US1712570A - Oscillograph galvanometer - Google Patents

Description

May 14, 1929. J, w LEG@ 1,712,570

OSCILLOGRAPH GrALVANOMETERA Filed Jan. 2'7, 1925 INVENTOR WITNESS 1 r 32 3437 /5 Jaso/f /f/ Q99 Patented May 14, 1929.

UNITED STATES VPATENT orifice.

JOSEPH W. LEGG, OF WILKINSBUBG, PENNSYLVANIA, ASSIGNOB TO WFS'IINGEEOUSEy ELECTRIC da MAN'UFAGTURING'l COMPANY, .A CORPORATION OF PENNSYLVANIA.

OSCILLOGRAPH GALVANOMETER.

Application led January 27, 1925. serial No. 5,166.

My invention relates to galvanometers and particularly to galvanometers for use in oscillographs.

One object of my invention is to provide a galvanometer that shall comprise a permanent magnet constructed of a single homogeneous mass of magnetic material and of such coercive :force and such small dimensions as compared with the magnets of galvanometers heretofore employed for the same purposes, as to render the galvanometer extremely compact in construction, light in weight and eli'ective to indicate the phenomena of commercial and other electric circuits.l

Another object of my inventionis to provide a galvanometer that shall be rugged and 'durable in construction and economical to manufacture.

Another object of my invention is to provide a galvanometer that shall permit an oscillograph, for which it is adapted, to be more lreadily portable than oscillographs of the prior art.

Another object of my invention is to provide a galvanometer comprising a permanent magnet that shall be so shaped as to materially increase the eii'ectiveness of. the instrument.

and well-known types, it has been customary to employ permanent magnets constructed of materials having low coercive orce, and other objectionable characteristics. A magnet having low coercive force limits the use ot galvanometers to the measurement of relatively small currents, such'as laboratory-test galvanometers.

The objection has been overcome, to a very au limited extent, by employing a plurality of magnets or a plurality of large magnets having relatively large pole ends but even these measures have not rendered permanent .magnets suitable for use in oscillographs having any considerable variety of application.

in oscillographs for measuring'transient and current phenomena of commercial and other circuits, it is necessary to have currents ot certain relatively large magnitudes te traverse the galvanometer elements. lt has been usual to employ electromagnets tor controlling the movements of the elements. ln such structures, the electromagnets have been relatively heavy and expensive and have been Heretofore, in galvanometers of the usual character having such shape, dimensions and other characteristics as to render the galvanometer an improvement, in vsubstantially all of its features, over similar galvanometers heretofore employed.

A magnetized structure or member constructed in accordance with my invention preferably comprises cobalt steel having a composition substantially as outlined in U. S. Patent 1,678,001, issued to P. H. Brace, J uly 24.-, 1928. It shall be understoodz however, that my invention is not to be limited to the utilization of material such as described in, v80` netizable material having the desired degree j the aforesaid Brace patent, since any mag` ot coercivity may be utilized in lieu of the material described in said Brace patent.

However, the particular shape, size, disposition and relation of the magnet to other elements herein described, are important elements in the production of the improved galvanometer oi my invention, and it is these features, in the combinations set "forth, which I claim as new.

Figure 1 ot the accompanying drawings is a plan view ot a galvanometer structure of my invention, embodying a plurality of in dividual galvanometer unit-s, one of which is shown in section,

' Fig. 2 is a side elevational View of the device showii in Fig. l, with one of the galva nometer units similarly shown in section, and

Fig. 3 is a sectional view, taken through one oit the galvanometer units ot the other figures, at right angles thereto.

The device comprises, in general, a base member or plate l, vertical galvanometersupporting plates Q, a rear-wall plate 3 and a plurality oi galvanometers l. The plates 1, 2 and 3 are preferably constructed ot relatively hard insulating material, such as fibrous material, impregnated with a binder,

that are provided with rabbet joints 6k and 7 and are suitably held together, as by screws 8.

Each galvanometer 4 comprises a liquidtight casing or well structure 10 that is constructed of a single homogeneous mass of material preferably insulating material, and is provided with a cover member 11.4 Each well structure 10 is pivoted between adjacent pairs of the members or plates 2 by trunnion screws 12. Spacing flanges 14 on the screws 12 are disposed between the well structure 10 and the partitions 2.

Each well structure 10 is provided with a main or upper interior recess 15Vhaving a downwardly projecting opening or recess 16 to provide a shoulder or shelf -17 between the top and bottom ends of the structure 10.

A permanent magnet 18, of substantially annu ar shape and having an eccentric opening 19, is'mounted on the shoulder 17 and secured in position thereon, as by screws 20. A relatively narrow slot 22is provided in the perimeter of the magnet 18 to'provide concentrated pole ends 23 that are disposed opposite an opening or window 24 in the side wall ofthe well 10. A lens 25 and a light shield 26 are provided over the openingl 24 in the well 10, the lens 25 being slightly inclined to prevent reflection.

The gal-vanometer element comprises an elongated lamentary conductor 29 that is doubled back on itself to have its adjacent ends attached to extensions 27 .of terminal posts 30 and a looped intermediate portion or end 31 disposed around a pulley 32. The pulley 32 is mounted on a lever 34 that is pivoted to a depending portion 35 of a stationary supporting structure 36, as by a pin 37, and adapted to be held under predetermined tension by a spring 39 which extends between a pin 40 at one end of the lever 34, and screw 42. The screw 42 is adjustably mounted in a threaded projection 43 on the supporting structure 36. The supportin structure 3 6 is positioned on the cover mem er 11 by a centering post 44.

The filamentary conductor or conductors 29 may extend across the window 24 between bridging posts 45 on the supporting structure 36 and carry Va'mirror 47 for eo-operation with a light source, a vpolygon of mirrors and a photographic chart (not shown).

The m1rror-47is-adapted for adjustment about a vertical axis by a rack-and-screw device in which the rack 51 is secured to the supporting structure `36 and the screw 52 is v journaled in the cover member 11.. Adjustment of the mirror 47 about a horizontal axis is 'efected' through the medium of an adjusting device'54, which com rises lateral projections and 56;on the and on the structure 10, respectively, and an adjusting screw rod 57, in a -well known manner. l Injthe above-described structure, each galack-wall member 3` vanometer 4 is a self-contained unit, in contradistinction to previous oscillograph galvanometers in which the controllin kelectromagnets are inter-related or in whicii a single powerful electromagnet supplies flux to separate pairs of pole pieces for each galvanom eter element.

So far as I am aware, the structure herein set forth is the first in which a single homogeneous permanent magnet member of such compact nature and eiiective operation. has been emplo ed or in which the other parts are adapte to receive such ma net. This magnet, not only by virtue of t e material of which it is composed, but also, by reason of its annular shape and other features is, so f ar as I am aware, more effective .than any previous permanent magnet that has been employed for similar purposes. Further, siee the other parts of the alvanometer are adapted tol co-operate wit i the im roved magnet, an instrument is obtained which embodles combinations of elements that are different from those of the prior art and which render the instrument an improvement over the old combinations in nearly every feature.

One im roved function provided by my invention 1s a bodily movement of the magnet 18,' as a whole, with the galvanometer 4 when the latter is tilted about its horizontal axis, thus avoiding separation of relatively movable magnetic members and,l thereb materially decreasing the reluctance of t e magnetic circuit.

Making the magnet 18 of annular shape also,reduces the space occupied by a given quantity of the magnetic material and facilitates manufacture of the magnet.

By making the main central openin 19 through the magnet 18 also annular an eccentrically disposed relative to the outer annular surface, together with the relatively -narrow air gap '22 and parallel pole-end surfaces 23 from which the adjacent side and end surfaces slope toward the main body surfaces, a magnet is provided which ensures substantially maximum fiux efficiency adjacent to .the galvanometer element 29.

The structure, in which the mainrcess 15 and the downwardly projecting recess 16 are provided and the magnet 18, conforming to the main recess 15, is mounted on the shou der 17 and enclosed by the well structure 10, facilitates manufacture and assembly, ensures economy of space and materials and in general, renders the device of my invention an improvement in the art.

While I have shown and desc ibed a parlticular form of ymy invention, c anges may 'be effected therein without departing from the spirit and scope thereof, as set forth in the appended claims.

In the appended claims, the expression chrome permanent magnet steel shall be understood as referring to chrome steel of the type ordinarily utilized in electrical instruments for forming a magnetizable structure, the aforesaid chrome steel ordinarily comprising approximately 2% of chromium and 1% of carbon.

l claim as my invention:

l. A portable-oscilloigraph galvanometer comprising a well structure, and a highperiod vibratory elementand a control magnet therefor both-disposed entirely Within said Well structure. t

2."The combination with a supporting structure, of a `galvanometer comprising a movable element 'and a control magnet for said movable element, said galvanometer, including said movable element and said control magnet, being mounted on said supporting structure and movable as a unit in different angularly-related directions relative thereto to adjust the position of the movable element;

3. The combination With a supporting structure, of a galvanometer comprising a Well structure movable in dierent angularlyrelated directions relative thereto, a movable galvanometer element disposed in the well structure and a control magnet for the galvanometer element carried by the movable.

' Well structure.

1l. The combination With a supporting structure, of a galvanometer comprising a Well structure mounted on' said supporting structure and movable in different angularlyrelated directions relative thereto, and a movable galvanometer element and a control magnet for the galvanometer element disposed in said Well structure.

5. A galvanometer comprising a Well structure, a galvanometer element, an elongated supporting structure for said element disposed longitudinally in said well structure, and a permanent control magnet disposed in said Well structure and having pole-end portions embracing an intermediate portion of the galvanometer element. p

6. A. galvanomcter comprising a Well structure having an intermediate shoulder portion therein, a galvanometer element, 'a supportino' structure for said element disposed longitudinally in said well structure on opposite sides of said shoulder portion, and a permanent control magnet positioned on saidrshoulder and havingpole-end portions at opposite sides of said element.

7 A galvanometer comprising a cylindrical permanent magnet, a well structure `having a main cylindrical recess to snugly receive said magnet and an otlfset recess extending downwardly from said main recess, a galvanometer element and a support for the element, said magnet surrounding said support between said recesses.

8. The combination with a deflecting system freely responsive to frequencies of the order of 3000 cycles per second and including a light-reflecting mirror, of means for actuating said detlecting system comprising a permanently magnetized structure the coercive force of which is several times greater than that of chrome permanent magnet steel.

9. The combination With a casing, of a deflecting system freely and substantially uniormly responsive to frequencies ranging upwardly to 3000 cycles per second, said system including a light-reflecting mirror, and a magnetizable structure comprising a permanently ma netized member disposed entirely Within sai casing for actuating said deecting system.l

l0. The combination with a casing, of a deflecting system freely responsive to frequencies of the order of 3000 cycles per second and including a light-redecting mirror, and a magnetizable structure comprising a permanently magnetized member disposed entirely Within said casing tor actuating said deiiecting system, the coercive force ot' said magnetized member vbeing several times.

greater than that of chrome permanent magnet steel.

In testimony whereof, I have hereunto subscribed my name this 22nd day of January,

J OSEEH. W. LEGG.

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