CA2004533A1 - Magnetic linkage for bourdon tube gauges - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

A Bourdon tube (20) pressure gauge (10) has a movement amplifying mechanism (32) comprising a pinion (30) of segment (25) shaped permanent bar magnets (29a) extending radially and terminating at a circular edge magnetically driven by a pivotally mounted rack segment (25) having an arcuate band (29) of permanent bar magnets (29a) arranged in parallel alignment with polar axes extending radially of the rack and transversely of the band (29). One of the poles of each of the magnets (29a) of the band (29) is located along a driving arcuate edge thereof which faces and magnetically drives the circular edge of the pinion (30) by magnetic attraction of opposite poles. The polarity of adjacent magnets (29a) on both the pinion (30) and rack segment (25) is reversed providing alternate N and S Poles around the pinion (30) circular edge and along the driving edge of (29) the band (29), respectively. In one form of movement, the rack segment (25) is formed with an opening and the driving arcuate edge faces the opening in which the pinion (30) is positioned for operative magnetic engagement between the band (29) and pinion (30). In another form of movement, the pinion (30) is positioned radially beyond the rack segment (25). The movement is housed in a rear compartment of the gauge (10) which is lined with a magnetic flux barrier material.

Description

!-' 2004S33 ;

1. TITLE: MAGNETIC LINK~GE FOR BOURDON TUBE GAUGES ~ ;~
Il. TECHNICAL FIELD

The present invention relates to irnprovements in pressur~ gauges having pressure sensitive Bourdon tubes each operatively connected by an ~ -arcuate rack and pinion linkage to its r~tating pointer of the dial, and more particularly, to a ma~netlc drlve between the rack segment and the pinion in place of conventional gear teeth.

111. BACKGROUiYD ART

A representative structural arrangement of Bourdon tube pressure ~;gauges is shown in the drawing of U.S. Patent No. 3,975,967 in which the relatively small movemcnt of the Bourdon tube pressure sensitive free end ~ ~-29 is connecte~ by a llnkage 30 to the amplifying movement 32 for rotating shaft 34 and pointer 36. Amplifying movement 32 comprises an arcuate rack segment which, whetl pivoted by the movement of 60urdon tube free end 29 through an acut~s angle, rotates the pinion mounted to ~ ~
turn shaft 34 and pointer 36. Amplifying movement 32 thus rotates ~ ~-pointer 36 through at least one complete rotation when Bourdon tube free ~ -end 29 moves between its limits. A hair spring, operating between shaft ~ ~
34 and a portion of the housing, maintains a consistent and accurate ~ .
reading by the pointer 36 on the dial 40 by taking up any slack in the gear teeth engagement between the rack segment and pinion. This geared rack ~;
segment and pinion, with or without ihe hair spring biasing, has proved to be the weakest component in the gauge and is responsible for m~st of the .
failures and need for repairs. The hair spring has ~ tendency to break when abrupt movement of the mechanism occurs due to sudden Pressure changes and the broken spring catches in the ~ear teeth. Also, these abrupt movements cause the teeth to ~ear excessively.

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200~533, A need, therefore, exists for an improved movement amplifying mechanism which will eliminate the above described problems and provide a more reliable gauge.
,. - ~, i , i s Other patents describing the closest subject matter provid~ for a ` -number of more or less complicated features that fail to solve the problem in an efficient and economical way. None of these patents suggest the novel features of the present invention.

IY. SUMMARY OF THE INVENTION

Among the objects of the invention is to satisfy the hereinbefore mentioned need whicll will provide a rnovement amplifying mechanism of -simple and relatlvely inexpenslve construction readilY adaptable to existing Bourdon tube pressure gauges by a minimum of modification and which will be reliable and foolproof in operation and provide accuracy of readings at least ~qual to and expectedly greater than those of existing -gear teeth drives, : ~ ~
Th~ movem~nt amplifying rnechanism comprises a pivotally mounted rack segment provided with ma~netic means adapted to drive ;, ~ -complementary magnetic means provided on a pinion which rotates the ;
pointer, the pinion magnetic means comprising segment shaped magnets ; ;~
extending radially and terminating at the circular edge of the pinion. The --~
magnetic means of the rack segment constitutes an arcuate band bordering ;~
the circumference of the rack and comprises a plurality of permanent bar ;;~
magnets arranged in substantial parallel alignment with their polar axes extending radially of the rack and transversely of the band. One of the .. . . - . . . -:
.. , . .
, . . . -; .,, . ' .,: ' - ' ; ' ' ',, . ' : ~ ~ ' ;

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~ r poles of each of the magnets is located along a driving arcuate edge of the band which faces and drives the circular edge of the pinion. The polarity of adjac~nt rnaanets on both the pinion and rack segment is reversed to provlde alternate N and S poles around the pinion circular edge and along the driving edge of tho band, respectively. Thc magnets of both rack and pinion are sized for registration with each other whereby pivoting of the rack by Bourdon tube action results in accurate predetermined rotation of the pinion. A thin sheet of magnetic flux barrier material separates each ~ ~-of the adjacent magnets on both the rack and pinion se.rving to pr~vent dissipation of magnetic forces across the interfaces thereof.

In a preferred form of the invention, the rack segment has a sector -shaped opening defined by the arcuate band and a pair of radial arms extending from the hub at which the segment p!vots. The band, whlch Is supported at opposite ends by the radial arms, has an Inner arcuate edgo facing the opening and an outer arcuate edge forming the circumference of the rack with the aligned magnets extending therebetween. Also in the ~ .
preferred form, the pinion is located in the opening so that the poles of the magnets along the inner ~dgo of tho bank 6~rV~ ~8 tho drivln~ moans for the pinion an~d the relative posltions of the piniqn and the arcuate bank place the driving inner edge of the bank In prPper alignlnent with and slightly spaced franl the drlvon clrcular edgo ~ the plnlon. A shinl of soft iron extends along th~ outer ed~e of the bank covering the poles of all the magnets to direct the flux toward the inner edge of the band and hence toward the po!es of the magnets on the pinion for maximum magnetic -attraction.

In a modifiod form of the invention, the rack segment, pinion and associated ma~nots arc proportioned for locating the pinion beyond the -.

ZOO~S33 4 ~

rack segment wh~reby the outer edgo of the band faces- and drives the pinion and the shim extends alo~g the innor ed0e of the band. ~ -It is an object of this present inventlon to pr~vid~ such a device that is inexpensive to nlanufacture and maintain while retaining its effectiveness.

Further objects of the invention will be brought out in the following part of the specification, whorein detailed desoription is for the purpose of fully disclosln~ the inventlon without placlng limitations thorean.

V. BRIEF DESCRIPTION OF THE PRAWINGS

With the above and other related objects In view, the invention consists in the details of construction and co~bination of parts as will be more fully und~rstood from the followin~ description, when read in ~ ~;
conJunction with th~ accompanyin~ drawings In whlch~

Flgure 1 Is a left perspective view of a gauge embodying the . ~:
invention with parts cut away to show interior construction. ~ ;~

Figure 2 shows a vertical sectional taken substantially along line ~-2 in figure 1 showing the rack and pinion engagement.

Fi~ur~ 3 illustrat~s an enlargcd detailed fragmentary view of the rack and i?inion engagement shown in Fig. 2.

Figure 4 is a view similar to Fig. 4 but showing a modified rack and pinion arrangement.

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-~ ZOO~533 Vl. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
,: ,., Referring now to figure 1, where the present invention is generally ;-referred to with numeral 10, it can be observed that it basically includes the pressure gauge embodying the invention, seen in Fig. 1 to comprise a tubular casing 11 having an integrally formed transverse wall 12 dividing the casing into front and rear compartments. A portion of casing 11, projecting forwardly beyond wall 12, terminates in radial flange 11a . - . .
which mounts bezel 13 for retaining a lens 14 as the see-through closure for the front compartment. The latter contains dial 15 and pointer 16 which is balanced and mounted on the end of shaft 17 projecting through wall 12.

The rear compartment houses Bourdon tube 20, which may be of any ~ ~-suitable construction well known in the art, a linkage 21, and the '!-movement amplifying mechanism for pointer ~6, which mechanism comprises rack segment 25 and pinion 30. Bourdon tube 20 is supported in ~ -operative position by fitting 19 which is secured to oasing 11 and has a threaded end 19a extending therethrough for attachment to a suitable ~;
conduit communicating with a pressurized system to be monitored by ; ~
gauge 1~. A rear closure plate 11b removably attaches to the rear of ~ ~ ;
casing 11. ;~

Rack segment 25 and pinion 30 are located substantially in the plane of Bourdon tube 20, pinion 30 being mounted on shaft 17 which extends axially of casing 11 and is.suitably journaled in ~wo spaced~gs 17a and 17b for maximum support and for ease of rotation with minimum friction. Bearing 17a journals shaft 17 at an intermediate portion thereof between pointer 16 and pinion 30 and is located in wall 12 enabling shaft ~ -~
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r 6 Z00~533 17 to ext~nd ther~throu~h. Bearing 17b, which terminates the rear end of shaft 17 beyond pinion 30, is carried by a support plate 18. The latter is spaced rearwardly of wall 12 and is retain~d in position by suitable means, herein shown as two posts 12a integrally formed with front wall 12 to extend into the rear compartment and terminating in interior threaded portions to receive anchoring screws 18a in the mounting of plate 18. A pivot pin 24, supported by and extending between wall 12 and plate 18, pivotally mounts rack s~gment 25 in operative relation to pinion 30.

As practiced in the art, the relatively small radial movemel~t of the ~;
free closed end 20a of Bourdon tube 20 responsive to pressure changes within the latter is ultimately translated to rot~tion of shaft 17. To this end, linkage 21, connecting Bourdon tube free end 20a to rack segment 25, may be of any suitable construction, herein seell to ¢omprise T-sl~aped Iink 22 and bar 23. Link 22 pivots freely and h~s an e!ongated slot 22a in which a pivot pin carrier 22b is adjustably mounted. Bar 23 pivots at one end on pin 22c of carrier 22b and at the opposite end carries pivot pln 23a ,which engages and freely slides in a slot 27~ form0d in radial extonslon 27 of rack segment 25.

As shown in Figs. 2 and 3, rack segment 25 comprises a hub 26 from which radial extenslon 27 and sector portion 28 extend in opposite directions. Hub 26 mounts a suitable bearing for journaling rack segment 25 on pivot pin 24. Sector portion 28 comprises a pair of radially extending arms 28a supporting an arcuate ba,nd 29 extending therebetween to provide an opening 28b which likewise may be sector shaped. Sector portion 28 and opening 28b are proportioned and located by pivot pin 24 to accornmodate shaft 17 and pinion 30 passing therethrough. Arcuate band ..
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200~S33 29 is form~d to provid~ about ten bar magnets 29a arranged in substantial ~ -parallel alignment with polar ax~s extending radially and separated from each other by thln sheets 29b of a magnetic flux barrier material, such as lead, which may have a thickness of about .020 inches. The polarity of adjacent magnets 29a are reversed so that the poles bordering the interior edge 29c of ~and 29 are in alt~rnating sequence as indicated in the drawings. ~ shim or cover 29e may be positioned to extend along the exterior edge 29d of band 29, shim 29e being made of a magnetic material, such as soft iro~l, which will serve to direct and intensify the magnetic fîux of magnets 29a toward magnets 31a of pinion 30.
. ~ ~
Pinion 30 comprises a plurality of bar magnets 31a separated by - .
barrier sheets 31b. Magnets 31a radiate from a hum 31, which is also made of a magnetic barrier material, to a circular edge 31c, the polarity of adjacent magnets like that of magnets 29a being reversed to-provide poles bordering edge 31c in alternating sequence. Pinion 30 is mounted along shaft 17 for planar ali~nment with rack segment 25 and is -~positioned so that interior edge 29c of band 29 and circular edge 31c of ~ -pinion 30 are out of contact with each other, the spacillg being very sllght, such as, .0101to .020 inches.

All parts of gauga 10 will be made of a non-magnetic metal, plastic or the like. For example, casin~ 11 rnay bc c~st ~llJmlnum, ~vhlch not only serves as a non-magnetic metal but Is used In th~ prlor art wherein transverse wall 12 protects the operator should Bourdon tube 20 rupture.
The other parts, such as, rear closure plate 11c, shaft 17, support plate 18, fitting 19, Bourdon tube 20, linkage 21 and rack segment 25, are made of non-magnetic stainless steel, brass or the like metal alloys. To protect the magnetic operation af rack segment 25 and pinion 30 from ;: ' :'' ' ' .... ' ~'' : ' ' . '. ' ' ' ' .

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200~533 exterior magnetic fields, the interior surfaces of the walls of the rear compartment have a lining 11c of magnetic barrier sheet material, such as the lead of sheets 29b and 31b. Magnets 29a and 31a are preferably ceramic but may bf made of other suitable types, sueh as alnico 8, samarium cobalt 18 and the like.
~, The practieal utility and operation of ~a~ge 10 wlll now be apparent.
Rack segment 25 thrpugh linkage 21 responds to movement of Bourdon tube free end 20a in the conventional well understood m~nner. When gauge 10 is assembled, linkage 21 will position rack segment 25 so that the -~
lower end of arcuate band 29 aligns with pinion 30 to correspond to the relaxed minlmum pre6sure position of Bourdon tube 20. The gauge -assembly includ~s adjustin~ pinion 30 by rotation with respect to rack se~m~nt 2S wh~r~by pointer 16 extends vertically downwardly to indicate ~n appropria.te readln~ ~n dial 16 approximately as shown in Fig. 2. The alternat~ N and S p~les loeat~d alon~ interior edge 29c of arcuate band 29 will always attract an opposite S and N pole on circular edge 31c of pinion 30. This attraction between magnetic poles on pinion 30 and unlike poles ~-;
in registered alignn~ent on band 29 will cause pinion 30 to rotate in perfect unison with the rotation of rack se~jment 25 as driv~n by the action of Bourdon tube 20. Whereas, pinion 30 is initially mounted on shaft 17 to properly position pointer 16 with respect to dial 15, minor adjustment of rack segment 25 to achieve more accurate aligllment of pointer 16 with dial 15 may. be made by movement of pivot pin earrier 22b in slot 22a. Dial 15 may also be rotatable by suitable exterior means (not shown) as is practiced in the prior art to provide dial oalibration.

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~-. 9 ~-ZOO~533 In the illustrated emdodiment, it is intended that pinion 30 have a :
diam~ter of about .3 inches which provides suitable dimension for eight equally sized sector shaped magnets 3ia to sequentially register with ten correspondingly sized magnets 2sa on band 29. As seen in Fig. 2, wh~n Bourdon tube fr~e end 20a is in minimum pressure position, the second magnet from the lower end of magnets 29a on band 29 is the primary operative magnet with which a facing magnet 31a of opposite polarity o~
pinion 30 aligns, positioning pointer 16 at 6 o'clock, whlch conventlon~lly is the minimum reading on dial 15. As the pressure rises in Bourdon tube 20 and free end 20a moves radially outwardly, rack segment 25, through linkage 21, is rotated clockwise on pin 24 which rotates pinion 30, shaft 17 and pointer 16 also in a clockwise directlon as Is conventional for reading pressure indications on dial 15. When Bourdon tube 20 is at ~ -substantially maximum pressure, rack s~msnt 25 will be in an approximato extrerne clockwise posltion so that the uppermost magnet on band 29 wlll operatlvely face plnlon 30 whlch has been rotated approximately 360 degrees by the movement of rack segment 25 so that pointer 16 is again close to 6 o'clock.

The rack segment 25 and pinion 30 may be proportioned tor a pointer sweep in excess of 360 degrees between mlnlm~m and maximum Bourdon tube pressurq respons~s and conventional means, well known in the art, . -may bo used for a dial indication that pointer 16 is in the second revotution. -Fig. 4 Illustrates a modified rack segment and pinion arrangement in which pinion 40 is located radially beyond the rack segment 35. Pinion ~ -40, which is similar to pinion 30, has hub 41 with radial bar magnets 41a separated by sheets 41b. Rack segment 35 is similar to segment 25, ... , . - ~ - - ......... . .. - . - ~ ~

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-. : . . : - - .:

~-; 10 - ZOO~533 having band ~9 and bar magn~ts 39a s~parat~d by sheets 39b. The poles of magnets 41a at circular ~d~e 41c operatively ~ace the opposite poles of bar magnets 39a arranged alon3 th~ extsrior edg~ 39d of arcuat~ band 39 of rack segm~nt 35 and a shim 39e is carried on the interior edge 39c of band 39.

In order to preserve the conventional clockwise rotation of pointer 16 from minirnum to maximum readings on dial 15, Bourdon tub~ 20 is positioned so that free end 20a is located on the left slde of the ~asing 11 as seen from the front when rack segment 25 and pinion 30 are used, as -~
shown in Figs. 1 a,ld 2, and, accordingly, the parts are reversed and located in the conventional manner on the right side of the casing when employing the modified arrangement of rack segment 35 and pinion 40. n;
. ,~" ~.

The magnetic linkage for Bourdon tube gauges llerein disclosed is seen to achieve the several obJects of the imention an~ t~ be well adapted to meet conditions of practical use. As various possible embodiments might be made of this invention, and as various changes might be made in the disclosed device, it is to be understood that all matters herein set -forth or shown in the accompanying drawings are to be interpreted as -~
illustrative and not in a limitin~ sense.

It is believed the fore~oin~ ~escription conveys the best understandin~ of the objects and advanta~s of tha present invention.
Different embodlments may be made of the Inventive concept of this invention. It is to be understood that all mattar disclosed herein is to be interpreted marely as illustrative, and not in a limitin~ sense. -~,. . ~.

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200~533 Vll. INDUSTRIAL APPLICA~ILITY
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It is apparent from the previous paragraphs that an improvement of the type for such a magnetic linkage is quite desirable for a movement . : -:
amplifying mechanism of simple and relatively inexpensive construction ~: ;
readily adaptable to existing Bourdon tube pressure ~auges by a rninimum of modification and which will be reliable and foolproof in operation and provide accuracy of readings at least equal to and expecte~ly greater than those of existing gear teeth drives........ . :
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Claims (10)

1. A movement amplifying mechanism for converting a relatively short radial movement of the free end of a pressure gauge Bourdon tube to the rotary motion of a shaft on which a pointer is mounted for indicating pressure values on a circular dial, said movement amplifying mechanism comprising a rack segment pivotally mounted for acute angular movement and pinion mounted on said shaft, a linkage connecting said Bourdon tube free end for pivoting said rack segment in response to said Bourdon tube end movement, said rack segment having an arcuate band carrying magnetic means, said pinion having complementary magnetic means located for operative magnetic engagement with said rack segment by said Bourdon tube free end movement rotates said pinion and shaft for predetermined pressure indication on said dial by said pointer.

2. The movement amplifying mechanixm defined in claim 1 in which said pinion magnetic means comprises radially extending segment shaped permanent magnets terminating at a circular edge of the pinion, said arcuate band magnetic means comprising a plurality of permanent bar magnets arranged in parallel alignment with respective polar axes extending radially of the rack and transversely of the band, one of the poles of each of said magnets being located along a driving arcuate edge of said band which faces and drives said circular edge of said pinion, the polarity of adjacent magnets on both the pinion and arcuate band being reversed, the respective magnetic poles along said arcuate band driving edge and around said pinion circular edge being sized for registration between magnets of opposite poles facing each other on the respective edges results in said pinion rotation.

3. The movement amplifying mechanism defined in claim 2 in which a sheet of magnetic flux barrier material separates the adjacent magnets on both said arcuate band and said portion.

4. The movement amplifying mechanism defined in claim 3 in which said pinion has a hub of magnetic flux barrier material from which said segment shaped magnets radiate.

5. The movement amplifying mechanism defined in claim 2 in which said rack segment is formed with an opening, said arcuate band and driving arcuate edge bordering said opening, and said pinion being located in said opening for operative magnetic engagement of said circular edge with said arcuate edge.

6. The movement amplifying mechanism defined in claim 5 in which said arcuate band has an exterior edge along which the other poles of the magnets of said band extend, and a cover of magnetic material extending along said exterior edge for directing and intensifying the magnetic flux of said magnets of the arcuate band toward the magnets of said pinion.

7. The movement amplifying mechanism defined in claim 2 in which said rack segment is formed with an opening, said arcuate band having an interior edge bordering said opening and an exterior edge serving as said driving edge, said magnets extending transversely between said edges, said pinion being located radially outwardly of said rack segment for operative magnetic engagement of said circular edge with said exterior driving edge, and a cover of magnetic material extending along said interior edge directing and intensifying the magnetic flux of said magnets of the arcuate band toward the magnets of said pinion.

8. A Bourdon tube pressure gauge comprising a tubular casing having a transverse wall dividing the casing into front and rear compartment, a Bourdon tube mounted at one end on said casing in said rear compartment and having an opposite free end adapted to move radially outwardly and inwardly in response to pressure changes within said Bourdon tube, a movement amplifying mechanism for converting the relatively short radial movement of said Bourdon tube free end to the rotary motion of a shaft on which a pointer is mounted for indicating pressure values on a circular dial, said movement amplifying mechanism comprising a rack segment pivotally mounted for acute angular movement and a pinion mounted on said shaft, a linkage connecting said Bourdon tube free end for pivoting said rack segment in response to said Bourdon tube free end movement, said rack segment having an arcuate band carrying magnetic means, said pinion having complementary magnetic means located for operative magnetic engagement with said rack segment by said Bourdon tube free end movement rotates said pinion and shaft for predetermined pressure indication on said dial by said pointer, a rear closure plate for said rear compartment mounted on said casing, said casing Bourdon tube, rear closure plate, rack segment; linkage and shaft being made of a non-magnetic material, and said rear compartment having a lining of magnetic flux barrier material to isolate said arcuate band magnetic means and pinion complementary magnetic means from external magnetic interference.

9. The Bourdon tube pressure gauge defined in claim 8 in which said pinion magnetic means comprises radially extending segment shaped permanent magnets terminating at a circular edge of the pinion, said arcuate band magnetic means comprising a plurality of permanent bar magnets arranged in parallel alignment with respective polar axes extending radially of the rack and transversely of the band, one of the poles of each of said magnets being located along a driving arcuate edge of said band which faces and drives said circular edge of said pinion, the polarity of adjacent magnets on both the pinion and arcuate band being reversed, the respective magnetic poles along said arcuate band driving edge and around said pinion circular edgy being sized for registration with each other whereby the magnetic attraction between magnets of opposite poles facing each other on the respective edges results in said pinion rotation, a sheet of magnetic flux barrier material separating the adjacent magnets on both said arcuate band and said pinion, and said pinion having a hub of magnetic flux barrier material from which said segment shaped magnets radiate.

10. The Bourdon tube pressure gauge defined in claim 8 in which said rack segment is formed with an opening, said arcuate band and driving arcuate edge bordering said opening, said pinion being located in said opening for operative magnetic engagement of said circular edge with said arcuate edge, and said arcuate band having an exterior, and a cover of magnetic material extending along said exterior edge for directing and intensifying the magnetic flux of said magnets of the arcuate band toward the magnets of said pinion.