Title of Invention	AN AIR HORN WITH IMPROVED COVER SECURING AND MOUNTING MEANS
Abstract	An air horn having a plurality of said unit horns comprises pressure bar(s) for securing the end covers thereof to their respective housings and L-shaped mounting brackets having openings in the vertical sides thereof such that access to the mounting fasteners is available from both sides. Pressure means are located on said bar(s) at one or more transition zone(s) thereof said zone(s) being the bar portions that are close to the centrepoints between adjacent housings. In a twin unit horn embodiment the ends of said bar are truncated at about the housing centrepoints and a common said bracket is provided the vertical side whereof is substanti-ally entirely open. Said pressure means are screw type and include locking means to prevent bar rotation. The construction offers cost savings, lesser inventory and weight and easy maintenance.

Title of Invention

AN AIR HORN WITH IMPROVED COVER SECURING AND MOUNTING MEANS

Abstract

An air horn having a plurality of said unit horns comprises pressure bar(s) for securing the end covers thereof to their respective housings and L-shaped mounting brackets having openings in the vertical sides thereof such that access to the mounting fasteners is available from both sides. Pressure means are located on said bar(s) at one or more transition zone(s) thereof said zone(s) being the bar portions that are close to the centrepoints between adjacent housings. In a twin unit horn embodiment the ends of said bar are truncated at about the housing centrepoints and a common said bracket is provided the vertical side whereof is substanti-ally entirely open. Said pressure means are screw type and include locking means to prevent bar rotation. The construction offers cost savings, lesser inventory and weight and easy maintenance.

Full Text	'This invention relates to air horns for vehicles and for other applications. Horns are sometimes referred to as signalling devices and warning devices. Similarly, air horns are also sometimes referred to by the term 'trumpets'. In this specification, the term 'air horn' is uniformly used and is intended to cover the various equivalent terms used such as warning devices, signalling devices, trumpets, air pressure horns and others. As regards the term 'trumpet', it is exclusively used in this specification to refer only to that part of an air horn that amplifies and/or directs the sound produced in the air horn. Such trumpets usually comprise a generally cylindrical tubular section and/or a conical tubular portion with or vidthout flaring provided at the mouth of the trumpet. The axis of the trumpet in an air horn may be straight, or curved, as for example, in an U-shaped or a spiral shaped trumpet. The scope of the invention covers horns for vehicles such as for road, rail, water, air and combinations thereof Specifically it includes vehicles such as cars, automobiles, motor cycles, mopeds, scooters, lorries, trucks, tractors, trailers, three-wheelers, earthmoving and other construction vehicles, in general, any vehicle having a source of compressed air. The scope of the invention also covers air horns for applications other than vehicular, for example, as alarm devices, in alarm systems and in annunciatory devices and systems, as the air horns of the invention are easily adapted for said alarm and annunciatory applications. However, in the description, hereinbelow, references to air horns are limited to their applications in vehicles. This is in the interests of clarity and conciseness without affecting the scope of the invention. An air horn comprises a vibratory diaphragm located in a housing, the edges thereof being secured within, or to said housing. A part of said diaphragm, generally the central portion thereof, sits on a port which when open allows flow of air to a trumpet. Said port comprises a seating upon which said diaphragm sits tightly under the action of a spring means thus ensuring closure thereof An air horn, during operation is supplied with compressed air under action of which said diaphragm lifts upwards from said seating and uncovers said port. This causes the compressed air to flow into said trumpet. Said flow of air leads to a drop in the air pressure acting on the diaphragm which under the action of said spring means now closes said port cutting off the air to the trumpet. This cycle of air pressure acting on the diaphragm and the opening and closing of said port causes the vibration of said diaphragm and the sound so generated is amplified and/or directed by said trumpet. In this specification, the port side of the diaphragm is referred to as the 'forward' or 'front' side or part thereof and the other side as the 'back' or 'rear' side/part thereof Correspondingly, said housing is also considered to comprise the forward or front side/part and the back or rear side/part. These terms are also used in reference to the air horn as a whole and the dividing line is considered to be the diaphragm so that all parts of the horn on said port side are referred to as being forward/front and those on the opposite side as back/rear. Similar interpretation is implied wherever references are made to the forward direction or the reverse/backward direction in this specification. In the most common arrangement of air horns found in the art, said housing is generally circular in cross section and comprises a body and an end cover. Said diaphragm is also circular and is mounted such that the axes of the diaphragm and housing are coincident. Said common axis, or just axis, is referred hereinbelow as the horn axis. Said body thus comprises a generally cylindrical cavity wherein are located said port and the seating thereof Cormecting means are provided on the outside of said body, by means of which said trumpet is attached to said housing. Such connecting means may be of any known type such as threaded coupling, flanged arrangement or others and communicates with said port such as to provide a passage for flow of air from the housing to the trumpet. A trumpet may also be integral with the housing or connected thereto by means of a pipe, tube or hose which may be of metallic or non-metallic construction and flexible or rigid. Trumpets of air horns generally have straight axes and are mounted such that the axes thereof coincide with the respective horn axes. Air horns are commonly mounted on vehicles such that the axes thereof are horizontal and the trumpets thereof extend forwards both with respect to the horn and the vehicle. This is the arrangement considered for discussion in this specification and this has been done in the interests of clarity and conciseness without limiting in any way the scope of the invention. It will be noted that several other arrangements are feasible such as for example the trumpet axis being inclined to the horn axis or offset thereto or being curved or others. A further connection hereinafter referred to as a nozzle, is provided on said body and forms the compressed air inlet to the housing. This connection may also be any one of known types such as threaded or others. Said back cover is attached to said body upon assembly of the horn and closes the housing. It also provides access to the housing and parts therein during maintenance. The closure of said body is either by attaching said back cover to the body by screw means or by crimping together the outer edges of said back cover and body or by the use of a pressure bar acting on said back cover. At least, two methods are known in the art for securing edges of said diaphragm. In one method, the diameter of the diaphragm is about the same as that of said end cover and the edge of the open end of said body. Securing is achieved by crimping together said edges of said body, diaphragm and end cover. Alternatively, the edge of said diaphragm is clamped between said edges of the body and end cover in a flange-type arrangement by means of suitable screw means. The scope of the invention also covers other methods of securing of said diaphragms. In the second method, both said diaphragm and end cover are smaller in diameter than said body such that when assembled they are housed within, that is, somewhat inside said cylindrical cavity. The edge of said diaphragm sits on a circular ring seat provided within said cavity while pressure for effective sealing is provided by means of a corresponding sized ring/flange located on said end cover. Where required suitable gaskets of elastomeric or other material are provided, for example, on each side of said diaphragm edge and on said seating. The spring means associated with said vibratory diaphragm may comprise a coil spring or others. In one arrangement found in the art, a conical coil spring is used which is attached to the inside of said end cover and acts upon the rear side of said diaphragm. As mentioned hereinabove, an air pressure hom(air horn) comprises a housing, a spring loaded vibratory diaphragm and a trumpet. Such a horn is referred to hereinabelow as a singular, or single horn. Two such single horns may be combined to give a twin horn. In such a twin horn the two housings thereof are either attached to, or integral with each other. If the parameters of the two individual horns of a twin horn are substantially identical both would produce sound of substantially the same frequency. The purpose of such a twin horn would be to obtain a louder sound of a particular frequency. However, if the parameters of said two individual horns are different, for example, if the two trumpets are of different configurations one would obtain a sound of broadly two separate frequencies. Such a horn is referred to as a twin tone horn and is widely used in the transport industry. They are also referred to as two-tone horns. Similarly 3-tone, 4-tone and higher tone horns are also found in the industry. Such multi-tone horns often have a programmed sequence of operation of the individual horns thereof and are referred to also as musical horns. Thus we have single air horns, twin horns and higher order horns, the latter two being referred to as multi-horns. Mostly, multi-horns are multi-tone horns but multi-horns wherein their unit horns generate substantially the same frequency are also feasible. In the specification further hereinbelow, the term 'air horn' is intended to cover any of the aforementioned types: single, twin or higher order and more particularly, single tone, twin tone and muhi-tone of higher order. To describe and elaborate the invention in a clear and concise manner, it is described in relation to a twin-tone horn but this is without Hmitation to the scope of the invention. Further, the individual horns of a twin or multi-horn unit are referred to as unit horns. Thus, when reference is made to a unit horn of an air horn, the latter may be a single, twin or muhi-hom unit. To summarise, a twin tone horn of prior art comprises two unit horns having different frequencies and each comprising a said diaphragm, spring means, end cover, housing body, port with seating, inlet port(nozzle) and trumpet. Each end cover is provided with securing means for securing the former to the respective housing body and each housing comprises mounting means for mounting and securing the horn to the vehicle. Said two housings may be attached to, or integral with each other and similarly said two securing means may be attached to, or integral, with each other or may comprise common securing means for said two end covers. Further, said two mounting means may be attached to, or integral with each other or may comprise common mounting means for the two units. Said securing means and mounting means, common or otherwise may be attached to, or integral, with the housings. A number of variations in air horn design have been discussed. This is with a view to emphasise that the novel features of the invention can be simply and easily adapted to them as also to other such design variations which may be conceived or contemplated by persons skilled in the art. This invention is about air horns comprising a novel arrangement of securing said end covers to their respective bodies and a novel means for mounting of said horns on vehicles. As mentioned hereinabove, the prior art provides three methods of securing said end covers to said body. i. by direct fastening by screw means, ii. by crimping, and iii. by means of a pressure bar. The first arrangement is shown in Fig. 1 of the accompanying drawings. As shown, the end cover is secured to the body by means of three screws located around the edges thereof In the case shown, the securing means for said end cover and diaphragm are combined. However, the securing means for said diaphragm may be separate fi'om that of the end cover. The number of screws(fastener means) used would depend on the size of the housing and range from three for the smallest housing to six and more. The drawbacks of this prior art system in comparison to the novel securing means of the invention are: i. more number of parts, that is, larger inventory, ii. a bulkier and heavier body and end cover system, in view of the extra space required for said securing screws on said body and end cover, and corresponding to the greater number of fasteners required; iii. more time involved in assembly and thus, increased manufacturing costs; and iii. lesser convenience in maintenance. In the second arrangement mentioned hereinabove and shown in Fig. 2, the edges of said end cover and body are crimped together. The diaphragm may also be secured by crimping together with said body and end cover. Alternatively, the securing of the diaphragm may be by other means. In this arrangement, said body and end cover are lighter than in said first. This is because the ring-shaped(flange like) zone in the body, end cover and diaphragm of said first arrangement becomes redundant in said second and is therefore not provided. The chief drawback of the second arrangement is that it is less amenable to maintenance. The securing arrangement in the air horns of the invention retains the weight advantage of said second while still providing ease of maintenance. The third arrangement referred to hereinabove, provides for a pressure bar by means of which pressure is applied upon said end cover for closure of said body and securing of the end cover thereto and further optionally, for the securing of the diaphragm. It may be mentioned that it is advantageous to combine securing of said end cover and diaphragm and therefore it is common practice in the art. As will be observed, the end cover, body and diaphragm in this arrangement are somewhat smaller and therefore, this arrangement also offers said weight advantage. The closure, sealing and securing of said body, diaphragm and end cover are achieved by pressure applied by a said pressure bar acting through said circular ring/flange located on said end cover and acting upon said circular ring seat. In turn, pressure is applied upon said pressure bar by means of screw means. However, any other clamping arrangements available in the art may also be used for the application of pressure on said bar. A typical pressure bar arrangement, that is, said third arrangement of prior art is shown in Fig. 3. In this example, a common pressure bar is shown which is used for securing the end covers of the two unit horns of a twin horn. Each said housing may be associated with a pressure bar or a pressure bar may serve, two more or all of the housings in an array. The advantages offered by this arrangement over the first and second are: i. reduced inventory of parts; ii. reduced weight, iii. simpler assembly and consequent reduction in manufacturing costs, and iv. ease of maintenance. It is stressed that the novel pressure bar arrangement in the air horns of the invention provides further reduction in the number of parts and in weight over said third arrangement and consequently offers further costs saving in manufacturing and ease of maintenance. The advantages and benefits offered by the third arrangement over the other two have already been enumerated. It follows therefore that the novel pressure bar arrangement of the invention is advantageous over all said three arrangements of prior art. As mentioned, pressure is applied on said pressure bar by means of screw means. Said screw means are located one each at each of the end portions of said bar in said third arrangement. Further, said screw means, may be located in the middle portion of said bar depending on the length of said bar, that is, on the number of housings of the array for which it is required to provide said closure/sealing. Said screw means located in said middle portion may be positioned at one or more transition zones on the bar, the term 'transition zone' being defined as that portion of said bar generally extending between the end of one said housing and the commencement of the next. In other words, said transition zone is that space on said bar corresponding , that is, opposite, to the space between a pair of adjacent housings. Where said housings in an adjacent pair abut each other said transition zone is the portion of said bar generally opposite the centre point between said pair of adjacent housings. To summarise, the construction in said third arrangement of prior art, said screw means(pressure means) are located one each at each end portion of said bar and may be located in one or more of said transition zones. However, it must be mentioned that there is apparently no mention in the prior art nor any instance of said bars being used for providing pressure for assemblies of more than two housings and therefore, there appear to be no instances in prior art of said bars having said pressure means located in said transition zones. That is, the location of said pressure means in said transition zones and the use of the pressure bar for assemblies of more than two housings have not been visualised, considered or contemplated in prior art and are consequently novel features of this invention. In contrast, in the air horns of the invention said pressure means located at said end portions have been done away with and pressure means are confined to one or more of said transition zones both of these practices being novel. According to the invention, only one said pressure means is provided in a twin horn, the location thereof being said transition zone between the two housings. This invention further provides for a shorter said bar, that is, said bar extends generally only upto the centre points of said housings in a twin horn and does not extend to the end portions or outer portions thereof In general, said bar in the invention is not required to extend generally beyond the centre points of the two end housings of an array. Referring again to a twin horn, the advantages offered by the invention over said third arrangement, are savings obtained by the eUmination of one number pressure means and two said end portions of the pressure bar. This is because the application of pressure by said pressure bar is at the centre points of the housings so that portions of said bar extending beyond the centre points of the two outermost housings of an array are quite redimdant. The elimination of these redundant portions, by this invention results in considerable material saving and weight reduction. It will be observed that the saving offered by the elimination of one number said pressure means is not at ail insignificant as it involves not only elimination of the pressure applying screw but also the heavy boss containing the female thread portion associated therewith. The invention also offers other cost advantages, that is, cost savings in manufacture and assembly and further, even greater ease of maintenance over said third arrangement. Clearly, the invention offers enhanced savings and advantages over and above that provided by said third arrangement and indeed, also over said first and second. All three prior art securing arrangements although potentially applicable to single, twin and higher order horns no instances were discovered in prior art of their having been used, or considered for horns of order greater than two. Whereas, the novel securing arrangement in air horns of the invention is particularly applicable to twin and higher order of horns that is, of order two and above. However, the description further hereinbelow, is with respect to a twin horn only and is without limitation to the scope of the "invention. The application of the novel securing means to horns of other orders are easily visualised and in this respect the following table provides a summary of the gains and advantages. It must be mentioned, that there is apparently no reference in prior art of horns of order higher than two having said third arrangement. Also no reference was apparently available in the prior art, where the question of reduction of numbers of said securing means for a pressure bar has been discussed or considered and similarly, the possibility of reduction in the lengths of said pressure bars has also not been considered or discussed in prior art. The securing means of the invention can be adapted to the wide range of air horns discussed hereinabove and also to other variations which would suggest to persons skilled in the art. In prior art, the mounting and securing of air horns to the vehicles is done by means of generally L-shaped brackets, that is, brackets having a generally L-shaped cross section. Typical brackets of prior art are shown in Figs. 4 and 5. The horn housing is either attached to, or integral with the vertical side of the 'L' and the horizontal side of the 'L' is mounted on and secured by fastener(s) to a suitable horizontal surface on the vehicle. Suitable hole(s)/slot(s) are provided on said horizontal side for said fastener(s). Said bracket may comprise one or more ribs/webs extending from said vertical side to horizontal side to provide rigidity and strength thereto. Said webs/ribs are generally triangular in configuration. Two orientations of said brackets are found in the art, one in which said horizontal side extends towards the front of the horn from the junction of the 'L' and the other in which it extends backwards, the object of which is to take into account the nature of the location in the vehicle where the horn is required to be mounted and the accessibility thereof It will be observed that in both said orientations said horn securing fastener(s) would be accessible from one side only, that is, either from the forward side or from the backward side with respect to the bracket. This limitation in the approach(access) available has not apparently been observed in prior art literature nor a solution provided or suggested therein. It would be undoubtedly advantageous and an extra point of considerable convenience and ease of assembly and maintenance if said brackets were to have access to the fastener(s) thereof from both said forward and backward sides that is, have dual access. S^pwn in Fig 4 is a schematic arrangement of an L-shaped bracket comprising said vertical and horizontal sides, said hole for mounting fasteners and two generally triangular webs/ribs extending between said horizontal and vertical sides and located at the outer edges thereof. In this arrangement the bracket would be attached to, or integral with said housing at the upper portion of said vertical side. Said vertical side is required to be only generally vertical, that is, it may be substantially vertical or even inclined at small angles to the vertical if required for aesthetic or other considerations. The angle of the 'L' would then be either substantially 90 degrees or deviating by small amounts therefrom. Furthermore, in the simplest configuration said vertical side forms a substantially flat plane which as mentioned may be substantially vertical or slightly inclined thereto. Several other configurations of said vertical side are feasible such as a curved plane, corrugated plane and others. Said variations in the angle of inclination and planar configuration of said vertical side have not been observed in prior art but are discussed here so as to emphasise that the invention is easily and simply adapted to any said variations. Fig. 4 shows a pair of housings for a twin horn which are integral with each other and with said L-shaped brackets. Said two brackets for said two housings are substantially independent of each other and said webs/ribs thereof are not vertical but extend in a diagonal plane lying between the vertical and horizontal planes. Said brackets comprise slots for said mounting fasteners. Fig. 5 also shows a pair of housings for a twin horn wherein, as in Fig. 4, said housings and brapjket are integral with each other. It will be observed that in this configuration there is an integrated said L-shaped bracket rather than two substantially independent brackets as in Fig. 4. Further said vertical side is generally triangular and comprises two ribs placed centrally on the vertical side rather than being at the outer edges of said sides. Said two ribs cross each other at right angles. The bracket comprises holes for said mounting fasteners. In the two constructions represented by Figs. 4 and 5, it will be observed that access to said mounting fasteners is only from one direction. In case of Fig. 4 said access is from the forward side whereas in Fig. 5 it is from the rearward side. The horns of the invention provide dual access that is, from both said forward and backward directions. It will also be observed that all three said constructions are bulky and heavy in contrast to the construction provided in the invention. The brackets of the invention therefore, offer a clear advantage of simplicity of construction, lightness of construction, time-saving in manufacture, assembly and maintenance and above all said dual access. This will be further apparent from the description further hereinbelow. The mounting means of the invention are simply and easily adapted to the wide range of air horns discussed hereinabove and also other design variations which can be easily contemplated by persons in the art. While on the subject of the prior art L-shaped brackets it may be mentioned that each housing in a twin or a higher order horn may be associated with one said L-shaped bracket or alternatively one L-shaped bracket may be attached to, or integral with two or more said housings. Indeed, all the housings of a multi-horn may have just a single common said bracket. Said dual access has been provided in the horns of the invention by providing openings in said vertical side corresponding to locations(s) of said fastener(s). However, any said opening(or aperture) would impose a limit to the manouvreability and the extent of the access for the tightening means for said fasteners. As would be observed in the specific embodiment described in detail hereinbelow said vertical side has been substantially done away with, that is, in the horns of the invention said openings(apertures) extend subtstantially over the whole of said vertical side. It may be mentioned here that operationally said vertical side is not required to be strictly vertical and for aesthetic or other reasons the vertical sides of said L-shaped brackets may be somewhat inclined to the vertical. It will be observed that the construction of the invention can be simply adapted to such other constructions of the vertical side and they are therefore within the scope of the invention. The elimination of said vertical side required strengthening of said bracket from the point of view of load, buckling, torsion and vibration and this has been achieved by broadening said webs and providing greater thickness thereto. It will be observed that the construction of the invention has resuhed in added simplicity, considerably reduced weight, broad unfettered said access from both sides and an The mounting brackets according to the invention have been tested extensively from the point of view of rigidity and vibration. This is further elaborated; hereinbelow. According to the invention, therefore, there is provided an air horn comprising a plurality of unit horns each said unit horn comprising a body(housing) and an end cover therefor, a vibratory diaphragm and a trumpet; said air horn further comprising one or more securing means for securing said end covers to their respective said bodies and one or more mounting means for mounting of said unit horns on a vehicle, each said securing means comprising a pressure bar and means for applying pressure on said covers through said bar, each said mounting means comprising a substantially L-shaped bracket, and characterised in that said pressure means is/are provided at said transition zones along the bar and in that opening(s) is/are provided in the j substantially vertical sides of said brack:et(s) such: as to provide access to the mounting fastener(s) thereof both from the front and rear sides thereof, and wherein one, more or all of said housings, securing means and mounting means may be attached to, or integral with each other. As mentioned hereinabove, an air horn of the invention comprises two or more said unit horns, each said unit horn comprising said housing body with &n end cover, a diaphragm, a said outlet port with seating, a said inlet port(nozzle) and a trumpet and furthermore one or more said securing means and mounting means of the invention. Said housing body, and cover and diaphragm are circular in shape in said specific embodiment but other constructions such as polygonal, elliptical are within the scope of the invention. In said specific embodiment, common securing of said body, end cover and diaphragm has been provided, this being best adapted for closure/sealing by said pressure bar arrangement. However, configurations wherein diaphragm securing is separate are also feasible and within the scope of the invention. The housing body in said specific embodiment is of cast metal construction and is an aluminium alloy die casting. Other constructions, in particular sheet metal fabricated housing are also within the scope of the invention. Also, there is wide choice in the range of materials of construction for said bodies and the same are within the scope of the invention. In the twin tone horn of said specific embodiment, the two housings thereof are integral with each other, that is, they are a single aluminium alloy die casting together with said boss(es) of the pressure means and said mounting means. Said mounting means in said specific embodiment comprises a single said L-shaped bracket wherein said opening(s) extend substantially over the whole of said vertical side. Said L-shaped bracket with said vertical side removed has a generally channel-shaped (U-shaped) configuration with the arms of said channel, that is, of'U' being integral with said housings. The generally vertical arms of said channel(lJ) correspond to said webs/ribs. In said specific embodiment said webs/ribs are not triangular but of uniform width equal to that of the horizontal side of the "L". This uniform width extending over the whole of the U' and furthermore a slight increase in the thickness thereof was found to more than compensate for loss of strength and rigidity arising out of the removal said vertical side. The resulting mounting bracket of generally U-configuration was found to be stronger, more rigid, and more torsion and vibration resistant and yet offered lower materiaf costs, lighter construction, an aesthetic and streamlined appearance and ease of assembly and maintenance. Within the scope of the invention said housings may be attached to each other as opposed to being integral and adjacent housings may abut each other even to the extent that their individual outlines are not quite apparent. In the specific embodiment, a single mounting bracket serves the two housings. In this respect other configurations such as each mounting bracket serving one, two or more said housings or serving all of the housings of a horn are feasible and within the scope of the invention. Any one, more or all said brackets in an air horn may be attached to the housings rather than being integral therewith. The pressure bar in said specific embodiment comprises a rod of generally rectangular cross section and extends from the centre point of one housing to that of the other. Said housing centre points also constitute the said pressure points such that when said pressure means is operated pressure(thrust) is applied on the two end covers substantially at said centre points on the end covers and substantially in line with the respective axes of the unit horns. Said pressure means comprises a screw which engages with a threaded boss located between the two housings, that is, in said transition zone. A square peg is provided on said pressure bar, which engages in a square hole in said boss. This is to prevent the rotation of said bar about the screw axis should the screw get accidentally loosened during use. This locking arrangement prevents the unit horns getting dis¬assembled upon loosening of said screw accidentally or due to vibrations during use. However, adequate torque is applied during assembly of said pressure means so as to lock the same and prevent said loosening thereof As will be observed, said pressure means is located in said transition zone between the two housings and not at the ends of said bar as in the prior art. Said bar is therefore not required to extend beyond said centre points as in prior art. In fact, said bar in said specific embodiment extends generally only upto said centre points, that is, pressure points, resulting in considerable saving of material and weight The single screw arrangement of the invention further provides ease of assembly and maintenance over prior art constructions. The reduction in the number of said bosses from two to one as in the specific embodiment also contributes to saving in material and weight. The scope of the invention covers other configurations of said bar and also a wide choice of materials therefor and also includes other said locking arrangements available in the art. Furthermore, other methods are available in the art for application of said pressure on said bar and these are also within the scope of the invention. The diaphragm edge is secured between said circular ring seat located within said cavity and the edge of said end cover, said end cover edge acting as a flange to provide the necessary pressure for said securing. Said pressure bar and pressure means provide the desired pressure on said flange. Said pressure applying flange can also have the configuration of a circular pressure ring projecting forward from the front of said end cover. A gasket is provided on each side of said diaphragm edge for effective securing and sealing. Other constructions for said securing can be conceived by persons in the art and are within the scope of the invention. The components in the closure system for said port are said conical coil spring, a thrust pad at each end of said coil spring, said port seating and a gasket provided thereon. Said pads are shaped generally like round shallow trays such as to hold the ends of said coil spring. The forward said tray abuts said diaphragm and rearward one is housed in a cavity in said end cover. Alternative designs can be easily conceived by persons in the art and they are within the scope of the invention. For example, said thrust pads may be ring shaped instead of being shallow round disc like trays. When said pressure means are operated pressure(thrust) is applied at said diaphragm edges through said ring/flange to provide said securing and sealing of said diaphragm and closure of the housing by said end cover. Simultaneously, thrust is exerted through said pads to urge said central portion of said diaphragm upon said port seating to ensure closure of said port. Source of compressed air is connected to the air horn at said nozzle while trumpets are connected to said two housings by means of said connecting means provided at the front of the housing. A common nozzle is provided at the front for said compressed air connection and serves both said housings in the specific embodiment. In order to provide a clearer understanding of the invention and without limitation to the scope of the invention an embodiment thereof will now be described with respect to the accompanying drawings where in like numerals refer to like parts. Said drawings are; Fig 1 showing the first method of securing end cover to housing body employed in prior art. Fig 2 showing the second method of securing end cover to housing body employed in prior art. Fig 3 showing the third method, namely, the pressure bar method of securing end cover to housing body employed in prior art. Fig 4 showing one type of L-shaped mounting bracket used in prior art. Fig 5 showing a second type of L-shaped mounting bracket used in prior art. Fig 6 showing an exploded view of the air horn according to the invention. Fig 7 showing a view of the air horn of the invention from rear side, and Fig 8 showing a sectional view of the air horn of the invention together with details of the assembled housing. Fig 9 showing a different partial sectional view showing the pressure means and the nozzle. Referring to Figs. 6, 7 and 8, reference numeral 1 denotes the housing body which houses the vibratory diaphragm 2 and said port 3 with seating 4 and the gasket 5 thereof Diaphragm 2 is urged onto said seating 4 by conical coil spring 6 which is provided with thrust pads 7,8 respectively at the forward and rear ends thereof The rear thrust pad 8 sits within a cavity in the end cover 9. The circular edge 10 of end cover 9' constitutes said circular ring/flange which upon assembly of the horn secures diaphragm 2 against circular ring seat 11 located within cavity 12 of housing body 1. For effective securing ring gaskets 13,14 are placed one each on each side of diaphragm edge 15. Reference numeral 16 denotes the threaded connecting means to which is attached the trumpet 17. As the horn depicted in Figs. 6,7 and 8 is a twin tone horn, it comprises two housing assemblies and two trumpets. However, in the interests of clarity and for convenient reference, only one set of parts have been numbered For corresponding parts in the other horn like numerals have been used but with suffix 'A' added thereto. It will be observed that certain number of parts are common to the two horns, namely, pressure bar, pressure means, nozzle, and mounting bracket. At the front of the housing 1 is located nozzle 18 to which compressed air supply is connected. Nozzle 18 serves both housings. Said securing arrangement comprises pressure bar 19, pressure applying screw(pressure means) 20 and boss 21. Pressure applying screw 20 engages with threads in boss 21. Tightening of pressure screw 20 generates pressure on end covers 9,9 A which results in securing of diaphragms 2,2A and closure of ports 3,3A. Required torque is applied to pressure screw 20 to ensure firm closure/sealing and eliminate risk of loosening of the assembly during use. Pressure bar 19 further comprises a square section portion 22 which engages with a square hole 23 in boss 21. This locks said bar 19 preventing rotation thereof during use even in the unlikely event of the pressure screw 20 coming loose. It will be noted that if said lock 22,23 were not provided and pressure screw 20 accidently became loose, the two housing assemblies could fall apart. Said mounting arrangement comprises L-shaped bracket 24 wherein the vertical side thereof has been removed to provide said dual access to mounting holes 25,26. In the absence of said vertical side, the general configuration of said bracket 24 is channel-shaped, that is, in the form of a 'U' with arms 27,28 flaying outwards somewhat fi-om the vertical. Outer ends 29,30 of said arms 27,28 are integral with housing bodies 1,1 A respectively. Trumpets 17,17A are of somewhat different configuration such that during operation of the horn they produce sounds of differing frequencies, that is a two-tone sound. During operation a control valve on the compressed line to the horn is operated to supply compressed air thereto. The air pressure causes diaphragm 2,2A to lift firom their port seatings 4,4A causing air to flow through said ports 3, 3A and connecting means 16,16A to trumpets 17,17A. The opening of ports 3,3 A leads to a drop in air pressure acting on the front side of the diaphragm 2,2A. At this moment, spring means 6,6A force diaphragm 2,2 A back on their respective port seatings 4,4A causing closure of ports 3,3 A. The closure of ports 3,3A restores the air pressure acting on said front side of diaphragms 2,2A causing it to lift once again from seatings 4,4A. This cycle of operations is continuously repeated and causes the vibration of diaphragms 2,2 A and the sound so generated is amplified by trumpets 17,17 A. Various embodiments and variations other than described above which are within the art are within the scope and spirit of the invention. I claim: 1. An air horn comprising a plurality of unit horns each said unit horn comprising a body(housing) ant} an end cover therefor, a vibratory diaphragm and a trumpet; said air horn further comprising one or more securing means for securing "aid end covers to their respective said bodies and one or more mounting means for mounting of said unit horns on a vehicle, each said securing means comprising a pressure bar and means for applying pressure on said covers through said bar, each said mounting means comprising a substanuially L-shaped bracket, and characterised in that said presaure means is/are provided at said transition zones along the bar and in that opening(s) is/are provided in the substantially vertical sides of said bracket(s) such as to provide access to the mounting fastener(s) thereof both from the front and rear sides thereof, and wherein one, more or all of said housings, securing means and mounting means may be attached to, or integral with each other. 2. The air horn as claimed in the preceding claim 1 and comprising two said unit horns. 3. The air horn as claimed in the preceding Claim 2 and comprising a common air inlet nozzle for said two unit horns. 4. The air horn as claimed in the preceding Claim 3 and comprising one said securing means. The air horn as claimed in the preceding Claim 4 and comprising one said mounting means. 6. The air horn as claimed in preceding claim 5, wherein said pressure bar extends from about the centre point of one said housing to about the centre point of the other, and comprises one said pressure means. 7. The air horn as claimed in any of the preceding claims 1 to 6, wherein said opening extends over substantially the whole of said substantially vertical side. 8. The air horn as claimed in any of the preceding claims 1 to 7, wherein said housings, said securing means and said mounting means are a single integral piece. 9. The air horn as claimed in the preceding Claim 8 wherein said integral piece is an aluminium alloy die casting. 10. An air horn substantially as hereindescribed with reference to and as illustrated in Figs. 6 to 9 of the accompanying drawings.

Full Text

'This invention relates to air horns for vehicles and for other applications.
Horns are sometimes referred to as signalling devices and warning devices. Similarly, air horns are also sometimes referred to by the term 'trumpets'. In this specification, the term 'air horn' is uniformly used and is intended to cover the various equivalent terms used such as warning devices, signalling devices, trumpets, air pressure horns and others. As regards the term 'trumpet', it is exclusively used in this specification to refer only to that part of an air horn that amplifies and/or directs the sound produced in the air horn. Such trumpets usually comprise a generally cylindrical tubular section and/or a conical tubular portion with or vidthout flaring provided at the mouth of the trumpet. The axis of the trumpet in an air horn may be straight, or curved, as for example, in an U-shaped or a spiral shaped trumpet.
The scope of the invention covers horns for vehicles such as for road, rail, water, air and combinations thereof Specifically it includes vehicles such as cars, automobiles, motor cycles, mopeds, scooters, lorries, trucks, tractors, trailers, three-wheelers, earthmoving and other construction vehicles, in general, any vehicle having a source of compressed air.
The scope of the invention also covers air horns for applications other than vehicular, for example, as alarm devices, in alarm systems and in annunciatory devices and systems, as the air horns of the invention are easily adapted for said alarm and annunciatory applications. However, in the description, hereinbelow, references to air horns are

limited to their applications in vehicles. This is in the interests of clarity and conciseness without affecting the scope of the invention.
An air horn comprises a vibratory diaphragm located in a housing, the edges thereof being secured within, or to said housing. A part of said diaphragm, generally the central portion thereof, sits on a port which when open allows flow of air to a trumpet. Said port comprises a seating upon which said diaphragm sits tightly under the action of a spring means thus ensuring closure thereof
An air horn, during operation is supplied with compressed air under action of which said diaphragm lifts upwards from said seating and uncovers said port. This causes the compressed air to flow into said trumpet. Said flow of air leads to a drop in the air pressure acting on the diaphragm which under the action of said spring means now closes said port cutting off the air to the trumpet. This cycle of air pressure acting on the diaphragm and the opening and closing of said port causes the vibration of said diaphragm and the sound so generated is amplified and/or directed by said trumpet.
In this specification, the port side of the diaphragm is referred to as the 'forward' or 'front' side or part thereof and the other side as the 'back' or 'rear' side/part thereof Correspondingly, said housing is also considered to comprise the forward or front side/part and the back or rear side/part. These terms are also used in reference to the air horn as a whole and the dividing line is considered to be the diaphragm so that all parts of the horn on said port side are referred to as being forward/front and those on the opposite

side as back/rear. Similar interpretation is implied wherever references are made to the forward direction or the reverse/backward direction in this specification.
In the most common arrangement of air horns found in the art, said housing is generally circular in cross section and comprises a body and an end cover. Said diaphragm is also circular and is mounted such that the axes of the diaphragm and housing are coincident. Said common axis, or just axis, is referred hereinbelow as the horn axis.
Said body thus comprises a generally cylindrical cavity wherein are located said port and the seating thereof Cormecting means are provided on the outside of said body, by means of which said trumpet is attached to said housing. Such connecting means may be of any known type such as threaded coupling, flanged arrangement or others and communicates with said port such as to provide a passage for flow of air from the housing to the trumpet. A trumpet may also be integral with the housing or connected thereto by means of a pipe, tube or hose which may be of metallic or non-metallic construction and flexible or rigid.
Trumpets of air horns generally have straight axes and are mounted such that the axes thereof coincide with the respective horn axes. Air horns are commonly mounted on vehicles such that the axes thereof are horizontal and the trumpets thereof extend forwards both with respect to the horn and the vehicle. This is the arrangement considered for discussion in this specification and this has been done in the interests of clarity and conciseness without limiting in any way the scope of the invention. It will be

noted that several other arrangements are feasible such as for example the trumpet axis being inclined to the horn axis or offset thereto or being curved or others.
A further connection hereinafter referred to as a nozzle, is provided on said body and forms the compressed air inlet to the housing. This connection may also be any one of known types such as threaded or others. Said back cover is attached to said body upon assembly of the horn and closes the housing. It also provides access to the housing and parts therein during maintenance. The closure of said body is either by attaching said back cover to the body by screw means or by crimping together the outer edges of said back cover and body or by the use of a pressure bar acting on said back cover.
At least, two methods are known in the art for securing edges of said diaphragm. In one method, the diameter of the diaphragm is about the same as that of said end cover and the edge of the open end of said body. Securing is achieved by crimping together said edges of said body, diaphragm and end cover. Alternatively, the edge of said diaphragm is clamped between said edges of the body and end cover in a flange-type arrangement by means of suitable screw means. The scope of the invention also covers other methods of securing of said diaphragms.
In the second method, both said diaphragm and end cover are smaller in diameter than said body such that when assembled they are housed within, that is, somewhat inside said cylindrical cavity. The edge of said diaphragm sits on a circular ring seat provided within said cavity while pressure for effective sealing is provided by means of a corresponding

sized ring/flange located on said end cover. Where required suitable gaskets of elastomeric or other material are provided, for example, on each side of said diaphragm edge and on said seating.
The spring means associated with said vibratory diaphragm may comprise a coil spring or others. In one arrangement found in the art, a conical coil spring is used which is attached to the inside of said end cover and acts upon the rear side of said diaphragm.
As mentioned hereinabove, an air pressure hom(air horn) comprises a housing, a spring loaded vibratory diaphragm and a trumpet. Such a horn is referred to hereinabelow as a singular, or single horn. Two such single horns may be combined to give a twin horn. In such a twin horn the two housings thereof are either attached to, or integral with each other. If the parameters of the two individual horns of a twin horn are substantially identical both would produce sound of substantially the same frequency. The purpose of such a twin horn would be to obtain a louder sound of a particular frequency. However, if the parameters of said two individual horns are different, for example, if the two trumpets are of different configurations one would obtain a sound of broadly two separate frequencies. Such a horn is referred to as a twin tone horn and is widely used in the transport industry. They are also referred to as two-tone horns. Similarly 3-tone, 4-tone and higher tone horns are also found in the industry. Such multi-tone horns often have a programmed sequence of operation of the individual horns thereof and are referred to also as musical horns.

Thus we have single air horns, twin horns and higher order horns, the latter two being referred to as multi-horns. Mostly, multi-horns are multi-tone horns but multi-horns wherein their unit horns generate substantially the same frequency are also feasible. In the specification further hereinbelow, the term 'air horn' is intended to cover any of the aforementioned types: single, twin or higher order and more particularly, single tone, twin tone and muhi-tone of higher order. To describe and elaborate the invention in a clear and concise manner, it is described in relation to a twin-tone horn but this is without Hmitation to the scope of the invention. Further, the individual horns of a twin or multi-horn unit are referred to as unit horns. Thus, when reference is made to a unit horn of an air horn, the latter may be a single, twin or muhi-hom unit.
To summarise, a twin tone horn of prior art comprises two unit horns having different frequencies and each comprising a said diaphragm, spring means, end cover, housing body, port with seating, inlet port(nozzle) and trumpet. Each end cover is provided with securing means for securing the former to the respective housing body and each housing comprises mounting means for mounting and securing the horn to the vehicle. Said two housings may be attached to, or integral with each other and similarly said two securing means may be attached to, or integral, with each other or may comprise common securing means for said two end covers. Further, said two mounting means may be attached to, or integral with each other or may comprise common mounting means for the two units.

Said securing means and mounting means, common or otherwise may be attached to, or integral, with the housings.
A number of variations in air horn design have been discussed. This is with a view to emphasise that the novel features of the invention can be simply and easily adapted to them as also to other such design variations which may be conceived or contemplated by persons skilled in the art.
This invention is about air horns comprising a novel arrangement of securing said end covers to their respective bodies and a novel means for mounting of said horns on vehicles.
As mentioned hereinabove, the prior art provides three methods of securing said end covers to said body.
i. by direct fastening by screw means,
ii. by crimping, and
iii. by means of a pressure bar.
The first arrangement is shown in Fig. 1 of the accompanying drawings. As shown, the end cover is secured to the body by means of three screws located around the edges thereof In the case shown, the securing means for said end cover and diaphragm are combined. However, the securing means for said diaphragm may be separate fi'om that

of the end cover. The number of screws(fastener means) used would depend on the size of the housing and range from three for the smallest housing to six and more.
The drawbacks of this prior art system in comparison to the novel securing means of the invention are:
i. more number of parts, that is, larger inventory,
ii. a bulkier and heavier body and end cover system, in view of the extra space
required for said securing screws on said body and end cover, and corresponding
to the greater number of fasteners required;
iii. more time involved in assembly and thus, increased manufacturing costs; and
iii. lesser convenience in maintenance.
In the second arrangement mentioned hereinabove and shown in Fig. 2, the edges of said end cover and body are crimped together. The diaphragm may also be secured by crimping together with said body and end cover. Alternatively, the securing of the diaphragm may be by other means. In this arrangement, said body and end cover are lighter than in said first. This is because the ring-shaped(flange like) zone in the body, end cover and diaphragm of said first arrangement becomes redundant in said second and is therefore not provided. The chief drawback of the second arrangement is that it is less amenable to maintenance. The securing arrangement in the air horns of the invention retains the weight advantage of said second while still providing ease of maintenance.

The third arrangement referred to hereinabove, provides for a pressure bar by means of which pressure is applied upon said end cover for closure of said body and securing of the end cover thereto and further optionally, for the securing of the diaphragm. It may be mentioned that it is advantageous to combine securing of said end cover and diaphragm and therefore it is common practice in the art. As will be observed, the end cover, body and diaphragm in this arrangement are somewhat smaller and therefore, this arrangement also offers said weight advantage. The closure, sealing and securing of said body, diaphragm and end cover are achieved by pressure applied by a said pressure bar acting through said circular ring/flange located on said end cover and acting upon said circular ring seat. In turn, pressure is applied upon said pressure bar by means of screw means. However, any other clamping arrangements available in the art may also be used for the application of pressure on said bar.
A typical pressure bar arrangement, that is, said third arrangement of prior art is shown in Fig. 3. In this example, a common pressure bar is shown which is used for securing the end covers of the two unit horns of a twin horn. Each said housing may be associated with a pressure bar or a pressure bar may serve, two more or all of the housings in an array. The advantages offered by this arrangement over the first and second are:
i. reduced inventory of parts;
ii. reduced weight,
iii. simpler assembly and consequent reduction in manufacturing costs, and
iv. ease of maintenance.

It is stressed that the novel pressure bar arrangement in the air horns of the invention provides further reduction in the number of parts and in weight over said third arrangement and consequently offers further costs saving in manufacturing and ease of maintenance. The advantages and benefits offered by the third arrangement over the other two have already been enumerated. It follows therefore that the novel pressure bar arrangement of the invention is advantageous over all said three arrangements of prior art.
As mentioned, pressure is applied on said pressure bar by means of screw means. Said screw means are located one each at each of the end portions of said bar in said third arrangement. Further, said screw means, may be located in the middle portion of said bar depending on the length of said bar, that is, on the number of housings of the array for which it is required to provide said closure/sealing. Said screw means located in said middle portion may be positioned at one or more transition zones on the bar, the term 'transition zone' being defined as that portion of said bar generally extending between the end of one said housing and the commencement of the next. In other words, said transition zone is that space on said bar corresponding , that is, opposite, to the space between a pair of adjacent housings. Where said housings in an adjacent pair abut each other said transition zone is the portion of said bar generally opposite the centre point between said pair of adjacent housings. To summarise, the construction in said third arrangement of prior art, said screw means(pressure means) are located one each at each end portion of said bar and may be located in one or more of said transition zones.

However, it must be mentioned that there is apparently no mention in the prior art nor any instance of said bars being used for providing pressure for assemblies of more than two housings and therefore, there appear to be no instances in prior art of said bars having said pressure means located in said transition zones. That is, the location of said pressure means in said transition zones and the use of the pressure bar for assemblies of more than two housings have not been visualised, considered or contemplated in prior art and are consequently novel features of this invention.
In contrast, in the air horns of the invention said pressure means located at said end portions have been done away with and pressure means are confined to one or more of said transition zones both of these practices being novel. According to the invention, only one said pressure means is provided in a twin horn, the location thereof being said transition zone between the two housings. This invention further provides for a shorter said bar, that is, said bar extends generally only upto the centre points of said housings in a twin horn and does not extend to the end portions or outer portions thereof In general, said bar in the invention is not required to extend generally beyond the centre points of the two end housings of an array. Referring again to a twin horn, the advantages offered by the invention over said third arrangement, are savings obtained by the eUmination of one number pressure means and two said end portions of the pressure bar. This is because the application of pressure by said pressure bar is at the centre points of the housings so that portions of said bar extending beyond the centre points of the two outermost housings of an array are quite redimdant. The elimination of these redundant portions, by this invention results in considerable material saving and weight reduction.

It will be observed that the saving offered by the elimination of one number said pressure means is not at ail insignificant as it involves not only elimination of the pressure applying screw but also the heavy boss containing the female thread portion associated therewith. The invention also offers other cost advantages, that is, cost savings in manufacture and assembly and further, even greater ease of maintenance over said third arrangement. Clearly, the invention offers enhanced savings and advantages over and above that provided by said third arrangement and indeed, also over said first and second.
All three prior art securing arrangements although potentially applicable to single, twin and higher order horns no instances were discovered in prior art of their having been used, or considered for horns of order greater than two. Whereas, the novel securing arrangement in air horns of the invention is particularly applicable to twin and higher order of horns that is, of order two and above. However, the description further hereinbelow, is with respect to a twin horn only and is without limitation to the scope of the "invention. The application of the novel securing means to horns of other orders are easily visualised and in this respect the following table provides a summary of the gains and advantages.

It must be mentioned, that there is apparently no reference in prior art of horns of order higher than two having said third arrangement. Also no reference was apparently available in the prior art, where the question of reduction of numbers of said securing means for a pressure bar has been discussed or considered and similarly, the possibility of reduction in the lengths of said pressure bars has also not been considered or discussed in prior art.
The securing means of the invention can be adapted to the wide range of air horns discussed hereinabove and also to other variations which would suggest to persons skilled in the art.
In prior art, the mounting and securing of air horns to the vehicles is done by means of generally L-shaped brackets, that is, brackets having a generally L-shaped cross section.

Typical brackets of prior art are shown in Figs. 4 and 5. The horn housing is either attached to, or integral with the vertical side of the 'L'
and the horizontal side of the 'L' is mounted on and secured by fastener(s) to a suitable horizontal surface on the vehicle. Suitable hole(s)/slot(s) are provided on said horizontal side for said fastener(s). Said bracket may comprise one or more ribs/webs extending from said vertical side to horizontal side to provide rigidity and strength thereto. Said webs/ribs are generally triangular in configuration. Two orientations of said brackets are found in the art, one in which said horizontal side extends towards the front of the horn from the junction of the 'L' and the other in which it extends backwards, the object of which is to take into account the nature of the location in the vehicle where the horn is required to be mounted and the accessibility thereof It will be observed that in both said orientations said horn securing fastener(s) would be accessible from one side only, that is, either from the forward side or from the backward side with respect to the bracket. This limitation in the approach(access) available has not apparently been observed in prior art literature nor a solution provided or suggested therein. It would be undoubtedly advantageous and an extra point of considerable convenience and ease of assembly and maintenance if said brackets were to have access to the fastener(s) thereof from both said forward and backward sides that is, have dual access.
S^pwn in Fig 4 is a schematic arrangement of an L-shaped bracket comprising said vertical and horizontal sides, said hole for mounting fasteners and two generally triangular webs/ribs extending between said horizontal and vertical sides and located at

the outer edges thereof. In this arrangement the bracket would be attached to, or integral with said housing at the upper portion of said vertical side.
Said vertical side is required to be only generally vertical, that is, it may be substantially vertical or even inclined at small angles to the vertical if required for aesthetic or other considerations. The angle of the 'L' would then be either substantially 90 degrees or deviating by small amounts therefrom. Furthermore, in the simplest configuration said vertical side forms a substantially flat plane which as mentioned may be substantially vertical or slightly inclined thereto. Several other configurations of said vertical side are feasible such as a curved plane, corrugated plane and others. Said variations in the angle of inclination and planar configuration of said vertical side have not been observed in prior art but are discussed here so as to emphasise that the invention is easily and simply adapted to any said variations.
Fig. 4 shows a pair of housings for a twin horn which are integral with each other and with said L-shaped brackets. Said two brackets for said two housings are substantially independent of each other and said webs/ribs thereof are not vertical but extend in a diagonal plane lying between the vertical and horizontal planes. Said brackets comprise slots for said mounting fasteners.
Fig. 5 also shows a pair of housings for a twin horn wherein, as in Fig. 4, said housings and brapjket are integral with each other. It will be observed that in this configuration there is an integrated said L-shaped bracket rather than two substantially independent

brackets as in Fig. 4. Further said vertical side is generally triangular and comprises two ribs placed centrally on the vertical side rather than being at the outer edges of said sides. Said two ribs cross each other at right angles. The bracket comprises holes for said mounting fasteners.
In the two constructions represented by Figs. 4 and 5, it will be observed that access to said mounting fasteners is only from one direction. In case of Fig. 4 said access is from the forward side whereas in Fig. 5 it is from the rearward side. The horns of the invention provide dual access that is, from both said forward and backward directions. It will also be observed that all three said constructions are bulky and heavy in contrast to the construction provided in the invention. The brackets of the invention therefore, offer a clear advantage of simplicity of construction, lightness of construction, time-saving in manufacture, assembly and maintenance and above all said dual access. This will be further apparent from the description further hereinbelow.
The mounting means of the invention are simply and easily adapted to the wide range of air horns discussed hereinabove and also other design variations which can be easily contemplated by persons in the art.
While on the subject of the prior art L-shaped brackets it may be mentioned that each housing in a twin or a higher order horn may be associated with one said L-shaped bracket or alternatively one L-shaped bracket may be attached to, or integral with two or

more said housings. Indeed, all the housings of a multi-horn may have just a single common said bracket.
Said dual access has been provided in the horns of the invention by providing openings in said vertical side corresponding to locations(s) of said fastener(s). However, any said opening(or aperture) would impose a limit to the manouvreability and the extent of the access for the tightening means for said fasteners. As would be observed in the specific embodiment described in detail hereinbelow said vertical side has been substantially done away with, that is, in the horns of the invention said openings(apertures) extend subtstantially over the whole of said vertical side. It may be mentioned here that operationally said vertical side is not required to be strictly vertical and for aesthetic or other reasons the vertical sides of said L-shaped brackets may be somewhat inclined to the vertical. It will be observed that the construction of the invention can be simply adapted to such other constructions of the vertical side and they are therefore within the scope of the invention. The elimination of said vertical side required strengthening of said bracket from the point of view of load, buckling, torsion and vibration and this has been achieved by broadening said webs and providing greater thickness thereto. It will be observed that the construction of the invention has resuhed in added simplicity, considerably reduced weight, broad unfettered said access from both sides and an
The mounting brackets according to the invention have been tested extensively from the point of view of rigidity and vibration. This is further elaborated; hereinbelow.

According to the invention, therefore, there is provided an air horn comprising a
plurality of unit horns each said unit horn comprising a body(housing) and an end
cover therefor, a vibratory diaphragm and a trumpet; said air horn further comprising
one or more securing means for securing said end covers to their respective said
bodies and one or more mounting means for mounting of said unit horns on a vehicle,
each said securing means comprising a pressure bar and means for applying pressure
on said covers through said bar, each said mounting means comprising a substantially
L-shaped bracket, and characterised in that said pressure means is/are provided at said
transition zones along the bar and in that opening(s) is/are provided in the j
substantially vertical sides of said brack:et(s) such: as to provide access to the
mounting fastener(s) thereof both from the front and rear sides thereof, and wherein
one, more or all of said housings, securing means and mounting means may be
attached to, or integral with each other.
As mentioned hereinabove, an air horn of the invention comprises two or more said
unit horns, each said unit horn comprising said housing body with &n end cover, a
diaphragm, a said outlet port with seating, a said inlet port(nozzle) and a trumpet and
furthermore one or more said securing means and mounting means of the invention.
Said housing body, and cover and diaphragm are circular in shape in said specific
embodiment but other constructions such as polygonal, elliptical are within the scope
of the invention.
In said specific embodiment, common securing of said body, end cover and
diaphragm has been provided, this being best adapted for closure/sealing by said
pressure bar arrangement. However, configurations wherein diaphragm securing is
separate are also feasible and within the scope of the invention.

The housing body in said specific embodiment is of cast metal construction and is an aluminium alloy die casting. Other constructions, in particular sheet metal fabricated housing are also within the scope of the invention. Also, there is wide choice in the range of materials of construction for said bodies and the same are within the scope of the invention.
In the twin tone horn of said specific embodiment, the two housings thereof are integral with each other, that is, they are a single aluminium alloy die casting together with said boss(es) of the pressure means and said mounting means. Said mounting means in said specific embodiment comprises a single said L-shaped bracket wherein said opening(s) extend substantially over the whole of said vertical side. Said L-shaped bracket with said vertical side removed has a generally channel-shaped (U-shaped) configuration with the arms of said channel, that is, of'U' being integral with said housings. The generally vertical arms of said channel(lJ) correspond to said webs/ribs. In said specific embodiment said webs/ribs are not triangular but of uniform width equal to that of the horizontal side of the "L". This uniform width extending over the whole of the U' and furthermore a slight increase in the thickness thereof was found to more than compensate for loss of strength and rigidity arising out of the removal said vertical side. The resulting mounting bracket of generally U-configuration was found to be stronger, more rigid, and more torsion and vibration resistant and yet offered lower materiaf costs, lighter construction, an aesthetic and streamlined appearance and ease of assembly and maintenance.

Within the scope of the invention said housings may be attached to each other as opposed to being integral and adjacent housings may abut each other even to the extent that their individual outlines are not quite apparent. In the specific embodiment, a single mounting bracket serves the two housings. In this respect other configurations such as each mounting bracket serving one, two or more said housings or serving all of the housings of a horn are feasible and within the scope of the invention. Any one, more or all said brackets in an air horn may be attached to the housings rather than being integral therewith.
The pressure bar in said specific embodiment comprises a rod of generally rectangular cross section and extends from the centre point of one housing to that of the other. Said housing centre points also constitute the said pressure points such that when said pressure means is operated pressure(thrust) is applied on the two end covers substantially at said centre points on the end covers and substantially in line with the respective axes of the unit horns. Said pressure means comprises a screw which engages with a threaded boss located between the two housings, that is, in said transition zone. A square peg is provided on said pressure bar, which engages in a square hole in said boss. This is to prevent the rotation of said bar about the screw axis should the screw get accidentally loosened during use. This locking arrangement prevents the unit horns getting dis¬assembled upon loosening of said screw accidentally or due to vibrations during use. However, adequate torque is applied during assembly of said pressure means so as to lock the same and prevent said loosening thereof

As will be observed, said pressure means is located in said transition zone between the two housings and not at the ends of said bar as in the prior art. Said bar is therefore not required to extend beyond said centre points as in prior art. In fact, said bar in said specific embodiment extends generally only upto said centre points, that is, pressure points, resulting in considerable saving of material and weight The single screw arrangement of the invention further provides ease of assembly and maintenance over prior art constructions. The reduction in the number of said bosses from two to one as in the specific embodiment also contributes to saving in material and weight. The scope of the invention covers other configurations of said bar and also a wide choice of materials therefor and also includes other said locking arrangements available in the art. Furthermore, other methods are available in the art for application of said pressure on said bar and these are also within the scope of the invention.
The diaphragm edge is secured between said circular ring seat located within said cavity and the edge of said end cover, said end cover edge acting as a flange to provide the necessary pressure for said securing. Said pressure bar and pressure means provide the desired pressure on said flange. Said pressure applying flange can also have the configuration of a circular pressure ring projecting forward from the front of said end cover. A gasket is provided on each side of said diaphragm edge for effective securing and sealing. Other constructions for said securing can be conceived by persons in the art and are within the scope of the invention.

The components in the closure system for said port are said conical coil spring, a thrust pad at each end of said coil spring, said port seating and a gasket provided thereon. Said pads are shaped generally like round shallow trays such as to hold the ends of said coil spring. The forward said tray abuts said diaphragm and rearward one is housed in a cavity in said end cover. Alternative designs can be easily conceived by persons in the art and they are within the scope of the invention. For example, said thrust pads may be ring shaped instead of being shallow round disc like trays.
When said pressure means are operated pressure(thrust) is applied at said diaphragm edges through said ring/flange to provide said securing and sealing of said diaphragm and closure of the housing by said end cover. Simultaneously, thrust is exerted through said pads to urge said central portion of said diaphragm upon said port seating to ensure closure of said port.
Source of compressed air is connected to the air horn at said nozzle while trumpets are connected to said two housings by means of said connecting means provided at the front of the housing. A common nozzle is provided at the front for said compressed air connection and serves both said housings in the specific embodiment.
In order to provide a clearer understanding of the invention and without limitation to the scope of the invention an embodiment thereof will now be described with respect to the accompanying drawings where in like numerals refer to like parts.

Said drawings are;
Fig 1 showing the first method of securing end cover to housing body employed in prior art.
Fig 2 showing the second method of securing end cover to housing body employed in prior art.
Fig 3 showing the third method, namely, the pressure bar method of securing end cover to housing body employed in prior art.
Fig 4 showing one type of L-shaped mounting bracket used in prior art.
Fig 5 showing a second type of L-shaped mounting bracket used in prior art.
Fig 6 showing an exploded view of the air horn according to the invention.
Fig 7 showing a view of the air horn of the invention from rear side, and
Fig 8 showing a sectional view of the air horn of the invention together with details of the assembled housing.

Fig 9 showing a different partial sectional view showing the pressure means and the nozzle.
Referring to Figs. 6, 7 and 8, reference numeral 1 denotes the housing body which houses the vibratory diaphragm 2 and said port 3 with seating 4 and the gasket 5 thereof Diaphragm 2 is urged onto said seating 4 by conical coil spring 6 which is provided with thrust pads 7,8 respectively at the forward and rear ends thereof The rear thrust pad 8 sits within a cavity in the end cover 9. The circular edge 10 of end cover 9' constitutes said circular ring/flange which upon assembly of the horn secures diaphragm 2 against circular ring seat 11 located within cavity 12 of housing body 1. For effective securing ring gaskets 13,14 are placed one each on each side of diaphragm edge 15.
Reference numeral 16 denotes the threaded connecting means to which is attached the trumpet 17. As the horn depicted in Figs. 6,7 and 8 is a twin tone horn, it comprises two housing assemblies and two trumpets. However, in the interests of clarity and for convenient reference, only one set of parts have been numbered For corresponding parts in the other horn like numerals have been used but with suffix 'A' added thereto. It will be observed that certain number of parts are common to the two horns, namely, pressure bar, pressure means, nozzle, and mounting bracket. At the front of the housing 1 is located nozzle 18 to which compressed air supply is connected. Nozzle 18 serves both housings.

Said securing arrangement comprises pressure bar 19, pressure applying screw(pressure means) 20 and boss 21. Pressure applying screw 20 engages with threads in boss 21. Tightening of pressure screw 20 generates pressure on end covers 9,9 A which results in securing of diaphragms 2,2A and closure of ports 3,3A. Required torque is applied to pressure screw 20 to ensure firm closure/sealing and eliminate risk of loosening of the assembly during use. Pressure bar 19 further comprises a square section portion 22 which engages with a square hole 23 in boss 21. This locks said bar 19 preventing rotation thereof during use even in the unlikely event of the pressure screw 20 coming loose. It will be noted that if said lock 22,23 were not provided and pressure screw 20 accidently became loose, the two housing assemblies could fall apart.
Said mounting arrangement comprises L-shaped bracket 24 wherein the vertical side thereof has been removed to provide said dual access to mounting holes 25,26. In the absence of said vertical side, the general configuration of said bracket 24 is channel-shaped, that is, in the form of a 'U' with arms 27,28 flaying outwards somewhat fi-om the vertical. Outer ends 29,30 of said arms 27,28 are integral with housing bodies 1,1 A respectively.
Trumpets 17,17A are of somewhat different configuration such that during operation of the horn they produce sounds of differing frequencies, that is a two-tone sound.
During operation a control valve on the compressed line to the horn is operated to supply compressed air thereto. The air pressure causes diaphragm 2,2A to lift firom their port

seatings 4,4A causing air to flow through said ports 3, 3A and connecting means 16,16A to trumpets 17,17A. The opening of ports 3,3 A leads to a drop in air pressure acting on the front side of the diaphragm 2,2A. At this moment, spring means 6,6A force diaphragm 2,2 A back on their respective port seatings 4,4A causing closure of ports 3,3 A. The closure of ports 3,3A restores the air pressure acting on said front side of diaphragms 2,2A causing it to lift once again from seatings 4,4A. This cycle of operations is continuously repeated and causes the vibration of diaphragms 2,2 A and the sound so generated is amplified by trumpets 17,17 A.
Various embodiments and variations other than described above which are within the art are within the scope and spirit of the invention.

I claim:
1. An air horn comprising a plurality of unit horns each said unit horn comprising a body(housing) ant} an end cover therefor, a vibratory diaphragm and a trumpet; said air horn further comprising one or more securing means for securing "aid end covers to their respective said bodies and one or more mounting means for mounting of said unit horns on a vehicle, each said securing means comprising a pressure bar and means for applying pressure on said covers through said bar, each said mounting means comprising a substanuially L-shaped bracket, and characterised in that said presaure means is/are provided at said transition zones along the bar and in that opening(s) is/are provided in the substantially vertical sides of said bracket(s) such as to provide access to the mounting fastener(s) thereof both from the front and rear sides thereof, and wherein one, more or all of said housings, securing means and mounting means may be attached to, or integral with each other.
2. The air horn as claimed in the preceding claim 1 and comprising two said unit horns.
3. The air horn as claimed in the preceding Claim 2 and comprising a common air inlet nozzle for said two unit horns.
4. The air horn as claimed in the preceding Claim 3 and comprising one said securing means.

The air horn as claimed in the preceding Claim 4 and comprising one said mounting means.
6. The air horn as claimed in preceding claim 5, wherein said pressure bar extends from
about the centre point of one said housing to about the centre point of the other, and
comprises one said pressure means.
7. The air horn as claimed in any of the preceding claims 1 to 6, wherein said opening
extends over substantially the whole of said substantially vertical side.
8. The air horn as claimed in any of the preceding claims 1 to 7, wherein said housings,
said securing means and said mounting means are a single integral piece.
9. The air horn as claimed in the preceding Claim 8 wherein said integral piece is an
aluminium alloy die casting.
10. An air horn substantially as hereindescribed with reference to and as illustrated in
Figs. 6 to 9 of the accompanying drawings.

Documents:

0354-mas-2001 abstract duplicate.pdf

0354-mas-2001 abstract.pdf

0354-mas-2001 claims duplicate.pdf

0354-mas-2001 claims.pdf

0354-mas-2001 correspondence others.pdf

0354-mas-2001 correspondence po.pdf

0354-mas-2001 description (complete) duplicate.pdf

0354-mas-2001 description (complete).pdf

0354-mas-2001 drawings.pdf

0354-mas-2001 form-1.pdf

0354-mas-2001 form-19.pdf

0354-mas-2001 form-26.pdf

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Patent Number

198431

Indian Patent Application Number

354/MAS/2001

PG Journal Number

20/2006

Publication Date

19-May-2006

Grant Date

17-Jan-2006

Date of Filing

02-May-2001

Name of Patentee

RAMASWAMY, KRISHNASWAMY

Applicant Address

MANAGING DIRECTO ROOTS AUTO PRODUCTS PRIVATE LTD., ULAVAGAM, GANAPATHY P.O, COIMBATORE - 641 006.

Inventors:

#	Inventor's Name	Inventor's Address
1	RAMASWAMY, KRISHNASWAMY	DIRECTO ROOTS AUTO PRODUCTS PRIVATE LTD., ULAVAGAM, GANAPATHY P.O, COIMBATORE - 641 006.

PCT International Classification Number

G10K9/02

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA