Abstract: The invention relates to a silencer comprising an inner component and an outer component surrounding said inner component, said inner component defining an inner wall provided with openings and said outer component defining an outer wall extending along said inner wall. For improving the silencing characteristics as well as the flexibility of the silencer, the outer wall is implemented as a bellows which defines together with the inner wall individual cavities, the openings of the inner wall opening into said cavities. Furthermore, the outer wall is produced from a material having a density of at least 1.5 g/cm3.

Abstract: A damper that has chemical resistance, that can be used under a high-pressure environment, and that can remove pressure pulsations is provided. This damper includes a fluid chamber into and out of which a fluid flows, a diaphragm defining at least one surface of the fluid chamber, and a separate chamber adjacent to the fluid chamber in a fluid-tight manner, with the diaphragm disposed therebetween. The diaphragm includes a first film having chemical resistance and a second film having pressure resistance.

Abstract: A main flow line and relief valve assembly comprising: a main line fitted with a standpipe; a relief valve fitted within the standpipe; and a sleeve inserted in the standpipe below the relief valve, with a distal end of the sleeve configured to prevent aero-acoustic resonances of the deep cavity formed by the relief valve and standpipe assembly. The aero-acoustic resonance is prevented by separating the vortex shedding frequency associated with the free shear layer convecting across the mouth of the deep cavity and the acoustic cavity frequencies of the deep cavity and by disrupting the free shear layer at the mouth of the deep cavity such that the vertical structure does not remain coherent and/or does not impact upon the downstream edge of the cavity mouth.

Abstract: An integrated heat exchanger and muffler unit (50,120,140) is provided for transferring heat between a first fluid and a second fluid, and for muffling the noise of the first fluid. The unit includes a housing (52) including a first inlet (60) for the first fluid, a first outlet (62) for the first fluid, a second inlet (64) for the second fluid, and a second outlet (66) for the second fluid. The unit (50,120,140) further includes a resonator (76) in the housing (52) and connected between the first inlet and outlet (60,62) to muffle noise in the first fluid, and a heat exchanger core (11,122) in the housing (52) connected to the first and second inlets and outlets to transfer heat between the first and second fluids. In one embodiment, the heat exchanger core surrounds the resonator. In another embodiment, the resonator surrounds the heat exchanger core.

Abstract: A sound absorber includes an inner component and an outer component surrounding the inner component, the inner component defining an inner wall provided with apertures, and the outer component defining an outer wall extending along the inner wall. For improving the sound-absorbing properties as well as the flexibility of the sound absorber, the outer wall is implemented as a bellows which, together with the inner wall, defines individual cavities, the apertures of the inner wall opening into the cavities.

Abstract: An interference-based exhaust noise attenuation device and method for exhaust flow from an internal combustion engine that generates compressive waves in the exhaust flow. The device includes at least a direct path for the exhaust flow; a looped path for the exhaust flow, with volumes of the direct path and the looped path differing by an amount that results in a staggered rearrangement of the compressive waves in the paths; a splitter that splits the exhaust flow into the direct path and the looped path; and a merger that merges the exhaust flow from the direct path and the looped path. When the exhaust flow from the direct path and the looped path are merged, at least some noise cancellation occurs. In other embodiments, plural direct paths, looped paths, splitters, and/or mergers can be used in various combinations.

Abstract: A noise control apparatus for a motorcycle exhaust system. The apparatus includes at least one exhaust pipe assembly having a direct pass-through mode and an indirect mode wherein exhaust gases are optionally directed through noise attenuating means. The apparatus includes at least one valve for controlling exhaust gas flow, a motor, a switch controlling said motor, a wire carrier, a wire connected between the carrier and the valve(s), and a rotary threaded drive shaft driven by the motor for moving the positioner. The threaded drive shaft includes radially extending and circumferentially facing stop means on both sides of said wire carrier. The valve is positioned under the control of the switch.

Abstract: In a hermetic compressor in a freezing refrigerating system or an air-conditioning system such as a refrigerator or a showcase, a construction is disclosed for intending to provide a low-noise hermetic compressor by effectively attenuating a pressure pulsation having occurred in a compression chamber with a suction muffler. By this construction, since a muffler cover 20 has a planar simple shape, the deformation upon molding becomes little and it can come into fully close contact with a muffler main body 19. Therefore, the pressure pulsation hardly leaks through the connecting portion between the muffler main body 19 and the muffler cover 20. The full silencing effect that the suction muffler 18 has is obtained and thereby noise can be reduced more effectively.

Abstract: An exhaust system for a motorcycle that inhibits generation of flow noise without diminishing external appearance. The exhaust system has a tail cap and a ring shaped outer cap that is fixed to a rear end edge of a casing. An inner cap is fixed to a rear end wall of the casing and has a tail hole having a size that allows a tail pipe to pass through it with a gap therebetween. A gap s is formed in a boundary region between the inner cap and the outer cap.

Abstract: A motorcycle having a tail pipe formed from a pair of branch pipes that branch from a main pipe and that ensures a sound absorbing effect. A muffler has a casing that surrounds a rear section of an exhaust pipe, and a sound absorbing material that is filled between the casing and the rear section of the exhaust pipe. The rear section of the exhaust pipe includes a main pipe that is connected to the exhaust pipe and that extends to the rear, and first and second branch pipes that are connected to and branch from the main pipe and extend to the rear. A cross sectional area of the casing, when viewed from an exhaust gas flow direction becomes larger as the casing extends toward the branch pipe side.

Abstract: A muffler system is provided for use with an auxiliary power unit. In one embodiment, and by way of example only, the system includes an outer can, an annular baffle, and a tube. The outer can has a sidewall including a forward end, an aft end, and a cavity extending therebetween. The sidewall is disposed about a first longitudinal axis, and the cavity has a first cross-sectional area and a smaller second cross-sectional area. The annular baffle is coupled to and extends radially inward from the outer can sidewall and has an opening that is disposed about a second longitudinal axis that is non-coincident with the first longitudinal axis. The tube extends through the annular baffle opening and is spaced apart from the annular baffle to define a radial gap therebetween, comprises acoustic material, and has a length and a substantially uniform cross-sectional area along the length.

Abstract: The shell main body for a muffler includes an inner shell in a cylindrical shape with a cross-section of an imperfect circle defined by small arc portions alternating with large arc portions; and an outer shell wrapping the inner shell and formed in a cylindrical shape similar to the inner shell. An end portion of the inner shell and an end portion of the outer shell are overlapped in a circumstantial direction of the shell main body to form a shell overlap portion that is capable of discharging vapor in a gap of the large arc portions formed between the inner shell and the outer shell into one of an outside and an inside of the shell main body. This shell overlapping portion is located in one of the small arc portions.

Abstract: A resonator and method of designing a resonator including a cavity having an effective length that exceeds ?/8 such that a standing wave having an anti-node will form in the cavity. First and second necks each having first ends are attached to and in fluid communication with the cavity, the first neck being positioned adjacent the anti-node and thereby operable to interfere with said standing wave.

Abstract: The gas flow sound attenuation device includes a number of variations each having at least one pressure pulse reflecting chamber, i.e., a Helmholtz chamber, installed in axial alignment with the upstream gas flow. Gas flow is transferred laterally externally to the chamber, with the single opening of the chamber receiving substantially all incoming pressure pulse energy to maximize the reflection and canceling of those pulses back into the upstream duct. The device may incorporate any practicable number of chambers, so long as each has at least some length of upstream pipe or duct axially aligned with the chamber opening. The chambers may have any practicable shape and/or may include internal baffling. The device may be applied to any gas flow system, e.g., heating, ventilation, and air conditioning systems, but is particularly effective in reducing the sound output of internal combustion engine exhaust systems.

Abstract: A control system (10) controls a variable acoustical damping device (20) disposed in a sound producing channel (5) of a vehicle engine (1). The control system includes a controller (12) and a selection device (14). The controller is coupled to the variable acoustical damping device and stores a plurality of control patterns (A. B) for different levels of acoustical damping of the acoustical damping device. The selection device outputs a selection signal to the controller so that the controller controls the variable acoustical damping device based on one of the control patterns corresponding to the selection signal.

Abstract: A resonator for a vehicle air intake system is disclosed, wherein the resonator is variable tuned to militate against the emission of sound waves caused by the engine and other sources at a wide range of engine speeds.

Abstract: A suction apparatus is provided with noise reduction means in one or more airflow passages for reducing noise emission from an airflow generator or the like, wherein at least one airflow passage is provided with at least one indentation with a predetermined depth extending substantially perpendicularly to the general direction of the noise in the passage.

Abstract: The present invention provides a resonator for attenuating acoustic vibration from an air intake passage. The resonator includes a neck, a resonator chamber, a piston-type member, and an actuator. The neck is attached between the air passage and the resonator chamber. The neck has two overlapping portions allowing the neck to extend within the resonator chamber. The piston-type member is located within the resonator chamber and is translated by the actuator to change the volume of the resonator and the neck length. By changing the volume and neck length of the resonator, the frequency attenuated by the resonator can be adjusted.

Abstract: A communicating pipe is disposed on an outer periphery of an air intake pipe, and a conduit is formed so as to be parallel to an air intake passage. A plurality of first communicating apertures are disposed through the air intake pipe so as to be arranged in a single row in a conduit direction and communicate between the conduit and the air intake passage. A resonance chamber is mounted to the communicating pipe so as to communicate with a first end of the conduit. A movable member is disposed so as to be movable in the conduit direction by sliding in contact with the inner wall surface of the communicating pipe. A second communicating aperture is disposed through the movable member so as to be placed above the first communicating apertures. A communicating channel length between the air intake passage and the resonance chamber is adjusted by changing a position of overlap of the second communicating aperture relative to the first communicating apertures by moving the movable member in the conduit direction.

Abstract: The invention concerns a suction muffler for a hermetic refrigerant compressor with a housing having an inlet and an outlet and limiting at least one muffling chamber, and a gas supply channel located in the muffling chamber between the inlet and the outlet. It is endeavoured to prevent too much oil from remaining in the refrigerant gas flow. For this purpose, the gas supply channel forms a throttling path and ends in the muffling chamber, and that in the area of the inlet of the gas supply channel an oil extraction opening is located, which ends in the muffling chamber.

Abstract: An acoustic fluid machine includes an acoustic resonator, a valve device, a piston, and an actuator. The acoustic resonator has a larger-diameter base and a smaller-diameter upper end. The valve device is provided on the upper end of the acoustic resonator and has a sucking hole and a discharge hole. The piston is provided in the base of the acoustic resonator and has a surface such that the distance between the upper end of the acoustic resonator and the upper surface of the piston is substantially constant over the whole surface of the piston. The actuator is connected to the piston and reciprocates the piston at high speed axially with a very small amplitude so that a gas is sucked into the acoustic resonator via the sucking hole and discharged via the discharge hole by virtue of pressure fluctuations within the acoustic resonator.

Abstract: An active exhaust muffler for an exhaust system of an internal combustion engine, having a housing through which a pipe system passes, the pipe system designed to be permeable for airborne sound in a first space, having an antisound generator which is arranged in a second space and antisound acting upon a third space through a wall opening during operation, the wall opening being provided in a partition that separates the second space from the third space, whereby airborne sound is transmitted from the first space to the third space through a sound outlet. To increase the lifetime of the antisound generator and thus the exhaust muffler, a labyrinth is provided in the third space, blocking a direct path between the sound outlet and the wall opening, and providing at least one indirect bypass for the propagation of airborne sound between the sound outlet and the wall opening.

Abstract: A cylindrical shell main body constituting a muffler main body is formed of two layers of an inner shell and an outer shell and has a cylindrical shape with a cross section that is not a perfect circle but is defined by alternated small arc portions and large arc portions similarly to an oval, or the like. The outer shell of the shell main body has, in each of their small arc portions, four radially projecting beads continuously extending in a circumferential direction along the small arc portions and being a predetermined distance apart from one another in an axial direction, thereby allowing an upper and lower gaps between the inner shell and the outer shell in the respective large arc portions of the shell main body to communicate with each other through passages formed by the beads.

Abstract: The invention relates to an exhaust silencer or muffler for an internal combustion engine, in particular a silencer with the damping characteristics of a resonator with the absorptive characteristics of a dissipative silencer. The silencer of the present invention provides an improved silencer or muffler for use with an internal combustion engine that incorporates both a dissipative silencer and a resonator in a single muffler assembly suitable for use with standard automotive construction techniques.

Abstract: An acoustic filter is provided with a single flow chamber for exposure of a flexible rubber layer to liquid undergoing flow through the flow chamber with noise producing acoustic energy therein. The flexible rubber layer is supported on a cylindrical drum with slanted holes therein through which the exposure to the liquid in the flow chamber is effected. An axially sectioned drum with dimensionally different diameters, radial thicknesses and slanted holes therein is positioned over the rubber layer within an outer casing to establish a plurality of gas-filled cavities of different axial lengths and separated from each other along the axial length of the liquid flow chamber which is connected at its opposite axial ends by pipe sections to a piping system from which the liquid within the flow chamber is derived.

Abstract: A muffler which reduces noises of a wide frequency band with a simple structure. Sound waves of an intake duct enter into and are received in a resonance box via a branch pipe. At the branch pipe, a movable body slidingly abuts a peripheral portion of an opening of a cut-out portion. Due to the movable body rotating, a range of opening/closing of the cut-out portion is changed, and a length of a neck portion formed by the branch pipe and an arc-shaped plate, and a lateral cross-sectional surface area of a distal end of the neck portion, are changed.

Abstract: An acoustic fluid machine such as an air compressor comprises an acoustic resonator, a valve device and a piston. Air is sucked into the resonator through the valve device at one end of the resonator. The piston at the other end of the resonator is reciprocated by an actuator to compress the air in the resonator to cause resonance to increase pressure of the air significantly. The inner surface of the resonator is suitably curved to comply with the formula of a half-period cosine function.

Abstract: A sound dampening assembly adapted to engage an exhaust pipe in an automotive engine exhaust system adjacent an outlet of an internal combustion engine. The assembly includes a bottle portion having a single opening and an interior defining a predetermined amount of volume and a neck portion having a first end attached to the opening of the bottle portion and extending from the bottle portion. The neck portion is in fluid communication with the bottle portion interior and includes a second end adapted to be attached to the exhaust pipe. The neck portion has an interior defining a predetermined amount of volume and the bottle portion and the neck portion are sized to attenuate vibration at a predetermined frequency in the exhaust system.

Abstract: An exhaust volume (20) of the type including a muffler (24) having a casing provided with an inlet (29) and an outlet (30) for passing gases and adapted to enable the muffler to be mounted in an exhaust system (14). The volume further includes an additional enclosure (26) forming an accumulation cavity communicating solely with the casing of the muffler (24) via at least one connection pipe (28), the additional enclosure (26) being placed outside the muffler (24). The additional enclosure (26) is of a structure whose ability to withstand high temperature is lower than that of the structure of the muffler (24).

Abstract: A resonator for damping pressure waves or instabilities in a system supported by acoustic energy wherein the resonator adopts the use of counter-bored openings on the downstream side of the resonator within the flow path of the system. The resonator includes a first member and a second member where the second member includes a plurality of openings therethrough with each hole having a counter-bore on its upstream side. The first member has a size substantially smaller than the diameter of said flow path and a first plurality of openings therethrough. The openings are in fluid communication with the flow path. The second member has a size generally equal to the first member and a second plurality of openings therethrough, which openings are in fluid communication with the flow path.

Abstract: An in-line resonator for an air induction system of an internal combustion engine is provided. The system includes a resonator housing, an upstream duct, a downstream duct, a conduit, a partition, and a sleeve. The conduit extends through the resonator housing connecting the upstream duct and the downstream duct. The partition is moveable within the resonator housing and divides the housing into an upstream chamber and a downstream chamber. The downstream chamber, the conduit, and the downstream sleeve cooperate to form a first Helmholtz resonator that is in fluid communication with the downstream duct. The upstream chamber, the conduit, and the upstream sleeve cooperate to form a second Helmholtz resonator that is in fluid communication with the upstream duct. Further, a means is provided to axially move the partition to vary the volume of the chambers concurrently with the length and/or area of the passages.

Abstract: A system for attenuating exhaust noise from an engine with a first group of active cylinders and a second group of deactivatable cylinders includes a first exhaust manifold connected to the first group of active cylinders and a second exhaust manifold connected to the second group of deactivatable cylinders. The second exhaust manifold is connected to the first exhaust manifold such that the second exhaust manifold acts as a resonator to attenuate sound from the first group of active cylinders when the second group of cylinders is deactivated.

Abstract: An HQ tube arrangement suitable for packaging within a vehicle may be designed by creating a mathematical model representing a tube arrangement having a first passageway and a second passageway fluidly connected to the first passageway at first and second junctions. The second passageway is divided by the junctions into first, second, and third passages. Lengths are associated with each of the first passageway and the first, second, and third passages. A filter parameter, based upon an average transmission loss for a particular frequency over a standard deviation, is analyzed as a function of the lengths. Lengths are chosen based upon analysis of the filter parameter. Portions of the outer walls of the first and second passageways may be secured to or common to one another so that lengths of the passageways run along side of each other to provide a more compact HQ tube arrangement.

Abstract: The invention relates to an exhaust silencer or muffler for an internal combustion engine, in particular a silencer with the damping characteristics of a resonator with the absorptive characteristics of a dissipative silencer. The silencer of the present invention provides an improved silencer or muffler for use with an internal combustion engine that incorporates both a dissipative silencer and a resonator in a single muffler assembly suitable for use with standard automotive construction techniques.

Abstract: A continuously variable Helmholtz resonator for a vehicle air intake system having a vibratory input to the resonator wall to dynamically adjust the cancellation frequency for time-varying acoustical signals, and at least one of mean resonator volume control, mean resonator neck length control, and mean resonator neck diameter control whereby control of both the dynamic and the mean properties of the resonator provides a wide-tuning spectrum and facilitates canceling of time-varying acoustical signals.

Abstract: A passive device is provided for reducing vibration and noise in a hydraulic system. The passive device includes a tubular element having an open end and a closed end. The open end of the tubular element is adapted to be attached to a fluid conduit carrying pressurized fluid in the system so that the tube fills with the pressurized fluid. The area and length of the tube are such that the fluid within the tube has a resonant condition at a frequency that is the same as at least one frequency of the vibration and noise that is to be reduced or removed in the hydraulic system. A helicopter is also provided having a hydraulic system of pressurized fluid for reducing the transfer of vibrations from the transmission to the airframe including the passive device. Several such passive devices may be applied at selected locations in a hydraulic system for effectively reducing high frequency vibration and noise due to, for example, helicopter transmission gear clashing.

Abstract: A controllable muffler system is sued for use with an engine that produces a power by burning fuel. The system comprises a first passage section extending from the engine for having an exhaust gas of the engine flow therethrough. The first passage section has a catalytic converter mounted thereon. The system further comprises a dual passage section including second and third passage sections which extend separately from an end of the first passage section. The second passage has a control valve for controlling the flow rate of the exhaust gas flowing therethrough. The system further comprises a fourth passage section extending from respective ends of the second and third passage sections to the open air. The fourth passage section has a rear muffler mounted thereon. The system further comprises a control unit which controls the control valve of the second passage section in accordance with an operation condition of the engine.

Abstract: A muffler for an internal combustion engine is disclosed which is capable of effectively enhancing its muffling effect without any substantial increase in size, weight or manufacturing cost. The exhaust gas ejected from an exhaust port of the internal combustion engine is divided in the muffler into at least two flows. The divided exhaust gas flows are subsequently impinged against each other before the divided exhaust gas flows are finally discharged from a final exhaust port to the external atmosphere. More specifically, this muffler comprises an expansion chamber into which the exhaust gas is to be introduced from the exhaust port, and the expansion chamber is provided with at least two impingement openings for enabling the exhaust gas to be divided into at least two exhaust gas flows which are designed to be subsequently impinged against each other.

Abstract: A number of embodiments of acoustical devices for improving either or both the intake and exhaust sounds emanated from an internal combustion engine. This is achieved by employing acoustical devices which are configured so as to discharge the desired sound waves to the atmosphere rather than by attempting to dampen the undesired sound waves generated in the system.

Abstract: A variable tuned telescoping resonator which militates against the emission of noise energy caused by intake air in a vehicle wherein the connector length and the volume of the resonator are varied as a function of engine speed simultaneously to provide attenuation of noise energy over a wide frequency range.

Abstract: An exhaust pipe is branched into a right side connecting portion and a connecting portion. The right side connecting portion is connected to a first muffler while the connecting portion is connected to a second muffler through a space under a boundary between a driver's seat and a passenger's seat. It is possible to eliminate the need for reducing the thickness of a portion, corresponding to each of the driver's seat and the passenger's seat, of a cushioning material of the seat and to ensure a sufficient range of vertical movement of a rear wheel. The aforementioned arrangement permits the weight of the exhaust system to be reduced without sacrificing the cushioning characteristic of the seat and the range of vertical movement of the rear wheel.

Abstract: A device for silencing a flowing gas which includes a valve housing in which a valve is mounted. A separate pressure regulator is provided which is in communication with the flowing gas and which is responsive to gas pressure to thereby influence movement of a mechanical actuating device which controls movement of the valve such that the valve may be opened at least two different rates dependent upon the pressure of the flowing gas.

Abstract: A side-branch resonator which has a resonator chamber connected to an air intake pipe with two necks. The necks extend into the resonator chamber and provide a conduit for sound to travel to and from the air intake pipe. The presence of two necks increases the magnitude of attenuation at the resonant frequency and the bandwidth of attenuation of other lower frequency engine noises. The two necks also effectively attenuate higher frequencies by utilizing standing waves found within the resonator chamber.

Abstract: A resonator for noise damping in a sound-conducting tubular channel (2) is provided with an actively controllable sound generator (4) which is arranged in a resonator chamber (12) to generate interference noise (16) to be superimposed on the tubular channel noise. The resonator chamber (12) is connected via a sound-transmitting opening in a tube wall (3) of the tubular channel (2) to the inside of the tubular channel. A measurement signal from a sound sensor (8) arranged in the tubular channel (2), containing information about the sound spectrum in the channel, is connected amplified, to the sound generator (4) with the same frequency and with inverse phase position. To amplify the active suppression of the sound level by the resonator with a resonator of the smallest possible overall size, the sound-transmitting opening in the tube wall is constructed as a peripheral annular gap in the tube wall.

Abstract: A high performance muffler for an internal combustion engine of a passenger vehicle includes a straight through main pipe and a side branch open at one end to the main pipe and at the other end to the atmosphere. The side branch is tuned to attenuate a noise frequency that is loudest in the passenger compartment of the vehicle when the engine is operated without a muffler. Numerous embodiments of the invention are disclosed including arrangements in which the side branch pipe has acoustic path sections that are folded on one another to reduce the axial length of a main envelope of the side branch pipe.

Abstract: An acoustic absorber (10) comprises a housing or wall (11), defining an interior absorber chamber (12) connected by openings (13) to a duct (20) to reduce the sound in the duct (20). The natural frequency and impedance of the absorber (12) are variable, so that the absorber (12) can be adapted to a sound field in the duct (20) in a manner corresponding to the respective operating conditions. Such adaptation is achieved mechanically, for example, by an elastic membrane (15) for varying the volume of chamber (12), or thermally, for example, by a heating wire (14) or a wire braid (17).

Abstract: A noise reduction device has a side branch silencer. The side branch silencer is formed within a discharge valve assembly which includes is divided into a discharge muffler, a gasket, a discharge valve piece and a valve plate. The side branch silencer is provided with a cutout formed through the gasket to communicate with a discharge passage formed through the gasket. The cutout is blocked vertically by both a lower surface of a muffler plate of the discharge muffler and an upper surface of the discharge valve piece.

Abstract: A reactive silencer intended for industrial supply air or exhaust air channels has a sound attenuator chamber (10), to which is fitted a partition wall (12) dividing the sound attenuator chamber into a first and second chamber part (14, 16). The partition wall (12) is fitted with two or more channels or pipes (26, 26′, 26″) which connect the first chamber part (14) to the second chamber part (16). In this way a silencer of small size and simple structure is obtained for attenuating noise, especially that produced by large or several small air channels.

Abstract: A resonator provided for air system that includes a body defining a passageway. A wall is disposed within the chamber and the wall and the chamber are movable relative to one another to define a length and a volume of the cavity. The length and the volume of the cavity define a noise attenuating frequency. By moving the wall and chamber relative to one another the noise attenuating frequency may be changed as the frequency changes during the engine operation. The drive mechanism moves the wall in the chamber relative to one another to change the noise attenuating frequency. The chamber may be a branched type resonator or an inline type resonator. Accordingly, the above described invention provides a resonator that may be adjusted during engine operation to attenuate noise over a variety frequencies.

Abstract: The device for attenuation of noise in a tube intended to transport a gas includes a branch tube having two ends which open into said tube by two connections, and at least one tube referred to as quarter wave tube having a closed end referred to as the free end and another end which is connected to said tube at the level of the connections of the branch tube, thus forming three sections of circulation of gas entering into said tube. The invention can be applied in the field of motor vehicles.