Field of the invention The present invention relates primarily to suppression of noise or sparks produced by exhaust gases of an internal combustion engine of a vehicle. The invention particularly refers to an auxiliary device which either can be used in combination with the existing vehicle's silencer or used as a stand alone device. It should be understood however that the present invention is not limited to the suppression of noise produced by gases of an internal combustion engine. The invention can be also used in other applications associated with generation of exhaust gases and requiring suppression of noise and sparks.

Background of the invention There are known various silencers or mufflers which have been devised for suppression of noise of exhaust gases escaping an internal combustion engine.

Those devices are well known in the art and are described in numerous patents.

In US4700805 there is disclosed a muffler for exhaust gases consisting of a gas expansion chambers defined by partitions arranged in a muffler casing and of a sound-absorbing body. The sound-absorbing body comprises a perforated pipe surrounded by a porous sound-absorbing material with a thin metal film sandwiched therebetween. The noise is suppressed by virtue of loss of energy when the gases pass the perforations and then due to absorption within the sound-absorbing layer surrounding the pipe.

The exhaust system similar to the above-described muffler is manufactured by SAM Stefanson Automotive AB, Sweden. This system comprises a double-jacketed silencer in which a perforated stainless pipe is arranged. A sound absorber made of rock wool surrounds the pipe and the pipe is in communication with an expansion chamber where the exhaust gases are subverted.

In US5025890 there is disclosed and engine exhaust apparatus comprising a cylindrical silencer which interior is divided by partitions into at least three separate compartments. An inlet pipe bypasses the first and second compartments and enters the gases directly into the third compartment. That sections of the inlet pipe which pass the first and second compartments are provided with perforations for communication with the interior of those compartments and at least one of the sections is covered by a sound-absorbing layer. An outlet pipe bypasses the second and third compartments and lets the gases to exit directly from the first compartment.

Those sections of the outlet pipe which pass the second and third compartments are provided with perforations for communication with the interior of those compartments and at least one section is covered by a sound-absorbing layer. The gases enter directly into the third compartment via the inlet pipe and into the first and second compartment via perforations. During passing through the perforations the energy of entering combustion gases is at least partly dissipated. Then the gases proceed from the first compartment to the outlet pipe. Before the muffler the gases penetrate the perforations in the pipe and the noise is absorbed within the outside sound-absorbing layer.

In an international application PCT/IL98/00259 there is disclosed an exhaust muffler comprising an expansion chamber with an inlet pipe for the entry of gases. an acoustic damper residing within the chamber, a housing surrounding the chamber and an outlet pipe for releasing the gases to the atmosphere. The chamber walls and the damper are provided with perforations and the housing is located with respect to the chamber in such a manner that it overlaps the perforated section of the chamber.

It should be understood however that despite existence of various silencers the problem of noise suppression of exhaust gases a ! ways needs its better solution and therefore it is always desired to devise a new and improved device therefor.

The known devices are not sufficiently efficient for noise suppression since the energy of the exhaust gases flowing within the silencer is dissipated solely by virtue of passing the gases via perforations or by virtue of expansion of the gases within the expansion chamber.

Ol) iects of the invention The object of the present invention is to provide a new and improved device for silencing the exhaust gases of an internal combustion engine.

In particular the main object of the invention is to provide for a new and more efficient noise suppression device implementing frontal collision of the exhaust gases for more efficient dissipation of the noise energy.

The further object of the invention is to provide a new and versatile noise suppression device which can be used as a separate item or retrofitted within the existing silencer.

The other object of the present invention is to provide a new and improved sound suppression device, which is inexpensive, simpie and can be easily manufactured from available materials.

The above and other objects and advantages of the present invention can be achieved in accordance with the following combination of its essential features, referring to the different embodiments thereof.

The first preferred embodiment of the present invention refers to a noise suppression device primarily for suppression of noise produced by combustion gases of an internal combustion engine, said device comprising a housing, an inlet end, an outlet end and at least one hollow suppression chamber situated therebetween, said suppression chamber is located within the housing so as to provide a free space between the inwardly facing wall of the housing and the outwardly facing wall of the suppression chamber, the suppression chamber is provided with guide openings configured to enable entering the combustion gases from the free space via said openings into the suppression chamber and to cause frontal collision of said combustion gases within the suppression chamber, said suppression chamber is in communication with the outlet end of the housing.

According to one of the embodiments the suppression chamber can be formed as a hollow cylinder mounted within the housing co-axially with the longitudinal axis thereof and said guide openings are situated on the cylindrical periphery of said cylinder.

In the other embodiment the lower end of the suppression chamber which is opposite to the inlet end of the housing can be configured as a cone having its apex facing the flow of the gases entering the housing, said cone is capable to distribute the flow of combustion gases uniformly within the free space.

As per further embodiment-said guide openings may comprise at least one couple of diametrically opposite circular holes.

According to the other embodiment the holes can be connected by a tubular channel, said channel extends diametrically within the interior of the suppression chamber, the periphery of said channel is perforated so as to be in communication with the interior of the suppression chamber.

In yet further embodiment at least one of said holes can be provided with an inlet extending diametrically towards the interior of the suppression chamber.

As per further embodiment the suppression chamber can be configured as a cone and said cone can be mounted within the housing co-axially with the longitudinal axis thereof, the apex of the cone to be adjacent to the inlet end of the housing and the guide openings comprise plurality of slots cut in the cone's periphery.

In still another said slots are provided with flap means capable to direct the combustion gases to proceed through said slots from the free space into the suppression chamber.

And in accordance with the further the said guide openings may comprise two couples of holes. the holes of the first couple are connected by the first tubular channel and the holes of the second couple are connected by the second tubular channel, said tubular channels extend diametrically within the interior of the suppression chamber and the first tubular channel is perpendicular to the second tubular channel, said tubular channels on at least part of their periphery are perforated so as to be in communication with the interior of the suppression chamber.

For a better understanding of the present invention as well of its benefits and advantages, reference will now be made to the following description of its embodiments taken in combination with the accompanying drawings.

Brief description of the drawings The above embodiments of the present invention will be set forth in detail with reference to the drawings, in which: Figs. la. b are schematic views correspondingly showing how the noise suppression device of the present invention is used as a stand alone unit or is retrofitted within the existing silencer.

Figs. 2 is an isometric view of a noise suppression device according to one of the preferred embodiments.

Fig. 3 is a frontal partially cross-sectioned view of the noise suppression device depicted in fig. 2.

Figs. 4 is an isometric view of a noise suppression device according to the second preferred embodiment.

Fig. 5a is an isometric view of a noise suppression device according to the third preferred embodiment.

Fig. 5b is an enlarged fragment offig. 5a showing construction offtap means.

Fig. 6. is a frontal partially cross-sectioned view of the noise suppression device depicted in fig. 5a.

Fig. 7 is a frontal partially cross-sectioned view of the noise suppression device provided with suppression chamber as shown in fig. 3 and with expansion chamber according to an additional embodiment.

Fig. 8 is a frontal partially cross-sectioned view of the noise suppression device provided with expansion chamber as shown in fig. 7 and with suppression chamber according to an additional embodiment.

Detailed description of specific embodiments With reference to fig. la it is shown how the noise suppression device 10 of the present invention is connected with an outlet pipe 12 of a source of combustion gases 14, for example an internal combustion engine of a vehicle. The

combustion gases enter the device and are released therefrom via the outlet end 16 to the atmosphere.

In fig. la the noise suppression device constitutes a silencer which is used as an independent unit.

In fig. l b is shown an additional possibility for using the suppression device of the present invention. In this case the sound suppressing device 16 is used as a preliminary silencing device retrofitted within an existing silencer 18.

Now with reference to figs. 2, 3 the first embodiment of the sound suppressing device will be explained. The sound suppressing device comprises a suppression chamber 20 formed as hollow cylinder placed within an external housing 22. The suppression chamber is mounted co-axially with the housing and is provided with a lower conical end 24 facing the inlet end 26 of the housing. Since the outer diameter of the suppression chamber is less then the inner diameter of the housing there is provided a free space 28 therebetween. In fig. 3 there is shown how the sound suppressing device 10 is retrofitted within an existing silencer provided with an expansion chamber 30 for example as described in the above referred-to international application PCT/IL98/00259. It can be seen that the upper end 32 of the suppression chamber is in communication with the expansion chamber of the silencer. It can be appreciated that by virtue of this provision the combustion gases after they have passed the suppression chamber proceed further to the expansion chamber and escape therefrom via the outlet end of the silencer.

On the cylindrical periphery of the suppression chamber are made two oppositely situated circular openings 34,36. A tubular channel 38 extending diametrically across the interior of the suppression chamber connects the openings.

The channel is formed as a cylinder and its periphery is provided with perforations 38 enabling communication between the interior of the suppression chamber and the interior of the channel. It should be appreciated that the openings can be of other shape and not necessarily circular. Accordingly the channel may be formed not as a cylinder but as tubular member having cross-sectional configuration differing of circle.

The combustion gases entering the device via the inlet end 26 meet the lower conical end 24 and are distributed thereby around the periphery of the housing adjacent the inwardly facing wall thereof. The gases pass the free space 28 as designated by an arrow A 1 and enter the suppression chamber from two opposite sides through the circular openings 34,36 as designated by arrows A2. A3. Since the openings are situated opposite to each they guide the gases as two frontally encountering flows. The encountering flows collide and mix within the tubular channel. It was empirically revealed that the frontal collision effect is associated with deceleration of the gases velocity, reducing of pulsation of the gas pressure and consequently with the dissipation of the noise energy and noise suppression. The collided gases penetrate through the perforations into the upper part of the suppression chamber and escape therefrom as separated flows via the upper end 32. From here the weakened flow of combustion gases may proceed to further silencing within the expansion chamber 30.

In accordance with the further embodiment of the noise suppression device as shown in fig. 4 the openings 34, 36 instead of being connected by a contiguous tubular channel can be formed with respective circular inlets 340,360 that slightly protrude toward the free space and terminate within the interior of the chamber. The inlets guide the encountering flows of incoming gasses to the central part of the interior of the suppression chamber. Here the collision effect takes place followed by the noise suppression.

Now with reference to figs. 5a, b, 6 still further preferred embodiment of the present invention will be described. In accordance with this embodiment the suppression chamber is configured as a cone 40 having its apex 42 facing the inlet end 26 so as to meet the flow of combustion gases entering therein. Since the conical chamber is mounted within the housing co-axially therewith the apex 42 similar to the conical end 24 of the cylindrical suppression chamber i. e. it distributes the flow of entering combustion gases uniformly around the periphery of the housing adjacent the inwardly facing wall thereof. Base 46 of the cone is adjacent to the entrance of the expansion chamber. As seen in fig. 5a a free space 280 is provided between the outwardly facing wall of the chamber and the inwardly facing wall of the housing.

Extending along the conical periphery of the suppression chamber annular slots 44 are cut therein to enable the combustion gases to enter within the suppression chamber. It is advantageous if at least a portion of the conical periphery adjacent to the respective slot is somewhat slanted outside so as to serve as a flap means 48 capable to direct the gases flow from the free space 280 inside the chamber. This provision is shown in more details with reference to fig. 5b.

With reference to fig. 6 the noise suppression device of the present invention is retrofitted within an existing silencer. It is shown by arrow that the flow of combustion gases enters under pressure the inlet end of the silencer and after being uniformly distributed by conical end 42 of the suppression chamber it proceeds to the free space 280. After the combustion gases have reached the upper part of the suppression chamber they turn around and enter the chamber's interior through plurality of slots 44. By virtue of the slots the gases enter the suppression chamber as plurality of encountering currents which collide and mix inside the chamber. The collision effect as in the previous embodiments is associated with the dissipation of the noise energy and noise suppression. The weakened flow of combustion gases proceeds further through the outlet end of the housing to expansion chamber 30 of the silencer.

It should be appreciated that the present invention is not limited to the above-described embodiments and that changes and one ordinarily skilled in the art can make modifications without deviation from the scope of the invention, as will be defined later in the appended claims.

For example as shown in fig. 7 the interior of the expansion chamber can be provided with a cone 40'that is similar to the cone 40 explained earlier in connection with the suppression chamber shown in fig. 6. The cone 40'is mounted within the expansion chamber in such a manner that its apex 42'is adjacent to the outlet end 48 of the expansion chamber and its base 46'is adjacent to the upper end 32 of the suppression chamber.

The suppression chamber can be provided also with an additional couple of opposite situated circular openings connected by a tubular channel extending diametrically across the chamber's interior. This option is shown in fig. 8 in which is seen the first couple of openings 34,36 and connecting therebetween channel 38 as well the additional couple of openings and connecting therebeween tubular channel

52. In fig. 8 only opening 50 is designated. It can be seen that all openings are made in the cylindrical periphery of the suppression chamber and are located in such a manner that the first tubular channel 38 extends diametrically perpendicular to the second tubular channel. Similar to the embodiment explained with reference to fig. 3 the tubular channels are provided with perforations. However in the embodiment shown in fig. 8 it is advantageous if these perforations are located on the lower part of the channels as designated at 54,56.

It should also be appreciated that the features disclosed in the foregoing description, and/or in the following claims, and/or in the accompanying drawings may, both separately and in any combination thereof, be material for realizing the present invention in diverse forms thereof.