US1726200A - Electromagnetic receiver and transmitter - Google Patents

Description

Aug. 27, 1929. A. A. THMAs 1,726,200A

` ELECTROHAGNETIC RECEIVER AND TRANSMITTER Filed June 4, 1928 INVENTOR /WMV PatentedAug. 27, 1929. I

UNITED sT- A'TES ADoLrH A. THOMAS,

oFNEw Yonx, N.- Y.

` EILEcTnoMAeNETIc RECEIVER AND TRANSMITTER.

Application filed June 4,

I This invention is for an electromagnetic' translating device of novel construction and improved operation for converting electric impulses to mechanical vibration `and vice versa. One of the main uses of my invention is for operating loudspeakers, especially those ofthe cone type. My new instrument is exceedingly simple and compact, and per mitsa short direct connection between armature and diaphragm without lost motion, so that a high degree of efliciency is attained. My new electromognetic device' in 4a preferred embodiment comprises a magnet frame having two pairs of pole pieces between which thepends of a centrally sup-o ported armature vibrate. The armature is rigidly connected at the center tothe central or neutral part of the field magnet structure. The latter is preferably of circular or ell-iptical shape with adiametric arm to which the armature is secured at right angles thereto. The armature is an elastic reed free to vi-L, brate at both kends andcarrying one orv two" polarizing coils. When operating l,a large diaphragmfthe armature has both ends rigidly connectedfto the diaphragm by short stout rods which are free from disturbing vibrations. This short direct connection is possible because the driving unit as a whole can be mounted very close to the center of the diaphragm.

In the accompanying drawings, which illustrate two practical embodiments-tof my Fig. 1 is a face'.-viewof an'electromagnetic actuating unit for loudspeakers;

Fig.'2 is a section on line 2--2 of Fi`g. 1;'

Fig. 3 is a section on line 3-3 of Fig. 1;

Fig. 4 shows a perspective of the -ieldA magnet .frame u sed in the construction. of Figs. 1-3;

Fig. 5 shows amodification-employing two f U-shaped magnets; and

l Fig. 6 represents-a section on line 6.-6 of Fig. 5 to show how a portion ofthe field finzi is short-circuited for controlling the operation of the instrument.

yReferring to Figs. 1-4, there 10 mounted in a casing orother suitable support 12. In the present instance,'the magnet 10 isa one-piece structure substantially4 *circular .in shape, comprising adlametrlc arm' 13 ,and two pairs of lateral extensions4 14' and 15. 'These/ extensions terminate in isa magnet .secured at the center to the arm 13, as by rivets 22 or otherwise.- As seen 1n Fig. 1,-

1928. Serial N o. 282,589.

two pairs of pole pieces 16--16 and 17--17 which provide two airgaps 18 and 18. For distinction I have marked the -pole pieces 16 and 16' as south and north poles respectively,

^ neutral points by the cross-bar 13. The indicated polarity, however, is not essential, for the steel frame 10 canbe .so magnetized that the pole pieces 16 and 16 are of one polarity and the pole pieces 17--17 of the other polarity.` I n that case, the field iuX would pass4 through the diametric bar 13 and from there split into two'parallel paths through the polar extensions v1414 and -15 across the two airgaps 18--18. l

The magnet 10 may be solid or laminated, and can be punched A'from sheet steel. It may be a permanent magnet, or of the elec# .tromagnetm type. The polar extensions 14 and 15 maybe made as separate pieces attached to the arm 13, and those extensions need 'not be circular, but they maybe ellipticalg rectangular, or of any other practical shape. A simple way to secure ,the magnet titi 10' tothe support 12 is by providing the latter with a pair of bosses 19 adapted to receive screws or bolts 20, which ,passthrolgh the ends of arm 13. It goes'without saying that the support 12 is of..nonmag`neti-c materiil and may b e cast-orf'molded as a single mei'nber' of aluminum, brass, bakelite., or any other material u'seul for that purpose.

When the magnet 10 is cut or 4punched from sheet steel, the semi-circular extensions 14 and .15 are .cutas a complete circle which is slit at right angles to the arm 13. The v slit ends arethen dlsplacedy relativel to each other, as indicated in Fig. 4. he pole pieces 17 and 17 are 'attached separately to ,overlap the pole. pieces 16 and 16.. There are other ,ways .of making the eld magnet, and the suggestion just made is not to be considered-inet restrictive sense.

A flexible reedf or armature 21 rigidly the armature 21 is arranged approximately at right angles to the supporting arm 13, and Ghefvibratory ends 23 and "24 of the armaturel extend into the magnetic airgaps the coils 25 can be used like elastic pads con- 18 and 18 respectively. When the armature 21 is at rest, its ends are substantially midway of the airgaps, as shown in Fig. 2. The vibratory member 21 is prefeiably made of a magnetic metal or alloy having a higher degree of permeability than the steel body of field magnet 10, so that iiux variations produced in thearmature encounter the lowest possible resistance. The strip or blade 21 canbe stamped out of solid sheetmetal,

or it may consist of thin magnetic laminae Welded together or otherwise rigidly secured.

The armature 21 is polarized by one or two coils 25 mounted on opposite sides of the central supporting arm 13. Only one coil is necessary, but I prefer to use two coils in series, so as to secure better magnetic balance and higher eiiiciency of the `instrument. The coils 25 are held in place bya pair of non-magnetic brackets 26, which: are 4secured to the arm 13 by suitable fastening stantly pressing against the armature to dampen its movements without interfering with its instant response to iux variations produced by the speech coils. The inherent elasticity of armature 21 and the width of airgaps 18-j18 are so correlated thatl the armature ends do not strike the pole pieces even when maximum current passes through coils 25. I y l The reed or armature 21 is connected to a vibratory member 30, which is diagrammatically shown in Fig. 2 .as a cone diaphragm. I want it understood, however,

` that in the broad aspect of my invention, the

part 30 represents any vibratory member capable, of performing a useful invention.

When the member 30 is a cone diaphragm,

theo latter -is preferably provided with al ring 31', which is connected to the armature 21 by a pair of rods 32 of sufficient strength and rigidity. The ends of' these rods are firmly secured to armature 21 andy ring 31 in any practical way, as by riveting, welding, screw-threading and the like. rIhe rods 32 are preferably connected to ring 31 at diametrically opposite points. Since the entire unit is lat and can be brought close to diaphragm 30, the connecting rods 32 can be made very short, so as te be practically free from disturbing vibrations of theinwown. This short direct connection between arma ture and diaphragm is of great. practical advantage, as will be understood by those fav miliarl with cone speakers.

The operation of the instrument will be clear from the preceding description, but I may summarize it in a few sentences. Referring to Fig. 2, let us assume that at any instant the magnetic flux due to the speech coil or coils 25 produces a south pole at 23 and a north pole at 24. The armature ends will therefore be attracted toward the north pole 17 and the south pole 17 respectively, A

and the diaphragm 30 is pulled toward the left (asviewed in Fig. 2). W'hen the speech flux in armature 21 produces a north pole at 23 and a south pole at 24, the armature ends are attracted toward the-'southpole 16 and the north pole 16 respectively, so that the diaphragm is now pushed towardthe right,

These vibratory movements of the armature end's vary in direction and amplitude in accordance with the flux produced by the variable current impulses in'coils 25. I do not consider it necessary to show or describe any circuit connections for the coils, because the art is replete with transmission and receiving systems in which the coils 25 can be connected.

Attention is called to the fact that the vibratory movements of the armature ends 23 and 24 are transmitted with increased lever- 'age to the diaphragm 30, due to the fact that the rods 32 are connected to the armature at acertain distance from the outer ends thereof. While such a connection transmits the armature vibrations in decreased ratio to-the diaphragm, the resultant gain in poweris a highly desirable advantage, particularly in. I

large cone diaphragms that require less amof vibrationn and greater drivingl power. Also, it should be noticed that the plitude magnetic effect at the ends of the arma-ture is .two-fold the polarized ends are not only attracted to the field poles of opposite polarity, but they are also simultaneously re-y pelled by the otherfield poles. This cumu-4 lative magnetic elfect at the armature ends cincreases the power and eiiciency of the instr ument. AThe diaphragm 30 is positively actuated in both directions by a push-pull eifect. Another factor contributing to the iid eiiicieiicy and sensitiveness of the instrument is thefact that the main field flux does not pass through the body of the armature. This permits the variable Hu'x -produced by the speech coils 25 to exert its full effect on the polaiends of the armature. The points at which the rods 32 are connected to the arma-Y ture are so chosen in each particular design' of instrument as to obtain the best practical results. The nearer those connections are to the center of the armature', the smaller will be the transmission ratio between armature and diaphragm with correspondingly increased driving power. Conversely, by connecting the rods 32 to the armature at points ities 'indicated in Figs.'1, 2 and 3, the speech coils 25 are so Woundas to cause opposite -polarities at lthe ends of armature 21. As

previously mentioned, the magnet l() may be so polarized that the ole pieces 16-1'6 are of one polarity and t e pole pieces 17--17 of the other polarity.` With a magnet so4 polarized, the coils should be so Wound and .connected as to produce like polarities at the vibratory ends of the armature, in

order that the polarized armature ends shall,

vibrate simultaneously in the same direction 4to give the push-pulll efl'ect above described.

The magnetic arm 13, to which the armature 21 is connected in good magnetic contact,

provides a path for the talking flux when the coils produce like (and therefore opposing) polarities at the center of the armature. p

In the modification of Figs. 5 and 6, the field magnet 33 consists'of a pair` of U-shaped 'permanent magnets .34 connected along their. inner legs 35. SinceA the outer legs 'are of opposite polarity, the inner legs 35 consti- `tute-the neutral portion of the magnet. A

reed or armature 36 is rigidly connected at the center to the central -leg 35 ofthe magnet. A simple way of mounting the Aarmature on the field magnet is by means of a- U-shaped magnetic'bracket 37 secured to the neutral. leg 35 by a bolt or rivet 38, or otherwise. The armature 36 is rigidly mounted on the magnetic bracket 37 by suitable fastening means 39, which may be a rivet or the like. The coil or coils 25 are so wound and connected as to produce opposite polarities'l at the ends .of armature 36, which is connected to the .diaphragm 40 by Lrods 41? The diaphragm 40 carries a ring 42 to which the rods 41 are connected, as more fully explained in connection with Fig. 2. Asthe flux through the armature 36. varies, the

free ends thereof are simultaneously attracted to and repelled by the field poles 43 and 44. This will be understood without further explanation.'

. The construction of 5 and 6inay be provided with means for regulating the effective field strengtht the pole pieces 43 and 44 by short-circuitinv a portion vof the macgnetic flux. For this purpose`I mount a e'xible magnetic bladeor strip 45on a y ythe screw 49 is turned down to force the yoke 47 against the flexible magnetic stripl 45, the ends of the latter are brought closer to the outer limbs of the magnet, as roughly indicated by the dotted outline' 45. The

closer the ends of strip 45 are brought to the outer limbs of magnet 33, the greater will ged and easily assembled. My invent-ion` has special advantages as a driving unit for large diaphragms in loud speakers. The short-direct connection between armature and diaphragm eliminates lost motion and undesirable vibrations. The double driving rods and the increased power tranmission between armature and diaphragm make it possiblefor a comparatively small instrument to operate efficiently a large diahra m;

Although I have shown and described certain specific constructions, I want it distinctly understood that my invention is not limited to the details set forth. The basic features of my invention may be mechanically embodied in various other Ways Without departingfrom the scope of the invention as defined in the following claims.

I claim as my invention:

1. In an electromagnetic device, a flexible magnetic reed rigidly supported at the eenter, means for polarizing said `reed, magnetic poles operatively associatedy with the vibratory ends of said reed, anda vibratory member connected to said reed.

2. In an electromagnetic device, a flexible Dmagnetic reed rigidly supported at the center, means for polarizing said reed, magnetic poles operatively associatedwiththe vibratory ends of said reed, a pair of rods con-l nected to said reed near'its vibratory ends, anl a vibratory member connected to said ro s.

3. In an electromagnetic device, the com- 'bination. of a field magnet, a flexible magnetic reed secured at the center to 'a neutral portion of said magnet, the vibratory ends of said reed being in operative relation to the poles of said magnet, a vibratory member connected to said reed near the ends thereof, and 'a coil operatively associated with said reed.

4. In an electromagnetic device, the combination of afield magnet having two pairs of pole pieces arranged to provide two airgaps, a flexible magnetic reed secured at the center tothe central portion of said magnet, the vibratory. ends of v/said reed extending into said airgaps, a coilKl operatively associated with said reed, and a vibratory member connected to said armature.

5. As a new article of manufacture for use in electromagnetic devices, a eld magnet r consisting of a pair of lateral extensions connected centrally by a cross arm, said 'extensions terminating in overlapping pole pieces arranged .to provide two'airgaps.

6. As a -new article of manufacture for use inA electromagnetic devices, a field magnet I lconsisting of^apair of 'substantially semicircular extensions connected by a d1ametr1c arm, said extensions terminatng in pole -pieces arranged to provide two airgaps the ends of said reed extending into said a1rgaps, and a coil in operative relat1on to vsaid reed.

8. In an electromagnetic device, a flexible magnetic reed su ported for vibratory movement at one en magnetic pole pieces arranged in operative relation to thevibratory end of said reed, a coil mounted on said reed `near its point of support, and means for holding said coil in place, said coil engaging said reed in yieldable pressure contact and thereby exerting a damping effect on its vibrations.

9.- In an electromagnetic device, a flexible magnetic reed rigidly supported at the ce'nter, magnetic poles .operatively associated with the vibratory ends of said reed, a pair of polarizing coils .mounted on said reed at opposite sides of its central support, said coils engaging said reed in yieldable pressure contact'to exert a damping effect on its vibrations, and avibratory member connected to said reed. l

10. In an electromagnetic device, a flexible magnetic reed rigidly supported at the' center, means for polarizing said reed, magnetic poles operatively associated with the" vibratory ends of said reed, a pair of rods connected to said reed at points between its central support and said magnetic poles, so that the vib ations at the free ends of said reed are tr' nsmitted to said rods in decreased ratio and at increased leverage, and a vibra- -torymember connected to said rods.

11. An electromagnetic translating device` comprising a field magnet structure having 'a central portion and polar extensions. on opposite sides of said' central portion, an

. armature secured at the center to said lcentral portion of the magnet structure, the free vibratory' ends of -said armature being in operative relation to said polar'fextenslons,

means for polarizing said arfmature, and a.v

-vibratory member operatively connected to said armature.

12. An electromagnetic driving. unit for loudspeakers comprising a field magnet structure having a central portion and polar extensions on opposite sides of said central portion, an armature secured at the center to said central portion of the magnet structure, the free vibratory ends of said armature being in operative relation to said polar extensions, a speech coil -surrounding said armature, a pair of rods connected to said armature near the free ends thereof, and a diaphragm connected to said rods.`

13. An electromagnetm translating device comprising a field magnet having a`pair-` of lateral extensions connected by a cross-arm, said extensions terminatmg 1n pole p1eces arranged to provide two airgaps, an armature secured at the center to the center of said arm, the `free ends of said armature extending into said airgaps for vibratory movement, a coil in operative relation to said armature, and a vibratory member -connected to said armature.

14. An electromagnetic translating device comprising a field magnet having a pair of lateral extensions connected centrally by a cross-arm, said extensions terminating in` pole pieces arranged to provide two airgaps, an armature secured at the center to the center'of said arm substantially at right 4angles thereto, the free en ds of' said armature extending intov said alrgaps for vibratory movement, a coil inoperative relation to said armature, a paii` of rods connected to said armature near the free ends thereof, and a vibratory member connected 'to said rods.

15.l An electromagnetic driving unit for loudspeakers comprising a field magnet'having a pair of lateral extensions connected centrally by a cross-arm, said extensions terminating in pole pieces arranged to provide two airgaps, an armature secured at the center to the center of said arm' substantially at right angles thereto, the free ends of -saidarmature extending into said air- 'apsfor vibgatory movement, a speech coil for said armature, a pair of rods connected to said armature near the free ends thereof,

and a diaphragm connected to s aid rods.

16. An electromagnetic driving unit for loudspeakers comprising a field magnet having a pair of substantially semi-circular ex` tenslons connected by a dlametrlc arm, sald' extensions terminating in pole pieces arranged to provide two airgaps, an armature securedatthe center to the center of said diametric arm and substantially atright angles thereto, the free ends of said'armature extending intosaid airgaps for vibratory movement, a coil in operative relation to said armatureya cone diaphragm, and

connecting means between the end portions of said armature and said diaphragm.

17. An electromagnetic driving unit for loudspeakers comprising a field magnet hav- 'ing a pair of substantially semi-circular extensions connected by a diametric arm, saidv extensions terminating in pole pieces arranged to provide two airgaps, an armature secured at the center to the center of said diametric arm and substantially at right angles thereto, the free ends of said armature extending into said airgaps for vibratory movement, a pair of coils mounted on said armature at opposite sides of its central support, means on said magnet to hold said coils 1n place, and a diaphragm connected to said armature near the ends thereof.

18. An electromagnetic driving unit for loudspeakers4 comprising a field magnet structure havinga central portion and polar extensions on opposite sides of said central portion, an armature secured at `the center to said central portion of the magnet structure, the vibratory ends of said armature being in operative relation to said polar extensions, a pair of speech coils mounted on said armature at opposite sidesfof its central support, a pair ofrods connected to said' armature at points between said coils and said polar extensions, whereby the vibrations at the free ends of said' armature as transmitted to said rods in decreased ratio and at' 19. An electromagnetic driving unit forV 'l loudspeakers comprising a field Vmagnet structure having a centralv portion and. polar portion, an armature secured at the center to saidcentral portion of the magnet structure, the 'vibratory ends of Saidarmature l being in operative relation to said polar extensions, a speech coil in operative relation to said armature, apair of rods connected to said armature near the free ends thereof, a cone diaphragm arranged substantially in axial alignment with the central portion of said armature, a ring secured centrally to said diaphragm, and meansafor connecting said rods to said ring.

20. An ,electromagnetic driving unit for loudspeakers comprising a field magnet structure having a central portion and polar extensions on opposite sides of said. central portion,lan armature secured at the center to said central portion, of the magnety structure, the vibratory ,ends of' said armaturebeing in operative relation tosaid polar extensions, a pair ofcoils mounted on said armature at opposite sides of itscentral support, a pair of rods connected to said armature at points between said coils and said.

polar extensions, whereby the vibrations at 'the free ends of said armature are transmitted 'to said rods in decreased ratio and at increased leverage, a cone diaphragm arranged substantially in axial alignment with the central portion of said armature, a ring secured centrally to said diaphragm, and means for connecting said rods to said ring approximately at* diametrically opposite points.

' ADoLrH A. THOMAS.

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