range, such as, for example, ambient to 5000 p.s.i. or higher while maintaining a high rangeability of, for example, at least 10:1 for ambient and increasing with line pressure for gas or dense fluid, such as highly compressed gas, to 13:1 or more at 300 p.s.i. The present invention includes a body or housing in which is contained a bilateral, and sometimes symmetrical, configuration of a flow meter. The flow meter includes flow diffusers at each end located in the flow passage of the body and a detector at an interior wall of the body. A rotor is mounted on a rotor shaft between the two flow diffusers. The rotor optimally has twelve flat blades with optimal blade angles of 45°. A close clearance is maintained between the blades and the interior of the meter body which is optimally between .008" and .012". For gas that is not highly compressed, this is achieved through use of specific stiffness of the blade which stems from the use of a set of notches to form the blades having optimal size for oval notches of width to height ratio of 1.5 to 2.0, such as .169" x .094" for a two inch meter. The notches for most meters would be oval in shape but at the extreme small and large sizes may be other shapes, such as tear drop. A magnetic pick-up is located in the magnet housing immediately juxtaposed with the blades and separated from the blade by the interior wall of the body and the small clearance discussed above. The magnetic strength of such magnet located in the interior wall of the body is between 50 and 200 gauss. The rotor is mounted on the rotor shaft of the shaft by bearings which are precision ball bearings for optimal results. Blade thickness may vary between .01 and .025 of the rotor diameter, such as .020" and .050" for a two inch meter while maintaining the small size of the turbine meter. For liquids and highly compressed or otherwise dense fluids, flat blades may be used in place of the notched blades.

In a preferred embodiment, a flow diffuser is located in the flow passage of the body and a detector at an interior wall of the body. A cantilevered rotor shaft is connected to or formed as a part of the diffuser. The rotor is mounted over the rotor shaft having a bearing between it and the rotor shaft at the end juxtaposed to the diffuser. The rotor also overhangs the outer end of the rotor shaft having a bearing and a washer between the rotor and the rotor shaft. The bearing and washer are maintained by a nut and jam nut or other interlock device to maintain a fixed position of the components. Brief Description of the Drawing For a further understanding of the nature and objects of the present invention, reference is made to the following drawings in which like parts are given like reference numbers and wherein:

FIG. 1 is a perspective view of an alternate embodiment of the present invention of the turbine meter; FIG. 2 is a side, partial cross-sectional view of alternate embodiments of the present invention of the turbine meter;

FIG. 3 is a partial side cross-sectional view of a portion of the alternate embodiments of FIG. 2;

FIG. 4 is a plan view of the rotor shaft of an alternate embodiment of the present invention of the turbine meter;

FIG. 5 is a cross-sectional view of the housing of the preferred and alternate embodiments of the present invention of the turbine meter;

FIG. 6 is a plan view of the gas rotor of the preferred embodiment and alternate embodiments of the present invention of the turbine meter prior to the formation of the blade configuration;

FIG. 7 is an enlarged view of the portion of FIG. 6 labelled "A"; FIG. 8 is a side view of the rotor shaft lock washer or retainer of the preferred and alternate embodiments of the present invention of the turbine meter;

FIG. 9 is an exploded view of another alternate embodiment of the turbine meter of the present invention; FIG. 10 is an exploded view of the alternate embodiment of FIG. 1 of the turbine meter of the present invention;

FIG. 11 is a partial side cross-sectional view of a preferred embodiment of the gas turbine meter of the present invention which is capable of being interposed between diffusers as in FIG. 18;

FIG. 12 is a side view of the diffuser and rotor shaft of a preferred embodiment of the turbine meter of the present invention;

FIG. 13 is a side view, partially in phantom line of the bearing spacer of the turbine meter of the present invention;

FIG. 14 is a side view, partially in phantom line of the washer of the turbine meter of the present invention;

FIG. 15 is a side, cross-sectional view of the bearing housing of the turbine meter of the present invention; FIG. 16 is a side view of a rotor structure of another preferred embodiment of a liquid or dense or highly compressed fluid turbine meter of the present invention which is capable of being interposed between diffusers of the sort shown in FIGS. 11 and 18; FIG. 17 is a front view of the rotor structure of FIG. 16;

FIG. 18 is a side, cross-sectional view of the preferred embodiment of FIG. 11 showing its use with two diffusers; FIG. 19 is an exploded view of a preferred embodiment of FIG. 18 of the turbine meter of the present invention for gas service; and

FIG. 20 is an exploded view of a preferred embodiment of FIG. 18 of the turbine meter of the present invention for liquid or dense or highly compressed fluid service. Description of the Preferred Embodiments A turbine meter 1 is shown in FIG. 1 having sealing faces 10 for appropriate mounting in line. Turbine meter 1 further includes interior opening 11 surrounded by interior wall 12 of body 13. Substantially identical diffusers 15 (FIG. 9) are mounted in opening 11 by spacers 20 which extend from diffusers 15 to an interior hub 14 sized to fit in interior wall 12 of body 13. In this manner, as shown in FIG. 9, turbine meter 1 is symmetrical and can be installed with either end facing the upstream. Locator pins 16 hold hubs 14 onto the interior wall 12. Retainer rings 17 engage grooves 18 in wall 12 to lock hubs 14 in place. Hubs 14 abut interior shoulders 21 formed in wall 12. Referring to FIGS. 2, 3, 9 and 10, the diffusers 15 are shown in two different configurations for contrast only. The alternate configuration of diffuser 15 is designated by indicator 30 (see FIG. 9) , and the other diffuser is indicated by indicator 25 (see FIG. 10) . The difference between the diffuser types is in the back edge 35, 40 of the diffusers 25, 30, respectively. The back edge 35 of diffuser 25 extends inwardly much farther than the back edge 40 of diffuser 30.

As shown in FIG. 2, rotor shaft 45 is located such that its longitudinal axis is substantially identical with the longitudinal axis of the diffusers 15. The ends 50, 59 of rotor shaft 45 extend into interior openings 55 of diffusers 15. Openings 55 have a first bore 60 and a second bore 65 being substantially coaxial, with bore 60 having a larger diameter than bore 65. Bores 60, 65 form a shoulder 70 therebetween.

Rotor shaft 45 is positioned to be substantially coaxial with opening 55 by bearings 75 mounted in bore 60 and abutting shoulder 70 at one end. Rotor shaft 45 is shaped to include shoulders 80, 89. Shoulder 80 is formed between extended shaft porticn 50 and raised portion 85. Shoulder 89 is formed between extended portion 59 and raised portion 88. Rotor hub or shaft 45 also includes a central extended diameter raised portion 100, one side 105 of which faces extended portion 85, and the other side 110 of which faces extended section 88. A bearing 75 also abuts shoulder 80 on the side of face 105, and a second bearing 75 abuts shoulder 89 on the side of face 110, thereby centering extended shafts 50, 59 of rotor shaft 45 in opening 55. Because of bearings 75, rotor shaft 45 is rotatably mounted within opening 55. Bearings 75 are preferably precision ball bearings, instead of other bearings such as jewel bearings. Precision ball bearings increase life at high speeds and because of the remainder of the features of the preferred embodiment of the present invention, may be used at low flow rates instead of jewel bearings. Jewel bearings and shaft assembly operating at high revolutions per minute do not last very long.

Rotor 120 is slidably mounted on enlarged shaft portion 88 by sliding an opening 130 formed in the center of rotor 120 to fit over extended portions 59, 88. Before the blades are formed in rotor 120, openings or notches 140 are formed in a rotor blank comprising a circular piece of metal. The notches 140 for most meters would be oval in shape but at the extreme small and large sizes may be other shapes, such as tear drops. For oval notches, the width to height ratio would be preferably 1.5 to 2.0. Typically, for a two inch meter the dimensions would be .169" x .094". The notches 140 are located symmetrically about the center of rotor 120 and radially displaced from the center of rotor 120 by at least twenty-five percent of the radius of the rotor 120. The interior end 160 and the opposing exterior end 155 of notches 140 have a radius of curvature of, for example, .047 inches for a two inch meter, and the outer end 155 of each of the notches 140 includes a narrow channel 145, having a width less than or equal to the material thickness of the blades, for example, .025 inches for a two inch meter, extending to the outer circumference 150 of rotor 120. Typically, these notches 140 extend above the interior end curved portion 160, approximately starting at .315 inches from the center (for a two inch turbine meter) of opening 130 and end at the beginning of the exterior end curved portion 155 which typically starts .484 inches from the center (for a two inch turbine meter) of opening 130. The material between openings 140 forms a shaft 170 leading to flat blade portions 180 that extend from the exterior curved surface of the exterior end 155 to the outer circumference 150 of rotor 120. With regard to the thickness of the flat blade portion 180, blade thickness is preferably in the range of .01 and .025 of the rotor diameter, such as .020 inches for a two inch meter. Shaft 170 permits the flexibility to twist the blade portion 180 relative to the interior of rotor 120.

The blanks for the rotor 120 are not preferably formed by a stamping die. The edges 350 of the flat blade portions 180 are important to the performance of the turbine meter rotor 120 and must be sharp. Sharp edges 350 are needed for liquid as well as gas meters. Accordingly, with a single stage stamping die, care cannot be taken as to what type of edge 350 can be provided, and whether the edges 350 may have to be machined or have additional stamping die stages to be sharp. For rotor blank fabrication, milling or laser cutting will be preferably used for sharpness of leading and trailing edges 350 which effect linearity. The openings or notches 140 effect the stiffness of the flat blade portion 180. Stiffness is important * xι a turbine meter to minimize clearances and thus lower weight and size and cost of substantially all components while maintaining accuracy. The preferred notch 140 size ratio for an oval notch is, as set out above, preferably 1.5 to 2.0, for example, .169 inches by .094 inches for a two inch turbine meter. In addition, because of the extra stiffness, the number of blades may be increased. The flat blade portions 180 may retain the stiffness because of notches 140 while increasing the number of flat blade portions 180, such as above six flat blade portions, such as a range between six to and including twelve flat blade portions 180 with the optimal being twelve flat blade portions 180. The larger number of blades in combination with blade angle gives a greater resolution or frequency to the signal produced by the turbine meter.

The blade angles of flat blade portions 180 are turned in a range between 30° and 60° with respect to the longitudinal axis of the flow path, with an optimal angle of 45°. The angle determines to some extent the speed of the turning of the rotor, which as the angle increases, the speed increases. Slower turning decreases resolution. However, speed decreases bearing life, and speed must be chosen to optimize bearing life and resolution. The use of a 45° angle yields the frequency which typically for a meter of the preferred embodiment is at or above 3000 hertz at the maximum flow rate which is believed to be significantly higher than meters of the prior art. The 45° angle requires the extra stiffness in order to be functional at maximum speeds. In addition, lower angles are much less responsive at low flows, and thus cut the rangeability of the meter at low flow rates and low pressures. Because of the stiffness, the length of the flat blade portions 180 may be increased, thereby reducing th^ clearance between the outer surface 150 of blade 180 and the interior surface 360 of portion 320 of interior wall 12. Such clearance in the preferred embodiment is in a range between .008 and .012 inches. The smaller this distance is; the closer the flat blade portions 180 come to the pick-up coil 400 to obtain accurate readings because at high pressure the thickness of portion 320 must be sufficient to withstand the high pressure in the interior opening 11 of the body or housing 13. Further, the weight of the flat blade portions 180 is important so that at low end flow rates, magnetic drag is not experienced as greatly. In addition, at the high end of the pressure range, flexing of the blades 180 can cause collision with the interior surface 360 or alternately may open the gap to surface 360 thereby decreasing signal strength. However, because at the low end, magnetic drag is a factor, increasing weight is not the solution to the stiffening, but the optimizing of the notch 140 is required as discussed above.

Because of the size of the notch 140, the thickness of the flat blade portions 180, the support of extension 100, a large free diameter of the flat blade portions 180 may be used, such as preferable a diameter of five times the diameter of extension 100 to surface 240. This causes significant weight saving.

Rotor 120 is attached to enlarged diameter portion 100 by small welds 200 or with special bonding agents such that one side of rotor 120 securely abuts surface 110. The other side of rotor 120 abuts a lock washer 210 which is fastened to rotor 120 by a small weld 230 or with special bonding agents. Thus, lock washer 210 and rotor 120 are rotatably mounted about the center axis of opening 55. Preferably resistance welding would be used in manufacturing instead of spot welding. The welding 200, 230 of the rotor shaft assembly also improves the attachment of the rotor 120. The welding 200, 230 eliminates potential problems with other types of bonding agents, such as Loctite™, although Loctite™ may be used as a bonding agent. The problems of other type of bonding agents would include improper assembly procedures and part cleaning which are necessary for a bonding of this type to perform the appropriate tasks. The welds 200, 230 or other welding techniques, unlike other techniques, can be visually inspected to determine acceptability, whereas incorrect procedures of assembly and bonding cannot be detected until the equipment falls apart. Because the meter 1 may be used in bi-directional flow, the welding 200, 230 also becomes important because thrust forces on the rotor 120 are transmitted to the lock washer 210 in the reverse flow mode. Further, a welded rotor 120 may increase the maximum temperature limit of the meter 1. Care should be taken to insure that a flat surface of rotor 120 abuts the flat surface 110 of extension 100.

As shown in FIGS. 2 and 3, the diffuser 25 includes interior surface 35 which extends substantially over the entire outer circumference 240 of extension 100. Optionally, as shown in FIG. 2, a machine cut or interior surface 250 also may be formed into surface 35, but surface 35 would still cover outer circumference 240. The clearance between outer circumference 240 and the interior surface 250 of extension 35 is very close. Thus, dust would tend not to leak into the bearing 75 area of the mounting of the rotor 120 and rotor shaft 45 with the preferred diffusers 25. In addition, these surfaces will tend to capture the rotor 120 should the bearings fail, preventing damage to the interior 11 of body or housing 13. While not shown in FIG. 3, if a diffuser 25 is used on both sides in place of diffuser 30 (shown on one side of FIG. 2) , it would substantially cover the outer circumference of lock washer 210.

Accordingly, the diffuser modification will hold the rotor 120 in place longer after failure of bearings 75, giving some indication of flow for a longer period of time and preventing the rotor 120 from damaging the bore or interior wall 12 of body 13 and, especially the thin wall 320 under the coil 400. The housing 13 includes a pressure tap 300 centrally located for which a pressure transducer and transmitter may be attached to measure the pressure in the interior 11 close to the flat blade portions 180. The housing or body 13 further includes an indented exterior portion 310 that houses the pick-up coil 400 graphically depicted in FIG. 1 and shown in FIGS. 9 and 10 which, except as described below, is standard in the art. The pick-up coil 400 includes coils typical of the art which are wound and placed within opening 330. In the preferred embodiment of the present invention, because the blades are so close to the interior wall 360 of the housing 13, and there are so many flat blade portions 180, magnetic strength of the pick-up coil 40 should be optimized to improve meter performance at low flow rates and avoid magnetic drag. The magnetic strength of the pick-up coil 400 is preferably between 50 and 200 gauss as a function of the number of windings and the wire size of the pick-up coil 400. The thickness 320 below the opening 330 for the pick-up coil 400 must be sufficient to contain the pressure within the interior 11 of the housing or body 13.

A preferred embodiment of the present invention is shown in FIG. 11. FIG. 11 illustrates a gas turbine as does FIGS. 1-10. However, instead of diffusers 25, 30, a combination diffuser and bearing shaft 500 having a diffuser section 505 and a shaft section 510 as a single piece is shown. The diffuser section 505 has an overhang 511, cylindrical in shape, formed by bore 515 at the end of the diffuser section 505 of the diffuser and bearing shaft 510. Overhang 511 forms the outer cylindrical surface surrounding bore 515 formed around the center of diffuser and bearing shaft 510. Overhang 511 includes an end having surface 525. A shoulder 520 is formed in the inner radial end of bore 515 between (i) central raised portion or hub 526, formed at the transition between diffuser section 505 and shaft section 510 and (ii) the shaft section 510. The surface 250 of overhang 511 extends axially away from diffuser section 505 a greater distance than the longitudinal axial extension of hub 526.

The outer facing diffuser surface 530 of diffuser section 505, surface 530 facing opposite to surface 525, is substantially the same as the outer facing surface of diffusers 25, 30.

As shown in FIG. 11, shaft section 510 is located such that its longitudinal axis is substantially coaxial with the central longitudinal axis of the diffuser section 505. The end of shaft section 510 is threaded with threads 535.

A set of bearings 75 are positioned around shaft section 510, abutting shoulder 520 at one of its ends. A bearing spacer 540, being cylindrical in shape and having an axis substantially the same as the axis of shaft section 510, is positioned around shaft section 510 and abuts the other end of bearing set 75. A bearing housing 545, having a cylindrically shaped center with an axis substantially the same as the axis of shaft section 510 is slidingly mounted over shaft section 510. As best seen in FIG. 15, bearing housing 545 is shaped to include a first cylindrical open section or bore 550 and a second cylindrical open section or bore 560, such open sections being cylindrical in shape with substantially the same inner bore diameter. The bore sections 550, 560 are connected by a smaller diameter third cylindrical section or bore 555 having exterior surface 595. All bores 550, 555, 560 are coaxial with each other and substantially coaxial with shaft section 510. The inner diameter of section 550, being larger than the inner diameter of section 555, forms shoulder 565 therebetween. A collar 570, having outward facing surface 590, is formed around third section 555, the outer diameter of which is larger than the exterior diameter of section 550, forming shoulder 571 therebetween. The outer diameter of collar 570 is also larger than the exterior diameter of the remainder of section 555 and section 560, which have substantially the same exterior diameter, thereby forming shoulder 575 therebetween. The inner diameter of bore 560, being substantially larger than the inner diameter of bore 555, forms a shoulder 580 therebetween. The inner diameter of bores 550, 560 are substantially equal to the outer diameter of bearing set 75. The inner diameter of bore 555 is slightly larger than the outer diameter of bearing spacer 540.

Bearing set 75, mounted against shoulder 520, also abuts shoulder 565 and fits axially within the axial space formed by the inner circumference of bore 550. A cylindrically shaped bearing spacer 540 having an inner diameter substantially equal to the outer diameter of shaft section 510 is mounted over shaft section 510 and abuts bearing set 75. Thus bearing set 75 is held on its sides between shoulder 520 on one side and shoulder 565 and bearing spacer 540 on the other side. In this manner, as seen in FIG. 11, a gap 585, similar in dimension to the gap between surface 240 and surface 250. is formed between the inner surface 250 of diffuser overhang 511 and the outward facing surface 591 of the outer surface of the portion of bearing housing 545 surrounding bore 550. Thus shoulder 571 being in proximity to surface 525 and surface 250 being in proximity with surface 591 yields only a small opening. This small opening rejects dust and other foreign particles from reaching bearing set 75. Third section 555 is juxtaposed with bearing spacer 540 leaving a narrow space 596 therebetween. At the end of bearing spacer 540 opposite to the end abutting bearing set 75, there is located another bearing set 76 which substantially abuts bearing spacer 540 and shoulder 580 on one of its ends. Bearing set 76 is substantially identical to bearing set 75 and has substantially the same outer diameter as the inner diameter of bore 560. Bearing set 76 is held in place at its other end by a washer 260. Thus there is substantially no room for dirt or other contaminants to reach bearing set 76. With bearing sets 75, 76 in place, bearing housing 545 rotates about its longitudinal axis around shaft section 510. A nut 597 and a jam nut 598 are threaded onto threads 535 at the end of shaft section 510 to hold washer 260 in place.

Rotor 120 is mounted on the exterior surface 595 of middle section 555 in the same manner as for the alternate embodiments and is attached by welds 200, 230 or other mechanisms as with the alternate embodiments. Accordingly, a rotor retainer 210 maintains rotor 120 in place.

In assembly, a second diffuser 506 having an interior bore 507 shaped to fit around the nuts 597, 598 may be placed at the other end of turbine 1. In this manner, substantially the same configuration externally may be achieved as that of FIGS. 1, 2 and 9, but with an important difference. The presently preferred embodiment has the entire rotor assembly cantilevered from diffuser section 505, close tolerance in spacing with regard to diffuser 506 is not necessary. Thus clearance becomes noncritical and misalignment is avoided. In addition, the cantilevered shaft section 510 is very short and its mass is much greater than the mass of the bearing sets 75, 76, rotor 120, rotor retainer 210 and bearing spacer 540. Thus no loss of alignment will occur.

Also with regard to the preferred embodiment of FIG. 11, it is possible to have easily interchangeable rotor sections for water or other liquid or other dense or highly compressed fluids in operation rather than the gas operation of FIG. 11. In FIG. 16, there is shown a bearing housing 600. Bearing housing 600 has substantially coaxial bores 610, 605, 615, corresponding respectively to and substantially identical to bores 550, 555, 560 and being substantially coaxial with the axis of shaft section 510. Bores 610, 605, 615 having substantially the same inner diameters as bores 550, 555, 560 form shoulders 665, 680 substantially identical to shoulders 565, 580, respectively. A collar 620 is formed on the exterior surface of middle section 605 of bearing housing 600 substantially adjacent to bore 610, except it is formed on the exterior of bore 605. Blades 630 having outer circumferential surfaces 650, sharp lateral edges and the same angle as blades 180 are formed on the outer surface of collar 620. Blades 630 are however substantially rectangular in shape. Preferably there are eight blades.

To convert meter 1 of the preferred embodiment from gas measurement using blades 150 to liquid or other dense or highly compressed fluid measurement using blades 630, nuts 597 and 598 are removed. Washer 260 and bearing set 76 are then removed. Thereafter, bearing housing 545 may be removed from shaft section 510. Bearing housing 600 may then replace bearing housing 545 with shoulder 665 abutting bearing 75 and with bore 605 surrounding bearing spacer 540. Bearing 76 may then be replaced in bore 615, and washer 260 also placed into bore 615. Nuts 597 and 598 may then be reattached to the threads 535 of shaft section 510. Thereafter, diffuser 506 may be replaced so that the assembly is complete and ready to measure liquids rather than gas. Rotor housing 600 with a rotor formed by blades 630 may be cast as one piece, preferably.

In use, after assembly, flow may be introduced on either diffuser 505, 25, or 30 of meter 1 which will deflect the flow against the surface of flat blade portions 180 or 630 facing the flow. The impingement of the flat blade portions 180 or 630 cause flat blade portions 180 or 630 to rotate around the axis of shaft section 510 or rotor shaft 45. As the flat blade portions 180 or 630 rotate under the pick-up coil 400 located over surface 320, the presence of the flat blade portions 180 or 630 of the rotor 120 or collar 620 will be detected as pulses having a width dependent on the time that surface 150 or 650 is juxtaposed in whole or in part with pick-up coil 400. The pulses are subject to signal smoothing and shaping and amplification and other conditioning by preamplification and ultimately used for flow rate and/or flow volume measurement. The shift on the meter curve as a function of line pressure is dependent on the ratio of the total drag on the rotor to the turning moment on the rotor. Major contributors to the drag are mechanical, frictional, viscous, and magnetic. At the same flow rate with the increasing density of the fluid, the turning moment also increases. For a meter with a mechanical drive, the main source of drag is from the drive. Drag causes a significant shift in the meter curve as a function of increasing line pressure. The rate of change of the shift in the meter curve decreases with increasing line pressure. Therefore, a negligible shift of the meter curve occurs at a higher line pressure. With a low gauss or magnet strength magnetic pick-up coil, the drag is significantly reduced. Hence, the negligible shift on the meter curve occurs at a much lower line pressure than that of a turbine meter with mechanical drive or other relatively high drag devices. For the miniature turbine meter 1 a significant contribution of drag is from the magnetic field of the pick-up coil. The combination of magnetic pick-up coil strength, choice of bearing, blade thickness, blade angle, and blade clearance has a synergistic effect to minimize the shift of the meter curve to line pressures to be substantially asymptotic to zero as low as ambient condition. The curve shift is then insignificant for these embodiments and included within the accuracy of the meter.

The embodiments set forth herein are merely illustrative and do not limit the scope of the invention or the details therein. For example, sizing will cause adjustments in various dimensions. It will be appreciated that many other modifications and improvements to the disclosure herein may be made without departing from the scope of the invention or the inventive concepts herein disclosed. Because many varying and different embodiments may be made within the scope of the inventive concept herein taught, including equivalent structures or materials hereafter thought of, and because many modifications may be more in the embodiments herein detailed in accordance with the descriptive requirements of the law, it is to be understood that the details herein are to be interpreted as illustrative and not in a limiting sense.

Claims

What is claimed is:

1. A turbine meter having high rangeability over a large pressure range, comprising: a housing having an interior passage and surface and an entrance to said interior passage; a diffuser mounted in said interior passage facing said entrance having a shaft section fixedly connected to said diffuser and with an outer end extending away from said diffuser into said interior passage, and shaft section supported by said diffuser in a cantilevered mounting;

a bearing assembly rotatably mounted on said shaft section and having a rotor including blades; and

holding means for holding said bearing assembly on said shaft section.

2. The turbine meter of claim 1, wherein said rotor is formed by a rotor blank with an outer circumference and having a center opening sized to fit on said shaft section and having notches formed about said center opening, said notches being elongated, said elongated portion being radial outward with material therebetween, and said notches having channels extending from the center of the outer end of said notches to said outer circumference forming said rotor blades, said blades being turned from the plane of the surface of said blank, said material forming the shaft of said blades.

3. The turbine meter of claim 2, wherein said notches are oval in shape.

4. The turbine meter of claim 1, wherein the number of said blades is in a range from seven to twelve

5. The turbine meter of claim 1, wherein the number of said blades is twelve.

6. The turbine meter of claim 2, wherein the angle of turning of said blades from the plane of the surface of said blank is in a range above thirty degrees.

7. The turbine meter of claim 2, wherein the angle of turning of said blades from the plane of the surface of said blank is in a range from thirty degrees to sixty degrees.

8. The turbine meter of claim 2, wherein the angle of turning of said blades from the plane of the surface of said blank is forty-five degrees.

9. The turbine meter of claim 2,. wherein the width of said channels is less than or equal to the thickness of said blades.

10. The turbine meter of claim 2, wherein the thickness of said blades is in a range of .01 to .045 of the diameter of said rotor.

11. The turbine meter of claim 2, wherein said notches are located symmetrically about said center opening and radially displaced from said center opening by at least twenty-five percent of the radius of said blank.

12. The turbine meter of claim 1, wherein said housing includes a second, opposing entrance and there : ' included a second diffuser mounted in said interior passage facing said second entrance, said rotor shaft having an end juxtaposed to said second diffuser in said interior passage, said second diffuser shrouding said outer end, whereby the clearance between said diffusers is noncritical and misalignment of said shaft section is avoided.

13. The turbine meter of claim 1, wherein there is included bearings interposed between said rotor shaft and said bearing assembly.

14. The turbine meter of claim 16, wherein said bearings are precision ball bearings.

15. The turbine meter of claim 1, wherein said blades are flat.

16. The turbine meter of claim 1, wherein said blades have sharp lateral edges.

17. The turbine meter of claim 1, wherein said bearing assembly further includes: an extension; said rotor abuts said extension; and the diameter of said rotor is at least five times the diameter of said extension_*

18. The turbine meter of claim 1, wherein said blades are adapted to measure gas flow.

19. The turbine meter of claim 1, wherein said blades are adapted to measure liquid flow.

20. The turbine meter of claim 22, wherein said bearing assembly is molded to include said rotor.

21. The turbine meter of claim 1, wherein said bearing assembly includes: two sets of bearings and a bearing spacer; and said bearings and said bearing spacer are mounted around said shaft section.

22. The turbine motor of claim 24, wherein: said bearing assembly includes - a first bore at one of the ends of said bearing assembly and abutting the first of said bearing sets, and a second bore at the other end of said bearing assembly and abutting the second of said bearing sets, and a third bore between said first bore and said second bore, said bearing spacer mounted in said third bore and separating said bearing sets; and said diffuser abuts said first bearing set.

23. The turbine meter of claim 1, wherein the number of said blades is eight.

24. The turbine meter of claim 1, wherein said shaft section is molded on said diffuser.

25. A flow meter, comprising: a body having an interior surface, said interior surface defining an interior opening through said body; a diffuser section located in said interior opening of said body, said diffuser comprising a shaft oriented in cantilever relationship to said diffuser, said cnatilever shaft further oriented in substantial coincidence with a longitudinal axis of said interior opening; a rotor assembly comprising a plurality of rotor blades and a bearing set; and wherein said rotor assembly is rotatably secured to said cantilever shaft.

26. The flow meter of claim 28, further comprising a second diffuser adjacent said rotor assembly and spaced therefrom.

27. The flow meter of claim 28, further comprising a bearing housing for housing said bearing set, said plurality of rotor blades fixedly secured to said bearing housing.

28. The flow meter of claim 30, wherein said bearing housing houses a plurality of bearing sets.

29. The flow meter of claim 29, wherein said first and second diffusers each further comprise an overhang for shrouding at least a portion of said bearing set, said overhangs spaced apart from said bearing set.

30. The flow meter of claim 28, wherein said rotor assembly is removably secured to said cantilever shaft.

31. The flow meter of claim 33, wherein said rotor assembly is removably and rotatably secured to said cantilever shaft with a threaded fastener.

32. The flow meter of claim 28, further comprising a magnetic pickup located in said body adjanced said rotor blades.

33. The flow meter of claim 28, wherein said plurality of rotor blades are formed form a single rotor blank.

34. The flow meter of claim 28, wherein said bearing set is substantially protected against contaminate intrusion.

35. The flow meter of claim 28, wherein said bearing set is sealed.