Abstract:
The present invention relates to a hood ( 40 ) of a multi cyclone block ( 12 ) and an air cleaner ( 10 ). The cyclone block ( 12 ) has a plurality of cyclone cells ( 28 ). The hood ( 40 ) having at least one hood-inlet ( 50 ) and at least one hood-outlet ( 52 ) for air to be fed to the cyclone cells ( 28 ). The at least one hood-outlet ( 52 ) is designed for surrounding, a plurality of cell-inlets ( 36 ) of the cyclone cells ( 28 ) of the cyclone block ( 12 ). A wall ( 70 ) of the hood ( 40 ) defines a distributor volume ( 72 ) inside the hood ( 40 ), which is located between the at least one hood-inlet ( 50 ) and the at least one hood-outlet ( 52 ). The wall ( 70 ) has at least one line or area of inflection ( 74 ), where at least one inner surface of the wall ( 70 ) changes its curvature.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This Application is a continuation of currently pending U.S. application Ser. No. 14/725,813, filed 29 May 2015. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention relates to a hood of a multi cyclone block, in particular an in-line multi cyclone block, of an air cleaner of an intake system of an internal combustion engine in particular of a motor vehicle, wherein the cyclone block is comprising a plurality of cyclone cells, wherein the hood having at least one hood-inlet and at least one hood-outlet for air to be fed to the cyclone cells. 
         [0003]    The invention further relates to an air cleaner of an intake system of an internal combustion engine in particular of a motor vehicle, wherein the air cleaner having at least one multi cyclone block, in particular at least one in-line multi cyclone block, wherein the at least one cyclone block comprising a plurality of cyclone cells and a hood, wherein the hood having at least one hood-inlet and at least one hood-outlet for air to be fed to the cyclone cells and the at least one hood-outlet is connected air-ducting with the cell-inlets of the cyclone cells. 
       BACKGROUND 
       [0004]    A multi cyclone block of an air cleaner known from the market has a plurality of cyclone cells. Each cyclone cell has a cell-inlet, where the raw air streams in a hood having at a hood-inlet and a hood-outlet for the air to be cleaned. The hood is connected air-ducting with the cell-inlets by the hood-outlet. The cyclone cells separate particles from the air to be cleaned. The separated particles being collected in the cyclone block. The collected particles must be removed from the cyclone block at regular maintenance intervals. Therefore, a scavenging system is required. Such hoods are also sometimes referred to as cowls. 
         [0005]    It is an object of the invention to provide a hood and an air cleaner of the above-mentioned kind, where a pre-separation efficiency (PSE) for particles can be improved and/or a maintenance interval can be extended and/or a maintenance can be simplified. 
       SUMMARY OF THE DISCLOSURE 
       [0006]    It is an object of the invention to provide a hood and an air cleaner of the above-mentioned kind, where a pre-separation efficiency (PSE) for particles can be improved and/or a maintenance interval can be extended and/or a maintenance can be simplified. 
         [0007]    The object is achieved by that the at least one hood-outlet is designed for covering, in particular for surrounding, a plurality of cell-inlets, in particular all cell-inlets, of the cyclone cells of the cyclone block such that a fluid tight connection is provided between the hood and the cyclone cell inlets. A wall of the hood defines a distributor volume inside the hood, which is located between the at least one hood-inlet and the at least one hood-outlet, and wherein the wall includes at least one point of inflection, in particular at least one line or area of inflection, where at least one inner surface of the wall changes its curvature. 
         [0008]    According to the invention, at the at least one point of inflection at least the inner surface of the wall changes from being concave to convex or vice versa. Thus, the shape of the distributor volume has at least one according concavity or convexity. Such concavities and convexities influence the airflow in the hood. The in-coming raw air will be guided by use of the inventive shape of the wall of the hood. The raw air is the air to be cleaned by the air cleaner, in particular by the cyclone block. The hood can be mounted on the inlet side for air of the cyclone block. The incoming air will be uniformly distributed and supplied to the cyclone cells by the hood. In the cyclone cells particles, in particular dust, will be separated from the raw air. The separated particles will be collected in the cyclone block and can be removed at regular maintenance intervals or if necessary. The removing of the collected particles is necessary for maintaining the pre-separation efficiency of the cyclone block. For removing the collected particles, a process of scavenging can be used. 
         [0009]    Favorably, the wall can comprise at least one line of inflection and/or at least one area of inflection. The at least one line of inflection and/or the at least one area of inflection can be defined by multiple points of inflection each. 
         [0010]    With the inventive hood, the pre-separation from the raw air can be improved. The pre-separation efficiency of the cyclone block can be improved. Additionally, the cyclone cells can be loaded more uniformly with separated particles. So, a maintenance interval of the cyclone block can be extended. In particular, a frequency of scavenging the cyclone cells can be reduced. Favorably, scavenging can become obsolete. Accordingly, a scavenging system for the cyclone block can be simpler or become obsolete. With an inventive hood with a special designed shape connected to a cyclone block of an air cleaner a pre-separation efficiency up to 80% and more can be achieved without the need of scavenging. 
         [0011]    Favorably, the hood can be designed to guide the raw air to the plurality of cell-inlets of the cyclone block. The cell-inlets can define a multi direction inlet of the cyclone block. The hood can be flexible designed to supply the raw air in the multi direction inlet. 
         [0012]    With its inventive design, the hood is suitable for use in confined spaces. 
         [0013]    Favorably, an air duct or air hose can be connected to the at least one hood-inlet of the hood. The at least one air duct or air hose can lead to a suction place for the raw air which can be distant from the multi cyclone block, in particular the air cleaner. 
         [0014]    Favorably, downstream of the multi cyclone block, at least one air filter of the air cleaner with at least one air filter element can be arranged in the flow-way of the air to be cleaned. With the at least one air filter element the air can be filtered. 
         [0015]    A cyclone outlet of the cyclone block for air can be connected to an filter inlet for air of a filter housing of the at least one air filter. The cyclone outlet of the cyclone block can be connected air-ducting to cell-outlets of the cyclone cells and/or the cell-outlets can define the cyclone outlet. 
         [0016]    Favorably, the multi cyclone block and the at least one air filter can be arranged in-line. So, a main flow-way of the air between the cyclone outlet of the multi cyclone block and the filter inlet of the at least one air filter can be straight. In this case, the multi cyclone block can be termed in-line multi cyclone block. An in-line multi cyclone block can be arranged space-saving. 
         [0017]    The invention can be used with an intake system of an internal combustion engine of a motor vehicle. The invention can also be used in a technical area beyond automotive engineering. In particular, the invention can be used with industrial engines. 
         [0018]    According to a favorable embodiment of the invention, at least the inner surface of the wall of the hood at least in direction from the at least one hood-inlet to the at least one hood-outlet includes multiple curves so that a main flow path for air in the hood can be curved multiple, in particular at least the inner surface of the wall and/or the main flow path may have a S-shaped profile. In this way, the uniform distribution of the raw air can be further improved. Further, the at least one hood-inlet and the at least one hood-outlet can be arranged staggered. So, the multi cyclone block, in particular the air cleaner, can be arranged more flexible particularly in constricted and/or in narrow and winding installation spaces, particularly in an engine compartment. 
         [0019]    According to a further favorable embodiment of the invention, a plane with a flow cross-section on the inlet side of the at least one hood-inlet can be inclined to a plane with a flow cross-section on the outlet side of the at least one hood-outlet, in particular said plane of the at least one hood-inlet can be perpendicular to said plane of the at least one hood-outlet. In this way, a main flow direction of the raw air on the inlet side of the hood-inlet can be inclined to a main flow direction of the raw air on the outlet side of the hood-outlet. So, the cyclone block with the hood can be arranged more space-saving and/or more flexible in constricted and/or in narrow and winding installation spaces. A possible air duct or air hose can be inclined to a main flow path of the air in the cyclone block. 
         [0020]    Favorably, said planes can be perpendicular. In this way, the main flow directions also can be perpendicular. In case of an in-line multi cyclone block, the main flow-way of the intake air can be perpendicular to an axis of the cyclone block, in particular of the air cleaner. 
         [0021]    According to a further favorable embodiment of the invention, a flow cross-section of the at least one hood-inlet can be smaller than a flow cross-section of the at least one hood-outlet. In this way, the hood can act as a kind of adapter between a possible air duct or air hose on the side of the at least one hood-inlet and a connection of the cyclone block on the side of the at least one hood-outlet. An according connection section of the cyclone block can be larger than the possible air duct or the air hose. 
         [0022]    According to a further favorable embodiment of the invention, a profile of a flow cross-section of the at least one hood-inlet can be different or equal to a profile of a flow cross-section of the at least one hood-outlet, in particular the profile of the at least one hood-inlet can be round or oval and the profile of the at least one hood-outlet can be oval or round. 
         [0023]    Favorably, the hood-inlet can be designed as a connection to an air hose or an air duct. The connection side of the possible air hose or air duct can have a profile different to the profile of the inlet side of the cyclone block. So, the hood can be connected with the hood-inlet to a respective air duct or air hose. On the other hand, the hood can be connected with the hood-outlet to the inlet side of the cyclone block. 
         [0024]    Favorably, the at least one hood-inlet can be round. So, it can be connected to a round connection side of the possible air duct or air hose. Alternatively, the at least one hood-inlet can be oval. 
         [0025]    Favorably, the at least one hood-outlet can be oval. So, it can be connected to an oval connection side of the cyclone box. Thus, the hood can be used in combination with a flat cyclone box. Alternatively, the at least one hood-outlet can be round. 
         [0026]    The hood can combine the advantages of a connection with the profile, in particular a round profile, of an air hose or air duct on one hand and the profile, in particular an oval profile, assembled to the cyclone block on the other hand. 
         [0027]    According to a further favorable embodiment of the invention, the at least one hood-inlet can be arranged on a short side or on a long side of an oblong hood-outlet. 
         [0028]    If the at least one hood-inlet is on the short side of the hood-outlet, the extent of the cyclone block with the hood can be reduced in direction of the short side, in particular in direction of a short minor axis of an oval hood-outlet. 
         [0029]    If the at least one hood-inlet is on the long side of the hood-outlet, the extent of the cyclone block with the hood can be reduced in direction of the long side, in particular in direction of a long principle axis of an oval hood-outlet. 
         [0030]    According to a further favorable embodiment of the invention, the hood can be asymmetrical regarding to a center axis of the at least one hood-outlet. So, an uniform distribution of the separated particles over the cyclone cells can be further improved. Further, the hood so can easier be adapted to an available installation space. 
         [0031]    Favorably, the hood can be at least partly flexible, in particular elastic. So, the hood can compensate operational tolerances and/or vibrations. Additionally, a mounting and installation can be simplified. 
         [0032]    According to a further favorable embodiment of the invention, the hood can comprise or consist of rubber, favorably synthetic rubber, in particular ethylene-propylene-diene-polymethylene. The hood can easy be formed of rubber, particularly synthetic rubber, in particular by use of an injection (die) molding technique or a casting method. 
         [0033]    Favorably, the synthetic rubber can comprise or consist of ethylene-propylene-diene-polymethylene (EPDM) can be used. 
         [0034]    Rubber, particularly synthetic rubber, can be flexible, in particular elastic. 
         [0035]    As an alternative, the hood can comprise or consist of injection molded plastic, especially polyethylene, polyester, polyamide or similar. The injection molded plastic can comprise carbon or glass fiber for added rigidity in an amount up to 50 weight-%. 
         [0036]    According to a further favorable embodiment of the invention, the at least one hood-outlet can comprise a connection section for connection with a corresponding connection section on an inlet side of the cyclone block. With the connection section, the hood can easy be connected to the cyclone block. 
         [0037]    Favorably, the at least one hood-outlet can comprise or consist of a cylindrical sleeve. The at least one hood-outlet can be plugged on or in the connection section of the housing of the cyclone block. 
         [0038]    A cylindrical connection section of the hood-outlet can surround the plurality of cell-inlets of the cyclone block. 
         [0039]    According to a further favorable embodiment of the invention, the hood can comprise at least one means, in particular at least one snap-fit and/or at least one hose clamp, for fastening the hood on/in/at the cyclone block in particular on the side of the at least one hood-outlet. With the at least one means for fastening the hood can be fixed on the cyclone block. 
         [0040]    Favorably, at least one means for fastening can comprise or consist of at least one snap-fit. One part of the at least one snap-fit can comprise or consist of at least one notch on the side of the hood. The at least one notch can be combined with a possible cylindrical connection section of the at least one hood-outlet. At least one according collar can be located on side of the cyclone block. The at least one collar can latch in the at least one notch for fastening the hood on the cyclone block. Alternatively or additionally at least one collar can be arranged on the side of the hood and at least one corresponding notch can be arranged on side of the cyclone block. 
         [0041]    Favorably, alternatively or additionally, at least one means of fastening can have or consist at least one hose clamp. The at least one hose clamp can be combined with a possible cylindrical connection section of the at least one hood-outlet. If the cylindrical connection section is plugged on the according connection section of the cyclone block, the at least one hose clamp can clasp the cylindrical connection section of the hood and press it against the according connection section of the cyclone block. So, a tightness and/or stability of the connection between the hood and the cyclone block can be improved. Alternatively, the possible cylindrical connection section of the hood can be plugged in an according connection section of the cyclone block. In this case, the at least one hose clamp can clasp the connection section of the cyclone block accordingly. 
         [0042]    The object further is achieved by the air cleaner in that the at least one hood-outlet is designed for covering, in particular for surrounding, a plurality of cell-inlets, in particular all cell-inlets, of the cyclone cells of the cyclone block, wherein a wall of the hood is defining a distributor volume inside the hood, which is located between the at least one hood-inlet and the at least one hood-outlet, and wherein the wall comprises at least one point of inflection, in particular at least one line or area of inflection, where at least one inner surface of the wall changes its curvature. 
         [0043]    The above-mentioned advantages and characteristic features of the inventive hood apply analogously to the inventive air cleaner and its favorable embodiments and vice versa. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0044]    The present invention together with the above-mentioned and other objects and advantages may best be understood from the following detailed description of the embodiments, but not restricted to the embodiments, wherein is shown schematically 
           [0045]      FIG. 1  a longitudinal section of an air cleaner with an in-line multi cyclone block, comprising a hood according to a first embodiment, which is connected to a cyclone inlet of the cyclone block; 
           [0046]      FIG. 2  a detailed view of a connection of the hood with the cyclone block of  FIG. 1 ; 
           [0047]      FIG. 3 to 5  a perspective view of the hood of  FIGS. 1 and 2 ; 
           [0048]      FIG. 6  a longitudinal section of the hood of  FIGS. 1 and 2 ; 
           [0049]      FIG. 7  a perspective view of the hood of  FIGS. 1 and 2 ; 
           [0050]      FIG. 8  a view looking into the hood outlet of the hood of  FIGS. 1 and 2 ; 
           [0051]      FIG. 9, 10, 14  view looking into the hood outlet of a second embodiment of the hood of  FIGS. 1 and 2 ; 
           [0052]      FIG. 11, 13  perspective views of the hood of  FIGS. 9, 10, 14 ; 
           [0053]      FIG. 12  a longitudinal section of the hood of  FIGS. 9, 10, 14 ; 
           [0054]      FIG. 15, 16, 19  view looking into the hood outlet of a third embodiment of the hood of  FIGS. 1 and 2 ; 
           [0055]      FIG. 17, 18  perspective views of the hood of  FIGS. 15, 16, 19 ; 
           [0056]      FIG. 20  a longitudinal section of the hood of  FIGS. 15, 16, 19 ; 
           [0057]      FIG. 21, 22, 26  view looking into the hood outlet of a fourth embodiment of the hood of  FIGS. 1 and 2 ; 
           [0058]      FIG. 23, 25  perspective views of the hood of  FIGS. 21, 22, 26 ; 
           [0059]      FIG. 24  a longitudinal section of the hood of  FIGS. 21, 22, 26 ; 
           [0060]      FIG. 27, 32  view looking into the hood outlet of a fifth embodiment of the hood of  FIGS. 1 and 2 ; 
           [0061]      FIG. 28, 29,31  perspective views of the hood of  FIGS. 27, 32 ; 
           [0062]      FIG. 30  a longitudinal section of the hood of  FIGS. 27, 32 ; 
           [0063]      FIG. 33, 37  view looking into the hood outlet of a sixth embodiment of the hood of  FIGS. 1 and 2 ; 
           [0064]      FIG. 34, 35, 36  perspective views of the hood of  FIGS. 33, 37 ; and 
           [0065]      FIG. 38  a longitudinal section of the hood of  FIGS. 33, 37 . 
       
    
    
       [0066]    In the drawings, equal or similar elements are referred to by equal reference numerals. The drawings are merely schematic representations, not intended to portray specific parameters of the invention. Moreover, the drawings are intended to depict only typical embodiments of the invention and therefore should not be considered as limiting the scope of the invention. Further, the drawings are not true to scale. 
       DETAILED DESCRIPTION 
       [0067]    In  FIG. 1  an air cleaner  10  is shown in a longitudinal section. The air cleaner  10  is designed for the cleaning of combustion air of an internal combustion engine of a motor vehicle. The air cleaner  10  is arranged in an air intake system of the internal combustion engine. 
         [0068]    The air cleaner  10  has a pre-separator in form of an in-line multi cyclone block  12  and an air filter  14  with an air filter element  16 . The air cleaner  10  is designed as an in-line system, which means that the cyclone block  12  and the air filter  14  are arranged in-line relating to a main axis  18 . 
         [0069]    The air filter  14  has a filter housing  20  with a filter inlet  22  for the air to be filtered and a filter outlet  24  for the filtered air. The filter outlet  24  and the filter inlet  22  are on opposite sides of the filter housing  20 . The filter outlet  24  and the filter inlet  22  are coaxial to the main axis  18  each. The air filter element  16  is arranged in the filter housing  20  between the filter inlet  22  and the filter outlet  24 . The filter inlet  22  is connected to a cyclone outlet  26  of the cyclone block  12 . The filter outlet  24  is connected to a not shown connection hose, which leads to the internal combustion engine. 
         [0070]    The cyclone block  12  comprises a plurality of cyclone cells  28 . The cyclone cells  28  are functionality parallel arranged in a frame  30  of the cyclone block  12 . Respective axis  32  of the cyclone cells  28  are parallel to the main axis  18 . Cell-outlets  34  define the cyclone outlet  26 . The cell-outlets  34  are connected air-ducting to the filter inlet  22 . 
         [0071]    Cell-inlets  36  are on the opposite side of the cell-outlets  34  regarding to the main axis  18 . The cell-inlets  36  are surrounded by a connection section  38  of the frame  30 . The connection section  38  of the frame  30  is designed for connecting with a hood  40  of the cyclone block  12 . The radial outer surface of the connection section  38  of the frame  30  is oval cylindrical and coaxial to the main axis  18 . A detailed view of the connection of the hood  40  with the frame  30  is shown in  FIG. 2 . The hood  40  is depicted in different views in  FIGS. 3 to 8 . 
         [0072]    Near its free edge, which is on the axial opposite side of the air cleaner  10 , the connection section  38  has a collar  42 . The collar  42  is coaxial to the main axis  18 . The collar  42  extends in radial direction respective to the main axis  18 . The collar  42  is part of a snap-fit  44 , which is a first means for fastening the hood  40  on the frame  30  of the cyclone block  12 . 
         [0073]    A dust discharge  46  leads through a side wall of the frame  30 . In the normal operating orientation, which is shown in  FIG. 1 , the dust discharge  46  is on the underside of the cyclone block  12 . Particles separated from the air can be collected at the bottom of the frame  30  and can be removed through the dust discharge  46 . 
         [0074]    In  FIG. 1  a main flow path of the air to be cleaned through the cyclone block  12  is depicted with straight arrows  48 . The main flow path  48  through the cyclone block  12  is parallel to the main axis  18 . 
         [0075]    The hood  40  is made of synthetic rubber, namely ethylene-propylene-diene-polymethylene. The hood  40  has a hood-inlet  50  and a hood-outlet  52  for air to be fed to the cyclone cells  28 . 
         [0076]    The hood-outlet  52  is oval cylindrical and coaxial to the main axis  18 . In the described embodiment, the main axis  18  coincides with a center axis of the hood-outlet  52 . 
         [0077]    A part of the hood-outlet  52  realizes a connection section  54  for connecting with the connection section  38  of the frame  30 . The connection section  54  is on the side of the hood-outlet  52  which is opposite to the hood-inlet  50  in regard to an air flow direction through the hood  40 . In the completed air cleaner  10 , the connection section  54  is facing toward the cyclone block  12 . 
         [0078]    The connection section  54  has a notch  56  on the side facing the hood-inlet  50 . In the completed air cleaner  10 , the notch  56  is on the far side of the cyclone cells  28 . The notch  56  is regarding to the main axis  18  coaxial arranged on the radial inner circumferential side of the connection section  54 . The notch  56  is part of the snap-fit  44 . It is corresponding to the collar  42  of the connection section  38  of the frame  30 . 
         [0079]    The hood  40  further comprises a hose clamp  58  as a second means for fastening the hood  40  on the cyclone block  12 . The hose clamp  58  is arranged on the radial outer circumferential side of the connection section  54  of the hood-outlet  52 . In the completed air cleaner  10 , the hose clamp  58  presses the connection section  54  of the hood-outlet  52  against the connection section  38  of the frame  30 . 
         [0080]    On the side of the connection section  54  which is facing the hood-inlet  50 , a plane  60  with a flow cross-section  62  of the hood-outlet  52  is defined. The plane  60  is perpendicular to the main axis  18  and to a flow path  48  on the outlet side of the hood-outlet  52 . The profile of the flow cross-section  62  of the hood-outlet  52  is oval. 
         [0081]    The hood-inlet  50  is on a short side of the oblong hood-outlet  52 . In all, the hood  40  is asymmetrical regarding to the center axis of the hood-outlet  52 , namely the main axis  18 . In the completed air cleaner  10 , the hood-inlet  50  is on the opposite side of the dust discharge  46  of the cyclone block  12 . In the normal operating orientation, the hood-inlet  50  is on the upper side of the hood  40 . 
         [0082]    A plane  64  with a flow cross-section  66  of the hood-inlet  50  is perpendicular to the flow path  68  of the air on the inlet side. In  FIG. 1 , the main flow path  68  in the hood  40  is indicated with a curved arrow. Said plane  64  of the hood-inlet  50  is inclined to the plane  60  with the flow cross-section  62  on the outlet side of the hood-outlet  52 . Said plane  64  of the hood-inlet  50  is perpendicular to said plane  60  of the hood-outlet  52 . 
         [0083]    A profile of the flow cross-section  66  of the hood-inlet  50  is different to the profile of the flow cross-section  62  of the hood-outlet  52 . The profile of the hood-inlet  50  is round. The flow cross-section  66  of the hood-inlet  50  is smaller than the flow cross-section  62  of the hood-outlet  52 . 
         [0084]    A wall  70  of the hood  40  is defining a distributor volume  72  inside the hood  40 . The distributor volume  72  is arranged between the hood-inlet  50  and the hood-outlet  52 . In the distributor volume  72 , the air to be cleaned is uniformly distributed over all cell-inlets  36 . 
         [0085]    The wall  70  comprises two areas of inflection  74  where the inner surface of the wall  70  changes its curvature. Each area of inflection  74  is defined by multiple points of inflection. 
         [0086]    The inner surface of the wall  70  of the hood  40  in a flow-direction from the hood-inlet  50  to the one hood-outlet  52  this curved multiple. Starting from the hood-inlet  50 , the inner surface of the wall  70  on the opposite side of the hood-inlet  50  has a first concavity  76 , a first area of inflection  74 , a convexity  78 , a second area of deflection  74  and a second concavity  80 . The main flow path  68  for air in the hood  40  is curved multiple. The inner surface of the wall  70  and the main flow path  68  have an S-shaped profile each. This is shown for example in  FIGS. 1 and 6 . 
         [0087]    For assembling the air cleaner  10 , the cyclone block  12  being connected with its outlet side to the inlet side of the housing  20  of the air filter  14 . 
         [0088]    The connection section  38  of the frame  30  of the cyclone block  12  being plugged into the connection section  54  of the hood-outlet  52  of the hood  40 . In the correct mounting position, the collar  42  of the connection section  38  of the frame  30  snaps into the notch  56  of the connection section  54  of the hood  40 . The hose clamp  58  being mounted on the outer circumferential side of the connection section  54  of the hood  40 . The hood-outlet  52  so is connected air-ducting with the cell-inlets  36  of the cyclone cells  28 . The hood-outlet  52  is surrounding all cell-inlets  36  of the cyclone cells  28  of the cyclone block  12 . 
         [0089]    The air filter element  16  being arranged in the housing  20  of the air filter  14 . The housing  20  being closed. 
         [0090]    The filter outlet  24  of the air cleaner  10  being connected to the connection hose of the internal combustion engine. The hood-inlet  50  of the hood  40  being connected with the air hose, which leads to the suction place. 
         [0091]      FIGS. 9 to 14  depict a second embodiment of a hood  40 . Those parts which are equal to those of the first embodiment according to  FIGS. 1 to 8  have the same reference numbers. Different to the first embodiment, according to the second embodiment the hood-inlet  50  is on a long side of the oblong hood-outlet  52 . The hood-inlet  50  is sideways of a short minor axis  182  of the oval hood-outlet  52 . The short minor axis  182  of the hood-outlet  52  is shown in  FIG. 14 . In the normal working orientation of the hood  40 , which is shown for example in  FIGS. 9 to 11 , the hood-inlet  50  is approximately on a level with the upper half of the long side of the hood-outlet  52 . 
         [0092]      FIGS. 15 to 20  depict a third embodiment of a hood  40 . Those parts which are equal to those of the second embodiment according to  FIGS. 9 to 14  have the same reference numbers. Different to the second embodiment, according to the third embodiment the hood-inlet  50  is on the opposite long side of the oblong hood-outlet  52 . 
         [0093]    Further, the profile of the hood-inlet  50  of the third embodiment is oval, as shown in  FIG. 18 . The short minor axis of the oval hood-inlet  50  is parallel to the long principal axis of the oval hood-outlet  52 . 
         [0094]      FIGS. 21 to 26  depict a fourth embodiment of a hood  40 . Those parts which are equal to those of the first embodiment according to  FIGS. 1 to 8  have the same reference numbers. 
         [0095]      FIGS. 27 to 32  depict a fifth embodiment of a hood  40 . Those parts which are equal to those of the second embodiment according to  FIGS. 9 to 14  have the same reference numbers. Different to the second embodiment, according to the fifth embodiment the two areas of inflection  74  where the inner surface of the wall  70  changes its curvature are closer to each other. Further, the profile of the hood-inlet  50  of the fourth embodiment is round, which is shown in  FIG. 28 . 
         [0096]      FIGS. 33 to 38  depict a sixth embodiment of a hood  40 . Those parts which are equal to those of the fifth embodiment according to  FIGS. 27 to 32  have the same reference numbers. Different to the fifth embodiment, according to the sixth embodiment the hood-inlet  50  is on the opposite long side of the oblong hood-outlet  52 . 
         [0097]    Further, the profile of the hood-inlet  50  of the sixth embodiment is oval, as shown in  FIG. 34 . The short minor axis of the oval hood-inlet  50  is parallel to the long principal axis of the oval hood-outlet  52 .