CA1059032A

CA1059032A - Gas flow transducer utilizing rolling piston

Info

Publication number: CA1059032A
Application number: CA261,644A
Authority: CA
Inventors: William R. Leonards; Charles E. Wierzbicki
Original assignee: Sparton Corp
Current assignee: Sparton Corp
Priority date: 1975-12-15
Filing date: 1976-09-21
Publication date: 1979-07-24
Also published as: DE2647074C3; DE2647074A1; DE2647074B2; GB1517488A; JPS5273768A; US4034606A

Abstract

ABSTRACT OF THE DISCLOSURE

A transducer for proportionally indicating small quanti-ties of gas flow utilizing a rolling piston in association with a flexible electrical conducting band engaging terminals within the piston chamber. Gas flows from the chamber at an increas-ing rate proportional to piston displacement and the transducer is characterized by its low friction operation and capability to accurately sense low rates of gas flow.

Description

1059~3Z
1. The field of the invention pertains to electric trans-

2. ducers for sensing gaseous flow and proportlonally indicating

3 the rate of such flow.

4 The rate of gas and fluid flow within conduits is often required information in gas and li~uid treating systems, such as 6. found in the chemical and petroleum processing arts. Flow 7, meters take a variety of forms employing paddle wheels, pro-8. pellers, dye and visual devices, and some use the viscosity of 9 the moving medium to produce displacement of indicia means, such 10, as a ball, 11. Difficulty has been encountered in accurately sensing and 12. indicating low rates of gas flow since such low rates and small 13. volumes must overcome the friction of displaceable means to pro-14. duce gaging, and as many flow meters operate on a resistance 15, principle wherein the resistance of flow about a displaceable 16. member is used to displace the member, relatively high rates of 17. flow are usually required in order to produce sensing. Dis-18. placeable balls have been used in gas flow meters, and electri-19. cal means have also been used in flow gages to indicate the 20. position of the displaceable member. Further, a rolling piston 21. has been employed in a flow meter utilizing a variable area out-22. let and rolling pistons have been used in gas indlcators. How-23. ever, prlor art device~ have not been of such character as to 24. provide an accurate electrical signal proportional to the rate 25. of low fas flow volume and the present invention has been found 26. to produce superior performance over those devices known to the 27. appllcants.
28. It is an ob~ect of the invention to provide a gas flow 29. transducer capable oP produclng an electric s$gnal proportional 30. to the rate of gas flow even though such rate may be small.
31. Another ob~ect of the invention is to provide an accurate 32. gas flow tran~ducer producing electrlc signals proportional to 33 the degree of piston displacement within a chamber wherein the 1, ~' 1. operating characteristics of the piston are such as to produce 2. very low frlction, and piston displa¢ement accurately reflects 3, the rate of gas flow, even though such flow may be very small.
4 A further ob~ect of the invention ls to provide a gas flow transducer utilizing a displaceable piston wherein piston 6. displacement is electrically sensed~ and the piston consists of 7 a flexible and electrical conducting band and the band engages 8. terminals within the piston chamber by a nonsliding engagement.
9, Yet 8 further ob~ect of the invention is to provide a low 10. volume gas flow transducer which is relatlvely economlcal to 11. manufacture, rugged, dependable in operatlon, self-resetting, 12. and does not require springs or mechanical biasing means in its 13 operation 14. In the practice of the invention, a pair Or cylindrical 15. rollers constituting a piston are interconnected by a flexible 16. band having its ends affixed to the chamber in which the piston 17. is displ~ceable. The band ~s adapted to engage electrical ter-18. minals deflned on a printed circuit board within the chamber and 19. the chamber is provided with gas lnlet and outlet ports spaced 20. such that piston displa¢ement permits flow from the chamber 21. through the outlet port. The outlet port openlng unlformly ln-22. creases proportional to plston dl8placement indlcatlng increased 23 gas flow, 24. As the plston rollers occupy the entire cross-sectional 25. configuratlon of the chamber, all of the gas within the chamber 26, is utilized to produce piston displacement and piston movement 27. itself controls gas flow through the outlet port.
28. In the practice of the invention only three movable ele-29. ments are utillzed and the piston rollers are displaceable a-30, gainst gravitational forces with very little frictional engage-31. ment with the chamber walls The low frictional operating 32. characteristics, in con~unction with the fact that the flexible 33. band is directly "laid" upon the printed circuit board terminals, lasso32 1. rather than resulting in a sliding engagement, assures a high 2. degree of accuracy even though the rate of gas flow may be small.
3, The aforementioned ob~ects and advantages of the invention 4, will be appreciated from the following description and the

5, accompanying drawlngs wherein:

6. Flg. 1 is a diametrical elevational sectional view of a

7, gas flow transducer in accord with the invention, the piston

8, being shown in the zero or inactive position,

9, Fig. 2 is an elevational substantially diametrical section-

10. al view taken along section II-II of Fig. 1,

11. Flg. 3 is a plan sectional view taken along section III-

12. III of Fig. 1,

13. Fig, 4 is a detail elevational sectional view lllustrating

14, the printed circuit board as taken along section IV-IV of Fig,l,

15, Flg. 5 is a detail sectional view similar to Fig, 1 illus-

16. trating the piston rollers in an eleYated gas flow sensing posi-

17. tion,

18. Fig. 6 is a plan sectional view taken through section VI-

19. VI of Fig. 5~

20. Fig. 7 ls a detail elevational sectional view illustrating

21. the chamber sidewall in which the outlet port is defined as

22. taken along section VII-VII of Fig. 5

23. Fig, 8 i5 a perspective view of the section rollers and

24. associated band, per se, and

25. Fig. 9 is a schematic illustration of a typical electric

26. circuit used with the transducer.

27. With reference to the drawings~ a gas flow transducer in

28. accord with the invention includes a cylindrical housing 10

29. closed at its lower end by lower head 12 and at its upper end

30, by upper head 14. The housing and heads may be formed of a

31. synthetic plastic material and assembled by screws, or solvents,

32. to define a gas tight volume. The upper head 14 is threaded to

33, receive an electrical conductor fitting 16 and a gas discharge 1059~3Z

1. fitting 18. The lower head 12 includes a chamber inlet port 20 2. communicating with the threaded gas inlet fltting 22 to whlch 3. the gas supply source is attached by appropriate conduits, not 4 shown.
A cylindrlcal caslng 24 ls attached to the head 12 by 6. screws 26 and the casing is of a length less than the dlstance 7, separating the heads 12 and 14 and includes a central rectangu-8, lar bore or opening 28 having a height equal to that of the cas-9, ing height, Fig. 1, and a length represented by the vertical di-10. menæion as shown in Fig. 6 and a width as represented by a hori-11, zontal dimension, Flg. 6. The port 20 communlcates with the 12, lower end of the opening 28.
13, The left sidewall of the opening 28, as shown in Fig, 1, 14. has a dielectric printed circuit board 30 attached thereto and 15, in the preferred embodiment the board haæ a width equal to the 16, length of the opening, as will be appreciated from Fig. 6 where-17. in the board, in effect, defines one of the sidewalls of the 18. effective gas chamber, as later described. Th~ board 30 ln-19. cludes a plurallty of elongated conductlng termlnals 32, Flg. 4, 20. deflned upon lts surface faclng the gas chamber, and the ter-21. minals are connected to reslstors 34 attached to the upper por-22. tlon of the board whlch extends above the upper end of the 23. ca~lng 24, Flg. 1. Electrical connectors passing through flt-24, ting 16 are connected to the printed circuit board and to the 25, flexible band or strap utilized with the plston, as later des-26, crlbed.
27. An elongated outlet port 36 is defined ln the opening 28. sidewall 38 and centrally located thereln, as will be appreci-29. ated from Figs. 6 and 7. The port 36 is of an elongated con-30, figurat,lon and has a variable area as defined by obllquely 31, oriented vane 40. The lower inner edge of the vane is substan-32, tially aligned with the plane of the sidewall 38 while the upper 33. portion of the vane edge is disposed to the rl~ht of the side-1059~32 1. wall 38, as apparent in Fig. 5. The oblique angle Or the vane 2. 40 will be predetermined in accord with the various flow char-3. acteristlcs desired to be sensed by the transducer, and the vane 4. is pivoted on a pin 42 for ad~ustment and is fixed in position, 5. such as by a set screw 44, Fig. 6.
6. A piston 46 is displaceably mounted within the opening 28 7. and this piston collectively consists Or a pair Or cylindrical 8. rollers 48 and 50 interconnected by a S-shaped metal band or 9. strap 52. The rollers and band constitute an apparatus known in 10. the mechanical arts as a "Rolamite". In the practice o~ the in-11. vention, the rollers 48 and 50 are of a length only slightly less 12. than the length of the opening 28, Fig. 6, and the diameter of 13. the rollers i~ less than the wldth Or the opening 28. The upper 14. roller 48 is disposed ad~acent sidewall 38, while the lower 15. roller 50 is dlsposed ad~acent the printed circuit board 30.
16. The configuration of the band 52 will be readily apprecia-17. ted from Fig. 8, and the band includes a metering slot 54, an 18. upper end 56 and a lower end 58. The upper end 56 o~ the band is 19. attached to the printed circuit board 30 bg a screw 60 passing 20. through stop block 62l as shown in Flg. 1, whlle the lower end 21. 58 is attached to the sldewall 38 ad~acent the head 12 by screw 22. 64 and its assoclated block~ As wlll be noted in Fig, 5, the 23, band end 58 extends vertically upwardly past the outlet portion 24. 66, closing the same to gas flow.
25. The metering slot 54 defines a flow passage through the 26. band ln alignment wlth the elongated outlet port 36.
27. It will be appreclated that a chamber 68 is deflned below 28. the piston 46 in communication with the lnlet port 20 and upon 29. the introduction Or gas into the chamber 68 the rollers 48 and 30. 50 wi~ be displaced upwardly due to the pressure within the 31. chamber. Upward displacement Or the rollers produces clockwise 32. rotation of roller 48 and counterclockwise rotation Or roller 33. 50, and the movement Or the rollers is a true rolling movement 5.

1. and the only sliding frictional contact between the rollers and 2. the caslng 24 is the nominal friction existing between the ends 3. of the rollers and the casing walls.
4. As the piston rollers move vertically two occurrences simultaneously result First, the terminals 32 defined upon the 6. printed circuit board 30 engaged by the conducting band 52 will 7 vary determined by the position of the piston 46. Secondly, the 8. rate at whlch the gas is vented from the chamber 68 will also 9, vary in accordance with the vertical position of the plston.
10. The path of gas flow through the chamber 68 is $11ustrated 11. by the arrows ln Flg 5. Gas within the chamber passes through 12. the band metering slot 54 and around the periphery of the upper 13. roller 48 into the opening defined in the outlet port 36 between 14. the roller pe~phery and the oblique vane 40. The higher the pis-15. ton 46 is located in the opening 28 the greater wlll be the 16. cross-~ectional area through the outlet port and the greater the 17. gas flow therethrough. As the gas flow through the chamber 68 dl-18. minlshes gravitational ~orces acting upon the piston causes the 19. rollers 48 and 50 to lower, and upon gas flow terminating the 20. rollers will be in the posltion shown in Figs. 1 and 2.
21. It will, therefore, be appreciated that the introductlon 22. of gas into the chamber 68 causes varlouB terminals 32 to be en-23. gaged by the conducting band 52 and through the reslstances 34 24. connected to the terminals the electrlcal characteristlcs Or the 25. clrcuit flowing through the board vary proportional to plston 26. movement. The electrlcal characteristics desired can readily 27~ be varied by varying the pattern and vertical dimension of the 28. terminals 32 on the printed circuit board and the value of the 29, resistors and, ir desired, a large number Or terminals may be 30. located on the board to achieve a very precise differential vol-31. tage during minute vertlcal displacement of the plston.
32. Due to the vertical operatlonal orientation o~ housing 10, 33. the roller 48 will impose its weight upon the lower roller 50 1059~32 l. in an oblique manner biasing the roller 50 toward the printed 2. clrcuit board 30 and such gravitational biasing force will in-3, sure that the roller 50 is always biased toward the printed cir-4 cuit board to maintain an effective electrical engagement be-5, tween the band 52 and the terminals 32 in horizontal alignment 6. with the diameter of the roller 50. As the piston rollers move 7 vertlcally the band ls rolled and unrolled upon the terminals 8. without a sliding action and the wear problems attendant with 9 sliding electrical contacts are ellmlnated. Excessive vertlcal lO, displacement of the piston 46 is prevented by stop block 62 en-ll. gaging wlth the lower roller.
12. The range and calibration of the transducer can be varied 13. by changlng the angle Or the vane 40, and also by varying the 14. weight Or the rollers 48 and 50. The rollers may be hollowJ as 15. lllustrated, and by varylng the roller wall thlckness the roller 16. weight ls readlly predetermlned.
17. O~ course, it will be appreciated that the gas flowlng 18. through the outlet port 36 into the upper portion of the hous-l9. ing 10 wlll leave the houslng through the fittlng 18 and the 20. approprlate conduit attached thereto, not shown.
21. If a vlsual lndlcatlon o~ the rate Or gas ~low 19 desired, 22. a8 well as an electrlc 9ignal, the houslng lO and caslng 24 may 23. be rormed Or a transparent materlal or portlons Or the houslng 24. and caslng may be formed Or a transparent materlal ln order to 25. permlt observance Or the posltlon of the piston rollers within 26. the opening 28. 5uch vlsual observance may be deslred in par-27. tlcular appllcatlons Or usage.
28. Flg. 9 illustrates a sample of circuitry which may be em-29. ployed and the components thereon utllize those reference num-30, bers previously employed. It will be readlly appreciated that 31. the clrcultry deflned on the prlnted clrcuit board may be var-32. led in accord with those electrical results and sensitivity de-33. sired.

~059~3Z
1, It is to be understood that modirications to the arore-2. described embodiment may be apparent to those skilled in the 3. art without departing from the spirit and scope Or the inven-4. tion

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A gas flow transducer comprising, in combination, a casing of a rectangular transverse cross section having a width and a length defining a chamber, a gas inlet port communicating with said chamber, a piston movably mounted in said chamber mov-able between minimum and maximum gas flow positions dependent upon the rate of gas flow into said chamber, said piston compris-ing a pair of cylindrical rollers each having a diameter less than the width of said chamber, parallel axes, and a length slightly less than the length of said chamber, an elongated gas outlet port communicating with said chamber at a location spaced from said inlet port and extending in the direction of piston movement, said piston controlling the location of gas flow into said outlet port, an electric signal circuit having a plurality of conducting terminals within said chamber spaced in the direc-tion of piston movement, and electric conducting means mounted upon said piston engaging said terminals comprising a flexible band of electrical conducting material having a first end fixed with respect to said terminals, a central region passing about more than half of the circumferences of said rollers in an S-configuration and a second end fixed to said casing within said chamber, one of said rollers holding said band against said terminals during piston movement whereby said circuit produces an electric signal having characteristics dependent upon the position of said piston within said chamber.

2. In a gas flow transducer as in claim 1 wherein said chamber includes an end wall and a side wall, said inlet port being defined in said end wall and said outlet port being defined in said side wall, said outlet port having an elongated configuration parallel to said side wall and of an increasing dimension in a direction away from said end wall.

3. In a gas flow transducer as in claim 1 wherein said chamber is vertically oriented having a lower end wall and opposed side walls, said inlet port being located in said end wall and said outlet port being defined in one of said side walls, said one roller constituting a lower roller and the other roller constituting an upper roller, said terminals being located on the chamber side wall in opposed relation to said one side wall and said upper roller being disposed adjacent said one side wall and outlet port.

4. In a gas flow transducer as in claim 3 wherein said outlet port has an increasing dimension in an upward direc-tion, said upper roller determining the effective dimension of the outlet port venting said chamber.

5. In a gas flow transducer as in claim 4, a printed circuit board within said chamber defining at least a portion of the chamber side wall opposed to said one side wall, said terminals being defined upon said board and engageable with said conducting band.

6. In a gas flow transducer as in claim 4 wherein said band includes an open central region defining a metering slot aligning with said outlet port when said band is disposed within said chamber adjacent said one side wall.

7. A gas flow transducer comprising, in combination, an elongated casing, a chamber defined in said casing having an end and a rectangular transverse cross section having a width defined by first and second parallel sidewalls and a length, a piston movably mounted within said chamber consisting of first and second parallel cylindrical rollers each having a diameter less than said width of said chamber and a length slightly less than the length of said chamber, an inlet port communicating with said chamber adjacent said end, an elongated outlet port defined in said second side wall extending in the direction of piston movement and transverse to the length of said rollers, a printed circuit board defining said first side wall, terminals defined upon said board within said chamber, a flexible electri-cal conducting band having a first end affixed to said board passing about said first roller toward said chamber end, be-tween said rollers and about said second roller in an S-config-uration and having a second end attached to said second side wall adjacent said end, said band being held against said termi-nals by said first roller whereby selected terminals are engaged by said band at predetermined positions of said rollers, and conducting means connected to said terminals.

8. In a gas flow transducer as in claim 7 wherein said outlet port uniformly increases in dimension in a direction away from said end, the location of said second roller deter-mining the chamber venting dimension of said outlet port.

9. In a gas flow transducer as in claim 8 wherein said band includes a central region having a metering slot de-fined therein aligning with said outlet port when said band is disposed within said chamber adjacent said second side wall.