US2281539A - Horn - Google Patents

Description

April 28, 1942.

L. v. GROVER HORN Filed Nov. 4, 1939 2 Sheets-Sheet 1 Ly/wo/v M Gkavak April 1942- 1.. v. GROVER 2,281,539

HORN

Filed Nov. 4, 1939 2 Sheets-Sheet 2 1E 7 9 ZYI/EHZUI" Lr/wQ/v M GRowsR Patented Apr. 28, 1942 TENT OFICE HORN Application November 4, 1939, Serial No. 362,795

11 Claims.

This invention relates to fluid operated horns, and more particularly to signaling horns suitable for use on automobiles, trains, boats, coast guard signals, sentry signals, flre alarms, and the like.

This application is a continuation in part of my copending application Serial No. 227,155, filed August 2'7, 1938.

It is now generally accepted by sound engineers that the most desirable sound or note for a horn is one of low pitch. In the past it has been possible to obtain horns of low pitch and high volume of sound provided high air pressure were employed and if the fluid consumption for operating the horn were high. If a heavy diaphragm were employed with low pressure to obtain a low note in the past, only a low volume of sound resulted. If a light diaphragm were employed with high pressure in order to reduce the air consumption, it has been found that the dia-,

phragm breaks easily. Furthermore, if a light diaphragm were employed with relatively low pressure to obtain a low note, only low volume of sound resulted. It is also characteristic of the prior art devices that high notes may be obtained in horns more efliciently than low notes, but these high notes are objectionable in that they do not have the penetrating properties of low notes nor are they pleasing to the ear.

It is an object of the present invention to provide a novel fluid operated horn which is capable of providing a low note at low operating pressures with low fluid consumption but which will give a high volume of sound and have great penetrating properties.

For example, in the past, it has been customary to employ an air pressure of approximately one hundred pounds per square inch to obtain a satisfactory low note and large volume of sound. In a construction of the type herein described, a low note of similar pitch and of equally high volume of sound may be obtained with fluid pressures of approximately thirty pounds per square inch. This great reduction in fluid pressure required to operate the horn permits the use of much more economical apparatus, particularly the compressor unit which is to be employed in conjunction with the horn.

Another object of the present invention is to produce a horn having exceptionally high efficiency in that it produces a greater volume of sound in proportion to the fluid applied than has heretofore been possible.

A further object of this invention is to provide a novel horn construction which is economical to manufacture, which is rugged and reliable in use,

and which may furthermore be operated with great efliciency.-

Another and further object of this invention is to provide means for insuring an accurate and positive fit for the vibrating diaphragm on its seat when in normal position.

Another and still further object of my invention is to provide a dual horn, operated by a single sound unit, which is of particular Value in train signalling, public warnings, and the like where it is desired to simultaneously project the sound in opposite directions.

Another object of the present invention is to provide a novel horn construction, certain relative dimensions of which are constructed to fall within certain critical ranges.

The novel features which I believe to be characteristic of my invention are set forth with particularity in the appended claims. My invention itself, however, both as to its organization, manner of construction, and method of operation, together with further objects and advantages thereof, may best be understood by reference to the following description, taken in connection with the accompanying drawings, in which:

Figure 1 is a longitudinal section of the sound unit in a single trumpet type embodiment of my invention;

Figure 2 is an end view of the sound unit taken along the line IIII of Figure 1, with the rear shell or casing member removed;

Figure 3 is a longitudinal section of the sound unit for a dual horn made in accordance with my invention;

Figures 4 and 5 are alternate form of diaphragms suitable for use in the dual type horn 0 Figure 3;

Figure 6 is a modified form of diaphragm cup suitable for use in either of the forms shown in Figures 1 or 3;

Figure 7 is a longitudinal section of a horn similar to that shown in Figure 1 but with a modified form of casing construction and having the diaphragm disposed in a slightly different manner;

Figure 8 is a sectional view of a horn similar to the horns shown in Figures 1 and 7 but having a modified form of casing construction;

Figure 9 is a sectional view of a diiferent em-, bodiment of the present invention;

Figure 10 is an enlarged diagrammatic view illustrating the manner of operation of the horn shown in Figure 9; and v Figure 11 is a diagrammatic view illustrating two parallel disposed spaced surfaces between which air is rushing which illustrates one theory of operation of a horn constructed in accordance with the teachings of the present invention.

In Figures 1 and 2 of the drawings, a fluid pressure operated horn is shown comprising, in general, a casing It in which the sound producing elements are housed, a trumpet or bugle II, and a source of fluid pressure I2. The casing I includes a front housing member I3 and a rear housing member I4 which are secured together around abutting peripheral flanges I5 and I6 by means of bolts I! or the like. A diaphragm I8 is mounted within the casing I0 and is disposed to extend completely across the interior thereof to divide the casing into a forward pressure chamber I9, and a rear chamber which is ported to the atmosphere through a suitable opening 2I in the rear housing member I4.

The bugle Ii, as shown, is provided with a separate rear end assembly which co-operates with the diaphragm I3 to form a sound producing unit. This rear end assembly includes an externally threaded bushing 22 which is mounted in and threaded through the forward end wall 23 of the forward housing member I3. The bugle H is mounted and supported on the bushing 22 in any suitable manner such as by making a tight telescoping fit therewith.

A cup shape end piece 24 is provided on the rear end of the bushing 22 and may be secured to the bushing 22 in any suitable manner such as by making a tight telescoping fit therewith. This cup shape end piece 26 has a base portion 25 which is disposed substantially parallel to the diaphragm I8 and is shaped to be relatively shallow compared to its width and its width relatively great compared to the internal diameter of the rear end of the bushing 22. As will presently be discussed in detail, the dimensions of this cup shape end piece 28 with respect to certain other dimensions of the sound unit are very critical and must be kept Within certain definite limits in order ta produce an efficient sound producing unit.

While I have shown the bugle I I together with its rear end assembly as being formed of a number of separate pieces, it is, of course, to be understood that this entire assembly including the bugle I I, the bushing 22 and the cup shape member 24 may be formed in a single piece, each element of the assembly being integral with the other elements thereof.

N The outer peripheral wall 26 of the cup shape end piece 24 provides a seat for the diaphragm I8 when the diaphragm I8 is at rest. When the diaphragm I8 is seated on the peripheral wall 25 of the cup shape end piece 24 it will be observed that the pressure chamber I9 formed by the forward housing member I3 and the diaphragm I8 is completely separated from communication with the bugle II.

The spacing of the cup shape end piece 24 with respect to the diaphragm I8 is made adjustable by virtue of the fact that the bushing 22 is threaded through the forward end wall 23 of the forward housing member I3. In order to retain the cup end piece 24 in desired position after its spacing with respect to the diaphragm I8 has once been adjusted, a set screw 21 is provided in the forward housing member I3 which may be screwed into tight clamping engagement with the bushing 22.

In some instances, it has been found desirable to augment the inherent resiliency of the diaphragm- I8 which tends to hold the diaphragm IS on the peripheral wall 26 of the cup shape end piece 24 by a biasing spring 28. The biasing spring 28 is shown as a coiled spring which rests at one end on the diaphragm l8 and which rests in a metal cap 29 at its opposite end. The metal cap 29 rests on the end of a bolt 30 which is threaded through the rear wall of the rear housing member I l and through a boss 3| which is formed on the inner surface of the housing member I l. A lock nut 32 is also provided to retain the bolt 30 in its desired adjusted position. As will at once be apparent to those skilled in the art, the bolt 36 provides a convenient means for adjusting the tension in the coil spring 28 and hence the biasing force which tends to hold the diaphragm I'8 seated on the peripheral wall 26 of the cup shape end piece 24.

The diaphragm- I8 of the embodiment of the present invention shown in Figures 1 and 2 is mounted in an annular slot 33 which is located substantially at the junction of the forward housing member I 3 and the rear housing member I4. This slot 33 may be formed entirely in either one or the other of the two housing members I3 and I4 or may be formed partly in one and partly in the other. The annular slot 33 is shown as being disposed at a slight angle to the normal plane of the sound unit and by virtue of this fact the diaphragm I8 is caused to bow forwardly a slight amount thus presenting a portion of a spherical surface to the cup shape end piece 24. This bowing of the diaphragm I8 tends to increase its stiffness characteristics and to thus cause it to seat very firmly and evenly on the peripheral wall 26 of the cup shape end piece 24 and it further tends to require a greater pressure to unseat the diaphragm I8. It will of course be understood by those skilled in the art that this bowing of the diaphragm I8 must be very slight in order not to make the diaphragm too stiff and in order that the diaphragm will not rupture on repeated vibration.

The diaphragm I8 may be made of any suitable material but is preferably formed of a piece of very thin metal plate such, for example, as phosphor bronze.

Air under pressure is introduced into the pressure chamber I9' through an inlet passage or port 34 in the forward housing member I3. The passageway '34 communicates with a source of fluid under pressure through a nipple 35, a valve 36 and a fluid pressure supply line 31. Although not shown, a storage tank may be provided in the fluid pressure supply line in a manner and for a purpose well-known to those skilled in the art. The valve 36 is diagrammatically illustrated as being electrically operated by a solenoid 38 which is energized from a battery 39. A switch 40 is provided in the energizing circuit from the battery 319 to the solenoid 38 to control the operation thereof.

When it is desired to operate the horn, air

under pressure is introduced into the pressurelifted slightly off of its seat on the cup shape end piece 24, allowing a sudden flow or plop of air from the pressure chamber I9 to pass into the cup shape end piece 24. This reduces the pressure in the chamber I9, and allows th'e'dia'phrag'm [8 to again engage the peripheral Wall 26, whereupon pressure again begins to build up in the chamber 19 until it is sufficient to again force the diaphragm l8 off its seat. This cycle of action repeats very rapidly, the frequency of the diaphragm vibrations depending, of course, upon the inherent resiliency of the diaphragm l8, its weight, the angle of the slot 33, the tension in the spring 28, the pressure of the air in the air supply line 31, and the area of the diaphragm I8 which is exposed to and forms a wall of the pressure chamber 59. This interrupted or pulsating flow of air across the peripheral wall 26 into the cup shape end piece 24 and bushing 22 produces sound waves which are amplified by the bugle I I.

A preferred commercial form of the present invention is shown in Figure '7. Parts of this construction which are similar to parts of the construction shown in Figure 1 have been given the same reference numerals. More particularly, the construction shown in Figure 7 is similar to that shown in Figure 1 with the exception that the cup shape end piece 24 has been made integral with the bushing 22, the diaphragm I8 is flat and lies in a single plane, and the rear housing member I4 is arranged to be threaded on to the forward housing member l3 rather than to be bolted thereto.

As may be seen from the drawings, the rear housing member I4 of the construction shown in Figure 7 is provided with a forwardly extending flange iii which is internally threaded for threaded co-operation with the externally threaded portion 42 of the forward housing member [3. A shoulder 53 is provided on the forward housing member I3 upon which the diaphragm I8 i seated. Adjacent the shoulder 43 is an upstanding annular flange M which fits into a complementary groove or channel 45 in the rear housing member it. The portion 46 of the rear housing member l4 which lies radially inwardly of the annular channel or groove 45 is arranged to bear against the diaphragm l8 and pressed into tight engagement with the shoulder 43 of the forward housing member l3.

A coil spring 41 is disposed between the diaphragm I8 and the rear housing member It and co-operates in the assembly for the same purpose and in the same manner as that described in connection with the construction shown in Figure 1. The rear end of the coil spring 4-1 in this instance, however, bears directly against the rear housing member [4 around a small circular locating flange 48 which is formed integral on the inner surface of the rear housing member M. A vent hole 43 is provided in the rear housing member l4 at the center thereof. It is to be understood, however, that this vent hole may be located anywhere in the rear housing member since it is only important that the diaphragm I8 be subjected to atmospheric pressure on the rear side thereof.

In Figure 8 of the drawings I have shown a construction substantially the same as that shown in Figure 7 with the exception that the rear housing member M has been removed and a clamping ring 50 has been substituted in its place. A comparison of Figures 7 and 8 will show that the clamping ring 50 is .of substantially the same construction as the marginal portion of the rear housing member I4 of Figure 7, The horn construction shown in Figure 8 operates in precisely the same manner as that described in connection with Figures 1 and '7 with the exception that the entire biasing force which tends to hold the diaphragm l8 seated on the cup shape end piece 24 is supplied by the inherent resiliency of the diaphragm itself and is not supplemented by any spring biasing force. It will be observed that in the construction shown in Figure 8 the rear surface of the diaphragm I8 is subjected to atmospheric pressure precisely as it is in the construction shown in Figure '7.

The cardinal feature of the present invention which distinguishes the present invention over the previously known types of horns and which enables the highly efficient and desirable results previously referred to, to be obtained, is the cup shape end piece 24 and the manner in which it co-operates with the diaphragm l8 in each of the constructions shown in Figures 1, 7' and 8. It has been found by repeated tests and experiments that the shape and general dimensions of this cup with respect to certain other critical dimensions of the horn construction must be kept within certain limits to produce the desired result.

Referring now particularly to Figure '7, let us identify certain important dimensions in the following manner:

A=the distance between the base 25 of the cup shape end piece 24 and the diaphragm l8.

B=the inside diameter of the bushing 22 at the point where it merges into the cup shape end piece 24.

C=the mean cup diameter or, in other words, the mean value of the inside diameter of the cup shape end piece 24 and the outside diameter of the cup shape end piece 24 at the rear edge of the peripheral wall portion 26.

D=the diameter of the free portion of the diaphragm 18 or, in other words, the diameter of the inside edge of the seat 43 on the front housing member I3.

By way of example and not by way of limitation, one extremely satisfactory set of dimensions are as follows:

D 2/I In this horn construction whose dimensions are given by way of example above, the wall thickness of the peripheral wall 26 of the cup shape end piece 24 was and the diaphragm thickness was 7 It has been found that the spacing A of the base 25 of the cup shape end piece 24 from the diaphragm 18 may vary from to for a cup diameter of 1%". It has further been found that the free diaphragm diameter may vary from 1.3 the cup diameter to 2.2 the cup diameter. The bugle opening or dimension B is preferably kept within a ratio of %":1 to /.;":1%;" of the cup diameter.

While a horn will under most circumstances operate when its relative dimensions are out-- side of the critical ranges referred above, it has been found that the high efficiency and desirable operating characteristics may only be obtained when the relative dimensions are kept within the ranges above indicated. It has further been found that the ratios of the important dimensions will remain substantially the same through a wide range of sizes of horn. V

I do not know why a horn constructed in accordance with the teachings of the present invention does operate to produce such greatly improved results over horns of the type previously known to the art. In order to afforda comparison, it might be said that one conventional type of prior art horn construction the rear end of the bushing extends directly into contact with the diaphragm and is not provided with an enlarged cup shape end portion. There are other prior art types of construction wherein the rear end of the bugle is flared to some extent as it approaches the diaphragm. Neither of these prior art types of construction, however, are capable of producing the highly efiicient result obtainable with the construction of the present invention. More particularly, they are not capable of producing a low pitched note with great carrying qualities under low air pressure. For example, a conventional horn of the prior art might require approximately 100 pounds per square inch air pressure to obtain a satisfactory low note and large volume of sound while the horn constructed in the manner shown in Figure 7 under the teachings of the present invention requires only approximately 30 pounds per square inch air pressure to obtain a similar pitch note of equally high volume of sound.

One explanation which has been advanced to explain the theory underlying the operation of the horn construction of the present invention is to the effect that the closing of the diaphragm on the seat is not entirely due to decrease in pressure in the pressure chamber but is also due to the fact that the rush of fluid in passing the lip upon which the diaphragm seats creates a decrease in static pressure perpendicular to the flow direction. This is a well-known hydro-dynamic principle. As is shown in Figure 11, the flow of air indicated by the arrows M causes the pressure in the direction of the arrows N to be less than the uniform static pressure P in the stationary fluid outside which tends to draw the diaphragm down onto the valve seat the same as if two opposed spaced surfaces are placed parallel and fluid rushes between them they tend to draw together. An explanation for the reason of the greater efficiency of a horn constructed in accordance with the teachings of the present invention over the prior art type of horn is the fact that this hydro-dynamic principle is employed to cause a faster seating of the diaphragm, thus conserving fluid pressure and volume which is an important feature in air horns, and at the same time permits a larger volume of sound output of deeper tone qualities due ,to the increased peripheral diameter of the valve and cup. The hydro-dynamic action takes place first at the lip of the cup shape end piece 24 Where, due to the fact that the spacing between the lip of the cup 24 and the diaphragm I8 is very slight, the air passes with great velocity. The subsequent rush of the air over the surface of the base portion 25 of the cup shape end piece 24 and the opposed face of the diaphragm I8 creates a tremendous area of low pressure between these two spaced opposed surfaces. It is to be noted that the tolerances of these spaced opposed surfaces are extremely important if the advantages are to be gained and these proportions were determined through ex-' perimental work and described above.

If the cup diameter is too great with respect to the free diaphragm diameter it interferes with the free rush of air from the pressure chamber and thus lowers the static attraction and furthermore if the cup diameter is too great with respect to the free diaphragm diameter it decreases or prevents normal resilient action of the diaphragm in opening and closing. If the cup diameter is too small with respect to the free diaphragm diameter the surface attraction is not sufiicient to permit a fast closing of the diaphragm and thus more fluid or fluid under greater pressure is required to operate the horn.

It will also be understood that if the spacing of the base portion 25 of the cup shape end piece 24 from the diaphragm I8 is too great the benefits of the hydro-dynamic principle above referred to will be lost since the attraction will decrease to a point where it has no useful effect, it being remembered that the above referred to hydro-dynamic principle takes place when fluid rushes between two relatively closely spaced surfaces. If this spacing of the base of the cup shape end portion 24 from the diaphragm I8 is too small, volume of sound is lost through not loading the inlet to the bugle sufficiently and also by not lowering the pressure in the pressure chamber [9 rapidly enough.

A second embodiment of the present invention is illustrated in Figures 9 and 10 of the drawings, comprising front and rear housing members 5| and 52 between which is clamped a diaphragm 53 having a central opening 54 therein. The rear housing member 52 is provided with a forwardly extending flange 55 which is internally threaded for co-operation with an externally threaded marginal portion 56 of the front housing member 5|. A bushing 51 extends through the end wall 58 of the forward housing member 5| in the same manner as that described in connection with the construction shown in Figure 1. The bugle l I makes a telescoping pressed fit with the bushing 5'! and is thereby supported and mounted thereon.

Mounted in the rear end of the bushing 51 is a spider 59 which supports a hollow post 60 in any suitable manner. A valve plate t! extends across the opening 55 in the diaphragm 53 and extends a substantial distance beyond the edge of the opening for a purpose which will presently be explained. This valve plate El is provided with a pin 62 which telescopes and slides freely inside the hollow post 69. The pin 52 may be bolted on by means of a small bolt 63 or secured to the valve plate 6i in any suitable manner.

In this form of construction air under pressure is introduced into the rear chamber through a suitable air supply line 64. When it is desired to operate the horn as shown in Figures 9 and 10, air under pressure is introduced into the rear chamber formed by the diaphragm 53 and the rear housing member 52 and pressure is built up in this rear chamber until it is sufficient to push the valve plate 5! back off of its seated engagement with the diaphragm 53, a spring 65 be-- ing provided for normally holding the valve plate 51 in seated engagement on the diaphragm 53. Due to the fact that the diaphragm plate Bl extends a substantial distance beyond the edge of the opening 56 in the diaphragm 53 it will be observed that we have in this case a situation similar to that described in connection with Figures 1 and 7 in that air under pressure is rushing between two relatively closely spaced parallel surfaces as the valving action takes place. As soon as the pressure in the rear chamber drops the diaphragm plate 6! is urged rearwardly again into seated engagement with the dipahragm 53 by the biasing spring 65. Pressure again builds up in the rear chamber until a point is reached in which the valve plate 55 again opens. This cycle of operation repeats very rapidly and more particularly at the frequency of the tone to be produced by the horn. It is believed that in this type of horn as in the previous types of horns described the hydro-dynamic effect of fluid rushing between two closely disposed parallel surfaces is employed to aid in a fast closing of the valve plate 6| which supplements the action of the biasing spring 65.

A third embodiment of the present invention is illustrated in Figures 3, 4 and 5 of the drawings. In these figures a dual horn construction is illustrated which employs cup shape end pieces for the bugles of the type described in Figures 1 and '7 but wherein the form of horn is of the so-called reed type. In the construction illustrated, two housing members 66 and 6! are bolted together as at B8 to provide a unitary casing for the construction. Housing members 66 and '61 are provided with end walls 69 and ill respectively through which externally threaded bushings H and 12 respectively pass. Bushings H and 12 are substantially similar to bushing 22 of Figure 1 and each has mounted on the outer end thereof a bugle H and on the inner end a cup shape end piece 24. The cup shape end pieces 24 are press fitted on the inner ends of the bushings H and 12 as described in connection with Figure 1. Spaced opposed shoulders 13 and M are provided on the housing members 66 and 51 respectively between which a diaphragm i5 is loosely disposed. The diaphragm 15 may either be of the form illustrated in Figure 4 or of the form illustrated in Figure 5. The former has arcuate cut-out portions 16 in the sides thereof and the latter have straight side edges 11. The diaphragm 15 in this form of the invention differs radically from that illustrated in Figure l in that only portions of its edge engage the housing members 66 and 61 and also in the fact that the diaphragm is loosely mounted in the housing members rather than being tightly clamped therebetween.

The diaphragm 15 is disposed to extend between the cup shape end pieces 24 which are mounted on the bushings TI and 12 respectively. The cup shape end pieces 24 are so disposed and spaced from the diaphragm 15 that the diaphragm I5 is seated first on the outer wall portion 26 of one of the cup shape end pieces and then on the outer Wall portion 26 of the other cup shape end piece 24. Due to the fact that marginal portions of the diaphragm 15 are cut back it will be understood that the chamber 18 on one side of the diaphragm 15 is always in direct and constant communication with the chamber 19 formed on the other side of the diaphragm.

Air or other fluid under pressure is supplied to the unit through the conduit 89 which may be connected to either one of the housing members. As shown, the conduit 80 extends into a passageway 8| formed in th housing member 66.

The operation and function of the cup shape end pieces 24 of this construction as shown in Figure 3 is substantially the same as previously described in connection with Figures 1 and 7. It is to be understood, however, that the horn itself operates as a reed type horn rather than as a pressure type horn as described in Figures 1 and 7. When air under pressure is introduced into the chambers l3 and T9, the inrush of air causes the diaphragm to raise off of its seat on one of the cup shape end pieces 24 and to move over against the other cup shape end piece 24, thus allowing a pulsation of air to fiow into the expansion chamber which is provided by the interior bore of the bushing H or 12. Since the diaphragm I5 is loosely mounted in the groove provided by the spaced shoulders 13 and I4, it takes practically no pressure to moveit from one seat to the other, and conesquently a rapid vibrating or fluttering action is obtained, causing a rapid series of air pulsations to flow over the seat into the respective expansion chambers, which results in sound waves which are amplified and admitted by the two sound chambers and the two bugles I l.

A slight variation in shape of the cup shape end piece 24 which may be used in any one of the embodiments of the invention hereinbefore described is illustrated in Figure 6. In this form of construction instead of having a fiat base portion 25 as has previously been described, an annular channel 82 is formed in thebase of the cup. This type of end piece construction while not giving as satisfactory performance as one with a flat base portion, nevertheless does provide certain advantages which are not obtainable in the prior art types of construction. The spacing of the channel shape portion of the cup shape end piece 24 shown in Figure 6 must, however, bear the same general relation to the diaphragm, to the diaphragm diameter, and to the diameter of the inner end of the bugle as has previously been described.

While I have shown particular embodiments of my invention, it will, of -course,,be understood, that I do not wish to be limited thereto, since many modifications may be made, and I, therefore, contemplate by the appended claims to cover all such modifications as fall within the true spirit and scope of my invention.

I claim as my invention:

1. A sound producing unit of the character described which includes: a casing defining a chamber; a diaphragm mounted in said casing so as to divide the interior thereof into a forward chamber and a rear chamber; a tubular member mounted in the forward wall of said casing extending rearvvardly in said forward chamber, said tubular memberbeing provided on its inner end with an expansion cup of a substantially greater diameter than said tubular member and having an annular base surrounding the inner end of said tubular member and generally normal to the axis thereof, the rim of said cup being normally in contact with said diaphragm, whereby fluid entering said cup from said forward chamber by reason of the disengagement of said diaphragm with said cup rim will be caused to reverberate several times between said annular cup base and said diaphragm, thereby aiding the vibration of said diaphragm before passing into said tubular member; and means in said forward chamber for introducing fluid therein.

2. A fluid operated pressure horn comprising, a casing, a sound projector mounted on said casing, a diaphragm extending completely across the interior of said casing and dividing said easing into a pressure chamber and a second chamber, said sound projector having a rear end portion projecting through said casing into said pressure chamber, said projector end having an enlarged cup shaped extremity facing said diaphragm and providing a seat therefor around its peripheral edge, said cup shaped extremity having a base portion disposed substantially parallel to said diaphragm and being relatively shallow compared to its width and its width being relatively great compared to the diameter of said projector adjacent said cup shaped extremity, said casing having an inlet passage into said pressure chamand into said pressure chamber, said projector end having an enlarged cup shaped extremity facing said diaphragm and providing a seat therefor around its peripheral edge, biasing means in said second chamber for normally holding said diaphragm in seated engagement on the peripheral edge of said cup shaped extremity, said cup shaped extremity having a base portion disposed substantially parallel to said diaphragm and said cup shaped extremity being relatively shallow compared to its width and its width being relatively great compared to the diameter of said projector adjacent thereto, and said casing having an inlet passage into said pressure chamber through which fluid under pressure is passed to operate said horn, and means for adjusting the biasing pressure exerted on said diaphragm by said biasing means.

4. A dual fluid operated reed type horn comprising a casing, oppdsitely extending bugles mounted on said casing each having a rear end portion projecting into said casing, a diaphragm disposed between said bugle end portions and loosely mounted in said casing, said diaphgram being shaped to provide for the free passage of fluid around the greater portion of its edge, each of said bugle end portions having an enlarged cup shaped extremit facing said diaphragm and providing a seat therefor around its peripheral edge, each of said cup shaped extremities having a base portion disposed substantially parallel to said diaphragm, and each cup shaped extremity being relatively shallow compared to its width and its width being relatively great compared to the diameter of its respective bugles adjacent thereto, and said casing having an inlet passage s communicating therewith through which fluid under pressure is passed to operate said horn.

5. A fluid operated horn comprising a casing, a sound projector mounted on said casing, a diaphragm extending across the interior of said casing, said sound projector having a, rear end portion projecting through said easing into the interior thereof, said projector end portion having an enlarged cup shaped extremity facing said diaphragm and providing a seat therefor around its peripheral edge, said cup shaped extremity having a base portion in which an annular groove is formed directly facing said diaphragm, said cup shaped extremity being relatively shallow compared to its width and its width being relatively great compared to the diameter of said projector adjacent said cup shaped extremity, and said casing having an inlet passage communicating therewith through which fluid under pressure is passed to operate said horn.

6. A fluid operated pressure horn comprising a chamber wall, a sound projector mounted on said chamber wall, a diaphragm mounted on and secured to said chamber wall and forming with said chamber wall a pressure chamber, said sound projector having a rear end portion projecting through said chamber wall into said pressure chamber, said projector end having an enlarged cup shaped extremity facing said diaphragm and providing a seat therefor around its peripheral edge, said cup shaped extremity having a base portion disposed substantially parallel with said diaphragm and being relatively shallow compared to its-width and its width being relatively great compared to the diameter of said projector adjacent said cup shaped extremity, said chamber wall having an inlet passage into said pressure chamber through which fluid under pressure is passed to operate said horn.

7. A fluid operated horn comprising a housing member, a diaphragm mounted on said housing member and forming with said housing member a fluid pressure chamber, a bugle mounted on said housing member and having a rear end portion projecting through said pressure chamber and terminating in close proximity to said dia-, phragm, said rear end portion of said bugle having an open cup shaped extremity upon which said diaphragm is normally seated, the base of said cup being disposed substantially parallel with said diaphragm and having a central opening therein communicating with said bugle, the spacing between the base of said cup and said diaphragm being between .075 and .150 of the diameter of said 'cup.

8; A fluid operated horn comprising a housing member, a diaphragm mounted on said housing member and forming with said housing member a fluid pressure chamber, a bugle mounted on said housing member and having a rear end portion projecting through said pressure chamber and terminating in close proximity to said diaphragm, said rear end portion of said bugle having an open cup shaped extremity upon which said diaphragm is normally seated, the base of said cup being disposed substantially parallel to said diaphragm and having a central opening therein communicating with said bugle, the spacing between the base of said cup and said diaphragm being be- 1 tween .075 and .150 of the diameter of said cup,

and said free diaphragm diameter being between 2.2 and 1.3 x the diameter of said cup.

9. A fluid operated horn comprising a housing member, a diaphragm mounted on said housing member and forming with said housing member a fluid pressure chamber, a bugle mounted on said housing member and having a rear end portion projecting through said pressure chamber and terminating in close proximity to said diaphragm, said rear end portion of said bugle having an open cup shaped extremity upon which said diaphragm is normally seated, the base of said cup being disposed substantially parallel to said diaphragm and having a central opening therein communicating with said bugle, the spacing between the base of said cup and said diaphragm being between .075 and .150 of the diameter of said cup, and the opening in the base of said cup communicating with said bugle being between .3 and .6 of the diameter of said cup.

10. A fluid operated horn comprising a housing member, a diaphragm mounted on said housing member and forming with said housing member a fluid pressure chamber, a bugle mounted on said housing member and having a rear end portion disposed substantially parallel to said diaphragm and having a central opening therein communicating with said bugle, the spacing between the base of said cup and said diaphragm being approximately one-tenth of the diameter of said cup, the free diaphragm diameter being approximately 1.6- x the diameter of said cup, and the opening in the base of said cup communicating with said bugle being substantially two-fifths of 10 the diameter of said cup.

LYNDON V. GROVER.

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