US1730508A - Loud-speaker - Google Patents

Description

Oct. 8, 1929. M. c. HOPKINS LOUD SPEAKER 4 Sheets-Sheet Original Filed Dec. 22, 1925 illlljlllllllllll lull' I.. lll liu l. Il llll l ll New Oct. s, 1929. M HOPKNS f 1,730,508

LOUD SPEAKER Original Filed Dec. 22, 1925 4 Sheets- Sheet 2 iiiiiiii-iiiiiiiiiiiiiiiiiiill d Oct- 3, 1929- M. c. HOPKINS 1,730,508

LOUD SPEAKER Original Filed Deo. 22, 21,925v 4 Sheets-Sheet 5 Gtbmmga Oct. 8, 1929. M C, HOPKlNs 1,730,508

I LOUD SPEAKER Y Original Filed Dec. 22, 1925 4 Sheets-Sheet 4 {Yy/ Umm@ 76 M /4 vvueno ara/3 Halo/m56 44 wmp@ )ffm M Patented Oct. 8, 1929 UNITED STATES PATENT oFFIcE MARCUS C. HOPKINS, OF WASHINGTON, DISTRICT 0F COLUMBIA, ,ASSIGNOR TO 'HOP- .'KINS CORPORATION, OF JERSEY CITY, NEW JERSEY, A CORPORATION OF DELA- WARE LOUD-SPEAKER Application filed December 22, 1925, Serial No. 77,030. Renewed April 15, 1929.

The present invention embraces a loud speaker suitable for use on a radio receiving set, and also suitable for use'as an annunciator on wired radio systems, and in general, wherever speech current is to be translated into/audible sound.

It is an object of the present invention to produce a translating device of the cone type whereby clarity of tone and faithfulness in translating may be attained with reliability and at low cost. The preferred form of the device embodies an electrical movement of rugged construction wherein the vibrating armature is made up of a plurality of resilient plates spaced apartA from one another to give good flexibility, these plates being of ample width and thickness so that in the aggregate they form a path of low magnetic reluctance. The cone to which this vibratory armature is connected may bel of paper, or

like material, and preferably has lits outer tion edge bent forward to form a brim or rim by which the cone is yieldingly attached to an annular wood frame 'capable of acting as a resonator to supplement the sound producing action of the cone. v

Other objects and advantages will become clear from the following detailed description taken in conjunction with the accompanying drawings whereinl Fig. l is a front speaker;

Fig. 2 is a side elevation of the same;

Fig. 3 is a sectional elevation on the line 3-3 of Fig. 4

Fig. 4 is a front elevation with the paper cone removed to disclose the electrical movenient; .l

Fig. 5 vshows the electrical movement in front elevation'with certain parts in section;

Fig.- 6 -shows said element in side elevaelevation of the loud Fig. 7 is a transverse section on the line 7-7 of Figu;

Fig. 8 is a plan view of the electrical movement; j

Fig. 9 is a sectional detail of the laminated armature thereof; 'y

Fig. 10 shows the slots in the adjustable pole shoe of the unit, and Fig. ll is a detail of one of the pole pieces.

'The preferred embodiments disclosed in the drawings comprise a wood base l having a slot in which is glued the lower edge of a circular resonator 2. AThis resonator is preferably made of three ply wood. Three ply fir three eighths of an inch thick is suitable, and there is advantage in having the grain of the inner ply 3 disposed at right angles to the grain of the two adjacent outer plies. An annular groove 4 is turned in this resonator, and at the outer edge of this groove `the wood is beveled at 5 to form a seat to which may be glued the outwardly bent brim 6 of the sound producing cone 7. This cone may be made of paper. Paper of the quality known as'cover paper is suitable. The cone can be cut from a flat sheet and then bent into shape and glued along a radial seam. The outer edge of the conical. structure so formed is then bent at 8 to form an outwardly flaring brim. The brim will naturally take on a frusto conical form making an angle to the vertical plane substantially equal to the angle at which radial elements of the cone intersect the vertical plane. It is important thatl the outer part only of this brim 6 be fastened to the woodresonator at the beveled surface 5 for the inner portion of the brim is relied on to form a resilient support or hinge whereby the cone 7 may move` bodily without substantial distortion. For a paper cone 12 in outside diameter the brim may be 1% of an inch wide and the glued portion may have a width of lih or thereabout.

The electrical movement'for actuating the cone comprises a permanent magnet 9 suitably clamped to the wooden disc 2 as by a cross bar 10 and machine screw l11. Secured to pole 12 of the ma net by a screw 13 (Fig. 5) is a pole piece 14 o irregular shape. This pole provided with a pole piece 18V`l1eld in place 100..

by a screw 19 and carrying a transverse bolt 20 whereby the vibratory armature is supported.

The vibratory arma-ture consists of a plurality of blued steel laminations 21, say four in number, spaced apart on bolt 20 by iron washers 22, with"which the laminations make close magnetic contact. `At their other ends the laminations are spaced apart by soft iron washers 23, and are held in close contact therewith by a soft iron element 24, one end of which is riveted over to form an annu.- lar ange 25 tightly holding the laminations and Washers' together. This element 24 is in part hollow to receive a transmission rod 26, preferably made of phosphorbronze and se cured to element 24 by solder 27. The forward end of the transmission rod 26 passes through a hollow rivet 28 at the apex of the cone, and may there be rigidlyl attached by a soldered connection 29 (Fig. Or if desired, as shown in Fig'. 6, a set screw 30 may be used in place of or as supplemental to a soldered connection 31. Conical brass plates 32 and 33 serve to strengthen the apex of the cone and are held in ti ht engagementwith the paper at the apex o? the cone by the hol low rivet 28.

The electromagnet to which 'speech current is delivered for actuating' the armature comprises a simple solenoid 34. About 6000'turns of No. 40'enameled wire mounted on a bakelite or composition spool 35 is suitable for this pur ose. An insulating face late 36 may be, use as a guide and anchor or the leading in wires 37 and 38. Mounted to move within this coil is a soft iron pole shoe 39, a portion of which is threaded at 40 for engagement with threads cut inthe pole piece 14. There is also provided a knob 41 positioned at the back of the Wood resonator and by which pole shoe v39 may be advanced or retracted to increase or decrease the air gap between it andy the opposing element 24. The pole shoe is preferably provided with intersecting slots42 and 43 (Fig. 10) to reduce eddy currents.

Fig. 1 shows pole piece 14 in rear elevation.

`I find that it is advantageous to first drill this pole piece to receive the threaded pole shoe 39 and then to slot it at 44 through the tapped hole. The two fingers` thus produced are then squeezed inward toward one another by such an extent as may be needed to giveI a frictional grip on the threadedportion 40 of the pole shoe 39. This prevents that` pole shoe from working loose duringl shipment and also holds the pole shoe in ri id position irrespective of the vibration to'which the ole shoe is subjected when in actual use. is slot 44 has the further function of 4reducing eddy current losses in that-part ofthe pole piece lying nearest to coil 34. This one ex- .pedient increases the effectiveness of the device to a very noticeable extent. with the elements constructed and arranged as above described a speech current passed through winding 34, as from a radio receiving set or a wire annunciator system or circuit, will produce a corresponding vibration, of the laminated armature and such movement of the transmission rodv 26 as to translate the electrical impulses into audible sound thereby in eii'ect reproducing the speech or other signal represented by the speech current.

The conical diaphragm 7 can mo've bodily because of its lyieldingor hinged connection with the Wood resonator, and I have found is capable of transmitting its vibrations through the hinge to the wood. This is particularly true with respect to tones low in the musical scale. The Wood taires up the vibrations and together with the cone transmits the vibra.- tions to the surrounding air with results that are highly satisfactory.' The pole shoe can be advanced or retracted through coil 34 by suitably manipulating the knob 41, and in this mannerthe Width of the air gapV can be coordinated to the strength of the signals being received'. Any .expansion or contraction of the diaphragm due to atmospheric conditions is not of serious consequence because the free end of the armature can move with the cone and readjustment of the air gap to rcompensate for such changes requires nothing more thanv manipulation of knob4l.

I attach very considerable importance to the use of a laminated vibratory element or armature. The laminations can be wide enough so that in the aggregate they afford a largecross section and a resulting low magnetic reluctance, while at the same time have ygood resilience. The armatures` resist-ance to bending does not increase as rapidly as would be the case ifthe armature were of solid metal of the sameaggregate cross section. i In addition, the movements of the transmission rod 26 are more nearly axial than if this rod were rigidly attac-hed near the end of a solidvibratory armature. Within the narrow range of movement incident to normal use the successive positions of rod 26 are almost in parallel relation to one another.

The loud speaker or annunciator above described may bemade in various sizes, and is compact, rugged, and .inexpensive to build. When built yinto a radio receiving set or cabinet, 'or when used as an accessory in other resonator but leaving a part of the brim free n i to act as a hinge.

Also in my copending application, Serial No. 7 7 ,029, filed December 22nd, 1925, claims are presented on the use of a Wood panel the outer portion of which serves as a resonator,

and the inner portion of which serves as the support for the electrically actuating unit.

I claim: l

1. In a loud speaker,.the combination of a speech coil and a vibratory armature therefor, said armature comprising a plurality of spaced laminations, andmagnetic inserts arranged at intervals transversely of said laminations to retain them in spaced relation.

2. In a loud speaker the combination of a speech coil, a polarized vibratory armature therefor, said armature comprising a plurality of laminations spaced apart at their ends by iron inserts.

3. In a cone type loud speaker, the combination vof a magnet, a pole piece secured to each pole of said magnet, one of said pole pieces having a flat surface lying in a plane substantially parallel with the plane of the 1nagnet, a speech vcoilf housed within said magnet with its axis at right angles to the plane of the magnet and mounted against said flat surface of one of the pole pieces, a pole shoe movable forward or backward through said coil, a polarized armature secured at one end to the opposing pole piece, and a transmission rod secured to said armature.

4. In a cone type loud speaker, the combination of a permanent magnet, a pole piece secured to each pole of said magnet, a speech coil mounted on one'of said pole pieces, a pole shoe passing through saidA coil and having threaded engagement with its pole piece, said threaded engagement permitting advancement or retraction of said pole piece, a polarized armature rigidly secured to the opposing pole piece, and a transmission rod securedl to said armature and adapted to move with a substantially axial movement to transmit energy to sound producing means.

5. In a cone type loudspeaker the combination of a permanent magnet, a pole piece secured to each pole of said magnet, one of said pole pieces having a ilat surface lying in a plane substantially parallel with the plane ofthe magnet, a speechcoil housedy within said magnet with its axis atA right angles to the plane of the `magnet and mounted against said ilat face of'one of the pole pieces, a pole shoe passing through said coil and having threaded engagement lpermitting its advancement or retraction through said coil, a polar'- ized armature secureil to the opposing pole piece and carrying a magnetizable element opposite said adjustable pole shoe, and a transmission rod secured to said magnetizable element for transmitting energy to sound producing means.

6. In a cone type bination of a magnet, a pole piece secured to each pole of said magnet, a speech coil housed within said magnet substantially coaxial therewith and mounted against the flat surface of oney of said pole pieces, a pole shoe movableforward or backward through said coil, a polarized armature secured at one end to the opposing pole piece said armature comprising laminations spaced apart fora part atleast of their length, a magnetizable element securing the opposite ends of said laminations, and a transmission rod secured to said magnetizable element.

7 In a cone type loud speaker the combination of a permanent magnet, a pole pie secured to each pole of said magnet, a speech coil mounted on one of said pole pieces, a pole shoe assing through said coil and having threa ed engagement with its pole piece, said. threaded engagement permitting advancement or retractlon of said pole piece, a polarized armature rigidly secured to the opposing pole piece, and comprising a plurality of laminations spaced apart for a part of their length, a magnetizable element clamping the opposite ends of said laminations, and a transmission rod rigidly secured to said magnetizable element and adapted to move with a substantially axial movement totransmit energy to sound producing means.

8. In a cone type loud speaker the combination of a permanent magnet, a pole piece secured to each pole of said magnet, a speechcoil housed within said magnet and mounted against one of said pole p1eces'a .pole-shoe passing through said coil and lhaving a threaded engagement permitting advancement or retraction through Saidcoil, fasten- -ing means passed through the opposing pole piece, a laminated armature held in position thereby, a magneti'zable element clamping the opposite ends of-.said laminations, and a transmission rod secured to said magnetizable element and actuated thereby to transmit energy to sound producing means, substantially as described.

9. In a cone type loud speaker the combination of a permanent magnet, a pole piece bolted to each pole of said magnet, a speech.

coil housed within said magnet and mounted against the iiat face of one of said pole pieces, a slotted pole shoe passing through said coil and having threaded engagement with its pole piece and having meansv whereby the pole shoe may be rotated for advancement or retraction through said coil, fastening means passed through the-opposing pole piece, iron laminations and iron 4washers between their ends thereby to provide a polarized armature of large cross section. and relatively high resiliency, and a transmission rod secured to said polarized armature and adapted to move with a substantially axial movement to transmit energy to sound producing means.

loud speaker the coms l0. In a cone'type loud speaker the combination of a permanent magnet, a stamped pole piece bolted to each pole of said magnet, each of said pole pieces having an extension with integral lugs engaging an end of the magnet to insure rigidity of the bolted connection, a speech coil housed Within said magnet substantially coaxial therewith and mounted against the Hat face of one of said pole, pieces, a slotted pole shoe passing through said coil. andshaving threaded en gagement with its pole piece and having a knlob whereby the pole shoe may be rotated for advancement or retraction through said coil, a bolt passed through the opposing pole piece, iron laminations and iron washers threaded alternately on said bolt and held in close engagement thereby, a magnetizable element clamping the opposite ends of said laminations with iron Washers between said ends, thereby to provide a polarized arma- .ture of large cross section and relatively high resiliency, and a transmission rod secured to said magnetizable element and adapted to move with a substantially axial movement to transmit energy to a sound producing cone, substantially as described.

11. In a loud speaker, the combination of a speech coil, a pole shoe passing through said coil and a slotted pole piece into which said pole shoe is threaded and by which it is yieldingly gripped.

In a loud speaker, the combination o'f a speech coil, a polarized vibratory armature therefor, a pole piece on which one end of said coil is seated, and a pole shoe passing through said coil into operative relation Wit-l1 said armature, said pole shoe having threaded engagement With said pole piece, and said po e piece being slotted in that portion ad- ]acent to the coil thereby to. reduce eddy current losses.

13. In a loud speaker, the combination ofa speech coil, an armature therefor, a pole piece on which said coil is mounted, said pole piece being'slott'ed adjacent to said coil to reduce eddy current losses and a pole' shoe passing through said pole piece and movable toward and from the free end of said armature to regulate the width of its air gap.

14. In a loud speaker, the combination of a speech coil, a polarized armature therefor, a pole piece against the flat face of which said coil is mounted, said pole piece having a threaded opening thereinand'a slot intersect-ing said opening to forma pair of fingers, and va pole shoe threaded through said opening and yieldingly gripped therein by said fingers, saidv pole shoebeing movable toward or from the free-wend of said armature to.

regulate the width of its air gap.

15. In a loud speaker, the combination of a speech coil and a vibratory armature therefor, said armature comprising a plurality of laminations ofmagnetizable material whereby relatively loW reluctance and high resilience is obtained.

16. In a loud speaker, a permanent magnet, aspeech coil housed within said magnet with its axis substantially at right angles to the plane of the magnet, a pole piece connected to one pole of said magnet and connected to one end of said speech coil, and a vibratory armature connected to the other pole of said magnet andarranged adjacent the other end of said speech coil.

17. In a loud speaker, a permanent magnet, a speech coil housed Within said magnet With its axis substantially at right angles `to the plane of the magnet, a pole piece connected to one pole of said magnet and connected to one end of said speech coil, a pole piece connected to the other pole of said magnet, and a vibratory armature carried by said second pole piece and arranged adjacent the other end of said speech coil.

In testimony whereof I afl'ix my signature.

MARCUS C. HOPKINS.

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