US2288607A - Pneumatically operated loudspeaker - Google Patents

Description

assembly is ment l t It isan `object of the-present invention toprovide a loud-speaker in `which these `disadvantages lare 'eliminated 'or minimizediand which isrela-` tvelvinexpen's'ive'to make, rugged and durable. "Other `objects and' advantages will iappearifrom the detailed description that follows; y The invention,- in lbrief, t comprises `a t speaker "including aj tubular air valve provided with ports,V

receive"directlythel air the-air valve;` f i Patented Julv 7, 1942 A ffuru'rlzl)` STATES PATENTl OFFICE g l PNEUMATICALLY oPEna'rED LOUD` f M. SPEAKER` `i dward Chandlen'rgoklyn, N, Y., assignr of Y nner-half to Stewart PiFoltzfNew Castleda. I Applicationpecemberzl, i939, serial No. 310,361

' 1c claims.

'A This invention relatesg'to fa 'pneumatically ope-:Lrg l"erated loud-speaker of fthe-class* in which` com- 'pressed gas is"fcaused to vpassA through a :valve :actuated in 4its" openings and closings by'soun'd Awhich: is to be amplified.` n In such loudspeaker`s it iscustomary to controlfthefvalveby itheruaivoice fcoil pran'electroinag'netic'un'it of the-magneticf'or dynamic-type.

"It is customary;lalso,` in such iloudspeakrs to flasselmble` a `grid member "as `the air 'valvefand `a coaoting plate,` so that relative movement `loe-ffii tween the grid member and the plate servesto open andclose the valve, inaccordance withfth'e characteristics `of the' sound being ampliiiedl AThe valves are ordinarily of theypoppetifor "slidingvalveltypes The former are subjecttov high leakage of gas"c"ausing a l hissing` sound l in the speaker' and` requiring an unnecessarily large consumption-of gas`.""Tl'.ie latter are uotfadaptedI for'isatisfactoryoperationat anyone-settingover 4 y ,my driving member- 3 vibrations,characteristicof a Wide range `o 'f frequencies There is a tendencvlof'thevalveassemblylto chatter orvibrate-fwith the production `of unden sired noise and a metallicfquality inthe sound.

.'Iuhe parts of the conventional assembly :require careful and extensive*initialfmachiningf and theo,

diliicult to keep in proper4 adjusta'ltubularfcover or seat tting over-thevalveand provided 'with ports adapted tofrgister with `the 4ports thevalvegmeans for holding thelvalve normally* inthe position ot non-communication vbetweenltheportsirithevalvegand cover, means energizedfby sou-nd,l through either .fa voice.' coil or aneletrmagneticunitjior rocking the valve nits longitudinal" axis; soA asfto `place the ports *ini the valve and cover: in. communication,1` means forsupplyingagas under pressure tothe outslde.

of the valvecoverfsothatair'passes as puffsor f `llaststhroughthe valve assembly-Whenv the ports are placed in communication; andmeansfor 1re-` '3 taining the valve tous normar position when the fenergiain'g` electfceasesz'" Preferably the speaker? includes-an vvexponential"horn fsoplaced-es to' passes ythustlirough The invention will be illustrated by description (c1. 17o-ina) imgreater detail in connection `with the `attached drawing, to-which referenceisinade. u

, f Fig. `l-is -anwendview,` partly ink section, von line L-l-L-.Iof FBZtZ; l k Q 5 Figfis a -plan view, partly in section, online `Z--Ziof Fig. 1;

air valve assembly; von lline A A of Fig. 2, showing diierent relative positions of the inner andouter mfparts ofthe assembly; i u u,

Fig. 'I` a longitudinal section of a inodiied "form, oifembodiment; and V L u fxFigl, 8 is ,awview showing a sectional'view` ,4 of `*Fig-'italien on thelinesf, Q l A, l 15 FIhereare` shown ,a base member. ,I including Aelectrical binding posts 2.a, Extending lroin4 the base is the link 3 constituting `the`sound,"energizeddri-vingmember.

f1@ Disposedwithinthe bas "btt ntfshv 20.. suitable' conventional means forimpartingto the .sound Waves.` Thus, the'base may contain a unit ofjthe magnetic` or .of thedynamic type such as .used in common loud-speakers, the unitreceiving its impulses-through the electriccurrent supplied to; the binding posts 2 and beingkvinitially .generated .by `the sound which is to be amplified,

, as bymeans of `a'milcrophone or like circuit.`v` i The'speaker includes `a casing indicated gen- 3oerally at 4, an inlet 5 for compressed gas and a sound andr air outlet 6. The outlet is connected to a usual type of speaking hrnl (notshown). 1 Thencasing is suitably Vmade in tvvo` partsmne to the leftandone .to the right in' Fig. 2, held together by conventional bolts or clamps'v (not shown) ,acting uponllanges or lugs of usual type projecting from thertwo parts.. t u Y Extending between the air inlet and the outlet an -air valveassembly including a tubular tubular members, so that all the ports in onemember` may `be placed at one time in communication, .in full registration if desired, with ports in theother of the members.Y I The relative posi- -tion of Vthe ports at registration is shownin Fig.

3.,? Figs. tand. 6 show theports in communicamation-'but notin registration. l

Thelandstl of thetubular coverlaure at least as large in all dimensions as and preferably are somewhat wider than the ports 8 in the valve, as shown in Figs. and 6, so that the ports 8 may be closed completely by the lands I2.

The tubular cover fits tightly within the casing 4 of the speaker and is prevented from slipping in the direction ofthe sound outlet by the shoulder I3 of the casing. the cover is prevented from moving lengthwise `by the nut I4 which closes the hand hole and terminates at the inner end of the said cover.

The tubular valve 1 is rotatable to the extent that it may be rocked back and forth through a small angle, within the valve cover I0. In

this manner, ports within the two members may be made alternately to communicate and not to communicate.

At the other end tially no important passage of air into the outlet E.

Whatever small leakage may occur between the members 1 and I0 does not cause chattering, since the air chamber 21 extends completely around the grid portion of the tubular cover I0 and the pressure of the air is exerted equally in all directions upon the outside of the cover and of the tubular valve member 1. Because the conforming portions of the valve 1 and cover member I0 are relatively short between the said ports An element such as the lug I5 extends from the outside of the tubular valve cover, substantially in the direction of an extended radius thereof, that is, transversely with respect to the longitudinal a'xis of the cover. A set screw I6, with lock nut I1, acts upon one side of the said elementjwhe'reas the stop I8 is forced by spring I9 against the other side of the element. v By changing the position of the set screws I6, the

element I5 and attached tubular cover I0 are rotated slightly. At all times the element I5 is held in firm, non-rattling manner between the lend `of the set screw and the spring-pressed stop.

The inner of the concentric tubes constituting lthe air valve 1 is attached, as by a web member to a bolt or shaft member 2|. The latter passes through a guide member 22, which is continuous with a 'hook-like extension 22a of the tubular valve cover l0.

The sleeve or enlargement 23 around the bolt 2| rests 'at one end against the web member 20 and at the other end against the guide 22, as illustrated, and prevents lengthwise movement of the 5 valve member 1 towards the said guide. Lengthwise movement of the valve 1 in the other direction is prevented by abutment against the shoulder I3 of the' casing.

vA torsion spring 24, advantageously of flat spring steel, is secured at one end 25 to the casing, asby extending into a slit in a plug seated non-rotatably in the casing. At the other end,

the spring is held in a slit in the end of shaft 2|. The right hand end of the shaft 2|, in turn,

is fixed to theweb member 20, as by being welded thereto, so that the spring is held in established `relation at 'one end to the air valve-1 and at the other to the casing of the speaker.

Anelement 2S extends from the enlargement 23 around the shaft 2|, generally transversely with respect to the axis of the shaft and of the valve member 1. Means such as a small screw attach the driving member 3 to the end of this element 26 that is remote from the said shaft.

" The casing defines a chamber 21 that extends completely `around the part of the valve cover provided with the ports and that is continuous with the gas inlet 5.

` 'The operationof the lloud speaker willbe Ain part evident from the description of it that has been given. More specifically, it is as follows.

At the outset, the tubular cover member III is set angularly, by turning the set screw I6, so that the ports 8 and Il are non-communicating. Gas under pressure, ordinarily air, is then admitted through the inlet 5, so that the air is supplied to one side, the outside of the valve assembly. Because the ports in the ltwo concentric tubes 1 and I0 are non-communicating, there is substanand the ends of valve and cover members adjacent to the sound outlet and relatively long at the other end, whatever leakage of air does occur is largely in the direction of the outlet 6, because of the lesser resistance to leakage at that end of the assembly.

' With gas under pressure in the chamber 21 and the tubular cover I0 set so that the ports therein are not in communication wilh the ports in the air valve (Fig. 5), the speaker is ready for operation. When sound energized impulses are transmitted'through the driving member 3, the air valve 1 is caused to rock slightly upon its longitudinal axis or center line, say, to the position shown in Fig. 4for Fig. 6, at a frequency characteristic of the sound which energizes the mem- -ber 3. Also, the extent of the rocking and the nearness of complete registration of ports in valve 1 with the ports in the coverID are determined by the characteristics of the sound being amplified, especially by the intensity thereof.

As the valve 1 is rocked, the torsion spring r24 is twisted, so that it comes to exert a force tending to return the valve 1 to its original position. As soon as'the energizing force transmitted through member 3 causes toa-ct, this restoration is made by the spring.

This operation, of course, is repeated in rapid succession, so that air is caused to pass through the valve assembly ina series of short puffs or blasts which generate sound of great intensity. In fact, the apparatus is adapted to amplify the human voice so that it may be heard under favorable outdoor condition for a distance of apf approximately four miles.

The amplified sound shows only a minimum .of metallic quality and is substantially free from noises created by vibration of the valve or cover.

The speaker, once adjusted, holds the adjustment very well. The torsion spring clamps the rocking of the valve and gives a sharp air cut 01T without hammering.

Because my valve is balanced and housed so 'that weight is not much of a factor, thicker walls and hence deeper slots may be employed. Such deep slots afford viscous air-now resistance, in distinction to the predominantly turbulent air-flow which is set up in other types of valves. The modulation of air-flow, by the variation of such a viscous resistance, produces a better tone quality than that obtained by variations fof a turbulent resistance; in the latter case, the tendency toward non-linear distortion and toward a reduction of the per cent modulation at larger initial valve clearances is greater.

. For similar reasons, the load carrying capacity of my improved valve is large.

The valve, being balanced about the axis upon which it turns and being under fluid pressure that is equally distributed over its entire active surface, requires only limited clearance between the valve and its tubular cover or seat, thereby reducing leakage and hiss The valve in the casing or housing is protected andpractically `immune to damage during use.l ChfitteldueA to occasional over-loading is'elimi natedor minilii reduced byutl'ieV design of the ytort'ion' howling due to selfmumfacoustic icii'ncyniay be obtained, i "isc 'y 4to ypr vide a" conduit thorn) of llyn 'icl-easing cross-sectionfrom ,the throttling arca tothe `mouth of tlieconduit.

"Itis not-necessary'to the invention, however,

lIn coiistructngthe apparatus, `the casing may `be east of aluminum," brass, iron, orf other suitable me'taILfThe amount'o'f machining'necessary is smaila For"bestresultsjthechamber which holds the tubular cover 'i0 is machined as vare the exthe normal angular position of the air valve, so that 'theports in the cover `and valve are/noncommunicating, means energized by the sound to:

` tion to the casing,V saidfspring being `ariangedto restore the airvalve tothe'position of non-communication of the ports therein with the` ports in the cover when the energizing action ceases.

` `2. A loud-speaker asdescribed in claim 1, the

` means forrocking the air valve `including a coil terior land interior faces of the cover il) and the exterior face of the "tubular'va-lve member "l." v

'Thefports that 'are at this time preferred are substantially rectangular slotsextending length; wise of the concentric tubularmembers'l `and i0.

r Theportsvalve lmaybe ofequal dimensions" at the inside andthe outside-of the tube. "That they are` nonffilairig.` The:` imperforate" areas or lands 9A and I2`` interveningbetween non-far ing slots,on,the other hand,` flarenecessarilyand become wider towards the outside. r

In the preferred embodiment the ports in the mountedA coaxially with'the air valve, andmeans for supporting saidcoil for oscillation about the longitudinal axis of the air valve. @3. A loud-'speaker as described 1in claim 1, the tubular valve cover fitting tightly within the said casingin angularly adjustable manner and having la memberv extending outwardly'. therefrom, and opposed adjustable screw and springmeans 'carriedfby -the` casing" and pressing againstrthe f opposite sides offsaid extending member.

cover I are somewhat longer than those in the valve l', to facilitate lengthwise `adjustment ofV parts 'land l0. The tubular members 'l and I0 are suitably constructed of metal, brass, aluminum, stainlesssteel, or the like, and have relatively thick walls. The valve coveris made of such sizey as to fit snugly over the'selected valve. The base of the casing, in turn, is made to fit in substantially air-tight manner around the Valve cover Ill. f

In the modihed form of construction illustrated in Figures 7 and 8, the voice coil motor is of the natureof a-darsonval galvanometer having `a stationary magnet element D and a movable coil element` 5|, the last-named element being mounted for rocking on a fiat steel `spring 52 about the longitudinal axis'thereof. The rocking movements of element 5I are transmitted to a Valve 53, which is similar to the valve 1 of the previous modification. The straight line coupling of the actuating motor and valve reduces the opportunity for the introduction of self-imposed frequencies and thus reduces undesired noises. This arrangement also permits a reduction inthe weight of moving parts. The fluid medium is delivered to the unit through `a pipe 54 and freed from dust `by means of a filter 55. The air and gas which enter through pipe 54 are caused to flow over the actuating motoronits way to the` valve thereby cooling the motor. r

It will be understood that the details `given are for the purpose of illustration, not restriction,

, and that Variations within `the spirit of the intubular members provided with `ports angularly spaced around the circumference ofV the said `membersand constituting an outer valve cover and an inner air valve, respectively, means for mounting the valve cover in fixed position within the casing, means supportingthe'air valve rotatively Within the cover, means for establishing i 4. A loud-'speaker asdescribed in `claim 1, comprising anfelement extending transversely from the side of the tubular valve-cover, portions of the said casing fitting tightly around thecover, a set screw extending through a part of the casing and acting upon one sidepf the transversely extending element, and a springpressed stop` contacting the other side of the said element, so that the angular setting of the element and attached valve cover may be adjusted and the element held rmly between the said screw and stop.

5. A-pneumatically operated loud-speaker comprising a speaking horn, a casing member provided with an inlet for airunder pressure and an outlet to the horn, an air valve assembly disposed between the said inlet and outlet and including snugly fitting concentric tubes provided each with air ports spaced similarly in the two tubes, apart of the casing defining a chamber the inner tube being in free communication withthe horn, and the means for rocking the inner tube including an element extendinggenerally transversely with respect to the longitudinal axis of the inner tube, a driving member energized by the vibrations of a sound-actuated diaphragm, the driving member extending at approximately right angles to the said axis and to the direction of extension of the said element, and means connecting the drivingmember to the said element at a position remote from the said axis.

6. A pneumatically operated loud-speaker comprising a hollow valve member provided with a series of rectangular shaped, axially `extending ports about its periphery, an actuating motor for rocking .said valve member-about its axis, said motor being of the dArsonval galvanometer type,

and means for establishing the flow of air over` said motorand through saldvalve member. u

7. A pneumatically operated loud-speaker comprising a speaking horn, a casing` member provided with Aan inlet for `air-under pressure and an outlet to the horn, an air'valve assembly disposed between the said inlet and outlet and including snugly ttlng concentric tubes provided each with air ports spaced similarly in the two tubes, a partr of the casing defining a chamber around the portion of the concentric tubes provided with ports, means for adjusting the angular` position of the outer of the tubes withreference to the casing and means energized by the sound to 'be amplified for rocking the inner of the tubes about its longitudinal axis, said means comprising a voice coil element4 mounted for oscillation about the longitudinaly axis of the tubes.

8. A loud-speaker as set forth in claim '1 in which one end of the voice coil element is provided with a horizontally extending supporting spring.

9. A pneumatically operated loud-speaker comprising a speaking horn, a casing member provided with an inlet for air under pressure and an outlet to the horn, an air valve assembly disposed between the said inletV and outlet andincluding a pair of snugly fitting concentric` tubes provided each with airports spaced similarly in the two tubes, a part of the casing defining a chamber around the portion of the concentric tubes provided with ports, means cooperating with the casing for adjusting the angular position of one of the tubes with respect to the casing, means energized by the sound to be amplied for rocking the other of thel tubes on its longitudinal axis. a torsion spring, and means holding the torsion spring at one end in fixed relation to the casing and at the other end in fixed relation to said other tube, the inlet for air being continuous with lthesaid chamber, the inner tube being in free communication with the horn, and the means for rocking said other tube including an element extending therefrom generally transversely with respect to the longitu`

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