US1780349A - Apparatus for radiating sound waves - Google Patents

Description

Nov. 4, 1930. R. D. FAY

APPARATUS FOR RADIATING SOUND WAVES Filed Dec. 10, 1927 5 Sheets-Sheet l Nov. 4, 1930. R. D, FAY 1,780,349

APPARATUS FOR RADIATING SOUND WAVES Filed Dec. 10, 1927 V 5 Sheets-Sheet 2 Nov. 4, 1930. R. FAY

APPARATUS FOR RADIATING SOUND WAVES Filed Dec. 10, 1927 5 Sheets-Sheet 4 N QQ I JJENTU ATTEIRNEI'L:

Ndv. 4, 1930. R, D, FAY 1,780,349

APPARATUS FOR RADIATING SOUND WAVES Filed Dec. l0, 1927 5 Sheets-Sheet 5 B ATTEI H EL! Patented Nov. 4, 1930 PATENT OFFICE RICHARD D. FAY, 0F CAMBRIDGE, MASSACHUSETTS APPARATUS FOR RADIATING SOUND WAVES Application filed December 10, 1927. Serial No. 239,178.

distinct iron circuits, one of which carries a constant magnetic flux, and the other a varia'ble flux, said constant magnetic flux passing through a portion or portions of said armature normal to the plane thereof.

stant magnetic field, and an armature which is preferably a closed electric circuit resiliently suspended in a gap across which said constant magnetic flux flows normal to the plane of said conductor, a coil or winding energized by variable currents such as those of the output circuit of the tube in the last audio stage of a radio receiving set, said coil being inductively related to said. closed conductor and a tympanum suchyas a cone supported, preferably, only at its apex on said closed electric circuit, whereby a force will be exerted on said closed electric circuit perpendicular to the constant magnetic flux and the current induced in said closed electric circuit by the variable currents in said winding, said force being proportional tosuch induced current.

An illustrative embodiment of my invention is shown in the accompanying drawings in which c Figure 1 is, a plan view ofa radio loud speaker embodying my invention;

Figure 2 is a vertical elevation;

Figure 3 is a horizontal section taken on the liine 33 of Fig. 2;

Figure 1 is a longitudinal vertical section taken on the line 414 of Figure 1;

Figure 5 is a transverse vertical section taken on the line 5-5 of Fig. 2; and

Figure 6 is a fragmentary sectional view showing one wayin which the tympanum can be mounted on the armature.

In the illustrative embodiment of my inventlon shown in the accompanying drawings, 10 represents a base carrying at its opposite ends the brackets 11, secured to which are the oppositely-disposed permanent or horse-shoe magnets 12, the juxtaposed ends of which are separated by narrow gaps and are maintained in fixed relative position by the non-magnetic plates 13 attached to the outer faces thereof, and the bolts 13 pass- My invention contemplates the use of permanent or electromagnets for creating a con-i ing transversely through the legs of the magnet. 7

It will be understood of course that electromagnets may be employed in place of the permanent magnets illustrated.

A pair of brackets 14 are secured to the opposite sides of the base for supporting the closed laminated core 15 of a transformer,

the primary of which consists of the coils 16 and the, secondary of the closed electrical circuit 17, shown in the present instance as a thin rectangular copper plate having its center'portionremoved so as to form a single turn of conductor closed on itself. The secondary 17 is in close inductive relation to the primary 16. A transformer of this type is generally known as a closely-coupled transformer. h

Obviously a variety. of means may be employed for supporting the said transformer in the proper position with respect to the other elements of the system, and that I do not limit myself to the means specifically shown and described.

In the present instance, two parallel vertical plates 18 separated apart by the blocks 19 are attached to the brackets 14 by the screws 20, and the laminations of said core 15, which preferably are of the E-type are threaded through the primary windings 16, and the closed circuit secondary 17 until the core has been built up to the desired size, whereupon the said laminations are clamped together by the bolts 22 and bars 21 which are then secured in adjusted position to said plates 18 by the bolts 23.

The closed circuit secondary 17 is suspended preferably resiliently in the gaps between the permanent magnets by three sets of filaments 24 of resilient material, such as bronze, which, as indicated in Figs. 2 and 4, may pass through holes near the edge of said secondary, preferably making a turn through said holes, and then around the tightening screws 25, after passing through notches 26 in the plates 27 which are secured to the inner sides of the brackets 14.

It is quite essential that said filamentary suspensions be maintained in parallel relation each with the others on the same side i of the secondary or armature 17, to allow maximum freedom of motion thereof.

Secured to, or as shown, preferably integral with the secondary 17, are two forwardly-projecting members to which the bakelite yoke 28 is suitably attached, as by molding the same thereto, and molded to said yoke is a horizontally-disposed threaded stud 29 to which the tympanum shown in Fig. 6 as a cone 30, may be attached in any suitable manner.

It will be noted that at least one portion, and preferably two oppositely disposed portions of the closed circuit secondary 17, viz, the upright sides thereof, lie in the gaps between the magnets 12, and also that the primary windings 16 are outside the field of said permanent magnets, in order to reduce the gaps between the magnets 12 to a practicable length. If the primary windings were not outside the field of the permanent magnets, it would be necessary to have a gap of such great length that it would be impossible to maintain a field of suificient strength to give effective results.

There is, therefore, a magnetic circuit, namely, that of the permanent magnets, carrying a constant magnetic flux, and a second independent closed magnetic circuit, namely, the core 15 of the transformer 16 17, in which a variable magnetic flux is created by the variable currents energizing the primary of the transformer. The said variable magnetic flux induces currents in the closed secondary 17 which, being suspended in the path of the constant magnetic flux, will be given a vibratory motion in the direction of its plane, that is to say, will move edgewise, against the tension of the filamentary suspension members. While the system is 5 mounted to allow such edgewise motion,

there is great restriction to any other form of motion.

It will be observed that the closed circuit secondary constitutes an extremely light rigid armature which has no electrical or magnetic contact with the rest of the system, that said secondary has very low inductive reactance, that a comparatively small magneto-motive force is required to maintain the field, because no insulation material is required in the gap, that the suspension members ma be extremely light, because there is no orce other than the working force and gravity on the moving sys tem, that the disposition of the parts allows a closed iron core for the transformer which carries no permanent fluX, and hence suffers no loss of permeability, and that there are two separate and distinct iron circuits, one carrying a constant magnetic flux and the other, which is in effect the core of a transformer, carrying a variable flux, all of which features make for simplification and efficiency and also fidelity of reproduction.

Having thus described an illustrative embodiment of my invention without however limiting the same thereto, what I claim and desire to secure by Letters Patent is:

1. A sound-radiating device comprising in combination, means creating a constant magnetic field having two oppositely-disposed gaps, a primary winding without said field, a closed secondary inductively related to said primary and having two oppositelydisposed portions thereof located within said gaps, means suspending said secondary for motion in the direction of its plane, and a tympanum secured to said secondary.

2. A sound-radiating device comprising in combination, a magnetic circuit carrying a constant magnetic flux, a closed magnetic circuit magnetically independent of the firstmentioned magnetic circuit, means creating a variable magnetic flux in said closed magnetic circuit, a closed electric circuit suspended in the path of said constant magnetic flux and linked by said variable magnetic flux, and a tympanum secured to said closed electric circuit.

3. A sound-radiating device comprising in combination a winding, a conductor closed on itself and inductively related to said winding, a suspension for said. conductor, said suspension comprising a plurality of filaments of resilient material attached, respectively, to the opposite sides of said conductor, means for variably tensioning said filaments,means creating a constant magnetic flux passing through a portion of said conductor normal to the plane thereof and a tympanum secured to said conductor.

4. An electromagnetic mechanism comprising in combination means for creating a constant magnetic field, a closely coupled transformer havinga closed magnetic circuit independent of said field, a primary winding Without said field and a closed secondary in close inductive relation to said primary,a portion of said secondary being located Within said magnetic field, and means suspending said secondary for motion in the direction of its plane.

' In testimony whereof, I have hereunto subscribed my name this 9th day of December, 1927.

RICHARD D. FAY.

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