US1942027A

US1942027A - String galvanometer

Info

Publication number: US1942027A
Authority: US
Publication date: 1934-01-02
Anticipated expiration: 1951-01-02

Description

Jan. 2, 1934. F. o. HINDLE STRING GALVANOMETER a Shets-Sheet 1 Filed Feb. 27, 1935 Jan. 2, 1934. R Q HlNDLE A 1,942,027

STRING GALVANOMETER I Filed Feb. 27, 1933 3 Sheets-Sheet 2 Jan. 2, 1934. F o HiNDLE 1,942,027

STRING GALVANOMETER Filed Feb. 27, 1933 3 Sheets-Sheet 3 Patented Jan. 2, 1934 UNETED STATES PATENT QFFICE STRING GALVANOMETER Application February 27, 1933. Serial No. 658,782

15 Claims.

This invention relates to new and useful im-' provements in string galvanometers, and has particular relation to improvements in the type of instrument disclosed in my prior Patents Nos.

1,416,824. of May 23, 1922 and 1,702,650 of February 19, 1929, and is intended especially for use in the Electro-cardiograph, although it is not limited to this use.

An object of the invention is to provide a string galvanometer including a pole piece construction whereby the pole pieces are permanent- 1y secured together against any relative movement.

Another object is to provide an improved meth- 0d of manufacturing and mounting the pole pieces for a string galvanometer.

A further object is to provide a string galvanometer including means mounting the electro conductive string member and means so securing the mounting means that it may be easily and quickly removed and anothersubstituted should a string break or should another string for any other reason be required.

A still further object is to provide an improved $5 construction whereby it is not necessary to bore out the centers of the poles of the magnets to receive the microscope tubes with the consequent reduction in field strength.

An additional object is to provide a string gal-- vanometer of generally improved'construction including an improved base or mounting means and improved. and simplified means for mounting the parts thereon.

Other objects and advantages will become ap- 85 parent from a consideration of the following detailed description taken in connection with the accompanying drawings wherein a satisfactory embodiment of the invention is shown. However, it will be understood that the invention is not limited to the details disclosed but includes all such variations and modifications as fall within the spirit of the invention and the scope of the appended claims.

In the drawings:

Fig. l is a front elevational view of the improved device, parts being broken away to show detaiis of construction;

Fig. 2 is a transverse vertical sectional view taken substantially along the line 2-2 of Fig. 1;

3 is a view partly in section and, partly in elevation, the view being taken substantially along the lines 3-3 of Fig. 1; t

Fig. l is a sectional View taken substantially along the line H of Fig. 3;

Fig. 5 is a front elevational view of the base or mounting member alone;

Fig. 6 is a bottom plan view of the base with the magnet pole pieces in place thereon;

Fig. '7 is a perspective View of the pole pieces; 30

Fig. 8 is a transverse sectional view illustrating a step in the manufacture of the pole pieces;

Fig. 9 is a sectional view through the completed pole pieces;

Fig. 10 is a view somewhat similar to Fig. 8 but a; showing a modified construction; and

Fig. 11 is a perspective view of a portion of a field magnet employed.

Referring in detail to the drawings, my improved instrument includes a base or mounting 79 means generally indicated at 12 and best shown in Figs. 5 and 6. This mounting member includes a plate-like portion 13 preferably in the form of a casting of non-magnetic metal, as for example aluminum. Integral with the plate 13 and extending nearly from end to end thereof, at a point midway between its side edges, is a raised portion or rib 14 slightly hollow or grooved in its upper surface to provide flanges 15 the purpose of which will later appear. Substantially centrally or in other location as desired the member 12 is provided with an opening 16 for the passage of a screw or other fastening means, and adjacent the respective ends of the rib 14 openings or screw holes 17 are provided and the purpose of these openings will later be fully set forth.

At diametrically opposite points on the side edges of the plate 13 and in parallel relation with the rib 14 and with one another a pair of outwardly extendingprojections or bearing

members

18 and 19 are provided each of said projections being hollow or formed with an opening therethrough, the opening 20 in the outer portion of each projection being of greater diameter than 95 the opening 21 in the inner portion thereof. Later in the description of the assembled device the functions of these parts will be made clear. Strengthening ribs 22 are formed on the inner surface of plate 13 and connect with the end portions of the rib 14, and other strengthening ribs 23 are similarly formed on the plate 13 and connect the intermediate portion of the raised portion or rib 14 with the projections or bearing

members

18 and 19.

According to the present

invention pole pieces

24 and 25 are so constructed and connected as to form substantially a solid-unit wherein the said pole pieces can have absolutely no relative moven permanently connected.

ment. To attain the most efiicient Way of causing the magnetic flux to concentrate at the center it is well known that these pole pieces should be substantially wedge shaped in transverse section and should be arranged with their narrow edges in opposed relationship. In manufacturing the pole pieces I .take a .cross sectionally square or rectangular bar 526 isee Fig. of {magnetic ,rnaterial as iron and mill or cut away a portion thereof to provide a ll-shaped groove 27 the angle of the side walls of which may be anything desired but usually is approximately 45. The apex of this groove is located slightly to one-side-of the center or the bar 26.

Next, according to one anathodgl welding-ether the two walls of the grooye by depositing welding material (non-mag n etic metal such as bronze) 28 in said groove until it is entirely or substantially entirely filled as best shownin 9. The magnetic bar 26 is first heated to a point that as the metal :28 :is melted and-deposited it adheres firmly to the iron landtller-mS aibodyiused to and dcrnring .a weld laetiween 11118 ;Side Walls the groove127-whereby said avails are inieaidlyand 'ilhis process is (continued ezntil the groove is dill-led with :the henm netic metal isnbstantial y in e ral si'iiuctnre provided. ":llhereafiter, (see Fig. 19) a similar groove 29 is formed in the @pposite :Side of said bar of metal an a :the cornpletion of she groove a saw or tether .slot :39 is provided separating :the remain n 19 215 0135. the bar into the pole pieces i261 Iwd 125.. This .slot 30 may extend slightly into -:the non-magneti 1 metal 28 and is of a width to properly space the said pole pieces.

Another method of this p le member is to clap. L t. e two

triangular pole pieces

24 and 25 in then proper relative positions in a snitalbl support then fill in .the groove at one side with the nonrma-gnetic Weld metal 128 as de scribed.

As an alternative method .(see Fig. 10) after the groove 2'] is formed, .or the two triangular pole pieces clamped proper itelation, New

31 of non-magnetic metal. as for example brass, bronze, or the like, may be secured or arsed in position filling the groeve, as by brazing, the hard connecting brass er solder bemg at 32. According to this method the solid her would then be grooved inits opposite serface sawed or otherwise cut through ts sepa rzate ts remaining portions into pole pieces the proper distance apart. In each instance the magnetic pole pieces are 59 connected as t form a iitary strucyure in which these pole pieces weuld ibe incest-isle of rela ive m vemen as they are welded together.

Th H arr po piece stru ture made as above set icrth may no b pro ided i h tanned recesses 33 arrange one in the outer race or each pole djacent each end the eof.- A so aligned. ne. h s 34: a e pr ided in he pole pieces th c nter of he e la open ngs be ns i nm nt w t the ce te of th slo o space 3.0 tor-med between the pol pie es s abo e d scribed. It will e ppa ent th t t e ta o en inss 33 and if des r d the aligned 9 er ii s 3e d 5 a be provid d n t e ba 26 e p e uch bar is treated to form the pole pieces.

The pole piece unit constructed as above described is arranged on the rib 14 with its nonmagnetic body portion 2-8 disposed against the outer surface of said rib and the unit is of such width as to fit snugly between the flanges -15 of the rib whereby the unit is held against lateral movement. A screw 36 is then passed through the opening 16 in plate 13 and threaded into a tapped opening 37 in the portion 28 of the pole piece unit, or additional screws may be provided, whereby said unit is drawn tightly against the face tof :the rib i114 and held against movement outwardly of the flanges 15 of said rib. From this it will be seen that the unit is easily mounted and is firmly held against any movement relaitive to plate or base 13.

Pairs pf coils

38 and 39 are arranged at the respective ends or adjacent the respective ends (Of the ;pole pieces and one coil of each pair is arranged at the router side of the pole piece 24 "Whil .the :remaining coils are arranged at the outer side .of the polepiece 25. The coils enclose cores 40 through which extend screws or bolts 41 having their inner ends threaded into the tapped openings 33 before referred to. A substantially 1U.- shaped or horseshoe 'fie'ld piece 42 is arranged :at each end of the device 'or instrument :and adjacent :the free end of each of its arms :each of said field 21116088 is provided with an (opening through which the screws 41 extend whereby said field :pieces are mounted with their ends in close relation .to the :cores and. with the cores clamped between said ends and the :pole :pieces. with this arrangement any stress or strain resulting from the strong :mag- 13 netic (fierce present when :the machine is operating will inotlbe sequined to be :taken up by the parts 42 and their connections and will not result in any relative movement between the

pole pieces

24 and 25,.

Improved means are provided for supporting an electric conductive string member 43 in the space '30 between the

oppcsed pole pieces

24 and 25. This means as here show-n includes an-elonliLG gated block or strip 44 of insulating material as 1555 for example bakel-ite or the like. At its inner side and between its ends the strip 44 carries an elongated block 45 to the rapper end of which is secured an insulating block '46 having a metal contact member 47 thereon and to which is se- 129 cured one end of the string 43.

Adiiaeent its lower end the block 45 is provided with a slot snugly receiving the outer end portion of a flat spring member 43, the inner or projecting end-0f is loaded-or strengthened -5 lon arm is provided with an opening throu h hich passe the inner of a Screw 52 whereby the is held a ainst lat ral mov m n As indicated above as the free portion of spring 48 is short this lateral movement of arm 51 is also practically prevented independently of screw 53 This insures the conductor string 43 will not be throvwn laterally or out of center when its tensi n- 1 adju ted.

The lower end or string member 43 is secured 9 1. 5. 0 a m 5.0 of the L .shaped and 149 passing through the strip 4e and the block 45 is a screw 53 the inner end of which. engages the upper end portion of arm 51. This screw 53 includes an operating head 54 at the outer side of mounting strip 44 and it will be understood 150 that by adjusting this screw the long arm of the L-shaped member may be pressed inwardly to rock said member by flexing the spring 48 whereby the short arm of the member will be moved downwardly. This, of course, will result in increasing the tension of the string member 43.

A plate (see Fig. 3) is secured to the outer side of each of the

pole pieces

24 and 25 as by screws 56, and at their inner edges these plates abut the outer edges of the flanges 15, and at their outer edges these plates fit into grooves provided for that purpose in the supporting strip 44. These plates serve to assist in properly positioning the supporting means for the string member whereby to locate said string member in the space 30 between the opposing faces of the pole pieces. Additionally, a leg or arm member 57 is secured to the inner side of the strip 44 adjacent each of its ends, and these arm members are of a width to snugly fit between the flanges 15 on the rib 14 and are of such length that when they engage the upper surface of said rib 14 the parts are so arranged that the string member 43 is properly located within the space between the pole pieces.

The strip 44 and the parts carried thereby; form the support for the electro conductive string member 43, and to secure this support in place screws 59 are passed through the openings 17 in the base, and at their inner or forward ends are threaded into the said strip as best shown in Fig. 2. Obviously, should the string member break, the screws 59 may be retracted and the entire support for the string member lifted from the device. A second support having a string member properly mounted thereon may then be readily applied and secured in place by a tightening of the screws 59. The string members may be properly located on the supports at the factory and one or more extra supports kept on hand by the user who may then readily replace a support should its string break or should it be desired to replace it for any other reason. No skill is required in mounting or dismounting a support from the device, and therefore much time and trouble is saved by the user over the old devices where if a string conductor broke a new one had to be mounted and centered, which was a very delicate and long tedious operation.

Extending through the projection or bearing 18 and centered therein as by screws 60 is a microscope 61. The inner end portion of this microscope is arranged in the opening 35 in the pole piece 24 and the microscope is focused on the string member 43. A second microscope 62 is mounted in the bearing member 19 and is' centered therein as by the screws 63. This microscope 62 has its inner end portion located in the opening 34 through the pole piece 25 and is also focused on the string member 43. It will be noted that with the arrangement of the pole pieces and the coils and their cores as above described and illustrated it is not necessary to bore out the magnets to receive the microscope with consequent reduction in field strength, but there is required only a

small hole

34 or 35 in the center of the magnet pole pieces to admit the microscopes. In the use of the machine a bright white light is focussed on the string by one microscope, as for example the microscope 61, and the shadow cast by the string member is picked by the second microscope and enlarged and passed to any suitable camera means, not shown, operating with a sensitized strip. The use of the ma: chine in making charts is fully understood and fully disclosed in the prior art and a further description thereof is believed unnecessary. The leads from a suitable source of exciting current and the leads for the current to be measured or recorded are connected to the magnet coils and the, string conductor respectively in the usuall manner.

From the foregoing description taken irr connection with the drawings it will be appreciated that I have provided a. string galvanometer of a simplified construction. Further, it will be noted. that the device is not of the usual extremely heavy constructionheretofore employed for the purpose" of holding the magnet pole pieces against relative movement. By the method disclosed the pole pieces are so secured together as to form a rigid strong unit whereinrelative movement between the pole pieces is impossible. With thepresent construction the parts are few and easily assembled and in the event of the breakage of a string member the entire string support may be easily and. quickly removed and another support and string substituted.

Heretofore, heavy constructions have beenemployed in devices of this kind. In the present device the field pieces 42 are not secured directly 1,90: to the plate or support 13 and are held in placesolely by the screws 41. Further, the ends of these pieces 42 do not abut the edges of the projections l8 and 19 but are spaced slightly there from whereby movement resulting from the application of current to the coils is permitted by the field pieces without displacing the pole pieces or the string conductor. 1

It will thus be evident that with my improved construction the pole faces are held rigid in per- 11; feet alignment with the microscopes. The pole faces are also held a certain fixed distance apart and they may be placed close together to secure maximum magnetic flux. It has heretofore been impossible to economically construct a means of 11;; holding the magnetic pole pieces immovable due to the tremendous attraction of the two pole pieces when under the magnetic strain. This was a serious difficulty as any movement of the pole pieces or their faces will cause misalignment 12a of the microscopes or the string conductor. The shifting of either of these component parts causes difficulties in using the instrument. These difficulties are effectively overcome in my improved device as the pole pieces are in efiect integral with each other and are mounted on the non-magnetic metal frame, the microscopes are mounted on the same frame and the mag-, netic cores for the coils, and the connecting field pieces are attached to the pole faces only. 13-3 Therefore any distortion or magnetic striction is absorbed by the yielding of the field pieces.

Having thus set forth the nature of my invention, what I claim is:

l. Ina galvanometer, a pair of pole pieces of magnetic material wedge shaped in cross section arranged with a pair of their narrower edges in; opposed spaced relation, and non-magnetic metal filling the space between a pair of side walls of said pieces and fused to these Walls to provide a unitary structure.

2. In a galvanometer, an electro magnet having opposed spaced pole pieces, an electro conductive string member, means supporting said member with the member disposed in the space between said opposed pole pieces, each of said pole pieces wedge-shaped in transverse section and said pole pieces disposed with their narrower portions in opposed relation, means holding said pole pieces against relative movement, and said i;"

' ass-1r or a posed slightly's'paced pole" pieces} each of said pole pieces wedge shaped in transverse section and pure ieces stressed with their narrower edges dpposisgreiatien, h'o'i'cl ing said r al-alepieces against relative movement arid sulistan'tialh' filling the space them at" their under oes said means disguising: a; body' of non-magnetic; material" fused tosaid pore pieces wuerety" to form; them into at said unit disposed iii and saugl yntting between the: wens or tire g' rodve' base mews engaging said andhoidii'ig roove, an electro' conductive string member; creams supportirig' saidstr'ing member in the space between said we pieces.

i. in a gaivanoxneter; ereetremagnet com prising opposed spaced 15616 pieces, each 6t pole pieces wedge shaped in transverse": section and said pol pieces Witl'i their narrow r edges in opposing relation, means holding psie rees against relative movement sobsti'ai-itiail'yfilling the space Between them at their urid'ef'side's; and said; means; comprising a body of nos-magnetic mati ial idsed t6) eachor said pole pieces whereby: to miss them into a v 5. The iiithd of a rigid unit im1ad-- iiig a pair of tr ansv'ersergr wedge shaped po'l piecesaffaiigd iii s aces relationship with; their narrower edges in opposes relation, the same comprising" pfvidifig a or magnetic mittens},- fdfriiiiig a v-greove one side or said bar, fill ing s'aidgrooi e with nonmagnetic metal fused t6 tirewant of tne groove, forming: a simi- Iar' gi'odve the opposite side at said and their cutting through the remaining portion of the at the apex: of said second grdove.

6. method orienting a rigid unit mama: mg a 6! transversely Wedge shapes opposed pole pieces arranged inspaced r'ilatidrisliip with their saris i edges he opposed reiatiori, the same comprising providing a car or magnetic metal, forming a v groov' one side or said bar, filling said groove with non-ma netic ifit'al deposits ing molten non-magnetic Ifitaltherein whereby t6 weld together the walls of said groove, remi mg a similar groove in the opposite side or said bar, and then cutting through the remaining portion of the bar at the apex of said second roove.-

'7; The frithod of forming a rigid unit memomg a pair of transversely wdg' shaped opposed pole pieces arranged iii spaced relationship with their narrower edges in opposed relation, the same comprising providing a liar of inagfietic metal, forming a V-groove in one side of said bar, filling said groove by brazing to the walls thereof a wedge shaped block or non-magnetic metal, forming a similar groove in the opposite side or said bar, and then cutting through the remaining portion of the bar at the apex of said second groove. I

8. In a galvanometer, a base or mounting member, said member comprising a plate-like portion of non-magnetic inetal, a centrally located raised portion on said plate, a pair of outwardly directed parallel projections on said piste and a1- iari'ged at diametrically opposite points thereon and at the sides of said raised portion, opposed slightly spaced pole pieces mounted on said raised portion, a pair of coils at each fid of said plate and arranges one at each side of and closely adjacent said pole pieces, a substantially U shaped field piece at each end of said plate and each hearingits respective endsdisposed at the outer'endoi one of said pairs of coils, a bar passing through each of said coils and mounting the same, said bars having their outer ends secured.

tdthe adjacent ends 0t said field pieces and having their inner ends secured to one of said pole pieces, an electro conductive string member, means supporting said member to dispose it between said pole pieces, aligned openings through said pole pieces, a telescope mounted in each of said projections, and said telescopes focussed on said string member through the openings in the pole piecest 91- In a ga lv'anornetei",- a mounting member, said member including a plate-like" portion of nonmagnetic metal, opposed spaced pole pieces mounted on said plate, a pair of coils adjacent each end or said pole pieces, said coils at the respsctive ends of-' the pole pieces arrangedv one can at the outer side of and closely adjacent each of said pole pieces, a substantially iii-shaped field piece" arranged toward each end of said plate, said field pieces at the respectiveends of the plate having their ends disposed at the outer ends of coils adjacent the respective ends of the plate, a bar connected to each of said field piece ends and passing through the adjacent coil and into the adjacent pole piece whereby to mount the field pieces and coils, an electro conductive string member, and means supporting said member to dispose it in the space between said pole pieces.

10.- In a galvanometer, a mounting member, a pair of parallel spaced flanges on said member and forming a groove, a pair of opposed spaced pole pieces on said member, a support, an electro- Gonductiv'e string member mounted on said support, a pair of arms on said support and adapted to enter said groove and engage the bottom thereof to dispose said string member in the space between said pole pieces, and means to secure said support to said mounting member with said arms in said groove and engaging the bottom thereof.

11. In a galvanom'eter', a mounting member, a pair of parallel spaced flanges on said member and forming a groove, a pair of opposed spaced pole pieces on said member, a support, an electro conductive string member mounted on said support, a pair of arms on said support adapted to enter said groove and engage the bottom thereof to dispose said string member in the space between said pole pieces, and screws passing through said mounting member and into said support and securing said support to the mounting if member with the ends of said arms drawn tightly into engagement with the bottom of said groove.

12. In a g'alvanometer, a mounting member, a pair of opposed spaced pole pieces on said memher, a support, an electro conductive string memi ber, means mounting said string member on said support, said means disposed at the inner side of said support and including an L-shape-cl member, a short flat spring having the short arm of said L-shaped member rigidly secured thereto, said u string member having one end secured to the short arm of said L -shape'd member, means engaging the other arm of said L-shaped member and adjustable to rock it by flexing said spring to tension said string member, and means to secure said i.

support to said mounting member with said string member disposed in the space between said pole pieces.

13. In a galvanorneter, a mounting member, a pair of parallel spaced flanges on said member and forming a groove, a pair of opposed spaced pole pieces on said member, a support, an electro conductive string member, means mounting said string member on said support, said means disposed at the inner side of said support and including an L-shaped member, a short flat spring having the short arm of said L-shaped member rigidly secured thereto, said string member having one end secured to the short arm of said L-shaped member, means engaging the other arm of said L-shaped member and adjustable to rock it by flexing said spring to tension said string member, a pair of arms on said support and adapted to enter said groove and engage the bottom thereof to dispose said string member in the space between said pole pieces, and means to secure said support to said mounting member with said arms in said groove and engaging the bottom thereof.

i l. In a galvanometer, a mounting member, a pair of opposed spaced pole pieces on said member, a support, an electro conductive string member, means mounting said string member on said support, said means disposed at the inner sidev of said support and including an L-shaped member, a short flat spring having the short arm of said L-shaped member rigidly secured thereto, said string member having one end secured to the short arm of said L-shaped member, means engaging the other arm of said L-shaped mem ber and adjustable to rock it by flexing said spring whereby to tension said string member, said means including a screw extending through said support and operable from the outer side thereof, and means to secure said support to said mounting member with said string member disposed in the space between said pole pieces.

15. In a galvanometer, a mounting member, said member comprising a plate-like portion of non-magnetic metal, a centrally located raised portion on said plate, said raised portion grooved in its outer surface to provide a pair of parallel flanges, a unit comprising a pair of opposed spaced transversely wedge-shaped pole pieces connected at their undersides by a body of nonmagnetic metal fused to them, said unit disposed on said raised portion of the mounting member and snugly fitting between the walls of the groove thereof, a screw passing through said mounting member and into said body of non-magnetic material and serving to draw said unit tight against the bottom of said groove, field magnets associated with said pole pieces, an electro conductive string member, and means supporting said string member in the space between said pole pieces.

FREDERIC O. HINDLE.