[1]3 , 0 1 3 , 2 3 3 United States Patent Office Patented Dec. 12, 1961 3,013,233 PRESSURE RESPONSIVE ELECTRICAL l[r-4STRLTMENTS Marlan E. Bourns, 2482 Carlton Place, Rivel@side, Calif. Continuation of application Ser. No. 591,370, June 14, 5 1956. This appheation Apr. 11, 1960, Ser. No. 21,361 8 Claims. (Cl. 338-40) The prese@it invention relates to pressure tr ansducers, 10 and is a continuation of my pending application, Serial No. 591,370, filed June 14, 1956 now Patent No. 2,932,807, entitled Pressure Responsive Electrical Instruments. More specifically, the present invention is concerned 1,5 with pressure transducers of the ]3ourdon tube type embodyin@- a variable resistor wherein movement of the free end of the Boi-irdor@ tube responsive to changes in the pressure differential betwe.-n the inside and outs;de of the ]Boljrdon tube is coiiverted into an electrical signal 20 th,e, can be utilized to actuate a meter or t-he like, or to control some mechanism, or which can be telemetered to a remote control center. The primary object of the present invention is to provide a Dressure transducer of the Bourdon ti-ibe type, which 25 is extremely sensitive in response, and in which the fre,- end of the Bourdon tube moves over an extended range of travel, thereby providiig improved resolution of the electrical signal. Another object of the invention is to provide aii in- 30 strument of the class described which is substantially unaff-ected by vibration and acceleration forces. A furt-her object of the invention is to provide a sensitive pressure responsive instrument embodying a coiled Bourdon tube hn-ii-ing a plurality of turns, wherein the 35 free end of the Bourdon tube is supported by pivotal support means so that it is f-ree to turn responsive to c-hanges in pressure differential between the inside and outside of the Bourdon tube, but is restrained against displacement in any other direction due to vibration or 40 acceleration. Still another object of the invention is to provide a dif@lerential pressur,e responsive instrument for producing an electrical signal that is a function of the sum or differeiice of two different fluid pressures, and which is extre.nely sensitive to the fluid pressures being measured, 45 yet at the same time relatively insensitive to the effects of vibration and acceleration forces. The foregoing objects are achieved in the pres,-nt invention by using a coiled B,)urdon tube having a pluralit r y )0 of turns, and a variable resistor having a rotary me-mber and a stationary member. The rotary member of the variable resistc>r is oonnected dir-.ctly to the movable end of the Bourdon tube so as to elim;nate b,ack-lash movable end of the Bourdon tube is pivotally supported with respect to the stationary member of the variable resistor so that the free end of the Bourdon tube is restrained against movement other than rotational move- 60 -ment about the center of rotation of the said rotary tnember. For the purpose of measuring differential pressures, the present invention provides two helical Bourdon tubes arranged end-to-end, the movable ends of the - Bourdon 65 tube bein.- disposed adjacent one another and being connected to.-ether by p'@Votal means, whereby the ends of the Bourdon tubes are restrained against sideways movement with respect to one another. The resistance element of the variable resistor is mounted on one of the 70 helical Bourdon tubes, and the contact member is mounted on the otlier. Two different fluid pressure sources may 2 be connected to the two Bourdon tubes, and the relativedisplacement of the contact member with respect to the resistance member is a function of the sum or difference of the fluid pressures, dependi-@ig upon which way the two helioal Bourdon tubes are coiled. The foregoing and other objects and advant-,iges of tie pres-nt invent;on will become apparent to those skilled in the art upon consideration of the followin.- detailed description of the preferred embodiment tli,-reof, reference being had to the accompanyin- drawings, wherein: FIGURE I is a loligitudinally s--ctio-@ied view of a pressure responsive instrument embodying the principles of the present invention; FIGURE 2 is a transverse section of ,he same, taken at 2-2 in FIGURE 1; and FIGURE 3 is a sectional view, taken at 3-3 in FIGURE 1. In the drawings, the reference numeral 10 designates tfie pressure transducer in its entirety. The i@istrument 10 includes a housing consisting of a tubular case 11 which is closed at both ends by circular end plates 12 and 13. The end plates 12 and 13, toge'ther with ',h-. tubular case 11, enclose a cavity 15 within which are disposed two helically coiled Bourdon tubes 16 and 17. The Bourdon tubes 16, 17 are arranged end-to-eiid, and are coaxial with respect to oile another. Ti@e otiter ends of the Bourdon tubes 16, 17 are bent outwardly to provide axially projectin.- portions 20 which are s,-cured witbin holes i-@i the end plates 12, 13. The iTiterior of Bourdon tube 16 is connected by a short passageway 21 to a tlireaded aperture 22, which is adapted to receive a pipe fitting connecting the Botirdon tube to a suitable source of fluid pressure. The other Bourdon tube 17 is likewise connected by a short passageway 23 to a threaded aperture 24, into which another pipe fitting may be screwed to connect the Bourdon tube 17 to a second source of fluid pressure. The inner ends of the Bourdon tubes 16, 17 are plugged in the usual manner, and these ends are movable responsive to changes in the pressure differential between the inside and outside of the Bourdon tube. As the pressi-ire on the inside of the Bourdon tube incr-.ases, the helically wound tube tends to unwind, thereby cai-ising the free end of the Bourdon tube to move in a substailtially circular path around the axis of the helix. A radially extending bar 25 is fixed to the movable end of Bourdon tube 16, and projecting from the outer face of the said bar is a pivot pin 26. The pin 26 is rotatably received within a sleeve bearing 27 fixed to another i rad ally extending bar 28 which is attached to the movable end of Bourdon tube 17. Tlius, the adjacent ends of the Bourdon tubes 16, 17 are pivotally connected together by means of the pivot pin 26 and sleeve bearin27, so that the movable ends of the Bourdon tubes ar@e spect to one another' Mounted on the outer face of the bar 25 concentric with the pin 26 is a disc 30 of dielectric -rnaterial, such as plastic or the like, and secured on the outer face of the disc 30 is an arcuate resistance element 31 which may be of composition material, or it may be of the wirewound variety. As best shown in FIGURE 2, the center of curvature of the arcuate resistance elem-.nt 31 coincides with the center of the pivot pin 26. Mounted on the outer face of the bar 28 concentric with the sleeve bearing 27 is another disc 32 of dielectric material, and attached to the face of the disc 32 adjacent the outer periphery thereof is a sprin- contact member 33 which extends across the gap to th. resistance, element 31, and presses lightly against the surface thereof to ma'Ke electrical contact therewith. The contact and other problems inherent in systems using mechanical 55. free to turn with respect to one another, but are reamplificatio-@i of the travel of the Bourdon tlibe. The strained against radial, or sideways, movement with re-
[2]3 33 is connected by a wit-e 34 to a termilial 35 on end ,olate 13, while the resistance element 31 is connected at or@c end thereof to a 'Lerminal 36 on end plate 12 by means of a wire 37. If desired, 'he two ends of the resi s'ance,clemen'L 3-1 may be con-@iected to two separate terminal posts, so that the electrical signal means of the instrumeiit may be used as a potentiometer. 'f'he operation of the invention is believed to be clear from th.- fore-oing description and the drawings. Fluid pressure is introduced into the interior of each of the h--Iically Poiled Bourdon tubes 16, 17, causing the movFtble ends thereof to rotate in a circular path as the Do,-,.rdon tube attempts to straighten out. The pivotal conri,-ctions 2(3, 27 provides a support for the movable end ol' the BoLircloii tube between the contact 33 and resistapee eleme-nt 31 other than rotational movement about the pivc,@t centcr. Thus, relative sidcways movement betwee,i the contact member and resista-@ice element di-ie to v:ibrat;on or acceleration forces is prevented, and the instrtiment is relatively irsersist,.ve to such forces. The M-LI.Itiple turns of the helical Boiirdon tubes provide a lar@e tra@,Lcl of the movable ends for any given incremetit of pressure clan@e, and this eliminates the need for r-ritiltiplying linkage to ampliiiy the travel of the' Bourdon tube so as to provide enough length of travel of tric co@qt,,ict 33 alon@- the length of the resistance element for adc@quate ran.-e and resolut-lon of the electrical sigr@al. @ c Bourdoi tube 17 may b ev -L h acuated to a vacuum and the throad.-d aperture 24 scaled by a suitable plug. 1-@i t!,iis condit;o-.q, the iistrument ,vould provide an absolute i)rcssure gage readin- for fluid presstire admitted to the interior of Bourdon tub-@ 16. Alternatively, the t'iirv,ded aperture 24 mi,-ht b-z opened to the atrnosphere, in which case the instrument would indicate the difference betw,-en the fluid pressure admitted to Bourdon tube 16 and atmost)lieric vressure. The cavity 15 r-@iay be evacuated, or filled with -as at some predetermined pressure, and is the-@i sealed so as to maintain a constant pressure on the o@itside of the Bourdon tubes 16, 17. Where it is desired to measure the sum or difference of tvio d;fferent fluid pressures, one of the sources of @Iiiid pressure m,-,y be connected to the interior of Bourdon tub-- and the other connected to t'Qe interior of Boil-rdon tiibe 17. In this case, the two Bourdon tubes "LS, '@-7 will react to their resp.-ctive pressure differentials, produc;Til- reiative r@ioveme-it of the contact member 33 m7ith resp-et to tile resistance element 31 that is a funetion of the sum or diff.-rence of the fluid pressures, d.,-pending upon the direction in which the Coils of the h-,-,@ices 16, 17 are wound. W'--iile I have shown and described in considerable detail what I b.-lieve to be the preferred form of my inv,-ntion, it will be understood t,i-,t various chan.-cs may be mad-, ;n the shap,- apd arrqn,@ement of the several p,,irts k@,ithout from the broad scope of the iiivention, as defined in the appended claims. l cl-,iim: 1. A pressure responsive instrument comprising a liousipg, a coiled BoLirdon tube mounted at one end on said hotisi,.i-, the other end of said Bourdon tube being movable in an arcuate path respoisive to changes in thep.-esslire differential between the inside and outside of said Bourdon tube, a resistance member and a contact member disposed for movement relative to one another, said conlact meniber being adapted to wipe on said resista-@ice Tremb,-r along thelen.-thwise dimension thereof, one of said members bein.- mounted on said movable end of said Bo--irdon ttibe, support means for the other of said P-.embLrs, rigid means on said Bourdon tube extendin.g laterally from the movable end thereof through the center of the arcuate path traversed by said movable c-@id, aiid a pivotal connection between said last-named means and s-,tid support me-,qns, said pivotal c(>nnection 3,013,23@ 4 bei-@i- located at the center of arcuate movement of said movab@e end of said Bourdon tube -@nd serving to prevent disi)la6ement of said contact member with respect to said resistancc member other th,,in along the le-.igthwise dimension thereof. 2. A pressure responsive instrtiment as defined in P-laim 1, wherein said Bourdon tube is coiled into the form of a helix. 'o. A pressure responsive instrument as defined in 10 claim 1, wherein said contact member is mounted on said m,,azable end of said Bourdon tube, and said rcsistance Ti-iember is mounted on sa:id support means. 4. A pressure responsive instrument comprisin.@ a housing, a coiled Bourdon tube tube mounted -,it one end I r) on said housin.-, the other end of said Bourdon tube bein.- movable in an arcuate path resi)onsive to changes in the pressure differential between the ins-ide and outside of said Bourdon tube, a resistance elemcnt mount.,d withi-ii said housing generally parallel to the line of 20 tra@iel of said movable end of said Bourdon tube, supporting mc,,ins pivot-zd for rotation about a center point slibstantially at the center of curvature of said coiled Bourdon tube, said supporting mcaiis being connected with said movable end of said Bourdon 25 tube to support the same for arcuate movement about said c,-nter point and to restrain said movable end of said Bourdon tub.- against radial movement with respect to said center point, and a contact memberoperatively coii nected to said movable end of 30 said Bourdon tube and wipin,a on said resistance element. 5. A pressure responsive instrument as defined in claim 4, wherein said Bourdon tube is coiled into the form of a helix. 6. A pressure responsive instrument comprising a 35 housing, a @irst coiled Bourdon tube mountp-d at one end on said housing, a second coiled Bourdon tube mounted at one end on said housing coaxial with said first coiled Do-tirdon tube, the free ends of said Bourdon tui)es t)eing movable in concentric circular paths responsive to 40 elianges in the pressure differential between the inside and outside of said Bourdon tubes, m,-ans pivota]Iy connecting the free ends of said Bourdon tubes to,-ether whereby said said free ends are rotatable with respect to 45 one another but restrained against radial movement with respect to one another, a resistance element mounted on the free end of one of said Bourdon tubes, and a contact memb.-r mounted on the free end of the other Bourdon ttibe, said contact member widin.- on said resistance ele50 ment. 7. A pressure responsive instrument as defined in claim 6, wherein said resistance element is curved into the form of a circular arc havin.- its center of curvature coincident with the center of said pivotal connecting means and said contact member is movable in an arcu55 ate paih concentric with the ciirvature of said resistance element. 8. A diff-erential pressure responsive instrument as defined in clair-r,. 6, wherein said Boiirdon tubes are coiled into the form of helices, said first and second Bourdon 60 tubes b@-ina disposed end to end, with their respective free ends closely adjacent one another, and rneans for introducing fluid pressure media from two different pressure sources to the interiors of said Bourdon tubes, re65 spectively. Referenceg Cited in the file of this patent UNITED STATES PATENTS TO 2,622,177 Klose ---------------- Dec. 16, 1952 2,810,800 Hasselhorn ------------ Oct. 22, 1957 FOREIGN PATEI\TTS 714,507 Great Britain ---------- SePt. 1, 1954
[3]UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,013,233 December 12, 1961 Marlan E. Bourns It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as co.-rected below. Column 3., line 149 for "connections 26, 27 provides a support" read -- connection 26, 27 provides support line 29, after "vacuum" insert a comma, column 4, line 14, strike out "tubefl, second occurrence. Signed and sealed this 25th day of September 1962 (SEAL) Attest: ERNEST W. SWIDER DAVID L. LADD Attesting Officer Commissioner of Patents
