MXPA98008856A - Integrated system of resonator and fil - Google Patents

Abstract

The present invention relates to an in-line filter and resonator apparatus, characterized in that it comprises: a) a housing having an upstream inlet and a downstream outlet, b) a fluted filter element positioned within the housing; filter includes one side upstream and one side downstream, the upstream side is aligned in line with the inlet, c) a resonant chamber placed inside the housing, the resonant chamber comprises a Helmholtz resonator, the resonant chamber is: i) downstream of the filter element ii) aligned in line with the outlet and the downstream side of the filter element, and iii) integral with the filter element, and d) a tube structure within the resonant chamber; The tube extends between the downstream side of the filter element and the outlet of the housing.

Description

INTEGRATED SYSTEM OF RESONATOR AND FILTER ANI? C-lbiDENTES D? THE INVENTION 1. Field of the Invention The present invention is directed to an integrated filter and a resonator apparatus for filtering air and reducing noise, and in particular to an apparatus which is inserted in line in a duct. 2. Description of the Previous Technique Systems for filtering air and systems to reduce noise with engines such as internal combustion engines are well known. Internal combustion engines typically have ducts to direct air to the engine which usually includes an inlet vent, an air cleaner, an inlet duct and an inlet manifold. In addition, there is a regulating mechanism or regulating body found in internal combustion engines powered by spark plugs. The air cleaning component has evolved from filters with oil applied to the filter medium to trap particulates up to filters folded in annular configurations REF: 28719 placed on top of the motor. Filters in current automobiles typically used are panel-type filters configured to be placed in smaller tight-packed engine compartment spaces. However, it can be seen that more efficient and smaller filters are needed in current and future vehicle designs which can be placed online in a pipeline. Helmhotz resonator devices require a large volume to form a resonator chamber and a type of connection to the noise source. However, the large volume requires the use of valuable space in the engine compartment which is very expensive in current car designs. In addition, since the resonator chamber typically requires a large volume, it can be placed away from the source of noise, therefore it is required that a working duct be directed to the camera capturing the additional volume. Since filters and resonators typically each require an enlarged chamber for satisfactory operation, it can be appreciated that an enlarged volume can be combined to decrease the total volume needed to separate the filter and resonator devices. In addition to the volume required for the two separate devices, an additional volume is required for the work duct for the two devices instead of a single combined device.

It can be seen then that a new resonator device is needed and the improved filter which occupies less volume than traditional devices. Such a device must be provided for the use of a single volume to accommodate both the resonator and the filter device. In addition, the filter apparatus must provide a substantially straight line flow which can lead to a resonator device. The device must also be insertable directly in line in a duct or another camera and at the same time occupy less volume. The present invention solves this as well as other problems associated with filter and resonator devices.

BRIEF DESCRIPTION OF THE INVENTION The present invention is directed to an integrated resonator filter apparatus for filtering fluid and reducing noise. The apparatus includes a grooved filter element in a preferred embodiment. Downstream of the filter element is a resonator device integrated in the same housing. A Helmhotz resonator having an enclosure with a straight tube of such dimensions so that the enclosure resonates at a single frequency determined by the geometry of the resonator various modalities are used. The resonator device is usually coupled directly to a duct that leads to a motor plenum or other source of noise. The resonator and the filter are in an integrally formed device that shares a remoteness in a preferred embodiment which is insertable in line in a duct, which serves as a portion of the duct. These characteristics of novelty and variations of other advantages which characterize the invention are indicated with particularity in the appended claims to the present and forming part thereof. Nevertheless, for a better understanding of the invention, its advantages and the objectives obtained by its use, reference should be made to the drawings which form an additional part thereof, and to the appended descriptive material, in which a plurality is illustrated and described. preferred of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings, where the like reference letters and numbers indicate corresponding elements through the various views: Figure 1 shows a perspective view of a double-faced fluted filter medium for the filter apparatus according to the principles of the present invention; Figures 2A-2B show diagrammatic views of the manufacturing process of the filter medium shown in Figure 1; Figure 3 shows a perspective view of the laminated filter media stratified in a block configuration according to the principles of the present invention; Figure 4 shows a perspective view in detail of a layer of single-sided filter medium for the filter element shown in Figure 3, - Figure 5 shows a perspective view of the fluted filter medium placed in spiral form; in a cylindrical configuration according to the principles of the present invention; Figure 6 shows a perspective view in detail of a portion of the fluted filter means placed in spiral form for the filter element shown in Figure 5; Figure 7 shows an end view of a first embodiment of a resonator and filter apparatus in accordance with the principles of the present invention; Figure 8 shows a partially exploded top plan view of the resonator and the filter apparatus shown in Figure 7; Figure 9 shows a side sectional view of the resonator and filter apparatus taken along the line 9-9 of Figure 8; Figure 10 shows a partially exploded side elevational view of a second embodiment of a resonator and filter apparatus; Figure 11 shows a partially exploded top plan view of the resonator and the filter apparatus shown in Figure 10; Figure 12 shows an end elevation view of a third embodiment of a resonator and filter apparatus according to the principles of the present invention; Figure 13 shows a side sectional view taken along line 13-13 of Figure 12; Figure 14 shows an end elevation view of a fourth embodiment of a resonator and filter apparatus according to the principles of the present invention; Figure 15 shows a sectional view of a resonator and filter apparatus taken along line 15-15 of Figure 14; Figure 16 shows a sectional view taken through line 16-16 of the resonator of the resonator and filter apparatus shown in Figure 15; Figure 17 shows an end elevation view of a fifth embodiment of a resonator and filter apparatus, in accordance with the principles of the present invention; Figure 18 shows a side sectional view of a resonator and filter apparatus taken along line 18-18 of Figure 17; Figure 19 shows a perspective view of a modular filter / resonator attached to an input manifold of a typical internal combustion engine; Figure 20 shows a perspective view of an integrated filter and a resonator apparatus integrated in the input manifold of an internal combustion engine; Figure 21 shows a perspective view of an integral resonator and a filter apparatus having the resonator volume integrated in the input manifold downstream from the filter element; and Figure 22 shows a graph of noise attenuation versus frequency for the resonator apparatus shown in Figure 14.

DESCRIPTION rpptat.t.DA OF THE PREFERRED MODALITY Referring now to the drawings and in particular to Figure 1, there is shown a portion of a layer of a double-sided permeable corrugated filter media, generally designated as 22. Corrugated filter means 22 includes a multiplicity of grooves 24 which form a modified corrugated type material. The bead chambers 24 are formed by a central fluted sheet 30 which forms peaks 26 and alternating valleys 28 mounted between the exposed sheets 32, which include a first exposed sheet 32A and a second sheet 32B exposed. The valleys 28 and peaks 26 divide the grooves into an upper row and a lower row. In the configuration shown in Figure 1, the upper grooves form the groove chambers 36 closed at the downstream end, while the upstream closed end grooves 34 are the lower row of the groove chambers. The groove chambers 34 are closed by a first end flange 38 which fills a portion of the upstream end of the groove between the grooved sheet 30 and the second exposed sheet 32B. Similarly, a second end flange 40 closes the downstream end of the alternating grooves 36. Adhesive adhesives 42 connect the peaks 26 and valleys 28 of the grooves 24 to the exposed sheets 32A and 32B. The grooves 24 and flanges 38 and 40 provide a filter element which is structurally self-supporting without a housing. When filtered, the unfiltered fluid enters the groove chamber 36 which has its upstream ends open, as indicated by the dotted arrows. Upon entering the groove chambers 36, the unfiltered fluid flow is closed by the second end flange 40. Therefore, the fluid is forced to advance through the corrugated sheet 30 or the exposed sheets 32. As the unfiltered fluid passes through the corrugated sheet 30 or the exposed sheets 32, the fluid is filtered through the layers of filter media, as indicated by the white arrows. The fluid is then free to pass through the channel chambers 34, which have their upstream end closed and to flow out of the downstream end, out of the filter means 22. With the configuration shown, the unfiltered fluid can be filtered through the corrugated sheet 30, the exposed upper sheet 32A or the exposed lower sheet 32B, and into the groove chamber 34 open on its downstream side. Referring now to FIGS. 2A-2B, there is shown a manufacturing process for a grooved filter medium which can be stacked or wound to form filter elements, as explained in the following. It can be seen that when a filter medium is stratified or spirally placed, with adjacent layers in contact with each other, only an exposed sheet 32 which can serve as the upper part of the fluted layer, and the lower sheet is required. for another ribbed layer. Therefore, it can be seen that the corrugated sheet 30 needs only an exposed sheet 32 to be applied to it. As shown in Figure 2A, a first sheet 30 of filtration medium is supplied from a series of opposed compression rollers 44 which form a constriction. The rollers 44 have intermeshed corrugated surfaces to bend the first sheet 30 as it is pressed between the rollers 44 and 45. As shown in Fig. 2B, the first sheet 30 now corrugated, and a second flat sheet of filter medium 32 are fed. together to a second constriction formed between the first of the bender rollers 44 and an opposite roller 45. A sealant applicator 47 applies a sealant 46 along the upper surface of the second sheet 32 prior to contact between the bender roller 44 and the opposite roller 45. At the beginning of a manufacturing run, as the first sheet 30 and the second sheet 32 pass through rollers 44 and 45, the sheets fall away. However, as a sealant is applied, the sealant 46 forms a first end flange 38 between the ribbed sheet 30 and the exposed sheet 32. The valleys 28 have adherent rims 42 applied at spaced intervals along their corners or otherwise attached to the exposed sheet 32 to form chambers 34 of groove. The resulting structure of the exposed sheet 32 sealed at one edge to the grooved sheet 30 is a stratifiable single-sided filter medium 48., shown in Figure 4. Referring now to Figure 3, it can be seen that the layer 48 of single-sided filter medium has a single back sheet 32 and a single end flange 38 and can be stratified to form a block type filter element generally designated with the number 50. A second flange 40 is placed on an opposite edge outside the grooves so that adjacent layers 48 can be added to block 50. In this way, the first flanges 38 at the end are placed between the upper part of the exposed sheet and the lower part of the corrugated sheet 30 as shown in Figure 4, while the space between the upper part of the corrugated sheet 30 and the lower part of the sheet 32 In addition, the peaks 26 adhere to the lower part of the exposed sheet 32 to form grooves 36. In this manner, a block 50 of fluted filter medium 50 is obtained which utilizes a second flange 40. The ribbed layers 48 shown in FIG. 4. The filter element 50 includes adjacent grooves having alternating closed first ends and closed second ends to provide a substantially straight through flow of fluid between the upstream flow and the downstream flow.

Returning now to FIGS. 5 and 6, it can be seen that the single-sided filter means 48 shown in FIG. 4 can be placed spirally to form a cylindrical filter element 52. The cylindrical filter element 52 is wound around a central mandrel 54 or other element to provide a mounting member for winding, which can be removed or left to engage the center. It can be seen that the center not rounded, the winding members can be used to manufacture other forms of filter element such as filter elements having an oblong or oval profile. Since the first flange 38, as shown in Figure 4, has already been placed on the layer 48 of filter medium, it is necessary to place a second flange 40 with the sealing device 47, shown in Figure 5, in a second end at the top of the ribbed layer 30. Therefore, the exposed sheet 32 acts as both an inner exposed sheet as well as an outer exposed sheet, as shown in detail in Figure 6. In this manner, a single exposed sheet 32 rolled into layers is all that is needed to form a cylindrical grooved filter element 52. It can be seen that the outer periphery of the filter element 52 must be closed to prevent the coil from unrolling and to provide a sealable element against a housing or duct. Although in the embodiment shown, the single exposed filter medium layers 48 are wound with a flat sheet 32 on the outside, there are many applications where the exposed sheet 32 is wound onto the inside of the corrugated sheet 30. Referring now to FIGS. 7 to 9, a first embodiment of an integrated filter and a Helmholtz resin apparatus are shown, designated generally with the number 60. The filter and noise control apparatus 60 includes filter elements 62 positioned as pathways of the filter. parallel fluid flow. In the preferred embodiment, the filter elements 62 are spiral shaped, corrugated filter elements, as shown in FIGS. 5 and 6. The air enters the elements 62 at the enlarged inlet 64 and exits at the reduced outlet 66. A housing 68 retains the elements in a side-by-side arrangement and a coaxial Helmholtz resonator tube 70 is mounted intermediate and offset from the filter elements 62 and substantially aligned with the outlet 66. The seals 72 and 74 retain the filter elements in a sealed configuration which drives the fluid through the elements and prevents contaminants from being derived from the filter elements 62. Although the integral filter and resonator apparatus 60 is shown alone, it should be appreciated that additional ducts can be connected to the inlet 64 to extract fluid from remote positions. In addition to the coaxial resonator tube 60, the volume surrounding the filter element 62 generates a Helmholtz resonator volume which can be tuned to control the induction noise generated by the operation of the motor. The configuration of the coaxial resonator tube 70 is on one side of the outlet of the filter element 62 to control the noise that passes directly from a downstream motor. The coaxial design improves the coupling path of the Helmholtz resonator to the motor noise which propagates directly through the plenum on the downstream side of the filter element 62. Referring now to FIGS. 10-11, a second embodiment of the Helmholtz filter / resonator integrated apparatus is shown, designated generally with the number 80. The resonator and filter apparatus 80 includes a housing 82 with a filter element 84, volume 81 Helmholtz resonator and a coaxial Helmholtz resonator tube 86. In the embodiment shown in Figs. 10-11, the filter element 84 is a substantially rectangular block type filter utilizing the fluted filter means 50, as shown in Fig. 3. The fluid enters the housing 82 in the input 88 and output at an output 90. Output 90 is directly coupled to the motor induction plenum in a preferred embodiment. Although the filter element 84 shown has a square cross section profile, it can be seen that this profile can be formed in any suitable common form to optimize the filter loading area and use the available space.

The downstream area of the filter element 84 includes a narrow chamber 92 that surrounds the coaxial Helmholtz resonator tube 86. The coaxial resonator tube extends substantially with the prevailing flow direction and bends upward at its upstream end and for contacting a hole in the wall of the narrow chamber 91. It can be seen that the volume between the accommodation 82 and the chamber 92 forms the volume 81 of the Helmholtz resonator. Referring now to Figures 12 and 13, a third embodiment of an integral filter and a Helmholtz resonator apparatus, designated generally with the numeral 100, is shown. The resonator and filter 100 include a Helmholtz resonator 102 in battery and a portion 104 of filter upstream of the resonator portion 102. A housing 106 includes an inlet 108 close to the filter 104 and an outlet 110 downstream from the portion 102 of the resonator. The Helmholtz resonator 102 includes a volume 112 and a coaxial tube 114, substantially coaxial with the outlet 110 and including an upstream end portion 116 that bends to extend radially and connect to an orifice in the wall of a volume chamber 118 resonant. The filter 104 may include a radial seal 120 which forms a seal around the periphery of the filter 104 with the housing 106. The seal 120 is formed integrally with the body of the filter element 104 in a preferred embodiment. In the preferred embodiment, the filter 104 is a grooved filter element, as shown in Figures 5 and 6. The outlet 110 is preferably directly bonded to an engine inlet plenum when used with internal combustion engines. It can be appreciated that the embodiment shown in Figures 12 and 13, the Helmholtz resonator filter apparatus 100 in battery can be coupled with an inlet duct or respirator which requires very little additional volume from an engine compartment. In this manner, the motor may have an inlet located outside the engine compartment while the battery resonator and filter apparatus 100 are located within the engine compartment. Referring now to Figs. 14 to 16, a fourth embodiment of an integral Helmholtz filter and resonator apparatus, designated generally with the number 120, is shown. As with the embodiment shown in Figs. 12 and 13, the apparatus 120 of Figs. resonator and filter includes a Helmholtz 122 resonator and a filter portion 124. A housing 126 includes an inlet 128 and an outlet 130. The filter may include a seal 132 which forms a seal between the housing 126 and the periphery of a filter element 134. The seal 132 is provided to remove the upstream end of the housing 126 and replace the filter element 134.

Helmholtz resonator 122 includes an annular tube 136 which extends from outlet 130 upstream into portion 122 of the resonator. In addition, a coaxial tube 138 extends downstream into the annular tube 136. The annular tube 136 opens at its upstream end between an enlarged area 140 of the coaxial tube 138 and the volume 142 of the Helmholtz resonator. In addition, the coaxial tube 138 opens at the downstream end to the annular tube 136. Therefore, an open annular conduit is formed between the outlet 130 at the downstream end and the volume 142 of the Helmholtz resonator at the upstream end. By sizing the coupling areas, the Helmholtz tube created by the tubes 136 and 138, and the resonator 142 to match the wavelengths of the given noise frequencies, the noise can be greatly reduced with the present invention. In addition, the previous advantages of the other modalities related to the placement of the entrance and the required volume are retained. As shown in Figure 16, the coaxial tube may include offset side portions 144 which further reduce the size of the conduit between the coaxial tube 136 and the annular tube 138. In this way, two upper and lower chambers are generated, as shown in figure 16, for the Helmholtz connection tube to the resonator volume 142. This provides additional tuning of noise reduction and greater accuracy in the coincidence of the target noise wavelengths. Referring now to Figures 17 and 18, there is shown a fifth embodiment of an integral Helmholtz-filter resonator apparatus, generally designated as 150. The integral resonator and filter apparatus 150 includes a Helmholtz resonator 152 and a portion 154 of filter. A housing 156 includes an inlet 158 and an outlet 160. In the preferred embodiment, a filter element 162 is a cylindrical grooved filter type element, as shown in Figures 5 and 6. The grooved filter element 162 preferably includes a seal 164 intermediate the filter element 160 and the housing 156. As with the other embodiments, a Helmholtz resonator 152 is downstream from the filter element 162. The Helmholtz resonator 152 includes a communication tube 166 that extends to a volume 168 upstream from the communication tube 166. The communication tube extends into the outlet 160. A second resonant structure includes coupled chambers having a communication chamber 170 at the outlet 160 which has the communication tube 166 partially extending therein. In addition, the communication chamber 170 extends downstream beyond the communication tube 166 that receives the flow from the outlet 160. Within the housing 156 is a resonant chamber 172 surrounding the enlarged portion of the volume 168 Helmholtz. The various resonator structures provide noise reduction over a wide range of frequencies. The various elements can be configured so that particular frequencies over the wide range are precisely tuned. Now with reference to FIGS. 19 to 21, embodiments of a filter apparatus mounted on an input manifold are shown. As shown in Figure 19, an integral filter / resonator apparatus 200 includes a resonator section 202 with a filter section 204 which can be separate modular components which are housed together to form the integral resonant filter unit 200. The resonator-filter apparatus 200 is mounted upstream of the motor manifold 206 and the regulator body 208. A duct 210 is connected from the regulating body to the output side of the resonator 200 so that the resonator is in direct fluid connection with the source of noise in the manifold 206. It can be seen that the mode shown, the filter apparatus 200 it forms a portion of the duct upstream from the manifold 206. In this arrangement, no additional space or work pipe is required to connect to a remote device for filtering or noise reduction. It can also be appreciated that an additional work duct can be connected to the filter element 204 to extract air from a remote position. Referring now to Figure 20, a second embodiment of a resonator and filter apparatus 220 is shown, which includes a filter portion 222 and a resonator portion 224 housed together to form the filter and resonator unit 220. The resonator-filter apparatus 220 is mounted upstream from the input manifold 226 and the regulator body 228, and is directly connected by a duct 230. In the embodiment shown, the filter and resonator apparatus are parts of the duct which is extends through the interior of the manifold so that no additional space is required. The manifold slides form the outer layer of the resonator chamber 224 to provide support and at the same time reduce the noise emitted by the resonator portion 224. It can be seen that the resonator portion 224 is directly connected by the duct 230 to the noise source for further noise reduction. It can also be seen that an additional work duct can be connected to the inlet to extract air from a remote source. As shown in figure 21, another embodiment of a resonator / filter apparatus 240 is described. The resonator and filter apparatus is integrated into an input manifold 248. In the embodiment shown, the 242 Helmholtz resonator includes a large volume within the arc of the manifold slides.

In this way, the slides of the manifold form the outer layer of the resonator volume and provide the support and at the same time reduce the noise emitted by the volume cover. Similar to other embodiments, the Helmholtz resonator tube is attached to the intermediate inlet duct to the filter 244 and to the regulator body 250. Therefore, the resonator tube is integral to the inlet plenum 252. The filter portion 244 is connected via a tube 246 to the resonator portion 242. The filter and the resonator are upstream from the manifold 248 and the regulator body 250 and are connected via a plenum 252 input. In the configuration shown, the filter element 244 is directly upstream of the plenum 252 and the manifold 248. It can be seen that the space inside the manifold 248 is used as a resonator volume so that very little additional space is required. In addition, the upstream duct from the plenum 252 has the filter element 244 integrated therein so that no additional space is required for the filter. Referring now to Figure 22, a typical graph of noise attenuation in decibels over a frequency range assigned to the Helmholtz resonator structure is shown. It can be seen that the loss is substantial, especially in the range between 70 and 100 hertz. The graph is shown for the Helmholtz resonator and the filter apparatus 120 shown in Figures 14 to 16. By tuning the resonator structure 122 to match certain wavelengths for noise at corresponding frequencies, the overall noise is greatly reduced. . The variations of volumes, lengths, diameters and relative positions provide elimination of target wavelengths. If the resonator connecting the tube length and the volume are a constant area through and are not subject to enlargements or constrictions, the peak noise attenuation frequency of the Helmholtz resonator can be estimated using the relationship: Where TAN is the trigonometric tangent function p = 3.14159 C = sound velocity lt = length of the connecting tube lv = length of the volume that passes through the sound At = connection tube area A? = volume cross-sectional area fr = maximum noise loss frequency. The above equation can be applied to the modalities 60, 80, 100, 120 and 180.

If the tube connecting the resonator or volume changes in the cross-sectional area along the sound propagation length such as in mode 150, the formula mentioned above can not be used directly. In this case, the tube, the volume and the air cleaner must be modeled by computer and its operation must be evaluated to accurately predict the resonant frequency. The equation mentioned above provides an approximation of the resonant frequency for a given volume and a connection tube. An alternative method for computer modeling is prototype construction, testing and evaluation. If the connecting tube and the volume lengths are less than one tenth of the wavelength of the noise frequency of the maximum loss, the Helmholtz equations, well known to those familiar in the art, can be used to relate the connecting tube length and area, volume and resonant frequency. However, this condition is generally violated by connecting tube lengths for the modes shown and the frequency range of interest. The attenuation in decobeads can not be accurately estimated because it depends on the flow losses in the connecting pipe and the inlets between the pipe and the volume. The test apparatus must be constructed and the attenuation measured.

However, it should be understood that although numerous features and advantages of the present invention have been established in the foregoing description, together with details of the structure and function of the invention, the description is only illustrative and changes can be made in detail, especially as regards the shape, size and arrangement of the parts within the principles of the invention to their full extent indicated by the broad general meaning of the terms in which the attached claims are expressed. It is noted that in relation to this date, the best method known by the applicant to carry out the aforementioned invention, is the conventional one for the manufacture of the objects to which it relates. Having described the invention as above, property is claimed as contained in the following:

Claims (19)

REIVUSIDIC-ATIONS

1. A resonator and in-line filter apparatus for a housing having a flow therethrough from upstream to downstream, characterized in that it comprises: a fluted filter means placed in line in the housing, the filter means comprises a fluted sheet and at least one exposed sheet forming groove chamber walls defining a plurality of groove chambers extending in a longitudinal direction having a closed end and an open end, wherein the adjacent chambers have alternating open and closed opposite ends. , wherein the flow passes within the open upstream ends through the walls of the groove chamber and outward to the open downstream ends; a resonant chamber positioned within the housing downstream of the filter element near the open downstream ends; a tube located inside the resonant chamber.

The apparatus according to claim 1, characterized in that the filtering means and the resonating chambers are integrally formed in a single housing.

3. The apparatus according to any of claims 1 or 2, characterized in that the tube extends longitudinally in the housing.

The apparatus according to any of claims 1 or 2, characterized in that the fluted filter means comprises a first filter element and a second filter element 'located side by side in the housing.

The apparatus according to claim 4, characterized in that the resonant chamber surrounds the filter elements.

6. An in-line filter and resonator apparatus, according to claim 1, characterized in that the apparatus is mounted on a motor, the motor has an input manifold with arched slides, wherein the resonant chamber is connected to the input manifold located inside a space formed by the arched members.

The apparatus according to claim 1, characterized in that the filter element has a rectangular cross section.

The apparatus according to claim 1, characterized in that the filter means comprises a first module, and the resonant chamber is formed in a resonator module configured to make contact with the filter module.

9. An in-line filter and resonator apparatus, according to claim 1, characterized in that the grooved filter means comprises first and second parallel filter elements extending longitudinally in the housing.

10. The apparatus according to claim 9, characterized in that the tube is coaxial with an outlet.

The apparatus according to any of claims 9 to 10, characterized in that each of the filter elements includes an associated sealing means.

12. The apparatus according to any of claims 9 to 11, characterized in that the filter elements are cylindrical.

13. An in-line filter and resonator apparatus, according to claim 1, characterized in that it further comprises: an annular tube assembly including a first tube coupled to the downstream side of the filter element, and a second tube extending coaxially with the first tube radially outwardly from the first tube and an opening at the end upstream to the resonant chamber.

The apparatus according to claim 1, characterized in that it further comprises a first and a second resonator, aligned coaxially with the housing.

The apparatus according to claim 14, characterized in that the first resonator comprises a chamber having a tubular portion extending into the chamber from the downstream side.

16. The apparatus according to any of claims 14 or 15, characterized in that the second resonator comprises a chamber surrounding the first resonator and receiving a flow of fluid from the filter element.

The apparatus according to any of claims 14 to 16, characterized in that an outlet comprises a portion of a downstream duct having a reduced cross section, and wherein the tubular portion extends at least partially into the outlet .

18. The apparatus according to any of claims 1 to 3, characterized in that the filtering means and the resonant chamber are aligned coaxially. The apparatus according to any of claims 1 to 5 or 18, characterized in that the housing includes an inlet and an outlet coaxial with the inlet.