US2609410A - Babaud - Google Patents

Description

Sept. 2, 1952 J. BABAUD 2,609,410

MOVABLE MAGNET OSCILLOGRAPH Filed Oct. 11, 1949 Jan 54 baud Patented Sept. 2 1952 :MOVABLELMAGNET 'osci' ttoc tsrn that examine, i aris, 1 France, "to Etablissements Charles B-eairdoiiim- Paris,

Application gotte -{11, 1949, S er ial 420,725

QInf. FrancelOctober 15, 1948 i 6;. "This invention relates {to osiliograph of the movable magnet tyiiai'andits object is to vide a "movable magnet "oscillog'raphpf new an improved construction, of 'greatlyireduced "buik a's cbmpa'red with' conventional apparatus of similar typejwhile at the same time possessing increased accuracyi'andcapablebf retaining over very long periods f time "its desir'aibie "characteristics "of sensibilityan'd precision.

' For-"man ye'ars' inthe tonstruction-or certain hysteresis-into; the circuitffinal'ly,'itis difficult tosecure uniform damping regardless of the'tem perature. At the present timehoweverfirriet'al alloys 'areknownhaving suitable magnetic characteristics for the construction of magnetic vane elements and iron circuits'a'nii moreover it has been 'rouriu that certam substances aregadap ted to Provide a highly successful damping' mdiumc Thus, it-is-an object of this invention to provide a movable magnet oscillograph of such construction"'a'sto constitute an instrument whichyvi'l'lnot break "easily; which ishandy to *operateand :p'ossesses'fve'ryreduced dimensions'and compr es-a suitable sus ending and damping arrangement fora magnetic'vaneelement.

It is another object of the invention to provide an oscillograph of the type described which, on account of the peculiar relative arrangement, to be described, between the magnetic vane element and the field elements thereof, as well as the use of special materials, to be specified, for the construction of the fixed armature and the damping medium, will possess a very high sensitivity and a desirably high fidelity.

According to the invention, an improved oscillograph comprises a body terminating in an armature of reduced diameter serving as a centering means for a circular coil winding which provides the field-generating means, and adapted to receive over the end thereof a carrier means for a movable structure formed with a central optic'al "aperture, said "carrier, in cooperation a. disc member of resilient material-placed b" a it and separatin it'irom theheidmea name a e'aieu enclosure fore-harsher in" the movable magnetic structure ist'suspendeufiird wiiichis fih u withscanning-hum.

"The rnetal'rrcm The damping medium "comprises 'atransp enft liquid the 'visctsity offwhi'c does 'fot vary'sreatiy with tempersture'suchas e? The 'use "of the .specified'mate possible'fto construct langapparatus w icn w lie having desirable sens tiv tyarrurretu" 'l'f' eney to characteristics, win he ,or greatly uu ed tux :eorrrpareaitox'whet "it "wasgptssibie' r eor strieteu byiimit topswinpr al r sitive 'andquic'k-"operating p'o1arized""gna1meahs The above-described and further fobiet matures of theintentioniwiii appear" rof'm the nsuing description or heernbouim'nt o vention, selected torpur oses'of musv atib not oriiimitation, fwitnfrererence toth'e'.

arse-tube io i rue-eta 'Eiguel Li's .alons i paratu 7 g 'Fig're is a crosseseetion ion" l'i'n'e'iII v Figured. 3 v

JA's shown the j'drawifngs, the eary: instrument is "formed towardsits rear-"en ward the left as shown in Figure 1) and for the purpose of mounting it on a support not shown, with a transversely extending notch 2 with which a presser spring 3 and a set screw 4 are associated.

Toward the front or right-hand end (as in Fig. 1) the body I is formed with a cylindrical part 5 extended by a core section 6 of reduced diameter, over which an annular coil 1 is seated, the wires 8 of said coil being adapted for connection with a circuit on which measurements are to be ef fected.

The structure including the cylindrical part 5 and the winding 1 is covered by a sleeve 9 terminating flush with the end or" the core and externally formed with a screw-thread III. This V. V 3 screw-thread is adapted to receive thereover the rear portion of a bushing ll provided with an inwardly-directed flange [2 at it front end, said flange being adapted to engage the outer face of a magnet-carrier l3 inserted in said bushing to clamp said carrier against a sealing gasket or disc I4 made of a resilient material, seated against the coreand against the end of .the sleeve.

The magnet-carrier I3 is formed with a hole extending from its front and axially of the core and opening into a recess containing an optical system l5 comprising for example a simple lens sealingly secured within said recess. The rear part of the magnet-carrier I3 is bored to define a cylindrical chamber [6 sealed rearwardly with the sealing disc (4.

The mirror-carrying vane-shaped magnet member I! is made of metal having a high coercive force such as an aluminium-nickel-cobalt, a platinum-cobalt, or a silicon-manganese-alualloy, or certain suitable sintered oxidesi V It is secured at the center of a torsion strip 18 anchored and soldered at both ends in oppositely-located holes formed in a copper ring I9.

The ring (Fig. 2) is formed with an opening or slot 20 in the vicinity of one of said holes and is weakened in certain sections thereof by being externally milled. The segment 28 tapers down towards its free end adjacent the slot and the strip is soldered after first having placed said segment under tension by imparting a slight camber thereto. The other segment is weak ened throughout its extent except at a number of contact bosses 22, so as to concentrate on said segment any bending strains occurring upon the ring being forced into the bore. In this way, the segment 2i will continue to supply the requisite tension since it does not undergo any distorsion as the ring is inserted into the bore. The'sealed chamber I6 is filled with a suitable damping fluid, such as silicone oil. The chamber capacity is restricted by the disc 1% and only contains a very small quantity of damping liquid and, owing to the presence of said resilient disc, it may be completely filled, as the resilient disc will allow for any variations in volume of the liquid due to expansion. I .The use of special allows such as the aluminium-nickel-cobalt alloy known as Alnico, for the construction of the magnetic vane, and the useof suitably heat-treated ferro- -nickel for the armature, and of silicone oil as a damping medium, make it possible to obtainhigh accuracy and excellent sensitivity in the apparatus. Thus witha .400 ohm winding, anatural frequency of 180 cycles and a fidelity index of 1%, mirror-displacements of about 190 millimeters per milliampere have been obtained at a distance of one meter.

It will of course be understood that the invention is not restricted to the specific embodiment illustrated and described, given by way of example only. Thus, a similar arrangement could be adopted in constructing a polarized signal means, in which the magnet vane is either suspended to a strip, as in the example shown, or supported on a spring-plate or the like, and its movements restricted by two stops.

What I claim is:

l. A movable magnet oscillograph comprising in combination a body of magnetic material forming the armature of an electromagnet with a central core extension, an electrical winding on said core, a sleeve secured to said body around said core, a sealing gasket of non magnetic material against the end of said sleeve and core, a hollow cover against said gasket having a centrally apertured end fitted with a lens and defining a closed chamber in front of said gasket, means tightly clamping said cover with the interposed gasket against said body, an annular fitting of non magnetic material inserted in said chamber and formed with an arcuate peripheral arm, a torsion strip attached under tension between said arm and the diametrically opposed point of said fitting, a mirror carrying vaneshaped magnet mounted on said torsion strip, and a, damping liquid filling said chamber.

2. A movable magnet oscillograph according to claim 1, in which in combination the said armature of the electromagnet is of a magnetic material of low hysteresis, such as ferro-nickel, the said vane-shaped magnet is of an alloy having a high coercive force such as an aluminumnickel-cobalt alloy and the said clamping liquid is a liquid the viscosity of which varies but little with temperature, such as silicone oil.

3. A movable magnet oscillograph according to claim 1, wherein the said chamber is cylindrical and said fitting is a split ring, one half of which is tapered in a circumferential direction toward the split, and the other half of which comprises an arcuate segment having a weakened section throughout its length except for three outwardly directed bosses which center said ring in said cylindrical chamber- JEAN BABAUD.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS

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