US2173951A - Pneumatic horn - Google Patents

Description

Sept. 26, 1939.

D. PATTERSON v PNEUMATIC HORN Filed July 50, 1937 INVENTOR DAV l D PATTERSON.

ATTORNEY Patented Sept. 26, 1939 UNITED STATES PATENT OFFICE PNEUMATIC HORN Application July 30, 1937, Serial No. 156,449

3 Claims.

This invention relates to a signaling device and particularly to an improved pneumatic horn.

As usually constructed, horns of the pneumatic type employ flexible diaphragms formed of sheet metal, and when the horn is operated to produce a warning sound, the diaphragm is caused to vibrate at a rapid rate. It has been found that this rapid vibration or repeated flexing or bending in opposite directions causes the diaphragms to break or crack after a short period of use, thereby rendering the horn inoperative and necessitating replacement of the diaphragm.

It is an object of this invention to provide an improved pneumatic horn which is capable of producing a warning sound having a large volume.

A further object of the invention is to provide an improved horn in which the diaphragm employed therein has a long useful life.

20 Another object of the invention is to provide an improved horn of the type described which incorporates adjusting means to enable the horn to be adjusted to provide the most desirable operation thereof.

25 A further object of the invention is to provide an improved horn which is simple in construction and which can be produced at low cost.

Other objects of the invention and features of novelty will be apparent from the following 30 description taken in connection with the accompanying drawing, in which Fig. 1 is a fragmentary sectional view of a horn embodying my invention,

Fig. 2 is a fragmentary elevational view show- 35 ing the locking means employed in the horn shown in Fig. 1,

Fig. 3 is an enlarged sectional view of a portion of the horn shown in Fig. 1, and

Fig. 4 is a fragmentary sectional view showing a modified form of construction embodying my invention.

Referring to the drawing, the horn shown therein has a body I which may be formed of any suitable material, such as cast metal, and

45 has formed integral therewith a horn bell 2,

while the body also has formed integral therewith a bracket, not shown, by means of which the body may be secured to a support.

The body i has formed therein a cylindrical 5 cavity located opposite the small end of the horn bell, while the passage through the horn bell is surrounded by an annular seat rib 5 formed integral with the body I and projecting into the cavity in the body.

55 The body I has formed thereon an annular surface in the form of a shoulder 6, which is substantially concentric of the seat rib 5 and is disposed in a plane spaced from the plane of the face of the seat rib 5. e

A diaphragm unit indicated generally by the 5 reference numeral 8 is mounted in the cavity in the body I. As shown the diaphragm unit 8 comprises a plurality of substantially circular, flexible metallic discs 9 of approximately the diameter of the cavity in the body I. A sub- 0 stantially rigid seating element III in the form of a circular metal disc of slightly larger diameter than the seat rib 5 is provided and is secured centrally of the discs 9 by means of the rivet 12 which also serves to secure the discs 9 together. 15 A spacer l3 of substantially smaller diameter than the seating element I0 is mounted on the rivet [2 between the discs 9 and the seating element l0, while washers l4 and I5 are also mounted on the rivet I2.

The various parts of the diaphragm unit 8 are proportioned so that when the unit is in position in the cavity in the body I in engagement with the annular surface or shoulder 6 without force being exerted on the central part of the discs 9, the discs will be substantially flat, and will hold the seating element l0 away from the seat rib 5 a short distance.

The wall of the cavity in the body I has threads formed in the inner face thereof adjacent the open end of the cavity, as indicated at I1, and adapted to receive a circular member I B having threads formed thereon. The member I8 has a cavity in the external face thereof into which extend projections [9 by means of which the member l8 may be turned.

The portion of the wall of the cavity in the body I in which the threads I! are formed has cut therein a slot 2| extending across the threads l1, while the body I has formed integral therewith ears 22 located on opposite sides of the slot 2|. The ears 22 have therein aligned openings in which are mounted a bolt 23 having a head on one end which engages a face on one of the ears 22, while the other end of the bolt 23 hasa lock washer 24 and a nut 25 secured thereon which press against a face of the other of the ears to draw the ears together and thereby contact the body about the member 18 to lock it in the position to which it is adjusted.

The member l8 has formed thereon an annular surface in the form of a narrow annular shoulder or bead 26 which is arranged substantially concentric of the seat rib 5. The surface 26 is of smaller diameter than the surface 6 on the body I, and engages the disc 9 at one face of the diaphragm unit 8 in a region radially inwardly of the region at the other face of the diaphragm unit engaged by the shoulder 6-.

When the member I8 is advanced in threads of the body H, the surface 26 presses against the face of a disc 9 so that the marginal portion of the disc 9 at the other face of the diaphragm unit 8 presses against the surface 6 and forms a seal therewith to prevent flow of fluid under pressure around the periphery of the diaphragm, and to prevent further movement of the marginal portion of the discs 9 towards the seat rib 5, while the central portions of the discs 9 are deflected towards the seat rib 5 so that the seating element in engages and seats upon the face of the seat rib 5 to cut off communication between the chamber 39 at the face of the diaphragm unit 8 outwardly of the seat rib 5, and the passage 3! within the seat rib 5. As the seating element it is held away from the discs 9 by the spacer i3, the seating element It] may move slightly relative to the discs 9-, and thereby adjust itself to the seat rib 5so that the seating element can engage the face of this seat rib throughout its entire circumference.

This horn incorporates means for supplying fluid under pressure at a restricted rate to the chamber 39. This means comprises a threaded opening formed in the body I and in which is secured one end of a pipe-33 leading from'a source of fluid under pressure, not shown, while this pipe may have interposed therein a valve, not shown, for controlling the flow of fluid through the pipe. r

The end wall of the threaded opening in the body I has a restricted opening or port 34.there-' in through whichfluid mayflow at a restricted rate to the chamber 30, while a small drain passage 35 leads from the lower portion of the chamber 39 to the atmosphere to'permit moisture which may accumulate in the chamber 30 to drain therefrom.

The member 18 has a vent passage 38 extending therethrough to permitfluidto flow between .the atmosphere and the chamber between the member [8 and the face of the diaphragm unit 8.

In operation, on the supply'of fluid under pressure to the pipe 33, fluid flows at a restricted rate through the port 34 to the chamber 39. At this time the seating element lll is held in engagement with the face of the seat rib 5 by the flexible discs 9 to prevent flow of fluid from the chamber 39 to the passage 3! within the horn bell 2. Accordingly, on the supply of fluid under pressure through the choke or restricted 'port-34, there'is an increase in the" pressure of the fluid in the chamber 30, with a corresponding increase in the force exerted on the discs 9 ofthe diaphragm unit 8 tending to move seating'element- H] away from the face of the seat rib 5.

The discs 9 of the diaphragm unit 8 are constructed so they will not yield until the pressure of the fluid in the chamber 39 increases to a predetermined value. The chamber 39 is of relatively small volume, however, and the'p'ressure of the fluid therein will quickly build up tothis value, whereupon the centralportions of the discs 9 of the diaphragm unit Bare moved to the left, as viewed in the drawing, thereby moving the seatinkg 5element l9 away from the face of the seat r1 On movement of the seating element l9 away from the face of the seat rib 5, fluid may flow from the chamber 30 past'the seat rib 5 to the passage 3| within the horn bell 2. Fluid may flow past the seat rib 5 throughout the entire circumference thereof, and, therefore, fluid may flow from the chamber 30 at a substantially more rapid rate than fluid is supplied to the chamber through the port 34. Accordingly, on movement of the seating element l9 away from the seat rib 5 there is a reduction in the pressure of the fluid in the chamber 39, and a corresponding reduction in the force exerted on the discs 9 of the diaphragm unit 8 tending to move the seating element In away from the seat rib 5.

However, the mass of the various parts of the diaphragm unit 8 is such that once the seating element l0 starts to move away from the seat rib 5 it will continue to move in this direction even though the pressure of the fluid in the chamber 30 is reduced by flow past the seat rib 5 toa value substantially lower than that required to initiate movement of the seating element in this direction. Accordingly, the seating element [0 will be moved away from the seat rib 5 far enough to open a communication of large flow capacity through which fluid is released from chamber 30 to the passage 3| within the horn bell 2, and the pressure of the fluid in the chamber 30 is quickly reduced to a low value, even though fluid under pressure continues to be supplied thereto through the port 34.

When the seating element I0 is moved away from the seat rib 5, the discs 9 of the diaphragm unit 8 are stressed, and the farther they are deflected the greater their resistance to further movement, After a predetermined deflection of the central portion of the discs 9 of the diaphragm unit 8 their increasing resistance to further deflection, and the decreasing force exerted by the reducing fluid pressure in the chamber 39, operate to prevent further movement of the diaphragm unit 8 in this direction, and the discs 9, because of the inherent resiliency of the material of which they are constructed, tend to return to their former position and move the seating element It towards the face of the seat rib 5.

On this movement of the diaphragm unit 8 there is a reduction in'the rate of escape of fluid from the chamber 39, -and'an accompanying increase in the pressure of the fluid in the chamber 39. However, the mass of the various parts of the diaphragm unit 8 is such that once the discs 9 start to move the seating element I9 towards the seat rib 5, they will continue to move the seating element in this direction against the increasing fluid pressure in the chamber 30, and will move the seating element into engagement with the seat rib 5.

On movement of the seating element In into engagement with the seat rib 5, the escape of fluid from the chamber 30 is cut off, and because of the continued supply of I fluid under pressure thereto through the port 34, there is a rapid increase in the pressure of the fluid in the chamber 39, and a corresponding increase in the force eX- erted by this fluid upon the discs 9 of the diaphragm unit 8.

The pressure of the fluid in the chamber 39 will quickly increase to the value sufficient to cause movement of the diaphragm unit 8 away from the face of the seat rib 5, and the cycle of operation described in detail above will again be repeated.

In operation, movement of the discs 9 of the diaphragm unit 8 will occur at a rapid rate, and the repeated movement of the seating element l0 towards and away from the seat rib 5 will cause vibrations of the air column in the passage 3| within the horn hell 2, and thereby cause the horn to emit an audible sound.

The vibrations of the discs 9 of the diaphragm unit 8 will continue as long as fluid under pressure is supplied to the pipe 33, and when the supply of fluid through this pipe is cut off the discs 9 will hold the seating element ID in engagement with the seat rib 5 substantially as shown inFig. l of the drawing.

On the supply of fluid under pressure to the chamber 30, fluid flows therefrom at a restricted rate through the drain passage 35, but the flow capacity of this passage is such that the escape of fluid under pressure therethrough is without consequence.

The rate of vibration of the diaphragm unit 8, and therefore the tone of the note produced by the horn, may be regulated by adjusting the member [8. When this member is advanced in the threads I! in the body I, the diaphragm discs 9 are first deflected until the seating element l0 engages the seat rib 5. Further movement of the member. l8 causes the discs 9 to exert a pressure on the seating element ID to press the element against the seat rib with a force dependent upon the extent of movement of the member l8. On an increase in the force exerted to press the seating element It! against the seat rib 5 there will be a corresponding increase in the pressure to which the fluid in the chamber 3i! must increase before the seating element [0 will be moved away from the seat rib 5, while there will be a similar change in the conditions necessary to effect movement of the seating element In towards the face of the seat rib 5.

When the member 18 has been adjusted to pro duce the desired tone, it may be locked in the adjusted position by means of the bolt 23 and nut 25 which contract the body portion I about the member l8.

It will be seen that the diaphragm unit of the horn provided by this invention is constructed of a plurality of thicknesses of material. Accordingly, the diaphragm unit is much stronger than one formed of a single thickness of material, and will withstand long periods of operation without breaking.

It will be seen also that the horn provided by this invention incorporates adjusting means by which the force exerted by the diaphragm to press the seating element to the seated position may be adjustably varied to thereby permit the tone of the note produced by operation of the horn to be correspondingly varied.

In Fig. 4 of the drawing there is shown a modified form of construction provided by my invention. In the form shown in this figure, the horn has a body la which is similar to the body of the horn shown in Fig. 1, and has a chamber therein in which is mounted a diaphragm unit 8a, which is substantially identical in construction with the unit employed in the horn shown in Fig. 1. The body la of the horn has a bore therein, the inner face of the wall of which is substantially concentric with the seat rib surrounding the end of the horn bell, not shown, while an annular ring 40 is mounted in this cavity against a shoulder formed on the body la.

The ring 40 has a concave frusto-conical face thereon which is adapted to be engaged by the marginal portion of the disc at one face of the diaphragm unit 8a.

The horn shown in Fig. 4 includes another annular ring 42 having a convex frusto-conical face thereon, the radially inner portion of which is adapted to engage the disc at the face of the diaphragm unit 8a opposite from the face engaged by the ring 40.

The cavity in the body of a cover plate 43, which is held in place by a plurality of cap screws 44, one of which is shown in the drawing. The cover plate 43 has formed thereon an annular flange 45 which extends within the cavity in the body la, while a plurality of shims 41 in the form of thin sheet metal rings are interposed between the flange 45 and the ring 42. When the cover plate 43 is secured in position it causes the ring 42 to press against the face of the disc at one face of the diaphragm unit 8a while the disc at the other face of the diaphragm unit is pressed against the ring 40 with the result that the central portion of the diaphragm unit is deflected towards the seat rib on the body I a in substantially the same manner as the diaphragm unit 8 of the horn shown in Fig. 1 is deflected.

The frusto-conical faces on the rings 40 and 52 provide clearance so that the discs of the diaphragm unit 8a may flex freely. Thus, as is clearly shown in Fig. 4 of the drawing, the inner margin of the ring 40 is spaced from the face of the diaphragm unit so that the diaphragm unit may be deflected by the ring 42 when force is applied to the ring 42. Similarly, the peripheral portion of the face of the ring 42 is spaced from the face of the diaphragm unit 811 so that movement of the peripheral portion of the diaphragm unit, such as occurs during flexing of the discs of the diaphragm unit when the device is operated, will not be obstructed.

In addition, the sloping faces on the rings 40 and 42 result in a gradual change in the areas of contact between the rings and the faces of the diaphragm unit on flexing of the discs of which the unit is constructed. It also results in a gradual change throughout the areas of con tact between the rings and the faces of the diaphragm unit of the degree of pressure between the engaging surfaces. This is advantageous as it prevents concentration of stresses in an extremely narrow zone in the discs of the diaphragm unit which might result in cracking and failure of the discs.

The shims 41 provide means by which the degree of deflection of the diaphragm unit 8a may be adjustably varied if desired. In order to change the degree of deflection of the diaphragm unit 8a, shims 41 are either added or removed from between the flange 45 and the ring 42.

In operation the form of horn shown in Fig. 4 of the drawing is substantially the same as that shown in Fig. 1 of the drawing.

While two embodiments of the improved pneumatic horn provided by this invention have been illustrated and described in detail, it should be understood that the invention is not limited to these details of construction, and that numerous changes and modifications may be made without departing from the scope of the following claims.

Having now described my invention, what I claim as new and desire to secure by Letters Patent, is:

1. In a horn device, in combination, a hollow body having an annular seat therein, a flexible diaphragm cooperable with said annular seat, said body having an annular shoulder engaging one side of said diaphragm at the peripheral marginal edge thereof in a manner to provide la is closed by means for rocking movement of said edgeon said shoulder, a member attachable to and adjustably movable with respect to said body and having a thin annular projecting portion engaging the side of said diaphragm opposite to that engaged by said annular body shoulder and on a diameter appreciably smaller than that of said annular body shoulder, said thin annular projecting portion spacing said diaphragm from said member radially outwardly of said thin annular projecting portion, and. means for admitting fluid pressure to one side of said diaphragm to cause vibration thereof with respect to said annular seat.

2. A horn device as claimed in claim 1 further characterizedby a seating element being attached to the diaphragm and being normally held in engagement with said annular. seat by the tension produced in the diaphragm due to engagement of said thin annular projecting portion with said diaphragm.

3. In a horn device, in combination, a body having an annular seat rib thereon, a flexible diaphragm associated with said body, said body having associated therewith an annular concave frusto-conical surface of larger diameter than said seat rib and arranged substantially concentric thereof, said surface being arranged so that the radially outward portion only thereof engages the peripheral marginal edge of one face of the diaphragm to provide for rockingvmovement of the diaphragm edge on said radially outward portion, a member associated with said body and adjustable relative thereto, said memher having thereon an annular convex frustoconical surface substantially concentric of said seat rib and arranged so that on adjustment of said member relative to said body the radially inward portion thereof only engages the other face of the diaphragm radially inwardly of the region engaged by the other frusto-conical surface to deflect the central portion of' said diaphragm against said seat rib, and means for supplying fluid under pressure to the area at the face of the diaphragm on one side of said seat rib.

DAVID PATTERSON.

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