HIGH TONE TRUMPET HORN
Field of invention
This invention relates to an automotive horn. More particularly, the present invention relates to trumpet horn which is compact and produces high decibel sound for automotive use.
Background of Invention
The horns generally used for bikes and cars are Disc horns. They are based on the same principle as that of electric bell. These horns consist of housing assembly and diaphragm assembly as explained further. The housing assembly consists of sheet metal housing which encases a fixed iron core rigidly held to its bottom and aligned to its centre axis. Around fixed iron core a coil is mounted and the one end of which is taken out of the housing by means of insulated terminal and the other end is routed through circuit breaker (CB) assembly which is held offset from centre axis of housing and taken out of it through another insulated terminal. The CB assembly mainly consists of 2 metallic strip carrying contacts and one of the strips is of thin spring steel sheet also called spring. They are insulated from each other by insulating tab except at the contacts on their ends. Normally in idle horn, these contacts touch each other. The diaphragm assembly consisting of moving iron core fixed to a sheet metal diaphragm, the periphery of which is rigidly held in the housing by crimping or bolting. As DC supply from DC source is switched on the current start increasing and with which magnetic flux through fixed iron core also start increasing. This causes the moving iron core fixed on diaphragm to be pulled towards the fixed iron core. During its forward motion towards the fixed iron core pushes the spring and in turn moves the contacts away thus breaking the circuit. This stops the current further and causes the magnetic flux to decrease. Due to elasticity of material of diaphragm, the diaphragm pulls back the moving iron core back to its neutral position. As the moving iron core moves back, the spring also return to its original position and thus contacts are again touching each other. The circuit is now closed and current start flowing again. This process repeats again at a 500 +/- 10 cycles per second (cps) in case of high tone (HT) horns and 420 +/- 10 cps in case of low tone (LT) horn. This way, diaphragm with iron core is set into periodic motion. The diaphragm assembly additionally carries a round sheet metal part called resonator which has several circular stamped impressions. As resonator vibrates with higher amplitude than the corresponding movement of diaphragm, the

overall effect is the sound of higher SPL (Sound pressure level). Due to direct hitting of iron cores, the sound produced is usually not pleasant.
The other type of horn which is also used is a trumpet horn. The trumpet horns comprise all elements of the disc horn except for the resonator. In place of the resonator, the trumpet horn comprises a platine and housing formed with a trumpet like structure. The construction of the trumpet horn is such that the moving core does not come in contact with the fixed iron core and maintains an air gap during forward motion towards fixed iron core. Due to the movement of the diaphragm, the air between the diaphragm and the platine is compressed and decompressed. The platine comprises a hole which allows the compressed air to be communicated to the trumpet section, where the sound is appropriately amplified and outputted.
It has been observed that the construction of the trumpet horn as described do not produce pleasant high tone sound and hence, needs improvement.
Object of the Invention
The main object of the present invention is to provide a horn.
Yet another object of the present invention is to provide a small size trumpet horn which produces pleasant tone/sound.
Summary of the Invention
In accordance with an object of the present invention, the invention provides a trumpet horn for producing sound, said trumpet horn comprising a diaphragm (19), a means for energizing the diaphragm (19), a platine (21), a trumpet (22) comprising various sections of dissimilar construction. Platine (21) is placed axially opposite to the diaphragm (19) forming an air gap/closed volume (29) between platine (21) and diaphragm (19). The energizing means causes periodic motion of diaphragm (19) which pushes a column of air present in closed volume (29) to the sound tube (27) through the pocket (28) which further travels through the sound tube (27).
Brief Description of Accompanying Drawings
In order that the invention may be readily understood and put into practical effect, reference will now be made to exemplary embodiments as illustrated with reference to the accompanying

drawings, where like reference numerals refer to identical or functionally similar elements throughout the separate views. The figures together with a detailed description below, are incorporated in and form part of the specification, and serve to further illustrate the embodiments and explain various principles and advantages, in accordance with the present invention where:
Figure 1 shows an exploded view of trumpet horn assembly in according to an embodiment of the present invention.
Figure 2 shows the top view of the high tone trumpet horn assembly according to an embodiment of the present invention.
Figure 3 shows the cross section view through the centre of trumpet horn assembly (illustrated in figure 2) according to an embodiment of the present invention.
Figure 4 shows the dissimilar sections of trumpet horn removing the Platine (21) from horn assembly according to an embodiment of the present invention.
Skilled artisans will appreciate that elements in the drawings are illustrated for simplicity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the drawings may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.
Detailed Description of the Invention
While the invention is susceptible to various modifications and alternative forms, specific embodiment thereof has been shown by way of example in the drawings and will be described in detail below. It should be understood, however that it is not intended to limit the invention to the particular forms disclosed, but on the contrary, the invention is to cover all modifications, equivalents, and alternative falling within the spirit and the scope of the invention as defined by the appended claims.
Before describing in detail embodiments it may be observed that the drawings are showing only those specific details that are pertinent to understanding the embodiments of the present

invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having benefit of the description herein.
The terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a setup, device that comprises a list of components does not include only those components but may include other components not expressly listed or inherent to such setup or device. In other words, one or more elements in a system or apparatus proceeded by "comprises... a" does not, without more constraints, preclude the existence of other elements or additional elements in the system or apparatus. The following paragraphs explain present invention wherein a trumpet horn (as shown in figure 1). The invention in respect of the same may be deduced accordingly.
Accordingly, the present invention relates to a trumpet horn, comprising:
a trumpet (22);
a diaphragm (19) fitted on top of the trumpet (22);
a platine (21) comprising an air exit hole sandwiched between the trumpet (22) and the
diaphragm (19); and
a means for imparting vibration in the diaphragm (19), such that upon vibration, the diaphragm
(19) pushes a column of air through the air exit hole of the platine (21) into the trumpet (22);
the said trumpet (22) comprises a first portion for receiving the air column, an air exit port
located radially outwardly and a radially extending channel portion connecting the first portion
to the air exit port, the said channel (27) portion comprising an uniform section (30), a tapered
section (31) and an exponential section (32) arranged sequentially between first portion and the
air exit port.
In one embodiment of the present invention, the first portion for receiving the air column is in the form of a round pocket (28) and the exit hole of the platine (21) is directly above and aligned to the round pocket (28).
Another embodiment of the present invention, the round pocket (28) has an opening allowing propagation of the sound wave in to the channel (27).

In still another embodiment, the length of the uniform section is equal to about 27% of X, the length of the tapered section is equal to about 7% of ,and the length of the tapered section is equal to about 6% of  for low tone (i.e. for a contact making and breaking cycle of 420 +/- 10 cycles per second), wherein  is wavelength of fundamental frequency of sound wave propagating through the horn and wherein all of the ratios given can vary by not more than ±5%.
In still another embodiment, the length of the uniform section (measured from exit hole of platine to the start of tapered portion) is equal to about 24% of X, the length of the tapered section is equal to about 9% of ,and the length of the tapered section is equal to about 7% of for high tone (i.e. for a contact making and breaking cycle of 500 +/- 10 cycles per second), wherein  is wavelength of fundamental frequency of sound wave propagating through the horn and wherein all of the ratios given can vary by not more than ±5%.
In still another embodiment, a ratio of effective area of diaphragm and cross section of uniform section is equal to about 42, wherein said ratio can vary by not more than ±5%.
In still another embodiment, a ratio of an area of the mouth of end portion of tapered portion and cross section of uniform section is equal to about 3.3, wherein said ratio can vary by not more than ±5%.
In still another embodiment, a ratio of an area of the mouth of end portion of Exponential portion and an area of the mouth of end portion of tapered portion is equal to about 4.6, wherein said ratio can vary by not more than ±5%.
The present provides a horn for an automotive for producing pleasant sound. Referring to figure 1, which shows an exploded view of the trumpet horn of the present invention, it can be observed that the same comprises: Bracket - 1; Lock nut - 2; Rivets - 3 and 4; Terminal- 5; Terminal block - 6;

Fixed nucleus-7; Adjusting screw-8; Housing-9; Spool-10; Washer-11; Spring-12; Insulation tab-13; Contact rivet-14; Support plate-15; Insulation piece-16; Moving nucleus-17; Becker washer-18; Diaphragm-19; Diaphragm washer-20; Platine-21; Trumpet-22; Housing assembly-23; Terminal block assembly-24; Diaphragm assembly-25; Trumpet assembly-26;
Referring to figure 1, the housing assembly (23) consists of sheet metal housing (9) which encases a fixed iron core or alternatively referred to as fixed nucleus (7) rigidly held to its bottom and aligned to its centre axis. Around fixed iron core a coil or a spool (10) is mounted and receives electricity via terminal assembly (formed of terminals (5), rivets (3 and 4) and terminal block (6)), to produce a magnetic field. The magnetic field thus produced attracts the moving iron core fixed to the diaphragm (19) in such a manner that an electrical supply being supplied to the spool is interrupted and thereby the magnetic field ceases to act. This is attained by the placement of the spring (12), which acts as a contact breaker.

More particularly, as DC supply from DC source is switched on the current start increasing and with which magnetic flux through fixed iron core also start increasing. This causes the moving iron core fixed on diaphragm to be pulled towards the fixed iron core. During its forward motion towards the fixed iron core pushes the spring and in turn moves the contacts (14) away thus breaking the circuit. This stops the current further and causes the magnetic flux to decrease. Due to elasticity of material of diaphragm, the diaphragm pulls back the moving iron core back to its neutral position. As the moving iron core moves back, the spring also return to its original position and thus contacts are again touching each other. The circuit is now closed and current start flowing again. This process repeats again at a 500 +/- 10 cycles per second (cps) in case of high tone (HT) horns and 420 +/- 10 cps in case of low tone (LT) horn. This way, diaphragm with iron core is set into periodic motion.
The construction of the trumpet horn is such that the moving core does not come in contact with the fixed iron core and maintains a gap at its least distance position. Due to the movement of the diaphragm, the air between the diaphragm and the platine is compressed and decompressed. The platine comprises a hole which allows the compressed air to be communicated to the trumpet section, where the sound is appropriately amplified and outputted.
Referring to figure 3, trumpet assembly consisting of two parts - trumpet (22) and platine (21). The platine (21) comprising an air exit hole is sandwiched between the trumpets (22) and the diaphragm (19). The platine (21) fits on top of trumpet (22) and is generally held on to it with the aid of silicon rubber or some advanced processes such as ultrasonic welding. The hollow channel (27) disposed between the platine (21) and trumpet (22) is the sound tube (27). The construction of the sound tube (27) or the channel may be circular or rectangular or combination thereof. Proper fitment of platine (21) over trumpet (22) is important to have no loss in sound pressure inside sound tube (27). The trumpet assembly (26) is fixed to horn sub assembly such that face of platine (21) is opposite the diaphragm (19) and both parts are held together at periphery by locking means. Both parts enclose a volume (29) which has exit at the centre hole in platine (21). This centre hole is directly above and aligned to the round pocket (28) of trumpet. Pocket (28) may be round or rectangular in section and even may be linear or developed into a spiral to conserve space. The pocket (28) has a rectangular side cut which opens into the sound tube (27) which is also rectangular and have same shape and size as of the inlet of the channel

(27) (as shown in figure 4). To have the sound pressure flow toward the sound tube (27), the pocket (28) may be appropriately contoured to allow smooth flow of sound pressure from enclose volume (29).
Further, a means for imparting resonance in the diaphragm (19) is provided, such that upon resonance the diaphragm (19) pushes a column of air through the air exit hole of the platine (21) into the trumpet assembly (26). The closed volume between the diaphragm (19) and neck of platine (21) is large enough to accommodate the movement of diaphragm (19) during upward movement. Periodic motion of diaphragm (19) compresses and decompressed the air in closed volume which may also called as a compression chamber (29). Due to changes in pressure the sound wave is generated which travels down/propagates through the entry hole into sound tube (27).
Referring to figure 4, the sound tube (27) of trumpet (22) have three dissimilar section - a first section i.e. uniform section (30); a second section i.e. tapered or linearly varying section (31); and a third section i.e. exponential section (32).
The first section (30) is uniform in construction. Due to the construction of first portion i.e. uniform section (30) sound travels with negligible loss in attenuation if the walls of trumpet (22) are finished properly. The second section (31) is linearly varying in construction. At the start of second section i.e. tapered or linearly varying section (31), impedance is less thus part of wave is reflected and part of wave is transmitted to third portion i.e. an exponential section (32). The exponential section is formed of such dimensions that it even present lower impedance and a large part of sound wave is transmitted to free atmosphere. The part of reflected wave as reaches back, the reflected wave adds constructively with newly generated wave add to the final SPL coming out of trumpet.
However the preferable dimensions of various portions to generate sound in spiral or linear trumpet as applicable have been found as given below:
• The length of uniform section depends upon the wavelength of the fundamental
frequency of sound wave. The ratios for low tone and high tone trumpet horn to be
followed as given below.

/Lu= 3.75 or Lv = 0-27 for low tone.
/Lu = 4.25 or Lv = 0.24. for high tone.
Where, A. is the wavelength of fundamental frequency of sound wave.
Lu is the length of uniform section.
• The ratio of effective area of diaphragm and cross section of uniform section of trumpet
to be followed as given below.
AD/Au=42
Where AD is the effective area of diaphragm
And Au is the area of uniform portion.
• The length and area of tapered portion to be followed as given below.
/LT =13.6 or LT = 0.07, for low tone.
/LT =11.4 or LT = 0.09 for high tone.
AT/Au=3.3
Where, LT is the length of tapered portion.
AT is the area of the mouth of end portion of tapered portion.
• The length and area of exponential portion to be followed as given below.
/LE = 18 or LE = 0.06 for low tone.
/LE = 15 or LE = 0.07 for high tone.
AE/AT=4.6
Where, LE is the length of exponential portion.
AE is the area of the mouth of end portion of Exponential portion.
All ratios can vary by not more than +/-5 %, otherwise the same will result in production
of weaker and impure sound.
The present invention is described with reference to the figures and specific embodiments; this description is not meant to be construed in a limiting sense. Various alternate embodiments of the invention will become apparent to persons skilled in the art upon reference to the description of the invention. It is therefore contemplated that such alternative embodiments form part of the present invention.

We claim:
1. A trumpet horn, comprising:
a trumpet (22);
a diaphragm (19) fitted on top of the trumpet (22);
a platine (21) comprising an air exit hole sandwiched between the trumpet (22) and the diaphragm (19); and
a means for imparting vibration in the diaphragm(19), such that upon vibration, the diaphragm(19) pushes a column of air through the air exit hole of the platine (21) into the trumpet (22);
the said trumpet (22) comprises a first portion for receiving the air column, an air exit port located radially outwardly and a radially extending channel (27) portion connecting the first portion to the air exit port, the said channel (27) portion comprising an uniform section, a tapered section and an exponential section arranged sequentially between first portion and the air exit port.
2. The trumpet horn as claimed in claim 1, wherein the first portion for receiving the air column is in the form of a round pocket (28) and the exit hole of the platine (21) is directly above and aligned to the round pocket (28).
3. The trumpet horn as claimed in claim 1, wherein the round pocket (28) has an opening allowing propagation of the sound wave in to the channel (27).
4. The trumpet horn as claimed in claim 1, wherein the length of the uniform section is equal to about 27% of X, the length of the tapered section is equal to about 7% of ,and the length of the tapered section is equal to about 6% of X for low tone (i.e. for a contact making and breaking cycle of 420 +/- 10 cycles per second), wherein X is wavelength of fundamental frequency of sound wave propagating through the horn and wherein all of the ratios given can vary up to ±5%.
5. The trumpet horn as claimed in claim 1, wherein the length of the uniform section (measured from exit hole of platine to the start of tapered portion) is equal to about 24% of , the length of the tapered section is equal to about 9% of ,and the length of the
tapered section is equal to about 7% of  for high tone (i.e. for a contact making and breaking cycle of 500 +/- 10 cycles per second), wherein  is wavelength of fundamental frequency of sound wave propagating through the horn and wherein all of the ratios given can vary up to ±5%.
6. The trumpet horn as claimed in claim 1, wherein a ratio of effective area of diaphragm
and cross section of uniform section is equal to about 42, wherein said ratio can vary up
to ±5%.
7. The trumpet horn as claimed in claim 1, wherein a ratio of an area of the mouth of end
portion of tapered portion and cross section of uniform section is equal to about 3.3,
wherein said ratio can vary up to ±5%.
8. The trumpet horn as claimed in claim 1, wherein a ratio of an area of the mouth of end
portion of Exponential portion and an area of the mouth of end portion of tapered portion
is equal to about 4.6, wherein said ratio can vary up to ±5%.
9. A trumpet horn substantially as herein described with reference to the accompanying drawings and the foregoing description.