AU2006228061A1

AU2006228061A1 - Improvements in oval rotor flowmeters having direct pulse generation

Info

Publication number: AU2006228061A1
Application number: AU2006228061A
Authority: AU
Inventors: Wayne Frederick Fuller
Original assignee: Trimec Industries Pty Ltd
Current assignee: Trimec Industries Pty Ltd
Priority date: 2005-10-17
Filing date: 2006-10-13
Publication date: 2007-05-03

Description

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PATENTS ACT 1990 ORIGINAL COMPLETE SPECIFICATION STANDARD PATENT Invention title IMPROVEMENTS IN OVAL ROTOR FLOWMETERS HAVING DIRECT PULSE GENERATION The following statement is a full description of this invention, including the best method of performing known to me.

IDThis invention relates to apparatus for flow measurement. More particularly, although not exclusively, it discloses an improved oval rotor positive Sdisplacement flowmeter and a method of constructing said meter.

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Oval rotor positive displacement flowmeters use a pair of oval shaped rotors as the primary measuring elements. With those flowmeters having direct pulse 0 generation magnets are fitted to the rotors. These rotors rotate in accordance with c-i N- fluid flow passing through the meter. Fixed sensors (also called pulse generators) Ssuch as a reed switch, hall effect device, coil, proximity switch etc. are excited to generate an electrical pulse each time one of said rotor mounted magnets passes.

A regularly spaced output train or series of such pulses is necessary for the purpose of flow rate integration and calculation. With oval rotor flowmeters however the rotors in mesh are offset by 90 degrees and exhibit a varying (e.g.

sinusoidal) change in rotational velocity. This can adversely affect the quality and point accuracy of the flowmeter output.

In order to provide a regular pulse output prior art flowmeters typically have arrangements as shown in figures 1 to 4. In figure 1 a single magnet 1 mounted on a lobe 2 of one of the rotors 3 passes a single fixed sensor 4 on the end plate of the rotor casing 5. The sensor is thereby excited to generate one pulse per rotor revolution. In figure 2 a pair of magnets 6, 6A are placed diagonally opposite on the two lobes 7, 8 of one of the rotors 9. These trigger a single fixed sensor 10 located on the end plate of the rotor housing 11 adjacent to the rotational path of the magnets 6 and 6A to produce two pulses per rotor revolution. In figure 3 pairs of magnets 13, 14 and 15, 16 are placed diagonally opposite on lobes 17-20 of the rotors 21, 22 to generate four pulses for each rotor revolution from a single centrally located fixed sensor 23. The flowmeter of IDfigure 4 uses the same arrangement of rotor magnets 24-27 on the rotors 28, 29 but has two fixed sensors 30, 31. These can be connected in parallel and are located diagonally opposite on the end plate of the rotor housing 32, whereby

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each sensor is activated separately by its respective rotor magnets to produce four pulses for each rotor revolution when connected in parallel.

0 Generally, the greater the number of regularly spaced pulses generated per rotor oo revolution the more accurate the flowmeter output is particularly when metering 0relatively small volumes of liquid. In each of these prior art arrangements however either one sensor/magnet pair only is used (giving poor output resolution) or the location of the sensors/magnets is restricted to set positions based on flowmeter geometry which limit the signal output to a maximum of four regularly spaced pulses per rotor revolution.

It is therefore an object of this invention to ameliorate the aforementioned disadvantages and accordingly a method of constructing a direct pulse generation flowmeter is disclosed, said method including the step of using a timing apparatus to determine the positions of one or more rotor magnets and/or pulse generators to produce at one selected flow rate of the meter an increased number of regularly spaced signals which in subsequent use of the flowmeter can be processed to represent a range of flow rates.

Preferably said signals comprise electrical pulses.

It is further preferred that said increased number exceeds four pulses per rotor revolution.

IND It is further preferred that said timing apparatus comprises an oscilloscope or the 0 like.

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In another aspect the invention also discloses a direct pulse generation flowmeter which has been constructed in accordance with the aforementioned method.

0Currently preferred examples of the invention will now be described with 00oO reference to the attached drawings in which:-

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cl figure 5 is a schematic cross-sectional view of a first example of a flowmeter constructed according to the invention in which four rotor mounted magnets and two fixed sensors are used, figure 5A shows the preferred form of parallel connecting circuit for the two pulse generation sensors of figure figure 6 is a schematic cross-sectional view of a second example of a flowmeter constructed according to the invention in which eight rotor mounted magnets and one fixed sensor are used, and figure 7 is a schematic cross-sectional view of a third example of a flowmeter constructed according to the invention in which twelve rotor mounted magnets and two fixed sensors are used.

Referring first to figure 5 a rotor arrangement is shown schematically in which four magnets are used in diagonally opposite pairs 35, 36 and 37, 38 whereby one magnet is adjacent each of the rotor lobes 39-42. There are also two fixed IDsensors or pulse generators 43, 44 which are spaced apart vertically along a Scentral intersection line of the two rotor chambers 45, 46. Preferably by connecting these sensors in parallel as shown in figure 5A and positioning said

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sensors and/or magnets in accordance with the method of the invention eight regularly spaced pulses are able to be generated for each rotor revolution. The correct position of said sensors and/or magnets is not limited to set positions as 0 with the prior art but is uniquely determined for this particular arrangement using 00 oo an oscilloscope or other suitable timing device (not shown) to obtain regularly spaced output pulses at a fixed meter flow rate of say 2 litres/second. It has been found through trials by the inventor that obtaining regular output pulses at one such fixed flow rate also determines the correct sensor and/or magnet positions for pulses over the usable range of the flowmeter.

The above reference to connecting the sensors in parallel includes connecting said sensors in parallel either integrally at the flowmeter or remote from the flowmeter.

It is also to be noted that the sensors may be arranged so that they are not connected in parallel and that their respective outputs are multiplexed by another circuit in order to achieve a like result.

Figure 6 shows another arrangement in accordance with this invention for producing eight regularly spaced pulses for each rotor revolution. There are four magnets 47-54 placed along the flanks of each of the rotors 55, 56 and there is one fixed sensor 57 placed along the vertical intersecting line of the two rotor chambers 59, 60. The exact positions of the magnets 47-54 along the rotor flanks is uniquely determined for this arrangement using an oscilloscope or the like to IDproduce eight regularly spaced pulses per rotor revolution at a fixed flow rate of 0 say 10 litres/second.

.)a Figure 7 shows a flowmeter arrangement in which six magnets 61-72 are mounted on each of the rotors 73, 74. The magnets are all located equal distance from the axis of their respective rotors and are arranged in groups of three 0between the opposite sides or flanks of the rotors. There are two fixed sensors 00 oo 75, 76 located on a horizontal line passing through the rotor axes and positioned

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to be activated when the respective groups of magnets on each rotor pass. By c' connecting the sensors in parallel in a similar manner to that shown in 5A and adjusting the positions of the magnets for this particular arrangement using an oscilloscope or the like twelve regularly spaced pulses per rotor revolution are obtained at a selected flow rate of say 20 litres per second. This enables a higher resolution and more accurate output over the normal range of meter flow rates.

It will thus be appreciated that this invention at least in the form of the examples disclosed provides a novel and improved direct pulse generation flowmeter and method of constructing said meter. Clearly however the examples described are only the currently preferred forms of the invention and a wide variety of modifications may be made which would be apparent to a person skilled in the art. For example the type of timing device used, the flow output rate at which the position determining measurements are made and the number and type of sensors/magnets used may all be changed according to design preference.

Expressions such as "vertical", "vertically", "horizontal", "horizontally" etc. as used in this specification refer to the flowmeters in one position of use as illustrated and are not to be read as necessarily limiting.

Claims

2. The method as claimed in claim 1 wherein said timing apparatus is used to position a plurality of said pulse generators at spaced apart locations along a central intersection line of rotor chambers of said flowmeter and said pulse generators are connected in parallel whereby in use of the flowmeter the pulse generators are activated by magnets located adjacent the lobes of rotors rotating within said rotor chambers to produce said regularly spaced signals.
3. The method as claimed in claim 2 wherein said timing apparatus is used to position two pulse generators at spaced apart positions on said intersection line, four magnets are located one each on respective lobes of said rotors and said regularly spaced signals number eight.
4. The method as claimed in claim I wherein said timing apparatus is used to position magnets along the flanks of flowmeter rotors whereby in use of said flowmeter a pulse generator located on a central intersection line of chambers for said rotors is activated by said magnets to produce said regularly spaced signals. NO O 5. The method as claimed in claim 4 wherein said timing apparatus is used to O position four magnets along the flanks of the flowmeter rotors and said O Cc regularly spaced signals number eight.
6. The method as claimed in claim 1 wherein said timing apparatus is used to INO 0 position magnets in groups between opposite sides or flanks of flowmeter 00 C rotors whereby in use of said flowmeter pulse generators located on a INO Shorizontal line passing through axes of said flowmeter rotors are activated by said magnets to produce said regularly spaced signals.
7. The method as claimed in claim 6 wherein the timing apparatus is used to position two groups of six magnets between opposite sides or flanks of said flowmeter rotors, two pulse generators are located on said horizontal line and said regularly spaced signals number twelve.
8. The method as claimed in any one of claims 1 to 7 wherein said timing apparatus is an oscilloscope.
9. A method of constructing a direct pulse generation flowmeter, said method being substantially as described herein with reference to figure or 6 or 7. A direct pulse generation flowmeter which has been constructed using the method as claimed in any one of claims 1 to 9. Dated this 10th day of October, 2006 Trimec Industries Pty Limited By Our Patent Attorney MICHAEL ANDERSON-TAYLOR