US1788557A

US1788557A - Loud-speaker motor

Info

Publication number: US1788557A
Application number: US303878A
Authority: US
Inventors: Jr Wilson Aull; Harry W Houck
Original assignee: Individual
Current assignee: Individual
Priority date: 1928-09-04
Filing date: 1928-09-04
Publication date: 1931-01-13
Anticipated expiration: 1948-01-13

Description

Jan. 13, 1931. w. AULL. J'R., ET AL 1,788,557

' ILOUD SPEAKER MOTOR Filed Sept. 4, 1928 2 Sheets-Sheet 1 INVENTORS Jan. 13, 1931. w. uLL. JR. ET AL 1,788,557

LOUD SPEAKER MOTOR Filed,Sept. 4. 1928' 2 Sheets-Sheet 2 Patented Jan. 13,

UNITED STATE-SPA T WILSON AULL, JR, or ASTOR-IA, AND HARRY-w. nouox, or Moimr vnnuou,

nEwYonK I I Application filed. September .'l.his invention relates toielectromagnetic reproducers, and particularly applicable to loud speakers such are used in radio broadcast reception, although its application is not necessarily limited thereto. I

One object of this invention is to provide an electrical sound reprodiicer adapted to be used in the output of conventional receivers whose armature or moving element is not limited in action by the pole pieces or other obstruction when strong currents are applied to the windings. I

Another object is to provide a method by means of which, if so; desired, all signals, speech, music, etc. are limited in volume to a predetermined maximum amount, regardless of strength in order that listeners will not be annoyed when tuning in, by extremely loud stations, accidently or otherwise before the volume control is properly adjusted.

Another object is to limit disturbances, noise, atmospherics, etc. to this predctermined sound level.

Another object is to provide an efficient but inexpensive loud speaker driving motor which may be easily duplicated in quantities with great uniformity of electrical. and acoustical characteristics.

A further object isto provide avdriving unit for incorporating into a complete loud speaker and which maybe built intoradio broadcast receivers or readily attached to standard broadcast receivers. Other objects and advantages of our invention will become apparent later in the specification. 7

As is well known in theart, standard electromagnetic telephone receivers, While very sensitive, cannot be supplied with more than a certain amount of signal enery without the diaphragm hitting the pole pieces of the magnets, making the'music or speech practi cally unintelligible and distorted, causing what is often called blasting in the case of the reproduction of music. Many loud speakers of the past have used merely enlarged magnetic telephone receiver elements as the motivating unit to drivethe sound reproducing diaphragm. Probably the most Widely used driver for loud speakers in the 4, 1928. Serial No. 303,8'3'8.

radio art, at present is the so-called balanced armature type'of unit which is subject to the same objection. Comparatively narrow energy level is required to be furnished to the unit, above which. satisfactory reception may not be attained, even though undulatory currents of practically undistorted characteristics be furnished the driving'unit.

Broadly speaking our invention conte1nplates the use of a forked armature so an ranged that thevmovabletips can not strike any abutment Within its operating range of movement.

Referring to the drawings, it will readily be appreciated that in the various forms our unit may be built, the vibrating armature is spaced apart from and cannot come in contact With pole pieces or other parts, regardless of the signal energy-suppliedthe system, a

and the only limiting factors are those such as affecting the burning out 'otthe magnet windingsor saturation of the vibrating armature, design features which may be predetermined and set to suit the service for which the unit is intended.

At the same time the units shown may be designed to be sufficiently sensitive to re spoud to very weak impulses. Thus our invention provides aloud speaker driving unit for the usual type of output circuit by means of which satisfactory reproductionof sound may be obtained even thoughjsupplied with widely varying energy levels, as compared to units now in common use.

Fig. 1 is a side View of'one form of our invention in which the energizing coils are mountedon the pole pieces of a permanent magnet core and the armature has two off set arms centrally pivoted between the coils.

Fig. 2 is an endview of the same.

Fig. 3 is a side view of another form similar to Fig. 1 but with the coils on'or around I the armature. 1

Fig. 4 is an endview of the same.

Fig. 5 is a side View of a form inwhich the forked armature is pivoted to one pole piece of the magnet and the coils are supported in place so thatthe armature tips can vibrate Within'them. p r

Fig. 6 is an end View of the same.

similar to the ones above described.

branches or arms I iorksg, 35 are preferably connected together cross piece 36 7 wire 37 is secured. The

coils

31 and 32 are 7 Fig. 7 is a side viewof another form with a forked armature having its shank secured to one magnet pole and. two coils on the.

' differentially wound coils.

Fig.9 is a sectional view of another form hav ng magnetizing coils 1n place oithe permanent magnet and. With. 11 Yos il i llg' forked armature and a single energizing cqil. 10 1s a diagrammatlc vlew showing one form ofoutput circuit with a reproducer according to our invention. 7

In the form shown in Figs. 1 and 2 the magnet 12 is provided with two pole pieces 13 each of which is preferably laminated to reduced ed dy current losses and each of which has two

tips

14, 14. The armature has a pivot shaft 15 with two arms 16,16 set crosswiseso that their tips are respectively'ab'ove and below the adjacent tips of the pole pieces. The armature is connected in any suitable manner for instance by means of a drive, rod or wire 17 to any suitable form of diaphragm or air vibrator 18. The coils 1.9 which are connected in the audio output circuit of the receiver (not shown) may be suitably mount ed upon or around either the polepieces of the magnet orthe armature. 'In Figs. 1 and 2 these coils are mounted on the tips 14 of the magnet polelpieces.

The construction shown in Figs. ..3 and 1 is similar to that of FigsRl and 2'except that the. coils 2O are mounted "so to surround the armature, members, nstead ofthe pole pieces of the stationary magnet. V In both forms of construction, however, it will be noted-that the armature when it vibrates can not come in contact with the pole pieces of the magnet and, thereiore, there can be no blasting nor crashing sound 'even when an excessive current is applied to the circuit.

in the form shown in' Figs. Sand 6 the stationary magnet-audits pole pieces are The armature shaft 21 howeverin this case mounted close to the pole pieces 22 and the armature is provided with twoarms the tips of which are located above and below respectively the tips of the pole piece 24, The pole pieces are shaped to most eil ectively coa ct with thearmature. The coils 25 are supported at 26 and the armature tips extend through these coils. 7 in the form shown in Figs. 7 and 8 the pole pieces 30 support the

coils

31, 32 and the armature 33 is supported on the'other pole of the magnet and provided with U two Two branches or to which the drive rod or differentially wound so as toproperl'y coact with the armature members. I 1

In the construction shown in Fig. 9 the magnet 40 may beof thenon-permanent type and provided with windings 11 for providlng the necessary field strength. In this case the pole pieces'lQ are suitably secured to the main part of the magnet. The magnetic armature has two tips 43. supported by-abar 4A1 also. of magnetic material which passes through the energizing coil 15 and the tips of th arma ur -,fo ks re ar nged Close to the tips of the pole pieces 12 but in position so that they can not touch no matter what the vibration of the armature may be. The upper endoi the armature may be adjusted by set screws'ifi which are supported in a strap 47. viln'ating member. g I

Fig. 10 shows a typical circuit arrangement for use with our invention. In this case the primary of the transformer fiO is' connected in the plate circuit of the output tube 51 of the receiver and the secondary is 'con-.

nected by leads 52 to supply energy to actuate the armature of the motor 53 to drive the diaphragm 54.

1V hile we have shown the loud speaker con- 48 is the drive rod connected to the air.

ill;

nected with the output tube through an out- It is expected, of course, that the physical laws obtaining for loud speaker motors, known to those skilled in developing these units, be applied in the design of our unit together with the output circuit for which it is intended. lit-transformer coupling is used from the output or power tube, it should have aprnnary unpedance at very low audio frequencies, approximately equal tothe as ternal impedance of the tube. Thesecondary of the transformer should" be equal to or match? the impedance of the actuating coil system, and should'be coupled to the primary in such a, manner that practically equal e'fiic ency of transfer obta ns over the audio frequency spectrum. Likewise the mechanical dynamic impedance of the driving-system should equal that for the driven "diaphragm or other sound producing arrangement. v

' The volume obtainable before the'limiting action begins is determined by'the' distance the armature travels towardthe field'pole until further travel does not reducethe air gap. hen the nearest edge'of an armature tip is opposite an. edge of a field pole further armature "travel does not materially reduce the air gap which is the principal part of the reluctance of the magnetic circuit. Consequently a very jstrong'signal'will give but little increase in volume over a Weaker signal that is strong enough to place the armature at instant-s of full current amplitude, in the position of least reluctance. The slight difference in volume between two such signals would be due to the inertia of the stronger carrying the armature slightly past this position; In no case can the armature come in contact with the fieldpoles, and i if the strong signal as delivered to the loudspeaker is free from distortion, and the loud speaker is correctly designed, as pleasing reproduction will result from very strong music or speech as from that of moderate intensity;

, To obtain this reuslt, the air gap should be such that the maximum working range of the armature is suitable for the services intended, i. e., home broadcast receiving as compared to a public address. service; the armature must not saturate with the strongest signal the output tube is capable-0f delivering and the diaphragm mustnot rattle with the maximum volume that the air gap is set for. V r

WVith such a reproducer, interfering disturbances, atmospherics, etc., are limited in Y amplitude to that of the accompanying music or speech, though initially many times stronger. Likewise the annoying effects of 1 fading are partly done away with inasmuch as the amplifier may be adjusted for great sensitivity and the signal will be of practically constant volume as long as it does not fall below the level necessary for this volume requirement.

lVe claim: 7 a

l. A loud, speaker motor comprising a magnetic core having pole pieces and coil windings and an armature supported at one end and having the other end forked and with tips disposed adjacent the pole pieces of the magnet.

2. A loud speaker motor comprising a magnetic core having pole pieces-and coil Windings and an armature supported at one end and having the other end forked and with 3 tips disposed adjacent the pole pieces of the magnet and means for limiting the vibration of the armature.

3. A loud speaker unit having two armatures, a field magnet coacting therewith and means comprising differential windings for simultaneously increaslng the flux denslty of one armature while decreasing the flux density in the other armature.

WVIL SON AULL, JR. HARRY W. HOUCK. I