Abstract:
A two stage filter device includes a cyclonic pre-separator ( 10 ) designed as a pre-filter that separates the particles from the gas flow and a main filter element ( 20 ) arranged downstream as a second stage operable to filter by guiding the particles through at least one filter medium ( 24 ). The main filter element ( 20 ) is received in a filter housing ( 30 ). The main filter element ( 20 ) includes at least one retaining element ( 22 ) for stabilizing the position of the main filter element ( 20 ) in the housing ( 30 ).

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a US Bypass Continuation Application of International Application No. PCT/EP2010/064980 having a filing date of Oct. 7, 2010 and designating the United States, the International Application claiming a priority date of Oct. 12, 2009 based on prior filed German patent application No. 10 2009 049 170.8 and a priority date of Apr. 8, 2010 based on prior filed German patent application No. 10 2010 014 277.8. The entire contents of the aforesaid international application PCT/EP2010/064980 and the aforesaid German patent applications 10 2009 049 170.8 and 10 2010 014 277.8 being incorporated herein by reference. 
     
    
     TECHNICAL FIELD 
       [0002]    This disclosure relates generally to a filter device that is in particular of a two-stage configuration for separating liquid and/or solid particles out of a gas stream to be purified, in particular a two-stage air filter for an internal combustion engine. 
       BACKGROUND OF THE INVENTION 
       [0003]    A filter device according is disclosed in publication DE 10 2008 011 186 A1. Moreover, an air filter of the aforementioned kind for an internal combustion engine is disclosed in publication DE 298 19 335 U1. In the known filter elements, the main filter element is received with play in the filter housing. 
       SUMMARY OF THE INVENTION 
       [0004]    The invention has the object to further develop a filter element of the aforementioned kind such that the main filter element is arranged so as to be immobile within the filter housing and that in particular the filter element is prevented from falling out of the filter device when mounted overhead. 
         [0005]    This object is solved by a filter device with the features disclosed in claim  1 . Advantageous embodiments and expedient further developments of the present invention are defined in the dependent claims. 
         [0006]    Accordingly, the present invention is based on the main filter element or primary element having at least one retaining element that stabilizes the position of the main filter element in the filter housing. This retaining element extends, beginning at a circumferential side of the main filter element, in the direction toward the filter housing and is configured to position the main filter element at a defined spacing relative to the filter housing. The retaining element prevents thus that the main filter element moves within the filter housing. 
         [0007]    Preferably, the main filter element has four retaining elements arranged on the respective circumferential sides wherein two of these retaining elements, respectively, are substantially positioned opposite each other or are positioned obliquely opposite each other. 
         [0008]    In addition to stabilization of the main filter element in the filter housing, the retaining element can also serve to prevent the main filter element from undesirably falling out of the filter housing, for example, when opening the filter housing. For this purpose, the filter housing has at least one projection, beginning at the circumferential side of the filter housing and extending in the direction toward the main filter housing, that supports the retaining element and prevents the main filter element from falling out of the filter housing by itself. 
         [0009]    In order for the main filter element to be insertable into the filter housing or removable therefrom in a simple way, the retaining element is preferably made of elastic material, for example, polyurethane. Accordingly, the retaining element can be moved, for example, with somewhat increased force expenditure, across the projection of the filter housing. 
         [0010]    In one embodiment, the filter housing is provided at the inflow side with a front attachment wherein the front attachment is a cyclone preseparator, a protective screen, an induction pipe, or a raw air conduit. 
         [0011]    In an advantageous embodiment, the cyclone preseparator comprises several individual cyclones. Such a multi-cell cyclone or multi-cyclone that is provided for prepurifying the gas stream with a plurality of guide vanes that cause the gas stream to rotate, is disclosed, for example, in the publication DE 10 2008 011 186 A1. In this connection, the cyclone preseparator, as is disclosed in the publication DE 103 30 296 A1, can be embodied as a two-stage preseparator. 
         [0012]    As a main filter element or primary element that is received in the filter housing, for example, a compact air filter with a plurality of passages that are closed off alternatingly in the area of the inlet-side and outlet-side end surfaces and that are formed by placing a flat layer and a corrugated layer on each other is conceivable in which the gas stream is guided linearly through the filter passages. Alternatively, a single or multi-bellows filter with annularly closed, zigzag-folded filter bellows, preferably a double bellows filter with a larger annular filter element arranged about a smaller annular filter element, or a zigzag-folded planar filter element can be used. 
         [0013]    The filter medium is preferably substantially annular or oval. For example, as described in the publication DE 10 2008 011 186 A1, in case of the multi-bellows filter each filter bellows can be embodied as a star filter with filter folds that are arranged in a star shape and at the inflow side and/or at the outflow side are tacked together. It is particularly advantageous when the end face edges of the filter folds are tacked together at the inflow side and/or at the outflow side, for example, by means of a so-called end face bonding. 
         [0014]    The above features and advantages and other features and advantages of the present invention are readily apparent from the following detailed description of the best modes for carrying out the invention when taken in connection with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    The accompanying Figures, where like reference numerals refer to identical or functionally similar elements throughout the separate views and which together with the detailed description below are incorporated in and form part of the specification, serve to further illustrate various embodiments and to explain various principles and advantages all in accordance with the present invention. 
           [0016]    Features of the present invention, which are believed to be novel, are set forth in the drawings and more particularly in the appended claims. The invention, together with the further objects and advantages thereof, may be best understood with reference to the following description, taken in conjunction with the accompanying drawings. The drawings show a form of the invention that is presently preferred; however, the invention is not limited to the precise arrangement shown in the drawings. 
           [0017]      FIG. 1  shows in perspective illustration an embodiment for a two-stage filter device according to the present invention; 
           [0018]      FIG. 2  shows in an exploded illustration the filter device of  FIG. 1 , wherein the filter housing, the cover of the filter housing, and the main filter element are individually illustrated; 
           [0019]      FIG. 3  shows the inlet side of the main filter element of the filter device according to  FIG. 1  received in the filter housing; 
           [0020]      FIG. 4  shows a detail view of the inlet side of  FIG. 3 , wherein in particular a retaining element of the main filter element and a projection of the filter housing are illustrated; 
           [0021]      FIG. 5  shows in perspective illustration the filter device of  FIG. 1  upon removal of the main filter element; 
           [0022]      FIG. 6  shows a detail view of the filter device of  FIG. 5  wherein in particular the retaining elements that are resting of the projections of the filter housing are illustrated; 
           [0023]      FIG. 7  shows a detail view of one of the retaining elements of  FIG. 6  resting on the projections of the filter housing; and 
           [0024]      FIG. 8  show a side view of the filter device of  FIG. 1  upon removal of the main filter element. 
       
    
    
       [0025]    Same or similar configurations, elements or features are provided in  FIGS. 1 to 8  with identical reference numerals. Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention. 
       DETAILED DESCRIPTION 
       [0026]    Before describing in detail embodiments that are in accordance with the present invention, it should be observed that the embodiments reside primarily in combinations of apparatus components related to a filter device and to a filter element for a filter device, as disclosed and enabled herein. Accordingly, the apparatus components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein. 
         [0027]    In this document, relational terms such as first and second, top and bottom, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. The terms “comprises,” “comprising,” or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element preceded by “comprises . . . a” does not, without more constraints, preclude the existence of additional identical elements in the process, method, article, or apparatus that comprises the element. 
         [0028]    The two-stage filter device or two-stage separator  100  illustrated in  FIG. 1  is an air filter for an internal combustion engine. This air filter  100  is comprised of a filter housing  30  in which a main filter element  20 , a so-called primary element, is received; a cyclone preseparator  10 ; as well as a downstream secondary element  50 . The gas stream that is passed through the air filter  100  is purified in a first filter stage in the cyclone preseparator  10  and in a second filter stage in the main filter element  20 . The secondary element  50  prevents that when exchanging the main filter element  20  dirt can pass into the internal combustion engine. 
         [0029]    The filter housing  30  has at its circumferential side an opening  36  that is covered by a cover  60  that is arranged to be detachable and lockable by means of closure element  62 . By means of this opening  36  in the wall surface of the filter housing  30 , the main filter element  20  and expediently also the secondary element  50  can be inserted radially or transverse to the axial direction of the filter device  100  into the receiving space within the filter housing  30  or removed therefrom. The filter housing  30  has a raw-side inlet  32  and a clean-side outlet  34  for the gas stream to be purified. 
         [0030]    The cyclone preseparator  10  is arranged in the area of the inlet  32  of the filter housing  30 . In the cyclone preseparator  10  the dirt particles of the axially supplied air are carried by centrifugal force in a rotating air stream outwardly and separated. By means of particle outlet  12  that can be oriented in downward direction, the dirt particles that have been separated in the cyclone preseparator  10  can be removed. The cyclone preseparator  10  is embodied as a separate component that is connected with the filter housing  30 . The fluid that has been prefiltered in cyclone preseparator  10  is axially supplied to the inflow side at the end face of the filter element in axial direction. Cyclone preseparator  10 , main filter element  20 , and secondary element  50  can be positioned in axial direction behind each other and can be flowed through in axial direction in particular without deflection of the combustion air to be purified. Passage without deflection can be achieved, for example, when compact air filter elements are employed that have alternatingly closed passages in the main flow direction. 
         [0031]      FIG. 2  shows the filter device  100  of  FIG. 1  wherein the cover  60  and the main filter element  20  have been removed. The main filter element  20  has at its side that is facing the raw-side inlet  32  of the filter housing  30  an inflow-side sealing element  40  that is embodied for producing a gas-tight connection between two annular, zigzag-folded filter bellows of the main filter element  20  that are arranged within each other. This inflow-side sealing element  40  is preferably made of elastic material, for example, of polyurethane and has at its circumferential sides retaining elements, i.e., polyurethane knobs or spacer knobs  22  that secure the main filter element  20  mounted in the filter housing  30  at a defined spacing relative to the filter housing  30  (compare  FIGS. 3 and 4 , wherein  FIG. 4  shows a detail view of the area that is encircled in  FIG. 3  by dashed lines). Moreover, the polyurethane knobs  22  when opening the cover  30  of the filter housing  30  serve as a protection that protects by knobs the main filter element  22  from falling out. As shown in the  FIGS. 5 to 7  ( FIG. 7  shows a detail view of the area that is encircled in  FIG. 5  by dashed lines), the polyurethane knobs  22 , with the cover  60  open, interact with projections  38  of the filter housing  30  and secure the main filter element  20  in the filter housing  30 . Since the lateral polyurethane knobs  22  are resting on the projections  38  of the filter housing  30 , they prevent the main filter element  20  from falling out by itself. As a result of the elasticity of the polyurethane knobs  22 , the main filter element  20  can still be pulled out at increased force expenditure from the filter housing  30 . In this connection, the polyurethane knobs  22  are compressed and glide across the projections  38 . 
         [0032]    In  FIGS. 3 and 4 , the polyurethane knobs  22  are arranged at a spacing to the projections  38  of the filter housing  30 . This is so because the  FIGS. 3 and 4  show the main filter element mounted in the filter housing. When the cover  30  is open, the main filter element  20  slides in the direction of the opening  36  and the spacer knobs  22  secure the main filter element  20  in the filter housing (compare  FIGS. 5 to 8 ). 
         [0033]      FIG. 8  shows a side view of the filter device  100  when removing the primary element  20 . A sealing element  42  at the outlet side is positioned in the sealing seat  70  of the clean-side outlet  34  of the filter housing  30 , in such a way that the raw side is separated from the clean side. The filter element  20  is prevented from falling out of the filter housing  30  by the two polyurethane knobs  22  that are arranged at the inflow-side sealing element  40  that are caught on the projections  38  of the filter housing  30  and the outlet-side sealing element  42  that is resting against the sealing seat  70 . The polyurethane knobs  22  that serve for stabilizing the main filter element  20  in the filter housing  30  serve thus additionally as a protection from falling out and secure the main filter element  20  against accidental sliding out of the filter housing  30 . 
         [0034]    In the foregoing specification, specific embodiments of the present invention have been described. However, one of ordinary skill in the art appreciates that various modifications and changes can be made without departing from the scope of the present invention as set forth in the claims below. Accordingly, the specification and figures are to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of the present invention. The benefits, advantages, solutions to problems, and any element(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential features or elements of any or all the claims The invention is defined solely by the appended claims including any amendments made during the pendency of this application and all equivalents of those claims as issued.